Patent Publication Number: US-2017361801-A1

Title: Mounting structure for driver-seat airbag device

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2016-119735, filed on Jun. 16, 2016, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates to a mounting structure for a driver-seat airbag device for mounting an airbag device to a main body of a steering wheel. 
     2. Description of the Related Art 
     JIB-A-2016-30552 discloses a mounting structure of mounting a driver-seat airbag device (hereinafter referred to as an airbag device) to a main body of a steering wheel of an automobile. 
     In JP-A-2016-30552, a through hole is formed in a core metal which constitutes the main body of the steering wheel. A clip is mounted to a rear surface of the core metal along the rear surface so as to cross the through hole. When a pair of snap pins provided on the rear surface of the airbag device are inserted into the through hole of the core metal and engaged with the clip, the airbag device is mounted to the main body. 
     In recent years, while the airbag device tends to be miniaturized according to market needs, from an object of reducing the vibration transmitted from the tire to the steering wheel, a boss portion of the core metal into which the steering shaft is inserted is tend to increase in diameter. Therefore, it is difficult to secure a space for mounting the snap pin in the hub portion having the boss portion of the core metal. 
     Therefore, in a steering wheel described in JP-A-2010-116060, a base plate is mounted to a front surface of the hub portion of the core metal. A pair of insertion holes are formed in the base plate so as to interpose the boss portion therebetween. A clip having an inverted U-shape is mounted to the rear surface of the base plate along the rear surface so as to cross the pair of insertion holes. Further, a pair of hook portions (corresponding to the snap pins of JP-A-2016-30552) provided on the rear surface of the airbag device are respectively inserted through the pair of insertion holes of the base plate, and are engaged with the clip. Thus, the airbag device is mounted to the main body. 
     However, in the mounting structure described in JP-A-2010-116060, the snap pin is held by being in contact with the inner peripheral surface of the insertion hole of the base plate and is engaged with the clip. However, since the thickness of the base plate, that is, the thickness of the inner peripheral surface of the insertion hole is small, it is difficult to properly hold the snap pin. In contrast, it is conceivable to secure the thickness of the inner peripheral surface of the insertion hole, for example, by setting the thickness of the portion including the insertion hole to be partly thicker than the other portions. However, in this case, there is a contradiction in which the shape of the base plate becomes complicated. 
     SUMMARY 
     An object of the present invention is to provide a mounting structure for a driver-seat airbag device capable of suppressing complication of the shape of a base plate, while properly holding a snap pin. 
     In order to achieve the above object, according to an aspect of the present invention, according to an aspect of the invention, there is provided a mounting structure for a driver-seat airbag device for mounting an airbag device to a main body of a steering wheel, the mounting structure including: a core metal provided on the main body of the steering wheel; and a base plate mounted to the core metal; a snap pin provided on the airbag device, the snap pin protruding toward the base plate; a separate holding member mounted to a mounting portion of the base plate; and a clip engaged with the holding member, wherein the snap pin is held by the holding member and is engaged with the clip so that the airbag device is mounted to the main body. 
     According to this configuration, since the separate holding members that hold the snap pins are provided in the mounting portion of the base plate, it is possible to secure the thickness of the member on the main body side for properly holding the snap pin by the holding member. 
     Further, according to the above configuration, since the clip is mounted to the base plate via the holding member, it is not necessary to provide the base plate with a portion for mounting the clip. 
     Therefore, it is possible to prevent the shape of the base plate from becoming complicated, while properly holding the snap pin. 
     According to the mounting structure for the driver-seat airbag device of the present invention, the clip may have: a pair of arms disposed with a boss portion of the main body interposed therebetween; and a connecting portion configured to connect base ends of the pair of arms, and the holding member may include a pair of first holding members provided to correspond to the pair of arms and respectively engaged with the pair of arms. 
     According to the above configuration, since the pair of snap pins of the airbag device are held by the pair of first holding members, respectively, and engaged with the pair of arms, respectively, the airbag device is mounted to the main body. Therefore, the airbag device is stably mounted to the main body. 
     According to the mounting structure for the driver-seat airbag device of the present invention, the holding member may include a second holding member provided to correspond to the connecting portion and engaged with the connecting portion. 
