JP2001150041A - Bead Mold - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To suppress the warpage of a metal plate formed with a bead, regardless of the difference in mechanical properties and the thickness of the metal plate, and regardless of the difference in the thickness of the metal plate. Provided is a bead molding die capable of performing bead molding with the same mold. A female mold 1 which is reciprocally movable and has a bead forming groove 1b and a contact surface 1a which contacts a metal plate 6;
The female die 1 includes a male die 2 having a convex bead forming portion 2a corresponding to the bead forming groove 1b and a plate holder 3 on which a metal plate 6 is placed. The contact surface 1a is provided with a protruding portion formed of a convex curved surface including an apex 1c extending in a direction substantially perpendicular to the extending direction of the bead forming groove 1b and protruding toward the male mold 2, and a plate retainer 3 is provided. The upper surface 3a on which the metal plate 6 is placed is formed as a flat surface. The metal plate 6 is placed on the plate holder 3, and the female mold 1 is moved in the male mold 2 direction. By pressing the metal plate 6, the bead 6a is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bead forming die for forming a convex bead used as a reinforcing portion or the like on a metal plate, and more particularly to a bead forming metal suitable for suppressing warpage of a metal plate. About the type.

[0002]

2. Description of the Related Art FIGS. 13A and 13B show a first example of a conventional bead molding die, wherein FIG. 13A is a front view, and FIG.
It is K sectional drawing. The first example is a mold having no function of suppressing the warpage generated in the formed metal plate. As shown in FIG. 13, the first example of the related art includes a female mold 20 which is reciprocally movable in a vertical direction and has a bead forming groove 20a and a contact surface 20b which comes into contact with a metal plate 6 to be formed. A male mold 12 disposed opposite to the female mold 20 and having a convex bead forming portion 12a corresponding to the bead forming groove 20a;
A plate holder 13 on which the metal plate 6 is placed, an elastic body 14 that pushes the plate holder 13 upward, and a plate holder bolt (not shown) that restricts the plate holder 13 from rising are provided.

In the first example, the female die 20 is moved in the direction of the male die 12 while the metal plate 6 is placed on the plate holder 13 and the metal plate 6 is pressed, whereby the male die 12 is pressed. Is inserted into the bead forming groove 20a of the female die 20 to form a convex bead on the metal plate 6. In such a structure, as shown in FIG. 6C described later, an R-shaped warp in which the bead side is on the outside is generated.

A conventional bead forming die for preventing such warpage due to bead forming is disclosed in, for example, Japanese Patent Laid-Open No.
The technique described in JP 143022 is known. A bead molding die as shown in this publication is, for example, shown in FIG.
Alternatively, it is configured as shown in FIG. Here, FIG.
FIG. 3A is a diagram showing a second example of a conventional bead molding die, and FIG.
Is a front view, and (b) is an LL sectional view of (a). 15A and 15B show a third conventional example, in which FIG. 15A is a front view, and FIG. 15B is a sectional view taken along line MM of FIG. 15A.

[0005] The female mold 17 shown in FIGS.
It is held and fixed to the ram of the press machine. Male mold 12,
The plate holder 18 is inserted into a central opening 18 a and held and fixed to a bed of a press machine so as to face the female die 17. Base portion 12b of male mold 12 and lower surface 18b of plate retainer 18
An elastic body 14 is interposed between them, so that when the female mold 17 is lowered, the bead forming portion 12a of the male mold 12 projects above the opening 18a of the plate retainer 18. The male mold 12 is provided on the contact surface 17a of the female mold 17 with the metal plate 6.
The bead forming groove 17 having a cross section having a size large enough to accommodate the bead forming portion 12a
b is formed. Then, the contact surface 17a of the female mold 17
A convex curved surface having a radius of curvature r1 is formed in the same direction as the extending direction of the bead forming groove 17b.
On the upper surface 18c, a concave curved surface having a radius of curvature R1 corresponding to the convex curved surface of the contact surface 17a of the female die 17 is formed. That is, in the bead forming, by making the contact surface 17a and the upper surface 18c of the plate holder 18 curved surfaces opposite to those of the bead forming, a reverse warp is given to the formed metal plate 6, thereby correcting the warp. What you want to do.

