JP2024039227A - Manufacturing method and manufacturing facility for press-molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve accuracy of dimensions of a press-molded product.

SOLUTION: A manufacturing method for a press-molded product K3 comprises an arrangement step (e) of arranging an intermediate molded product K2, and pressing steps (f)-(h) of press-molding the intermediate molded product K2. The intermediate molded product K2 includes a center part CH, a pair of large R parts LR, a small R part SR and an extending part EN. The large R parts LR are bent in a convex shape toward a first direction, and the small R part SR is bent in a convex shape toward the opposite direction of the first direction. A curvature radius of the small R part SR is smaller than curvature radiuses of the large R parts LR. In the arrangement step (e), at least portions of the large R parts LR are arranged at positions where the portions overlap with a shoulder part 5b of a first metal mold 5 when viewed from a pressing direction. In the pressing step, the large R parts LR are bent along the shoulder part 5b, and the small R part SR is press-molded into a shape extending along a side surface 5c while being bent back.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to press molding technology using a mold.

In general, press equipment places the material to be pressed between a pair or more of molds, and moves the pair or more of the molds close to each other until they reach the bottom dead center. Press mold into a shape according to the shape. After a press-formed product is removed from a mold, its shape may change due to residual stress at the bottom dead center. This phenomenon is called springback (SB), elastic recovery, etc., and is a cause of a decrease in shape accuracy.

As a countermeasure against springback, Japanese Patent Laid-Open No. 2006-015404 (Patent Document 1) describes a method of forming a Z-shaped member or a hat channel-shaped member having a flange portion. This method includes a first forming step of bending a metal plate to form a temporarily formed member, and a second forming step of bending and forming the temporarily formed member to obtain a formed member having a target shape. In the temporarily formed member formed in the first forming step, a temporary vertical flat part is connected from one end of the temporary horizontal flat part through a temporary bent part, and a temporary vertical flat part is connected from the other end of the temporary vertical flat part through a second bent part. It has a shape in which the flange portions are connected. In the first molding step, the metal plate is deformed and molded between a pair of mold parts for molding the temporary vertical flat part so that two arch parts with convex parts facing in opposite directions are formed. In the second forming step, the temporary horizontal flat portion of the temporarily formed member is bent and formed, and the temporarily bent portion is bent back and formed.

Furthermore, in JP-A No. 2017-196646 (Patent Document 2), when press-molding a press-molded part having a hat-shaped cross section having a top plate part, a vertical wall part, and a flange part, the walls of the press-formed part are opened due to springback. A press molding method that suppresses this is described. This forming method includes a first forming process in which a metal blank is formed into a temporarily formed part using a first mold, and a second forming process in which the temporarily formed part is formed into a target shape using a second mold. It has a process. In the first molding step, a temporarily molded part is molded which includes a vertical wall portion having a mountain-shaped cross section whose cross section in the molding direction is outwardly convex compared to the target shape.

Japanese Patent Application Publication No. 2006-015404 Japanese Patent Application Publication No. 2017-196646

In the above conventional technology, the intermediate molded product temporarily formed in the first molding step is molded into the target shape in the second molding step. In the second molding step, the second mold is lowered with the intermediate molded product placed on the convex portion of the first mold. The intermediate molded product is sandwiched between the first mold and the second mold at the bottom dead center and molded into the target shape. However, the inventors have discovered that in the above-mentioned conventional technology, the molded product tends to spring back, resulting in a decrease in dimensional accuracy.

An object of the present disclosure is to improve the dimensional accuracy of a press-formed product.

The method for manufacturing a press-formed product in an embodiment of the present disclosure includes:
arranging the intermediate molded product between a first mold having a convex portion convex in the pressing direction and a second mold having a concave portion corresponding to the convex portion;
a pressing step of bringing the first mold and the second mold relatively close together and press-molding the intermediate molded product into a shape that corresponds to the convex part of the first mold and the concave part of the second mold; and has.
The convex portion of the first mold has a top surface, a pair of shoulders at both ends of the top surface, and side surfaces extending from the pair of shoulders, respectively.
The intermediate molded product includes a central portion, a pair of large R portions on both sides of the central portion, small R portions on the outside of each of the pair of large R portions, and an extending portion on the outside of the small R portion. including;
The large R portion is curved convexly in a first direction, and the small R portion is curved convexly in a second direction opposite to the first direction.
The radius of curvature of the small R portion is smaller than the radius of curvature of the large R portion,
In the arrangement step, the intermediate molded product is placed so that the first direction is a direction toward the first mold in the press direction, and the second direction is a direction toward the second mold in the press direction. is arranged, and at least a part of each of the pair of large radius parts is arranged at a position overlapping each of the pair of shoulders of the convex part of the first mold when viewed from the press direction,
In the pressing step, the pair of large R portions of the intermediate molded product are bent along the pair of shoulders of the convex portion of the first mold, and the small R portion is bent back to form the convex portion. It is press-molded into a shape that follows the side surface.

FIG. 1 is a diagram showing steps in a method for manufacturing a press-formed product in this embodiment. FIG. 2 is a diagram showing an example of the pressing process of the second press device in more detail. FIG. 3 is a diagram for explaining the function of the large R portion LR. FIG. 4 is a diagram for explaining the positional relationship between the first mold 5 and the intermediate molded product K2. FIG. 5 is a sectional view showing a configuration example of the first press device 10. As shown in FIG. FIG. 6 is a sectional view showing a configuration example of the second press device 20. As shown in FIG. FIG. 7 is a side view of the first mold 3 shown in FIG. 5 and the first mold 5 shown in FIG. 6 as viewed from the width direction (y direction). FIG. 8 is a diagram for explaining the relationship between the configurations of the molds of the first press device and the molds of the second press device. FIG. 9 is a diagram showing an example of the configuration of the intermediate molded product K2. FIG. 10 is a diagram showing a modification of the first mold. FIG. 11 is a diagram showing another modification of the first mold. FIG. 12 is a diagram for explaining another modification of the intermediate molded product. FIG. 13 is a diagram for explaining another modification of the intermediate molded product. FIG. 14 is a diagram showing a modification of the first press device 10. As shown in FIG. FIG. 15 is a diagram showing a further modification of the first press device 10 shown in FIG. 14. FIG. 16 is a diagram showing a modification of the second press device 20. As shown in FIG. FIG. 17 is a diagram showing another modification of the second press device 20. FIG. 18 is a diagram showing another modification of the second press device 20. FIG. 19 is a diagram showing the shape of a press-formed product to be analyzed in the example. FIG. 20 is a diagram showing a comparative construction method. FIG. 21 is a diagram showing an example construction method. FIG. 22 is a diagram showing evaluation items of the example. FIG. 23 is a diagram showing evaluation items of the example.

(Manufacturing method 1)
The method for manufacturing a press-formed product in an embodiment of the present disclosure includes:
arranging the intermediate molded product between a first mold having a convex portion convex in the pressing direction and a second mold having a concave portion corresponding to the convex portion;
a pressing step of bringing the first mold and the second mold relatively close together and press-molding the intermediate molded product into a shape that corresponds to the convex part of the first mold and the concave part of the second mold; and has.
The convex portion of the first mold has a top surface, a pair of shoulders at both ends of the top surface, and side surfaces extending from the pair of shoulders, respectively.
The intermediate molded product includes a central portion, a pair of large R portions on both sides of the central portion, small R portions on the outside of each of the pair of large R portions, and an extending portion on the outside of the small R portion. including;
The large R portion is curved convexly in a first direction, and the small R portion is curved convexly in a second direction opposite to the first direction.
The radius of curvature of the small R portion is smaller than the radius of curvature of the large R portion,
In the arrangement step, the intermediate molded product is placed so that the first direction is a direction toward the first mold in the press direction, and the second direction is a direction toward the second mold in the press direction. is arranged, and at least a part of each of the pair of large radius parts is arranged at a position overlapping each of the pair of shoulders of the convex part of the first mold when viewed from the press direction,
In the pressing step, the pair of large R portions of the intermediate molded product are bent along the pair of shoulders of the convex portion of the first mold, and the small R portion is bent back to form the convex portion. It is press-molded into a shape that follows the side surface.

According to the above manufacturing method 1, at the beginning of the pressing process, the top surface of the first mold comes into contact with the center of the intermediate molded product, and the second mold moves the intermediate molded product toward the first mold. push. At this time, the large R portion is curved convexly relative to the shoulder portion inside the small R portion. Therefore, from the beginning of the pressing process, at least a portion of the large radius portion is in contact with the shoulder and is bent in the opposite direction to the original curve while being pushed by the shoulder. That is, from the beginning of the pressing process, the intermediate molded product is bent in the opposite direction while wrapping around the shoulder of the first mold. In this way, as the forming progresses while the large R part firmly attaches to the shoulder, the material around the shoulder is stretched, reducing the compressive stress on the inside of the bend due to the shoulder, and the stress on the inside and outside of the bend increases. The stress difference between the front and back surfaces is reduced. As a result, the moment of wall opening that attempts to undo the bending caused by the shoulder due to residual stress is reduced. Furthermore, by bending back at least a portion of the small radius portion, tensile stress acts on the inside of the molded product and compressive stress acts on the outside during molding. Therefore, when springback occurs, compressive stress is generated on the inside of the molded product and tensile stress is generated on the outside. That is, a springback wall opening moment and a wall closing moment opposite to each other are generated. The combination of the molding behavior of the large radius portion and the small radius portion reduces springback and improves the dimensional accuracy of the press-formed product.

The large radius portion and the small radius portion are curved portions. The curved portion is a portion of the plate material of the intermediate molded product that is not flat but curved. The large radius portion and the small radius portion may also be referred to as a large curved portion and a small curved portion, respectively. The convex direction of curvature of the large radius portion and the convex direction of curvature of the small radius portion are opposite to each other. A form in which the radius of curvature of the small R part is smaller than the radius of curvature of the large R part is, for example, a form in which the curvature of the small R part is larger than the curvature of the large R part, that is, the bend is sharp enough to be visually recognizable. There may be. Note that the curvature of the large-R portion and the small-R portion is a curvature in a cross section perpendicular to the longitudinal direction of the central portion of the intermediate molded product.

(Manufacturing method 2)
In the manufacturing method 1, in the arrangement step, the following line lengths 1A, 1C, 1F, 2A, and 2C in a cross section perpendicular to the longitudinal direction of the convex portion are:
2C<1F, 1A<2C, 2A<1C
It is preferable that the intermediate molded product is arranged so as to have the following relationship. This improves the fit of the large radius portion to the shoulder portion during molding, and further increases the effect of reducing springback by bending back the small radius portion.
The line length 1A is the length (line length) of a line along the intermediate molded product from a reference point in the center of the intermediate molded product to the radius stop on the inside of the large radius portion.
The line length 1C is the line length from the reference point to the radius stop outside the large radius section.
1F is the line length from the reference point to the outer R stop of the small R portion.
2A is the length ( line length).
2C is the line length from the mold reference point to the radius stop on the outside of the shoulder.

By arranging the intermediate molded product with respect to the first mold as in the above manufacturing method 2, at the bottom dead center of the pressing process, the part including at least the inner R stop of the shoulder of the convex part of the first mold The portion that was the large radius portion contacts, and at least a portion of the portion that was the small radius portion contacts the side surface of the convex portion.
Note that the line length of the intermediate molded product in the cross section is the length of the line along the surface of the placed intermediate molded product on the first mold side. Further, the line length of the first mold in the cross section is the length of the line along the surface of the first mold.

The longitudinal direction of the convex part of the first mold is perpendicular to the press direction, and is the direction in which the intermediate line between the ridge lines of the pair of shoulders of the convex part extends when viewed from the press direction. The longitudinal direction of the convex portion is perpendicular to the pressing direction. The longitudinal direction of the convex portion may be a straight line or may be curved when viewed from the pressing direction.
The shape of the central part of the intermediate molded product corresponds to the shape of the top surface of the convex part of the first mold. The intermediate molded product is arranged with respect to the first mold such that the longitudinal direction of the central portion is substantially the same as the longitudinal direction of the convex portion. The longitudinal direction of the central part of the intermediate molded product is the direction in which the intermediate line between the pair of large R parts extends when viewed from the pressing direction.
In the arrangement step, at least a portion of each of the pair of large radius portions of the intermediate molded product is located over the entire longitudinal direction of the convex portion of the first mold when viewed from the pressing direction. It is preferable that the shoulder portions are arranged at positions overlapping each other.

