Patent Publication Number: US-2023147969-A1

Title: Vehicle seat

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is the U.S. National Stage entry of International Application No. PCT/JP2021/016016 filed under the Patent Cooperation Treaty on Apr. 20, 2021, which claims priority to U.S. Provisional Pat. Application No. 63/013770 filed on Apr. 22, 2020 and Japanese Patent Application No. 2020-114675 filed on Jul. 2, 2020, both of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a vehicle seat. 
     BACKGROUND ART 
     Patent Document 1 discloses a seat back including a lumber support member and left and right shoulder support members. The left and right shoulder support members are integrally formed at an upper end of the lumber support member. Patent Document 2 discloses a seat back including a single shoulder support member that extends laterally. In Patent Document 2, the shoulder support member is independent from the lumber support member and is joined to the blower. 
     PRIOR ART DOCUMENT(S) 
     Patent Document(s) 
     [Patent Document 1] JP2015-209082A [Patent Document 2] JP2015-209062A 
     SUMMARY OF THE INVENTION 
     Task to be Accomplished by the Invention 
     The shoulder support member can support the seated person comfortably by moving and deforming along the shoulder portion of the seated person. However, since the shoulder support member of Patent Document 1 is joined to the lumber support member, there is a problem that it is difficult to move and deform. Similarly, the shoulder support member of Patent Document 2 is joined to the blower, and therefore, there is a problem that it is difficult to move and deform. Accordingly, there is a problem that the shoulder support members of Patent Documents 1 and 2 cannot support the shoulder portion of the seated person comfortably. 
     In view of the foregoing background, an object of the present invention is to provide a vehicle seat capable of supporting the shoulder portion of the seated person comfortably. 
     Means to Accomplish the Task 
     To achieve the above object, there is provided a vehicle seat ( 1 ) provided with a seat cushion ( 3 ) and a seat back ( 4 ), wherein the seat back comprises: left and right side members ( 22 ) extending up and down; a lower cross member ( 24 ) extending laterally and joined to the left and right side members; a cross member ( 25 ) extending laterally above the lower cross member and joined to the left and right side members; at least one wire member ( 31 ) extending up and down and joined to the lower cross member and the cross member; and at least one shoulder support member ( 32 ) supported on an upper portion of the wire member, and the shoulder support member comprises: a first plate part ( 32 A) facing in a front-rear direction and joined to the upper portion of the wire member; and a second plate part ( 32 C) facing in the front-rear direction and connected to the first plate part via a flexible part ( 32 B). 
     According to this aspect, the second plate part can be displaced relative to the first plate part with deformation of the flexible part. Therefore, when the shoulder support member is pushed by the shoulder portion of the seated person, the first plate part and the second plate part can move to be along the shoulder portion. Thereby, a vehicle seat capable of supporting the shoulder portion of the seated person comfortably can be provided. 
     In the above aspect, preferably, a plate-shaped lumber support member ( 44 ) facing in the front-rear direction is supported on a lower portion of the wire member. 
     According to this aspect, it is possible to support the shoulder support member by using the wire member supporting the lumber support member. 
     In the above aspect, preferably, the wire member includes a first portion ( 31 A) and a second portion ( 31 B) that are inclined relative to each other via a bending portion, and the first plate part of the shoulder support member includes a first locking portion ( 34 ) that locks the first portion and a second locking portion ( 35 ) that locks the second portion. 
     According to this aspect, since the first locking portion and the second locking portion lock the first portion and the second portion that are inclined relative to each other, the position of the shoulder member relative to the wire member can be fixed. 
     In the above aspect, preferably, the first plate part of the shoulder support member includes a positioning part ( 36 ) between the first locking portion and the second locking portion, the positioning part contacting the first portion and the second portion. 
     According to this aspect, due to the positioning part contacting the first portion and the second portion, the position of the shoulder member relative to the wire member can be fixed even more reliably. 
      In the above aspect, preferably, the first plate part and the flexible part are disposed between the left and right side members as seen from front, and at least a part of the second plate part is disposed in front of the side member. 
     According to this aspect, the first plate can be displaced rearward relative to the second plate part along the back of the seated person. 
     In the above aspect, preferably, the flexible part extends up and down along a laterally inner side edge of the side member as seen from front. 
     According to this aspect, the first plate part can be displaced rearward without interfering with the side member. 
     In the above aspect, preferably, the flexible part has a slit ( 39 ) penetrating therethrough in the front-rear direction and extending up and down with a lower end opened. 
     According to this aspect, the first plate part can be easily displaced relative to the second plate part. 
     In the above aspect, preferably, a fluid bag assembly ( 52 ) that inflates upon supply of fluid is provided on a front surface of the shoulder support member. 
     According to this aspect, the fluid bag can change the shape of the pad disposed in front of the shoulder support member. Thereby, the vehicle seat can support the shoulder portion of the seated person comfortably. 
     In the above aspect, preferably, the shoulder support member includes a support surface ( 32 F) extending along a first direction and facing forward, a fluid supply device ( 53 ) is connected to the fluid bag assembly, one side in the first direction is referred to as a first side and another side in the first direction is referred to as a second side, the fluid bag assembly comprises: a first fluid bag ( 56 ) disposed on the support surface; a second fluid bag ( 57 ) which includes, in an end portion on the first side, a first joining part ( 61 ) joined to the first fluid bag, and communicates with the first fluid bag; and a third fluid bag ( 58 ) which includes, in an end portion on the first side, a second joining part ( 62 ) joined to the second fluid bag, and communicates with the second fluid bag, and in a state in which the fluid bag assembly is deflated, a first side edge ( 61 A), which is a side edge of the first joining part on the second side, and a second side edge ( 62 A), which is a side edge of the second joining part on the second side, each extend linearly and extend in mutually different directions, as seen in a direction perpendicular to the support surface. 
     According to this aspect, since the first side edge and the second side edge extend in mutually different directions, it is possible to vary the inflation direction of the second fluid bag and the inflation direction of the third fluid bag. Thereby, the shape of the fluid bag assembly when inflated can be diversified. 
     In the above aspect, preferably, the second side edge is disposed further on the second side than the first side edge. 
     According to this aspect, the shape of the fluid bag assembly when inflated can be diversified. 
     In the above aspect, preferably, a length of the second fluid bag in the first direction is longer than a length of the third fluid bag in the first direction. 
     According to this aspect, the shape of the fluid bag assembly when inflated can be diversified. 
     In the above aspect, preferably, the fluid supply device is connected to the first fluid bag, the first fluid bag and the second fluid bag are connected by a first communication hole ( 61 B) passing through the first joining part, and the second fluid bag and the third fluid bag are connected by a second communication hole ( 62 B) passing through the second joining part. 
     According to this aspect, the structure for connecting the air supply device and the fluid bag assembly can be made simple. 
     In the above aspect, preferably, the first fluid bag, the second fluid bag, and the third fluid bag extend in the first direction. 
     According to this aspect, the shape of the fluid bag assembly when deflated can be made simple. 
     In the above aspect, preferably, the first fluid bag includes a tab ( 56 D) protruding to a side, and the tab is fastened to a side surface perpendicular to the support surface of the shoulder support member. 
     According to this aspect, the shoulder support can be made compact in size and the fluid bag assembly can be made compact in size. 
