Belt retractor for a seat belt system of an automobile

Abstract

To provide a belt retractor that improves the winding and unwinding process of a seat belt. [Solution] A belt retractor (1) for a seat belt device of a motor vehicle, comprising: a belt shaft (2) rotatably mounted on a frame, which winds up a seat belt, the frame having two opposing wall portions (3, 4) oriented parallel to each other, each having a bearing opening (12, 13), and within the wall portion the belt shaft (2) is rotatably mounted; and a spring housing (51) fixed to one of the wall portions (3, 4) and having a return spring (53) disposed therein, the return spring (53) being connected to the spring housing (51) at a first end (55) and connected to the belt shaft (2) at a second end (54) so ​​as to be rotatably fixed, the spring housing (51) being radially elastically held on the wall portions (3, 4).

Description

[Technical field]

[0001] The invention relates to a belt retractor for a seat belt system of a motor vehicle having the features according to the preamble of claim 1.

[0002] A belt retractor of a seat belt device of a motor vehicle has a rotatably mounted belt shaft that is fixedly fastened to the vehicle and can retract the seat belt of the seat belt device. The belt shaft is rotatably mounted to a frame that is fixedly fastened to the vehicle, which at the same time serves to fixedly fasten the belt retractor to the vehicle, the vehicle structure or the vehicle seat. Furthermore, a return spring is provided that is supported on the frame of the belt retractor and spring-biases the belt shaft in the seat belt retracting direction, so that the seat belt can be unwound by pulling the return spring and, after being unwound by driving the belt shaft in the retracting direction, is retracted by the tensioned return spring. It has proven useful to form the return spring by a spiral spring arranged in a spring housing, which is fixed for co-rotation to the frame of the belt retractor and also serves to fasten the outer end of the spiral spring. The inner end of the spiral spring, also called the spring core, is connected to the belt shaft for co-rotation. Furthermore, the spiral spring is wound to pretension the belt shaft in the winding direction via a spring core and is fixedly supported on the vehicle by the outer end of the frame via a spring housing. The return spring is preassembled and fixed in the spring housing and is attached to the belt retractor together with the spring housing as a preassembled assembly, also known as a spring cassette.

[0003] The frame has two opposing bearing openings, each located on a leg of the frame oriented parallel to one another, and the belt shaft is mounted radially in the bearing openings by means of a bearing flange. During assembly, the spring cassette is placed laterally with the spring core on the central axial extension of the belt shaft, connected for co-rotation and fastened to one of the legs of the frame via a spring housing. The spring cassette is designed so that the extension of the belt shaft can be connected to the spring core with a bearing clearance of + / - 1 mm in the axial direction.

[0004] From DE 2 720 959 A1 a belt retractor is known in which the belt shaft is additionally mounted on a point bearing in a spring housing via an axial extension in which a spring core is held.

[0005] From DE 10 2004 008 278 A1, a belt retractor is also known in which the spring core is fixed in a spring cassette by means of locking elements to simplify assembly and is then removed or destroyed once the spring core is connected to the axial extension of the belt shaft.

[0006] From DE 31 08 632 A1 a belt retractor is also known in which the spring cassette is fixed to the legs of the frame via a number of expansion pins which are provided in the spring housing.

[0007] The basic problem is that a return spring designed as a spiral spring not only exerts a circumferential force on the belt shaft: due to its shape and its radially outer fastening to the spring housing in conjunction with its radially inner fastening to the belt shaft, it also exerts radial forces on the belt shaft and on the spring housing. These radial forces must also be absorbed by the belt shaft bearings and can adversely affect the winding and unwinding process of the seat belt, for example by increasing the friction in the belt shaft bearings.

[0008] Against this background, it is an object of the present invention to provide a belt retractor which is improved with regard to the winding and unwinding process of the seat belt.

[0009] To achieve the object, a seat belt retractor is proposed having the features of claim 1. Further advantageous developments of the invention can be taken from the dependent claims, the figures and the associated description.

