Magnetic Shield Eddy Current Suppression

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Solution Overview

Problem

Magnetic flux leakage from power transmission systems leads to electromagnetic field radiation, which is not effectively suppressed by existing magnetic shields, resulting in inefficiencies in noncontact power transmission.

Innovation Solution

A magnetic shield configuration with a first magnetic sheet, a conductive metal sheet, and a second magnetic sheet is employed, where the conductive sheet generates an eddy current that is contained by the second magnetic sheet, preventing electromagnetic field leakage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a metal sheet is used in the magnetic shield to block magnetic flux leakage, then the shielding effect is improved, but electromagnetic field radiation increases due to eddy current generation

Engineering Contradiction:
Improvemagnetic flux leakageVSAvoidelectromagnetic field radiation
Core Design Contradiction:
Object-affected harmful factorsVSObject-generated harmful factors

Solution Approach 1:

The magnetic shield is segmented into multiple layers with different material properties: a first magnetic sheet for guiding magnetic flux, a metal sheet for blocking magnetic flux leakage, and a second magnetic sheet for containing eddy currents. This segmentation allows each layer to perform its specific function while mitigating the overall harmful effects.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The second magnetic sheet acts as an intermediary between the metal sheet and the external environment. It contains the eddy currents generated in the metal sheet and prevents them from radiating electromagnetic fields outward, thus mediating between the necessary metal sheet component and the harmful radiation effect.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If a double-layer magnetic shield structure is used to suppress magnetic flux leakage, then the shielding effectiveness is improved, but eddy current generation and electromagnetic field radiation are not adequately suppressed

Engineering Contradiction:
Improvemagnetic flux leakageVSAvoidelectromagnetic field suppression
Core Design Contradiction:
Object-affected harmful factorsVSReliability

Solution Approach 1:

The magnetic shield uses a composite structure combining different materials: magnetic sheets (for magnetic flux management) and metal sheets (for magnetic flux blocking). This composite approach leverages the strengths of each material while addressing their individual weaknesses through proper layering and configuration.

Inventive Principle:
Principle #40Composite materials

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 effectively suppresses electromagnetic field radiation to the outside, enhancing the reliability of power transmission and reception in noncontact power systems.

Implementation Method 1

magnetic flux that reaches the metal sheet generates an eddy current on a surface of the metal sheet

Methodology Applied
Scientific EffectEddy current: Eddy Currents

Implementation Method 2

magnetic flux emitted from the coil enters the inside of the magnetic sheet, thereby suppressing the leakage of the magnetic flux to the outside

Methodology Applied
Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 3

a magnetic shield configured by a first magnetic sheet, a second magnetic sheet, and a conductive sheet interposed between the first magnetic sheet and the second magnetic sheet

Methodology Applied
Scientific EffectMagnetic shielding: Magnetic Field

Data Source

PatentEP2927917B1Power receiving device and power transmission device
Publication Date: 2020.05.06 TOYOTA JIDOSHA KK
  • EP2927917B1 patent drawingFigure 1
  • EP2927917B1 patent drawingFigure 2
  • EP2927917B1 patent drawingFigure 3

AI summary

This power receiving device (200) includes a magnetic shield (500), and the magnetic shield (500) includes: a first magnetic sheet (520) located beside the power receiving unit (210); a conductive sheet (510) located opposite to the power receiving unit (210) with the first magnetic sheet (520) interposed therebetween; and a second magnetic sheet (530) located opposite to the first magnetic sheet (520) with the conductive sheet (510) interposed therebetween.