Belt retractor with tensioning device

Abstract

To provide a belt retractor having a tensioning device that reduces maximum material stresses on the housing. [Solution] A tensioning device for a belt retractor includes a frame (3), a belt shaft (1) mounted in a bearing opening (4) of a frame leg (14), and a tensioner drive wheel (10) rotatably fixed thereto. A pot-shaped housing (6) is fastened to one of the frame legs (14) and has the tensioner drive wheel (10) arranged inside. The pot-shaped housing (6) has an opening (15) with teeth (9), and has thickened portions (8) at the edges of the opening (15) and in the area of ​​the teeth (9), with the housing teeth (9) arranged inside the thickened portions (8). The thickened portions (8) are formed by protrusions (12) on one side facing the frame leg (14) to which the pot-shaped housing (6) is fastened.

Description

[Technical Field]

[0001] The invention relates to a belt retractor having a tensioning device having the features of the preamble of claim 1 .

[0002] This general type of belt retractor is used in automobile safety belt systems to retract one end of a safety belt. The belt retractor itself has a frame for fastening to the vehicle, the frame having two parallel, opposing frame legs, each with a bearing opening in which a belt shaft is rotatably mounted, onto which one end of the safety belt can be retracted. The belt shaft is pretensioned in the safety belt retraction direction by a main spring supported by the frame. Furthermore, the belt shaft can be blocked by a blocking device that can be controlled by a sensor device sensitive to vehicle acceleration and / or belt webbing extension acceleration when a predetermined vehicle deceleration and / or belt webbing extension acceleration is exceeded in the safety belt extension direction. The blocking device is formed by a blocking claw that is pivotally mounted on the belt shaft or on a part connected to the belt shaft in a rotatably fixed manner, and the blocking claw engages with a frame-fixed blocking tooth to block the belt shaft.

[0003] Furthermore, a typical belt retractor has a tensioning device that, when activated, drives the belt shaft in the retracting direction and applies tension to the safety belt. This tensioning device can be reversible, for example, by a repeatedly operable electric motor, or irreversible, for example, by a one-time operable pyrotechnic drive. This tensioning device has a tensioner drive wheel that is rotatably connected to the belt shaft or can be connected to the belt shaft via a switchable clutch. Furthermore, a tensioner housing is provided that covers the tensioning device at least in the region of the drive wheel and can be a carrier for further components of the belt retractor and the tensioning device.

[0004] Such a belt retractor is known from German Patent Application No. 10 2008 059 387 (A1). The tensioner housing is designed as a pot-shaped housing, fastened to the outer frame legs of the belt retractor frame, and has a circular opening with teeth, into which blocking pawls engage to block the belt shaft. The teeth are formed by radially inwardly directed teeth arranged on the annular edge of the opening. The belt shaft consists of two parts, a belt shaft body and a profiled head, which are rotatably connected to each other via a torsion bar. The torsion bar forms a force limiting device and connects the profiled head and the belt shaft body to a torsionally fixed connection up to their plastic deformation limit. The belt shaft body is used to retract the safety belt, while the profiled head carries the blocking pawls and extends through an opening in the tensioning device housing. A blocking pawl pivotally mounted on the profile head is positioned to overlap the teeth of the opening so that when the blocking pawl pivots out it engages the teeth and blocks the belt shaft in the direction of extension. The torsion bar forms a force limiting device that allows force-limited belt webbing extension when the profile head is blocked, limiting the load on the occupant during an accident. The profile head also functions to hold a tensioner drive wheel located in a pot-like housing, so that when actuated via the profile head, the tensioning device drives the belt shaft in the retraction direction.

[0005] The pot-shaped housing of the tensioning device therefore not only covers the tensioner drive wheel, but also functions to absorb and transmit the restraining forces that arise when the occupant is restrained, and must therefore be designed to be dimensionally stable and load-bearing. Particular importance is attached to the teeth, which must absorb particularly large forces locally in the region of the engaging blocking pawls in the event of a restraint event, which leads to particularly high material stresses in the pot-shaped housing.

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

[0007] According to the basic idea of ​​the invention, it is proposed that the pot-shaped housing has at least partially thickened portions in the region of the edge of the opening and the teeth, the teeth being arranged inside the thickened portions, the thickened portions being formed by protrusions on one side facing the frame leg to which the pot-shaped housing is fastened, and the side of the edge of the opening and the teeth opposite the frame leg being formed by flat surfaces.

