Rearview Mirror Conductive Elastomer RF Shielding
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Solution Overview
Problem
The challenge is to enhance safety in automotive rearview mirror assemblies by effectively managing RF energy propagation and providing a reliable low-impedance grounding connection to prevent the electrochromic dimming mirror element from acting as a passive antenna, while also ensuring efficient backlighting for the LCD display.
Innovation Solution
The solution involves using a conductive elastomer pad for creating a low impedance electrical connection between the electrochromic element bus bar and the LCD shield, along with a reflector matrix for optimized LED backlighting, and incorporating advanced driver assist features like lane departure warning, adaptive cruise control, and pedestrian recognition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the electrochromic dimming mirror element is used for rearview display, then the mirror provides dynamic dimming capability and display function, but the mirror element may act as a passive antenna and propagate RF energy
Solution Approach 1:
A conductive elastomer pad is introduced as an intermediary component between the electrochromic element bus bar and the LCD shield. This pad provides a low-impedance electrical connection that grounds the electrochromic element, preventing it from acting as an antenna while maintaining its dynamic dimming functionality. The elastomer material allows flexible electrical connection without compromising the electrochromic effect.
Solution Approach 2:
The patent converts the potential harmful effect of the electrochromic element acting as an antenna into a beneficial grounding connection. By intentionally providing a low-impedance path to ground through the conductive elastomer pad, the system prevents RF energy propagation while maintaining the electrochromic dimming capability. The same conductive property that could enable antenna behavior is harnessed to create a grounding solution.
2Use of energy by moving object
If LEDs are used for LCD backlighting, then energy efficiency and lifespan are improved, but heat generation from LEDs needs to be managed
Solution Approach 1:
A thermally conductive adhesive is introduced as an intermediary material between the LED array and the heat sink. This adhesive serves dual functions: electrically isolating the LEDs while thermally conducting heat away from the LED junctions. The thermally conductive property allows efficient heat transfer to the heat sink, preventing temperature buildup that would reduce LED lifespan and efficiency.
3Loss of information
If the LCD display is integrated into the rearview mirror, then driver assist information is provided, but RF energy may interfere with the display quality
Solution Approach 1:
An RF shield is introduced as an intermediary barrier between the LCD display and the external environment. This shield creates a Faraday cage effect that blocks RF energy from interfering with the LCD display, ensuring clear presentation of driver assist information. The RF shield is strategically positioned to protect the display while allowing necessary electrical connections.
Solution Approach 2:
The patent converts the potential harmful RF interference into a protective shielding solution. By implementing the RF shield, the system uses the same RF energy that could interfere with the display to instead demonstrate the effectiveness of electromagnetic shielding, ensuring display quality while maintaining other mirror functions.
4Adaptability or versatility
If multiple components are integrated into the mirror assembly, then functionality is enhanced, but manufacturing complexity increases
Solution Approach 1:
Multiple functional components are merged into a single integrated mirror assembly, including the electrochromic element, LCD display, LED backlighting with heat sink, and RF shielding. This consolidation reduces the number of separate parts and assembly steps, simplifying manufacturing while providing enhanced functionality. The components are designed to work together within a unified structure.
Solution Approach 2:
The mirror assembly is designed as a multi-functional universal component that provides electrochromic dimming, LCD display for driver assist information, LED backlighting, heat management, and RF shielding. This multi-functionality reduces the need for separate components and simplifies the overall vehicle interior configuration, easing manufacturing and installation.
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 effectively prevents RF energy propagation, ensures reliable grounding, and enhances safety through dynamic scaling of LCD display information and integration of advanced driver assist features, improving the overall performance and safety of the automotive rearview mirror system.
Implementation Method 1
an elastomeric conductor for providing a grounding connection from the bus bar to the RF shield
Implementation Method 2
a plurality of light emitting diodes formed into a matrix configuration mounted to the PCB for providing LCD backlighting
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A vehicular rearview mirror assembly (600) includes an electrochromic (EC) glass element (303) and a printed circuit board (603) for mounting electrical components. A liquid crystal display (LCD) (615) is mounted to the printed circuit board (603), while a plurality of light emitting diodes (LEDs) (608) are also mounted to the same printed circuit board below the LCD (603) for providing backlighting.