JP6680146B2 - Control device for internal combustion engine - Google Patents

Description

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

  Patent Document 1 describes a control device for an internal combustion engine that detects the occurrence of knocking and sets the retard amount of the ignition timing. In such ignition timing control, the ignition timing is retarded as the knocking frequency increases.

JP-A-3-185237

  By the way, in the internal combustion engine, the actual compression ratio can be changed by changing the closing timing of the intake valve. Specifically, when changing the closing timing of the intake valve on the retard side from the intake bottom dead center, the actual compression ratio becomes smaller as the closing timing is set to the retard side, and the closing timing is changed. The actual compression ratio increases as the angle is advanced.

  When the actual compression ratio is large, the torque sensitivity to the ignition timing retard is high. Therefore, if the retard amount from the basic ignition timing in the ignition timing control increases, the torque may decrease.

Hereinafter, the means for solving the above-mentioned problems and the effects thereof will be described.
An internal-combustion-engine control apparatus for solving the above problem is an internal-combustion-engine control apparatus that controls an internal combustion engine including a variable valve mechanism that can change the closing timing of an intake valve. This control device for an internal combustion engine includes an ignition timing control unit that performs ignition timing control that retards the ignition timing as the frequency of knocking increases, and a closing timing of the intake valve on the retard side relative to the intake bottom dead center. And a valve operating system control unit that controls the variable valve operating mechanism so as to be changed. Then, in this control device for the internal combustion engine, the valve train control unit controls the closing timing of the intake valve to be the retard amount when the retard amount of the ignition timing from the basic ignition timing is a predetermined amount or more. The variable valve mechanism is controlled so as to be on the retard side as compared with the case where is smaller than the predetermined amount.

  According to the above configuration, when the retard amount of the ignition timing from the basic ignition timing is equal to or greater than the predetermined amount, the closing timing of the intake valve is delayed compared to when the retard amount of the ignition timing is smaller than the predetermined amount. It becomes the corner side, and the actual compression ratio becomes smaller. This can reduce the sensitivity of the torque to the retard of the ignition timing. Therefore, it is possible to prevent the torque from becoming small due to the ignition timing being greatly retarded from the basic ignition timing through the ignition timing control.

FIG. 3 is a relationship diagram showing a relationship between an ECU that is an embodiment of a control device for an internal combustion engine and each part of the internal combustion engine that is a control target thereof. 6 is a timing chart illustrating a mode of changing the opening / closing timing of an intake valve by a valve timing changing mechanism controlled by a valve operating system control unit of the same ECU. 6 is a timing chart for explaining a mode of changing the working angle of the intake cam and the maximum lift amount of the intake valve by the valve lift amount changing mechanism controlled by the valve system control unit of the ECU. The flowchart which shows the flow of the basic process in the ignition timing control which the ignition timing control part of the same ECU performs. The flowchart which shows the flow of the learning process in ignition timing control. Explanatory drawing explaining the setting aspect of ignition timing by ignition timing control. The graph which shows the relationship between the ignition timing retard amount and the torque change rate. The flowchart which shows the flow of the switching process of the control aspect of the variable valve mechanism which the valve train control part of the same ECU performs. The flowchart which shows the flow of the determination value change process which the valve operating system control part of the same ECU performs. The flowchart which shows the flow of the retardation history flag update process which the valve operating system control part of the same ECU performs.

Hereinafter, an electronic control unit (hereinafter referred to as an ECU), which is an embodiment of a control device for an internal combustion engine, will be described with reference to FIGS. 1 to 10.
As shown in FIG. 1, in an internal combustion engine 1 controlled by the ECU 100, an intake passage 3 is connected to a combustion chamber 2. A fuel injection valve 4 is provided in the intake passage 3. In the internal combustion engine 1, air is sucked into the combustion chamber 2 through the intake passage 3 and fuel injected from the fuel injection valve 4 is supplied to the combustion chamber 2. Although the internal combustion engine 1 includes a plurality of combustion chambers 2, only one of them is shown in FIG. An exhaust passage 8 is connected to the combustion chamber 2.

  When a mixture of air and fuel introduced into each combustion chamber 2 is ignited by a spark plug 5 provided in each combustion chamber 2, the mixture burns and a piston 6 reciprocates. The crankshaft 7, which is the output shaft of the internal combustion engine 1, rotates. Then, the burned air-fuel mixture is sent out from each combustion chamber 2 to the exhaust passage 8 as exhaust gas.

  Between each combustion chamber 2 and the intake passage 3 in the internal combustion engine 1, an intake valve provided by the intake camshaft 11 works by the action of an intake camshaft 11 that rotates in conjunction with the crankshaft 7 to operate the intake valve. When 9 is opened and closed, it is connected and disconnected. In addition, between each combustion chamber 2 and the exhaust passage 8 in the internal combustion engine 1, due to the rotation of the exhaust cam shaft 12 that rotates in conjunction with the crankshaft 7, the action of the exhaust cam provided on the exhaust cam shaft 12 is performed. The exhaust valve 10 is opened / closed so that the exhaust valve 10 is opened / closed.

