PUB – Analytical approach to calculate the rotation angle-dependent compensation ratio of the cylinder block – valve plate contact in axial piston machines
A paper on “Analytical approach to calculate the roation angle-dependent compensation ratio of the cylinder block – valve plate contact in axial piston machines” was published in Scandinavian International Conference on Fluid Power.Copyright: ifas
Hydraulic piston machines are commonly used in many industry fields because of their high power density and high efficiency. One of the most important components in axial piston machines that determines the efficiency is the valve plate, which is in lubricated contact with the rotating cylinder block. The fluid force, generated by the fluid film and acting against the load force, lifts the cylinder block to reduce the solid friction with the valve plate. The ratio of the fluid and load force, called compensation ratio or balance ratio, is used in the industry as design parameter, representing a number for the complex trade-off between losses and robust operation under all conditions. To calculate the compensation ratio, many analytical calculation methods have been introduced on a fixed position. In practice, however, the effective pressurized area varies depending on the angle of rotation, therefore changing the fluid force. Thus, the calculation method has an inconsistent accuracy over one revolution, depending on the shape of the valve plate.
This paper discusses an analytical approach to calculate the rotation angle-dependent compensation ratio of the cylinder block and valve plate. A proposed calculation method differs from the conventional method in that it can calculate the rotation angle dependent compensation ratio. In order to check the accuracy of the proposed method, the analytical results are compared to simulation results using a verified EHD (Elasto-Hydrodynamic) simulation under the same operating conditions. The comparison shows that the maximum error is less than 2 %. Moreover, the relation of the compensation ratio and the design parameters is analyzed.