Patent ID: 6393834
Filing Date: 2002-05-28
Classification: F01N,F02D,Y02A,Y02T

Abstract:
An exhaust purifying apparatus, provided in an exhaust system of an internal combustion engine and provided with a nitrogen oxide absorbent, which absorbs nitrogen oxide when an air-fuel ratio of an exhaust gas is leaner than a stoichiometric air-fuel ratio, and reduces nitrogen oxide when the air-fuel ratio of the exhaust gas is richer than the stoichiometric air-fuel ratio, comprising:an air-fuel ratio controlling device for controlling the air-fuel ratio of a mixture supplied to the engine, and a fuel feeder for feeding fuel upstream of said nitrogen oxide absorbent; a temperature raising device for raising the temperature of said nitrogen oxide absorbent by controlling the air-fuel ratio of the mixture so as to become leaner than the stoichiometric air-fuel ratio of the air-fuel ratio controlling device and feeding fuel means of said fuel feeder, when an absorbing capability of said nitrogen oxide absorbent is catalyst poisoned by accumulated sulfur compounds; and a restoring device for restoring the nitrogen oxide absorbing capability of said nitrogen oxide absorbent by controlling the air-fuel ratio of the mixture so as to become richer than the stoichiometric air-fuel ratio of said air-fuel ratio controlling device after the temperature of the nitrogen oxides absorbent is raised by said temperature raising device; wherein the temperature of said nitrogen oxide absorbent is raised by the temperature raising device when the temperature of said nitrogen oxide absorbent drops below a predetermined temperature while restoring the nitrogen oxide by the restoring device.