Research on Contact and Wear Characteristics of the Planetary Roller Screw Mechanism with Screw Misalignments

Abstract

Misalignments are unavoidable in most applications of the planetary roller screw mechanism (PRSM) due to many potential causes. However, the effect of screw misalignments on the contact characteristics for the PRSM have not been thoroughly investigated. In this paper, a comprehensive analytical procedure for the PRSM performance considering screw misalignments is proposed. First, the contact positions and clearances of the PRSM with screw misalignments are calculated. Next, an improved model is presented for evaluation of the load distribution, in which the variation of axial clearances is taken into consideration. The numerical results are validated by finite element analysis. Then, the precision loss model caused by wear is derived considering the variation of contact forces. The results indicate that the contact positions slightly change due to the misalignment angle of the screw, while the axial clearances and load distribution at the screw-roller interface are significantly affected. At the same time, the contact forces over thread vary periodically. In addition, the screw misalignment aggravates the wear of the PRSM, resulting in accuracy degradation. The theoretical investigations lay the foundation for the engineering application of the PRSM.