Shielded Wire Sheath Friction Design for Bending Resistance
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Solution Overview
Problem
Conventional shielded wires with high bendability suffer from reduced flexibility due to the contractile force of the sheath, leading to potential wire breakage and compromised shielding performance when bent.
Innovation Solution
A shielded wire design featuring a tubular sheath made of insulating resin with a specific inner diameter and thickness, and coefficients of static friction between the shield braid and the wire and sheath, which satisfies a relational expression to prevent excessive constriction and enhance bending resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sheath is added to cover the shield braid, then the insulation and protection are improved, but the bendability is reduced due to the contractile force of the sheath
Solution Approach 1:
The patent changes the physical parameters of the sheath by establishing specific mathematical relationships between the inner diameter in free state (D2), inner diameter when disposed (D1), thickness (t), modulus of elasticity (E), and friction coefficients (μA, μB). By controlling these parameters to satisfy specific inequalities, the sheath provides adequate protection while maintaining the bendability of the shielded wire.
Solution Approach 2:
The patent applies different friction characteristics at different interfaces: the coefficient of static friction between the shield braid and electrical wire (μA) and between the shield braid and sheath (μB) are considered separately in the design criteria, allowing optimized local interactions to balance protection and flexibility.
2Reliability
If the sheath contracts to provide tight fit, then the shielding performance is improved, but the wire may break at early stage due to excessive constriction
Solution Approach 1:
The patent establishes a mathematical relationship that limits the contraction force of the sheath by relating the inner diameter in free state (D2) to other parameters (D1, t, E, μA, μB). This ensures the sheath provides sufficient shielding through appropriate contraction while preventing excessive constriction that would cause wire breakage.
Solution Approach 2:
The design criteria established in the patent act as a preventive measure, calculating and limiting the sheath's contractile force before actual use. By satisfying the specified inequalities during design, the system prevents wire breakage before it occurs during operation.
3Reliability
If the thickness of copper members is increased, then the grounding process is improved, but the bendability is lowered
Solution Approach 1:
The patent optimizes the thickness of copper members within specific ranges to achieve adequate grounding capability while preventing excessive thickness that would reduce bendability. This parameter optimization is integrated with the overall design criteria for the shielded wire structure.
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 design significantly improves the bending resistance of the shielded wire and wire harness by reducing the likelihood of wire breakage during repeated bending cycles, ensuring a bending resistance of 5 million times or more.
Implementation Method 1
the degree of freedom is lost because of the contractile force of the sheath
Implementation Method 2
a shield braid in which electrically conductive wire members are braided, and which covers an outer circumference of the electrical wire
Implementation Method 3
μB is a coefficient of static friction between the shield braid and the sheath
Data Source
AI summary
A shielded wire includes an electrical wire including a conductor portion and a covering portion, a shield braid in which electrically conductive wire members are braided, and which covers an outer circumference of the electrical wire, a tubular sheath disposed on an outer circumference of the shield braid and made of an insulating resin.