Studies On Lubrication Characteristics Of Helical Grooved Piston-copper Pair

Swash-plate axial piston pump is a common component in mechanical hydraulic systems.Its performance directly affects the reliability of various types of mechanical equipment.The contact status between piston and copper pair has significant influence on the performance of the pump among its key parts.In recent years,In recent years,some researchers apply the concept of surface texture design to the design of piston pair to improve the lubrication performance.In this paper,with the design of the pre-spiral grooved piston of the author,the deep research on the lubrication characteristics of the piston-copper pair is carried out.In order to study the lubricating characteristics of the helical grooved piston-copper pair,the modeling and solution of helical grooved piston-copper pair lubrication number theory and performance analysis under the influence of variable parameters are conducted.Simultaneously,the experimental study on the reciprocating friction and the leakage test of the grooved piston pair under the lubrication condition are conducted.Specified contents and conclusions are as followed.(1)The lubrication theoretical model of helical grooved piston-copper pair is constructed without considering the influence of piston inclination and piston inclination.The oil film pressure control equation and oil film thickness equation are established.The equation is solved by finite difference method.At the same time,the case analysis is carried out,and the distribution of oil film thickness and oil film pressure distribution under three kinds of working conditions are given.And the bearing capacity of the oil film,friction coefficient,leakage amount and the size of friction loss are analyzed and compared.Results show that the grooved structure can improve the lubrication performance of the piston-copper pair.The lubrication performances of the piston-copper pair under the tilting condition are improved.The numerical solution method has some feasibility and rationality,which lay the foundation for the analysis of the lubrication characteristics of the helical grooved piston-copper pair.(2)Combined with the actual working conditions of the piston pump,the study is only done when considering the effect of piston tilt.In this paper,the effects of groove helix angle and groove dimension on the piston-copper pair lubrication characteristics and the lubrication performance of helical grooved piston-copper pair under different working conditions are mainly studied.The variation of oil film pressure distribution,oil film bearing capacity,friction coefficient,leakage and frictional power loss are analyzed emphatically.Results show that compared with the non-grooved structure and the annulargrooved structure,the helical grooved structure is more conducive to improve the lubrication performance of the piston pair;helical grooved structure due to the larger range of oil film pressure increases so that the overall piston oil film bearing capacity increased,the maximum increase under high pressure conditions is 22.6%;friction coefficient decreased significantly,the maximum decrease of 34.8%;helical grooved structure reduces the flow resistance of oil flow,increasing the pressure differential flow,leading to the amount of leakage of piston pair relatively increased.When the helix angle of the groove is3 °,the increase of the leakage is only 4.4%.The helical groove with reasonable design can improve the lubrication performance of the plunger pair and increase the leakage of the plunger pair by acceptable range;to some extent,increase the groove helical angle can further enhance the performance of the plunger pair.With the increase of the grooved depth,the bearing capacity of the piston-copper pair was decreased,the friction coefficient,the leakage amount and the friction power loss increased,but the decrease and the increase were not obvious.With the increase of the grooved width,bearing capacity,friction coefficient,leakage and friction power loss were increased.In the influence of the characteristic parameters,with the increase of the inclination angle of the piston,the dynamic pressure of the oil film was enhanced;the oil film bearing capacity was improved;the friction coefficient,the leakage amount and the friction power loss were reduced.When the axial velocity was opposite to the oil supply pressure,it could enhance the dynamic pressure effect and the lubrication performance of the piston-copper pair.The rotation speed of the piston had little effect on the lubrication performance of the piston-copper pair.(3)A test device for the lubrication performance of the piston-copper pair was established by using a friction and wear test platform.Then the reciprocating friction test and leakage test of the helical grooved piston-copper pair were conducted.The influence of the helical grooved structure on the lubrication characteristics of the piston-copper pair was discussed by comparing the COF and the leakage amount of each specimen under full lubrication.Results showed that frictional characteristics of piston-copper pair were improved by helical grooved structure under full lubrication.When the helical angle is 12°,the COF of the piston was the largest,reaching 54.2%.At the same time,the leakage of piston-copper pair was improved by helical grooved structure under full lubrication.Under the same oil supply pressure,the piston specimen with helical angle of 12 ° had the largest increased in the leakage.Based on the results of numerical and tests studies concluded above,it can be concluded that under the condition of sufficient lubrication,the helical grooved structure can improve the lubrication performance of the piston-copper pair.Numerical modeling and solving methods have some rationality,which can provide reference for optimizing the lubrication performance of piston-copper pair.