seat belt retractor

Abstract

To provide a retractor for a seat belt that can secure rigidity in a length direction of a movement member while reducing resistance caused when an engagement tooth bites into the movement member.SOLUTION: The retractor for a seat belt includes a winding drum and a pretensioner. The pretensioner has a driving wheel 7 having a plurality of engagement teeth 71 sharpened outward in a radial direction arranged in a circumferential direction, which rotates together with the winding drum, and a rod-like movement member that is not engaged with the driving wheel 7 in a normal time and moves toward the driving wheel 7 in an emergency to engage with at least one of the engagement teeth 71, so as to rotate the driving wheel 7 in a winding direction of a webbing. The movement member is bitten by the engagement teeth 71 to plastically deform. Each of the engagement tooth 71 has a gear tooth-like shape whose direction along a rotary shaft of the driving wheel 7 is a width direction. In tooth tips of the engagement teeth 71, one or more concave parts 73 recessed inwardly in the radial direction of the driving wheel 71 are formed at sides closer to inside than both end parts of the tooth tips 72.SELECTED DRAWING: Figure 3

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] Pretensioners have a variety of structures, and in recent years, a pretensioner has been proposed that uses a rod-shaped moving member and a drive wheel driven by the moving member. For example, Patent Document 1 discloses a seat belt retractor 100 (referred to as a "webbing retractor" in Patent Document 1) as shown in Figure 12.

[0004] Specifically, the seat belt retractor 100 includes a winding drum (referred to as a "spool" in Patent Document 1) 110 that can rotate in the winding and unwinding directions of the webbing, and a pretensioner 120 that rotates the winding drum 110 in the winding direction in the event of a vehicle emergency.

[0005] The pretensioner 120 includes a drive wheel (referred to as a "rotating body" in Patent Document 1) 130 that rotates together with the take-up drum 110, and a rod-shaped moving member 140 (FIG. 12 shows its cross-sectional shape) that is normally disengaged from the drive wheel 130. The drive wheel 130 has a plurality of engagement teeth 131 arranged circumferentially and pointed outward in the radial direction. Each engagement tooth 131 has a gear-tooth shape with the direction along the rotation axis of the drive wheel 130 as the width direction.

[0006] The moving member 140 is disposed inside a pipe (not shown), and moves from inside the pipe toward the drive wheel 130 by the pressure of gas supplied from the gas generator in the event of a vehicle emergency, and engages with at least one of the engagement teeth 131. This causes the drive wheel 130 and the take-up drum 110 to rotate in the webbing take-up direction.

[0007] The moving member 140 is made of a material softer than the engaging teeth 131, and when the moving member 140 engages with at least one of the engaging teeth 131, it is plastically deformed by the biting of the engaging teeth 131. In the seat belt retractor 100 of Patent Document 1, in order to reduce the resistance when the engaging teeth 131 bite into the moving member 140, each engaging tooth 131 is formed in a shape such that the thickness of the engaging tooth 131 decreases from both ends toward the center. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 6620069 Summary of the Invention [Problem to be solved by the invention]

[0009] However, in the seat belt retractor 100 of Patent Document 1, the tip of each engagement tooth 131 of the drive wheel 130 is linear and parallel to the rotation axis of the drive wheel 130, so when the engagement tooth 131 bites into the moving member 140 and the moving member 140 undergoes plastic deformation, the rigidity (i.e., compressive rigidity) of the moving member 140 in the longitudinal direction decreases, and the efficiency with which the kinetic energy of the moving member is transmitted to the drive wheel decreases accordingly.

[0010] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a seat belt retractor that can ensure the rigidity of the moving member in the longitudinal direction while reducing the resistance when the engaging teeth bite into the moving member. [Means for solving the problem]

[0011] In order to solve the above-mentioned problems, the present invention provides a seat belt retractor comprising: a winding drum that winds up a webbing and is rotatable in a webbing winding direction and an unwinding direction; and a pretensioner that rotates the winding drum in the winding direction in the event of a vehicle emergency, the pretensioner including: a drive wheel that rotates together with the winding drum and has a plurality of engagement teeth that are arranged circumferentially and point radially outward; and a rod-shaped moving member that is normally disengaged from the drive wheel and that moves toward the drive wheel in the event of an emergency and engages with at least one of the plurality of engagement teeth, causing the drive wheel to rotate in the webbing winding direction, wherein the moving member is plastically deformed when it engages with at least one of the plurality of engagement teeth due to the engagement of the engagement teeth, each of the plurality of engagement teeth has a gear-tooth shape with a width direction along the rotation axis of the drive wheel, and at least one recess that is recessed radially inward of the drive wheel, is formed on the tip of each of the plurality of engagement teeth, inward from both ends of the tooth tip.

