JP2010030502A - Seat belt retractor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a seat belt retractor capable of reliably reducing a load on a chest of an occupant by reliably disconnecting a spindle for winding a seat belt from an electric actuator when a force limiter mechanism is operated. <P>SOLUTION: An unlock ring 84 constituting a changing device 85 of a force limiter mechanism 16 is operated so as to change the energy absorbing force of a torsion bar to release the engagement of a second gear 58 of a power transmission mechanism 17, and to cut off power transmission between a spindle assembly 12 and a motor 34. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a seatbelt retractor, and more particularly to a seatbelt retractor including an electric actuator using a motor, an explosive actuator (pretensioner mechanism), and a force limiter mechanism.

  Conventionally, in this type of seat belt retractor, when there is a possibility of collision, the sensor is activated before the collision, the electric actuator is activated to wind up the seat belt (webbing), the passenger is lightly restrained, At the time of a collision, the seat belt is wound up by the pretensioner mechanism, and the occupant is restrained more reliably. Furthermore, it is known that when a load greater than the set value is applied to the belt, the belt is extended while absorbing energy by a force limiter mechanism to reduce the burden on the occupant's chest (for example, see Patent Document 1). ).

  In the seatbelt retractor described in Patent Document 1, in a power transmission mechanism that transmits power from the electric actuator to the spindle, a clutch is interposed to prevent rotation from the spindle side from being transmitted to the electric actuator.

  The clutch includes a gear wheel and a rotor that are rotated by transmission of rotation of the electric actuator. The rotor is supported by a pawl that is constantly urged in the direction of engagement with the spindle by an urging member, and this pawl is normally held in a disengaged position from the spindle by a holding member provided on the rotor. Has been. When the rotor is rotated about one axis by the driving force of the motor, the holding of the pawl by the holding member is released, and the pawl is engaged with the spindle by the urging force of the urging member. Thereby, the rotation of the rotor is transmitted to the spindle and the spindle rotates. On the other hand, when the rotor rotates around the axis to the other, the holding member moves and holds the pawl to the disengagement position with the spindle against the urging force of the urging member.

In addition, the holding member and the pawl form an inclined surface that generates a drag force in the separation direction so as to maintain the mutual holding state in a state where the rotor is stopped, thereby preventing erroneous clutch engagement.
JP 2006-103657 A

  By the way, in the seat belt retractor, the pawl needs to be held at the disengagement position with the spindle when the force limiter mechanism is operated. there is a possibility.

  Further, depending on the situation of the collision, the electric actuator may be activated after the pretensioner mechanism is activated. In this case, depending on the performance of the ECU that controls the electric actuator, the operation signal of the electric actuator may be continuously sent for a predetermined period after the pretensioner mechanism is operated, and the pawl may engage with the spindle. For this reason, there exists a subject of having a bad influence on operation | movement of a pretensioner mechanism or a force limiter mechanism.

  The present invention has been made in view of the above-described circumstances. An electric actuator that generates power for rotating the spindle, a pretensioner mechanism that generates other power for rotating the spindle, and a load exceeding a set value are applied to the belt. When the force limiter mechanism is actuated, the retractor for the seat belt includes a force limiter mechanism that extends the belt while absorbing energy and reduces the burden on the occupant's chest. An object of the present invention is to provide a seat belt retractor that can reliably reduce the burden on the occupant's chest by reliably disconnecting the connection between the spindle and the electric actuator.

