Pretensioner, retractor and seatbelt device

Abstract

To provide a pretensioner, a retractor, and a seat belt device, which can relax constraint conditions for designing the pretensioner while suppressing discharge of operation gas.SOLUTION: A power transmission device 32 of a pretensioner 3 includes: a piston 32d which is arranged between a gas generator 32c and a power transmission member 32a; and a restraining section 32g which restrains the piston 32d formed in a guide member 32b. The piston 32d has through holes (first through hole 32r and second through hole 32s) communicating front and back spaces with each other and guide flow passages (first groove 321c and second groove 321d) for guiding operation gas to the through holes. The guide flow passages have at least a bent section (first bent section 321e and second bent section 321f).SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a pretensioner, a retractor, and a seat belt device, and more particularly to a pretensioner, a retractor, and a seat belt device that are suitable for a configuration in which a power transmission member is moved by a gas generator. [Background technology]

[0002] In vehicles such as automobiles, a seat belt device for restraining an occupant is generally provided on a seat having a seat portion on which the occupant sits and a backrest portion located behind the occupant. Such a seat belt device includes a webbing for restraining the occupant, a retractor for winding up the webbing, a buckle located on the side of the seat, and a tongue located on the webbing, and the occupant is restrained to the seat by the webbing by fitting the tongue into the buckle. In addition, it is becoming common for the retractor to have a pretensioner for removing slack in the webbing in an emergency such as a vehicle collision.

[0003] Such pretensioners often include a power transmission device that includes a power transmission member that rotates a spool that winds up the webbing, a long, thin, cylindrical pipe (guide member) that guides the power transmission member, and a gas generator that imparts a propulsive force to the power transmission member by supplying a working gas into the pipe (see, for example, Patent Document 1).

[0004] As described in Patent Document 1, if the power transmission member is entirely discharged from the pipe when the pretensioner is activated, the working gas may be released to the outside, generating noise and smoke. Therefore, Patent Document 1 proposes various means for closing the final section of the pipe with the power transmission member (mass body or drive cylinder) so that the working gas is not released to the outside of the pipe.

[0005] Recently, research and development has been conducted on the use of elongated rod-shaped resin parts as power transmission members for pretensioners. For example, Patent Document 2 discloses a configuration in which a piston equipped with a deceleration element and a sealing element comes into contact with a stopper formed inside a pipe, and the deceleration element plastically deforms the stopper, thereby stopping the piston inside the pipe. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 4654204 [Patent Document 2] Special Publication No. 2016-523198 Summary of the Invention [Problem to be solved by the invention]

[0007] The inventions described in Patent Documents 1 and 2 are both configured to completely seal the pipe by a moving body (mass body, piston, etc.) that moves along the pipe. Because the pretensioner needs to wind up the webbing instantaneously (for example, within one second), the kinetic energy of the moving body inevitably tends to be large.

[0008] Therefore, in order to completely stop the moving body inside the pipe, the pretensioner must be designed to have a structure that can withstand the kinetic energy of the moving body when it collides with the stopper, which imposes strict constraints on the design of the pretensioner.

[0009] The present invention has been devised in view of the above problems, and has an object to provide a pretensioner, a retractor, and a seat belt device that can relax the constraints on the design of the pretensioner while suppressing the release of working gas. [Means for solving the problem]

[0010] According to the present invention, there is provided a pretensioner including a ring gear connected to a spool that winds up a webbing for restraining an occupant, and a power transmission device that transmits power to the ring gear in an emergency, wherein the power transmission device includes a power transmission member that transmits power to the ring gear, a cylindrical guide member that guides the power transmission member to the ring gear, a gas generator that supplies a working gas to the inside of the guide member, a piston arranged between the gas generator and the power transmission member, a seal member that seals a gap between the piston and the guide member, and a restraint portion formed in the guide member that restrains the piston, wherein the piston has a through hole that communicates between front and rear spaces, and a guide flow path that guides the working gas to the through hole, and the guide flow path has at least one bent portion.

[0011] The guide passage may be defined by a plug attached to the piston.

[0012] The guide passage may be defined by a gap between a groove formed on an outer surface of the plug and an inner surface of the piston.

[0013] The guide passage may be defined by a fine hole formed in the plug in the axial direction.

[0014] The plug may include a protrusion formed so as to be insertable into the through hole with a predetermined gap therebetween.

[0015] The piston may include a head portion having the through hole, and a cylindrical body portion formed rearward of the head portion.

[0016] The through hole may be configured to be sealable by a member located in front of the piston until the through hole reaches the restraint portion.

[0017] The through hole may be configured in multiple stages with a plurality of holes having different diameters.

[0018] The power transmission device may include an elastic body that is disposed between the piston and the power transmission member and configured to be able to pass through the restraint portion.