(Manufacturing method 3)
In the manufacturing method 2, in the arrangement step, in a cross section perpendicular to the longitudinal direction of the convex portion, the following line lengths 1B and 2E are:
2C<1E, 2A<1B<2C
It is preferable that the intermediate molded product is arranged so as to have the following relationship. This improves the fit of the large radius portion to the shoulder portion during molding, and further increases the effect of reducing springback by bending back the small radius portion.
The line length 1B is the line length from the reference point to the midpoint of the line along the intermediate molded product between the inner R stop and the outer R stop of the large R portion.
The line length 1E is the line length from the reference point to the midpoint of the line along the intermediate molded product between the inner R stop and the outer R stop of the small R portion.

In the manufacturing method 3, in the pressing step, the middle point of the large radius portion is in contact with the shoulder of the convex portion of the first mold, and more than half of the small radius portion is in contact with the side surface of the convex portion, An intermediate molded product is placed against the first mold.

(Manufacturing method 4)
In the manufacturing method 2 or 3, in the arrangement step, in a cross section perpendicular to the longitudinal direction of the convex portion, a line length 1D from the reference point to the inner R end of the small R portion is:
2C<1D
It is preferable that the intermediate molded product is arranged so as to have the following relationship. This improves the fit of the large radius portion to the shoulder portion during molding, and further increases the effect of reducing springback by bending back the small radius portion.

In manufacturing method 4, the intermediate molded product is placed with respect to the first mold in the pressing step so that the entire small radius portion is in contact with the side surface of the convex portion.

In any of the manufacturing methods 2 to 4 and the following manufacturing methods 5 to 9, in the arranging step, in a cross section perpendicular to the longitudinal direction of the convex part, from the reference point to the inner R end of the small R part The line length 1D is
1D<2C+(2C-2A)
It is preferable that the intermediate molded product is arranged so as to have the following relationship. This improves the fit of the large radius portion to the shoulder portion during molding, and further increases the effect of reducing springback by bending back the small radius portion. In this case, in the pressing process, the intermediate molded product is formed so that the small radius portion touches the inner side (i.e., the top plate side) of the side surface of the convex portion than the position spaced from the shoulder by the line length of the shoulder. is placed relative to the first mold. With this positional relationship, when the molded product is released, even if the wall of the molded product springs back in the direction of opening at the shoulder, the wall near the shoulder will spring back in the direction of closing, resulting in Approach the target dimensions.

In any of the manufacturing methods 2 to 4 and the following manufacturing methods 5 to 9, in the arranging step, in a cross section perpendicular to the longitudinal direction of the convex part, from the reference point to the inner R end of the small R part It is preferable that the line length 1D is smaller than the line length 2E from the mold reference point to the midpoint of the side surface of the convex portion (1D<2E). This improves the fit of the large radius portion to the shoulder portion during molding, and further increases the effect of reducing springback by bending back the small radius portion. In this case, in the pressing step, the intermediate molded product is placed with respect to the first mold such that the small radius portion contacts the inside of the middle of the side surface of the convex portion (ie, on the top plate side).
Further, it is more desirable that the line length 1D is smaller than the smaller of 2C+(2C-2A) and 2E. That is, when 2C+(2C-2A)<2E, 1D<2E is desirable, and 1D<2C+(2C-2A) is more desirable. In the case of 2E<2C+(2C-2A), for example, when the line length of the side surface is short, 1D<2C+(2C-2A) is desirable, and 1D<2E is more desirable.

(Production method 5)
In any of the above manufacturing methods 1 to 4, in the arranging step, the intermediate molded product may be arranged so that the extension portion of the intermediate molded product extends from the small R portion toward the outside in a direction perpendicular to the press direction or obliquely toward the first mold side. This increases the arc length in the cross section of the curve of the small R portion of the intermediate molded product, and in press forming, the moment opposite to the springback moment caused by bending back the small R portion can be increased. In addition, the intermediate molded product has a shape in which the extension portion does not protrude toward the second mold side in the press direction beyond the small R portion. Therefore, it is possible to suppress an increase in the dimension of the entire intermediate molded product in the press direction. This makes it possible to suppress an increase in the thickness of the mold for creating the intermediate molded product.

(Manufacturing method 6)
In any of the above manufacturing methods 1 to 5, the intermediate molded product has a flange R portion that curves convexly in the first direction from an outer end of the extension portion, and a flange extending from the flange R portion. You may. With this configuration, compared to a configuration in which a flange is not provided on the outside of the extension part and the flange-equivalent part is extended as it is in the extension direction of the extension part, the size of the small R part on the outside of the intermediate molded product in the extension direction is becomes smaller. In the pressing process, the small radius portion or the extended portion is pressed by the second die, the large radius portion is bent, and the extending direction of the extended portion is inclined toward the first die. In a configuration with a flange, compared to a configuration without a flange, the outer end of the extension part is less likely to come into contact with the first mold during the pressing process. By avoiding contact of the extension portion with the first mold during the pressing process, it is possible to avoid deterioration of dimensional accuracy due to stress caused by contact.

(Manufacturing method 7)
In the pressing step, at least from the start of pressing until the small radius portion is bent back, the tip portion of the intermediate molded product does not come into contact with either the first mold or the second mold. A first mold and the second mold may be formed. In the press process, if the tip of the intermediate molded product comes into contact with the first or second mold during bending of the large R part and unbending of the small R part, unnecessary stress will be generated and the dimensional accuracy of the press molded product will be affected. may decrease. Therefore, by forming the first mold and the second mold so as to avoid this contact, it is possible to avoid a decrease in dimensional accuracy due to contact.

For example, by providing a recess or a setback part on the surface of the first mold or the second mold other than the area that contacts the intermediate molded product at the bottom dead center, it is possible to provide a groove or a setback part in the surface of the first mold or the second mold to avoid contact with the tip of the intermediate molded product in the pressing process. Contact can be avoided. In this case, in the pressing process, the end of the intermediate molded product being molded passes through the space of the recessed or retreated portion.

(Manufacturing method 8)
Any of the above manufacturing methods 1 to 7 may further include an intermediate molded product pressing step of producing the intermediate molded product by press-molding the plate material using an intermediate molding die.

The intermediate molding mold may include a first intermediate molding mold and a second intermediate molding mold. The first intermediate molding die may have a first intermediate molding surface corresponding to the center portion, large radius portion, small radius portion, and extension portion of the intermediate molded product. The second intermediate molding die may also have a second intermediate molding surface corresponding to the center portion, large radius portion, small radius portion, and extension portion of the intermediate molded product. The first intermediate molding surface may be integrally formed with a continuous surface. The second intermediate molding surface may also be integrally formed with a continuous surface. That is, the intermediate molded product pressing step may be a step of press-molding the plate material using an intermediate molding die that does not use a pad. In press molding without using a pad, the first intermediate molding surfaces are integrated and the second intermediate molding surfaces are integrated and approach each other. At the bottom dead center, the plate material is sandwiched between the integrated first intermediate forming surface and the integrated second intermediate forming surface, and the plate material is placed on both the first intermediate forming surface and the second intermediate forming surface. come into contact with When molding using a pad, the pad may float during molding. By molding the intermediate molded product by press molding (sometimes called stamping molding) without using a pad, there will be no situation where the material cannot be firmly clamped between the pad and the first mold for intermediate molding during molding. . This further improves the dimensional accuracy of the intermediate molded product. As a result, the shape accuracy of the press-formed product is further improved. Further, it is possible to avoid complicating the mechanism for intermediate forming, and it is possible to reduce the size of the intermediate forming mold in the pressing direction. Therefore, the manufacturing cost of the intermediate molded product can be reduced.

The longitudinal direction of the center plane of the first intermediate molding die is perpendicular to the pressing direction, and is the direction in which the intermediate line between the pair of large radius surfaces extends when viewed from the pressing direction. The longitudinal direction of the central plane may be straight or curved when viewed from the press direction. The shape of the central surface of the first intermediate mold when viewed from the press direction corresponds to the top surface of the convex portion of the first mold when viewed from the press direction. The longitudinal direction of the central plane corresponds to the longitudinal direction of the convex portion.

(Manufacturing method 9)
In any of the above manufacturing methods 1 to 8, the second mold includes a pad arranged to face the convex part of the first mold in a pressing direction, and a pad arranged on both sides of the pad. The mold body may include a second mold main body. In the pressing step, the first mold and the second mold main body are brought relatively close to each other with at least a part of the central part of the intermediate molded product being sandwiched between the pad and the convex part, The intermediate molded product may be press-molded. Thereby, by sandwiching the center portion between the pads, it is possible to suppress displacement of the material during molding. Therefore, press molding with a deeper molding height becomes possible. That is, the dimension of the press-formed product at the bottom dead center in the pressing direction can be increased. Moreover, since the shape of the central portion is formed in the intermediate molded product, it can be stably held by the pads.

When the above manufacturing methods 8 and 9 are combined, for example, in the pressing step of the intermediate molded product, the center portion of the intermediate molded product may be molded into a shape that matches the molding surface of the pad in the next press molding step. This makes it difficult for the pad to lift during the press molding process. As a result, the dimensional accuracy of the press-formed product is improved.

(Configuration 1)
The manufacturing equipment in the embodiment of the present disclosure includes a first press device including a first intermediate molding die and a second intermediate molding die for press-molding a plate material to produce an intermediate molded product;
A second press device including a first mold and a second mold for press-molding the intermediate molded product to produce a press-formed product.
The first mold has a convex portion that is convex in the pressing direction, and the second mold has a concave portion that corresponds to the convex portion.
The first mold for intermediate molding and the second mold for intermediate molding mold the plate material into a central portion, a pair of large R portions on both sides of the central portion, and the outer sides of each of the pair of large R portions. and an extending portion outside the small radius portion.
The large R portion is curved convexly in a first direction, and the small R portion is curved convexly in a second direction opposite to the first direction, and the small R portion is curved convexly in a second direction opposite to the first direction. The radius of curvature of the portion is smaller than the radius of curvature of the large radius portion.
In the second press device, the convex portion of the first mold has a top surface, a pair of shoulders at both ends of the top surface, and side surfaces extending from the pair of shoulders, respectively.
In the first mold, the pair of large R portions of the intermediate molded product are bent along the pair of shoulders of the convex portion of the first mold, and the small R portion is bent back. It is configured to be press-molded into a shape along the side surface of the convex portion.

According to the manufacturing equipment of configuration 1, the first press device produces an intermediate molded product having a central portion, a pair of large radius portions, a pair of small radius portions, and a pair of extension portions. In press forming by the second press device, the large radius portion of the intermediate molded product has good attachment to the shoulder portion of the first mold, and the small radius portion can be bent back. This reduces the springback of the press-formed product and improves the dimensional accuracy of the press-formed product.

(Configuration 2)
In the above structure 1, the first mold for intermediate molding and the second mold for intermediate molding each have a central surface forming the central portion of the intermediate molded product and a pair of molds forming the large R portion. It may have a large-R surface, a pair of small-R surfaces forming the small-R portion, and a pair of extending surfaces forming the extension portion.
A first reference point on the central plane and the outside of one of the pair of small R surfaces in a cross section of the intermediate forming mold perpendicular to the longitudinal direction of the central portion of the first intermediate mold. The line length is 10F, which is the length of the line along the first mold for intermediate forming between the R stop, and the R stop inside the large R part of one of the pair of large R surfaces between the first reference point and the pair of large R surfaces. and a line length of 10C between the first reference point and the outer radius stop of the large radius surface.
R on the inside of one of the pair of shoulders from a second reference point corresponding to the first reference point in a cross section at a position corresponding to the intermediate mold cross section of the first mold. The line length 20A along the first mold until the stop, and the line length 20C between the second reference point and the R stop outside the shoulder part are:
20C<10F, 10A<20C, 20A<10C
It is preferable to have the following relationship. This improves the fit of the large radius portion to the shoulder portion during press molding, and further increases the effect of reducing springback by bending back the small radius portion.
Note that the line length of the first intermediate mold in the cross section of the intermediate mold is the length of the line along the surface of the first intermediate mold. The same cross section as the cross section of the intermediate molded product at the bottom dead center in the cross section of the intermediate molding mold appears in a corresponding cross section of the first mold in which the intermediate molded product is placed. That is, the cross section of the first mold corresponding to the cross section of the intermediate molding mold is determined based on the intermediate molded product. A second reference point corresponding to the first reference point is also determined based on the intermediate molded product.

(Configuration 3)
In the above structure 2, the first reference point and one of the large R surfaces of the pair of large R surfaces in the intermediate forming mold cross section perpendicular to the longitudinal direction of the central part of the first intermediate forming mold. The line length 10B between the midpoint of the line along the first intermediate molding die, and the line length 10B between the first reference point and the intermediate molding point of one of the pair of small radius surfaces. The line length 10E between the midpoint and the line along one mold is
20C<10E, 20A<10B<20C
It is preferable to have the following relationship. This improves the fit of the large radius portion to the shoulder portion during press molding, and further increases the effect of reducing springback by bending back the small radius portion.

