JP2011144782A - Control device of internal combustion engine equipped with variable valve mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suitably satisfy both the scavenging of a residual gas and the inhibition of vibration at stop of an internal combustion engine, with respect to the control device of internal combustion engine equipped with a variable valve mechanism. <P>SOLUTION: The control device is equipped with an intake-stroke variable valve mechanism 46 for enabling a closing period of an intake valve 68 to be changed. When a halting demand has been issued for the internal combustion engine 10, the control device controls the internal combustion engine 10 so that the closing period IVC of the intake valve 68 becomes in the vicinity of a lower dead center of an intake stroke. Thereafter, after the closing period IVC of the intake valve 68 has shifted to the vicinity of the lower dead center of the intake stroke, the closing period IVC of the intake valve 68 is retarded so that the actual compression ratio of the internal combustion engine 10 decreases. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an internal combustion engine control device including a variable valve mechanism.

  Conventionally, for example, Patent Document 1 discloses a stop control device for an internal combustion engine. In this conventional control device, the magnitude of the compression pressure in the cylinder when the internal combustion engine is stopped is estimated based on the engine temperature state. Only when the estimated compression pressure is large, the actual compression ratio is reduced by retarding the closing timing of the intake valve.

JP 2004-308598 A JP 2004-316492 A JP 2008-163792 A JP 2006-257997 A JP 2001-280170 A JP 2000-352327 A

  By the way, if the combustion (burned) gas remains in the intake passage or combustion chamber after the stop operation of the internal combustion engine is left for a long period of time, corrosion of parts around the combustion chamber such as an injector and a valve seat Etc. becomes a problem. According to the above-described conventional control, it is possible to suppress vibration based on the compression reaction force of each cylinder during the stop operation of the internal combustion engine. However, since the in-cylinder gas is blown back to the intake side due to the delay of the closing timing of the intake valve, the residual gas in the intake passage cannot be scavenged sufficiently. As described above, conventionally, when the vibration of the internal combustion engine during the stop operation is reduced, the above corrosion due to the gas remaining in the intake passage and the combustion chamber is not taken into consideration.

  The present invention has been made to solve the above-described problems, and is an internal combustion engine having a variable valve mechanism that can suitably balance residual gas scavenging and vibration suppression during a stop operation of the internal combustion engine. An object is to provide a control device.

A first invention is a control device for an internal combustion engine comprising a variable valve mechanism,
An intake variable valve mechanism that can change the closing timing of the intake valve;
Stop request detecting means for detecting a stop request of the internal combustion engine;
First intake closing timing control means for controlling the closing timing of the intake valve to a first control timing in the vicinity of the intake bottom dead center when the stop request is issued;
The internal combustion engine is compared with a case where the closing timing of the intake valve is controlled to the first control timing after the closing timing of the intake valve has shifted to the first control timing during the stop operation of the internal combustion engine. Second intake closing timing control means for controlling the closing timing of the intake valve to a second control timing so that the actual compression ratio of
It is characterized by providing.

The second invention is the first invention, wherein
Scavenging completion determining means for determining whether or not scavenging of the residual gas in the intake passage and the combustion chamber has been completed after the closing timing of the intake valve has shifted to the first control time during the stop operation;
The second intake closing timing control means sets the closing timing of the intake valve when the scavenging completion determining means determines that scavenging of the residual gas in the intake passage and the combustion chamber is completed during the stop operation. It is a means to control at the 2nd control time, It is characterized by the above-mentioned.

The third invention is the first or second invention, wherein
The internal combustion engine is an internal combustion engine that is automatically stopped when a predetermined automatic stop condition is satisfied during startup of the vehicle system,
When the stop request is accompanied by the establishment of the automatic stop condition, the second intake closing timing control means does not go through the control of the intake valve closing timing by the first intake closing timing control means. The system further comprises a stop-time control switching means for controlling the closing timing of the intake valve.

Moreover, 4th invention is 2nd or 3rd invention,
An intake opening timing control means for controlling the opening timing of the intake valve to be exhaust top dead center when the stop request is issued;
An exhaust valve that is set in advance so that the closing timing becomes exhaust top dead center, or is controlled so that the closing timing becomes exhaust top dead center when the stop request is issued;
Is further provided.

According to a fifth invention, in any one of the second to fourth inventions,
An exhaust gas recirculation valve for opening and closing an exhaust gas recirculation passage connecting the exhaust passage and the intake passage;
An exhaust recirculation valve full closing means for fully closing the exhaust recirculation valve when the stop request is issued in a state where the exhaust gas recirculation is being performed by adjusting the opening of the exhaust gas recirculation valve;
Is further provided.

The sixth invention is the fifth invention, wherein
The scavenging completion determining means includes
A residual gas amount estimating means for estimating a residual gas amount existing in the passage volume based on a passage volume of a section from the exhaust gas recirculation valve to the intake valve;
Acquiring an integrated intake amount for acquiring an integrated value of the intake amount taken into the combustion chamber after the exhaust gas recirculation valve is fully closed by the exhaust gas recirculation valve closing means and the fuel injection is stopped during the stop operation Means,
When the accumulated value is equal to or greater than the estimated value of the residual gas amount, it is determined that scavenging of the residual gas in the intake passage and the combustion chamber is completed.

