Swing type hydraulic servo-actuator

Abstract

A hydraulic servo-actuator has a casing embracing therein a hydraulic fluid chamber which is divided into two hydraulic drive chambers by a vane projecting from a first shaft. To each of the divided chambers are connected an oil feeding passage provided with a variable restrictor and intended for the feeding of pressurized oil and an oil discharge passage intended for the discharging of the pressurized oil. A second shaft is coaxially disposed relative to the first shaft, and the first and second shafts are correlated with each other in such a way that the relative rotary displacement occurring between the two shafts controls the aperture of the oil discharge passages communicating with the divided chambers. The difference between the static pressures which are consequently produced within the divided chambers because of the aperture of the oil discharge passages causes the vane to swing, making it possible to control the torque even when the vane is in the neighborhood of its neutral position. In addition, the variable restrictors provided in the oil feeding passages serve the purpose of regulating the amount of the pressurized oil to be fed. Hence, the hydraulic servo-actuator is capable of stably controlling the torque.