Abstract:
A vehicular lamp includes a lamp body; a plurality of LED light sources disposed inside a lamp chamber formed by a front cover positioned in front of the lamp body; and a lighting circuit portion positioned behind the LED light sources. The LED light source is electrically connected to a conductive bus bar, and forms a light-emitting surface at a position opposite the front cover. The lighting circuit portion is formed on the back side of the light-emitting surface of the LED light source with respect to the front cover, and a circuit element thereof is electrically connected to the conductive bus bar. The conductive bus bar to which the LED light source is connected and the conductive bus bar to which the circuit element is connected are conductively connected.

Description:
BACKGROUND OF INVENTION 
   1. Field of the Invention 
   The present invention relates to a vehicular lamp using an LED as a light source. 
   2. Background Art 
   In recent years, a variety of LEDs with excellent light emission efficiency and power consumption characteristics are being used as a light source in a vehicular lamp (see Patent Document 1 for an example). Such a vehicular lamp is provided with an LED light source assembly portion mounted with an LED and a unit that combines the LED light source assembly portion with a control circuit portion. As shown in  FIG. 12 , a conventional control circuit portion uses a printed circuit board  8 , which is connected to the back side of the LED light source assembly portion by a jump cord  15 . 
   [Patent Document 1] U.S. Pat. No. 6,715,909 
   SUMMARY OF INVENTION 
   In order to make a smaller overall unit, it is preferable that the control circuit portion and an LED light source assembly portion  9  are arranged adjacent to one another. However, a certain amount of space must be left due to the heat emitted by the printed circuit board  8 , and the arrangement can only be made so compact using the conventional structure. For the purpose of suppressing heat, the conventional printed circuit board also needs dispersion resistors in order to disperse voltage or current. As a consequence, as more resistors are used, the size of the control circuit portion increases. If the problem of heat generation were resolved, then it would be possible to achieve both a smaller control circuit portion and an adjacent arrangement with the LED light source assembly portion. 
   One or more embodiments of the present invention provide a compact vehicular lamp that achieves downsizing of a control circuit portion, and downsizing of the overall unit through an adjacent arrangement with an LED light source assembly portion. 
   In one or more embodiments of the present invention, a vehicular lamp has a lamp body; a plurality of LED light sources that are inside a lamp chamber formed by a front cover positioned in front of the lamp body; and a lighting circuit portion that is positioned behind the LED light sources, wherein the LED light source is electrically connected to a conductive bus bar, and forms a light-emitting surface at a position opposite the front cover, the lighting circuit portion is formed on the back side of the light-emitting surface of the LED light source with respect to the front cover, and a circuit element thereof is electrically connected to the conductive bus bar, and the bus bar to which the LED light source is fixed and the bus bar to which the circuit element is fixed are conductively connected. 
   According to the above configuration, the LED light source and the lighting circuit portion are both structured using bus bars with high heat loss. Therefore, the LED light source and the lighting circuit portion can achieve an adjacent arrangement. In addition, by using the bus bars with high heat loss, dispersion resistors to compensate for heat generation can be eliminated or reduced in number. Therefore, the lighting circuit portion itself can be downsized. As a consequence, a unit structured by the LED light source and the lighting circuit portion can be downsized, thereby achieving a more compact lamp overall. 
   In one or more embodiments of the present invention, the bus bar to which the LED light source is fixed and the bus bar to which the circuit element is fixed are formed as a combined bus bar. According to such a configuration, the bus bars of the LED light source and the lighting circuit portion are combined, and following the assembly of electronic components, are subjected to bending. The unit can thus be downsized, thereby achieving a more compact lamp overall. 
   In one or more embodiments of the present invention, the bus bar to which the LED light source is fixed and the bus bar to which the circuit element is fixed are respectively held on separate boards, and the board holding the bus bar to which the circuit element is fixed is bendably formed on the back of the board holding the bus bar to which the LED light source is fixed. According to such a configuration, after the bus bars of the LED light source and the lighting circuit portion are separately formed, both are bendably joined. Likewise, the unit can thus be downsized, thereby achieving a more compact lamp overall. 
