Patent Abstract:
An engaging member supporting structure having a rotating body being connected to a spool, transmitting rotation to the spool and having rotation from the spool transmitted thereto; a support body provided coaxially with the rotating body; an engaging member provided at the support body and rotating in one direction to engage with the rotating body; a shaft potion formed at one of the support body or the engaging member; and a bearing portion formed at the other of the support body or the engaging member in such a manner that the shaft portion is inserted therein, whereby the engaging member is rotatably provided at the support body, wherein, in a state in which the engaging member engages with the rotating body, a clearance is formed between an outer peripheral surface of the shaft portion and a portion of an inner peripheral surface of the bearing portion.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority under 35 USC 119 from Japanese Patent Application No. 2009-266662 filed Nov. 24, 2009, the disclosure of which is incorporated by reference herein. 
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to an engaging member supporting structure for supporting an engaging member such as a pawl in, for example, a clutch, and also relates to a webbing take-up device in which a spool can be rotated in such a manner that driving force of a driving member is transmitted to the spool via the clutch. 
     2. Related Art 
     In a webbing take-up device disclosed in Japanese Patent Application Laid-Open (JP-A) No. 2004-42788, a clutch is interposed between a motor and a spool, and when a base plate of the clutch is rotated in a take-up direction by driving force of the motor, a pawl provided in the base plate rotates and engages with a rotary disk. In the above-described state, when the pawl rotates in the take-up direction together with the base plate, the rotary disk is pressed by the pawl to rotate in the take-up direction, and the pawl meshes with an external tooth of an adapter. The pawl is connected to the spool in a state of being not rotatable relative to the spool, and therefore, if the pawl rotates in the take-up direction together with the base plate in the above-described state, the adapter pressed by the pawl rotates in the take-up direction and the spool also rotates in the take-up direction. As a result, a webbing belt is taken up around the spool from its longitudinal direction base end side. 
     When the pawl which rotates in the take-up direction together with the base plate meshes with the stationary adapter, a reaction force corresponding to a pressing force from the pawl pressing the adapter acts on the pawl. For this reason, a boss which is provided in a base portion of the base plate so as to support the pawl in a rotatable manner is made sufficiently thick such that the boss has a enough strength sustainable to the above-described reaction force. However, making the boss thick increases friction between an outer peripheral portion of the boss and an inner peripheral portion of a circular hole formed in the pawl, and a loss caused when the pawl rotates around the boss becomes large. 
     In view of the above-described circumstances, the present invention provides an engaging member supporting structure and a webbing take-up device, which can reduce an impact imparted from a rotating body to an engaging member such as a pawl, and also which can lessen a rotational loss of the engaging member caused by resistance between an outer peripheral portion of a shaft portion and an inner peripheral portion of a bearing portion. 
     SUMMARY OF THE INVENTION 
     A first aspect of the present invention is an engaging member supporting structure comprising a rotating body that is connected to a spool and transmits rotation to the spool and have rotation from the spool transmitted thereto; a support body provided coaxially with the rotation body; an engaging member provided at the support body and rotating in one direction to engage with the rotating body; a support shaft formed in one of the support body or the engaging member; and a bearing portion formed in the other of the support body or the engaging body in such a manner that the support shaft is inserted therein, whereby the engaging member is rotatably provided at the support body, wherein in a state in which the engaging member engages with the rotating body, a clearance is formed between an outer peripheral surface of the support shaft and a portion of an inner peripheral surface of the bearing portion. 
     According to the engaging member support structure of the first aspect, the engaging member is supported at the support body in a rotatably manner. When the engaging member rotates in a direction of engagement, which is one rotating direction of the support body, the engaging member engages with the rotating body. As a result, displacement of the support body is transmitted to the rotating body via the engaging member, so that the rotating body rotates or rotation of the rotating body is regulated. 
     In the structure in which displacement of the support body is transmitted to the rotating body by engagement of the engaging member with the rotating body, or rotation of the rotating body is regulated, a pressing force or a pressing reaction force is imparted from the rotating body to the engaging member. 
     In the state in which the engaging member and the rotating body engage with each other, a clearance is formed between a surface of the inner peripheral surface of the bearing portion, which portion is close to the position at which the engaging member and the rotating body engage with each other, and the outer peripheral surface of the support shaft. For this reason, all or a large part of the above-described pressing force or pressing reaction force is not transmitted to the support shaft which supports the engaging member. Therefore, mechanical strength which resists force transmitted from the rotating body to the engaging member may not be given to the support shaft. 
     In the above first aspect, when the engaging member engages with the rotating body, the clearance may be formed between a portion of the outer peripheral surface of the support shaft that faces a direction of a force applied to the engaging member from the rotating body and the inner peripheral surface of the bearing portion. 
