In powersplit systems, which are state-of-the-art in tractor transmissions, the efficiency is of much higher importance than in most other vehicles. Key for high efficiency is to transmit only some power hydrostically and a high amount mechanically (Fig. 1 and 2) because the mechanical path has higher efficiency than the hydrostatic path. The hydrostatic path is needed to get an infinitely variable transmission.
The understanding of powerloss characteristics of hydrostatic components helps to choose between swashplate and bent axis components. Best total efficiencies of 97% are key arguments for using 45° bent axis technology. This is the reason for a dominant use of 45° bent axis in powersplit transmissions.
The search for further reduction in powerloss shows the weak volumetric efficiency at small displacements and high pressure levels. The compression loss is now a dominant subject for improvement. The paper will explain a new design for reduced compression loss, which can be applied to 45° bent axis units. The powerloss reduction will be shown for a powersplit transmission with 2 and 3 modes, which are state of the art today [7].
