US20090014577A1

US20090014577A1 - Belt spool for a belt retractor, and belt retractor

Info

Publication number: US20090014577A1
Application number: US12/217,534
Authority: US
Inventors: Konrad Elsaesser; Helmut Gross; Thomas Kielwein; Bernd Gentner; Karl Hudelmaier
Original assignee: TRW Automotive GmbH
Current assignee: ZF Automotive Germany GmbH
Priority date: 2007-07-10
Filing date: 2008-07-07
Publication date: 2009-01-15
Also published as: DE102007032054A1; DE102007032054B4

Abstract

A belt spool for a belt retractor with a force limiter has at least one flange (16) with a front face (27) and one insert (28) provided on the front face (27) of the flange (16). The insert (28) constitutes the portion that is cut by the force limiter. The invention further relates to a belt retractor.

Description

TECHNICAL FIELD

The present invention relates to a belt spool for a belt retractor and to a belt retractor.

BACKGROUND OF THE INVENTION

Disclosed in the prior art are belt retractors having force limiters which, once a specific belt webbing withdrawal force in the safety belt is exceeded, allow a rotation of the belt spool in spite of the belt spool being blocked. This limits the forces exerted on a vehicle occupant by the safety belt.
DE 103 43 534 A1 shows a belt retractor in which, in addition to a first force limiting device which contains a torsion bar, a second force limiting device may be active at the same time which uses a material cutting process. In particular by means of the cutting width and cutting depth parameters, a progressive, degressive or constant evolution of the level of force is allowed in sections.
The invention provides a belt spool which allows the force level to be adjusted more flexibly. The invention furthermore provides a belt retractor including a force limiter the force level of which can be adjusted more flexibly.

BRIEF SUMMARY OF THE INVENTION

According to the invention, a belt spool for a belt retractor with a force limiter has at least one flange and one insert provided on the front face of the flange, the insert constituting a portion that is cut by the force limiter. According to the invention, the belt spool is not made in one piece, but that portion which is cut by a force limiter is in the form of an insert part. The basic idea is that the material that is used for the separate part is different from the material that is used for the belt spool. The insert may be made of different materials having respectively different mechanical properties and may have different contours. In this way, the cutting width and cutting depth of the force limiter, which is more particularly a cutting body, may be varied, which changes the level of force and its evolution.
Preferably, a bead having an axial height and a radial width is provided on the insert. The height and the width of the bead may be used to adjust the force level and the evolution thereof.
The axial height and the radial width of the bead may vary at least in sections, so that with an increasing cutting width and/or cutting depth a progressive evolution may be achieved and with a decreasing cutting width and/or cutting depth a degressive evolution is achieved.
More particularly, the insert is fastened to the belt spool. The insert is glued to or pressed into the belt spool, for example. The insert may just as well be placed into the casting mold of the belt spool. When casting is completed, the insert is integrally cast with the belt spool.
Preferably, the insert is made of steel. Steel is suitable to be cut uniformly. If the steel is heat-treated, the strength of the insert may vary in sections, resulting in a change in the depth of cut of a cutting body, which will lead to a variation in the evolution of force.
The present invention further relates to a belt retractor comprising a frame, a belt spool of the type mentioned above which is rotatably mounted in the frame, a force limiter, and a disk which is adapted to be blocked at the frame so as to be non-rotatable relative thereto. As regards the advantages, reference is made to the explanations above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic sectional view of a belt retractor with a belt spool and a force limiter;

FIG. 2 shows a perspective view of a belt spool for a belt retractor according to the prior art; and

FIG. 3 shows a perspective view of a belt spool according to the invention for a belt retractor.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT

The belt retractor shown schematically in FIG. 1 includes a frame 10 and a belt spool 12 rotatably mounted in the frame 10. Belt webbing 14 can be withdrawn from the belt spool 12. A flange 16 of the belt spool 12 has a disk 18 applied thereto which, by a blocking mechanism 20, can be caused to rest at the frame 10 so that rotation is prevented. The disk 18 may be connected with the flange 16 of the belt spool 12 by shear pins 22 for joint rotation up to a specific torque.
Arranged in the hollow interior of the belt spool 12 is a torsion bar 23 which is coupled at one axial end for joint rotation with the disk 18 and at the opposite end for joint rotation with the belt spool 12.
On its side facing the flange 16 the disk 18 has a recess in which a cutting body 24 is inserted. The cutting body 24 protrudes axially beyond the face of the disk 18 facing the flange 16.
A bead 26 is formed in the front face 27 of the flange 16 facing the disk 18 (cf. FIG. 2), the cutting body 24 projecting into the bead 26.
When a locking is activated in a vehicle-sensitive or belt webbing-sensitive manner, the blocking mechanism 20 blocks the disk 18 on the frame 10 of the belt retractor so as to prevent rotation. This also locks the belt spool 12 so as to be locked in rotation on the frame 10 via the torsion bar 23, but only up to a belt load in which as yet no torsion of the torsion bar 23 occurs. As soon as this belt load is exceeded, the belt spool 12 will rotate in relation to the disk 18 and the torsion bar 23 will be twisted at the same time. In this relative rotation the cutting edge of the cutting body 24 will come into engagement with the material of the flange 16 of the belt spool 12. Any further relative rotation is possible only by the cutting body 24 cutting a chip from the bead 26. This means that a conversion of energy takes place by a cutting of material, which occurs in parallel to the conversion of energy by the torsion bar 23 being twisted.
FIG. 3 shows the belt spool 12 according to the invention, which may be inserted into a belt retractor. The components already mentioned are denoted by the same reference numerals, and reference is made in this respect to the explanations above.
The belt spool 12 differs from the belt spool 12 described with reference to FIGS. 1 and 2 in that an annular insert 28 made of steel is provided on the flange 16 facing the disk 18. The insert 28 is adhesively fastened to the belt spool 12. The insert 28 may just as well be placed into a casting mold for the belt spool 12. When casting is completed, the insert is integrally cast with the belt spool 12. The insert 28 could also be pressed into the spool body.
The insert 28 includes the bead 26 which has already been discussed and from which the cutting body 24 can cut a chip. In the embodiment shown, the radial width B of the bead 26 decreases along the cutting path, so that a degressive evolution of the force level is attained. The radial width could just as well increase, which would result in a progressive evolution, or the axial height could decrease or increase. Further, the axial height H (see FIG. 1) could vary.
The insert 28 made of steel is cut more uniformly than the brittle cast material of the belt spool, which was cut in the prior art. Diecast aluminum or diecast zinc serves as the casting material for the belt spool.
The mode of functioning of the belt retractor is the same as that explained above, reference being hereby made thereto.

Claims

1. A belt spool for a belt retractor with a force limiter, comprising

at least one flange (16) with a front face (27) and

one insert (28) provided on said front face (27) of said flange (16),

said insert (28) constituting a portion that is cut by said force limiter.

2. The belt spool according to claim 1, wherein said insert (28) is substantially annular.

3. The belt spool according to claim 1, wherein a bead (26) having an axial height (H) and a radial width (B) is provided on said insert (28).

4. The belt spool according to claim 3, wherein said axial height (H) and said radial width (B) of said bead (26) vary at least in sections.

5. The belt spool according to claim 1, wherein said insert (28) is fastened to said belt spool (12).

6. The belt spool according to claim 1, wherein said insert (28) is made of steel.

7. A belt retractor comprising

a frame (10),

a belt spool (12) according to claim 1 which is rotatably mounted in said frame (10),

a force limiter, and a disk (18) which is adapted to be blocked at said frame (10) so as to be non-rotatable relative thereto.

8. The belt retractor according to claim 7, wherein said force limiter is a cutting body (24) adapted to cut said insert (28).