JP2010070161A - Method of manufacturing gas conduit for pretensioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means allowing to manufacture a compact, lightweight gas conduit for a pretensioner readily at low cost, the gas conduit having a circular cross section at one straight tube part and a rectangular cross section at the other straight tube part. <P>SOLUTION: A process of manufacturing a gas conduit for a pretensioner comprises a bending step, preforming step, and a rectangular tube forming step. In the bending step, a straight tube shaped cylindrical member P1 made of a metallic material and a cross section thereof is a perfect circle is bent to create a bent tube P2 having a first straight tube part 1, a second straight tube part 2, and a bent tube part 3. In the preforming step, the second straight tube part 2 of the bent tube P2 is preformed such that a cross section thereof is oval to create a preform body P3. In the rectangular tube forming step, the second straight tube part 2 of the preform body P3 whose cross section is oval is molded such that a cross section thereof is rectangular to form a rectangular tube part 5, thereby completing a gas conduit P4. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a gas conduit for a pretensioner in which a cross section of one straight pipe portion is circular and a cross section of the other straight pipe portion is square.

  Generally, an automobile is provided with a seat belt device that fixes or restrains an occupant to a seat with a belt in the event of a collision. However, if the belt is slack at the time of a car collision, the seat belt device cannot sufficiently fix the occupant to the seat. Therefore, in recent years, pretensioners that remove the slack of the belt almost instantly at the time of a car collision and ensure the fixation of the occupant to the seat are becoming widespread.

As such a pretensioner, a gas generator that generates high-pressure gas at the time of a car collision, a movable member that is connected to the belt and is moved by the high-pressure gas to remove the slack of the belt by winding the belt, A gas pressure actuated pretensioner is known that includes a gas conduit that guides high-pressure gas from a generator to a movable member and accommodates the movable member (see, for example, Patent Documents 1 and 2).
JP 2000-326824 A (paragraph [0034], FIG. 7) Japanese Unexamined Patent Publication No. 2000-52924 (paragraph [0024], FIG. 2)

  By the way, in this type of pretensioner, depending on the structure or layout requirements, the gas conduit includes a first straight pipe portion that houses the gas generator, and a second straight pipe portion (cylinder portion) that houses the movable member. In some cases, it is necessary to provide a bent pipe composed of a bent pipe portion positioned between both straight pipe portions. The second straight pipe portion may be required to have a rectangular cross section due to the structure of the movable member or the like or other circumstances. On the other hand, the cross section of the first straight pipe portion that houses the gas generator is generally circular. In such a gas conduit, it is desirable to shorten the entire length of the gas conduit while securing the effective length of the second straight pipe portion (cylinder portion) so as not to impair the function of the pretensioner.

As described above, a gas conduit composed of a bent pipe in which the cross section of the first straight pipe section and the cross section of the curved pipe section are circular and the cross section of the second straight pipe section is a quadrangle (hereinafter, for convenience, such a pipe is used. Conventionally, the gas conduit is referred to as a “shaped cross-section gas conduit”).
(1) One end of a straight tubular cylindrical member is molded by a required length so that the cross section becomes a quadrangle, and the straight pipe part (hereinafter referred to as “square tube part”) having a quadrilateral cross section. .).
(2) Bending is performed in the vicinity of the boundary portion between the square tube portion and other portions to form a straight tube portion having a circular cross section and a bent tube portion having a substantially circular cross section.

  In such a conventional method for manufacturing the irregular cross-section gas conduit, it is easy to mold the cylindrical member so that the cross section is a quadrangle. However, in the subsequent bending process, the cylindrical member in which the rectangular tube portion has already been formed is centered on the boundary portion or the transition portion between the portion having a circular cross section and the portion having a square cross section (square tube portion). Since it is bent, a part of the square tube portion is bent, the effective length of the square tube portion (the length of the straight tubular portion) is reduced, and a square tube portion having a necessary length cannot be obtained. There is. Here, in order to ensure the effective length of the square tube portion, it is conceivable to make the square tube portion longer than necessary. However, when this is done, there arises a problem that the total length of the gas conduit is increased, the size and weight thereof are increased, and the material cost is increased.

  The present invention has been made to solve the above-described conventional problems, and is a compact and lightweight pretensioner in which the cross section of one straight pipe portion is circular and the cross section of the other straight pipe portion is square. It is an object to be solved to provide a means capable of easily and inexpensively manufacturing the gas conduit.

