Rotary tensioner for a seatbelt

Abstract

The invention relates to a rotary tensioner for a seatbelt, comprising a drive device in the form of a mass body chain (3) that is guided in a tube (5) to which compressed gas is supplied, said mass body chain consisting of a plurality of identical individual masses (4), in order to drive a belt reel (10) in the winding direction of the seatbelt and comprising a drive wheel (1) which is rotationally fixed to the belt reel (10) and comprises a plurality of recesses (2) that are arranged on the radial outer face in a uniform manner and are congruently shaped with respect to at least one sub-section of the outer shape of the individual masses (4), said drive wheel being rotatable about a rotational axis (D) when the drive device is activated, wherein the recesses (2) are dimensioned such that a respective individual mass (4) of the mass body chain (3) can be received in each of the recesses (2), and a shaped element (6) is arranged on the mass body chain (3) end facing the drive wheel (1), said shaped element (6) having a flat support surface (14), by means of which the shaped element (6) rests against the first individual mass (4), on the shaped element face facing the first individual mass (4) of the mass body chain (3) at least in the region of the second sub-mass (9).

Description

[0001] Rotational tensioner for a seat belt

[0002] The present invention relates to a rotation tensioner for a safety belt having the features of the preamble of claim 1.

[0003] The basic design of such a rotational tensioner is known from EP 0 755 340 B1. In this rotational tensioner, a mass body chain consisting of spherical individual masses is fired at a drive wheel by the activation of a pyrotechnic propellant charge. The drive wheel has recesses that match the shape of the individual masses. The individual masses thus engage with the recesses and drive the drive wheel in a rotary drive movement. The drive wheel is connected either permanently or via a coupling in a rotationally fixed manner to a belt shaft of a belt retractor, onto which a safety belt can in turn be wound. The rotary drive movement of the drive wheel is then transferred either via the fixed connection or via the coupling into a rotary movement of the belt shaft in the winding direction, whereby the safety belt is wound onto the belt shaft and tightened.It would also be conceivable to transmit the drive movement of the drive wheel to a belt buckle or end fitting via suitable power transmission devices. The individual masses of the mass body chain are guided in a tube, the end of which is sealed by the pyrotechnic propellant charge. Upon activation, the propellant charge suddenly generates a very large gas flow, which is introduced into a pressure chamber between the propellant charge and the first individual mass or piston, driving the mass body chain.

[0004] One problem to be solved with such a rotation tensioner is that the individual masses must be brought into positive engagement with the recesses to ensure smooth running of the drive movement.

[0005] To solve this problem, it is already proposed in WO 01 / 00460 A1 that a shaped element is provided between the first individual mass facing the drive wheel, which shaped element has a search section in the form of a first partial mass and a second partial mass connected to the first partial mass via a connecting rib for the synchronous control of the individual masses into the recesses.

[0006] Due to the only partially formed contour of the first partial mass of the shaped element, which is referred to here as the seeker section, it is possible for the shaped element to engage with the seeker section in one of the recesses regardless of the position of the drive wheel. During the further drive movement, the shaped element then causes the position of the drive wheel to be corrected if necessary through the engagement of the seeker section by rotating it through a certain angle until it reaches a position in which the shaped element enters the subsequent recess in synchronization with the second partial mass. Since the individual masses rest on the second partial mass of the shaped element in a defined alignment, the individual masses are introduced into the subsequent recesses of the drive wheel during the subsequent movement of the mass body chain and the drive wheel and thus drive the drive wheel in a synchronized manner.

[0007] One problem with such a rotary tensioner is that the shaped element rests in a point-like contact with the first individual mass of the mass body chain and can thus tilt relative to it, causing the shaped element with the finder section to pivot relative to the inner wall of the pipe and, in extreme cases, to become wedged between the drive wheel and the pipe. This wedging of the shaped element creates an additional resistance force that must be overcome by the tensioner drive and reduces the tightening performance. In extreme cases, the wedging of the shaped element can also lead to a blockage of the tightening movement or to mechanical damage to the pipe or the drive wheel, which at least adversely affects the subsequent tightening drive movement.

[0008] Against this background, the invention is based on the object of improving a rotary tensioner of the generic type to such an extent that the probability of the shaped element tilting and thus disrupting the tensioning movement is reduced. To achieve this object, a rotary tensioner with the features of claim 1 is proposed. Further preferred developments can be found in the dependent claims, the figures, and the associated description.

