Patent ID: 6167696
Filing Date: 2001-01-02
Classification: F01N,Y02A,Y02T

Abstract:
An exhaust gas purification system for an internal combustion engine comprising: a hydrocarbon trap; an electrically heated catalyst located downstream of said hydrocarbon trap; an integrated NO.sub.x trap-particulate filter downstream of said electrically heated catalyst; first and second temperature sensors providing first and second temperature signals upstream and downstream of said electrically heated catalyst, respectively; and an engine control module including a central processing unit and associated memory, said central processing unit programmed to perform the following steps: monitor the level of accumulated particulate matter in said NO.sub.x trap-particulate filter; monitor the level of absorbed sulfur in said NO.sub.x trap-particulate filter; and if the total amount of particulate matter accumulated in said NO.sub.x trap-particulate filter exceeds a predetermined level, then operate the engine at a lean air-fuel setpoint, and activate said electrically heated catalyst for a first predetermined period of time, otherwise; if the total amount of sulfur absorbed in said NO.sub.x trap exceeds a predetermined level, then operate the engine at a rich air-fuel setpoint, and activate said electrically heated catalyst for a second predetermined period of time.