Abstract:
A webbing retractor for webbing belt retraction and restraint of a vehicle occupant during sudden deceleration. In a preferred embodiment, the webbing retractor includes a spring, and is for connection to an axially rotatable shaft having a locking device. The locking device includes a rotator coaxially rotatable with the shaft and a locking mechanism. The spring resiliently urges the shaft to retract the webbing belt, which can be ordinarily unwound against the spring tension. During sudden deceleration, the locking mechanism is activated and limits or prevents unwinding of the webbing belt. The retractor includes wall portions provided at the rotator and the shaft, with the spring disposed between these portions. A hole for insertion of the spring is provided between the wall portions. The hole is sized such that the spring must be at least partially compressed for insertion therethrough. The arrangement facilitates insertion of the spring, and stable connection of the spring in the assembly.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a webbing retractor for a webbing belt which restrains a vehicle occupant. 
     2. Description of the Related Art 
     A locking device is provided at a webbing retractor which forms a main portion of what is known as a seat belt apparatus, which restrains a vehicle occupant by means of an elongated belt-shaped webbing belt. When a vehicle rapidly decelerates, the locking device locks a winding shaft to oppose a force applied by a body of the vehicle occupant, which begins to move toward the front of the vehicle due to inertia in the rapid deceleration state and starts to pull out the webbing belt. In this way, the locking device increases the restraining force of the webbing belt at the time of rapid deceleration of the vehicle. 
     An example of this type of locking device is briefly described below. 
     The locking device is provided with one or a plurality of lock plates attached to the winding shaft so as to be displaceable within a predetermined range along a radial direction of the winding shaft. Ratchet teeth are formed at an outer peripheral portion of each of these lock plates. When the lock plates are displaced, with respect to the winding shaft, outward in a radial direction of the winding shaft, the ratchet teeth mesh with ratchet teeth of a ratchet hole formed in one of a pair of leg plates that form a frame of the webbing retractor, thereby locking the winding shaft. 
     A rotating body is provided in a vicinity of these lock plates so as to be rotatable coaxially with the winding shaft. The rotating body is mechanically coupled to the winding shaft by an urging member such as a compression coil spring, a torsion coil spring, or the like, and rotates along with the winding shaft. When an external force that opposes this rotation with the winding shaft is applied to the rotating body, the urging member deforms elastically and the rotating body rotates relatively to the winding shaft. The rotating body is engaged with the lock plates, and when the rotating body rotates relative to the winding shaft, the lock plates are displaced outward in the radial direction of the winding shaft. 
     An acceleration sensor is provided at a side of the rotating body. The acceleration sensor is provided with a locking member which locks rotation of the rotating body when the acceleration sensor detects a vehicle deceleration of a predetermined magnitude or more. 
     When the body of the vehicle occupant pulls out a webbing belt due to inertia at a time of rapid deceleration of the vehicle, the winding shaft rotates in a pulling-out direction (i.e. in a direction in which the webbing belt is pulled out). However, when the acceleration sensor detects such a state of rapid deceleration, the locking member locks rotation of the rotating body, and therefore, relative rotation occurs between the winding shaft and the rotating body. The relative rotation of the rotating body at this time displaces the lock plates outward in the radial direction of the winding shaft. The rotation of the winding shaft is locked by the ratchet teeth of the lock plates meshing with the ratchet teeth of the ratchet hole, and pulling-out of the webbing belt is limited. 
     In the locking device described above, a compression coil spring may be used as the urging member. In the locking device described above, as well as in other devices, a compression coil spring may be attached by the following method. First, a cylindrical boss having a slightly smaller outside diameter than an inside diameter of the compression coil spring is formed as a projection, from a portion to which one end portion of the compression coil spring abuts, along an axial direction of the compression coil spring (specifically, the axial direction of the compression coil spring when it is regarded from the shape thereof as a cylinder). Then, the compression coil spring is attached to the boss such that the boss is inserted into the compression coil spring. Displacement of the compression coil spring in a direction perpendicular to the axial direction of the boss is limited by the boss. 
     The above-described method for attaching a compression coil spring is usual. However, it has the following problems when applied to attachment of a compression coil spring in the locking device described above. 
