JP2003200240A - Manufacturing method of twin ball for seat belt pre- tensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology of forging a twin ball for a seat belt tensioner integrally comprising a ball part, an accessory part, a fin part, a groove part and a partial ball part. <P>SOLUTION: The twin ball has the ball part, the accessory part, the fin part, the groove part and the partial ball part, and a primary forming step of cold-forging the twin ball, the axial direction of a columnar stock is set to be vertical, and the ball part, the accessory part, the fin part, and the groove part are partially formed by a die and a punch. During the primary forming, a projecting part for promoting the plastic deformation is formed on a tip of a semi-spherical ball part forming predetermined portion, the fibrous structure inside the ball part forming predetermined portion is changed to be the structure easily to be deformed in a spherical shape toward the axial direction. In the secondary forming step, when the stock is compressed and formed in the direction orthogonal to the axial direction, the ball part can be formed beautiful by the fibrous structure easily to be deformed in the spherical shape. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method of manufacturing twin balls for a seat belt pretensioner.

[0002]

2. Description of the Related Art A seatbelt pretensioner installed in an automobile or the like is designed to prevent a seatbelt from restraining an occupant by forcibly rotating a seatbelt winding shaft in a winding direction by gas pressure in the event of a vehicle collision. This is a device for enhancing the safety of collision by forcibly winding the seat belt and bringing the seat belt into close contact with the occupant.

Conventionally, an engaging body which is rotatable integrally with a seat belt retracting shaft is provided, and a plurality of ball members are fired to the engaging body by gas pressure so as to be engaged in order, whereby the seat belt retracting device is wound. A seat belt pretensioner in which a winding force is transmitted to a shaft to forcibly rotate the seat belt winding shaft in a winding direction is put to practical use.

As a seat belt pretensioner of this type, a twin ball having a ball portion 2 and an attachment portion 3 continuous with the ball portion 2 shown in FIGS. Those provided with 1 are being put to practical use.

When manufacturing such a twin ball,
A casting method in which a twin-ball model is made of wax, the periphery of the model is covered with a fire-resistant mold material, and the wax model is burned to form a molding cavity, and molten metal is injected into the cavity (lost wax). Law) has been adopted. However, mass production of twin balls is difficult, and the manufacturing cost of twin balls becomes high.

[0006]

[Problems to be Solved by the Invention] If a cold forging method of applying a compressive load to a massive metal material with a die, a punch, a forming die or the like to form into various shapes is applied to the production of twin balls, twin balls can be produced. The mass production of the twin balls is facilitated, the manufacturing cost of the twin balls can be reduced, and the mechanical strength of the twin balls is improved.

[0007] Therefore, the applicant of the present invention has studied the twin ball forging technology. Initially, a raw material obtained by cutting a solid round bar of S45C into a predetermined length is prepared, and in the primary forming step, the raw material is forged in the axial direction with a die and a punch to form a ball portion and an attachment portion. Partially molded, 2
In the next molding step, an attempt was made to forge the primary molded product from the direction orthogonal to the axial center to finish-mold the ball part and the accessory part.

However, the twin ball 1 having the ball portion 2 and the attachment portion 3 as shown in FIGS. 1 to 6 according to the embodiment.
In the case of forging by using the above materials, the ball portion could not be molded reliably and neatly.

In the primary molding step, if the ball portion and the accessory portion are partially molded from the material, a substantially hemispherical ball portion to be molded can be formed. However, one end of the ball portion forming planned portion has a flat surface orthogonal to the axis, and the metal structure inside the ball portion forming planned portion has a fibrous structure that is easily plastically deformed into a spherical shape in the axial direction. Therefore, in the secondary molding process, even if the ball part to be molded is forged so that it is compressed in the direction orthogonal to the axial center, the semi-spherical ball part to be molded becomes a beautiful ball part that is nearly spherical. It was impossible to mold.

An object of the present invention is to forge a twin ball having a ball portion and an attachment portion continuous to the ball portion. In particular, the twin ball is improved so that a clean ball portion can be surely forged. , It is possible to realize the mass production of twin balls, and to provide a technology that can reduce the manufacturing unit price of twin balls.

