柱销式双螺母行星滚柱丝杠预紧机理研究

为了实现行星滚柱丝杠正反转双向精密驱动，迫切需要开展含预紧的行星滚柱丝杠传动研究。构建了一种柱销式双螺母行星滚柱丝杠无背隙传动构型。它利用双螺母的相对转角提供预紧力，并使用柱销固定该转角从而维持预紧力。建立了包含有双螺母、双滚柱以及丝杠螺纹双向受载状态的静力学模型。提出了仅受预紧力与考虑外载荷时，柱销式双螺母行星滚柱丝杠的受力和变形计算方法。通过与有限元模型载荷分布和预紧力计算结果的对比，验证了所建模型的正确性。分析了初始预紧力对螺母相对转角和柱销剪切力的影响，以及不同外载荷作用下，螺母预紧力、柱销剪切力和螺纹载荷分布的变化。结果表明，较小的螺母相对转角便会产生较大的初始预紧力，柱销剪切力远小于初始预紧力或外载荷。当外载荷增加时，螺母#1所受预紧力和柱销剪切力均会增加，螺母#2所受预紧力会减小。使得螺母#2预紧力消失时的外载荷远大于初始预紧力。

Preload Mechanism of the Double-nut Planetary Roller Screw Mechanism with Pins

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.