Assembly formed by a seat belt retractor belt shaft and a drive wheel

Abstract

The invention relates to an assembly formed by a belt retractor shaft (10) and a drive wheel (20), on which a belt tensioner can act in order to drive the belt reel (10) in the reeling direction of the belt, wherein an overload coupling is provided between the drive wheel (20) and the belt reel (10), the overload coupling comprising a plurality of shear elements (24), in particular shear pins, each of which is inserted into an opening of the belt reel (10) and / or the drive wheel (20), the opening extending in the axial direction from the front side of the belt reel (10).

Description

[0001] The invention relates to a subassembly formed by a take-up shaft for a seat belt retractor and a drive wheel on which a belt tensioner can act to drive the take-up shaft in a reeling direction of the seat belt.

[0002] The subassembly is part of a seat belt retractor, which is used, for example, to provide a seat belt to a vehicle occupant of a motor vehicle. For this purpose, the reel shaft is rotatable so that the seat belt can be stretched against the force of a wind-up spring in order to tighten the seat belt. When the vehicle occupant releases the seat belt again, the wind-up spring rotates the reel shaft in the winding direction so that the seat belt is wound up again.

[0003] The belt tensioner serves to drive the belt reel in the winding direction if necessary in order to remove so-called belt slack, ie to tighten the seat belt so that the vehicle occupant participates in the deceleration of the motor vehicle as early as possible.

[0004] Various embodiments of seat belt tensioners are known. They all have in common the fact that they can apply a relatively high torque to the belt reel, thereby tensioning the seat belt with a high force. Depending on the embodiment, the force may be in the range of up to about 3.5 kN.

[0005] The belt tensioner is configured to achieve the required webbing force even when a certain length of the seat belt has to be retracted for this purpose, e.g. when the vehicle occupant is wearing heavy clothing. This capability of the belt tensioner results in the fact that high forces may act if the belt reel cannot rotate or can rotate only very slightly after the belt tensioner is activated.

[0006] The object of the invention is to limit the maximum forces acting in such circumstances.

[0007] To achieve this object, in a subassembly of the type mentioned at the outset, an overload clutch is provided between the drive wheel and the take-up shaft, the overload clutch comprising a plurality of shearing elements, in particular shearing pins, each of which is inserted into an opening in the take-up shaft and / or the drive wheel, the opening extending in the axial direction from the front side of the take-up shaft. In short, the invention is based on the basic idea of ​​providing a predetermined breaking point between the drive wheel on which the belt tensioner acts and the take-up shaft. If the belt tensioner is activated while the take-up shaft is blocked and excessive torques act on the drive wheel, the predetermined breaking point ensures that the drive wheel is detached from the take-up shaft and can rotate substantially freely. This can, for example, prevent excessive pressures from building up in a pyrotechnic belt tensioner. By arranging the shearing elements on the front side of the take-up shaft, it is possible to transmit high torques with small dimensions of the shearing elements and a compact design.

[0008] Preferably, the shearing elements extend in an axial direction. This facilitates easy installation of the subassembly.

[0009] According to one embodiment of the invention, each shearing element is arranged to be formed integrally with the drive wheel or with the belt take-up shaft, for example cast in one piece. This reduces assembly costs.

[0010] According to another embodiment of the invention, each shearing element is arranged to be inserted into an opening of the drive wheel or the take-up shaft, which opening extends in the axial direction starting from the front side of the drive wheel. The opening can be introduced when manufacturing the drive wheel or the take-up shaft, for example when casting the drive wheel or the take-up shaft.

[0011] Alternatively, each shearing element may be inserted into a hole in the drive wheel, the hole extending in the axial direction starting from the front side of the drive wheel.The hole may be manufactured after manufacturing the drive wheel.

[0012] Basically, it is conceivable to adjust the size of the transmittable moment by providing a different number of openings or holes and shearing elements. In this way, the subassembly can be adapted to different requirements without any structural modification.

[0013] When the shearing elements are exposed on the side of the drive wheel remote from the take-up shaft, these shearing elements can be inserted into the opening or hole from the side remote from the take-up shaft.

[0014] According to an alternative embodiment, each shearing element is arranged to be located in a recess of the drive wheel, which recess extends in a radial direction from the outer peripheral surface of the drive wheel. For example, when the damping element is arranged between the belt take-up shaft and the drive wheel, these "pockets" in which the shearing elements are located can allow a certain rotation of the drive wheel relative to the belt take-up shaft.

