Patent ID: 7096663

Claim:
An air-fuel ratio control apparatus for an internal combustion engine of a vehicle, the air-fuel ratio control apparatus comprising: an air-fuel ratio sensor located upstream of a three-way catalyst in an exhaust system of the internal combustion engine, wherein the air-fuel ratio sensor detects an engine air-fuel ratio based on a concentration of oxygen in exhaust gas; and an oxygen sensor located downstream of the three-way catalyst, wherein the oxygen sensor detects the engine air-fuel ratio based on the concentration of oxygen in exhaust gas, wherein the control apparatus: performs feedback control of an amount of fuel based on output of the air-fuel ratio sensor such that the engine air-fuel ratio seeks a stoichiometric air-fuel ratio; performs sub-feedback control by computing a sub-feedback correction value based on output of the oxygen sensor, wherein the sub-feedback correction value corrects the fuel amount in the feedback control; learns a learning value based on the sub-feedback correction value, wherein the learning value is used for compensating for a stationary difference between the stoichiometric air-fuel ratio and the engine air-fuel ratio, which stationary difference is based on output characteristics of the air-fuel ratio sensor; stores the learning value; executes fuel cutoff control in a predetermined period; and inhibits the fuel cutoff control until the learning is stabilized when learning of the stored learning value is performed after the stored learning value is cleared.