JP2576114B2 - Failure detection method for exhaust gas recirculation system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for detecting a failure of an exhaust gas recirculation device that recirculates a part of exhaust gas of an internal combustion engine to an intake passage.

(Conventional technology and its problems) Conventionally, an exhaust gas recirculation device that recirculates a part of exhaust gas of an internal combustion engine to an intake passage to reduce the amount of harmful gas components such as NOx in the exhaust gas is well known. This exhaust gas recirculation system
An exhaust gas recirculation path that connects the exhaust gas passage and the intake air passage, an exhaust gas recirculation valve disposed in the middle of the exhaust gas recirculation passage to open and close the exhaust gas recirculation passage (hereinafter referred to as a “BGR valve”), and operation control of the BGR valve The opening and closing of the BGR valve is controlled in accordance with the operating state of the engine to return an appropriate amount of exhaust gas to the intake passage.

However, there is a problem that the exhaust gas characteristics are deteriorated when carbon or the like in the exhaust gas accumulates on the BGR valve or the like of the exhaust gas recirculation device and blocks the passage, so that the required amount of exhaust gas cannot be recirculated to the intake passage. . Such an abnormality or failure of the exhaust gas recirculation device is difficult to be detected by a normal driver or the like unless some failure detection means is provided and detected.

Therefore, when the exhaust gas recirculation device is in a state of operation, a temperature sensor (hereinafter referred to as an “EGR temperature sensor”) is attached to the exhaust gas recirculation passage near the EGR valve or the like through an exposure or a wall. There is known a method of detecting a gas temperature to detect a failure of the exhaust gas recirculation device. In this method, when the EGR valve or the like normally operates and the required amount of exhaust gas recirculation gas flows, the exhaust gas recirculation gas does not flow at all due to an abnormality in the EGR valve or the like, or the amount of the exhaust gas recirculation gas is extremely small even if it flows. There is a large difference in the temperature detected by the above-described EGR temperature sensor between the time when the temperature is low and the temperature of the exhaust gas recirculation device detected by the EGR temperature sensor. If the gas temperature is equal to or lower than the predetermined failure determination temperature, it is determined that the exhaust gas recirculation device has failed.

However, in the exhaust gas recirculation device failure detection method described above, when the engine has not yet been warmed up immediately after starting, the operation state of the engine is not stable,
Therefore, the exhaust gas recirculation gas temperature is also unstable. If the failure determination of the exhaust gas recirculation device is performed while the engine is in such a state, the failure determination cannot be performed accurately, and there is a risk of erroneous diagnosis.

The present invention has been made to solve such a problem, and an object of the present invention is to provide an exhaust gas recirculation device failure detection method capable of accurately and reliably detecting an abnormality or failure of an exhaust gas recirculation device.

(Means for Solving the Problems) According to the present invention, in order to achieve the above-described object, an exhaust gas recirculation device that recirculates a part of exhaust gas of an internal combustion engine to an intake passage is to be operated. A failure detection method for detecting a temperature related to a temperature of a gas circulating in the exhaust gas recirculation device, and determining that the exhaust gas recirculation device has failed when the detected temperature is lower than a failure determination value. The engine temperature immediately after the start of the engine is detected, a determination prohibition time is set according to the detected engine temperature immediately after the start of the engine, the elapsed time after the engine is started is measured, and the failure is performed until the elapsed time reaches the determination prohibition time. A method for detecting a failure of an exhaust gas recirculation device is provided, wherein the determination is prohibited.

(Operation) After the start of the engine, the warm-up of the engine is completed when the determination prohibition time has elapsed, and when the warm-up of the engine is completed, the engine operates stably, so that the exhaust gas recirculation gas temperature is also stabilized. Further, even if the engine is already in the warm-up completed state at the time of engine start, unstable combustion immediately after engine start is stopped and the engine operates stably after the above-described determination prohibition time has elapsed. Is performed, the failure determination can be performed more accurately and reliably. Therefore, if the failure determination is prohibited until the determination prohibition time elapses after the engine is started, erroneous diagnosis of the failure determination is avoided.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

First, an 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 an intake side of an internal combustion engine 10 and an exhaust pipe 13 is connected to an exhaust side. I have. A throttle valve 14 is provided 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.

