PV/MF is axial piston pump/motor of swashplate design for hydrostatic closed circuit transmissions.　1.Side fit of involute spline between the cylinder block and the shaft, obtaining good centering and definite self returning effect.　2.Plane hydrostatic control area:the cylinder block runs against a bronze coated steel spacer, the nine pistons run in a bronze sleeved steel cylinder block, providing 'material match' for the rubbing couples and good maintance for the products. 3.Type V grooves are designed in the transition area of the kidney ports in the valve plate in order to decrease the impact of the hydraulic pressure and lower the noise. Storing oil area is designed in the supporting plane of the spacer in order to store oil for lubrication among the rubbing planes and increasing the speed.