JP2009030545A - Control device of engine for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of an engine for a vehicle, detecting abnormal combustion in a cylinder before ignition while distinguishing between preignition and generation of knocking. <P>SOLUTION: The control device of an engine for a vehicle, comprises: an ionic current detection circuit 8d detecting an ionic current caused by ions in a combustion chamber 6 of the engine 1; and a PCM 30 determining the abnormal combustion in the cylinder in the engine 1 based on the ionic current. The PCM 30 has a first threshold value T<SB>1</SB>and a second threshold value T<SB>2</SB>indicating relation between an increase rate (determination value) of the ionic current before the ignition and the abnormal combustion. The PCM 30 determines the combustion in the cylinder is normal when the increasing rate calculated based on the ionic current before the ignition is less than the first threshold value T<SB>1</SB>, determines the generation of the knocking in the cylinder when the increasing rate is the first threshold value T<SB>1</SB>or more and less than the second threshold value T<SB>2</SB>, and determines the generation of the preignition in the cylinder when the increasing rate is the second threshold value T<SB>2</SB>or more. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control device for a vehicle engine, and more particularly to a control device for a vehicle engine that detects the occurrence of abnormal combustion by an ion current.

2. Description of the Related Art Conventionally, in a spark ignition type internal combustion engine, a technique for detecting a precursor state of pre-ignition generation based on detection of an ionic current flowing through ions existing in a combustion chamber has been proposed (for example, Patent Document 1). reference).
In the internal combustion engine described in Patent Document 1, it is determined that the pre-ignition is likely to occur when the peak generation time of the ionic current is detected and the peak generation time is advanced from a predetermined limit time. The suppression control is performed.

JP 2006-46140 A

  However, in the internal combustion engine described in Patent Document 1, it has been impossible to distinguish between occurrence of pre-ignition and occurrence of knocking in the cylinder before ignition. Therefore, it was impossible to distinguish between pre-ignition and knocking and to control each occurrence early.

  The present invention has been made to solve such problems, and provides a vehicle engine control device that can detect abnormal combustion in a cylinder before ignition by distinguishing between occurrence of pre-ignition and knocking. The purpose is to do.

In order to achieve the above object, the present invention provides an ionic current detecting means for detecting an ionic current caused by ions in a combustion chamber of a vehicle engine, and a vehicle based on an ionic current detected by the ionic current detecting means. An abnormal combustion determination means for determining abnormal combustion in the cylinder of the engine, the abnormal combustion determination means based on the occurrence of knocking and pre-ignition and an ionic current before ignition A first threshold value and a second threshold value representing a relationship with the calculated determination value, and the determination value calculated based on the ion current before ignition is less than the first threshold value. It is determined that normal combustion is occurring in the engine, and it is determined that knocking has occurred in the cylinder of the vehicle engine when it is equal to or greater than the first threshold and less than the second threshold. I am characterized in determining that preignition is occurring in the cylinder of a vehicle engine.
According to the present invention configured as described above, the occurrence of knocking and the occurrence of pre-ignition are identified and detected based on the magnitude of the determination value calculated based on the ion current that can be detected before ignition. Can do.

Preferably, the present invention further includes a pre-ignition suppression unit that suppresses pre-ignition, and the pre-ignition suppression unit is configured to detect the in-cylinder temperature or the in-cylinder in the engine cycle in which the abnormal combustion determination unit determines occurrence of the pre-ignition. Pre-ignition is suppressed by reducing the compression ratio.
According to the present invention configured as described above, when a pre-ignition is detected, the expansion of the pre-ignition in the same engine cycle is suppressed by the decrease of the in-cylinder temperature or the in-cylinder compression ratio by the pre-ignition suppression unit. Can do.

Preferably, in the present invention, the pre-ignition suppression means injects additional fuel by an in-cylinder fuel valve capable of directly injecting fuel into the cylinder when the abnormal combustion determination means determines the occurrence of pre-ignition.
According to the present invention configured as described above, even if the occurrence of pre-ignition is detected in the compressed state, the in-cylinder temperature can be lowered by the additional fuel injection from the in-cylinder fuel injection valve, thereby It is possible to suppress the expansion of pre-ignition.

