Insulated Wire Cracking Prevention via Solvent Buffer

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Solution Overview

Problem

Insulated wires in electrical equipment face issues with thermal shrinkage and mechanical stress, leading to cracking in the covering resin layer, which can compromise the insulation performance and reliability, especially when the space factor is improved.

Innovation Solution

The use of a multilayer insulated wire structure with a thermosetting resin layer and a thermoplastic resin layer, where a predetermined amount of organic solvent with a specific boiling point is allowed to remain, enhancing interlayer adhesion and reducing stress propagation, thereby preventing cracks from reaching the conductor.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the covering resin layer is firmly adhered to the enamel-baked layer to improve adhesion, then interlayer adhesion is improved, but cracking is easily propagated from the covering resin layer to the enamel-baked layer and conductor under thermal and mechanical stress

Engineering Contradiction:

Improveinterlayer adhesionVSAvoidcrack propagation

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A buffer layer is introduced between the enamel-baked layer and the covering resin layer. This buffer layer acts as an intermediary that absorbs thermal shrinkage stress and mechanical stress, preventing crack propagation from the covering resin layer to the enamel-baked layer and conductor, while maintaining adequate interlayer adhesion.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The adhesion strength between layers is optimized by controlling the solvent content in the enamel-baked layer. By adjusting the solvent content to 1000-20000 ppm, the adhesion is reduced to an appropriate level that prevents excessive stress transmission, thereby reducing crack propagation while maintaining sufficient bonding.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If the space factor is improved by using rectangular wire and increasing coil density, then productivity and performance are improved, but mechanical stress on the insulated wire is increased leading to cracking

Engineering Contradiction:

Improvespace factorVSAvoidmechanical stress induced cracking

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The buffer layer is provided in advance before the wire undergoes winding and coil assembly processes. This buffer layer cushions the mechanical stress that will be applied during high-density coil packing, preventing cracking even when the space factor is improved through rectangular wire usage.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Manufacturing precision

If the amount of solvent remaining in the enamel-baked layer is reduced to improve appearance, then appearance quality is improved, but adhesion between the enamel-baked layer and covering resin layer is reduced

Engineering Contradiction:

Improveappearance qualityVSAvoidinterlayer adhesion

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The solvent content is precisely controlled within the range of 1000-20000 ppm. This parameter optimization balances appearance quality (by keeping solvent content low enough to prevent excessive bubbling or defects) with adhesion performance (by maintaining sufficient solvent to ensure proper bonding between layers).

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 proposed solution effectively prevents cracks from reaching the conductor, ensuring high reliability and improved insulation performance even under mechanical and thermal stress, enhancing the performance of electrical equipment.

Implementation Method 1

contains a liquid component that is liquid at 25°C and has a boiling point of 150°C or higher in a proportion of 1,000 ppm or more and 20,000 ppm or less in the thermosetting resin layer

Methodology Applied

Scientific EffectSolvent retention effect:

Implementation Method 2

a thermoplastic resin layer on the thermosetting resin layer... preventing cracks from reaching the conductor

Methodology Applied

Scientific EffectViscoelasticity: Viscoelasticity

Data Source

PatentEP3093855B1Insulated electric wire, coil and electric/electronic device, and cracking prevention method for insulated electric wire

Publication Date: 2019.11.27 FURUKAWA ELECTRIC CO LTD

Figure 1~3

AI summary

An insulated wire, having a thermosetting resin layer, directly or by interposing an insulated layer, on a conductor having a rectangular cross-section, and a thermoplastic resin layer on the thermosetting resin layer, wherein the insulated wire contains a liquid component that is liquid at 25°C, and has a boiling point of 150°C or higher in a proportion of 1,000 ppm or more and 20,000 ppm or less in the thermosetting resin layer; a coil formed by winding processing the insulated wire; and electrical/electronic equipment having the coil; and a method of preventing cracking of an insulated wire, wherein cracking caused in a thermoplastic resin layer as a covering resin layer is prevented from reaching the thermosetting resin layer by using the insulated wire which contains the liquid component in the proportion of 1,000 ppm or more and 20,000 ppm or less in the thermosetting resin layer.