JP3052661B2 - Fuel injection control device for diesel engine - Google Patents

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 a diesel engine.

[0002]

2. Description of the Related Art For example, Japanese Patent Application Laid-Open No. 63-266149 discloses a fuel injection control device for an internal combustion engine.
This fuel injection control device is connected to a fuel injection valve via a fuel supply passage to supply fuel, a pressure accumulator having a fixed volume provided in the fuel supply passage, and attached to the fuel supply passage. A fuel pressure sensor, discharge pressure control means for controlling a discharge pressure of fuel supplied from the fuel supply pump to the accumulator in accordance with an output signal from the fuel pressure sensor, and intake temperature detection means for detecting intake temperature. And a correcting means for correcting the discharge pressure of the fuel supply pump to a higher pressure side as the temperature detected by the discharge pressure control means by the intake air temperature detecting means is lower. That is, as the intake air temperature is lower, the discharge pressure of the fuel supply pump is corrected to a higher pressure side to increase the fuel injection pressure, thereby promoting the atomization of fuel,
Improves combustion to reduce black smoke.

[0003]

However, in the above-described fuel injection control device, when the load is higher than a predetermined load, the fuel injection amount is increased due to the high load, but the fuel injection amount increases with the intake air temperature. Since the fuel injection pressure is corrected to the low pressure side, atomization of the fuel becomes worse. In addition, the intake air density decreases due to the rise in intake air temperature, resulting in a shortage of air.
There is a risk that the amount of air taken in by the fuel decreases, combustion deteriorates, and the amount of black smoke and particulate matter generated increases.

Accordingly, an object of the present invention is to suppress the generation of black smoke and particulate matter by increasing the fuel injection pressure in accordance with an increase in the intake air temperature when the load is higher than a predetermined load.

[0005]

As shown in FIG. 1, a fuel injection control apparatus for a diesel engine according to the present invention comprises a load detecting means M1 for detecting a load state of the engine, and a load detected by the load detecting means M1. A fuel injection amount control means M2 for increasing the fuel injection amount supplied to the engine with the rise, an intake air temperature detection means M3 for detecting the intake air temperature, a fuel injection pressure control means M4 for controlling the fuel injection pressure, A fuel injection means M5 for injecting fuel based on the output of the fuel injection amount control means M2, wherein the fuel injection pressure control means M4 detects the intake air temperature detected by the intake air temperature detection means M3. In a fuel injection control device for a diesel engine having first correction means M6 for correcting the fuel injection pressure to a low pressure side as the load rises, the load detected by the load detection means M1 is limited. When the load is higher than the load, the fuel injection pressure control means M4 is provided with a second correction means M7 for correcting the fuel injection pressure to a high pressure side in accordance with an increase in the intake air temperature detected by the intake air temperature detection means M3. It is characterized by.

[0006]

According to the above means, the load state of the engine is detected by the load detecting means, and the fuel injection amount is increased by the fuel injection amount control means with an increase in the detected load. Then, with the rise of the intake air temperature detected by the intake air temperature detecting means, the first correction means of the fuel injection pressure control means corrects the fuel injection pressure to a lower pressure side. Fuel is injected by the fuel injection means with the fuel injection amount and the fuel injection pressure determined in this way. However, when the load of the engine detected by the load detection means is equal to or more than a predetermined load, the second correction means provided in the fuel injection pressure control means is controlled by the second correction means provided with the rise of the intake air temperature detected by the intake temperature detection means. Correct the injection pressure to the high pressure side.

[0007]

2 and 3 relate to a first embodiment of the present invention.
2 is a configuration diagram of a diesel engine according to the present invention, and FIG. 3 is a side sectional view of the diesel engine. 2 is a diesel engine body, 4 is a cylinder block, 6 is a cylinder head, 8 is a piston, 10 is a combustion chamber, 12 is an intake valve, 14 is an exhaust valve, 16 is a fuel injection valve arranged in the combustion chamber 10, 18 Denotes an intake pipe, and an inlet of the intake pipe 18 is connected to the supercharger 20. The fuel injection means is a fuel injection valve 1
6, a fuel supply pump 30, and a path therebetween. The fuel injection valve 16 is connected via a fuel supply pipe 22 to a fuel accumulator pipe 24 common to each cylinder. Fuel pressure storage tube 2
4 has a pressure accumulating chamber 26 having a constant volume therein, and the fuel in the pressure accumulating chamber 26 is supplied through the fuel supply pipe 22 to the fuel injection valve 1.
6. On the other hand, the pressure accumulation chamber 26 is connected via a fuel supply pipe 28 to a discharge port of a fuel supply pump 30 whose discharge pressure can be controlled. The suction port of the fuel supply pump 30 is connected to a discharge port of a fuel pump 32, and the suction port of the fuel pump 32 is connected to a fuel reservoir tank 34. Fuel pump 3
Numeral 2 is provided to feed the fuel in the fuel reservoir tank 34 to the fuel supply pump 30, and the fuel pump 32
If the fuel can be sucked into the fuel supply pump 30 without the above, the fuel pump 32 need not be provided. On the other hand, the fuel supply pump 30 is provided for discharging high-pressure fuel, and the high-pressure fuel discharged from the fuel supply pump 30 is accumulated in the accumulator 26 through the fuel supply pipe 28. Each fuel injection valve 16 is connected to a fuel reservoir tank 34 via a fuel return conduit 36, and the fuel not used for combustion is returned to the fuel reservoir tank 34 via the fuel return conduit 36.

