A novel planetary thread roller bearing: Design and analysis of load characteristic
Abstract A novel planetary thread roller bearing (PTRB) was proposed in this paper based on Herz theory combined with multiple principles (e.g. equivalent steel ball, multi-point meshing and power dividing). A significant improvement in load-carrying capacity, comparing the current bearing, was achieved and thus providing a new option for the advanced equipment with high thrust-to-weight ratio requirement. The newly proposed PTRB exhibited a 83 % increase in dynamic axial load rating while a comparable static axial load rating comparing with the thrust ball bearing with a comparable size. In addition, the relationship between friction torque and bearing rotating speed, contact point number and axial load was discussed. It was found that, given a proper installation space, increasing the thread roller number could not only significantly improve the axial load rating of PTRB, but also reduce the friction torque. Furthermore, the working efficiency of the new PTRB was constantly higher than 97 %. A self-degradation operation was achieved by the system when some thread rollers were stuck, which improved the system fault tolerance. Finally, friction torque tests were performed on the self-developed test instrument. The results showed a good agreement with the theoretical analysis.