Strain Wave Gear Coupling for Runout-Induced Jamming
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Solution Overview
Problem
Strain wave gears in aircraft experience loss of rotation and jamming due to the stacking of radial tolerances, which leads to the loss of essential clearances between moving parts, even with low runout on high-precision components.
Innovation Solution
A strain wave gear design that includes a rotatable wave generator and a coupler allowing displacement of the driver shaft relative to the wave generator, along with a coupling frame providing clearance in multiple directions to accommodate eccentric runout, and the use of low friction elements to reduce frictional forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high precision parts are used with low runout values, then manufacturing precision is improved, but essential clearances are lost due to stacking of radial tolerances
Solution Approach 1:
The coupler is designed to be movable relative to the wave generator, allowing dynamic adjustment of the driver shaft position. This movement capability enables the system to maintain essential clearances by accommodating radial tolerance variations, preventing jamming while using high precision parts with low runout values.
Solution Approach 2:
The invention changes the positional parameter of the driver shaft by allowing it to move radially through the coupler. This parameter change accommodates the stacking of radial tolerances and maintains the necessary clearances between moving parts, resolving the contradiction between high manufacturing precision and reliability.
2Loss of energy
If clearances are reduced to minimize friction, then energy loss is reduced, but loss of rotation and jamming occur due to tolerance stacking
Solution Approach 1:
The movable coupler provides dynamic clearance management, allowing the driver shaft to move radially to maintain optimal clearances. This prevents jamming and ensures continuous rotation while minimizing frictional losses by avoiding excessive clearances that would increase energy loss.
Solution Approach 2:
The coupler acts as an intermediary element between the driver shaft and wave generator, absorbing the effects of tolerance stacking. It mediates the interaction between components, maintaining necessary clearances to prevent jamming while minimizing frictional energy losses through controlled movement.
3Device complexity
If rigid coupling is used between driver shaft and wave generator, then device complexity is reduced, but eccentric runout causes loss of rotation and jamming
Solution Approach 1:
The coupler introduces a controlled degree of freedom to the coupling structure, allowing it to move radially in response to eccentric runout. This dynamic capability accommodates runout variations without causing jamming, maintaining rotation continuity while adding minimal complexity to the overall device.
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
Prevents loss of rotation and jamming by maintaining clearances in multiple directions, allowing the strain wave gear to operate effectively despite radial tolerance stacks, while minimizing frictional losses.
Implementation Method 1
The low friction element may comprise a ball bearing or a low friction coating
Data Source
Figure 1~2
AI summary
A strain wave gear comprising: a wave generator configured to contact a spline, the wave generator being rotatable; and a coupler configured to couple a driver shaft to the wave generator, the coupler permitting displacement of the driver shaft relative to the wave generator.