CN114655156A

CN114655156A - Safety belt retractor

Info

Publication number: CN114655156A
Application number: CN202011537983.4A
Authority: CN
Inventors: 刘崇庆
Original assignee: Yanfeng Automotive Safety Systems Co Ltd
Current assignee: Yanfeng Automotive Safety Systems Co Ltd
Priority date: 2020-12-23
Filing date: 2020-12-23
Publication date: 2022-06-24

Abstract

The invention relates to a seatbelt retractor, comprising a rotatably mounted belt drum (3) which is designed for winding up a webbing belt, a prestressing device (10) which is designed for driving the belt drum in a webbing belt winding-up direction when it is activated in order to pretension the webbing belt, and a force limiting device (20) which has a drive member and a driven wheel (2) which is designed for limiting the tension of the webbing belt when the webbing belt is pulled out of the belt drum, wherein the driven wheel is connected to the belt drum in a rotationally fixed manner, wherein the rotationally fixed connection of the driven wheel to the belt drum is released beyond a predetermined torque threshold of the belt drum relative to the driven wheel in the webbing belt pulling-out direction. The safety belt retractor can realize a good pre-tightening function and a force limiting function, and at least partially solves the problem of pre-tightening overload.

Description

Safety belt retractor

Technical Field

The present invention relates to a seatbelt retractor. The belt retractor can be used, for example, in vehicles in general, such as motor vehicles, in particular passenger cars.

Background

At present, seat belt retractors are known in the vehicle technology field, which have a pretensioning function and a force limiting function. For the pretensioning function of these seat belt retractors, typically a gas generator is used, which can generate high-pressure gas after an ignition, and drives a driven wheel via a ball or other driving medium, so that the driven wheel drives a belt drum to rotate in the direction of retracting the webbing, thereby pretensioning the webbing. After the pretensioning function is activated, when the occupant pulls the webbing due to inertia, so that the webbing take-up drum of the seatbelt retractor rotates in a webbing pull-out direction opposite to the webbing take-up direction, the force limiting device functions to provide a stable restraining force for the occupant to avoid or reduce injury of the occupant.

In the prior art, the direction of rotation of the belt drum changes during the process from the pretensioning function to the force limiting function, during which the sum of the various resistances in the interior of the belt retractor has to be overcome. These resistances are mainly the residual reverse thrust generated by the gas generator, the friction of the meshing transmission, and the torsion of the torsion bar. After the pulling force of the mesh belt overcomes the residual reverse thrust and the friction force and the belt winding drum rotates in the pulling direction of the mesh belt, the torsion force of the torsion bar which is relatively stable is output to the belt winding drum, so that the force limiting function is realized. Before the force limiting means is activated, i.e., before the spool is rotated in the webbing-pull-out direction, the sum of various resistances needs to be overcome, which causes a peak in the restraining force of the webbing against the occupant. The magnitude of this peak is related to a number of factors and is continuously applied to the spool and ultimately to the fabric. A problem associated therewith can be referred to as a pretension overload problem, wherein the pretension overload situation can also be unstable and thus lead to a low robustness of the protection performance of the restraint system.

In order to reduce the preload overload, it is conceivable to reduce the residual reverse thrust generated by the gas generator. This may mean, however, that a low operating pressure of the gas generator needs to be selected, which, however, also reduces the pretensioning performance; or venting of the gas after the gas generator has been ignited, but this is also at the expense of pretensioning performance and can produce smoke or even open flames when the gas is vented.

Disclosure of Invention

The object of the invention is to provide a belt retractor with which the problem of pretensioning overload can be eliminated.

The object is achieved by a seatbelt retractor comprising a rotatably mounted belt drum configured for winding a webbing belt, a pretensioning device configured for driving the belt drum in a webbing belt take-up direction when the pretensioning device is activated, so that the webbing belt is pretensioned, and a force limiting device having a drive member and a driven wheel, the force limiting device being configured for limiting a tension of the webbing belt when the webbing belt is pulled out of the belt drum, the driven wheel being connected to the belt drum in a rotationally fixed manner, wherein the rotationally fixed connection of the driven wheel to the belt drum is released when a predetermined torque threshold of the belt drum relative to the driven wheel in the webbing belt pull-out direction is exceeded.