[0006]

However, in the above-described second and third conventional examples, the elastic body 4 (known as
Urethane springs and coil springs are often used for the elastic body of the mold. ) Causes the metal plate 6 to be warped in reverse, due to differences in the mechanical properties (tensile strength, elongation, etc.) of the metal plate 6 and variations in the thickness of the metal plate 6 due to its manufacture. It is actually difficult to obtain a bead molded product in which springback or warpage is suppressed.

In these second and third conventional examples, the upper surface 18c of the plate holder 18 is fixed to the contact surface 17 of the female die 17.
A concave curved surface corresponding to a (convex shape) (assuming that the thickness of the metal plate 6 as a workpiece is T1, the radius of curvature of the convex curved surface is r
1. Since the radius of curvature of the concave curved surface is R1, R1
= R1 + T1. ), And a concave curved surface having a different radius of curvature R1 according to the thickness T of the metal plate 6 is required. For example, the thickness T of the metal plate 6 is 1 mm, 3 mm,
When it changes to 5 mm, the curvature radius R1 of the concave curved surface differs in each case. Therefore, it is necessary to provide individual bead forming dies in accordance with the difference in thickness T of the metal plate 6 forming the bead, and there is a problem that the total number of dies becomes uneconomical.

In each of the first, second, and third conventional examples described above, since the bead forming grooves are linear, when the beads are formed continuously and cumulatively, the trajectory is reduced. In order to form a bead in which only a straight bead can be formed and the trajectory includes a curved line, a special integrated mold is required. For this reason, in the case of bead forming in which such a locus includes a curve, there is also a problem in that the total cost of the mold increases when bead forming of metal plates 6 having various thicknesses is considered.

The present invention has been made in view of the actual situation in the above-mentioned prior art, and has as its object the purpose of forming a bead on a metal plate regardless of the difference in mechanical properties and the thickness of the metal plate. It is an object of the present invention to provide a bead forming die capable of suppressing warpage and performing bead forming with the same die regardless of a difference in thickness of a metal plate.

[0010]

Means for Solving the Problems In order to achieve the above object, the invention according to claim 1 of the present application is reciprocally movable,
A female mold having a bead forming groove, and a contact surface that comes into contact with a metal plate to be formed, and a male mold that is disposed to face the female mold and has a convex-shaped bead forming portion corresponding to the bead forming groove. A metal plate mounted on the metal plate, the metal plate is disposed between the female die and the male die, the female die is moved toward the male die, the metal plate In the bead molding die for forming a bead on the metal plate by pressing the metal plate, the contact surface of the female mold extends in a direction substantially perpendicular to the extending direction of the bead molding groove and faces the male mold. And a surface on which the metal plate of the plate retainer is placed is formed as a flat surface.

According to the first aspect of the present invention, at the same time as the bead forming, the projecting portion of the contact surface of the female mold is set between the flat surface of the plate holder and both sides of the bead projecting side of the metal plate. Due to the local overpressure, residual compressive stress remains at the locally overpressed portion on the bead extension side, and tensile residual stress remains at the locally overpressed portion on the side opposite to the bead extension. As a result, a reverse warp occurs, which is opposite to the R-shaped warp with the bead projecting side facing outward, and the warp and the reverse warp cancel each other, regardless of the difference in the mechanical properties of the metal plate and the variation in the plate thickness. The bead molding which suppressed the problem can be performed. Further, when the thickness of the metal plate is different, it is sufficient to simply consider the pressing force, and the bead forming can be performed with the same mold regardless of such a difference in the thickness of the metal plate.

According to a second aspect of the present invention, in order to achieve the above object, in the first aspect of the present invention, the female protrusion has a convex curved surface.

According to the second aspect of the invention, both sides of the bead on the bead projecting side of the metal plate are locally strongly pressed by the convex curved surface.

According to a third aspect of the present invention, in order to achieve the above-mentioned object, in the first aspect of the present invention, the female projection is provided with a projection and the projection is connected to the projection. And a flat portion.

According to the third aspect of the present invention, both sides of the bead on the bead projecting side of the metal plate are locally strongly pressed by the protrusions.

According to a fourth aspect of the present invention, in order to achieve the above-mentioned object, in the first aspect of the present invention, the female projecting portion is connected to a flat portion and the flat portion. And a tapered portion.

In the invention according to the fourth aspect, both sides of the bead on the bead projecting side of the metal plate are locally strongly pressed by the flat portion.

