Abstract:
A lock plate ( 46 ) chatter preventing structure which, under a predetermined condition, directly or indirectly engages with a take-up shaft that takes up a passenger-restraining webbing belt to deter the rotation of the take-up shaft in a webbing belt pullout direction. The lock plate chatter preventing structure includes: a support member that rotatably supports the lock plate ( 46 ); and an urging portion ( 128 ) formed continuously from the support member. The urging portion includes a leading end ( 128 B) that pressingly contacts one axial-direction end portion ( 116 ) of the lock plate and urges the lock plate toward the other axial-direction end.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims priority under 35 USC 119 from Japanese Patent Application No. 2005-037734, the disclosure of which is incorporated by reference herein.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a structure that prevents the chatter of a rotating member rotatably supported by a rotating shaft of a support member and to a webbing take-up device including a lock mechanism that deters the rotation, in a webbing belt pullout direction, of a take-up shaft that takes up in layers a passenger-restraining webbing belt when a predetermined condition, such as the sudden deceleration of a vehicle disposed with the webbing take-up device, is fulfilled.  
         [0004]     2. Description of the Related Art  
         [0005]     Among webbing take-up devices attached to vehicles, there is a webbing take-up device including a lock mechanism that deters the rotation, in a webbing belt pullout direction, of a take-up shaft that takes up in layers a webbing belt when the vehicle disposed with the webbing take-up device experiences an emergency situation. An example thereof is disclosed in Japanese Patent Application Publication (JP-A) No. 10-500648.  
         [0006]     The lock mechanism includes a lock gear that rotates coaxially with the take-up shaft, for example, and ratchet teeth are formed on the outer peripheral surface of the lock gear. The lock mechanism also includes a lock plate corresponding to the lock gear. The lock plate is pivotably supported by a rotating shaft of a support member attached to a frame for supporting the take-up shaft. The lock plate is configured to be engageable with the ratchet teeth of the lock gear when the lock plate pivots around its axis. There is also a lock mechanism that does not include a lock gear but whose lock plate is directly engageable with the take-up shaft.  
         [0007]     Webbing take-up devices including such a lock mechanism include an acceleration sensor that detects when the vehicle suddenly decelerates. When the acceleration sensor detects the acceleration (deceleration) of the vehicle and the acceleration (deceleration) of the vehicle is equal to or greater than a certain level, the acceleration sensor activates the lock mechanism. When it is detected by the acceleration sensor that the acceleration (deceleration) of the vehicle is equal to or greater than the certain level, the lock mechanism is activated, and the lock plate directly or indirectly (via the lock gear) engages with the take-up shaft, receives the rotational force (load) of the take-up shaft in the webbing belt pullout direction, and deters the rotation of the take-up shaft in the webbing belt pullout direction.  
         [0008]     Incidentally, because the lock plate is simply rotatably supported by the support member, the lock plate chatters in its own axial direction. For this reason, it is conceivable to prevent the lock plate from chattering by disposing an urging member such as a spring washer between the lock plate and the support member.  
         [0009]     However, when an urging member such as a spring washer is disposed between the lock plate and the support member, there is the problem that the number of parts in the device and the number of man-hours required for assembly end up increasing. For this reason, there has been desired a measure for suppressing the chatter of the lock plate without disposing an urging member such as a spring washer between the lock plate and the support member.  
       SUMMARY OF THE INVENTION  
       [0010]     In view of this problem, it is an object of the present invention to obtain a rotating member chatter preventing structure that can suppress the chatter of a rotating member in the axial direction without increasing the number of parts and a webbing take-up device including the chatter preventing structure.  
         [0011]     A first aspect of the invention provides a rotating member chatter preventing structure that regulates the displacement, in an axial direction, of a rotating member including one axial-direction end portion that is rotatably supported by a support member, the rotating member chatter preventing structure including an urging portion formed continuously from the support member, wherein the urging portion includes a leading end that pressingly contacts the one axial-direction end portion of the rotating member and urges the rotating member toward the other axial-direction end.  