When the pretensioning device is activated during operation of the seatbelt retractor, for example due to a vehicle collision, after the pretensioning process has ended, before the force limiting process or at the beginning of the force limiting process, the torsion-resistant connection of the driven wheel to the belt drum can be released by means of the webbing tension, so that the pretensioning overload is no longer transmitted to the webbing in a superimposed manner with the load generated by the force limiting device, and thus the pretensioning overload problem is eliminated and a robust webbing restraint force is achieved.

In some embodiments, the drive member may be a set of spheres, in particular steel balls, and thus the driven wheel may be a ball gear.

In some embodiments, the drive member may be a flexible element, such as a flexible gear or a flexible strip, that is engageable with the driven wheel. The flexible strip may be referred to figuratively as a "snake" because it may travel like a snake in a tortuous guide tube under the impetus of the gas generated by the gas generator.

In some embodiments, the rotationally fixed connection can be realized in the form of a positive-locking connection and/or a material-locking connection.

In some embodiments, the driven wheel and the winding reel can be connected in a rotationally fixed manner by means of at least one pin element.

In some embodiments, the rotationally fixed connection can be realized by a set of pin elements, wherein the winding reel can have a set of circumferentially distributed, preferably axially extending, first recesses, and the driven wheel can have a set of circumferentially distributed, preferably axially extending, second recesses, each of which can be inserted into one of the first recesses and one of the second recesses.

In some embodiments, the seatbelt retractor may include an integral fixing member, which may have a ring from which the set of pin elements axially project. The fixing member may be made of a plastic material, for example, by injection molding.

In some embodiments, at least one pin element of the set of pin elements may have a rated break point.

In some embodiments, all pin elements may be identically formed.

In some embodiments, the tape reel may have a journal projecting axially on the first end side thereof, the driven wheel may be fitted over the journal, the journal may have the set of first grooves, and the driven wheel may have the set of second grooves on an inner circumferential surface thereof.

In some embodiments, the seatbelt retractor may comprise a detent device which is transitionable by the drive member from an inactive state to an active state when the pretensioning device is activated, in which the detent device is capable of locking the driven wheel unidirectionally in a webbing-pull-out direction.

In some embodiments, the stopping means may comprise:

a ratchet wheel provided to the driven wheel;

a movably, preferably pivotably supported pawl;

a spring element biasing the pawl toward the ratchet; and

a movable part which in an initial position, against the biasing force of the spring element, disengages the pawl from the ratchet, which movable part, upon activation of the pretensioning means, can be moved by the drive member out of the initial position, such that the pawl engages the ratchet and thus unidirectionally locks the ratchet in the webbing-pull direction.

In some embodiments, the ratchet wheel can be a separate component and be in driving connection, preferably rotationally fixed, with the driven wheel or can be formed integrally with the driven wheel. Instead of a direct drive connection, the ratchet wheel can also be in drive connection with the driven wheel via a drive mechanism, which can be, for example, a planetary gear mechanism or a spur gear mechanism.

In some embodiments, the retaining device may comprise a base.

In some embodiments, the movable part is guided in a translatory movement.

In some embodiments, the base may have a guide rail, and the movable member is guided by the guide rail.

In some embodiments, the pawl is pivotally supported on the base, such as on a pivot of the base. Alternatively, the pawl is supported on the base body in a translatory manner.

In some embodiments, the spring element may be mounted on the base. The spring element may be, for example, a sheet metal profiled spring, a wire spring, a coil spring, a helical torsion spring or other springs.

In some embodiments, the guide rail may be formed by a sliding hole in the base.

