JPH07189831A - Diagnosing device for fuel evaporative gas suppressing device - Google Patents

Abstract

PURPOSE:To properly determine occurrence of an abnormal condition such as clogging or leakage in a discharge passage by diagnosing whether there is an abnormal condition or not from a change in an inlet negative pressure generated according to an opening/closing action of a purge valve means on the basis of a signal from a pressure detecting means detecting the inlet negative pressure. CONSTITUTION:A canister 32 adsorbing evaporative fuel from a fuel tank 31 and an intake pipe 36 on the downstream of a throttle valve 35 communicates with each other by means of a discharge passage 37. A purge valve means 38 is arranged in the middle of the discharge passage 37, and the opening/closing action of the purge valve means 38 is controlled by means of a controlling means 41. In such a fuel evaporative gas suppressing device, if clogging or leakage occurs in the discharge passage 37, or if a desired opening cannot be obtained because of defective operation of the purge valve means 38, purge gas quantity runs short, and a change quantity of a pressure in the intake pipe 36 is below the determination value. Then, a change in a pressure generated in opening/closing of the discharge passage 37 is detected according to the output of the pressure detecting means 43, and on the basis of the detected result, it is determined that a fuel evaporative gas suppressing device is in an abnormal condition by means of the diagnosing means 42.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diagnostic device for a fuel evaporative emission control system.

[0002]

2. Description of the Related Art In order to prevent the fuel vaporized in a fuel tank of a vehicle from being released into the atmosphere, the vaporized fuel is adsorbed by activated carbon in a canister when the engine is stopped and developed during the operation of the engine. Using the negative pressure
There is provided a fuel evaporative emission control device that separates the evaporated fuel from the activated carbon in the canister by the outside air introduced into the canister and guides it to the intake passage.

By the way, in an operating state in which the desired opening cannot be obtained due to clogging or leakage in the discharge passage connecting the canister and the intake pipe, or malfunction of the purge valve means for opening and closing the discharge passage, the discharge passage is discharged from the discharge passage. The amount of purge gas introduced into the intake pipe may be insufficient.

As a measure against this fail-safe, a diagnostic device for a fuel evaporative emission control device disclosed, for example, in Japanese Patent Laid-Open No. 2-136558, detects the air-fuel ratio of the air-fuel mixture supplied to the engine and detects the air-fuel ratio. A change in the air-fuel ratio that accompanies the opening / closing operation of the purge valve means is checked on the basis of the signal from to determine whether or not there is an abnormality in the device.

[0005]

However, in such a conventional diagnostic device for the fuel evaporative emission control device, the canister is introduced into the intake pipe through the discharge passage even if the diagnostic conditions are limited by the fuel temperature and the like. There is a possibility that the air-fuel ratio of the purge gas will vary, and it is not possible to accurately diagnose whether or not there is an abnormality in the device.

Therefore, an object of the present invention is to accurately diagnose whether or not an abnormality has occurred in the fuel evaporative emission control system.

[0007]

The present invention, as shown in FIG. 1, includes a fuel tank 31 for storing fuel and a fuel tank 3.
A canister 32 that communicates with 1 to adsorb evaporated fuel;
A discharge passage 37 that connects the canister 32 and an intake pipe 36 downstream of the throttle valve 35, a purge valve means 38 that opens and closes the discharge passage 37, and a purge valve means 38 that opens and closes according to the operating state of the engine to open the canister 32. In the fuel evaporative emission control device including the control means 41 for supplying the purge gas from the intake pipe 36 to the intake pipe 36, the pressure detection means 43 for detecting the intake negative pressure on the downstream side of the throttle valve 35 of the intake pipe 36, and the pressure detection means 43. And a means 42 for diagnosing whether or not there is an abnormality from a change in the suction negative pressure caused by the opening and closing operation of the purge valve means 38 based on the signal from the.

[0008]

In the operating state in which the fuel evaporative emission control device is operating normally, the purge gas introduced from the discharge passage 37 into the intake pipe 36 as the discharge passage 37 is opened and closed via the purge valve means 38. When the amount changes, the pressure in the intake pipe 36 changes with a predetermined characteristic.

