BLANK MATERIAL, METHOD FOR PRESS MOLDING BLANK MATERIAL, AND PRESS MOLDING DEVICE

Abstract

A molding recessed part of a lower mold constituting a press molding device is provided with a first blank holder, and a circular second blank holder is freely movably provided on one outer peripheral side of the first blank holder. Meanwhile, of first and second blank holes opened in blank material, straight-line parts of the second blank hole have formed therein a pair of tensile force adjusting parts, and arched parts of first and second opening parts are mounted on the second blank holder. Furthermore, when draw forming of the blank material is performed, the tensile force imparted to the straight-line parts to the outside is adjusted by the tensile force adjusting parts, and the tensile force imparted to the arched parts to the outside in the radial direction is adjusted by the second blank holder.

Description

TECHNICAL FIELD

The present invention relates to a blank material including an opening part, and a press forming method and a press forming device for performing draw forming for the blank material (a blank material, a method for press molding the blank material, and a press molding device).

BACKGROUND ART

A side panel of an automobile is conventionally manufactured by, for example, performing press-forming of a metal plate material, and this side panel is formed by deep draw forming. The whole periphery of the side panel that is formed in advance and the whole periphery of the edge part of an opening part that is formed in advance similarly are held by a blank holder, so that the deep draw forming is performed.

In recent years, it has been known that an upper part of a rear wheel arch in the side panel is formed such that the upper part has a more convex shape by the deep draw forming, for example, in order to improve the design of the automobile. When this side panel is formed from a single sheet of plate material by the deep draw forming, a wrinkle or wrinkles occur easily and tension is required particularly in a straight line part that is close to the convex shape of the upper part of the rear wheel arch of the opening part for a rear door that is formed in advance on the side of the rear wheel arch because inflow of the material to the convex shape of the upper part of the rear wheel arch is large in the forming.

Moreover, in the opening part for the rear door, an R part in an up-down direction is extended due to the inflow of the material and easily cracks. Thus, it is required that an extending amount of the material is small. Therefore, it is necessary to deal with the R part and the straight line part differently in the opening part. Note that the rear wheel arch and the side panel may be formed separately and connected by welding, for example; however, it is a problem that the manufacturing process is increased and the manufacturing cost is also increased in this case.

For example, in a press forming method disclosed in Japanese Patent No. 3814711, when a concave part is formed from a metal plate material, a slit is formed in advance along the whole inner periphery of a part to become a scrap in a formed article. Thus, force acts on only the outside of the slit in draw forming, so that the forming can be performed without a crack or the like on an end part of the slit.

However, in the above press forming method, the draw forming is performed to form the concave part such that a bead is disposed only on an inside part of a central part of one side of the part to become the scrap. Thus, it is difficult to apply tension on a straight line part where the tension is required.

Furthermore, in a press forming device disclosed in Japanese Laid-Open Utility Model Publication No. 63-145519, a storage groove is formed at a position that is near a blank holder disposed on an outer peripheral side in a punch corresponding to a lower die, and a floating punch is provided to this storage groove so that the floating punch can move through a cylinder in the up-down direction. In a state where a work is mounted on an upper surface of the punch, a die descends from the upper side so that the outer edge part of the work is held by the die and the blank holder, the die descends further and is brought into contact with the floating punch such that the work is held, and the draw forming is performed for the work between the die and the lower die.

SUMMARY OF INVENTION

The present invention has been made in relation with the above suggestions, and an object is to provide a blank material, and a press forming method and a press forming device for the blank material in which, in draw forming for the blank material including an opening part, a formed article with high quality can be obtained while a crack in the opening part is prevented.

In order to achieve the above object, the present invention provides a blank material for which draw forming is performed in a press forming device to make a body panel of an automobile, the blank material including an opening part including arched parts provided in an up-down direction of the body panel and connection parts each having an approximately straight line shape provided in a front-rear direction of the body panel that is approximately orthogonal to the arched parts and connected to the arched parts, wherein a tension adjusting part is provided to the connection part, the tension adjusting part extending to an inside of the opening part and configured to adjust tension applied outwardly in forming.

