JP4205794B2 - Torsional stress absorbing shaft for seat belt device and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a torsional stress absorbing shaft for a seat belt device used for a torsion bar or the like in a retractor, and a method for manufacturing the shaft.
[0002]
[Prior art]
As shown in FIG. 5, a webbing retractor 100 that constitutes a seat belt device of a vehicle includes a type having a torsion bar 102. The torsion bar 102 is made of a plastically deformable metal and is formed in a substantially cylindrical shape, and hexagonal portions 102A and 102B are formed at both ends.
[0003]
The hexagonal portion 102 </ b> A is inserted into a hexagonal insertion hole 104 </ b> A formed in the pretensioning shaft 104. The pretensioning shaft 104 is fixed to a spool 108 that winds up the webbing 106 and rotates together with the spool 108. For this reason, the torsion bar 102 rotates together with the spool 108 via the pretensioning shaft 104.
[0004]
On the other hand, the hexagonal portion 102 </ b> B is inserted into a hexagonal insertion hole 110 </ b> A formed in the locking shaft 110, and the locking shaft 110 rotates together with the torsion bar 102.
[0005]
In such a configuration, during normal driving of the vehicle, the torsion bar 102, the pretension shaft 104, and the lock shaft 110 rotate together through the spool 108. Thereby, the webbing 106 can be pulled out and taken up.
[0006]
On the other hand, at the time of sudden deceleration of the vehicle, the locking shaft 110 is locked by a lock mechanism (not shown), and the webbing 106 is not pulled out.
[0007]
Next, when a pulling force acts in the pulling direction of the webbing 106 due to the reaction of the occupant, since the locking shaft 110 is already locked, the hexagonal portion 102B of the torsion bar 102 cannot rotate, but the hexagonal portion 102A It can be rotated. For this reason, the torsion bar 102 is twisted, the spool 108 is rotated relative to the locking shaft 110, the webbing 106 is pulled out, and the impact acting on the occupant is reduced.
[0008]
On the other hand, the end portion of the locking shaft 110 is formed with a male screw portion 110C having a stepped portion 110B provided at the end portion thereof, and a ring break ring 111 is screwed.
[0009]
When the lock shaft 110 is locked and the spool 108 rotates relative to the lock shaft 110 via the torsion bar 102, the ring ring 111 can rotate with the spool 108. Slides and contacts the stepped portion 110B, so that the stroke of the broken ring 111 is limited.
[0010]
By the way, the stress that the conventional torsion bar 102 can withstand, as shown in FIG. 3A, reaches a peak and twists at a predetermined angle and then decreases at a time. For this reason, when the pulling-out force of the webbing 106 is decreased stepwise, another control method is required.
[0011]
[Problems to be solved by the invention]
In view of the above-described facts, an object of the present invention is to obtain a torsional stress absorbing shaft for a seat belt device that can reduce the drawing force of the webbing in a stepwise manner with a simple structure.
[0012]
[Means for Solving the Problems]
According to the first aspect of the present invention, in the torsional stress absorbing shaft for seat belt apparatus, the shaft to which the torsional stress is applied is pressed into the hollow part of the hollow member and the hollow part of the hollow member to form a multi-layered shape. A plurality of absorbing members that are engaged with each other and have different breaking points with respect to torsional stress.
According to the first aspect of the present invention, a hollow member is provided in the shaft to which torsional stress is applied, and a plurality of different breaking points with respect to torsional stress are formed in the hollow portion of the hollow member in a polygonal shape. The absorbing member is press-fitted to form a multilayer. Thereby, the shaft to which the torsional stress is applied can reduce the applied torsional stress stepwise.
[0013]
In other words, when this shaft is used as a torsion bar of a webbing take-up device that constitutes a seat belt device, when the torsion bar is locked, the applied torsional stress is gradually reduced, so that the reaction that the occupant receives from the webbing Becomes smaller.
[0014]
Here, the energy absorbing member has a multilayer structure in which the breaking points of the respective layers with respect to torsional stress are different.
[0015]
For this reason, it is possible to combine members of different materials for each layer and break them in stages to change the energy absorption amount, and the manufacturing cost is low.
[0016]
Moreover, it is set as the polygon which the inner peripheral surface and outer peripheral surface of each layer mutually engage.
[0017]
For this reason, even if a torsional stress is applied to the outer layer, the inner layer does not idle, and the torsional stress is reliably transmitted to the inner layer.
[0018]
According to a second aspect of the present invention, there is provided a method for manufacturing a torsional stress absorbing shaft for a seat belt device, wherein a hollow portion is formed in the shaft, and a plurality of absorbing members having different breaking points with respect to torsional stress are press-fitted into the hollow portion. And a polygon in which the inner peripheral surface and the outer peripheral surface of each layer are engaged with each other by compression processing.