     A second aspect of the present invention is a webbing take-up device comprising: a spool to which one end in a longitudinal direction of an elongated band-shaped webbing belt is locked and the spool rotates in a take-up direction thereby taking up the webbing belt and accommodating the webbing belt on the spool; a driving member that rotates an output shaft by a driving force; a first rotating body connected to the output shaft and rotating by rotation of the output shaft being transmitted thereto; a second rotating body connected to the spool and rotating by rotation of the first rotating body being transmitted thereto, the second rotating body transmitting rotation of the first rotating body to the spool to rotate the spool; an engaging member supported at a supporting position apart from the rotation center outwardly in a radial direction of the first rotating body, rotating around the rotation center of the first rotating body together with the first rotating body, the engaging member swinging around the supporting position in a predetermined direction of engagement so as to engage with the second rotating body and transmitting rotation of the first rotating body in another predetermined direction to the second rotating body so as to rotate the second rotating body; a support shaft formed at one of the first rotating body or the engaging member; and a bearing portion formed at the other one of the first rotating body or the engaging body in such a manner that the support shaft is insertable therein, wherein when the support shaft is inserted in the bearing portion, the engaging member is supported rotatably at the supporting position, and in a state in which the engaging member engages with the second rotating body, a clearance is formed between the support shaft and an inner peripheral surface of the bearing portion close to a position at which the engaging member and the second rotating member engage with each other. 
     According to the webbing take-up device of the second aspect, when driving force is output from the driving member to rotate the output shaft, rotation of the output shaft is transmitted to the first rotating body and the first rotating body rotates in the predetermined direction. The engaging member is provided at a predetermined position on a radial-direction outer side from the rotation center of the first rotating body. When the first rotating body rotates, the engaging member rotates together with the first rotating body. Further, the support shaft and the bearing portion are provided in the first rotating body and the engaging member. With the support shaft being supported by the bearing portion, the engaging member is supported rotatably with respect to the first rotating body. 
     When the first rotating body rotates in the predetermined direction, the engaging member swings around the shaft center of the support shaft in the direction of engagement while rotating together with the first rotating body. Due to swinging of the engaging member, the engaging member engages with the second rotating body. When the engaging member rotates together with the first rotating body in the predetermined direction in a state in which the engaging member and the second rotating body engage with each other, the engaging member presses the second rotating body and rotates the second rotating body in the predetermined direction. The second rotating body is directly or indirectly connected to the spool, and rotation transmitted from the first rotating body to the second rotating body via the engaging member is further transmitted to the spool, whereby the spool rotates. 
     In the state in which a webbing belt pulled out from the spool is fastened to the body of a vehicle occupant, when rotating force of the take-up direction is transmitted from the driving member to the spool via the first rotating body, the engaging member, and the second rotating body, the webbing belt is taken up on the spool from its base end side, thereby removing slight looseness, or so-called “slack” of the webbing belt fastened to the body of a vehicle occupant. 
     In a case in which the engaging member engages with the second rotating body while rotating together with the first rotating body in the predetermined direction as described above, the engaging member receives reaction force from the second rotating body. 
     In the state in which the engaging member and the second rotating body engage with each other, a clearance is formed between the support shaft and the inner peripheral surface of the bearing portion close to a position at which the engaging member and the second rotating body engages with each other. Therefore, all or a large part of the above-described reaction force is not transmitted to the support shaft portion. For this reason, mechanical strength which resists reaction force transmitted from the second rotating body to the engaging member may not be given to the support shaft. 
     In the above second aspect, when the engaging member engages with the second rotating body, the clearance may be formed between a portion of the outer peripheral surface of the support shaft that faces a direction of a force applied to the engaging member from the second rotating body and the inner peripheral surface of the bearing portion. 
     In the above-described aspect, the bearing portion is formed so that an inner peripheral shape thereof is a circular hole whose inner periphery is circular, and the support shaft may have a shape in which a portion of a circular column is scraped off in the axial direction of the support shaft. A side surface of the support shaft close to the position at which the engaging member and the second rotating body engage with each other is scraped off, and a distance between the center of the support shaft and the outer periphery of the scraped support shaft is shorter than a radius of the bearing portion, and a remaining portion of the support shaft may have a radius of curvature substantially equal to the radial dimension of the inner peripheral portion of the bearing portion. 
     According to the above-described aspect, the bearing portion is formed into a circular hole whose inner periphery is circular. 
     The support shaft is formed by scraping off a portion of a circular column in a direction along the axial center, and a side of the support shaft away from the position at which the engaging member and the second rotating body engage with each other is not scraped off. The radius of curvature of the outer peripheral surface of the support shaft is substantially equal to the radial dimension of the inner peripheral portion of the bearing portion. The support shaft is supported by the bearing portion so as to be rotatable around the central axis of the bearing portion. 
