Automotive LED module with heat sink and fan

Lamp module cooling system 10 contains vehicle solid-state light source 12 coupled to an extruded first heat sink 2 and an extruded second heat sink 20 in thermal communication with one another and with fluid flow directed from fan air outlet 42 of fan 40 over respective heat dissipation first and second ribs 8, 28 to direct warmed air through existing apertures 115 in headlamp bezel 110 aligned with headlamp optics 130 to defog or de-ice headlamp cover 100. Housing cover 30 and cover 32 define air flow path 50, 52, 54 improving warm air guidance and efficient spatial packaging of lightweight lamp module cooling system 10.

CROSS REFERENCE TO RELATED APPLICATIONS

TECHNICAL FIELD

The present disclosure relates to heat sinks for solid state illumination systems, and more particularly pertains to compact module with air flow path directing warmed air to defog a headlamp lens cover.

BACKGROUND

While solid state light sources, e.g., light emitting diodes (LEDs) may generate less thermal energy compared to traditional bulbs (e.g., incandescent light bulbs), solid state light sources nevertheless generate thermal energy which should be managed in order to control the junction temperature. A higher junction temperature generally correlates to lower light output, lower luminaire efficiency, and/or reduced life expectancy.

Solid-state illumination systems include heat sinks to dissipate thermal energy away from the solid state light source in order to manage the junction temperature. A two-component heat sink is known in US Pat. Pub. 2014/0338878 (Tessnow). Other examples of heat sinks and air flow are in U.S. Pat. No. 7,683,395 (Huber); U.S. Pat. No. 9,115,861 (Sieme); U.S. Pat. No. 6,497,507 (Weber); U.S. Pat. No. 7,329,033 (Glovatsky); Pub. US2011/0310631 (Davis); and European EP 2 020 569 (Barthel); and German DE 10 2011 084 114 (Wais).

It is known that solid-state light-emitting diodes (LEDs) are efficient and used in automotive low beam and high beam headlamps. Higher power LEDs are now used in such applications, such as those sold by OSRAM Opto Semiconductors under the trade designation Oslon Black Flat S (Model KW HLL531.TE) which has 5 chips generating 2000 lumens and a 20 Watt thermal load (28 total electrical Watts, 8 Watts emitted as light). Such LEDs need relatively large heat sinks. Since it is desired that the headlamps are moveable so as to be aimed, the heat sinks are internal to a sealed housing. The heat sinks for such large thermal loads are large and heavy, consuming about 500 grams of aluminum, which presents a lampset packaging problem. Simultaneously, however, the thermal power of these LEDs is nonetheless too small to melt ice or defog lenses as was commonly done by the traditional but less efficient filament incandescent or halogen lamps. Even when using the higher power LEDs and passive heat sinks the radiated heat remains behind the headlamp housing's bezel which conceals the light source and the front lens cover stays relatively cool. Conventional solutions have involved hot air generating fans with complicated air ducts that required breaking holes into the bezel, undesirable from a standpoint of a vehicle manufacturer's styling goals.

DETAILED DESCRIPTION

By way of an overview, one aspect consistent with the present disclosure features an extruded heat sink as part of a vehicle solid-state lamp module cooling system that incorporates a fan to direct air across the heat-dissipating ribs.

The heat sink of the present disclosure provides numerous benefits and solves several problems. For example, while cast aluminum heat sinks are inexpensive and allow complex heat sink shapes, cast aluminum has a low thermal conductivity (e.g., about 90 W/mK) which may not be able to transfer enough thermal energy away from the solid state light source to maintain the desired junction temperature. While present inventors are aware of some cast aluminum heat sink material having a somewhat higher thermal conductivity (e.g., about 120 W/mK) than conventional cast aluminum, it is considered exotic and expensive, and for practical purposes extruded aluminum is considered to have a thermal conductivity about twice that of cast aluminum. Additionally, the low thermal conductivity of cast aluminum may require the cast aluminum heat to be unacceptably bulky and/or heavy. While extruded aluminum heat sinks have substantially higher thermal conductivity compared to cast aluminum heat sink (e.g., about 200 W/mK), extruded aluminum heat sinks suffer from limited design flexibility. For example, the shape of extruded aluminum heat sinks is generally limited to a symmetric shape unless post-extrusion machining (e.g., to include mounting holes and/or irregular shapes) is utilized. Unfortunately, the post-extrusion machining adds cost to the heat sink and can limit high volume production. Further details are disclosed in US Pat. Pub. 2014/0338878 (Tessnow), incorporated by reference herein.

