| 摘要 |
An exhaust purification apparatus for internal combustion engine having a selective reduction catalyst that while maintaining a high NOx reduction ratio, inhibits any ammonia discharge downstream of the selective reduction catalyst. In the exhaust purification apparatus (2), a urea selective reduction catalyst (23) comprises a first selective reduction catalyst (231) and, provided downstream of the first selective reduction catalyst (231) in an exhaust passageway (11), a second selective reduction catalyst (232). Further, the exhaust purification apparatus (2) includes a urea injection unit (25) for feeding of a reducing agent upstream of the urea selective reduction catalyst (23) in the exhaust passageway (11) and an ammonia sensor (26) for detection of the ammonia concentration at a site between the first selective reduction catalyst (231) and the second selective reduction catalyst (232) in the exhaust passageway (11). The rate of urea injection, GUREA, by the urea injection unit (25) is determined so that the value of ammonia concentration, NH3CONS, detected by the ammonia sensor (26) is greater than“0.” |
