JP2021060001A - Controller of internal combustion engine - Google Patents

Abstract

To enable knocking to be suppressed appropriately during execution of ignition spark advance control of advancing an ignition timing from an optimum ignition timing at the time of cold working, regarding a controller of an internal combustion engine.SOLUTION: A controller of an internal combustion engine controls an internal combustion engine comprising an igniter that ignites an air-fuel mixture in a combustion chamber. The controller executes ignition spark advance control of advancing an ignition timing from an optimum ignition timing at the time of cold working in the internal combustion engine. Then, when knocking is detected during the execution of the ignition spark advance control, the controller corrects the ignition timing to the advance side.SELECTED DRAWING: Figure 5

Description

The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for a spark ignition type internal combustion engine.

For example, Patent Document 1 discloses an ignition control system for an internal combustion engine. In this ignition control system, when the amount of fuel adhering to the wall surface in the cylinder is large when it is cold, the ignition timing is advanced from the optimum ignition timing (MBT). As a result, the amount of unburned fuel discharged from the cylinder can be reduced, and the exhaust emission can be reduced.

JP-A-2009-013998

When performing ignition advance control that advances the ignition timing from the optimum ignition timing when it is cold for the purpose of reducing exhaust emissions, the basic ignition timing during ignition advance control is determined in advance so that knocking can be suppressed. To. However, even if such a basic ignition timing is used, knocking can occur due to various variability factors.

The present invention has been made in view of the above-mentioned problems, and is an internal combustion engine capable of suitably suppressing knocking during execution of ignition advance control that advances the ignition timing from the optimum ignition timing when it is cold. It is an object of the present invention to provide a control device for an engine.

The internal combustion engine control device according to the present invention controls an internal combustion engine including an ignition device that ignites an air-fuel mixture in a combustion chamber. The control device executes ignition advance control that advances the ignition timing from the optimum ignition timing when the internal combustion engine is cold. Then, when knocking is detected during the execution of the ignition advance control, the control device corrects the ignition timing to the advance side.

According to the control device of the internal combustion engine according to the present invention, when knocking is detected during execution of ignition advance control, the ignition timing advances, unlike general knock control using the retard of the ignition timing. It is corrected to the corner side. As a result, it becomes possible to more reliably end combustion before the arrival of the knocking occurrence region located near the compression top dead center. Therefore, knocking can be effectively suppressed during execution of ignition advance control.

It is a figure for demonstrating the system configuration which concerns on embodiment. It is a Pθ diagram which showed the change of the cylinder pressure at the time of ignition advance control in comparison with normal ignition control. It is a figure for demonstrating the relationship between ignition timing and knocking occurrence. It is a time chart for demonstrating the control method of the ignition timing at the time of using the ignition advance control which concerns on embodiment. It is a flowchart which shows the routine of the process which concerns on knock control which concerns on embodiment. It is the figure which showed the relationship between the ignition timing and the engine output.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. When the number, quantity, quantity, range, etc. of each element is referred to in the embodiment shown below, the number mentioned is not specified unless otherwise specified or clearly specified in principle. However, the present invention is not limited. In addition, the structures, steps, and the like described in the embodiments shown below are not necessarily essential to the present invention, unless otherwise specified or clearly specified in principle.

1. 1. Example of System Configuration FIG. 1 is a diagram for explaining a system configuration according to an embodiment. The system shown in FIG. 1 includes an internal combustion engine (eg, a spark ignition engine) 10. The number of cylinders and the cylinder arrangement of the internal combustion engine 10 are not particularly limited. Further, as an example, the internal combustion engine 10 is mounted on a conventional vehicle using only the internal combustion engine 10 as a drive source. However, the internal combustion engine 10 may be mounted on various types of hybrid vehicles.

A piston 14 is arranged in each cylinder 12 of the internal combustion engine 10. The piston 14 reciprocates inside the cylinder 12. Each cylinder 12 includes a combustion chamber 16 formed on the top side of the piston 14. An intake passage 18 and an exhaust passage 20 communicate with each other in the combustion chamber 16. An electronically controlled throttle valve 22 is arranged in the intake passage 18 for adjusting the intake air amount.

