JP2016000973A - Control device for internal combustion engine - Google Patents

Abstract

A control device for an internal combustion engine capable of suppressing deterioration of combustion by quickly grasping a change in a combustion state.
A control device for an internal combustion engine having a plurality of cylinders includes a cylinder pressure sensor (CPS) mounted on a representative cylinder. In addition, the control device is configured to be capable of EGR operation that introduces EGR gas into the cylinder through the EGR passage, and when a request for EGR operation is issued, it calculates a predicted value of the transport delay time of EGR gas To do. Based on the calculated predicted value, the operation timing of the EGR valve is controlled so that the cylinder into which the EGR gas is first introduced becomes the representative cylinder.
[Selection] Figure 5

Description

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

  Conventionally, for example, Japanese Patent No. 5263184 discloses a technique related to engine control in which some cylinders of a plurality of cylinders are provided with in-cylinder pressure sensors. In this control, the specific heat ratio of the mixed gas before combustion is calculated from the change in the in-cylinder pressure during the period from when the intake valve is closed to when combustion starts. Then, utilizing the fact that there is a certain relationship among the specific heat ratio, the EGR rate, and the A / F, the EGR rate and the A / F are calculated from the specific heat ratio, and precise combustion control using these is performed. .

Japanese Patent No. 5263184 JP 2013-217263 A Japanese Patent Laid-Open No. 10-9011 JP 2010-249068 A Japanese Patent No. 4525729

  However, although the above-described conventional technology can grasp the combustion state of the cylinder provided with the in-cylinder pressure sensor, it cannot grasp the combustion state of the cylinder not provided with the in-cylinder pressure sensor. For this reason, even if the combustion state of the cylinder not provided with the in-cylinder pressure sensor changes first, the change until the combustion state of the cylinder provided with the in-cylinder pressure sensor is grasped can be grasped. However, there is a possibility that precise combustion control cannot be performed during that period.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a control device for an internal combustion engine capable of suppressing deterioration of combustion by quickly grasping a change in combustion state.

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 provided in a representative cylinder of the plurality of cylinders;
An EGR passage connecting an intake passage and an exhaust passage of the internal combustion engine;
An EGR valve provided in the EGR passage;
EGR control means for operating the EGR valve and performing an EGR operation for introducing EGR gas into the cylinder through the EGR passage,
The EGR control means calculates a predicted value of a transport delay time from when the EGR valve is operated to when EGR gas is introduced into the cylinder when a request for the EGR operation is issued, The operation timing of the EGR valve is controlled based on the value so that the cylinder into which the EGR gas is first introduced becomes the representative cylinder.

  According to the first invention, when a request for an EGR operation is issued, a predicted value of the transport delay time from when the EGR valve is operated until EGR gas is introduced into the cylinder is calculated. Based on the calculated predicted value, the operation timing of the EGR valve is controlled so that the cylinder into which the EGR gas is first introduced becomes the representative cylinder. Thereby, since the deterioration of the combustion state due to the introduction of the EGR gas can be grasped quickly, it becomes possible to take measures to suppress the deterioration of the combustion at an early timing.

It is a time chart for demonstrating the change of the EGR valve opening degree, in-cylinder EGR rate, and CA50 when an EGR operation is started. It is a time chart for demonstrating the change of the EGR valve opening degree, in-cylinder EGR rate, and CA50 when the valve opening timing of the EGR valve is shifted and the EGR operation is started. In the control apparatus of this Embodiment, it is a time chart which shows the change of the EGR valve opening degree, in-cylinder EGR rate, and CA50 when the EGR operation is started. It is a time chart which shows the change of EGR valve opening degree at the time of correct | amending transport delay time, the in-cylinder EGR rate, and CA50. 3 is a flowchart showing a routine for control executed by the ECU in the first embodiment.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described with reference to the drawings.

[Configuration of Embodiment 1]
The control device of the present embodiment includes an internal combustion engine. The internal combustion engine is configured as a spark ignition type multi-cylinder engine using gasoline as fuel. A piston that reciprocates inside the cylinder of the internal combustion engine is provided. A combustion chamber is formed between the piston and the cylinder head. One end of an intake passage and an exhaust passage communicate with the combustion chamber. An intake valve and an exhaust valve are disposed at the communication portion between the intake passage and the exhaust passage and the combustion chamber, respectively. A fuel injection valve for injecting fuel into the cylinder is incorporated in the cylinder head. In addition, an in-cylinder pressure sensor (hereinafter also referred to as “CPS”) for detecting an in-cylinder pressure is incorporated in one cylinder (hereinafter referred to as a representative cylinder) of a plurality of cylinders of a multi-cylinder engine.