         [0012]     According to the rotating member chatter preventing structure pertaining to this aspect, the one axial-direction end portion of the rotating member is rotatably supported by the support member.  
         [0013]     The urging portion is formed continuously from the support member and pressingly contacts the one axial-direction end portion of the rotating member. For this reason, the rotating member is urged toward the other axial-direction end. Thus, the rotating member is held against a frame or plate that supports the other axial-direction end portion of the rotating member, whereby the chattering of the rotating member in its axial direction is suppressed.  
         [0014]     Consequently, the rotating member chatter preventing structure based on this aspect can suppress the chattering of the rotating member in its axial direction without the need to dispose an urging member such as a spring washer between the rotating member and the support member.  
         [0015]     Also, the number of parts in the device and the number of man-hours required for assembly can be reduced because it is not necessary to dispose an urging member such as a spring washer between the rotating member and the support member.  
         [0016]     In a second aspect of the invention, the leading end of the urging portion is positioned in the vicinity of the axial position of the rotating member.  
         [0017]     According to the rotating member chatter preventing structure based on this aspect, the leading end of the urging portion is positioned in the vicinity of the axial position of the rotating member. Thus, the rotating member is always pressingly contacted by the urging portion regardless of whether or not the rotating member itself has rotated (regardless of the rotational amount of the rotating member when the rotating member has rotated). For this reason, the rotating member is always urged toward the other axial-direction end. Thus, the rotating member is always held against a frame or plate that supports the other axial-direction end portion of the rotating member. Consequently, the rotating member chatter preventing structure of this aspect can effectively absorb the chattering of the rotating member in its axial direction.  
         [0018]     A third aspect of the invention provides a webbing take-up device comprising: a take-up shaft that takes up a webbing belt for restraining a passenger; lock means configured to include a lock plate that includes one axial-direction end portion rotatably supported by a support member with the lock plate rotating under a predetermined condition and directly or indirectly engaging with the take-up shaft to deter the rotation of the take-up shaft in a webbing belt pullout direction; and an urging portion that is formed continuously from the support member and includes a leading end that pressingly contacts the one axial-direction end portion of the lock plate and urges the lock plate toward the other axial-direction end.  
         [0019]     In the webbing take-up device based on this aspect, when the passenger places the webbing belt around his/her body, the webbing belt is pulled out from the take-up shaft and placed around the body of the passenger. Thus, the body of the passenger is restrained.  
         [0020]     Also, in the webbing take-up device, the one axial-direction end portion of the lock plate of the lock means is rotatably supported by the support member, and when a predetermined condition is fulfilled (e.g., when the vehicle suddenly decelerates), the lock plate rotates and directly or indirectly engages with the take-up shaft. Thus, because the rotation of the take-up shaft in the webbing belt pullout direction is deterred, the webbing belt is not pulled out from the take-up shaft and the body of the passenger can be restrained by the webbing belt even under the predetermined condition.  
         [0021]     Incidentally, in the webbing take-up device, the urging portion is formed continuously from the support member and includes a leading end that pressingly contacts the one axial-direction end portion of the lock plate. For this reason, the lock plate is urged toward the other axial-direction end, and the chattering of the lock plate as the rotating member in its axial direction is suppressed because the lock plate is held against a frame or plate that supports the other axial-direction end portion of the lock plate.  
         [0022]     Consequently, the webbing take-up device based on this aspect can suppress the chattering of the lock plate in its axial direction without the need to dispose an urging member such as a spring washer between the lock plate and the support member.  
         [0023]     Also, the number of parts in the device and the number of man-hours required for assembly can be reduced because it is not necessary to dispose an urging member such as a spring washer between the rotating member and the support member.  
         [0024]     In a fourth aspect of the invention, the leading end of the urging portion is positioned in the vicinity of the axial position of the lock plate.  