     On the contrary, the support shaft is formed by scraping off a portion of a circular column in a direction along the axial center, and a side of the support shaft close to the position at which the engaging member and the second rotating body engage with each other is scraped off. As a result, a clearance is formed between the outer peripheral portion of the support shaft and the inner peripheral portion of the bearing portion, and all or a large part of the above-described reaction force is not transmitted to the support shaft. 
     In the above-described aspect, the remaining portion of the support shaft that is not scraped off may be set in the range of 180.degree, or more around the shaft center. 
     According to the above-described embodiment, the curved surface of the outer peripheral portion of the support shaft has a radius of curvature substantially equal to the radius in the inner peripheral portion of the bearing portion and is formed in the range of 180.degree, or more around the shaft center of the support shaft. Accordingly, if the engaging member attempts to be displaced in the radial direction of the bearing portion, the outer peripheral of the support shaft and the inner peripheral portion of the bearing portion interfere with each other. As a result, unnecessary displacement of the engaging member in the radial direction of the bearing portion is restrained. 
     In the above-described aspect, the first rotating body may include an interference supporting portion that is provided further toward an outer peripheral side in the radial direction of the first rotation member than the engaging member and interferes with the engaging member to which a reaction force is imparted from the second rotating body. 
     According to the above-described aspect, if the engaging member attempts to be displaced by receiving the reaction force from the second rotating body in the state in which the engaging member and the second rotating member engage with each other, the interference supporting portion provided outside of the engaging member interferes with the engaging member. As a result, displacement of the engaging member is regulated. In this manner, the reaction force which attempts to displace the engaging member is imparted to the interference supporting portion. Therefore, it suffices that the relationship between the support shaft and the bearing portion is determined such that the engaging member is rotatably supported by the support shaft, and mechanical strength which resists the above-described reaction force may not be given to the support shaft. 
     As described above, the present invention makes it possible to reduce the influence of a force imparted from the second rotating body to the engaging member, and also decrease loss hindering rotation of the engaging member caused by a friction resistance between the outer peripheral portion of the support shaft and the inner peripheral portion of the bearing portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention will be described in detail based on the following figures, wherein: 
         FIG. 1  is an exploded perspective view showing the structure of a principal portion of a webbing take-up device according to an embodiment of the present invention; 
         FIG. 2  is an enlarged side view showing the structure of a principal portion of a webbing take-up device according to an embodiment of the present invention; 
         FIG. 3  corresponds to  FIG. 2  and indicates a side view showing a state in which an engaging member engages with a second rotating body; and 
         FIG. 4  is a perspective view showing a state in which an interference member is mounted in a gear box. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Herebelow, an example of an exemplary embodiment of the present invention will be described in detail with reference to the drawings. 
     &lt;Structure of an Exemplary Embodiment of the Present Invention&gt; 
       FIG. 1  shows an exploded perspective view of the structure of a webbing take-up device  10  according to an exemplary embodiment of the present invention. 
     The webbing take-up device  10  includes a frame  12  which is fixed to a vehicle constituting member such as a vehicle framework member or a reinforcing member. The frame  12  includes leg plates  14 ,  16  which face each other substantially in a front-back direction of a vehicle when the frame  12  is mounted to a vehicle body. 
     A spool  18  is provided between the leg plates  14  and  16 . The spool  18  is formed in a substantially cylindrical shape. A longitudinal direction base end portion of a webbing belt  20 , which is formed in an elongated band shape, is fixed to the spool  18 . When the spool  18  rotates in a take-up direction, the webbing belt  20  is taken up and accommodated from its longitudinal direction base end side. When a vehicle occupant pulls the webbing belt  20  in order to fasten the webbing belt  20  to one&#39;s body, the webbing belt  20  wound around the spool  18  is pulled out, and the spool  18  rotates in a pull-out direction which is the reverse direction of the take-up direction. 
     A torsion shaft (not shown) is provided inside the spool  18 . The torsion shaft is formed as a bar-shaped member, the axial direction of the torsion shaft is aligned with the axial direction of the spool  18 . A leg plate  16  side of the torsion shaft is connected to the spool  18  and the coaxial rotation of the torsion shaft relative to the spool  18  is not permitted. 
     A housing  24  of a lock mechanism  22  serving as a lock unit is mounted at a side opposite to the leg plate  16  of the leg plate  14 . An end portion of the torsion shaft at a leg plate  14  side is directly or indirectly supported by the housing  24  so as to be rotatable around the central axis of the spool  18 . Accommodated inside the housing  24  are various parts which constitute a so-called “VSIR mechanism” which is activated in a case in which a vehicle is in a state of sudden deceleration, so as to regulate rotation of the end portion of the leg plate  14  side of the torsion shaft in a pull-out direction, and various parts which constitute a so-called “WSIR mechanism” which is activated due to the torsion shaft rotating rapidly in the pull-out direction, so as to regulate rotation of the end portion of the leg plate  14  side of the torsion shaft in the pull-out direction. 
