JPS63259148A - How to detect failure of exhaust gas recirculation system - Google Patents

Abstract

PURPOSE:To prevent the wrong diagnosis of failure judgment, in the case where a failure in an exhaust reflux equipment is judged when the detected temperature of the reflux exhaust gas is lower than a preset temperature, by prohibiting the failure judgment from being performed when the detected temperature of an engine is lower than a preset temperature. CONSTITUTION:An electronic control unit 20 causes a solenoid valve 18 to open, when an engine 10 is in a prescribed operating condition, according to each of the detection signals from an intake temperature sensor 24, a water temperature sensor 25 and an atmospheric pressure sensor 26. And then, an EGR valve 16 is caused to open so that a part of exhaust gas in an exhaust pipe 13 is caused to flow back through an exhaust reflux passage 15 into an intake pipe 12. Subsequently, when the detected temperature of the reflux exhaust gas is lower than a preset temperature, it is judged that an exhaust reflux equipment is out of order, and an alarm lamp 28 is turned on. In this case, until the detected temperature of the engine 10 reaches a preset temperature, the failure judgment on the exhaust reflux equipment is prohibited. Thereby, the wrong diagnosis of failure judgment due to an unstable temperature condition can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a failure detection method for an exhaust gas recirculation device that recirculates part of the exhaust gas of an internal combustion engine to an intake passage.

(Prior Art and its Problems) Conventionally, an exhaust gas recirculation device that recirculates a portion of the exhaust gas of an internal combustion engine to an intake passage to reduce the amount of residual gas components such as NOx in the exhaust gas is well known. This exhaust recirculation device is
An exhaust gas recirculation passage that communicates the exhaust passage and the intake passage, an exhaust gas recirculation valve (hereinafter referred to as an "rEGR valve") disposed in the middle of the exhaust gas recirculation passage that opens and closes the exhaust gas recirculation passage, and an operation control of the EGR valve. The control device controls the opening and closing of the EGR valve according to the engine operating state, so that an appropriate amount of exhaust gas is returned to the intake passage.

However, there is a problem in that if carbon, etc. in the exhaust gas accumulates on the EGR valve of the exhaust gas recirculation device and blocks the passage, and the required amount of exhaust gas cannot be returned to the intake passage, the exhaust gas characteristics deteriorate. . Normally, it is difficult for a driver or the like to detect such an abnormality or failure of the exhaust gas recirculation system unless some kind of Yji detection means is provided to detect it.

Therefore, when the exhaust gas recirculation device is in the state where it should be operating, a temperature sensor (hereinafter referred to as "EGR temperature sensor") is installed exposed in the exhaust recirculation passage near the EGR valve or across a wall, and the exhaust gas recirculation A method of detecting a failure of an exhaust gas recirculation device by detecting gas temperature is known. This method is used when the EGR valve etc. is operating normally and the required amount of exhaust recirculation gas is flowing, and when the EGR valve etc. is abnormal and the exhaust recirculation gas does not flow at all or even if it is flowing, the amount of gas is extremely low. There is a large difference in the temperature detected by the above-mentioned EGR temperature sensor between when the EGR temperature sensor is low and when the EGR temperature sensor is low.
If the exhaust gas recirculation gas temperature detected by the temperature sensor is below a predetermined failure determination temperature, it is determined that the exhaust gas recirculation device is malfunctioning.

However, in the above-described failure detection method for the exhaust gas recirculation system, when the engine has not yet been warmed up immediately after starting, the operating state of the engine is not stable, and therefore the temperature of the exhaust gas recirculation is also unstable. in a state. When the engine is in such a state, if the exhaust gas recirculation device is determined to be malfunctioning, the malfunction cannot be determined accurately and there is a risk of misdiagnosis.

The present invention has been made to solve such problems, and it is an object of the present invention to provide a failure detection method for an exhaust gas recirculation system that can accurately and accurately detect abnormalities or failures in the exhaust gas recirculation system.

(Means for Solving the Problems) In order to achieve the above-mentioned object, according to the present invention, an exhaust gas recirculation device is created which recirculates a part of the exhaust gas of an internal combustion engine to the intake passage. JJ A malfunction in which a temperature related to the temperature of the gas recirculating through the exhaust gas recirculation device is detected when the exhaust gas recirculation device is in the state that it should be in, and when the detected temperature is lower than a failure determination value, it is determined that the exhaust gas recirculation device is malfunctioning. There is provided a failure detection method for an exhaust gas recirculation device, characterized in that the failure determination is prohibited until a temperature representing engine temperature reaches a predetermined value.

