Patent Application
20070127252
1. Field of the Invention
The invention relates generally to a headlamp assembly for a motor vehicle. More specifically, the invention relates to the cooling of a headlamp assembly by conducting heat from the light source to the exterior of the headlamp assembly via conductive heat sinks.
2. Related Technology
Headlamp assemblies have a light source, such as an incandescent lamp, a light emitting diode (LED) or high intensity discharge (HID) lamp, positioned within a headlamp chamber and electrically connected to a power source. The headlamp chamber is typically defined by a transparent or translucent lens, located forward of the light source, and a reflector located rearward and/or surrounding the light source. As used herein, the terms forward and rearward are referenced with respect to the position of the light source and the direction of the area that the light from the source is intended to illuminate. Thus, light from the assembly is intended to illuminate an area forward of the assembly.
During an operation cycle of the headlamp assembly, the light sources and other components of the lamp generate heat while “on” and cool while “off”, causing the chamber to undergoes temperature fluctuation and causing the air located within to expand and contract. To maintain a relative-constant chamber pressure, the chamber typically includes at least one opening that permits an air exchange between the chamber and the ambient air. However, to prevent contaminants, such as dust and debris, from entering the chamber, the opening is relatively small and is typically covered with an air-permeable membrane.
In order to attain the optimal performance of newer light sources, such as LED'S and their electrical components in the lamp assembly, it is desirable to maintain the internal temperature of the lamp assembly below the maximum operating temperature of these sources and components. Therefore, it is advantageous to provide the headlamp assembly with a mechanism that cools the chamber and the LED'S located therein.
Headlamp assemblies are also typically located on the vehicle in a position that is adjacent to the engine compartment. The temperature within the engine compartment is often significantly higher than the temperature outside of the engine compartment (the ambient temperature). For example, during operation of the vehicle, various components, such as the engine and the engine cooling system, output heat into the engine compartment. As another example, during periods of vehicle use and non-use, the air trapped within the engine compartment may become heated by solar energy. Therefore, it is advantageous to provide the headlamp assembly with a mechanism that isolates the chamber, and the light sources located therein, from the relatively high temperatures of the engine compartment.
In view of the above, it is beneficial to have a headlamp assembly that has a mechanism that effectively cools the assembly's internal components while minimizing air exchange between the inner chamber and the atmosphere and while isolating the inner chamber from the engine compartment and the relatively high temperatures associated therewith.
In overcoming the above limitations and other drawbacks, a headlamp assembly for a motor vehicle is provided that includes a lens and a housing, cooperating to at least partially define an inner chamber that is generally fluidly isolated from the atmosphere. A base is mounted within the inner chamber and a light source is mounted onto the base, as is a reflector. The reflector includes portions that are adapted to reflect light from the light source forward through the lens and portions that define a heat sink.
In one aspect, the reflector is a one piece component made from an alloy selected from the group including magnesium alloys, aluminum alloys, and zinc alloys, and is formed by casting. Among others, such alloys include magnesium alloys, aluminum alloys, and zinc alloys.
In another aspect, the reflector is a one piece component made from a thixotropic alloy. Among others, such alloys include magnesium alloys, aluminum alloys.
In a further aspect, the reflector is formed by semi-solid metal injection molding.
In yet another aspect, the portions of the reflector that are adapted to reflect light from the light source are polished to a reflective finish.
In still another aspect, the portions of the reflector that reflect light from the light source are evaporation coated with a reflective aluminum coating.
Further objects, features and advantages of this invention will become readily apparent to persons skilled in the art after a review of the following description, with reference to the drawings and claims that are appended to and form a part of this specification.
Referring to
A series of bases 18 are mounted within the inner chamber 16 to an inner surface 19 of the housing 14. Referring to
Preferably, the reflector 22 is a single piece component made from metal or a metal alloy, such as magnesium alloys, aluminum alloys, and zinc alloys. The reflector 22 can be made by casting or other suitable processes to create a single piece component. One preferred method for making the reflector 22 is semi-solid metal injection molding (SSMIM). The SSMIM process is particularly advantageous for this application because the process produces near net shaped parts, thereby reducing the amount of finishing and improving the quality of the parts. SSMIM yields parts having dimensional stability, low porosity, tight tolerances with reduced shrinkage, residual stress, and component distortion, thereby making SSMIM ideal for producing parts having extremely thin wall thicknesses.
The reflective surface 24 can be polished to a reflective finish or may have a reflective coating applied to it by a process such as evaporation coating. In such an instance, the reflective coating can be an aluminum coating or any other suitable reflective coating.
The housing 14 and the lens 12 are connected with one another such that the inner chamber 16 is substantially sealed from the atmosphere. The inner chamber 16 is, however, provided with pressure vents (not shown) that permit a relatively small amount of airflow into and out of the inner chamber 16 to account for air pressure fluctuations during temperature changes within the chamber 16.
The light source 20, is preferably a light emitting diode (LED). The light source 20, hereinafter just “LED 20”, is attached to a printed circuit board (PCB) 28 that includes electronic controls and connections for the LED 20. The LED 20 and the PCB 28 are mounted together on the base 18 within the inner chamber 16. Preferably, the LED 20 and the PCB 28 are mounted onto the base 18 with a thermal conductive adhesive.
As shown in
Referring to
During operation of the headlamp assembly 10, the LEDs 20 generate heat causing an increase in the temperature of the air, components and structures located within the inner chamber 16. The LEDs 20 and/or other electronic components, however, may experience diminished performance or failure if their maximum operating temperatures are exceeded. To reduce the temperature of these components and the chamber 16, the LEDs 20 are mounted onto the bases 18, and bases are mounted to the reflectors 22. As such, heat from the LEDs 20 is conducted through the bases 18, to the reflector 22, and specifically to the portions of the reflector 22 that define heat sink fins 30 located outside of the inner chamber 16. Ambient air flowing across the heat sink fins 30 cools the heat sink fins 30, thereby dissipating the heat conducted from within the inner chamber 16.
It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting, and that it be understood that it is the following claims, including all equivalents, that are intended to define the spirit and scope of this invention.