     A pretensioner  26  as a compulsory tension member is provided at the leg plate  14 . The pretensioner  26  is operated when the vehicle is in a state of sudden deceleration, and is adapted to apply a rotation force in the take-up direction to the spool  18  or the end portion of the leg plate  14  side of the torsion shaft and to compulsorily rotate the spool  18  in the take-up direction. 
     A motor  40  serving as a driving member is provided below the spool  18 . The motor  40  is electrically connected via an ECU as a control member (not shown) to a battery that is mounted to the vehicle. The motor  40  is also connected to a forward monitoring device such as a radar device that measures a distance with respect to another vehicle traveling in front of the own vehicle or an obstruction in front of the own vehicle. When the ECU determines that the distance to another vehicle traveling in front of the own vehicle or an obstacle in front of the own vehicle is less than a predetermined value on the basis of electrical signals output from the forward monitoring device, the ECU operates the motor  40 . The motor  40  is configured that the axial direction of an output shaft  42  is in the same direction as the axial direction of the spool  18 , and the leading end of the output shaft  42  protrudes to the opposite direction of the leg plate  14  side of the leg plate  16  via a through hole (not shown) formed at the leg plate  16 . 
     A driving force transmission mechanism  50  is provided at the opposite side of the leg plate  14  side of the leg plate  16 . The driving force transmission mechanism  50  includes a gear box  52  as a holding member that is attached to the leg plate  16 . The gear box  52  is formed into a concave shape that is opened to. A hole portion  54  is formed at the bottom portion of the gear box  52 , and the output shaft  42  of the motor  40  passing through the hole portion of the leg plate  16  gets into the gear box  52  via the hole portion  54 . 
     A gear  56 , which is an external tooth gear and a spur gear, is mounted to a leading end side of the output shaft  42  coming into the gear box  52  so as to be coaxial and integral with the output shaft  42 . A support shaft  58  is formed laterally from the gear  56  on the bottom portion of the gear box  52 . The axial direction of the support shaft  58  is same as the axial direction of the output shaft  42 . A two-staged gear  60  is supported rotatably around the support shaft  58 . The two-staged gear  60  includes a large-diameter gear  62  which is an external tooth gear and a spur gear. The large-diameter gear  62  has a diameter larger than that of the gear  56  and has more teeth than those of the gear  56 . The large-diameter gear  62  meshes with the gear  56 . A small-diameter gear  64 , which is an external tooth gear and a spur gear and a diameter thereof is smaller than that of the large-diameter gear  62 , is formed at a side in the axial direction of the large-diameter gear  62  so as to be coaxial and integral with the large-diameter gear  62 . 
     A support shaft  68  is formed at a side in the radial direction of the two-staged gear  60  on the bottom portion of the gear box  52 . The axial direction of the support shaft  68  is same as the axial direction of the output shaft  42  and the support shaft  58 . A two-staged gear  70  is supported around the support shaft  68 . The two-staged gear  70  includes a large-diameter gear  72  which is an external tooth gear and a spur gear. The large-diameter gear  72  has a diameter larger than that of the small-diameter gear  64  and has more teeth than those of the small-diameter gear  64 . The large-diameter gear  72  meshes with the small-diameter gear  64 . A small-diameter gear  74 , which is an external tooth gear and a spur gear and a diameter thereof is smaller than that of the large-diameter gear  72 , is formed at a side in the axial direction of the large-diameter gear  72  so as to be coaxial and integral with the large-diameter gear  72 . 
     A support shaft  78  is formed at a side in the radial direction of the two-staged gear  70  on the bottom portion of the gear box  52 . The axial direction of the support shaft  78  is same as the axial direction of the output shaft  42  and the support shafts  58  and  68 . A gear  80 , which is an external tooth gear and a spur gear, is supported by the support shaft  78  so as to be rotatable about the support shaft  78 . The gear  80  has a diameter larger than that of the small diameter gear  74 , and has more teeth than those of the small diameter gear  74 , where the gear  80  meshes with the small diameter gear  74 . 
     A clutch  90  is provided at a side in a radial direction of the gear  80 . The clutch  90  includes an input gear  92  serving as a first rotating body or a support body. The input gear  92  includes a bottom wall portion  94 . A circular hole  96  is formed in the bottom wall portion  94 . A ring-shaped supporting portion  98  is formed in the gear box  52  so as to correspond to the circular hole  96 . From a peripheral of the circular hole  96 , a raised portion is formed to the opposite direction of the leg plate  14  side on the bottom portion of the input gear  92 . Further, the supporting portion  98  is formed so that the central axis thereof becomes substantially coaxial with the central axis of the spool  18 . 
