Safety belt retractor with tensioning device

Abstract

The invention relates to a safety belt retractor with a tensioning device, comprising: a frame (3) which can be fixed to a vehicle and which has two frame legs (14) arranged parallel to each other, each frame leg having a bearing opening (4); and a belt shaft (1), which is arranged between the frame legs (14) and is rotatably mounted in the bearing openings (4) of the frame legs (14); the invention relates to a safety belt (1) for a motor vehicle, comprising frame legs (14), a belt shaft (1), and a tensioner drive wheel (10), which is connected in a rotationally fixed manner to the belt shaft (1) or can be connected via a clutch, in which a pot-shaped housing (6), which has a substantially constant wall thickness (D1), is fastened to one of the frame legs (14) on the side facing away from the other frame leg (14), and in which the pot-shaped housing (6) is fastened to the other frame leg (14) on the side facing away from the other frame leg (14). The opening (15) of the pot-shaped housing (6) has a toothing (9), and the pot-shaped housing (6) at least partially has a thickening (8) in the region of the edge of the opening (15) and of the toothing (9), in which thickening (8) the toothing (9) of the housing is arranged, the thickening (8) being formed by a projection (12) directed on one side of the frame leg (14), a pot-like housing (6) is fastened to the frame leg.

Description

[0001] The present invention relates to a seat belt retractor with a tensioning device, the seat belt retractor having the features as recited in the preamble of claim 1.

[0002] This general type of seat belt retractor is used in a seat belt device of a motor vehicle and for retracting one end of the seat belt of the seat belt device. The seat belt retractor itself has a frame for fastening to the vehicle, the frame having two parallel and opposite frame legs, each frame leg having a bearing opening in which a seat belt shaft is rotatably mounted, and one end of the seat belt can be wound around the seat belt shaft. The seat belt shaft is pre-tensioned in the winding direction of the seat belt by means of a main spring supported on the frame. In addition, when a pre-determined vehicle deceleration and / or seat belt webbing extension acceleration is exceeded in the extension direction of the seat belt, the seat belt shaft can be locked by means of a locking device, which can be controlled by a sensor device sensitive to vehicle acceleration and / or a sensor device sensitive to seat belt webbing extension acceleration. The locking device is formed by a locking pawl, which is pivotally mounted on the seat belt shaft or is mounted in a rotationally fixed manner on a part connected to the seat belt shaft, and the locking pawl engages a locking tooth engagement fixed to the frame to lock the seat belt shaft.

[0003] In addition, the general seat belt retractor has a tensioning device, which drives the seat belt shaft in the winding direction at startup to tension the seat belt. The tensioning device can be reversible, for example, with an electric motor that can be restarted repeatedly, or can be irreversible, for example, with a pyrotechnic actuator that can be actuated once. The tensioning device has a tensioner drive wheel, which is connected to the seat belt shaft in a rotationally fixed manner or can be connected to the seat belt shaft by means of a switchable clutch. In addition, a tensioner housing is provided, which at least covers the tensioning device in the area of the drive wheel and can be a carrier for other components of the seat belt retractor and the tensioning device.

[0004] Such seat belt retractors are known from DE 10 2008 059 387 A1. The pretensioner housing is designed as a pot-shaped housing which is fastened to the outside of the frame legs of the seat belt retractor frame and has a circular opening with a toothing, into which a locking pawl engages to lock the seat belt shaft. The toothing is arranged in the annular edge of the opening and is formed by teeth pointing radially inwards. The seat belt shaft consists of two parts, a seat belt shaft body and a profile head, which are connected to one another in a rotationally fixed manner via a torsion bar. The torsion bar forms a force-limiting device and connects the profile head and the seat belt shaft body to a torsionally fixed connection up to its plastic deformation limit. The seat belt shaft body is used for retracting the seat belt, while the profile head carries the locking pawl and extends through the opening of the pretensioner housing. The locking pawl, which is pivotally mounted on the profile head, is arranged such that it overlaps with the toothing of the opening, so that the locking pawl engages in the toothing when pivoted out and locks the seat belt shaft in the extending direction. The torsion bar forms a force-limiting device and enables a force-limited seat belt webbing extension in the case where the profile head is locked, in order to limit the occupant load during an accident. The profile head is also used to hold the pretensioner drive wheel arranged in the pot-shaped housing, so that the pretensioner drives the seat belt shaft in the winding direction when activated via the profile head.