         [0025]     According to the webbing take-up device based on this aspect, the leading end of the urging portion is positioned in the vicinity of the axial position of the lock plate. Thus, the lock plate is always pressingly contacted by the urging portion regardless of whether or not the lock plate itself has rotated (regardless of the rotational amount of the lock plate when the lock plate has rotated). For this reason, the lock plate is always urged toward the other axial-direction end. Thus, the lock plate is always held against a frame or plate that supports the other axial-direction end portion of the lock plate.  
         [0026]     Consequently, the webbing take-up device of this aspect can effectively absorb the chattering of the lock member in its axial direction.  
         [0027]     As described above, the rotating member chatter preventing structure and the webbing take-up device including the chatter preventing structure pertaining to the present invention have the excellent effect that they can suppress the chatter of a rotating member (a lock plate in a webbing take-up device) without increasing the number of parts. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]      FIG. 1  is an exploded perspective view showing the vicinity of a portion where a lock plate and a support member are coupled together in a webbing take-up device pertaining to an embodiment of the invention;  
         [0029]      FIG. 2  is an exploded perspective view, seen from one side and diagonally above, showing the webbing take-up device pertaining to the embodiment of the invention; and  
         [0030]      FIG. 3  is a cross-sectional view corresponding to  FIG. 1  showing the vicinity of the portion where the lock plate and the support member are coupled together. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0031]      FIG. 2  is an exploded perspective view, seen from one side and diagonally above, showing the relevant portions of a webbing take-up device  10  pertaining to an embodiment of the invention.  
         [0032]     The webbing take-up device  10  includes a frame  12  that is made of metal and is substantially U-shaped when seen from above. The frame  12  is fixed to the inside of a cabin in a vehicle. A cutout  13 A for rotatably disposing therein a lock portion  48  of a later-described lock plate  46  is formed in one side wall  12 A of the frame  12 . A cutout  13 B for rotatably disposing therein a shaft receiving portion  116  of the later-described lock plate  46  is formed in another side wall  12 B of the frame  12 .  
         [0033]     A coupler piece  14  is disposed on the frame  12  such that the coupler piece  14  spans the distance between the upper end of the one side wall  12 A and the upper end of the other side wall  12 B of the frame  12 . The coupler piece  14  is fixed to the inside of the cabin and includes an insertion hole  16 .  
         [0034]     A spool  18  serving as a take-up shaft is rotatably supported between the one side wall  12 A and the other side wall  12 B of the frame  12 . A long band-like webbing belt  20  for restraining a passenger is wound onto the spool  18 . A circular column-like shaft  22  disposed on the base end of the webbing belt  20  is attached to the spool  18 , and the vicinity of the base end of the webbing belt  20  is passed through the spool  18 , whereby the webbing belt  20  is attached to the spool  20 .  
         [0035]     The vicinity of the portion of the webbing belt  20  wound onto the spool  18  is inserted through the insertion hole  16 , and the webbing belt  20  is placed around the body of a passenger in the vehicle. The webbing belt  20  is taken up as a result of the spool being rotated in a take-up direction, and is pulled out as a result of the spool  18  being rotated in a pullout direction (webbing belt pullout direction).  
         [0036]     A torsion shaft  24  that configures lock means is disposed in the center axial portion of the spool  18 . The torsion shaft  24  is configured to be twistingly deformable as a result of a twist load equal to or greater than a predetermined twist load being imparted thereto. The other end of the torsion shaft  24  is attached to the other end of the spool  18 , such that the torsion shaft  24  rotates integrally with the spool  18 . A screw member  26  is screwed into the other end of the torsion shaft  24 .  