(Function) After the engine starts, when the temperature representing the engine temperature, for example, the engine cooling water temperature, reaches a predetermined value, it means that the engine has warmed up. As the system operates, the temperature of the exhaust gas recirculation becomes stable, and if the failure of the exhaust recirculation system is determined under such conditions,
Failure determination can be made more accurately and reliably. Therefore, if failure determination is prohibited until the temperature representing the engine temperature reaches a predetermined value, misdiagnosis of failure determination can be avoided.

(Example) Hereinafter, one embodiment of the present invention will be described based on the drawings.

First, the overall configuration of an exhaust gas recirculation system for implementing the method of the present invention will be described with reference to FIG. 1. An intake pipe 12 is connected to the intake side of an internal combustion engine 10, and an exhaust pipe 13 is connected to the exhaust side of the internal combustion engine 10. There is. A throttle valve 4 is disposed in the middle of the intake pipe 12, one end of an exhaust gas recirculation path 15 is connected to the intake pipe 12 downstream of the throttle valve 14, and the other end of the exhaust gas recirculation path 15 is connected to the exhaust pipe 13. ing.

There is an exhaust gas recirculation valve (CEGR valve) 16 in the middle of the exhaust gas recirculation path 15.
is installed. This EGR valve 16 is connected to the exhaust gas recirculation path 1
5, and an actuator 16b that opens and closes the valve body 16a.
b includes a housing 16c, a diaphragm 16d housed in the housing 16c and defining it into a negative pressure chamber 16f and an atmospheric pressure chamber 16g, and connected to the valve body 16a, and a diaphragm 16d housed in the negative pressure chamber 16f; The spring 16e presses the diaphragm 16d in the direction of closing the valve body 16a.

A negative pressure path 17 is provided in the negative pressure chamber 16f of the actuator 16ty.
One end of the negative pressure path 17 is connected, and the other end of the negative pressure path 17 is connected to the throttle valve 1.
4 is connected to the intake pipe I2 downstream of the throttle valve 14, and the intake pipe 1 downstream of the throttle valve 14 is connected to the negative pressure chamber 16f via the negative pressure path 17.
The negative pressure generated within 2 is guided. A normally closed solenoid valve 18 is disposed in the middle of the negative pressure path 17, and the solenoid valve 18 is connected to an electronic control unit (ECU) 20, which will be described later.
The negative pressure is supplied to the negative pressure chamber 16f of the actuator 16b when the valve is opened by a valve opening drive signal supplied from the electronic control unit 20.

An EGR temperature sensor 22 is installed on the side wall 16h of the EGR valve 16.
is attached, and its tip temperature sensor part 22a
is exposed facing into the exhaust gas recirculation path 15 downstream of the valve body 16f, and this EGR temperature sensor 22 detects the exhaust gas recirculation gas temperature and supplies a detection signal to the electronic control unit 20.

The engine 1 is connected to the input side of the electronic control unit 20.
Various sensors detect the operating state of 0, for example, an intake air temperature sensor 24 installed near the atmosphere-opening end of the intake pipe 12 and detects the intake air temperature, and detects the cooling water temperature of the engine lO as a temperature representing the engine temperature. water temperature sensor 25,
An atmospheric pressure sensor 26 for detecting atmospheric pressure, an engine speed sensor (not shown), an intake air amount sensor, etc. are connected, and detection signals from these various sensors are supplied to the electronic control unit 20. An alarm lamp 28 is connected to the output side of the electronic control unit 20 to warn of a failure when a failure of the exhaust gas recirculation system is detected. There is.

Next, the operation of the exhaust gas recirculation device configured as described above will be explained.

The valve body 16a of the EGR valve 16 is normally pressed in the valve closing direction by the spring 16e, and the EGR valve 16 is closed. The electronic control unit 20 outputs a valve opening drive signal to the electromagnetic valve 18 to open it when the engine IO is in a predetermined operating state based on detection signals from the various sensors described above.

When the electromagnetic valve 18 opens, negative pressure generated in the intake pipe 12 downstream of the throttle valve 14 is supplied to the negative pressure chamber 16F of the actuator 16b via the negative pressure path 17. Negative pressure chamber 16f
When negative pressure is supplied to the atmospheric pressure chamber 1 of the diaphragm 16d
The atmospheric pressure acting on the negative pressure chamber 16f side overcomes the negative pressure acting on the negative pressure chamber 16f side, and moves the diaphragm 16d1 and therefore the valve body 16a upward in the figure against the spring force of B, f (16e).
GR valve 16 is opened. When the EGR valve 16 opens, a portion of the exhaust gas in the exhaust pipe 13 will flow back to the intake pipe 12 via the exhaust gas recirculation path 15.

