JPH06249080A - Method for judging failure in exhaust gas recirculating method - Google Patents

Abstract

PURPOSE:To avoid the erroneous judgement of a failure in an EGR by correcting at least one of differential pressure or judging value according to a change in the opening of a bypass valve before and after the opening and closing of the EGR valve. CONSTITUTION:A bypass path 4 bypassing a throttle valve 3 provided in an intake path 2 of an engine 1 is provided. A bypass valve (ISC valve) 5 controlled according to the running condition of the engine 1 is provided in the bypass path 4. An EGR valve 9 in the deceleration region of the engine 1 is temporarily turned on and off to detect the differential pressure of intake pressure and check an exhaust gas recirculating device(EGR). Then, a throttle valve 3 before and after the opening and closing of the EGR valve 9 is bypassed to detect a change in the opening of the ISC valve 5 in the bypass path 4. In the presence of the change in the opening, at least one of the differential pressure or judging value is corrected according to the change in the opening to avoid the erroneous judgement of a failure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation device failure determination method.

[0002]

Exhaust gas components of a gasoline engine are mainly carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NOx), which are contained in the air-fuel mixture due to the high temperature during combustion. Most of the nitrogen oxides contained in the exhaust gas of an automobile are NO, which are produced by the reaction between nitrogen and oxygen. Even if the air-fuel ratio is the same, if the amount of the inactive component in the air-fuel mixture is increased, the combustion temperature is lowered and the generation of NO is reduced. An exhaust gas recirculation device (hereinafter referred to as “EGR”) is a device that purifies the exhaust gas by returning a part of the exhaust gas to the intake system as the inactive component and adding it to the mixture.

As a method of diagnosing this EGR failure,
There is a "diagnosis method for exhaust gas recirculation control device" disclosed in JP-A-2-9937. This diagnostic method is executed when the engine is in the deceleration region where fuel cut is being performed.When the engine is in a stable state after completion of warming up, the microcomputer system opens and closes the negative pressure switching valve. The intake air pressure is introduced into the negative pressure passage, and the exhaust gas recirculation is performed so that the intake pressure can act on the negative pressure chamber of the EGR valve via the EGR modulator. When the pressure difference between the atmospheric pressure and the intake pressure after recirculation is less than the set value, it is determined that the EGR is out of order.

That is, when the throttle valve is fully closed (deceleration region), the EGR check mode is turned on to start the EGR check, and after a predetermined time has elapsed, the EGR is forcibly turned on and off until the check is completed. , Inspiratory pressure ie
It is determined that the change amount of the intake manifold pressure (hereinafter referred to as “manifold pressure”) is normal when the change amount is equal to or more than a predetermined range, and the failure is when the change amount is less than the predetermined range.

[0005]

By the way, in the electronically controlled engine, the idle speed control (ISC) is one of the control items for automatically adjusting the idle speed to a predetermined target speed. There is a function and I in the bypass passage that bypasses the throttle valve.
An SC valve is provided to adjust the idle speed. That is, when the idle speed is set low, the engine may stall when a relatively large electric load such as an air conditioner or a power steering / pump drive load is applied. Therefore, the ISC valve is opened to reduce the idle speed. I am trying to raise it.

However, the above fault diagnosis method is
If the ISC valve opening changes during the R check, the manifold pressure changes accordingly, and the failure cannot be correctly determined. For example, when the EGR check is started at the point A at the reference opening of the ISC valve shown by the solid line in FIG. 1 and the check is completed at the point A ′ at the ISC idle up shown by the dotted line, the manifold pressure becomes high and the EGR becomes Even if it is a failure, it may be erroneously determined to be normal. On the contrary, when the EGR check is started at the point A ′ in FIG. 1 and the check is completed at the point A, the manifold pressure becomes low, and there is a possibility that it may be determined to be a failure even if the EGR is normal. There is.

The present invention has been made in view of the above points, and when the intake air amount bypassing the throttle valve changes during the EGR check, the intake pressure is corrected according to the change amount to avoid erroneous determination. It is an object of the present invention to provide a method for determining a failure of the exhaust gas recirculation device.