The above object of the present invention is achieved by the following configurations.
(1) a spindle for winding up a seat belt;
An electric actuator that generates power to rotate the spindle;
A pretensioner mechanism for generating other power for rotating the spindle;
A power transmission mechanism capable of transmitting power from the electric actuator to the spindle via a plurality of gears;
Switching between a torsion bar having a plurality of shaft portions having different torsional torques arranged in a force transmission path between the spindle and the pretensioner mechanism, and a plurality of shaft portions of the torsion bar as the force transmission path, A force limiter mechanism having a switching device for switching the energy absorption power of the torsion bar;
A seat belt retractor comprising:
The switching device includes an unlock ring that is arranged coaxially with the spindle and is rotatable so as to switch an energy absorption force of the torsion bar, and a drive device for rotationally driving the unlock ring.
The unlock ring operates so as to switch the energy absorption force of the torsion bar, and disengages any one of the plurality of gears of the power transmission mechanism, so that the power of the spindle and the electric actuator A retractor for a seat belt characterized by disconnecting transmission.
(2) The plurality of gears of the power transmission mechanism are:
A first gear that rotates under the power of the electric actuator;
A second gear disposed around a support shaft formed on the unlock ring and capable of engaging with and disengaging from the first gear according to rotation of the unlock ring;
A third gear that engages with the second gear and that receives the rotation of the second gear and transmits power to the spindle when the first gear and the second gear are engaged;
The retractor for a seat belt according to (1), comprising:
(3) The seat belt retractor according to (2), wherein the first gear includes a torque limiter mechanism that blocks power transmission between a spindle main body and the electric actuator.
(4) The unlocking ring positions the unlocking ring so as to maintain the engagement state between the first gear and the second gear, and is a positioning pin that is broken by the operation of the driving device. The retractor for a seat belt according to (2) or (3), comprising:

  According to the seatbelt retractor of the present invention, the unlocking ring constituting the force limiter mechanism switching device operates to switch the energy absorbing power of the torsion bar, and one of the plurality of gears of the power transmission mechanism. The power transmission between the spindle and the electric actuator is disconnected. As a result, the force from the electric actuator is disconnected during the energy absorption operation, and a belt pulling-out operation can be obtained while absorbing energy stably.

  Next, an example of a seatbelt retractor according to an embodiment of the present invention will be described in detail with reference to the drawings.

  As shown in FIG. 1, a retractor 10 for a seat belt including a retractor according to this embodiment includes a spindle assembly (spindle) 12 that winds up a seat belt (not shown), and the spindle assembly 12 that winds up the seat belt. Winding spring device 13 that biases in the direction, lock mechanism 14 that locks the pull-out operation of the seat belt in accordance with acceleration detected by an acceleration sensor (not shown), and power that rotates the spindle assembly 12 is generated. A motor 34 that is an electric actuator that rotates, a pretensioner mechanism 15 that generates other power for rotating the spindle assembly 12, and a force that feeds out the seat belt while absorbing energy when a load exceeding a set value is applied to the seat belt. The limiter mechanism 16 (see FIG. 2) and the power from the motor 34 are coupled to the spindle assembly. It has a power transmission mechanism 17 capable of transmitting to the body 12, a.

  As shown in FIG. 2, the spindle assembly 12 includes a spindle main body 61, a tread head 62 that closes one end side opening thereof, a torque pipe 63 disposed in the spindle main body 61, a torque tube 64, and a limit torsional torque. The first and second torsion bars 65 and 66 constituted by a plurality of different shaft portions, the lock piece 67 guided by the outer peripheral surface of the tread head 62, and the pair of through holes 61a formed in the spindle 61 are rotated. A locking element 68 that is movably attached, and an end piece 69, a spindle ring 70, and a switch ring 73 that are attached to the periphery from the other end of the spindle 61 are provided. In FIG. 2, reference numeral 71 is a drum ring, and 72 is an omega spring.

  The first torsion bar 65 has a larger shaft diameter than the second torsion bar 66, and both end portions 65a, 65b, 66a, 66b of each torsion bar are formed in a Torx (registered trademark) shape. In the present embodiment, the second torsion bar 66 having a small shaft diameter acts as the force limiter mechanism 16, and the first torsion bar 65 has a twist torque larger than the torque generated by the operation of the pretensioner mechanism 15. The thickness and hardness are designed as follows.

