Belt retractor with a tensioning device

Abstract

The invention relates to a belt retractor comprising a tensioning device having a frame (3) which can be fixedly secured to the vehicle, the frame comprising two frame members (14) which are arranged in parallel with one another, each frame member comprising a bearing opening (4), and a belt shaft (1) which is arranged between frame members (14) and is rotatably mounted in the bearing openings (4) of the frame members (14), and a tensioner drive wheel (10) which is connected to the belt shaft (1) for conjoint rotation or can be connected thereto for conjoint rotation via a coupling. A pot-shaped housing (6) having a substantially constant wall thickness (D1) is fastened on one of the frame members (14) on the side facing away from the other frame member (14), in which pot-shaped housing the tensioner drive wheel (10) is arranged. The pot-shaped housing (6) has an opening (15) comprising a toothing (9), and the pot-shaped housing (6) has, at least in portions, a thickening (8) in the region of the edge of the opening (15) and the toothing (9), in which thickening a toothing (9) of the housing is arranged, wherein the thickening (8) is formed by a protrusion (12) on one side, the protrusion being directed toward the frame member (14) on which the pot-shaped housing (6) is fastened.

Description

[0001] Belt retractor with a tensioning device

[0002] The present invention relates to a belt retractor with a tensioning device having the features of the preamble of claim 1.

[0003] Belt retractors of this type are used in safety belt systems for motor vehicles and serve to wind up one end of a safety belt of the safety belt system. The belt retractor itself has a frame for attachment to the vehicle, which frame has two parallel, oppositely arranged frame legs, each with a bearing opening, in which a belt shaft is rotatably mounted, onto which the safety belt can be wound at one end. The belt shaft is pretensioned in the winding direction of the safety belt by means of a drive spring supported on the frame. Furthermore, the belt shaft can be blocked in the extension direction of the safety belt by means of a blocking device, which can be controlled by a sensor device sensitive to vehicle acceleration and / or a sensor device sensitive to belt extension acceleration, if a predetermined vehicle deceleration and / or belt extension acceleration is exceeded.The blocking device is formed by a blocking pawl pivotally mounted on the belt shaft or on a part connected to it in a rotationally fixed manner, which engages a frame-fixed blocking toothing to block the belt shaft.

[0004] Furthermore, the generic belt retractor has a tensioning device which, when activated, drives the belt shaft in the winding direction to tension the seat belt. The tensioning device can be reversible, e.g., with a repeatedly activated electric motor, or irreversible, with a pyrotechnic drive that can be activated once. The tensioning device has a tensioner drive wheel which is connected to the belt shaft in a rotationally fixed manner or can be connected to it via a switchable clutch. Furthermore, a tensioner housing is provided which covers the tensioning device at least in the area of ​​the drive wheel and can support other components of the belt retractor and the tensioning device. Such a belt retractor is known from DE 10 2008 059 387 A1.The tensioner housing is designed as a pot-shaped housing that is attached to the outside of a frame leg of the belt retractor frame and has a circular opening with teeth into which the blocking pawl engages to block the belt shaft. The teeth are arranged in the annular edge of the opening and are formed by radially inward-facing teeth. The belt shaft is designed in two parts with a 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 belt shaft body to form a rotationally fixed assembly up to its plastic deformation limit. The belt shaft body is used to wind up the seat belt, while the profile head supports the blocking pawl and extends through the opening in the tensioner housing.The locking pawl, pivotally mounted on the profile head, is arranged in such a way that it overlaps the teeth of the opening, so that when the locking pawl pivots out, it engages the teeth and blocks the belt shaft in the extension direction. The torsion bar forms a force-limiting device and, when the profile head is blocked, enables force-limited belt webbing extension to limit the occupant load during an accident. The profile head also serves to mount the tensioner drive wheel, which is located in the pot-shaped housing, so that when activated, the tensioner drives the belt shaft in the winding direction via the profile head.