(Configuration 4)
In the above configuration 2 or 3, the first reference point and one of the pair of small radius surfaces in the cross section of the intermediate forming die perpendicular to the longitudinal direction of the central part of the first intermediate forming die. The line length 10D between the small R surface and the inner R end is
20C<10D
It is preferable to have the following relationship. This improves the fit of the large radius portion to the shoulder portion during press molding, and further increases the effect of reducing springback by bending back the small radius portion.

In any of the above configurations 2 to 4 and the following configurations 5 to 8, the first reference point in the intermediate mold cross section perpendicular to the longitudinal direction of the central part of the first intermediate mold; The line length 10D between one of the pair of small R surfaces and the inner R stop is,
10D<20C+(20C-20A)
It is preferable to have the following relationship. This improves the fit of the large radius portion to the shoulder portion during press molding, and further increases the effect of reducing springback by bending back the small radius portion.

In any of the configurations 2 to 4 and the configurations 5 to 8 below, the first reference point in the intermediate mold cross section perpendicular to the longitudinal direction of the central part of the first intermediate mold; A line length 10D between one of the pair of small radius surfaces and the inner radius stop is the second reference point in the cross section of the first mold corresponding to the intermediate mold cross section. , is preferably smaller than the line length 20E of the line along the mold surface between the midpoint of one of the pair of side surfaces (10D<20E). This improves the fit of the large radius portion to the shoulder portion during molding, and further increases the effect of reducing springback by bending back the small radius portion.

(Configuration 5)
In any one of the above configurations 1 to 4, the first intermediate molding mold and the second intermediate molding mold each have a central surface forming the central portion of the intermediate molded product and a large R portion. It may have a pair of large R surfaces forming the small radius portion, a pair of small radius surfaces forming the small radius portion, and a pair of extending surfaces forming the extension portion. In each of the first intermediate molding mold and the second intermediate molding mold, the extending surface extends outward from the small radius surface in a direction perpendicular to the press direction or in the first intermediate molding mold. It may be formed to extend obliquely toward the mold side. This makes it possible to suppress an increase in the thickness of the intermediate mold.

(Configuration 6)
In any of the above configurations 1 to 5, the first intermediate molding mold and the second intermediate molding mold are configured to form the plate material into the center portion, the large R portion, the small R portion, and In addition to the extension part, the flange R part is configured to have a shape having a flange R part curved convexly in the first direction on the outside of the extension part, and a flange extending outward from the flange R part. You can. For example, the first mold for intermediate molding and the second mold for intermediate molding are formed on the central surface, the pair of large R surfaces, the pair of small R surfaces, and the pair of extended surfaces, respectively. In addition, it may have a flange R surface forming the flange R portion and a flange surface forming the flange.

(Configuration 7)
In any one of the above configurations 1 to 6, the first mold has a base surface extending outward from an end opposite to the top of both side surfaces of the convex portion, and the base surface has a recess. may be provided. This digging can prevent the leading end of the intermediate molded product from coming into contact with the base surface during press molding using the second press device.

(Configuration 8)
In any of the above configurations 1 to 7, the second mold may have a second side surface facing the side surface of the convex portion in the pressing direction, and a second base surface facing the base surface. . The second base surface may be provided with a recess. Alternatively, the second base surface may have a separation part spaced apart from the first mold base surface in the press direction so as not to contact the press-formed product at the bottom dead center.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Identical or corresponding parts in the drawings are denoted by the same reference numerals and their description will not be repeated. The dimensional ratios between the constituent members shown in each figure do not necessarily represent the actual dimensional ratios.

(Example of manufacturing process)
FIG. 1 is a diagram showing steps in a method for manufacturing a press-formed product K3 in this embodiment. The manufacturing method of this embodiment includes a step of producing an intermediate molded product K2 using a first press device 10 ((a) to (c) in FIG. 1), and a step of producing a press molded product K3 using a second press device 20. ((e) to (g)).

As shown in FIG. 1(a), a first mold 3 for intermediate molding (hereinafter simply referred to as the first mold 3) and a second mold 4 for intermediate molding (hereinafter simply referred to as the first mold 3) of the first press device 10 are shown in FIG. A plate material K1 is placed between the two molds (referred to as a second mold 4). As shown in FIG. 1(b), the first mold 3 and the second mold 4 approach each other, and the plate material K1 is press-molded. As shown in FIG. 1(c), at the bottom dead center, the plate material K1 is held between the first mold 3 and the second mold 4 while maintaining the shape of the intermediate molded product K2.

The intermediate molded product K2 shown in FIG. 1(d) has a central portion CH, a pair of large radius portions LR, a pair of small radius portions SR, and a pair of extended portions EN on both sides of the central portion CH. The central portion CH includes a non-curved portion, that is, a flat portion. There is a small radius portion SR on the outside of each of the pair of large radius portions LR, and an extension portion EN is located on the outside of the small radius portion SR. The extension portion EN includes a non-curved portion, that is, a flat portion. Both the large radius portion LR and the small radius portion SR are curved portions. The convex direction of curvature of the large radius portion LR is opposite to the convex direction of curvature of the small radius portion SR. The radius of curvature of the large radius portion LR is larger than the radius of curvature of the small radius portion.

As shown in FIG. 1(e), an intermediate molded product K2 is placed between the first mold 5 and the second mold 6 of the second press device 20. As shown in FIG. The first mold 5 has a convex portion that is convex in the pressing direction, and the second mold 6 has a concave portion that corresponds to the convex portion. The convex portion of the first mold 5 has a top surface 5a, a pair of shoulders 5b at both ends of the top surface 5a, and side surfaces 5c each extending from the pair of shoulders 5b. In the example shown in FIG. 1, the direction perpendicular to the paper surface is the longitudinal direction of the convex portion of the first mold 5. The longitudinal direction of the central portion CH of the intermediate molded product K2 is also perpendicular to the paper surface.

In FIG. 1(e), the intermediate molded product K2 is arranged so that the large R portion LR is convex toward the first mold 5 and the small R portion SR is convex toward the second mold 6. . Furthermore, at least a portion of each of the pair of large radius portions is arranged at a position overlapping each of the pair of shoulder portions 5b of the convex portion of the first mold 5 when viewed from the press direction.

Moreover, in the example of FIG. 1, the second mold 6 of the second press device 20 has a pad 6B provided at a position facing the top surface 5a of the convex portion of the first mold 5 in the pressing direction. The second mold 6 includes a pair of second mold main bodies 6A provided on both sides of the pad 6B. The pair of second mold body parts 6A are provided on the pair of shoulder parts 5b of the first mold 5, respectively, at positions facing each other in the press direction. Note that the pair of second mold body parts 6A may be integrally formed. For example, the second mold main body 6A may be formed to surround the entire circumference of the pad 6B when viewed from the press direction. As shown in FIG. 1(f), the second press device 20 clamps the intermediate molded product K2 between the pad 6B and the first mold 5.

As shown in FIG. 1(g), in the pressing process, the second press device 20 is in a state in which at least a part of the central part CH of the intermediate molded product K2 is sandwiched between the pad 6B and the top surface 5a of the first mold 5. Then, the first mold 5 and the second mold main body 6A are brought relatively close to each other, and the intermediate molded product K2 is press-molded. In the pressing process, the pair of large R portions LR of the intermediate molded product K2 are bent along the pair of shoulders 5b of the first mold 5, and at least a portion of the small R portion SR is bent back to form the first mold. It is press-molded into a shape along the side surface 5c of the mold 5.

As shown in FIG. 1(h), at the bottom dead center, the portion corresponding to the large R portion LR is bent to become convex opposite to the original curve and wraps around the shoulder portion 5b, and the small R portion SR is , is bent back and at least a portion thereof is in contact with the side surface 5c. Thereby, a press-molded product K3 having a shape corresponding to the molding surfaces of the first mold 5 and the second mold 6 is obtained. The press-formed product K3 includes at least a top plate, shoulders at both ends of the top plate, and a pair of vertical walls extending from the shoulders.

In this way, by bending the large radius portion LR while wrapping it around the shoulder portion 5b, and further bending the small radius portion SR back, springback is reduced and dimensional accuracy is improved in the press-formed product K3. . That is, in the pressing process, at least a portion of each of the pair of large R portions LR of the intermediate molded product K2 is bent along each of the pair of shoulders 5c of the convex portion of the first mold 5, and At least a portion of each R portion SR is press-molded into a shape along the side surface 5c of the convex portion while being bent back. This improves dimensional accuracy.

In the example shown in FIG. 1, the press-formed product K3 has a flange extending from the opposite end of each of the pair of vertical walls to the top plate. In this case, a curved flange R portion is formed between the vertical wall and the flange. The press-formed product K3 may have a shape without a flange or a flange R portion (for example, a U-shaped cross section). If the press-formed product K3 has a shape without a flange or flange R portion, the flange or flange R portion will not be held between the molds at the bottom dead center.

FIG. 2 is a diagram showing an example of the pressing process of the second press device 20 in more detail. As shown in FIG. 2(a), the intermediate molded product K2 is arranged so that the large R portion LR faces the shoulder portion 5b of the first mold 5 in the pressing direction. As shown in FIGS. 2(b) and 2(c), in the pressing process, the large radius portion LR and the small radius portion SR are bent back, that is, bent in the opposite direction to the original curve. At the bottom dead center, at least a portion of the small radius portion SR is bent back and becomes a portion of the vertical wall of the press-formed product K3. At least a portion of the large R portion LR is bent to become a shoulder portion of the press-formed product K3. As shown in FIG. 2(b), during molding, when the small radius portion SR is bent back, tensile stress acts on the inside of the member and compressive stress acts on the outside of the member. When the large R portion LR is bent along the shoulder portion 5b, compressive stress acts on the inside of the member and tensile stress acts on the outside of the member. The large radius portion LR is bent in a direction opposite to the original curve while wrapping around the shoulder portion 5b of the first mold 5 from an early stage of molding. That is, the large radius portion LR is molded while being well adapted to the shoulder portion 5b. As a result, in the portion in contact with the shoulder portion 5b, the member in contact with the shoulder portion 5b is stretched outward from the top surface 5a (toward the right side in the paper), thereby reducing the compressive stress on the inside of the bend. At the bottom dead center shown in FIG. 2(c), a wall-opening moment is generated at the shoulder portion of the press-formed product K3, and a wall-closing moment opposite to this is generated at the vertical wall. The springback is caused by the combination of the reduction of the wall opening moment due to the reduction of the compressive stress on the inside of the bend due to the attachment of the large radius portion LR to the shoulder portion 5b, and the generation of the wall closing moment due to the bending back of the small radius portion SR. is significantly reduced. As a result, the dimensional accuracy of the press-formed product K3 becomes higher. That is, the shape of the press-formed product can be made closer to the target shape.

FIG. 3 is a diagram for explaining the function of the large R portion LR. FIG. 3A shows an example during molding of an intermediate molded product K2 including a large R portion LR, a small R portion SR, and an extension portion EN. FIG. 3(b) shows an example of an intermediate molded product without a large radius portion being molded. As shown in FIG. 3(a), in the initial stage of molding, the small R portion SR or the extended portion EN is moved toward the first mold 5 by the second mold 6 (second mold main body 6A). Pushed. The large R portion LR curves convexly toward the first mold 5. Therefore, the large radius portion LR is pressed against the shoulder portion 5b of the first mold 5 from the initial stage of molding, and is bent in the opposite direction while being wrapped around the shoulder portion 5b. That is, the large R portion LR is bent while being adapted to the shoulder portion 5b. In contrast, in FIG. 3(b) the member is bent away from the shoulder 5b. That is, the molding progresses without the member coming into contact with the shoulder portion 5b, and the member comes into contact with the shoulder portion 5b at the bottom dead center. In this case, in the press-formed product, the residual stress that tries to return to the unattached state during molding becomes large. Therefore, springback may increase and dimensional accuracy may decrease.

The height in the pressing direction of the intermediate molded product K2 having the large R portion LR in FIG. 3(a) can be made smaller than that of the intermediate molded product K2 having the large R portion LR in FIG. 3(b). Thereby, in the first press device 10, it is possible to reduce the cost of the mold for press forming the intermediate molded product K2. That is, the large radius portion LR can improve the fit to the shoulder portion 5b, improve dimensional accuracy, and reduce manufacturing costs.