         [0037]     A lock gear  28  that configures the lock means together with the torsion shaft  24  is disposed on the one side of the spool  18 . The lock gear  28  is attached to the vicinity of the one end of the torsion shaft  24 . The lock gear  28  rotates integrally with the torsion shaft  24  and the spool  18  at times other than when the torsion shaft  24  is twistingly deformed. Ratchet teeth  30  are formed on the outer periphery of the lock gear  28 . A substantially circular column-like knurl hole  32  is formed in the center of the lock gear  28 . The knurl hole  32  opens to the one side, and a knurled surface  34  is formed as a result of the entire outer periphery of the knurl hole  32  being knurled.  
         [0038]     An urging mechanism  36  is disposed on the other side of the frame  12 . The urging mechanism  36  includes a spring sheet  38  that is attached to the outer side of the other side wall  12 B of the frame  12 . The spring sheet  38  covers the other side surface of the spool  18  in a state where the screw member  26  has been caused to protrude toward the other side. The other side of the spring sheet  38  is covered by a spring cover  40  serving as a support member. The spring cover  40  is attached to the outer side of the other side wall  12 B of the frame  12 . The spring cover  40  comprises a resin material, for example. A substantially circular column-like concave portion  42  that opens toward the one side is formed in the spring cover  40 .  
         [0039]     A coil spring  44  is disposed inside the concave portion  42  of the spring cover  40 . The outer end of the coil spring  44  is fixed to the inner peripheral surface of the concave portion  42 . The inner end of the coil spring  44  is fixed to the screw member  26 . The coil spring  44  urges the torsion shaft  24 , the spool  18  and the lock gear  28  in the take-up direction via the screw member  26 .  
         [0040]     The spring cover  40  includes, on its lower portion, a circular column-like rotating shaft  41  that protrudes toward the one side. The rotating shaft  41  is formed continuously with the lower portion of the spring cover  40  and corresponds to the later-described lock plate  46 .  
         [0041]     The portion of the spring cover  40  below the rotating shaft  41  is formed in a plate-like shape whose plate thickness direction is in the axial direction of the rotating shaft  41 . An inverted U-shaped cutout  126  is formed in this plate-like portion, whereby a plate spring  128  serving as an urging portion is formed.  
         [0042]     The plate spring  128  includes a base end portion  128 A that is formed continuously with the spring cover  40  at the lower end position of the cutout  126  (the lower end position in the vertical direction of  FIG. 2 ). The plate spring  128  also includes a leading end portion  128 B that is formed such that the leading end portion  128 B protrudes toward the later-described lock plate  46  (toward the one side) in the vicinity of the rotating shaft  41  (i.e., the leading end portion  128 B is positioned in the vicinity of the axial position of the later-described lock plate  46 ). The plate spring  128  is configured to be elastically deformable in the axial direction of the lock plate  46  (the axial direction of the rotating shaft  41 ). As shown in  FIG. 3 , the plate spring  128  always pressingly contacts the lock plate  46  (or more specifically, the other side wall of the shaft receiving portion  116  of the later-described lock plate  46 ). Thus, the plate spring  128  urges, with its own elastic force, the lock plate  46  toward the one side in the axial direction of the lock plate  46  (toward the one side in the axial direction of the rotating shaft  41 ).  
         [0043]     The lock plate  46  configures the lock means together with the torsion shaft  24  and the lock gear  28 . The lock plate  46  is disposed such that it spans the distance between the one side wall  12 A and the other side wall  12 B of the frame  12 .  
         [0044]     As shown in  FIG. 1 , the lock plate  46  includes the shaft receiving portion  116 , which corresponds to the cutout  13 B of the frame  12 . The shaft receiving portion  116  is a plate-like body formed in a general L shape. A shaft receiving hole  117  is formed along the plate thickness direction in one end portion of the shaft receiving portion  116 . The rotating shaft  41  of the spring cover  40  is inserted through the shaft receiving hole  117  of the shaft receiving portion  116 . The lock plate  46  is rotatably supported by the rotating shaft  41 , and the shaft receiving portion  116  is configured to be pivotable inside the cutout  13 B.  
