JPH0261333B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of forming a circular tube, and particularly to a method of press-feeding and bending a circular tube using an edge bending method.

As a method for manufacturing a long circular tube from a flat plate, a roll forming method and a U-O forming method using a press mold are known. The former requires large equipment because it processes by arranging a large number of rolls in a line, and although the forming speed is fast, it is difficult to respond to changes in pipe diameter and plate thickness. It is also unsuitable when making circular pipes from special materials.
The problem was that it was not suitable for high-mix, low-volume production of circular pipes. On the other hand, since the latter is a press process, it can accommodate changes in diameter, etc.
The disadvantages are that it requires two processes: U-forming and O-forming, that the O-forming process requires a large processing force, that the mold length becomes large, and that it requires somewhat large-scale equipment. The disadvantage was that the product shape was limited to a closed cross section, and products with flanges or half-open cross sections could not be molded.

The present invention solves the above-mentioned disadvantages in manufacturing long circular pipes.
Eliminating the drawbacks, long circular tubes with high precision can be manufactured using simplified processes and molds with shortened overall length, and with low machining force. Furthermore, the product shape is not limited to closed cross sections, but can also be manufactured with flanges, with flanges, etc. The aim is to provide a molding method that can easily produce various types of products, such as those with holes or half-open ones. The purpose is to form a circular tube gradually and continuously.

That is, the present invention provides a method for feeding and bending a strip plate into a circular pipe, in which the press bending mold has an inlet on the inlet side that is composed of side curved surfaces on both sides for edge bending and a flat bottom surface connecting the side curved surfaces. A semicircular groove having the same radius as the side curved surface is formed on the exit side so that the bending line forming the boundary between the bottom surface and the side curved surface approaches continuously between the entrance groove and the semicircular groove. A grooved die with a groove width narrowing at the bottom, a starting end on the inlet side consisting of a flat top surface corresponding to the bottom surface and a side curved surface corresponding to the side curved surface, and a semicircular groove on the outlet side. Using a punch that has a corresponding semicircular part and a width that is continuously narrowed between the starting end and the semicircular part, feed the strip from one end into the press bending mold for a predetermined length, and then The punch and groove die of the press bending die are moved up and down relative to each other in synchronization with the press bending type, and the punch is pushed into the groove die with the same stroke length over the entire length, causing it to bottom out. In this method, the tube is gradually bent from both ends in the same direction as the tube to be manufactured, with the same radius until the desired tube shape is obtained, and then the tube is sequentially sent out from the press bending die.

Embodiments of the present invention will be described above based on the accompanying drawings.

Figures 1 to 3 show an embodiment of the press-feed bending method for circular pipes using the edge bending method according to the present invention, in which 1 is a press bending die consisting of a grooved die 2 and a punch 3. . 4 is a strip plate, the grooved die 2 is fixed to a bolster (not shown) by a die plate or a die holder 5, and the punch 3 is fixed to a bolster (not shown).
is fixed to a punch plate or punch boulder 7 by a mounting jig 6, and is moved up and down by a press ram (not shown). The strip 4 is progressively fed into the press bending mold 1 by an arbitrary feeding mechanism 8 such as a roller.

Here, the present invention uses a special structure as the press bending die 1, that is, as shown in FIG. An inlet groove 20 consisting of a flat bottom surface 22 connecting the side curved surfaces 21, 21 is recessed, and a semicircular groove (exit groove) 23 having the same radius as the side curved surfaces 21, 21 is formed on the exit side. Between the entrance groove and the semicircular groove 23, the groove width gradually narrows so that the bending lines 24, 24 forming the boundaries between the bottom surface 22 and the side curved surfaces 21, 21 continuously approach each other.

The punch 3 has a shape similar to the grooved die 2, that is, a flat top surface 32 corresponding to the bottom surface 22 of the entrance groove 20, a side curved surface (punch shoulder) 31 corresponding to the side curved surfaces 21, 21, 31 on the inlet side, and has a semicircular part 33 corresponding to the semicircular groove 23 on the outlet side.
The width between the semicircular portion 33 and the semicircular portion 33 is continuously narrowed.

