| 摘要 |
PURPOSE:To prevent the decrease of engine speed particularly in deceleration of an engine by providing an increase/decrease means for flow passage area, and performing increase/decrease control of an effective flow passage area with the means according to the result of comparison between the engine speed and preset idle upper/lower limit speeds. CONSTITUTION:An increase/decrease means for flow passage area is composed of an auxiliary air passage 4 provided for bypassing a throttle valve 3 in an air intake passage 2 and an electromagnetic switch valve 6 interposed therein, and the electromagnetic switch valve 6 is controlled by a control unit 5 so that engine speed is controlled. The output signals of an engine speed sensor 7, a water temperature sensor 8 and an idle switch 9 are input into the control unit 5 which controls the switch valve 6 to increase an effective flow passage area when the engine speed is lower than the preset idle lower limit speed. On the other hand, the control unit 5 controls the switch valve 6 to decrease the effective flow passage area when the engine speed is higher than the preset idle upper limit speed.
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