JP2013147980A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine that can suppress a trigger of abnormal combustion while achieving to secure responsiveness for avoiding knocking and suppress torque deterioration.SOLUTION: A control device for an internal combustion engine having a plurality of cylinders includes an ignition retard control means for executing an ignition retard control for retarding the ignition timing by a predetermined crank angle if a knocking generation is detected. Existence or nonexistence of an abnormal combustion reduction request associated with generation history of abnormal combustion is determined for the each cylinder. If the knocking generation is detected and an operational range is within an abnormal combustion generation range, execution of the ignition retard control is inhibited at the cylinder at which the abnormal combustion reduction request exists. A suction air amount to be supplied to the plurality of cylinders is suppressed if the execution of the ignition retard control is inhibited.

Description

  The present invention relates to an internal combustion engine control apparatus, and more particularly to an internal combustion engine control apparatus suitable for executing control of an internal combustion engine mounted on a vehicle.

  Conventionally, a KCS (knock control system) that controls the ignition timing of a gasoline engine to a limit at which knocking does not occur is known. The KCS has a mechanism in which the control unit delays the ignition timing when the knock sensor detects the occurrence of knocking. According to the ignition retard control, knocking can be avoided with high responsiveness.

Further, as disclosed in Patent Document 1, a knock detection means for detecting knocking strength is provided, and when the detected knocking strength exceeds a preset threshold, the intake air amount of the next cycle is limited. Control for avoiding knocking is known.
The applicant has recognized the following documents including the above-mentioned documents as related to the present invention.

JP 2009-215989 A JP 2010-133367 A JP 11-093757 A JP 2004-044421 A JP 2007-177772 A JP 2009-222201 A JP 2007-309123 A Japanese Patent Laid-Open No. 2005-226482

  Controls for avoiding knocking include (A) ignition retard, (B) intake air amount suppression, and (C) A / F increase. (C) has a lot of tradeoffs such as fuel consumption and smoke deterioration. (B) has a large torque drop and poor response compared to (A). For this reason, control by the ignition delay of (A) is usually desirable.

  In recent years, a supercharged downsize engine that has been developed has a low operating speed and high load. Since the time required for the air-fuel mixture to react at a low rotation speed is secured and the pressure at the compression top dead center increases at a high load, the minimum ignition energy of the air-fuel mixture decreases in a low rotation high load region. For this reason, abnormal combustion such as pre-ignition (a phenomenon in which combustion starts earlier than the ignition timing and excessive in-cylinder pressure is generated) is likely to occur in the low rotation high load region. When knocking due to abnormal combustion occurs, performing ignition retard control by conventional KCS increases the possibility of inducing abnormal combustion. When knocking occurs, the deposits accumulated in the combustion chamber peel off or the temperature in the combustion chamber (wall) rises. If ignition delay is performed in this state, the reaction time of the air-fuel mixture further increases. This is thought to increase.

  As a countermeasure, it is conceivable to limit the amount of intake air when the knocking strength exceeds a threshold as in the configuration of Patent Document 1. However, when the knocking intensity simply exceeds the threshold value, if the intake air amount is limited instead of the ignition delay angle, the deterioration of the response of avoiding knocking and the decrease in torque become problems. Therefore, it is required to suppress the induction of abnormal combustion while ensuring the responsiveness of avoiding knocking and suppressing the decrease in torque.

  The present invention has been made to solve the above-described problems, and provides a control device for an internal combustion engine that can suppress the induction of abnormal combustion while ensuring responsiveness to avoiding knocking and suppressing torque reduction. The purpose is to do.

In order to achieve the above object, a first invention is a control device for an internal combustion engine having a plurality of cylinders,
Knocking detection means for detecting occurrence of knocking;
An ignition retard control means for executing ignition retard control for retarding the ignition timing by a predetermined crank angle when occurrence of knocking is detected;
Determining means for determining the presence or absence of an abnormal combustion reduction request corresponding to the occurrence history of abnormal combustion for each cylinder;
When the occurrence of knocking is detected and the operation region is in the abnormal combustion generation region, execution of the ignition delay control is prohibited for the cylinder having the abnormal combustion reduction request. Means,
An intake air amount suppression unit that suppresses an intake air amount supplied to the plurality of cylinders when the ignition delay control execution prohibiting unit prohibits the execution of the ignition delay control. .

The second invention is the first invention, wherein
The occurrence history of abnormal combustion includes at least one of the occurrence frequency of abnormal combustion, an integrated value of the number of occurrences of abnormal combustion, and an estimated value of in-cylinder deposit accumulation amount,
The determination means determines that there is an abnormal combustion reduction request when an evaluation value based on the occurrence history of the abnormal combustion exceeds a threshold value.

The third invention is the first or second invention, wherein
The knocking detection means detects the occurrence of knocking for each cylinder,
The ignition retard control means executes ignition retard control for retarding the ignition timing of the predetermined cylinder by a predetermined crank angle when occurrence of knocking is detected in the predetermined cylinder;
The ignition retard control execution prohibiting unit is configured to detect that abnormal combustion is reduced when the occurrence of knocking is detected in the predetermined cylinder and when the operation region is in the abnormal combustion generation region. In this case, execution of the ignition retard control is prohibited for the predetermined cylinder.

According to a fourth invention, in any one of the first to third inventions,
When the operating range is within the range where deposit deposit control can be performed, for cylinders where the estimated value of in-cylinder deposit accumulation exceeds the threshold, the fuel injection amount is reduced to make the air-fuel ratio lean, and the ignition timing is advanced. Deposit loss control means,
When the deposit disappearance means is executed, the exhaust gas stoichiometric means is further provided to increase the fuel injection amount of other cylinders other than the cylinder by increasing the amount reduced by the cylinder to enrich the air-fuel ratio. And

According to a fifth invention, in any one of the first to fourth inventions,
A coolant flow rate control means that can variably control the coolant flow rate for cooling the intake passage according to the operating state, and is set so that the cooling capacity is maximized in an operation region of high rotation and high load,
Cooling water flow rate for correcting an increase in the cooling water flow rate by the cooling water flow control means when the operating region is in the abnormal combustion occurrence region of low rotation and high load and when there is a request for reducing the abnormal combustion in at least one cylinder And an increasing means.