[0010] To achieve this object, according to claim 1, a belt retractor for a seat belt device of a motor vehicle is proposed, in which a belt shaft is rotatably mounted in a frame for winding up a seat belt of the seat belt device, the frame having two opposing wall parts oriented parallel to each other and each having a bearing opening in which the belt shaft is rotatably mounted, and a spring housing fixed to one of the wall parts, connected at a first end to the spring housing and in which a return spring is arranged, the return spring being fixed at a second end for co-rotation with the belt shaft, the spring housing being radially elastically held in the wall parts.

[0011] By holding the spring housing radially elastically on the frame or a wall portion of the frame of the belt retractor, the spring housing, and therefore also the first end of the return spring held therein, can perform at least a small radial movement, so that the radial force acting on the belt shaft can be reduced, in turn, In particular, this makes it possible to compensate for the radial force exerted by the return spring itself, which actually deforms itself by allowing the first end to flex radially outward or inward.

[0012] The spring housing can preferably have a main housing with a fastening portion arranged radially outwardly, which can preferably be connected to the main housing via an elastically deformable portion. Thus, the fastening of the spring housing is on the one hand intentionally designed to be fixed and on the other hand radially elastic, the fastening via the fastening portion being correspondingly fixed, and the radially elastic mobility of the spring housing is achieved by an intentionally provided deformation portion between the main housing and the fastening portion. The radially elastic mobility of the spring housing is achieved in particular by the design and arrangement of the deformation portion, while the fastening portion can be designed for a functionally reliable and correspondingly secure fastening of the spring housing.

[0013] It is further proposed that the fastening parts are each connected to the main housing via two deformation parts, which together with the deformation parts provided on the fastening parts each define a free space relative to the main housing. The advantage of this solution is that even if one of the deformation parts is damaged, the main housing is still connected to the fastening part via the other deformation part in a functionally reliable manner. Furthermore, the deformation parts and the fastening part complement each other in such a way that they define a free space relative to the main housing, and thus the deformation parts form a continuous connection line together with the fastening parts arranged between them, and the mobility is achieved by the free space formed relative to the main housing and the deformability of the deformation parts.

[0014] It is further proposed that four fastening parts are provided, two fastening parts in each case being arranged symmetrically with respect to one another with respect to the central axis of the belt retractor. The proposed number and arrangement of fastening parts allows a very uniform balancing of the radial forces, directionally neutral with respect to the central axis, by the corresponding deflection movement of the spring housing.

[0015] It is further proposed that the fastening parts are each arranged to form a stop, which limits the radial deflection of the spring housing permitted by the deformation parts. The radial elastic fastening of the spring housing is thus limited to a maximum spring stroke. The elastic spring stroke of the spring housing is preferably dimensioned to be greater than the bearing clearance of the belt shaft at the bearing opening, so that the radial force exerted by the seat belt on the belt shaft stretches the belt shaft at its bearing point, in which case the spring housing does not come into contact with the fastening parts, and therefore the fastening parts are not loaded.

[0016] It is further proposed that the spring housing comprises a cover which is rigidly connected to the spring housing on the side facing the wall section, the cover having an axially projecting annular collar which engages in the bearing opening and is arranged to surround the part of the belt shaft which passes through the bearing opening. In this case, the axially projecting collar additionally forms a bearing ring with an enlarged bearing surface in the bearing opening for the belt shaft. An additional bearing shell or bearing ring in the bearing opening can thus be dispensed with.

[0017] It is further proposed that the wall section in the region of the bearing opening thickens in the axial direction of the belt shaft. With the proposed further development, the wall section itself forms an enlarged contact or riding surface for the belt shaft or the bearing ring.

[0018] It is further proposed that the return spring is connected at its second end in a co-rotating manner to a connecting piece which is connected in a co-rotating manner with the belt shaft, the connecting piece serving for connection to the belt shaft and for this purpose being provided with, for example, a compound tooth or polygonal profile respectively, while the return spring is firmly attached or fastened to the connecting piece by means of its second end.