     According to this configuration, the second holding member is also engaged with the connecting portion that connects the base ends of the pair of arms. Further, since the snap pin of the airbag device is held by the second holding member and engaged with the connecting portion, the airbag device is mounted to the main body. Therefore, the airbag device is more stably mounted to the main body. 
     According to the mounting structure for the driver-seat airbag device of the present invention, the mounting portion may be an engaging hole formed in the base plate; and the holding member may have a storage portion configured to store the snap pin and is engaged with the engaging hole. 
     According to the configuration, the shape of the base plate is simplified, and the base plate can be easily formed. 
     According to the mounting structure for the driver-seat airbag device of the present invention, the engaging hole may be a circular hole, and the holding member may be rotatably engaged with the engaging hole in a state in which the clip is not engaged with the holding member, and the holding member may be non-rotatably engaged with the engaging hole in a state in which the clip is engaged with the holding member. 
     According to this configuration, since the engaging holes are circular holes, the shape of the base plate is simplified. In addition, by inserting the holding member into the engaging holes, the holding member can be easily engaged with the engaging holes. When the clip is engaged with the holding member, since the holding member engaged with the engaging holes cannot rotate, it is possible to perform positioning of the holding member simultaneously with mounting of the clip. 
     According to the mounting structure for the driver-seat airbag device of the present invention, the base plate may be provided with a pair of holding portions capable of holding the pair of arms of the clip, respectively, in a state in which the holding member is not engaged with the engaging hole. 
     According to such a configuration, in a state in which the holding member is not engaged with the engaging holes, the pair of arms of the clip are held by the pair of holding portions of the base plate. Therefore, it is possible to easily and smoothly perform the assembling work for engaging the holding member with the engaging holes of the base plate and holding the clip on the holding member. 
     According to the mounting structure for the driver-seat airbag device of the present invention, the holding member may have a tapered shape toward an end portion on the main body side of the holding member. 
     According to this configuration, the holding member can be easily inserted into and engaged with the engaging hole. 
     According to the mounting structure for the driver-seat airbag device of the present invention, an engaging recess with which the pair of arms are engaged may be formed on a peripheral wall of the first holding member, the first holding member may have an inclined surface formed by cutting the peripheral wall so as to incline with respect to a central axis from the engaging recess to a leading end, and the holding member may have the tapered shape toward the end portion on the main body side of the holding member by the inclined surface. 
     According to the above configuration, when the first holding member is inserted into the engaging holes of the base plate, since the clip relatively moves on the inclined surface of the first holding member, the insertion of the first holding member into the engaging holes is guided and the engagement of the clip to the engaging recess is guided. Thus, the clip can be easily engaged with the engaging recess. 
     According to the mounting structure for the driver-seat airbag device of the present invention, an inner peripheral surface of the storage portion of the holding member may be reduced in diameter toward the main body. 
     According to this configuration, the snap pin is easily inserted into the storage portion of the holding member, and the snap pin is smoothly guided toward the engagement position with the clip. Therefore, the mounting of the airbag device can be easily performed. 
     According to the mounting structure for the driver-seat airbag device of the present invention, each of the pair of arms may have: inclined portions which are inclined so as to be closer to each other toward the leading end sides of the pair of arms; and a leading end portion which extends from a leading end of the inclined portion; an engaging recess with which the leading end portions of the pair of arms are engaged may be formed on the peripheral wall of the pair of first holding members, the pair of first holding members may be engaged with the engaging holes in a posture in which the engaging recess is opened inward in a width direction, and the base plate may be provided with a guide portion which is brought into contact with the inclined portions of the pair of arms, respectively, and guides the inclined portions in a direction of coming closer to each other with the movement of the clip from the base end sides of the pair of arms to the leading end sides. 
     According to this configuration, when the clip is moved from the base end side of the pair of arms toward the leading end side with respect to the base plate, the inclined portions of the pair of arms are guided in a direction of coming closer to each other due to the action of the guide portion. As a result, the leading end portions of the pair of arms are displaced inward in the width direction and the engagement with the engaging recess of the pair of holding members is released, and thus, the airbag device can be detached from the main body. 
     According to the mounting structure for the driver-seat airbag device of the present invention, a plurality of positioning protrusions may be formed on the core metal, and the base plate may be formed with a plurality of through holes through which the plurality of protrusions penetrate, respectively. 
