Patent Publication Number: US-2019168709-A1

Title: Webbing take-up device

Description:
TECHNICAL FIELD 
     The present disclosure relates to a webbing take-up device that enables rotation of a spool in a pull-out direction to be restricted as a result of a locking component being moved towards a locking side. 
     BACKGROUND ART 
     A webbing tale-up device exists in which, in a vehicle emergency, the rotation of a spool in a pull-out direction is restricted as a result of a locking component of a locking mechanism being moved towards a locking side (see, for example, Japanese Unexamined Patent Application Laid-Open (JP-A) No. H9-277904). In this type of webbing take-up device, the spool-side surface of the locking component comes into contact with a locking base or with the spool. Because of this, when the locking component is moved, if a tilt is generated in the locking component, then an outer peripheral edge of the locking component (namely, a corner portion of the locking component) comes into contact with the locking base or the spool, and this causes friction resistance to be generated between the locking component and the locking base or spool. 
     SUMMARY OF THE INVENTION 
     Technical Problem 
     The present disclosure was conceived in view of the above-described circumstances and provides a webbing take-up device that enables friction resistance between a locking component and a sliding contact surface with which the locking component is in sliding contact to be either prevented or inhibited from increasing. 
     Solution to the Problem 
     A webbing take-up device of a first aspect of the present disclosure includes a spool that is rotated in a pull-out direction as a result of a webbing of a seatbelt device being pulled out, a sliding contact surface that is provided at a side, in a rotation axis direction, of the spool, and a locking component that, as a result of the locking component being moved towards a locking side, causes rotation of the spool in the pull-out direction to be restricted. A curved surface portion that bulges towards the sliding contact surface side is provided at an inner side from an outer peripheral edge side at the sliding contact surface side of the locking component, and the curved surface portion is made to slide across the sliding contact surface by the movement of the locking component towards the locking side. 
     According to the webbing take-up device of the first aspect, a curved surface portion of a locking component is made to slide across a sliding contact surface by a movement of the locking component towards the locking side. Here, the curved surface portion is provided at an inner side from an outer peripheral edge side of the locking component, and this curved surface portion bulges towards the sliding contact surface side. Because of this, even if the locking component does become tilted when the locking component is being moved, the outer peripheral edge of the locking component is inhibited from coming into contact with the sliding contact surface, so that friction resistance between the locking component and the sliding contact surface is either prevented or inhibited from increasing. 
     In a webbing take-up device of a second aspect of the present disclosure, in the webbing take-up device of the first aspect, the curved surface portion is provided further toward the inner side of the locking component than a portion at the locking side of an outer peripheral edge at the sliding contact surface side of the locking component. 
     According to the webbing take-up device of the second aspect, the curved surface portion of the locking component is provided further toward the inner side of the locking component than a portion at the locking side of the outer peripheral edge at the sliding contact surface side of the locking component. Because of this, even if the locking component is moved towards the locking side so that, as a result of this movement, the locking component becomes tilted and the locking side of the outer peripheral edge at the sliding contact surface side of the locking component approaches close to the sliding contact surface, the outer peripheral edge of the locking component is inhibited from coming into contact with the sliding contact surface. 
     A webbing take-up device of a third aspect of the present disclosure, in the webbing take-up device of the first aspect or the second aspect, further comprises an engaging component at which are formed engaging teeth with which locking teeth that are formed at the locking component intermesh as a result of the movement of the locking component towards the locking side, rotation of the spool in the pull-out direction is restricted by the locking teeth intermeshing with the engaging teeth. The curved surface portion is provided further toward the inner side of the locking component than a portion of the locking teeth that is set at an outer peripheral edge at the sliding contact surface side of the locking component. 
     According to the webbing take-up device of the third aspect, the curved surface portion of the locking component is provided further toward the inner side of the locking component than a portion of the locking teeth, which intermesh with the engaging teeth of the engaging component, at the outer peripheral edge at the sliding contact surface side of the locking component. Because of this, even if the locking component is moved towards the locking side so that the locking teeth of the locking component approach close to the engaging teeth of the engaging component, and so that, as a result of this movement, the locking component is tilted and the portion of the locking teeth at the outer peripheral edge at the sliding contact surface side of the locking component approaches close to the sliding contact surface, the portion of the locking teeth at the outer peripheral edge of the locking component is inhibited from coming into contact with the sliding contact surface. 