[0008] By thickening the housing in the edge region of the opening, where the teeth are also provided, the housing is particularly reinforced in the area where the blocking claws engage during arrest. On the one hand, the thickened portion increases the contact surface of the blocking claws, and on the other hand, the housing's resistance to deformation in this area increases due to the increased thickness. The thickened portion is intentionally formed by a raised ridge toward the frame leg, i.e., toward the inside of the housing, while the outside of the housing is intentionally 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 protrusions and the flat surface on the outside intentionally use the installation space inside the housing to reinforce the housing. Furthermore, this allows the housing to be manufactured cost-effectively, since the thickened portion only needs to be formed on one side of the housing. Furthermore, the proposed arrangement of the protrusions shifts the force vector acting on the teeth and the edge of the opening during binding, due to the force exerted by the blocking claws, toward the inside of the pot-shaped housing, making the housing more rigid against the forces acting during binding. As a result, when the blocking claws engage, a torque is exerted on the edge of the opening of the housing, pushing the edge of the opening inward and thus counteracting the expansion of the housing. During this deformation of the housing edge, the housing is further reinforced and stabilized by the compressive stresses induced in the protrusions. Overall, a fairly rigid housing can be achieved with simple measures with respect to the forces acting during binding.

[0009] It is further proposed that the thickness of the toothing in the direction of the belt shaft's rotation axis corresponds to the thickness of the thickened portion in the direction of the belt shaft's rotation axis. This means that the entire width of the thickened portion is used to form the toothing and thus transmit the load during engagement of the blocking claws, thereby maximally reducing material stresses. Furthermore, the toothing can be produced particularly easily in a stamping or rolling process by deforming the entire edge area of ​​the thickened portion to form the toothing.

[0010] Furthermore, it is proposed that the thickness be dimensioned so that the centers of the teeth, which are arranged perpendicular to the rotation axis of the belt shaft and extend through the thickness, and the centers of the blocking pawls, which are arranged perpendicular to the rotation axis of the belt shaft, lie in one plane. Due to the proposed dimensioning of the thickness and the blocking pawls aligned with it, when the blocking pawls engage with the teeth, both the blocking pawls themselves and the housing in the area of ​​the thickness are loaded as uniformly and symmetrically as possible, which also reduces the maximum material stresses in the housing and the blocking pawls. This also reduces the tilting moment that may act on the blocking pawls when they engage with the teeth.

[0011] It is further proposed that the housing has a thickness in the region 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 design of the thickened portion allows, on the one hand, to sufficiently reinforce the housing in the region of the teeth against loads, and, on the other hand, to form the thickened portion during the manufacturing process of the housing, for example by a multiple molding process or an injection molding process, without the need to add additional material.

[0012] Furthermore, it is proposed that the radial thickness of the toothing be greater than the tooth depth of the toothing. This means that the toothing is located completely within the thickness, and the reaction forces absorbed when restraining an occupant are completely absorbed by the housing in the area of ​​the proposed thickness. Therefore, the housing is thickened over the entire radial extent of the toothing.

[0013] Furthermore, it is proposed that the thickness of the thickened portion decreases radially outward. This means that the housing is thicker in the region of the tooth tips and therefore dimensionally more stable than in the tooth roots. This is advantageous because the tooth forms an enlarged force transmission surface for the engaging blocking pawl in the region of its front side or tip and on both lateral sides of the adjacent tooth.

[0014] Furthermore, it is proposed that the thickened portion has a greater thickness in the radially inward facing front region of the tooth than in the radially outwardly arranged tooth base.

[0015] Furthermore, it is proposed that the pot-shaped housing be harder in the area of ​​the thickened portion and the teeth located therein at the edge of the opening than in the area containing the tensioner drive wheel. The proposed higher hardness makes the housing more dimensionally stable and more wear-resistant in the area of ​​the teeth, which is particularly advantageous for the transmitted binding force and for the dimensional stability of the housing when binding occurs.

[0016] The hardness of the toothing may preferably decrease radially outward, so that the toothing is particularly dimensionally stable and wear-resistant, especially in the areas at the tooth tips and on both lateral sides of adjacent teeth. [Brief explanation of the drawings]

[0017] The present invention will be described below using preferred embodiments with reference to the accompanying drawings. [Figure 1] 1 is a diagram showing details of a belt retractor according to the present invention; [Figure 2] FIG. 2 shows an enlarged detail of FIG. 1 with a block pawl and a pot-shaped housing. [Figure 3] FIG. 3 is a further enlarged view of the details of FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0018] FIG. 1 shows details of a belt retractor according to the present invention, including a frame 3 that can be fixedly fastened to a vehicle and a belt shaft 1 rotatably mounted therein. The frame 3 is U-shaped with two frame legs 14 arranged parallel to each other, only one of which is shown. Each of the frame legs 14 has an opening 4 in which the belt shaft 1 is rotatably mounted. The belt shaft 1 is formed in two parts, including a belt shaft body 13 and a profile head 2, through which a safety belt (not shown) can be wound around the belt shaft body 13. The belt shaft body 13 and the profile head 2 are connected to each other via a torsion bar 5 up to the plastic deformation limit of the torsion bar 5, forming a torsionally fixed connection. The profile head 2 is formed integrally with a tensioner drive wheel 10 and is also a carrier for a blocking pawl 7 pivotally mounted thereon. The tensioner drive wheel 10 has a profile on its outer side consisting of several carrots arranged adjacent to each other for engaging a pyrotechnically driven mass chain. Depending on the type of drive, the tensioner drive wheel 10 may be a gear or similar power transmission wheel. The drive may be an irreversible drive, such as a pyrotechnic drive, or a reversible drive, such as an electric motor. Furthermore, a gear may additionally be provided between the drive and the tensioner drive wheel.