According to the present invention, the blank material that is formed by the draw forming in the press forming device includes the opening part including the arched parts provided in the up-down direction of the body panel and the connection parts with the approximately straight line shape provided in the front-rear direction of the body panel and connected to the arched parts, wherein the tension adjusting parts extending to the inside of the opening part are provided to the connection parts and the tension applied to the connection parts outwardly can be adjusted when the draw forming is performed.

Therefore, even when deep draw forming is performed for the blank material including the opening part, inflow to the outside of the connection parts with the approximately straight line shape is adjusted as appropriate with respect to the arched parts. Thus, a wrinkle at a formed part with a convex shape provided in the front-rear direction of the opening part is prevented, so that a formed article with high quality can be obtained.

Moreover, in order to prevent the wrinkle due to the inflow of a material to the convex shape of an upper part of a rear wheel arch in the forming, the tension adjusting part may be formed for each of a pair of the connection parts. Thus, the tension can be applied by gripping the tension adjusting part by (first and second) blank holders of the press forming device, so that it is possible to prevent the wrinkle.

Furthermore, in order to prevent a crack due to the inflow of the material to the arched part (R part) in the opening part for a rear door, each of the arched parts may be formed in a manner that the arched part is smaller than a formed arched part of a formed body in which the arched part has been formed, and the arched part has a shape that is close to the formed arched part. Thus, it is possible to prevent the crack by reducing an extending amount of the material in the arched part.

In addition, the present invention provides a press forming method in which draw forming is performed for a blank material including an opening part that includes arched parts and connection parts each having an approximately straight line shape and connected to the arched parts, wherein an edge of the opening part is pressurized and held between an upper die and a first blank holder provided to a lower die, and the arched parts positioned outside a held part of the blank material held between the upper die and the first blank holder is pressurized and held between the upper die and a second blank holder provided outside the first blank holder.

According to the present invention, when the draw forming is performed for the blank material including the opening part, the edge of the opening part is pressurized and held between the first blank holder provided to the lower die and the upper die, and the arched parts of the opening part positioned outside the held part of the blank material held between the first blank holder and the upper die is pressurized and held between the second blank holder provided outside the first blank holder and the upper die.

Accordingly, the edge of the opening part can be held between the first blank holder and the upper die, and at the same time, the arched parts positioned outside the held part can be held between the upper die and the second blank holder provided outside the first blank holder.

As a result, since the opening part is formed such that the arched parts are positioned outside the first blank holder, the crack can be prevented by suppressing the inflow to the outside in the forming and the draw forming can be performed for sure by the second blank holder.

Moreover, a bead may be formed by holding, between the upper die and the first blank holder, a tension adjusting part extending from the connection part to an inside of the opening part. Thus, the tension can be applied to the blank material more effectively.

In addition, the present invention provides a press forming device configured to perform draw forming for a blank material including an opening part that includes arched parts and connection parts each having an approximately straight line shape and connected to the arched parts, the press forming device including: an upper die; a lower die disposed so as to face the upper die and including a mounting surface on which the blank material is mounted; a first blank holder disposed so as to face the upper die and configured to hold an edge of the opening part of the blank material with the upper die; and a second blank holder disposed outside the first blank holder and configured to hold, between the second blank holder and the upper die, the arched parts positioned outside a held part of the blank material held between the first blank holder and the upper die, wherein the first blank holder and the upper die include a bead configured to hold with pressure a tension adjusting part extending from the connection part of the blank material to an inside.

According to the present invention, the press forming device that performs the draw forming for the blank material including the opening part that includes the arched parts and the connection parts includes the first blank holder that faces the upper die and holds the edge of the opening part in the blank material with the upper die, and the second blank holder that is positioned outside the first blank holder, wherein the second blank holder is provided such that the arched parts positioned outside the held part of the blank material held between the first blank holder and the upper die can be held between the second blank holder and the upper die.