In order to achieve the above object, the invention according to claim 5 is the invention according to claims 1 to 4, wherein the female mold is provided on at least one of both side portions sandwiching the projecting portion. And a non-contact portion that does not contact the metal plate during molding.

According to the fifth aspect of the present invention, by rotating the metal plate when the bead being formed is located at the non-contact portion of the female mold, it is easy to form the bead having a locus including a curved line. Can be realized.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of a bead forming die of the present invention will be described in detail with reference to the drawings. 1 to 5
The first part of the bead mold according to claims 1 and 2 of the present invention.
It is explanatory drawing which shows embodiment. 1A and 1B show a state before molding according to the first embodiment of the present invention, wherein FIG. 1A is a front view, and FIG. 1B is a cross-sectional view taken along line AA of FIG. FIG. 2 shows FIG.
FIG. 3 is a diagram showing the lower surface of the female mold when viewed from the direction B of FIG. 3, FIG. 3 is a diagram showing the surface of the male mold when viewed from the direction C of FIG.
Shows a state at the time of molding of the first embodiment shown in FIG.
5A is a front view, FIG. 5B is a cross-sectional view taken along line D-D of FIG.
FIGS. 2A and 2B are diagrams showing an example of a metal plate formed according to the first embodiment shown in FIG. 1, wherein FIG. 1A is a plan view, FIG.
(C) is a front view.

As shown in FIGS. 1 to 5, also in the first embodiment, the female die 1 is held and fixed to a ram (not shown) of a press machine. The male mold 2 is held and fixed to a bed (not shown) of a press machine. The contact surface 1a of the female mold 1 is formed so as to cross the central portion, and can accommodate the bead molded part 2a when the convex bead molded part 2a of the male mold 2 relatively protrudes from the plate holder 3. It has a bead forming groove 1b having a size. The contact surface 1a has a convex curved surface R having an apex 1c in the same direction as the bead forming groove 1b.
Is formed. That is, the portion connecting the vertices 1c extends in a direction substantially perpendicular to the extending direction of the bead forming groove 1b, and forms a projecting portion projecting toward the male mold 2. The plate holder 3 has an upper surface 3 on which the metal plate 6 is placed.
a has a flat surface, and has an opening 3c into which the bead forming part 2a of the male mold 2 is inserted. An elastic body 4 is arranged between the upper surface 2c of the base portion 2b of the male mold 2 and the lower surface 3b of the plate retainer 3, and supports the plate retainer 3 in a state where the plate retainer 3 is pushed upward at regular intervals. The presser bolt 5 regulates the amount of rise of the plate presser 3.

Next, the operation of the first embodiment configured as described above and the bead molded product obtained by the first embodiment will be described. First, place the metal plate 6 on the plate holder 3
Is set on the upper surface 3a. Next, when the ram of the press machine is lowered to lower the female die 1, the metal plate 6 is sandwiched between the contact surface 1 a of the female die 1 and the upper surface 3 a of the plate holder 3. When the female mold 1 is further lowered, the elastic body 4 is compressed, and the bead forming portion 2a of the male mold 2 projects from the upper surface 3a of the plate holder 3. Thereby, the metal plate 6 is stretched and plastically deformed to form a bead 6a. At this time, the female die 1 descends until the lower surface 3b of the plate retainer 3 and the upper surface 2c of the base portion 2b of the male die 2 come into close contact. In this state, as shown in FIG.
The metal plate 6 has a bead 6a on the bead bulging side 6b located between the vertex 1c of the contact surface 1a of the female die 1 and the plate holding upper surface 3a.
Only the region on both sides 6c of the bead is strongly pressed locally. Therefore, as shown in FIG. 5 (a), a residual compressive stress 6f remains in the local high pressure portion 6e on the bead overhanging side 6b, and a tensile residual stress 6g remains in the local high pressure portion 6e on the bead overhanging side 6d. .

FIG. 6 is a diagram for comparing the metal plate 6 formed by the first embodiment shown in FIG. 1 with the metal plate 6 formed by the above-described first example of the conventional bead forming die. (A) is a plan view, (b) is a side view, and (c) is a front view.

