JP2000018077A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

(57) Abstract: Provided is a fuel injection control device for an internal combustion engine, which can surely prevent the occurrence of torque shock accompanying switching of fuel injection mode. An electronic control unit (ECU) includes an electromagnetic valve (3).
To switch the fuel injection mode from the injector 2 between a main injection mode in which only the main injection is executed and a pilot injection mode in which both the main injection and the pilot injection are executed. ECU
50 gradually changes the engine torque until the transient torque value, which is the torque value after the switching of the fuel injection mode, by gradually changing the injection timing of the main injection before the switching of the fuel injection mode. After switching the fuel injection mode, the ECU 50
By gradually changing the injection timing of the main injection again, the engine torque is gradually changed from the transient torque value to the steady-state torque value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control device for an internal combustion engine, and more particularly, to a fuel injection control device for an internal combustion engine that executes a pilot injection according to an engine operating state.

[0002]

2. Description of the Related Art The combustion process in a diesel engine can be broadly divided into a premixed combustion period and a diffusion combustion period following the premixed combustion period. During the premixed combustion period, the fuel injected into the combustion chamber becomes a combustible air-fuel mixture and self-ignites, so that the combustion of the fuel proceeds rapidly. In the diffusion combustion period, fuel is injected into the combustion gas generated in the combustion chamber during the premixed combustion period, so that the fuel is continuously burned. By the way, in the premixed combustion period, since the combustion proceeds rapidly as described above, the rate of increase in the combustion pressure in the combustion chamber becomes large, and the combustion temperature tends to become extremely high. Therefore, if the premixed combustion period is prolonged, that is, if the proportion of fuel that burns rapidly due to self-ignition increases, combustion noise increases and nitrogen oxides (NOx) in exhaust gas increase.

[0003] In order to prevent such an increase in combustion noise and NOx, a fuel injection device for performing pilot injection has conventionally been proposed. In this fuel injection device,
After a part of the fuel to be injected into the combustion chamber is injected (pilot injection), the fuel injection is temporarily stopped. Then, when the pilot-injected fuel is ignited, the remaining fuel is injected again (main injection). By performing such pilot injection, the premixed combustion period is shortened, and the proportion of fuel that rapidly burns due to self-ignition is reduced, so that the combustion pressure rises slowly and the combustion temperature in the combustion chamber also decreases. . Therefore, according to the fuel injection device, it is possible to prevent an increase in combustion noise and an increase in NOx in exhaust gas.

In general, pilot injection is performed only when the engine is running at a low load and at a low speed. This is because, when the pilot injection is executed even at the time of high load or high rotation, the exhaust gas concentration tends to increase and the engine output tends to decrease. For this reason, in the conventional fuel injection device, the fuel injection mode is selectively switched between a mode in which the pilot injection and the main injection are executed and a mode in which only the main injection is executed according to the engine operating state. I have.

However, if the fuel injection mode is switched as described above, even if the total amount of fuel injected into the combustion chamber is the same in both modes, the combustion state in the combustion chamber is changed in accordance with the switching. Because of a large change, a sudden change in the engine torque may cause a so-called torque shock.

Therefore, in the "diesel engine fuel injection control device" described in Japanese Patent Application Laid-Open No. 5-1609, when the fuel injection mode is switched, the injection interval (pilot injection interval) between pilot injection and main injection is set. I try to change it gradually. In other words, this fuel injection control device attempts to suppress the occurrence of torque shock by gradually changing the pilot injection interval to make the change in the combustion state slow.

[0007]

The operation by the pilot injection as described above is based on the premise that the main injection is executed after the fuel injected by the pilot self-ignites. That is, when the pilot injection interval is shortened and the main injection is performed before the fuel by the pilot injection self-ignites, or after the self-ignition, the main injection is performed in an extremely short time. In the case of, since the fuel by the pilot injection no longer functions as a spark, the change in the combustion state in the combustion chamber is the same as when only the main injection is performed, despite the execution of the pilot injection. It is almost the same.

Therefore, in the above-described conventional fuel control system, the engine torque can be reliably controlled by gradually changing the pilot injection interval only when the pilot injection interval is set to be relatively long. Is set to be short and the fuel injected by the pilot does not function as a spark, the engine torque cannot be controlled even if the pilot injection interval is changed. For these reasons, there is naturally a limit to the torque shock that can be suppressed by the conventional fuel control device, and it is not possible to cope with the torque shock that occurs when the engine torque before and after switching the fuel injection mode is significantly different. Had become.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fuel injection control device for an internal combustion engine that can reliably prevent the occurrence of torque shock accompanying switching of the fuel injection mode. Is to do.

[0010]

In order to achieve the above object, according to the first aspect of the present invention, a first injection method for performing one injection during one stroke of each cylinder of an internal combustion engine and each cylinder are provided. When switching from the first injection method to the second injection method, the first injection method is used in a fuel injection control device for an internal combustion engine that selectively uses the second injection method that performs a plurality of injections during one stroke. The injection state based on the second injection method is corrected so as to approach the engine torque after switching to the second injection method, and when switching from the second injection method to the first injection method, a plurality of times based on the second injection method are performed. Of the injection having a large injection amount among the above injections, the correction state is corrected so as to approach the torque after switching to the first injection method.

[0011] According to the above configuration, based on the first injection method, the correlation with the engine torque is higher than the injection state of the injection with a small injection amount among the multiple injections based on the second injection method. Since the injection state and the injection state of the injection with a large injection amount among the multiple injections based on the second injection method are corrected, the engine torque can be reliably controlled, and the fuel injection mode Abrupt change in engine torque accompanying the switching of the engine speed is suppressed.

According to the second aspect of the present invention, the fuel injection for the internal combustion engine is performed based on the operating state of the engine, and the main fuel injection and the pilot injection are both performed. The fuel injection control device for an internal combustion engine configured to switch between the fuel injection mode and the fuel injection mode includes a torque change suppressing unit that suppresses a change in engine torque due to a change in the fuel injection mode based on a change in a control value related to the main injection. I have to.

According to a third aspect of the present invention, in the fuel injection control apparatus for an internal combustion engine according to the second aspect, the torque change suppressing means includes at least one of an injection timing, an injection amount, and an injection pressure as a control value related to the main injection. One of them is to change.

According to a fourth aspect of the present invention, in the fuel injection control device for an internal combustion engine according to the third aspect, the torque change suppressing means changes the control value for the main injection when the fuel injection mode is switched. A torque control means is provided for gradually changing the engine torque from a pre-switching torque value before switching of the fuel injection mode to a post-switching torque value after switching based on the switching.

According to a fifth aspect of the present invention, in the fuel injection control device for an internal combustion engine according to the third aspect,
The torque change suppressing unit is configured to switch the engine torque between the pre-switching torque value before the switching of the fuel injection mode and the post-switching torque value after the switching based on the change of the control value related to the main injection when the fuel injection mode is switched. And a torque control means for controlling the transient torque value.

Since the control values relating to the main injection, particularly the control values such as the injection timing, the injection amount, and the injection pressure of the main injection have a direct effect on the engine combustion state,
The correlation with the engine torque is higher than the pilot injection interval. Therefore, according to the second to fifth aspects of the present invention, it is possible to reliably control the engine torque by changing the control value related to the main injection, and to sharply control the fuel injection mode. A change in the engine torque is suppressed.

In particular, in the invention described in claim 4, when the fuel injection mode is switched, the engine torque is gradually changed from the pre-switching torque value to the post-switching torque value. The change in the engine torque becomes slow.

According to the fifth aspect of the invention, when the fuel injection mode is switched, the engine torque is controlled so as to be a transient torque value between the torque value before switching and the torque value after switching. In addition, the change in the engine torque accompanying the switching of the fuel injection mode becomes slow.

According to a sixth aspect of the present invention, in the fuel injection control device for an internal combustion engine according to the fifth aspect, the torque control means sets the engine torque to a transient torque value in the injection mode before the fuel injection mode is switched. Control value setting means for setting a control value related to the main injection of the control as a transient control value,
The control value for the main injection is gradually changed to the transient control value after the fuel injection mode switching determination and before the actual switching, and the engine torque is switched from the transient control value to the post-switching torque value during the fuel injection mode switching. Control value changing means for changing the control value to a control value for performing the control.

In the above configuration, the engine torque is gradually changed from the pre-switching torque value to the transient torque value by gradually changing the control value relating to the main injection to the transient control value before switching the fuel injection mode. Changes to Therefore, before the switching of the fuel injection mode, it is possible to control the change in the engine torque in accordance with the gradual change speed of the control value related to the main injection, and the sudden change in the engine torque is reliably suppressed. Become so. Further, by changing the engine torque in this way, the difference between the engine torque immediately before the fuel injection mode is switched and the post-switching torque value is reduced.
For this reason, even when the control value for the main injection is changed from the transient control value to the control value for changing the engine torque to the post-switching torque value when the fuel injection mode is switched, the torque change amount at that time is relatively large. Will be small.

According to a seventh aspect of the present invention, in the fuel injection control device for an internal combustion engine according to the fifth aspect, the torque control means sets the engine torque to a transient torque value in the injection mode after the fuel injection mode is switched. Control value setting means for setting a control value related to the main injection of the control as a transient control value,
Control that changes the control value for the main injection to a transient control value when switching the fuel injection mode, and gradually changes from the transient control value to a control value for changing the engine torque to the post-switching torque value after switching the fuel injection mode. Value changing means.

In the above configuration, the control value for the main injection is changed to the transient control value when the fuel injection mode is switched, so that the engine torque changes from the pre-switching torque value to the transient torque value. Here, since the transient torque value is set as a torque value between the pre-switching torque value and the post-switching torque value, the transient torque value is compared with the case where the engine torque changes from the pre-switching torque value to the post-switching torque value. In addition, the amount of change in the engine torque generated when the fuel injection mode is switched becomes relatively small. Further, after the fuel injection mode is switched, the control value relating to the main injection is gradually changed from the transient control value to the control value for changing the engine torque to the post-switching torque value. It gradually changes to the torque value after switching. Therefore, after the switching of the fuel injection mode, it is possible to control the change in the engine torque according to the gradual change speed of the control value related to the main injection, and the sudden change in the engine torque is reliably suppressed. Become like

According to an eighth aspect of the present invention, in the fuel injection control apparatus for an internal combustion engine according to the fifth aspect, the torque control means switches the engine torque to the pre-switching torque value in the injection mode before the fuel injection mode is switched. The first between the post-torque value
The control value for the main injection for setting the transient torque value is set as the first transient control value, and the engine torque is set between the pre-switching torque value and the post-switching torque value in the injection mode after the fuel injection mode switching. Control value setting means for setting, as a second transient control value, a control value related to main injection for setting the second transient torque value as a second transient torque value; Before the actual switching, the temperature is gradually changed to the first transient control value, and when the fuel injection mode is switched, the first transient control value is changed to the second transient control value. Control value changing means for gradually changing the engine control torque from the second transient control value to the control value for setting the engine torque to the post-switching torque value.

In the above configuration, the engine torque is gradually changed from the pre-switching torque value to the first transient torque by changing the control value related to the main injection to the first transient control value before switching the fuel injection mode. It gradually changes to the value. Therefore, before the switching of the fuel injection mode, it is possible to control the change in the engine torque in accordance with the gradual change speed of the control value related to the main injection, and the sudden change in the engine torque is reliably suppressed. Become so.

Next, when the fuel injection mode is switched, the control value relating to the main injection is changed from the first transient control value to the second transient control value, so that the engine torque becomes equal to the first transient torque value. To the second transient torque value. Here, since each of these transient torque values is set as a torque value between the torque value before switching and the torque value after switching, when the engine torque changes from the torque value before switching to the torque value after switching. As compared with the above, the change amount of the engine torque generated when the fuel injection mode is switched becomes relatively small.

Further, after the fuel injection mode is switched, the control value related to the main injection is gradually changed from the second transient control value to a control value for changing the engine torque to the post-switching torque value. The engine torque gradually changes from the second transient torque value to the post-switching torque value. Therefore, after the switching of the fuel injection mode, it is possible to control the change in the engine torque according to the gradual change speed of the control value related to the main injection, and the sudden change in the engine torque is reliably suppressed. Become like

According to a ninth aspect of the present invention, in the fuel injection control device for an internal combustion engine according to the eighth aspect, the control value setting means makes the first transient torque value equal to the second transient torque value. In this manner, the first transient control value and the second transient control value are set.

In the above configuration, the control value for the main injection is changed from the first transient control value to the second
The engine torque does not change even if the transient control value is changed to. Therefore, according to the above configuration, in addition to the effect of the invention described in claim 8, in particular, a sudden change in the engine torque that occurs simultaneously with the switching of the fuel injection mode can be reliably suppressed.

According to a tenth aspect of the present invention, in the fuel injection control device for an internal combustion engine according to any one of the second to ninth aspects, the torque change suppressing means includes at least an injection of the main injection as a control value related to the main injection. The timing is changed, and the injection pressure of the main injection is changed to a low pressure side as the injection timing is changed to the advance side.

Generally, as the injection timing of the main injection is changed to the advanced side, the initial combustion is performed in the compression stroke, so that the proportion of the premixed combustion in the combustion process increases, and the rapid combustion increases. Combustion noise tends to increase due to the increase in pressure. Conversely, when the injection timing of the main injection is changed to the retard side, the proportion of premixed combustion in the combustion process is reduced, so that although the combustion noise is reduced, the combustion speed is reduced and the fuel It tends to lead to an increase in smoke concentration due to incomplete combustion.

In this respect, according to the above configuration, when the injection timing of the main injection is changed to the relatively advanced side, the atomization of the injected fuel is suppressed by the decrease of the injection pressure. The rise will be suppressed. On the other hand, when the injection timing of the main injection is relatively retarded, the increase in the injection pressure promotes atomization of the injected fuel, so that incomplete combustion of the fuel is suppressed. Become.

According to an eleventh aspect of the present invention, in the fuel injection control device for an internal combustion engine according to any one of the second to ninth aspects, the torque change suppressing means includes a main injection and a pilot injection when the fuel injection mode is switched. An injection interval control means for gradually changing an injection interval with the injection and a pilot injection quantity control means for controlling the injection quantity so that the injection quantity of the pilot injection decreases as the injection interval becomes shorter.

According to the above configuration, in addition to the effect of the invention described in any one of claims 2 to 9, when the fuel injection mode is switched, the injection interval between the main injection and the pilot injection, that is, the pilot injection interval is changed. Since it is gradually changed, the change in the engine combustion state accompanying the switching of the fuel injection mode becomes slow.

When the pilot injection interval is set to be relatively short by gradually changing the pilot injection interval as described above, the combustion pressure increased by the pilot injection is not reduced yet. Since the main injection may be performed, there is a concern that combustion noise may increase due to a rapid increase in combustion pressure.

In this respect, according to the above configuration, when the pilot injection interval is set to be relatively short, the injection amount of the pilot injection is reduced, so that the combustion pressure temporarily increased by the pilot injection is reduced. Begins to decline earlier. Therefore, when the combustion pressure increased by the pilot injection is sufficiently reduced, the main injection is executed, and a rapid increase in the combustion pressure is suppressed.