[0019] The power transmission device may further include a protective member made of resin and disposed between the elastic body and the power transmission member to protect the elastic body.

[0020] The power transmission member may be made of resin and have a rod shape.

[0021] The power transmission member may have a spherical rear end.

[0022] The restraining portion may be a throttle portion formed in a part of the guide member.

[0023] According to the present invention, there is also provided a retractor comprising a pretensioner having the above-mentioned configuration.

[0024] According to the present invention, there is also provided a seat belt device comprising a retractor equipped with a pretensioner having the above-mentioned configuration. Effect of the Invention

[0025] According to the pretensioner, retractor, and seat belt device of the present invention described above, by forming a through hole and a guide passage in the piston, after the piston is restrained by the restraint section, the working gas can be released from the through hole via the guide passage, thereby reducing the kinetic energy of the piston.

[0026] In addition, by forming a bent portion in the guide passage, it is possible to prevent the working gas from flowing in a straight line when released, and it is also possible to lower the temperature of the working gas. Therefore, according to the present invention, it is possible to relax the constraints on the design of the pretensioner while minimizing the release of the working gas. [Brief description of the drawings]

[0027] [Figure 1] FIG. 2 is a parts exploded view showing a retractor according to an embodiment of the present invention. [Diagram 2] 2A is an enlarged view of the plug shown in FIG. 1, in which (A) is a perspective view, (B) is a cross-sectional view including the groove portion when installed, and (C) is a cross-sectional view not including the groove portion when installed. [Diagram 3] 1A and 1B are perspective views showing modified examples of the plug, where FIG. 1A shows a first modified example, and FIG. [Figure 4] 1A to 1C are cross-sectional views showing modified examples of the piston, where (A) shows a first modified example, (B) shows a second modified example, and (C) shows a third modified example. [Diagram 5] 10A to 10C are cross-sectional views showing modified examples of the plug, where (A) shows a third modified example, (B) shows a fourth modified example, and (C) shows a fifth modified example. [Figure 6] 2A and 2B are conceptual diagrams explaining the action of the piston shown in FIG. 1, in which (A) shows the state before the gas generator is activated, (B) shows the state after the gas generator is activated, (C) shows the state when the piston reaches the restraint section, and (D) shows the state when the working gas is released from the piston. [Figure 7] 2A to 2C are cross-sectional views showing the operation of the pretensioner shown in FIG. 1, in which (A) shows the state before operation, (B) shows the state when the piston has reached the restraining portion, and (C) shows the state when the working gas has been released from the piston. [Figure 8] 2A to 2D are conceptual diagrams showing modified examples of the power transmission device shown in FIG. 1, in which (A) shows the state before the gas generator is activated, (B) shows the state when the elastic body reaches the restraint section, (C) shows the state when the elastic body passes through the restraint section, and (D) shows the state when the working gas is released from the piston. [Figure 9] 1 is an overall configuration diagram showing a seat belt device according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Hereinafter, an embodiment of the present invention will be described with reference to Fig. 1 to Fig. 9. Fig. 1 is a parts exploded view showing a retractor according to one embodiment of the present invention. Fig. 2 is an enlarged view of the plug shown in Fig. 1, where (A) is a perspective view, (B) is a cross-sectional view including the groove when attached, and (C) is a cross-sectional view not including the groove when attached.

[0029] 1, a retractor 1 according to one embodiment of the present invention includes a spool 2 that winds up a webbing for restraining an occupant, and a pretensioner 3 that winds up the webbing to remove slack in an emergency, and the pretensioner 3 includes a ring gear 31 connected to the spool 2, and a power transmission device 32 that transmits power to the ring gear 31 in an emergency. Note that the webbing is omitted from FIG. 1.

[0030] The power transmission device 32 includes, for example, a power transmission member 32a having a rod shape made of resin and transmitting power to the ring gear 31, a cylindrical guide member 32b that guides the power transmission member 32a to the ring gear 31, a gas generator 32c that supplies working gas to the inside of the guide member 32b, a piston 32d arranged between the gas generator 32c and the power transmission member 32a, a sealing member 32e that seals the gap between the piston 32d and the guide member, a spacer 32f that fills the gap between the gas generator 32c and the piston 32d, a restraining portion 32g formed in the guide member 32b that restrains the piston 32d, and a guide member 32h that supports the power transmission member 32a when the power transmission member 32a and the ring gear 31 start to mesh with each other.

[0031] The spool 2 is a winding drum that winds up the webbing, and is rotatably housed in a base frame 11 that forms the framework of the retractor 1. The base frame 11 has, for example, a first end face 111 and a second end face 112 that face each other, and a side face 113 that connects these end faces. The base frame 11 may include a tie plate 114 that faces the side face 113 and is connected to the first end face 111 and the second end face 112. In addition, a bracket 115 for fixing the base frame 11 may be fixed to the side face 113.