Accordingly, when the draw forming is performed for the blank material, the tension applied to the connection parts of the opening part outwardly can be adjusted as appropriate by the bead of the tension adjusting part and at the same time, the tension applied outwardly can be adjusted by holding the arched parts through the second blank holder.

As a result, when the draw forming is performed for the blank material including the opening part, both the tension adjustment for the connection parts and the tension adjustment for the arched parts are performed as appropriate at the same time. Here, the connection parts crack less easily even if the inflow of the blank material is large, and the arched parts easily crack if the inflow is large. Thus, it is possible to prevent the wrinkle in the edge of the connection parts and the crack in the edge of the arched parts in the forming, so that the formed article with high quality in which the drawing is deep can be obtained.

Moreover, the second blank holder may have a circular shape. Thus, the tension adjusting part of the connection part is gripped by the second blank holder. Therefore, the tension can be applied more effectively.

Furthermore, the bead may extend along a direction that is approximately orthogonal to an extending direction of the tension adjusting part. Thus, the tension can be applied equally to the blank material.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a front view of a side outer panel for an automobile formed by a press forming device according to an embodiment of the present invention;

FIG. 2 is a front view expressing a blank material before the side outer panel in FIG. 1 is formed;

FIG. 3 is a magnified plan view expressing the vicinity of a second blank hole of the formed blank material;

FIG. 4 is a plan view of a lower die, and first and second blank holders included in the press forming device;

FIG. 5 is a magnified plan view of a second holder part of the first blank holder and the second blank holder in FIG. 4;

FIG. 6 is a cross-sectional view along a line VI-VI in FIG. 5;

FIG. 7 is a cross-sectional view along a line VII-VII in FIG. 5; and

FIG. 8A is a schematic diagram expressing change in a cross-section before and after a straight line part in FIG. 2 is formed, and FIG. 8B is a schematic diagram that is used to compare an arched part in FIG. 2 before forming and a formed arched part after the forming.

DESCRIPTION OF EMBODIMENT

A press forming device 10 is used to perform press forming of a blank material 14. Here, a case where a side outer panel (body panel) 12 for automobiles is formed from a steel plate corresponding to the blank material 14 by using the press forming device 10 is described.

First, the side outer panel 12 corresponding to a formed article is described with reference to FIG. 1. For example, this side outer panel 12 constitutes a side part of a body of the automobile and includes a front pillar part 16 formed on a front side (arrow A direction) along a vehicle direction, a rear pillar part 18 that is formed on a rear side (arrow B direction), a center pillar part 20 that is formed in an approximately center part in the vehicle direction, a roof part 22 that connects upper ends of the front pillar part 16, the center pillar part 20, and the rear pillar part 18, and a side sill part 24 that connects lower ends of the front pillar part 16, the center pillar part 20, and the rear pillar part 18.

In the side outer panel 12, a first door opening part 26 that is surrounded by the front pillar part 16, the center pillar part 20, the roof part 22, and the side sill part 24 is formed, and a second door opening part 28 that is surrounded by the center pillar part 20, the rear pillar part 18, the roof part 22, and the side sill part 24 is formed. On a rear side of this second door opening part 28 (arrow B direction), a rear fender part 30 is formed at a position above a rear tire that is not shown.

Next, the blank material 14 to be press-formed is described with reference to FIG. 2 and FIG. 3.

This blank material 14 is made of, for example, a steel plate with certain plate thickness, and formed as a long piece along a front-rear direction of a vehicle (arrow A or B direction). In addition, the blank material 14 includes a first blank hole 32 that is formed on one end side (arrow A direction) of the blank material 14 and serves as the first door opening part 26 of the formed article (side outer panel 12), and a second blank hole (opening part) 34 that is formed on the other end side (arrow B direction) and serves as the second door opening part 28 of the formed article. The first blank hole 32 and the second blank hole 34 are open while being separated from each other by a predetermined distance along the front-rear direction (arrow A or B direction) of the vehicle.

