Research On Key Technology Of High-flow Servo Valve’s Hydraulic Match Grinding Measurement

Spool valves are commonly used as the hydraulic power amplifier stage in electric- hydraulic servo valves with high precision. Due to the discharge amplificational coefficient is larger than other stages in servo valves, it requires high precision in spool valves’ manufacturing. The spool valves change the discharge by changing the size of spool valve orifices, which is caused by the axial displacement of valve spool. Thus the relative dimension of valve spool’s edge and valve sleeve’s square orifice, as we called the overlap value of spool valve, becomes a key index in spool valves’ manufacturing. The tolerance of valve spool’s overlap value is commonly 1 μm and cannot be interconverted. We make it possible via match and fit processes, which make the measurement of spool valve’s overlap value important. Because the leakage through the radial clearance of spool valve causes theoretical measurement error in pneumatic measurement, and make it impossible to maintain the overlap value of spool valve within its tolerance, so the research on key technologies of hydraulic measurement of high-flow servo spool valves’ overlap value becomes important.To improve the precision and efficiency of hydraulic measurement of spool valve’s overlap value, the article quantificationally analyses the causes of the measurement’s precision and provides a way to compensate. The article also study about the technology of valve spool ’s displacement driving, and analyses its effect on the precision and efficiency of measurement. A measuring system is also been built, by which experiments are performed to prove the former theoretical analyses. The precision of measurement is also improved in the measuring system.Firstly, we study the theory of hydraulic discharge measurement method. We analyses the influences of valve orifice’s shape and changing of flow stage on the precision of overlap value’s measurement. We also analyses the effect of discharge, displacement’s measuring precision and pressure, temperature’s controlling precision on measuring precision of overlap value. A series of compensation method is also been provided accordingly.Secondly, the article studies about the technology of valve spool’s displacement driving. We designs a new kind of displacement driving device, and established a dynamic model of measuring process to estimate the influence of valve spool’s displacement driving on measuring precision and efficiency. During the study we uses feedforward and PID feedback compounding control method to establish the model of hydraulic system, with the help of emulational software Simulink, we are able to provide theoretical basis of improving the precision and efficiency of overlap value’s measurement.Finally, we build up measuring system for spool valves of high-flow servo--valves, modified the design in mechanical and hydraulic systems, compile programme which is able to measure the overlap value, pressure amplificational coefficient and zero-point leakage of spool valve automatically. A series of experiments are also been performed on the measuring system, which not only prove the former theoretical analyses, and also achieves the improvement of measuring precision.