JP2023179918A - Press molding method and press die for the same - Google Patents

Abstract

To provide a press molding method and a press die for the same which can decrease cracking due to elongation of a press part and improve shape freezing property when one side wall part of a hat-shaped cross section shape part of the press part is elongated at a curvature ratio larger than that of the other side wall part to be curved in a direction for flange formation.SOLUTION: A press molding method comprises: a punch 21 which includes a first side wall formation part 211 forming one side wall part of a hat-shaped cross section, a second side wall formation part 212 forming the other side wall part, and a flange formation part 212H forming a flange part extending from the other side wall part; a cushion 22 with a wrinkle pressing part 221 which forms a flange part extending from the one side wall part; a pad 23; and a die 24. The die and the punch approach each other while the pad presses a material W on a top plate formation part 213 of the punch and the wrinkle pressing part of the cushion and the die sandwich the material, so that the one side wall part and the flange part of the same are drawn, and the other side wall part and the flange part of the same are bended.SELECTED DRAWING: Figure 3

Description

The present invention relates to a press molding method and a press mold thereof, and more particularly, the present invention relates to a press molding method and a press die thereof, and more particularly, the present invention has a hat-shaped cross-sectional portion continuous in the longitudinal direction, and one side wall portion of the hat-shaped cross-sectional portion is curved from the other side wall portion. The present invention relates to a press forming method for forming a press part curved in a direction of stretch flange forming with a curvature greater than the curvature ratio, and a press die thereof.

Generally, a press part 100 having a hat-shaped cross-sectional shape continuous in the longitudinal direction is made of a material (steel plate) SS with a top plate part 101 having a hat-shaped cross-section, left and right side wall parts 102, as shown in FIG. 14(A). It is known that it can be obtained by a press forming method of bending into 103. That is, the press part 100 includes a lower die punch 201 on which a forming surface with a hat-shaped cross section is formed, a pad 202 that presses the material SS against the top plate forming part of the lower die punch 201, and a pad 202 located on the outer peripheral side of the pad 202. and an upper die 203 having bending edges 203D formed along the left and right side walls of the hat-shaped cross section, and the upper die 203 is lowered with the pad 202 pressing the material SS against the lower punch 201, It can be obtained by a press forming method in which the bending blade 203D presses the material SS against the lower die punch 201 and bends it into a shape along the forming surface of the lower die punch 201.

However, in the press part 100 having a hat-shaped section, the hat-shaped section is often curved in the longitudinal direction, and in that case, one side wall section 102 of the hat-shaped section is stretch-flange formed, and the other The side wall portion 103 is often shrunk and flanged. When this press part 100 is formed by a bending method, tensile stress remains in the stretch-flange-formed side wall part 102, and compressive stress remains in the shrink-flange-formed side wall part 103.

Therefore, as shown in FIG. 14(B), in the press part 100 after release, the stretch-flange formed side wall portion 102 deforms inwardly (in the direction of arrow There was a problem in that the side wall portion 103 was deformed outward (in the direction of arrow X2) due to residual compressive stress, making it difficult to freeze into a normal shape. In addition, as the left and right side walls 102 and 103 deform in the same direction (X1, X2), the entire hat-shaped cross-sectional portion is twisted and deformed, making it difficult to set the mold for the next process. . Furthermore, if the material SS is a so-called high-tensile steel plate (for example, a steel plate with a tensile strength of about 1 to 1.2 GPa), the amount of twist of the press part 100 after bending becomes increasingly large, so that the forming process in the press mold is difficult. There was a problem in that it was necessary to repeatedly make corrections to the surface estimates.

To solve this problem, it is conceivable to form the press part 100 by a draw forming method to improve the ability to fix the shape to a regular shape. There was a problem in that stretch cracks were likely to occur in the side wall portion 102 of the molding.

In this regard, Patent Document 1 describes, as shown in FIGS. 15 and 16, a lower die punch 301, a pad 302 that presses the material SS against the lower die punch 301, and an upper die having a molding surface on the outer peripheral side of the pad 302. A pressed part having a substantially hat-shaped cross section that continues in the longitudinal direction, and has a stretch flange molding part 402 and a contraction flange molding part 403 formed at opposing positions with a top plate part 401 in between. 400 is a press forming method in which the developed material SS is cold bent and formed, and the material portion SS1A of the top plate portion 401 is formed at a position separated from the stretch flange forming portion 402 and the shrinkage flange forming portion 403. With the pad 302 pressing the upper die 303, the upper die 303 moves the material portions SS2 and SS3, which are close to the lower punch 301 and will form the stretch flange forming part 402 and the shrinkage flange forming part 403, against the lower die punch 301. A press forming method is disclosed in which the material is rotationally moved from the shrinkage flange forming side to the stretch flange forming side, and then pressed against a lower die punch 301.

According to this press forming method, the material SS can be supplied from the contraction flange forming part 403 side to the stretch flange forming part 402 side, so that there is an effect that stretch cracks in the stretch flange forming part 402 can be reduced.

JP 2017-6926 Publication

However, in the press forming method disclosed in Patent Document 1, if the stretch flange forming part 402 and the contraction flange forming part 403 are not formed at opposing positions with the top plate part 401 in between, the stretch flange forming part 402 and the shrink flange forming part 403 are The material parts SS2 and SS3 forming the forming part 402 and the shrinkage flange forming part 403 cannot be moved from the shrinkage flange forming side to the stretch flange forming side with respect to the lower die punch 301.

Therefore, the hat-shaped cross-sectional portion is continuous in the longitudinal direction, and one side wall of the hat-shaped cross-sectional portion is curved in the direction of stretch flange forming at a curvature rate greater than the curvature of the other side wall. (For example, when one side wall of a hat-shaped cross-sectional part is curved with a large curvature in the direction of stretch flange forming, but the other side wall extends in a straight line.) (or when the curve is curved with a small curvature ratio so that it becomes slightly shrink flanged), the supply of material to one side wall part of stretch flanging is insufficient, and the one side wall part that becomes stretch flanging is There was a problem that stretching cracks occurred.

The present invention has been made in order to solve the above-mentioned problem, and one side wall portion of the hat-shaped cross-sectional portion is curved in the direction of stretch flange forming with a curvature ratio greater than the curvature ratio of the other side wall portion. An object of the present invention is to provide a press forming method and a press die thereof that can improve shape fixability while reducing elongation cracking of pressed parts.

In order to achieve the above object, a press molding method and a press mold according to the present invention have the following configuration.
(1) It has a hat-shaped cross-sectional portion that continues in the longitudinal direction, and one side wall of the hat-shaped cross-sectional portion is curved in the direction of stretch flange forming with a higher curvature than the other side wall. A press forming method for forming a pressed part, the press forming method comprising:
A top plate molding part forming a top plate part with a hat-shaped cross section, a first side wall molding part forming the one side wall part, a second side wall molding part forming the other side wall part, and the other side wall. a flange forming part forming a flange part extending from the punch;
a cushion formed to be movable up and down with respect to the punch, having a wrinkle suppressing part that is divided from the first side wall molding part and forming a flange part extending from the one side wall part;
a pad that presses a material against the top plate forming part of the punch;
a die having a die forming part facing the punch and the cushion, disposed along the outer periphery of the pad, and forming the both side walls and the flanges;
a cushion pressing device that presses the cushion against the die with a pressing force greater than the pressing force of the pad;
The die and the punch are brought close to each other with the pad pressing the material against the top molding part of the punch and the wrinkle suppressing part of the cushion and the die molding part of the die sandwiching the material. According to the present invention, the one side wall portion and the flange portion extending from the one side wall portion are drawn, and the other side wall portion and the flange portion extending from the other side wall portion are formed by bending.

In the present invention, the top plate molding part forms the top plate part with a hat-shaped cross section, the first side wall molding part forms one side wall part, the second side wall molding part forms the other side wall part, and the other side wall molding part forms the top plate part. a punch having a flange forming part forming a flange extending from the side wall of the first side wall, and a wrinkle suppressing part forming a flange extending from one side wall, which is divided from the first side wall forming part; a cushion formed to be movable up and down, a pad that presses the material against the molded top plate of the punch, and a pad that faces the punch and cushion and is arranged along the outer periphery of the pad, and has side walls and both flanges. and a cushion pressing device that presses the cushion against the die with a pressing force greater than the pressing force of the pad, and the pad presses the material against the top molding part of the punch. , one side wall portion and a flange portion extending from the one side wall portion are drawn by drawing the die and the punch in close proximity with the material being sandwiched between the wrinkle suppressing portion of the cushion and the die forming portion of the die; Since the other side wall portion and the flange portion extending from the other side wall portion are bent and formed, it has a hat-shaped cross-sectional portion that is continuous in the longitudinal direction, and one side wall portion of the hat-shaped cross-sectional portion is connected to the other side wall portion. It is possible to improve shape fixability to a regular shape while reducing stretch cracks in one side wall portion of a press part that is curved in a direction to be stretch flanged with a curvature ratio greater than the curvature ratio.

