Internal-combustion engines – Charge forming device – Having fuel vapor recovery and storage system
Reexamination Certificate
2000-06-27
2001-12-18
Moulis, Thomas N. (Department: 3747)
Internal-combustion engines
Charge forming device
Having fuel vapor recovery and storage system
Reexamination Certificate
active
06330879
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an evaporative emission control system for an internal combustion engine, and more particularly to such a system that the emission of evaporative fuel is prevented by maintaining the pressure in a fuel tank at a negative pressure.
For example, Japanese Patent Laid-open No. 11-50919 discloses an evaporative emission control system including an evaporative fuel passage for connecting a fuel tank directly to an intake pipe of an internal combustion engine to maintain the pressure in the fuel tank at a negative pressure (a pressure lower than the atmospheric pressure). This conventional system further includes a tank pressure control valve provided in the evaporative fuel passage. When the pressure in the fuel tank is higher than the pressure in the intake pipe, valve opening control of the tank pressure control valve is enabled to be carried.
In the conventional system mentioned above, however, since the pressure in the intake pipe always varies according to engine operating conditions, there is a case that in the open condition of the tank pressure control valve, the pressure in the intake pipe becomes higher than the pressure in the fuel tank during the period between successive detections of the pressure in the fuel tank, causing an increase in the pressure in the fuel tank.
SUMMARY OF THE INVENTION
It is accordingly an object of the present invention to provide an evaporative emission control system which can reliably avoid the case that the pressure in the fuel tank increases during opening operation of the tank pressure control valve, due to the variation of the pressure in the intake pipe.
In accordance with the present invention, there is provided in an evaporative emission control system of an internal combustion engine, including an evaporative fuel passage for connecting a fuel tank and an intake system of the internal combustion engine, a control valve provided in the evaporative fuel passage for opening and closing the evaporative fuel passage, and control means for controlling the opening degree of the control valve so that the pressure in the fuel tank becomes lower than an atmospheric pressure; the improvement comprising: tank pressure detecting means for detecting the pressure in the fuel tank, intake pressure detecting means for detecting the pressure in the intake system, and enabling means for enabling the opening operation of the control valve in the case that the pressure in the fuel tank is higher than or equal to a pressure value obtained by adding the pressure in the intake system and a predetermined pressure.
Preferably the predetermined pressure is set to a value slightly larger than a maximum value of possible changes in the pressure in the intake system during the period between successive detections of the pressure in the fuel tank.
Alternatively, the predetermined pressure is set to a value slightly larger than a maximum value of pressure differences between an actual intake pressure and the detected intake pressure due to a detection delay in the intake pressure detecting means.
Other objects and features of the invention will be more fully understood from the following detailed description and appended claims when taken with the accompanying drawings.
REFERENCES:
patent: 4703737 (1987-11-01), Cook et al.
patent: 5080078 (1992-01-01), Hamburg
patent: 6216674 (2001-04-01), Corkill
patent: 2001/0004844 (2001-06-01), Yamaki
patent: 11-50919 (1999-02-01), None
Ishiguro Tetsuya
Kitamura Toru
Kurokawa Naohiro
Suzuki Norio
Arent Fox Kintner & Plotkin & Kahn, PLLC
Honda Giken Kogyo Kabushiki Kaisha
Moulis Thomas N.
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