JP3158340B2 - Failure diagnosis device for 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 failure diagnosis device for an exhaust gas recirculation device for an internal combustion engine that recirculates a part of engine exhaust to an intake system.

[0002]

2. Description of the Related Art Conventionally, in automobile internal combustion engines,
As a device for reducing NOx in the engine exhaust gas, a portion of the engine exhaust gas is recirculated to the intake system, thereby lowering the maximum combustion temperature and reducing exhaust gas recirculation (E
GR) devices are known. Here, if the desired exhaust gas recirculation amount cannot be obtained due to the failure of the exhaust gas recirculation device, N
On the other hand, there is a concern that the amount of Ox emission may increase, but if the amount of exhaust gas recirculates too much, the combustion may be excessively deteriorated, the operability may be deteriorated, and the emission of HC, CO, black smoke and the like may be excessively increased. Therefore, it is desired to provide a device capable of diagnosing whether desired exhaust gas recirculation is performed.

[0003] Therefore, the applicant of the present invention has proposed an exhaust gas recirculation (EGR).
Attention is paid to the characteristic that the output torque of the engine changes according to ON / OFF of the engine, and a failure in the exhaust gas recirculation device based on the change of the combustion pressure and the compression pressure (compression pressure) when the exhaust gas recirculation is forcibly turned ON / OFF. A diagnostic device for diagnosing presence / absence of a defect was previously proposed (Japanese Patent Application No. 5-78177,
See Japanese Patent Application No. 173519/1995).

[0004]

However, in the conventional devices, the EGR is turned on during steady operation.
Since the failure diagnosis is performed by switching OFF, there is an adverse effect such as deterioration of driving performance such as torque shock and deterioration of exhaust performance accompanying the switching of EGR ON / OFF.

The present invention has been made in view of the above-mentioned circumstances, and even if the failure diagnosis is performed by switching the EGR ON / OFF, the driving performance is not deteriorated as much as possible, and the exhaust performance is not deteriorated with high accuracy. An object of the present invention is to provide a failure diagnosis device that can diagnose a failure of an exhaust gas recirculation device.

[0006]

Therefore, in the invention according to the first aspect of the present invention, as shown in FIG. 1, a part of the engine exhaust gas passes through an exhaust gas recirculation passage provided with an exhaust gas recirculation control valve. A failure diagnosis device for an exhaust gas recirculation device for an internal combustion engine that recirculates the exhaust gas to an intake system of the engine, wherein in-cylinder pressure correlation information detecting means for detecting information correlating with the in-cylinder pressure of the engine; Forcible opening / closing means for opening / closing control, deceleration fuel cut detection means for detecting during engine deceleration fuel cut, and opening and closing the exhaust gas recirculation control valve via the forced opening / closing means during deceleration fuel cut. sampling means for sampling the information that correlates the in-cylinder pressure detected by the cylinder pressure correlation information detecting means in each of the states of the control state and a closed control state, Sa by the sampling means
In the open control state of the exhaust gas recirculation control valve
The information correlated with the cylinder pressure and the cylinder pressure in the closed control state
Deviation calculation means for calculating a deviation from the information
Deviation prediction means for setting a predicted value of the deviation in accordance with
The deviation calculated by the deviation calculation means is calculated by the deviation prediction means.
By comparing the value divided by the set forecast value with the predetermined value,
Diagnosis based on deviation to determine whether the exhaust gas recirculation device has a failure
And disconnecting means .

That is, if the exhaust gas recirculation control valve is normally opened according to the instruction of the forced opening / closing means during the deceleration fuel cut,
Even if the throttle valve is substantially fully closed, a relatively large amount of air is introduced into the intake passage or the cylinder via the exhaust passage and the exhaust gas recirculation passage. On the other hand, if the exhaust gas recirculation control valve is normally closed, the throttle valve is almost fully closed, and it becomes difficult for air to be introduced from the exhaust gas recirculation passage into the intake passage or the cylinder. , The in-cylinder pressure becomes relatively small (the intake pressure increases toward the negative pressure side).

Therefore, based on information (in-cylinder pressure, intake pressure, etc.) correlating to the in-cylinder pressure before and after the forcible opening and closing of the exhaust recirculation control valve during deceleration fuel cut, a failure of the exhaust gas recirculation device may occur. Can be detected. For example, if the deviation of the in-cylinder pressure or intake pressure when the exhaust gas recirculation control valve is forcibly opened and closed during deceleration fuel cut can be determined to be normal if the deviation is equal to or more than a predetermined value, and if the deviation does not exceed the predetermined value, The fact that the exhaust gas recirculation control valve is not controlled in response to the control due to some abnormality can be detected with high accuracy with a simple configuration. Also, the deviation of information correlated with the actual in-cylinder pressure
A configuration that compares the value divided by the predicted value with a predetermined value
The deviation can be standardized and the operating conditions (engine speed and emission
Irrespective of the degree of opening of the gas recirculation control valve, etc.)
By doing so, a diagnosis can be made.

