Internal-combustion engines – Charge forming device – Having fuel vapor recovery and storage system
Reexamination Certificate
2000-02-04
2001-08-21
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
Having fuel vapor recovery and storage system
C123S519000
Reexamination Certificate
active
06276344
ABSTRACT:
FIELD OF THE INVENTION
The present invention concerns an evaporated fuel treatment apparatus for an internal combustion engine fuel tank system, which releases the evaporated fuel generated inside the fuel tank into the air intake system of the internal combustion engine. More concretely, the present invention concerns an evaporated fuel leak detection apparatus for an internal combustion engine fuel tank system that makes it possible to ascertain the presence or absence of leakage in an evaporated fuel discharge prevention system extending from the fuel tank to the engine air intake system.
BACKGROUND OF THE INVENTION
A method for judging the presence or absence of leakage in the discharge prevention system of an evaporated fuel treatment apparatus is described in Japanese Patent Application Kokai No. Hei 7-12016. In this method, in cases where the detected tank pressure is a negative pressure that differs from atmospheric pressure by a predetermined value or greater, this indicates that purging is being performed in a normal evaporated fuel treatment system (in the case of ordinary engine operation). Accordingly, it is judged in such cases that the evaporated fuel treatment system is in a normal state, with no leakage of evaporated fuel from said system. In cases where the system is not judged to be normal in this judgment process, e.g., in cases where the internal pressure of the fuel tank remains stationary in the vicinity of atmospheric pressure for a predetermined period of time, it is considered that there is a possibility of leakage, and a negative pressure diagnostic process is actuated. In this process, the discharge prevention system is placed in a state of negative pressure, and the presence or absence of leakage is ultimately detected from the ability of the system to maintain this negative pressure.
Furthermore, an evaporated fuel treatment apparatus which is equipped with a bypass that bypasses the pressure adjustment valve in a charging passage that causes the fuel tank to communicate with the abovementioned canister, and which separately judges the presence or absence of leakage in the tank system on the fuel tank side of the bypass valve and the presence or absence of leakage in the canister system on the canister side of the bypass valve, is described in Japanese Patent Application Kokai No. Hei 9-317572. Judgment of the presence or absence of leakage in the tank system is accomplished as follows: Immediately after the engine is started, the bypass valve is opened so that the system is caused to move toward atmospheric pressure. If the shift in the pressure of the fuel tank in this case is greater than a predetermined value, it is judged that the tank system is in a normal state with no leakage. If there is leakage in the tank system, the pressure of the fuel tank prior to the starting of the engine will be more or less equal to atmospheric pressure, so that the shift in pressure is small.
As consideration for the environment has become more important, there has been a demand for stricter criteria for judging the presence or absence of leakage. However, the internal pressure in a fuel tank constantly varies due to various factors such as the temperature of the fuel, the extent to which excess fuel from the engine space is returned, the load conditions of the vehicle, and vibration, etc. As a result, difficulties have been experienced in the accurate detection of leakage caused by very small holes.
In cases where leakage is detected in spite of the fact that there is actually no leakage, the frequent lighting of a warning lamp, or other indicator lowers the practical utility of the vehicle. Conversely, if no leakage is detected in spite of the fact that leakage is actually occurring, evaporated fuel continues to be emitted into the atmosphere. Accordingly, an object of the present invention is to provide an evaporated fuel treatment apparatus that enables the correct detection of leakage caused by very small holes (e.g., holes with a diameter of 0.5 mm).
SUMMARY OF THE INVENTION
In order to solve the abovementioned problems, according to one aspect of the invention, an evaporated fuel leak detection apparatus for an internal combustion engine is provided, which has a fuel tank, a canister which has an opening to the atmosphere, a charging passage which allows the fuel tank to communicate with the canister, a pressure adjustment valve which is installed in the charging passage, an internal pressure sensor which is installed on the upstream side of the pressure adjustment valve for detecting the internal pressure of the fuel tank, and a controller which detects leakage in the fuel tank system on the upstream side of the pressure adjustment valve in accordance with the output of the sensor, the controller determining that there is no leakage when the internal pressure sensor indicates a negative pressure and the engine is not in high-load operating conditions.
It has been discovered that even in cases where a very small hole is opened in an evaporated fuel treatment apparatus, the tank pressure temporarily shows a negative pressure if the vehicle is operating under a high load, e.g., during rapid acceleration, etc. According to one aspect of the invention, a judgment is made that there is no leakage when the internal pressure sensor shows a negative pressure and the vehicle is not in a high-load operating state. Accordingly, the erroneous interpretation of a negative-load state in the tank system arising from a high-load state as a state in which there is no leakage in the tank system can be prevented.
According to another aspect of the invention, an evaporated fuel treatment apparatus is provided for an internal combustion engine that has a fuel tank, a canister that has an opening to the atmosphere, a charging passage that allows the fuel tank to communicate with the canister, a pressure adjustment valve that is installed in the charging passage, an internal pressure sensor that is installed on the upstream side of the pressure adjustment valve for detecting the internal pressure of the fuel tank, and a controller that detects leakage in the fuel tank system on the upstream side of the pressure adjustment valve in accordance with the output of the sensor, the controller judging that there is no leakage when the internal pressure sensor indicates a negative pressure and the variation of atmospheric pressure is less than a predetermined value.
It has been discovered that even in cases where a very small hole is opened in an evaporated fuel treatment apparatus, the tank pressure detected by the internal pressure sensor varies toward a negative pressure if the atmospheric pressure varies in the direction of increase, e.g., when the vehicle moves from a higher altitude toward a lower altitude. According to another aspect of the invention, a judgment is made that there is no leakage when the internal pressure sensor shows a negative pressure and there is no variation exceeding a predetermined value in the atmospheric pressure. Accordingly, the erroneous interpretation of a negative-load state in the tank pressure arising from a change in atmospheric pressure as a state in which there is no leakage in the tank system can be prevented.
REFERENCES:
patent: 5765539 (1998-06-01), Isobe et al.
patent: 5775307 (1998-07-01), Isobe et al.
patent: 5799639 (1998-09-01), Isobe et al.
patent: 5826566 (1998-10-01), Isobe et al.
patent: 5845625 (1998-12-01), Kidokoro et al.
patent: 5954034 (1999-09-01), Takagi
patent: 07 012016 (1995-01-01), 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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