JP2006112267A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide technology quickly improving combustion condition while suppressing occurrence of knocking after deterioration of a combustion condition in a control device for an internal combustion engine. <P>SOLUTION: A combustion condition determination means determining a combustion condition in a cylinder and an ignition timing retarding means retarding ignition timing of a cylinder in which combustion condition is determined deteriorated by the combustion condition determination means in a next cycle as compared with that when the combustion condition is not deteriorated are provided on an internal combustion engine provided with a plurality of cylinders. Deterioration of fuel economy or the like can be suppressed by suppressing knocking by retarding ignition timing in the combustion deterioration cylinder and executing normal control in other cylinders. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

  In a multi-cylinder internal combustion engine, the combustion state may deteriorate in any cylinder depending on the engine operating state. For example, in an internal combustion engine capable of lean combustion, since combustion is performed at a lean air-fuel ratio, the combustion state tends to become unstable, and the difference between a cycle with a good combustion state and a bad cycle becomes large. When misfire occurs when the load on the internal combustion engine is high, a gas containing a large amount of unburned fuel remains in the cylinder. Since this residual gas is compressed once in the compression stroke, it tends to ignite, and knocking may occur in the next cycle.

In contrast, in a multi-cylinder internal combustion engine, if it is determined that misfire has occurred in any of the cylinders, the ignition timing is retarded or the excess air ratio is reduced to suppress misfire after the next cycle. A technique is known (for example, refer to Patent Document 1).
JP 2001-98999 A JP 2000-265893 A Special table 97-33082 gazette Japanese Patent Laid-Open No. 11-200935

However, in a multi-cylinder internal combustion engine, if the ignition timing is retarded in all cylinders, there is a risk that the generated torque and fuel consumption will be reduced, or harmful substances may be generated in the cylinder.
The present invention has been made in view of the above-described problems, and provides a technique capable of quickly improving the combustion state while suppressing the occurrence of knocking after the deterioration of the combustion state in the control device for the internal combustion engine. The purpose is to do.

In order to achieve the above object, an internal combustion engine control apparatus according to the present invention employs the following means. That is,
In an internal combustion engine having a plurality of cylinders,
Combustion state determination means for determining the combustion state in the cylinder;
Ignition timing retarding means for retarding the ignition timing in the next cycle of the cylinder determined to be deteriorated by the combustion state determining means than when the combustion state is not deteriorated;
It is provided with.

  The greatest feature of the present invention is that the ignition timing of the cylinder whose combustion state has deteriorated is retarded, and the ignition timing of the cylinder whose combustion state has not deteriorated is set to the normal ignition timing, so that the cylinder where unburned fuel remains This is to suppress the deterioration of fuel consumption while suppressing the occurrence of knocking.

Here, the combustion state determination means determines whether combustion in the cylinder is normally performed or whether the combustion state is deteriorated. The combustion state determination means may determine the combustion state for each cylinder, or may determine the combustion state of a specific cylinder of the multi-cylinder internal combustion engine. The deterioration of the combustion state means that if the mixture does not ignite, or if the flame is not extinguished after the mixture is ignited and the flame is extinguished, the flame is propagated but there is still a lot of mixture remaining. Includes cases that have disappeared. Further, the case where the combustion state is deteriorated may be a case where an air-fuel mixture exceeding the allowable ratio of the air-fuel mixture supplied into the cylinder remains unburned. Furthermore, the case where the combustion state is deteriorated may be the case where a misfire has occurred.

  Further, the ignition timing retarding means retards the ignition timing of the next cycle in the cylinder in which the combustion state is worse than that in the normal control. This normal control is ignition timing control performed when the combustion state has not deteriorated.

  And the combustion state of the cylinder in which the combustion state is deteriorating can be improved by retarding the ignition timing. In addition, since a normal ignition timing can be applied to a cylinder with a good combustion state, a reduction in torque, a reduction in fuel consumption, and generation of harmful substances can be suppressed.

The present invention further comprises load detection means for detecting the load of the internal combustion engine,
The ignition timing retarding device can retard the ignition timing when the load of the internal combustion engine detected by the load detecting means is equal to or higher than a specified load.

This specified load may be a high load region where knocking may occur.
In other words, knocking is likely to occur in the high load region, so that the occurrence of knocking can be suppressed by retarding the ignition timing of the cylinder whose combustion state has deteriorated.

