JP2007332912A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine, capable of improving drivabiliy by surely preventing engine failure or the like at the time of starting without giving a sense of incongruity to a driver. <P>SOLUTION: When a diesel engine 10 is in an idle state, whether a clutch pedal is operated or not is determined (step 102). When operation of the clutch pedal is detected, or presence of a starting intention is determined, a requested actual compression ration is calculated based on intake air temperature, cooling water temperature or the like (step 104). The requested actual compression ratio is set higher than an actual compression ratio in general idling. A valve timing of an intake valve 52 such that the requested actual compression ratio can be attained is calculated (step 106). An intake variable valve system 54 is controlled so that the actual valve timing becomes the target valve timing (step 108). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine.

  In an automobile with a manual transmission, when starting, a driver creates a so-called half-clutch state by operating an accelerator pedal and a clutch pedal, and then the clutch is brought into a connected state. Depending on the manner of operation during this time, an engine stall (hereinafter referred to as “engine stall”) may occur. Therefore, techniques for reliably preventing engine stall at the time of starting have been studied.

  For example, Japanese Patent Application Laid-Open No. 8-277729 discloses a technique for preventing deterioration of combustion by reducing the amount of internal EGR by reducing the valve overlap at the time of starting, thereby reliably preventing engine stall. ing. Although not the engine stall, Japanese Patent Laid-Open No. 5-71373 discloses a technique for preventing the occurrence of knocking in an internal combustion engine equipped with a compression ratio switching mechanism by lowering the compression ratio at the time of starting. ing. These two technologies are considered mainly for gasoline engine vehicles.

Japanese Patent Laid-Open No. 5-71373 JP-A-8-277729 JP 2000-154739 A JP 2002-130017 A JP 2005-127277 A

  On the other hand, in the case of a diesel engine vehicle in recent years, there are the following circumstances when starting. Currently, exhaust gas regulations for diesel engine vehicles are becoming extremely strict. In order to meet such strict regulations, in recent diesel engine vehicles, combustion is made as slow as possible during idling when power is not required. This is because NOx emissions are suppressed by slowing down the combustion. As a method of slowing down combustion during idling, a method of performing a large amount of exhaust gas recirculation (EGR) is usually employed.

  In such a recent diesel engine vehicle, the following situation occurs when starting. In an idle state where a large amount of EGR is performed, the ratio of EGR gas in the cylinder is large. When starting, in order to allow a large amount of fuel to burn in the cylinder, it is necessary to reduce the amount of EGR gas in the cylinder and increase the amount of air. However, when a large amount of EGR is being performed, a large amount of exhaust gas exists in the intake system. For this reason, even after the EGR valve of the EGR passage is closed, the exhaust gas remaining in the intake system continues to flow into the cylinder for a while, so the amount of air in the cylinder does not increase immediately. Therefore, when connecting the clutch at the time of starting, it becomes difficult to burn the required amount of fuel in the cylinder. As a result, the torque tends to be insufficient at the time of starting and tends to be stalled.

  Conventionally, in order to prevent the engine stall as described above, when the clutch pedal is depressed during idling, the engine speed (idle speed) is controlled to increase in preparation for starting. Has been done. However, since the engine speed increases unintentionally immediately after the clutch pedal is depressed, it is easy for the driver to feel uncomfortable (surprise).

  The present invention has been made in view of the above points, and is an internal combustion engine that can reliably prevent engine stall and the like and can improve drivability without causing the driver to feel uncomfortable when starting. An object of the present invention is to provide a control device.

In order to achieve the above object, a first invention is a control device for an internal combustion engine,
An apparatus for controlling an internal combustion engine mounted on a vehicle,
A start preparation operation detecting means for detecting a start preparation operation performed with the intention of the driver to start the vehicle;
In-cylinder temperature raising means for starting in-cylinder temperature raising control for increasing the in-cylinder temperature in the vicinity of the compression top dead center when compared with that during normal idling when a predetermined start preparation operation is detected,
It is characterized by providing.

The second invention is the first invention, wherein
The internal combustion engine is controlled so that the engine speed does not change before and after the start of the in-cylinder temperature rise control.

The third invention is the first or second invention, wherein
The predetermined start preparation operation includes depression of a clutch pedal.

According to a fourth invention, in any one of the first to third inventions,
The predetermined start preparation operation includes switching from an unstartable gear position to a startable gear position.

According to a fifth invention, in any one of the first to fourth inventions,
The predetermined start preparation operation includes release of a parking brake.

According to a sixth invention, in any one of the first to fifth inventions,
An actual compression ratio varying means for varying the actual compression ratio of the internal combustion engine;
The in-cylinder temperature raising means controls the actual compression ratio variable means so that the actual compression ratio becomes higher than that during normal idling when the in-cylinder temperature raising control is executed, thereby providing a cylinder near the compression top dead center. The internal temperature is raised.

According to a seventh invention, in any one of the first to fifth inventions,
A variable valve mechanism for varying at least the closing timing of the intake valve of the internal combustion engine;
The in-cylinder temperature raising means controls the variable valve mechanism so that when the in-cylinder temperature raising control is executed, the closing timing of the intake valve is closer to the bottom dead center than during normal idling. By raising the value, the in-cylinder temperature near the compression top dead center is raised.

The eighth invention is the sixth or seventh invention, wherein
Vehicle load information acquisition means for acquiring vehicle load information related to a load when starting the vehicle;
Control amount determination means for determining a control amount related to the degree of increase in the actual compression ratio when increasing the actual compression ratio in the in-cylinder temperature rise control, based on the vehicle load information;
It is further provided with the feature.

According to a ninth invention, in any of the sixth to eighth inventions,
The required actual compression ratio when increasing the actual compression ratio in the in-cylinder temperature rise control based on at least one of the cooling water temperature of the internal combustion engine, the intake air temperature, and vehicle load information related to the load when starting the vehicle Required actual compression ratio calculating means for calculating
When the required actual compression ratio exceeds a predetermined maximum actual compression ratio, the engine speed is increased as compared with that during normal idling according to the deviation between the required actual compression ratio and the maximum actual compression ratio. Idle up means to perform,
Is further provided.

The tenth invention is the ninth invention, wherein
The start preparation operation detecting means is capable of detecting a first start preparation operation and a second start preparation operation performed after the first start preparation operation,
When the required actual compression ratio exceeds the maximum actual compression ratio, the in-cylinder temperature raising means starts the in-cylinder temperature raising control on the condition that the first start preparation operation is detected, The idle up means starts the idle up on the condition that the second start preparation operation is detected,
If the required actual compression ratio is less than or equal to the maximum actual compression ratio, the in-cylinder temperature raising means starts the in-cylinder temperature raising control on condition that the second start preparation operation is detected. It is characterized by.

The eleventh aspect of the invention is the tenth aspect of the invention,
The first start preparation operation is depression of a clutch pedal, and the second start preparation operation is release of a parking brake or switching from a gear position where starting is impossible to a gear position where starting is possible. Features.

According to a twelfth aspect of the invention, any one of the first to fifth aspects of the invention,
An EGR device that performs external EGR to recirculate exhaust gas in the exhaust passage of the internal combustion engine to the intake passage;
Internal EGR amount varying means for varying the amount of internal EGR that is EGR inside the internal combustion engine;
Further comprising
The in-cylinder temperature raising means controls the EGR device and the internal EGR amount variable means so that the ratio of the internal EGR amount to the total EGR amount is larger than that during normal idling when the in-cylinder temperature raising control is executed. By doing this, the in-cylinder temperature near the compression top dead center is raised.

