Patent Publication Number: US-11639152-B2

Title: Seatbelt assist device and vehicle seat

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/887,226, filed May 29, 2020, now U.S. Pat. No. 10,933,840, which is a continuation of U.S. patent application Ser. No. 16/253,864, filed Jan. 22, 2019, now U.S. Pat. No. 10,668,893, which is a continuation of U.S. patent application Ser. No. 15/501,720, filed Feb. 3, 2017, now U.S. Pat. No. 10,449,926, which is the National Stage Entry application of PCT Application No. PCT/JP2015/072179, filed Aug. 5, 2015, which claims the priority benefit of Japanese Patent Application No. 2014-160884, filed on Aug. 6, 2014, Japanese Patent Application No. 2014-160885, filed on Aug. 6, 2014, Japanese Patent Application No. 2014-160886, filed on Aug. 6, 2014, and Japanese Patent Application No. 2015-102041, filed on May 19, 2015, the contents of each being incorporated herein by reference. 
    
    
     BACKGROUND 
     The present disclosure relates to a seatbelt assist device and a vehicle seat. Particularly, the present disclosure relates to a seatbelt assist device and a vehicle seat capable of moving at least a portion of a seatbelt to a position easily reachable by a seated passenger&#39;s hand. 
     Typically, it has been known that in order for a seated passenger on a vehicle seat to easily take a seatbelt, a belt movable member provided at an upper portion of a seat back protrudes forward or upward to push a portion of the seatbelt forward or upward, for example, as described in Japanese Patent Publication JP 2004-306642A and Japanese Patent Publication JP 06-060562U. 
     In the seatbelt integrated vehicle seat described in JP 2004-306642A, the belt movable member is attached to an upper portion of a lateral portion of the seat back in a right-to-left direction, the upper portion being capable of housing the belt movable member. The seatbelt extends downward from a belt guide (a pullout port) provided at an upper position of the belt movable member in the lateral portion, and is placed on the lateral portion. The belt movable member is disposed to move between a housing position at which the belt movable member is housed in a housing portion of the seat back and an extension position at which the belt movable member is extended forward of the seat from the housing position to push a portion of the seatbelt forward. With the above-described configuration, workability in fastening of the seatbelt by the seated passenger is improved. 
     In the vehicle rear seat described in JP 06-060562U, the belt guide integrated belt movable member (a belt anchor) is attached to an upper portion of a center portion of the seat back in a right-to-left width direction, the upper portion being capable of housing the belt movable member. The seatbelt is guided by a belt guide on an upper surface of the center portion, and extends from the upper surface to a front surface of the center portion. Thus, the seatbelt is placed on the center portion. The belt movable member is rotatably disposed between a housing position at which the belt movable member is housed in a recessed housing portion of the seat back and a protruding position at which the belt movable member protrudes upward of the seat from the housing position to push a portion of the seatbelt upward. With the above-described configuration, the belt movable member can constantly protrude when the passenger is seated on a rear middle seat of a vehicle, and can be housed to ensure rearward visibility when no passenger is seated. 
     However, the belt movable member as described in JP 2004-306642A has a relatively-complicated extension mechanism configured to push a portion of the seatbelt forward, leading to a size increase of the mechanism. In the belt movable member as described in JP 06-060562U, size reduction is made using a rotation mechanism. However, since the belt movable member is of the belt guide integrated type, it is necessary to provide a mechanism configured to guide the seatbelt. This leads to a size increase. Moreover, since the belt movable member protrudes upward from the seat back after the passenger has seated, there is a likelihood that such a state interferes with the passenger to be seated. 
     Further, the belt movable member as described in JP 2004-306642A and JP 06-060562U protrudes forward or upward of the seat from the upper portion of the seat back to push a portion of the seatbelt forward or upward, and therefore, the seated passenger can easily take the seatbelt. For this reason, a design to further improve the workability in fastening of the seatbelt is desirable. 
     In addition, in the belt movable member as in JP 2004-306642A, when the seated passenger pulls the seatbelt toward one&#39;s body to fasten the seatbelt, if a portion of the belt movable member still contacts and pushes out the seatbelt, play of the seatbelt is caused. As a result, this might interfere with the performance of restraining the seated passenger by the seatbelt. For this reason, a design to ensure a favorable performance of restraining the seated passenger by the seatbelt is desirable. 
     Moreover, in the vehicle seat as in JP 2004-306642A and JP 06-060562U, no arrangement has been particularly made to use an indicator section such as sound or vibration to inform the seated passenger of the belt movable member being at the extension position (the protruding position). Thus, there is a possibility that the seated passenger accidentally contacts the belt movable member at the extension position (the protruding position) or that other members contact such a belt movable member. 
     SUMMARY 
     The present disclosure has been made in view of the above-described problems, and describes embodiments of a seatbelt assist device and a vehicle seat configured to use a simple compact configuration to move a seatbelt to a position easily reachable by a seated passenger. Moreover, the present disclosure provides an embodiment of a seatbelt assist device and a vehicle seat configured to improve workability in fastening of a seatbelt by a seated passenger. Further, the present disclosure describes an embodiment of a seatbelt assist device and a vehicle seat configured to ensure a favorable performance of restraining a seated passenger by a seatbelt. In addition, the present disclosure describes an embodiment of a seat belt assist device and a vehicle seat configured to move a portion of a seatbelt to a position easily reachable by a seated passenger and informing the seated passenger that the portion of the seatbelt has been moved. 
     The above-described problems are solved by one or more embodiments of the present seatbelt assist device. The present seatbelt assist device is a seatbelt assist device attached to a seat back as a backrest of a vehicle seat and being configured to move at least a portion of a seatbelt placed on the seat back to a position easily reachable by a seated passenger. The seatbelt assist device includes a rotary member attached to the seat back via a rotary shaft and configured to move between a housing position at which the rotary member is housed in the seat back and a protruding position at which the rotary member protrudes forward of the seat back to push out a portion of the seatbelt. The rotary member is disposed forward of a belt guide provided at an upper end of the seat back or at the periphery of the upper end of the seat back. 
     As described above, in order for the seated passenger to more easily take the seatbelt, the rotary member rotates to protrude forward of the seat to push out a portion of the seatbelt, and the rotary member and the belt guide are provided as separate bodies. Thus, the seatbelt assist device having a simple compact configuration is provided. 
     In this state, the rotary member may be attached to an upper portion of the seat back, and when moved to the protruding position, the rotary member may push out a portion of the seatbelt from behind of the portion of the seatbelt such that a clearance is formed between a front surface of the seat back and the seatbelt and between the upper end of the seat back and the seatbelt. With the above-described configuration, the rotary member forms the clearance between the front surface of the seat back and the seatbelt and between the upper end of the seat back and the seatbelt, and therefore, the seated passenger can much more easily take the seatbelt as compared to a typical case. 
     In this state, the rotary member may be attached to a lateral portion of the seat back in a right-to-left direction. The rotary member may be, via the rotary shaft, attached to a recessed housing portion provided at the lateral portion, the recessed housing portion being configured to house the rotary member. The rotary shaft may be pivotally supported to extend in the right-to-left direction in the recessed housing portion. As described above, the rotary shaft is pivotally supported to extend in the right-to-left direction in the recessed housing portion. Thus, the rotary member is compactly disposed using a rotation mechanism, and rotates in an upper-to-lower direction to easily push out the seatbelt. 
     In this state, a support plate configured to rotatably support the rotary member may be attached between the rotary member and the recessed housing portion. The rotary shaft may be attached to an upper end portion or lower end portion of the rotary member, and may be pivotally supported by the support plate. As described above, since the support plate is provided, clearance formation between the rotary member and the recessed housing portion can be reduced, leading to favorable appearance. Moreover, since the rotary shaft is attached to the upper end portion or lower end portion of the rotary member, the trajectory of rotation of the rotary member becomes larger, and the amount of movement of a portion of the seatbelt can be increased. 
     In this state, the rotary shaft may be attached to an upper end portion of the rotary member. The rotary member may be configured to rotate, when moving from the housing position to the protruding position, upward about the rotary shaft to protrude forward of the seat. The rotary member may be configured such that when moved to the protruding position, an angle of the rotary member with respect to the seat back is equal to or smaller than about 90 degrees. With the above-described configuration, the probability of tangling the seatbelt due to more upward rotation of the rotary member than necessary can be reduced. Moreover, even when the seated passenger accidentally pushes the rotary member upward, the rotary member can be biased toward the housing position by its own weight, and the probability of deforming the rotary member due to a load received from the outside can be reduced. 
     In this state, the rotary member may be disposed at a lower position of a lower end of a head rest as a head portion of the vehicle seat, and may be disposed at a lower position of the upper end of the seat back. With the above-described configuration, the rotary member is, in the present embodiment, disposed at a position more apart from the face of the seated passenger as compared to the typical case where the rotary member moves at a position near the face of the seated passenger. Thus, a feeling of discomfort of the seated passenger can be reduced. 
     In this state, the rotary member may be provided with a position restriction portion configured to restrict the position of the seatbelt in the right-to-left direction on a surface contacting the seatbelt when the rotary member is at the protruding position. With the above-described configuration, when the rotary member is at the protruding position at which a portion of the seatbelt is pushed out, displacement of the seatbelt in the right-to-left direction can be reduced by the position restriction portion. 
     In this state, the rotary member may be attached to the lateral portion of the seat back in the right-to-left direction, and one of right and left end portions of the rotary member close to a center portion of the seat back may be provided with a cutout portion cut out toward the other one of the right and left end portions farther from the center portion of the seat back. With the above-described configuration, when the seatbelt is pulled toward a seated passenger&#39;s body so that the seated passenger can fasten the seatbelt, contact between the rotary member at the protruding position and the seatbelt is easily reduced. Thus, a favorable performance of restraining the seated passenger by the seatbelt can be ensured without causing play of the seatbelt. Moreover, the probability of pinching a portion of the seatbelt between the rotary member at the protruding position and the seat back after fastening of the seatbelt is also reduced. 
     In this state, the rotary member may be attached to the recessed housing portion provided at the seat back, the recessed housing portion being configured to house the rotary member. A support plate configured to support the rotary member may be attached between the rotary member and the recessed housing portion, the support plate being configured to house the rotary member. A portion of the support plate corresponding to the cutout portion may be provided with a protruding raised portion protruding toward the rotary member. With the above-described configuration, when the rotary member is housed in the support plate, recess formation at the front surface of the seat back can be reduced. Thus, the probability of foreign material entry can be reduced. Moreover, the feeling of discomfort of the seated passenger is eliminated, and favorable appearance and merchantability are provided. 
     In this state, the rotary member may be attached to the recessed housing portion provided at the seat back, the recessed housing portion being configured to house the rotary member. The seatbelt assist device may further include a motor housed in the recessed housing portion, and a drive shaft interposed between the motor and the rotary member and configured to move up and down in association with driving of the motor to rotate the rotary member. With the above-described configuration, the driven type seatbelt assist device having a relatively simple compact configuration can be provided. 
     In this state, the rotary member may include an indicator section configured to inform that the rotary member is at the protruding position. With the above-described configuration, the seatbelt assist device can be provided, which is configured to use the indicator section such as illumination, sound, or vibration to inform the seated passenger that a portion of the seatbelt has been moved to the position easily reachable by the seated passenger. 
     In this state, the indicator section may include a light emission device attached to the rotary member or the periphery of the rotary member, and the indicator section may be configured to cause the light emission device to emit light when the rotary member is at the protruding position. As described above, since the light emission device informs the seated passenger by light emission, such informing is easily noticeable by the seated passenger. 
     A vehicle seat including the seatbelt assist device and the seat back as described above can be also provided. With the above-described configuration, the vehicle seat is provided, which is configured to use a simple compact configuration to move the seatbelt to the position easily reachable by the seated passenger. 
     Moreover, a vehicle seat including the seatbelt assist device and the seat back as described above can be also provided. The seat back includes a support portion configured to support the back of the seated passenger from behind of the back of the seated passenger, and a lateral portion positioned at the side of the support portion. At least one of front surfaces of the support portion and the lateral portion has an opposing region facing a belt portion of the seatbelt when the seatbelt is at a standby position in an unlocked state. At least a portion of the opposing region is provided with a space formation portion formed by a recessed or raised portion. When the seatbelt is at the standby position in the unlocked state, the space formation portion forms a space between the opposing region and the belt portion. In the above-described configuration, the space formation portion formed by the recessed or raised portion is provided in at least a portion of the opposing region facing the belt portion of the seatbelt. With such a space formation portion, the space (a clearance) is formed between the opposing region and the belt portion when the seatbelt is at the standby position in the unlocked state. Using such a space (simply, inserting a finger into the space), the belt portion can be more easily grasped. 
     In this state, the space formation portion may be formed by the recessed portion. When the seatbelt is at the standby position in the unlocked state, one end of the recessed portion in a horizontal width direction may be positioned farther from one end of the belt portion in a width direction than from the other end of the belt portion in the width direction, and the other end of the recessed portion in the horizontal width direction may be positioned between one end and the other end of the belt portion in the width direction. In the above-described configuration, the recessed portion is provided at the position close to one of the ends of the belt portion of the seatbelt in the width direction. According to such a configuration, the finger is, for example, inserted into the space of the recessed portion from one end side of the belt portion in the width direction so that the belt portion can be easily grasped. 
     According to an embodiment, the rotary member rotates to protrude forward of the seat to push out a portion of the seatbelt, and the rotary member and the belt guide are provided as separate bodies. Thus, the seatbelt assist device having a simple compact configuration can be provided. According to an embodiment, the seated passenger can much more easily take the seatbelt as compared to a typical implementation. According to an embodiment, the rotary member is compactly disposed using the rotation mechanism, and rotates in the upper-to-lower direction to easily push out the seatbelt. 
