| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a catalyst deterioration-determination device improving deterioration determination accuracy by determining deterioration at an appropriate timing in response to a slip rate of reducing agent. <P>SOLUTION: This deterioration-determination device 1 for a catalyst 7 arranged in the exhaust passage 5 of an internal combustion engine 3, calculates a slip rate parameter sumkact2 indicating the amount of the reducing agent passed through the catalyst 7 according to a detected downstream oxygen concentration parameter KACT2, after switching exhaust gas led to flow into the catalyst 7 from an oxidation atmosphere to a reduction atmosphere. Deterioration of the catalyst 7 is determined based on a comparison result of an upstream oxygen concentration parameter KACT1 with a downstream oxygen concentration parameter respectively acquired before determination is made that the slip rate parameter reaches a threshold kref after the exhaust gas is switched from the oxidation atmosphere to the reduction atmosphere. <P>COPYRIGHT: (C)2010,JPO&INPIT |
