Driving wheel for seatbelt tensioners and seatbelt tensioners for a seatbelt system

Abstract

A drive wheel for a belt tensioner is adapted to be coupled to a belt reel and includes an external tooth system including plural teeth distributed along the circumference. The teeth are inclined in a first circumferential direction and/or the teeth have at least one end face facing away from the central axis of the drive wheel and being inclined in a first circumferential direction and/or the clearances between neighboring teeth are not symmetrical with respect to planes defined by radial and axial directions. The teeth have no symmetry with respect to planes extending tangentially relative to the circumferential direction.

Claims

1. A drive wheel (14) adapted to be coupled to a belt reel (12) for a belt tensioner comprising an external tooth system including plural teeth (30) distributed along the circumference, wherein the teeth (30) are inclined in a first circumferential direction (B), each of the teeth having a first flank and a second flank, a substantial portion of both the first flank and the second flank being inclined in the first circumferential direction, or a substantial portion of one of the first flank and the second flank being inclined more strongly in the first circumferential direction than a substantial portion of one other of the first flank and the second flank in a second circumferential direction opposite the first circumferential direction, and wherein the teeth each have a central line, the central lines of the teeth intersecting at points spaced apart from a central axis of the drive wheel.

2. The drive wheel (14) according to claim 1, wherein the drive wheel (14) comprises plural partial drive wheels (44a, 44b, 44c) axially arranged in series.

3. The drive wheel (14) according to claim 2, wherein the partial drive wheels (44a, 44b, 44c) are staggered.

4. The drive wheel (14) according to claim 1, wherein the external tooth system is formed as helical gearing at least in portions.

5. The drive wheel (14) according to claim 1, wherein at least some of the teeth (30) are twisted about radial axes relative to the remaining drive wheel (14).

6. The drive wheel (14) according to claim 1, wherein the drive wheel (14) is formed in one part or integrally with a belt retractor axle.

7. The drive wheel according to claim 1, wherein the teeth have at least one end facing away from the central axis of the drive wheel and being inclined in the first circumferential direction.

8. The drive wheel according to claim 1, wherein clearances between neighboring teeth are not symmetrical with respect to planes defined by radial and axial directions.

9. A belt tensioner for a seatbelt system, comprising a force transmission element (20) and means for driving the force transmission element, a drive wheel adapted to be coupled to a belt reel of the belt tensioner comprising an external tooth system including plural teeth distributed along the circumference, wherein the teeth are inclined in a first circumferential direction, each of the teeth having a first flank and a second flank, a substantial portion of both the first flank and the second flank being inclined in the first circumferential direction, or a substantial portion of one of the first flank and the second flank being inclined more strongly in the first circumferential direction than a substantial portion of one other of the first flank and the second flank in a second circumferential direction opposite the first circumferential direction, and wherein the teeth each have a central line, the central lines of the teeth intersecting at points spaced apart from a central axis of the drive wheel, the force transmission element (20) acting on the external tooth system of the drive wheel upon activation of the drive means so as to rotate the drive wheel (14).

10. The belt tensioner according to claim 9, wherein the force transmission element (20) is formed of a solid substantially deformable material.

11. The belt tensioner according to claim 10, wherein the force transmission element (20) is formed in one piece.

12. The belt tensioner according to any one of the claim 9, wherein the drive wheel (14) is arranged so that the force transmission element (20) drives the drive wheel (14) in a second circumferential direction (C) opposite to the first circumferential direction (B).

13. The drive wheel according to claim 9, wherein the teeth have at least one end face facing away from the central axis of the drive wheel and being inclined in the first circumferential direction.

14. The drive wheel according to claim 9, wherein clearances between neighboring teeth are not symmetrical with respect to planes defined by radial and axial directions.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features and advantages of the invention are resulting from the subsequent description and the enclosed drawings which are referred to, showing in:

(2) FIG. 1 an exploded view of a belt retractor comprising a belt tensioner according to the invention;

(3) FIG. 2 a sectional view of the assembled belt retractor;

(4) FIG. 3 an axial view of a drive wheel according to the invention;

(5) FIG. 4 a perspective view of the drive wheel of FIG. 3;

(6) each of the FIGS. 5a, 5b to 10a, 10b an axial or perspective view of further embodiments of the drive wheel according to the invention; and

(7) FIGS. 11a, 11b an axial or perspective view of a different embodiment of the drive wheel according to the invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

(8) In FIG. 1 the substantial components of a belt retractor comprising a pyrotechnically driven belt tensioner are shown. In FIG. 2 the belt retractor is illustrated in the assembled state.

