Patent ID: 6679050
Filing Date: 2004-01-20
Classification: F01N,F02D,Y02T

Abstract:
An exhaust emission control device of an internal combustion engine provided with an exhaust gas pipe, comprising:a front three-way catalyst disposed in said exhaust gas pipe, a rear three-way catalyst disposed in said exhaust gas pipe, said rear three-way catalyst being provided downstream of said front three-way catalyst, and a microprocessor programmed to: control said engine so that an air-fuel ratio of the exhaust gas flowing into said front three-way catalyst is made to periodically fluctuate to rich or lean about the stoichiometric air-fuel ratio, increase the amplitude of air-fuel ratio fluctuation when the temperature of said rear three-way catalyst is raised, and lessen the degree of increase in the amplitude of air-fuel ratio fluctuation with increasing levels of deterioration of said front three-way catalyst.