Split Flexspline Harmonic Drive for Interference-Free Assembly

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Solution Overview

Problem

Harmonic drive transmissions face limitations in gear and spline tooth profile configurations due to interference during assembly, restricting design flexibility and complicating manufacturing and assembly processes.

Innovation Solution

A split flexspline configuration is introduced, comprising two flexsplines with axially adjacent sets of splines, allowing for reduced interference and simplified manufacturing and assembly, while maintaining design flexibility.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single flexspline is used to engage center and ground gears, then the structure is simpler, but the gear and spline tooth profile configurations are limited due to interference during assembly

Engineering Contradiction:

Improvestructure simplicityVSAvoidtooth profile configuration flexibility

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The single flexspline is divided into two separate flexsplines, each with its own set of splines. This segmentation allows each flexspline to be independently configured without interference from the other, enabling greater design flexibility in tooth profiles while maintaining assembly simplicity

Inventive Principle:

Principle #1Segmentation

2Quantity of substance

If a single flexspline is used, then fewer parts are required, but manufacturing and assembly processes become more complex due to interference issues

Engineering Contradiction:

Improvenumber of flexsplinesVSAvoidmanufacturing and assembly simplicity

Core Design Contradiction:

Quantity of substanceVSEase of manufacture

Solution Approach 1:

By segmenting the single flexspline into two separate flexsplines, each can be manufactured independently using standard processes without the need for complex interference-checking or special assembly procedures. This actually simplifies both manufacturing and assembly despite increasing part count

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The interference problem is extracted and eliminated by separating the splines into distinct components. Each flexspline can be manufactured and prepared separately, removing the interference constraint that would complicate single-piece manufacturing and assembly

Inventive Principle:

Principle #2Taking out (Extraction)

3Ease of operation

If interference between gear and spline teeth is avoided in a single flexspline configuration, then assembly is simplified, but the tooth profile configurations are restricted

Engineering Contradiction:

Improveassembly easeVSAvoidtooth profile design options

Core Design Contradiction:

Ease of operationVSAdaptability or versatility

Solution Approach 1:

Dividing the flexspline into two separate components eliminates tooth interference during assembly while allowing each component to have optimized, independent tooth profiles. This segmentation enables designers to select from a broader range of tooth profile configurations without compromising assembly ease

Inventive Principle:

Principle #1Segmentation

Data Source

PatentEP4283164B1Harmonic drive transmission with split flexspline

Publication Date: 2025.12.24 HAMILTON SUNDSTRAND CORP

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AI summary

A harmonic gearset, having: a drive shaft (58); first and second ground gears (62, 64) spaced apart from each other along the drive shaft; an output gear (66) disposed on the drive shaft, between the first and second ground gears; a first flexspline (80) disposed radially between the drive shaft, the first ground gear and the output gear; and a second flexspline (90) disposed radially between the drive shaft, the second ground gear and the output gear, wherein the first and second flexsplines are axially adjacent to each other.