seat belt retractor

Abstract

To provide a retractor for a seat belt capable of making a rotation amount of a driving wheel one cycle or more and of shortening length of a pressure container.SOLUTION: In a pretensioner 2 of a retractor for seat belt according to one embodiment, a storage chamber 4 housing a drive wheel 5 forms an evacuation space 42 for a moving member 7. The moving member 7 is housed in a bag member 8 inside a pressure container 6. The moving member 7 has length that can pressurize two or more engagement teeth 51 of the driving wheel 5 in a winding-up direction of a webbing. The bag member 8 has: a cylindrical part 82 encircling the moving member 7; an end part 81 spreading outward in a radial direction from one end of the cylindrical part 82; and a bottom part 83 connected to the other end of the cylindrical part 82. In emergency, the bottom part 83 of the bag member 8 is pressurized by gas generated by a gas generator 9, and the cylindrical part 82 rotates in order from one end while the bottom part 83 and the cylindrical part 82 move together with the moving member 7.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a seat belt retractor that is mounted on a vehicle and that pulls out and retracts a webbing that serves as a seat belt. [Background technology]

[0002] Seat belt retractors that prevent the webbing from being pulled out in an emergency such as a vehicle collision have been known for some time. Some seat belt retractors are equipped with a pretensioner that removes slack from the webbing in an emergency.

[0003] There are various types of pretensioners, but in recent years, a pretensioner using a rod-shaped moving member and a drive wheel driven by the moving member has been proposed. For example, Patent Document 1 discloses a seat belt retractor 100 as shown in Figure 10.

[0004] Specifically, the seat belt retractor 100 includes an unillustrated winding drum (referred to as a "spool" in Patent Document 1) that can rotate in the winding and unwinding directions of the webbing, and a pretensioner 110 that rotates the winding drum in the winding direction in the event of a vehicle emergency.

[0005] The pretensioner 110 includes a drive wheel (referred to as a "ring gear" in Patent Document 1) 130 that rotates together with the winding drum, a storage chamber 120 that stores the drive wheel 130, a cylindrical pressure vessel 140 that has an end that opens at a position adjacent to the drive wheel 130 and a base end that is provided with a gas generator (not shown), and a rod-shaped movable member 150 that is normally stored within the pressure vessel 140.

[0006] The drive wheel 130 has a plurality of engagement teeth 131 arranged in the circumferential direction and pointing outward in the radial direction. The moving member 150 engages with the engagement teeth 131 while being pushed out of the pressure vessel 140 by the gas generated by the gas generator in an emergency, causing the drive wheel 130 to rotate in the webbing winding direction.

[0007] The storage chamber 120 has a guide surface 121 that guides the moving member 150 that is pushed out from the pressure vessel 140. The storage chamber 120 also forms a retraction space 122 for the moving member 150 on the side of the pressure vessel 140. In the retraction space 122, a portion of the moving member 150 that has been disengaged from the drive wheel 130 is disposed.

[0008] Furthermore, Patent Document 2 discloses a seatbelt retractor 200 including a pretensioner 210 in which a spherical moving member 240 is employed instead of a rod-shaped moving member, as shown in Fig. 11. Specifically, in this seatbelt retractor 200, a circular storage chamber 221 is provided in a housing 220, and a drive wheel 230 (referred to as a "sleeve" in Patent Document 2) is stored in the storage chamber 221. Further, the housing 220 is provided with a storage hole 222 that stores the moving member 240. In addition to the moving member 240, a folded bag member 250 and a gas generator 260 are stored in the storage hole 222.

[0009] When the gas generator 260 generates gas in an emergency, the bag member 250 expands and pushes the moving member 240 out of the storage hole 222, and the moving member 240 engages with one of the engagement teeth of the drive wheel 230 and presses against the engagement tooth, and the bag member 250 also presses against the engagement tooth of the drive wheel 230, causing the drive wheel 230 to rotate in the direction of winding up the webbing. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 2019-214258 [Patent Document 2] Japanese Patent Application Publication No. 11-255073 Summary of the Invention [Problem to be solved by the invention]

[0011] In the seatbelt retractor 100 shown in Fig. 10, the length of the moving member 150 increases in accordance with the amount of rotation of the drive wheel 130. Therefore, the length of the pressure vessel 140 also increases. In contrast, in the seatbelt retractor 200 shown in Fig. 11, a spherical moving member 240 is used, and therefore the length of the storage hole 222 is short.

