JPH0658096B2 - Exhaust gas recirculation device failure detection method - Google Patents

Description

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

(Prior Art and Its Problems) Conventionally, an exhaust gas recirculation device is known in which a part of exhaust gas of an internal combustion engine is recirculated to an intake passage to reduce the amount of harmful gas components such as NOx in the exhaust gas. This exhaust gas recirculation device includes an exhaust gas recirculation passage that connects the exhaust gas passage and the intake air passage, and an exhaust gas recirculation valve (hereinafter, referred to as an "EGF valve") that is provided in the middle of the exhaust gas recirculation passage and opens and closes the exhaust gas recirculation passage. , And a control device for controlling the operation of the EGR valve, and controls the opening and closing of the EGR valve in accordance with the engine operating state to recirculate an appropriate amount of exhaust gas to the intake passage.

However, if carbon or the like in the exhaust gas is deposited on the EGR valve or the like of the exhaust gas recirculation device to block the passage and the required amount of exhaust gas cannot be recirculated to the intake passage, the exhaust gas characteristic deteriorates. . It is difficult for a normal driver or the like to detect such an abnormality or failure of the exhaust gas recirculation device unless some kind of failure detection means is provided to detect it.

Therefore, when the exhaust gas recirculation device should be operating, a temperature measuring sensor (hereinafter referred to as "EGR temperature sensor") is attached to the exhaust gas recirculation passage near the EGR valve, etc., by exposing it or separating the wall. A method of detecting a gas temperature to detect a failure of an exhaust gas recirculation device is known. In this method, when the EGR valve or the like operates normally and a required amount of exhaust gas recirculation gas flows, when the exhaust gas recirculation gas does not flow at all due to an abnormality in the EGR valve or the like, the amount of the gas even if it flows is extremely high. A large difference occurs in the temperature detected by the above-mentioned EGR temperature sensor when it is low, and the exhaust recirculation detected by the EGR temperature sensor is intended to detect a failure of the exhaust gas recirculation device by paying attention to this temperature difference. If the gas temperature is below a 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 is not warmed up immediately after starting, the operating state of the engine is not stable, and therefore the exhaust gas recirculation gas temperature is also unstable. Is in a state. If the exhaust gas recirculation device is determined to be faulty while the engine is in such a state, the fault determination cannot be accurately made, and there is a risk of misdiagnosis.

The present invention has been made to solve such a problem, and an object thereof is to provide a method for detecting a failure in an exhaust gas recirculation device that can accurately and reliably detect an abnormality or a failure in the exhaust gas recirculation device.

(Means for Solving the Problems) According to the present invention in order to achieve the above-mentioned object, according to the present invention, the exhaust gas recirculation device for recirculating a part of the exhaust gas of the internal combustion engine to the intake passage should be in the operating state. At one time, in a failure detection method for detecting a temperature related to a gas temperature recirculating through the exhaust gas recirculation device and determining that the exhaust gas recirculation device has a failure when the detected temperature is lower than a failure determination value, at engine start-up. If the detected engine temperature is below the temperature at which the detected engine temperature can be regarded as warmed up, the detected engine temperature warms up the prohibition time corresponding to the time required to reach the warmed up state. If the temperature is higher than the temperature that can be regarded as completed, a step of setting a predetermined minimum prohibition time, detecting the engine temperature after the prohibition time has elapsed, and the engine temperature after the prohibition time has passed is higher than the predetermined temperature. And a step of determining whether or not the failure determination is performed until the engine temperature detected after the prohibition time has elapsed is detected to be higher than the predetermined temperature. A failure detection method is provided.

(Operation) After the engine is started, when the temperature representing the engine temperature, for example, the engine cooling water temperature reaches a predetermined value, it means that the engine warm-up is completed, and when the engine warm-up ends, the engine becomes stable. Since it operates, the exhaust gas recirculation gas device is also stable, and if a failure judgment of the exhaust gas recirculation device is made in this state,
The failure determination can be made more accurately and surely.

Further, even if the engine is already warmed up at the time of starting, the operation of the engine is unstable immediately after starting. Therefore, a minimum prohibition time is set according to the engine temperature detected at the time of engine start, failure determination is prohibited until the prohibition time elapses, and the engine temperature detected after the prohibition time elapses to a predetermined temperature. If the failure determination is prohibited until it is detected that the value is higher than the above, it is possible to avoid misdiagnosis of the failure determination and set the time during which the failure determination is prohibited to the required minimum value.

