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Research Papers: Applications

A Study on Force and Lubrication Characteristics of Ball Piston in Eccentric Ball Piston Pump

[+] Author and Article Information
Lu Xu

Science and Technology on
Vehicle Transmission Laboratory,
Beijing Institute of Technology,
5 Zhongguancun South Street,
Beijing 100081, China
e-mail: xulu19861012@163.com

Chao Wei

Science and Technology on
Vehicle Transmission Laboratory,
Beijing Institute of Technology,
5 Zhongguancun South Street,
Beijing 100081, China
e-mail: bitweichao@126.com

Chongbo Jing

Professor
Science and Technology on
Vehicle Transmission Laboratory,
Beijing Institute of Technology,
5 Zhongguancun South Street,
Beijing 100081, China
e-mail: jingchongbo@bit.edu.cn

Jianhao Liu

Science and Technology on
Vehicle Transmission Laboratory,
Beijing Institute of Technology,
5 Zhongguancun South Street,
Beijing 100081, China
e-mail: liujianhao@163.com

1Corresponding author.

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received January 11, 2016; final manuscript received July 18, 2016; published online March 17, 2017. Assoc. Editor: Jordan Liu.

J. Tribol 139(4), 041101 (Mar 17, 2017) (10 pages) Paper No: TRIB-16-1012; doi: 10.1115/1.4034955 History: Received January 11, 2016; Revised July 18, 2016

Ball piston is an essential design element in eccentric ball piston pump. The objective of this paper is to investigate the dynamic force and lubrication characteristics of the ball piston. In this study, a tribodynamic model of the ball piston is proposed. The model couples the elastohydrodynamic lubrication model of ball–ring pair and the elastohydrodynamic model of ball–cylinder pair with the dynamic model of the ball piston. The interaction between tribological behavior and dynamic performance and the effects of centrifugation and structural deformation of the ball piston are considered. The pressure distributions and film profiles of the ball–ring pair and ball–cylinder pair are calculated. The dynamic normal contact forces and friction forces are analyzed. The friction torque loss and mechanical efficiency of the whole pump are obtained by combing the tribodynamic model of the ball piston with a simplified friction torque model of cylinder-valve shaft pair. A test bench is established for validating the simulation results. The results show that the normal contact force of the ball–ring pair waves in each stroke, and in discharge stroke, the contact force is much bigger than that in suction stoke because of loading force, while the friction force changes very little for the ball sliding in the outer ring. Comparing with the average friction force of the ball–ring pair, the average friction force of the ball–cylinder pair is small, which reflects that the ball–ring pair is more prone to wear. For the ball–ring friction pair, when the load increases, the secondary contact pressure peak appears, the profile of film presents a horseshoe shape, and the classical shrinkage appears at the outlet of contact region. For the ball–cylinder pair, the film pits and the contact pressure jumps at the entrance of contact region for the heavy load and the high shear stain of film. In addition, the friction torque presents a nonlinear growth trend with the increasing working pressure

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References

Figures

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Fig. 1

Eccentric ball piston pump

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Fig. 2

Three friction pairs of ball piston pump

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Fig. 3

Motion analysis of ball piston

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Fig. 4

Force analysis of ball piston

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Fig. 5

The contact region of ball–ring pair

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Fig. 6

Flowchart of numerical solution

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Fig. 7

(a) Schematic of test rig and (b) photograph of test rig

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Fig. 8

Force characteristics of ball–ring pair

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Fig. 9

Force characteristics of ball–cylinder pair

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Fig. 10

Pressure and film thickness distribution of ball–ring pair: (a) 5 MPa, (b) 10 MPa, (c) 15 MPa, and (d) 20 MPa

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Fig. 11

Pressure and film thickness of ball–cylinder pair: (a) t = 1/4T, (b) t = 1/2T, (c) t = 3/4T, and (d) t = 1T

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Fig. 12

Friction torque of ball piston pump

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Fig. 13

Comparison of experiment results and simulation results

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