(9) A belt reel 12 onto which the belt strap can be wound or from which the belt strap can be withdrawn is pivoted in a retractor frame 10. A drive wheel 14 having an external tooth system is pivoted onto the frame 10. The drive wheel 14 is coupled either permanently to the axle (belt reel 12) of the belt retractor or can selectively be coupled to the same. In the former case the drive wheel 14 can be formed in one part or integrally with the belt retractor axle.

(10) The belt tensioner of the belt retractor further has a pyrotechnical drive unit including an igniter 16 and a force transmission element 20 disposed in a tensioner tube 18 and adapted to be driven by the drive unit. The force transmission element 20 is preferably integrally formed of a solid substantially deformable material. The components of the belt tensioner are at least partly accommodated in a tensioner casing 22 fixed to the retractor frame 10.

(11) Furthermore a stop disc 24, a helical spring 26 disposed therein and a cover 28 are attached to the drive wheel 14. These components form a spring side of the belt retractor, as it is called, which is not important to the function of the belt tensioner, however.

(12) In FIG. 3 an embodiment of the drive wheel 14 is shown. The drive wheel 14 has a central axis A about which it is rotatable in the mounted state of the belt tensioner. Accordingly, hereinafter axial directions mean directions along the central axis A, radial directions mean directions along a radius starting from the central axis A and circumferential directions mean directions in parallel to the direction of rotation of the drive wheel 14.

(13) The drive wheel 14 includes an external tooth system having a plurality of teeth 30 distributed along the circumference. The teeth 30 can be distributed, as shown in FIG. 3, evenly or else unevenly.

(14) According to a first criterion, the teeth 30 are inclined in a first circumferential direction B, i.e. either both flanks 32, 34 of a tooth 30 (or substantial portions of the flanks 32, 34) are inclined in the circumferential direction B or either of the flanks 32, 34 (or a substantial portion of said flank) is inclined more strongly in the first circumferential direction B than the other flank (or a substantial portion of said flank) in the opposite circumferential direction C. The central lines of the teeth do not intersect the central axis of the drive wheel.

(15) According to a second criterion, the end faces 36 of the teeth 30 are inclined in the first circumferential direction B, i.e. starting from the crest 38 of a tooth 36 (the point of the tooth 30 that is most distant from the central axis A) the end face 36 declines in the first circumferential direction B toward the basis 40 of the tooth 30 as shown in FIG. 3 by the angle which is smaller than 90. The end faces 36 of the teeth 36 thus are not machined either in a circular or tangential manner or else symmetrically with respect to planes defined by radial and axial directions.

(16) In accordance with a third criterion, the clearances 42 between two neighboring teeth 30 are not symmetrical with respect to planes defined by radial and axial directions.

(17) In accordance with a fourth criterion, the teeth 30 show no symmetry with respect to planes extending tangentially relative to a circumferential direction. In FIG. 3 such plane E is exemplified.

(18) In the mounted state of the belt tensioner the drive wheel 14 is arranged so that the force transmission element moved in a direction D drives the drive wheel 14 in the second circumferential direction C. Thus a comparatively large contact surface presents itself to the impacting force transmission element entailing an improved torque transmission.

(19) The FIGS. 5a, 5b to 10a, 10b show another six embodiments that satisfy the first and/or the second and/or the third and the fourth of the afore-mentioned criteria.

(20) In FIGS. 11a and 11b an example of an embodiment is shown in which the drive wheel 14 consists of plural parts axially arranged in series. Each part per se constitutes a partial drive wheel 44a, 44b or 44c. At least one of the partial drive wheels 44a, 44b, 44c, preferably all partial drive wheels 44a, 44b, 44c satisfies or satisfy the first and/or the second and/or the third and the fourth of the afore-mentioned criteria. The partial drive wheels 44a, 44b, 44c are staggered. The partial drive wheels 44a, 44b, 44c can be manufactured as punched parts.

(21) In accordance with a further embodiment (not shown) the external tooth system of the drive wheel 14 is in the form of a helical gearing at least in portions. Also twisting of the teeth 30 about radial axes relative to the remaining drive wheel 14 is possible. In any case, however, the first and/or the second and/or the third and the fourth of the afore-mentioned criteria is/are satisfied.