JP2011230558A - Seat belt retractor and seat belt device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect an element of a driving force transmission mechanism using a torque limiter without increasing operation noise, generating an unstable torque limit value or increasing work and cost burdens in design and manufacture processes.SOLUTION: The seat belt retractor 1 includes: a spool 2 that winds a webbing; a motor 11 that generates a rotational driving force to the spool 2; a driving force transmission mechanism 12 that decelerates the rotational driving force of the motor 11 and transmits the force to the spool 2; and a torque limiter 31 that is installed on the driving force transmission mechanism 12 side of the spool 2 and outside the driving force transmission mechanism 12, and that limits torque transmission when a torque of a predetermined level or higher is added to the spool 2. The torque limiter 31 includes a carrier 28, a friction member 38 that comes into surface contact with a friction receiving member at a predetermined contact pressure to generate a frictional force for torque transmission, and a belleville spring 39 that presses the friction member 38 against the carrier 28.

Description

  The present invention relates to a seat belt retractor and a seat belt device provided in a seat belt device for restraining a vehicle occupant in an emergency.

  A seat belt device for restraining an occupant in the event of a vehicle collision or sudden deceleration includes a webbing for restraining the occupant, a seat belt retractor capable of winding the webbing, and a buckle device for setting the webbing. ing. As a seat belt retractor, a motor retractor that winds a webbing by a motor drive has already been proposed. The motor retractor includes a motor for rotating the spool for winding the webbing in the winding direction, and a driving force transmission mechanism with a reduction in rotational speed, and transmits the rotational driving force of the motor to the spool via the driving force transmission mechanism. To do.

  As this motor retractor, one provided with a torque limiter is known (for example, see Patent Documents 1 to 5). The torque limiter transmits torque between the spool and its drive system (consisting of a motor, a driving force transmission mechanism, etc.) when a certain level or more of torque is applied to the spool by generating a certain level of tension on the webbing. Restrict. Thereby, it is possible to prevent excessive torque from being applied to the mechanism elements of the drive system, that is, the gears of the motor and the driving force transmission mechanism (= mechanism element protection function).

  The torque limiters in Patent Documents 1 to 5 all have an “engagement type” structure. This “engagement type” is a system in which torque transmission is limited by engagement of a projecting engagement element with a concave engagement receiving element. Specifically, it is possible to transmit torque below a predetermined limit value by engaging the projecting engagement element with the concave engagement receiving element under an appropriate engagement biasing force such as a spring. To do. On the other hand, when a torque exceeding the predetermined limit value is applied, the engagement element is detached from the engagement receiving element. Thereby, torque transmission can be limited. Such a structure can also be referred to as a “ratchet type” because the engagement relationship between the engagement receiving element and the engagement element is the same as or similar to the ratchet structure.

  The torque limiters disclosed in Patent Documents 1 to 5 are further incorporated into a driving force transmission mechanism in which the torque limiter is integrated as in the structure described in Patent Documents 1 to 4 (= a built-in driving force transmission mechanism type). As in the structure described in Patent Document 5, the torque limiter can be classified into a type (= independent type) that is incorporated independently as a drive system element without being incorporated in the driving force transmission mechanism.

  In addition, as a structure of a motor retractor provided with a torque limiter other than the above, there are conventional techniques described in Patent Document 6 and Patent Document 7.

JP 2004-42788 A JP 2006-282097 A Japanese Patent Laid-Open No. 2005-53422 WO 2006-123750 gazette DE102008004127 publication JP 2010-30592 A JP 2007-22492 A

  The driving force transmission mechanism built-in type torque limiter described in Patent Documents 1 to 4 is not necessarily sufficient for protecting the mechanism elements. That is, until the torque exceeding the limit value is applied to the torque limiter, the excess torque is also added to the mechanism element of the driving force transmission mechanism. In other words, it is unavoidable that torque that transiently exceeds the limit value when torque transmission is limited is added to the mechanism element of the driving force transmission mechanism, which results in insufficient mechanism element protection.

  On the other hand, in the independent type torque limiter described in Patent Document 5, since the torque exceeding the limit value from the spool is directly added to the torque limiter, unlike the above, sufficient mechanism element protection is possible. . However, even with this independent type torque limiter, the following inconvenience derived from the engagement type is inevitable.

