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Because of their smooth torque transmission, high efficiency, low noise, and high running accuracy, planetary roller type traction drive units are becoming a common, widely used a speed increaser that can achieve rotational speeds of ten thousand RPM, or a speed reducer that has very small angular velocity fluctuation. When it is utilized as a transmission, particularly grease lubrication, traction damage is caused by excessive torque load and lubricant deterioration. This paper examines traction damage caused by torque load, using a machine tool high rotational speed planetary roller type traction drive unit with grease lubrication, and the practicality of an oil film monitor using electrical resistance, and direct current power source for monitoring the oil film condition of traction surface.

Whilst infinitely variable traction drive transmissions (IVT) have demonstrated the potential to provide significant fuel economy benefits through the optimisation of the vehicle powertrain, greater emphasis is now being placed on reducing the overall package size. The inevitable increase in power density places increased demands on the variator elements to withstand the heavily loaded rolling contact conditions. Described in this paper are the results of an experimental fatigue test program undertaken to establish the fatigue life of the variator rolling contacts when operating with the latest traction fluids. The experimental work utilised a number of full scale variator durability test rigs: all tests were conducted with real transmission contact operating conditions up to 220kW. Qualitative and quantitative analysis of the contact surfaces, including SEM, 3D area surface profile data and metallurgical analysis has been carried out.

Nowadays, bearings for motorcycle engines are required to be compact and light weight and have a considerably high performance. In order to meet these requirements, two measures were developed, that is High Refining Steel (HRS) and Special Heat Treatment (SH Treatment). In this paper described are the characteristics of HRS and SH Treatment and the results of investigation on them. The investigation results show that bearings of HRS and bearings with SH Treatment have more than twice longer life than standard bearings, particularly the bearings with SH Treatment have longer life even under lubricating conditions with a low viscous lubricating oil or with a contaminated lubricating oil. As a matter of fact, the bearings of HRS and the bearings with SH Treatment are used for the motorcycle engines and show excellent performances.

A full-toroidal CVT has been expected as a new generation of transmission. However, high contact pressure is needed to generate traction force and temperature due to shear in contact areas becomes very high. Therefore, the fatigue life of variator is insufficient. This paper describes the application of developed bearing steel to improve the fatigue life of the varitator. Failure due to pitting depends on a film parameter Λ so that the limitation of Λ to prevent failure has been determined by a two roller test machine. Durability test of the variator made of developed bearing steel with the larger Λ than the limitation has been carried out to confirm the prevention of pitting by a dual-cavity full-toroidal CVT's variator test rig. The thickness of EHD (Elastohydrodynamic) fluid film has also been calculated by isothermal Newtonian EHD analysis with spin motion to confirm whether adequate film thickness is provided to avoid failure.