As described above, the small radius portion SR is bent back during molding and becomes flat, generating a wall closing moment. The radius of curvature (R_S) of the small radius portion SR is preferably small enough that no traces of the small radius portion remain when bent back. Further, from the viewpoint of ensuring wall closing moment, it is preferable that the entire small radius portion be bent back in the press forming process, for example, as in the above example. If the radius of curvature of the large radius portion LR is small, the effect of returning to the original curved shape will be greater than the effect of improving conformity, so it is desirable that the radius of curvature is large to some extent. From these viewpoints as well, it is preferable that the radius of curvature of the large radius portion LR>the radius of curvature of the small radius portion SR.

The wall closing moment due to unbending of the small radius portion SR is proportional to the product of the value (magnitude) of the moment and the area where the moment occurs. It is desirable that the moment due to unbending of the small radius portion SR be of a certain degree. If the radius of curvature R_S of the small radius portion SR is too large, the area where a moment occurs becomes large, but the value of the moment becomes small. On the other hand, if the radius of curvature R_S of the small radius portion SR is too small, the value of the moment becomes large, but the area where the moment occurs becomes small. For example, it is preferable that R_S≦20 mm. This makes it easier to generate a moment in the opposite direction due to the bending back of the small radius portion SR, which is more suitable for offsetting the moment of wall opening due to press forming. From the same viewpoint, R_S≦18 mm is more preferable, and R_S≦15 mm is even more preferable. Further, for example, 5 mm≦R_S may be satisfied. Thereby, while securing a region where a moment occurs, marks from the small radius portion SR are less likely to remain after molding. From the same viewpoint, 10 mm≦R_S is more preferable.

Assuming that the radius of curvature of the shoulder of the convex portion of the first mold is Rp, the radius of curvature R_L of the large radius portion LR relative to Rp is not limited to this, but may be, for example, 1.5Rp≦R_L. This allows the large radius portion to fit better into the shoulder portion. From this point of view, it is more preferable that 1.75Rp≦R_L. The upper limit of R_L is not particularly limited, but may be, for example, R_L≦3.0Rp.

The relationship between the radius of curvature R_S of the small radius portion SR and the radius of curvature R_L of the large radius portion LR is not limited to this, but for example, if the difference between R_S and R_L is greater than the plate thickness t of the intermediate molded product (R_S+t<R_L ) may be done. Moreover, it is good also as 1.5R_S≦R_L. Furthermore, it is more preferable that 2.0R_S≦R_L. Thereby, the effect of reducing springback due to the combination of the molding behavior of the large radius portion and the small radius portion can be further enhanced. Further, R_L≦6.0R_S can be satisfied. Thereby, the effect of reducing springback due to the combination of the molding behavior of the large radius portion LR and the small radius portion SR can be further enhanced.

The radius of curvature of each of the small radius portion SR and the large radius portion LR is the radius of curvature of the curve between the inner radius end and the outer radius end of the member surface on the inside of the bend in a cross section perpendicular to the respective ridge lines. The radius of curvature is the radius of a circle passing through three points: the round ends at both ends and the midpoint between them. The radius of curvature of the shoulder of the mold is determined at three points: the inside R stop, the outside R stop, and the midpoint between the inside R stop and the outside R stop of the mold surface in a cross section perpendicular to the longitudinal direction of the convex part of the mold. The radius of the circle calculated from is the radius of curvature. In addition, the radius of curvature of the small R part and the large R part is defined in the cross section by three points on the line on the inner side of the bending (radially inner side of the radius of curvature) of the intermediate molded product (the R stops at both ends and the midpoint between them). ) is the radius of the circle passing through.

In the example shown in FIG. 1, the first press device 10 forms the entire plate material K1 by sandwiching it between the first mold 3 and the second mold 4 without using a pad. This is called stamping molding, crushed foam molding, or pressing. The intermediate molded product K2 has a smaller dimension in the pressing direction than the press molded product K3. Therefore, in the press molding of the intermediate molded product K2, the molding depth can be reduced. In this case, the intermediate molded product can be formed with high precision by stamping molding without using a pad.

Generally, when press-forming high-strength materials (high-strength materials) into U-shaped or hat-shaped members, drawing molding tends to break, so pad bending (form molding) in which the top plate is held down with a pad and the punch shoulder is bent. ) will be adopted. By pressing the top plate with a pad while forming, it prevents the material from shifting during press forming. However, for example, if the top plate has a shape such as a step or a groove, if the load (spring constant) of the elastic member that supports the pad is small, the shape of the top plate cannot be firmly held in the initial stage of press forming. However, the pad may float during molding. This may lead to a decrease in dimensional accuracy. Therefore, as shown in FIG. 1, if the top plate of the press-formed product has a shape such as a step or a groove, in order to suppress the floating of the pad 6B in the second press device 20, the first press device 10 The shape of the top plate can be formed. In the first press device 10, it is desirable to perform press molding using a mold that does not use a pad. In the first press device 10, since the forming depth is small, it is easy to ensure dimensional accuracy by press forming without using a pad.

(Example of arrangement of intermediate molded products)
FIG. 4 is a diagram for explaining the positional relationship between the first mold 5 and the intermediate molded product K2. FIG. 4 shows a state in which the intermediate molded product K2 is placed in the first mold 5. As shown in FIG. FIG. 4 shows the first mold 5 and the intermediate molded product K2 in a cross section perpendicular to the longitudinal direction of the convex portion of the first mold. In this cross section, an arbitrary point in the center CH of the intermediate molded product K2 is defined as a reference point O1. A point obtained by projecting the reference point O1 onto the top surface 5a of the first mold 5 in the press direction is defined as a mold reference point O2.

The length of the line L_1A along the intermediate molded product K2 from the reference point O1 to the inner radius stop of the large radius portion LR is line length 1A. Hereinafter, a line along the intermediate molded product K2 is a line along the surface of the intermediate molded product K2 on the first mold 5 side. Similarly, the length of the line on the intermediate molded product K2 from the reference point O1 to the outer R stop of the large R part LR is the line length 1C, and from the reference point O1 to the inner R stop and the outer R stop of the large R part LR. The length of the line along the intermediate molded product between the lines to the midpoint is the line length 1B. The distance between the inner R stop of the large R section and the midpoint of the large R section is equal to the distance between the outer R stop of the large R section and the midpoint of the large R section. The line length 1D is the line length from the reference point O1 to the inner R stop of the small R portion SR, and the line length 1F is the line length from the reference point O1 to the outer R stop of the small R portion SR. The line length 1E is the line length from the reference point O1 to the midpoint between the outer R end and the inner R end of the small R portion SR. The distance between the inside radius stop of the small radius section and the midpoint of the small radius area is equal to the distance between the outside radius stop of the small radius area and the midpoint of the small radius area.

The length of the line L_2A along the mold surface from the mold reference point O2 to the outer R stop of the shoulder portion 5b of the first mold 5 is line length 2A. Similarly, the length of the line on the mold surface from the mold reference point O2 to the radius stop on the outside of the shoulder portion 5b is the line length 2C. The length of the line from the mold reference point O2 to the midpoint of the line along the mold surface between the inside R stop and the outside R stop of the shoulder portion 5b is the line length 2B. In addition, the line length of the line along the mold surface between the mold reference point O2 and a point separated outward by the line length of the mold surface of the shoulder part 5b from the outside R stop of the shoulder part 5b is as follows: It becomes 2C+(2C-2A).

Note that the radius stop in a mold or intermediate molded product is the boundary between a curved part and a flat part (straight part), or the boundary between a curved part and an adjacent curved part whose convex direction is opposite, when viewed in cross section. It is a boundary. In other words, if the curvature of the curved part in the convex direction is positive, the curvature of the uncurved flat part (straight part) is 0, and the curvature of the curved part in the concave direction is negative, then the boundary where the positive and negative of the curvature is reversed, or The boundary where the curvature changes from a positive or negative value to 0 is called an R stop. In the first mold 5, the inside radius stop of the shoulder 5b is the boundary between the shoulder 5b and the top surface 5a, and the outside radius stop of the shoulder 5b is the boundary between the shoulder b and the side surface 5c.

In the pressing process, at least a portion of the large R portion LR contacts the shoulder portion 5b of the first mold 5 at the bottom dead center, and at least a portion of the small R portion SR contacts the side surface 5c near the shoulder portion 5b. is preferred. In this case, the large radius portion LR is made to fit better into the shoulder portion 5b during molding, and in combination with the bending back of the small radius portion, the effect of reducing springback is enhanced.

From this point of view, it is preferable that the small radius portion SR be located at a position where it contacts the shoulder portion 5b and the side surface 5c at the bottom dead center. Further, it is preferable that the small radius portion SR has a larger portion in contact with the side surface 5c than the portion in contact with the shoulder portion 5b at the bottom dead center. A certain degree of effect can also be obtained when all of the small radius portions SR contact either the shoulder portion 5b or the side surface 5c at the bottom dead center. It is preferable that the small radius portion SR is not too far away from the shoulder portion 5b at the bottom dead center.

The large R portion LR may be in contact with at least one of the top surface 5a or the side surface 5c in addition to the shoulder portion 5b at the bottom dead center. It is preferable that the large radius portion LR has a large portion in contact with the shoulder portion 5b at the bottom dead center. It is preferable that more than half of the large R portion LR be in contact with the shoulder portion 5b at the bottom dead center. Further, it is preferable that all or most of the large R portion LR be in contact with the shoulder portion 5b at the bottom dead center. A certain degree of effect can also be obtained when all of the large R portion LR contacts the top surface 5a at the bottom dead center.

Based on the above, the positional relationship between the first mold 5 and the intermediate molded product K2 in the placement process is such that the line lengths 1A, 1C, 1F, 2A, and 2C are, for example,
2C<1F, 1A<2C, 2A<1C
It is preferable that the following conditions are satisfied. As a result, the large radius portion LR comes into contact with the shoulder portion 5b at the bottom dead center, and the small radius portion SR comes into contact with the outer shoulder portion 5b or the side surface 5c.

Furthermore, the wire lengths 1B and 2E are
2C<1E, 2A<1B<2C
The intermediate molded product K2 may be arranged with respect to the first mold 5 so as to have the following relationship. As a result, a larger portion of the large R portion LR comes into contact with the shoulder portion 5b at the bottom dead center.

Moreover, the intermediate molded product K2 may be arranged with respect to the first mold 5 so that the line length 1D satisfies 2C<1D. Thereby, all of the small radius portions SR come into contact with the side surface 5c at the bottom dead center.

The intermediate molded product K2 may be arranged with respect to the first mold 5 such that the line length 1D satisfies, for example, 1D<2C+(2C-2A). In this case, the small radius portion SR comes into contact with the shoulder portion 5b or the side surface 5c near the shoulder portion 5b at the bottom dead center. Moreover, the intermediate molded product K2 may be arranged so that the line length 1D is smaller than the line length 2E from the mold reference point O2 to the middle of the side surface 5c (1D<2E). Thereby, the small radius portion SR can be prevented from being too far away from the shoulder portion 5b at the bottom dead center. In the example shown in FIG. 1, 2C+(2C-2A)<2E. It is more desirable that the line length 1D is smaller than the smaller value of 2C+(2C-2A) and 2E (2E in the example of FIG. 1).

(Example of mold configuration)
FIG. 5 is a sectional view showing a configuration example of the first press device 10. As shown in FIG. In the example shown in FIG. 5, the first press device 10 includes a first mold 3, a second mold 4, a bed 12, a slide 13, and mold holders (mold bases) 14 and 15. The first mold 3 is, for example, a punch. The second mold 4 is, for example, a die. The first mold 3 and the second mold 4 extend in a direction (y direction) intersecting the plane of the paper in FIG. 5 . Hereinafter, for convenience of explanation, regarding the first press device 10 and its constituent parts, the direction in which the central surface 3CH of the first mold 3 extends is defined as the longitudinal direction. In this example, the press direction, that is, the direction in which the first mold 3 and the second mold 4 approach and separate from each other is the up-down direction (vertical direction) (z direction in the figure). The direction perpendicular to the plane consisting of the longitudinal direction and the vertical direction (the x direction in the figure), that is, the direction across the first mold 3 and the second mold 4 is referred to as the left-right direction or the width direction. Further, regarding the first press device 10 and its constituent parts, a cross section cut along a plane perpendicular to the longitudinal direction is referred to as a cross section.

The first die 3 is supported by a bed 12, which is part of the main body of the first press device 10, via a die holder 14. That is, the die holder 14 is fixed to the bed 12, and the first die 3 is placed on this die holder 14.