[0012] However, in the seat belt retractor 200 shown in Fig. 11, since the storage chamber 221 is circular, the drive wheel 230 can only rotate up to an angle obtained by subtracting one pitch of the engagement teeth from 360 degrees. In order to increase the rotation amount of the drive wheel 230, it is conceivable to form the shape of the storage chamber 221 into an oval shape that bulges upward in Fig. 11, for example, to form a retraction space for the moving member 240 above the drive wheel 230, as in the seat belt retractor 100 shown in Fig. 10, and to configure the moving member 240 by a plurality of balls. In this case, since the length of the moving member 240 becomes long, it is preferable to employ a pressure vessel instead of the storage hole 222 and store the plurality of balls that configure the moving member 240 in the pressure vessel.

[0013] However, when the seatbelt retractor 200 is modified as described above, not only the moving member 240 (plurality of balls) but also the bag member 250 is stored in the pressure vessel. Although the bag member 250 is stored in a folded state in the pressure vessel, the length of the bag member 250 in an unfolded state needs to be approximately the same as the stroke of the moving member 240, and the length of the bag member 250 in the folded state also becomes somewhat long. Therefore, the pressure vessel becomes longer by that amount.

[0014] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a seat belt retractor in which the amount of rotation of the drive wheels can be increased to nearly one revolution or more, and the length of the pressure vessel can be shortened. [Means for solving the problem]

[0015] In order to solve the above-mentioned problems, the present invention provides a vehicle having a take-up drum that is rotatable in a webbing take-up direction and an unwinding direction, and that takes up a webbing; and a pretensioner that rotates the take-up drum in the take-up direction in the event of a vehicle emergency, wherein the pretensioner includes: a drive wheel that rotates together with the take-up drum at least in an emergency and has a plurality of engagement teeth that are arranged in the circumferential direction and that are pointed radially outward; a cylindrical pressure vessel that has an end portion that opens at a position adjacent to the drive wheel and a base end portion that is provided with a gas generator; a moving member that is normally housed in the pressure vessel and, in an emergency, is pushed out of the pressure vessel by gas generated by the gas generator while engaging with at least one of the plurality of engagement teeth, thereby rotating the drive wheel in the webbing take-up direction; and a storage chamber having a guide surface that guides the moving member pushed out from the pressure vessel and that forms an evacuation space for the moving member; a cylindrical portion that stores the moving member within the pressure vessel and surrounds the moving member; a tip portion that extends radially outward from one end of the cylindrical portion and is fixed to the end portion of the pressure vessel; and a bag member connected to the other end of the cylindrical portion and having a bottom portion that can come into contact with the moving member, wherein the moving member has a length that enables it to press two or more of the plurality of engaging teeth in the retracting direction of the webbing, and in an emergency, the bottom portion of the bag member is pressed by gas generated by the gas generator, causing the bottom portion and the cylindrical portion to move together with the moving member, while the cylindrical portion is reversed in place from the one end.

[0016] According to the above configuration, the movable member has a length sufficient to press two or more of the engagement teeth, and the storage chamber that stores the drive wheel forms a retraction space for the movable member, so the amount of rotation of the drive wheel can be made nearly one revolution or more. Furthermore, the bag member that stores the movable member inside the pressure vessel includes a tubular portion and a bottom portion, and the movable member is pushed out of the pressure vessel while the tubular portion of the bag member is inverted, so the length of the pressure vessel can be made shorter than when a folded bag member is stored inside the pressure vessel. Moreover, because the length of the tubular portion is approximately half the stroke of the movable member, the length of the bag member can be made shorter.

