There is provided a webbing take-up device including: a seating portion formed to a cylinder shaped body and facing towards a cylinder shaped body axial direction second side; a bar shaped body housed at the inside of the cylinder shaped body and comprising a protrusion portion protruding out from the bar shaped body towards the cylinder shaped body axial direction second side; a push nut attached by fitting over the protrusion portion; and a washer through which the protrusion portion is inserted, the washer being seated against the seating portion with a face of the washer on the side of the washer away from the seating portion in contact with the push nut, and the rigidity to bending of the washer set higher than the rigidity to bending of the push nut.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 USC 119 from Japanese Patent Application No. 2010-168565 filed on Jul. 27, 2010, the disclosure of which is incorporated by reference herein.

BACKGROUND

1. Technical Field

The present invention relates to a webbing take-up device.

2. Related Art

As a webbing take-up device there are, for example, devices in which two energy absorbing members, a main shaft and a sub shaft, are disposed as torsion shafts in a straight line inside a spool (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 2009-113551).

However, when the main shaft and the sub shaft are retained inside the spool at an axial direction intermediate portion, for example, in a structure assembled with a fixing component for use in retention inserted from a direction orthogonal to the axis of the torsion shaft, the axial direction length of the torsion shaft becomes longer, making the device bigger.

SUMMARY

The present invention is made in consideration of the above circumstances and is directed towards the provision of a webbing take-up device capable of suppressing such an increase in device size.

A webbing take-up device according to a first aspect of the present invention includes: a seating portion formed to a cylinder shaped body and facing towards a cylinder shaped body axial direction second side; a bar shaped body housed at the inside of the cylinder shaped body and including a protrusion portion protruding out from the bar shaped body towards the cylinder shaped body axial direction second side; a push nut attached by fitting over the protrusion portion; and a washer through which the protrusion portion is inserted, the washer being seated against the seating portion with a face of the washer on the side of the washer away from the seating portion in contact with the push nut, and the rigidity to bending of the washer set higher than the rigidity to bending of the push nut.

According to the webbing take-up device of the first aspect of the present invention, the seating portion is formed to the cylinder shaped body and faces towards the cylinder shaped body axial direction second side, and the bar shaped body is housed at the inside of the cylinder shaped body and includes the protrusion portion protruding out from the bar shaped body towards the cylinder shaped body axial direction second side. The push nut is attached by fitting over the protrusion portion, and the washer, through which the protrusion portion is inserted, is seated against the seating portion with the face of the washer on the side of the washer away from the seating portion in contact with the push nut, and the rigidity to bending of the washer set higher than the rigidity to bending of the push nut. Suppression of the rigidity of the push nut is thereby enabled, and suppression of rigidity of the push nut achieves good assembly characteristics by suppressing the load input requirement when fitting the push nut over the protrusion portion. Since the protrusion portion is supported against the seating portion by the push nut and the washer a more compact structure for retaining the bar shaped body is achieved.

A webbing take-up device according to a second aspect of the present invention includes: a spool formed in a tubular shape on which a webbing belt is wound in layers; a seating portion that is formed at an axial direction intermediate portion of a through hole formed passing through an axial center portion of the spool and faces towards a spool axial direction second side; a first torsion shaft housed in the through hole of the spool, disposed along the axial direction of the spool and including a main body portion disposed further to a spool axial direction first side than the seating portion and a protrusion portion that protrudes out from the main body portion towards the spool axial direction second side; a second torsion shaft housed in the through hole of the spool further to the spool axial direction second side than the seating portion, the second torsion shaft disposed along the spool axial direction so as to be in a straight line next to the first torsion shaft and retained at an axial direction intermediate portion of the spool; a push nut disposed further to the spool axial direction first side than the second torsion shaft and attached by fitting over the protrusion portion; and a washer through which the protrusion portion is inserted, the washer being seated against the seating portion with a face of the washer on the side of the washer away from the seating portion in contact with the push nut, and the rigidity to bending of the washer set higher than the rigidity to bending of the push nut.

According to the webbing take-up device of the second aspect of the present invention, the seating portion is formed at the axial direction intermediate portion of the through hole formed passing through the axial center portion of the spool and faces towards the spool axial direction second side. The first torsion shaft is housed in the through hole of the spool, disposed along the axial direction of the spool and includes the main body portion disposed further to the spool axial direction first side than the seating portion and the protrusion portion that protrudes out from the main body portion towards the spool axial direction second side. The second torsion shaft is housed in the through hole of the spool further to the spool axial direction second side than the seating portion, disposed along the spool axial direction so as to be in a straight line next to the first torsion shaft and retained at the axial direction intermediate portion of the spool.