In the present invention, since the failure diagnosis is performed during the fuel cut, combustion is not performed in the cylinder and the exhaust pressure is low, so that the exhaust gas is normally introduced into the cylinder and the intake passage via the exhaust gas recirculation device. Since the combustion does not affect the in-cylinder pressure and the intake pressure which differ depending on whether or not the failure is detected, the accuracy of the failure diagnosis can be improved also in this respect. Also,
Since the failure diagnosis is performed during fuel cut during deceleration,
Since combustion is not performed in the cylinder, deterioration of operating performance (torque shock) and exhaust performance due to opening and closing of the exhaust gas recirculation control valve (combustion fluctuation) can be suppressed to the utmost. Even if the failure is diagnosed by forcibly opening and closing the exhaust gas recirculation control valve, the failure of the exhaust gas recirculation device can be diagnosed with high accuracy without deteriorating the operating performance as much as possible and without deteriorating the exhaust performance. According to a second aspect of the present invention , before sampling by the sampling means,
Information relating to the in-cylinder pressure when the exhaust gas recirculation control valve is open
Between the information and the information correlated with the in-cylinder pressure in the closed control state
Means for calculating the deviation, and predicting the deviation according to the operating conditions.
A deviation predicting means for setting a measured value, and calculating by the deviation calculating means.
The average value of the issued deviations and the deviation set by the deviation prediction means
By comparing the predicted value with the predicted value, it is determined whether the exhaust gas recirculation device has a failure.
Diagnostic means for determining a deviation.

According to such a configuration, the information correlated with the in-cylinder pressure is obtained.
By calculating the average value of the deviations of the
Improve diagnostic accuracy by eliminating the effects of deviations
Can be made. In the invention according to claim 3, the deviation
Before the diagnosis means determines the average value of the deviations.
Change the dead zone of diagnosis according to the number of data of the deviation
The configuration was adopted.

According to this configuration, the average value of the deviation is calculated as
The larger the number of deviation data at the time of calculation, the more the average value
As reliability increases, the dead zone for diagnosis can be increased according to the number of data.
To make a false judgment when reliability is low.
Avoiding, while collecting data and increasing reliability
Thus, a highly accurate determination can be made. In the invention according to claim 4, the number of diagnoses in the diagnostic means based on the deviation is large.
The more the exhaust valve is forced to open by the forced opening / closing means.
Forced opening / closing opening change means to increase the opening of the recirculation control valve
The configuration was provided.

Thus, the initial stage of the diagnosis (the number of times of diagnosis is small)
When there is no driving performance, the driving performance deteriorates (the engine braking force is low).
To reduce as much as possible)
The opening of the exhaust gas recirculation control valve that is forcibly opened
In the diagnostics
Exhaust gas that is forcibly opened during fault diagnosis as the number increases
Increasing the degree of opening of the recirculation control valve, gradually sacrificing drivability
While gradually increasing the accuracy of failure diagnosis
To do. That is, a state in which the deterioration of drivability has been minimized.
It is possible to increase the detection accuracy of failure diagnosis
You. In other words, it is not known whether there is a failure or not
Open the exhaust gas recirculation control valve with a large opening
After the fault diagnosis, it is normal to operate for fault diagnosis
Unnecessarily deteriorates the performance (engine braking force, etc.)
That means that we can avoid this situation as much as possible.
Become. In the invention according to claim 5, the deviation predicting means includes:
At least the engine speed or the opening of the exhaust gas recirculation control valve
On the basis of the above, the prediction value of the deviation is set.

That is, the opening degree of the exhaust gas recirculation control valve (in other words,
If the exhaust gas recirculation rate is large, the information
The change is larger and the exhaust recirculation control valve opening is the same.
(Exhaust gas recirculation rate), but the engine speed is low
The more the information related to the cylinder pressure changes, the greater the change
The change in information that correlates with the in-cylinder pressure increases as the rolling speed increases.
It becomes smaller during such a deceleration fuel cut during deceleration.
Of information correlated to the in-cylinder pressure associated with the switching of the gas recirculation control valve
Engine speed or exhaust gas return that has a relatively large effect on changes
Consider at least one of the flow control valve openings
By doing so, the diagnostic accuracy can be effectively improved.
Wear. Considering both characteristics will improve the diagnostic accuracy.
Needless to say, it can be further increased, which is desirable.
According to the sixth aspect of the present invention, each sampled
Based on information correlated with the in-cylinder pressure in the state.
A configuration including a diagnosis unit for determining the presence or absence of a failure in the reflux device
The more the number of diagnoses in the diagnostic means,
Exhaust gas recirculation control when the valve is forcibly opened by the forcible opening / closing means
A mechanism for changing the opening degree of the valve to increase the opening degree of the valve is provided.
It was successful.

