Patent Application
20070127257
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 in which the light from the source is intended to be seen. Thus, light from the assembly is intended to be seen from a forward position.
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 typically relatively small and is covered with an air-permeable membrane.
In order to attain designed optimal performance of newer light sources, 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 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 typically secured to a portion of the vehicle frame 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 heated air 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 mechanism's internal components while minimizing air exchange between the headlamp assembly chamber and the atmosphere and while isolating the 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 that define an inner chamber that is generally fluidly isolated from the atmosphere. The housing includes portions that extend from an interior surface of the housing into the inner chamber to define a base having a light source mounted thereon. The housing further includes portions that extend from an exterior surface of the housing to define a plurality of fins exposed to ambient air. A reflector is positioned behind the light source and is adapted to reflect light from the light source forward.
In one aspect, the headlamp assembly includes a flow channel positioned adjacent the exterior surface of the housing. The flow channel is adapted to direct ambient air flowing therethrough. The fins extend into the flow channel such that heat from within the inner chamber is conducted through the base portion of the housing to the fins of the housing to the air flowing through the flow channel.
In another aspect, air flow through the flow channel can be achieved by natural convention, forced convection, induced forced convection, or any combination thereof.
In yet another aspect, the flow channel is positioned behind the headlamp assembly and is at least partially defined by the exterior surface of the housing.
In still another aspect, the flow channel includes an inlet and an outlet. The inlet of the flow channel includes venturi openings and the outlet of the flow channel is positioned in a low pressure region within the motor vehicle. Air air is drawn in through the ventui openings at the inlet and flows toward the low pressure region at the outlet. The venturi openings at the inlet of the flow channel include one way valves.
In still another aspect, the housing is made from a conductive material selected from the group: metal, metal alloy, silicon, and graphite.
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
The housing 14 includes an interior surface 18 and an exterior surface 20. Portions of the housing 14 extend from the interior surface 18 into the inner chamber 16 to define a base 22 that operates as a support and mount for a light source 24. Portions of the housing 14 also extend from the exterior surface 20 to define a plurality of fins 26 that are exposed to ambient air outside of the chamber 16, as shown in
As shown in
The headlamp assembly 10 further includes surfaces that cooperate to focus light rays 28 from the light sources 24 into a beam having desired characteristics and direct the light rays 28 towards the lens 12. As shown, a plurality of reflectors 30 are positioned within the inner chamber 16, one reflector 30 being positioned relative to each light source 24, to achieve this. The reflectors 30 re-direct the light rays 28 received thereby in a forward direction and through the lens 12.
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 therein.
The light sources 24, are preferably light emitting diodes (LEDs). Each light source 24, hereinafter just “LED 24”, is attached to a printed circuit board (PCB) 32 that includes electronic controls and connections for the LED 24. Furthermore, each LED 24 and PCB 32 are supported on the base portion 22 of the interior surface 18 of the housing 14 in a well known manner. Preferably, the housing 14 is constructed of a material having a relatively high thermal conductivity, such as metals, metal alloys, silicon, and graphite.
During operation of the headlamp assembly 10, each LED 24 generates heat and increases the temperature of the air, components and structures located within the inner chamber 16. However, the LED 24 and/or other electronic components may experience diminished performance or failure if their maximum operating temperature is exceeded. To reduce the temperature of these components, the LEDs 24 and PCBs 32 are mounted onto the base portion 22 of the interior surface 18 of the housing 14 such that heat from the light sources 24 will be conducted through the base 22 to the fins 26 extending from the exterior surface 20 of the housing 14, and thus outside of the inner chamber 16. Ambient air flowing across the fins 26 will cool the fins 26, thereby dissipating the heat conducted from within the inner chamber 16.
To insure that ambient air is directed over and around the fins 26, the headlight assembly 10 may include a flow channel 34 positioned adjacent the housing 14. As shown in
The flow channel 34 is adapted to direct ambient air flowing therethrough, wherein the fins 26 extend into the flow channel 34 such that heat from within the inner chamber 16 is conducted through the base 22, to the fins 26, and to the air flowing through the flow channel 34.
Referring to
Referring to
In either instance, the headlamp assembly 10 shown in
Referring to
When the vehicle 42 is moving, air will naturally flow from higher pressure to the low pressure region at the outlet 40b of the flow channel 34b. The low pressure region will draw air in through the venturi openings 54 in the flow channel wall 36b, as indicated by arrows 56, and through the flow channel 34b, thereby developing a flow of air from the region near the inlet 38b, which is relatively higher pressure than the low pressure region near the outlet 40b. Heat from within the inner chamber 16 is conducted through the base 22, to the fins 26, and to the air flowing through the flow channel 34b, as indicated by arrows 58, to cool the inner chamber 16 and the housing 14. One way valves (not shown) could be placed at the venturi openings 54 to insure that the flow of air is restricted to only flowing into the flow channel 34b through the venturi openings 54.
Referring to
By making the housing 14 from a thermally conductive material and using portions of the interior surface 18 to define the base 22 and portions of the exterior surface 20 to define the fins 26, the housing 14 acts both as the housing 14 and as an additional heat sink to conduct heat away from the inner chamber 16. The housing 14 can be made from any suitable thermally conductive materials such as metal, metal alloy, silicon, or graphite material, and more specifically, aluminum. Alternatively, the housing 14 may include a plurality of conductive components, such as a metal, a metal alloy, or a graphite material, embedded within a base material, such as a polymer. In this design, the benefits discussed above are equally applicable.
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 scope of this invention.