     In the locking device described above, a disc or the like for limiting displacement of the lock plates and of the winding shaft itself along the axial direction of the winding shaft is integrally provided at the winding shaft at a side of the lock plates opposite to the side at which the rotating body is disposed. Between the disc and the rotating body, the abutting portion and the boss described above are formed and the compression coil spring is disposed. In this case, an opening is provided in the rotating body in advance in order to facilitate attachment of the compression coil spring. The compression coil spring is disposed between the rotating body and the disc through this opening. 
     In order that the compression coil spring can be attached and that secure attachment can be confirmed, the opening needs to be formed so that one end of the opening in the longitudinal direction thereof is at a position which is almost coplanar with the plane in which the base portion of the boss exists and, further, the length from a position corresponding to a distal end of the boss to the other end portion of the opening in the longitudinal direction thereof is longer than the total length of the compression coil spring when the compression coil spring is fully compressed. 
     However, providing a boss at each of both longitudinal direction ends of the compression coil spring is fundamentally difficult. Hence, the compression coil spring is only supported by the boss provided at the one longitudinal direction end portion of the compression coil spring. Therefore, the other longitudinal direction end portion of the compression coil spring is extremely unstable, and the compression coil spring can easily come off through the opening having the size described above. 
     Further, when the compression coil spring is attached to a structure as described above, the compression coil spring cannot pass through the opening unless it is fully compressed in advance. Therefore, it is extremely difficult to automate the attachment process of the compression coil spring. 
     SUMMARY OF THE INVENTION 
     In view of the aforementioned, an object of the present invention is to provide a webbing retractor which facilitates reliable attachment of a compression coil spring, and from which such an attached compression coil spring does not easily come off. 
     A first aspect of the present invention is a webbing retractor for connection to an axially rotatable winding shaft having a webbing belt with an end, the end being connected to the winding shaft, which takes-up the webbing belt by rotation in a retracting direction, the webbing belt being for restraining a vehicle occupant, the winding shaft having a locking device with a rotating body coaxially rotatable with the winding shaft in a pulling-out direction, the pulling-out directing being opposite to the retracting direction, the locking device including a locking mechanism preventing rotation of the winding shaft in the pulling-out direction when there is a sudden vehicle deceleration, the webbing retractor including: a pair of wall portions with a first wall portion provided at the rotating body and a second wall portion provided at the winding shaft at a retracting direction side of the first wall portion and faces the first wall portion; a compression coil spring which is disposed between the pair of wall portions, and which is compressed by a pressing force applied from the second wall portion due to rotation of the winding shaft in the pulling-out direction, and which presses the first wall portion by restoring force from the compressed state of the compression coil spring; limiting portions, at least one of which is provided integrally with the rotating body and at least one of which is provided integrally with the winding shaft, and which limit at an outer side of the compression coil spring displacement of the compression coil spring along a direction perpendicular to an axis of the compression coil spring; and an insertion hole provided between the pair of wall portions and penetrating the rotating body at a position further toward the second wall portion than to the first wall portion, and an opening dimension of the insertion hole along a direction from the first wall portion to the second wall portion is larger than a total length of the compression coil spring in a compressed state and smaller than a total length of a natural length of the compression coil spring, and the compression coil spring is inserted through the insertion hole between the pair of wall portions and into a region at an inner side of the limiting portions from a side of the rotating body opposite a side at which the wall portions exist. 
     In the webbing retractor with the above structure, when the winding shaft rotates in the pulling-out direction in a normal state, the second wall portion provided at the winding shaft begins to compress the compression coil spring by pressing the compression coil spring in the pulling-out direction, and the compression coil spring receiving the pressing force presses the first wall portion provided at the rotating body by an elastic force thereof. Thus, the rotating body rotates in the pulling-out direction, following the rotation of the winding shaft. 
     When the webbing belt is pulled out and the winding shaft is rotated in the pulling-out direction in a state in which rotation of the rotating body is limited or an external force in the retracting direction is applied to the rotating body, the second wall portion compresses the compression coil spring whereas the first wall portion opposes the elastic force of the compression coil spring. Therefore, the rotating body rotates in the retracting direction relatively to the winding shaft. When the rotating body relatively rotates, the locking mechanism operates to lock rotation of the winding shaft in the pulling-out direction. Thus, the webbing belt cannot be pulled out further in this state. 
