Performance of Single Stage Four Nozzles Pintle Type Hydraulic Servovalves

In this paper, the static characteristics of the four-nozzle pintle type servovalve are studies theoretically, under constant supply pressure and constant supply flow conditions.The study is on an eye to the effect of the valve improper configuration, the required pintle driving torque, and the effect of using unsymmetrical loads on the static characteristics.Errors in valve control gaps resulting from inaccurate initial adjustment, wear of else showed to affect slightly the load flow at each load pressure and input displacement.Units driven by unsymmetrical actuators showed to have lower valve flow forces and higher valve efficiency than symmetrical actuators.The minimum flow gain and flow pressure coefficient are obtained when the load is symmetric.The study showed that the flow forces have two instability sources, decentering nature and similar values at different input displacements.The study discussed the selection of the pintle centering spring to overcome the problems of instability.