Deterministic Design for Load Capacity Enhancement in Planetary Roller Screw Mechanism With Different Thread Profiles

Abstract Load distribution in the planetary roller screw mechanism (PRSM) is typically non-uniform, leading to extremely high contact pressure and shortening the service life. This study presented a deterministic design method to address the inherent non-uniformity of load distribution. By the matching design of screw, roller, and nut pitch, the deformation coordination that causes uneven load distribution was effectively compensated. The structural parameters and thread profile of PRSM were further optimized to enhance load capacity. The effects of installation configurations, structural parameters, and thread profiles on the load capacity performance of PRSM were comprehensively explored. A larger nominal diameter ratio of roller to screw reduces the maximum contact pressure on the nut–roller interface consistently, while the pressure on the screw–roller interface decreases initially and then increases, with an about 5/8 ratio offering the optimal balance for load capacity performance across both interfaces. A smaller pitch leads to a more uniform load distribution and a reduction in the maximum contact pressure. Additionally, convex–concave–concave thread profiles for screw, roller, and nut effectively minimize the maximum contact pressure on both interfaces. This study provides a highly effective and innovative tool for the structural design of PRSM with high load capacity.