The internal combustion engine 10 includes a fuel injection valve 24 and an ignition device 26 (only the spark plugs arranged in each cylinder 12 are shown). The fuel injection valve 24 is arranged for each cylinder 12, and injects fuel into, for example, the intake port 18a of the intake passage 18. The internal combustion engine 10 may include an in-cylinder injection type fuel injection valve that injects fuel directly into the cylinder 12 in place of the port injection type fuel injection valve 24. The igniter ignites the air-fuel mixture in the combustion chamber 16.

The system of this embodiment includes a control device 30 for controlling the internal combustion engine 10. The control device 30 is an electronic control unit (ECU) having a processor 30a and a memory 30b. The memory 30b stores a program for controlling the internal combustion engine 10. The processor 30a reads a program from the memory 30b and executes it. The control device 30 may be composed of a plurality of ECUs.

The control device 30 takes in sensor signals from various sensors. The various sensors include an air flow sensor 32, a crank angle sensor 34 and a water temperature sensor 36 for detecting the intake air flow rate, the crank angle and the engine cooling water temperature, respectively, and a knock sensor 38 for detecting knocking. Further, the processor 30a executes various programs using the captured sensor signals, and outputs operation signals for operating various actuators (including the throttle valve 22, the fuel injection valve 24, and the ignition device 26).

2. Ignition Timing Control In this embodiment, "ignition advance control" is executed during cold (typically, cold start). In the ignition advance control referred to here, the ignition timing is advanced more than the optimum ignition timing (that is, MBT: Minimum Advance for the Best Torque).

2-1. Outline of Ignition Advance Control FIG. 2 is a Pθ diagram showing a change in the in-cylinder pressure during ignition advance control in comparison with that during normal ignition control. The ignition timing SA1 of the in-cylinder pressure waveform shown by the broken line in FIG. 2 corresponds to an example of the ignition timing used during normal ignition control (MBT control). The ignition timing SA2 of the in-cylinder pressure waveform shown by the solid line in the figure corresponds to an example of the ignition timing used at the time of ignition advance control. When the ignition advance is controlled, the ignition is ignited earlier than when the normal ignition is controlled, so that the ignition timing of the air-fuel mixture is also earlier. As a result, the amount of the air-fuel mixture that burns before the compression top dead center increases, so that the effect of increasing the pressure and raising the temperature by burning the air-fuel mixture is added to the effect of increasing the pressure and increasing the temperature by the raising operation of the piston 14. As a result, as shown in FIG. 2, the pressure (in-cylinder pressure) and the peak temperature of the in-cylinder gas are higher than those in the normal ignition control, and the wall surface temperature in the cylinder 12 is also higher. As a result, vaporization and combustion of the fuel adhering to the wall surface in the cylinder 12 and the fuel before adhering to the wall surface are promoted.

Therefore, according to the ignition advance control, the discharge of unburned fuel (HC) from the cylinder 12 to the exhaust passage 20 can be effectively suppressed. That is, exhaust emissions can be reduced. Further, when the ignition advance control is executed, the wall surface temperature of the cylinder 12 becomes high as described above. This leads to an increase in the temperature of the engine cooling water flowing around the cylinder 12. As a result, the heating of the vehicle interior using the engine cooling water can be used at an early stage after the engine is started. As described above, the ignition advance control is executed in the cold state based on, for example, an exhaust emission reduction request, a catalyst warm-up request, or a heating request.

In general ignition timing control after the engine warm-up is completed (the above-mentioned normal ignition control), knocking occurs depending on operating conditions such as a high load. According to the normal ignition control, when knocking is detected by a knock sensor or the like, the ignition timing is retarded. On the other hand, the above-mentioned ignition advance control is basically executed when it is cold, but even when it is cold, knocking may occur due to the following factors, for example. That is, when it is cold, the amount of intake air may be increased due to the warming up of the catalyst. In addition, a high compression ratio may be adopted for higher efficiency in recent years. In such a case, knocking can occur even when it is cold.

