Analysis of Load Capacity for Planetary Roller Screw Mechanism with Pitch Diameter Modification

This paper proposed the pitch diameter modification method of the screw and the roller for the standard planetary roller screw mechanism (PRSM) to increase its load capacity. Firstly, the kinematics modeling of the standard PRSM is introduced, which reveals the matching relationship of screw parameters among the screw, the roller and the nut. Based on the meshing principle of space cross threads between the screw and the roller, constraint equations of contact points between the two components are further completed, and the exact pitch diameter of the screw is determined by iterative methods. And then, the pitch diameter modification of the screw and the roller is proposed. Finally, simulations about motions and load capacity are analyzed. The results show that the pitch diameter modification method can effectively ensure the assembly and load capacity optimization of the standard PRSM.