| 摘要 |
The present invention comprises a selective reduction type NOx catalyst located in an exhaust passage and being capable of purifying NOx with ammonia, an oxidation catalyst located downstream of the selective reduction type NOx catalyst, an upstream sensor located between the selective reduction type NOx catalyst and the oxidation catalyst and having ability to detect both ammonia and NOx, a downstream sensor located downstream of the oxidation catalyst and having ability to detect both ammonia and NOx, and determining means for determining a component passing through the selective reduction type NOx catalyst, based upon a relation between output of the upstream sensor and output of the downstream sensor. |