According to a twelfth aspect of the present invention, there is provided a first injection method for performing one injection during one stroke of each cylinder of an internal combustion engine and a second injection method for performing a plurality of injections during one stroke of each cylinder. In a fuel injection control device for an internal combustion engine that properly uses an injection method,
When switching from the first injection method to the second injection method, the injection state based on the first injection method is corrected so as to approach the engine torque after switching to the second injection method, When switching from the second injection method to the first injection method, the injection state of the injection having the largest injection amount among the multiple injections based on the second injection method is changed to the first injection method. A fuel injection control device for an internal combustion engine including a correction unit that corrects the torque so as to approach the torque after the switching is provided.

According to the above configuration, the first injection method has a high correlation with the engine torque as compared with the injection state of the injection with a small injection amount among a plurality of injections based on the second injection method. Since the injection state and the injection state of the injection with the largest injection amount among the multiple injections based on the second injection method are corrected, the engine torque can be reliably controlled, and the fuel injection can be performed. An abrupt change in the engine torque accompanying the switching of the form is suppressed.

[0038]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] FIGS. 1 to 1 show a first embodiment in which a fuel injection control device for an internal combustion engine according to the present invention is applied to a diesel engine.
13 will be described.

FIG. 1 is a schematic configuration diagram showing a fuel injection control device according to this embodiment. Diesel engine 1
Indicates a plurality of cylinders (four cylinders in this embodiment) {1}
4. The diesel engine 1 is provided with injectors 2 corresponding to the combustion chambers of the cylinders # 1 to # 4, respectively.
, Fuel is injected into each combustion chamber.
The injector 2 includes an electromagnetic valve 3 for injection control, and the injector 2 is controlled based on the opening / closing operation of the electromagnetic valve 3.
Is controlled. The mode of fuel injection by the injector 2 can be switched between a pilot injection mode and a main injection mode.

The injector 2 is connected to a common rail 4 common to the cylinders # 1 to # 4. The common rail 4 is connected to a discharge port 6 a of a supply pump 6 via a supply pipe 5 provided with a check valve 7.

The suction port 6b of the supply pump 6 is connected to the fuel tank 8 via the filter 9. The return port 6c of the supply pump 6 and the return port 3a of the solenoid valve 3 are both connected to the return pipe 11
Is connected to the fuel tank 8.

The supply pump 6 has a plunger (not shown) which reciprocates in synchronization with the rotation of a crankshaft (not shown) of the diesel engine 1. The fuel is pressurized, and the pressurized fuel is discharged from the discharge port 6a to the common rail 4
To pump. The fuel pumping amount of the supply pump 6 is adjusted based on the opening / closing operation of a pressure control valve (hereinafter abbreviated as “PCV”) 10 provided near the discharge port 6a.

The diesel engine 1 is provided with various sensors for detecting various state quantities related to the operation. That is, near the accelerator pedal 15, an accelerator sensor 20 for detecting the amount of depression of the pedal 15 (accelerator opening ACCP) is provided. A water temperature sensor 2 for detecting the temperature of the cooling water (cooling water temperature THW) is provided on a cylinder block of the diesel engine 1.
1 is provided. Further, the common rail 4 is provided with a fuel pressure sensor 22 for detecting a fuel pressure (fuel pressure PC) inside the common rail 4. Return pipe 11 has
A fuel temperature sensor 23 for detecting the temperature of the fuel (fuel temperature THF) is provided. The intake passage 16 of the diesel engine 1 is provided with an intake pressure sensor 24 for detecting the pressure of the intake air (intake pressure PM) in the passage 16.

In the vicinity of the crankshaft,
A crank sensor 25 is provided, and a cam sensor 26 is provided near a camshaft (not shown) that rotates in synchronization with the rotation of the crankshaft. The crank sensor 25 and the cam sensor 26 are sensors for detecting the number of rotations of the crankshaft per unit time (engine speed NE) and the rotation angle of the crankshaft (crank angle CA).

The output signals of these sensors 20 to 26 are:
The electronic control unit of the diesel engine 1 (hereinafter referred to as “EC
U "). This ECU 50
Comprises a CPU, a memory, an input / output circuit, a drive circuit (all not shown), and the like. ECU50
Performs reading and calculation of various state quantities related to the operation of the diesel engine 1 based on the output signals of the sensors 20 to 26, and executes the electromagnetic valve 3 and the PCV.
By controlling the fuel injection control 10, the fuel injection control is executed.

That is, the ECU 50 controls the accelerator sensor 2
0, based on each output signal of the water temperature sensor 21, the fuel pressure sensor 22, the fuel temperature sensor 23, and the intake pressure sensor 24,
Accelerator opening ACCP, cooling water temperature THW, fuel pressure PC,
The fuel temperature THF and the intake pressure PM are read. Further, the ECU 50 calculates the engine speed NE and the crank angle CA based on the output signals of the crank sensor 25 and the cam sensor 26.

Further, the ECU 50 controls the fuel injection mode, the injection amount, the injection timing, and the injection pressure (fuel pressure of the common rail 4) based on the various state quantities. Hereinafter, an outline of such fuel injection control will be described.

[Setting of Fuel Injection Mode] When setting the fuel injection mode, the ECU 50 first sets the accelerator opening ACC
Basic injection amount QMAIN based on P and engine speed NE
Calculate B. The basic injection amount QMAINB most accurately reflects the operation state of the diesel engine 1, and is used when calculating various control values related to fuel injection control.

The memory of the ECU 50 stores the basic injection amount QMAINB, the engine speed NE and the accelerator opening AC.
Function data that defines the relationship with the CP is stored,
The ECU 50 refers to the function data and refers to the basic injection amount Q
MAINB is calculated.

Next, the ECU 50 calculates the steady-state pilot injection amount QPLT2 based on the basic injection amount QMAINB and the engine speed NE calculated as described above.
This steady-state pilot injection amount QPLT2 is determined by combustion noise,
In consideration of smoke concentration and the like, the amount becomes the most suitable amount for the engine operating state at a steady state, that is, when a sufficient time has elapsed from the time when the fuel injection mode is switched from the main injection mode to the pilot injection mode. It is set as follows.

The memory of the ECU 50 stores function data defining the relationship between the steady-state pilot injection amount QPLT2, the engine speed NE and the basic injection amount QMAINB, as shown in FIG. This function data is referred to when calculating the constant pilot injection amount QPLT2.

Next, the ECU 50 sets the fuel injection mode based on the engine operating state. That is, the ECU 50 calculates the steady-state pilot injection amount QPLT2 and the engine speed N
When both of the following conditional expressions (1) and (2) regarding E are satisfied (when the steady-state pilot injection amount QPLT2 and the engine speed NE are in the area indicated by the dots in FIG. 2):
, Set the fuel injection mode to pilot injection mode,
If either one is not satisfied, the fuel injection mode is set to the main injection mode.

NElow ≦ NE ≦ NEhigh (1) QPLT2 ≧ QPLT2low (2) NElow, NEhigh: constant QPLT2low: constant For example, when the engine operation state is in the low-load low-speed region (engine speed NE) When the basic injection amount QMAINB is the predetermined values NE1 and QMAINB1 shown in FIG. 2), the pilot injection mode is selected as the fuel injection mode. Therefore, when the engine operation state is in the low-load low-speed range, the pilot injection is executed,
Combustion noise can be reduced.

On the other hand, when the engine operating state is in the high-load high-speed range (engine speed NE, basic injection amount QMA).
When INB is the predetermined value NE2 or QMAINB2 shown in the figure), the main injection mode is selected as the fuel injection mode. Therefore, when the engine operating state is in the high-load high-speed range, the pilot injection is stopped, the increase in the smoke concentration is suppressed, and the predetermined engine output is secured.

[Fuel injection timing control and fuel injection amount control]
Next, the control of the fuel injection timing and the injection amount performed based on the fuel injection mode selected as described above will be described.

FIGS. 3A and 3B are timing charts showing the manner of change of the on / off state of the solenoid valve 3 controlled by the ECU 50. FIG.
Shows the same change mode in the main injection mode.

[Pilot injection mode] When the pilot injection mode is selected as the fuel injection mode,
The ECU 50 executes both the main injection and the pilot injection prior to the main injection.

That is, as shown in FIG.
0 means that the current crank angle CA is equal to the pilot injection timing AP
When LT is reached, an ON signal (valve opening signal) is output to the solenoid valve 3. Therefore, the injector 2 is in the valve open state, and the pilot injection is started.

The pilot injection timing APLT is based on the compression top dead center (shown as “TDC” in the figure) of the cylinders # 1 to # 4 to which fuel is to be injected, and is a relative angle before the compression top dead center. Is defined as For example, if the pilot injection timing APLT is “30 ° CA” (CA: Crank
Angle), an ON signal is output to the solenoid valve 3 when the crank angle CA becomes 30 ° CA before the compression top dead center.

The pilot injection timing APLT
Is calculated based on the following equation (3). APLT = APLTM + AINT (3) APLTM: main injection timing AINT: pilot injection interval In the above equation (3), the main injection timing APLTM is a timing at which the main injection is started in the pilot injection mode. Similar to the APLT, it is defined as a relative angle before the compression top dead center with respect to the compression top dead center. The main injection timing APLTM, the engine speed NE and the basic injection amount Q are stored in the memory of the ECU 50.
Function data defining the relationship with MAINB is stored, and the ECU 50 calculates the main injection timing APLTM with reference to the function data.

In the above equation (3), the pilot injection interval AINT is a time interval (crank angle interval) between the start timing of the pilot injection and the start timing of the main injection.

As described above, when a predetermined period Tp has elapsed since the ON signal was output to the solenoid valve 3 and the injector 2 was opened, the ECU 50 sets the solenoid valve 3
Outputs an OFF signal (valve closing signal). Therefore,
The injector 2 is closed, and the pilot injection is stopped. The predetermined period Tp is determined based on the final pilot injection amount QPLT1 and the fuel pressure PC of the common rail 4. The final pilot injection amount QPLT1 is the amount of fuel injected into the combustion chamber during execution of pilot injection. After the pilot injection is performed, the fuel injection by the injector 2 is temporarily stopped for a predetermined period Toff (corresponding to the pilot injection interval AINT).

Next, the ECU 50 outputs an ON signal to the solenoid valve 3 when a predetermined period Toff has elapsed since the pilot injection was stopped and the current crank angle CA reaches the main injection timing APLTM. Therefore, the injector 2 is again opened, and the main injection is started.

When a predetermined period Tmp has elapsed since the start of the main injection, the ECU 50 sets the solenoid valve 3
Again outputs an OFF signal. Accordingly, the injector 2 is closed, and the main injection is stopped. The predetermined period Tmp is determined based on the final main injection amount QMAIN and the fuel pressure PC of the common rail 4. The final main injection amount QMAIN is the amount of fuel injected into the combustion chamber during execution of the main injection in the pilot injection mode. The ECU 50 calculates the final main injection amount QMAIN based on the following equation (4). calculate.

QMAIN = QMAINB−QPLT1 (4) [Main Injection Mode] On the other hand, when the main injection mode is selected as the fuel injection mode, ECU
50 executes only the main injection.

That is, as shown in FIG.
0 means that the current crank angle CA is equal to the main injection timing AMAI
When it becomes N, an ON signal is output to the solenoid valve 3. Therefore, the injector 2 is in the valve open state, and the main injection is started.

Here, the main injection timing AMAIN is the main injection timing APLT in the pilot injection mode.
Similar to M, it is defined as a relative angle before the compression top dead center with respect to the compression top dead center.

When a predetermined period Tmm has elapsed since the start of the main injection, the ECU 50 sets the solenoid valve 3
Output an OFF signal. Accordingly, the injector 2 is closed, and the main injection is stopped. The predetermined period Tmm is determined based on the final main injection amount QMAIN and the fuel pressure PC of the common rail 4, similarly to the predetermined period Tmp in the pilot injection mode. By the way, if the value of the predetermined period Tmm is the same total injection amount (the sum of the pilot injection amount and the main injection amount in the pilot injection mode) and the same injection pressure (fuel pressure), the predetermined time period in the pilot injection mode It is set longer than the period Tmp. In the main injection mode, the final pilot injection amount QPLT1 is "0".
This is because the final main injection amount QMAIN is set equal to the basic injection amount QMAINB, as is apparent from the above equation (4).

[Fuel Injection Pressure Control] Next, the fuel injection pressure,
That is, control related to the fuel pressure of the common rail 4 will be described.

The ECU 50 calculates the basic injection amount QMA
A reference target fuel pressure PCRB is calculated based on INB and the engine speed NE. This reference target fuel pressure PCRB is
This is a target pressure related to the fuel pressure of the common rail 4, and is set to be a pressure most suitable for the engine operating state in consideration of combustion noise, smoke concentration, and the like. In the memory of the ECU 50, a reference target fuel pressure PCRB as shown in FIG.
Function data that defines the relationship between the engine speed NE and the basic injection amount QMAINB is stored.
The reference target fuel pressure PCRB is calculated with reference to the function data. As shown in the figure, the reference target fuel pressure PCRB
Is calculated to be higher as the basic injection amount QMAINB and the engine speed NE are larger. This is because, at the time of high load or high rotation, it is necessary to increase the fuel injection pressure to promote the atomization of the injected fuel.

The ECU 50 calculates the final target fuel pressure PCR by correcting the calculated reference target fuel pressure PCRB. Then, the ECU 50 determines that the fuel pressure PC of the common rail 4 detected by the fuel pressure sensor 22 matches the final target fuel pressure PCR.
The open / close state of the PCV 10 is feedback-controlled to adjust the amount of fuel pumped from the supply pump 6.

Next, an example of the control mode of the fuel injection mode, the injection timing, the injection amount and the injection pressure by the fuel injection control device of the present embodiment will be described with reference to the timing chart shown in FIG. 5 and FIG. I do.

FIGS. 5A to 5D show changes of control flags used in various controls by the fuel injection control device of the present embodiment. That is, FIG.
9 shows how the pilot injection mode flag XPLT1 changes. This pilot injection mode flag XPLT1
Is a flag for determining whether or not the engine operation state is a state in which the fuel injection mode is set to the pilot injection mode, and both of the conditional expressions (1) and (2) are satisfied. Is sometimes set to “1”, and conditional expression (1),
"0" when either one of (2) is not satisfied
Is set to

FIG. 9B shows the manner in which the pilot injection execution flag XPLT2 changes. This pilot injection execution flag XPLT2 is a flag for determining whether or not pilot injection is actually being executed, and is set to "1" when the determination pilot injection amount QPLT3 is equal to or larger than a predetermined amount A (> 0). When the pilot injection amount for determination QPLT3 is smaller than the predetermined amount A, it is set to "0". Note that the predetermined amount A is set as the minimum amount of the pilot injection that can stably execute the pilot injection.

For example, even if the engine operation state is such that the fuel injection mode is to be in the pilot injection mode and the pilot injection mode flag XPLT1 is changed from "0" to "1", this pilot injection execution is performed. Flag X
When PLT2 is “0”, pilot injection is not performed. Conversely, pilot injection mode flag XPL
Even if T1 is changed from "1" to "0", if the pilot injection execution flag XPLT2 is set to "1", the pilot injection is continuously executed.

The pilot injection amount QPL for determination
T3 is a control value temporarily set for control in order to determine whether or not to execute pilot injection, and is also reflected in a final pilot injection amount QPLT1 described later. FIG. 7E shows the pilot injection amount Q for determination.
9 shows a variation of PLT3.

