Abstract:
A horn switch device includes a retractable body, an unmoving body facing the retractable body, a biasing member between the retractable body and the unmoving body, a pair of contact members attached to, and moving with, the retractable body, and a contacting body, formed on the unmoving body, for contacting one of the contact members when the retractable body retracts. The contacting body stops the retraction of the contacted contact member, thereby bringing the contact members into contact with each other so as to sound the horn. The horn switch device facilitates positioning of the contact members relative to each other, thereby simplifying the assembly of a steering wheel and an airbag system.

Description:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT 
   The present invention relates to a horn switch, and in particular, it relates to a horn switch device provided in an airbag system and constructed such that, when depressed, a module cover is retracted to turn on a horn switch. The invention also relates to an airbag system and a steering wheel that include the horn switch device. 
   Driver-seat airbag systems mounted to car steering wheels are known in which when the module covers of the airbag systems are depressed, horn switches are turned on to sound horns. For example, Japanese Unexamined Patent Application Publication No. 10-100832 and Japanese Unexamined Patent Application Publication No. 2001-114057 describe airbag systems in which, when depressed, a module cover is retracted to turn on a horn switch. 
   In the conventional horn switch devices, however, one of the contact members is mounted to the module cover, and the other is mounted to a retainer. The separate contact members increase the difficulty associated with assembly work to position the contact members with high accuracy. 
   Accordingly, it is an object of the present invention to provide a horn switch device in which a pair of contact members is provided only on one of a retractable body such as a module cover, and an unmoving body such as a retainer or a steering wheel. Thus, the contact members can be easily positioned. 
   It is also an object of the present invention to provide an airbag system and a steering wheel that include the horn switch device. 
   Further objects and advantages of the invention will be apparent from the following description of the invention and the associated drawings. 
   SUMMARY OF THE INVENTION 
   A horn switch device according to the present invention includes a retractable body that is retracted by depression by an occupant; an unmoving body that faces the retractable body; a biasing member interposed between the retractable body and the unmoving body, for biasing the retractable body in the restoring direction; and a pair of contact members which comes into or out of contact with each other by the movement of the retractable body. Both of the pair of contact members move together with the retractable body. The unmoving body has a contacting body that comes into contact with one of the contact members when the retractable body retracts, to stop the retraction of the contact member, thereby bringing the contact members into contact with each other. 
   According to a first embodiment of the horn switch device, the retractable body is a module cover of an airbag system. 
   In the first embodiment of the invention, the unmoving body is a member extending from a retainer of the airbag system. 
   According to a second embodiment of the horn switch device, the retractable body is an airbag system. 
   In the second embodiment of the invention, the unmoving body is a steering wheel or a member extending from the steering wheel. 
   In another embodiment of the invention, an airbag system includes a horn switch device according to one of the first and second embodiments of the invention. 
   In another embodiment of the invention, a steering wheel includes a horn switch device according to one of the first and second embodiments of the invention. 
   In still another embodiment of the invention, a steering is equipped with an airbag system that includes a horn switch device according to one of the first and second embodiments of the invention. 
   In the horn switch device according to the invention, the contact members are apart from each other when the retractable body, such as a module cover or an airbag system, is in a restored position (undepressed state). When the retractable body is depressed, one of the contact members comes into contact with the contacting body to bring the contact members into contact with each other, thereby sounding the horn. 
   In the horn switch device, the contact members are provided only to the retractable body. Accordingly, the contact members can easily be positioned, thereby improving the workability in assembling the airbag system, the steering wheel, etc. 
   In the invention, the retractable body may be either a module cover or an airbag system. When the retractable body is a module cover, the unmoving body is preferably a member extending from a retainer. When the retractable body is an airbag system, the unmoving member is preferably a steering wheel or a member extending from the steering wheel. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a cross-sectional view of a steering wheel equipped with an airbag system including a horn switch device according to a first embodiment of the present invention. 
       FIGS. 2(   a ) and  2 ( b ) are cross-sectional views of the horn switch device depicted in  FIG. 1 . 
       FIG. 3  is a cross-sectional view of a steering wheel equipped with an airbag system including a horn switch device according to a second embodiment of the present invention. 
       FIGS. 4(   a ) and  4 ( b ) are cross-sectional views of the horn switch device depicted in  FIG. 3 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Embodiments of the present invention will be specifically described hereinafter with reference to the accompanying drawings. 
