Roof Module Spacer Design for Surface Flatness
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Solution Overview
Problem
Existing roof module manufacturing techniques for motor vehicles face issues such as air entrapment leading to indentations, water absorption, and mechanical property deterioration due to the use of honeycomb cardboard spacers, which result in uneven surfaces and potential delamination.
Innovation Solution
A roof module design featuring an exterior skin, a material layer with a different thermal expansion coefficient, and a spacer layer with a fiber-reinforced polyurethane core, where the spacer layer does not fully cover the material layer, allowing a circumferential zone covered by fiber-reinforced plastic to absorb stresses and prevent deformation, while the material layer buffers unevenness and surface defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If honeycomb cardboard is used as spacer in LFI PUR method, then weight reduction is achieved, but air entrapment occurs causing indentations on sheet surface
Solution Approach 1:
The patent removes the honeycomb cardboard spacer from the LFI PUR process entirely. Instead, it uses a pre-formed PUR foam layer with integrated glass fiber reinforcement as the spacer structure, eliminating the source of air entrapment and indentation problems while maintaining weight reduction benefits
Solution Approach 2:
The patent changes the material parameter from honeycomb cardboard to PUR foam with glass fiber reinforcement. This material substitution eliminates porosity and air pockets inherent in cardboard structures, preventing air entrapment during the foaming process while maintaining the spacer function
2Volume of moving object
If honeycomb cardboard is compressed to reduce thickness, then weight and thickness are reduced, but air cushions form causing sheet indentations
Solution Approach 1:
The patent extracts the problematic honeycomb cardboard structure from the process and replaces it with a solid PUR foam layer that has been pre-formed to the desired thickness. This eliminates the compression step that traps air while achieving the same thickness reduction goal
Solution Approach 2:
The patent uses a composite structure of PUR foam combined with glass fiber reinforcement layers. This composite material provides the necessary mechanical strength and dimensional stability without the air-trapping cellular structure of honeycomb cardboard, preventing surface indentations
3Ease of manufacture
If deep-drawn sheets are used for roof modules, then formability is improved, but air entrapment between sheet and mold causes bulging and visible indentations
Solution Approach 1:
The patent applies a PUR foam layer with glass fiber reinforcement to the deep-drawn sheet before the final molding process. This pre-applied layer acts as a barrier that prevents air from becoming trapped between the sheet and mold during forming, eliminating bulging and surface indentations while preserving the formability benefits of deep-drawn sheets
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 ensures a class A surface finish, maintains mechanical strength, and prevents delamination by effectively managing thermal and mechanical stresses, reducing the risk of indentation and water absorption, thus enhancing the durability and appearance of the roof module.
Implementation Method 1
The material layer (b) has a thermal expansion coefficient different from that of exterior skin (a) and is selected to essentially avoid deformation of the composite upon a temperature change
Implementation Method 2
the spacer layer does not fully cover the material layer, allowing a circumferential zone covered by a fiber-reinforced plastic material to absorb stresses and prevent deformation
Implementation Method 3
the material layer buffers unevenness and surface defects
Data Source
AI summary
A roof module for motor vehicles is disclosed having an exterior skin, a material layer adjacent thereto, a spacer layer, and a circumferential plastic material.