     According to an embodiment, clearance formation between the rotary member and the recessed housing portion can be reduced, leading to a more favorable appearance. Moreover, the trajectory of rotation of the rotary member becomes larger, and the amount of movement of the seatbelt can be ensured. According to an embodiment, the probability of tangling the seatbelt can be reduced. Moreover, the rotary member can be biased toward the housing position by its own weight, and the probability of deforming the rotary member due to the load received from the outside can be reduced. According to an embodiment, the rotary member is disposed at the position more apart from the face of the seated passenger as compared to a typical implementation. Thus, the feeling of discomfort of the seated passenger can be reduced. According to an embodiment, displacement of the seatbelt in the right-to-left direction can be reduced by the position restriction portion. 
     According to an embodiment, when the seatbelt is attached to a buckle, it is easy to reduce the state in which the rotary member at the protruding position remains to push out a portion of the seatbelt. Thus, a favorable performance of restraining the seated passenger by the seatbelt can be ensured. Moreover, the probability of pinching a portion of the seatbelt between the rotary member at the protruding position and the seat back is also reduced. According to an embodiment, recess formation at the front surface of the seat back can be reduced. Thus, the probability of foreign material entry can be reduced. Moreover, the feeling of discomfort of the seated passenger is reduced, and favorable appearance and merchantability are provided. According to an embodiment, a driven type seatbelt assist device having a relatively simple compact configuration can be provided. 
     According to an embodiment, the seatbelt assist device can be provided, which is configured to use the indicator section such as illumination, sound, or vibration to inform the seated passenger that a portion of the seatbelt has been moved to the position easily reachable by the seated passenger. According to an embodiment, since the light emission device informs the seated passenger by light emission, such informing is easily noticeable by the seated passenger. According to an embodiment, the vehicle seat is provided, which is configured to use the simple compact configuration to move the seatbelt to the position easily reachable by the seated passenger. According to an embodiment, the vehicle seat is provided, which is configured to use a relatively simple configuration to realize easy grasping of the belt portion. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is an external perspective view of a vehicle seat of an embodiment. 
         FIG.  2    is an enlarged view of a main portion of  FIG.  1   , and is an external perspective view of a belt assist device. 
         FIG.  3    is an exploded perspective view of the belt assist device. 
         FIG.  4 A  is a side cross-sectional view of the belt assist device, and is a view of a housing position. 
         FIG.  4 B  is a view of a protruding position of the belt assist device. 
         FIG.  5    is a block diagram of an electric structure of the belt assist device. 
         FIG.  6    is a flowchart of an example method of control of the belt assist device. 
         FIG.  7    is an external perspective view of a belt assist device of a second embodiment. 
         FIG.  8    is an exploded perspective view of the belt assist device of the second embodiment. 
         FIG.  9 A  is a side cross-sectional view of the belt assist device of the second embodiment, and is a view of a housing position. 
         FIG.  9 B  is a view of a protruding position of the belt assist device. 
         FIG.  10 A  is an external perspective view of a belt assist device of a third embodiment, and is a view of a housing position. 
         FIG.  10 B  is a view of a protruding position of the belt assist device. 
         FIG.  11    is a perspective view of a belt assist device of a fourth embodiment, and is a view in the state in which a rotary member is at a protruding position. 
         FIG.  12    is a perspective view of the belt assist device of the fourth embodiment, and is a view in the state in which the rotary member is at a housing position. 
         FIG.  13    is an exploded perspective view of the belt assist device of the fourth embodiment. 
         FIG.  14    is a perspective view of the belt assist device of the fourth embodiment from a back side. 
         FIG.  15    is a cross-sectional view of the belt assist device of the fourth embodiment, and is a view in the state in which a cover material is hooked with the cover material being sandwiched between a support plate and a housing plate. 
         FIG.  16 A  is a view of a front cover for protecting a motor and a drive shaft of the fourth embodiment. 
         FIG.  16 B  is a view of a back cover for protecting the motor and the drive shaft. 
         FIG.  17    is a longitudinal sectional view of the belt assist device of the fourth embodiment, and is a view in the state in which the drive shaft, a worm gear, and a wheel gear engage with each other. 
         FIG.  18    is an external perspective view of a belt assist device of a fifth embodiment. 
         FIG.  19    is an exploded perspective view of the belt assist device of the fifth embodiment. 
         FIG.  20 A  is a side cross-sectional view of the belt assist device of the fifth embodiment, and is a view for describing a housing position. 
         FIG.  20 B  is a view for describing a protruding position of the belt assist device. 
         FIG.  21    is a block diagram of an electric structure of the belt assist device of the fifth embodiment. 
         FIG.  22    is a flowchart of an example method of control of the belt assist device of the fifth embodiment. 
         FIG.  23    is an external perspective view of a belt assist device of a sixth embodiment. 
         FIG.  24    is an exploded perspective view of the belt assist device of the sixth embodiment. 
         FIG.  25    is an exploded perspective view of the belt assist device of the sixth embodiment. 
         FIG.  26    is an external perspective view of a belt assist device of a seventh embodiment. 
         FIG.  27    is a side cross-sectional view of the belt assist device of the seventh embodiment. 
         FIG.  28    is an external perspective view of a belt assist device of an eighth embodiment. 
         FIG.  29    is a front cross-sectional view of the belt assist device of the eighth embodiment. 
         FIG.  30    is an external perspective view of a belt assist device of a ninth embodiment. 
         FIG.  31    is a perspective view of a vehicle seat of a tenth embodiment. 
         FIG.  32    is a view for describing a space formation portion of the tenth embodiment, and is a cross-sectional view along an A-A line of  FIG.  31   . 
         FIG.  33    is an exploded view of the space formation portion of the tenth embodiment. 
         FIG.  34    is a view for describing the space formation portion of the tenth embodiment, and is a cross-sectional view along a B-B line of  FIG.  32   . 
         FIG.  35    is a view of a variation of the shape of the space formation portion. 
         FIG.  36    is a perspective view of a vehicle seat of an eleventh embodiment. 
         FIG.  37    is a view of a variation regarding the number of space formation portions to be arranged. 
         FIG.  38    is a view of a variation regarding the arrangement position of each space formation portion, and is a schematic cross-sectional view of a lateral portion along the horizontal plane. 
         FIG.  39    is a perspective view of a vehicle seat of a twelfth embodiment. 
         FIG.  40    is a view for describing a space formation portion of the twelfth embodiment, and is a cross-sectional view along a C-C line of  FIG.  39   . 
         FIG.  41    is a view for describing a space formation portion of a thirteenth embodiment, and is a schematic cross-sectional view of the periphery of the space formation portion along the vertical plane at a first time. 
         FIG.  42    is a view for describing the space formation portion of the thirteenth embodiment, and is a schematic cross-sectional view of the periphery of the space formation portion along the vertical plane at a second time. 
     
    
    
     DETAILED DESCRIPTION 
     First to fifth embodiments of the present disclosure are described below with reference to  FIGS.  1  to  17   . 
     First Embodiment of Belt Assist Device 
     The present embodiment relates to a vehicle seat including a seatbelt assist device attached to a lateral portion of a seat back and being configured to move a portion of a seatbelt placed on the lateral portion to a position easily reachable by a seated passenger. The seatbelt assist device includes a rotary member attached to a recessed housing portion of the lateral portion via a rotary shaft and configured to rotate up and down between a housing position at which the rotary member is housed in the seat back and a protruding position at which the rotary member rotates to protrude forward of the seat back to push out a portion of the seatbelt. The rotary member is disposed forward of a belt guide provided at the periphery of an upper end of the seat back. Note that in the description herein, a passenger seating side with respect to the seat back of the vehicle seat is referred to as a front side. 
     A vehicle seat S of the present embodiment is a rear seat equivalent to a back seat of a vehicle, for example Note that the vehicle seat S can be also utilized as a middle seat in the second row in a vehicle including three rows of seats in a vehicle front-to-back direction. As illustrated in  FIG.  1   , the vehicle seat S generally includes a seat body having a seat cushion  1 , a seat back  2 , and a head rest  3 ; and a seatbelt assist device  30  (hereinafter referred to as “belt assist devices  30 ”) attached to an upper portion of a lateral portion of the seat back  2  in a right-to-left direction. Note that a belt guide  13  configured to guide an extension direction of a seatbelt  10  is provided at the periphery of an upper end of the lateral portion of the seat back  2  in the right-to-left direction, specifically a back portion with respect to the lateral portion in the right-to-left direction. 
     The vehicle seat S is a seat utilizing the belt assist device  30  to move at least a portion of the seatbelt  10  placed on the lateral portion of the seat back  2  in the right-to-left direction to a position easily reached by a seated passenger&#39;s hand. Specifically, the vehicle seat S is a seat configured to operate the belt assist device  30  to push out a portion of the seatbelt  10  from behind such that a clearance is formed between a front surface of the seat back  2  and the seatbelt  10  and between an upper end of the seat back  2  and the seatbelt  10 . Details are described below. 
     As illustrated in  FIG.  1   , the seat cushion  1  is a seating portion configured to support the passenger from below, and is configured such that a cushion pad placed on a cushion frame (not shown) as a framework is covered with a cover material from above the cushion pad. The seat back  2  is a backrest configured to support the back of the passenger from behind, and is configured such that a cushion pad placed on a back frame (not shown) as a framework is covered with a cover material. The lateral portion of the seat back  2  in the right-to-left direction is formed as a back side portion  20  configured to support an upper side portion of the seated passenger. The head rest  3  is a head portion configured to support the head of the passenger from behind, and is configured such that a cushion pad placed on a pillar (not shown) as a core is covered with a cover material. 
     The seatbelt  10  is a band-shaped member configured to restrain the upper body of the passenger, and is placed to extend from an upper surface to a front surface of the back side portion  20  of the seat back  2 . A tongue plate  11  is slidably attached to the seatbelt  10 , and is fitted into a buckle  12  provided at a predetermined position of the seat cushion  1 . A lower end side  10   a  of the seatbelt  10  is pulled in between a lower end of the seat back  2  and a back end of the seat cushion  1 , and then, is fixed to a predetermined position of a vehicle body member behind the seat body. Moreover, an upper end side  10   b  is slidably inserted into the belt guide  13  behind an upper end of the back side portion  20 , and is pulled toward a location behind a back surface of the seat back  2  from a back portion of the upper end of the seat back  2 . Then, the pulled end portion is attached to an automatic winding device (not shown). 
     The belt guide  13  is a member made of hard resin and configured to guide the extension direction of the seatbelt  10  toward the front side, and is provided with a guide hole  13   a  into which the seatbelt  10  can be inserted. The belt assist device  30  is disposed at a front position of the belt guide  13 . 
     The back side portion  20  is configured such that a cushion pad  20   b  ( FIG.  15   ) placed on a resin side base  20   a  is covered with a cover material  20   c . As illustrated in  FIG.  2   , the side base  20   a  includes a frame member having a substantially inverted L-shaped longitudinal section, and is configured to house the belt assist device  30  and an airbag module  50 . The side base  20   a  is provided with a recessed housing portion  21  recessed backward from an upper wall portion to a front wall portion at an upper position of the side base  20   a , a recessed airbag housing portion  22  recessed backward at the front wall portion at a lower position of the recessed housing portion  21 , and a belt facing recessed portion  23  recessed backward at the front wall portion at a lower position of the recessed airbag housing portion  22 . 
     As illustrated in  FIG.  3   , the recessed housing portion  21  is formed in such a manner that a recessed housing plate  21   b  is, by snap-fitting, fixed to a substantially rectangular opening  21   a  provided at the side base  20   a . Similarly, the recessed airbag housing portion  22  is formed in such a manner that a recessed housing plate  22   b  is, by snap-fitting, fixed to a substantially rectangular opening  22   a  provided at the side base  20   a , and the belt facing recessed portion  23  is formed in such a manner that a recessed housing plate  23   b  is, by snap-fitting, fixed to a substantially rectangular opening  23   a  provided at the side base  20   a . In the above-described configuration, the belt assist device  30  is housed from the front side in the recessed housing portion  21 , and the airbag module  50  is housed from the front side in the recessed airbag housing portion  22 , as illustrated in  FIGS.  2  and  3   . 
     As illustrated in  FIG.  1   , the belt facing recessed portion  23  is a recessed portion elongated along the extension direction of the seatbelt  10 , and is disposed at a position facing a portion of the seatbelt  10 . Moreover, the belt facing recessed portion  23  is formed to be wider than the seatbelt  10 . A clearance is formed between the belt facing recessed portion  23  and the seatbelt  10 , and therefore, arrangement is made such that a child as the seated passenger can grasp the seatbelt  10  while inserting her hand into the clearance, for example. 
     As illustrated in  FIG.  2   , the belt assist device  30  is an assist device configured to push a portion of the seatbelt  10  forward and upward. As illustrated in  FIG.  3   , the belt assist device  30  generally includes a motor  31  housed in the recessed housing portion  21 , a recessed support plate  32  fixed, by snap-fitting, to the recessed housing portion  21  to cover the motor  31  from the front side, a rotary shaft  33  pivotally supported in the support plate  32 , a rotary member  34  attached via the rotary shaft  33 , and an auxiliary spring  35  configured to bias the rotary member  34  toward a protruding position. 
