| 摘要 |
PROBLEM TO BE SOLVED: To provide a method and a device for diagnosing a deterioration in an exhaust emission control system which can remove NOx in a wide temperature area, with high accuracy and simple constitution,.SOLUTION: The device for diagnosing a deterioration in an exhaust emission control system includes a NOx trap part trapping NOx in an exhaust gas and having a NOx trap material which desorbs NOx in two exhaust gas temperature ranges i.e. a first temperature range and a second temperature range. On the basis of NOx desorption characteristics of the NOx trap part in the first temperature range and the second temperature range which are experimentally obtained in advance, the device for diagnosing a deterioration in an exhaust emission control system sets flow rate reference values (A1), (A2) in the first temperature range and the second temperature range in a NOx discharge amount (A) from an engine, and on the basis comparison between the reference values (A1) and a NOx amount (B1) in the first temperature range which is detected by NOx amount detection means arranged downstream of the NOx trap part and comparison between the reference values(A2) and a NOx amount (B2) in the second temperature range, the device determines a degree of a deterioration in the NOx trap part. |