An exhaust gas recirculation valve (EGR valve) 16 is provided in the exhaust gas recirculation pipe 15. The EGR valve 16 includes a valve body 16a for opening and closing the exhaust gas recirculation path 15, and an actuator 16 for opening and closing the valve body 16a.
b, and the actuator 16b has a housing 16c
And housed in a housing 16c, which is defined as a negative pressure chamber 16f and an atmospheric pressure chamber 16g, and a diaphragm 16d connected to the valve body 16a, and housed in the negative pressure chamber 16f to open and close the valve body 16a. And a bar 16e that presses the diaphragm 16d in the direction of movement.

One end of a negative pressure path 17 is connected to the negative pressure chamber 16f of the actuator 16b, and the other end of the negative pressure path 17 is connected to the intake pipe 12 downstream of the throttle valve 14.The negative pressure path is connected to the negative pressure chamber 16f. Negative pressure generated in the intake pipe 12 downstream of the throttle valve 14 is led through 17. A normally closed solenoid valve 18 is provided in the middle of the negative pressure passage 17, and the solenoid valve 18 is electrically connected to an electronic control unit (ECU) 20 described later and supplied from the electronic control unit 20. The negative pressure is supplied to the negative pressure chamber 16f of the actuator 16b by opening the valve according to the valve opening drive signal.

An EGR temperature sensor 22 is attached to a side wall 16h of the EGR valve 16, and a tip temperature sensor 22a is exposed in the exhaust gas recirculation path 15 downstream of the valve element 16f.
The R temperature sensor 22 detects the exhaust gas recirculation gas temperature and supplies a detection signal to the electronic control unit 20.

The engine 10 is on the input side of the electronic control unit 20.
Various sensors for detecting the operating state of the
, An intake air temperature sensor 24 for detecting an intake air temperature, a water temperature sensor 25 for detecting a cooling water temperature of the engine 10 as an engine temperature, an atmospheric pressure sensor 26 for detecting an atmospheric pressure, and an engine rotation (not shown). A number sensor, an intake air amount sensor, and the like are connected, and detection signals from these various sensors are supplied to the electronic control unit 20. When a failure of the exhaust gas recirculation device is detected, an alarm lamp 28 for warning the failure is connected to the output side of the electronic control unit 20, and the alarm lamp 28 is attached to, for example, an instrument panel in a vehicle compartment. I have.

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

The valve element 16a of the EGR valve 16 is normally pressed in the valve closing direction by a spring 16e, and the EGR valve 16 is closed. Then, when the engine 10 is in a predetermined operating state based on the detection signals from the various sensors described above,
A valve opening drive signal is output to the electromagnetic valve 18 to open it.
When the solenoid valve 18 is opened, a negative pressure generated in the intake pipe 12 downstream of the throttle valve 14 is applied to the actuator 16b through the negative pressure path 17.
Is supplied to the negative pressure chamber 16f. When a negative pressure is supplied to the negative pressure chamber 16f, the atmospheric pressure acting on the atmospheric pressure chamber 16g side of the diaphragm 16d overcomes the negative pressure acting on the negative pressure chamber 16f side, and the diaphragm 16
d, that is, the valve body 16a is moved upward in the drawing against the spring force of the spring 16e, and the EGR valve 16 is opened. When the EGR valve 16 opens, a part of the exhaust gas in the exhaust pipe 13 returns to the intake pipe 12 via the exhaust return path 15.

Next, a procedure for detecting a failure of the exhaust gas recirculation device by the electronic control unit 20 will be described with reference to FIGS.

FIG. 2 shows a state in which the exhaust gas recirculation device is to be operated, that is, a state in which the EGR valve 16 is opened and the exhaust gas is to be recirculated to the intake pipe 12 through the exhaust gas recirculation passage 15. This is a program to be executed, and it is determined by this program routine whether or not the exhaust gas recirculation device is in a state in which a failure determination may be performed.

