Patent ID: 7716924
Filing Date: 2010-05-18
Classification: B01D,F01N,F02D,Y02T

Abstract:
1. A device for purifying exhaust gas of an internal combustion engine which is equipped with a supercharger and effects the supercharging in the operation at a lean air-fuel ratio, comprising: a NOx occluding and reducing catalyst which is arranged in the exhaust gas passage of the engine, occludes the NOx in the exhaust gas by absorption, adsorption or both when the exhaust gas flowing in has a lean air-fuel ratio, and reduces and purifies the occluded NOx when the exhaust gas flowing in has the stoichiometric air-fuel ratio or a rich air-fuel ratio; wherein when the engine is in operation at a lean air-fuel ratio, a rich spike operation is executed by changing the engine operating air-fuel ratio over to a rich air-fuel ratio for a short period of time to supply the exhaust gas of the rich air-fuel ratio to the NOx occluding and reducing catalyst, in order to reduce and purify the NOx occluded by the NOx occluding and reducing catalyst; and wherein, when the supercharged pressure of the engine becomes higher than a preset value at which blow-by occurs at the NOx occluding and reducing catalyst, the richness degree of the engine operating air-fuel ratio during the rich spike operation is controlled in accordance with the supercharged pressure of the engine.