Belt retractor
The belt retractor design addresses the challenge of compact integration and progressive force limitation by using a threaded bushing and torsion bars with different deformation limits, achieving efficient and safe force control in vehicle seatbelt systems.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- AUTOLIV DEV AB
- Filing Date
- 2025-12-01
- Publication Date
- 2026-06-11
Smart Images
Figure EP2025084918_11062026_PF_FP_ABST
Abstract
Description
[0001] seatbelt retractor
[0002] The present invention relates to a belt retractor having the features of the preamble of claim 1.
[0003] Seatbelt retractors consist of a load-bearing frame and a belt spool rotatably mounted within the frame, onto which a seatbelt can be wound. Besides supporting the belt spool, the frame also serves to attach the retractor to a seat structure or vehicle body and is therefore made of a sufficiently thick sheet of steel bent into a U-shape.
[0004] Furthermore, modern seatbelt retractors are equipped with force-limiting devices to reduce occupant stress. In an accident, these devices allow for a force-limited extension of the seatbelt until the occupant is, for example, restrained by an airbag. Plastically deformable torsion bars have proven effective for this purpose. One end of these bars is rotationally fixed to the belt reel, while the other end is connected to a section (profile head) that can be locked to the vehicle in an accident via a first locking mechanism. The force-limiting level of the belt extension achieved by such a force-limiting device is defined by the plastic deformation limit of the torsion bar.
[0005] From German patent application DE 199 27 427 A1, a belt retractor is known which has a two-stage torsion bar with two torsion sections having different plastic deformation limits, separated from each other by a central profiled section. The two-stage torsion bar is non-rotatably connected to the profiled head at its free end, which forms the end of the torsion section with the higher force limiting level. The other free end is non-rotatably connected to the belt spool. Furthermore, a switchable second locking device with a torque tube is provided, wherein the torque tube is connected to a profile of the torsion bar in the profiled central section. The switchable second locking device also includes two releasable locking pawls that lock the torque tube relative to the frame of the belt retractor.This means that the torsional section with the lower plastic deformation limit, and thus the lower force limitation level, is bridged at the beginning of the force-limited belt extension. The force-limited belt extension is then enabled at the beginning of the force limitation phase by plastic deformation of the torsional section with the higher plastic deformation limit, resulting in a higher force limitation level. When the second locking device is activated, the locking of the torque tube is released, and further force-limited belt extension is enabled by plastic deformation of the torsional section with the lower plastic deformation limit, again at the lower force limitation level. The two-stage torsion bar, together with the torque tube, is arranged in a cavity of the belt spool, necessitating a belt spool with a correspondingly large cavity and outer diameter.
[0006] Furthermore, it is known to equip seat belt retractors with force-limiting devices featuring a progressive force-limiting curve, i.e., with a continuously or stepwise increasing force-limiting level, provided that the occupant is to be restrained with an increasing restraint force. Such seat belt retractors are used by some vehicle manufacturers to restrain occupants in the rear seats.
[0007] Furthermore, it is known to equip vehicle seats with integrated seat belt systems, in which at least the belt retractors of the seat belt systems are mounted in the backrests of the vehicle seats. In this case, due to the lack of a load-bearing B-pillar and for reasons of access to the rear seats or distance from the rear vehicle structure, the belt retractors are preferably integrated into the backrests of the vehicle seats, which must therefore also be designed to absorb the tensile forces acting in the event of a restraint. The belt retractors themselves have all the basic components of a standard belt retractor and are only equipped with various additional assemblies specifically designed for installation in the backrest, such as a self-aligning inertial sensor.Integrating the system into the backrests is problematic because the available installation space is very small, and the backrests cannot be arbitrarily enlarged or their basic structure modified to accommodate the installation. The backrest structure, specifically designed to absorb the restraining forces in an accident, consists of a truss of struts intended to provide the stiffest possible structure with the lowest possible weight.
[0008] From publication DE 10 2020 211 209 A1, a belt retractor is known which can be attached, for example, to a backrest and has a very compact, and in particular slim, design, in that the torsion bars, the belt shaft, and the profile head are arranged coaxially and in series with each other. Furthermore, axially projecting annular extensions are provided on the facing end faces of the belt spool and the profile head, into which the torsion bars extend. Profiled receptacles are also provided in the annular extensions in which the torsion bars are fixed at one end to prevent rotation.
[0009] Against the background of these requirements, the invention is based on the objective of providing a compact belt retractor with a force limiting device with a simple design and a progressive force limiting characteristic.
[0010] To solve the problem, a belt retractor with the features of claim 1 is proposed. Further preferred developments can be found in the dependent claims, the figures, and the accompanying description.
