Strain Wave Gear Differential for High Reduction Without Extra Gears
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Solution Overview
Problem
Existing harmonic drive systems with differential gear configurations require additional reduction gears for high gear reduction, leading to increased weight, volume, and failure modes.
Innovation Solution
A harmonic drive system with a strain wave gear differential configuration that includes a ground ring, flex splines, input shafts with wave generators, and a circular gear with specific spline configurations, allowing for high gear reduction within a compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a differential gear configuration is used to achieve dual motor drive with redundancy, then reliability is improved, but device complexity increases due to requiring additional larger reduction gear downstream
Solution Approach 1:
The patent merges the differential gear function with the reduction gear function into a single integrated unit. The planetary gear set is configured such that the carrier serves as the output of the differential while simultaneously providing the required reduction ratio, eliminating the need for separate downstream reduction gears.
Solution Approach 2:
The planetary gear set performs multiple functions simultaneously: it acts as both the reduction mechanism and the differential mechanism. The sun gear, planet gears, and ring gear are configured to provide both torque multiplication and differential motion distribution to multiple output shafts.
2Speed
If additional larger reduction gear is added downstream of differential gear configuration, then desired rotational output is achieved, but weight increases
Solution Approach 1:
The reduction gear and differential gear are combined into a single planetary gear assembly, eliminating the weight of separate downstream reduction gears. The planetary gears provide both the required reduction ratio and differential function in one compact unit.
3Speed
If additional larger reduction gear is added downstream of differential gear configuration, then desired rotational output is achieved, but volume increases
Solution Approach 1:
The differential and reduction functions are merged into a single planetary gear unit, significantly reducing the overall volume compared to having separate differential gear and downstream reduction gear assemblies.
4Speed
If additional larger reduction gear is added downstream of differential gear configuration, then desired rotational output is achieved, but failure modes increase
Solution Approach 1:
By combining the differential and reduction functions into a single planetary gear unit, the number of separate gear components and potential failure points is reduced. Fewer meshing interfaces and fewer separate assemblies mean fewer potential failure modes.
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
The proposed harmonic drive system achieves high gear reduction while minimizing weight, volume, and failure modes, providing a compact and reliable solution for actuation systems like those in aircraft control surfaces.
Implementation Method 1
a first flex spline extending axially from the ground ring; a first input shaft that is radially exterior to the first flex spline, wherein the first input shaft includes a first wave generator that engages the first flex spline
Data Source
AI summary
A harmonic drive, having: a ground ring; a first flex spline extending axially from the ground ring; a first input shaft that is radially exterior to the first flex spline, the first input shaft includes a first wave generator that engages the first flex spline; a second flex spline, radially within the first flex spline and rotationally coupled to the first flex spline, a second input shaft that is radially within the second flex spline, the second input shaft includes a second wave generator that engages the second flex spline; an output shaft coupled to the second flex spline, the first flex spline includes a first spline that faces radially inward; the second flex spline includes a second spline that faces radially outward; a circular gear having a third spline that face outwardly and engages the first spline; a fourth spline that faces radially inward and engages the second spline.