Pipe production method

Abstract

To inhibit occurrence of buckling.SOLUTION: A production method of a pipe extending along an axis includes: molding a blank into a U-shaped member which is a member extending along the axis and has a U-shaped cross section; and molding the U-shaped member into a shape of the pipe. The pipe has a large diameter part, a small diameter part, and a diameter reduction part. The diameter reduction part connects the large diameter part with the small diameter part. In the production method of the pipe, at least one bead extending along the axis of the pipe is formed at a portion corresponding to the diameter reduction part of the blank or the U-shaped member.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a pipe. [Background technology]

[0002] As described in Patent Document 1, a technique is known in which UO bending is used to form a pipe having a large diameter portion, a small diameter portion that is smaller in diameter than the large diameter portion, and a reduced diameter portion that connects the large diameter portion and the small diameter portion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-070040 Summary of the Invention [Problem to be solved by the invention]

[0004] However, if the diameter of the large diameter portion is increased or the length of the reduced diameter portion in the pipe extension direction is shortened, there is a risk that buckling will occur in the reduced diameter portion when the pipe is bent in an O-shape. In one aspect of the present disclosure, it is desirable to reduce the occurrence of buckling. [Means for solving the problem]

[0005] One aspect of the present disclosure is a method for manufacturing a pipe extending along an axis. The manufacturing method includes forming a blank, which is a metal plate-like member, into a U-shaped member that extends along the axis and has a U-shaped cross section perpendicular to the axis, and forming the U-shaped member into a pipe shape. The pipe has a large diameter portion, a small diameter portion, and a tapered diameter portion. The large diameter portion has a relatively large cross-sectional diameter. The small diameter portion has a relatively small cross-sectional diameter. The tapered diameter portion connects the large diameter portion and the small diameter portion, and the cross-sectional diameter decreases toward the small diameter portion. The pipe manufacturing method further includes forming at least one bead extending along the axis of the pipe in a portion of the blank or U-shaped member corresponding to the tapered diameter portion.

[0006] According to the above configuration, the bead improves the rigidity of the portion of the blank corresponding to the reduced diameter portion, thereby preventing buckling when the U-shaped member is formed into a pipe shape.

[0007] In one aspect of the present disclosure, the U-shaped member may have a first end including a first end of a cross section and a second end including a second end of the cross section. The method for manufacturing a pipe may further include bending the first and second ends so that the first and second ends approach each other. A bead may be formed in the first and / or second ends when bending the first and second ends of the U-shaped member.

[0008] According to the above configuration, a bead can be suitably formed in the reduced diameter portion. In one aspect of the present disclosure, the pipe may further have a butt joint where the first end and the second end of the cross section of the U-shaped member are joined. At least two beads may be formed in a portion of the blank or the U-shaped member corresponding to the reduced diameter portion, and when the U-shaped member is formed into the shape of the pipe, the two beads may be arranged in the reduced diameter portion so as to sandwich the butt joint.

[0009] According to the above configuration, the bead can be provided in a portion where stress tends to concentrate when the U-shaped member is formed into a pipe shape, thereby more effectively suppressing the occurrence of buckling. In one aspect of the present disclosure, when the U-shaped member is formed into the shape of a pipe, the bead may pass through the boundary between the reduced diameter portion of the pipe and the large diameter portion or near the boundary.

[0010] According to the above configuration, the bead can be provided in a portion where stress tends to concentrate when the U-shaped member is formed into a pipe shape, thereby more effectively suppressing the occurrence of buckling. In one aspect of the present disclosure, the pipe may further have a butt portion where the first end and the second end of the cross section of the U-shaped member are joined. When the U-shaped member is formed into the shape of the pipe, the bead may extend along the butt portion around the butt portion in the reduced diameter portion.

[0011] According to the above configuration, the bead can be provided in a portion where stress tends to concentrate when the U-shaped member is formed into a pipe shape, thereby more effectively suppressing the occurrence of buckling. In one aspect of the present disclosure, the pipe may be used for instrument panel reinforcement of a vehicle.