According to such a configuration, as in claim 4,
In the early stage of diagnosis (when the number of diagnosis is small),
(The engine braking force decreases or changes)
Exhaust gas recirculation forcibly opened at the time of failure diagnosis to prevent as much as possible
Keep the control valve opening small and prioritize ensuring drivability
On the other hand, as the number of diagnoses increases,
Increase the opening of the exhaust gas recirculation control valve, which is forcibly opened during diagnosis
To check for failure diagnosis while gradually sacrificing drivability.
Try to gradually increase the output accuracy. In the invention according to claim 7, the diagnostic means is provided with a sampling means.
In the open control state of the exhaust gas recirculation control valve
The information correlated with the cylinder pressure and the cylinder pressure in the closed control state
Deviation calculating means for calculating a deviation from the information
By comparing the average value of the deviation calculated by the means with a predetermined value,
Diagnosis based on deviation to determine whether the exhaust gas recirculation device has a failure
And disconnecting means.

According to this configuration, the information correlated with the in- cylinder pressure is obtained.
By calculating the average value of the deviations of the
Improve diagnostic accuracy by eliminating the effects of deviations
Can be made. In the invention according to claim 8, the deviation
Before the diagnosis means determines the average value of the deviations.
Change the dead zone of diagnosis according to the number of data of the deviation
The configuration was adopted.

According to this configuration, the average value of the deviation is calculated as
The larger the number of deviation data at the time of calculation, the more the average value
As reliability increases, the dead zone for diagnosis can be increased according to the number of data.
To make a false judgment when reliability is low.
Avoiding, while collecting data and increasing reliability
Thus, a highly accurate determination can be made. According to the ninth aspect of the present invention, the in-cylinder sampled by the sampling means.
The information that correlates to the pressure is the in-cylinder pressure in the specified crank angle range.
It is configured to be an integrated value of information correlated with.

As described above, the sampling means is used for sampling.
As information correlated with the in-cylinder pressure to be
The integrated value of the information correlated with the in-cylinder pressure within the
With a simple configuration, the noise
Minimizes the influence of noise and minimizes information related to in-cylinder pressure with high accuracy
Can be sampled. According to the tenth aspect of the present invention, the in-cylinder sampled by the sampling means is provided.
The information correlated to the pressure is the in-cylinder pressure at the specified crank angle position.
It is configured to be information correlated with.

As described above, the sampling means is used for sampling.
As information correlated with the in-cylinder pressure to be
Sampling information correlated with in-cylinder pressure at the angle position
With this configuration, the configuration can be extremely simplified and can be correlated with the in-cylinder pressure.
Information can be sampled.

[0019]

[0020]

Embodiments of the present invention will be described below. In FIG. 2 showing a system configuration of an embodiment, an exhaust manifold 2 and an intake manifold 3 of an engine 1 are shown.
The exhaust gas recirculation passage 4 is provided so that the exhaust gas recirculation passage 4 is opened and closed by an EGR control valve 5 (exhaust gas recirculation control valve).

The EGR control valve 5 is a diaphragm type valve which is opened by applying a suction negative pressure of the engine against a biasing force of the coil spring in a 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 that is turned on and off by a control unit 8 is interposed in the negative pressure introduction 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. The reference numeral 10 indicates that the diaphragm is activated by the exhaust pressure and the manifold negative pressure,
This is a diaphragm type BPT valve that determines a negative pressure for controlling the R control valve 5.

The control unit 8 receives detection signals such as cooling water temperature, engine speed, intake air amount, etc. from respective sensors, and also receives on / off signals of an ignition switch, and discriminates them. The EGR control solenoid 9 based on engine operating conditions
On / off control. The control unit 8 receives an in-cylinder pressure (one of information correlated with the in-cylinder pressure) detection signal from an in-cylinder pressure sensor 11 as in-cylinder pressure correlation information detecting means. The in-cylinder pressure sensor 11 is a ring-shaped sensor including a piezoelectric element and mounted as a washer of the ignition plug 12 as disclosed in Japanese Utility Model Laid-Open No. 63-17432. When the ignition plug 12 receives the in-cylinder pressure and lifts to change the set load, a signal corresponding to the in-cylinder pressure is output.

However, in addition to the type mounted as the washer of the ignition plug 12 as described above, a type that detects the in-cylinder pressure by directing the sensor unit directly into the combustion chamber may be used.
In this embodiment, the idle switch (I) capable of detecting at least a substantially fully closed state of the throttle valve 6 is detected.
A DLE / SW 13 is provided, and a signal from the idle switch 13 is input to the control unit 8.

The control unit 8 in the present embodiment performs a failure diagnosis of the exhaust gas recirculation device having the above-described configuration based on the in-cylinder pressure detected by the in-cylinder pressure sensor 11 as shown in the flowcharts of FIGS. It has a function to perform. In the present embodiment, the functions of the diagnostic means, the forced opening / closing means, the deceleration fuel cut detecting means, the sampling means, the deviation calculating means, and the diagnostic means based on the deviation are as shown in the flowcharts of FIGS. The control unit 8 is provided as software.

