Pin-Cavity Adhesive Joint Assembly for Shrinkage-Stable Positioning
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Solution Overview
Problem
Adhesive joints in lighting devices for motor vehicles face challenges due to volumetric shrinkage of adhesives during curing, which can alter the position of light sources or optical components, affecting the lighting effect and compliance with regulations.
Innovation Solution
A method involving the use of a flexible spacer positioned between the bottom surface of a cavity and the facing end of a pin, preventing the pin from repositioning during adhesive curing by eliminating adhesive volume below the pin and allowing only horizontal shrinkage effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive is used to join pin to cavity, then components are fastened together, but volumetric shrinkage during curing causes position alteration
Solution Approach 1:
A support structure is introduced as an intermediary element between the pin and cavity bottom. This support structure receives the pin during adhesive curing, preventing position alteration caused by adhesive shrinkage. The support structure acts as a mediator that transfers the load from the pin to the cavity walls, eliminating the harmful effect of volumetric shrinkage while maintaining joint strength.
Solution Approach 2:
The support structure is positioned in the cavity before the pin is inserted and before adhesive curing begins. This preliminary placement ensures that the pin is already supported in its target position when curing starts, preventing any position drift during the curing process. The support structure is pre-configured to match the expected pin position and geometry.
2Strength
If pin extends deeply into cavity, then joint strength increases, but pin becomes susceptible to shrinkage-induced subsidence
Solution Approach 1:
The support structure serves as a mediator that interrupts the direct adhesive bond between the pin end and cavity bottom. By providing an alternative load path through the support structure, the pin is prevented from subsiding into the cavity due to adhesive shrinkage. This allows the pin to extend deeply into the cavity for strength while the support structure maintains vertical position accuracy.
3Strength
If adhesive volume is increased, then joint strength improves, but shrinkage effects are amplified
Solution Approach 1:
The adhesive bonding is segmented into two distinct regions: a first adhesive region between the pin lateral surface and cavity walls, and a second adhesive region between the support structure and cavity bottom. This segmentation allows the support structure to bear the vertical load while the adhesive primarily provides lateral bonding, reducing the adhesive's role in vertical position maintenance and thereby minimizing shrinkage-induced position changes.
Solution Approach 2:
The support structure acts as an intermediary that reduces the functional demand on the adhesive for vertical position maintenance. By transferring the vertical load through the support structure, the adhesive's shrinkage has less impact on position stability, allowing greater adhesive volume for strength without proportionally increasing position instability.
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 method effectively stabilizes the pin in the target position, preventing both vertical and horizontal shifts due to adhesive shrinkage, thus maintaining precise positioning and ensuring consistent lighting performance.
Implementation Method 1
A major issue concerning such adhesive joints is the effect of volumetric shrinkage of the adhesive during curing, caused e.g. by the evaporation of a solvent or by a crosslinking reaction.
Implementation Method 2
positioning a flexible spacer on the bottom surface of the cavity
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The invention relates to a method of joining a pin (1) member of a first component (1a) to a second component (2a) with a cavity (2) by means of an adhesive (3) in order to fasten the pin (1) in a target position extending at least partially into the cavity (2) with a distance (D) between the bottom surface (20) of the cavity (2) and the facing end (10) of the pin (1), wherein the method comprises at least the following steps: - positioning (100) a flexible spacer (4) on the bottom surface (20) of the cavity (2), wherein the thickness (40) of the spacer (4) equals or exceeds the distance (D) between the bottom surface (20) of the cavity (2) and the facing end (10) of the pin (1) in the target position, - filling (200) the adhesive (3) into the cavity (2) onto the flexible spacer (4), - positioning (300) the pin (1) to the target position, - curing (400) the adhesive (3) and obtaining a joint between the pin (1) and the second component (2a).