The thirteenth aspect of the invention is any one of the first to twelfth aspects of the invention.
The internal combustion engine is a diesel engine;
An EGR device for recirculating exhaust gas in the exhaust passage of the diesel engine to the intake passage;
An EGR control device that performs external EGR by the EGR device during idling;
Is further provided.

  According to the first aspect of the present invention, it is possible to detect a start preparation operation performed with the intention of the driver to start the vehicle. For this reason, the start can be predicted in advance. When a predetermined start preparation operation is detected, the in-cylinder temperature near the compression top dead center can be made higher than that during normal idling. Therefore, even when a start is started and a large amount of fuel is injected, misfire hardly occurs and the fuel can be sufficiently burned. That is, a large torque can be generated when starting. For this reason, engine stall can be reliably prevented. Further, even if the in-cylinder temperature near the compression top dead center is increased, the engine sound and the engine vibration hardly change, so the driver is unlikely to notice it. Therefore, it is possible to avoid making the driver feel uncomfortable. Furthermore, according to the first invention, the in-cylinder temperature rise control is not started until a predetermined start preparation operation is detected, so that the in-cylinder temperature can be kept low. For this reason, the amount of NOx emission during idling can be sufficiently reduced.

  According to the second invention, the internal combustion engine can be controlled so that the engine speed does not change before and after the start of the in-cylinder temperature raising control. For this reason, since it can prevent more reliably that an engine sound and an engine vibration change immediately before starting, it can prevent more reliably that a driver feels uncomfortable.

  According to the third aspect of the present invention, the in-cylinder temperature raising control can be prevented from starting until at least the clutch pedal is depressed. For this reason, the amount of NOx emission during idling can be sufficiently reduced. In addition, since the clutch pedal is always stepped on before starting, the in-cylinder temperature raising control can be surely started at the time of starting.

  According to the fourth aspect of the present invention, the in-cylinder temperature raising control can be prevented from starting until the gear position is shifted from a gear position that cannot start to a gear position that can start. For this reason, the amount of NOx emission during idling can be sufficiently reduced. Further, since the gear shift is always performed before starting, in-cylinder temperature raising control can be surely started at the time of starting.

  According to the fifth aspect, the in-cylinder temperature rise control can be prevented from starting until at least the parking brake is released. For this reason, the amount of NOx emission during idling can be sufficiently reduced. In addition, since the parking brake is always released before starting, the in-cylinder temperature raising control can be surely started at the time of starting.

  According to the sixth aspect, when the in-cylinder temperature rise control is executed, the in-cylinder temperature near the compression top dead center can be raised by making the actual compression ratio higher than that during normal idling. Therefore, the in-cylinder temperature near the compression top dead center can be reliably and sufficiently increased immediately before starting. As a result, engine stall can be prevented more reliably.

  According to the seventh invention, when the in-cylinder temperature rise control is executed, the actual compression ratio is increased by controlling the variable valve mechanism so that the closing timing of the intake valve is closer to the bottom dead center than during normal idling. Thus, the in-cylinder temperature near the compression top dead center can be raised. Therefore, the in-cylinder temperature near the compression top dead center can be reliably and sufficiently increased immediately before starting. As a result, engine stall can be prevented more reliably. In addition, since this effect can be obtained by using a variable valve mechanism, the structure of the internal combustion engine is not complicated.

  According to the eighth aspect of the invention, it is possible to acquire vehicle load information related to the load when starting the vehicle. And the control amount regarding the raise degree of an actual compression ratio at the time of making an actual compression ratio high in in-cylinder temperature rising control can be determined based on the vehicle load information. For this reason, even when the vehicle load is large, the engine stall can be prevented more reliably.

  According to the ninth aspect, the required actual compression ratio in the in-cylinder temperature rise control is calculated based on at least one of the coolant temperature, the intake air temperature, and the vehicle load information, and the required actual compression ratio is the maximum actual compression ratio. When exceeding, it is possible to perform idling up in which the engine speed is made higher than that during normal idling according to the deviation between the two. According to the ninth aspect of the invention, when the vehicle load is particularly large and the required actual compression ratio exceeds the maximum actual compression ratio, idle up can be used together. The engine stall can be prevented more reliably. In that case, control is performed so that the required minimum idle increase amount is obtained according to the deviation between the required actual compression ratio and the maximum actual compression ratio, so that the amount of change in engine sound and engine vibration immediately before starting is minimized. It can be kept in. Therefore, it is possible to suppress the driver from feeling uncomfortable.

  According to the tenth aspect, the first start preparation operation and the second start preparation operation performed after that can be detected. When the required actual compression ratio exceeds the maximum actual compression ratio, the in-cylinder temperature rise control is started on the condition that the first start preparation operation is detected, and the second start preparation operation is detected. Idle up can be started on the condition. For this reason, according to the tenth aspect, when performing idle up, the timing of performing idle up can be delayed. Therefore, it is possible to more reliably suppress the driver from feeling uncomfortable due to idle-up, and to minimize an increase in emissions such as NOx. Furthermore, when the required actual compression ratio exceeds the maximum actual compression ratio, that is, when the vehicle load is large, the start timing of the in-cylinder temperature rise control can be made relatively early. That is, when the vehicle load is large, the in-cylinder temperature rise control can be performed from a relatively early stage after the start is predicted, and the in-cylinder temperature can be sufficiently increased. For this reason, it is possible to reliably create a state in which the fuel is easily combusted immediately before the start, so that the engine stall at the start can be more reliably prevented. On the other hand, according to the tenth aspect, when the required actual compression ratio is equal to or less than the maximum actual compression ratio, the in-cylinder temperature rise control can be started on the condition that the second start preparation operation is detected. it can. For this reason, when the required actual compression ratio does not exceed the maximum actual compression ratio, that is, when the vehicle load is not so large, the start timing of the in-cylinder temperature rise control can be delayed. If the vehicle load is not so large, the possibility of engine stall is small even if the in-cylinder temperature rise control is not performed from an early timing. Thus, the NOx emission amount can be further reduced by delaying the start timing of the in-cylinder temperature raising control as much as possible.

  According to the eleventh aspect of the invention, the first start preparation operation is a depression of the clutch pedal, and the second start preparation operation is a release of the parking brake or from a gear position where the start is impossible to a gear position where the start is possible. It can be switched. For this reason, in-cylinder temperature rise control and idle-up can be started at appropriate timings.

  According to the twelfth aspect, when the in-cylinder temperature rise control is performed, the ratio of the internal EGR amount to the total EGR amount is larger than that during normal idling, so that the in-cylinder temperature near the compression top dead center. Can be raised. Therefore, the in-cylinder temperature near the compression top dead center can be reliably and sufficiently increased immediately before starting. As a result, engine stall can be prevented more reliably.

  According to the thirteenth aspect, external EGR can be performed when the diesel engine is idling. For this reason, the amount of NOx emission during idling can be extremely reduced. According to the thirteenth invention, even in such a diesel engine, the engine stall can be reliably prevented and the driver can be prevented from feeling uncomfortable.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted.

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. The system shown in FIG. 1 includes a four-cycle diesel engine 10. The diesel engine 10 is mounted on a vehicle (not shown), and drives the drive shaft of the vehicle via a manual transmission (not shown). Although the illustrated diesel engine 10 is an in-line four-cylinder type, in the present invention, the number of cylinders and the cylinder arrangement are not limited thereto.

