JP2011148430A - Torsion bar - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a torsion bar in a seat belt rolling-up device further increasing energy absorption ability at a low temperature. <P>SOLUTION: In the torsion bar, energy is absorbed by twisting a torsion part at starting of rotation suppression in a belt drawing out direction by a lock mechanism for necessarily suppressing rotation in the belt drawing out direction of a reel for rolling-up the seat belt. The torsion part includes a fixed diameter part, a thick diameter part having a thicker diameter than the fixed diameter part, a base taper part positioned at one end part of the torsion part and having a diameter gradually increased toward one end of the torsion bar continued to one end, and the other base taper part positioned at the other end part of the torsion part and having a diameter gradually increased toward the other end of the torsion bar continued to the other end. A ratio of an average diameter of the thick diameter part and a diameter of the fixed diameter part is 1.0004-1.05:1. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to the field of a seat belt retractor for retracting a seat belt so that the seat belt can be withdrawn, and in particular, when preventing the seat belt from being pulled out in an emergency, the torsion bar is twisted by a load applied to the seat belt to reduce the impact. About.

A seat belt device equipped in a vehicle such as an automobile protects the occupant by restraining the occupant from jumping out of the seat by restraining the occupant with the seat belt in an emergency such as a collision.

Such a seat belt device includes a seat belt retractor that retracts the seat belt so that the seat belt can be pulled out. The seat belt retractor includes an urging force applying means such as a spiral spring that constantly urges a reel that winds up the seat belt in the winding direction. When the seat belt is not worn, the seat belt is wound around the reel. By the urging force of the urging force applying means, the seat belt is pulled out against the urging force when worn and is attached to the occupant. In an emergency, the lock mechanism is activated to prevent the reel from rotating in the pull-out direction, thereby preventing the seat belt from being pulled out. This ensures that the seat belt restrains the occupant in an emergency.

In such a seat belt retractor of the seat belt device, when the seat belt restrains and protects the occupant in an emergency such as a vehicle collision, the vehicle is greatly decelerated and a large inertial force forward toward the occupant causes a large force on the seat belt. A load is applied and the occupant receives a large impact force from the seat belt.

  For this reason, a seat belt retractor provided with a mechanism for absorbing this impact force by twisting a torsion bar is disclosed (see, for example, Patent Document 1). In such a device, in the event of an emergency, tension is applied to the seat belt due to the inertial movement of the occupant forward, and the seat belt take-up shaft rotates while twisting the twisted portion of the torsion bar, and the impact energy of the occupant is absorbed. The When the torsion bar is twisted by a predetermined amount, the rotation of the seat belt take-up shaft is prevented, thereby preventing the seat belt from being pulled out and protecting the occupant, and preventing the torsion bar from being twisted. Bar breakage is prevented.

By the way, the conventional torsion bar used for such a purpose may be cut at a relatively small number of torsional rotations due to flaws and the like existing on the surface. The amount of rotation of the seat belt take-up shaft until it is cut may be low. For this reason, the maximum allowable torsion at which the twisted portion is not broken is limited to a small size, and it may be difficult to ensure a sufficient amount of belt withdrawal. As described above, when the belt drawing amount is not sufficiently secured, there is a limit to further increase the energy absorption capacity. In particular, there is a limit to further increase the energy absorption capability at a low temperature of about -40 ° C.

Japanese Utility Model Publication No. 61-11085

The objective of this invention is providing the torsion bar in the seatbelt winding device which increases more the energy absorption capability in low temperature.

The gist of the present invention is a torsion bar that absorbs energy by twisting the torsion portion at the start of rotation prevention in the belt drawing direction by a lock mechanism that blocks rotation of the reel that winds up the seat belt when necessary.
The torsion portion and a large diameter portion of larger diameter than the constant diameter portion and the constant diameter portion, the ratio of the diameter d ₁ of the average diameter d _a and the constant diameter portion of the large-diameter portion d _a: d ₁ is 1 The torsion bar is .0004 to 1.05: 1.

