Heatable Cover Plate With Nano-Tube Layer for Uniform Vehicle Lighting
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Solution Overview
Problem
Existing motor vehicle lighting devices with plastic cover plates experience significant temperature gradients due to discrete heating elements, leading to undesirable variations in light distribution caused by temperature-dependent changes in the refractive index of the plastic material.
Innovation Solution
A motor vehicle lighting device with a transparent carrier film coated with an electrically conductive nano-tube layer applied to the cover plate, which provides homogeneous heating and maintains a constant refractive index across the surface, preventing local variations in light distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If discrete conductor tracks are used for heating the cover plate, then defrosting function is achieved, but strong temperature gradients are created leading to light distribution variations
Solution Approach 1:
The patent applies a transparent heating layer with spatially varying electrical conductivity to the cover plate. The heating element has higher conductivity in central regions and lower conductivity at peripheral regions, creating non-uniform heating distribution that compensates for the natural heat dissipation pattern. This ensures uniform temperature distribution across the cover plate surface, preventing light distribution variations while maintaining effective defrosting function.
2Reliability
If heating element is applied to inside of cover plate, then defrosting effectiveness is improved, but light transmission is reduced
Solution Approach 1:
The patent uses a transparent thin-film heating layer that can be applied to the cover plate surface. This thin-film structure provides sufficient heating capability for defrosting while maintaining high light transmission properties, avoiding the light blocking issues associated with traditional discrete conductor tracks or opaque heating elements.
3Illumination intensity
If heating element is applied to outside of cover plate, then light transmission is maintained, but defrosting effectiveness is reduced
Solution Approach 1:
The patent modifies the electrical conductivity parameter of the heating layer to create a gradient distribution. By varying the conductivity spatially (higher in center, lower at edges), the system achieves uniform heat distribution that effectively defrosts the cover plate while maintaining transparency. The heating layer can be applied to either inside or outside of the cover plate depending on specific design requirements.
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
Ensures effective defrosting and de-icing of the cover plate while maintaining a consistent light distribution, ensuring the full transparency and functionality of vehicle assistance systems even in adverse weather conditions.
Implementation Method 1
The current flowing through the layer encounters the resistance of the nanotubes, whereby electrical energy is converted into heat.
Implementation Method 2
the refractive index of the plastics used for cover plates is highly temperature-dependent. This means that the refractive index of the cover plate is subject to strong fluctuations across its entire surface
Data Source
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AI summary
The invention relates to a motor vehicle lighting device (4) comprising a housing (10) with a light emission opening (14) closed by a transparent cover plate (12) and a light module (18) arranged in the housing (10) for generating a light distribution and for emitting the light distribution along a beam path (19) through the cover plate (12). The cover plate (12) is heatable. In order to enable the most homogeneous heating of the cover plate (12) possible, it is proposed that the cover plate (12) in the beam path (19) has an electrically conductive layer (26) with nanotubes made of at least one electrically conductive material and that an electrical voltage (U) is applied at least temporarily to the layer (26), so that an electric current (I) flows through the layer (26), as a result of which the layer (26) heats up uniformly and the heat of the layer (26) heats the cover plate (12).