The sixth invention is the fourth invention, wherein
A coolant flow rate control means that can variably control the coolant flow rate for cooling the intake passage according to the operating state, and is set so that the cooling capacity is maximized in an operation region of high rotation and high load,
An ignition advance prohibiting means for prohibiting the advance of the ignition timing by the deposit disappearance control means when the knocking is not caused by the advance angle; and
When the ignition advance angle prohibiting means prohibits the advance of the ignition timing, the cooling water flow control means further comprises a cooling water flow rate reducing means for correcting the cooling water flow rate to be reduced.

According to the first invention, in principle, the ignition retard control is executed when the occurrence of knocking is detected. Therefore, knocking can be avoided with high responsiveness. Further, torque reduction can be suppressed compared to suppression of the intake air amount.
As an exception, when the operation region is in the abnormal combustion occurrence region, execution of the ignition retard control is prohibited only for the cylinders for which there is an abnormal combustion reduction request, and the intake air amount is also suppressed. For cylinders where abnormal combustion should be reduced, the induction of abnormal combustion can be suppressed by prohibiting the ignition retard that increases the probability of occurrence of abnormal combustion. On the other hand, for other cylinders that do not have an abnormal combustion reduction request, the ignition delay control is performed and the intake air amount is suppressed, so that knocking during the response delay of the intake air amount can be minimized. . According to such control, even if it is unclear to which cylinder knocking occurred, it is possible to reduce the probability of occurrence of abnormal combustion while minimizing knock during response delay of the intake air amount. Is possible.
For this reason, according to the present invention, induction of abnormal combustion can be suppressed while ensuring responsiveness of knocking avoidance and suppressing torque reduction.

  According to the second invention, it is possible to determine whether there is an abnormal combustion reduction request based on the frequency of occurrence of abnormal combustion, the integrated value of the number of occurrences of abnormal combustion, and the estimated value of the in-cylinder deposit accumulation amount.

According to the third aspect of the invention, when it is possible to specify in which cylinder knocking has occurred, in principle, the ignition retard control is executed only in the knocking cylinder. The decrease can be suppressed. In addition, since the case where the ignition retard control is prohibited as an exception is limited to the case where there is a request for reducing abnormal combustion in the knocking cylinder, the suppression of the intake air amount is minimized as compared with the first invention. It is possible to make the best use of ignition delay control with good responsiveness.
For this reason, according to this invention, compared with 1st invention, the induction | guidance | derivation of abnormal combustion can be suppressed, aiming at ensuring the responsiveness of knocking avoidance, and suppressing a torque fall.

  According to the fourth aspect of the present invention, lean combustion and knocking can be realized by making the air-fuel ratio lean and ignition advance in the cylinder where the deposit is desired to disappear, and rich combustion can be realized in other cylinders so as to achieve exhaust stoichiometry. . For this reason, according to the present invention, it is possible to ensure the catalyst performance, reduce the deposit and reduce the frequency of occurrence of abnormal combustion in a state where the knocking is minimal and the influence of sound is small.

  According to the fifth aspect of the present invention, when the operating region is in the abnormal combustion occurrence region and when there is a request for reducing abnormal combustion in at least one cylinder, the cooling capacity is increased and the intake air temperature is decreased, thereby causing abnormal combustion. Can be reduced.

  According to the sixth aspect of the present invention, even if it is not the region where knocking is possible due to the advance angle, it is possible to promote the occurrence of knocking by increasing the intake air temperature. Compared to the fourth invention, knocking control for deposit disappearance can be executed in a wider area.

It is a figure for demonstrating the system configuration | structure in Embodiment 1 of this invention. It is a figure showing the operation area | region where abnormal combustion is easy to generate | occur | produce. In Embodiment 1 of this invention, it is a figure for demonstrating the specific example when knocking generate | occur | produces in the abnormal combustion generation | occurrence | production area | region. It is a figure which shows the relationship between driving | running | working time (or driving | running | working distance) and a component stress parameter | index, and a stress accumulation worst assumption line. In Embodiment 1 of this invention, it is a flowchart of the control routine which ECU50 performs. In Embodiment 2 of this invention, it is a flowchart of the control routine which ECU50 performs. In Embodiment 3 of this invention, it is a flowchart of the control routine which ECU50 performs. It is a figure which shows a deposit | disappearance loss control executable area. In Embodiment 4 of this invention, it is a figure for demonstrating the control outline | summary of the cooling water quantity according to the presence or absence of the abnormal combustion reduction request | requirement. In Embodiment 4 of this invention, it is a flowchart of the control routine which ECU50 performs. In Embodiment 5 of this invention, it is a flowchart of the control routine which ECU50 performs.

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

Embodiment 1 FIG.
[System Configuration of Embodiment 1]
FIG. 1 is a diagram for explaining a system configuration according to Embodiment 1 of the present invention. The system shown in FIG. 1 includes an internal combustion engine 10 that is downsized by supercharging. The internal combustion engine 10 includes a plurality of cylinders. A piston 12 is provided in the cylinder. A combustion chamber 14 is formed on the top side of the piston 12 in the cylinder. An intake passage 16 and an exhaust passage 18 communicate with the combustion chamber 14.

  An air flow meter 20 that outputs a signal corresponding to the flow rate of air sucked into the intake passage 16 is provided in the vicinity of the inlet of the intake passage 16. A compressor 22 a of the supercharger 22 is disposed in the intake passage 16 on the downstream side of the air flow meter 20. A water-cooled intercooler 23 is provided in the intake passage 16 on the downstream side of the compressor 22a. The fresh air sucked through the air cleaner is compressed by the compressor 22 a of the supercharger 22 and then cooled by the intercooler 23. Further, an electronically controlled throttle valve 24 is provided in the intake passage 16 downstream of the intercooler 23. An intake valve 25 that opens and closes between the intake passage 16 and the combustion chamber 14 is provided at the downstream end of the intake passage 16.