The second mold 4 is arranged at a position facing the first mold 3 in the pressing direction. The second mold 4 is attached to the slide 13 via a mold holder 15. That is, the mold holder 15 is fixed to the slide 13, and the second mold 4 is fixed to the mold holder 15. The slide 13 is configured to be movable up and down relative to the first mold 3 by, for example, a mechanical or hydraulic mechanism (not shown) provided in the first press device 10 . As the slide 13 moves up and down, the second mold 4 also moves up and down with respect to the first mold 3 .

The first mold 3 and the second mold 4 have molding surfaces that contact the molded product at the bottom dead center. The molding surface has a shape corresponding to the intermediate molded product K2. The molding surface of the first mold 3 includes a central surface 3CH, a pair of large R surfaces 3LR, a pair of small R surfaces 3SR, and a pair of extended surfaces 3EN. These are surfaces for respectively forming the center portion CH, large radius portion LR, small radius portion SR, and extension portion EN of the intermediate molded product K2. The molding surface of the second mold 4 includes a central surface 4CH, a pair of large R surfaces 4LR, a pair of small R surfaces 4SR, and a pair of extended surfaces 4EN. Large R surfaces 3LR and 4LR are provided on both sides of the center surfaces 3CH and 4CH in the width direction. Small radius surfaces 3SR and 4SR are provided outside the large radius surfaces 3LR and 4LR. Extended surfaces 3EN and 4EN are provided on the outside of the small radius surfaces 3SR and 4SR. The large R surfaces 3LR, 4LR and the small R surfaces 3SR, 4SR are curved so as to be convex in opposite directions. The radius of curvature of the small radius surfaces 3SR and 4SR is smaller than that of the large radius surfaces 3LR and 4LR. Further, as an example, in the first press device 10, the size of the mold (in the example of FIG. The radius of curvature of the R surface (4LR) can be made larger than the radius of curvature of the small R surface (3SR) of the other mold (in the example of FIG. 5, the first mold 3) that is in contact with the inside bending of the small R section. can.

FIG. 6 is a sectional view showing a configuration example of the second press device 20. As shown in FIG. In the example shown in FIG. 6, the second press device 20 includes a first mold 5, a second mold 6, a pad 6B, a bed 22, a slide 23, and mold holders (mold bases) 24 and 25. . The first mold 3 is, for example, a punch. The second mold 6 is, for example, a die. The first mold 5 and the second mold 6 extend in a direction (y direction) intersecting the plane of the paper in FIG. 6 . Regarding the second press device 20 and its constituent parts, the direction in which the convex portion of the first mold 5 extends is defined as the longitudinal direction. In this example, the press direction, that is, the direction in which the first mold 5 and the second mold 6 approach and separate from each other is the vertical direction (vertical direction) (z direction in the figure). The direction perpendicular to the plane consisting of the longitudinal direction and the vertical direction (the x direction in the figure), that is, the direction across the first mold 5 and the second mold 6 is referred to as the left-right direction or the width direction. Further, regarding the second press device 20 and its constituent parts, a cross section cut along a plane perpendicular to the longitudinal direction is referred to as a cross section. In this embodiment,

The first mold 5 is supported by a bed 22, which is a part of the main body of the second press device 20, via a mold holder 24. That is, a mold holder 24 is fixed to the bed 22, and the first mold 5 is placed on this mold holder 24.

The second mold 6 is arranged at a position facing the first mold 5 in the pressing direction. The second mold 6 includes a pad 6B and a second mold main body 6A disposed on both sides of the pad 6B. The second mold 6 is attached to the slide 23 via a mold holder 25. In the example of FIG. 6, a mold holder 25 is fixed to the slide 23, and a second mold main body 6A is fixed to the mold holder 25. Pad 6B is attached to mold holder 25 via support member 6Bc. The slide 23 is configured to be movable up and down relative to the first mold 5 by, for example, a mechanical or hydraulic mechanism (not shown) provided in the second press device 20. As the slide 23 moves up and down, the second mold 6 also moves up and down with respect to the first mold 5.

The first mold 5 has a convex portion that is convex in the pressing direction. The convex portion extends in the longitudinal direction (y direction). In this example, the longitudinal direction of the convex portion extends linearly and is the same as the longitudinal direction of the first mold 5. Note that the longitudinal direction of the convex portion may be curved when viewed from the pressing direction. Further, the longitudinal direction of the convex portion may not be the same as the longitudinal direction of the first mold 5. The second mold 6 has concave portions corresponding to the convex portions. The convex portion of the first mold 5 has a top surface 5a, a pair of shoulders 5b at both ends of the top surface 5a, and side surfaces 5c each extending from the pair of shoulders 5b.

The pad 6B is provided at a position facing the top surface 5a of the convex portion of the first mold 5 in the pressing direction. A second mold 6 is arranged at a position facing the first mold 5 in the pressing direction and on the side of the pad 6B. Here, the lateral direction is a direction perpendicular to both the longitudinal direction of the convex portion and the pressing direction. The pad 6B is configured to be movable with respect to the second mold 6. That is, the pad 6B can move in the pressing direction independently of the second mold 6. Pad 6B is attached to slide 23 via mold holder 25. The pad 6B is movable up and down relative to the first mold 5.

Pad 6B is supported by support member 6Bc. The pad 6B has a pressing surface 6Ba that faces the top surface 5a of the first mold 5. The pressing surface 6Ba is formed in a shape corresponding to the top surface 5a of the first mold 5. In this example, the pressing surface 6Ba and the top surface 5a have a shape corresponding to the shape of the top plate of the press-formed product. The support member 6Bc elastically supports the pad 6B with respect to the mold holder 25. The support member 6Bc is an elastic member that can be expanded and contracted, and is formed of a spring such as a gas spring or a coil spring, a fluid cylinder, or the like.

In the second mold main body 6A, the second mold 6 includes a top surface 6a (second top surface) opposite to the top surface 5a of the first mold 5 in the press direction, and a shoulder portion 5b of the first mold 5. and a corner 6ac facing the pressing direction, a side surface 5c of the first mold 5, and a side surface 6c (second side surface) facing the pressing direction. The second mold 6 also has a shoulder 6b (second shoulder) at the end near the first mold 5 among both ends of the side surface 6c, and a base surface 6d (second base surface) extending outward from the shoulder 6b. ). The shoulder portion 6b is, for example, a die shoulder.

In the example of FIG. 6, the pair of shoulders 5b of the first mold 5 are formed outside the pad profile P, which is the boundary between the pad 6B and the second mold body 6A. That is, a pad 6B is provided at a position facing a part of the top surface 5a of the first mold 5 in the press direction, and a second pad 6B is provided at a position facing the other portion of the top surface 5a, the shoulder portion 5b, and the side surface 5c. A mold main body portion 6A is provided.

(Correspondence between the mold for intermediate molded products and the mold for press-formed products)
Next, an example of the relationship between the configurations of the molds of the first press device 10 and the molds of the second press device 20 will be described. The shape of the cross section perpendicular to the longitudinal direction of the center surface 3CH of the first mold 3 of the first press device 10 and the shape of the corresponding cross section of the mold of the second press device 20 have a certain relationship.

Here, a cross section of the mold of the second press device that corresponds to a cross section of the mold of the first press device 10 will be explained using FIG. 7. FIG. 7 is a plan view as seen from the press direction (z direction) and a side view as seen from the longitudinal direction (y direction) of the first mold 3 shown in FIG. 5 and the first mold 5 shown in FIG. 6. be. In FIG. 7, in the first mold 3, a region 3S where the intermediate molded product K2 is placed at the bottom dead center is indicated by a broken line. In the first mold 5, a region 5S in which the intermediate molded product K2 is placed before molding is indicated by a broken line. The region 5S is a region where the intermediate molded product K2 placed in the first mold 5 is projected onto the first mold 5 in the pressing direction. In the first mold 3, consider a cross section D1 perpendicular to the longitudinal direction at a distance y1 in the longitudinal direction from one end of the central plane 3CH in the longitudinal direction in the region 3S. The cross section of the first mold 5 corresponding to this cross section D1 is the cross section D2 perpendicular to the longitudinal direction, which is located at the same distance y1 in the longitudinal direction from the corresponding end of the convex portion in the longitudinal direction in the region 5S. Become. In the cross section D1, an arbitrary point on the line of the central plane 3CH is defined as a first reference point O3. In the cross section D2, a linear point on the top surface 5a corresponding to the first reference point O3 becomes a second reference point O4. The distance x1 from one end of the region 3S in the width direction to the first reference point O3 is equal to the distance x1 from one end of the region 5S in the width direction to the second reference point O4.
Note that the position of the intermediate molded product K2 with respect to the first mold 3 in the first press device 10 and the position of the intermediate molded product K2 with respect to the first mold 5 in the second press device 20 are, for example, , can be determined by positioning means such as pilot pins PP1 and PP2 provided on the first mold 5. The pilot pin protrudes from the mold and passes through a hole in the intermediate molded product K2. The positioning means for the intermediate molded product K2 is not limited to the pilot pin, and for example, a guide arranged so as to be in contact with the outer periphery of the intermediate molded product K2 may be used as the positioning means.

FIG. 8 is a diagram for explaining the relationship between the configurations of the molds of the first press device and the molds of the second press device. FIG. 8 shows, as an example, the shape of the first mold 3 of the first press device 10 in one cross section D1 and the shape of the first mold 5 of the second press device 20 in the corresponding cross section D2.

As shown in FIG. 8(a), in the first mold 3 for producing an intermediate molded product, a line L_A10 along the mold surface from the first reference point O3 to the inner R stop 3A of the large R surface 3LR The length of the line is 10A. The line length 10C is the length of the line along the mold surface between the first reference point O3 and the outer radius stop 3C of the large radius surface 3LR. The line length 10B is the length of the line along the mold surface between the first reference point O3 and the midpoint 3B of the large R surface 3LR. The midpoint 3B of the large R surface 3LR is the midpoint on the line along the mold surface between the inner R stop 3A and the outer R stop 3C of the large R surface 3LR. On the line along the mold surface, the distance from the midpoint 3B to the inner R stop 3A of the large R surface 3LR is equal to the distance from the midpoint 3B to the outer R stop 3C of the large R surface 3LR. The line length 10D is the length of the line along the mold surface between the first reference point O3 and the inner radius stop 3D of the small radius surface 3SR.

As shown in FIG. 8(b), in the first mold 5 for producing a press-formed product, a line L_20A along the mold surface from the second reference point O4 to the inner R stop 2a of the shoulder portion 5b. The length is 20A. The line length 20C is the length of the line along the mold surface from the second reference point O4 to the outer R stop 2c of the shoulder portion 5b. The line length 20B is the length of the line along the mold surface between the second reference point O4 and the midpoint 2b of the shoulder portion 5b. The midpoint 2b of the shoulder 5b is the midpoint on the line along the mold surface between the inner R stop 2a and the outer R stop 2c of the shoulder 5b. On the line along the mold surface, the distance between the midpoint 2b and the inner R stop 2a of the shoulder 5b is equal to the distance between the midpoint 2b and the outer R stop 2c of the shoulder 5b. The line length 20D is the line length between the second reference point O4 and the point 2d on the side surface 5c. Point 2d is a point located at a distance (20C-20A) along the line of the mold surface from shoulder 5b on side surface 5c. The distance (20C-20A) is the same as the line length of the shoulder portion 5b. The line length 20E is the length of the line along the mold surface between the second reference point O4 and the midpoint 2e of the side surface 5c.

The positional relationship between the intermediate molded product K2 and the first mold 5 for press-formed products shown with reference to FIG. 4 corresponds to the structural relationship between the first mold 3 and the first mold 5. . Therefore, from the viewpoint of improving the attachment of the large R part LR to the shoulder part 5b during the above-mentioned molding and increasing the effect of reducing springback by combining with the bending back of the small R part, intermediate molded product K2 and the first metal The configuration of the first mold 3 and the first mold 5 can be designed based on a preferable positional relationship with the mold 5.

Line lengths 10F, 10A, 10C in cross section D1 of first mold 3 for intermediate molded products and line lengths 20C, 20A in corresponding cross section D2 of first mold 5 for press molded products are as follows:
20C<10F, 10A<20C, 20A<10C
It is preferable to have the following relationship. This relationship corresponds to the conditions of the positional relationship between the intermediate molded product K2 and the first mold 5 in the above-mentioned arrangement step, 2C<1F, 1A<2C, and 2A<1C.

The line lengths 10E and 10B in the cross section D1 of the first mold 3 for intermediate molded products and the line lengths 20C and 20A in the corresponding cross section D2 of the first mold 5 are as follows:
20C<10E, 20A<10B<20C
It is preferable to have the following relationship. This relationship corresponds to the conditions of the positional relationship between the intermediate molded product K and the first mold 5 in the above arrangement step, 2C<1E, 2A<1B<2C.