[0017] The bag member includes an initial inner layer that forms an inner surface in a normal state and an initial outer layer that forms an outer surface in a normal state, and the initial inner layer and the initial outer layer may be made of different materials. With this configuration, the initial inner layer and the initial outer layer can be given different properties that are suited to them.

[0018] The initial inner layer may have a strength greater than that of the initial outer layer. When the tubular portion is inverted, the initial inner layer becomes the outer side and comes into contact with the engaging teeth of the drive wheel. Therefore, if the strength of the initial inner layer is greater than that of the initial outer layer, damage to the bag member by the drive wheel can be prevented.

[0019] The initial outer layer may have a higher heat resistance than the initial inner layer. The initial outer layer comes into contact with gas when the gas generator generates the gas. Therefore, if the heat resistance of the initial outer layer is higher than that of the initial inner layer, the output of the gas generator can be set higher. This allows the webbing retraction force of the pretensioner to be increased.

[0020] The initial outer layer may have higher slidability than the initial inner layer. When the gas generator generates gas, the initial outer layer slides against the inner circumferential surface of the pressure vessel. Therefore, if the slidability of the initial outer layer is higher than that of the initial inner layer, it is possible to reduce the frictional resistance between the inner circumferential surface of the pressure vessel and the tubular portion of the bag member.

[0021] A gap may be provided between the inner circumferential surface of the pressure vessel and the tubular portion of the bag member. According to this configuration, the gas generated by the gas generator can be guided to the tip end of the bag member or the inverted portion of the tubular portion through the gap between the inner circumferential surface of the pressure vessel and the bag member. Therefore, the bottom of the bag member can be not only pressed by the gas generated by the gas generator, but also pulled up by utilizing the pressure applied to the tip end of the bag member or the inverted portion of the tubular portion.

[0022] The seat belt retractor may further include a protective member that covers the bottom of the bag member on the side opposite to the moving member. With this configuration, the gas generated by the gas generator does not directly hit the bottom of the bag member, so the heat resistance required for the bag member is reduced. Therefore, the thickness and cost of the bag member can be reduced.

[0023] The movable member may be rod-shaped and have a first protrusion that engages with at least one of the plurality of engagement teeth and a second protrusion that engages with at least one of the plurality of engagement teeth, and a recess that is formed between the first protrusion and the second protrusion to avoid interference with some of the plurality of engagement teeth. With this configuration, the cylindrical portion can be more easily reversed than when the movable member is rod-shaped and has a constant thickness along its entire length. [Effects of the Invention]

[0024] According to the present invention, the amount of rotation of the drive wheel can be increased to nearly one revolution or more, and the length of the pressure vessel can be shortened. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a perspective view of a seat belt retractor according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view of the pretensioner according to the first embodiment. [Figure 3] FIG. 2 is an enlarged view of the main parts of the pressure vessel, the bag member, and the moving member. [Figure 4] FIG. [Figure 5] 5(a) to 5(c) are diagrams illustrating the operation of a pretensioner. [Figure 6] 5(a) is a cross-sectional view taken along line VIA-VIA in FIG. 5(b), and FIG. 5(b) is a cross-sectional view taken along line VIB-VIB in FIG. 5(c). [Figure 7] FIG. 10 is a cross-sectional view of a pretensioner according to a second embodiment. [Figure 8] 5(a) to 5(c) are diagrams illustrating the operation of a pretensioner. [Figure 9] FIG. 10 is a cross-sectional view of a pretensioner according to another embodiment. [Figure 10] FIG. 1 is a cross-sectional view of a pretensioner of a conventional seatbelt retractor. [Figure 11] FIG. 10 is a cross-sectional view of a pretensioner of another conventional seatbelt retractor. DETAILED DESCRIPTION OF THE INVENTION

[0026] (First embodiment) 1 shows a seatbelt retractor 1 according to a first embodiment of the present invention. The seatbelt retractor 1 includes a housing 11, a take-up drum 12, and a pretensioner 2.