According to a seventh invention, in any one of the second to fifth inventions,
An intake air temperature detecting means which is installed in an intake manifold provided in the intake passage and detects an intake air temperature;
The scavenging completion determining means determines that scavenging of the residual gas in the intake passage and the combustion chamber is completed when the intake air temperature detected by the intake air temperature detecting means is lower than a predetermined value. .

Further, an eighth invention is any one of the second to fifth inventions,
Further comprising air-fuel ratio detection means for detecting the air-fuel ratio of the gas flowing through the exhaust passage,
The scavenging completion determining means determines that scavenging of the residual gas in the intake passage and the combustion chamber is completed when the air-fuel ratio of the gas detected by the air-fuel ratio detecting means is higher than a predetermined value. And

According to a ninth invention, in any one of the second to fifth inventions,
An intake pressure detection means for detecting an intake pressure, which is installed in an intake manifold provided in the intake passage;
The scavenging completion determining means determines that scavenging of the residual gas in the intake passage and the combustion chamber is completed when the intake pressure detected by the intake pressure detecting means is lower than a predetermined pressure. .

According to a tenth invention, in any one of the second to fifth inventions,
Exhaust temperature detecting means for detecting the temperature of the exhaust gas flowing through the exhaust passage,
The scavenging completion determining means determines that scavenging of the residual gas in the intake passage and the combustion chamber is completed when the temperature of the exhaust gas detected by the exhaust temperature detecting means is lower than a predetermined value. And

  According to the first invention, when a request to stop the internal combustion engine is issued, first, the intake valve closing timing is controlled to the first control timing in the vicinity of the intake bottom dead center. Residual gas can be sufficiently scavenged. After that, by controlling the closing timing of the intake valve to the second control timing so that the actual compression ratio of the internal combustion engine decreases, the start of the internal combustion engine during the stop operation can be reduced. As a result, it is possible to suitably achieve both the scavenging of residual gas and the suppression of vibration during the stop operation of the internal combustion engine.

  According to the second aspect of the present invention, the scavenging completion determining means is provided, so that after the scavenging of the residual gas in the intake passage and the combustion chamber is reliably completed during the stop operation, the intake valve is controlled to suppress the vibration of the internal combustion engine. The closing time can be controlled to the second control time.

  If a stop request is issued in response to the establishment of the automatic stop condition, the engine is restarted in a relatively short time after the internal combustion engine is temporarily stopped. For this reason, in such a case, it can be said that corrosion of parts around the combustion chamber is not a problem. Therefore, according to the third invention, in such a case, the control of the closing timing of the intake valve by the first intake closing timing control means is omitted, so that vibration can be further suppressed during the stop operation. It becomes possible.

  According to the fourth invention, when a stop request is issued, the valve overlap period is made zero in such a manner that the exhaust valve is closed and the intake valve is opened at the exhaust top dead center. Thereby, residual gas in the combustion chamber can be prevented from being blown back to the intake passage side, and exhaust gas (internal EGR gas) recirculating from the exhaust passage side to the combustion chamber can be eliminated.

  According to the fifth aspect of the present invention, when a stop request is issued, it is possible to prevent the exhaust gas from recirculating to the intake side via the exhaust gas recirculation passage so that the remaining gas can be sufficiently scavenged. Become.

  According to the first aspect of the present invention, when the stop request is issued, the closing timing of the intake valve is controlled to the first control timing near the intake bottom dead center, thereby preventing the combustion chamber gas from being blown back to the intake passage side. Has been. Therefore, according to the sixth aspect of the invention, the integrated value of the amount of intake air taken into the combustion chamber after the exhaust gas recirculation valve is fully closed by the exhaust gas recirculation valve closing means and the fuel injection is stopped during the stop operation is Scavenging is completed by determining that scavenging of residual gas in the intake passage and combustion chamber is complete when the residual gas in the passage volume in the section from the exhaust gas recirculation valve to the intake valve exceeds the estimated value. The time can be accurately determined.

  Since the exhaust gas after being subjected to combustion is hot, if the exhaust gas remains in the intake manifold, the gas temperature in the intake manifold will be higher than when normal temperature fresh air circulates. . Therefore, according to the seventh aspect, by setting the predetermined value to a value that can distinguish the intake air temperature between the case where the burned gas remains and the case where only fresh air is present, the timing for completing the scavenging of the residual gas Can be accurately determined.

  When scavenging of the residual gas in the intake passage and the combustion chamber is completed and the combustion chamber is filled with fresh air, the gas detected by the air-fuel ratio detection means becomes fresh air, and the burned fuel after being subjected to combustion Larger and leaner values are detected than when gas flows. Therefore, according to the eighth aspect of the present invention, the completion timing of the scavenging of the residual gas can be accurately determined by setting the predetermined value to a value that can distinguish the burned gas from the fresh air.

  Since the exhaust gas after being subjected to combustion is hot, when the exhaust gas remains in the intake manifold, it expands due to the heat received from the exhaust gas compared to when normal temperature fresh air circulates. The pressure of the gas in the intake manifold increases. Therefore, according to the ninth aspect, by setting the predetermined value to a value that can distinguish the intake pressure between the case where the burned gas remains and the case where only the fresh air is present, the timing for completing the scavenging of the residual gas Can be accurately determined.

