Abstract:
Headlight components including a bulb and a reflector are contained in a headlight housing, and a rear opening of the headlight housing is closed with a back cover. A circuit board is mounted on an inner surface of the back cover, and an impact-alleviating member is connected to or formed on an outer surface of the back cover. An external impact applied to circuit board through the back cover is alleviated by resiliency or plasticity of the impact-alleviating member. Thus, the circuit board is well protected from the external impact. The impact-alleviating member may be plural projections standing up from the outer surface of the back cover, or may be formed in various shapes.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application is based upon and claims benefit of priority of Japanese Patent Application No. 2004-58532 filed on Mar. 3, 2004, the content of which is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to an automobile headlight housing in which a circuit board for controlling lighting operation is contained.  
         [0004]     2. Description of Related Art  
         [0005]     It has been proposed to contain a circuit board for controlling lighting operation of a headlight such as a metal-halide lamp in order to save a space and to suppress emission of noises from a high voltage components mounted on the circuit board. An example of a headlight housing in which a circuit board is mounted on an inner surface of a back cover is disclosed in JP-A-2003-51212.  
         [0006]     In such a conventional structure of the headlight housing, there has been a possibility that tools for mounting the headlight housing on a vehicle or for performing maintenance hit the back cover and cause damages to the circuit board contained inside the back cover.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention has been made in view of the above-mentioned problem, and an object of the present invention is to provide an improved automobile headlight housing, wherein a circuit board contained therein is well protected from an external impact imposed on a back cover of the housing.  
         [0008]     Components of the automobile headlight including a bulb and a reflector are contained in a headlight housing. A rear opening of the headlight housing is closed with a back cover. A circuit board for controlling lighting operation including a substrate such as a ceramic substrate is mounted on an inner surface of the back cover. A member for alleviating an external impact imposed on the circuit board through the back cover is connected to or formed on an outer surface of the back cover.  
         [0009]     The impact-alleviating member is resiliently or plastically deformed when the external impact is applied thereto to thereby absorb or decrease the external impact imposed on the circuit board. Thus, the circuit board is prevented from being damaged by the external impact. The circuit board is well protected even when it includes a ceramic substrate that is not strong against the external impact.  
         [0010]     The impact-alleviating member may be a member having plural projections sticking out from the outer surface of the back cover. The projection may have a cross-section such as a rectangular, stepped rectangular, triangular or tapered cross section. The projection may include a thin portion at its foot, tip or middle portion to provide more resiliency or plasticity to the projection. Alternatively, one or more rubber sheets may be pasted on the outer surface of the back cover as the impact-alleviating member. The impact-alleviating member maybe formed to include an inner hollow space so that the impact-alleviating member easily deforms in response to the external impact. The impact-alleviating member may be made in an L-shape forming a hollow space between the outer surface of the back cover and the impact-alleviating member. One or more pairs of the L-shaped members may be formed on the outer surface of the back cover. Plural knurls functioning as the impact-alleviating member may be formed on the outer surface of the back cover.  
         [0011]     Other objects and features of the present invention will become more readily apparent from a better understanding of the preferred embodiment described below with reference to the following drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1A  is a cross-sectional view showing a headlight housing in which a circuit board is contained, as an embodiment of the present invention;  
         [0013]      FIG. 1B  is a cross-sectional view showing an impact-alleviating member used in the housing shown in  FIG. 1A ;  
         [0014]      FIG. 2A  is a cross-sectional view showing a headlight housing in which a circuit board is contained, as a modified form;  
         [0015]      FIG. 2B  is a cross-sectional view showing an impact-alleviating member used in the housing shown in  FIG. 2A ;  
         [0016]      FIG. 3A  is a cross-sectional view showing a headlight housing in which a circuit board is contained, as a modified form;  
         [0017]      FIG. 3B  is a cross-sectional view showing an impact-alleviating member used in the housing shown in  FIG. 3A ;  
         [0018]      FIG. 4A  is a cross-sectional view showing a headlight housing in which a circuit board is contained, as a modified form;  
         [0019]      FIG. 4B  is a cross-sectional view showing an impact-alleviating member used in the housing shown in  FIG. 4A ;  