The fuel supply pump 30 supplies the amount of fuel set by the pump discharge amount driving device 37 into the accumulator 26. The pump discharge amount driving device 37 is connected to an electronic control device 38, The fuel pressure is set by controlling the discharge amount per rotation of the fuel supply pump 30 in accordance with a command from the device 38.

A fuel injection valve 16 for injecting fuel is of an electrostrictive type using a piezoelectric element. The fuel injection valve 16 opens only during a period in which a positive voltage is applied. The fuel is injected at the pressure in the accumulator 26. This injection period changes according to the load.

The electronic control unit 38 as the fuel injection amount control means, the fuel injection pressure control means, the first correction means, and the second correction means includes a well-known CPU 40, a RAM 42, a ROM 44,
It has an input port 46 and an output port 48 and is interconnected by a bidirectional bus 47. AD converters 50, 52, 54, 56 are connected to the input port 46, and drive circuits 58, 60, 62, 64, 66 are connected to the output port 48.
Is connected. The AD converter 50 is connected to a water temperature sensor 68 provided in the diesel engine main body 2, the AD converter 52 is connected to a fuel pressure sensor 70 provided in the accumulator 26, and the AD converter 54 is provided in the intake pipe 18. A is connected to an intake air temperature sensor 72 serving as an intake air temperature detecting means.
The D converter 56 is connected to a load sensor 74 as load detection means provided on the accelerator pedal 76. In addition, a rotation angle sensor 80 provided near the crankshaft 78 for calculating the engine speed and a cylinder determination sensor 82 for determining which fuel injection valve is to be operated are also connected to the input port 46. . The driving circuit 58 is connected to the pump discharge amount driving device 37, and the driving circuits 60, 62, 64,
Reference numerals 66 are respectively connected to the fuel injection valves 16.

The operation of the fuel injection control device for a diesel engine constructed as described above will be described with reference to the flowchart of FIG. 4 showing the main routine stored in the ROM 44 and the flowchart of FIG. 5 for controlling the fuel injection pressure. explain. Rotation angle sensor 80 indicating engine speed N
And the output signal of the cylinder discriminating sensor 82, the accelerator pedal 7
6, the output signal of the load sensor 74 representing the depression amount L of the engine 6, the output signal of the water temperature sensor 68 representing the cooling water temperature Tw of the engine, the output signal of the fuel pressure sensor 70 representing the fuel pressure P in the accumulator 26, and the inside of the intake pipe 18. Temperature sensor 72 indicating the intake temperature Ta of the engine
Is input into the CPU 40 through the input port 46, and the engine speed N is calculated from the output signals of the rotation angle sensor 80 and the cylinder discrimination sensor 82. These engine speed N, depression amount L of accelerator pedal 76, cooling water temperature Tw, fuel pressure P, and intake air temperature Ta are stored in RAM 42 (step 100).

Next, the depression amount L of the accelerator pedal 76 is
, The injection amount τ is determined according to a map stored in the ROM 44 in advance (step 200). The injection amount τ is set to increase as the load increases.

Next, the engine speed N and the accelerator pedal 76
The injection timing is determined according to the map stored in advance in the ROM 44 from the depression amount L of the engine (step 30).
0).

