KR920007814B1 - Fault detecting method of exhaust gas recirculation system - Google Patents

Abstract

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Description

Fault detection method of exhaust reflux system

1 is a block diagram showing a schematic configuration of an exhaust reflux device for implementing the method of the present invention.

FIG. 2 is a program flow diagram executed by the electronic control unit (ECU) 20 shown in FIG. 1 and showing a process of determining whether or not a failure determination of the exhaust reflux device may be performed.

3 is a graph showing the relationship between the fault determination prohibition time ts and the cooling mercury Tw immediately after engine start.

4 is a flowchart of an EGR failure determination routine shown in the stem 40 of FIG.

5 is a graph showing the relationship between the failure detection temperature T _GX and the initial temperature Pa.

The sixth turning failure determination failure determination temperature T _GX and a graph showing the relationship between the atmospheric pressure Pa is set according to the temperature adapted to the case of the atmospheric pressure Pa T _GX.

* Explanation of symbols for main parts of the drawings

10: engine 12: intake pipe

13 exhaust pipe 14 throttle valve

The present invention relates to a failure detection method of an exhaust reflux device for refluxing a part of exhaust gas of an internal combustion engine (hereinafter referred to as an engine) to an intake passage.

2. Description of the Related Art Exhaust reflux apparatuses have been known to reflux a part of the exhaust gas of an engine to an intake passage and reduce the amount of harmful gas components such as NO _X in the exhaust gas. The exhaust reflux device is provided between an exhaust reflux path communicating between the exhaust path and the intake path and an exhaust reflux valve (hereinafter referred to as "EGR valve") which opens and closes the exhaust reflux path and controls the operation of the EGR valve. It is composed of a control device for controlling the opening and closing of the EGR valve in accordance with the engine operation state so that an appropriate amount of exhaust gas is returned to the intake passage.

However, there is a problem that the exhaust gas characteristics deteriorate when carbon in the exhaust gas is deposited on the EGR valve or the like of the exhaust reflux device to close the passage and the required amount of exhaust gas cannot be returned to the intake passage. It is difficult for an ordinary driver or the like to detect such an abnormality or failure of such an exhaust reflux device unless a failure detection means is provided to detect it.

Therefore, when the exhaust reflux system is in the operating state, the temperature sensor (hereinafter referred to as "EGR temperature sensor") is installed in the exhaust reflux passage such as near the EGR valve or by blocking the wall to detect the exhaust reflux gas temperature. There is a method of detecting a failure of the exhaust reflux device. In this method, the EGR temperature sensor detects when the required amount of exhaust reflux gas flows due to the normal operation of the EGR valve or the like, and when the exhaust reflux gas does not flow at all due to the abnormality of the EGR valve or the like. A large difference occurs in the detected temperature, and when the exhaust reflux gas temperature detected by the EGR temperature detection is below a predetermined fault determination temperature, the exhaust reflux device is determined to be in a fault state by focusing on the temperature difference. Doing.

However, in the above-described fault detection method of the exhaust reflux device, the exhaust reflux gas temperature varies greatly depending on the air state sucked into the engine, for example, the temperature or the atmospheric pressure of the intake air, so that the predetermined fault determination temperature is a predetermined value. The failure determination temperature should be set to a low value considering various operating conditions. In addition, if the exhaust reflux device is used for failure determination using such a low failure determination temperature, there may be a case in which there is a misdiagnosis that there is no failure despite the failure state.

In addition, in the above-described fault detection method of the exhaust reflux device, when the engine is not completely warmed up immediately after starting, the operating state of the engine is not stable and therefore the exhaust reflux gas temperature is also unstable. If the engine is in such a state and the exhaust reflux system is judged to be faulty, the fault determination cannot be made correctly and there is a risk of misdiagnosis.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fault detection method of an exhaust reflux device which can accurately and reliably detect an abnormality or a failure of the exhaust reflux device, and thus can promptly take appropriate processing such as repair of a failed exhaust reflux device. .

According to the present invention, when the exhaust reflux apparatus is in a state in which it is necessary to perform an operation of refluxing a part of the exhaust gas of the engine to the intake passage, the temperature relating to the gas temperature for refluxing the exhaust reflux apparatus is detected, and the detected temperature is broken. A failure detection method is provided that determines that the exhaust reflux device is broken when lower than the discriminated value.

The fault discrimination value of the fault detection method of the present invention is set in accordance with the air state sucked into the engine, for example, the state of intake air temperature, atmospheric pressure and the like.

Further, preferably, the temperature indicating the engine temperature is detected, and the fixed determination is prohibited until the detected temperature indicating the engine temperature after the engine starts reaches a predetermined value.

More preferably, it is preferable to measure the elapsed time from the start of the engine start and to prohibit the fixed determination until a predetermined time has elapsed after the engine start.

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description based on the accompanying drawings.