  In the present invention, the specified load may be changed based on a factor of ease of occurrence of knocking. For example, the state of the internal combustion engine (for example, water temperature, oil temperature, compression ratio, valve timing), the octane number of the fuel, the cetane number, the outside air temperature, etc. affect the occurrence of knocking. That is, if these values are different, knocking is easy, or conversely, knocking is difficult. Therefore, the ease of knocking can be determined based on any of these values. Furthermore, the threshold value for retarding the ignition timing is changed by changing the specified load based on the ease of knocking. That is, when knocking is likely to occur, the ignition timing is retarded at a lower load by reducing the prescribed load. Since knocking is likely to occur as the load increases, the occurrence of knocking can be further suppressed if the ignition timing is retarded at a lower load. In the case where knocking is unlikely to occur, the ignition timing is retarded at a higher load condition by increasing the specified load. Therefore, the ignition timing is unnecessarily retarded. Since it is suppressed, deterioration of fuel consumption and drivability can be suppressed.

  In the present invention, when it is determined by the combustion state determination means that the combustion state of the same cylinder is continuously deteriorated, in the next cycle, the ignition timing is retarded while the ignition timing is retarded. The air-fuel ratio can be made richer than the cycle in which the combustion state deteriorates.

  When the combustion state is not improved, the combustion state can be improved by making the air-fuel ratio in the cylinder richer.

  In the control apparatus for an internal combustion engine according to the present invention, in the next cycle of the cylinder whose combustion state has deteriorated, the occurrence of knocking after the deterioration of the combustion state is suppressed by retarding the ignition timing of the cylinder whose combustion state has deteriorated. In addition, a good combustion state can be obtained promptly.

  Hereinafter, specific embodiments of a control device for an internal combustion engine according to the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine 1 to which the control device for an internal combustion engine according to this embodiment is applied and its intake / exhaust system.
The internal combustion engine 1 shown in FIG. 1 is a water-cooled four-cycle lean burn gasoline engine that can be operated by lean combustion.

The internal combustion engine 1 includes four cylinders 2, and each cylinder 2 includes a spark plug 3.
An intake passage 4 is connected to the internal combustion engine 1. The intake passage 4 is branched into four and connected to each cylinder 2. The branched intake passage 4 is provided with a fuel injection valve 5 for injecting gasoline as fuel for each cylinder 2.

On the other hand, an exhaust passage 6 is connected to the internal combustion engine 1. The exhaust passage 6 communicates with the atmosphere downstream.
The internal combustion engine 1 configured as described above is provided with an ECU 10 that is an electronic control unit for controlling the internal combustion engine 1. The ECU 10 is a unit that controls the operation state of the internal combustion engine 1 in accordance with the operation conditions of the internal combustion engine 1 and the request of the driver.

  The ECU 10 outputs an accelerator opening sensor 11 that outputs a signal according to the accelerator opening, a crank position sensor 12 that outputs a signal according to the rotational speed of the internal combustion engine 1, and a signal according to the coolant temperature of the internal combustion engine. The water temperature sensor 13 to be connected is connected via an electric wiring, and an output signal from the sensor or the like is input.

On the other hand, the ignition plug 3 and the fuel injection valve 5 are connected to the ECU 10 via electric wiring, and the ECU 10 controls the ignition plug 3 and the fuel injection valve 5.
In this embodiment, each cylinder 2 is provided with an in-cylinder pressure sensor 14 that outputs a signal corresponding to the pressure in the cylinder 2. The in-cylinder pressure detected by the in-cylinder pressure sensor 14 determines the combustion state in the cylinder 2. For example, the relationship between the rotational speed of the internal combustion engine, the load, and the in-cylinder pressure in a good combustion state is obtained in advance by experiments and mapped, and the actual in-cylinder pressure obtained from the map is lower than the specified pressure It can be assumed that the combustion state is deteriorated. Alternatively, it may be determined that the combustion state has deteriorated when the pressure increase rate after the ignition signal is output from the ECU 10 is equal to or less than a specified value.

  When the cylinder 2 in which the combustion state is deteriorated is detected based on the output signal of the in-cylinder pressure sensor 14, the ECU 10 sets the ignition plug in the next cycle of only the cylinder 2 in which the combustion state is deteriorated. The ignition timing of 3 is retarded.

