| 摘要 |
PURPOSE:To reduce the exhaust emission and reduce the abnormal odor of catalyst exhaust by installing air-fuel ratio sensors on the upstream and downstream sides of a catalyst and varying the comparison voltage of the downstream side sensor according to the load. CONSTITUTION:Air-fuel ratio sensors 13 and 15 are installed on the upstream and downstream sides of a catalytic converter 12 in an exhaust pipe 11. A controller 10 detects the engine load by receiving the signal of an air flow meter 3, and varies the comparison voltage of the second air-fuel ratio sensor 15 according to the load. Further, the air-fuel ratio is controlled according to the result of the comparison of the both air-fuel ratio sensors 13 and 15 with each comparison voltage. In other words, the control to the rich side is performed in case of a high load, and control to the lean side is performed in case of a low load. Thus, the exhaust emission and abnormal exhaust door of catalyst can be reduced.
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