[0008]

In order to achieve the above object, according to the present invention, a bypass passage bypassing a throttle valve provided in an intake passage of an engine, and an EGR connecting the intake passage and the exhaust passage with each other. A bypass valve that is controlled according to the operating state of the engine is provided in the bypass passage, and an EGR valve that is controlled according to the operating state of the engine is provided in the EGR passage. The EGR valve is temporarily opened and closed in the deceleration region of the engine, the differential pressure of the intake pressure before and after the opening and closing is compared with a determination value, and it is determined whether the differential pressure is less than or equal to the determination value and exhaust gas recirculation is performed. An exhaust gas recirculation device failure determination method for determining a device failure, comprising the steps of:
At least one of the differential pressure and the determination value is corrected in accordance with a change in the opening degree of the bypass valve before and after opening and closing the valve.

[0009]

In the deceleration region of the engine, the EGR valve is temporarily turned on and off to detect the differential pressure of the intake pressure to detect the EGR.
When performing the check, the change in the opening of the bypass valve provided in the bypass passage that bypasses the throttle valve before and after the opening and closing of the EGR valve is detected, and when there is a change in the opening, the difference according to the change in the opening is detected. At least one of the pressure and the determination value is corrected to avoid a false error determination.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 2 shows an outline of an exhaust gas recirculation system to which the method of the present invention is applied. A bypass passage 4 that bypasses the throttle valve 3 is provided in the intake passage 2 of the engine 1, and the bypass passage 4 is idle. A speed control valve (hereinafter referred to as “ISC valve”) 5 is provided. The EGR valve 9 is interposed in a passage 8 that connects a downstream side of the surge tank 6 of the intake passage 2 and an upstream side of the exhaust passage 7 to the catalyst device, and recirculates a part of the exhaust gas (recirculation) to the intake passage 2. ). The negative pressure chamber 9a of the EGR valve 9 is connected to the intake passage 2 on the downstream side of the throttle valve 3 and can communicate with the atmosphere via an EGR solenoid valve (electromagnetic valve) 10.

The EGR valve 9 is closed when the negative pressure chamber 9a communicates with the atmosphere to close the passage 8, and the negative pressure chamber 9a is connected to the intake passage 2 to supply a manifold pressure (negative pressure). Then, the valve is opened and a part of the exhaust gas in the exhaust passage 7 is returned to the intake passage 2 through the passage 8. EGR solenoid valve 10
Is opened when deenergized (OFF) to communicate the negative pressure chamber 9a of the EGR valve 9 with the atmosphere, and closed when energized (ON) to communicate the negative pressure chamber 9a of the EGR valve 9 with the intake passage 2. Let

An engine rotation sensor 11 for detecting the rotation of the crankshaft is provided in the engine 1, a pressure sensor 12 is provided in the surge tank 6 of the intake passage 2, and an O ₂ is provided in the exhaust passage 7.
A sensor 13 is provided. Electronic control unit (ECU)
15 is an engine rotation sensor 11, a pressure sensor 12, O
₂ sensor 13, air flow sensor, idle switch (turned on when throttle valve 3 is fully closed), cooling water temperature sensor, air conditioner switch, power steering switch, etc. (not shown) From the engine rotation sensor and the air flow sensor to calculate the intake air amount (A / N) per cylinder, engine speed, A / N, operating state of each auxiliary machine and exhaust gas. The fuel injection amount from the injector 14, the valve opening degree of the ISC valve 5, the valve opening degree of the EGR valve 9 and the like are set according to the oxygen concentration in the inside.
The ISC valve 5 is driven by a stepper motor,
The GR solenoid valve 10 is duty-controlled.

When the EGR valve 9 opens and closes (ON-OFF), the internal pressure of the surge tank 6 changes with the change of the EGR flow rate, and the EGR flow rate when the EGR valve 9 is open (ON) is smaller than that in the normal state. Since the pressure change is less than or equal to the predetermined value, it is possible to detect the EGR failure. Further, in order to suppress the torque fluctuation of the engine due to the opening and closing of the EGR valve 9 as much as possible, the EGR failure determination is monitored in the deceleration region (zone).

