JPH05133283A - Failure diagnostic device for exhaust circulation device - Google Patents

Abstract

PURPOSE:To make an accurately judgement of failure of a device and improve reliability by detecting an opening of an auxiliary pneumatic control valve in an auxiliary pneumatic passage which bypasses a throttle valve of an intake passage, and correcting a measurement value of pressure fluctuation or the like in the intake passage according to the detected result. CONSTITUTION:In an exhaust circulation device, an auxiliary pneumatic control valve 4 is arranged in an auxiliary pneumatic passage 3 which bypasses a throttle valve 2 of an intake passage 1. An exhaust circulation passage 6 is provided for circulating a part of exhaust to the intake passage 1 on a downstream side of the throttle valve 2 when an exhaust circulation valve 5 connected to a valve closing means 7 is opened. A means 8 detects a pressure in the intake passage 1 on the downstream side of the throttle valve 2. A means 9 measures the pressure fluctuation. A means 10 judges failure by comparing the measurement value to a judgment value. In such a construction, an opening of the auxiliary pneumatic control valve 4 is detected by a means 11. The measurement value or the judgment value of the pressure fluctuation is corrected by a means 12 according to the detected opening.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a failure diagnostic device for an exhaust gas recirculation system for an internal combustion engine.

[0002]

2. Description of the Related Art An exhaust gas recirculation device (EGR device) for recirculating a part of exhaust gas into intake air has been widely put into practical use for the purpose of reducing NOx emitted from an internal combustion engine.

By the way, an exhaust gas recirculation valve (EGR valve) is provided in the exhaust gas recirculation passage of the exhaust gas recirculation device to set the exhaust gas recirculation amount according to the operating conditions of the engine. As a result, if the exhaust gas recirculation valve malfunctions or the exhaust gas recirculation passage is blocked, proper exhaust gas recirculation cannot be performed.

For this reason, the exhaust gas recirculation valve is forcibly closed during exhaust gas recirculation, the pressures in the intake passages before and after the exhaust gas recirculation valve are compared, and when the difference is small, a failure is determined and an alarm is issued. An apparatus has been proposed (see Japanese Patent Laid-Open No. 62-51746, etc.).

[0005]

However, in this conventional example, an auxiliary air control valve (an idle control valve or the like) is provided in a passage for guiding auxiliary air by bypassing the throttle valve of the intake passage.
In the engine provided with, even if there is no abnormality in the exhaust gas recirculation valve or the like, the pressure in the intake passage may not change so much before and after the exhaust gas recirculation valve is closed.

When the exhaust gas recirculation valve is closed, when the opening is originally small, the difference in pressure in the intake passage before and after that is small, but if the opening of the auxiliary air control valve is large at this time, intake air is before and after that. The pressure in the passage does not differ so much.

Therefore, when the opening degree of the auxiliary air control valve is large, there is a problem that it is easy to make a failure determination.

Further, since the pressure in the intake passage varies depending on the opening of the auxiliary air control valve, there is a problem that the determination cannot be performed accurately.

The object of the present invention is to solve such a problem.

[0010]

According to the present invention, as shown in FIG. 1, an auxiliary air control valve 4 is provided in a passage 3 for bypassing a throttle valve 2 in an intake passage 1 to guide auxiliary air, while exhaust gas recirculation is performed. When the valve 5 is opened, a part of the exhaust gas is throttled and the intake passage 1 downstream of the throttle valve 2 is opened.
A closing means 7 for forming an exhaust gas recirculation passage 6 for recirculating the exhaust gas and forcibly closing the exhaust gas recirculation valve 5, a means 8 for detecting the pressure in the intake passage 1 downstream of the throttle valve 2, and an exhaust gas during exhaust gas recirculation. Exhaust of an internal combustion engine provided with a means 9 for temporarily closing the recirculation valve 5 to measure a pressure change in the intake passage 1 downstream of the throttle valve 2 and a failure determination means 10 for comparing the measured value with a determination value. In the recirculation device, a means 11 for detecting the opening degree of the auxiliary air control valve 4 and a correction for correcting the measured value of the pressure change or the judgment value for comparing the measured value according to the opening degree of the auxiliary air control valve 4. Means 12 are provided.

[0011]

Therefore, when the exhaust gas recirculation valve 5 is closed, the pressure change in the intake passage 1 changes depending on the opening of the auxiliary air control valve 4, but the intake passage is changed according to the opening of the auxiliary air control valve 4. Since the measured value of the pressure change of 1 or the judgment value for comparing the measured values is corrected, the failure judgment can be accurately performed.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 2, 20 is an engine, 21
Is an intake passage and 22 is an exhaust passage.

