Patent ID: 6263666
Filing Date: 2001-07-24
Classification: F01N,F02D,F02P,Y02T

Abstract:
An exhaust emission control device for an engine comprising:an exhaust pipe,a catalyst provided in said exhaust pipe which traps and stores NOx in exhaust gas and reduces the stored NOx according to an air-fuel ratio of the exhaust gas flowing into said catalyst,a microprocessor programmed to:determine whether or not conditions for discharging SOx stored in said catalyst are satisfied,raise the temperature of said catalyst to discharge SOx when SOx discharge conditions are satisfied and the running conditions of said engine are in a predetermined SOx discharge running region, andprohibit lean air fuel ratio running of said engine from when SOx discharge conditions are satisfied to when SOx discharge is complete, anda sensor which detects an NOx concentration downstream of said catalyst, and wherein said microprocessor is further programmed to:detect an NOx storage capacity of said catalyst based on said detected NOx concentration, andprohibit lean air-fuel ratio running of said engine when an NOx storage capacity detected after SOx discharge is complete, is less than a predetermined capacity.