Multi-Rotor Electric Machine Gear Phasing for Torque Ripple Relief
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Solution Overview
Problem
Multi-rotor electric machines suffer from unsteady output torque characteristics and low durability due to variability in torque at the rotor level, requiring complex configurations and expensive, high-strength gears that are prone to fretting damage.
Innovation Solution
The electric machine system comprises multiple rotors with phased indexing and gear configurations that provide torque phase offsets between rotors, reducing torque ripple and cyclic stress on gears, allowing for the use of less expensive materials and enhancing durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple rotors are used to enhance power output, then power capability is improved, but torque ripple and cyclic stress increase causing durability degradation
Solution Approach 1:
The system divides the power generation function across multiple independent rotor-stator assemblies (first, second, and third electric machines), each contributing to the total power output. This segmentation allows the torques to be phase-offset so they do not peak simultaneously, reducing the cyclic stress on individual components while maintaining high overall power capability.
Solution Approach 2:
The patent employs periodic phase-offset indexing of rotors relative to their stators, where adjacent rotors are offset by specific angles (e.g., 120 degrees). This creates a periodic distribution of torque peaks in time, ensuring that when one rotor produces peak torque, others are producing lower torque, thereby smoothing the total output torque and reducing cyclic stress on the gear system.
2Power
If complex configurations are used to achieve multi-rotor operation, then power enhancement is possible, but device complexity increases
Solution Approach 1:
The patent merges multiple rotor-stator assemblies into a single integrated system that shares common structural elements such as the housing, cooling system, and output shaft. By combining these functions, the patent achieves enhanced power output without proportionally increasing overall system complexity, as the shared components serve multiple rotors simultaneously.
Solution Approach 2:
The patent arranges multiple rotors in different spatial dimensions (axially stacked or radially positioned) around a common output shaft, rather than placing them in a single plane. This dimensional arrangement allows for compact integration of multiple power-generating units while maintaining clear separation of their magnetic circuits and reducing electromagnetic interference between them.
3Reliability
If high-strength gears are used to handle torque variability, then durability is improved, but cost and material requirements increase
Solution Approach 1:
The phase-offset rotor configuration acts as a cushioning mechanism that prevents extreme torque peaks from occurring simultaneously on all gear contacts. By distributing the torque peaks in time, the system reduces the maximum instantaneous load on individual gears, allowing the use of standard-strength materials rather than requiring expensive high-strength alloys or oversizing the gear components.
Solution Approach 2:
The patent changes the temporal distribution parameter of torque delivery through phase-offset indexing, transforming the torque profile from a series of sharp, simultaneous peaks to a smoother, distributed pattern. This parameter change reduces the stress amplitude on gear teeth, enabling the use of conventional manufacturing processes and standard materials while maintaining gear durability.
Data Source
AI summary
An electric machine system described herein comprises a first electric machine rotor, a first gear and a second gear. The first gear is connected to the first electric machine rotor and to a first input/output shaft. The second gear is connected to the first electric machine rotor and to a second input/output shaft. The first electric machine rotor is disposed between the first gear and the second gear.