Harmonic Drive Bearing Assembly for Compact High-Torque Gearboxes
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Solution Overview
Problem
Existing gearboxes with harmonic wave type reduction action are large and cumbersome due to the need for multiple radial bearings to handle radial forces and sealing, which is a challenge in robotics and automotive applications requiring miniaturization and robustness.
Innovation Solution
A harmonic wave reduction and bearing assembly with an input and output radial or radiaxial bearing in axial alignment, featuring a harmonic wave reduction stage sandwiched between the bearings, utilizing concentric rings that are extensions of the input and output bearings, providing a compact and robust design with integrated radial force bearing capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional motor designs are used, then manufacturing simplicity is maintained, but electromagnetic harmonics cause torque ripple and acoustic noise
Solution Approach 1:
The stator is divided into multiple stator segments (first, second, third stator segments) with different tooth pitch values. This segmentation allows each segment to contribute differently to the overall magnetic field distribution, enabling harmonic cancellation while maintaining a modular construction approach that balances complexity with performance benefits.
2Reliability
If standard bearing assemblies are used, then assembly simplicity is maintained, but electromagnetic forces cause bearing currents and premature failure
Solution Approach 1:
A bearing assembly with a conductive bridge is introduced as an intermediary component between the rotor and stator. The conductive bridge provides a controlled path for electromagnetic forces and currents, preventing harmful bearing currents while maintaining mechanical support. This intermediary structure protects the bearings without significantly complicating the overall assembly.
3Object-generated harmful factors
If high precision manufacturing is implemented, then harmonic reduction is achieved, but manufacturing cost and complexity increase
Solution Approach 1:
Different stator segments are designed with different tooth pitch values (first tooth pitch, second tooth pitch, third tooth pitch), creating local variations in magnetic field characteristics. This local quality approach allows harmonic cancellation through deliberate asymmetry in tooth dimensions while using standard manufacturing tolerances, avoiding the need for high-precision manufacturing across the entire stator.
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 achieves a compact, cost-effective, and durable gearbox with minimized bending moments, ensuring concentric alignment of rings and reduced exposure of rolling elements to excessive forces, while allowing for high torque and precise speed reduction.
Implementation Method 1
The bearing assembly may be configured to reduce radial and/or axial vibrations of the rotor
Implementation Method 2
The motor may be configured to reduce acoustic noise and/or torque ripple
Data Source
Figure 1A~1D
Figure 2
Figure 3A~3D
AI summary
The present invention concerns a harmonic wave reduction and bear- ing assembly and an electric motor arrangement. The assembly comprises an input side radial or radiaxial bearing and an output side radial or radiaxial bearing in axial alignment with the input side bearing, the input side bearing and the output side bearing each having a plurality of rolling elements positioned between an outer bearing ring and an inner bearing ring, the assembly further comprising a har- monic wave reduction stage located axially in between the input side bearing and the output side bearing, the reduction stage being configured to perform a wave-type reduction action and having an inner reduction stage ring, a central reduction stage ring and an outer reduction stage ring that are concentric with each other as well as with the input side bearing and the output side bearing, wherein the inner reduction stage ring is configured to rotate with the inner ring of the input side bearing, the central reduction stage ring is configured to rotate with the inner ring of the output side bearing and the outer - 24 - reduction stage ring is configured to be coupled to the outer rings of both the input side bearing and the output side bearing.