JP2011220159A - Controller of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent combustion variation or flame out due to the deterioration of the condition of an ignition plug in a direct injection spark ignition type internal combustion engine forming a gaseous combustion mixture around the ignition plug and carrying out a stratified charge combustion operation.SOLUTION: The controller of the internal combustion engine is provided with a fuel injection valve for directly injecting the fuel to the combustion chamber of the internal combustion engine, a fuel injection quantity control means for controlling the quantity of the fuel injection from the fuel injection valve, an intake flow rate control means for controlling the intake flow rate of air flowing into the combustion chamber, an ignition plug for spark-igniting a gaseous mixture formed of fuel injected from the fuel injection valve and air flowing into the combustion chamber and an ignition plug condition detecting means for detecting the condition of the ignition plug. When it is detected by the ignition plug condition detecting means that the condition of the ignition plug is made worse, the concentration of the gaseous mixture in the combustion chamber is raised while keeping the stratified charge combustion operation.

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for a direct injection spark ignition internal combustion engine in which a flammable mixture is formed in the vicinity of a spark plug and a stratified combustion operation is performed.

  In a direct-injection spark-ignition internal combustion engine in which stratified combustion is performed, fuel is directly injected into the combustion chamber of the internal combustion engine during the compression stroke to form a combustible mixture only in the vicinity of the spark plug, thereby realizing stratified lean combustion. Can do. In stratified lean combustion, an air-fuel mixture in the combustible range exists in the vicinity of the spark plug, and air is occupied in other areas. Therefore, when controlling the output of the internal combustion engine, the amount of the air-fuel mixture in the vicinity of the spark plug is controlled. There is no need to control the amount of intake mixture as in an internal combustion engine that supplies a general homogeneous mixture. Therefore, the output loss due to the pumping loss can be reduced, which is effective as a fuel efficiency improvement measure.

  The fuel injected in the compression stroke forms a combustible air-fuel mixture in the vicinity of the spark plug while taking in air together with splitting and evaporation after being injected from the injection port. This combustible mixture is burned by spark discharge in the spark discharge gap of the spark plug. However, as the operating conditions such as the engine speed and load change, the temperature of the combustion chamber and the intake air flow also change, so the state of splitting and evaporation of the injected fuel also changes, and the mixture formation near the spark plug also occurs. Change.

  When the operating conditions in which fuel splitting or evaporation is difficult to proceed and the mixture concentration tends to be lower than the flammable range continue continuously, non-evaporated liquid phase fuel tends to exist near the spark plug, and the spark plug The adhering fuel becomes carbon without complete combustion, and smoldering fouling of the spark plug. When the smoldering contamination of the spark plug progresses, even if a high voltage for spark discharge is applied between the electrodes of the spark plug, it will flow as a leak current without spark discharge in the spark discharge gap. It falls into misfire.

  Therefore, conventionally, in an in-cylinder injection engine control apparatus that performs stratified combustion by setting the air-fuel ratio of the entire combustion chamber to be higher than the stoichiometric air-fuel ratio, there is an ignition abnormality caused by carbon adhesion to the spark plug. When detected, switching to carbon removal operation that lowers the air-fuel ratio than at the time of stratified combustion operation and advances the injection timing of at least a part of the fuel, prevents the engine operating condition from deteriorating An apparatus is disclosed (for example, see Patent Document 1).

  According to the conventional device disclosed in Patent Document 1, the combustion state is improved by switching from the stratified combustion operation to the carbon removal operation and lowering the air-fuel ratio compared to the stratified combustion operation, and the carbon adhering to the spark plug is self-generated. By the cleaning action, it is incinerated by itself and the ignition abnormality is eliminated.

JP-A-11-125131

  In the case of the conventional technique disclosed in Patent Document 1, since the stratified combustion operation is switched to the carbon removal operation immediately after the ignition abnormality is detected, the fuel consumption is greatly deteriorated. Immediately after the ignition abnormality is detected, the fuel injection timing is advanced before the intake stroke in which homogeneous combustion is performed, and the output loss due to the pumping loss is larger than that in the stratified combustion, and the fuel consumption is deteriorated. Further, when the fuel injection timing is advanced in the compression stroke that is stratified combustion, the timing at which the fuel spray reaches the spark plug is advanced, so that it is necessary to change the ignition timing. Normally, the ignition timing is set to the timing at which the combustion efficiency is the best, but the fuel consumption deteriorates to compensate for the decrease in combustion efficiency due to the ignition timing change.