     According to such a configuration, by disposing the base plate on the core metal so that the plurality of protrusions of the core metal penetrate through the plurality of through holes of the base plate, respectively, the base plate can be easily positioned on the core metal. Therefore, it is possible to easily perform the operation of mounting the base plate to the core metal. 
     According to the present invention, it is possible to prevent the shape of the base plate from becoming complicated, while properly holding the snap pin. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawing which is given by way of illustration only, and thus is not limitative of the present invention and wherein: 
         FIG. 1  is a perspective view illustrating a steering wheel provided with a mounting structure in an embodiment of the mounting structure for a driver-seat airbag device; 
         FIG. 2  is a side view illustrating a main body of the steering wheel and the airbag device in the embodiment in a state of being separated from each other; 
         FIG. 3  is a front view illustrating a state in which the airbag device and the left and right bezels are detached from the steering wheel in the embodiment; 
         FIG. 4A  is a front view illustrating a base plate in a state in which a holding member and a clip of the embodiment are mounted, and  FIG. 4B  is a rear view illustrating the base plate; 
         FIG. 5  is a perspective view illustrating the base plate from the back side in a state in which the clip is mounted via the holding member of the embodiment; 
         FIG. 6  is a perspective view illustrating the holding member of the embodiment; and 
         FIG. 7A  is a cross-sectional view illustrating a way of inserting the holding member into the engaging hole of the base plate of the embodiment,  FIG. 7B  is a cross-sectional view illustrating a state in which the holding member is engaged with the engaging hole and the clip is engaged with an engaging recess, and  FIG. 7C  is a cross-sectional view illustrating a state in which the snap pin is held by the holding member and engaged with the clip. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An embodiment will be described below with reference to  FIGS. 1 to 7C . In the following description, a vertical direction (a vertical direction illustrated in  FIG. 3 ) when the steering wheel is viewed from the front is defined as a “vertical direction”, and a width direction (a horizontal direction illustrated in  FIG. 3 ) when the steering wheel is viewed from the front is defined as a “width direction W”. 
     As illustrated in  FIGS. 1 to 3 , a main body  10  of a steering wheel includes a hub portion  11 , a ring portion  12  positioned on an outer peripheral side of the hub portion  11 , a pair of true spoke portions  13  and a pseudo-spoke portion  14  which connect the hub portion  11  and the ring portion  12 . A driver-seat airbag device (hereinafter referred to as an airbag device  80 ) is mounted to the main body  10  from the front side. 
     As illustrated in  FIG. 3 , the main body  10  is provided with a core metal  15  forming a skeleton, and a base plate  20  mounted to the core metal  15  from the front side. The airbag device  80  is mounted to the main body  10  via the base plate  20 . 
     The core metal  15  has a core metal hub portion  16  constituting the hub portion  11 , a ring portion (not illustrated) constituting the ring portion  12 , and a pair of core metal spoke portions  17  constituting the pair of true spoke portions  13 . The core metal  15  is integrally formed of a metallic material such as an aluminum alloy. The core metal  15  does not exist in the interior of the pseudo-spoke portion  14 . A cylindrical boss  16 A made of a metal material harder than the core metal  15  such as a steel material is fitted to the hole formed in the center of the core metal hub portion  16 . As indicated by the two-dot chain line in  FIG. 2 , one end portion of the steering shaft  18  is inserted and fixed to the boss  16 A. 
     As illustrated in  FIGS. 1 and 2 , a back cover  70  that forms a design surface is mounted to the rear side of each of the hub portion  11  and the spoke portions  13  and  14 . A pair of bezel covers  71  that form a design surface are mounted to the front side of the pair of true spoke portions  13 . A bezel cover  72  that forms a design surface is mounted to the front side of the pseudo-spoke portion  14 . 
     Next, the base plate  20  will be described. 
     As illustrated in  FIGS. 3, 4A, 4B, and 5 , the base plate  20  has a symmetrical shape in a front view. That is, the base plate  20  includes a base portion  21  positioned below the boss  16 A and extending along the width direction W, and a pair of extending portions  22  extending upward from both end portions in the width direction W of the base portion  21 , and has a generally U-shape opened upward as a whole. The pair of extending portions  22  are located outside the boss  16 A in the width direction W, respectively. The peripheral edge of the base plate  20  has a shape bent toward the front side, and the rigidity of the base plate  20  is enhanced. The base plate  20  is made of a metal material such as an aluminum alloy. 
