Patent Publication Number: US-7717746-B2

Title: Bulb socket structure for onboard interior lighting system

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a bulb socket structure for an onboard interior lighting system provided to a ceiling of a vehicle. 
   2. Description of the Related Art 
     FIG. 1  is an exploded, perspective view showing a conventional model of bulb socket structure disclosed in Japanese Patent Application Laid-Open No. Hei. 7-254466 (Patent Document 1).  FIG. 2  is a front view of a chief section of the conventional model of bulb socket structure. This conventional model of bulb socket structure is of a type to which a wedge base bulb  120  is attached. This model of bulb socket structure includes: a resin-made socket main body  100  (equivalent to a housing); and paired power supply terminals  110 ,  110  fixed to the inside of a bulb attachment hole  101  of the socket main body  100 . This bulb socket structure enables a base  122  of the wedge base bulb  120  to be attached to the paired power supply terminals  110 ,  110 . 
   Each power supply terminal  110  includes: a base plate  111  fitted into a fitting groove  102  of the socket main body  100 ; paired holding pieces  112 ,  112  folded upright from the base plate  111 ; and paired restricting protrusions  113 ,  113  folded upright from the base plate  111 . The proximal end sides of the respective paired holding pieces  112 ,  112  are fixed to the base plate  111 . The distal end sides of the paired holding pieces  112 ,  112  are free ends, respectively. A portion between the proximal end and the free end of one holding piece  112  and a portion between the proximal end and the free end of the other holding piece  112  are both bent inward in such a way as to come closer to each other. The restricting protrusions  113 ,  113  restrict excessive deformations of the holding pieces  112 ,  112 , respectively. 
   The wedge base bulb (hereinafter referred to as a “bulb”)  120  includes: a bulb part  121  having a filament housed therein; and the base  122  which is flat in shape, and which is formed integrally with the bulb part  121  at the lower portion of the bulb part  121 . Concave parts  123  are symmetrically formed in the base  122 . When the inward-bent portions of the paired holding pieces  112 ,  112  of each power supply terminal  110  engage with the concave parts  123 , electricity is conducted between the terminals of the base  122  and the power supply terminals  110 ,  110  through their contacts. In addition, a columnar part  124  is provided in the center portion of the base  122  in its width direction. 
   When the bulb  120  is attached to this bulb socket structure, the bulb  120  is inserted into the bulb attachment hole  101  in the socket main body  100  with the base  122  facing the bulb attachment hole  101 . Once the bulb  120  is inserted in the bulb attachment hole  101 , the extremity of the base  122  abuts onto the inner surfaces of the distal ends of the paired holding pieces  112 ,  112  of each power supply terminal  110 , respectively. When the bulb  120  is inserted further into the bulb attachment hole  101  from this position, the free end sides of the paired holding pieces  112 ,  112  deform in directions in which the free ends of the paired holding pieces  112 ,  112  are separated away from each other. This deformation allows the base  122  of the bulb  120  to be inserted into the interstice between the paired holding pieces  112 ,  112  beyond the inward-bent portions of the paired holding pieces  112 ,  112 . When the base  122  of the bulb  120  is inserted to a location sufficiently deep so that the concave parts  123 ,  123  of the base  122  reach the inward-bent portions of the holding pieces  112 ,  112 , the holding pieces  112 ,  112  return to their initial positions while deforming in directions in which the holding pieces  112 ,  112  thereof come closer to each other. Thus, the inward-bent portion of each holding piece  112  is fitted into and engaged with its corresponding concave part  123  of the base  122 . Thereby, the bulb  120  finishes being attached to the bulb socket structure, and the base  122  of the bulb  120  is held by the paired holding pieces  112 ,  112  of each power supply terminal  110  with their forces produced due to return from the deformation. 
   An onboard interior lighting system disclosed in another issue of Japanese Patent Gazette which carries Japanese Patent Application Laid-Open No. 2007-245795 (Patent Document 2) has been known as a conventional model of lighting system using a wedge base bulb as a light source. This onboard interior lighting system has a functional section which is provided on the exterior side of a ceiling board of a vehicle. A bulb socket structure to which a bulb is designed to be attached diagonally is provided to a resin-made housing constituting the main body of the functional section. 