In some embodiments, the sliding bore and the body of the movable member may have complementary non-circular cross-sections. For example, the sliding hole may have the cross-sectional shape of a keyhole.

In some embodiments, the movable member may have a stop projecting laterally from its body.

In some embodiments, in the initial position, the stop may abut against a free end of the pawl.

In some embodiments, the movable part may have a ramp for co-acting with the drive member.

In some embodiments, the pretensioning device can comprise a guide tube in which a plurality of balls are accommodated as drive means and a gas generator arranged on the end of the guide tube remote from the driven wheel, which balls can be guided by the guide tube toward the driven wheel when the gas generator is ignited, the driven wheel being designed as a ball gear having ball sockets between adjacent teeth for receiving the balls.

In some embodiments, the guide tube may have a fully enclosed gas chamber for containing gas generated by the gas generator. A "completely closed gas chamber" can be understood in that no leakage path is provided for the gas chamber for venting gas. Typically, a gas chamber may have a slight leakage of gas due to unintentional gaps that may exist between the components forming the gas chamber. Typically, the gas chamber can be closed off on one side by the gas generator and on the other side by the piston. In contrast, in some prior art there may be a specially designed leakage path in the piston or between the piston and the wall of the guide tube, thereby solving the problem of preload overload. The solution according to the invention with a completely closed gas chamber eliminates the problems associated with gas leakage, while also avoiding the problems of pretension overload. In addition, due to the use of a completely closed gas chamber, a gas generator of lower design pressure can be used, which can have a smaller size and lower cost and improved safety, than in the case of a gas chamber with a leakage path. In an alternative embodiment, the gas chamber may also have a leakage path for venting gas. For example, the leakage path can be designed smaller than in the prior art.

In some embodiments, the force-limiting device can be connected to the winding reel with play, so that the winding reel can be rotated by a free-wheeling angle relative to the force-limiting device. Through the connection with a gap, the superposition of the preload overload and the torsion of the force limiting device can be at least reduced.

In some embodiments, the idle angle can be greater than or equal to a maximum value of a travel angle, wherein, when the pretensioning device is activated, the belt drum is rotated in the webbing-pull-out direction by the travel angle when the belt drum is pulled by the webbing in the webbing-pull-out direction such that the torsion-resistant connection of the driven wheel to the belt drum is released. By the technical measure, superposition of pre-tightening overload and torsion of the force limiting device can be avoided, so that before the force limiting device acts, the effect of the pre-tightening overload on the belt winding drum is relieved, and after the force limiting device acts, the woven belt is only subjected to the torsion load of the force limiting device.

In some embodiments, the free-wheeling angle may be greater than or equal to the sum of a corner and a graduation angle of the teeth of the ratchet wheel, wherein a rotation of the belt drum relative to the driven wheel in the webbing-pull-out direction by the corner releases the rotationally fixed connection of the belt drum to the driven wheel.

In some embodiments, the force limiting device can comprise a torsion bar which is connected with a first end to the spool in a rotationally fixed manner and with a second end to the axle stub in a rotationally fixed manner, wherein the rotationally fixed connection of the first end of the torsion bar to the spool has the gap. In an alternative embodiment, the rotationally fixed connection of the second end of the torsion bar to the axle head is provided with the gap.

In some embodiments, the first and second ends of the torsion beam may have a spline head, respectively, the spool may have a spline recess which is a clearance fit with the spline head of the first end of the torsion beam, and the shaft head may have a spline recess which is an interference fit with the spline head of the second end of the torsion beam.

The individual features mentioned above and those yet to be mentioned below and those which can be derived from the drawings can be combined with one another as desired, provided that the individual features combined with one another are not mutually inconsistent.

Drawings

Exemplary embodiments of the invention are described below with reference to the schematic drawings, in which identical components or functionally identical components are denoted by the same reference numerals.

Fig. 1 is an exploded view of a seatbelt retractor according to an embodiment of the present invention.

Fig. 2 is a perspective view of the seatbelt retractor of fig. 1 in an assembled state.