     Since displacement of the compression coil spring in a direction along a direction perpendicular to the axis of the compression coil spring is limited from the outer side of the compression coil spring by limiting portions provided at at least one of the rotating body and the winding shaft, malfunction or the like due to an inadvertent displacement of the compression coil spring in the direction perpendicular to the axis of the compression coil spring is prevented. 
     Further, since the limiting portions limit displacement of the compression coil spring at the outer side of the compression coil spring, it suffices for the compression coil spring to be inserted between the limiting portions when it is assembled. Therefore, assembly of the compression coil spring is easier than in a conventional structure in which displacement of the compression coil spring is limited by a boss. 
     Furthermore, in the present webbing retractor, even though the compression coil spring is still assembled by being inserted between the rotating body and the winding shaft through the insertion hole formed in the rotating body, the insertion hole opens at a wall portion other than the wall portion where the limiting portions of the rotating body and the winding shaft are provided, and the length of the insertion hole in a direction along the axial direction of the compression coil spring is long enough for the compression coil spring to be able to pass therethrough in a compressed state. Therefore, the length of the insertion hole in the direction along the axial direction of the compression coil spring can be made smaller than the length thereof in a conventional structure using a boss, and the compression coil spring can be prevented from coming off after assembly. 
     The webbing retractor of the present invention, preferably further includes a pressing portion provided integrally with the winding shaft at a side of the second wall portion which side is opposite to a side at which the first wall portion exists, the pressing portion pressing the first wall portion toward the retracting direction when the winding shaft rotates in the retracting direction. 
     In the webbing retractor of the above structure, when the winding shaft rotates in the retracting direction, the second wall portion moves in a direction of moving away from the first wall portion. However, in this case, the pressing portion presses the first wall portion provided at the rotating body side, and the rotating body thereby follows the rotation of the winding shaft in the retracting direction. That is, in the present webbing retractor, since the rotating body is made to follow the rotation of the winding shaft without using the elastic force of the compression coil spring when the winding shaft rotates in the retracting direction, the compression coil spring only need to be disposed between the pair of wall portions. Therefore, an end portion of the compression coil spring does not particularly need to be fixed, and assembly of the compression coil spring is even easier. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an enlarged exploded perspective view of a structure of main portions of a webbing retractor relating to an embodiment of the present invention. 
     FIG. 2 is a plan view of a V-gear of the webbing retractor relating to the embodiment of the present invention. 
     FIG. 3 is a sectional view along a line  3 — 3  of FIG. 2 showing how a compression coil spring is assembled into the webbing retractor. 
     FIG. 4 is a vertical sectional view showing an overall structure of the webbing retractor relating to the embodiment of the present invention. 
     FIG. 5 is a side view showing an unlocked state of the webbing retractor relating to the embodiment of the present invention. 
     FIG. 6 is a side view showing a locked state of the present webbing retractor relating to the embodiment of the present invention. 
     FIG. 7 is a front view of a torsion shaft shown in FIG.  4 . 
     FIG. 8 is a side view of a base lock shown in FIG.  4 . 
     FIG. 9 is a front view of a lock plate shown in FIG.  4 . 
     FIG. 10 is a side view of an acceleration sensor which is not illustrated in FIG.  4 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 4 is a vertical sectional view illustrating an overall structure of a webbing retractor  10  relating to the present embodiment. As shown in this figure, the webbing retractor  10  includes a frame  14  formed, when viewed from above, substantially in a U shape. The frame  14  is fixed to a vehicle body. The frame  14  includes a first leg plate  16  and a second leg plate  18 , which are extended parallel to each other. A spool  12  is a winding shaft which is made by die-casting. The spool  12  is rotatably supported between the first leg plate  16  and the second leg plate  18 . 
     The spool  12  is formed by a cylindrical spool shaft  12 A forming an axial center portion, and a pair of substantially disc-shaped flange portions, each of which is formed respectively at one of both end portions of the spool shaft  12 A (hereinafter, the flange portion disposed at the first leg plate  16  side is called “first flange portion  12 B” and the flange portion disposed at the second leg plate  18  side is called “second flange portion  12 C”). 
     A shaft insertion hole  20  is formed at the axial center portion of the spool shaft  12 A. A base lock receiving portion  22  is coaxially formed as a recess which has a larger diameter than that of the shaft insertion hole  20 , at the first flange portion  12 B side of the shaft insertion hole  20 . The base lock receiving portion  22  includes a recess body  22 A, which forms most of the base lock receiving portion  22 , and a recess end portion  22 B, which has a larger diameter than that of the recess body  22 A. 