  The manufacturing method of the gas conduit | pipe (pretensioner pipe) of the pretensioner which operate | moves with the gas pressure based on this invention made | formed in order to solve the said subject has a bending process process and a square tube part formation process. Then, in the bending step, the straight tubular cylindrical member is bent, and the first straight pipe portion located on one end side, the second straight pipe portion located on the other end side, A bending pipe having a curved pipe portion positioned between the first straight pipe portion and the second straight pipe portion is created. In the square tube portion forming step, the square tube portion is formed by molding the second straight tube portion so that the cross section thereof is a quadrangle (for example, a rectangle, a square, etc.). Here, the “cross section” means a section perpendicular to the direction in which the central axis of the cylindrical member extends.

  In the method of manufacturing a gas conduit for a pretensioner according to the present invention, a preforming step of preforming the second straight pipe portion so that the cross section thereof becomes an oval shape between the bending step and the square tube portion forming step. And a square tube portion having a rectangular cross section may be formed in the square tube portion forming step. In this preforming step, the second straight pipe part is sandwiched between at least two opposing press dies and pressed (press-molded) in a direction perpendicular to the central axis of the second straight pipe part. Is preferably preformed. Here, “oval” means “round shape with a non-constant diameter” such as an ellipse or a field track shape.

  In the pretensioner gas conduit manufacturing method according to the present invention, in the square tube portion forming step, the second straight tube portion is disposed in a rectangular hollow portion (cross section is square) of a square forming die, and a square forming punch (cross section) is formed. Is preferably inserted into the hollow portion of the second straight pipe portion to form the second straight pipe portion. Further, in the bending process, the portion where the second straight pipe portion of the cylindrical member is to be formed is disposed in the die, while the portion where the curved pipe portion of the cylindrical member is to be formed and the portion where the first straight pipe portion is to be formed It is preferable that a bent tube is created by gripping a part or all of this with a clamper and rotating the clamper. In the bending process, bending may be performed so that the first straight pipe portion and the second straight pipe portion are perpendicular to each other.

  According to the method of manufacturing a gas pipe for a pretensioner according to the present invention, after bending a cylindrical member to form a bent pipe, the second straight pipe portion is molded so that the cross section thereof becomes a square and is square. Since the pipe portion is formed, a compact and lightweight pretensioner gas conduit is easily and inexpensively manufactured in which the cross section of one straight pipe portion is circular and the cross section of the other straight pipe portion is square. Can do.

  Hereinafter, a method of manufacturing a pretensioner gas conduit according to a preferred embodiment of the present invention (the best mode for carrying out the present invention) will be described with reference to the accompanying drawings. Although not shown in the drawings, this pretensioner is a pretensioner for a seat belt device, which is connected to the belt by a gas generator that generates high-pressure gas and is moved by the high-pressure gas to wind the belt. A movable member for removing the slack of the belt and a gas conduit for guiding the high-pressure gas from the gas generator to the movable member and accommodating the movable member are provided.

  When a strong impact due to a collision or the like is applied to the automobile and an ignition signal is applied to the gas generator, a gas generating agent loaded in the gas generator is ignited, and high-pressure gas is almost instantaneously emitted. The gas is generated and the gas is guided to the movable member via the gas conduit. The present invention relates to a method of manufacturing such a pretensioner gas conduit (pretensioner pipe).

  First, an outline of a method of manufacturing a pretensioner gas conduit according to the present invention will be described with reference to FIGS. In the method of manufacturing a gas pipe for a pretensioner according to the present invention, first, a straight tubular cylindrical member P1 (see FIG. 2) made of a metal material and having a perfect cross section is bent, and FIG. The 1st straight pipe part 1 located in one edge part side as shown in FIG. 2, the 2nd straight pipe part 2 located in the other edge part side, the 1st straight pipe part 1, and the 2nd straight pipe part 2 The bending pipe P2 provided with the curved pipe part 3 located between is produced (bending process). In addition, the pipe expansion part 4 for hold | maintaining a gas generator is previously formed in one edge part (end part on the side which forms the 1st straight pipe part 1) of the cylindrical member P1.