  Each cylinder of the internal combustion engine 10 has a fuel injection valve 26 for directly injecting fuel into the combustion chamber 14 (in-cylinder), a spark plug 28 for igniting the air-fuel mixture, and a cylinder pressure for detecting the in-cylinder pressure. An in-cylinder pressure sensor 34 is provided.

  An exhaust valve 29 that opens and closes between the exhaust passage 18 and the combustion chamber 14 is provided at the upstream end of the exhaust passage 18. In the exhaust passage 18, a turbine 22 b of the supercharger 22 is disposed. A catalyst 30 for purifying exhaust gas is disposed in the exhaust passage 18 on the downstream side of the turbine 22b. The exhaust passage 18 is connected to a bypass passage (not shown) that bypasses the upstream and downstream sides of the turbine 22b. The bypass passage is provided with a WGV (a waste gate valve, not shown) that can open and close the passage arbitrarily.

  Further, the system shown in FIG. 1 includes an ECU (Electronic Control Unit) 50. ECU50 is comprised by the arithmetic processing apparatus provided with the memory circuit containing ROM, RAM, etc., for example. On the input side of the ECU 50, in addition to the air flow meter 20 and the in-cylinder pressure sensor 34 described above, the internal combustion engine 10 such as a crank angle sensor 52 for detecting the crank position and crank angular velocity, a knock sensor 54 for detecting knocking strength, and the like. Various sensors for detecting the driving state are connected. Various actuators for controlling the operation of the internal combustion engine 10, such as the throttle valve 24, the fuel injection valve 26, the spark plug 28, and the WGV, are connected to the output side of the ECU 50.

  The ECU 50 controls the operating state of the internal combustion engine 10 by driving various actuators according to a predetermined program based on various sensor outputs. For example, the crank angle and the engine speed (engine speed) NE are calculated based on the output of the crank angle sensor 52, and the intake air amount is calculated based on the output of the air flow meter 20. Further, an engine load (load factor) KL is calculated based on the intake air amount, the engine speed, and the like. Then, the fuel injection timing and ignition timing are determined based on the crank angle, and when these timings arrive, the fuel injection valve 26 and the spark plug 28 are driven.

  Moreover, ECU50 performs control of KCS (Knock Control System). In KCS control, the ignition timing is controlled to a limit at which knocking does not occur. Specifically, it is determined whether or not the knocking intensity detected by the knock sensor 54 is greater than or equal to the knock threshold, and if it is greater than or equal to the knock threshold, it is determined that knocking has occurred. When knocking occurs, the ignition timing is retarded by a predetermined angle within a range that does not exceed the retard upper limit that causes misfire. On the other hand, when knocking does not occur, the ignition timing is advanced by a predetermined angle within a range not exceeding the advance angle upper limit value. According to KCS control, knocking can be suppressed with high responsiveness.

  FIG. 2 is a diagram showing an operation region in which abnormal combustion (a phenomenon in which combustion starts earlier than the ignition timing and excessive cylinder pressure is generated) is likely to occur. In a supercharged downsize engine like this system, the operating range is low and the load is high. Since the time required for the air-fuel mixture to react at a low rotation speed is secured and the pressure at the compression top dead center increases at a high load, the minimum ignition energy of the air-fuel mixture decreases in a low rotation high load region. The deposit accumulated in the combustion chamber 14 is peeled off, and the possibility of ignition is improved when the combustion chamber burns and stays in the combustion chamber until the next cycle. Therefore, abnormal combustion tends to occur easily in the low rotation and high load region. Hereinafter, this operation region is referred to as an abnormal combustion occurrence region. Further, as shown in FIG. 2, the frequency of occurrence of abnormal combustion is higher as the rotation speed is lower. When large knocking occurs due to abnormal combustion, both the in-cylinder pressure and temperature rise and stress is applied to the internal combustion engine 10.

  When knocking occurs in the abnormal combustion occurrence region and the ignition delay control is performed by KCS, the mixture reaction time further increases due to the ignition delay. As a result, the possibility of occurrence of abnormal combustion greatly increases, and the possibility of inducing abnormal combustion increases.

  In order to avoid this, it is conceivable to reduce the amount of intake air. The reduction of the intake air amount is executed by an actuator such as a throttle valve 24 or a WGV. However, since the response speed of these actuators is slow and affected by air inertia, the response to avoid knocking is worse than the ignition delay angle by KCS control. There is also concern about torque reduction. Therefore, it is desired that the induction of abnormal combustion can be suppressed while the basic control is to avoid knocking by ignition delay angle with high responsiveness and small torque reduction.

[Characteristic Control in Embodiment 1]
Next, characteristic control of this embodiment that solves such a problem will be described. The outline of the characteristic control of this embodiment is as follows. As a premise, in the knocking detection in the present embodiment, it is possible to detect that knocking has occurred in any of the cylinders, but it is not possible to specify to which cylinder knocking has occurred.
1. As a general rule, when the occurrence of knocking is detected, ignition retardation control by KCS is executed. As described above, in the present embodiment, since it is impossible to grasp in which cylinder knocking has occurred, in principle, ignition retardation control by KCS is executed in all cylinders.
2. As an exception, even when knocking is detected, if the operating region is in the abnormal combustion occurrence region, execution of ignition delay control by KCS is prohibited for a cylinder having an abnormal combustion reduction request to be described later. The
3. When execution of ignition retard control by KCS is prohibited, control for reducing the amount of intake air supplied to each cylinder is executed.

  FIG. 3 is a diagram for describing a specific example when knocking occurs in the abnormal combustion occurrence region. FIG. 3 shows an example in which there is an abnormal combustion reduction request in the # 4 cylinder of a 4-cylinder engine.