  The torsion bar may have a base taper portion located at an end portion of the torsion portion and gradually increasing in diameter toward the end of the torsion bar toward at least one end portion of the torsion portion. .

  In the torsion bar, the root taper portion may have a slope of 0.3 ° to 3 °, a length of 3 mm or more, and 0.2 times or less of the length of the torsion portion.

  In the torsion bar, the large-diameter portion has a large-diameter constant-diameter portion larger than the constant-diameter portion, and is interposed between the large-diameter constant-diameter portion and the constant-diameter portion from the constant-diameter portion. There may be a connecting taper portion whose diameter gradually increases toward the large diameter constant diameter portion.

  In the torsion bar, the ratio of the large diameter constant diameter portion to the diameter of the constant diameter portion may be 1.0005 to 1.05: 1.

  In the torsion bar, the connecting taper portion may have a slope of 0.4 ° to 0.6 ° and a length of 1 to 11 mm.

  The torsion bar may have the root taper portion continuous with the large diameter constant diameter portion, and the sum of the length of the base taper portion and the length of the large diameter constant diameter portion is 0. 0 of the length of the torsion portion. It can be 1 to 0.5 times.

  In the torsion bar, the material of the torsion bar may be a steel material having a carbon content of 0.05% by weight or less.

ADVANTAGE OF THE INVENTION According to this invention, the torsion bar in the seatbelt winding device which increases more the energy absorption capability in low temperature is provided.

It is a longitudinal cross-sectional view which shows an example of the seatbelt winding device with which the torsion bar of this invention is applied. It is a principal part front schematic diagram which shows an example of the aspect of the torsion bar of this invention. It is a principal part front schematic diagram which shows another example of the aspect of the torsion bar of this invention. It is a principal part front schematic diagram which shows another example of the aspect of the torsion bar of this invention. It is a principal part front schematic diagram which shows the aspect of the conventional torsion bar.

FIG. 1 is a longitudinal sectional view showing an example of a seat belt retractor using a torsion bar according to the present invention. Such a seat belt retractor that can use the torsion bar according to the present invention is disclosed in, for example, Japanese Utility Model Publication No. 61-11085, Japanese Patent Publication No. 2003-515482, Japanese Patent Application Laid-Open No. 2001-163178, Japanese Patent Application Laid-Open No. 2003-313626, and the like. ing.

In FIG. 1, a seat belt retractor 1 includes a U-shaped frame 2, and the seat belt 3 is wound around a reel 4 that is rotatably supported between both side walls of the frame 2. Reference numeral 6 denotes a lock mechanism which is actuated by a deceleration sensing means (not shown) to prevent rotation of at least the reel 4 in the belt pull-out direction, and 7 is loosely fitted and penetrated axially in the center of the reel 4 and locked to the reel 4 A torsion bar 8 for rotationally connecting the mechanism 6 is spring means for constantly urging the reel 4 in the belt winding direction by a spring force. The lock mechanism 6 prevents rotation of the reel that winds up the seat belt in the belt pull-out direction when necessary.

The lock mechanism 6 includes a pawl holder 14. The pawl holder 14 is normally supported by the reel 4 so as to rotate integrally with the reel 4, stop in an emergency, and generate relative rotation with the reel 4. Is held swingably. A male screw shaft portion 15 is formed in the pawl holder 14. A nut-like stopper member 16 that rotates integrally with the reel 4 is screwed onto the male screw shaft portion 15. Further, the torsion bar 7 has a first torque transmission unit 17 engaged with the pawl holder 14 so as not to rotate relative to the pawl holder 14 and a second torque transmission unit 18 engaged with the reel 4 so as not to rotate relative to each other. Each is formed.

The belt winding torque generated by the pretensioner is transmitted to the reel 4 through the torsion bar 7, whereby the reel 4 winds up the seat belt 3 by a predetermined amount.

