JP2010169067A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make both improvements in drivability and fuel consumption by suppressing torque step, at high levels, in a control device for an internal combustion engine, capable of adjusting the ignition timing of the internal combustion engine for each cylinder. <P>SOLUTION: There is provided a controller of an internal combustion engine with a plurality of cylinders. The controller includes an in-cylinder pressure sensor for detecting in-cylinder pressure of each cylinder of the internal combustion engine, a first ignition timing control means for setting the ignition timing of each cylinder of the internal combustion engine at the optimal ignition timing, a second ignition timing control means for setting independently the ignition timing of each cylinder of the internal combustion engine so that generated torque of each cylinder are approximately become equel based on a detection signal of the in-cylinder sensor, and a switching control means for giving instructions to a switching operation from the first ignition timing control means to the second ignition timing control means when a torque-down request when issued to the internal combustion engine. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an internal combustion engine control device, and more particularly to an internal combustion engine control device capable of adjusting the ignition timing of the internal combustion engine for each cylinder.

  Conventionally, for example, Japanese Patent Laid-Open No. 9-209814 discloses a device that detects the in-cylinder pressure for each cylinder and advances or retards the ignition timing so that the generated torque of each cylinder becomes the average torque of all the cylinders. ing. According to this apparatus, the torque generated in each cylinder can be controlled in the vicinity of the average value of all the cylinders, so that a torque step generated between the cylinders can be easily absorbed.

Japanese Patent Laid-Open No. 9-209814 JP 2007-291977 A JP 2006-138280 A

  According to the above-described conventional apparatus, the torque step between the cylinders can be suppressed, so that drivability can be improved. However, if the ignition timing is advanced or retarded from the MBT in order to suppress the torque level difference, the fuel consumption may be reduced. As described above, the conventional apparatus cannot achieve both improvement of drivability and fuel efficiency, and there is room for improvement.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a control device for an internal combustion engine capable of achieving both high level of drivability and high fuel efficiency by suppressing torque steps. And

In order to achieve the above object, a first invention is a control device for an internal combustion engine having a plurality of cylinders,
An in-cylinder pressure sensor for detecting an in-cylinder pressure of each cylinder of the internal combustion engine;
First ignition timing control means for setting the ignition timing of each cylinder of the internal combustion engine to an optimum ignition timing;
Second ignition timing control means for individually setting the ignition timing of each cylinder of the internal combustion engine based on the detection signal of the in-cylinder pressure sensor so that the generated torque of each cylinder is substantially the same;
Switching control means for instructing switching between the first ignition timing control means and the second ignition timing control means in response to a torque request to the internal combustion engine,
The switching control means instructs switching from the first ignition timing control means to the second ignition timing control means when a torque down request is issued to the internal combustion engine.

According to a second invention, in the first invention,
The switching control unit instructs switching from the first ignition timing control unit to the second ignition timing control unit when a torque request to the internal combustion engine is smaller than a predetermined value.

According to a third invention, in the first or second invention,
Further comprising generated torque acquisition means for acquiring the generated torque of each cylinder based on the detection signal of the in-cylinder pressure sensor;
The switching control means instructs switching from the first ignition timing control means to the second ignition timing control means when the difference in torque generated between the cylinders is larger than a predetermined value. To do.

A fourth invention is any one of the first to third inventions,
Detecting means for detecting a cylinder in which abnormal combustion occurs;
Limiting means for limiting the retard amount of the ignition timing of the cylinder when a cylinder in which abnormal combustion has occurred is detected by the detecting means;
The control device for an internal combustion engine according to any one of claims 1 to 3, further comprising:

  According to the first invention, when a torque down request is issued to the internal combustion engine, the ignition timing control for setting the ignition timing of each cylinder of the internal combustion engine to the optimum ignition timing is based on the detection signal of the in-cylinder pressure sensor. Thus, the control is switched to the ignition timing control in which the ignition timing of each cylinder of the internal combustion engine is individually set so that the generated torque of each cylinder becomes substantially the same. For this reason, according to the present invention, when the torque step between the cylinders becomes relatively large due to the torque reduction, it is possible to switch to the control that suppresses the occurrence of the torque step. Can be compatible.