Fig. 3 is a front view of the seatbelt retractor of fig. 1 in an assembled state.

Fig. 4 is a sectional view taken along section line B-B in fig. 3.

Fig. 5 is a side view of the seatbelt retractor of fig. 1 in an assembled state.

Fig. 6 is a sectional view taken along sectional line C-C in fig. 5.

Fig. 7 is a plan view of a fixing member of the seatbelt retractor of fig. 1.

Fig. 8 is a cross-sectional view of a single pin element.

Fig. 9 is a perspective view of components of the seatbelt retractor of fig. 1.

Fig. 10 is an enlarged partial front view of the assembly of fig. 9.

Fig. 11 is a cross-sectional view of the assembly of fig. 9 taken along the mid-plane of the driven wheel.

Fig. 12 is a view corresponding to fig. 10 in another state.

Fig. 13 is an exploded view of the stop device.

FIG. 14 is a cross-sectional view of the take-up reel in a section engaged with the quincunx head of the torsion bar.

Detailed Description

A general overview of a seat belt retractor according to an embodiment of the present invention is shown in fig. 1 to 6, in which a mounting frame, a mechanical side cover and a coil spring side cover of the seat belt retractor and other components not critical in the present invention are omitted. For example, the seatbelt retractor may include a vehicle feel component and a belt feel component, not shown. The guide tube 7 of the pretensioning device is also omitted in fig. 1 for the sake of simplicity.

The seatbelt retractor may include a spool 3 rotatably supported in the mounting frame. The webbing, not shown, may be wound onto the spool 3 in the webbing take-up direction, and may be pulled out from the spool 3 in a webbing pull-out direction opposite to the webbing take-up direction. The winding reel 3 is configured as a hollow cylinder and has a journal 32 projecting axially on its first end side. On the circumference of the shaft journal 32 there is a set of axially extending first grooves 31 distributed in the circumferential direction. The hollow chamber of the winding reel 3 is open on the second end side of the winding reel. The driven pulley 2, which will be described below, can be placed on the journal 32 in a rotationally fixed manner, and the spindle head 52 can be inserted with its projection into the hollow space of the winding reel 3 on the second end side in a rotatable manner.

The seatbelt retractor may comprise a pretensioning device 10 configured for driving the spool 3 in the webbing retraction direction when it is activated, so that the webbing is pretensioned, enabling a pretensioning function. The pretensioning device 10 can have a gas generator 9, a guide tube 7, a drive member 8 (see fig. 6) and a driven wheel 2. The gas generator 9 may be arranged on the end of the guide tube 7 remote from the driven wheel 2 and may define, with a piston, not shown, movable in the guide tube 7, a gas chamber, which may be, for example, a completely closed gas chamber. A plurality of balls may be accommodated as drive members 8 in the guide tube 7. When the gas generator 9 is ignited, the balls can be driven by the piston and guided by the guide tube 7 towards the driven wheel 2 and thus drive the driven wheel 2 to rotate in the webbing take-up direction. The driven wheel 2 can be designed as a ball gear with ball sockets between adjacent teeth for receiving balls.

The output pulley 2 is connected in a rotationally fixed manner to the winding reel 3, wherein the rotationally fixed connection of the output pulley 2 to the winding reel 3 can be released when a predetermined torque threshold value in the webbing-belt-pulling-out direction of the winding reel 3 relative to the output pulley 2 is exceeded. For this purpose, the seatbelt retractor may comprise an integrated fastening member 1, which may have a ring 12, from which ring 12 a set of pin elements 11 may axially project, and the driven wheel 2 may have on its inner circumferential surface a set of axially extending second grooves 21 distributed in the circumferential direction. Each of the pin elements 11 can be inserted into one of the first recesses 31 and one of the second recesses 21, so that the driven wheel 2 is connected in a rotationally fixed manner to the winding reel 3 by means of the pin elements 11 in a form-fitting manner. The pin element 11 may be made of plastic and/or metal. Preferably the entire fixation member 1 is made entirely of plastic.