The flowchart of FIG. 3 shows the main routine of the diagnosis control according to the present embodiment. First, in step 1 (S1 in the figure, the same applies hereinafter), the engine speed Ne and the basic fuel injection amount are set. Tp, cooling water temperature T
Information such as W, throttle valve opening TVO, and vehicle speed VSP is read.

The basic fuel injection amount Tp is a fuel amount calculated by the control unit 8 as a value proportional to the cylinder intake air amount, and is a value representative of the engine load. In step 2, it is determined whether a predetermined diagnosis permission condition is satisfied. Here, the fuel cut during deceleration operation is a condition for satisfying the predetermined diagnostic condition. For example, during fuel cut and IDLE / S
W (idle switch) is ON (throttle valve is almost fully closed)
Can be determined based on the fact that This is to distinguish it from a so-called over-rev or a fuel cut (limiter) for limiting the vehicle speed. Turning ON / OFF the EGR during fuel cut by such a limiter deteriorates drivability. This is because it is difficult to perform a failure diagnosis because the operating state is in an unstable region, and it is desirable not to perform the diagnosis in such a region.

At the time of deceleration, the exhaust gas recirculation is cut off (the EGR control valve 5).
Is to be closed. See FIG. 8). If YES, proceed to Step 3; if NO, return.
In step 3, in the exhaust gas recirculation cut state, FIG.
The data sampling is performed by executing the subroutine A shown in the flowchart of FIG.

In step 4, the in-cylinder pressure data PIFC obtained in step 4 is set in PIFC1 as data in the exhaust gas recirculation OFF control state. In step 5, the EGR control valve 5 is forcibly opened at a predetermined opening through the control of the EGR control solenoid 9 to recirculate exhaust gas. It is preferable that the predetermined opening is gradually increased according to the number of diagnoses as shown in FIG. 6 (forcible opening / closing opening changing means) . That is, in the initial stage of the diagnosis start (when the number of diagnoses is small), the drivability is deteriorated (for example, by opening the EGR control valve 5, the intake resistance is reduced, the pumping loss is reduced, and the engine braking force is reduced or changed. The EGR control valve 5, which is forcibly opened at the time of failure diagnosis, has a small opening, and priority is given to ensuring operability, and the failure is detected with relatively low detection accuracy. On the other hand, as the failure cannot be detected and the number of diagnoses increases, the opening of the EGR control valve 5, which is forcibly opened at the time of failure diagnosis, is increased to detect the failure while gradually sacrificing the drivability. Gradually increase the accuracy. As a result, it is possible to increase the detection accuracy of the failure diagnosis while minimizing the deterioration in drivability.

That is, if the EGR control valve 5 is suddenly opened with a large opening to diagnose the failure without any failure, the operability (engine braking force, etc.) becomes unnecessary for the failure diagnosis. As described above, such an inconvenience can be minimized by gradually increasing the opening as the number of diagnoses increases, as described above.

Note that foot brake (or exhaust)
When the vehicle is operated or downshifted, in order to obtain a degree of deceleration that meets the driver's request, that is, to prevent the driver from feeling uncomfortable or to ensure safety, It is desirable to cancel the diagnostic control so that the engine braking force caused by opening and closing the EGR control valve 5 does not decrease or increase.

Then, in the next step 6, it is determined whether or not a predetermined time has elapsed since the exhaust gas recirculation ON, and the exhaust gas recirculation ON state is stabilized before proceeding to step S7.
In step 7, sampling of the in-cylinder pressure in the exhaust gas recirculation ON state is performed by subroutine A shown in the flowchart of FIG.
Is performed. In step 8, the in-cylinder pressure data PIFC obtained in step 7 is set in PIFC2 as data in the exhaust gas recirculation ON control state.

At step 9, control is performed to return the exhaust gas recirculation which has been ON for diagnosis to the exhaust gas recirculation OFF state.
In step 10, the in-cylinder pressure data PIFC1, PIFC
The presence or absence of an abnormality in the exhaust gas recirculation device is diagnosed based on FC2. Specifically, as shown in detail in the flowchart of FIG. 5, basically, the in-cylinder pressure (compression pressure of the in-cylinder working gas; compression pressure) during fuel cut changes depending on the presence or absence of exhaust gas recirculation. The diagnosis is performed based on

That is, the exhaust gas recirculation is actually changed to O
When the NGR is turned off and the EGR control valve 5 is normally opened, even if the throttle valve 6 is almost fully closed, a relatively large amount of air is introduced into the cylinder via the exhaust passage 3 and the exhaust recirculation passage 4. , The compression pressure (compression pressure, in other words, PIFC2) in the cylinder becomes relatively large, whereas if the EGR control valve 5 is normally closed,
When the throttle valve 6 is substantially fully closed and the exhaust gas recirculation passage 4
Therefore, it becomes difficult to introduce air into the cylinder, so that the compression pressure (compression pressure, in other words, PIFC1) in the cylinder becomes relatively small.