  According to the second invention, when a predetermined low torque request is issued, the generated torque of each cylinder becomes substantially the same from the ignition timing control that sets the ignition timing of each cylinder of the internal combustion engine to the optimum ignition timing. As described above, the ignition timing control for individually setting the ignition timing of each cylinder of the internal combustion engine is switched. Therefore, according to the present invention, it is possible to switch to control that suppresses the occurrence of the torque step in a low torque region where the torque step between the cylinders is relatively large. It can be compatible.

  According to the third aspect of the present invention, when the torque difference between the cylinders is larger than a predetermined value, the generated torque of each cylinder is determined from the ignition timing control that sets the ignition timing of each cylinder of the internal combustion engine to the optimum ignition timing. It is switched to ignition timing control that individually sets the ignition timing of each cylinder of the internal combustion engine so as to be substantially the same. For this reason, according to the present invention, when the torque level difference between the cylinders becomes large, it is possible to switch to the control that suppresses the generation of the torque level level, so that both fuel efficiency and drivability can be achieved at a high level.

  According to the fourth invention, when a cylinder in which abnormal combustion occurs is detected, the ignition delay amount in the cylinder is limited. For this reason, according to the present invention, it is possible to effectively suppress the occurrence of misfire in a cylinder with unstable combustion.

In Embodiment 1 of this invention, it is a figure for demonstrating the state of each cylinder in case the internal combustion engine is performing MBT driving | operation. In Embodiment 1 of this invention, it is a figure for demonstrating the state of each cylinder when the torque reduction request | requirement is issued to the internal combustion engine. In Embodiment 2 of this invention, it is a figure for demonstrating the state of each cylinder in case the internal combustion engine is performing MBT driving | operation. In Embodiment 2 of this invention, it is a figure for demonstrating the state of each cylinder when the torque reduction request | requirement is issued to the internal combustion engine.

  Several embodiments of the present invention will be described below with reference to the drawings. In addition, the overlapping description is abbreviate | omitted about the common element in each figure. The present invention is not limited to the following embodiments.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
The internal combustion engine of the present embodiment is configured as a spark ignition type multi-cylinder engine (for example, 6 cylinders) using gasoline as fuel. An in-cylinder pressure sensor is attached to each cylinder head of the internal combustion engine so as to protrude from the top of the combustion chamber of each cylinder into the combustion chamber. The internal combustion engine has the same configuration as that of a known internal combustion engine except that it includes the above-described in-cylinder pressure sensor, and thus detailed description thereof is omitted.

[Operation of Embodiment 1]
In the internal combustion engine of the present embodiment, the operation at the optimal ignition timing (hereinafter referred to as “MBT operation”) is performed. In the MBT operation, the optimum ignition timing is set in consideration of the knock limit, the combustion efficiency, and the like, so that the optimum fuel consumption can be realized.

  FIG. 1 is a diagram for explaining the state of each cylinder when the internal combustion engine is performing MBT operation. Note that (A) the air amount in each cylinder in this figure is the air amount calculated based on the in-cylinder pressure at a predetermined crank angle after the intake stroke of each cylinder is completed. As the in-cylinder pressure of each cylinder, a detection signal of an in-cylinder pressure sensor at a predetermined crank angle is used. Further, (B) the efficiency of each cylinder in this figure corresponds to the ignition timing, and the dotted line indicates MBT. In addition, the generated torque of each cylinder (C) in this figure shows the torque calculated based on the air amount of each cylinder of (A). Further, # 1 to # 6 in this figure correspond to each cylinder of the internal combustion engine.