The heat sink of the present disclosure solves certain disadvantages and limitations discussed above. The heat sink is preferably formed in two parts which are coupled together, each part being preferably of extruded aluminum component (and its relatively high thermal conductivity) and is able to effectively and efficiently spread the thermal energy of the solid state light source across the heat sink. A fan is arranged to direct air across heat dissipating ribs of each heat sink. Moreover, extruded aluminum heat sinks are relatively inexpensive, and expensive post-manufacture machining may be minimized because of the simplicity of joining the two pieces by drilling simple through-holes in each extruded heat sink to receive bolts, whereby two bolts join the two heat sinks together and to a housing, further reducing the manufacturing cost of the module.

Turning now toFIG. 1andFIG. 2, one embodiment of a vehicle solid-state lamp module cooling system10consistent with the present disclosure is generally illustrated as an exploded perspective view. The cooling module10includes first heat sink2and second heat sink4that are thermally coupled to each other. First heat sink component2has first base4having a first exposed surface6. With lamp module cooling system10mounted in operational relationship on a headlamp frame120, first exposed surface6is directed toward reflector optic130. Heat dissipation first ribs8extend away from first base4. First heat dissipation ribs8are preferably formed integral with first base4. The first base4and first heat dissipation first ribs8are preferably formed integral of extruded material. First ribs8define air flow channels50.

FIG. 1also shows cooling module10having second heat sink component20which has second base24having a second exposed surface26. Heat dissipation second ribs28extend away from second base24. Second heat dissipation ribs28are preferably formed integral with second base24. The second base24and second heat dissipation first ribs28are preferably formed integral of extruded material. Second ribs28define air flow channels50,52. Suitable holes drilled as a first post-extrusion machining step in first base4and second base24permit two bolts18,18to couple heat sinks2,20in thermal communication with one another. As shown inFIG. 1, a second post-extrusion machining step is performed on second heat sink20by cutting away a portion of second base24in order that first base4seats transversely to second base24.

First base4is disposed transverse to second base24, such as being perpendicular, or substantially perpendicular, to second base24. Thus first ribs8and second ribs28abut and collectively define continuous air flow paths that wrap around the rear faces (opposite first and second exposed surfaces6,26) of first and second heat sinks2,20.

The extruded first heat sink component2is formed from any suitable first material which includes any alloy thereof that can be extruded. The extruded second heat sink component20is formed from any suitable second material, including an alloy thereof, which can be extruded. Preferably first heat sink component2and first ribs8are formed from a first aluminum material which includes any aluminum alloy that can be extruded. Preferably second heat sink component20and second ribs28are formed from a second aluminum material which includes any aluminum alloy that can be extruded. The second aluminum material may be the same as or different than the first aluminum material, but is preferably the same aluminum material. Examples of the first and/or second aluminum materials may include, but are not limited to, AA 6061 (as designated by the Aluminum Association), AA 6063, or the like. Of course, these are just examples, and the present disclosure is not limited to any particular aluminum material unless specifically claimed as such. The use of aluminum materials for both the extruded first heat sink component2and the second heat sink component20allows the lamp module cooling system10of the present disclosure to be manufactured inexpensively compared to other heat sink designs while still allowing the heat sinks2,20to dissipate enough heat for use in high-power solid state lighting applications with limited space and/or weight constraints. Having both first and second heat sinks2,20formed of aluminum rather than one of aluminum and e.g. the other of a different material, e.g. copper, avoids adjacent materials having different electrode potentials, thus minimizing the likelihood of galvanic corrosion.

