Contractible Lip Grommet for Low Insertion Force Assembly
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Solution Overview
Problem
Existing grommets require high insertion force due to increased lap width for high holding force, degrading assemblability.
Innovation Solution
A grommet design featuring a central shaft with a circular connection portion, a V-shaped ring-like lip, and a flange portion, where the lip is extensible and contractible, reducing insertion force by decreasing diameter during assembly and increasing holding force by expanding diameter post-assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the lap width of the elastic expansion portion is increased to ensure high holding force, then the holding force is improved, but the insertion force increases and assemblability is degraded
Solution Approach 1:
The lip is designed to dynamically change its diameter: contracted during insertion to reduce insertion force, and expanded after insertion to provide high holding force. This dynamic transformation allows the same structure to satisfy both assemblability and holding force requirements at different stages
Solution Approach 2:
The lip is preliminarily contracted before insertion to facilitate easy assembly. After the grommet is inserted into the through hole, the lip is then expanded to achieve the desired holding force. This preliminary action sequence resolves the contradiction by preparing the structure in advance for the specific operational stage
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 assemblability by reducing insertion force while maintaining high holding force, ensuring the grommet is securely attached without slipping off.
Implementation Method 1
the lip is extensible and contractible in a direction of a shaft center line of the central shaft
Implementation Method 2
the elastic expansion portion is elastically restored from the deformed state
Data Source
AI summary
A grommet (1) has a central shaft (2)through which a wire harness (5) is inserted. A circular connection portion (31) is provided continuously to the periphery of the central shaft(2.) A convex cross-sectionally V-shaped ring-like lip (32) is extensibly provided to the circular connection portion (31) in the direction of the center of the central shaft. A flange portion (33) is provided continuously to the lip portion (32.) When the grommet (1) is assembled to a body panel (10,) the lip (32) of the grommet (1) is extended in the direction of the center of the central shaft (2) of the grommet (1,) thereby reducing the diameter of the lip (32.) Then, the lip(32) is inserted into the through hole (12) of the body panel (10.) Thus, a low insertion force is sufficient when the grommet is inserted thereinto. Consequently, the assemblability of the grommet (1)is enhanced.