First, with reference to FIG. 1, the whole structure of the exhaust reflux apparatus which implements this method is demonstrated.

The intake pipe 12 is connected to the intake side of the engine 10, and the exhaust pipe 13 is connected to the exhaust side, respectively. A throttle valve 14 is disposed in the intake pipe 12, and one end of the exhaust reflux path 15 is connected to the intake pipe 12 downstream of the throttle valve 14, and the other end of the exhaust reflux path 15 is exhaust pipe. It is connected to (13).

An exhaust reflux valve (EGR valve) 16 is disposed in the middle of the exhaust reflux path 15. The EGR valve 16 is composed of a valve member 16a for opening and closing the exhaust reflux path 15 and an actuator 16b for opening and closing the valve member 16a. The actuator 16b includes a housing 16c and a housing. A diaphragm 16d which is built in the 16c and divides the inside of the housing 16c into a negative pressure chamber 16f and an atmospheric pressure chamber 16g and is connected to the valve member 16a; It is comprised by the spring 16a which is built in the negative pressure chamber 16f and presses the diaphragm 16d in the direction which closes the valve member 16a.

The one end of the 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, whereby the throttle valve 14 The negative pressure generated in the downstream intake pipe 12 flows into the negative pressure chamber 16f via the negative pressure path 17. In the middle of the negative pressure path 17, a normally closed solenoid valve 18 is provided and electrically connected to the electronic control unit (ECU) 20. The solenoid valve 18 opens the valve in response to the open valve signal supplied from the electronic controller 20 to hydraulic pressure the negative pressure into the negative pressure chamber 16f of the actuator 16b.

The EGR temperature sensor 22 is provided in the side wall 16h of the EGR valve 16, and the temperature sensor part 22a is provided in the front-end | tip. The temperature sensor 22a is exposed to the exhaust gas return path 15 and communicates with the exhaust gas return path 15 downstream of the valve member 16f. The EGR temperature sensor 22 detects the exhaust reflux gas temperature and supplies the detection signal to the electronic controller 20.

On the input side of the electronic control device 20, various sensors for detecting the operating state of the engine 10, for example, are provided near the air open end of the intake pipe 12, and the intake air temperature sensor 24 for detecting the intake air temperature, the engine As the temperature indicating temperature, a water temperature sensor 25 for detecting the coolant temperature of the engine 10, an atmospheric pressure sensor 26 for detecting the atmospheric pressure, an engine speed sensor (not shown), an intake air amount detector (not shown), and the like are connected. Various detection signals from these detectors are supplied to the electronic controller 20. On the output side of the electronic control apparatus 20, an alarm lamp 28 for warning the failure when a failure of the exhaust reflux device is detected is connected, and this lamp 28 is installed in, for example, an instrument panel of an automobile.

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

Since the valve member 16a of the EGR valve 16 is normally pressed in the open valve direction by the spring 16e, the EGR valve 16 is in the closed valve state. The electronic controller 20 outputs an open valve driving signal to the solenoid valve 18 to open the valve 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 is opened, the 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. When the negative pressure is supplied to the negative pressure chamber 16f, the atmospheric pressure applied to the surface of the diaphragm 16d in contact with the atmospheric pressure chamber 16g is greater than the negative pressure applied to the surface of the diaphragm 16d in contact with the atmospheric pressure chamber 16f. . As a result, the atmospheric pressure causes the EGR valve 16 to be opened by moving the valve member 16a upward in the drawing in response to the repulsive force of the spring 16e. When the EGR valve 16 is opened, a part of the exhaust gas of the exhaust pipe 13 is returned to the intake pipe 12 via the exhaust return path 15.

Next, the procedure of detecting the failure of the exhaust reflux apparatus by the electronic control apparatus 20 will be described with reference to FIGS.

2 is a program executed when the exhaust reflux device is in operation, that is, when the EGR valve 16 is opened and the exhaust gas is to be returned to the intake pipe 12 through the exhaust reflux path 15. This program routine determines whether or not it is in a state where it is possible to perform the fixed discrimination of the exhaust reflux device.

The electronic control apparatus 20 first determines in step 30 whether ts time (unit amount) has elapsed since the start of the engine 10. The engine 10 is not yet warmed up immediately after starting, and the exhaust gas temperature returned through the exhaust reflux path 15 during the movement is not stable. If the exhaust reflux device is fixed in this state, there is a fear of misjudgment. have. Therefore, when the determination result of step 30 is No, that is, when the engine 10 has not yet warmed up, the program routine is terminated without executing the failure determination described later.

