CONTROL SYSTEM OF INTERNAL COMBUSTION ENGINE

摘要

An internal combustion engine comprises an exhaust purification catalyst 20. A control system of the engine comprises a downstream side air-fuel ratio sensor 41 at a downstream side of the exhaust purification catalyst, and an air-fuel ratio control device which controls the air-fuel ratio of the exhaust gas. The target air-fuel ratio is set to a lean air-fuel ratio when an output air-fuel ratio of the sensor becomes a rich judged air-fuel ratio or less and is set to a rich air-fuel ratio when an output air-fuel ratio becomes a lean judged air-fuel ratio or more. When the engine operating state is a steady operation state and is a low load operation state, at least one of an average lean degree of the target air-fuel ratio while the target air-fuel ratio is set to a lean air-fuel ratio and an average rich degree of the target air-fuel ratio while the target air-fuel ratio is set to a rich air-fuel ratio is increased.