The fuel injection pressure determined in step 400 will be described with reference to FIG. A reference injection pressure Pdb is determined from the engine speed N and the depression amount L of the accelerator pedal 76 according to a map stored in the ROM 44 in advance (step 401). Then, the ROM 44
The correction coefficient K is determined according to the graph of the correction coefficient for the load (the amount of depression L of the accelerator pedal 76) in FIG. This correction coefficient K
Is set to a negative value in a low / medium load range and a positive value in a high load range above a predetermined load. In the drawing, Ld is a boundary between the low / medium load region and the high load region. By multiplying the correction coefficient K by the intake air temperature Ta, a corrected injection pressure Pdc is obtained (step 403). As described above, the correction coefficient K is changed to the intake air temperature T.
Since the corrected injection pressure Pdc is obtained by multiplying by a, the absolute value of the corrected injection pressure Pdc increases as the intake air temperature Ta increases with the same rotation speed and the same load. The reason why the absolute value is described here is that the reference injection pressure Pdb is corrected to the low pressure side or corrected to the high pressure side depending on the load condition. The actual injection pressure Pd is determined from the sum of the reference injection pressure Pdb and the corrected injection pressure Pdc (step 404). Next, it is determined whether or not the absolute value of the difference between the fuel pressure P in the accumulator 26 and the actual injection pressure Pd is smaller than ΔP (step 40).
5). If the absolute value is larger than ΔP, the fuel pressure P is compared with the actual injection pressure Pd (Step 406). When the fuel pressure P is higher than the actual injection pressure Pd, the discharge amount of the fuel supply pump 30 is controlled by the pump discharge amount driving device 37 in the decreasing direction, the discharge pressure of the fuel supply pump 30 is reduced, and the pressure in the accumulator chamber 26 is reduced. The fuel pressure P decreases (step 40)
7). When the fuel pressure P is lower than the actual injection pressure Pd, the discharge amount of the fuel supply pump 30 is controlled in the increasing direction by the pump discharge amount driving device 37, so that the discharge pressure of the fuel supply pump 30 is increased and the pressure in the pressure accumulation chamber 26 is increased. The fuel pressure P increases (Step 408). If the absolute value is smaller than ΔP, the process ends. Thus, the fuel pressure P in the accumulator 26 is
Is maintained at the actual injection pressure Pd.

FIG. 7 is a diagram showing the relationship between the intake air temperature and the actual injection pressure in the low / medium load region according to the present invention when the same load and the same rotational speed are used. FIG. 8 shows the relationship when the same load and the same rotational speed are used. FIG. 4 is a diagram illustrating a relationship between an intake air temperature and an actual injection pressure in a high load region according to the present invention. Since the correction injection pressure Pdc is obtained by multiplying the correction coefficient K by the intake air temperature Ta as described above, the correction coefficient K becomes a negative value according to FIG. 6 in the low / medium load range, and the actual injection pressure Pd increases with the intake air temperature Ta. Is corrected to the low pressure side. In the high load region, the correction coefficient K becomes a positive value according to FIG. 6, and the actual injection pressure Pd is corrected to the high pressure side with the increase in the intake air temperature Ta.

As described above, according to the fuel injection control device for a diesel engine in the first embodiment of the present invention, in a high load region where the load detected by the load sensor 74 is equal to or more than a predetermined load, the intake temperature detected by the intake temperature sensor 72 is determined. Since the actual injection pressure Pd is increased by increasing the correction injection pressure Pdc with the rise of the temperature Ta and the fuel injection is performed, the atomization of the injected fuel is promoted even in a high load region where the fuel injection amount is large. The amount of air taken in by the fuel is increased, the combustion is improved, and the amount of generated black smoke and particulate matter is reduced. Although the amount of generated NOx is slightly increased by improving the combustion, the effect of reducing the amount of black smoke and particulate matter is greater.

In a low / medium load range below a predetermined load, the correction injection pressure Pdc is reduced by increasing the intake air temperature Ta detected by the intake air temperature sensor 72, the actual injection pressure Pd is reduced, and fuel injection is performed. Therefore, the atomization of the fuel is suppressed, the amount of air taken in by the fuel is reduced, and the combustion becomes slow, and
Ox generation is reduced. In addition, since the intake air amount is excessive when the load is less than the predetermined load in the diesel engine, the amount of generated black smoke and particulate matter hardly changes even if the intake air temperature changes.
It doesn't matter much in terms of quantity.

FIG. 9 is a graph showing a correction coefficient with respect to the load (the amount of depression L of the accelerator pedal 76) according to the second embodiment of the present invention. The correction coefficient K is set to a negative value in a low load range, zero in a middle load range, and a positive value in a high load range above a predetermined load. In the drawing, Lc is a boundary between the low load region and the medium load region, and Ld is a boundary between the middle load region and the high load region. The other configuration is the same as that of the first embodiment, and the operation is the same as that of the first embodiment except that the reference injection pressure Pdb is not corrected in the middle load range.

