Seat belt retractor with hydraulic load limiting

#The invention relates to a seat belt retractor with hydraulic load limiting.

#A known seat belt retractor comprises a belt reel for the seat belt and a blocking means for blocking rotation of a blockable part of the belt reel. The known seat belt retractor further comprises a load limiter, which consumes energy when the blocking means is activated and when the belt webbing carrier is rotated in the belt take-off direction relative to the blocked part of the belt reel. A load limiter is known from DE 199 63 580 C2 which comprises a cylinder filled with a viscous fluid, in which a piston is moved linearly with an opening comprising a variable flow cross-section as a flow path.

#There is provided in accordance with the present invention A seat belt retractor comprising a frame with a belt reel having an axis of rotation rotatably mounted in the frame, a blocking means for blocking rotation of a blockable part of the belt reel, and a substantially drum-shaped belt webbing carrier on the belt reel, wherein in the belt webbing carrier there is arranged a rotor that is in rotary drive connection with the belt webbing carrier, the belt webbing carrier drives a toothed outer rotor and the rotor comprises a toothed inner rotor, wherein chambers filled a free-flowing medium are formed by intermeshing teeth of the outer rotor and the inner rotor and upon rotation of the rotor the volumes of at least two chambers filled with the free-flowing medium are varied, wherein the chambers rotate about the belt reel axis, and in the free-flowing medium flows in each case from a chamber diminishing in volume into a chamber increasing in volume.

#FIG. 1 is a longitudinal section through an exemplary embodiment of a seat belt retractor, illustrating the components necessary for an understanding of the invention.

#FIG. 2 is a cross-section through the exemplary embodiment illustrated in FIG. 1 in a first operating position.

#FIG. 3 is a cross-section through the exemplary embodiment in a second operating position.

#FIG. 1 is a longitudinal section through an exemplary embodiment of a seat belt retractor according to the present invention, illustrating the components necessary for an understanding of the invention. The seat belt retractor illustrated has a belt reel 1, which is mounted rotatably in a frame 12. The belt reel 1 comprises a substantially drum-shaped belt webbing carrier 4, onto which seat belt webbing 13 may be wound and unwound. A blocking means 2, which may for example take the form of a catch means mounted movably on the frame 12, allows the belt reel 1 to be blocked against rotation. To this end, the blocking means 2 engages a blockable part of the belt reel 1. This blockable part may take the form of a toothed disk, or disks, arranged on one side or both sides of the belt reel 1. In the normal operating state, the at least one toothed disk (blockable part 3) is connected non-rotatably with the belt webbing carrier 4, for example via shearing pins (not described in any more detail) or by frictional engagement with the belt webbing carrier 4 of the belt reel 1. The inside of the belt webbing carrier 4 is closed in a fluid-tight manner by end disks 14. A rotor 5 is located inside the belt webbing carrier 4. The rotor includes an axle 15 mounted eccentrically relative to the belt reel axis 7, on which axle 15 a toothed inner rotor 11 is mounted rotatably eccentrically relative to the belt reel axis 7. The eccentric mounted axle 15 is mounted about the belt reel axis 7 inside the belt reel 1 for example on the end disks 14 or axle journals 16 connected firmly with the blockable parts 3, so as to be rotatable about the belt reel axis 7.

#FIG. 2 is a cross-section through the exemplary embodiment illustrated in FIG. 1 in a first operating position. To achieve joint rotation of the belt webbing carrier 4 and the rotor 5, both in the case of the load-limiting function and in the case of torque transmission (coupling function), the rotor preferably takes the form of a toothed inner rotor 11, as in the case of a rotor set of an internal axis rotary piston machine, wherein the teeth of the inner rotor engage the toothed outer rotor 8. The outer rotor is in rotary drive connection with the belt webbing carrier and may preferably be rigidly connected therewith. The teeth 9 of an outer rotor 8 may move into rotary drive connection with the teeth 10 of the inner rotor 11. The outer rotor 8 is in rotary drive connection with the belt webbing carrier 4. The toothed outer rotor 8 is preferably connected in a torsionally rigid manner with the belt webbing carrier 4 or is formed in one piece therewith.

#The seat belt retractor according to the invention may be so constructed that the nested arrangement of belt webbing carrier, rotor and the medium filling the chambers formed has a load-limiting function or a coupling function or both. The in particular free-flowing medium filling the chambers preferably takes the form of a fluid of adjustable viscosity. An electro- and/or magneto-rheological fluid is particularly suitable for this purpose. Between the teeth 9, 10, which extend over the entire length of the inner chamber between the two end disks 14 of the belt reel 1 there are formed chambers 6, which are filled with a fluid or free-flowing medium. The free-flowing medium preferably is a fluid of adjustable viscosity.