[0005] The cup-shaped housing of the tensioning device therefore serves not only to cover the tensioner drive gear, but also to absorb and transmit the restraint forces that occur when the occupant is restrained. Therefore, it must be dimensionally stable and load-bearing. A particularly critical point is the toothing, as it must absorb particularly large forces locally in the area of ​​the engaging locking pawl when the occupant is restrained, leading to particularly high material stresses in the cup-shaped housing.

[0006] Against this background, the invention is based on the object of providing a generic

[0007] To provide a belt retractor with a tensioning device, in which the load is absorbed in the

[0008] The retention effect of the housing is improved and the resulting maximum material stresses in the housing are reduced.

[0009] According to the basic idea of ​​the invention, it is proposed that the pot-shaped housing in the region of the edge of the opening and the toothing at least partially has a thickening in which the toothing is arranged, wherein the thickening is formed by a one-sided elevation which is directed towards the frame leg to which the pot-shaped housing is fastened, and the side of the edge of the opening and the toothing facing away from the frame leg is formed by a flat surface.

[0010] By thickening the housing in the edge area of ​​the opening, where the teeth are also provided, the housing is specifically stiffened in the area into which the blocking pawl engages when held back. On the one hand, the thickening enlarges the contact surface for the blocking pawl and, on the other hand, the deformation resistance of the housing in this area is increased due to the increased thickness. The thickening is specifically designed so that it is formed by a raised area towards the frame leg, i.e. towards the inside of the housing, while the outside of the housing is formed by a flat surface in the area of ​​the edge of the opening and the teeth. The pot-shaped housing is therefore more dimensionally stable in the area of ​​the teeth without increasing the required installation space.The proposed arrangement of the raised portion and the flat outer surface deliberately utilize the space within the housing to stiffen the housing. Furthermore, this enables cost-effective production of the housing as the thickened portion only needs to be formed on one side of the housing. Furthermore, this allows the housing to be made stiffer to withstand the forces acting during retention because the proposed arrangement of the raised portion shifts the force vector acting on the toothing and the edge of the opening towards the inside of the pot-shaped housing due to the forces exerted by the blocking pawl during retention. As a result, when the blocking 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 housing edge, the housing is further stiffened and stabilized by the compressive stresses generated in the raised area. Overall, this allows for a significantly stiffer housing with respect to the forces acting during restraint.

[0011] It is further proposed that the thickness of the toothing in the direction of the belt shaft's rotational axis correspond to the thickness of the thickened portion in the direction of the belt shaft's rotational axis. This utilizes the entire width of the thickened portion to form the toothing and thus to transfer load during engagement of the locking pawl, which in turn minimizes material stresses. Furthermore, the toothing can be manufactured particularly easily in a stamping or rolling process by deforming the entire edge area of ​​the thickened portion to form the toothing.

[0012] It is further proposed that the thickened portion be dimensioned such that the center of the toothing, which is arranged perpendicular to the rotational axis of the belt shaft and runs through the thickened portion, and the center of the locking pawl, which is arranged perpendicular to the rotational axis of the belt shaft, lie in the same plane. Through the proposed dimensioning of the thickened portion and the blocking pawl aligned therewith, both the blocking pawl itself and the housing in the area of ​​the thickened portion are loaded as evenly and symmetrically as possible when the blocking pawl engages the toothing, so that the maximum material stresses in the housing and the blocking pawl can be reduced. Furthermore, this can reduce potential tilting moments acting on the blocking pawl when it engages the toothing.

[0013] It is further proposed that the housing have a thickness in the area of ​​the thickened portion that is at least 20 percent and at most 80 percent greater than the wall thickness of the pot-shaped housing. The proposed dimensioning of the thickened portion enables sufficient stiffening of the housing in the area of ​​the toothing for the load case and, on the other hand, the shaping of the thickened portion during the housing manufacturing process, e.g., through multiple forming or an injection molding process, without the need to add additional material. It is further proposed that the thickened portion be greater in the radial direction than the toothing depth. The toothing is thus completely arranged in the thickened portion, so that the reaction forces to be absorbed when restraining the occupant are completely absorbed by the housing in the area of ​​the proposed thickened portion.The housing is thus thickened over the entire radial extent of the gearing.