     In a webbing take-up device of a fourth aspect of the present disclosure, in the webbing take-up device of the first aspect through the third aspect, a tilt inhibiting portion is disposed at the locking component at an opposite side, in the spool rotation axis direction, from the sliding contact surface, the locking component is sandwiched between the tilt inhibiting portion and the sliding contact surface, and in a case in which a tilt action is generated at the locking component, the locking component comes into contact with the tilt inhibiting portion so that tilting of the locking component is inhibited. 
     According to the webbing take-up device of the fourth aspect, a tilt inhibiting portion is provided at the locking component at an opposite side, in the spool rotation axis direction, from the sliding contact surface, and the locking component is sandwiched between the sliding contact surface and the tilt inhibiting portion. If a tilting action is generated at the locking component, the locking component comes into contact with the tilt inhibiting portion and, as a result of this, tilting of the locking component is inhibited. Because of this, even if a tilting action is generated in the locking component so that the portion of the locking teeth at the outer peripheral edge at the sliding contact surface side of the locking component approaches closer to the sliding contact surface, the portion of the locking teeth at the outer peripheral edge of the locking component is inhibited from coming into contact with the sliding contact surface. 
     In a webbing take-up device of a fifth aspect of the present disclosure, in the webbing take-up device of the fourth aspect, the locking component is moved towards the locking side as a result of the locking component receiving a load at a tilt inhibiting portion side on the opposite side from the curved surface side. 
     According to the webbing take-up device of the fifth aspect, the locking component is moved towards the locking side as a result of the opposite side of the locking component from the curved surface side receiving a load at the tilt inhibiting portion side. Because of this, although it is easy for a tilting action to be generated in the locking component when the locking component is being moved towards the locking side, even if the locking component does tilt such that the locking side of the outer peripheral edge at the sliding contact surface side of the locking component approaches the sliding contact surface, the outer peripheral edge of the locking component is inhibited from coming into contact with the sliding contact surface due to the curved surface portion being provided at the locking component. 
     Advantageous Effects of the Disclosure 
     As has been described above, in the webbing take-up device according to the present disclosure, friction resistance between the locking component and the sliding contact surface with which the locking component comes into contact is prevented or inhibited from increasing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front cross-sectional view showing the structure of a webbing take-up device according to an exemplary embodiment of the present disclosure. 
         FIG. 2  is an exploded perspective view of a spool, a locking base, and a locking plate of a webbing take-up device. 
         FIG. 3A  is a front cross-sectional view showing an enlargement of a spool, a locking base, a locking plate, and a V gear, and shows a state prior to the locking plate being rotated. 
         FIG. 3B  is a front cross-sectional view showing an enlargement of a spool, a locking base, a locking plate, and a V gear, and shows a state after the locking plate has been rotated. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Next, an exemplary embodiment of the present disclosure will be described based on the respective drawings shown in  FIG. 1  through  FIG. 3 . Note that an arrow FR, an arrow OUT, and an arrow UP that are shown in each drawing respectively indicate a front side, an outer side in a vehicle width direction, and an upper side of a vehicle in which a webbing take-up device  10  of the present exemplary embodiment has been applied. 
     Structure of the Present Exemplary Embodiment 
     As is shown in  FIG. 1 , the webbing take-up device  10  according to the present exemplary embodiment is provided with a frame  12  which serves as an engaging component. The frame  12  is fixed to a vehicle lower side portion of a center pillar (not shown in the drawings) which serves as a vehicle body. Additionally, the frame  12  is provided with leg plates  14  and  16 , and the leg plates  14  and  16  face each other substantially in the vehicle front-rear direction. 
     A spool  18  is provided in the frame  12 . The spool  18  is formed in a substantially circular cylinder shape. A direction of a central axis of the spool  18  extends in the direction in which the leg plate  14  and the leg plate  16  face each other (in other words, substantially in the vehicle front-rear direction), so that the spool  18  is able to rotate around the central axis thereof. A base end portion in a longitudinal direction of an elongated belt-shaped webbing  20  is anchored to the spool  18 , so that when the spool  18  is rotated in a take-up direction (i.e., in the direction shown by an arrow A in  FIG. 2 ), the webbing  20  is taken up by the spool  18  from the base end side in the longitudinal direction thereof. A distal end side in the longitudinal direction of the webbing  20  extends towards the vehicle upper side from the spool  18 , and the distal end side in the longitudinal direction of the webbing  20  passes through a slit hole formed in a through anchor (not shown in the drawings) which is supported on the center pillar at the vehicle upper side of the frame  12 , and is then folded back towards the vehicle lower side. 