  The present invention has been made to solve the above-described problems in conventional devices, and minimizes deterioration in fuel consumption when combustion becomes unstable due to smoldering fouling of a spark plug. An object of the present invention is to provide a control apparatus for an internal combustion engine that can stabilize the combustion state by returning the spark plug to a normal state while suppressing the ignition plug.

  An internal combustion engine control apparatus according to the present invention includes a fuel injection valve that directly injects fuel into a combustion chamber of the internal combustion engine, a fuel injection amount control means that controls the amount of fuel injected from the fuel injection valve, An intake flow rate control means for controlling the intake flow rate of the intake air, an ignition plug that sparks and ignites a combustible air-fuel mixture formed by the fuel injected from the fuel injection valve and the air sucked into the combustion chamber, A direct-injection spark-ignition internal combustion engine that includes a spark plug state detection means for detecting a state, and that performs a stratified combustion operation on the combustible air-fuel mixture formed in the vicinity of the spark plug by spark ignition of the spark plug. When the ignition plug state detection means detects the deterioration of the ignition plug state, the mixture concentration in the combustion chamber is increased while the stratified combustion operation is being performed.

  According to the control device for an internal combustion engine according to the present invention, when the deterioration of the ignition plug state is detected by the ignition plug state detection means, the mixture concentration in the combustion chamber is increased while the stratified combustion operation is maintained. By increasing the concentration of the air-fuel mixture in the vicinity, combustion near the spark plug is improved, and the carbon adhering to the spark plug is naturally incinerated by the self-cleaning action, thereby eliminating smoldering fouling of the spark plug while suppressing fuel consumption deterioration. Good combustion without combustion fluctuations and misfires can be obtained.

It is a schematic block diagram which shows the control apparatus of the internal combustion engine by Embodiment 1 and Embodiment 2 of this invention. It is a block diagram which shows the internal structure of ECU in the control apparatus of the internal combustion engine by Embodiment 1 and Embodiment 2 of this invention. It is explanatory drawing which shows the fuel spray shape in the fuel-injection timing at the time of stratified combustion execution in the control apparatus of the internal combustion engine by Embodiment 1 and Embodiment 2 of this invention. It is a flowchart which shows the control content in the control apparatus of the internal combustion engine by Embodiment 1 of this invention.

It is explanatory drawing explaining the ion current value waveform at the time of a spark plug normal, and the time of smoldering pollution. It is a flowchart which shows the control content in the control apparatus of the internal combustion engine by Embodiment 2 of this invention. It is explanatory drawing which shows the relationship between the exhaust temperature in the control apparatus of the internal combustion engine by Embodiment 2 of this invention, and combustion temperature. It is a figure which shows the corrected amount based on the combustion temperature in the control apparatus of the internal combustion engine by Embodiment 2 of this invention.

Embodiment 1 FIG.
FIG. 1 is a schematic configuration diagram showing an internal combustion engine control apparatus according to Embodiments 1 and 2 of the present invention. The internal combustion engine shown in FIG. 1 is a direct-injection spark ignition internal combustion engine, and the internal combustion engine main body 1 includes a plurality of cylinders, but only one cylinder is shown for convenience of explanation. In FIG. 1, an internal combustion engine body 1 is provided with a piston 3 that reciprocates in a combustion chamber 2. By reciprocating, air is introduced into the combustion chamber 2 via an intake valve 9, The combustion pressure is converted into kinetic energy, and the burned gas after combustion is discharged from the exhaust valve 8. An intake pipe 4 and an exhaust pipe 5 are connected to the internal combustion engine body 1 via an intake valve 9 and an exhaust valve 8. The fuel injection valve 10 is provided in the internal combustion engine body 1 and directly injects pressurized fuel into the combustion chamber 2.

  In the vicinity of the exhaust valve 8 in the exhaust pipe 5, an exhaust temperature sensor 6 for detecting the exhaust temperature for estimating the combustion temperature is provided. The throttle valve 7 provided in the middle of the intake pipe 4 is controlled in its opening / closing amount by, for example, a DC motor or a stepping motor, and controls the intake flow rate to the combustion chamber 2.

