JP2000117325A - Method for producing tube with closed polygonal cross section and apparatus therefor - Google Patents

Abstract

(57) [Problem] To produce a polygonal and closed tube continuously as viewed in a cross section perpendicular to the feed direction of a strip, and to reliably realize a reduction in product cost. A method and an apparatus therefor are provided. As a straightening welding step, a rough pipe W0 after a rough pipe forming step is straightened from inside and outside near the exits of a die 3, a pressure punch 4, and straightening punches 13 and 14, and both ends are formed. e1 and e2 are the first electrode 20 and the second electrode 2
1 is spot-welded at predetermined intervals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is capable of continuously producing a polygonal closed tube when viewed in a cross section perpendicular to the feed direction by applying a feed bending method to a metal strip. And a device therefor. The pipe obtained by the present invention can be used for reinforcing materials such as bumpers.

[0002]

2. Description of the Related Art In a feed bending method, for example, a punch and a die are used as a first die and a second die, and a metal strip is fed between these punches and a die by a fixed length, and synchronously with this. This is a method of pressing a strip with a punch and a die. This feed bending method is a method of pressing while feeding a strip at a fixed length, so that an extremely small punch or the like can be employed. For this reason, this feed bending method is a general press working method in which a strip of a predetermined length is formed at a time using a large-sized press device, or a method in which a number of rolls are sequentially aligned at a predetermined angle to form a strip. There is an advantage that the production cost in the case of small-lot production of many kinds can be reduced as compared with the roll forming processing method for forming.

Heretofore, the present applicant has continuously reviewed the past feed bending method to continuously produce polygonal and closed pipes in a cross section orthogonal to the feed direction of the strip. In addition, a technique has been proposed in which the obtained pipe is not brittle due to metal fatigue and is of high precision (JP-A-9-271847). In this technique, as a rough pipe forming step, a rough pipe continuous with a strip (work) is obtained from the vicinity of the entrance to the center of the first mold and the second mold to the vicinity of the center. At this time, since the planned ridge line of the work constituting the ridge line of the pipe extends in the feed direction, the work is only gradually bent at the planned ridge line, and does not induce embrittlement due to metal fatigue. The obtained rough pipe has an interior angle at each predetermined ridge line substantially equal to the interior angle of the corresponding ridge line of the pipe, and has both ends substantially flush with each other so as to be in contact with each other. Further, in the initial stage of the rough pipe forming step, a notch is formed in the work so as to extend in the width direction at a pitch corresponding to the length of the pipe, and a joint portion may remain on a single surface of the pipe. As the next straightening step, the rough pipe is straightened from inside and outside near the outlets of the first mold and the second mold. As a result, a tube that is polygonal and closed when viewed in a cross section orthogonal to the feed direction is obtained continuously with the coarse tube. Thereafter, the tube is cut by a cut to obtain a product.

[0004]

However, according to the above-mentioned conventional proposed technique, a pipe cut after the straightening process is transported to another place of a welding facility, where both ends of the pipe are welded to produce a product. Was. For this reason, in this technique, since it is necessary to transport the pipes, equipment and time for the pipe transport are required, and there has been a limit in reducing the product cost.

[0005] Further, in this technique, it has not been sufficiently studied which welding method can secure the cross-sectional strength of the product. Therefore, in order to ensure the cross-sectional strength of the product, it is necessary to ensure the cross-sectional strength of the product. Arc welding that forms a continuous bead at both ends was employed. For this reason, in this technique, since thermal distortion of the tube due to the arc heat is inevitable, it is necessary to predict the amount of deformation due to the thermal distortion before performing the roughing process and the straightening process. For this reason, the design of the first type and the second type of the manufacturing apparatus is troublesome, and this also limits the cost reduction of the product.

The present invention has been made in view of the above-mentioned conventional circumstances, and continuously manufactures a polygonal and closed pipe when viewed in a cross section orthogonal to the feeding direction of a strip. An object of the present invention is to provide a manufacturing method and an apparatus therefor that can surely realize a reduction in product cost.