FIGS. 5C and 5D show how the main injection control permission flag XJPLT1 and the pilot injection control permission flag XJPLT2 change. The main injection control permission flag XJPLT1 indicates that the pilot injection mode flag XPLT1 has changed from "0" to "1".
Alternatively, it is set to “1” when switching from “1” to “0”, and the determination pilot injection amount QPLT3 is
It is set to “0” when it becomes equal to the constant pilot injection amount QPLT2 or when it becomes “0”.
Incidentally, the operation of the various control flags is performed by a “control flag operation routine” described later.

The pilot injection control permission flag XJ
The PLT 2 is set to “1” in the first control cycle after the main injection control permission flag XJPLT1 is set to “1” in the “control flag operation routine”, and is the same as the main injection control permission flag XJPLT1. , Is set to “0” when the pilot injection amount for determination QPLT3 becomes equal to the pilot injection amount for normal operation QPLT2 or when it becomes “0”.

In the fuel injection control device according to the present embodiment, control for changing the injection timing and injection pressure of the main injection (hereinafter referred to as “main injection control”) is performed in order to suppress the occurrence of torque shock accompanying the switching of the fuel injection mode. ")
Control for gradually changing the pilot injection amount and the pilot injection interval (hereinafter, referred to as “pilot injection control”) is executed. The main injection control permission flag XJPLT1 is a flag for determining the start timing of the main injection control.
Changes between "1" and "0", the main injection control is started. The pilot injection control permission flag XJPLT2 is a flag for determining the execution timing of the pilot injection control.
When T2 is set to "1", the pilot injection control is started.

FIG. 5F shows how the final pilot injection amount QPLT1 changes. The final pilot injection amount QPLT1 is always set to “0” when the pilot injection execution flag XPLT2 is “0”, and the determination pilot injection amount QPLT3 is set when the flag XPLT2 is set to “1”. Set to be equal.

FIG. 9G shows a variation of the injection timing correction amount APL1. This injection timing correction amount APL1
Is a correction amount for correcting the injection timing of the main injection to an advanced or retarded timing. Also, FIG.
FIG. 7 (i) shows how the pilot injection interval AINT changes, and FIG. 7 (i) shows how the fuel pressure correction amount PCRPL changes. The fuel pressure correction amount PCRPL is a correction amount for calculating the final target fuel pressure PCR by correcting the reference target fuel pressure PCRB (see FIG. 4) to a low pressure or a high pressure.

The control values QPLT3 and QPLT based on the main injection control and the pilot injection control described above will now be described.
A description will be given of how T1, APL1, AINT, and PCRPL change.

When both of the conditional expressions (1) and (2) are satisfied at the timing t1 by changing the engine speed NE and the steady-state pilot injection amount QPLT2, the pilot injection mode flag XPLT1 is set.
Is set to “1”, and the main injection control permission flag XJPLT1 is also set to “1”.

As described above, the main injection control permission flag XJ
When PLT1 is set to “1”, the main injection control is executed after timing t1. That is, the injection timing correction amount APL1 is gradually increased by a predetermined amount, and with the change of the injection timing correction amount APL1, the above-described main injection timing AMAIN is gradually changed to a timing on the advance side. Note that during the period from timing t1 to t4, the pilot injection is not executed because the final pilot injection amount QPLT1 is set to “0”.

When pilot injection control permission flag XJPLT2 is set to "1" at timing t2, pilot injection control is executed after timing t2. That is, the pilot injection interval AINT is increased by a predetermined amount, and the pilot injection amount QPLT3 for determination is also gradually increased by a predetermined amount.

FIG. 6A shows the main injection timing APLTM in the pilot injection mode and the main injection timing AMAIN in the main injection mode (hereinafter, when both are not particularly distinguished, they are simply referred to as “main injection timing”). 5 is a graph showing the relationship between the torque and the engine torque.

As described above, the main injection timing AMAIN
Is gradually changed to the timing on the advance side, so that the engine torque gradually increases from the state indicated by the point A1 to the state indicated by the point B1 in FIG. Become like Here, the main injection timing has a higher correlation with the engine torque as compared with the pilot injection interval AINT and the like, and has a large influence on the torque. Therefore, by changing this, the magnitude of the engine torque is surely increased. It is possible to control.

Therefore, according to the fuel injection control device of this embodiment, even if the engine torque difference in each state indicated by the points A1 and B1 is large, the main injection timing AMAI
By adjusting the change speed of N, that is, the increase speed of the injection timing correction amount APL1, the change speed of the engine torque is surely controlled so that the torque shock does not occur.
The engine torque in the main injection mode can be changed to the torque value at the time when the pilot injection is executed.

Also, as described above, the main injection timing AMAI
When N is changed, the reference main injection timing AMAINB
(See FIG. 6A.) Fuel injection is performed at a more advanced timing. This reference main injection timing AMAIN
B is set as a relative angle before the compression top dead center based on the compression top dead center as in the case of the main injection timing AMAIN, and is set in consideration of the engine torque, combustion noise, smoke exhaust concentration, and the like. It is set to be the most suitable time for the operating state.

Therefore, when the fuel injection is performed at a timing advanced from the reference main injection timing AMAINB thus set, the proportion of the premixed combustion in the combustion process increases, and the combustion pressure increases rapidly. , The combustion noise tends to increase.

In the fuel injection control device according to the present embodiment, in order to suppress such an increase in combustion noise, the timing t1 at which the main injection timing AMAIN is changed to the advanced timing.
In the period from to t4, the fuel pressure correction amount PCRPL is changed to the negative predetermined value P. Such a fuel pressure correction amount PCRP
By changing L, the final target fuel pressure PCR is lower than the reference target fuel pressure PCRB (= PCRB + P <PCR
B), and the fuel pressure PC of the common rail 4 decreases.

Therefore, according to the fuel injection control device of the present embodiment, the injection pressure of the fuel injected from the injector 2 is reduced, and the atomization of the injected fuel is suppressed. Is suppressed, and the main injection timing A
It is possible to suppress an increase in combustion noise caused by the MAIN being changed to the advanced timing.

Next, when the pilot injection amount QPLT3 for determination exceeds the predetermined amount A at timing t4, the pilot injection execution flag XPLT2 is set to "1". Further, by setting the final pilot injection amount QPLT1 equal to this determination pilot injection amount QPLT3, the pilot injection is executed.

After the timing t2, the first correction limit value APL1LMT1 is increased by a predetermined amount.
(> 0), the injection timing correction amount APL1 reaches the second correction limit value APL1LM at this timing t4.
It is changed to T2 (<0). The first correction limit value APL1LMT1 and the second correction limit value APL1LM
T2 will be described later.

The injection timing correction amount APL1
With the change of the main injection timing APLTM in the pilot injection mode, the reference main injection timing APLTMB
The timing is changed to a timing that is more retarded than (see FIG. 6A).
Similar to the main injection timing APLTM, the reference main injection timing APLTM is set based on the compression top dead center and set as a relative angle before the compression top dead center, and includes engine torque, combustion noise, smoke concentration, and the like. In consideration of the above, the timing is set to be the most suitable time for the engine operating state. FIG. 6A illustrates a case where the reference main injection timing AMAINB and the reference main injection timing APLTMB match.

Further, after the timing t4, the final pilot injection amount QPLT1 gradually increases with an increase in the determination pilot injection amount QPLT3. Then, at timing t6, the determination pilot injection amount QPLT3
Reaches the steady-state pilot injection amount QPLT2, after the same timing t6, the pilot injection amount for determination QPLT3
Is set equal to the steady-state pilot injection amount QPLT2, so that the final pilot injection amount QPLT1 is also set to be equal to the steady-state pilot injection amount QPLT2.

Further, the pilot injection interval AINT, which has been gradually increased by a predetermined amount after the timing t2, continues to increase even in the period after the timing t4. Then, at timing t6, the pilot injection interval A
When INT becomes equal to the steady-state pilot injection interval AINTB, the pilot injection interval A starts after the same timing t6.
INT is set to be equal to this steady-state pilot injection interval AINTB. This steady-state pilot injection interval AINTB is equal to the steady-state pilot injection amount QPLT.
As in 2, in consideration of combustion noise, smoke concentration, etc.,
That is, the amount is set so as to be the most suitable for the engine operating state at the time when a sufficient time has elapsed since the time when the fuel injection mode was switched from the main injection mode to the pilot injection mode.

As described above, during the period from the timing t4 to the timing t6, the main injection timing APLTM, the final pilot injection amount QPLT1, and the pilot injection interval AINT are changed, so that the engine torque is reduced as shown in FIG.
(A) changes from the state shown by the point B1 to the state shown by the point C1.

Here, in the fuel injection control device of this embodiment, each engine torque Tb, Tc in the state shown by each point B1, C1 in FIG. 6A, that is, the main injection timing AMAIN in the main injection mode. To the first correction limit value APL1LMT
The torque value (hereinafter referred to as “first transient torque value”) Tb when changed by one minute and the main injection timing APLTM in the pilot injection mode are set to a second correction limit value APL1.
The torque value when changed by LMT2 (hereinafter referred to as “second
) Tc and the following conditional expressions (5
-A) and (5-b) such that at least one of the correction limit values APL1LMT1, APL1LM is satisfied.
The size of T2 is set in advance.

Ta ≦ Tb = Tc ≦ Td (5-a) Td ≦ Tb = Tc ≦ Ta (5-b) Ta: Reference torque value in main injection mode Td: Reference torque in pilot injection mode In the above formulas (5-a) and (5-b), the main injection mode reference torque value Ta is obtained by using the main injection timing AMAIN in the main injection mode as the reference main injection timing AMAINB.
The pilot injection mode reference torque value Td is obtained by subtracting the main injection timing APLTM in the pilot injection mode from the reference main injection timing APLTMB.
Is the torque value when

As described above, each correction limit value APL1LMT
1, because APL1LMT2 is set,
Even if the fuel injection mode is switched from the main injection mode to the pilot injection mode during the period from the timing t4 to the timing t6, the change in the engine torque due to the switching hardly occurs.

Therefore, according to the fuel injection control device of the present embodiment, it is possible to reliably prevent the occurrence of torque shock when the fuel injection mode is switched from the main injection mode to the pilot injection mode.

In the fuel injection control device of this embodiment, when the fuel injection mode is switched from the main injection mode to the pilot injection mode (timing t4)
Instead of immediately changing the pilot injection interval AINT to the steady-state pilot injection interval AINTB, the pilot injection interval AINT is gradually increased from an interval shorter than the steady-state pilot injection interval AINTB to the identification constant pilot injection interval AINTB.

Therefore, according to the fuel injection control device of the present embodiment, the change in the engine combustion state accompanying the switching of the fuel injection mode can be made slow, and the occurrence of torque shock can be suppressed more reliably. Can be.

By the way, as described above, the pilot injection interval AINT is temporarily set shorter than the steady-state pilot injection interval AINTB (at timing t).
4 to t6) Although effective in suppressing torque shock, the main injection may be executed before the combustion pressure increased by the pilot injection has not yet decreased. It is feared that combustion noise will increase due to this.

In this regard, in the fuel injection control device of this embodiment, the final pilot injection amount QPLT1 is gradually increased until it becomes equal to the steady-state pilot injection amount QPLT2, so that the pilot injection interval AINT is relatively short ( At timings t4 to t6), the final pilot injection amount QPLT1 is set to be smaller than the steady-state pilot injection amount QPLT2. For this reason, the combustion pressure temporarily increased by the pilot injection starts to decrease earlier.

Therefore, according to the fuel injection control device of the present embodiment, the main injection is executed when the combustion pressure increased by the pilot injection is sufficiently reduced.
A sharp increase in combustion pressure can be suppressed to prevent an increase in combustion noise.

After the fuel injection mode is switched from the main injection mode to the pilot injection mode in this way, at timing t6, the main injection control permission flag XJPL
Both T1 and pilot injection control permission flag XJPLT2 are set to “0”. Then, in a period after the timing t6, the main injection control is executed again. That is, the injection timing correction amount APL1 is increased by the predetermined amount from the second correction limit value APL1LMT2 until it reaches “0” at timing t8. And
With the change of the injection timing correction amount APL1, the main injection timing APLTM is gradually changed to a timing on the advance side.

As described above, the main injection timing APLTM
Is changed, the engine torque becomes equal to the timing t.
During the period from 6 to t8, the state gradually increases from the state shown by the point C1 in FIG. 6A to the state shown by the point D1.

Here, according to the fuel injection control device of the present embodiment, even when the engine torque difference in each state indicated by points C1 and D1 in FIG. 6A is large, the main injection timing APLTM , Ie, the injection timing correction amount APL1
By adjusting the increase speed of the engine torque, the engine torque in the pilot injection mode can be increased to the steady-state torque value while reliably controlling the change speed of the engine torque so as not to generate a torque shock.

In the period from timing t4 to timing t8 when the injection timing correction amount APL1 takes a negative value, the main injection timing APLTM is changed to the reference main injection timing APLTMB (FIG. 6).
Since the timing is set on the more retarded side than (see (a)), the combustion speed becomes slow, and the smoke exhaust concentration tends to increase due to incomplete combustion of the fuel.

In this regard, in the fuel injection control device of the present embodiment, at the timing t4, the fuel pressure correction amount PCRPL
Is changed from the predetermined value P (<0) to a positive predetermined value R. During the period from timing t4 to timing t8 when the main injection timing APLTM is changed to a timing on the retard side from the reference main injection timing APLTMB, the fuel pressure correction amount PCR
PL is maintained at this predetermined value R. By changing the fuel pressure correction amount PCRPL, the final target fuel pressure PC
R is a pressure higher than the reference target fuel pressure PCRB (= PCR
B + R> PCRB), and the fuel pressure PC of the common rail 4 increases.

Therefore, according to the fuel injection control device of the present embodiment, since the fuel injection pressure is increased and the atomization of the injected fuel is promoted, incomplete combustion of the fuel is suppressed,
It is possible to prevent the above-mentioned increase in the exhaust gas density.

At timing t8, when the injection timing correction amount APL1 becomes equal to "0", the fuel pressure correction amount PCRPL is changed from the predetermined value R to "0". During the period from timing t8 to timing t9, the injection timing correction amount APL1 and the fuel pressure correction amount PCRP
L is kept at “0”. As a result, pilot injection in a steady state is performed.

Next, when one of the conditional expressions (1) and (2) is not satisfied at the timing t9 due to a change in the engine speed NE and the steady-state pilot injection amount QPLT2, the pilot injection is started. The mode flag XPLT1 is set to “0”, and the main injection control permission flag XJPLT1 is set to “1”.

As described above, the main injection control permission flag XJ
When PLT1 is set to “1”, the main injection control is executed after timing t9. That is, the injection timing correction amount APL1 is gradually reduced by a predetermined amount, and the main injection timing APL1 is changed with the change of the injection timing correction amount APL1.
TM is gradually changed to the retard side. Incidentally, during the period from timing t9 to t12, the final pilot injection amount QPLT1 is set to “0” or more,
The pilot injection is continuously performed.

When pilot injection control permission flag XJPLT2 is set to "1" at timing t10, pilot injection control is executed after timing t10. That is, the pilot injection interval AINT is reduced by the predetermined amount, and the pilot injection amount QPLT3 for determination is gradually reduced by the predetermined amount. Therefore, the pilot injection amount QPLT for such determination
3, the final pilot injection amount QPLT1 is gradually reduced, and the pilot injection interval AINT is reduced.
Is gradually reduced from the pilot injection interval AINTB during the steady state.

