ENGINE EXHAUST PURIFICATION ARRANGEMENT

摘要

A controller (6) computes an oxygen storage amount of a catalyst (3) separately as a high speed component/amount and a low speed component/amount according to predetermined release/adsorption characteristics. A target air-fuel ratio of an engine is computed and the air-fuel ratio of the engine is controlled so that the high speed component is maintained constant. The target air-fuel ratio of the engine (1) is limited by an upper limiter and lower limiter so that the high speed component converges to the target value, an excessively large variation of the air-fuel ratio is prevented, and impairment of drivability and fuel cost-performance is also prevented. Further, after lean running due to fuel cut, etc., the lower limiter is lowered to the rich side, and the oxygen storage amount is rapidly induced to converge on the target value.