Patent ID: 6205773
Filing Date: 2001-03-27
Classification: F01N,F02D,Y02T

Abstract:
An exhaust gas purification device for an internal combustion engine comprising:an NOx occluding and reducing catalyst disposed in an exhaust gas passage of the internal combustion engine to absorb NOx in the exhaust gas when the air-fuel ratio of the exhaust gas flowing in is larger than a stoichiometric air-fuel ratio and to release and reduce the absorbed NOx when the air-fuel ratio of the exhaust gas flowing in becomes smaller than the stoichiometric air-fuel ratio, said NOx occluding and reducing catalyst exhibiting a decrease in the capability of absorbing, releasing and reducing the NOx as it adsorbs or absorbs contaminants in the exhaust gas;a holding amount estimation means for estimating the amount of said contaminants adsorbed or absorbed by said NOx occluding and reducing catalyst;a heating means for releasing said contaminants from the NOx occluding and reducing catalyst by heating said NOx occluding and reducing catalyst when the amount of said contaminants increases to be in excess of a predetermined judging value and when the operating condition of the engine turns into a predetermined heating-conducting condition; anda heating-conducting condition-setting means for setting said heating-conducting condition depending upon the amount of said contaminants that are held in the NOx occluding and reducing catalyst.