Internal combustion engine

An internal combustion engine comprising an exhaust purification catalyst arranged in an exhaust passage of the internal combustion engine and able to store oxygen, a downstream side air-fuel ratio sensor arranged at a downstream side, in a direction of exhaust flow, of the exhaust purification catalyst and detecting an air-fuel ratio of exhaust gas flowing out from the exhaust purification catalyst, and an ECU, wherein

• the ECU is configured to perform air-fuel ratio control for feedback-controlling an amount of fuel fed to a combustion chamber of the internal combustion engine so that an air-fuel ratio of exhaust gas flowing into the exhaust purification catalyst becomes a target air-fuel ratio and performs learning control to correct a parameter relating to air-fuel ratio based on an air-fuel ratio of exhaust gas detected by the downstream side air-fuel ratio sensor;
• the target air-fuel ratio is switched between a plurality of different air-fuel ratios other than the stoichiometric air-fuel ratio, and
• the learning control includes stoichiometric air-fuel ratio stuck learning wherein when the target air-fuel ratio is set to an air-fuel ratio deviated to one side of the stoichiometric air-fuel ratio, if the air-fuel ratio detected by the downstream side air-fuel sensor is maintained in a region of air-fuel ratio near the stoichiometric air-fuel ratio, between a rich judgement air-fuel ratio richer than the stoichiometric air-fuel ratio and a lean judgement air-fuel ratio leaner than the stoichiometric air-fuel ratio, for a stoichiometric air-fuel ratio maintenance judgement time or more, the parameter relating to an air-fuel ratio is corrected so that the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst changes to said one side in the air-fuel ratio control.