[0005] The pot-shaped housing of the pretensioner thus not only serves to cover the pretensioner drive wheel, but also to absorb and transmit the restraint forces generated when the occupant is restrained and must therefore be designed to be dimensionally stable and load-bearing. A particularly critical point is the toothing, because in the event of a restraint event, the toothing must absorb locally particularly large forces in the area of engagement of the locking pawl, which causes particularly high material stresses in the pot-shaped housing.

[0006] Against this background, the object of the present invention is to provide a universal seat belt retractor with a pretensioner, in which the load absorption in the event of a restraint is improved by the housing and the maximum material stresses generated in the housing are reduced.

[0007] According to the basic idea of the present invention, it is proposed that the pot-shaped housing at least partially has thickenings in the region of the edge of the opening and the toothing, in which the toothing is arranged, wherein the thickenings are formed by projections on the side pointing towards the frame leg to which the pot-shaped housing is fastened, and the edge of the opening and the side of the toothing remote from the frame leg are formed by flat surfaces.

[0008] By thickening the housing in the edge region of the opening which is also provided with a toothing, specifically the housing in the region where the locking pawl engages in the constrained situation is strengthened. On the one hand, the thickened portion increases the contact surface of the locking pawl, and on the other hand, due to the increased thickness, the deformation resistance of the housing in this region also increases. The thickened portion is deliberately designed such that it is formed by a convex portion facing the frame leg, i.e., facing the inner side of the housing, while the outer side of the housing is formed by a flat surface in the edge region of the opening and in the region of the toothing. Thus, the dimensions of the pot-shaped housing in the region of the toothing are more stable without increasing the required installation space. The proposed arrangement of the protrusion and the flat surface on the outer side deliberately uses the installation space on the inner side of the housing to strengthen the housing. In addition, since the thickened portion only needs to be formed on one side of the housing, this enables the housing to be produced economically and efficiently. Furthermore, since the proposed arrangement of the protrusion causes the force vector acting on the toothing and the edge of the opening to be transferred towards the inner side of the pot-shaped housing when a constraint occurs due to the force exerted by the locking pawl, the housing can be made more robust to withstand the forces acting in the constrained situation. Thus, when the locking pawl engages, a torque is exerted on the edge of the opening in the housing, which pushes the edge of the opening inwards and thus counteracts any expansion of the housing. During this deformation of the edge of the housing, the compressive stress generated in the protrusion additionally strengthens the housing and stabilizes it. Overall, a relatively rigid housing with respect to the forces acting in the constrained situation can be achieved by a simple device.

[0009] It is also proposed that the thickness of the toothing in the direction of the rotational axis of the seat belt shaft corresponds to the thickness of the thickened portion in the direction of the rotational axis of the seat belt shaft. This means that the entire width of the thickened portion is used to form the toothing and thus to transfer the load during the engagement of the locking pawl, which in turn minimizes the material stress. In addition, during the stamping process or the rolling process, the toothing can be produced particularly easily by deforming the entire edge region of the thickened portion to form the toothing.

[0010] It is also proposed that the dimensions of the thickened portion are set such that the center of the toothing arranged perpendicular to the rotational axis of the seat belt shaft and extending through the center of the thickened portion and the center of the locking pawl arranged perpendicular to the rotational axis of the seat belt shaft are in one plane. Due to the proposed sizing of the thickened portion and the locking pawl aligned therewith, when the locking pawl engages the toothing, both the locking pawl itself and the housing in the region of the thickened portion are subjected to as uniform and symmetric a load as possible, such that the maximum material stress generated in the housing and the locking pawl can also be reduced. In addition, this can reduce the tilting moment that may act on the locking pawl when engaging the toothing.

[0011] It is also proposed that the thickness of the housing in the region of the thickening is at least 20% and at most 80% greater than the wall thickness of the can-shaped housing. On the one hand, for the load case, the proposed design of the thickening enables the housing in the region of the toothing to be sufficiently strengthened. On the other hand, the proposed design of the thickening enables the thickening to be formed during the production of the housing, for example, by means of multiple forming processes or injection molding processes, without the need to add additional material.