  The internal combustion engine 1 is provided with a variable valve mechanism 15 that makes the opening / closing characteristics of the intake valve 9 variable. The variable valve mechanism 15 of the internal combustion engine 1 includes a valve timing changing mechanism 13 that changes the relative rotational phase of the intake camshaft 11 with respect to the crankshaft 7, a working angle of the intake cam with respect to the intake valve 9, and a maximum lift of the intake valve 9. A valve lift amount changing mechanism 14 that makes the amount variable is provided. The opening / closing characteristics of the intake valve 9 are changed by the operations of the valve timing changing mechanism 13 and the valve lift amount changing mechanism 14.

  As shown in FIG. 2, when the valve timing changing mechanism 13 is operated and the relative rotation phase of the intake camshaft 11 with respect to the crankshaft 7 is changed, the opening period of the intake valve 9 is held constant, Both the opening timing and the closing timing of the intake valve 9 can be advanced or retarded.

  Further, as shown in FIG. 3, when the valve lift amount changing mechanism 14 is operated, the working angle of the intake cam with respect to the intake valve 9 changes, and in synchronization with this, the maximum lift amount of the intake valve 9 also changes. .

  Therefore, according to the variable valve mechanism 15, the working angle of the intake cam with respect to the intake valve 9 can be changed while changing the relative rotational phase of the intake camshaft 11 with respect to the crankshaft 7. As a result, in the internal combustion engine 1, the closing timing of the intake valve 9 can be changed without changing the opening timing of the intake valve 9.

  The internal combustion engine 1 is controlled by the ECU 100. The ECU 100 includes a central processing unit that performs various kinds of arithmetic processing related to control of the internal combustion engine 1, a memory that stores programs and data for controlling the internal combustion engine 1, calculation results of the central processing unit, and various sensors. It is configured by a memory or the like that stores the detection result and the like.

  As shown in FIG. 1, the ECU 100 is provided with an accelerator position sensor 28 that detects an accelerator operation amount that is a depression amount of an accelerator pedal 27 and a throttle opening degree that is an opening degree of a throttle valve 29 provided in the intake passage 3. A throttle position sensor 30 for detecting is connected. In addition, the ECU 100 includes an air flow meter 32 that detects an intake air amount that is an amount of air that is taken into the combustion chamber 2 through the intake passage 3, a crank angle that is a rotation angle of the crankshaft 7, and an engine rotation speed. The crank position sensor 34, which outputs a signal corresponding to the change of the crank angle used for, is also connected.

  Further, to the ECU 100, a cam position sensor 35 that outputs a signal corresponding to the rotational position of the intake camshaft 11, a drive amount detection sensor 37 that detects the drive amount of the valve lift amount changing mechanism 14, a combustion chamber of the internal combustion engine 1. A knock sensor 31 that outputs a signal corresponding to the strength of knocking generated in 2 is also connected.

  Further, the ECU 100 controls the throttle valve 29 to adjust the throttle opening, the throttle valve control unit 120 to control the variable valve mechanism 15, and the ignition plug 5 to adjust the ignition timing. An ignition timing control unit 130 and a fuel injection amount control unit 140 that controls the fuel injection valve 4 to adjust the fuel injection amount are provided.

  The ECU 100 controls the internal combustion engine 1 through the throttle control unit 110, the valve system control unit 120, the ignition timing control unit 130, and the fuel injection amount control unit 140 based on the signals input from the various sensors.

  For example, the throttle control unit 110 of the ECU 100 estimates the magnitude of the required torque based on the engine rotation speed and the accelerator operation amount, and throttles the throttle valve so as to realize the intake air amount necessary to realize the torque. Adjust the opening. Further, the fuel injection amount control unit 140 of the ECU 100 controls the fuel injection valve 4 according to the intake air amount and adjusts the fuel injection amount so that the air-fuel ratio of the air-fuel mixture approaches the stoichiometric air-fuel ratio.

  Further, the valve train control unit 120 of the ECU 100 delays the closing timing of the intake valve 9 greatly from the intake bottom dead center during the low load operation in which a large torque is not required, so that the intake stroke reaches the middle of the compression stroke. The retard side valve timing control is performed to keep the valve 9 open. When such retarded valve timing control is being performed, the air that has once been sucked into the combustion chamber 2 can be blown back into the intake passage 3 in the compression stroke, and excess air can be discharged into the intake passage 3, so the throttle valve The torque can be adjusted by opening 29. Therefore, if such retarded valve timing control is performed, compared with the case where the intake air amount is limited and the torque is adjusted by closing the throttle valve 29 without utilizing the blowback of air in the compression stroke. The pumping loss can be reduced and the fuel consumption rate can be improved.

  On the other hand, the valve operating system control unit 120 basically advances the valve closing timing of the intake valve 9 during the high load operation in which a large torque is required, as compared with when the retard side valve timing control is performed. Performs valve timing control on the advance side, which is set to the angle side. The amount of air blown back to the intake passage 3 in the compression stroke is smaller when performing the valve timing control on the advance side than when performing the valve timing control on the retard side. Since the charging efficiency of is high, a large torque can be generated. In addition, the closing timing of the intake valve 9 in the advance side valve timing control is set in accordance with the engine rotation speed or the like so that the efficiency of filling the combustion chamber 2 with air can be increased by utilizing the inertia of the intake air. It is set to the retard side from the bottom dead center of intake air.