     A base lock  24 , which is made by die-casting, is mounted to the base lock receiving portion  22  such that removal of the base lock  24  therefrom is prevented. The base lock  24  is mounted by insertion of the base lock  24  into the base lock receiving portion  22 , after which the base lock  24  is grasped by an unillustrated stopper (a removal prevention member), formed substantially in a U shape when viewed from the front and press fitted in a direction perpendicular to the axis. While the base lock  24  is made by die-casting in the present embodiment, the base lock  24  is not necessarily made by die-casting. As will be apparent from the operation and effects described later, the base lock  24  may be formed of a material which allows the base lock  24  to engage with ratchet teeth  38 A by deforming plastically when the base lock  24  is pressed against the ratchet teeth  38 A at a time of rapid deceleration of a vehicle. 
     The base lock  24  is formed in a cylindrical shape having a collar, and is formed by a base portion  24 A which is fitted into the recess body  22 A of the base lock receiving portion  22 , an intermediate portion  24 B which has a larger diameter than that of the base portion  24 A and is fitted into the recess end portion  22 B of the base lock receiving portion  22 , and a retaining portion  24 C which has a larger diameter than that of the intermediate portion  24 B and is disposed so as to abut the outer side surface of the first flange portion  12 B. A fitting hole  26  which is in a hexagon socket shape is formed at a portion of the base lock  24  other than an outer end of the axial center portion thereof. Further, a small hole  28  which communicates with the axial center portion of the fitting hole  26  and has a smaller diameter than that of the fitting hole  26  is formed at the outer end of the axial center portion of the base lock  24 . 
     A sleeve receiving portion  30 , which is a recess having a larger diameter than that of the shaft insertion hole  20 , is formed at the second flange portion  12 C side of the shaft insertion hole  20  of the spool shaft  12 A. A female spline is formed at an inner circumferential portion of the sleeve receiving portion  30 . A sleeve  34 , having a male spline formed at an outer circumferential portion thereof and a hexagon socket-shaped fitting hole  32  formed at an axial center portion thereof, is fitted into the sleeve receiving portion  30 . An inner end of an urging means (a power spring) which urges the spool  12  to rotate in a retracting direction (i.e., a direction opposite to a direction in which the webbing belt is pulled out) is secured to a tip portion of the sleeve  34  via an unillustrated adapter. The sleeve  34  with the structure described above is one of the structural components of a pretensioner which rotates the spool  12  in the retracting direction promptly at a time of rapid deceleration of the vehicle. 
     The base lock  24  and sleeve  34  described above are coupled with each other through a torsion shaft  36 . As also shown in FIG. 7, the torsion shaft  36  is formed by a shaft portion  36 A which forms the main portion thereof, a hexagonal head portion  36 B which is formed at one end portion of the shaft portion  36 A, a hexagonal fitting portion  36 C which is formed at the other end portion of the shaft portion  36 A, a small diameter portion  36 D extended coaxially with the shaft portion  36 A from the axial center portion of the fitting portion  36 C, a gear-holding portion  36 E whose diameter is reduced from that of the small diameter portion  36 D through a tapered surface, and subsequently increased so as to form an annulus, and a tip portion  36 F extended coaxially further from the gear-holding portion  36 E and having a key formed thereat. As shown in FIG. 4, the head portion  36 B of the torsion shaft  36  is fitted into the hexagon socket-shaped fitting hole  32  formed in the sleeve  34 , and the fitting portion  36 C of the torsion shaft  36  is fitted into the hexagon socket-shaped fitting hole  26  formed in the base lock  24 . The torsion shaft  36  is thereby integrated with the spool shaft  12 A via the base lock  24  and the sleeve  34 . The torsion shaft  36  of the structure described above is a main structural component of a force limiter which performs energy absorption by torsional deformation when a webbing tension greater than a predetermined value acts on the spool  12  at a time of rapid deceleration of the vehicle. 
     As shown in FIGS. 5 and 6, an internal-teeth ratchet  38  is formed, by punching, at an upper portion of the first leg plate  16  of the frame  14 . Ratchet teeth  38 A of the internal-teeth ratchet  38  are formed so as to have high strength. 
