Patent ID: 6564544
Filing Date: 2003-05-20
Classification: F01N,F02D,Y02T

Abstract:
An exhaust purification arrangement for an engine, comprising:a catalyst provided in an exhaust passage of the engine, said catalyst containing a material which stores oxygen in a form of a first amount which is rapidly adsorbed and released from the material and which stores oxygen in a form of a second amount which is slowly adsorbed and released from the material; a front sensor which detects an air-fuel ratio of exhaust flowing into the catalyst; and a processor programmed to: compute the first amount of oxygen stored in the catalyst, based on the detected exhaust air-fuel ratio; compute a target air-fuel ratio to be supplied to the engine so that an amount of oxygen in the exhaust maintains the first amount of oxygen at a predetermined target value; limit the target air-fuel ratio to a lower limiter when the computed target air-fuel ratio is less than the lower limiter; and control an air-fuel ratio of the engine based on the target air-fuel ratio after limitation.