     Four screw holes  23  are formed at both end portions of the base portion  21  in the width direction W and at the outer portion of each extending portion  22  in the width direction W. When the screw  60  is inserted through the screw holes  23  and the screw  60  is screwed into a female screw (not illustrated) formed in the core metal hub portion  16  of the core metal  15 , the base plate  20  is mounted to the core metal  15 . 
     As illustrated in  FIGS. 4A, 4B, and 5 , circular engaging holes  24 A and  24 B are formed in the upper end portions of the respective extending portions  22 . A central portion of the base portion  21  in the width direction W protrudes downward in a substantially arcuate shape, and a circular engaging hole  24 C is formed in the protruding portion thereof. All the engaging holes  24 A to  24 C have the same shape. 
     An upper through hole  25 A and a lower through hole  25 B are formed below the engaging holes  24 A and  24 B in each extending portion  22 . Between the through holes  25 A and  25 B, a holding portion  26  protruding toward the rear side from the upper edge portion of the upper through hole  25 A and the lower edge portion of the lower through hole  25 B is formed. The holding portion  26  is connected to the main body of the base plate  20  at both ends in the width direction W, respectively. 
     A through hole  27  is formed in a portion of each extending portion  22  that is closer to the base end side than each lower through hole  25 B. A guide protrusion  28  is formed on an inner peripheral edge on the outer side of the through hole  27  in the width direction W. The guide protrusion  28  extends toward the inner peripheral side and is bent and protrudes toward the rear side. Each of the guide protrusions  28  is a surface facing the inner side in the width direction W, and has a guide surface  28 A that is inclined so as to be located on the inner side in the width direction W with approach to the upper side. 
     A through hole  29  having a diameter smaller than that of the screw hole  23  is formed above the screw hole  23  in each extending portion  22 . A pair of positioning protrusions  19  projecting to the front surface of the metal core  15  penetrate through the pair of through holes  29 . 
     Next, the holding member  40  will be described. 
     As illustrated in  FIGS. 3, 4A, 4B, and 5 , the holding members  40  having a substantially cylindrical shape are respectively inserted and engaged from the front side into the engaging holes  24 A to  24 C of the base plate  20 . Further, the holding member  40  engaged with the left and right engaging holes  24 A and  24 B corresponds to the first holding member, and the holding member  40  engaged with the lower engaging hole  24 C corresponds to the second holding member. 
     As illustrated in  FIG. 6 , the holding member  40  has a cylindrical base end portion  41  and a reduced diameter portion  42  having a diameter smaller than that of the base end portion  41 , and is integrally formed of a rigid resin material. 
     As illustrated in  FIG. 7C , a step portion formed by the base end portion  41  and the reduced diameter portion  42  is engaged with the inner peripheral edge of the engaging hole  24 C. Therefore, the holding member  40  is rotatably engaged with the engaging holes  24 A to  24 C in a state in which the clip  30  to be described later is not engaged with the holding member  40 . 
     As illustrated in  FIGS. 7A to 7C , the inner peripheral surface  41 A of the base end portion  41  is reduced in diameter toward the main body  10 , and the inner diameter of the leading end of the base end portion  41  is set to be the same as the inner diameter of the reduced diameter portion  42 . 
     As illustrated in  FIG. 6 , the peripheral wall  43  of the reduced diameter portion  42  is formed with an engaging recess  44  which is cut out over substantially a half circumference at a predetermined width. An inclined surface  46  is formed by an end surface that a portion of the peripheral wall  43  of the reduced diameter portion  42  on the leading end side (body  10  side) is cut to incline with respect to the central axis C 1  of the holding member  40  from the engaging recess  44  to the leading end. Accordingly, the holding member  40  has a tapered shape toward the end portion of the holding member  40  on the side of the main body  10  due to the inclined surface  46 . 
     On the inner peripheral surface of the reduced diameter portion  42 , a planar portion  42 A extending along the central axis C 1  is formed on the opposite side of the engaging recess  44  with the central axis C 1  interposed therebetween. 