     Additionally, the distal end portion in the longitudinal direction of the webbing  20  is anchored to an anchor plate (not shown in the drawings). The anchor plate is formed from a metal plate material such as steel or the like, and is fixed to a floor portion (not shown in the drawings) of the vehicle, or to a frame member or the like of a sheet (not shown in the drawings) that corresponds to this webbing take-up device  10 . 
     A vehicle seatbelt device in which the present webbing take-up device  10  is being used is provided with a buckle device (not shown in the drawings). The buckle device is disposed on the inner side in the vehicle width direction of the seat in which the present webbing take-up device  10  is being used. When the webbing  20  has been pulled over the body of a vehicle occupant who is sitting in this seat, a tongue (not shown in the drawings) provided at the webbing  20  is engaged with the buckle device resulting in the webbing  20  being fitted over the body of the vehicle occupant. 
     As is shown in  FIG. 1 , a spring housing  22  is provided at the vehicle front side of the leg plate  14  of the frame  12 . A spool urging mechanism such as a spiral spring or the like (not shown in the drawings) is provided at an inner side of the spring housing  22 , and the spool  18  is urged in the take-up direction by urging force imparted by the spool urging mechanism. 
     A pretensioner  24  is provided between the leg plate  14  of the frame  12  and the spring housing  22 . The pretensioner  24  is operated in the event of a vehicle emergency such as a vehicle collision or the like. When the pretensioner  24  is operated, the spool  18  is rotated in the take-up direction so that the webbing  20  is taken up by the spool  18 . As a result, the restraining force restraining the vehicle occupant provided by the webbing  20  is increased. 
     Additionally, the present webbing take-up device  10  is provided with a torsion bar  26  that forms a force limiter mechanism. The torsion bar  26  is formed in a bar shape that is elongated substantially in the vehicle front-rear direction. A vehicle front-side portion of the torsion bar  26  is disposed at an inner side of the spool  18 , and is connected to the spool  18  such that any relative rotation thereof relative to the spool  18  is prevented. 
     Additionally, the present webbing take-up device  10  is provided with a locking mechanism  28 . The locking mechanism  28  is provided with a locking base  30 . The locking base  30  is provided at the vehicle rear side of the spool  18  so as to be able to rotate freely around the central axis of the spool  18 . A vehicle rear-side portion of the torsion bar  26  is inserted into the locking base  30  so that any relative rotation of the locking base  30  relative to the torsion bar  26  is prevented. As a result of this, the locking base  30  is connected to the spool  18  via the torsion bar  26 , so that a relative rotation of the locking base  30  relative to the spool  18  is prevented. 
     As is shown in  FIG. 2 , a locking plate placement portion  32  is formed at the locking base  30 . The locking plate placement portion  32  is created by forming an opening in a portion of an outer periphery of the locking base  30 , so as to form a notch shape that is open on both sides in the vehicle front-rear direction of the locking base  30 . A main body portion of a locking plate  34 , which serves as a locking component, is disposed at the inner side of the locking plate placement portion  32 . A tail portion  36  extends from an end portion on a take-up direction side of the main body portion of the locking plate  34 . The tail portion  36  is formed in a plate shape whose thickness dimension (i.e., whose dimension in the vehicle front-rear direction) is smaller than that of the main body portion of the locking plate  34 . The tail portion  36  is formed on a spool  18  side (i.e., on the vehicle front side) of a central portion in the thickness direction (i.e., in the vehicle front-rear direction) of the main body portion of the locking plate  34 . 