In both the first embodiment and the first conventional example described above, an aluminum alloy material is used for the metal plate 6 to be processed, and a length L = 1000 mm and a width B in FIG.
= 500 mm, plate thickness T = 3.2 and 2.3 mm, bead length LB = 700 mm, bead width BB = 15 mm, and bead height BH = 6.5 mm.
Two rows were formed at 0 mm. The bead length LB is obtained by moving the metal plate 6 to a very small amount, for example, about 1 to 5 mm, and forming 700 mm each time. As a result, in the case of the first example formed in the related art, the warpage amount δ is about 25 mm.
On the other hand, in the one formed according to the first embodiment, the amount of warpage δ could be suppressed to 1 mm or less.

In the first embodiment configured as described above,
The metal plate 6 is not reversely warped by the elastic body at the time of molding, and the apex 1c of the convex curved surface of the contact surface 1a of the female mold 1 forming the projection and the upper surface 3a forming the flat surface of the plate holder 3 are formed.
Thus, the local high-pressure portion 6e is formed to give a reverse warp, and the difference in mechanical properties of the metal plate 6 or the metal plate 6
It is possible to form the above-described local high-pressure portion 6e almost without being affected by the variation in the plate thickness due to the production of
It is possible to obtain a high quality bead molded product having high warpage suppressing accuracy.

Further, even if the thickness of the metal plate 6 forming the bead 6a is variously different, such as 1 mm, 3 mm, 5 mm, etc., the female die 1 presses the metal plate 6 as necessary. In consideration of the pressure, a desired local high-pressure portion 6e can be obtained. Therefore, irrespective of the difference in the thickness of the metal plate 6, bead molding can be performed with the same mold, the number of molds can be reduced, and excellent economic efficiency can be obtained.

FIGS. 7 (a) and 7 (b) show a female mold which constitutes a main part of a second embodiment according to the third aspect of the present invention. FIG. 7 (a) is a front view, and FIG. It is a figure which shows the lower surface of the said female mold when it sees. In the second embodiment, the male mold 2 is formed on the projecting portion of the female mold 1, that is, on the contact surface 1 a, and extends in a direction substantially orthogonal to the extending direction of the bead forming groove 1 b.
The protrusion protruding toward (not shown here) is constituted by a protrusion 1e having a width B and a height H, and a flat portion 1h connected to the protrusion 1e. Other configurations are the same as those of the above-described first embodiment.

In the second embodiment configured as described above, at the time of bead forming, the protrusions 1e cause the bead projecting side 6b (shown in FIG. 4 described above) of the metal plate 6 to bead both sides 6c.
Is locally strongly pressed, and the same operation and effect as in the first embodiment described above can be obtained.

FIGS. 8 (a) and 8 (b) are views showing a female mold constituting a main part of a third embodiment according to the fourth aspect of the present invention. FIG. 8 (a) is a front view, and FIG. It is a figure which shows the lower surface of the said female mold when it sees. In the third embodiment, the protruding portion of the female mold 1 is constituted by a flat portion 1f having a width dimension B and a tapered portion 1g having an inclination angle θ continuously provided with the flat portion 1f. Other configurations are the same as those of the above-described first embodiment.

In the third embodiment configured as described above, the bead forming side 6b (shown in FIG. 4) of the metal plate 6 is formed by the flat portion 1f when forming the bead.
Is locally strongly pressed, and the same operation and effect as in the first embodiment described above can be obtained.

FIGS. 9A and 9B are views showing a female mold constituting a main part of a fourth embodiment according to the fifth aspect of the present invention. FIG. 9A is a front view, and FIG. 9B is a view from the G direction of FIG. FIG. 10 is a diagram showing the lower surface of the female mold when viewed, FIG. 10 is a diagram showing a state of the fourth embodiment having the female mold shown in FIG. 9 at the time of molding, (a) is a front view,
(B) is an HH cross-sectional view of (a), and FIG. 11 is a plan view showing an example of a metal plate formed according to the fourth embodiment shown in FIGS.

In the fourth embodiment, as shown in FIG. 9, a bead forming groove 1b extending across the center of the female mold 1 and a direction perpendicular to the bead forming groove 1b are provided. A contact surface 1a having a convex curved surface having a radius of curvature R having an apex 1c, and a non-contact portion 1d provided continuously on one side of the contact surface 1a and not contacting the metal plate 6 during molding. I have. Other configurations are the same as those of the above-described first embodiment.

