BELT RETRACTOR WHICH HAS A FORCE-LIMITING DEVICE AND A DECOUPLING DEVICE

Abstract

The invention relates to a belt retractor for a seat belt of a motor vehicle, comprising a belt shaft (2) which is rotatably mounted in a housing frame (1), a profiled head (3) which can be locked relative to the housing frame (1), and a force-limiting device (4), wherein the force-limiting device (4) is coupled on the one hand to the profiled head (3) and on the other hand to the belt shaft (2) and wherein the force-limiting device (4) allows a force-limited rotation of the belt shaft (2) relative to the locked profiled head (3), characterized by an actively releasable decoupling device (5).

Claims

1. A belt retractor for a seat belt of a motor vehicle having a belt shaft rotatably mounted in a housing frame, a profiled head which can be locked in relation to the housing frame, and a multistage first force-limiting device, wherein the first force-limiting device is coupled on the one hand to the profiled head and on the other hand to the belt shaft and wherein the first force-limiting device allows a force-limited rotation of the belt shaft relative to the locked profiled head, wherein an actively triggerable decoupling device is formed, by means of which the belt shaft can be uncoupled from the force limiter of the multistage first force-limiting device.

2. The belt retractor according to claim 1, wherein a second force-limiting device is provided, wherein the second force-limiting device allows a force-limited rotation of the belt shaft relative to the locked profiled head.

3. The belt retractor according to claim 2, wherein the second force-limiting device is coupled to the profiled head and to the belt shaft both before and after decoupling of the belt shaft from the force limitation of the multistage first force-limiting device.

4. The belt retractor according to claim 2, wherein the second force-limiting device comprises at least one force-limiting element of the following group: a band which deforms during the force limitation, a torsion bar driven for torsion via a gearwheel, a disk arrangement comprising in particular two disk elements, a torsion bar arranged directly in series with the force-limiting elements of the multistage first force-limiting device.

5. The belt retractor according to claim 1, wherein the decoupling device comprises at least one coupling element and one shaft ring, wherein the coupling element is held in an initial state by the shaft ring in a coupling position.

6. The belt retractor according to claim 5, wherein the decoupling device comprises an actively triggerable decoupling drive and, after the decoupling drive has been triggered, the shaft ring is moved by the decoupling drive in such a way that the at least one coupling element is released.

7. The belt retractor according to claim 6, wherein the decoupling drive comprises an adjusting ring and a drive element, wherein the adjusting ring driven by the drive element axially displaces the shaft ring after the decoupling drive is triggered.

8. The belt retractor according to claim 5, wherein the at least one coupling element is wedge-shaped and is mounted so as to be pretensioned radially outward and engages in the coupling position in a positively locking manner in a force-limiting element of the first force-limiting device.

9. The belt retractor according to claim 1, wherein the decoupling device is arranged at least partially in the axial direction between a belt webbing wound onto the belt shaft and an axially mounted housing cap.

10. The belt retractor according to claim 1, wherein the multistage first force-limiting device comprises an actively triggerable switching device by means of which the force-limited relative rotation of the belt shaft can be switched from a first stage to a second stage.

11. The belt retractor according to claim 10, wherein the switching device comprises at least one pawl and one shaft ring, wherein the pawl is held in an initial state by the shaft ring in a position coupling the belt shaft to a first force-limiting element of the first force-limiting device.

12. The belt retractor according to claim 11, wherein the switching device comprises an actively triggerable switching drive and, after the switching drive has been triggered, the shaft ring is moved by the switching drive in such a way that the at least one pawl is released, so that the belt shaft is coupled to a second force-limiting element of the first force-limiting device.

13. The belt retractor according to claim 12, wherein the switching drive comprises an adjusting ring and an drive element, wherein the adjusting ring driven by the drive element displaces the shaft ring axially after the switching drive is triggered.

14. The belt retractor according to one of the preceding claims, wherein the decoupling device is connected in series with a switching device of the multistage first force-limiting device.

15. The belt retractor according to one of the preceding claims, characterized in that an especially pyrotechnic drive of the decoupling device and an especially pyrotechnic drive of a switching device of the multistage first force-limiting device are arranged in a common housing.

16. The belt retractor according to claim 15, wherein the drives are arranged radially offset from one another.

17. The belt retractor according to claim 16, wherein receiving openings for the drives in the common housing overlap in the axial direction.

18. The belt retractor according to claim 15, wherein the common housing is arranged on an end of the belt shaft facing away from the profiled head.

