Evaporative fuel-processing system for internal combustion engines

摘要

An evaporative fuel-processing system for an internal combustion engine includes a charging passage extending between the canister and the fuel tank of the engine, a purging passage extending between the canister and the intake system of the engine, an open-to-atmosphere passage for communicating the interior of the canister to the atmosphere, a first control valve for selectively opening and closing the purging passage, and a second control valve for selectively opening and closing the open-to-atmosphere passage. A tank internal pressure sensor detects pressure within the evaporative fuel-processing system, and an ECU determines abnormality of the evaporative fuel-processing system, based on a variation in the detected pressure after the interior of the evaporative fuel-processing system is negatively pressurized into a predetermined negative pressure state. An amount of evaporative fuel generated within the evaporative fuel-processing system is detected based on an the output from the exhaust gas concentration sensor obtained when the first control valve is opened. The abnormality detection is restricted when the detected amount of evaporative fuel is larger than a predetermined amount.