High-pressure behavior of toroidal CVT fluid for automobile

Practical toroidal-type continuously variable transmission (t-CVT) is subjected to extremely severe operating conditions, viz., maximum contact pressure is very high at 4 GPa, rolling speed exceeds over 30 m/s and lubricant temperature goes up over 140 °C. Traction measurements were recently made at wide range of contact pressures, oil temperatures and rolling speeds by USCAR Group. The objective of this research is to investigate high-pressure rheology of the traction characteristics at extremely severe EHL contact conditions. The effects of contact pressure and temperature on maximum traction coefficient were evaluated using the phase diagram and the liquid/solid transition lubrication diagram.