  The fuel injection valve 10 is opened based on a signal from an engine control unit (hereinafter referred to as ECU) 12 and directly injects pressurized fuel into the combustion chamber 2. A stratified mixture is formed in the combustion chamber 2 by the injected fuel and air flowing from the intake pipe 4, and is ignited by the spark plug 11.

  The ECU 12 provided in the passenger compartment or the like is constituted by a microcomputer system that executes fuel injection amount control for controlling the fuel injection amount by the fuel injection valve 10, intake air flow control for controlling the intake air flow from the intake pipe 4, and the like. And an input / output interface 13, a central processing unit 14, a ROM 15, a RAM 16, and a drive circuit 17.

An exhaust temperature sensor 6, other various sensors (not shown), and switches (not shown) are connected to the input side of the ECU 12. Outputs of the exhaust temperature sensor 6 and various sensors input to the input / output interface 13 are A / D converted and taken into the ECU 12. The central processing unit 14 executes various kinds of arithmetic processing based on the A / D converted input signal. The drive circuit 17 outputs various actuator control signals based on the calculation result by the central processing unit 14, and drives the fuel injection valve 10, the throttle valve 7, and the like.

  Further, as means for detecting the state of the spark plug 11, an ion current detection circuit 18 is provided for detecting the combustion state based on ions generated during combustion in the combustion chamber 2. If the combustion state is good, the state of the spark plug 11 is good, and if it is bad, it is determined that the state of the spark plug 11 is bad. By applying a bias voltage to the spark plug 11 from a bias circuit (not shown) provided in the ion current detection circuit 18, ions generated in the combustion chamber 2 flow, and the ions generated in the combustion chamber 2 are ion current detection circuits. 18 is detected as an ion current.

  FIG. 2 is a block diagram of the control executed by the control apparatus for an internal combustion engine according to the first and second embodiments of the present invention, and includes a spark plug state detecting means 121, a combustion mode switching means 122, a combustion temperature. An estimation unit 123, an intake air flow rate control unit 124, and a fuel injection amount control unit 125 are provided.

  The spark plug state detection unit 121 detects the state of the spark plug 11 based on the ion current detected by the ion current detection circuit 18 and inputs a signal indicating the state of the spark plug 11 to the combustion mode switching unit 122. When the input signal from the spark plug state detection unit 121 indicates that the state of the spark plug 121 has not deteriorated, the combustion mode switching unit 122 takes in a signal to keep the combustion mode as stratified combustion. Input to the flow rate control means 124 and the fuel injection amount control means 125. The intake flow rate control means 124 and the fuel injection amount control means 125 that have received a signal to keep the combustion mode as stratified combustion from the combustion mode switching means 122 respectively multiply the correction amount “1.0” and the intake flow rate, and The fuel injection amount is calculated.

  On the other hand, when the signal from the spark plug state detection unit 121 input to the combustion mode switching unit 122 indicates that the state of the spark plug 11 has deteriorated, the combustion mode switching unit 122 switches the combustion mode. And a signal indicating the combustion mode for which switching is determined is input to the intake flow rate control means 124 and the fuel injection amount control means 125. For example, when the combustion mode switching means 122 receives a signal indicating that the state of the ignition plug has deteriorated, the combustion mode remains stratified combustion if the number of corrections in the above calculation is 20 or less. If the number of corrections exceeds 20, it is determined that it is difficult to recover the spark plug in stratified combustion, and the combustion mode is determined to be switched from stratified combustion to homogeneous combustion. This is input to the control means 124 and the fuel injection amount control means 125.

  The intake flow rate control means 124 and the fuel injection amount control means 125, which have received the signal corresponding to the switching described above, return the spark plug 11 to the return of the spark plug 11 previously obtained from experiments in order to increase the mixture concentration. Multiply the necessary correction amount to calculate the intake air flow rate and the fuel injection amount. Therefore, the combustion temperature estimating means 123 can be omitted. Also, instead of switching to homogeneous combustion immediately after detecting the deterioration state of the spark plug 11, the mixture concentration in the vicinity of the spark plug is increased with stratified combustion to aim at the return of the spark plug 11 to minimize the deterioration of fuel consumption. Limit to the limit.