First, in step 30, the electronic control unit 20 determines whether or not the time t _s (unit) has elapsed after the start of the engine 10. Immediately after the start of the engine 10, the engine has not been warmed up yet, and the temperature of the exhaust gas recirculated through the exhaust gas recirculation path 15 during this period is not stable. There is a risk of misjudgment. Therefore, if the determination result of step 30 is negative (No), that is,
If the engine 10 has not been warmed up yet, the program routine ends without executing the failure determination described later.

Since the time required to complete the warm-up after the start of the engine 10 is affected by the cooling water temperature state at the time of the start of the engine 10, the above-described determination inhibition time t _s is set immediately after the start of the engine 10 by the water temperature sensor 25. It is desirable to set according to the engine water temperature detected by the above. FIG. 3 is a graph showing a relationship between the determination inhibition time t _s and the water temperature Tw at the time of starting, and the determination inhibition time t _s is shown.
Is based on the water temperature Tw detected immediately after the start of the engine 10,
The higher the water temperature Tw, the shorter the time is set. Engine 10
The temperature T _WH at which the water temperature Tw at the start of
Even in the above case, the judgment inhibition time t _{s is set} to the minimum time t
It is desirable to set _s0 (for example, 2 minutes) and wait for the engine 10 to completely stabilize before performing a failure determination described later.

If the determination result of step 30 is affirmative (Yes), it is determined whether or not the engine coolant 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, it is determined whether or not the engine 10 has been sufficiently warmed up. If the determination result is negative, the program routine is executed without executing the failure determination described later. finish.

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). When the intake air temperature Ta is high (step
If the determination at 34 is negative), the EGR valve 16 and the EGR temperature sensor 22 themselves may be at a high temperature even if the exhaust gas is not recirculated through the exhaust gas recirculation path 15. In this case, since the exhaust gas recirculation gas temperature cannot be accurately measured, the program routine ends without executing a failure determination described later.

Next, if the determination result of step 34 is affirmative, step
Proceeding to 36, it is determined whether or not the atmospheric pressure Pa detected by the atmospheric pressure sensor 26 is equal to or greater than a predetermined determination value Pax (for example, 700 mmHg). When the engine 10 is operated under low atmospheric pressure, such as at high altitudes, the exhaust gas temperature decreases and the exhaust gas recirculation gas temperature also decreases. Therefore, when the atmospheric pressure Pa is lower than the predetermined determination value Pax and the decrease in the exhaust gas recirculation gas temperature cannot be ignored (the determination result in step 36 is negative), the program routine is executed without executing the failure determination described later. finish.

If the determination result in each step described above is affirmative, it means that there is no problem in performing the failure determination of the exhaust gas recirculation device. In such a case, the electronic control unit 20 proceeds to step 40 and proceeds to the fourth step. A failure determination routine of the exhaust gas recirculation device (EGR 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. The determined temperature _TGX is determined by an intake air temperature Ta detected by the intake air temperature sensor 24 from a table stored in a storage device (not shown) of the electronic control unit 20.
Is read out according to. FIG. 5 shows a discrimination temperature _TGX table stored in the storage device. The discrimination temperature _TGX is set to a higher temperature value as the intake air temperature Ta increases. The discrimination temperature _TGX is given as a function of the intake air temperature Ta, but various factors such as the shape of the EGR valve 16, the size of the exhaust gas recirculation path 15, the amount of exhaust gas recirculated gas, the mounting position of the EGR temperature sensor 22, etc. Influences, the discrimination temperature T shown in FIG.
_{The GX} table is preferably set experimentally for each engine.

Next, the electronic control unit 20 is connected to the EGR temperature sensor 2
The exhaust gas recirculation gas temperature T _G is compared with the exhaust gas recirculation gas temperature T _G detected in step 2 and the discrimination temperature T _GX set in step 41.
Is higher than the determination temperature T _GX (step 4
2). When the EGR valve 16 is opened and the exhaust gas recirculation gas is normally circulating through the exhaust gas recirculation path 15, that is, when the exhaust gas recirculation device is operating normally, the exhaust gas detected by the EGR temperature sensor 22 is detected. recirculation gas temperature T _G is sufficiently higher than the determination temperature T _GX, if such, the question of the step 42 becomes affirmative, the electronic control unit 20 resets the timer to be described later (step 44), the fault determination routine finish.