  As shown in (B) of this figure, when the MBT operation is performed, the ignition timing of all the cylinders is set to the optimum ignition timing (MBT). Hereinafter, the ignition timing control for setting the ignition timings of all the cylinders to the optimal ignition timing is referred to as “first ignition timing control”. The fuel efficiency of the internal combustion engine when the first ignition timing control is performed is the optimum fuel efficiency.

  Here, when the air amounts of the respective cylinders shown in (A) of this figure are compared, it can be seen that these values vary from cylinder to cylinder. As the amount of air increases, the generated torque increases. For this reason, as shown in (C) of this figure, strictly speaking, the torque generated in each cylinder varies depending on the difference in the air amount. The level difference due to the torque variation becomes a cause of deterioration of drivability.

  However, since this torque step is a torque difference resulting from a slight difference in the air amount of each cylinder, it does not occupy a large proportion of the torque generated by the internal combustion engine. For this reason, in an operating state in which the internal combustion engine generates a certain amount of torque, deterioration in drivability associated with a torque step does not become a problem. For this reason, in this driving state, it is desirable to ensure optimum fuel consumption by MBT driving.

  On the other hand, in the operating state where the torque generated by the internal combustion engine is small, the ratio of the torque difference resulting from the difference in the air amount between the cylinders becomes relatively large. For this reason, in such a small torque region, the influence of the deterioration of drivability due to the torque step appears remarkably.

  Therefore, in the present embodiment, when the operating state of the internal combustion engine is in a state where the influence of the deterioration in drivability due to the torque step appears remarkably, priority is given to improving the drivability by suppressing the torque step. And More specifically, when a predetermined torque reduction request is issued to the internal combustion engine and the ignition timing is retarded, a retard amount different for each cylinder is set. Hereinafter, the ignition timing control in which the ignition timing for each cylinder is individually set is referred to as “second ignition timing control”. FIG. 2 is a diagram for explaining a state of each cylinder when a torque down request is issued to the internal combustion engine. In FIG. 2C, white circles indicate the generated torque of each cylinder during MBT operation, double circles indicate the generated torque when the retard amount is set by the first ignition timing control, and black circles indicate the second generated torque. The generated torques when different retard amounts shown in (B) are set for each cylinder by the ignition timing control are shown.

  As shown in (A) of this figure, the air amount of each cylinder varies from cylinder to cylinder. This does not vary due to the torque reduction request, but is due to engine design, throttle valve operation timing, and the like. For this reason, the generated torque during MBT operation varies according to the air amount, as indicated by white circles in FIG.

  Here, let us consider a case where the same retard amount is set for each cylinder by the first ignition timing control when a torque reduction request is issued to the internal combustion engine. In this case, as shown by a double circle in FIG. 6C, the generated torque of all the cylinders is uniformly reduced while maintaining the variation between the cylinders in the generated torque during the MBT operation. As described above, the lower the generated torque, the larger the ratio of the torque difference between the cylinders. For this reason, if the above-described ignition delay control is performed uniformly for all the cylinders when the torque is reduced, the influence of the deterioration of drivability due to the torque step appears remarkably.

  Therefore, in the present embodiment, when a torque down request is issued to the internal combustion engine, switching from the first ignition timing control to the second ignition timing control is performed. More specifically, the efficiency of each cylinder for realizing the required torque based on the air amount of each cylinder calculated using the detection signal of the in-cylinder pressure sensor so that the generated torque of each cylinder is the same. (Ignition timing) is calculated. FIG. 2B shows the ignition timing of each cylinder set in this way. According to such ignition timing, as indicated by black circles in (C) of this figure, the generated torque of each cylinder can be made substantially the same, so that deterioration in drivability due to a torque step can be suppressed. it can.

  As described above, according to the present embodiment, by switching from the first ignition timing control to the second ignition timing control in response to the torque reduction request, the torque step is reduced in the small torque region of the internal combustion engine. By controlling, priority is given to drivability, and in other driving regions, priority is given to the optimum fuel consumption by MBT driving. That is, drivability is prioritized over optimal fuel consumption only when drivability deteriorates significantly, so that both fuel economy and drivability can be achieved at a high level.