  It should be noted that the intake air flow rate and the fuel injection amount are multiplied and corrected in accordance with the combustion temperature estimated by the combustion temperature estimating means 123 based on the exhaust gas temperature detected by the exhaust gas temperature sensor 6 instead of the correction amount previously obtained from the experiment. By doing so, it is possible to perform highly accurate correction in accordance with the combustion temperature that contributes to fuel splitting and evaporation. This case will be described later as an internal combustion engine control device corresponding to Embodiment 2 of the present invention.

  The throttle valve 7 and the fuel injection valve 10 are driven based on the intake flow rate and the fuel injection amount calculated by reflecting the correction by the intake flow rate control means 124 and the fuel injection amount control means 125, respectively.

  With the above-described configuration, by increasing the air-fuel mixture concentration in the vicinity of the spark plug 11, combustion in the vicinity of the spark plug 11 is improved, and carbon or the like adhering to the spark plug 11 is naturally incinerated by a self-cleaning action. As a result, smoldering fouling of the spark plug can be solved while minimizing the deterioration of the ignition plug, and good combustion without combustion fluctuation and misfire can be obtained.

  Here, the air-fuel mixture formation in the direct injection spark ignition internal combustion engine in which stratified combustion is performed will be described. FIG. 3 is an explanatory diagram showing a fuel spray shape at the fuel injection timing when stratified combustion is executed in the control apparatus for an internal combustion engine according to the first and second embodiments of the present invention. In FIG. 3, the combustion chamber 2, the piston 3, the exhaust valve 8, the intake valve 9, the fuel injection valve 10, and the spark plug 11 are as described with reference to FIG. A region 19 surrounded by a solid line indicates a liquid phase region in which the fuel injected from the fuel injection valve 10 is insufficiently evaporated and contains a large amount of liquid spray. A region 20 surrounded by a broken line outside the liquid phase region 19 is fuel injected in the same manner as the liquid phase region 19, but is an outer peripheral portion of the spray. Indicates the area.

  Stratified combustion is a method in which the fuel injected from the fuel injection valve 10 is spark-ignited by a spark plug 11 installed in the vicinity of the fuel injection valve 10. For this reason, the electrode at the tip of the spark plug 11 needs to include the gas phase region 20 that can be ignited. If the liquid phase region 19 is included in the electrode at the tip of the spark plug 11, the air-fuel mixture becomes over-rich, and the electrode of the spark plug 11 is wetted by the fuel and the spark discharge is hindered or misfires. Combustion fluctuations increase due to combustion of liquid phase fuel. On the contrary, when the electrode at the tip of the spark plug 11 is separated from the gas phase region 20, it becomes over lean, and the combustion fluctuation increases as in the case of over rich.

  When the combustion is unstable, the combustion temperature is low, and fuel splitting or evaporation does not proceed, so the gas phase region 20 is narrowed and the air-fuel mixture near the spark plug 11 becomes over lean. Due to overlean, the ignition performance is reduced, and a part of the fuel in the liquid phase region that is difficult to burn adheres to the spark plug, resulting in smoldering.

  In the control apparatus for an internal combustion engine according to the first and second embodiments of the present invention, when the spark plug 11 deteriorates, the mixture concentration is increased by controlling the fuel injection amount and the intake air flow rate, so that the outer periphery of the spray is increased. This increases the amount of fuel splitting or evaporating, and the gas phase region 20 in the vicinity of the spark plug 11 spreads to improve the ignition performance. Further, by increasing the air-fuel mixture concentration in the combustion chamber 2, the energy generated by combustion increases and the combustion temperature rises, so that the effect of promoting fuel evaporation is improved and a stratified air-fuel mixture that becomes a combustible range is easily formed, The combustion state is improved. As a result, the self-cleaning action of the spark plug due to the complete combustion of the fuel is effectively exhibited, so that the carbon adhering to the spark plug is burned out and smoldering contamination can be eliminated.

  The internal combustion engine control apparatus according to Embodiment 1 of the present invention will be specifically described below. As described above, when the deterioration of the spark plug 11 is detected, the gas phase region 20 is expanded to the vicinity of the spark plug 11 by increasing the air-fuel mixture concentration to improve the ignition performance, and the generated energy due to combustion is increased. Raise the combustion temperature. By raising the combustion temperature, fuel splitting and evaporation can be promoted, so that the air-fuel mixture can be returned to the combustible range and the spark plug 11 can be returned to the normal state by complete combustion of the fuel.

