| 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, G UREA , by the urea injection unit (25) is determined so that the value of ammonia concentration, NH3 CONS , detected by the ammonia sensor (26) is greater than "0." |