  Next, the second straight pipe portion 2 of the bending pipe P2 is preformed so that the cross section thereof becomes an oval shape, and a preformed body P3 is created (preliminary molding step). Further, the second straight pipe portion 2 of the preform P3 having an oblong cross section is molded so that the cross section is rectangular to form the square pipe portion 5, thereby completing the gas conduit P4. (Square tube forming step). In addition, when forming the square tube part 5 whose cross section is a square, it is not necessary to implement a preforming process. Further, even when the rectangular tube portion 5 having a rectangular cross section is formed, when the ratio of the vertical side to the horizontal side of the rectangle is close to 1 (for example, 0.8 to 1.2), the preliminary molding process is omitted. May be.

Hereinafter, the manufacturing method of the gas conduit of the pretensioner according to the present invention will be described in detail for each step with reference to FIGS.
(Bending process)
First, the bending process will be described with reference to FIGS. In the bending process, as shown in FIG. 2, a bending die 6 integrally formed with a bending roller 6a, a first clamper 7, a second clamper 8, a booster 9 having a protruding portion 9a, and a curved tip portion. The bending apparatus M1 provided with the metal core 10 having 10a is used.

  Hereinafter, for the sake of convenience, in the positional relationship in FIG. 2, the right side (first and second clampers 7 and 8 side) is referred to as “front”, and the left side (bending die 6 side) is referred to as “rear”. In the positional relationship in FIG. 2, the side where the first clamper 7 is located in the direction perpendicular to the front-rear direction is referred to as “upper”, and the side where the second clamper 8 is located is referred to as “lower”. In this bending apparatus M1, the bending die 6 with the bending roller 6a is a single member, but a separate bending die composed of two parts, an upper member and a lower member, that are separable from each other is used. May be. In this case, the bending roller may be a separate member from both members, or may be formed integrally with the lower member.

  When bending the cylindrical member P1 by the bending apparatus M1, the cylindrical member P1 is first disposed in the circular hollow portion 11 formed in the bending die 6 and having a circular cross section. As described above, the expanded portion 4 for holding a gas generator (not shown) is formed in advance at the first end portion 12 of the cylindrical member P1. Here, the part which should become the 2nd straight pipe part 2 is located in the circular hollow part 11, and the part which should become the 1st straight pipe part 1 and the part which should become the curved part 3 are circular hollow parts. It arrange | positions in the bending die 6 so that it may expose from 11 toward the front. Then, the portion exposed from the circular hollow portion 11 of the cylindrical member P1 is gripped (clamped) by the first clamper 7 and the second clamper 8.

  Thus, after the cylindrical member P1 is disposed in the bending die 6 and is gripped by the first clamper 7 and the second clamper 8, the booster 9 is inserted into the hollow portion of the cylindrical member P1. In this manner, the bending die 6 is inserted into the circular hollow portion 11 from the rear side. Further, the metal core 10 is inserted into the hollow portion of the cylindrical member P1 from the front side of the first clamper 7 in such a manner that the curved tip portion 10a is positioned in the vicinity of the front end portion of the circular hollow portion 11.

  Thereafter, as shown in FIG. 3, the first clamper 7, the second clamper 8, and the metal core 10 are indicated by an arrow A <b> 2 while urging or pressing the booster 9 in the direction (forward) indicated by the arrow A <b> 1. Turn or turn 90 °. At this time, the curved tip portion 10a of the metal core 10 restricts or restrains the shape change of the inner surface of the cylindrical member P1, and prevents or suppresses the flat deformation of the cylindrical member P1. Further, the booster 9 pushes the cylindrical member P1 forward with the rotation of the first and second clampers 7 and 8 and the core metal 10, that is, the change of the bending angle, so that the cylindrical member P1 is cracked or reduced in thickness. It is prevented or suppressed from occurring.

  Thus, a substantially L-shaped bent pipe P2 including the first straight pipe part 1, the second straight pipe part 2, and the curved pipe part 3 is created. In this bending process, compared to the conventional bending process, the curved pipe part 3 having a small radius of curvature of the inner curved part (that is, the minimum R) can be easily formed, the length of the second straight pipe part 2; As a result, the effective length of the square tube part 5 can be lengthened. For this reason, the edge part of the square tube part 5 can be brought close to a gas generator.