In the seat belt retractor 1, a belt retracting torque generated by a pretensioner (not shown) in an emergency is transmitted to the reel 4, and the reel 4 retracts the seat belt 3 by a predetermined amount to restrain the occupant. On the other hand, the deceleration sensing means is activated to activate the lock mechanism 6. As a result, the pawl 13 of the locking mechanism 6 rotates and engages with the internal teeth 19 on the side wall of the frame 2 to prevent the pawl holder 14 from rotating, and the reel 4 rotates relative to the pawl holder 14. For this reason, since the first and second torque transmission parts 17 and 18 of the torsion bar 7 rotate relative to each other, the torsion part 20 is twisted between the first and second torque transmission parts 17 and 18. Thereafter, the reel 4 rotates in the belt pulling direction while twisting the torsion portion 20 of the torsion bar 7, so that the load applied to the seat belt 3 is limited by the torsion of the torsion portion 20 and the impact applied to the occupant is absorbed. Is done.

The reel 4 rotates relative to the pawl holder 14 by the torsion of the torsion portion 20, thereby rotating relative to the male screw shaft portion 15 with which the stopper member 16 is screwed. Move towards. When the right end of the stopper member 16 in the drawing contacts the pawl holder 14, the stopper member 16 is prevented from further rotating and the reel 4 is also prevented from rotating. In this way, the torsional portion 20 is restricted to be twisted below the maximum allowable twisting at which the torsion portion 20 is not broken, and the torsion portion 20 is prevented from being cut by twisting. Thus, the torsion bar 7, the male threaded shaft portion 15 of the pawl holder 14, and the stopper member 16 constitute a mechanism that limits the load applied to the seat belt in an emergency.

  An example of the aspect of the torsion bar of the present invention will be described. The torsion bar 7 of the present invention shown in FIG. 2 is a torsion in which the torsion part 20 twists and absorbs energy when rotation prevention in the belt drawing direction is started by a lock mechanism that prevents rotation of the reel that winds up the seat belt when necessary. The torsion part 20 is a constant diameter part 50, a large diameter part 60 having an average diameter larger than the constant diameter part 50, and one root taper part 54 and a torsion part located at one end 52 of the torsion part 20. The other end taper part 64 located in the other end part 55 of 20 is comprised. Reference numerals 80 and 82 denote thick collar portions respectively located at both end portions of the torsion bar 7 and correspond to the first and second torque transmitting portions 17 and 18 in FIG.

  As shown in FIG. 2, one base taper portion 54 has a large diameter and forms a step 78 in the thick collar portion 80 and is connected coaxially, and is connected to the large diameter portion 60 on the small diameter side without causing a step. The large diameter portion 60 and the constant diameter portion 50 are connected without causing a step. In the embodiment shown in FIG. 2, the other base taper portion 64 is connected to the constant diameter portion 50 on the small diameter side without causing a step, and a step 77 is formed coaxially on the thick collar portion 82 with a large diameter. The large diameter side of one base taper portion 54 forms a step 78 and is coaxially connected to the thick plate portion 80. The so-called R of the base of the thick portion 80 with the one base taper portion 54 and the so-called R of the base of the thick portion 82 with the other base taper portion 64 are conventional products from the viewpoint of cold forging. (R1 = about 1.0 mm).

  When the torsion bar of the present invention having such a configuration is twisted in an emergency, the constant diameter portion 50 having a relatively small diameter is first torsionally deformed and plastically cured. Then, the torsional deformation of the large diameter portion 60 proceeds and plastically hardened, and finally the plastic hardening of the entire torsion portion 20 advances and the torsion bar is cut. Thus, by setting the phase of torsional deformation to two stages, it is possible to increase the number of times of twisting until cutting even at a low temperature below the freezing point.

