Harmonic Drive Wave Generator for Stable Multi-Point Tooth Engagement

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Solution Overview

Problem

Conventional harmonic drives experience frequent misalignment of teeth engagement between the circular spline and the flex spline due to external forces, leading to the Dedoi-dal phenomenon, which affects the stability and performance of the gear reduction.

Innovation Solution

A wave generator with a circular cam plate and protrusions at regular intervals on its outer surface, elastically deforming the flex spline to engage teeth at three or more positions simultaneously with the circular spline, preventing misalignment and enhancing engagement stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional wave generator with an oval plug is used, then the structure is simple, but the teeth engagement becomes unstable under external forces causing Dedoi-dal phenomenon

Engineering Contradiction:

Improveteeth engagement stabilityVSAvoidwave generator structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The wave generator is segmented into multiple protrusions (at least three) distributed around the circumferential direction, each independently engaging with corresponding teeth of the flex spline. This segmentation allows multiple engagement points to simultaneously constrain the flex spline, preventing Dedoi-dal phenomenon and improving engagement stability without requiring a completely new structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The protrusions are positioned at specific locations around the circumferential direction to create localized engagement zones. By strategically placing protrusions at optimal angular intervals, the design ensures that teeth engagement occurs at multiple discrete points simultaneously, providing stable constraint while maintaining a relatively simple overall wave generator structure.

Inventive Principle:

Principle #3Local quality

2Power

If teeth engagement occurs at only one or two positions, then the structure is simple, but the engagement rate and torque transmission are insufficient

Engineering Contradiction:

Improverated torque and peak torqueVSAvoidnumber of engagement positions

Core Design Contradiction:

PowerVSDevice complexity

Solution Approach 1:

The wave generator employs multiple protrusions (at least three) distributed around the circumferential direction, creating multiple simultaneous engagement points between the flex spline and circular spline. This segmentation of engagement locations increases the total engagement rate, allowing higher torque transmission capacity while maintaining a relatively simple wave generator body structure.

Inventive Principle:

Principle #1Segmentation

3Speed

If the wave generator rotates, then speed reduction is achieved, but the teeth may momentarily come out of alignment under external forces

Engineering Contradiction:

Improverotation speed reductionVSAvoidteeth alignment stability

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The protrusions are positioned at specific angular intervals around the circumferential direction to create localized engagement zones. By strategically placing protrusions at optimal positions, the design ensures that during rotation, at least three teeth remain engaged with the circular spline simultaneously, maintaining stable alignment even when the wave generator rotates under external forces.

Inventive Principle:

Principle #3Local quality

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 solution significantly increases the teeth engagement rate, rated torque, and peak torque performance by maintaining stable tooth engagement, thereby preventing the Dedoi-dal phenomenon and improving overall reducer performance.

Implementation Method 1

protrusions formed on the outer circumferential surface of the cam plate elastically deform the three or more positions inside the flex spline

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Implementation Method 2

a ball bearing formed on the outer face thereof to surround the cam plate and elastically deformed by the protrusions formed on the outer circumferential surface of the cam plate

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Data Source

PatentUS11572941B2Wave generator for reducer of harmonic drive structure

Publication Date: 2023.02.07 ROBOSTAR

AI summary

Disclosed herein is a wave generator for a reducer of a harmonic drive structure. The reducer of a harmonic drive structure includes: a circular spline of a ring shape; a flex spline mounted inside the circular spline and having teeth engaged with teeth formed at three or more positions of the inner circumferential surface of the circular spline to be rotated; and a wave generator mounted inside the flex spline, and including a cam plate of a circular shape, and three or more protrusions formed at three or more positions of the outer circumferential surface of the circular cam plate so that the protrusions formed on the outer circumferential surface of the cam plate elastically deform the three or more positions inside the flex spline.