     FIG. 1  is a cross-sectional view of a steering wheel equipped with an airbag system including a horn switch device according to a first embodiment of the present invention. 
     FIGS. 2(   a ) and  2 ( b ) are enlarged views of the horn switch device depicted in  FIG. 1 .  FIG. 2(   a ) shows “an undepressed” state in which a module cover  40  is not depressed, and  FIG. 2(   b ) shows “a module-cover depressed state” in which the module cover  40  is depressed to sound a horn. 
   The airbag system  1  is a driver-seat airbag system disposed in the center (a base  101 ) of a steering wheel  100 . The airbag system  1  includes a metal retainer  10 , an airbag  20  mounted to the retainer  10  with an airbag-fixing ring  24 , an inflator  30  for inflating the airbag  20 , a synthetic-resin module cover  40  that covers the folded airbag  20 , and a horn switch device  60 . 
   According to the first embodiment of the invention, the module cover  40  is a retractable body. The module cover  40  has a groove-like tear line  40   a . When the airbag  20  is inflated by the inflator  30 , the module cover  40  is cleaved along the tear line  40   a.    
   The retainer  10  has a substantially rectangular main plate  11 . The main plate  11  has an opening  12  for the inflator  30  to pass through. Around the opening  12  are provided through holes for stud bolts  25  extending from the airbag-fixing ring  24 . 
   An anchor piece  14  extends downward (i.e., in  FIG. 1 , in the direction opposite to the occupant of the vehicle) from the outer rim of the main plate  11  of the retainer  10 . The anchor piece  14  is used to fix the airbag system  1  to the steering wheel  100 . The anchor piece  14  has openings  14   a  for bolts or rivets to pass through. The steering wheel  100  has an airbag-system mounting piece  102  rising from the base  101  thereof. The mounting piece  102  also has an opening  102   a  for a bolt or a rivet to pass through. 
   In mounting the airbag system  1  to the steering wheel  100 , the anchor piece  14  is placed on the mounting piece  102 , and they are joined with a bolt or a rivet  103  through the openings  14   a  and  102   a . The openings  14   a  and  102   a  may be screw sections for bolts. 
   An enclosure  15  extends upward (i.e., in  FIG. 1 , toward the occupant) from the outer rim of the main plate  11  of the retainer  10 . An extension  16  extends laterally (to the side of the airbag system  1 ) from the distal end of the enclosure  15  in the standing direction. In this embodiment, the extension  16  is an unmoving body. 
   To the extension  16  is fixed a nut  17 , to which the lower end of a guide shaft  50  is threaded. 
   The airbag  20  has a structure in which the periphery of an inflator insertion hole  22  thereof is placed on the periphery of the inflator opening  12  of the retainer main plate  11 , on which the airbag-fixing ring  24  is placed. The stud bolts  25  are passed through the bolt insertion holes provided around the inflator insertion hole  22  of the airbag  20 . Each stud bolt  25  is then passed through a bolt insertion hole of the retainer  10 . The stud bolt  25  is then passed through a bolt insertion hole of a flange  31  of the inflator  30 , on which a nut  26  is tightened. The airbag  20  and the inflator  30  are thus fixed to the retainer  10 . 
   The module cover  40  has a main surface  41  that faces the occupant, and a leg  42  extending from the back of the main surface  41 . The leg  42  is molded integrally with the main surface  41  by injection molding of synthetic resin, and has a substantially rectangular frame shape similar to the enclosure  15  of the retainer  10 . The periphery  41   a  of the main surface  41  overhangs outward from the leg  42 . 
   The leg  42  provides a mount for an overhang  45 . The overhang  45  extends outward in the direction perpendicular to the direction in which the module cover  40  retracts. The overhang  45  has an opening  45   a  for the guide shaft  50  to pass through. 
   As shown in  FIGS. 2(   a ) and  2 ( b ), the lower end of the guide shaft  50  is threaded into the nut  17  of the extension  16  to be fixed to the extension  16 , and extends from the extension  16  toward the occupant. The guide shaft  50  projects upward relative to the overhang  45  through the opening  45   a  and has a flange  51  at the upper end as a stopper. Between the flange  51  and the overhang  45  is interposed a washer  52  made of an electrical insulation material such as rubber. 
   An electrically insulating pedestal  53  extends downward from the lower end of the overhang  45  in parallel with the guide shaft  50 . A projecting first contact member  61  is provided at the lower end of the pedestal  53 . 