  In the embodiment shown in FIG. 2, the large diameter portion 60 is interposed between the large diameter constant diameter portion 70 having a larger diameter than the constant diameter portion 50, and the large diameter constant diameter portion 70 and the constant diameter portion 50. It consists of a connecting tapered portion 72 whose diameter gradually increases from the portion 50 toward the large diameter constant diameter portion 70. The slope of the connecting tapered portion 72 is preferably 0.4 to 0.6 °, and the length LR is preferably 1.5 to 7 mm. If this gradient exceeds 0.6 °, stress concentration may occur during torsion. When this gradient is less than 0.4 °, the tapered portion 72 becomes too long, and it is difficult to obtain the effect of the present invention.

In the present invention, the ratio d _a : d ₁ between the average diameter d _a of the large diameter portion 60 and the diameter d _{1 of the} constant diameter portion 50 is 1.0004 to 1.05: 1. In the embodiment shown in FIG. 2, d _a is a weighted average of the average diameter of the connecting tapered portion 72 and the diameter d ₂ of the large diameter constant diameter portion 70.

Diameter d ₁ of the constant diameter portion is a standard diameter which is determined by the value of fracture specified torque, in which it is specified in a predetermined stage due vehicle type seat belt retractor is applied.

  The slopes of the base taper portions 54 and 64 are preferably 0.3 ° to 3 °, and the length L2 is preferably 3 mm or more and 0.2 times or less the length L of the torsion portion 20.

In the embodiment shown in FIG. 2, the ratio d ₂ : d ₁ between the diameter d ₂ of the large diameter constant diameter portion 70 and the diameter d ₁ of the constant diameter portion 50 is preferably 1.0005 to 1.05: 1. .

  The sum LY of the length LF of the large diameter portion 60 and the length L2 of the one base taper portion 54 is preferably 0.1 to 0.6 times the length L of the torsion portion 20.

  The length LT of the constant diameter portion 50 is preferably 0.2 to 0.9 times the length L of the torsion portion 20. More preferably, it is 0.3 to 0.5 times.

  In the embodiment shown in FIG. 2, the sum LX of the length L1 of the large diameter constant diameter portion 70 and the length L2 of the one base taper portion 54 is 0.1 to 0.5 times the length L of the torsion portion 20. It is preferable that

  In another aspect of the present invention, as shown in FIG. 3, the large diameter portion 60 includes a large diameter tapered portion 74 having a truncated cone shape. The large diameter tapered portion 74 is connected to the root tapered portion 54 having a large diameter and the constant diameter portion 50 having a small diameter without causing a step.

  In yet another aspect of the present invention, as shown in FIG. 4, the large diameter portion 60 includes one large diameter constant diameter portion 70a and another large diameter constant diameter portion 70b. One large diameter constant diameter portion 70a is connected to one root taper portion 54 at one end without generating a step, and the other end is connected to one end of the constant diameter portion 50 through one connecting taper portion 72a without generating a step. Connect. The other large diameter constant diameter portion 70b is connected to the other base taper portion 64 at one end without causing a step, and the other end of the constant diameter portion 50 at the other end via the other connecting taper portion 72b without causing a step. Articulated. As described above, the large-diameter portion 60 includes a portion including one large-diameter constant-diameter portion 70a and one connecting tapered portion 72a, and a portion including another large-diameter constant-diameter portion 70b and another connecting tapered portion 72b. Composed.

  The torsion bar of the present invention is obtained by cold forging a steel (alloy containing iron as a main component). As the steel material, a known steel material for a conventional torsion bar can be used. The carbon content of the steel material is preferably 0.05% by weight or less. More preferably, the content is 0.0001 to 0.05% by weight.

Production of torsion bar:
Two types of steel, steel type A (carbon content 0.015% by weight) and steel type B (carbon content 0.06% by weight) are used as steel materials. Controlled cooling is performed after hot rolling, and then cold-drawn wire is used as the material. Then, cold forging into a predetermined shape was performed.