  As shown in FIGS. 2 and 3, a torx-shaped hole 62 a is formed on the inner peripheral surface of the tread head 62, and one end 65 a of the first torsion bar 65 is fitted. A torque-shaped annular groove 64a is also provided on the inner peripheral surface of the torque tube 64 from the tread head side beyond the intermediate portion in the axial direction, and the other end 65b of the first torsion bar 65 and the second torsion bar. One end portion 66a is fitted. The other end 66 b of the second torsion bar 66 is fitted and fixed to a Torx-shaped recess 61 b formed on the inner peripheral surface on the other end side of the spindle 61. As a result, the first and second torsion bars 65 and 66 are arranged in the force transmission path between the spindle 61 and the pretensioner mechanism 15.

  The torque pipe 63 has a plurality of convex portions 63a and 63b on the outer peripheral surfaces of both ends, and the convex portion 63a on one end side is formed in a concave portion 64b formed on the inner peripheral surface of the other end portion of the torque tube 64, and The convex portion 63b is disposed around the second torsion bar 66 in a state where the convex portion 63b is fitted and fixed to a concave portion 61c formed on the inner peripheral surface on the other end side of the spindle 61.

  The locking element 68 is mounted in a through hole 61 a formed in the spindle 61 and rotates so as to advance and retreat in a connecting recess 64 c formed in an end portion of the torque tube 64. In a state where the locking element 68 is pressed against the inner peripheral surface of the spindle ring 70, as shown in FIG. 5 (a), the locking element 68 advances into the connecting recess 64c of the torque tube 64 and rotation is suppressed. Thereby, the torque tube 64 is coupled to the spindle 61 via the pair of locking elements 68, and the spindle 61 and the torque tube 64 rotate integrally. The end piece 69 is made of resin, and the spindle ring 70 is positioned and fixed with respect to the spindle 61.

  The switch ring 73 includes a ring-shaped portion 73a and an arc portion 73c having an inclined surface 73b facing in the axial direction at a part of the outer peripheral side thereof. The switch ring 73 moves in the axial direction by rotation of an unlocking ring 84 described later, and shifts the spindle ring 70 in the axial direction.

  For example, the pretensioner mechanism 15 strongly pushes a ball (not shown) by gas generated by igniting explosive, and the ball moves along the groove of the pretension ring 26. The rotation of the pretension ring 26 is transmitted to the tread head 62, the first torsion bar 65, and the spindle assembly 12 through the lock mechanism 14 and the lock piece 67. If the pretensioner mechanism 15 is configured to be coupled to the spindle assembly 12 via the first and second torsion bars 65 and 66 in this way, the second torsion bar 66 and the spindle constituting the fall limiter mechanism 16 are configured. The pretensioner mechanism 15 is not interposed between the assembly 12 and the operation of the pretensioner mechanism 15 is not affected when the force limiter mechanism 16 is operated. The technology described in Japanese Patent Application No. 2007-008211 can be applied to the specific configuration of the pretensioner mechanism 15.

  A lower cover 25 is attached to the left side surface of the support frame 11 in FIG. Between the lower cover 25 and the support frame 11, a switch housing 81, a switch piston 82 that is a driving device, a path switching gas generator 83, and an unlock ring 84 are provided.

  As shown in FIGS. 4 and 6, the switch housing 81 is formed in the recess 81 b, a cylinder portion 81 a that houses the switch piston 82, a recess 81 b that rotatably holds and holds the unlock ring 84, and A cylindrical portion 81c arranged coaxially with the spindle body 61, a shear pin 81d that is a positioning pin protruding in the axial direction from the side surface in the recess 81b, and a through hole 81e that opens in the side surface of the recess 81b and extends in the axial direction And are formed.