[0012] It is also proposed that the thickening in the radial direction is greater than the toothing depth of the toothing. This means that the toothing is completely arranged within the thickening, such that the reaction forces to be absorbed during the restraint of the occupant are completely absorbed by the housing in the region of the proposed thickening. Accordingly, the housing is thickened over the entire radial extent of the toothing.

[0013] It is also proposed that the thickness of the thickening decreases outwards in the radial direction. This means that the housing is thicker and thus dimensionally more stable in the region of the tooth tips of the toothing than in the region of the tooth roots of the toothing. This is advantageous since the toothing forms an enlarged force transmission surface for engaging the locking pawl in the region of its front side or tip and the adjacent tooth flank.

[0014] It is also proposed here that the thickness of the thickening in the region of the radially inwardly directed front side of the toothing is greater than the thickness in the region of the roots of the toothing arranged radially on the outside.

[0015] It is also proposed that the housing is harder in the region of the thickening at the edge of the opening and of the toothing arranged therein than in the region including the pretensioner drive wheel. Due to the higher hardness proposed, the housing is dimensionally more stable and wear-resistant in the region of the toothing, which is particularly advantageous with regard to the binding forces to be transmitted in the case of restraint and the dimensional stability of the housing.

[0016] The hardness of the toothing can preferably decrease radially outwards, such that the toothing is particularly dimensionally stable and wear-resistant, especially in the region of the tooth tips and the adjacent tooth flanks.

[0017] The invention is explained below with reference to the preferred embodiments using the drawings.

[0018] Figure 1 Details of a seat belt retractor according to the invention are shown;

[0019] Figure 2 Shows Figure 1 of the enlarged details of the locking pawl and the can-shaped housing;

[0020] Figure 3 Is shown in a further enlarged view Figure 2 of the details.

[0021] Figure 1Details of a seat belt retractor according to the invention are shown, which has a frame 3 that can be fixedly fastened to a vehicle and a seat belt shaft 1 rotatably mounted in the frame. The frame 3 is U-shaped and has two frame legs 14 arranged parallel to each other, only one of which is shown. In each frame leg 14, an opening 4 is provided, in which the seat belt shaft 1 is rotatably mounted. The seat belt shaft 1 is formed in two parts with a seat belt shaft body 13 and a contoured head 2, onto which a seat belt (not shown) can be wound. The seat belt shaft body 13 and the contoured head 2 are connected to each other by a torsion bar 5 until the plastic deformation limit of the torsion bar 5 is reached, in order to form a torsionally fixed connection. The contoured head 2 is integrally formed with a pretensioner drive wheel 10 and is additionally a bearing part for a locking pawl 7 pivotally mounted thereon. The pretensioner drive wheel 10 has a contour on its outer side consisting of a plurality of caps arranged successively for engaging a pyrotechnically driven mass body chain. Depending on the drive type, the pretensioner drive wheel 10 can also be a gear or a comparable power transmission wheel. As a drive, an irreversible drive such as a pyrotechnic drive or a reversible drive such as an electric motor can be envisaged. Additionally, a gear can be provided between the drive and the pretensioner drive wheel.

[0022] On the outer side of the frame leg 14, i.e., on the side of the frame leg 14 remote from the other frame leg (not shown), a can-shaped housing 6 is fastened, which at least partially surrounds the pretensioner drive wheel 10. The can-shaped housing 6 has an opening 15 through which the contoured head 2 passes. The locking pawl 7 is arranged such that it is pivotally mounted on the part of the contoured head 7 passing through the opening 15. A toothing 9 is arranged in the opening 15 of the can-shaped housing 6, into which the locking pawl 7 engages when pivoted out.

