Abstract:
A light assembly and reflector are provided for redirecting light from a light source in a motor vehicle. The reflector generally includes a first parabolic trough, a second parabolic trough, and third trough. The first and second parabolic troughs define first and second trough axes. The third trough has a third trough axis. The first and second parabolic troughs are positioned on opposing sides of the third trough, and the first and second trough axes are angled relative to the third trough axis. In this manner, the reflector collects and reflects a sufficient amount of light while providing control over the beam pattern spread, particularly in the horizontal direction, whereby a single LED may be employed such that constraints imposed by heat dissipation are significantly reduced.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to reflectors for light sources used in automotive applications, and more particularly relates to trough reflectors for LED light sources.  
       BACKGROUND OF THE INVENTION  
       [0002]     Modern automotive light modules typically use a filament bulb as their light source. While such modules have a long and successful history, filament bulbs consume a large amount of power and have a relatively short life. In an attempt to overcome these shortcomings, others have proposed to utilize LED light sources to replace the filament bulbs since LED&#39;s consume significantly less power and have a long life span.  
         [0003]     Unfortunately, LED solutions also have their drawbacks. In particular, automotive light assemblies utilizing LED light sources typically use a large number LED&#39;s, typically eight or more, which thus requires increasing amounts of power over a single LED bulb. Furthermore, these light modules using LED light sources suffer from poor efficiency, that is, the amount of original light from the light source which is actually directed outwardly away from the vehicle to illuminate the surrounding area.  
         [0004]     In some applications, trough reflectors have been used for LED light sources. However, these reflectors usually result in a wider horizontal spread of the light beam than is required or desired. While side walls have been proposed to cut down on the horizontal spread, such reflectors overly constrain the light distribution. Furthermore, the use of side walls results in wasted light which is beyond the driver&#39;s field of vision. Additionally, the light collection efficiency of the trough reflector depends on its width, and the wider the trough the more horizontal the spread. Likewise, to collect a sufficient amount of light for a given width of the trough, numerous LED&#39;s must be placed at regular intervals along the trough axis. The use of multiple LED&#39;s increases the horizontal spread even further and also increases the amount of power consumed and the heat which must be dissipated.  
         [0005]     Accordingly, there exists a need to provide a light assembly and trough reflector for a motor vehicle which can collect a sufficient amount of light, preferably from a single LED, while at the same time providing control over the horizontal spread as well as other beam pattern characteristics.  
       BRIEF SUMMARY OF THE INVENTION  
       [0006]     One embodiment of the present invention provides a reflector for redirecting light from a light source in a motor vehicle along a longitudinal axis. The reflector generally includes a first parabolic trough, a second parabolic trough, and third trough. The first and second parabolic troughs define first and second trough axes. The third trough has a third trough axis. The first and second parabolic troughs are positioned on opposing sides of the third trough. The first and second trough axes are angled relative to the third trough axis. In this manner, a reflector is provided which collects and reflects a sufficient amount of light while providing control over the beam pattern spread, particularly in the horizontal direction, whereby a single LED may be employed such that constraints imposed by heat dissipation are eliminated.  
         [0007]     According to more detailed aspects, the first and second trough axes are angled in the range of 5 degrees to 45 degrees relative to the third trough axis. The third trough axis is generally perpendicular to the longitudinal axis. The third trough may be parabolic trough, or alternately may follow a complex curvature. Forming the third trough with a complex curvature permits increased control over the beam spread pattern and the creation of “hot spots”. The third trough may include a plurality of facets and most preferably includes two side facets connected to opposite sides of a center facet. In this case, the two sided facets are angled relative to the center facet, and each of the facets extend from an upper edge to the lower edge of the third trough.  
