| 摘要 |
PROBLEM TO BE SOLVED: To provide a deterioration determination system for an exhaust emission control device having a selective reduction type NOx catalyst, for increasing the accuracy of deterioration determination by suppressing erroneous determination of deterioration when determined.SOLUTION: The deterioration determination system for the exhaust emission control device includes the NOx catalyst using ammonia as reductant, and a catalyst having oxidation ability, in sequence. It calculates at least one of or a total value for the amount of the ammonia flowing out of the catalyst having the oxidation ability and the amount of the ammonia inverted into NOx in the catalyst having the oxidation ability, out of the amount of the ammonia flowing into the catalyst having the oxidation ability, when the amount of the ammonia adsorbed to the NOx catalyst is greater than an equilibrium adsorption amount as the amount of the ammonia adsorbed thereto in the equilibrium state, and restricts the use of a value detected by a NOx sensor in deterioration determination or prohibits the deterioration determination itself when the value exceeds a threshold value. |