  Moreover, although this embodiment demonstrates the case where this invention is applied to control of a diesel engine (compression ignition internal combustion engine), this invention is not limited to control of a diesel engine, A gasoline engine (spark ignition) Internal combustion engine) It can be applied to control of various other internal combustion engines.

  Each cylinder of the diesel engine 10 is provided with an injector 12 that injects fuel directly into the cylinder. The injectors 12 of each cylinder are connected to a common common rail 14. In the common rail 14, high-pressure fuel pressurized by the supply pump 16 is stored. Then, fuel is supplied from the common rail 14 to each injector 12.

  An exhaust passage 18 of the diesel engine 10 is branched by an exhaust manifold 20 and connected to an exhaust port 22 (see FIG. 2) of each cylinder. The diesel engine 10 according to this embodiment includes a turbocharger 24. The exhaust passage 18 is connected to the exhaust turbine of the turbocharger 24.

  An exhaust purification device 26 that purifies exhaust gas is provided in the exhaust passage 18 downstream of the turbocharger 24. As the exhaust purification device 26, for example, one of an oxidation catalyst, a NOx storage reduction type or selective reduction type NOx catalyst, a DPF (Diesel Particulate Filter), a DPNR (Diesel Particulate-NOx-Reduction system), or a combination thereof Etc. can be used.

  An air cleaner 30 is provided near the inlet of the intake passage 28 of the diesel engine 10. The air drawn through the air cleaner 30 is compressed by the intake compressor of the turbocharger 24 and then cooled by the intercooler 32. The intake air that has passed through the intercooler 32 is distributed by the intake manifold 34 to the intake ports 35 (see FIG. 2) of the respective cylinders.

  An intake throttle valve 36 is installed between the intercooler 32 and the intake manifold 34 in the intake passage 28. Further, an air flow meter 38 for detecting the amount of intake air is installed in the vicinity of the intake passage 28 downstream of the air cleaner 30.

  One end of the external EGR passage 40 is connected to the exhaust passage 18 in the vicinity of the exhaust manifold 20. The other end of the external EGR passage 40 is connected to the vicinity of the intake manifold 34 of the intake passage 28. In this system, a part of the exhaust gas (burned gas) in the exhaust passage 18 can be recirculated to the intake passage 28 through the external EGR passage 40, that is, external EGR (Exhaust Gas Recirculation) can be performed. Hereinafter, the exhaust gas recirculated through the external EGR passage 40 is referred to as “external EGR gas”.

  In the middle of the external EGR passage 40, an EGR cooler 42 for cooling the external EGR gas is provided. An EGR valve 44 is provided downstream of the EGR cooler 42 in the external EGR passage 40. When the opening degree of the EGR valve 44 is increased, the amount of exhaust gas passing through the external EGR passage 40, that is, the amount of external EGR can be increased. Conversely, if the opening degree of the EGR valve 44 is reduced, the amount of external EGR can be reduced.

  In this system, the external EGR amount and the external EGR rate (the ratio of the external EGR gas in the gas flowing into the cylinder) are determined not only by the opening degree of the EGR valve 44 but also by the opening degree of the intake throttle valve 36. Can be adjusted. When the opening of the intake throttle valve 36 is reduced to throttle the intake air, the intake pressure decreases, so the differential pressure from the back pressure (exhaust pressure) increases. That is, the differential pressure before and after the external EGR passage 40 is increased, and the external EGR gas flows more easily. For this reason, the external EGR amount and the external EGR rate can be increased. Conversely, when the opening degree of the intake throttle valve 36 is increased, the external EGR amount and the external EGR rate are decreased.

  An intake pressure sensor 46 that detects the intake pressure is installed downstream of the intake throttle valve 36 in the intake passage 28. Furthermore, the system of the present embodiment includes an accelerator opening sensor 48 that detects the amount of depression of the accelerator pedal (accelerator opening) of a vehicle on which the diesel engine 10 is mounted, and a clutch pedal sensor 66 that detects depression of the clutch pedal. It has.

  The system includes an ECU (Electronic Control Unit) 50. The ECU 50 is connected to the various sensors and actuators described above. ECU50 controls the driving | running state of the diesel engine 10 by driving each actuator according to a predetermined program based on the signal from each sensor.

  FIG. 2 is a view showing a cross section of one cylinder of the diesel engine 10 in the system shown in FIG. Hereinafter, the diesel engine 10 will be further described. As shown in FIG. 2, a crank angle sensor 62 that detects the rotation angle (crank angle) of the crankshaft 60 is attached in the vicinity of the crankshaft 60 of the diesel engine 10. The crank angle sensor 62 is connected to the ECU 50. According to the signal from the crank angle sensor 62, the engine speed and the like can be detected. Further, a cooling water temperature sensor 68 for detecting the cooling water temperature is attached to the diesel engine 10.

  Further, the diesel engine 10 is provided with an intake variable valve mechanism 54 that drives the intake valve 52. The intake variable valve mechanism 54 is connected to the ECU 50. In the present embodiment, the intake variable valve mechanism 54 continuously varies the phase of a cam (not shown) that drives the intake valve 52, thereby opening the valve opening phase (opening timing and closing timing) of the intake valve 52. ) Is continuously variable. In the first embodiment, the intake variable valve mechanism 54 may be any mechanism that continuously varies at least the closing timing of the intake valve 52. That is, only the closing timing may be made variable while the opening timing of the intake valve 52 remains unchanged. Further, the intake variable valve mechanism 54 may be capable of changing the lift amount and operating angle of the intake valve 52. The specific configuration of the intake variable valve mechanism 54 is not particularly limited. For example, a mechanical mechanism using various cam mechanisms, an electromagnetically driven valve that can be opened and closed at an arbitrary timing, a hydraulically driven valve, or the like is used. be able to.

[Features of Embodiment 1]
(Slow combustion control during idling)
When the diesel engine 10 is idling, the slow combustion control is performed to make the combustion as slow as possible. In the slow combustion control during idling, a large amount of exhaust gas (external EGR gas) is recirculated to the intake passage 28 through the EGR passage 40. This slows down combustion and lowers the combustion temperature,
The amount of NOx emission can be extremely reduced.

  While the vehicle is stopped, the diesel engine 10 is in an idle state with slow combustion control as described above. In this state, since a large amount of exhaust gas (EGR gas) exists in the cylinder, the amount of air in the cylinder is small. For this reason, at the time of starting when the torque of the diesel engine 10 is required, it is necessary to increase the amount of air in the cylinder so that a large amount of fuel can be combusted in the cylinder. Therefore, when the accelerator pedal is depressed from the idle state, the EGR valve 44 is closed (the opening degree is reduced), and control is performed to reduce the EGR amount.

  However, a large amount of exhaust gas is present in the intake passage 28 (intake manifold 34, intake port 28, etc.) in a state where a large amount of EGR is performed as in the idle state with the slow combustion control. For this reason, even after the EGR valve 44 is closed, the exhaust gas remaining in the intake passage 28 continues to flow into the cylinder for a while, so the amount of air in the cylinder does not increase immediately. Therefore, during this time, even if a large amount of fuel is injected from the injector 12, the fuel cannot be completely burned in the cylinder, so that sufficient torque cannot be obtained. As a result, the engine speed tends to drop when the clutch is engaged (so-called half-clutch state), and the engine tends to become stalled.