That is, a top plate molding part that forms a top plate part with a hat-shaped cross section, a first side wall molding part forming one side wall part, a second side wall molding part forming the other side wall part, and the other side wall part. a punch having a flange forming part forming a flange extending from the first side wall forming part; and a wrinkle suppressing part separating from the first side wall forming part and forming a flange extending from one side wall; a pad that presses the material against the molded top plate of the punch; and a pad that faces the punch and the cushion and is arranged along the outer periphery of the pad, forming both side walls and both flanges. Since the punch and pad are equipped with a die having a die forming part that presses the cushion against the die with a pressing force greater than the pressing force of the pad, the punch and pad can clamp the material on the top plate side. While the cushion and die sandwich the material on one side wall, the punch and die come close to each other, thereby squeezing one side wall and the flange extending from the other side wall to form a stretch flange. Can be molded. Furthermore, by sandwiching the material on the top plate side between the punch and the pad and bringing the punch and die close to each other, it is possible to bend and form the other side wall and the flange extending from the other side wall.

In addition, in the initial stage when the punch, cushion, pad, and die work together to draw and form one side wall part and the flange part extending from the other side wall part, which will be stretch flange forming, the punch and die work together to form a stretch flange. The material on the other side wall portion is hardly bent and formed. Therefore, by pressing the cushion against the die with a pressure greater than the pressure of the pad, the cushion pressure device suppresses the flow of material from one side wall side into the punch side for stretch flange forming. At the same time, the material can be flowed from the other side wall side to the one side wall side where stretch flange forming is to be performed.

In addition, when the pad presses the material against the top molding part of the punch, and the wrinkle suppressing part of the cushion and the die molding part of the die sandwich the material, the die and punch come close to each other, so that one side wall part and the flange extending from one side wall are drawn, and the other side wall and the flange extending from the other side wall are bend-formed, so that the material is not transferred from the other side wall to the one side wall. By drawing and forming one side wall part and the flange part extending from one side wall part while receiving supply, the elongation rate of the one side wall part and the flange part extending from one side wall part is reduced, and the elongation rate is reduced. The tensile residual stress can also be reduced accordingly. As a result, it is possible to reduce stretch cracking of one side wall portion subjected to stretch flange molding and the flange portion extending from the one side wall portion, and improve shape fixability.

Therefore, according to the present invention, it is possible to reduce stretch cracking of a press part in which one side wall portion of the hat-shaped cross-sectional portion is curved in the direction of stretch flange forming with a curvature ratio greater than that of the other side wall portion. At the same time, it is possible to provide a press molding method that can improve shape fixability.

(2) In the press forming method described in (1),
The other side wall portion is formed to have a bending angle smaller than the normal bending angle with respect to the top plate portion, and is formed to have the normal bending angle in a post process.

In the present invention, the other side wall part is formed so that the bending angle with respect to the top plate part is smaller than the normal bending angle, and is formed to the normal bending angle in a post process, so that one side wall part and one side wall part When drawing forming the flange portion extending from the top plate portion, the other side wall portion is formed so that the bending angle with respect to the top plate portion is smaller than the normal bending angle. Therefore, when one side wall part and the flange part extending from one side wall part are drawn, the material on the other side wall part easily passes through the gap between the pad and the punch top molded part, and the other side wall part It is possible to allow more material to flow from the wall side to one side wall side where stretch flange forming is performed. As a result, it is possible to further reduce stretch cracks when drawing and forming one side wall portion and the flange portion extending from the one side wall portion, and further improve shape fixability.

(3) In the press forming method described in (1) or (2),
The pad is divided into a plurality of parts corresponding to a region where the elongation rate is large and a region where the elongation rate is small in the stretch flange forming on the one side wall portion,
The pressing force of the pad corresponding to the area where the elongation rate is high is smaller than the pressing force of the pad corresponding to the area where the elongation rate is small.

In the present invention, the pad is divided into a plurality of parts corresponding to the area where the elongation rate is large and the area where the elongation rate is small due to stretch flange forming on one side wall, and the pad is pressed in the area where the elongation rate is large. Since the pressure is smaller than the pressing force of the pad corresponding to the area where the elongation rate is low, when drawing forming one side wall part and the flange part extending from the one side wall part, the elongation rate of the stretch flange forming of one side wall part In a region where the amount of material is large, the amount of material flowing from the other side wall side to the one side wall side can be further increased. Therefore, during drawing forming, it is possible to further reduce the stretch cracking of one side wall part of the region where the elongation rate of stretch flanging is large and the flange part extending from the one side wall part, and it is possible to further improve the shape fixability.

Furthermore, when drawing forming one side wall portion and a flange portion extending from one side wall portion, the pressing force of the pad becomes relatively large in the region where the elongation rate of stretch flanging of one side wall portion is small. It is possible to reduce the amount of material flowing from the other side wall side to the one side wall side. Therefore, in the other side wall portion and the flange portion extending from the other side wall portion, deformation due to the inflow of the material can be suppressed, and shape fixability can be improved.

(4) It has a hat-shaped cross-sectional shape that continues in the longitudinal direction, and one side wall of the hat-shaped cross-sectional shape is curved in the direction of stretch flange forming with a higher curvature than the other side wall. A press mold for forming a pressed part,
A top plate molding part forming a top plate part with a hat-shaped cross section, a first side wall molding part forming the one side wall part, a second side wall molding part forming the other side wall part, and the other side wall. a flange forming part forming a flange part extending from the punch;
a cushion formed to be movable up and down with respect to the punch, having a wrinkle suppressing part that is divided from the first side wall molding part and forming a flange part extending from the one side wall part;
a pad that presses a material against the top plate forming part of the punch;
a die having a die forming part facing the punch and the cushion, disposed along the outer periphery of the pad, and forming the both side walls and the flanges;
a cushion pressing device that presses the cushion against the die with a pressing force greater than the pressing force of the pad;
The die and the punch are brought close to each other with the pad pressing the material against the top molding part of the punch and the wrinkle suppressing part of the cushion and the die molding part of the die sandwiching the material. According to the present invention, the one side wall portion and the flange portion extending from the one side wall portion are drawn, and the other side wall portion and the flange portion extending from the other side wall portion are formed by bending.

In the present invention, the top plate molding part forms the top plate part with a hat-shaped cross section, the first side wall molding part forms one side wall part, the second side wall molding part forms the other side wall part, and the other side wall molding part forms the top plate part. a punch having a flange forming part forming a flange extending from the side wall of the first side wall, and a wrinkle suppressing part forming a flange extending from one side wall, which is divided from the first side wall forming part; a cushion formed to be movable up and down, a pad that presses the material against the molded top plate of the punch, and a pad that faces the punch and cushion and is arranged along the outer periphery of the pad, and has side walls and both flanges. and a cushion pressing device that presses the cushion against the die with a pressing force greater than the pressing force of the pad, and the pad presses the material against the top molding part of the punch. , one side wall portion and a flange portion extending from the one side wall portion are drawn by drawing the die and the punch in close proximity with the material being sandwiched between the wrinkle suppressing portion of the cushion and the die forming portion of the die; Since the other side wall portion and the flange portion extending from the other side wall portion are bent and formed, it has a hat-shaped cross-sectional portion that is continuous in the longitudinal direction, and one side wall portion of the hat-shaped cross-sectional portion is connected to the other side wall portion. It is possible to improve shape fixability while reducing stretch cracks in one side wall of a press part that is curved in the direction of stretch flanging with a curvature greater than the curvature.

That is, a top plate molding part that forms a top plate part with a hat-shaped cross section, a first side wall molding part forming one side wall part, a second side wall molding part forming the other side wall part, and the other side wall part. a punch having a flange forming part forming a flange extending from the first side wall forming part; and a wrinkle suppressing part separating from the first side wall forming part and forming a flange extending from one side wall; a pad that presses the material against the molded top plate of the punch; and a pad that faces the punch and the cushion and is arranged along the outer periphery of the pad, forming both side walls and both flanges. Since the punch and pad are equipped with a die having a die forming part that presses the cushion against the die with a pressing force greater than the pressing force of the pad, the punch and pad can clamp the material on the top plate side. While the cushion and die sandwich the material on one side wall, the punch and die come close to each other, thereby squeezing one side wall and the flange extending from the other side wall to form a stretch flange. Can be molded. Furthermore, by sandwiching the material on the top plate side between the punch and the pad and bringing the punch and die close to each other, it is possible to bend and form the other side wall and the flange extending from the other side wall.

In addition, in the initial stage when the punch, cushion, pad, and die work together to draw and form one side wall part and the flange part extending from the other side wall part, which will be stretch flange forming, the punch and die work together to form a stretch flange. The material on the other side wall side is hardly bent and formed. Therefore, by pressing the cushion against the die with a pressure force greater than the pressure force of the pad, the cushion pressure device suppresses the amount of material flowing into the material punch side on one side wall side for stretch flange forming. , material can be flowed from the other side wall side to one side wall side where stretch flange forming is to be performed.

In addition, when the pad presses the material against the top molding part of the punch, and the wrinkle suppressing part of the cushion and the die molding part of the die sandwich the material, the die and punch come close to each other, so that one side wall part and the flange extending from one side wall are drawn, and the other side wall and the flange extending from the other side wall are bend-formed, so that the material is not transferred from the other side wall to the one side wall. By drawing and forming one side wall part and the flange part extending from one side wall part while receiving supply, the elongation rate of the one side wall part and the flange part extending from one side wall part is reduced, and the elongation rate is reduced. The tensile residual stress can also be reduced accordingly. As a result, it is possible to reduce stretch cracking of one side wall portion subjected to stretch flange molding and the flange portion extending from the one side wall portion, and improve shape fixability.

