Belt retractor

Abstract

The present invention relates to a belt retractor comprising a force-limiting device (2) surrounding a belt reel (1) rotatably mounted in a frame and having at least one plastically deformable first torsion rod (9), the first torsion rod (9) having a first end (11) rotationally fixed to the belt reel (1) and a second end (12) rotationally fixed to a profiled head (7), the second end (12) being capable of being blocked so that the profiled head (7) is fixed relative to the vehicle via a first blocking device. The belt reel (1), the first torsion rod (9), and the profiled head (7) are arranged coaxially and in series with one another.

Description

[Technical Field]

[0001] The invention relates to a belt retractor having the features of the preamble of claim 1 .

[0002] The belt retractor has as its basic components a load-bearing frame and a belt reel, which is rotatably mounted in the frame and onto which the safety belt can be wound. The frame not only serves to mount the belt reel but also to fasten the belt retractor to the seat structure or vehicle structure, and for this purpose it is made from a steel plate of appropriate thickness bent into a U-shaped frame.

[0003] Furthermore, modern belt retractors are equipped with force-limiting devices to reduce the load on the occupant, allowing for force-limited belt strap retraction until the occupant is trapped by the airbag in the event of an accident. For this purpose, plastically deformable torsion rods have proven effective. One end of the torsion rod is rotationally fixed to the belt reel, and the other end is fixed to a part (profile head) that can be blocked via a first blocking device so that it is fixed relative to the vehicle in the event of an accident. In such torsion rods, the force limiting level of the force-limited belt strap retraction is predetermined by their plastic deformation limits.

[0004] German Patent Application Publication No. 199 27 427 A1 discloses a belt retractor having a two-stage torsion rod with two torsion sections having different plastic deformation limits. The two-stage torsion rod is rotatably fixed to a profiled head at its free end, which forms the end of the torsion section with a higher force limiting level. The other free end is rotatably fixed to a belt reel. A switchable second blocking device is provided with a torque tube. The torque tube is connected to the profiled section of the torsion rod at its profiled central section, which separates the two torsion sections. The switchable second blocking device further includes two releasable blocking claws that block the torque tube against the belt retractor frame. Thus, the torsion section with the lower plastic deformation limit, i.e., the lower force limiting level, is bridged at the start of force-limiting belt strap withdrawal, while the plastic deformation of the torsion section with the higher plastic deformation limit allows force-limiting belt strap withdrawal at a higher force limiting level. When the second blocking device is switched, the torque tube is unlocked, allowing further force-limited belt strap withdrawal by plastic deformation of the torsion section, which has a lower plastic deformation limit, at a lower force limit level. The two-stage torsion rod is placed in the belt reel cavity together with the torque tube. This requires a belt reel with a correspondingly large cavity and a correspondingly large outer diameter.

[0005] It is also known to provide vehicle seats with an integrated safety belt system in which at least the belt retractor of the seat belt system is fastened to the seat back of the vehicle. In this case, due to the lack of a load-bearing B-pillar and for reasons related to rear seat access or distance from the rear vehicle structure, the belt retractor is preferably integrated into the seat back of the vehicle, and therefore must also be designed to absorb the tension forces acting in the event of restraint. The belt retractor itself has all the basic components of a standard belt retractor, only equipped with various additional subassemblies, such as a self-aligning inertial sensor, specifically designed for installation in the seat back. Installation in the seat back is problematic in that the available installation space is very small, and the seat backs cannot be enlarged as desired for installation, nor can their basic structure be modified as desired. In this case, the seat back structure is designed to absorb the restraint forces in the event of an accident, particularly using a braced structure intended to form a structure that is as rigid as possible with as low a dead weight as possible. This requirement necessitates a structure with long struts that is as continuous as possible and divides the interior of the backrest into several elongated free spaces, with only limited scope for modification.

[0006] In the case of belt retractors, in particular when the belt retractor is provided for installation in a seat back, the problem arises that the belt retractor must be designed as compact as possible and in particular must also be designed for installation in very narrow and elongated installation spaces.

[0007] To achieve the object, a belt retractor is proposed having the features of claim 1. Further preferred embodiments can be found in the dependent claims, the figures and the associated description.

[0008] According to the basic concept of the invention, it is proposed that the belt reel, the first torsion rod and the profile head are arranged coaxially and in series with respect to one another.