     A tail portion placement portion  38  is formed at the locking base  30  so as to correspond to the tail portion  36  of the locking plate  34 . The tail portion placement portion  38  is formed as a recessed portion that is opened at a vehicle front-side surface of the locking base  30 . The tail portion placement portion  38  is created by forming an opening in an outer peripheral portion of the locking base  30 , and the tail portion placement portion  38  is connected to the locking plate placement portion  32  on a pull-out direction side (i.e. on the side in the direction indicated by an arrow B in  FIG. 2 ). The dimension in the vehicle front-rear direction of the tail portion placement portion  38  is set either the same as the thickness dimension of the tail portion  36  of the locking plate  34 , or slightly larger than the thickness dimension of the tail portion  36 . 
     When the main body portion of the locking plate  34  has been disposed within the locking plate placement portion  32  of the locking base  30 , the tail portion  36  is disposed within the tail portion placement portion  38  of the locking base  30 . A supporting hole  40  is formed at the tail portion  36 . A supporting pin  42  that is formed at the tail portion placement portion  38  protruding towards the vehicle front side is inserted into the supporting hole  40  at the locking plate  34 , so that the locking plate  34  is able to pivot around the supporting pin  42 . 
     A portion of the tail portion placement portion  38  that faces the tail portion  36  of the locking plate  34  in the vehicle front-rear direction is formed as an opposing wall  38 A which serves as a tilt inhibiting portion. If, due to looseness (i.e., due to a gap) between the supporting hole  40  at the locking plate  34  and the supporting pin  42  at the tail portion placement portion  38 , the locking plate  34  becomes tilted so that the direction of the central axis of the supporting hole  40  becomes tilted relative to the direction of the central axis of the supporting pin  42 , the locking plate  34  comes into contact with the opposing wall  38 A of the tail portion placement portion  38 . As a result, the tilting of the locking plate  34  is inhibited. 
     Moreover, a plurality of locking teeth  44  are formed at the locking plate  34 . These locking teeth  44  are formed at an end portion of the main body portion of the locking plate  34  on the opposite side from the tail portion  36 . A ratchet hole  46  is formed at the leg plate  16  of the frame  12  so as to correspond to the locking teeth  44 . The ratchet hole  46  is formed coaxially with the spool  18 , and is provided with ratchet teeth which are internal teeth serving as engaging teeth. When the locking plate  34  is pivoted towards the locking side (i.e., towards the side in the direction indicated by an arrow C in  FIG. 2 ) around the supporting pin  42 , the opposite side from the tail portion  36  side of the main body portion of the locking plate  34  is moved towards an outer side in a radial direction of the locking base  30 . When, as a result of this, the locking teeth  44  intermesh with the ratchet teeth of the ratchet hole  46  at the leg plate  16 , rotation of the locking base  30  in the pull-out direction is restricted. 
     Additionally, a guide pin  48  is formed at the locking plate  34 . The guide pin  48  protrudes towards the vehicle rear side from a vehicle rear-side surface of the main body portion of the locking plate  34 . The guide pin  48  is inserted into a guide hole  52  of a V gear  50 , which is serving as a rotating body of the locking mechanism  28  and which is provided at a vehicle rear side of the locking base  30 . The V gear  50  is supported at a supporting shaft  54  that extends towards the vehicle rear side from a vehicle rear-side end portion of the torsion bar  26 , so that the V gear  50  is able to rotate freely coaxially with the spool  18 . 
     A follower spring (not shown in the drawings) is provided between the V gear  50  and the locking base  30 , so that the V gear  50  is able to be rotated by urging force from the follower spring following the rotation of the locking base  30 . Moreover, the locking base  30  is also able to perform a relative rotation in the pull-out direction relative to the V gear  50  by resisting the urging force of the follower spring. In this way, when the locking base  30  is rotated in the pull-out direction relative to the V gear  50 , the guide pin  48  of the locking plate  34  is guided by the guide hole  52  of the V gear  50  so that, as a result of this, the locking plate  34  is pivoted towards the locking side around the supporting pin  42 . 
     In addition, the locking mechanism  28  is provided with a VSIR mechanism  56  and a WSIR mechanism  58 . The VSIR mechanism  56  of the locking mechanism  28  is operated, for example, as a result of the vehicle suddenly decelerating during a vehicle collision or the like, and the rotation of the V gear  50  in the pull-out direction is restricted due to the VSIR mechanism  56  being operated. In contrast to this, The WSIR mechanism  58  of the locking mechanism  28  is operated, for example, as a result of a rotation acceleration in the pull-out direction of the V gear  50  reaching a predetermined size or greater, and the rotation of the V gear  50  in the pull-out direction is restricted due to the WSIR mechanism  58  being operated. 