For example, the first blank hole 32 is formed such that the cross-sectional shape thereof is an approximately triangle shape, and on the other hand, the second blank hole 34 is formed so as to have an approximately oval shape which is elongate in an up-down direction (arrow C direction) that is approximately orthogonal to the front-rear direction of the blank material 14. This second blank hole 34 includes a first opening part 36 and a second opening part 38 that are open at an upper part and a lower part each with a semicircular shape, a pair of straight line parts (connection parts) 40a, 40b that connects the first opening part 36 and the second opening part 38, and a pair of tension adjusting parts 42a, 42b extending from the straight line parts 40a, 40b to the inside.

This first opening part 36 includes an arched part 44a that is formed on an upper side and curves such that the cross-sectional shape thereof is arched toward the upper side, and the second opening part 38 includes an arched part 44b that is formed on a lower side with respect to the first opening part 36 and curves such that the cross-section shape thereof is arched toward the lower side. As illustrated in FIG. 3, the arched parts 44a, 44b are formed so as to be positioned a little more on the inside in a radial direction than a formed arched part 46 of the formed article after forming.

In other words, the arched parts 44a, 44b are formed such that the radius thereof is less than the radius of the formed arched part 46 of the formed article, and the arched part 44a is close to the upper formed arched part 46 and the arched part 44b is close to the lower formed arched part 46.

That is to say, the second blank hole 34 is formed such that the first opening part 36 and the second opening part 38 face each other in the up-down direction, the straight line part 40a and the straight line part 40b are formed so as to face each other in the front-rear direction (arrow A or B direction) between the first and second opening parts 36, 38.

The straight line part 40a connects one end part of the arched part 44a of the first opening part 36 and one end part of the arched part 44b of the second opening part 38, and the straight line part 40b connects the other end part of the arched part 44a of the first opening part 36 and the other end part of the arched part 44b of the second opening part 38.

The tension adjusting parts 42a, 42b respectively extend inward so as to be approximately orthogonal to the pair of straight line parts 40a, 40b, are formed with a predetermined width in the up-down direction (arrow C direction), and protrude from the straight line parts 40a, 40b by a predetermined length. In other words, the pair of tension adjusting parts 42a, 42b extends so as to approach each other toward the center of the second blank hole 34.

Next, the press forming device 10 that performs the press forming of the above blank material 14 is described.

This press forming device 10 is used to perform what is called draw forming, and includes a lower die 48 as a forming die to perform a deep drawing process for a work corresponding to the blank material 14, an upper die 50 that approaches or moves away from the lower die 48 under the action of a lifting mechanism that is not shown, and first and second blank holders 52, 54 to hold the blank material 14 as illustrated in FIG. 4 to FIG. 7.

The lower die 48 is a fixed type that is fixed to a base or the like that is not shown. An outer edge part 56 (see FIG. 6 and FIG. 7) of the lower die 48 has a convex shape and the lower die 48 includes a forming concave part 58 with a concave shape on an approximately central part. The upper die 50 is a movable type that is displaceable in a vertical direction (arrow D direction in FIG. 6 and FIG. 7) and includes a forming convex part 60 that can be inserted into the forming concave part 58 of the lower die 48. On a lower surface of this forming convex part 60, protruding parts 62 are formed at positions that face the top of the first blank holder 52.

When the upper die 50 and the lower die 48 are closed, the forming convex part 60 of the upper die 50 is inserted into the forming concave part 58 of the lower die 48. Thus, a cavity is formed so as to have the shape of the formed article (side outer panel 12) between the upper die 50 and the lower die 48.

The first blank holder 52 is provided in the forming concave part 58 of the lower die 48 such that the first blank holder 52 can move in the vertical direction, and includes a first holder part 64 that forms the periphery of the first blank hole 32 of the blank material 14 and a second blank holder part 66 that forms the periphery of the second blank hole 34 of the blank material 14. The first and second holder parts 64, 66 are formed so as to be separated from each other along the front-rear direction of the lower die 48 (arrow A direction) (see FIG. 4).