FIG. 3 is a diagram for explaining the relationship between the ignition timing and the occurrence of knocking. The vertical axis of FIG. 3 is the combustion mass ratio MFB, and the horizontal axis is the crank angle. The combustion mass ratio MFB starts to increase from 0% when combustion starts, and the timing when this reaches 100% corresponds to the timing when combustion ends. Knocking is a self-ignition phenomenon that occurs when an unburned air-fuel mixture is placed under high temperature and high pressure conditions for a certain period of time or longer. The “knocking generation area” shown in FIG. 3 is located near the compression top dead center where the gas in the cylinder is most compressed by the piston. Then, the knocking occurrence region indicates that knocking actually occurs when ignition is performed at a timing such that combustion ends in that region.

The MFB waveform shown by the broken line in FIG. 3 corresponds to the normal ignition timing. This normal ignition timing is generally predetermined in consideration of thermal efficiency and knocking occurrence. More specifically, as the normal ignition timing, MBT is used on the low load side, and ignition is retarded by the amount of retardation as small as possible with respect to MBT so that knocking can be suppressed on the high load side where knocking is likely to occur. Timing is used. In this example of the normal ignition timing, in the knocking generation region, since most of the combustion is completed, the temperature and pressure in the cylinder are high, and an unburned air-fuel mixture is present in the cylinder. If the ignition timing is advanced beyond the normal ignition timing, knocking will occur.

Next, the MFB waveform shown by the alternate long and short dash line in the figure corresponds to the ignition timing delayed from the above-mentioned normal ignition timing. In this example of the ignition timing retard, the combustion mass ratio MFB is low (that is, the combustion is not so advanced) in the knocking generation region, so that the temperature and pressure inside the cylinder are not so high. Therefore, although the unburned air-fuel mixture exists in the knocking generation area, it can be said that knocking does not occur.

Next, the MFB waveform shown by the solid line in the figure corresponds to the ignition timing at the time of executing the above-mentioned ignition advance control. In the example of this ignition timing advance, in the knocking generation region, the inside of the cylinder has a high temperature and high pressure, but since combustion has already been completed, there is no unburned air-fuel mixture. In other words, in this example of ignition timing advance, knocking (self-ignition) occurs because ignition is performed at a timing such that combustion ends (the unburned air-fuel mixture disappears) before the knocking occurrence region arrives. Can be said not to occur.

Next, FIG. 4 is a time chart for explaining an ignition timing control method when using the ignition advance control according to the embodiment. In FIG. 4, the ignition advance control is executed during the equal output operation of the internal combustion engine 10. The term "equal output operation" as used herein refers to a time when the internal combustion engine 10 is required to exert a constant output, such as when the amount of depression of the accelerator pedal is constant, and is referred to as an idling operation. Including.

The "ignition timing region R where knocking occurs" in FIG. 4 corresponds to the "knocking occurrence region" in FIG. 3, and when the ignition timing is within this ignition timing region R, combustion occurs within the knocking occurrence region. It indicates that it ends and knocking occurs. Such an ignition timing region R can be specified in advance by conducting an experiment or the like.

The time point t0 in FIG. 4 corresponds to the time point when the execution request for ignition advance control is issued. At this point t0, the ignition timing is set to MBT. In the example shown in FIG. 4, the ignition timing is gradually advanced from the MBT toward the "basic ignition timing at the time of ignition advance control". This basic ignition timing is predetermined as a desired value located on the advance angle side of the ignition timing region R.

If the ignition timing is advanced beyond the MBT, the engine output will decrease due to the decrease in combustion efficiency. In the example shown in FIG. 4, the intake air amount is increased along with the advance angle of the ignition timing in order to keep the engine output constant.

