Grommet for Wire Harness with Inclined Engagement Recess
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Solution Overview
Problem
Conventional grommets for wire harnesses in vehicles with burring holes face challenges in ensuring waterproof sealing due to variations in burring height and curvature, leading to insufficient gripping force and increased assembly complexity and cost.
Innovation Solution
A one-piece rubber or elastomer grommet with an annular body engagement recess featuring an inclined or arcuate bottom surface, allowing the burring to be wedged and pressed against the grommet's seal point, independent of burring radius variations, ensuring stable waterproof performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional grommet with seal lip is used on a burring hole, then the grommet can be engaged with the through-hole, but the seal pressure cannot be controlled due to burring height and curvature variations
Solution Approach 1:
The invention changes the geometric parameters of the engagement recess, specifically designing it with an inclined surface that allows the burring to be compressed and deformed during insertion. This parameter change enables the burring's front end surface to contact the bottom surface of the engagement recess at a controlled position, making seal pressure independent of burring height variations
Solution Approach 2:
Instead of having the seal lip press against the burring (conventional approach), the invention inverts the approach by having the burring press against the bottom surface of the engagement recess. The burring itself becomes the sealing element by deforming and contacting the recess bottom, reversing the traditional sealing mechanism
2Reliability
If the grommet is designed to accommodate burring variations, then sealing may be improved, but the engagement amount becomes insufficient leading to insufficient gripping force
Solution Approach 1:
The invention adds a dimensional element by designing the engagement recess with an inclined bottom surface that extends in the axial direction. This allows the burring to be compressed axially during insertion, creating engagement through deformation rather than relying solely on radial overlap. The inclined surface provides an additional dimension for engagement that accommodates burring variations while maintaining sufficient gripping force
3Strength
If a large engagement amount is used to improve gripping force, then the grommet can grip the burring better, but the insertion force increases
Solution Approach 1:
The invention introduces dynamic deformation of the burring through the inclined engagement recess. During insertion, the burring is dynamically compressed and deformed to engage with the recess, creating gripping force through the deformation process rather than requiring large static overlap. This dynamic engagement reduces insertion force while maintaining adequate gripping force
4Reliability
If a two-piece grommet structure is used to accommodate burring variations, then sealing performance can be maintained, but assembly complexity and cost increase
Solution Approach 1:
The invention merges the sealing function and the engagement function into a single integrated structure. The engagement recess with its inclined bottom surface combines both the sealing mechanism (through burring deformation and contact) and the engagement mechanism (through the recess geometry), eliminating the need for separate seal lips or multi-piece constructions. This single-component design reduces assembly complexity while maintaining waterproof performance
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 provides stable waterproof sealing by controlling the burring projection size and facilitating easy design, reducing assembly complexity and cost by using a single-component grommet.
Implementation Method 1
The projecting front end surface of the burring is wedged in and pressed into contact with the inclined bottom surface portion or the arcuate bottom surface portion
Data Source
AI summary
Waterproof performance of a grommet is stabilized, the grommet being inserted and engaged with a through-hole having a burring in a body panel. A grommet for a wire harness is externally fitted to the wire harness routed in a vehicle and is mounted to a through-hole from which a burring of a body panel projects. The grommet includes a one-piece molded component of one of rubber and elastomer and an annular body engagement recess in an outer peripheral surface of a tubular portion through which the wire harness is inserted. A size between two side surfaces that define a bottom surface of the body engagement portion is set to be less than a projection size of the burring projecting from a periphery of the through-hole. A projecting front end surface of the burring is wedged in and pressed into contact with one of the side surfaces to serve as a seal point.