JP3060771B2 - Failure determination method for exhaust gas recirculation system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Exhaust gas components of a gasoline engine are mainly carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NOx). Most of the nitrogen oxides produced by the reaction between nitrogen and oxygen and contained in the exhaust gas of automobiles are NO. Even if the air-fuel ratio is the same, if the amount of inert components in the air-fuel mixture is increased, the combustion temperature is reduced, and the generation of NO is reduced. An exhaust gas recirculation device (hereinafter, referred to as "EGR") is a device for purifying exhaust gas by returning a part of the exhaust gas as an inert component to the intake system and adding the mixture to the air-fuel mixture.

As a method of diagnosing the EGR failure,
There is a "method of diagnosing failure of the exhaust gas recirculation control device" disclosed in Japanese Patent Application Laid-Open No. 2-9937. This diagnosis method is executed when the engine is in a deceleration region where fuel cut is performed. When the engine is in a stable state after the completion of warm-up, the microcomputer switches the negative pressure switching valve from closed to open. The intake air is introduced into the negative pressure passage, and the exhaust gas is recirculated through the EGR modulator so that the intake pressure can be applied to the negative pressure chamber of the EGR valve. If 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 has failed.

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

[0005]

However, the above-mentioned failure diagnosis method is characterized in that when the EGR check is released from the fuel cut mode or the fuel cut mode is entered from outside the fuel cut mode, the change in the manifold pressure due to the presence or absence of combustion occurs. , The failure determination cannot be performed correctly. For example, when the EGR check is started at the point A at the time of the fuel cut indicated by the solid line in FIG. 1 and the check is completed at the point A ′ outside the fuel cut indicated by the dotted line, the manifold pressure becomes as shown by the solid line in FIG. As a result, even if the EGR is faulty, it is erroneously determined to be normal.
Conversely, 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 changes as shown by the dotted line in FIG. 2, and as a result, the EGR is normal. Also has the problem that it is determined to be a failure.

The present invention has been made in view of the above points, and when there is a mode change relating to the presence or absence of combustion during an EGR check, the EGR check is stopped to avoid an erroneous determination. An object of the present invention is to provide a method for determining a failure of a circulation device.

[0007]

According to the present invention, an EGR valve provided in a passage connecting an exhaust passage and an intake passage of an engine is temporarily provided in a deceleration region of the engine. In the exhaust gas recirculation device failure judging method for judging the failure of the exhaust gas recirculation device by comparing the intake pressure before and after the switching when the opening and closing are switched, and before and after the switching,
At the time of fuel cut control
Storing Te, the state of the fuel cut control during the intake pressure detecting period between after switching before and switching of the EGR valve is the
The failure determination is stopped when the state changes to a state different from the stored state .

[0008]

In the deceleration region of the engine, the EGR valve is temporarily turned on and off to detect a differential pressure of the intake pressure and to detect the EGR.
When the EGR check is performed, the fuel control mode of the engine at the start and the completion of the EGR check is detected to determine whether or not the change relating to the combustion matches. Then, when there is a mode change related to combustion during the failure determination, the determination is stopped to avoid erroneous determination.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 3 shows an outline of an exhaust gas recirculation device to which the method of the present invention is applied. In the intake passage 2 of the engine 1, a bypass passage 4 that bypasses a throttle valve 3 is provided. 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 the downstream side of the surge tank 6 in the intake passage 2 and the upstream side of the catalyst device in the exhaust passage 7, and recirculates a part of the exhaust gas to the intake passage 2 (recirculation). ). The negative pressure chamber 9 a 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.

When the negative pressure chamber 9a is communicated with the atmosphere, the EGR valve 9 is closed 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
The valve is opened when deenergized (off) to communicate the negative pressure chamber 9a of the EGR valve 9 with the atmosphere, and is closed when energized (on) to communicate the negative pressure chamber 9a of the EGR valve 9 with the intake passage 2. Let it.

