Wire Harness Insulator Viscoelasticity Vibration Resistance
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Solution Overview
Problem
Wire harnesses used in automobiles, especially those connecting inverters and motors, face issues with insulator cracking and fracturing due to vibration when bent, especially when soft insulators are used to increase flexibility, leading to potential cuts in the molded resin portion during insert molding.
Innovation Solution
A wire harness design with an insulator having a storage modulus of 100 MPa or less at 25°C and 1 MPa or more at 250°C, and a starting temperature of the rubbery plateau region of 150°C or less, which maintains flexibility while preventing deformation and cutting into the insulator during molding, thereby reducing the risk of cracks and fractures under vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a softer and thinner insulator is adopted to increase the flexibility of the electric wire, then the flexibility is improved, but the insulator significantly deforms inward in the diameter direction during insert molding, causing the molded resin portion to cut into the insulator
Solution Approach 1:
The patent applies parameter changes by precisely controlling the storage modulus of the insulator at different temperatures. The insulator is designed to have a storage modulus of 100 MPa or less at 25°C to ensure flexibility, while maintaining 1 MPa or more at 250°C to prevent deformation during molding. The starting temperature of the rubbery plateau region is set to 150°C or less, creating an optimal parameter window that resolves the contradiction between flexibility and shape stability.
2Ease of operation
If a soft insulator is used to maintain flexibility in bent states, then the flexibility is improved, but cracks appear in the insulator due to vibration when the wire harness is used
Solution Approach 1:
The patent resolves this contradiction by changing the temperature-dependent mechanical parameters of the insulator. By setting the storage modulus to 100 MPa or less at 25°C, the insulator remains soft and flexible during normal use and vibration. The rubbery plateau region starting at 150°C or less provides a transition that prevents brittle fracture, while the high-temperature modulus requirement ensures structural integrity during manufacturing processes.
3Ease of operation
If the insulator is made of soft material to increase flexibility, then the flexibility is improved, but the inner edge portion of the molded resin portion has a shape that cuts into the insulator
Solution Approach 1:
The patent uses parameter changes to control the insulator's dimensional stability during the molding process. The storage modulus requirement of 1 MPa or more at 250°C ensures that the insulator maintains its shape when exposed to high temperatures during insert molding, preventing the molded resin from cutting into the insulator's inner edge portion, while still allowing flexibility at operating temperatures.
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 wire harness effectively suppresses cracks and fracturing of the insulator due to vibration without compromising the flexibility of the electric wire, ensuring reliable performance in severe bending conditions and high-temperature environments.
Implementation Method 1
a storage modulus E' of the insulator that is measured using a dynamic viscoelasticity measurement device in a tensed mode at a temperature increase rate of 5° C./min and a frequency of 10 Hz is 100 MPa or less at 25° C. and 1 MPa or more at 250° C.
Implementation Method 2
a starting temperature of a rubbery plateau region is 150° C. or less
Data Source
AI summary
A wire harness that includes an electric wire provided with a conductor and an insulator that coats an outer periphery of the conductor, a terminal connected to the conductor at a terminal end of the electric wire, and a molded resin portion that covers an outer periphery of the insulator at the terminal end of the electric wire and an outer periphery of an end portion on the electric wire side of the terminal. A storage modulus E′ of the insulator that is measured using a dynamic viscoelasticity measurement device in a tensed mode at a temperature increase rate of 5° C./min and a frequency of 10. Hz is 100 MPa or less at 25° C. and 1 MPa or more at 250° C., and a starting temperature (T) of a rubbery plateau region (G) is 150° C. or less.