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Research Papers: Hydrodynamic Lubrication

Lubrication Characteristics of Electric Sliding Contacts Consisting of Rotating Circular Grooved Disk and Stationary Rider With Spherical Surface Under Lubricated Condition

[+] Author and Article Information
Satoru Kaneko

Professor
Department of Mechanical Engineering,
Nagaoka University of Technology,
1603-1 Kamitomiokamachi,
Nagaoka-shi, Niigata 940-2188, Japan
e-mail: kaneko@mech.nagaokaut.ac.jp

Hiroo Taura

Associate Professor
Department of Mechanical Engineering,
Nagaoka University of Technology,
1603-1 Kamitomiokamachi,
Nagaoka-shi, Niigata 940-2188, Japan
e-mail: htaura@mech.nagaokaut.ac.jp

Ryosuke Fukasawa

Department of Mechanical Engineering,
Nagaoka University of Technology,
1603-1 Kamitomiokamachi,
Nagaoka-shi, Niigata 940-2188, Japan

Hitoshi Kanai

Oiles Corporation,
1-6-34 Kounan,
Minato-ku,
Tokyo 100-0011, Japan

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received October 7, 2014; final manuscript received June 19, 2015; published online September 22, 2015. Assoc. Editor: Daniel Nélias.

J. Tribol 138(1), 011705 (Sep 22, 2015) (9 pages) Paper No: TRIB-14-1252; doi: 10.1115/1.4031393 History: Received October 07, 2014; Revised June 19, 2015

Electric sliding contacts are widely used in various electrical components such as for home appliances and automobiles. The purpose of the present study is to improve the performance characteristics of the electric sliding contacts operating under the lubricated condition by the combination of circular grooved disk and rider with a spherical surface. The experimental and theoretical analyses have been carried out to investigate the effect of cross-sectional area of circular grooves provided in the rotating disk surface on the frictional characteristics and the electrical conductivity. The experimental analysis is conducted with a pin-on-disk friction tester to measure the frictional force and the contact voltage between the sliding contacts under the lubricated condition. The oil-film force and the frictional force between the rider and disk are also calculated with the Reynolds equation and they are found to be closely corresponding to the experimental results. The results obtained in the present study show that increasing the cross-sectional area of the circular grooves on the disk extends the operation condition yielding the metal contact to a higher value of the bearing characteristic number S, which is defined by ηU0L0λ/W (η is the lubricant oil viscosity, U0 is the sliding velocity, L0 is the rider arc length in the sliding direction at the middle of radial width, W is the applied load, and λ is the aspect ratio of rider), and also decreases the frictional force at the maximum value of S at which the rider could contact with the disk surface. These are expected since upstream lubricant oil dragged into the contact region tends to easily leak out along the circular grooves, yielding a lower oil-film force between the rider and disk and enhancing the metal contact.

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Figures

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Fig. 1

Physical model and coordinate system

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Fig. 2

Schematic view of grooves and clearance in contact region (cross section in radial direction): case A corresponds to the case where rider center Oc locates in the middle of groove width gw, and case B to the case where Oc locates in the middle of land width lw

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Fig. 3

Schematic illustrations of experimental apparatus

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Fig. 4

Overview images of (a) rider and (b) grooved disk

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Fig. 5

Schematic views of rider and grooved disk: (a) top view of rider and (b) top view of grooved disk

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Fig. 6

Numerical results on relationships of dimensionless minimum film thickness ĥmin, dimensionless frictional force F̂fx, and coefficient of friction μ to bearing characteristic number S for various curvature radii of groove ĝr: case A corresponds to the case where rider center Oc locates in the middle of groove width, and case B to the case where Oc locates in the middle of land width

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Fig. 7

Experimental results on relationships of degree of separation τ, dimensionless frictional force F̂fx, and coefficient of friction μ to bearing characteristic number S for various combinations of applied load W and disk rotating velocity N for ĝr=0.02. Closed symbols denote the point at which τ begins to drop from unity with decreasing S.

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Fig. 8

Experimental results on relationships of degree of separation τ, dimensionless frictional force F̂fx, and coefficient of friction μ to bearing characteristic number S for various curvature radii of groove ĝr

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Fig. 9

Numerical and experimental results on relationships of minimum film thickness ĥ0 corresponding to Λ = 3.0, dimensionless frictional force F̂fx, and coefficient of friction μ to bearing characteristic number S for various curvature radii of groove ĝr

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Fig. 10

Comparisons of numerical and experimental results on relationships of critical bearing characteristic number Sc, critical dimensionless frictional force F̂fxc, and critical coefficient of friction μc to curvature radius of groove ĝr

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