JP3139095B2 - Diagnosis device for evaporative fuel control system of vehicle - Google Patents

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 vapor control system for a vehicle, and more particularly, to a canister for providing a passage connecting an intake passage of an internal combustion engine and a fuel tank, and adsorbing and holding the evaporated fuel along the passage. The present invention relates to a diagnostic device for an evaporative fuel control system for a vehicle provided with the above.

[0002]

2. Description of the Related Art Evaporated fuel leaking into the atmosphere from a fuel tank, a float chamber of a vaporizer, etc. contains a large amount of hydrocarbons (HC) and is one of the causes of air pollution. Because of the connection, various techniques for preventing this are known. As a typical example, the fuel vapor in the fuel tank is temporarily adsorbed and held in a canister containing an adsorbent such as activated carbon, and the fuel vapor adsorbed and held in the canister is released (purged) during operation of the internal combustion engine.
There is an evaporation system that supplies the fuel to the internal combustion engine.

As an evaporative fuel control device for an internal combustion engine, as disclosed in Japanese Patent Application Laid-Open No. 2-130255,
A supply passage for guiding the fuel gas adsorbed by the adsorbent of the canister into the intake pipe by a negative pressure generated in the intake pipe;
A control valve for opening and closing the supply passage according to the operation state of the internal combustion engine is provided, and pressure detecting means for detecting a pressure between the canister and the control valve is provided. The canister supply passage, the control valve and the control valve are provided based on the pressure detected by the pressure detecting means. There is an abnormality detection means for detecting an abnormality in the supply of fuel gas to the intake pipe due to any of the above.

Further, as a self-diagnosis device of a fuel purge system in a fuel tank evaporative gas processing apparatus, as disclosed in Japanese Patent Application Laid-Open No. 3-26862, a fuel purge system in a fuel tank evaporative gas processing apparatus is disclosed. Means for determining whether or not the area is a purge area;
Means for detecting the pressure of the purge line, and means for detecting or calculating the boost pressure on the downstream side of the purge fuel introduction portion of the intake passage are provided, and the detection signal output from each of these detection means provides a fuel purge area or In some cases, a determination means is provided for determining whether the system is normal or abnormal based on the pressure of the purge line and the boost pressure when it is determined that the pressure is outside the region.

[0005]

The conventional diagnostic apparatus for a fuel vapor control system for a vehicle has a failure diagnosis function for detecting a so-called leak in which hydrocarbon (HC) generated in a fuel tank leaks to the atmosphere. Some do not have.

As a result, when a leak occurs in the evaporative fuel control system, it is not possible to prevent hydrocarbons (HC) from leaking into the atmosphere, which is a factor of air pollution and is disadvantageous in practical use. There is.

[0007]

SUMMARY OF THE INVENTION Therefore, in order to eliminate the above-mentioned disadvantages, the present invention provides a fuel tank for a vehicle having a canister for adsorbing and holding the fuel vapor in a passage connecting an intake passage of an internal combustion engine and a fuel tank. In the diagnostic device of the control system, a first solenoid valve for opening and closing the atmosphere is provided in the canister, a second solenoid valve for purging is provided in the passage between the internal combustion engine and the canister, and a pressure passage is provided in the passage between the canister and the fuel tank. A pressure sensor for detecting a pressure in the fuel tank through the fuel tank, closing both the first solenoid valve for opening and closing the atmosphere and the second solenoid valve for purging. The second solenoid valve is opened, and the change in the pressure in the tank at this time causes the second solenoid for leak checking and purging. The air flow check of the air valve is performed, and when it is determined that each check is normal, the first solenoid valve for opening and closing the atmosphere is opened and the second solenoid valve for purging is closed. A control unit for performing an airflow check of the first solenoid valve for opening and closing is provided.

[0008]

According to the invention described above, the first solenoid valve for opening and closing the atmosphere and the second solenoid valve for purging are both closed, and when a predetermined condition is satisfied, the second solenoid valve for purging is opened by the control unit. Then, a leak check and an air flow check of the second solenoid valve for purging are performed based on the change in the pressure in the tank at this time, and when it is determined that each check is normal, the first solenoid valve for opening and closing the atmosphere is thereafter opened and The second solenoid valve for purging is closed, and the change in the pressure in the tank at this time is used to check the air flow of the first solenoid valve for opening and closing the atmosphere, thereby preventing leakage of hydrocarbons (HC) from the system to the atmosphere.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 and FIG. 2 show an embodiment of the present invention. In FIG. 1, 2 is an internal combustion engine, 4 is an air cleaner, 6 is a throttle valve, 8 is a surge tank, 10 is an intake passage, 12 is a combustion chamber, 14 is an exhaust passage, and 16 is a fuel tank. The internal combustion engine 2 has a fuel injection valve 18 provided in the intake passage 10 so as to be directed toward the combustion chamber 12.
The fuel injection valve 18 is connected to the fuel tank 16 by a fuel passage (not shown).

