Ball Spline Device Retainer-Free Nut Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional ball spline devices face challenges in downsizing due to the thickness of retainers, which obstruct nut member movement and require complex assembly, leading to increased diameter and manufacturing difficulties.
Innovation Solution
The ball spline device eliminates the retainer between the spline shaft and nut member, using the spline shaft's profile to guide balls out of the rolling grooves directly into non-load grooves, reducing the need for scooping portions and allowing for a more compact design with enhanced manufacturing simplicity and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a retainer is used to form ball returning paths, then the ball circulation function is achieved, but the nut member diameter increases and movement is obstructed
Solution Approach 1:
The invention extracts and eliminates the retainer component from the ball spline device. By removing the retainer that previously formed the ball returning paths, the patent achieves ball circulation directly through the nut member structure, thereby reducing the nut member diameter and eliminating movement obstruction while maintaining the ball circulation function.
Solution Approach 2:
The invention merges the ball returning path formation function from the separate retainer component into the nut member itself. The nut member now directly provides both the load bearing paths and the ball returning paths, eliminating the need for a separate retainer and reducing overall diameter.
2Ease of operation
If ball scooping portions are provided on the retainer, then balls can be guided out of rolling grooves, but assembly accuracy becomes difficult to maintain
Solution Approach 1:
The invention removes the ball scooping portions from the retainer structure. By eliminating the retainer entirely, the complex ball scooping portions are also removed, thereby eliminating the assembly accuracy issues associated with positioning these scooping portions relative to the ball rolling grooves.
Solution Approach 2:
The spline shaft profile itself serves the function of guiding balls out of the rolling grooves. The spherical profile of the spline shaft automatically guides the balls during operation without requiring additional scooping portions, thereby simplifying the structure and eliminating assembly accuracy problems.
3Length of moving object
If the retainer is made thin to reduce diameter, then downsizing is achieved, but deformation occurs and movement is obstructed
Solution Approach 1:
The invention eliminates the retainer component entirely, removing the source of deformation and movement obstruction. By using the nut member structure directly to provide ball circulation paths without a separate retainer, the patent achieves downsizing while maintaining movement smoothness.
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 enables a smaller nut member diameter, increased spline shaft diameter for enhanced rigidity and torque transmission, and improved assembly accuracy, reducing manufacturing time and costs while maintaining reliability.
Implementation Method 1
a spline shaft provided with multiple ball rolling grooves extending in the axial direction thereof, and a nut member assembled to the spline shaft through an intermediation of a large number of balls
Implementation Method 2
the balls roll while bearing load acting between the nut member and the spline shaft
Implementation Method 3
U-shaped direction converting paths for coupling the load path and the ball returning path with each other
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Provided is a ball spline device, in which an outer diameter of a nut member can be downsized to the maximum while sufficiently performing an original function, and which can keep reliability while being capable of being simply manufactured at lower cost without involving time and effort in assembly, in which a nut member (2) has a track groove (30) which is formed on an inner peripheral surface facing a spline shaft (1), the balls (3) circulating in the track groove (30), the track groove (30) comprises: a linear load groove (31) formed so as to face the ball rolling groove (10a, 10b) of the spline shaft (1); a linear non-load groove (32) provided parallel to the linear load groove (31); and a pair of ball deflection grooves (33) for communicably coupling the linear load groove (31) and the linear non-load groove (32) with each other so as to allow the balls (3) to intercommunicate therebetween, and the ball deflection grooves (33) forcibly change an advancing direction of the balls (3) rolling in the ball rolling groove (10a, 10b) and cause the balls (3) to depart from the ball rolling groove (10a, 10b) with use of a profile of the spline shaft (1).