     The supporting portion  98  passes through the circular hole  96  and supports the input gear  92  rotatably around the central axis of the supporting portion  98 . A gear  100 , which is an external tooth gear and a spur gear, is formed in the outer peripheral portion of the bottom wall portion  94 . The gear portion  100  is formed so as to be coaxial with the circular hole  96 , and the input gear  92  has a diameter larger than that of the above-described gear  80  and also has more teeth than those of the gear  80 . The gear portion  100  meshes with the gear  80 . As described above, the gear  80  is mechanically connected to the gear  56 , which is provided at the output shaft  42  of the motor  40 , via the two-staged gears  70 ,  60 . Therefore, when the motor  40  is activated and the output shaft  42  rotates by the driving force of the motor  40 , rotation of the output shaft  42  is transmitted to the gear portion  100  while the rotation is decelerated, and the input gear  92  rotates. 
     A pair of support shafts  102  is provided inside the gear portion  100 . Each of the support shafts  102  is formed so that its axial direction is same as the axial direction of the circular hole  96 , and protrudes from the bottom wall portion  94  of the input gear  92  in the opposite direction of the leg plate  16  side. The support shafts  102  are formed so as to face each other with the axis of the circular hole  96  interposed therebetween. A connection pawl  110  as an engaging member is provided at each of the support shafts  102 . A circular hole  112  serving as a bearing portion is formed at each of the connection pawl  110 . The support shaft  102  passes through the circular hole  112 , and each of the connection pawl  110  is supported by the corresponding circular hole  112  so as to be rotatable about the central axis of the circular hole  112 . 
     A ratchet gear  114  serving as a second rotating body or a rotating body is provided inside the gear portion  100 . The ratchet gear  114  is mounted at an adapter  116  that passes through the circular hole  96  of the bottom wall portion  94  and gets into the gear portion  100 . The adapter  116  is mounted at the end portion of the torsion shaft in a state incapable of rotating relative to the torsion shaft. The ratchet gear  114  is mounted at the adapter  116  in a state incapable of rotating relative to the adapter  116 . The ratchet gear  114  is indirectly connected to the spool  18  via the adapter  116  and the torsion shaft in a state incapable of rotating coaxially relative to the spool  18 . 
     External ratchet teeth are formed on the outer peripheral portion of the ratchet gear  114 . A meshing portion  122  is formed at the connection pawl  110  so as to correspond to the ratchet teeth of the ratchet gear  114 . When the connection pawl  110  rotates in one direction about the support shaft  102 , the meshing portion  122  moves close to the outer peripheral portion of the ratchet gear  114  as shown in  FIG. 3 , and the meshing portion  122  meshes with the ratchet teeth of the ratchet gear  114 . When the meshing portion  122  meshes with the ratchet teeth of the ratchet gear  114  and the input gear  92  rotates in the webbing take-up direction about the support portion  98 , the connection pawl  110  rotates in the take-up direction together with the input gear  92 , and the meshing portion  122  presses the ratchet gear  114  in the take-up direction, thereby rotating the ratchet gear  114  in the take-up direction together with the input gear  92 . 
     As shown in  FIG. 2  and  FIG. 3 , in the present exemplary embodiment, the outer peripheral shape of the support shaft  102  is not completely circular. Namely, a part of the outer periphery of the support shaft  102  is formed to have a flat surface portion  102 A. The flat surface portion  102 A is formed in such a manner that a part of the support shaft  102  which is made circular is scraped off in the axial direction thereof at a position deviated in the radial direction from the center of the circular shape of the support shaft  102 . In the state in which the connection pawl  110  and the ratchet gear  114  mesh with each other as shown in  FIG. 3 , the flat surface portion  102 A is formed so as to substantially face from the center of the circular hole  112  toward the position at which the connection pawl  110  and the ratchet gear  114  come into contact with each other (a meshing position). 
     On the contrary, the outer peripheral surface of the support shaft  102  excluding the flat surface portion  102 A is formed as a curved portion  102 B. The center of curvature of the curved portion  102 B is set at the same position as that on the central axis of the support shaft  102  when the outer peripheral surface of the support shaft  102  is made circular without forming the flat surface portion  102 A. Namely, in a state in which the support shaft  102  gets into the circular hole  112 , the center of curvature of the curved portion  102 B and the center of the circular hole  112  substantially coincide with each other. Further, the curved portion  102 B is set in the range of 180° or more around the central axis of the support shaft  102 . 
     Further, as shown in  FIG. 2  and  FIG. 3 , a supporting portion  113  is provided in the input gear  92 . The supporting portion  113  is provided at an outer side from the connection pawl  110  along the radial direction of the input gear  92 . An interference portion  113 A is provided in the supporting portion  113 . The interference portion  113 A is formed at a position opposite to a direction to which the flat surface portion  102 A in the support shaft  120  faces, with respect to the connection pawl  110 , and is curved so as to correspond to a region in the vicinity of the circular hole  112 . The interference portion  113 A and the connection pawl  110  come into contact with each other or are apart from each other at a very short distance. When the connection pawl  110  attempts to be displaced in the direction opposite to the direction in which the flat surface portion  102 A faces, namely, in a direction opposite to a position (a meshing position) at which the connection pawl  110  and the ratchet gear  114  comes into contact with each other, the interference portion  113 A interferes with the connection pawl  110 . 
