| 摘要 |
PURPOSE:To stabilize the number of revolutions by converting the frequency of signal pulses from a micro-computer, a duty ratio thereof changes in response to the control of an idling-speed control valve, into frequency, hysteresis thereof is minimum. CONSTITUTION:The idling-speed control valve 13 set up into a bypass in the throttling of an internal-combustion engine is driven by a drive circuit 35 to which pulse signals 36, the duty ratio thereof changes, are inputted from the micro-computer so that the internal-combustion engine is turned at the optimum number of revolutions corresponding to the state of operation of the engine. The integration circuit 38 of the drive circuit 35 integrates pulse signals 36, and the integration value is compared with an output from a sawtooth waveform generating circuit 40 generating the sawtooth wave of frequency (such as 400Hz) minimizing the hysteresis of the idling-speed control valve by a comparator 39, and converted into frequency. |
