Theoretical And Experimental Research On The Lubrication Characteristics In Whole Cycle Of The Gap Between Piston And Cylinder In Axial Piston Pumps

Swash plate axial piston pump is a kind of hydraulic component which convers the mechanical energy into hydraulic energy. Axial piston pump is one of the most widely used hydraulic components in modern hydraulic transmission and is also one of the core power and the executive components. Axial piston pump has the following advantages: high working pressure, high volume efficiency, high power density and convenient control mechanism. The pump with high pressure and high speed is becoming the research tendency with the requiring of the high power and high power density transmission. Axial piston pump has three key friction pairs: piston/cylinder pair, slipper bearing and distribution pair, which directly affects the performance and lifetime of the axial piston pump. As one of the three key friction pairs, the piston pair plays an important role in realizing high speed and high pressure of the axial piston pump. The research on the piston pair are as follows.Firstly, the lubrication model and numerical algorithm of solving the pressure distribution was discussed. The distribution of the oil film pressure can be obtained by solving the Reynolds, and then the pressure of the oil film pressure can also be acquired. The influence of the tilting angle of the piston on the leakage were analyzed.Then, the dynamic change of the gap was simulated. The forces exerted on the piston are different in different shaft angle, and the gap height distribution also changes. Then it need to solve dynamical equations to obtain the pressure distribution and gap height distribution. The metal contact may exist in some situations or not. The problem of solving the dynamical equations was transformed into optimization problem. Golden section method and Coordinate rotation were used to solve the dynamical equations. The dynamic change of the gap height distribution, the change of the contact forces, the change of viscous friction exerted on piston and cylinder and the change of leakage were analyzed.Finally, a test bench was designed for test the gap height. The displacement sensors were used to test the gap height of the piston pair. The influence of the gap height were analyzed. And the influences of the pressure and speed on the eccentricity and tilting angle of piston were analyzed.The research has the following conclusions. In high pressure, differential pressure flow has mian effect on the leakage. In low pressure, shear flow has main effect on the leakage. The viscous friction of the circumferential direction is less than the axial viscous friction force. The solid contact force can reach kN. When the motor speed is more than 500r/min, the fluid power lubrication is well formed.