JPH03138444A - Trouble diagnosing device for egr device - Google Patents

Abstract

PURPOSE:To discriminate the operation function of an EGR device, including the deterioration of a system with a high precision, by judging the EGR region from the engine revolution speed and the engine load and diagnosing the trouble of function when the detected temperature of the flowing gas is higher than a previously set comparison standard value. CONSTITUTION:In an EGR device, a portion of the exhaust gas in the exhaust pipe 3 of an internal combustion engine 1 is allowed to recirculate into an intake pipe 2 through the pipes 4 and 5 between which an EGR valve 6 is interposed midway, and a temperature sensor 8 for detecting the temperature of the recirculation gas is installed on the downstream side (desirably in the vicinity of a valve body 7) of the EGR valve 6. The detection signal of the temperature sensor 8 is inputted into a computer 11 through a signal conditioner 10 built in a module 9. Further, into the computer 11, the engine operation information (e.g. engine revolution speed, car speed, intake air quantity, etc.) is inputted, and the comparison standard value is set on the basis of the operation information. When the temperature detection value is larger than a comparison standard value, the trouble of function is judged, and a display device 14 is operated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for diagnosing whether or not the function of an exhaust gas recirculation device (hereinafter referred to as an EGR device) of an internal combustion engine is operating normally.

[Conventional technology]

The harmfulness of nitrogen oxides (NOx) in exhaust gas has become even stronger, and the emission regulations for automobiles have been reduced to 0.4 from 1990.
This is the reason behind the implementation of the limit value of g/ml.

Under these circumstances, exhaust recirculation equipment (
It is well known that an EGR device (hereinafter referred to as an EGR device) is effective.

However, if the function of this EGR device malfunctions or is intentionally stopped, the amount of NOx in the exhaust will naturally increase;
This phenomenon has the troublesome aspect of being undetectable from those around you.

As a means of detecting this malfunction, there has conventionally been a method of measuring NOx concentration at a dealer or the like, but this method requires an exhaust gas analyzer and cannot easily diagnose the function of the EGR device.

In addition, as a method for diagnosing this EGR device while mounted on a vehicle, as shown in Japanese Patent Application Laid-Open No. 62-282950, ``Failure Diagnosis Device for rEGR Device'', the EGR device can be diagnosed based on the correlation between changes in EGR temperature and acceleration conditions of the vehicle. Something that performs functional diagnosis is oscillating.

However, according to this method, the failure mode of the EGR device,
In particular, there have been problems in that it is not possible to diagnose a failure mode (open stick phenomenon) in which the valve body that opens and closes the circulation passage is stuck open.

There is also a method of monitoring the operation by providing means for detecting the position of the valve body, such as an open/close switch or a position sensor, when the valve body is stuck.

Due to harsh environmental conditions such as vibration, the reliability of position detection means
There are problems with durability, and the connection between the valve body and the position detection means becomes complicated and expensive.

[Problem to be solved by the invention]

The object of the present invention is to eliminate the drawbacks of the prior art described in item 2 and to provide a device that accurately identifies the operational functions of an EGR device, including system deterioration, while being mounted on a vehicle, and diagnoses the exhaust gas purification function. There is a particular thing.

[Means to solve the problem]

The above object can be achieved by monitoring the temperature of the recirculation gas passage of the EGR device, that is, the temperature change downstream of the valve that limits the flow rate of the recirculation gas, as a representative of the functional operation of the EGR device.

[Effect]

That is, the temperature at the above-mentioned portion changes randomly depending on the flow rate of the recirculating gas (determined by the operating state of the engine). Therefore, if a failure occurs in the function of the EGR device, the temperature of this part will operate slowly and have no organic relationship with the operating state of the engine, so the EGR
It is possible to appropriately determine whether the R device is operating normally or abnormally without malfunction.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a block diagram of a failure diagnosis device for an EGR device, which is an embodiment of the present invention, and the EGR valve 6 is connected to a portion of each of the exhaust pipe 3 and intake pipe 2 of the engine 1 through pipes 5 and 4. There is. This EGR valve recirculates a part of the exhaust gas to the intake side according to the engine operating condition, reducing NOx in the exhaust gas.
The purpose is to reduce the E C,'
The recirculation amount of R is limited by the amount of movement of the valve body 7 of the EGR valve provided in the middle of the recirculation passage, and this amount of movement is limited by the pressure source generated by the throttle valve 15 provided on the second side of the intake pipe. It is configured to be carried out via transducer 16.

