ENGINE EXHAUST PURIFICATION DEVICE

摘要

A microprocessor (6) computes an oxygen storage amount of a catalyst (3) separately for a high speed component and a low speed component in accordance with real characteristic. A target air-fuel ratio of an engine (1) is computed and air-fuel ratio control of the engine (1) it is performed so that the high speed component is constant. The deterioration of the catalyst (3) is determined by integrating the high speed component of the oxygen storage amount computed during the air-fuel ratio control process for a predetermined number of times, and comparing its average value with a determining value. The oxygen storage amount of the high speed component which is sensitive to catalyst deterioration is integrated so as to obtain a highly precise determining result to determine the deterioration.