Study On Oil Film Characteristics Of Micro-Textured Piston Pair In Axial Piston Pump

Swash plate axial piston pump,as the key power source of hydraulic system,is widely used in construction machinery.With high pressure and high speed,the market for the increasingly complex working environment of the piston pump performance requirements are more stringent.In this paper,the piston pair is taken as the research object.Due to its complex force in the movement of the cylinder hole,the oil film is easy to be damaged in the two end faces of the plunger and the cylinder,resulting in wear,biting cylinder and other problems,which directly affect the working efficiency and service life of the pump.Aiming at the above problems and combining with the working characteristics of the plunger pump,this paper proposes a surface micro-texture plunger structure with "high bearing capacity,low leakage,Low risk and low friction".The numerical simulation method was used to study the vortex phenomenon in the oil film flow field during the movement of the micro-textured plunger and the bearing capacity,leakage characteristics and friction characteristics of the plunger pair.The optimal surface micro-textured parameters were determined,which laid a foundation for the design and manufacture of the surface micro-textured plunger.The main contents are as follows:(1)Based on Pump Linx,the pressure variation law of the piston chamber was obtained,and the flow field simulation model of the micro-textured piston pair was established.The oil film bearing capacity characteristics and leakage characteristics of the smooth and micro-textured piston pair flow field were mainly analyzed by using Fluent dynamic mesh and sliding mesh technology.The results show that: The placement of micro-texture changes the original motion state of the oil in the flow field.The velocity decreases and the dynamic pressure in the flow field in the gap increases,thus increasing the bearing capacity of the oil film.Compared with other micro-textured piston secondary flow fields,the trapezoidal structure bearing capacity changes stably,and the oil passes through the micro-textured gap area close to the upper wall to form a larger vortex core area,which reduces the through-through effect of oil,and thus has a smaller leakage rate compared with other micro-textured structure.The trapezoidal up and down ratio 0.667 microtexture piston is determined to take into account large oil film bearing capacity and small leakage rate comprehensive performance.(2)Based on Workbench platform,unidirectional fluid-structure coupling simulation research was conducted on the piston pair.The results show that,compared with smooth piston,the structure of surface micro-texture piston is relatively weak in the micro-texture region,and the phenomenon of local stress concentration is easy to occur,but the maximum equivalent stress is far less than the yield limit,and the maximum shape variable is only about 1μm.From the Angle of piston safety margin,the width-length ratio of semi-ellipse 1.214 is better than that of trapezoid up and down 0.667.From the Angle of cylinder safety margin,the trapezoidal ratio 0.667 is better than the semi-ellipse width-length ratio 1.214.(3)Based on Archard model,dry friction simulation of micro-textured piston and cylinder block was established.The results show that: The end face of friction between the piston and the cylinder body has ring scratches.Compared with smooth piston pair,the extreme wear values of the surface of the piston and cylinder body show ring distribution.The extreme wear values of the surface of the micro-texture piston are more concentrated,and the contact area between the piston and cylinder body is reduced due to the insertion of micro-texture.The wear morphology of the inner surface of the cylinder is improved.Therefore,the optimal micro-texture scheme for increasing the oil film bearing capacity,having smaller leakage rate,lower risk and high wear resistance is determined to be the micro-texture piston with a trapezoidal ratio of 0.667.