  Further, the control device of the present embodiment includes an EGR passage that connects the intake passage and the exhaust passage. The EGR passage is provided with an EGR valve for adjusting the opening degree of the EGR passage.

  The control device of the present embodiment includes an ECU (Electronic Control Unit). Various sensors such as the in-cylinder pressure sensor (CPS) described above are connected to the input unit of the ECU. Various actuators such as the fuel injection valve and the EGR valve described above are connected to the output portion of the ECU. The ECU controls the operating state of the internal combustion engine based on various types of input information.

[Operation of Embodiment 1]
(EGR valve opening timing control in EGR operation)
The in-cylinder pressure sensor (CPS) is a very effective sensor in that the in-cylinder combustion characteristics can be directly detected. For this reason, the output of the CPS is used as a control parameter for various controls of the internal combustion engine. For example, the detected in-cylinder pressure is used for calculation of combustion parameters such as a 50% combustion point (hereinafter, CA50) and a period from the ignition timing to the 10% combustion point (SA-CA10).

  In the internal combustion engine of the present embodiment, a request for an EGR operation for introducing EGR gas into the cylinder through the EGR passage may be issued. When the EGR valve is operated to the valve opening side and EGR gas is introduced into the cylinder, combustion in the cylinder becomes slow. In this case, since CA50 is shifted to the retard side or SA-CA10 is delayed, correction of the ignition timing, EGR amount, and the like is necessary.

  Here, in the internal combustion engine of the present embodiment, the CPS is arranged only in the representative cylinder from the viewpoint of arrangement space and manufacturing cost. In a multi-cylinder engine, combustion in each cylinder is performed in order. For this reason, when the EGR operation is started and the introduction of EGR gas from a cylinder other than the representative cylinder is started, the period of time until the combustion state of the representative cylinder is grasped by the CPS is maintained in the combustion state by the EGR operation. It will not be possible to grasp the changes.

  FIG. 1 is a time chart for explaining changes in the EGR valve opening, the in-cylinder EGR rate, and the CA 50 when the EGR operation is started. In this figure, # 1 to # 6 are cylinders of a 6-cylinder engine, and an example in which # 1 cylinder is a representative cylinder equipped with CPS is shown. As shown in this figure, when the EGR valve is opened at the combustion timing of the # 6 cylinder, a delay in transportation occurs until the EGR gas flowing through the EGR path reaches the cylinder, so the in-cylinder EGR rate is # 2 Cylinder combustion has changed. In the # 2 cylinder, the CA50 changes due to the change in the in-cylinder EGR rate, and the combustion state deteriorates.

  Thereafter, the change in CA50 is grasped in the combustion of the # 1 cylinder (representative cylinder). Then, the ignition timing is corrected so that CA50 becomes MBT (Minimum advance for Best Torque) from the combustion of the # 2 cylinder, which is the next combustion of the # 1 cylinder. Thus, in the example shown in FIG. 1, the state where the combustion state is deteriorated by the EGR operation continues from the combustion of the # 2 cylinder to the combustion of the # 1 cylinder.

  Therefore, in the control device of the present embodiment, when an EGR operation request is issued, the EGR valve opening operation is started so that the introduction of EGR gas is started in the combustion of the # 1 cylinder (representative cylinder). The timing will be changed. FIG. 2 is a time chart for explaining changes in the EGR valve opening degree, the in-cylinder EGR rate, and the CA50 when the EGR operation is started by shifting the opening timing of the EGR valve. In this figure, as in FIG. 1, # 1 to # 6 are cylinders of a six-cylinder engine, and an example in which # 1 cylinder is a representative cylinder equipped with CPS is shown.

  In the control device according to the present embodiment, when an EGR operation request is issued, a predicted value of the transport delay time of EGR gas when the EGR valve is first opened is calculated. The predicted value of the transport delay time can be calculated based on, for example, the differential pressure between the inlet pressure and the outlet pressure of the EGR passage and the opening degree of the EGR valve. Then, as shown in this figure, the EGR valve is opened so that the cylinder into which the EGR gas is first introduced becomes the # 1 cylinder (representative cylinder) in consideration of the calculated predicted value of the transport delay time. .