  Then, the valve closing timing of the intake valve 9 in the retard side valve timing control is adjusted to the engine rotational speed or the like so as to be on the retard side further than the valve closing timing of the intake valve 9 in the advance side valve timing control. It is set to the retard side from the bottom dead center of intake air.

  That is, the valve train control unit 120 in the ECU 100 switches the valve closing timing of the intake valve 9 to the retard side from the intake bottom dead center by switching between the retard side valve timing control and the advance side valve timing control. The variable valve mechanism 15 is controlled to change.

  Further, the ignition timing control unit 130 of the ECU 100 performs ignition timing control for suppressing knocking. The ignition timing control gradually advances the ignition timing when the occurrence of knocking is not detected, and gradually retards the ignition timing when the occurrence of knocking is detected, until just before the knocking occurrence limit. It is performed to advance the ignition timing. In this ignition timing control, a learning process for learning a change in the likelihood of knocking which gradually changes over time due to deposit accumulation on the piston 6 is also executed.

  FIG. 4 shows a basic processing flow in ignition timing control. This series of processing is repeatedly executed by the ignition timing control unit 130 of the ECU 100 during a predetermined control cycle while the internal combustion engine 1 is operating. It should be noted that the ignition timing is represented by a crank angle to the advance side with reference to the compression top dead center. That is, the value indicating the ignition timing becomes larger as the ignition timing is closer to the advance side than the compression top dead center.

  When this series of processes is started, the ignition timing control unit 130 first calculates the basic ignition timing ABSE and the limit retarded ignition timing AKMF based on the engine speed and the load in step S100. The load is obtained from the amount of intake air detected by the air flow meter 32 and the like.

  The basic ignition timing ABSE is the timing on the retarded side of the optimum ignition timing at which the torque generation efficiency of the internal combustion engine 1 is maximized or the knock limit ignition timing that is the advance limit of the ignition timing. The knock limit ignition timing is a limit value on the retard side of the ignition timing range in which it is confirmed that knocking occurs. Further, the limit retarded ignition timing AKMF is a limit value on the advance side of the ignition timing range in which it is confirmed that knocking does not occur even under conditions where knocking easily occurs.

  In terms of improving the fuel consumption rate, it is advantageous to set the finally set ignition timing (target ignition timing AOP) as close to the basic ignition timing ABSE as possible. On the other hand, even if the target ignition timing AOP is set to a timing on the retard side of the limit retarded ignition timing AKMF, it is meaningless in terms of suppressing knocking. Therefore, in the ignition timing control, the target ignition timing AOP is controlled within the range from the limit retarded ignition timing AKMF to the basic ignition timing ABSE.

  Next, in step S101, the ignition timing control unit 130 sets the difference between the basic ignition timing ABSE and the limit retarded ignition timing AKMF as the value of the limit retarded amount AKMAX. The limit retard amount AKMAX is the upper limit value of the retard amount of the target ignition timing AOP with respect to the basic ignition timing ABSE in the ignition timing control.

  Subsequently, in step S102, the ignition timing control unit 130 confirms whether or not knocking has occurred, based on the detection result of the knock sensor 31. When the occurrence of knocking is confirmed in step S102 (step S102: YES), the ignition timing control unit 130 advances the process to step S103.

  Then, the ignition timing control unit 130 increases the value of the knock control amount AKCS in step S103. The knock control amount AKCS is represented by a crank angle, and a larger value indicates that the amount by which the ignition timing is retarded is larger, and the initial value is “0”. The increase amount of the knock control amount AKCS at this time is set according to the detected knocking intensity and the occurrence frequency. Here, the higher the knocking intensity or the higher the knocking occurrence frequency, the larger the increase amount of the knock control amount AKCS.

  On the other hand, when it is confirmed in step S102 that knocking has not occurred (step S102: NO), the ignition timing control unit 130 advances the process to step S104.

Then, the ignition timing control unit 130 reduces the value of the knock control amount AKCS in step S104. The reduction amount of the knock control amount AKCS at this time is a constant.
After updating the knock control amount AKCS in steps S103 and S104, the ignition timing control unit 130 advances the process to step S105.

  Then, in step S105, the ignition timing control unit 130 calculates the ignition timing retard amount AKNK which is the retard amount of the ignition timing from the basic ignition timing ABSE. The ignition timing retard amount AKNK is calculated by adding the knock control amount AKCS to the limit retard amount AKMAX and subtracting the knock learning amount AGKNK (AKNK ← AKMAX + AKCS-AGKNK). The knock learning amount AGKNK is represented by a crank angle, and a larger value indicates a larger amount by which the ignition timing is advanced, and is a value set in a learning process described later.