[0009] The proposed solution allows for a narrow, elongated belt retractor basic structure. Compared to solutions known from the prior art, the first torsion rod is removed from the belt reel and arranged coaxially with it. As a result, the cavity previously required in the belt reel for the torsion rod is eliminated, allowing for a smaller belt reel outer diameter. Furthermore, the profile head, which can be blocked via the first blocking device to secure it to the vehicle, is also arranged coaxially and in-line with the belt reel, so that it is also released from the belt reel. Therefore, the belt reel can be smaller in size, since the profile head is no longer arranged directly on the belt reel. Furthermore, the coaxial in-line arrangement of the three basic components allows for a very narrow, elongated belt retractor basic structure, which allows for easier placement in existing narrow, elongated installation spaces in the seat back or vehicle structure. However, they can also be slightly modified to accommodate insufficient installation spaces.

[0010] The first torsion rod is preferably arranged in series between the belt reel and the profile head. The first torsion rod essentially forms the connection between the profile head and the belt reel. When the profile head is blocked, the second end of the first torsion rod is blocked, and the first end of the first torsion rod can rotate together with the belt reel relative to the blocked profile head under plastic deformation of the portion located between the first and second ends of the first torsion rod. This results in a simple and clear basic structure with as linear a force flow as possible, allowing the belt retractor to be designed very compactly to absorb restraining forces.

[0011] Furthermore, it is proposed that the profile head and the belt reel are mounted in separate radial bearings at an axial distance from each other. In previous arrangements of the profile head on the belt reel, the profile head simultaneously forms the radial bearing of the belt reel, and arranging the torsion rod and the radial bearing of the belt reel in the profile head resulted in a relatively large outer diameter of the belt reel. Thanks to the proposed separate radial bearing, the mounting of the belt reel can be carried out more easily and therefore in a manner optimized for the installation space. Furthermore, as a result of the axial distance between the two provided bearings and the radial bearing, the mounting can be made more stable.

[0012] It is further proposed that the first torsion rod is held in a rotationally fixed manner with a first end in an axially outwardly opening receptacle of the belt reel, whereby the first torsion rod is rotationally fixed to the outer first end of the belt reel and extends axially outward from the belt reel and coaxially from the receptacle.

[0013] Furthermore, it is proposed that at least one second torsion rod is arranged coaxially and in series with the belt reel between the first torsion rod and the profile head, which allows for a higher or lower force limiting level of the force-limited belt strap puller depending on the type of actuation.

[0014] The second and first torsion rods may preferably have different plastic deformation limits, so that a gradual progression of force-limiting properties can be achieved by sequential actuation of the two torsion rods.

[0015] Preferably, a torque tube can be provided that is rotationally fixed relative to the belt reel via a switchable second blocking device, and the torque tube connects two opposing ends of the first torsion rod and the second torsion rod in a rotationally fixed manner. The torque tube can be intentionally bridged by the first torsion rod to activate the second torsion rod in a first stage of force limitation. The first torsion rod is then activated by switching the second blocking device.

[0016] It is further proposed that an axially protruding projection is provided on the belt reel, and the torque tube is fixed to the projection via a switchable second blocking device. The axially protruding projection defines a force transmission surface on the belt reel against which the torque tube is supported. The arrangement of the projections provides a force transmission surface that does not increase the outer diameter of the belt reel, and allows for a particularly simple coaxial serial arrangement of the torsion rod relative to the belt reel.

[0017] Here, the axial protrusion may preferably be annular, and the torque tube may protrude radially inward into the axial annular protrusion or may surround the radial outside of the axial annular protrusion, so that the torque tube has additional radial support and is radially fitted onto the protrusion, particularly during rotational movement and after switching and disengaging the second blocking device.

[0018] It is further proposed that an axially projecting annular projection be provided on the profile head, with the torque tube projecting radially inward into the annular projection or surrounding the radially outer side of the annular projection. The proposed solution is advantageous in that the torque tube has support on the profile head via the annular projection and is fitted into the profile head during the execution of the associated rotational movement. This is advantageous, in particular, due to the increase in the overall axial length of the belt retractor required by the solution according to the invention.

[0019] It is further proposed that the belt reel be designed as a solid shaft. As a result of this solid shaft design, a particularly compact design can be realized that simultaneously provides very high dimensional stability for the belt reel. For example, a secure locking design can be provided in the belt reel for connecting the belt strap. In both cases, the cavity previously required for arranging the torsion rod can be omitted. Furthermore, by designing the belt reel as a solid shaft, an axial receptacle for fixing the first end of the first torsion rod in a rotationally fixed manner can be particularly easily realized. [Brief explanation of the drawings]

[0020] The present invention will be described below using preferred embodiments with reference to the accompanying drawings, in which: [Figure 1] 1 is a cross-sectional view of a belt retractor having various additional subassemblies. [Figure 2] 1 shows a belt retractor with a force limiting device.

