Study of Half Toroidal Continuously Variable Transmission: (2nd Report, Some Findings on the Traction Surface)

Explication of the traction surface is one of the most important subjects for the traction-drive-type continuously variable transmission for automotive use. We made a half-toroidal CVT which could be installed in a 1300cc motorcycle engine, and performed a life test successfully at the fixed ratio. The temperature of the traction oil was 110-120°C. The maximum contact pressure of the traction surface was 2.15 GPa and the surface velocity was 24.2 m/s. After the life test, the shape of the disc and roller was measured. The traction surface roughness of the input disc was also measured and was observed by scanning electron microscope. Oil film thickness was calculated by Hamrock's formula in a life test condition. Owing to the observation of the traction surface and oil film calculation, we estimated that a 0.3 μm oil film could exist between two rolling elements of heavy traction drive.