  That is, in the engagement type, torque transmission is performed in a state where the engagement element is engaged with the engagement receiving element by the engagement biasing force. Torque transmission is limited by the engagement element being disengaged against the engagement biasing force when the engagement element is engaged with the engagement receiving element. However, in the case of the engagement type, an intermediate state in which the engagement element is not engaged with the engagement receiving element may occur transiently. In this case, there is a possibility that the torque transmission restriction may be performed with an unstable torque limit value that is different from either the torque transmission state or the torque transmission restriction state. In addition, when torque transmission is limited, the engagement receiving element and the engagement element are repeatedly detached and engaged, and the repetition of the disengagement and engagement is accompanied by a periodic operation sound such as “click” or “click”. is there.

  Further, as described above, the engagement type is a structure in which the engagement element of the protruding structure is engaged with the engagement receiving element of the concave structure, so that a lot of fine and complicated parts are required and the necessary torque limit value is obtained. It is also necessary to give these parts the strength necessary to withstand. Furthermore, since the torque limit value depends on the dynamic friction coefficient between the engagement receiving element and the engagement element (which is much smaller than the static friction coefficient), a large urging force is required as the engagement urging force. The performance requirements of the “spring” for biasing the engagement are severe. As a result, the work burden and cost burden in the process of design and manufacture increase.

  In addition, the prior art described in Patent Document 6 is different from the above-described Patent Documents 1 to 5 in main points. That is, in this prior art, a torque limiter is used to cut off the reduced speed ratio path when attempting to rotate the spool through the high speed ratio path of the two speed reduction paths having different speed ratios. For this reason, the torque limit value is set to be considerably smaller than the torque limiters described in Patent Documents 1 to 5 so as to operate when the winding force is relatively small. Not applicable for.

  The prior art described in Patent Document 7 is also different from the above Patent Documents 1 to 5. That is, in this prior art, not only the seat belt is wound by the power of the motor, but also the knee protector is moved backward. For this reason, the torque transmission path is the order of the motor, the gear train, the spool, the torque limiter, the pulley, and the knee protector. That is, the torque limiter is not provided in the transmission path between the motor and the spool, and there is no mechanism element protection function of the driving force transmission mechanism.

  The object of the present invention is to protect the driving force transmission mechanism using a torque limiter without causing operation noise, destabilizing the torque limit value, and increasing the work / cost burden in the design / manufacturing process. It is to provide a seat belt retractor that can be achieved.

  To achieve the above object, the first invention provides a spool for winding a webbing, a motor for generating a rotational driving force to the spool, and a driving force transmission for decelerating and transmitting the rotational driving force of the motor to the spool. And a torque limiter provided on the side of the driving force transmission mechanism of the spool and outside the driving force transmission mechanism, and for limiting transmission of torque when a torque exceeding a certain level is applied to the spool. A seat belt retractor, wherein the torque limiter includes a friction receiving member, a friction member that makes a surface contact with the friction receiving member at a predetermined contact pressure to generate a friction force for torque transmission, and the friction member. A pressing spring that presses against the friction receiving member.

  The torque limiter provided in the seat belt retractor according to the first aspect of the present invention is a friction type by the surface contact of the friction member with the friction receiving member. In the friction formula by surface contact, by ensuring a sufficient friction contact surface, the limit value of the torque that can be transmitted can be increased, and the torque required as the torque limiter of the retractor can be transmitted reliably.

  At this time, the torque limiter is provided outside the driving force transmission mechanism on the side of the driving force transmission mechanism of the spool. Thus, unlike the torque limiter with a built-in driving force transmission mechanism, torque exceeding the limit value is not added to the mechanism element of the driving force transmission mechanism, and the mechanism element can be sufficiently protected.

  In addition, such a friction type torque limiter only stops sliding on the friction surface when shifting from the torque transmission limited state to the torque transmission state, so the transient state such as the engagement type is Absent. Therefore, it is possible to avoid the possibility of performing torque transmission restriction by an unstable torque limit value as in the above engagement type, and almost no operation noise is generated.