[0027] The housing 11 is made of sheet metal and includes a pair of side walls facing each other. Each of these side walls has an opening through which the take-up drum 12 is inserted. The take-up drum 12 takes up the webbing 10 and is rotatable in the take-up direction and the unwinding direction of the webbing 10.

[0028] The pretensioner 2 rotates the take-up drum 12 in the take-up direction in the event of a vehicle emergency. As shown in Figures 1 and 2, the pretensioner 2 includes a drive wheel 5, a moving member 7 that drives the drive wheel 5 in an emergency, a cylindrical pressure vessel 6 that normally houses the moving member 7, and a cover 3 that covers the drive wheel 5 and a portion of the pressure vessel 6.

[0029] The drive wheel 5 rotates together with the spool 12 at least in an emergency. The drive wheel 5 may be connected to the spool 12 and always rotate together with the spool 12. Alternatively, a clutch may be provided between the drive wheel 5 and the spool 12 so that the drive wheel 5 rotates together with the spool 12 in the webbing winding direction only in an emergency. When a clutch is provided, for example, when the drive wheel 5 is rotated by the moving member 7 in the webbing winding direction and rotates relative to the spool 12 by a predetermined angle, the clutch couples the drive wheel 5 and the spool 12 so that they can rotate integrally.

[0030] As shown in Fig. 4, the drive wheel 5 has a plurality of (11 teeth in this embodiment) engagement teeth 51 arranged in the circumferential direction and pointed outward in the radial direction. Each engagement tooth 51 has a gear tooth shape with the width direction along the direction of the rotation axis of the drive wheel 5. In this embodiment, a recess 53 recessed inward in the radial direction of the drive wheel 5 is formed in the center of the tip 52 of each engagement tooth 51. However, the shape of the tip 52 of each engagement tooth 51 can be changed as appropriate.

[0031] In this embodiment, the moving member 7 is rod-shaped with a constant thickness on a plane perpendicular to the axial direction of the drive wheel 5. In this embodiment, the cross-sectional shape of the moving member 7 is circular, as shown in Fig. 6(a). However, the cross-sectional shape of the moving member 7 may be another shape.

[0032] 2, in this embodiment, under normal circumstances, the entire moving member 7 is housed within the pressure vessel 6. However, it is also possible for most of the moving member 7 to be housed within the pressure vessel 6, with the remainder protruding from the pressure vessel 6. The moving member 7 is housed in a bag member 8 within the pressure vessel 6.

[0033] The pressure vessel 6 has a distal end 61 that opens at a position adjacent to the drive wheel 5, and a proximal end 62 in which the gas generator 9 is provided. In this embodiment, the gas generator 9 is inserted into the proximal end 62. As shown in FIG. 3 , the bag member 8 has a distal end 81, a cylindrical portion 82, and a bottom portion 83. The bag member 8 has sufficient airtightness so that when the gas generator 9 generates gas, the gas pressure presses and moves the moving member 7, causing the drive wheel 5 to rotate.

[0034] In this embodiment, the cylindrical portion 82 has a length similar to that of the moving member 7 and surrounds the moving member 7. The tip portion 81 extends radially outward from one end (the lower end in FIG. 3 ) of the cylindrical portion 82 and is fixed to the terminal end 61 of the pressure vessel 6 in an airtight manner. In this embodiment, the tip portion 81 is folded back so as to enclose the terminal end 61 of the pressure vessel 6. However, the tip portion 81 does not necessarily have to be folded back, and may be flat in a direction perpendicular to the axial direction of the pressure vessel 6.

[0035] In this embodiment, the entire bag member 8 has a two-layer structure having an initial inner layer 8a and an initial outer layer 8b. The initial inner layer 8a forms the inner surface in normal conditions, and the initial outer layer 8b forms the outer surface in normal conditions. However, at least one of the tip portion 81, the tubular portion 82, and the bottom portion 83 may have a single-layer structure. Alternatively, at least one of the tip portion 81, the tubular portion 82, and the bottom portion 83 may have a three-layer structure having an intermediate layer between the initial inner layer 8a and the initial outer layer 8b.

