| 摘要 |
PROBLEM TO BE SOLVED: To provide a hydraulic control device which is favorable from the viewpoints of energy saving and measures to power failure. SOLUTION: Hydraulic fluid in an oil tank 1 is supplied by a hydraulic pump 2 to a servo valve 3. The servo valve 3 changes a supply direction and a supply quantity of the hydraulic fluid in accordance with a command of a servo amplifier to supply the hydraulic fluid to a hydraulic cylinder 4, and return oil from the hydraulic cylinder 4 is returned to the hydraulic tank 1. Excessive hydraulic fluid left unsupplied to the servo valve 3 is returned through a relief valve 5 to the hydraulic tank 1. To a motor control circuit 9, a three- phase 200 V power source and a single-phase 100 V power source are connected, and the three-phase 200 V power source is normally used, while the single-phase 100 V power source is selected and used at the time of power failure of the other power source. Output of a servo control device 14 to operate the servo valve 3 is supplied to the servo valve 3, and it is also supplied to an inverter 13 simultaneously, thereby a rotation number of the hydraulic pump 2 is changed in accordance with the opening of the servo valve 3.
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