The fuel in the fuel tank 16 is supplied to a fuel injection valve 18 via a fuel passage by a fuel pump (not shown), and supplied to the combustion chamber 12 together with air to be burned. The exhaust gas generated by the combustion is discharged through the exhaust passage 14.

An intake passage 10 of the internal combustion engine 2, for example, a passage 20 for connecting the surge tank 8 and the fuel tank 16 downstream of the throttle valve 6 is provided, and a canister 22 for adsorbing and holding the evaporated fuel is provided in the middle of the passage 20. .

The passage 20 is formed by a first passage 24 connecting the fuel tank 16 and the canister 22 and a second passage 26 connecting the canister 22 and the intake passage 10.

The canister 22 is provided with a first solenoid valve 28 for opening and closing the atmosphere, and a second solenoid valve 30 for purging is provided in the middle of the second passage 26 between the internal combustion engine 2 and the canister 22. A pressure sensor 34 for detecting the pressure in the fuel tank 16 via a pressure passage 32 is provided in the first passage 24 between the fuel tanks 16 via a pressure passage 32. At the start of the detection, a first solenoid valve 28 for opening and closing the atmosphere and a second solenoid valve for purging are provided. When both the solenoid valves 30 are closed and a predetermined condition is satisfied, the second solenoid valve 30 for purge is opened, and a leak check and an air flow check of the second solenoid valve 30 for purge are performed by a change in the pressure in the tank at this time. If the checks are judged to be normal, then the first air opening / closing
Opening the solenoid valve 28 and purging the second
The solenoid valve 30 is closed, and a control unit 36 for checking the air flow of the first solenoid valve 28 for opening and closing the atmosphere based on the change in the tank pressure at this time is provided.

More specifically, a first solenoid valve 28 is provided in the atmosphere opening / closing passage 38 of the canister 22.

The canister 22 and the fuel tank 1
One end of the pressure passage 32 is connected to the fuel tank 16 side end of the first passage 24 in the middle of the first passage 24 between the six. A pressure sensor 3 for detecting the pressure inside the fuel tank 16 is provided at the other end of the pressure passage 32.
4 are provided.

The control section 36 is connected to first and second solenoid valves 28 and 30 and a pressure sensor 34.

The controller 36 starts detection when a predetermined condition is satisfied, for example, when a predetermined operation state is reached during operation, and ends the detection in a short time.

The leak check by the control unit 36 is as follows.
The evaporative system is closed and sealed from the atmosphere by the first solenoid valve 28, and the determination is made based on the negative pressure level per time when the negative pressure is applied by the second solenoid valve 30.

In this case, the negative pressure level is determined by using the purge flow rate (control duty value) set as the evaporative system, or by specifying the control duty value of the special second solenoid valve 30 at the same time as the start of the determination. There is.

That is, the control unit 36 starts determination when the quotient obtained by dividing the pressure change ΔP1 of the pressure action time ΔT1 by the pressure action time ΔT1 after the start of the detection becomes less than the first set value A1.

In this determination, the quotient obtained by dividing the pressure change ΔP2 of the negative pressure action time ΔT2 by the negative pressure action time ΔT2 is the second.
A leak check is performed based on whether or not the value exceeds the set value A2. When the quotient exceeds the second set value A2, it is determined that there is no leak.

The airflow check is performed in the first and second airflow checks.
The determination is made by checking the conduction of the solenoid valves 28 and 30.

That is, when the first solenoid valve 28 is closed, the second solenoid valve 30 is opened from the closed state, and when a negative pressure is detected, it is determined that the second solenoid valve 30 is conductive.

Further, when the second solenoid valve 30 is changed from the open state to the closed state, and when the pressure rise is detected when the first solenoid valve 28 is changed from the closed state to the open state, it is determined that the first solenoid valve 28 is conductive. .

Next, the operation will be described.

When the set operating conditions are satisfied during the operation, as shown in FIG. 2, the first solenoid valve 28 for opening and closing the atmosphere is closed, and the second solenoid valve 30 for purging is closed.
Of the pressure action time ΔT1 and the pressure change ΔP1 of the pressure action time ΔT1
When the quotient when divided by T1 is less than the first set value A1, the determination is started with the duty of the second solenoid valve 30 set to 50%, and the negative pressure action time ΔT from the start of the determination.
2 is determined by whether or not the quotient obtained by dividing the pressure change ΔP2 by the pressure action time ΔT2 exceeds the second set value A2.