Therefore, according to the present invention, it is possible to reduce stretch cracking of a press part in which one side wall portion of the hat-shaped cross-sectional portion is curved in the direction of stretch flange forming with a curvature ratio greater than that of the other side wall portion. At the same time, it is possible to provide a press die that can improve shape fixability.

(5) In the press mold described in (4),
The cushion includes a connecting part disposed on the outer peripheral side of the flange forming part, and the connecting part and the wrinkle suppressing part are connected in a ring shape surrounding the punch,
The connecting portion or the die may be equipped with a distance block that comes into contact with a seat of the opposing die or a seat of the connecting portion.

In the present invention, the cushion is provided with a connecting part disposed on the outer peripheral side of the flange forming part, the connecting part and the wrinkle suppressing part are connected in a ring shape surrounding the punch, and the connecting part or the die is provided with a connecting part arranged on the outer peripheral side of the flange forming part. Since the distance block that comes into contact with the seat of the die or the seat of the connecting part is attached, the wrinkle suppressing part of the cushion and the die forming part of the die sandwich the material, and the distance block is attached to the connecting part or the die. The distance blocks can abut opposing die seats or coupling section seats. Therefore, when drawing forming one side wall part and a flange part extending from one side wall part, the cushion is prevented from tilting in the vertical direction with respect to the punch, and the wrinkle suppressing part of the cushion and the die forming part of the die are prevented. The clearance can be maintained at a predetermined value. Therefore, it is possible to more stably reduce the expansion cracking caused by drawing of the one side wall portion and the flange portion extending from the one side wall portion, and improve shape fixability.

(6) In the press mold described in (4) or (5),
The cushion pressurizing device is a fluid cylinder device in which a cylinder case is attached to the die base of the punch, and a cylinder rod that expands and contracts with respect to the cylinder case presses the cushion, and the pad presses the cushion after press molding is completed. The cylinder rod is characterized by having a locking mechanism that stops the extension of the cylinder rod until it is separated from the top plate part.

In the present invention, the cushion pressurizing device is a fluid cylinder device in which a cylinder case is attached to a mold base of a punch, and a cylinder rod that expands and contracts with respect to the cylinder case presses the cushion, and the pad presses the cushion after press molding is completed. The cylinder rod has a locking mechanism that stops the extension of the cylinder rod until it separates from the top plate, so it can be pressed without deforming the press part after press forming is completed, without using a die cushion pin with a locking mechanism of the press machine. It can be released from the mold. Therefore, this press mold can be installed in a general-purpose press machine that is not equipped with a die cushion pin with a locking mechanism. Therefore, productivity in press molding can be increased while maintaining product accuracy after the shape of the press part is frozen.

According to the present invention, one side wall portion of the hat-shaped cross-sectional portion is curved in the direction of stretch flanging at a curvature ratio greater than the curvature ratio of the other side wall portion, while reducing stretch cracking of the press part. It is possible to provide a press molding method and a press mold thereof that can improve shape fixability.

1 is a schematic perspective view of a press part formed by a press molding method according to an embodiment of the present invention. 2 is a cross-sectional view of the press part shown in FIG. 1, (A) shows a C1-C1 cross-sectional view shown in FIG. 1, (B) shows a C2-C2 cross-sectional view shown in FIG. 1, and (C) shows a cross-sectional view of the press part shown in FIG. 1 is a cross-sectional view taken along C3-C3 shown in FIG. FIG. 2 is a sectional view of the main part when the press part shown in FIG. 1 is press-formed with the cross section shown in FIG. A sectional view of the main parts upon completion is shown. FIG. 3 is a distribution diagram of the plate thickness increase/decrease rate in area A of the press part shown in FIG. 1, in which (A) is a distribution diagram of the plate thickness increase/decrease rate in the A region of the press part shown in FIG. Fig. 3 shows a distribution diagram of the plate thickness increase/decrease rate in area A when there is an inflow of material from the other side wall side to one side wall side in the press forming method shown in Fig. 3. A distribution map of the rate of increase/decrease is shown. FIG. 4 is a cross-sectional view of a main part of a first modification of the press forming method shown in FIG. 3, in which (A) is a cross-sectional view of a main part when press forming is completed in the first step of forming the other side wall to a small bending angle; (B) is a cross-sectional view of the main part upon completion of press forming in the second step of forming the bending angle of the other side wall portion to a regular bending angle. FIG. 4 is a plan view of essential parts of a second modification of the press forming method shown in FIG. 3; 7 is a cross-sectional view of a main part taken along the line DD shown in FIG. 6. FIG. FIG. 2 is a cross-sectional view of a press mold for press-molding the press part (C1-C1 cross section) shown in FIG. 1 at the time of starting molding. FIG. 9 is a cross-sectional view of the press die shown in FIG. 8 during molding. FIG. 9 is a cross-sectional view of the press die shown in FIG. 8 upon completion of molding. FIG. 9 is a cross-sectional view of the press mold shown in FIG. 8 after the press part is released from the mold. FIG. 9 is a sectional view of a modified example of the press mold shown in FIG. 8 at the time of starting molding. FIG. 13 is a cross-sectional view of the press die shown in FIG. 12 during molding. FIG. 2 is a cross-sectional view of a main part of a press part having a conventional hat-shaped cross-sectional shape, in which (A) shows a cross-sectional view of a main part of a press forming method using bending, and (B) shows a process of releasing the press part formed by bending. A later sectional view of the main part is shown. FIG. 2 is a plan view of the press molding method described in Patent Document 1. 16 is a sectional view of a main part during molding in the press molding method shown in FIG. 15. FIG.

Next, a press molding method and a press mold according to an embodiment of the present invention will be described in detail with reference to the drawings. First, the press parts formed by the press forming method according to the present embodiment and the press forming method thereof will be explained, and the results of CAE analysis of the plate thickness distribution after press forming will be explained. Next, the press mold used in this press molding method will be explained.

<Press parts formed by this press forming method>
First, a press part formed by the press molding method according to the present embodiment will be explained using FIGS. 1 and 2. FIG. 1 shows a schematic perspective view of a press part formed by a press molding method according to an embodiment of the present invention. FIG. 2 is a sectional view of the press part shown in FIG. 1, in which (A) shows a C1-C1 sectional view shown in FIG. 1, (B) shows a C2-C2 sectional view shown in FIG. C) shows a C3-C3 sectional view shown in FIG.

As shown in FIGS. 1 and 2, a press part 10 formed by the press forming method according to the present embodiment has a hat-shaped cross-sectional portion 1 continuous in the longitudinal direction, and one of the hat-shaped cross-sectional portions 1 This is a press part 10 in which the side wall portion 11 is curved in the direction of stretch flanging at a curvature ratio X1 larger than the curvature ratio X2 of the other side wall portion 12. The press part 10 is applied to, for example, a floor member constituting the body of an automobile, and in that case, it is preferable to use a high-tensile steel plate as the material W. As the material W, for example, a high tensile strength steel plate having a tensile strength of 980 MPa or more can be used.

Here, one side wall portion 11 of the hat-shaped cross-sectional portion 1 is curved with a large curvature ratio X1 in the direction of stretch flanging, and the other side wall portion 12 is slightly shrunk and curved with a small curvature ratio X2 in the direction of flanging. However, it is not necessarily limited to this. The other side wall portion 12 may be curved with a small curvature X2 in the direction of slight stretch flanging, for example, or may be extended substantially linearly. Note that the curvature ratios X1 and X2 are percentages of the reciprocals of the radii R1 and R2 forming the curved surfaces extending in the longitudinal direction of the side wall parts 11 and 12, and the side wall parts 11 and 12 have a plurality of curvature ratios X1, When it is formed with a curved surface of X2, it means the largest one.

Further, the hat-shaped cross-sectional portion 1 includes a top plate portion 13, side wall portions 11 and 12 that are bent from both widthwise ends of the top plate portion 13 toward the inside of the plate, and bent toward the outside of the plate from the tips of the side wall portions 11 and 12. It includes flange portions 11H and 12H. In FIGS. 2(A) and 2(B), the other side wall portion 12 and the flange portion 12H shown by solid lines are bent at a regular bending angle α0 with respect to the top plate portion 13, and the other side wall portion shown by imaginary lines 12a and the flange portion 12Ha are bent with respect to the top plate portion 13 at a bending angle α smaller than the normal bending angle α0. This is molded in a plurality of steps, which will be explained in detail in a modification of the present press molding method.

Further, one side wall portion 11 is formed in an area A that is about half of the length of the top plate portion 13, and the other side wall portion 12 is formed in a region B that is the entire length of the top plate portion 13. , A area, and B area are not necessarily limited to these. Further, as shown in FIG. 2(C), the top plate portion 13 is bent outward at an obtuse angle θ at the intermediate portion in the longitudinal direction, resulting in a gently warped shape. It is not limited to. In addition, in this press forming method described later, the A area is drawn and the B area is bent.

<This press molding method>
Next, the press molding method according to this embodiment will be explained using FIGS. 1 to 3. FIG. 3 is a sectional view of the main part when press forming the press part shown in FIG. 1 with the cross section shown in FIG. ) shows a sectional view of the main part after press forming is completed.

