Air-Fuel ratio control apparatus for an internal combustion engine and controlling method

摘要

An air-fuel ratio control apparatus for an internal combustion engine in which an air-fuel ratio is always controlled to be a target value with accuracy when purge air is introduced is obtained.The air-fuel ratio control apparatus for an internal combustion engine is provided with purge control quantity setting means 31 that introduces fuel vapor as purge air into an intake system on the basis of a value detected by an operating condition detecting means 30 detecting an operating conditions of an internal combustion engine 6 and controls a quantity of the introduced purge air, a fuel injection quantity calculating means 41 controlling an air-fuel ratio to be a target value on the basis of a value detected by an air-fuel ratio sensor 16 detecting an air-fuel ratio of air-fuel mixture fed into the internal combustion engine 6, a purging state detecting means 39 detecting a state of introduction of the purge air, and a purge air introduction correcting means 40 calculating a correction coefficient for correcting the air-fuel ratio which is changed by starting the introduction of the purge air on the basis of signals of the operating condition detecting means 30 and the purging state detecting means 39, and when the purge air introduction correcting means 40 detects the start of the introduction of the purge air, the correction coefficient is calculated and the fuel injection quantity is corrected.