[0011] According to the basic idea of the invention, it is proposed that a threaded bushing, guided in a rotationally fixed and axially displaceable manner on the second extension of the profile head, is provided, which engages with the torque tube via a threaded drive and, when the second torsion bar is activated, performs a linear displacement movement relative to the torque tube and relative to the second extension, and that a stop is provided to limit the linear displacement movement of the threaded bushing, and that in the contact position against the stop the threaded bushing forms a rotationally fixed connection of the second extension with the torque tube.
[0012] The proposed solution limits the force-limited belt extension to a lower force limitation level, which is made possible by the plastic deformation of the second torsion bar, thus implementing a stop function. In the stop position, the threaded bushing, due to the blocked rotation of the torque tube, forms a rotationally fixed connection between the extension of the profile head and the torque tube. Since the torque tube itself is rotationally fixed to the extension of the belt spool via the second switchable locking device, the belt spool is thus rotationally fixed to the profile head via the torque tube and the threaded bushing. This results in an abrupt increase in the force limitation level for the occupant.Depending on the activation and timing of the second locking device, the connection between the belt spool and the torque tube is released, thus activating the first torsion bar. The force limitation level is then defined by the higher plastic deformation limit of the first torsion bar.
[0013] The stop can preferably be arranged directly on the torque tube, so that the stop position can be defined very precisely due to the elimination of intermediate parts and the resulting shortened tolerance chain.
[0014] It is further proposed that the threaded bushing be formed by a ring that encompasses the torque tube, and that the ring have a radially inwardly projecting collar at one end, and that the stop be formed by an end face of the torque tube against which the threaded bushing comes into contact with the collar during the sliding movement. This allows for a compact and cost-effective design of the belt retractor by utilizing the end face of the torque tube as a stop, thus eliminating the need for additional shaping or machining of the torque tube.
[0015] Alternatively, the stop can preferably be formed indirectly by a part supported on the torque tube, so that the stop can be positioned more favorably for the movement of the threaded bushing, regardless of the shape of the torque tube. Furthermore, it is proposed that the second switchable locking device be switchable by the increasing torque acting between the belt spool and the torque tube when the threaded bushing is in the stop position. Due to the locking of the threaded bushing and the tensile force exerted on the belt spool by the seat belt, the torque exerted by the belt spool on the torque tube increases abruptly, thus subjecting the torque tube to a sudden, higher torque load.This increased torque acting in the connection is now used to switch the second locking device, so that the force limiting device automatically switches from the first lower force limiting level to the higher force limiting level of the first torsion bar.
[0016] It is further proposed that the threaded bushing be connected to the torque tube in a rotationally fixed manner, at least in the contact position against the stop, via a positive locking mechanism. This positive locking mechanism increases the torque that can be transmitted between the threaded bushing and the torque tube. It also increases the available force application area for torque transmission.
[0017] The invention is explained below with reference to preferred embodiments and the accompanying figures.
[0018] Fig. 1 shows a belt retractor according to the invention in sectional view before the activation of a force limiting device, and
[0019] Fig. 2 shows the belt retractor according to the invention in sectional view after activation of the force limiting device, and
[0020] Figure 1 shows a seatbelt retractor 1 with a belt spool 2 rotatably mounted in a frame 3, which is equipped with various additional components. These include a force limiting device 4 and an irreversible pyrotechnic tensioning device 6. The seatbelt retractor 1, together with the frame 3 and the belt spool 2 mounted therein, can be held in a larger housing along with the additional components, or it can be attached directly to the vehicle structure via the frame 3. The housing can be used to mount the seatbelt retractor 1 in the backrest of a vehicle seat or in an elongated installation space within a vehicle structure. Furthermore, an electric motor can be provided for reversible belt tensioning and various other comfort functions, such as a retraction aid, spring adjustment, or seatbelt warning.
[0021] The force limiting device 4 comprises a first torsion bar 8, a second torsion bar 9, a profile head 5, and a second switchable locking device 16, which is coupled to a switching device 17 that may be designed, for example, according to the model of the switching device disclosed in DE 199 27 427 A1. The profile head 5 is a carrier of a first locking device 7 in the form of a pivotable locking pawl, which, when activated by a belt extension acceleration-sensitive sensor device and / or a vehicle acceleration-sensitive sensor device, locks the profile head 5 by engaging a toothed connection on the frame 3 in the extension direction of a safety belt (not shown) wound on the belt spool 2.
[0022] The belt spool 2 has a first tubular extension 11, which is arranged on an end face of the belt spool 2 and extends towards the profile head 5. The first tubular extension 11 has a profiled receptacle that is open axially to the outside. The first torsion bar 8 is fixedly fixed at its first end 25 in the receptacle of the first extension 11 and has an outer profile corresponding to the profile of the receptacle. Furthermore, a torque tube 10 is provided, which projects into the first extension 11 and encompasses the first torsion bar 8. The torque tube 10 is connected to the first extension 11 and thus to the belt spool 2 via the switchable second locking device 16.