  Therefore, first, the air-fuel mixture concentration is increased by increasing the fuel injection amount and decreasing the intake flow rate. Immediately after the detection of the deterioration of the spark plug 11, the combustion mode is not changed, and the air-fuel mixture only in the vicinity of the ignition plug 11 in the stratified combustion state is made combustible to suppress the deterioration of fuel consumption to a minimum. If it is not improved by the correction in the stratified combustion state, the combustion mode is switched to the homogeneous combustion, so that the ignition plug 11 is more reliably restored to the normal state from the deteriorated state.

  While stratified combustion creates a combustible air-fuel mixture only in the vicinity of the spark plug 11, homogeneous combustion uses the entire combustion chamber 2 as a combustible air-fuel mixture, improving the ignition performance. Further, in the homogeneous combustion, a combustible air-fuel mixture is formed with respect to the air in the entire combustion chamber 2, and the amount of fuel injection is increased as compared to the time of stratified combustion. As the combustion temperature becomes higher, fuel splitting and evaporation become active, and the effect of returning the spark plug becomes larger.

  FIG. 4 is a flowchart showing the contents of control in the control apparatus for an internal combustion engine according to Embodiment 1 of the present invention. In FIG. 4, first, in step S101, the state of the spark plug 11 is detected using the ion current. The ionic current is a weak electric current of about microampere generated mainly from an intermediate product having a charge called radical in a flame in the course of combustion of a hydrocarbon fuel such as gasoline.

  FIG. 5 is a waveform diagram showing ion current values when the ignition plug is normal and when smoldering is dirty in the control apparatus for an internal combustion engine according to the first and second embodiments of the present invention. In FIG. 5, the vertical axis represents the ion current value, and the horizontal axis represents the crank angle. As shown in FIG. 5, the leakage current is superimposed when the ionic current is detected when the spark plug 11 is smoldering dirty. Focusing on this point, in step S101 in FIG. 4, the state of the spark plug 11 is detected by monitoring the behavior of the current detected by the ion current detection circuit 18.

  Therefore, in step S101, the ionic current value is determined at the crank angle other than the ionic current generation period generated when the air-fuel mixture burns, for example, at the timing of the crank angle d1 at which the exhaust stroke ends as shown in FIG. Is greater than or equal to a predetermined determination value corresponding to 10% of the ionic current peak value, it is determined that the spark plug 11 has deteriorated due to smoldering contamination (Y). 11 is determined to be good (N).

  If it is determined in step S101 that the spark plug 11 has not deteriorated (N), it is not necessary to correct the intake air flow rate and the fuel injection amount. And then proceeds to step S103 to multiply the fuel injection amount by the correction amount “1.0”. In the next step S104, the number of corrections is reset and this routine is terminated. Here, the number of corrections means the number of corrections of the fuel injection amount and the intake flow rate.

On the other hand, if it is determined in step S101 that the state of the spark plug 11 has deteriorated (Y), the process proceeds to step S105, and in order to determine whether the combustion mode should be switched to homogeneous combustion, the fuel injection amount and the intake air It is determined whether or not the correction number of the flow rate has exceeded 20 times, for example. If it is determined in step S105 that the number of corrections is 20 or less (N), the flow proceeds to step S106, the combustion mode remains as stratified combustion, and then the flow proceeds to step S107 to increase the air-fuel mixture concentration. As shown in FIG. 11, the fuel injection amount is corrected to decrease by 20%, and then in step S108, the fuel injection amount is corrected by 20%. As the correction amount in the intake air flow rate correction in step S107 and the fuel injection amount correction in step S108, a fixed value calculated in advance from an experiment is used.

  A gas phase region is formed in the vicinity of the spark plug 11 by increasing the air-fuel mixture concentration to increase the amount of fuel to be split or evaporated, and the generated energy due to combustion increases, so that the combustion temperature rises and fuel injection occurs. The combustion chamber temperature will inevitably increase. The air-fuel mixture concentration in the vicinity of the spark plug 11 deviating from the combustible range due to the deterioration of the spark plug 11 and the combustion state being deteriorated and the combustion temperature being lowered can be returned to the combustible range by increasing the combustion temperature. Next, in step S112, “1” is added to the number of corrections, and this routine is terminated.