[0036] It is desirable that the initial inner layer 8a and the initial outer layer 8b are made of different materials. For example, the initial inner layer 8a may be stronger than the initial outer layer 8b. To achieve this, for example, the initial inner layer 8a may be a mesh made of metal wire or aramid fiber thread, and the initial outer layer 8b may be a woven or nonwoven fabric made of a resin such as nylon, polyester, or polyamide.

[0037] Alternatively, the initial inner layer 8a may be a woven or nonwoven fabric made of resin such as nylon, polyester, or polyamide, and the initial outer layer 8b may be a coating layer made of synthetic rubber or silicone resin.

[0038] The initial outer layer 8b may have higher heat resistance than the initial inner layer 8a. To achieve this, for example, the initial inner layer 8a may be made of a woven or nonwoven fabric made of a resin such as polyester, and the initial outer layer 8b may be a coating layer made of a silicone resin.

[0039] The initial outer layer 8b may have higher sliding properties than the initial inner layer 8a. To achieve this, for example, the initial outer layer 8b may be made of a woven or nonwoven fabric made of a resin such as polyester, and the initial inner layer 8a may be made of a mesh made of metal wires.

[0040] In this embodiment, the outer diameter of the cylindrical portion 82 is set smaller than the inner diameter of the pressure vessel 6, thereby providing a gap 65 between the inner circumferential surface of the pressure vessel 6 and the cylindrical portion 82 of the bag member 8. However, the outer diameter of the cylindrical portion 82 may be set equal to the inner diameter of the pressure vessel 6, thereby omitting the gap 65. Alternatively, a plurality of grooves extending in the axial direction may be provided on the circumferential surface of the moving member 7, and the cylindrical portion 82 may be partially fitted into these grooves, thereby providing the gap 65 between the inner circumferential surface of the pressure vessel 6 and the cylindrical portion 82 of the bag member 8.

[0041] The bottom 83 is connected to the other end (the upper end in FIG. 3 ) of the tubular portion 82 and can abut against the moving member 7. In this embodiment, the moving member 7 is fixed to the bottom 83 of the bag member 8 with an adhesive or the like. However, the bottom 83 may be spaced apart from the moving member 7, in which case the moving member 7 may be at least partially in contact with the initial inner layer 8a of the bag member 8, and the moving member 7 may be held within the bag member 8 by friction between the moving member 7 and the initial inner layer 8a of the bag member 8.

[0042] In an emergency, the moving member 7 engages with at least one of the engagement teeth 51 of the drive wheel 5 while being pushed out of the pressure vessel 6 by the gas generated by the gas generator 9, causing the drive wheel 5 to rotate in the direction of retracting the webbing 10. The moving member 7 has a length that enables it to press two or more of the engagement teeth 51 in the direction of retracting the webbing 10. In this embodiment, the length of the moving member 7 corresponds to approximately 6.7 pitches of the engagement teeth 51 on the tip circle of the drive wheel 5.

[0043] A substantially U-shaped guide member 31 is disposed within the cover 3 along the inner surface of the cover 3. The cover 3 and the guide member 31 form a storage chamber 4 for storing the drive wheels 5.

[0044] The storage chamber 4 has a semicircular guide surface 41 that guides the moving member 7 being pushed out of the pressure vessel 6. The storage chamber 4 also forms a retraction space 42 for the moving member 7 on the side of the pressure vessel 6. More specifically, the storage chamber 4 has a wall surface 43 that is continuous with the guide surface 41 and is parallel to the axial direction of the pressure vessel 6, and the retraction space 42 is formed between this wall surface 43 and the pressure vessel 6.

