Halbach Array Stator Assembly to Prevent Magnet Detachment

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Solution Overview

Problem

The detachment of magnets from the stator core due to different magnetization directions of circumferentially adjacent magnets is a concern, particularly for radially magnetized magnets, which experience a relatively large radially inward force.

Innovation Solution

A stator design incorporating a Halbach array with magnets arranged in a specific configuration, including radial and circumferential magnets with inclined end surfaces and projections, and optionally using intermediate members to enhance magnetic flux distribution and prevent detachment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If a Halbach array with radially magnetized magnets is used to concentrate magnetic flux radially inward, then magnetic flux concentration is improved, but the risk of magnet detachment increases due to large radially inward forces

Engineering Contradiction:
Improvemagnetic flux concentrationVSAvoidmagnet detachment risk
Core Design Contradiction:
PowerVSReliability

Solution Approach 1:

The patent converts the harmful radially inward force that causes magnet detachment into a beneficial locking mechanism. By designing inclined end surfaces on adjacent magnets, the radially inward force generates a circumferential component that presses the magnets against each other's inclined surfaces, creating a self-locking effect that prevents detachment while maintaining the Halbach array's magnetic flux concentration capability

Inventive Principle:
Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The inclined end surfaces act as intermediary contact surfaces between adjacent magnets. These surfaces mediate the force transmission between magnets, converting the radially inward magnetic force into a beneficial inter-magnet contact force that prevents detachment rather than allowing direct detachment from the stator core

Inventive Principle:
Principle #24Intermediary (Mediator)

2Power

If magnets with different magnetization directions are arranged circumferentially in a Halbach array, then magnetic flux distribution is improved, but the structural stability of magnets on stator teeth deteriorates

Engineering Contradiction:
Improvemagnetic flux distributionVSAvoidmagnet structural stability
Core Design Contradiction:
PowerVSStability of the object's composition

Solution Approach 1:

The patent transforms the force imbalance caused by different magnetization directions into a stabilizing mechanism. The inclined end surfaces convert the net radial force into a circumferential pressing force between adjacent magnets, creating mutual support that enhances structural stability while preserving the required magnetic flux distribution pattern

Inventive Principle:
Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The inclined end surfaces introduce asymmetry in the mechanical contact geometry between magnets. This asymmetric inclination is specifically designed to convert radial forces into circumferential locking forces, providing directional stability that counteracts the destabilizing effect of different magnetization directions

Inventive Principle:
Principle #4Asymmetry

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 the detachment of magnets by generating radially outward forces, stabilizing the magnets on the stator teeth, and facilitates easier assembly by reducing the movement required during assembly.

Implementation Method 1

there is concern that the magnets may come off from teeth of the stator core due to the different magnetization directions of circumferentially adjacent magnets

Methodology Applied
Scientific EffectHalbach array: Halbach Array

Implementation Method 2

The present inventors have devised the application of a Halbach array which concentrates the magnetic flux radially inward of the stator

Methodology Applied
Scientific EffectMagnetic flux concentration: Magnetic Field

Implementation Method 3

a radially outward force acts on the first radial magnet, preventing the first radial magnet from coming off from the plurality of teeth

Methodology Applied
Scientific EffectMagnetic force: Lorentz Force

Data Source

PatentEP4708649A1Stator, magnetic gear electric machine, and method for assembling stator
Publication Date: 2026.03.11 MITSUBISHI HEAVY IND LTD
  • EP4708649A1 patent drawingFigure 1
  • EP4708649A1 patent drawingFigure 2
  • EP4708649A1 patent drawingFigure 3

AI summary

A group of magnets in a Halbach array constituting a stator includes: a first radial magnet magnetized radially outward; a first circumferential magnet disposed on one side of the first radial magnet in the circumferential direction and magnetized to the one side; and a second circumferential magnet disposed on the other side of the first radial magnet in the circumferential direction and magnetized to the other side. At least one of one end surface or the other end surface of the first radial magnet in the circumferential direction has a first inclined end surface that slopes toward the center of the first radial magnet in the circumferential direction as it extends radially inward. At least one of the other end surface of the first circumferential magnet in the circumferential direction or one end surface of the second circumferential magnet in the circumferential direction has a first contact inclined end surface that is in contact with the first inclined end surface and slopes toward the center of the first radial magnet in the circumferential direction as it extends radially inward.