| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device for an internal combustion engine and a deterioration detecting method for an exhaust emission control catalyst capable of accurately determining deterioration of an NO<SB>X</SB>occlusion catalyst. <P>SOLUTION: When oxygen concentration in exhaust emissions is lowered, temperature of the exhaust emissions in a downstream side of the NO<SB>X</SB>occlusion catalyst 14 is once decreased, almost constantly maintained in a decreased state for a while and afterwards turned to be increased. In the case of deteriorated NO<SB>X</SB>occlusion catalyst 14, such a phenomenon is observed that duration ΔT from a time point P0 when the oxygen concentration is lowered to a time point P1 when the exhaust emission temperature is turned to be increased is shorter than that of the new NO<SB>X</SB>occlusion catalyst 14. Using the phenomenon, the exhaust emission temperature after the oxygen concentration is lowered is measured at a prescribed time interval with an exhaust emission temperature sensor 16 provided in the downstream side of the NO<SB>X</SB>occlusion catalyst 14 and the duration ΔT till the exhaust emission temperature is turned to be increased is measured. Accordingly a deteriorated state of the NO<SB>X</SB>occlusion catalyst 14 is grasped, and the deterioration of the NO<SB>X</SB>occlusion catalyst 14 can be accurately determined. <P>COPYRIGHT: (C)2005,JPO&NCIPI |