The push nut and the washer are disposed further to the spool axial direction first side than the second torsion shaft. The push nut is attached by fitting over the protrusion portion of the first torsion shaft. The washer, through which the protrusion portion of the first torsion shaft is inserted, is seated against the seating portion with the face of the washer on the side of the washer away from the seating portion in contact with the push nut, and the rigidity to bending of the washer set higher than the rigidity to bending of the push nut. Accordingly, even though a load acts on the first torsion shaft in a direction pulling towards the spool axial direction first side, this load is supported by the seating portion of the spool through the washer, suppressing the first torsion shaft from falling out. Due to the rigidity to bending of the washer being greater than that of the push nut, even though bending load from the first torsion shaft side is input to the push nut, bending deformation of the push nut is prevented or effectively suppressed by the support from the washer. The axial direction length of the first torsion shaft is suppressed by retaining the protrusion portion of the first torsion shaft using the push nut and the washer.

A webbing take-up device of a third aspect of the present invention is the webbing take-up device of the second aspect, wherein: a first groove is formed in the through hole of the spool extending along the spool axial direction at a location further to the spool axial direction first side than the seating portion; a second groove is formed in the through hole of the spool extending along the spool axial direction further to the spool axial direction second side than the first groove, partially out of alignment with the first groove in rotation about the spool axis and connected to the first groove; and the seating portion is formed by a terminal end wall portion towards the spool axial direction second side at a terminal end portion facing of the end of the second groove adjacent to the first groove, a projection tab is formed to an external peripheral portion of the washer, the projection tab being insertable in the second groove and supported by the terminal end wall portion.

According to the webbing take-up device of the third aspect of the present invention, the first groove is formed in the through hole of the spool extending along the spool axial direction at a location further to the spool axial direction first side than the seating portion. The second groove is formed extending along the spool axial direction further to the spool axial direction second side than the first groove, partially out of alignment with the first groove in rotation about the spool axis and connected to the first groove. The seating portion is formed by the terminal end wall portion facing towards the spool axial direction second side at the terminal end portion of the end of the second groove adjacent to the first groove, and the projection tab is formed to the external peripheral portion of the washer insertable in the second groove and supported by the terminal end wall portion. The washer can be supported by the seating portion by supporting the projection tab of the webbing with the terminal end wall portion formed by the first groove and the second groove being partly out of alignment with each other in rotation about the spool axis, even while suppressing the internal diameter of the through hole at the spool axial direction second side location.

A webbing take-up device of a fourth aspect of the present invention is the webbing take-up device configured as the second or the third aspect, wherein a recess is formed at an end portion of the second torsion shaft on the side facing towards the first torsion shaft and the protrusion portion intrudes into the recess.

According to the webbing take-up device of the fourth aspect of the present invention, the recess is formed at the end portion of the second torsion shaft on the side facing towards the first torsion shaft and the protrusion portion of the first torsion shaft intrudes into the recess. The axial direction length of the second torsion shaft is accordingly suppressed in comparison to configurations not formed with the recess.

As explained above, according to the webbing take-up device of the first aspect of the present invention an excellent effect is exhibited of enabling suppression of the device from becoming bigger.

According to the webbing take-up device of the second aspect of the present invention an excellent effect is exhibited of enabling suppression of the device from becoming bigger even while there are two torsion shafts disposed in a straight line inside the spool.

According to the webbing take-up device of the third aspect of the present invention an excellent effect is exhibited of enabling suppression of the device from becoming bigger by suppressing the internal diameter of the through hole at the spool axial direction second side location while also suppressing the axial direction length of the first torsion shaft.

According to the webbing take-up device of the fourth aspect of the present invention an excellent effect is exhibited of enabling suppression of the device from becoming bigger by suppressing the axial direction length of the two torsion shafts.

DETAILED DESCRIPTION

First Exemplary Embodiment

FIG. 1is a cross-section of a webbing take-up device10according to a first exemplary embodiment of the present invention.FIG. 2is an exploded perspective view of relevant portions (a shaft assembly) of the webbing take-up device10. The arrow A direction in the drawings indicates an axial direction second side of a spool12serving as a cylinder shaped body in the webbing take-up device10, and the arrow B direction indicates an axial direction first side of the spool12.