[0007]

According to the present invention, a method of manufacturing a tube having a polygonal cross section in a closed state is to feed a metal strip between a first mold and a second mold by a fixed length and synchronize with the metal strip. Then, by a feed bending method in which the strip is pressed with the first mold and the second mold, a method for continuously producing a polygonal and closed pipe as viewed in a cross section orthogonal to the feed direction. Then, from near the entrance of the first mold and the second mold to near the center,
Of the planned ridge lines extending in the feed direction of the band plate constituting the ridge line of the pipe, by gradually bending to those at the center part sequentially from those near both ends in the width direction of the band plate, A rough pipe is formed to be continuous with the strip plate, the inner angle at each of the predetermined ridge lines being substantially equal to the inner angle of each of the corresponding ridge lines of the pipe, and having both ends substantially flush with each other so as to be in contact with each other. In the tube forming step, near the outlet of the first mold and the second mold,
A straightening welding step of straightening the rough pipe from the inside and the outside and spot-welding both ends at predetermined intervals to obtain the pipe continuous with the rough pipe; and And a dividing step of cutting the pipe at the outlet with the mold 2.

In the method of the present invention, the straightening welding step includes:
Near the outlets of the first mold and the second mold, the rough pipe after the rough pipe forming step is straightened from inside and outside, and both ends are spot-welded at predetermined intervals. Therefore, in this method,
This eliminates the need for a conventional pipe transport operation, and saves equipment and time therefor, thereby realizing a reduction in product cost. In particular, in this method, when the pressing force for performing the correction also serves to press the first electrode and the second electrode of the spot welding, equipment for pressurizing only the first electrode and the second electrode is provided. This is unnecessary, and the product cost can be further reduced.

Further, in this method, both ends are spot-welded at predetermined intervals, and the cross-sectional strength of the product is ensured even with less heat input than conventional arc welding. Therefore, this method hardly causes deformation of the tube due to thermal distortion. In addition, since the rough pipe is corrected at the same time as the spot welding, the deformation can be corrected. For this reason, in this method, it is not necessary to design the first and second molds of the manufacturing apparatus in which the amount of deformation due to thermal strain is predicted,
This can also reduce the product cost.

[0010] The apparatus for producing a tube having a closed polygonal section according to the present invention feeds a metal strip between the two at a constant length.
An apparatus for continuously manufacturing a polygonal and closed pipe as viewed in a cross section perpendicular to the feed direction by a feed bending method in which the strip is pressed by the two in synchronization with the feed pipe. From the vicinity of the entrance to the vicinity of the center,
Of the planned ridge lines extending in the feed direction in the strips constituting the ridges of the pipe, by gradually bending from those near both ends in the width direction of the strips to those at the center sequentially and gradually, A rough pipe which is continuous with the strip plate, the inner angle at each of the predetermined ridge lines is substantially equal to the inner angle of each of the corresponding ridge lines of the pipe, and both ends of the rough pipe are substantially flush with each other, After this, near the outlet, the first and second molds for straightening the rough pipe from the inside and the outside and spot welding the both ends at predetermined intervals to obtain the pipe continuous with the rough pipe are provided.
The first mold comprises a die body extending from the vicinity of the entrance to the vicinity of the center, and a core metal continuous with the outer surface of the die body and fixed to the die body and extending to the exit,
The cored bar is provided with a first electrode, the second die is provided with a pressing punch capable of facing the die body and the cored bar, and a correction punch facing the cored bar and movable in the width direction left and right. Wherein the pressure punch or the correction punch is provided with a second electrode that can be spot-welded in pairs with the first electrode.

[0011] In the manufacturing apparatus of the present invention, the first electrode and the second electrode which can be spot-welded to the first-type cored bar and the second-type pressure punch or straightening punch are provided. For this reason,
In the straightening welding step, the rough pipe after the roughing step is straightened from inside and outside near the outlet of the first mold and the second mold, and both ends can be spot-welded at predetermined intervals. For this reason, it is not necessary to carry out the work of transporting the pipes, and it is not necessary to design the first and second molds of the manufacturing apparatus in which the amount of deformation due to thermal strain is predicted.