      In the above aspect, preferably, the shoulder support member includes a pair of left and right shoulder support members and the fluid bag assembly includes a pair of left and right fluid bag assemblies, the left and right shoulder support members are disposed on a left part and a right part of an upper portion of the seat back such that the first side is directed laterally inward and downward, and in the state in which the fluid bag assembly is deflated, each of the first side edge and the second side edge extends obliquely downward in a laterally outward direction, as seen from front. 
     According to this aspect, the fluid bag assemblies can make parts of the seat back corresponding to the shoulders of the seated person swell laterally inward and downward. Thereby, a seat back in conformity with the position and shape of the shoulders of the seated person can be provided. 
     In the above aspect, preferably, the second plate part and the side member contact each other in the front-rear direction. 
     According to this aspect, the position of the second plate part in the seat back can be fixed. 
     In the above aspect, preferably, the second plate part extends along the side member as seen from front. 
     According to this aspect, since the second plate member exists between the shoulder portion of the seated person and the side member, the shoulder portion of the seated person can be supported comfortably. 
      In the above aspect, preferably, the second plate part includes a butting portion ( 37 ) that protrudes rearward in a rear portion thereof, and the second plate part contacts the side member at the butting portion. 
     According to this aspect, the second plate part and the side member can reliably contact each other. 
     In the above aspect, preferably, the second plate part and the side member contact each other in the front-rear direction via a cushioning material ( 38 ). 
     According to this aspect, the cushioning material prevents friction and rattling between the second plate part and the side member, whereby generation of noise is prevented. 
     In the above aspect, preferably, a rear surface of the second plate part is provided with a reinforcement structure ( 41 ). 
     According to this aspect, it is possible to improve the stiffness of the second plate part that contacts the side member. 
     In the above aspect, preferably, the wire member includes a pair of left and right wire members, and the shoulder support member includes a pair of left and right shoulder support members corresponding to the left and right wire members. 
     According to this aspect, the left and right shoulder support members can be displaced independently from each other so as to be along the shoulder portion of the seated person. Thereby, a vehicle seat capable of supporting the shoulder portion of the seated person comfortably can be provided. 
     In the above aspect, preferably, a laterally inner side edge of the first plate part is inclined laterally outward toward an upward direction. 
     According to this aspect, a space can be formed between upper portions of the left and right shoulder supports. Devices such as a blower may be disposed in the space 
     In the above aspect, preferably, a blower ( 46 ) is provided in a central portion of an upper portion of the seat back, and the left and right shoulder supports are disposed to left and right of the blower. 
     According to this aspect, the fluid bag assembly and the blower can be disposed within the seat back so as not to interfere with each other. 
     In the above aspect, preferably, the blower includes: a blower main body ( 36 ) provided with an impeller; and a duct ( 46 B) extending from the blower main body, wherein the blower main body is disposed in the central portion of the upper portion of the seat back, the duct extends up and down on a side of the blower main body, and one of the left and right shoulder supports is disposed to left or right of the duct. 
     According to this aspect, the fluid bag assembly and the blower can be disposed within the seat back so as not to interfere with each other. 
      In the above aspect, preferably, one of left and right side portions of the seat back is provided with a first side airbag ( 48 ), another of the left and right side portions of the seat back is provided with a second side airbag ( 49 ), each of the first side airbag and the second side airbag extends up and down, an upper end of the first side airbag is positioned higher than an upper end of the second side airbag, and a lower end of each of the left and right shoulder supports is positioned higher than the upper end of the second side airbag. 
     According to this aspect, the fluid bag assembly and the side airbag can be disposed within the seat back so as not to interfere with each other. 
     In the above aspect, preferably, each of the left and right fluid bag assemblies has a recess that is recessed laterally outward on a laterally inner side edge thereof, and left and right side portions of the blower are disposed in the respective recesses. 
     According to this aspect, the fluid bag assemblies and the blower can be disposed at a high density. 
     Effect of the Invention 
     To achieve the above object, there is provided a vehicle seat ( 1 ) provided with a seat cushion ( 3 ) and a seat back ( 4 ), wherein the seat back comprises: left and right side members ( 22 ) extending up and down; a lower cross member ( 24 ) extending laterally and joined to the left and right side members; a cross member ( 25 ) extending laterally above the lower cross member and joined to the left and right side members; at least one wire member ( 31 ) extending up and down and joined to the lower cross member and the cross member; and at least one shoulder support member ( 32 ) supported on an upper portion of the wire member, and the shoulder support member comprises: a first plate part ( 32 A) facing in a front-rear direction and joined to the upper portion of the wire member; and a second plate part ( 32 C) facing in the front-rear direction and connected to the first plate part via a flexible part ( 32 B). 
     According to this aspect, the second plate part can be displaced relative to the first plate part with deformation of the flexible part. Therefore, when the shoulder support member is pushed by the shoulder portion of the seated person, the first plate part and the second plate part can move to be along the shoulder portion. Thereby, a vehicle seat capable of supporting the shoulder portion of the seated person comfortably can be provided. 
     In the above aspect, preferably, a plate-shaped lumber support member ( 44 ) facing in the front-rear direction is supported on a lower portion of the wire member. 
     According to this aspect, it is possible to support the shoulder support member by using the wire member supporting the lumber support member. 
     In the above aspect, preferably, the wire member includes a first portion ( 31 A) and a second portion ( 31 B) that are inclined relative to each other via a bending portion, and the first plate part of the shoulder support member includes a first locking portion ( 34 ) that locks the first portion and a second locking portion ( 35 ) that locks the second portion. 
     According to this aspect, since the first locking portion and the second locking portion lock the first portion and the second portion that are inclined relative to each other, the position of the shoulder member relative to the wire member can be fixed. 
     In the above aspect, preferably, the first plate part of the shoulder support member includes a positioning part ( 36 ) between the first locking portion and the second locking portion, the positioning part contacting the first portion and the second portion. 
      According to this aspect, due to the positioning part contacting the first portion and the second portion, the position of the shoulder member relative to the wire member can be fixed even more reliably. 
     In the above aspect, preferably, the first plate part and the flexible part are disposed between the left and right side members as seen from front, and at least a part of the second plate part is disposed in front of the side member. 
     According to this aspect, the first plate can be displaced rearward relative to the second plate part along the back of the seated person. 
     In the above aspect, preferably, the flexible part extends up and down along a laterally inner side edge of the side member as seen from front. 
     According to this aspect, the first plate part can be displaced rearward without interfering with the side member. 
     In the above aspect, preferably, the flexible part has a slit ( 39 ) penetrating therethrough in the front-rear direction and extending up and down with a lower end opened. 
     According to this aspect, the first plate part can be easily displaced relative to the second plate part. 
     In the above aspect, preferably, a fluid bag assembly ( 52 ) that inflates upon supply of fluid is provided on a front surface of the shoulder support member. 
     According to this aspect, the fluid bag can change the shape of the pad disposed in front of the shoulder support member. Thereby, the vehicle seat can support the shoulder portion of the seated person comfortably. 