     The retaining portion  24 C of the base lock  24  is disposed inside the internal-teeth ratchet  38 . The small diameter portion  36 D of the torsion shaft  36  is inserted into the aforementioned small hole  28  formed at the axial center portion of the retaining portion  24 C. An accommodating portion  40  (see FIGS. 2,  5 ,  6 , and  8 ) is a recess formed at the front side of the retaining portion  24 C in the peripheral direction of the small hole  28 . One end portion of the accommodating portion  40  is closed, while the other end portion of the accommodating portion  40  is open. The other end portion side of the accommodating portion  40  is beveled so as not to interrupt the engaging movement of a lock plate  42  (described below) with the internal-teeth ratchet  38 . The single lock plate  42  is overall substantially in a circular arc plate shape (see FIGS. 5,  6 , and  9 ) and forms a locking device as one of the structural components of a locking mechanism. The lock plate  42  is accommodated in the accommodating portion  40 . A thin disc shaped lock cover  44  is non-rotatably attached to the outer surface of the retaining portion  24 C of the base lock  24 , in order to prevent the lock plate  42  from falling out. 
     As shown in FIG.  9  and other figures, the lock plate  42  is formed of a plate body  42 A substantially in a circular arc plate shape and made of metal, a rectangular projecting portion  42 B extending from one end portion of the plate body  42 A, high strength locking teeth  42 C formed at the peripheral portion of the other end portion of the plate body  42 A which mesh with the ratchet teeth  38 A of the internal-teeth ratchet  38  of the first leg plate  16 , and a guide pin  42 D standing from the other end portion of the plate body  42 A. The added length of the width of the plate body  42 A and the projecting length of the projecting portion  42 B is approximately equal to the width of a wide portion  40 A of the accommodating portion  40  of the base lock  24  (see FIGS.  5  and  6 ). 
     A substantially disc-shaped V-gear  46 , which is a rotating body forming the locking device and which has a diameter larger than that of the base lock  24 , is disposed at a position adjacent to the base lock  24 . As shown in FIG. 2, a cylindrical boss  48  is formed at the axial center portion of the V-gear  46 , and is rotatably supported by the gear-holding portion  36 E of the torsion shaft  36  so as to enable rotation of the V-gear  46  following rotation of the torsion shaft  36 . Further, a substantially L-shaped curved guide hole  50  is formed in the V-gear  46 . The guide pin  42 D standing from the lock plate  42  is inserted into the guide hole  50 . Further, locking teeth  46 A are integrally formed at the outer peripheral portion of the V-gear  46 . 
     As shown in FIGS. 1 through 3, a rectangular insertion hole  102  is formed through the V-gear  46  along the thickness direction thereof between the central portion and the peripheral portion thereof. The insertion hole  102  is in a rectangular shape whose longitudinal axis forms a string of an assumed arc on the V-gear  46 . The total length in the longitudinal direction of the insertion hole  102  is shorter than the natural length of the compression coil spring  104  shown in FIGS. 1 through 3, and is longer than or equal to the length of the compression coil spring  104  when it is fully compressed. Further, the length in the width direction of the insertion hole  102  is longer than the outside diameter dimension of the compression coil spring  104 . 
     Further, a wall portion  106  is formed, as a wall portion of a rotating body (one of a pair of wall portions), at an end surface that faces the base lock  24  when the V-gear is assembled. Of two longitudinal direction end portions of the insertion hole  102  described above, an end portion  102 A is relatively in the retracting direction, which is the direction of rotation of the spool  12  when the spool  12  is retracting the unillustrated webbing belt (the direction of arrow C in FIG.  2 ), and the other end is an end portion  102 B. The wall portion  106  is formed on the opposite side of the end portion  102 B from the end portion  102 A, at a position spaced from the end portion  102 A by a predetermined distance along the longitudinal direction of the insertion hole  102 . 
     The distance from the end portion  102 A of the insertion hole  102  to the wall portion  106  is such that the total longitudinal direction dimension of the insertion hole  102  (including the distance from the wall portion  106  to the other insertion hole  102  longitudinal direction end portion  102 B) is sufficiently shorter than the natural length of the compression coil spring  104 . 