Therefore, according to the manufacturing method and the manufacturing apparatus of the present invention, when the cross section is perpendicular to the feeding direction of the strip, polygonal and closed pipes are continuously manufactured, and the product cost is low. Can be realized reliably.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below with reference to the drawings. In this embodiment, FIGS.
The manufacturing apparatus shown in FIG. In this apparatus, a movable table 2 is positioned above a fixed table 1, and the movable table 2 is provided with a press ram (not shown) that can move in a downward pressing direction P. A die 3 as a first die is fixed to the fixed base 1 via a base 1a, and a pressing punch 4 as a part of the second die is fixed to the movable base 2. At the right end of the apparatus, a transport unit (not shown) that feeds a strip (work) W (see FIGS. 4 and 5) in a horizontal feed direction S is provided.

As shown in FIG. 2, the die 3 extends from the entrance, which is the exit side of the transfer section, to the vicinity of the center on the left side, and protrudes from the upper end of the left end surface of the die body 5 to the exit. And a metal core 6. The die body 5 is the first member 5 on the right end side.
1, a central second member 52 and a third member 53, which are integrally fixed. The upper outer surface 5b of the first member 51 is formed horizontally at the entrance when viewed in a cross section orthogonal to the feeding direction S, and the second member 52
After gradually bending to 90 ° at a portion where the planned ridge lines L1 and L2 (see FIG. 5B) are leveled, the two planned ridge lines L3 and L4 of the work W in the third member 53 (FIG. 5C). (See Reference)) and gradually bend to 90 °. Here, as shown in FIGS. 5A to 5C, the respective scheduled ridge lines L1, L2 of the work W are both ends e1, e in the width direction of the work W.
2 and each scheduled ridge line L3, L4
Next, it is near the both ends e1 and e2 in the width direction, that is, at the center, and each of the planned ridge lines L1 to L4 extends in the feed direction S. Thus, as shown in FIG. 2, the lower part of the die body 5 is narrowed in accordance with the narrowing of the both ends of the outer surface 5b.

Outer surface 4b at the lower part of pressure punch 4 shown in FIG.
Are formed horizontally at the entrance when viewed in a cross section orthogonal to the feed direction S, and then the two scheduled ridge lines L1, L2 of the workpiece W
The work W is gradually bent to 90 °, and then gradually bent to 90 ° at the part where the two scheduled ridge lines L3 and L4 of the work W are smoothed. As shown in FIG. 3, on the exit side of the apparatus, a pair of slide stands 7 and 8 are fixed to the left and right of the fixed stand 1 when viewed in a cross section orthogonal to the feed direction S. Sliders 11, 12 urged by pressing springs 9, 10 in directions away from each other are slidably provided. Correcting punches 13 and 14 for correcting the rough pipe W0 (see FIGS. 4 and 5) are fixed to the sliders 11 and 12 together with the lower part of the pressing punch 4 facing the metal core 6 and the metal core 6. . These straightening punches 13,
Reference numeral 14 forms a second die together with the press punch 4. On the other hand, slide cams 15 and 16 are fixed to the movable base 2, and sliders 11 and 12 are
Inclined surfaces 15a and 16a are formed so as to be aligned with the inclined surfaces 11a and 12a. Slope 15
a, 11a are positioned above the inclined surfaces 16a, 12a, and thereby the correction punches 13, 1
4 can be shifted in timing.

[0016] Further, a pair of first power supply devices is provided near the outlet of the device.
The electrode 20 and the second electrode 21 are both ends e1 and e of the rough tube W0.
2 is provided so as to sandwich it from above and below. First electrode 20
Is slidably embedded in the metal core 6 so that the lower end protrudes,
It is urged downward by the pressing spring 22. Also, the second
The electrode 21 is slidably embedded in the correction punch 14 so that the upper end protrudes, and the lower end of the second electrode 21 is in contact with the rod 23a. Air cylinder body 2 on fixed base 1
5 is fixed, and a flexible hose 26 is connected to the air cylinder body 25. Flexible hose 2
The other end of 6 is provided with an operation unit 23 that can extend the rod 23 a by high-pressure air sent from the air cylinder body 25, and this operation unit 23 is fixed to the correction punch 14.

Using the apparatus configured as described above, the die body 5, the metal core 6, the pressure punch 4, the correction punch 13,
14, a metal work W is fed by a fixed length, and in synchronization with this, a die body 5, a cored bar 6, a pressure punch 4
The work W is pressed by the correction punches 13 and 14. The pipe W1 shown in FIGS. 4 and 5 is continuously manufactured by performing the feed bending method on the work W and spot welding the both ends e1 and e2 of the work W.