     As illustrated in  FIGS.  4 A and  4 B , the belt assist device  30  is a device configured to rotate the rotary member  34  between a housing position at which the rotary member  34  is housed in the recessed housing portion  21  of the seat back  2  and the protruding position at which the rotary member  34  protrudes forward of the seat back  2  to push out a portion of the seatbelt  10 . The belt assist device  30  is configured as follows: when the rotary member  34  is at the housing position as illustrated in  FIG.  4 A , the belt assist device  30  is substantially integrally housed without protruding beyond an outer surface of the seat back  2 ; and when the rotary member  34  is at the protruding position illustrated in  FIG.  4 B , the belt assist device  30  partially protrudes beyond the outer surface of the seat back  2  to push a portion of the seatbelt  10  forward and upward. 
     As illustrated in  FIGS.  3 ,  4 A, and  4 B , the motor  31  is a stroke motor configured to move up and down the rotary member  34 , and is attached to an attachment target portion  32   a  provided in the support plate  32 . The motor  31  generally includes a motor body  31   a  and a cylinder  31   b  attached to move up and down relative to the motor body  31   a , and is connected to a vehicle power source  42  via a drive circuit  41  (described below). When drive power is supplied to the motor body  31   a , the cylinder  31   b  is configured to lower to a predetermined lowered position in response to each sensor (described below) and to lift to a predetermined lifted position (a standby position) in response to each sensor. When supply of the drive power is stopped, the cylinder  31   b  is configured to be stopped and held at a stop position. 
     A support shaft  31   c  extending in the right-to-left direction is pivotally supported in the state in which the support shaft  31   c  is inserted into an opening provided at a protruding tip end portion of the cylinder  31   b . The support shaft  31   c  passes through an opening  32   b  provided at a back surface of the support plate  32 , and then, is further pivotally supported by a support hole  34   b  provided at a back surface of the rotary member  34 . With the above-described configuration, the motor  31  can move up and down the cylinder  31   b  to operate the rotary member  34  via the support shaft  31   c  in an interlocking manner. 
     The support plate  32  is a resin plate configured to rotatably support the rotary member  34 , and a pair of support holes  32   c  configured to pivotally support the rotary shaft  33  are formed respectively at right and left lateral wall portions of the support plate  32 . The rotary shaft  33  extends in the right-to-left direction, and is further pivotally supported by a shaft hole  34   c  and a pair of shaft holes  34   d  of the rotary member  34  with the rotary shaft  33  being pivotally supported by the pair of support holes  32   c . The rotary shaft  33  is attached to upper portions (upper end portions) of the support plate  32  and the rotary member  34 . 
     As illustrated in  FIG.  3   , the rotary member  34  includes a substantially recessed resin plate. The rotary member  34  is a member configured to push out a portion of the seatbelt  10  from behind, and is rotatably provided between the housing position of  FIG.  4 A  and the protruding position of  FIG.  4 B . A reinforcement rib  34   a  is formed to extend backward from a center portion of a back surface of a front wall portion of the rotary member  34  in the right-to-left direction. The reinforcement rib  34   a  is provided with the support hole  34   b  configured to pivotally support the support shaft  31   c  and the shaft hole  34   c  configured to pivotally support the rotary shaft  33 . Moreover, the pair of shaft holes  34   d  configured to further pivotally support the rotary shaft  33  are formed respectively at right and left lateral wall portions of the rotary member  34 . 
     In the above-described configuration, the rotary member  34  is disposed to move to the protruding position of  FIG.  4 B  in such a manner that the rotary member  34  rotates upward about the rotary shaft  33  from the housing position of  FIG.  4 A  to protrude forward of the seat. The rotary member  34  is configured such that an angle with the seat back  2  is equal to or smaller than about 90 degrees when the rotary member  34  has moved to the protruding position. 
     Moreover, in the above-described configuration, the rotary member  34  includes the right and left lateral wall portions each bent continuously from a corresponding one of right and left end portions of the front wall portion and extending backward. Thus, when the rotary member  34  moves from the housing position to the protruding position or when the rotary member  34  is at the protruding position, pinching of the seatbelt  10  can be reduced. 
     Further, in the above-described configuration, the reinforcement rib  34   a  is formed on the back surface of the front wall portion of the rotary member  34 . The reinforcement rib  34   a  pivotally supports the support shaft  31   c  and the rotary shaft  33 . Thus, rigidity of the rotary member and attachment rigidity of the rotary member can be improved. 
     In addition, in the above-described configuration, a curvature radius is provided to a corner portion between the front wall portion and an upper wall portion of the rotary member  34  and a corner portion between the front wall portion and a bottom wall portion of the rotary member  34 . Thus, these corner portions have no sharp edge, and therefore, safety can be ensured. Moreover, rigidity of the corner portions can be ensured, leading to favorable moldability. 
     Moreover, in the above-described configuration, a pair of protruding portions (not shown) protruding forward are formed respectively at right and left end portions of a front surface of the rotary member  34 . The pair of protruding portions functions as a position restriction portion configured to sandwich a portion of the seatbelt  10  in the right-to-left direction when the rotary member  34  is at the protruding position, leading to reduction in displacement of the seatbelt  10  in the right-to-left direction. 
     Further, in the above-described configuration, a front surface of the front wall portion as an outer surface of the rotary member  34  is covered with the same cover material as that of the back side portion  20 . Thus, a feeling of discomfort of the seated passenger between the back side portion  20  and the rotary member  34  (the belt assist device  30 ) can be reduced, and a favorable appearance is also provided. Note that the resin rotary member  34  and the cover material may be integrally molded, or may be bonded together. 
     Control Section of Belt Assist Device 
     As illustrated in  FIG.  5   , the belt assist device  30  includes an electronic control unit (ECU) circuit  40  as a control section, the drive circuit  41  configured to supply the drive power to the motor  31 , and the vehicle power source  42  connected to the motor via the drive circuit. 
     The ECU  40  is configured to control the drive power supplied from the drive circuit  41  to the motor  31  to control ON or OFF of current of an electromagnetic clutch (not shown), thereby controlling lifting/lowering of the motor  31 , i.e., rotation of the rotary member  34 . Moreover, the ECU  40  is connected to a seating sensor  43  provided at the seat cushion  1  and configured to detect that the passenger has been seated on the seat body, a door sensor  44  provided at a vehicle door and configured to detect that the vehicle door has been closed, and a buckle sensor  45  provided at each buckle  12  and configured to detect that the tongue plate  11  has been coupled with the buckle  12 . In the above-described configuration, the ECU  40  controls operation of the motor  31 , i.e., operation of the rotary member  34 , based on a signal input from each sensor. 
     Processing of a flowchart of  FIG.  6    is repeatedly executed during a period for which, e.g., control is made by the ECU  40  to turn on an ignition switch of a vehicle. In a normal state, the belt assist device  30  is at the housing position illustrated in  FIG.  4 A , and is integrally housed without protruding beyond the outer surface of the seat back  2  as illustrated in  FIG.  1   . The seatbelt  10  substantially closely contacts the outer surface of the seat back  2 . 
     When the processing of the flowchart of  FIG.  6    begins, it is, at a step ST 1 , first determined whether or not the seating sensor  43  is ON. When the seating sensor  43  is not ON (step ST 1 : No), nobody is seated on the vehicle seat S. Thus, an OFF signal is transmitted to the drive circuit  41 , and supply of the drive power from the drive circuit  41  to the motor  31  is stopped to terminate the processing. 
     When the seating sensor  43  is ON (step ST 1 : Yes), it is, at a step ST 2 , further determined whether or not the door sensor  44  is ON. When the door sensor  44  is not ON (step ST 2 : No), the passenger has been seated on the vehicle seat S, but the vehicle door is not closed. Thus, the step ST 2  is repeated until the vehicle door is closed. 
     When the door sensor  44  is ON (step ST 2 : Yes), it is determined that the passenger has been seated on the vehicle seat S, and that the vehicle door has been closed. However, it is determined that the seatbelt  10  has not been fastened yet. Thus, at a step ST 3 , an ON signal is transmitted to the drive circuit  41 , and the drive power is supplied from the drive circuit  41  to the motor  31 . Accordingly, the motor  31  (the cylinder  31   b ) lowers to the predetermined lowered position, and such lowering movement is transmitted to the rotary member  34  via the support shaft  31   c . Then, the rotary member  34  rotates upward about the rotary shaft  33  to the protruding position. The rotary member  34  rotates upward to protrude forward, thereby pushing the seatbelt  10  forward and upward. 
     Next, at a step ST 4 , it is determined whether or not the buckle sensor  45  at a position corresponding to the seating sensor  43  in an ON state is ON. When the buckle sensor  45  is not ON (step ST 4 : No), it is determined that the passenger has been seated but the seatbelt  10  has not been fastened yet, and the drive power is continuously supplied from the drive circuit  41  to the motor  31 . Note that when the motor  31  (the cylinder  31   b ) has already lowered to the lowered position, the motor  31  (the cylinder  31   b ) is held at the lowered position even when supply of the drive power is stopped. 
     The step ST 4  is repeated until the buckle sensor  45  is turned on or until a predetermined period of time is elapsed after start of lowering of the motor  31  at a step ST 5 . Accordingly, the motor  31  (the cylinder  31   b ) is held at the predetermined lowered position, and the rotary member  34  is held at the protruding position. The seatbelt  10  is held with the seatbelt  10  being pushed out by the rotary member  34 . Note that at this point, an announcement such as “please fasten the seatbelt,” warning sound, or vibration may be simultaneously emitted. 
     When the buckle sensor  45  is ON (step ST 4 : Yes), the seated passenger on the vehicle seat S has fastened the seatbelt  10 . Thus, at a step ST 6 , another ON signal is transmitted to the drive circuit  41 , and the drive power is supplied from the drive circuit  41  to the motor  31 . Accordingly, the motor  31  (the cylinder  31   b ) lifts to the predetermined lifted position (the standby position), and such lifting movement is transmitted to the rotary member  34  via the support shaft  31   c . Then, the rotary member  34  rotates downward from the protruding position to the housing position. Alternatively, when the predetermined period of time has been elapsed at the step ST 5 , the seated passenger does not fasten the seatbelt  10  yet, but the processing proceeds to a step ST 6 . 
     When the motor  31  (the cylinder  31   b ) has lifted to the predetermined lifted position (the standby position) (step ST 7 : Yes), an OFF signal is transmitted to the drive circuit  41  at a step ST 8 . Then, supply of the drive power from the drive circuit  41  to the motor  31  is stopped. Accordingly, the motor  31  is held at the lifted position, and the rotary member  34  is held at the housing position. Note that when the motor  31  does not lift to the lifted position (step ST 7 : No), the step ST 7  is repeated. The processing of  FIG.  6    ends through the steps ST 1  or ST 8  described above. 
     By the above-described processing flow, before the seated passenger on the vehicle seat S fastens the seatbelt  10 , the belt assist device  30  can move at least a portion of the seatbelt  10  to the position easily reached by the seated passenger&#39;s hand. After the seated passenger has fastened the seatbelt  10 , the belt assist device  30  is integrally housed in the vehicle seat S without causing obstruction. 
     Note that in the above-described processing flow, determination on both of the seating sensor  43  and the door sensor  44  is required at the steps ST 1 , ST 2 , but the embodiments of the present disclosure are not limited to such a configuration. Needless to say, determination on any one of the seating sensor  43  or the door sensor  44  may be omitted. Moreover, when the predetermined period of time has been elapsed at the step ST 5 , the processing also proceeds to the step ST 6  to start lifting of the motor  31  to start movement of the rotary member  34  from the protruding position to the housing position. However, it may be configured such that the processing does not proceed to the step ST 6  until the buckle sensor  45  is turned on at the step ST 4 , needless to say. 
     Second Embodiment of Belt Assist Device 
     Next, the second embodiment of the belt assist device is described with reference to  FIGS.  7  to  9   . Note that contents overlapping with those of the above-described belt assist device  30  will not be repeated. A belt assist device  130  of the second embodiment is attached to an upper portion of a back side portion  120 . 
     The belt assist device  130  generally includes a support  132  fixed, by snap-fitting, to a substantially inverted T-shaped opening  121   a  provided at a side base  120   a , a rotary shaft  133  pivotally supported in the support  132 , and a rotary member  134  attached via the rotary shaft  133 . Note that a drive motor (not shown) configured to drive the rotary member  134  is attached to the rotary member  134 . 
     As illustrated in  FIGS.  9 A and  9 B , the belt assist device  130  is a device configured to rotate the rotary member  134  between a housing position at which the rotary member  134  is housed in a housing portion  121  of the back side portion  120  and a protruding position at which the rotary member  134  protrudes forward of the back side portion  120  to push out a portion of a seatbelt  10 . 
     The support  132  is a resin body configured to rotatably support the rotary member  134 , and a pair of support holes  132   c  configured to pivotally support the rotary shaft  133  are formed respectively at right and left lateral wall portions of the support  132 . Moreover, a plurality of substantially columnar coupling portions  132   d  coupling the right and left lateral wall portions together are provided at an upper portion of the support  132 . The rotary shaft  133  extends in a right-to-left direction, and is further pivotally supported by a shaft hole  134   c  of the rotary member  134  with the rotary shaft  133  being pivotally supported by the pair of support holes  132   c . Further, the rotary shaft  133  is attached to lower portions (lower end portions) of the support  132  and the rotary member  134 . 
     As illustrated in  FIG.  8   , the rotary member  134  is a member including a resin plate and configured to push out a portion of the seatbelt  10  from behind. The rotary member  134  is rotatably provided between the housing position of  FIG.  9 A  and the protruding position of  FIG.  9 B . A reinforcement rib  134   a  illustrated in  FIGS.  9 A and  9 B  is formed to extend backward from a center portion of a back surface of the rotary member  134  in the right-to-left direction. Moreover, the shaft hole  134   c  extending in the right-to-left direction is, across the right-to-left direction, integrally attached to a lower portion of the back surface of the rotary member  34 . The rotary shaft  133  is inserted into the shaft hole  134   c  across the right-to-left direction. 