   In the case of the bulb socket structures described in each patent document, it is likely that the base of the bulb may collide against the power supply terminals in the bulb attachment hole when the wedge base bulb is inserted into the bulb attachment hole, and that the power supply terminals may be accordingly deformed. In particular in the case of the bulb socket structure for the lighting system disclosed in Patent Document 2, since the bulb is designed to be attached to the bulb socket structure obliquely to the functional section main body, the power supply terminals tend to be deformed by the base if the wedge base bulb is inserted into the bulb attachment hole at a wrong angle. 
   In the case of each conventional model of bulb socket structure, the bulb is designed to be held by the holding pieces of each power supply terminal with their spring forces (forces produced due to return from deformation) only. For this reason, after the bulb is inserted into and detached from the holding pieces of each power supply terminal repeatedly, the spring forces of the holding pieces of each power supply terminal decrease, and the holding forces of the holding pieces thereof accordingly reduces. As a result, the bulb tends to be loose and shaky in the holding pieces thereof. Once the bulb becomes loose and shaky in the holding pieces thereof, the bulb contacts the power supply terminals  110  in a wrong condition, and the shake of the bulb causes abnormal noises. These are problems with the conventional model of bulb socket structure. 
   SUMMARY OF THE INVENTION 
   The present invention has been made with the foregoing conditions taken into consideration. For this reason, an object of the present invention is to provide a bulb socket structure for an onboard interior lighting system which allows a bulb to be attached to its power supply terminals smoothly with no power supply terminals being deformed inadvertently, as well as which is capable of preventing the bulb from being in a wrong contact with the power supply terminal, and from causing abnormal noises, due to its loose and shaky contact condition. 
   For the purpose of achieving the above-described object, a first aspect of the present invention is a bulb socket structure for an onboard interior lighting system, which includes: a resin-made housing constituting the onboard interior lighting system; a bulb attachment hole formed in the housing, the bulb attachment hole being that to which a wedge base bulb is attached; power supply terminals configured to contact, and conduct electricity to, terminals of a base arranged under a bulb part of the wedge base bulb when the base is inserted into the inside of the bulb attachment hole, the power supply terminals being provided in the inside of the bulb attachment hole; and a spacer configured to be attached to the bulb attachment hole, the spacer including a supporting cylindrical part capable of supporting the bulb part of the wedge base bulb from its outer periphery, and the spacer being capable of causing the terminals of the base of the wedge base bulb to contact the respective power supply terminals while protecting the power supply terminals. 
   The first aspect of the present invention is capable of avoiding deformation of the power supply terminals which would otherwise occur due to inadvertent collision of the base of the wedge base bulb (hereinafter referred to as a “bulb”) against the power supply terminals when the bulb is inserted into the bulb attachment hole. That is because the first aspect of the present invention is capable of causing the spacer to protect the power supply terminals provided in the inside of the bulb attachment hole. In addition, the first aspect of the present invention is capable of checking the bulb from being loose and shaky in all the directions, of preventing the power supply terminals from contacting the terminals of the bulb in a wrong condition, and accordingly of enhancing the reliability, even if an external force is applied to the bulb. That is because the first aspect of the present invention causes the supporting cylindrical part of the spacer to support the bulb part of the bulb from its outer periphery while the bulb is being attached to the bulb attachment hole. Furthermore, the first aspect of the present invention makes the housing not to require any extra element which has a function for protecting the power supply terminals from a forced deformation, thereby avoiding the housing having a complicated configuration. That is because the first aspect of the present invention causes the spacer produced independently of the housing to be attached to the housing, and accordingly because the first aspect thereof is capable of preventing the forced deformation of the power supply terminals which would otherwise occur. 
   A second aspect dependent on the first aspect of the present invention is the bulb socket structure for the onboard interior lighting system according to the first aspect, in which the spacer is detachably attached to the inside of the bulb attachment hole, and in which fixing means configured to lock the spacer when the spacer is attached to the inside of the bulb attachment hole is provided to both the spacer and the housing. 
   The second aspect of the present invention makes it possible to replace one spacer with another freely. That is because the second aspect of the present invention causes the spacer to be detachably attached to the housing. 
   A third aspect dependent on the first aspect of the present invention is the bulb socket structure for the onboard interior lighting system according to the first aspect, in which a guiding slope is provided in the inside of the supporting cylindrical part, the guiding slope being configured to guide the base of the wedge base bulb to a right position in the inside of the bulb attachment hole along with the insertion of the base of the wedge base bulb into the inside of the supporting cylindrical part. 
   The third aspect of the present invention is capable of enhancing the bulb attachment performance. That is because the third aspect of the present invention causes the guiding slope configured to guide the base of the bulb into the right position to be provided in the inside of the supporting cylindrical part of the spacer. 
