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Research Papers

Traction and Efficiency Performance of the Double Roller Full-Toroidal Variator: A Comparison With Half- and Full-Toroidal Drives

[+] Author and Article Information
L. De Novellis, G. Carbone, L. Mangialardi

Dipartimento di Ingegneria Meccanica e Gestionale,  Politecnico di Bari, v.le Japigia 182, 70126 Bari, Italy

J. Mech. Des 134(7), 071005 (Jun 08, 2012) (14 pages) doi:10.1115/1.4006791 History: Received September 12, 2011; Revised May 02, 2012; Published June 07, 2012; Online June 08, 2012

In this paper, we analyze in terms of efficiency and traction capabilities a recently patented toroidal traction drive variator: the so-called double roller full-toroidal variator (DFTV). By employing a relatively simple model of the elastohydrodynamic contact behavior between the disks and rollers, we compare the performance of the DFTV with classical solutions as the single-roller full-toroidal variator (SFTV) and the single-roller half-toroidal variator (SHTV). Interestingly, the DFTV shows an improvement of the mechanical efficiency over a wide range of transmission ratios, and in particular at the unit speed ratio, as in such conditions the DFTV allows for zero-spin thus strongly enhancing its traction capabilities. The relation between the torque transmission and the operational volume is also investigated for the three toroid geometries. In this case, the better performance is achieved by the SHTV, whereas the other two geometries show a similar behavior.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

The three toroid geometries: SHTV (a), SFTV (b), and DFTV (c)

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Figure 2

The geometrical quantities of the double full-toroidal vairator (DFTV in (a)) and of the half-toroidal variator (SHTV in (b))

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Figure 3

The kinematic quantities of the DFTV (a) and SHTV (b)

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Figure 4

The kinematic quantities of the DFTV (a) and SHTV (b) in no-spin conditions

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Figure 5

The spin coefficients at the input and output disks as a function of the geometric speed ratio. The DFTV variator shows smallest spin values, the SHTV has better behavior than the SFTV which shows largest spin values over the whole range of the considered geometric ratios.

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Figure 6

The forces and moments acting on the DFTV elements

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Figure 7

The reference frames

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Figure 8

The DFTV variator performance. The dimensionless output torque tout as a function of the overall creep coefficient Cr and the overall mechanical efficiency ν as a function of the input torque coefficient tin for the three geometric ratios (srID=0.5, srID=1, srID=2). Calculations are shown for FN  = 20 kN.

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Figure 9

The dimensionless output torque tout as a function of the overall creep coefficient Cr and the overall efficiency ν as a function of the input traction coefficient tin for the three toroid geometries (DFTV, SFTV, SHTV). Calculations are shown for different geometric ratios and for a constant normal load FN  = 20 kN.

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Figure 10

The dimensionless output torque tout as a function of the overall creep coefficient Cr and the overall efficiency ν as a function of the input traction coefficient tin for the three toroid geometries (DFTV, SFTV, SHTV). Calculations are shown for different geometric speed ratios and for a constant normal load FN  = 20 kN.

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Figure 11

The torque efficiency νT as a function of the input traction coefficient tin for the three toroid geometries (DFTV, SFTV, SHTV). Calculations are done at different geometric ratios and keeping constant the normal load at the value FN  = 20 kN.

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Figure 12

The input and output spin momentum coefficients χ as a function of the overall creep coefficient Cr and the overall efficiency ν as a function of the input traction coefficient tin for the three toroid geometries (DFTV, SFTV, SHTV). Calculations are shown for different geometric ratios and for a constant normal load FN  = 20 kN.

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Figure 13

The output torque Tout as a function of the operational volume Vo for the three toroid geometries: DFTV, SFTV, SHTV. Calculations are shown for srID=0.5, μin  = 0.05 and for FN  = 5, 12 kN.

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