[0021] FIG. 1 shows a belt retractor having a belt reel 1 rotatably mounted on a frame 8, which is provided with various additional subassemblies, such as a force limiting device 2, an electric motor 5, a transmission 4, and a non-reversible pyrotechnic clamping device 19. With the frame 8 and the belt reel 1 mounted therein, the belt retractor, together with the additional subassemblies, is mounted in an upper housing 20. The housing 20 also serves to fasten the belt retractor to a vehicle seat back or an elongated installation space in the vehicle structure. The electric motor 5 is provided for reversible belt tightening and various other comfort functions, such as a retraction assist, a spring adjustment, or a belt operating means. The driving rotational movement of the electric motor 5 is converted via the transmission 4 and transmitted via a transmission bar 6 to the force limiting device 2, which in turn drives the belt reel 1.

[0022] 2 the belt retractor can be seen in an enlarged view together with the belt reel 1 and the force limiting device 2. The frame 8 is supported on a housing 20 which forms a vehicle-fixed abutment for the frame 8 in its mounted position on the vehicle or seat. The force limiting device 2 is arranged on an end face of the belt reel 1 in a coaxial orientation with the axis of rotation of the belt reel 1 and is connected to the belt reel 1.

[0023] 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 for a blocking claw (not shown) forming the first blocking device, which blocks the profiled head 7 during operation of a sensor device for detecting belt strap unwinding acceleration and / or a sensor device for detecting vehicle acceleration in the unwinding direction of a safety belt (also not shown) wound on the belt reel 1. The belt reel 1 is rotatably mounted on a frame 8, which in turn is fixed in a rotationally fixed manner in a housing 20 and can be fastened to a vehicle or a seat back. The profiled head 7 is radially fitted at an axial distance into a web 22 fixed to the housing 20. Thus, in deviating from the basic principle used up to now, the belt reel 1 and the profiled head 7 are mounted independently of each other and axially spaced apart from each other. Thus, the belt reel 1 in the frame 8 and the profile head 7 in the web 22 have separate radial bearings that are axially spaced apart. As a result, the subassembly consisting 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 operation of the force limiting device 2.

[0024] The belt reel 1 has a profiled receptacle 15 that opens axially outward. The first torsion rod 9 is rotationally fixed at its first end 11 in the receptacle 15 and has an outer profile that corresponds to the profile of the receptacle 15. The receptacle 15 is surrounded by an annular projection 17 that extends axially away from the end face of the belt reel 1. A torque tube 16 is further provided, engaging the projection 17 and surrounding the first torsion rod 9. The torque tube 16 is rotationally fixed to the projection 17 via a second blocking device 3 that can be switched via two blocking pawls, which are disengaged according to the switching principle described in DE 199 27 427 A1.

[0025] The torque tube 16 simultaneously serves to rotationally securely connect the second profiled end 12 of the first torsion rod 9 to the first profiled end 13 of the second torsion rod 10. To this end, the torque tube 16 has a central portion with radially inwardly directed protrusions that engage the outer profiles of the second end 12 of the first torsion rod 9 and the first end 13 of the second torsion rod 10, thereby rotationally securing the ends to one another.

[0026] Furthermore, profile head 7 has a central profile receptacle 18 surrounded by an axially extending annular projection 21. Second end 14 of second torsion rod 10 has an outer profile corresponding to the profile of receptacle 18 and is rotationally fixed within receptacle 18 relative to profile head 7. Torque tube 16 further surrounds the radially outer side of annular projection 21 and is supported on profile head 7. Profile head 7 is then mounted separately from belt reel 1, thereby forming a frame-fixed abutment for torque tube 16.

[0027] When a predetermined belt withdrawal acceleration or vehicle deceleration is exceeded, the profile head 7 is blocked in a first step so as to be fixed relative to the vehicle via a first blocking device in order to activate the force limiting device 2. The exceeding of the predetermined limit value is detected by the above-mentioned sensor device.