In addition, since the time required to complete the warm-up after starting the engine 10 affects the coolant temperature state at the start of the engine 10, the above-described determination prohibition time ts is determined by the water temperature sensor immediately after the engine 10 starts. It is preferable to set according to the engine water temperature detected by 25). 3 is a graph showing the relationship between the determination prohibition time ts and the water temperature ts at startup, and the determination prohibition time ts is set in a short time as the water temperature Tw is higher in accordance with the water temperature Tw detected immediately after the engine 10 is started. Further, even when the water temperature Tw at the start of the engine 10 is equal to or higher than the temperature Tw _H considered to be in the warm-up state, the determination prohibition time ts is set to at least tso (for example, 2 minutes) to wait for the engine 10 to be completely stabilized. It is preferable to perform the failure determination described later.

When the determination result of step 30 is YES, it is determined whether the engine stud Tw is more than predetermined value Twx (for example, 80 degreeC) (step 32). This step 32 determines whether or not the engine 10 is sufficiently warmed up in addition to the above-described determination of step 30. If the result of the determination in step 32 is NO, the program routine is terminated without executing the failure determination described later.

If the determination result of step 32 is YES, the electronic controller 20 determines whether or not the intake air temperature Ta detected by the intake air temperature sensor 24 is lower than the predetermined determination value Tax (for example, 60 ° C) (step). 34). When the intake temperature Ta is high (when the determination of step 34 is NO), the EGR valve 16 and the EGR temperature sensor 22 themselves are maintained at a high temperature even though the exhaust gas is not refluxed via the exhaust reflux path 15. In this case, the exhaust reflux gas temperature cannot be measured accurately, and thus the program routine is terminated without executing the fixed judgment described later. Incidentally, the determination of the step 34 was made by the intake air temperature sensor 24 installed near the air open end of the intake pipe 12, but the ambient temperature (atmosphere temperature) of the engine 10 in place of the intake air temperature sensor 24. ) May be determined to determine whether or not the fault determination described later may be executed.

Next, if the determination result of step 34 is YES, it progresses to step 36, and it determines whether atmospheric pressure Pa detected by the atmospheric pressure sensor 26 is more than predetermined discrimination value Pax (for example, 700 mmHg). When the engine 10 is operated under an atmospheric condition having a low atmospheric pressure as in a high altitude delay, the exhaust temperature is lowered and the exhaust reflux gas temperature is also lowered. Therefore, when the atmospheric pressure Pa is lower than the predetermined determination value Pax and the decrease in the exhaust reflux gas temperature cannot be ignored (the determination result of the system 36 is no), the program routine is terminated without executing the fixed determination described later. .

If the above-described determination results in each step are all yes, it means that there is no problem even if the exhaust reflux device is troubled. In such a case, the electronic control device 20 proceeds to step 40. Shown in 4 shows a fixed decision routine of the exhaust reflux device (EGR device).

First, the electronic controller 20 sets the failure determination temperature T _GX by the exhaust reflux gas temperature in step 41 of the fixed determination routine. This discrimination temperature T _GX is read out according to the intake air temperature Ta detected by the intake air temperature sensor 24 from the table stored in the storage device (not shown) of the electronic control device 20. 5 shows a discrimination temperature T _G x table stored in the storage device, and the discrimination temperature T _G x is set to a higher temperature value as the Ta is raised. This discrimination temperature T _G x is given as a function of the intake temperature Ta, but the shape of the EGR valve 16, the size of the exhaust reflux path 16, the reflux amount of the exhaust reflux gas, the installation position of the EGR temperature sensor 22, and the like. Since it changes according to various factors, it is preferable to set the discrimination temperature T _Gx table shown in FIG. 5 experimentally for each engine.

Next, the electronic controller 20 compares the exhaust reflux gas temperature T _G detected by the EGR temperature sensor 22 with the discrimination temperature T _G x set in step 41 to determine the exhaust reflux gas temperature T _G. determines whether or not higher than a temperature T x _G (step 42). The exhaust reflux gas detected by the EGR temperature sensor 22 when the EGR valve 16 is opened and the exhaust reflux gas is normally refluxed through the exhaust reflux path 15, that is, when the exhaust reflux device operates normally. The temperature T _G is higher than the determination temperature T _G v. In this case, the determination result of step 42 is an example, and the electronic controller 20 resets the timer described later (step 44), thereby terminating the failure determination routine. do. When the exhaust reflux gas temperature T _G is lower than the determination temperature T _G x, that is, when the determination result of step 42 is no, the electronic controller 20 determines when the determination at step 42 initially shows no. It is determined whether the predetermined time t _G (e.g., 30) seconds has elapsed, i.e., whether the timer reset by the normal operation of the exhaust reflux device in step 44 has counted up by the predetermined time t _G. This timer may be a hard timer built in the electronic control apparatus 20, or may be a so-called soft timer that monitors the passage of time by executing a program. If the predetermined time T _G has not elapsed, the exhaust reflux device is not judged to have a failure even if the exhaust reflux gas temperature T _G is lower than the discrimination temperature T _G x, and the failure determination routine ends. This determination can avoid misjudgment due to noise or the like.