At this time, the first solenoid valve 28 is open, and the duty of the second solenoid valve 30 is 0%.

Thereafter, the detection is terminated by setting the duty of the second solenoid valve 30 to 50%.

The air flow check is performed in the first,
The determination is made based on the conduction of the second solenoid valves 28 and 30. The conduction of the second solenoid valve 30 is performed simultaneously with the start of the above-described determination of the leak check.

That is, when a negative pressure is detected when the duty of the second solenoid valve 30 is set to 50% when the first solenoid valve 28 is closed, it is determined that the second solenoid valve 30 is conductive.

The conduction of the first solenoid valve 30 is as follows.
This is performed after the negative pressure action time ΔT2 from the start of the leak check determination.

That is, when the first solenoid valve 28 that is closed is opened and the pressure rise ΔP3 is detected when the duty of the second solenoid valve 30 whose duty is 50% is set to 0%, the first solenoid valve 28 is turned on. It is determined that conduction has occurred.

Thus, the presence or absence of a leak can be determined based on the detected tank pressure, and the leak of the evaporative system can be reliably detected, and the leak of hydrocarbon (HC) from the system to the atmosphere can be prevented. One factor of air pollution can be eliminated, which is practically advantageous.

Further, in the device for determining the presence or absence of a leak, it is possible to diagnose a failure of the first and second solenoid valves 28 and 30 which is an air flow check.

Further, since the configuration of the diagnostic device of the evaporative fuel control system is simple, the cost can be reduced, and
In addition to being economically advantageous, the time for failure diagnosis is shorter than that of the conventional one, and the usability can be improved.

[0037]

As described in detail above, according to the present invention, the first solenoid valve for opening and closing the atmosphere is provided in the canister, and the second purge valve is provided in the middle of the passage between the internal combustion engine and the canister.
A solenoid valve is provided, a pressure sensor is provided in the passage between the canister and the fuel tank via a pressure passage to detect the pressure in the fuel tank, and the first solenoid valve for opening and closing the atmosphere and the second solenoid valve for purging are both closed. When the predetermined conditions are satisfied, the second solenoid valve for purge is opened, and a leak check and an air flow check of the second solenoid valve for purge are performed based on the change in the pressure in the tank at this time, and each check is normal. Then, the controller opens the first solenoid valve for opening and closing the atmosphere and closes the second solenoid valve for purging, and checks the airflow of the first solenoid valve for opening and closing the atmosphere based on the change in the pressure in the tank at this time. Is installed, it is possible to determine the presence or absence of a leak, and Securely together may be detected, it can be prevented leakage of hydrocarbons to the atmosphere (HC) from the system,
It can eliminate one factor of air pollution. In addition, since the configuration of the diagnostic device of the evaporative fuel control system is simple, the cost can be reduced, which is economically advantageous, and the failure diagnosis time is shorter than that of the conventional one, and the usability is improved. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a diagnostic device for an evaporative fuel control system according to a first embodiment of the present invention.

FIG. 2 is a time chart of a diagnostic device of the fuel vapor control system.

[Explanation of symbols]

 Reference Signs List 2 internal combustion engine 4 air cleaner 6 throttle valve 8 surge tank 10 intake passage 12 combustion chamber 14 exhaust passage 16 fuel tank 18 fuel injection valve 20 passage 22 canister 24 first passage 26 second passage 28 first solenoid valve for opening and closing atmosphere 30 for purging Second solenoid valve 32 Pressure passage 34 Pressure sensor 36 Control unit 38 Atmospheric opening / closing passage

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-260365 (JP, A) JP-A-2-102360 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02M 25/08 F02M 25/08 301

Claims (1)

(57) [Claims] 1. A diagnostic device for an evaporative fuel control system for a vehicle having a canister for adsorbing and holding evaporative fuel in a passage connecting an intake passage of an internal combustion engine and a fuel tank. A purge second solenoid valve is provided in the passage between the internal combustion engine and the canister, and a pressure sensor is provided in the passage between the canister and the fuel tank to detect the pressure in the fuel tank via a pressure passage. , Open to the atmosphere
First solenoid valve for closing and second solenoid for purging
When both valves are closed and the specified conditions are satisfied ,
Open the 2nd solenoid valve for purging.
For leak check and purge by changing the pressure in the tank
Check the air flow of the second solenoid valve and check each
If it is determined that the check is normal, then the first solenoid valve for opening and closing the atmosphere is opened and the second solenoid valve for purging is opened .
Close the solenoid valve and change the tank pressure at this time.
Air flow of the first solenoid valve for opening and closing the atmosphere
Diagnostic apparatus for evaporative fuel control system for a vehicle, characterized in that a control unit for performing over check.