Segmented Flex Spline for Compound Harmonic Generator Stress Reduction

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Solution Overview

Problem

Existing systems for flight control surfaces on aircraft wing structures, particularly those with thin wing designs, face challenges in reducing stress and fatigue in actuators that use compound harmonic generators, as they require effective gear reduction while minimizing space and weight.

Innovation Solution

A flex spline system comprising a primary flex spline with a specific number of teeth driven by a harmonic wave generator and at least one secondary flex spline with a different number of teeth, both in meshed contact with respective ring gears, allowing independent rotation and reducing stress and fatigue through a compact, high gear ratio and torque-to-weight ratio configuration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a compound harmonic generator is used to provide gear reduction in actuators for thin wing designs, then the gear reduction ratio is improved, but stress and fatigue in the flex spline increase

Engineering Contradiction:

Improvegear reduction ratioVSAvoidstress and fatigue

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The invention divides the single flex spline into multiple separate flex splines (primary and secondary), each engaging with its own ring gear. This segmentation allows each spline to carry a portion of the load independently, reducing the stress and fatigue on any single spline while maintaining the compound gear reduction ratio.

Inventive Principle:

Principle #1Segmentation

2Volume of moving object

If a compact actuator design is used for thin wing aircraft control surfaces, then the space requirement is reduced, but the torque-to-weight ratio must be optimized

Engineering Contradiction:

Improveactuator spaceVSAvoidtorque-to-weight ratio

Core Design Contradiction:

Volume of moving objectVSPower

Solution Approach 1:

The invention employs a nested configuration where secondary flex splines and secondary ring gears are positioned within or alongside the primary flex spline and primary ring gear assembly. This nesting allows multiple gear reduction stages to be compacted into a smaller volume, achieving high gear reduction ratios in space-constrained applications while maintaining adequate torque output.

Inventive Principle:

Principle #7Nested doll (Nesting)

3Reliability

If independent rotation of secondary flex splines is implemented, then stress distribution is improved, but device complexity increases

Engineering Contradiction:

Improvestress distributionVSAvoidnumber of rotating components

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The harmonic wave generator serves multiple functions simultaneously: it drives the primary flex spline, drives the secondary flex splines, and coordinates their independent rotations. This multi-functionality allows the system to achieve improved stress distribution through independent spline rotation without proportionally increasing the complexity of driving mechanisms.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS9915334B2Flex spline for use with a compound harmonic generator

Publication Date: 2018.03.13 HAMILTON SUNDSTRAND CORP

AI summary

A method and system providing a flex spline for a compound harmonic generator having a harmonic wave generator, a primary ring gear, and a secondary ring gear, includes a primary flex spline with a first number of primary teeth, the primary flex spline driven by the harmonic wave generator and in meshed contact with the primary ring gear, and at least one secondary flex spline with a second number of secondary teeth, the at least one secondary flex spline driven by the harmonic wave generator and in meshed contact with the secondary ring gear, wherein the at least one secondary flex spline rotates independently from the primary flex spline.