Patent ID: 6409973
Filing Date: 2002-06-25
Classification: B01D,F01N,F02B

Abstract:
An exhaust gas purification device for an internal combustion engine which has an exhaust passage, the engine being operated at an air-fuel ratio higher than a stoichiometric air-fuel ratio, the device comprising:a first NOx absorbent bed and second NOx absorbent bed disposed in an exhaust passage of an engine and connected to each other in series by an exhaust connecting passage, each of the NOx absorbent beds absorbing NOx components in an exhaust gas when an air-fuel ratio of the exhaust gas flowing into the NOx absorbent beds is lean, and releasing absorbed NOx components when an oxygen concentration in the exhaust gas becomes lower than a predetermined amount; a reducing agent supply means for supplying a reducing agent into the exhaust gas in the exhaust connecting passage between the first and the second NOx absorbent beds; a switching means for switching the direction of the exhaust gas flow between a first direction in which the exhaust gas flows through the first NOx absorbent bed to the exhaust connecting passage and into the second NOx absorbent bed in this order, and a second direction in which the exhaust gas flows through the second NOx absorbent bed to the exhaust connecting passage and into the first NOx absorbent bed in this order; and a control means for controlling the switching means so that the direction of the exhaust gas flow is switched between the first and second direction.