| 摘要 |
PURPOSE:To suppress a variation of a working fluid by providing plural solenoid valves connected in parallel between a PWM generating device and an actuator, and shifting an operating phase of the solenoid valve. CONSTITUTION:A signal from a PWM generating device 2 is applied in parallel to each solenoid valve 5, 6, and an actuator 4 is operated by plural solenoid valves 5, 6. This PWM driving device uses the solenoid valves 5, 6 having a capacity of half of the total flow rate required for the actuator 4, therefore, when the duty is between 0% and 50%, the same characteristic as the case when one solenoid valve has been driven by doubling the actual PWM period and duty is obtained. Also, since the solenoid valve of a small flow rate is used, the solenoid valve can be driven to switch by an earlier PWM period than the case of the solenoid valve of a large flow rate. On the other hand, in case when the duty is 50%-100%, the same characteristic as the case when one solenoid valve is held in an open state and the other is driven by doubling the PWM period and duty is obtained, a variation of a working fluid by switching is reduced, and a variation of a flow rate can be suppressed.
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