As shown in FIGS. 1 to 3, this press forming method has a hat-shaped cross-sectional shape part 1 that is continuous in the longitudinal direction, and one side wall part 11 of the hat-shaped cross-sectional shape part 1 is different from the other side wall part. A press molding method for molding a press part 10 curved in the direction of stretch flange molding with a curvature ratio X1 larger than a curvature ratio X2 of 12, comprising: a punch 21, a cushion 22, a pad 23, a die 24, A state in which the pad 23 presses the material W against the top plate forming part 213 of the punch 21, and the material W is held between the wrinkle pressing part 221 of the cushion 22 and the die forming part 241 of the die 24. By bringing the die 24 and the punch 21 close together, one side wall 11 and the flange 11H extending from the other side wall 11 are drawn, and the other side wall 12 and the flange 11H extending from the other side wall 12 are drawn. This is a press forming method of bending and forming the portion 12H.

Here, the punch 21 includes a top plate forming part 213 forming the top plate part 13 having a hat-shaped cross section, a first side wall forming part 211 forming one side wall part 11, and a first side wall forming part 211 forming the other side wall part 12. It has two side wall molded parts 212 and a flange molded part 212H that forms a flange part 12H extending from the other side wall part 12. Further, the cushion 22 is divided from the first side wall molding portion 211 of the punch 21 and has a wrinkle suppressing portion 221 that forms a flange portion 11H extending from one side wall portion 11, and is movable up and down with respect to the punch 21. It is formed. At the start of molding, the cushion 22 is raised to a position where the wrinkle suppressing part 221 and the top molding part 213 of the punch 21 are approximately at the same height. Therefore, the wrinkle pressing part 221 of the cushion 22 and the die forming part 241 of the die 24 sandwich the material W at the same time or slightly after the pad 23 presses the material W against the top plate forming part 213 of the punch 21. .

Further, the pad 23 is formed to press the material W against the top molding portion 213 of the punch 21 with a predetermined pressing force P1. The pressing device 26 of the pad 23 is attached to a mold stand that supports the die 24. Furthermore, the die 24 has a die forming part 241 that faces the punch 21 and the cushion 22, is arranged along the outer peripheral edge of the pad 23, and forms both side walls 11 and 12 and both flange parts 11H and 12H. . Further, the cushion pressing device 25 is formed to press the cushion 22 against the die 24 with a pressing force P2 that is greater than the pressing force P1 of the pad 23. Note that the cushion pressurizing device 25 includes a locking mechanism that stops the operation (raising) of the cushion 22 from the time when press molding is completed until the pad 23 is separated from the top plate portion 13.

According to the above press forming method, the hat-shaped cross-sectional shape part 1 is continuous in the longitudinal direction, and one side wall part 11 of the hat-shaped cross-sectional shape part 1 has a curvature ratio greater than the curvature ratio X2 of the other side wall part 12. It is possible to improve shape fixability to a regular shape while reducing stretch cracks in one side wall portion 11 of the press part 10 that is curved in the direction of stretch flanging at X1.

That is, a top plate molding part 213 that forms the top plate part 13 with a hat-shaped cross section, a first side wall molding part 211 that forms one side wall part 11, and a second side wall molding part 212 that forms the other side wall part 12. and a flange forming part 212H that forms a flange part 12H extending from the other side wall part 12, and a wrinkle part that is divided from the first side wall forming part 211 and forming a flange part 11H extending from one side wall part 11. A cushion 22 that has a holding part 221 and is formed to be vertically movable with respect to the punch 21 , a pad 23 that presses the material W against the top molding part 213 of the punch 21 , and a pad 23 that faces the punch 21 and the cushion 22 A die 24 having a die forming part 241 arranged along the outer peripheral edge of the pad 23 and forming both side wall parts 11 and 12 and both flange parts 11H and 12H, and a pressing force of the pad 23 that is greater than or equal to the pressing force P1. Since it is equipped with a cushion pressurizing device 25 that presses the cushion 22 against the die 24 at P2, the punch 21 and the pad 23 sandwich the material W on the top plate part 13 side, and the cushion 22 and the die 24 are pressed together. By bringing the punch 21 and die 24 close to each other while holding the material W on one side wall 11 side, one side wall 11 and a flange 11H extending from one side wall 11 are squeezed to form a stretch flange. Can be molded. Further, the punch 21 and the pad 23 sandwich the material W on the top plate part 13 side, and the punch 21 and the die 24 are brought close to each other, so that the other side wall part 12 and the flange part 12H extending from the other side wall part 12 are connected to each other. can be bent and formed.

In addition, in the initial stage when the punch 21, the cushion 22, the pad 23, and the die 24 cooperate to draw and form one side wall portion 11 and the flange portion 11H extending from the one side wall portion 11, which will be stretch flange-formed. , the punch 21 and the die 24 hardly bend the material W on the other side wall portion 12 side. Therefore, the cushion pressurizing device 25 presses the cushion 22 against the die 24 with a pressurizing force P2 that is greater than the pressurizing force P1 of the pad 23, so that the material W on the one side wall portion 11 side, which is stretch-flange formed, is transferred to the punch 21. The raw material W can be made to flow from the other side wall portion 12 side to the one side wall portion 11 side where stretch flange forming is to be performed, while suppressing the amount of flow flowing to the side. Further, by suppressing the amount of material W on one side wall portion 11 side flowing into the punch 21 side, the amount of elongation in the direction of stretch flange forming can also be suppressed.

Moreover, the amount of inflow of the material W on the one side wall portion 11 side that will be stretch flanged is suppressed in the amount flowing into the punch 21 side and the amount of elongation in the direction that will be stretch flanged, and from the other side wall portion 12 side to one side. By drawing-forming one side wall part 11 and a flange part 11H extending from one side wall part 11 while receiving the supply of material W to the side wall part 11 side, one side wall part 11 and one side wall part 11 The elongation rate of the flange portion 11H extending from the flange portion 11H is reduced, and as the elongation rate is reduced, tensile residual stress can also be reduced. As a result, it is possible to reduce the stretch cracking of the one side wall portion 11 and the flange portion 11H extending from the one side wall portion 11 which are subjected to stretch flanging, and it is possible to improve the shape fixability to the regular shape.

Therefore, according to this press forming method, one side wall part 11 of the hat-shaped cross-sectional shape part 1 is curved in the direction of stretch flange forming with a curvature ratio X1 larger than the curvature ratio X2 of the other side wall part 12. It is possible to provide a press forming method that can improve shape fixability while reducing stretch cracks in the component 10.

<Thickness distribution after press forming>
Next, the results of CAE analysis of the plate thickness distribution after press forming will be explained using FIG. 4. FIG. 4 is a distribution diagram of the plate thickness increase/decrease rate in area A of the press part shown in FIG. A distribution diagram of the plate thickness increase/decrease rate in area A when the inflow of the material is prevented, and (B) shows the distribution diagram of the rate of increase/decrease in plate thickness in the A region when the inflow of the material is prevented from flowing from the other side wall side to the one side wall side in the press forming method shown in Fig. 3. A distribution diagram of the plate thickness increase/decrease rate in area A when there is a plate thickness is shown.

In addition, in FIG. 4, the board thickness increase/decrease rate is displayed by the distribution density of dots. In areas where the dot distribution density is high, the plate thickness decrease rate is large, and in areas where the dot distribution density is low, the plate thickness increase rate is large. Here, if the plate thickness reduction rate exceeds 10%, it is determined that elongation cracking has occurred. The locations where stretch cracks have occurred are shown in white. Further, if the plate thickness increase rate exceeds 10%, it is determined that wrinkles have occurred. No wrinkles occur here.

As shown in FIG. 4(A), when the flow of the material W from the other side wall portion 12 side to the one side wall portion 11 side is prevented in the press forming method shown in FIG. In region A of section 11 (including the flange section), the plate thickness reduction rate exceeds 10% at multiple locations, and stretch cracks have occurred. On the other hand, as shown in FIG. 4(B), when the material W flows from the other side wall 12 side to the one side wall 11 side in the press forming method shown in FIG. In region A of the side wall portion 11 (including the flange portion), the plate thickness reduction rate does not exceed 10%, and no elongation cracking occurs.

Therefore, according to the present press forming method, one side wall portion 11 of the hat-shaped cross-sectional shape portion 1 has a curvature larger than the curvature ratio It can be inferred that the shape fixability can be improved while reducing the stretch cracks of the press part 10 which is curved in the direction of stretch flanging at a rate of X1.

<Modified example of this press molding method>
Next, modified examples of the present press forming method will be explained using FIGS. 5 to 7. FIG. 5 is a cross-sectional view of the main part of the first modification of the press forming method shown in FIG. 3, in which (A) shows the main part when the press forming is completed in the first step of forming the other side wall with a small bending angle; A sectional view is shown, and (B) is a sectional view of a main part when press forming is completed in the second step of forming the bending angle of the other side wall part to a regular bending angle. FIG. 6 shows a plan view of essential parts of a second modification of the press forming method shown in FIG. 3. FIG. 7 shows a sectional view of a main part taken along the line DD shown in FIG. 6.

(First modification of this press forming method)
This press molding method can be modified into various forms without changing the gist of the present invention. For example, in the first modification of the present press forming method, as shown in FIG. Form to the regular bending angle α.

