Patent Publication Number: US-2023158927-A1

Title: Vehicle seat

Description:
TECHNICAL FIELD 
     The present invention relates to a vehicle seat such as a car seat, and particularly to a vehicle seat configured to absorb a shock given to a neck of an occupant in a rear-end collision. 
     BACKGROUND ART 
     In a rear-end collision of a car that occurs when a rear end of your car is struck by another car or when a rear end of your car which is being reversed strikes another car or a construct, a head of an occupant seated on a seat cushion of a car seat would largely tilt back by inertia, and in reaction thereto, the neck of the occupant would likely be given a large shock. With this in view, the car seat is commonly provided with a headrest for receiving the head of the occupant from a back side so as to absorb a shock given to the neck of the occupant in a rear-end collision of the car. 
     Herein, an occupant seated on a seat cushion and driving a car is, in many cases, postured in an in-seat position with a head slightly apart from the headrest to the front, and many of other passengers not driving the car also have similar in-seat positions. When a car in which an occupant/passenger is seated in such a posture is rear-ended, the head of the occupant would tilt slightly to the rear before being received, and would go tilted back to the front in reaction thereto, so that its benefit of absorbing a shock given to the neck of the occupant would be reduced. 
     Against this backdrop, there are proposed a vehicle seat and a seat back device which are configured such that in a rear-end collision of the car, an upper body of an occupant tending to move rearward by inertia is caused to subside into a seat back disposed at his/her rear side so that the head of the occupant is swiftly received by the headrest (e.g., see Patent Literatures 1, 2). 
     A vehicle seat described in Patent Literature 1 includes a pressure-receiving member connected rearward-movably to a seat back frame, as a member for receiving an upper body of an occupant by means of a seat back pad (seat back cushion) within a seat back. A seat back device described in Patent Literature 2 includes a sheet-like elastic member corresponding to the pressure-receiving member described in Patent Literature 1. 
     In the vehicle seat described in Patent Literature 1 and the seat back device described in Patent Literature 2, the pressure-receiving member (sheet-like elastic member) moves together with the seat back pad to the rear relative to the seat back frame when the rear-end collision of a vehicle causes a rearward motion load to be imposed on an occupant and thus presses an upper body of the occupant against the seat back. As a result, the upper body of the occupant subsides into the seat back, allowing the head of the occupant to be swiftly received by the headrest; in this way, the shock be given to the neck of the occupant can be absorbed. 
     On the other hand, a vehicle seat having a seat structure in which a side air bag device is provided is generally known (e.g., see Patent Literature 3). The structure disclosed in this Patent Literature 3 is such that an insert wire (tuck-in wire) for attaching a seat skin inside a vertical groove formed in the seat back pad is embedded in a seat back pad. 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Literature 1: JP 2010-179748 A 
         Patent Literature 2: JP 2010-254126 A 
         Patent Literature 3: JP 10-76084 A 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     The vehicle seat described in Patent Literature 1 and the seat back device described in Patent Literature 2 do not have any special structure adopted such that the upper body of an occupant is allowed to subside into the seat back sufficiently in a rear-end collision of a car. 
     The structure in which an insert wire is embedded in a seat back pad has a problem that if there are many portions in the seat back pad from which the insert wire is exposed to outside, the seat back pad would be susceptible to damage at the edges of the seat back pad adjoining the wire. 
     The present invention is made in view of the technical background as described above, and a challenge to be taken up is to provide a vehicle seat which allows an upper body of an occupant to subside into a seat back sufficiently in a rear-end collision of a vehicle to effectively suppress tilting-back of a head of the occupant so that a shock to be given to his/her neck can be sufficiently absorbed, and in which adhesion between a tuck-in wire and a seat back pad is improved. 
     Solution to Problem 
     A vehicle seat configured to solve the aforementioned challenge according to the present invention comprises a seat cushion, a seat back covered with a skin material and incorporating left and right side frames, a headrest, a pressure-receiving member connected rearward-movably to the left and right side frames, a seat back pad with which at least a front surface of the pressure-receiving member and a seat back frame are covered, and tuck-in wires embedded in the seat back pad. This vehicle seat is configured such that a rearward motion load received from an upper body of an occupant seated on the seat cushion and acting on the seat back causes the pressure-receiving member to move rearward to cause the upper body of the occupant to subside into the seat back. The seat back pad includes a central portion configured to face a back of the upper body of the occupant and side portions configured to face sides of the upper body of the occupant, the side portions being provided continuously to the central portion, the seat back pad having a groove for tucking the skin material therein, the groove being formed at borders between the central portion and the side portions. In a bottom of the groove, a hole is formed along the groove. Each tuck-in wire includes a plurality of tuck-in portions provided along the groove, and a connecting portion detouring around the hole and connecting the plurality of the tuck-in portions. 