         [0020]      FIG. 5A  is a cross-sectional view showing a headlight housing in which a circuit board is contained, as a modified form;  
         [0021]      FIG. 5B  is a cross-sectional view showing an impact-alleviating member used in the housing shown in  FIG. 5A ;  
         [0022]      FIG. 6  is a cross-sectional view showing a headlight housing in which a circuit board is contained, as a modified form;  
         [0023]      FIG. 7  is a cross-sectional view showing a headlight housing in which a circuit board is contained, as a modified form;  
         [0024]      FIG. 8A  is a cross-sectional view showing a headlight housing in which a circuit board is contained, as a modified form;  
         [0025]      FIG. 8B  is a cross-sectional view showing an impact-alleviating member used in the housing shown in  FIG. 8A ;  
         [0026]      FIG. 9A  is a cross-sectional view showing a headlight housing in which a circuit board is contained, as a modified form;  
         [0027]      FIG. 9B  is a cross-sectional view showing an impact-alleviating member used in the housing shown in  FIG. 9A ;  
         [0028]      FIG. 10A  is a cross-sectional view showing a headlight housing in which a circuit board is contained, as a modified form;  
         [0029]      FIG. 10B  is a cross-sectional view showing an impact-alleviating member formed on an outer surface of a back cover used in the housing shown in  FIG. 10A ; 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0030]     A preferred embodiment of the present invention will be described with reference to accompanying drawings.  FIGS. 1A, 2A ,  3 A,  4 A,  5 A,  6 ,  7 ,  8 A,  9 A and  10 A are all similar except that respectively different impact-alleviating members  50  are used. Therefore, the following description is common to all of these drawings.  
         [0031]     A headlight  100  includes a headlight housing  1  containing a bulb  2  such as a metal-halide lamp therein. The front side of the headlight housing  1  is covered with an integrally formed transparent lens  3 , and the rear side is closed with a back cover  4 . A reflector  5  for reflecting light from the bulb  2  toward the lens  3  is disposed behind the bulb  2 . A holder  6  for holding the bulb  2  is positioned behind the reflector  5 . A shade  7  for partially interrupting light from the bulb  2  is positioned in front of the bulb  2 .  
         [0032]     A circuit board  8  for controlling lighting operation is mounted on an inner surface  4   a  of the back cover  4 . The circuit board  8  is electrically connected to an outside power source through a connector  9  and to the bulb  2  through a high voltage wire  10  and a high voltage connector  11 . The circuit board  8  is composed of a ceramic substrate and components mounted on the ceramic substrate. Such components include a hybrid IC, a DC-DC converter, an inverter, a starting coil and a control circuit. The ceramic substrate is connected to the inner surface  4   a  of the back cover  4  with adhesive.  
         [0033]     An impact-alleviating member  50  is disposed on the outer surface  4 b of the back cover  4 . As the impact-alleviating member  50 , variously modified members may be used. The impact-alleviating member  50  is resiliently or plastically deformed when an external force is applied thereto thereby to alleviate the external force applied to the circuit board  8 . The circuit board  8  is prevented from being damaged by the external force inadvertently applied to the back cover  4  by tools or the like when the headlight  100  is mounted on a vehicle or when maintenance work is performed. The resiliency of the impact-alleviating member  50  absorbs the external impact, and the external impact is decreased by the plastic deformation.  
         [0034]     The impact-alleviating member  51  used in the headlight housing  1  shown in  FIG. 1A  is shown in an enlarged scale in  FIG. 1B . The impact-alleviating member  51  includes plural projections standing from the outer surface  4   b  at a right angle. Each projection has a rectangular cross-section as shown in  FIG. 1B . The projections may be integrally formed on a rubber sheet and pasted to the outer surface  4   b  with adhesive. The projections are resiliently deformable.  
         [0035]     The impact-alleviating member  52  used in the headlight housing  1  shown in  FIG. 2A  is shown in an enlarged scale in  FIG. 2B . The impact-alleviating member  52  includes plural projections standing from the outer surface  4   b  at a right angle. Each projection has a stepped rectangular cross-section as shown in  FIG. 2B . The foot portion of each projection is thick and the tip portion  52   a  is thin. The projections maybe integrally formed on a rubber sheet and pasted to the outer surface  4   b  with adhesive. The tip portion  52   a  resiliently deforms much easier than the foot portion.  
         [0036]     The impact-alleviating member  53  used in the headlight housing  1  shown in  FIG. 3A  is shown in an enlarged scale in  FIG. 3B . The impact-alleviating member  53  includes plural projections standing from the outer surface  4   b  at a right angle. Each projection has a triangular cross-section as shown in  FIG. 3B . The projections may be integrally formed on a rubber sheet and pasted to the outer surface  4   b  with adhesive. The projections are resiliently deformable.  