As described above, during the period from timing t9 to t12, the main injection timing APLTM, the final pilot injection amount QPLT1, and the pilot injection interval AINT are changed, so that the engine torque is reduced as shown in FIG.
In (a), it gradually decreases from the state indicated by the point D1 to the state indicated by the point C1. This timing t9 to t1
In the period 2, the points C1 and D1 of FIG.
Even when the engine torque difference in each state indicated by is large, by adjusting the changing speed of the main injection timing APLTM, that is, the increasing speed of the injection timing correction amount APL1,
After reliably controlling the rate of change of the engine torque so that torque shock does not occur, the engine torque in the pilot injection mode can be changed from the steady-state torque value to the torque value at which the pilot injection is stopped. it can.

In the period between timings t9 and t12, the fuel pressure correction amount PCRPL changes from "0" to a positive predetermined value Q.
(> 0). Therefore, the final target fuel pressure PCR
Is higher than the reference target fuel pressure PCRB (= PCRB
+ Q> PCRB), and the fuel pressure PC of the common rail 4 increases. As a result, similarly to the case during the period from the timing t4 to the timing t8, it is possible to prevent an increase in the smoke exhaust density due to the main injection timing APLTM being set to a timing that is more retarded than the reference main injection timing APLTMB. Can be.

Further, as described above, the timing t10
From time t12 to time t12, the final pilot injection amount QPLT1 is gradually reduced, and the pilot injection interval AINT is also changed to the steady-state pilot injection interval AINT.
It is changed from B to be gradually shorter. Accordingly, similar to the case during the period from the timing t4 to the timing t6 described above,
The change in the combustion state of the engine accompanying the switching of the fuel injection mode is made slower, so that the occurrence of torque shock can be suppressed more reliably, and the main injection is executed when the combustion pressure increased by the pilot injection is sufficiently reduced. Therefore, it is possible to suppress a rapid increase in the combustion pressure and prevent an increase in combustion noise.

Next, determination pilot injection amount QPLT3
Is reduced to fall below the predetermined amount A at the timing t12, the pilot injection execution flag XPL
T2 is set to “0”, the final pilot injection amount QPLT1 is changed to “0”, and the execution of pilot injection is stopped.

Further, at this timing t12, the injection timing correction amount APL1 becomes equal to the second correction limit value APL1LM.
From T2, it is changed to the first correction limit value APL1LMT1. With the change of the injection timing correction amount APL1, the main injection timing AMAIN in the main injection mode becomes
The timing is changed to a timing advanced from the reference main injection timing AMAINB (see FIG. 6A).

Thus, the final pilot injection amount QPLT
1 and the main injection timing AMAIN are changed, the engine torque changes from the state indicated by the point C1 in FIG. 6A to the state indicated by the point B1.

As described above, in the fuel injection control device according to the present embodiment, the first transient torque value Tb and the second transient torque value Tc are made to coincide with each other. Even if the mode is switched from the pilot injection mode to the main injection mode, almost no change in engine torque is caused by the switching. Therefore, the occurrence of torque shock can be reliably prevented.

Further, the pilot injection amount for determination QPLT3
Is reduced and becomes equal to “0” at the timing t14, the main injection control permission flag XJPLT1 and the pilot injection control permission flag XJPLT2 are both set to “0”. And this timing t14 ~
In the period of t16, the injection timing correction amount APL1 is reduced by a predetermined amount from the first correction limit value APL1LMT1 until it becomes equal to "0". By reducing the injection timing correction amount APL1, the main injection timing AMAIN is gradually changed to a timing on the retard side.

By changing the main injection timing AMAIN in this manner, the engine torque is reduced to the point B in FIG.
1 gradually decreases from the state shown by 1 to the state shown by point A1. In the period between the timings t14 and t16, the torque shock is generated by adjusting the changing speed of the main injection timing AMAIN, that is, the increasing speed of the injection timing correction amount APL1, as in the period between the timings t1 and t4. The engine torque in the main injection mode can be changed to a steady-state torque value after reliably controlling the changing speed of the engine torque so as not to cause it.

Then, after the timing t16, the injection timing correction amount APL1 is held at "0", so that the main injection timing AMAIN is set to be equal to the reference main injection timing AMAINB. As a result, steady-state main injection is performed.

During the period from timing t12 to t16, the main injection timing AMAIN is changed to the reference main injection timing A.
The fuel pressure correction amount PCRPL is changed from a predetermined value Q to a negative predetermined value S (<0) during this period. Therefore, at timing t1
Similarly to the period from t4 to t4, the fuel pressure PC of the common rail 4 decreases and the atomization of the injected fuel is suppressed, so that an increase in combustion noise can be prevented.

Hereinafter, an example of a control procedure for realizing the above fuel injection control will be described in detail with reference to the flowcharts shown in FIGS. 7 to 13 and the timing chart of FIG. In the following description, corresponding timings in the above timing chart are shown in parentheses [].

FIGS. 7 and 8 are flowcharts showing the respective processes of the "control flag operation routine". This routine includes various control flags XPLT1, XPLT2, XJPLT used in each processing routine described later.
1, for performing operations of XJPLT2, EC
By U50, every predetermined crank angle (for example, 180 ° CA
This is executed as an interrupt process for each).

When the processing shifts to this routine, first,
In step 100, the ECU 50 determines whether or not the current engine operation state is a state where the fuel injection mode should be the pilot injection mode. This determination process is performed based on whether each value of the engine speed NE and the steady-state pilot injection amount QPLT2 satisfies both of the conditional expressions (1) and (2) described above.

If the determination in step 100 is affirmative [timing t1 to t8], the ECU 50 sequentially executes the processing of steps 102 to 116. The processes in steps 102 to 116 are executed when the fuel injection mode is switched from the main injection mode to the pilot injection mode.

First, in step 102, the ECU 50 sets the pilot injection mode flag XPLT1 to "1". Next, in step 104, the ECU 50 determines whether or not the pilot injection execution flag XPLT2 is set to “0”. If a negative determination is made here [timing t5 to t8], the ECU 50 shifts the processing to step 116 shown in FIG. Step 1
04 [Timing t1 to t
4], the ECU 50 shifts the processing to Step 106.

At step 106, the ECU 50
It is determined whether main injection control permission flag XJPLT1 is set to “0”. If the determination is affirmative here [timing t1], the ECU 50 proceeds to step 110.
, The main injection control permission flag XJPLT1 is changed from “0” to “1”. On the other hand, when a negative determination is made in step 106 [timing t2 to t4],
In step 108, the ECU 50 sets the pilot injection control permission flag XJPLT2 to “1”.

After executing the processing in steps 108 and 110, the ECU 50 compares the pilot injection amount QPLT3 for determination with the predetermined amount A in step 112 shown in FIG. Here, the pilot injection amount for determination QP
If it is determined that LT3 is less than the predetermined amount A [timing t1 to t3], the ECU 50 proceeds to step 11
Move to 6. On the other hand, if it is determined in step 112 that the determination pilot injection amount QPLT3 is equal to or larger than the predetermined amount A [timing t4], the ECU 50 determines in step 114 that the pilot injection execution flag XPLT2
Is set to “1”, and the process proceeds to step 116.

At step 116, the ECU 50
The determination pilot injection amount QPLT3 is compared with the steady-state pilot injection amount QPLT2. When the pilot injection amount QPLT3 for determination is equal to the pilot injection amount QPLT in the steady state,
When it is determined that it is 2 or more [timing t6 to t
8] The ECU 50 sets the main injection control permission flag XJPLT1 to “0” in step 140,
Further, in step 142, the pilot injection control permission flag XJPLT2 is set to "0".

After executing the processing of step 142 or in step 116, the pilot injection quantity Q for determination
If it is determined that PLT3 is smaller than the steady-state pilot injection amount QPLT2 [timing t1 to t5], the ECU
50 temporarily ends the processing of this routine.

On the other hand, if it is determined in step 100 that the current engine operating state is not the state in which the fuel injection mode should be the pilot injection mode [timing t9 to t16], the ECU 50 proceeds to step 122. To 136 are sequentially executed. The processes in steps 122 to 136 are executed when the fuel injection mode is switched from the pilot injection mode to the main injection mode.

That is, in step 122, the ECU 50 sets the pilot injection mode flag XPLT1 to "0".
Set to. Then, in step 124, the ECU 50 sets the pilot injection execution flag XPLT2 to “1”.
It is determined whether or not is set. If an affirmative determination is made here [timing t9 to t12], the ECU 50
The process moves to step 126. Step 12
No. 4 [Timing t13 to 1
6], and the ECU 50 executes the processing in step 136 shown in FIG.
Move to

At step 126, the ECU 50
It is determined whether main injection control permission flag XJPLT1 is set to “0”. If an affirmative determination is made [timing t9], the ECU 50 proceeds to step 130.
, The main injection control permission flag XJPLT1 is changed from “0” to “1”. On the other hand, when a negative determination is made in step 126 [timing t10 to t1
2] In step 128, the ECU 50 sets the pilot injection control permission flag XJPLT2 to “1”.

After executing the processing of steps 128 and 130, the ECU 50 determines in step 132 shown in FIG.
Compare with Here, the determination pilot injection amount QPLT
If it is determined that 3 is equal to or more than the predetermined amount A [timing t9 to t11], the ECU 50 proceeds to step 136.
Move to On the other hand, if it is determined in step 132 that the determination pilot injection amount QPLT3 is less than the predetermined amount A [timings t12 to t16], the ECU 50 determines
In step 134, the pilot injection execution flag XP
After setting LT2 to “0”, the process proceeds to step 136.

Then, at step 136, the ECU
50 compares the pilot injection amount QPLT3 for determination with “0”. Here, the determination pilot injection amount QPLT3
Is greater than “0” [timing t9
-T13], the ECU 50 once ends the processing of this routine. On the other hand, if it is determined in step 136 that the determination pilot injection amount QPLT3 is equal to or less than “0” [timing t14 to t16], the ECU 50 executes the processing of steps 140 and 142 described above, and then executes this routine. The process ends once.

Based on the processing of this routine described above, various control flags XPLT1, XPLT2, XJP
LT1 and XJPLT2 are set to values corresponding to the engine operating state.

Next, each process of the "injection amount calculation routine" will be described with reference to the flowchart shown in FIG.
This routine is for calculating the fuel injection amounts of the pilot injection and the main injection, and is executed by the ECU 50 as the above-mentioned "control flag operation routine" as an interruption process for each crank angle (for example, every 180 ° CA). Is done.

When the processing shifts to this routine, first,
In step 200, the ECU 50 determines whether or not the pilot injection mode flag XPLT1 is set to “1”. If a positive determination is made here, the ECU 5
If “0”, the process proceeds to step 202. Step 20
In 2, the ECU 50 determines whether the main injection control permission flag XJPLT1 is set to “1”. If an affirmative determination is made here, the ECU 50 shifts the processing to step 204 and further determines whether or not the pilot injection control permission flag XJPLT2 is “0”.

If an affirmative determination is made in step 204, the ECU 50 sets the determination pilot injection amount QPLT3 equal to the predetermined amount B in step 206 [timing t1]. This predetermined amount B is an initial value for the determination pilot injection amount QPLT3. FIG.
The timing chart shown in FIG. 3 shows an example of a control mode when the predetermined amount B is set to “0”.

On the other hand, if a negative determination is made in step 204, the ECU 50 adds a predetermined amount C (> 0) to the current determination pilot injection amount QPLT3 in step 208, Value (= QP
LT3 + C) with the new pilot injection quantity QPL for determination.
Set as T3. By repeatedly executing the processing of step 208, the timing t2 shown in FIG.
In the period from to t6, the pilot injection amount QP
LT3 (see FIG. 9E) gradually increases.

After executing the processing of steps 206 and 208, the ECU 50 compares the pilot injection amount QPLT3 for determination with the pilot injection amount QPLT2 at steady state in step 210. If it is determined that the determination pilot injection amount QPLT3 is equal to or larger than the steady-state pilot injection amount QPLT2, the ECU 50 proceeds to step 2
At 30, the determination pilot injection amount QPLT3 is set equal to the steady-state pilot injection amount QPLT2. Also, when a negative determination is made in step 202 described above, the ECU 50 executes the process of step 230 in the same manner.

By executing the processing of steps 202, 210, and 230, the timing t shown in FIG.
In the period from 6 to t9, the pilot injection amount for determination QP
LT3 (see (e) in the figure) is kept equal to the steady-state pilot injection amount QPLT2 (dashed line in (e) in the figure).

On the other hand, if a negative determination is made in step 200 described above, the ECU 50 determines in step 220 whether the main injection control permission flag XJPLT1 is set to "1". If an affirmative determination is made here, the ECU 50 further proceeds to step 222.
It is determined whether pilot injection control permission flag XJPLT2 is set to "1". If a negative determination is made here [timing t9], the ECU 50 executes the process of step 230 described above.

On the other hand, if the determination in step 222 is affirmative, in step 224, the ECU 50 subtracts the predetermined amount D (> 0) from the current pilot injection amount QPLT3 for determination, and the value after the subtraction (= QPLT3
-D) is set as a new determination pilot injection amount QPLT3. By repeatedly executing the process of step 224, timings t10 to t1 shown in FIG.
In the period of 3, the pilot injection amount for determination QPLT3
(See FIG. 7E) gradually decreases.

Then, in step 226, the ECU 50 compares the determination pilot injection amount QPLT3 with "0". Here, the determination pilot injection amount QPLT3
Is determined to be less than “0”, the ECU 50
In step 228, the determination pilot injection amount QP
Set LT3 to “0”. Also, as described in step 2
20 is negative [timing t14-
t16], the ECU 50 also determines in step 228
Execute the processing of

By executing the processing of steps 220, 226, and 228, the timing t shown in FIG.
During the period from 14 to t16, the determination pilot injection amount QPLT3 (see FIG. 9E) is maintained at "0".

After executing the processing of steps 228 and 230, the ECU 50 shifts the processing to step 232. Also, when it is determined in step 210 that the determination pilot injection amount QPLT3 is less than the steady-state pilot injection amount QPLT2, and when it is determined in step 226 that the determination pilot injection amount QPLT3 is “0” or more, The ECU 50 proceeds to step 23.
Move to 2.

At step 232, the ECU 50
The determination pilot injection amount QPLT3 is compared with the predetermined amount A. Here, if it is determined that the determination pilot injection amount QPLT3 is the predetermined amount A, the ECU 50 proceeds to step 234, where the final pilot injection amount QPLT1 is determined.
Is set to be equal to the determination pilot injection amount QPLT3 (≧ A> 0). Thus, the final pilot injection amount QPL
By setting T1, the timing t shown in FIG.
In the period from 4 to t12, the pilot injection is performed.

On the other hand, if it is determined in step 232 that the pilot injection amount for determination QPLT3 is smaller than the predetermined amount A, the ECU 50 sets in step 236 the final pilot injection amount QPLT1 to “0”. By setting the final pilot injection amount QPLT1 in this manner, the timings t1 to t4 shown in FIG.
During the period from t12 to t16, the execution of the pilot injection is stopped.

