| 摘要 |
PROBLEM TO BE SOLVED: To provide a pump unit capable of obtaining high discharging pressure by a motor having comparatively small torque, and decreasing noise/vibrations at the time of large flow operation. SOLUTION: A first pump 1 made from a gear pump of a small capacity, and a second pump made from a gear pump of a large capacity are directly united by a variable speed motor 3 controlled in the number of revolutions by a control device 4. In a first mode. a discharge line 5 of the first pump is diverted from a discharging line 8 of the second pump, and the first pump is unloaded to carry out constant horsepower operation, thereby making a discharge fluid have high pressure by comparatively small torque. In a second mode, the discharging line 5 of the first pump is merged with the discharging line 8 of the second pump to carry out the constant horsepower operation, thereby discharging the large flow amount of the discharge fluid at a comparatively low number of revolutions. When the number of revolutions of the variable speed motor is lower than a specified value, a switch valve 6 is switched from a merging state to a diverting state. When discharging pressure is lower than a specified value, the switch valve 6 is switched from the diverting state to the merging state. COPYRIGHT: (C)2004,JPO
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