  When the scavenging of the residual gas in the intake passage and the combustion chamber is completed and the combustion chamber is filled with fresh air, the gas detected by the exhaust temperature detection means becomes fresh air, and the burned gas after being subjected to combustion The detected temperature is greatly reduced compared to when gas flows. Therefore, according to the tenth aspect, by setting the predetermined value to a value that can distinguish between burned gas and fresh air, it is possible to accurately determine the completion timing of scavenging of the residual gas.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a time chart for demonstrating the characteristic control at the time of engine stop operation in Embodiment 1 of this invention. It is a figure showing the intake valve timing used during the stop operation of an internal combustion engine. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a figure for demonstrating the scavenging effect of the residual gas by scavenging mode. It is a figure for demonstrating the discrimination method of the scavenging completion time in Embodiment 2 of this invention. It is a flowchart of the routine performed in Embodiment 2 of this invention.

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 compression ignition type internal combustion engine 10. Here, as an example of a compression ignition type internal combustion engine, the internal combustion engine 10 is assumed to be an in-line four-cylinder diesel engine.

  Each cylinder of the internal combustion engine 10 is provided with an injector 12 that directly injects fuel into the cylinder. The injectors 12 of each cylinder are connected to a common common rail 14. Fuel in a fuel tank (not shown) is pressurized to a predetermined fuel pressure by a supply pump 16, stored in the common rail 14, and supplied from the common rail 14 to each injector 12.

  An exhaust passage 18 of the internal combustion engine 10 is branched by an exhaust manifold 20 and connected to an exhaust port of each cylinder. The internal combustion engine 10 of the present embodiment includes a turbocharger 22. The exhaust passage 18 is connected to the turbine of the turbocharger 22.

  Further, an exhaust gas purification device 24 for purifying exhaust gas is provided on the exhaust passage 18 downstream of the turbocharger 22. Furthermore, an A / F sensor 26 for detecting the air-fuel ratio of the exhaust gas and an exhaust temperature sensor 28 for detecting the temperature of the exhaust gas are respectively provided in the exhaust passage 18 upstream of the turbocharger 22. is set up.

  An air cleaner 32 is provided near the inlet of the intake passage 30 of the internal combustion engine 10. The air sucked through the air cleaner 32 is compressed by the compressor of the turbocharger 22 and then cooled by the intercooler 34. The intake air that has passed through the intercooler 34 is distributed to the intake port of each cylinder by the intake manifold 36.

  An intake throttle valve 38 is installed between the intercooler 34 and the intake manifold 36. An air flow meter 40 for detecting the intake air amount is installed in the vicinity of the downstream side of the air cleaner 32. The intake manifold 36 is provided with an intake air temperature sensor 42 for detecting the temperature of intake air flowing through the intake manifold 36 and an intake air pressure sensor 44 for detecting intake air pressure.

  Further, the system shown in FIG. 1 has the variable valve opening mechanism 46 that can change the valve opening characteristic of the intake valve 68 (see FIG. 5) of each cylinder and the valve opening characteristic of the exhaust valve 66 (see FIG. 5). An exhaust variable valve mechanism 48 that can be changed is provided. More specifically, here, the intake variable valve mechanism 46 has a function (lift variable function) capable of continuously changing the lift amount and operating angle of the intake valve 68 and an intake cam (illustrated) using hydraulic pressure or a motor. It is assumed that the mechanism has a function (phase variable function) that can change the opening / closing timing of the intake valve 68 by changing the phase of (omitted). The exhaust variable valve mechanism 48 is a mechanism having a phase variable function similar to the intake variable valve mechanism 46. Further, the intake variable valve mechanism 46 includes an intake cam angle sensor 50 for detecting the rotational position (advance amount) of the intake camshaft. The exhaust variable valve mechanism 48 includes the intake cam angle sensor 50 and the intake cam angle sensor 50. An exhaust cam angle sensor 52 having the same configuration is provided.

  In addition, one end of an exhaust gas recirculation passage (hereinafter referred to as an “EGR (Exhaust Gas Recirculation) passage”) 54 is connected to the vicinity of the intake manifold 36. The other end of the EGR passage 54 is connected to the exhaust manifold 20 of the exhaust passage 18. An exhaust gas recirculation valve (hereinafter referred to as “EGR valve”) 56 is provided in the EGR passage 54 in the vicinity of the connection port 30a on the intake side. By changing the opening degree of the EGR valve 56, it is possible to adjust the amount of exhaust (burned) gas that recirculates from the exhaust side to the intake side through the EGR passage 54, that is, the amount of external EGR gas.

  Further, an EGR bypass passage 58 that bypasses the EGR passage 54 is formed in the middle of the EGR passage 54. An EGR cooler 60 for cooling the exhaust gas (EGR gas) passing through the passage 58 is provided in the middle of the EGR bypass passage 58. A bypass valve 62 that opens and closes the connection port 58a is attached to the connection port 58a on the exhaust side in the EGR bypass passage 58. According to such a bypass valve 62, the EGR gas can be cooled by the EGR cooler 60 as necessary.

  The system of this embodiment includes an ECU (Electronic Control Unit) 70. In addition to the various sensors described above, the ECU 70 is connected to a crank angle sensor 72 for detecting the crank angle and the engine speed, an ignition switch (IG switch) 74 for the vehicle, and the like. The ECU 70 is connected to the various actuators described above. The ECU 70 controls the operating state of the internal combustion engine 10 by driving each actuator in accordance with a predetermined program based on those sensor signals and information.

