| 摘要 |
Provided is a method for determining degradation of a NOx storage reduction catalyst in an exhaust gas aftertreatment device, with which sulfur poisoning and thermal degradation of a NOx storage reduction catalyst can be discriminated. In this method for determining degradation in a NOx storage reduction catalyst in an exhaust gas aftertreatment device, a storage cycle and a rich reduction cycle are repeated alternately in a NOx storage reduction catalyst (26) connected to the exhaust pipe (20) of an engine (E), and when the NOx storage rate decreases while the storage cycle and the rich reduction cycle are being repeated, an S-purge is performed. A NOx storage map, which indicates the NOx storage amount of the NOx storage reduction catalyst (26), as affected by aging degradation, during the storage cycle, is created in advance, and an ideal NOx storage amount is determined on the basis of the NOx storage map. The actual NOx storage amount during a storage cycle is calculated from a NOx sensor value, and on the basis of the difference between the ideal NOx storage amount and the actual NOx storage amount, degradation of the NOx storage reduction catalyst due to sulfur poisoning, and thermal degradation of the NOx storage reduction catalyst, are discriminated. |
