| 摘要 |
<p>A converter (70) which houses a NOx storage/reduction catalyst is provided in an exhaust passage (2) of an engine (1). At a front half portion (inlet side portion) (7a) of a carrier of the NOx storage/reduction catalyst in the converter (70), the amount of an oxygen storage component is made less than it is at a rear half portion (outlet side portion) (7b) of the carrier, and a NOx storage capacity is made larger than it is at the rear half portion (7b) of the carrier. As a result, unpurified NOx released from the front half portion (7a) of the carrier at the beginning of a rich spike due to an 02 storage operation is able to be stored in the rear half portion (7b) of the carrier, and so is not exhausted outside the catalyst. Moreover, the amount of HC and CO components in the exhaust gas that are needlessly consumed by the 02 storage operation without being used to purify NOx is reduced, making it possible to purify NOx efficiently.</p> |
