Split Nanocrystalline Annular Core for Cable Noise Suppression

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Solution Overview

Problem

Fe-based nanocrystalline alloys are brittle and difficult to mold into split-type annular magnetic bodies, limiting their use in noise control applications due to chipping and inadequate shape control, which impedes effective noise reduction.

Innovation Solution

An annular magnetic body composed of thin strips of soft magnetic metal laminated radially, with split pieces forming an annular shape and controlled surface roughness and coercivity (FL×Hc ≤ 7.0 μm/A/m) to enhance noise reduction, using Fe-based nanocrystalline alloys with high impedance relative permeability (μrz ≥ 6000 at 100 kHz).

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If Fe-based nanocrystalline alloys are used for noise control, then noise reduction performance is improved, but the material is brittle and difficult to mold into split-type configurations

Engineering Contradiction:

Improvenoise reduction performanceVSAvoidmoldability into split-type configuration

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The annular magnetic body is divided into multiple split pieces that can be separately manufactured and then assembled. This segmentation allows each piece to be molded more easily while maintaining the overall annular structure, resolving the contradiction between using brittle nanocrystalline alloys and achieving split-type configuration.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent controls specific parameters including flatness of split surfaces (FL), coercivity (Hc), surface roughness (Ra≤0.7μm, Rz≤10μm), and radial crushing strength (≥50 MPa) to enable the brittle nanocrystalline alloy to be successfully manufactured as split-type components with adequate handling properties.

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If split-type configuration is used for ease of attachment, then convenience is improved, but manufacturing precision deteriorates due to chipping and shape control limitations

Engineering Contradiction:

Improveconvenience of attachment to cableVSAvoidshape control and surface flatness

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The patent specifies precise parameter ranges including flatness (FL), surface roughness (Ra≤0.7μm, Rz≤10μm), and radial crushing strength (≥50 MPa) to ensure that split surfaces maintain adequate flatness and shape control while still allowing easy attachment. This resolves the contradiction by defining controlled parameters that balance manufacturability with precision.

Inventive Principle:

Principle #35Parameter changes

3Length of stationary object

If nanocrystalline alloy is used, then impedance relative permeability is improved, but the material is easily chipped and limited in shape

Engineering Contradiction:

Improveimpedance relative permeabilityVSAvoidresistance to chipping

Core Design Contradiction:

Length of stationary objectVSStrength

Solution Approach 1:

Dividing the annular magnetic body into multiple pieces reduces the size of each individual component, making them less prone to chipping while maintaining the high impedance relative permeability (μrz≥6000 at 100 kHz) characteristic of nanocrystalline alloys.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent controls radial crushing strength (≥50 MPa) and surface roughness parameters to enhance the resistance to chipping of nanocrystalline alloy components, allowing them to maintain their superior magnetic properties while improving mechanical durability.

Inventive Principle:

Principle #35Parameter changes

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 solution provides a split-type annular magnetic body with superior noise reduction capabilities, surpassing conventional ferrite cores by achieving impedance relative permeability of 6000 or more at 100 kHz, reducing noise effectively while being easier to handle and attach to cables.

Implementation Method 1

an annular magnetic body for noise control including thin strips of soft magnetic metal laminated along a radial direction

Methodology Applied

Scientific EffectMagnetic impedance: Electromagnetic Induction

Implementation Method 2

a product FL×Hc of a flatness FL of the split surfaces and a coercivity Hc of the split pieces is 7.0 μm·A/m or less

Methodology Applied

Scientific EffectCoercivity: Magnetic Hysteresis

Data Source

PatentUS12476030B2Annular magnetic body for noise control and member for noise control

Publication Date: 2025.11.18 RIKEN CO LTD

AI summary

A split-type annular magnetic body for noise control, which has been difficult to produce with Fe-based nanocrystalline alloys, is provided and obtains an excellent noise reduction effect. The annular magnetic body for noise control includes thin strips of soft magnetic metal laminated along a radial direction and is used by having a cable inserted therethrough. The annular magnetic body for noise control includes a plurality of split pieces divided into a non-annular shape and is used by placing split surfaces of the split pieces in contact with each other to form an annular shape. The product FL×Hc of the flatness FL of the split surfaces and the coercivity Hc of the split pieces is 7.0 μm·A/m or less. The flatness FL is the sum of absolute values of the maximum value and the minimum value of a cross-sectional curve measured in accordance with JIS B 0601:2001.