In this embodiment, in order to apply compressive force to the circular tube at the final stage and improve the roundness, the semicircular groove of the grooved die 2 is
A regular part 25 is formed by extending the punch 3 by a predetermined length, and a regular part 35 is also formed on the punch 3 by extending the semicircular part 33.

When forming a circular tube, the feeding mechanism 8 feeds the strip 4 of a predetermined length from one end into the press bending mold 1, and in synchronization with this feeding, the press ram punches the punch 3. is moved up and down, and the starting end 30 of the punch 3 is moved up and down for each descending process.
The semicircular portion 33 is pushed into the entrance groove 20 or the semicircular groove 23 of the grooved die 2 with a stroke length equal to that of the groove, and the bottoming force of the punch 2 is used to gradually bend the strip plate 4 from the plate edge to the same radius as the tube. It is something that will continue.

Figure 2 shows the deformed shape when the strip is fed to each position in the bending die, Figure 3 shows the deformed shape at each position in the bending die, and Figure 4 schematically shows the changing process of the strip. One end of the strip plate 4 is pressed into the press bending die 1.
When the punch 3 is lowered, the width W of the strip plate 4 matches the bending line 2 of the entrance groove 20.
When the strip plate 4 is smaller than 4, 24, it remains flat as shown in Fig. 3 A, and when the strip plate 4 advances to the next feed length and the punch 3 descends, the side curved surfaces 21, 21 of the grooved die 2 and the punch A stage in which the plate edge portions 41, 41 beyond the bending lines 24, 24 are bent by the side curved surfaces 31, 31 to the same radius as the tube to be manufactured, as shown in FIG. In this case, the parts 42, 42 which are closer to the center of the strip width than the bending line position in B are bent to the same radius as the tube to be manufactured, resulting in the state shown in C, and furthermore, such bending is performed on the center side of the strip for each feed length. 3, the plate edges 43, 43 approach each other as shown in FIG. The feed length is then sent out. In this embodiment, the semi-circular groove 23 has a straight part 25 extending therefrom, and the half-circular part 35 corresponding to the semi-circular part 33 is formed so as to extend. During the passage, distortion in the circumferential direction of the pipe is corrected, improving roundness.

The side curved surfaces 21, 21 of the groove-shaped die 2 are continuously close to each other in the longitudinal direction of the die, and the side curved surfaces 31, 31 of the punch 3 are similarly spaced continuously close to each other in the longitudinal direction. From this, as shown in Fig. 2, the position of the bending line for edge bending of the strip plate 4 gradually shifts toward the center of the plate in the longitudinal direction, and the degree of forming continuously increases, as shown in Fig. 4. It becomes a circular tube through a smooth deformation process like this. Methods for forming circular tubes from strip plates include circular bending, in which the entire plate is bent at the same radius and the radius is gradually made smaller, and center bending, in which the plate is bent from the center to the same radius as the tube. There is a method, U-O
Forming is based on this center bending method, but the path length of the plate edge is extremely large, approximately 4.9 times the radius, and it is possible to suppress edge waves and improve roundness during U-bending, which is preforming. Quite difficult. On the other hand, the trajectory length of the plate edge in the circular bending method is approximately 4.4 times the radius.

On the other hand, in the edge bending method of the present invention, the trajectory length of the plate edge is the shortest, approximately four times the radius, and as mentioned above, the bending lines 24, 24 are continuously changed from the inlet to the outlet. Using a bending die, it is only necessary to repeatedly bend the edges at the same radius as the pipe, and there is no need for U-forming, which tends to adversely affect the quality of the product, so it has the advantage that shape defects are less likely to occur.

In the case of U-O forming, even if it is performed by progressive bending, the length of the mold becomes large because it requires a U forming part and an O forming part, but the combination of the edge bending method and feeding bending of the present invention According to the method, since the O molding process and the mold part required for this are unnecessary,
Mold length can be significantly reduced. In other words, in Fig. 4, the strip forming area length OC, the footprint length of the plate edge AB
Then, the average strain at the edge of the plate is = AB/OC-1, and to make it similar to the average strain at the edge of the plate ≦0.3% in conventional U-O forming, D/
In relation to (D: center diameter of tube thickness, : forming area length), if D is 15 mm, mold length OC is 480 mm.
That's enough. In the case of U-O molding, if D is 15 mm, the mold length needs to be 1600 mm.