[0019] A pot-shaped housing 6 is fastened to the outside of the frame legs 14, i.e., on one side of the frame leg 14 and on the opposite side of the other frame leg (not shown), and the pot-shaped housing 6 at least partially surrounds the tensioner drive wheel 10. The pot-shaped housing 6 has an opening 15 through which the profile head 2 passes. The blocking claw 7 is arranged so as to be pivotally mounted in the part of the profile head 7 that passes through the opening 15. A toothing 9 is arranged in the opening 15 of the pot-shaped housing 6, and this toothing 9 engages with the blocking claw 7 when it is pivoted outward.

[0020] The blocking pawl 7 is part of a blocking device which also comprises a corresponding sensor device which forces a pivoting movement of the blocking pawl 7 depending on exceeding a predetermined extension acceleration of the safety belt and / or exceeding a predetermined vehicle deceleration associated with the control disc. In the engagement position of the blocking pawl 7 in the toothing 9 of the pot-shaped housing 6, the belt shaft 1 is blocked in the extension direction in a known manner, and the holding or blocking force is transmitted from the toothing 9 via the pot-shaped housing 6, the fastening of the pot-shaped housing 6 to the frame 3 and finally the fastening of the frame 3 to the vehicle structure or the fastening of the vehicle seat to the vehicle structure.

[0021] The pot-shaped housing 6 has a thickened portion 8 in the area of ​​the edge of the opening 15, in which teeth 9 are arranged. The thickened portion 8 is formed by a protrusion 12 on one side located on the inside of the pot-shaped housing 6, i.e. on the side of the housing 6 facing the frame leg 14, while the outside of the housing 6 in the area of ​​the thickened portion 8, i.e. on the side opposite the frame leg 14, is formed by a flat surface 11.

[0022] 2 is an enlarged view of a detail of a belt retractor, including a housing 6 and a blocking pawl 7. The housing 6 has an at least approximately constant wall thickness D1 in the region including the tensioner drive wheel 10, while in the region of the edge of the opening 15 a thickened portion 8 having a thickness D2 is formed. The thickness D2 of the thickened portion 8 is formed by a protrusion 12 thickening the housing 6 in this region by a thickness D3 in addition to the wall thickness D1 of the housing 6. The thickened portion 8 can be realized by a forming process of the edge of the opening 15 during the manufacturing process of the housing 6, for example in a stamping process or an equivalent molding process. The protrusion 12 can be considered as a kind of bead or cam surrounding the opening 15, and particularly stabilizes the edge of the opening 15 under the loads that occur, as will be explained in more detail below.

[0023] The thickened portion 8 is dimensioned to have a radial extent relative to the rotation axis S of the belt shaft 1 shown in Figure 1 that is greater than the depth of the toothing 9, so that the toothing 9 is located completely within the thickened portion 8. The thickened portion 8 is intentionally oriented on one side so that the protrusions 12 are directed towards the inside of the housing 6, while the outside of this area is formed by a flat surface. Thus, the installation space inside the housing 6 is used to realize the thickened portion 8, while the outside is optimized with respect to the installation space requirements by forming a flat surface.

[0024] As can be seen in FIG. 3 , the protrusions 12 expand the force application surface of the toothing 9 toward the inside of the housing 6, so that the force vector F resulting from the total load on the toothing 9 is offset toward the inside of the housing 6. This offset is illustrated in FIG. 3 by the distance of the force vector F relative to the neutral line or center M3 of the housing 6 in the area without the thickened portion 8. This displacement of the force vector F caused by the thickened portion 8 arranged inside the housing exerts a moment on the edge of the housing 6 when the blocking pawl 7 engages with the toothing 9. This moment, directed clockwise as viewed in FIG. 3 , pushes the edge of the opening 15 inward toward the position highlighted by the dashed line in FIG. 3 . In this case, compressive stresses are generated in the protrusions 12 arranged inside the housing, which oppose deformation and compensate for the rigidity of the housing 6 itself during deformation, thereby limiting the deformation of the edge.