  When the ignition timing retard amount AKNK is calculated in step S105, the ignition timing control unit 130 advances the process to step S106, and sets the target ignition timing AOP in step S106. The target ignition timing AOP is set by correcting the basic ignition timing ABSE to the retard side by the ignition timing retard amount AKNK. Specifically, the difference obtained by subtracting the ignition timing retard amount AKNK from the basic ignition timing ABSE is set as the target ignition timing AOP. (AOP ← ABSE-AKNK).

  When the target ignition timing AOP is thus set in step S106, the ignition timing control unit 130 once ends this series of processes. Then, the ignition timing control unit 130 controls the spark plug 5 so that the target ignition timing AOP set here is ignited.

  Next, the learning process in the ignition timing control will be described with reference to FIG. This learning process continues from the basic process of ignition timing control described with reference to FIG. 4 and continues until the series of processes described with reference to FIG. It is executed by the unit 130.

  When this learning process is started, the ignition timing control unit 130 first determines in step S200 whether or not the gradual change value of the knock control amount AKCS is larger than a prescribed positive value “α”. The gradual change value of the knock control amount AKCS is a value obtained by subjecting the knock control amount AKCS to a process of slowing down the increasing / decreasing speed thereof, a so-called smoothed value.

  When it is determined in step S200 that the gradual change value of knock control amount AKCS is larger than “α” (step S200: YES), ignition timing control unit 130 advances the process to step S201.

  Then, the ignition timing control unit 130 reduces the value of the knock learning amount AGKNK by a prescribed amount in step S201. In step S201, the value of knock learning amount AGKNK is decreased by a specified amount, and the value of knock control amount AKCS is also decreased by a specified amount. The initial value of the knock learning amount AGKNK is "0", and the specified amount is smaller than "α". In this way, when the value of the knock learning amount AGKNK is updated in step S201, the ignition timing control unit 130 once ends this learning process.

  On the other hand, when it is determined in step S200 that the gradual change value of knock control amount AKCS is equal to or less than "α" (step S200: NO), ignition timing control unit 130 advances the process to step S202.

Then, in step S202, ignition timing control unit 130 determines whether or not the gradual change value of knock control amount AKCS is smaller than “−α”.
When it is determined in step S202 that the gradual change value of knock control amount AKCS is smaller than “−α” (step S202: YES), the ignition timing control unit 130 advances the process to step S203.

  Then, in step S203, ignition timing control unit 130 increases the value of knock learning amount AGKNK by a prescribed amount. In step S203, the value of knock learning amount AGKNK is increased by a prescribed amount, and the value of knock control amount AKCS is also increased by a prescribed amount. Further, the specified amount is set to a value smaller than “α”. In this way, even when the value of the knock learning amount AGKNK is updated in step S203, the ignition timing control unit 130 once ends this learning process.

  When it is determined in step S202 that the gradual change value of the knock control amount AKCS is equal to or greater than “−α” (step S202: NO), the ignition timing control unit 130 changes the value of the knock learning amount AGKNK and knocks. The value of the controlled variable AKCS is not changed, and the learning process is temporarily terminated. In this case, the gradual change value of the knock control amount AKCS is “−α” or more and “α” or less.

  As shown in FIG. 6, according to such ignition timing control, the ignition timing retarding amount AKNK, which is the retarding amount of the ignition timing from the basic ignition timing ABSE, is set to the limit retarding amount AKMAX and the knock learning amount. The correction amount is set to be decreased by the value of AGKNK, and the correction amount is set to be increased to be increased by the value of knock control amount AKCS. As described above, the value of the knock control amount AKCS increases when the occurrence of knocking is confirmed, and decreases when it is not confirmed. Therefore, the target ignition timing AOP, which is the ignition timing retarded by the ignition timing retard amount AKNK from the basic ignition timing ABSE, is gradually advanced until knocking is confirmed. The value becomes settled at the ignition timing advanced until just before the ignition timing at which knocking occurs. The value of the knock learning amount AGKNK is updated through the learning process so that the absolute value of the knock control amount AKCS becomes smaller when the absolute value of the knock control amount AKCS becomes larger.

  The value of the knock control amount AKCS is reset to “0” when the ignition switch is turned “OFF”, but the value of the knock learning amount AGKNK is stored and stored in the memory even after the ignition switch is turned “OFF”. Then, the ignition timing control at the time of the next engine operation is succeeded.

  By the way, when the valve timing control on the advance side is executed, the actual compression ratio becomes larger than when the valve closing timing of the intake valve 9 is set on the retard side as in the valve timing control on the retard side. Therefore, the sensitivity of the torque to the retard of the ignition timing increases, and the amount of decrease in the torque when the ignition timing retard amount AKNK increases through the ignition timing control increases.

  In FIG. 7, the solid line shows the relationship between the ignition timing retard amount AKNK and the torque change rate when the advance valve timing control is executed. Note that FIG. 7 shows the torque change rate with the torque when the ignition timing retard amount AKNK is “0” being “1”. In addition, in FIG. 7, similarly to the retard side valve timing control, the ignition timing delay when the valve closing timing of the intake valve 9 is set to the retard side more than when the advance side valve timing control is executed. The relationship between the angular amount AKNK and the rate of change of torque is shown by a dashed line as a comparative example.

