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. The following results are obtained: (1) Braking of the oil film under an even load in the traction drive unit could be monitored. (2) The oil film condition in the traction drive unit at 10 m/s of mean rolling speed could be monitored. (3) The replacement period for the grease in traction drive unit could be determined.