Abstract:
A center high mounted stop lamp ( 12 ) including a plurality of LEDs ( 34 ) mounted on a printed circuit board ( 30 ). TIR lenses ( 40 ) are employed to focus the light from the LEDs ( 34 ) to give an even lighting appearance. The TIR lenses ( 40 ) include a prism ( 44 ) for directing the light in a desired direction. The circuit board ( 30 ) and lenses ( 40 ) are mounted in a housing ( 18 ) so that each LED ( 34 ) includes a separate lens ( 40 ) configured relative thereto to provide the desired collection and reflectance of the light. The housing ( 18 ) includes a plurality of posts ( 70 ) that extend through openings ( 48, 50 ) in the circuit board ( 30 ) and the lenses ( 40 ) to align the LEDs ( 34 ) to the lenses ( 40 ) relative to the housing ( 18 ).

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to vehicle lighting employing light emitting diodes (LEDs) and, more particularly, to automotive signal lighting, such as a center high mounted stop lamp (CHMSL) for a vehicle, where the CHMSL employs LEDs and a TIR lens assembly. 
     2. Discussion of the Related Art 
     Vehicle styling and appearance provides significant and important advantages for attracting customers. One recognized area that is known to enhance vehicle attraction is the appearance and design of the various vehicle lights, sometimes referred to as the vehicle&#39;s jewels, including, but not limited to, headlights, tail lights, turn signals, back-up lights, CHMSLs, running lights, fog lamps, etc. In fact, modem vehicle designs pay close attention to the styling and design of the vehicle lights. 
     Current vehicle lights employ various types of light sources suitable for different designs and conditions. For example, vehicle lighting designs have employed incandescent lamps, neon bulbs, halogen lamps, etc. Some modem vehicle light designs have employed light emitting diodes (LEDs) that are able to provide different colors in an inexpensive and durable arrangement. Known LED designs for vehicles have employed LEDs mounted on a circuit board, where the circuit board is secured within a housing. A total internal reflecting (TIR) lens is positioned over each LED to collect most of the light emitted therefrom and focus it in for a field pattern. A lens of this type is disclosed in U.S. Pat. No. 5,404,869 titled “Faceted Totally Internally Reflecting Lens with Individually Curved Faces on Facets,” issued Apr. 11, 1995 to Parkyn, Jr. et al. This combination of LEDs and lenses provides high intensity light at relatively low power. 
     Vehicle lights are typically mounted in class A vehicle body panels. Because typical vehicle lights have a thickness in the range of 40-70 mm, the recessed area for the light cannot be stamped in the vehicle body panel because metal stamping operations providing the necessary depth that will wrinkle, tear and damage the body panel. Thus, it is necessary to weld a separate metal pocket to a hole cut in the body panel to provide the recessed area for the vehicle light. However, the separate metal pocket causes variations in the welding process, variations in the alignment tooling for holding the pocket to the body panel and variations in the actual pocket itself, sometimes resulting in poorly fitting light assemblies in the body panel. Further, the connection point between the pocket and the body panel has to be sealed. Thus, the pocket increases the vehicle part count, requires more assembly time, and possibly creates leaks. Because LED assemblies for vehicle lights can typically be thin, these designs are sometimes conducive to be mounted in stamped recesses in vehicle body panels. However, heretofore, such designs have been limited and ineffective. 
     SUMMARY OF THE INVENTION 
     In accordance with the teachings of the present invention, a vehicle light is disclosed that employs a plurality of LEDs that are mounted on a printed circuit board. TIR lenses are coupled to the LEDs to collect and focus the light from the LEDs to give an even lighting appearance. In one embodiment, the TIR lenses include a prism for directing the light in a desired direction. The circuit board and lenses are mounted in a housing so that each LED includes a separate lens precisely aligned thereto to provide the desired collection and focusing of the light. An outer lens is then rigidly secured to the housing. The housing and/or outer lens include a plurality of datum points to align the circuit board and the lenses relative to each other. In one embodiment, the datum points are posts integrally molded to a base portion of the housing. The posts are inserted through cooperating holes in the circuit board and the TIR lenses. In an alternate embodiment, the TIR lenses are a part of a common body, where alignment tabs of different lengths extend from an edge of the body. The circuit board includes a series of cooperating slots around its outer edge. The tabs are inserted in the slots to align the lenses to the LEDs. In one embodiment, the housing includes an integral electrical connector including rigid electrodes that eliminates wires. 
