Slipping Motion in Nutless Planetary Roller Screw Mechanisms of Linear Electromechanical Drives

Abstract

Rolling screw mechanisms, used in linear electromechanical drives, have many advantages and disad-vantages as well. The most important of these is slipping. The most promising roller screw mechanisms are planetary roller screw mechanisms, the manufacture of threaded parts of which requires expensive special machines manufactured by Western companies. Taking into account the import substitution strategy, nut-less roller screw mechanisms (NRSM) were developed and patented in Russia, in which a threaded part that is the most difficult to manufacture, namely a nut, the high-precision internal multistart thread of which is tempered to a high hardness, is absent. Using domestic universal machines, prototype NRSM samples were made, which were subject to comprehensive experimental studies. It turned out that the neg-ative impact of slipping is felt to a greater extent for prototype NRSM samples than for known designs of planetary roller screw mechanisms. To reduce this impact, the paper considers in detail the process of slipping and the main reasons that cause it. In addition, the results of experimental studies of this phe-nomenon using prototype samples are analyzed. It turned out that the slipping motion depends on: the value of the angular velocity of the input link of the mechanism, the value of the axial force that the out-put link of the mechanism overcomes over the full (forward and reverse) stroke, the manufacturing accuracy of threaded parts of NRSM, the direction of the axial force (along the longitudinal axis x or against it). The latter is an important scientific finding in the study of the slipping motion in NRSM. Another rea-son for a slipping motion is the design feature of the prototype sample, which had rollers with a modified profile. Usually, the profile of the roller turns is drawn along the arc of the circle, the center of which is located on the roller axis. The modified profile of the roller turns consists of three series-connected straight line segments, which affects the transmission ratio of the mechanism. For comparison, it is neces-sary to perform an experiment with a mechanism having rollers with a traditional profile of turns.