  Further, the vehicle on which the internal combustion engine 10 according to the present embodiment is mounted automatically activates the internal combustion engine 10 when a predetermined automatic stop condition is satisfied while the vehicle system is being started (when the IG switch 74 is turned on). It is assumed that the vehicle has a function of stopping automatically. More specifically, the system of the present embodiment has a system in which such an automatic stop condition is established when the vehicle is temporarily stopped and the internal combustion engine 10 is in an idling state, that is, an idling stop function. It is assumed that the system has Note that the present invention is not limited to such a system having an idling stop function. In a hybrid vehicle including an internal combustion engine and another power source such as a motor, when the predetermined automatic stop condition is satisfied during startup of the vehicle system, the internal combustion engine May be a system that automatically stops.

  By the way, if the combustion (burned) gas remains in the intake passage 30 or the combustion chamber after the stop operation of the internal combustion engine 10 is left for a long period of time, the surroundings of the combustion chamber such as the injector 12 and the valve seat Corrosion of parts becomes a problem. On the other hand, in order to avoid such a problem, if a large amount of fresh air is sucked into the combustion chamber when the internal combustion engine 10 is stopped, the combustion gas remaining in the intake passage 30 and the combustion chamber is sufficiently removed. Although scavenging can be performed, the vibration of the internal combustion engine 10 increases due to compression and expansion of a large amount of fresh air sucked into the combustion chamber.

[Characteristic control during engine stop operation in Embodiment 1]
FIG. 2 is a time chart for explaining control during characteristic engine stop operation in the first embodiment of the present invention. More specifically, FIG. 2A shows a waveform representing changes in ON / OFF of the IG switch 74, FIG. 2B shows a waveform representing changes in the opening degree of the EGR valve 56, and FIG. C) shows a waveform representing a change in the intake valve timing (closing timing IVC of the intake valve 68), FIG. 2D shows a waveform showing a change in the fuel injection amount, and FIG. 2E shows an engine speed. Each waveform represents a change. FIG. 3 is a diagram showing the intake valve timing used during the stop operation of the internal combustion engine 10. In the present specification, a period from when the stop request for the internal combustion engine 10 is issued until the stop of the internal combustion engine 10 is completed is referred to as “during the stop operation of the internal combustion engine 10”.

  In the present embodiment, the following control is performed in order to solve the above-described problems in contradiction. That is, as shown in FIG. 2, when a request for stopping the internal combustion engine 10 is issued by turning off the IG switch 74, the EGR valve is set so as to shift to the scavenging mode before stopping the fuel injection. The opening degree and the valve timing of the intake valve 68 are controlled. More specifically, in the scavenging mode, the EGR valve 56 is controlled to be fully closed, and the valve timing (opening / closing timing) of the intake valve 68 is controlled as shown in FIG.

  As shown in FIG. 3A, in the scavenging mode, the intake valve 68 is opened to eliminate a valve overlap period with the exhaust valve 66 set to be closed at the exhaust top dead center (TDC). The timing IVO is controlled to be exhaust top dead center. Further, the closing timing IVC of the intake valve 68 is controlled to be close to the intake bottom dead center (BDC).

  Next, in the control at the time of the engine stop operation shown in FIG. 2, when the EGR valve opening is fully closed and the closing timing IVC of the intake valve 68 is controlled to the intake bottom dead center, that is, the transition to the scavenging mode. Is completed, fuel injection is stopped as shown in FIG. Further, in the present embodiment, at least two exhaust strokes have elapsed in all cylinders in order to ensure scavenging of residual gas in each cylinder after completion of the transition to the scavenging mode. It is determined that the scavenging of the residual gas has been completed in all the cylinders at the time when the period during which the period has elapsed.

  Next, in the control at the time of the engine stop operation shown in FIG. 2, when it is determined that scavenging of the residual gas is completed in all the cylinders while the scavenging mode is continued, the EGR valve opening degree is controlled to be fully closed. In order to reduce the actual compression ratio of the internal combustion engine 10, the control for delaying the closing timing IVC of the intake valve 68 from the intake bottom dead center is executed. In the present embodiment, the mode in which the closing timing IVC of the intake valve 68 is controlled in this way is referred to as a “vibration reduction mode”. As shown in FIG. 2, this vibration reduction mode is selected until the stop operation of the internal combustion engine 10 is completed.

  FIG. 3B shows the setting of the intake valve timing in the vibration reduction mode. As shown in FIG. 3B, in the vibration reduction mode, the opening timing IVO of the intake valve 68 is controlled to the exhaust top dead center, and the closing timing IVC of the intake valve 68 is higher than the intake bottom dead center as described above. Is also controlled to be a predetermined timing on the retard side.

  Furthermore, in the system of the present embodiment in which the internal combustion engine 10 is mounted on a vehicle having an idle stop function, when a stop request is issued in response to the establishment of the automatic stop condition in the idle stop function, the scavenging mode is passed through. Without stopping the fuel injection, the vibration reduction mode is immediately started.

FIG. 4 is a flowchart showing a control routine executed by the ECU 70 in the first embodiment in order to realize the control during the engine stop operation described above.
In the routine shown in FIG. 4, it is first determined whether or not a request for stopping the internal combustion engine 10 has been issued (step 100). The engine stop request determined in step 100 includes a stop request when the IG switch 74 is turned off by the driver of the vehicle, and a stop request accompanying the establishment of the automatic stop condition in the idling stop function. .

  If it is determined in step 100 that an engine stop request has been issued, it is determined whether or not the current stop request is due to the establishment of the automatic stop condition (step 102).