[0012] According to the above configuration, the occurrence of buckling can be suppressed in the manufacturing process of the instrument panel reinforcement. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 2 is a front view of a pipe used as an instrument panel reinforcement. [Figure 2] FIG. [Figure 3] FIG. 2 is a cross-sectional view of the reduced diameter portion of the pipe, taken perpendicular to the axis. [Figure 4] FIG. [Figure 5] FIG. 1 is an explanatory diagram of a U-bend. [Figure 6] FIG. [Figure 7] FIG. [Figure 8] FIG. 10 is a perspective view of a U-shaped member with its ends bent. [Figure 9] FIG. 1 is an explanatory diagram of O-bending. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings. [1. Pipe configuration] As shown in Fig. 1, a pipe 1 of this embodiment is made of metal and is used, for example, as an instrument panel reinforcement. The instrument panel reinforcement is a cylindrical part that is provided in the instrument panel of a vehicle along the width direction of the vehicle. The instrument panel reinforcement is provided with a steering support 15, and the instrument panel reinforcement is configured to support a steering column, an instrument panel, etc. via the steering support 15.

[0015] Additionally, an upper end of a skeleton bracket 16 is joined to an end of the large diameter portion 10 (details of which will be described later) of the pipe 1, which is the instrument panel reinforcement, adjacent to the reduced diameter portion 12. A lower end of the skeleton bracket 16 is joined to the body of the vehicle, and the instrument panel reinforcement is supported from below by the skeleton bracket 16.

[0016] The pipe 1 has a cylindrical shape extending straight along an axis A, and a cross section perpendicular to the axis A (hereinafter simply referred to as a cross section) is substantially circular. The cross section of the pipe 1 may also be substantially elliptical. The pipe 1 has a large diameter portion 10, a small diameter portion 11, and a tapered diameter portion 12 (see FIG. 2).

[0017] The large diameter portion 10 and the small diameter portion 11 are portions with a substantially constant cross-sectional diameter. The cross-sectional diameter of the large diameter portion 10 is larger than the cross-sectional diameter of the small diameter portion 11. As an example, the large diameter portion 10 extends to a first end of the pipe 1, and the small diameter portion 11 extends to a second end of the pipe 1.

[0018] The reduced diameter portion 12 is a portion that connects the large diameter portion 10 and the small diameter portion 11. The reduced diameter portion 12 is formed in a tapered shape, and the cross-sectional diameter decreases at a substantially constant rate toward the small diameter portion 11. Of course, this is not a limitation, and the rate at which the cross-sectional diameter of the reduced diameter portion 12 decreases toward the small diameter portion 11 may vary.

[0019] As an example, in this embodiment, axis A passes through approximately the center of the cross section of each of large diameter portion 10, small diameter portion 11, and contracted diameter portion 12. However, this is not limited to this, and large diameter portion 10, small diameter portion 11, and contracted diameter portion 12 may have an eccentric structure. In other words, the center of the cross section of large diameter portion 10 and the center of the cross section of small diameter portion 11 may not be on the same line, and the center of the cross section of contracted diameter portion 12 may be located on a line extending in a direction different from the extension direction of large diameter portion 10 and small diameter portion 11.

[0020] The pipe 1 also has a butt joint 14 extending along the axis A. The butt joint 14 is formed by welding together both ends in the width direction of the blank material, in other words, both ends in the cross section of the U-shaped member, which are made to face each other by UO bending, which will be described later.

[0021] Also, as an example, the pipe 1 has a substantially constant thickness. However, this is not limiting, and the pipe 1 may have multiple sections with different thicknesses. Also, as an example, the pipe 1 is made of a single metal material, but may have multiple sections made of different metal materials. Also, the outer circumferential surface of the pipe 1 may be formed with a flat seat, which is a flat section for attaching other components, etc.

[0022] [2. Beads] As an example, two beads 13 are formed in the reduced diameter portion 12 (see FIGS. 2 and 3). The beads 13 are deformed portions of the pipe 1 and extend along the axis A. As an example, the beads 13 are curved portions that protrude outward in the cross section of the pipe 1. However, the shape of the beads 13 is not limited to this, and the beads 13 may be curved portions that protrude inward in the cross section of the pipe 1, or may be bent at one or more points in the cross section so as to protrude inward or outward.

[0023] The two beads 13 are arranged side by side in the circumferential direction (hereinafter also simply referred to as the circumferential direction) about the axis A so as to sandwich the butt portion 14 therebetween, and are located around the periphery of the butt portion 14. Each bead 13 extends along the butt portion 14. In other words, the circumferential distance between each bead 13 and the butt portion 14 is approximately constant, and each bead 13 extends approximately parallel to the butt portion 14.