     Additional advantages and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a rear view of a vehicle including a CHMSL, according to an embodiment of the present invention; 
         FIG. 2  is a rear, perspective view of the CHMSL shown in  FIG. 1  removed from the vehicle; 
         FIG. 3  is an exploded, perspective view of the CHMSL shown in  FIG. 2 ; 
         FIG. 4  is a cross-sectional view of the CHMSL shown in  FIG. 2  through line  4 - 4 ; 
         FIG. 5  is a cut-away top view of the CHMSL shown in  FIG. 2  with an upper housing portion removed; 
         FIG. 6  is a cross-sectional view of the TIR lens assembly removed from the CHMSL; 
         FIG. 7  is a cross-sectional view of the CHMSL shown in  FIG. 2 , according to another embodiment of the present invention; 
         FIG. 8  is a rear, perspective view of a CHMSL, according to another embodiment of the present invention; 
         FIG. 9  is an exploded, perspective view of the CHMSL shown in  FIG. 8 ; 
         FIG. 10  is a cross-sectional view through line  10 - 10  of the CHMSL shown in  FIG. 8 ; and 
         FIG. 11  is a cut-away top view of the CHMSL shown in  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The following discussion of the embodiments of the invention directed to an LED assembly for a vehicle is merely exemplary in nature and is in no way intended to limit the invention, or its application or uses. For example, the discussion below is particularly directed to a CHMSL for a vehicle employing an LED design. However, as will be appreciated by those skilled in the art, the LED design of the present invention may have application for other vehicle lights. 
       FIG. 1  is a rear view of a vehicle  10  including a CHMSL  12 , according to an embodiment of the present invention. As is known in the art, a CHMSL is a light device conspicuously positioned at the rear of a vehicle that allows drivers to readily determine that the vehicle in front of them is braking. CHMSLs are known to come in a variety of designs and can be mounted to the vehicle in a variety of locations. CHMSLs offer vehicle designers the ability to provide an aesthetically pleasing appearance, and to establish vehicle identity. The CHMSL  12  in this design is mounted to a body panel  20  of a trunk  24  of the vehicle  10  in a manner that will be discussed in more detail below. As will also be discussed below, the CHMSL  12  of the invention employs LED technology to provide certain design and lighting advantages. 
       FIG. 2  is a perspective view,  FIG. 3  is an exploded perspective view and  FIG. 4  is a cross-sectional view of the CHMSL  12  removed from the vehicle  10 . The CHMSL  12  includes an enclosure  14  made of a single piece outer lens  16  and a single piece housing  18 . The outer lens  16  has a certain elongated curved appearance in this design, but as will be appreciated by those skilled in the art, this is merely by way of example in that any other suitable shape can be provided. The outer lens  16  and the housing  18  are plastic parts molded by a suitable molding process, such as injection molding. The outer lens  16  and the housing  18  can be made of any plastic, such as polycarbonate and acrylic, that is suitable to stand up to the rigors of the vehicle environment and provide the desired appearance and color. Further, the lens  16  has any suitable optical quality, translucence and color. In this example, the lens  16  is red in appearance. 
     The lens  16  includes a recessed area  26  that accepts a rim  28  of the lower housing  18  so as to define a cavity  22  when the outer lens  16  is secured to the lower housing  18 , as shown. The outer lens  16  and the housing  18  are secured together by any suitable technique, such as gluing, sonic welding, heat welding, etc. A seal  38  is provided in an outer notch  52  of the lower housing portion  18  to provide a seal surface that seals the CHMSL  12  to a cooperating edge in an opening in the body panel  20 . 
     The CHMSL  12  includes a printed circuit board (PCB)  30  and an TIR lens assembly  32  mounted within the enclosure  14 .  FIG. 5  is a cut-away, top view of the CHMSL  12 . The PCB  30  includes a plurality of LEDs  34  mounted thereto. In this embodiment, the LEDs  34  are “chip on board” LEDs in that they are mounted to the PCB  30  and interconnected with other circuit elements  54 , such as resistors, as components when the PCB  30  is manufactured. In other words, instead of the LEDs  34  being formed in a separate protective package prior to being mounted to the PCB  30  and interconnected to the circuit elements  54 , the LEDs  34  are mounted to the PCB  30  in their component state. This saves assembly and part costs. The lens assembly  32  includes a plurality of cut-out portions  62  that accommodate the various circuit elements  54 . 
     The several LEDs  34  and the circuit elements  54  are interconnected on the PCB  30  by electrical traces  56 . Wires  36  are electrically coupled to the PCB  30  and to the vehicle electrical system to provide power to the LEDs  34 . Protective layers are deposited over the LEDs  34  and the rest of the board  30 . In this example, a dome  58  of a suitable protective material, such as polyurethane, is deposited over each LED  34  after the LEDs  34  are attached to and coupled within the PCB  30 . In one embodiment, the inner lens assembly  32  is heat staked to the PCB  30  and the housing  18 . However, other suitable techniques of securing the lens assembly  32  and the PCB  30  within the enclosure  14  can be used. 