If the exhaust gas recirculation gas temperature _TG is lower than the determination temperature _TGX , that is, if the determination result of step 42 is negative, the electronic control unit 20 determines the predetermined time t _G (for example, 30 Second) has elapsed, ie, when the exhaust gas recirculation device operates normally,
Reset the timer, it is determined whether or not the counted up the predetermined time t _G in 44. This counter may be a hard timer built in the electronic control unit 20, or a so-called soft timer that measures the passage of time by executing a program. If the predetermined time t _G has not elapsed, the exhaust gas recirculation gas temperature _TG becomes equal to the discrimination temperature T _GX
Even if it is lower, the failure determination routine is terminated without immediately determining that the exhaust gas recirculation device has failed. Thereby, erroneous determination due to noise or the like can be avoided.

EGR gas temperature T _G continues is lower than the determination temperature T _GX, the predetermined time step 46 is repeatedly executed t _G
Only after elapse, the electronic control unit 20 determines that the exhaust gas recirculation device has failed, executes step 48, turns on the alarm lamp 28, and warns the driver or the like of the failure of the exhaust gas recirculation device. Thus, the driver can recognize the failure of the exhaust gas recirculation device, and the driver who has recognized the failure can take an appropriate measure immediately.

In the above embodiment, the engine cooling water temperature has been described as an example of the engine temperature. However, the present invention is not limited to this.
Engine oil temperature or the like may be used as the engine temperature.

(Effect of the Invention) As described in detail above, according to the exhaust gas recirculation device failure detection method of the present invention, the engine temperature immediately after the start of the internal combustion engine is detected, and the determination is made according to the detected engine temperature immediately after the engine start. The prohibition time is set, the elapsed time after the engine is started is measured, and the failure determination of the exhaust gas recirculation device is prohibited until the elapsed time reaches the determination prohibition time. And can be performed accurately and reliably.

[Brief description of the drawings]

1 shows an embodiment of a method for detecting a failure of 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 for implementing the method of the present invention, and FIG. Is a program flowchart showing a procedure executed by the electronic control unit (ECU) 20 to determine whether or not the failure determination of the exhaust gas recirculation device may be performed. FIG. 3 is a failure determination inhibition time t _s and immediately after the engine is started. Cooling water temperature Tw
FIG. 4 is a graph showing the relationship with step 40 in FIG.
Is a flowchart of the EGR failure determination routine shown in FIG. 5, and FIG. 5 is a graph showing the relationship between the failure determination temperature _TGX and the intake air temperature Ta. 10 ... internal combustion engine, 12 ... intake pipe (intake passage), 13 ...
... exhaust pipe, 15 ... exhaust recirculation path, 16 ... exhaust recirculation valve (EGR
Valve), 20 ... Electronic control unit (ECU), 24 ...
… Intake air temperature sensor, 25 …… Engine cooling water temperature sensor, 28
…… Alarm lamp.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Susumu Saito 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (72) Hiroshi Tanaka 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (72) Inventor Takeshi Jimbo 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (56) References JP-A-63-38678 (JP, A)

Claims (1)

(57) [Claims] When an exhaust gas recirculation device for recirculating a part of exhaust gas of an internal combustion engine to an intake passage is to be operated, a temperature related to a gas temperature recirculating the exhaust gas recirculation device is detected, In the failure detection method for determining that the exhaust gas recirculation device has failed when the detected temperature is lower than the failure determination value, an engine temperature immediately after the start of the internal combustion engine is detected, and the detected engine temperature is determined according to the detected engine temperature immediately after the engine start. A method for detecting a failure in an exhaust gas recirculation device, comprising: setting a determination prohibition time, measuring an elapsed time after starting the engine, and prohibiting the failure determination until the elapsed time reaches the determination prohibition time.