In the present invention, preferably, the pre-ignition suppression means opens at least one of the intake and exhaust valves by electromagnetic VVT when the abnormal combustion determination means determines the occurrence of pre-ignition.
According to the present invention thus configured, even if pre-ignition is detected in a compressed state, the in-cylinder compression ratio is reduced by forcibly opening at least one of the intake and exhaust valves by the electromagnetic VVT. As a result, it is possible to suppress the expansion of the pre-ignition.

Preferably, the present invention further includes knocking suppression means for suppressing knocking, and the knocking suppression means delays the ignition timing in the engine cycle in which the abnormal combustion determination means determines the occurrence of knocking.
According to the present invention configured as described above, when knocking is detected, expansion of knocking can be suppressed by retarding the ignition timing by the knocking suppression means.

  According to the control apparatus for a vehicle engine of the present invention, the abnormal combustion in the cylinder can be detected by distinguishing the occurrence of pre-ignition and knocking from the ion current detected before ignition.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. First, a control device for a vehicle engine according to a first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a diagram showing a configuration of a vehicle engine, FIG. 2 is a diagram showing an ignition circuit, FIGS. 3 and 4 are graphs showing changes in engine cylinder pressure and ion current, and FIG. 5 is an explanatory diagram of abnormal combustion detection processing. 6 is a diagram showing a threshold value of abnormal combustion, FIG. 7 is a flowchart of abnormal combustion detection processing, and FIG. 8 is an explanatory diagram of fuel injection timing.

First, a schematic configuration of the engine 1 of the present embodiment will be described with reference to FIGS. 1 and 2.
The engine 1 is an in-line multi-cylinder spark ignition direct gasoline engine. The engine 1 has an engine body including a cylinder block 2 and a cylinder head 3 fixed to the cylinder block 2. The upper end of the cylinder 4 that opens to the upper end surface of the cylinder block 2 is closed by the lower surface of the cylinder head 3.
A piston 5 is fitted into the cylinder 4 so as to be able to reciprocate. A combustion chamber 6 is defined between the upper surface of the piston 5 and a pent roof-type lower surface (ceiling surface) of the cylinder head 3. On the other hand, a crankshaft (not shown) is disposed in the crankcase below the piston 5, and is connected to the piston 5 by a connecting rod.

  A crank angle sensor 26 is provided in the crankcase below the cylinder block 2 of the engine 1. The crank angle sensor 26 detects the rotation angle (crank angle) of the crankshaft, and is provided on the outer peripheral portion of the rotor 27 attached so as to rotate integrally with the end portion of the crankshaft. It consists of an electromagnetic pickup coil that outputs a signal corresponding to the passage of the convex portion.

  Further, a water temperature sensor 28 for detecting the temperature state of the cooling water is provided on a water jacket (not shown) of the cylinder block 2. Further, an engine oil temperature sensor 29 is attached.

A plurality of spark plugs 7 are provided corresponding to each cylinder 4, and are attached to the cylinder head 3 so that the tip electrode of the spark plug 7 faces each combustion chamber 6. In addition, each spark plug 7 is connected to an ignition circuit 8.
In the present embodiment, a plurality of ignition circuits 8 are provided corresponding to the respective spark plugs 7. However, the present invention is not limited to this, and one or a plurality of ignition circuits 8 may be provided corresponding to the plurality of spark plugs 7.

As shown in FIG. 2, the ignition circuit 8 includes an igniter 8a composed of a power transistor, an ignition coil 8b composed of a primary winding and a secondary winding, a capacitor 8c connected to the ignition coil 8b, and a capacitor 8c. And an ion current detection circuit 8d connected between the ground potential. The ion current detection circuit 8d corresponds to the ion current detection means of the present invention.
The ignition circuit 8 corresponding to each cylinder 4 turns on the igniter 8a while energizing the ignition coil 8b while receiving a control signal for igniting and discharging the spark plug 7 from the PCM 30. When the ignition circuit 8 no longer receives a control signal after a predetermined energization time, the igniter 8a is turned off, whereby an ignition discharge current flows from the secondary winding of the ignition coil 8b, and the ignition plug 7 is ignited. .