(In-cylinder temperature rise control by increasing actual compression ratio)
In order to reliably prevent the engine stall at the time of starting as described above, in this embodiment, when it is detected that the clutch pedal is depressed during idling, the in-cylinder temperature near the compression top dead center is set to normal idling. In-cylinder temperature rise control was made to be higher than the hour. FIG. 3 is a diagram for explaining the lift characteristics of the intake valve 52 during the in-cylinder temperature rise control.

  The solid line graph in FIG. 3 is the lift curve of the intake valve 52 during normal idling. In the present embodiment, at the time of normal idling, the closing timing (IVC) of the intake valve 52 is after the bottom dead center (BDC). On the other hand, the broken line graph in FIG. 3 is the lift curve of the intake valve 52 during the in-cylinder temperature rise control. As shown in the lift curve, at the time of in-cylinder temperature rise control, the valve timing of the intake valve 52 is advanced, and the closing timing of the intake valve 52 is controlled to approach the bottom dead center.

  The compression stroke starts substantially when the intake valve 52 is closed. For this reason, when the closing timing of the intake valve 52 approaches the bottom dead center, the substantial compression stroke becomes longer, so that the substantial compression ratio (hereinafter referred to as “actual compression ratio”) increases. When the actual compression ratio increases, the temperature and pressure in the cylinder increase when the piston 64 is near the compression top dead center, that is, when fuel is injected from the injector 12.

  The ease of fuel ignition is greatly affected by the temperature and pressure in the cylinder near the compression top dead center. That is, the higher the temperature near the compression top dead center, the easier it is to ignite (less misfire), and the higher the pressure near the compression top dead center, the easier it is to ignite (hard to misfire).

  For this reason, when the in-cylinder temperature rise control is performed, even when a large amount of fuel is injected as compared with the case of normal idling, misfire is unlikely to occur and combustion can be sufficiently performed. For this reason, when starting, a larger torque can be generated, so that engine stall can be reliably prevented.

  In the present embodiment, as shown in FIG. 3, it is assumed that the closing timing of the intake valve 52 is after the bottom dead center at the time of normal idling, but the closing timing of the intake valve 52 at the time of normal idling is It may be before the bottom dead center. In this case, at the time of in-cylinder temperature rise control, the actual compression ratio can be increased by delaying the closing timing of the intake valve 52 to approach the bottom dead center.

  Further, when the in-cylinder temperature rise control is performed, the in-cylinder temperature near the compression top dead center is increased, and the combustion temperature is increased accordingly. For this reason, the NOx emission amount is slightly increased as compared with normal idling. In view of this, in the present embodiment, the in-cylinder temperature rise control is not performed until the depression of the clutch pedal is detected, that is, until the driver's intention to start the vehicle is detected. I am going to do that. For this reason, the effect of preventing engine stall can be obtained while keeping the NOx emission amount low.

  Further, in the present embodiment, it is assumed that operating conditions (for example, fuel injection amount, fuel injection timing, etc.) are controlled so that the engine speed does not change before and after the start of in-cylinder temperature raising control. In other words, even after the in-cylinder temperature raising control is started, the engine speed is controlled to maintain the normal idle speed until the accelerator pedal is depressed. As a result, a phenomenon in which the engine speed increases without the driver depressing the accelerator pedal does not occur, and the driver can be prevented from feeling uncomfortable.

[Specific Processing in Embodiment 1]
FIG. 4 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. According to the routine shown in FIG. 4, it is first determined whether or not the diesel engine 10 is in an idle state (step 100). If it is not in the idle state, it is not necessary to perform the control of the present embodiment, so the following processing is not executed.

  If it is determined in step 100 that the engine is in the idle state, it is then determined whether or not the clutch pedal is depressed based on the signal from the clutch pedal sensor 66 (step 102). When the clutch pedal is not depressed, it can be determined that the driver does not intend to start. For this reason, in this case, the following processing is not yet performed.

  On the other hand, if it is detected in step 102 that the clutch pedal has been depressed, it can be determined that the driver has an intention to start, and that an operation for starting the vehicle is performed immediately thereafter. In this case, an optimal actual compression ratio (required actual compression ratio) is first calculated to execute the in-cylinder temperature rise control (step 104). Here, for example, based on the intake air temperature detected by the intake air temperature sensor 46 and the cooling water temperature detected by the cooling water temperature sensor 68, the required actual compression ratio to be executed in the in-cylinder temperature increase control is calculated. The ECU 50 stores in advance a map that defines the relationship between the required actual compression ratio, the intake air temperature, the coolant temperature, and the like. When the intake air temperature or the cooling water temperature is low, the fuel tends to hardly burn, so it is preferable to further increase the actual compression ratio accordingly. Therefore, in step 104, by referring to the map, the required actual compression ratio is calculated to be higher as the intake air temperature or the cooling water temperature is lower.

  Subsequently, the valve timing of the intake valve 52 is calculated such that the required actual compression ratio calculated in step 104 is reached (step 106). The ECU 50 stores in advance a map that defines the relationship between the actual compression ratio and the valve timing (closing timing) of the intake valve 52. In step 106, the valve timing of the intake valve 52 corresponding to the required actual compression ratio is calculated by referring to the map.

  Thus, when the target valve timing of the intake valve 52 in the in-cylinder temperature rise control is calculated, the intake variable valve mechanism 54 is then controlled so that the actual valve timing becomes the target valve timing. (Step 108). As a result, the actual compression ratio of the diesel engine 10 becomes higher than that during normal idling, so both the temperature and pressure near the compression top dead center are increased. For this reason, when the accelerator pedal is depressed and the fuel injection amount is increased, the fuel can be burned satisfactorily without causing misfire or a state close thereto. Therefore, since sufficient torque can be generated, it is possible to reliably prevent engine stall when the clutch is engaged.

  Further, as described above, when the actual compression ratio is increased by the in-cylinder temperature rise control, the engine speed is controlled so as not to change. For this reason, there is no change in engine sound or engine vibration, so that the driver does not feel uncomfortable.

  By the way, in Embodiment 1 described above, during the in-cylinder temperature rise control, the actual compression ratio is increased by bringing the closing timing of the intake valve 52 close to the bottom dead center. However, a method for increasing the actual compression ratio is described below. However, it is not limited to such a method. For example, the actual compression ratio may be increased by using a variable compression ratio mechanism that changes the compression ratio by changing the height of the piston 64 or the height of the cylinder block.

  In the first embodiment described above, the depression of the clutch pedal is the “predetermined start preparation operation” in the first invention, and the clutch pedal sensor 66 is the “start preparation operation detecting means” in the first invention. The intake variable valve mechanism 52 corresponds to the “actual compression ratio variable means” in the sixth aspect of the present invention. Further, the “in-cylinder temperature raising means” in the first, sixth, and seventh inventions is realized by the ECU 50 executing the processing of steps 104 to 108 described above.

Embodiment 2. FIG.
Next, the second embodiment of the present invention will be described with reference to FIG. 5 and the like. However, the difference from the above-described first embodiment will be mainly described, and the description of the same matters will be simplified. Or omitted. The present embodiment can be realized by causing the ECU 50 to execute a routine shown in FIG. 5 described later instead of the routine shown in FIG. 4 described above, using the hardware configuration shown in FIGS. 1 and 2. it can.