FIG. 5 shows another embodiment of the molding method according to the present invention. In the embodiments of FIGS. 1 to 3, the bending lines 24, 24 are straight from the mold entrance to the mold exit. On the other hand, in this embodiment, the bending line is curved, and the longitudinal center line of the mold is curved in the y-z plane.
The die shoulders 26, 26 side curved surfaces 21, 21 and bending lines 24, 24 are continuous curves so as to form a convex shape toward the inside of the groove between the inlet groove 20 and the outlet groove (semicircular groove) 23. In addition, the inlet groove 2
0 and the outlet groove 23 remain the same, the entire die including the upper surfaces 27, 27 of the die is formed into a curved shape so that it is concave with respect to the punch 2, and the outlet side is lower and the inlet side is higher. The punch is also configured to have a curved shape so as to correspond to the shape of the grooved die 2.

The important point in forming circular tubes using the edge bending method is to minimize warpage, edge waves, and opening in the longitudinal direction. It is related to the feed length of the board. According to the studies conducted by the present inventors, the following was found. That is, if the bottom thrust force is small, the cross section will be insufficiently formed, and if the bottom thrust force is increased, the cross section will be sufficiently formed, so the opening will be reduced and the diameter accuracy will be improved. On the other hand, warping increases as the bottoming force increases. This is because when the cross section is shaped and the opening becomes smaller, the elongation of the plate edge increases. If the bottom thrust force is appropriate, the warpage, opening, and diameter accuracy will be almost constant. The appropriate range depends on the plate thickness, plate material, molded tube diameter, etc., but in cases where the material is SPC, the plate thickness is 1 mm, and the diameter is 16 mm, a bottom thrust force of 3 tons or more is suitable.

On the other hand, the edge wave height is influenced more by the feed length of the strip than by the bottoming force, and as the feed length increases, the amount of waves generated decreases, but the wave height increases and the opening also increases. Since the warpage is conversely reduced by increasing the edge wave height and the opening, an intermediate value is the appropriate feed length based on the relationship between the warpage and the edge wave height. Therefore, in the embodiments shown in Figures 1 to 3 as well, by setting a large bottom thrust force and shortening the feed length, it is possible to form a circular tube with fairly high accuracy, but the opening and warpage are It is difficult to completely prevent the occurrence.

Fig. 5 shows a further improvement to this, which eliminates the waves on the edge of the plate and also eliminates the warpage.
The appropriate conditions for the degree of curve of the bending line, the degree of curve of the center line, and the amount of rise of the entrance groove are as follows.

First, in FIG. 5, if the bending line is curved as die profile Z and the center line is curved as punch profile Y, then Z=A・x ⁿ , Y=B・
z ^m However, A=L/(π・R) ⁿ and B=C/L ^m . In this equation, n is the index of the bending line (Die index), m is the index of the center line (Punch index), and C is the amount of rise (Punch variable).

6 and 7 show the analysis method. In FIG. 6, the centers of the plate widths corresponding to arbitrary points P and Q are R and S. Each point P, Q, R, S is x,
Expressed using the y, z coordinate system, R(o, y _i , z _i ),
S (o, y _i , z _j ), P (x _i , y _i , z _i ) Q (x _j , y _j , z _j )
The forming angle θ is θ=π・(Z/L)1/n, and z _i
The plate edge strain e _ij between and z _j is e _ij = PQ−RS/RS.