[0009] According to the basic idea, claim 1 proposes that the shaped element, at least in the region of the second partial mass, on its side facing the first individual mass of the mass body chain, have a support surface formed by a flattened portion, with which the shaped element bears against the first individual mass. Due to the flattened support surface, the first individual mass bears against a flattened contact surface on the shaped element instead of a curved contact surface, thereby reducing the effective tilting moments upon lateral deflection of the shaped element relative to the first individual mass or vice versa. This counteracts the tendency of the shaped element to tilt relative to the first individual mass, relative to the tube, and relative to the drive wheel.

[0010] It is further proposed that the support surface, starting from the center of the shaped element, has a greater extension towards the side of the pipe facing away from the drive wheel than towards the side of the pipe facing the drive wheel. This deliberately counteracts a tendency for the shaped element with the second partial mass to tilt towards the drive wheel, since the first individual mass rests against the flat support surface over a longer section during such a deflection than during a reverse deflection. The correspondingly lower support of the shaped element when tilting in the other direction is acceptable insofar as the deflection in this direction is limited by the side of the pipe wall facing away from the drive wheel.

[0011] It is further proposed that the support surface be formed by an elongated surface which, at least in a central section in the direction of the width of the drive wheel, parallel to the axis of rotation of the drive wheel, has a constant width in relation to the longer central axis and is arranged symmetrically to a central axis of the shaped element. The compressive force exerted by the first individual mass on the shaped element is converted into a circumferential force exerted on the drive wheel, wherein the compressive force is deflected. This deflection and the contact with the drive wheel are the cause of the possible tilting and jamming of the shaped element. The direction of the force deflection also brings about a preferred direction of tilting, which is taken into account by the elongated shape with the one-sided longer extension of the support surface.In the direction parallel to the rotational axis of the drive wheel, however, the pressing forces act symmetrically, and there is no preferred direction of tilting of the shaped element, so that the first individual mass does not have a preferred direction of deflection relative to the shaped element. For this reason, the support surface is designed with a constant width in this direction and is arranged symmetrically to a first center axis of the shaped element. This results in a direction-neutral support of the shaped element on the first individual mass with respect to this direction.

[0012] It is further proposed that the support surface be aligned in a plane perpendicular to the rotational axis of the drive wheel. Due to the aligned orientation, the support surface forms a straight support surface in the event of lateral tilting of the shaped element, thus effectively counteracting the tendency of the shaped element to tilt. The shaped element rolls, with the support surface being straight in this direction, on the second partial mass on the surface of the first individual mass. The possible roll angle of the shaped element is reduced by the straight design of the support surface compared to a previously used curved support surface.

[0013] It is further proposed that the support surface has a curvature in an extension parallel to the rotational axis of the drive wheel, forming the support surface into a concave groove. Due to the proposed curved shape of the support surface in the extension parallel to the rotational axis of the drive wheel, the shaped element is also better supported by the first individual mass in the event of tilting in this direction by reducing the possible roll angle of the shaped element compared to the first individual mass. The curvature of the support surface is directed opposite to the outer curvature of the shaped element in the region of the second partial mass, so that the support surface forms a concave groove on the second partial mass. The invention is explained below using preferred embodiments with reference to the attached figures.

[0014] Fig. 1 a rotary tensioner with the individual parts before assembly;

[0015] Fig. 2 a shaped element as a single part in an oblique view;

[0016] Fig. 3 the mold element in view of the second partial mass;

[0017] Fig. 4 shows a section through a rotary tensioner with a drive wheel and a shaped element engaging in the drive wheel according to the prior art;

[0018] Fig. 5 shows a section through a rotary tensioner according to the invention with a drive wheel and a shaped element engaging in the drive wheel;

[0019] Fig. 6 the mold element in a side view of the second partial mass.

[0020] Figure 1 shows a rotary tensioner with a drive wheel 1, a tube 5, a drive device in the form of a mass body chain 3 guided in the tube 5 and comprising a plurality of individual masses 4, and a shaped element 6 resting on the end face of the mass body chain 3, on the first individual mass 4. The individual masses 4 are designed as spheres, and the drive wheel 1 has recesses 2 which are designed in the form of partially spherical half-shells or calottes shaped congruently to the individual masses 4.

[0021] The drive wheel 1 is connected in a rotationally fixed manner to a belt spool 10, onto which a safety belt (not shown) of a safety belt device can be wound. The belt spool 10 itself is rotatably mounted in a frame 11 that can be fixedly fastened to the vehicle. Furthermore, the tube 5 is provided, in which the mass body chain 3 is arranged and guided, and in whose end a gas generator 15 is fastened, e.g. by crimping. Furthermore, a first tensioner housing half 13 and a second tensioner housing half 12 are provided, which are fastened to the outside of the frame 11 and fix the tube 5 with the mass body chain 3 to the frame 11. The first tensioner housing half 13 is fastened directly to the frame 11, and the second tensioner housing half 12 is fastened to the first tensioner housing half 13 and thus indirectly fastened to the frame 11.The first and / or second tensioner housing halves 13 and 12 serve not only to fasten the tube 5 but also to guide the individual masses 4 after they emerge from the tube 5 and during engagement with the drive wheel 1.