     In the above-described configuration, the rotary member  134  is disposed to move to the protruding position of  FIG.  9 B  in such a manner that the rotary member  134  rotates downward about the rotary shaft  133  from the housing position of  FIG.  9 A  to protrude forward of a seat. The rotary member  134  is configured such that an angle with the back side portion  120  is equal to or smaller than about 90 degrees when the rotary member  134  has moved to the protruding position. 
     Moreover, in the above-described configuration, when the rotary member  134  has moved to the protruding position, the reinforcement rib  134   a  is disposed to contact the coupling portions  132   d  of the support  132 . Thus, the rotary member  134  can be positioned at the protruding position, and can be stably supported by the support  132 . 
     Third Embodiment of Belt Assist Device 
     Next, the third embodiment of the belt assist device is described with reference to  FIGS.  10 A and  10 B . A belt assist device  230  of the third embodiment is attached to an upper portion of a back side portion  220 . The belt assist device  230  generally includes a rotary shaft  233  pivotally supported in a side base  220   a , and a rotary member  234  attached via the rotary shaft  233 . Note that a drive motor (not shown) configured to drive the rotary member  234  is attached to the rotary member  234 . 
     As illustrated in  FIGS.  10 A and  10 B , the belt assist device  230  is a device configured to rotate the resin rotary member  234  having a rotary shape between a housing position at which the rotary member  234  is housed in a housing portion  221  of the back side portion  220  and a protruding position at which the rotary member  234  partially protrudes forward of the back side portion  220  to push out a portion of a seatbelt  10 . With the above-described configuration, the belt assist device  230  having a simple compact configuration can be provided. 
     Fourth Embodiment of Belt Assist Device 
     Next, the fourth embodiment of the belt assist device is described with reference to  FIGS.  11  to  17   . A belt assist device  330  of the fourth embodiment is a device configured to rotate a rotary member  334  between a protruding position illustrated in  FIG.  11    and a housing position illustrated in  FIG.  12   . 
     The rotary member  334  is attached to a lateral portion of a seat back  2  in a right-to-left direction as illustrated in  FIG.  1   . Of right and left end portions of the rotary member  334 , an inner end portion close to a center portion of the seat back  2  is provided with a cutout portion  334   d  cut out in a substantially rectangular shape toward an outer end portion farther from the center portion of the seat back  2 . As illustrated in  FIG.  11   , the cutout portion  334   d  is more cut out toward the outer end portion when extending from a lower end portion to an upper end portion of the rotary member  334 . Thus, as illustrated in  FIG.  11   , when a seatbelt  10  is pulled toward a seated passenger&#39;s body so that a seated passenger can fasten the seatbelt  10 , the rotary member  334  is easily used without a portion of the seatbelt  10  being pinched in a clearance between the rotary member  334  at the protruding position and the seat back  2 . 
     Moreover, as illustrated in  FIG.  11   , lower end portions of right and left end portions of a front surface of the rotary member  334  are provided respectively with a position restriction portion  334   e  protruding forward and configured to restrict movement of the seatbelt  10  in the right-to-left direction. In other words, the rotary member  334  is in such a shape that a center portion of the front surface of the rotary member  334  is recessed backward of the right and left end portions. Thus, when the rotary member  334  is at the protruding position at which a portion of the seatbelt  10  is pushed forward, the right and left position restriction portions  334   e  can reduce displacement of the seatbelt  10  in the right-to-left direction, and therefore, the seatbelt  10  can be stably pushed out. 
     The rotary member  334  is attached to a recessed housing portion  321  provided at the seat back  2 , the recessed housing portion  321  being configured to house the rotary member  334 . As illustrated in  FIGS.  12  and  13   , a support plate  332  configured to support the rotary member  334  is attached between the rotary member  334  and the recessed housing portion  321 , the support plate  332  being configured to house the rotary member  334 . A portion of the support plate  332  corresponding to the cutout portion  334   d  is provided with a protruding raised portion  332   e  protruding forward toward the rotary member  334 . The protruding raised portion  332   e  includes a substantially rectangular body, and is substantially formed flush with the front surface of the rotary member  334  when a front surface of the protruding raised portion  332   e  is at the housing position illustrated in  FIG.  12   . 
     The recessed housing portion  321  is formed in such a manner that a recessed housing plate  321   b  is attached to an opening formed at the seat back  2 . Specifically, as illustrated in  FIGS.  12  and  13   , back attachment portions  321   c  protruding respectively toward outer right and left sides and being attachable respectively to attachment target portions (not shown) provided at the seat back  2  are formed respectively at right and left end portions of the housing plate  321   b . As illustrated in  FIG.  14   , a body attachment portion  321   d  protruding backward toward a vehicle body (a transportation body) and being attachable to an attachment target portion (not shown) provided at a vehicle body is formed on a back surface of the housing plate  321   b . Thus, assembly rigidity of the housing plate  321   b  with the seat back  2  and the vehicle body is stabilized. 
     Note that as illustrated in  FIG.  14   , a rotary shaft  333  of the rotary member  334  is disposed at a position facing the body attachment portion  321   d  in a direction of attachment of the housing plate  321   b  to the support plate  332 . Thus, the rotary shaft  333  is, at the housing plate  321   b , disposed near the body attachment portion  321   d  whose rigidity is relatively enhanced, and therefore, rotation of the rotary member  334  is easily stabilized. 
     Of the housing plate  321   b , a substantially center portion and a portion corresponding to the protruding raised portion  332   e  are provided with a snap-fit hole  321   e  facing a hole (not shown) provided at a back surface of the support plate  332  and being attachable to the support plate  332  by snap-fitting, as illustrated in  FIGS.  13  and  14   . Thus, assembly of the housing plate  321   b  with the support plate  332  is stabilized. 
     As illustrated in  FIGS.  14  and  15   , a plurality of hook claw portions  321   f  for hooking of an end portion of a cover material  20   c  are formed at outer right and left surfaces of the housing plate  321   b , the hook claw portions  321   f  being formed with spacing in an upper-to-lower direction. Specifically, the end portion of the cover material  20   c  extends to cover a cushion pad  20   b , and then, is attached with the cover material  20   c  being sandwiched in a front-to-back direction between the housing plate  321   b  and the support plate  332 , as illustrated in  FIG.  15   . Opening holes  20   ca  provided on a tip end side of such an end portion are hooked onto the hook claw portions  321   f . Thus, attachability of the end portion of the cover material  20   c  is stabilized, and appearance and merchantability are improved without causing recesses, wrinkles, gaps, etc. at the end portion of the cover material  20   c  at the periphery of the rotary member  334 . 
     Further, the belt assist device  330  generally includes, as illustrated in  FIG.  14   , a motor  331  housed in the recessed housing portion  321 , and a drive shaft  331   b  interposed between the motor  331  and the rotary member  334  and configured to move up and down in association with driving of the motor  331  to rotate the rotary member  334 . 
     As illustrated in  FIGS.  14  and  16   , the motor  331  is a rotary motor including a drive shaft extending in the right-to-left direction, and is attached to the back surface of the housing plate  321   b . Specifically, the motor  331  is assembled with the motor  331  being sandwiched in the front-to-back direction between a front cover  336  and a back cover  337  as resin molded articles. Moreover, the motor  331  is held with the motor  331  being sandwiched in the upper-to-lower direction between upper and lower protruding holding portions  321   g  formed on the back surface of the housing plate  321   b . Further, the front cover  336  and the back cover  337  are assembled with these covers  336 ,  337  being sandwiched in a lateral cover  338  in the front-to-back direction. Thus, assembly of the motor  331  with the housing plate  321   b  is stabilized. 
     As illustrated in  FIG.  17   , a wheel gear  331   d  configured to rotate about an axis along the right-to-left direction in association with driving of the motor  331  and a worm gear  331   e  engaging with the wheel gear  331   d  and configured to rotate about an axis along the front-to-back direction in association with rotation of the wheel gear  331   d  are attached to a tip end of the drive shaft of the motor  331 . A screw gear portion of the drive shaft  331   b  on an outer surface thereof engages with the worm gear  331   e  such that the drive shaft  331   b  lifts/lowers while rotating about an axis along the upper-to-lower direction in association with rotation of the worm gear  331   e.    
     As illustrated in  FIG.  17   , the drive shaft  331   b  is configured such that an upper end side thereof is attached to a reinforcement rib  334   a  provided on a back surface of the rotary member  334  and such that a lower end side thereof is attached to the drive shaft of the motor  331 . The drive shaft  331   b  is disposed forward of a seat with respect to the drive shaft of the motor  331 . As illustrated in  FIGS.  16  and  17   , a support  331   f  coupling the rotary member  334  (the reinforcement rib  334   a ) and the drive shaft  331   b  together and including a support shaft portion  331   c  extending along the right-to-left direction is attached to an upper end portion of the drive shaft  331   b . Thus, lifting/lowering of the drive shaft  331   b  can be efficiently transmitted to the rotary member. 
     The support  331   f  includes a substantially T-shaped body. An upper portion of the support  331   f  is the support shaft portion  331   c  configured to support the rotary member  334 , and a lower portion of the support  331   f  is a portion coupled with the drive shaft  331   b . The support  331   f  is configured to transmit lifting/lowering of the drive shaft  331   b  to the rotary member  334 . Note that a structure is preferably made, in which the drive shaft  331   b  idles in the support  331   f . Note that the support  331   f  and the support shaft portion  331   c  may be formed as separate bodies. In the case of the separate bodies, it may be configured such that the support shaft portion  331   c  is pivotally supported by an opening provided at the support  331   f.    
     In the above-described configuration, the motor  331  is disposed without protruding outward from upper and lower ends of the housing plate  321   b  and without protruding outward from right and left ends of the housing plate  321   b , as illustrated in  FIG.  14   . Thus, compact attachment to the seat back  2  can be provided, and a clearance with respect to a vehicle-side body panel or other peripheral components is easily ensured. 
     Moreover, in the above-described configuration, the motor  331  is disposed at a lower portion of the back surface of the housing plate  321   b  at a position different from an upper portion provided with the body attachment portion  321   d , as illustrated in  FIG.  14   . Thus, contact between the motor  331  and each of the body attachment portion  321   d  and the vehicle body can be reduced, leading to compact arrangement. 
     Other Embodiments 
     In the above-described embodiment, the belt assist device  30  is configured to rotate the rotary member  34  by lifting/lowering of the motor  31  as illustrated in  FIGS.  3  and  4   , but the present disclosure is not limited to the stroke motor. Driving of other well-known drive motors, actuators, springs, etc. may be utilized to rotate the rotary member  34 . 
     Moreover, in the above-described embodiment, the rotary member  34  is attached to the upper portion of the back side portion  20  of the seat back  2  as illustrated in  FIGS.  1  and  2   , but the present disclosure is not limited to such a configuration. Needless to say, the rotary member  34  may be attached to a center or lower portion in the upper-to-lower direction. For example, the rotary member  34  is preferably disposed at a lower position of a lower end of the head rest  3 , and is preferably disposed at a lower position of the upper end of the seat back  2 . 
     Further, in the above-described embodiment, the rotary member  34  is formed as the resin member, but is changeable without limiting the present disclosure to such a rotary member. For example, the rotary member  34  may be formed as a metal member. Note that when the rotary member  34  is made of resin, the reinforcement rib  34   a , a lateral wall flange portion, etc. can be integrally molded, and rigidity can be relatively easily improved. 
     In addition, in the above-described embodiment, a rubber member such as an elastomer material may be separately attached to upper end portions and lower end portions of the rotary member  34 . With such a configuration, positioning is facilitated in opening/closing of the rotary member  34 , and rattling can be reduced. 
     Moreover, in the above-described embodiment, the pair of protruding portions (not shown) protruding forward is formed respectively at the right and left end portions of the front surface of the rotary member  34 , and function as the position restriction portion for the position of the seatbelt  10  in the right-to-left direction. However, this is changeable without limiting the present disclosure to such a configuration. For example, a recessed portion recessed backward at a center portion of the front surface of the rotary member  34  in the right-to-left direction may be formed as the position restriction portion. 
     Fifth to ninth embodiments of the present disclosure are described with reference to  FIGS.  18  to  30   . 
     Fifth Embodiment of Belt Assist Device 
     The present embodiment relates to a vehicle seat including a seatbelt assist device attached to a seat back and being configured to move a portion of a seatbelt placed on the seat back to a position easily reachable by a seated passenger. The seatbelt assist device includes a movable member attached to a recessed housing portion of the seat back via a rotary shaft and configured to rotate up and down between a housing position at which the movable member is housed in the seat back and a protruding position at which the movable member rotates to protrude forward of the seat back to push out a portion of the seatbelt, and an indicator section configured to inform the seated passenger, by light emission, that the movable member is at the protruding position. Note that the movable member is equivalent to a rotary member. 
     As illustrated in  FIG.  18   , a vehicle seat S is a seat configured to inform a seated passenger by light emission while a belt assist device  30  is pushing out a portion of a seatbelt  10 . The belt assist device  30  is an assist device configured to push a portion of the seatbelt  10  forward and upward, as well as being configured to inform the seated passenger, by light emission, that a portion of the seatbelt  10  has been pushed out. 
     As illustrated in  FIG.  19   , the belt assist device  30  generally includes a motor  31 , a support plate  32 , a rotary shaft  33 , a movable member  34 , and an auxiliary spring  35 . Moreover, the belt assist device  30  further includes a light emission device  60  (a light guide body  62 ) assembled such that a portion of the light emission device  60  is exposed behind the movable member  34  in the movable member  34  and being configured to emit light from the exposed portion. 
