Exhaust purification apparatus for an engine

摘要

An exhaust purification apparatus for an engine uses a catalytic converter provided in an exhaust system of the engine. First and second exhaust sensors are provided on upstream and downstream sides, respectively, of the catalyst converter in the exhaust system. Detected values from the first and second exhaust sensors are used for feed back control of air fuel ratio and judging deterioration of the catalyst of the catalytic converter, respectively. A control constant of the air fuel ratio of the feed back control is changed so that the second exhaust sensor detects in accordance with a condition of the catalyst.