The ECU 50 executes the above steps 234, 2
After performing the process of step 36, in step 238, the final main injection amount QMAIN is
Is calculated. Therefore, when the final main injection amount QMAIN has been calculated through the processing of step 234, the final main injection amount QMAIN becomes the basic injection amount QMAINB.
Is subtracted from the final pilot injection amount QPLT1. On the other hand, when the final main injection amount QMAIN is calculated through the processing of step 236, the final main injection amount QMAIN is changed to the basic injection amount QMAINB.
Is calculated as a value equal to. After executing the process of step 238, the ECU 50 temporarily ends the process of this routine.

As described above, by the processing of this routine, the pilot injection amount QPLT3 for determination, the final main injection amount QMAIN, and the final pilot injection amount QPLT1 are determined.
Are calculated respectively.

Next, each process of the "pilot injection interval calculation routine" will be described with reference to the flowchart shown in FIG. This routine is for calculating the pilot injection interval AINT, and is executed by the ECU 50 as an interrupt process at the same crank angle (for example, at every 180 ° CA) as the “control flag operation routine”.

When the processing shifts to this routine, first,
In step 300, the ECU 50 determines whether or not the pilot injection mode flag XPLT1 is set to “1”. If a positive determination is made here, the ECU 5
If it is 0, the process proceeds to step 302. Step 30
In 2, the ECU 50 determines whether the main injection control permission flag XJPLT1 is set to “1”. If an affirmative determination is made here, the ECU 50 shifts the processing to step 304 and further determines whether or not the pilot injection control permission flag XJPLT2 is “0”.

If the determination in step 304 is affirmative, the ECU 50 sets the pilot injection interval AINT equal to the predetermined amount E in step 306 [timing t1]. This predetermined amount E is equal to the pilot injection interval AI.
This is the initial value for NT. The timing chart shown in FIG. 5 shows an example of the control mode when the predetermined amount E is set to “0”.

On the other hand, if a negative determination is made in step 304, the ECU 50 adds a predetermined amount F (> 0) to the current pilot injection interval AINT in step 308, and the value after the addition ( AINT +
F) is set as a new pilot injection interval AINT.

Therefore, by repeatedly executing the processing of step 308, the timing t2 shown in FIG.
Pilot injection interval AINT in the period
(See FIG. 7H) gradually increases.

After executing the processes of steps 306 and 308, the ECU 50 determines in step 310 that the pilot injection interval AINT and the steady-state pilot injection interval A
Compare with INTB. Where the pilot injection interval AI
If it is determined that NT is equal to or longer than the steady-state pilot injection interval AINTB, the ECU 50 sets the pilot injection interval AINT to be equal to the steady-state pilot injection interval AINTB in step 330. Similarly, when a negative determination is made in step 302 described above,
The ECU 50 executes the process of step 330.

By executing the processing of steps 302, 310, and 330, the timing t shown in FIG.
In the period from 6 to t9, the pilot injection interval AINT
(See (h) in the figure) shows the pilot injection interval AI in the steady state.
NTB (the dashed line in FIG. 7H) is maintained.

On the other hand, if a negative determination is made in step 300 described above, the ECU 50 proceeds to step 3
At 20, the main injection control permission flag XJPLT1
Is set to “1”. If an affirmative determination is made here, the ECU 50 further proceeds to step 322 to further control the pilot injection control permission flag XJPLT2.
Is set to “1”. If a negative determination is made here, the ECU 50 proceeds to step 33 described above.
0 is executed.

On the other hand, if the determination in step 322 is affirmative, the ECU 50 subtracts a predetermined amount G (> 0) from the current pilot injection interval AINT in step 324, and newly adds the value (AINT-G) after the subtraction. Is set as the pilot injection interval AINT.

Therefore, by repeatedly executing the process of step 324, the timing t9 shown in FIG.
Pilot injection interval AINT during the period from
(See FIG. 7H) gradually decreases.

In step 326, the ECU 50 compares the pilot injection interval AINT with "0". If it is determined that the pilot injection interval AINT is less than “0”, the ECU 50 proceeds to step 32.
At 8, the pilot injection interval AINT is set to “0”. Similarly, when a negative determination is made in step 320 described above, the ECU 50 returns to step 328
Execute the processing of

By executing the processing of steps 320, 326, and 328, the timing t shown in FIG.
In the period from 14 to t16, the pilot injection interval AI
NT will be held at "0".

After executing the processing of steps 328 and 330, the ECU 50 once ends the processing of this routine. Also, if it is determined in step 310 that pilot injection interval AINT is less than steady-state pilot injection interval AINTB, or if it is determined in step 326 that pilot injection interval AINT is equal to or greater than "0", ECU 50 The processing of this routine is once ended.

As described above, the pilot injection interval AINT is calculated by each process of this routine. Next, each process of the “injection timing calculation routine” will be described with reference to FIG.
And a flowchart shown in FIG.
This routine is for calculating the injection timings of the pilot injection and the main injection, and is executed by the ECU 50 as an interruption process at the same crank angle (for example, at every 180 ° CA) as the “control flag operation routine”. You.

When the processing shifts to this routine, first,
In step 400, the ECU 50 determines whether or not the pilot injection mode flag XPLT1 is set to "1". If a positive determination is made here, the ECU 5
If it is 0, the process proceeds to step 402. Step 40
In 2, the ECU 50 determines whether the main injection control permission flag XJPLT1 is set to “1”. If an affirmative determination is made here, the ECU 50 shifts the processing to step 404 and further determines whether or not the pilot injection control permission flag XJPLT2 is “0”.

If the determination in step 404 is affirmative, the ECU 50 sets the injection timing correction amount APL1 equal to the predetermined amount H in step 406. On the other hand, if a negative determination is made in step 404, the ECU 50
In step 408, the current injection timing correction amount A
A predetermined amount J is added to PL1 and the value (A
PL1 + J) is set as a new injection timing correction amount APL1.

After executing the processing in steps 406 and 408, the ECU 50 determines in step 410 that the absolute value | APL1 | of the injection timing correction amount APL1 and the absolute value | APL1LMT1 of the first correction limit value APL1LMT1.
|.

Here, the first correction limit value APL1LMT
1 is calculated based on the engine speed NE and the basic injection amount QMAINB, and is set so as to satisfy at least one of the conditional expressions (5-a) and (5-b) as described above. ing. The memory of the ECU 50 stores the first correction limit value APL1LMT1 and the engine speed NE.
And the function data defining the relationship with the basic injection amount QMAINB. Further, the memory of the ECU 50 further stores function data that defines the relationship between the predetermined amounts H and J and the engine speed NE and the basic injection amount QMAINB. The ECU 50 calculates the first correction limit value APL1LMT1 and the predetermined amounts H and J, respectively, by referring to the function data when executing the processes of the steps 406, 408, 410 and the like.

For example, as shown in FIG. 6A, when the reference torque value Ta in the main injection mode is smaller than the reference torque value Td in the pilot injection mode, the first correction limit value APL1LMT1 becomes positive. Value (APL1LMT
1> 0). When the first correction limit value APL1LMT1 is calculated as a positive value, the predetermined amounts H and J are also positive values (H> 0, H> 0).
J> 0).

As described above, the first correction limit value APL1LM
When T1 is calculated as a positive value, the injection timing correction amount A during the period from timing t1 to t4 shown in FIG.
PL1 (see (g) in the figure) is the first correction limit value APL1
It gradually increases to LMT1.

On the other hand, for example, as shown in FIG. 6B, the situation where the reference torque value Ta in the main injection mode becomes larger than the reference torque value Td in the pilot injection mode does not depend on the engine operating state. (The engine speed NE and the basic injection amount QMAINB). In such a case, the first correction limit value APL1LMT1 is calculated as a negative value (APL1LMT1 <0). When the first correction limit value APL1LMT1 is calculated as a negative value, the predetermined amounts H and J are similarly calculated as follows.
It is calculated as a negative value (H <0, J <0).

As described above, the first correction limit value APL1LM
When T1 is calculated as a negative value, the injection timing correction amount A during the period from timing t1 to timing t4 shown in FIG.
PL1 is different from the change mode shown in FIG. 11G, and the first correction limit value APL1LMT1 set as a negative value
Until it gradually decreases. Further, as described above, the injection timing correction amount APL1 is equal to the first correction limit value APL.
Along with being gradually changed to 1LMT1, the main injection timing AMAIN is also gradually changed. That is, when the first correction limit value APL1LMT1 is calculated as a positive value, the main injection timing AMAIN is gradually changed to a timing on the advance side [timing t1 to t4], and the first correction limit value APL1LMT1 is set. Is calculated as a negative value, the main injection timing AMAIN is gradually changed to a timing on the retard side. Further, each of the predetermined amounts H,
J is the absolute value | H |, | J | of the main injection timing AMAIN so that a torque shock does not occur with the change of the main injection timing AMAIN.
Is set small enough.

In step 410, the absolute value | APL1 | of the injection timing correction amount APL1 is changed to the absolute value | APL1LMT1 | of the first correction limit value APL1LMT1.
If it is determined that this is the case [timing t3], EC
U50 determines the injection timing correction amount A in step 412.
After setting PL1 equal to the first correction limit value APL1LMT1, the process proceeds to step 414. On the other hand, if it is determined in step 410 that the absolute value | APL1 | of the injection timing correction amount APL1 is less than the absolute value | APL1LMT1 | of the first correction limit value APL1LMT1, the ECU 50 similarly proceeds to step 414. Transition.

At step 414, the ECU 50
It is determined whether pilot injection execution flag XPLT2 is set to “1”. If a negative determination is made here, the ECU 50 proceeds to step 460 shown in FIG.
Move to On the other hand, if an affirmative determination is made in step 414, the ECU 50 sets the injection timing correction amount APL1 to the second correction limit value APL1LM in step 416.
Set equal to T2.

By executing the processes of steps 414 and 416, at timing t4 shown in FIG. 5, the injection timing correction amount APL1 becomes equal to the first correction limit value AP.
The value is changed from L1LMT1 to the second correction limit value APL1LMT2, and is kept equal to the second correction limit value APL1LMT2 also at the timing t5. After executing the processing of step 416, the ECU 50 executes the processing in FIG.
The process moves to step 460 shown in FIG.

On the other hand, if a negative determination is made in step 402 described above, the ECU 50 shifts the processing to step 440 shown in FIG. At step 440,
The ECU 50 adds the predetermined amount M to the current injection timing correction amount APL1, and sets the value (APL1 + M) after the addition as a new injection timing correction amount APL1.

This predetermined amount M is calculated based on the engine speed NE and the basic injection amount QMAINB, as in the case of the predetermined amounts H and J. In the memory of the ECU 50,
The predetermined amount M, the engine speed NE and the basic injection amount QMA
Function data defining the relationship with INB is stored, and the ECU 50 refers to the function data to determine the predetermined amount M
Is calculated. When the first correction limit value APL1LMT1 is calculated as a positive value, the predetermined amount M is calculated as a positive value (M> 0), similarly to the predetermined amounts H and J. When the correction limit value APL1LMT1 is calculated as a negative value, a negative value (M <0) is also used.
Is calculated as

For example, when the predetermined amount M is set to a positive value, the processing of step 440 is repeatedly executed, so that the injection timing correction amount during the period from timing t6 to timing t8 shown in FIG. APL1 (see (g) in the figure) gradually increases, and when the predetermined amount M is set to a negative value, the injection timing correction amount APL1
(See FIG. 7G) gradually decreases.

With the change in the injection timing correction amount APL1, the main injection timing APLTM is also gradually changed to a timing advanced or retarded with respect to the reference main injection timing APLTMB. The absolute value | M | is set to be sufficiently small so that the torque shock accompanying the change of the main injection timing APLTM does not occur.

Next, in step 442, the ECU 50 determines whether or not the sign of the injection timing correction amount APL1 has changed, that is, whether the injection timing correction amount APL1 which has been “0” or a negative value in the previous control cycle. Whether or not the value has changed to a positive value in the current control cycle, or conversely, the injection timing correction amount APL1 which was “0” or a positive value in the previous control cycle
Is changed to a negative value in the current control cycle. If an affirmative determination is made here, the ECU 50 sets the injection timing correction amount APL1 to “0” in step 444. After executing the process of step 444, or when a negative determination is made in step 442, the ECU 50 shifts the process to step 460.

By executing the processing of steps 442 and 444 described above, after the timing t8 shown in FIG.
The injection timing correction amount APL1 is held at "0", and the main injection corresponding to the steady state is executed.

On the other hand, step 40 shown in FIG.
If a negative determination is made at 0, the ECU 50 shifts the processing to step 420. In step 420,
The ECU 50 sets a main injection control permission flag XJPLT1
Is set to “1”. If an affirmative determination is made here, the ECU 50 proceeds to step 42
2 and the pilot injection control permission flag XJ
It is determined whether PLT2 is set to "1".

If a negative determination is made in step 422, the ECU 50 sets the injection timing correction amount APL1 equal to the predetermined amount L in step 426. On the other hand, if the determination in step 422 is affirmative, the ECU 50
Is the current injection timing correction amount AP in step 424
A predetermined amount K is subtracted from L1 and the value after the subtraction (AP
L1−K) is set as a new injection timing correction amount APL1.

After executing the processing of steps 424 and 426, the ECU 50 determines in step 428 that the absolute value | APL1 |
Absolute value | APL1 of second correction limit value APL1LMT2
LMT2 |.

Here, the second correction limit value APL1LMT
2 is calculated based on the engine speed NE and the basic injection amount QMAINB, and is set so as to satisfy at least one of the conditional expressions (5-a) and (5-b) as described above. ing. The memory of the ECU 50 stores the second correction limit value APL1LMT2 and the engine speed NE.
And the function data defining the relationship with the basic injection amount QMAINB. Further, the memory of the ECU 50 further stores function data defining the relationship between the predetermined amounts L and K, the engine speed NE and the basic injection amount QMAINB, respectively. The ECU 50 calculates the second correction limit value APL1LMT2 and the predetermined amounts L and K, respectively, by referring to the function data when executing the processing of steps 424, 426, and 428.

For example, as shown in FIG. 6A, when the reference torque value Ta in the main injection mode is smaller than the reference torque value Td in the pilot injection mode, the second correction limit value APL1LMT2 becomes a negative value. (APL1LMT2 <
0). When the second correction limit value APL1LMT2 is calculated as a negative value, the predetermined amounts L and K are calculated as positive values (L> 0, K> 0).

As described above, the second correction limit value APL1LM
When T2 is calculated as a negative value and each of the predetermined amounts L and K is calculated as a positive value, the injection timing correction amount APL1 (see (g) in FIG. 5) during the period from timing t9 to t12 shown in FIG.
Gradually decreases from “0” to the second correction limit value APL1LMT2.

On the other hand, for example, as shown in FIG. 6B, when the reference torque value Ta in the main injection mode is larger than the reference torque value Td in the pilot injection mode, the second correction limit value APL1LMT2 Is a positive value (AP
L1LMT2> 0). When the second correction limit value APL1LMT2 is calculated as a positive value, the predetermined amounts L and K are negative values (L <L).
0, K <0).

As described above, the second correction limit value APL1LM
When T2 is calculated as a positive value and each of the predetermined amounts L and K is calculated as a negative value, the injection timing correction amount APL1 changes during the period from timing t9 to t12 shown in FIG. Unlike the mode, the second correction limit value A is set from “0”
It gradually increases to PL1LMT2.

