| 摘要 |
<P>PROBLEM TO BE SOLVED: To prevent false determination caused by the change of temperature of a catalyst while increasing opportunities for the determination. <P>SOLUTION: The catalyst deterioration determining device comprises oxygen sensors 23 and 24 disposed on the upstream side and downstream side of the three-way catalyst 17 for exhaust emission control in an exhaust pathway 3 of an engine 1, and an electronic control unit ECU 30. The ECU 30 controls an injector 7 based on the output signals, etc., of the oxygen sensors 23 and 24, and feedback-controls the air/fuel ratio of the engine at the theoretical air/fuel ratio. The ECU 30 calculates the ratio of the length of output locus of the upstream side oxygen sensor 23 to that of the downstream side oxygen sensor 24 during the feedback control, and determines deterioration of the three- way catalyst 17 by comparing the calculated ratio of the length of output locus and the determined value. At the time, the ECU 30 estimates the temperature of the three-way catalyst 17 based on the engine operation condition, and corrects the determined value based on the estimated value, etc., so that the determination in response to the change of the temperature of the catalyst is implemented. <P>COPYRIGHT: (C)2003,JPO |
