JP5985153B2 - Combustion control device for internal combustion engine - Google Patents

Description

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

Conventionally, in a spark-ignition internal combustion engine, pre-ignition or post-ignition, which is a precursor of the ignition, occurs until the compression stroke in the cylinder ends due to a rise in the temperature of the center electrode of the spark plug. Sometimes. When pre-ignition and post-ignition occur, the combustion efficiency and durability of the internal combustion engine deteriorate. Therefore, several configurations have been proposed for the purpose of detecting and suppressing pre-ignition and post-ignition before the occurrence. As a typical example of this, for example, Japanese Patent Laid-Open No. 2006-46140 (hereinafter “Patent Document 1”) is known.

In Patent Document 1, the internal combustion engine detects a combustion ion current in the combustion chamber by means of a spark plug that ignites an air-fuel mixture in the combustion chamber. Then, based on the detected combustion ion current, it is determined when the maximum value of the combustion pressure is generated, and it is determined whether or not post ignition, which is a pre-ignition phenomenon, has occurred in the combustion chamber. There has been proposed an operation control device for an internal combustion engine that suppresses pre-ignition when the post-ignition occurs, such as by increasing the fuel or retarding the ignition timing.

JP 2006-46140 A

However, the above-described conventional operation control device for an internal combustion engine has the following problems. That is, in the operation control device for an internal combustion engine disclosed in Patent Document 1, the time when the maximum value of the combustion pressure is generated is determined based on the detected combustion ion current, but the discharge period from the spark plug into the cylinder is fixed. On the other hand, since the combustion period in the cylinder advances as the engine speed increases, the maximum value of the combustion pressure advances to the discharge period. Since the ion current cannot be detected during the discharge period, there arises a problem that the maximum value cannot be detected when the maximum value of the combustion pressure enters the combustion period.

The present invention has been made in view of the above problems, and an object thereof is to provide a combustion control device for an internal combustion engine that detects and suppresses pre-ignition and post-ignition, which is a precursor thereof, regardless of the operating state of the internal combustion engine.

In order to solve the above problems, the present invention provides the following combustion control device for an internal combustion engine. An ignition plug that ignites an air-fuel mixture supplied into a cylinder of the internal combustion engine, an ignition coil that supplies a high voltage to the ignition plug, a switching element that supplies an ignition signal to the ignition coil, and the internal combustion engine An ion current detection circuit that detects an ion current generated in the spark plug by combustion of the gas, a combustion determination unit that determines the combustion state of the air-fuel mixture supplied into the cylinder, and information processing based on information of the internal combustion engine In an internal combustion engine combustion control device comprising:
A calculation process for calculating an inclination value (or an inclination value of the ion current waveform and an ion current detection time) of the ion current waveform detected by the ion current detection circuit; and the inclination value (or an inclination value of the ion current waveform and The determination process for determining the occurrence of pre-ignition based on the calculation result of the ion current detection time) functions,
In the determination process, the slope value after the peak value of the ion current waveform is calculated, and the occurrence of pre-ignition is determined based on the calculation result of the slope value after the peak value.

In the above configuration, the combustion determination unit may determine pre-ignition based on the fact that the slope of the ionic current waveform is greater than or equal to a reference value, and the combustion determination unit may be in a normal operating state of the internal combustion engine. A reference inclination may be set. Further, the combustion determination unit may determine preignition based on an end time of the ion current waveform being advanced from a reference time, and the combustion determination unit may determine that the accumulated value of the ion current waveform is a reference value. The pre-ignition may be determined based on the following. Further, the combustion determination unit may set a reference time or a reference value in a normal operation state of the internal combustion engine, and the combustion determination unit may perform at least two or more times in a normal operation state of the internal combustion engine. An average value of the calculation results of the combustion cycle may be set as a reference value, and the combustion determination unit may determine pre-ignition for each cylinder of the internal combustion engine.

