Ball Nut Radial Outboard Raceways for Bending Load Isolation
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Solution Overview
Problem
Conventional ball nut and screw assemblies are prone to wear and seizing due to radial loads induced by bending moments, especially in articulating actuators like door opening systems and spoilers, as the outermost balls are excessively loaded, leading to reduced lifespan.
Innovation Solution
The design incorporates additional radial outboard raceways formed between concave grooves in outboard components and the external surface of the screw, which react radial loads independently of the conventional helical raceway, protecting the axial load-bearing balls from bending moments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional helical raceways are used in ball nut and screw assemblies, then axial load-bearing capacity is maintained, but radial loads from bending moments cause excessive wear and seizing of outermost balls
Solution Approach 1:
The invention divides the load-bearing function into separate segments: the conventional helical raceway handles axial loads while the additional radial outboard raceways handle radial loads from bending moments. This segmentation allows each raceway type to optimize for its specific load direction, preventing the outermost balls in the helical raceway from experiencing combined axial-radial loading that causes wear and seizing.
Solution Approach 2:
The invention adds radial outboard raceways at the ends of the ball nut that operate in a different dimensional plane (radial direction) compared to the conventional helical raceways (axial direction). This dimensional addition provides a separate load path for radial forces, isolating the axial load-bearing balls from bending moment effects.
2Duration of action of moving object
If additional radial outboard raceways are added to handle radial loads, then lifespan is extended, but device complexity increases
Solution Approach 1:
The invention merges the additional radial outboard raceways with the existing ball nut structure, allowing both helical and radial raceways to coexist in a single integrated component. The ball nut simultaneously accommodates balls in both raceway types, combining multiple functions (axial and radial load bearing) into one unified structure rather than requiring separate components.
Solution Approach 2:
The ball nut is designed with multi-functionality, serving both as the housing for conventional helical raceways and as the structure containing additional radial outboard raceways. This universal design allows a single component to handle both axial and radial loads, reducing the need for additional separate components and simplifying the overall system.
Data Source
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AI summary
A ball nut and screw assembly is described herein comprising: a screw (15), and a nut (11) received on the screw (15), a first raceway (16) having a helical portion defined between a convex groove of the screw (15) and a concave groove of the nut (11); said first raceway (16) having adjacent concave grooves to provide said helical portion, a first plurality of balls (13) provided in said first raceway (16), and further comprising a first radial outboard raceway (18) provided at a first end of said first raceway (16) and a second radial outboard raceway (19) provided at a second end of said first raceway (16), and wherein said first and second outboard radial raceways (18, 19) are formed between a concave groove formed in a first outboard component (20a) and the outermost, external surface of the screw (15) that is in a position between said adjacent grooves of said screw (15) and at least a first bearing ball (13a) provided in said first radial outboard raceway (18) and at least a second bearing ball (13b) provided in said second radial outboard raceway (19).