In this research, the friction within the cylinder bore of a swash-plate type axial-piston machine is examined. Unlike previous research, this work develops a mathematical model for the friction based upon lubricating conditions which are described by the well-known Stribeck curve. Furthermore, a test device is built for measuring the frictional characteristics during low pressure and low speed operation and these results are compared with the mathematical model. For high pressure and high speed considerations, a numerical investigation based upon the model is conducted and it is shown that the friction associated with a pumping piston is greater than the friction associated with a motoring piston. It is also shown that increased piston speeds usually reduce the friction within the cylinder bore; however, a “cross-over” condition may exist where the increased speed will actually increase the friction as a result of increased fluid shear. Furthermore, it is shown that speed changes have a more significant impact on motoring pistons as opposed to pumping pistons due to a difference in the location of hydrodynamic lubrication within the cylinder bore. It is noted that this difference exits due to the bore geometry and the direction of piston travel.

1.
Ezato, M., and Ikeya, M., 1986, “Sliding Friction Characteristics Between a Piston and Cylinder for Staring and Low-Speed Conditions in the Swashplate-Type Axial Piston Motor,” 7th International Fluid-Power Symposium, Bath, England.
2.
Hutchings, I. M., 1992, Tribology: Friction and Wear of Engineering Material, CRC Press, London.
3.
Kazama
T.
, and
Yamaguchi
A.
,
1993
, “
Application of a Mixed Lubrication Model for Hydrostatic Thrust Bearings of Hydraulic Equipment
,”
ASME Journal of Tribology
, Vol.
115
, pp.
686
91
.
4.
Koc
E.
,
Hooke
C. J.
, and
Li
K. Y.
,
1992
, “
Slipper Balance in Axial Piston Pumps and Motors
,”
ASME Journal of Tribology
, Vol.
114
, pp.
766
72
.
5.
Pang
Z.
,
Zhai
W.
, and
Shun
J.
,
1993
, “
The Study of Hydrostatic Lubrication of the Slipper in a High-Pressure Plunger Pump
,”
Tribology Transactions
, Vol.
36
, pp.
316
20
.
6.
Puormovahed, A., 1992, “Uncertainty in the Efficiencies of a Hydrostatic Pump/Motor,” Winter Annual Meeting of the ASME, Anaheim, CA.
7.
Shigley, J. E., and Mitchell, L. D., 1983, Mechanical Engineering Design. 4th ed., New York, McGraw-Hill.
8.
Stachowiak, B. W., and Batchelor, A. W., 1993, Amsterdam, Elsevier Science Publishers, Engineering Tribology.
9.
Tanaka
K.
,
Nakahara
T.
, and
Kyogoku
K.
,
1993
, “
Piston Rotation and Frictional Forces Between Piston and Cylinder of Piston and Motor
,”
Transactions of the Japan Society of Mechanical Engineers C
, Vol.
59
, No.
560
, pp.
1192
97
.
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