| 摘要 |
In an internal combustion engine, an exhaust purification catalyst and a hydrocarbon feed valve are arranged in an exhaust passage. When a temperature of the exhaust purification catalyst falls in a first catalyst temperature region (I), a first NOx purification method is performed, while when a temperature of the exhaust purification catalyst falls in a second catalyst temperature region (II), a second NOx purification method is performed. When the temperature of the exhaust purification catalyst falls in a region (IIP) in the second catalyst temperature region close to the first catalyst temperature region, the temperature of the exhaust purification catalyst is made to increase to shift the region in which the temperature of the exhaust purification catalyst falls to the first catalyst temperature region to thereby switch the NOx purification method used from the second NOx purification method to the first NOx purification method. |