  The unlock ring 84 operates to switch the energy absorption force of the torsion bar, that is, to switch the force transmission path so as to pass through the second torsion bar 66. The unlock ring 84 is disposed so as to be rotatable coaxially with the spindle assembly 12 by the hole portion 84a being interposed in the cylindrical portion 81c of the switch housing 81, and extends radially to the cylinder portion 81a. A driven portion 84b, an extending portion 84c extending in the radial direction on the opposite side of the driven portion 84b with respect to the hole portion 84a, and a second gear shaft (supporting) described later extending in the axial direction from the extending portion 84c. Shaft) 84d and a positioning hole 84e into which the shear pin 81d is inserted. Accordingly, the shear pin 81d inserted into the hole portion 84e positions the unlock ring 84 so as to maintain an engagement state between a first small gear 59 and a second gear 58, which will be described later, and generates a path switching gas. It is broken by the operation of the vessel 83.

  In the through hole 81 e of the switch housing 81, the arc portion 73 c of the switch ring 73 is disposed so as to extend, and the inclined surface 73 b of the arc portion 73 c faces the side surface of the driven portion 84 b of the unlock ring 84.

  Therefore, the switching device 85 that switches the energy absorption force of the torsion bar by switching a plurality of shaft portions (first and second torsion bars 65 and 66) as the force transmission path includes the locking ring element 68, the end It is mainly composed of a piece 69, a spindle ring 70, a switch ring 73, a switch housing 81, a switch piston 82, a path switching gas generator 83, and an unlock ring 84. The force limiter mechanism 16 includes the switching device 85, a torque The pipe 63, the torque tube 64, and the first and second torsion bars 65 and 66 are mainly configured.

  A space for accommodating the power transmission mechanism 17 is formed between the lower cover 25 and the upper cover 53 attached thereto, and a motor assembly 37 is attached to a lower portion of the lower cover 25, that is, a position below the support frame 11. It has been. The motor assembly 37 includes a rear cap 31, a harness 32, a rear case 33, a motor 34, a motor gear 35, and a front case 36. The motor gear 35 is attached to the rotating shaft of the motor 34, is inserted into the lower cover 25, and meshes with the first large gear 57 of the torque limiter mechanism 19 provided in the power transmission mechanism 17.

  The torque limiter mechanism 19 is supported by a first gear shaft 25 a formed on the lower cover 25, and a first small gear 59 that meshes with the second gear 58, and a spring holder 55 that is attached to the first small gear 59 so as to be integrally rotatable. And a plurality of limit springs 56 held by the spring holder 55, and a first large gear 57 that is arranged coaxially with the first small gear 59 and meshes with the motor gear 35. While the limit spring 56 is held by the spring holder 55, one end is engaged with an uneven surface (not shown) formed on the inner peripheral surface of the first large gear 57 and elastically deformed to form the first. The relative rotation of the large gear 57 with respect to the first small gear 59 is allowed.

  In the torque limiter mechanism 19, the first large gear 57 and the first small gear 59, which are the first gear in the normal state, receive the power of the motor 34, and the relative phase is maintained by the limit spring 56 in the same direction. Rotate. The torque limiter mechanism 19 operates when the seat belt is withdrawn, such as during energy absorption after a pretensioner mechanism is activated or during a light collision. When the spindle 61 rotates in the seat belt pull-out direction and a predetermined pull-out torque is applied to the gear of the power transmission mechanism 17, the limit spring 56 is elastically deformed and one end of the limit spring 56 and the first large gear 57 are uneven. The engagement with the surface is released, and the first large gear 57 and the first small gear 59 start to idle. As a result, power transmission between the spindle main body 61 and the motor 34 in the above state is interrupted by the torque limiter mechanism 19 so that an excessive load is not transmitted to these gears and motors.

  In the present embodiment, a gear assembly is configured by the motor gear 35, the first small gear 59, the first large gear 57, the second gear 58, and a third gear 47 which is a final gear described later. The power from the motor 34 is transmitted to the spindle assembly 12 through the plurality of gears 35, 59, 57, 58 and 47. The final gear 47 is coupled to the joint 22 integrally attached to the spindle assembly 12 by internal teeth (not shown) and rotates integrally with the spindle assembly 12. An off-clutch mechanism (not shown) may be added to the final gear 47. This off-clutch mechanism works when the seat belt operates in the winding direction. Specifically, when the spindle rotates at high speed in the belt winding direction, such as when the pretensioner mechanism operates, the off-clutch mechanism causes the spindle 61 to rotate. And the gear assembly are shut off.