[0022] The shaped element 6 according to the prior art and the shaped element 6 according to the further development of the invention can be seen in Figs. 4 and 5 in the engaged position in the drive wheel 1. The basic structure of the two shaped elements 6 is identical and comprises a finder section in the form of a first partial mass 7 and a second partial mass 9, wherein the second partial mass 9 is connected to the first partial mass 7 via a connecting rib 8.

[0023] The first and second partial masses 7 and 9 are each formed by partially formed individual masses 4, or in other words, by completing the shape of the first partial mass 7 and the second partial mass 9, these would have an identical shape to the individual masses 4. Furthermore, the first and second partial masses 7 and 9 are designed and connected to one another via the connecting rib 8 such that the distance between the body centers of the imaginary, shape-completed individual masses 4 of the shaped element 6 has a distance that also corresponds to the distance between the body centers of the successive individual masses 4 of the mass body chain 3 that engage in the recesses 2. The shaped element 6 can therefore be understood as two incompletely formed individual masses 4 that are connected to one another via a connecting rib 8.

[0024] The shaped element 6 of the rotary tensioner further developed according to the invention can be seen in Figure 2 as an individual part in an oblique view and in Figure 3 in a view of the end face of the second partial mass 9. The shaped element 6 has a support surface 14 on the end face of the second partial mass 9, which is designed in the shape of an elongated oval with two parallel edge sides. The support surface 14 is formed in the form of a flattened portion, which is formed by an imaginary section through the second partial mass 9 and is defined in its shape by the shape of the base body of the second partial mass 9 in the region of the cut surface.

[0025] The support surface 14 is shaped and arranged such that the shaped element 6 with the support surface 14 rests against the first individual mass 4 of the mass body chain 3, as can be seen in Figure 5. The support surface 14 is shaped and arranged such that the longer center axis L of the support surface 14 has a straight orientation perpendicular to the axis of rotation D of the drive wheel 1, wherein the axis of rotation D of the drive wheel 1 extends perpendicularly through the plane of the illustration in Figure 5.

[0026] The support surface 14 has two edge sides aligned parallel to one another and parallel to the central axis L, the distance between which, at least in a central section, defines a constant width B of the flattened portion 14 of preferably 3.0 mm. The central axis L of the support surface 14 corresponds to a first central axis M1 of the shaped element 6. Furthermore, the support surface 14 is aligned symmetrically to the central axis L and to the first central axis M1 of the shaped element 6, so that the shaped element 6, with the support surface 14, bears symmetrically against the first individual mass 4 on both sides of the first central axis M1. The support surface 14 is further shaped and arranged such that it is arranged asymmetrically to a second central axis M2, which is aligned perpendicular to the first central axis M1.Starting from the center of the shaped element 6 defined by the second center axis M2, the support surface 14 has a smaller extension H1 of approximately 1.5 to 2.0 mm in one direction and a larger extension H2 of 2.5 to 3.2 mm in the other direction. For this purpose, the shaped element 6 is designed accordingly in its basic shape in the area of ​​the second partial mass 9, so that the different extensions H1 and H2 result solely from the arrangement of the imaginary cut through the base body of the second partial mass 9. The term "cut" is of course not to be understood as meaning cutting off or any other subsequent processing of the shaped element 6, since the shaped element 6 is preferably manufactured as a one-piece injection-molded part, e.g., as a plastic injection-molded part, which is already produced in its final shape during the injection molding process.The term “section” is intended only to provide a simplified representation of the shape of the support surface 14.

[0027] The shaped element 6 is arranged in the tube 5 of the rotary tensioner such that the support surface 14 with the larger extension H2 is directed toward the wall of the tube 5 facing away from the drive wheel 1, while the smaller extension H1 is directed toward the wall of the tube 5 facing the drive wheel 1. Thus, the support surface 14 forms an asymmetric support for the shaped element 6 perpendicular to the rotational axis D of the drive wheel 1 and a symmetrical support for the shaped element in the direction of the rotational axis.

[0028] Figure 4 shows the prior art rotary tensioner, in which the shaped element 6 does not have a flattened support surface 14, but instead has a curved or partially spherical surface in the region of the second partial mass 9. Under unfavorable force conditions, as can be seen in Figure 4, the shaped element 6 tilts with the second partial mass 9 in the direction of the drive wheel 1 due to the compressive force exerted by the first individual mass 4, whereby the shaped element 6 rolls with the surface of the second partial mass 9 against the surface of the first individual mass 4 over a comparatively large rolling angle. This rolling is favored by the curved surface of the shaped element 6 in the region of the second partial mass 9 and the curved surface of the first individual mass 4.

