Patent ID: 8671661

Claim:
An exhaust gas purification system comprising: a NOx occlusion-reduction catalyst for purifying NOx in exhaust gas, a hydrocarbon-adsorbing member for only adsorbing hydrocarbons in the exhaust gas, and one of a catalyzed diesel particulate filter or an oxidation catalyst for purifying particulate matter in the exhaust gas, in this order from an upstream side of an exhaust passage of an internal combustion engine; and a controller configured, during NOx regeneration control for restoring NOx occlusion capacity of the NOx occlusion-reduction catalyst, to when an index temperature indicative of a temperature of the hydrocarbon-adsorbing member is not higher than a first judgment temperature, perform a first air-fuel ratio control by controlling an air-fuel ratio of the exhaust gas to be set at 0.8 to 1.1 in terms of excess air factor, when the index temperature is between the first judgment temperature and a second judgment temperature, supply reducing agent to the exhaust gas passage, by post infection of the internal combustion engine or by direct injection of a reducing agent supplying apparatus provided in the exhaust passage, to perform a second air-fuel ratio control by controlling the air-fuel ratio of the exhaust gas to be set at 1.0 to 1.1 in terms of excess air factor, and when the index temperature is higher than the second judgment temperature, perform a third air-fuel ratio by controlling the air-fuel ratio of the exhaust gas to be set at 0.8 to 1.1 in terms of excess air factor.