Internal-combustion engines – Charge forming device – Including exhaust gas condition responsive means
Patent
1996-08-15
1997-12-23
Moulis, Thomas N.
Internal-combustion engines
Charge forming device
Including exhaust gas condition responsive means
123520, F02M 2508, F02D 4114
Patent
active
056997787
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a fuel evaporative emission suppressing apparatus.
BACKGROUND ART
To prevent air pollution etc., the engine or vehicle body of an automobile is equipped with various devices for treating harmful emissions. Examples of such devices known in the art include a blow-by gas recirculating apparatus for introducing blow-by gas, which is a gas that leaks from a combustion chamber of the engine to a crankcase and contains unburned fuel component (HC) as its main component, into the intake pipe, and a fuel evaporative emission suppressing apparatus for introducing evaporative fuel gas, which is produced in a fuel tank and contains HC as its main component, into the intake pipe.
The fuel evaporative emission suppressing apparatus comprises a canister filled with activated charcoal for adsorbing evaporative fuel gas, a large number of pipes, etc. The canister has an inlet port communicating with the fuel tank, an outlet port communicating with the intake pipe, and a vent port opening to the atmosphere. In this canister storage-type fuel evaporative emission suppressing apparatus, the evaporative fuel gas in the fuel tank is introduced into the canister so as to be adsorbed by the activated charcoal. By allowing the negative pressure in the intake pipe to act upon the outlet port, the atmospheric air (purge air) is introduced into the canister through the vent port, so that the evaporative fuel gas adsorbed by the activated charcoal is separated therefrom by the purge air and then introduced into the intake pipe together with the purge air. The evaporative fuel gas thus introduced into the intake pipe burns together with air-fuel mixture in the combustion chamber of the engine, thus preventing the emission of evaporative fuel gas into the atmosphere.
If, however, the purge air containing evaporative fuel gas is inappropriately introduced into the intake pipe, the air-fuel ratio of a mixture deviates from a proper range, causing large fluctuation of the rotational speed or torque of the engine. As a result, the ride quality or drivability of the vehicle deteriorates. This disadvantage is noticeable particularly in the case where the purge air is introduced while the engine is operated in an idling region in which the quantity of intake air is small.
To eliminate the disadvantage, a purge control valve, as purge adjusting means for controlling the quantity of purge air to be introduced, is arranged in a purge passage connecting the canister and the intake pipe, and is opened to introduce the purge air into the engine only when the engine is operated in a predetermined operating region. Purge control valves are generally classified into a mechanical type which is responsive to the intake negative pressure, and an electric type which is subjected to on-off control by an electronic control unit in accordance with operation information such as throttle opening degree, intake air flow rate and the like. The mechanical type is inexpensive and thus is widely used, but from the viewpoint of performance, the electromagnetic type is superior because the introduction and cutoff of purge air can be accurately controlled as desired.
However, the fuel evaporative emission suppressing apparatus equipped with such purge control valve still has a problem associated with the introduction of purge air. For example, if the vehicle is parked for a long time in the summertime or the like in which the outside air temperature is high, a large quantity of evaporative fuel gas is produced within the fuel tank and adsorbed by the canister. In this case, as soon as the engine operation enters the predetermined operating region after the start of the engine, purge air having a very high content of evaporative fuel gas is supplied to the engine, making the air-fuel mixture extremely enriched. As the engine operation in the predetermined operating region is continued, separation of the evaporative fuel gas progresses in the canister, and thus the concentration of the fuel component in the purge air
REFERENCES:
patent: 4967713 (1990-11-01), Kojima
patent: 5020503 (1991-06-01), Kanasashi
patent: 5351193 (1994-09-01), Poirier et al.
patent: 5423307 (1995-06-01), Okawa et al.
patent: 5469832 (1995-11-01), Nemoto
patent: 5535719 (1996-07-01), Morikawa et al.
Matsumoto Takuya
Muraguchi Tomokazu
Mitsubishi Jidosha Kogyo Kabushiki Kaisha
Moulis Thomas N.
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