New design of gapless planetary roller screw mechanism

Abstract

Advanced planetary roller screw mechanisms (PRSM) are divided into mechanisms with gaps and gapless devices, where gaps are compensated using various methods. Gapless mechanisms are superior in accuracy and rigidity compared to mechanisms with gaps, but inferior to them in load capacity and useful life, i.e. there appears a contradiction between accuracy and rigidity, on the one hand, and load capacity and useful life, on the other. The given article is aimed at overcoming this contradiction and proposes a new method for compensating gaps in a PRSM and a new design of gapless mechanism. This design consists of a power mechanism and a mechanism for converting rotational motion into translational motion. The most important component of the power mechanism is a split collet, which when interacting with the housing reduces the pilot hole diameter. The most significant component of the mechanism designed to convert rotational motion into translational motion is a solid nut manufactured in the form of a thin-walled cylindrical shell. When the split collet is compressed, the solid nut-shell is deformed in radial direction and compensates for gaps between all the threaded components. Two half nuts are used in the known designs of a gapless PRSM. It should be noted that in this case only a single half nut is exposed to the working axial force, and in the new design of a gapless PRSM that is the solid nut. Therefore, the new mechanism is provided with significantly greater load capacity and ensures longer useful life.