| 摘要 |
<p>PROBLEM TO BE SOLVED: To surely prevent error discrimination of deterioration in a three way catalyst by computing a deterioration index value indicating a degree of deterioration of the ternary catalyst during execution of air-fuel ratio feedback control, inspecting validity of the computed deterioration index value, and prohibiting deterioration discrimination of the ternary catalyst invalidity. SOLUTION: In an air flow meter 13 provided with a crank angle sensors 15, 16 and a water temperature sensor 19, O2 sensor 113, 114, whose signals are inputted to a control circuit 100, are arranged on the upstream side and on the downstream side of a catalyst converter 112 individually. On the basis of the output from the upstream side O2 sensor 113, an internal combustion engine air-fuel ratio is feedback controlled to a target air-fuel ratio, and on the basis of the output from the downstream side O2 sensor 114 during this feed back control, a deterioration index value indicating a degree of deterioration in the ternary catalyst is computed. Then, deterioration index value and the deterioration determination value are compared with each other, and determination of the catalyst is carried out. In this process, validity of the index value is inspected, and if invalidity is determined, deterioration determination is prohibited.</p> |