Further, when it is determined as pre-ignition by the combustion determination unit, the fuel injection amount in the subsequent combustion cycle may be increased, and when it is determined as pre-ignition by the combustion determination unit, The proportion of exhaust gas recirculated into the cylinder in the combustion cycle may be reduced. Further, when it is determined that the ignition is determined by the combustion determination unit, the ignition signal from the switching element in the subsequent combustion cycle may be retarded, or when the combustion determination unit determines that the ignition is pre-ignition Alternatively, the compression ratio of the internal combustion engine in the subsequent combustion cycle may be reduced. Further, when the pre-ignition is not determined by the combustion determination unit, the subsequent combustion cycle may be returned to the normal state.

As described above, the calculation unit calculates the slope or / and ion current detection time of the waveform of the ion current detected by the ion current detection circuit, and the combustion determination unit has the slope or / and ion current detection time of the ion current waveform. The pre-ignition and post-ignition are determined based on the calculation result of the engine, and when the pre-ignition and post-ignition are determined by the combustion determination unit, the operating state of the internal combustion engine is increased by increasing the fuel injection amount in the subsequent combustion cycle. Therefore, it is possible to realize a combustion control apparatus for an internal combustion engine that reliably detects and suppresses pre-ignition and post-ignition that is a precursor thereof.

1 is a cross-sectional view of a combustion control device for an internal combustion engine according to a first embodiment of the present invention. 1 is a circuit diagram of a combustion control apparatus for an internal combustion engine according to a first embodiment. FIG. 1 is a block diagram of an ECU of an internal combustion engine according to a first embodiment. It is a time chart which shows the ignition signal and ion current waveform of the internal combustion engine which is a 1st Example. It is a time chart which shows calculation of the inclination of the ion current waveform made into the 1st example. It is a time chart which shows calculation of the advance angle difference of the ionic current waveform which is a 1st Example. It is a flowchart showing the control performed with the combustion control apparatus of the internal combustion engine which is a 1st Example.

An example showing an embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a sectional view of a combustion control apparatus for an internal combustion engine according to a first embodiment of the present invention, FIG. 2 is a circuit diagram of the combustion control apparatus for the internal combustion engine, and FIG. 3 is a block diagram of an ECU of the internal combustion engine. FIG. 4 is a time chart showing the ignition signal and ion current waveform of the internal combustion engine, FIG. 5 is a time chart showing calculation of the slope of the ion current waveform, and FIG. 6 is a time chart showing calculation of the lead angle difference of the ion current waveform. FIG. 7 is a flowchart showing the control executed by the combustion control device for the internal combustion engine.

1 to 3, an intake manifold 78 for supplying a fuel / air mixture into a cylinder 70 of an internal combustion engine 90 is provided, and a fuel injection device 60 for injecting fuel into the intake manifold 78 is provided. An exhaust manifold 80 for discharging exhaust gas from the inside 70 is provided. Further, the intake manifold 78 is provided with an intake side valve 76 for adjusting the intake amount into the cylinder 70, and the exhaust manifold 80 is provided with an exhaust side valve 77 for adjusting the exhaust amount from the cylinder 70. Yes. Further, the internal combustion engine 90 includes a piston 72 for compressing the air-fuel mixture in the cylinder 70 and a crank 74 for converting the combustion motion of the cylinder 70 transmitted to the piston into a rotational motion.

The internal combustion engine 90 includes an ignition plug 10 and an ignition coil 12 for igniting the air-fuel mixture in the cylinder 70. The ignition coil 12 has a primary coil 14 having a primary winding and a secondary winding. The secondary coil 16 has an iron core 18, and the switching element 20 supplies an ignition signal to the primary coil. Further, the internal combustion engine 90 is provided with an ECU 40 that performs electrical control on the internal combustion engine 90. The ECU 40 includes an ion current detection circuit 30, a calculation unit 46, a combustion determination unit 42, a storage unit 44, and a CPU 48. Has been.