[0012] According to the above configuration, recesses are formed at the tips of the engaging teeth, which reduces resistance when the engaging teeth bite into the moving member. Moreover, plastic deformation of the moving member is suppressed at the positions corresponding to the recesses, ensuring rigidity in the longitudinal direction of the moving member. Therefore, the efficiency with which the kinetic energy of the moving member is transmitted to the drive wheels can be improved compared to conventional methods.

[0013] The at least one recess may be located on the same circumference in all of the plurality of engagement teeth. With this configuration, the portion of the movable member where the rigidity in the longitudinal direction is ensured can be made continuous in the longitudinal direction of the movable member. Therefore, the efficiency of transmitting the kinetic energy of the movable member to the drive wheels is increased compared to, for example, a case where the positions of the recesses in the width direction of the engagement teeth are offset between adjacent engagement teeth.

[0014] At least one recess formed on the tip of each of the plurality of engagement teeth may include a plurality of recesses aligned in the width direction of the engagement tooth. This configuration makes it easy to adjust the resistance when the engagement tooth bites into the moving member and the range over which the engagement tooth bites into the moving member.

[0015] The movable member may have a cross-sectional shape in which the center in a width direction, which is a direction along the rotation axis of the drive wheel, rises toward the engaging tooth, and at least one recess formed in the tip of each of the plurality of engaging teeth is located at the center of the tip, and the width of the recess may narrow toward the bottom. With this configuration, it is easy to make the amount of biting of the engaging tooth into the movable member uniform in the width direction of the engaging tooth.

[0016] The movable member may be pressed against a reaction surface when the engagement teeth bite into the movable member, and a minimum distance from the reaction surface to a bottom of the recess in a radial direction of the drive wheel may be greater than a thickness of the movable member. With this configuration, it is possible to prevent the engagement teeth from biting into the movable member within the recess.

[0017] The at least one recess formed in at least one of the plurality of engagement teeth may have a shape different from the at least one recess formed in another of the plurality of engagement teeth. This configuration makes it easy to adjust the resistance when the engagement tooth engages with the moving member and the range over which the engagement tooth bites into the moving member. [Effects of the Invention]

[0018] According to the present invention, it is possible to ensure the rigidity of the moving member in the length direction while reducing the resistance when the engaging teeth bite into the moving member. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a perspective view of a seat belt retractor according to an embodiment; [Figure 2] (a) and (b) are cross-sectional views taken along line II-II in FIG. 1, where (a) shows normal operation and (b) shows emergency operation. [Figure 3] FIG. 2 is a perspective view of a drive wheel used in the embodiment. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 2. [Figure 5] FIG. 10 is a perspective view of a drive wheel of a first modified example. [Figure 6] FIG. 10 is a cross-sectional view of a portion of a seat belt retractor when a driving wheel of a first modified example is used. [Figure 7] 10 is a cross-sectional view of a portion of a seatbelt retractor when a drive wheel of a second modified example and a moving member of a modified example are used. FIG. [Figure 8] 10 is a cross-sectional view of a portion of a seatbelt retractor when a driving wheel of a third modified example and a moving member of a modified example are used. FIG. [Figure 9] FIG. 10 is a perspective view of a drive wheel of a fourth modified example. [Figure 10] FIG. 10 is a cross-sectional view of a portion of a seat belt retractor when a driving wheel of a fourth modified example is used. [Figure 11] FIG. 11 is a perspective view of a drive wheel of a fifth modified example. [Figure 12] FIG. 1 is a cross-sectional view of a conventional seat belt retractor. DETAILED DESCRIPTION OF THE INVENTION

[0020] Fig. 1 shows a seatbelt retractor 1 according to one embodiment of the present invention. Fig. 2(a) and (b) are cross-sectional views taken along line II-II in Fig. 1, where (a) shows a normal state and (b) shows an emergency state.

[0021] The seat belt retractor 1 includes a housing 2, a take-up drum 3, and a pretensioner 4. The housing 2 is made of sheet metal and includes a pair of side walls that face each other. Each of these side walls is provided with an opening through which the take-up drum 3 is inserted. The take-up drum 3 takes up the webbing 10 and is rotatable in the take-up direction and the unwinding direction of the webbing 10.