  By the way, in the above-described embodiment, the case where the torque reduction request is issued to the internal combustion engine has been described as an example as the case where the operation state of the internal combustion engine is in the small torque region. However, this is not limited to the case where the operating state of the internal combustion engine is in the small torque region. When a predetermined small torque request is issued to the internal combustion engine, or the generated torque difference between the cylinders becomes abnormal at a predetermined ratio. In this case, the ignition timing may be set so that the generated torque of each cylinder is substantially the same. As a result, drivability can be improved even when torque reduction is not requested due to the ignition delay.

Embodiment 2. FIG.
[Features of Embodiment 2]
Next, the features of the second embodiment will be described with reference to FIGS. The second embodiment can be realized using a multi-cylinder internal combustion engine in which an in-cylinder pressure sensor is provided in each cylinder, as in the first embodiment.

  In the first embodiment described above, when a torque down request is issued to the internal combustion engine, the retard amount of the ignition timing is individually set for each cylinder so that the generated torque of each cylinder is substantially the same. It is said. Here, in the internal combustion engine, there are cases where an imbalance of the combustion state between the cylinders occurs due to various factors such as ignition failure of the spark plug. FIG. 3 is a diagram for explaining a state of each cylinder when the internal combustion engine is performing the MBT operation. In the example shown in this figure, the generated torque of the # 4 cylinder is smaller than that of the other cylinders. This indicates that the combustion of the # 4 cylinder is unstable. For this reason, if the ignition retard control at the time of torque reduction described above is executed for such an unstable combustion cylinder, misfire may occur.

  Therefore, in the present embodiment, when the retard control of the ignition timing is executed in response to the torque down request, the retard amount of the unstable combustion cylinder is limited. FIG. 4 is a diagram for explaining a state of each cylinder when a torque down request is issued to the internal combustion engine. As shown in this figure, when a torque down request is issued, the retard amount of the other cylinders except # 4 is set for each cylinder so that the generated torque is substantially the same. On the other hand, the retard amount of the # 4 cylinder, which is an unstable combustion cylinder, is limited by the limit at which combustion can be maintained in the unstable combustion cylinder, as shown in FIG. Thereby, when the ignition timing is retarded in response to the torque down request, it is possible to effectively suppress a situation where misfire occurs.

Claims (4)

A control device for an internal combustion engine having a plurality of cylinders,
An in-cylinder pressure sensor for detecting an in-cylinder pressure of each cylinder of the internal combustion engine;
First ignition timing control means for setting the ignition timing of each cylinder of the internal combustion engine to an optimum ignition timing;
Second ignition timing control means for individually setting the ignition timing of each cylinder of the internal combustion engine based on the detection signal of the in-cylinder pressure sensor so that the generated torque of each cylinder is substantially the same;
Switching control means for instructing switching between the first ignition timing control means and the second ignition timing control means in response to a torque request to the internal combustion engine,
The internal combustion engine, wherein the switching control means instructs the switching from the first ignition timing control means to the second ignition timing control means when a torque down request is issued to the internal combustion engine. Control device.   The switching control means instructs switching from the first ignition timing control means to the second ignition timing control means when a torque request to the internal combustion engine is smaller than a predetermined value. Item 2. A control device for an internal combustion engine according to Item 1. Further comprising generated torque acquisition means for acquiring the generated torque of each cylinder based on the detection signal of the in-cylinder pressure sensor;
The switching control means instructs switching from the first ignition timing control means to the second ignition timing control means when the difference in torque generated between the cylinders is larger than a predetermined value. The control apparatus for an internal combustion engine according to claim 1 or 2. Detecting means for detecting a cylinder in which abnormal combustion occurs;
Limiting means for limiting the retard amount of the ignition timing of the cylinder when a cylinder in which abnormal combustion has occurred is detected by the detecting means;
The control device for an internal combustion engine according to any one of claims 1 to 3, further comprising:

Images