Here, in a first step using a press mold 20B shown in FIG. , the bending angle α with respect to the top plate portion 13 is formed to be smaller than the normal bending angle α0. Further, in a second step using a press mold 30 shown in FIG. 5(B), the other side wall portion 12 is formed to have a regular bending angle α0 with respect to the top plate portion 13.

Note that the press die 20B for the first step includes a punch 21B, a cushion 22, a pad 23, a die 24B, and a cushion pressurizing device 25, similar to the press die 20 used in the present press molding method described above. The punch 21B and the die 24B are formed along the other side wall portion 12a and the flange portion 12Ha, which are bent at a bending angle α with respect to the top plate portion 13. The press mold 30 in the second step includes a punch 31 formed in a hat-shaped cross section, a pad 33 for pressing the material W against the punch 31, and a die 32 for forming the other side wall portion 12 and its flange portion 12H. ing.

In this case, when drawing forming one side wall part 11 and the flange part 11H extending from one side wall part 11, the other side wall part 12 is formed so that the bending angle α with respect to the top plate part 13 is smaller than the normal bending angle α0. Therefore, when drawing forming one side wall portion 11 and the flange portion 11H extending from one side wall portion 11, the material W on the other side wall portion 12 side easily passes through the gap between the pad 23 and the punch 21, It is possible to make a larger amount of the material W flow from the other side wall portion 12 side to the one side wall portion 11 side where stretch flange forming is to be performed. As a result, it is possible to further reduce stretch cracks when drawing the one side wall portion 11 and the flange portion 11H extending from the one side wall portion 11, and to further improve shape fixability.

(Second modification of this press forming method)
In the second modification of the present press forming method, as shown in FIGS. 6 and 7, the pad 23 has a region Y1 in which the elongation rate β (β1) of the stretch flange forming in one side wall portion 11 is large and the elongation rate β The pressing force P11 of the pad 23a corresponding to the region Y2 where the elongation rate β (β2) is small is divided into a plurality (for example, two), and the pressing force P11 of the pad 23a corresponding to the region Y1 where the elongation rate β (β1) is large is the elongation rate β (β2) is smaller than the pressing force P12 of the pad 23b corresponding to the small region Y2. Note that the press mold 20C used in the second modification of the present press molding method is equipped with different pad pressing devices 26a and 26b corresponding to the pressing forces P11 and P12. Further, the pressing forces P11 and P12 of the pads 23a and 23b mean the load per unit area of the punch 21 on the top plate forming portion 213.

In this case, when drawing forming the one side wall part 11 and the flange part 11H extending from the one side wall part 11, the pad 23a is Since the pressing force P11 becomes relatively small, the frictional force of the material W held between the pad 23a and the top plate forming part 213 of the punch 21 decreases, and the force of the material W is pushed from the other side wall part 12 side to one side wall. The inflow amount γ1 of the material W flowing into the portion 11 side can be further increased. Therefore, during drawing forming, it is possible to further reduce the stretch cracking of the one side wall part 11 in the region Y1 where the elongation rate β1 (β) of stretch flanging is high and the flange part 11H extending from the one side wall part 11, and the shape fixability. can be further enhanced.

Further, when drawing forming one side wall portion 11 and a flange portion 11H extending from one side wall portion 11, in a region Y2 where the elongation rate β2 (β) of stretch flanging of one side wall portion 11 is small, Since the pressing force P12 becomes relatively large, the frictional force of the material W sandwiched between the pad 23b and the top plate molding part 213 of the punch 21 increases, and one side wall part is pushed from the other side wall part 12 side to the other side wall part 12 side. The inflow amount γ2 of the material W flowing into the 11 side can be reduced. Therefore, in the other side wall portion 12 and the flange portion 12H extending from the other side wall portion 12, deformation due to the inflow of the material W can be suppressed, and shape fixability can be improved.

<Main press mold>
Next, a press mold according to another embodiment will be explained using FIGS. 1 and 8 to 11. FIG. 8 shows a cross-sectional view of a press mold for press-forming the press part (C1-C1 cross section) shown in FIG. 1 at the time of starting molding. FIG. 9 shows a cross-sectional view of the press mold shown in FIG. 8 during molding. FIG. 10 shows a cross-sectional view of the press die shown in FIG. 8 upon completion of molding. FIG. 11 shows a cross-sectional view of the press die shown in FIG. 8 after the press part is released.

As shown in FIGS. 1 and 8 to 11, the press mold 20 according to this other embodiment has a hat-shaped cross-sectional portion 1 that is continuous in the longitudinal direction, and has one of the hat-shaped cross-sectional portions 1. A press die 20 for forming a press part 10 in which a side wall part 11 is curved in a direction of stretch flanging with a curvature ratio X1 larger than a curvature ratio X2 of the other side wall part 12,
A top plate molding part 213 that forms the top plate part 13 with a hat-shaped cross section, a first side wall molding part 211 that forms one side wall part 11, and a second side wall molding part 212 that forms the other side wall part 12; a punch 21 having a flange forming part 212H forming a flange part 12H extending from the other side wall part 12;
A cushion 22 is formed to be movable up and down with respect to the punch 21, and has a wrinkle suppressing part 221 that is separated from the first side wall forming part 211 and forms a flange part 11H extending from one side wall part 11;
a pad 23 that presses the material W against the top plate forming part 213 of the punch 21;
A die 24 having a die forming part 241 that faces the punch 21 and the cushion 22, is arranged along the outer periphery of the pad 23, and forms both side walls 11 and 12 and both flange parts 11H and 12H;
A cushion pressing device 25 that presses the cushion 22 against the die 24 with a pressing force P2 that is greater than the pressing force P1 of the pad 23,
The pad 23 presses the material W against the top molding part 213 of the punch 21, and the wrinkle pressing part 221 of the cushion 22 and the die molding part 241 of the die 24 sandwich the material W, and the die 24 and the punch 21 A press die that draws and forms one side wall portion 11 and a flange portion 11H extending from one side wall portion 11 and bend-forms the other side wall portion 12 and a flange portion 12H extending from the other side wall portion 12 by being brought close to each other. It is 20.

Here, regarding the punch 21, cushion 22, pad 23, die 24, and cushion pressurizing device 25 of the present press mold 20, the points in common with those already explained in the present press molding method are redundant, so the explanation will be omitted. We will omit this and mainly explain the points that are not explained in this press molding method.

The press mold 20 includes a mold stand 28 that supports the punch 21 and a mold stand 29 that supports the die 24. Further, the cushion pressing device 25 includes a pressing pin 251 that presses the cushion 22 toward the die 24, and a support plate 252 that supports the pressing pin 251 so as to be movable up and down.

Further, the pressure pin 251 and the support plate 252 are housed in the mold stand 28 of the punch 21 so as to be movable up and down. A fall stopper 253 is attached to the die base 28 of the punch 21 to catch the support plate 252 in the lowered position. The support plate 252 is formed so as to come into contact with the die cushion pin 3 of the press machine and transmit the pressing force of the die cushion pin 3 to the pressure pin 251. The pressure pin 251 has a head 251T with an enlarged diameter, and the head 251T is accommodated in the seat 281 of the mold stand 28 when the support plate 252 is in the lowered position. Note that the press machine is equipped with a locking mechanism that temporarily stops the die cushion pin 3 at the bottom dead center.

Further, a bending blade 24M made of steel is inserted into the die 24 at a position of a die forming portion 241 that forms the other side wall portion 12 and the flange portion 12H extending from the other side wall portion 12. A pressing device 26 for pressing the pad 23 toward the punch 21 is attached to the mold stand 29 of the die 24. The pressing device 26 of the pad 23 is constituted by, for example, a gas pressurizing cylinder in which a cylinder rod 261 extends and contracts in the vertical direction from a cylinder case filled with nitrogen gas. Further, the cylinder rod 261 of the pressing device 26 for the pad 23 is extended so that the pad 23 comes into contact with the material W before the die forming part 241 at the start of molding.

This press mold 20 operates as follows. First, as shown in FIG. 8, the die cushion pin 3 of the press machine is activated to raise the pressure pin 251 of the cushion pressure device 25 to the raised position, and the wrinkle pressing part 221 of the cushion 22 is moved to the top of the punch 21. It is moved to approximately the same height as the plate forming part 213. Then, by placing the material W on the wrinkle suppressing portion 221 and the top plate forming portion 213 and bringing the die 24 and the punch 21 close to each other, the pad 23 moves the material W onto the top plate forming portion 213 of the punch 21. is pressed with a predetermined pressing force P1.

Next, as shown in FIG. 9, the die 24 and the punch 21 are brought closer to each other, so that the die forming part 241 of the die 24 and the wrinkle suppressing part 221 of the cushion 22 press the material W on one side wall part 11 into a predetermined position. One side wall portion 11 and a flange portion 11T extending from one side wall portion 11 are drawn and formed while being held under a pressing force P2. At this early stage of drawing forming, the gap between the die forming part 241 and the second side wall forming part 212 and the flange forming part 212H of the punch 21 is large, and the material W on the other side wall part 12 side is in a slightly bent state. It is. Further, the pressing force P2 at which the die molding part 241 of the die 24 and the wrinkle suppressing part 221 of the cushion 22 sandwich the material W on one side wall part 11 side is such that the pad 23 presses the material W into the top plate molding part 213 of the punch 21. It is larger than the pressing force P1.