In the figure, on the downstream side of the EGR valve (located on the intake side with respect to the valve body 7, preferably near the valve body) is a temperature sensor 8 (hereinafter referred to as a TEOR sensor) that detects the temperature of the recirculating gas. has been established.

The signal from the TEGR sensor is connected to a signal conditioner 10 built into the module 9, and this output signal is input to a computer 11. On the other hand, the computer contains the operating information 12 of the engine 1 described above (for example, engine rotation speed (N), cooling water temperature (Tw)).

Vehicle speed (Vsp) r Power supply voltage (VB), intake air amount (Q
^), as well as an idle switch (Idle SW) and a full open switch (WOT) linked to the throttle valve 15 described above.
SW), etc.] are also input.

The output from the computer is connected to a display device 14 via an amplifier 13, and is configured to display diagnostic information of the EGR device corresponding to the engine condition.

FIG. 2 shows an example of the relationship between the EGR recirculation rate (ratio of intake air amount and exhaust gas recirculation amount) of an internal combustion engine, engine speed, and engine load.

A, B, C, and D, respectively, from the region with the highest reflux rate.

NOx generally emitted from engines, divided in the order of E
Increase the EGR rate for the operating region where many
It is well known that measures are taken to suppress x formation. The magnitude of this EGR rate has a strong correlation with the temperature of the EGR recirculating gas described above, and when the EGR rate is high, the temperature of the recirculating gas also becomes high.

FIG. 3 shows an example of a time chart showing the operating state of the engine and the operation of the EGR device in which an experiment was conducted using the apparatus of the embodiment shown in FIGS. 1 and 2 described above. 4
The chart in the book shows vehicle speed from the bottom.

The engine speed, the temperature of the recirculating gas (the signal from the TEOR sensor 8), and the control pressure (the signal from the transducer 16) are shown.

From this figure, it was verified that the EGR recirculation gas temperature TEGR changes in response to changes in the control pressure depending on the operating state of the engine.

Furthermore, when looking at the vehicle speed, engine speed, and temperature of the recirculated gas, they exhibit a mode that closely follows changes in vehicle speed (
It was also confirmed that the temperature of the recirculating gas had a delay time of ΔVsp/t 5 m), and it was also found that the change in the recirculating gas temperature with respect to the change in the control pressure had a time of α.

From these results, it was discovered in the above-mentioned Japanese Patent Application Laid-Open No. 62-282950 that failure diagnosis of the EGR system was made possible by monitoring the temperature of the EGR recirculated gas corresponding to the operating conditions of the engine.
No., Utility Model Application Publication No. 1985-1.85456, etc., as disclosed in detail.

FIG. 4 is a flowchart for diagnosing an open stick failure in the EGR device shown in FIG. 1, and an embodiment in which the diagnosis is performed in fixed time processing (task 80 ms) will be described in detail.

When the time processing of step 100 is entered, first step 300
It is determined whether or not the open stick flag is set, and if YES, the process moves to step 307, where the warning lamp is lit and the display device 14 shown in FIG. 1 is driven. On the other hand, if the result of step 300 is No, step 30
Move to 1.

In step 301, in order to determine whether the engine conditions are appropriate for performing diagnostic processing, the power supply voltage Vn is set to a desired value VBIO (for example, greater than or equal to IOV), and the engine temperature Tw is set to a desired value Tw.
It is determined whether or not the temperature is higher than oo (for example, cooling water temperature 60° C.). Here, T w < T w e o, or VB < V
When it is BIO, it is assumed that it is outside the diagnostic conditions and the process moves to step 130.
Wait for the next diagnostic processing time. On the other hand, Vn≧V B t o
At the same time, when the condition Tw≧Twoo is satisfied, the process moves to step 302 and a failure diagnosis process for the EGR device is started.