  In the example of FIG. 3, when the occurrence of knocking is detected by the KCS (FIG. 3A), the ignition timing is retarded for all cylinders (# 1 to # 3) that do not have an abnormal combustion reduction request ( FIG. 3 (C) to FIG. 3 (E)). On the other hand, for the # 4 cylinder having an abnormal combustion reduction request, the retard control of the ignition timing is prohibited (FIG. 3 (F)) and the intake air amount is suppressed (FIG. 3 (B)). As a result, as shown in FIG. 3G, the average knock level (knock noise) is reduced as compared to the case where the ignition delay control is prohibited and the intake air amount is reduced in all cylinders (broken line 60). It becomes possible to reduce it early (solid line 62).

(About abnormal combustion reduction request)
As described above, control for reducing the amount of intake air is executed to avoid a situation that induces abnormal combustion. However, control for reducing the amount of intake air is more responsive than the ignition retard control, and torque There is a problem of decline. Therefore, in principle, ignition retard control should be performed and control for reducing the intake air amount should not be performed more than necessary. Therefore, in the present embodiment, when knocking is detected and the operation region is in the abnormal combustion occurrence region, execution of the ignition delay control by the KCS is prohibited only for the cylinder having the abnormal combustion reduction request. Only in this case, control for reducing the intake air amount is executed.

  The presence or absence of the above-mentioned abnormal combustion reduction request means whether or not abnormal combustion is likely to be induced. Abnormal combustion such as the frequency of occurrence of abnormal combustion, the cumulative number of occurrences, and the estimated value of in-cylinder deposit accumulation It is set based on the occurrence history of.

  The frequency of occurrence of abnormal combustion can be calculated based on the number of occurrences of abnormal combustion within a predetermined period. The occurrence of abnormal combustion can be detected on a cylinder-by-cylinder basis by determining that the maximum in-cylinder pressure greater than that at the time of normal combustion is detected at a crank position advanced from that at the time of normal combustion. When the number of occurrences of abnormal combustion within a predetermined period exceeds the threshold, it is possible to set that there is an abnormal combustion reduction request (abnormal combustion reduction request flag ON) for the cylinder.

  Further, the presence or absence of an abnormal combustion reduction request may be set by paying attention to the integrated value of the number of occurrences of abnormal combustion. The ECU 50 stores in advance a component stress index corresponding to the travel time (or travel distance) as shown in FIG. The component stress index is a weight integrated value of the number of occurrences of abnormal combustion and the maximum in-cylinder pressure at the time of occurrence of abnormal combustion. When the component stress index corresponding to the running time exceeds the stress accumulation worst assumption line 64, it is possible to set that there is an abnormal combustion reduction request (abnormal combustion reduction request flag ON) for the cylinder.

  Further, whether or not there is an abnormal combustion reduction request may be set by paying attention to the in-cylinder deposit accumulation amount. The in-cylinder deposit accumulation amount can be estimated from the occurrence frequency of abnormal combustion, etc., and when the estimated in-cylinder deposit accumulation amount exceeds a predetermined threshold, there is an abnormal combustion reduction request (abnormal combustion reduction) Request flag ON).

(flowchart)
FIG. 5 is a flowchart of a control routine executed by the ECU 50 in order to realize the above-described operation. This routine is executed, for example, every cycle. In the routine shown in FIG. 5, first, the ECU 50 acquires the knocking strength by the knock sensor 54 (step S100), and determines whether or not the knocking strength is equal to or higher than the knock threshold (step S105). If it is less than the knock threshold, the routine is terminated.

  On the other hand, when the knocking strength is equal to or higher than the knock threshold, occurrence of knocking is detected. The ECU 50 acquires the current engine speed NE and the load factor KL (step S110), and determines whether or not the current operation region determined by the engine speed NE and the load factor KL is in the abnormal combustion occurrence region ( Step S115).

  When the current operation region is not in the abnormal combustion occurrence region, the ECU 50 acquires a predetermined required ignition retardation amount by KCS (step S120), and the required ignition retardation amount is equal to or less than a retardation upper limit value that causes misfire. It is determined whether or not (step S125). The required ignition retard amount is stored in the ECU 50 in advance. When the required ignition retard amount is equal to or less than the retard upper limit value, the ECU 50 executes the ignition retard control according to the required ignition retard amount (step S130). Thereafter, the processing of this routine is terminated.

  On the other hand, when the required ignition retard amount is larger than the retard upper limit value, the ECU 50 responds to the retard amount of the required ignition retard amount that exceeds the retard upper limit value (the amount that is insufficient to avoid knocking). A suppression amount of the intake air amount is calculated (step S135). The ECU 50 stores in advance the relationship between the retard amount and the amount of intake air suppression. The ECU 50 sets the ignition timing to the retard upper limit value, and reduces the target value of the intake air amount according to the suppression amount (step S140). Thereafter, the processing of this routine is ended, and the spark plug 28 and the throttle valve 24 are driven according to the target values of the ignition timing and the intake air amount.

  Further, when it is determined in step S115 described above that the current operation region is in the abnormal combustion occurrence region, the ECU 50 acquires an abnormal combustion reduction request flag for each cylinder (step S145), and an abnormality is detected for each cylinder. It is determined whether the combustion reduction request flag is ON or OFF (step S150). For the cylinder group in which the abnormal combustion reduction request flag is OFF, the ECU 50 executes the processes after step S120 described above.

  On the other hand, for the cylinder group for which the abnormal combustion reduction request flag is ON, the ECU 50 prohibits ignition retardation control by KCS (step S155). Further, a suppression amount of the intake air amount for avoiding knocking according to the prohibited ignition retardation amount is acquired (step S160). The ECU 50 stores in advance the relationship between the ignition retard amount and the intake air amount suppression amount. The ECU 50 reduces the target value of the intake air amount according to the suppression amount (step S165). Thereafter, the processing of this routine is ended, and the spark plug 28 and the throttle valve 24 are driven according to the target values of the ignition timing and the intake air amount.