On the other hand, in an operating state in which the desired opening cannot be obtained due to clogging or leakage in the discharge passage 37 or malfunction of the purge valve means 38, the discharge passage 3
7, the amount of purge gas introduced into the intake pipe 36 is insufficient,
The amount of change in the pressure of the intake pipe 36 falls below a preset determination value.

Therefore, by detecting the pressure fluctuation that occurs when the discharge passage 37 is opened and closed, it is possible to accurately determine whether the fuel evaporative emission control device is operating normally without being affected by the evaporative emission concentration of the purge gas. Can be determined.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 2, 1 is a fuel tank for storing fuel, 4 is a canister, and the fuel evaporated in the fuel tank 1 is guided to a canister 4 through a passage 2 to an activated carbon 4a in the canister 4. Adsorbed. Reference numeral 3 is a check valve that blocks a backflow from the canister 4 to the fuel tank 1. A normally closed bypass valve 12 is provided in parallel with the check valve 3.

The canister 4 is connected to an intake pipe 8 downstream of the throttle valve 7 through a discharge passage 6, and a normally closed purge valve 9 driven by a step motor is connected to the discharge passage 6.
Is provided.

Certain conditions (for example, low load range after warm-up)
Then, when the purge valve 9 is opened in response to a signal from the control unit 21, a new suction valve provided at the lower portion of the canister 4 (shown above the canister 4 in the figure) due to the suction negative pressure developing downstream of the throttle valve 7. Fresh air is introduced into the canister 4 from the air introduction path 5. Activated carbon 4 with this fresh air
The evaporated fuel separated from a is introduced into the intake pipe 8 together with fresh air and burned in the combustion chamber. A normally open drain cut valve 11 is provided in the fresh air introduction path 5.

When the purge valve 9 opens due to a failure, the purge gas (a mixed gas of vaporized fuel separated from activated carbon and fresh air) is introduced even during warm-up. , The mixture becomes too rich. As a measure against this fail-safe, a normally closed diaphragm actuator 13 is provided in series with the purge valve 9. Under conditions other than the condition for introducing the purge gas into the intake pipe 8, the discharge passage 6 is blocked by the normally closed diaphragm actuator 13, so that the purge gas is introduced into the intake pipe 8 under the condition other than the condition for introducing the purge gas into the intake pipe 8. Never be done. When the purge valve 9 is opened to introduce the purge gas, the purge cut valve 14 is simultaneously opened to introduce the negative pressure of the intake pipe downstream of the throttle valve 7 into the negative pressure working chamber of the diaphragm actuator 13, and the negative pressure causes the return spring to act as a return spring. Against this, the diaphragm is pulled upward in the figure and the discharge passage 6 is opened.

A pressure sensor 22 for detecting the pressure of the purge line is provided on the upper wall of the fuel tank 1, and a fuel temperature sensor 23 is provided in the fuel tank 1. These temperature signals are used as a water temperature sensor 24 and a rotation speed sensor 25. , And is input to the control unit 21 together with the signal from the air flow meter 26. The control unit 21 determines the four valves (purge valve 9, drain cut valve 11, bypass valve 12, purge cut valve 14) according to the operating conditions of the engine 10 based on these detection signals.
The flow of the purge gas is controlled by controlling the opening and closing of.
The control unit 21 also controls the fuel injection amount from the injector 15 according to the operating state of the engine 10.

In order to diagnose whether or not the operation of the fuel evaporative emission control device is abnormal, a pressure sensor 20 for detecting a suction negative pressure generated downstream of the throttle valve 7 is provided. The control unit 21 diagnoses whether or not there is an abnormality in the operation of the fuel evaporative emission control device based on changes in the suction negative pressure that occur when the discharge passage 6 is opened and closed via the purge valve 9 and the purge cut valve 14.

The flowchart of FIG. 3 shows a diagnostic control program executed by the control unit 21, which is executed at regular intervals.

First, in step 1, it is judged whether or not a predetermined diagnostic condition that the discharge passage 6 is opened is satisfied. If the diagnostic condition is not satisfied, the process goes to step 9 to end this routine.

