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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.

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.