| 摘要 |
PURPOSE:To enable elimination of disturbance of control, by a method wherein, in a double O2 sensor system, when a rapid change in an intake air amoun is detected, an air-fuel ratio feed back control by an O2 sensor on the downstream side is stopped. CONSTITUTION:A first O2 sensor 13 is situated to an exhaust manifold 11 on the upper stream side of a catalyst converter 12, and a second O2 sensor 15 to an exhaust pipe 14 on the downstream side. The O2 sensors 13 and 15 generate different output voltages to an A/D converter 101 of a control circuit 10 according to an air-fuel ratio being on the lean side or the rich side to a theoretical air-fuel ratio. The air-fuel ratio of an engine is regulated according to first and second air-fuel ratio corecting amounts computed depending upon outputs from the first and second O2 sensors 13 and 15. In which case, when inversion of the second O2 sensor 15, designed on condition that it responds to a slow change in an air-fuel ratio, is detected, it is considered that a rapid change occurs to an intake air amount, and computation of a second air-fuel ratio correction amount is stopped.
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