[0032] Also, for example, the spring unit 4 is disposed on the first end face 111 side, and the pretensioner 3 and the locking mechanism 5 are disposed on the second end face 112 side. Note that the arrangement of the spring unit 4, the pretensioner 3, the locking mechanism 5, etc. is not limited to the configuration shown in the figure.

[0033] An opening 111a through which the shaft portion of the spool 2 is inserted is formed in a first end surface 111 of the base frame 11, and an opening 112a having internal teeth engageable with a pawl (not shown) of the locking mechanism 5 is formed in a second end surface 112 of the base frame 11. A part of the pretensioner 3 (e.g., ring gear 31) is disposed inside the second end surface 112 of the base frame 11. The locking mechanism 5 is disposed outside the second end surface 112 of the base frame 11, and the locking mechanism 5 is housed in a retainer cover 51.

[0034] A vehicle sensor 6 for detecting sudden deceleration or tilt of the vehicle body may be disposed on the retainer cover 51. The vehicle sensor 6 has, for example, a spherical mass body (not shown) and a sensor lever 61 that is swung by the movement of the mass body. The vehicle sensor 6 may be fitted and fixed in an opening 112b formed in the second end surface 112 of the base frame 11.

[0035] The spool 2 may have a cavity in the center, through which a torsion bar 21 that forms an axis is inserted. A first end of the torsion bar 21 is connected to a locking base 52 of the locking mechanism 5 that is connected to an end of the spool 2, and a second end is fixed to the spool 2 and connected to a spring core of the spring unit 4. Therefore, the spool 2 is connected to the spring unit 4 via the locking base 52 and the torsion bar 21, and is biased in a direction to wind up the webbing by a spiral spring stored in the spring unit 4.

[0036] The means for applying a winding force to the spool 2 is not limited to the spring unit 4, but may be other means such as an electric motor.

[0037] The locking base 52 is provided with a pawl (not shown) arranged so as to be able to protrude from and retract into a side surface of the locking base 52. When the locking mechanism 5 is activated, the pawl is caused to protrude from the side surface of the locking base 52, thereby engaging with internal teeth formed in the opening 112a of the base frame 11, thereby restricting the rotation of the locking base 52 in the webbing-pulling out direction.

[0038] Therefore, even if a load is applied in the webbing-pulling direction with the locking mechanism 5 activated, the spool 2 can be held in a non-rotating state until a load equal to or greater than a threshold value is applied to the torsion bar 21. When a load equal to or greater than a threshold value is applied to the torsion bar 21, the torsion bar 21 twists, causing the spool 2 to rotate relatively, and the webbing is pulled out.

[0039] The lock mechanism 5 also includes a lock gear 53 disposed adjacent to the locking base 52. The lock gear 53 includes a flywheel (not shown) disposed so as to be able to swing, and when the webbing is pulled out faster than a normal speed, the flywheel swings to engage with internal teeth formed on the retainer cover 51. When the vehicle sensor 6 is activated, the sensor lever 61 engages with external teeth formed on the side surface of the lock gear 53.

[0040] In this way, the rotation of the lock gear 53 is restricted by the operation of the flywheel or the vehicle sensor 6. When the rotation of the lock gear 53 is restricted, a relative rotation occurs between the locking base 52 and the lock gear 53, and the pawl protrudes from the side surface of the locking base 52 in accordance with this relative rotation.

[0041] The lock mechanism 5 is not limited to the configuration shown in the figure, and various conventional configurations can be selected and used as desired. Also, the spool 2 may be provided with a shock absorbing mechanism formed by combining a shaft and a wire-like or plate-like plastic deformation member, instead of the torsion bar 21.

[0042] The pretensioner 3 includes, for example, a ring gear 31 having engaging teeth on its outer periphery, a power transmission device 32, a pretensioner cover 33 that houses the ring gear 31, and a pin 34 that restricts movement of the power transmission member 32a. Although not shown, the pretensioner 3 may also include a guide spacer that forms a movement space for the power transmission member 32a within the pretensioner cover 33.

[0043] The ring gear 31 is disposed so as to be located in a space formed between the pretensioner cover 33 and the base frame 11 (the second end surface 112). The ring gear 31 may also be referred to as a drive wheel or a rotating member.

[0044] The pretensioner cover 33 is disposed, for example, on the inside of the second end surface 112 of the base frame 11. In addition, the pretensioner cover 33 is fixed to the base frame 11 (the second end surface 112) together with the guide member 32b or directly by a fastener 35, for example.

[0045] The power transmission device 32 is, for example, arranged in the following order from the rear end to the front end of a guide member 32b formed of a cylindrical pipe: a gas generator 32c, a spacer 32f, a seal member 32e, a piston 32d, and a power transmission member 32a. The power transmission member 32a, the seal member 32e, and the piston 32d are housed in the guide member 32b, and move within the guide member 32b by the working gas generated by the gas generator 32c arranged at the rear end of the guide member 32b.