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings.

First, the overall structure of an exhaust gas recirculation system for carrying out 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 thereof. There is. A throttle valve 14 is provided in the middle of the intake pipe 12, one end of an exhaust gas recirculation passage 15 is connected to the intake pipe 12 downstream of the throttle valve 14, and the other end of the exhaust gas recirculation passage 15 is connected to an exhaust pipe 13. There is.

An exhaust gas recirculation valve (EGR valve) 16 is provided in the middle of the exhaust gas recirculation passage 15.
Is provided. The EGR valve 16 is used for the exhaust gas recirculation passage 1
5, a valve body 16a for opening and closing 5, and an actuator 16b for driving the valve body 16a to open and close. The actuator 16b is housed in a housing 16c and a housing 16c, which are divided into a negative pressure chamber 16f and an atmospheric pressure chamber 16g. The diaphragm 16d is defined and connected to the valve body 16a, and the spring 16e is housed in the negative pressure chamber 16f and presses the diaphragm 16d in the direction to close the valve body 16a.

One end of the negative pressure passage 17 is connected to the negative pressure chamber 16f of the actuator 16b, and the other end of the negative pressure passage 17 is connected to the throttle valve 14
The negative pressure chamber 16f is connected to the downstream intake pipe 12, and the negative pressure chamber 16f is connected via a negative pressure passage 17 to the intake pipe 12 downstream of the throttle valve 14.
The negative pressure generated inside is introduced. A normally-closed solenoid valve 18 is disposed in the middle of the negative pressure path 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 in response to the valve opening drive signal.

An EGR temperature sensor 22 is provided on the side wall 16h of the EGR valve 16.
Is attached to the tip of the temperature sensor 22a.
Is exposed in the exhaust gas recirculation passage 15 downstream of the valve body 16f, and the 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 on the input side of the electronic control unit 20.
Various sensors for detecting the operating state of 0, for example, an intake air temperature sensor 24 attached near the atmosphere open end of the intake pipe 12 for detecting the intake air temperature, and detecting the cooling water temperature of the engine 10 as a temperature representing the engine temperature. A 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 sent to the electronic control unit 2.
Supplied to zero. An alarm lamp 28 is connected to the output side of the electronic control unit 20 to warn the failure of the exhaust gas recirculation device when the failure is detected. The alarm lamp 28 is attached to, for example, an instrument panel in the vehicle compartment. There is.

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

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. Then, the electronic control unit 20 outputs a valve opening drive signal to the solenoid valve 18 to open it when the engine 10 is in a predetermined operating state based on the detection signals from the various sensors described above. When the solenoid valve 18 opens, the throttle valve 14
The negative pressure generated in the downstream intake pipe 12 is supplied to the negative pressure chamber 16f of the actuator 16b via the negative pressure passage 17.
When negative pressure is supplied to the negative pressure chamber 16f, the diaphragm 16d
The atmospheric pressure acting on the atmospheric pressure chamber 16g side overcomes the negative pressure acting on the negative pressure chamber 16f side and moves the diaphragm 16d, and thus the valve body 16a, upward in the figure against the spring force of the spring 16e, and the EGR valve 16 is opened. When the EGR 16 is opened, a part of the exhaust gas in the exhaust pipe 13 is recirculated to the intake pipe 12 via the exhaust gas recirculation passage 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 should be operating, that is, when the EGR valve 16 is open and exhaust gas should be recirculated to the intake pipe 12 via the exhaust gas recirculation passage 15. This is a program to be executed, and this program routine determines whether or not the failure determination of the exhaust gas recirculation device can be performed.

The electronic control unit 20 starts with step 30.
At, it is determined whether or not _ts time (unit: minutes) has elapsed since the engine 10 was started. Immediately after the engine 10 is started, the engine has not been warmed up yet, and the temperature of the exhaust gas recirculated through the exhaust gas recirculation path 15 is not stable during this time. There is a risk of misjudgment.

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

Since the time required to complete the warm-up after starting the engine 10 is affected by the cooling water temperature state at the time of starting the engine 10, the above-described determination prohibition time t _s is the water temperature sensor 25 immediately after starting the engine 10. It is desirable to set according to the engine water temperature detected by. FIG. 3 shows the judgment prohibition time t
_s and a graph showing the relationship between the coolant temperature Tw at the start, the determination prohibition time t _s is in accordance with the coolant temperature Tw is detected immediately after start of the engine 10, the coolant temperature Tw is set to a high shorter time. Further, by setting the temperature T in the case of the above _WH also determine inhibition time t _s water temperature Tw at the start causes regarded to be in warm-up state of the engine 10 to the minimum time t _{so (e.g.,} 2 minutes) It is desirable to wait for the engine 10 to completely stabilize before performing the failure determination described later.