   A fourth aspect dependent on the first aspect of the present invention is the bulb socket structure for the onboard interior lighting system according to the first aspect, in which: as the power supply terminal, two power supply terminals each including paired holding pieces configured to hold the base of the bulb between the paired holding pieces are provided; an insertion groove into which to insert the base of the bulb is formed in the spacer; paired guiding slopes are provided in such a way as to be opposed to each other with the insertion groove interposed in between, and in order to guide the base to the insertion groove; and bent parts convex inward of the respective paired holding pieces of each power supply terminal protrude into the insertion groove. 
   The fourth aspect of the present invention is capable of holding the bulb in a way that the bulb is not loose or shaky, and thus of securely causing the power supply terminals to contact, and conduct electricity to, the respective terminals of the base. That is because the fourth aspect of the present invention causes the paired holding pieces of each power supply terminal to hold the base of the bulb between the paired holding pieces. In addition, the fourth aspect of the present invention is capable of causing the guiding slopes to guide the base of the bulb to the insertion groove without force, and of causing the base to be held between the bent parts of the paired holding pieces of each power supply terminal which bent parts protrude into the insertion groove once the base is inserted into the insertion groove. That is because the fourth aspect of the present invention causes the insertion groove to be formed in an interstice between the paired guiding slopes. Particularly in a case where the base is inserted into the insertion groove in a way that the base is directed at an angle, or even in a case where the insertion groove and the base are not positioned to each other correctly, the fourth aspect thereof is capable of causing the base to be guided to the insertion groove while correcting the orientation of the base through the guiding function of the guiding slopes. For this reason, the fourth aspect thereof is capable of smoothly attaching the base of the bulb to the interstice between the holding pieces of each power supply terminal, and accordingly capable of securely conducting electricity between the terminals of the base and the respective power supply terminals, even if the bulb is inserted therein by touch. 
   A fifth aspect dependent on the fourth aspect of the present invention is the bulb socket structure for the onboard interior lighting system according to the fourth aspect, in which a columnar hole part into which to insert a columnar part located in a center portion of the base of the bulb in the width direction of the base is provided in a center portion of the insertion groove in its width direction, and in which arcuate walls continuous with the lower ends of the guiding slopes are provided in the periphery of the columnar hole part, respectively. 
   The fifth aspect of the present invention is capable of causing the base of the bulb to be inserted in the interstice between the holding pieces of each power supply terminal with the base thereof being securely positioned thereto in the width direction. That is because the fifth aspect of the present invention causes the columnar hole part into which to insert the column-shape part located in the center portion of the base in its width direction to be provided in the center portion of the insertion groove in its width direction, and concurrently causes the arcuate walls continuous with the lower ends of the guiding slopes to be provided in the periphery of the columnar hole part, respectively. 
   A 6th aspect dependent on the fourth aspect of the present invention is the bulb socket structure for the onboard interior lighting system according to the fourth aspect, in which the direction in which the axis of the bulb extends to the housing tilts to a base surface of the housing, and in which the paired guiding slopes are arranged on the upper and lower sides in a direction in which the axis of the bulb tilts, respectively. 
   The 6th aspect of the present invention is capable of causing the upper and lower guiding slopes to guide the base of the bulb to the insertion groove at a right angle even in a case where the bulb has to be attached to the housing in a way that the bulb is directed diagonally. Although it is difficult to hold the bulb at a right angle particularly in the case where the bulb is attached to the housing in a way that the bulb has to be directed diagonally, the 6th aspect of the present invention is capable of automatically placing the base of the bulb in a right position just by inserting the base thereof into the spacer by guess even if the base thereof is inserted into the spacer with no consideration being given to the angle of the base. Accordingly, the 6th aspect of the present invention is capable of enhancing the bulb attachment performance. 
   A 7th aspect dependent on the 6th aspect of the present invention is the bulb socket structure for the onboard interior lighting system according to the 6th aspect, in which an angle at which each guiding slope inclines corresponds to an angle at which an inclined part extending from the lower end of the bulb part to the base of the bulb inclines. 
   The 7th aspect of the present invention is capable of supporting the bulb more stably. That is because the 7th aspect of the present invention is capable of holding the inclined part extending from the lower end of the bulb part to the base of the bulb by causing the inclined part to abut on the guiding slopes. 
   An 8th aspect dependent on the first aspect of the present invention is the bulb socket structure for the onboard interior lighting system according to the first aspect, in which the spacer is formed of a resin material whose heat radiating performance is better than a material of the housing. 