     In the above aspect, preferably, the shoulder support member includes a support surface ( 32 F) extending along a first direction and facing forward, a fluid supply device ( 53 ) is connected to the fluid bag assembly, one side in the first direction is referred to as a first side and another side in the first direction is referred to as a second side, the fluid bag assembly comprises: a first fluid bag ( 56 ) disposed on the support surface; a second fluid bag ( 57 ) which includes, in an end portion on the first side, a first joining part ( 61 ) joined to the first fluid bag, and communicates with the first fluid bag; and a third fluid bag ( 58 ) which includes, in an end portion on the first side, a second joining part ( 62 ) joined to the second fluid bag, and communicates with the second fluid bag, and in a state in which the fluid bag assembly is deflated, a first side edge ( 61 A), which is a side edge of the first joining part on the second side, and a second side edge ( 62 A), which is a side edge of the second joining part on the second side, each extend linearly and extend in mutually different directions, as seen in a direction perpendicular to the support surface. 
     According to this aspect, since the first side edge and the second side edge extend in mutually different directions, it is possible to vary the inflation direction of the second fluid bag and the inflation direction of the third fluid bag. Thereby, the shape of the fluid bag assembly when inflated can be diversified. 
     In the above aspect, preferably, the second side edge is disposed further on the second side than the first side edge. 
      According to this aspect, the shape of the fluid bag assembly when inflated can be diversified. 
     In the above aspect, preferably, a length of the second fluid bag in the first direction is longer than a length of the third fluid bag in the first direction. 
     According to this aspect, the shape of the fluid bag assembly when inflated can be diversified. 
     In the above aspect, preferably, the fluid supply device is connected to the first fluid bag, the first fluid bag and the second fluid bag are connected by a first communication hole ( 61 B) passing through the first joining part, and the second fluid bag and the third fluid bag are connected by a second communication hole ( 62 B) passing through the second joining part. 
     According to this aspect, the structure for connecting the air supply device and the fluid bag assembly can be made simple. 
     In the above aspect, preferably, the first fluid bag, the second fluid bag, and the third fluid bag extend in the first direction. 
     According to this aspect, the shape of the fluid bag assembly when deflated can be made simple. 
     In the above aspect, preferably, the first fluid bag includes a tab ( 56 D) protruding to a side, and the tab is fastened to a side surface perpendicular to the support surface of the shoulder support member. 
     According to this aspect, the shoulder support can be made compact in size and the fluid bag assembly can be made compact in size. 
     In the above aspect, preferably, the shoulder support member includes a pair of left and right shoulder support members and the fluid bag assembly includes a pair of left and right fluid bag assemblies, the left and right shoulder support members are disposed on a left part and a right part of an upper portion of the seat back such that the first side is directed laterally inward and downward, and in the state in which the fluid bag assembly is deflated, each of the first side edge and the second side edge extends obliquely downward in a laterally outward direction, as seen from front. 
     According to this aspect, the fluid bag assemblies can make parts of the seat back corresponding to the shoulders of the seated person swell laterally inward and downward. Thereby, a seat back in conformity with the position and shape of the shoulders of the seated person can be provided. 
     In the above aspect, preferably, the second plate part and the side member contact each other in the front-rear direction. 
     According to this aspect, the position of the second plate part in the seat back can be fixed. 
     In the above aspect, preferably, the second plate part extends along the side member as seen from front. 
      According to this aspect, since the second plate member exists between the shoulder portion of the seated person and the side member, the shoulder portion of the seated person can be supported comfortably. 
     In the above aspect, preferably, the second plate part includes a butting portion ( 37 ) that protrudes rearward in a rear portion thereof, and the second plate part contacts the side member at the butting portion. 
     According to this aspect, the second plate part and the side member can reliably contact each other. 
     In the above aspect, preferably, the second plate part and the side member contact each other in the front-rear direction via a cushioning material ( 38 ). 
     According to this aspect, the cushioning material prevents friction and rattling between the second plate part and the side member, whereby generation of noise is prevented. 
     In the above aspect, preferably, a rear surface of the second plate part is provided with a reinforcement structure ( 41 ). 
     According to this aspect, it is possible to improve the stiffness of the second plate part that contacts the side member. 
     In the above aspect, preferably, the wire member includes a pair of left and right wire members, and the shoulder support member includes a pair of left and right shoulder support members corresponding to the left and right wire members. 
     According to this aspect, the left and right shoulder support members can be displaced independently from each other so as to be along the shoulder portion of the seated person. Thereby, a vehicle seat capable of supporting the shoulder portion of the seated person comfortably can be provided. 
     In the above aspect, preferably, a laterally inner side edge of the first plate part is inclined laterally outward toward an upward direction. 
     According to this aspect, a space can be formed between upper portions of the left and right shoulder supports. Devices such as a blower may be disposed in the space. 
     In the above aspect, preferably, a blower ( 46 ) is provided in a central portion of an upper portion of the seat back, and the left and right shoulder supports are disposed to left and right of the blower. 
     According to this aspect, the fluid bag assembly and the blower can be disposed within the seat back so as not to interfere with each other. 
     In the above aspect, preferably, the blower includes: a blower main body ( 36 ) provided with an impeller; and a duct ( 46 B) extending from the blower main body, wherein the blower main body is disposed in the central portion of the upper portion of the seat back, the duct extends up and down on a side of the blower main body, and one of the left and right shoulder supports is disposed to left or right of the duct. 
      According to this aspect, the fluid bag assembly and the blower can be disposed within the seat back so as not to interfere with each other. 
     In the above aspect, preferably, one of left and right side portions of the seat back is provided with a first side airbag ( 48 ), another of the left and right side portions of the seat back is provided with a second side airbag ( 49 ), each of the first side airbag and the second side airbag extends up and down, an upper end of the first side airbag is positioned higher than an upper end of the second side airbag, and a lower end of each of the left and right shoulder supports is positioned higher than the upper end of the second side airbag. 
     According to this aspect, the fluid bag assembly and the side airbag can be disposed within the seat back so as not to interfere with each other. 
     In the above aspect, preferably, each of the left and right fluid bag assemblies has a recess that is recessed laterally outward on a laterally inner side edge thereof, and left and right side portions of the blower are disposed in the respective recesses. 
     According to this aspect, the fluid bag assemblies and the blower can be disposed at a high density. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of a seat according to an embodiment; 
         FIG.  2    is a perspective view of a frame of the seat according to the embodiment; 
         FIG.  3    is a front view of a seat back frame; 
         FIG.  4    is a front view of the seat back frame with fluid bags omitted; 
         FIG.  5    is a perspective view showing a fluid bag assembly and a shoulder support member; 
         FIG.  6    is a perspective view showing a rear surface of the shoulder support member; 
         FIG.  7    is a rear view of an upper portion of the seat back frame; 
         FIG.  8    is an exploded perspective view of the fluid bag assembly; 
         FIG.  9    is an explanatory diagram for showing the fluid bag assembly (A) in a deflated state, (B) in a partially inflated state, (C) in an inflated state; 
         FIG.  10    is a sectional view of the fluid bag assembly in the inflated state; 
         FIG.  11    is a perspective view showing a rear surface of a shoulder support member according to a modification; 
         FIG.  12    is a sectional view of the fluid bag assembly in the inflated state; 
         FIG.  13    is a sectional view of the fluid bag assembly in the inflated state; and 
         FIG.  14    is a front view of a seat back frame according to a partially modified embodiment. 
     