Fig. 7 is a plan view of the fixing member 1, and fig. 8 is a cross-sectional view of a single pin element 11. As can be seen from fig. 7, the fixing member 1 has 11 pin elements 11 distributed uniformly in the circumferential direction. Each pin element has a circumferential extension angle a. The extension angle alpha is about 10 deg. in the embodiment shown. In order to facilitate a precise loosening of the rotationally fixed connection under a predetermined load, a part of the pin elements 11 or all of the pin elements 11 may have a predetermined breaking point 13 in order to shear the pin elements 11 by rotation of the tape reel 3 relative to the driven wheel 2. By suitably designing the number of pin elements 11, the effective active length, the cross-sectional area, the rated breaking point, etc., a predetermined load for loosening the torsion-resistant connection can be determined.

The seatbelt retractor may include a force limiting device 20 configured to limit a pulling force of the webbing when the webbing is pulled out from the spool 3. The force limiting device 20 can comprise a torsion bar 4, which torsion bar 4 is connected with a first end in a rotationally fixed manner to the spool 3 and with a second end in a rotationally fixed manner to the axle stub 5. Specifically, the first end portion and the second end portion of the torsion beam 4 may have a

quincunx head

41, 42, respectively. The spool 3 can have a recess 33, see fig. 14, which cooperates with a wobbler head 41 at the first end of the torsion bar 4, in particular a clearance fit, in which the direction of rotation of the spool 3 relative to the torsion bar 4 in the webbing-pull-out direction is indicated by a dashed arrow. The stub shaft 5 may have a quincuncial recess 51 cooperating, in particular an interference fit, with the quincuncial head 42 of the second end of the torsion bar 4. The torsion bar 4 may be twisted off when a predetermined torsion threshold is exceeded and thus limit the maximum restraint force of the webbing. Furthermore, the axle stub 5 can interact with a main locking device, for example, for locking the axle stub 5 and thus the tape reel 3, by means of a locking pawl which is guided in a recess 52 of the axle stub 5 and engages with a toothed ring of the mounting frame when the vehicle-or belt-sensing device is activated.

Advantageously, the force-limiting device 20 can be connected to the winding reel 3 with play, so that the winding reel 3 can be rotated relative to the force-limiting device 20 by a free-wheeling angle β (see fig. 14), which can be, for example, approximately 15 °. It is further advantageous if the free-wheeling angle β is greater than or equal to a maximum value of the stroke angle, wherein, when the pretensioning device 20 is activated, the spool 3 is rotated in the webbing-pull-out direction by the stroke angle when the spool 3 is pulled by the webbing in the webbing-pull-out direction such that the rotationally fixed connection of the driven pulley 2 to the spool 3 is released. In particular, in the embodiment shown, the quincunx head 41 of the first end of the torsion bar 4 has play with the anti-rotation connection of the quincunx recess 33 of the belt drum 3, so that the belt drum 3 can be rotated relative to the torsion bar 4 by a free-wheeling angle β which is greater than or equal to the sum of one rotational angle α which, as will be explained later with reference to fig. 9, can be, for example, approximately 5 °, and the indexing angle γ of the teeth 22 of the ratchet wheel 23, wherein a rotation of the belt drum 3 relative to the driven wheel 2 in the webbing-pull-out direction by the rotational angle α can cause the pin element 11 to shear and thus the anti-rotation connection of the belt drum 3 to the driven wheel 2 to be released. In this preferred embodiment, the problem of overloading the pretensioning is completely avoided, since β ≧ α + γ the rotationally fixed connection of the winding reel 3 to the driven wheel 2 is released after the pretensioning process has ended and before the force limiting process has begun. In a less preferred embodiment, a reduced idle angle, such as α + γ > β ≧ α + γ)/2, or even no idle angle, may also be employed. Preferably, β ≦ 2(α + γ), e.g., β ≦ 1.5(α + γ).