[0022] The pretensioner 4 rotates the take-up drum 3 in the take-up direction in the event of a vehicle emergency. Specifically, the pretensioner 4 includes a drive wheel 7 that rotates together with the take-up drum 3, a rod-shaped moving member 8 that drives the drive wheel 7 in the event of an emergency, a pipe 6 in which the moving member 8 is disposed, and a cover 5 that covers the drive wheel 7 and a portion of the pipe 6.

[0023] 3, the drive wheel 7 has a plurality of engagement teeth 71 arranged in the circumferential direction and pointed outward in the radial direction. Each engagement tooth 71 has a gear tooth shape with the direction along the rotation axis of the drive wheel 7 as the width direction.

[0024] At least one recess 73 recessed radially inward of the drive wheel 7 is formed in the tip 72 of each engagement tooth 71, on the inside of both ends of the tip. In this embodiment, three recesses 73 are formed in the tip 72 of each engagement tooth 71, aligned in the width direction of the engagement tooth 71. Each recess 73 is a groove with a V-shaped cross section. The number of recesses 73 formed in the tip 72 of each engagement tooth 71 may be one, two, four or more.

[0025] In this embodiment, the recesses 63 are located on the same circumference in all of the engagement teeth 71. In other words, the positions of the recesses 63 in the width direction of the engagement teeth 71 are the same for all of the engagement teeth 71.

[0026] The moving member 8 is normally housed in the pipe 6 as shown in Figure 2(a) and is not engaged with the drive wheel 7. In an emergency such as a vehicle collision, the moving member 8 moves from inside the pipe 6 toward the drive wheel 7 due to the pressure of gas supplied from the gas generator and engages with at least one of the engagement teeth 71. This causes the drive wheel 7 and the take-up drum 3 to rotate in the webbing take-up direction.

[0027] The moving member 8 is made of a material softer than the engaging teeth 71, and when it engages with at least one of the engaging teeth 71, it is plastically deformed by the biting of the engaging teeth 71. When the engaging teeth 71 bite into the moving member 8, the moving member 8 is pressed against the reaction surface 9. In this embodiment, the reaction surface 9 is formed by an extended portion of the pipe 6. In the illustrated example, the reaction surface 9 is flat, but the reaction surface 9 may also be a curved surface similar to the cross-sectional shape of the moving member 8.

[0028] The moving member 8 has a width direction along the rotation axis of the drive wheel 7 and a thickness direction along the radial direction of the drive wheel 7. In this embodiment, as shown in FIG. 4, the cross-sectional shape of the moving member 8 is circular. Therefore, the width and thickness of the moving member 8 are the same. However, the cross-sectional shape of the moving member 8 does not necessarily have to be circular and may be another shape.

[0029] It is desirable that the height of the engagement teeth 71 (the distance in the radial direction of the drive wheel 7 from a reference circle passing through the roots between the engagement teeth 71 to the tooth tip 72) be smaller than the thickness of the moving member 8.

[0030] As described above, in the seat belt retractor 1 of this embodiment, the recessed portions 73 are formed in the tooth tips 72 of each engagement tooth 71 of the drive wheel 7, thereby reducing the resistance when the engagement tooth 71 bites into the moving member 8. Moreover, plastic deformation of the moving member 8 is suppressed at the positions corresponding to the recessed portions 73, thereby ensuring the rigidity of the moving member 8 in the longitudinal direction. Therefore, the efficiency with which the kinetic energy of the moving member 8 is transmitted to the drive wheel 7 can be improved compared to conventional techniques.

[0031] Furthermore, in this embodiment, the recesses 73 are located on the same circumference in all of the engagement teeth 71, so the portion of the movable member 8 where the rigidity in the longitudinal direction is ensured can be made continuous in the longitudinal direction of the movable member 8. Therefore, the efficiency with which the kinetic energy of the movable member 8 is transmitted to the drive wheel 7 is increased compared to when, for example, the positions of the recesses 73 in the width direction of the engagement teeth 71 are misaligned between adjacent engagement teeth 71.

[0032] Furthermore, if multiple recesses are formed on the tooth tip 72 of each engagement tooth 71 as in this embodiment, it is easy to adjust the resistance when the engagement tooth 71 bites into the movable member 8 and the range (biting depth) to which the engagement tooth 71 bites into the movable member 8.

[0033] (Variation) 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.