  According to such control, in the combustion of the # 1 cylinder (representative cylinder), the CA50 changes first, and this change is grasped by the CPS. Then, an ignition timing feedback correction amount (advance amount) is calculated such that CA50 becomes MBT. Thus, since the ignition timing can be corrected from the combustion of the # 2 cylinder, which is the next combustion of the # 1 cylinder, the combustion state deteriorated by the EGR operation can be stabilized in a short period of time. In the above-described control, it is also possible to perform control to gradually increase the EGR amount and stop the increase in the EGR amount when the SA-CA 10 reaches the limit value.

  By the way, in the control device of the above-described embodiment, the opening timing of the EGR valve is controlled so that the cylinder into which the EGR gas is first introduced in the EGR operation becomes the representative cylinder. However, the control that can be executed in the control device of the present embodiment is not limited to this. That is, for example, in the purge operation in which the purge gas including the fuel vapor is introduced into the cylinder by operating the purge VSV, the opening timing of the purge VSV is controlled so that the cylinder to which purge gas is first introduced becomes the representative cylinder. It is good as well. In the purge operation, when a purge gas having a high fuel vapor concentration is introduced, the A / F becomes rich and the SA-CA 10 becomes shorter. On the other hand, when a purge gas having a low fuel vapor concentration is introduced, the A / F becomes lean and the SA-CA 10 becomes longer. If the purge gas is first introduced into the representative cylinder, the change in the SA-CA 10 can be grasped quickly and the increase / decrease correction of the purge gas can be executed, so that the period during which the combustion state is deteriorated can be shortened.

  In the lean control for controlling the A / F to be lean, the lean control may be performed from the representative cylinder. If the A / F is too lean, it may cause misfire. Therefore, if lean control is first performed in the representative cylinder, the lean limit can be estimated from SA-CA10 and the A / F limit of all cylinders can be determined quickly, so that the combustion state due to misfire can quickly suppress deterioration. Is possible.

(Correction of predicted value of transport delay time)
In the control device of the above-described embodiment, the estimated value of the transport delay time of the EGR gas is calculated based on the differential pressure between the inlet pressure and the outlet pressure of the EGR passage and the opening degree of the EGR valve. It is also assumed that the transport delay time will not be as calculated. FIG. 3 is a time chart showing changes in the EGR valve opening, the in-cylinder EGR rate, and the CA50 when the EGR operation is started in the control device of the present embodiment. In this figure, as in FIG. 1, # 1 to # 6 are cylinders of a six-cylinder engine, and an example in which # 1 cylinder is a representative cylinder equipped with CPS is shown. In the example shown in this figure, when the EGR valve is opened so that EGR gas is first introduced into the # 1 cylinder (representative cylinder) based on the predicted value of the calculated transport delay time, the actual EGR The case where the gas transportation delay time is longer than the calculated predicted value is shown. In this case, since the CA50 detected in the # 1 cylinder has not changed, the ignition timing is not corrected, and the combustion deterioration period is prolonged.

  Therefore, in the control device of the present embodiment, when there is no change in the combustion state of the representative cylinder, it is determined that the predicted value of the transport delay time is short, and the correction for increasing the predicted value of the next transport delay time is performed. I will give it.

  FIG. 4 is a time chart showing changes in the EGR valve opening, the in-cylinder EGR rate, and the CA50 when the transport delay time is corrected. In this figure, as in FIG. 3, # 1 to # 6 are cylinders of a six-cylinder engine, and an example in which # 1 cylinder is a representative cylinder equipped with CPS is shown. In the example shown in this figure, EGR gas is first introduced into the # 1 cylinder by correcting the predicted value of the transport delay time to be longer. Thereby, the deterioration of the combustion state can be eliminated from the combustion of the next cylinder.

(Selection of CPS cylinder)
In the control device of the above-described embodiment, the representative cylinder in which the CPS is mounted is not particularly limited, but it is preferable to mount the CPS in a cylinder in which the EGR gas is most easily introduced. The cylinder in which the EGR gas is most easily introduced means that the cylinder in which the misfire and the combustion deterioration are most likely to occur. Therefore, if CPS is installed in a cylinder into which EGR gas is most easily introduced, and EGR control is performed so that the combustion state such as misfire does not deteriorate in the cylinder, in other cylinders not equipped with CPS. It is possible to effectively suppress the deterioration of the combustion state.

  Also, in the above-described purge operation, CPS is installed in a cylinder in which purge gas is most likely to enter, that is, a cylinder having the largest intake air distribution amount, or CPS is installed in a cylinder having the worst tumble characteristics. It is possible to effectively suppress deterioration of the combustion state in a cylinder not equipped with.