Therefore, the in-cylinder pressure data PIFC1, PFC
If the EGR control valve 5 is operating normally, the IFC 2 should have a deviation greater than or equal to a predetermined value. This will be a significant indication that it is not being controlled. Also, since the fuel is being cut, combustion is not performed in the cylinder and the exhaust pressure is low, so that the combustion does not affect the detected cylinder pressure. Therefore, a failure based on the deviation between the cylinder pressure data PIFC1 and PIFC2. Diagnosis is highly accurate. In step 11,
It is determined whether or not OK or NG has been determined as the diagnosis result, and this routine is repeated until one of the determination results is determined. Here, the subroutine A for data sample executed in the above-described steps 4 and 8 will be described with reference to the flowchart of FIG.

In step 21, the output of the crank angle sensor and the output of the in-cylinder pressure sensor 11 are read. In step 22, it is determined whether or not the crank angle is equal to or greater than a predetermined angle a ° CA (crank angle). If YES, the process proceeds to step 23. If NO, the process is repeated until the crank angle becomes equal to or more than the predetermined angle a ° CA.

In step 23, the cylinder pressure Pi detected by the cylinder pressure sensor 11 is sampled. Step 24
Then, the in-cylinder pressure Pi sampled in step 24 is
Are sequentially integrated, and the integrated value PIE is updated (PIE = P
IE + Pi). In step 25, it is determined whether or not the crank angle is equal to or greater than the predetermined angle b ° CA. If YES, the sampling of the in-cylinder pressure Pi is terminated, and the routine proceeds to step 26. In the case of NO, the crank angle is equal to the predetermined angle b ° CA
Repeat until later.

In step 26, the integrated value PIE is calculated as
This is set to the in-cylinder pressure data PIFC, and the flow ends. The predetermined angle a ° CA is set before the top dead center, and the predetermined angle b ° CA is set after the top dead center, so that the peak value of the in-cylinder pressure (compression pressure) is included in the integrated region. Is preferable in terms of diagnostic accuracy and the like. For example, if the position near the top dead center (maximum compression pressure position) is included, the in-cylinder pressure exceeds the maximum pressure detected by the in-cylinder pressure sensor 11 and the diagnostic accuracy is reduced. In this case, the position near the top dead center does not have to be included in the predetermined crank angle range for sampling the in-cylinder pressure, and the crank angle range for performing the failure diagnosis of the present invention based on the presence or absence of exhaust gas recirculation may be appropriately set. The good thing is, of course. If the storage capacity and the calculation speed do not matter, the predetermined crank angle range in which sampling is performed may be the entire crank angle range in one cycle. Next, the subroutine B for failure diagnosis executed in step 12 will be described with reference to the flowchart of FIG.

In step 31, the in-cylinder pressure data PIFC2 (integrated value within a predetermined crank angle range) obtained in the exhaust gas recirculation ON control state and the in-cylinder pressure data PIFC2 (predetermined crank angle) obtained in the exhaust gas recirculation OFF control state are determined. Deviation of the integrated value within the range) and ΔPIFC (ΔPIFC = PIFC)
2-PIFC1) is determined. In step 32, a target deviation is calculated. The target deviation is a predicted value of the deviation ΔPIFC obtained when the exhaust gas recirculation control device is normal, and is the in-cylinder pressure data PIFCP obtained when the exhaust gas recirculation is OFF.
1 and the exhaust gas recirculation rate when it is turned on (the opening degree of the EGR control valve 5).

This is because, as the exhaust gas recirculation rate (opening of the EGR control valve 5) increases, the in-cylinder pressure change caused by forcibly opening and closing the EGR control valve 5 increases. However, if the in-cylinder pressure at that time (compression pressure increases substantially in proportion to the engine rotation speed) is large, the in-cylinder pressure change due to the presence or absence of exhaust gas recirculation becomes small (see FIG. 7).
It is set based on the exhaust gas recirculation rate and the in-cylinder pressure data PIFC1. The in-cylinder gas temperature changes depending on the engine temperature, the outside air temperature, and the gas temperature in the exhaust passage, and the in-cylinder pressure changes.

For example, when a so-called ISC valve or the like for introducing fresh air into the cylinder by bypassing the throttle valve 6 is provided, even if the opening of the EGR control valve 5 is kept constant, the opening of the ISC valve is maintained. Degree (bypass resistance)
Changes, the exhaust gas recirculation amount changes with the change, and consequently, the compression pressure changes to lower the diagnostic accuracy. Therefore, the target deviation should be set in consideration of the opening degree of the ISC valve and the like. Is preferred. Alternatively, while the ISC valve is open,
Failure diagnosis may be prohibited. In step 33, the average value obtained by dividing the deviation ΔPIFC by the target deviation is calculated as the EGR flow rate decrease rate DLTPN.

DLTPN = 1 / n · Σ (ΔPIFC / Target Deviation) That is, every time the deviation ΔPIFC is obtained, it is divided by the target deviation at that time and standardized, in other words, the deviation ΔPIFC
In this case, the influence of the difference in the engine speed and the exhaust gas recirculation rate at the time of obtaining is eliminated, and the average value of the standardized values is obtained. In step 34, a determination value (NG determination value and OK determination value) of the EGR flow rate reduction rate DLTPN is set according to the sample number n of the deviation ΔPIFC when the EGR flow rate reduction rate DLTPN is obtained. The characteristics of the determination value setting will be described later.