[0024] Furthermore, each bead 13 extends from the boundary between the reduced diameter portion 12 and the large diameter portion 10 (hereinafter referred to as the first end) or its vicinity to the boundary between the reduced diameter portion 12 and the small diameter portion 11 (hereinafter referred to as the second end) or its vicinity. However, this is not limiting, and each bead 13 may extend from the first end of the reduced diameter portion 12 or its vicinity to a position away from the second end of the reduced diameter portion 12, or conversely, from the second end of the reduced diameter portion 12 or its vicinity to a position away from the first end of the reduced diameter portion 12. Alternatively, both ends of each bead 13 may be away from both ends of the reduced diameter portion 12.

[0025] Further, as an example, each bead 13 is provided only in the reduced diameter portion 12, but this is not limiting, and each bead 13 may extend to the large diameter portion 10 and / or the small diameter portion 11. Furthermore, the reduced diameter portion 12 may be provided with one bead 13 or three or more beads 13 arranged in the circumferential direction. Also, the reduced diameter portion 12 may be provided with a plurality of beads 13 arranged in the direction of the axis A. Specifically, for example, the beads 13 may be provided near the first end and near the second end of the reduced diameter portion 12, respectively.

[0026] [3. Pipe manufacturing method] The pipe 1 is manufactured by press-forming (UO bending) a flat metal plate. The manufacturing method of the pipe 1 includes (1) a blanking process, (2) a U-bending process, (3) an end bending process, (4) an O-bending process, and (5) a welding process. In this manufacturing method, a bead is formed in a process prior to (4) the O-bending process.

[0027] [(1) Blanking process] In the blanking process, a flat metal member is cut to form a blank material 2, which is a flat metal member (see FIG. 4). The blank material 2 has an elongated shape extending along the direction of the axis A, and has a long width portion 20, a narrow width portion 22, and a short width portion 21 aligned along the direction.

[0028] The long width portion 20 is a portion for forming the large diameter portion 10 of the pipe 1, and has a generally rectangular shape extending along the axis A. The long width portion 20 has a generally constant length in the direction perpendicular to the axis A (hereinafter referred to as width).

[0029] The short width portion 21 is a substantially rectangular portion that forms the small diameter portion 11 of the pipe 1, and has a substantially constant width. The width of the short width portion 21 is narrower than the width of the long width portion 20. The reduced width portion 22 is a portion for forming the reduced diameter portion 12 of the pipe 1. The reduced width portion 22 is also a portion that connects the long width portion 20 and the short width portion 21, and the width becomes narrower toward the short width portion 21 side.

[0030] [(2) U-bending process] In the U-bending process, the blank 2 is U-bent by press forming using first and second dies 30 and 35 (see FIG. 5). The first and second dies 30 and 35 extend in the direction of the axis A of the blank 2 to be U-bent. The first die 30 has a recess 31 whose cross section is curved in a U-shape. The second die 35 has a protrusion 36 whose cross section is curved in a U-shape so as to have a shape corresponding to the recess 31.

[0031] In the U-bending process, the first and second dies 30, 35 are arranged so that the recessed portion 31 faces the protruding portion 36. As an example, the first die 30 is arranged on the upper side and the second die 35 is arranged on the lower side, but the positions of the first and second dies 30, 35 can be determined appropriately. The blank 2 is arranged between the first and second dies 30, 35.

[0032] Then, the first and second molds 30, 35 are brought close to each other, and the convex portions 36 are inserted into the concave portions 31. As a result, the blank piece 2 is sandwiched and pressed between the convex portions 36 and the concave portions 31, and is formed into the U-shaped member 4 (see FIG. 6). Note that after the U-bending step, a cutting step may be further performed in which the end portions of the U-shaped member 4 are cut to adjust the shape of the U-shaped member 4.

[0033] The U-shaped member 4 extends along the axis A and has a U-shaped cross section. The portions of the U-shaped member 4 corresponding to the long width portion 20, the short width portion 21, and the narrow width portion 22 of the blank 2 are referred to as the long width portion 40, the short width portion 41, and the narrow width portion 42, respectively. The U-shaped member 4 also has a first end portion 43, which is a portion including a first end 44 of the cross section, and a second end portion 45, which is a portion including a second end 46 of the cross section. The first and second ends 43, 45 are provided from the first end to the second end of the U-shaped member 4 in the direction of the axis A, and the long width portion 40, the short width portion 41, and the narrow width portion 42 have the first and second end portions 43, 45, respectively. The U-shaped curved portion of the U-shaped member 4 in the cross section is referred to as a bottom portion 47.