As described above, according to the routine shown in FIG. 5, in principle, when the occurrence of knocking is detected, ignition retardation control by KCS is executed in each cylinder. Therefore, knocking can be avoided with high responsiveness. Further, torque reduction can be suppressed compared to suppression of the intake air amount.
As an exception, when the operation region is in the abnormal combustion occurrence region, execution of ignition delay control by KCS is prohibited only for the cylinder group with the abnormal combustion reduction request flag ON, and the opening degree of the throttle valve 24 is also lowered. For cylinders where abnormal combustion should be reduced, the induction of abnormal combustion can be suppressed by prohibiting the ignition retard that increases the probability of occurrence of abnormal combustion. On the other hand, for the cylinder group with the abnormal combustion reduction request flag OFF, since the intake air amount is suppressed while the ignition delay control is performed by KCS, knocking during the response delay of the intake air amount is minimized. Can do. For this reason, even if it is unknown to which cylinder knocking occurred, it is possible to reduce the probability of occurrence of abnormal combustion while minimizing knock during response delay of the intake air amount.
As described above, according to the system of the present embodiment, it is possible to suppress the induction of abnormal combustion while ensuring the responsiveness of avoiding knocking and suppressing the decrease in torque.

  The engine to which the present invention is applied is not limited to the in-cylinder direct injection engine as in the above-described embodiment. The present invention can also be applied to a port injection type engine. This also applies to the following embodiments.

  In the first embodiment described above, the ECU 50 executes the process of step S105, so that the “knocking detection means” in the first aspect of the invention is the process of step S105 and steps S120 to S130 (KCS). By executing the control, the “ignition retarding control means” in the first invention performs the processing of steps S145 and S150, so that the “determination means” in the first invention performs the steps S150 and S150. And by executing the process of step S155, the “ignition retarding control execution prohibiting means” in the first aspect of the invention executes the processes of step S160 and step S165 described above, and the “intake air amount” of the first aspect of the invention. "Suppression means" is realized respectively. Furthermore, in the first embodiment, the abnormal combustion reduction request flag acquired in step S145 corresponds to the “abnormal combustion reduction request” in the first or second invention.

Embodiment 2. FIG.
[System Configuration of Embodiment 2]
Next, a second embodiment of the present invention will be described with reference to FIG. The system of the present embodiment can be realized by causing the ECU 50 to execute the routine of FIG. 6 described later in the configuration shown in FIG.

[Characteristic Control in Embodiment 2]
In the first embodiment, the knocking avoidance control in the case where the knocking detection unit cannot specify in which cylinder knocking has occurred has been described. On the other hand, in the present embodiment, a more preferable knocking avoidance control that is realized when the knocking detection unit can identify in which cylinder knocking has occurred will be described.

The outline of the characteristic control of this embodiment is as follows. As a premise, in the knocking detection in the present embodiment, it is possible to specify up to which cylinder knocking has occurred.
1. As a general rule, when the occurrence of knocking is detected, ignition retardation control by KCS is executed. In this embodiment, since it is possible to grasp in which cylinder knocking has occurred, ignition retardation control by KCS is executed in the cylinder in which knocking has been detected (hereinafter referred to as knocking cylinder).
2. As an exception, even if a knock generation cylinder is present, if the operation region is in the abnormal combustion generation region and if there is an abnormal combustion reduction request (detailed in the first embodiment) in the knock generation cylinder, the knock generation occurs. For cylinders, execution of ignition delay control by KCS is prohibited.
3. When execution of ignition retard control by KCS is prohibited, control for reducing the amount of intake air supplied to each cylinder is executed.

(flowchart)
FIG. 6 is a flowchart of a control routine executed by the ECU 50 in order to realize the above function. This routine is executed for each cylinder, for example, every cycle. In the routine shown in FIG. 6, first, the ECU 50 acquires the cylinder number X in the order of ignition (step S200). Knocking strength is acquired for each cylinder (step S205). The knocking strength for each cylinder is acquired based on, for example, the detection value of the knock sensor 54 at the ignition timing (crank angle) of each cylinder, the detection value of the in-cylinder pressure sensor 34 provided for each cylinder, or the like. Subsequently, the ECU 50 determines whether or not the knocking strength of the cylinder number X is greater than or equal to the knock threshold (step S210). If it is less than the knock threshold, the routine is terminated.

  On the other hand, when the knocking strength is equal to or higher than the knock threshold, occurrence of knocking is detected. The ECU 50 acquires the current engine speed NE and the load factor KL (step S215), and determines whether or not the current operation region determined by the engine speed NE and the load factor KL is in the abnormal combustion occurrence region ( Step S220).

  When the current operation region is not in the abnormal combustion occurrence region, the ECU 50 acquires a predetermined required ignition delay amount by KCS for the cylinder number X (step S225), and the required ignition delay amount causes a delay that causes misfire. It is determined whether or not the angle is not more than the upper limit value (step S230). The required ignition retard amount is stored in the ECU 50 in advance. When the required ignition retard amount is equal to or smaller than the retard upper limit value, the ECU 50 executes the ignition retard control according to the required ignition retard amount (step S235). Thereafter, the processing of this routine is terminated.

  On the other hand, when the required ignition retard amount is larger than the retard upper limit value, the ECU 50 responds to the retard amount of the required ignition retard amount that exceeds the retard upper limit value (the amount that is insufficient to avoid knocking). A suppression amount of the intake air amount is calculated (step S240). The ECU 50 stores in advance the relationship between the retard amount and the amount of intake air suppression. The ECU 50 sets the ignition timing to the retardation upper limit value, and reduces the target value of the intake air amount according to the suppression amount (step S245). Thereafter, the processing of this routine is ended, and the spark plug 28 and the throttle valve 24 are driven according to the target values of the ignition timing and the intake air amount.

  If it is determined in step S220 described above that the current operation region is in the abnormal combustion occurrence region, the ECU 50 acquires an abnormal combustion reduction request flag for cylinder number X (step S250), and the abnormal combustion is obtained. It is determined whether the reduction request flag is ON or OFF (step S255). When the abnormal combustion reduction request flag is OFF, the ECU 50 executes the processes after step S225 described above for the cylinder number X.