[Features of Embodiment 2]
In the first embodiment described above, when the clutch pedal is depressed during idling, it is determined that the driver is willing to start and in-cylinder temperature rise control is started. On the other hand, in the present embodiment, in addition to the depression of the clutch pedal, when it is detected that the manual transmission is shifted from the neutral state to the gear position where it can start, or in addition to them Thus, when it is further detected that the parking brake is released, the in-cylinder temperature raising control is started.

  In order to realize the above function, the system of the present embodiment detects a gear position sensor 70 that detects the gear position of a manual transmission mounted on the vehicle, and detects whether the parking brake is in an engaged state or a released state. It is assumed that a parking brake sensor 72 is further provided (see FIG. 1).

[Specific Processing in Second Embodiment]
FIG. 5 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. In FIG. 5, the same steps as those shown in FIG. 4 are denoted by the same reference numerals, and the description thereof is omitted or simplified. The routine shown in FIG. 5 is the same as the routine shown in FIG. 4 except that step 102 is replaced with step 110.

  According to the routine shown in FIG. 5, when the diesel engine 10 is in an idle state, it is determined whether or not the driver intends to start (step 110). Specifically, when it is detected that the clutch pedal is depressed and the gear position is shifted to a startable gear position, it is determined that there is an intention to start, otherwise, It is determined that there is no intention to start. As the gear positions at which the vehicle can start, for example, only the first speed and reverse may be used, or all gear positions other than neutral may be used.

  In step 110, when it is further detected that the parking brake has been released in addition to the depression of the clutch pedal and the shift to a gear position where the vehicle can start, it is determined that there is an intention to start. Otherwise, it may be determined that there is no intention to start.

  If it is determined in step 110 that there is an intention to start, in-cylinder temperature increase control for increasing the actual compression ratio is started as in the first embodiment (steps 104 to 108).

  According to the routine processing shown in FIG. 5, the start timing of the in-cylinder temperature raising control can be further delayed from that of the first embodiment, and can be brought closer to the actual start time (accelerator pedal depression start timing). When the actual compression ratio increases due to the start of the in-cylinder temperature rise control, engine noise and engine vibration may change somewhat. Even in such a case, the driver does not feel uncomfortable if the change in engine sound or engine vibration is almost the same time as the depression of the accelerator pedal. For this reason, according to this embodiment, the discomfort felt by the driver can be further reduced.

  Further, according to the present embodiment, the start timing of the in-cylinder temperature raising control can be delayed as much as possible. That is, until that time, the normal idling state in which the amount of NOx emission is extremely small can be maintained. For this reason, the NOx emission amount can be further reduced as compared with the first embodiment.

  In the second embodiment described above, the depression of the clutch pedal, switching from the neutral (gear position where the vehicle cannot start) to the gear position where the vehicle can start, and the release of the parking brake are the “predetermined” in the first invention. The clutch pedal sensor 66, the gear position sensor 70, and the parking brake sensor 72 correspond to the “start preparation operation detecting means” in the first aspect of the invention.

Embodiment 3 FIG.
Next, the third embodiment of the present invention will be described with reference to FIG. 6 and the like. The description will focus on the differences from the first and second embodiments described above, and the same matters will be described. Simplify or omit. This embodiment is realized by causing the ECU 50 to execute a routine shown in FIG. 6 described later instead of the routine shown in FIG. 4 or FIG. 5 described above, using the hardware configuration shown in FIG. 1 and FIG. can do.

[Features of Embodiment 3]
When starting on an uphill road, more torque of the diesel engine 10 is required than when starting on a flat ground. For this reason, in order to more reliably prevent the engine stall when starting on an uphill road, it is desirable that the diesel engine 10 be in a state capable of generating a larger torque than on a flat ground. Therefore, in the present embodiment, an uphill gradient is detected, and the required actual compression ratio at the time of in-cylinder temperature rise control is increased as the uphill gradient is larger.

  In the present embodiment, the uphill slope is detected based on the vehicle posture. In order to enable detection of the vehicle posture, the system of this embodiment includes a front suspension sensor 74 that detects the amount of depression of the front suspension of the vehicle, and a rear suspension sensor 76 that detects the amount of depression of the rear suspension. It is further assumed that it is provided (see FIG. 1). In the present invention, the method of detecting the uphill slope is not limited to the above method, and any method may be used.

[Specific Processing in Embodiment 3]
FIG. 6 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. In FIG. 6, the same steps as those shown in FIG. 4 or 5 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  According to the routine shown in FIG. 6, when the diesel engine 10 is in an idle state, it is determined whether or not the driver intends to start (step 110). The processing in step 110 is the same as that in the second embodiment. If it is determined that there is an intention to start, next, a process of estimating an uphill slope is performed based on the vehicle posture (step 112). Specifically, the sinking amounts of the front and rear suspensions are detected, and the climbing slope is determined to be stiffer as the rear suspension sinks more than the front.

  Subsequently, the required actual compression ratio to be performed in the in-cylinder temperature rise control is calculated based on the climb slope, the intake air temperature, the cooling water temperature, etc. calculated in step 112 (step 114). The ECU 50 stores in advance a map that defines the relationship between the required actual compression ratio, the uphill slope, the intake air temperature, the cooling water temperature, and the like. According to this map, the required actual compression ratio is calculated to be higher as the uphill slope is tighter.

  Once the required actual compression ratio is calculated, the valve timing of the intake valve 52 is then calculated so that the required actual compression ratio is realized, and the intake variable valve mechanism 54 is controlled so as to be the valve timing. (Step 116).

  According to the processing of the routine shown in FIG. 6 described above, the actual compression ratio at the time of starting can be increased and the temperature and pressure near the compression top dead center can be further increased as the climbing slope is tighter. The higher the temperature and pressure near the compression top dead center, the more difficult it is to misfire and more fuel can be burned. That is, the diesel engine 10 can generate a larger torque. For this reason, according to the present embodiment, engine stall can be reliably prevented even when the vehicle starts on an uphill road.

  In the present embodiment, the case where the uphill gradient is estimated and the required actual compression ratio in the in-cylinder temperature rise control is calculated based on the uphill gradient has been described, but in the present invention, vehicle load information other than the uphill gradient is calculated. Based on the above, the required actual compression ratio may be calculated. For example, the total vehicle weight or the loaded load may be estimated and calculated so that the required actual compression ratio increases as the values increase. The total vehicle weight or the loaded load can be estimated based on detection signals from the front suspension sensor 74 and the rear suspension sensor 76, for example.

  In the third embodiment described above, the uphill slope corresponds to the “vehicle load information” in the eighth invention, and the valve timing of the intake valve 52 corresponds to the “control amount” in the eighth invention. Yes. Further, when the ECU 50 executes the process of step 112, the “vehicle load information acquisition means” in the eighth invention executes the processes of steps 114 and 116, whereby “control” in the eighth invention is executed. A “quantity determination means” is realized.

Embodiment 4 FIG.
Next, the fourth embodiment of the present invention will be described with reference to FIG. 7 and the like, but the description will focus on the differences from the first to third embodiments described above, and the same matters will be described. Simplify or omit. The present embodiment is realized by causing the ECU 50 to execute a routine shown in FIG. 7 described later instead of the routine shown in FIGS. 4 to 6 described above, using the hardware configuration shown in FIGS. 1 and 2. can do.

[Features of Embodiment 4]
In the present embodiment, as in the third embodiment described above, the required actual compression ratio in the in-cylinder temperature rise control is calculated according to the estimated uphill slope and the like. In this case, it may be considered that the calculated required actual compression ratio exceeds the maximum actual compression ratio of the diesel engine 10 when the uphill slope is extremely tight.

