Abstract:
A LED bulb and light module utilizes a LED light source and directs light therefrom in a manner which improves efficiency and illumination. Ideally, the LED bulb is structured to create a virtual image whereby the efficiency of light directed out of the module is greatly improved, even with a single LED light source.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to a light module for a motor vehicle, and more particularly relates to an LED bulb for use in such a light module.  
       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]     Accordingly, there exists a need to provide an automotive light source which utilizes an LED light source to significantly reduce power consumption, have long life, while at the same time efficiently direct the light to provide adequate illumination.  
       BRIEF SUMMARY OF THE INVENTION  
       [0005]     The present invention provides a LED bulb and light module which utilizes a LED light source and directs light therefrom in a manner which improves efficiency and illumination. Ideally, the LED bulb is structured to create a virtual image whereby the efficiency of light directed out of the module is greatly improved, even with a single LED light source. The LED bulb generally includes a light pipe, a conical reflector, and a plurality of ribs on the outer surface of the light pipe. The light pipe receives light from the LED light source and guides the light downstream along a longitudinal axis defined by the light pipe. The conical reflector redirects the light radially outwardly. The plurality of ribs redirects the light to define a virtual image of the LED light source.  
         [0006]     According to more detailed aspects, the LED bulb is plastic molded from a clear optical grade material, whereby the aforementioned components are integrally formed. The conical reflector preferably includes a series of alternating first and second surfaces, the first surface is oriented generally parallel to the longitudinal axis and the second surface is angled relative to the longitudinal axis. The ribs are axial aligned with the second surface of the conical reflector to receive the redirected light. The ribs are axially spaced apart from each other a distance corresponding to the axial distance spanned by each first surface.  
         [0007]     The ribs are preferably tapered and have a triangular shape. The downstream side of each rib is angled relative to the longitudinal axis. A set of the upstream ribs may include at least one rib which is shorter than the other ribs. The ribs redirect the light upstream to define the virtual image. An upstream end of the light pipe preferably includes a recess for receiving the LED light source. The upstream end defines a lens adjacent the recess for focusing the light longitudinally downstream. Similarly, the upstream end is structured to collimate light from the LED light source and direct the light longitudinally downstream.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     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:  
         [0009]      FIG. 1  is a perspective view of an embodiment of a light module for an automobile constructed in accordance with the teachings of the present invention;  
         [0010]      FIG. 2  is a perspective view of an LED bulb forming a portion of the light module depicted in  FIG. 1 ;  
         [0011]      FIG. 3  is a side view of the LED bulb depicted in  FIGS. 1 and 2 ; and  
         [0012]      FIG. 4  is a side view of the light module depicted in  FIG. 1 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]     Turning now to the figures,  FIG. 1  depicts a perspective view of a light module  10  having a LED bulb  20  constructed in accordance with the teachings of the present invention. Among other things, the light module  10  includes a reflector  12  defining a reflective surface  13  which receives light from a source cavity defined by the reflector and directs the light outwardly away from the vehicle. The reflector  12  includes an opening  14  which receives an LED bulb  20 . The bulb  20  is generally defines by a light pipe  22  which extends through the opening  14  in the reflector  12 . The light pipe  22  directs light received from a LED light source  18  ( FIG. 2 ).  
         [0014]     The details of the LED bulb  20  will now be described with reference to  FIG. 2 . The entire light pipe  22  is generally integrally formed, and preferably is formed by injection molding a clear optical grade material. The material must be capable of conducting light in the visible wave length range, and is preferably a plastic such as acrylic which allows a molding process to be used for producing the part. The light pipe  22  directs the light utilizing the principles of total internal reflection and a number of angled internal surfaces for reflecting and directing the light. The light pipe  22  generally includes an upstream end  24  and a downstream end  26 . Light from the LED light source  18  flows downstream from the upstream end  24  to the downstream end  26 . A main body  28  of the light pipe  22  is generally cylindrical in nature, and includes a plurality of flanges  30  attached to its outer surface for connecting the LED bulb  20  to the other structural components of the light module  10  or other support structures of the vehicle. The downstream  26  of the light pipe  22  includes a conical reflector  32  for redirecting the light in the light pipe  22  radially outwardly through ribs  50 , as will be described in more detail below.  
         [0015]     As shown in  FIG. 3 , the conical reflector  32  defines an inner reflective surface  34  that acts as a reflector using the principle of total internal reflection inside the light pipe  22 . The inner surface  34  alternates between a first set of surfaces  36  and a second set of surfaces  38 . The light pipe  22  defines a longitudinal axis  15 , and the first surfaces  36  are generally parallel to the longitudinal axis  15 . The second surfaces  38 , interspersed between the first surfaces  36 , are generally angled relative to the longitudinal axis  15 , preferably around 45°.  
