Internal Deflector Ball Screw Geometry for Stable Ball Return
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Solution Overview
Problem
Internal deflector type ball screws face issues with entering-exiting fluctuation of balls due to complex three-dimensional curve shapes in ball return paths, leading to reduced smooth circulation and potential load imbalance, and existing solutions either deform during heat treatment or have reduced load capacity due to interposed elastic bodies.
Innovation Solution
The ball screw design includes a circulation portion with a ball return path where the maximum inclination angle of the ball return path is optimized to reduce entering-exiting fluctuation, using specific formulas to determine the angle based on lead and ball diameter, ensuring smooth circulation and load balance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a complex three-dimensional curve shape is used for the ball return path, then the circulation path can be formed inside the circulation internal deflector, but entering-exiting fluctuation of balls occurs and smooth circulation is reduced
Solution Approach 1:
The patent optimizes geometric parameters of the ball return path, specifically setting the maximum inclination angle α within 15° to 45° and the curvature radius R to satisfy R/Da ≥ 1.5 (where Da is ball diameter). These parameter optimizations reduce the expansion and contraction of the ball row, minimizing entering-exiting fluctuation and ensuring smooth ball circulation through the three-dimensional curved path.
2Reliability
If elastic bodies are interposed between balls to absorb fluctuation, then entering-exiting fluctuation can be reduced, but load capacity is reduced and number of balls must be reduced
Solution Approach 1:
The patent removes the elastic bodies from the ball circulation system and instead optimizes the geometric parameters of the ball return path itself. By extracting the fluctuation absorption function from separate elastic components and integrating it into the path design, the system maintains load capacity while reducing entering-exiting fluctuation through proper angle and curvature optimization.
3Ease of manufacture
If holes or grooves are provided in the nut for the circulation internal deflector, then the deflector can be fitted, but the holes or grooves are easily deformed during heat treatment
Solution Approach 1:
The patent designs the circulation internal deflector with an outer peripheral shape that corresponds to the protruding shape of the nut, allowing the deflector to be mounted on the outer peripheral surface rather than requiring holes or grooves to be formed in the nut. This preliminary design consideration eliminates the need for post-heat treatment deformation-prone features while maintaining proper fitting and alignment.
Data Source
Figure 1~2
Figure 3A~3C
Figure 4~5
AI summary
A ball screw includes: a screw shaft (10) having a spiral first screw groove (11) formed in an outer peripheral surface thereof; a nut (20) disposed on the periphery of the screw shaft (10) and having a spiral second screw groove (21) formed in an inner peripheral surface thereof; a plurality of balls (30) accommodated in a rolling path (23) formed by the opposing screw grooves (11, 21); and a circulation piece (40) that forms a ball return passage (42) for circulating the plurality of balls (30) through one circuit or less of the rolling path (23). Traffic variation is made to be small by determining the maximum angle of inclination (a) of the ball return passage (42) in an expression using the lead (L), the ball diameter (Da), and the lead angle (β).