As described above, as the injection timing correction amount APL1 is gradually changed to the second correction limit value APL1LMT2, the main injection timing APLTM is also gradually changed. That is, when the second correction limit value APL1LMT2 is calculated as a negative value, the main injection timing AP
The LTM is gradually changed to a timing on the retard side [timing t
9 to t12], when the second correction limit value APL1LMT2 is calculated as a positive value, the main injection timing A
The PLTM is gradually changed to the advanced timing. Each of the predetermined amounts L and K is determined by the main injection timing AP.
The absolute values | L | and | K | are set to be sufficiently small so that the torque shock does not occur due to the change of the LTM.

The second correction limit value APL1LM
T2 and the aforementioned first correction limit value APL1LMT1
Can be arbitrarily set if at least one of the conditional expressions (5-a) and (5-b) is satisfied with respect to the first transient torque value Tb and the second transient torque value Tc. it can. For example, as shown in FIG.
Each of the correction limit values A is set so that each of the transient torque values Tb and Tc is substantially an intermediate value between the reference torque value Ta in the main injection mode and the reference torque value Td in the pilot injection mode.
In addition to setting PL1LMT1 and APL1LMT2, each of the transient torque values Tb and Tc is set to a value closer to the reference torque value Ta in the main injection mode or to a value closer to the reference torque value Td in the pilot injection mode. Each of the correction limit values APL1LMT1, APL1L
It is also possible to set MT2.

However, these correction limit values APL
If the absolute values of 1LMT1 and APL1LMT2 are set too large, the main injection is performed at a timing that is significantly different from the reference main injection timings AMAINB and APLTMB, that is, the injection timings based on the engine operating state, in each injection mode. Therefore, combustion noise and smoke concentration may be increased. For this reason, in the fuel injection control device of the present embodiment, the above-described correction limit values APL1LMT1 and APL1LMT2 are set so that such an increase in the combustion noise and smoke concentration is suppressed within an allowable range.

As described above, as the injection timing correction amount APL1 is gradually changed to the second correction limit value APL1LMT2, the main injection timing APLTM is also gradually changed. That is, when the second correction limit value APL1LMT2 is calculated as a negative value, the main injection timing AM
AIN is gradually changed to a timing on the retard side, and when the second correction limit value APL1LMT2 is calculated as a positive value, on the contrary, the main injection timing AMAIN is gradually changed to a timing on the advance side. Become like

If it is determined in step 428 that the absolute value | APL1 | of the injection timing correction amount APL1 is equal to or smaller than the absolute value | APL1LMT2 | of the second correction limit value APL1LMT2 [timing t11], the ECU proceeds to step 428.
50 is the injection timing correction amount AP in step 430.
After setting L1 equal to the second correction limit value APL1LMT2, the process proceeds to step 432. On the other hand, if it is determined in step 428 that the injection timing correction amount APL1 is larger than the second correction limit value APL1LMT2, the ECU 50 similarly shifts the processing to step 432.

In step 432, the ECU 50
It is determined whether pilot injection execution flag XPLT2 is set to “0”. If a negative determination is made here, the ECU 50 proceeds to step 460 shown in FIG.
Move to On the other hand, when an affirmative determination is made in step 432 [timing t12], in step 434, the ECU 50 sets the injection timing correction amount APL1 to be equal to the first correction limit value APL1LMT1, and then proceeds to step 460.

On the other hand, if a negative determination is made in step 420 described above, ECU 50 shifts the processing to step 450 shown in FIG. At step 450,
The ECU 50 subtracts the predetermined amount N from the current injection timing correction amount APL1, and sets the subtracted value (= APL1-N) as a new injection timing correction amount APL1.

The predetermined amount N is calculated based on the engine speed NE and the basic injection amount QMAINB, similarly to the predetermined amounts L and K. In the memory of the ECU 50,
The predetermined amount N, the engine speed NE and the basic injection amount QMA
Function data defining the relationship with INB is stored, and the ECU 50 refers to this function data to determine the predetermined amount N
Is calculated. When the second correction limit value APL1LMT2 is calculated as a negative value, the predetermined amount N is calculated as a positive value, similarly to the predetermined amounts L and K.
When the second correction limit value APL1LMT2 is calculated as a positive value, it is calculated as a negative value.

For example, when the predetermined amount N is set to a positive value, the processing of step 450 is repeatedly executed, so that the timings t14 to t1 shown in FIG.
In the period of 6, the injection timing correction amount APL1 (see (g) in the figure) gradually decreases, and the predetermined amount N
Is set to a negative value, the injection timing correction amount A
PL1 (see FIG. 9G) gradually increases.

Then, with the change of the injection timing correction amount APL1, the main injection timing AMAIN is also gradually changed to a timing advanced or retarded with respect to the reference main injection timing AMAINB. The absolute value | N | is set to a sufficiently small value so that torque shock accompanying the change of the main injection timing AMAIN does not occur.

Next, at step 452, the ECU 50 determines whether or not the sign of the injection timing correction amount APL1 has changed, similarly to step 442 described above. If the determination is affirmative here [timing t16], the ECU 50
In step 454, the injection timing correction amount APL1
Is set to “0”. After executing the process of step 454, or if a negative determination is made in step 452, the ECU 50 shifts the process to step 460.

By executing the processing of each of the above-described steps 452 and 454, the injection timing correction amount APL1 is held at "0" after the timing t16 shown in FIG. 5, and the main injection corresponding to the steady state is performed. Will be executed.

In step 460, the ECU 50 sets
It is determined whether or not the pilot injection execution flag XPLT2 is set to "1". If the determination is affirmative, the ECU 50 proceeds to step 462 where the main injection timing APLTM (FIG.
(See (a)).

APLTM = APLTMB + APL1 (6) Next, in step 466, the ECU 50 determines in step 466 the pilot injection timing AP based on the aforementioned equation (3).
Calculate LT.

[0212] On the other hand, if a negative determination is made in step 460, the ECU 50 proceeds to step 464.
The main injection timing AMAI described above based on the following equation (7)
N (see FIG. 3B) is calculated.

AMAIN = AMAINB + APL1 (7) The memory of the ECU 50 stores the reference main injection timing AMAI.
NB, reference main injection timing APLTMB, and function data defining the relationship between the engine speed NE and the basic injection amount QMAINB are stored, respectively. When the ECU 50 executes the processing of steps 462 and 464, The reference main injection timing AMAINB and the reference main injection timing APLTMB are calculated with reference to the respective function data.

After executing the processing of step 464 or step 466, the ECU 50 once ends the processing of this routine. As described above, the main injection timing AMAI in the main injection mode is obtained by each processing of this routine.
N, pilot injection timing AP in pilot injection mode
LT and main injection timing APLTM are calculated respectively.

Next, each process of the "target fuel pressure calculation routine" will be described with reference to the flowchart shown in FIG. This routine is for calculating a target fuel pressure related to the fuel pressure PC of the common rail 4.
0 is executed as an interrupt process at the same crank angle (for example, at every 180 ° CA) as in the “control flag operation routine”.

When the processing shifts to this routine, first,
In step 500, the ECU 50 determines whether or not the pilot injection mode flag XPLT1 is set to “1”. If a positive determination is made here, the ECU 5
In step 502, it is determined whether or not the pilot injection execution flag XPLT2 is set to "0". If a positive determination is made here, the ECU 50
In step 504, the fuel pressure correction amount PCRPL is set equal to the predetermined value P.

On the other hand, if a negative determination is made in step 502, the ECU 50 determines in step 506 whether the injection timing correction amount APL1 is "0". If an affirmative determination is made here, the ECU 50 sets the fuel pressure correction amount PCRPL to “0” in step 507. On the other hand, if a negative determination is made in step 506, the ECU 50 sets the fuel pressure correction amount PCRPL equal to the predetermined value R in step 508.

Here, the predetermined value P is the engine speed NE.
And the basic injection amount QMAINB. When the first correction limit value APL1LMT1 is calculated as a positive value, it is set as a negative value (P <0).
When the first correction limit value APL1LMT1 is calculated as a negative value, it is calculated as a positive value (P> 0).

Therefore, as shown in FIG. 5, the injection timing correction amount APL1 (see FIG. 5 (g)) is the first correction limit value AP.
By being changed to approach L1LMT1, the main injection timing AMAIN becomes the reference main injection timing AMAI.
Timing t1 to be changed to a timing advanced from NB
In the period of t4, the predetermined value P is calculated as a negative value.

The predetermined value R, like the predetermined value P, is calculated based on the engine speed NE and the basic injection amount QMAINB.
When L1LMT2 is calculated as a positive value, the second correction limit value APL1LMT is set to a negative value (R <0).
Positive value (R> 0) when 2 is calculated as a negative value
Is calculated as

Therefore, as shown in FIG. 5, when the injection timing correction amount APL1 (see FIG. 5G) is changed to the second correction limit value APL1LMT2 at the timing t4, the main injection timing APLTM is changed to the reference main timing. The predetermined value R is calculated as a positive value during a period from timing t4 to timing t8 in which the injection timing is shifted to a timing that is more retarded than the injection timing APLTMB.

In the memory of the ECU 50, function data defining the relationship between the predetermined values P and R, the engine speed NE and the basic injection amount QMAINB are stored, respectively. , Predetermined values P, R with reference to these function data, respectively.
Is calculated.

If a negative determination is made in step 500, the ECU 50 returns to step 510
It is determined whether pilot injection execution flag XPLT2 is set to “1”. If a positive determination is made here, the ECU 50 sets the fuel pressure correction amount PCRPL equal to the predetermined value Q in step 512.

On the other hand, if a negative determination is made in step 510, the ECU 50 determines in step 514 whether the injection timing correction amount APL1 is "0". If an affirmative determination is made here, the ECU 50 sets the fuel pressure correction amount PCRPL to “0” in step 515. On the other hand, if a negative determination is made in step 514, the ECU 50 sets the fuel pressure correction amount PCRPL equal to the predetermined value S in step 516.

Here, the predetermined value Q is the engine speed NE.
When the second correction limit value APL1LMT2 is calculated as a negative value, the second correction limit value APL1LMT2 is calculated as a positive value (Q> 0).
When the second correction limit value APL1LMT2 is calculated as a positive value, it is calculated as a negative value (Q <0).

Therefore, as shown in FIG. 5, the injection timing correction amount APL1 (see FIG. 5G) is changed to the second correction limit value AP.
By being changed to approach L1LMT2,
The main injection timing APLTM is the reference main injection timing APL
Timing t9 when the timing is changed to a timing that is more retarded than TMB
In the period from to t12, the predetermined value Q is calculated as a positive value.

The predetermined value S is calculated based on the engine speed NE and the basic injection amount QMAINB, similarly to the predetermined value Q. The first correction limit value AP
When L1LMT1 is calculated as a positive value, the first correction limit value APL1LMT is set to a negative value (S <0).
When 1 is calculated as a negative value, a positive value (S> 0)
Is calculated as

Therefore, as shown in FIG. 5, when the injection timing correction amount APL1 (see FIG. 5G) is changed to the first correction limit value APL1LMT1 at the timing t12, the main injection timing AMAIN becomes the reference main injection timing. The predetermined value S is calculated as a negative value during the period from the timing t12 to the timing t16 in which the injection timing is shifted to the timing advanced from the injection timing AMAINB.

In the memory of the ECU 50, function data defining the relationship between the predetermined values Q and S and the engine speed NE and the basic injection amount QMAINB are stored, respectively. The predetermined values Q and S are calculated with reference to these function data. The timing chart shown in FIG. 5 shows an example of a control mode when the predetermined value P and the predetermined value S are set to be equal and the predetermined value R and the predetermined value Q are set to be equal.

The above steps 504, 507, 508,
After executing the processes of 512, 515, and 516, the ECU
In step 520, the above-mentioned final target fuel pressure PCR is calculated based on the following equation (8).

PCR = PCRB + PCRPL (8) After executing the processing of step 520, the ECU 50 once ends the processing of this routine.

According to the fuel injection control device of the present embodiment,
By controlling the fuel injection timing, injection amount, injection pressure, and pilot injection interval based on the control procedure described above, the following effects can be obtained.

(1) According to the fuel injection control device of the present embodiment, the torque value in the steady state before switching the fuel injection mode (the reference torque value Ta in the main injection mode, the reference torque value Td in the pilot injection mode). From the transient torque value T
After b and Tc, the engine torque is gradually changed to the steady-state torque values Ta and Td after the switching of the fuel injection mode, and such a gradual change control of the engine torque is performed by changing the main injection timings AMAIN and APLTM. Therefore, unlike the configuration in which the engine torque is gradually changed based on, for example, a change in the pilot injection interval, the change rate of the engine torque is reliably controlled to switch the fuel injection mode. This can reliably prevent the occurrence of torque shock.

(2) In particular, in the fuel injection control device according to the present embodiment, the fuel injection is performed so that the magnitudes of the engine torque immediately before and after the switching of the fuel injection mode, that is, the transient torque values Tb and Tc become equal. Since the main injection timings AMAIN and APLTM before and after the mode switching are controlled, torque shock generated at the time of switching the fuel injection mode can be more reliably prevented.

(3) In the fuel injection control device of the present embodiment, as described above, the main injection timings AMAIN, AP
When changing the LTM, the main injection timing AMAIN, A
Since the fuel pressure PC of the common rail 4 is controlled to the lower pressure side as the PLTM is shifted to the advanced side, the combustion noise and smoke emission due to the change of the main injection timings AMAIN and APLTM are increased. An increase in concentration can be prevented.

(4) According to the fuel injection control device of this embodiment, the pilot injection interval AINT is gradually changed in accordance with the switching of the fuel injection mode. The change in state can be made slow, and the occurrence of torque shock can be suppressed more reliably.

(5) Further, in the fuel injection control device of the present embodiment, when the pilot injection interval AINT is gradually changed as described above, the shorter the pilot injection interval AINT is, the smaller the final pilot injection amount QPLT1 is. Therefore, when the combustion pressure increased by the pilot injection is sufficiently reduced, the main injection is executed, and a rapid increase in the combustion pressure can be suppressed to prevent an increase in combustion noise. .

[Second Embodiment] Hereinafter, a second embodiment will be described focusing on differences from the first embodiment. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

In the first embodiment, the main injection timings AMAIN and APLTM are changed to prevent the occurrence of the torque shock accompanying the switching of the fuel injection mode. In the present embodiment, the final main injection is performed. Quantity Q
By changing the MAIN, the occurrence of such a torque shock is prevented.

In this embodiment, in addition to the above-described "control flag operation routine", "injection amount calculation routine", and "pilot injection interval calculation routine", the following "main injection amount correction routine" is executed. .

In the “injection amount calculation routine” shown in FIG. 9, in step 238, the final main injection amount QMA
Although IN is calculated, in the present embodiment, the process of step 238 is omitted, and after the processes of steps 234 and 236 are executed, the process is temporarily terminated. . In the present embodiment, the main injection timings AMAIN and APLTM are always set to be equal to the reference main injection timings AMAINB and APLTMB, respectively, and the final target fuel pressure PCR is always set to be equal to the reference target fuel pressure PCRB. Shall be.