As shown inFIG. 1andFIG. 2, the webbing take-up device10according to the first exemplary embodiment is provided with a spool12configuring a take-up shaft. The spool12is cast in a substantially circular cylindrical shape and is rotatably supported at portions at the two axial direction ends by a frame (not shown in the drawings) fixed to a vehicle.

As shown inFIG. 2, a webbing insertion slot15is formed opening in a long rectangular shape along the axial direction in the spool12. As shown inFIG. 3, an enlarged cross-section taken along line3-3inFIG. 1, the webbing insertion slot15is formed so as to pass through the spool12along a chord on the external peripheral side of the axial center of the spool12. As shown inFIG. 2, a long strip-shaped webbing belt14is inserted through the webbing insertion slot15in a state such that a portion at the proximal end of the webbing belt14is stopped from pulling out from the webbing insertion slot15. The webbing belt14is wound in layers from its proximal end onto the spool12. The webbing belt14is taken up onto the spool12by rotating the spool12in a take-up direction (the arrow C direction inFIG. 2). The spool12is rotated in a pullout direction (the arrow D direction inFIG. 2) by pulling the webbing belt14out from the spool12.

A through hole16is formed in the spool12as an assembly hole so as to pass through the axial center of the spool12. As shown inFIG. 1, seating portions22are formed at an axial direction intermediate portion of the through hole16so as to face towards the spool12axial direction second side (the right hand side inFIG. 1).

A first mounting hole section18is provided in the through hole16of the spool12at a location further towards the spool12axial direction first side (towards the left hand side inFIG. 1) than the seating portions22. As shown inFIG. 5, an enlarged cross-section taken on line3-3ofFIG. 1to illustrate only the spool12, plural individual first grooves18A (four in the present exemplary embodiment) are formed with substantially trapezoidal cross-sections at the outer peripheral side of the first mounting hole section18. The first grooves18A extend along the spool12axial direction (seeFIG. 1), and are disposed alongside each other at even intervals around the circumferential direction of the spool12. The first groove18A formed at the front side in the cross-section shown inFIG. 1is depicted with double-dashed intermittent lines (the same applies toFIG. 4).

As shown inFIG. 1, a second mounting hole section20is formed in the through hole16of the spool12further towards the spool12axial direction second side (the right hand side inFIG. 1) than the first mounting hole section18(the first grooves18A). As shown inFIG. 5, plural individual second grooves20A (four grooves in the present exemplary embodiment) are formed at the outer peripheral side of the second mounting hole section20. The second grooves20A extend along the spool12axial direction (seeFIG. 1) and are partly out of alignment in rotation about the spool axis with the first grooves18A and connected to the first grooves18A. The plural individual second grooves20A are disposed at even intervals around the spool12circumferential direction.

The seating portions22illustrated inFIG. 1are formed in the spool12as terminal end wall portions that face towards the spool12axial direction second side (the right hand side inFIG. 1) at the end portion on the side of the second grooves20A adjacent to the first grooves18A. In the cross-section shown inFIG. 1, the seating portions22are disposed at the boundary region between the first mounting hole section18and the second mounting hole section20. In the present exemplary embodiment, as shown inFIG. 5, the diameter at the troughs of the second grooves20A is set greater than the diameter at the troughs of the first grooves18A in order to set a larger surface area for the seating portions22.

As shown inFIG. 1, a main torsion shaft24and a sub torsion shaft30, serving as a first torsion shaft and a bar shaped body, respectively, configuring a force limiter mechanism are housed in (inside) the through hole16of the spool12. The main torsion shaft24and the sub torsion shaft30are disposed next to each other in a straight line along the spool12axial direction and fall within the broad definition of “energy absorbing members”. While most of the main torsion shaft24is housed in the through hole16of the spool12further to the spool12axial direction first side (the left hand side inFIG. 1) than the seating portions22, the sub torsion shaft30is housed therein further to the spool12axial direction second side (the right hand side inFIG. 1) than the seating portions22.

The length of the main torsion shaft24is set longer than the axial direction length of the sub torsion shaft30. A substantially circular pillar shaped main body portion26of the main torsion shaft24is disposed further to the spool12axial direction first side than the seating portions22. A retained portion26A is formed at the spool12axial direction second side of the main body portion26. The retained portion26A is formed in cross-section orthogonal to the axial direction with a similar shape to the inside peripheral shape of the first mounting hole section18, but with a slightly smaller profile to the inside peripheral shape of the first mounting hole section18(seeFIG. 2). A short circular pillar shaped protrusion portion28protrudes out from the main body portion26towards the spool12axial direction second side.