As illustrated in FIG. 6 and FIG. 7, the first and second holder parts 64, 66 are supported by a plurality of cushion pins 68 whose lower ends extend from an energizing means that is not shown, and the first blank holder 52 including the first and second holder parts 64, 66 are displaced in accordance with forward (upward) or backward (downward) movement of the cushion pins 68 along the vertical direction (arrow D direction).

Moreover, the top of the first and second holder parts 64, 66 that faces the upper die 50 has an approximately plane shape, and a circular groove part 70 is formed near an outer edge part on the top of this first holder part 64. On the other hand, on the top of the second holder part 66, a pair of groove parts 72 extending in an approximately up-down direction of the lower die 48 is formed. When the blank material 14 is formed between the upper die 50 and the first blank holder 52, the protruding part 62 (see FIG. 6) of the upper die 50 is inserted into the circular groove part 70 and the groove parts 72 in a state where the blank material 14 is held between the upper die 50 and the first blank holder 52. Thus, a bead 74 is formed in the blank material 14 near each of the first and second blank holes 32, 34.

Note that the bead 74 formed by the first holder part 64 has a circular shape in accordance with the circular groove part 70, and the beads 74 formed by the second holder part 66 has a straight line shape in accordance with the pair of groove parts 72 (see FIG. 3).

The second blank holder 54 has a circular shape so as to surround the second holder part 66 in the first blank holder 52, a plurality of cylinders 76 are provided below the second blank holder 54, and the second blank holder 54 is supported by a cylinder rod 78. A forming surface 54a of the second blank holder 54 that faces the upper die 50 is formed so as to rise from the side of the first blank holder 52 corresponding to the inside to the side of the lower die 48 corresponding to the outside in the radial direction.

In accordance with forward (upward) or backward (downward) movement of the cylinder rod 78 of the cylinder 76, the second blank holder 54 moves forward/backward (upward/downward) with respect to the lower die 48 in the vertical direction.

The press forming device 10 according to the embodiment of the present invention is basically structured as described above. Next, a method for forming the blank material 14 is described.

First, the blank material 14 is disposed between the lower die 48 and the upper die 50 that are opened. At this time, the first and second blank holders 52, 54 are positioned at a top dead center that is the highest point of the first and second blank holders 52, 54 under the energizing action of the cushion pin 68 and the cylinder 76, respectively. The first and second blank holders 52, 54 are mounted such that the blank material 14 is in contact with the top (mounting surface) of the first and second blank holders 52, 54.

The blank material 14 is mounted such that the first blank hole 32 thereof faces the first holder part 64 of the first blank holder 52, the straight line parts 40a, 40b and the tension adjusting parts 42a, 42b of the second blank hole 34 face the second holder part 66, and the arched parts 44a, 44b of the first and second opening parts 36, 38 face the second blank holder 54.

Then, in order to perform the press forming, the upper die 50 moves downward to approach the lower die 48 under the driving action of the lifting mechanism that is not shown, and the forming convex part 60 of the upper die 50 is inserted into the forming concave part 58 of the lower die 48. Thus, first, the surface of the forming convex part 60 that faces the first blank holder 52 touches and presses a part of the blank material 14 that is mounted on the first blank holder 52.

Therefore, the first blank holder 52 receives pressing power from the upper die 50 and descends while pressing down the cushion pin 68, and the blank material 14 is pressed into the circular groove part 70 of the first holder part 64 by the protruding part 62 of the upper die 50 so as to be plastically deformed to have the bead 74 with the circular shape. At the same time, the tension adjusting parts 42a, 42b of the second blank hole 34 are held between the upper die 50 and the top of the second holder part 66. Thus, as illustrated in FIG. 3, the two beads 74 with the straight line shape that are depressed downward are formed in the tension adjusting parts 42a, 42b. These beads 74 are formed along a width direction of the tension adjusting parts 42a, 42b corresponding to the up-down direction of the blank material 14.