[0034] In this embodiment, as an example, only the bottom portion 47 of the U-shaped member 4 is curved in its cross section. However, the present invention is not limited to this, and the U-shaped member 4 may be curved at multiple points in its cross section.

[0035] [(3) Edge bending process] In the end bending process, the end of the U-shaped member 4 is bent by press molding using third and fourth dies 50, 55, and beads 42A are formed in the reduced width portion 42 of the U-shaped member 4 (see FIG. 7). The third and fourth dies 50, 55 extend in the direction of the axis A of the U-shaped member 4 whose end is to be bent.

[0036] The third mold 50 has a bottom portion 51, a protrusion 52, two frame portions 53, and two bead forming portions . The protrusion 52 is a portion curved in a U-shape in cross section, and protrudes from the center in the width direction of the bottom 51. The width direction is a direction perpendicular to the direction of the axis A and the direction in which the third and fourth dies 50, 55 face each other during end bending.

[0037] The two frame portions 53 are provided at both ends of the bottom portion 51 in the width direction, and are adjacent to the protrusions 52. A gap 53A is formed between the inner peripheral surface of each frame portion 53 and the outer peripheral surface of the protrusions 52, allowing the U-shaped member 4 to enter.

[0038] The two bead forming portions 54 are provided in the third mold 50 at positions that press the reduced width portion 42 of the U-shaped member 4. Each bead forming portion 54 is provided corresponding to a corresponding frame portion 53. Each bead forming portion 54 is provided across the inner circumferential surface of the corresponding frame portion 53 and the outer circumferential surface of the bottom portion 51 that faces the inner circumferential surface. The bead forming portions 54 are portions for forming the bead 13 of the pipe 1, and the section of the gap 53A where the bead forming portions 54 are provided has a shape that corresponds to the bead 13.

[0039] The fourth mold 55 has a recess 56 having a shape corresponding to the protrusion 52 of the third mold 50. The recess 56 has a shape corresponding to the bottom 47 of the U-shaped member 4. In the end bending process, the first and second end portions 43, 45 of the U-shaped member 4 are bent so that the first end 44 and the second end 46 approach each other (in other words, so that they are inclined inward). Note that end bending may be performed on the entire U-shaped member 4, or on the reduced width portion 42, a portion of the long width portion 40 near the reduced width portion 42, and a portion of the short width portion 41 near the reduced width portion 42. At this time, a bead 42A extending along the axis A is formed on each of the first and second end portions 43, 45 of the reduced width portion 42. For example, the bead 42A of the first end portion 43 is located near the first end 44 and extends along the first end 44. Similarly, the bead 42A of the second end portion 45 is located near the second end 46 and extends along the second end 46, for example.

[0040] Specifically, in the end bending process, the third and fourth molds 50, 55 are arranged so that the convex portion 52 faces the concave portion 56. As an example, the third mold 50 is arranged on the upper side and the fourth mold 55 is arranged on the lower side, but the positions of the third and fourth molds 50, 55 can be determined as appropriate.

[0041] Furthermore, with the bottom 47 placed in the recess 56 of the fourth mold 55, the U-shaped member 4 is placed between the third and fourth molds 50, 55. At this time, the bottom 47 abuts against the recess 56, and the first end 44 and the second end 46 of the U-shaped member 4 face the third mold 50.

[0042] Then, the third and fourth molds 50, 55 are brought closer to each other, and the convex portion 52 is inserted between the first and second end portions 43, 45 of the U-shaped member 4. At this time, the first and second end portions 43, 45 each enter two gaps 53A between each frame portion 53 and the convex portion 52. As a result, the first and second end portions 43, 45 of the U-shaped member 4 are bent so that the first end 44 and the second end 46 approach each other, and beads 42A are formed at the first and second end portions 43, 45 of the reduced width portion 42, respectively (see FIG. 8).

[0043] [(4) O-bending process] In the O-bending process, the U-shaped member 4 that has been end-bent is O-bent by press forming using fifth and sixth dies 60, 65 (see FIG. 9). The fifth and sixth dies 60, 65 extend in the direction of the axis A of the U-shaped member 4 that is to be O-bent. The fifth and sixth dies 60, 65 each have recesses 61, 66 that are curved in a semicircular cross section.