  Furthermore, in the friction type torque limiter, the main components of the friction receiving member, the friction member, and the pressing spring can all be formed as a simple flat plate structure, etc. can do. Therefore, the work burden and cost burden in the process of design and manufacture can be greatly reduced.

  According to a second aspect, in the first aspect, the driving force transmission mechanism includes a speed reduction mechanism including a planetary gear mechanism, and a carrier to which a planetary gear in the planetary gear mechanism is assembled is used as the friction member. It is characterized by.

  In a motor retractor, the drive force transmission mechanism usually includes a speed reduction mechanism. In some cases, this reduction mechanism is constituted by a planetary gear mechanism and has a carrier to which a planetary gear in the planetary gear mechanism is assembled. In the second invention of the present application, the carrier which is a standard part in the motor retractor is also used as the friction member.

  Since the carrier is the final output end of the rotational driving force for the spool of the driving system consisting of the motor and the driving force transmission mechanism, it can be limited by incorporating the torque limiter in a position that is reliably independent of the driving force transmission mechanism. It is possible to reliably prevent the torque exceeding the value from being applied to the mechanism element of the driving force transmission mechanism. Further, there is an effect that the structure of the torque limiter can be further simplified.

  According to a third invention, in the first or second invention, a disc spring is used as the pressing spring.

  In order to take advantage of the simplification of the structure of the friction type torque limiter, it is preferable to form the friction receiving member and the friction member with a flat plate structure. When the friction receiving member or the friction member is formed in a flat plate structure, the friction member can be more effectively pressed by using a disc spring as the pressing spring.

  In order to achieve the above object, the fourth invention provides a webbing for restraining an occupant, a seat belt retractor capable of winding the webbing, a buckle connected to a fixed member, and the buckle. The seat belt retractor includes a spool that winds up the webbing, a motor that generates a rotational driving force to the spool, and a motor that decelerates the rotational driving force of the motor to the spool. A transmission force transmission mechanism that transmits the torque, and a torque that is provided on the drive force transmission mechanism side of the spool and outside the drive force transmission mechanism, and that restricts torque transmission when a certain amount of torque is applied to the spool A torque limiter, wherein the torque limiter is in surface contact with the friction receiving member at a predetermined contact pressure and transmits torque. A friction member for generating a frictional force, and having a spring pressing presses the friction member to the friction receiving member.

  The torque limiter provided in the seat belt retractor of the seat belt device according to the fourth aspect of the present invention is a friction type by surface contact of the friction member with the friction receiving member. In the friction formula by surface contact, by ensuring a sufficient friction contact surface, the limit value of the torque that can be transmitted can be increased, and the torque required as the torque limiter of the retractor can be transmitted reliably.

  At this time, the torque limiter is provided outside the driving force transmission mechanism on the side of the driving force transmission mechanism of the spool. Thus, unlike the torque limiter with a built-in driving force transmission mechanism, torque exceeding the limit value is not added to the mechanism element of the driving force transmission mechanism, and the mechanism element can be sufficiently protected.

  In addition, such a friction type torque limiter only stops sliding on the friction surface when shifting from the torque transmission limited state to the torque transmission state, so the transient state such as the engagement type is Absent. Therefore, it is possible to avoid the possibility of performing torque transmission restriction by an unstable torque limit value as in the above engagement type, and almost no operation noise is generated.

  Furthermore, in the friction type torque limiter, the main components of the friction receiving member, the friction member, and the pressing spring can all be formed as a simple flat plate structure, etc. can do. Therefore, the work burden and cost burden in the process of design and manufacture can be greatly reduced.

  According to the present invention, the mechanism elements of the driving force transmission mechanism can be protected by using the torque limiter without causing the generation of operating noise, destabilizing the torque limit value, and increasing the work / cost burden in the design / manufacturing process. Can be planned.

It is a front view showing the whole structure of a seatbelt device provided with a seatbelt retractor by one embodiment of the present invention with a crew member. It is a disassembled perspective view which shows the structure of the seatbelt retractor by one Embodiment of this invention. It is a disassembled perspective view which expands and shows the structure of a torque limiter. It is a figure which simplifies and shows the relationship between a torque limiter and a deceleration mechanism.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a front view showing an entire structure of a seat belt apparatus including a seat belt retractor according to an embodiment of the present invention together with an occupant.

