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Article

Application of a System Level Model to Study the Planetary Load Sharing Behavior

[+] Author and Article Information
Avinash Singh

Advanced Gear Systems Group, Advanced Power Transfer, GM Powertrain  General Motors Corporation, 30240 Oak Creek Drive, Wixom, MI 48393 avinash.singh@gm.com

J. Mech. Des 127(3), 469-476 (Jun 23, 2004) (8 pages) doi:10.1115/1.1864115 History: Received August 22, 2003; Revised June 23, 2004

In planetary transmissions, the input torque is split between a number of parallel sun-pinion-ring gear paths. Under ideal conditions, each parallel path carries the same amount of torque. However, manufacturing errors in the pinion pin-hole location cause unequal load sharing between the parallel paths. The nature of this load sharing behavior depends upon the number of pinions in the planetary system. This load sharing behavior is studied for 4, 5, and 6-pinion variants of a planetary transmission. Critical manufacturing tolerances are identified and loss function curves are generated. The effects of sun gear support stiffness and pinion needle bearing stiffness on the load sharing results are also studied. It is shown that as the number of pinions in a planetary transmission increases, the pin-hole position error tolerance has to be tightened in order to reap the full benefits of load sharing between the pinions. Gear system analysis modules (GSAM) is an analytical tool that can model entire gear systems and will be used in this paper to quantify the load sharing between pinions. The numerical techniques implemented in GSAM will be briefly reviewed.

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Copyright © 2005 by American Society of Mechanical Engineers
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Figures

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Figure 1

Examples of GSAM models of (a ) planetary, (b ) ravigneaux (double pinion), (c ) countershaft gear sets

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Figure 2

A planetary carrier model

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Figure 3

(a ) Schematic contact model; (b ) contacting grid cells in a spur gear example, (c ) resulting contact pressure distribution, (d ) resulting load distribution

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Figure 4

Pin-hole position error

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Figure 5

Effect of radial and tangential pin-hole position error on load sharing in a four-pinion planetary transmission (floating sun gear)

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Figure 6

Influence of sun gear support condition

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Figure 7

Mesh load sharing—five pinion design variant (floating sun gear)

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Figure 8

Mesh load sharing—six-pinion design variant (floating sun gear)

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Figure 9

Loss function curves for the four, five, and six-pinion variants

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Figure 10

Mesh load sharing as a percentage of total load

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Figure 11

Trade-off study: (a ) four and five-pinion variants and (b ) five and six-pinion variants

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Figure 12

Effect of reducing the bearing stiffness (floating sun gear)

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Figure 13

Mesh load sharing for reduced bearing stiffness

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