   The 8th aspect of the present invention is capable of enhancing the heat resistance of the periphery of the bulb, and accordingly allows a brighter bulb with a larger heating value to be used for the bulb socket structure. 

   
     BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS 
     The above and further objects and novel features of the present invention will more fully appear from the following detailed description when the same is read in conjunction with the accompanying drawings, in which: 
       FIG. 1  is an exploded, perspective view showing an example of a conventional model of bulb socket structure; 
       FIG. 2  is a front view of a chief section of the conventional mode of bulb socket structure; 
       FIG. 3  is an exploded, perspective view showing a constitution of a functional section of an onboard interior lighting system including a bulb socket structure according to an embodiment of the present invention; 
       FIG. 4  is a perspective view showing an inner structure of a bulb attachment hole of the bulb socket structure in a magnified scale; 
       FIG. 5  is a perspective view showing how a spacer is attached to the bulb attachment hole; 
       FIG. 6  is a cross-sectional view used for explaining an operation through which a wedge base bulb is attached to the bulb attachment hole to which the spacer is attached as shown in  FIG. 5 ; 
       FIG. 7  is an external, perspective view showing a constitution of the functional section to which the wedge base bulb is attached; 
       FIG. 8  is an auxiliary cross-sectional view of the functional section taken along the VIII-VIII line of  FIG. 7 ; and 
       FIG. 9  is an auxiliary cross-sectional view of the functional section taken along the IX-IX line of  FIG. 7 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Descriptions will be provided hereinbelow for the embodiment of the present invention by referring to  FIGS. 3 to 9 . 
   First of all, an onboard interior lighting system, to which a bulb socket structure according to the embodiment is applied, includes a functional section  1 . The functional section  1  shown in  FIG. 3  is provided to an exterior side of a ceiling board (a rear side of the ceiling) of a vehicle. This functional section  1  includes: a resin-made housing  10  serving as a functional section main body; a wedge base bulb  21  (hereinafter simply referred to as a “bulb”) and a switch  22 ; an electric wire protecting cover  24 . The housing  10  includes: an electric wire connector  14  to which the wires are connected; a bulb attachment (a bulb attachment hole  12 ) to which the bulb  21  as a light source is attached; and a switch attachment  13  to which the switch  22  is attached. The switch  22  is that with which to select one among modes of conducting electricity to the bulb  21 . The bulb  21  is attached to the bulb attachment (the bulb attachment hole  12 ) of the housing  10 , whereas the switch  22  is attached to the switch attachment  13  of the housing  10 . The electric wire protecting cover  24  is configured to be attached to the electric wire connector  14  of the housing  10  after electric wires (whose illustrations are omitted from the drawings) are connected to the electric wire connector  14 , and thus to protect the electric wires connected to the electric wire connector  14 . 
   The bulb attachment hole  12  is provided in one end side of the housing  10  constituting the functional section. The bulb socket structure according to the present embodiment is applied to the bulb attachment hole  12 . In this case, the bulb attachment hole  12  tilts to a base surface (a surface on which the designed section located on the interior side of the ceiling board and the functional section located on the exterior side of the ceiling board are attached to each other)  10   a  of the housing  10 . The bulb  21  is designed to be attached to the bulb attachment (bulb attachment hole  12 ) in a way that the axis of the bulb  21  tilts to the base surface  10   a  of the housing  10 . 
   As shown in not only  FIG. 3  but also  FIG. 6 , the bulb  21  has a flat base  21   b  under a cylinder-shaped bulb part  21   a  with an inclined part  21   c  interposed between the bulb part  21   a  and the base  21   b . Terminals are provided to the base  21   b . In addition, a columnar part (whose illustration is omitted from the drawings) is provided in a center portion of the base  21   b  in its width direction. 
   As shown in  FIG. 4 , paired power supply terminals  15 ,  15  are provided in the inside of the bulb attachment hole  12 . The paired power supply terminals  15 ,  15  are configured to contact, and conduct electricity to, terminals of the base  21   b  when the base  21   b  of the bulb  21  is inserted into the inside of the bulb attachment hole  12 . The paired power supply terminals  15 ,  15  are formed in bus bars which are included in different systems, respectively. Each power supply terminal  15  is provided with paired holding pieces  15   a ,  15   a  configured to hold the base  21   b  of the bulb  21  between the paired holding pieces  15   a ,  15   a . The paired holding pieces  15   a ,  15   a  of each power supply terminal  15  are capable of deforming so as to expand an interstice between the paired holding pieces  15   a ,  15   a.    