[0014] It is further proposed that the thickness of the thickened portion decreases radially outward. This makes the housing thicker and therefore more dimensionally stable in the area of ​​the tooth tips than in the tooth base. This is advantageous because the toothing forms an enlarged force transmission surface for the engaging locking pawl in the area of ​​its front faces or tips and the adjacent tooth flanks.

[0015] It is further proposed that the thickening in the area of ​​the radially inwardly directed end faces of the toothing has a greater thickness than in the radially outwardly arranged tooth base.

[0016] It is further proposed that the pot-shaped housing be of a higher hardness in the area of ​​the thickened portion and the toothing arranged therein at the edge of the opening than in the area surrounding the tensioner drive gear. Due to the proposed higher hardness, the housing is more dimensionally stable and wear-resistant in the area of ​​the toothing, which is particularly advantageous for the retaining forces to be transmitted and the dimensional stability of the housing itself in the event of a retaining action.

[0017] The hardness of the toothing can preferably decrease radially outwards, so that the toothing is particularly dimensionally stable and wear-resistant, particularly in the area of ​​the tooth tips and the adjoining tooth flanks.

[0018] The invention is explained below using preferred embodiments with reference to the accompanying figures. Figure 1 shows a section of a belt retractor according to the invention;

[0019] Fig. 2 is an enlarged section of Figure 1 with the locking pawl and the pot-shaped housing;

[0020] Fig. 3 shows the section of Figure 2 in a further enlarged view.

[0021] Figure 1 shows a section of a belt retractor according to the invention with a frame 3 that can be fixedly attached to the vehicle and a belt shaft 1 arranged therein. The frame 3 is U-shaped with two frame legs 14 arranged parallel to one another, only one of which is shown. An opening 4 is provided in each of the frame legs 14, in which the belt shaft 1 is rotatably mounted. The belt shaft 1 is formed in two parts with a belt shaft body 13 and a profile head 2, wherein a safety belt (not shown) can be wound onto the belt shaft body 13. The belt shaft body 13 and the profile head 2 are connected to one another via a torsion bar 5 to form a rotationally fixed assembly up to the plastic deformation limit of the torsion bar 5. The profile head 2 is formed in one piece with a tensioner drive wheel 10 and additionally supports a blocking pawl 7 pivotally mounted thereon.The tensioner drive wheel 10 has a profile on its outer surface consisting of a plurality of adjacent spherical caps for engagement with a pyrotechnically driven mass body chain. Depending on the drive type, the tensioner drive wheel 10 can also be a gear or a similar force-transmitting wheel. Irreversible drives, such as pyrotechnic drives, or reversible drives, such as electric motors, are conceivable as drives. Furthermore, a transmission can be provided between the drive and the tensioner drive wheel.

[0022] A cup-shaped housing 6 is attached to the outer side of the frame leg 14, i.e., on the side of the frame leg 14 facing away from the other frame leg (not shown), which at least partially encloses the tensioner drive gear 10. The cup-shaped housing 6 has an opening 15 through which the profile head 2 passes. The blocking pawl 7 is arranged such that it is pivotally mounted on the section of the profile head 7 passing through the opening 15. A toothing 9 is arranged in the opening 15 of the cup-shaped housing 6, into which the blocking pawl 7 engages when pivoted out.