         [0008]     Another embodiment of the present invention provides a light assembly for a motor vehicle which generally comprises a single LED light source and an embodiment of the reflector described above. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention, and together with the description serve to explain the principles of the invention. In the drawings:  
         [0010]      FIG. 1  depicts a schematic side view of an automotive light assembly having a reflector constructed in accordance with the teachings of the present invention;  
         [0011]      FIG. 2  is a front view of the reflector depicted in  FIG. 1 ;  
         [0012]      FIG. 3  is a top view of the reflector depicted in  FIGS. 1 and 2 ;  
         [0013]      FIG. 4  is a perspective view of the reflector depicted in  FIGS. 1-3 ;  
         [0014]      FIG. 5  is a front view of an alternate embodiment of reflector depicted in  FIGS. 1-4 ;  
         [0015]      FIG. 6  is a side view of the reflector depicted in  FIG. 5 ;  
         [0016]      FIG. 7  is a front view of yet another embodiment of the reflector depicted in  FIGS. 1-4 ;  
         [0017]      FIG. 8  is a top view of the reflector depicted in  FIG. 7 ; and  
         [0018]      FIG. 9  is a side view of the reflector depicted in  FIGS. 7 and 8 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]     Turning now to the figures,  FIGS. 1-4  depict a light assembly  20  having a single LED light source  22  producing light (depicted as lined arrows  26 ) from a source point  24 . The light assembly  20  further includes a reflector  30  positioned adjacent the LED bulb  22  which redirects the light  26  outwardly along a longitudinal axis  10  of assembly  20 , which correspond with the longitudinal axis of the motor vehicle. Specifically, the reflector  30  is structured to collect the light  26  and collimate the light vertically by reflecting the light outwardly along the axis  10 .  
         [0020]     As best seen in  FIGS. 2-4 , the reflector  30  generally comprises a first trough  32 , a second trough  34  and a third trough  36 . The first and second troughs  32 ,  34  are positioned on opposing sides of the third trough  36 , and hence the reflector  30  is a compound trough. In this embodiment, all of the troughs  32 ,  34 ,  36  are constructed as parabolic troughs having a curvature which follows a parabola, as best seen in  FIG. 1 . This parabolic curvature results in the vertical collimation of light as previously noted.  
         [0021]     In order to control the beam pattern spread and to prevent excess horizontal spread, the first and second parabolic troughs  32 ,  34  are angled relative to the third trough  36 . As best seen in  FIG. 3 , the first, second and third troughs  32 ,  34 ,  36  each include a trough axis, namely first, second and third trough axes  42 ,  44 ,  46 . The central trough axis  46  is generally perpendicular to the longitudinal axis  10 . As used herein, the term “generally” refers to a slight variation from absolute perpendicularity by less than about 3 degrees.  
         [0022]     It can therefore be seen that the first and second trough axes  42 ,  44  are rotated relative to the third trough axis  36 . In the present embodiment, the first and second troughs have been rotated about 23 degrees relative to the third trough  36 , but the angle of rotation is preferably in the range of 5 degrees to 45 degrees depending on the beam spread requirements. Likewise, angles of rotation for the first and second troughs  32 ,  34  outside of this range may be utilized for other lighting applications which require such beam spread characteristics. Preferably, the first trough  32  and second trough  34  are rotated identical amounts and thus represent mirror images of each other relative to the longitudinal axis  10 , although it will be recognized that varying angles of rotation may be used depending on the particular application and beam spread requirements. Generally, the troughs  32 ,  34 ,  36  are connected along seams  38 ,  40 . The first and second troughs  32 ,  34  may be connected to the third trough  36  by any conventional means, such as by integrally and unitarily molding the reflector  30 , welding, adhesives, mechanical attachment means such as fasteners, threaded fasteners, rivets, etc., and plastic welding techniques.  
         [0023]     The focal lengths of the first, second and third parabolic troughs  32 ,  34 ,  36  may also be varied. For example, the first and second parabolic troughs  32 ,  34  have been depicted as having a focal length of about 12 mm, while the third parabolic trough  36  has a focal length of about 10 mm. The compound trough forming the reflector  30  is structured to have an overall width of about 40 mm and the height is limited to about 35 mm, although it will be recognized by those skilled in the art that numerous variations and the size may be employed depending on the particular application and beam spread requirements. As used herein, the focal length refers to the shortest distance between the focal point of the parabola and a surface of the particular reflector trough  32 ,  34 ,  36 . With reference to  FIG. 1 , the LED light source  22  preferably has a source point  24  that is located at the focal point of the third trough  36  and aligned with the longitudinal axis  10  (i.e. centered horizontally in the reflector  30 ). Since the LED light source  22  is centered within the reflector  30 , the distance between the LED bulb  22  to the first and second troughs  32 ,  34  on the sides of the reflector  30  is somewhat greater than the distance to the third trough  36 .  
