New Servo Motor Driving Hydraulic System

Hydraulic pump is driven and controlled by electric servo motor

Electric servo motor drives hydraulic pump to control the pressure and the speed.
Energy saving i.e. 1/3 of conventional hydraulic system, precise control and low level noise i.e. about 50 dB, are now achieved.
Feed back control is adopted utilizing big power from compact size of hydraulic unit while minimizing the influence of oil temperature.
The system can be employed to change the conventional hydraulic system to the latest versatile system.

Features

Energy saving is realized same as in the case of direct driven servo system as the servo motor drives hydraulic pump, but does not activate it unless controlled object is not moved.
Also, the motor and the pump can be downsized and energy saving as the motor rotation can be variable from zero to 3,000 rpm.
Control signals both of speed and pressure for the servo motor driving the pump are DC zero to 10 volts level and can be used easily in the same way as to of proportional valve control.
The control system is simple as follows:
Oil tank is downsized by 1/3 to 1/2 as the pump delivers oil only when driving is necessary.
The servo motor stops rotation when the power is not necessary while the motor rotates at the minimum r.p.m. to keep the hydraulic pressure in the stalled condition. Oil cooler is not required in most cases.
Low level of noise, i.e. 50 dB, is accomplished by way of using specially designed internal gear pump which can be driven at up to 3,000 r.p.m.
Maintenance cost is same as conventional hydraulic system.

Note : This system is employed in the clamp unit of Sanjo's vertical injection molding machine, SJ series (Servo-controlled model) .