[0023] The torque tube 10 simultaneously serves as a rotationally fixed connection between the second profiled end 26 of the first torsion bar 8 and the first profiled end 27 of the second torsion bar 9. For this purpose, the torque tube 10 has a central section with radially inwardly directed projections with which it engages in the outer profiles of the second end 26 of the first torsion bar 8 and the first end 27 of the second torsion bar 9, thereby connecting both ends to each other in a rotationally fixed manner.
[0024] The profile head 5 also has a central profiled receptacle, which is arranged in a second extension 12 extending in the axial direction. The second extension 12 of the profile head 5 is located on the end face of the profile head 5 and extends towards the belt spool 2, i.e., towards the first extension 11 of the belt spool 2. Furthermore, the torque tube 10 has an annular extension at its end, with which it bears against the second extension 12 of the profile head 5. Since the profile head 5 is itself mounted separately from the belt spool 2, it forms a frame-fixed abutment for the torque tube 10 in the locked position.
[0025] To activate the force limiting device 2, the profile head 5 is first locked to the vehicle via the first locking device 7 when a predetermined belt extension acceleration or vehicle deceleration is exceeded, whereby the exceeding of the predetermined limit values is detected by means of the sensor devices described above.
[0026] If the occupant moves forward due to inertia during an accident, the seat belt is extended, and the restraining force, i.e., the tensile force in the seat belt, increases. This causes the belt spool 2 to rotate in the extension direction of the seat belt until further rotation is blocked by the locking mechanism of the profile head 5. Subsequent extension of the seat belt is only possible if this is enabled by activation of the force limiting device 4 and plastic deformation of the two torsion bars 8 and 9.
[0027] Before the second locking device 16 is engaged, the torque tube 10 is rotationally fixed to the belt spool 2, the first extension 11, the second end 26 of the first torsion bar 8, and the first end 27 of the second torsion bar 9, so that the first torsion bar 8 is decoupled from the force flow. During this phase, the second torsion bar 9 is plastically deformed about its longitudinal axis if the pull-out force of the seat belt exceeds the pull-out force defined by the force limiting level of the second torsion bar 9.
[0028] The second torsion bar 9 has a lower force limitation level than the first torsion bar 9, so that a lower force limitation level is effective during this force limitation phase. In this case, the torque tube 10 rotates relative to the blocked profile head 5 and is supported on the second extension 12 of the profile head 7.
[0029] Furthermore, the force limiting device 4 has a threaded bushing 13, which has a cylindrical shape with a radially inwardly extending collar 29 at its right end. The threaded bushing 13 has an internal thread 15 in its left section, which engages with an external thread 14 of the torque tube 10. The collar 29 defines a radially internal non-circular opening in the threaded bushing 13, by which it is guided rotationally fixed and slidably on the second extension 12 of the profile head 5.
[0030] The threaded bushing 13 is thus supported in a rotationally fixed manner against the second extension 12 of the profile head 5 via the collar 29 during the rotational movement of the belt spool 2 in the extension direction. At the same time, due to the thread engagement of the internal thread 15 with the external thread 14, the threaded bushing 13 forms a threaded drive with the torque tube 10, which converts the rotational movement of the belt spool 2 and the torque tube 10 during the force-limited belt extension into a displacement movement of the threaded bushing 13 relative to the second extension 12 of the profile head 5 in the direction of the arrow in Fig. 1.
[0031] The threaded bushing 13 is then moved until it comes to rest with an edge side 30 of the collar 29 against an end face 18 of the torque tube 10, as shown in Fig.
[0032] 2. The end face 18 of the torque tube 10 thus forms a stop to limit the displacement of the threaded bushing 13 and therefore the rotation of the first extension 11 and the belt spool 2. This achieves a force-limiting characteristic with a stop of the force-limited belt extension, which is made possible by the plastic deformation of the second torsion bar 9 at the lower force-limiting level. The torque tube 10 is supported on the first extension 11 either by its rear end face contacting a cone 19 of the cavity in the extension 11 or by a shoulder on the end face of the extension 11. In the stop position of the threaded bushing 13, the torque tube 10 thus provides either direct support or indirect, rotationally fixed support of the threaded bushing 13 on the first extension 11 of the belt spool 2.As a result of the rotationally fixed fixing of the threaded bushing 13 in the stop position, the threaded bushing 13 forms a rotationally fixed connection of the belt spool 2 via the extension 11, the switchable locking device 16, the torque tube 10 with the extension 12 and the blocked profile head 5, so that the force limitation level increases abruptly.