Description

[0034] The invention and the technical environment are explained below by way of example with reference to the figures. The figures show schematically

[0035] FIG. 1: a longitudinal section through a belt retractor in an initial state,

[0036] FIG. 2: a cross-section (B-B) of FIG. 1 provided by the belt retractor, 30

[0037] FIG. 3: a further cross section (C-C) of FIG. 1 through the belt roller;

[0038] FIG. 4: components of the belt retractor according to FIG. 1.

[0039] FIG. 5: further components of the belt retractor included in FIG. 1 in the initial state,

[0040] FIGS. 6-9: the belt retractor after actuating a switching device with a changed force-limiting level

[0041] FIGS. 10-13: the force retractor after actuating a decoupling device in a decoupling state,

[0042] FIG. 14: a partial exploded view of a second embodiment of a belt retractor with a torsion bar of a second force-limiting device drivable by means of a gearwheel,

[0043] FIG. 15: a sectional view through the embodiment of FIG. 14;

[0044] FIG. 16a: a partial exploded view of a third embodiment with a disk arrangement as a force-limiting element of a second force-limiting device,

[0045] FIG. 16b: the disk arrangement from FIG. 16a in plan view,

[0046] FIG. 17: a sectional view of FIG. 16 according to the embodiment,

[0047] FIG. 18: a plan view of a fourth embodiment with a deformable band as a force-limiting element of a second force-limiting device,

[0048] FIG. 19: a sectional view through the embodiment of FIG. 18 in the region of the band in the initial state,

[0049] FIG. 20: the view of FIG. 19 at the end of the force limitation,

[0050] FIG. 21: a partial exploded view of a fifth embodiment with a torsion bar of a second force-limiting device connected in series with the force-limiting elements of the first force-limiting device,

[0051] FIG. 22: a sectional view through the embodiment according to FIG. 21; and

[0052] FIG. 23: a representation of a force profile with three force levels.

[0053] FIG. 24a: examples of connection of force-limiting elements

[0054] FIG. 24b: another example of a connection of the force-limiting elements with reduced installation space

[0055] FIG. 24c: another example of a connection of the force-limiting elements with reduced installation space

[0056] The belt retractor shown in FIGS. 1 to 13 comprises a housing frame 1 in which a belt shaft 2 is rotatably mounted.

[0057] The belt retractor comprises a two-stage first force-limiting device 4 via which the belt shaft 2 is coupled to a profiled head 3 in a first force-limiting stage and in a second force-limiting stage.

[0058] For this purpose, the first force-limiting device 4 comprises a switching device 13 which has two pawls 14, a shaft ring 15, an adjusting ring 16, and a drive element 17 in the form of a gas generator. In the initial state shown in FIGS. 1 to 5 the pawls 14 pivotably mounted with a self-opening tendency are held by the shaft ring 15 in a coupling position, in which the belt shaft 2 is non-rotatably coupled to a transfer tube 20.

[0059] A first force-limiting element 11 in the form of a torsion bar and a second force-limiting element 12 in the form of a further torsion bar are arranged inside the transfer tube 20. The first force-limiting element 11 is non-rotatably coupled to the profiled head 3 on the one hand and on the other hand is non-rotatably connected thereto in the interior of the transfer tube 20. On the one hand, the second force-limiting element 12 is non-rotatably connected to the first force-limiting element 11 and on the other hand in the initial state shown in FIGS. 1 to 5 is non-rotatably connected to the belt shaft 2 via a coupling element 6 of a decoupling device 5.

[0060] The decoupling device 5 further comprises a shaft ring 7, which in the initial state holds the radially outwardly pretensioned coupling elements 6 in the coupling position. The decoupling device 5 additionally comprises an adjusting ring 8, which can be driven by means of a drive element 9 in the form of a gas generator.

[0061] The drive element 9 of the decoupling device 5 and the drive element 17 of the switching device 13 are arranged in a common housing 18, wherein the housing 18 in each case has a receiving opening 19 for the drive elements 9, 17. The receiving openings 19 are offset relative to one another in the radial direction with respect to the belt shaft 2 but overlap in the axial direction, as can be seen in particular from FIG. 1.

[0062] It can be seen from FIG. 4 that the adjusting ring 8 which can be driven by the drive element 9 into a rotational movement and the adjusting ring 16 which can be driven by the drive element 17 into a rotational movement, each rest against a starting angle 21, so that the rotational movement of the adjusting rings 8, 16 caused by the drive elements 9, 17 results in a displacement movement in the axial direction of the belt shaft 2.

