External Circulation Ball Screw Return Groove for Smooth Ball Flow
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Solution Overview
Problem
Existing external circulation ball screws experience unsmooth ball flow and ball squeezing due to the height difference between the nut and return plate, leading to large impact forces when the ball diameter is small.
Innovation Solution
The design incorporates a return groove with a radius of curvature between 1.2 and 1.5 times the ball diameter, connected non-tangentially to the through holes, reducing the inner space and minimizing the reaction force upon ball impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of stationary object
If the return passage and through holes are connected in a tangential manner, then the inner space of the return section is relatively large, but the balls will inertially hit the wall surface causing ball squeezing and large impact force
Solution Approach 1:
The return passage is designed with a curved structure where the return section circles around a reference point with an arc-shaped outer wall surface. The radius of curvature is specifically controlled to be 1.2 to 1.5 times the ball diameter, creating a smooth curved path that guides balls away from direct impact with the wall surface while maintaining adequate inner space.
2Object-generated harmful factors
If the radius of curvature is increased to reduce ball impact, then the inner space of the return section increases, but this may affect the compactness of the ball screw
Solution Approach 1:
The patent specifies a precise parameter range for the radius of curvature (1.2 to 1.5 times the ball diameter) that optimizes the balance between reducing ball impact force and maintaining compact dimensions. This parameter optimization ensures smooth ball flow with minimal impact while keeping the return section size controlled and the overall ball screw compact.
3Volume of moving object
If the ball diameter is decreased for miniaturization, then the ball screw size is reduced, but the impact force and unsmoothness become more noticeable
Solution Approach 1:
The curved return passage with optimized radius of curvature creates a gradual transition path that is particularly effective for small-diameter balls. The curvature radius being 1.2 to 1.5 times the ball diameter ensures that even miniature balls can flow smoothly through the return section without sharp impacts or unsmooth motion, solving the miniaturization challenge.
Data Source
AI summary
An external circulation ball screw includes: a screw shaft; a nut sleeved on the screw shaft and including a through hole having an opening end; and a return member mounted on the nut, and including a return groove having a return section and a continuation section, one end of the return section connected to the through hole including a connecting end which abuts against the opening end. The opening end and the connecting end are non-tangentially connected, the return section circles around a reference point, the outer wall surface of the return section is arc-shaped and centered on the reference point, a distance between the outer wall surface and the reference point is a radius of curvature, and the radius of curvature is greater than or equal to 1.2 times the ball diameter, but is less than or equal to 1.5 times the ball diameter.