  That is, according to the intake variable valve mechanism 54, the actual compression ratio can be increased as the closing timing of the intake valve 52 is brought closer to the bottom dead center, but more than the closing timing of the intake valve 52 is set to the bottom dead center. Cannot increase the actual compression ratio. The actual compression ratio at this time is the maximum actual compression ratio.

  When the required actual compression ratio exceeds the maximum actual compression ratio, the actual compression ratio at the time of in-cylinder temperature rise control cannot be increased to the required actual compression ratio. For this reason, it is conceivable that the torque at the start is slightly insufficient as compared with the target torque. Therefore, in the present embodiment, when the required actual compression ratio exceeds the maximum actual compression ratio, in addition to increasing the actual compression ratio, control for increasing the idle speed is also performed.

[Specific Processing in Embodiment 4]
FIG. 7 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. In FIG. 7, the same steps as those shown in FIGS. 4 to 6 are denoted by the same reference numerals, and the description thereof is omitted or simplified. In FIG. 7, the actual compression ratio is represented by the symbol ε.

  The routine shown in FIG. 7 is the same as the routine shown in FIG. 6 except that step 116 is replaced with steps 118 to 120. That is, according to the routine shown in FIG. 7, when it is determined that the diesel engine 10 is in the idle state (step 100) and the driver has an intention to start (step 110), first, the vehicle posture is set. Based on this, an uphill slope is estimated (step 112). Subsequently, a required actual compression ratio to be executed in the in-cylinder temperature rise control is calculated based on the uphill slope, the intake air temperature, the cooling water temperature, and the like (step 114).

  Once the required actual compression ratio is calculated, the valve timing of the intake valve 52 is then calculated so that the required actual compression ratio is realized, and the intake variable valve mechanism 54 is controlled so as to be the valve timing. (Step 118). In step 118, when the required actual compression ratio exceeds the maximum actual compression ratio of the diesel engine 10 stored in advance, the valve timing of the intake valve 52 is calculated so that the maximum actual compression ratio is realized. It is assumed that the intake variable valve mechanism 54 is controlled so that the valve timing is reached.

  Subsequently, it is determined whether or not the required actual compression ratio exceeds the maximum actual compression ratio (step 120). If it is determined that the required actual compression ratio does not exceed the maximum actual compression ratio, there is no need to increase the idle speed, and thus the processing of this routine is terminated as it is. On the other hand, if it is determined that the required actual compression ratio exceeds the maximum actual compression ratio, a process for increasing the idle speed (engine speed) is then executed (step 122). The ECU 50 stores in advance a map that defines a relationship between a deviation between the required actual compression ratio and the maximum actual compression ratio and an idle-up amount corresponding to the deviation. According to this map, the larger the deviation is, the more the idle up amount is calculated. In step 122, the engine speed is controlled to increase by the idle up amount calculated in this way.

  According to the processing of the routine shown in FIG. 7 described above, when the required actual compression ratio exceeds the maximum actual compression ratio because the vehicle load at the start is particularly large, for example, when the slope is extremely steep, the idle increase occurs. Can be used in combination. For this reason, even when the vehicle load at the time of starting is particularly large, the engine stall at the time of starting can be more reliably prevented.

  In step 122, control is performed so that the required minimum idle-up amount is obtained in accordance with the deviation between the required actual compression ratio and the maximum actual compression ratio. For this reason, since the amount of change in engine sound and engine vibration immediately before starting can be minimized, it is possible to prevent the driver from feeling uncomfortable.

  In the above-described fourth embodiment, the ECU 50 executes the processes of steps 112 and 114, so that the “required actual compression ratio calculation means” in the ninth aspect performs the processes of steps 120 and 122. By executing this, the “idle-up means” in the ninth aspect of the invention is realized.

Embodiment 5 FIG.
Next, the fifth embodiment of the present invention will be described with reference to FIG. 8 and the like. The difference from the first to fourth embodiments described above will be mainly described, and the same matters will be described. Simplify or omit. The present embodiment is realized by causing the ECU 50 to execute a routine shown in FIG. 8 described later instead of the routine shown in FIGS. 4 to 7 described above, using the hardware configuration shown in FIGS. 1 and 2. can do.

[Features of Embodiment 5]
In the present embodiment, as in the above-described fourth embodiment, when the required actual compression ratio exceeds the maximum actual compression ratio, in addition to in-cylinder temperature rise control (actual compression ratio up), idle up is also performed. I am going to do that. In this case, in this embodiment, the in-cylinder temperature rise control is started on the condition that the depression of the clutch is detected, and then the idle up is started on the condition that the parking brake is released. .

  Further, when the required actual compression ratio does not exceed the maximum actual compression ratio, only the in-cylinder temperature increase control is performed without performing idle-up as in the fourth embodiment described above. In this case, in the present embodiment, the in-cylinder temperature rise control is started on the condition that the parking brake is released.

[Specific Processing in Embodiment 5]
FIG. 8 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. In FIG. 8, the same steps as those shown in FIGS. 4 to 7 are denoted by the same reference numerals, and description thereof is omitted or simplified.

  According to the routine shown in FIG. 8, when it is determined that the diesel engine 10 is in an idle state (step 100), an uphill slope is estimated based on the vehicle posture (step 112). Subsequently, a required actual compression ratio to be executed in the in-cylinder temperature rise control is calculated based on the uphill slope, the intake air temperature, the cooling water temperature, and the like (step 114).

  Subsequently, it is determined whether or not the required actual compression ratio exceeds the maximum actual compression ratio (step 124). If it is determined that the required actual compression ratio exceeds the maximum actual compression ratio, it is next determined whether or not the clutch pedal has been depressed (step 126). When it is determined that the clutch pedal has been depressed, the valve timing of the intake valve 52 that achieves the maximum actual compression ratio is calculated, and the intake variable valve mechanism 54 is set so as to be the valve timing. Controlled (step 128). Subsequently, it is determined whether or not the parking brake is released (step 130). When it is detected that the parking brake has been released, a process for increasing the idle speed (engine speed) is executed (step 132). In this step 132, the engine speed is increased by the minimum idle increase amount necessary for reliably preventing engine stall based on the deviation between the required actual compression ratio and the maximum actual compression ratio.

  According to the processing so far of the routine shown in FIG. 8, when performing idle-up, the start timing of idle-up can be set at the time of releasing the parking brake. In general, the release of the parking brake is the final stage of the start preparation operation performed by the driver. That is, according to the above processing, the timing for performing idle-up can be delayed as much as possible. For this reason, it is possible to more reliably suppress the feeling of the driver due to idle-up, and to minimize the increase in emissions such as NOx.

  Further, according to the processing so far of the routine shown in FIG. 8, in-cylinder temperature rise control (actual compression ratio up) when the required actual compression ratio exceeds the maximum actual compression ratio, that is, when the vehicle load is large. The start timing can be set when the clutch pedal is depressed. In general, the depression of the clutch pedal is a relatively early stage of the start preparation operation performed by the driver. Therefore, according to the above processing, when the vehicle load is large, after the start is predicted, the in-cylinder temperature rise control is performed from a relatively early stage to sufficiently raise the in-cylinder temperature. Can do. For this reason, it is possible to reliably create a state in which the fuel is easily combusted immediately before the start, so that the engine stall at the start can be more reliably prevented.

