Internal-combustion engines – Charge forming device – Having fuel vapor recovery and storage system
Reexamination Certificate
2000-02-04
2001-05-01
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
Having fuel vapor recovery and storage system
Reexamination Certificate
active
06223732
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an evaporated fuel treatment apparatus for an internal combustion engine that releases evaporated fuel generated inside the fuel tank into the intake manifold of the internal combustion engine. More specifically, the present invention concerns an evaporated fuel treatment apparatus for an internal combustion engine that facilitates determination of the presence or absence of leakage in an evaporated fuel discharge prevention system extending from the fuel tank to the engine intake system.
BACKGROUND OF THE INVENTION
A system for determining the presence or absence of leakage in a tank system is described in Japanese Patent Application Kokai No. Hei 7-83125. In this system, the pressure in an evaporated fuel discharge prevention system is lowered to a predetermined pressure. The target pressure reduction value of the pressure in the fuel tank is alternately set at an upper-limit value and a lower-limit value, and a feedback pressure reduction process is performed, which gradually causes the pressure in the fuel tank to converge on the target pressure reduction value. The amount of pressure shift in the fuel tank per unit time is calculated (leak down checking mode). In order to eliminate the effect of vapor on the judgment results, the amount of pressure shift per unit time caused by the evaporated fuel is calculated as a correction value. Determination of the presence or absence of leakage in the tank system is accomplished on the basis of a value obtained by subtracting, from the amount of pressure shift calculated in the above-mentioned leak down checking mode, a value produced by multiplying a coefficient by the amount of pressure shift obtained in the correction checking mode. If this value is equal to or less than a predetermined value, it is judged that the tank system is normal, with no leakage. On the other hand, if this value exceeds the predetermined value, it is judged that there is leakage in the tank system.
However, in cases where the leaking hole that is to be detected is a very small hole with a diameter of approximately 0.5 mm, a high degree of precision is required in the diagnostic results indicating the presence or absence of leakage. A disadvantage of the above-described approach is that errors may occur in the diagnostic results in cases where the tank pressure shifts in the negative pressure direction in the correction mode during tank pressure reduction monitoring or prior to tank pressure reduction monitoring.
SUMMARY OF THE INVENTION
The invention relates to an evaporated fuel treatment apparatus for an internal combustion engine having a fuel tank, a canister having an opening to the atmosphere, a passage allowing the fuel tank to communicate with the canister, a purging passage allowing the canister to communicate with the intake manifold of the engine, the intake manifold having a reduced pressure as the engine intakes air, and a pressure sensor for detecting the internal pressure of the fuel tank.
The apparatus includes a controller for controlling opening of the fuel tank to the atmosphere and alternately to a negative pressure, said controller detecting the presence or absence of leakage on the basis of the change in negative pressure that occurs after the fuel tank has been placed under a negative pressure, wherein said controller prohibits the detection of the presence or absence of the leakage in response to a change in the internal pressure of the fuel tank in the direction of negative pressure when a bypass valve is closed.
The apparatus of the invention detects the presence or absence of leakage on the basis of the change in negative pressure that occurs after the fuel tank has been placed under a negative pressure. In the present invention, detection of the presence or absence of leakage is prohibited in cases where the internal pressure of the fuel tank varies in the negative pressure direction when the bypass valve is closed. Accordingly, erroneous detection results can be avoided, and the precision of detection can be improved.
REFERENCES:
patent: 5327873 (1994-07-01), Ohuchi et al.
patent: 5443051 (1995-08-01), Otsuka
patent: 5501199 (1996-03-01), Yoneyama
patent: 5775307 (1998-07-01), Isobe et al.
patent: 5873352 (1999-02-01), Kidokora et al.
patent: 5878727 (1999-03-01), Huls
patent: 7-012016 (1995-01-01), None
patent: 9-317572 (1997-12-01), None
Isobe Takashi
Kiso Satoshi
Yamaguchi Takashi
Honda Giken Kogyo Kabushikikaisha
Moulis Thomas N.
Seed IP Law Group PLLC
Tarleton E. Russell
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