Therefore, while suppressing the amount of material W on one side wall 11 side that will undergo stretch flanging flowing into the punch 21 side, the material W from the other side wall 12 side flows into one side wall 11 side that will undergo stretch flanging. W can be allowed to flow in. Further, by suppressing the amount of material W on one side wall portion 11 side flowing into the punch 21 side, the amount of elongation in the direction of stretch flange forming can also be suppressed.

Next, as shown in FIG. 10, the die 24 and the punch 21 are brought close to each other until they are at the bottom dead center, and an area A consisting of one side wall part 11 and a flange part 11H extending from one side wall part 11 is drawn. The forming is completed, and the bending of the B region consisting of the other side wall portion 12 and the flange portion 12H extending from the other side wall portion 12 is completed. In this state of the bottom dead center, the locking mechanism operates and the die cushion pin 3 of the press machine temporarily stops rising.

Next, as shown in FIG. 11, when the die 24 separates from the punch 21 and moves to the top dead center, the locking mechanism of the die cushion pin 3 is released and the pressure pin 251 is moved to the raised position. At this time, the cushion 22 releases the press part 10 that has been in contact with the wrinkle pressing part 221 and has been molded from the punch 21 . In addition, by attaching the lift device 4 to the punch 21 and lifting the flange portion 12H extending from the other side wall portion 12 with the lift pin 41 of the lift device 4, the press part 10 after forming is completed can be well-balanced without being deformed. The mold can be released from the punch 21.

As described above, in this press mold 20, the pad 23 presses the material W against the top plate forming part 213 of the punch 21, and the wrinkle suppressing part 221 of the cushion 22 and the die forming part 241 of the die 24 sandwich the material W. In this state, the die 24 and the punch 21 are brought close to each other, so that the one side wall portion 11 and the flange portion 11H extending from the one side wall portion 11 are drawn, and the other side wall portion 12 and the flange portion 11H extending from the other side wall portion 12 are drawn. The extending flange portion 12H is bent and formed. Therefore, by drawing-forming one side wall part 11 and the flange part 11H extending from one side wall part 11 while receiving the supply of the material W from the other side wall part 12 side to the one side wall part 11 side, one side wall part 11 can be drawn. The elongation rate of the side wall portion 11 and the flange portion 11H extending from one side wall portion 11 is reduced, and as the elongation rate is reduced, tensile residual stress can also be reduced. As a result, stretch cracking of the one side wall portion 11 and the flange portion 11H extending from the one side wall portion 11 that are stretch flanged can be reduced, and shape fixability can be improved.

Therefore, according to the press mold 20, one side wall portion 11 of the hat-shaped cross-sectional portion 1 is curved in the direction of stretch flange forming with a curvature ratio X1 greater than the curvature ratio X2 of the other side wall portion 12. It is possible to provide a press die 20 that can improve shape fixability while reducing stretch cracks in the component 10.

In addition, in this press mold 20, as shown in FIGS. 8 to 11, the cushion 22 includes a connecting part 222 arranged on the outer peripheral side of the flange forming part 212H, and the connecting part 222 and the wrinkle suppressing part 221 are connected in a ring shape surrounding the punch 21, and the connecting portion 222 or the die 24 is equipped with a distance block 27 that comes into contact with the seat portion 242 of the opposing die 24 or the seat portion 223 of the connecting portion 222. preferable. Further, it is preferable that the pressure position of the cushion pressurizing device 25 on the cushion 22 (the position of the pressure pin 251) be provided at both the position of the wrinkle pressing part 221 and the position of the connecting part 222.

In this case, with the material W being held between the wrinkle suppressing part 221 of the cushion 22 and the die forming part 241 of the die 24, the distance block 27 attached to the connecting part 222 or the die 24 is moved to the seat part of the opposing die 24. 242 or the seat portion 223 of the connecting portion 222 . Therefore, when drawing forming the one side wall part 11 and the flange part 11H extending from the one side wall part 11, the cushion 22 is prevented from tilting in the vertical direction with respect to the punch 21, and the wrinkle suppressing part of the cushion 22 is prevented. The clearance between 221 and the die forming portion 241 of the die 24 can be maintained at a predetermined value. Therefore, it is possible to more stably reduce stretch cracks caused by drawing of the one side wall portion 11 and the flange portion 11H extending from the one side wall portion 11, and improve shape fixability.

<Modified example of this press mold>
Next, a modification of this press mold will be described using FIGS. 12 and 13. FIG. 12 shows a cross-sectional view of a modified example of the press mold shown in FIG. 8 at the time of starting molding. FIG. 13 shows a cross-sectional view of the press mold shown in FIG. 12 during molding.

This press die 20 can be modified into various forms without changing the gist of the present invention. For example, the cushion pressurizing device 25 described above includes a pressurizing pin 251 that presses the cushion 22 toward the die 24 and a support plate 252 that supports the pressurizing pin 251 in a vertically movable manner. It is formed so as to come into contact with the die cushion pin 3 of the machine and transmit the pressurizing force of the die cushion pin 3 to the pressure pin 251. However, the cushion pressurizing device 25 is not necessarily limited to this.

For example, as shown in FIGS. 12 and 13, in the cushion pressurizing device 25D, the cylinder case 252D is attached to the die base 28D of the punch 21D, and the cylinder rod 251D, which extends and contracts with respect to the cylinder case 252D, presses the cushion 22D. The fluid cylinder device 25D may include a locking mechanism 25DR that stops the extension of the cylinder rod 251D from the time press molding is completed until the pad 23 separates from the top plate portion 13.

In this case, without using the die cushion pin 3 with a locking mechanism of the press machine, the press part 10 after press molding can be released from the press die 20D without being deformed. Therefore, the present press mold 20D can be installed in a general-purpose press machine that is not equipped with the die cushion pin 3 with a locking mechanism. Therefore, productivity in press molding can be increased while maintaining product accuracy after the shape of the press part 10 is frozen.

In addition, by arranging the fluid cylinder device 25D in a well-balanced manner with respect to the cushion 22D, the cushion 22 is placed in a well-balanced manner with respect to the punch 21 when one side wall portion 11 and the flange portion 11H extending from the one side wall portion 11 are drawn. It is preferable to prevent tilting in the vertical direction and maintain the clearance between the wrinkle suppressing part 221 of the cushion 22 and the die forming part 241 of the die 24 at a predetermined value.

Further, as described above, the cushion 22D includes a connecting portion 222 disposed on the outer peripheral side of the flange forming portion 212H, and the connecting portion 222 and the wrinkle suppressing portion 221D are connected in a ring shape surrounding the punch 21, The connecting portion 222 or the die 24 may be equipped with a distance block 27 that comes into contact with the seat portion 242 of the opposing die 24 or the seat portion 223 of the connecting portion 222. In this case as well, it is preferable that the pressure positions of the cushion pressurizing device 25D (the position of the cylinder rod 251D) on the cushion 22D are provided at the wrinkle suppressing part 221D and the connecting part 222. As a result, it is possible to more stably reduce stretch cracks caused by drawing of the one side wall portion 11 and the flange portion 11H extending from the one side wall portion 11, and improve shape fixability.

<Effect>
As described above in detail, according to the press molding method of the present embodiment, the top plate forming part 213 forming the top plate part 13 having a hat-shaped cross section, and the first side wall forming part forming one side wall part 11 punches 21, 21B, and 21D each having a second sidewall forming portion 212 forming the other sidewall portion 12, and a flange forming portion 212H forming the flange portion 12H extending from the other sidewall portion 12; A cushion 22 is divided from the side wall molding part 211 and has wrinkle suppressing parts 221 and 221D forming a flange part 11H extending from one side wall part 11, and is formed to be vertically movable with respect to the punches 21, 21B and 21D. , 22D, pads 23, 23C that press the material W against the top plate forming portion 213 of the punches 21, 21B, 21D, and pads 23, 23C that face the punches 21, 21B, 21D and the cushions 22, 22D, Dies 24, 24B having die forming portions 241 arranged along the periphery and forming both side wall portions 11, 12 and both flange portions 11H, 12H, and pads 23, 23C with a pressing force P2 greater than the pressing force P1. The pads 23, 23C press the material W against the top molding parts 213 of the punches 21, 21B, 21D, and the cushion pressing devices 25, 25D press the cushions 22, 22D against the dies 24, 24B. With the wrinkle suppressing parts 221 of 22, 22D and the die forming parts 241 of the dies 24, 24B sandwiching the material W, the dies 24, 24B and the punches 21, 21B, 21D are brought close to each other, so that one side wall part 11 and the flange portion 11H extending from one side wall portion 11 are drawn and formed, and the other side wall portion 12 and the flange portion 12H extending from the other side wall portion 12 are formed by bending, so that a hat-shaped cross-sectional shape that continues in the longitudinal direction is formed. 1, and one side wall 11 of the hat-shaped cross-sectional portion 1 is curved in the direction of stretch flanging at a curvature X1 larger than the curvature X2 of the other side wall 12. It is possible to improve shape fixability to a regular shape while reducing elongation cracking of the side wall portion 11.