  As a result, when it is determined that the current engine stop request is not a stop request due to the establishment of the automatic stop condition, that is, when it is determined that the IG switch 74 is turned OFF, Transition to the scavenging mode is started (step 104). Specifically, the target EGR valve opening is set to fully closed (step 106), and the target valve timing is set to a value for the scavenging mode (see FIG. 3A) (step 108).

  Next, it is determined whether or not the actual timing (closing timing IVC) of the intake valve and the actual EGR valve opening have converged to the target values, respectively (step 110). As a result, when the determination in step 110 is established, the fuel injection is stopped (step 112), and the crank position (crank angle) at the time of stopping the fuel injection is acquired (step 114).

  Next, the change amount of the current crank angle with respect to the crank angle at the time of stopping the fuel injection acquired in step 114 is acquired (calculated) (step 116). Next, based on the amount of change in the crank angle, it is determined whether or not a predetermined cycle has elapsed since the fuel injection was stopped (step 118). As described above, the predetermined cycle in step 118 is the number of cycles required until the exhaust stroke in all the cylinders has passed at least twice after the fuel injection is stopped.

  If it is determined in step 118 that the predetermined number of cycles has elapsed, the transition to the vibration reduction mode is started (step 120). Specifically, the target valve timing is set to a value for the vibration reduction mode (see FIG. 3B) (step 122).

  On the other hand, if it is determined in step 102 that the current engine stop request is a stop request due to the establishment of the automatic stop condition, the fuel injection is stopped (step 124), and then the scavenging mode is entered. Immediately, the transition to the vibration reduction mode is started (step 120).

  According to the routine shown in FIG. 4 described above, when the engine stop request is issued by turning off the IG switch 74, the scavenging mode is first executed. FIG. 5 is a diagram for explaining the scavenging effect of the residual gas in the scavenging mode. In the scavenging mode, the gas flowing through the combustion chamber 64 after the fuel injection is stopped until the discharge of the residual gas is completed. It represents the behavior.

  In the scavenging mode, since the EGR valve 56 is controlled to be fully closed, the recirculation of the exhaust gas to the intake passage 30 via the EGR passage 54 is prohibited. In addition, the residual gas is scavenged by the operation shown in FIG.

  FIG. 5A shows the compression stroke in the first cycle in which the fuel injection is stopped. In this case, combustion gas remaining in the combustion chamber 64 without being discharged from the combustion chamber 64 in the previous cycle is present. Further, residual gas blown back to the intake manifold 36 from its own cylinder or other cylinders is present in the intake manifold 36.

  When the exhaust stroke comes from the state shown in FIG. 5A through the expansion stroke and the exhaust valve 66 is opened, the residual gas in the combustion chamber 64 is discharged to the exhaust manifold 20 as shown in FIG. 5B. The According to the scavenging mode, the valve overlap period is controlled to be eliminated in such a manner that the exhaust valve 66 is closed and the intake valve 68 is opened at the exhaust top dead center. Therefore, it is possible to prevent the residual gas staying in the combustion chamber 64 from returning to the intake manifold 36 side, and the combustion gas returned to the intake manifold 36 from the exhaust manifold 20 side via the combustion chamber 64. (Internal EGR gas) can be eliminated.

  Thereafter, when the intake stroke arrives and the intake valve 68 is opened, the residual gas remaining in the intake manifold 36 or the EGR passage 54 on the downstream side of the EGR valve 56 is removed as shown in FIG. It is sucked into the combustion chamber 64. In this case, since the closing timing IVC of the intake valve 68 is controlled to be the intake bottom dead center, the residual gas sucked into the combustion chamber 64 during the current intake stroke is prevented from blowing back to the intake manifold 36 side. In addition, the amount of gas sucked into the combustion chamber 64 can be maximized.

  Thereafter, after the compression stroke and the expansion stroke, the exhaust stroke arrives and the exhaust valve 66 is opened. As shown in FIG. 5D, the residual gas in the combustion chamber 64 is discharged to the exhaust manifold 20. Thereby, the discharge (scavenging) of residual gas from the intake manifold 36 and the combustion chamber 64 is completed.

  Further, according to the routine shown in FIG. 4, after the scavenging mode is executed, it is determined that scavenging of the residual gas from the intake passage 30 and the combustion chambers 64 of all the cylinders is completed, and then the vibration is performed. A reduction mode is executed. According to this vibration reduction mode, the actual compression ratio is reduced and the amount of air taken into the combustion chamber 64 is reduced by retarding the closing timing IVC of the intake valve 68 with respect to the intake bottom dead center. it can. Thereby, the vibration of the internal combustion engine 10 that occurs during the stop operation can be suppressed. Further, according to the routine processing, the vibration reduction mode is executed after the scavenging of the residual gas is completed in the scavenging mode, so that the combustion is performed by retarding the closing timing IVC of the intake valve 68. Even if the gas sucked into the chamber 64 is blown back to the intake manifold 36 side, the combustion gas is not returned to the intake passage 30. Further, even when this vibration reduction mode is executed, the valve overlap period is made zero in such a manner that the exhaust valve 66 is closed and the intake valve 68 is opened at the exhaust top dead center. As a result, the amount of internal EGR gas can be made zero, and the burned gas discharged to the exhaust manifold 20 at the time of scavenging completion determination does not return into the combustion chamber 64.

  According to the control of the present embodiment having the scavenging mode and the vibration reduction mode described above, it is possible to suitably achieve both the scavenging of residual gas and the suppression of vibration during the stop operation.

