Wire Harness Grommet Sealing Structure for Positional Gap Control
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Solution Overview
Problem
Conventional grommets fail to effectively suppress the occurrence of gaps due to positional deviation between members, compromising waterproofness in wire harnesses.
Innovation Solution
A grommet design incorporating a base member formed of insulating hard resin, a waterstop member with integrated first and second waterstop members of different hardnesses, and a holding mechanism to secure the assembly, ensuring effective sealing against liquid ingress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a conventional split grommet is used, then the grommet can be easily installed, but gaps occur due to positional deviation between members reducing waterproofness
Solution Approach 1:
The grommet is divided into a first grommet member and a second grommet member that are coupled together. The first member has a first fitting portion that fits into the through hole, while the second member has a second fitting portion that fits into the first member. This segmented structure with nested coupling reduces positional deviation and improves waterproofness while maintaining installation ease.
Solution Approach 2:
The second grommet member is nested within the first grommet member through a coupling structure where the second fitting portion is inserted into the first fitting portion. This nesting arrangement ensures precise positioning and eliminates gaps between members, thereby improving waterproofness without complicating the installation process.
2Ease of manufacture
If the grommet structure is simplified, then manufacturing is easier, but positional deviation between members increases reducing sealing effectiveness
Solution Approach 1:
The grommet is segmented into multiple members with standardized fitting portions. Each member can be manufactured independently using standard processes, and the modular design maintains manufacturing simplicity while the precise fitting portions ensure accurate positioning when assembled.
Solution Approach 2:
The fitting portions are designed with specific dimensional parameters and tolerances that ensure precise alignment and minimal positional deviation during assembly. By optimizing these geometric parameters, the invention achieves high positional accuracy without requiring complex manufacturing processes.
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
Enhances waterproofness by preventing liquid entry through gaps between the grommet and the through hole, even under high-pressure conditions, while maintaining structural integrity and positional stability.
Implementation Method 1
the second waterstop member having an annular shape, formed of a soft resin softer than the hard resin and elastically deformable, and configured to be in close contact with at least an outer circumferential surface of the outer peripheral edge of the flange over one circumference in the circumferential direction, and the second waterstop member has a contact portion having an annular shape and configured to be, in elastically deformed state, in close contact with the peripheral edge over one circumference in the circumferential direction
Data Source
AI summary
A grommet includes: a base member, a waterstop member, and a holding mechanism. The base member includes: a flange that causes an outer peripheral edge to face the peripheral edge with a gap; a tubular body that protrudes from an inner peripheral edge of the flange and allows passage of a wiring member inside the body; and a cylindrical body that protrudes from the flange so as to be inserted through the through hole. The waterstop member includes: a first waterstop member and a second waterstop member in an integrated state outside a radial direction. The first waterstop member covers an annular wall surface. The second waterstop member is in close contact with an outer circumferential surface of the outer peripheral edge over one circumference in the circumferential direction. The second waterstop member has a contact portion configured be in close contact with the peripheral edge.