Abnormality detecting apparatus for use in fuel transpiration prevention systems

A fuel transpiration prevention system for preventing transpiration of a fuel gas generated by fuel encased within a liquid fuel tank and supplied to an internal combustion engine, said system comprising:

• pressure detecting means for detecting a pressure within said fuel tank;
• canister means encasing an absorbing device for absorbing said fuel gas generated within said fuel tank;
• first supply passage means for introducing said fuel gas from said fuel tank to said canister means;
• pressure adjusting valve means for keeping a pressure within said canister in a predetermined range;
• second supply passage means for leading the fuel gas absorbed by said absorbing device into an intake pipe of said internal combustion engine;
• control valve means provided within said second supply passage means and arranged to open and close in accordance with an operating condition of said internal combustion engine;
• and
• supply abnormality detecting means for detecting an abnormality in a supply of said fuel gas to said intake pipe due to an abnormality in at least one of said canister, said first supply passage means, said second supply passage means, said control valve means and said fuel tank, on the basis of said detected pressure obtained when said control valve means takes opening and closing states.

A fuel transpiration prevention system for preventing transpiration of a fuel gas generated by fuel encased within a liquid fuel tank and supplied to an internal combustion engine, said apparatus comprising:

• a fuel gas supply system including:
• canister means encasing an absorbing device for absorbing said fuel gas generated within said fuel tank and further having an opening in communication with an atmosphere;
• first passage means provided between said canister and said fuel tank for introducing said fuel gas from said fuel tank to said canister means;
• second passage means provided between said canister and an intake pipe of said internal combustion engine for leading the fuel gas absorbed by said absorbing device into said intake pipe of said internal combustion engine due to a negative pressure generated within said intake pipe;
• and
• first valve means provided in said second passage means for opening and closing said second passage in accordance with an operating condition of said internal combustion engine;
• pressure detecting means for detecting a pressure within said fuel tank and generating a signal indicative of the detected pressure;
• second valve means for opening and closing said atmosphere-communicated opening of said canister;
• deviation calculating means responsive to said signal generated from said pressure detecting means for calculating a deviation between the pressure detected when said first valve means opens said second passage means and said second valve means opens said atmosphere-communicated opening and the pressure detected when said first valve means opens said second passage means and said second valve means closes said atmosphere-communicated opening;
• and
• abnormality decision means for deciding an abnormality of said fuel gas supply system on the basis of said deviation calculated by said deviation calculating means.

A fuel transpiration prevention system for preventing transpiration of a fuel gas generated by fuel encased within a liquid fuel tank and supplied to an internal combustion engine, said apparatus comprising:

• a fuel gas supply system including:
• canister means encasing an absorbing device for absorbing said fuel gas generated within said fuel tank;
• first passage means provided between said canister and said fuel tank for introducing said fuel gas from said fuel tank to said canister means;
• second passage means provided between said canister and an intake pipe of said internal combustion engine for leading the fuel gas absorbed by said absorbing device into said intake pipe of said internal combustion engine due to a negative pressure generated within said intake pipe;
• and
• valve means provided in said second passage means for opening and closing said second passage in accordance with an operating condition of said internal combustion engine;
• pressure detecting means for detecting a pressure within said fuel tank and generating a signal indicative of the detected pressure;
• bypass control means provided between said first and second passage means for allowing a direct communication to be established between said first and second passage means so as to by-pass said canister;
• deviation calculating means responsive to said signal generated from said pressure detecting means for calculating a deviation between the pressure detected when said valve means opens said second passage means and said bypass control means by-passes said canister and the pressure detected when said valve means opens said second passage means and said bypass control means does not by-pass said canister;
• and
• abnormality decision means for deciding an abnormality of said fuel gas supply system on the basis of said deviation calculated by said deviation calculating means.

An apparatus for detecting an abnormality of a fuel transpiration prevention system which includes a canister with an absorbing device and a control valve provided in a passage between a fuel tank and an intake pipe of an internal combustion engine so that a fuel gas generated within said fuel tank is absorbed by said absorbing device of said canister and introduced into said intake pipe by opening and closing said control valve in accordance with an operating state of said internal combustion engine, said apparatus comprising:

• pressure detecting means for detecting a pressure within said fuel transpiration prevention system;
• switching valve means for opening and closing an opening of said canister which communicates with an atmosphere;
• sealing means for closing both said control valve and switching valve means so as to seal said fuel transpiration prevention system;
• pressure adjusting means for adjusting a pressure within the sealed fuel transpiration prevention system to predetermined pressures;
• pressure variation detecting means responsive to an output of said pressure detecting means for detecting predetermined pressure variation states while said pressure adjusting means adjusts the pressure within the sealed system or after said pressure adjusting means has adjusted the pressure within the sealed system;
• and
• abnormality detecting means for detecting an abnormality of said fuel transpiration prevention system on the basis of said predetermined pressure variation state detected by said pressure variation detecting means.