Patent Application
20070121333
The present invention relates to a light source for automotive lighting systems and the like. More specifically, the present invention relates to a semiconductor light engine to provide light for automotive lighting systems and the like.
Automotive lighting systems, and in particular headlamp systems, require light sources capable of producing relatively bright light which can be formed into the necessary beam patterns, as defined and required by various safety regulations. Incandescent bulbs were employed as light sources for headlamp systems for many years with reasonably acceptable results.
To provide more light to improve the beam patterns produced by headlamp systems, quartz halogen (“Halogen”) and high intensity discharge (“HID”) bulbs are now commonly used instead of incandescent bulbs, as Halogen and HID bulbs produce significantly more light than incandescent bulbs. However, such Halogen and HID light sources suffer from disadvantages in that they create a significant amount of waste heat which the headlamp must be designed to withstand. Further, Halogen and HID headlamps require carefully designed optics to remove defects, from bulb filaments or bulb envelope influences, in the pattern of light they produce.
Accordingly, to withstand this heat and/or to provide the necessary optics, the enclosures of Halogen and HID headlamps must be relatively large and such large enclosures limit the aesthetic and/or aerodynamic designs which automotive designers could otherwise produce.
More recently, interest has developed in employing semiconductor light sources, such as light emitting diodes (“LED”s), as light sources for headlamp systems. LEDs which produce white light have become available and the amount of light produced by such LEDs has increased significantly in recent years. Ideally, headlamps employing LEDs as light sources will be able to be constructed with smaller enclosures than those required for conventional headlamps, allowing for the variety of aesthetic and aerodynamic vehicle designs to be increased.
However, LED-based headlamp systems also suffer from some disadvantages. The amount of light produced by available white LEDs is still insufficient to produce the required headlamp beam patterns and thus several closely positioned LEDs must be jointly employed to produce sufficient light. Further, the semiconductor junction in each LED produces a relatively large amount of waste heat when operating and this heat must be removed, by heat sinks, heat pipes and/or cooling fans and the like or the junction will fail. Thus, to provide for the proper arrangement of the multiple LED sources with respect to the lens of the LED headlamp and to provide adequate cooling of the LED sources, the enclosure of LED headlamps tend to be larger than is otherwise desired.
It is an object of the present invention to provide a novel light engine which obviates or mitigates at least one disadvantage of the prior art.
According to a first aspect of the present invention, there is provided a light engine for an automotive lighting system, comprising: at least one substrate; a plurality of semiconductor light sources mounted to each of the at least one substrates, each adjacent semiconductor light source being spaced from each other adjacent semiconductor light source on the substrate to enhance cooling of the semiconductor light sources during operation thereof; and at least one a transfer device operable to receive light emitted by the semiconductor light sources on the at least one substrate and to transfer the received light to at least one location spaced from the substrate, wherein the transfer device comprises at least one light pipe, each light pipe having a receiving end to receive light emitted from a semiconductor light source and an emitting end to emit the received light.
Preferred embodiments of the present invention will now be described, by way of example only, with reference to the attached Figures, wherein:
A first embodiment of a light engine in accordance with the present invention is indicated generally at 20 in
As shown in
Substrate 24b is substantially the same as substrate 24a but, if light engine 20 contains no additional substrates 24 to be stacked with substrate 24b or if substrates 24a or 24b are not to be stacked at all, then substrates 24a or 24b need not include apertures 46, but such apertures can be included in substrates 24a and 24b without harm, to allow for uniformity of manufacture of substrates 24.
Semiconductor light sources 40 are mounted to each substrate 24 with sufficient spacing between adjacent semiconductor light sources 40 to ensure that their junction temperatures can be maintained within the acceptable operating temperature range.
Substrates 24 can be formed of any suitable material as will be apparent to those of skill in the art and examples of such materials include ceramics, such as those used in packaging semiconductor integrated circuits, phenolics and/or epoxies, such as those used to fabricate printed circuit boards, etc.
Preferably, substrates 24 include at least one layer 48 of a heat transfer material, such as copper or aluminum, which assists in the removal of waste heat generated within semiconductor light sources 40. Layer 48 can be connected to a suitable heat sink, heat pipe or heat wick when substrates 24 are mounted in a headlamp system. Layer 48, in combination with the above mentioned spacing of semiconductor light sources 40 on substrates 24, ensures that semiconductor light sources 40 can be operated within their specified operating temperature range.
By employing more than one substrate 24 on which to mount semiconductor light sources 40, the necessary number of semiconductor light sources 40 to provide the desired amount of illumination from light engine 20 can be spaced across the faces each substrate 24, which are separated from each other substrate 24. In this manner, a less dense arrangement of semiconductor light sources 40 on each substrate 24 can be obtained to enhance cooling of the junctions of semiconductor light sources 40.