Next, a procedure for detecting a failure in the exhaust gas recirculation system using the electronic control unit 20 will be explained with reference to FIGS. 2 to 5.

FIG. 2 shows a state in which the exhaust gas recirculation device should be operating, that is, a state in which the EGR valve 16 should be open and exhaust gas should be flowing back to the intake pipe 12 via the exhaust gas recirculation path 15. This is a program that is executed, and it is determined by this program routine whether or not the exhaust gas recirculation device is in a state where it is possible to perform failure determination.

The electronic control unit 20 first performs step 30.
, it is determined whether 1 s time (unit: minute) has elapsed after the start of the engine IO. Immediately after the engine 10 is started, it has not been warmed up yet, and during this time the temperature of the exhaust gas recirculated through the exhaust gas recirculation passage No. 15 is not stable. There is a risk of misjudgment.

Therefore, if the determination result in step 30 is negative (NO), that is, if the engine 10 has not been warmed up yet, the program routine is ended without executing the failure determination described later.

Note that the time required to complete warm-up of the engine 10 after starting is affected by the coolant temperature state at the time of starting the engine 10, so the above-mentioned judgment prohibition time t is determined by the time when the water temperature sensor 25 It is desirable to set it according to the engine water temperature detected by. FIG. 3 is a graph showing the relationship between the judgment prohibition time t and the water temperature Tw at the time of starting,
The determination prohibition time t is set to a shorter time as the water temperature Tw is higher, depending on the water temperature Tw detected immediately after the engine 10 is started. Also, the temperature T at which the water temperature Tw at the time of starting the engine IO can be considered to be in the warm-up state. Even in the case of 19 or more, the determination prohibition time t is the minimum time t. (for example, 2 minutes) and wait until the engine 1o is completely stabilized before making the failure determination described later.

If the determination result in step 30 is affirmative (Yes), it is determined whether or not the engine water temperature Tw is equal to or higher than a predetermined value Twx (for example, 80° C.) (step 32), in conjunction with the determination in step 30 described above. Then, it is determined whether or not the engine 10 has been warmed up sufficiently, and if the determination result is negative, the program routine is ended without executing the failure determination described later.

If the determination result in step 32 is affirmative, the electronic control unit 20 determines whether the intake air temperature Ta detected by the intake air temperature sensor 24 is lower than a predetermined determination value Tax (for example, 60° C.) (step 34).

If the intake air temperature Ta is high (if the determination in step 34 is negative), the EGR valve 16 and the EGR temperature sensor 2
2 itself may be at high temperature, in such case,
Since the exhaust gas recirculation gas temperature cannot be accurately measured, the program routine is terminated without executing the failure determination described later.

Next, if the determination result in step 34 is affirmative, the process proceeds to step 36, where the atmospheric pressure Pa detected by the atmospheric pressure sensor 26 is set to a predetermined determination value Fax (for example, 700 mmHg).
It is determined whether or not the value is greater than or equal to the value. When the engine 10 is operated under atmospheric conditions with low atmospheric pressure, such as at high altitudes, the exhaust gas temperature decreases, and the exhaust gas recirculation gas temperature also decreases.

Therefore, if the atmospheric pressure Pa is lower than the predetermined determination value Fax and the decrease in exhaust gas recirculation gas temperature cannot be ignored (if the determination result in step 36 is negative), the program routine is executed without executing the failure determination described later. finish.

If the determination results in each of the above steps are positive, it means that there is no problem in determining the failure of the exhaust gas recirculation system, and in such a case, the electronic control unit 20 proceeds to step 40 and performs the fourth A failure determination routine for the exhaust gas recirculation system (flcEGR device) shown in the figure is executed.

First, in step 41 of the failure determination routine, the electronic control unit 20 sets a failure determination temperature TGX based on the exhaust gas recirculation gas temperature. This discrimination temperature TGM is read out from a table stored in a storage device (not shown) of the electronic control unit 20 in accordance with the intake air temperature Ta detected by the intake air temperature sensor 24. FIG. 5 shows a discrimination temperature TOX table stored in the storage device, and the discrimination temperature TGX is set to a higher temperature value as the intake air temperature Ta increases. This discrimination temperature TGX is the intake air temperature Ta
However, since the shape of the EGR valve 16, the size of the exhaust gas recirculation path 15, the amount of recirculation of exhaust gas recirculation, and the mounting position of the EGR temperature sensor 22 are affected by various factors, as shown in FIG. The determination temperature TGX table shown in is preferably set experimentally for each engine.