  In the ignition circuit 8, the capacitor 8c is charged by this ignition discharge. The ionic current detection circuit 8d detects the current that flows when the charge of the capacitor 8c is discharged as an ionic current. The ignition circuit 8 outputs an ion current detection signal to the PCM 30.

  Further, the cylinder head 3 is formed with two intake ports 9 and two exhaust ports 10 communicating with each combustion chamber 6. In addition, opening and closing operations are independently performed at predetermined timings at port openings of the intake port 9 and the exhaust port 10 by electromagnetic variable valve timing mechanisms 13a and 13b (hereinafter referred to as “electromagnetic VVT (Variable Valve Timing)”). Intake and exhaust valves (intake valve 11 and exhaust valve 12) are provided.

  Therefore, the intake valve 11 and the exhaust valve 12 are not mechanically linked to the crankshaft, and are opened and closed by changing the operating state of the intake-side electromagnetic VVT 13a and the exhaust-side electromagnetic VVT 13b regardless of the rotational position of the crankshaft. The That is, when the electromagnetic VVTs 13a and 13b are demagnetized, the intake valve 11 and the exhaust valve 12 are closed by return springs (not shown). When the electromagnetic VVTs 13a and 13b are excited, the intake valve 11 and the exhaust valve 12 are closed. Are opened against the return springs.

  The intake valve 11 and the exhaust valve 12 can be opened and closed by the electromagnetic VVTs 13a and 13b so that the opening / closing operation timing can be changed to the advance side and the retard side, thereby changing the overlap period and remaining in the combustion chamber 6. The amount of the combustion gas (hereinafter referred to as “internal EGR”) can be changed.

  An intake passage (intake manifold) 15 communicating with the intake port 9 is disposed on the intake side of the cylinder head 3. The intake passage 15 has a branch passage that branches toward each cylinder 4 and a forked passage that branches from the branch passage toward two intake ports 9 of each cylinder 4. One of the bifurcated passages is provided with a tumble swirl control valve (hereinafter referred to as “TSCV”) 14 for adjusting the strength of the intake air flow in the combustion chamber 6.

The intake passage 15 has an air cleaner 16 from the upstream side, an air flow sensor 17 for detecting the intake flow rate, and a throttle that throttles the intake passage 15 by an electric motor 18a between the upstream end of the intake passage 15 and the TSCV valve 14. A valve 18 is provided. In addition, an intake air temperature sensor 23 is provided in the vicinity of the air cleaner 16 in the intake passage 15.
Further, the cylinder head 3 is provided with a plurality of injectors (in-cylinder fuel valves) 19 corresponding to the respective cylinders 4 for directly injecting fuel into the respective combustion chambers 6.

An exhaust passage (exhaust manifold) 20 for discharging burned gas (exhaust gas) from each combustion chamber 6 is disposed on the exhaust side of the cylinder head 3 so as to communicate with the exhaust port 10. Like the intake passage 15, the exhaust passage 20 has a branch passage and a bifurcated passage, and each bifurcated passage is connected to the exhaust port 10.
The exhaust passage 20 is provided with an oxygen concentration sensor (hereinafter referred to as “O ₂ sensor”) 21 for detecting the air-fuel ratio of the air-fuel mixture based on the oxygen concentration in the exhaust gas from the upstream side, and for purifying the exhaust gas. The catalytic converter 22 is disposed.

Further, one end of an exhaust gas recirculation passage 24 (hereinafter referred to as “EGR passage”) is branchedly connected to the exhaust passage 20 upstream of the O ₂ sensor 21. The other end of the EGR passage 24 communicates with the intake passage 15 on the downstream side of the throttle valve 18. The EGR passage 24 is provided with an electric flow control valve 25 (hereinafter referred to as “EGR valve”) whose opening degree can be adjusted, and exhaust gas (hereinafter referred to as “external”) that is recirculated through the EGR passage 24 by the EGR valve 25. EGR ")) can be adjusted.

