A Self-Actuating Traction-Drive Speed Reducer

[+] Author and Article Information
Donald R. Flugrad, Abir Z. Qamhiyah

Department of Mechanical Engineering,  Iowa State University, Ames, IA 50010

J. Mech. Des 127(4), 631-636 (Sep 09, 2004) (6 pages) doi:10.1115/1.1897410 History: Received July 30, 2003; Revised September 09, 2004

Traction-drive speed reducers offer certain advantages over geared speed reducers. In particular, they generally run quieter than geared units and provide an opportunity for higher efficiency by eliminating sliding motion between contacting elements. In order to generate a sufficiently high output torque, some means must be provided to create a normal force between the rolling elements. This normal force, along with the friction coefficient, enables the device to transmit torque from one rolling member to the next. The speed reducer proposed here is designed so that the configuration of the rolling elements creates the needed normal force in response to the torque exerted back on the system by the downstream loading. Thus the device is self-actuating. Since the normal force is only present when needed, the rolling elements of the device can readily be disengaged, thus eliminating the need for a separate clutch in the drive system. This feature can be exploited to design a transmission with several distinct speed ratios that can be engaged and disengaged in response to changing speed requirements.

Copyright © 2005 by American Society of Mechanical Engineers
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Figure 2

Traction-drive speed reducer with midplate in place

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Figure 3

Possible traction-drive configuration for transmission application

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Figure 4

Geometry and forces related to one set of intermediate rollers

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Figure 1

Typical configuration of self-actuating, traction-drive speed reducer

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Figure 5

Geometry and forces for one typical outer intermediate roller



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