The exhaust gas recirculation passage 23 branches from the exhaust gas passage 22 and is connected to the intake passage 21 downstream of the throttle valve 24, and a diaphragm type exhaust gas recirculation valve 25 is arranged in the middle of the exhaust gas recirculation passage 23.

The pressure chamber 26 of the exhaust gas recirculation valve 25 is connected to a negative pressure passage 27 that opens into the intake passage 21 near the throttle valve 24 and guides a VC negative pressure (Venturi negative pressure). Solenoid valve 2 that opens the pressure chamber 26 to the atmosphere in the middle of
8 are provided.

When the VC negative pressure of the throttle valve 24 is introduced into the pressure chamber 26 via the negative pressure passage 27, the exhaust gas recirculation valve 25 is opened to an opening degree corresponding to the negative pressure, and the solenoid valve 28 is turned off. When the pressure chamber 26 is opened to the atmosphere, the exhaust gas recirculation valve 25 is closed.

On the other hand, an auxiliary air passage 29 is formed in the intake passage 21 to bypass the throttle valve 24 and guide the auxiliary air, and an auxiliary air control valve (idle control valve) 30 is interposed in the auxiliary air passage 29.

The idle control valve 30 is provided with an opening sensor (not shown) for detecting the opening of the valve 30, and
The opening degree is controlled by a control unit 31, which will be described later, and a predetermined amount of auxiliary air is introduced into a predetermined low speed range including when the engine is idle.

A pressure sensor 32 for detecting the pressure in the intake passage 21 is installed in the intake passage 21 on the downstream side of the throttle valve 24, and this signal is sent to the control unit 31 together with the signal of the opening sensor of the idle control valve 30. Be done.

An air flow sensor 33 for detecting the intake air amount (engine load) is installed in the intake passage 21 upstream of the throttle valve 24, and a rotation sensor 34 for detecting the engine speed is installed on the crankshaft side of the engine 20. , These signals are also sent to the control unit 31.

The control unit 31 includes the CPU 3
5, the RAM 36, the ROM 37, and the I / O 38, and controls the ON / OFF of the solenoid valve 28 and the opening degree of the idle control valve 30 based on the signals.

Next, the operation will be described.

First, in the exhaust gas recirculation region based on the engine speed and engine load, the solenoid valve 28 is turned on and the throttle valve 2
The exhaust gas recirculation valve 25 is opened by the VC negative pressure of 4, and the predetermined exhaust gas recirculation is performed by the opening degree of the exhaust gas recirculation valve 25 and the throttle valve 24.

Then, when the engine enters a steady operation during the exhaust gas recirculation, the failure determination processing of FIG. 3 is executed.

In this case, in step 101, the solenoid valve 28
Is turned off, the exhaust gas recirculation valve 25 is forcibly closed, and the difference ΔP between the pressure in the intake passage 21 before closing the valve and the pressure in the intake passage 21 after closing the valve is measured from the signal of the pressure sensor 32. To do.

Subsequently, at step 102, the opening of the idle control valve 30 (AAC / V) is detected, and if the opening is within the allowable value A, steps 103 to 104,
Proceeding to 105, the pressure difference ΔP is corrected.

In step 104, the idle control valve 30
The correction value of the pressure difference ΔP is read from the data table set based on the opening degree of, and in step 105, the correction value is multiplied by the correction value ΔP to obtain the corrected pressure difference ΔPs.
The correction value takes a larger value according to the opening degree of the idle control valve 30 as the opening degree increases.

At step 106, the lower limit judgment value 1 and the upper limit judgment value 2 of the failure judgment are calculated. This judgment value 1,
2 is obtained from the pressure in the intake passage 21 after the exhaust gas recirculation valve 25 is closed.

Then, in steps 107 and 108, the corrected pressure difference ΔPs is compared with the judgment values 1 and 2, and the judgment values 1 and 2 are compared.
If it is within the range of 2, it is determined to be normal.

On the other hand, if the pressure difference ΔPs is smaller than the judgment value 1, the amount of recirculation when the exhaust gas recirculation valve 25 is open is less than or equal to the desired value, and malfunctions of the exhaust gas recirculation valve 25, blockage of the exhaust gas recirculation passage 23, etc. Judge as a failure.