    
    
     MODE(S) FOR CARRYING OUT THE INVENTION 
     In the following, an embodiment in which a vehicle seat according to the present invention is applied to a seat of an automobile will be described with reference to the drawings. In the following description, an up-down direction is a direction along the vertical direction. Also, a front-rear direction is a direction perpendicular to the vertical direction, a direction in which the seat back is positioned relative to the seat cushion is a rearward direction, and the direction opposite to the rearward direction is a forward direction. Also, a lateral direction is a direction perpendicular to the up-down direction and the front-rear direction and is defined based on the forward direction. 
      As shown in  FIG.  1   , a seat  1  includes a seat cushion  3  provided on a floor  2  of an automobile and a seat back  4  extending upward from a rear portion of the seat cushion  3 . The seat cushion  3  supports the buttocks of an occupant and the seat back  4  supports the back of the occupant. As shown in  FIG.  2   , the seat cushion  3  may be provided on the floor  2  via a slide rail  5  The slide rail  5  includes left and right lower rails  5 A joined to the floor  2  and left and right upper rails  5 B supported by the left and right lower rails  5 A, respectively, to be slidingly movable. The seat cushion  3  is joined to the left and right upper rails  5 B. A lift device may be interposed between the seat cushion  3  and the upper rails  5 B. 
     The seat cushion  3  includes a seat cushion frame  11  forming a skeleton, a pad  12  supported on the seat cushion frame  11 , and a skin member  13  covering a surface of the pad  12 . The seat back  4  includes a seat back frame  15  forming a skeleton, a pad  16  supported on the seat back frame  15 , and a skin member  17  covering a surface of the pad  16 . The seat cushion frame  11  and the seat back frame  15  are coupled to each other via a reclining device  19  and constitute a frame  20  of the seat  1 . In the following description, the seat back  4  is disposed in an initial position in which the seat back  4  extends up and down. 
     As shown in  FIGS.  2  and  3   , the seat back frame  15  includes left and right back side members  22  extending up and down, an upper cross member  23  extending laterally and joined to an upper end of each of the left and right back side members  22 , a lower cross member  24  extending laterally and joined to a lower portion of each of the left and right back side members  22 , and a middle cross member  25  extending laterally between the upper cross member  23  and the lower cross member  24  and joined to each of the left and right back side members  22 . 
     The lower portions of the left and right back side members  22  are formed of sheet metal members having surfaces facing left and right. The upper portions of the left and right back side members  22  and the upper cross member  23  are formed of a continuous pipe member. The pipe member includes a laterally extending central portion and left and right end portions bent relative to the central portion and extending downward. The left and right end portions of the pipe member are joined to surfaces of the left and right sheet metal members that face laterally inward. 
     The upper cross member  23  is provided with a pair of left and right headrest support members  27 . Each of the headrest support members  27  is formed in a tubular shape and extends up and down. Each of the headrest support members  27  is joined to the front surface of the upper cross member  23  by welding or the like. The headrest support members  27  are disposed in a laterally central portion of the upper cross member  23  to be spaced laterally. A resin collar (not shown in the drawings) is fitted on each of the headrest support members  27 . A pair of left and right pillars  29 A (see  FIG.  1   ) that extend from the headrest  29  are inserted into the headrest support members  27  via the collars and are supported thereby. 
     As shown in  FIGS.  2  and  3   , the seat back frame  15  includes at least one wire member  31  extending up and down and joined to the lower cross member  24  and the middle cross member  25 . In the present embodiment, a pair of left and right wire members  31  is provided. Each wire member  31  is made of a metal rod and has flexibility. The left and right wire members  31  each include a first portion and a second portion that are inclined relative to each other via a bending portion. In the present embodiment, the left and right wire members  31  each include an upper end portion  31 A joined to one of the left and right end portions of the middle cross member  25  and extending downward, an upper intermediate portion  31 B extending from the lower end of the upper end portion  31 A laterally inward and downward in an oblique manner, a lower intermediate portion  31 C extending downward from the lower end of the upper intermediate portion  31 B, and a lower end portion  31 D extending from the lower end of the lower intermediate portion  31 C laterally outward and downward and joined to the lower cross member  24 . The upper end portion  31 A and the upper intermediate portion  31 B are inclined relative to each other via a bending portion. Thus, the upper end portion  31 A corresponds to the first portion, and the upper intermediate portion  31 B corresponds to the second portion. The left and right lower end portions  31 D may be joined to each other by a connecting portion  31 E. 
      As shown in  FIG.  4   , at least one shoulder support member  32  is provided on the upper portions of the wire members  31 . In the present embodiment, a pair of left and right shoulder support members  32  are provided on the laterally corresponding wire members  31 . 
     The left and right shoulder support members  32  are preferably made of metal or resin, for example. In the present embodiment, the shoulder support members  32  are made of resin. The left and right shoulder support members  32  are formed in bilaterally symmetrical shapes. In the following, description will be made of the right shoulder support member  32 . 
     As shown in  FIGS.  4  to  6   , the shoulder support member  32  includes a first plate part  32 A facing in the front-rear direction and joined to the upper portion of the wire member  31  and a second plate part  32 C facing in the front-rear direction and connected to the first plate part  32 A via a flexible part  32 B. In the right shoulder support member  32 , the first plate part  32 A extends obliquely rightward and upward, the second plate part  32 C is disposed to the right and extends up and down, and the flexible part  32 B extends up and down between the first plate part  32 A and the second plate part  32 C. A laterally inner side edge  32 D of the first plate part  32 A is inclined laterally outward toward the upward direction. The inner side edge  32 D of the first plate part  32 A is provided with a plate-shaped fastening part  32 E that protrudes rearward. The fastening part  32 E extends along the inner side edge  32 D. 
     The flexible part  32 B has a flexibility higher than the flexibilities of the first plate part  32 A and the second plate part  32 C. With elastic deformation of the flexible part  32 B, the first plate part  32 A can be displaced relative to the second plate part  32 C. 
     As shown in  FIG.  6   , the first plate part  32 A includes a first locking portion  34  that lock the upper end portion  31 A as the first portion and a second locking portion  35  that locks the upper intermediate portion  31 B as the second portion. Further, the first plate part  32 A includes a positioning part  36  between the first locking portion  34  and the second locking portion  35  such that the positioning part  36  contacts the upper end portion  31 A and the upper intermediate portion  31 B. The first locking portion  34  includes a pair of first elastic claws  34 A protruding rearward from the rear surface of the first plate part  32 A and a first contact part  34 B protruding rearward from the rear surface of the first plate part  32 A. The pair of first elastic claws  34 A oppose each other and sandwich the upper end portion  31 A between them. The first contact part  34 B contacts the upper end portion  31 A sandwiched between the pair of first elastic claws  34 A from the front thereby to determine the position of the first plate part  32 A relative to the upper end portion  31 A. The pair of first elastic claws  34 A extend in the up-down direction. 
     The second locking portion  35  includes a pair of second elastic claws  35 A protruding rearward from the rear surface of the first plate part  32 A and a second contact part  35 B protruding rearward from the rear surface of the first plate part  32 A. The pair of second elastic claws  35 A oppose each other and sandwich the upper intermediate portion  31 B between them. The second contact part  35 B contacts the upper intermediate portion  31 B sandwiched between the pair of second elastic claws  35 A from the front thereby to determine the position of the first plate part  32 A relative to the upper intermediate portion  31 B. The pair of second elastic claws  35 A extend laterally inward and downward along the upper intermediate portion  31 B. 
     The positioning part  36  includes a tubular base portion  36 A protruding rearward from the rear surface of the first plate part  32 A and a wall portion  36 B protruding further rearward from a part of the rear end edge of the base portion  36 A. As seen from the rear, the wall portion  36 B extends up and down and is curved to be convex laterally inward. With the rear end edge of the base portion  36 A contacting the upper end portion  31 A and the upper intermediate portion  31 B from the front, the upper end edge of the wall portion  36 B contacting the upper end portion  31 A from the left, and the lower end edge of the wall portion  36 B contacting the upper intermediate portion  31 B from above and left, the position of the shoulder support member  32  relative to the wire member  31  is fixed. 
      As shown in  FIG.  4   , as seen from front, the first plate part  32 A and the flexible part  32 B are disposed between the left and right back side members  22 , and at least a part of the second plate part  32 C is disposed in front of the right back side member  22 . Preferably, the second plate part  32 C extends along the right back side member  22  As seen from front. The second plate part  32 C and the right back side member  22  contact each other in the front-rear direction. The second plate part  32 C includes a butting portion  37  that protrudes rearward in a rear portion thereof, and the second plate part  32 C contacts the right back side member  22  at the butting portion  37 . Preferably, the butting portion  37  is formed in a tubular shape extending rearward and contacts the front surface of the right back side member  22  at the rear end edge. 
