| 摘要 |
PROBLEM TO BE SOLVED: To provide a system which can easily determine deterioration of a catalyst. SOLUTION: A selective NOx reduction catalyst 10 is arranged in the exhaust gas pipe 8 of a diesel engine 1, and determined whether or not it is deteriorated based on temperature difference between a catalyst temperature detected by a catalyst temperature sensor 32 and an inlet gas temperature detected by an inlet gas temperature sensor 31. When a deterioration determining process is performed, a large amount of fuel several, times as large as a normal secondary injection amount required for purifying NOx is complementarily ejected, and a reducing agent several time a normal period is supplied to the NOx reduction catalyst 10. |
