| 摘要 |
An exhaust gas purification system for an internal combustion engine is characterized by being equipped with a NOx trap catalyst 22 provided in an exhaust passage 18, a selective reduction catalyst 26 that is provided downstream therefrom and is capable of adsorbing NH3 contained in the exhaust gas, and that selectively reduces NOx in the exhaust gas by means of the adsorbed NH3, and an air-fuel ratio control unit 42 that controls the air-fuel ratio, the air-fuel ratio control unit 42 being equipped with: an NH3 generation unit 50 that desorbs NOx stored in the NOx trap catalyst 22 during lean combustion operation by subjecting the NOx to a rich combustion operation, and that generates NH3 in the NOx trap catalyst 22 and supplies this NH3 to the selective reduction catalyst 26; and an enriching control unit 52 that controls the degree of enriching in the rich combustion operation on the basis of an indicator indicating the NOx reduction performance of the selective reduction catalyst 26. |
