Integrated Rotor Shaft and Back Iron for Stiff 4-Pole Machines
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Solution Overview
Problem
Existing electric machines for aircraft, particularly 4-pole designs, face challenges in achieving structural stiffness and torque output due to limited space for internal shafts and weaknesses in bonded laminations, leading to inefficiencies in rotor design and performance, especially in high-frequency environments.
Innovation Solution
The rotor design integrates a shaft and back iron formed from high saturation magnetic flux density material, allowing the shaft to function as part of the back iron, eliminating the need for a separate structural shaft and enhancing stiffness, while using a single unitary piece of soft magnetic material simplifies manufacturing and increases power density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an internal shaft is used to provide structural stiffness in a 4-pole rotor, then the rotor stiffness is improved, but the available space for the shaft is very limited making it extremely challenging to design a sufficiently stiff shaft
Solution Approach 1:
The patent merges the shaft and back iron into a single integrated component made of soft magnetic material. The shaft is formed as an integral part of the back iron structure, eliminating the need for a separate shaft while providing sufficient structural stiffness. This combination allows the rotor to achieve the required stiffness without requiring additional space for a separate shaft component.
Solution Approach 2:
The shaft region of the back iron performs multiple functions: it provides structural support and stiffness like a traditional shaft, while simultaneously serving as part of the magnetic flux path like traditional back iron. The soft magnetic material enables the shaft region to conduct magnetic flux between poles while maintaining structural integrity, combining mechanical and magnetic functions in a single component.
2Strength
If a separate structural element (sleeve or can) is added externally to the rotor core to increase stiffness, then the rotor structural stiffness is improved, but the airgap between rotor and stator increases reducing torque output
Solution Approach 1:
Instead of adding an external sleeve or can, the patent integrates the structural shaft function directly into the back iron structure. The shaft is formed as an integral part of the back iron, eliminating the need for external structural elements that would increase the rotor outer diameter and airgap. This integration maintains the magnetic airgap while providing the necessary structural stiffness.
3Ease of manufacture
If bonded laminations are used for the rotor, then manufacturing is simplified, but the structural strength in the longitudinal direction is very limited due to weaknesses in the bonds between layers
Solution Approach 1:
The patent combines the shaft and back iron into a single integrated component that can be manufactured as one piece using various techniques including forging, casting, or machining from solid material. This eliminates the need for bonding multiple lamination layers together, providing continuous longitudinal strength while still allowing for manufacturing through conventional processes. The integrated structure removes the weak bonds between layers.
4Ease of manufacture
If the shaft and back iron are formed as separate components, then manufacturing flexibility is improved, but the device complexity increases and space utilization decreases
Solution Approach 1:
The patent merges the shaft and back iron into a single integrated component, reducing the total number of parts and simplifying the assembly process. While this reduces manufacturing flexibility compared to separate components, it significantly decreases device complexity and improves space utilization within the rotor. The integration eliminates the need for assembly operations and reduces the overall rotor diameter.
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
This approach increases rotor stiffness, reduces weight, and enhances torque output by allowing magnetic flux to flow between poles, making 4-pole rotors suitable for high-frequency applications without the need for external structural support, thus improving the overall performance and efficiency of electric machines.
Implementation Method 1
The back iron portion is configured to provide a path for magnetic flux to flow between adjacent poles of the core pack portion
Data Source
AI summary
The present invention relates to a rotor of an electric machine for use in an aircraft. By forming the shaft of the rotor such that it performs, at least partially, the function of the back iron, components of the rotor can be combined. Further, by forming the rotor components in this manner, an internal shaft with an increased diameter can be used to provide a rotor with greater stiffness than equivalent prior art devices.