| 摘要 |
<p>PROBLEM TO BE SOLVED: To prevent excess electric power consumption by detecting an inflection point of an electric current value flowing to a coil when driven by constant voltage, and controlling the ON/OFF ratio of pulse width modulating voltage impressed on the coil on the basis of the electric current value. SOLUTION: A CPU 101 turns on a solenoid in a 100% duty to start to detect an electric current value to judge whether or not an electric current waveform reaches an inflection point. When the electric current waveform does not reach the inflection point, whether or not it is an abnormal electric current is judged, and abnormality is processed. When the electric current waveform reaches the inflection point, required holding power is determined from a expression of [required holding power = suction force of an inflection point + an applying load + an allowance], and next, the duty ratio of pulse width modulating voltage impressed on a coil 105 capable of securing the required holding power is searched from a prestored table, and a solenoid driving signal is outputted. In an abnormal electric current, abnormality is processed, and when becoming OFF time, a solenoid is turned off to finish processing. Thus, the solenoid and a clutch are driven in the necessary sufficient duty ratio to save power consumption.</p> |
