Measuring and testing – With fluid pressure – Motor part or auxiliary
Reexamination Certificate
1999-04-02
2001-05-08
Williams, Hezron (Department: 2856)
Measuring and testing
With fluid pressure
Motor part or auxiliary
C073S040000, C073S04050R, C073S049500, C073S049200, C073S049700, C073S118040, C123S518000, C123S519000, C123S520000
Reexamination Certificate
active
06227037
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to diagnostic technique for an evaporative emission control system, and in particular to diagnostic systems and methods for detecting leakage in an evaporative emission control fluid circuit for a vehicle.
An evaporative emission control system mounted on a vehicle is designed to prevent the escape of gasoline vapors to the atmosphere by using a canister filled with activated carbon or charcoal. While the engine is out of operation, the fuel vapors are directed through tubing to the canister, and the activated carbon or charcoal adsorbs the fuel vapors. When the engine starts, a purge line or passage is opened under a predetermined engine operating condition, and fresh air is drawn through the canister by the action of engine vacuum. The flow of the fresh air removes the fuel vapors from the carbon and carries the fuel vapors to the intake passage downstream of the throttle valve, so that they are burned in the engine.
A Japanese Patent Kokai Publication No. 7(1995)-139439 discloses a diagnostic system for performing a leak diagnosis to detect leakage in such an evaporative emission control system.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide diagnostic system and method enabling a leak diagnosis without delay after a start of the engine, and reducing a disturbance in the air fuel ratio due to the diagnosis.
According to the present invention, a diagnostic apparatus for an evaporative emission control system comprises:
a first passage conveying evaporative fuel vapor from a fuel tank to a canister;
a second passage extending between the canister and an intake passage section downstream of a throttle valve;
a valve system;
a pressure sensor sensing a pressure in a fluid passage from the fuel tank to the second passage;
a controller holding the fluid passage from the fuel tank to the second passage in a state of a closed space by controlling the valve system when an engine is out of operation, and performing a leak diagnosis by checking a pressure decrease due to condensation of the fuel vapor in the fluid passage held in the state of a closed space when the engine is started.
In an illustrated preferred embodiment of the present invention, the valve system comprises a purge control valve opening and closing the second passage, and a drain cut valve opening and closing an atmospheric port of the canister.
According to the present invention, a diagnostic process for an evaporative emission control system comprises:
holding a fuel vapor recovery passage extending from the fuel tank through the canister to the second passage in a closed state to confine fuel vapor in the fuel vapor recovery passage during an off period of the engine; and
detecting leakage in the fuel vapor recovery passage at an end of the off period by checking a pressure decrease in the fuel vapor recovery passage held in the closed state during the off period.
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Kawamura Katsuhiko
Kawano Akihiro
Foley & Lardner
Garber Charles D
Nissan Motor Co,. Ltd.
Williams Hezron
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