Internal-combustion engines – Charge forming device – Having fuel vapor recovery and storage system
Patent
1997-09-22
1999-01-26
Moulis, Thomas N.
Internal-combustion engines
Charge forming device
Having fuel vapor recovery and storage system
F02M 3304
Patent
active
058627952
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an evaporative control system for a multicylinder internal combustion engine and, more particularly, to one that purges fuel vapor, to equally distribute the fuel vapor into cylinders, whereby a fluctuation of the air-fuel ratio of the engine is controlled and the exhaust gas is better purified.
BACKGROUND ART
An evaporative control system for a multicylinder internal combustion engine, in general, has a purge passage that connects a canister for temporarily storing evaporated fuel from a fuel tank and an intake air passage of an internal combustion engine (hereinafter simply referred to as an engine) and a purge control valve disposed in the intake air passage. The purge control valve is activated depending on the engine operating condition, and is opened and closed at a given frequency in response to a pulse signal having a given duty factor. If a period of the pulse signal is substantially synchronized with an engine cycle, fuel purged from the canister will be drawn into a specific cylinder of the engine to make an air-fuel ratio in the cylinder rich and an air-fuel ratio in any other cylinder that draws no purged fuel lean, thereby fluctuating an air-fuel ratio in the engine as a whole and causing misfires in the lean cylinders. To solve this problem, a technique to change the driving frequency of the purge control valve to another driving frequency when the driving frequency is substantially synchronized with an engine cycle is disclosed (Refer to Japanese Patent Publication No. 6-241129).
However, the technique disclosed in Japanese Patent Publication No. 6-241129 suddenly changes the driving frequency of the purge control valve at a boundary where it is substantially synchronized with an engine cycle. This results in fluctuating an air-fuel ratio in the engine, and the exhaust emission is deteriorated. To converge the fluctuating air-fuel ratio to a target air-fuel ratio, the disclosure corrects a fuel injection quantity. It takes time, however, until the fluctuation is stabilized at the target air-fuel ratio.
DISCLOSURE OF INVENTION
Therefore, it is an object of the present invention to solve the above problems and provide an evaporative control system for a multicylinder internal combustion engine, capable of keeping an air-fuel ratio stabilized even if the driving period of a purge control valve is substantially synchronized with an engine cycle, thereby maintaining exhaust purifying performance and preventing lean misfires.
FIG. 1 is a drawing showing a basic constitution of the present invention. The evaporative control system for a multicylinder internal combustion engine according to the present invention which solves the above problems, comprises a canister 37 for temporarily storing evaporated fuel from a fuel tank 15, a purge passage 39 for connecting the canister 37 to an intake passage of the engine 1, and a purge control valve 41 disposed in the purge passage 39, to control the quantity of gas to be purged from the canister 37 into the intake passage by opening and closing the valve at a given frequency. The evaporative control system is characterized in that it comprises a drive condition detecting means A for detecting driving conditions (for example the revolution speed) of the engine 1, a delay time setting means B for setting a delay time to delay the valve opening start timing in the driving period from the start of the driving period in response to the engine driving conditions detected by the drive condition detecting means A, and a purge control valve driving means C for driving the purge control valve 41 with a delay time set by the delay time setting means B.
In the evaporative control system for a multicylinder internal combustion engine according to the present invention, the drive condition detecting means A comprises an equal distribution judging means that detects on-off periods of the intake valve of the engine 1 and judges whether or not the purged gas is equally distributed into cylinders of the engine 1 on the
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patent: 5694904 (1997-12-01), Osanai
patent: 5699778 (1997-12-01), Muraguchi et al.
patent: 5706789 (1998-01-01), Yamada et al.
Copending U.S. Appln. Serial No. 08/548,887, filed Oct. 26, 1995.
Copending U.S. Appln. Serial No. 08/785,456, filed Jan. 17, 1997.
Copending U.S. Appln. Serial No. 08/785,446, filed Jan. 17, 1997.
Moulis Thomas N.
Toyota Jidosha & Kabushiki Kaisha
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