   In one or more embodiments of the present invention, the board is structured by the lamp body, and the bus bar is supported by both sides of the lamp body. According to such a configuration, it is possible to accurately fix a bus bar of the LED light source and a bus bar of the lighting circuit portion that have been formed and processed into complex shapes such as a stepped configuration. Accordingly, the unit can be efficiently accommodated regardless of whether the front cover has a curved shape, and thus achieve a more compact lamp overall. 
   According to one or more embodiments of the present invention, the LED light source and the lighting circuit portion are both structured using bus bars with high heat loss. Therefore, the LED light source and the lighting circuit portion can achieve an adjacent arrangement. In addition, by using the bus bars with high heat loss, dispersion resistors to compensate for heat generation can be eliminated. Therefore, the lighting circuit portion itself can be downsized. As a consequence, a unit structured by the LED light source and the lighting circuit portion can be downsized, thereby achieving a more compact lamp overall. 
   Other aspects and advantages of the invention will be apparent from the following description and the appended claims. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  is a horizontal cross-sectional view showing a structure of a vehicular lamp according to an embodiment of the present invention. 
       FIG. 2  is a perspective view showing a first structure example of a bus bar unit in the vehicular lamp according to an embodiment of the present invention. 
       FIG. 3  is a schematic diagram showing a pre-molding board in the bus bar unit of the first structure example. 
       FIG. 4  is a perspective view showing a second structure example of a bus bar unit in the vehicular lamp according to an embodiment of the present invention. 
       FIG. 5  is a perspective view showing a third structure example of a bus bar unit in the vehicular lamp according to an embodiment of the present invention. 
       FIG. 6  is circuit diagram showing an example of a control circuit portion structured by the bus bar in the vehicular lamp according to an embodiment of the present invention. 
       FIG. 7  is a schematic diagram showing an example of a bus bar circuit of the control circuit portion in the vehicular lamp according to an embodiment of the present invention. 
       FIG. 8  is a schematic diagram roughly showing the joining of components (caulking) in the bus bar circuit. 
       FIG. 9  is a schematic diagram roughly showing the joining of components (welding) in the bus bar circuit. 
       FIG. 10  is a schematic diagram roughly showing the joining of components (pressure welding) in the bus bar circuit. 
       FIG. 11  is a schematic diagram showing another embodiment of the bus bar unit in the vehicular lamp according to an embodiment of the present invention. 
       FIG. 12  is a schematic diagram showing a conventional structure of the control circuit portion and an LED light source assembly portion in the vehicular lamp. 
       FIG. 13  is a circuit diagram in a case where the same functions of the control circuit portion structured by the bus bar are achieved with a printed circuit board. 
       FIG. 14  is a schematic diagram showing a conventional control circuit portion structured by the printed circuit board. 
       FIG. 15  is a schematic diagram roughly showing soldering on the printed circuit board. 
   

   DETAILED DESCRIPTION 
     FIG. 1  is a horizontal cross-sectional view showing a structure of a vehicular lamp according to one or more embodiments of the present invention. Here, a tail and stop lamp, i.e., a marker lamp, will be used in the following description as an example of a vehicular lamp according to one or more embodiments of the present invention. 
   A tail and stop lamp  100  is mainly structured from a lamp body  1 , a curved front cover  2 , a lamp chamber  3  that is defined by the lamp body  1  and the front cover  2 , a curved reflector  4  that is disposed inside the lamp chamber  3 , and a bus bar unit  5  that is provided on the back side of the reflector  4 . The bus bar unit  5  is a unit provided with an LED light source assembly portion  55  that is mounted with an LED  10 , which acts as a light source of the tail and stop lamp  100 , and a control circuit portion  56  that controls the light emission of the LED. In the example shown in the drawing, the bus bar unit  5  is fixed to the reflector  4  on a vehicle width-direction centerward side  41  and a vehicle left-side vicinity  42  of the reflector  4 . Structuring the control circuit portion  56  from a bus bar circuit as well as the conventional LED light source assembly portion  55  is an important characteristic in the vehicular lamp according to one or more embodiments of the present invention. 