[0046] The power transmission member 32a is formed in a rod shape having a linear shape before being inserted into the guide member 32b, and is housed inside the guide member 32b in a state following the shape of the guide member 32b, for example, by pressing the power transmission member 32a into the guide member 32b from the tip side of the guide member 32b, as shown in Fig. 1. The power transmission member 32a has, for example, a spherical rear end (the end on the piston 32d side). The rear end of the power transmission member 32a may be flat.

[0047] As shown in FIG. 1, for example, the guide member 32b has a curved shape that passes through the upper part of the first end face 111, the upper part of the tie plate 114, and the upper part of the second end face 112, and extends downward from the upper part of the inside of the corner formed by the second end face 112 and the side face 113.

[0048] A guide member 32h is disposed at the tip of the guide member 32b. An opening 32i is formed at the tip of the guide member 32b, through which the power transmission member 32a guided by the guide member 32h is released from the guide member 32b to a space formed by the pretensioner cover 33. The guide member 32b also includes a notch 32j that communicates from the tip of the guide member 32b to the opening 32i, and an insertion hole 32k that inserts a fastener 35 formed below the opening 32i.

[0049] The opening 32i is formed in the guide member 32b at a position adjacent to the guide member 32h, and constitutes an outlet portion of the power transmission member 32a. The notch 32j has a function of positioning the guide member 32h in the circumferential direction, and a protrusion of the guide member 32h is inserted into the notch 32j.

[0050] The guide member 32h has, for example, a generally cylindrical shape that can be inserted into the tip of the guide member 32b, and a sliding surface 32m that guides the power transmission member 32a to the opening 32i is formed obliquely at the end of the insertion side. The sliding surface 32m may have a groove shape that is curved along the outer shape of the power transmission member 32a.

[0051] Further, a notch 32n through which the fastener 35 is inserted is formed in the lower part of the sliding surface 32m. Further, a bolt hole 32o (see FIG. 7) into which a bolt (not shown) for fixing the guide member 32h and the guide member 32b to the base frame 11 (side surface 113) is screwed is formed in the back side of the sliding surface 32m.

[0052] The restraining portion 32g is a portion that allows the power transmission member 32a to pass and stops the piston 32d within the guide member 32b. The restraining portion 32g is, for example, a throttle portion formed in a part of the guide member 32b, and forms a protruding convex portion protruding from the inside of the guide member 32b. The restraining portion 32g is formed, for example, by pressing a part of the outer periphery of the guide member 32b. Note that the restraining portion 32g may be formed by fixing a separate part such as a pin to the guide member 32b.

[0053] The spacer 32f is also a component that fills a gap between the gas generator 32c and the piston 32d that occurs when assembling the pretensioner 3. By disposing the spacer 32f, it is possible to reduce abnormal noise that occurs due to the movement of the piston 32d during normal operation. The spacer 32f is formed of, for example, a metallic coil spring.

[0054] The piston 32d is a metal part composed of a head 32p having a substantially spherical shape and a body 32q having a substantially cylindrical shape formed behind the head 32p (on the flat surface side), for example, as shown in Figures 1 and 2(B).

[0055] The head 32p has an outer diameter larger than the inner diameter of the restraint portion 32g. A first through hole 32r and a second through hole 32s that communicate the spaces before and after the piston 32d are formed in the center of the head 32p. The first through hole 32r is formed with a smaller diameter than the second through hole 32s. In this manner, the through hole may be configured in multiple stages by a plurality of holes having different diameters.

[0056] The first through hole 32r is configured to be sealable by the rear end of a member (e.g., the power transmission member 32a) located in front of the piston 32d until the piston 32d reaches the restraint portion 32g. The amount of the working gas discharged can be controlled by the size of the diameter of the first through hole 32r. The weight of the piston 32d can be reduced by increasing the diameter of the second through hole 32s.

[0057] A seal member 32e is disposed on the outer periphery of the body 32q. The seal member 32e is, for example, a substantially cylindrical elastomer part. The outer diameter of the seal member 32e is, for example, formed slightly larger than the inner diameter of the guide member 32b, and is press-fitted into the guide member 32b. Therefore, the seal member 32e moves while maintaining contact with the inner surface of the guide member 32b due to the pressure of the working gas supplied from the gas generator 32c.

[0058] The inner diameter of the body 32q is, for example, larger than the diameter of the second through hole 32s. The plug 321 shown in Fig. 2(A) is attached to the body 32q by press-fitting. The body 32q is not limited to a cylindrical shape, and may be a rectangular tubular shape.