  That is, in the lean burn engine, if the combustion state deteriorates when operating with the lean burn, unburned fuel remains in the cylinder 2. Therefore, in the next cycle, the fuel is supplied with the lean air-fuel ratio as a target. However, the air-fuel ratio of the air-fuel mixture in the cylinder 2 becomes an air-fuel ratio in the vicinity of the stoichiometry or slightly lean (weak lean) than the stoichiometry. However, since the ignition timing of the spark plug 3 is set on the premise of the target lean air-fuel ratio, in the next cycle after the cycle in which the combustion state has deteriorated, there is a possibility that the advance amount is too large and knocking may occur. is there.

  In that respect, by retarding the ignition timing in the next cycle of the cylinder 2 whose combustion state has deteriorated, the occurrence of knocking in the cylinder 2 whose combustion state has deteriorated can be suppressed. This retard amount is obtained by mapping an optimum value obtained in advance by experiments or the like and stored in the ECU 10.

Next, the flow of ignition timing control according to this embodiment will be described.
FIG. 2 is a flowchart of ignition timing control according to this embodiment. This routine is executed after the ignition timing of each cylinder 2 has passed a specified time.

In step S101, the ECU 10 detects the combustion state. The combustion state is detected based on the output signal of the in-cylinder pressure sensor 14.
In step S102, the ECU 10 determines whether or not the load on the internal combustion engine 1 is higher than the load determination value. The load of the internal combustion engine 1 is detected based on the output signal of the accelerator opening sensor 11. Further, the load determination value may be a high load or a load that may cause knocking. This load determination value is set in advance.

If an affirmative determination is made in step S102, the process proceeds to step S103. On the other hand, if a negative determination is made, this routine is temporarily terminated.
In step S103, the ECU 10 determines whether or not the combustion state has deteriorated in any of the cylinders 2.

If an affirmative determination is made in step S103, the process proceeds to step S104. On the other hand, if a negative determination is made, this routine is temporarily terminated.
In step S104, the ECU 10 retards the ignition timing of the cylinder 2 whose combustion state has deteriorated only for the next cycle. The ECU 10 delays the transmission timing of the ignition signal to the spark plug 3 attached to the cylinder in which the combustion state is worse than usual. Thereby, occurrence of knocking is suppressed.

  As described above, according to the present embodiment, the occurrence of knocking in the cylinder 2 whose combustion state has deteriorated is suppressed by retarding the ignition timing only in the next cycle of only the cylinder 2 whose combustion state has deteriorated. Is done. Further, in the other cylinders 2 in which the combustion state has not deteriorated, the ignition timing is not retarded, so that the fuel consumption is deteriorated, the drivability is deteriorated, and the exhaust gas is exhausted rather than the ignition timing is retarded in all cylinders. An increase in temperature can be suppressed.

  In the present embodiment, the combustion state of each cylinder 2 is determined based on the output signal of the in-cylinder pressure sensor 14, but instead of this, the ionic current in the cylinder 2 is detected or the internal combustion engine 1 is detected. It is also possible to determine the combustion state of each cylinder 2 by detecting the rotational fluctuation of the cylinder 2. For example, when the amount of ion current detected in the cylinder 2 is smaller than a specified value after the ignition signal is transmitted from the ECU 10 to the spark plug 3, it can be determined that the combustion state has deteriorated. . For example, after the ignition signal is transmitted from the ECU 10 to the spark plug 3, the combustion state is deteriorated when the increase rate of the engine speed obtained from the output signal from the crank position sensor 13 is smaller than a specified value. Can be determined.

In this embodiment, the load determination value used in step S102 is changed according to whether or not knocking is likely to occur.
For example, when the octane number of the fuel is high, the load determination value is increased. For example, when the water temperature detected by the water temperature sensor 13 is low, the load determination value is increased. Further, for example, when the intake valve closing timing is delayed more than the bottom dead center and the intake air amount of the internal combustion engine decreases, the load determination value is increased.

  As described above, when knocking is difficult to occur, knocking does not occur even when the load is higher. Therefore, even if the load determination value is increased, the possibility of knocking is low. In other words, knocking may occur on the higher load side, so the lower limit of the load that retards the ignition timing is moved to the higher load side. Thus, when knocking is difficult to occur, the load determination value is increased.

Conversely, the load determination value may be reduced when knocking is likely to occur.
Here, for example, the relationship between the engine speed and the engine load when knocking occurs using high-octane fuel is previously determined by experiment and mapped, and the engine speed when knocking occurs It can be determined whether the gasoline being used has a high octane number from the engine load.

