| 摘要 |
PROBLEM TO BE SOLVED: To suppress the occurrence of HC poisoning in an ammonia slip catalyst when supplying HC to a catalyst to increase the temperature of the catalyst.SOLUTION: A fuel addition valve for adding fuel into exhaust gas, a front-stage catalyst as a catalyst having an oxidative function, a filter for supporting a selective reduction type NOx catalyst, and the ammonia slip catalyst are provided beginning at the upstream side in an exhaust passage of the internal combustion engine. When the fuel is supplied to the front-stage catalyst and when the ammonia slip catalyst is not in an active state, the amount of the fuel to be added into the exhaust gas by the fuel addition valve, out of the amount of the fuel to be supplied to the front-stage catalyst, is set to be not greater than a predetermined fuel amount as the amount of the fuel to be oxidized by the front-stage catalyst, and the fuel of which the amount is obtained by subtracting the amount of the fuel to be added into the exhaust gas by the fuel addition valve from the amount of the fuel to be supplied to the front-stage catalyst is discharged from the internal combustion engine with the post injection in the internal combustion engine. |