     Preferably, the flexible part  32 B extends up and down along a laterally inner side edge of the right back side member  22  as seen from front. In the present embodiment, the flexible part  32 B has a slit  39  penetrating therethrough in the front-rear direction and extending up and down with a lower end opened. Due to the slit  39 , the first plate part  32 A and the second plate part  32 C are connected to each other at the upper end portions thereof via the flexible part  32 B. Thereby, the first plate part  32 A can be displaced forward and rearward relative to the lower portion of the second plate part  32 C. 
     An edge wall  42  that protrudes rearward may be provided on the edge part of the first plate part  32 A and the second plate part  32 C. The edge wall  42  improves the stiffness of the first plate part  32 A and the second plate part  32 C. 
     A lumber support member  44  having a plate shape and facing in the front-rear direction is supported on the lower portions of the wire members  31 . Namely, the left and right shoulder support members  32  are disposed on the lumber support member  44 . The lumber support member  44  is disposed in a lower portion of the seat back  4  and supports the hip of the occupant. Preferably, the lumber support member  44  is made of resin. 
      In the central portion of the upper portion of the seat back  4 , a blower  46  is provided. The blower  46  includes a blower main body  46 A provided with an impeller and a duct  46 B extending from the blower main body  46 A. The blower  46  is mounted to a bracket  46 C that is joined to at least one of the upper cross member  23  and the middle cross member  25 . In the present embodiment, the bracket  46 C extends up and down and has an upper end joined to a laterally central portion of the upper cross member  23  and a lower end joined to a laterally central portion of the middle cross member  25  The blower main body  46 A may be a centrifugal fan, for example. The blower main body  46 A is formed in a flat cylindrical shape and is fixed to the front surface of the bracket  46 C such that the axis thereof extends in the front-rear direction. The blower main body  46 A is disposed in the central portion of the upper portion of the seat back  4 . More specifically, the blower main body  46 A is disposed between the upper cross member  23  and the middle cross member  25 . Also, the blower main body  46 A is preferably disposed between the left and right headrest support members  27  with respect to the lateral direction. Further, the blower  46  is disposed between the left and right shoulder support members  32   
     The duct  46 B has one end joined to the central portion of the rear surface of the blower main body  46 A and another end forming a suction port  46 D. The duct  46 B includes a lateral part  46 E extending from the one end rightward behind the bracket  46 C and the right headrest support member  27  and a vertical part  46 F extending from the right end of the lateral part  46 E downward and forward. Namely, the duct  46 B extends up and down on the side of the blower main body  46 A. The suction port  46 D is provided at the lower end of the vertical part  46 F. The vertical part  46 F extends up and down at a position to the right of the blower main body  46 A, and the suction port  46 D is positioned lower than the lower end of the blower main body  46 A. In another embodiment, the lateral part  46 E may extend leftward from the one end so that the vertical part  46 F is disposed to the left of the blower main body  46 A. In the present embodiment, the blower main body  46 A takes in air from the central portion via the duct  46 B and discharges air from an outer circumferential portion. A duct through which the discharged air flows (not shown in the drawings) may be connected to the outer circumferential portion of the blower main body  46 A. In another embodiment, the duct  46 B may be omitted and the blower main body  46 A may take in air directly. 
     One of the left and right side portions of the seat back  4  is provided with a first side airbag  48 , and the other of the left and right side portions of the seat back  4  is provided with a second side airbag  49 . In the present embodiment, the first side airbag  48  is provided on the right side surface of the right back side member  22 , and the second side airbag  49  is provided on the left side surface of the left back side member  22 . Each of the first side airbag  48  and the second side airbag  49  extends up and down. The upper end of the first side airbag  48  is positioned higher than the upper end of the second side airbag  49 . Also, the first side airbag  48  is formed to be longer than the second side airbag  49  in the up-down direction. In the present embodiment, the seat  1  is a left seat of the vehicle, the first side airbag  48  is a far side airbag that is remote from the side wall of the vehicle, and the second side airbag  49  is a near side airbag that is close to the side wall of the vehicle. 
     In the seat  1 , fluid bag assemblies  52  that inflate and deflate are disposed between the frame  20  and the skin members  13 ,  17 . The fluid bag assemblies  52  are provided on the front surfaces of the shoulder support members  32 . In the present embodiment, a single fluid supply device  53  is connected to the left and right fluid bag assemblies  52 . The left fluid bag assembly  52  is disposed between the left shoulder support member  32  and the pad  16 , and the right fluid bag assembly  52  is disposed between the right shoulder support member  32  and the pad  16 . In the present embodiment, the fluid supplied to the fluid bag assembly  52  is air, and the fluid supply device  53  includes an air pump In another embodiment, the fluid may be a liquid such as water or oil. The fluid supply device  53  is preferably provided on the inner side surface of one of the left and right back side members  22 . Preferably, a driving device  19 A for driving the reclining device  19  is provided on the inner side surface of the other of the left and right back side members  22 . Namely, the fluid supply device  53  and the driving device  19 A are provided on the inner side surfaces of the different back side members  22 . Preferably, the driving device  19 A includes an electric motor and a speed reduction mechanism. 
      The shoulder support members  32  each include a support surface  32 F extending along a first direction and facing forward. The support surface F is consisted of the front surfaces of the first plate part  32 A, the flexible part  32 B, and the second plate part  32 C. Here, one side in the first direction is referred to as a first side and another side in the first direction is referred to as a second side. In the present embodiment, the left and right shoulder support members  32  are disposed on a left part and a right part of an upper portion of the seat back  4  such that the respective support surfaces  32 F face forward and the first side is directed laterally inward and downward. Each shoulder support member  32  includes a side surface  51 B perpendicular to the support surface  32 F. In the present embodiment, the shoulder support member  32  extends in the first direction. 
     The left and right shoulder support members  32  are disposed to the left and right of the blower  46 , respectively. Also, the left and right shoulder support members  32  are provided to the left and right of the duct  46 B. The right shoulder support member  32  is disposed to the right of the duct  46 B, and the left shoulder support member  32  is disposed to the left of the duct  46 B. Preferably, the lower ends of the left and right shoulder support members  32  are each positioned higher than the upper end of the lumber support member  44 . Also, preferably, the lower ends of the left and right shoulder support members  32  are each positioned higher than the upper end of the second side airbag  49 . 
     As shown in  FIGS.  5  and  8   , the fluid bag assembly  52  includes a first fluid bag  56 , a second fluid bag  57 , and a third fluid bag  58 . The first fluid bag  56  is disposed on the support surface  32 F of the shoulder support member  32 . The second fluid bag  57  includes, in an end portion on the first side, a first joining part  61  joined to the first fluid bag  56 , and communicates with the first fluid bag  56 . The third fluid bag  58  includes, in an end portion on the first side, a second joining part  62  joined to the second fluid bag  57 , and communicates with the second fluid bag  57 . Each of the first to third fluid bags  56  to  58  is formed by welding edge parts of superposed sheet materials. For example, the fluid bag may be formed of two sheet materials that are mutually superposed and the edge parts thereof are bonded to each other. Also, the fluid bag may be formed of a single sheet material that is folded such that the folded portions are superposed and the edge parts thereof are bonded to each other. 
     The first fluid bag  56  includes a first sheet  56 A and a second sheet  56 B that are mutually superposed. The first sheet  56 A and the second sheet  56 B are joined to each other by a third joining part  56 C which extends along the respective edge parts and forms a closed ring shape. The third joining part  56 C preferably is a part where the first sheet  56 A and the second sheet  56 B are welded or adhered to each other. Between the edge parts of the first sheet  56 A and the second sheet  56 B, an introduction pipe  63 , which is a pipe having both ends opened, is interposed so as to cross the third joining part  56 C. The outer circumferential surface of the introduction pipe  63 , the first sheet  56 A, and the second sheet  56 B are sealed airtightly. 
     The first fluid bag  56  contacts the support surface  32 F at the first sheet  56 A and extends in the first direction. At least one of the first sheet  56 A and the second sheet  56 B includes a tab  56 D that protrudes laterally in an intermediate portion in the first direction. In the present embodiment, the tab  56 D is provided on a laterally inner side edge of an intermediate portion of each of the first sheet  56 A and the second sheet  56 B in the first direction. The tabs  56 D of the first sheet  56 A and the second sheet  56 B are preferably joined to other. The tabs  56 D are bent to be along the fastening part  32 E of the shoulder support member  32  and are fastened to the fastening part  32 E by means of a fastening member  65  such as a clip or a rivet. The first fluid bag  56  is fixed to the shoulder support member  32  via the tabs  56 D. As seen in a direction perpendicular to the support surface  32 F of the shoulder support member  32 , the end portion of the first fluid bag  56  on the first side is disposed in a position coinciding with the end portion of the shoulder support member  32  on the first side, and the end portion of the first fluid bag  56  on the second side is disposed in a position coinciding with the end portion of the shoulder support member  32  on the second side. 
