Internal-combustion engines – Charge forming device – Fuel flow regulation between the pump and the charge-forming...
Reexamination Certificate
2000-11-03
2002-09-10
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel flow regulation between the pump and the charge-forming...
C123S519000
Reexamination Certificate
active
06446614
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosures of Japanese Patent Application Nos. HEI 11-314284 filed on Nov. 4, 1999 and 2000-137880 filed on May 10, 2000, including the specifications, drawings and abstracts are incorporated herein by reference in their. entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel storage apparatus and an abnormality diagnostic method of the apparatus, and, more particularly, to a fuel storage apparatus that purges fuel vapor formed in a fuel tank that is divided into a fuel chamber and an air chamber by a partition membrane, and an abnormality diagnostic method of the apparatus.
2. Description of the Related Art
A known fuel vapor process apparatus that purges fuel vapor formed in a fuel tank into an intake passage to prevent emission of fuel vapor from the fuel tank into the atmosphere is disclosed in, for example, Japanese Patent Application Laid-Open No. HEI 10-184464. The fuel tank has a deformable partition membrane that separates an internal space of the fuel tank into a fuel chamber and an air chamber in a tightly closed fashion in order to reduce the occurrence of fuel vapor. The fuel vapor process apparatus has a canister for adsorbing fuel vapor from the fuel tank, and a purge control valve for controlling the open/close state between the canister and the intake passage. When the purge control valve of this apparatus is opened during operation of the internal combustion engine, negative pressure is introduced into the intake passage, so that air flows from the fuel tank toward the intake passage. In this case, together with flow of air, fuel adsorbed in the canister is purged toward the intake passage. Hence, the above-described fuel vapor process apparatus is able to supply fuel vapor formed in the fuel tank into the engine as a fuel without letting it out into, the atmosphere.
However, if the partition membrane of the fuel tank has a hole, or if the piping connected to the fuel chamber has a crack or a disconnected pipe, fuel may leak from the fuel chamber into the air chamber due to such an abnormality, so that there is a danger of emission of a portion of the fuel vapor into the atmosphere. Therefore, in the fuel tank divided into the fuel chamber and the air chamber by the partition membrane, it is necessary to diagnose whether there is fuel leakage from the fuel chamber to the air chamber. The proportion of fuel vapor to the amount of gas pre sent in the air chamber (hereinafter, referred to as “vapor concentration”) is relatively low when there is no fuel leakage from the fuel chamber to the air chamber. The vapor concentration becomes relatively high if fuel is leaking from the fuel chamber to the air chamber. Therefore, as a technique for diagnosing whether there is fuel leakage from the fuel chamber to the air chamber, it is conceivable to detect the vapor concentration in the air chamber.
In order to secure good exhaust emissions from an internal combustion engine, it is necessary to keep the actual air-fuel ratio at a value near the theoretical air-fuel ratio. If fuel vapor formed in the fuel tank is supplied to the engine, the air-fuel ratio shifts to a fuel-rich side. In that case, therefore, the fuel injection duration set for the fuel injection valve of the engine is corrected in the decreasing direction by an amount of time corresponding to the amount of fuel vapor supplied to the engine. As the vapor concentration in the gas supplied to the engine increases, the rich tendency of the air-fuel ratio continues for an increased length of time, so that the amount of decrease correction of the fuel injection duration increases. Therefore, by detecting the air-fuel ratio after fuel vapor from the fuel tank is supplied to the engine, it becomes possible to detect the vapor concentration in the gas supplied from the fuel tank side to the engine.
Therefore, as a technique for detecting the vapor concentration in the air chamber, it is conceivable to interrupt purge of fuel adsorbed in the canister toward the intake passage, and to purge gas from the air chamber directly into the intake passage, bypassing the canister, and detect the air-fuel ratio afterwards. With the vapor concentration in the air chamber detected, it becomes possible to determine whether there is fuel leakage from the fuel chamber to the air chamber.
However, if the above-described fuel vapor process apparatus is used for a long time, the vapor concentration in the air chamber becomes high in some cases because the amount of fuel vapor that permeates through the partition membrane and flows into the air chamber increases. Furthermore, if the canister for adsorbing fuel is saturated, fuel adsorbed in the canister may flow back into the air chamber, thereby increasing the vapor concentration. Still further, in a construction in which the vapor concentration is detected based on the air-fuel ratio as described above, when the engine is in a transitional state, the air-fuel ratio considerably fluctuates, so that it becomes impossible to accurately detect the vapor concentration in the air chamber.
Therefore, if under the above-described condition, it is determined whether there is fuel leakage from the fuel chamber to the air chamber based on the vapor concentration in the air chamber as described above, there is a possibility of false determination that there is fuel leakage from the fuel chamber to the air chamber when there is actually no fuel leakage from the fuel chamber to the air chamber caused by an abnormality in the system, such as a hole in the partition membrane, a disconnected pipe, etc.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide a fuel storage apparatus capable of preventing a false determination regarding the presence/absence of fuel leakage from a fuel chamber to an air chamber in a fuel tank.
In accordance with a first aspect of the invention, a fuel storage apparatus includes a fuel tank divided into a fuel chamber and an air chamber by a partition membrane, concentration detecting means for detecting a fuel vapor concentration in the air chamber based on a change in an air-fuel ratio occurring when gas is purged from the air chamber toward an intake passage of an internal combustion engine, and fuel leakage determining means for determining whether there is a fuel leakage from the fuel chamber to the air chamber based on a result of detection by the concentration detecting means. It is determined by the fuel leakage determining means whether there is a fuel leakage from the fuel chamber to the air chamber, while a predetermined operational state of the internal combustion engine is maintained.
In this aspect, the determination by the fuel leakage determining means as to whether there is fuel leakage from the fuel chamber to the air chamber is performed under a condition that the predetermined operational state of the engine is maintained. That is, if the engine is in a transitional state, the determination regarding the presence/absence of fuel leakage is not performed. Therefore, at the time of determination regarding the presence/absence of fuel leakage from the fuel chamber to the air chamber, no fluctuation in the air-fuel ratio is caused by the situation where the engine is in the transitional state, so that it becomes possible to accurately detect the fuel vapor concentration in the air chamber. Hence, according to the invention, it is possible to prevent a false determination regarding the presence/absence of fuel leakage from the fuel chamber to the air chamber.
In accordance with a second aspect of the invention, a fuel storage apparatus includes a fuel tank divided into a fuel chamber and an air chamber by a partition membrane, concentration detecting means for detecting a fuel vapor concentration in the air chamber based on a change in an air-fuel ratio occurring when gas is, purged from the air chamber toward an intake passage of an internal combustion engine, and fuel leakage determining means for determining whether there is a fuel leakage from th
Hyoudou Yoshihiko
Matsuoka Takuya
Takagi Naoya
Yoshioka Mamoru
Kenyon & Kenyon
Moulis Thomas N.
Toyota Jidosha & Kabushiki Kaisha
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