Flex Spline End Clamping for Compact Harmonic Drives
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Small diameter, high ratio gear applications face challenges with flex spline shafts having cup and hat shaped end sections that reduce usable volume and offer lower torque capacity and efficiency compared to turned end sections.
Innovation Solution
A harmonic drive design featuring a flex spline with tapered ends and annular channel clamps that prevent rotation, utilizing annular C-shaped clamps with threaded profiles and screws to securely clamp the flex spline within the drive housing, eliminating the need for outward or inward flanges, thus maintaining efficiency and torque capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cup and hat shaped end sections are used on the flex spline shaft, then the flex spline can be secured within the drive housing, but the usable volume within the drive is reduced
Solution Approach 1:
The flex spline shaft is divided into distinct segments: a central cylindrical section and separate tapered end sections. This segmentation allows the ends to be secured without requiring large flanges that would reduce usable volume, as each end section can be independently clamped by the annular clamps.
Solution Approach 2:
The solution transitions from using axial flanges (cup and hat shapes) to using radial clamping forces applied at the ends. The annular clamps apply force in the radial direction to secure the tapered ends, changing the dimension of the securing action from axial to radial, thereby preserving usable volume.
2Volume of moving object
If pancake style flat end sections are used on the flex spline shaft, then the usable volume within the drive is increased, but the torque capacity and efficiency are reduced
Solution Approach 1:
The end sections are designed with a specific taper angle parameter that optimizes both the securing capability and torque transmission. The tapered geometry, with its gradually increasing diameter, provides sufficient surface area for clamping while maintaining the structural integrity needed for high torque capacity, avoiding the flat pancake design.
3Volume of moving object
If pancake style flat end sections are used on the flex spline shaft, then the usable volume within the drive is increased, but the efficiency is reduced
Solution Approach 1:
The tapered end sections are designed with optimized geometric parameters including taper angle and length, which improve the contact surface quality and reduce stress concentrations. This enhances the efficiency of torque transmission while maintaining compact dimensions that preserve usable volume.
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A harmonic drive, having a housing (60) extending from first to second outer ends (60A, 60B0, the housing has radial outer and inner walls (210, 215) that extend axially between the first and second outer ends of the housing to define an annular channel (50) having first and second ends (50A, 50B) that taper toward the first and second outer ends of the housing; a flex spline (20) that extends axially between first and second ends (20A, 20B) and has a radial outer surface (20D), and the first and second ends of the flex spline taper radially outwardly, the flex spline is located within the annular channel so that the first end of the flex spline is located within the first end of the annular channel and the second end of the flex spline is located within the second end of the annular channel; and first and second clamps (30, 40) that are clamped against the first and second ends of the annular channel.