  In FIG. 1, a seat belt device 101 includes a webbing (seat belt) 102, a seat belt retractor 1 that winds up one side of the webbing 102 so that the webbing 102 can be pulled out, a tongue 104 that is slidably provided on the webbing 102, A buckle device 105 that engages with the tongue 104 is provided. One side of the webbing 102 is taken up by the seat belt retractor 1, and is passed through the shoulder anchor 106 on the way, and the other side end is rotatably connected to the vehicle body 108 side by a stopper 107.

2 is an exploded perspective view showing a configuration of a main part of the seat belt retractor according to the present embodiment, FIG. 3 is an exploded perspective view showing an enlarged configuration of a torque limiter (described later), and FIG. It is a figure which simplifies and shows the relationship between a limiter and a deceleration mechanism.
The

  2 to 4, the seat belt retractor 1 includes a spool 2, a lock mechanism (ELR mechanism) 3, a pretensioner 4, and a drive mechanism 5.

  The spool 2 is rotatably supported by a frame 6 formed in a generally box shape, and winds up a webbing 102 (not shown). The spool 2 winds the webbing 102 by the rotational driving force transmitted from the driving mechanism 5 as described later. Further, the torsion bar 7 is assembled to the spool 2 so as to rotate integrally except during a collision.

  The lock mechanism 3 operates in response to the output of a sensor (not shown) that senses when a certain deceleration or more is applied to the vehicle or when the webbing 102 is pulled out at a certain acceleration. Then, the lock mechanism 3 locks the spool 2 with respect to the rotation of the webbing 102 in the pull-out direction. When the lock mechanism 3 is operated, the impact is mitigated by the torsion bar 7. In other words, if the tension of the webbing 102 is applied by the inertial movement of the occupant restrained by the webbing 102 in the state where the rotation of the spool 2 in the pull-out direction is locked by the lock mechanism 3, the torsion bar 7 is twisted and deformed. Then, the torsional deformation of the torsion bar 7 relieves the tension applied to the webbing 102, and thus the impact on the occupant due to the tension applied to the webbing 102 is relieved.

  The pretensioner 4 is a gas generation type, and operates by rapidly generating gas in an emergency such as a vehicle collision. When the pretensioner 4 is operated, the webbing 102 is quickly wound by the spool 2 and the occupant is restrained by the webbing 102.

  The drive mechanism 5 rotationally drives the spool 2 in the winding direction. For this purpose, the drive mechanism 5 includes a motor 11, and the rotational drive force generated by the motor 11 is transmitted to the spool 2 by the drive force transmission mechanism 12. The drive mechanism 5 is assembled to the frame 6 via the retainer 13. Specifically, the motor 11 is mounted on the motor mounting portion 14 of the retainer 13, the driving force transmission mechanism 12 is stored in the driving force transmission mechanism storage portion 15 of the retainer 13, and the driving force transmission mechanism storage portion 15 is retained by the retainer cover. 16 is covered.

  The driving force transmission mechanism 12 has a connect gear 21 that inputs the driving force of the motor 11 via a motor gear 18 fixed to the rotating shaft 17 of the motor 11. The connect gear 21 is formed by integrating a large-diameter input gear 22 and a small-diameter output gear 23, each of which is a spur gear. The connect gear 21 inputs the driving force of the motor 11 by engaging the input gear 22 with the motor gear 18, while outputting the driving force from the output gear 23 to the speed reduction mechanism 24.

  The speed reduction mechanism 24 constitutes a part of the driving force transmission mechanism 12. The speed reduction mechanism 24 is formed of a planetary gear mechanism, and includes an input gear 25, a sun gear 26 (see FIG. 4), a planetary gear 27, and a carrier 28. Further, the speed reduction mechanism 24 further incorporates a clutch mechanism related to transmission of driving force.

  The input gear 25 meshes with the output gear 23 of the connect gear 21 to decelerate the rotational output from the connect gear 21 and input it to the speed reduction mechanism 24. The input gear 25 is integrally formed with a sun gear 26 as shown in FIG.

