The present invention belongs to the field of lamps for automotive vehicles, and more specifically, to the design of headlamps to avoid fogging in the outer glass.
Current headlamps have to fulfil different requirements which sometimes involve contradictory design paths. One example of this is related to demisting problems.
Misting is caused when water vapour condenses on the internal surface of a glass. Micro-drops are unaesthetic and affect the light behaviour, so great efforts are put to solve this problem. However, in order to design modern and efficient lighting devices, walls of opaque materials must surround the light source, to avoid light leakage. But these opaque walls are an obstacle for a free path of dry air to reach the glass surface and avoid condensation.
Hence, the better a solution is for avoiding light leakage, the worse for avoiding glass condensation because these opaque walls create a tortuous defogging air path that will have a very low flow rate and, consequently, a very slow defogging velocity.
The invention provides a solution for this problem by the provision of an automotive lighting device according to claim 1. Preferred embodiments of the invention are defined in dependent claims.
Unless otherwise defined, all terms (including technical and scientific terms) used herein are to be interpreted as is customary in the art. It will be further understood that terms in common usage should also be interpreted as is customary in the relevant art and not in an idealised or overly formal sense unless expressly so defined herein.
In this text, the term "comprises" and its derivations (such as "comprising", etc.) should not be understood in an excluding sense, that is, these terms should not be interpreted as excluding the possibility that what is described and defined may include further elements, steps, etc.
The permeable element is opaque enough to avoid light leakage, but offers an easier path for the dry flow to reach the glass and avoid misting. Hence, both problems are satisfactorily solved with a solution which is simple and inexpensive.
In some particular embodiments, the permeable element comprises a valve.
A valve is a suitable solution for a permeable material as defined in the present invention, since it allows water vapour to pass through but does not allow light to pass through.
In some particular embodiments, the permeable element comprises a porous material.
A porous material is a suitable solution for a permeable material as defined in the present invention, since it allows water vapour to pass through but does not allow light to pass through.
In some particular embodiments, the whole opaque element is made of a porous material. These embodiments include a porous material that is able to resist loads. In other embodiments, the main part of the opaque element is made of a solid material and only the second portion is made of a porous material, in order to avoid loads on this second portion.
In some particular embodiments, the first portion of the opaque element is made of plastic injection with a pore generation process. In other embodiments, the first portion of the opaque element is manufactured out of a sintering process
These are suitable ways of obtaining a porous material from well-known manufacturing processes and inexpensive materials.
In some particular embodiments, the porous material is one of PTFE, pumice stone or a textile material.
These materials have proved to be suitable for this invention, since they provide a good pore size and good mechanical properties.
In a particular embodiment, at least a portion of the opaque element is located less than 5cm from the outer glass.
Such an arrangement helps to define a straightforward path for the dry current, and is very useful in current designs where size is growing smaller. In some embodiments, this portion of the opaque element could even touch the outer glass.
In some particular embodiments, the opaque element is a bezel. In other embodiments, the opaque element is a harness cover. These are common elements in a lighting device, and are close enough to the glass so that the porosity of the first portion has a positive impact in the path of the dry flow.
In some particular embodiments, the lighting device further comprises a deflector arranged to direct an airflow from the ventilation element to the first portion of the opaque element.
This deflector makes still easier the path of the dry flow from the ventilation element comprised in the housing and the glass which is intended to be demisted.
In some particular embodiments, the first portion has a hydrophobic or super-hydrophobic surface treatment.
These treatments are useful since, otherwise, the pores would become a humidity store, and the dry current would become a wet current when crossing the porous material, thus losing the demisting properties.
In some particular embodiments, the internal face of the outer glass has an anti-mist surface treatment.
This anti-mist treatment is also helpful to cooperate with the dry current in achieving the demisting of the glass surface.
In some particular embodiments, the light source is a solid-state light source.
The term "solid state" refers to light emitted by solid-state electroluminescence, which uses semiconductors to convert electricity into light. Compared to incandescent lighting, solid state lighting creates visible light with reduced heat generation and less energy dissipation. The typically small mass of a solid-state electronic lighting device provides for greater resistance to shock and vibration compared to brittle glass tubes/bulbs and long, thin filament wires. They also eliminate filament evaporation, potentially increasing the life span of the illumination device. Some examples of these types of lighting comprise semiconductor light-emitting diodes (LEDs), organic light-emitting diodes (OLED), or polymer light-emitting diodes (PLED) as sources of illumination rather than electrical filaments, plasma or gas.
To complete the description and in order to provide for a better understanding of the invention, a set of drawings is provided. Said drawings form an integral part of the description and illustrate an embodiment of the invention, which should not be interpreted as restricting the scope of the invention, but just as an example of how the invention can be carried out. The drawings comprise the following figures:
The example embodiments are described in sufficient detail to enable those of ordinary skill in the art to embody and implement the systems and processes herein described. It is important to understand that embodiments can be provided in many alternate forms and should not be construed as limited to the examples set forth herein.
Accordingly, while embodiment can be modified in various ways and take on various alternative forms, specific embodiments thereof are shown in the drawings and described in detail below as examples. There is no intent to limit to the particular forms disclosed. On the contrary, all modifications, equivalents, and alternatives falling within the scope of the appended claims should be included. Elements of the example embodiments are consistently denoted by the same reference numerals throughout the drawings and detailed description where appropriate.
In this lighting device 101 the dry path which comes from the ventilation element 104 follows a tortuous path 107 from this ventilation element until reaching the outer glass 105.
In the particular embodiment shown in this figure, the opaque element 6 is a bezel, which is located between 1cm and 5cm from the outer glass.
This bezel 6 comprises a first portion 7 which is made of a porous material. The location of this first portion 7 is optimum to provide the dry current the fastest path 8 to reach the outer glass. As may be seen from the comparison of
The bezel 6 is made of a plastic injection material, where the first portion 7 is subject to a pore formation process. The rest of the bezel keeps its original structure, so that it may resist loads, while the first portion is made porous to provide the advantageous feature to the lighting device. Further, the porous material has a hydrophobic surface treatment, to avoid humidity being stored in the pores.
In this embodiment, the first portion 7 of the opaque element 6 is smaller, since the deflector 9 directs the flow towards the particular first portion, and the rest of the bezel does not receive the dry flow. As a consequence, there is no need to arrange such a big first portion as in the preceding example. This has a positive outcome in the mechanical properties of the final bezel, since the porous materials have, in general, poorer mechanical properties than solid materials.
This automotive vehicle 100 will have their headlamps easily demisted without using particular and expensive active elements. There is no need to force any current, since the particularly advantageous structure of the lighting device 1 according to the invention is enough to cause demisting in a faster way than in the headlamps which are known in the state of the art.
The bezel 6 is usually seen, but the first portion is not seen in this figure. Since solid plastic materials are aesthetically preferred to porous materials, this feature turns out to be advantageous.
This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.