In the second aspect of the invention, the shaft has a hollow portion, and a plurality of absorbing members having different breaking points with respect to torsional stress are press-fitted into the hollow portion to form a multilayer. Further, the end portion of the shaft is formed into a polygon in which the inner peripheral surface and the outer peripheral surface of each layer are engaged with each other by compression processing.
[0019]
For this reason, an energy absorption member can be manufactured easily. Moreover, since it is formed by compression processing, mechanical strength can be improved compared with casting.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
A webbing take-up device using a torsional stress absorbing shaft for a seat belt device applied to this embodiment will be described.
[0021]
As shown in FIG. 1, the webbing retractor 10 includes a pair of support plates 14 and 16 that are attached to a vehicle (not shown). Between the support plates 14 and 16, there is disposed a spool 18 which is formed in a substantially cylindrical shape and has a flange extending radially from both ends in the axial direction.
[0022]
One end of the webbing 20 is fixed to the spool 18 and the webbing 20 is wound up. In addition, a substantially cylindrical torsion bar 24 slightly longer than the axial length is disposed inside the spool 18 so as to be coaxial with the center axis of the spool 18.
[0023]
As will be described later, the torsion bar 24 is made of a plastically deformable material, and is plastically deformed when a torsional stress of a predetermined value or more acts in the circumferential direction.
[0024]
Further, hexagonal columnar hexagonal portions 24A and 24B are formed at both ends of the torsion bar 24, respectively. The hexagonal portion 24A is inserted into a hexagonal insertion hole 26A formed in a pretensioning shaft 26 rotatably supported by the support plate 14, and the torsion bar 24 and the pretensioning shaft 26 rotate together. It is possible.
[0025]
A gear 28 is formed on the pre-tensioning shaft 26 and meshes with a gear 30 formed on the spool 18 so that the spool 18 and the pre-tensioning shaft 26 rotate integrally. For this reason, the torsion bar 24 can rotate integrally with the spool 18 via the pretensioning shaft 26.
[0026]
Further, on the hexagonal portion 24B side of the torsion bar 24, a lock shaft 32 rotatably supported by the support plate 16 is disposed. The locking shaft 32 is formed in a substantially cylindrical shape, and has a hexagonal insertion hole 32A. A hexagonal portion 24B is inserted into the insertion hole 32A, so that the torsion bar 24 and the locking shaft 32 can rotate together.
[0027]
Therefore, during normal running of the vehicle, the torsion bar 24, the pretensioning shaft 26 and the locking shaft 32 rotate together through the spool 18, and the webbing 20 is pulled out and taken up.
[0028]
On the other hand, a cylindrical drum 34 made of a metal softer than the pretension shaft 26 is inserted into the outer periphery of the pretension shaft 26. A wire 35 is wound around the outer periphery of the drum 34.
[0029]
The other end of the wire 35 is connected to a piston inserted in a cylinder (not shown), and when a gas generator (not shown) is operated, the wire 35 can be drawn into the cylinder.
[0030]
When the wire 35 is drawn into the cylinder, the winding force of the wire 35 increases, and when the wire 35 exceeds a predetermined value, the drum 34 is deformed. The deformed drum 34 bites into the pretensioning shaft 26, and the drum 34 and the pretensioning shaft 26 are integrated. Further, the webbing 20 is rotated in the winding direction (arrow B direction) by the pulling force of the wire 35.
[0031]
On the other hand, the end portion of the locking shaft 32 is formed with a male threaded portion 32C having a stepped portion 32B provided at the terminal end portion, and the broken ring 33 is screwed.
[0032]
The ring ring 33 can be rotated together with the spool 18 when the locking shaft 32 is locked and the spool 18 rotates relative to the locking shaft 32 via the torsion bar 24. Is in contact with the stepped portion 32B, the stroke of the broken ring 33 is limited.
[0033]
Next, the operation of the webbing take-up device will be described.
[0034]
As shown in FIG. 1, when the vehicle is suddenly decelerated, the locking shaft 32 is locked by a lock mechanism (not shown), and the rotation in the webbing 20 pull-out direction (arrow A direction) is locked.
[0035]
At the same time, a gas generator (not shown) is operated, the wire 35 wound around the drum 34 is pulled, the diameter of the drum 34 is reduced, and the pre-tension shaft 26 is bitten. Then, the pre-tensioning shaft 26 and the spool 18 are rotated via the drum 34 (in the direction of arrow B) to wind up the webbing 20 without slack and restrain the occupant to the seat.
[0036]
Next, when the pulling force in the pulling-out direction of the webbing 20 is applied due to the reaction of the occupant, the hexagonal portion 24B cannot be rotated together with the locking shaft 32, so the hexagonal portion 24A side of the torsion bar 24 is twisted while being twisted. Rotates and the webbing 20 is pulled out (in the direction of arrow A).