It could be considered ideal if it were possible to form the combined shape of first and second heat sinks2,20as one integral piece, but the complex shape and, in preferred embodiments, near 90-degree angle from their mutually orthogonal arrangement likely prevents such a piece from being extruded integrally. Furthermore, if such an integral piece were molded, as noted above, existing cast aluminum or cast magnesium would have a significantly lower thermal conductivity than extruded aluminum, and even if that shape could be integrally molded, the thin fins on both surfaces could not wrap around so costly and extremely precise post-mold machining would be required.

The extruded heat sink components2,20may have any profile which can be extruded. For example, first and second heat sinks2,20may have the same cross-sectional profile along at least one dimension (e.g. the same cross-sectional profile along the length). For example, the first and second heat sinks2,20include one or more ribs or fins8,28extending outward to increase the surface area of the respective first and second heat sink2,20to dissipate thermal energy. The heat-dissipating fins8,28are co-extruded with respective bases4,24of the first and second heat sink components2,20.

FIGS. 1-2also show a solid-state light source12, such as light-emitting diodes (LEDs) mounted on printed circuit board (PCB)14which is coupled to first exposed surface6as a mounting surface. PCB14is of any desired conventional construction, such as a metal core board (MCPCB) known to those in the art that supplies electrical connection to LEDs12and provides a mounting surface and permits thermal transfer to first heat sink2. Exemplary LEDs12are high-powered LEDs such as those sold by OSRAM Opto Semiconductors under the trade designation Oslon Black Flat S (Model KW HLL531.TE) which has 5 chips generating 2000 lumens and a 20 Watt thermal load (28 total electrical Watts, 8 Watts emitted as light). In operational position with lamp module cooling system10mounted on headlamp frame120, light source12is directed toward reflector optic130(FIG. 7).FIGS. 1-2shows light source12coupled to first exposed surface6. Optionally light source12is coupled to second exposed surface26(not shown) if the headlamp system optics arrangement is suitable therefore.

Fan40is in fluid communication with first heat sink2and second heat sink20. Fan40has fan air inlet44and fan air outlet42. Fan40is preferably an axial fan, though in other embodiments fan40could be configured as a radial fan. Fan40is preferably disposed with its air outlet42in confronting relation to second heat sink20, in particular to heat dissipation second ribs28which form flow channels. In other embodiments, not shown, fan40could be disposed with air outlet42in confronting relation to first heat sink2, such as in confronting relation to heat dissipation first ribs8. In a preferred embodiment fan40is coupled to housing30in which it is securely held at a rearward cavity region34thereof, housing30being attached by bolts18to hold first and second heat sinks2,20. Fan40can provide sufficient airflow of about 9 cfm (cubic feet per minute) operating at full voltage (12V) and provides enough flow that the lamp module cooling system10still operates well at low voltage (9V) conditions. Fan40can be mounted to housing30with additional screws but in a preferred embodiment housing30has a receptacle or receiving cavity34at a rearward location that accommodates fan40with second heat sink20, such as by shape or slight friction fit. Housing30is molded of suitable thermoplastic material such as polycarbonate or other high-temperature resistant plastic. Housing30has mounting regions to couple to vehicle headlamp frame120.

As shown inFIGS. 1-3, optional housing30not only mechanically retains components of lamp module cooling system10but also helps define air flow paths. Housing30has a cover region32which extends at least partially over and across, in a length and width direction, one of said first heat sink2or said second heat sink20. As depicted inFIGS. 1-2, cover32extends across the width of, and along a length of, first ribs8to help define, or bound, air flow channel50(FIG. 3) which has an air inlet region52and an air outlet region54. Optional housing30helps keep the air flow close to ribs8,28of the heat sinks until it exits towards the front, and the presence of housing30with cover32helping to define air flow channel50makes the effect of lamp module cooling system10more controlled and efficient. Since the top of bezel110(FIG. 9) typically conceals light source12from direct view, air outlet region54is directed slightly downward to pass through aperture115for the headlamp optic130. Housing30has mounting regions to couple to vehicle headlamp frame120and to align light source12with reflector130.

