Patent ID: 6932069

Claim:
An air fuel ratio control apparatus for an internal combustion engine, including an exhaust gas purification device provided on an exhaust passage of an internal combustion engine, an air fuel ratio detection device disposed at a location downstream of said exhaust gas purification device, an air fuel ratio feedback value calculation device that calculates an air fuel ratio feedback value based on a difference between an air fuel ratio of a mixture detected by said air fuel ratio detection device and a target air fuel ratio, an air fuel ratio learning value calculation device that calculates an air fuel ratio learning value based on said air fuel ratio feedback value and said target air fuel ratio, and an exhaust gas air fuel ratio control device that controls the air fuel ratio of an exhaust gas flowing into said exhaust gas purification device based on said air fuel ratio feedback value and said air fuel ratio learning value, said apparatus comprising: a temperature detection device that detects the temperature of said exhaust gas purification device; a determination device that makes a determination that when a difference between a detection value of said temperature detection device and a target temperature is greater than a specified range, the detection value of said air fuel ratio detection device shifts to a rich side, whereas when said difference is less than said specified range, the detection value of said air fuel ratio detection device shifts to a lean side; and an air fuel ratio learning value update inhibition device that inhibits the update of said air fuel ratio learning value when said determination device determines that the detection value of said air fuel ratio detection device shifts to a rich side or to a lean side.