     As illustrated in  FIGS.  20 A and  20 B , the belt assist device  30  is a device configured to rotate the movable member  34  between a housing position at which the movable member  34  is housed in a recessed housing portion  21  of a seat back  2  and a protruding position at which the movable member  34  protrudes forward of the seat back  2  to push out a portion of the seatbelt  10 . It is configured to inform, by light emission from the light emission device  60 , the seated passenger of the movable member  34  being at the protruding position. 
     At a center portion of a back surface of a front wall portion of the movable member  34  in a right-to-left direction, a reinforcement rib  34   a  is formed to extend backward as illustrated in  FIG.  19   . The reinforcement rib  34   a  is provided with a support hole  34   b  configured to pivotally support a support shaft  31   c  and a shaft hole  34   c  configured to pivotally support the rotary shaft  33 . Moreover, a pair of shaft holes  34   d  configured to further pivotally support the rotary shaft  33  are formed respectively at right and left lateral wall portions of the movable member  34 . 
     A support rib  34   e  slightly extending toward the seated passenger in the right-to-left direction and configured to support the light guide body  62  (described below) in an assembled state thereof is formed at an extending end portion of the reinforcement rib  34   a . A substantially L-shaped slit  34   f  is formed to continuously extend across a front surface of the movable member  34  and a lateral surface of the movable member  34  close to the seated passenger in the right-to-left direction. The slit  34   f  is provided such that the light guide body  62  (described below) is partially exposed in the assembled state of the light guide body  62 . 
     The light emission device  60  is a device configured to inform the seated passenger, by light emission, that the movable member  34  is at the protruding position. The light emission device  60  generally includes a light source body  61  configured to emit light as illustrated in  FIGS.  20 A and  20 B , and the light guide body  62  configured to guide the light emitted from the light source body  61  as illustrated in  FIGS.  19  and  20   . The light emission device  60  is connected to a vehicle power source  42  via a drive circuit  46  equivalent to a harness (described below). The light source body  61  is an LED light source unit. The light source body  61  is attached to an inner surface of an upper wall portion of the movable member  34 , and is disposed in such a direction that light can be emitted to the light guide body  62 . Moreover, the light source body  61  is connected to the vehicle power source  42  via the drive circuit  46 . 
     The light guide body  62  is a light guide plate made of polycarbonate resin, and is in such a shape that the light guide body  62  can be assembled with a seated-passenger-side half of an inner back portion of the movable member  34  in the right-to-left direction. The light guide body  62  is assembled such that a portion of the light guide body  62  is exposed to the outside through the slit  34   f  of the movable member  34 . The light guide body  62  is designed to receive light into the light guide body  62  via a light reception surface close to the light source body  61  and to optionally reflect and guide the received light toward a front surface and a seated-passenger-side lateral surface, specifically an exposed portion  62   a  exposed through the movable member  34 . The exposed portion  62   a  protrudes toward a front side and a seated passenger side (a lateral side) with respect to a body portion of the light guide body  62 . 
     In the above-described configuration, the light guide body  62  is attached to a back surface of the movable member  34  on a seat back side when the movable member  34  is at the housing position illustrated in  FIG.  20 A . Thus, the light guide body  62  can be protected when the movable member  34  is at the housing position, and an increase in the size of the belt assist device  30  can be suppressed. 
     Moreover, in the above-described configuration, the light guide body  62  is, as illustrated in  FIGS.  19  and  20   , disposed on the seated-passenger-side lateral surface of the movable member  34  in the right-to-left direction and on a protruding tip end side of the movable member  34 . Thus, light emission from the light guide body  62  is more noticeable by the seated passenger, and a light emission area of the light guide body  62  can be easily ensured. 
     Further, in the above-described configuration, the light guide body  62  is attached so that the light guide body  62  and the movable member  34  can be together housed in the recessed housing portion  21 , and is disposed at a front position of the recessed housing portion  21  when the movable member  34  is at the protruding position. Thus, the light guide body  62  can be protected from scratching, contamination, etc. while the light emission area of the light guide body  62  can be easily ensured. 
     In addition, in the above-described configuration, the light guide body  62  is supported in the state in which the light guide body  62  is surrounded by the front wall portion, the seated-passenger-side lateral wall portion, the reinforcement rib  34   a , and the support rib  34   e  of the movable member  34 . Thus, ease of assembly of the light guide body  62  is improved. 
     Moreover, in the above-described configuration, it is configured such that reflection prisms are formed respectively on the seated-passenger-side lateral surface and the opposite lateral surface of the light guide body  62  in the right-to-left direction and that a slightly embossed portion is formed (e.g., frosted) on the seated-passenger-side lateral surface by, e.g., sandblasting. Thus, light can be preferentially surface-emitted from the seated-passenger-side lateral surface of the light guide body  62 . In addition, surface emission can be made with light being diffused as in frosted glass. Thus, designability is improved. 
     Further, in the above-described configuration, the light guide body  62  and the movable member  34  show color tones or color patterns with a contrast between the light guide body  62  and the movable member  34 . Specifically, the light guide body  62  is mixed with a pigment, a colorant, or a fluorescence agent such that at least the exposed portion  62   a  has a “warm” resin color such as amber or red. On the other hand, the movable member  34  is formed to have a “cold” resin color such as white or blue. Thus, e.g., when control is made not to emit light from the light guide body  62  during the day and to emit light from the light guide body  62  during the night, the seated passenger can easily recognize the presence of the movable member  34  by the warm color during the day, and can easily recognize the presence of the movable member  34  by light emission during the night. In particular, since the light guide body  62  and the movable member  34  show the color tones or the color patterns with the contrast, even when the seated passenger is an aged person with reduced vision, such a seated passenger can easily recognize the presence of the movable member  34 . Note that a cover material of a vehicle rear seat typically has a color of black or a similar color, and therefore, the contrast between the light guide body  62  and the movable member  34  become more visually prominent. 
     Next, a control section of the belt assist device  30  is described with reference to  FIGS.  21  and  22   . As illustrated in  FIG.  21   , the belt assist device  30  includes an ECU  40 , the drive circuits  41 ,  46  configured to supply drive power to the motor  31  and the light emission device  60 , and the vehicle power source  42  connected to the motor  31  via the drive circuit  41  and connected to the light emission device  60  via the drive circuit  46 . 
     The ECU  40  is configured to control the drive power supplied from the drive circuit  41  to the motor  31  to control ON or OFF of current of an electromagnetic clutch (not shown), thereby controlling lifting/lowering of the motor  31 , i.e., rotation of the movable member  34 . Moreover, the ECU  40  is configured to control the drive power supplied from the drive circuit  46  to the light emission device  60  to control ON or OFF of current of the electromagnetic clutch (not shown), thereby controlling ON/OFF of the light emission device  60 . 
     The ECU  40  is provided at a seat cushion  1 , and is connected to a seating sensor  43 , a door sensor  44 , a buckle sensor  45 . In the above-described configuration, the ECU  40  controls operation of the motor  31 , i.e., operation of the movable member  34 , and light emission from the light emission device  60  based on a signal input from each sensor. 
     Processing of a flowchart of  FIG.  22    is repeatedly executed during a period for which, e.g., control is made by the ECU  40  to turn on an ignition switch of a vehicle. In a normal state, the belt assist device  30  is at the housing position illustrated in  FIG.  20 A , and is integrally housed without protruding beyond an outer surface of the seat back  2 . The seatbelt  10  substantially closely contacts the outer surface of the seat back  2 . 
     When the processing of the flowchart of  FIG.  22    begins, it is, at a step ST 11 , first determined whether or not the seating sensor  43  is ON. When the seating sensor  43  is not ON (step ST 11 : No), nobody is seated on the vehicle seat S. Thus, an OFF signal is transmitted to the drive circuit  41 , and supply of the drive power from the drive circuit  41  to the motor  31  is stopped to terminate the processing. 
     When the seating sensor  43  is ON (step ST 11 : Yes), it is, at a step ST 12 , further determined whether or not the door sensor  44  is ON. When the door sensor  44  is not ON (step ST 12 : No), the passenger has been seated on the vehicle seat S, but a vehicle door is not closed. Thus, the step ST 12  is repeated until the vehicle door is closed. 
     When the door sensor  44  is ON (step ST 12 : Yes), the passenger has been seated on the vehicle seat S, and the vehicle door has been closed. However, it is determined that the seatbelt  10  has not been fastened yet. Thus, at a step ST 13 , an ON signal is transmitted to the drive circuit  41 , and the drive power is supplied from the drive circuit  41  to the motor  31 . Accordingly, the motor  31  (a cylinder  31   b ) lowers to a predetermined lowered position, and such lowering movement is transmitted to the movable member  34  via the support shaft  31   c . Then, the movable member  34  rotates upward about the rotary shaft  33  to the protruding position. The movable member  34  rotates upward to protrude forward, thereby pushing the seatbelt  10  forward and upward. 
     Next, at a step ST 14 , an ON signal is transmitted to the drive circuit  46 , and the drive power is supplied from the drive circuit  46  to the light emission device  60 . Accordingly, the light guide body  62  (the exposed portion  62   a ) begins emitting light in response to (in association with) lowering of the motor  31 . The light guide body  62  preferably begins, as the timing of beginning light emission, emitting light in time with start of movement of the movable member  34 . 
     Next, at a step ST 15 , it is determined whether or not the buckle sensor  45  at a position corresponding to the seating sensor  43  in an ON state is ON. When the buckle sensor  45  is not ON (step ST 15 : No), it is taken as the passenger being seated but the seatbelt  10  being not fastened yet, and the drive power is continuously supplied from the drive circuit  41  to the motor  31 . Note that when the motor  31  (the cylinder  31   b ) has already lowered to the lowered position, the motor  31  (the cylinder  31   b ) is held at the lowered position even when supply of the drive power is stopped. 
     The step ST 15  is repeated until the buckle sensor  45  is turned on or until a predetermined period of time is elapsed after start of lowering of the motor  31  at a step ST 16 . Accordingly, the motor  31  (the cylinder  31   b ) is held at the predetermined lowered position, and the movable member  34  is held at the protruding position. The seatbelt  10  is held with the seatbelt  10  being pushed out by the movable member  34 . At this point, the light guide body  62  continuously emits light while the movable member  34  is at the protruding position. Note that at this point, an announcement such as “please fasten the seatbelt,” warning sound, or vibration may be simultaneously emitted. 
     When the buckle sensor  45  is ON (step ST 15 : Yes), the seated passenger on the vehicle seat S has fastened the seatbelt  10 . Thus, at a step ST 17 , another ON signal is transmitted to the drive circuit  41 , and the drive power is supplied from the drive circuit  41  to the motor  31 . Accordingly, the motor  31  (the cylinder  31   b ) lifts to a predetermined lifted position (a standby position), and such lifting movement is transmitted to the movable member  34  via the support shaft  31   c . Then, the movable member  34  rotates downward from the protruding position to the housing position. Alternatively, when the predetermined period of time has been elapsed at the step ST 16 , the seated passenger has not yet fastened the seatbelt  10 , but the processing proceeds to the step ST 17 . 
     When the motor  31  (the cylinder  31   b ) has lifted to the predetermined lifted position (the standby position) (step ST 18 : Yes), an OFF signal is transmitted to the drive circuit  46  at a step ST 19 . Then, supply of the drive power from the drive circuit  46  to the light emission device  60  is stopped. This turns off the light emission device  60 . Further, at a step ST 20 , an OFF signal is transmitted to the drive circuit  41 , and supply of the drive power from the drive circuit  41  to the motor  31  is stopped. Accordingly, the motor  31  is held at the lifted position, and the movable member  34  is held at the housing position. Note that when the motor  31  does not lift to the lifted position (step ST 18 : No), the step ST 18  is repeated. The processing of  FIG.  22    ends through the steps ST 11  or ST 20  described above. 
     By the above-described processing flow, before the seated passenger on the vehicle seat S fastens the seatbelt  10 , the belt assist device  30  can move at least a portion of the seatbelt  10  to a position easily reached by a seated passenger&#39;s hand, and can inform, by light emission from the light emission device  60 , the seated passenger of the seatbelt  10  being moved. After the seated passenger has fastened the seatbelt  10 , the belt assist device  30  is integrally housed in the vehicle seat S, and turns off the light emission device  60 . Thus, no obstruction is caused. 
     Sixth Embodiment of Belt Assist Device 
     Next, the sixth embodiment of the belt assist device is described with reference to  FIGS.  23  to  25   . A belt assist device  130  of the sixth embodiment is attached to an upper portion of a back side portion  120 . 
     The belt assist device  130  generally includes a support  132  fixed, by snap-fitting, to a substantially inverted T-shaped opening  121   a  provided at a side base  120   a , a rotary shaft  133  pivotally supported in the support  132 , and a movable member  134  attached via the rotary shaft  133 . Moreover, a plate-shaped light guide body  162  (a light emission device  160 ) and a plate-shaped cover member  163  covering the movable member  134  and the light guide body  162  are attached to a seated-passenger-side half of a back surface of the movable member  134  in a right-to-left direction. 
     The belt assist device  130  is a device configured to rotate the movable member  134  between a housing position at which the movable member  134  is housed in a housing portion  121  of the back side portion  120  and a protruding position at which the movable member  134  protrudes forward of the back side portion  120  to push out a portion of a seatbelt  10 . 
     The support  132  is a resin body configured to rotatably support the movable member  134 , and a pair of support holes  132   c  configured to pivotally support the rotary shaft  133  are formed respectively at right and left lateral wall portions of the support  132 . Moreover, a plurality of substantially columnar coupling portions  132   d  coupling the right and left lateral wall portions together are provided at an upper portion of the support  132 . The rotary shaft  133  extends in the right-to-left direction, and is further pivotally supported by shaft holes  134   c  of the movable member  134  with the rotary shaft  133  being pivotally supported by the pair of support holes  132   c . Further, the rotary shaft  133  is attached to lower portions (lower end portions) of the support  132  and the movable member  134 . 