[0045] The minimum distance between the guide surface 41 and the tip circle of the drive wheel 5 is greater than the thickness of the movable member 7. In this embodiment, the movable member 7 is made of a material softer than the engaging teeth 51, and when it engages with at least one of the engaging teeth 51, it is plastically deformed by the engagement of the engaging teeth 51, as shown in FIGS. 5(a) and 5(b) and FIG. 6(a). For example, the movable member 7 is made of a material such as nylon or polyacetal. As shown in FIG. 6(a), in this embodiment, a recess 53 is formed in the center of the tip 52 of each engaging tooth 51, which makes it easier to uniform the amount of engagement of the engaging teeth 51 into the movable member 7 across the width of the engaging teeth, thereby making it easier for the engaging teeth 51 to bite into the movable member 7.

[0046] In an emergency, when the gas generator 9 generates gas, the gas presses against the bottom of the bag member 8, causing the bottom 83 and the tubular portion 82 to move together with the moving member 7, while the tubular portion 82 is inverted sequentially from one end, as shown in Figures 5(a) and (b). In this embodiment, as shown in Figure 6(b), a recess 53 is formed in the center of the tooth tip 52 of each engaging tooth 51, which makes it easy to make uniform the contact between the bag member 8 and the tooth tip 52. This prevents the bag member 8 from coming into partial strong contact with the tooth tip 52 due to the pressure of the gas, preventing damage to the bag member 8.

[0047] In the present embodiment, a gap 65 is provided between the inner peripheral surface of the pressure vessel 6 and the tubular portion 82 of the bag member 8, and therefore the gas generated by the gas generator 9 can be guided to the tip portion 81 of the bag member 8 or the inverted portion of the tubular portion 82 through the gap 65. Therefore, the bottom portion 83 of the bag member 8 can not only be pressed by the gas generated by the gas generator 9, but can also be pulled up by utilizing the pressure applied to the tip portion 81 of the bag member 8 or the inverted portion of the tubular portion 82.

[0048] The moving member 7 moves until the inversion of the cylindrical portion 82 of the bag member 8 reaches the other end and the bag member 8 is completely turned over, causing the drive wheel 5 to make approximately 1.1 rotations (12 teeth of the engaging teeth 51). At this time, as shown in FIG. 5(c), the part of the moving member 7 that has been disengaged from the drive wheel 5 is located in the retraction space 42.

[0049] As described above, in the seat belt retractor 1 of this embodiment, the moving member 7 has a length that enables it to press two or more of the engagement teeth 51, and the storage chamber 4 that stores the drive wheel 5 forms the retraction space 42 for the moving member 7, so the amount of rotation of the drive wheel 5 can be made nearly one revolution or more. Furthermore, the bag member 8 that stores the moving member 7 in the pressure vessel 6 includes a tubular portion 82 and a bottom portion 83, and the moving member 7 is pushed out of the pressure vessel 6 while the tubular portion 82 of the bag member 8 is inverted, so the length of the pressure vessel 6 can be made shorter than when a folded bag member is stored in the pressure vessel 6. Moreover, because the length of the tubular portion 82 is about half the stroke of the moving member 7, the length of the bag member 8 can be made shorter.

[0050] In addition, in this embodiment, since the initial inner layer 8a and the initial outer layer 8b of the tubular portion 82 and the bottom portion 83 of the bag member 8 are made of different materials, the initial inner layer 8a and the initial outer layer 8b can be given different properties that are suitable for them.

[0051] When the cylindrical portion 82 is inverted, the initial inner layer 8a becomes the outer side and comes into contact with the engaging teeth 51 of the drive wheel 5. Therefore, if the strength of the initial inner layer 8a is greater than the strength of the initial outer layer 8b, damage to the bag member 8 by the drive wheel 5 can be prevented.

[0052] The initial outer layer 8b comes into contact with the gas generated by the gas generator 9. Therefore, if the heat resistance of the initial outer layer 8b is higher than that of the initial inner layer 8a, the output of the gas generator 9 can be set higher, thereby increasing the webbing retraction force of the pretensioner 2.

[0053] When the gas generator 9 generates gas, the initial outer layer 8b slides against the inner circumferential surface of the pressure vessel 6. Therefore, if the slidability of the initial outer layer 8b is higher than that of the initial inner layer 8a, the frictional resistance between the inner circumferential surface of the pressure vessel 6 and the tubular portion 82 of the bag member 8 can be reduced.