Therefore, first of all, if we look at the influence of the index n, it is as shown in Figure 8.
In the illustrated embodiment, the plate edge strain gradually increases immediately after the start of molding, and a drastic change in strain occurs just before the molding is completed. This sudden change in strain occurs when the edge of the plate, which has been elongated, returns to its original size, and this causes waves to occur at the edge of the plate. On the other hand, when n<1, that is, when the curve is convex toward the inside of the die groove, the strain becomes large after the start of forming the material, then becomes small again, and becomes zero when forming is completed.
Therefore, n<1 is preferable, and n≈0.7 is particularly good. Next, looking at the Ponch index m, in Figure 9 there is a large difference with m = 1 as the boundary, and m≦1.
In this case, bending is performed in the longitudinal direction on the exit side, which adversely affects the product, so it is better to asymptotize toward the exit side such that m>1. Figure 10 shows the actual effect of m. The larger m is, the larger the strain change after the start of molding is in the compression direction, and as molding progresses, it reverses to the tensile direction, and then shifts back to the compression direction. There is a strong tendency to fall. The larger m is, the more the boat is sledding,
If m is small, it becomes a blind. Therefore, it is appropriate for the Punch index m to be in the range 1<m<2.

Further, the appropriate range of the punch variable C is determined by the punch index m, and generally, as shown in FIG. 11, as C increases, the strain distribution decreases in the compression direction. In other words, if C is small, warping in the longitudinal direction is likely to occur in the product, and if C is large, bottom warping is likely to occur. From this Figure 11, the exit, (orthodontic part entrance if there is one)
The strain is zero, no edge waves occur, and the positive extensional strain and negative compressive strain are well balanced and within ±0.2% of the plastic strain, so no longitudinal warpage occurs, resulting in extremely accurate circles. It can be made into a pipe.

Although FIGS. 5 to 11 show improvements in precision by changing the shape of the mold, the precision in the tube circumferential direction and longitudinal direction can also be improved by using secondary correction means. FIG. 12 shows an example of this, in which a block shape is provided at the back position corresponding to the front part 35 of the punch 3, which is in contact with the front end of the mounting jig 6 and whose width is approximately equal to the width of the grooved die. Attach the correct punch 9. The positive punch 9 has a semicircular groove 2 that is paired with the semicircular groove 23.
3' is formed, and this semicircular groove 23' surrounds a regular punch into which the shaped strip can be inserted through a gap. Since this jig is incorporated into the same mold, no additional steps are required, and since correction is performed simultaneously in the circumferential direction and the longitudinal direction between the die groove and the die groove, opening and edge waves can be easily eliminated.

Although the basic configuration of the present invention is as described above, the present invention can be further applied in various ways. 13 and 14 show the forming of a flanged pipe. A press bending die equipped with an upper die 10 and a lower die 11 for flange bending is provided on the inlet side of the press bending die 1. Both edges of the strip 4 are linearly fed and flange-bent using the lower die 11, and then the flange-bent strip 4' is fed into the press bending die 1 at a predetermined feed length and edge-bent as described above. It is used to perform deing.

At this time, the inclined surface 2 that guides the flange bending parts 45, 45 to the groove die entrance of the press bending die 1
7 and 27, and the same punch as in the case of forming a flangeless pipe may be used.
By this method, a long circular tube with a flanged cross section as shown in FIG. 14 can be easily obtained.

15 and 16 show the forming of a perforated tube, in which on the inlet side of the strip 4 a punch 12, which is operated either by a common press ram or by a separate punch 12 alongside the punch 3 of the press bending die 1, is shown. At the same time, a die 13 is provided either integrally or separately adjacent to the groove die 2, and before the strip 4 enters the press bending die 1, a hole 14 of a desired shape is formed with a punch 12 and die 13, and then the hole 14 is pressed as it is. It is fed into the bending die 1 and formed by edge bending as described above.

By using this method, there are almost no restrictions on the shape or position of the holes, and a tube with holes can be easily obtained in the same process. Drilling a rectangular or star-shaped hole in a conventionally formed tube is a difficult process, resulting in low productivity and poor accuracy, but the present invention can eliminate these difficulties.

Furthermore, in the present invention, forming is performed using a combination of a press-feed bending die and an edge bending method, so a half-open tube can be formed by simply reducing the width of the strip and feeding it into the press-bending die 1. The opening amount can be changed simply by changing the .

Next, specific examples of the present invention will be shown.

Example 1 The bending line shown in Fig. 2 is a straight line (die index n=
1), the die groove and punch are horizontal (punch index m
Using a press bending die with C = 0 and punch variable C = 0), a circular tube was fed and bent by the edge bending method.