As is well known, a PCM (Power-train Control Module) 30 includes a CPU, a ROM, a RAM, an I / O interface circuit, and the like. The PCM 30 includes an air flow sensor 17, an O ₂ sensor 21, a crank angle sensor 26, a water temperature sensor 28, an engine oil temperature sensor 29, an intake air temperature sensor 23, an accelerator opening sensor 32 that detects an operation amount of an accelerator pedal, and an engine speed. Output signals from the engine speed sensor 33 and the ignition circuit 8 are detected.

  The PCM 30 determines the operating state of the engine 1 based on the output signals from the sensors and the like, and controls the operation of the engine 1 according to this. That is, the PCM 30 outputs a signal for controlling the operation timing of the intake valve 11 and the exhaust valve 12 to the electromagnetic VVTs 13a and 13b in order to change the amount of internal EGR, and controls the intake flow rate to the throttle valve 18. A signal for controlling the strength of the intake air flow in the combustion chamber 6 to the TSCV 14 of each cylinder 4, and the fuel injection amount and the injection timing to the injector 19 of each cylinder 4 are controlled. A signal for controlling the amount of exhaust gas (external EGR) circulating to the intake system through the EGR passage 24 to the EGR valve 25, and igniting the ignition circuit 8 at a predetermined timing. A control signal for igniting and discharging the plug 7 is output.

  Further, the PCM 30 determines the occurrence and magnitude of pre-ignition and knocking in the engine 1 based on the ion current detection signal from the ignition circuit 8, as will be described later. Then, when the occurrence of pre-ignition and knocking is detected, the PCM 30 performs pre-ignition suppression control and knocking suppression control based on the detected pre-ignition and knock magnitude. The PCM 30 corresponds to the abnormal combustion determination means of the present invention.

Specifically, after determining the occurrence of pre-ignition, the pre-ignition suppression control is, for example, control for additionally injecting fuel into the cylinder by the injector 19 to lower the in-cylinder temperature, or the intake valve 11 by the electromagnetic VVTs 13a and 13b. In addition, the internal EGR amount is decreased by opening operation of at least one of the exhaust valves 12 and the in-cylinder compression ratio is decreased. The PCM 30, the injector 19, and the VVTs 13a and 13b correspond to pre-ignition suppression means of the present invention.
The knocking suppression control is specifically control for retarding the ignition timing by the ignition circuit 8 after determining the occurrence of knocking. The PCM 30 and the ignition circuit 8 correspond to the knocking suppression means of the present invention.

Next, the outline of detection of abnormal combustion (pre-ignition and knocking) according to this embodiment will be described with reference to FIGS.
First, an outline of pre-ignition detection according to the present embodiment will be described with reference to FIG. FIG. 3 shows the outline of the change in the combustion chamber pressure with respect to the crank angle in the compression stroke and the expansion stroke (FIG. 3A) and the outline of the change in the ion current with respect to the crank angle (FIG. 3B).
In FIG. 3 and similar graphs thereafter, the alternate long and short dash line represents the change during normal combustion, and the solid line represents the change during abnormal combustion.

  As indicated by the alternate long and short dash line in FIG. 3A, during normal combustion, the pressure in the cylinder 4 gradually increases in the compression stroke with the advance of the crank angle, and reaches a peak (maximum value) near the top dead center (TDC). ) The engine 1 of this embodiment is a high compression ratio type engine, and the set period is set so that the spark plug 7 is ignited and discharged after top dead center. This set period is determined in advance by the operating state of the engine 1. Due to this ignition discharge, the air-fuel mixture in the combustion chamber 6 is combusted and expanded, and the in-cylinder pressure increases, peaks again, and then the in-cylinder pressure gradually decreases.