  As shown in FIG. 7, when the ignition timing retard amount AKNK is small, the torque in the case of the comparative example indicated by the alternate long and short dash line executes the valve timing control on the advance side indicated by the solid line. It becomes smaller than the torque when This is because the actual compression ratio is reduced by retarding the closing timing of the intake valve 9.

  However, in the case of the comparative example in which the actual compression ratio is small, the torque sensitivity with respect to the ignition timing retard angle is low, and therefore the torque decrease amount when the ignition timing retard angle amount AKNK becomes large is It is smaller than the torque reduction amount when the side valve timing control is executed. Therefore, as the ignition timing retard amount AKNK increases, the torque in the case of the comparative example indicated by the alternate long and short dash line and the torque during execution of the valve timing control on the advance side indicated by the solid line. The difference between and becomes small, and it comes to reverse on the way.

  During high load operation, it is preferable to execute the valve timing control on the advance side to increase the actual compression ratio to increase the efficiency of filling the combustion chamber 2 with air. However, when the actual compression ratio is large, the sensitivity of the torque to the ignition timing retard angle is high. Therefore, as shown in FIG. 7, when the ignition timing retard angle amount AKNK is increased, the engine is operating under a high load condition. The torque may be reduced.

  Therefore, the ECU 100 switches the control mode of the variable valve mechanism 15 during high load operation according to the ignition timing retard amount AKNK through the control mode switching process of the variable valve mechanism 15 shown in FIG. I have to. In the control mode switching process, the valve operation of the ECU 100 is performed during operation of the internal combustion engine 1 after a predetermined period of time in which the internal combustion engine 1 is started and the series of processes shown in FIGS. 9 and 10 is executed. The system control unit 120 repeatedly executes the control every specified control cycle.

  When this process is started, the valve train control unit 120 of the ECU 100 first determines in step S300 whether or not the throttle opening is equal to or larger than a predetermined opening. Here, it is determined whether or not the engine is under high load operation by determining whether or not the throttle opening is equal to or larger than a predetermined opening. Therefore, the predetermined opening degree, which is the determination threshold value, is set to a value that can be determined to be during high load operation when the throttle opening degree is equal to or larger than the predetermined opening degree. For example, the predetermined opening degree is "50%" when the fully open state is "100%" and the fully closed state is "0%". The throttle opening does not exceed the predetermined opening when the retard valve timing control is executed during the low load operation.

  When it is determined in step S300 that the throttle opening is smaller than the predetermined opening (step S300: NO), that is, during low load operation, the valve train control unit 120 advances the process to step S304.

  Then, in step S304, the valve operating system control unit 120 selects the retard side valve timing control as the control mode of the variable valve operating mechanism 15. When the retard side valve timing control is selected in this way, the valve train system control unit 120 temporarily ends this series of processes. Then, the valve operating system control unit 120 executes the retard side valve timing control for controlling the variable valve mechanism 15 so that the closing timing of the intake valve 9 is on the retard side as compared with the case of the advance side valve timing control. Run.

  On the other hand, when it is determined in step S300 that the throttle opening is equal to or larger than the predetermined opening (step S300: YES), that is, during high load operation, the valve train control unit 120 advances the process to step S301.

  Then, in step S301, the valve operating system control unit 120 determines whether or not the ignition timing retard amount AKNK is equal to or greater than the predetermined amount A. The predetermined amount A that is the determination threshold here is, like the value shown by the broken line in FIG. 7, the valve closing timing of the intake valve 9 as compared with the case where the advance side valve timing control is executed (solid line). Is set to a value of the ignition timing retard amount AKNK that increases the torque when the engine is retarded (dashed line).

  When it is determined in step S301 that the ignition timing retard amount AKNK is equal to or larger than the predetermined amount A (step S301: YES), the valve system control unit 120 advances the process to step S302.

  Then, the valve operating system control unit 120 sets the retarding history flag to "ON" in step S302. The retard history flag is "OFF" in the initial state. The retard history flag is stored and held in the memory even after the ignition switch is turned "OFF", and is taken over at the next engine operation.

When the retarding history flag is turned “ON” through step S302, the valve operating system control unit 120 advances the process to step S303.
On the other hand, if it is determined in step S301 that the ignition timing retard amount AKNK is smaller than the predetermined amount A (step S301: NO), the valve train system control unit 120 does not perform the process of step S302 and executes the process. To Step S303.

In step S303, the valve operating system control unit 120 determines whether or not the retard angle history flag is “ON”.
When it is determined in step S303 that the retard history flag is "OFF" (step S303: NO), the valve train control unit 120 advances the process to step S305.

  Then, in step S305, the valve operating system control unit 120 selects the advance side valve timing control as the control mode of the variable valve operating mechanism 15. When the valve timing control on the advance side is selected in this way, the valve train system control unit 120 once ends this series of processes. Then, the valve operating system control unit 120 performs advance side valve timing control for controlling the variable valve mechanism 15 so that the closing timing of the intake valve 9 is on the advance side as compared with the case of the retard side valve timing control. Run.