     The internal space of the holding member  40  functions as a storage portion  45  for storing the snap pin  91  of the airbag device  80  to be described later. 
     Next, the clip  30  will be described. 
     As illustrated in  FIGS. 4A, 4B, and 5 , a clip  30  is provided on the rear side of the base plate  20 . 
     The clip  30  has a symmetrical shape in a front view. That is, the clip  30  has a pair of left and right arms  31  arranged with the boss  16 A of the main body  10  interposed therebetween, and a connecting portion  32  which connects the base ends of the pair of arms  31  to each other, and has a substantially inverted U-shape as a whole. 
     Each arm  31  has a base end portion  33  extending from the connecting portion  32  and extending upward in the vertical direction, and an inclined portion  34  extending from the leading end of the base end portion  33  and extending obliquely so as to be positioned on the inner side in the width direction W with approach to the upper side. Therefore, the inclined portions  34  of the respective arms  31  are inclined so as to be closer to each other toward the leading end side. 
     Each arm  31  has a leading end portion  35  that extends from the leading end of the inclined portion  34  and extends obliquely so as to be located on the outer side in the width direction W toward the upper side, and each of the leading end portions  35  serves as a free end. 
     The leading end portions  35  of the respective arms  31  pass through the respective lower through holes  25 B of the base plate  20  from the lower side, and pass through the upper through holes  25 A through the front sides of the respective holding portions  26 . 
     As illustrated in  FIG. 5 , in a state in which the clip  30  is engaged with the holding member  40 , the left and right holding members  40  are engaged with to the engaging holes  24 A and  24 B in a posture in which the engaging recesses  44  are opened inward in the width direction W, respectively. The leading end portions  35  of the arms  31  are engaged with the engaging recesses  44  from the inside in the width direction W, respectively. At this time, the leading end portion  35  is engaged with the holding member  40  so as to cross the storage portion  45 . 
     Further, the lower holding member  40  is engaged with the engaging hole  24 C in a posture in which the engaging recess  44  is opened upward. The connecting portion  32  of the clip  30  is engaged with the engaging recess  44  from the upper side. At this time, the connecting portion  32  is engaged with the holding member  40  so as to cross the storage portion  45 . 
     The inclined portion  34  of each arm  31  of the clip  30  is in contact with each guide surface  28 A of the base plate  20 . 
     In a state in which the clip  30  is engaged with each holding member  40 , each holding member  40  is non-rotatably engaged with the engaging holes  24 A to  24 C. 
     In a state in which the clip  30  is not engaged with each holding member  40 , each of the leading end portions  35  of the clip  30  tends to spread outward in the width direction W by the restoring force. At this time, the respective leading end portions  35  of the clip  30  are held by the holding portions  26 , and thus the leading end portion  35  is held. 
     Next, the airbag device  80  will be described. 
     As illustrated in  FIG. 2 , the airbag device  80  is provided with a pad  81  which is formed of a rigid resin material and constitutes a design surface on the front side. Further, a bag holder  82 , which is formed of a conductive metal material and holds an air bag (not illustrated) between the pad  81 , is mounted to the back side of the pad  81 . An inflator  83  for supplying inflation gas to the airbag is mounted to the back side of the bag holder  82 . 
     As illustrated in  FIG. 7C , a mounting hole  82 A is formed at a position corresponding to the engaging hole  24 C of the base plate  20  in the bag holder  82 . Mounting holes (not illustrated) having the same shape as the mounting holes  82 A are also formed at positions corresponding to the other two engaging holes  24 A and  24 B in the bag holder  82 . The horn device  100  is electrically connected to the bag holder  82 . 
     As illustrated in  FIGS. 2 and 7C , a horn switch mechanism  90  to be described later is mounted to each mounting hole  82 A from the front side. 
     As illustrated in  FIG. 2 , the snap pins  91  of each horn switch mechanism  90  protrude toward the main body  10  from the bag holder  82 . 
     Next, the horn switch mechanism  90  will be described. 
     As illustrated in  FIG. 7C , the snap pin  91  of the horn switch mechanism  90  is formed of a conductive metal material. The snap pin  91  has a shaft portion  91 A, a tapered head portion  91 B, and an annular locking groove  91 C formed between the shaft portion  91 A and the head portion  91 B. A flange portion  91 D is formed at a base end portion of the snap pin  91 . 
