Rotor Bridge Structure for Strength and Magnet Demagnetization Control

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Solution Overview

Problem

Existing rotating electrical machines with permanent magnets face challenges in maintaining the strength of the rotor iron core against centrifugal forces and preventing irreversible demagnetization of the permanent magnets.

Innovation Solution

The rotor design incorporates specific magnetic voids and bridge portions in the rotor iron core to enhance structural support and includes retention protrusions to prevent demagnetization, while maintaining efficient magnet accommodation and reducing weight.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the rotor iron core structure is simplified to reduce manufacturing complexity, then the manufacturing cost decreases, but the strength to resist centrifugal force deteriorates

Engineering Contradiction:

Improvemanufacturing complexityVSAvoidrotor iron core strength

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The rotor iron core is segmented into multiple functional regions: magnet accommodation areas for holding permanent magnets, bridge portions connecting different regions, and magnetic voids for flux management. This segmentation allows each region to be optimized independently for both strength and manufacturability, resolving the contradiction between structural complexity and manufacturing ease

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the rotor iron core are designed with locally optimized properties: bridge portions have enhanced structural strength to resist centrifugal forces, while magnet accommodation areas are optimized for magnet retention. This local quality differentiation allows the overall structure to maintain strength without requiring uniform complexity throughout

Inventive Principle:

Principle #3Local quality

2Weight of moving object

If the rotor iron core is made lighter to reduce overall weight, then the weight decreases, but the ability to maintain strength under centrifugal force deteriorates

Engineering Contradiction:

Improverotor weightVSAvoidrotor iron core strength

Core Design Contradiction:

Weight of moving objectVSStrength

Solution Approach 1:

The rotor iron core uses segmented magnetic voids and bridge portions that create a lightweight yet strong structure. The voids reduce material usage and weight, while the strategically positioned bridge portions maintain structural integrity and strength distribution, resolving the weight-strength contradiction

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The rotor iron core incorporates magnetic voids (air gaps) within the iron core structure, creating a porous-like configuration. This reduces the overall density and weight of the rotor while the remaining iron material is strategically distributed to maintain necessary mechanical strength under centrifugal loading

Inventive Principle:

Principle #31Porous materials

3Power

If the permanent magnets are positioned closer to the outer circumferential surface to improve magnetic performance, then the magnetic energy product increases, but the risk of irreversible demagnetization due to centrifugal force increases

Engineering Contradiction:

Improvemagnetic energy productVSAvoidpermanent magnet stability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

Retention protrusions are built into the rotor iron core structure in advance at strategic positions. These protrusions engage with the permanent magnets before centrifugal forces act on them during rotation, providing preliminary mechanical support that prevents the magnets from moving outward despite high-speed rotation, thus preventing demagnetization while allowing optimal positioning

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The retention protrusions act as intermediary elements between the rotor iron core and the permanent magnets. They transfer and distribute the centrifugal loads from the magnets to the stronger iron core structure, protecting the magnets from direct centrifugal stress that would cause demagnetization while maintaining the magnets' optimal positioning for magnetic performance

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS12456889B2Rotor and rotating electrical machine

Publication Date: 2025.10.28 KK TOSHIBA

AI summary

According to one embodiment, a rotor includes, for each magnetic pole of a rotor iron core, first and second outer circumferential side bridge portions, and first and second inner circumferential side bridge portions. The first and second outer circumferential side bridge portions are provided such that a mutual interval is decreased from an outer circumferential side of the rotor iron core to an inner circumferential side. The first and second inner circumferential side bridge portions are provided such that a mutual interval is decreased from the outer circumferential side of the rotor iron core to the inner circumferential side, and are connected to the first and second outer circumferential side bridge portions, respectively.