If the exhaust reflux gas temperature T _G is lower than the discrimination temperature T _G x, so that the step 46 is repeatedly executed over the predetermined time t _G , the electronic controller 20 determines that the exhaust reflux device is in a fault state. If it is determined that it is, the step 48 is executed, and the alarm lamp 28 is turned on to warn the driver lamp of the exhaust reflux device failure. In this way, the driver can recognize the failure of the exhaust reflux system and the driver who recognizes the failure can immediately take appropriate treatment. In addition, in the above-described embodiment, the EGR temperature sensor 22 is installed on the side wall 16h near the valve member 16a of the EGR valve 16. However, the installation place of the EGR temperature sensor 22 is not limited thereto, but the exhaust gas is not limited thereto. You may install in the middle of the reflux path 15, the upstream of the EGR valve 16, or a suitable position in either of the downstream layers.

The EGR temperature sensor 22 measures the exhaust reflux gas temperature directly, but the present invention is not limited thereto. The EGR temperature sensor 22 measures the temperature related to the exhaust reflux gas temperature or, for example, The temperature sensor 22 may be provided on the side wall 16k near the valve member 16a of the EGR valve 16 to measure the temperature of the exhaust reflux gas indirectly passing through the side wall 16h.

In the above embodiment, the engine coolant temperature has been described as an example of the temperature representing the engine temperature. However, the present invention is not limited thereto, and the engine oil temperature may be used as the temperature representing the engine temperature.

Incidentally, in the above-described embodiment, the failure determination temperature T _G x is set as a function of the intake air temperature Ta, but may be set in accordance with the ambient temperature (atmosphere temperature) of the engine 10 instead. Further, the temperature T _G x can be set in accordance with the atmospheric pressure or both the intake temperature ta and the atmospheric pressure.

In addition, in the case of an engine mounted on a vehicle where the atmospheric pressure is not frequently performed at a place where the atmospheric pressure is significantly lower than the standard atmospheric pressure, such as at a high altitude, the failure determination temperature T _G x is It may be set to a value not related to atmospheric pressure (for example, may be a fixed value), and the failure determination of the exhaust reflux device may be prohibited when the engine is operated at a high altitude where the atmospheric pressure is lower than a predetermined value. . However, when the engine is operated in a region where the atmospheric pressure is largely changed, it is preferable to set the failure determination temperature T _G x in accordance with the atmospheric pressure.

When setting the failure determination temperature T _G x in accordance with the atmospheric pressure, the electronic controller 20 at step 41 of the failure determination routine, the atmospheric pressure Pa detected by the failure determination temperature T _G x atmospheric pressure sensor 26. For example, the operation is set by the following expression (1).

T _G x = (Pa / Po) × T _G o ....................... (1)

Po is the standard atmospheric pressure (760mmHg), and T _G o is the standard fault discrimination temperature set in standard atmospheric pressure.

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

T _G x = T _G o- △ T _G ........................ (2)

Here, T _G o is a reference failure discrimination temperature set at atmospheric pressure as in the case of equation (1), and ΔT _G is from a table stored in a storage device (not shown) of the electronic control device 20. It is a correction value read according to the atmospheric pressure Pa detected by the atmospheric pressure sensor 26. 6 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 discrimination temperature correction value ΔT _G is given as an atmospheric pressure Pa function and is shown in FIG. 6 because it varies depending on various factors such as the shape of the EGR valve 16, the size of the exhaust reflux path 15, and the reflux amount of the exhaust reflux gas. It is preferable that the discrimination temperature set value DELTA T _G to be set experimentally for each engine.

Claims (7)

When the exhaust reflux device for returning a part of the exhaust gas of the engine to the intake passage is in a state to be operated, it detects a temperature related to the gas temperature for refluxing the exhaust reflux device, and when the detected temperature is lower than the failure determination value A failure detection method for determining that an exhaust reflux device is broken, the failure detection method for an exhaust reflux device characterized by detecting an air state sucked by the engine and setting the failure discrimination value according to the detected intake state. The fault detection method according to claim 1, wherein the air state is an intake air temperature, the intake air temperature is detected, and the fault discrimination value is set according to the detected intake air temperature. The fault detection method according to claim 1, wherein the air state is atmospheric pressure, and the fault discrimination value is set according to the atmospheric pressure detected by detecting the atmospheric pressure. The fault detection method of claim 1, wherein the fault determination is prohibited until the temperature indicating the engine temperature reaches a predetermined value after the engine is started. 5. The method of claim 4, wherein the temperature representing the engine temperature is an engine coolant temperature. The fault detection method of claim 1, wherein the fault determination is prohibited until a predetermined time elapses after the engine is started. The fault detection method of claim 6, wherein the predetermined time is set according to an engine temperature detected immediately after the engine is started.

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