Patent ID: 6138453
Filing Date: 2000-10-31
Classification: B01D,F01N,F02D,Y02T

Abstract:
An exhaust gas purification device for an internal combustion engine, comprising:a NO.sub.X occluding and reducing catalyst disposed in an exhaust gas passage of an internal combustion engine, the catalyst absorbing NO.sub.X in exhaust gas when an inflowinq air-fuel ratio of exhaust gas flowing into the catalyst is lean and releasing and reducing previously absorbed NO.sub.X when the inflowinq air-fuel ratio is one of a stoichiometric air-fuel ratio and a rich air-fuel ratio;an air-fuel ratio sensor disposed in the exhaust gas passage downstream of the catalyst and detecting an outflowing air-fuel ratio of exhaust gas flowing out of the catalyst;air-fuel ratio control means for switching the inflowing air-fuel ratio from a rich air-fuel ratio to a lean air-fuel ratio; andevaluating means for evaluating an ability of the catalyst based on length of time during which the outflowing air-fuel ratio is maintained at a stoichiometric air-fuel ratio after the inflowing air fuel ratio is switched by the air-fuel ratio control means.