  On the other hand, if it is determined in step S105 that the number of corrections exceeds 20 (Y), if the state of the spark plug 11 is still not improved, the return of the spark plug 11 in stratified combustion is In step S109, the stratified charge combustion is switched to the homogeneous combustion. For switching to homogeneous combustion, the fuel injection timing is changed from the compression stroke to the intake stroke, and in steps S110 and S111, the intake air flow rate and the fuel injection amount are respectively corrected to values corresponding to the homogeneous combustion, and step S112. Then, the process is terminated by adding “1” to the number of corrections. By making the combustion form homogeneous combustion and making the entire combustion chamber a combustible mixture, the ignition performance is improved and the fuel can be burned completely, so that the carbon adhering to the spark plug 11 is surely burned out and the smoldering of the spark plug is ensured. Can be resolved.

  As described above, according to the control apparatus for an internal combustion engine according to the first embodiment of the present invention, the ignition performance can be improved and the combustion state can be improved by increasing the mixture concentration in the vicinity of the spark plug. The carbon adhering to the carbon is naturally incinerated by the self-cleaning action, and the smoldering contamination of the spark plug can be eliminated. Immediately after detecting the deterioration of the spark plug, the stratified combustion is performed to recover from the deterioration state of the spark plug, so that it is possible to obtain good combustion without fluctuation of combustion and misfire while minimizing deterioration of fuel consumption. it can.

Embodiment 2. FIG.
In the first embodiment, when it is determined that the state of the spark plug has deteriorated, the correction of the intake air flow rate and the fuel injection amount is a fixed value calculated in advance from experiments, but in the second embodiment, it is estimated from the exhaust temperature. By correcting the intake air flow rate and the fuel injection amount according to the combustion temperature, a highly accurate correction corresponding to the combustion temperature contributing to fuel splitting and evaporation is performed. The configuration shown in FIG. 1 and FIG. 2 in the first embodiment is the same in the second embodiment.

  Hereinafter, a control apparatus for an internal combustion engine according to Embodiment 2 of the present invention will be described. FIG. 6 is a flowchart showing the control contents in the control apparatus for an internal combustion engine according to the second embodiment of the present invention. In FIG. 6, the processing when the spark plug 11 is normal from step S201 to step S204 is the same as that in the first embodiment, and thus the description thereof is omitted.

  If it is determined in step S201 that the spark plug 11 has deteriorated, the combustion temperature is estimated based on the exhaust temperature detected by the exhaust temperature sensor 6 installed in the vicinity of the exhaust valve 8 in step S205. The estimation is based on the relationship between the exhaust temperature and the combustion temperature shown in FIG. That is, FIG. 7 is an explanatory view showing the relationship between the exhaust temperature and the combustion temperature in the control apparatus for an internal combustion engine according to the second embodiment of the present invention. In FIG. 7, the vertical axis represents the combustion temperature, and the horizontal axis represents the exhaust temperature.

  Next, the process proceeds to step S206, and in the same manner as in the first embodiment, whether or not the number of corrections of the fuel injection amount and the intake air flow rate exceeds 20, for example, to determine whether the combustion mode should be switched to the homogeneous combustion. Judging. If it is determined in step S206 that the number of corrections is 20 or less (N), the process proceeds to step S207, where the combustion mode is left as stratified combustion, and then in step S208 and step S209, the air-fuel mixture In order to increase the concentration, a correction amount corresponding to the combustion temperature estimated with reference to FIG. 8 is derived, and corrected by multiplying the intake air flow rate and the fuel injection amount by the respective correction amounts.

  FIG. 8 is a diagram showing a correction amount based on the combustion temperature in the control apparatus for an internal combustion engine according to the second embodiment of the present invention. The vertical axis shows the correction amount, and the horizontal axis shows the combustion temperature. As shown in FIG. 8, the correction amount of the intake flow rate and the fuel injection amount is set to be small when the combustion temperature is high, and is set to be large when the combustion temperature is low. The correction amount may be determined by estimating the combustion temperature from a cylinder pressure waveform other than the exhaust temperature.

