| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a catalyst deterioration determination method capable of estimating the maximum occluded amount of oxygen necessary for a catalyst deterioration determination in a rather short period while minimizing the exhausted amount of harmful components. <P>SOLUTION: This catalyst deterioration determination method controls the air/fuel ratio of an engine to a specified lean air/fuel ratio at times t1 to t3, and makes the oxygen occluding amounts of a first catalyst and a second catalyst on the downstream side of the first catalyst arrive at the maximum oxygen occluding amount. Next, until a time t4 when a first catalyst downstream air/fuel ratio sensor output Voxs1 changes to a rich air/fuel ratio, the air/fuel ratio is controlled to an air/fuel ratio slightly lower than the lower limit value of a window width obtained when a catalyst apparatus formed of the first and second catalysts is new, and the maximum oxygen occluding amount CSCmax of the first catalyst is estimated. Next, until a time t5 when a second catalyst downstream air/fuel ratio sensor output Voxs2 changes to the rich ratio, the air/fuel ratio is controlled to that near the lower limit value of the window width obtained at the present time of the catalyst device which is narrowed according to the degree of deterioration of the catalyst device, and the maximum oxygen occluding amount CSCmax of the first catalyst is estimated. <P>COPYRIGHT: (C)2004,JPO</p> |