A method of determining a failure of the exhaust gas recirculation device will be described below with reference to the flowcharts of FIGS. 3 and 4. The electronic control unit 15 first initializes all flags and timers necessary for failure determination (step S in FIG. 3).
1) It is determined whether or not it is in the EGR check zone (step S2). In this EGR check zone, the engine rotation speed Ne is a predetermined rotation speed equal to or higher than the idle rotation speed, for example, 1300 rpm or higher (Ne ≧ 1300 rp).
m) and the deceleration region where the idle switch is on (FIG. 9). Then, when the engine is not in this EGR check zone, the process returns to step S1, and when it is in the EGR check zone, it is determined whether or not the engine has stayed in the EGR check zone for a predetermined time T ₁ or more (step S3). If the determination result in step S3 is negative (NO), the process returns to step S2, and if affirmative (YES), the EGR solenoid valve 10 is turned off to close the EGR valve 9 and EGR is turned off (step S4). After turning off, it is determined whether a predetermined time T ₂ has elapsed (step S5).

The time T ₁ in step S3 is a confirmation timer time for confirming that the engine operating region is in the EGR check zone, and the time T ₂ in step S5 is a confirmation timer for confirming that the EGR is off. It's time. Then, the electronic control unit 15 determines that the monitor condition for the EGR failure determination is satisfied when these times T ₁ and T ₂ have elapsed (FIG. 10A).

The electronic control unit 15 returns to step S2 when the determination result of step S5 is negative (NO), and when the determination result is affirmative (YES), that is, when the monitor condition is satisfied, whether the flag F is 1 or not is determined. Judge (step S
6). At this time, the flag F is still 0, so the determination result is negative (NO) and the EGR check is started. Then, the manifold pressure (P ₁ ) and the opening degree (θ ₁ ) of the ISC valve 5 at the start of the EGR check are stored in the memory (step S7), and the flag F is set to 1 (step S8). Next, the electronic control unit 15 turns on the EGR solenoid valve 10 (FIG. 10 (b)), and the EGR solenoid valve 10 is turned on.
The valve 9 is opened to turn on the EGR (step S
9).

The electronic control unit 15 judges whether or not a predetermined time T ₃ (for example, 1 second) has elapsed after turning on the EGR (step S10), and when the predetermined time T ₃ has not elapsed, a step S2 When the predetermined time T _{3 has} elapsed, the EGR check is completed, and the manifold pressure (P ₂ ) and the opening degree (θ ₂ ) of the ISC valve 5 at the time when the EGR check is completed are stored in the memory. This time T ₃ is EGR
Is for a sufficient time to confirm that is on (EGR valve 9 is open). Then, the electronic control unit 15
ISC valve opening θ ₂ at the time of completion of EGR check
And the ISC valve opening θ ₁ at the start of the EGR check (θ ₂ −θ ₁ ) is obtained, and the ISC opening correction value P _CNE of the _manifold pressure corresponding to the difference (θ ₂ −θ ₁ ) is _calculated from the map. Obtain (step S12). This ISC opening correction value P _CNE is
As shown in FIG. 5, the snap change amount of the ISC valve 5, that is, the number of steps of the stepper motor and the intake pressure are in a proportional relationship. Therefore, the correction value P of the manifold pressure according to the opening difference (θ ₂ −θ ₁ ) is obtained. You can ask for _CNE . This correction value P
_{The CNE} is stored in the map shown in FIG.

Next, the electronic control unit 15 obtains a differential pressure (ΔP = P ₂ −P ₁ ) between the manifold pressure P ₂ at the time of completing the EGR check and the manifold pressure P ₁ at the time of starting the EGR check, and further the differential pressure. wherein by adding the correction value P _CNE corrected Mani pressure in accordance with the opening degree variation of the ISC valve 5 to the (P ₂ -P ₁
+ P _CNE ), this corrected manifold pressure is the failure judgment value ΔP _EGR
(FIGS. 10 (c) and 10 (d)) is determined (step S13). For example, as shown in FIG. 7, when the ISC valve opening is larger than the reference opening at the EGR check start time A ′ and changes to the reference opening during the check, the correction value P is added to the manifold pressure at the completion of the EGR check. _CNE is added to raise from point A to point A ". On the contrary, as shown in FIG.
When the valve opening is at the reference opening and becomes larger than the reference opening during the check, the correction value P _CNE is subtracted from the _manifold pressure at the time when the EGR check is completed, and the value is lowered from the point A ′ to the point A ″.