         [0045]     A connector portion  114  is formed continuously with the other end (opposite from the shaft receiving hole  117 ) of the shaft receiving portion  116 . The connector portion  114  is a plate-like body that is long in the spanning direction of the lock plate  46 . The shaft receiving portion  116  is vertically disposed at the other end portion of the connector portion  114  such that the plate thickness direction of the shaft receiving portion  116  is at a right angle with respect to the plate thickness direction of the connector portion  114 .  
         [0046]     The lock portion  48  is formed continuously with the end portion of the connector portion  114  opposite from the shaft receiving portion  116  (i.e., the end portion of the connector portion  114  near the one side wall  12 A). The lock portion  48  is a generally T-shaped plate-like body that extends from the end portion at the one side of the connector portion  114  toward one side in the plate thickness direction of the connector portion  114  (the side in the plate thickness direction of the connector portion  114  where the shaft receiving portion  116  is vertically disposed).  
         [0047]     A shaft portion  124  that protrudes toward the one side is integrally disposed on the lock portion  48 . The shaft portion  124  is formed in a circular column-like shape and is disposed on one end side of the lock portion  48  with its axial direction being shifted from the axial position of a support shaft  120  parallel to the other end side in the width direction.  
         [0048]     The support shaft  120  is integrally disposed on the lock portion  48  and protrudes from the lock portion  48  toward the one side. The support shaft  120  is formed in a circular column-like shape and is disposed on one end side of the lock portion  48  with its axial position being identical with the axial position of the shaft receiving hole  117  of the shaft receiving portion  116 .  
         [0049]     The support shaft  120  of the lock portion  48  is inserted through a support hole  55  formed in the lower portion of a gear case  52  serving as a plate. The lock portion  48  is rotatably supported by the gear case  52  such that the lock portion  48  is rotatable inside the cutout  13 A. In this state, the lock portion  48  is disposed diagonally below the lock gear  28 , as shown in  FIG. 2 . Lock teeth  50  (see  FIG. 1 ) are formed on the other end of the lock portion  48 . The lock portion  48  is disposed on the opposite side of the lock gear  28  and placed in a state where the lock teeth  50  cannot mesh with the ratchet teeth  30  of the lock gear  28 .  
         [0050]     As shown in  FIG. 2 , the gear case  52  is attached to the outer side of the one side wall  12 A of the frame  12  and covers the one side of the lock gear  28 . A circular through hole  54  is formed in the center of the gear case  52 . The knurl hole  32  of the lock gear  28  is exposed through the through hole  54 , and the torsion shaft  24  is passed through the through hole  54 .  
         [0051]     The circular support hole  55 , whose diameter is smaller than that of the through hole  54 , is formed diagonally below the through hole  54 . The support hole  55  corresponds to the support shaft  120  of the lock plate  46 . The support shaft  120  of the lock plate  46  is inserted through the support hole  55 , and the gear case  52  rotatably supports the lock portion  48  of the lock plate  46  as described above to allow the lock portion  48  to rotate inside the cutout  13 A of the frame  12 . In this manner, the gear case  52  rotatably supports the lock plate  46  in cooperation with the spring cover  40 , and the connector portion  14  of the lock plate  46  spans the distance between the one side wall  12 A and the other side wall  12 B of the frame  12 .  
         [0052]     A pretensioner mechanism  56  is disposed on the outer side of the one side wall  12 A of the frame  12 . The pretensioner mechanism  56  includes a pinion  58 . The pinion  58  is disposed on the one side of the gear case  52  and is rotatably supported on the torsion shaft  24 . Pinion teeth  60  are formed on the one side portion of the pinion  58 .  
         [0053]     A cam  62  is formed on the other side portion of the pinion  58 . Concavo-convexities are alternately formed on the outer periphery of the cam  62 . The cam  62  is inserted into the knurl hole  32  via the through hole  54  of the gear case  52  and does not contact the knurled surface  34 , so that the lock gear  28  is rotatable independent of the pinion  58 .  
