| 摘要 |
PROBLEM TO BE SOLVED: To increase accuracy for determining deterioration of an ammonia oxidation catalyst.SOLUTION: An exhaust passage of an internal combustion engine includes a selective reduction type NOx catalyst and an ammonia oxidation catalyst from an upstream side. When the temperature of the selective reduction type NOx catalyst is equal to or more than a predetermined value, a reducing agent more than necessary for the reduction of NOx in the selective reduction type NOx catalyst is supplied, wherein an NHamount oxidized in the ammonia oxidation catalyst is calculated on the basis of the difference between an NHconcentration in exhaust flowing into the ammonia oxidation catalyst and a detection value of an NHsensor downstream of the ammonia oxidation catalyst, and deterioration determination of the ammonia oxidation catalyst is performed by comparing the NHamount oxidized in the ammonia oxidation catalyst with a threshold. |