     Substantially the entire vehicle front-side surface of the locking plate  34  forms a curved surface portion  60 . The curved surface portion  60  is curved such that an inner side thereof bulges towards the vehicle front side beyond an outer peripheral edge of the vehicle front-side surface of the locking plate  34 . As is shown in  FIG. 3A , in the locking plate  34 , a portion of the curved surface portion  60  that is furthest to the vehicle front side is in contact with a vehicle rear-side surface  18 A of the spool  18 , with this vehicle rear-side surface  18 A serving as a seating surface which is an aspect of a sliding contact surface. 
     Furthermore, a portion of the curved surface portion  60  of the locking plate  34  that is furthest to the vehicle front side is set further toward an opposite side (i.e., on a side in the direction indicated by an arrow D in  FIG. 2 ) from the locking side than a locking side edge portion  60 A of an edge portion on the vehicle front side of each locking tooth  44  of the locking plate  34 . Moreover, the portion of the curved surface portion  60  that is furthest to the vehicle front side is also set further toward the locking side than an anti-locking side edge portion  60 B which is on an opposite side from a locking side of the outer peripheral edge of the vehicle front-side surface of the locking plate  34 . 
     Because of this, as is shown in  FIG. 3A , when the portion of the curved surface portion  60  of the locking plate  34  that is furthest to the vehicle front side is in contact with the vehicle rear-side surface  18 A of the spool  18 , the locking side edge portion  60 A of each locking tooth  44  shown in  FIG. 2  is provided further toward the vehicle rear side than the vehicle rear-side surface  18 A of the spool  18 , and the anti-locking side edge portion  60 B of the locking plate  34  is also provided further toward the vehicle rear side than the vehicle rear-side surface  18 A of the spool  18 . 
     In addition, a distal end of each locking tooth  44  has a certain amount of thickness in the vehicle front-rear direction, and the distal end of each locking tooth  44  and the ratchet teeth of the ratchet hole  46  in the leg plate  16  face each other in the radial direction of the spool  18 . As a consequence of this, in spite of the vehicle front-side surface of the locking plate  34  being formed as the curved surface portion  60 , the distal ends of the respective locking teeth  44  are able to intermesh with the ratchet teeth of the ratchet hole  46  in the leg plate  16 . 
     Actions and Effects of the Present Exemplary Embodiment 
     Next, actions and effects of the present exemplary embodiment will be described. 
     In the present webbing take-up device  10 , if the vehicle suddenly decelerates in the event of a vehicle emergency such as a vehicle collision or the like, the VSIR mechanism  56  of the locking mechanism  28  is operated. Moreover, if the body of a vehicle occupant performs an inertial movement towards the vehicle front side during the vehicle emergency, the webbing  20  that has been drawn across the body of the vehicle occupant is pulled. As a result, the locking base  30  is rotated in the pull-out direction together with the spool  18  and, furthermore, the V gear  50  is also rotated in the pull-out direction following the locking base  30 . If the rotational acceleration of the V gear  50  in the pull-out direction exceeds a predetermined size, then the WSIR mechanism  58  of the locking mechanism  28  is operated. 
     In case in which the VSIR mechanism  56  or the WSIR mechanism  58  is operated, rotation of the V gear  50  of the locking mechanism  28  in the pull-out direction is restricted. If, in this state, the webbing  20  is pulled out further so that the locking base  30  is rotated in the pull-out direction together with the spool  18 , then the locking base  30  performs a relative rotation in the pull-out direction relative to the V gear  50 . In the event that the locking base  30  is rotated in the pull-out direction relative to the V gear  50 , the guide pin  48  of the locking plate  34  receives a load from an internal side surface of the guide hole  52  in the V gear  50  and, as a result of this, the locking plate  34  is pivoted towards the locking side around the supporting pin  42 . 
     When the locking plate  34  is pivoted towards the locking side, the locking teeth  44  of the locking plate  34  are moved close to the ratchet teeth of the ratchet hole  46  in the leg plate  16 , and the locking teeth  44  intermesh with the ratchet teeth of the ratchet hole  46  in the leg plate  16 . As a result, rotation of the locking base  30  in the pull-out direction is restricted, and rotation of the spool  18  in the pull-out direction is also restricted. In this way, because the pulling out of the webbing  20  from the spool  18  is restricted as a result of the rotation of the spool  18  in the pull-out direction being restricted, the body of the vehicle occupant can be effectively restrained by the webbing  20 . 
