Dynamic Modeling of Floating Valve Plate Motion in an Axial Piston Pump

The objectives of this study were to analytically and experimentally investigate the motion of the floating valve plate in an axial piston pump under various operating conditions. To achieve the objectives of the analytical investigation, the equations of motion for the valve plate were coupled with a time-dependent lubrication model. The balance pistons that support the floating valve plate were represented by equivalent spring and dashpot systems. The system of equations was then solved using the Runge-Kutta and the control volume finite difference methods to determine the pressure, film thickness, and motion of the valve plate for various operating conditions. To achieve the experimental objectives, a previously developed axial piston pump test rig was instrumented with proximity probes to measure the motion of the valve plate. The stiffness and damping of the balance pistons supporting the floating valve plate were determined using the impact and frequency response methods. Using the experimentally determined stiffness and damping coefficients in the coupled dynamic lubrication model, the analytical and experimental results of the valve plate motions were compared. The model was then used to conduct a parametric study to determine the overall system stiffness and damping coefficients during pump operation. Using the stiffness and damping coefficients from the parametric study in the dynamic lubrication model, the pressure, film thickness, and motion of the valve plate were calculated for various operating conditions. The experimental and analytical displacements of the valve plate were then corroborated and found to be in good agreement.