Patent ID: 6622478
Filing Date: 2003-09-23
Classification: F01N,F02D,Y02T

Abstract:
An exhaust purification device for an engine, comprising:a first catalyst provided in an exhaust pipe of the engine; a second catalyst provided downstream of the first catalyst; a front sensor which detects an exhaust characteristic flowing into the first catalyst; a rear sensor which detects an exhaust characteristic flowing out of the second catalyst; and a processor programmed to: compute an oxygen storage amount of the first catalyst using the exhaust characteristic detected by the front sensor; control an air-fuel ratio of the engine based on the computed oxygen storage amount so that the oxygen storage amount of the first catalyst is a target amount; and set a target air-fuel ratio to a predetermined fixed rich air-fuel ratio until the exhaust characteristic detected by the rear sensor becomes richer than a predetermined value, after running at a predetermined lean state.