         [0054]     The pretensioner mechanism  56  also includes a clutch plate  64  that is disposed between the gear case  52  and the pinion  58 . Plural mesh pawls  66  are formed in the center of the clutch plate  64 , and each of the mesh pawls  66  protrudes from the clutch plate  64  toward the other side. The mesh pawls  66  fit together with the concave portions of the cam  62 . Thus, the clutch plate  64  is attached to the pinion  58 . The mesh pawls  66  are inserted into the knurl hole  32  via the through hole  54  of the gear case  52  together with the cam  62  and do not contact the knurled surface  34 , so that the lock gear  28  is rotatable independent of the clutch plate  64 .  
         [0055]     The pretensioner mechanism  56  also includes a cylinder  68  that is circular and substantially L-shaped. The cylinder  68  is fixed to the outer side of the one side wall  12 A of the frame  12  below the pinion  58 . A gas generator  70  is disposed on, and a generator cap  72  that has a bottomed circular column-like shape is fixed to, the lower end of the cylinder  68 . The gas generator  70  closes off the lower end of the cylinder  68  in a state where it is covered with the generator cap  72 .  
         [0056]     The pretensioner mechanism  76  also includes a piston  74  that is inserted into the cylinder  68  from the upper end of the cylinder  68 . An O-ring  76  that seals the space between the lower end of the piston  74  and the cylinder  68  is disposed on the lower end of the piston  74 . A rack  78  is formed on the portion of the piston  74  other than the lower end of the piston  74 .  
         [0057]     The pretensioner mechanism  76  also includes a cover plate  80  that is shaped like a substantially triangular columnar vessel. The cover plate  80  is fixed to the outer side of the one side wall  12 A of the frame  12 . The torsion shaft  24  is inserted through the lower portion of the cover plate  80  such that the cover plate  80  rotatably supports the torsion shaft  24 . The other side surface and the lower surface of the cover plate  80  are open. The cover plate  80  houses therein the pinion  58 , the clutch plate  64  and the upper portion of the piston  74 , and nips the gear case  52  between itself and the one side wall  12 A of the frame  12 .  
         [0058]     A sensor mechanism  82  that configures the lock means together with the torsion shaft  24 , the lock gear  28  and the lock plate  46  is disposed on the one side of the pretensioner mechanism  56 . The sensor mechanism  82  includes a box-like sensor holder  84  whose other side is open. The sensor holder  84  is fixed to the one side wall  12 A of the frame  12  in a state where the torsion shaft  24  has been passed through the upper portion of the sensor holder  84 . The one side of the sensor holder  84  is covered by a box-like sensor cover  86  whose other side is open. The sensor cover  86  is fixed to the sensor holder  84  and the one side wall  12 A of the frame  12 .  
         [0059]     An acceleration sensor  88  is retained in the lower portion of the sensor holder  84  and is disposed in the space between the sensor holder  84  and the sensor cover  86 . The acceleration sensor  88  includes a mount  90 . A substantially inverted cone-shaped concave portion is formed in the upper surface of the mount  90 , and a sphere  92  is mounted in the concave portion of the mount  90 . A movable pawl  94  is pivotably supported above the sphere  92 , and the movable pawl  94  is placed on top of the sphere  92 .  
         [0060]     A V gear  96  is disposed in the space between the sensor holder  84  and the sensor cover  86 . The one side end of the torsion shaft  24  is attached to the V gear  96 , such that the V gear  96  rotates integrally with the torsion shaft  24 . Ratchet teeth  98  are formed on the outer periphery of the V gear  96 .  
         [0061]     A W pawl  100  is pivotably supported on the V gear  96 . A W mass  102  is fixed to the W pawl  100 . A sensor spring  104  is disposed such that it spans the distance between the V gear  96  and the W pawl  100 . The sensor spring  104  urges the V gear  96  in the take-up direction with respect to the W pawl  100 .  