[0037]
As shown in FIG. 2B, when a torsional stress (drawing force) of a predetermined value or more is applied to the torsion bar 24, the outer layer 40 is first broken and the drawing force of the webbing 20 is reduced. Next, when a load is further applied with the reduced pulling force, the webbing 20 is pulled out again, but as shown in FIG. 2C, the middle layer 42 is broken and the pulling force is further reduced. Then, only the inner layer 44 receives the pulling force and pulls out the webbing 20. However, before the inner layer 44 breaks, the broken ring 33 comes into contact with the step portion 32B of the locking shaft 32, and the webbing 20 is pulled out. Is limited.
[0038]
As described above, the torsion bar 24 is broken for each layer, and the pulling stress is decreased stepwise, so that the reaction received by the occupant from the webbing 20 is reduced.
[0039]
The action of the torsion bar 24 at this time will be specifically described.
[0040]
As shown in FIG. 2A, the torsion bar 24 includes three layers. The outer layer 40 is made of steel, the intermediate layer 42 is made of tempered steel, and the inner layer 44 is made of non-ferrous metal containing steel and alloys.
[0041]
As described above, since materials having different mechanical properties are used, the outer layer 40, the middle layer 42, and the inner layer 42 have different break points with respect to torsional stress.
[0042]
That is, as shown in FIG. 2 (A), when the torsional stress is applied to the torsion bar 24 and the yield point (P1) is reached, the amount of plastic deformation (torsion angle) increases, as shown in FIG. 2 (B). Thus, the outer layer 40 is broken. For this reason, the torsional stress is not transmitted to the outer layer 40 but is transmitted only to the middle layer 42 and the inner layer 44.
[0043]
Therefore, the torsional stress is reduced to the approximate yield point (P2) of the middle layer 42 and the inner layer 44, but when the reduced torsional stress is applied, the torsion angle is further increased. Next, as shown in FIG. 2C, when the middle layer 42 breaks, the torsional stress is transmitted only to the inner layer 44, so that the torsional stress decreases to the approximate yield point (P3) of the inner layer 44.
[0044]
In this way, by forming a multilayer structure, breaking each layer, and reducing the torsional stress, the force applied to the webbing can be reduced stepwise, so the reaction received by the occupant from the webbing 20 is reduced.
[0045]
Note that the same material may be used to change the breaking point for torsional stress by heat treatment such as quenching. In addition, the thickness of the same material may be changed so that the breaking point with respect to torsional stress is different.
[0046]
Next, a modified example of the torsion bar according to this embodiment will be described.
[0047]
FIG. 3 shows the relationship between the torsional stress applied to the torsion bar and the torsion angle.
[0048]
First, the torsion bar 102 shown in FIG. 3A is made of conventional solid iron and is formed of one kind of material. Next, FIG. 3B shows the torsion bar 24 of this embodiment, which is omitted because it has already been described above.
[0049]
The outer layer 52A of the torsion bar 52 shown in FIG. 3C is made of steel, the middle layer 52B is made of tempered steel, and the inner layer 52C is made of steel. Further, the outer layer 54A of the torsion bar 54 shown in FIG. 3 (D) is made of steel, the inner layer 54C is made of non-ferrous metal and steel, and the inner layer 54C is coated with a steel thin film (middle layer 54B).
[0050]
As described above, by using three kinds of materials, when torsional stress is applied to the torsion bars 52 and 54, first, the outer layers 52A and 54A are broken, and the torsional stress can be reduced. Next, the middle layers 52B and 54B break and the torsional stress can be further reduced.
[0051]
For this reason, since the torsional stress of the torsion bars 52 and 54 is reduced in three stages, the force applied to the webbing 20 is reduced in three parts, and the reaction received by the occupant from the webbing 20 is reduced.
[0052]
Next, the torsion bars 56 and 58 shown in FIGS. 3E and 3F are made of two types of materials, an outer layer and an inner layer.
[0053]
The outer layer 56A of the torsion bar 56 is formed of steel, and the inner layer 56B is formed of steel that has been subjected to tempering such as quenching. The torsion bar 58 is formed of the same material as the torsion bar 56, but the thickness of the outer layer 58A is thicker than the thickness of the outer layer 56A.
[0054]
As described above, when torsional stress is applied to the torsion bars 56 and 58 by using two kinds of materials, first, the outer layers 56A and 58A are fractured (however, the outer layer 58A is thicker than the outer layer 56A). As compared with the outer layer 56A, the amount of plastic deformation (torsion angle) is increased), and the torsional stress can be reduced.
[0055]
For this reason, the torsional stresses of the torsion bars 56 and 58 are reduced in two stages, the force applied to the webbing 20 is reduced in two steps, and the reaction received by the occupant from the webbing 20 is reduced.