If the pressure difference ΔPs is larger than the judgment value 2, it is judged that the recirculation amount of the exhaust gas recirculation valve 25 at the time of opening is greater than or equal to a predetermined value, and the malfunction of the exhaust gas recirculation valve 25 (open too much) or the like occurs. To do.

In this way, the pressure change in the intake passage 21 before and after the exhaust gas recirculation valve 25 is closed is corrected according to the opening degree of the idle control valve 30 in the auxiliary air passage 29, and the failure determination is made based on the corrected value. Therefore, the failure can be accurately determined.

That is, when the opening degree of the exhaust gas recirculation valve 25 is small, the larger the opening degree of the idle control valve 30 is, the smaller the pressure change in the intake passage 21 before and after the closing of the exhaust gas recirculation valve 25 is. When a VC negative pressure is used for the exhaust gas recirculation valve 25, the VC negative pressure is weaker as the opening degree of the idle control valve 30 is larger, and the original opening degree of the exhaust gas recirculation valve 25 is smaller, so that the pressure change is similar. It gets smaller,
In this case, the larger the opening degree of the idle control valve 30,
Since the pressure change is increased and corrected, it can be accurately judged whether it is normal or abnormal by comparing the corrected value with the judgment value.
This makes it possible to accurately diagnose a device failure.

FIG. 4 shows another embodiment of the present invention, in which the judgment values 1 and 2 of the failure judgment are corrected and calculated with respect to the opening degree of the idle control valve 30.

In this case, in steps 201 and 202, the pressure difference ΔP in the intake passage 21 before and after closing the exhaust gas recirculation valve 25,
When the opening degree of the idle control valve 30 is measured, step 20
At 4, the lower limit and upper limit determination values 1 and 2 are obtained from the data table set based on the opening degree of the idle control valve 30.

The judgment values 1 and 2 are large when the opening degree of the idle control valve 30 is small, and the judgment values 1 and 2 are large.
The larger the opening, the smaller the value.

Then, after step 205, the pressure difference Δ
The failure determination is performed by comparing P with the determination values 1 and 2.

[0038]

As described above, according to the present invention, the auxiliary air control valve is provided in the passage for guiding the auxiliary air by bypassing the throttle valve in the intake passage, while a part of the exhaust gas is throttled when the exhaust gas recirculation valve is opened. An exhaust gas recirculation passage that recirculates to the intake passage downstream of the valve is formed,
A valve closing means forcibly closing the exhaust gas recirculation valve, a means for detecting the pressure in the intake passage downstream of the throttle valve, and an intake passage downstream of the throttle valve by temporarily closing the exhaust gas recirculation valve during exhaust gas recirculation. In the exhaust gas recirculation device for an internal combustion engine, which is provided with a means for measuring a pressure change of the auxiliary air and a failure judgment means for comparing the measured value with a judgment value, a means for detecting the opening degree of the auxiliary air control valve, and the auxiliary air Since the correction means for correcting the measured value of the pressure change or the judgment value for comparing the measured values according to the opening degree of the control valve is provided, the failure of the device can be accurately judged and high reliability can be secured.

[Brief description of drawings]

FIG. 1 is a block diagram of the invention.

FIG. 2 is a configuration layout diagram.

FIG. 3 is a flowchart of failure determination.

FIG. 4 is a flowchart of another embodiment.

[Explanation of symbols]

 21 intake passage 22 exhaust passage 23 exhaust gas recirculation passage 24 throttle valve 25 exhaust gas recirculation valve 28 solenoid valve 29 auxiliary air passage 30 auxiliary air control valve 31 control unit 32 pressure sensor 33 air flow sensor 34 rotation sensor

Claims (1)

[Claims] 1. An auxiliary air control valve is provided in a passage for guiding auxiliary air by bypassing a throttle valve in the intake passage, while a part of exhaust gas is returned to an intake passage downstream of the throttle valve when the exhaust gas recirculation valve is opened. A valve closing means that forms an exhaust gas recirculation passage and forcibly closes the exhaust gas recirculation valve, a means that detects the pressure in the intake passage downstream of the throttle valve, and an exhaust gas recirculation valve that is temporarily closed during exhaust gas recirculation. In the exhaust gas recirculation device for an internal combustion engine, which is provided with a means for measuring a pressure change in the intake passage downstream of the throttle valve and a failure determination means for comparing the measured value with a determination value, the opening degree of the auxiliary air control valve is detected. And a correction means for correcting the measured value of the pressure change or the judgment value for comparing the measured value according to the opening degree of the auxiliary air control valve. ..