Pressure Characteristics of Hydraulic Spool Valve with Symmetric and Equal Overlaps Considering Radial Clearance Between Spool and Sleeve
Considering the radial clearance between spool and sleeve,a mathematical model of hydraulic spool valve with symmetrical and equal negative openings is established,and the pressure characteristic curve family and basic characteristics of overlapped spool are obtained.The influence of clearance and overlap on the pressure characteristics of overlapped valve is analyzed by simulation.The results show that there is an inflection point in the pressure characteristic curve of overlapped valve where the spool displacement is equal to overlaps.Laminar flow is assumed before the inflection point,so the load pressure changes linearly with the spool displacement.After the inflection point,the flow is turbulent,so the load pressure has a nonlinear relationship with the spool displacement.The overlapped valve can compensate the gap leakage of the spool and the pressure gain of the proportional valve decreases with the increase of the overlap.The established mathematical model can provide technical support for the development and production of electro-hydraulic servo valves,high-end proportional valves and spool valves.
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