     Further, in the present exemplary embodiment, one support shaft  102  is formed to deviate from the other support shaft  102  by 180° about the rotation center of the input gear  92 . On the contrary, the number of the external ratchet teeth formed on the ratchet gear  114  is set to be odd. Due to this configuration, when the meshing portion  122  of the connection pawl  110  supported by the one support shaft  102  meshes with a ratchet tooth of the ratchet gear  114 , the meshing portion  122  of the connection pawl  110  supported by the other support shaft  102  comes into contact with the intermediate portion of a slope of a ratchet tooth in the rotary circumferential direction of the ratchet gear  114  and does not mesh with the ratchet tooth. With such a configuration, when the ratchet gear  114  rotates by an angle corresponding to a half of an interval of the ratchet teeth, the meshing portion  122  of either one of the connection pawls  110  meshes with the ratchet tooth of the ratchet gear  114 . 
     A supporting pin  124  is formed at the side in a webbing pull-out direction of each of the support shafts  102  along the circumferential direction of the input gear  92  on the bottom wall portion  94 . A return spring  126  is attached to each of the supporting pins  124 . The return spring  126  is a helical torsion spring whose intermediate portion is coiled, and one end of the return spring is locked at a locking portion (not shown) formed in the bottom wall portion  94 . The other end side of the return spring  126  comes into pressure contact with a spring contact portion  128  of the connection pawl  110 , and urges the connection pawl  110  in a direction in which the meshing portion  122  is separated from the outer periphery of the ratchet gear  114  around the support shaft  120 . 
     Further, the clutch  90  includes a pair of interference pieces  140 . As shown in  FIG. 4 , the interference piece  140  includes a base portion  142 . The base portion  142  is formed into a narrow plate whose transverse direction coincides with the axial direction of the spool  18 . An outer holding ring  146  and an inner holding ring  148  are formed in the bottom portion of the above-described gear box  52  so as to correspond to the base portion  142 . 
     The outer holding ring  146  and inner holding ring  148  are each formed into a ring coaxial with the support portion  98 , and are formed upright from the bottom portion of the gear box  52  to the side opposite to a side at which the bridge plate  16  is disposed. The base portion  142  of the interference piece  140  is interposed between the outer holding ring  146  and the inner holding ring  148 , and come into pressure contact with the inner peripheral portion of the outer holding ring  146  and the outer peripheral portion of the outer holding ring  148  due to the spring property thereof. 
     An interference portion  152  extends from one end portion in the widthwise direction and a center part in the longitudinal direction of the base portion  142 . That is, the interference portion  152  is disposed at a side opposite to the other side of the base portion  142  facing the bottom portion of the supporting portion  98 , when the base portion  142  is interposed between the outer holding ring  146  and the inner holding ring  148 ). As shown in  FIGS. 2 and 3 , a through hole  154  is formed in the bottom wall portion  94  of the input gear  92  so as to correspond to the interference portion  152 . The through hole  154  is formed in the vicinity of the meshing portion  122  of the connection pawl  110  supported by the support shaft  102 . When the interference piece  140  is disposed between the outer holding ring  146  and the inner holding ring  148 , the interference portion  152  passes through the through hole  154  and faces the meshing portion  122  in the take-up direction of the meshing portion  122  along the rotary circumferential direction of the input gear  92  when the interference piece  140  is in the initial state. 
     As shown in  FIG. 1 , a blocking plate  162  is provided at an end side of an opening of the gear box  52 . The blocking plate  162  is attached to the gear box  52  by fastening members such as a bolt or screw (not shown). The blocking plate  162  attached to the gear box  52  blocks the side opposite to the leg plate  16  side of the opening of the gear box  52  and regulates the separation of the two-staged gears  60  and  70 , the gear  80 , or the input gear  92  (clutch  90 ). In addition, since the blocking plate  162  blocks not only the opening of the gear box  52  but also the input gear  92  at which the connection pawl  110  and the return spring  126  are accommodated, and the separation of the connection pawl  110  and the return spring  126  from the inside of the input gear  92  is regulated. 
     A through hole  164  is formed at the blocking plate  162  so as to perforate the blocking plate  162  in the thickness direction. A shaft portion  166  protruding from the adapter  116  passes through the through hole  164  and protrudes to the outside of the blocking plate  162 . A spring housing  172  is provided at the outside opposite to the gear box  52  of the blocking plate  162 . 
