Measuring and testing – With fluid pressure – Leakage
Reexamination Certificate
1998-11-13
2001-02-27
Williams, Hezron (Department: 2856)
Measuring and testing
With fluid pressure
Leakage
C123S520000
Reexamination Certificate
active
06192742
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to leakage diagnosis in an evaporated gas purge system for diagnosing existence or absence of leakage (pressure leakage) of an evaporated gas purge system for purging (discharging) evaporated gas caused by evaporation of fuel in a fuel tank to an intake pipe of an internal combustion engine.
2. Description of Related Art
Conventionally, in an evaporated gas purge system, in order to prevent evaporated gas generated from inside of a fuel tank from leaking out to the atmosphere, the evaporated gas is adsorbed in a canister via an evaporated gas passage at the inside of the fuel tank, a purge control valve is installed midway of a purge passage for purging evaporated gas adsorbed in the canister to an intake pipe of an internal combustion engine and opening and closing of the purge control valve is controlled in accordance with an operating state of the internal combustion engine by which, the flow rate of the evaporated gas purged from the canister to the intake pipe is controlled. In order to prevent extensive leakage of evaporated gas from the evaporated gas purge system to atmosphere, the leakage of the evaporated gas needs to be detected at an early stage.
Hence, as disclosed in, for example, Japanese Patent Application Laid-Open No. Hei-5-125997, a purge system, in which existence or absence of leakage is diagnosed based on pressure in the purge system or an amount of pressure change after atmosphere or negative pressure of an intake pipe is introduced and hermetically sealed in the purge system including a fuel tank and a canister, is known.
The leakage diagnosing operation may be carried out during idling of an engine and therefore, the filler cap of the fuel tank may be opened for supplying fuel or the like when leakage diagnosis is being carried out by which the purge system may be opened to the atmosphere during leakage diagnosing operation. That is, when fuel supply is carried out while running an engine, the filler cap may be opened (filler opening may be opened) during leakage diagnosing operation.
When the filler cap is opened and the purge system is opened to the atmosphere during leakage diagnosing operation, the purge system is erroneously diagnosed as having leakage even when the system is normal from the start since the system is brought into a state the same as that when a large hole is opened in the purge system.
In order to prevent such an erroneous diagnosis, as disclosed in Japanese Patent Application Laid-Open No. Hei-9-137756, there is a known system in which a fuel temperature sensor is installed to a fuel tank, existence or absence of lowering of fuel temperature is monitored and when the fuel temperature is lowered, it is determined that fuel is being supplied and leakage diagnosis is prohibited.
However, according to this related art, the fuel temperature sensor needs to be installed at the fuel tank.
Further, when the temperature difference between temperature of fuel in the fuel tank and temperature of the supplied fuel is small, it cannot be determined that fuel is being supplied. Furthermore, if the leakage diagnosis is finished after the filler cap is opened and before the fuel supply is started, it is not determined that fuel is being supplied, and accordingly, the system is erroneously diagnosed without canceling the diagnosed result even when it is diagnosed that the leakage is caused by opening the filler cap. After all, according to the determination of fuel supply by fuel temperature, an erroneous diagnosis caused by opening the filler cap may not be prevented, and reliability of leakage diagnosis cannot be improved sufficiently.
SUMMARY OF THE INVENTION
The present invention is made in light of the foregoing problems, and it is an object of the present invention to provide leakage diagnosis device for an evaporated gas purge system which is capable of preventing erroneous determination of leakage when leakage determination is carried out while a vehicle is not running (the vehicle is stopped). Particularly, it is an object of the present invention to provide leakage diagnosing for an evaporated gas purge system capable of preventing erroneous diagnosis caused by opening a filler cap of a fuel tank, capable of improving the reliability of leakage diagnosis, and reducing the number of parts and integration steps.
According to an exemplary leakage diagnosing device for an evaporated gas purge system of the present invention, leakage diagnosing means reintroduces air into a purge system when it is determined during idling of an engine that leakage exists in the purge system. Then, the leakage diagnosing means further cancels its determination of leakage existence according to the pressure of the purge system after starting the reintroduction of air.
If it is determined that there is a leakage in the purge system when the engine is in an idling state (that is, a situation where the filler cap is likely to be opened), the pressure reintroducing operation for introducing air into the purge system is carried out again, and any diagnosis result indicating the existence of leakage is canceled unless still indicated according to the inner pressure of the purge system. Accordingly, erroneous diagnosis caused by opening the filler cap is prevented, and reliability of leakage diagnosis is improved.
According to another aspect of the leakage diagnosing device for an evaporated gas purge system of the present invention, when leakage diagnosing means determines while a vehicle is stopped that leakage exists in a purge system, the leakage diagnosing means executes the leakage diagnosis again while the vehicle is running.
Therefore, even if it is determined that there is a large amount of leakage after execution of the leakage determination when the vehicle is not running and a fuel supply port of a fuel tank is opened, it is possible to confirm whether there is real leakage because the second leakage determination is carried out while the vehicle is running after closing the fuel supply port. Accordingly, an erroneous leakage determination is prevented, and the reliability of leakage determination is improved.
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Majima Yoshihiro
Miwa Makoto
Denso Corporation
Nixon & Vanderhye P.C.
Politzer Jay L.
Williams Hezron
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