(Preliminary molding process)
Next, the preforming process will be described with reference to FIGS. 4 (a) and 4 (b) and FIGS. 5 (a) and 5 (b). In the preforming step, as shown in FIGS. 4A and 4B, a first press die 15 having a groove-shaped recess 15a having a rectangular cross section and a flat plate-like second press die 16 face each other. A preforming device M2 arranged in this manner is used. Here, the depth of the groove-like recess 15a is smaller than the outer diameter of the second straight pipe portion 2 of the bending pipe P2. On the other hand, the width of the groove-like recess 15a is larger than the outer diameter of the second straight pipe portion 2 of the bending pipe P2.

  That is, the depth of the groove-shaped recess 15a is set so that the second straight pipe portion 2 of the bending pipe P2 is preliminarily molded so that the cross section thereof becomes an oval shape, and is shorter than the short side of the second straight pipe portion 2. It is set to match the diameter. On the other hand, the width of the groove-shaped recess 15a is such that the second straight pipe portion 2 of the bending pipe P2 is preliminarily molded so that the cross section thereof is oval and the longer outer diameter of the second straight pipe portion 2 is longer. Is set to match.

  When preforming the bending pipe P2 with the preforming apparatus M2, the first press die 15 and the second press die 16 are slightly connected to each other so that the groove-shaped recess 15a faces the second press die 46. It arrange | positions so that it may space apart and oppose. And the 2nd straight pipe part 2 whose cross section of the bending pipe P2 is circular is inserted in the groove-shaped recessed part 15a. FIG. 4A shows a state in which the second straight pipe portion 2 is thus inserted into the groove-like recess 15a. And the force of the direction shown by arrow A3, A4 is applied to the 1st press die 15 and the 2nd press die 16, and the 2nd straight pipe part 2 is pressed, and the state is shown in FIG.4 (b). The first press die 15 and the second press die 16 are brought into contact with each other.

  As a result, the second straight pipe portion 2 is press-molded, and the transverse cross section of the second straight pipe portion 2 is the same as the width of the groove-like recess 15a, and the shorter outer diameter is the same as the depth of the groove-like recess 15a. It becomes a certain oval. Thus, the preform P3 is obtained. In addition, in this way, the cross section of the second straight pipe portion 2 is made into an oval shape, as described later, by inserting the second straight pipe portion 2 into the square molding die 17 (see FIG. 6). This is to facilitate the molding of the second straight pipe part 2 in the square pipe part forming step.

(Square tube forming process)
Hereinafter, the square tube portion forming step will be described with reference to FIGS. 6 and 7. In the square tube portion forming step, as shown in FIG. 6, a square tube portion forming apparatus M <b> 3 including a square molding die 17, a holding clamper 18, and a square molding punch 19 is used. Here, a rectangular hollow portion 20 having a rectangular cross section is formed in the square molding die 17, and this rectangle corresponds to the shape of the outer edge of the cross section of the square tube portion 5. Further, the cross section of the square molding punch 19 is basically a rectangle, and this rectangle corresponds to the shape of the inner edge of the cross section of the square tube portion 5. In this square tube portion forming apparatus M3, the square molding die 17 is a single member, but a separate type square molding die composed of two parts of an upper member and a lower member that can be separated from each other may be used. Good.

  When the square tube portion forming process is performed on the preform P3 by the square tube forming apparatus M3, as shown in FIG. 6, first, the preform P3 is formed into the second straight tube portion 2 having an oblong cross section. Are arranged in the square molding die 17 in such a manner as to be accommodated in the rectangular hollow portion 20. In addition, the 1st straight pipe part 1 and the curved pipe part 3 of the preforming body P3 are exposed ahead of the square molding die 17. Here, since the cross section of the second straight pipe portion 2 is oval, the second straight pipe portion 2 can be inserted into the rectangular hollow portion 20 of the square molding die 17 without hindrance. In addition, when the cross section of the 2nd straight pipe part 2 is circular, when the diameter of this circle is longer than the short side of the rectangle of the cross section of the rectangular hollow part 20 of the square shaping | molding die 17, the 2nd straight pipe part 2 Cannot be inserted into the rectangular hollow portion 20 of the square die 17.

  Next, the first straight pipe portion 1 and the curved pipe portion 3 of the preform P3 are restrained (clamped) by the pressing clamper 18. The reason for restraining the first straight pipe portion 1 and the curved pipe portion 3 in this way is to prevent or suppress the occurrence of buckling or meandering in the curved pipe portion 3 due to the molding load of the square molding punch 19. .

