柱销式双螺母行星滚柱丝杠预紧机理研究

In order to use the planetary roller screw mechanism (PRSM) to achieve the high precision transmission at the forward and reverse directions, the study of the preloaded PRSM is urgently needed. A double-nut PRSM with pins is developed, which is a backlash free mechanism. The relative angle of the double-nut is used to provide preloads and the value of the angle is fixed by pins. A static model is proposed, which includes the double-nut, double-roller and screw. The flowchart to calculate the forces and elastic deformation of parts in the mechanism with/without external forces are given. By comparing the load distribution and preload obtained from a finite element model, the feasibility of the proposed model is validated. The influence of the initial preload on the relative angle of nuts and the shearing force of pins is analyzed. Preloads of nuts, the shearing force of pins and the load distribution of threads are computed, when external forces act on the nut #2. The results show that a small relative angle could provide a large initial preload. The shearing force of pins is much smaller than the initial preload or external force. When the external force is increased, the preload of the nut #1 and the shearing force of pins are increased and the preload of the nut #2 is decreased. The value of the external force is much larger than that of the initial preload when the preload acting on the nut #2 is equal to zero.