     A cylindrical portion  98  made of an insulating rigid resin material is put on the outer peripheral surface of the base end portion of the shaft portion  91 A. The base end of the cylindrical portion  98  is in contact with the flange portion  91 D. 
     A cylindrical elastic member  94  made of an elastic material such as rubber (e.g., EPDM, silicone rubber) or an elastomer is put on the outer peripheral surface of the cylindrical portion  98 . 
     A cylindrical damper holder  95  formed of an insulating rigid resin material is put on the outer peripheral surface of the base end portion of the elastic member  94 . The leading end portion of the damper holder  95  is reduced in diameter to cover the leading end portion of the cylindrical portion  98  from the leading end side. 
     The leading end portion of the damper holder  95  is inserted into the mounting hole  82 A of the bag holder  82 , and a mounting portion (not illustrated) of the damper holder  95  is mounted to the bag holder  82 . The elastic member  94  is held slidably along the central axis C 2  of the mounting hole  82 A by the damper holder  95 . 
     On the outer peripheral surface of the damper holder  95 , a bottomed cylindrical contact holder  92  which is formed of an insulating rigid resin material and covers the flange portion  91 D of the snap pin  91  from the front side is mounted by a claw fitting (not illustrated) or the like. 
     A movable side contact portion  93  is mounted to the inner bottom surface and the inner peripheral surface of the contact holder  92 . The movable side contact portion  93  is in contact with the bag holder  82 . 
     On the outer peripheral surface of the snap pin  91 , a substantially cylindrical auxiliary member  96  which is formed of an insulating rigid resin material and covers a portion on the base end side of the locking groove  91 C and a part of the shaft portion  91 A connected to the locking groove  91 C is covered. 
     An annular storage portion  96 A protrudes from the outer peripheral surface of the auxiliary member  96 . A coil spring  97  is interposed between the storage portion  96 A and the damper holder  95 . 
     When the air bag device  80  is pushed down, the force applied to the air bag device  80  causes the contact holder  92 , the movable side contact portion  93 , and the damper holder  95  to slide to the rear side, while receiving the elastic repulsive force of the coil spring  97  along the snap pin  91 . At this time, when the movable side contact portion  93  is brought into contact with the flange portion  91 D of the snap pin  91  which is the fixed side contact portion, and is conductively connected thereto, the horn device  100  is operated. 
     The leading end portion of the snap pin  91  is stored by the storage portion  45  of the holding member  40 , and the auxiliary member  96  is held by the inner peripheral surface of the holding member  40 . At this time, the clip  30  (in this case, the connecting portion  32 ) is engaged with the locking groove  91 C of the snap pin  91 . In this way, the airbag device  80  is mounted to the main body  10 . 
     Next, a procedure for assembling the clip  30  and the holding member  40  to the base plate  20  will be described. 
     First, the clip  30  is assembled to the rear surface of the base plate  20 . At this time, the inclined portion  34  of the clip  30  is brought into contact with the guide surface  28 A of the base plate  20 , and the leading end portion  35  of the clip  30  is held by the holding portion  26 . 
     Subsequently, as illustrated in  FIG. 7A , the holding member  40  is inserted into the engaging hole  24 C of the base plate  20  from the front side. At this time, as the clip  30  relatively moves on the inclined surface  46  of the holding member  40 , the insertion of the holding member  40  into the engaging hole  24 C is guided, and the engagement of the clip  30  to the engaging recess  44  is guided. As a result, as illustrated in  FIG. 7B , the clip  30  is engaged with the engaging recess  44  of the holding member  40 . 
     Also, in the other two engaging holes  24 A and  24 B, the holding member  40  is inserted from the front side in the same manner as the engaging hole  24 C, and the leading end portion  35  of each arm  31  of the clip  30  is engaged into the engaging recess  44  of each holding member  40 . 
     As illustrated in  FIGS. 4A and 4B , in a state in which the clip  30  is engaged with each holding member  40 , a downward force acts on each inclined portion  34  of the clip  30  by each guide surface  28 A of the base plate  20 . Therefore, the connecting portion  32  of the clip  30  is pressed downward against the engaging recess  44  of the lower holding member  40 . Therefore, the connecting portion  32  is prevented from coming-off from the engaging recess  44 . 