When it is judged that the diagnostic condition is satisfied, the routine proceeds to step 2, where the discharge passage 6 is closed via the purge valve 9 or the purge cut valve 14.

Next, in step 3, the pressure sensor 20
It is determined whether the pressure difference P ₁ -P ₂ generated before and after the discharge passage 6 is closed is equal to or larger than the determination value P ₀ based on the detection signal from

When the pressure difference P ₁ -P ₂ is judged to be the judgment value P ₀ or more, the routine proceeds to step 4, where the discharge passage 6 is reopened,
It proceeds to step 5 and determines that there is no abnormality.

If it is judged that the pressure difference P ₁ -P ₂ is smaller than the judgment value P ₀ , the routine proceeds to step 6, where the discharge passage 6 is opened again via the purge valve 9 and the purge cut valve 14, and then proceeds to step 7. pressure difference P ₃ -P ₄ occurring before and after the discharge path 6 is opened determines whether the determination value P ₀ or more.

When the pressure difference P ₃ -P ₄ is judged to be the judgment value P ₀ or more, the routine proceeds to step 5 where it is judged that there is no abnormality.

If it is determined that the pressure difference P ₃ -P ₄ is smaller than the determination value P ₀ , the process proceeds to step 8 and it is determined that there is an abnormality.

In the operating state where the fuel evaporative emission control device is operating normally, as the discharge passage 6 is opened and closed via the purge valve 9 or the purge cut valve 14,
When the amount of purge gas introduced from the discharge passage 6 into the intake pipe 8 changes, the pressure in the intake pipe 8 changes with a predetermined characteristic.

On the other hand, in an operating state in which the desired opening cannot be obtained due to clogging or leakage in the discharge passage 6 or malfunction of the purge valve 9, it is introduced from the discharge passage 6 into the intake pipe 8. Insufficient amount of purge gas, intake pipe 8
The amount of change in the pressure is below a preset determination value.

Therefore, by detecting the pressure fluctuation that occurs when the discharge passage 6 is opened and closed, it is possible to accurately determine whether or not an abnormality has occurred in the fuel evaporative emission control device without being affected by the evaporative emission gas concentration of the purge gas. can do.

[0028]

According to the present invention, there is provided a fuel evaporative emission control device, comprising: a control means for opening and closing the purge valve means according to the operating condition of the engine to supply the purge gas from the canister to the intake pipe through the discharge passage. Of the intake negative pressure on the downstream side of the throttle valve and the change in the intake negative pressure caused by the opening / closing operation of the purge valve means based on the signal from the pressure detecting means to determine whether there is any abnormality. When the discharge passage is clogged or leaks, or an abnormality occurs in which the desired opening cannot be obtained due to a malfunction of the purge valve means,
This abnormality can be accurately determined.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to a claim of the present invention.

FIG. 2 is a system diagram of an embodiment.

FIG. 3 is a flowchart for explaining abnormality diagnosis.

[Explanation of symbols] 1 fuel tank 2 passage 4 canister 6 passage 7 throttle valve 8 intake pipe 9 purge valve 13 diaphragm actuator 14 purge cut valve 20 pressure sensor 21 control unit 23 fuel temperature sensor 24 water temperature sensor 31 fuel tank 32 canister 35 throttle valve 36 Intake Pipe 37 Discharge Passage 38 Purge Valve Means 41 Control Means 42 Diagnostic Means 43 Pressure Detecting Means

Claims (1)

[Claims] 1. A fuel tank for storing fuel, a canister for communicating with the fuel tank to adsorb evaporated fuel, a discharge passage for communicating the canister with an intake pipe downstream of a throttle valve, and a purge for opening / closing the discharge passage. A fuel evaporative emission control device comprising valve means and control means for opening and closing the purge valve means according to the operating state of the engine to supply the purge gas from the canister to the intake pipe. And a means for diagnosing whether or not there is an abnormality from a change in suction negative pressure caused by opening / closing operation of the purge valve means based on a signal from the pressure detection means. A diagnostic device for a fuel evaporative emission control device.