The belt retractor may comprise a stop means 6. Fig. 9 to 13 show an embodiment of the locking device 6. The locking device 6 can be switched by the drive member 8 from an inactive state (see fig. 9 and 10) to an active state (see fig. 12) when the pretensioning device 20 is activated, in which state the locking device 6 can lock the secondary pulley 2 in the webbing-pull direction in one direction.

In the shown embodiment, said arresting means 6 may comprise a ratchet wheel 22 assigned to the driven wheel 2, the teeth 23 of which are one-way teeth, so that the ratchet wheel 22 and thereby the driven wheel 2 can be locked in the webbing-pull-out direction and cannot be locked in the webbing-take-up direction. Advantageously, the ratchet 22 can be formed integrally with the driven wheel 2.

The detent 6 may comprise a pivotably supported pawl 64 and a spring element 63, and a movable part 62, the spring element 63 biasing the pawl 64 towards the ratchet wheel 22, the movable part 62 in an initial position overcoming the biasing force of the spring element 63 such that the pawl 64 is out of engagement with the teeth 23 of the ratchet wheel 22, the movable part 62 being movable away from the initial position by the drive member 8 upon activation of the pretensioning device 20 such that the pawl 64 is engaged with the teeth 23 of the ratchet wheel 22 and thus unidirectionally locks the ratchet wheel 22 in the webbing-pull direction. The direction of rotation of the pawl 64 from the deactivated state to the activated state is indicated by an arrow in fig. 12. Advantageously, the stop means 6 may comprise a base 61, the pawl 64 and the spring element 63 and the movable part 62 may all be mounted on the base 61. The base body 61 can be fixedly mounted, for example, on a mounting frame of a seat belt retractor. In the embodiment shown, the base body 61 can have a guide 66, which is formed in the form of a sliding bore having the cross section of a keyhole. The movable part 62 is guided, preferably translationally movable, by a guide rail 66. The pawl 64 is pivotably supported on a pivot 65 of the base body, and the spring element 63 surrounds the pawl 64. The movable part 62 may have a stop 67 projecting laterally from its body, the stop 67 bearing against a free end 69 of the pawl 64 in the initial position, as shown in fig. 9 and 10. The movable part 62 may also have a ramp 68 for co-action with the drive member 8. As shown in fig. 11, when the prestressing device 20 is activated, the drive member 8, which is formed by a set of balls, is pushed out towards the driven wheel 2. The direction of movement of these spheres is shown by the solid arrows in figure 11. When the foremost ball meets the movable part 62 in the initial position, the ball loads the inclined surface 68 of the movable part 62, so that the movable part 62 moves away from the initial position, and the moving direction of the movable part 62 is shown by the dashed arrow in fig. 11. After the movable part 62 has moved away from the initial position, the stop 67 has moved away from the free end 69 of the pawl 64, the pawl 64 engaging the ratchet wheel 22 under the spring force of the spring 63, embedding in the tooth space between two adjacent teeth 23 of the ratchet wheel 22 (see fig. 12). After the pawl 64 engages the ratchet wheel 22, the ratchet wheel 22 can only still rotate in the webbing take-up direction and cannot rotate in the webbing pull-out direction. When the pawl 64 engages the ratchet wheel 22, the ratchet wheel may have a backlash angle in the reverse rotation from the webbing take-up direction to the webbing pull-out direction, which may randomly be between 0 and the indexing angle γ (see fig. 9) of the teeth of the ratchet wheel.

In the embodiment shown, the driven wheel 2 and the winding reel 3 are interconnected by means of pin elements 11, which pin elements 11 can transmit torque between the driven wheel 2 and the winding reel 3 within set shear limits. When the torque to be transmitted is greater than the shearing limit, the pin element 11 is sheared, during which the spool 3 is rotated relative to the driven wheel 2 by an angle α in the webbing-pull-out direction.

