Patent ID: 6494037
Filing Date: 2002-12-17
Classification: F02D

Abstract:
An exhaust purification device for an engine, comprising:a catalyst provided in an exhaust passage of the engine; a sensor which detects the characteristics of the exhaust flowing into the catalyst, a sensor which detects the temperature of a cooling fluid of the engine, and a microprocessor programmed to: store the temperature of the cooling fluid of the engine and temperature of the catalyst when the engine stops, estimate the temperature of the catalyst on engine startup based on the temperature of the cooling fluid of the engine on engine startup, and the temperature of the cooling fluid of the engine and the temperature of the catalyst on the immediately preceding occasion when the engine stopped, estimate an oxygen storage amount of the catalyst on engine startup based on the estimated temperature of the catalyst on engine startup, compute the oxygen storage amount of the catalyst based on the detected exhaust characteristics, using the oxygen storage amount on engine startup as an initial value, and control the air fuel ratio of the engine based on the computed oxygen storage amount so that the oxygen storage amount of the catalyst is a target value.