[0056]
In addition, since the relationship between torsional stress and torsional angle differs depending on each material and wall thickness, the configuration of the torsion bar may be changed according to the specification without being limited to the above form.
[0057]
Next, a manufacturing method of the torsion bar 62 composed of the inner layer and the outer layer will be described.
[0058]
As shown in FIG. 4A, a steel material 64 and a tempered steel material 66 tempered by quenching or the like are used. First, the steel material 64 is extruded to form a recess (64A) shown in FIG. 4B, and as shown in FIG. 4C, the recess is passed through to form an outer layer 68.
[0059]
Next, the tempered steel material 66 shown in FIG. 4D is press-fitted into the outer layer 68 to form a two-layer structure. And as shown in FIG.4 (E), ironing is performed and the surface of the outer layer 68 is smoothed, the external dimensions are made uniform, and the shape accuracy is increased.
[0060]
Here, although two kinds of manufacturing methods can be considered, one of them will be described.
[0061]
As shown in FIG. 4F, hexagonal portions 62A and 62B of the torsion bar 62 are formed after ironing. First, annealing is performed to reduce the internal stress of the outer layer 68 and the inner layer 66 shown in FIG. Next, as shown in FIG. 4 (H), a hexagonal portion 62A is formed at one end by upsetting, and then a hexagonal portion 62B is formed at the other end as shown in FIG. 4 (I).
[0062]
Therefore, the outer peripheral surfaces 70A and 70B of the inner layer 70 are plastically deformed according to the shape of the outer shape hexagonal portions 62A and 62B by upsetting, and the inner peripheral surfaces 72A and 72B of the outer layer 72 are engaged with each other. And the hexagonal part 62B is formed. Therefore, even if a torsional stress is applied to the outer layer 72, the inner layer 70 does not idle, and the torsional stress is reliably transmitted to the inner layer 70.
[0063]
Moreover, since it is formed by compression processing such as upsetting, the mechanical strength can be improved compared to casting.
[0064]
On the other hand, as another manufacturing method, first, as shown in FIG. 4J, a hexagonal portion 76A is formed at one end by extrusion. Next, annealing is performed to reduce the internal stress of the outer layer 78 and the inner layer 80 shown in FIG. Then, as shown in FIG. 4 (L), the corners of the hexagonal portion 76A are clarified by upsetting, and then the hexagonal portion 76B is formed at the other end as shown in FIG. 4 (M).
[0065]
【The invention's effect】
Since the present invention has the above-described configuration, the torsional stress applied is reduced stepwise in the invention described in claim 1. In addition , it is possible to combine members of different materials for each layer and break them step by step to change the amount of energy absorption, and the manufacturing cost is low. Further , even when a torsional stress is applied to the outer layer, the inner layer does not idle, and the torsional stress is reliably transmitted to the inner layer. In invention of Claim 2 , an energy absorption member can be manufactured easily. Moreover, since it is formed by compression processing, mechanical strength can be improved compared with casting.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a webbing take-up device using a torsional stress absorbing shaft for a seat belt device according to the present embodiment.
FIG. 2 is a diagram showing a torsional stress and a surface state of a torsional stress absorbing shaft for a seat belt device according to the present embodiment.
FIG. 3 is a diagram showing a torsional stress and a twisting angle according to the configuration of the stress absorbing shaft for the seat belt device.
FIG. 4 is a manufacturing process diagram of a torsional stress absorbing shaft for a seat belt device according to the present embodiment.
FIG. 5 is a schematic view showing a conventional webbing retractor using a torsional stress absorbing shaft for a seat belt device.
[Explanation of symbols]
24 Torsion bar (energy absorbing member)
52 Torsion bar (energy absorbing member)
54 Torsion bar (energy absorbing member)
56 Torsion bar (energy absorbing member)
58 Torsion bar (energy absorbing member)
62 Torsion bar (energy absorbing member)
70A Outer peripheral surface (polygon)
70B Outer peripheral surface (polygon)
72A Inner peripheral surface (polygon)
72B Inner peripheral surface (polygon)

Claims (2)

Shaft torsional stress is the load,
A hollow member;
A plurality of absorbing members that are press-fitted into the hollow portion of the hollow member to form a multilayer, have a polygonal shape, engage with each other, and have different breaking points with respect to torsional stress,
A torsional stress absorbing shaft for a seatbelt device.   A hollow portion is formed in the shaft, and a plurality of absorbing members having different breaking points with respect to torsional stress are press-fitted into the hollow portion to form a multilayer, and a polygonal shape in which the inner peripheral surface and the outer peripheral surface of each layer are engaged with each other by compression processing A method of manufacturing a torsional stress absorbing shaft for a seat belt device.

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