Glazing Crack Sensor via Capacitive Coupling
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Solution Overview
Problem
Existing glazing systems face challenges in effectively detecting cracks without causing hotspots or fires, particularly in laminated heated windshields, due to the complexity of edge connectors and potential for arcing, which can propagate cracks and compromise safety.
Innovation Solution
A glazing system utilizing a surface contact connected by capacitive coupling to a sensor that detects voltage modulations caused by damage to the glazing material, allowing for fewer edge connectors and simpler electronics, with the sensor being frangible and capable of inducing or applying voltages to detect arcing or discontinuities, and operating within specific frequency ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sensor lead encircles the periphery of the glazing to detect cracks at any edge portion, then crack detection coverage is improved, but the number of edge connectors increases to four
Solution Approach 1:
The invention extracts the crack detection function from the edge connectors and integrates it into the heating element itself. The heating element is configured to sense voltage modulations caused by cracks, eliminating the need for separate sensor leads and multiple edge connectors. This reduces the number of edge connectors while maintaining crack detection coverage.
Solution Approach 2:
The heating element is designed to perform dual functions: providing heating/defogging/de-icing and detecting cracks. By making the heating element universal, the patent eliminates the need for separate sensor leads and reduces the number of edge connectors required, while maintaining reliable crack detection.
2Reliability
If five edge connectors are used to connect sensor leads to tabs on the coating, then crack detection is enabled, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The invention merges the heating element and crack sensor into a single integrated component. The heating element is configured to sense voltage modulations caused by cracks, eliminating the need for separate sensor leads and multiple edge connectors. This reduces the number of edge connectors from five to fewer, simplifying manufacturing while maintaining crack detection capability.
3Measurement precision
If a frangible wire is positioned around the periphery for crack detection, then crack detection sensitivity to breakage is improved, but the system only detects complete glazing rupture rather than partial cracks
Solution Approach 1:
The heating element is designed with local quality variations that create different electrical paths. When a crack occurs, it disrupts these local electrical paths, causing voltage modulations that can be detected. This allows detection of partial cracks without requiring complete glazing rupture, while maintaining safety functionality.
4Reliability
If DC voltage or low-frequency AC voltage is applied to the antenna for crack detection, then resistance measurement for crack detection is enabled, but mutual interference with AM/FM amplifier function occurs
Solution Approach 1:
The invention segments the electrical circuit by using the heating element's voltage modulations rather than applying external DC or low-frequency AC voltage. The heating element itself generates the sensing signal through its heating function, eliminating the need for separate crack detection electronics and avoiding interference with AM/FM amplifier operations.
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 solution provides a reliable crack detection function with fewer edge connectors, minimizing the risk of hotspot formation and fire, while ensuring immediate detection of cracks and integration with existing heating elements, enhancing safety and reducing complexity.
Implementation Method 1
a surface contact connected by capacitive coupling to a sensor such that a voltage modulated by damage to a ply of glazing material is detectable at the surface contact
Implementation Method 2
Arcing or non-uniform current distribution around such a discontinuity may cause a hotspot in a part of the glazing
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A glazing (10) having a means for detecting a crack in the glazing comprises as sensor (16), substantially circumscribing a ply of glazing material (11). A surface contact (17), bonded to the glazing, is configured with a portion (16b) of the sensor to form a capacitive coupling for transferring AC signals in a frequency range. Preferably the sensor (16) is frangibleand voltage may beapplied by a second surface contact. Alternatively, the glazing 10 further comprises an electrically resistive element (13), such as a coating for heating the glazing, and voltage may be applied to the sensor (16) by a spur from a busbar (15) such that damage to coating, busbar or sensor resulting in arcing is detectable at the surface contact (17). An electronics module (20) attached to the surface contact (17) generates an alarm.