   Note that the reflector  4  is curved on a three-dimensional plane in the up-down and right-left directions, and is provided with a plurality of parabolic reflective surface portions  44 . Back vertex portions of the parabolic reflective surface portions  44  are provided with an LED engagement portion  43 . By engaging an LED body  11  with the LED engagement portion  43 , the center of light emission from an LED  10  is self-positioned with respect to the parabolic reflective surface portion  44 . Reference numeral  20  denotes a fish-eye lens that is provided in a region that corresponds to an entire formation region of at least the parabolic reflective surface portions  44  of the reflector  4  on the back side of the front cover  2 . 
   The LED engagement portion  43  of the reflector  4  is also provided with an elastic hook  45  that grasps and holds the LED body  11 . Through elastic deformation of the elastic hook  45 , the LED body  11  (the bus bar unit  5 ) is easily attached to and removed from the LED engagement portion  43  from the back surface side of the reflector  4 . 
   Reference numerals  6  and  7  denote reflex reflectors that are attached to the front surface sides of the right and left side edge portions of the reflector  4 . Note that a region of the front cover  2  corresponding to the reflex reflectors  6  and  7  is a non-stepped region where the fish-eye lens  20  is not formed. 
   Following next is a description of a joining pattern for the LED light source assembly portion  55  and the control circuit portion  56 , which structures the bus bar unit  5 . 
     FIG. 2  is a perspective view showing a first structure example of a bus bar unit in the vehicular lamp according to an embodiment of the present invention.  FIG. 3  is a schematic diagram showing a pre-molding board in the bus bar unit of the first structure example. As shown in  FIGS. 2 and 3 , a bus bar unit  50 , i.e., the first structure example, is formed by assembling components such as an LED, a diode, a resistor, and the like to a bus bar circuit, which is an integration of the LED light source assembly portion  55  and the control circuit portion  56 . Thereafter, a bus bar board that supports the bus bar circuit is subjected to bending (processing such as folding the LED light source assembly portion  55  into a stepped configuration). 
   As shown in  FIG. 3 , a region on one side of the bus bar unit  50  is formed with the LED light source assembly portion  55 , that is, an LED module wherein the LED  10  emitting red light in a grid configuration is disposed on the bus bar circuit. In other words, one of a pair of contact terminals  12  leading out from the LED body  11  on two adjacent bus bars  16  is respectively joined according to a joining method to be described later in order to structure a power supply route for the LED  10 . The LED  10  has a structure in which a pair of tab-shaped metal contact terminals lead out in an L-shape configuration from the back side of the LED body  11 , which is an oblong-shaped body formed from synthetic resin. As described above, the end sides of the contact terminals  12  are respectively engaged with the bus bars  16  of the bus bar unit  50  and together form the LED light source assembly portion  55 . 
   In addition, a region on the opposite side of the bus bar unit  50  is formed with the control circuit portion  56 , which is connected to the LED light source assembly portion  55  and controls the lighting of the LED  10 . 
   In a conventional vehicular lamp, even if the LED light source assembly portion is structured using bus bars, the control circuit portion was still formed using a printed circuit board, and therefore it was impossible to achieve the bus bar unit  50  by forming the two in a combined manner. However, in the vehicular lamp according to one or more embodiments of the present invention, the circuitry of the control circuit portion also uses bus bars  17 , making it possible to achieve a combined formation. 
   Next,  FIG. 4  is a perspective view showing a second structure example of a bus bar unit in the vehicular lamp according to the embodiment of the present invention. As shown in  FIG. 4 , a bus bar unit  51 , i.e., the second structure example, is structured by using a joint terminal  13  to join a bus bar board of the LED light source assembly portion  55  and a bus bar board of the control circuit portion  56 , which were formed in a separate process. 