[0019] It is further proposed that an axial spring is provided between the connecting piece and the belt shaft, which biases the connecting piece into the bearing of the spring housing. The connecting piece is connected to the belt shaft for co-rotation and therefore also performs the rotational movement of the belt shaft. The proposed solution improves the bearing of the connecting piece in its movement, and a fixed spring housing is purposely used for the bearing and at the same time forms the attachment point for the first end of the return spring. The bearing point is preferably a spherical bearing in the form of a hemisphere or part sphere in the spring housing, which due to its shape can preferably absorb both axial and radial forces in a direction-neutral manner.

[0020] It is further proposed that the axial spring is a conical spring, which due to its shape pretensions the connecting piece both axially and radially relative to the bearing point. The pretensioning or radial centering of the connecting piece can be achieved particularly easily by abutting the belt shaft with a conical spring having a larger diameter, so that the conical spring having a smaller diameter abuts the connecting piece and simultaneously centers it.

[0021] It is further proposed that a force limiting device is provided having a profile head which can be blocked by a blocking claw against a block wall section of the frame, the wall section having a bearing opening being arranged on one side of the block wall section, the bearing clearance of the bearing opening in the wall section which is at a greater distance from the block wall section being larger than the bearing clearance of the bearing opening in the wall section which is at a smaller distance from the block wall section. The proposed further development makes it possible to improve the bearing with respect to the bearing forces acting during the operation of the force limiting device, by allowing the belt shaft to bend at an angle and still extend uniformly in the bearing opening. [Brief description of the drawings]

[0022] The present invention will now be described by way of preferred embodiments with reference to the accompanying drawings, in which:

[0023] [Figure 1] 1 shows a belt retractor having a belt shaft and a force limiting device in a cross-sectional view of the belt shaft. [Diagram 2] FIG. 2 shows an exploded view of the belt retractor in a first perspective view. [Diagram 3] FIG. 2 shows an exploded view of the belt retractor in a second perspective view. [Figure 4] 1 shows a cross-sectional view of a belt retractor having a belt shaft and a spring cassette. [Diagram 5] 4 shows an enlarged cross-sectional view of the spring cassette in the region of the connecting piece. [Figure 6] 3 shows an enlarged cross-sectional view of the spring cassette in the area of ​​the connecting piece and the belt shaft. [Figure 7] 5 shows the spring cassette of FIG. 4 as seen from the left towards the spring housing. [Figure 8] 5 shows the spring cassette 5 of FIG. 4 after it has been fastened to the wall section, seen from the right, before the belt shaft is inserted. [Figure 9] 1 shows a belt retractor with a bearing opening having a thickened wall portion. [Figure 10] 1 shows a belt retractor having a spring cassette with a cover having a radial annular collar.

[0024] 1 shows a belt retractor 1 according to the invention with a belt shaft 2 and a force limiting device 6. The belt shaft 2 and the force limiting device 6 are respectively attached to wall parts 3 and 4 oriented parallel to one another. The wall parts 3 and 4 are fixed and divide the interior of a frame (not shown) formed from one or more profiled rails. Alternatively, the wall parts 3 and 4 may be formed by folded legs of a U-shaped frame. The wall parts 3 and 4 are fixedly fastened to the vehicle when the belt retractor 1 is in the fastened state to the vehicle.

[0025] The force limiting device 6 comprises a blockable profile head 8 fixed to the vehicle at the blocking wall portion 7 via a blocking claw 9 and one or more torsion bars (not shown) having one end connected to the profile head 8 and the other end connected or capable of being connected to the belt shaft 2, which, when the profile head 8 is blocked, allows force-limited belt webbing extension of the seat belt by plastic deformation, thereby allowing rotation of the belt shaft 2 in the extension direction.

[0026] Furthermore, a spring cassette 5 is fastened to the left front outer side of the wall portion 3, the structure of which will be described in more detail below. The spring cassette 5 is preassembled and fastened to the wall portion 3 of the belt retractor 1 as an assembly.