In step 302, the EGR rate range determined from the engine speed and engine load described in FIG. 2 is determined. Here, the areas are A and B in FIG.

In the case of C or D, the process moves to step 303, where the EGR function operation under active conditions is diagnosed based on the relationship between the engine operating conditions and the temperature of the recirculated gas, and then step 1 is performed.
Move to 30. The diagnostic routine of step 303 is disclosed in, for example, Japanese Patent Laid-Open No. 62-282950.

When the result of step 302 is in the region E shown in FIG. 2, the process moves to step 304, and after taking in the temperature TE (J) of the reflux gas, the process moves to step 305.

In step 305, a predetermined first comparison reference value TEO
R■ is compared with the temperature TEGR taken in step 304, and if TEoR<TEan@, it is assumed that there is no failure of the EGR device, and the process moves to step 130 to wait for the next time processing request.

When the result of step 305 is TEGR≧Tpat+69, the process moves to step 306. In step 306, EGR
After determining that there is an open stick error in the device, first setting a flag and performing storage processing in memory, step 307
Move to. Here, the stored open stick flag is held until a clearing process (not shown, for example, a memory power release process) is performed, and the clearing process is performed when the repair for the failure of the EGR device is completed.

In step 307, as described above, the warning lamp is lit to indicate the EGR device failure to the driver, and then
The configuration is configured to proceed to step 130.

As described above, according to this embodiment, the function of the EGR device can be accurately detected as a systematic failure of the system, and in particular, by separating the EGR rate region, open stick failure of the valve body of the EGR device can be reliably detected. has a detectable effect.

In the explanation, it is expressed as the first comparison reference value set TEcMD, but the same functions and effects can be obtained even with a plurality of reference values determined from the engine speed and the engine load.

Further, a similar function can be obtained even if a means for adding/subtracting an element of outside temperature (not shown) to the comparison reference value is provided.

〔Effect of the invention〕

According to the present invention, diagnosis of the functional operation of the entire system of the EGR device can be realized by monitoring the flow of the recirculating gas in the EGR passage as a repeated temperature operation, so there is a means for forcibly monitoring the EGR device. There is no need to use an electric EGR device, two mechanical EGR devices, etc., or regardless of differences between target engines
This has the effect of being able to diagnose failures, deterioration, etc. of the R device.

In addition, in both the actual vehicle state and the driver's unconscious state, E
Since a self-check of the GR device function is executed, the driver does not feel anxious or nervous.

Furthermore, according to the present invention, failures of all related equipment in the EGR system are also monitored by representing the above-mentioned temperature of the recirculating gas, thereby notifying the driver of NOx deterioration at the time of system failure and taking appropriate action. It has the effect that it can be used effectively to eliminate air polluting factors.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a failure diagnosis device for an EGR device showing an embodiment of the present invention, Fig. 2 is a regional distribution diagram of the EGll rate of the engine, and Fig. 3 is a diagram of the actual engine according to the embodiment shown in Fig. 1. FIG. 4 is a control flowchart of the embodiment shown in FIG. 1.

Claims (1)

[Claims] 1. Exhaust gas recirculation device for an internal combustion engine, comprising a passage for recirculating a part of exhaust gas into the intake air, a valve body for opening and closing the passage, and a means for measuring the temperature of the gas flowing through the passage. , comprising means for detecting the speed and load of the internal combustion engine, for determining an exhaust gas recirculation region from the engine speed and engine load, and determining the temperature detected by the circulating gas temperature measuring means at a predetermined first comparison reference value. A failure diagnosis device for an EGR device, characterized in that it diagnoses a functional failure when the problem is greater than that. 2. The failure diagnosis device for an EGR device according to claim 1, characterized in that the predetermined first comparison reference value has at least one value for engine speed and engine load. A failure diagnosis device for EGR equipment. 3. E characterized by providing means for detecting the temperature of the outside air of the internal combustion engine, adding or subtracting the detected outside air temperature to a predetermined first comparison reference value, and rewriting the comparison reference value.
Failure diagnosis device for GR equipment.