Wire Harness Shield Member for Impedance Matching
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Solution Overview
Problem
Existing wire harnesses experience excessive surge voltage due to impedance mismatch between the inverter unit, wire harness, and motor unit, leading to noise and radiation issues, which are exacerbated by the close proximity of electric wires causing high electrostatic capacitance.
Innovation Solution
A wire harness design featuring a shield member interposed between adjacent electric wires to adjust and reduce electrostatic capacitance, with the shield member positioned between the wires and extending to the central axis, and exterior members pressing the shield member to maintain the desired interval and prevent capacitance leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the distance between adjacent electric wires is reduced, then the wire harness size is reduced, but the electrostatic capacitance between wires increases causing noise and surge voltage
Solution Approach 1:
A shield member is introduced as an intermediary component between adjacent electric wires. This shield member includes a ground wire and shield wires that are interposed between the adjacent electric wires, thereby reducing the electrostatic capacitance between them while allowing the wires to remain closely spaced for compact harness design
Solution Approach 2:
The space between adjacent electric wires is segmented by introducing the shield member structure. The shield member divides the electromagnetic field environment, creating separate zones for each wire and reducing mutual capacitance effects, which allows compact wiring without noise issues
2Reliability
If the impedance of the wire harness is increased to match the motor unit impedance, then voltage reflections are suppressed, but the electrostatic capacitance must be reduced which increases wire spacing and harness size
Solution Approach 1:
The shield member acts as an intermediary that enables impedance matching without increasing wire spacing. By introducing the ground wire and shield wires between adjacent electric wires, the electrostatic capacitance is reduced, thereby increasing the wire harness impedance to match the motor unit impedance while maintaining compact dimensions
Solution Approach 2:
The impedance of the wire harness is adjusted by changing the electrostatic capacitance parameter between adjacent wires. The shield member modifies the electrical parameters (capacitance) between wires, enabling impedance matching with the motor unit without requiring physical spacing changes that would increase harness size
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 effectively adjusts electrostatic capacitance to match impedance, suppressing voltage reflections and reducing noise, thereby preventing excessive surge voltage.
Implementation Method 1
the electrostatic capacitance of the wire harness needs to be reduced... the electrostatic capacitance between the respective electric wires to be large... the shield member is disposed to be interposed between adjacent electric wires... such that a predetermined value of electrostatic capacitance is established between the electric wires
Data Source
AI summary
A wire harness includes: a wire part including a plurality of electric wires gathered in a same direction; and a shield member which collectively surrounds an outer periphery of the wire part. The shield member is disposed to be interposed between adjacent electric wires of the plurality of electric wires in the wire part. The adjacent electric wires in the wire part are arranged at a predetermined interval such that a predetermined value of electrostatic capacitance is established between the electric wires.