That is, first, a notch 17 is formed in the work W by a not-shown projection of the pressure punch 4 and a not-shown hole of the first member 51. The cut 17 is a long hole extending in the width direction at a pitch corresponding to the length of the pipe W1, and the connecting portions 18 are left at both ends in the width direction. Next, as a rough pipe forming step including first and second steps, a rough pipe W0 continuous with the work W is obtained by the die body 5 and the pressure punch 4. At this time, each scheduled ridge line L1 to L
4 extend in the feed direction S, the work W
Is only gradually bent at each of the planned ridge lines L1 to L4, and does not induce embrittlement due to metal fatigue.

As shown in FIGS. 5A and 5B,
The bend of the work W is changed to the expected ridge line L near both ends e1 and e2.
1 and L2, the length of the flange surfaces F1 and F2 in the pressing direction P is short, and the warpage of the workpiece W in the reverse direction is minimized. In the second step in which the forming is further advanced, as shown in FIGS. 4 and 5, the work W is bent at the predetermined ridge lines L3 and L4. The coarse pipe W0 thus obtained has an interior angle at each of the planned ridge lines L1 to L4 substantially equal to the interior angle of the corresponding ridge line L5 to L8 of the pipe W1.
And both ends e1 and e2 are substantially flush with each other and can contact each other. However, since both ends e1 and e2 of the rough pipe W0 undergo elongation and contraction due to sequential bending, the end is likely to be opened due to residual stress.

For this reason, in the next straightening welding step, near the outlet of the apparatus, each straightening punch 13, 14 moves the coarse tube W 0 inward together with the lower part of the portion of the pressure punch 4 facing the core 6 and the core 6. And correct from outside. At this time, FIG.
As shown in the figure, when the slide cams 15 and 16 descend,
Since the correction punch 13 moves earlier than the correction punch 14, as shown in FIG.
1 wraps around the cored bar 6 and then the short end e2
Wraps around the cored bar 6. Thus, both ends e1 and e2 in the terminal opening state are overlapped.

In the final stage of the straightening welding process, the first electrode 20 and the second electrode 21 use both ends e1,
e2 is spot-welded at intervals of 50 mm to form nuggets 24, respectively. At this time, the pressing force for performing the correction is adjusted by the pressing spring 22 and the air cylinder main body 25, and also serves to press the first electrode 20 and the second electrode 21 for spot welding. The welding current is supplied for about 0.5 seconds, during which the press ram stops. When the interval between the nuggets 24 is longer than the feed pitch of the work W,
The high-pressure air in the air cylinder body 25 is removed, and the welding current is not supplied to the first electrode 20 and the second electrode 21.

In this manner, both ends e1,
A total of 14 nuggets 24 are formed on e2 to secure the cross-sectional strength of the product. Then, as shown in FIG. 4 and FIG. 5 (C), a tube W1 in a square and closed state is obtained continuously from the rough tube W0 when viewed in a cross section orthogonal to the feed direction. Then, in the dividing step, the pipe W1 is cut. Thus, the pipe W1 is reliably cut at a desired location, and a product W2 having a desired size is obtained. This product W2 was used as a reinforcing material for the bumper.

As described above, in the present embodiment, as the straightening welding step, the rough pipe W0 after the rough pipe forming step is straightened from inside and outside, and both ends e1 and e2 are spot-welded at intervals of 50 mm. For this reason, in the present embodiment, the conventional pipe transport operation is not required, and the equipment and time for the operation can be omitted, and the cost of the product can be reduced. Further, the pressing force for performing the correction by the correction punches 13 and 14 and the cored bar 6 is equal to the first electrode 20 and the second electrode 20 of the spot welding.
Since a part of the pressurization of the electrode 21 is also used, equipment for pressurizing only the first electrode 20 and the second electrode 21 is not required, and the cost of the product can be further reduced.

In this embodiment, both ends e1, e2
Are spot-welded at intervals of 50 mm, so that the cross-sectional strength of the product W2 can be ensured even under a less heat input than conventional arc welding. Therefore, in the present embodiment, the product W2 hardly deforms due to thermal strain. Moreover,
Since the rough pipe W0 is corrected at the same time as the spot welding, the deformation can be corrected. For this reason,
In the present embodiment, it is not necessary to design the die 3, the pressure punch 4, and the correction punches 13 and 14 of the manufacturing apparatus in which the deformation amount due to the thermal strain is predicted, and thus the cost of the product can be reduced.

