| 摘要 |
<p>The determination of deterioration of a NOx storage reduction catalyst (4) is carried out more accurately. When a reducing agent is supplied from a supply device (5) to the NOx catalyst (4), a first supply of the reducing agent and a second supply of the reducing agent are carried out in a sequential manner by adjusting an amount of the reducing agent in such a manner that an air fuel ratio of the exhaust gas becomes a predetermined rich air fuel ratio, and a determination whether or not the NOx catalyst (4) has deteriorated is made based on a detected value of a detection device (8), which detects NH 3 in the exhaust gas at the downstream side of the NOx catalyst (4), after a predetermined period of time has elapsed from the start of the first supply of the reducing agent, and after the start of the second supply of the reducing agent.</p> |
