Thread load balance design method of planetary roller screw mechanism

In order to achieve thread load balance design of planetary roller screw mechanism (PRSM), i. e. to make the applied load uniformly distributed among the threads of roller, two sections which include structural parameters design and thread tolerance design are studied in this paper. Firstly, two criteria are presented to guide the parameters design of thread form, which include intensity criterion and yield criterion of contact, and base on which, the rated load and limit load of thread and the criteria of parameter design are developed. Secondly, the effects of parameters of PRSM on load distribution are investigated by univariate analysis, and the nature of effect of parameters on load distribution are obtained. Results show that the nature of parameters optimal design is to search for a combination of shaft section stiffness of screw, roller and nut which can help to reach a uniform load distribution. Lastly, the effects of pitch deviations that obey normal distribution on load distribution are investigated, and approach of tolerance design are presented, which is identified to be effective to reach a uniform distribution of applied load among threads of roller.