Patent ID: 8418446

Claim:
An exhaust gas purification system for an internal combustion engine comprising: an exhaust passage; a NOx storage reduction catalyst provided in the exhaust passage of the internal combustion engine; and an electronic control unit (ECU) that includes control logic, so that when the NOx storage reduction catalyst is active and NOx stored in the NOx storage reduction catalyst is to be reduced, the ECU; instructs the internal combustion engine to perform a normal combustion if a temperature of the NOx storage reduction catalyst is below a specific temperature; instructs the internal combustion engine to perform a low temperature combustion if the temperature of the NOx storage reduction catalyst is equal to or higher than the specific temperature; and decrease an air-fuel ratio of ambient atmosphere around the NOx storage reduction catalyst to a target air-fuel ratio by decreasing the air-fuel ratio of exhaust gas discharged from the internal combustion engine, thereby reducing the NOx stored in the NOx storage reduction catalyst.