As described above, the valve operating system control unit 120 executes the advance valve timing control when the engine is operating under a high load and the retard history flag is "OFF".
On the other hand, if it is determined in step S303 that the retard history flag is "ON" (step S303: YES), the valve operating system control unit 120 advances the process to step S304. Then, in step S304, the valve operating system control unit 120 selects the retard side valve timing control as the control mode of the variable valve operating mechanism 15. That is, when the ignition timing retarding amount AKNK is equal to or greater than the predetermined amount A and the retarding history flag is set to "ON", the valve train system control unit 120 retards the ignition side even during high load operation. Executes valve timing control.

  As a result, when the ignition timing retarding amount AKNK is equal to or greater than the predetermined amount A, the valve operating system control unit 120 compares the valve closing timing of the intake valve 9 with that when the advance side valve timing control is selected. The variable valve mechanism 15 is controlled so as to be on the retard side.

  As a result, the actual compression ratio becomes smaller, so that the sensitivity of the torque to the retard of the ignition timing can be reduced. Therefore, according to the ECU 100, it is possible to prevent the torque from becoming small due to the ignition timing being greatly retarded from the basic ignition timing ABSE through the ignition timing control.

  As shown in FIG. 6, the ignition timing retard amount AKNK is a limit retard amount determined according to the basic ignition timing ABSE and the limit retard ignition timing AKMF calculated according to the engine speed and the load. It is calculated by correcting AKMAX with the knock learning amount AGKNK and the knock control amount AKCS. Therefore, the ignition timing retard amount AKNK changes according to the engine rotation speed and the load. Therefore, when the determination result in step S301 is reflected as it is in the switching of the control mode of the variable valve mechanism 15, the closing timing of the intake valve 9 is repeatedly changed, which may cause hunting. . That is, the control mode of the variable valve mechanism 15 at the time of high load operation is changed to the retard side valve timing control once, and then the control mode of the variable valve mechanism 15 is changed according to the variation of the ignition timing retard amount AKNK. , The retard side valve timing control and the advance side valve timing control are switched back and forth.

  On the other hand, in this ECU 100, the valve operating system control unit 120 switches the control mode of the variable valve operating mechanism 15 according to the state of the delay angle history flag that is set by reflecting the determination result in step S301. As a result, after the ECU 100 determines that the ignition timing retard amount AKNK is equal to or greater than the predetermined amount A, the control of the variable valve mechanism 15 during the high load operation causes the ignition timing retard amount AKNK to become larger. Regardless, the retard side valve timing control is executed. Therefore, it is possible to suppress the occurrence of hunting in which the closing timing of the intake valve 9 is repeatedly changed according to the variation of the ignition timing retarding amount AKNK.

  It should be noted that from the time the internal combustion engine 1 is started until the predetermined period of time elapses, that is, the series of processing shown in FIGS. 9 and 10 is being executed, the processing described with reference to FIG. If not, similarly to the advance side valve timing control, the engine operation is performed without greatly retarding the closing timing of the intake valve 9 as in the retard side valve timing control.

  By the way, the situation where the ignition timing retarding amount AKNK becomes larger as the ignition timing retarding amount AKNK exceeds the predetermined amount A often occurs because knocking is likely to occur gradually due to accumulation of deposits on the piston 6.

  The accumulation of deposit is difficult to be eliminated once it progresses, and is eliminated by removing the deposit by maintenance or continuing high-load operation for a long time. Therefore, knocking is likely to occur due to the accumulation of deposits, and when the ignition timing retard amount AKNK is equal to or greater than the predetermined amount A, the situation where knocking is likely to occur is likely to continue thereafter.

  Therefore, when the control mode of the variable valve mechanism 15 at the time of high load operation is switched to the retard side valve timing control, the engine operation is ended and the engine operation is performed next time. It is preferable to execute the retard side valve timing control during high load operation.

  On the other hand, when deposit accumulation is eliminated by performing maintenance or continuing high-load operation for a long time, the control mode of the variable valve mechanism 15 during high-load operation is set to the advance side valve. It is preferable to return to timing control.

  Therefore, the ECU 100 switches the control mode of the variable valve mechanism 15 in accordance with such a situation, and therefore the value of the ignition timing retard amount AKNK at the time of engine start is confirmed through the retard history flag updating process shown in FIG. Then, the retard history flag is updated.

Next, with reference to FIG. 9 and FIG. 10, a description will be given of the processing relating to the update of the delay angle history flag, which is performed during the predetermined period from the engine start.
When the internal combustion engine 1 is started, the ECU 100 confirms the state of the delay angle history flag stored in the memory. The process of confirming the state of the delay angle history flag is repeatedly executed a plurality of times until it can be confirmed whether the delay angle history flag is "ON" or "OFF".

  The determination value changing process shown in FIG. 9 is executed by the valve train control unit 120 of the ECU 100 when the state of the retarding history flag is confirmed after the engine is started. When this process is started, the valve operating system control unit 120 first determines in step S400 whether or not the delay angle history flag is "ON".

  When it is determined in step S400 that the retarding history flag is “ON” (step S400: YES), the valve operating system control unit 120 advances the process to step S401. Then, in step S <b> 401, the valve operating system control unit 120 sets the difference calculated by subtracting the correction amount B from the predetermined amount A as the determination value C.