As shown inFIG. 4, a push nut36(an element within the broad definition of a “fastener”) is disposed to the spool12axial direction first side of the sub torsion shaft30. The push nut36is formed, for example, by pressing out from a resilient metal plate. As shown inFIG. 2andFIG. 4, the push nut36has a push hole36C formed through the center of a ring portion36A, with plural engagement claws36B formed around a peripheral region of the push hole36C. The engagement claws36B are disposed in a radiating shape when view face on with the free ends of the engagement claws36B facing towards the center of the push hole36C. The engagement claws36B project out at a specific angle away from a washer34.

As shown inFIG. 4, the push nut36is attached by fitting the protrusion portion28of the main torsion shaft24inside. Namely, the protrusion portion28of the main torsion shaft24is pushed into the push hole36C of the push nut36such that the engagement claws36B are in an engaged state with the protrusion portion28by pressing against the resilient force of the engagement claws36B.

The washer34is disposed sandwiched between the push nut36and the seating portions22. Namely the washer34is seated on the seating portions22and the face of the washer34on the side away from the seating portions22makes contact with the push nut36. The washer34is a high rigidity metal plate-shaped washer set with a higher rigidity to bending than that of the push nut36. In the present exemplary embodiment, the relationship between the plate thickness t1of the push nut36and the plate thickness t2of the washer34is t1<t2. The protrusion portion28of the main torsion shaft24is inserted into the washer34.

As shown inFIG. 3, projection tabs34A are formed to an external peripheral portion of the washer34so as to be insertable in the second grooves20A and be supported by the seating portions22(the terminal end wall portions). A straight-line cut-out is formed to a portion on the outer peripheral side of the washer34(a bottom portion inFIG. 2) in order to secure a passing portion at an axial direction intermediate portion in the spool12for insertion of the webbing belt14. The washer34is accordingly not symmetrically shaped about its center when viewed in profile along the axial direction.

As shown inFIG. 1, a lock gear38configuring a first lock mechanism50is attached to an axial direction intermediate portion of the main torsion shaft24on the spool12axial direction first side (the left hand side inFIG. 1). The portion of the main torsion shaft24for mounting the lock gear38is provided with crimp-on ribs to suppress play in the radial direction, with the lock gear38rendered incapable of rotation with respect to the main torsion shaft24. Ratchet teeth38A are formed to an external peripheral portion of the lock gear38. A lock plate (not shown in the drawings) configuring the first lock mechanism50is provided to a frame (not shown in the drawings) so as to correspond to the ratchet teeth38A. The lock plate is capable of moving relative to the ratchet teeth38A so as to make contact with or move away from the ratchet teeth38A. In an actuated state of the first lock mechanism50, initiated when a rapid vehicle deceleration state arises or there is abrupt rotation of the spool12in the pullout direction, the lock plate is configured so as to mesh with the ratchet teeth38A and restrict rotation of the ratchet teeth38A in the pullout direction.

As shown inFIG. 4, a retained portion32is provided as an end portion disposed on the main torsion shaft24side of the sub torsion shaft30. Engagement projections are formed at the outer peripheral side of the retained portion32of the sub torsion shaft30to engage with the inside of the spool12. The sub torsion shaft30is thereby retained at an axial direction intermediate portion of the spool12. An end portion (end face) on at the end of the retained portion32of the sub torsion shaft30facing the main torsion shaft24is formed with a recess32A into which the protrusion portion28of the main torsion shaft24intrudes. In other words configuration is made such that the retained portion32end of the sub torsion shaft30and a portion of the protrusion portion28of the main torsion shaft24overlap with each other in the axial direction.

While detailed explanation is omitted, a sleeve40is disposed so as to fit inside the spool12at the outer peripheral side of the leading end portion of the sub torsion shaft30(the end portion of the sub torsion shaft30away from the retained portion32), as shown inFIG. 1. The sleeve40also makes contact with a flange section42A of a screw42fastened into the leading end portion of the sub torsion shaft30.