Torsion bar dimensions:
A torsion bar having the shape shown in FIG. 2 is used, the length L of the torsion part is 50 mm, the length LR of the connecting taper part 72 is 5.8 mm, the taper angle of the base taper parts 54 and 64 is 0.5 °, and the length. L2 is 5 mm, the sum A of the length LT of the constant diameter portion 50, the length LR of the connecting taper portion 72 and the length L2 of the root taper portion 64 is 30.8 mm, and the diameter d _{1 of the} constant diameter portion 50 is 9 .25 mmΦ. The diameter _{d 2} of the thick径定diameter 70 9.35mmΦ (Example 1), was 9.45Mmfai (Example 2).

Comparative example

A torsion bar having the shape shown in FIG. 5 (Comparative Example 1) and a torsion bar having the shape shown in FIG. 2 (Comparative Example 2) were prepared by cold forging using the same steel material as in the example. The length (Lc, L) of the torsion part 20 is 50 mm, the taper angle of the base taper parts 54 and 64 is 0.5 °, the length L2 is 5 mm, and the diameter (d ₁₎ of the columnar part 90 in Comparative Example ₁ ) Was 9.25 mmΦ.

Torsion test The torsion bar was continuously twisted and rotated at 3000 rpm in one direction at -40 ° C.
Table 1 shows the twist results (number of rotations until breakage).

From Table 1, it was found that the torsion bar of the example had excellent torsional ductility even at a temperature below freezing point and can be suitably used as a torsion bar for a seat belt.

1: Seat belt retractor 2: Frame 3: Seat belt 4: Reel 6: Lock mechanism 7: Torsion bar 17: First torque transmission unit 18: Second torque transmission unit 20: Torsion unit 50: Constant diameter unit 60: Large diameter portion 54: One root taper portion 54: Other root taper portion 64: Other root taper portion 70: Large diameter constant diameter portion 70a: One large diameter constant diameter portion 70b: Other large diameter constant diameter portion 72 : Connection taper part 72a: One connection taper part 72b: Other connection taper part 74: Large diameter taper part 80, 82: Thick collar part

Claims (8)

In the torsion bar in which the torsion part twists and absorbs energy at the start of rotation prevention in the belt drawing direction by a lock mechanism that blocks rotation of the reel that winds up the seat belt when necessary,
The torsion part has a constant diameter part and a large diameter part thicker than the constant diameter part, and the ratio of the average diameter of the large diameter part to the diameter of the constant diameter part is 1.0004 to 1.05: A torsion bar that is 1. 2. The torsion according to claim 1, wherein the torsion portion has a root taper portion located at an end portion of the torsion portion and gradually increasing in diameter toward the end of the torsion bar toward at least one end portion of the torsion portion. bar.   The torsion bar according to claim 2, wherein the root taper portion has a gradient of 0.3 ° to 3 °, a length of 3 mm or more, and 0.2 times or less of the length of the torsion portion. The large-diameter portion has a large-diameter constant-diameter portion larger than the constant-diameter portion, and is interposed between the large-diameter constant-diameter portion and the constant-diameter portion, and the constant-diameter portion changes to the large-diameter constant-diameter portion The torsion bar according to any one of claims 1 to 3, further comprising a connecting tapered portion whose diameter gradually increases toward the surface. The torsion bar according to claim 4, wherein a ratio of the large diameter constant diameter portion to the diameter of the constant diameter portion is 1.0005 to 1.05: 1.   The torsion bar according to claim 4 or 5, wherein the connecting tapered portion has a gradient of 0.4 ° to 0.6 ° and a length of 1 to 11 mm. The root taper portion is connected to the large diameter constant diameter portion, and the sum of the length of the base taper portion and the length of the large diameter constant diameter portion is 0.1 to 0.5 times the length of the torsion portion. The torsion bar according to any one of claims 4 to 6. The torsion bar according to any one of claims 1 to 7, wherein a material of the torsion bar is a steel material having a carbon content of 0.05% by weight or less.

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