BELT RETRACTOR

Abstract

The invention relates to a belt retractor surrounding a belt reel which is rotatably mounted in a frame, and comprising a force-limiting device with at least one plastically deformable first torsion rod, wherein the first torsion rod has a first end rotationally fixed to the belt reel and a second end rotationally fixed to a profiled head which can be blocked via a first blocking device in a fixed manner relative to the vehicle. The belt reel, the first torsion rod and the profiled head are arranged coaxially to one another and in series relative to one another.

Claims

1. A belt retractor comprising a belt reel which is rotatably mounted in a frame, and a force-limiting device having at least one plastically deformable first torsion rod, wherein the first torsion rod has a first end rotationally fixed to the belt reel and a second end rotationally fixed to a profiled head which can be blocked via a first blocking device in a fixed manner relative to the vehicle, wherein the belt reel the first torsion rod and the profiled head are arranged coaxially to one another and in series relative to one another.

2. The belt retractor according to claim 1, wherein the first torsion rod is arranged in series between the belt reel and the profiled head .

3. The belt retractor according to claim 2, wherein the profiled head and the belt reel are mounted at an axial distance from one another in separate radial bearings.

4. The belt retractor according to claim 1, wherein the first torsion rod is held in a rotationally fixed manner with the first end in a receptacle of the belt reel that is open toward the axial outer side.

5. The belt retractor according to claim 1, wherein at least one second torsion rod is arranged coaxially to and in series relative to the belt reel between the first torsion rod and the profiled head.

6. The belt retractor according to claim 5, wherein the second and the first torsion rod have different plastic deformation limits.

7. The belt retractor according to claim 5, wherein a torque tube is provided which is fixed in relation to the belt reel in a rotationally fixed manner via a switchable second blocking device, wherein the torque tube connects the two mutually facing ends of the first torsion rod and of the second torsion rod to each other in a rotationally fixed manner.

8. The belt retractor according to claim 7, wherein an axially projecting protrusion is provided on the belt reel in relation to which the torque tube is fixed via the switchable second blocking device.

9. The belt retractor according to claim 8, wherein the axial protrusion is annular, and the torque tube projects radially inwardly into the annular protrusion or surrounds the annular protrusion radially on the outside.

10. The belt retractor according to claim 7, wherein an axially projecting annular protrusion is provided on the profile head, and the torque tube projects radially inwardly into the annular protrusion or surrounds the annular protrusion radially on the outside.

11. The belt retractor according to claim 1, wherein the belt reel is designed as a solid shaft.

Description

[0020] The invention is explained below using preferred embodiments with reference to the accompanying figures. The following are shown:

[0021] FIG. 1 shows a belt retractor with various additional subassemblies in a sectional view, and

[0022] FIG. 2 shows the belt retractor with the force-limiting device.

[0023] FIG. 1 shows a belt retractor having a belt reel 1, which is rotatably mounted in a frame 8, which belt retractor is provided with various additional subassemblies. A force-limiting device 2, an electric motor 5, a transmission 4 and an irreversible pyrotechnic tightening device 19 are thus provided. The belt retractor is mounted with the frame 8 and the belt reel 1 mounted therein together with the further additional subassemblies in a superordinate housing 20. The housing 20 also serves for fastening the belt retractor in a backrest of a vehicle seat or else in an elongated installation space of a vehicle structure. The electric motor 5 is provided for a reversible belt tightening and different other comfort functions, for example, as a winding aid, as a spring adjustment or as a belt operator. The driving rotational movement of the electric motor 5 is translated via the transmission 4 and transmitted via a transfer bar 6 to the force-limiting device 2, which then in turn drives the belt reel 1.

[0024] In FIG. 2, the belt retractor together with the belt reel 1 and the force-limiting device 2 can be recognized in an enlarged view. The frame 8 is supported on the housing 20, which forms a vehicle-fixed abutment for the frame 8 in the position mounted on the vehicle or on the seat. The force-limiting device 2 is arranged in an orientation coaxial to the axis of rotation of the belt reel 1 on the end face of the belt reel 1 and is connected to the belt reel 1.

[0025] The force-limiting device 2 comprises a first torsion rod 9, a second torsion rod 10, a profiled head 7 and a second switchable blocking device 3. The profiled head 7 is a carrier of a blocking pawl (not shown) which forms a first blocking device and blocks the profiled head 7 during actuation of a sensor device that is sensitive to the belt strap pull-out acceleration and/or a sensor device that is sensitive to the vehicle acceleration in the pull-out direction of a safety belt (also not shown) wound onto the belt reel 1. The belt reel 1 is rotatably mounted in the frame 8, which in turn is fixed in a rotationally fixed manner in the housing 20 and can be fastened to the vehicle or in the backrest. The profiled head 7 is radially mounted with axial spacing in a web 22 fastened in the housing 20. Thus, in a departure from the basic principle used heretofore, the belt reel 1 and the profiled head 7 are mounted independently of one another and axially spaced apart from one another. The belt reel 1 in the frame 8 and the profiled head 7 in the web 22 thus have separate and axially spaced radial bearings. As a result, the subassembly made up of the belt reel 1 and the force-limiting device 2 can be mounted in a more stable configuration overall, which is advantageous in particular during the activation of the force-limiting device 2.