  On the other hand, when the abnormal combustion reduction request flag for cylinder number X is ON, the ECU 50 prohibits the ignition retard control by the KCS for cylinder number X (step S260). Further, a suppression amount of the intake air amount for avoiding knocking according to the prohibited ignition retardation amount is acquired (step S265). The ECU 50 stores in advance the relationship between the ignition retard amount and the intake air amount suppression amount. The ECU 50 reduces the target value of the intake air amount according to the suppression amount (step S270). Thereafter, the processing of this routine is ended, and the spark plug 28 and the throttle valve 24 are driven according to the target values of the ignition timing and the intake air amount.

As described above, according to the routine shown in FIG. 6, in principle, the ignition delay control by the KCS is executed in the cylinder in which the occurrence of knocking is detected (knock generation cylinder). Therefore, knocking can be avoided with high responsiveness. Further, since the ignition retard control is executed only in the knocking cylinder, the torque reduction can be suppressed as compared with the system of the first embodiment that executes the ignition retard control for each cylinder.
As an exception, only when the operation region is in the abnormal combustion occurrence region and the abnormal combustion reduction request flag of the knock generation cylinder is ON, the execution of the ignition delay control by the KCS of this knock generation cylinder is prohibited, At the same time, the opening of the throttle valve 24 is lowered. Since it is limited when the knocking cylinder flag is ON, the suppression of the intake air amount can be minimized as compared with the first embodiment, and the ignition delay control with good responsiveness can be utilized to the maximum.
As described above, according to the system of the present embodiment, it is possible to suppress the induction of abnormal combustion while further ensuring the responsiveness of avoiding knocking and suppressing the decrease in torque as compared with the first embodiment.

  In the second embodiment described above, the ECU 50 executes the processes of steps S200 and S205, so that the “knocking detection means” in the third aspect of the invention performs the processes of steps S210 and S225 to S235. By executing (KCS control), the “ignition retarding control means” in the third aspect of the invention is executed, and the “determination means” in the third aspect of the invention is executed by executing the processes of steps S250 and S255. By executing the processing of step S255 and step S260, the “ignition retarding control execution prohibiting means” in the third aspect of the invention executes the processing of step S265 and step S270 described above, thereby performing the “inhalation” in the third aspect of the invention. The “air amount suppression means” is realized. Furthermore, in the second embodiment, the abnormal combustion reduction request flag acquired in step S250 corresponds to the “abnormal combustion reduction request” in the third aspect of the invention.

Embodiment 3 FIG.
[System Configuration of Embodiment 3]
Next, Embodiment 3 of the present invention will be described with reference to FIGS. The system of the present embodiment can be realized by causing the ECU 50 to execute a routine of FIG. 7 described later in addition to the control routine of FIG. 6 of the second embodiment described above in the configuration shown in FIG.

[Characteristic Control in Embodiment 3]
The occurrence frequency of abnormal combustion is high when it is determined that the occurrence of abnormal combustion is high due to deposit (carbon) accumulation in the combustion chamber 14 and there is a cylinder that needs to be controlled as in the second embodiment. It is effective to eliminate the deposit in order to lower the value. In order to eliminate the deposit, it is effective to cause lean combustion to generate knocking. However, leaning needs to be exhaust stoichiometric from the purification performance of the catalyst 30, and knocking has a problem of sound.

  Therefore, in the system according to the present embodiment, lean air-fuel ratio (A / F) is made only in the cylinders where deposits are to be lost, and the KCS knock threshold (hereinafter also referred to as KCS threshold) is lowered to advance the ignition, thereby performing lean combustion. In addition, knocking was realized, and the other cylinders were made to perform rich combustion so that exhaust stoichiometry. As a result, the catalyst performance is ensured, the deposit disappears with only one cylinder having the minimum knocking and the influence of sound is small, and the occurrence frequency of abnormal combustion can be reduced.

(flowchart)
FIG. 7 is a flowchart of a control routine executed by the ECU 50 in order to realize the above-described function. This routine is executed for each cylinder, for example, every cycle. In the routine shown in FIG. 7, first, the ECU 50 obtains an estimated value of the in-cylinder deposit accumulation amount of the cylinder number X (step S300). For example, the ECU 50 has a predetermined relationship between the occurrence frequency of abnormal combustion and the estimated value of the in-cylinder deposit accumulation amount. The ECU 50 accumulates in-cylinder deposits according to the occurrence frequency of abnormal combustion based on this relationship. Get an estimate of the quantity.

  The ECU 50 determines whether or not the estimated value of the in-cylinder deposit amount for the cylinder number X is greater than or equal to a threshold value (step S305). If it is equal to or greater than the threshold value, the ECU 50 acquires the current engine speed NE and the load factor KL (step S310), and the current operating region determined by the engine speed NE and the load factor KL can be subjected to deposit disappearance control. It is determined whether it is in the area (step S315). FIG. 8 is a diagram showing a deposit disappearance control executable region. As shown in FIG. 8, the high load region is a region with a small margin against abnormal combustion such as pre-ignition, and the deposit disappearance control executable region is set to a low load region.

  When the current operation region is in the deposit disappearance control executable region, the ECU 50 sets the deposit disappearance control flag of the cylinder number X to ON (step S320). Subsequently, the ECU 50 reduces (relaxes) the KCS threshold value of the cylinder number X (step S325). As a result, the ignition timing of the cylinder number X is easily controlled to the advance side, and knocking easily occurs. The fuel injection amount supplied to the cylinder number X is reduced (step S330). As a result, the cylinder number X is made A / F lean. Thereafter, the processing of this routine is terminated.

  If it is determined in step S315 that the current operation region is not in the deposit disappearance control executable region, it is determined that the ignition advance should not be performed, and the processing of this routine is terminated.

  If it is determined in step S305 that the estimated value of the in-cylinder deposit amount for cylinder number X is less than the threshold value, the ECU 50 sets the deposit disappearance control flag for cylinder number X to OFF (step S335).

  Subsequently, the ECU 50 acquires deposit disappearance control flags for all other cylinders other than the cylinder number X (step S340), and determines whether the deposit disappearance control flags for other cylinders are ON or OFF (step S345). ). When the deposit disappearance control flag of the other cylinder is OFF, the process of this routine is ended.