In step 35, it is determined whether or not the EGR flow rate decrease rate DLTPN is equal to or less than an NG determination value.
When DLTPN is equal to or less than the NG determination value, the routine proceeds to step 36, where it is determined whether an abnormality has occurred in the exhaust gas recirculation control device. In other words, if the change in the in-cylinder pressure due to the compression pressure due to the ON / OFF of the exhaust gas recirculation is smaller than in the normal state, it is determined that the exhaust gas recirculation amount has not changed in response to the control, and the occurrence of an abnormality is determined. Is what you do.

When it is determined that an abnormality has occurred, the result of the determination is warned by lamp display or the like, and
It is preferable to stop the subsequent exhaust gas recirculation control. On the other hand, when it is determined in step 35 that DLTPN exceeds the NG determination value, the process proceeds to step 37, where the DLTP
It is determined whether or not N is equal to or greater than the OK determination value.

Here, if the DLTPN is equal to or larger than the OK determination value, the routine proceeds to step 38, where it is determined that the exhaust gas recirculation control device is normal. If the DLTPN is less than the OK determination value, that is, if the DLTPN is not small enough to be recognized as abnormal but not large enough to be recognized as normal, the process proceeds to step 39 and the diagnosis is suspended.

Therefore, if the NG determination value is exceeded and the
The range less than the determination value is a dead zone for diagnosis, and in step 34, the deviation Δ
The OK judgment value is made larger and the NG judgment value is made smaller so that the smaller the number of PIFC samples n is, the wider the dead zone becomes. This is because when the number n of samples of the deviation ΔPIFC is small, the reliability of the DLTPN is low, and it is premature to make a final decision. Therefore, the diagnosis is suspended except when it is clearly recognized as abnormal or normal. ,
When the reliability of the DLTPN is increased by increasing the number of samples n, the dead zone sandwiched between the OK determination value and NG is narrowed so that one of the determination results is obtained.

FIG. 8 is a time chart showing the state of the EGR failure diagnosis in the above-described embodiment. By the way, in the present embodiment, the in-cylinder pressure Pi is sequentially integrated, and the failure diagnosis is performed using the integrated value PIE. However, a predetermined crank angle (for example, top dead center or the like) is described.
The failure diagnosis may be performed by using the in-cylinder pressure Pi in the above. Further, it is a matter of course that the failure diagnosis may be performed by using the indicated average effective pressure in the predetermined crank angle range instead of the in-cylinder pressure Pi.

In this embodiment, a diaphragm-type EGR control valve 5 provided in the exhaust gas recirculation passage 4 and an EGR control solenoid 9 for controlling the introduction of the engine suction negative pressure to the valve 5 are provided. However, it is clear that an exhaust gas recirculation device having a configuration in which a solenoid valve is directly interposed in the exhaust gas recirculation passage 4 may be used.

For diagnosis, exhaust gas recirculation is forced to O
ON / OFF of exhaust gas recirculation for N ・ OFF
The exhaust gas recirculation amount may be gradually changed to a predetermined opening degree in order to avoid occurrence of a sudden change in torque accompanying the above.
By the way, the present invention has been described as performing the failure diagnosis by detecting the in-cylinder pressure.
Pressure sensor for detecting the intake pressure (information correlated with the in-cylinder pressure) in the intake manifold 3 on the downstream side of the connection between the intake manifold 3 and the intake manifold 3, and the intake pressure difference between before and after opening and closing the EGR control valve during deceleration fuel cut It is also possible to make a failure diagnosis of the exhaust gas recirculation device based on the above. That is, EG
When the R control valve is opened, if it is normal, the exhaust gas recirculation is introduced into the intake manifold 3 and the intake negative pressure changes to the atmospheric pressure side. However, if the EGR valve is closed due to a failure or the like, Has a characteristic that the intake negative pressure remains low because the exhaust gas recirculation is not introduced into the intake manifold 3. Therefore, if this characteristic is used, the fuel cut during deceleration can be performed in the same manner as the above-described case based on the in-cylinder pressure. It is possible to diagnose the failure of the exhaust gas recirculation device based on the intake pressure difference before and after opening and closing the middle EGR control valve.

[0050]

As described above, according to the first aspect of the present invention, based on the information correlated with the in-cylinder pressure when the exhaust gas recirculation control valve is forcibly opened and closed during deceleration fuel cut. Since the failure diagnosis of the exhaust gas recirculation device is performed,
Compared to the conventional method of diagnosing a malfunction of the exhaust gas recirculation system by forcibly opening and closing the exhaust gas recirculation control valve during steady-state operation, it is possible to suppress torque shock etc. due to combustion fluctuation so as not to deteriorate operating performance as much as possible. And without deteriorating the exhaust performance, and at the same time as the actual in-cylinder pressure.
The value obtained by dividing the deviation of the information correlated with
The deviation can be standardized by comparing the
Conditions (engine speed, opening of exhaust recirculation control valve, etc.)
Make a diagnosis by comparing with a certain predetermined value
be able to.