     In this vehicle seat, the rearward motion load received from the upper body of the occupant and acting on the seat back in a rear-end collision of the vehicle causes the pressure-receiving member to move rearward together with the seat back pad relative to the seat back frame, so that the upper body of the occupant subsides into the seat back. In this motion, the central portion of the seat back pad which faces the back of the upper body of the occupant and which is bordered with the groove having a hole is caused to move rearward easily and sufficiently relative to the side portions. Thus, the upper body of the occupant is allowed to subside sufficiently into the seat back. As a result, tilting-back of a head of the occupant is suppressed sufficiently so that a shock which would be given to his/her neck can be sufficiently absorbed. Moreover, since the tuck-in wire is configured to partially lie along the groove so as to detour around the hole, the tuck-in wire is not exposed through the hole, so that adhesion between the seat back pad and the tuck-in wire can be improved. Accordingly, damage of the seat back pad at the edges of the seat back pad adjoining the wire is suppressed. 
     In the vehicle seat as described above, the tuck-in wire may preferably be embedded in a position shifted from the groove to a central portion side of the seat back pad around the hole. In this configuration, the tuck-in wire may have a two-dimensionally bent simple shape, and thus the productivity for the tuck-in wires can be improved. 
     In the vehicle seat as described above, the hole may preferably be disposed in a position outside relative to the pressure-receiving member and inside relative to the left or right side frame with respect to a lateral direction. 
     With this configuration, since the hole is disposed in a position outside relative to the pressure-receiving member and inside relative to the left or right side frame with respect to the lateral direction, a region in which the pressure-receiving member and the side frames are shifted relative to each other in the front-rear direction and a region in which the seat back pad deforms substantially coincide with each other. This makes the seat back pad easily deformable and the pressure-receiving member smoothly movable rearward. 
     The vehicle seat as described above may preferable comprise a connecting wire which includes two end portions connected to the left and right side frames and a middle portion supporting the pressure-receiving member, wherein the connecting wire includes extra-length portions bowed to deviate from an axial line connecting the two end portions of the connecting wire, the extra-length portions being formed in left and right sections of the connecting wire between the side frames and the pressure-receiving member. 
     With this configuration, when the upper body of the occupant is caused to subside into the seat back, the connecting wire by which the pressure-receiving member is rearward-movably connected to the side frames sags rearward and extends while the left and right extra-length portions acts as torsion springs. Accordingly, the rearward-motion stroke of the pressure-receiving member increases and thus the upper body of the occupant subsides deeply into the seat back. As a result, the tilting-back of the head of the occupant is suppressed sufficiently so that a shock to be given to his/her neck can be absorbed sufficiently. 
     In the vehicle seat with the connecting wire as described above, the hole may preferably be disposed in positions facing to the extra-length portions of the connecting wire. In this configuration, a region in which the connecting wire deforms and a region in which the seat back pad deforms coincide with each other, and thus the seat back pad and the extra-length portions are made easily deformable, so that the pressure-receiving member can be caused to smoothly move rearward. 
     The connecting wire may preferably be configured such that two end portions connected by the side frames are disposed in positions higher than the middle portion supporting the pressure-receiving member. In this configuration, the pressure-receiving member is suspended via the connecting wire on the side frames, and thus the pressure-receiving member achieves a stabilized posture when it is being mounted to the seat back frame and after it has been mounted. 
     Assuming that the extra-length portions of the connecting wire are bowed upwardly, when the upper body of the occupant is caused to subside into the seat back in a rear-end collision of the vehicle, the extra-length portions properly block shoulder regions of the occupant from subsiding, so that the occupant achieves a stabilized seat-in posture in the rear-end collision. 
     Assuming that webbing mounting hardware for a side air bag device is welded to at least one of the left and right side frames, it is preferable that at least one end portion of the connecting wire is connected to a position adjacent to a welded spot of the webbing mounting hardware. With this configuration, the rearward motion load imposed on the pressure-receiving member is received effectively by a higher-rigidity portion(s) of the side frame(s). 
     The extra-length portions of the connecting wire may preferably be bowed toward directions away from the webbing mounting hardware welded to the side frame(s). With this configuration, the extra-length portions do not interfere with the webbing mounting hardware, and thus the workability in attachment of the connecting wire is improved. 
