| 摘要 |
PROBLEM TO BE SOLVED: To provide a hydraulic unit simple in structure, small in size, inexpensive and less in noise, energy loss and exothermic heat. SOLUTION: An inverter controller 13 controls the revolution of a synchronous motor 12 in response to a flow commanding signal so as to let the required amount of oil be delivered out of a fixed displacement type hydraulic pump 11. Meanwhile, a little amount of oil is delivered to a tank 16 out of a relief valve 15 by means of pressure override characteristics. The inverter controller 13 controls the revolution of the synchronous motor 12 based on an output signal equivalent to the pressure of oil from a current sensor 31 and a pressure commanding signal so as to control the pressure of a discharge line 7 based on the revolution of the fixed displacement type hydraulic pump. Pressure is so controlled as to be fed back by means of the current sensor 31, the inverter controller 13, the synchronous motor 12 and the fixed displacement type hydraulic pump 11.
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