     The spring housing  172  is integrally connected to the gear box  52 . The shaft portion  166  passing through the through hole  164  is inserted into the spring housing  172  and is rotatably supported by a bearing portion (not shown) formed inside the spring housing  172 . In addition, a helical spring (not shown) is accommodated in the spring housing  172 . The outer end portion of the helical spring in the helical direction is directly or indirectly locked to the spring housing  172 , and inner end portion of the helical spring is directly or indirectly locked to the shaft portion  166  inserted into the spring housing  172 . 
     The helical spring is wound and tightened when the shaft portion  166  is rotated in the pull-out direction, and urges the shaft portion  166  in the take-up direction. When the webbing belt  20  pulled out from the spool  18  in a normal state is wound and accommodated in the spool  18 , the helical spring rotates the spool  18  in the take-up direction by means of its urging force. 
     &lt;Operation and Effect of the Present Exemplary Embodiment&gt; 
     Next, the operation and effect of the present exemplary embodiment are described by way of illustration of the operation of the webbing take-up device  10 . 
     In the webbing take-up device  10 , when the ECU determines that the distance with respect to another vehicle traveling in front of the own vehicle or an obstacle in front of the own vehicle is less than a predetermined value on the basis of electrical signals output from the forward monitoring device, the ECU passes electric current to the motor so as to activate the motor  40 . When the motor  40  is activated and the output shaft  42  is rotated, the gear  56  transmits rotation of the output shaft  42  to the large-diameter gear  62  of the two-staged gear  60  to thereby rotate the two-staged gear  60 . Further, the small-diameter gear  64  of the two-staged gear  60  meshes with the large-diameter gear  72  of the two-staged gear  70 , and therefore, rotation of the two-staged gear  60  is transmitted to the two-staged gear  70  so that the two-staged gear  70  rotates. This rotation of the two-staged gear  70  is transmitted to the gear  80  meshing with the small-diameter gear  74 , and further, is transmitted to the gear portion  100  meshing with the gear  80  while the initial rotation is decelerated. As a result, the input gear  92  rotates in the webbing take-up direction. 
     Due to the input gear  92  rotating in the take-up direction, the support shaft  102  formed at the input gear  92  also rotates in the take-up direction, thereby resulting in that the connection pawl  110  supported by the support shaft  102  rotates in the take-up direction. As described above, the interference portion  152  of the interference piece  140  is located at the take-up direction side of the meshing portion  122  of the connection pawl  110  therefore, when the connection pawl  110  rotates in the take-up direction together with the input gear  92 , the meshing portion  122  abuts against the interference portion  152  thereby presses the interference portion  152  in the take-up direction. 
     In the interference piece  140 , the base portion  142  is disposed between the outer holding ring  146  and the inner holding ring  148  in a curved state while resisting its elasticity and comes into pressure contact with the outer holding ring  126  and the inner holding ring  148 . Due to this configuration, unless the base portion  142  is pressed by a force more than the maximum static frictional force at the contact portion between the base portion  142  and the outer holding ring  146  and the contact portion between the base portion  142  and the inner holding ring  148 , the base portion  142  does not move in the circumferential direction of the outer holding ring  146  and the inner holding ring  148  within those holding rings  146  and  148 . 
     Accordingly, when the pressing force of the meshing portion  122  to the interference portion  152  does not surpass the maximum static frictional force at the contact portion between the base portion  142  and the outer holding ring  146  and the contact portion between the base portion  142  and the inner holding ring  148 , a pressing reaction force from the interference portion  152  is imparted to the meshing portion  122 , and the connection pawl  110  rotates around the support shaft  102  against the urging force of the return spring  126 , and the meshing portion  122  moves close to the outer peripheral portion of the ratchet gear  114 . Due to rotation of each connection pawl  110 , as shown in  FIG. 3 , when the meshing portion  122  of one connection pawl  110  (the upper side connection pawl in  FIG. 3 ) meshes with the ratchet tooth of the ratchet gear  114 , the meshing portion  122  presses the ratchet tooth in the take-up direction. 
     Further, in this state, since further rotation of the connection pawl  110  is regulated, the meshing portion  122  of the connection pawl  110  keeps pressing the interference portion  152 . Accordingly, when the pressing force in the take-up direction applied to the interference portion  152  is more than the maximum static frictional force at the contact portion between the base portion  142  and the outer holding ring  146  and the contact portion between the base portion  142  and the inner holding ring  148 , the interference piece  140  is guided by the outer holding ring  146  and the inner holding ring  148  to be rotated in the take-up direction. 