[0023] The blocking pawl 7 is part of a blocking device, which additionally comprises corresponding sensor devices which, in conjunction with a control disk, force the pivoting movement of the blocking pawl 7 depending on the exceeding of a predetermined extension acceleration of the seat belt and / or the exceeding of a predetermined vehicle deceleration. When the blocking pawl 7 is engaged with the toothing 9 of the cup-shaped housing 6, the belt shaft 1 is blocked in the extension direction in a known manner, wherein the restraining forces or blocking forces are transmitted from the toothing 9 via the cup-shaped housing 6, the attachment of the cup-shaped housing 6 to the frame 3, and finally via the attachment of the frame 3 to the vehicle structure or a vehicle seat into the vehicle structure.

[0024] The cup-shaped housing 6 has a thickened portion 8 in the region of the edge of the opening 15, in which the toothing 9 is arranged. The thickened portion 8 is formed by a one-sided elevation 12, which is arranged on the inside of the cup-shaped housing 6 or, in other words, on the side of the housing 6 facing towards the frame leg 14, while the outside of the housing 6 in the region of the thickened portion 8, i.e., on the side facing away from the frame leg 14, is formed by a flat surface 11.

[0025] Figure 2 shows an enlarged section of the belt retractor with the housing 6 and the blocking pawl 7. The housing 6 has an at least substantially constant wall thickness D1 in the area encompassing the tensioner drive wheel 10 and is formed into a thickened portion 8 with a thickness D2 in the area of ​​the edge of the opening 15. The thickness D2 of the thickened portion 8 is formed by the housing 6 being thickened in this area by the elevation 12 by the thickness D3 in addition to the wall thickness D1 of the housing 6. The thickened portion 8 can be realized, for example, by a forming process of the edge of the opening 15, in a manufacturing process of the housing 6 in a stamping process or in a comparable shaping process. The elevation 12 can be viewed as a type of bead or cams surrounding the opening 15, which specifically stabilize the edge of the opening 15 under the occurring load, as will be explained in more detail below.

[0026] The thickening 8 is dimensioned such that, in the radial direction relative to the rotational axis S of the belt shaft 1, visible in Figure 1, it has a greater extension than the depth of the toothing 9, so that the toothing 9 is completely arranged within the thickening 8. The thickening 8 is deliberately oriented on one side, specifically so that the elevation 12 faces the inside of the housing 6, while the outside in this area is formed by the flat surface. Thus, the installation space within the housing 6 is utilized to create the thickening 8, while the outside is optimized in terms of installation space requirements by forming the flat surface.

[0027] As can be seen in Figure 3, the elevation 12 enlarges the force application surface of the toothing 9 towards the inside of the housing 6, so that the force vector F resulting from the total load on the toothing 9 is offset towards the inside of the housing 6. The offset is shown in Figure 3 by the distance of the force vector F to the neutral fiber or center M3 of the housing 6 in the area without the thickened portion 8. Due to this displacement of the force vector F caused by the thickened portion 8 arranged on the inside of the housing, when the blocking pawl 7 engages the toothing 9, a moment is exerted on the edge of the housing 6. This moment is oriented clockwise in the illustration in Figure 3 and pushes the edge of the opening 15 inwards into the position shown exaggeratedly by the dashed lines in Figure 3.In this case, a compressive stress is generated in the elevation 12 arranged on the inside of the housing, which counteracts the deformation and stiffens the housing 6 itself during the deformation, which in turn limits the deformation of the edge.

[0028] Due to this force shift of the force vector F, the housing 6 is deformed in the region of the edge of the opening 15 toward the inside of the housing 6 when subjected to load. This counteracts a tendency for the housing 6 to "expand" toward the outside upon engagement of the locking pawl 7. The shift of the force vector F can also be recognized in Figure 3 by the shift of the center M1 of the housing 6 in the thickened portion 8 relative to the center M3 of the housing 6 in the area without the thickened portion 8.

[0029] Ideally, the thickening 8 is dimensioned or the blocking pawl 7 is arranged in relation to the thickening 8 in such a way that the center M2 of the blocking pawl 7 and the center M1 of the thickening 8 lie in one plane, so that the housing 6 in the area of ​​the toothing 9 and the thickening 8 and the blocking pawl 7 are loaded as evenly as possible.