In the fourth embodiment configured as described above, the molding is continuously and cumulatively performed by a punching machine having a predetermined feeding device and an indexing mechanism rotatable about the center axis of the mold. A bead 6a having the shape shown in practice in FIG. 11 was formed. The dashed line indicates an unformed part. In FIG. 11, 6S is a molding start point, 6F is a molding end point, and 6j is a bead locus.
6h is a bead straight portion, and 6i is a bead curve portion.

The bead straight portion 6h is formed by moving the female mold 1 up and down while moving the metal plate 6 in the X or Y direction by a predetermined feeding device. The bead curved portion 6i moves the predetermined metal plate 6 in the X or Y direction, rotates the bead forming die of the fourth embodiment appropriately by the indexing mechanism, and then moves the female die 1 up and down. It is formed.

When the metal plate 6 is rotated as described above, the metal plate 6 can be rotated by the non-contact surface 1d of the female die 1 without damaging the formed bead 6a.

In the fourth embodiment configured as described above, as in the first embodiment described above, at the time of molding,
The apex 1c of the contact surface 1a of the female mold 1 locally presses both sides of the protruding side of the metal plate 6 so that warpage can be suppressed and the bead 6a including the linear bead 6a and the curved bead 6a can be easily formed. Can be obtained. Therefore,
There is no need for a special integrated mold as a mold for molding the bead 6a whose trajectory includes a curved line, and the overall mold cost can be reduced.

In the above-described embodiment, a convex curved surface including a vertex 1c is provided as a projecting portion provided on the contact surface 1a of the female mold 1. However, instead of such a convex curved surface, the projecting portion is replaced with a convex curved surface. A projection 1e similar to that of the second embodiment shown in FIG. 7 and a flat portion 1b connected to the projection 1e may be used.
A flat portion 1f similar to that in the embodiment and a tapered portion 1g connected to the flat portion 1f may be used. With such a configuration as well, it is possible to easily obtain a bead forming having a locus including a curved line, and it is possible to reduce the mold cost as in the fourth embodiment.

FIG. 12 shows a fifth embodiment according to the fifth aspect of the present invention.
It is a figure which shows the female mold which comprises the principal part of embodiment, (a) is a front view, (b) is a figure which shows the lower surface of the said female mold when it sees from J direction of (a). In the fifth embodiment, FIG.
As shown in FIG. 1, the female mold 1 has a contact surface having a bead forming groove 1b provided so as to cross the center and a convex surface having an apex 1c extending in a direction orthogonal to the bead forming groove 1b. 1a and a non-contact surface 1d which is provided continuously on both sides of the contact surface 1a and does not contact the metal plate 6 during molding. Other configurations are the same as those of the above-described first embodiment. Also in the fifth embodiment configured as described above, the bead forming including the curved bead 6a can be easily performed similarly to the above-described fourth embodiment, and the same operation and effect as the fourth embodiment can be obtained. .

In the fifth embodiment, a convex curved surface including an apex 1c is provided as a projecting portion provided on the contact surface 1a of the female mold 1. However, instead of such a convex curved surface, the projecting curved surface is used. A protrusion 1e similar to that in the second embodiment shown in FIG. 7 and a flat portion 1b connected to the protrusion 1e are provided.
And a flat portion 1f similar to that in the third embodiment shown in FIG. 8 and a tapered portion 1g connected to the flat portion 1f. This configuration also has the same operation and effect as those in the fifth embodiment.

[0040]

As described above, according to the invention of each claim of the present application, the warpage of the bead-formed metal plate can be reduced irrespective of the difference in the mechanical properties of the metal plate and the variation of the plate thickness. It is possible to obtain a bead molded product which can be suppressed and has higher quality than the conventional one. In addition, bead molding can be performed with the same mold regardless of the difference in the thickness of the metal plate, and the number of molds can be reduced as compared with the related art, and excellent economic efficiency can be obtained. .

In particular, according to the fifth aspect of the invention,
The bead molding whose locus includes a curve can be easily obtained,
Therefore, as a mold for molding a bead including a curved line, there is no need for a special integrated molding die as in the related art, and the overall cost of the molding can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a state before molding of a bead molding die according to a first embodiment of the present invention, wherein (a) is a front view and (b) is (a).
It is AA sectional drawing of.

FIG. 2 is a view showing a lower surface of the female mold as viewed from a direction B in FIG. 1;

FIG. 3 is a view showing a male surface when viewed from a direction C in FIG. 1;

4A and 4B are views showing a state of the first embodiment shown in FIG. 1 at the time of molding, wherein FIG. 4A is a front view, and FIG. 4B is a sectional view taken along the line DD of FIG.