[0059] The plug 321 includes, for example, a shaft portion 321a inserted into the body portion 32q, and a flange portion 321b disposed on the rear end side of the body portion 32q. A first groove 321c is formed in the outer surface of the shaft portion 321a along the axial direction. A second groove 321d communicating with the first groove 321c is formed in the surface of the flange portion 321b on the piston 32d side.

[0060] When the plug 321 is attached, a portion that seals the inner surface of the body 32q of the piston 32d is formed as shown in Fig. 2(C), and a portion that forms a space that communicates with the second through hole 32s on the inner surface of the body 32q of the piston 32d is formed as shown in Fig. 2(B). Therefore, a guide flow passage that guides the working gas to the through hole is formed by the first groove 321c and the second groove 321d.

[0061] As shown in FIG. 2(B), the guide flow path has a first bent portion 321e formed between a step portion formed between the inner surface of the body portion 32q and the second through hole 32s and the tip portion of the shaft portion 321a, and a second bent portion 321f formed between the first groove 321c and the second groove 321d.

[0062] In this way, by attaching the plug 321 to the piston 32d, a bent guide passage is formed, and it is possible to prevent the working gas from passing straight through the piston 32d. By forming such a guide passage, the resistance of the working gas when passing through the piston 32d is increased, and the time that the working gas contacts the piston 32d is lengthened, so that the temperature of the working gas can be lowered by the heat exchange action with the piston 32d.

[0063] The path of the guide flow passage is not limited to the configuration shown in the figure. For example, the plug 321 may be configured integrally with the piston 32d, or the plug 321 and the piston 32d may be configured to be separated by different parts, and the first groove 321c and the second groove 321d may be twisted in the circumferential direction.

[0064] In the present embodiment, a pair of guide channels (first groove 321c and second groove 321d) are disposed at positions facing each other, but the number of guide channels may be one or three or more. When multiple guide channels are formed, they are preferably disposed at equal intervals in the circumferential direction.

[0065] Here, Fig. 3 is a perspective view showing modified plugs, where (A) shows a first modified plug and (B) shows a second modified plug. Plug 321 shown in Fig. 3(A) is configured only with shaft portion 321a, omitting flange portion 321b of plug 321 shown in Fig. 2(A). Even with this configuration, at least one bent portion (first bent portion 321e) can be formed by first groove 321c.

[0066] 3B shows plug 321 having a plurality of C-shaped protrusions 321g arranged in the circumferential direction of shaft portion 321a. The adjacent protrusions 321g are arranged so that their open ends are not adjacent to each other. When plug 321 is attached, protrusions 321g form grooves (guide flow paths) that are formed in the axial and circumferential directions between protrusions 321g and the inner surface of body portion 32q.

[0067] The shape of the protrusion 321g is not limited to a C-shape, and may be an arc shape that defines a plurality of openings in the circumferential direction, or may be a spiral shape that extends to both ends of the plug 321. In addition, a flange portion 321b may be formed on the plug 321 shown in FIG. 3(B).

[0068] Here, Fig. 4 is a cross-sectional view showing modified pistons, where (A) shows a first modified piston, (B) shows a second modified piston, and (C) shows a third modified piston. The piston 32d shown in Fig. 4(A) has a through hole formed by one through hole 32t. In this way, the through hole may be a single hole, or may be configured in multiple stages as in the above-mentioned embodiment.

[0069] The piston 32d shown in Fig. 4(B) has a recess 32u formed at the tip of the head 32p. This configuration makes it easier to fit the spherical shape of the power transmission member 32a. The piston 32d shown in Fig. 4(C) has a hollow portion 32v formed in the second through hole 32s. This configuration makes it possible to reduce the weight of the piston 32d.

[0070] Here, Fig. 5 is a cross-sectional view showing modified plugs, where (A) shows a third modified plug, (B) shows a fourth modified plug, and (C) shows a fifth modified plug. Plug 321 shown in Fig. 5(A) is obtained by forming protruding portion 321h at the tip of shaft portion 321a of plug 321 shown in Fig. 2(B). Protruding portion 321h is a substantially cylindrical portion formed so as to be insertable into second through-hole 32s of piston 32d with a predetermined gap therebetween.

[0071] With this configuration, a part of the guide flow path can be formed by the gap between the protruding portion 321h and the second through hole 32s. Also, the third bent portion 321i can be formed by a step portion formed between the first through hole 32r and the second through hole 32s of the piston 32d. Therefore, by employing the plug 321 of the third modified example, the temperature of the working gas can be further reduced.

[0072] In plug 321 shown in Fig. 5(B), a guide flow path is formed by pore 321j extending in the axial direction in shaft portion 321a, instead of first groove 321c and second groove 321d formed in plug 321 of the third modified example shown in Fig. 5(A). Pore 321j is formed so as to penetrate a step portion between shaft portion 321a and protruding portion 321h.