Hereinafter, each process of the "main injection amount correction routine" will be described with reference to the flowchart shown in FIG. 14, and FIGS. 5 and 15. This routine is for correcting the final main injection amount QMAIN, and is executed by the ECU 50 as an interrupt process at the same crank angle (for example, at every 180 ° CA) as the “control flag operation routine”. You.

When the processing shifts to this routine, first,
In step 600, the ECU 50 determines whether or not the pilot injection mode flag XPLT1 is set to “1”. If a positive determination is made here, the ECU 5
If it is 0, it is determined in step 602 whether or not the pilot injection execution flag XPLT2 is set to “1”. If a negative determination is made here, the ECU 50
In step 622, the final main injection amount QMAIN
The main injection correction amount QMAIN1 which is the correction amount of
[Timings t1 to t4 shown in FIG. 5]. On the other hand, if a positive determination is made in step 602, the EC
U50 sets the main injection correction amount QMAIN1 equal to the correction limit value X in step 604 [timing t4].

Next, in step 606, the ECU 50 sets the main injection control permission flag XJPLT1 to "1".
It is determined whether or not is set. If a negative determination is made here, the ECU 50 shifts the processing to step 608. In step 608, the ECU 50 adds the predetermined amount Y to the current main injection correction amount QMAIN1, and sets the added value (= QMAIN1 + Y) as a new main injection correction amount QMAIN1 [timing t
6, t7].

Subsequently, in step 610, the ECU 50 determines whether or not the sign of the main injection correction amount QMAIN1 has changed, ie, whether the main injection correction amount QMAIN1 has been “0” or a negative value in the previous control cycle. Whether the value has changed to a positive value in the current control cycle, or conversely, the main injection correction amount QMAIN1, which was “0” or a positive value in the previous control cycle, has changed to a negative value in the current control cycle. It is determined whether or not. If a positive determination is made here, the ECU 50 sets the main injection correction amount QMAIN1 to “0” in step 612 [timing t8].

On the other hand, the ECU 50 shifts the processing to step 630 when an affirmative determination is made in step 606, when a negative determination is made in step 610, or after the processing of step 612 is performed.

If the determination in step 600 is negative, the ECU 50 determines in step 620 whether or not the pilot injection execution flag XPLT2 is set to "1". If an affirmative determination is made here, the ECU 50 subtracts the predetermined amount Z from the current main injection correction amount QMAIN1 in step 624, and sets the subtracted value (= QMAIN1-Z) as a new main injection correction amount QMAIN1. [Timing t9, t10].

Next, at step 626, the ECU 5
0 is the absolute value | QMA of the main injection correction amount QMAIN1.
IN1 | and the absolute value | X | of the correction limit value X are compared.
Here, the absolute value of the main injection correction amount QMAIN1 | QMA
When it is determined that IN1 | is larger than the absolute value | X | of the correction limit value X, the ECU 50 sets the main injection correction amount QMAIN1 to be equal to the correction limit value X in step 628 [timing t11], and then proceeds to step 628. Move to step 630. On the other hand, in step 626, the absolute value | QMAIN1 | of the main injection correction amount QMAIN1 |
Is smaller than or equal to the absolute value | X | of the correction limit value X, the ECU 50 executes the process of step 630.

On the other hand, if a negative determination is made in step 620, the ECU 50 shifts the processing to step 622. Then, in step 622, after setting the main injection correction amount QMAIN1 to “0” [timing t13 to t16], the ECU 50 executes the process of step 630.

In step 630, the ECU 50 sets
The final main injection amount QMAIN is calculated based on the following equation (9). QMAIN = QMAINB + QMAIN1-QPLT1 (9) After executing the processing of step 630, the ECU 50
Terminates the process of this routine once.

Here, the correction limit value X and the predetermined amounts Y and Z are determined by the engine speed NE and the basic injection amount QMAINB.
It is calculated based on The memory of the ECU 50 stores the correction limit value X, the predetermined amounts Y and Z,
Function data defining the relationship between the engine speed NE and the basic injection amount QMAINB are stored, respectively, and are stored in the ECU.
50 is used to calculate the correction limit value X and the predetermined amounts Y and Z.
Reference these function data.

The correction limit value X is set such that at least one of the following conditional expressions (10-a) and (10-b) is satisfied. Te = Tf ≦ Tg (10-a) Tg ≦ Tf = Te (10-b) Te: Reference torque value in main injection mode Tg: Reference torque value in pilot injection mode Tf: Transient torque value In the main injection mode reference torque value Te,
The final main injection amount QMAIN in the main injection mode is
From the basic injection amount QMAINB to the final pilot injection amount QP
This is a torque value when LT1 is subtracted (= QMAINB-QPLT1), and the pilot injection mode reference torque value Tg is obtained by subtracting the final main injection amount QMAIN in the pilot injection mode from the above amount (QMAINB-QPLT).
This is the torque value when 1) is set. In the pilot injection mode, the transient torque value Tf is calculated by subtracting the final main injection amount QMAIN from the above amount (QMAINB-QPLT).
This is the torque value when the amount is increased or decreased by the correction limit value X from 1).

For example, as shown in FIG. 15A, when the reference torque value Te in the main injection mode is smaller than the reference torque value Tg in the pilot injection mode, the correction limit value X becomes a negative value (X < 0). When the correction limit value X is calculated as a negative value,
Each of the predetermined amounts Y and Z is a positive value (Y> 0, Z>
0).

In the case where the correction limit value X is calculated as a negative value, as shown in FIG.
, The main injection correction amount QMAIN1 ((j) in FIG.
) Decreases from “0” to the correction limit value X. As a result, at the timing t4, the fuel injection mode is switched from the main injection mode to the pilot injection mode, and at the same time, the final main injection amount QMAIN is reduced by the correction limit value X. Accordingly, the engine torque changes from the state shown by the point E1 in FIG.
It changes to the state shown by.

Here, in the fuel injection control device of the present embodiment, the engine torque in the state indicated by the points E1 and F1, that is, the reference torque value Te in the main injection mode and the transient torque value Tf match. (10-a), (10-
b)), the engine torque hardly changes when the fuel injection mode is switched. Therefore, it is possible to reliably prevent the occurrence of torque shock accompanying the switching of the fuel injection mode.

In the period between timings t6 and t8,
The main injection correction amount QMAIN1 (see FIG. 5 (j)) gradually increases from the correction limit value X to “0”. As a result, in the period from the timing t6 to the timing t8, the final main injection amount QMAIN is gradually increased from a state reduced by the correction limit value X to a steady state amount (= QMAINB-QPLT1). . Therefore, the engine torque gradually increases from the state indicated by the point F1 in FIG. 15A to the state indicated by the point G1.

Here, the final main injection amount QMAIN is
Since the correlation with the engine torque is higher than the pilot injection interval AINT and the like, and the influence on the torque is large,
By changing this, it is possible to reliably control the magnitude of the engine torque. Therefore, according to the fuel injection control device of the present embodiment, even when the engine torque difference in each state indicated by the points F1 and G1 is large, the increasing speed of the final main injection amount QMAIN, that is, Quantitative Y
The engine torque is gradually controlled from the transient torque value Tf to the pilot injection mode reference torque value Tg by appropriately adjusting the magnitude of the engine torque so as to surely control the changing speed of the engine torque so as not to generate a torque shock. Can be increased.

Further, during the period from timing t9 to t12, the main injection correction amount QMAIN1 decreases from "0" until it becomes equal to the correction limit value X. As a result, in the period from timing t9 to t12, the final main injection amount QM
AIN is a steady state amount (= QMAINB-QPLT1)
Is gradually reduced to the amount reduced by the correction limit value X. Therefore, the engine torque is as shown in FIG.
In (a), it gradually decreases from the state shown by the point G1 to the state shown by the point F1.

In the period between the timings t9 and t12, as in the period between the timings t6 and t8, the decreasing speed of the final main injection amount QMAIN, that is, the magnitude of the predetermined amount Z is appropriately adjusted. ,
The engine torque can be gradually reduced from the pilot injection mode reference torque value Tg to the transient torque value Tf after reliably controlling the changing speed of the engine torque so that the torque shock does not occur.

At timing t12, the main injection correction amount QMAIN1 is increased from the correction limit value X to "0". As a result, this timing t12
In, the fuel injection mode is switched from the pilot injection mode to the main injection mode, and at the same time, the final main injection amount QMAIN is increased by the correction limit value X. Therefore, the engine torque becomes equal to the point F in FIG.
The state changes from the state indicated by 1 to the state indicated by the point E1.

As described above, even when the fuel injection mode is switched, as in the case of the timing t4, there is almost no change in the engine torque at the time of the switching, so that the occurrence of torque shock can be reliably prevented. .

On the other hand, as shown in FIG. 15 (b), a situation in which the reference torque value Te in the main injection mode becomes larger than the reference torque value Tg in the pilot injection mode also occurs in the engine operating state (engine rotation state). It can occur depending on the number NE and the basic injection amount QMAINB). In such a case,
The correction limit value X is calculated as a positive value (X> 0). When the correction limit value X is calculated as a positive value as described above, each of the predetermined amounts Y and Z is a negative value (Y
<0, Z <0).

According to the fuel injection control device of this embodiment, even when the correction limit value X is calculated as a positive value, the above-described correction limit value X is calculated as a negative value. As in the case described above, it is possible to prevent the torque shock at the time of switching the fuel injection mode, and to surely control the changing speed of the engine torque so that the torque shock does not occur.
From the reference injection torque to the reference torque value Tg in the pilot injection mode, or from the reference torque value Tg in the pilot injection mode to the transient torque value Tf.

According to the present embodiment described above, the following effects can be further obtained in addition to the effects (4) and (5) of the above-described first embodiment. (6) According to the fuel injection control device of the present embodiment, the transient torque from the torque value in the steady state (the reference torque value Te in the main injection mode and the reference torque value Tg in the pilot injection mode) in the steady state before the fuel injection mode is switched After the value Tf, the torque value T in the steady state after the fuel injection mode is switched
e, gradually change the engine torque to Tg,
Such a gradual control of the engine torque is performed by using the final main injection amount QM
Because it is done by changing the AIN,
For example, unlike the configuration in which the engine torque is controlled gradually based on the change of the pilot injection interval, the rate of change of the engine torque is reliably controlled to reliably prevent the occurrence of torque shock due to switching of the fuel injection mode. can do.

(7) In particular, in the fuel injection control device of the present embodiment, the magnitude of the engine torque immediately before and after the switching of the fuel injection mode, that is, the transient torque value Tf and the reference torque value Te in the main injection mode. Since the final main injection amount QMAIN is controlled before and after the switching of the fuel injection mode so as to be equal to each other, the torque shock generated at the time of switching the fuel injection mode can be more reliably prevented.

Although the embodiments embodying the present invention have been described above, these embodiments can also be implemented by changing the configuration as described below. In the first embodiment, by changing the injection timing of the main injection, and in the second embodiment, by changing the injection amount of the main injection, the occurrence of the torque shock accompanying the switching of the fuel injection mode is reduced. The torque shock can be prevented by changing the injection pressure of the main injection. More specifically, the fuel pressure correction amount PCRPL, which is the correction amount of the final target fuel pressure PCR described above, is changed in the same manner as the main injection correction amount QMAIN1 shown in FIG. 5 (j), for example. .

That is, when the engine torque increases when the fuel injection mode is switched from the main injection mode to the pilot injection mode, first, the fuel injection mode is switched from the main injection mode to the pilot injection mode. At the same time, the fuel pressure correction amount PCRPL is decreased from "0" by a predetermined amount to lower the final target fuel pressure PCR [timing t4 shown in FIG. 5]. As a result, the injection pressure decreases, so that a change in engine torque due to switching of the fuel injection mode can be suppressed. Next, after the fuel injection mode becomes the pilot injection mode, the fuel pressure correction amount PCR
By gradually increasing PL to “0”, the final target fuel pressure PCR is increased [timing t6 to t6
8]. As a result, the engine torque gradually increases to the steady state torque value.

On the other hand, when the fuel injection mode can be switched from the pilot injection mode to the main injection mode, first, before switching the fuel injection mode, the fuel pressure correction amount PC
RPL is gradually decreased from "0" to reach the final target fuel pressure P
CR is reduced [timing t9 to t12]. next,
At the same time as switching the fuel injection mode from the pilot injection mode to the main injection mode, the fuel pressure correction amount PCRPL is increased to "0" to increase the final target fuel pressure PCR (timing t12).

Also with the above configuration, the injection pressure of the main injection has a high correlation with the engine torque similarly to the injection timing and the injection amount, and has a large influence on the torque. Is reliably controlled to prevent the occurrence of a torque shock accompanying the switching of the fuel injection mode.

In the second embodiment, the final main injection amount QMAIN is changed in order to prevent torque shock. However, in addition to the final main injection amount QMAIN, as in the first embodiment, Main injection timing AMA
IN and APLTM are changed, and the final main injection amount QMAIN and the main injection timings AMAIN, AMAIN are changed.
The torque shock may be prevented by changing both of the PLTM. With this configuration,
Each of the above-described correction limit values APL1LMT1, APL1LM
Absolute value of T2 | APL1LMT1 |, | APL1LMT
2 | and the absolute value | X | of the correction limit value X can be set small, so that these final main injection amount QMAIN and main injection timings AMAIN, APLT
It is possible to minimize the increase in the combustion noise and the exhaust gas density due to the change of M.

In the first embodiment, the first transient torque value Tb and the second transient torque value Tc are made to coincide with each other. However, the torque shock generated when the fuel injection mode is switched cannot be felt. If the absolute difference | Tb−Tc | between the two torque values Tb and Tc is set to be small so as to suppress the transient torque values Tb and Tc, the transient torque values Tb and Tc may be set to different values. Also, in the second embodiment, the transient torque value Tf and the reference torque value Te in the main injection mode are made to coincide with each other, but similarly, these two torque values Tf, Te are set to different values. It may be.

In the first embodiment, the control modes of the main injection timing include, for example, the following control modes [a],
It can be changed as shown in [b]. [A] When the fuel injection mode is switched from the pilot injection mode to the main injection mode, a state in which the main injection timing APLTM is set to the reference main injection timing APLTB in the pilot injection mode (FIG. 16A: point A)
At the same time as switching the fuel injection mode from 2), the main injection timing AMAIN in the main injection mode is set to the reference main injection timing so that the torque values Ta and Tc before and after the switching substantially match (see FIG. 16A). AMAINB
(Point A2 → point C2). Next, the main injection timing AMAIN is gradually changed from the retarded timing to the reference main injection timing AMAINB to the advanced timing (point C2 → point D2). Accordingly, the engine torque is set to a predetermined value Ta (= Tc) as shown in FIG.
From T to a predetermined value Td.

On the other hand, when switching the fuel injection mode from the main injection mode to the pilot injection mode, first, before switching, the torque values Ta and Tc before and after the switching of the fuel injection mode become substantially the same. Up to this point, the main injection timing AMAIN in the main injection mode is gradually changed from the reference main injection timing AMAINB to a timing on the retard side (point D2 → point C2). Next, at the same time as switching the fuel injection mode, the main injection timing APLTM in the pilot injection mode is set to the reference main injection timing APLTB (point C2 → point A2). Accordingly, the engine torque is changed from the predetermined value Td to the predetermined value Ta (= T
It gradually decreases to c).