Further, as indicated by the alternate long and short dash line in FIG. 3B, during normal combustion, the ionic current increases with a predetermined slope until ignition discharge is started, and reaches a peak after ignition discharge.
In the configuration of the present embodiment, the ionic current is detected using the spark plug 7, and during the ignition discharge, the ignition discharge current is placed on the ionic current, so that only the ionic current cannot be detected. However, only the ion current is illustrated in the graphs including the subsequent changes in ion current including FIG. 3 for easy understanding.

On the other hand, as shown by the solid line in FIG. 3 (A), when pre-ignition occurs, the in-cylinder pressure increases at a larger rate of change than before normal combustion from the top dead center due to the pre-flame reaction. Then, after the top dead center, the in-cylinder pressure rapidly increases before the start of ignition discharge, reaches a large peak earlier than during normal combustion, and then gradually decreases.
Further, as shown by the solid line in FIG. 3B, when pre-ignition occurs, the ion current increases at a larger rate of change from before the top dead center (before starting ignition discharge) than during normal combustion due to the pre-flame reaction. Then, the ion current becomes a large peak earlier than the normal combustion after the top dead center, and then gradually decreases.

  As described above, when the pre-ignition occurs, a difference occurs in the change of the ion current as compared with the normal combustion. That is, the rate of increase in ion current before the start of ignition discharge is greater when pre-ignition occurs than when normal combustion is performed. In the present embodiment, the occurrence of pre-ignition is determined based on the magnitude of the increase rate of the ion current before the start of ignition discharge.

  Next, an outline of knocking detection according to the present embodiment will be described with reference to FIG. FIG. 4 shows the outline of the change in the combustion chamber pressure with respect to the crank angle in the compression stroke and the expansion stroke (FIG. 4A) and the outline of the change in the ion current with respect to the crank angle (FIG. 4B). The change at the time of normal combustion shown with the dashed-dotted line of FIG. 4 is the same as that of FIG.

As shown by the solid line in FIG. 4A, when knocking occurs, the in-cylinder pressure rises at a larger increase rate than before normal combustion due to the pre-flame reaction. Then, after top dead center, the in-cylinder pressure changes so that pressure fluctuations due to knocking are superimposed on the same changes as during normal combustion.
Further, as shown by the solid line in FIG. 4B, when knocking occurs, the ionic current rises at a larger increase rate than before normal combustion from before top dead center (before starting ignition discharge) due to the pre-flame reaction. Then, like the in-cylinder pressure change, it changes so that the vibration of the ion current due to knocking is superimposed on the same change as in normal combustion.

  Here, comparing the changes in ion current when preignition occurs and when knocking occurs, the rate of increase in ion current around the top dead center (before ignition discharge) is greater when preignition occurs than when knocking occurs. You can see that it ’s big. In the present embodiment, the occurrence of pre-ignition and the occurrence of knocking are identified from the rate of increase of the ion current in a predetermined period before and after top dead center (before ignition discharge), thereby preventing subsequent pre-ignition or knocking expansion. It is configured to be prevented separately.

As shown in FIG. 5, in this embodiment, the PCM 30 calculates an increase rate (= dI / dθ), which is a determination value, from the increase amount dI of the ionic current with respect to the width dθ of the predetermined crank angle before ignition discharge.
Further, the PCM 30 stores data representing the relationship between normal combustion, knocking and pre-ignition, and an increase rate of ion current as shown in FIG. This data is set in advance by experiments or the like. As shown in FIG. 6, the increase rate is set to normal combustion when the first thresholds T ₁ less than the range, set to knocking occurs when the second threshold value T ₂ less than the range rate of increase in the first threshold value above T ₁ is, the increase rate is set to preignition occurs when the second threshold value T ₂ or more ranges. Therefore, the PCM 30 can determine whether the subsequent combustion state is normal combustion, knocking, or pre-ignition by determining in which range the increase rate of the ion current is.

