JP7421150B2 - Press molded body manufacturing method and press molded body manufacturing apparatus - Google Patents

Description

The present invention relates to a method for manufacturing a press-formed body and an apparatus for manufacturing a press-formed body.
This application claims priority based on Japanese Patent Application No. 2020-071036 filed in Japan on April 10, 2020, the contents of which are incorporated herein.

In order to reduce the weight of automobile parts due to global environmental issues and to improve collision safety of automobiles, it is necessary to make automobile parts stronger and thinner. On the other hand, as the thickness becomes higher and the thickness becomes thinner, molding defects such as breakage and wrinkles tend to occur. As a method for suppressing this type of molding defect, for example, a method for manufacturing a press-formed body described in Patent Document 1 below is known.

Patent No. 5569661

As a result of intensive studies, the inventors of the present application have found that, for example, when press-molding a front side member, which is one of the frame parts of an automobile, the front side member has an inwardly curved portion in a top view, a saddle shape in a side view, etc. It has been found that wrinkles are likely to occur in the ridgeline portions where each part (part where shrinkage deformation occurs during press molding) is formed.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to suppress the occurrence of wrinkles during press molding.

(1) A method for manufacturing a press-formed body according to one aspect of the present invention includes: a first wall; a second wall extending in a direction crossing the first wall; and a first wall and the second wall. an inwardly curved part in which the second wall is recessed toward the first wall when viewed from the normal direction of the first wall; A method for producing a press-formed body, comprising a pressing step of press-working the blank by moving a die closer from the pad side to the punch side while sandwiching and pressing the blank between a punch and a pad, In the pressing step, at least a portion of the second wall is formed in the inwardly curved portion while pressing a portion of the ridgeline portion of the blank with the punch and the pad.

(2) The method for manufacturing a press-formed body according to one aspect of the present invention includes: a first wall; a second wall extending in a direction crossing the first wall; and a first wall and the second wall. and a ridgeline portion that connects the two walls and forms a curve when viewed in cross section , and a saddle-shaped portion in which the first wall is recessed toward the second wall when viewed from the normal direction of the second wall. A method for producing a press-formed body comprising: a pressing step of press-working the blank by moving a die close from the pad side to the punch side while sandwiching and pressing the blank between a punch and a pad; In the step, at least a portion of the second wall is molded in the saddle-shaped portion while a portion of the ridgeline portion of the blank is pressed by the punch and the pad.

The inventors of the present application discovered the following matters regarding the occurrence of wrinkles in a manufacturing method for manufacturing a press-molded body from a blank.
(A) Wrinkles are likely to occur in the ridgeline portions forming the inwardly curved portions and saddle-shaped portions of the press-formed body.
(B) One of the causes of the above-mentioned wrinkles is that when forming the second wall with a punch and die, the blank shrinks and deforms at the inwardly curved part and saddle-shaped part of the press-formed body. There is a phenomenon.
(C) The aforementioned deflection occurs when the blank is stretched and flanged in the process of forming the second wall.
(D) In each of the inwardly curved portion and the saddle-shaped portion of the press-formed body, the second wall is stretch flanged from the start to the end of molding.
(E) The aforementioned deflection can be suppressed by molding at least a portion of the second wall while pressing a portion of the ridgeline portion of the blank with a pad.

The above (D) will be explained in more detail.
In the inwardly curved part of the press-formed body, in the process of forming a part of the blank into the second wall of the press-formed body, the part of the blank that will become the second wall stretches along the inwardly curved part and is deformed into a flange. It will be done. Furthermore, the amount of elongation deformation of the blank in the portion that will become the second wall increases as press forming progresses. That is, the farther away from the first wall part of the second wall part, the greater the amount of elongation deformation. On the other hand, material flow from the surroundings occurs in the ridgeline portion and the first wall portion of the inwardly curved portion of the press-formed body. Compressive deformation caused by this material flow causes wrinkles to occur.
Further, in the saddle-shaped portion of the press-formed body, in the process of forming a part of the blank into the second wall of the press-formed body, a portion of the blank that will become the second wall is pressed by a die and bent. At this time, the portion that will become the second wall is stretched along the saddle-shaped portion and deformed into a flange. The amount of elongation deformation of the blank in the portion that becomes the second wall increases as the press forming progresses, similar to the inwardly curved portion. That is, the farther away from the first wall part of the second wall part, the greater the amount of elongation deformation. On the other hand, material flow from the surroundings occurs in the ridgeline portion and the first wall portion of the saddle-shaped portion, similar to the inwardly curved portion described above. Compressive deformation caused by this material flow causes wrinkles to occur.