[0073] That is, the fine hole 321j is a through hole having a diameter smaller than the radial width of the step between the shaft portion 321a and the protruding portion 321h. According to the configuration of the fourth modification, the first bent portion 321e and the third bent portion 321i can be formed in the guide flow passage. The fine hole 321j may be one or more. The fine hole 321j is formed at a position where the working gas can be discharged toward the first bent portion 321e.

[0074] The plug 321 shown in Fig. 5(C) is a plug 321 having a shaft portion 321a, a flange portion 321b, and a fine hole 321j attached to the piston 32d of the first modified example shown in Fig. 4(A). Even with this configuration, at least one first bent portion 321e can be formed in the guide flow passage. The fine hole 321j is formed at a position where the working gas can be discharged toward the first bent portion 321e.

[0075] Next, the action of the piston 32d will be described with reference to Fig. 6(A) to Fig. 6(D). Fig. 6 is a conceptual diagram for explaining the action of the piston shown in Fig. 1, in which (A) shows the state before the gas generator is activated, (B) shows the state after the gas generator is activated, (C) shows the state when the piston has reached the restraint portion, and (D) shows the state when the working gas has been released from the piston.

[0076] As shown in FIG. 6(A), before the gas generator 32c is activated, the piston 32d is inserted into the guide member 32b in a state where it is pressed against the rear end of the power transmission member 32a by the spacer 32f.

[0077] When the gas generator 32c is activated and the working gas is supplied into the guide member 32b, as shown in FIG. 6(B), the piston 32d moves the power transmission member 32a forward while remaining in contact with the rear end of the power transmission member 32a due to the pressure of the working gas.

[0078] Thereafter, as shown in Fig. 6(C), when the piston 32d reaches the restraint portion 32g, the piston 32d collides with the restraint portion 32g and stops, as shown in Fig. 6(D), and the power transmission member 32a moves forward due to inertial force and the pressure of the working gas loaded from the first through hole 32r. The working gas discharged from the first through hole 32r is finally discharged to the outside of the guide member 32b from the gap between the power transmission member 32a and the guide member 32b.

[0079] Therefore, according to this embodiment, after the piston 32d is restrained by the restraint portion 32g, the working gas can be released from the first through hole 32r via the guide flow path (the first groove 321c and the second groove 321d), the kinetic energy of the piston 32d can be reduced, and the constraints on the design of the pretensioner can be relaxed while minimizing the release of the working gas.

[0080] Furthermore, according to this embodiment, by forming bends (first bend 321e and second bend 321f) in the guide flow path, it is possible to hinder the linearity of the working gas when it is released and to lower the temperature of the working gas, thereby further relaxing the constraints on the design of the pretensioner.

[0081] Here, the operation of the pretensioner 3 will be described with reference to Figures 7(A) to 7(C). Figure 7 is a cross-sectional view showing the operation of the pretensioner shown in Figure 1, where (A) shows the state before operation, (B) shows the state when the piston has reached the restraint portion, and (C) shows the state when the working gas has been released from the piston.

[0082] 7(A), before the activation of the pretensioner 3, the power transmission member 32a is housed in the guide member 32b. At this time, the tip end of the power transmission member 32a is inserted to a position facing the guide member 32h.

[0083] In the event of an emergency such as a vehicle collision, the pretensioner 3 is activated, and working gas is supplied from the gas generator 32c into the guide member 32b, and the power transmission member 32a is pushed out via the piston 32d and moves along the guide member 32b. At this time, the tip of the power transmission member 32a collides with the sliding surface 32m of the guide member 32h, is deflected toward the opening 32i, moves along the sliding surface 32m, and is released toward the engagement teeth formed on the outer periphery of the ring gear 31.

[0084] The power transmission member 32a released from the guide member 32b collides with the engaging teeth of the ring gear 31, causing the ring gear 31 to rotate. Thereafter, the power transmission member 32a moves along the path formed by the pretensioner cover 33 while being plastically deformed by the engaging teeth of the ring gear 31.

[0085] As shown in Fig. 7(B), when the piston 32d moves while the movement of the power transmission member 32a is restricted by the pin 34, the piston 32d collides with and reaches the restraint portion 32g. Then, as shown in Fig. 7(C), the piston 32d collides with the restraint portion 32g and stops, and the power transmission member 32a is compressed by the inertial force and the pressure of the working gas, and the rear end of the power transmission member 32a separates from the piston 32d.

[0086] Therefore, when the piston 32d is restrained, the working gas can be discharged to the outside from the first through hole 32r of the piston 32d without being confined in the guide member 32b, and the kinetic energy of the piston 32d can be reduced. In addition, in this embodiment, by forming the guide flow path, the temperature of the working gas discharged from the first through hole 32r can be reduced.