The time point t1 corresponds to the time when the ignition timing reaches the lower limit of the ignition timing region R. When the ignition timing falls within the ignition timing region R, knocking occurs. Therefore, in the example shown in FIG. 4, the ignition timing is switched so as not to use (jump) the ignition timing region R at the subsequent time point t2. During the period from the time point t1 to the time point t3, the ignition timing is switched so as not to change the engine output as much as possible with respect to the change in the intake air amount. The time point t4 corresponds to the time when the ignition timing reaches the basic ignition timing of the ignition advance control.

At the time point t5, the operation for returning the ignition timing to the MBT is started in response to the request to end the ignition advance control. Specifically, the ignition timing is gradually retarded while reducing the intake air amount. Also in this retarding process, the ignition timing is switched so as not to use (jump) the ignition timing region R at the time point t6, as in the above-mentioned advance angle process.

According to the ignition advance control execution method as shown in FIG. 4, the ignition advance is avoided (at least suppressed) in the process of the advance at the start of the control and the retard at the end of the control. Control can be performed. When executing the ignition advance control, for example, instead of the example shown in FIG. 4, the ignition timing is stepped between the MBT and the basic ignition timing of the ignition advance control while rapidly changing the intake air amount. May be switched.

2-2. Ignition timing correction method when knocking is detected (knock control)
According to the ignition advance control execution method described with reference to FIG. 4, as described above, the process of switching the ignition timing between the start and end of the ignition advance control (MBT and the basic ignition timing). ), The occurrence of knocking can be avoided (suppressed). However, knocking can occur due to various variable factors even during use of the basic ignition timing set so as not to cause knocking. The “variation” here refers to variations in fuel properties, the amount of deposit accumulated in the combustion chamber 16, the intake air temperature, the amount of residual gas in the cylinder 12, and the dimensions of each part of the internal combustion engine 10.

In general knock control, as described above, when knocking is detected, the ignition timing is retarded. On the other hand, in the present embodiment, when knocking is detected during the execution of the ignition advance control, the ignition timing is corrected to the advance side. More specifically, knocking is detected during use of the basic ignition timing located on the advance side of the MBT (more specifically, on the advance side of the ignition timing region R located on the advance side of the MBT). In that case, the ignition timing is further advanced than the basic ignition timing. Then, as an example, this advance correction is repeatedly executed every time knocking is detected. On the other hand, if knocking is no longer detected during advance correction, the ignition timing is returned to the basic ignition timing.

2-3. Processing by the control device FIG. 5 is a flowchart showing a routine of processing related to knock control according to the embodiment. This routine is repeatedly executed in a predetermined control cycle.

In the routine shown in FIG. 5, the control device 30 first determines in step S100 whether or not the ignition advance control is being executed. The ignition advance control is executed when the internal combustion engine 10 is cold, for example, based on the above-mentioned exhaust emission reduction request, catalyst warm-up request, or heating request.

When the determination result of this step S100 is negative (when the ignition advance control is not being executed (for example, after cold start)), the ignition timing is basically controlled to the basic ignition timing. , It is corrected to the retard side from the basic ignition timing depending on the presence or absence of knocking detection. The basic ignition timing used here corresponds to the normal ignition timing shown in FIG. If the determination result in step S100 is negative in this way, the process proceeds to step S102.

In step S102, the control device 30 determines whether or not knocking has been detected. This determination is performed using, for example, the knock sensor 38. The knocking detection method is not limited to the one using the knock sensor 38 (a type sensor that detects the vibration of the cylinder block caused by knocking). For example, in an internal combustion engine provided with an in-cylinder pressure sensor, the in-cylinder pressure sensor may be used to detect knocking.

If knocking is detected in step S102, the process proceeds to step S104. In step S104, the control device 30 retards the ignition timing by a predetermined amount from the current value. Specifically, in this step S104, a retard correction value is added to the basic ignition timing. This retard correction value is increased by a predetermined amount each time knocking is detected in step S102. Therefore, according to the process of step S104, the ignition timing is retarded by a predetermined amount from the current value each time knocking is detected. In the case of the first correction, the ignition timing is corrected to the retard side by a predetermined amount from the basic ignition timing.

