| 摘要 |
PURPOSE:To attain a large-capacity control circuit which is operated with pulse width modulation control as the whole by combining a turn-on/off solenoid valve of a low flow rate, which is operated with pulse width modulation control, and a turn-on/off solenoid valve of a flow rate equal to or higher than that of said turn-on/off solenoid valve to constitute a composite valve. CONSTITUTION:The turn-on/off solenoid valve of a low flow rate which is operated with pulse width modulation control and the turn-on/off solenoid valve of a flow rate equal to or higher than that of said turn-on/off solenoid valve are combined to constitute the composite valve. For example, a turn-on/off solenoid valve 5 whose flow rate is controlled by pulse width modulation control and turn-on/off solenoid valves 61-63 whose flow rates are made higher successively than a maximum flow rate of the solenoid valve 5 are connected in parallel to constitute a composite valve 4. A hydraulic pump 1 and a hydraulic motor 2 are connected through the composite valve 4, and individual turn-on/off solenoid valves of the composite valve 4 are connected to a valve controller 7. An input voltage eIN is converted to currents I1-I3 through an A/D converter 8 and voltage-current converters 121-123 to control turn-on/off solenoid valves 61-63, and the turn-on/off solenoid valve 5 is controlled through a D/A converter 9, a subtractor 10, a pulse width converter 11, etc. |
