Heated Side Laminated Glazing With External Busbar Placement
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Solution Overview
Problem
The use of busbars to supply current to heatable coated laminated automotive glazing units, particularly those with thin or ultrathin glass sheets, leads to issues such as delamination, bubble formation, and uneven heating due to varying electrical resistance, which can cause damage and visibility problems.
Innovation Solution
The placement of busbars on the exterior sheet not covered by the thin interior sheet, combined with specific thickness and curvature ratios of the glass sheets, ensures uniform heating and prevents delamination, allowing for the production of heatable coated laminated glazing units with asymmetrical shapes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If busbars are placed within the laminated structure to supply current to the conductive coating layer, then the glazing panel can be heated for de-misting or de-icing, but the thickness of the busbars causes bubbles and delamination in thin or ultrathin glass sheets
Solution Approach 1:
The busbars are extracted from the interior of the laminated structure and placed on the exterior surface of the glass sheet. This removes the source of mechanical stress and delamination from within the thin glass structure, while still allowing electrical current to be supplied to the conductive coating layer for heating purposes.
Solution Approach 2:
The busbars are positioned on the external surface of the glass rather than being embedded within the laminated layers. This dimensional relocation from interior to exterior surface eliminates the interference with the thin glass structure while maintaining the electrical connection function.
2Adaptability or versatility
If spaced busbars diverge at portions along their length to accommodate irregular glazing shapes, then the glazing can cover complex automotive surfaces, but the varying distance between busbars creates uneven heating and local overheating
Solution Approach 1:
The conductive coating layer itself is used to distribute current laterally across the glass surface, creating localized heating zones that can be controlled independently. This allows different regions of the glazing to receive appropriate heating levels based on their specific requirements, maintaining uniformity despite irregular overall shapes.
Solution Approach 2:
The conductive coating layer acts as an intermediary between the busbars and the glass surface. It receives current from the busbars and distributes it uniformly across the coating area, preventing direct concentration of current at varying distances from the busbars and thereby eliminating local overheating.
3Strength
If monolithic thick glass sheets are used for side windows, then mechanical strength and anti-intrusion qualities are achieved, but the weight and thickness prevent integration with movable window mechanisms
Solution Approach 1:
The glazing uses a composite structure with a thin glass sheet combined with a conductive coating layer and externally positioned busbars. This composite approach maintains the necessary electrical and mechanical properties while reducing overall weight and thickness compared to traditional monolithic thick glass.
Solution Approach 2:
The use of thin glass sheets (rather than thick monolithic glass) combined with external busbars creates a more flexible, lighter-weight structure that can be integrated with movable window mechanisms while still providing the necessary strength and heating capabilities.
4Shape
If the distance between busbars varies along their length to accommodate irregular glazing shapes, then the glazing can be shaped for automotive applications, but the electrical resistance varies causing non-uniform heat generation
Solution Approach 1:
The conductive coating layer provides localized current distribution across different regions of the glazing. Each area receives current through the coating's lateral conduction, ensuring uniform heating regardless of the varying distances from the busbars, thus maintaining manufacturing precision in heating uniformity.
Solution Approach 2:
The conductive coating layer serves as an intermediary that equalizes current distribution across the glazing surface. It mediates between the non-uniform busbar positioning and the requirement for uniform heating, ensuring consistent temperature distribution despite variations in busbar spacing.
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 approach enables uniform heating across the glazing surface, preventing delamination and ensuring consistent de-misting or de-icing, while maintaining mechanical and optical properties, thus addressing the challenges of using thin glass sheets in laminated glazing units.
Implementation Method 1
When submitting such glazing panels to a given voltage, the amount of heat generated will be substantially uniform throughout the whole surface of the glazing panel covered with the conductive coating layer
Data Source
AI summary
The invention relates to an electrically heatable laminated automotive glazing unit comprising an exterior glass sheet that is curved and tempered and a thin glass interior sheet that is also tempered, these sheets being joined by means of a thermoplastic interlayer sheet, the glazing unit is configured to receive mechanical moving and/or fastening means and a portion of the exterior sheet is not covered by the thin interior sheet, and the glazing unit is fastened in the zone not covered by the thin sheet, the glazing unit comprising at least one electrically heatable zone comprising (i) a substantially transparent, electrically conductive coating layer and (ii) spaced busbars adapted to supply electrical voltage across the substantially transparent, electrically conductive coating layer. According to the present invention the spaced busbars are placed in the portion of the exterior sheet which is not covered by the thin interior sheet.