A second lock mechanism52is provided at the spool12axial direction second side in the webbing take-up device10. A simple explanation regarding the second lock mechanism52is that plural clutch components configuring the second lock mechanism52are disposed at side of the spool12and on the outer peripheral side of the sleeve40. Namely a rotation body that rotates as a single unit with the sleeve40is fitted over the sleeve40, and a mechanism is provided that restricts rotation of the rotation body in the pullout direction by directly or indirectly engaging with the rotation body. In the present exemplary embodiment the configuration is made such that the second lock mechanism52is capable of operating coupled to the first lock mechanism50. Configuration is made, for example, such that a body frame detection section is provided to the webbing take-up device10for detecting information about the body frame of an occupant seated on a seat, such as their weight. The second lock mechanism52in then switched between an operable state and a non-operable state according to detection results of the body frame detection section.

Operation and Effect

Explanation follows regarding operation and effect of the exemplary embodiment described above.

Explanation follows first regarding the operation and effect of the webbing take-up device10as shown inFIG. 1from a functional perspective.

In the webbing take-up device10, when an acceleration sensor of the first lock mechanism50detects a rapid vehicle deceleration state, or when the spool12is abruptly rotated in the pullout direction by the body of an occupant abruptly pulling on the webbing belt14fitted over the body as the body of the occupant attempts to relatively move rapidly towards the vehicle front under inertia during rapid deceleration, first the lock plate (not shown in the drawings) meshes with the ratchet teeth38A of the lock gear38in the first lock mechanism50. A first lock state is thereby adopted in which rotation of the lock gear38in the pullout direction is restricted. By restricting rotation of the lock gear38in the pullout direction rotation of the main torsion shaft24in the pullout direction is also restricted.

The main torsion shaft24and the spool12are prevented from rotating relative to each other due to there being only an extremely small gap present between the similar non-circular shaped profiles of the external peripheral profile of the retained portion26A of the main torsion shaft24and the inner peripheral profile of the first mounting hole section18of the through hole16. Consequently, by restricting rotation of the main torsion shaft24in the pullout direction as described above, the rotation of the spool12in the pullout direction is also restricted. The main torsion shaft24undertakes twisting deformation when a rotational force is imparted to the spool12in this state of a magnitude that exceeds the rigidity to twisting of the main torsion shaft24, resulting in corresponding rotation of the spool12being permitted and energy being absorbed.

In the present exemplary embodiment, the push nut36and the washer34are disposed on the spool12axial direction first side of the sub torsion shaft30. The push nut36is attached with the protrusion portion28of the main torsion shaft24fitted inside. The washer34is seated on the seating portions22with the face of the washer34on the side away from the seating portions22in contact with the push nut36. The rigidity to bending of the washer34is set higher than that of the push nut36, and the protrusion portion28of the main torsion shaft24is inserted into the washer34. Accordingly, even though a load acts on the main torsion shaft24in a direction pulling towards the spool12axial direction first side, this load is supported by the seating portions22of the spool12through the washer34, suppressing the main torsion shaft24from falling out (thrust direction fixing). Due to the rigidity to bending of the washer34being greater than that of the push nut36, even though bending load from the main torsion shaft24side is input to the push nut36, bending deformation of the push nut36is prevented or effectively suppressed by the support from the washer34.

Accordingly, the axial direction length of the main torsion shaft24is suppressed by retaining the protrusion portion28of the main torsion shaft24with the push nut36and the washer34. Enabling a simple shape to be adopted for the fixing section of the main torsion shaft24of the spool12, a shape not requiring complicated processing to be performed, also enables a reduction in cost to be achieved.

If, for example, the washer34is made to slightly warp when the protrusion portion28of the main torsion shaft24is fitted into the push nut36by pressing the washer34through the push nut36with a jig, then the restoring force of the washer34acts on the main torsion shaft24in a pulling direction (namely a force towards the spool12axial direction second side (the arrow A direction). The lock gear38attached to the main torsion shaft24is accordingly pressed against the spool12side, suppressing movement between the lock gear38and the spool12and suppressing unwanted noise generation.

Provision of the washer34having a higher rigidity to bending than the push nut36enables the rigidity of the push nut36itself to be suppressed. In turn, suppression of rigidity of the push nut36achieves good assembly characteristics by suppressing the load input requirement when fitting the push nut36over the protrusion portion28of the main torsion shaft24.

