| 摘要 |
PROBLEM TO BE SOLVED: To prevent a filter from harmful clogging caused by accumulation of particulates by oxidative removal of particulates which is done by the affection of breakthrough NO2 to the diesel particulate filter as oxidizing agent, here, breakthrough NO2 is generated by forcing the NOx occludent reduction catalyst to occlude NOx excessively. SOLUTION: During usual operation in lean condition, NO is oxidized mainly to NO2 by NOx occludent reduction catalyst 8 and occluded therein, and breakthrough NO2 is generated by continuous operation. Utilizing this NO2 as oxidizing agent, oxidative removal of particulates which are trapped on the DPF (particulate filter) is practiced. In the next place, catalyst 8 is regenerated by reductive removal of NO2 occluded therein, by switching the engine operation to rich condition. After regeneration, it returns to the continuous operation of DPF cleaning by breakthrough NO2 in lean condition, and then, the cycle of regeneration of NOx occludent reduction catalyst is repeatedly carried out. |