[0044] Furthermore, two bead holding portions 62 are provided in the recess 61 of the fifth mold 60 at a portion that presses the reduced width portion 42 of the U-shaped member 4. The bead holding portions 62 are groove-shaped portions that extend along the axis A. The bead holding portions 62 are provided at positions spaced at approximately equal intervals from the center of the cross section of the recess 61 in the width direction.

[0045] In the end bending process, the fifth and sixth molds 60, 65 are arranged so that the recesses 61, 66 face each other. As an example, the fifth mold 60 is arranged on the upper side and the sixth mold 65 is arranged on the lower side, but the positions of the fifth and sixth molds 60, 65 can be determined as appropriate.

[0046] Furthermore, with the bottom 47 placed in the recess 66 of the sixth mold 65, the U-shaped member 4 is placed between the fifth and sixth molds 60, 65. At this time, the bottom 47 abuts against the recess 66, and the first end 44 and the second end 46 of the U-shaped member 4 face the recess 61 of the fifth mold 60.

[0047] Then, the fifth and sixth molds 60, 65 are brought close to each other. As a result, first, the recess 61 of the fifth mold 60 abuts against the first end 44 and the second end 46 of the U-shaped member 4 and presses these portions. At this time, the beads 42A formed at the first and second ends 43, 45 of the reduced width portion 42 abut against the bead holding portions 62, respectively. Then, while the shape of the beads 42A is maintained by the bead holding portions 62, O-bending is performed, and the U-shaped member 4 is formed into the shape of the pipe 1. At this time, the first end 44 and the second end 46 of the U-shaped member 4 face each other to form the butt portion 14, and beads 13 are formed on both sides of the butt portion 14.

[0048] [(5) Welding process] In the welding step, the butt joint 14 of the pipe 1 formed in the O-bending step, in other words, the first end 44 and the second end 46 of the U-shaped member 4 formed into the shape of the pipe 1, are welded together. In this way, the pipe 1 is formed.

[0049] [4. Effects] (1) When a pipe 1 having a large diameter portion 10, a small diameter portion 11, and a reduced diameter portion 12 is used as, for example, an in-vehicle component, more specifically, as an instrument panel reinforcement, it may be necessary to increase the diameter of the large diameter portion 10 in order to improve rigidity. In such a case, it may be necessary to shorten the length of the reduced diameter portion 12 in the direction of the axis A in order to ease the mounting conditions for other components on the vehicle. It is considered that shortening the reduced diameter portion 12 increases the inclination of the reduced diameter portion 12, in other words, the degree of change in the cross-sectional diameter at the reduced diameter portion 12 increases.

[0050] Due to the increase in the diameter of the large diameter portion 10, the amount of material movement in the vicinity of the large diameter portion 10 in the reduced diameter portion 12 increases during O-bending. Furthermore, due to the increased slope of the reduced diameter portion 12, the reduced diameter portion 12 becomes more susceptible to the stress generated in the direction of the axis A during O-bending. For this reason, when forming the pipe 1 by UO-bending, buckling may occur in the reduced diameter portion 12 at a relatively early stage of O-bending.

[0051] In contrast, in the above embodiment, a bead 42A is formed in the reduced width portion 42, which is a portion corresponding to the reduced diameter portion 12 in the U-shaped member 4, at a stage prior to the O-bending process. This improves the section modulus of the reduced width portion 42 (in other words, the reduced diameter portion 12), and makes it possible to suppress buckling at the reduced width portion 42 during O-bending. This allows the lead time for manufacturing the pipe 1 to be shortened.

[0052] (2) Furthermore, the bead 42A is formed in the width-reduced portion 42 in the end bending process. Therefore, the bead 42A can be formed in the U-shaped member 4 with a simple configuration that utilizes the third die 50 used for end bending.

[0053] (3) Furthermore, two beads 42A are formed in the reduced width portion 42 of the U-shaped member 4 so that the two beads 13 are lined up on either side of the butt joint 14 in the reduced diameter portion 12 of the pipe 1. This allows the beads 42A to be provided in locations where stress tends to concentrate during O-bending, thereby more effectively suppressing the occurrence of buckling.

[0054] (4) Furthermore, the bead 42A is formed in the reduced width portion 42 of the U-shaped member 4 so that the bead 13 passes through or near the boundary on the large diameter portion 10 side of the reduced diameter portion 12 of the pipe 1. This allows the bead 42A to be provided in a location where stress is likely to concentrate during O-bending, thereby more effectively suppressing the occurrence of buckling.

