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Research Papers

Operation and Kinematic Analysis of a Cam-Based Infinitely Variable Transmission

[+] Author and Article Information
Derek Lahr

Department of Mechanical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061dlahr@vt.edu

Dennis Hong

Department of Mechanical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061dhong@vt.edu

J. Mech. Des 131(8), 081009 (Jul 27, 2009) (7 pages) doi:10.1115/1.3179004 History: Received April 06, 2008; Revised May 12, 2009; Published July 27, 2009

In this paper, the operation and analysis of a novel, highly configurable, infinitely variable transmission of the ratcheting drive type is presented. This particular drive uses a cam and a number of cam followers rotatably mounted to a carrier plate to generate an oscillatory motion in an equal number of planet gears. A number of indexing clutches are then used to rectify this motion into a rotational output. A full description of the mechanism, including its components, operation, and kinematic equations, are presented. There are a number of inversions of this device, and their characteristics and limitations are discussed. In addition, a method is presented to select the most suitable inversion, gearing, and maximum follower velocity for a given set of requirements.

Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Simplified portrayal of the cam-based IVT

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Figure 2

Complete computer aided design (CAD) model of the cam-based IVT

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Figure 3

Motion of cam-based IVT with the cam as the input and sun as the output

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Figure 4

Motion of cam-based IVT with the sun gear as the input and carrier as the output

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Figure 5

Two degree of freedom shifter assembly of the cam-based IVT

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Figure 6

Prototype cam-based IVT with shifter ring and guides visible

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Figure 7

The follower’s velocity and position as a function of the cam rotation

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Figure 8

Overlay of two velocity profiles shows that a smooth output velocity is attainable

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Figure 9

Planet gearset representative of the cam-based IVT

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Figure 10

Trapezoidal acceleration curve and the modified version for improved cam performance

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Figure 11

Follower position versus the carrier angle and the follower position along the length of the cam

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Figure 12

Resulting camoid shape

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Figure 13

Reference for contact force equations

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Figure 14

Sum of the moments on the follower about its axis of rotation

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Figure 15

Contact force between the roller and the cam versus follower velocity and initial follower position

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Figure 16

Maximum offset of the followers during normal operation

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