Next, the electronic control unit 20 compares the exhaust recirculation gas temperature T detected by the EGR temperature sensor 22 with the determination temperatures T and X set in step 41, and determines whether the exhaust recirculation gas temperature TG is higher than the determination temperature TGX. It is determined whether or not (step 42), when the EGR valve 16 is opened and the exhaust recirculation gas is normally recirculating through the exhaust recirculation path 15, that is, when the exhaust recirculation device is operating normally. In such a case, the exhaust gas recirculation gas temperature T6 detected by the EGRi degree sensor 22 is sufficiently higher than the determination temperature T'cx.
The determination result in step 42 is affirmative, and the electronic control unit 20 resets a timer, which will be described later (step 44), and ends the failure determination routine.

When the exhaust gas recirculation gas temperature T is lower than the determination temperature T'c++, that is, when the determination result in step 42 is negative, the electronic control unit 20 controls the temperature for a predetermined period of time tr from the time when the first negative determination is made in step 42, (for example, , 30 seconds) have elapsed, that is, whether the timer reset in step 44 during normal operation of the exhaust gas recirculation system has counted up a predetermined amount of time. This counter may be a hard timer built into the electronic control unit 20, or may be a so-called soft timer that measures the passage of time by executing a program.If the predetermined time t has not elapsed, Even if the exhaust gas recirculation temperature T is lower than the determination temperature TGX, the system does not immediately determine that the exhaust gas recirculation device is malfunctioning.
The failure determination routine ends. This makes it possible to avoid erroneous determinations caused by noise or the like.

Only when the exhaust gas recirculation gas temperature T, continues to be lower than the determination temperature Tr, *, step 46 is repeatedly executed, and the predetermined time 1G has elapsed, the electronic control unit 20 determines that the exhaust gas recirculation device is malfunctioning. Then, step 48 is executed, and the alarm lamp 28 is turned on to warn the driver etc. of the failure of the exhaust gas recirculation system. In this way, the driver can recognize a malfunction in the exhaust gas recirculation system, and upon recognizing the malfunction, the driver can immediately take appropriate measures.

In addition, in the above-mentioned embodiment, the engine cooling water temperature was explained as an example of the temperature representing the engine temperature, but the present invention is not limited to this, and the temperature representing the engine temperature may be, for example, the engine oil temperature. good.

(Effects of the Invention) As detailed above, according to the exhaust gas recirculation device failure detection method of the present invention, failure determination of the exhaust gas recirculation device is prohibited until the temperature representing the engine temperature reaches a predetermined value. It is possible to accurately and reliably determine the failure of the exhaust gas recirculation device without misdiagnosing it.

[Brief explanation of the drawing]

The drawings show an embodiment of a failure detection method for an exhaust gas recirculation device according to the present invention, FIG. 1 is a block diagram showing a schematic configuration of an exhaust gas recirculation device that implements the method of the present invention, and FIG. A third program flowchart showing a procedure executed by the electronic control unit (ECU) 20 shown in FIG.
The figure is a graph showing the relationship between the failure determination prohibition time t and the cooling water temperature Tw immediately after the engine starts, Figure 4 is a flowchart of the EGR failure determination routine shown in step 40 of Figure 2, and Figure 5 is the failure determination temperature. It is a graph showing the relationship between TGX and intake air temperature Ta. lO... Internal combustion engine, 12... Intake pipe (intake passage), 13... Exhaust pipe, 15... Exhaust recirculation path, 16...
・・Exhaust return 2FMF (EG R valve), 20...
Electronic control unit (ECU), 24... Intake temperature sensor, 25... Engine coolant temperature sensor, 2
8...Alarm lamp. Applicant Mitsubishi Motors Corporation Agent Patent Attorney Kanji Nagado Figure 1 Figure 2 Figure 3 ts (minutes) Figure 5 Intake Air Dust ('C)

Claims (2)

[Claims] (1) When the exhaust gas recirculation device that recirculates part of the exhaust gas of the internal combustion engine to the intake passage is in a state where it should be operating, detect a temperature related to the temperature of the gas recirculating the exhaust gas recirculation device; A failure detection method for determining that the exhaust gas recirculation device is malfunctioning when the temperature is lower than a failure determination value, characterized in that the failure determination is prohibited until a temperature representing engine temperature reaches a predetermined value. fault detection method. (2) A failure detection method for an exhaust gas recirculation device according to claim 1, wherein the temperature representing the engine temperature is an engine cooling water temperature.