     The vehicle seat as described above may comprise an upper connecting member configured to connect an upper portion of the pressure-receiving member to the left and right side frames, which upper connecting member comprises a wire having a springiness. This vehicle seat may preferably be configured to comprise a cross member disposed above the pressure-receiving member and bridging the left and right side frames, wherein the cross member comprises a rod having a rigidity higher than that of the upper connecting member, with a plurality of bent portions formed therein, the bent portions being bowed downwardly relative to two end portions fixed to the side frames. 
     With this configuration, the rearward motion of the shoulder regions of the occupant is received and blocked by the plurality of bent portions of the cross member when the upper body of the occupant is caused to subside into the seat back, so that the upper body of the occupant subsides into the seat back in a safe in-seat posture with his/her back being hunched. As a result, the clearance between the head of the occupant and the headrest swiftly decreases, and thus the tilting-back of the head is suppressed effectively, so that the shock given to the neck is absorbed satisfactorily. 
     Since the bent portions are bowed downwardly relative to the two end portions fixed to the side frames, the two end portions fixed to the side frames serve as pivots about which the bent portions deform so as to turn rearward in an intense rear-end collision; therefore, the bent portions can absorb the shock without imposing a great force on the occupant. 
     The plurality of bent portions of the cross member may preferably be disposed rearwardly relative to an initial position of the pressure-receiving member before moving rearward. With this configuration, after the shoulder regions of the occupant subside slightly into the seat back, the upper body of the occupant becomes postured with his/her back being hunched, and the head of the occupant is swiftly brought close to the headrest and received by the headrest. 
     Herein, the bent portions of the cross member may preferably be configured to comprise four bilaterally symmetrical bent portions of which an inner pair of left and right bent portions is disposed with lower ends thereof located above the pressure-receiving member and an outer pair of left and right bent portions is disposed with lower ends thereof located laterally outside the pressure-receiving member above the pressure-receiving member. With this configuration, the rearward motion load given from the shoulder regions of the occupant to the seat back is received by the four bent portions in a well-balanced fashion, so that the occupant achieves a stabilized in-seat posture. 
     The side frames may preferably be configured to include pad shape retainer portions each shaped like a plate jutting frontward to retain shapes of the side portions of the seat back pad, and pipe portions protruding upward beyond the pad shape retainer portions, wherein a plate-like bracket is fixed to the pipe portions and protrudes frontward. 
     With this configuration, since the pad shape retainer portions and the bracket disposed above in the side frames serve to suppress rearward deformation of the seat back pad at upper and lower portions of the seat back pad when the upper body of the occupant is caused to subside into the seat back, the occupant is likely to become postured with his/her back being hunched, and thus the central region of his/her back subsides into the seat back pad antecedently; therefore, the clearance between the head and the headrest swiftly decreases, so that the shock given to the neck can be absorbed. 
     The bracket may preferably comprise a plate member shaped like a letter U in cross section with flanges at an upper end and a lower end thereof. With this configuration, the rigidity of the bracket can be increased, and the in-seat posture of the occupant in a rear-end collision be made easily controllable. 
     The bracket may preferably be configured as a mount bracket to which an attachment is attached, such that the bracket is fixed to a laterally inner side portion of an outer peripheral surface of the pipe portion. With this configuration, the portion at which the bracket is fixed to the pipe portion, for example, the welded spot, is located at a laterally inner side of the pipe portion, and thus this fixed portion is not exposed to the outside of the side frame; therefore, the attachment can be attached thereto from outside with ease. 
     The bracket may preferably be configured as a mount bracket to which an attachment is attached, and the attachment is arranged to extend along the pipe portion, wherein the bracket has a slot for attaching an attachment thereto, and a direction of a length of the slot is parallel to a direction of a length of the pipe portion. With this configuration, the attachment is disposed along the pipe portion of the side frame, and the slot for allowing a positioning error which would be introduced when the attachment is attached extends in parallel to the pipe portion; therefore, the attachment is prevented from becoming misaligned in the front-rear direction even when a positioning error is introduced for the attachment. Accordingly, the attachment can be arranged with the side frame in such a manner as to achieve compactness, and the workability in attachment is improved due to allowance of the positioning error to be introduced for the attachment. 
     The tuck-in wires and the pressure-receiving member may preferably have portions overlapping each other as viewed from a front-rear direction. 
     With this configuration, when a load is imposed on the tuck-in wires from frontward, the pressure-receiving member receives this load; therefore, unevenly balanced imposition of the load on the tuck-in wires can be suppressed. 
     It may be preferably that webbing mounting hardware for a side air bag device is welded to at least one of the left and right side frames, and the webbing mounting hardware is located rearwardly of the side portion. 
     With this configuration, the webbing mounting hardware serves to suppress excessive deformation of the side portion toward rearward. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a perspective view of a car seat showing one embodiment of a vehicle seat according to the present invention. 