  A plurality of (5 in this example) planetary gears 27 are used. Each planetary gear 27 is assembled to the carrier 28 by a reduction pin 29 via a reduction plate 30 in a predetermined arrangement (in the example shown in the figure, since there are five planetary gears 27), the planetary gears 27 are assembled. The planetary gears 27 can rotate (spin) while meshing with the sun gear 26 in such an assembled state to the carrier 28.

  The carrier 28 is formed in a disc shape and serves as a final output end of the driving force transmission mechanism 12 via the torque limiter 31. That is, since the planetary gear 27 is assembled to the carrier 28, the carrier 28 is rotated by the revolution that the planetary gear 27 performs with respect to the sun gear 26, and the rotation is the output of the speed reduction mechanism 24, that is, the final driving force transmission mechanism 12. Is transmitted to the spool 2 via the torque limiter 31.

  In this example, the clutch mechanism exhibits a clutch function using a ratchet mechanism. That is, the clutch ring 32 and the clutch pawl 33 are provided. The clutch ring 32 is formed in an annular shape, and ratchet teeth 34 for functioning as a ratchet gear in the ratchet mechanism are formed on the outer periphery. The clutch ring 32 is formed with an internal gear 35 that meshes with each planetary gear 27 on the inner periphery, and rotates according to the rotation of each planetary gear 27. The clutch pawl 33 functions as a pawl in the ratchet mechanism. When the clutch is turned on, the clutch pawl 33 is engaged with the ratchet teeth 34 of the clutch ring 32 by the clockwise rotation of the clutch spring 36 in the state shown in FIG. Make it non-rotatable.

  The torque limiter 31 is interposed between the driving force transmission mechanism 12 and the spool 2 so as to be located outside the driving force transmission mechanism 12. The torque limiter 31 limits torque transmission between the driving force transmission mechanism 12 and the spool 2 when a certain level or more of torque is applied to the spool 2 by generating a certain level of tension on the webbing 102. At this time, the torque limiter 31 performs the torque transmission limiting function as described above in a frictional manner by surface contact. Therefore, as shown in FIGS. 3 and 4, the torque limiter 31 includes an upper plate so as to sandwich the friction member, the upper plate 61 as a friction receiving member, a disc spring 39 (pressing spring), and the disc spring 39. And a lower plate 62 fixed to the plate 61 (see FIGS. 3 and 4).

  The upper plate 61 and the lower plate 62 are integrally configured to have a U shape in cross section, and the disc spring 39 and the carrier 28 of the speed reduction mechanism 24 are included in the U shape. Is placed. The lower plate 62 is fixed to the connector 45 connected to the spool 2, and the disc spring 39 is fixed to the lower plate 62. As a result, the upper plate 61, the lower plate 62, the connector 45, and the disc spring 39 rotate integrally. At this time, the spring force of the disc spring 39 acts in a direction in which the U-shape is to be expanded. At this time, the carrier 28 is also used as a friction member. That is, by receiving the spring force of the disc spring 39 on the back surface of the carrier 28 (the surface opposite to the assembly surface of the planetary gear 27), the carrier 28 also serves as a "friction member". Further, an annular friction surface 41 (see FIG. 4) is provided in a region facing the upper plate 61 on the surface of the carrier 28 (the surface on the assembly surface side of the planetary gear 27), and the pressing force by the spring force is provided. Thus, the friction surface 41 is pressed against the upper plate 61. Thereby, the upper plate 61 functions as a friction receiving member.

  The disc spring 39 is a pressing spring, and causes the friction surface 41 of the carrier 28 to uniformly contact the upper plate 61. As a result, the disc spring 39 generates a frictional resistance between the carrier 28 and the upper plate 61 that enables transmission of torque below a predetermined limit value.

  Next, the operation of the seat belt retractor 1 configured as described above (particularly, the operation in the range related to the function of the torque limiter 31) will be described.

  In a state where the occupant does not wear the webbing 102, the webbing 102 is wound around the spool 2 by the rotational driving force of the motor 11 and the spring spring built in the retainer cover 16. When the non-mounted webbing 102 is properly wound, the motor 11 is stopped and the clutch pawl 33 is separated from the ratchet teeth 34 of the clutch ring 32, so that the clutch ring 32 can rotate. It has become.

