Wire Harness Grommet Structure for Misalignment Stress Absorption
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Solution Overview
Problem
Existing grommets face challenges in maintaining waterproofing performance when wire harnesses are inserted at an angle or with positional errors, leading to stress on the mounting portion and potential gaps that allow water ingress.
Innovation Solution
A grommet design featuring an annular mounting portion with a tubular stress-absorbing portion and a tubular insertion portion, where the stress-absorbing portion includes a flexible side wall and a bottom wall with the insertion portion protruding inside the stress-absorbing portion, effectively absorbing stress and maintaining seal integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the flexible portion has a plurality of pleats arranged in a direction orthogonal to the center axis of the mounting portion to absorb large amounts of stress, then the stress absorption capability is improved, but the size of the grommet increases in the direction orthogonal to the center axis
Solution Approach 1:
The pleats in the flexible portion are arranged in the axial direction of the mounting portion rather than in a direction orthogonal to it. This dimensional reorientation allows the pleats to absorb stress along the axis while minimizing the grommet's footprint in the orthogonal direction, thus resolving the contradiction between stress absorption capability and compact size.
2Adaptability or versatility
If the insertion portion is pulled strongly away from the mounting portion or significantly inclined due to wire harness insertion errors, then the connection portion must absorb large stress, but this causes deformation of the mounting portion and gaps that reduce waterproofing performance
Solution Approach 1:
The flexible portion is designed as a thin-walled structure with pleats that can bend and deform elastically. This flexible shell structure absorbs the stress from insertion portion displacement and inclination without transmitting it to the rigid mounting portion, thereby preventing gaps and maintaining waterproofing performance while adapting to posture changes.
3Adaptability or versatility
If the flexible portion is designed to absorb large stress through multiple pleats, then the stress absorption is improved, but the device complexity increases
Solution Approach 1:
The flexible portion is segmented into multiple pleats that can independently deform. This segmentation allows each pleat to contribute to stress absorption while maintaining a relatively simple overall structure. The pleats are formed as continuous folds in the wall rather than separate components, balancing complexity with functionality.
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
This design effectively suppresses the decrease in waterproofing performance while preventing an increase in grommet size, by absorbing stress through the flexible side wall and maintaining seal integrity, even with angled or misaligned wire harness insertions.
Implementation Method 1
the side wall is flexible
Data Source
AI summary
A grommet according to one aspect of the present disclosure includes: an annular mounting portion that is to be fixed to a surrounding portion of an insertion hole of a vehicle body panel; and a tubular stress-absorbing portion that includes a tubular side wall that extends from an inner circumferential rim portion of the mounting portion toward one side in an axial direction, and a bottom wall that partially closes off the tubular side wall at a front end of the tubular side wall. Furthermore, the grommet includes tubular insertion portions that are provided integrally with the bottom wall, and that cover the outer circumferences of wire harnesses inserted into the insertion hole. The mounting portion includes an annular seal portion that comes into close contact with the surrounding portion of the insertion hole of the vehicle body panel. The side wall is flexible.