Three-Point Harmonic Drive Radial Stability
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Solution Overview
Problem
Two-point contact arrangements in harmonic drive gears are radially unstable, requiring additional bearings for radial alignment, which complicates their use in applications requiring high torque and low speed.
Innovation Solution
A three-point harmonic drive system is developed, incorporating a toothed harmonic ring gear, a harmonic wave generator with a rotor element featuring an outer wave profile with three lobes, and a harmonic flex spine with a toothed portion and a bearing element, which maintains radial stability with a less robust bearing support, allowing for high torque and low speed actuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a two-point contact arrangement is used in harmonic drive gears, then the gear ratio is increased, but radial stability deteriorates requiring additional bearings
Solution Approach 1:
The wave generator is divided into multiple lobes (at least three) around its circumference, creating multiple contact points with the flex spline. This segmentation of the contact arrangement from two points to three or more points simultaneously maintains high gear ratio while improving radial stability without requiring additional bearings.
Solution Approach 2:
The contact arrangement transitions from a two-point arrangement to a multi-point arrangement distributed around the circumference of the wave generator. This dimensional distribution of contact points around the circular path provides radial stability while maintaining the gear reduction function.
2Stability of the object's composition
If additional bearings are added to support radial alignment, then radial stability is improved, but device complexity increases
Solution Approach 1:
The multi-lobe wave generator structure itself provides the radial stability function that would otherwise require separate bearing components. The geometric configuration of three or more lobes inherently maintains radial alignment during operation, making the system self-supporting and eliminating the need for additional bearing elements.
3Stability of the object's composition
If a three-point contact arrangement is used, then radial stability is achieved without additional bearings, but the structure becomes more complex
Solution Approach 1:
The wave generator with multiple lobes performs multiple functions simultaneously: it provides the gear reduction function through its interaction with the flex spline, maintains radial stability through its multi-point contact arrangement, and eliminates the need for separate bearing components. This multi-functionality consolidates what would otherwise require separate components into a single integrated structure.
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 three-point harmonic drive system achieves radial stability without the need for additional bearings, enabling high torque and low speed actuation in compact designs, suitable for applications like aircraft flight control surfaces.
Implementation Method 1
the stator element includes a hub, a plurality of spokes extending radially outwardly from the hub and conductive elements wound around the spoke to form windings
Data Source
AI summary
A harmonic drive is provided and includes a toothed harmonic ring gear, a harmonic wave generator including a rotor element, which includes an outer three-lobe wave profile, and a stator element configured to drive rotation of the rotor element. The harmonic drive further includes a harmonic flex spine radially interposed between the harmonic ring gear and the rotor element. The harmonic flex spine includes a toothed portion and a bearing element rotatably supportive of the rotor element within the toothed portion. The toothed portion is disposed to register with the toothed harmonic ring gear at three contact points defined by the outer three-lobe wave profile in accordance with the rotation of the rotor element.