| 摘要 |
PROBLEM TO BE SOLVED: To provide an exhaust emission control device for an internal combustion engine, for restraining NOx spike during rich air-fuel ratio operation after fuel cutting-off and highly maintaining the purification performance of NOx, CO and HC. SOLUTION: This control device has an HC selective oxidizing function for selectively oxidizing HC rather than CO, and a CO occlusion function for occluding CO under a reducing atmosphere, and comprises three-way catalytic converters (30, 30a) in which oxygen occlusion capability for occluding oxygen under an oxidizing atmosphere is lower than CO occluding capability with the CO occlusion function; an air-fuel ratio modulating means (40) of forcibly changing the air-fuel ratio of exhaust gas flowing into the three-way catalytic converter between the rich air-fuel ratio and a lean air-fuel ratio; and a modulation characteristic changing means (40) of changing the modulation characteristics corresponding to a CO occlusion amount correlation value having a correlation with the CO occlusion capability with the CO occlusion function. COPYRIGHT: (C)2004,JPO
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