On the other hand, if knocking is not detected in step S102, the process proceeds to step S106. In step S106, the control device 30 determines whether or not the retard angle correction is in progress (that is, whether or not the retard angle correction value obtained by the process of step S104 is not zero).

As a result, when it is determined in step S106 that the retard correction is not being performed (that is, when the basic ignition timing is used as the ignition timing), the control device 30 ends the current processing cycle. On the other hand, if it is determined that the retard angle correction is in progress, the process proceeds to step S108. In step S108, the control device 30 advances the ignition timing by a predetermined amount from the current value, up to the limit of returning to the basic ignition timing. Specifically, each time it is determined in step S106 that the retard angle correction is in progress, the above-mentioned retard angle correction value is reduced by a predetermined amount.

On the other hand, when the determination result in step S100 is positive (when the ignition advance control is being executed), the ignition timing is basically the basic ignition timing of the ignition advance control (see FIG. 4). While being controlled, it is corrected to the advance angle side from the basic ignition timing depending on the presence or absence of knocking detection. Specifically, in this case, the process proceeds to step S110.

In step S110, the control device 30 determines whether or not knocking has been detected, as in step S102. If knocking is detected in step S110, the process proceeds to step S112. In step S112, the control device 30 advances the ignition timing by a predetermined amount from the current value. Specifically, in this step S112, the advance angle correction value is added to the basic ignition timing of the ignition advance angle control. This advance correction value is increased by a predetermined amount each time knocking is detected in step S110. Therefore, according to the process of step S112, the ignition timing is advanced by a predetermined amount from the current value each time knocking is detected. In the case of the first correction, the ignition timing is corrected to the advance angle side by a predetermined amount from the basic ignition timing.

On the other hand, if knocking is not detected in step S110, the process proceeds to step S114. In step S114, the control device 30 determines whether or not the advance angle correction is in progress (that is, whether or not the advance angle correction value obtained by the process of step S112 is not zero).

As a result, when it is determined in step S114 that the advance angle correction is not being performed (that is, when the basic ignition timing is used as the ignition timing), the control device 30 ends the current processing cycle. On the other hand, if it is determined that the advance angle correction is in progress, the process proceeds to step S116. In step S116, the control device 30 retards the ignition timing by a predetermined amount from the current value, up to the limit of returning to the basic ignition timing. Specifically, each time it is determined in step S114 that the advance angle correction is in progress, the advance angle correction value is reduced by a predetermined amount.

In addition, according to the routine processing shown in FIG. 5 described above, the direction of correction of the ignition timing at the time of knocking detection (whether it is the advance angle side or the retard angle side) depending on whether or not the ignition advance angle control is executed. ) Is changed.

3. 3. Effect As described above, according to the routine processing shown in FIG. 5, when knocking is detected during execution of ignition advance control, what is general knock control using the retard of ignition timing? Unlike, the ignition timing is corrected to the advance angle side. As a result, it becomes possible to more reliably terminate the combustion before the knocking occurrence region shown in FIG. 3 arrives. Therefore, when knocking is detected during execution of ignition advance control, knocking can be effectively suppressed. In addition, if knocking is suppressed by using the ignition timing retardation during execution of ignition advance control, the ignition timing may be significantly retarded beyond the ignition timing region R (see FIG. 4) and MBT. You will need it. On the other hand, according to the method of the present embodiment, knocking can be suppressed while reducing the correction amount of the ignition timing as compared with the case of using the retard angle correction.

4. Engine output control using ignition timing adjustment during ignition advance control During execution of ignition advance control according to the above-described embodiment, the following engine output control is additionally performed by using ignition timing adjustment. It may be executed.

