Permanent Magnet Rotor Bridge Structure for Centrifugal Stress Control
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Solution Overview
Problem
Conventional rotary electric machines face issues with increased thickness of bridge portions leading to deformation under centrifugal force and decreased magnetic flux density due to increased leakage magnetic flux, especially at higher rotation speeds.
Innovation Solution
A rotary electric machine design incorporating a bridging portion that connects the outer and inner peripheral sides of the rotor core, distributing centrifugal stress without increasing the thickness of the bridge portions, thereby reducing leakage magnetic flux and maintaining magnetic flux density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness of the outer bridge portion and center bridge portion is increased to suppress deformation by centrifugal force, then the strength and deformation resistance of the bridge portion is improved, but the size of the rotor increases and the magnetic flux density decreases due to increased leakage magnetic flux
Solution Approach 1:
The bridge portion is segmented into an outer bridge portion and a center bridge portion that are connected through a notched portion. This segmentation allows each part to bear specific loads while maintaining overall structural strength without increasing total thickness, thereby preventing excessive leakage magnetic flux.
Solution Approach 2:
A notched portion is introduced at a specific location of the center bridge portion to create local stress concentration that enhances overall structural strength. This localized feature allows the bridge portion to resist centrifugal force without requiring uniform thickness increase across the entire structure, thus maintaining magnetic flux density.
2Reliability
If the thickness of the bridge portion is increased to prevent deformation under centrifugal force, then the reliability of the rotor structure is improved, but the leakage magnetic flux increases and magnetic flux density decreases
Solution Approach 1:
The bridge portion is divided into outer and center segments connected by a notched portion, creating a structure that maintains high reliability through strategic stress distribution while minimizing the material volume that could generate leakage magnetic flux.
Solution Approach 2:
The notched portion introduces a local geometric parameter change that significantly enhances structural reliability by creating stress concentration points, allowing the bridge portion to withstand centrifugal forces without requiring increased thickness that would generate harmful leakage magnetic flux.
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 design effectively suppresses bridge deformation and maintains magnetic flux density by distributing centrifugal stress, enhancing the machine's operational stability and torque performance.
Implementation Method 1
a rotor provided with a rotor core for embedding a plurality of pairs of permanent magnets arranged in a V shape extending toward the stator
Implementation Method 2
a large centrifugal force acts on the bridge portion due to the rotation of a rotor
Data Source
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AI summary
To provide a rotary electric machine capable of suppressing a bridge portion from being deformed by a centrifugal force without increasing the thickness of the bridge portion and suppressing a decrease in magnetic flux density in accordance with an increase in leakage magnetic flux. [Solution] A rotor core 21 includes a first flux barrier 25A formed adjacent to each of outer peripheral ends of a pair of permanent magnets 23A and 23B, a second flux barrier 25B formed adjacent to inner peripheral ends of the pair of permanent magnets 23A and 23B, an outer bridge portion 32 circumferentially extending along an outer peripheral surface of the rotor core 21 on an outer peripheral side of the first flux barrier 25A, a center bridge portion 31 radially extending through the second flux barrier 25B and connecting an outer peripheral side and an inner peripheral side of the rotor core 21, and a bridging portion 33 passing through the first flux barrier 25A and connecting the outer bridge portion 32 and an inner peripheral portion of the rotor core 21.