According to the second aspect of the present invention, the deceleration fuel
When the exhaust gas recirculation control valve is forcibly opened and closed during cutting
Fault diagnosis of exhaust gas recirculation system based on information correlated with in-cylinder pressure
During the normal operation as in the past.
The exhaust gas recirculation control valve is forcibly opened and closed, and
Torque caused by fluctuations in combustion
So that driving performance can be minimized.
And not degrade exhaust performance.
And the average value of the deviation of the information correlated with the in-cylinder pressure
The deviation of the information deviation that correlates with the in-cylinder pressure
The influence can be eliminated and the diagnostic accuracy can be improved.
According to the third aspect of the present invention, an average value of the deviation is obtained.
The larger the number of deviation data at the time of
As the reliability increases, the dead zone of the diagnosis changes according to the number of data.
To avoid erroneous judgments when reliability is low.
While avoiding, when the number of data gathers and reliability increases
High-precision determination can be performed. According to the fourth and sixth aspects of the present invention, in the early stage of the diagnosis, priority is given to ensuring drivability.
While performing fault detection, the number of diagnoses increases
Detects failure diagnosis while gradually sacrificing drivability
Accuracy was gradually increased, so driving performance was minimized.
Increasing the accuracy of failure diagnosis detection while suppressing deterioration
It becomes possible.

[0052] As in the embodiment described in claim 5, a relatively large engine rotational speed or the exhaust gas recirculation is affected by changes in the information that correlates the in-cylinder pressure caused by the opening and closing switching of the exhaust gas recirculation control valve in deceleration fuel cut If at least one of the opening degrees of the control valve is considered, the accuracy of diagnosis can be effectively improved.

According to the seventh aspect of the present invention, the in- cylinder pressure
By calculating the average value of the deviation of the correlated information,
Eliminating the influence of the deviation of the correlated information,
The degree can be improved. According to the invention as set forth in claim 8, the data of the deviation when calculating the average value of the deviation
The higher the number, the more reliable the average value is.
The dead zone of the diagnosis is changed according to the
Data collection while avoiding erroneous judgments
High-precision judgment when reliability is improved
And

According to the ninth aspect of the invention, a simple structure is provided.
Noise and other effects as much as possible
Information can be sampled with high accuracy. According to the tenth aspect of the present invention , the cylinder has a very simple configuration,
Information correlated to the internal pressure can be sampled.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of the invention according to claim 1;

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

FIG. 3 is a flowchart illustrating a main routine of diagnostic control according to the embodiment.

FIG. 4 is a flowchart (subroutine A) showing a state of in-cylinder pressure sampling in the embodiment.

FIG. 5 is a flowchart (subroutine B) showing a state of diagnosis using in-cylinder pressure data in the embodiment.

FIG. 6 is a view for explaining the relationship between the number of diagnoses and the opening degree of the EGR control valve at the time of forced opening.

FIG. 7 is a view for explaining the relationship between the engine speed and ΔPIFC.

FIG. 8 is a time chart showing a state of failure diagnosis according to the present invention.

[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 13 Idle switch

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-6-288303 (JP, A) JP-A-2-9937 (JP, A) JP-A-7-158499 (JP, A) JP-A-4- 175450 (JP, A) JP-A-5-52707 (JP, A) JP-A-3-1254 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02M 25/07 550 F02M 25/07 570 F02D 45/00 368

Claims (10)