     The second fluid bag  57  includes a third sheet  57 A and a fourth sheet  57 B that are mutually superposed. The third sheet  57 A and the fourth sheet  57 B are joined to each other by a fourth joining part  57 C which extends along the respective edge parts and forms a closed ring shape. The fourth joining part  57 C preferably is a part where the third sheet  57 A and the fourth sheet  57 B are welded or adhered to each other. The second fluid bag  57  extends in the first direction and is superposed on the first fluid bag  56 . The third sheet  57 A of the second fluid bag  57  contacts the second sheet  56 B of the first fluid bag  56 . As seen in a direction perpendicular to the support surface  32 F of the shoulder support member  32 , the end portion of the second fluid bag  57  on the first side is disposed in a position coinciding with the end portion of the first fluid bag  56  on the first side, the end portion of the second fluid bag  57  on the second side is disposed in a position coinciding with the end portion of the first fluid bag  56  on the second side. 
     The end portion of the third sheet  57 A on the first side and the end portion of the second sheet  56 B on the first side are joined to each other by the first joining part  61 . The first joining part  61  preferably is a part where the third sheet  57 A and the second sheet  56 B are welded or adhered to each other. The first joining part  61  has a first side edge  61 A which is a side edge on the second side. The first side edge  61 A extends linearly. The first fluid bag  56  and the second fluid bag  57  are connected by a first communication hole  61 B that passes through the first joining part  61 . The first communication hole  61 B is formed in the second sheet  56 B and the third sheet  57 A. 
     The third fluid bag  58  includes a fifth sheet  58 A and a sixth sheet  58 B that are mutually superposed. The fifth sheet  58 A and the sixth sheet  58 B are joined to each other by a fifth joining part  58 C which extends along the respective edge parts and forms a closed ring shape. The fifth joining part  58 C preferably is a part where the fifth sheet  58 A and the sixth sheet  58 B are welded or adhered to each other. The third fluid bag  58  extends in the first direction and is superposed on the second fluid bag  57 . The fifth sheet  58 A of the third fluid bag  58  contacts the fourth sheet  57 B of the second fluid bag  57 . As seen in a direction perpendicular to the support surface  32 F of the shoulder support member  32 , the end portion of the third fluid bag  58  on the first side is offset to the second side relative to the end portion of the second fluid bag  57  on the first side, and the end portion of the third fluid bag  58  on the second side is disposed in a position coinciding with the end portion of the second fluid bag  57  on the second side. Namely, the length of the second fluid bag  57  in the first direction is longer than the length of the third fluid bag  58  in the first direction. 
     The end portion of the fifth sheet  58 A on the first side and an intermediate portion of the fourth sheet  57 B in the first direction are joined to each other by a second joining part  62 . The second joining part  62  preferably is a part where the fourth sheet  57 B and the fifth sheet  58 A are welded or adhered to each other. The second joining part  62  has a second side edge  62 A which is a side edge on the second side. The second side edge  62 A extends linearly. The second fluid bag  57  and the third fluid bag  58  are connected by a second communication hole  62 B that passes through the second joining part  62 . The second communication hole  62 B is formed in the fourth sheet  57 B and the fifth sheet  58 A. 
     The introduction pipes  63  of the left and right fluid bag assemblies  52  are connected to the fluid supply device  53  via tubes  67 . The fluid bag assemblies  52  inflates when the fluid is supplied and deflates when the fluid is discharged. 
     As shown in  FIG.  3    and  FIG.  9 (A) , in the state in which the fluid bag assembly  52  is deflated, the first side edge  61 A and the second side edge  62 A extend in mutually different directions as seen in a direction perpendicular to the support surface  32 F of the shoulder support member  32 . Namely, as seen in a direction perpendicular to the support surface  32 F of the shoulder support member  32 , an angle defined between the first side edge  61 A and the first direction differs from an angle defined between the second side edge  62 A and the first direction. Also, the second side edge  62 A is disposed further on the second side than the first side edge  61 A. 
     The first side edge  61 A and the second side edge  62 A is preferably positioned lower than the central axis of the blower main body  46 A. Also, the first side edge  61 A and the second side edge  62 A are preferably positioned lower than the upper end of the first side airbag  48 . Further, the upper end of the fluid bag assembly  52  is preferably positioned lower than the central axis of the blower main body  46 A. Also, the upper end of the fluid bag assembly  52  is preferably positioned lower than the upper end of the first side airbag  48 . 
     The first to third fluid bags  56  to  58  each have a planar shape and are mutually superposed in the deflated state. When the fluid supply device  53  is driven and air is supplied to the fluid bag assembly  52 , the fluid bag assembly  52  inflates. The air supplied from the fluid supply device  53  via the tube  67  flows into the first fluid bag  56  by passing through the introduction pipe  63 , flows from the first fluid bag  56  into the second fluid bag  57  by passing through the first communication hole  61 B, and flows from the second fluid bag  57  into the third fluid bag  58  by passing through the second communication hole  62 B. Thereby, the fluid bag assembly  52  inflates. 
     In the inflated state, the thickness of each of the first to third fluid bags  56  to  58  gradually increases from the edge part toward the central portion. As a result, as shown in  FIG.  10   , in the inflated state, the second fluid bag  57  is bent about the first side edge  61 A so that the end portion of the second fluid bag  57  on the second side is separated from the end portion of the first fluid bag  56  on the second side. Also, the third fluid bag  58  is bent about the second side edge  62 A so that the end portion of the third fluid bag  58  on the second side is separated from the end portion of the second fluid bag  57  on the second side. Thereby, the end portion of the fluid bag assembly  52  on the second side spreads more in a direction perpendicular to the support surface  32 F of the shoulder support member  32  than the end portion of the same on the first side. 
     In the state in which the left and right fluid bag assemblies  52  is deflated, each of the first side edge  61 A and the second side edge  62 A extends obliquely downward in the laterally outward direction, as seen from front. Thereby, at the time of inflation, the end portion of the second fluid bag  57  on the second side moves or rotates laterally inward and downward about the first side edge  61 A. Likewise, at the time of inflation, the end portion of the third fluid bag  58  on the second side moves or rotates laterally inward and downward about the second side edge  62 A. Since the first side edge  61 A and the second side edge  62 A extend in mutually different directions, the end portion of the second fluid bag  57  on the second side and the end portion of the third fluid bag  58  on the second side move in different directions. In the present embodiment, at the time of inflation, the end portion of the second fluid bag  57  on the second side moves forward and laterally inward and downward, and the end portion of the third fluid bag  58  on the second side moves forward and laterally inward. Thereby, the fluid bag assembly  52  inflates as shown in  FIGS.  9 (A) to  9 (C) . 
     As shown in  FIG.  2   , the seat cushion frame  11  includes left and right cushion side members  71  extending in the front-rear direction, a front member  72  extending laterally and coupling the front ends of the left and right cushion side members  71  to each other, a rear member  73  extending laterally and coupling the rear ends of the left and right cushion side members  71  to each other, and a movable frame  74  supported on the front member  72  to be movable forward and rearward. Between the front member  72  and the rear member  73 , a buttocks support  75  for supporting the buttocks of the occupant extends. The buttocks support  75  preferably includes a plate-shaped member made of resin and multiple wire springs joined to the plate-shaped member. 
     The movable frame  74  includes an upper plate  74 A provided on the upper surface of the front member  72  and supported to be movable forward and rearward relative to the front member  72  and a front plate  74 B extending downward from the front end of the upper plate  74 A to be disposed in front of the front member  72 . The left end and the right end of the rear portion of the upper plate  74 A extend rearward than the central part of the same. The front plate  74 B is formed in an arc shape that is convex forward as seen in the lateral direction. 
     As shown in  FIGS.  12  and  13   , an accommodation recess  72 A that is recessed downward is formed in a laterally central portion of the upper surface of the front member  72 . The front end and the rear end of the accommodation recess  72 A may reach the front end and the rear end of the front member  72 . A pair of left and right rails  77 A extending in the front-rear direction are provided on the parts of the upper surface of the front member  72  to the left and right of the accommodation recess  72 A. Each of the left and right rails  77 A is provided with a slider  77 B so as to be movable forward and rearward relative to the rail  77 A. The upper plate  74 A of the front member  72  is joined to the left and right sliders  77 B by bolts  78 . Thereby, the movable frame  74  is provided on the front member  72  to be movable forward and rearward via the sliders  77 B and the rails  77 A. The accommodation recess  72 A is provided in a part of the front member  72  below the upper plate  74 A. 
     With the upper plate  74 A being displaced forward and rearward, the movable frame  74  moves relative to the front member  72  between an initial position and a protruding position. The movable frame  74  moves forward from the initial position to reach the protruding position. Also, the movable frame  74  moves rearward from the protruding position to return to the initial position. 
     The pad  12  of the seat cushion  3  is disposed to cover the upper surface and the front surface of the movable frame  74 . When the movable frame  74  moves from the initial position to the protruding position, the movable frame  74  slides relative to the pad  12 . The pad  12  has a sufficient length to cover the front plate  74 B of the movable frame  74  even when the movable frame  74  is in the protruding position. Preferably, when the movable frame  74  is in the initial position, the front edge of the pad  12  extends more downward than the lower edge of the front plate  74 B of the movable frame  74 . 
     The seat  1  further includes an actuator  80  for moving the movable frame  74  forward and rearward relative to the front member  72 . The actuator  80  includes a first actuator  81  that urges the movable frame  74  forward, a second actuator  82  that urges the movable frame  74  rearward, a case  85  accommodating the first actuator  81  and the second actuator  82 , and a control device (not shown in the drawings) for controlling the urging force generated by each of the first actuator  81  and the second actuator  82 . 