When this upper die 50 has descended further, the draw forming is performed between the outer edge part 56 of the forming convex part 60 and an inner edge part of the forming concave part 58 in the vertical direction (arrow D direction) as illustrated in FIG. 6. Accordingly, the inside of the blank material 14 is pulled by predetermined tension outwardly corresponding to the rear side of the vehicle (arrow B direction). At this time, the straight line parts 40a, 40b of the second blank hole 34 are adjusted by the tension adjusting parts 42a, 42b held between the upper die 50 and the first blank holder 52 through the beads 74 such that the tension becomes predetermined tension. Accordingly, inflow of the blank material 14 in the front-rear direction (arrow A or B direction) of the vehicle is adjusted.

As illustrated in FIG. 8A, in the straight line parts 40a, 40b, a deformation amount in the vertical direction (arrow D direction) becomes large because of the upper die 50 and the lower die 48. However, since the inflow of the blank material 14 to the outside (arrow E direction) is large, a crack does not occur in the forming.

At the same time, along with the descent of the upper die 50, as illustrated in FIG. 7, the cylinder rod 78 of the cylinder 76 is pressed downward and the second blank holder 54 is pushed down through the blank material 14, and the arched parts 44a, 44b of the first and second opening parts 36, 38 of the second blank hole 34 are held and pressurized by the second blank holder 54 so that the draw forming is performed on the forming surface 54a.

In this case, as illustrated in FIG. 3, the arched parts 44a, 44b of the first and second opening parts 36, 38 of the second blank hole 34 are formed, in advance, in the shape that is close to the formed arched part 46 in the radial direction that has been formed. Thus, the inflow of the blank material 14 to the outside in the radial direction with respect to the second blank hole 34 is small.

Here, in the aforementioned arched part 44a of the second blank hole 34, the variation of the inflow of the blank material 14 in the forming is described briefly with reference to FIG. 8B. Note that in FIG. 8B, a part of the arched part 44a before the forming is regarded as a first arched portion R1, and the formed arched part 46 in which the first arched portion R1 is formed by the press forming is regarded as a second arched portion R2.

As can be understood from FIG. 8B, the length of the first arched portion R1 corresponding to a part of the arched part 44a is L1. When the first arched portion R1 is formed, this part is pushed out and expanded by a predetermined distance to the outside in the radial direction and then, this part becomes the second arched portion R2 of the formed arched part 46 that has been formed. The length of the second arched portion R2 is L2 that is longer than the length of the first arched portion R1.

That is to say, if the inflow of the blank material 14 corresponding to the push-out distance in the radial direction is F1, the difference between the length L2 of the second arched portion R2 after the forming and the length L1 of the first arched portion R1 before the forming is L2-L1.

On the other hand, for example, if a third arched portion R1′ before the forming (see dashed line in FIG. 8B) is set to a position that is more on the inside than the first arched portion R1 in the radial direction such that the inflow of the blank material 14 to the outside in the radial direction with respect to the first arched portion R1 becomes large, inflow F2 (distance) that is larger than the above one is required in order to form the second arched portion R2 from the third arched portion R1′. In addition, the difference between the length L1′ of the third arched portion R1′ and the length L2 of the second arched portion R2 after the forming is L2-L1′.

Thus, if the forming is performed by the amount of the inflow F2 in which the blank material 14 flows more largely to the outside in the radial direction, the difference from the length L2 of the second arched portion R2 increases for L1-L1′, compared with a case where the forming is performed by the amount of the inflow F1.

In this arched part 44a, as illustrated in FIG. 8B, as the inflow of the blank material 14 to the outside in the radial direction is larger in the forming, the crack occurs more easily. Thus, it is preferable that the shape of the arched portion before the forming be set such that the inflow is as small as possible with respect to the second arched portion R2 after the forming, that is, the separation distance in the radial direction is small.

Note that the arched part 44a of the first opening part 36 is described above. Since the arched part 44b of the second opening part 38 is similar to the arched part 44a of the first opening part 36, the detailed description of the arched part 44b of the second opening part 38 is omitted.