The line length 10D in the cross section D1 of the first mold 3 for intermediate molded products and the line length 20C in the corresponding cross section D2 of the first mold 5 are:
20C<10D
It is preferable to have the following relationship. This relationship corresponds to the condition of the positional relationship between the intermediate molded product K and the first mold 5 in the above arrangement step, 2C<1D.

The line length 10D in the cross section D1 of the first mold 3 for intermediate molded products and the line length 20D in the corresponding cross section D2 of the first mold 5 are as follows:
10D<20D (=20C+(20C-20A))
It is preferable to have the following relationship. This relationship corresponds to the condition of the positional relationship between the intermediate molded product K and the first mold 5 in the above arrangement process, 1D<2C+(2C-2A).

The line length 10D in the cross section D1 of the first mold 3 for intermediate molded products and the line length 20E in the corresponding cross section D2 of the first mold 5 are as follows:
10D<20E
It is preferable to have the following relationship. This relationship is based on the condition of the positional relationship between the intermediate molded product K and the first mold 5 in the above arrangement step, 1D<(the line along the mold surface from the mold reference point O2 to the midpoint of the side surface 5c) (line length).

(Example of configuration of extension part)
In the placement process in the second press device 20 shown in FIG. The intermediate molded product K2 is arranged so as to extend diagonally. In this case, the intermediate molded product K2 is molded by the first press device 10 into a shape in which the extension portion EN does not protrude further toward the second mold 4 than the small radius portion SR in the pressing direction. Thereby, an increase in the molding depth of the first press device 10 can be suppressed. Further, the arc length in the cross section of the small R portion SR can be increased. By increasing the arc length of the small radius portion SR, the wall closing moment due to unbending increases, further improving dimensional accuracy.

FIG. 9A is a diagram showing a configuration example of an intermediate molded product K2 formed using the first mold 3. FIG. In the example shown in FIG. 9(a), the extending portion EN is formed so as not to protrude from the small radius portion SR in the press direction (vertical direction). That is, the depth F1 in the press direction of the deepest point ENa in the press direction outside the small R part SR of the intermediate molded product K2, based on the inner R stop of the large R part LR, is the depth F1 in the press direction outside the small R part SR. The relationship between the height H in the press direction based on the inner R end of LR is -F1≦H. Here, for the value of F1, in the press direction, the direction of the convexity of the large radius portion is positive (+), and the direction of the convexity of the small radius portion is negative (-). Although the slope of the extension portion EN is not particularly limited, from the viewpoint of suppressing the molding depth, it is preferable that the slope is not too large. That is, it is preferable that the inclination of the extending surface 3EN of the first mold 3 is not too large from the viewpoint of suppressing the molding depth. For example, it is preferable that the depth F1 of the deepest point ENa in the press direction outside the small radius portion SR of the intermediate molded product K2 is not more than twice the height H of the small radius portion SR (F1≦2×H). Moreover, from the same viewpoint, for example, it is preferable that the deepest point ENa on the outside of the small radius portion SR of the intermediate molded product K2 is not deeper than the central portion CH in the pressing direction. In the example of FIG. 9(a), the outer end of the extension portion EN is the deepest point in the press direction outside the small radius portion SR.

FIG. 9(b) is a diagram showing a modification of the intermediate molded product K2 formed using the first mold 3. As shown in FIG. The intermediate molded product K2 in FIG. 9(b) has a flange R portion FRR that curves from the outer end of the extension portion EN, and a flange FR that extends from the flange R portion FRR. For this purpose, the first mold 3 has a flange surface 3FR on the outside of the extension surface 3EN. The flange surface 3FR extends from the outer end of the extension surface 3EN toward the second mold 4 side. In the example of FIG. 9(b), the flange R portion FRR is the deepest point in the pressing direction of the intermediate molded product K2. In this case as well, it is preferable that -F1≦H, and more preferably that F1≦2×H.

(Height of small radius surface)
As shown in FIGS. 9(a) and (b), the height of the small radius portion SR of the intermediate molded product is preferably equal to or greater than the depth F2 of the central portion CH (H≧F2). The depth F2 of the central portion CH is the depth of the deepest point of the central portion C based on the inner radius stop of the large radius portion. For the value of F2, in the press direction, the direction of the convexity of the large radius portion is positive (+), and the direction of the convexity of the small radius portion is negative (-). By increasing the height H and inclining the extension portion EN, the arc length of the small radius portion SR can be increased. By increasing the arc length of the small radius portion SR, the effect of suppressing wall opening can be strengthened. By setting H≧F2, the arc length of the small R portion SR can be increased, and a more appropriate wall opening moment can be generated. In addition, the height H and the depth F2 are distances in the press direction based on the inner R end of the large R surface 3LR.

In addition to H≧F2, the height H of the small radius portion SR of the intermediate molded product preferably also satisfies the following formula.
H≧0.13×R_L+0.13×R_S
By increasing H, the arc length of the small radius portion SR can be increased to some extent, and a more appropriate wall opening moment can be generated.

From the perspective of dimensional accuracy, the arc length of the small radius portion SR can be increased by extending the extension portion EN diagonally toward the first mold 5 side or by increasing the height H of the extension portion EN in the pressing direction. It is desirable to make it long. On the other hand, from the viewpoint of suppressing manufacturing costs (mold costs for intermediate molded products), it is desirable to suppress the molding depth. The reason why both can be established as in this embodiment is because there is a large R portion LR. Since the large radius portion LR protrudes toward the second mold 4 side, the arc length of the small radius portion SR can be increased while the molding depth can be suppressed. Note that the dimensions of H, F1, and F2 in the intermediate molded product are based on the surface on the outside of the bend of the large radius portion (radially outside of the radius of curvature) of both surfaces of the plate of the intermediate molded product.

(Modified example of intermediate molded product)
FIG. 10 is a diagram showing a modification of the first mold 3 for producing the intermediate molded product K2. In the example shown in FIG. 10, in the first mold 3, a flat surface 3FL is provided between the large R surface 3LR and the small R surface 3SR. Thereby, in the intermediate molded product K2, a flat portion that is not curved is formed between the large radius portion LR and the small radius portion SR. In this way, the large R portion LR and the small R portion SR may be continuously connected, or a flat portion may be provided between the large R portion LR and the small R portion SR. By providing the flat portion, for example, the positions of the large radius portion LR and the small radius portion SR can be adjusted.

FIG. 11 is a diagram showing another modification of the first mold 3. As shown in FIG. In the example shown in FIG. 11, a plurality of small radius surfaces 3SR are formed outside the large radius surface 3LR. A flat surface 3FL is provided between the plurality of small radius surfaces 3SR. In this case, the intermediate molded product K2 has a shape including a plurality of small radius portions SR on the outside of the large radius portion LR. In this manner, by providing a plurality of small radius portions SR on at least one of both sides of the central portion CH of the intermediate molded product K2, the effect of the wall closing moment can be increased. However, when the small radius portion SR separates from the large radius portion LR, the bent portion of the small radius portion SR separates from the bent portion formed by the shoulder portion 5b of the first mold 5 during press molding. Therefore, as the small radius portion SR moves away from the large radius portion LR, the effect of the wall closing moment on the small radius portion SR becomes smaller. In order to efficiently obtain the wall closing moment effect, it is preferable to limit the number of small radius portions SR outside the large radius portion LR to a certain number. Although not limited to this, for example, it is preferable that the number of small radius portions SR outside the large radius portion LR is four or less.

Note that the number of large R portions LR is not limited to two, one on each side of the center portion CH. In addition, in consideration of the balance between the effect of the large R part on conforming and the effect of returning to the original shape, it is preferable that the large R part LR is provided in two locations, one on each side of the central part CH. .

When a plurality of small radius sections are provided outside the large radius section, the height H of the small radius section described above is the height of the small radius section located at the highest position. At least a portion of at least one innermost small R section among the plurality of small R sections outside the large R section is bent back in the pressing process. The conditions regarding the line lengths 1D to 1F and 10D to 10F of the above small R portions and other conditions for bending back the above small R portions by press forming are as follows: This applies to the innermost small radius portion (or small radius surface). In addition, when multiple large R parts are provided outside the central part, the conditions regarding the line lengths 1A to 1C and 10A to 10C of the large R parts described above and other large R parts described above are press-formed into the first mold. The conditions for bending along the shoulders of the center part CH (or center plane) apply to the outermost large R part (or large R plane) on each of both sides of the center part CH (or center plane). At least a portion of the outermost large radius portion among the plurality of large radius portions outside the center portion is bent along the shoulder of the first mold in the pressing process.

FIG. 12 is a diagram for explaining another modification of the intermediate molded product K2. FIG. 12(a) shows the process of arranging the plate material in the first press device 10. As shown in FIG. FIG. 12(b) shows the bottom dead center of press forming by the first press device 10. FIG. 12(c) shows a state in which the intermediate molded product K2 is placed in the second press device 20 and sandwiched between the pad 6B and the first mold 5. As shown in FIG. 12(b), the intermediate molded product K2 produced by the first press device 10 has a flange R portion that curves from the outer end of the extension portion EN, and a flange that extends from the flange R portion. The flange R portion curves convexly in the same direction as the large R portion LR.

Therefore, as shown in FIG. 12(a), the first mold 3 of the first press device 10 has a central surface 3CH, a large R surface 3LR, a small R surface 3SR, an extended surface 3EN, and a flange surface 3FR. has. The flange surface 3FR extends from the outer end of the extension surface 3EN to the second mold 4 side via the flange corner.

As shown in FIG. 12(c), in the second press device 20, the intermediate molded product K2 is arranged in such a state that the flange of the intermediate molded product K2 extends in the direction toward the second mold 6 from the outer end of the extension part EN. be done.

As shown in FIG. 12, by forming the flange FR on the intermediate molded product K2, for example, the end of the intermediate molded product does not come into contact with the first mold 5 during press forming by the second press device 20. can be avoided. This avoids a decrease in dimensional accuracy due to stress caused by contact. In addition, in the example shown in FIG. 12, the extension surface 3EN is inclined with respect to the horizontal plane. Therefore, the extension portion EN is formed to be inclined with respect to the horizontal plane. By inclining the extension portion EN in this manner, it is possible to prevent the flange FR from protruding toward the second mold 4 side from the small radius portion SR in the press direction. This can prevent the molding depth from increasing due to the flange FR. In FIG. 12(a), the blank is supported on the outside of the flange surface 3FR of the first mold 3. As this modified example, in the first mold 3, the height Lv1 in the press direction of the highest point in the press direction of the small radius surface 3SR and the height Lv2 of the highest point in the press direction on the outside of the flange surface 3FR are made the same. Good too. In this case, the first mold 3 can support the blank before molding on the outside of the pair of small radius surfaces 3SR and flange surfaces 3FR. Therefore, the blank can be stably supported.

FIG. 13 is a diagram for explaining another modification of the intermediate molded product K2. FIG. 13(a) shows the middle of press forming when no flange is formed on the intermediate molded product K2. FIG. 13(b) shows the middle of press forming when a flange is formed on the intermediate molded product K2. As shown in FIG. 13(a), when no flange is formed on the intermediate molded product K2, the dimension of the extending portion EN in the extending direction becomes correspondingly longer. Therefore, for example, as shown in FIG. 13(a), when the extension part EN is pressed by the second mold 6 during molding, the tip of the extension part EN may come into contact with the first mold 5. Yes (see broken line part A1). In this way, when the intermediate molded product K2 is further pressed by the second mold 6 with the tip portion in contact with the first mold 5, the portion corresponding to the extended portion EN is bent (see broken line portion A2). . This may generate extra stress and reduce dimensional accuracy.

As shown in FIG. 13(b), by forming a flange extending from the outer end of the extension part EN toward the second mold 6 on the intermediate molded product K2, the intermediate molded product K2 It is possible to prevent the tip of the mold from coming into contact with the first mold 5 (see broken line portion A3). Thereby, a decrease in dimensional accuracy due to contact of the tip of the intermediate molded product K2 can be avoided.

In addition, the flange FR and the flange R part FRR of the intermediate molded product K2 can be formed into the target shape of the flange and the flange curved part of the press molded product K3 by press forming by the first press device 10. That is, when the intermediate molded product K2 is press-formed into the press-formed product K3, the flange R portion and the flange of the intermediate molded product K2 are positioned at the bottom dead center of the flange R portion and the flange of the press-formed product K3. It is desirable to leave it there. This can prevent unnecessary deformation and stress from occurring in the flange R portion and the flange formed by the intermediate molded product K2 during press molding by the second press device 20, thereby preventing a decrease in dimensional accuracy.

