| 摘要 |
<p>PURPOSE:To unwastefully work a catalyst until it is judged that the catalyst is badly deteriorated. CONSTITUTION:A feedback constant is calculated by a calculating means 23 based on an output from a sensor 22 situated upper stream from a catalyst and by using the feedback constant, an air-fuel ratio feedback correction amount alphais calculated by a calculating means 24. A fundamental injection amount Tp is corrected by means of the air-fuel ratio feedback correction amount alphaand a fuel injection amount is calculated by a calculating means 25. When a diagnosing condition is set to a specified value, a feedback constant calculated by a calculating means 23 in a direction in which an air-fuel ratio is deviated from a theoretical air-fuel ratio is varied to a feedback constant for diagnosis by a varying means 28. By means of a feedback constant for diagnosis, outputs from two sensors 22 and 27 situated upper stream and downstream from a catalyst are compared with each other in state that an air-fuel ratio is deviated from a theoretical air-fuel ratio, and it is decided by a deciding means 29 that either high deterioration or middle deterioration occurs to a catalyst.</p> |
