Roller Screw Preloading Structure for Backlash-Free Rolling Contact
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional planetary roller screw transmission devices suffer from gaps due to manufacturing or assembly errors, leading to skidding and idling of rollers, reduced frictional force, and decreased efficiency and accuracy.
Innovation Solution
A roller screw bidirectional and alternated preloading structure with built-in metal springs applies two directionally opposite axial preloads to rollers using elastic protrusions from metal springs, compensating for fitting gaps and ensuring stable rolling contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional planetary roller screw transmission device is used with standard retainer units, then the structure is simple and easy to manufacture, but gaps form between rollers and screw/nut due to manufacturing tolerances, causing skidding and reduced transmission efficiency
Solution Approach 1:
The patent applies preliminary action by pre-loading the rollers against the screw and nut using elastic elements (springs or elastomeric materials) before operation begins. This preliminary pre-loading compensates for manufacturing gaps, ensuring immediate pure rolling contact and preventing skidding from the start of operation, thereby maintaining high transmission efficiency without complex assembly procedures
Solution Approach 2:
The patent changes the physical state and mechanical properties of the contact interface by introducing elastic elements that continuously apply force, transforming the static gap condition into a dynamic pre-loaded contact state. This parameter change (from zero force to continuous elastic force) eliminates backlash and ensures stable rolling contact, improving transmission efficiency while keeping the overall structure relatively simple
2Device complexity
If retainer units are used to limit roller positions, then the structure is simple, but the rollers cannot maintain stable rolling contact due to gaps, leading to increased wear and reduced service life
Solution Approach 1:
The patent applies preliminary action by pre-loading the rollers against the screw and nut using elastic elements (springs or elastomeric materials) before operation begins. This preliminary pre-loading compensates for manufacturing gaps, ensuring immediate pure rolling contact and preventing skidding from the start of operation, thereby maintaining high transmission efficiency without complex assembly procedures
Solution Approach 2:
The patent applies beforehand cushioning by using elastic elements (springs or elastomeric materials) that continuously cushion and compensate for manufacturing gaps between rollers and the screw/nut. This prior cushioning ensures stable rolling contact and prevents harmful skidding and wear, thereby improving reliability without significantly increasing device complexity
3Manufacturing precision
If manufacturing tolerances are reduced to eliminate gaps, then rolling contact stability is improved, but manufacturing cost and complexity increase significantly
Solution Approach 1:
The patent changes the physical state and mechanical properties of the contact interface by introducing elastic elements that continuously apply force, transforming the static gap condition into a dynamic pre-loaded contact state. This parameter change (from zero force to continuous elastic force) eliminates backlash and ensures stable rolling contact, improving transmission efficiency while keeping the overall structure relatively simple
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances rolling stability, reduces wear, and extends service life by maintaining pure rolling contact and eliminating backlash, thereby improving transmission efficiency and accuracy.
Implementation Method 1
a left and a right metal spring (27, 27a) are respectively formed with a plurality of elastic protrusions (271), which radially inward extended from and axially tilt toward the roller unit (R)
Implementation Method 2
the first and the second pointed ends are pressed against the elastic protrusions on the two metal springs to deform the elastic protrusions
Data Source
AI summary
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.