Hydrostatic actuator

摘要

A hydrostatic actuator possesses as hydraulic final control element, for example, a double-acting piston-cylinder unit. The chambers of the hydraulic final control element are fed by a reversible variable displacement pump, the pump being driven by a constant-speed motor. If the variable displacement pump is in the neutral position, i.e. the delivery flow is zero, the heat produced in the pump is unable to flow off with the hydraulic fluid. To avoid overheating when the actuator is fixed in a given position, a further, fixed displacement pump is connected in parallel with the variable displacement pump and to the chambers of the hydraulic final control element. The fixed displacement pump delivers a given volumetric flow continuously from one of the chambers into the other chamber. Consequently, the variable displacement pump is forced to compensate for the volumetric flow delivered by the fixed displacement pump in order to maintain a rest position of the final control element. As a result, heat is carried away.