[0029] Figure 5 shows the further developed rotary tensioner according to the invention, in which the shaped element 6 has the flattened support surface 14 in the region of the end face of the surface of the second partial mass 9. The shaped element 6 is aligned such that the support surface 14 with the longer extension H2 is directed towards the left wall of the tube 5, i.e. in the direction of the wall of the tube 5 facing away from the drive wheel 1. This is advantageous because the shaped element 6 is thereby particularly supported against the tilting direction shown in Figure 4. Towards the other side, i.e. in the direction of the drive wheel 1, the flat support surface 14, on the other hand, has the shorter extension H1, since the deflection of the shaped element 6 with the first partial mass 9 to the other side is limited anyway by the wall of the tube 5.

[0030] The flattened support surface 14 thus has a preferred support direction of the shaped element 6 against tilting with the second partial mass 9 in the direction of the drive wheel 1 about a pivot axis directed parallel to the axis of rotation D. Due to the symmetrical design of the support surface 14 to the first center axis M1, the shaped element 6 is supported equally, i.e. directionally neutrally, in both pivot directions when tilting about a pivot axis running perpendicular to the axis of rotation D and, in the illustration, horizontally.

[0031] In Figure 6, the shaped element 6 can be seen as an individual part in view of the second partial mass 9 with the support surface 14 arranged on the lower side in the perspective direction of the first central axis M1 of Figure 3. The flattened support surface 14 has a curvature R, which forms the flattened support surface 14 into a concave groove in this direction. For this purpose, the curvature R is directed opposite to the curvature of the outer surface of the shaped element 6 in the region of the second partial mass 9, so that the support surface 14 is recessed into the second partial mass 9. The curvature R here has a preferred radius of 20 mm.

[0032] Due to the negative curvature R directed into the second partial mass 9, the possible roll angle of the shaped element 6 on the first individual mass 4 is further reduced in this direction. If the curvature R corresponds to the curvature of the outer shape of the first individual mass 4, this can even achieve a flat contact of the shaped element 6 on the first individual mass 4.

Claims

Claims:

1. Rotation tensioner for a safety belt with -a drive device in the form of a mass body chain (3) consisting of a plurality of identical individual masses (4) guided in a tube (5) which can be pressurised with compressed gas, for driving a belt reel (10) in the winding direction of the safety belt, and -a drive wheel (1) connected to the belt reel (10) in a rotationally fixed manner and having a plurality of recesses (2) regularly arranged on the radial outer side and congruent in shape with at least a partial section of the outer shape of the individual masses (4), which can be driven to a rotational movement about a rotational axis (D) upon activation of the drive device, wherein -the recesses (2) are dimensioned such that in each of the recesses (2) an individual mass (4) of the mass body chain (3) can be accommodated, wherein -a shaped element (6) is provided at the end of the mass body chain (3) facing the drive wheel (1), wherein -the shaped element (6) has a first partial mass (7) forming a finder section in the form of a partially formed individual mass (4) and a second partial mass (9) connected to the first partial mass (7) via a connecting rib (8) in the form of an at least partially formed individual mass (4), characterized in that -the shaped element (6) has, in the region of the second partial mass (9), on its side facing the first individual mass (4) of the mass body chain (3), a support surface (14) formed by a flattened portion, with which the shaped element (6) bears against the first individual mass (4).

2. Rotational tightener according to claim 1, characterized in that -the support surface (14) has a greater extension (H2) starting from the center of the shaped element (6) in the direction of the side of the tube (5) facing away from the drive wheel (1) than towards the side of the tube (5) facing the drive wheel (1).

3. Rotation tensioner according to one of claims 1 or 2, characterized in that - the support surface (14) is formed by an elongated surface which, at least in a central section in the direction of the width of the drive wheel (1) parallel to the axis of rotation (D) of the drive wheel (1), has a constant width (B) in relation to the longer central axis (L) and is symmetrical to a first central axis (Ml) of the shaped element (6).

4. Rotary tensioner according to one of claims 1 to 3, characterized in that - the support surface (14) has a straight orientation in a plane running perpendicular to the axis of rotation (D) of the drive wheel (1).

5. Rotary tensioner according to one of claims 1 to 4, characterized in that - the support surface (14) has a curvature forming the support surface (14) into a hollow groove in an extension directed parallel to the axis of rotation (D) of the drive wheel (1).

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