Abstract: Balanced piston direct-acting relief valve can improve the pressure control performance of hydraulic system. In order to supplement the parameter matching method of balanced piston direct-acting relief valve used in aerospace servomechanism, this study establishes the basic equations and transfer functions of the balanced piston direct-acting relief valve, deduces the stability criteria for this valve, and provides the parameter calculation expressions for the balanced piston based on the mathematical relationship between the valve stability criteria and the piston clearance hydraulic conductivity. The results indicate that the smaller the piston clearance, the better the stability of the relief valve, but its response speed will be affected. Furthermore, when the aircraft performs centrifugal motion, the valve poppet deviates from the central position due to the action of centrifugal force, and the piston clearance becomes an eccentric ring clearance, which will increase the hydraulic conductivity of the clearance and affect the pressure regulation stability of the balanced piston direct-acting relief valve. A time-domain simulation model was constructed to study the dynamic characteristics of the balanced piston direct-acting relief valve, and finally, the correctness of the theoretical analysis is verified through experiments.

Key words: relief valve, balance piston, stability, damping, structural parameter