When the determination result of step 30 is affirmative (Yes), it is determined whether the engine water temperature Tw is equal to or higher than a predetermined value Twx (for example, 80 ° C.) (step 32). This step is combined with the determination in step 30 described above, and the engine 10
Is determined by detecting the actual engine temperature. If the determination result is negative and the engine water temperature Tw has not yet reached the predetermined value Twx, the failure determination described later. The program routine is terminated without executing.

If the determination result of step 32 is affirmative, the electronic control unit 20 detects the intake air temperature T detected by the intake air temperature sensor 24.
It is determined whether or not a is lower than a predetermined determination value Tax (for example, 60 ° C.) (step 34). When the intake air temperature Ta is high (when the determination in step 34 is negative), the EGR is performed even if the exhaust gas is not recirculated through the exhaust gas recirculation passage 15.
There is a possibility that the valve 16 and the EGR temperature sensor 22 themselves are at a high temperature. In such a case, since the exhaust gas recirculation gas temperature cannot be accurately measured, the program routine ends without executing the failure determination described later.

Next, if the determination result of step 34 is affirmative, step 36
Then, it is determined whether or not the atmospheric pressure Pa detected by the atmospheric pressure sensor 26 is a predetermined determination value Pax (eg, 700 mmHg) or more. When the engine 10 is operated under atmospheric conditions where the atmospheric pressure is low, such as in highlands, the exhaust gas temperature drops, and the exhaust gas recirculation gas temperature also drops. Therefore, the atmospheric pressure Pa is the predetermined determination value Pax
If the lowering of the exhaust gas recirculation gas temperature cannot be ignored (if the determination result of step 36 is negative), the program routine is terminated without executing the failure determination described later.

If the determination result in each of the above-mentioned steps is affirmative, it means that it is possible to perform the failure determination of the exhaust gas recirculation device. In such a case, the electronic control unit 20 proceeds to step 40, and FIG. The failure determination routine of the exhaust gas recirculation device (EGR device) shown in is executed.

First, the electronic control unit 20 sets the failure determination temperature T _GX based on the exhaust gas recirculation gas temperature in step 41 of the failure determination routine. The determination temperature T _GX is read from a table stored in a storage device (not shown) of the electronic control unit 20 according to the intake air temperature Ta detected by the intake air temperature sensor 24. FIG. 5 shows the discrimination temperature T _GX table stored in the storage device, and the discrimination temperature T _GX is set to a higher temperature value as the intake air temperature Ta rises. This determination temperature T _GX 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 passage 15, the recirculation amount of the exhaust gas recirculation gas, the mounting position of the EGR temperature sensor 22, etc. Since it affects, the determination temperature T _GX table shown in FIG. 5 is preferably set experimentally for each engine.

Then, the electronic control unit 20 compares the determination temperature T _GX set in exhaust recirculation gas temperature T _G and step 41 detected by the EGR temperature sensor 22, is higher than the determination temperature T _GX exhaust recirculation gas temperature T _G It is determined whether or not (step 42). The exhaust gas detected by the EGR temperature sensor 22 when the EGR valve 16 is opened and the exhaust gas recirculation gas is normally recirculating through the exhaust gas recirculation path 15, that is, when the exhaust gas recirculation device is normally operating. Reflux gas temperature T
_G is sufficiently higher than the determination temperature T _GX , and in this case, the determination result of step 42 is affirmative, and the electronic control unit 20 resets the timer described later (step 4
4) Then, the failure determination routine ends.

When the exhaust gas recirculation gas temperature T _G is lower than the determination temperature T _GX , that is, when the determination result of step 42 is negative, the electronic control unit 20 determines a predetermined time t _G (for example, 30 _G ) from the time when the determination of step 42 is negative. Sec) has elapsed, that is, the timer reset in step 44 at the time of normal operation of the exhaust gas recirculation device has a predetermined time t _G.
It is determined whether or not the count has been incremented. This counter may be a hard timer built in the electronic control unit 20, or may be a so-called soft timer that measures the elapsed time by executing a program. If the predetermined time t _G has not elapsed, the exhaust recirculation gas temperature T
_{Even if G} is lower than the determination temperature T _GX , the failure determination routine is ended without directly determining that the exhaust gas recirculation device has failed. This makes it possible to avoid erroneous determination due to noise or the like.