     As illustrated in  FIG.  24   , the movable member  134  is a member including a resin plate and configured to push out a portion of the seatbelt  10  from behind. The movable member  134  is rotatably provided between the housing position and the protruding position. A reinforcement rib  134   a  illustrated in  FIG.  25    is formed to extend backward from a center portion of the back surface of the movable member  134  in the right-to-left direction. Moreover, the pair of shaft holes  134   c  extending in the right-to-left direction are integrally attached respectively to right and left end portions of a lower portion of the back surface of the movable member  134 . The rotary shaft  133  is inserted into the pair of shaft holes  134   c  across the right-to-left direction. 
     In the above-described configuration, the movable member  134  is disposed to move to the protruding position of  FIG.  23    in such a manner that the movable member  134  rotates downward about the rotary shaft  133  from the housing position to protrude forward of a seat. 
     Moreover, in the above-described configuration, when the movable member  134  has moved to the protruding position, the reinforcement rib  134   a  is disposed to contact the coupling portions  132   d  of the support  132 . Thus, the movable member  134  can be positioned at the protruding position, and can be stably supported by the support  132 . 
     The light emission device  160  is a device configured to inform the seated passenger, by light emission, that the movable member  134  is at the protruding position. The light emission device  160  generally includes a light source body  161  configured to emit light, and the light guide body  162  configured to guide the light emitted from the light source body  161 , as illustrated in  FIG.  25   . The light guide body  162  is a light guide plate made of polycarbonate resin, and is configured to receive light into the light guide body  162  via a light reception surface close to the light source body  161  and to optionally reflect and guide the received light toward a front surface and a seated-passenger-side lateral surface. 
     In the above-described configuration, the movable member  134 , the light guide body  162 , and the cover member  163  show color tones or color patterns with a contrast between adjacent ones of these components. Specifically, the movable member  134  and the cover member  163  are formed to have a “cold” resin color such as white or blue, and the light guide body  162  is formed to have a “warm” resin color such as amber or red. Thus, the seated passenger can more easily recognize the presence of the movable member  134  by the warm color during the day, and can easily recognize the presence of the movable member  134  by light emission during the night, for example. 
     Seventh Embodiment of Belt Assist Device 
     Next, the seventh embodiment of the belt assist device is described with reference to  FIGS.  26  and  27   . A belt assist device  430  of the seventh embodiment is attached to an upper portion of a back side portion  420 . As illustrated in  FIG.  26   , the belt assist device  430  generally includes a rotary shaft  433  pivotally supported in a side base  420   a , and a movable member  434  attached via the rotary shaft  433 . Moreover, a flat plate-shaped light guide body  462  (a light emission device  460 ) and a light emission body  466  (a light emission device  465 ) on a back surface (a bottom surface) of the light guide body  462  are attached to a back surface (a bottom surface) of the movable member  434  in a substantially flat plate shape. 
     The light emission device  460  is a device configured to inform the seated passenger, by light emission, that the movable member  434  is at a protruding position. The light emission device  460  generally includes a light source body (not shown) and the light guide body  462  configured to guide the light emitted from the light source body. The light emission device  465  is a device configured to irradiate a seated passenger with light when the movable member  434  is at the protruding position. The light emission device  465  generally includes the light emission body  466  having an LED light source unit, and an assembly member  467  for assembly of the light emission body  466 , as illustrated in  FIG.  27   . 
     The light emission body  466  generally includes a light source  466   a , a substrate  466   b  to which the light source  466   a  is fixed, a dome-shaped lens  466   c  configured to converge or diverge light emitted from the light source  466   a , and a knob  466   d  configured to adjust a light distribution angle of the lens  466   c.    
     In the above-described configuration, the rotary shaft  433  is attached to an upper end portion of the movable member  434 , and the light emission device  465  is attached to a lower end portion of the movable member  434 . Thus, a simple compact configuration is provided, and a light emission area of the light emission device  465  is easily ensured. 
     Moreover, in the above-described configuration, the light emission device  465  is the device configured to irradiate the seated passenger with light, and includes the knob  466   d  configured to adjust a light distribution angle of the light emission body  466 . Thus, the light emission body  466  can illuminate an optional site of the seated passenger, and can also serves as, e.g., a reading light in addition to the function of informing the seated passenger of the presence of the movable member  434 . Note that in the case of utilizing the light emission body  466  as the reading light, the color of light emitted from the light emission body  466  is preferably white or a light bulb color. 
     Eighth Embodiment of Belt Assist Device 
     Next, the eighth embodiment of the belt assist device is described with reference to  FIGS.  28  and  29   . A belt assist device  530  of the eighth embodiment is attached to an upper portion of a back side portion  520 . As illustrated in  FIG.  28   , the belt assist device  530  generally includes a rotary shaft  533  pivotally supported in a side base  520   a , and a movable member  534  attached via the rotary shaft  533 . Moreover, a flat plate-shaped light guide body  562  (a light emission device  560 ), a cover member  563  having a substantially recessed shape on a back surface (an upper surface) of the light guide body  562 , and a light emission body  566  (a light emission device  565 ) on a seated-passenger-side lateral surface of the cover member  563  are attached to a back surface (an upper surface) of the movable member  534  in a substantially flat plate shape. 
     The light emission device  560  is a device configured to inform the seated passenger, by light emission, that the movable member  534  is at a protruding position. The light emission device  560  generally includes a light source body (not shown) and the light guide body  562 . The light emission device  565  is a device configured to irradiate a seated passenger with light when the movable member  534  is at the protruding position. The light emission device  565  generally includes the light emission body  566  having an LED light source unit, and an assembly member  567  for assembly of the light emission body  566 , as illustrated in  FIG.  29   . 
     In the above-described configuration, the light emission device  565  is the device configured to irradiate the seated passenger with light, and is attached to the seated-passenger-side lateral surface of the cover member  563 . Moreover, the light emission device  565  includes a knob  566   d  configured to adjust a light distribution angle of the light emission body  566 . Thus, the light emission body  566  can more easily illuminate an optional site of the seated passenger, and can be also effectively utilized as, e.g., a reading light in addition to the function of informing the presence of the movable member  534 . 
     Ninth Embodiment of Belt Assist Device 
     Next, the ninth embodiment of the belt assist device is described with reference to  FIG.  30   . A belt assist device  630  of the ninth embodiment is attached to an upper end portion of a back side portion  620 , and is disposed forward of a belt guide  613 . The belt assist device  630  is a device configured to move up and down a movable member  634  between a housing position at which the movable member  634  is housed in the back side portion  620  and a protruding position at which the movable member  634  protrudes upward of the back side portion  620  to push a portion of a seatbelt  10  upward. 
     The movable member  634  generally includes a flat plate-shaped belt support  634   a  configured to support a portion of the seatbelt  10 , and a pair of slide legs  634   b  configured to support the belt support  634   a  from below. A light guide body  662  (a light emission device  660 ) having a flat plate shape is attached to a seated-passenger-side end portion of the belt support  634   a  in a right-to-left direction. The light emission device  660  is a device configured to inform the seated passenger, by light emission, that the movable member  634  is at the protruding position. The light emission device  660  generally includes a light source body (not shown) and the light guide body  662 . 
     Other Embodiments 
     In the above-described embodiment, the light emission device  60  is attached to the movable member  34  of the belt assist device  30  as illustrated in  FIG.  19   , but the present disclosure is not limited to such a configuration. The light emission device  60  may be attached onto the seat back  2  at the periphery of the belt assist device  30 , or may be attached to the inside of the seat back  2 . Needless to say, the light emission device  60  may be attached to the vehicle body. 
     Moreover, in the above-described embodiment, the light guide body  62  of the light emission device  60  is, as an indicator section, controlled to continuously emit light while the movable member  34  is at the protruding position. However, the light guide body  62  may be controlled to emit light while blinking. Such a configuration can more easily inform the seated passenger of the position of the movable member  34  by blinking light emission of the light guide body  62 . 
     Further, in the above-described embodiment, the light guide body  62  is the light guide plate designed such that polycarbonate resin is injection-molded and the slightly embossed portion and the reflection prisms are provided for light emission. However, this is changeable without limiting the present disclosure to such a configuration. For example, the light guide body  62  may be a light guide plate made of acrylic resin, or may be a soft side light emission fiber etc., needless to say. Similarly, the light source body  61  is not limited to the LED light source. For example, the light source body  61  may be an organic electroluminescent (EL) light source, a light bulb, etc. With such a configuration, the light guide body and the light source body providing brightness, a light emission area, a light emission color optimal for the shape structure of the belt assist device  30  can be selected. 
     The tenth to thirteenth embodiments of the present disclosure are described below with reference to  FIGS.  31  to  42   . 
     Basic Structure of Vehicle Seat 
     A vehicle seat (hereinafter referred to as a “present seat S”) of the present embodiments is first described with reference to  FIG.  31   . The present seat S forms a back seat of a vehicle. Note that contents of the present disclosure are applicable not only to the back seat, but also to a front seat on a vehicle front side. 
     Moreover, in a configuration illustrated in  FIG.  31   , two present seats S are arranged next to each other to sandwich a movable arm rest S 4  and a housing box S 5  of the arm rest S 4 . Note that the two right and left present seats S are bilaterally symmetrical, but have substantially similar configurations. Thus, only the structure of the present seat S positioned on the left side (the left side as viewed in  FIG.  31   ) is described below. 
     As illustrated in  FIG.  31   , the present seat S includes a seat back S 1  on which the upper body of a seated passenger on the seat leans, a seat cushion S 2  on which the hip of the seated passenger is placed, and a head rest S 3  configured to support the head of the seated passenger. The present disclosure is generally characterized by the seat back S 1 , and therefore, the seat back S 1  is generally described below. 
     As illustrated in  FIG.  31   , the seat back S 1  includes a support portion S 11  configured to support the back of the seated passenger from behind, and a lateral portion S 12  positioned lateral to the support portion S 11  (precisely, a side close to a vehicle door). The support portion S 11  is configured such that a pad material (not shown) placed on a seat back frame (not shown) is covered with a cover material. Moreover, the head rest S 3  is attached to the center of an upper end surface of the support portion S 11  via a head rest pillar. 
     The lateral portion S 12  is positioned at the side of the seated passenger on the present seat S, and is configured such that a resin plate  75  illustrated in  FIG.  32    is covered with a cover material  76 , for example. Moreover, the lateral portion S 12  is disposed such that a front surface of the lateral portion S 12  is inclined with respect to a front surface of the support portion S 11 . Further, in the present embodiment, an upper end of the lateral portion S 12  is at the same position as that of an upper end of the support portion S 11  in an upper-to-lower direction, and a lower end of the lateral portion S 12  is at the substantially same position as that of a lower end portion of the support portion S 11  in the upper-to-lower direction. A pullout port  73  is provided at an upper back position of the upper end of the lateral portion S 12 . A webbing  71  of a seatbelt is pulled out of the pullout port  73 . 
     The webbing  71  is equivalent to a belt portion (a band-shaped portion) of the seatbelt. When the seatbelt is at a standby position in an unlocked state, the webbing  71  is disposed at a position illustrated in  FIG.  31   . The unlocked state described herein means a state in which the posture of the seated passenger is not restrained and a state in which a tongue (a lock metal fitting)  71   a  attached to a predetermined portion of the webbing  71  is not fixed to a buckle  72  disposed at the side of the seat. Moreover, the standby state means the position of the seatbelt before the seatbelt is fastened (e.g., when the passenger boards the vehicle). 
     Moreover, when the seatbelt is at the standby position in the unlocked state, the webbing  71  is in such a posture that the webbing  71  is stretched in the upper-to-lower direction by a retractor (not shown) and that the webbing  71  extends longitudinally across the lateral portion S 12  as illustrated in  FIG.  31   . In other words, the front surface of the lateral portion S 12  of the seat back S 1  includes a region (hereinafter referred to as an “opposing region”) facing the webbing  71  from the upper end to the lower end of the lateral portion S 12 . As illustrated in  FIG.  31   , the opposing region is a band-shaped region positioned at a center portion of the lateral portion S 12  in a width direction. When the seatbelt is at the standby position in the unlocked state, the opposing region faces the webbing  71  from an upper end to a lower end of such a region. 
     On the other hand, when the seatbelt is fastened, the webbing  71  in the above-described posture is grasped and pulled forward by the seated passenger, and is bridged from the shoulder (the right shoulder) to the left side of the seated passenger. In such a state, when the tongue  71   a  is attached to the buckle  72 , the webbing  71  is locked, and the posture of the seated passenger is restrained by the webbing  71 . 
     Note that when the seatbelt is at the standby position in the unlocked state, the webbing  71  faces a predetermined region of the front surface of the lateral portion S 12  in the present embodiments, but the present disclosure is not limited to such a configuration. When the seatbelt is at the standby position in the unlocked state, the webbing  71  may face a predetermined region of the front surface of the support portion S 11 . 
     Tenth Embodiment 
     Next, the tenth embodiment is described with reference to  FIGS.  31  to  35   . In the tenth embodiment, a space formation portion  80  is provided in an opposing region formed at a front surface of a lateral portion S 12  of a seat back S 1 . The space formation portion  80  is provided for forming a space between the opposing region and a webbing  71  as illustrated in  FIG.  34    when a seatbelt is at a standby position in an unlocked state. In particular, as illustrated in  FIG.  31   , the space formation portion  80  is provided across the substantially entirety of the opposing region in an upper-to-lower direction. 