[0023] The locking pawl 7 is part of a locking device, which additionally includes a corresponding sensor device that forces the locking pawl 7 to pivot together with a control disk based on an acceleration exceeding a predetermined extension of the seat belt and / or a vehicle deceleration exceeding a predetermined value. In the position where the locking pawl 7 engages in the toothing 9 of the can-shaped housing 6, the seat belt shaft 1 is locked in the extension direction in a known manner, wherein the holding force or locking force is transmitted from the toothing 9 via the can-shaped housing 6, the can-shaped housing 6 fastened to the frame 3, and finally via the frame 3 fastened to the vehicle structure or vehicle seat into the vehicle structure.

[0024] The can-shaped housing 6 has a thickening 8 in the region of the edge of the opening 15, in which the toothing 9 is arranged. The thickening 8 is formed by a projection 12 arranged on one side on the inner side of the can-shaped housing 6, or in other words, on the side of the housing 6 facing the frame leg 14, while the outer side of the housing 6 in the region of the thickening 8, i.e., on the side remote from the frame leg 14, is formed by a flat surface 11.

[0025] Figure 2 An enlarged detail of a seat belt retractor with the housing 6 and the locking pawl 7 is shown. The wall thickness D1 of the housing 6 in the region including the tensioner drive wheel 10 is at least substantially constant, and the housing is formed with a thickening 8 having a thickness D2 in the region of the edge of the opening 15. The thickness D2 of the thickening 8 is formed in such a way that in this region the housing 6 is thickened by a thickness D3 in addition to the wall thickness D1 of the housing 6 by means of the projection 12. The thickening 8 can be achieved, for example, during the production of the housing 6 in a stamping process or a comparable forming process, by forming the edge of the opening 15. The projection 12 can be regarded as a kind of bead or cam around the opening 15, which specifically stabilizes the edge of the opening 15 when subjected to the occurring loads, as will be explained in more detail below.

[0026] The dimensions of the thickening 8 are designed such that its extension in the radial direction with respect to Figure 1 the axis of rotation S of the seat belt shaft 1 shown is greater than the depth of the toothing 9, such that the toothing 9 is completely arranged within the thickening 8. The thickening 8 is deliberately oriented on one side such that the projection 12 points towards the inner side of the housing 6, while the outer side in this region is formed by a flat surface. Thus, the installation space on the inner side of the housing 6 is used to realize the thickening 8, while the outer side is optimized in terms of installation space requirements by forming a flat surface.

[0027] As Figure 3 can be seen, the projection 12 increases the force application surface of the toothing 9 towards the inner side of the housing 6, such that the force vector F resulting from the total load on the toothing 9 is offset towards the inner side of the housing 6. Figure 3 The offset, i.e., the distance of the force vector F to the neutral fiber or center M3 of the housing 6 in the region without the thickening 8, is shown. Due to this displacement of the force vector F caused by the thickening 8 arranged on the inner side of the housing, when the locking pawl 7 engages the toothing 9, a moment is applied to the edge of the housing 6, which moment is Figure 3 oriented clockwise in the view of Figure 3 and pushes the edge of the opening 15 inwards into the position exaggerated in dashed lines in In this case, compressive stresses are generated in the projection 12 arranged on the inner side of the housing, which compressive stresses counteract the deformation and strengthen the housing 6 itself during the deformation, which in turn limits the deformation occurring at the edge.

[0028] Due to this force transfer of the force vector F, the housing 6 deforms towards the inside of the housing 6 in the region of the edge of the opening 15 when under load. This counteracts the tendency of the housing 6 to "expand" towards the outside when the locking pawl 7 engages. It is also possible to Figure 3 identify the displacement of the force vector F that occurs by the displacement of the center M1 of the housing 6 in the thickening 8 compared to the center M3 of the housing 6 in the region without the thickening 8.

[0029] In an ideal case, the dimensions of the thickening 8 are set or the locking pawl 7 is arranged relative to the thickening 8 such that the center M2 of the locking pawl 7 and the center M1 of the thickening 8 lie in a plane, such that the housing 6 is loaded as evenly as possible in the region of the toothing 9 as well as the thickening 8 and the locking pawl 7.

[0030] The thickness D2 of the thickening 8 preferably corresponds to the thickness of the toothing 9, such that the entire cross-section of the thickening 8 is used to form the toothing 9.