         [0062]     A substantially discoid gear sensor  106  is disposed in the space between the sensor holder  84  and the sensor cover  86  at the one side of the V gear  96 . The gear sensor  106  is rotatably supported on the one side end edge of the torsion shaft  24 . A coil spring  108  is disposed such that it spans the distance between the gear sensor  106  and the inner surface of the sensor cover  86 . The coil spring  108  urges the gear sensor  106  in the take-up direction.  
         [0063]     An engagement pawl  110  is rotatably supported at the one side on the lower portion of the gear sensor  106 . The axis of the center of rotation of the engagement pawl  110  is parallel to the axial direction of the torsion shaft  24 , and the engagement pawl  110  is configured to be meshable with the ratchet teeth  98  of the V gear  96 . A push piece  112  is formed at the other side on the lower portion of the gear sensor  106 .  
         [0064]     Next, the action of the present embodiment will be described.  
         [0065]     In the webbing take-up device  10  having the above-described configuration, the coil spring  44  of the urging mechanism  36  urges the torsion shaft  24 , the spool  18  and the lock gear  28  in the take-up direction via the screw member  26 , whereby the webbing belt  20  is urged in the direction in which it is taken up onto the spool  18 .  
         [0066]     In the webbing take-up device  10 , when the passenger is to place the webbing belt  20  around his/her body, the webbing belt  20  is pulled out from the spool  18  and placed around the body of the passenger. Thus, the body of the passenger is restrained.  
         [0067]     Also, in the webbing take-up device  10 , the acceleration sensor  88  of the sensor mechanism  82  detects the fact that the acceleration of the vehicle (the moving acceleration of the spool  18 ) is equal to or greater than a predetermined acceleration. That is, when the acceleration of the vehicle is equal to or greater than a predetermined acceleration (e.g., when the vehicle suddenly decelerates), the sphere  92  of the acceleration sensor  88  moves and rises in the concave portion of the mount  90  in the direction opposite to the acceleration direction and pushes up the movable pawl  94 . Thus, the movable pawl  94  causes the engagement pawl  110  of the gear sensor  106  to rotate and engage with the ratchet teeth  98  of the V gear  96 , whereby the gear sensor  106  becomes coupled to the V gear  96 .  
         [0068]     The W pawl  100 , the W mass  102  and the sensor spring  104  of the sensor mechanism  82  detect the fact that the pullout acceleration of the webbing belt  20  (the rotational acceleration of the webbing belt  20  in the pullout direction) is equal to or greater than a specific acceleration. That is, when the pullout acceleration of the webbing belt  20  is equal to or greater than a specific acceleration, the rotation of the W pawl  100  and the W mass  102  in the pullout direction is suppressed by inertia with respect to the V gear  96  that is rotated in the pullout direction via the spool  18  and the torsion shaft  24 , whereby the W pawl  100  and the W mass  102  are pivoted with respect to the V gear  96 .  
         [0069]     Thus, the W pawl  100  causes the engagement pawl  110  of the gear sensor  106  to rotate and engage with the ratchet teeth  98  of the V gear  96 , whereby the gear sensor  106  becomes coupled to the V gear  96 .  
         [0070]     When the gear sensor  106  becomes coupled to the V gear  96  as described above, the V gear  96  and the gear sensor  106  are rotated somewhat in the pullout direction via the spool  18  and the torsion shaft  24  due to the pullout load on the webbing belt  20  from the passenger. In this case, the rotational force of the V gear  96  and the gear sensor  106  is reduced by the urging force of the sensor spring  104  that has increased due to the inertia of the W pawl  100  and the W mass  102 .  
         [0071]     The shaft receiving portion  116  of the lock plate  46  is rotatably supported by the rotating shaft  41  of the spring cover  40 . Additionally, the lock portion  48  of the lock plate  46  is rotatably supported by the gear case  52  as a result of the support shaft  120  integrated with the lock portion  48  being inserted through the shaft receiving hole  55  of the gear case  52 . That is, the lock plate  46  spans the distance between the one side wall  12 A and the other side wall  12 B of the frame  12  and is rotatably supported by the spring cover  40  and the gear case  52 .  