FIG. 10 is a graph showing a correction coefficient with respect to the load (the amount of depression L of the accelerator pedal 76) according to the third embodiment of the present invention. The correction coefficient K is set to a negative value in a low / medium load range and a positive value in a high load range above a predetermined load, and has a slope with respect to the load. In the drawing, Ld is a boundary between the low / medium load region and the high load region. Other configurations and operations are the same as those of the first embodiment.

In the above embodiment, the intake air temperature T
Although a is used, the reference injection pressure Pdb may be corrected with a temperature change similar to the change in the intake air temperature Ta. For example, the intake pipe temperature, the atmospheric temperature, the engine cooling water temperature, etc. may be detected to estimate the intake air temperature, or the atmospheric pressure and the intake pressure may be detected and interpolated with each other to improve the accuracy.

[0021]

According to the present invention, when the load of the diesel engine is higher than a predetermined load, the fuel injection pressure control means is provided with a second correction means for correcting the fuel injection pressure to a high pressure side with an increase in the intake air temperature. Therefore, when the load is higher than a predetermined load, that is, in a region where the fuel injection amount is large with respect to the intake air amount, the fuel injection pressure increases with an increase in the intake air temperature, and the atomization of the fuel is promoted and the air intake amount of the fuel is increased. Increase. Therefore, since the combustion becomes good, the amount of black smoke and particulate matter generated can be reduced.

Further, when the load of the diesel engine is a low / medium load less than a predetermined load, the fuel injection pressure control means has a first correction means for correcting the fuel injection pressure to a low pressure side with an increase in the intake air temperature. Therefore, at low / medium loads below a predetermined load, that is, in a region where the fuel injection amount is small with respect to the intake air amount, the fuel injection pressure decreases with the intake air temperature rise, fuel atomization is suppressed, and fuel Air intake is reduced. Therefore,
Combustion becomes slow and the amount of generated NOx can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating the configuration of the present invention.

FIG. 2 is a configuration diagram of a diesel engine according to the present invention.

FIG. 3 is a side sectional view of a diesel engine.

FIG. 4 is a flowchart showing a main routine.

FIG. 5 is a flowchart for controlling a fuel injection pressure.

FIG. 6 is a graph of a correction coefficient with respect to a load in the first embodiment of the present invention.

FIG. 7 is a diagram showing a relationship between intake air temperature and actual injection pressure in a low / medium load region according to the first embodiment of the present invention.

FIG. 8 is a diagram showing a relationship between intake air temperature and actual injection pressure in a high load region according to the first embodiment of the present invention.

FIG. 9 is a graph of a correction coefficient with respect to a load in the second embodiment of the present invention.

FIG. 10 is a graph of a correction coefficient with respect to a load in the third embodiment of the present invention.

[Explanation of symbols]

 2 ... diesel engine body 16 ... fuel injection valve 22, 28 ... fuel supply pipe 26 ... pressure accumulating chamber 30 ... fuel supply pump 37 ... pump discharge amount driving device 38 ... electronic Control device 70: fuel pressure sensor 72: intake air temperature sensor 74: load sensor

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-5474 (JP, A) JP-A-63-266149 (JP, A) JP-A-59-138737 (JP, A) JP-A-4- 350343 (JP, A) JP-A-62-168941 (JP, A) JP-A-4-246261 (JP, A) JP-A-63-124845 (JP, A) JP-A-60-162053 (JP, A) JP-A-3-275977 (JP, A) JP-A-3-9050 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02D 41/38 F02D 41/04 395

Claims (1)

(57) [Claims] A load detecting means for detecting a load state of the engine; a fuel injection amount controlling means for increasing a fuel injection amount supplied to the engine in accordance with a load increase detected by the load detecting means; and detecting an intake air temperature. Intake temperature detection means, a fuel injection pressure control means for controlling the fuel injection pressure, and a fuel injection means for injecting fuel based on the output of the fuel injection pressure control means and the fuel injection amount control means, In a fuel injection control device for a diesel engine, the fuel injection pressure control unit includes a first correction unit that corrects a fuel injection pressure to a low pressure side in accordance with an increase in intake air temperature detected by the intake air temperature detection unit. When the detected load is a high load equal to or higher than a predetermined load, the second correction means for correcting the fuel injection pressure to a high pressure side in accordance with an increase in the intake air temperature detected by the intake air temperature detection means is provided. The fuel injection control apparatus for a diesel engine, characterized in that provided in the fuel injection pressure control means.