         [0016]     It will also be seen in  FIG. 3  that an outer peripheral surface of the downstream end  26  of the light pipe  22  includes a plurality of ribs  50  projecting radially outwardly. The ribs  50  have a tapered shape, and most preferably have a triangular cross-sectional shape defined by a first upstream face  52  and a second downstream face  54 . The upstream face  52  is generally perpendicular (in the range of 85°-90°) to the longitudinal axis  50 , while the downstream face  54  is generally angled (in the range of 30°-89°) relative to the longitudinal axis  15 . It will be recognized by those skilled in the art that both of the faces  52 ,  54  can be angled relative to the longitudinal axis  15  (or the relative angling reversed) to achieve the desired effect of directing light outwardly from the light pipe  22  to create a virtual image. The ribs  50  are aligned along the longitudinal axis  15  with the second surfaces  38  of the conical reflector  32 . The ribs  50  are axially spaced apart from each other a distance corresponding to the axial distance spanned by each first surface  36 . It will be recognized that an upstream set of the ribs  50 , namely the first four ribs, alternate between taller ribs and shorter ribs. This allows light which is redirected more in the upstream director to exit the light pipe without interference from adjacent ribs  50 .  
         [0017]     The upstream end  24  of the light pipe  22  has a tapered shape in the upstream direction, and generally is structured to collimate the light from the LED light source  18  and direct the light longitudinally downstream generally parallel with the longitudinal axis  15 . By the term generally, it is meant that the light follows a path which is within 3° of parallel to the longitudinal axis  15 .  
         [0018]     The upstream end  24  includes a recess  40  for receiving the LED light source  18 . The recess is defined by a slight tapering surface  42  which extends longitudinally and ends at an axially facing surface  44  which is structured as a lens that focuses the light longitudinally downstream. The lens  44 , the surface  42  of the recess  40 , and the reflective surface  46  of the tapered upstream end  24  all cooperate to direct the light from the LED light source  18  downstream and generally parallel to the longitudinal axis  15 . As such, the upstream end is structured to act as a collimater.  
         [0019]     The path of light through the LED bulb  20  will now be described with reference to  FIG. 3 . Rays of light  48  are generated by LED light source  18  and begin at a point of origin  19 . Some light  48  follows a path through the lens  44  and is directed longitudinally downstream as shown. The remainder of the light  48  flows through the upstream end  24  and is redirected by recess surface  42  and the upstream end surface  46  longitudinally downstream as shown. The collimated light rays  48  thus flow through the main body  28  of light pipe  22  until they encounter the conical reflector  32 .  
         [0020]     As the light is generally traveling parallel to the longitudinal axis  15 , it also travels parallel to the first surfaces  36  of the conical reflective surface  34 , and is thus not immediately redirected. The light  48  will then encounter the second angled surface  38  of the inner surface  34 , which redirects the light radially outwardly towards the outer periphery of the light pipe  22 . The 45° angle of the second surfaces  38  thus reflects the light  48  along a path that is generally perpendicular to the longitudinal axis  15 . Since the ribs  50  are axially aligned with the second angled surfaces  38 , the light rays  48  will encounter one of the ribs  50 . The upstream and downstream surfaces  52 ,  54  of the ribs  50  are structured to redirect the light rays  48  in the upstream direction and radially outwardly. It can be seen in the figure that the ribs  50  are structured to redirect the light rays  48  in a manner that the light rays  48  appear to have come from a different origin point  19   a , which is referred to as a virtual origin point. Thus, the structure of the LED bulb  20  and its light pipe  22  defines a virtual image  19   a  of the LED light source  18 . It can be seen in  FIG. 4 , the light rays  48  exiting the downstream end  26  of the light pipe  22  are directed towards the reflector  12  and its reflective surface  13  for further redirection of the light rays  48  out of the light module  10  and away from the motor vehicle.  
         [0021]     It can also be seen from  FIG. 4  that the downstream end  26  of the LED bulb  20  is positioned in front of the reflector  12 , while the upstream end  24  extends through the aperture  14  and is positioned behind the reflector  12 . Stated another way, the virtual image and focus point  19   a  needs to be positioned in front of the reflector  12 , allowing the true LED light source  18  to be positioned outside of the cavity and behind the reflector  12 . The virtual image and source point  19   a  is positioned in front of the reflector to direct light toward the reflective surface  13 .  
         [0022]     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.