     On the other hand, when the clip  30  is detached from the base plate  20 , the clip  30  is moved upward with respect to the base plate  20 . At this time, as the connecting portion  32  of the clip  30  engaged with the lower holding member  40  moves upward, the engagement state between the engaging recess  44  and the connecting portion  32  is released. Also, when each inclined portion  34  of the clip  30  is guided by each guide surface  28 A, the respective inclined portions  34  are deformed to approach each other in the width direction W. As a result, since the leading end portion  35  of the clip  30  engaged with the left and right holding members  40  moves inward in the width direction W, the engagement state between the engaging recess  44  and the leading end portion  35  is released. 
     According to the mounting structure of the airbag device for a driver-seat of the present embodiment described above, the following operational effects can be obtained. 
     (1) A separate holding member  40  is engaged with the engaging holes  24 A to  24 C of the base plate  20 . When the clip  30  is engaged with the holding member  40 , and the snap pin  91  is stored and held by the storage portion  45  of the holding member  40  and is engaged with the clip  30 , the airbag device  80  is mounted to the main body  10 . 
     According to such a configuration, since the separate holding members  40  that hold the snap pins  91  are provided in the engaging holes  24 A to  24 C of the base plate  20 , it is possible to secure the thickness of the member on the main body  10  side for properly holding the snap pin  91  by the holding member  40 . 
     Further, according to the above configuration, since the clip  30  is mounted to the base plate  20  via the holding member  40 , it is not necessary to provide the base plate  20  with a portion for mounting the clip  30 . 
     Therefore, it is possible to prevent the shape of the base plate  20  from becoming complicated, while properly holding the snap pin  91 . 
     (2) The holding member  40  is mounted to the base plate  20 , by engaging the holding member  40  with the engaging holes  24 A to  24 C of the base plate  20 . Therefore, the shape of the base plate  20  is simplified, and the base plate  20  can be easily formed. 
     (3) The holding member  40  includes a pair of holding members  40  provided to correspond to the pair of arms  31  and engaged with the pair of arms  31 , respectively. 
     According to such a configuration, since the pair of snap pins  91  of the airbag device  80  are held by the pair of holding members  40 , respectively, and engaged with the pair of arms  31 , respectively, the airbag device  80  is mounted to the main body  10 . Therefore, the airbag device  80  is stably mounted to the main body  10 . 
     (4) The holding member  40  includes a holding member  40  provided to correspond to the connecting portion  32  and engaged with the connecting portion  32 . 
     According to such a configuration, the holding member  40  is also engaged to the connecting portion  32  that connects the base ends of the pair of arms  31 . Further, since the snap pin  91  of the airbag device  80  is held by the holding member  40  and engaged with the connecting portion  32 , the airbag device  80  is mounted to the main body  10 . Therefore, the airbag device  80  is stably mounted to the main body  10 . 
     (5) Since the engaging holes  24 A to  24 C are circular holes. The holding member  40  is rotatably engaged with respect to the engaging holes  24 A to  24 C in a state in which the clip  30  is not engaged with the holding member  40 . Meanwhile, the holding member  40  is non-rotatably engaged with the engaging holes  24 A to  24 C in a state in which the clip  30  is engaged with the holding member  40 . 
     With such a configuration, since the engaging holes  24 A to  24 C are circular holes, the shape of the base plate  20  is simplified. In addition, by inserting the holding member  40  into the engaging holes  24 A to  24 C, the holding member  40  can be easily engaged with the engaging holes  24 A to  24 C. When the clip  30  is engaged with the holding member  40 , since the holding member  40  engaged with the engaging holes  24 A to  24 C cannot rotate, it is possible to perform positioning of the holding member  40  simultaneously with mounting of the clip  30 . 
     (6) The base plate  20  is provided with a pair of holding portions  26  capable of respectively holding the pair of arms  31  of the clip  30  in a state in which the holding member  40  is not engaged with the engaging holes  24 A to  24 C. 
     According to such a configuration, in a state in which the holding member  40  is not engaged with the engaging holes  24 A to  24 C, the pair of arms  31  of the clip  30  are held by the pair of holding portions  26  of the base plate  20 . Therefore, it is possible to easily and smoothly perform the assembling work for engaging the holding member  40  with the engaging holes  24 A to  24 C of the base plate  20  and holding the clip  30  on the holding member  40 . 