         FIG.  2    is a perspective view of a seat frame incorporated in the car seat shown in FIG. 
         FIG.  3    is a front elevation of a seat back frame shown in  FIG.  2   . 
         FIG.  4    is a perspective view of a support tab shown in  FIG.  3    and its vicinity. 
         FIG.  5    is a perspective view of a mount bracket shown in  FIG.  2    and its vicinity. 
         FIG.  6    show partially enlarged views of a side air bag device shown in  FIG.  2    and its vicinity, in which (a) is a perspective view, and (b) is a side elevation. 
         FIG.  7    is a front elevation of a seat back pad incorporated in the seat back shown in  FIG.  1   . 
         FIG.  8    is a sectional view taken along line VIII-VIII of  FIG.  7   . 
         FIG.  9    is a sectional view of a seat back illustrated with an in-seat posture of an occupant during a normal driving operation of the car. 
         FIG.  10    is a sectional view of the seat back illustrated with an in-seat posture of an occupant in a moderate rear-end collision or at an early stage in a rear-end collision. 
         FIG.  11    is a sectional view of the seat back illustrated with an in-seat posture of an occupant in an intense rear-end collision. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereafter, a description will be given of one embodiment of a vehicle seat according to the present invention with reference made to the accompanying drawings. The vehicle seat according to one embodiment is configured as a car seat S arranged in a location of a driver&#39;s seat of an automobile, for example as shown in  FIG.  1   . This car seat S includes a seat cushion S 1 , a seat back S 2  and a headrest, in which a pad material made of a cushion material such as urethane foam is covered with a skin material such as a synthetic leather or a cloth. 
     The seat cushion S 1  and the seat back S 2  incorporate a seat frame F as shown in  FIGS.  2  and  3   . This seat frame F comprises a seat cushion frame F 1  which constitutes a frame of the seat cushion S 1  and a seat back frame F 2  which constitutes a frame of the seat back S 2 . The headrest S 3  incorporates a headrest frame (not shown) which constitutes its frame. 
     The seat cushion frame F 1  shown in  FIG.  2    is installed, for example, on a floor for a driver&#39;s seat via slide rails SL, in such a manner that its position in the front-rear direction is adjustable, where the directions are designated as front-rear, left-right (lateral) and upward-downward (upper-lower) directions in view of the eyes of an occupant assumed to be seated on the seat cushion S 1  shown in  FIG.  1   . A lower portion of the seat back frame F 2  is pivotally linked to a rear portion of the seat cushion frame F 1  via a reclining mechanism RL whereby the seat back frame F 2  is rendered tiltable frontward and rearward. 
     The seat back frame F 2  is configured in the shape of a frame with an upper frame  10 , left and right side frames  20  and a lower frame  30  integrally joined together by welding or the like. Inside this frame-shaped seat back frame F 2 , a pressure-receiving member  40  for supporting an upper body of an occupant in a manner that renders the upper body movable rearward is disposed. 
     The upper frame  10 , made by bending tubing, includes a transverse pipe portion  11  and vertical pipe portions  13 ,  13  extending from the left and right ends of the transverse pipe portion  11 , and is formed like an inverted U. A pair of left and right support brackets  12 ,  12  for attaching a pair of left and right headrest stays (designation by reference characters is omitted) protruding from a lower portion of the headrest S 3  are fixed to a front side of the transverse pipe portion  11  by welding. 
     The vertical pipe portions  13 ,  13  are integrated with left and right side frame main body portions  21 ,  21  which are continuously welded to lower portions of the vertical pipe portions  13 ,  13 , so as to constitute the left and right side frames  20 . The side frame main body portions  21 ,  21  are made of sheet metal, and upper portions thereof are configured to wrap the vertical pipe portions  13 ,  13  of the upper frame  10 , and are integrally spot-welded to the vertical pipe portions  13 ,  13 . The side frame main body portions  21 ,  21  are configured to jut frontward to retain the shapes of side portions of a seat back pad which will be described later, to constitute pad shape retainer portions (see positions designated by the reference numeral  21 ). 
     The pressure-receiving member  40  is made of a sheet-like plastic plate, and an upper portion thereof is connected to the left and right side frames  20  via an upper connecting wire  22  configured as an upper connecting member, while a lower portion thereof is connected to the left and right side frames  20  via a lower connecting wire  23  (see  FIG.  3   ) configured as a lower connecting member. 
     As shown in  FIG.  4   , a left end portion  22 A of the upper connecting wire  22  is bent downward along the vertical pipe portion  13  of the upper frame  10 , and the left end portion  22 A of the upper connecting wire  22  is wrapped with a support tab  14  fixed by welding to the left vertical pipe portion  13  of the upper frame  10 , and connected to the vertical pipe portion  13 . 