  On the other hand, when it is determined in step S400 that the retarding history flag is “OFF” (step S400: NO), the valve train control unit 120 advances the process to step S402. Then, in step S402, the valve operating system control unit 120 sets the predetermined amount A as the determination value C as it is.

When the determination value C is set in step S401 or step S402 in this way, the valve system control unit 120 ends this process.
When the determination value changing process for setting the determination value C is completed in this way, the valve operating system control unit 120 starts the retard angle history flag updating process shown in FIG. 10. This process is repeatedly executed after the judgment value changing process described with reference to FIG. 9 is completed and until the elapsed period from the engine start reaches a predetermined period.

When this process is started, the valve train system control unit 120 first determines in step S500 whether or not the ignition timing retard angle amount AKNK is greater than or equal to the determination value C.
When it is determined in step S500 that the ignition timing retard amount AKNK is equal to or greater than the determination value C (step S500: YES), the valve system control unit 120 advances the process to step S501. Then, the valve operating system control unit 120 sets the delay angle history flag to “ON” in step S501.

  On the other hand, if it is determined in step S500 that the ignition timing retard amount AKNK is smaller than the determination value C (step S500: NO), the valve operating system control unit 120 advances the process to step S502. Then, the valve operating system control unit 120 sets the delay angle history flag to “OFF” in step S502.

When step S501 or step S502 is executed in this way, the valve system control unit 120 temporarily ends this processing.
As described above, the ECU 100 determines whether the ignition timing retard amount AKNK by the ignition timing control is equal to or greater than the determination value C during the predetermined period from the engine start, and the ignition timing retard amount AKNK is determined from the determination value C. If it is determined that is also small, the delay angle history flag is updated to "OFF".

  Therefore, when the accumulation of deposits is eliminated and the ignition timing retard amount AKNK is reduced due to the maintenance or the continuation of the high load operation for a long time, the variable valve mechanism 15 during the high load operation is performed. The control mode of (3) is returned to the valve timing control on the advance side.

  It should be noted that the change in the likelihood of knocking due to deposit accumulation or the like gradually progresses over a long period of time, and is reflected in the knock learning amount AGKNK through the learning process described with reference to FIG. When the engine is started, the knock control amount AKCS is reset to "0", but since the knock learning amount AGKNK is inherited from the previous engine operation, the ignition timing retard amount AKNK at the engine start is knock learned. The amount AGKNK is reflected as it is. The ECU 100 confirms the magnitude of the ignition timing retard amount AKNK at the time of engine start, which directly reflects the change in the likelihood of knocking due to such accumulation of deposits, and updates the retard history flag. I am trying to do it.

  Further, in this ECU 100, in the determination value changing process described with reference to FIG. 9, when the retard history flag is “ON”, the determination value C is the difference obtained by subtracting the correction amount B from the predetermined amount A. I am trying to. As a result, when the delay angle history flag is “ON”, the determination value C becomes smaller than when the delay angle history flag is “OFF”. Therefore, although the delay angle history flag is likely to be changed from “OFF” to “ON”, it is difficult to be changed from “ON” to “OFF”.

As a result, it is possible to suppress frequent changes in the engine output characteristics during high load operation due to changes in the control mode of the variable valve mechanism 15.
According to the embodiment described above, the following effects can be obtained.

(1) It is possible to prevent the torque from becoming small due to the ignition timing being greatly retarded from the basic ignition timing ABSE through the ignition timing control.
(2) After the retard side valve timing control is executed during the high load operation, the retard side valve timing control is executed during the high load operation regardless of the magnitude of the ignition timing retard amount AKNK. Since it is executed, it is possible to suppress the occurrence of hunting in which the closing timing of the intake valve 9 is repeatedly changed.

  (3) Since the amount of the ignition timing retard amount AKNK is confirmed and the retard history flag is updated during a predetermined period from the engine start, the knocking may occur due to elimination of deposit accumulation. When it is difficult to occur, the valve timing control on the advance side can be executed again during the high load operation.

  (4) If the engine operation was performed in a state in which the control mode of the variable valve mechanism 15 during the high load operation in the previous engine operation was changed to the retard side valve timing control, the retard angle history flag update process In, it becomes difficult for the retard history flag to be changed to “OFF”. Therefore, the state in which the control mode of the variable valve mechanism 15 during high load operation is changed to the retard side valve timing control is likely to continue, and the engine output characteristic changes due to the change of the control mode of the variable valve mechanism 15. Therefore, it is possible to suppress the frequent occurrence every time the engine is operated.

The above-described embodiment can be implemented in the following forms in which this is appropriately modified.
The combination of the valve timing changing mechanism 13 and the valve lift amount changing mechanism 14 is illustrated as the variable valve operating mechanism 15, but the configuration of the variable valve operating mechanism is not limited to such a configuration. That is, the variable valve mechanism may be one that can change the closing timing of the intake valve 9.