The ion current detection circuit 30 detects an ion current generated in the spark plug 10 by the combustion of the internal combustion engine 90 via the secondary coil 16, and the combustion determination unit 42 detects the combustion state of the internal combustion engine 90. Has determined pre-ignition and post-ignition. Further, the CPU 48 supplies an ignition signal to the switching element 20 in accordance with the operating state of the internal combustion engine 90, and the ECU 40 controls the amount of fuel injected by the fuel injection device 60.

With the above configuration, when the ignition signal from the CPU 48 is turned on, a current flows through the switching element 20 and a primary current flows through the primary coil 14. When the ignition signal from the CPU 48 is turned off, the primary current of the primary coil 14 is cut off, a secondary current is generated in the secondary coil 16 and discharged to the spark plug 10.

Next, in FIG. 4, the ignition signal waveform is a waveform obtained by switching on / off the ignition signal from the CPU 48 for one ignition of the internal combustion engine 90, as shown in FIG. Further, when the ignition signal waveform is switched from on to off, discharge into the cylinder 70 starts, and the inside of the cylinder 70 shifts to the combustion period. Further, as shown in FIG. 4B, the ion current waveform is generated by the combustion in the cylinder 70. However, since the ion current cannot be detected during the combustion period, the ion current is not detected after the combustion period ends. It becomes a detected waveform.

In FIG. 5, the ion current waveform detected by the ion current detection circuit 30 at the time of normal combustion is a waveform as shown by a solid line, and the ion current detection circuit 30 at the time of abnormal combustion (pre-ignition and post-ignition). The detected ion current waveform is a waveform as shown by a broken line. In addition, the point where the ion current waveform during normal combustion calculates the slope in the decreasing direction from the maximum value is point C, and the point where the ion current waveform during abnormal combustion calculates the slope in the decreasing direction from the maximum value is the point D. The slopes of C and point D are calculated.

In FIG. 6, the ion current waveform detected by the ion current detection circuit 30 at the time of normal combustion becomes a waveform as indicated by a solid line, and the ion current detection circuit 30 at the time of abnormal combustion (pre-ignition and post-ignition). The detected ion current waveform is a waveform as shown by a broken line. Further, the broken line indicating the combustion start time in the cylinder 70 is E line, the broken line indicating the end time of the ion current waveform at normal time is F line, the broken line indicating the end time of the ion current waveform at abnormal time is G line, A time T1 from the E line to the F line and a time T2 from the E line to the G line are calculated.

Next, the operation of the combustion control device for the internal combustion engine will be described with reference to FIG. In FIG. 7, it is determined whether one cycle has elapsed since the start of combustion of the internal combustion engine or the previous combustion stroke (S1), and the ion current detection circuit 30 is generated in the spark plug 10 by the combustion of the internal combustion engine 90. Detecting the ionic current to be detected (S2), determining the slope value of the ionic current waveform at the time of normal combustion and the reference time for the end time of the ionic current waveform as the reference in the rotational speed of the internal combustion engine 90 (S3), The unit 46 calculates the slope of the ion current waveform detected by the ion current detection circuit 30 (S4), and the calculation unit 46 detects the ion current waveform detected by the ion current detection circuit 30 from the combustion start time in the cylinder 70. The calculation unit 46 calculates a calculated value (slope / time) from the calculated slope of the ion current waveform and the time difference of the ion current waveform (S6), The combustion determination unit 42 exceeds the reference value (slope / time) calculated by the calculation unit 46 above the reference value (slope / time) based on the ion current waveform serving as a reference during normal combustion at the rotational speed of the internal combustion engine 90. (S7), and if the calculated value (slope / time) calculated by the calculation unit 46 exceeds the reference value (slope / time), the combustion state is determined to be an abnormal state (pre-ignition and post-ignition). (S8), when the fuel injection amount of the fuel injection device 60 in the subsequent combustion cycle of the internal combustion engine 90 is increased (S9), and the calculated value (slope / time) calculated by the calculation unit 46 is below the reference value Determines that the combustion state is normal combustion, and stores the calculated value (slope / time) calculated by the calculation unit 46 in the storage unit 44 as a reference value (slope / time) in the subsequent combustion cycle (S11). Combustion judgment part 42 determines whether the previous combustion state is determined to be abnormal (pre-ignition and post-ignition) (S12). If the previous combustion state is determined to be abnormal (pre-ignition and post-ignition), then the internal combustion The fuel injection amount of the fuel injection device 60 in the combustion cycle of the engine 90 is returned to the initial state (S13).

