Patent ID: 7003945
Filing Date: 2006-02-28
Classification: F01N,F02D,Y02T

Abstract:
1. An exhaust emission control device for internal combustion engine, comprising: a three-way catalyst which is located in an exhaust passage of an internal combustion engine and combines an oxygen storage component capable of storing oxygen and a reducing agent storage component capable of storing a reducing agent; air-fuel ratio modulating means which modulates the air-fuel ratio of exhaust gas flowing into the three-way catalyst between a lean air-fuel ratio and a rich air-fuel ratio; oxygen storage estimating means for estimating an oxygen storage by the oxygen storage component; reducing agent storage estimating means for estimating a reducing agent storage by the reducing agent storage component; and air-fuel ratio modulation adjusting means which adjusts a lean period to be longer or the degree of leaning to be higher, during which the exhaust air-fuel ratio is a lean air-fuel ratio, compared with when the oxygen storage estimated by the oxygen storage estimating means exceeds a first given value if the oxygen storage is not higher than the first given value, and adjusts a rich period to be longer or the degree of enriching to be higher, during which the exhaust air-fuel ratio is a rich air-fuel ratio, compared with when the reducing agent storage estimated by the reducing agent storage estimating means exceeds a second given value if the reducing agent storage is not higher than the second given value.