| 摘要 |
PROBLEM TO BE SOLVED: To enhance the operability with a simple structure without wasteful energy consumption by controlling a specified number of control valve with a specified arithmetic value on the basis of the manipulated variable of this control valve, the total sum of manipulated variable of all devices, and the flow rate of a hydraulic pump. SOLUTION: The virtual feed flow rate of an i-th control valve 4 to an actuator 1 is calculated from the pump discharge quantity, the manipulated variable of an electric control input device 10 of the control valve 4, and the manipulated variable of all control input devices, and the difference between the feed flow rate and the actuator flow rate is divided by the value obtained by multiplying the bleed-off area suitable to each actuator 1 by the orifice flow rate coefficient followed by squaring to calculate the control valve output pressure command value. The i-th control valve 4 is controlled with an arithmetic value obtained by subtracting the load pressure detected from each actuator 1 from the command value. Accordingly, the bleed-off control can be virtually performed within a CPU, and the actual hydraulic loss can be eliminated to save the energy. Since the device is also simplified by use of a control valve free from a center bypass passage, and no fluid force is generated in control, the operability can be enhanced.
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