     FIG. 5  is a perspective view showing a third structure example of a bus bar unit in the vehicular lamp according to the embodiment of the present invention. As shown in  FIG. 5 , a bus bar unit  52 , i.e., the third structure example, is structured by using a terminal cord  14  to join a bus bar board of the LED light source assembly portion  55  and a bus bar board of the control circuit portion  56 , which were formed in a separate process. 
   Although the bus bar units  51  and  52  have more components than in the case of a combined unit, they also have the advantage of enabling standardization of the bus bar board of the control circuit portion  56 . The bus bar unit  52  has the further advantage of not necessarily being limited to an adjacent arrangement when the layout of the lamp chamber is restricted, and instead allows placement in other suitable arrangements. 
   Next, the circuitry of the control circuit portion  56  will be described.  FIG. 6  is circuit diagram showing an example of a control circuit portion structured by the bus bar in the vehicular lamp according to an embodiment of the present invention. The number of resistors can be reduced as compared to the circuit diagram (see  FIG. 13 ) where the same functions are realized with a printed circuit board. Therefore, downsizing of the bus bar board itself in the control circuit portion  56  can be achieved. 
   The following is a description of modes for joining electronic components in the control circuit portion  56 .  FIG. 7  is a schematic diagram showing an example of a bus bar circuit of the control circuit portion in the vehicular lamp according to an embodiment of the present invention. A conventional control circuit portion (see  FIG. 14 ) structured using a printed circuit board required joining by soldering. However, in the vehicular lamp according to an embodiment of the present invention, structuring the control circuit portion using the bus bar  18  enables joining by caulking, welding, pressure welding, or the like, thus eliminating the need for soldering. 
     FIGS. 8 to 10  are schematic diagrams showing the joining of components in the bus bar circuit. In the control circuit portion of the vehicular lamp according to an embodiment of the present invention, components are joined in the bus bar circuits by methods such as caulking ( FIG. 8 ), welding ( FIG. 9 ), and pressure welding ( FIG. 10 ), thus eliminating the need for joining by soldering. Regarding the soldered portion (see  FIG. 15 ) of the printed circuit board, the soldering melts at high temperatures. Therefore, dispersion resistors must be used to keep the heat generated at the soldering portion under a specific tolerance, similar to the problem of heat generation in the printed circuit board. As a consequence, the number of resistors increases. However, if the components are joined by a method such as shown in  FIGS. 8 to 10  using a bus bar, then the problem of heat generation related to the soldering is resolved, and the number of resistors can be reduced. Thus, the unit including the control circuit portion and the LED light source assembly portion, and by extension, the overall lamp, can be downsized. 
     FIG. 11  is a schematic diagram showing the bus bar unit in the vehicular lamp according to an embodiment of the present invention. If the front cover of the tail and stop lamp is flat without curvature and there is no need to process the LED light source assembly portion  55  in a stepped configuration as shown in  FIG. 1 , then the bus bar unit  50  with a combined formation can be folded at a 90-degree angle ( FIG. 11(   a )) or at a 180-degree angle ( FIG. 11(   b )) so that the bus bar circuit portion takes up less space. 
   While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims. 
   DESCRIPTION OF THE REFERENCE NUMERALS 
   
       
         1  LAMP BODY 
         2  FRONT COVER 
         3  LAMP CHAMBER 
         4  REFLECTOR 
         5  BUS BAR UNIT 
         6 , 7  REFLEX REFLECTOR 
         8  PRINTED CIRCUIT BOARD 
         9  LED LIGHT SOURCE ASSEMBLY PORTION 
         10  LED 
         11  LED BODY 
         12  CONTACT TERMINAL 
         13  JOINT TERMINAL 
         14  TERMINAL CORD 
         15  JUMP CORD 
         16 ,  17 ,  18  BUS BAR 
         20  FISH-EYE LENS 
         43  LED ENGAGEMENT PORTION 
         44  PARABOLIC REFLECTIVE SURFACE PORTION 
         45  ELASTIC HOOK 
         50 ,  51 ,  52  BUS BAR UNIT 
         55  LED LIGHT SOURCE ASSEMBLY PORTION 
         56  CONTROL CIRCUIT PORTION 
         100  TAIL AND STOP LAMP