| The swashplate axial piston pump is the most common hydraulic one,such as aerospace,vehicles and construction machinery and other high-voltage high-power fields because of its compact structure,high power density,high pressure rating and volumetric efficiency.With development of hydraulic technology,axial piston pumps is also developing towards the direction of high speed,high pressure,high reliability and service life.The performance and service life of each friction pair in the pump are required to be higher.In the design process of high-performance axial piston pump,the traditional empirical design method are difficult to meet the requirements.The thermo-hydro-mechanical interaction in each friction pair of axial piston pump can not be ignored.Slipper-swashplate interface,as the key friction pair in axial piston pumps,has complicated force and motion and plays the role of bearing,sealing and lubrication.The lubrication mechanism of slipper-swashplate interface is deeply studied.The micro-motion and lubrication characteristics of slipper-swashplate interface with hydrostatic balance and residual compression force are analyzed.The influence of structural parameters and working conditions on the lubrication characteristics is profoundly researched to provide a theorectical basis for the optimization design of slipper,which has important research value in academic and engineering fields.The fluid-solid-thermal coumpling algorithm of slipper-swashplate interface in axial piston pumps is proposed.The oil film thickness and micro motion extrusion speed of the slipper pair are described by three control points on the outer circumference of the sealing belt.The micro-motion extrusion speed satisfying the dynamic balance of the slipper is solved by Newton iterative algorithm and the numerical model of the oil film of the slipper pair is established.A description method of slipper micro-motion posture is proposed and and its mathematical model is developed.The elastic deformation influence matrix of swashplate and slipper is obtained.The thermoelastic deformation of swashplate and slipper at steady temperature is calculated and the elasticdeformation of swash plate and slipper and viscosity-temperature equation are introduced into the numerical model.The fluidsolid-thermal coupling model of slipper pair is proposed.The pressure model of piston chamber is established and solved.The solved dynamic pressure is taken as the pressure boundary of the numerical model of slipper pair.On this basis,the micro-motion and lubrication characteristics of hydrostatic balance slipper pair are studied.Lubrication mechanism and the influence of working conditions on lubrication characteristics are analyzed.The influence of lengthdiameter ratio of fixed damping hole and outer-inner diameter ratio of sealing belt on the micro-motion and lubrication characteristics of hydrostatic balance slipper pair are deeply researched.The difference between hydrostatic balance and residual compression force slipper pair is compared.Based on the boundary condition of dynamic pressure in displacement chamber and the lubricantion oil film numerical model of slipper pair,the micro-motion and lubrication characteristics of residual compression force slipper are analyzed.The causes of eccentric wear are explored.Three improved slipper micro-structures are proposed,such as micro-chamfer,micro-fillet and microstep.The effects of micro-structures and their parameters on the micro-motion and lubrication characteristics are analyzed.The results show that three kinds of slipper micro-structures can make the residual compression force slipper produce effective dynamic pressure effect,forming a certain lubrication oil film to improve the lubrication characteristics.A parameters optimization method for slipper microstructures is proposed,and the optimal parameters of micro-chamfer and micro-step are obtained.The simulation results show that lubrication film performance of slippers with the optimal parameters are are basically consistent with the optimal theoretical film performance,which verifies the correctness of the optimization method and the optimization results.The oil film experimental rig of slipper-swahplate interface is designed and built by rotating swashplate and fixed cylinder block.Two check valves are used to replace the valve plate for valve oil distribution to complete the oil suction and discharge function of the experimental pump.In experimental rig,because of rotating swashplate and fixed cylinder block,the centrifugal moment of slipper is ignored.The slipper will only incline along the trajectory under the action of viscous friction torque.Two eddy current micro displacement sensors are symmetrically arranged on both sides of the measured slipper.The central oil film thickness the slipperswashplate interface with micro-chamfer and the inclination angle of the slipper are measured.The measured results have the same trend as the simulation results,which verifies the correctness of the numerical simulation model of the slipper-swahplate interface.In addition,the viscous friction power loss of slipper pair under different speed and load pressure is also measured on the experimental platform.The experimental viscous friction power loss of slipper pair is basically consistent with the simulation results,which further verifies the correctness of the simulation model. |
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