     Since the space formation portion  80  forms the space between the opposing region and the webbing  71 , a seated passenger easily grasps the webbing  71 . Specifically, since the above-described space is formed, a space is ensured, into which the seated passenger inserts one&#39;s finger between the opposing region and the webbing  71  to grasp the webbing  71 . 
     The space formation portion  80  is provided in the opposing region as described above, and is formed by a recessed portion recessed with respect to the periphery of a portion provided with the space formation portion  80 . In order to provide such a recessed portion in the opposing region, a decorative component illustrated in  FIGS.  32  and  33    is used. The decorative component (i.e., the space formation portion  80 ) for formation of the recessed portion includes two components, and specifically includes an inner portion  81  and an outer portion  82 . The materials of the inner portion  81  and the outer portion  82  are not particularly limited, but a resin molded article or a metal member is a preferable material, for example. 
     The inner portion  81  includes, as a body, a quadrangular frame body  81   a , and the outer portion  82  is housed in a housing space  81   c  formed in the frame body  81   a . Moreover, each portion of the frame body  81   a  has an L-shaped cross sectional shape. Tongue-shaped protrusions  81   b  extend outward respectively from corner and center portions of the frame body  81   a , as illustrated in  FIG.  33   . These tongue-shaped protrusions  81   b  are attached to the opposing region of the lateral portion S 12  by fasteners such as bolts or screws. Specifically, as illustrated in  FIG.  33   , a rectangular hole  74  corresponding to the outer shape of the frame body  81   a  is formed in the opposing region. The frame body  81   a  is fitted into the rectangular hole  74  while the protrusions  81   b  are fastened to a portion of the lateral portion S 12  at the periphery of the rectangular hole  74 . 
     The outer portion  82  has a half cylindrical curved portion  82   a  and a lateral end portion attached to each lateral end of the curved portion  82   a  and having a substantially L-shaped cross section. The curved portion  82   a  is a portion forming a recessed portion. Specifically, when the outer portion  82  is assembled with the inner portion  81 , the curved portion  82   a  is fitted into the inside of the frame body  81   a  of the inner portion  81 , i.e., the housing space  81   c , in the state in which a surface on a recessed side is positioned on a front side. Note that for the purpose of improving decorativeness of the outer portion  82 , a cover material similar to a cover material  76  used as the material of the lateral portion S 12  may be attached to the surface of the curved portion  82   a  on the recessed side. 
     Of the L-shaped lateral end portion, a portion forming one side is a protruding portion  82   b  protruding outward from each end of the curved portion  82   a . The protruding portion  82   b  is screwed to the frame body  81   a  of the inner portion  81  when the outer portion  82  is assembled with the inner portion  81 . Of the L-shaped lateral end portion, a portion forming the other side is a perpendicular portion  82   c  extending in a direction perpendicular to the protruding portion  82   b . When the outer portion  82  is assembled with the inner portion  81 , the perpendicular portion  82   c  is inserted into the housing space  81   c  formed in the frame body  81   a . Subsequently, the perpendicular portion  82   c  engages, at a tip end portion in an extension direction thereof, with the frame body  81   a  as illustrated in  FIG.  32   . Since the perpendicular portion  82   c  engages with the frame body  81   a  as described above, a favorable assembly state of the outer portion  82  and the inner portion  81  is held. 
     The decorative component configured such that the outer portion  82  is assembled with the inner portion  81  is fixed to the lateral portion S 12  in the state in which the decorative component is fitted into the rectangular hole  74  formed at the lateral portion S 12 , thereby functioning as the space formation portion  80 . More specifically, in a vehicle equipped with a present seat S, the above-described decorative component is disposed in the opposing region such that an opening of the outer portion  82  assembled with the inner portion  81  faces the front surface of the lateral portion S 12 . On the other hand, as illustrated in  FIG.  31   , when the seatbelt is at the standby position in the unlocked state, the webbing  71  is at a front position of the above-described opening. As a result, as illustrated in  FIG.  34   , when the seatbelt is at the standby position in the unlocked state, the space of the recessed portion formed by the outer portion  82  is formed between the webbing  71  and the front surface (precisely, the opposing region) of the lateral portion S 12 . 
     In the present embodiment, the length of the above-described recessed portion in a horizontal width direction is longer than the width of the webbing  71  as illustrated in  FIG.  32   . Thus, when the seatbelt is at the standby position in the unlocked state, one end and the other end of the webbing  71  in the width direction are positioned between one end and the other end of the recessed portion in the horizontal width direction. The horizontal width of the recessed portion described herein is the opening width of the recessed portion, and the horizontal width direction is a direction along the width direction of the present seat S. 
     Simply speaking, each end of the recessed portion in the horizontal width direction is positioned outside a corresponding one of the ends of the webbing  71  in the width direction. Thus, the size (particularly, the length in the horizontal width direction) of the recessed portion is large, but the finger can be inserted into the space of the recessed portion from each end of the webbing  71  in the width direction. This allows the seated passenger to more easily grasp the webbing  71 . 
     Note that in the above-described embodiment, each end of the recessed portion in the horizontal width direction is positioned outside a corresponding one of the ends of the webbing  71  in the width direction. However, the present disclosure is not limited to such a configuration. Only one of the ends of the recessed portion in the horizontal width direction may be positioned outside a corresponding one of the ends of the webbing  71  in the width direction. In other words, when the seatbelt is at the standby position in the unlocked state, one end (the left end) of the recessed portion in the horizontal width direction may be positioned farther from one end (the right end) of the webbing  71  in the width direction than from the other end (the left end) of the webbing  71  in the width direction, and the other end of the recessed portion in the horizontal width direction may be positioned between one end and the other end of the webbing  71  in the width direction. In such a positional relationship, the recessed portion is provided at a position close to one end side of the webbing  71  in the width direction. According to such a configuration, e.g., when the finger is inserted into the space of the recessed portion, the finger is inserted only from one end side (the left side) of the webbing  71  in the width direction. Although there are certain limitations on a direction in which the finger is inserted as described above, the size of the recessed portion can be more reduced according to the above-described configuration. 
     When compactness of the size of the recessed portion is more emphasized than easy grasping of the webbing  71 , each end of the recessed portion in the horizontal width direction may be positioned inside both ends of the webbing  71  in the width direction. 
     Of the dimensions of the recessed portion, a length in a direction (i.e., the upper-to-lower direction) intersecting the horizontal width direction of the recessed portion is, in the present embodiment, longer than a length in the horizontal width direction as illustrated in  FIGS.  31  and  33   . Simply speaking, the recessed portion forming the space formation portion  80  is an elongated recessed portion in the tenth embodiment. In this case, the space of the recessed portion is also formed elongated. With such an elongated recessed portion, the seated passenger can easily grasp the webbing  71  regardless of the body type of the seated passenger. 
     Moreover, in the present embodiment, the recessed portion forming the space formation portion  80  has a cross-sectional shape such that the webbing  71  can be more easily grasped. Specifically, the recessed portion is provided with an opening  80   a  facing the webbing  71  and a bottom surface  80   b  positioned opposite to the opening. In the tenth embodiment, the area of the opening of the recessed portion is larger than that of the bottom surface of the recessed portion. More specifically, the recessed portion of the present embodiment expands from the bottom surface toward an opening end as illustrated in  FIG.  34   . As long as the recessed portion is in a shape such that the opening is larger than the bottom surface as described above, the finger can be more easily inserted into the recessed portion. Thus, the webbing  71  can be much more easily grasped. 
     The degree of expansion of the recessed portion from the bottom surface  80   b  toward the opening  80   a  is lower in the upper-to-lower direction than in the horizontal width direction. In other words, a difference between the length of the opening  80   a  and the length of the bottom surface  80   b  is smaller in the upper-to-lower direction than in the horizontal width direction. With such a size relationship, the size of the recessed portion can be further reduced. 
     Further, in the present embodiment, the component forming the space formation portion  80  and a component forming a peripheral portion of the space formation portion  80  are separate components as illustrated in  FIG.  33   . Specifically, the decorative component forms the space formation portion  80 , and is incorporated into the present seat S in such a manner that the decorative component is fitted into the rectangular hole  74  formed in the opposing region of the lateral portion S 12  of the seat back S 1 . The decorative component incorporated into the present seat S is assembled and integrated with a portion of the lateral portion S 12  at the periphery of the decorative component. As described above, in the present embodiment, the component forming the space formation portion  80  is separated from the peripheral component, and therefore, the degree of freedom in molding of the space formation portion  80  is increased. Thus, in the present embodiment, the space formation portion  80  molded into a desired shape can be more easily obtained. 
     In the configuration in which the component forming the space formation portion  80  and the peripheral component are separated from each other, a seat manufacturing cost is increased by such a configuration. On the other hand, when the component forming the space formation portion  80  and the peripheral component are integrally molded, the cost can be reduced to a lower cost. Note that examples of such a method include a method in which the above-described recessed portion is integrally (simultaneously) molded with the lateral portion S 12  (precisely, a resin plate  75  as a base portion of the lateral portion S 12 ) when the lateral portion S 12  is molded by vacuum molding. 
     In the present embodiment, the recessed portion forms the space formation portion  80 , and particularly, the recessed portion formed by the half cylindrical component (specifically, the outer portion  82  of the decorative component) forms the space formation portion  80 . The shape of the recessed portion described herein is not particularly limited. For example, a bowl-shaped component may form the recessed portion as illustrated in  FIG.  35   . The component illustrated in  FIG.  35    is equivalent to a variation of the outer portion  82  of the decorative component forming the recessed portion, and is hereinafter referred to as an “outer portion  82 X” of the variation. The outer portion  82 X of the variation has, as illustrated in  FIG.  35   , a bowl-shaped portion  82 Xa functioning as a portion forming the recessed portion, and a flange portion  82 Xb as a peripheral edge portion of an opening end of the bowl-shaped portion  82 Xa. The bowl-shaped portion  82 Xa is equivalent to the curved portion  82   a  of the outer portion  82  described above, and the flange portion  82 Xb is equivalent to the protruding portion  82   b  of the outer portion  82 . Using the outer portion  82 X of the variation, the bowl-shaped recessed portion is formed. 
     In addition, in the present embodiment, the recessed portion forms the space formation portion  80  as described above, but the present disclosure is not limited to such a configuration. That is, as long as the space is formed between the opposing region and the webbing  71  when the seatbelt is at the standby position in the unlocked state, the space formation portion  80  is not limited to the recessed portion, and a raised portion may form the space formation portion  80 . 
     Eleventh Embodiment 
     Next, the eleventh embodiment is described with reference to  FIGS.  36  to  38   . In the eleventh embodiment, an airbag module M is built in a lateral portion S 12  of a seat back S 1 . The airbag module M is a module of an airbag (precisely, a side airbag) configured to expand when a lateral impact load acts on a vehicle and equipment relating to the airbag. Note that in the present embodiment, the airbag module M (indicated by a dashed line in  FIG.  36   ) is disposed on a back side of an opposing region of the lateral portion S 12  as illustrated in  FIG.  36   . 
     In the present embodiment, each space formation portion  180  is, in the opposing region, provided to deviate from a portion where the airbag module M is disposed behind. Specifically, as illustrated in  FIG.  36   , the space formation portions  180  are provided respectively at upper and lower positions of the portion where the airbag module M is disposed behind. Each space formation portion  180  is different from the space formation portion  80  of the tenth embodiment in size (particularly, a length in an upper-to-lower direction), but has functions and a basic structure common to those of the space formation portion  80  of the tenth embodiment. As described above, in the present embodiment, since each space formation portion  180  is, in the opposing region, provided to deviate from the portion where the airbag module M is disposed behind, influence of the space formation portions  180  on actuation of the airbag module M can be reduced. 
     Note that in a case illustrated in  FIG.  36   , the space formation portions  180  are, in the opposing region, provided respectively at the upper and lower positions deviating from the portion behind which the airbag module M is disposed. Note that the present disclosure is not limited to such a configuration, and the space formation portion  180  may be provided only at the lower position of the portion where the airbag module M is disposed behind as illustrated in  FIG.  37   . 
     Alternatively, as illustrated in  FIG.  38   , the space formation portions  180  may be arranged respectively at positions different from the arrangement position of the airbag module M in a right-to-left direction. In this case, the space formation portions  180  may be arranged to avoid a portion where a webbing Ma extending from the airbag module M is connected to the lateral portion S 12 , i.e., a portion as a break line TL in airbag expansion. Note that in  FIG.  38   , the space formation portions  180  are provided respectively on both sides of the break line TL for the sake of illustration, but the space formation portion  180  may be actually provided on one side. That is, when a seatbelt is at a standby position in an unlocked state, if the webbing  71  is positioned on the right side of the break line TL, the space formation portion  180  is preferably provided on the right side of the break line TL. If the webbing  71  is positioned on the left side of the break line TL, the space formation portion  180  is preferably provided on the left side of the break line TL. 
     Although not shown in the figure, it may be configured such that the space formation portion  180  is, in the opposing region, provided at the portion behind which the airbag module M is disposed. With such a configuration, a space between the webbing  71  and the airbag module M is effectively utilized so that the space formation portion  180  can be efficiently disposed. 
     Twelfth Embodiment 
     Next, the twelfth embodiment is described with reference to  FIGS.  39  and  40   . In the twelfth embodiment, a belt reacher  90  as a pushout mechanism is attached to an upper portion of an opposing region as illustrated in  FIG.  39   . As illustrated in  FIG.  40   , the belt reacher  90  includes a pushout body  91  formed in a substantially triangular shape as viewed from the side. The pushout body  91  is housed in a housing space provided at a lateral portion S 12  of a seat back S 1 . Moreover, the pushout body  91  is supported by a rotary shaft  91   a  provided in the housing space, thereby freely rotating back and forth and up and down. The pushout body  91  receives force from an actuator (not shown) to rotate about the rotary shaft  91   a.    