   A ring  63  is disposed under the lower surface of the overhang  45  via a flat washer  54 . The washer  54  and the ring  63  are disposed coaxially, through which the guide shaft  50  passes. A coil spring  90  is interposed between the ring  63  and the extension  16  while having a reserve of energy. The biasing force of the coil spring  90  pushes the washer  54  and the ring  63  against the overhang  45 . 
   A second contact member  62  extends from the ring  63 . The second contact member  62  extends toward the extension  16  in a downward slanting direction with increasing distance from the ring  63 . The second contact member  62  curves to extend out toward the guide shaft  50  relative to a line that connects the distal end and the base end. 
   A contacting body  55  rises from the upper surface of the extension  16  in parallel with the guide shaft  50 . The contacting body  55  is located between the pedestal  53  and the guide shaft  50 . The contacting body  55  has a window  56  in the middle. The second contact member  62  passes through the window  56  to extend to the position below the first contact member  61 . 
   As shown in  FIG. 2(   a ), before the module cover  40  is depressed, the second contact member  62  is located at a specified distance apart from the lower rim of the window  56 . 
   The horn-sounding action of the steering wheel  100  equipped with the airbag system  1  including the horn switch device  60  will now be described. 
   As shown in  FIG. 2(   a ), before the module cover  40  is depressed, the second contact member  62  is apart from the first contact member  61 . 
   When the module cover  40  is depressed, the overhang  45  is pushed down, so that the first and second contact members  61  and  62  descend together. With the descent, the coil spring  90  is compressed. 
   The extension  16  extends from the retainer  10  fixed to the steering wheel  100 , so that the extension  16  is not displaced even if the module cover  40  is depressed. Also the guide shaft  50  fixed to the extension  16  is not displaced. 
   As the first and second contact members  61  and  62  are pushed down, the second contact member  62  is brought into contact with the lower rim of the window  56 , so that further descent of the second contact member  62  is stopped. Since the first contact member  61  continues descending thereafter, the contact members  61  and  62  come into contact with each other. Thus, the horn switch device  60  is turned on to sound the horn. 
   On release from the module cover  40 , the first and second contact members  61  and  62  and the module cover  40  are pushed up by the repulsive force of the coil spring  90  into the state shown in  FIG. 2(   a ). The contact members  61  and  62  are thus pushed open to stop sounding the horn. 
   In the horn switch device  60 , as described above, both of the first and second contact members  61  and  62  are mounted to or supported by the module cover  40 , so that they can be positioned easily and accurately. This reduces the difficulty in assembling the horn switch device  60  or the airbag system  1 . 
   While the above-described first embodiment has a structure in which only the module cover is retracted by depression, the invention can also be applied to an airbag system in which the module cover and the retainer move vertically together.  FIG. 3  is a cross-sectional view of a steering wheel  100 A equipped with an airbag system  1 A with such a structure according to a second embodiment of the invention.  FIGS. 4(   a ) and  4 ( b ) are enlarged views of the horn switch device depicted in  FIG. 3 .  FIG. 4(   a ) shows “an undepressed” state in which a module cover is not depressed, and  FIG. 4(   b ) shows “a module-cover depressed state” in which the module cover is depressed to sound a horn. 
   The airbag system  1 A also includes a retainer  10 A, an airbag  20  mounted to the retainer  10 A with a ring  24 , an inflator  30  for inflating the airbag  20 , a module cover  40 A that covers the folded airbag  20 , and a horn switch device  60 . According to this second embodiment of the invention, the entire airbag system  1 A is a retractable body. 
   The retainer  10 A of this embodiment also has a substantially rectangular main plate  11 . The airbag  20  and the inflator  30  are mounted to the main plate  11 , whose mounting structure is the same as that of the airbag system  1  depicted in  FIG. 1 . 
   An enclosure  15 A extends upward (i.e., in  FIG. 3 , toward the occupant) from the outer rim of the main plate  11  of the retainer  10 A. An extension  16 A extends laterally (i.e., to the side of the airbag system  1 A or in the direction perpendicular to the direction in which the airbag system  1 A retracts (vertically in FIG.  3 )), from the distal end of the enclosure  15 A in the standing direction. 
   The module cover  40 A has a main surface  41  that faces the occupant and a leg  42 A extending downward (i.e., in  FIG. 3 , in the direction opposite to the occupant) along the inner wall of the enclosure  15 A from the back of the main surface  41 . The leg  42 A is fixed to the enclosure  15 A with a fixing member (not shown) such as a rivet. 