[0054] (Second embodiment) 7 shows a pretensioner 2A for a seatbelt retractor according to a second embodiment of the present invention. In this embodiment, the same components as those in the first embodiment are given the same reference numerals, and redundant explanations will be omitted.

[0055] This embodiment employs a rod-shaped moving member 7A that is slightly different in shape from that of the first embodiment. This moving member 7A has a first protrusion 71 that engages with at least one of the engagement teeth 51 of the drive wheel 5, and a second protrusion 72 that engages with at least another of the engagement teeth 51. A recess 73 is formed between the first protrusion 71 and the second protrusion 72 to avoid interference with some of the engagement teeth 51, as shown in FIGS. 8(a) to (c).

[0056] In this embodiment, the length of the first protrusion 71 in the axial direction of the moving member 7A is set to be smaller than the distance between the tooth tips 52 of adjacent engagement teeth 51, and the first protrusion 71 engages with only one engagement tooth 51. However, the length of the first protrusion 71 in the axial direction of the moving member 7A may be set to be larger than the distance between the tooth tips 52 of adjacent engagement teeth 51, and the first protrusion 71 may engage with two engagement teeth 51. In this case, similar to the first embodiment, when the first protrusion 71 engages with the second engagement tooth 51, the engagement tooth 51 bites into it and causes plastic deformation.

[0057] Similarly, in this embodiment, the length of the second protrusion 72 in the axial direction of the moving member 7A is set to be smaller than the distance between the tooth tips 52 of adjacent engagement teeth 51, and the second protrusion 72 engages with only one engagement tooth 51. However, the length of the second protrusion 72 in the axial direction of the moving member 7A may be set to be larger than the distance between the tooth tips 52 of adjacent engagement teeth 51, and the second protrusion 72 may engage with two engagement teeth 51. In this case, similar to the first embodiment, when the second protrusion 72 engages with the second engagement tooth 51, it is plastically deformed by biting into that engagement tooth 51.

[0058] In this embodiment, the distance between the first protrusion 71 and the second protrusion 72, in other words the length of the recess 73, corresponds to approximately five pitches of the engaging teeth 51 on the tip circle of the drive wheel 5.

[0059] If the moving member 7 is rod-shaped with a constant thickness along its entire length as in the first embodiment, the already-inverted and uninverted portions of the cylindrical portion 82 are pressed against the moving member 7 by the engaging teeth 51 of the drive wheel 5, which may make it difficult for the cylindrical portion 82 to invert. In contrast, if the recess 73 is formed in the moving member 7A as in this embodiment, the cylindrical portion 82 can be easily inverted.

[0060] In this embodiment, a guide member 44 is provided between the pressure vessel 6 and a wall surface 43 in the storage chamber 4. This guide member 44 extends along the axial direction of the pressure vessel 6 from a position adjacent to the drive wheel 5. A retraction space 42A for the movable member 7 is formed between the wall surface 43 and the guide member 44. As shown in FIG. 8(c), the portion of the movable member 7 that has disengaged from the drive wheel 5 moves along the guide member 44 and is positioned within the retraction space 42. In this embodiment, the retraction space 42A is formed parallel to the pressure vessel 6, but the retraction space 42A may also extend in a direction toward or away from the pressure vessel 6.

[0061] In the first embodiment, the evacuation space 42 is formed adjacent to the pressure vessel 6, which makes it easy to make the storage chamber 4 compact, but in this embodiment, the evacuation space 42A is provided at a position away from the pressure vessel 6, which makes it easier to freely position the evacuation space 42A.

[0062] (Other embodiments) The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the gist of the present invention.

[0063] For example, the moving member 7 (or 7A) may be made up of multiple pieces. Each piece may be spherical or shaped like a divided rod. Alternatively, a spherical piece and a piece shaped like a divided rod may be used in combination. When the moving member 7 (or 7A) is made up of multiple pieces, it is preferable that a guide member 44 be provided in the storage chamber 4, as in the second embodiment, to move the piece that has disengaged from the drive wheel 5 along the wall surface 43 of the storage chamber 4.

