FORCE ANALYSIS OF A PLANETARY ROLLER DRIVE TAKING INTO ACCOUNT THE CONTACT COMPLIANCE OF THE MATING THREAD TURNS OF ITS PARTS

Abstract

The objects of study are planetary roller drives (PRD), which have high performance characteristics and are the most promising mechanical converters of rotational motion into linear motion. They are widely used as part of high-tech machines. Their design requires reliable force analysis. To do this, we need to determine the forces acting on the roller, which is an intermediate part between the nut and the screw. Several works provide approximate methods for the force calculation of the PRD, but in them, as an assumption based on similar calculations of machine parts, the distribution of the load between the roller thread turns interacting with the screw turns and with the nut turns is accepted. In this work, based on the fundamental principles of mechanics, using the necessary assumptions, a numerical method for determining forces is developed. These forces act in the PRD between the mating thread turns of the roller and the screw and between the mating thread turns of the roller and the nut, taking into account only one influencing factor – the momentum that overturns the roller. To implement this method, due to the very large amount of calculations, a computer program was developed. Usually, for force calculations of roller drives, the coefficient of uneven loading (Кн) of roller thread turns is introduced. For the control calculation of a PRD of standard size 20×8 with a four-thread screw and a length of the threaded part of the nut of 56 mm, Кн = 1.509, which is a very large value and shows the large influence of the overturning momentum on the load distribution between the roller threads. To determine the real unevenness of load distribution in the PRD, it is necessary to conduct further research that takes into account other factors influencing the uneven distribution of load in the PRD. In this case, the next most important factor is the uneven distribution of the total axial force between the rollers. This force is applied to the PRD from the actuator.