Ball Spline Shaft Design for Machining Efficiency and Rigidity
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Solution Overview
Problem
Conventional ball splines face inefficiencies in machining due to large sectional area reduction ratios during drawing, high production costs, and insufficient rigidity and flexural rigidity, especially with non-cylindrical spline shafts, leading to poor torque transmission and potential displacement issues.
Innovation Solution
A ball spline design featuring a spline shaft with a circular sectional configuration and torque transmission grooves, where ball rolling faces are formed on land parts between grooves, and a spline nut with load rolling faces and endless circulation paths, mimicking the DB-type angular contact ball bearing contact structure to enhance rigidity and machining efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If ridge portions are provided at three circumferential positions of a round shaft, then torque transmission capability is improved, but the sectional area reduction ratio during drawing increases, resulting in poor machining efficiency
Solution Approach 1:
The invention uses a circular sectional configuration for the spline shaft instead of a round shaft with ridge portions. This maintains torque transmission capability through the circular geometry while eliminating the need for extensive drawing operations that would reduce sectional area, thereby improving machining efficiency.
2Force
If wide groove portions are provided in both side surfaces of a rectangular bar material, then torque transmission capability is improved, but the sectional area reduction ratio during drawing increases, resulting in poor machining efficiency
Solution Approach 1:
The invention transitions from a rectangular bar material with wide groove portions to a circular spline shaft configuration. This eliminates the need for extensive material removal and drawing operations, improving machining efficiency while maintaining torque transmission through the circular geometry with appropriately positioned ball rolling faces.
3Force
If the sectional configuration of the spline shaft is rectangular, then torque transmission capability is improved, but the end machining time increases, resulting in high production cost
Solution Approach 1:
The invention adopts a circular sectional configuration for the spline shaft, which simplifies end machining operations compared to rectangular configurations. The circular shape requires less complex machining at the ends, reducing production time and cost while maintaining effective torque transmission through the ball spline mechanism.
4Ease of manufacture
If the contact structure is similar to DF type angular contact ball bearing, then ease of assembly is improved, but rigidity between spline shaft and spline nut is insufficient, leading to displacement under large torque
Solution Approach 1:
The invention positions the ball rolling faces asymmetrically on the spline shaft with specific orientations. This asymmetric arrangement creates a contact structure that generates both radial and axial reaction forces, providing sufficient rigidity to prevent displacement under large torque while maintaining ease of assembly through the systematic configuration.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design reduces the sectional area reduction ratio during machining, lowers production costs, and provides improved rigidity and flexural rigidity while maintaining efficient torque transmission without displacement, thus addressing the inefficiencies of prior art.
Implementation Method 1
a ball spline in which a spline shaft and a spline nut are combined with each other through the intermediation of a large number of balls so as to be capable of relative linear movement
Data Source
AI summary
a ball spline enabling easy machining of a spline shaft by drawing and manufacturable at low cost. The ball spline includes a spline shaft in which multiple lines of ball rolling faces are formed along the longitudinal direction; and a spline nut having a hollow hole for inserting the spline shaft therein, having load rolling faces opposed to the ball rolling faces of the spline shaft. Multiple lines of torque transmission grooves along the longitudinal direction are formed at equal intervals around the spline shaft, and the ball rolling faces are formed on the lateral both sides of these torque transmission grooves. Further, a distance between a pair of ball rows rolling on both sides of the land parts of the spline shaft is set larger than a distance between a pair of ball rows rolling on both sides of the torque transmission grooves.