The first threshold value T ₁ and the second threshold value T ₂ for determining the combustion state are determined based on experiments and the like, the intake air amount, intake temperature, engine speed, EGR introduction amount, air-fuel ratio, intake / exhaust valve timing, engine It is defined as a function of any one of parameters such as water temperature or a combination of these. Qualitatively, the larger the intake air amount, the higher the intake air temperature, the lower the engine speed, the greater the EGR introduction amount, the leaner the air-fuel ratio, the greater the compression ratio due to the intake and exhaust valve timing, and the higher the engine water temperature. Abnormal combustion is likely to occur. Therefore, as will be described later, the PCM 30 reads values related to these parameters from the sensor for each engine cycle, and determines the first threshold T ₁ and the second threshold T ₂ based on these parameter values.

Next, the abnormal combustion suppression processing flow of this embodiment will be described with reference to FIG.
FIG. 7 is a main flow of the abnormal combustion suppression process of the PCM 30, and is executed for each engine cycle.
First, the PCM 30 reads the various parameters described above (engine speed, intake air amount, etc.) (step S1). The PCM 30 first sets the fuel injection amount, the injection timing, and the like based on these parameters (step S2). In the present embodiment, as shown in FIG. 8, in order to improve the fuel mixing, the fuel injection timing is set to be divided into a period F1 during the intake stroke and a period F2 during the compression stroke. .

Next, the PCM 30 sets the ignition discharge timing based on the read parameters and data indicating the correspondence between the engine speed and the engine load (step S3).
Next, the PCM 30 detects and stores the ion current in a predetermined crank angle range before the ignition discharge (step S4), and calculates the ion current change rate (= dI / dθ) based on this (step S5). Then, the PCM 30 determines the first threshold T ₁ and the second threshold T ₂ based on the read parameters, and determines whether or not the change rate of the ionic current is equal to or higher than the first threshold T ₁ (Step S6). ).

If the rate of change of the ion current is not the first threshold value above T ₁ (step S6; No), the process ends because it is normal combustion state.
On the other hand, when the change of the ion current is first thresholds T ₁ or more (step S6; Yes), further the rate of change is equal to or second threshold value T ₂ or more (step S7).

When the change rate of the ionic current is equal to or greater than the second threshold T ₂ (step S7; Yes), the PCM 30 determines that pre-ignition is occurring in the cylinder (step S8). Based on this determination of pre-ignition, the PCM 30 performs a pre-ignition suppression control process (step S9), and ends the process. In the pre-ignition suppression control process, the additional fuel injection timing and the injection amount are set so that the suppression amount increases as the change rate of the ionic current increases. As shown in FIG. 8, the additional fuel injection is performed at a timing F3 before the ignition discharge, thereby reducing the in-cylinder temperature and suppressing the expansion of the pre-ignition.
Note that, as the pre-ignition suppression control process, the PCM 30 may change the operating state of the electromagnetic VVTs 13a and 13b before ignition discharge to lower the in-cylinder compression ratio.

On the other hand, when the rate of change of the ionic current is not equal to or greater than the second threshold T ₂ (step S7; No), the rate of change of the ionic current is equal to or greater than the first threshold T ₁ and less than the second threshold T ₂ . In step S10, it is determined that knocking is occurring. Based on this determination of knocking, the PCM 30 performs a knocking suppression control process (step S11) and ends the process. In this knocking suppression control process, a process of retarding (retarding) the ignition discharge timing with respect to the ignition discharge timing set in step S3 is performed so that the suppression amount increases as the rate of change of the ionic current increases. Thereby, expansion of knocking can be suppressed.

  Thus, in the present embodiment, abnormal combustion detection can be performed by distinguishing the occurrence of pre-ignition and knocking based on the rate of increase of ion current before ignition discharge. When occurrence of pre-ignition is detected, pre-ignition suppression control processing is performed in the same engine cycle, and further expansion of pre-ignition can be suppressed. When occurrence of knocking is detected, knocking suppression control processing is performed in the same engine cycle, and further expansion of knocking can be suppressed.