     Accordingly, the input gear  92  is further rotated in the take-up direction, and the rotation of the input gear  92  is transmitted to the ratchet gear  114  via the connection pawl  110 , thereby rotating the ratchet gear  114  in the take-up direction. Since the ratchet gear  114  is connected to the spool  18  via the adapter  116  and the torsion shaft so as not to be rotatable relative to the spool  18 , the spool  18  is rotated in the take-up direction when the ratchet gear  114  is rotated in the take-up direction. In this manner, as the spool  18  is rotated in the take-up direction, the webbing belt  20  is wound around the spool  18 , thereby removing slight looseness, or so-called “slack” of the webbing belt  20  fastened to an occupant body in the vehicle. 
     When the meshing portion  122  of the connection pawl  110  meshes with the ratchet teeth of the ratchet gear  114  in the state in which the connection pawl  110  rotates in the take-up direction together with the input gear  92 , reaction force F (refer to  FIG. 3 ) from the ratchet teeth of the ratchet gear  114  is imparted to the meshing portion  122 , and the connection pawl  110  attempts to be displaced in the direction in which the reaction force F acts. 
     Note that the outer peripheral portion of the support shaft  102  does not have the shape of perfect circle. The flat surface portion  102 A is formed in the support shaft  102 , and the curved portion  102 B excluding the flat surface portion  102 A comes into contact with the inner peripheral portion of the circular hole  112  so as to support the connection pawl  110 . Namely, a clearance is formed between the flat surface portion  102 A and the inner peripheral portion of the circular hole  112 . A direction of a line which connects a contact portion between the meshing portion  122  and the ratchet tooth, and the center of curvature of the curved portion  102 B of the support shaft  102  is set along a direction in which the reaction force F acts. The plane of the flat surface portion  102 A faces against the acting direction of the reaction force F. 
     Accordingly, even if the reaction force F acts on the connection pawl  110 , the inner peripheral portion of the circular hole  112  does not come into contact with the flat surface portion  102 A. Thus, the reaction force F is not applied to the flat surface portion  102 A and the support shaft  102 . Therefore, such a mechanical strength as to resist the reaction force F is not required in the support shaft  102 , and the outer peripheral shape of the support shaft  102  can be made smaller or the support shaft  102  can be made thin. 
     In this manner, due to the support shaft  102  can be made thin, a contact area where the outer peripheral portion of the support shaft  102  and the inner peripheral portion of the circular hole  112  come into contact with each other can be made smaller. Therefore, when the connection pawl  110  rotates, frictional resistance generated between the outer peripheral portion of the support shaft  102  and the inner peripheral surface of the circular hole  112  becomes smaller and loss hindering rotation of the connection pawl  10  is decreased. 
     Further, the curved surface  102 B of the support shaft  102 , which comes into contact with the inner peripheral portion of the circular hole  112  is set in the range of 180° or more around the center of curvature of the support shaft  102 . Therefore, if the connection pawl  110  attempts to be displaced in the radial direction of the support shaft  102 , a portion of the curved surface  102 B in the vicinity of the flat surface portion  102 A interferes with the inner peripheral portion of the circular hole  112 . As a result, displacement of the connection pawl  110  in a direction orthogonal to the axial direction of the support shaft  102  can be restrained, and the connection pawl  110  can be excellently supported rotatably. 
     In addition, the interference portion  113 A of the supporting portion  113  provided in the input gear  92  is formed at an opposite side of the connection pawl  110  to the flat surface portion  102 A of the support shaft  102  faces, in other word, the interference portion  113 A is provided at an opposite side of the connection pawl  110  to a position where the connection pawl  110  and the ratchet gear  114  come into contact with each other (mesh with each other). Accordingly, if the connection pawl  110  attempts to be displaced by the reaction force F, the interference portion  113 A interferes the connection pawl  110 . As a result, displacement of the connection pawl  110  by the above-described reaction force F is regulated, and therefore, the connection pawl  110  is not displaced in a direction orthogonal to the axial direction of the support shaft  102  that is, in the radial direction of the support shaft  102 , so that the connection pawl  110  rotates around the center of curvature of the curved portion  102 B of the support shaft  102  and the meshing portion  122  can excellently mesh with the ratchet tooth of the ratchet gear  114  at a proper timing. 
     In the present exemplary embodiment, the structure in which the circular hole  112  serving as a bearing portion is formed in the connection pawl  110  and the support shaft  102  serving as a shaft portion is formed in the input gear  92  is given. However, a structure in which the support shaft  102  is formed in the connection pawl  110  and the circular hole  112  is formed in the input gear  92  may also be employed. 
     Further, in the present exemplary embodiment, the present invention is applied to the structure in which the clutch  90  is interposed between the motor  40  and the spool  18 , but the present invention is not limited to the clutch  90 . For example, the present invention may be applied to a structure of supporting an engaging member such as a pawl that engages with a rotating body such as a ratchet gear by swinging in the above-described lock mechanism  22 . 
     The foregoing description of the exemplary embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The exemplary embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.

Technology Classification (CPC): 1