AIR-FUEL RATIO CONTROL DEVICE FOR INTERNAL COMBUSTION ENGINE

摘要

PROBLEM TO BE SOLVED: To provide an air-fuel ratio control device for an internal combustion engine which can perform air-fuel ratio control with high accuracy while sufficiently securing purging frequency of fuel vapor. SOLUTION: Vapor fuel generated in a fuel tank 1 and temporarily captured in a canistor 14 is purged into an intake passage 10 through a purge control valve 22. An electronic control unit 51 performs air-fuel ratio feedback control based on an air-fuel ratio sensed by an oxygen sensor 46 arranged on an exhaust passage 12. The electronic control unit 51 varies a flow amount of the vapor fuel by means of the purge control valve 22. Dislocation of a vapor density leaned value FGPG is corrected based on a variation amount of a feedback correction factor FAF at this time. Dislocation of the air-fuel ratio is obtained by eliminating influence of purging from the corrected vapor density learned value FGPG. An air-fuel ratio learned value KG is corrected according to the dislocation.