(Cylinder difference correction)
As described above, when there is an inter-cylinder difference regarding the introduction of EGR gas, the inter-cylinder difference is grasped in advance, and the above-described inter-cylinder difference with respect to various control correction amounts calculated in the representative cylinder equipped with the CPS. It is preferable to multiply by a coefficient corresponding to.

  For example, in a parallel 4-cylinder engine composed of # 1, # 2, # 3, and # 4 cylinders, the cylinder in which EGR gas is most easily introduced is the # 1 cylinder, and the CPS is mounted on the # 1 cylinder. The case where this is done will be described. Distribution of EGR gas to each cylinder is determined by engine hardware design. Therefore, here, it is assumed that the distribution of EGR gas is 90% for the # 2 cylinder, 80% for the # 3 cylinder and 70% for the # 4 cylinder, based on the reference (100%) of the # 1 cylinder. When the ignition delay amount in the CA50 of the # 1 cylinder calculated by CPS is 2CA, the ignition retardation amounts of the # 2, # 3, and # 4 cylinders are each 1. 8CA, 1.6CA and 1.4CA. Thereby, it is possible to prevent the advance angle of the ignition timing and achieve optimal combustion in all the cylinders. The correction of the inter-cylinder difference can be applied not only to the EGR control but also to the above-described purge control, A / F lean control, and the like.

[Specific Processing in First Embodiment]
Next, specific processing of EGR control executed in the control device of the present embodiment will be described with reference to a flowchart. FIG. 5 is a flowchart showing a routine for control executed by the ECU in the first embodiment. In this routine, first, when an EGR introduction request is issued in step S2, a predicted value of the EGR gas transport delay time when the EGR valve is operated is calculated (step S4). Next, based on the predicted value of the transport delay time calculated in step S4, it is determined whether or not it is the timing when the first cylinder into which the EGR gas is introduced becomes the CPS-equipped cylinder (representative cylinder) (step S6). . If the determination in step S6 is not accepted, this routine is temporarily terminated and this routine is executed again from the beginning. On the other hand, if the determination in step S6 is accepted, the process proceeds to the next step, and the EGR valve is operated to the valve opening side (step S8).

  Next, combustion parameters such as CA50 and CA10 are calculated based on the detected value of CPS (step S10). Then, it is determined whether or not there is a change in the combustion parameter calculated in step S10 (step S12). As a result, if there is no change in the combustion parameter, it is determined that the EGR gas has not reached the representative cylinder when the predicted value of the transport delay time calculated in step S4 has elapsed, and the next step Then, the predicted value of the transport delay time is corrected (step S14). Here, specifically, a predetermined time is added to the predicted value of the transport delay time calculated in step S4. When the process of step S14 is executed, this routine is once ended, and this routine is executed again from the beginning.

  On the other hand, if there is a change in the combustion parameter in step S12, it is determined that the EGR gas has reached the representative cylinder when the transportation delay time calculated in step S4 has elapsed, and the next step is performed. Then, using the combustion parameters calculated in the representative cylinder on which the CPS is mounted, correction amounts such as ignition timing and EGR amount are calculated (step S16). Next, correction coefficients for cylinders other than the representative cylinder are calculated (step S18). Specifically, the correction coefficient corresponding to the difference between the cylinders in the EGR amount specified from the hardware characteristics is calculated with the representative cylinder as a reference. Next, the correction amount of the cylinders other than the representative cylinder is calculated using the correction coefficient calculated in step S18 (step S20). Next, it is determined whether it is the control timing of each cylinder (step S22). As a result, when it is not the control timing of each cylinder, this routine is terminated, and when it is the control timing of each cylinder, correction of the corresponding cylinder is executed (step S24).

  As described above, according to the control device of the first embodiment, when an EGR operation request is issued, the cylinder into which the EGR gas is first introduced can be matched with the representative cylinder equipped with the CPS. . Thereby, the correction | amendment for stabilizing a combustion state can be performed quickly.

Claims (1)

A control device for an internal combustion engine having a plurality of cylinders,
An in-cylinder pressure sensor provided in a representative cylinder of the plurality of cylinders;
An EGR passage connecting an intake passage and an exhaust passage of the internal combustion engine;
An EGR valve provided in the EGR passage;
EGR control means for operating the EGR valve and performing an EGR operation for introducing EGR gas into the cylinder through the EGR passage,
The EGR control means calculates a predicted value of a transport delay time from when the EGR valve is operated to when EGR gas is introduced into the cylinder when a request for the EGR operation is issued, A control apparatus for an internal combustion engine, wherein an operation timing of the EGR valve is controlled based on a value so that a cylinder into which the EGR gas is first introduced becomes the representative cylinder.

Images