With components mounted in operational relationship shown inFIG. 3, and also with reference toFIG. 10, air drawn in through headlamp frame120(such as from underneath the vehicle or from the engine compartment) by fan40through fan air inlet44is forced out fan outlet42across second ribs28to be received at cover air inlet52and directed over first ribs8guided through air flow channel50and expelled out air outlet54of cover30and first ribs8to be directed towards headlamp lens cover100, whereby the warmed lens cover100can be defogged or de-iced. An additional or secondary airflow46exiting fan outlet42and passing over second ribs28can be directed downwards.

As shown inFIG. 9, a conventional headlamp frame120also supports a styling bezel110which provides styling accents visible to users and purchasers from exterior to the vehicle, and also helps conceal a light source, such as lamp module cooling system10, mounted behind bezel110. Bezel110typically has apertures115therein, one for each light source and module10with its associated reflector optic130, two exemplary systems being shown. With the present embodiment of lamp module cooling system10it was unnecessary to create additional apertures or ducts in bezel110; rather, warmed air exiting air outlet54is directed to lens cover100by flowing out of existing apertures115.

In operation, outlet flow54of warm air to lens cover100reduces relative humidity and allows condensation on front lens100to be absorbed by the air and transported to cooler section, thereby defogging lens cover100.

In an embodiment in which first and second heat sinks2,20are extruded from aluminum (such as aluminum of density 2.7 g/cm3), the ribs can be advantageously small, and matched to the footprint of axial fan40given the available vertical clearance behind bezel110in a top-mount system as depicted inFIGS. 7-10. While a top mount system is illustrated, lamp module cooling system10will work equally in a side or bottom mount system or at any angle therebetween, by simply rotating the system about the optical axis. A fan40can have a size of 40×40×20 mm delivering 8.9 cfm airflow at full voltage (12V), such as Sunon Model EF40201B1. Extruded second ribs28have fins of thickness 1 mm (typical) spaced at 2 mm gaps, with the fins having 20 mm fin height and a fin length along a face of fan outlet42corresponding to a full height (40 mm) of fan40. Extruded first ribs8have also fins of thickness 1 mm (typical) spaced at 2 mm gaps, with fins of a 10 mm height, that is, about half the height of the second ribs28, due to a design goal of compactness in a top mount system where LED light source12is close to top of housing30. First heat sink2weighs 35 gram; second heat sink20weighs 52 gram; fan40weighs 33 gram; housing30weighs 22 gram; the LED light source12and its PCB14weigh 3 gram, thus the major components together providing lamp module cooling system10weighing about 145 gram, thus providing a lightweight and compact package.

In appropriate situations, lamp module cooling system10can be used not only with a reflector optic130but also with a lens optics if the bezel is so constructed that air can go around the lens to be directed at lens cover100.

While the principles of the present disclosure have been described herein, it is to be understood by those skilled in the art that this description is made by way of example and not as a limitation as to the scope of the embodiments. The features and aspects described with reference to particular embodiments disclosed herein are susceptible to combination and/or application with various other embodiments described herein. Such combinations and/or applications of such described features and aspects to such other embodiments are contemplated herein. Other embodiments are contemplated within the scope of the present invention in addition to the exemplary embodiments shown and described herein. Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present invention, which is not to be limited except by the following claims.

THE FOLLOWING IS A LIST OF REFERENCE NUMERAL USED IN THE SPECIFICATION:2first heat sink4first base6first exposed surface8heat dissipation first ribs10lamp module cooling system12solid-state light source, e.g. LED14printed circuit board (PCB)18bolts20second heat sink24second base26second exposed surface28heat dissipation second ribs30housing32cover of housing34receptacle cavity (receiving region)40fan42fan air outlet44fan air inlet46secondary air flow50air flow channel52channel inlet54warm air outlet flow100headlamp lens cover110headlamp bezel115aperture in bezel120headlamp frame130headlamp reflector