Compound Harmonic Drive Assembly With Radial Gear Layout
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Solution Overview
Problem
Prior compound harmonic drives with axially adjacent gears are complex to manufacture and have high rotating inertia due to their design, which reduces system response and increases complexity.
Innovation Solution
A compact compound harmonic drive with radially adjacent gears, featuring a flex spline with outward and inward-facing teeth, a wave generator with non-circular inner and outer profiles, and journal bearings, which reduces complexity and rotating inertia, allowing for continuous output rotation with higher torque density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If axially adjacent gears are used in compound harmonic drives, then the drive can achieve high torque output, but the device complexity increases and manufacturing becomes more difficult
Solution Approach 1:
The patent transitions from axial arrangement to radial arrangement of gear sets. The first and second ring gears are positioned radially adjacent to each other around the wave generator, with gear teeth that are radially offset and axially aligned. This dimensional change from axial to radial configuration reduces the number of axial layers needed, simplifying the overall drive structure while maintaining the compound gear ratio functionality and high torque output capability.
2Force
If axially adjacent gears are used in compound harmonic drives, then the drive can achieve high torque output, but manufacturing precision requirements increase
Solution Approach 1:
By arranging gear teeth radially offset and axially aligned rather than axially adjacent, the patent reduces the cumulative tolerance stacking that occurs in multi-layer axial configurations. The radial offset allows for more forgiving manufacturing tolerances while the axial alignment simplifies the meshing geometry, thereby reducing manufacturing precision requirements while still achieving high torque output through the compound gear ratio.
3Power
If traditional compound harmonic drive design is used, then high gear ratio is achieved, but rotating inertia increases reducing system response
Solution Approach 1:
The radial arrangement of gear sets with axially aligned teeth creates a more compact moment of inertia distribution. By positioning mass closer to the rotation axis through radial offset rather than extending axially, the patent reduces the rotating inertia of the moving components. This enables the system to maintain high gear ratios while improving acceleration response and reducing the time constant of the drive system.
4Device complexity
If axially adjacent gears are used, then the drive structure is established, but the drive length increases
Solution Approach 1:
The patent reconfigures the gear sets from an axial stack to a radial arrangement around the wave generator. The first and second ring gears are positioned at different radial distances from the center, with their gear teeth axially aligned rather than stacked axially. This radial compacting significantly reduces the axial length of the drive assembly while maintaining the compound gear ratio functionality through the radial offset configuration.
Data Source
AI summary
Disclosed is a compound harmonic drive including: an inner ring gear including a first set of gear teeth; a flex spline including a flex spline inner ring and a flex spline outer ring, the flex spline inner ring forms a second set of gear teeth that engage the first set of gear teeth and the flex spline outer ring forms a third set of gear teeth; an outer ring gear including a fourth set of gear teeth that are engaged by the third set of gear teeth; and a wave generator disposed between the flex spline inner ring and the flex spline outer ring, wherein the gear system rotates about an axis and each set of gear teeth is axially aligned with each other and radially offset from each other about the axis.