JPH0658097B2 - 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 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 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 “EGR 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. The opening / closing of the EGR valve is controlled according to the engine operating state so that an appropriate amount of exhaust gas is circulated 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, the exhaust gas recirculation gas does not flow at all when the EGR valve or the like normally operates and the required amount of the exhaust gas recirculation gas flows, but 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 recirculation gas is extremely large. 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 above-described exhaust gas recirculation device failure detection method, the exhaust gas recirculation gas temperature greatly changes depending on the atmospheric pressure. Therefore, if a constant value is used as the above-mentioned predetermined failure determination temperature, the failure determination temperature will be in various operating states. Assuming that the temperature has to be set to a low temperature, and if the exhaust gas recirculation device is subjected to failure determination using such a failure determination temperature, it may be misdiagnosed as not having a failure despite having a failure. obtain.

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 a certain time, in a failure detection method of detecting a temperature related to a temperature of gas 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, an atmospheric pressure is determined. A failure detection method for an exhaust gas recirculation device is provided, which detects and sets the failure determination value according to the detected atmospheric pressure, and the failure determination value that is set is lower when the atmospheric pressure is low than when it is high. It

(Function) The temperature of the exhaust gas recirculated to the intake passage depends on the atmospheric pressure, and the exhaust gas temperature decreases as the atmospheric pressure decreases. By setting the failure determination value to a value corresponding to the atmospheric pressure, Therefore, it becomes possible to detect the failure of the exhaust gas recirculation device more accurately and surely.

(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 provided in the exhaust gas recirculation passage 15
The actuator 16b is housed in a housing 16c and a housing 16c, which is divided into a negative pressure chamber 16f and an atmospheric pressure chamber 16g. And a spring 16e that is housed in the negative pressure chamber 16f and presses the diaphragm 16d in the direction of closing 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 and exposed in the exhaust gas recirculation passage 15 downstream of the valve element 16a, 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 temperature sensor 24 installed near the open end of the intake pipe 12 for detecting the intake air temperature, a water temperature sensor 25 for detecting the cooling water temperature of the engine 10, an atmospheric pressure. Atmospheric pressure sensor 2 for detecting
6, an engine speed sensor, an intake air amount sensor, etc., which are not shown, 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 of the exhaust gas recirculation device. 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 valve 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 the engine 10 is started is affected by the cooling water temperature state at the time of starting the engine 10, the above-described determination prohibition time _ts is the water temperature sensor immediately after the engine 10 is started. It is desirable to set according to the engine water temperature detected by 25. FIG. 3 is a graph showing the relationship between the determination prohibition time t _s and the water temperature Tw at the time of starting,
The determination inhibition time t _s 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. Even when the water temperature Tw at the time of starting the engine 10 is equal to or higher than the temperature T _WH that can be considered to be in a warm-up state, the determination prohibition time t _{s is set} to the minimum time t _so (for example, 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). Together with the determination of step 30 described above, it is to determine whether or not the engine 10 has been sufficiently warmed up. If the determination result is negative, then the program routine is executed without executing the later-described failure determination. To finish.

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), even if the exhaust gas is not recirculated through the exhaust gas recirculation passage 15, the EGR valve 16 and the EGR temperature sensor 2
2 itself may be hot, in which case
Since the exhaust gas recirculation gas temperature cannot be accurately measured, the program routine is ended without executing the failure determination described later. The determination in step 34 is made by the intake air temperature sensor 24 mounted near the open end of the intake pipe 12, but instead of the intake air temperature sensor 24, the ambient temperature (ambient temperature) of the engine 10 is measured, and this will be described later. It may be determined whether or not to perform the failure determination.

If the determination result in each of the above-mentioned steps is affirmative, it means that there is no problem in determining the exhaust recirculation device failure. In such a case, the electronic control unit 20 proceeds to step 40, and the fourth An exhaust gas recirculation device (EGR device) failure determination routine shown in the figure 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 calculated and set according to the atmospheric pressure Pa detected by the atmospheric pressure sensor 26, for example, by the following equation (1).

T _GX = (Pa / Po) × T _GO (1) where Po is the standard atmospheric pressure (760 mmHg) and T _GO is the standard failure determination temperature set at the standard atmospheric pressure.

From the above equation (1), when the atmospheric pressure Pa takes a value larger than the standard atmospheric pressure Po, the failure judgment temperature T _GX takes a value larger than the reference failure judgment temperature T _GO , and the atmospheric pressure Pa becomes the standard atmospheric pressure P.
It can be seen that when the value is smaller than o, the failure determination temperature T _GX is smaller than the reference failure determination temperature T _GO .

The determination temperature T _GX may be calculated and set by the following equation (2) instead of the above equation (1).