  On the other hand, when the deposit disappearance control flag of the other cylinder is ON, the ECU 50 acquires the fuel injection amount reduction information of the other cylinder (step S350) and calculates the required fuel increase value of the cylinder number X (step S350). S355). Thereby, the cylinder number X is A / F rich. The required fuel increase value of the cylinder number X is set so as to be exhaust stoichiometric together with the decrease value of the other cylinders.

  As described above, according to the routine shown in FIG. 7, only the cylinders whose deposits are to be lost are A / F leaned and ignition advanced to achieve lean combustion and knocking by the processing in steps S300 to S330. The cylinder can perform rich combustion so as to be exhaust stoichiometric. As described above, according to the system of the present embodiment, the catalyst performance is ensured, the deposit disappears with only one cylinder having the minimum knocking and the influence of sound is small, and the occurrence frequency of abnormal combustion can be reduced.

  In the third embodiment described above, the ECU 50 executes the processes of steps S300 to S330 so that the “deposit loss control means” in the fourth invention performs the processes of steps S335 to S355. By executing, the “exhaust stoichiometric means” in the fourth aspect of the present invention is realized.

Embodiment 4 FIG.
[System Configuration of Embodiment 4]
Next, a fourth embodiment of the present invention will be described with reference to FIGS. The system of the present embodiment has the configuration shown in FIG. In addition, the ECU 50 can variably control the flow rate of the cooling water flowing through the water-cooled intercooler 23 by pump control or the like. The system of the present embodiment can be realized by causing the ECU 50 to execute the routine of FIG.

[Characteristic Control in Embodiment 4]
The higher the combustion chamber temperature at the compression top dead center, the higher the frequency of occurrence of abnormal combustion. In addition, in a water-cooled intercooler system that can variably control the coolant flow rate, the cooling capacity is designed under the high-rotation and high-load output conditions where the amount of intake air is high. It is not necessary to the limit, and the operation is performed while suppressing the cooling water flow rate optimum for fuel consumption.

  Therefore, in the system of the present embodiment, when there is a request for reducing abnormal combustion due to the occurrence frequency of abnormal combustion, stress accumulation, etc. as in the first to third embodiments, the cooling capacity of the intercooler 23 in the abnormal combustion occurrence region is set. The intake air temperature was lowered to increase the probability of abnormal combustion.

  FIG. 9 is a diagram for explaining an outline of control of the cooling water amount in accordance with the presence or absence of an abnormal combustion reduction request in the system of the present embodiment. It is assumed that the operation region is an abnormal combustion occurrence region. In the system of the present embodiment, when the abnormal combustion reduction request flag is turned on as shown at time t0, the water cooling intercooler system corrects the cooling water flow rate to increase and increases the cooling water pump work (cooling capacity). . As a result, the intake air temperature can be lowered. On the other hand, when the abnormal combustion reduction request flag is turned OFF as shown at time t1, the increase correction is stopped, and the water cooling intercooler system variably controls the cooling water flow rate according to the operation state as usual. .

(flowchart)
FIG. 10 is a flowchart of a control routine executed by the ECU 50 in order to realize the above-described function. This routine is executed, for example, every cycle. In the routine shown in FIG. 10, first, the ECU 50 obtains the current engine speed NE and the load factor KL (step S400), and the current operation region determined by the engine speed NE and the load factor KL is the abnormal combustion occurrence region. It is determined whether or not (step S405). If the current operation region is not in the abnormal combustion occurrence region, the process of this routine is terminated.

  On the other hand, when the current operation region is in the abnormal combustion occurrence region, the ECU 50 acquires the abnormal combustion reduction request flag of each cylinder (step S410), and the abnormal combustion reduction request flag is ON in any cylinder. It is determined whether or not (step S415). When the abnormal combustion reduction request flag is OFF for all the cylinders, the routine is terminated.

  On the other hand, if the abnormal combustion reduction request flag is ON in any of the cylinders, the ECU 50 acquires the coolant flow rate (step S420) and determines whether the coolant flow rate is less than the upper limit value ( Step S425). The upper limit value is, for example, the maximum value of the pump capacity. When the cooling water flow rate is less than the upper limit value, the ECU 50 maximizes the cooling water flow rate (step S430). Thereafter, the processing of this routine is terminated.

  As explained above, according to the routine shown in FIG. 10, when there is an abnormal combustion reduction request in any cylinder in the abnormal combustion occurrence region, the intake air temperature is lowered by maximizing the cooling capacity of the water-cooled intercooler system. Thus, the occurrence probability of abnormal combustion can be reduced.

  In the fourth embodiment described above, the intercooler 23 and the ECU 50 correspond to the “cooling water flow rate control means” in the fifth aspect of the invention. Further, here, the “cooling water flow rate increasing means” in the fifth aspect of the present invention is realized by the ECU 50 executing the processing of steps S400 to S430.

Embodiment 5 FIG.
[System Configuration of Embodiment 5]
Next, a fifth embodiment of the present invention will be described with reference to FIG. The system of the present embodiment has the configuration shown in FIG. In addition, the ECU 50 can variably control the flow rate of the cooling water flowing through the water-cooled intercooler 23 by pump control or the like. The system of the present embodiment can be realized by causing the ECU 50 to execute a routine of FIG. 11 described later in addition to the control routine of FIG.

[Characteristic Control in Embodiment 5]
With respect to the third embodiment, knocking is unlikely to occur in the low load region, and a considerable amount of ignition advance is required for the occurrence, and there are conditions that do not occur depending on the conditions. Therefore, in the system of the present embodiment, when knocking is to be generated by the deposit disappearance control request of the third embodiment under a condition that is not an abnormal combustion occurrence region, the intake water temperature is corrected by reducing the cooling water flow rate of the intercooler 23. The probability of occurrence of knocking is increased by controlling the height of the motor. Thereby, knocking control for deposit disappearance can be executed in a wide area.