Each substrate 24 also preferably includes at least two electrical layers 52 and 56, each being a respective one of a positive and negative electrical conductor to which semiconductor light sources 40 are connected and are powered thereby. Alternatively, positive and negative electrical conductors can be provided as conductive traces on the top, bottom or both of the top and bottom of substrate 24.
It is contemplated that it may be desired to illuminate semiconductor light sources 40 in groups, for example to form low beam or high beam lighting patterns. In such case additional electrical conductors, whether in the form of conducting layers in substrate 24, conducting traces on the top or bottom of substrate 24, etc. can be provided to supply energy to such groups of semiconductor light sources 40.
Each reflector 44 preferably includes a parabolic shaped surface which surrounds its respective semiconductor light source 40 and reflectors 44 can be fabricated from any suitable material, such as acrylic, epoxy or polycarbonate, to which a suitable reflective coating can be applied or reflectors 44 can be fabricated from a reflective material such as aluminum.
In the illustrated embodiment, each reflector 44 is shown as being a separate component mounted to a substrate 24 individually, but it is also contemplated that reflectors 44 can be fabricated as a unit. For example, reflectors 44 can be molded as an assembly from an epoxy material, to which a reflective material is then applied, and the assembly being mounted to a substrate 24, over semiconductor light sources 40, after semiconductor light sources 40 have been mounted to substrate 24.
Similarly, reflectors 44 can be machined and polished as an assembly from a piece of aluminum, or the like, and then mounted to substrate 24. In this latter case, the assembly of reflectors 44 can also assist in the removal of waste heat produced by semiconductor light sources 40.
As shown in
At receiving end 32 of transfer device 28, best shown in
Preferably, the receiving ends of the light pipes 60 include surfaces 64 which are shaped and positioned with respect to semiconductor light sources 40 on each substrate to capture a substantial portion of the light emitted by semiconductor light sources 40. The receiving ends of the light pipes are maintained in place by any suitable means, such as epoxy 68 or by mechanical means (not shown).
Preferably, the receiving ends of the light pipes are tapered, from a geometry (size and shape) substantially corresponding to the geometry of the outer end of reflector 44 (if present) or substantially corresponding to the geometry of semiconductor light source 40 (if no reflector 44 is present) to a larger geometry along the length of light pipe 60 to emitter end 36. As will be understood by those of skill in the art, such a taper will improve the amount of the light, emitted by semiconductor light source 40, which is received by the respective light pipe 60 and transmitted along its length.
As will also be understood by those of skill in the art, the length of light pipe 60 need not have the same cross-sectional shape as the receiver end of light pipe 60, for example the receiver end of light pipe 60 can have a rectangular geometry, in cross section, to correspond to the semiconductor light source while the length of light pipe 60 can be circular in cross-sectional shape, etc.
While in the illustrated embodiment substrates 24a and 24b are shown as being planar, the present invention is not so limited and either or both substrates 24 can include a curved surface, etc. if required to fit within a headlamp system with a small, or irregular, volume. In such a case, the length of the light pipes 60 in transfer device 28 may not all be the same.
As shown in
Forming member 72 can be an epoxy member cast about the ends of the light pipes 60 in transfer device 28, or can be a phenolic or epoxy board, aluminum sheet, etc. with suitably sized apertures to receive and maintain the respective ends of light pipes 60 in their desired configuration. As will be apparent, forming member 72 need not hold the individual light pipe ends of emitting end 36 in a planar arrangement and can instead hold the individual light pipe ends in convex, concave or another arrangement as might be desired.
Forming member 72 can also be used as a mounting member to retain emitter ends 36 in a desired position with respect to a lens system 76, or other component, within a headlamp system or the like. It is contemplated that forming member 72 can be mechanically mounted to one or more stepper motors 80, or other devices, to allow forming member 72 and the emitter ends of light pipes 60 to be moved with respect to lens system 76 to, for example, alter the emitted beam pattern and/or to compensate for loading and/or pitch or roll of a vehicle.
While not illustrated, it is also contemplated that light pipes 60 at emitting end 36 can taper from the above-mentioned larger geometry of the majority of their run length to a geometry which is smaller and/or a different cross sectional shape at their ends adjacent forming member 72 to increase the amount of light emitted from each light pipe 60.
As will be apparent, the spacing between the emitting ends of light pipes 60 can be much closer than the spacing of semiconductor light sources 40 on substrates 24. Thus, transfer device 28 allows semiconductor light sources 40 to be spaced and or located, on one or more substrates 24, to meet thermal requirements and yet allows the light emitted by semiconductor light sources 40 to be provided to a headlamp lens system in a much closer spaced configuration.
Further, the arrangement of emitter ends 36 of light pipes 60 in forming member 72 need not be the same as the arrangement of the receiving ends 32 of light pipes 60 at substrates 24. For example, light pipes 60 whose receiving ends 32 are located by adjacent semiconductor light sources 40 on a substrate 24 can be located non-adjacently on forming member 72. It is contemplated that this non-symmetry of the arrangement of the receiving ends 32 and emitter ends 36 of light pipes 60 provides numerous advantages.