  Further, as described above with reference to FIG. 5, after the fuel injection is stopped after the transition to the scavenging mode is completed, at least two exhaust strokes are allowed to elapse in all the cylinders to stop the fuel injection. The scavenging of the residual gas existing in the intake passage 30 and the combustion chamber 64 is completed. Therefore, in the routine shown in FIG. 4, as a predetermined cycle for continuing the scavenging mode after completion of the transition to the scavenging mode, the exhaust stroke is performed at least twice in all cylinders from the time of stopping fuel injection in each cylinder (required for completion of scavenging). It is possible to determine in the shortest time that the scavenging of the residual gas has been completed by setting the period until the elapsed cycle (the detailed number of cycles varies depending on the volume of the intake manifold 36 and the exhaust amount). Become. Thereby, it is possible to shift to the vibration reduction mode immediately after the scavenging of the residual gas is completed, and to sufficiently suppress the vibration during the stop operation of the internal combustion engine 10.

  Further, according to the routine shown in FIG. 4, when a stop request accompanying the establishment of the automatic stop condition is issued, fuel injection is stopped without passing through the scavenging mode, and the vibration reduction mode is immediately performed. Transition to is started. When the internal combustion engine 10 is automatically stopped by the idle stop function during the start of the vehicle system, the internal combustion engine 10 is temporarily stopped as compared with the case where the internal combustion engine 10 is stopped when the IG switch 74 is turned off. Restarting takes place in a relatively short time. For this reason, in such a case, it can be said that corrosion of parts around the combustion chamber is not a problem. Therefore, in such a case, by omitting the implementation of the scavenging mode, it is possible to shift to the vibration reduction mode at an early stage and to further suppress the vibration.

  By the way, in the first embodiment described above, the closing timing IVC of the intake valve 68 is set to the retard side from the intake bottom dead center in the vibration reduction mode. However, in the present invention, the method of controlling the closing timing of the intake valve so as to reduce the actual compression ratio is not limited to this, and the closing timing of the intake valve is set to an advance side from the intake bottom dead center. Also good.

  Further, in the above-described first embodiment, the description has been given by taking as an example a configuration that is set in advance so that the closing timing of the exhaust valve 66 becomes the exhaust top dead center. However, the present invention is not limited to this. When a request to stop the internal combustion engine is issued, the opening timing of the intake valve is controlled while controlling the closing timing of the exhaust valve to be exhaust top dead center. Control may be performed so that the exhaust top dead center is reached.

  In the first embodiment described above, the compression ignition type internal combustion engine has been described as an example. However, the internal combustion engine to which the present invention is applied is not limited to this, and may be a spark ignition internal combustion engine such as a gasoline engine. When the control of the present embodiment is applied to the spark ignition type internal combustion engine, the ignition may be stopped simultaneously when the fuel injection is stopped.

In the first embodiment described above, the ECU 70 executes the process of step 100, so that the “stop request detecting means” in the first aspect of the invention executes the process of step 108. The “first intake closing timing control means” in the first invention realizes the “second intake closing timing control means” in the first invention by executing the processing of step 122 described above.
Further, the “scavenging completion determining means” according to the second aspect of the present invention is realized by the ECU 70 executing the processes of steps 114 to 118 described above.
Further, the “stop-time control switching means” according to the third aspect of the present invention is realized by the ECU 70 executing the processing of step 102 described above.
Further, the “intake opening timing control means” according to the fourth aspect of the present invention is realized by the ECU 70 executing the processing of step 108 described above.
Further, the “exhaust gas recirculation valve fully closing means” in the fifth aspect of the present invention is realized by the ECU 70 executing the processing of step 108 described above.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG. 6 and FIG.
The system of the present embodiment can be realized by causing the ECU 70 to execute a routine shown in FIG. 7 described later instead of the routine shown in FIG. 4 using the hardware configuration shown in FIG.

FIG. 6 is a diagram for explaining a scavenging completion time determination method according to Embodiment 2 of the present invention, and schematically shows the configuration of the internal combustion engine 10 shown in FIG.
The system of this embodiment is the same as the system of Embodiment 1 described above, except that the method for determining whether or not scavenging of residual gas is completed after shifting to the scavenging mode.

  In the present embodiment, the passage volume in the section from the EGR valve 56 to the intake valve 68 (more precisely, the volume of the EGR passage 54 in the section from the EGR valve 56 to the connection port 30a and the intake valve 68 from the connection port 30a). Based on the total volume of the intake manifold 36 in the previous section), the amount of residual gas remaining in the passage volume is estimated. More specifically, the passage volume is a known value determined according to the specifications of the internal combustion engine 10, and the temperature and pressure of the gas in the passage volume are determined by the intake air temperature sensor 42 and the intake air pressure sensor 44. Can be detected. Therefore, the amount of residual gas staying in the passage volume can be calculated according to the gas equation of state.

  In addition, in this embodiment, the integrated value of the intake air amount (integrated intake air amount) that is taken into the combustion chamber 64 after the EGR valve 56 is fully closed during the stop operation and the fuel injection is stopped is calculated. ing. The intake amount per intake stroke sucked into the combustion chamber 64 varies depending on the engine speed. For this reason, by storing a predetermined map in relation to the engine speed in the intake air amount per time in the ECU 70, the intake air amount per time according to the engine speed can be acquired. . Then, by integrating the intake air amount per time, the integrated intake air amount can be calculated as the cycle progresses.