[0031] The thickness D2 of the thickening 8 is preferably increased by at least 20% and at most 80% compared to the wall thickness D1 of the housing 6. In the present embodiment, the thickness D2 of the thickening 8 is 2 to 2.8 mm, and the wall thickness D1 of the housing 6 is 1.75 mm. The thickness D2 of the thickening 8 can be reduced in the radial direction. Thus, the thickness D2 in the region of the tip of the toothing 9 can be 2.8 mm, while the thickness D2 in the region of the radially outer tooth root of the toothing 9 can be 2 mm.

[0032] Furthermore, the hardness of the housing 6 in the region of the thickening 8 and the toothing 9 is greater than the hardness in the part of the housing 6 that includes the tensioner drive wheel 10 and does not have the thickening 8. In particular, the hardness of the teeth of the toothing 9 at their tips and adjacent tooth surfaces is higher than the hardness of the thickening in the radially outwardly adjacent part. This enables the toothing 9 to be designed to be particularly dimensionally stable and wear-resistant.

Claims

1. A seat belt retractor with a tensioning device, the tensioning device comprising: - Frame (3), which can be fixed to a vehicle and has two frame legs (14) arranged parallel to each other, each frame leg being provided with a bearing opening (4); and - A seat belt shaft (1) which is arranged between the frame legs (14) and is rotatably mounted in the bearing openings (4) of the frame legs (14); and - A tensioner drive wheel (10) which is rotationally fixed to the seat belt shaft (1) or can be connected to the seat belt shaft by a clutch, wherein, - A can-shaped housing (6) with a substantially constant wall thickness (D1) is fastened to one of the frame legs (14) on the side remote from the other frame leg (14), and the tensioner drive wheel (10) is arranged in the other frame leg, wherein, - The opening (15) of the can-shaped housing (6) has a toothing (9), and - A locking pawl (7) pivotally mounted on the seat belt shaft (1) engages the toothing (9) of the opening (15) of the can-shaped housing (6) to lock the seat belt shaft (1) in the extending direction, characterized in that - The can-shaped housing (6) at least partially has a thickening (8) in the region of the edge of the opening (15) and the toothing (9), and the toothing (9) is arranged in the thickening, wherein, - The thickening (8) is formed by a protrusion (12) on the side pointing to the frame leg (14), and the can-shaped housing (6) is fastened to the frame leg, and - The edge of the opening (15) and the side of the toothing (9) remote from the frame leg (14) are formed by a flat surface (11).

2. The seat belt retractor according to claim 1, characterized in that - The thickness of the toothing (9) in the direction of the rotational axis (S) of the seat belt shaft (1) corresponds to the thickness (D2) of the thickening (9) in the direction of the rotational axis (S) of the seat belt shaft (1).

3. The seat belt retractor according to claim 1 or claim 2, characterized in that - The size of the thickening (8) is set such that the center (M1) of the toothing (9) which is arranged perpendicular to the rotational axis (S) of the seat belt shaft (1) and extends through the thickening (8) and the center (M2) of the locking pawl (7) which is arranged perpendicular to the rotational axis (S) of the seat belt shaft (1) are located in a plane.

4. The seat belt retractor according to any one of claims 1 to 3, characterized in that - The thickness (D2) of the can-shaped housing (6) in the region of the thickening (8) is at least 20% greater and at most 80% greater than the wall thickness (D1) of the can-shaped housing (6).

5. The seat belt retractor according to any one of claims 1 to 4, characterized in that The thickening (8) is greater than the toothing depth of the toothing (9) in the radial direction.

6. The seat belt retractor according to any one of claims 1 to 5, characterized in that - The thickness (D2) of the thickened portion (8) decreases outward in the radial direction.

7. The seat belt retractor according to claim 6, characterized in that - The thickness (D2) of the thickened portion (8) in the region of the radially inward-facing front side of the toothing portion (9) is greater than the thickness in the toothing root portion arranged radially on the outside.

8. The seat belt retractor according to any one of claims 1 to 7, characterized in that - The thickened portion (8) of the can-shaped housing (6) at the edge of the opening (15) and the region of the toothing portion (9) arranged therein are harder than the region including the tensioner drive wheel (10).

9. The seat belt retractor according to claim 8, characterized in that - The hardness of the toothing portion (9) decreases radially outward.

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