In the embodiment shown, during pretensioning of the webbing, the driven pulley 2 transfers a torque smaller than the shear limit to the spool 3 via the pin element 11, the pin element 11 is not sheared, the spool 3 is rotated in the webbing take-up direction, and the webbing is pretensioned. After the pretensioning process is finished, the webbing is pulled by the load of the occupant to the spool 3. At this time, the detent 6 has been activated, and the spool 3 is unidirectionally locked by the detent 6 and cannot rotate in the webbing-pull-out direction. When the pulling force of the webbing on the spool is sufficiently great, the pin element 11 is sheared off after the spool 3 has passed the idle angle, which may be between 0 and the angle γ, in the webbing-pull-out direction against the resistance and after continued rotation of the angle α in the webbing-pull-out direction relative to the follower 2. Since the sum of the angle α and the angle γ is smaller than or equal to the angle β, the webbing does not have to overcome the resistance force generated by the torsion bar 4 during the shearing of the pin member 11. When the pin member 11 is sheared, the spool 3 can continue to rotate in the webbing-pull-out direction until the idle-stroke angle β is completely eliminated, and then the torsion bar 4 acts to provide a stable force-limiting output to prevent injury to the occupant due to excessive webbing pull.

Although the invention is explained in more detail above with reference to the drawings by means of specific embodiments, the invention is not restricted thereto. The particular embodiments shown are exemplary. Various modifications may be made by those skilled in the art.

For example, as an alternative or in addition to "the driven wheel 2 is positively connected to the winding reel 3 by means of the pin element 11", the driven wheel 2 can be connected to the winding reel 3 in a cohesive manner, for example by welding, which can be broken when a predetermined load threshold is exceeded, and therefore the driven wheel 2 can be released from the winding reel 3. For example, instead of a positive-locking connection by means of a pin element, the driven wheel 2 and the belt drum 3 can also be connected by a serration which can fail when a predetermined load threshold is exceeded. In the embodiment shown, the pin element 11 is mounted in the axial direction. Alternatively, the pin elements can also be mounted radially, and thus the driven wheel 2 and the tape reel 3 can have corresponding radial bores.

For example, instead of an integral torsion bar 4, a torsion bar having two bar sections which can be plugged into one another with a predetermined rotational play in the plugged-in region and which can be connected to the spool 3 and the axle stub 5 in a rotationally fixed manner without play can also be used.

It will be understood that if an element is referred to as being "on," "coupled to" or "connected to" another element, it can be directly on, coupled or connected to the other element or intervening elements may be present. Conversely, if the expressions "directly on … …", "directly coupled with … …", and "directly connected with … …" are used herein, then there are no intervening elements present. Other words used to describe the relationship between elements, such as "between … …" and "directly between … …", "attached" and "directly attached", "adjacent" and "directly adjacent", etc., should be similarly interpreted.

Finally, it is pointed out that the above-described embodiments are only intended to be understood as an example of the invention and do not limit the scope of protection of the invention. It will be apparent to those skilled in the art that modifications may be made in the foregoing embodiments without departing from the scope of the invention.

Claims

1. A seatbelt retractor comprising a rotatably supported spool (3) configured for winding up a webbing, a pretensioning device (10) configured for driving the spool in a webbing take-up direction when it is activated such that the webbing is pretensioned, and a force limiting device (20) having a driving member (8) and a driven wheel (2), the force limiting device being configured for limiting a pulling force of the webbing when the webbing is pulled out of the spool, characterized in that the driven wheel is connected to the spool in a rotationally fixed manner, wherein the rotationally fixed connection of the driven wheel to the spool is released beyond a predetermined torque threshold of the spool relative to the driven wheel in the webbing pull-out direction.