  In the present embodiment, when the integrated intake air amount calculated as described above becomes equal to or larger than the estimated value of the residual gas amount in the passage volume, the residual in the intake passage 30 (intake manifold 36) and the combustion chamber 64 is retained. It is determined that gas scavenging has been completed. According to the scavenging mode, the gas in the combustion chamber 64 is prevented from blowing back to the intake manifold 36 side. Therefore, it is determined that scavenging of the residual gas in the combustion chamber 64 together with the intake passage 30 (intake manifold 36) is completed by determining that the residual gas in the intake manifold 36 has been sucked by the method of the present embodiment. It becomes possible.

  FIG. 7 is a flowchart showing a control routine executed by the ECU 70 in the second embodiment in order to realize the control during the engine stop operation of the present invention. The routine shown in FIG. 7 is the same as the routine shown in FIG. 4 except that the processing in steps 114 to 118 is replaced by step 200 described later. Steps that are the same as steps are assigned the same reference numerals, and descriptions thereof are omitted or simplified.

  In the routine shown in FIG. 7, after the transition to the scavenging mode is completed and the fuel injection is stopped (step 112), it is then determined whether or not scavenging of the residual gas is completed by the scavenging mode (step 112). 200). In step 200, the scavenging completion time is determined based on the method described with reference to FIG. If it is determined in step 200 that scavenging has been completed, the transition to the vibration reduction mode is started (step 120).

  Also by the routine shown in FIG. 7 described above, the same effect as the routine shown in FIG. 4 of the first embodiment described above can be obtained.

  By the way, in the second embodiment described above, the integrated intake air amount after the EGR valve 56 is fully closed during the stop operation and the fuel injection is stopped is equal to or greater than the estimated value of the residual gas amount in the passage volume. In this case, it is determined that scavenging of the residual gas in the intake passage 30 and the combustion chamber 64 has been completed. However, the scavenging determination method in the present invention is not limited to this, and for example, the following method may be used.

  That is, when the intake air temperature detected by the intake air temperature sensor 42 installed in the intake manifold 36 becomes lower than a predetermined value, it is determined that scavenging of the residual gas in the intake passage 30 (and the combustion chamber 64) is completed. May be. Since the exhaust gas after being subjected to combustion has a high temperature, when the exhaust gas remains in the intake manifold 36, the gas temperature in the intake manifold 36 is higher than when normal temperature fresh air circulates. Get higher. Therefore, according to this method, whether or not scavenging of the residual gas is completed by setting the predetermined value to a value that can distinguish the intake air temperature between the case where the burned gas remains and the case of only fresh air. Can be determined.

  Further, the scavenging determination method in the present invention may be the following method. That is, the scavenging of the residual gas in the intake passage 30 and the combustion chamber 64 is completed when the air-fuel ratio of the exhaust gas detected by the A / F sensor 26 installed in the exhaust passage 18 becomes higher than a predetermined value. You may judge. When scavenging of the residual gas in the intake passage 30 and the combustion chamber 64 is completed and the combustion chamber 64 is filled with fresh air, the gas detected by the A / F sensor 26 becomes fresh air and is subjected to combustion. As compared with the case where the burned gas flows after the flow, the lean value is detected. Therefore, according to the present method, it is possible to determine whether or not scavenging of the residual gas is completed by setting the predetermined value to a value that can distinguish the burned gas from the fresh air.

  Further, the scavenging determination method in the present invention may be the following method. Even when it is determined that scavenging of the residual gas in the intake passage 30 (and the combustion chamber 64) has been completed when the intake pressure detected by the intake pressure sensor 44 installed in the intake manifold 36 becomes lower than a predetermined value. Good. Since the exhaust gas after being subjected to combustion is high temperature, when the exhaust gas remains in the intake manifold 36, the exhaust gas expands by receiving heat from the exhaust gas as compared with the case where fresh air at normal temperature is circulated. As a result, the pressure of the gas in the intake manifold 36 increases. Therefore, according to this method, whether or not scavenging of the residual gas is completed by setting the predetermined value to a value that can distinguish the intake pressure between the case where the burned gas remains and the case where only fresh air is present. Can be determined.

  Further, the scavenging determination method in the present invention may be the following method. That is, when the temperature of the exhaust gas detected by the exhaust temperature sensor 28 installed in the exhaust passage 18 becomes lower than a predetermined value, it is determined that scavenging of the residual gas in the intake passage 30 and the combustion chamber 64 is completed. May be. When scavenging of the residual gas in the intake passage 30 and the combustion chamber 64 is completed and the combustion chamber 64 is filled with fresh air, the gas detected by the exhaust temperature sensor 28 becomes fresh air and is subjected to combustion. The detected temperature is greatly reduced as compared with the case where the burned gas flows after. Therefore, according to the present method, it is possible to determine whether or not scavenging of the residual gas is completed by setting the predetermined value to a value that can distinguish the burned gas from the fresh air.

