Insulated Electric Wire with Asymmetric Inner Layer for Bending
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Solution Overview
Problem
Existing insulated electric wires face issues with adhesion between the insulating film and conductor wire during edgewise bending, leading to delamination and wrinkles, which compromise insulation performance and heat resistance, especially when the film thickness is increased to improve adhesion.
Innovation Solution
A two-layer insulating film structure is applied to the conductor wire, where the inner layer has a greater thickness on one short side and a lower elastic modulus than the outer layer, allowing it to absorb compression stress and maintain adhesion during edgewise bending, while the outer layer provides higher elastic modulus and yield stress for improved insulation and heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the film thickness is increased to improve adhesion, then adhesion between insulating film and conductor wire is improved, but the film becomes prone to delamination and wrinkles during edgewise bending
Solution Approach 1:
The insulating film is divided into two distinct layers: a first insulating film layer in direct contact with the conductor wire, and a second insulating film layer covering the first layer. This segmentation allows each layer to have optimized properties - the first layer provides adhesion with controlled thickness, while the second layer provides insulation and heat resistance, resolving the contradiction between adhesion improvement and prevention of delamination/wrinkles
Solution Approach 2:
Different regions of the insulating film structure are assigned different qualities and functions. The first layer has properties optimized for adhesion to the conductor, while the second layer has properties optimized for insulation and heat resistance. This local differentiation allows the system to achieve both good adhesion and high reliability without the film delaminating or wrinkling during bending
2Strength
If the film thickness is increased to improve adhesion, then adhesion between insulating film and conductor wire is improved, but compression stress during bending increases causing wrinkles and delamination
Solution Approach 1:
By segmenting the film into two layers, the compression stress during bending is distributed across both layers rather than concentrated in a single thick layer. The first layer maintains adhesion with controlled thickness, while the second layer provides additional protection, collectively reducing the harmful compression stress that causes wrinkles and delamination
Solution Approach 2:
The insulating film is constructed as a composite structure with two different insulating film layers, each potentially having different material properties. This composite structure allows optimization of stress distribution during bending, where the combined layers provide both adhesion and resistance to compression stress, preventing wrinkles and delamination while maintaining good bonding
Data Source
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AI summary
There is provided an insulated electric wire formed by covering a rectangular conductor wire having a rectangular cross-sectional shape with an insulating film. The insulating film is formed of an inner layer covering a surface of the rectangular conductor wire, and an outer layer covering a surface of the inner layer. A thickness (t1) of a section of the inner layer, which covers one short side of two facing short sides of the same length of a rectangular cross section of the rectangular conductor wire, is greater than a thickness (t2) (including that t2 = 0) of a section of the inner layer which covers the other short side. An elastic modulus and/or a yield stress of the inner layer are less than an elastic modulus and/or a yield stress of the outer layer.