JP2855395B2 - Self-diagnosis device in exhaust gas recirculation system of internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-diagnosis device for an exhaust gas recirculation system for an internal combustion engine for recirculating a part of engine exhaust gas to an intake system.

[0002]

2. Description of the Related Art Conventionally, in automobile internal combustion engines,
BACKGROUND ART As a device for reducing NOx in engine exhaust, an exhaust gas recirculation device (EGR) that lowers the maximum combustion temperature and reduces NOx generation by recirculating a part of the engine exhaust to an intake manifold is known. I have.

[0003]

Here, if the intended exhaust gas recirculation cannot be performed due to the failure of the exhaust gas recirculation device,
Since the amount of NOx emission would be increased, it has been desired to provide a device capable of performing a self-diagnosis as to whether or not intended exhaust gas recirculation is performed. As the self-diagnosis device,
Although the EGR flow rate is determined by a temperature sensor provided in the EGR passage, there has been a problem that it is difficult to determine with high accuracy.

The present invention has been made in view of the above problems, and has as its object to enable a self-diagnosis of an exhaust gas recirculation device to be performed with high accuracy by a simple configuration.

[0005]

SUMMARY OF THE INVENTION Therefore, the present invention provides an exhaust gas recirculation system for an internal combustion engine having exhaust gas recirculation control means for opening and closing an exhaust gas recirculation passage for recirculating part of engine exhaust to an intake system in accordance with engine operating conditions. The self-diagnosis device in FIG.
1 is configured.

In FIG. 1, first output fluctuation detecting means is provided.
Is an opening control of the exhaust gas recirculation passage by the exhaust gas recirculation control means.
In the state, the engine output fluctuation is detected, and the second output fluctuation is detected.
The detection means is an exhaust gas recirculation passage by the exhaust gas recirculation control means.
In the closed control state, the output fluctuation of the engine is detected . Soshi
The output fluctuation deviation calculating means is configured to output the first and second output fluctuations.
The deviation of the output fluctuation detected by the motion detection means.
The self-diagnosis means is calculated by the output fluctuation deviation calculation means.
When the deviation of the output fluctuations falls below a predetermined value,
Determine whether the reflux device is abnormal.

[0007]

When you do [action] exhaust gas recirculation, since the combustion becomes unstable,
For example, if the exhaust gas recirculation passage is controlled to be switched from the closed control state to the open control state, assuming that the intended exhaust gas recirculation is performed, the output will be increased due to unstable combustion . Therefore, in the case exhaust gas recirculation passage is closed control state and when in an open control state, respectively to detect the output <br/> fluctuation, showing a deviation of these output variation was commensurate with the opening and closing control of the exhaust gas recirculation passage Whether or not the desired exhaust gas recirculation is being performed is diagnosed based on whether or not the exhaust gas recirculation is performed.

[0008]

Embodiments of the present invention will be described below. In FIG. 2 showing the system configuration of one embodiment, an exhaust gas recirculation passage 4 for communicating the exhaust manifold 2 and the intake manifold 3 of the engine 1 is provided.
It is opened and closed by a GR control valve 5.

The EGR control valve 5 is a diaphragm type valve which is opened by applying a suction negative pressure of the engine against the urging force of the coil spring in the valve closing direction, and has a pressure chamber and a throttle valve. A negative pressure introducing passage 7 is provided for communicating with the intake manifold 3 on the downstream side 6, and the valve is opened by introducing the suction negative pressure of the engine 1 to the pressure chamber through the negative pressure introducing passage 7.

An EGR control solenoid 9 which is turned on / off by a control unit 8 is interposed in the negative pressure introducing passage 7, and the EGR control valve 5 is opened and closed by controlling the opening and closing of the EGR control solenoid 9. Opening / closing, that is, on / off of exhaust gas recirculation can be controlled.

Reference numeral 10 denotes a diaphragm type BPT which determines the negative pressure for controlling the EGR control valve 5 by operating the diaphragm by the exhaust pressure and the manifold negative pressure.
The EGR control valve 5, the EG
The exhaust gas recirculation control means is constituted by the R control solenoid 9, the BPT valve 10, and the control unit 8.

To the control unit 8, detection signals such as a cooling water temperature, an engine speed, and an intake air amount are inputted from respective sensors, and an ON / OFF signal of an ignition switch is inputted and discriminated from these. The EGR control solenoid 9 based on engine operating conditions
On / off control.

The control unit 8 includes:
An in-cylinder pressure detection signal is input from the in-cylinder pressure sensor 11. The in-cylinder pressure sensor 11 is provided in
No. 432 discloses an in-cylinder pressure sensor of a type mounted as a washer of the ignition plug 12. However, in addition to the type mounted as the washer of the ignition plug 12 as described above, a type in which the sensor section is directly exposed to the combustion chamber and the in-cylinder pressure is detected as an absolute pressure may be used.

Here, the control unit 8 corresponds to FIG.
As shown in the flowchart of FIG. 7, the self-diagnosis function of the exhaust gas recirculation device having the above configuration is provided. In this embodiment, the first output fluctuation detecting means and the second output fluctuation
Detecting means, output fluctuation deviation calculation means, functions as a self-diagnostic unit, the as shown in the flowchart of Figure 3, is implemented by the software functions by the control unit 8 and the cylinder pressure sensor 11.