     A pair of limiting walls  108  and  110  are formed, as limiting portions, at both end portions of the wall portion  106  in the width direction thereof toward the end portion  102 B of the insertion hole  102 . Further, a limiting wall  112  is formed as a limiting portion from an end portion of the wall portion  106  which is opposite to a portion coupled to the V-gear  46 , so as to connect the limiting walls  108  and  110 . The limiting wall  112  and the limiting walls  108  and  110  together make up a spring box  114 . A distance between the limiting walls  108  and  110  and a distance between the limiting wall  112  and the V-gear  46  are both slightly larger than the outside diameter dimension of the compression coil spring  104 . One end portion of the compression coil spring  104  in the axial direction thereof (specifically, the axial direction of the compression coil spring  104  when it is regarded from the form thereof as a cylinder) is accommodated inside the spring box  114 , and the one end portion of the compression coil spring  104  abuts the inside of the spring box  114  when accommodated therein. 
     Further, a rectangular small window  116  is formed through the V-gear  46  along the thickness direction thereof. The small window  116  is formed so as to have longitudinal sides along the width direction of the insertion hole  102 . Both end portions of the small window  116  in the longitudinal direction thereof correspond to the limiting walls  108  and  110 , and the one end portion in the width direction of the small window  116  corresponds to the wall portion  106 . Thus, the small window  116  communicates between the inside of the spring box  114  and an opposite side of the V-gear  46  from the spring box  114 , and the vicinity of a bottom portion of the spring box  114  (i.e. the limiting wall  112 ) can be inspected from this opposite side. 
     A through-hole  118 , which is substantially in a shape of a traditional fan and through which the spring box  114  passes when the V-gear  46  is in an assembled state, is formed in the aforementioned lock cover  44 . The through-hole  118  is formed so that not only can the spring box  114  pass through the through-hole  118  but also, while passed through the through-hole  118 , the spring box  114  can rotate within a predetermined angle around the center of the V-gear  46 . Thus, relative rotation of the V-gear  46  coaxially with the lock cover  44  is enabled within the predetermined angle. 
     Further, a spring-accommodation portion  120 , which accommodates the compression coil spring  104  and the spring box  114  which passes through the through-hole  118  when the V-gear  46  is in an assembled state, is formed at the retaining portion  24 C of the aforementioned base lock  24 . 
     The spring-accommodation portion  120  is a recess with an open end portion, which is at a side corresponding to the V-gear  46  when the base lock  24  and the V-gear  46  are in an assembled state. A portion of the spring-accommodation portion  120  has substantially the same form as the aforementioned through-hole  118 . A portion of the inside peripheral wall that is relatively toward a pulling-out direction side (i.e., a direction of rotation when the webbing belt is pulled out) of the spring-accommodation portion  120  is a pressing wall  122 , which serves as a pressing portion. When the base lock  24  rotates in the retracting direction, which is opposite to the pulling-out direction, the pressing wall  122  presses the spring box  114 . On the other hand, the inside peripheral wall of the spring-accommodation portion  120  further toward the retracting direction side than an intermediate portion of the spring-accommodation portion  120 , along the direction of the rotation, forms a limiting recess  130 , made up of a wall portion  124  and limiting walls  126  and  128 , which face each other. 
     A dimension between the limiting walls  126  and  128  of the limiting recess  130  is slightly larger than the outside diameter dimension of the compression coil spring  104 . Therefore, a portion of the axial direction other end of the compression coil spring  104  can be accommodated between the limiting walls  126  and  128 . The wall portion  124  of the limiting recess  130  faces the wall portion  106  generally along the longitudinal direction of the aforementioned insertion hole  102 . When the V-gear  46 , the base lock  24 , and the compression coil spring  104  are in an assembled state, the other axial direction end portion of the compression coil spring  104  abuts the wall portion  124 . 
     A known acceleration sensor  52  for VSIR (Vehicle Sensitive Inertia Reel) which forms a locking device as one of the structural components of the locking mechanism is provided at the lower side of the V-gear  46  (see FIG.  10 ). The acceleration sensor  52  is not illustrated in FIG.  4 . At a time of rapid deceleration of the vehicle, a ball  54  of the acceleration sensor  52  rolls over a sensor housing  56  to swing a sensor lever  58 , and then a locking pawl  58 A of the sensor lever  58  engages with the locking teeth  46 A of the V-gear  46 . 