  The ignition timing control may be one that retards the ignition timing as the knocking frequency increases. For example, the learning process may not be performed. Further, in the process shown in FIG. 4, the increase amount of the knock control amount AKCS is changed according to only the strength regardless of the knocking occurrence frequency, or is changed by a constant amount each time the occurrence of knocking is confirmed. You may do so. Even in this case, by repeatedly executing the series of processes shown in FIG. 4, the knock control amount AKCS increases repeatedly as the knocking occurrence frequency increases, and the ignition timing retard amount AKNK increases.

  An example has been shown in which the ignition timing retard amount AKNK is confirmed and the retard history flag is updated during a predetermined period from the engine start. However, the retard history flag is updated at a different timing. Good. For example, the processing of FIGS. 9 and 10 may be periodically executed during the operation of the internal combustion engine 1 to update the delay angle history flag.

  It is also possible to employ a configuration in which the retard angle history flag is not updated, as in the processes of FIGS. 9 and 10. Also in this case, when the maintenance is performed, the control mode of the variable valve mechanism during the high load operation can be returned to the advance side valve timing control by resetting the delay angle history flag to “OFF”.

The judgment value changing process for changing the size of the judgment value C depending on the state of the delay angle history flag as shown with reference to FIG. 9 can be omitted.
In the process described with reference to FIG. 8, the configuration that changes the control mode of the variable valve mechanism during high load operation with reference to the delay angle history flag is adopted, and the control mode during high load operation is delayed. After being changed to the side valve timing control, the retard side valve timing control is continuously selected regardless of the magnitude of the ignition timing retard amount AKNK during high load operation. On the other hand, a configuration for referencing the retarding history flag is omitted, and a configuration for simply changing the control mode of the variable valve mechanism during high load operation according to the magnitude of the ignition timing retarding amount AKNK is adopted. May be. For example, step S302 and step S303 in FIG. 8 are omitted, and if it is determined in step S301 that the ignition timing retard angle amount AKNK is equal to or greater than the predetermined amount A, the process proceeds to step S304, and in step S301 the ignition timing delay amount is delayed. If it is determined that the angular amount AKNK is smaller than the predetermined amount A, the process may proceed to step S305.

  The manner of changing the opening / closing timing of the intake valve 9 by the variable valve mechanism is not limited to switching between the retard side valve timing control and the advance side valve timing control as described above. By retarding the valve closing timing to reduce the actual compression ratio, it is possible to prevent the torque from becoming small due to the ignition timing being greatly retarded from the basic ignition timing ABSE through the ignition timing control. You can Therefore, for example, when the ignition timing retarding amount AKNK is equal to or more than a predetermined amount, a configuration may be adopted in which the closing timing of the intake valve 9 is corrected to the retarding side.

  When the ignition timing retard amount AKNK is large, the closing timing of the intake valve 9 may be retarded even during low load operation. In short, regardless of whether the engine is in the high load operation or the low load operation, when the ignition timing retarding amount AKNK is equal to or more than the predetermined amount, the intake valve 9 is smaller than when the ignition timing retarding amount AKNK is smaller than the predetermined amount. The valve closing timing of may be retarded. Even in this case, the valve closing timing of the intake valve 9 is retarded to reduce the actual compression ratio, and the sensitivity of the torque to the ignition timing retard is reduced. Therefore, it is possible to prevent the torque from becoming small.

  DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine, 2 ... Combustion chamber, 3 ... Intake passage, 4 ... Fuel injection valve, 5 ... Spark plug, 6 ... Piston, 7 ... Crankshaft, 8 ... Exhaust passage, 9 ... Intake valve, 10 ... Exhaust valve, 11 ... Intake camshaft, 12 ... Exhaust camshaft, 13 ... Valve timing changing mechanism, 14 ... Valve lift amount changing mechanism, 15 ... Variable valve mechanism, 27 ... Accelerator pedal, 28 ... Accelerator position sensor, 29 ... Throttle valve, 30 ... Throttle position sensor, 31 ... Knock sensor, 32 ... Air flow meter, 34 ... Crank position sensor, 35 ... Cam position sensor, 37 ... Drive amount detection sensor, 100 ... ECU (electronic control unit), 110 ... Throttle control section, 120 ... Valve system control unit, 130 ... Ignition timing control unit, 140 ... Fuel injection amount control unit.

Claims (1)

A control device for an internal combustion engine for controlling an internal combustion engine having a variable valve mechanism capable of changing the closing timing of an intake valve,
An ignition timing control unit that performs ignition timing control to retard the ignition timing as the frequency of occurrence of knocking increases,
A valve operating system control unit that controls the variable valve operating mechanism so as to change the closing timing of the intake valve on the side of a retard angle with respect to the intake bottom dead center,
The valve operating system controller controls the variable valve mechanism such that when the retarding history flag is ON, the closing timing of the intake valve is on the retarding side compared to when the retarding history flag is OFF. Control the
When the retard history flag is OFF, the retard history is provided on condition that the throttle opening is equal to or greater than a predetermined value and the ignition timing from the basic ignition timing is retarded to a predetermined amount or more. The flag is switched to ON,
When the retarding history flag is ON, the retarding history flag is kept ON regardless of the magnitude of the retardation amount of the ignition timing from the throttle opening and the basic ignition timing . Control device.

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