Wire Harness Sheet Material with Localized Softness for Ultrasonic Welding
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Solution Overview
Problem
Existing methods for attaching electrical wires to sheet-like exterior members in vehicle wire harnesses often result in deformation of the insulating covering during thermal processing, such as ultrasonic welding, due to the rigidity difference between the insulating covering and the sheet material.
Innovation Solution
A wire harness design where the electrical wire fixing part is softer than the insulating covering, achieved by using a material with a higher plasticizer-to-polyvinyl chloride ratio or lower polymerization degree, allowing for minimal deformation during thermal processing, and a sheet material structure with a softer electrical wire fixing part that absorbs energy and reduces stress on the insulating covering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermal processing (ultrasonic welding) is applied to attach electrical wires to sheet material, then attachment reliability is improved, but the insulating covering of the electrical wire deforms
Solution Approach 1:
The sheet material is designed with different hardness levels in different regions: the electrical wire fixing part has lower hardness (higher plasticizer ratio) to reduce stress on the insulating covering, while other parts maintain normal hardness for structural integrity. This local differentiation resolves the contradiction by concentrating stress reduction where needed during thermal processing.
Solution Approach 2:
The hardness parameter of the sheet material is changed in the electrical wire fixing part by adjusting the plasticizer-to-polyvinyl chloride ratio or polymerization degree, making it softer than the insulating covering. This parameter change allows the fixing part to deform more easily during thermal processing, protecting the insulating covering from deformation while maintaining attachment reliability.
2Strength
If the sheet material is made harder to improve structural integrity, then strength is improved, but deformation of the insulating covering increases during thermal processing
Solution Approach 1:
The sheet material employs local quality differentiation where only the electrical wire fixing part has reduced hardness, while the rest of the sheet maintains high hardness for structural integrity. This resolves the contradiction by localizing softness only where stress reduction is needed during thermal processing.
Solution Approach 2:
The sheet material functions as a composite structure with regions of different material properties - the electrical wire fixing part has modified composition (higher plasticizer ratio or lower polymerization degree) making it softer, while other regions maintain original composition for strength. This composite approach allows simultaneous achievement of strength and deformation protection.
3Ease of manufacture
If the insulating covering and sheet material have similar hardness, then manufacturing is simplified, but thermal processing causes stress concentration on the electrical wire
Solution Approach 1:
The sheet material is designed with local quality variation where the electrical wire fixing part has different hardness than other regions. This localized softness reduces stress concentration on the electrical wire during thermal processing while maintaining overall manufacturing feasibility through a single-material construction with compositional variation.
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 minimizes deformation of the insulating covering during thermal processing, ensuring reliable attachment with reduced stress on the electrical wire, even when using general automobile electrical wires or round wires, while allowing for easier manufacturing and improved sheet material quality.
Implementation Method 1
thermal processing such as ultrasonic welding
Implementation Method 2
a part of the main surface having contact with the electrical wire is thermally processed with the insulating covering of the electrical wire
Data Source
AI summary
A wire harness includes: an electrical wire including a core wire and an insulating covering for covering the core wire; and a sheet material in which the electrical wire is disposed on a resin main surface, and a part of the main surface having contact with the electrical wire is thermally processed with the insulating covering of the electrical wire, thereby forming an electrical wire fixing part. A part of the sheet material including the electrical wire fixing part is softer than the insulating covering.