T _GX = T _GO −ΔT _G (2) Here, T _GO is the reference failure determination temperature set at the standard atmospheric pressure as in the case of the above formula (1), and ΔT _G is the electronic control unit 20. Is a correction value read according to the atmospheric pressure Pa detected by the atmospheric pressure sensor 26 from a table stored in a storage device (not shown). FIG. 5 shows the discrimination temperature correction value ΔT _G table stored in the storage device, and the discrimination temperature correction value ΔT _G is set to a larger value as the atmospheric pressure Pa decreases. This determination temperature correction value ΔT _G is given as a function of the atmospheric pressure Pa,
Various factors such as the shape of the R valve 16, the size of the exhaust gas recirculation passage 15, the recirculation amount of the exhaust gas recirculation gas, etc. affect the determination temperature correction value ΔT _G shown in FIG. 5 experimentally set for each engine. It is preferable.

Next, the electronic configuration roll 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 EGR valve 16 is opened, and the exhaust gas recirculation path 1
When the exhaust gas recirculation gas is normally recirculating through 5, that is, when the exhaust gas recirculation device is normally operating, the exhaust gas recirculation gas temperature T _G detected by the EGR temperature sensor 22 is detected.
Is sufficiently higher than the determination temperature T _{GX, in} which case the determination result of step 42 is affirmative, and the electronic control unit 20 resets a 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 gas recirculation gas temperature T _G
Even if the temperature is lower than the determination temperature T _GX , the failure determination routine is ended without directly determining that the exhaust gas recirculation device has a failure. 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 , the step 46 is repeatedly executed, and the predetermined time t _G has elapsed, the electronic control unit 20.
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. Thus, the driver can be made aware of the malfunction of the exhaust gas recirculation system, and the driver who is aware of the malfunction can take appropriate action directly.

In the case of an internal combustion engine mounted on a vehicle that is not frequently operated in a place where the atmospheric pressure is significantly lower than the standard atmospheric pressure, such as in high altitudes, the failure determination temperature T _GX is set to a fixed value. The failure determination of the exhaust gas recirculation device may be prohibited when the engine is operated in a high altitude where the atmospheric pressure is lower than a predetermined value. In this case, more specifically, the second
In a step subsequent to step 34 in the figure, the atmospheric pressure Pa detected by the atmospheric pressure sensor 26 is set to a predetermined determination value P _ax (for example, 70
0 mmHg) or more, and when the atmospheric pressure Pa is lower than the predetermined determination value Pax and the decrease of the exhaust gas recirculation gas temperature cannot be ignored, the program routine shown in FIG. 2 is ended without executing the failure determination. do it.

In the above embodiment, the EGR temperature sensor 22 is the EGR valve 16
Was attached to the side wall 16h near the valve body 16a of
The mounting location of the temperature sensor 22 is not limited to this, and may be mounted at any suitable position upstream or downstream of the EGR valve 16 as long as it is in the exhaust gas recirculation path 15.

Although the EGR temperature sensor 22 directly measures the exhaust gas recirculation gas temperature, the present invention is not limited to this, and the EGR temperature sensor 22 is not limited to this.
The R temperature sensor 22 may measure the temperature related to the exhaust gas recirculation gas temperature. For example, the R temperature sensor 22 may be attached to the side wall 16h near the valve body 16a of the EGR valve 16 and the exhaust gas recirculation gas temperature may be measured by separating the side wall 16h. Good.

(Effects of the Invention) As described in detail above, according to the exhaust gas recirculation device failure detection method of the present invention, the failure determination value is set according to the atmospheric pressure. Can be accurately and reliably detected regardless of the change in the exhaust gas, and thus appropriate measures such as repair of the exhaust gas recirculation device that has failed can be promptly taken.

[Brief description of drawings]

The drawings show an embodiment of a failure detection method for 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. FIG. 3 is a program flowchart that is executed by the electronic control unit (ECU) 20 and shows the procedure for determining whether or not the failure determination of the exhaust gas recirculation device may be performed. FIG. 3 shows the failure determination inhibition time t _s and the time immediately after the engine is started. A graph showing the relationship with the cooling water temperature Tw, FIG. 4 is a flowchart of the EGR failure determination routine shown in step 40 of FIG. 2, and FIG. 5 shows the relationship between the failure determination temperature correction value ΔT _G and the atmospheric pressure Pa. It is a graph. 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), 26 ... atmospheric pressure sensor, 28 ... alarm lamp.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Susumu Saito 5-33-8 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-63-195370 (JP, A)

Claims (1)

[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 a 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, atmospheric pressure is detected, and the failure determination value is set and set according to the detected atmospheric pressure. The method of detecting a failure of an exhaust gas recirculation device, wherein the determined failure determination value is smaller when the atmospheric pressure is low than when the atmospheric pressure is high.