     In the event that the locking base  30  performs a relative rotation in the pull-out direction relative to the V gear  50 , the guide pin  48  of the locking plate  34  that receives a load from the internal side surface of the guide hole  52  of the V gear  50  is provided on the vehicle rear side of the locking plate  34 . In contrast to this, when the locking plate  34  is pivoted towards the locking side, friction resistance is generated between the curved surface portion  60 , which is the vehicle front-side surface of the locking plate  34 , and the vehicle rear-side surface  18 A of the spool  18 . Because of this, when the guide pin  48  receives the load from the internal side surface of the guide hole  52  of the V gear  50  so that the locking plate  34  is pivoted towards the locking side, as is shown in  FIG. 3B , the locking plate  34  may become tilted in the direction indicated by an arrow E in  FIG. 3B . 
     Here, the vehicle front-side surface of the locking plate  34  forms the curved surface portion  60  that bulges towards the vehicle front side, and the locking plate  34  comes into contact with the vehicle rear-side surface  18 A of the spool  18  via the portion of the curved surface  60  that is furthest to the vehicle front side. Because of this, in a state prior to the locking plate  34  being pivoted towards the locking side, the locking side edge portion  60 A of the edge portion on the vehicle front side of each locking tooth  44  is located further toward the vehicle rear side than the vehicle rear side surface  18 A of the spool  18 . 
     As a consequence of this, when the locking plate  34  is tilted in the direction indicated by the arrow E in  FIG. 3B  as a result of the locking plate  34  being pivoted around the supporting pin  42  towards the locking side, the locking side edge portion  60 A of each locking tooth  44  is either prevented or inhibited from coming into contact with the vehicle rear-side surface  18 A of the spool  18 . As a consequence, friction resistance between the locking plate  34  and the vehicle rear-side surface  18 A of the spool  18  can be inhibited from increasing, and the locking plate  34  can pivot smoothly towards the locking side. 
     In addition, when the outer peripheral edge of the vehicle front-side surface of the locking plate  34  comes into contact with the vehicle rear-side surface  18 A of the spool  18 , resistance to the pivoting of the locking plate  34  towards the locking side increases. Here, in the present exemplary embodiment, as is described above, in a state prior to the locking plate  34  being pivoted towards the locking side, the locking side edge portion  60 A of each locking tooth  44  is located further toward the vehicle rear side than the vehicle rear side surface  18 A of the spool  18 . 
     Because of this, when the locking plate  34  begins to pivot towards the locking side, the locking side edge portion  60 A of each locking tooth  44  does not come into contact with the vehicle rear side surface  18 A of the spool  18 . As a consequence of this, friction resistance between the locking plate  34  and the vehicle rear-side surface  18 A of the spool  18  can be inhibited from increasing. As a result, the locking plate  34  is inhibited from tilting when this locking plate  34  is being pivoted, and any contact between the locking side edge portion  60 A of each locking tooth  44  and the vehicle rear-side surface  18 A of the spool  18  that might be generated by such a tilting of the locking plate  34  can be effectively prevented or inhibited. 
     Moreover, as is shown in  FIG. 2 , if the tail portion  36  of the locking plate  34  is sandwiched between the opposing wall  38 A of the tail portion placement portion  38  and the vehicle rear-side surface  18 A of the spool  18 , so that a tilt of a predetermined angle or greater in the vehicle front-rear direction is generated at the locking plate  34 , then the tail portion  36  of the locking plate  34  comes into contact with the opposing wall  38 A of the tail portion placement portion  38  of the locking base  30 . Because tilting of the locking plate  34  is inhibited, it is possible to effectively prevent or inhibit the locking side edge portion  60 A of each locking tooth  44  from being brought into contact with the vehicle rear-side surface  18 A of the spool  18  due to tilting of the locking plate  34 . 