     As shown in FIG. 4, the acceleration sensor  52  is held by a sensor holder  60  serving as a cover and made of resin. A sensor cover  62  made of resin and having a shape similar to the sensor holder  60  is provided outside the sensor holder  60 . The sensor holder  60  and the sensor cover  62  are fixed together as one body to the first leg plate  16  of the frame  14 . A short cylindrical boss  60 A is integrally formed at the axial center portion of the sensor holder  60 , and the boss  60 A is rotatably supported by the tip portion  36 F of the torsion shaft  36 . That is, the sensor holder  60  is allowed to function as a bearing for the torsion shaft  36 . In that sense, the sensor holder  60  is an element which may in a broad sense be regarded as a bearing member or a supporting member. From a more simplistic point of view, the sensor holder  60  could also be regarded as a holding member or a cover body. 
     Internal teeth which can engage with a pawl for an unillustrated WSIR (Webbing Sensitive Inertia Reel), which pawl is rotatably supported by the V-gear  46 , are integrally formed at an inside peripheral portion of the sensor holder  60 . 
     The operation and effects of the present embodiment are described next. 
     A vehicle occupant holds an unillustrated tongue plate which is inserted through the webbing and pulls out the webbing belt from the spool  12  against the urging force of the power spring, and then engages the tongue plate with an unillustrated buckle device. Thus, the occupant is fastened by the webbing of a three-point seat belt apparatus. Specifically, a portion of the webbing belt from an unillustrated shoulder anchor provided at an upper portion of a center pillar to the tongue plate is a shoulder webbing belt, and a portion of the webbing belt from the tongue plate to the webbing retractor is a lap webbing belt. 
     In a case of a normal pulling-out of the webbing belt as described above, when the spool  12  is rotated in the pulling-out direction by the vehicle occupant pulling the webbing belt, the wall portion  124 , which is a part of the inside peripheral wall of the spring-accommodation portion  120  of the base lock  24  which is provided integrally with the spool  12 , begins to compress the compression coil spring  104  by pressing the axial direction other end portion thereof. When the compression coil spring  104  is acted on by the pressing force from the wall portion  124 , the compression coil spring  104  presses with an elastic force thereof the wall portion  106 , to which the axial direction one end portion of the compression coil spring  104  abuts and rotates the V-gear  46  in the pulling-out direction. Therefore, at a normal pulling-out, the V-gear  46  rotates along with the spool  12 . 
     When the vehicle, having gone from this state to a driving state, rapidly decelerates, an unillustrated pretensioner operates via the sleeve  34  to rotate the spool  12  promptly in the retracting direction. At the same time, the acceleration sensor  52  detects the rapid deceleration of the vehicle. That is, the ball  54  of the acceleration sensor  52  rolls over the sensor housing  56  and swings the sensor lever  58 . The locking pawl  58 A of the sensor lever  58  thereby engages with the locking teeth  46 A of the V-gear  46  to block rotation of the V-gear  46  in the pulling-out direction. 
     Meanwhile, the body of the vehicle occupant, which begins to move toward the front of the vehicle due to inertia at the time of rapid deceleration, pulls the webbing belt which is applied to the vehicle occupant, and the spool  12  begins to rotate in the pulling-out direction due to tension applied to the webbing by the vehicle occupant. Therefore, a relative rotation is generated between the spool  12  beginning to rotate in the pulling-out direction and the V-gear  46 , whose rotation in the pulling-out direction is blocked. The relative rotation opposes the urging force of the compression coil spring  104 . As can be seen by comparing FIGS. 5 and 6, when the relative rotation between the spool  12  and the V-gear  46  is generated, the guide pin  42 D of the lock plate  42 , which is retained in the accommodating portion  40  formed at the retaining portion  24 C of the base lock  24 , is guided by the guide hole  50  of the V-gear  46  and moved outward substantially in a radial direction of the base lock  24 . The locking teeth  42 C of the lock plate  42  thereby mesh with the ratchet teeth  38 A of the internal-teeth ratchet  38  which is provided at the first leg plate  16  of the frame  14 . 