[0025] This force transfer of force vector F causes the housing 6 to deform inwards in the region of the edges of the openings 15 when loaded. This acts to counteract the tendency of the housing 6 to "blow out" outwards when the blocking pawls 7 engage. The displacement of force vector F can also be seen in Figure 3 by the displacement of the centre M1 of the housing 6 at the thickened section 8 compared to the centre M3 of the housing 6 in the region without the thickened section 8.

[0026] Ideally, the thickened portion 8 is dimensioned or the blocking claw 7 is positioned relative to the thickened portion 8 so that the center M2 of the blocking claw 7 and the center M1 of the thickened portion 8 lie in one plane, so that the housing 6 in the region of the toothing 9, the thickened portion 8 and the blocking claw 7 are loaded as evenly as possible.

[0027] The thickness D2 of the thickened portion 8 preferably corresponds to the thickness of the toothing 9, so that the entire cross section of the thickened portion 8 is used to form the toothing 9.

[0028] The thickness D2 of the thickened portion 8 is preferably increased by at least 20 percent and at most 80 percent compared to the wall thickness D1 of the housing 6. In this 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 tip region of the toothing 9 can be 2.8 mm, and the thickness D2 in the root region radially outside the toothing 9 can be 2 mm.

[0029] Furthermore, the housing 6 has a higher hardness in the region of the thickened portion 8 and the toothing 9 than the portion of the housing 6 comprising the tensioner drive wheel 10, which does not have the thickened portion 8. In particular, the teeth of the toothing 9 have a higher hardness at their tips and on both lateral sides of the adjacent teeth than the thickened portion in the radially outward adjacent portion. This makes it possible to design the toothing 9 to be particularly dimensionally stable and highly wear-resistant.

Claims

1. A belt retractor having a tensioning device, The tension applying device is a frame (3) that can be fixed to the vehicle, the frame (3) having two frame legs (14) arranged parallel to each other and each having a bearing opening (4); - a belt shaft (1) arranged between the frame legs (14) and rotatably mounted in the bearing openings (4) of said frame legs (14); a tensioner drive wheel (10) connected to said belt shaft (1) in a rotatably fixed manner or which can be connected via a clutch; Equipped with a pot-shaped housing (6) with a substantially constant wall thickness (D1) fastened to one of said frame legs (14) and opposite to the other said frame leg (14), in which said tensioner drive wheel (10) is located; - said pot-like housing (6) has an opening (15) with teeth (9); a belt retractor, comprising a pivotally mounted blocking pawl (7) on the belt shaft (1), which engages with the teeth (9) of the opening (15) of the pot-like housing (6) to block the belt shaft (1) in the direction of extension, - the pot-shaped housing (6) has, at least partially, thickened portions (8) in the area of ​​the edge of the opening (15) and the teeth (9), the teeth (9) being arranged in the thickened portions (8); - said thickened part (8) is formed by a projection (12) on one side directed towards the frame leg (14) to which said pot-shaped housing (6) is fastened; and the edge of the opening (15) and the tooth (9) opposite the frame leg (14) are formed by a flat surface (11); Belt retractor.

2. A belt retractor according to claim 1, wherein the thickness of the tooth portion (9) in the direction of the rotation axis (S) of the belt shaft (1) corresponds to the thickness (D2) of the thickened portion (9) in said direction of the rotation axis (S) of the belt shaft (1).

3. 3. A belt retractor according to claim 1 or 2, wherein the thickened portion (8) is dimensioned so that the centers (M1) of the teeth (9) that are arranged perpendicular to the rotation axis (S) of the belt shaft (1) and that extend through the thickened portion (8) and the centers (M2) of the blocking pawls (7), that are arranged perpendicular to the rotation axis (S) of the belt shaft (1), lie in one plane.

4. A belt retractor according to any one of claims 1 to 3, wherein the pot-shaped housing (6) has a thickness (D2) in the region of the thickened portion (8) that is at least 20 percent and at most 80 percent greater than the wall thickness (D1) of the pot-shaped housing (6).

5. A belt retractor according to any one of claims 1 to 4, wherein the thickened portion (8) is radially greater than the tooth depth of the toothed portion (9).

6. A belt retractor according to any one of claims 1 to 5, wherein the thickness (D2) of the thickened portion (8) decreases radially outward.

7. A belt retractor according to claim 6, wherein the thickened portion (8) has a greater thickness (D2) in the front region directed radially inward of the tooth portion (9) than in the tooth base located radially outward.

8. A belt retractor according to any one of claims 1 to 7, wherein the pot-shaped housing (6) is harder at the edge of the opening (15) in the region of the thickened portion (8) and the teeth (9) arranged therein than in the region including the tensioner drive wheel (10).

9. A belt retractor according to claim 8, wherein the hardness of the teeth (9) decreases radially outwards.

Images