| 摘要 |
The present invention provides a deterioration detection system of an exhaust purification device, comprising a selective reduction-type catalyst located in an exhaust passage of an internal combustion engine, a reductant addition valve located in an exhaust passage upstream of the selective reduction-type catalyst, and an NOx sensor located in an exhaust passage downstream of the selective reduction-type catalyst; wherein the present invention addresses the problem of making it possible to detect deterioration in the selective reduction-type catalyst early, and increasing detection precision. To solve this problem, this deterioration detection system of an exhaust purification device is designed so that when the reductant addition valve is controlled so as to add a reductant, the reductant addition valve is controlled in order to vary the intervals of adding reductant while keeping the added amount per a certain timeframe constant, and deterioration of the selective reduction-type catalyst is determined based on the difference in the NOx purification rate between times when the addition intervals are varied and times when the addition intervals are not varied. |