Specifically, during constant output operation including idling operation, the actual engine output may fluctuate with respect to the required engine output due to the influence of various disturbances even if the required engine output is kept constant. In order to realize good vibration and noise performance, it is desired to suppress such fluctuations in the actual engine output (fluctuations in the engine rotation speed) and stably operate the internal combustion engine.

In a spark-ignition type internal combustion engine such as the internal combustion engine 10, the engine output is usually controlled by adjusting the intake air amount. However, when low output operation is performed while lowering the combustion efficiency by using ignition advance control for the purpose of reducing exhaust emissions or warming up the catalyst when cold, as described with reference to FIG. In addition, the amount of intake air is increased as compared with the case of using MBT. Therefore, it may be difficult to change the engine output with high responsiveness when trying to further increase the intake air amount. This is also one of the factors, and it can be said that the responsiveness of the engine output control during the execution of the ignition advance control is superior to the adjustment of the intake air amount in the adjustment of the ignition timing.

Specifically, FIG. 6 is a diagram showing the relationship between the ignition timing and the engine output. As shown in FIG. 6, the ignition advance control is performed by using an ignition timing region of about 120 to 50 BTDC as an example. FIG. 6 also shows an execution region for ignition retard control (eg, −10 to −30 BTDC) for comparison. This ignition retard control is generally performed for the purpose of warming up the catalyst or the like.

From FIG. 6, in the ignition advance control execution area and the ignition retard control execution area for comparison, the amount of change in engine output with respect to a predetermined amount of change in ignition timing is larger than that in the normal use area near the MBT. You can see that it is big. However, while the general ignition retard control is being executed, the engine output is increased by advancing the ignition timing, whereas during the ignition advance control, the ignition timing is retarded. Engine output increases.

Therefore, when the engine output is increased in response to a request to increase the engine output, the ignition timing is advanced while the ignition retard control is being executed, whereas the ignition timing is advanced while the ignition advance control is being executed. Be retarded. Further, when the engine output is reduced in response to the engine output reduction request, the ignition timing is retarded if the ignition retard control is being executed, whereas the ignition timing is delayed during the ignition advance control. Is advanced.

More specifically, in the example in which the internal combustion engine 10 is mounted on the conventional vehicle as in the above-described embodiment, the engine output control at the time of ignition advance control referred to here is performed as follows, for example. Can be done. That is, in the conventional vehicle, the request for increasing the engine output is issued when the actual engine rotation speed detected by the crank angle sensor 34 drops by a predetermined value with respect to the desired target rotation speed. Then, in response to the request to increase the engine output, the ignition timing is retarded by a predetermined amount. On the contrary, when the actual engine rotation speed increases by a predetermined value with respect to the target rotation speed, a request for lowering the engine output is issued, and the ignition timing is advanced by a predetermined amount.

Further, in an example in which the engine output can be calculated in a hybrid vehicle equipped with an electric motor connected to an internal combustion engine, an engine increase request is issued when the calculated engine output drops by a predetermined value with respect to the required engine output, and the ignition timing is ignited. May be retarded. Further, when the calculated engine output increases by a predetermined value with respect to the required engine output, an engine lowering request may be issued and the ignition timing may be advanced.

As described above, during the execution of the ignition advance control, the vibration noise during the constant output operation may be reduced by executing the engine output control by using the ignition timing adjustment by the above-mentioned method.

10 Internal combustion engine 12 Cylinder 14 Piston 16 Combustion chamber 18 Intake passage 20 Exhaust passage 22 Throttle valve 24 Fuel injection valve 26 Ignition device 30 Control device 32 Airflow sensor 34 Crank angle sensor 36 Water temperature sensor 38 Knock sensor

Claims (1)

A control device that controls an internal combustion engine equipped with an ignition device that ignites an air-fuel mixture in a combustion chamber.
The control device is
When the internal combustion engine is cold, the ignition advance control for advancing the ignition timing from the optimum ignition timing is executed.
A control device for an internal combustion engine, characterized in that when knocking is detected during execution of the ignition advance control, the ignition timing is corrected to the advance side.

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