A frictional heat model of planetary roller screw mechanism considering load distribution

Planetary roller screw (PRS), with higher thrust, higher load capacity, and higher speed, is the best choice of the transmission component of the servo system. However, spinning sliding of rollers and support bearings can cause frictional moments and frictional heat, which is an undesirable phenomenon. Besides, frictional heat will further result in high temperature that causes deterioration of lubrication and eventually lead to destruction of the mechanism. Therefore, it is important to predict frictional moments which result in frictional heat. In order to predict the magnitude of frictional heat of PRS mechanism and study the influence of structural parameters of thread and operating conditions on frictional heat, first, a frictional moment model of bearings is built, and frictional moments models of PRS considering the elastic hysteresis of material, the spinning sliding of the rollers, the viscosity of lubricating oil and the differential sliding of thread raceways are established in this paper, respectively. Second, heat generation models of bearing and PRS are presented, respectively. Finally, relationships between frictional heat in terms of operating conditions of PRS, contact angle, and helix angle of roller thread are investigated. The achievements of this project will provide theoretical basis for the design of PRS with lower frictional moments and higher transmission efficiency.