Evaporative fuel-processing system for internal combustion engines

In an evaporative fuel-processing system for an internal combustion engine having a fuel tank and an intake passage, said evaporative fuel-processing system including said fuel tank, a canister for adsorbing evaporative fuel generated from said fuel tank, said canister having an air inlet port communicating with the atmosphere, a charging passage connecting between said fuel tank and said canister, a first control valve arranged in said charging passage, a purging passage connecting between said canister and said intake passage of said engine, a second control valve arranged in said purging passage, a third control valve arranged in said air inlet port for opening and closing said air inlet port, and system internal pressure-detecting means arranged in said system at a location upstream of said first control valve for detecting pressure within said system,

• the improvement comprising:
• pressure-reducing means for effecting negative pressurization of said system until said pressure detected by said system internal pressure-detecting means reaches a predetermined negative value by opening said first control valve and said second control valve, and at the same time closing said third control valve;
• and
• first pressure change-detecting means for closing said first control valve, said second control valve, and said third control valve, after said negative pressurization of said system, and detecting a first amount of change in said pressure within said system in the resulting state of said system in which said first control valve, said second control valve, and said third control valve are closed;
• second pressure change-detecting means for opening said first control valve with said second control valve and said third control valve being kept closed after said first amount of change in said pressure within said system has been detected by said first pressure change-detecting means, and detecting a second amount of change in said pressure within said system having occurred after said first control valve has been opened;
• and
• abnormality-determining means for determining abnormality of said system based on said first amount of change and said second amount of change in said pressure within said system.

In an evaporative fuel-processing system for an internal combustion engine having a fuel tank and an intake passage, said evaporative fuel-processing system including said fuel tank, a canister for adsorbing evaporative fuel generated from said fuel tank, said canister having an air inlet port communicating with the atmosphere, a charging passage connecting between said fuel tank and said canister, a first control valve arranged in said charging passage, a purging passage connecting between said canister and said intake passage of said engine, a second control valve arranged in said purging passage, a third control valve arranged in said air inlet port for opening and closing said air inlet port, and system internal pressure-detecting means arranged in an intermediate portion of said system between said first control valve and said second control valve for detecting pressure within said system,

• the improvement comprising:
• pressure-reducing means for effecting negative pressurization of said system until said pressure detected by said system internal pressure-detecting means reaches a predetermined negative value by opening at least said second control valve of said first control valve and said second control valve, and at the same time closing said third control valve;
• and
• pressure change-detecting means for closing said first control valve, said second control valve, and said third control valve, and detecting an amount of change in said pressure within said system in the resulting state of said system in which said first control valve, said second control valve, and said third control valve are closed;
• and
• abnormality-determining means for determining abnormality of said system based on said amount of change in said pressure detected by said pressure change-detecting means.

In an evaporative fuel-processing system for an internal combustion engine having a fuel tank and an intake passage, said evaporative fuel-processing system including said fuel tank, a canister for adsorbing evaporative fuel generated from said fuel tank, said canister having an air inlet port communicating with the atmosphere, a charging passage connecting between said fuel tank and said canister, a first control valve arranged in said charging passage, a purging passage connecting between said canister and said intake passage of said engine, a second control valve arranged in said purging passage, a third control valve arranged in said air inlet port for opening and closing said air inlet port, and system internal pressure-detecting means arranged in said system at a location upstream of said first control valve for detecting pressure within, said system,

• the improvement comprising:
• pressure-reducing means for effecting negative pressurization of said system until said pressure detected by said system internal pressure-detecting means reaches a predetermined negative value by opening said first control valve and said second control valve, and at the same time closing said third control valve;
• comparing means for comparing a first value of said pressure within said system detected by said system internal pressure-detecting means when said first control valve and said second control valve are closed with said third control valve being kept closed, and a second value of said pressure within said system detected by said system internal pressure-detecting means after detection of said first value of said pressure when said first control valve is opened with said second control valve and said third control valve being kept closed;
• and
• abnormality determining means for determining abnormality of said system based on results of comparison by said comparing means.