5A and 5B are diagrams showing an example of a metal plate formed according to the first embodiment shown in FIG. 1, wherein FIG. 5A is a plan view, FIG. 5B is a side view, and FIG.

6A and 6B are diagrams for comparing a metal plate formed by the first embodiment shown in FIG. 1 with a metal plate formed by a conventional bead forming die, wherein FIG. 6A is a plan view and FIG. Is a side view, and (c) is a front view.

FIGS. 7A and 7B are views showing a female mold constituting a main part of the second embodiment of the present invention, wherein FIG. 7A is a front view, and FIG. 7B is a view of the female mold when viewed from a direction E in FIG. It is a figure showing a lower surface.

FIGS. 8A and 8B are views showing a female mold constituting a main part of the third embodiment of the present invention, wherein FIG. 8A is a front view, and FIG. 8B is a view of the female mold when viewed from the F direction of FIG. It is a figure showing a lower surface.

FIGS. 9A and 9B are views showing a female mold constituting a main part of a fourth embodiment of the present invention, wherein FIG. 9A is a front view, and FIG. 9B is a view of the female mold when viewed from a G direction of FIG. It is a figure showing a lower surface.

10A and 10B are views showing a state at the time of molding of the fourth embodiment having the female mold shown in FIG. 9, wherein FIG. 10A is a front view and FIG.
FIG.

FIG. 11 is a plan view showing an example of a metal plate formed according to the fourth embodiment shown in FIGS.

FIGS. 12A and 12B are views showing a female mold constituting a main part of a fifth embodiment of the present invention, wherein FIG. 12A is a front view, and FIG. 12B is a view of the female mold when viewed from the J direction of FIG. It is a figure showing a lower surface.

13A and 13B are diagrams showing a first example of a conventional bead molding die, wherein FIG. 13A is a front view, and FIG. 13B is a sectional view taken along line KK of FIG.

14A and 14B are diagrams showing a second example of a conventional bead molding die, wherein FIG. 14A is a front view and FIG. 14B is a sectional view taken along line LL of FIG.

15A and 15B are diagrams showing a third example of a conventional bead molding die, wherein FIG. 15A is a front view and FIG. 15B is a cross-sectional view taken along line MM of FIG.

[Explanation of symbols]

 Reference Signs List 1 female mold 1a contact surface 1b bead forming groove 1c vertex 1d non-contact surface 1e projection 1f flat surface 1g taper portion 1h flat portion 2 male mold 2a bead forming portion 2b base portion 2c upper surface 3 plate holder 3a upper surface 3b lower surface 3c opening 4 elastic body 5 Plate holding bolt 6 Metal plate 6a Bead 6b Bead overhanging side 6c Bead both sides 6d Bead overhanging opposite side 6e Local high pressure part

Continued on the front page (72) Inventor Hidenori Endo 1070 Ma, Hitachinaka-shi, Ibaraki Pref. In the elevator group of Hitachi, Ltd. (72) Inventor Osamu Kanekazu 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture F-term (Reference) in Production Technology Laboratory 4E050 AA14

Claims (5)

[Claims] 1. A female mold that is reciprocally movable, has a bead forming groove, and a contact surface that contacts a metal plate to be formed,
A male die having a convex bead forming portion corresponding to the bead forming groove, and a plate retainer on which the metal plate is placed, wherein the female die and the male die are provided. And a bead forming mold that moves the female mold toward the male mold and presses the metal plate to form a bead on the metal plate. The contact surface has a protruding portion extending in a direction substantially perpendicular to the extending direction of the bead forming groove and protruding toward the male mold, and the metal plate of the plate retainer is placed thereon. A bead mold having a flat surface. 2. The bead forming die according to claim 1, wherein said projecting portion of said female die has a convex curved surface. 3. The bead-forming mold according to claim 1, wherein said projecting portion of said female mold comprises a projection and a flat portion connected to said projection. 4. The bead-forming mold according to claim 1, wherein said projecting portion of said female mold comprises a flat portion and a tapered portion connected to said flat portion. 5. The female mold according to claim 1, wherein at least one of both side portions sandwiching the projecting portion has a non-contact portion that does not contact the metal plate during molding. A bead molding die as described in Crab.