     Although not illustrated, a right end portion  22 A of the upper connecting wire  22  is also wrapped with a similar support tab  14  and connected to the right vertical pipe portion  13  of the upper frame  10 . An engageable portion (not shown) formed on a rear side of an upper portion of the pressure-receiving member  40  is engaged with a middle portion of the upper connecting wire  22 , and thus the upper portion of the pressure-receiving member  40  is connected via the upper connecting wire  22  to the left and right side frames  20 . 
     On the other hand, two end portions of the lower connecting wire  23  are, as shown in  FIG.  3   , engaged with toggle stopper mechanisms  50 ,  50  disposed on inner sides of the left and right side frame main body portions  21 ,  21 . An engageable portion (not shown) formed on a rear side of a lower portion of the pressure-receiving member  40  is engaged with a middle portion of the lower connecting wire  23 , and thus the lower portion of the pressure-receiving member  40  is connected via the lower connecting wire  23  to the left and right side frames  20 . 
     It is appreciated that if the pressure-receiving member  40  is suspended from the side frames  20  by means of the upper connecting wire  22  and the lower connecting wire  23 , the posture of the pressure-receiving member  40  is kept stabilized during and after the pressure-receiving member  40  is attached to the seat back frame F 2 . In this respect, in order to stabilize the posture of the pressure-receiving member  40 , the upper connecting wire  22  and the lower connecting wire  23  are arranged such that the two end portions  22 B (the positions of the upper portions of the end portions  22 A led out from upper ends of the support tabs  14 ) at which the wires are connected to the side frames  20  are located in positions higher than the middle portions thereof supporting the pressure-receiving member  40 . 
     As shown in  FIG.  3    and  FIG.  6   , the toggle stopper mechanisms  50 ,  50  include pivotal link members  52 ,  52  that are pivotable rearward over dead points while resisting the tensions of extension springs  51 ,  51 , and the two ends of the lower connecting wires  23  are connected to lower ends of these pivotal link members  52 ,  52 . 
     In order to allow the pressure-receiving member  40  to swiftly and smoothly move rearward when a rearward motion load of a predetermined magnitude or greater from the upper body of an occupant seated on the seat cushion S 1  (see  FIG.  1   ) acts on the seat back S 2 , the upper connecting wire  22  and the lower connecting wire  23  are made of a wire such as of spring steel having a springiness. 
     The tensions of the extension springs  51 ,  51  of the toggle stopper mechanisms  50 ,  50  are set at appropriate tensions such that a rearward motion load of a predetermined magnitude or greater acting on the two end portions of the lower connecting wire  23  will be able to cause the pivotal link members  52 ,  52  to pivot over the dead points without fail. 
     Moreover, in order to increase the rearward motion stroke of the pressure-receiving member  40 , the extra-length portions  24 ,  24  bowed to deviate from an axial line connecting the two end portions  22 B of the upper connecting wire  22  are formed in left and right sections of the upper connecting wire  22  which are located between the side frames  20  and the pressure-receiving member  40  in the lateral direction. These extra-length portions  24 ,  24  are bowed upward and bent like an inverted U so as to face the back sides of the shoulder regions of the occupant. 
     Herein, as shown in  FIG.  3   , a cross member  15  made of a rod that is thicker and more rigid than the upper connecting wire  22  is provided to bridge the left and right vertical pipe portions  13 ,  13  of the upper frame  10  which constitute an upper portion of the side frame  20 . 
     The cross member  15  is configured such that its central portion is located in a position substantially as high as the two end portions fixed to the front sides of the left and right vertical pipe portions  13 ,  13  by welding, and in each of the sections at both sides of the central portion, two bent portions  16 ,  17  bowed downward to deviate from the position of its axial line (laterally extending line connecting the two ends of the cross member  15 ) are formed, respectively, in a bilaterally symmetrical position. 
     Outer bent portions  16 ,  16  closer to the vertical pipe portions  13 ,  13 , each bent in the form of a letter V with a rounded corner, have at least lower ends thereof located laterally outside the pressure-receiving member  40  above the pressure-receiving member  40 . On the other hand, inner bent portions  17 ,  17 , each bent in the form of a letter U with rounded corners, are located in their entireties (including lower ends thereof) above the pressure-receiving member  40 . 
     The left and right bent portions  16 ,  17  are disposed slightly rearwardly relative to the pressure-receiving member  40  in positions facing the back sides of the shoulder regions of the occupant, and also serve to retain the shape of the rear side of the seat back pad which will be described later. 