         [0037]     The impact-alleviating member  54  used in the headlight housing  1  shown in  FIG. 4A  is shown in an enlarged scale in  FIG. 4B . The impact-alleviating member  54  includes plural projections standing from the outer surface  4   b  at a right angle. Each projection has a rectangular cross-section having a thin portion  54   a  in the middle as shown in  FIG. 4B . The projections may be integrally formed on a rubber sheet and pasted to the outer surface  4   b  with adhesive. The projections are resiliently or plastically bent at the thin portion  54   a.    
         [0038]     The impact-alleviating member  55  used in the headlight housing  1  shown in  FIG. 5A  is shown in an enlarged scale in  FIG. 5B . The impact-alleviating member  55  includes plural projections standing from the outer surface  4   b  at a right angle. Each projection has a stepped rectangular cross-section having a thin base portion  55   a  as shown in  FIG. 5B . The projections may be integrally formed on a rubber sheet and pasted to the outer surface  4   b  with adhesive. The projections are resiliently or plastically deformable and easily bent at the thin base portion  55   a.    
         [0039]     The impact-alleviating member  56  used in the headlight housing  1  shown in  FIG. 6  is a single rubber sheet pasted on the outer surface  4   b  of the back cover  4 . The rubber sheet absorbs an external impact by its resilient deformation. The impact-alleviating member  57  used in the headlight housing  1  shown in  FIG. 7  is plural rubber sheets each pasted on the outer surface  4   b.  The plural rubber sheets absorb an internal impact by resilient deformation.  
         [0040]     The impact-alleviating member  58  used in the headlight housing  1  shown in  FIG. 8A  is shown in an enlarged scale in  FIG. 8B . The impact-alleviating member  58  is an L-shaped member composed of a base portion  58   a  standing from one end  4   c  of the back cover  4  and a parallel portion  58   b  extending in parallel to the outer surface  4   b  toward the other end  4   d  of the back cover  4 . A hollow space  71  is formed between the outer surface  4   b  and the parallel portion  58   b.  Two or more L-shaped members may be formed on the rear cover  4 . The L-shaped member is resiliently or plastically deformable.  
         [0041]     The impact-alleviating members  59 A and  59 B used in the headlight housing  1  shown in  FIG. 9A  is shown in an enlarged scale in  FIG. 9B . The impact-alleviating member  59 A is an L-shaped member composed of a base portion  59 Aa standing from one end  4   c  of the back cover  4  and a parallel portion  59 Ab extending in parallel to the outer surface  4   b  toward the other end  4   d  of the back cover  4 . The impact-alleviating member  59 B is an L-shaped member composed of a base portion  59 Ba standing from the other end  4   d  of the back cover  4  and a parallel portion  59 Bb extending in parallel to the outer surface  4   b  toward the one end  4   c  of the back cover  4 . The impact-alleviating members  59 A and  59 B constitute a pair facing each other as shown in  FIG. 9B , and the pair forms a hollow space  72  between the outer surface  4   b  of the back cover  4  and the parallel portions  59 Ab,  59 Bb. Tow or more pairs may be formed on the back cover  4 . The L-shaped members  59 A and  59 B are resiliently or plastically deformable.  
         [0042]     On the outer surface  4   b  of the back cover  4  used in the headlight housing  1  shown in  FIG. 10A , knurls that function as the impact-alleviating member  50  are formed. The knurls are shown in an enlarged scale in  FIG. 10B . The knurls are plastically deformable when an external impact is applied thereto.  
         [0043]     According to the present invention, the impact-alleviating member  50 , which may be variously modified as shown above, is connected to or formed on the outer surface  4   b  of the back cover  4 . The circuit board  8  mounted on the inner surface  4   a  of the back cover  4  is prevented from being damaged by an external impact force applied to the back cover  4 . In other words, the external impact is alleviated by the impact-alleviating member  50 . As the substrate of the circuit board  8 , various materials such as bakelite, glass-epoxy or ceramics, may be used. When the ceramics such as alumina which is not strong against the external impact are used as the substrate, the impact-alleviating member  50  according to the present invention is especially effective.  
         [0044]     While the present invention has been shown and described with reference to the foregoing preferred embodiment, it will be apparent to those skilled in the art that changes in form and detail may be made therein without departing from the scope of the invention as defined in the appended claims.