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RESEARCH PAPERS

# New Model of a CVT Rocker-Pin Chain With Exact Joint Kinematics

[+] Author and Article Information
Lutz Neumann

Department of Mechanical Engineering, Technical University of Munich, Boltzmannstrasse 15, 85748 Garching, Germanyneumann@amm.mw.tum.de

Heinz Ulbrich, Friedrich Pfeiffer

Department of Mechanical Engineering, Technical University of Munich, Boltzmannstrasse 15, 85748 Garching, Germany

J. Comput. Nonlinear Dynam 1(2), 143-149 (Nov 28, 2005) (7 pages) doi:10.1115/1.2162869 History: Received May 02, 2005; Revised November 28, 2005

## Abstract

The improvement of continuously variable transmissions (CVTs) is a challenging task. Detailed dynamic models of the system are needed for the optimization process. This paper introduces a new model of a rocker-pin chain, which is the central part of a chain CVT. During the derivation of the equations of motion, special attention is turned on the exact description of the joint kinematics. An interesting method to speed up the numerical simulation of the chain drive is introduced, which takes into account the special structure of the mass matrix. Simulation results show the strong influence of the geometry of the rocker-pin joints on the dynamics of the whole gear. Further reasonable gear efficiencies can be estimated for arbitrary joint geometries. This model is an excellent basis for further work on optimization of the CVT chain.

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## Figures

Figure 8

Comparison of gear efficiency for different chain models for joint geometry: r=0.03, r0=0.03, δ=0. Transmission ratio i=1.5, kinematical excitation of pulley A, ω=62.8rad∕s and external moment M2=−150Nm.

Figure 1

CVT drive

Figure 2

Rocker-pin chain

Figure 3

Inner contour of a rocker pin: two symmetric halves, each an involute to a circle. The pictured circle is only used for the construction of the upper half. The lower half is the reflection of the upper half with respect to the symmetry line SX0.

Figure 4

Angular position of a rocker pin relative to the corresponding link plate

Figure 5

Kinematics of an angled rocker-pin joint

Figure 6

Model of the rocker-pin chain

Figure 7

Comparison of the FFT of the bearing forces of pulley B (without static parts) for three different joint configurations: common rotational joint (top), rocker-pin joint without rotation (middle) and with rotation (bottom). Transmission ratio i=1.0, kinematical excitation of pulley A ω=104.7rad∕s and external moment M2=−50Nm.

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