         [0024]     The structure of the trough  30  depicted in  FIGS. 1-4  results in a light collection efficiency of 60 to 70 percent, with 85 percent reflectivity. Furthermore, the horizontal spread is limited to +/−25 to 40 degrees, depending upon the orientation of the side troughs, i.e., the angling of the first and second troughs  32 ,  34 . It can therefore be seen that the trough  30  provides a vast improvement over a traditional parabolic trough which typically exhibits a horizontal spread of +/−70 degrees. Also, unlike the multiple-LED trough with side walls, the compound trough  30  never wastes light in the foregoing area below or outside the driver&#39;s field of vision. Accordingly, the light assembly  20  and its reflector  30  may be used with a single LED light source  22 , eliminating the thermal constraints imposed by using a series or row of LED light sources.  
         [0025]     An alternate embodiment of the reflector constructed in accordance with the teachings of the present invention has been depicted in  FIGS. 5 and 6 . In this embodiment, the reflector  130  also includes first and second troughs  132 ,  134  connected to opposing sides of a third trough  136 . The troughs  132 ,  134  are connected to the third trough  136  at seams  138 ,  140  which may be formed in any of the manners previously described for the embodiment depicted in  FIGS. 1-4 . However, in this embodiment the third trough  136  is formed to follow a complex curvature, rather than a parabolic curve as in the prior embodiment. This curvature can be seen in  FIG. 6 , depicting a side view of the reflector  130 . It can also be seen that the seams  138 ,  140  are generally vertically oriented as opposed to the curved seams  38 ,  40  of the prior embodiment.  
         [0026]     By forming the third and central trough  136  to follow a complex curvature (i.e. a numerically generated curve), a particular vertical collimation of the light may be generated. For example, the central trough  136  may not perfectly collimate the light and in fact may result in some beam spread or focus in the vertical direction. In this manner, the reflector  130  may be used to form a “hot spot”, which is known in the art and is preferable for certain lighting applications such as head lamps. By using parabolic troughs for the first and second troughs  132 ,  134  the same benefits are achieved as in the prior embodiment, such as limiting the horizontal spread and preventing redirection of light in the foreground area below the driver&#39;s field of vision, while at the same time providing control over the beam spread characteristics.  
         [0027]     Yet another embodiment of a reflector  230  constructed in accordance with the teachings of the present invention has been depicted in  FIGS. 7-9 . As with the prior embodiments, the reflector  230  generally includes a compound trough having first trough  232 , a second trough  234 , and a third trough  236  oriented relative to a longitudinal axis  210 . However, in this embodiment the third and central trough  236  has been constructed of a plurality of facets  238 ,  240 ,  242 . Each of the facets  238 ,  240 ,  242  extend from an upper edge  244  to a lower edge  246  of the reflector  230 . While the facets  238 ,  240 ,  242  have been shown as vertically extending, it will be recognized by those skilled in the art that the facets may also extend horizontally (i.e. vertically stacked), thereby permitting further variation in the resulting beam spread characteristics while still achieving the benefits of the present invention.  
         [0028]     As with the embodiment depicted in  FIGS. 5-6 , each of the facets  238 ,  240 ,  242  follow a complex curvature, which is best seen in the side view of  FIG. 9 . As best seen in  FIG. 8 , the side facets  238 ,  242  are rotated relative to the center facet  240 . Particularly, the side facets  238 ,  242  include facets axes  256 ,  258  which are rotated relative to the facet axis  250  of the central facet  240 . Preferably these facets are rotated in the range of 1 to 20 degrees. As with the prior embodiments, the first and second parabolic troughs  232 ,  234  are also rotated relative to the center trough  236 , and particularly the center facet  240 , preferably in the range of 5 to 45 degrees as in the prior embodiments. Specifically, the first and second trough axes  252 ,  254  of the first and second troughs  232 ,  234  are rotated relative to the central facet axis  250  within the prescribed range, or outside of that range if needed for a particular lighting application. As with the prior embodiments, the trough axis  250  of the central trough  236  and particularly the central facet  240  is generally perpendicular to the longitudinal axis  210 .  
         [0029]     By using a complex curvature for the facets  238 ,  240 ,  242  and at the same time providing for variation in the rotation angle of the side facets  238 ,  240 , excellent control over the beam spread characteristics is provided. As with the prior embodiments, utilizing parabolic troughs  232 ,  234  on opposing sides of the central trough  236  results in improved light collection, efficiency and reflectivity, while also providing better limitation of the horizontal spread and preventing the waste of light in the foreground area out of the driver&#39;s field of vision.  
         [0030]     The foregoing description of various embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Numerous modifications or variations are possible in light of the above teachings. The embodiments discussed were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.