(Modified examples of press equipment and press process)
FIG. 14 is a diagram showing a modification of the first press device 10. As shown in FIG. In the example shown in FIG. 14(a), the first mold 3 of the first press device 10 is divided into a holder portion 3a and a main body portion 3b. A pair of main body parts 3b are arranged on both sides of the holder part 3a in a direction (lateral) perpendicular to the pressing direction. The holder portion 3a and the main body portion 3b are configured to be movable in the press direction independently of each other. With the plate material K1 being held between the holder part 3a and the second mold 4, the second mold 4 and the main body part 3b are brought relatively close to each other, whereby the plate material K1 is press-molded. In this way, by molding while being held by the holder part 3a, the plate material K1 becomes difficult to shift during molding.

For example, when forming the flange FR on the intermediate molded product K2, the forming depth of the first press device 10 may be deeper than when no flange is formed. If the molding depth is deep and press molding (stamping molding) is performed using a first mold and a second mold in which molding surfaces are integrally formed, there is a high possibility that the plate material will shift during molding. Therefore, when the molding depth becomes deep, such as when forming a flange, the effect of press molding using the holder portion is more effectively exhibited.

In the example shown in FIG. 14(a), the main body portion 3b is fixed to the bed 13. The holder portion 3a is movably supported in the press direction by a power mechanism 16. The power mechanism 16 may be, for example, a power mechanism included in the press device 10 such as a cushion. Power mechanism 16 may be, for example, a hydraulic or mechanical mechanism. Alternatively, the holder part 3a may be movably supported with respect to the mold holder (not shown) or the main body part 3b by a support member provided on a mold holder (not shown) that holds the first mold 3. . The support member may be an elastic member that can be expanded and contracted, such as a spring such as a gas spring or a coil spring, or a fluid cylinder. The mold holder is fixed to the bed 13. Note that by using the power mechanism included in the press device 10 as the power mechanism 16, the mold cost can be reduced compared to the case where a support member is arranged in the mold holder.

In the example shown in FIG. 14(a), the first mold 3 of the first press device 10 is divided into a holder part 3a and a main body part 3b, but the second mold 4 is divided into a holder part and a main body part. may be done. In this way, the first press device 10 may have a configuration in which at least one of the first mold 3 and the second mold 4 includes a holder portion.

FIG. 14(b) shows the state of the press apparatus 10 shown in FIG. 14(a) at the bottom dead center. As shown in FIG. 14(b), the first mold 3, at the bottom dead center, covers the center part of the intermediate molded product K2, a pair of large R parts, a pair of small R parts, a pair of extended parts, and a flange. , a pair of large radius surfaces 3LR, a pair of small radius surfaces 3SR, a pair of extension surfaces 3EN, and a pair of flange surfaces 3FR. In this example, the main body portion 3b is provided with a flange surface 3FR, and the holder portion 3a is provided with a central surface 3CH, a large radius surface 3LR, a small radius surface 3SR, and a portion of an extension surface 3EN. By providing the flange surface 3FR on either the holder portion 3a or the main body portion 3b and providing the center surface 3CH on the other, misalignment during molding can be efficiently suppressed.

FIG. 15 is a diagram showing a further modification of the first press device 10 shown in FIG. 14. In the example shown in FIG. 15, the position of the boundary between the holder portion 3a and the main body portion 3b is different from that in FIG. In the example of FIG. 14, the boundary between the holder portion 3a and the main body portion 3b is between the flange surface 3FR and the extension surface 3EN. On the other hand, in the example of FIG. 15, the boundary between the holder portion 3a and the main body portion 3b is between the center surface 3CH and the large R surface 3LR. In this case, with the plate material K1 being sandwiched between the center surface 3CH of the holder part 3a of the first mold 3 and the second mold 4, the main body part 3b and the second mold 4 are brought relatively close to each other and press-molded. be able to.

FIG. 16 is a diagram showing a modification of the second press device 20. As shown in FIG. In the example of FIG. 16, the first mold 5 has a base surface 5d extending in a direction perpendicular to the pressing direction from the outer ends of the side surfaces 5c on both sides of the convex portion. A recess 5e is provided in the base surface 5d. This recess 5e can prevent the end of the intermediate molded product K2 from coming into contact with the base surface 5d during press molding by the second press device 20.

FIG. 17 is a diagram showing another modification of the second press device 20. In the example of FIG. 17, the second mold 6 has a base surface 6d (second base surface) opposite to the base surface 5d of the first mold 5. A recess 6e is provided in the base surface 6d. This recess 6e can prevent the end (for example, flange FR) of the intermediate molded product K2 from coming into contact with the base surface 6d during press molding by the second press device 20. Furthermore, in this example, the distance in the pressing direction between the pressing surface 6Ba of the pad 6B at the initial position and the base surface 6d of the second mold 6 can be reduced by the height of the flange FR. Thereby, the size of the elastic member that is the support member 6Bc and the second mold 6 can be reduced.

FIG. 18 is a diagram showing another modification of the second press device 20. FIG. 18 shows the state of the second press device 20 at the bottom dead center. In the example of FIG. 18, the second mold 6 has a side surface 6c that faces the side surface 5c of the first mold 5 in the pressing direction, and a base surface 6d that faces the base surface 5d. A shoulder 6b is formed between the base surface 6d and the side surface 6c. The base surface 6d is formed at a position away from the base surface 5d toward the second mold in the press direction so as not to contact the press-formed product K3 at the bottom dead center. The shoulder portion 6b and the base surface 5d of the second mold 6 serve as a separating portion that is separated from the base surface 5d at the bottom dead center. Thereby, a space B1 is created between the shoulder portion 6b and base surface 6d of the second mold 6 and the press-formed product K3 at the bottom dead center. That is, the shoulder portion 6b and base surface 5d of the second mold 6 do not press the intermediate molded product K2 during the molding process.

For example, by press forming using the first press device 10, the flange FR and flange R portion FRR of the intermediate molded product K2 can be formed into the target shape of the flange and flange curved portion of the press molded product K3. In this case, the second press device 20 does not need to form the flange and the flange curved portion. In this case, the shoulder portion 6b and base surface 6d of the second die 6 at the bottom dead center may be spaced apart from the first die in the press direction. If the second press device 20 does not separate the shoulder portion 6b and the base surface 6d and clamps the flange between the second mold 6 and the first mold at the bottom dead center, it will be pressed twice and unnecessary. Deformation may occur and dimensional accuracy may decrease. Therefore, by using the shoulder portion 6b and the base surface 6d of the second mold 6 as separating portions, the flange R portion FRR and the flange FR can be prevented from being pinched during the pressing process of the second press device 20. This reduces the forming load on the second press device 20. Furthermore, since the size of the second mold 6 is reduced, mold costs can be reduced.

The method for manufacturing a press-formed product and the manufacturing equipment in this embodiment can be used, for example, to manufacture automobile parts. Automotive parts include, but are not limited to, side sills, bumpers, floor side members, pillars, floor tunnels, rear side members, and the like. These parts have, for example, a tensile strength of 590 MPa or more and 1900 MPa or less. The plate thickness is 0.8 mm or more and 2.3 mm or less. The tensile strength here is the value obtained when a tensile test piece is cut out from the flat surface of the top plate of the member and pulled. If it is not possible to cut out a tensile test piece due to size constraints, hardness can be used instead. As an example, the Vickers hardness at a load of 1 kg is 200 Hv or more and 600 Hv or less. Automotive parts often have grooves or steps on the top plate to improve crash characteristics and rigidity.
The press-formed product in this embodiment is a molded product with a flange or flange R as shown in FIGS. 1 to 18, but it may also be a molded product without a flange or flange R. Examples of automotive parts include reinforcing parts (side sills, bumpers, floor side members, pillars, floor tunnels, or rear side members), arm parts such as lower arms and upper arms, suspension members, and frame parts for ladder frames. It will be done. As an example, the reinforcing component has a tensile strength of 590 MPa or more and 1900 MPa or less. The plate thickness of the reinforcing component is, for example, 0.8 mm or more and 2.3 mm or less. For example, the arm parts, suspension members, and frame parts have a tensile strength of 590 MPa or more and 1400 MPa or less, and a plate thickness of 1.8 mm or more and 4.0 mm or less, for example.

Although FIGS. 1 to 18 illustrate the case where the cross-sectional shapes of the intermediate molded product K2 and the press-formed product K3 are symmetrical, the present invention is also applied to the production of asymmetrical press-formed products. I can do it.

The center portion CH of the intermediate molded product K2 and the top plate of the press molded product K3 may be flat or shaped. For example, if there is a shape, the surface of the central portion or top plate may include a flat surface and at least one of a convex surface and a concave surface. 1 to 18 illustrate a central portion or top plate that includes a concave surface. Note that the shape of the central portion or the top plate may change from a convex portion to a concave portion along the longitudinal direction of the central portion or the top plate. Further, as an example of a concave or convex surface, a step may be provided.

Although the present embodiment has been described above, the present invention is not limited to the above embodiment. For example, in the embodiment described above, the second press device 20 includes a pad 6B and a pair of second mold body portions 6A on both sides of the pad 6B. On the other hand, the second press device 20 may be configured without the pad 6B. For example, the second mold 6 of the second press device 20 may be configured as an integral mold with an integrally formed molding surface.

The press-formed product K3 produced by the second press device 20 is not limited to the above example. The press-formed product K3 can be a member having a hat-shaped or U-shaped cross section. Note that the top plate of the press-formed product K3 may have a shape such as a groove or a stepped shape, or may be flat. The press-formed product K3 may have a cross-sectional shape that extends linearly in the longitudinal direction while maintaining its shape, or may have a curved shape. Further, the press-formed product K3 may be a member whose cross section differs depending on the position in the longitudinal direction. In the above example, the cross-sectional shape of the vertical wall of the press-formed product K3 is a straight line, but the cross-sectional shape of the vertical wall may include a curved portion. That is, the cross-sectional shape of the side surface 5c of the convex portion of the first mold 5 of the second press device 20 may include a curved portion. In this case, the radius of curvature R_C of the curved portion of the vertical wall and side surface 5c is sufficiently larger than the radius of curvature R_S of the small radius portion SR, and for example, the difference in the radius of curvature is greater than the plate thickness t of the intermediate molded product (R_S+t< R_C), or the magnification can be 50 times or more (50×R_S≦R_C). In this case, the curved portion of the side surface 5c is less likely to impede the bending back of the small radius portion.

In the above example, in the second press device 20, the first mold 5 is fixed, and the second mold 6 is movable in the pressing direction. On the other hand, the first mold 5 may be movable and the second mold 6 may be fixed. Alternatively, both the first mold 5 and the second mold 6 may be movable. In either case, the first mold 5 and the second mold 6 can be brought relatively close to each other in the pressing process. In the first press device 10, either one of the first mold 3 and the second mold 4 may be fixed and the other may be movable, or both may be movable.

Before and after each of the pressing process of the intermediate molded product by the first press device 10 and the pressing process of the molded product by the second press device 20, other pressing steps or other processing steps may be performed. For example, after the pressing process of the second press device 20, a hole may be made in the molded product, an unnecessary portion of the molded product may be trimmed, or a part of the molded product (for example, a flange) may be bent.

As mentioned above, the round end of the shoulder of the convex part of the first mold is defined by the curved part of the shoulder in the cross section perpendicular to the longitudinal direction of the convex part and the flat part (straight part) on the outside or in the opposite direction. This is the boundary with the curved part. Also, for example, in cross-section, the top or side surface adjacent to the shoulder may be slightly curved in the same direction as the shoulder. In this case, the degree of curvature of the adjacent top or side surface is sufficiently smaller than the degree of curvature of the shoulder. In this case, in the cross section, the point where the degree of curvature changes is defined as the boundary between the shoulder and the adjacent top or side surface, that is, the rounded end of the shoulder. In this case, the radius of curvature of the side surface or top surface adjacent to the shoulder is larger than the radius of curvature of the shoulder, for example, 50 times or more. Note that the radius of curvature of the curved portion on the top or side surface is defined as the radius of curvature of a circle passing through the three points of the curved portion at both ends of the curved portion and the midpoint between them in a cross section perpendicular to the longitudinal direction of the convex portion, similar to the shoulder portion. Let be the radius. The R stop on the side opposite to the shoulder of the curved part of the side surface is the boundary between the curved part of the side surface and the flat part (straight part) on the outside thereof or the curved part in the opposite direction, similar to the R stop of the shoulder part described above. shall be. Even when the base surface adjacent to the shoulder portion is curved in the same direction as the curved portion of the side surface, the point at which the degree of curvature changes is defined as the R end, similarly to the above.

