| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a catalyst degradation determining device applied to a system having catalysts arranged in a plurality of exhaust passages which can determine a catalyst degradation which enables warning to notify the degradation of the catalyst at a suitable timing. <P>SOLUTION: This catalyst degradation determining device detects the update values of an amount of maximum oxygen occlusion of the same corresponding catalyst at the point while alternately switching a catalyst upstream air-fuel ratio to a sensor which is switched by turns at predetermined rich or predetermined lean air-fuel ratio whenever downstream side air-fuel ratio sensor output Voxs (A) and Voxs (B) switch from rich to lean or lean to rich after controlling each catalyst upstream air-fuel ratio of the catalysts 53A and 53B at a time t1 to considered lean air-fuel ratio and making the amount of oxygen occlusion of each catalyst reach the amount of maximum oxygen occlusion. A catalyst degradation as the whole catalyst is judged from the update values Cmax of the mean value of the newest values Cmax (A) and Cmax (B) of the amount of maximum oxygen occlusion in the point whenever it detects the update values of the amount of the maximum oxygen occlusion. <P>COPYRIGHT: (C)2004,JPO |