   Furthermore, as shown in  FIG. 5 , a resin-made spacer  30  is detachably attached to the inside of the bulb attachment hole  12 . The spacer  30  includes a supporting cylindrical part  31  capable of supporting the bulb part  21   a  of the bulb  21  from its outer periphery. This spacer  30  is formed in a shape which allows the spacer  30  to bring the power supply terminals  15 ,  15  into contact with the respective terminals of the base  21   b  of the bulb  21  while protecting the power supply terminals  15 ,  15 . This spacer  30  is fixed to the housing  10  by engaging four engaging claws  33 ,  33 ,  33 ,  33  with the respective four engaged parts (whose illustrations are omitted from the drawings). The four engaging claws are provided in the respective four locations in total, and the locations are the two sides of each of the two external walls  32  of the spacer  30 . The four engaged parts are provided in the inside of the bulb attachment hole  12 . 
   As shown in  FIG. 6 , guiding slopes  35 ,  35  configured to guide the base  21   b  of the bulb  21  to a right position in the inside of the bulb attachment hole  12  while the base  21   b  is being inserted into the inside of the bulb attachment hole  12  are provided in the inside of the supporting cylindrical part  31  of this spacer  30 . As shown in  FIG. 5 , the paired guiding slopes  35 ,  35  are provided there in such a way as to be opposed to each other with an insertion groove  36  interposed in between, and in order to guide the base  21   b  to the insertion groove  36 . As shown in  FIG. 6 , the paired guiding slopes  35 ,  35  are arranged on the upper and lower sides in a direction in which the axis of the bulb  21  tilts, respectively. 
   Furthermore, as shown in  FIG. 8 , the angle at which each of the paired guiding slopes  35 ,  35  inclines corresponds to the angle at which the inclined part  21   c  extending from the lower end of the bulb part  21   a  to the base  21   b  of the bulb  21  inclines. 
   Moreover, as shown in  FIG. 5 , a columnar hole part  36   a  into which to insert a columnar part located in a center portion of the base  21   b  of the bulb  21  in the width direction of the base  21   b  is provided in a center portion of the insertion groove  36  in its width direction. Arcuate walls  37 ,  37  continuous with the lower ends of the guiding slopes  35 ,  35  are provided in the periphery of the columnar hole part  36   a , respectively. In addition, bent parts are formed at the respective paired holding pieces  15   a ,  15   a  of each power supply terminal  15  so that the convex portions of the bent parts protrude into the insertion groove  36 . 
   Next, descriptions will be provided for how the bulb socket structure for the onboard interior lighting system operates. 
   First of all, the spacer  30  is attached to the inside of the bulb attachment hole  12  of the housing  10 , and is thus locked to the housing  10 , before the bulb  21  is attached to the bulb attachment hole  12 . Subsequently, the bulb  21  is inserted into the inside of the spacer  30  with the base  21  entering the inside of the spacer  30  first. At this time, the power supply terminals  15 ,  15  provided in the inside of the bulb attachment hole  12  are protected by the spacer  30 . For this reason, the bulb socket structure according to the present embodiment is capable of avoiding deformation of the power supply terminals  15 ,  15  which would otherwise occur due to inadvertent collision of the base  21   b  of the bulb  21  against the power supply terminals  15 ,  15 . 
   In addition, the paired guiding slopes  35 ,  35  are provided in the inside of the supporting cylindrical part  31  of the spacer  30 , and the insertion groove  36  into which to insert the base  21   b  is formed in the interstice between the paired guide slopes  35 ,  35 . For this reason, the bulb socket structure according to the present embodiment is capable of causing the guiding slopes  35 ,  35  to guide the base  21   b  of the bulb  21  to the insertion groove  36  without force, and of causing the base  21   b  to be held between the bent parts of the paired holding pieces  15   a ,  15   a  of each power supply terminal  15  which bent parts protrude into the insertion groove  36  once the base  21   b  is inserted into the insertion groove  36 . Accordingly, the bulb socket structure according to the present embodiment is capable of causing the power supply terminals  15 ,  15  to contact, and conduct electricity to, the respective terminals of the base  21   b.    