[0064] Furthermore, for example, when the entire bag member 8 has a single-layer structure, the bag member 8 may be made of a resin that is softened by high-temperature gas and becomes easy to invert.

[0065] 9, a protective member 85 that covers the bottom 83 of the bag member 8 on the side opposite to the moving member 7A (or 7) may be disposed inside the pressure vessel 6. With this configuration, the gas generated by the gas generator 9 does not directly hit the bottom 83 of the bag member 8, so the heat resistance required for the bag member 8 is lower. Therefore, the thickness and cost of the bag member 8 can be reduced. [Explanation of symbols]

[0066] 1 Seat belt retractor 10 Webbing 12 Winding drum 2, 2A, 2B pretensioner 4 Storage Room 41 Guide surface 42, 42A Evacuation space 43 Wall 44 Guide member 5 drive wheels 51 Engagement teeth 6. Pressure vessels 61 End 62 Proximal end 65 Gap 7,7A Moving member 71 1st protrusion 72 Second protrusion 73 Recess 8 Bag parts 81 Tip 82 Cylindrical part 8a Early inner layer 8b Initial outer layer 83 Bottom 85 Protective materials 9 Gas Generator

Claims

1. a winding drum that winds up the webbing and is rotatable in a webbing winding direction and a webbing unwinding direction; a pretensioner that rotates the winding drum in the winding direction in the event of a vehicle emergency, The pretensioner a drive wheel having a plurality of engagement teeth arranged in a circumferential direction and pointing radially outward, the drive wheel rotating together with the winding drum at least in an emergency; a cylindrical pressure vessel having a distal end that opens adjacent to the drive wheel and a proximal end that is provided with a gas generator; a moving member that is normally housed in the pressure vessel, and that, in an emergency, is pushed out of the pressure vessel by the gas generated by the gas generator and engages with at least one of the plurality of engaging teeth to rotate the drive wheel in the webbing winding direction; a storage chamber that stores the drive wheel, has a guide surface that guides the moving member pushed out of the pressure vessel, and forms a retraction space for the moving member; a cylindrical portion that houses the moving member within the pressure vessel and surrounds the moving member, a tip portion that extends radially outward from one end of the cylindrical portion and is fixed to the end portion of the pressure vessel, and a bag member that is connected to the other end of the cylindrical portion and has a bottom that can come into contact with the moving member, the moving member has a length capable of pressing two or more of the plurality of engagement teeth in the winding direction of the webbing, A seat belt retractor characterized in that, in an emergency, the bottom of the bag member is pressed by the gas generated by the gas generator, causing the bottom and the tubular portion to move together with the moving member, and the tubular portion is reversed sequentially from the one end.

2. the bag member includes an initial inner layer that forms an inner surface in a normal state and an initial outer layer that forms an outer surface in a normal state; 2. The seat belt retractor according to claim 1, wherein the initial inner layer and the initial outer layer are made of different materials.

3. 3. The seat belt retractor according to claim 2, wherein the initial inner layer has a strength greater than that of the initial outer layer.

4. 4. The seat belt retractor according to claim 2, wherein the initial outer layer has a higher heat resistance than the initial inner layer.

5. The seat belt retractor according to any one of claims 2 to 4, wherein the initial outer layer has higher slidability than the initial inner layer.

6. 6. The seat belt retractor according to claim 1, wherein a gap is provided between an inner peripheral surface of the pressure vessel and the tubular portion of the bag member.

7. 7. The seat belt retractor according to claim 1, further comprising a protection member that covers a bottom of the bag member on the side opposite to the moving member.

8. The seat belt retractor according to any one of claims 1 to 7, characterized in that the moving member is rod-shaped and has a first protrusion that engages with at least one of the plurality of engagement teeth and a second protrusion that engages with at least one of the plurality of engagement teeth, and a recess is formed between the first protrusion and the second protrusion to avoid interference with some of the plurality of engagement teeth.

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