[0027] In figures 2 and 3 the same belt retractor 1 can be seen in an exploded view from a different perspective, but without the force limiting device 6 and the right block wall part 7 of figure 1. Each of the wall parts 3 and 4 is provided with a bearing opening 12 and 13 in which a bearing ring 10 and 11 is arranged. The bearing rings 10 and 11 increase the bearing surface available for the belt shaft 2 in the bearing openings 12 and 13 and thus improve the overall bearing. Furthermore, each of the wall parts 3 and 4 is provided with four fastening openings 14 in which the spring cassettes 5 are fastened by means of fastening pins 58.

[0028] FIG. 4 shows in cross section the spring cassette 5 and the belt shaft 2 with the wall parts 3 and 4. The belt shaft 2 extends through the bearing openings 12 and 13 in which the bearing rings 10 and 11 are arranged. The bearing rings 10 and 11 are designed as plastic injection moulded parts and enlarge the bearing surface for the part of the belt shaft 2 passing through the bearing openings 12 and 13. The spring cassette 5 has a hood-shaped spring housing 51 open on one side, which is closed on the open side by a disk-shaped cover part 52. The spring housing 51 thus has a cavity covered by the cover part 52, in which a spiral return spring 53 is arranged. The return spring 53 is connected by its first radially outer end 55 to the spring housing 51 and by its second radially inner end 54 to a connecting piece 56 for co-rotation and thereby to the belt shaft 2 for co-rotation. For this purpose, the connecting piece 56 has a central opening 561 with a multi-toothed profile visible in FIG. 5, in which the belt shaft 2 engages with a correspondingly contoured extension 21 to achieve a co-rotating connection.

[0029] The spring cassette 5 is preassembled with the pretensioned return spring 53 by rotating the connecting piece 56 together with the radially inner second end 54 of the return spring 53 relative to the radially outer first end of the return spring 53 and then fixing it in a predefined pretensioned position relative to the spring housing 51 by means of the retaining clip 16. The connecting piece 56 is fixed in such a position that the spring cassette 5 with the preoriented connecting piece 56 and the multiple teeth arranged therein can be pressed onto the counter profile of the extension 21 and that the fastening pin 58 of the spring housing 51 is aligned with the fastening opening 14 of the wall part 3 and can be inserted therein. After the spring cassette 5 is installed, the retaining clip 16 is removed at the latest after the belt retractor 1 has been installed in the vehicle, so that the return spring 53 can relax and thereby apply the retracting force required for winding the seat belt on the belt shaft 2.

[0030] Furthermore, an axial spring 15 in the form of a conical spring is provided, which is placed on the extension 21 before the spring cassette 5 is installed. The axial spring 15 has a conical shape and is pressed onto the extension 21 with a winding of a larger diameter, so that the axial spring 15 rests axially on the belt shaft 2 with this winding. When the spring cassette 5 is mounted, it comes into axial contact with a connecting piece 56 on the winding of the axial spring 15 with a smaller diameter. Due to its conical shape, the axial spring 15 has a centering effect on itself and on the connecting piece 56, and presses the connecting piece 56 axially against a dome-shaped bearing point 57 in the spring housing 51. The connecting piece 56 has a partly spherical extension on the side facing the bearing point 57, whereby it rests on the surface of the bearing point 57, which is designed as a spherical bearing, as can be seen in Figures 5 and 6, and is therefore supported both axially and radially.

[0031] The belt shaft 2 and the connecting piece 56 are designed so that the spring cassette 5 with the connecting piece 56 can be mounted to the belt shaft 2 with an axial tolerance of + / - 1 mm.

[0032] In Fig. 7 the spring cassette 5 from Fig. 4 can be seen from the left towards the spring housing 51. In Fig. 8 the spring cassette 5 from Fig. 4 can be seen from the right after it has been fastened to the wall part 3 and before the belt shaft 2 is inserted. The spring cassette 5 is inserted into the fastening opening 14 in the wall part 3 by means of the fastening pin 58. The retaining clip 16 fixes the opening 561 and the connecting piece 56 with multiple teeth provided therein so that the belt shaft 2 together with the extension 21 can be inserted in a defined orientation.