  Thereafter, the square molding punch 19 is moved as indicated by arrows A5 and A6 and inserted into the hollow portion of the second straight pipe portion 2, whereby the second straight pipe portion 2 has a rectangular cross section. In this way, the square tube portion 5 is formed. Since the second straight pipe portion 2 is preliminarily molded so that the cross section thereof is oval, that is, a shape closer to a rectangle than a perfect circle, insertion of the square molding punch 19, that is, formation of the square tube portion 5 is performed. It can be done easily. Thus, the pretensioner gas conduit P4 is completed.

  As described above, according to the method for manufacturing the gas conduit P4 of the pretensioner according to the embodiment of the present invention, the cylindrical member P1 is bent to form the bending pipe P2, and the second straight pipe portion 2 of the bending pipe P is formed. After preforming the cross section to be oval, the second straight pipe portion 2 is molded so that the cross section is rectangular to form the square tube portion 5, so that the cross section is circular. A compact and lightweight pretensioner gas conduit composed of one straight pipe part 1, a second straight pipe part 2 having a rectangular cross section, and a curved pipe part 3 can be easily and inexpensively manufactured.

(A) is a side view of the bending pipe created by the manufacturing method which concerns on this invention, (b) is a side view of a preforming body, (c) is a side view of a gas conduit | pipe. It is side surface sectional drawing of a bending process apparatus. It is side surface sectional drawing of a bending process apparatus. (A) is a front view of a preforming apparatus, (b) is a side view of a preforming apparatus. (A) is a front view of a preforming apparatus, (b) is a side view of a preforming apparatus. It is side surface sectional drawing of a square tube part formation apparatus. It is side surface sectional drawing of a square tube part formation apparatus.

Explanation of symbols

  M1 bending device, M2 pre-forming device, M3 square tube forming device, P1 cylindrical member, P2 bending tube, P3 pre-formed body, P4 gas conduit, 1st straight tube portion, 2nd straight tube portion, 3 songs Tube part, 4 Expanded part, 5 Square tube part, 6 Bending die, 6a Bending roller, 7 First clamper, 8 Second clamper, 9 Booster, 9a Protruding part, 10 cored bar, 10a Curved tip, 11 Circular hollow Part, 12 1st edge part, 13 2nd edge part, 15 1st press type | mold, 15a Groove-shaped recessed part, 16 2nd press type | mold, 17 Square shaping | molding die, 18 Press clamper, 19 Molding punch, 20 Rectangular hollow part.

Claims (6)

A method of manufacturing a pretensioner gas conduit operating at gas pressure, comprising:
Bending the straight tubular cylindrical member, the first straight pipe part located on one end side, the second straight pipe part located on the other end side, the first straight pipe part and the above A bending step of creating a bending pipe provided with a bent pipe part located between the second straight pipe parts;
A method of manufacturing a gas conduit for a pretensioner, comprising: forming a square tube portion by molding the second straight tube portion so that a cross section thereof is a quadrangle. It is carried out between the bending step and the square tube portion forming step, and further includes a preforming step of preforming the second straight tube portion so that the cross section thereof is oval,
The method for producing a gas conduit for a pretensioner according to claim 1, wherein the square tube portion forming step forms a square tube portion having a rectangular cross section.   In the preliminary molding step, the second straight pipe part is preliminarily placed by pressing the second straight pipe part in a direction perpendicular to the central axis of the second straight pipe part with at least two opposing press dies. The method of manufacturing a gas conduit for a pretensioner according to claim 2, wherein the gas conduit is molded.   In the square tube portion forming step, the second straight tube portion is disposed in a rectangular hollow portion of a square forming die, and a square forming punch is inserted into the hollow portion of the second straight tube portion, whereby the second straight tube portion. The method for producing a pretensioner gas conduit according to any one of claims 1 to 3, wherein the portion is molded.   In the bending step, the part of the cylindrical member where the second straight pipe part is to be formed is placed in a die, while the part of the cylindrical member where the curved pipe part is to be formed and the first straight pipe part are The method of manufacturing a gas conduit for a pretensioner according to any one of claims 1 to 4, wherein the bending tube is created by holding a portion to be formed with a clamper and rotating the clamper. .   6. The pre-processing according to claim 1, wherein in the bending step, bending is performed so that the first straight pipe portion and the second straight pipe portion are perpendicular to each other. A method of manufacturing a tensioner gas conduit.

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