     At one end position (a position indicated by a dashed line in  FIG.  40   ) of a rotation area of the pushout body  91 , the pushout body  91  is completely housed in the housing space provided at the lateral portion S 12 . In such a state, the pushout body  91  does not protrude forward of a front surface of the lateral portion S 12 , and an opening of the housing space is substantially closed by a top surface of the pushout body  91  as illustrated in  FIG.  40   . On the other hand, at the other end position (a position indicated by a solid line in  FIG.  40   ) of the rotation area of the pushout body  91 , a top corner portion of the pushout body  91  somewhat protrudes forward of the front surface of the lateral portion S 12 . As a result, the top corner portion of the pushout body  91  comes into contact with a back surface of a portion of a webbing  71  of a seatbelt positioned right in front of the top corner portion of the pushout body  91 , thereby pushing such a portion forward. 
     As described above, in the present embodiment, since the belt reacher  90  is attached, the webbing  71  can be, in fastening of the seatbelt, more easily grasped by functions of the belt reacher  90 . Further, a space formation portion  280  is formed to deviate, in an upper-to-lower direction, from a portion attached to the belt reacher  90  in the opposing region. More specifically, the space formation portion  280  is, in the opposing region, provided at a lower position of the portion attached to the belt reacher  90  as illustrated in  FIG.  39   . Note that the space formation portion  280  of the present embodiment is different from the space formation portion  80  of the tenth embodiment in size (particularly, a length in the upper-to-lower direction), but has functions and a basic structure common to those of the space formation portion  80  of the tenth embodiment. 
     As described above, in the present embodiment, it is configured such that the belt reacher  90  and the space formation portion  280  are used in combination. With such a configuration, while the belt reacher  90  can be effectively utilized, the space formation portion  280  can be also used to much more easily grasp the webbing  71  of the seatbelt. Moreover, in the present embodiment, the belt reacher  90  and the space formation portion  280  can be utilized in a complementary manner. For example, when the pushout amount (the rotation amount) of the pushout body  91  is decreased, the space formation portion  280  covers a function lost by such a decrease. As a result, the size of the belt reacher  90  can be reduced while easy grasping of the webbing  71  can be ensured. Moreover, according to the above-described configuration, the space formation portion  280  can be efficiently disposed by effective utilization of a space at a lower position of the belt reacher  90 . 
     Note that in the present embodiment, the space formation portion  280  is, in the opposing region, provided at the lower position of the portion attached to the belt reacher  90 , but the present disclosure is not limited to such a configuration. The space formation portion  280  may be provided at an upper position of the portion attached to the belt reacher  90 . Alternatively, the space formation portions  280  may be provided respectively at the upper and lower positions of the portion attached to the belt reacher  90 . 
     Thirteenth Embodiment 
     Next, the thirteenth embodiment is described with reference to  FIGS.  41  and  42   . In the thirteenth embodiment, a space formation portion  380  is also provided in an opposing region of a front surface of a lateral portion S 12  of a seat back S 1  as in other embodiments. In the thirteenth embodiment, a component forming the space formation portion  380  is a movable member configured to move to switch an exposed surface. The exposed surface described herein is a surface positioned at the front surface of the lateral portion S 12  and facing a webbing  71  when a seatbelt is at a standby position in an unlocked state, i.e., a surface positioned in the opposing region. 
     The movable member forming the space formation portion  380  is a rotary member  381  rotatably supported by a rotary shaft  381   a . An axial direction of the rotary shaft  381   a  is along a width direction of a present seat S. Moreover, the rotary member  381  has two surfaces arranged on opposite sides with the rotary shaft  381   a  being sandwiched therebetween. A first surface  382  as one surface is equivalent to a recessed portion formation surface, and is a curved surface provided with an arc-shaped recess as illustrated in  FIGS.  41  and  42   . More specifically, the first surface  382  is curved such that a center portion of the first surface  382  in a rotation direction of the rotary member  381  is depressed. Note that both end portions of the first surface  382  in the rotation direction are somewhat raised with respect to the center portion. 
     Of the two surfaces of the rotary member  381 , a second surface  383  as the other surface is a surface not provided with a recess and formed along the front surface shape of the seat back S 1 . Moreover, the second surface  383  is formed by a cover material  384  attached to the rotary member  381 . Such a cover material  384  is similar to a cover material  76  used for the lateral portion S 12 . 
     Further, the rotary member  381  is housed in a half cylindrical cavity  77  formed at the lateral portion S 12 . The rotary member  381  rotates in the cavity  77  such that the surface exposed in the opposing region is switched between the first surface  382  and the second surface  383 . That is, the rotary member  381  reciprocates, by rotation about the rotary shaft  381   a , between a position at which only the second surface  383  of the first and second surfaces  382 ,  383  is exposed in the opposing region and a position at which the first surface  382  of the first and second surfaces  382 ,  383  is exposed in the opposing region. Note that the position at which only the second surface  383  of the first and second surfaces  382 ,  383  is exposed in the opposing region is equivalent to a position at which the recessed portion formation surface deviates from the opposing region. Specifically, such a position is a position illustrated in  FIG.  41   , and is hereinafter referred to as a “normal position.” On the other hand, the position at which the first surface  382  of the first and second surfaces  382 ,  383  is exposed in the opposing region is equivalent to a position at which the recessed portion formation surface is exposed in the opposing region. Specifically, such a position is a position illustrated in  FIG.  42   , and is hereinafter referred to as a “recessed portion formation position.” 
     The states of the rotary member  381  at the normal position and the recessed portion formation position are now described. In the state at the normal position, the second surface  383  is exposed through an opening of the cavity  77 . Moreover, when the rotary member  381  is at the normal position, the second surface  383  is at a position such that the second surface  383  is continuous to a portion of the front surface of the lateral portion S 12  at the periphery of the second surface  383  as illustrated in  FIG.  41   . Further, the second surface  383  is formed by the same cover material  384  as the cover material  76  used for the lateral portion S 12 . Thus, in the state of the rotary member  381  at the normal position, outer appearance is provided as if the rotary member  381  and the peripheral portion thereof are integrated together. Since the rotary member  381  is, for example, placed at the normal position as described above when the seatbelt is not fastened, the rotary member  381  (precisely, a recessed portion formed by the first surface  382 ) is hidden, and therefore, designability of the seat can be ensured. 
     When the rotary member  381  rotates from the normal position to reach the recessed portion formation position, the first surface  382  is exposed through the opening of the cavity  77  as illustrated in  FIG.  42   . When the first surface  382  is exposed, a space is formed between the opposing region of the front surface of the lateral portion S 12  and the webbing  71  as illustrated in  FIG.  42   . That is, the recessed portion formation position is a position that the rotary member  381  at the normal position rotates towards when a seated passenger fastens the seatbelt. The recessed portion formed by the rotary member  381  at the recessed portion formation position is utilized so that the webbing  71  can be more easily grasped. 
     In the state of the rotary member  381  at the recessed portion formation position, both end portions (equivalent to portions surrounding the recessed portion) of the first surface  382  in the rotation direction somewhat protrude outward of the cavity  77  as illustrated in  FIG.  42   . These protruding end portions (particularly, an upper end portion in  FIG.  42   ) of the first surface  382  in the rotation direction come into contact with a back surface of the webbing  71  positioned right in front of the end portions of the first surface  382 , thereby pushing the webbing  71  forward. As described above, in the present embodiment, the rotary member  381  has functions similar to those of the belt reacher  90  of the twelfth embodiment, and is used as both of the space formation portion  380  and the belt reacher. 
     When the rotary member  381  rotates from the normal position to reach the recessed portion formation position, a corner portion (specifically, a corner portion positioned on an upper end side of the second surface  383  and surrounded by a dashed line in  FIG.  42   ) of the rotary member  381  is locked in contact with an inner wall surface of the cavity  77  of the lateral portion S 12  as illustrated in  FIG.  42   . This can restrict further rotation of the rotary member  381  in the same rotation direction, and can hold the rotary member  381  at the recessed portion formation position. As described above, the corner portion of the rotary member  381  functions as a positioning portion  385  configured to hold the position of the rotary member  381 . With fulfillment of the function as the positioning portion  385 , the rotary member  381  is held at the above-described recessed portion formation position, and is utilized as the space formation portion  380  and the belt reacher. 
     Note that in the present embodiment, the component forming the space formation portion  380  is the rotary member  381 , and it is, by rotation of the rotary member  381 , switchable between the state in which the recessed portion is exposed and the state in which the recessed portion is hidden. With such a configuration, the above-described two states can be more easily switched. Note that the present disclosure is not limited to such a configuration, and the component forming the space formation portion may be other movable members than the rotary member  381  to switch the above-described two states by, e.g., slide movement. 
     The recessed portion formed at the first surface  382  of the rotary member  381  may be used for other purposes than the purpose of forming the space with respect to the webbing  71  of the seatbelt, and specifically, may be used for providing a space for housing of a small product. Thus, the rotary member  381  as the space formation portion is also used for forming the space for housing of the small product, and therefore, the rotary member  381  can be more effectively utilized. 
     In the above-described embodiment, the vehicle seat used for an automobile has been described as a specific example, but the present disclosure is not limited to such an example. The present disclosure can be utilized not only as vehicle seats for trains, buses, etc., but also as vehicle seats for airplanes, ships, etc. 
     In the above-described embodiment, the vehicle seat of the present disclosure has been generally described. Note that the above-described embodiments have been set forth merely as examples for the sake of easy understanding of the present disclosure, and are not intended to limit the present disclosure. Changes and modifications can be made to the present disclosure without departing from the gist of the present disclosure. Needless to say, the present disclosure includes equivalents thereof. 
     TABLE OF REFERENCE NUMERALS 
     
         
         S: vehicle seat (present seat) 
           1 : seat cushion 
           2 : seat back 
           3 : head rest 
           10 : seatbelt
         10   a : lower end side     10   b : upper end side     
           11 : tongue plate 
           12 : buckle 
           13 ,  413 : belt guide
         13   a : guide hole     
           20 ,  120 ,  220 ,  420 ,  520 ,  620 : back side portion
         20   a ,  120   a ,  220   a ,  420   a ,  520   a : side base     20   b : cushion pad     20   c : cover material
             20   ca : opening hole         
           21 ,  121 ,  221 ,  321 ,  421 ,  521 : recessed housing portion (housing portion)
         21   a ,  22   a ,  23   a ,  121   a : opening     21   b ,  22   b ,  23   b ,  321   b : housing plate     321   c : back attachment portion     321   d : body attachment portion     321   e : snap-fit hole     321   f : hook claw portion     321   g : protruding holding portion     
           22 : recessed airbag housing portion 
           23 : belt facing recessed portion 
           30 ,  130 ,  230 ,  330 ,  430 ,  530 ,  630 : belt assist device 
           31 ,  331 : motor
         31   a : motor body     31   b : cylinder     331   b : drive shaft     31   c ,  331   c : support shaft (support shaft portion)     331   d : wheel gear     331   e : worm gear     331   f : support
             331   g : insertion hole         
           32 ,  132 ,  332 : support plate (support)
         32   a : attachment target portion     32   b : opening     32   c ,  132   c : support hole     132   d : coupling portion     332   e : protruding raised portion     
           33 ,  133 ,  233 ,  333 ,  433 ,  533 : rotary shaft 
           34 ,  134 ,  234 ,  334 ,  434 ,  534 ,  634 : rotary member (movable member)
         34   a ,  134   a ,  334   a : reinforcement rib     34   b : support hole     34   c ,  34   d ,  134   c : shaft hole     334   d : cutout portion     334   e : position regulation portion     34   e : support rib     34   f : slit     634   a : belt support     634   b : slide leg     
           35 : auxiliary spring 
           336 : front cover 
           337 : back cover 
           338 : lateral cover 
           40 : ECU 
           41 : drive circuit 
           42 : vehicle power source 
           43 : seating sensor 
           44 : door sensor 
           45 : buckle sensor 
           46 : drive circuit 
           50 : airbag module 
           60 ,  160 ,  460 ,  560 ,  660 : light emission device 
           61 ,  161 : light source body 
           62 ,  162 ,  462 ,  562 ,  662 : light guide body
         62   a : exposed portion     
           163 ,  563 : cover member 
           465 ,  565 : light emission device 
           466 ,  566 : light emission body
         466   a : light source     466   b : substrate     466   c : lens     466   d ,  566   d : knob/angle adjuster     
           467 ,  567 : assembly member 
           71 : webbing (belt portion)
         71   a : tongue     
           72 : buckle 
           73 : pullout port 
           74 : rectangular hole 
           75 : resin plate 
           76 : cover material 
           77 : cavity 
           80 ,  180 ,  280 ,  380 : space formation portion
         80   a : opening of recessed portion     80   b : bottom surface of recessed portion     
           81 : inner portion
         81   a : frame body     81   b : tongue-shaped protrusion     81   c : housing space     
           82 : outer portion
         82   a : curved portion     82   b : protruding portion     82   c : perpendicular portion     
           82 X: outer portion of the variation
         82 Xa: bowl-shaped portion     82 Xb: flange portion     
           381 : rotary member
         381   a : rotary shaft     
           382 : first surface 
           383 : second surface 
           384 : cover material 
           385 : positioning portion 
           90 : belt reacher, belt pusher 
           91 : pushout body
         91   a : rotary shaft     
         M: airbag module
       Ma: webbing   
     
         S 1 : seat back 
         S 11 : support portion 
         S 12 : lateral portion 
         S 2 : seat cushion 
         S 3 : head rest 
         S 4 : arm rest 
         S 5 : housing box 
         TL: break line