     The number of LEDs  34 , the size of the LEDs  34 , the color of the LEDs  34  and the spacing between LEDs  34  are all application specific in that different designs can be made differently to satisfy different system requirements. LEDs  34  that provide certain colors require different semiconductor materials. For example, AlInGaP semiconductor materials provide colors in the red to amber wavelengths. InGaN semiconductor materials provide colors in the green to ultraviolet wavelengths. LEDs that emit white light are known by employing certain semiconductor materials in combination with phosphorous. U.S. Pat. No. 6,069,440 issued to Shimizu et al. discloses a white light emitting diode. 
     The lens assembly  32  is a single body member  64  made of a suitable transparent optical plastic by a suitable process, such as injection molding.  FIG. 6  is a cross-sectional view of the lens assembly  32  separated from the housing  14 . The assembly  32  includes a plurality of TIR lenses  40 , where a separate lens  40  is provided for each LED  34  and is aligned relative thereto. In alternate embodiments, the assembly  32  can be several lens assemblies each including a plurality of lenses  40 . Each lens  40  includes a hemispherical cavity  66  including a grating  42  that collects and focuses light from the associated LED  34 . Because the LEDs  34  are “chip on board,” they do not include the LED packaging of known designs, and thus, the light emitted therefrom is dispersed in all directions and not just at a particular angle. Therefore, the associated lens  40  can be positioned directly adjacent the LED  34  where the body member  64  contacts the PCB  30 , thus allowing the packaging to be thinner. 
     According to the invention, the lens assembly  32  includes a prism  44  formed to an upper surface of the body member  64  opposite to the LEDs  34 . Because the CHMSL  12  is mounted to the vehicle  10  at an angle (such as 10°) relative to the road surface because of the shape of the trunk  24 , the present invention proposes employing the prism  44  to redirect the light in a more parallel direction relative to the road surface. The prism  44  is integrally molded as part of the body member  64 . The prism  44  includes a series of diffraction lines  46  that redirect the light in a desirable direction. 
     To provide the desirable collection and focusing of light from the LEDs  34 , the lens  40  must be accurately aligned to its respective LED  34 . To provide this alignment, the present invention proposes a series of datum points to which the PCB  30  and the lens assembly  32  can be aligned. Particularly, a plurality of spaced apart posts  70  are integrally molded to the lower housing  18 , as shown. The posts  70  extend through associated holes  48  in the PCB  30  and associated holes  50  in the body member  64 . Thus, each lens  40  is closely aligned with its respective LED  34  to provide the highest degree of collection and focussing of the light. The posts  70  and the holes  48  and  50  compensate for thermal expansion and contraction between the housing  14 , the PCB  30  and the lens assembly  32 . In one embodiment, the CHMSL  12  employs at least three posts  70  to provide the desired alignment. 
     The combination of the chip on board LEDs  34  and the lens assembly  32  allows the CHMSL  12  to be made quite thin. In this embodiment, the CHMSL  12  is about 11 mm thick. Because the CHMSL  12  is relatively thin, the recess in the body panel  20  that the CHMSL  12  is mounted in can be relatively shallow. Thus, the recess can be formed in the body panel  20  by a metal stamping operation without wrinkling or otherwise damaging the body panel  20 . Known CHMSLs and other vehicle lights are relatively thick, requiring the recess to be formed by welding body parts together. This increased the assembly cost and vehicle part count. Further, the connection point between the parts needs to be sealed to prevent leakage. By employing a stamping process, only mounting holes and holes for the wires  36  need to be made in the body panel  20 . Alternately, a hole is pierced in the panel  20  and gaskets are provided on the CHMSL  12  to seal the holes to the environment. 
     In this embodiment, the CHMSL  12  is mounted to the body panel  20  by mounting posts  76 . The mounting posts  76  include a snap fit end  78  that allows the CHMSL  12  to be snap fit to the body panel  20 . The posts  76  are inserted through holes in the body panel  20 , and the ends  78  snap behind the panel  20  to hold the CHMSL  12  in place. Other types of mounting posts suitable for mounting the CHMSL  12  to the body panel  20  can also be used within the scope of the present invention. 
     Further, the CHMSL  12  is relatively light. Therefore, the CHMSL  12  can be taped to the body panel  20 .  FIG. 7  is a cross-sectional view of the CHMSL  12 , according to another embodiment of the invention, where the posts  76  have been replaced with a piece of double-sided tape  80 . The CHMSL  12  is secured to the body panel  20  by the tape  60 . 