[0063] The decoupling device 5 is arranged at least partially between the switching device 13 and a housing cap 10.

[0064] In the initial state shown in FIGS. 1 to 5 the belt shaft 2 is non-rotatably connected to the profiled head 3 via the pawls 14, the transfer tube 20, and the first force-limiting element 11, so that the belt shaft 2 and the profiled head 3 can perform a rotary movement jointly. If the profiled head 3 is now locked to the housing frame 1 by means of a locking device, which is not shown but known per se, a force-limited belt extension rotation of the belt shaft 2 is possible, with which the first force-limiting element 11 is twisted with the belt shaft 2 due to the coupling present via the transfer tube 20 and the pawls 14 and thus absorbs energy (first force-limiting level).

[0065] If a second stage of the force-limited belt webbing extension movement is to be initiated after reaching a specifiable time or a specifiable force-limited belt webbing extension movement, the drive element 17 is ignited in the form of a pyrotechnic gas generator, whereby a piston drives the adjusting ring 16 to rotate. Due to the starting angles 21 on the housing 18, the adjusting ring 16 is displaced axially, as shown in FIG. 6. The axial displacement of the adjusting ring 16 results in the shaft ring 15 also being displaced axially (see FIGS. 7 and 8), whereby the pawls 14 are released. The pawls 14 thus release the non-rotatable coupling between the belt shaft 2 and the transfer tube 20, so that the belt shaft 2 is rotatable relative to the transfer tube 20. In this second stage of the force-limited belt webbing extension movement, however, there continues to be a non-rotatable connection between the belt shaft 2 and the second force transmission element 12 by means of the coupling elements 6. Since the second force-limiting element 12 has a lower force-limiting level than the first force-limiting element 11, a twisting of the second force-limiting element 12 occurs.

[0066] If a maximum force-limited belt webbing extension is now achieved, the belt shaft 2 can be uncoupled from the profiled head 3. For this purpose, the drive element 9 of the decoupling device 5 is ignited, whereby the adjusting ring 8 is driven into a rotational movement which, on account of the starting angles 21, leads to a displacement of the adjusting ring 8 in the axial direction (see FIGS. 10 and 12). Due to the axial displacement of the adjusting ring 8, the shaft ring 7 of the decoupling device 5 is also displaced linearly in the axial direction (see FIG. 11), as a result of which the wedge-shaped coupling elements 6 are released and extend radially outward. As can be seen in particular from FIG. 13, in this state the coupling of the belt shaft 2 to the second force-limiting element 12 is canceled, so that the belt shaft 2 is no longer connected to the locked profiled head 3 and can rotate freely.

[0067] The belt retractor shown in FIGS. 14 and 15 differs from the belt retractor described above in that a gearwheel 24 is non-rotatably coupled to the profiled head 3 and that a torsion bar 25a is provided, which likewise carries at its end a gearwheel which meshes with the toothed wheel 24 in the assembled state. When the belt shaft 2 rotates relative to the profiled head 3, the torsion bar 25a is thus twisted. The torsion bar 25a is thus also coupled to the profiled head 3 after the decoupling device 5 is actuated, so that a force-limited belt webbing extension of the belt is possible even after the decoupling device 5 has been actuated. A second force-limiting device 22 is thus formed in addition to the multistage first force-limiting device 4 already explained above.

[0068] In the embodiment illustrated in FIGS. 16 and 17, a second force-limiting device 22 is formed by a disk arrangement 24 with radial recesses. The disk arrangement 24 includes an outer disk element 27b and an inner disk element 27a. The outer disk element 27b is non-rotatably coupled to the belt shaft 2 by means of a suitable form-fitting design. The inner disk element 27a is non-rotatably coupled to an extension of the profiled head 3 by means of a suitable form-fitting design. The inner disk element 27a has a projection design on its outer circumference and the outer disk element 27b on the inner circumference thereof has a recess design complementary to the projection design. The protrusion design and the recess design engage with each other in the initial state. During a relative rotation of the belt shaft 2 relative to the profiled head 3, the return design and/or the projection design are elastically and/or plastically deformed, whereby energy is absorbed.

[0069] In the embodiment shown in FIGS. 18 to 20, a second force-limiting device 22 is formed by a band 23. The band 23 is connected on the one hand to the belt shaft 2 and on the other hand to the profiled head 3. If a relative rotation occurs between the belt shaft 2 and the profiled head 3, the belt is deformed from the state shown in FIG. 19 into the state shown in FIG. 21, as a result of which the belt webbing extension is force-limited.

