| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a catalyst degradation-detecting device capable of accurately detecting the degree of degradation of a catalyst without almost deteriorating gas exhaust characteristics. <P>SOLUTION: According to a detected flow of suction air GAIR and the output of an oxygen concentration sensor 17 installed on the upstream side of a three-way catalyst 14a, an oxygen amount OS flowing into the three-way catalyst 14a is calculated. According to the results of comparison between the inflow oxygen amount OS and target values OSOBJR, OSOBJL, a control for changing an air-fuel ratio between rich and lean (perturbation) is performed. When the output SVO2 of an O2 sensor installed on the downstream side changes largely during the perturbation of air-fuel ratio, the three-way catalyst 14a is determined to be degraded. During the period from a time point when the target air-fuel ratio is changed to a time when the change of the air-fuel ratio is actually detected on the exhaust side, a correction value equivalent to the oxygen amount flowing into the three-way catalyst 14a is calculated. The target values OSOBJR, OSOBJL are corrected with the correction value. <P>COPYRIGHT: (C)2008,JPO&INPIT</p> |
