Air-fuel ratio variation suppressing apparatus for internal combustion engine

摘要

An evaporation fuel processing mechanism supplies fuel vapor in a fuel tank to a canister via a vapor passage and purges fuel in the canister to an air-intake passage of an internal combustion engine via a purge passage when the internal combustion engine is operated. This mechanism supplies fuel vapor in the fuel tank when refueling to the canister via a breather passage. The breather passage has a pressure sensitive valve that opens in response to a variation in pressure in the fuel tank during refueling. An air-fuel ratio variation limiting apparatus determines whether the pressure sensitive valve is open and limits a variation in the air-fuel ratio when the pressure sensitive valve is open.