In the second embodiment described above, the ECU 70 executes the processing of step 200 (the method described with reference to FIG. 6), whereby “residual gas amount estimating means” and “integration” in the sixth invention are described. "Intake amount acquisition means" is realized.
The intake air temperature sensor 42 corresponds to the “intake air temperature detecting means” in the seventh aspect of the invention.
The A / F sensor 26 corresponds to the “air-fuel ratio detecting means” in the eighth aspect of the invention.
The intake pressure sensor 44 corresponds to the “intake pressure detecting means” in the ninth aspect of the invention.
The exhaust temperature sensor 28 corresponds to the “exhaust temperature detecting means” in the tenth aspect of the present invention.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Injector 18 Exhaust passage 20 Exhaust manifold 26 A / F sensor 28 Exhaust temperature sensor 30 Intake passage 30a Inlet side connection port 36 of EGR passage 54 Intake manifold 42 Intake temperature sensor 44 Intake pressure sensor 46 Intake variable valve mechanism 50 Intake cam angle sensor 54 Exhaust gas recirculation passage (EGR passage)
56 Exhaust gas recirculation valve (EGR valve)
64 Combustion chamber 66 Exhaust valve 68 Intake valve 70 ECU (Electronic Control Unit)
74 IG switch

Claims (10)

An intake variable valve mechanism that can change the closing timing of the intake valve;
Stop request detecting means for detecting a stop request of the internal combustion engine;
First intake closing timing control means for controlling the closing timing of the intake valve to a first control timing in the vicinity of the intake bottom dead center when the stop request is issued;
The internal combustion engine is compared with a case where the closing timing of the intake valve is controlled to the first control timing after the closing timing of the intake valve has shifted to the first control timing during the stop operation of the internal combustion engine. Second intake closing timing control means for controlling the closing timing of the intake valve to a second control timing so that the actual compression ratio of
A control device for an internal combustion engine comprising a variable valve mechanism. Scavenging completion determining means for determining whether or not scavenging of the residual gas in the intake passage and the combustion chamber has been completed after the closing timing of the intake valve has shifted to the first control time during the stop operation;
The second intake closing timing control means sets the closing timing of the intake valve when the scavenging completion determining means determines that scavenging of the residual gas in the intake passage and the combustion chamber is completed during the stop operation. 2. The control device for an internal combustion engine having a variable valve mechanism according to claim 1, wherein the control device is means for controlling at a second control time. The internal combustion engine is an internal combustion engine that is automatically stopped when a predetermined automatic stop condition is satisfied during startup of the vehicle system,
When the stop request is accompanied by the establishment of the automatic stop condition, the second intake closing timing control means does not go through the control of the intake valve closing timing by the first intake closing timing control means. The control device for an internal combustion engine having a variable valve mechanism according to claim 1 or 2, further comprising a stop-time control switching means for controlling the closing timing of the intake valve. An intake opening timing control means for controlling the opening timing of the intake valve to be exhaust top dead center when the stop request is issued;
An exhaust valve that is set in advance so that the closing timing becomes exhaust top dead center, or is controlled so that the closing timing becomes exhaust top dead center when the stop request is issued;
The control apparatus for an internal combustion engine according to claim 2 or 3, further comprising: An exhaust gas recirculation valve for opening and closing an exhaust gas recirculation passage connecting the exhaust passage and the intake passage;
An exhaust recirculation valve full closing means for fully closing the exhaust recirculation valve when the stop request is issued in a state where the exhaust gas recirculation is being performed by adjusting the opening of the exhaust gas recirculation valve;
The control apparatus for an internal combustion engine of a variable valve mechanism according to any one of claims 2 to 4, further comprising: The scavenging completion determining means includes
A residual gas amount estimating means for estimating a residual gas amount existing in the passage volume based on a passage volume of a section from the exhaust gas recirculation valve to the intake valve;
Acquiring an integrated intake amount for acquiring an integrated value of the intake amount taken into the combustion chamber after the exhaust gas recirculation valve is fully closed by the exhaust gas recirculation valve closing means and the fuel injection is stopped during the stop operation Means,
6. The variable motion according to claim 5, wherein the scavenging of the residual gas in the intake passage and the combustion chamber is determined to be complete when the integrated value is equal to or greater than the estimated value of the residual gas amount. A control device for an internal combustion engine including a valve mechanism. An intake air temperature detecting means which is installed in an intake manifold provided in the intake passage and detects an intake air temperature;
The scavenging completion determining means determines that scavenging of the residual gas in the intake passage and the combustion chamber is completed when the intake air temperature detected by the intake air temperature detecting means is lower than a predetermined value. A control device for an internal combustion engine comprising the variable valve mechanism according to any one of claims 2 to 5. Further comprising air-fuel ratio detection means for detecting the air-fuel ratio of the gas flowing through the exhaust passage,
The scavenging completion determining means determines that scavenging of the residual gas in the intake passage and the combustion chamber is completed when the air-fuel ratio of the gas detected by the air-fuel ratio detecting means is higher than a predetermined value. A control device for an internal combustion engine comprising the variable valve mechanism according to any one of claims 2 to 5. An intake pressure detection means for detecting an intake pressure, which is installed in an intake manifold provided in the intake passage;
The scavenging completion determining means determines that scavenging of the residual gas in the intake passage and the combustion chamber is completed when the intake pressure detected by the intake pressure detecting means is lower than a predetermined pressure. A control device for an internal combustion engine comprising the variable valve mechanism according to any one of claims 2 to 5. Exhaust temperature detecting means for detecting the temperature of the exhaust gas flowing through the exhaust passage,
The scavenging completion determining means determines that scavenging of the residual gas in the intake passage and the combustion chamber is completed when the temperature of the exhaust gas detected by the exhaust temperature detecting means is lower than a predetermined value. A control device for an internal combustion engine comprising the variable valve mechanism according to any one of claims 2 to 5.

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