       FIG. 8  is a rear perspective view,  FIG. 9  is an exploded perspective view,  FIG. 10  is a cross-sectional view through line  10 - 10  in  FIG. 8  and  FIG. 11  is a cut-away top view of a CHMSL  90 , according to another embodiment of the present invention. The CHMSL  90  includes a single piece plastic housing  92  and an outer lens  94  secured thereto by a suitable adhesive or the like to define a cavity  96  therein. The housing  92  includes mounting posts  98  and  100  having resilient tabs  86  and  88 , respectively, that are inserted through holes in the body panel  20 , where the tabs  86  and  88  flex to secure the CHMSL  90  thereto. 
     The housing  92  further includes an integral connector  102  defining a chamber  104  therein. Electrodes  110  and  112  are secured within the plastic forming the connector  102 , and are electrically coupled to electrical connectors  114  mounted to a PCB  108 . When the CHMSL  90  is mounted to the body panel  20 , a vehicle mating connector (not shown) is inserted into the chamber  104  so that the electrodes  110  and  112  make electrical contact with an electrical system that provides power to the PCB  108 . Thus, the CHMSL  90  eliminates wires that could otherwise break affecting the integrity of the CHMSL  90 . 
     The PCB  108  is mounted to an inner surface  120  of the housing  92  within the cavity  96 . The PCB  108  is aligned to the housing  120  by inserting posts  124  and  126  integrally molded to the housing  92  through holes  128  and  130 , respectively, formed through the PCB  108 . Also, the electrodes  110  and  112  are inserted within the respective connector  114  to provide the electrical connection and help hold the PCB  108  in place. The PCB  108  includes a plurality of LEDs  136  mounted thereto. In this embodiment, the LEDs  136  are also “chip on board” LEDs in that they are mounted to metal portions on the PCB  108  and are interconnected with other circuit elements  138  by electrical traces  140 , as discussed above. 
     A TIR lens assembly  150 , similar to the lens assembly  32  discussed above, is also mounted within the cavity  96  relative to the PCB  108 . As above, the lens assembly  150  includes a plurality of lenses  152 , where a separate lens  152  is positioned relative to each LED  136 . The lens assembly  150  is a single body member made of a suitable transparent optical plastic by a suitable process, such as injection molding. Each lens  152  includes a grating  156  that collects and focuses light from the associated LED  136 , as discussed above. 
     The lens assembly  150  includes a plurality of tabs  160  extending downward from an edge or rim  162  of the assembly  150 , as shown. Further, the PCB  108  includes a plurality of associated slots  166  formed in an outer edge  168  of the PCB  108 , as shown. Each tab  160  has a particular length, width and location so that it can be inserted into an associated slot  166  having the same length, width and location. Therefore, by properly positioning the lens assembly  150  relative to the PCB  108  within the cavity  96 , each lens  152  will properly align to its respective LED  136 . 
     In this embodiment, the lens assembly  150  and the PCB  108  are secured to the surface  120  of the housing  92  by sonic welding or by a sonic tack. A series of integral energy directors are provided on the surface  120  to accept the heat from the sonic tack. Particularly, energy directors  170  are provided proximate the post  124 , energy directors  172  are provided proximate the post  126 , and energy directors  176  are provided proximate the connector  102 , as shown. When the PCB  108  and the lens assembly  150  are aligned relative to each other within the cavity  96 . The bottom surface of some of the tabs  160  are positioned directly over and in contact with the energy directors  170 ,  172  and  176 . Sonic energy is applied to the energy directors  170 ,  172  and  176  and the lens assembly  150  to secure the lens assembly  152  to the housing  92  and hold the PCB therebetween. This technique allows the CHMSL  90  to be formed in a curved manner to conform with the body panel  20 . 
     The outer lens  94  is then positioned on the housing  92  so that a rim  178  of the outer lens  94  aligns with an edge  180  of the housing  92  to be glued thereto. Once the cavity  96  is sealed by securing the outer lens  94  to the housing  92 , the integrity of the seal is tested by determining if the cavity  96  can hold a vacuum pressure. It is important that the cavity  96  be sealed so that moisture does not enter the cavity  96  during vehicle operation that would otherwise reduce its performance. To provide the pressure test, a vent hole  190  is provided through a wall  192  in the chamber  104 . Additionally, a vent hole  194  is provided in the PCB  108  so that the cavity  96  is in fluid communication with the hole  190 . During testing, a pressure device is coupled to the socket  102  to remove air from the cavity  96  to determine the seal integrity. 
     The foregoing discussion discloses and describes merely exemplary embodiments of the present invention. One skilled in the art will readily recognize from such discussion and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the spirit and scope of the invention as defined in the following claims.