Stacked Stator Core Retention Without Magnetic Path Interference

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Solution Overview

Problem

Conventional rotary electric machines face issues with stator core retention, leading to increased device size and reduced magnetic efficiency due to interference with the magnetic path and application of clamping forces that deteriorate magnetic properties.

Innovation Solution

The stator core is retained with tensile stress applied in a direction parallel to the surfaces of the movable parts and perpendicular to their movement, using thin sheets stacked in the movable direction, which enhances magnetic efficiency without increasing device size.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If retention members are fitted to holes penetrating in the stacking direction to retain the stator core, then the stator core is retained, but the retention members interfere with the magnetic path, leading to size increase and efficiency reduction

Engineering Contradiction:

Improvestator core retentionVSAvoidmagnetic efficiency

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The invention extracts the retention function from the magnetic path by applying tensile stress to the stacked sheets through external fastening structures, thereby removing the need for retention members within the magnetic path and eliminating their interference with magnetic flux

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention introduces an intermediary tensile stress mechanism that acts on the stacked sheets from the outside, mediating between the need for retention and the requirement to maintain an unobstructed magnetic path

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If clamping force is applied in the stacking direction to retain the stator core, then the stator core is retained, but the magnetic property of the stator core is deteriorated

Engineering Contradiction:

Improvestator core retentionVSAvoidmagnetic property

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

Instead of applying compressive clamping force from the stacking direction, the invention inverts the approach by applying tensile stress perpendicular to the stacking direction, thereby retaining the stator core without compressing the magnetic sheets and preserving their magnetic properties

Inventive Principle:

Principle #13The other way round (Inversion)

3Reliability

If the device size is increased to accommodate retention structures, then the stator core can be retained, but the overall device size increases

Engineering Contradiction:

Improvestator core retentionVSAvoiddevice size

Core Design Contradiction:

ReliabilityVSLength of stationary object

Solution Approach 1:

The invention moves the retention mechanism from the radial dimension (within the magnetic path) to the axial dimension (perpendicular to the magnetic path), allowing retention without increasing the radial size of the device

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS12199479B2Electromagnetic device having stator core formed with stacked thin sheets and aircraft in which electromagnetic device is used

Publication Date: 2025.01.14 MITSUBISHI ELECTRIC CORP

AI summary

This electromagnetic device includes: two movable parts movable in parallel or antiparallel to each other; and a stator core arranged with two surfaces thereof respectively opposed to the two movable parts. At least part of the stator core is formed by stacking thin sheets in a movable direction of the movable parts and is retained with tensile stress applied thereto in a direction parallel to the two surfaces opposed to the movable parts and perpendicular to the movable direction of the movable parts.