The engine 1 has an engine rotation sensor 11 for detecting rotation of a crankshaft, the surge tank 6 in the intake passage 2 has a pressure sensor 12, and the exhaust passage 7 has O _2.
A sensor 13 is provided. Electronic control unit (ECU)
Reference numeral 15 denotes an engine rotation sensor 11, a pressure sensor 12, and O
₂ Sensor 13, air flow sensor, idle switch (turns on when throttle valve 3 is fully closed), cooling water temperature sensor, or switch indicating the operating state of auxiliary equipment such as air conditioner switch, power steering switch, etc. (none is shown) And calculates the intake air amount (A / N) per cylinder based on the signals from the engine rotation sensor and the air flow sensor, and calculates the engine speed, A / N, the operating state of each accessory, and the exhaust gas. The fuel injection amount from the injector 14, the valve opening of the ISC valve 5, the valve opening 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 duty of the GR solenoid valve 10 is controlled.

When the EGR valve 9 opens and closes (on-off), the internal pressure of the surge tank 6 changes with the change in the EGR flow rate, and when the EGR valve 9 is open (on), the EGR flow rate is smaller than normal. Since the pressure change is equal to or less than the predetermined value, the EGR failure can be detected. Further, in order to minimize fluctuations in engine torque due to opening and closing of the EGR valve 9, EGR failure determination is monitored in a deceleration region (zone).

Hereinafter, a method for determining a failure of the exhaust gas recirculation device will be described with reference to the flowcharts of FIGS. The electronic control unit 15 first initializes all the flags and the timer necessary for the failure determination (step S
1) It is determined whether or not the vehicle is in the EGR check zone (step S2). In the 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 rpm).
m) and a deceleration region where the idle switch is on (FIG. 6). The engine determines whether this time not in the EGR check zone returns to step S1, when in EGR check zone staying predetermined time above T ₁ to the EGR check zone (step S3). When the determination result of step S3 is negative (NO), the process returns to step S2, and when affirmative (YES), the EGR solenoid valve 10 is turned off to close the EGR valve 9, and the EGR is turned off (step S4). determining whether or not a predetermined time T ₂ has elapsed after turning off the (step S5).

[0014] Time T ₁ at step S3 is the confirmation timer time to confirm that the operating region of the engine is in the EGR check zone, the time T ₂ at step S5, check for EGR is off Timer time. Then, the electronic control unit 15 determines that the monitoring condition for the EGR failure determination has been satisfied when these times T ₁ and T ₂ have elapsed (FIG. 7A).

The electronic control unit 15 returns to step S2 when the determination result in step S5 is negative (NO), and when it is affirmative (YES), that is, when the monitor condition is satisfied, it is determined whether the flag F is 1 or not. Judgment (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 ) at the start of the EGR check is stored in a memory, and it is determined whether or not the fuel cut mode is set. When the fuel cut mode is set, for example, the program variable M _F1 that stores the fuel control mode is stored in the memory. When the mode is outside the fuel cut mode, 0 is stored in the program variable M _F1 (step S7), and the flag F is set to 1 (step S8). Electronic control unit 15
Sets the flag F to 1 and determines whether or not the fuel cut mode is set. When the fuel cut mode is set, the program variable _MF2 for storing the fuel control mode is set to 0. When the fuel cut mode is not set, the program variable M _{F2 is set} to 0. 1 in _F2
Is stored (step S9).

Next, the electronic control unit 15 executes the program
Variable M_F1And M_F2Is determined to be the same as the
Step S10) If not the same, the fuel control mode changes
It is determined that the operation has been performed, and the check is stopped.
Return, if they are the same, the EGR solenoid valve 10
Is turned on (FIG. 7 (b)), and EGR is turned on (step
S11). In steps S9 and S10, E
Always monitor changes in fuel control mode during GR check,
If the fuel control mode changes even for one cylinder, the fuel
Stop the lock. The electronic control unit 15 turns on the EGR
After a predetermined time T_Three(For example, 1 second)
A determination is made (step S12) and a predetermined time T _ThreeHas passed
If not, determine whether the vehicle is in the EGR check zone
(Step S13), the EGR check zone
Return to step S9 and repeat the determination.
When the vehicle deviates from the shock zone, the process returns to step S1. This
Time T_ThreeIndicates that EGR is on (EGR valve 9 is open)
Make sure you have enough time.