[0011]

A method of manufacturing a twin ball for a seatbelt pretensioner according to claim 1 is a seatbelt pretensioner for forcibly rotating a seatbelt winding shaft in a winding direction by gas pressure in a vehicle emergency. A twin ball as an engaging member for transmitting a winding force, wherein a solid round bar is divided into a predetermined length in a method of manufacturing an engaging member having a ball portion and an attachment portion continuous to the ball portion. A material preparation step of preparing a material, and a die having a predetermined die and a punch to forge-mold the material in the axial direction of the material to partially form the ball portion and the attachment portion, and the upper end portion of the material. A primary forming step of forming a convex portion for accelerating plastic deformation on a first part, and a molded part of the primary forming is forged from a direction orthogonal to the axial center by a lower mold and an upper mold having a predetermined mold part and attached to a ball part. Part finish And a secondary molding step of shaping.

First, in a material preparing step, a solid round bar is cut into a predetermined length to prepare a material. Next, in the primary molding step, with a die having a predetermined mold part and a punch,
The material is forged in the axial direction to partially form the ball portion and the attachment portion, and the plastic deformation promoting convex portion is formed at the upper end portion of the material. Then, in the secondary molding process, 1
The molded product of the next molding with the lower mold and the upper mold having a predetermined mold part,
Forging is performed from the direction orthogonal to the axis, and the ball and accessory parts are finish-formed.

In the primary molding step, the material is forged in the axial direction to partially mold the ball portion and the attachment portion, and the convex portion for promoting plastic deformation is formed at the upper end portion of the material. The ball portion to be formed, which has a convex portion for promoting plastic deformation of the next formed product, has a fibrous structure (metal flow) that is easily plastically deformed in the axial direction when forging is performed by applying a compressive load from the direction orthogonal to the axial center. Therefore, in the secondary molding process, when the primary molded product is subjected to forging by applying a compressive load from the direction orthogonal to the axial center, the ball portion to be molded flows so as to expand in the axial direction from the plastic deformation promoting convex portion. Since it is easily plastically deformed, it becomes possible to surely finish-mold a beautiful ball portion together with the attachment portion.

Since the convex portion for promoting plastic deformation serves to promote plastic deformation when molding the ball portion in the secondary molding step (claim 2), the molded product of the primary molding is orthogonal to the axial center. It is possible to surely form a beautiful ball portion by forging.

The twin ball has a groove portion and a fin portion extending over the ball portion and the attachment portion, and has a groove portion and a fin portion which are oriented in a direction parallel to the axis of the material, and the fin portion is formed in the primary molding step. When molding (claim 3),
Since the fin portion can be formed in the same primary forming step together with the partial forming of the ball portion and the attachment portion and the formation of the convex portion for promoting plastic deformation, the twin ball manufacturing process can be simplified.

When a deburring step of deburring with a predetermined die and punch is provided after the secondary molding step (claim 4), the twin balls produced in the secondary molding step are surely deburred. Can be removed.

[0017]

Embodiments of the present invention will be described below. The present embodiment is a seatbelt pretensioner that is installed in an automobile or the like, and is a seatbelt pretensioner that forcibly rotates a seatbelt winding shaft in a winding direction by gas pressure in a vehicle emergency (such as a vehicle collision). 3 shows an example of a method for manufacturing twin balls as the winding force transmitting engagement member in FIG. 3 by cold forging.

The twin ball 1 will be described. Figure 1
As shown in FIG. 6, the twin ball 1 includes a ball portion 2,
The ball portion 2 has an attachment portion 3 continuous with the ball portion 2, a fin portion 4 and a groove portion 5 extending over the ball portion 2 and the attachment portion 3, and a partial ball portion 6 continuous with the fin portion 4 and the groove portion 5. A recessed hole portion 7 is formed in the groove portion 5 from the vicinity of the end portion of the groove portion 5 on the ball portion 2 side.

The seat belt pretensioner to which the twin ball 1 is applied is provided with an engaging body which is rotatable integrally with the seat belt winding shaft, and the twin ball 1 is engaged by the gas pressure generated in an emergency of the vehicle. The ball portion 2 is fired in a united state to engage the engaging body, and subsequently, the plurality of balls fired in the engaging body are sequentially engaged, whereby the seat belt retracting shaft is wound up with a winding force. Is transmitted. The fin portion 4 of the twin ball 1 is guided by the ball passage portion, and blades (not shown) are arranged along the groove portion 5, and one end portion of the fin portion 4 is attached so as to engage with the recessed hole portion 7. To be