[0028] If the occupant moves forward due to inertia in the event of an accident, the safety belt is pulled out, and the restraining force therefore increases the tension of the safety belt. As a result, the belt reel 1 rotates in the direction of safety belt unwinding until the rotational movement is blocked by the profile head 7. Further belt unwinding is then only possible if such belt unwinding is made possible by plastic deformation of the two torsion rods 9 and 10.

[0029] 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, thereby isolating the first torsion rod 9 from the force flow. Therefore, if the safety belt withdrawal force exceeds the force limiting level of the second torsion rod 10 during this phase, the second torsion rod 10 undergoes plastic deformation about its longitudinal axis. The second torsion rod 10 has a higher force limiting level than the first torsion rod 9, resulting in a higher force limiting level during this phase of force limitation. In this case, the torque tube 16 rotates relative to the blocked profile head 7 and engages in the annular protrusion 21 of the profile head 7.

[0030] By switching the second blocking device 3, the torque tube 16 is disconnected from the protrusion 17. The first torsion rod 9 is now positioned in the force flow. Because 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 its 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, causing the first torsion rod 9 to plastically deform around its longitudinal axis. Now, the torque tube 16 is blocked by its 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, with the protrusion 17 of the belt reel 1 also forming a bearing for the torque tube 16.

[0031] The present invention has been described with respect to a force limiting device 2 having two torsion rods 9 and 10 that allow for a graduated force limiting characteristic. The two torsion rods 9 and 10 are arranged coaxially and in series with one another, so that their arrangement does not increase the outer diameter, and therefore the belt retractor is only slightly longer.

[0032] In an alternative embodiment, the belt retractor can also be provided with a force-limiting device 2 that only includes the first torsion rod 9. In this case, the second end 12 of the first torsion rod 9 is rotationally fixed in the receptacle 18 of the profile head 7. The second switchable blocking device 3, the torque tube 16, and the second torsion rod 10 can therefore be omitted. In this case, the first torsion rod 9 provides a rotationally fixed connection of the belt reel 1 to the profile head 7 until the plastic deformation limit of the first torsion rod 9 is reached. In this exemplary embodiment, the belt retractor also has an elongated basic structure, and the belt reel 1 can have a significantly reduced outer diameter due to the outward shifting of the first torsion rod 9. Apart from the receptacle for the end of the safety belt, the belt reel 1 can be designed as a solid shaft and therefore have the smallest possible outer dimensions and maximum rigidity.

Claims

1. a belt reel (1) rotatably mounted within a frame; a force limiting device (2) having at least one plastically deformable first torsion rod (9); A belt retractor comprising: the first torsion rod (9) has a first end (11) rotationally fixed to the belt reel (1) and a second end (12) rotationally fixed to a profile head (7), the second end (12) being capable of being blocked so that the profile head (7) is fixed relative to the vehicle via a first blocking device, the belt reel (1), the first torsion rod (9) and the profile head (7) are arranged coaxially and in series with one another; At least one second torsion rod (10) is arranged coaxially and in series with the belt reel (1) between the first torsion rod (9) and the profile head (7), a torque tube (16) fixed in a rotationally fixed manner to the belt reel (1) via a switchable second blocking device (3); the torque tube (16) connects the two opposing ends (12, 13) of the first torsion rod (9) and the second torsion rod (10) to each other in a rotationally fixed manner; An axially protruding annular projection (21) is provided on the profile head (7), the torque tube (16) surrounds the radially outer side of the annular projection (21); A belt retractor characterized by the above.

2. the first torsion rod (9) is arranged in series between the belt reel (1) and the profile head (7); 2. The belt retractor according to claim 1, wherein:

3. the profile head (7) and the belt reel (1) are mounted in separate radial bearings at an axial distance from each other; 3. The belt retractor according to claim 2, wherein:

4. 4. The belt retractor according to claim 1, wherein the first torsion rod (9) is held in a rotationally fixed manner with the first end (11) in a receptacle (15) of the belt reel (1) that opens axially outward.

5. The second torsion rod (10) and the first torsion rod (9) have different plastic deformation limits; 5. The belt retractor according to claim 1, wherein:

6. a protrusion (17) protruding in an axial direction is provided on the belt reel (1), and the torque tube (16) is fixed to the protrusion (17) via the switchable second blocking device (3); 2. The belt retractor according to claim 1, wherein:

7. the axial projection (17) being annular; 7. The belt retractor according to claim 6, wherein:

8. the belt reel (1) is designed as a solid shaft, 8. The belt retractor according to claim 1, wherein:

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