[0087] Although not shown, the power transmission member 32a stops when it finishes winding up the slack in the webbing. Therefore, if the amount of slack in the webbing is small, the movement of the power transmission member 32a may stop before the piston 32d reaches the restraining portion 32g.

[0088] Next, modified examples of the power transmission device 32 will be described with reference to Figures 8(A) to 8(D). Figure 8 is a conceptual diagram showing a modified example of the power transmission device shown in Figure 1, in which (A) shows a state before the gas generator is activated, (B) shows a state in which the elastic body has reached the restraint portion, (C) shows a state in which the elastic body has passed through the restraint portion, and (D) shows a state in which the working gas has been released from the piston.

[0089] The power transmission device 32 shown in Figures 8(A) to 8(D) includes an elastic body 322 that is arranged between the piston 32d and the power transmission member 32a and is configured to be able to pass through the restraint section 32g, and a resin protective member 323 that is arranged between the elastic body 322 and the power transmission member 32a and protects the elastic body 322.

[0090] The elastic body 322 is, for example, an elastomer part formed in a substantially cylindrical shape. The elastic body 322 has an outer diameter smaller than the inner diameter of the guide member 32b in an unloaded state, and is configured to be able to contact the inner surface of the guide member 32b when compressed. The elastic body 322 also has an elastic force that allows it to deform into a shape that allows it to pass through the restraint portion 32g when compressed. The elastic body 322 may also have a fastening hole for engaging the protective member 323.

[0091] The protective member 323 is made of, for example, the same material as the power transmission member 32a. The protective member 323 has, for example, a substantially T-shaped cross section and is configured to be able to come into surface contact with the rear end of the power transmission member 32a. The protective member 323 may also have a protrusion that can be engaged with the elastic body 322.

[0092] Integrating the elastic body 322 and the protective member 323 makes it easier to handle when assembling the pretensioner 3. Note that the protective member 323 is not necessarily a component that must be connected to the elastic body 322, and the shapes of the protrusions and fastening holes may be changed or the protrusions and fastening holes may be omitted, as necessary.

[0093] The configurations of the elastic body 322 and the protective member 323 are not limited to those shown in the figures. For example, the connection structure may be changed, or the protective member 323 may be omitted as necessary.

[0094] As shown in Fig. 8(A), the elastic body 322 and the protective member 323 are inserted between the power transmission member 32a and the piston 32d before the gas generator 32c is activated. When the gas generator 32c is then activated and the working gas is supplied into the guide member 32b, the elastic body 322 and the protective member 323 are sandwiched between the power transmission member 32a and the piston 32d and compressed, and move forward together with the piston 32d in a deformed state so as to contact the inner surface of the guide member 32b, as shown in Fig. 8(B).

[0095] When the elastic body 322 and the protective member 323 reach the restraint portion 32g, they pass through the restraint portion 32g while being elastically deformed along the restraint portion 32g, as shown in Fig. 8(C). Then, when the piston 32d reaches the restraint portion 32g, the piston 32d collides with the restraint portion 32g and stops, and the elastic body 322 and the protective member 323 pass completely through the restraint portion 32g, as shown in Fig. 8(D).

[0096] Therefore, the first through hole 32r of the piston 32d is opened, and the working gas is discharged from the first through hole 32r to the outside of the guide member 32b through the gaps between the power transmission member 32a, the elastic body 322, the protective member 323, and the guide member 32b.

[0097] Next, a seat belt device according to one embodiment of the present invention will be described with reference to Fig. 9. Here, Fig. 9 is an overall configuration diagram showing a seat belt device according to one embodiment of the present invention. In Fig. 9, for convenience of explanation, components other than the seat belt device are illustrated by dashed lines.

[0098] The seat belt device 100 according to this embodiment shown in FIG. 9 includes a webbing W for restraining an occupant, a retractor 1 for winding up the webbing W, a guide anchor 101 provided on the vehicle body side for guiding the webbing W, a belt anchor 102 for fixing the webbing W to the vehicle body side, a buckle 103 arranged on the side of the seat S, and a tongue 104 arranged on the webbing W, and the retractor 1 has, for example, the configuration shown in FIG. 1.

[0099] Below, components other than the retractor 1 will be briefly described. The seat S includes, for example, a seating portion S1 on which an occupant sits, a backrest portion S2 located behind the occupant, and a headrest portion S3 that supports the occupant's head. The retractor 1 is built into, for example, a B-pillar R of a vehicle body. In general, the buckle 103 is often disposed on the side of the seating portion S1, and the belt anchor 102 is often disposed on the underside of the seating portion S1. The guide anchor 101 is often disposed on the B-pillar R. One end of the webbing W is connected to the belt anchor 102, and the other end is connected to the retractor 1 via the guide anchor 101.