     These bent portions  16 ,  17  have rigidities such that rearward motion of the shoulder regions can be limited properly when the upper body of the occupant subsides into the seat back S 2 , and if a great rearward motion load is received from the shoulders of the occupant, the bent portions are caused to pivot about the axial line of the cross member  15  and undergo plastic deformation, so that the shock given to the shoulder regions of the occupant can be absorbed. 
     Herein, as shown in  FIG.  5    and  FIG.  6   , a right end portion of the cross member  15  is fixed by welding to a front side of the right vertical pipe portion  13  of the upper frame  10 , and in a position directly below it, a mount bracket  61  for the side air bag device  60  as one example of an attachment is fixed thereto by welding. To be more specific, the mount bracket  61  is welded to an area at a laterally inner side (i.e., left side) of an outer peripheral surface of the vertical pipe portion  13 . 
     The mount bracket  61 , which is made of sheet metal, protrudes from the front side of the vertical pipe portion  13  frontward along a direction in which the side frame main body portion  21  juts out. The mount bracket  61  is provided with flanges  61 A,  61 B protruding therefrom inward at upper and lower edges thereof, respectively, to thereby have a U-shaped cross section, thus possessing a great rigidity. The mount bracket  61  has a slot  61 C formed therein, and the direction of the length of the slot  61 C is parallel to the direction of the length of the vertical pipe portion  13 . To the slot  61 C of the mount bracket  61 , an upper end portion of the side air bag device  60  disposed to extend along the right side surface of the side frame main body portion  21  and the vertical pipe portion  13  is fixed through a bolt-nut arrangement BN applied from a laterally outer side. 
     As described above, a portion at which the mount bracket  61  is fixed to the vertical pipe portion  13  is located at a laterally inner side of the vertical pipe portion  13 , and thus the portion at which the mount bracket  61  is fixed to the vertical pipe portion  13  is not exposed to the outside; therefore, the side air bag device  60  can be attached thereto from outside with increased ease. Furthermore, since the side air bag device  60  is disposed along the vertical pipe portion  13  of the side frame  20  and the slot  61 C is disposed to extend in parallel to the vertical pipe portion  13 , the side air bag device  60  is prevented from being misaligned in the front-rear direction even when a positioning error is introduced for the attachment. Accordingly, the side air bag device  60  can be arranged with the side frame  20  in such a manner as to achieve compactness, and the workability in attachment is improved due to allowance of the positioning error to be introduced for the attachment. 
     The side air bag device  60  includes webbing mounting hardware  62  for attaching webbing for restricting a direction of development of the air bag (not shown), to the side frame  20 . This webbing mounting hardware  62  is made of a rod bent in the shape of a vertically elongated letter U, and arranged to protrude to the pressure-receiving member  40  side, wherein an upper end portion thereof is fixed by welding to a position of the vertical pipe portion  13  adjacent to a portion to which the support tab  14  is fixed, and a lower end portion thereof is fixed to the side frame main body portion  21 . 
     The right extra-length portion  24  of the upper connecting wire  22  described above is bowed upward (toward a direction away from the webbing mounting hardware  62 ) so as not to interfere with the webbing mounting hardware  62 , and a right end portion of this upper connecting wire  22  is connected to a high-rigidity portion of the vertical pipe portion  13 , that is, a position adjacent to a spot at which the webbing mounting hardware  62  is welded thereto, whereby the strength of connection of the upper connecting wire  22  is enhanced. 
     As shown in  FIG.  7    and  FIG.  8   , the seat back S 2  is provided with a seat back pad  70  made of a cushion material such as urethane foam covered with a skin material  80  made of synthetic leather, fabric, or the like. This seat back pad  70  covers at least a front side of the pressure-receiving member  40  and the seat back frame F 2  which constitute a frame of the seat back S 2 . 
     The seat back pad  70  has a configuration in which a central portion  71  facing a back of an upper portion of an occupant, and left and right side portions  72 ,  72  jutting out from the left and right sides of the central portion  71  in an obliquely frontward and outward direction are continuously provided, and grooves  73  for tucking the skin material  80  therein are formed at borders between the central portion  71  and the left and right side portions  72 ,  72 . In order to allow the central portion  71  of the seat back pad  70  to easily move rearward together with the pressure-receiving member  40 , relative to the left and right side portions  72 ,  72  of the seat back pad  70 , the bottoms of the grooves  73  have a plurality of slot holes  74  as an example of holes pierced therethrough and arranged along the grooves  73  (see  FIG.  7   , in particular). 
