According to the previous analysis, when the initial orifice is fixed, one of the measures to achieve the basic symmetry of the tension and pressure resistance is that the spring stiffness of the compression throttle is slightly lower than that of the tension throttle. Another measure to achieve tension-compression symmetry is to adopt the same spring stiffness as the tension-compression throttle valve, but the initial compression force of the spring set for the tension-compression throttle valve is slightly greater than that of the throttle valve. Symmetrical linear feature. Through the discussion of the relationship between the resistance characteristics and the change of the orifice area, the stiffness of the spring can be designed according to the change of the orifice area.