[0100] Therefore, when the tongue 104 is fitted into the buckle 103, the webbing W is pulled out from the retractor 1 while sliding through the insertion hole of the guide anchor 101. When an occupant fastens the seat belt or releases the seat belt when getting off the vehicle, the spring unit 4 of the retractor 1 acts to retract the webbing W until a certain load is applied.

[0101] The above-mentioned seat belt device 100 is a normal seat belt device for the front seat, to which the retractor 1 according to the above-mentioned embodiment is applied. Therefore, according to the seat belt device 100 according to the present embodiment, after the piston 32d is restrained by the restraint portion 32g, the working gas can be discharged from the through hole via the guide flow path, and the kinetic energy of the piston 32d can be reduced and the temperature of the working gas can be lowered.

[0102] The seat belt device 100 according to the present embodiment is not limited to application to a front seat, and can be easily applied to a rear seat, for example, by omitting the guide anchor 101. The seat belt device 100 according to the present embodiment can also be used in vehicles other than automobiles.

[0103] In addition, in the above-described embodiment, the power transmission member 32a is described as having a rod shape made of resin, but the power transmission member 32a may be in the shape of a metal sphere (ball), or may be a rack of a rack-and-pinion drive system.

[0104] The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention. [Explanation of symbols]

[0105] 1 Retractor 2 Spools 3 Pretensioner 4 Spring unit 5 Locking mechanism 6 Vehicle Sensors 11 Base frame 21 Torsion bar 31 Ring Gear 32 Power transmission device 32a Power transmission members 32b Guide member 32c Gas Generator 32d Piston 32e Sealing material 32f Spacer 32g restraint part 32h Guide material 32i opening 32j Notch 32k insertion hole 32m sliding surface 32n Notch 32o bolt hole 32p head 32q Torso 32r First through hole 32s 2nd through hole 32t through hole 32u recess 32v hollow part 33 Pretensioner cover 34 pin 35 Fasteners 51 Retainer cover 52 Rocking Base 61 Sensor lever 100 Seat belt device 101 Guide Anchor 102 Belt anchor 103 Buckle 104 Tongs 111 First end face 111a opening 112 Second end face 112a,112b opening 113 Side 114 Thai Plate 115 Bracket 321 Plug 321a Shaft 321b Flange part 321c First groove 321d Second groove 321e First bending part 321f Second bending part 321g convex part 321h Protrusion 321i Third bend 321j pore 322 Elastic Body 323 Protective materials

Claims

1. A pretensioner including a ring gear connected to a spool that winds up a webbing for restraining an occupant, and a power transmission device that transmits power to the ring gear in an emergency, the power transmission device includes a power transmission member that transmits power to the ring gear, a cylindrical guide member that guides the power transmission member to the ring gear, a gas generator that supplies a working gas to an inside of the guide member, a piston disposed between the gas generator and the power transmission member, a seal member that seals a gap between the piston and the guide member, and a restraint portion formed in the guide member that restrains the piston, the piston includes a through hole communicating a front space with a rear space and a guide passage for guiding the working gas to the through hole, The guide channel has at least one bend. A pretensioner characterized by the above.

2. 2. The pretensioner of claim 1, wherein the guide passage is defined by a plug attached to the piston.

3. 3. The pretensioner according to claim 2, wherein the guide passage is defined by a gap between a groove formed on an outer surface of the plug and an inner surface of the piston.

4. The pretensioner according to claim 2 , wherein the guide passage is defined by a fine hole formed in the plug in an axial direction.

5. The pretensioner according to claim 2 , wherein the plug includes a protrusion formed so as to be insertable into the through hole with a predetermined gap therebetween.

6. 3. The pretensioner according to claim 2, wherein the piston includes a head portion having the through hole, and a cylindrical body portion formed behind the head portion.

7. The pretensioner according to claim 1 , wherein the through hole is configured to be sealable by a member located in front of the piston until the through hole reaches the restraint portion.

8. The pretensioner according to claim 1 , wherein the through hole is configured in multiple stages by a plurality of holes having different diameters.

9. The pretensioner according to claim 1 , wherein the power transmission device includes an elastic body disposed between the piston and the power transmission member and configured to be able to pass through the restraint portion.

10. 10. The pretensioner according to claim 9, wherein the power transmission device further comprises a protective member made of resin and disposed between the elastic body and the power transmission member to protect the elastic body.

11. The pretensioner according to claim 1 , wherein the power transmission member is made of resin and has a rod shape.

12. The pretensioner according to claim 11 , wherein the power transmission member has a rear end having a spherical shape.

13. The pretensioner according to claim 1 , wherein the restraining portion is a throttle portion formed in a part of the guide member.

14. A retractor comprising the pretensioner according to any one of claims 1 to 13.

15. A seat belt device comprising a retractor equipped with a pretensioner according to any one of claims 1 to 13.

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