Only when the exhaust recirculation gas temperature T _G continues to be lower than the determination temperature T _GX and step 46 is repeatedly executed and the predetermined time T _G elapses, the electronic control unit 20 is restarted.
Determines that the exhaust gas recirculation device is out of order, and step 48
Then, the alarm lamp 28 is turned on to warn the driver or the like of the failure of the exhaust gas recirculation device. In this way, the driver can recognize the malfunction of the exhaust gas recirculation system, and the driver who has recognized the malfunction can take appropriate action directly.

Although the engine cooling water temperature is described as an example of the temperature indicating the engine temperature in the above-described embodiment, the present invention is not limited to this, and the temperature indicating the engine temperature may be, for example, the engine oil temperature. good.

(Effects of the Invention) As described in detail above, according to the failure detection method of the exhaust gas recirculation device of the present invention, the engine temperature at the time of engine start is detected,
If the detected engine temperature is below the temperature at which the engine can be considered warmed up, the prohibition time corresponding to the time required to reach the warmed-up state is set to the temperature at which the detected engine temperature can be considered as warmed up. If it is higher, a step of setting a predetermined minimum prohibition time, a step of detecting an engine temperature after the prohibition time has elapsed, and determining whether the engine temperature after the prohibition time has elapsed is higher than a predetermined temperature is provided. Since the failure determination of the exhaust gas recirculation device is prohibited until it is detected that the engine temperature detected after the prohibition time has elapsed is higher than the predetermined temperature, the failure determination of the exhaust gas recirculation device can be accurately performed without misdiagnosis. And it can be performed reliably.

[Brief description of drawings]

The drawings show an embodiment of a method for detecting a failure of an exhaust gas recirculation system according to the present invention, FIG. 1 is a block diagram showing a schematic configuration of an exhaust gas recirculation system for carrying out the method of the present invention, and FIG. 2 is shown in FIG. A program flow chart showing a procedure executed by an electronic control unit (ECU) 20 shown to determine whether or not a failure determination of an exhaust gas recirculation device may be executed,
FIG. 4 is a graph showing the relationship between the failure determination prohibition time t _s and the cooling water temperature Tw immediately after the engine is started. FIG. 4 is a flowchart of the EGR failure determination routine shown in step 40 of FIG. 2, and FIG. 5 is the failure determination temperature. 7 is a graph showing the relationship between T _GX and intake air temperature Ta. 10 ... Internal combustion engine, 12 ... Intake pipe (intake passage), 13
...... Exhaust pipe, 15 ...... Exhaust gas recirculation passage, 16 ...... Exhaust gas recirculation valve (EGR valve), 20 ...... Electronic control unit (E
CU), 24 ... intake air temperature sensor, 25 ... engine cooling water temperature sensor, 28 ... alarm lamp,

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Susumu Saito 5-3-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation (72) Inventor Hiroshi Tanaka 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Automobile Industry Co., Ltd. (72) Inventor Takeshi Jimbo 5-3-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Industry Co., Ltd. (56) Reference JP-A-63-38678 (JP, A) JP-A-63- 243446 (JP, A) Actual public Sho 52-9471 (JP, Y1)

Claims (2)

[Claims] 1. When the exhaust gas recirculation device that recirculates a part of the exhaust gas of an internal combustion engine to an intake passage is in a state in which it should be operating, a temperature related to the temperature of the gas that recirculates in the exhaust gas recirculation device is detected, In the failure detection method for determining that the exhaust gas recirculation device has a failure when the detected temperature is lower than the failure determination value, the engine temperature at the time of engine start is detected, and the detected engine temperature can be regarded as a warm-up state. When the temperature is lower than the temperature, the prohibition time corresponding to the time required to reach the warm-up state is set, and when the detected engine temperature is higher than the temperature at which it can be considered that the warm-up is completed, the predetermined minimum prohibition time is set. A step of detecting the engine temperature after the prohibition time has passed and determining whether the engine temperature after the prohibition time has passed is higher than a predetermined temperature, It has been a failure detection method of the exhaust gas recirculation system and inhibits the malfunction determination until the engine temperature is detected to be higher than the predetermined temperature. 2. The exhaust gas recirculation device failure detection method according to claim 1, wherein the temperature representing the engine temperature is an engine cooling water temperature.