In the flowchart of FIG. 3 , first, in step 1 (S1 in the figure, the same applies hereinafter),
The in-cylinder pressure detected by the in-cylinder pressure sensor 11 is read. Then, in the next step 2, it is determined whether or not the EGR control solenoid 9 is in the open control state, in other words, whether or not the exhaust gas recirculation passage (EGR passage) 4 is in the open control state.

Here, the EGR control solenoid 9
When the condition is such that the exhaust gas is recirculated to the intake manifold 2 through the exhaust gas recirculation passage 4, the process proceeds to step 3, and the output fluctuation rate at the time of exhaust gas recirculation is determined based on the in-cylinder pressure input in step 1. (The first output
Force fluctuation detecting means) . Specifically, for example, by integrating the in-cylinder pressure for only one cycle of the engine, an average effective pressure equivalent value Pi is obtained. Further, a variation rate of the average effective pressure equivalent value Pi is calculated, and the variation rate is calculated as an output variation. A value equivalent to the rate.

It is to be noted that the variation of the rotation speed may be calculated without using the in-cylinder pressure, and the rotation variation may be set as a value corresponding to the output variation.
On the other hand, if it is determined in step 2 that the EGR control solenoid 9 is controlled to be closed and the exhaust gas recirculation through the exhaust gas recirculation passage 4 is stopped, the process proceeds to step 4, where the output fluctuation rate when the exhaust gas recirculation is stopped is calculated.
(Second output fluctuation detecting means) .

Here, the EGR control solenoid 9 may be forcibly opened and closed for self-diagnosis, and the output fluctuation rate in the open control state and the output fluctuation rate in the closed control state may be calculated respectively. . When the output fluctuation rate in the open control state and the output fluctuation rate in the closed control state are obtained as described above, a deviation between them is calculated in step 5 (output fluctuation deviation calculating means).

In step 6, the deviation of the output fluctuation rate is compared with a predetermined value to determine whether there is a deviation greater than a predetermined value between the output fluctuation rate in the open control state and the output fluctuation rate in the closed control state. I do. That is, assuming that the exhaust gas recirculation is performed normally, the combustion becomes unstable by performing the exhaust gas recirculation, and the output fluctuation should increase compared to when the exhaust gas recirculation is not performed (see FIG. 4) . ). For example, if the exhaust gas recirculation passage 4 is clogged and the desired exhaust gas recirculation cannot be performed, the exhaust gas is not actually recirculated even if the exhaust gas recirculation is on as the control state. As a result, the combustion becomes unstable and the output fluctuation does not increase, and the fluctuation rate is the same as the output fluctuation rate during the off control. Conversely, when the exhaust gas recirculation passage 4 is not closed by the closing control, the exhaust gas recirculation is performed irrespective of the control state, and the combustion is always unstable. This indicates the output fluctuation rate of the level.

Therefore, when the deviation of the output fluctuation rate is equal to or greater than a predetermined value, it can be considered that the exhaust gas recirculation control has been performed normally. In this case, the process proceeds to step 7 to determine the normality. . On the other hand, if the difference is less than the predetermined can be regarded as an abnormality in the exhaust gas recirculation control system has occurred, the abnormality determination proceeds to step 8 in this case (self Means) .

[0021]

According to the present invention as described in the foregoing, when the exhaust gas recirculation, by using a characteristic that the combustion becomes unstable, each determined output variable in the open control state and a closed control state of the exhaust gas recirculation passage kinematic The self-diagnosis of the exhaust gas recirculation device is performed based on whether or not the deviation indicates a value commensurate with the on / off state of the exhaust gas recirculation. effective.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is a system schematic diagram showing one embodiment of the present invention.

FIG. 3 is a flowchart showing a self-diagnosis of the real施例.

FIG. 4 is a diagram showing a relationship between an EGR rate and output fluctuation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Exhaust manifold 3 Intake manifold 4 Exhaust recirculation passage 5 EGR control valve 6 Throttle valve 7 Negative pressure introduction passage 8 Control unit 9 EGR control solenoid 10 BPT valve 11 In-cylinder pressure sensor 12 Spark plug

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F02M 25/07 550 F02D 45/00 364

Claims (1)

(57) [Claims] 1. A self-diagnosis apparatus in an exhaust gas recirculation system for an internal combustion engine provided with exhaust gas recirculation control means for opening and closing in accordance with the exhaust gas recirculation passage for recirculating part of the engine exhaust to the intake system of the engine operating conditions, the Exhaust gas recirculation passage open control state by exhaust gas recirculation control means
Output fluctuation detection for detecting engine output fluctuation in the engine
Means and a control state of closing the exhaust gas recirculation passage by the exhaust gas recirculation control means.
Output fluctuation detection for detecting engine power fluctuation in the engine
Means and the first and second output fluctuation detecting means respectively.
Output fluctuation deviation calculating means for calculating the deviation of the output fluctuation
And the deviation of the output fluctuation calculated by the output fluctuation deviation calculating means is
When the value is lower than a predetermined value, the abnormality of the exhaust gas recirculation device is determined.
A self-diagnosis device for an exhaust gas recirculation device for an internal combustion engine.