| 摘要 |
<P>PROBLEM TO BE SOLVED: To achieve an excellent exhaust gas conversion rate in either a lean combustion mode or a theoretical air fuel ratio combustion mode, and to reduce back pressure to increase output in an exhaust emission control device for an internal combustion engine. Ž<P>SOLUTION: This exhaust emission control device for the internal combustion engine includes a combustion mode change-over means changing over combustion mode between the lean combustion mode and the theoretical air fuel ratio combustion mode, a first exhaust gas passage 36 and a second exhaust gas passage 37 provided in parallel, an NOx catalyst 34 disposed in the first exhaust gas passage 36, and a three way catalyst 35 disposed in the second exhaust gas passage 37. A value provided by dividing the length L1 of the NOx catalyst 34 by the cross section is larger than a value provided by dividing the length L2 of the three way catalyst 35 by the cross section. Exhaust gas is made to flow in the NOx catalyst 34 without made to flow in the three way catalyst 35 in the lean combustion mode, and exhaust gas is made to flow in both of the NOx catalyst 34 and the three way catalyst 35 in the theoretical air fuel ratio combustion mode. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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