  On the other hand, according to the routine shown in FIG. 8, if it is determined in step 124 that the required actual compression ratio does not exceed the maximum actual compression ratio, it is next determined whether or not the parking brake is released. (Step 134). When it is detected that the parking brake is released, the valve timing of the intake valve 52 is calculated so that the required actual compression ratio calculated in step 114 is realized, and the valve timing is set. Then, the intake variable valve mechanism 54 is controlled (step 136). According to such processing, when the required actual compression ratio does not exceed the maximum actual compression ratio, that is, when the vehicle load is not so large, the start timing of the in-cylinder temperature rise control is set until the parking brake is released. Can be delayed. If the vehicle load is not so large, the possibility of engine stall is small even if the in-cylinder temperature rise control is not performed from an early timing. Thus, the NOx emission amount can be further reduced by delaying the start timing of the in-cylinder temperature raising control as much as possible.

  In the routine shown in FIG. 8, the determination of parking brake release (steps 130 and 134) may be replaced with the determination that the gear position is not neutral. Even in this case, the same effect as described above can be obtained.

  In the fifth embodiment described above, the depression of the clutch pedal is the “first start preparation operation” in the tenth invention, and the release of the parking brake is the “second start preparation operation in the tenth invention”. Respectively.

Embodiment 6 FIG.
Next, the sixth embodiment of the present invention will be described with reference to FIG. 9 and FIG. 10. The difference from the above-described first embodiment will be mainly described, and the same matters will be described. Simplify or omit. This embodiment can be realized by causing the ECU 50 to execute a routine shown in FIG. 10 described later instead of the routine shown in FIG. 4 described above, using the hardware configuration shown in FIGS. 1 and 2. it can.

[Features of Embodiment 6]
(Exhaust variable valve mechanism)
As shown in FIG. 2, the diesel engine 10 of the present embodiment is provided with an exhaust variable valve mechanism 58 that drives an exhaust valve 56. The exhaust variable valve mechanism 58 is connected to the ECU 50. In the present embodiment, the exhaust variable valve mechanism 58 continuously varies the phase of a cam (not shown) that drives the exhaust valve 56, thereby opening the exhaust valve 56 in the valve opening phase (opening timing and closing timing). ) Is continuously variable. In the sixth embodiment, the exhaust variable valve mechanism 58 may be any mechanism that continuously varies at least the closing timing of the exhaust valve 56. That is, it is possible to change only the closing timing while keeping the opening timing of the exhaust valve 56 as it is. Further, the exhaust variable valve mechanism 58 may be capable of changing the lift amount and the operating angle of the exhaust valve 56. The specific configuration of the exhaust variable valve mechanism 58 is not particularly limited. For example, a mechanical mechanism using various cam mechanisms, an electromagnetically driven valve that can be opened and closed at an arbitrary timing, a hydraulically driven valve, or the like is used. be able to.

(In-cylinder temperature rise control by increasing internal EGR ratio)
This embodiment is different from the first embodiment in the contents of the in-cylinder temperature rise control. In the in-cylinder temperature rise control of the first embodiment, the in-cylinder temperature and the in-cylinder pressure in the vicinity of the compression top dead center are increased by increasing the actual compression ratio. On the other hand, in this embodiment, at the time of in-cylinder temperature rise control, the in-cylinder temperature near the compression top dead center is increased by increasing the ratio of the internal EGR amount to the total EGR amount. FIG. 9 is a diagram for explaining the lift characteristics of the exhaust valve 56 during the in-cylinder temperature rise control in the present embodiment.

  The solid line graph in FIG. 9 is the lift curve of the exhaust valve 56 during normal idling. In the present embodiment, at the time of normal idling, the closing timing (EVC) of the exhaust valve 56 is after the top dead center (TDC). On the other hand, the broken line graph in FIG. 9 is the lift curve of the exhaust valve 56 during the in-cylinder temperature rise control. As shown in this lift curve, at the time of in-cylinder temperature rise control, the valve timing of the exhaust valve 56 is advanced, and the closing timing of the exhaust valve 56 is controlled to be before the bottom dead center.

  If the exhaust valve 56 is closed before the bottom dead center in this way, the exhaust valve 56 is closed before the burned gas in the cylinder completely flows out to the exhaust port 22. For this reason, EGR inside the diesel engine 10, so-called internal EGR occurs. The exhaust gas recirculated by the internal EGR is referred to as “internal EGR gas”. The earlier the closing timing of the exhaust valve 56, the greater the amount of internal EGR.

  The diesel engine 10 can perform both the above-described internal EGR and the above-described external EGR. Therefore, the total of the internal EGR amount and the external EGR amount is the total EGR amount. If the closing time of the exhaust valve 56 is advanced and the amount of internal EGR is increased, the external EGR gas becomes difficult to enter the intake passage 28 accordingly. For this reason, the ratio of the internal EGR amount to the total EGR amount increases. Further, when the opening degree of the EGR valve 44 is reduced, the external EGR gas is more difficult to enter, so that the ratio of the internal EGR amount to the total EGR amount is further increased. Thus, by adjusting the valve timing of the exhaust valve 56 and the opening degree of the EGR valve 44, it is possible to adjust the ratio of the internal EGR amount to the total EGR amount.

  In the case of external EGR, the EGR gas is cooled while passing through the EGR cooler 42 and the EGR passage 40, and the temperature of the EGR gas is lowered. On the other hand, in the case of internal EGR, the hot exhaust gas becomes the internal EGR gas as it is. That is, the temperature of the internal EGR gas is higher than that of the external EGR gas. For this reason, even if the total EGR rate is the same, the higher the ratio of the internal EGR amount to the total EGR amount, the higher the temperature of the gas sucked into the cylinder. Also gets higher.

  Therefore, in the present embodiment, in the in-cylinder temperature rise control, the temperature near the compression top dead center is raised by controlling the ratio of the internal EGR amount to the total EGR amount to be larger than that during normal idling. It was. Thereby, even if it is a case where a lot of fuel is injected, misfire does not occur easily and it can burn enough. For this reason, when starting, a larger torque can be generated, so that engine stall can be reliably prevented.

[Specific Processing in Embodiment 6]
FIG. 10 is a flowchart of a routine executed by the ECU 50 in the present embodiment in order to realize the above function. According to the routine shown in FIG. 10, first, when the diesel engine 10 is in an idle state and depression of the clutch pedal is detected (steps 100 and 102), next, in-cylinder temperature rise control is performed. An optimal ratio between the internal EGR and the external EGR (hereinafter referred to as “inside / outside ratio”) is calculated (step 138). Here, the required / external ratio is calculated so that the ratio of the internal EGR amount to the total EGR amount is larger than that during normal idling. Further, the required / external ratio may be calculated based on the intake air temperature or the coolant temperature. That is, when the intake air temperature or the cooling water temperature is low and the fuel tends to hardly burn, the required in / out ratio is calculated so that the ratio of the internal EGR amount to the total EGR amount is further increased. Also good.

  Subsequently, the valve timing (closing timing) of the exhaust valve 56 and the opening degree of the EGR valve 44 are calculated (step 140) so as to satisfy the demanded / outside ratio calculated in step 138. The ECU 50 stores in advance a map that defines the relationship between the required / external ratio, the valve timing of the exhaust valve 56, and the opening degree of the EGR valve 44. In step 140, by referring to the map, the valve timing of the exhaust valve 56 and the opening degree of the EGR valve 44 corresponding to the above-mentioned required / outside ratio are calculated.