     (7) The holding member  40  has a tapered shape toward the end portion of the holding member  40  on the side of the main body  10 . Therefore, the holding member  40  can be easily inserted into and engaged with the engaging holes  24 A to  24 C. 
     (8) The holding member  40  has an inclined surface  46  formed by cutting the peripheral wall  43  so as to incline with respect to the central axis C 1  from the engaging recess  44  formed in the peripheral wall  43  to the leading end. 
     According to such a configuration, when the holding member  40  is inserted into the engaging holes  24 A to  24 C of the base plate  20 , since the clip  30  relatively moves on the inclined surface  46  of the holding member  40 , the insertion of the holding member  40  into the engaging holes  24 A to  24 C is guided and the engagement of the clip  30  to the engaging recess  44  is guided. Thus, the clip  30  can be easily engaged with the engaging recess  44 . 
     (9) As the inner peripheral surface  41 A of the base end portion  41  of the holding member  40  approaches the main body  10 , the diameter thereof is reduced. Therefore, the snap pin  91  is easily inserted into the interior (the storage portion  45 ) of the base end portion  41  of the holding member  40 , and the snap pin  91  is smoothly guided toward the engagement position with the clip  30 . Therefore, the mounting of the airbag device  80  can be easily performed. 
     (10) The base plate  20  is provided with the guide surfaces  28 A which come into contact with the inclined portions  34  of the pair of arms  31 , respectively, and guide the inclined portions  34  in the direction of approaching each other with the movement of the clip  30  from the base end side to the leading end side of the pair of arms  31 . 
     According to such a configuration, when the clip  30  is moved from the base end side of the pair of arms  31  toward the leading end side with respect to the base plate  20 , the inclined portions  34  of the pair of arms  31  are guided in a direction of coming closer to each other due to the action of the guide surface  28 A. As a result, since the leading end portions  35  of the pair of arms  31  are displaced inward in the width direction and the engagement with the pair of holding members  40  is released, the airbag device  80  can be detached from the main body  10 . 
     (11) A pair of positioning protrusions  19  are formed on the core metal  15 , and the base plate  20  is formed with a plurality of through holes  29  through which the pair of protrusions  19  passes, respectively. According to such a configuration, by disposing the base plate  20  on the core metal  15  so that the pair of protrusions  19  of the core metal  15  penetrate through the pair of through holes  29  of the base plate  20 , respectively, the base plate  20  can be easily positioned on the core metal  15 . Therefore, it is possible to easily perform the operation of mounting the base plate  20  to the core metal  15  with the screw  60 . 
     Modified Example 
     Further, for example, the above embodiment can also be modified as follows. 
     It is also possible to omit the protrusion  19  for positioning the base plate  20  with respect to the metal core  15  and the through hole  29  of the base plate  20 . 
     The inner diameter of the inner peripheral surface  41 A of the holding member  40  may be set to be constant in the axial direction of the holding member  40 . 
     The inclined surface  46  of the holding member  40  can be omitted. 
     Unevenness may be provided on the inner peripheral surface of the engaging holes  24 A to  24 C or the outer peripheral surface of the holding member  40  so as to perform positioning by engaging with each other. Further, the engaging holes  24 A to  24 C can be changed to non-circular holes. 
     Instead of the engaging holes  24 A to  24 C, the holding member  40  may be mounted to the mounting portion protruding from the base plate  20 , by fitting or the like. 
     It is also possible to omit the guide surface  28 A (guide portion). In this case, the inclined portion  34  of the clip  30  can be omitted. 
     The shape of the holding portion  26  is not limited to the shape exemplified in the above embodiment. The holding portion may be anything as long as it is possible to hold the respective arms  31  of the clip  30 , and may be a hook-shaped portion protruding from the rear surface of the base plate  20 . Further, the holding portion  26  can be omitted. 
     It is also possible to omit the lower holding member  40  provided to correspond to the connecting portion  32  of the clip  30 . 
     In the above embodiment, the description has been given of a case where the snap pin  91  engaged with the clip  30  constitutes the horn switch mechanism  90 . Alternatively, a snap pin engaged with the clip  30  may be provided separately from the snap pin of the horn switch mechanism.