  When the webbing 102 is pulled out from the spool 2 so that the occupant wears the webbing 102, the spool 2 rotates in the pull-out direction. At this point, the clutch ring 32 can rotate as described above. Therefore, the rotation of the spool 2 is not transmitted to the motor 11 side, the spool 2 is in a state of rotating lightly, and the webbing 102 can be pulled out smoothly. When the tongue is inserted into the buckle after the webbing 102 is pulled out, the buckle switch is turned on and the motor 11 is ready for operation.

  When the motor 11 rotates in the winding direction (counterclockwise), the rotational driving force is changed from the motor gear 18 → the input gear 22 of the connect gear 21 → the output gear 23 of the connect gear 21 → the input gear 25 of the speed reduction mechanism 24 → the sun gear 26 → the planetary gear 27. And each planetary gear 27 rotates clockwise. At this time, the clutch ring 32 is rotatable. Therefore, the clutch ring 32 meshed with the planetary gear 27 rotates clockwise by the rotation of the planetary gear 27, so that the planetary gear 27 does not rotate and revolves only.

  On the other hand, since the connect gear 21 rotates clockwise, the clutch spring 36 assembled to the connect gear 21 rotates clockwise. Then, the clutch spring 36 rotates the clutch pawl 33 counterclockwise, so that the clutch pawl 33 can be engaged with the ratchet teeth 34 of the clutch ring 32. Since the clutch ring 32 rotates clockwise as described above in this engageable state, the clutch pawl 33 is engaged with the ratchet teeth 34, and the clutch ring 32 cannot be rotated. It becomes a state and the clutch is turned on.

  When the rotation of the clutch ring 32 is stopped, that is, when the clutch is turned on, each planetary gear 27 rotates in the counterclockwise direction with respect to the sun gear 26 in addition to the rotation, and the carrier 28 rotates counterclockwise by the revolution of each planetary gear 27. Rotate to. Then, the rotation of the carrier 28 is transmitted to the spool 2 via the torque limiter 31, whereby the spool 2 rotates in the winding direction and the webbing 102 is wound.

  In a state where the spool 2 is wound by the rotational driving force of the motor 11, a certain tension or more is generated on the webbing 102 to exceed a certain torque (a torque limit value set in the torque limiter 31 is exceeded). When torque is applied to the spool 2, the torque is transmitted to the torque limiter 31. As a result, torque exceeding the frictional resistance between the carrier 28 and the upper plate 61 is applied to the torque limiter 31. As a result, the upper plate 61 slides relative to the carrier 28 so as to rotate relative to the carrier 28 and torque transmission is limited. Thus, torque exceeding the limit value is prevented from being transmitted to the driving force transmission mechanism 12. On the other hand, unless the torque exceeding the limit value is applied to the spool 2, the carrier 28 and the upper plate 61 continue to rotate integrally, and the rotational driving force of the motor 11 can be stably transmitted to the spool 2.

  At this time, the torque limiter 31 is provided closer to the driving force transmission mechanism 12 than the spool 2 so as to be outside the driving force transmission mechanism 12. As a result, torque exceeding the limit value is not applied to each element (deceleration mechanism 24, connect gear 21 and the like) of the drive force transmission mechanism 12 unlike conventional torque limiters with a built-in drive force transmission mechanism. Each element can be well protected.

  This effect will be described more specifically. For example, it is assumed that the reduction ratio between the motor 11 and the spool 2 by the reduction mechanism 24 of the driving force transmission mechanism 12 is 1:40, and the efficiency of the torque transmission path in the driving force transmission mechanism 12 is 50%. In this case, when the motor 11 is driven and the spool 2 is driven, when the motor torque is T (appropriate value), the spool torque is 20T. Conversely, when the spool 2 is driven and the motor 11 is driven, the motor torque becomes T when the spool torque is 80T.

