Dynamic Modeling of the Milner Continuously Variable Transmission—The Basic Kinematics

[+] Author and Article Information
S. Akehurst, D. A. Parker

Powertrain & Vehicle Research Center,  University of Bath, Calverton Down, Bath, BA2 7AY, UK

S. Schaaf

 Intersyn Technologies, 2736 Albans, Houston, TX 77005

J. Mech. Des 129(11), 1170-1178 (Sep 19, 2006) (9 pages) doi:10.1115/1.2771573 History: Received December 06, 2005; Revised September 19, 2006

In the Milner continuously variable transmission altering the axial separation between two moveable halves of the outer race set allows the radial position of the planet balls to vary, along with the contact positions on the inner and outer races and, hence, the transmission ratio changes. An inelastic analytical model implemented in SIMULINK is presented which allows the component positions, speeds, forces, and torques to be calculated. Use of a free body approach for individual components allows both individual and coupled component motions to be studied. Examples of the steady-state results and experimental verification are presented. Use of the model for dynamic investigations and to improve future versions of the transmission is discussed.

Copyright © 2007 by American Society of Mechanical Engineers
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Figure 1

The Milner CVT: (a) Photograph of the Milner CVT; (b) MCVT schematic—low ratio (high gear); (c) MCVT schematic—high ratio (low gear)

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Figure 2

Geometry of the outer raceway to planet ball contact

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Figure 3

Inner raceway geometry

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Figure 4

Geometry of idler follower to planet ball contact

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Figure 5

Definition of kinematic relationships

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Figure 6

Definition of spin velocities at the inner and outer races

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Figure 7

Free body diagrams of components of the Milner CVT: (a) The input shaft of the transmission, including the fixed half of the inner raceway; (b) the free half of the inner raceway; (c) the fixed half of the outer raceway; (d) the free half of the outer raceway; (e) the inner ball-screw thread; (f) one planet ball; and (g) the idler follower

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Figure 8

Layout of MCVT model

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Figure 9

Forces in the MCVT: (a) Contact angles; (b) operating radii and ratio

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Figure 10

Forces in the MCVT: (a) Normal forces; (b) traction forces

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Figure 11

Speeds in the MCVT: (a) Rotational speeds; (b) spin speeds

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Figure 12

Measured MCVT ratio compared to predicted ratio in an IVT configuration

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Figure 13

IVT configuration




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