Next, a method of manufacturing the twin ball 1 will be described. In this manufacturing method, as shown in FIGS. 7 to 13, for example, a material preparing step of preparing a material 10 by dividing a solid round bar having a diameter of 10 mm into a predetermined length (for example, 12 mm) and a material 10 are performed. A primary molding step in which the ball portion 2a and the attachment portion 3a are partially molded by forging, and a convex portion 12 for promoting plastic deformation is formed on the upper end portion of the material 10, and a molded article 11 (1 A secondary molding step of forging a secondary molded article 11) to finish-mold the ball portion 2 and the accessory portion 3, a deburring step of removing a burr 13 formed in the secondary molding step, and finally a twin ball 1 And a polishing step for polishing.

The primary molding step will be described in detail. As shown in FIGS. 8 to 10, a die 20 and a punch 21 each having a predetermined mold portion 20a for molding the primary molded article 11 are used. As shown in 8, the material 1 is placed in the hole of the die 20.
0 is set in a vertical posture, and as shown in FIG. 10, the punch 21 is driven downward to press the raw material 10 downward, and forging is performed in the axial direction so as to be pushed into the die portion 20a of the die 20. Ball 2a, accessory 3a, and fin 4
A and the groove 5a are partially formed, and the plastic deformation promoting projection 12 is formed on the upper end of the material 10. In order to form the convex portion 12 for promoting plastic deformation, a concave portion 21a is formed at the center of the tip of the punch 21.

The material 10 is forged in the axial direction to partially form the ball portion 2a, the attachment portion 3a, the fin portion 4a, and the groove portion 5a, and the upper end portion of the material 10 has a convex portion 12 for promoting plastic deformation. Since this forms a convex portion 1 for promoting plastic deformation,
The part to be molded of the ball portion 2 having 2 has a partially spherical shape that is easily plastically deformed into a ball shape in the axial direction when forging is performed by applying a compressive load from the direction orthogonal to the axial center in the next secondary molding step. It has a fibrous structure (metal flow). Therefore,
In the next secondary molding step, the clean ball portion 2 can be surely finish-molded.

Next, in the secondary molding step, as shown in FIG. 12, the lower mold 2 having a predetermined mold portion 24 for finish-molding the twin ball 1 from the primary molded product 11 of FIG.
2 and the upper mold 23, the primary molded product 11 is set in the lower mold 22 in a horizontal orientation, and the lower mold 22 and the upper mold 23 are closed to move the primary molded product 11 from the direction orthogonal to the axial center. By forging,
The ball portion 2, the attachment portion 3, the fin portion 4, and the groove portion 5 are finish-molded. At this time, the portion to be formed of the ball portion 2 having the convex portion 12 for promoting plastic deformation flows due to the partially spherical fibrous structure so as to bulge in the axial direction and is easily plastically deformed. It becomes possible to surely and cleanly finish the accessory part 3, the fin part 4, and the groove part 5 together with the step 2.

As shown in FIG. 13, the twin ball 1 molded in the secondary molding process has burrs 13 on the mating surfaces of the lower mold 22 and the upper mold 23. Deburring is performed by punching using a die and a punch (not shown), and then, in a polishing step, a large number of twin balls 1 are housed in a barrel together with an abrasive and are rotated for a predetermined time. By polishing the surface of No. 1, the twin ball 1 shown in FIGS. 1 to 6 is completed.

As described above, the manufacturing method of this twin ball 1 is as follows.
As described above, the primary molding process and the secondary molding process are provided.
In the next forming step, the material 10 is forged in the axial direction to form the ball portion 2a, the attachment portion 3a, the fin portion 4a, and the groove portion 5a.
Since the plastic deformation promoting projections 12 are formed on the upper end of the material 11 while partially molding, the ball portion 2 and the ball portion 2 are attached so as to surely form a clean ball portion 2 in the secondary molding step. The portion 3, the fin portion 4, and the groove portion 5 can be finish-molded. Then, by using the method for manufacturing the twin balls 1, mass production of the twin balls 1 can be realized, and the manufacturing unit price of the twin balls 1 can be reduced.

The shape, size, and the like of the convex portion for promoting plastic deformation formed in the primary molding step can be variously set. The present invention can be implemented by adding various modifications without departing from the spirit of the present invention, and at least various manufacturing methods for manufacturing a twin ball having a ball portion and an attachment portion. Can be applied.