     In the seat back pad  70  as described above, tuck-in wires  76  for tucking the skin material  80  in by means of hook members  75  are embedded by an insert molding process. The tuck-in wires  76  include a plurality of tuck-in portions  76 A provided along the grooves  73 , and bent detour portions  76 B as an example of connecting portions which detour around the respective slot holes  74  and connecting the plurality of tuck-in portions  76 A. The tuck-in portions  76 A are embedded in the seat back pad  70  in a bent state such that the tuck-in portions  76 A are partially exposed (or slightly embedded) through a plurality of windows  77  provided in the bottoms of the grooves  73 . Supposing that the tuck-in wires  76  were configured to detour around the slot holes  74  to a laterally outer side (side portion  72  side), they should be bent three-dimensionally (not in a plane) so as to be routed along the frontwardly jutting shape of the side portion  72 , but they are herein configured to detour to the central portion  71  side, and can thus be configured to be bent in a plane, so that the productivity can be improved. As shown in  FIG.  8   , the tuck-in wires  76  have a portion overlapping the pressure-receiving member  40  as viewed from a front-rear direction. Therefore, when a load is applied to the tuck-in wires from the front, the pressure-receiving member receives this load, so that unevenly balanced imposition of the load on the tuck-in wires can be suppressed. 
     Herein, in order to make it possible to effectively transmit a rearward motion load generated when the upper body of an occupant moves rearward, from the central portion  71  of the seat back pad  70  to the whole pressure-receiving member  40 , the grooves  73  and the slot holes  74  are disposed in positions outside relative to the pressure-receiving member  40  and inside relative to the left or right side frame  20  with respect to the lateral direction. In order to make it possible to transmit the rearward motion load from the central portion  71  of the seat back pad  70  to the extra-length portions  24  of the upper connecting wire  22 , a pair of left and right slot holes  74  disposed in the highest positions among the plurality of slot holes  74  are arranged in positions facing the extra-length portions  24  of the upper connecting wire  22  (see  FIG.  3   ). 
     The webbing mounting hardware  62  is disposed rearwardly of the side portions  72 . 
     Next, referring to a car seat S configured as one embodiment of a vehicle seat according to the present invention, its operation and advantageous effects will be described. During a normal driving operation of a relevant car in which the car seat S shown in  FIG.  1    is installed as a driver&#39;s seat, in many cases, an occupant P seated on the seat cushion S 1  is usually postured in an in-seat position with his/her head slightly separate frontward from the headrest S 3 , as shown in  FIG.  9   . 
     When the relevant car with the occupant P having such an in-seat posture is rear-ended by another car or the rear end of the relevant car being reversed strikes another car or a construct, a rearward motion load of a predetermined magnitude or greater received from the upper body of the occupant P and acting on the seat back S 2  causes the pressure-receiving member  40  to move rearward together with the seat back pad  70  relative to the seat back frame F 2 . Accordingly, the upper body of the occupant P subsides into the seat back S 2  as shown in  FIG.  10   . During this time, the upper body of the occupant P becomes curved with his/her back being hunched, after the shoulder regions of the occupant P subside slightly into the seat back S 2 , because the bent portions  16 ,  17  of the cross member  15  are disposed slightly rearwardly relative to the pressure-receiving member  40 ; thus, the head of the occupant can be swiftly brought close to the headrest S 3 , and received by the headrest S 3 . 
     Furthermore, when the upper body of the occupant P subsides deeply into the seat back S 2  according to the rear-end collision load, the left and right bent portions  16 ,  17  of the cross member  15  and the left and right upwardly bowed extra-length portions  24 ,  24  of the upper connecting wire  22  operate together in harmony so as to receive and suppress the rearwardly moving shoulder regions of the occupant P. Therefore, in an intense rear-end collision, as shown in  FIG.  11   , the upper body of the occupant P subsides into the seat back S 2  while keeping his/her safe in-seat posture with his/her back being hunched. In case that the rearward motion load received from the shoulder regions of the occupant P by the left and right bent portions  16 ,  17  is extraordinary great, the bent portions  16 ,  17  are caused to pivot about the axial line of the cross member  15  and undergo plastic deformation, so that the shock given to the shoulder regions of the occupant P can be absorbed. 
     When the upper body of the occupant P subsides into the seat back S 2 , the left and right extra-length portions  24 ,  24  of the upper connecting wire  22  warp rearward while acting as a torsion spring, and extend greatly; therefore, the rearward motion stroke of the pressure-receiving member increases, and the upper body of the occupant P subsides more deeply into the seat back S 2 . Herein, the upper connecting wire  22  is arranged in such a manner that the right end portion thereof is connected to a position adjacent to a high-rigidity portion of the right vertical pipe portion  13  of the upper frame  10 , that is, a portion to which the webbing mounting hardware  62  of the side air bag device  60  is fixed by welding. Therefore, the upper connecting wire  22  can effectively receive the rearward motion load on the pressure-receiving member  40 . Since the extra-length portions  24 ,  24  are disposed in positions facing the slot holes  74 , a region in which the upper connecting wire  22  deforms when the pressure-receiving member  40  moves rearward and a region in which the seat back pad  70  deforms at the same time coincide substantially with each other, and thus the seat back pad  70  and the extra-length portion  24  are easily deformable, so that the rearward motion of the pressure-receiving member  40  is rendered smooth. 