[0026] The belt reel 1 has a profiled receptacle 15 which is open axially toward the outer side. The first torsion rod 9 is rotationally fixed with its first end 11 in the receptacle 15 and for this purpose has an outer profile corresponding to the profile of the receptacle 15. The receptacle 15 is surrounded by an annular protrusion 17 extending away from the end face of the belt reel 1 in the axial direction. Furthermore, a torque tube 16 is provided which engages in the protrusion 17 and surrounds the first torsion rod 9. The torque tube 16 is rotationally fixed to the protrusion 17 via the switchable second blocking device 3 via two blocking pawls, wherein the blocking pawls are released according to the switching principle described in DE 199 27 427 A1.

[0027] The torque tube 16 serves simultaneously for a rotationally fixed connection of the second profiled end 12 of the first torsion rod 9 to the first profiled end 13 of the second torsion rod 10. For this purpose, the torque tube 16 has a central section with radially inwardly directed projections with which it engages in outer profiles of the second end 12 of the first torsion rod 9 and of the first end 13 of the second torsion rod 10 and thereby rotationally fixes both ends to one another.

[0028] The profiled head 7 also has a central profiled receptacle 18, which is surrounded by an annular protrusion 21 extending in the axial direction. The second end 14 of the second torsion rod 10 is provided with an outer profile corresponding to the profiling of the receptacle 18 and is fixed in a rotationally fixed manner in the receptacle 18 relative to the profiled head 7. Furthermore, the torque tube 16 surrounds the annular protrusion 21 radially on the outside and is supported on the profiled head 7. Since the profiled head 7 is in turn mounted separately from the belt reel 1, it forms a abutment for the torque tube 16 that is fixed to the frame.

[0029] In order to activate the force-limiting device 2, the profiled head 7 in a first step is blocked via a first blocking device in a fixed manner relative to the vehicle when a predetermined belt pull-out acceleration or vehicle deceleration is exceeded, wherein the exceeding of the predetermined limit values is detected by means of the sensor devices described above.

[0030] If the occupant now moves forward in the event of an accident due to inertia, the safety belt is pulled out, and the restraining force thus increases the tensile force in the safety belt. As a result, the belt reel 1 rotates in the pull-out direction of the safety belt until the further rotational movement is blocked by the blocking of the profiled head 7. Subsequently, a further belt strap pull-out is possible only when such a belt pull-out is made possible by a plastic deformation of the two torsion rods 9 and 10.

[0031] Before the second blocking device 3 is switched, the torque tube 16 is rotationally fixed to the belt reel 1, the protrusion 17, the second end 12 of the first torsion rod 9 and the first end 13 of the second torsion rod 10, so that the first torsion rod 9 is decoupled from the force flow. Thus, in this phase the second torsion rod 10 is plastically deformed about its longitudinal axis when the pull-out force of the safety belt exceeds the pull-out force defined by the force-limiting level of the second torsion rod 10. The second torsion rod 10 has a higher force-limiting level than the first torsion rod 9, so that a high force-limiting level acts in this phase of the force-limitation. In this case, the torque tube 16 rotates relative to the blocked profiled head 7 and is mounted on the annular protrusion 21 of the profiled head 7.

[0032] By switching the second blocking device 3, the connection of the torque tube 16 to the protrusion 17 is canceled. Thus, the first torsion rod 9 is then located in the force flow. Since the first torsion rod 9 has a lower force-limiting level than the second torsion rod 10, the second torsion rod 10 acts as a fixed bearing and the second end 12 of the first torsion rod 9 is also blocked by the torque tube 16 due to the connection to the first end 13 of the second torsion rod 10. As a result, the first end 11 of the first torsion rod 9 rotates relative to the blocked second end 12, and the first torsion rod 9 is plastically deformed about its longitudinal axis. The lower force-limiting level now acts. In this case, the torque tube 16 is blocked by the positive-locking connection to the first end 13 of the second torsion rod 10, and the belt reel 1 rotates relative to the torque tube 16, and the protrusion 17 of the belt reel 1 additionally forms a bearing for the torque tube 16.

[0033] The invention has been described in reference to a force-limiting device 2 having two torsion rods 9 and 10, which enable a stepped force-limiting profile. The two torsion rods 9 and 10 are arranged coaxially to one another and in series relative to one another so that the outer diameter is not increased by their arrangement. The belt retractor is thus only slightly longer.

[0034] In an alternative embodiment, the belt retractor can also be provided with a force-limiting device 2 which has only a first torsion rod 9. In this case, the second end 12 of the first torsion rod 9 is fixed in a rotationally fixed manner in the receptacle 18 of the profiled head 7. The second switchable blocking device 3, the torque tube 16 and the second torsion rod 10 can thus be omitted. In this case, the first torsion rod 9 would provide a rotationally fixed connection of the belt reel 1 to the profiled head 7 until the plastic deformation limit of the first torsion rod 9 is reached. In this exemplary embodiment too, the belt retractor would have an elongated narrow basic structure, and the belt reel 1 could be made considerably smaller in its outer diameter by the outwardly shifted first torsion rod 9. Apart from a receptacle for the end of the safety belt, the belt reel 1 could be designed as a solid shaft and thus have a maximum rigidity with the smallest possible external dimensions.