As described above, when the blank material 14 is formed, the tension in the front-rear direction of the vehicle is controlled by adjusting the tension to be applied to the straight line parts 40a, 40b of the second blank hole 34 by the tension adjusting parts 42a, 42b, and the tension in the up-down direction to be applied to the arched parts 44a, 44b of the first and second opening parts 36, 38 is controlled by the second blank holder 54.

Note that each of the drawings (views) is simplified; however, a three-dimensional shape is formed on an inner edge of the second blank hole 34 of the blank material 14 in fact. In particular, as the forming process proceeds, tensile force toward the rear side (arrow B direction) acts on the straight line part 40b corresponding to the rear side of the vehicle (arrow B direction). By this tensile force, the deep draw forming is performed for the blank material 14 in the width direction that is approximately orthogonal to the vehicle direction, and the three-dimensional shape can be formed from the second door opening part 28 to the rear fender part 30 of the formed article.

Then, when the upper die 50 has reached a bottom dead center that is the lowest point of the upper die 50, the blank material 14 held between the lower die 48, the first and second blank holders 52, 54, and the upper die 50 is formed into the formed article (side outer panel 12) corresponding to the shape of the cavity that is formed by the forming concave part 58 and the forming convex part 60 that has entered the forming concave part 58.

After that, under the action of the lifting mechanism that is not shown, the upper die 50 is separated from the lower die 48 and the first and second blank holders 52, 54 to open the dies. Then, the formed article is detached from the press forming device 10. Thus, the press forming for the blank material 14 ends and the side outer panel 12 corresponding to the formed article is obtained. Note that when a trimming process is performed for the formed article, the side outer panel 12 with the first and second door opening parts 26, 28 opened is obtained.

As described above, in the present embodiment, in the press forming device 10 that performs the draw forming for the blank material 14 including the first and second blank holes 32, 34, the first blank holder 52 is provided in the forming concave part 58 of the lower die 48 and the second blank holder 54 with the circular shape is provided on the outer peripheral side of the second holder part 66 of the first blank holder 52 disposed on the vehicle rear side. The second blank hole 34 includes the first and second opening parts 36, 38 whose cross-sectional shape is semicircular, and the pair of straight line parts 40a, 40b that connects the first opening part 36 and the second opening part 38. The pair of tension adjusting parts 42a, 42b extending to the inside of the second blank hole 34 is provided to the straight line parts 40a, 40b.

Thus, when the draw forming is performed for the blank material 14, the upper die 50 and the first blank holder 52 hold the tension adjusting parts 42a, 42b, so that the bead 74 is formed. Therefore, the tension applied to the straight line parts 40a, 40b of the second blank hole 34 outwardly can be adjusted as appropriate. In this case, even if the inflow of the blank material 14 in the front-rear direction of the vehicle (arrow A or B direction) is large, the tension is adjusted as appropriate, so that the convex part near the rear fender part 30 of the side outer panel 12 can be formed without wrinkles.

Moreover, the arched parts 44a, 44b of the first and second opening parts 36, 38 in the second blank hole 34 where the crack occurs easily in the forming are set in advance such that the shape of the arched parts 44a, 44b is close to the shape of the formed arched part 46 after the forming in the radial direction. Thus, it is possible to suppress the inflow of the blank material 14 to the outside in the radial direction in the forming, so that the deformation amount (extending amount) after the forming is suppressed. Therefore, the crack can be prevented as appropriate.

Furthermore, even if the extension is caused to the outside of the arched parts 44a, 44b in the radial direction as described above, the arched parts 44a, 44b is held securely between the upper die 50 and the second blank holder 54 provided to the outer peripheral side of the first blank holder 52. Thus, the tension applied to the outside in the radial direction can be adjusted as appropriate without the bead.

