Research Papers

Axial Thrust Force of Compound Planetary Spur Gear Set

[+] Author and Article Information
Yang Fuchun, Zhou Jutao, Zhou Xiaojun

Zhu Hongqing

 Department of mechanical engineering, Zhejiang University, Hangzhou 310027, Chinazhuhongqing666@163.com

J. Mech. Des 133(9), 091004 (Sep 09, 2011) (7 pages) doi:10.1115/1.4004806 History: Received June 02, 2010; Revised July 26, 2011; Published September 09, 2011; Online September 09, 2011

Planetary gears are widely used in automotive and aerospace applications. Traditionally, automatic transmissions have four forward speeds, which can be achieved by using two planes of single pinion (sun-pinion-ring) planetary gear sets. Recently, there is a trend that transmissions have more than five forward speeds, which make compound planetary gear sets with two pinions (ring- or sun-pinion1-pinion2-ring) becoming common. Due to demands for higher power density and compactness, needle bearings are often used in these gear sets. There are significant axial thrust forces between the pinions and the carrier, which could lead to excessive wear of thrust faces and deterioration of bearing system performance. In this paper, we analyzed generation mechanism of axial thrust force in compound planetary spur gear set and calculated the axial thrust force. It was shown that axial thrust force always exists because of the torsional pendulum torque acting on the long planet. Experimental test for a compound planetary spur gear was taken to study axial thrust force and validate the theory calculation.

Copyright © 2011 by American Society of Mechanical Engineers
Topics: Force , Thrust , Gears , Spur gears , needles
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Figure 1

Structure of compound planetary spur gear set

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Figure 2

Compound planetary spur gear set and the test rig

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Figure 3

Special sensors for radial and axial forces measurement of planets

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Figure 4

Test results of No.1 long planet (a) Ωr1  = 0 rpm, Tc  = 1000–4000 Nm; (b) Ωr1  = 1200 rpm, Tc  = 1000–4000 Nm; (c) Tc  = 1931 Nm, Ωr1  = 200–1200 rpm with interval 100 rpm; (d) Ωr1  = 500 rpm (clockwise and anticlockwise), Tc  = 500–4000 Nm.

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Figure 5

Loadings on the long and short planets of compound planetary spur sets

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Figure 6

Forces on long planet and short planet

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Figure 7

Sketch map of planet tilt, needles skew and the load distributions

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Figure 8

Kinematic relationships of needle, planet bore and pin

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Figure 9

Axial thrust forces under different radial clearances and radial forces

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Figure 10

Relationship between axial thrust forces and radial forces of long planet



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