(Example)
CAE analysis was performed to form a press-formed product K3 having a cross section shown in FIG. 19. For the CAE analysis, LS-DYNA ver971 rev9.31, a general-purpose finite element method analysis software, was used. Molding analysis and springback analysis were performed as CAE analysis. The conditions for the material used in the analysis were a steel plate with a tensile strength of 1280 MPa, a 0.2% yield strength of 850 MPa, and a plate thickness of 1.6 mm. Swift's formula: σ=K(ε+ε0)^n (σ: equivalent stress, ε: equivalent plastic strain, K=1607 MPa, ε0=0.0002, n=0.078) was incorporated into the analysis.

In addition, as analysis conditions, the mesh size of the material was 1.6 mm square, the element was a shell reduction integral element, and the number of integral points was 9. The coefficient of friction between the material and the mold was 0.15 mm.

A press-formed product having a flange portion shown in FIG. 19 was analyzed using two methods: a comparative method and an example method. The comparative method was a pad bending method in which a flat plate was pressed while being pressed by a pad to form the shape shown in FIG. 19. FIG. 20 shows pad bending in the comparative example construction method. The example construction method includes a first pressing step in which a steel plate is pressed to form an intermediate molded product K2, and a second pressing step in which the intermediate molded product K2 is pressed and molded into the shape shown in FIG. 19. The first pressing step was stamping molding without using a pad or holder. Pad bending was used in the second pressing step. The pad conditions were a pad pressure of 150 kN and a pad stroke of 40 mm. FIG. 21 shows an example of the intermediate molded product model KM2 and the first mold model 5M in the second pressing step of the example construction method. For the intermediate molded product, both models were used: one without a flange as shown in FIG. 9(a), and one with a flange as shown in FIG. 9(b). The intermediate molded product had a H of 7.5 mm and an F2 of 2 mm. The first mold model 5M has a configuration corresponding to the first mold 5 described above.

As Examples and Comparative Examples, multiple analyzes were conducted under conditions in which the shape of the intermediate molded product K2 and the positional relationship with the first mold were different. Table 1 below shows the conditions of the positional relationship of the intermediate molded product with respect to the first mold. In Table 1, line lengths 1A to 1D and line lengths 2A to 2E are the same as the line lengths shown in FIG. 4 above. As examples, analyzes were conducted for cases in which only P1 is satisfied, only P1 and P2 are satisfied, only P1 to P3 are satisfied, and cases in which all P1 to P5 are satisfied.

The first evaluation item was the wall opening angle θ in the shape after springback analysis shown in FIG. The wall opening angle θ was the angle between the vertical wall of the analysis result and the vertical wall of the target shape. As the angle value, a positive value indicates the angle of wall opening, and a negative value indicates the angle of wall closing. The wall opening angle θ was determined by grades A to G shown in Table 2 below. G is the same as the comparative example, F has almost no effect, and A to E are effective.

The second evaluation item was the pad floating amount d (mm) shown in FIG. The pad floating amount is the amount of pad floating during molding. Further, the pad floating amount d was determined according to the grades X to Z shown in Table 3 below. Z is the same as the comparative example, Y has almost no effect, and X has an effect.

Tables 4 to 6 below show the analysis results.

In Table 4 above, Comparative Example 1 is the analysis result of the comparative construction method. Example 1 and Comparative Examples 2 and 3 are the analysis results of the example construction method. In Comparative Example 2, in the intermediate molded product, the radius of curvature of the large radius portion was set to be smaller than the radius of curvature of the small radius portion (R_S>R_L). In Comparative Example 3, in the second pressing step, the condition was such that the entire large radius portion was in contact with the outer side surface of the shoulder of the convex portion of the first mold (2C<1A).
The wall opening angle θ in Comparative Example 1 was 13.4°, and the evaluation was G.
In Example 1, θ was smaller than in Comparative Example 1, and the evaluation was B, indicating an improvement effect.
In Comparative Example 2, the evaluation of θ was F, and there was almost no improvement effect.
In Comparative Example 3, the evaluation of θ was F, and there was almost no improvement effect.
The pad floating amount d during molding in Comparative Example 1 was 2.6 mm, and the evaluation was Z. On the other hand, in Example 1, the thickness was less than 0.1 mm (evaluation: X), and a large improvement effect was observed.

Example 1 in Table 5 has the same conditions as Example 1 in Table 4. Example 201 differs from Example 1 only in the shape of the top plate of the intermediate molded product. In Example 201, the shape of the top plate of the intermediate molded product was made flat. The shape of the top plate of the intermediate molded product of Example 1 was the same as that of the press molded product. Example 1 received higher evaluations than Example 201 in both the wall opening angle θ and the floating amount of the pad.

Comparative Example and Example 1 are under the same conditions as Example 1 in Table 4. Examples 301 to 309 had better evaluation of θ than Comparative Example 1.

Example 301 is an analysis under the condition that F1 = -7.5 mm and the extension portion is horizontal. Compared to Example 301, in which the extending portion was inclined with F1=4 mm, the evaluation of θ was better in Example 1, in which the extending portion was inclined with F1=4 mm.

Example 302 is a condition in which R_S and R_L of the intermediate molded product are increased from Example 1 within the range of 5≦R_S≦18. In Example 302, the evaluation of θ was B, and the same improvement effect as in Example 1 was obtained.

Example 303 is a condition in which R_S and R_L of the intermediate molded product are increased outside the range of 5≦R_S≦18 from Example 1. In Example 303, the evaluation of θ was E, and the evaluation of θ was higher in Example 1 within the range of 5≦R_S≦18 than in Example 303.

Example 304 is a condition in which the number of small R parts outside the large R part of the intermediate molded product is increased from one to two from Example 1. The evaluation of θ of Example 304 was A, which was better than that of Example 1. The conditions for the small R portion shown in Table 6 are the conditions for the inner small R portion of the two outer small R portions of the large R portion.

Example 305 is a condition in which a flange is provided on the intermediate molded product from Example 1. The evaluation of θ in Example 305 was A, which was better than in Example 1.

Examples 306 to 308 are conditions in which the positional relationship between the large R part and the small R part of the intermediate molded product was changed from Example 1. As the positional relationship conditions were increased from P1 to P1 to P5, the evaluation of θ improved.

In Example 309 in which R_S was 4 mm, the evaluation of θ was B, and the same improvement effect as in Example 1 was obtained. In Example 309, since the small radius was small, traces of the small radius remained.

The pad floating amount d during molding in Examples 301 to 309 was all less than 0.1 mm (evaluation: X), and a large improvement effect was observed.

Although one embodiment of the present invention has been described above, the embodiment described above is merely an example for implementing the present invention. Therefore, the present invention is not limited to the embodiments described above, and can be implemented by appropriately modifying the embodiments described above without departing from the spirit thereof.

3 First mold for intermediate molding 4 Second mold for intermediate molding 5 First mold 6 Second mold 10 First press device 20 Second press device K1 Plate material K2 Intermediate molded product K3 Press molded product CH Center part LR Large R part SR Small R part EN Extension part

Claims (10)

A method for manufacturing a press-formed product, the method comprising:
arranging the intermediate molded product between a first mold having a convex portion convex in the pressing direction and a second mold having a concave portion corresponding to the convex portion;
a pressing step of bringing the first mold and the second mold relatively close together and press-molding the intermediate molded product into a shape that corresponds to the convex part of the first mold and the concave part of the second mold; and,
The convex portion of the first mold has a top surface, a pair of shoulders at both ends of the top surface, and side surfaces each extending from the pair of shoulders,
The intermediate molded product includes a central portion, a pair of large R portions on both sides of the central portion, small R portions on the outside of each of the pair of large R portions, and an extending portion on the outside of the small R portion. including;
The large R portion is curved convexly in a first direction, and the small R portion is curved convexly in a second direction opposite to the first direction.
The radius of curvature of the small R portion is smaller than the radius of curvature of the large R portion,
In the arrangement step, the intermediate molded product is placed so that the first direction is a direction toward the first mold in the press direction, and the second direction is a direction toward the second mold in the press direction. is arranged, and at least a portion of each of the pair of large radius portions is arranged at a position overlapping each of the pair of shoulders of the convex part of the first mold when viewed from the press direction,
In the pressing step, the pair of large R portions of the intermediate molded product are bent along the pair of shoulders of the convex portion of the first mold, and the small R portion is bent back to form the convex portion. A method for producing a press-formed product, which is press-formed into a shape along the side surface of the product.
A method for manufacturing a press-formed product according to claim 1, comprising:
In the arrangement step, in a cross section perpendicular to the longitudinal direction of the convex part,
A line length 1A that is the length of a line along the intermediate molded product from a reference point in the center of the intermediate molded product to the inner R stop of the large R portion;
a line length 1C from the reference point to the outer R end of the large R section;
a line length of 1F from the reference point to the outer R stop of the small R section;
A line length 2A from the mold reference point projected onto the top surface of the first mold in the press direction to the radius stop on the inside of the shoulder, and
The line length 2C from the mold reference point to the outside R stop of the shoulder is,
A method for manufacturing a press-formed product, wherein the intermediate molded product is arranged so as to have a relationship of 2C<1F, 1A<2C, and 2A<1C.

A method for manufacturing a press-formed product according to claim 2, comprising:
In the arrangement step, in a cross section perpendicular to the longitudinal direction of the convex part,
A line length 1B from the reference point to the midpoint of the line along the intermediate molded product between the inner R stop and the outer R stop of the large R part, and
The line length 1E from the reference point to the midpoint of the line along the intermediate molded product between the inner R stop and the outer R stop of the small R portion is:
A method for producing a press-formed product, wherein the intermediate molded product is arranged such that 2C<1E, 2A<1B<2C.
A method for producing a press-formed product according to claim 2 or 3,
In the arrangement step, in a cross section perpendicular to the longitudinal direction of the convex part,
The line length 1D from the reference point to the inner R end of the small R portion is
A method for manufacturing a press-formed product, wherein the intermediate molded product is arranged so as to have a relationship of 2C<1D.
A method for producing a press-formed product according to any one of claims 1 to 3, comprising:
In the arrangement step, the intermediate molded product is arranged such that the extending portion of the intermediate molded product extends outward from the small radius portion in a direction perpendicular to the pressing direction or diagonally toward the first mold side. A method for manufacturing a press-formed product.

A method for manufacturing a press-formed product according to any one of claims 1 to 3, comprising:
The method for manufacturing a press-molded product, wherein the intermediate molded product has a flange R portion that curves convexly in the first direction on the outside of the extension portion, and a flange that extends outward from the flange R portion.
A method for producing a press-formed product according to any one of claims 1 to 3, comprising:
In the pressing step, at least from the start of pressing until the small radius portion is bent back, the tip portion of the intermediate molded product does not come into contact with either the first mold or the second mold. A method for manufacturing a press-molded product, in which a first mold and a second mold are formed.
A method for producing a press-formed product according to any one of claims 1 to 3, comprising:
A method for manufacturing a press-formed product, further comprising an intermediate-formed product pressing step of producing the intermediate molded product by press-molding a plate material using an intermediate molding die.
A method for producing a press-formed product according to any one of claims 1 to 3, comprising:
The second mold includes a pad disposed to face the convex portion of the first mold in the pressing direction, and a second mold main body disposed on both sides of the pad,
In the pressing step, the first mold and the second mold main body are brought relatively close to each other with at least a part of the central part of the intermediate molded product being sandwiched between the pad and the convex part, A method for producing a press-formed product, comprising press-molding the intermediate molded product.
a first press device including a first mold for intermediate molding and a second mold for intermediate molding for press molding a plate material to produce an intermediate molded product;
a second press device including a first mold and a second mold for press-molding the intermediate molded product to produce a press-formed product;
The first mold has a convex part that is convex in the pressing direction, and the second mold has a concave part corresponding to the convex part,
The first mold for intermediate molding and the second mold for intermediate molding mold the plate material into a central portion, a pair of large R portions on both sides of the central portion, and the outer sides of each of the pair of large R portions. configured to have a shape including a small R portion and an extending portion outside the small R portion,
The large R portion is curved convexly in a first direction, and the small R portion is curved convexly in a second direction opposite to the first direction, and the small R portion is curved convexly in a second direction opposite to the first direction. The radius of curvature of the portion is smaller than the radius of curvature of the large R portion,
In the second press device, the convex portion of the first mold has a top surface, a pair of shoulders at both ends of the top surface, and side surfaces each extending from the pair of shoulders,
In the first mold, the pair of large R portions of the intermediate molded product are bent along the pair of shoulders of the convex portion of the first mold, and the small R portion is bent back. Manufacturing equipment configured to be press-molded into a shape along the side surface of the convex portion.

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