DEVICE FOR THE CONTROLLED DRIVING OF AT LEAST ONE HYDRAULIC SHAFT

摘要

A system that includes a pump driven by a variable speed electric motor, the pump being directly connected to a hydraulic actuator by an open hydraulic circuit. This setup allows using one motor pump combination to drive any number of axes sequentially. The main advantages are significant energy savings but also higher control quality achieved by the substitution of control valves. Power control is dedicated to electronic power transistors while hydraulics are used for power transmission. For two and four quadrant operation, a hydraulic accumulator is proposed exerting a spring load on the hydraulic actuator. This allows for driving and braking the actuator and the associated machine axis in both directions of motion while the hydraulic pressure is always applied to the same port of the pump. The other pump port can be connected to tank.