Roller screw bidirectional and alternated preloading structure with built-in metal springs

Abstract

A roller screw bidirectional and alternated preloading structure includes a screw, a nut fitted around the screw, a roller unit including first and second rollers alternately arranged between and meshing with the screw and the nut, two preload maintaining units located at two ends of the roller unit and respectively including a retainer including retaining holes for receiving locating ends of the rollers and a metal spring including circumferentially spaced elastic protrusions tilted toward the roller unit and radially offset from the retaining holes, and a retaining unit. Gaps are formed between bottoms of the retaining holes and the locating ends, while the elastic protrusions are pressed against and elastically deformed by pointed ends of the rollers to create two opposite preloads alternately applied to the first and second rollers from two directions. This structure compensates fitting gaps and enables increased transmission accuracy and motion stability of the roller screw.