As a result of the above control, the calculated value (slope / time) calculated by the calculation unit 46 increases, and the difference from the reference value (slope / time) that serves as a reference during normal combustion of the internal combustion engine 90 increases. The combustion of the internal combustion engine 90 is advanced, and there is a high possibility that pre-ignition and post-ignition have occurred.

As a modification of the first embodiment, the combustion determination unit 42 determines the slope of the ion current waveform detected by the ion current detection circuit 30 or the combustion start time in the cylinder to the end time of the ion current waveform. Only one of the time differences may be calculated to determine the combustion state. Further, when the internal combustion engine 90 has a high rotational speed, the combustion state is determined only by the slope of the ion current waveform, and at other times, both the slope of the ion current waveform and the end time of the ion current waveform are determined. It is good also as a structure which determines a combustion state. Further, the combustion determination unit 42 may be configured to individually determine the combustion state from the calculated slope of the ion current waveform and the end time of the ion current waveform.

In addition to the time difference between the end time of the ion current waveform detected by the combustion determination unit 42 and the combustion start time in the cylinder 70, the calculation unit 46 also calculates the ion current waveform detected by the combustion determination unit 42. Only the end time may be calculated, or a value obtained by accumulating the current value of the ion current waveform may be calculated. Further, the slope value of the reference ion current waveform may be changed according to the characteristics of the internal combustion engine 90 or the like.

Further, the storage unit 44 stores, as a reference value, an average value of the calculated values in the multiple combustion cycles calculated from the calculation unit 46 after the normal combustion cycle of the internal combustion engine 90 is performed a plurality of times. May be.

Further, the configuration requirements of the ECU 40 may be changed to any configuration depending on design circumstances, and the ion current detection circuit 30 may be any circuit configuration as long as it can detect the ion current generated in the spark plug 10. Also good. Further, the internal combustion engine 90 may be a direct injection internal combustion engine that directly injects fuel into the cylinder 70, and the ECU 40 is arranged for each cylinder 70 in the multi-cylinder internal combustion engine 90, The combustion state may be determined by the individual combustion determination unit 42 for each cylinder 70.

In addition, when the combustion determination unit 42 determines pre-ignition and post-ignition, the fuel of the fuel injection device 60 is calculated based on the inclination or end time calculated by the calculation unit 46 and the calculated value (inclination / time). The increase amount of the injection amount may be determined. Further, when it is determined by the combustion determination unit 42 as pre-ignition and post-ignition, it is limited to control for increasing the fuel injection amount of the fuel injection device 60 in the combustion cycle of the internal combustion engine 90 thereafter. Instead, the ratio of the exhaust gas recirculated into the cylinder 70 in the combustion cycle after the determination may be reduced by opening / closing control of the exhaust side valve 77 using variable valve timing or the like.

Further, the ignition timing of the internal combustion engine 90 may be retarded by the ECU 40 or the like in the ignition signal supplied from the switching element 20 to the primary coil 14 in the combustion cycle after the determination. Furthermore, the compression ratio of the internal combustion engine 90 in the combustion cycle after the determination may be lowered by opening / closing control of the exhaust side valve 77 using the variable valve timing or the like.

Further, when the combustion determination unit 42 determines the pre-ignition and the post-ignition and performs the above-described control, and when it is determined again as the pre-ignition and the post-ignition in the next combustion cycle, the above-described control is repeated or the above-mentioned Combinations of controls may be performed.

