Pump unit

Abstract

Provided is 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. 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 (3) 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.

Description

technical field [0001] The invention relates to pump units. Background technique [0002] As existing pump units such as Figure 4 shown. The pump unit has a fixed displacement pump 52 driven by a variable speed motor 51 with variable speed and a control unit 53 that controls the speed of the motor 51 by changing the frequency of the current supplied to the variable speed motor 51 . The control unit 53 receives the signal from the pressure sensor 54 that detects the pressure of the discharge path of the pump 52, and controls the speed of the pump 52 by controlling the speed of the variable speed motor 51, so that the pressure detected by the pressure sensor 54 The pressure value becomes a predetermined value. [0003] However, since the conventional pump unit drives a fixed displacement pump 52 with a variable speed motor 51, in order to increase the discharge pressure of the fixed displacement pump 52, it is necessary to use a large torque motor or a small capacity fixed ...

AI Technical Summary

Problems solved by technology

However, if the above-mentioned high-torque motor is used, it will lead to problems of increasing the size and cost of the pump unit

In addition, if the small-capacity fixed-displacement pump is used, the rotation speed of the pump and the motor becomes too high during high-flow operation, so there is a problem of excessive noise and vibration of the pump unit.

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