In other words, even if the arched parts 44a, 44b of the first and second opening parts 36, 38 in the second blank hole 34 are enlarged in diameter so as to be positioned more on the outer peripheral side than the first blank holder 52, the forming can be performed in the state where the arched parts 44a, 44b are securely held by the second blank holder 54.

That is to say, when the press forming device 10 performs the draw forming for the blank material 14, the tension adjusting parts 42a, 42b each including the bead 74 adjust as appropriate the tension applied to the straight line parts 40a, 40b of the second blank hole 34 outwardly. Also, the shape of the arched parts 44a, 44b is set so as to be close to the formed arched part 46 after the forming in the radial direction. Thus, the crack can be prevented and the tension applied outwardly can be adjusted by holding the arched parts 44a, 44b by the second blank holder 54.

As a result, when the deep draw forming is performed for the blank material 14 including the opening part, both the tension adjustment for the straight line parts 40a, 40b and the tension adjustment for the arched parts 44a, 44b of the first and second opening parts 36, 38 whose cross-section has the arched shape are performed as appropriate. Here, in the straight line parts 40a, 40b, a crack occurs less easily but wrinkles occurs easily even if the inflow of the blank material 14 is large, and in the arched parts 44a, 44b, the crack occurs easily if the inflow is large. Thus, even when the deep draw forming is performed, the crack does not occur at the second blank hole 34 of the blank material 14 including the arched parts 44a, 44b and the straight line parts 40a, 40b. For example, the deep draw forming is required in the side outer panel 12 (formed article) in the width direction of the vehicle from the second door opening part 28 to the rear fender part 30, and such side outer panel 12 for the automobile can be obtained thereby.

Note that the blank material, and the press forming method and the press forming device for the blank material according to the present invention are not limited to the above embodiment, and can employ various structures without departing from the gist of the present invention.

Claims

1. A blank material for which draw forming is performed in a press forming device to make a body panel of an automobile, the blank material comprising an opening part including arched parts provided in an up-down direction of the body panel and connection parts each having an approximately straight line shape provided in a front-rear direction of the body panel that is approximately orthogonal to the arched parts and connected to the arched parts,

wherein a tension adjusting part is provided to the connection part, the tension adjusting part extending to an inside of the opening part and configured to adjust tension applied outwardly in forming.

2. The blank material according to claim 1, wherein the tension adjusting part is formed for each of a pair of the connection parts.

3. The blank material according to claim 1 or 2, wherein each of the arched parts is formed in a manner that the arched part is smaller than a formed arched part of a formed body in which the arched part has been formed, and the arched part has a shape that is close to the formed arched part.

4. A press forming method in which draw forming is performed for a blank material including an opening part that includes arched parts and connection parts each having an approximately straight line shape and connected to the arched parts,

wherein an edge of the opening part is pressurized and held between an upper die and a first blank holder provided to a lower die, and

the arched parts positioned outside a held part of the blank material held between the upper die and the first blank holder is pressurized and held between the upper die and a second blank holder provided outside the first blank holder.

5. The press forming method according to claim 4, wherein a bead is formed by holding, between the upper die and the first blank holder, a tension adjusting part extending from the connection part to an inside of the opening part.

6. A press forming device configured to perform draw forming for a blank material including an opening part that includes arched parts and connection parts each having an approximately straight line shape and connected to the arched parts, the press forming device comprising:

an upper die;

a lower die disposed so as to face the upper die and including a mounting surface on which the blank material is mounted;

a first blank holder disposed so as to face the upper die and configured to hold an edge of the opening part of the blank material with the upper die; and

a second blank holder disposed outside the first blank holder and configured to hold, between the second blank holder and the upper die, the arched parts positioned outside a held part of the blank material held between the first blank holder and the upper die,

wherein the first blank holder and the upper die include a bead configured to hold with pressure a tension adjusting part extending from the connection part of the blank material to an inside.

7. The press forming device according to claim 6, wherein the second blank holder has a circular shape.

8. The press forming device according to claim 6 or 7, wherein the bead extends along a direction that is approximately orthogonal to an extending direction of the tension adjusting part.