[0034] For example, as in a drive wheel 7A of a first modified example shown in Figures 5 and 6, one recess 73 may be formed in the tip 72 of each engagement tooth 71 of the drive wheel 7A so as to be located at the center of the tooth tip 72. In Figures 5 and 6, the recess 73 is recessed in an arc shape, and the width of the recess 73 narrows toward the bottom.

[0035] As explained in the above embodiment, the fact that the cross section of the moving member 8 is circular can be rephrased as the moving member 8 having a cross section in which the center in the width direction rises toward the engaging teeth 71.

[0036] Furthermore, if the movable member 8 has a cross-sectional shape in which the center in the width direction rises toward the engaging tooth 71, and the width of the recess 73 located in the center of the tooth tip 72 narrows toward the bottom, it is easy to make the amount by which the engaging tooth 71 bites into the movable member 8 uniform in the width direction of the engaging tooth 71.

[0037] This effect can be similarly obtained when the recess 73 is V-shaped, as in the drive wheel 7B of the second modified example shown in Figure 7 (in this case, the width of the recess 73 located in the center of the tooth tip 72 narrows toward the bottom), or when the cross-sectional shape of the movable member 8 is rectangular on the reaction surface 9 side and semicircular on the engaging tooth 71 side, as shown in Figure 7 (in this case, the movable member 8 also has a cross-sectional shape in which the center in the width direction rises toward the engaging tooth 71).

[0038] Furthermore, as in a drive wheel 7C of a third modified example shown in Fig. 8, the recess 73 formed in at least one of the engagement teeth 71 may have a shape different from the recess 73 shown by the two-dot chain line in Fig. 8 formed in another engagement tooth 71. With this configuration, it is easy to adjust the resistance when the engagement tooth 71 engages with the moving member 8 and the extent to which the engagement tooth 71 bites into the moving member 8 (biting depth).

[0039] 9 and 10 , the minimum distance from the reaction surface 9 to the bottom of the recess 73 in the radial direction of the drive wheel 7D (in other words, the distance when the tooth tip 72 is closest to the reaction surface 9) may be greater than the thickness of the moving member 8. This configuration can prevent the engagement teeth 71 from biting into the moving member 8 within the recess 73.

[0040] In addition, when the depth of the recess 73 is increased, a portion of a circumferentially continuous slit 74 that crosses all of the engagement teeth 71 may constitute the recess 73 of each engagement tooth 71, as in the drive wheel 7E of the fifth modified example shown in Figure 11. [Explanation of symbols]

[0041] 1 Seat belt retractor 10 Webbing 3 Winding drum 4 Pretensioner 7 drive wheels 71 Engagement teeth 72 Tooth tip 73 Recess 74 Slit 8 Moving parts 9 Reaction surface

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, a drive wheel that rotates together with the winding drum and has a plurality of engagement teeth that are arranged in a circumferential direction and point outward in a radial direction; a rod-shaped moving member that is normally disengaged from the drive wheel and that moves toward the drive wheel in an emergency and engages with at least one of the plurality of engagement teeth, thereby rotating the drive wheel in the webbing winding direction; When the moving member engages with at least one of the plurality of engagement teeth, the moving member is plastically deformed by the engagement of the engagement teeth, Each of the plurality of engagement teeth has a gear tooth shape with a width direction along the rotation axis of the drive wheel, At least one recessed portion recessed radially inwardly of the drive wheel is formed on each tooth tip of the plurality of engagement teeth, the recessed portion being located inside both end portions of the tooth tip, the moving member is pressed against a reaction force surface when the engaging teeth bite into the moving member, A seat belt retractor, wherein a minimum distance from the reaction surface to the bottom of the recess in the radial direction of the drive wheel is greater than a thickness of the moving member.

2. The seat belt retractor according to claim 1 , wherein the at least one recess is located on the same circumference in all of the plurality of engagement teeth.

3. 3. The seat belt retractor according to claim 1, wherein the at least one recess formed on the tip of each of the plurality of engagement teeth includes a plurality of recesses aligned in a width direction of the engagement tooth.

4. the moving member has a cross-sectional shape in which the center in a width direction, which is a direction along the rotation axis of the drive wheel, rises toward the engaging teeth, 3. The seat belt retractor according to claim 1, wherein at least one recess formed in the tip of each of the plurality of engagement teeth is positioned at the center of the tip, and the width of the recess narrows toward the bottom.

5. The seat belt retractor according to any one of claims 1 to 4, wherein the at least one recess formed in at least one of the plurality of engagement teeth has a different shape from the at least one recess formed in another of the plurality of engagement teeth.

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