Developing the Durability of a Dual-Cavity Full-Toroidal IVT Variator

An infinitely variable traction drive transmission (IVT) has the potential to provide significant improvements in fuel economy, tailpipe emissions and driveability compared to conventional automotive transmissions. Recent developments in rolling contact materials and manufacturing methods have increased the ability of the variator elements to withstand the high Hertzian contact pressure, temperature and tangential shear force. Described in this paper are the results of an experimental study of the main factors influencing the spalling and surface distress fatigue life and surface texture modification of the variator elements. The experimental work utilised a number of full scale variator durability test rigs, all tests were conducted with realistic contact geometry and operating conditions. Qualitative and quantitative analysis of the contact surfaces, including optical micrographs, SEM, 3D areal surface profile data and metallurgical analysis before and after test has been carried out. The fatigue results are discussed and analysed in relation to current rolling contact fatigue theories.