Research Papers

Mapping the Efficiency for a Hydrostatic Transmission

[+] Author and Article Information
Noah D. Manring

Rolf Fluid Power Laboratory,
Mechanical and Aerospace
Engineering Department,
University of Missouri,
Columbia, MO 65211
e-mail: ManringN@missouri.edu

Contributed by the Dynamic Systems Division of ASME for publication in the JOURNAL OF DYNAMIC SYSTEMS, MEASUREMENT, AND CONTROL. Manuscript received March 11, 2015; final manuscript received November 30, 2015; published online January 12, 2016. Assoc. Editor: Luis Alvarez.

J. Dyn. Sys., Meas., Control 138(3), 031004 (Jan 12, 2016) (8 pages) Paper No: DS-15-1105; doi: 10.1115/1.4032289 History: Received March 11, 2015; Revised November 30, 2015

Efficiency maps have long been used by engineers to understand the topographical behavior of their machinery. Most commonly, efficiency maps have been generated for internal combustion engines, where the torque–speed curve for the engine shows the wide-open-throttle line with constant efficiency lines drawn beneath this maximum operating limit. From such maps, engineers have been able to determine the most efficiency operating point for the engine, given a desired output power (torque and speed). There currently exists a great interest in using hydrostatic transmissions for improving the operating efficiency of an internal combustion engine. However, efficiency maps for hydrostatic transmissions, similar to efficiency maps for internal combustion engines, do not exist in the literature and therefore it is difficult to assess the overall efficiency gains that are achieved when using a hydrostatic transmission in these applications. This paper proposes a method for generating efficiency maps for hydrostatic transmissions, and presents a typical set of maps that may be used as a first approximation for assessing transmission efficiency. The results of this paper are nondimensional and are generalized for a transmission of any size. As shown in this research, there are regimes of transmission operation in which the efficiency is nearly independent of either the output torque, or the output speed. Furthermore, it is shown that maximum operating efficiencies typically exist at high output speeds, and mid-to-high output torques.

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Fig. 1

Schematic of the hydrostatic transmission

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Fig. 2

Schematic of the pump, showing the mass and volumetric flow rates

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Fig. 3

The Stribeck curve for modeling the coefficient-of-friction

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Fig. 4

A typical efficiency map for the hydrostatic pump

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Fig. 5

A typical efficiency map for the hydrostatic motor

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Fig. 6

A typical efficiency map for the hydrostatic transmission



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