[0033] By activating the second locking device 16 via the switching device 17, the connection between the torque tube 10 and the first extension 11 is released. This places the first torsion bar 8, which has the higher plastic deformation limit, in the force flow from the belt spool 2 to the profile head 5 and thus to the frame 3. Since the first torsion bar 8 has a higher plastic deformation limit than the second torsion bar 9, this enables force-limited belt extension at a higher force limitation level compared to the activation of the second torsion bar 9.
[0034] Since the activation of the first torsion bar 8 depends on the release of the torque tube 10, i.e., the switching of the switching device 17, a force limiting characteristic with a low level and a stop can be achieved depending on the switching of the switching device 17 if the switching device 17 is not actuated, or a force limiting characteristic with three stages and a central peak or a very high force limiting level if the switching device 17 is switched late, or a purely two-stage force limiting characteristic if the switching device 17 is switched as close as possible to the same time as the fixing of the threaded bushing 13.
[0035] For this purpose, the switching device 17 can be designed such that the second blocking device
[0036] The second locking device 16 can be actively switched, for example, by the triggering of a pyrotechnic propellant and the resulting active release movement. Alternatively, the second locking device 16 can also be automatically switched by the torque that suddenly increases in the connection between the belt spool 2 and the torque tube 10 when the threaded bushing 13 is in its stop position, i.e., by the torque acting in the second locking device 16 itself and in the torque tube 10.
[0037] 1 seatbelt retractor
[0038] 2 belt reels
[0039] 3 frames
[0040] 4 Force limiting device 5 Profile head
[0041] 6 Penal Institution
[0042] 7 First blocking device
[0043] 8 First torsion bar
[0044] 9 Second torsion bar 10 Torque tube
[0045] 11 First extension
[0046] 12 Second Appendage
[0047] 13 Threaded bushing
[0048] 14 external threads 15 internal threads
[0049] 16 Second locking device
[0050] 17 Switching device
[0051] 18 Front
[0052] 19 cone 20 inner diameter
[0053] 21 Ring
[0054] 22 Ring
[0055] 23 ring heel
[0056] 24 Ring disc 25 First end
[0057] 26 Second Ending
[0058] 27 First End
[0059] 28 Second Ending
[0060] 29 Collar 30 Edge
Claims
Claims:
1. Belt retractor (1) comprising -a belt spool (2) rotatably mounted in a frame, and -a profile head (5) that can be locked to the vehicle via a first locking device (7), and -a force limiting device (4) arranged between the belt spool (2) and the profile head (5) with at least one first torsion bar (8) with a high plastic deformation limit and a second torsion bar (9) with a lower plastic deformation limit, wherein -the belt spool (2) has a first tubular extension (11) arranged on an end face of the belt spool (2), and -the profile head (5) has a second tubular extension (12) arranged on an end face of the profile head (5), wherein -the first torsion bar (8) in a radially inner cavity of the first extension (11) and the second torsion bar is arranged in a radially inner cavity of the second extension (12), and -a via a second switchable blocking device (16) with the first extension (11) torque tube (10) connected in a rotationally fixed manner -the first torsion bar (8) has a first end (25) connected to the belt spool (2) in a rotationally fixed manner and a second end (26) connected to the torque tube (10), and -the second torsion bar (9) has a first end (27) connected to the torque tube (10) in a rotationally fixed manner and a second end (28) connected to the profile head (7) in a rotationally fixed manner characterized in that -a rotationally fixed and axially displaceable on the second extension (12) of the profile head (5) a guided threaded bushing (13) is provided, which engages with the torque tube (10) via a threaded drive and, when the second torsion bar (9) is activated, performs a linear displacement movement relative to the torque tube (10) and relative to the second forcing set (12), and -a stop is provided to limit the linear displacement movement of the threaded bushing (13), and -the threaded bushing (13) in the contact position against the stop forms a rotationally fixed connection of the second forging set (12) with the torque tube (10).
2. Belt retractor (1) according to claim 1, characterized in that -the stop is located directly on the torque tube (11,12).
3. Belt retractor (1) according to claim 2, characterized in that -the threaded bushing (13) is formed by a ring which encompasses the torque tube (10), and -the ring has a radially inwardly projecting collar (29) arranged at one end, and -the stop is formed by an end face (18) of the torque tube (10), against which the threaded bushing (13) comes into contact with the collar (29) during the sliding movement.
4. Belt retractor (1) according to claim 1, characterized in that -the stop is formed indirectly by a part that is supported on the torque tube (10).
5. Belt retractor (1) according to one of claims 1 to 4, characterized in that -the second switchable locking device (16) can be switched by the torque acting between the belt spool (2) and the torque tube (10) in the stop position of the threaded bushing (13).
6. Belt retractor (1) according to one of claims 1 to 5, characterized in that -the threaded bushing (13) is connected to the torque tube (10) in a rotationally fixed manner at least in the contact position at the stop via a positive locking design.