The electronic control unit 15 determines in step S12
The result is affirmative (YES), that is, after the EGR is turned on.
Fixed time T_ThreeWhen the time has elapsed, the EGR check is completed,
The manifold pressure (P_Two)
Stored in memory and whether or not in fuel cut mode
The program when in the fuel cut mode.
Variable M_F20 when not in fuel cut mode
Is the program variable M_F2Is stored in (step S1).
4), program variable M_F1And M_F2Whether is the same as
Is finally determined (step S15). And professional
Gram variable M_F1And M _F2When it is different
Stop EGR check
Returning to step S1, if the values are the same, the EGR check
Mani pressure P at the time of completion_TwoAnd EGR check start
Mani pressure P at point₁(ΔP = P_Two−P₁) But failure
Judgment value P_EGR(Fig. 7 (c), (d))
Is determined (step S16), and the determination result is affirmative (YE
In the case of S), it is determined that the EGR is normal (step
17) If negative (NO), the EGR has failed
Is determined (step 18). The electronic control unit 15 is
When EGR is determined to have failed in step S18
Turn on the EGR check lamp (FIG. 7 (e),
(F)) Notifying the driver that the EGR has failed
You.

In the above embodiment, the point in time when the time T ₂ has elapsed since the EGR was turned off (that is, the point in time when the monitoring condition is satisfied).
From order to start the fuel control mode determination, but stores the data in the program variable M _F1 for storing the fuel control mode in step S7, the start timing of the fuel control mode determination may be earlier. That is, for example, instead of storing data in the program variable M _F1 in step S7,
The fuel control mode is stored in the program variable M _F1 before returning to step S2 (repeated) after the “NO” determination is made in step 3, and the stored data is used in step S10 and step S15.

In the above-described embodiment, steps S9 and S10 are provided to continuously determine the fuel control mode during the EGR failure determination. However, the steps S9 and S10 are performed as shown by broken lines in FIG. May be omitted and the determination of the mode change may be made only in step S15.

[0020]

As described above, according to the present invention, E
When there is a mode change related to the presence or absence of combustion during the GR check, by stopping the check, it is possible to avoid the erroneous determination of the failure of the exhaust gas recirculation device, and to correctly determine the failure of the device. This has the effect of becoming

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a manifold pressure and a fuel control mode.

FIG. 2 is a graph showing a change in a manifold pressure during an EGR check according to a change in a fuel control mode in FIG. 1;

FIG. 3 is a diagram showing an outline of an exhaust gas recirculation device of an engine for implementing a method for determining a failure of the exhaust gas recirculation device according to the present invention.

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

FIG. 5 is the remaining part of the flowchart showing the procedure of the method for determining a failure of the exhaust gas recirculation device according to the present invention.

FIG. 6 is a diagram showing an example of a monitor zone (deceleration region) for determining a failure of the exhaust gas recirculation device according to the present invention.

FIG. 7 is a time chart showing an outline of the operation of the exhaust gas recirculation device shown in FIG. 3;

[Explanation of symbols]

1 Engine 2 an 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 an engine rotation sensor 12 pressure sensor 13 O ₂ sensor 15 an electronic control unit

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazutoshi Noma 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (72) Inventor Yasuhisa Yoshida 5-33-8 Shiba, Minato-ku, Tokyo No. Mitsubishi Motors Corporation (56) References JP-A-2-9937 (JP, A) JP-A-4-14064 (JP, A) JP-A-4-47155 (JP, U) (58) Survey Field (Int.Cl. ⁷ , DB name) F02M 25/07 550 F02M 25/07 570

Claims (1)

(57) [Claims] An EGR valve provided in a passage connecting an exhaust passage and an intake passage of an engine is temporarily opened and closed in a deceleration region of the engine, and an intake valve before and after switching when the opening and closing is switched is switched. In the failure determination method for an exhaust gas recirculation device that determines the failure of the exhaust gas recirculation device by comparing the atmospheric pressures, when the EGR valve is not switched,
Point to determine whether fuel cut control is being performed.
憶then, the EGR valve switching before and switching the intake pressure detection duration state of the fuel cut control the storage in between after
A failure determination method for an exhaust gas recirculation device, wherein the failure determination is stopped when the state changes to a state different from the state performed .