Tribological optimization of a toroidal-type continuously variable transmission

Abstract

Continuously variable transmissions (CVTs) are mechanical devices that allow a continuous variation of the output velocity by adjusting its internal geometrical configuration. Through the use of an epicyclic gear set, a CVT can deliver an infinite number of transmission ratios, allowing the vehicle's engine to operate within a higher efficiency envelope for longer periods of time. This offers several advantages over traditional transmissions such as better fuel efficiency, quieter operation, and a lower mass. Current efforts to reduce the vehicles’ fuel consumption in order to protect the environment and save fuel have seen a recent revival in CVT research, especially in the automotive industry. This article documents a successfully implemented search algorithm for the dimensional optimization of a novel CVT design in order to determine the maximum theoretical efficiency of the device. In addition to showing an economical and simple method of calculating contact losses, this method of optimization also proved to be a powerful tool that can be used to select the dimensions of the transmission to fulfil any desired characteristics.

Keywords

optimization traction drive efficiency continuously variable transmission

Get full access to this article

View all access options for this article.

References

Boos

Mozer

Ecotronic: the continuously variable ZT transmission (CVT). SAE paper 970685, 1997.

Kluger

M. A.

Fussner

D. R.

An overview of current CVT mechanisms, forces and efficiencies. In Proceedings of the Transmission and Driveline Systems Symposium. 1997, SAE paper 970688, SP-1241, 81–88.

Cretu

O. S.

Glovnea

R. P.

Constant power continuously variable transmission (CP-CVT): operating principal and analysis. J. Mech. Des., 2005, 127(1), 114–119.

Tevaarwerk

J. L.

Johnson

K. L.

The influence of fluid rheology on the performance of traction drives. J. Lubr. Technol., 1979, 101(3), 1015–1022.

Anghel

Glovnea

R. P.

Spikes

H. A.

Friction and film-forming behaviour of five traction fluids. J. Synth. Lubr., 2004, 21(1), 13–32.

Newall

Lee

Measurement and prediction of spin losses in the EHL point contact of the full toroidal variator. Transient processes in tribology Dalmaz

Lubrecht

A. A.

Dowson

Priest

. In Proceedings of the 30th Leeds–Lyon Symposium on Tribology, Tribology and Interface Engineering Series, 2003, 43, 769–779 (Elsevier).

Tanaka

Power transmission of a cone toller toroidal traction drive. JSME Int. J. III, 1989, 32(1), 82–90.

Johnson

K. L.

Contact mechanics, 1985 (Cambridge University Press, Cambridge, UK).

Hirst

Moore

A. J.

Elastohydrodynamic lubrication at high pressures. Proc. R. Soc. Lond. A, 1978, 360(1702), 403–425.

10.

Chittenden

R. J.

Dowson

Dunn

J. F.

Taylor

C. M.

A theoretical analysis of the isothermal elastohydrodynamic lubrication of concentrated contacts. Proc. R. Soc. Lond. A, 1985, 397, 245–269.

11.

Witte

D. C.

Operating torque of tapered roller bearings. ASLE Trans., 1973, 16(1), available from http://www.informaworld.com/smpp/content~db=all~content=a781430109~frm=titlelink , 61–67.

12.

Boness

R. J.

Churning losses of disks and gears running partially submerged in oil. In Proceedings of the International Power Transmissions and Gearing Conference. 1989, Chicago, Illinois, 1, 255–359.

13.

Kennedy

Eberhart

Particle swarm optimization. In Proceedings of the IEEE International Conference on Neural networks IV. 27 November–1 December 1995, Perth, Australia, 1942–1948.

14.

Andrzej

Stanislaw

A new constraint tournament selection method for multi-criteria optimization using genetic algorithm. In Proceedings of the Congress on Evolutionary computation CEC’00. 16–19 July 2000, California, 501–508.

15.

Kluger

M. A.

Long

D. M.

An overview of current automatic, manual and continuously variable transmission efficiencies and their projected future improvements. SAE paper 1999-01-1259, 1999.