10: Spark plug
12: Ignition coil
14: Primary coil
16: Secondary coil
18: Iron core
20: Switching element
30: Ion current detection circuit
40: ECU
42: Combustion judgment section
44: Memory unit
46: Calculation unit
48: CPU
50: Battery
60: Fuel injector
70: Cylinder
72: Piston
74: Crank
76: Inlet valve
77: Exhaust side valve
78: Intake manifold
80: Exhaust manifold
90: Internal combustion engine

Claims (13)

An ignition plug that ignites an air-fuel mixture supplied into a cylinder of the internal combustion engine, an ignition coil that supplies a high voltage to the ignition plug, a switching element that supplies an ignition signal to the ignition coil, and combustion of the internal combustion engine An ion current detection circuit for detecting an ion current generated in the spark plug by means of, a combustion determination unit for determining the combustion state of the air-fuel mixture supplied into the cylinder, and information processing based on the information of the internal combustion engine In an internal combustion engine combustion control device comprising an ECU,
The calculation process for calculating the slope value of the ion current waveform detected by the ion current detection circuit and the determination process for determining the occurrence of pre-ignition based on the calculation result of the slope value function. ,
The internal combustion engine characterized in that the determination processing calculates an inclination value after the peak value of the ion current waveform and determines an occurrence of pre-ignition based on a calculation result of the inclination value after the peak value. Combustion control device. An ignition plug that ignites an air-fuel mixture supplied into a cylinder of the internal combustion engine, an ignition coil that supplies a high voltage to the ignition plug, a switching element that supplies an ignition signal to the ignition coil, and combustion of the internal combustion engine An ion current detection circuit for detecting an ion current generated in the spark plug by means of, a combustion determination unit for determining the combustion state of the air-fuel mixture supplied into the cylinder, and information processing based on the information of the internal combustion engine In an internal combustion engine combustion control device comprising an ECU,
A calculation process for calculating an inclination value and an ion current detection time of an ion current waveform detected by the ion current detection circuit, and a determination for determining occurrence of pre-ignition based on a calculation result of the inclination value and the ion current detection time Processing functions,
The determination process calculates an inclination value after the peak value of the ion current waveform, and determines the occurrence of pre-ignition based on a calculation result of the inclination value after the peak value. Combustion control device.   The combustion control device for an internal combustion engine according to claim 1 or 2, wherein the combustion determination unit determines preignition based on an inclination of an ion current waveform being equal to or greater than a reference value.   The combustion control device for an internal combustion engine according to claim 3, wherein the combustion determination unit sets a reference inclination in a normal operation state of the internal combustion engine.   The said combustion determination part determines pre-ignition based on the end time of an ionic current waveform having advanced from the reference time, The any one of Claims 1 thru | or 4 characterized by the above-mentioned. Combustion control device for an internal combustion engine.   6. The internal combustion engine according to claim 1, wherein the combustion determination unit determines preignition based on a cumulative value of an ion current waveform being equal to or less than a reference value. Engine combustion control device.   The combustion control device for an internal combustion engine according to claim 5 or 6, wherein the combustion determination unit sets a reference time or a reference value in a normal operation state of the internal combustion engine.   8. The combustion determination unit according to claim 1, wherein an average value of calculation results of at least two or more combustion cycles in a normal operation state of the internal combustion engine is set as a reference value. A combustion control apparatus for an internal combustion engine according to any one of the preceding claims.   The combustion control device for an internal combustion engine according to any one of claims 1 to 8, wherein the combustion determination unit determines pre-ignition for each cylinder of the internal combustion engine.   10. The combustion of the internal combustion engine according to claim 1, wherein when the pre-ignition is determined by the combustion determination unit, a fuel injection amount in a subsequent combustion cycle is increased. Control device.   The ratio of exhaust gas recirculated into the cylinder in a subsequent combustion cycle is reduced when the combustion determination unit determines that it is preignition. A combustion control device for an internal combustion engine according to claim 1.   The ignition signal from the switching element in a subsequent combustion cycle is retarded when the combustion determination unit determines that it is preignition. Combustion control device for internal combustion engine.   10. The internal combustion engine according to claim 1, wherein when the combustion determination unit determines that the ignition is pre-ignition, the compression ratio of the internal combustion engine in a subsequent combustion cycle is decreased. Engine combustion control device.

Images