  Note that the settings of the electromagnetic VVTs 13a and 13b, the throttle valve 18, the EGR valve 25, the ignition timing, and the like may be changed in order to suppress the occurrence of pre-ignition and knocking after the engine cycle in which abnormal combustion is detected. In addition to these, the engine 1 may be configured to reduce the variable compression ratio.

Next, based on FIG.9 and FIG.10, 2nd Embodiment of this invention is described.
In the first embodiment, abnormal combustion is determined based on the rate of increase of the ionic current before ignition discharge, but in the second embodiment, abnormal combustion is determined based on the peak time of the ionic current instead of the rate of increase of the ionic current.
As shown in FIG. 9, in this embodiment, the PCM 30 detects the peak (maximum value) of the ionic current before ignition discharge from the change in the ionic current. The change in ion current during normal combustion shown by the chain line, the peak at a crank angle P ₁ is observed. On the other hand, in the change of the ionic current at the time of abnormal combustion shown by the solid line, a peak is observed at the crank angle P ₂ that is advanced from the crank angle P ₁ .

In the present embodiment, the PCM 30 stores data in which the peak occurrence time (crank angle P ₁ ) of the ion current is defined as a function of the above parameters based on experiments or the like. Peak occurrence time of the ion current detected with respect to the crank angle P ₁ advance angle if (determination value) (crank angle P ₂₎ is set to the normal combustion when the first threshold value Q ₁ less than the range, the first threshold value Q ₁ As described above, when the range is less than the second threshold Q _2, knocking is set, and when the range is greater than or equal to the second threshold Q _2, pre-ignition is set. Therefore, the PCM 30 can determine whether the subsequent combustion state is normal combustion, knocking, or pre-ignition by determining in which range the peak generation time of the ion current is.

The first threshold value Q ₁ and the second threshold value Q ₂ for determining the combustion state are the intake air amount, intake air temperature, engine speed, EGR introduction amount, air-fuel ratio, intake / exhaust valve timing, as in the first embodiment. , Any one of parameters such as engine water temperature, or a function of a combination of these. Accordingly, the PCM 30 reads values related to these parameters from the sensor every engine cycle, and determines the first threshold value Q ₁ and the second threshold value Q ₂ based on these parameter values.

Next, the abnormal combustion suppression processing flow of the second embodiment will be described with reference to FIG.
Steps S21 to S24 are the same as steps S1 to S4 of the first embodiment, and thus description thereof is omitted.
Next, the PCM 30 calculates a peak value from the value of the ion current detected in step S24 (step S25), and further calculates a crank angle at which the peak value is generated (step S26).
Then, the PCM 30 determines the degree of advancement of the peak generation time (determination value) calculated from the peak generation time during normal combustion expected in the engine operating state at that time and the peak generation time of the ion current detected in this engine cycle. ) is equal to or a first threshold value Q ₁ or more (step S27).

If the advance angle if the peak occurrence of the ion current is not the first threshold value Q ₁ or more (step S27; No), the process ends because it is normal combustion state.
On the other hand, when the advance angle of the ion current peak generation is greater than or equal to the first threshold Q ₁ (step S27; Yes), it is further determined whether or not the advance angle is greater than or equal to the second threshold Q ₂ (step S27). S28).

If the advance angle if the peak occurrence of the ion current is the second threshold value Q ₂ or more (step S28; Yes), PCM 30 determines that preignition is being generated in the cylinder (step S29). Based on the determination of the preignition, the PCM 30 performs the preignition suppression control process similar to that of the first embodiment (step S30), and ends the process.
On the other hand, if the advance angle if the peak occurrence of the ion current is not the second threshold value Q ₂ or more (step S28; No), the peak occurrence of the ion current advance angle if the second below the threshold Q ₂ first threshold value Q ₁ or more Yes, the PCM 30 determines that knocking is occurring in the cylinder (step S31). Based on this knocking determination, the PCM 30 performs the same knocking suppression control process as in the first embodiment (step S32), and ends the process.