[0015] The number of shearing elements is selected so as to achieve an optimal compromise between the small size of the individual shearing elements, the space required to accommodate all the shearing elements and the reproducibility of the moments to which the shearing elements respond. 6 to 14 shearing elements have proven to be particularly suitable. However, 2 to 5 shearing elements, preferably arranged symmetrically, are also possible.

[0016] In order to facilitate mounting the drive wheel to the take-up shaft, the take-up shaft may be provided with a guide extension on which the drive wheel is arranged. The guide extension ensures optimal centering of the drive wheel relative to the take-up shaft.

[0017] A positioning design can be provided between the guide extension and the drive wheel, which positioning design ensures a "correct" angular distribution between the drive wheel and the belt take-up shaft, i.e. the shear element can be arranged to be mounted or inserted in a dedicated hole / opening. However, said positioning design cannot transmit significant torque between the guide extension and the drive wheel; the torque of the belt tensioner is (almost) only transmitted via the shear element.

[0018] In the following, the invention will be described by means of different embodiments shown in the accompanying drawings, in which:

[0019] - Figure 1 A seatbelt retractor including a seatbelt tensioner is shown in perspective view;

[0020] - Figure 2 Shows Figure 1 A seat belt retractor wherein the seat belt tensioner is partially removed;

[0021] - Figure 3 Shows Figure 2 A seat belt retractor wherein the drive wheel is unattached;

[0022] - Figure 4 Shown in different perspectives Figure 3 Seat belt retractor;

[0023] - Figure 5 A subassembly according to a first embodiment of the present invention is shown in an enlarged perspective view;

[0024] - Figure 6 With Figure 5 The views corresponding to the views show a subassembly according to a second embodiment of the present invention;

[0025] - Figure 7 With Figure 5 The views corresponding to the views show a subassembly according to a third embodiment of the present invention;

[0026] - Figure 8 With Figure 5The views corresponding to the views show a subassembly according to a fourth embodiment of the present invention;

[0027] - Fig. 9 shows in perspective an axial end portion of a subassembly according to a fourth embodiment of the invention;

[0028] - Fig.10 The fourth embodiment of the present invention is shown. Fig. 9 A top view of the end of the subassembly shown in FIG.

[0029] from Figures 1 to 5 As shown in FIG. 1 , the seat belt retractor 5 comprises a frame 7 in which a belt reel 12 is rotatably arranged.

[0030] A seat belt may be received on the reel shaft, the seat belt being adapted to restrain a vehicle occupant if required. Component parts such as a locking mechanism or a retractor spring are not shown here as they are not relevant to the understanding of the present invention.

[0031] A belt tensioner 14 is arranged on the belt retractor 5, which belt tensioner in the illustrated example has a pressure tube 16 in which a plastic rod (not shown here) is accommodated. When a schematically indicated gas generator 18 is activated, the plastic rod moves out of the pressure tube 16 so that it engages and captures a drive wheel 20. The drive wheel 20 is connected to the belt reel 10 in a rotationally fixed manner. When the belt tensioner is activated, the drive wheel contributes to pressurizing the belt reel 10 in the winding direction.

[0032] The drive wheel 20 comprises on its outer side a plurality of blades 22 which ensure a friction and form fit with the plastic rod.

[0033] In order to connect the drive wheel 20 to the belt take-up shaft 10 , a plurality of shear elements 24 are provided which are arranged on the drive wheel 20 and engage in corresponding openings 26 provided on the belt take-up shaft 10 .

[0034] exist Figures 1 to 5 In the first embodiment shown, the shearing elements 24 are formed integrally with the drive wheel 20, in particular are cast together with the drive wheel. These shearing elements take the form of circular journals.

[0035] The shearing element 24 extends in the axial direction from the front side of the drive wheel 20 facing the belt shaft 10 . Accordingly, the opening 26 is located on the front side of the belt shaft 10 facing the drive wheel 20 .

[0036] The front side of the take-up shaft 10 , where the opening 26 is provided, defines a plane perpendicular to the longitudinal axis of the take-up shaft 10 .

[0037] The take-up shaft 10 is provided with a guide extension 28 on which the drive wheel 20 is received. To ensure that the shearing element 24 is guided into the opening 26 when the drive wheel 20 is mounted, a suitable positioning design may be provided between the guide extension 28 and the inner face of the drive wheel 20 .