         [0072]     The lock plate  46  is rotated toward the spool  18  by the push piece  112  of the gear sensor  106  as a result of the gear sensor  106  being rotated somewhat in the pullout direction as previously mentioned. That is, the lock portion  48  rotates toward the lock gear  28 . Thus, a pullout load is imparted to the webbing belt  20  from the passenger, and a rotational force is imparted in the pullout direction to the spool  18 , the torsion shaft  24  and the lock gear  28 , whereby the lock teeth  50  of the lock portion  48  mesh with the ratchet teeth  30  of the lock gear  28 , the rotation of the lock gear  28  in the pullout direction is deterred, and the pullout of the webbing belt  20  is deterred.  
         [0073]     For this reason, even when the acceleration of the vehicle is equal to or greater than the predetermined acceleration (e.g., when the vehicle suddenly decelerates), the body of the passenger can be restrained by the webbing belt  20  without the webbing belt  20  being pulled out from the spool  18  (see  FIG. 2 ).  
         [0074]     Incidentally, in the webbing take-up device  10 , because the plate spring  128  is formed continuously from the spring cover  40  and the leading end portion  128 B of the plate spring  128  is positioned in the vicinity of the axial position of the lock plate  46  (in the vicinity of the rotating shaft  41 ), the leading end portion  128 B of the plate spring  128  always pressingly contacts the one axial-direction end portion of the lock plate  46  (the other side wall of the shaft receiving portion  116 ) regardless of whether or not the lock plate  46  has rotated (and regardless of the rotational amount of the lock plate  46  when the lock plate  46  has rotated, such as its position during rotation and its position after rotation). For this reason, the lock plate  46  is always urged toward the other axial-direction end (the one side) by the elastic force of the plate spring  128 .  
         [0075]     Thus, because the lock plate  46  is always held against the gear case  52  supporting the lock portion  48  of the lock plate  46 , for example, the chattering of the lock plate  46  in its axial direction is effectively suppressed (absorbed).  
         [0076]     Consequently, in the webbing take-up device  10 , the chattering of the lock plate  46  in its axial direction can be effectively suppressed (absorbed) even if an urging member such as a spring washer is not disposed between the lock plate  46  and the spring cover  40  (see  FIGS. 1 and 3 ).  
         [0077]     Also, because it is not necessary to dispose an urging member such as a spring washer between the lock plate  46  and the spring cover  40 , the number of parts in the device and the number of man-hours required for assembly can be reduced.  
         [0078]     In the present embodiment, the leading end portion  128 B of the plate spring  128  was configured to pressingly contact the shaft receiving portion  116  of the lock plate  46 , but the present invention is not limited to this. It suffices as long as the portion further toward the leading end portion  128 B side (i.e., the leading end side) than the base end portion  128 A of the plate spring  128  pressingly contacts the shaft receiving portion  116  of the lock plate  46 .  
         [0079]     Also, in the present embodiment, the lock plate  46  was configured such that it was held against the gear case  52  serving as a plate due to the inertia of the plate spring  128 , but the present invention is not limited to this. For example, in the case of a webbing take-up device  10  configured such that the cutout  13 A of the one side wall  12 A is not formed in the frame  12  and such that the lock portion  48  rotates between the one side wall  12 A and the other side wall  12 B, the lock plate  46  may be configured such that it is held against the one side wall  12 A of the frame  12  due to the inertia of the plate spring  128 .  
         [0080]     Also, the webbing take-up device  10  of the present embodiment was configured such that the lock portion  48  of the lock plate  46  engaged (indirectly engaged) with the spool  18  via the lock gear  28  and the torsion shaft  24 , but the present invention is not limited to this. The webbing take-up device  10  may also be configured such that the lock portion  48  directly engages with a spool that integrally includes a lock gear.