The molding length of the grooved die and punch is 480mm.
Front length 80mm, groove die side curved surface 8mmR,
The curved surface of the punch side was 7mmR, the semicircular groove was 16mmφ, and the interval between the bending lines of the entrance groove was 47.1mm.

The forming material is cold rolled steel plate SPC-C, thickness 1.0
mm, length 1900mm, plate width 47.1 (pipe circumferential compression ratio 0
%) was used. The strip feed length P was 20 to 80 mm, the bottom thrust force P _B was 1 to 5 tons, and a 100-ton hydraulic press was used as the press.

As a result of molding under the above conditions, the bottom thrust force was 3 tons.
By shortening the feed length to 30 mm or less, a circular tube with fairly high accuracy was obtained. However, with this method, a slight opening remains and warpage cannot be completely prevented. Therefore, next, we installed the cleaning jig shown in Fig. 12, set the strip width slightly larger than the inlet groove width, and set the strip width to 49.0 mm (compression ratio in the pipe circumferential direction 4%).
Molding was carried out using 10 tons and a feed length of 30 mm.

As a result, warpage in the longitudinal direction was eliminated as shown in FIG. 17, and opening of the mouth could be completely prevented. The results of measuring the roundness of the obtained circular tube are shown in FIG. From this figure 18, the roundness is also
It can be seen that it is within 1% of the JIS standard.

Example 2 A circular tube was molded according to the present invention using a curved mold shown in FIG. At this time, the die index n is
The same conditions as in Example 1 were used, except that the 0.7 punch index m was 1.3 and the punch variable C was 30. As a result, there are no edge waves and no longitudinal warpage at all.
An extremely high-precision circular tube with no openings was molded.

According to the present invention described above, in the method of feeding and bending a strip plate into a circular pipe, a press bending die 1 is provided with side curved surfaces 2 on both sides for edge bending on the entrance side.
1 and 21 and a flat bottom surface 22 connecting the side curved surfaces 21 and 21, and a semicircular groove 23 having the same radius as the side curved surface is formed on the exit side. A grooved die 2 in which the groove width is tapered so that the bending lines 24, 24, which define the boundary between the bottom surface 22 and the side curved surfaces 21, 21, continuously approach between the semicircular grooves 23, and the bottom surface. 22
It has a starting end 30 on the inlet side consisting of a flat top surface 32 corresponding to the curved side surface 32 and side curved surfaces 31, 31 corresponding to the side curved surfaces 21, 21, and a semicircular section 33 corresponding to the semicircular groove 23 on the outlet side. It has a starting end 30 and a semicircular groove 2.
Between 3 and 3, a punch 3 whose width is continuously narrowed is used to feed the strip from one end into the press bending die 1 by a predetermined length, and in synchronization with this, the press bending die 1 is inserted into the press bending die 1.
The punch 3 and the grooved die 2 are moved up and down relative to each other, and the punch 3 is pushed into the grooved die 1 with the same stroke length over the entire length to bottom out, and the bending line 2 is
4 and 24 and the side curved surfaces 21 and 21, a general-purpose hydraulic press and a feeding mechanism are used to gradually bend the strip plate from both ends in the width direction with the same radius as the pipe to be manufactured until the desired pipe shape is obtained. By using extremely simple equipment and processes that use strip plates without any special pre-processing such as medium and high height, it is possible to form highly accurate circular tubes through a smooth deformation process. Can freely respond to changes in diameter and plate thickness.

In addition, since the press uses both edge bending and feed bending, the mold length can be reduced, and the special press bending mold 1 with the above configuration can be used.
Since this method repeatedly bends the edges at the same radius as the target pipe, the processing force can be kept low, and of course, the problems of scratches caused by friction, changes in plate thickness, and wear of the mold that occur when using the drawing method can be avoided.