   Particularly in a case where, as shown in  FIG. 6 , the base  21   b  is inserted into the insertion groove  36  in a way that the base  21   b  is directed at an angle, or even in a case where the insertion groove  36  and the base  21   b  are not positioned to each other correctly, the bulb socket structure according to the embodiment is capable of causing the base  21   b  to be smoothly guided to the insertion groove  36  while correcting the orientation and position of the base  21   b  through the guiding function of the guiding slopes  35 ,  35 . For this reason, the bulb socket structure according to the present embodiment is capable of smoothly attaching the base  21   b  of the base  21  to the interstice between the holding pieces  15   a ,  15   a  of each power supply terminal  15  without the power supply terminals  15 ,  15  being deformed by force, even if the bulb is inserted therein by touch. 
   Additionally, as shown in  FIG. 5 , the columnar hole part  36   a  into which to insert the column-shape part located in the center portion of the base  21   b  of the bulb  21  in the width direction of the base  21   b  is provided in the center portion of the insertion groove  36  in its width direction, and concurrently the arcuate walls  37 ,  37  continuous with the lower ends of the guiding slopes  35 ,  35  are provided in the periphery of the columnar hole part  36   a , respectively. For this reason, the bulb socket structure according to the present embodiment is capable of causing the base  21   b  of the bulb  21  to be inserted in the interstice between the holding pieces  15   a ,  15   a  of each power supply terminal  15  with the base  21   b  thereof being securely positioned thereto in the width direction. 
   Although it is actually very difficult to hold the bulb  21  at a right angle particularly in a case where the bulb  21  is attached to the housing  10  in a way that the bulb  21  has to be directed diagonally, the bulb socket structure according to the present embodiment is capable of causing the upper and lower guiding slopes  35 ,  35  to guide the base  21   b  of the bulb  21  to the insertion groove  36  at a right angle so as to place the base  21   b  of the bulb  21  in a right position just by inserting the base  21   b  of the bulb  21  into the spacer  30  by guess even if the bulb  21   b  thereof is inserted into the spacer  30  with no consideration being given to the angle of the bulb  21 . Consequently, the bulb socket structure according to the present embodiment is capable of enhancing the performance of attaching the bulb  21  to the housing  10 . 
   Once the base  21   b  is inserted in the insertion groove  36  as described above, the base  21   b  is capable of being held between the paired holding pieces  15   a ,  15   a  of each power supply terminal  15 . For this reason, the bulb socket structure according to the present embodiment is capable of holding the bulb  21  in a way that the bulb  21  is not loose or shaky, and thus of securely causing the power supply terminals  15 ,  15  to contact, and conduct electricity to, the respective terminals of the base  21   b.    
   Moreover, as shown in  FIGS. 7 to 9 , the supporting cylindrical part  31  of the spacer  30  supports the bulb part  21   a  of the bulb  20  from its outer periphery while the bulb  21  is being attached to the bulb attachment hole  12 . For this reason, the bulb socket structure according to the present embodiment is capable of checking the bulb  21  from being loose and shaky in all the directions, of preventing the power supply terminals  15 ,  15  from contacting the terminals of the bulb  21  in a wrong condition, and accordingly of enhancing the reliability, even if an external force is applied to the bulb  21 . 
   In addition, the inclined part  21   c  extending from the lower end of the bulb part  21   a  to the base  21   b  of the bulb  21  abuts on the guiding slopes  35 ,  35 . For this reason, the bulb socket structure according to the present embodiment is capable of supporting the bulb  21  stably. 
   Additionally, as in this embodiment, the spacer  30  produced independently of the housing  10  is attached to the housing  10 . For this reason, the bulb socket structure according to the present embodiment can prevent forced deformation of the power supply terminals  15 ,  15  which would otherwise occur. Accordingly, the bulb socket structure according to present embodiment makes it unnecessary that an element having a function for protecting the power supply terminals  15 ,  15  from the forced deformation should be additionally included in the housing  10 , and is accordingly capable of avoiding the housing  10  having a complicated configuration. Furthermore, the spacer  30  is detachably attached to the housing  10 . For this reason, the bulb socket structure according to the present embodiment makes it possible to replace one spacer  30  with another freely. 
   Note that, in a case where the spacer  30  is formed of a resin material whose heat radiating performance is better than a material of the housing  10 , it is possible to enhance the heat resistance of the periphery of the bulb  21 . Accordingly, the use of such a resin material enables a brighter bulb with a larger heating value to be used for the bulb socket structure. 
   The present invention is not limited to the above-description and the above-described embodiments, and may be embodied in various different forms by making appropriate modifications thereto. 
   It should be noted that the entire content of Japanese Patent Application No. 2008-013926 (filed on Jan. 24, 2008) is incorporated herein by reference.