[0055] (5) Furthermore, in the reduced width portion 42 of the U-shaped member 4, a bead 42A is formed near the first end 44 or the second end 46 of the first and second end portions 43, 45, extending along the first end 44 or the second end 46. In other words, in the reduced diameter portion 12 of the pipe 1, a bead 13 is formed around the butt joint 14 so as to extend along the butt joint 14. Therefore, the bead 42A can be provided in a location where stress is likely to concentrate during O-bending, and buckling can be more effectively suppressed.

[0056] (6) In addition, in a pipe 1 used as an instrument panel reinforcement for a vehicle, it may be difficult to join other components, such as the skeletal bracket 16, to the reduced diameter portion 12. In contrast, according to the above embodiment, the reduced diameter portion 12 can be shortened, thereby expanding the number of locations on the pipe 1 where other components can be joined. As a result, the vehicle mounting conditions for other components joined to the pipe 1 can be relaxed. Specifically, for example, the skeletal bracket 16 can be mounted on the vehicle in a shape that is closer to a straight line, which can improve the rigidity of the skeletal bracket 16 and, therefore, the operability of the vehicle. Furthermore, by making the skeletal bracket 16 have a shape that is closer to a straight line, the weight and cost of the skeletal bracket 16 can be reduced, and the weight reduction can also improve the fuel efficiency and operability of the vehicle.

[0057] 5. Other Embodiments (1) In the manufacturing method of the pipe 1 according to the above embodiment, the bead 42A is formed in the U-shaped member 4 by the third die 50 in the end bending process. However, the timing of forming the bead 42A is not limited to this and may be determined as appropriate at a stage prior to the O-bending process.

[0058] Specifically, for example, a bead may be formed on the blank 2 at a stage prior to the U-bending step, or the bead 42A may be formed on the U-shaped member 4 during the U-bending step or between the U-bending step and the end bending step. Also, for example, the bead 42A may be formed on the U-shaped member 4 formed in the end bending step using a mold other than the third mold 50.

[0059] Furthermore, in the above manufacturing method, beads 42A extending along the first end 44 or the second end 46 are formed near the first end 44 or the second end 46 at the first and second ends 43, 45 of the reduced width portion 42 of the U-shaped member 4. However, the positions at which the beads 42A are formed and the number of the beads 42A are not limited to this and can be determined appropriately depending on the positions and number of the beads 13 in the pipe 1.

[0060] (2) The pipe 1 in the above embodiment is used as an instrument panel reinforcement, but is not limited thereto and may be used as an in-vehicle part other than an instrument panel reinforcement, or as a member not mounted on a vehicle. Furthermore, the pipe 1 may have, for example, a bent or curved shape.

[0061] (3) In the manufacturing method of the pipe 1 of the above embodiment, after O-bending, the bead 13 formed in the reduced diameter portion 12 may be crushed. In other words, the bead 13 formed in the reduced diameter portion 12 may be removed by applying pressure to the pipe 1. Specifically, the bead 13 may be crushed before the welding process, or may be crushed after the welding process.

[0062] (4) Multiple functions of one component in the above embodiments may be realized by multiple components, or one function of one component may be realized by multiple components. Also, multiple functions of multiple components may be realized by one component, or one function realized by multiple components may be realized by one component. Also, part of the configuration of the above embodiments may be omitted. Also, at least part of the configuration of the above embodiments may be added to or substituted for the configuration of another of the above embodiments.

[0063] [6. Technical Ideas Disclosed in the Present Specification] [Item 1] A method for manufacturing a pipe extending along an axis, comprising: A blank material that is a metal plate-like member is formed into a U-shaped member that is a member that extends along the axis and has a U-shaped cross section perpendicular to the axis; forming the U-shaped member into the shape of the pipe; Equipped with The pipe is a large diameter portion having a relatively large cross-sectional diameter; a small diameter portion having a relatively small cross-sectional diameter; a reduced diameter portion that connects the large diameter portion and the small diameter portion and whose cross-sectional diameter decreases toward the small diameter portion, The method for manufacturing the pipe further includes forming at least one bead extending along the axis of the pipe in a portion of the blank or the U-shaped member corresponding to the reduced diameter portion. Pipe manufacturing method.

[0064] [Item 2] A method for manufacturing the pipe according to item 1, the U-shaped member has a first end including a first end of the cross section and a second end including a second end of the cross section; The method for manufacturing the pipe further comprises bending the first and second ends so that the first and second ends approach each other; The bead is formed at the first and / or second end of the U-shaped member when the first and / or second end is bent. Pipe manufacturing method.

