Research And Simulation For The Characteristic Of Servo Sylinder And Relationship Between Friction And The Seal

As the terminal actuator of servo control system, servo cylinder plays a vital role init.To achieve a perfect control system which can operate rapidly and give a heavyoutput,the servo cylinder often work in high frequency with overload. Therefore, itsperformance directly decides dynamic and static quality and running accuracy of thewhole servo system. Compared with the ordinary hydraulic cylinder, servo cylinder wasneeded to meet the requirement of high frequency and large load, needed to maintain thelowest leakage in order to achieve the purpose of environmental protection. Then, thefriction and leakage become the important parameters to constant the quality of servocylinder. Friction mainly comes from the seal, and leaks are often because of poor sealing,so in the design of servo cylinder, the form and the structure of sealing become animportant research direction.This topic was about the servo cylinder rod sealing, launched from structure design totheoretical analysis, to the modeling simulation and performance comparison. Its mainresearch content can be divided into this several statements:First of all, according to the requirements for the servo cylinder design, I designed anew servo cylinder rod seal which use the double conical hydrostatic bearing as the mainbody and choose the labyrinth seal as the oil seal edge. The double conical hydrostaticbearing can provide the rod of radial support, the sudden enlargement effect fromlabyrinth groove will reduce the pressure of oil and in the same time the turbulence fromgrooves lower the velocity of laminar flowing in the crack which means the leakge fromcrack will be little.Secondly, I finished the structure of double conical hydrostatic bearing and labyrinthseal. To the double conical hydrostatic bearing, I choose an appropricte dimensions for thedraw ratio and the taper, because they can affect the effect of radial support easily. Then Idetermined the dimension of region annular on labyrinth seal and achieved the sizes andnumber of labyrinth grooves by CFD. In selecting a maze groove size, I follow theprinciple that it can produce the effective of turbulence or not.And when selecting the number of labyrinth grooves, I follow the principle that it must as far as possible to reduceleakage without complex structure.Again, in order to verify the performance of double conical hydrostatic bearing andlabyrinth seal of the rod, I builded different modles with variant speed, pressure andeccentricity.With these modles I analysized the diversity of leakage and friction by CFD.Simulation results show that the rod seal with new structure can form enough radialsupport in a reliable way. The friction force mainly formed by viscous friction is onlyaffected by speed. Its value is very small, and it doesn’t matter with eccentricity. Andleakage will change significantly on different pressure, moreover, it’s sensitive toeccentricity under the condition of same pressure.Finally, I get the friction of coaxial combination seal through the theoreticalcalculation and the actual measurement. Then I determined the friction of rod seal withdouble conical hydrostatic bearing and labyrinth by analyzing the CFD results above. Withthese two frictions I build the modle of hydraulic servo system by AMESim. The resultsshowed that compared with the coaxial combination seal, the performaces of seal withdouble conical hydrostatic bearing and labyrinth were enhanced obviously. Its responsespeed and stability have been improved significantly. These changes proved that thedesign is feasible.