[0033] The fixing pins 58 extend axially from the fixing part 59 and are connected to the spring housing 51 via elastically deformable parts 591 and 592, so that together with the fixing part 59 they each enclose a free space 593. The deformable parts 591 and 592 are designed as curved thin-walled webs. Furthermore, the deformable parts 591 and 592 are formed integrally with the spring housing 51 as plastic injection-molded parts. Due to their size, shape and material properties, the deformable parts 591 and 592 are elastically deformable to such an extent that the spring housing 51, to which the first end 55 of the return spring 53 is attached, can perform a slight radial movement relative to the fastening part 59. The fastening parts 59 are each flattened on the side facing the spring housing 51 to form a stop surface 594, so that the possible radial movement of the spring housing 51 is limited. The gap between the stop surface 594 and the spring housing 51 in the unloaded state, i.e. in the initial state without external load, is larger than the gap between the belt shaft 2 and the bearing rings 10 and 11, so that the radial movement of the belt shaft 2 cannot bring the spring housing 51 into contact with the stop surface 594, and the belt shaft 2 stretches over the bearing rings 10 and 11 beforehand during the radial movement. This makes it possible to prevent the stop surface 594 of the fastening part 59 from being loaded by the radial force applied by the seat belt to the belt shaft 2. The stop surface 594 is therefore only loaded when the spring housing 51 is loaded and deflected by the radial force applied by the return spring 53.

[0034] 9 shows an alternative embodiment in which the bearing rings 10 and 11 are not provided. Instead, the wall portions 3 and 4 are transformed by reshaping, such as a deep drawing or stamping process, into bearing portions 31 and 41 which are axially thickened and have correspondingly enlarged radial bearing surfaces.

[0035] 10 shows a further alternative embodiment in which the bearing rings 10 and 11 are not provided. Instead, the cover 52 of the spring cassette 5 has an annular, axially projecting collar 521 which projects into the bearing opening 12 in the left wall part 3 and surrounds the belt shaft 2 in the part that passes through the bearing opening 12.

[0036] Both solutions of Figures 9 and 10 for improving the bearing of the belt shaft 2 represent a feature independent of the mobility of the spring housing 51, which has the advantage that the previously provided bearing rings 10 and 11 can be omitted.

[0037] The proposed mobility of the spring housing 51 by the provided deformations 591 and 592 has the advantage that the radial forces acting on the belt shaft 2 can at least be reduced, since the spring housing 51 itself can be deflected and thereby compensate for the radial forces exerted by the return spring 53. Ideally, the return spring 53 exerts only circumferential forces on the belt shaft 2, so that the rotational movement of the belt shaft 2 during winding and unwinding can be significantly improved. This allows the running and support of the belt shaft 2 to be realized more easily and in particular with less friction.

[0038] As can be seen in Figure 1, the wall parts 3 and 4 are arranged on the same side, in this case to the left of the block wall part 7. In this case, the right-hand wall part 4 with the illustrated bearing opening 13 is at a smaller distance L1 from the block wall part 7, and the left-hand wall part 3 with the illustrated bearing opening 12 is at a larger distance L3 from the block wall part 7. The distance L2 between the two wall parts 3 and 4 with the bearing openings 12 and 13 corresponds to the difference between the larger distance L3 and the smaller distance L1.

[0039] The bearing opening 12 of the wall part 3, which is at a greater distance L3 relative to the block wall part 7, has a larger bearing clearance D2 (in this case 1.07 mm) than the bearing opening 13 of the wall part 4, which is at a smaller distance L1 relative to the block wall part 7, which has a smaller bearing clearance D1 (in this case 0.7 mm). Due to the proposed dimensions of the bearing clearances D1 and D2, the belt shaft 2 extends as uniformly as possible in the bearing openings 12 and 13 of the wall parts 3 and 4, even when the profile head 8 is blocked and the belt shaft 2 is deflected at an angle relative to the block head 8, which in turn results in a more uniform loading of the wall parts 3 and 4 and the belt shaft 2 in the area of ​​the bearing openings 12 and 13.