     Furthermore, when the upper body of the occupant P subsides into the seat back S 2 , the side frame main body portions  21  which constitute pad shape retainer portions and the mount bracket  61  for the side air bag device  60  fixed to the vertical pipe portion  13  which mount bracket is provided above the side frame main body portion  21  are configured to operate in harmony so as to constrain the upper and lower portions of the both side portions of the seat back pad  70  to some extent, thus suppressing the rearward deformation of these portions; therefore, the seat back pad  70  is easy to deform so that its midsection in the height direction thereof deforms rearward without undue strain. Accordingly, it becomes likely that the rearward motion load is transmitted from the central portion  71  of the seat back pad  70  to the pressure-receiving member  40  entirely without fail, so that the upper body of the occupant P subsides into the seat back S 2  sufficiently, and the clearance between the occupant P and the headrest S 3  swiftly decreases. 
     In addition, when the upper body of the occupant P subsides into the seat back S 2 , the central portion  71  of the seat back pad  70  which faces the back of the upper body of the occupant P moves rearward easily and sufficiently relative to the left and right side portions  72 ,  72  of the seat back pad  70 , which are defined therefrom by the borders at the grooves  73  in which a plurality of the slot holes  74  are formed. Accordingly, it becomes likely that the rearward motion load is transmitted from the central portion  71  of the seat back pad  70  to the pressure-receiving member  40  entirely without fail, so that the upper body of the occupant P subsides into the seat back S 2  sufficiently. However, since the webbing mounting hardware  62  is disposed rearwardly of the side portion  72 , excessive rearward deformation of the side portion  76  is suppressed. 
     Consequently, according to one embodiment of the car seat S, the tilting-back of the head of the occupant P can be suppressed sufficiently and effectively, moreover, the head of the occupant P can be received by the headrest S 3  sufficiently and effectively, and the shock to be given to the neck of the occupant can be reduced sufficiently and effectively. Furthermore, since the rearward motion load given from the shoulder regions of the occupant P and acting on the seat back S 2  is received by the left and right bent portions  16 ,  17  of the cross member  15  in a well-balanced fashion, the occupant P can be kept in a stabilized in-seat posture. 
     Since the tuck-in wire  76  detours around the slot holes  74 , the tuck-in wire  76  is not exposed through the slot holes  74 , so that exposed portions of the tuck-in wire  76  is reduced and thus adhesion between tuck-in wire  76  and the seat back pad  70  is improved, and damage of the seat back pad  70  at the edges of the seat back pad  70  adjoining the tuck-in wire  76  is suppressed. 
     Since the extra-length portions  24  are bowed toward directions away from the webbing mounting hardware  62 , interference of the extra-length portions  24  with the webbing mounting hardware  62  is prevented, and thus the workability in attachment of the upper connecting wire  22  is improved. 
     Although a description has been given of a car seat S as one embodiment of a vehicle seat according to the present invention, the vehicle seat according to the present invention is not limited to the one embodiment of the car seat S, and the configurations may be modified where appropriate. For example, a car seat of a bucket type may be applicable which includes no reclining mechanism RL and comprises a seat cushion S 1 , a seat back S 2  and a headrest S 3  that are integrally constructed together. 
     The vehicle seat according to the present invention may be configured as a seat for a ship or for an aircraft. 
     The number of the bent portions  16 ,  17  may not be limited to the total four as in an illustrated embodiment in which the bent portions are bilaterally symmetrically arranged, but may be two or three. 
     The extra-length portion  24  in one embodiment is illustrated to have an upwardly bowed U-shape (like an inverted U), but may alternatively have a frontwardly or rearwardly bowed shape or a downwardly bowed shape. The two end portions of the connecting wire  22  which are connected to the side frames  20  may be disposed in a position lower than the middle portion supporting the pressure-receiving member  40 . 
     The tuck-in wire  76  in one embodiment is configured to detour around the slot holes  74  toward a laterally center side, but may be configured to detour toward a laterally outer side. 
     In the above-described embodiment, the side air bag device  60  is illustrated as an example of an attachment, but a motor or a sensor may be adopted as an attachment.