The History and Future of Fluid Power Pumps and Motors

Abstract

Positive displacement pumps have been around for thousands of years, but it was first in the beginning of the 19th century they started to be used for power transmission purposes. At that time, the fluid was water, and the applications were primarily presses. During the century, the technology developed and towards its end, fluid power systems were used to transmit power to hundreds or even thousands of consumers within several cities. However, in the 20th century, these large-scale fluid power transmission systems were outcompeted by the electric grid. But at the same time, the focus for fluid power was shifted towards self-contained, oil-based systems, which were suitable in many mobile applications powered by combustion engines. Once again, fluid power systems are now undergoing a transition. This especially apply to mobile applications, where combustion engines are being replaced by electric motors. This puts new requirements on the hydraulic systems as well as the pumps and motors that are to be used. Electrification means increased focus on energy efficiency, and speed-control becomes more relevant than before. New system designs are therefore highly relevant. Depending on the architecture that is chosen, different requirements will be set on the pumps and motors. Aspects such as multi-mode operation, high- and low-speed performance, and displacement control will be discussed in this paper.