(flowchart)
FIG. 11 is a flowchart of a control routine executed by the ECU 50 in order to realize the above function. This routine is the same as the routine shown in FIG. 7 except that steps S500 to S525 are added between steps S315 and S320. In FIG. 11, the same steps as those shown in FIG. 7 are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 11, when it is determined in step S315 that the current operation region is the deposit disappearance control executable region, the ECU 50 determines whether or not the knocking occurrence region due to the advance angle is possible ( Step S500). When a sufficient ignition advance amount for generating knocking can be ensured without exceeding the upper limit value of the ignition advance amount, it is determined that the region where knocking is possible due to advance is made, and the ECU 50 performs the above-described step. The process after S320 is executed.

  On the other hand, when it is not the knockable occurrence region due to the advance angle, the ECU 50 calculates the required air temperature necessary for the occurrence of knocking (step S505). In the ECU 50, for example, a required air temperature corresponding to the load factor, the rotation speed, and the like is stored in advance. Subsequently, the ECU 50 calculates a required coolant flow rate for satisfying the required air temperature (step S510). The ECU 50 acquires the lower limit value of the cooling water flow rate (step S515), and determines whether or not the required cooling water flow rate is larger than the lower limit value (step S520). If it is less than the lower limit value, the routine is terminated.

  On the other hand, when the required cooling water flow rate is larger than the lower limit value, the ECU 50 sets the cooling water flow rate to the required cooling water flow rate by pump control or the like (step S525). Thereafter, the processing of this routine is terminated.

  As described above, according to the routine shown in FIG. 11, the occurrence of knocking is promoted by increasing the intake air temperature, even if it is not the region where knocking is possible due to the advance angle, by the processing of step S500 to step S525. It becomes possible. Therefore, knocking control for deposit disappearance can be executed in a wider area as compared with the third embodiment.

In the fifth embodiment described above, the intercooler 23 and the ECU 50 correspond to the “cooling water flow rate control means” in the sixth invention.
Also, here, the ECU 50 executes the process of step S500, so that the “ignition advance prevention means” in the sixth aspect of the invention executes the processes of step S505 to step S525, thereby executing the sixth step. The “cooling water flow rate reducing means” in the present invention is realized.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 14 Combustion chamber 16 Intake passage 18 Exhaust passage 20 Air flow meter 22 Supercharger 22a Compressor 22b Turbine 23 Intercooler 24 Throttle valve 25 Intake valve 26 Fuel injection valve 28 Spark plug 29 Exhaust valve 30 Catalyst 34 In-cylinder pressure sensor 50 ECU
52 Crank angle sensor 54 Knock sensor 64 Stress accumulation worst assumption line KL Load factor NE Engine speed

Claims (6)

A control device for an internal combustion engine having a plurality of cylinders,
Knocking detection means for detecting occurrence of knocking;
An ignition retard control means for executing ignition retard control for retarding the ignition timing by a predetermined crank angle when occurrence of knocking is detected;
Determining means for determining the presence or absence of an abnormal combustion reduction request corresponding to the occurrence history of abnormal combustion for each cylinder;
When the occurrence of knocking is detected and the operation region is in the abnormal combustion generation region, execution of the ignition delay control is prohibited for the cylinder having the abnormal combustion reduction request. Means,
An intake air amount suppressing unit that suppresses an intake air amount supplied to the plurality of cylinders when the ignition retard control execution prohibiting unit prohibits execution of the ignition delay control;
A control device for an internal combustion engine, comprising: The occurrence history of abnormal combustion includes at least one of the occurrence frequency of abnormal combustion, an integrated value of the number of occurrences of abnormal combustion, and an estimated value of in-cylinder deposit accumulation amount,
The determination means determines that there is an abnormal combustion reduction request when an evaluation value based on the occurrence history of the abnormal combustion exceeds a threshold;
The control device for an internal combustion engine according to claim 1. The knocking detection means detects the occurrence of knocking for each cylinder,
The ignition retard control means executes ignition retard control for retarding the ignition timing of the predetermined cylinder by a predetermined crank angle when occurrence of knocking is detected in the predetermined cylinder;
The ignition retard control execution prohibiting unit is configured to detect that abnormal combustion is reduced when the occurrence of knocking is detected in the predetermined cylinder and when the operation region is in the abnormal combustion generation region. And prohibiting execution of the ignition retard control for the predetermined cylinder,
The control apparatus for an internal combustion engine according to claim 1 or 2, characterized by the above-mentioned. When the operating range is within the range where deposit deposit control can be performed, for cylinders where the estimated value of in-cylinder deposit accumulation exceeds the threshold, the fuel injection amount is reduced to make the air-fuel ratio lean, and the ignition timing is advanced. Deposit loss control means,
An exhaust stoichiometric means for enriching the air-fuel ratio by increasing the fuel injection amount of other cylinders other than the cylinder by increasing the amount reduced by the cylinder when the deposit disappearance means is executed;
The control device for an internal combustion engine according to any one of claims 1 to 3, further comprising: A coolant flow rate control means that can variably control the coolant flow rate for cooling the intake passage according to the operating state, and is set so that the cooling capacity is maximized in an operation region of high rotation and high load,
Cooling water flow rate for correcting an increase in the cooling water flow rate by the cooling water flow control means when the operating region is in the abnormal combustion occurrence region of low rotation and high load and when there is a request for reducing the abnormal combustion in at least one cylinder Means for increasing the weight;
The control device for an internal combustion engine according to any one of claims 1 to 4, further comprising: A coolant flow rate control means that can variably control the coolant flow rate for cooling the intake passage according to the operating state, and is set so that the cooling capacity is maximized in an operation region of high rotation and high load,
An ignition advance prohibiting means for prohibiting the advance of the ignition timing by the deposit disappearance control means when the knocking is not caused by the advance angle; and
A cooling water flow rate reducing unit that corrects the cooling water flow rate by the cooling water flow control unit when the ignition timing advance unit prohibits the ignition timing advance;
The control apparatus for an internal combustion engine according to claim 4, further comprising:

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