     As shown in  FIG.  12   , each of the first actuator  81  and the second actuator  82  is formed by a fluid bag assembly that inflates when compressed air is supplied and deflates when the compressed air is discharged. Preferably, the control device includes a compressor for generating compressed air, a connection pipe connecting the compressor to the first actuator  81 , a connection pipe connecting the compressor to the second actuator  82 , a control valve provided in each of the connection pipes, an electronic control unit (ECU) for controlling the compressor and the control valves, an operation switch for inputting signals to the electronic control unit, and so on. 
     The case  85  is disposed in the accommodation recess  72 A and includes a bottom wall  85 A extending in the front-rear direction, a front wall  85 B extending upward from the front end of the bottom wall  85 A, and a rear wall  85 C extending upward from the rear end of the bottom wall  85 A. The bottom wall  85 A is fastened to the bottom portion of the accommodation recess  72 A. Also, the case  85  preferably includes left and right end walls  85 D extending in the front-rear direction along the left and right side edges of the bottom wall  85 A, respectively, and each joined to the front wall  85 B and the rear wall  85 C. The bottom wall  85 A, the front wall  85 B, the rear wall  85 C, and the left and right end walls  85 D cooperate each other to form a box structure that is opened upward. 
     In a central portion of the rear end of the upper plate  74 A of the movable frame  74 , a pressure receiving plate  74 C extending downward is provided. The pressure receiving plate  74 C is disposed between the front wall  85 B and the rear wall  85 C. Also, the pressure receiving plate  74 C is disposed between the left and right end walls  85 D. The first actuator  81  is disposed between the front wall  85 B and the pressure receiving plate  74 C, and the second actuator  82  is disposed between the pressure receiving plate  74 C and the rear wall  85 C. 
      In accordance with expansion and contraction of the first actuator  81  and the second actuator  82 , the pressure receiving plate  74 C moves relative to the front wall  85 B and the rear wall  85 C, and the movable frame  74  moves forward and rearward relative to the front member  72 . 
     The first actuator  81  and the second actuator  82  inflate when the compressed air is supplied to the first actuator  81  and the second actuator  82  corresponding thereto. When the control valves are in a holding state, the flow of air to the first actuator  81  and the second actuator  82  corresponding thereto is blocked, and the first actuator  81  and the second actuator  82  maintain the size. When the control valves are in a discharging state, the compressed air in the first actuator  81  and the second actuator  82  corresponding thereto is discharged to the outside, and the first actuator  81  and the second actuator  82  deflate. 
     The rear end of the cover member  86  is joined to a rear portion of the accommodation recess  72 A The cover member  86  includes a flange  86 A fastened to a part of the accommodation recess  72 A behind the rear wall  85 C of the case  85 , a vertical plate part  86 B extending from the front edge the flange  86 A upward behind the rear wall  85 C, and a lateral plate part  86 C extending forward from the upper end of the vertical plate part  86 B to be disposed above the upper plate  74 A of the movable frame  74 . The lateral plate part  86 C covers the rear portion of the upper plate  74 A. The lateral plate part  86 C supports the pad  12  from below. 
     In the shoulder support member  32  of the seat  1  described above, the second plate part  32 C can be displaced relative to the first plate part  32 A with deformation of the flexible part  32 B. Therefore, when the shoulder support member  32  is pushed by the shoulder portion of the seated person, the first plate part  32 A and the second plate part  32 C can move to be along the shoulder portion. Thereby, the seat  1  capable of supporting the shoulder portion of the seated person comfortably can be provided. 
      Since the first plate part  32 A and the flexible part  32 B are disposed between the left and right back side members  22  as seen from front and at least a part of the second plate part  32 C is disposed in front of the back side member  22 , the first plate part  32 A can be displaced rearward relative to the second plate part  32 C along the back of the seated person. Also, as seen from front, since the flexible part  32 B extends up and down along the laterally inner side edge of the back side member  22 , the first plate part  32 A can be displaced rearward without interfering with the back side member  22 . Since the flexible part  32 B has a slit  39 , the first plate part  32 A can be easily displaced relative to the second plate part  32 C. 
     Since the second plate part  32 C and the back side member  22  contact each other in the front-rear direction, the position of the second plate part  32 C in the seat back  4  can be fixed The second plate part  32 C extends along the back side member  22  as seen from front. Since the second plate part  32 C exists between the shoulder portion of the seated person and the back side member  22 , the shoulder portion of the seated person can be supported comfortably. 
     Since the left and right shoulder support members  32  are provided on the left and right wire members  31 , respectively, the left and right shoulder support members  32  can be displaced independently from each other so as to be along the shoulder portion of the seated person. 
     The fluid bag assemblies  52  can make parts of the seat back  4  corresponding to the shoulders of the seated person swell laterally inward and downward Thereby, the seat back  4  in conformity with the position and shape of the shoulders of the seated person can be provided. Since each of the left and right fluid bag assemblies  52  inflates forward and laterally inward and downward, the fluid bag assembly  52  is disposed in a position that does not interfere with other devices such as the blower device, the lumber support member  44 , and the near side airbag, in accordance with the physique of the seated person. 
      In the seat  1  according to the present embodiment, since the first side edge  61  A and the second side edge  62 A extend in mutually different directions, it is possible to vary the inflation direction of the second fluid bag  57  and the inflation direction of the third fluid bag  58 . Thereby, the shape of the fluid bag assembly  52  when inflated can be diversified. The first to third fluid bags  56  to  58  are joined at the first joining part  61  and the second joining part  62  and the first communication hole  61 B and the second communication hole  62 B are formed in the first joining part  61  and the second joining part  62 , respectively, whereby the structure is simple. The tab  56 D of the first fluid bag  56  is bent and is fastened to the side surface  51  B perpendicular to the support surface  32 F, whereby the shoulder support  51  can be made compact in size. 
     The fluid bag assemblies  52  can make parts of the seat back  4  corresponding to the shoulders of the seated person swell laterally inward and downward. Thereby, the seat back  4  in conformity with the position and shape of the shoulders of the seated person can be provided. Since each of the left and right fluid bag assemblies inflates forward and laterally inward and downward, the fluid bag assembly  52  is disposed in a position that does not interfere with other devices such as the blower device, the lumber support member  44 , and the near side airbag, in accordance with the physique of the seated person. 
     Concrete embodiments of the present invention have been described in the foregoing, but the present invention is not limited to the above embodiments and may be modified or altered in various ways. In another embodiment, the upper cross member  23  and the middle cross member  25  may be formed integrally. Also, the middle cross member  25  may be omitted, and the upper end of the wire member  31  may be joined to the upper cross member  23 . 
     As shown in  FIG.  11   , the second plate part  32 C and the right back side member  22  mat contact each other in the front-rear direction via a cushioning material  38 . The cushioning material  38  preferably is a member having flexibility, such as an unwoven fabric or a rubber sheet, for example. The cushioning material  38  preferably is interposed between the butting portion  37  and the front surface of the right back side member  22 . With the second plate part  32 C contacting the front surface of the right back side member  22  via the cushioning material  38 , generation of friction sound and rattling sound can be prevented. 
     Also, the rear surface of the second plate part  32 C may be provided with a reinforcement structure  41 . The reinforcement structure  41  improves the stiffness of the second plate part  32 C. Preferably, the reinforcement structure  41  is a rib(s) projecting from the rear surface of the second plate part  32 C. The reinforcement structure  41  is preferably provided on an upper portion of the rear surface of the second plate part  32 C. 
     The fluid bag assembly  52  may be provided in the seat cushion  3  and/or the headrest  29 . Also, the fluid bag assembly  52  may include four or more fluid bags without being limited to the three fluid bags  56  to  58 . For example, the fluid bag assembly  52  may include a fourth fluid bag joined to the third fluid bag  58  and a fifth fluid bag joined to the fourth fluid bag. 
     In an embodiment in which part of the above embodiment is modified, as shown in  FIG.  14   , the fluid bag assemblies  52  may be disposed close to the perimeter of the blower  46 . In this case, it is preferred if each fluid bag assembly  52  has a recess  101  that is recessed laterally outward in the laterally inner side edge thereof, and the left and right side portions of the blower  46  are disposed in the respective recesses  101 . Each recess  101  is preferably formed in a shape along the outer edge of the blower  46 . For example, it is preferred if the blower  100  is formed in a cylindrical shape and each recess  101  is formed in an arc shape having a radius same as that of the blower  100 . Thereby, it is possible to increase the size of each fluid bag assembly  52  while avoiding interference between the fluid bag assembly  52  and the blower  46 . Also, a support plate  102  of the lumber support member  44  may extend laterally so that the left end and the right end reach the left and right back side members  22 . The blower  46  may be supported on the support plate  102 . Also, the support plate  102  of the lumber support member  44  may constitute the shoulder support of each fluid bag assembly  52 . In this case, it is preferred if the fluid bag assembly  52  is joined to the support plate  102 . 
     LIST OF REFERENCE NUMERALS 
     
