To provide a high efficiency hydraulic pump provided with a mechanism to suppress the generation of internal leakage and abnormal noises and prolong the life of the hydraulic pump, in a system to control position/thrust by combining together the hydraulic pump, an electric motor, a hydraulic cylinder, a cylinder position detector, a load cell, a driver, a servo controller and the like.

By lightening the case material of the hydraulic pump and increasing material hardness of a pressure plate and disposing a synchronous mechanism between a case and a cylinder barrel in front of a bearing, rotation moment of a rotary part is decreased and a slight passage is secured between a distributor part and a port diameter and this constitution prevents the generation of noises due to containment.