Further, when the water temperature detected by the water temperature sensor 13 is lower than the temperature before warming up (for example, 80 ° C.), the load determination value may be increased because knocking hardly occurs.
Furthermore, in an internal combustion engine equipped with a variable valve timing mechanism, the opening / closing timing of the intake valve can be changed, but if the closing timing of the intake valve is far away from the bottom dead center, the intake valve closes until the intake valve closes. Since the air in the cylinder 2 is returned to the intake passage 4, the amount of air in the cylinder 2 decreases. In this case, even if air is compressed in the compression stroke, the increase in the pressure of the air is small and knocking is less likely to occur. Therefore, the load determination value can be increased.

  As described above, according to this embodiment, the load determination value is changed according to the ease of knocking. Therefore, when there is no risk of knocking, the ignition timing is not retarded and the fuel consumption is reduced. Deterioration, exhaust gas temperature rise, and drivability deterioration can be suppressed.

  In this embodiment, when it is determined that the combustion state continuously deteriorates in the same cylinder 2, the retard amount of the first ignition timing is maintained, and the ignition timing is retarded after the second time. Do not do. Instead, the fuel injection amount from the fuel injection valve 5 is changed so that the air-fuel ratio of the air-fuel mixture in the cylinder 2 whose combustion state has deteriorated is smaller, that is, the air-fuel ratio on the rich side. In addition, when the combustion state of the cylinder whose combustion state has deteriorated is improved, the retarded ignition timing is returned to the ignition timing at the time of normal control.

FIG. 3 is a flowchart of ignition timing control according to this embodiment. This routine is executed at a specified time before fuel injection of each cylinder 2.
In step S201, the ECU 10 determines whether or not ignition timing retardation control is being performed. That is, in step S104, it is determined whether or not the ignition timing is retarded.

If an affirmative determination is made in step S201, the process proceeds to step S202. On the other hand, if a negative determination is made, this routine is temporarily terminated.
In step S202, the ECU 10 determines whether or not the combustion state has been improved. That is, contrary to the step S103, it is determined whether or not the combustion state is good.

If an affirmative determination is made in step S202, the process proceeds to step S203, whereas if a negative determination is made, the process proceeds to step S204.
In step S203, the ECU 10 sets the ignition timing to the ignition timing during normal control.

  In step S204, the ECU 10 increases the fuel injection amount more than usual in order to shift the air-fuel ratio to a richer side. If the combustion state does not improve, the fuel injection amount is increased to shift to the rich side until the specified air-fuel ratio is reached. In this step, the fuel injection amount may be increased so as to achieve a rich air-fuel ratio.

As described above, according to the present embodiment, when the combustion state is improved, the ignition timing can be returned to that at the time of normal control, thereby suppressing the deterioration of fuel consumption. If the deterioration of the combustion state is not improved, the combustion state can be improved by reducing the air-fuel ratio while retarding the ignition timing.

It is a figure which shows schematic structure of the internal combustion engine which applies the control apparatus of the internal combustion engine which concerns on an Example, and its intake / exhaust system. 3 is a flowchart of ignition timing control according to the first embodiment. 7 is a flowchart of ignition timing control according to a third embodiment.

Explanation of symbols

1 Internal combustion engine 2 Cylinder 3 Spark plug 4 Intake passage 5 Fuel injection valve 6 Exhaust passage 10 ECU
11 Accelerator opening sensor 12 Crank position sensor 13 Water temperature sensor 14 In-cylinder pressure sensor

Claims (4)

In an internal combustion engine having a plurality of cylinders,
Combustion state determination means for determining the combustion state in the cylinder;
Ignition timing retarding means for retarding the ignition timing in the next cycle of the cylinder determined to be deteriorated by the combustion state determining means than when the combustion state is not deteriorated;
A control apparatus for an internal combustion engine, comprising: Load detecting means for detecting the load of the internal combustion engine,
2. The control device for an internal combustion engine according to claim 1, wherein the ignition timing retarding device retards the ignition timing when the load of the internal combustion engine detected by the load detecting means is equal to or greater than a specified load. .   3. The control device for an internal combustion engine according to claim 2, wherein the specified load is changed based on a factor of ease of occurrence of knocking.   When it is determined by the combustion state determination means that the combustion state of the same cylinder has been continuously deteriorated, in the next cycle, the air-fuel ratio in the cylinder is set to the combustion state while the ignition timing is retarded. 2. The control device for an internal combustion engine according to claim 1, wherein the control is performed on a richer side than the cycle in which the deterioration occurs.

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