Incidentally, in relation to the feed pitch of the work W,
A plurality of pairs of the first electrode and the second electrode may be used.

[Brief description of the drawings]

FIG. 1 is a schematic vertical sectional view of a manufacturing apparatus according to an embodiment.

FIG. 2 is a plan view of a die according to the manufacturing apparatus of the embodiment.

FIG. 3 relates to the manufacturing apparatus of the embodiment, and corresponds to III-I of FIG.
It is II sectional drawing.

4A is a plan view of a work, and FIG. 4B is a side view of the work according to the manufacturing method of the embodiment.

FIG. 5A relates to the manufacturing method of the embodiment, and FIG.
FIG. 4B is a cross-sectional view taken along arrow A, FIG.
FIG. 5C is a cross-sectional view taken along the line CC of FIG. 4.

[Explanation of symbols]

3, 5, 51, 52, 53, 6 ... first type (3 ... die, 5
... Die body (51 ... first member, 52 ... second member, 53 ...)
3rd member), 6 core metal) 4, 13, 14 ... second mold (4 ... pressing punch, 13, 14)
... Correcting punch) W ... Strip (work) W1 ... Pipe 18 ... Connecting part 17 ... Cut L5-L8 ... Ridge line S ... Sending direction L1-L4 ... Predetermined ridge line e1, e2 ... End W0 ... Coarse pipe 20 ... First Electrode 21: Second electrode

Claims (2)

[Claims] A metal strip is fed between a first mold and a second mold by a predetermined length, and the strip is pressed by the first mold and the second mold in synchronization with the feeding. A method for continuously manufacturing a pipe in a polygonal and closed state as viewed in a cross section orthogonal to a feed direction by a bending method, comprising: a portion near an inlet of the first mold and a portion near a center of the second mold. Up to, among the predetermined ridge lines extending in the feed direction of the strip constituting the ridge of the pipe, gradually bending from the one near the both ends in the width direction of the strip to the central one in order. Thus, the inner tube at each of the predetermined ridge lines is substantially equal to the inner angle of each of the corresponding ridge lines of the tube, and both ends thereof can be brought into contact with each other at substantially the same upper surface. A rough pipe forming step of obtaining the inner pipe and the outer pipe in the vicinity of the outlets of the first mold and the second mold. A straightening welding step of straightening and spot welding the two end portions at predetermined intervals to obtain the pipe continuous with the coarse pipe; and forming the pipe at an outlet of the first mold and the second mold. A method for producing a pipe having a polygonal cross section in a closed state, comprising: a dividing step of cutting. 2. A feed bending method in which a metal strip is fed between the two by a constant length and the strip is pressed in synchronization with the strip, as viewed in a cross section orthogonal to the feed direction. ,
An apparatus for continuously manufacturing a pipe in a polygonal and closed state, wherein the apparatus extends from the vicinity of an inlet to the vicinity of a center in the feeding direction of the strip forming a ridge line of the pipe. Of the planned ridge lines, those that are closer to both ends in the width direction of the strip are gradually bent toward the central portion and gradually bent to be continuous with the strip, and the inner angle at each of the planned ridge lines is equal to that of the pipe. Obtain a rough pipe substantially equal to the inner angle of each of the corresponding ridge lines, and both ends of the rough pipe can be brought into contact with each other with substantially the same upper surface, and thereafter, near the outlet, the rough pipe is straightened from inside and outside. And a first mold and a second mold for obtaining the pipe continuous with the coarse pipe by spot welding the both ends at predetermined intervals. The first mold extends from near the entrance to near the center. An existing die body, the die body being continuous with an outer surface of the die body. A metal core fixed and extending to an outlet, wherein the metal core is provided with a first electrode; the second die comprises a pressure punch capable of facing the die body and the metal core; A correction punch that faces gold and is movable in the width direction to the left and right, and the pressure punch or the correction punch is provided with a second electrode that can be spot-welded in pairs with the first electrode; An apparatus for manufacturing a pipe in a closed state having a polygonal cross section.