This paper deals with the power saving prediction of hydrostatic drivetrains achieved with a variable roller charge pump. Focusing on the charge pump in a hydrostatic transmission, shows, that fixed pumps don’t act in all operating conditions very efficient. The charge pump delivers in some conditions a higher flow than required. The unused energy is dissipated into heat. According to this assumption, using variable charge pump is another possible way to save energy. In the end it means reduce fuel consumption.

Generally, the power saving potential is depending on the application, but two main factors can be highlighted: the first one is the charge pump size and the second is the application of an intelligent loop flushing system. The standard loop flushing system demands more cooling flow than required in some conditions, but a variable charge pump is able to more efficiently cover demands of intelligent loop flushing system.

The power saving potential will be analyzed for two different example systems/vehicles in their typical operation conditions. All analyses are made with simulation models, which include simplified thermal behavior of the hydraulic circuit, also. The results in this paper confirmed the power saving potential for different applications with bigger charge pumps with an intelligent loop flushing function could be the most interesting applications.

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