  In this example, if the torque limiter 31 is provided immediately below the spool 2 (in this embodiment), the spool torque at which the torque limiter 31 operates when the spool 2 is driven and the motor 11 is driven is 20T. It can be. On the other hand, if the torque limiter 31 is provided immediately above the motor 11, the torque at which the torque limiter 31 operates needs to be set to T or more, and the spool torque at this time is 80T. That is, depending on whether the position where the torque limiter 31 is installed is directly below the spool 2 or just above the motor 11, the spool torque when the torque limiter is operated varies to 20T or 80T. When the spool torque when the torque limiter 31 is activated is 20T, the resistance strength of each element of the driving force transmission mechanism 12 may be 20T or more, but the spool torque when the torque limiter 31 is activated is In the case of 80T, the strength of each element of the driving force transmission mechanism 12 needs to be 80T or more, and when the strength is less than that, damage or the like may occur.

  In the present embodiment, since the torque limiter 31 is provided immediately below the spool 2 as described above, the spool torque when the torque limiter 31 operates is reduced, and thereby each element (deceleration mechanism) of the driving force transmission mechanism 12 is reduced. 24, connect gear 21 etc.) can be sufficiently protected.

  Further, the torque limiter 31 of the present embodiment only stops the sliding of the carrier 28 and the upper plate 61 when shifting from the torque transmission restricted state to the torque transmission state. There is no transitional state like a limiter. Therefore, it is possible to avoid the possibility of performing torque transmission restriction by an unstable torque limit value as in the engagement type, and almost no operation noise is generated.

  Further, in the torque limiter 31 of this embodiment, the carrier 28 and the disc spring 39, which are main constituent members, can be formed as a comparatively simple flat plate structure, etc. A simple structure can be obtained. Therefore, the work burden and cost burden in the process of design and manufacture can be greatly reduced.

  As mentioned above, although the form for implementing this invention was demonstrated, this is only a representative example and this invention can be implemented with various forms in the range which does not deviate from the meaning. For example, in the above embodiment, a disc spring is used as the pressing spring. However, a spring other than the disc spring may be used as long as it can press and bias the friction member appropriately.

DESCRIPTION OF SYMBOLS 1 Seat belt retractor 2 Spool 7 Torsion bar 11 Motor 12 Driving force transmission mechanism 24 Deceleration mechanism 27 Planetary gear 28 Carrier (friction member)
31 Torque limiter 39 Disc spring (pressing spring)
42 Friction plate part 43 Bracket part 44 Engagement part 45 Connector 53 Male thread part (screwing part)
54 engaging hole 61 upper plate (friction receiving member)
62 Lower plate

Claims (4)

A spool for winding the webbing;
A motor for generating a rotational driving force to the spool;
A driving force transmission mechanism that decelerates and transmits the rotational driving force of the motor to the spool;
A torque limiter that is provided on the driving force transmission mechanism side of the spool and outside the driving force transmission mechanism, and that restricts transmission of torque when a certain torque or more is applied to the spool;
A seat belt retractor comprising:
The torque limiter is
A friction receiving member;
A friction member that generates a friction force for torque transmission by surface contact with the friction receiving member at a predetermined contact pressure;
A seat belt retractor comprising: a pressing spring that presses the friction member against the friction receiving member. The seat belt retractor according to claim 1,
The driving force transmission mechanism is
Includes a speed reduction mechanism composed of a planetary gear mechanism,
As the friction member,
A seat belt retractor using a carrier to which a planetary gear in the planetary gear mechanism is assembled. In the seat belt retractor according to claim 1 or 2,
A seat belt retractor using a disc spring as the pressing spring. Webbing to restrain the occupant,
A seat belt retractor capable of winding the webbing;
A buckle connected to the stationary member;
A tongue provided on the webbing and engaged with the buckle;
The seat belt retractor is
A spool for winding the webbing;
A motor for generating a rotational driving force to the spool;
A driving force transmission mechanism that decelerates and transmits the rotational driving force of the motor to the spool;
A torque limiter that is provided on the driving force transmission mechanism side of the spool and outside the driving force transmission mechanism, and that restricts transmission of torque when a certain torque or more is applied to the spool;
With
The torque limiter is
A friction receiving member;
A friction member that generates a friction force for torque transmission by surface contact with the friction receiving member at a predetermined contact pressure;
A pressing spring that presses the friction member against the friction receiving member;
A seat belt device comprising:

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