Permanent Magnet Fractured Surface Configuration for Eddy Current Loss Reduction

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Solution Overview

Problem

Conventional fractured permanent magnets exhibit higher residual ratios of eddy-current loss due to large contact areas and thin surface oxide films on fractured surfaces, leading to increased energy loss in high-power motors.

Innovation Solution

The configuration of permanent magnets with fractured surfaces positioned out of contact and integrated with cut surfaces on the outer periphery, reducing contact area and enhancing surface oxide film thickness, thereby minimizing eddy-current loss.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If fractured surfaces are placed as contact surfaces to reduce manufacturing cost, then manufacturing cost is reduced, but residual ratio of eddy-current loss increases

Engineering Contradiction:

Improvemanufacturing costVSAvoideddy-current loss

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

The permanent magnet is divided into multiple separate permanent magnet pieces, each with fractured surfaces. By segmenting the magnet and strategically positioning pieces, the patent reduces manufacturing cost through fracturing while controlling eddy-current loss through selective placement of fractured and cut surfaces.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different surfaces of the permanent magnet pieces have different properties: some surfaces are fractured (for cost reduction) while others are cut surfaces (for lower eddy-current loss). The patent applies local quality by placing cut surfaces at contact interfaces where they are most effective at reducing eddy-current loss, while allowing fractured surfaces in non-contact positions.

Inventive Principle:

Principle #3Local quality

2Ease of manufacture

If fractured surfaces are used as contact surfaces, then insulation treatment cost is reduced, but contact area increases leading to higher eddy-current loss

Engineering Contradiction:

Improveinsulation treatment costVSAvoideddy-current loss

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

Instead of using fractured surfaces as contact surfaces (which increases eddy-current loss), the patent inverts the approach by using cut surfaces as contact surfaces. This inversion reduces eddy-current loss at contact interfaces while still maintaining the cost benefits of fracturing for non-contact surfaces.

Inventive Principle:

Principle #13The other way round (Inversion)

3Manufacturing precision

If fractured surfaces are placed at outer peripheral surface, then positional accuracy is improved, but manufacturing complexity increases

Engineering Contradiction:

Improvepositional accuracyVSAvoidmanufacturing complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent performs preliminary fracturing of the permanent magnet block before final assembly. By pre-forming the fractured surfaces and then strategically positioning the pieces during assembly, the patent achieves high positional accuracy while managing manufacturing complexity through a structured multi-step process.

Inventive Principle:

Principle #10Preliminary action

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 configuration significantly reduces the residual ratio of magnet eddy loss by minimizing contact area and increasing surface oxide film thickness, improving motor efficiency and positional accuracy.

Implementation Method 1

a surface oxide film on the cut surface of the cut permanent magnet is 30 nm, whereas a surface oxide film on the fractured surface of the fractured permanent magnet is 7 nm

Methodology Applied

Scientific EffectSurface oxide film: Oxidation

Implementation Method 2

eddy loss (eddy-current loss) represents the loss of electric energy caused by eddy-currents generated when magnetic flux distributes in a magnetic body

Methodology Applied

Scientific EffectEddy current: Eddy Currents

Data Source

PatentUS9214846B2Permanent magnet, motor rotor or stator, rotary electric machine

Publication Date: 2015.12.15 TOYOTA JIDOSHA KK

AI summary

A permanent magnet includes two or more separate permanent magnet pieces each having a rectangular parallelepiped shape with a fractured surface formed when a permanent magnet block is fractured. The separate permanent magnet pieces include a first separate permanent magnet piece and a second separate permanent magnet piece. At the time when the permanent magnet block is fractured, the first and second separate permanent magnet pieces are adjacently located and a first fractured surface of the first separate permanent magnet piece and a second fractured surface of the second separate permanent magnet piece are adjacent to each other. The permanent magnet is configured such that the first fractured surface of the first separate permanent magnet piece and the second fractured surface of the second separate permanent magnet piece are located in positions out of contact with each other.