◆ Vol.17 Comparison of HySerpack and Servovalves (1)

Basically there are two methods to control hydraulic cylinders precisely: one is by Direct Drive method by HySerpack and the other is by servovalves.

Both methods can control hydraulic cylinders precisely but those two systems are far apart from each other in terms of the concept of mechanical and controlling arrangements.

As shown Diagram 1 below, HySerpack rotates an oil pump by a servomotor to both directions to switch the direction of oil flow. The amount of oil flow is regulated by the speed of the oil pump in proportion to the number of rotation.  The oil pressure is also controlled by the torque of the motor which is in proportion to the oil pressure. Thus no valve is required in this system to control the direction and flow rate of oil.

Servovalve is, as shown Diagram 2, is developed and improved from 4-port switching valve to make a step-less control over the spools by servo control method and to enable to change the direction and flow rate of oil simultaneously at a high speed. In other words, servovalve works as orifices for each port individually at a high speed by adjusting the valve opening.