  Thus, when the target valve timing of the exhaust valve 56 and the target opening degree of the EGR valve 44 in the in-cylinder temperature rise control are calculated, the variable exhaust valve mechanism 58 and The EGR valve 44 is controlled (step 142). As a result, the ratio of the internal EGR amount to the total EGR amount becomes larger than that during normal idling, so that the temperature near the compression top dead center increases. For this reason, when the accelerator pedal is depressed and the fuel injection amount is increased, the fuel can be burned satisfactorily without causing misfire or a state close thereto. Therefore, since sufficient torque can be generated at the time of starting, engine stall at the time of clutch engagement can be reliably prevented.

  Although the sixth embodiment described above is based on the first embodiment, the in-cylinder temperature increase control by increasing the internal EGR ratio may be performed based on the second to fifth embodiments.

  In the sixth embodiment described above, the EGR passage 40, the EGR cooler 42 and the EGR valve 44 are the “EGR device” in the twelfth invention, and the exhaust variable valve mechanism 58 is the “internal It corresponds to “EGR amount varying means”. Further, the “in-cylinder temperature raising means” according to the twelfth aspect of the present invention is realized by the ECU 50 executing the processes of steps 134 to 18.

  Further, in each of the embodiments described above, the case of a vehicle with a manual transmission has been described, but the present invention can also be applied to a vehicle with an automatic transmission. When the present invention is applied to a vehicle with an automatic transmission, the creep strength can be increased immediately before starting. For this reason, for example, even when starting on an uphill road, there is an advantage that the vehicle can be reliably prevented from moving backward. As a start preparation operation in a vehicle with an automatic transmission, for example, release of a parking brake, shift from a parking range to a drive range, release of a brake pedal, and the like can be cited.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a figure which shows the cross section of one cylinder of the diesel engine in the system shown in FIG. It is a figure for demonstrating the lift characteristic of the intake valve at the time of the cylinder temperature rising control in Embodiment 1 of this invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a flowchart of the routine performed in Embodiment 3 of the present invention. It is a flowchart of the routine performed in Embodiment 4 of this invention. It is a flowchart of the routine performed in Embodiment 5 of this invention. It is a figure for demonstrating the lift characteristic of the exhaust valve at the time of the cylinder temperature rising control in Embodiment 6 of this invention. It is a flowchart of the routine performed in Embodiment 6 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Diesel engine 12 Injector 14 Common rail 18 Exhaust passage 20 Exhaust manifold 22 Exhaust port 24 Turbo supercharger 26 Exhaust purification device 28 Intake passage 34 Intake manifold 36 Intake throttle valve 38 Air flow meter 40 External EGR passage 44 EGR valve 46 Intake pressure sensor 50 ECU
52 Intake valve 54 Intake variable valve mechanism 56 Exhaust valve 58 Exhaust variable valve mechanism 62 Crank angle sensor 64 Piston 68 Cooling water temperature sensor

Claims (13)

An apparatus for controlling an internal combustion engine mounted on a vehicle,
A start preparation operation detecting means for detecting a start preparation operation performed with the intention of the driver to start the vehicle;
In-cylinder temperature raising means for starting in-cylinder temperature raising control for increasing the in-cylinder temperature in the vicinity of the compression top dead center when compared with that during normal idling when a predetermined start preparation operation is detected,
A control device for an internal combustion engine, comprising:   2. The control apparatus for an internal combustion engine according to claim 1, wherein the internal combustion engine is controlled so that the engine speed does not change before and after the start of the in-cylinder temperature rise control.   3. The control apparatus for an internal combustion engine according to claim 1, wherein the predetermined start preparation operation includes depression of a clutch pedal.   4. The control apparatus for an internal combustion engine according to claim 1, wherein the predetermined start preparation operation includes switching from a gear position incapable of starting to a gear position in which start is possible.   5. The control device for an internal combustion engine according to claim 1, wherein the predetermined start preparation operation includes release of a parking brake. An actual compression ratio varying means for varying the actual compression ratio of the internal combustion engine;
The in-cylinder temperature raising means controls the actual compression ratio variable means so that the actual compression ratio becomes higher than that during normal idling when the in-cylinder temperature raising control is executed, thereby providing a cylinder near the compression top dead center. 6. The control device for an internal combustion engine according to claim 1, wherein the internal temperature is increased. A variable valve mechanism for varying at least the closing timing of the intake valve of the internal combustion engine;
The in-cylinder temperature raising means controls the variable valve mechanism so that when the in-cylinder temperature raising control is executed, the closing timing of the intake valve is closer to the bottom dead center than during normal idling. The internal combustion engine control apparatus according to any one of claims 1 to 5, wherein the in-cylinder temperature in the vicinity of the compression top dead center is raised by increasing the value. Vehicle load information acquisition means for acquiring vehicle load information related to a load when starting the vehicle;
Control amount determination means for determining a control amount related to the degree of increase in the actual compression ratio when increasing the actual compression ratio in the in-cylinder temperature rise control, based on the vehicle load information;
The control device for an internal combustion engine according to claim 6 or 7, further comprising: The required actual compression ratio when increasing the actual compression ratio in the in-cylinder temperature rise control based on at least one of the cooling water temperature of the internal combustion engine, the intake air temperature, and vehicle load information related to the load when starting the vehicle Required actual compression ratio calculating means for calculating
When the required actual compression ratio exceeds a predetermined maximum actual compression ratio, the engine speed is increased as compared with that during normal idling according to the deviation between the required actual compression ratio and the maximum actual compression ratio. Idle up means to perform,
The control device for an internal combustion engine according to any one of claims 6 to 8, further comprising: The start preparation operation detecting means is capable of detecting a first start preparation operation and a second start preparation operation performed after the first start preparation operation,
When the required actual compression ratio exceeds the maximum actual compression ratio, the in-cylinder temperature raising means starts the in-cylinder temperature raising control on the condition that the first start preparation operation is detected, The idle up means starts the idle up on the condition that the second start preparation operation is detected,
If the required actual compression ratio is less than or equal to the maximum actual compression ratio, the in-cylinder temperature raising means starts the in-cylinder temperature raising control on condition that the second start preparation operation is detected. 10. The control device for an internal combustion engine according to claim 9.   The first start preparation operation is depression of a clutch pedal, and the second start preparation operation is release of a parking brake or switching from a gear position where starting is impossible to a gear position where starting is possible. 11. The control device for an internal combustion engine according to claim 10, wherein the control device is an internal combustion engine. An EGR device that performs external EGR to recirculate exhaust gas in the exhaust passage of the internal combustion engine to the intake passage;
Internal EGR amount varying means for varying the amount of internal EGR that is EGR inside the internal combustion engine;
Further comprising
The in-cylinder temperature raising means controls the EGR device and the internal EGR amount variable means so that the ratio of the internal EGR amount to the total EGR amount is larger than that during normal idling when the in-cylinder temperature raising control is executed. 6. The control apparatus for an internal combustion engine according to claim 1, wherein the in-cylinder temperature near the compression top dead center is raised. The internal combustion engine is a diesel engine;
An EGR device for recirculating exhaust gas in the exhaust passage of the diesel engine to the intake passage;
An EGR control device that performs external EGR by the EGR device during idling;
The control device for an internal combustion engine according to any one of claims 1 to 12, further comprising:

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