  As described above, in the present embodiment, abnormal combustion detection can be performed by distinguishing the occurrence of pre-ignition and knocking based on the advance angle of the peak generation of the ion current before ignition discharge. When occurrence of pre-ignition is detected, pre-ignition suppression control processing is performed in the same engine cycle, and further expansion of pre-ignition can be suppressed. When occurrence of knocking is detected, knocking suppression control processing is performed in the same engine cycle, and further expansion of knocking can be suppressed.

In the above embodiment, the abnormal combustion is detected by either the rate of increase of the ion current before ignition or the advance angle of the peak generation timing. However, the present invention is not limited to this. You may comprise so that combustion may be detected.
Moreover, in the said embodiment, although it was the type of engine 1 in which the ignition timing was set after the top dead center, it is not restricted to this, The engine of the type in which the ignition timing was set before the top dead center may be used. .

It is a figure showing the structure of the vehicle engine by 1st Embodiment of this invention. It is a block diagram of the ignition circuit by 1st Embodiment of this invention. 4 is a graph showing changes in engine cylinder pressure and ion current according to the first embodiment of the present invention. 4 is a graph showing changes in engine cylinder pressure and ion current according to the first embodiment of the present invention. It is explanatory drawing of the abnormal combustion detection process by 1st Embodiment of this invention. It is a figure showing the threshold value of abnormal combustion by 1st Embodiment of this invention. It is a flowchart of the abnormal combustion detection process by 1st Embodiment of this invention. It is explanatory drawing of the fuel-injection time by 1st Embodiment of this invention. It is explanatory drawing of the abnormal combustion detection process by 2nd Embodiment of this invention. It is a flowchart of the abnormal combustion detection process by 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Cylinder block 3 Cylinder head 4 Cylinder 5 Piston 6 Combustion chamber 7 Spark plug 8 Ignition circuit 8d Ion current detection circuit 9 Intake port 10 Exhaust port 11 Intake valve 12 Exhaust valve 13a, 13b Variable valve timing mechanism (electromagnetic VVT)
15 Intake passage 17 Air flow sensor 18 Throttle valve 19 Injector 20 Exhaust passage 23 Intake temperature sensor 24 Exhaust recirculation passage (EGR passage)
25 Flow control valve (EGR valve)
26 Crank angle sensor 30 PCM

Claims (5)

Ion current detection means for detecting an ion current caused by ions in a combustion chamber of a vehicle engine;
An abnormal combustion determination means for determining abnormal combustion in a cylinder of the vehicle engine based on the ion current detected by the ion current detection means,
The abnormal combustion determination means has a first threshold value and a second threshold value representing a relationship between occurrence of knocking and pre-ignition and a determination value calculated based on an ion current before ignition, and the ion current before ignition When the determination value calculated based on is less than the first threshold value, it is determined that normal combustion is occurring in the cylinder of the vehicle engine. When the determination value is greater than the first threshold value and less than the second threshold value, the vehicle It is determined that knocking has occurred in the cylinder of the engine, and it is determined that pre-ignition has occurred in the cylinder of the vehicle engine when the value is equal to or greater than the second threshold value. apparatus. Furthermore, a pre-ignition suppression means for suppressing pre-ignition is provided,
The pre-ignition suppression means suppresses the pre-ignition due to a decrease in in-cylinder temperature or in-cylinder compression ratio in an engine cycle in which the abnormal combustion determination means determines the occurrence of pre-ignition. Vehicle engine control device.   The pre-ignition suppression means injects additional fuel by an in-cylinder fuel valve capable of directly injecting fuel into the cylinder when the abnormal combustion determination means determines the occurrence of pre-ignition. The vehicle engine control device according to claim 2.   3. The vehicle engine according to claim 2, wherein the pre-ignition suppression unit opens at least one of the intake and exhaust valves by an electromagnetic VVT when the abnormal combustion determination unit determines the occurrence of pre-ignition. Control device. Furthermore, a knocking suppression means for suppressing knocking is provided,
2. The vehicle engine control device according to claim 1, wherein the knocking suppression unit controls the ignition timing to be retarded in an engine cycle in which the abnormal combustion determination unit determines the occurrence of knocking. 3.

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