     Further, when the locking teeth  42 C of the lock plate  42  mesh with the ratchet teeth  38 A of the internal-teeth ratchet  38  at this time, a reaction force acts on the retaining portion  24 C of the base lock  24 . This reaction force is significantly large, because it is generated by meshing of the high strength lock teeth  42 C and the ratchet teeth  38 A at the time of rapid deceleration of the vehicle, and naturally acts as well on the torsion shaft  36  passing through the axial center portion of the base lock  24 . Furthermore, since the tip portion  36 F of the torsion shaft  36  is rotatably supported by the boss  60 A of the resin sensor holder  60 , the reaction force acts on the boss  60 A through the tip portion  36 F and elastically deforms the boss  60 A in an acting direction of the reaction force, which is a direction away from an engaging position of the lock plate  42 . Therefore, a portion of the periphery of the retaining portion  24 C of the base lock  24  is pressed hard against the ratchet teeth  38 A of the internal-teeth ratchet  38 . Since the base lock  24  is produced by die-casting and is relatively soft, when it is pressed against the ratchet teeth  38 A, it plastically deforms and is cut by the ratchet teeth  38 A. Thus, the base lock  24  and the ratchet teeth  38 A are directly engaged. As a result, in the present embodiment, locking is obtained at two points opposing each other in a radial direction and sufficient locking strength can be ensured. 
     The compression coil spring  104  is employed in the present embodiment as a means to make the V-gear rotate along with the spool  12  in the case of a normal pulling-out, and make the V-gear  46  rotate relatively to the spool  12  when the V-gear is locked, as described above. 
     A procedure of an assembly operation of the compression coil spring  104  during assembly of the webbing retractor  10  is described below. 
     As shown in FIG. 3, when the base lock  24 , the lock cover  44 , and the V-gear  46  of the present webbing retractor  10  are in an assembled state, first the axial direction other end portion of the compression coil spring  104  is inserted into the spring-accommodation portion  120 , through the insertion hole  102  formed in the V-gear  46 , and is abutted against the wall portion  124 . 
     Then, a pressing force is applied to the axial direction one end portion of the compression coil spring  104  to compress the compression coil spring  104 . When the compression coil spring  104  is compressed to a length short enough that the axial direction one end portion of the compression coil spring  104  can pass through the insertion hole  102 , the axial direction one end portion of the compression coil spring  104  is inserted through the insertion hole  102  into the spring-accommodation portion  120 . When the axial direction one end portion of the compression coil spring  104  is accommodated in the spring-accommodation portion  120 , the pressing force applied to the compression coil spring  104  is released. The compression coil spring  104  elongates, trying to return to its natural length because of the elastic force therein, and abuts the wall portion  106  which forms the spring box  114 . Thus, assembly of the compression coil spring  104  is completed. 
     Displacement of the thus assembled compression coil spring  104  along the axial direction of the spool  12  is limited by the limiting wall  112 , the bottom portion of the spring-accommodation portion  120 , and the V-gear  46 . Moreover, displacement of the compression coil spring  104  in a direction along the width direction of the insertion hole  102  is limited by the limiting walls  108 ,  110 ,  126 , and  128 . Therefore, no malfunctions due to inadvertent displacement of the compression coil spring  104  will occur. 
     Further, since the limiting walls  108 ,  110 ,  126 , and  128  limit displacement of the compression coil spring  104  at both ends thereof  104  in the present webbing retractor  10 , both ends of the compression coil spring  104  are in a stable state. Moreover, unlike conventional methods for attaching a compression coil spring, there is no boss. Therefore, a portion of for of a compression coil spring insertion opening (which is equivalent to the insertion hole  102  in the present webbing retractor  10 ) corresponding in conventional methods to a length from a base portion to a tip portion of a boss is not necessary. Hence, the size of the insertion hole  102  in the longitudinal direction thereof can be reduced. Thus, the compression coil spring  104  can be reliably prevented from coming out, being removed, or the like from the insertion hole  102 . 
     Further, as described in the aforementioned assembling procedure, since the compression coil spring  104  is compressed at assembly in such a state that the axial direction other end portion of the compression coil spring  104  is abutted against the wall portion  124 , the compression coil spring  104  can be compressed by a pressing force applied only to the axial direction one end portion of the compression coil spring  104 . Therefore, no special support is necessary at the other end portion of the compression coil spring  104  in the axial direction thereof. 
     Thus, since the compression coil spring  104  can be easily assembled and, moreover, the compression coil spring  104  can be compressed by a pressing force applied only to the axial direction one end portion of thereof, the assembly process can be automated using a robot or the like. 
     As described above, in the present invention, a compression coil spring can be easily and reliably attached, and the attached compression coil spring will not easily come off.