Patent ID: 6901744

Claim:
An air-fuel ratio control apparatus of an internal combustion engine, comprising: oxygen storage amount estimating means for estimating an oxygen storage amount of an exhaust purifying catalyst located on an exhaust path of the internal combustion engine, based on a history of an oxygen adsorption/desorption amount calculated from an air-fuel ratio of said internal combustion engine; downstream exhaust air-fuel ratio detecting means located downstream of said exhaust purifying catalyst on said exhaust path, for detecting an exhaust air-fuel ratio downstream of said exhaust purifying catalyst; maximum oxygen storage amount estimating means for estimating a maximum oxygen storage amount, based on an oxygen storage amount estimate estimated when the exhaust air-fuel ratio detected by said downstream exhaust air-fuel ratio detecting means is a predetermined air-fuel ratio; air-fuel ratio target setting means for setting a target of a controlled air-fuel ratio, based on the maximum oxygen storage amount estimate; and further comprising storage amount target setting means for setting an oxygen storage amount target, based on the maximum oxygen storage estimate estimated, wherein said storage amount target setting means applies forced oscillation to the oxygen storage amount target.