| 摘要 |
PROBLEM TO BE SOLVED: To detect an abnormality of an exhaust emission control device while suppressing deterioration of exhaust emission in an exhaust emission control device provided with a selective reduction catalyst arranged in an exhaust passage of an internal combustion engine, a reduction agent addition valve arranged in an upstream exhaust passage from the selective reduction catalyst, and an NOsensor arranged in a downstream exhaust passage from the selective reduction catalyst.SOLUTION: In an abnormality detection system of an exhaust emission control device provided with a selective reduction catalyst arranged in an exhaust passage of an internal combustion engine, a reduction agent addition valve arranged in the upstream exhaust passage from the selective reduction catalyst, and an NOsensor arranged in the downstream exhaust passage from the selective reduction catalyst, the reduction agent addition valve to change the addition interval of a reduction agent is controlled while fixing the addition amount per constant period when being controlled so that the reduction agent addition valve adds the reduction agent, and abnormality of the reduction agent addition valve is determined on the basis of an NOexhaust emission control ratio difference before and after change. |
