THE DESIGN OF POWERSPLIT TRANSMISSIONS USING NEW TECHNOLOGIES OF HYDROSTATIC COMPONENTS

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. [GRAPHICS] . 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. [GRAPHICS] . 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].