Harmonic Drive Layout Flexibility via Inverted Wave Generator
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Solution Overview
Problem
Conventional harmonic drive gearing systems have limited layout flexibility and low rigidity, leading to restricted positioning and increased size, which affects usability and responsiveness, especially in applications like leg-type mobile robots.
Innovation Solution
A harmonic drive gearing system with a circular rigid gear, an annular flexible gear, and a motor rotor acting as a wave generator, where the rotor is positioned outside the flexible gear, allowing for radial deflection and improved torque transmission, reducing size and enhancing layout flexibility and responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the wave generator is positioned inside the flex spline, then the engagement mechanism works properly, but the layout flexibility is limited and the size in axial direction becomes large
Solution Approach 1:
The patent inverts the conventional arrangement by positioning the wave generator outside the flex spline instead of inside. This inversion allows the drive unit to achieve compact axial size while maintaining layout flexibility, as the wave generator can be arranged radially outward from the flex spline rather than requiring axial space inside it
2Power
If the pulley is positioned next to the wave generator, then the driving force can be transmitted, but the size in direction along the rotating shaft becomes large
Solution Approach 1:
The patent transitions the pulley positioning from an axial arrangement (along the rotating shaft) to a radial arrangement (perpendicular to the rotating shaft). By positioning the pulley radially outward from the wave generator, the driving force transmission is maintained while the length along the rotating shaft is significantly reduced, achieving a more compact design
3Ease of manufacture
If the flex spline is positioned at an end section of the rotating shaft, then the harmonic drive gearing can be mounted, but the degree of freedom in layout is reduced
Solution Approach 1:
The patent creates a universal mounting configuration where the harmonic drive gearing can be positioned at multiple locations along the rotating shaft rather than being restricted to end sections. The redesigned structure allows the flex spline and circular spline to be mounted at various positions, providing multi-functional layout options while maintaining proper engagement and manufacturing feasibility
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 system achieves compact size, high torque transmission, reduced torque ripple, and improved magnetic resistance, allowing for better torque output and reduced risk of harness damage, while maintaining high rigidity and flexibility in layout positioning.
Implementation Method 1
a motor rotor acting as a wave generator, where the rotor is positioned outside the flexible gear
Implementation Method 2
an annular flexible gear, positioned at the outside of the rigid gear... having inner teeth, which are engageable with the outer teeth of the rigid gear, formed on an inner peripheral surface
Data Source
AI summary
To provide a harmonic drive gearing with high degree of freedom in terms of layout. A harmonic drive gearing 10 includes a circular spline 1′, having outer teeth formed on an outer peripheral surface; an flexible spline 2, positioned at the outside of the circular spline 1′, and having inner teeth, which are engageable with the outer teeth of the circular spline 1′, formed on an inner peripheral surface; and a rotor 16 which is disposed at outside of the flexible spline 2 and serves as a wave generator, wherein the rotor 16 deflects the flexible spline 2 by minor axis portions of the inner peripheral surface of the flexible spline 2 and engages the inner teeth of the flex spline with the outer teeth of the circular spline 1′ and thereby the engagement position between the inner teeth and the outer teeth is adapted to move in a circumferential direction.