     At the same time, the curved surface portion  60 , which is the vehicle front-side surface of the locking plate  34 , bulges towards the vehicle front side. Because of this, the anti-locking side edge portion  60 B, which is on the opposite side from the locking side, of the outer peripheral edge of the vehicle front-side surface of the locking plate  34  is positioned on the vehicle rear side of the portion of the curved surface portion  60  that is located furthest to the vehicle front side. 
     Because of this, when the locking plate  34  that has been pivoted to the locking side is restored by being pivoted towards the opposite side from the locking side, the anti-locking side edge portion  60 B of the locking plate  34  can be prevented or inhibited from coming into contact with the vehicle rear-side surface  18 A of the spool  18 . As a result, when the locking plate  34  is restored by being pivoted towards the opposite side from the locking side, tilting of the locking plate  34  (for example, tilting of the locking plate  34  in the opposite direction from the direction indicated by the arrow E in  FIG. 3B ) can be inhibited. Because of this, friction resistance between the locking plate  34  and the vehicle rear-side surface  18 A of the spool  18  can be inhibited from increasing, so that the locking plate  34  is able to pivot smoothly towards the opposite side from the locking side. 
     Note that, in the present exemplary embodiment, a structure is employed in which the vehicle rear-side surface  18 A of the spool  18  is a sliding contact surface, and the curved surface portion  60  of the locking plate  34  comes into contact with this vehicle rear-side surface  18 A of the spool  18 . However, it is also possible for the sliding contact surface with which the curved surface portion  60  of the locking plate  34  comes into contact to be set at the locking base  30 , or at a different component from both the locking base  30  and the spool  18 . 
     Furthermore, in the present exemplary embodiment, a structure is employed in which the curved surface portion  60  is set on the vehicle front-side surface of the locking plate  34  , however, it is also possible, for example, for a curved surface portion to be set at a vehicle rear-side surface of the tail portion  36 , and for a vehicle front-side surface of the opposing wall  38 A of the tail portion placement portion  38  to be formed as a sliding contact surface, and for this curved surface portion on the vehicle rear-side surface of the tail portion  36  to slide over the vehicle front-side surface of the opposing wall  38 A of the tail portion placement portion  38  of the locking base  30 . 
     In a structure such as this, if a tilting action is generated in the locking plate  34 , then the outer peripheral edge of the tail portion  36  of the locking plate  34  comes into contact with the vehicle front-side surface of the opposing wall  38 A of the tail portion placement portion  38  and, as a result of this, friction resistance between the tail portion  36  of the locking plate  34  and the opposing wall  38 A of the tail portion placement portion  38  to be prevented or inhibited from increasing. In this way, the curved surface portion set at the locking plate  34  is not limited to being set at the vehicle front-side surface (i.e., the surface on the spool  18  side) of the locking plate  34 , and the curved surface portion may be set at the surface over which the locking plate  34  slides when the locking plate  34  is being pivoted (i.e., moved). 
     Moreover, in the present exemplary embodiment, a structure is employed in which the locking plate  34 , which is serving as a locking component, is provided at the locking base  30 . However, the location where the locking component is provided is not particularly limited, and it is also possible to employ a structure in which a locking component provided at the frame  12  is moved in such a way that this locking component is engaged with the locking base  30  so as to thereby restrict rotation of the spool  18  in the pull-out direction. 
     Furthermore, in the present exemplary embodiment, a structure is employed in which the entire vehicle front-side surface of the locking plate  34  is used to form the curved surface portion  60 . However, it is also possible to employ a structure in which, for example, the curved surface portion  60  is set in a portion of the vehicle front-side surface of the locking plate  34  that is at an inner side of the outer peripheral edge. In other words, it is also possible to form the curved surface portion  60  such that, when the portion of the curved surface  60  that is positioned furthest to the vehicle front side is in contact with the vehicle rear-side surface  18 A of the spool  18 , which is serving as a sliding contact surface, at least a locking-side portion of the outer peripheral edge of the vehicle front-side surface of the locking plate  34  is located further toward the vehicle rear side than the vehicle rear-side surface  18 A of the spool  18 . 
     Priority is claimed on Japanese Patent Application No. 2016-158951, the disclosure of which is incorporated herein by reference. 
     All references, patent applications and technical specifications cited in the present specification are incorporated by reference into the present specification to the same extent as if the individual references, patent applications and technical specifications were specifically and individually recited as being incorporated by reference.