[0027]

According to the invention of claim 1, in particular, the material is forged in the axial direction of the die with a die having a predetermined die and the ball and the accessory are partially formed. , Forming a convex portion for promoting plastic deformation on the upper end of the material 1
A secondary molding step and a secondary molding step in which a molded product of the primary molding is forged from a direction orthogonal to the axis center by a lower mold having a predetermined mold part and an upper mold to finish-mold the ball part and the accessory part. Since it is provided, the ball portion of the twin ball can be surely and cleanly molded, that is, the twin ball can be mass-produced and the manufacturing cost of the twin ball can be reduced.

According to the second aspect of the present invention, since the convex portion for promoting plastic deformation is used for promoting plastic deformation when molding the ball portion in the secondary molding step, a molded article for primary molding is obtained. A beautiful ball portion can be surely formed by forging from a direction orthogonal to the axis.

According to the third aspect of the present invention, the twin ball has a groove portion and a fin portion extending over the ball portion and the accessory portion, the groove portion and the fin portion extending in a direction parallel to the axis of the material. Since the fin portion is formed in the primary forming step, the fin portion can be formed in the same primary forming step together with the partial forming of the ball portion and the attachment portion and the formation of the convex portion for promoting plastic deformation. The manufacturing process of twin balls can be simplified.

According to the invention of claim 4, since the secondary molding step is provided with a deburring step of performing deburring using a predetermined die and punch, the twin ball formed in the secondary molding step is provided. The burr can be surely removed.

[Brief description of drawings]

FIG. 1 is a front view of a twin ball according to an embodiment of the present invention.

FIG. 2 is a view on arrow II in FIG.

FIG. 3 is a view on arrow III in FIG.

FIG. 4 is a perspective view of a twin ball.

5 is a sectional view taken along line VV of FIG.

6 is a sectional view taken along line VI-VI of FIG.

FIG. 7 is a flowchart showing a manufacturing process of a twin ball.

FIG. 8 is a partial cross-sectional view of the material, die and punch set in the primary molding process.

9 is a sectional view taken along line IX-IX in FIG.

FIG. 10 is a partial cross-sectional view of a primary molded product, a die, and a punch which are forged in the primary molding process. FIG. 3 is a partial cross-sectional view of a die, a punch and a raw material in the primary molding process.

FIG. 11 is a perspective view of a primary molded product.

FIG. 12 is a partial cross-sectional view of a twin ball, a lower mold, and an upper mold that are forged in the secondary molding process.

FIG. 13 is a perspective view of a twin ball with a burr.

[Explanation of symbols] 1 twin ball 2 ball section 3 accessories 4 fins 5 groove 6 fins 10 material 12 Plastic deformation promoting protrusions 20 dice 20a mold part 21 punch 22 Lower mold 23 Upper mold 24 mold part

Claims (4)

[Claims] 1. A twin ball as an engaging member for transmitting a winding force in a seat belt pretensioner for forcibly rotating a seat belt winding shaft in a winding direction by gas pressure in an emergency of a vehicle, the ball portion and the ball portion. In a method for manufacturing an engaging member having an attachment portion continuous to a ball portion, a raw material preparing step of dividing a solid round bar into a predetermined length to prepare a raw material, and a die having a predetermined die portion and a punch. A primary molding step of forming the ball portion and the attachment portion by forging the material in the axial direction thereof and forming a convex portion for promoting plastic deformation on the upper end portion of the material; A sheet characterized by comprising a secondary molding step in which a molded product is forged from a lower die having a predetermined die portion and an upper die in a direction orthogonal to the axial center to finish-form a ball portion and an accessory portion. Belt Pretensioner Tool Method of manufacturing a Nboru. 2. The seat belt pretensioner according to claim 1, wherein the convex portion for promoting plastic deformation is provided for promoting plastic deformation when forming the ball portion in the secondary forming step. Twin ball manufacturing method. 3. The twin ball has a groove portion and a fin portion that extend over the ball portion and the attachment portion, and has a groove portion and a fin portion that are oriented in a direction parallel to the axis of the material. Molding in a molding process, The manufacturing method of the twin ball for seatbelt pretensioners of Claim 1 or 2 characterized by the above-mentioned. 4. The sheet according to claim 1, further comprising a deburring step of deburring using a predetermined die and punch after the secondary forming step. Manufacturing method of twin balls for belt pretensioner.