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

[0031] The thickness D2 of the thickened portion 8 is preferably increased by at least 20 percent and a maximum of 80 percent compared to the wall thickness D1 of the housing 6. In the present exemplary embodiment, the thickness D2 of the thickened portion 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 thickened portion 8 can decrease in the radial direction. Thus, the thickness D2 in the area of ​​the tips of the toothing 9 can be 2.8 mm, while the thickness D2 in the area of ​​the radially outer toothing base of the toothing 9 can be 2 mm.

[0032] Furthermore, the housing 6 has a higher hardness in the area of ​​the thickened portion 8 and the toothing 9 than in the section of the housing 6 encompassing the tensioner drive gear 10 without the thickened portion 8. In particular, the teeth of the toothing 9 have a higher hardness at their tips and adjacent tooth flanks than the thickened portion in the radially outwardly adjoining section. This allows the toothing 9 to be designed to be particularly dimensionally stable and wear-resistant.

Claims

Claims:

1. Belt retractor with a tensioning device with -a frame (3) which can be fixed to the vehicle and has two frame legs (14) arranged parallel to one another, each with a bearing opening (4), and -a belt shaft (1) which is arranged between 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 connected in a rotationally fixed manner to the belt shaft (1) or can be connected via a coupling, wherein -on one of the frame legs (14) on the side facing away from the other frame leg (14) a pot-shaped housing (6) with a substantially constant wall thickness (Dl) is fastened, in which the tensioner drive wheel (10) is arranged, wherein -the pot-shaped housing (6) has an opening (15) with a toothing (9), and -a pivotably mounted blocking pawl (7) is provided on the belt shaft (1), which pawl engages the toothing (9) of the opening (15) of the pot-shaped housing (6) to block the belt shaft (1) in the extension direction, characterized in that -the pot-shaped housing (6) has, at least in sections, a thickening (8) in the region of the edge of the opening (15) and the toothing (9), in which the toothing (9) is arranged, wherein -the thickening (8) is formed by a one-sided elevation (12) which is directed towards the frame leg (14) to which the pot-shaped housing (6) is attached, and -the side of the edge of the opening (15) and the toothing (9) facing away from the frame leg (14) is formed by a flat surface (11).

2. 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 belt shaft (1) corresponds to the thickness (D2) of the thickening (9) in the direction of the rotational axis (S) of the belt shaft (1) Belt retractor according to claim 1 or 2, characterized in that -the thickening (8) is dimensioned such that the center (M1) of the toothing (9), which is arranged perpendicular to the axis of rotation (S) of the belt shaft (1) and runs through the thickening (8), and the center (M2) of the blocking pawl (7), which is arranged perpendicular to the axis of rotation (S) of the belt shaft (1), lie in one plane. Belt retractor according to one of claims 1 to 3, characterized in that -the pot-shaped housing (6) has a thickness (D2) in the region of the thickening (8) which is at least 20 percent and at most 80 percent greater than the wall thickness (D1) of the pot-shaped housing (6). Belt retractor according to one of claims 1 to 4, characterized in that the thickening (8) is greater in the radial direction than the toothing depth of the toothing (9). Belt retractor according to one of claims 1 to 5, characterized in that - the thickness (D2) of the thickened portion (8) decreases radially outwards. Belt retractor according to claim 6, characterized in that -the thickening (8) in the region of the radially inwardly directed end faces of the toothing (9) has a greater thickness (D2) than in the radially outwardly arranged toothing base. Belt retractor according to one of claims 1 to 7, characterized in that -the pot-shaped housing (6) has a higher hardness in the region of the thickening (8) and the toothing (9) arranged therein at the edge of the opening (15) than in the region comprising the tensioner drive wheel (10).

9. Belt retractor according to claim 8, characterized in that - the hardness in the toothing (9) decreases radially outwards.

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