  As shown in FIG. 4, the second gear 58 is disposed around a second gear shaft 84 d that is a support shaft of the unlock ring 84 extending from the arc hole 25 b formed in the arc shape in the lower cover 25. Yes. For this reason, before the path switching gas generator 83 which is the driving device of the force limiter mechanism 16 is operated, the second gear 58 is engaged with the first small gear 59 and the final gear 47, respectively. The rotation of 34 is transmitted to the second gear 58, and the final gear 47 receives the rotation of the second gear 58 and transmits power to the spindle assembly 12. Further, when the gas generator 83 is activated, the unlock ring 84 folds the shear pin 81d by the switch piston 82 and rotationally drives it. As a result, the first and second torsion bars 65 and 66 as the force transmission paths described above can be switched, and the second gear 58 supported by the second gear shaft 84d rotates while engaging with the final gear 47. Then, the power transmission between the spindle assembly 12 and the motor 34 is disconnected by releasing the engagement with the first small gear 59.

Next, the operation of the seatbelt retractor 10 including the retractor of the present embodiment will be described.
When there is a possibility of a collision, the spindle assembly 12 is rotated by the motor 34 via the power transmission mechanism 17 before the collision, so that the seat belt is wound to some extent to preliminarily restrain the passenger. When the possibility of the collision is lost, the motor 34 is reversed to return to the state before the collision. In this state, as shown in FIG. 7, the second gear shaft 84 d of the unlock ring 84 moves the second gear at a position where the second gear 58 engages both the first small gear 59 and the final gear 47. I support it.

  When a collision occurs, the pretensioner mechanism 15 directly rotates the spindle assembly 12 at a speed greater than the winding speed of the motor 34 before the collision to wind up the seat belt, thereby firmly restraining the occupant. At this time, the force transmission path during operation of the pretensioner mechanism 15 is the pretension ring 26, the tread head 62, the first torsion bar 65, the torque tube 64, the locking element 68, the spindle body 61, and the webbing.

  At this time, the rotation of the spindle body 61 is cut off from the power transmission between the spindle body 61 and the motor 34 by the clutch mechanism attached to the final gear 47.

  In the force limiter mechanism 16, the switching device 85 is operated at an appropriate timing in accordance with the switching of the force limiter mechanism 16 of the torsion bar. The operation timing of the switching device 85 is appropriately set in advance from the characteristics of the vehicle and the seat belt. For example, the switching device 85 can be set to operate after a predetermined time (ms) after the pretensioner is activated.

  The switching device 85 receives the path switching current and the path switching gas generator 83 ignites. Due to the gas pressure by the path switching gas generator 83, the unlock ring 84 folds the shear pin 81d by the switch piston 82 and rotationally drives it. Then, the side surface of the driven portion 84 b of the unlock ring 84 presses the inclined surface 73 b of the switch ring 73, the switch ring 73 is pushed in the direction of the arrow x in FIG. 3, and the spindle ring 70 is also pushed by the switch ring 73. It shifts in the direction of arrow x.

  When the spindle ring 70 moves in the direction of the arrow x, the relative rotation prevention between the spindle body 61 and the torque tube 64 is released, and the locking element 68 is rotatable in the radial direction of the spindle 61 within the connection hole 61a of the spindle 61. It becomes. For this reason, the profile moves outward from within the connecting recess 64c of the torque tube 64 by the connecting recess 64c of the torque tube 64 formed so as to push the locking element 68 outward (see FIG. 5B). Thereby, the spindle 61 and the torque tube 64 can be relatively rotated. However, in this state, since the spindle 61 and the torque tube 64 are connected by the torque pipe 63, relative rotation is not performed. Therefore, the force transmission path between the tread head 62 and the spindle 61 passes through the two paths of the second torsion bar 66 and the torque pipe 63 through the tread head 62, the first torsion bar 65, and the torque tube 64, and the spindle. The order is 61.

