| 摘要 |
PURPOSE:To ensure operability and simultaneously improve NOx reducing effect, by setting a target air-fuel ratio for a leaner side corresponding to an operation range, and controlling an air-fuel ratio for a richer side during a prescribed time in case that the operation range is shifted to a theoretical air-fuel ratio operation range. CONSTITUTION:The detected values of an air flow meter 8, a throttle valve opening sensor 10, an inlet pipe pressure sensor 11, a crank angle sensor 15, an oxygen sensor 17 and the like are inputted to a control unit 20, and the feedback control of an air-fuel ratio is carried out by setting a target air-fuel ratio for a leaner side than a theory air-fuel ratio during a part of a steady driving time. When the steady driving is shifted to, for example, an accelerating condition, the target air-fuel ratio is set for as the theoretical air-fuel ratio. But in the early time of the shifting, the target air-fuel ratio is set for a richer side than the theory air-fuel ratio during the shifting period, the effect of catalytic converter rhodium is exerted so as to make the atmosphere of the theory air-fuel ratio in early time.
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