For example, if light engine 20 includes a first set of semiconductor light sources 40 which are only illuminated to form a portion of a low beam headlamp pattern and a second set of semiconductor light sources 40 which are only illuminated to form a portion of a high beam headlamp pattern, the semiconductor light sources 40 in the first set can be mounted intermixed with the semiconductor light sources 40 of the second set, on one or both of substrates 24a and 24b. As only one set of semiconductor light sources 40 is illuminated at a given time, the spacing provided by the non-illuminated, but intermixed, semiconductor light sources 40 of the other set help reduce the thermal density of the waste heat produced by the operating semiconductor light sources 40.
In addition, by having differing arrangements of the emitter ends 36 and receiver ends 32 of light pipes 60, substrates 24 can be fabricated in different shapes to make better use of available space in a vehicle or other location. For example, while many headlamp beam patterns are substantially rectangular in shape, with the major axis of the rectangle being generally horizontal, substrates 24 can be square, round, rectangular, elliptical, irregular or any other shape which is desired. Further, substrates 24 can be oriented in any orientation which provides for efficient or desired use of the available volume for a headlamp or other vehicle lighting system using light engine 20.
Another contemplated advantage of light engine 20 is that, while receiving ends 32 of light pipes 60 preferably have a cross section which is selected to enhance the capture of the light emitted by their respective semiconductor light sources 40, the cross section and other characteristics of the emitter ends 36 can be varied as desired. For example, in some illumination patterns, such as a low beam headlamp pattern, sharp transitions or gradients between lighted and unlighted portions of the beam pattern are undesired.
Accordingly;
It is also contemplated that, if desired, emitter ends 36 can be treated to obtain desired beam pattern effects. Such treatments can include coatings applied to emitter ends 36 to diffuse their emitted light and/or other treatments as will occur to those of skill in the art.
It is contemplated that a single mixer 84 can have two or more emitter ends 36 connected to it, or that an emitter end 36 can have its own mixer 84 connected to it to provide diffuse light, as needed, for forming a desired beam pattern.
In the illustrated embodiment, emitter ends 36a and 36b, and their respective forming members 72a and 72b are located at different distances from lens system 76. Assuming that emitter ends 36a are at the focal point of lens system 76, focused light will be provided from emitter ends 36a and transfer device 28a. If emitter ends 36b are located outside the focal point of lens system 76, unfocussed (diffuse) light will be provided from emitter ends 36b and transfer device 28b.
It is also contemplated that emitter ends 36a and 36b can be located at different distances and/or orientations with respect to lens system 76 and that one or more additional optical elements, such as mixer plates, diffusers, lenses, etc., can be interposed between one or the other or both of emitter ends 36a and 36b to alter the beam pattern produced by lens system 76 as desired and, for example, to simultaneously provide focused and diffuse beam patterns.
As should now be apparent to those of skill in the art, a light engine in accordance with the present invention provides several advantages for semiconductor-based headlamps. In prior art semiconductor headlamp systems, the semiconductor light sources had to be located adjacent the lens of the headlamp system to form the desired beam patterns. Electrical connections and heat removal systems thus had to be designed and arranged to work with the location of the light sources and the resulting heat transfer characteristics would often be less efficient than desired while the overall enclosure size and/or shape for the headlamp system would also be less favorable than desired.
In contrast, with a light engine in accordance with the present invention, transfer device 28 removes the need for the semiconductor light sources themselves to be located at any specific location with respect to the lens of the headlamp system. Instead, emitter end 36 of transfer device 28 can be appropriately positioned with respect to the lens, but one or more substrates 24, with semiconductor light sources 40 and the required electrical and heat transfer connections thereto, can be located in a variety of locations within the enclosure of the headlamp system. For example, a substrate 24 can be located horizontally along the bottom of a headlamp enclosure and another substrate 24 “stacked” behind it while emitter end 36 of transfer device 28 is located at the front of the headlamp enclosure, adjacent the lens. In such a configuration, each substrate 24 can be thermally connected to one or more heat sinks which extend from the bottom of the headlamp enclosure, etc.
Further, light engine 20 can be used as a standard light engine from which a wide variety of headlamp or other lighting systems can be constructed. Light engine 20 provides a known amount of light and a headlamp system can employ one or more light engines 20, as needed, to produce a required lighting level. By producing standardized light engines 20, manufacturing costs can be reduced, design processes simplified and repair of headlamp systems simplified.
The above-described embodiments of the invention are intended to be examples of the present invention and alterations and modifications may be effected thereto, by those of skill in the art, without departing from the scope of the invention which is defined solely by the claims appended hereto.
