| 摘要 |
PROBLEM TO BE SOLVED: To excellently keep a NO<SB>x</SB>occlusion catalyst at a target NO<SB>x</SB>emission temperature. SOLUTION: An emission gas from each of cylinder groups 1, 2 is delivered into a common NO<SB>x</SB>occlusion catalyst 12. When SO<SB>x</SB>should be released from the NO<SB>x</SB>occlusion catalyst 12, a mean air-fuel ratio of the one cylinder group 1 is made rich, as well as a mean air-fuel ratio of the other cylinder group 2 is made lean. At this moment, an air-fuel ratio of each cylinder 3 of the one cylinder group 1 is to be either one target rich air-fuel ratio selected from predetermined two target rich air-fuel ratios, respectively, while an air-fuel ratio of each cylinder 3 of the other cylinder group 2 is to be either one target lean air-fuel ratio selected from predetermined two target lean air-fuel ratios, respectively. COPYRIGHT: (C)2008,JPO&INPIT
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