Two-Layer Permanent Magnet Rotor With Interlocking Magnet Interface

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Solution Overview

Problem

The existing two-layer structure permanent magnet rotor with ferrite and rare earth bonded magnets on the inner and outer peripheral sides, respectively, suffers from weak bonding strength between the two materials.

Innovation Solution

A permanent magnet rotor design featuring an inner peripheral magnet with recesses on its outer surface and an outer peripheral magnet with projections that fit into these recesses, enhancing the bonding strength between the two magnets.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a two-layer structure permanent magnet rotor is adopted with ferrite bonded magnet on inner peripheral side and rare earth magnetic bonded magnet on outer peripheral side, then both performance and cost are achieved, but bonding strength between inner peripheral magnet and outer peripheral magnet is weak

Engineering Contradiction:

Improvebonding strengthVSAvoidbonding strength between magnets

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The outer peripheral magnet is segmented into multiple projection portions that extend in the radial direction. These projections divide the bonding interface into multiple discrete bonding regions, allowing for localized stress distribution and improved overall bonding strength between the inner and outer magnets.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The bonding interface between inner and outer magnets is made asymmetric through the provision of projection portions on the outer magnet that extend radially inward. This asymmetric structure creates mechanical interlocking features that enhance bonding strength compared to a symmetric flat interface.

Inventive Principle:

Principle #4Asymmetry

2Reliability

If rare earth bonded magnet is used to increase magnetic force, then magnetic performance is improved, but material cost increases

Engineering Contradiction:

Improvemagnetic forceVSAvoidmaterial cost

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

Different material properties are assigned to different regions of the rotor. The inner peripheral magnet uses ferrite bonded magnet material while the outer peripheral magnet uses rare earth magnetic bonded magnet material. This local differentiation optimizes magnetic force where needed (outer region) while controlling overall material cost.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The permanent magnet rotor employs a composite structure combining two different magnet materials: ferrite bonded magnet and rare earth magnetic bonded magnet. This composite approach allows the system to achieve high magnetic force performance through the rare earth component while maintaining cost efficiency through the ferrite component.

Inventive Principle:

Principle #40Composite materials

Data Source

PatentUS20250105686A1Permanent magnet rotor

Publication Date: 2025.03.27 MITSUBISHI ELECTRIC CORP

AI summary

A permanent magnet rotor includes a rotation axis, an inner peripheral magnet that is a cylindrical bonded magnet including a plurality of recesses on an outer peripheral side and holding the rotation axis, and an outer peripheral magnet that is a cylindrical bonded magnet provided on the outer periphery side of the inner peripheral magnet. The outer peripheral magnet includes a plurality of projections that projects toward an inner peripheral side and is fitted into the plurality of recesses of the inner peripheral magnet.