[B] When switching the fuel injection mode from the pilot injection mode to the main injection mode, first, before switching, the torque values Tb and Td before and after the switching of the fuel injection mode (FIG. 16 (b) (See point A3 → point B3) until the main injection timing APLTM in the pilot injection mode is gradually advanced from the reference main injection timing APLTB until the reference injection timing APLTM becomes substantially the same. Next, at the same time as switching the fuel injection mode, the main injection timing AMAIN in the main injection mode is set to the reference main injection timing AMAINB (point B3 → point D3). Accordingly, the engine torque is changed from the predetermined value Ta to the predetermined value Td (= Td) as shown in FIG.
It gradually increases up to b).

On the other hand, when the fuel injection mode is switched from the main injection mode to the pilot injection mode, the main injection timing AMAIN is set to the reference main injection timing AMAINB in the main injection mode (point D3).
And at the same time, the main injection timing APLT in the pilot injection mode is set to a timing that is more retarded than the reference main injection timing APLTB so that the torque values Tb and Td before and after the switching are substantially the same. (Point D3 → point B3). Next, the main injection timing APLT in the pilot injection mode is set to the reference main injection timing APL.
The timing is gradually changed to the retard side until TB (point B3 → point A3). Accordingly, the engine torque gradually decreases from the predetermined value Td (= Tb) to the predetermined value Ta, as shown in FIG.

Even if the main injection timing is controlled based on each of the control modes [a] and [b] described above, the first
The same operational effects as those of the embodiment can be obtained. In the first embodiment, the correction limit values APL1LMT1 and APL1L for the injection timing correction amount APL1.
The MT2, the predetermined amounts H, J, M, L, K, N, and the predetermined values P, Q, R, and S relating to the fuel pressure correction amount PCRPL are calculated based on the engine operating state. If the tendency of the change in the engine torque accompanying the switching of the injection mode can be considered to be substantially constant irrespective of the engine operating state, these values may be set as constant values. In the second embodiment, the correction limit value X and the predetermined amounts Y and Z relating to the main injection correction amount QMAIN1 can be similarly set as constant values.

In the first embodiment, the predetermined values P, Q, R, and S relating to the fuel pressure correction amount PCRPL are calculated based on the engine speed NE and the basic injection amount QMAINB, respectively. , These parameters N
Each of the above values may be calculated based on the coolant temperature THW detected by the water temperature sensor 21 and the fuel temperature THF detected by the fuel temperature sensor 23 in addition to E and QMAINB. Thus, the cooling water temperature THW and the fuel temperature T
By calculating the above values according to the HF, the degree of atomization of the fuel can be more appropriately controlled.

The fuel injection control device of each of the above embodiments employs a structure in which fuel is supplied from the supply pump 6 into the common rail 4 and fuel is supplied from the common rail 4 to the injector 2. It is also possible to adopt a configuration in which a so-called distribution type supply pump is used, and fuel is supplied from the pump to each injector 2.

The technical ideas that can be grasped from the above embodiments are described below together with their effects. (1) In the fuel injection control device for an internal combustion engine according to claim 4, the control value setting means sets the transient control value so that the transient torque value becomes equal to the post-switching torque value. It is characterized by the following.

(2) In the fuel injection control device for an internal combustion engine according to claim 5, the control value setting means sets the transient control value such that the transient torque value becomes equal to the pre-switching torque value. Characterized in that:

According to the above configuration (1) or (2), the engine torque does not change when the fuel injection mode is switched, so that a rapid change in the engine torque that occurs simultaneously with the switching of the fuel injection mode is ensured. It is possible to suppress the occurrence of torque shock accompanying the switching of the fuel injection mode more reliably.

[0282]

According to the first aspect of the present invention, the correlation between the first injection and the engine torque is higher than the injection state of the injection with a small injection amount among a plurality of injections based on the second injection method. Since the injection state based on the injection method described above and the injection state based on the injection amount that is large among the multiple injections based on the second injection method are corrected, the engine torque can be reliably controlled. As a result, a sudden change in the engine torque accompanying the switching of the fuel injection mode is suppressed. As a result, it is possible to reliably prevent the occurrence of torque shock accompanying the switching of the fuel injection mode.

[0283] According to the second to eleventh aspects of the invention, the change in the engine torque accompanying the switching of the fuel injection mode is suppressed based on the change of the control value related to the main injection. Since the control value related to the main injection directly affects the combustion state of the engine, the control value has a higher correlation with the engine torque than the pilot injection interval. Therefore, by changing the control value related to the main injection, the engine torque can be reliably controlled, and a rapid change in the engine torque accompanying the switching of the fuel injection mode can be suppressed. As a result, it is possible to reliably prevent the occurrence of torque shock accompanying the switching of the fuel injection mode.

In particular, in the invention described in claim 4, when the fuel injection mode is switched, the engine torque is gradually changed from the pre-switching torque value to the post-switching torque value. The change in the engine torque becomes slow. As a result, it is possible to more reliably prevent the occurrence of the torque shock while reliably controlling the change in the engine torque according to the gradually changing speed.

According to the fifth to ninth aspects, when the fuel injection mode is switched, the engine torque is controlled so as to be a transient torque value between the torque value before switching and the torque value after switching. In addition, the change in the engine torque accompanying the switching of the fuel injection mode becomes slower. As a result, the occurrence of the torque shock can be more reliably prevented.

According to the invention as set forth in claim 6 or 7, the change of the engine torque before the switching of the fuel injection mode or after the switching of the fuel injection mode depends on the gradually changing speed of the control value related to the main injection. And a sudden change in the engine torque can be reliably suppressed.
Further, the amount of change in the engine torque when the fuel injection mode is switched becomes relatively small. As a result, it is possible to more reliably prevent the occurrence of torque shock accompanying the switching of the fuel injection mode.

According to the invention described in claim 8 or 9, the change in the engine torque before and after the switching of the fuel injection mode can be controlled according to the gradually changing speed of the control value related to the main injection. As a result, a sudden change in the engine torque is reliably suppressed. Further, the amount of change in the engine torque when the fuel injection mode is switched becomes relatively small. As a result, it is possible to more reliably prevent the occurrence of torque shock accompanying the switching of the fuel injection mode.

In particular, according to the ninth aspect of the present invention, since the engine torque does not change when the fuel injection mode is switched, a rapid change in the engine torque that occurs simultaneously with the switching of the fuel injection mode is reliably suppressed. It is possible to more reliably prevent the occurrence of a torque shock accompanying the switching of the fuel injection mode.

According to the tenth aspect of the present invention, as the injection timing of the main injection is changed to the advanced side in order to suppress the occurrence of a sudden change in the engine torque, the injection timing of the main injection increases. Changed to low pressure side. Therefore, when the injection timing of the main injection is relatively changed to the advance side,
Since the atomization of the injected fuel is suppressed by the decrease in the injection pressure, the rapid increase in the combustion pressure is suppressed. On the other hand, when the injection timing of the main injection is relatively retarded,
Since the atomization of the injected fuel is promoted by the increase in the injection pressure, incomplete combustion of the fuel is suppressed. As a result, it is possible to prevent an increase in combustion noise and an increase in smoke exhaustion density due to a change in the injection timing of the main injection.

According to the eleventh aspect of the present invention, when the fuel injection mode is switched, the injection interval between the main injection and the pilot injection, that is, the pilot injection interval is gradually changed. The change in state becomes slow. As a result, it is possible to more reliably prevent the occurrence of torque shock accompanying the switching of the fuel injection mode. Further, when the pilot injection interval is set to be relatively short, the injection pressure of the pilot injection is reduced, so that the combustion pressure temporarily increased by the pilot injection starts to decrease earlier. Become. Therefore, when the combustion pressure increased by the pilot injection is sufficiently reduced, the main injection is executed, and a rapid increase in the combustion pressure is suppressed. As a result, it is possible to effectively suppress the increase in combustion noise by effectively utilizing the action of mitigating the increase in combustion pressure caused by the pilot injection.

According to the twelfth aspect of the present invention, the first injection having a higher correlation with the engine torque than the injection state of the injection with a small injection amount among the multiple injections based on the second injection method. Since the injection state based on the method or the injection state of the injection with the largest injection amount among the multiple injections based on the second injection method is corrected, the engine torque can be reliably controlled. Thus, a sudden change in the engine torque accompanying the switching of the fuel injection mode is suppressed. As a result, it is possible to reliably prevent the occurrence of torque shock accompanying the switching of the fuel injection mode.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a fuel injection control device according to the present invention.

FIG. 2 is a graph showing the relationship between a steady-state pilot injection amount, an engine speed, and a basic injection amount.

FIG. 3 is a timing chart showing a change state of an on / off state of a solenoid valve.

FIG. 4 is a graph showing a relationship between a reference target fuel pressure, an engine speed, and a basic injection amount.

FIG. 5 is a timing chart for explaining an example of a control mode by a fuel injection control device.

FIG. 6 is a graph showing a relationship between a main injection timing and an engine torque in a pilot injection mode and a main injection mode.

FIG. 7 is a flowchart showing an operation procedure of a control flag.

FIG. 8 is a flowchart showing an operation procedure of a control flag.

FIG. 9 is a flowchart showing a procedure for calculating an injection amount in main injection and pilot injection.

FIG. 10 is a flowchart showing a procedure for calculating a pilot injection interval.

FIG. 11 is a flowchart showing a procedure for calculating an injection timing in main injection and pilot injection.

FIG. 12 is a flowchart showing a procedure for calculating an injection timing in main injection and pilot injection.

FIG. 13 is a flowchart showing a procedure for calculating a target fuel pressure.

FIG. 14 is a flowchart showing a procedure for correcting a main injection amount.

FIG. 15 is a graph showing the relationship between the final main injection amount and the engine torque in the pilot injection mode and the main injection mode.

FIG. 16 is a graph showing a relationship between a main injection timing and an engine torque in a pilot injection mode and a main injection mode.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Diesel engine, 2 ... Injector, 4 ... Common rail, 6 ... Supply pump, 8 ... Fuel tank, 15
... accelerator pedal, 20 ... accelerator sensor, 50 ... EC
U.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 41/38 F02D 41/38 B 45/00 364 45/00 364B

Claims (12)

[Claims] An internal combustion engine in which a first injection method for performing one injection during one stroke of each cylinder of the internal combustion engine and a second injection method for performing multiple injections during one stroke of each cylinder are selectively used. The fuel injection control device according to claim 1, wherein when switching from the first injection method to the second injection method, an injection state based on the first injection method is switched to the second injection method. When the correction is made so as to approach the engine torque, and when the second injection method is switched to the first injection method, the injection state in the injection with a large injection amount among the multiple injections based on the second injection method A fuel injection control device for an internal combustion engine, comprising: a correction unit that corrects the torque so as to approach the torque after switching to the first injection method. 2. The fuel injection mode for an internal combustion engine is switched between an injection mode in which only main injection is executed based on an engine operating state and an injection mode in which both the main injection and pilot injection are executed. A fuel injection control device for an internal combustion engine, comprising: a torque change suppression unit that suppresses a change in engine torque associated with switching of the fuel injection mode based on a change in a control value related to the main injection. Fuel injection control device. 3. The fuel injection control device for an internal combustion engine according to claim 2, wherein the torque change suppressing unit changes at least one of an injection timing, an injection amount, and an injection pressure as a control value related to the main injection. A fuel injection control device for an internal combustion engine, characterized in that: 4. The fuel injection control device for an internal combustion engine according to claim 3, wherein the torque change suppressing unit is configured to control the engine torque based on a change in a control value related to the main injection when a fuel injection mode is switched. And a torque control means for gradually changing the torque value from the pre-switching torque value before switching of the fuel injection mode to the post-switching torque value after switching. 5. The fuel injection control device for an internal combustion engine according to claim 3, wherein the torque change suppressing unit is configured to control the engine torque based on a change in a control value related to the main injection when a fuel injection mode is switched. A fuel injection control device for an internal combustion engine, comprising: a torque control unit for controlling a transient torque value between a pre-switching torque value before switching of the fuel injection mode and a post-switching torque value after switching. 6. The fuel injection control device for an internal combustion engine according to claim 5, wherein the torque control unit sets the engine torque to the transient torque value in an injection mode before switching the fuel injection mode. Control value setting means for setting the control value according to the above as a transient control value; and gradually changing the control value related to the main injection to the transient control value after the fuel injection mode switching determination and before the actual switching. A fuel injection control device for an internal combustion engine, comprising: control value changing means for changing the transient control value to a control value for setting the engine torque to the post-switching torque value when the fuel injection mode is switched. . 7. The fuel injection control device for an internal combustion engine according to claim 5, wherein the torque control unit is configured to set the engine torque to the transient torque value in an injection mode after fuel injection mode switching. Control value setting means for setting a control value according to the present invention as a transient control value, and changing the control value relating to the main injection to the transient control value at the time of switching the fuel injection mode, and the transient control value after switching the fuel injection mode. Control value changing means for gradually changing the engine torque to a control value for setting the engine torque to the post-switching torque value. 8. The fuel injection control device for an internal combustion engine according to claim 5, wherein the torque control means adjusts the engine torque in the injection mode before switching the fuel injection mode and the torque value before switching and the torque value after switching. And a control value for the main injection for setting a first transient torque value between the first and second transient torque values is set as a first transient control value, and the engine torque is set to the pre-switching torque in the injection mode after the fuel injection mode is switched. Control value setting means for setting, as a second transient control value, a control value related to the main injection for setting a second transient torque value between the value and the post-switching torque value; and control related to the main injection. The value is gradually changed to the first transient control value after the fuel injection mode switching is determined and before the actual switching, and the second transient control value is changed from the first transient control value during the fuel injection mode switching. Control value changing means for changing the engine torque to the control value for changing the engine torque from the second transient control value to the post-switching torque value after switching the fuel injection mode. A fuel injection control device for an internal combustion engine, comprising: 9. The fuel injection control device for an internal combustion engine according to claim 8, wherein the control value setting means sets the first transient torque value and the second transient torque value to be equal to each other. A fuel injection control device for an internal combustion engine, wherein the first transient control value and the second transient control value are set. 10. The fuel injection control device for an internal combustion engine according to claim 2, wherein the torque change suppressing unit changes at least an injection timing of the main injection as a control value related to the main injection. A fuel injection control device for an internal combustion engine, wherein the injection pressure of the main injection is changed to a lower pressure side as the injection timing is changed to an advanced side. 11. The fuel injection control device for an internal combustion engine according to claim 2, wherein the torque change suppressing unit is configured to inject the main injection and the pilot injection when a fuel injection mode is switched. An internal combustion engine further comprising: injection interval control means for gradually changing an interval; and pilot injection quantity control means for controlling the injection quantity so that the injection quantity of the pilot injection decreases as the injection interval becomes shorter. Fuel injection control device. 12. An internal combustion engine in which a first injection method for performing one injection during one stroke of each cylinder of the internal combustion engine and a second injection method for performing multiple injections during one stroke of each cylinder are selectively used. The fuel injection control device according to claim 1, wherein when switching from the first injection method to the second injection method, an injection state based on the first injection method is switched to the second injection method. Correction is made so as to approach the engine torque, and when switching from the second injection method to the first injection method, the second injection method is used.
An internal combustion engine comprising: a correction unit that corrects an injection state of an injection having the largest injection amount among a plurality of injections based on the injection method to approach a torque after switching to the first injection method. Fuel injection control device.