Then, when the determination result of step S13 is affirmative (YES), it is determined that the EGR is normal (step 14), and when it is negative (NO), it is determined that the EGR is defective (step 15). Electronic control unit 15
When it is determined that the EGR is out of order in step S15, the EGR check lamp (not shown) is turned on to inform the driver that the EGR is out of order (FIG. 10).
(E), (f)).

In the above embodiment, the difference in opening of the ISC valve before and after opening and closing the EGR valve (θ ₂ −θ ₁ )
Obtain a correction value P _CNE depending on, showed that by correcting the Mani pressure of the differential pressure (P ₂ -P ₁₎ in the correction value P _CNE, the correction instead of the pressure difference (P ₂ -P ₁₎ The failure determination value ΔP _EGR may be corrected with the value P _CNE .

[0021]

As described above, according to the present invention, E
When the ISC valve opening changes during the GR check, at least one of the manifold pressure and the judgment value is corrected in accordance with the change in the opening of the ISC valve before and after the opening and closing of the EGR valve to correct the exhaust gas recirculation device. There is an effect that it is possible to avoid erroneous determination of a failure, it is possible to correctly determine a failure, and it is possible to increase the chances of the determination.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between manifold pressure and ISC valve opening.

FIG. 2 is a diagram showing an outline of an exhaust gas recirculation device for an engine for carrying out a failure determination method for an exhaust gas recirculation device according to the present invention.

FIG. 3 is a part of a flowchart showing a procedure of a failure determination method for an exhaust gas recirculation device according to the present invention.

FIG. 4 is the rest of the flowchart showing the procedure of the failure determination method for the exhaust gas recirculation device according to the present invention.

FIG. 5 is a graph showing the relationship between changes in ISC valve opening and manifold pressure.

FIG. 6 is a diagram showing an example of a map in which a correction value of the manifold pressure according to the opening change amount of the ISC valve is stored.

[FIG. 7] IS at the time of failure determination of the exhaust gas recirculation device
It is a figure which shows correction | amendment of the manifold pressure accompanying the C opening change.

FIG. 8 IS at the time of failure determination of the exhaust gas recirculation device
It is a figure which shows correction | amendment of the manifold pressure accompanying the C opening change.

9 is a diagram showing an example of a monitor zone (deceleration region) for determining a failure of the exhaust gas recirculation device shown in FIG.

10 is a time chart showing an outline of the operation of the exhaust gas recirculation device shown in FIG.

[Explanation of symbols]

1 Engine 2 Intake Passage 3 Throttle Valve 4 Bypass Passage 5 ISC Valve 6 Surge Tank 7 Exhaust Passage 9 EGR Valve 10 EGR Solenoid Valve 11 Engine Rotation Sensor 12 Pressure Sensor 13 O ₂ Sensor 15 Electronic Control Unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazutoshi Noma 5-3-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (72) Yasuhisa Yoshida 5-33-8 Shiba, Minato-ku, Tokyo Within Mitsubishi Motors Corporation

Claims (1)

[Claims] 1. A bypass passage that bypasses a throttle valve provided in an intake passage of an engine, and an EGR passage that connects the intake passage and the exhaust passage are provided, and the bypass passage corresponds to an operating state of the engine. A bypass valve controlled in accordance with the operating state of the engine is provided in the EGR passage, and the EGR valve is temporarily opened and closed in the deceleration region of the engine. In the exhaust gas recirculation device failure determination method, which compares the differential pressure of the intake pressure before and after opening and closing with a determination value and determines whether the differential pressure is less than or equal to the determination value to determine the failure of the exhaust gas recirculation device, At least one of the differential pressure and the determination value is corrected corresponding to a change in the opening degree of the bypass valve before and after the opening and closing of the EGR valve. Exhaust gas recirculation device failure determination method.