[0065] [Item 3] A method for manufacturing a pipe according to item 1 or 2, The pipe further has a butt portion where the first end and the second end of the cross section of the U-shaped member are joined, At least two of the beads are formed in a portion of the blank or the U-shaped member corresponding to the reduced diameter portion, and when the U-shaped member is formed into the shape of the pipe, the two beads are arranged in the reduced diameter portion so as to sandwich the butt portion. Pipe manufacturing method.

[0066] [Item 4] A method for manufacturing a pipe according to any one of items 1 to 3, When the U-shaped member is formed into the shape of the pipe, the bead passes through the boundary between the reduced diameter portion of the pipe and the large diameter portion or near the boundary. Pipe manufacturing method.

[0067] [Item 5] A method for manufacturing a pipe according to any one of items 1 to 4, The pipe further has a butt portion where the first end and the second end of the cross section of the U-shaped member are joined, When the U-shaped member is formed into the shape of the pipe, the bead extends along the butt portion around the butt portion in the reduced diameter portion. Pipe manufacturing method.

[0068] [Item 6] A method for manufacturing a pipe according to any one of items 1 to 5, The pipe is used for vehicle instrument panel reinforcement. Pipe manufacturing method. [Explanation of symbols]

[0069] A...axis, 1...pipe, 10...large diameter portion, 11...small diameter portion, 12...reduced diameter portion, 13...bead, 14...butt portion, 16...skeletal bracket, 2...blank material, 20...long width portion, 21...narrow width portion, 22...reduced width portion, 30...first mold, 35...second mold, 4...U-shaped member, 40...long width portion, 41...narrow width portion, 42...reduced width portion, 42A...bead, 43...first end, 44...first end, 45...second end, 46...second end, 50...third mold, 51...bottom, 52...convex portion, 53...frame portion, 53A...gap, 54...bead forming portion, 55...fourth mold, 60...fifth mold, 61...recess, 62...bead retaining portion, 65...sixth mold.

Claims

1. A method for manufacturing a pipe extending along an axis, comprising the steps of: A blank material, which is a metal plate-like member, is formed into a U-shaped member, which is a member extending along the axis line and has a U-shaped cross section perpendicular to the axis line; forming the U-shaped member into the shape of the pipe; Equipped with The pipe is A large diameter portion having a relatively large cross-sectional diameter; A small diameter portion having a relatively small cross-sectional diameter; a reduced diameter portion that connects the large diameter portion and the small diameter portion and has a cross-sectional diameter that decreases toward the small diameter portion, The method for manufacturing the pipe further includes forming at least one bead extending along the axis of the pipe in a portion of the blank or the U-shaped member corresponding to the reduced diameter portion. Pipe manufacturing method.

2. A method for manufacturing the pipe according to claim 1, comprising the steps of: the U-shaped member has a first end including a first end of the cross section and a second end including a second end of the cross section; The method of manufacturing the pipe further comprises bending the first and second ends such that the first and second ends approach one another; The bead is formed at the first and / or second ends of the U-shaped member when the first and second ends are bent. A method for manufacturing pipes.

3. A method for manufacturing a pipe according to claim 1 or 2, comprising the steps of: The pipe further has a butt portion where the first end and the second end of the cross section of the U-shaped member are joined, At least two of the beads are formed in a portion of the blank or the U-shaped member corresponding to the reduced diameter portion, and when the U-shaped member is formed into the shape of the pipe, the two beads are disposed in the reduced diameter portion so as to sandwich the butt portion. A method for manufacturing pipes.

4. A method for manufacturing a pipe according to claim 1 or 2, comprising the steps of: When the U-shaped member is formed into the shape of the pipe, the bead passes through the boundary between the reduced diameter portion of the pipe and the large diameter portion or near the boundary. Pipe manufacturing method.

5. A method for manufacturing a pipe according to claim 1 or 2, comprising the steps of: The pipe further has a butt portion where the first end and the second end of the cross section of the U-shaped member are joined, When the U-shaped member is formed into the shape of the pipe, the bead extends along the butt portion around the butt portion in the reduced diameter portion. A method for manufacturing pipes.

6. A method for manufacturing a pipe according to claim 1 or 2, comprising the steps of: The pipe is used for vehicle instrument panel reinforcement. A method for manufacturing pipes.

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