[0070] In the embodiment shown in FIGS. 21 and 22, a second force-limiting device 22 is formed by a torsion bar 25b, which is arranged in series with the first force-limiting element 11 and the second force-limiting element 12 of the first force-limiting device 4. In this embodiment, a first transfer tube 20a and a second transfer tube 20b are provided, which are at least partially interlocked in the assembled state. As can be seen in particular from FIG. 22, the first force-limiting element 11 is non-rotatably connected to the profiled head 3 on the right side and is non-rotatably connected to the first transfer tube 20a at its left end. The second force-limiting element 12 is non-rotatably connected to the first force-limiting element 11 on its right side and non-rotatably connected to the second transfer tube 20b on its opposite end. On the other hand, the torsion bar 25b is non-rotatably connected to the second force-limiting element 12 at its right end and is rotatably fixed to the belt shaft 2 at its left end.

[0071] The connection of the force-limiting elements (25b, 11, 12) to one another or the connection to the transfer tubes (20a, 20b) can be effected by corresponding inner and outer contours, which are designed, for example, as internal and fixed toothings. In this case, these are inserted into one another and installation space is thus saved. This is shown by way of example in FIG. 22.

[0072] Alternatively, the parts may be joined together by friction welding, adhesive bonding or soldering. FIG. 24 shows various possibilities of how the force-limiting elements can be connected to one another. FIG. 24a shows a connection, for example friction-welding, of the force-limiting elements (25b, 11, 12), with which the force-limiting elements are connected to one another at their end faces. As shown in FIG. 24b, the end sections of the respective elements can be made thinner or, as illustrated in FIG. 24c, the section of a force-limiting element (25b, 11, 12) to be twisted can be welded directly to the end face of a force-limiting element (25b, 11, 12). Both embodiments of FIGS. 24b and 24c result in a smaller installation space for the arrangement of the force-limiting elements.

[0073] In an initial state, the belt shaft 2 is non-rotatably connected to the first transfer tube 20a via the pawls 14 and is non-rotatably connected to the second transfer tube 20b via the coupling elements 6. If a relative rotation of the belt shaft 2 now occurs after a locking of the profiled head 3, then firstly only the first force-limiting element 11 is twisted with the belt shaft 2 due to its coupling via the pawls 14 and the first transfer tube 20a (first force-limiting level). As soon as the switching device brings the pawls 14 into engagement with the first transfer tube 20a, a twisting of the second force-limiting element 12 takes place within the scope of the second force-limiting level, since these are connected via the coupling elements 6 to the rotating belt shaft 2 which rotates relative to the first transfer tube 20a. Since the force-limiting level of the second force-limiting element 12 is less than the force-limiting level of the first force-limiting element 11, only the second force-limiting element 12 twists.

[0074] When the decoupling device 5 is actuated, the non-rotatable connection from the second transfer tube 20b to the belt shaft 2 is also released, so that a rotation of the belt shaft 2 relative to the second transfer tube 20b is possible. This results in a twisting of the torsion bar 25b, since its force level is smaller than the force levels of the second force-limiting element 12 and the first force-limiting element 11. A belt webbing extension is thus effected at a third force level.

[0075] The time profile of the three-stage belt webbing extension with three force levels is shown in FIG. 23. After the profiled head 3 has been locked, a belt webbing extension at a first force level of, for example, 4-5 kN takes place first. After actuation of the switching device 13, a belt webbing extension is effected at a second force level of 2-3 kN, for example. After actuation of the decoupling device 5 a belt webbing extension is effected at a third force level of for example 1-2 kN.

LIST OF REFERENCE SIGNS

[0076] 1 Housing frame

[0077] 2 Belt shaft

[0078] 3 Profiled head

[0079] 4 First force-limiting device

[0080] 5 Decoupling device

[0081] 6 Coupling element

[0082] 7 Shaft ring

[0083] 8 Adjusting ring

[0084] 9 Drive element

[0085] 10 Housing cap

[0086] 11 First force-limiting element

[0087] 12 Second force-limiting element

[0088] 13 Switching device

[0089] 14 Pawl

[0090] 15 Shaft ring

[0091] 16 Adjusting ring

[0092] 17 Drive element

[0093] 18 Housing

[0094] 19 Receiving opening

[0095] 20, a, b Transfer tube

[0096] 21 Starting angle

[0097] 22 Second force-limiting device

[0098] 23 Band

[0099] 24 Gearwheel

[0100] 25a, b Torsion bar

[0101] 26 Disk arrangement

[0102] 27a, b Disk element