  When the movement of the ball of the pretensioner mechanism 15 is completed and the rotation of the spindle 61 in the winding direction is stopped, the belt is pulled out by the forward movement of the occupant. The force (force transmission path) acting in the belt pull-out direction passes through the spindle body 61, the second torsion bar 66, the torque pipe 63, and the torque tube 64, to the first torsion bar 65, the tread head 62, and the pretensioning ring 26. It is transmitted.

  When the pretension ring 26 is stopped from rotating in the belt pull-out direction, and further a force in the belt pull-out direction is applied and the belt load reaches the torsional load of the second torsion bar 66, the second torsion having a small shaft diameter in the force transmission path. The bar 66 is twisted while being plastically deformed, the spindle 61 rotates, and the seat belt is pulled out. At this time, the second gear 58 of the gear assembly has already been moved from the original position in accordance with the operation of the force limiter mechanism 16, and the power transmission path of the power transmission mechanism is cut off. As a result, even if the belt starts to rotate in the pull-out direction, the gears are mechanically switched without applying an extra load on the gear, so that the reliability of the entire apparatus is also increased.

  The torque pipe 63 is twisted at the same time as the second torsion bar 66 is twisted, but the torque pipe 63 generates a load when it is deformed by twisting, and is twisted off after completing a predetermined rotation. Therefore, in the initial stage of the force limiter operation, the load of the torque pipe 63 can be added in addition to the load at which the second torsion bar 66 starts to be twisted, and the torque pipe 63 starts to twist the second torsion bar 66. It plays a role of supplementing the load. In the torque pipe 63, the generated load and the number of rotations to be twisted are set in advance.

  After the torque pipe 63 is twisted, the force in the pulling direction acting on the spindle 61 absorbs energy by the second torsion bar 66 and the first torsion bar 65 and the tread head via the second torsion bar 66. 62, transmitted to the pretensioning ring 26.

  As shown in FIG. 8, the second gear supported by the second gear shaft 84d by the rotational drive of the unlock ring 84 that operates to switch the first and second torsion bars 65, 66 as the force transmission path. 58 rotates while engaging with the final gear 47 to release the engagement with the first small gear 59. Thereby, the power transmission between the spindle assembly 12 and the motor 34 is disconnected, and it is possible to prevent the force in the belt pulling direction when the force limiter mechanism 16 is operated from being transmitted to the motor 34.

  As described above, according to the seatbelt retractor 10 including the retractor described above, the unlock ring 84 constituting the switching device 85 of the force limiter mechanism 16 operates so as to switch the energy absorption force of the torsion bar and transmits power. The engagement of the second gear 58 of the mechanism 17 is released, and the power transmission between the spindle assembly 12 and the motor 34 is disconnected. As a result, when the force limiter mechanism 16 is activated, the connection between the spindle assembly 12 that winds up the seat belt and the motor 34 is securely disconnected, and the belt can be pulled out while absorbing stable energy. The burden on the chest can be reliably reduced.

  A retractor for a seat belt according to the present invention includes a seat belt (not shown) that directly restrains a generally known occupant to the above retractor, a buckle for fixing an end of the seat belt to a vehicle, and the like ( (Not shown). The seat belt retractor works integrally with the retractor, and can reliably restrain an occupant seated on the seat when the pretensioner is activated in an emergency.

  The seat belt retractor including the retractor described above is a preferable example of the present invention, and other embodiments can be implemented or performed by various methods. The invention is not limited to the detailed shape, size, configuration, and the like of the components shown in the accompanying drawings unless otherwise specified in the present specification. In addition, expressions and terms used in the present specification are for the purpose of explanation, and are not limited thereto unless otherwise specified.