That is, a top plate molding part 213 that forms the top plate part 13 with a hat-shaped cross section, a first side wall molding part 211 that forms one side wall part 11, and a second side wall molding part 212 that forms the other side wall part 12. and a flange forming part 212H forming a flange part 12H extending from the other side wall part 12, and a flange part 11H that is divided from the first side wall forming part 211 and extending from one side wall part 11. The material W is applied to the cushions 22, 22D, which are formed to be vertically movable with respect to the punches 21, 21B, 21D, and the top plate forming portions 213 of the punches 21, 21B, 21D. Opposed to the pressing pads 23, 23C, the punches 21, 21B, 21D, and the cushions 22, 22D, are arranged along the outer periphery of the pads 23, 23C, and are arranged along the outer periphery of the pads 23, 23C, and have side walls 11, 12 and both flanges 11H, 12H. a cushion pressing device 25 that presses the cushions 22, 22D against the dies 24, 24B with a pressing force P2 that is greater than the pressing force P1 of the pads 23, 23C; 25D, the punches 21, 21B, 21D and pads 23, 23C sandwich the material W on the top plate 13 side, and the cushions 22, 22D and dies 24, 24B sandwich the material W on the side wall 11 side. While holding the material W, the punches 21, 21B, 21D and the dies 24, 24B come close to each other, thereby drawing one side wall part 11 and the flange part 11H extending from the other side wall part 11, which will be stretch flange-formed. Can be molded. Further, the punches 21, 21B, 21D and the pads 23, 23C sandwich the material W on the top plate portion 13 side, and the punches 21, 21B, 21D and the dies 24, 24B are close to each other, so that the other side wall portion 12 and the flange portion 12H extending from the other side wall portion 12 can be formed by bending.

In addition, the punches 21, 21B, 21D, the cushions 22, 22D, the pads 23, 23C, and the dies 24, 24B cooperate to form one side wall 11 and a flange extending from the other side wall 11, forming a stretch flange. 11H, the punches 21, 21B, 21D and the dies 24, 24B have hardly bent the material W on the other side wall portion 12 side. Therefore, the cushion pressurizing devices 25, 25D press the cushions 22, 22D against the dies 24, 24B with a pressurizing force P2 that is greater than the pressurizing force P1 of the pads 23, 23C, so that one side wall portion is stretch-flange formed. While suppressing the amount of material W flowing into the punch 21 side, the material W can flow from the other side wall portion 12 side to the one side wall portion 11 side where stretch flange forming is to be performed.

Further, the pads 23 and 23C press the material W against the top plate forming portions 213 of the punches 21, 21B and 21D, and the wrinkle suppressing portions 221 of the cushions 22 and 22D and the die forming portions 241 of the dies 24 and 24B press the material W. By bringing the dies 24, 24B and the punches 21, 21B, 21D close to each other in the sandwiched state, one side wall portion 11 and the flange portion 11H extending from one side wall portion 11 are drawn, and the other side wall portion 12 is drawn. Since the flange portion 12H extending from the other side wall portion 12 is bent and formed, the material W is supplied from the other side wall portion 12 side to the one side wall portion 11 side while the one side wall portion 11 and the one side wall portion 12H are bent. By drawing and forming the flange portion 11H extending from the portion 11, the elongation rate of one side wall portion 11 and the flange portion 11H extending from the one side wall portion 11 is reduced, and as the elongation rate is reduced, tensile residual stress is also reduced. can. As a result, it is possible to reduce the stretch cracking of the one side wall portion 11 and the flange portion 11H extending from the one side wall portion 11 which are subjected to stretch flanging, and it is possible to improve the shape fixability to the regular shape.

Therefore, according to the present embodiment, one side wall portion 11 of the hat-shaped cross-sectional portion 1 is curved in the direction of stretch flange forming at a curvature ratio X1 larger than the curvature ratio X2 of the other side wall portion 12. It is possible to provide a press molding method that can improve shape fixability while reducing stretch cracks in No. 10.

Further, according to the present embodiment, the other side wall portion 12 is formed so that the bending angle α with respect to the top plate portion 13 is smaller than the normal bending angle α0, and is formed to the normal bending angle α in a post process. When drawing forming one side wall part 11 and a flange part 11H extending from one side wall part 11, the other side wall part 12 is formed so that the bending angle α with respect to the top plate part 13 is smaller than the normal bending angle α0. Therefore, when drawing forming one side wall part 11 and the flange part 11H extending from one side wall part 11, the material W on the other side wall part 12 side fills the gap between the pad 23 and the top plate forming part 213 of the punch 21B. It becomes easier to pass through, and more material W can flow from the other side wall portion 12 side to one side wall portion 11 side where stretch flange forming is to be performed. As a result, it is possible to further reduce stretch cracks when drawing the one side wall portion 11 and the flange portion 11H extending from the one side wall portion 11, and to further improve shape fixability.

Further, according to the present embodiment, the pad 23C corresponds to the area Y1 where the elongation rate β (β1) of stretch flange forming in one side wall portion 11 is large and the area Y2 where the elongation rate β (β2) is small. Divided into a plurality of parts, the pressing force P11 of the pad 23a corresponding to the region Y1 where the elongation rate β (β1) is large is smaller than the pressing force P12 of the pad 23b corresponding to the region Y2 where the elongation rate β (β2) is small. When drawing forming the side wall portion 11 and the flange portion 11H extending from one side wall portion 11, in a region Y1 where the elongation rate β1 (β) of one side wall portion 11 is large, one side wall is drawn from the other side wall portion 12 side. The inflow amount γ1 of the material W flowing into the portion 11 side can be further increased. Therefore, during drawing forming, stretch cracking of one side wall part 11 in region Y1 where the elongation rate β1 (β) of stretch flange forming is large and the flange part 11H extending from one side wall part 11 can be further reduced. can be further enhanced.

Moreover, when drawing forming one side wall part 11 and the flange part 11H extending from one side wall part 11, the pressing force P12 of the pad 23b is Since it becomes relatively large, it is possible to reduce the inflow amount γ2 of the material W flowing from the other side wall portion 12 side to the one side wall portion 11 side. Therefore, in the other side wall portion 12 and the flange portion 12H extending from the other side wall portion 12, deformation due to the inflow of the material W can be suppressed, and shape fixability can be improved.

According to the press molds 20, 20B, 20C, and 20D according to the other embodiments, the top plate molding part 213 forms the top plate part 13 with a hat-shaped cross section, and the first side wall molding forms the one side wall part 11. punches 21, 21B, and 21D each having a second sidewall forming portion 212 forming the other sidewall portion 12, and a flange forming portion 212H forming the flange portion 12H extending from the other sidewall portion 12; Cushions 22, 22D are separated from the side wall molding part 211, have a wrinkle suppressing part 221 forming a flange part 11H extending from one side wall part 11, and are formed to be movable up and down with respect to the punches 21, 21B, 21D. and pads 23, 23C that press the material W against the top plate forming portions 213 of the punches 21, 21B, 21D, facing the punches 21, 21B, 21D and the cushions 22, 22D, and on the outer periphery of the pads 23, 23C. The dies 24 and 24B have die forming parts 241 that are arranged along the side and form both the side walls 11 and 12 and both the flanges 11H and 12H, and the pads 23 and 23C. , 24B. With the wrinkle suppressing part 221 of 22D and the die forming part 241 of the dies 24, 24B sandwiching the material W, the dies 24, 24B and the punches 21, 21B, 21D are brought close to each other, so that one side wall part 11 and Since the flange portion 11H extending from one side wall portion 11 is drawn and formed, and the other side wall portion 12 and the flange portion 12H extending from the other side wall portion 12 are bent, the hat-shaped cross-sectional portion 1 continues in the longitudinal direction. One side wall of a press part 10 in which one side wall part 11 of the hat-shaped cross-sectional shape part 1 is curved in the direction of stretch flanging at a curvature ratio X1 larger than the curvature ratio X2 of the other side wall part 12. It is possible to improve shape fixability to the regular shape while reducing stretch cracks in the portion 11.

That is, a top plate molding part 213 that forms the top plate part 13 with a hat-shaped cross section, a first side wall molding part 211 that forms one side wall part 11, and a second side wall molding part 212 that forms the other side wall part 12. and a flange forming part 212H forming a flange part 12H extending from the other side wall part 12, and a flange part 11H that is divided from the first side wall forming part 211 and extending from one side wall part 11. The cushions 22, 22D are formed to be vertically movable with respect to the punches 21, 21B, 21D and have wrinkle suppressing parts 221, 221D that form the material. Pads 23, 23C that press W, punches 21, 21B, 21D, and cushions 22, 22D are arranged along the outer periphery of the pads 23, 23C, and both side walls 11, 12 and both flanges 11H , 12H, and a cushion pressurizing device that presses the cushions 22, 22D against the dies 24, 24B with a pressurizing force P2 that is greater than the pressurizing force P1 of the pads 23, 23C. 25, 25D, the punches 21, 21B, 21D and pads 23, 23C sandwich the material W on the top plate 13 side, and the cushions 22, 22D and dies 24, 24B hold the material W on one side wall. By bringing the punches 21, 21B, 21D and dies 24, 24B close to each other while holding the material W on the side 11, one side wall portion 11 and a flange portion 11H extending from the other side wall portion 11 undergo stretch flange forming. can be drawn and formed. Further, the punches 21, 21B, 21D and the pads 23, 23C sandwich the material W on the top plate portion 13 side, and the punches 21, 21B, 21D and the dies 24, 24B are close to each other, so that the other side wall portion 12 and the flange portion 12H extending from the other side wall portion 12 can be formed by bending.