Furthermore, excellent effects such as not only circular tubes with closed contours but also various types of tubes such as those with flanges, holes, and half-open tubes with notches can be easily produced.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway side view showing an outline of the feeding bending method for circular pipes using the edge bending method according to the present invention, and Fig. 2 is a press bending mold according to the present invention and the strips at various positions within the mold. 3 is a perspective view showing the deformation state at each position of the grooved die, FIG. 4 is an explanatory view showing the deformation process of the strip according to the present invention, and FIG. 5 is a perspective view showing the deformation state of the grooved die at each position. A perspective view showing another example of the press bending die used in the forming method, Figures 6 and 7 are coordinate diagrams for analyzing the press bending die shown in Figure 5, and Figure 8 shows the die index and strain distribution. 9 is an explanatory diagram of the Punch index and the Punch variable. FIG. 10 is a graph showing the relationship between the Punch index m and strain distribution. FIG. 11 is a graph showing the relationship between the Punch variable and strain distribution. Fig. 12 is a perspective view showing a punch with a precision jig attached for improving accuracy, Fig. 13 is a side view showing a method of forming a flanged pipe, and Fig. 14 is a perspective view showing the forming state.
Figure 15 is a side view showing the method of forming a tube with holes;
FIG. 6 is a perspective view showing a product example, FIG. 17 is a graph showing the relationship between longitudinal warp curvature and tube circumferential compressibility in the method of the present invention, and FIG. 18 is a graph showing the roundness measurement results. 1...Press bending die, 2...Groove die, 3...
Punch, 4...Strip plate, 20...Inlet groove, 21,2
1...Side curved surface, 23...Semicircular groove, (exit groove), 2
4...Bending line, 25, 25...Kiyou main section.

Claims (1)

[Claims] 1. In a method of feeding and bending a strip plate into a circular tube, the press bending die 1 includes side curved surfaces 21, 21 on both sides for edge bending on the entrance side and a flat surface connecting the side curved surfaces 21, 21. A semicircular groove 23 having the same radius as the side curved surface is formed on the outlet side, and the space between the inlet groove 20 and the semicircular groove 23 is formed by the bottom surface 22 and the side curved surface. Bending line 2 forming the boundary between 21 and 21
A grooved die 2 whose groove width is tapered so that the grooves 4 and 24 are continuously close to each other; a flat top surface 32 corresponding to the bottom surface 22; and side curved surfaces 31, 31 corresponding to the side curved surfaces 21, 21. It has a starting end 30 on the inlet side, a semicircular part 33 corresponding to the semicircular groove 23 on the exit side, and a starting end 30 on the outlet side.
0 and the semicircular part 33, using a punch 3 whose width is continuously narrowed, feed the strip from one end into the press bending mold 1 a predetermined length at a time, and in synchronization with this, press bending mold 1. 1
The punch 3 and the grooved die 2 are moved up and down relative to each other, and the punch 3 is pushed into the grooved die 1 with the same stroke length over its entire length to bottom out, and the bending lines 24, 24 and the side curved surfaces 21, 21 cause the punch 3 to bottom out.
Feeding of circular tubes by an edge bending method, which is characterized in that a strip is gradually edge bent from both ends in the width direction with the same radius as the tube to be manufactured until the desired tube shape is obtained, and then sequentially fed out from a press bending die 1. Bending forming method. 2. A method for feeding and bending a circular tube by an edge bending method according to claim 1, using a press bending die in which the bending lines 24, 24 are straight in the longitudinal direction of the die. 3 As a press bending mold, the bending lines 24, 24 form a convex curve toward the inside of the groove, and the groove rises in a curved shape from the outlet side to the inlet side while the entire groove remains the same depth. A method for feeding and bending a circular tube by an edge bending method according to claim 1, which uses a shaped die and a punch having a shape similar to the die. 4. As a press bending die, it has a opening part in which a semicircular groove is formed with the required length on the exit side of the grooved die, and the punch has a semicircular opening part corresponding to the said opening part and this hole. 2. A method for feeding and bending a circular tube by an edge bending method according to claim 1, which uses a punch having a semicircular groove that surrounds a center portion. 5. A method for feeding and bending a circular tube by the edge bending method according to claim 1, using a flat plate or a flat plate with holes made as the band plate. 6. A method for feeding and bending a circular tube by the edge bending method according to claim 1, using a flange-bent band plate.