2. The belt retractor according to claim 1, characterised in that the driven wheel is connected in a rotationally fixed manner to the belt drum by means of at least one pin element (11);

preferably, the rotationally fixed connection is realized by a set of pin elements, wherein the winding drum has a set of circumferentially distributed axially extending first grooves (31), the driven wheel has a set of circumferentially distributed axially extending second grooves (21), each pin element being inserted into one of the first grooves and one of the second grooves;

further preferably, the seatbelt retractor comprises an integral fixing member (1) having a ring (12) from which the set of pin elements axially projects.

3. The seatbelt retractor according to claim 1 or 2, characterized in that at least one pin element of the set of pin elements has a rated break point (13); and/or

The winding reel has a journal (32) projecting axially on its first end side, on which journal the driven wheel is fitted, the journal having the set of first grooves, the driven wheel having the set of second grooves on its inner circumferential surface.

4. A seatbelt retractor according to any one of claims 1 to 3, comprising a stop device (6) which, when the pretensioning device is activated, can be transferred by the drive member from an inactive state into an active state in which it can lock the driven wheel unidirectionally in a webbing-pull-out direction, wherein the stop device comprises:

a ratchet wheel (22) associated with the driven wheel;

a movably supported pawl (64);

a spring element (63) biasing the pawl towards the ratchet; and

a movable part (62) which in an initial position disengages the pawl from the ratchet wheel against the biasing force of the spring element, which movable part can be moved by the drive member out of the initial position upon activation of the pretensioning device such that the pawl engages the ratchet wheel and thereby unidirectionally locks the ratchet wheel in a webbing-pull-out direction.

5. The seatbelt retractor according to claim 4, wherein the ratchet is an integral part of the driven wheel or is drivingly connected as a separate component to the driven wheel; and/or

The pawl is pivotably supported and/or the movable part is guided in a translatory movement; and/or

The retaining device comprises a base body (61), wherein the retaining device has at least one of the following features:

a) the base body has a guide rail (66) by which the movable member is guided;

b) the pawl is pivotably supported on a pivot (65) of the base;

c) the spring element is mounted on the base body.

6. The seatbelt retractor according to any one of claims 1 to 5, wherein the movable member has a stop portion (67) projecting laterally from its body, which in the initial position abuts against a free end portion (69) of the pawl; and/or

The movable part has a ramp (68) for co-acting with the drive member.

7. The seatbelt retractor according to any one of claims 1 through 6, wherein the pretensioning means comprises a guide tube (7) having a fully closed gas chamber for accommodating gas generated by a gas generator and a gas generator (9) disposed on an end of the guide tube remote from the driven wheel; and/or

The force-limiting device is connected to the winding drum with a gap, so that the winding drum can be rotated by a free-wheeling angle (beta) relative to the force-limiting device.

8. The seatbelt retractor according to claim 7, wherein the idle travel angle (β) is greater than or equal to a maximum value of a travel angle, wherein the spool rotates in the webbing-pull-out direction by the travel angle when the spool is pulled by the webbing in the webbing-pull-out direction with the pretensioning device activated such that the anti-torque connection of the driven wheel with the spool is released; and/or

The force-limiting device is connected to the winding drum with a gap such that the winding drum can be rotated relative to the force-limiting device by a free-wheeling angle (β) which is greater than or equal to the sum of a rotational angle (α) and the graduation angle (γ) of the teeth of the ratchet wheel, wherein the rotation of the winding drum relative to the driven wheel in the webbing-pulling-out direction by the rotational angle enables a rotationally fixed connection of the winding drum to the driven wheel to be released.

9. The seatbelt retractor according to one of claims 1 to 8, wherein the force limiting device comprises a torsion bar (4) which is connected with a first end to the belt drum in a rotationally fixed manner and with a second end to the axle head (5) in a rotationally fixed manner, wherein the rotationally fixed connection of the first end of the torsion bar to the belt drum carries the gap;

preferably, the first and second ends of the torsion beam have a spline head (41, 42), respectively, the spool has a spline recess (33) which is a clearance fit with the spline head of the first end of the torsion beam, and the stub has a spline recess (51) which is an interference fit with the spline head of the second end of the torsion beam.