In addition, the punches 21, 21B, 21D, the cushions 22, 22D, the pads 23, 23C, and the dies 24, 24B cooperate to form one side wall 11 and a flange extending from the other side wall 11, forming a stretch flange. 11H, the punches 21, 21B, 21D and the dies 24, 24B have hardly bent the material W on the other side wall portion 12 side. Therefore, the cushion pressurizing devices 25, 25D press the cushions 22, 22D against the dies 24, 24B with a pressurizing force P2 that is greater than the pressurizing force P1 of the pads 23, 23C, so that one side wall portion is stretch-flange formed. While suppressing the amount of material W flowing into the punches 21, 21B, and 21D, the material W can flow from the other side wall portion 12 side to one side wall portion 11 side for stretch flange forming. .

Further, the pads 23 and 23C press the material W against the top plate forming portions 213 of the punches 21, 21B and 21D, and the wrinkle suppressing portions 221 of the cushions 22 and 22D and the die forming portions 241 of the dies 24 and 24B press the material W. By bringing the dies 24, 24B and the punches 21, 21B, 21D close to each other in the sandwiched state, one side wall portion 11 and the flange portion 11H extending from one side wall portion 11 are drawn, and the other side wall portion 12 is drawn. Since the flange portion 12H extending from the other side wall portion 12 is bent and formed, the material W is supplied from the other side wall portion 12 side to the one side wall portion 11 side while the one side wall portion 11 and the one side wall portion 12H are bent. By drawing and forming the flange portion 11H extending from the portion 11, the elongation rate of one side wall portion 11 and the flange portion 11H extending from the one side wall portion 11 is reduced, and as the elongation rate is reduced, tensile residual stress is also reduced. can. As a result, it is possible to reduce the stretch cracking of the one side wall portion 11 and the flange portion 11H extending from the one side wall portion 11 which are subjected to stretch flanging, and it is possible to improve the shape fixability to the regular shape.

Therefore, according to this other embodiment, one side wall part 11 of the hat-shaped cross-sectional shape part 1 is curved in the direction of stretch flange forming with a curvature ratio X1 larger than the curvature ratio X2 of the other side wall part 12. It is possible to provide press dies 20, 20B, 20C, and 20D that can improve shape fixability while reducing elongation cracking of the press part 10.

Further, according to this other embodiment, the cushion 22 includes a connecting portion 222 disposed on the outer peripheral side of the flange forming portion 212H, and the connecting portion 222 and the wrinkle suppressing portion 221 are arranged in a ring shape surrounding the punch 21. Since the distance block 27 that comes into contact with the seat 242 of the opposing die 24, 24B or the seat 223 of the coupling part 222 is attached to the coupling part 222 or the dies 24, 24B, wrinkles on the cushion 22 are prevented. With the holding portion 221 and the die forming portion 241 of the die 24, 24B sandwiching the material W, the distance block 27 attached to the connecting portion 222 or the die 24, 24B presses the seat portion 242 of the opposing die 24, 24B. Alternatively, it can come into contact with the seat portion 223 of the connecting portion 222. Therefore, when drawing forming one side wall part 11 and the flange part 11H extending from one side wall part 11, the cushion 22 is prevented from being inclined in the vertical direction with respect to the punches 21 and 21B, and wrinkles of the cushion 22 are prevented. The clearance between the holding part 221 and the die forming part 241 of the dies 24 and 24B can be maintained at a predetermined value. Therefore, it is possible to more stably reduce stretch cracks caused by drawing of the one side wall portion 11 and the flange portion 11H extending from the one side wall portion 11, and improve shape fixability.

Moreover, according to this other embodiment, the cushion pressurizing device 25D has a cylinder case 252D attached to the die base 28D of the punch 21D, and a cylinder rod 251D that extends and contracts with respect to the cylinder case 252D, which presses the cushion 22D. Since the cylinder device 25D has a locking mechanism 25DR that stops the extension of the cylinder rod 251D from the time press molding is completed until the pad 23 separates from the top plate 13, the die cushion pin with the locking mechanism of the press machine is used. 3, the press part 10 after press molding can be released from the press mold 20D without being deformed. Therefore, the present press mold 20D can be installed in a general-purpose press machine that is not equipped with the die cushion pin 3 with a locking mechanism. Therefore, productivity in press molding can be increased while maintaining product accuracy after the shape of the press part 10 is frozen.

The present invention has a hat-shaped cross-sectional portion that is continuous in the longitudinal direction, and one side wall portion of the hat-shaped cross-sectional portion is stretched in the direction of flanging with a higher curvature ratio than the other side wall portion. It can be used as a press molding method for molding curved press parts and a press mold thereof.

1 Hat-shaped cross-sectional portion 10 Press parts 11, 12, 12a Side wall portions 11H, 12H, 12Ha Flange portion 13 Top plate portion 20, 20B, 20C, 20D Press mold 21, 21B, 21D Punch 22, 22D Cushion 23, 23C, 23a, 23b Pad 24, 24B Die 25, 25D Cushion pressure device 25D Fluid cylinder device 25DR Lock mechanism 27 Distance block 28, 28D Mold stand 211 First side wall forming section 212 Second side wall forming section 213 Top plate forming section 212H Flange forming Parts 221, 221D Wrinkle suppressing part 222 Connecting part 223 Seat part 241 Die forming part 242 Seat part 251D Cylinder rod 252D Cylinder case P1, P11, P12 Pressing force P2 Pressing force W Material X1, X2 Curvature ratio Y1, Y2 Area α, α0 Bending angle β, β1, β2 Elongation rate

Claims (6)

A press that has a hat-shaped cross-sectional shape continuous in the longitudinal direction, and one side wall of the hat-shaped cross-sectional shape is curved in the direction of stretch flange forming with a higher curvature ratio than the other side wall. A press forming method for forming parts,
A top plate molding part forming a top plate part with a hat-shaped cross section, a first side wall molding part forming the one side wall part, a second side wall molding part forming the other side wall part, and the other side wall. a flange forming part forming a flange part extending from the punch;
a cushion formed to be movable up and down with respect to the punch, having a wrinkle suppressing part that is divided from the first side wall molding part and forming a flange part extending from the one side wall part;
a pad that presses a material against the top plate forming part of the punch;
a die having a die forming part facing the punch and the cushion, disposed along the outer periphery of the pad, and forming the both side walls and the flanges;
a cushion pressing device that presses the cushion against the die with a pressing force greater than the pressing force of the pad;
The die and the punch are brought close to each other with the pad pressing the material against the top molding part of the punch and the wrinkle suppressing part of the cushion and the die molding part of the die sandwiching the material. A press characterized in that the one side wall portion and the flange portion extending from the one side wall portion are drawn and formed by bending the other side wall portion and the flange portion extending from the other side wall portion. Molding method. In the press forming method according to claim 1,
The press molding method is characterized in that the other side wall portion is formed to have a bending angle smaller than a normal bending angle with respect to the top plate portion, and is formed to have the normal bending angle in a post process. In the press forming method according to claim 1 or claim 2,
The pad is divided into a plurality of parts corresponding to a region where the elongation rate is large and a region where the elongation rate is small in the stretch flange forming on the one side wall portion,
A press molding method characterized in that a pressing force of the pad corresponding to the area where the elongation rate is high is smaller than a pressing force of the pad corresponding to the area where the elongation rate is small. A press that has a hat-shaped cross-sectional shape continuous in the longitudinal direction, and one side wall of the hat-shaped cross-sectional shape is curved in the direction of stretch flange forming with a higher curvature ratio than the other side wall. A press mold for molding parts,
A top plate molding part forming a top plate part with a hat-shaped cross section, a first side wall molding part forming the one side wall part, a second side wall molding part forming the other side wall part, and the other side wall. a flange forming part forming a flange part extending from the punch;
a cushion formed to be movable up and down with respect to the punch, having a wrinkle suppressing part that is divided from the first side wall molding part and forming a flange part extending from the one side wall part;
a pad that presses a material against the top plate forming part of the punch;
a die having a die forming part facing the punch and the cushion, disposed along the outer periphery of the pad, and forming the both side walls and the flanges;
a cushion pressing device that presses the cushion against the die with a pressing force greater than the pressing force of the pad;
The die and the punch are brought close to each other with the pad pressing the material against the top molding part of the punch and the wrinkle suppressing part of the cushion and the die molding part of the die sandwiching the material. A press characterized in that the one side wall portion and the flange portion extending from the one side wall portion are drawn and formed by bending the other side wall portion and the flange portion extending from the other side wall portion. Type. In the press mold according to claim 4,
The cushion includes a connecting part disposed on the outer peripheral side of the flange forming part, and the connecting part and the wrinkle suppressing part are connected in a ring shape surrounding the punch,
A press mold characterized in that the connecting portion or the die is equipped with a distance block that comes into contact with a seat of the opposing die or a seat of the connecting portion. In the press mold according to claim 4 or claim 5,
The cushion pressurizing device is a fluid cylinder device in which a cylinder case is attached to the die base of the punch, and a cylinder rod that expands and contracts with respect to the cylinder case presses the cushion, and the pad presses the cushion after press molding is completed. A press mold characterized in that it has a locking mechanism that stops the extension of the cylinder rod until it is separated from the top plate part.

Images