[0040] Furthermore, the ratio of the distance L2 between the wall portions 3 and 4 to the distance L1 from the right wall portion 4 to the block wall portion 7 is approximately 2:1, i.e., 2 / 3 to 1 / 3. Therefore, the ratio of the distance L1 between the right wall portion 4 and the block wall portion 7 to the distance L3 between the left wall portion 3 and the block wall portion 7 is 2:3, which is ideally approximately the same as the ratio of the bearing gap D1 at the bearing opening 13 of the right wall portion 4 to the bearing gap D2 at the bearing opening 12 of the left wall portion 3, which is 0.7 / 1.07.

Claims

1. A belt retractor (1) for a seat belt system of a motor vehicle, comprising: a belt shaft (2) rotatably mounted on a frame for winding up a seat belt of the seat belt device, the frame having two opposing wall portions (3, 4) oriented parallel to one another, each having a bearing opening (12, 13), within which the belt shaft (2) is rotatably mounted; a spring housing (51) fixed to one of said wall portions (3, 4) and having a return spring (53) disposed therein, said return spring (53) being connected at a first end (55) to said spring housing (51) and at a second end (54) to co-rotate with said belt shaft (2); Equipped with characterised in that the spring housing (51) is held radially elastically on the wall parts (3, 4), Belt retractor (1).

2. The spring housing (51) has a main housing (511) having a fastening portion (59) disposed radially outwardly, The fastening portion (59) is connected to the main housing (511) via an elastically deformable portion (591, 592). A belt retractor (1) according to claim 1.

3. The fastening portions (59) are each connected to the main housing (511) via two deformation portions (591, 592); the fastening portions (59) together with the deformation portions (591, 592) provided thereon each define a free space (593) relative to the main housing (511), A belt retractor (1) according to claim 2.

4. 4. The belt retractor (1) according to claim 2 or 3, characterized in that four fastening portions (59) are provided, in each case two fastening portions (59) being arranged symmetrically with respect to a central axis (M) of the belt retractor (1).

5. 3. The belt retractor (1) according to claim 2, characterized in that the fastening portions (59) are each arranged to form a stop, which limits the radial deflection of the spring housing (51) permitted by the elastic deformation portions (591, 592).

6. the spring housing (51) has a cover (52) rigidly connected to the spring housing (51) on the side facing the wall portions (3, 4); characterised in that the cover (52) has an annular, axially protruding collar (521) which engages with the bearing openings (12, 13) and is arranged to surround the portion of the belt shaft (2) passing through the bearing openings (12, 13), A belt retractor (1) according to claim 1.

7. 2. The belt retractor (1) according to claim 1, characterized in that the wall portions (3, 4) are thickened in the axial direction of the belt shaft (2) in the region of the bearing openings (12, 13).

8. 2. The belt retractor (1) according to claim 1, characterized in that the return spring (53) is connected by the second end (54) for co-rotation to a connecting piece (56) connected to the belt shaft (2) for co-rotation.

9. The belt retractor (1) according to claim 8, characterized in that an axial spring (15) is provided between the connecting piece (56) and the belt shaft (2) for biasing the connecting piece (56) into a bearing (57) of the spring housing (51).

10. 10. The belt retractor (1) according to claim 9, characterized in that the bearing (57) is a spherical bearing in the form of a hemisphere or a partial sphere in the spring housing (51).

11. Belt retractor (1) according to claim 9 or 10, characterized in that the axial spring (15) is a conical spring.

12. 12. The belt retractor (1) according to claim 11, characterized in that the larger diameter of the conical spring is supported on the belt shaft (2).

13. a force limiting device (6) is provided having a profile head (8) which can be blocked by a blocking claw (9) against a blocking wall portion (7) of the frame, The wall portion (3, 4) having the bearing openings (12, 13) is arranged on one side of the block wall portion (7), a bearing gap (D2) of the bearing opening (12) in the wall portion (3) having a larger distance (L3) from the block wall portion (7) is larger than a bearing gap (D1) of the bearing opening (13) in the wall portion (4) having a smaller distance (L1) from the block wall portion (7).

2. The belt retractor of claim 1.

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