| 摘要 |
<P>PROBLEM TO BE SOLVED: To improve accuracy in judging deterioration of purifying capacity of a catalyst and thereby optimize exhaust emissions. <P>SOLUTION: In an engine system, a NOx catalyst 21 is provided in an exhaust pipe 18 of the engine 10 and an A/F sensor 24 is provided at least on its downstream side. An ECU 30 conducts rich purge that supplies NOx reduction component to the NOx catalyst 21 for reducing and removing NOx occluded in the NOx catalyst 21, calculates reduction required time TA from a detection result by the A/F sensor 24 during the rich purge execution and judges the purifying capacity deterioration. At this time, as the reduction required time TA includes an error caused by response delay which the A/F sensor 24 possesses, a rich degree of an air-fuel ratio in the rich purge execution is varied for properly calculating the reduction required time TA. <P>COPYRIGHT: (C)2007,JPO&INPIT |