   In this second embodiment, airbag-system supporting pieces  104  extend from the steering wheel  100 A along the outer wall of the enclosure  15 A. The supporting pieces  104  are provided in a number equal to the number of extensions  16 A, and are disposed such that the respective ends face the extensions  16 A from below. At the end of each supporting piece  104  is provided a facing part  105  that extends to the side of the airbag system  1 A (in parallel with the direction in which the extension  16 A extends) and faces the lower surface of the extension  16 A. In this embodiment, the facing part  105  is an unmoving body. To the facing part  105 , a nut  106  for fixing a guide shaft is fixed. 
   In this embodiment, the extension  16 A has an opening  45   a  (see  FIGS. 4(   a ) and  4 ( b )), through which the guide shaft  50  passes. The lower end of the guide shaft  50  is threaded into the nut  106  at the facing part  105  to be fixed to the facing part  105 , and extends upward from the facing part  105 . Also in this embodiment, a flange  51  is provided as a stopper at the upper end of the guide shaft  50 . Between the flange  51  and the extension  16 A is interposed an electrically insulating washer  52  made of rubber or the like. 
   In this second embodiment, a horn switch device  60  is disposed between the extension  16 A and the facing part  105 . The horn switch device  60  is substantially the same as that shown in  FIGS. 2(   a ) and  2 ( b ). In this embodiment, the overhang  45  in  FIGS. 2(   a ) and  2 ( b ) is replaced with the extension  16 A, and the extension  16  is replaced with the facing part  105 . 
   Specifically, in this embodiment, the pedestal  53  having the first contact member  61  projects from the lower surface of the extension  16 A, as shown in  FIGS. 4(   a ) and  4 ( b ). The ring  63  is disposed below the lower surface of the extension  16 A via the flat washer  54 , through the openings of which the guide shaft  50  passes. A coil spring  90  is interposed between the ring  63  and the facing part  105  while having a reserve of energy. The washer  54  and the ring  63  are pushed against the extension  16 A and held by the biasing force of the coil spring  90 . The contacting body  55  of this embodiment extends from the upper surface of the facing part  105 . 
   The other structures of this second embodiment are the same as those of the first embodiment depicted in  FIGS. 1 and 2(   a ) and  2 ( b ). The same reference numerals of  FIGS. 3 and 4(   a ) and  4 ( b ) as those of  FIGS. 1 and 2(   a ) and  2 ( b ) indicate the same components. 
   The horn-sounding action of the steering wheel  100 A equipped with the airbag system  1 A having this horn switch device  60  will be described. 
   As shown in  FIG. 4(   a ), before the module cover  40 A is depressed, the second contact member  62  is apart from the first contact member  61 . 
   When the module cover  40 A is depressed, the entire airbag system  1 A is pushed downward. Along with that, the extension  16 A and the first and second contact members  61  and  62  descend together. With the descent, the coil spring  90  is compressed. 
   The facing part  105  is integrated with the steering wheel  100 A, so that the facing part  105  is not displaced even if the module cover  40 A is depressed. Also the guide shaft  50  fixed to the facing part  105  is not displaced. 
   As the first and second contact members  61  and  62  are pushed down, the second contact member  62  comes into contact with the lower rim of the window  56 , so that further descent of the second contact member  62  is stopped. Since the first contact member  61  continues descending thereafter, the contact members  61  and  62  come into contact with each other. Thus, the horn switch device  60  is turned on to sound the horn. 
   On release from the module cover  40 A, the first and second contact members  61  and  62  and the extension  16 A are pushed up by the repulsive force of the coil spring  90  to return to the state shown in  FIG. 4(   a ). This opens the contact members  61  and  62  to stop sounding the horn. Along with that, the entire airbag system  1 A returns to the initial position. 
   Also in this second embodiment, both of the first and second contact members  61  and  62  are mounted to or supported by the airbag system  1 A, so that they can be positioned easily and accurately. This reduces the difficulty in assembling the horn switch device  60  or the airbag system  1 A. 
   The disclosures of Japanese Patent Application Nos. 2004-366357 filed on Dec. 17, 2004; 2005-11774 filed on Jan. 19, 2005; and 2005-183678 filed on Jun. 23, 2005, are incorporated herein.