When the second lock mechanism52is actuated with the first lock mechanism50is in an actuated state, a second lock state is achieved. The second lock state restricts rotation of the sub torsion shaft30in the pullout direction and restricts rotation of the spool12in the pullout direction. In this state the main torsion shaft24and the sub torsion shaft30both deform by twisting when a rotation force exceeding the sum of the twisting rigidities of both the main torsion shaft24and the sub torsion shaft30is imparted to the spool12in the pullout direction. Corresponding rotation of the spool12is thereby permitted and energy is absorbed.

The second lock mechanism52is configured coupled to the first lock mechanism50. Further, for example, the second lock mechanism52can be configured switched between an operable state and an non-operable state according to detection results of a body frame detector section provided to the webbing take-up device10to detect body frame data such as the body weight of an occupant seated in a seat. Rotation of the spool12is permitted when the second lock mechanism52in the operable state by imparting a rotation force in the pullout direction of a greater magnitude to the sum of the rigidity to twisting of both the main torsion shaft24and the sub torsion shaft30. However, rotation of the spool12is permitted when the second lock mechanism52in the non-operational state by imparting a rotation force in the pullout direction of a greater magnitude to the rigidity to twisting of the main torsion shaft24. Namely, the amount of the energy capable of absorption can be varied.

In the present exemplary embodiment, the recess32A for the protrusion portion28of the sub torsion shaft30intrude into is formed in an end portion of the sub torsion shaft30facing the main torsion shaft24. The axial direction length of the sub torsion shaft30is accordingly suppressed in comparison to configurations not formed with the recess32A.

A brief explanation follows next regarding an assembly method of the webbing take-up device10(an assembly method of the main torsion shaft24and the sub torsion shaft30).

In order to assemble the main torsion shaft24, the main torsion shaft24is inserted from the spool12axial direction first side into the through hole16, and the retained portion26A of the main torsion shaft24is inserted into the first mounting hole section18of the through hole16, stopping rotation of the main torsion shaft24. The washer34and the push nut36are inserted into the through hole16from the spool12axial direction second side, and assembly is achieved in which the main torsion shaft24is prevented from falling out by inserting the protrusion portion28of the main torsion shaft24into the washer34and the push nut36(fitting into the push nut36). The sub torsion shaft30is then inserted into the through hole16from the spool12axial direction second side and assembled to the spool12. During assembly the main torsion shaft24, the washer34, the push nut36and the sub torsion shaft30are accordingly inserted into the through hole16of the spool12from their respective directions, and assemble operation is facilitated because there directions are each along the spool12axial direction.

In the present exemplary embodiment, the first grooves18A are formed in the through hole16of the spool12so as to extend along the axial direction of the spool12at locations further to the spool12axial direction first side than the seating portions22. The second grooves20A are formed extending along the spool12axial direction further to the spool12axial direction second side than the first grooves18A, partly out of alignment in rotation about the spool axis to the first grooves18A and connected to the first grooves18A. The seating portions22are formed at terminal end portions in the second grooves20A extension direction as terminal end wall portions facing towards the spool12axial direction second side. As shown inFIG. 3, the projection tabs34A are formed to an external peripheral portion of the washer34so as to be insertable in the second grooves20A and be supported by the seating portions22(the terminal end wall portions). The washer34can be supported by the seating portions22by supporting the projection tabs34A of the washer34with the seating portions22formed by the first grooves18A and the second grooves20A being partly out of alignment with each other in rotation about the spool axis, even while suppressing the internal diameter of the through hole16at the spool12axial direction second side location. Good assembly operation characteristics are achieved since the washer34can be seated on the seating portions22by simply sliding the projection tabs34A of the washer34along the second grooves20A.

As explained above, in the present exemplary embodiment, the total length of the webbing take-up device10is suppressed even though there are two torsion shafts (the main torsion shaft24and the sub torsion shaft30) disposed in a straight line inside the spool12shown inFIG. 1, enabling the device to be suppressed from becoming bigger.

Second Exemplary Embodiment

Explanation follows regarding a webbing take-up device60according to a second exemplary embodiment of the present invention, with reference toFIG. 6andFIG. 7AandFIG. 7B.FIG. 6illustrates a cross-section of the webbing take-up device60according to the second exemplary embodiment of the present invention.FIG. 7AandFIG. 7Bare cross-sections showing states when fitting the push nut36. As shown inFIG. 6, the webbing take-up device60differs from the webbing take-up device10of the first exemplary embodiment (seeFIG. 1) in not being disposed with a sub torsion shaft30(seeFIG. 1) and in the position where a torsion shaft62, serving as a bar shaped body, is retained in the spool12. Other parts of the configuration are substantially the same as those of the first exemplary embodiment. Parts of the configuration essentially the same as those of the first exemplary embodiment are hence allocated the same reference numerals and further explanation is omitted.