  On the other hand, if it is determined in step S206 that the number of corrections is 20 or more (Y), the fuel injection amount is switched from step S210 to step S212 to homogeneous combustion in the same manner as in the first embodiment. And the intake air flow rate is corrected to a value in line with the homogeneous combustion, the process proceeds to step S213, and "1" is added to the number of corrections, and the process is terminated.

  As described above, according to the control apparatus for an internal combustion engine according to the second embodiment of the present invention, combustion is improved by accurately increasing the mixture concentration according to the estimated combustion temperature in the vicinity of the spark plug. Since the adhering carbon is naturally incinerated by the self-cleaning action, it is possible to eliminate smoldering fouling of the spark plug while suppressing deterioration of fuel consumption, and to obtain good combustion without combustion fluctuation and misfire.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine main body 2 Combustion chamber 3 Piston 4 Intake pipe 5 Exhaust pipe 6 Exhaust temperature sensor 7 Throttle valve 8 Exhaust valve 9 Intake valve 10 Fuel injection valve 11 Spark plug 12 ECU
13 I / O interface 14 Central processing unit 15 ROM 16 RAM
17 Drive circuit 18 Ion current detection circuit 121 Spark plug state detection means 122 Combustion mode switching means 123 Combustion temperature estimation means 124 Intake flow rate control means 125 Fuel injection amount control means

Claims (8)

A fuel injection valve for directly injecting fuel into the combustion chamber of the internal combustion engine;
Fuel injection amount control means for controlling the fuel injection amount injected from the fuel injection valve;
An intake flow rate control means for controlling an intake flow rate of air sucked into the combustion chamber;
A spark plug that sparks and ignites an air-fuel mixture formed by the fuel injected from the fuel injection valve and the air sucked into the combustion chamber;
Spark plug state detecting means for detecting the state of the spark plug;
A direct-injection spark-ignition internal combustion engine configured to perform stratified combustion operation by spark ignition of the spark plug in an air-fuel mixture formed in the vicinity of the spark plug,
The control apparatus for an internal combustion engine, wherein when the deterioration of the state of the spark plug is detected by the spark plug state detecting means, the mixture concentration in the combustion chamber is increased while the stratified combustion operation is continued.   2. The fuel injection amount by the fuel injection amount control unit is corrected so as to increase the fuel injection amount when the ignition plug state detection unit detects deterioration of the state of the spark plug. The control apparatus of the internal combustion engine described in 1.   3. The control apparatus for an internal combustion engine according to claim 2, wherein the correction of the fuel injection amount is performed based on a correction amount required for returning the state of the spark plug obtained in advance.   4. The intake flow rate by the intake flow rate control unit is corrected so as to decrease the intake flow rate when the ignition plug state detection unit detects deterioration of the state of the spark plug. The control apparatus for an internal combustion engine according to any one of the above.   5. The control apparatus for an internal combustion engine according to claim 4, wherein the correction of the intake air flow rate is performed based on a correction amount required for returning the state of the spark plug obtained in advance. Combustion temperature estimating means for estimating the combustion temperature of the air-fuel mixture in the internal combustion engine,
When the deterioration of the ignition plug state is detected by the ignition plug state detection unit, the fuel injection amount control unit increases the fuel injection amount based on the combustion temperature estimated by the combustion temperature estimation unit. The control apparatus for an internal combustion engine according to claim 1 or 2, wherein the injection amount is corrected. Combustion temperature estimating means for estimating the combustion temperature of the air-fuel mixture in the internal combustion engine,
When the ignition plug state detecting means detects deterioration of the state of the spark plug, the intake flow rate by the intake flow rate control means is reduced so that the intake flow rate is decreased based on the combustion temperature estimated by the combustion temperature estimating means. The control device for an internal combustion engine according to any one of claims 1, 4, and 6, wherein correction is performed. Combustion mode switching means for switching the combustion mode of the internal combustion engine from one of homogeneous combustion and stratified combustion to the other,
When it is determined that the correction has been performed more than a predetermined number of times when the deterioration of the spark plug state is detected, the combustion mode switching means switches from the stratified combustion to the homogeneous combustion. The control device for an internal combustion engine according to any one of claims 1 to 7.

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