Curvilinear Roller Screw Threads for Higher Load Capacity
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Solution Overview
Problem
Roller screw mechanisms are limited by point contact geometries, which restrict their load capacity and lifespan due to small areas bearing mechanical forces.
Innovation Solution
Implementing a roller screw mechanism with curvilinear contact geometries, where the threads of the rollers are complementary to those of the screw and nut, allowing contact along offset angular planes, thereby distributing forces over larger areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If point contact geometries are used in roller screw mechanisms, then the mechanism structure is simple, but the load capacity and lifespan are limited due to small contact areas
Solution Approach 1:
The patent applies curvilinear contact geometry where the threads of rollers, screw, and nut are designed with complementary curved profiles. This curvature transformation converts point contact into line contact, significantly increasing the contact area and distributing mechanical forces over larger surfaces, thereby enhancing load capacity and lifespan without fundamental structural changes to the mechanism
2Duration of action of stationary object
If point contact geometries are used in roller screw mechanisms, then the manufacturing is simpler, but the lifespan is reduced due to concentrated mechanical forces
Solution Approach 1:
The complementary curvilinear thread profiles are designed to create extended line contact zones between rollers, screw, and nut. This geometric configuration distributes stress over larger areas, reducing wear and fatigue, thereby extending the lifespan of the mechanism while maintaining manufacturability through precise but achievable curved surface geometries
3Reliability
If curvilinear contact geometries are implemented, then load capacity and lifespan are enhanced, but the thread profile complexity increases
Solution Approach 1:
The patent implements complementary curvilinear profiles specifically at the contact zones of the threads, while other portions of the components can maintain simpler geometries. This localized application of complex curvature where it is most needed (at contact surfaces) optimizes reliability without unnecessarily complicating the entire component structure
Solution Approach 2:
The curvilinear contact geometry creates extended line contact between mating threads, transforming point contact into line contact. This increases the effective contact area and distributes loads more evenly, enhancing reliability through improved stress distribution while the complementary nature of the curves ensures proper meshing
Data Source
AI summary
The invention relates to a roller screw mechanism comprising a screw (110) provided with an external thread; a nut (130) coaxially surrounding the screw (130) and provided with an internal thread; and rollers (120), each of which is provided with an external thread, each roller (120) being interposed between the screw (110) and the nut (130) so that the threads of the rollers mesh with the threads of the screw and of the nut; said roller screw mechanism being characterized in that the threads of the rollers are complementary to the threads of the screw and of the nut so that, at zero load, the threads of the rollers co-operate on both of their flanks with the threads of the screw and of the nut in a contact geometry having curvilinear segments.