As shown inFIG. 6, a seating portion64is configured in the through hole16of the spool12at an end portion on the spool12axial direction second side (the right hand side inFIG. 6), with the seating portion64facing towards the spool12axial direction second side. A torsion shaft62(an element in the broad definition of an “energy absorbing member”) configuring a force limiter mechanism is housed in (inside) the through hole16of the spool12so as to be disposed along the spool12axial direction. A short cylinder shaped protrusion portion66protrudes out from an end portion of the torsion shaft62on the spool12axial direction second side (the right hand side inFIG. 6) towards the spool12axial direction second side.

The push nut36is disposed at an end portion on the spool12axial direction second side (the right hand side inFIG. 6). The push nut36is attached by inserting the protrusion portion66of the torsion shaft62into the push nut36. A washer34is disposed so as to be sandwiched between the push nut36and a seating portion64. Namely the washer34is seated against the seating portion64with the face of the washer34on the side away from the seating portion64in contact with the push nut36.

Operation and Effect

Explanation follows regarding assembly of the torsion shaft62and operation and effect in the second exemplary embodiment.

As shown inFIG. 7A, during assembling the torsion shaft62the push nut36is fitted over the protrusion portion66of the torsion shaft62. During assembly, as shown inFIG. 7B, the washer34is pressed by a jig70through the push nut36, so as to slightly warp the washer34. The torsion shaft62is assembled in this state at the spool12axial direction second side.

When the torsion shaft62has been assembled at the spool12axial direction second side, pulling force due to the restoring force of the washer34(namely a force towards the spool12side (in the arrow A direction)) acts on the torsion shaft62as shown inFIG. 6. The lock gear38attached to the torsion shaft62is accordingly pressed against the side of the spool12, thereby suppressing movement between the lock gear38and the spool12and suppressing unwanted noise generation.

By provision of the washer34having a higher rigidity to bending than that of the push nut36the rigidity of the push nut36itself is suppressed. Suppressing the rigidity of the push nut36achieves good assembly characteristics by suppressing the load required when fitting the push nut36over the protrusion portion66of the torsion shaft62, as shown inFIG. 7A.

According to the webbing take-up device60of the second exemplary embodiment as explained above (seeFIG. 6), due to making the structure for retaining the torsion shaft62at the spool12axial direction second side more compact the device can be suppressed from becoming bigger.

In the above first exemplary embodiment, a preferable configuration from the perspective of suppressing the internal diameter of the through hole16in locations at the spool12axial direction second side is with: the seating portions22shown in drawings such asFIG. 4configured by terminal end wall portions at the terminal end portion of the second grooves20A adjacent to the first grooves18A facing towards the spool12axial direction second side; and with the projection tabs34A formed to the external peripheral portion of the washer34insertable into the second grooves20A and supported by the seating portions22(the terminal end wall portions). However, configuration may be made, for example, with the seating portion formed by forming a through hole in the spool with a step portion formed by setting the hole diameter at an axial direction second side larger than the hole diameter at an axial direction first side, such that a ring portion of a washer is supported by such a seating portion (the step portion).

In the first exemplary embodiment a preferable configuration, from the perspective of suppressing the axial direction length of the sub torsion shaft30, is with the recess32A for the protrusion portion28of the sub torsion shaft30to intrude into formed at the end portion of the sub torsion shaft30facing the main torsion shaft24. However, configuration may be made without a recess32A formed to the second torsion shaft (the sub torsion shaft30).

In the above first exemplary embodiment, the first torsion shaft is configured by the main torsion shaft24and the second torsion shaft is configured by the sub torsion shaft30, however the first torsion shaft may be configured as a main torsion shaft and the second torsion shaft configured as a sub torsion shaft.

In the above exemplary embodiments the cylinder shaped body is configured by the spool12, and the bar shaped body is configured by the main torsion shaft24or the torsion shaft62. However, configuration may be made with the cylinder shaped body configured by another component configuring a portion of the webbing take-up device other than the spool12. The bar shaped body may also be configured by another component configuring a portion of the webbing take-up device housed on the inside of the cylinder shaped body other than a torsion shaft (the main torsion shaft24or the torsion shaft62).