  For example, in the present embodiment, the inclined surface 73b is formed on the switch ring 73, but the inclined surface may be formed on the unlock ring 84 to move the switch ring 73 in the axial direction. Further, without providing the switch ring 73, the unlock ring 84 may directly shift the spindle ring 70 in the axial direction.

  The torsion bar of the present invention may be constituted by two or more torsion bar members, or may be constituted by a single torsion bar member having two or more portions having different shaft diameters.

For example, the technology of Japanese Patent Application No. 2007-145893 may be applied to the specific configuration of the off-clutch mechanism of the power transmission mechanism of the present invention.
Although the second gear of the power transmission mechanism of the present invention can be engaged and disengaged, another gear may be appropriately engaged and disengaged depending on the structure of the power transmission mechanism. In short, the gear assembly may be configured to disengage the gears.

It is a disassembled perspective view of the retractor for seatbelts concerning this invention. FIG. 2 is an exploded perspective view of the spindle assembly of FIG. 1. It is a fragmentary sectional view of the seatbelt retractor of FIG. FIG. 4 is an exploded perspective view partially showing a force limiter mechanism switching device and a power transmission mechanism arranged adjacent to each other. It is sectional drawing along the VV line of FIG. 3, (a) is the state before switching by a switching apparatus, (b) is the state after switching. It is a fragmentary sectional view of a switching device. (A) shows the state of the power transmission mechanism before switching by the switching device, and (b) is a schematic diagram showing the state of the switching device. (A) shows the state of the power transmission mechanism after switching by the switching device, and (b) is a schematic diagram showing the state of the switching device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Seatbelt retractor 12 Spindle 15 Pretensioner mechanism 17 Power transmission mechanism 34 Motor (electric actuator)
47 Final gear (3rd gear)
57 First large gear (first gear)
58 Second gear 59 First small gear (first gear)
61 Spindle 62 Tread head 63 Torque pipe 64 Torque tube 65 First torsion bar (shaft member)
66 Second torsion bar (shaft member)
81 Switch housing 82 Switch piston (drive device)
83 Gas generator for path switching (drive device)
84 Unlock ring 84d Second gear shaft (support shaft)

Claims (4)

A spindle that winds up the seat belt;
An electric actuator that generates power to rotate the spindle;
A pretensioner mechanism for generating other power for rotating the spindle;
A power transmission mechanism capable of transmitting power from the electric actuator to the spindle via a plurality of gears;
Switching between a torsion bar having a plurality of shaft portions having different torsional torques arranged in a force transmission path between the spindle and the pretensioner mechanism, and a plurality of shaft portions of the torsion bar as the force transmission path, A force limiter mechanism having a switching device for switching the energy absorption power of the torsion bar;
A seat belt retractor comprising:
The switching device includes an unlock ring that is arranged coaxially with the spindle and is rotatable so as to switch an energy absorption force of the torsion bar, and a drive device for rotationally driving the unlock ring.
The unlock ring operates so as to switch the energy absorption force of the torsion bar, and disengages any one of the plurality of gears of the power transmission mechanism, so that the power of the spindle and the electric actuator A retractor for a seat belt characterized by disconnecting transmission. The plurality of gears of the power transmission mechanism are
A first gear that rotates under the power of the electric actuator;
A second gear disposed around a support shaft formed on the unlock ring and capable of engaging with and disengaging from the first gear according to rotation of the unlock ring;
A third gear that engages with the second gear and that receives the rotation of the second gear and transmits power to the spindle when the first gear and the second gear are engaged;
The seatbelt retractor according to claim 1, further comprising:   The seat belt retractor according to claim 2, wherein the first gear includes a torque limiter mechanism that interrupts power transmission between a spindle body and the electric actuator.   The unlock ring includes a positioning pin that positions the unlock ring so as to maintain the engagement state between the first gear and the second gear, and is broken by the operation of the driving device. The retractor for a seat belt according to claim 2 or 3, wherein

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