Vehicle Windshield Heating Area Positioning to Reduce Thermal Stress
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Solution Overview
Problem
Existing glass panes with local heating areas for vehicle windshields experience significant thermal stresses due to temperature differences, making them susceptible to cracking from stone impacts and reducing their resilience, especially when heating elements are placed far from the edge.
Innovation Solution
The heating area is positioned within 15 mm of the glass pane's edge, allowing thermal conduction to extend the heated region to the edge, eliminating thin unheated strips and minimizing stress concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the heating area is positioned far from the edge of the glass pane, then the transmission region is effectively heated, but thermal stresses increase and the pane becomes susceptible to cracking
Solution Approach 1:
The heating area is positioned to extend to within 15 mm of the edge, creating a localized heated zone that eliminates the critical unheated strip at the edge while maintaining effective heating of the transmission region. This local modification of the heating area configuration resolves the stress concentration problem without requiring full-pane heating.
2Stress or pressure
If the heating area extends to the edge of the glass pane, then thermal stresses are minimized, but the heating element visibility increases and optical properties deteriorate
Solution Approach 1:
The heating area is extended partially to the edge (within 15 mm) rather than fully covering the transmission region or the entire pane. This partial extension is sufficient to eliminate the critical unheated strip and reduce thermal stresses, while avoiding excessive heating area that would compromise optical properties and increase visibility of heating elements.
3Reliability
If a thin unheated strip remains between the heating area and the edge, then the transmission region is adequately heated, but stress concentrations increase and crack susceptibility rises
Solution Approach 1:
The distance parameter between the heating area and the edge is changed from a larger value (creating a thin unheated strip) to a smaller value (within 15 mm). This parameter change eliminates the stress concentration zone while maintaining effective heating, thereby improving both reliability and strength.
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 configuration enhances the glass pane's resilience to stone impacts by reducing thermal stresses and preventing crack formation, while maintaining effective de-icing and defogging functionality.
Implementation Method 1
allowing thermal conduction to extend the heated region to the edge
Data Source
Figure 1a~1b
Figure 2a~2b
AI summary
The invention relates to a glass pane (1), comprising at least two individual panes and an adhesive layer located in between them, with the glass pane (1) having a local heating area (8) which only extends over part of the overall area of the pane (1) and which can be heated by means of a heating element. Furthermore, the invention relates to glass pane arrangements (1') or (101), comprising a glass pane (1) or (10) formed by at least two individual panes and an adhesive layer located in between them; and at least one optical functional element, or at least two optical functional elements at a distance (b) from one another, which are arranged on one side of the glass pane (1, 10) and which send signals to the opposite side of the glass pane (1, 10) and/or receive signals from the opposite side of the glass pane (1, 10) through an optical transmission region (4, 14) of the glass pane (1. 10); and at least one local heating area (8, 18) which only extends over part of the overall area of the glass pane (1, 10) but which at least extends over the entire transmission region (4, 14), with the transmission region (4, 14) being at a distance from an end face (3) of the glass pane (1) in all directions. In order to develop a glass pane (1, 10) or a glass pane arrangement (1', 10') of the type mentioned initially so that the stresses occurring due to the heated regions of the glass panes (1, 10) are minimized and the risk of damage to the pane by the formation of cracks after stone impact is reduced, the invention proposes that the distance (a) between the heating area (8) and the end face (3) of the glass pane (1) is less than 15 mm and preferably less than 10 mm, and that the heating area (18) also completely extends over an intermediate space (15) located between the two transmission regions (14).