Internal Deflector Ball Screw for Smooth Ball Return
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Solution Overview
Problem
Internal deflector type ball screws face issues with entering-exiting fluctuation 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 compromise load capacity.
Innovation Solution
A ball screw design where the ball return path's maximum inclination angle is optimized using specific formulas (α=22.63(L/Da)^2−32.17(L/Da)+27.00−β±5, α=5.86(L/Da)^2+2.09(L/Da)+2.45−β±5, or α=7.24(L/Da)^2−23.65(L/Da)+44.83−β±5) to minimize entering-exiting fluctuation, with the circulation internal deflector formed to ensure smooth ball circulation.
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 occurs and smooth circulation is reduced
Solution Approach 1:
The invention optimizes the geometric parameters of the ball return path by defining specific relationships between the curvature radius R and lead angle γ at different positions. The curvature radius is set to satisfy R≥0.06(L/Da)+1.25 Da and the lead angle to satisfy 15°≤γ≤45°, where L is the lead and Da is the ball diameter. These parameter optimizations reduce entering-exiting fluctuation and ensure smooth ball circulation while maintaining the compact three-dimensional curve configuration.
2Reliability
If elastic bodies are interposed between balls to absorb fluctuation, then entering-exiting fluctuation can be reduced, but the number of balls must be reduced and load capacity decreases
Solution Approach 1:
The invention extracts and eliminates the elastic bodies from the system by optimizing the ball return path geometry instead. By designing the curvature radius and lead angle to satisfy specific relationships, the path itself absorbs the entering-exiting fluctuation without requiring intermediate elastic elements. This allows maintaining the full complement of balls and preserving load capacity while still achieving fluctuation reduction.
3Ease of manufacture
If holes or grooves are provided in the nut to fit the circulation internal deflector, then the deflector can be mounted, but the holes or grooves are easily deformed during heat treatment
Solution Approach 1:
The invention performs preliminary action by designing the circulation internal deflector as a separate, pre-manufactured component that is mounted onto the nut after heat treatment rather than requiring holes or grooves to be formed in the nut itself. The deflector is equipped with mounting structures that engage with the nut's external features, allowing the nut to undergo heat treatment without deformation risks while still achieving secure deflector attachment.
Data Source
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 (α) of the ball return passage (42) in an expression using the lead (L), the ball diameter (Da), and the lead angle (β).