Internal-combustion engines – Charge forming device – Having fuel vapor recovery and storage system
Reexamination Certificate
2000-02-01
2001-04-10
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
Having fuel vapor recovery and storage system
Reexamination Certificate
active
06213102
ABSTRACT:
FIELD OF THE INVENTION
The present invention concerns an evaporated fuel treatment device for an internal combustion engine in which evaporated fuel generated inside the fuel tank is released into the intake system of the engine. More specifically, the present invention concerns an evaporated fuel treatment device for an internal combustion engine which makes it possible to ascertain the presence or absence of leakage of evaporated fuel in an evaporated fuel discharge prevention system which covers from the fuel tank to the engine intake system.
BACKGROUND OF THE INVENTION
A method for ascertaining the presence or absence of leakage in the discharge prevention system of an evaporated fuel treatment device is described in Japanese Patent Application Kokai No. Hei 7-12016. In this method, when the detected internal pressure of evaporated vapor in the tank is a negative pressure of a predetermined value or greater relative to atmospheric pressure, this indicates that purging is being performed in a normal evaporated fuel treatment system during ordinary engine operation; accordingly, it is determined that there is no leakage of evaporated fuel from the evaporated fuel treatment system, and that the system is therefore operating normally. In cases where, for example, the internal pressure of the fuel tank remains stationary for a predetermined period of time in the vicinity of atmospheric pressure when such a “normal” determination is obtained in the above-mentioned process, a negative pressure diagnostic process is performed assuming that there is a possibility of leakage; in this case, the discharge prevention system is placed under a negative pressure, and the presence or absence of leakage in the tank system is ultimately determined from the negative pressure maintenance capability.
Furthermore, Japanese Patent Application Kokai No. Hei 9-317572 describes an evaporated fuel treatment device which is equipped with a bypass valve that bypasses the pressure adjustment valve in the charging passage connecting the fuel tank and the canister, and which separately ascertains the presence or absence of leakage in the tank system on the fuel tank side of the bypass valve and in the canister system on the canister side of the bypass valve. A determination 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 tank pressure is caused to move toward atmospheric pressure. If the shift in the tank pressure at this time is greater than a predetermined value, it is determined that the tank system is normal with no leakage. If there is leakage in the tank system, then the pressure in the fuel tank prior to starting is more or less equal to atmospheric pressure; accordingly, the shift in pressure is small.
As consideration for the environment has become more important, there has been a demand for stricter criteria in determining the presence or absence of leakage. However, the internal pressure in a fuel tank constantly changes due to various factors such as the temperature of the fuel, the degree to which surplus fuel is returned from the engine space, the load conditions of the vehicle, and vibration, etc. As a result, difficulties have been encountered in the accurate detection of the presence or absence of leakage caused by minute holes.
If there is frequent lighting of a warning lamp, etc., due to the erroneous detection of leakage in cases where there is actually no leakage, this results in a lowering of the practical utility of the vehicle. On the other hand, if no leakage is detected in cases where leakage is actually occurring, evaporated fuel continues to be released into the atmosphere.
Accordingly, there is a need for an evaporated fuel treatment device that can correctly detect the presence or absence of leakage caused by minute holes (e.g., holes with a diameter in the range of 0.5 mm).
SUMMARY OF THE INVENTION
An evaporated fuel treatment device in accordance with one aspect of the invention is intended for use in an internal combustion engine which has (a) a fuel tank, (b) a canister which has an opening that opens the interior of the canister to the atmosphere, and which adsorbs evaporated fuel generated inside the fuel tank, (c) a charging passage which causes the fuel tank to communicate with the canister, (d) a pressure adjustment valve which is provided in the charging passage, (e) an internal pressure sensor which is provided upstream from the pressure adjustment valve, and which is used to detect the pressure inside the fuel tank, and (f) a controller which detects leakage in the fuel tank system on the upstream side of the pressure adjustment valve according to the output of the sensor. The controller has at least a first reference value for a first leak diameter to be detected and a second reference value for a second leak diameter to be detected. The controller detects the absence of leakage by comparing the output of the internal pressure sensor with the first and second reference values.
In accordance with one aspect of the invention, the first and second reference values are set corresponding to a first leak diameter and second leak diameter respectively that constitute objects of detection, and the presence or absence of leakage is determined by means of the respective reference values. Accordingly, actions can be taken relative to the respective detections.
In accordance with another aspect of the invention, the evaporated fuel treatment device of the invention relates to an internal combustion engine which has (a) a fuel tank, (b) a canister which has an opening that opens the interior of the canister to the atmosphere, and which adsorbs evaporated fuel generated inside the fuel tank, (c) a charging passage which causes the fuel tank to communicate with the canister, (d) a pressure adjustment valve which is provided in the charging passage, (e) a bypass passage which bypasses the pressure adjustment valve in the charging passage, (f) a bypass valve which opens and closes the bypass passage, (g) an internal pressure sensor which is provided upstream from the pressure adjustment valve, and which is used to detect the pressure inside the fuel tank, and (h) a controller which detects leakage in the fuel tank system on the upstream side of the pressure adjustment valve according to the output of the sensor when the bypass valve is opened from a closed state. The controller of the second embodiment has at least a first reference value for a first leak diameter to be detected and a second reference value for a second leak diameter to be detected. The system detects the absence of leakage by comparing with the first and second reference values the difference between the output value of the internal pressure sensor when the bypass valve is closed and the output value of the internal pressure sensor when the bypass valve is opened to open the fuel tank system to the atmosphere.
In this embodiment, the presence or absence of leakage is determined by comparing with first and second reference values the difference between the output value of the internal pressure sensor that is obtained immediately after the starting of the internal combustion engine and the output value of the internal pressure sensor that is obtained when the fuel tank system is opened to the atmosphere. Accordingly, the question of whether or not the fuel tank system continues to have the function of maintaining pressure when the internal combustion engine is stopped, i.e., the question of whether or not any holes have been formed in the fuel tank system, can be determined with respect to two judgement criteria.
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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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