[0038] The shear elements 24 are dimensioned so that they can transmit sufficient torque required to tighten the seat belt to the belt reel 10. If the torque is exceeded, the shear elements 24 will shear off so that no further torque is transmitted to the belt reel 10.

[0039] Figure 6 A second embodiment is shown. For component parts known from the first embodiment, the same reference numerals are used and in this respect reference is made to the preceding explanations.

[0040] The difference between the first and second embodiments lies in the fact that in the second embodiment the shearing elements 24 are formed by shearing pins which are formed separately from the drive wheel 20 (and also from the belt take-up shaft 10 ).

[0041] To receive the shearing elements 24, a plurality of continuous pocket openings 30 are provided in the drive wheel 20, which are arranged in an annular shoulder of the drive wheel 20 and are open on the side of the blades 22. Thus, the shearing elements 24 can be installed after the drive wheel 20 has been attached to the take-up shaft 10.

[0042] Figure 7 A third embodiment is shown. For the component parts known from the second embodiment, the same reference numerals are used and in this respect reference is made to the preceding explanations.

[0043] The difference between the second and third embodiments lies in the fact that in the third embodiment the opening 30 is in the form of a hole in the drive wheel 20 .

[0044] exist Figures 8 to 10 For the component parts known from the second and third embodiments, the same reference numerals are used and in this respect reference is made to the preceding explanations.

[0045] The difference between the fourth embodiment and the second and third embodiments lies in the fact that in the fourth embodiment the shearing elements are arranged in pockets 40 provided in a flange 42 of the drive wheel 20. Starting from the outer periphery of the flange 42 the pockets extend inwardly in radial direction.

[0046] Especially from Fig. 9 and Fig.10 As can be seen in FIG. 2 , the pocket has a dimension in the peripheral direction that is slightly larger than the diameter of the shearing element 24 .

Claims

1. A subassembly formed by a take-up shaft (10) for a seat belt retractor and a drive wheel (20), a seat belt tensioner being capable of acting on the drive wheel to drive the take-up shaft (10) in a seat belt winding direction, wherein: An overload clutch is arranged between the drive wheel (20) and the belt shaft (10), the overload clutch comprising a plurality of shearing elements (24), each of the shearing elements being inserted into an opening of the belt shaft (10) and / or the drive wheel (20), the opening extending in an axial direction from the front side of the belt shaft (10), wherein the shearing elements (24) are directly coupled to the belt shaft (10) and the drive wheel (20), and wherein the dimensions of the shearing elements (24) are determined so that they can transmit a sufficient torque required for tightening the seat belt to the belt shaft (10), and if the torque is exceeded, the shearing elements (24) will shear off so that no further torque is transmitted to the belt shaft (10).

2. The subassembly according to claim 1, characterized in that The shearing element (24) is a shearing pin.

3. The subassembly according to claim 1 or 2, characterized in that: The shearing element (24) extends in the axial direction.

4. The subassembly according to claim 1 or 2, characterized in that: Each of the shearing elements (24) is formed integrally with the drive wheel (20).

5. The subassembly according to claim 1 or 2, characterized in that: Each of the shearing elements (24) is inserted into an opening (30) of the drive wheel (20), the opening extending from the front side of the drive wheel (20) in the axial direction.

6. The subassembly according to claim 1 or 2, characterized in that: Each of the shearing elements (24) is inserted into a hole of the driving wheel (20), the hole extending from the front side of the driving wheel (20) in the axial direction.

7. The subassembly according to claim 5, characterized in that The shearing element (24) is exposed on a side of the driving wheel (20) away from the belt take-up shaft (10).

8. The subassembly according to claim 1 or 2, characterized in that: Each of the shearing elements (24) is located in a recess (40) of the driving wheel (20), the recess extending in a radial direction from an outer peripheral surface of the driving wheel (20).

9. The subassembly according to claim 1 or 2, characterized in that: The number of the shearing elements (24) ranges from 6 to 14.

10. The subassembly according to claim 1 or 2, characterized in that: The belt take-up shaft (10) is provided with a guide extension (28) on which the drive wheel (20) is arranged.

11. The subassembly according to claim 10, characterized in that No torque can be transmitted between the guide extension (28) and the drive wheel (20).

Images