Waterproof Wire Harness Structure Using Trapezoidal Damming Part
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Solution Overview
Problem
Existing waterproof structures for wire harnesses face challenges with water stop performance, manageability, and workability, particularly with one-component water stops and butyl rubber, which struggle to fill gaps effectively and are prone to molding defects, leading to insufficient waterproofness.
Innovation Solution
A waterproof structure for wire harnesses using a damming part with a trapezoidal shape in cross section, made of hard resin, combined with a water stop material and lightening parts to prevent water ingress, and a longer water stop material length to ensure stable sealing, even when the damming part deviates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a one-component water stop (silicon) is used to fill gaps between electric wires, then water stop performance is improved, but workability deteriorates due to long solidification time (several hours) and difficulty in managing the water stop agent
Solution Approach 1:
The invention divides the water stop function into two parts: a rigid damming part made of hard resin material that provides structural support and positioning, and a flexible water stop material that actually seals the gaps. This segmentation allows each component to optimize its properties - the damming part provides stability while the water stop material provides sealing capability without long solidification times.
Solution Approach 2:
The damming part acts as an intermediary component between the electric wire bundle and the water stop material. It positions the water stop material correctly and provides a stable base, while the water stop material is applied separately to fill gaps. This intermediary structure resolves the workability issues of direct silicon application by separating the positioning function from the sealing function.
2Reliability
If butyl rubber is used to fill gaps between electric wires, then water stop performance is improved when gaps are filled, but device complexity increases due to difficulty in managing the amount of butyl rubber and checking filling state
Solution Approach 1:
The water stop material is made visually distinguishable (through color or other visual properties) so that the filling state can be easily checked. This allows operators to confirm proper installation without complex inspection procedures, reducing the perceived complexity of managing the water stop process.
Solution Approach 2:
The damming part is installed first to establish the correct positioning and structure before the water stop material is applied. This preliminary action ensures that the water stop material is applied in the correct location and amount, eliminating the need for complex measurement and checking procedures during the water stop process.
3Reliability
If a mold structure with resin material is used to surround electric wire bundle, then waterproofing is improved, but manufacturing precision deteriorates due to resin unfilled spaces between adjacent electric wires when three or more wires are bundled
Solution Approach 1:
Instead of attempting to mold resin around the entire wire bundle (which creates unfilled spaces), the invention applies the water stop material locally to the specific gaps between wires after the damming part is in place. This local application ensures complete gap filling without the manufacturing defects associated with mold structures.
4Adaptability or versatility
If damming part with trapezoidal shape in cross section is used to match electric wire group insertion part, then adaptability is improved, but manufacturing precision deteriorates due to molding defects (sinks or voids) in thick-walled parts
Solution Approach 1:
The invention changes the material parameter from soft resin to hard resin material for the damming part. This parameter change allows the use of traditional molding methods without sinks or voids, while still achieving the required trapezoidal shape for adaptability to the insertion part. The hard resin material provides better molding characteristics.
Data Source
AI summary
A waterproof structure of a wire harness includes at least one bundle of an electric wire group in which a plurality of electric wires are linearly arranged, a damming part made of a hard resin material, the damming part which surrounds a part of the electric wire group in an extension direction of the electric wire group and which includes an outer periphery shape part according to a shape of a trapezoidal through hole in an electric wire group insertion part with a divided structure, and a water stop material which prevents water from entering a gap between the electric wire group insertion part and the outer periphery shape part and which is formed on an inner peripheral surface of the through hole.