(57) [Claims] 1. A failure diagnosis device for an exhaust gas recirculation device of an internal combustion engine for recirculating a part of the engine exhaust gas to an intake system of the engine through an exhaust gas recirculation passage provided with an exhaust gas recirculation control valve. In-cylinder pressure correlation information detecting means for detecting information correlated with the internal pressure, forcible opening / closing means for forcibly opening / closing the exhaust gas recirculation control valve, and deceleration fuel cut detection means for detecting during engine deceleration fuel cut During the deceleration fuel cut, the exhaust gas recirculation control valve is opened and closed via the forcible opening / closing means, and the in-cylinder pressure detected by the in-cylinder pressure correlation information detecting means in each of the open control state and the closed control state. Sampling means for sampling correlated information; and exhaust gas sampled by the sampling means.
Information related to in-cylinder pressure and closing of the flow control valve in the open control state
Bias to calculate the deviation from the information correlated with the in-cylinder pressure in the controlled state.
Difference calculating means, and a deviation prediction for setting a predicted value of the deviation according to operating conditions
Means, and the deviation calculated by the deviation calculation means is used as the deviation prediction means.
Compare the value divided by the predicted value set in
Therefore, the deviation that determines whether the exhaust gas recirculation device has a failure
Diagnostic means for an exhaust gas recirculation device for an internal combustion engine, the diagnostic device comprising: 2. An exhaust gas recirculation control valve intervenes a part of the engine exhaust gas.
Recirculated to the intake system of the engine through the exhaust gas recirculation passage
In- cylinder pressure correlation information , which is a failure diagnosis device for an exhaust gas recirculation device of a fuel engine and detects information correlated with the in-cylinder pressure of the engine.
Detecting means and a forced opening / closing means for forcibly opening / closing the exhaust gas recirculation control valve
Stage and deceleration fuel cut to detect during engine deceleration fuel cut
Detecting means, during deceleration fuel cut, through the forced opening and closing means,
Open and close the exhaust gas recirculation control valve, open control state and close control state
The in-cylinder pressure correlation information detecting means in each state of
Sampling information correlated with the in-cylinder pressure detected by
Sampling means; and the exhaust gas sampled by the sampling means.
Information related to in-cylinder pressure and closing of the flow control valve in the open control state
Bias to calculate the deviation from the information correlated with the in-cylinder pressure in the controlled state.
Difference calculating means, and a deviation prediction for setting a predicted value of the deviation according to operating conditions
Means, the average value of the deviation calculated by the deviation calculation means and the deviation
The exhaust gas return is compared with a predicted value set by the prediction means.
The trouble diagnosis device for the exhaust gas recirculation apparatus for an internal combustion engine that is configured to include a diagnostic means according to determined deviations whether a fault of the flow device. 3. The diagnostic means according to the deviation, comprising:
According to the number of data of the deviation when calculating the average value,
The fault diagnosing device for an exhaust gas recirculation device for an internal combustion engine according to claim 2, wherein the dead zone is changed . 4. The number of diagnoses in said diagnostic means based on said deviation
Increases, the forcible opening and closing by the forcible opening and closing means
Forced opening / closing opening change method to increase the opening of the exhaust gas recirculation control valve
4. The method according to claim 1, wherein a step is provided.
6. A failure diagnosis device for an exhaust gas recirculation device for an internal combustion engine according to any one of the above . 5. The apparatus according to claim 1, wherein said deviation predicting means includes at least engine rotation.
The deviation based on the speed or the opening degree of the exhaust gas recirculation control valve.
5. The method according to claim 1, wherein a predicted value is set.
A failure diagnosis device for an exhaust gas recirculation device for an internal combustion engine according to any one of the preceding claims . 6. An exhaust gas recirculation control valve is provided for part of the engine exhaust gas.
Recirculated to the intake system of the engine through the exhaust gas recirculation passage
In- cylinder pressure correlation information , which is a failure diagnosis device for an exhaust gas recirculation device of a fuel engine and detects information correlated with the in-cylinder pressure of the engine.
Detecting means and a forced opening / closing means for forcibly opening / closing the exhaust gas recirculation control valve
Stage and deceleration fuel cut to detect during engine deceleration fuel cut
Detecting means, during deceleration fuel cut, through the forced opening and closing means,
Open and close the exhaust gas recirculation control valve, open control state and close control state
The in-cylinder pressure correlation information detecting means in each state of
Sampling information correlated with the in-cylinder pressure detected by
Sampling means, and in-cylinder pressure in each of the sampled states.
Whether the exhaust gas recirculation device has a failure based on the correlated information
Diagnostic means for determining whether the number of diagnoses in the diagnostic means increases,
The opening degree of the exhaust gas recirculation control valve when the valve is forcibly opened by the
A failure diagnosis device for an exhaust gas recirculation device for an internal combustion engine, comprising: a forced opening / closing opening degree changing means for increasing the size . 7. The exhaust gas sampled by the sampling means , wherein the diagnostic means comprises :
Information related to in-cylinder pressure and closing of the flow control valve in the open control state
Bias to calculate the deviation from the information correlated with the in-cylinder pressure in the controlled state.
Difference calculating means, the average value of the deviation calculated by the deviation calculating means and a predetermined value
In comparison, the bias for determining whether or not the exhaust gas recirculation device has failed is determined.
7. The failure diagnosis device for an exhaust gas recirculation device for an internal combustion engine according to claim 6 , wherein the failure diagnosis device includes a diagnosis means based on a difference . 8. The diagnostic means based on the deviation, comprising:
According to the number of data of the deviation when calculating the average value,
The fault diagnosing device for an exhaust gas recirculation device for an internal combustion engine according to claim 7, wherein the dead zone is changed . 9. The sampling means performs sampling.
The information correlated with the in-cylinder pressure is
A contract value characterized by being an integrated value of information correlated with the internal pressure.
The failure diagnosis device for an exhaust gas recirculation device for an internal combustion engine according to any one of claims 1 to 8 . 10. The apparatus according to claim 10, wherein said sampling means performs sampling.
Information that correlates to the in-cylinder pressure
2. The information related to the in-cylinder pressure.
The failure diagnosis device for an exhaust gas recirculation device for an internal combustion engine according to any one of claims 8 to 8 .