       
         
           
               
               
            
               
                 
                   1 
                 
                 seat 
               
               
                 
                   3 
                 
                 seat cushion 
               
               
                 
                   4 
                 
                 seat back 
               
               
                 
                   15 
                 
                 seat back frame 
               
               
                 
                   22 
                 
                 back side member 
               
               
                 
                   23 
                 
                 upper cross member 
               
               
                 
                   24 
                 
                 lower cross member 
               
               
                 
                   25 
                 
                 middle cross member 
               
               
                 
                   31 
                 
                 wire member 
               
               
                   31 A 
                 upper end portion 
               
               
                   31 B 
                 upper side the intermediate portion 
               
               
                   31 C 
                 lower intermediate portion 
               
               
                   31 D 
                 lower end portion 
               
               
                   31 E 
                 connecting portion 
               
               
                 
                   32 
                 
                 shoulder support member 
               
               
                   32 A 
                 first plate part 
               
               
                   32 B 
                 flexible part 
               
               
                   32 C 
                 second plate part 
               
               
                   32 D 
                 inner side edge 
               
               
                   32 E 
                 fastening part 
               
               
                 
                   34 
                 
                 first locking portion 
               
               
                 
                   35 
                 
                 second locking portion 
               
               
                 
                   36 
                 
                 positioning part 
               
               
                 
                   37 
                 
                 butting portion 
               
               
                 
                   38 
                 
                 cushioning material 
               
               
                 
                   39 
                 
                 slit 
               
               
                 
                   41 
                 
                 reinforcement structure 
               
               
                 
                   44 
                 
                 lumber support member 
               
               
                 
                   46 
                 
                 blower 
               
               
                 
                   52 
                 
                 fluid bag assembly