The inventors of the present invention, who discovered the above matters, formed at least a part of the second wall with the punch and die while pressing a part of the ridgeline part of the blank between the punch and the pad. I came up with an idea. Thereby, compressive deformation associated with the above-mentioned stretch flange deformation can be suppressed. Therefore, the generation of wrinkles in the inwardly curved portion and the saddle-shaped portion due to the compressive deformation can be suppressed. As a result, it is possible to suppress the occurrence of wrinkles and to form a high-quality press-formed product.

(3) In the method for manufacturing a press-formed body according to (1) or (2) above, in the pressing step, the pad and the punch approach each other with the blank in between, thereby pressing the blank; Further, the die and the punch may move in the same direction as the direction in which the pad and the punch approach, and the die and the punch may press the second wall.

As described above, since the die and punch move in the same direction as the direction in which the pad and punch approach, there is no need for movement in a direction different from the direction in which the pad and punch approach. Therefore, by reducing the number of parts in the manufacturing equipment, maintenance and parts replacement work are reduced.

(4) An apparatus for manufacturing a press-formed body according to one aspect of the present invention includes a punch, a pad, and a die, and is used in the method for manufacturing a press-formed body according to any one of (1) to (3) above. The pad is provided on a first surface that presses a portion of the blank that becomes the first wall, and on a side edge of the first surface, and the pad is provided on a side edge of the first surface, and the pad is provided on a side edge of the first surface. a protrusion that presses a part of the ridgeline portion.

By providing the pad with a protrusion that presses the ridgeline portion of the molded body, it is possible to effectively press the portion of the blank that will become the ridgeline portion.

(5) In the press-formed body manufacturing apparatus according to (4) above, the protrusion may form a curve that is convex toward the punch side in a cross section that crosses the first surface and the protrusion.

When the protrusion forms a curve convex toward the punch side as described above, the above-mentioned pressing by the protrusion can be made more effective by appropriately adjusting the curvature of this curve.

(6) In the apparatus for manufacturing a press-formed body according to (4) or (5) above, in a cross section including the punch, the pad, and the die, an end surface of the pad is located on the second wall of the punch. A position that passes through a boundary between a contacting part and a part of the punch that contacts the ridgeline part, and is in contact with a straight line parallel to a direction of relative movement between the punch and the die, or is located closer to the first wall than the straight line. You can.

By arranging the pads as described above, the range pressed by the pads becomes part of the first wall and ridgeline portion of the blank. The second wall is pressed with a die. Thereby, a shape can be given to the second wall. Further, it is possible to suppress the blank from being bent (later becoming wrinkled) at the ridgeline portion that occurs during the second wall forming.

According to the present invention, it is possible to suppress the occurrence of wrinkles during press molding.

FIG. 1 is a perspective view of a press-formed body manufactured by a method for manufacturing a press-formed body according to an embodiment of the present invention. FIG. 2 is a top view of the press molded body shown in FIG. 1. FIG. FIG. 2 is a side view of the press-formed body shown in FIG. 1. FIG. FIG. 1 is an exploded perspective view of a press-formed body manufacturing apparatus used in a press-formed body manufacturing method according to an embodiment of the present invention. FIG. 5 is a cross-sectional view of the manufacturing apparatus shown in FIG. 4, showing a state in which the blank is not pressed. FIG. 5 is a cross-sectional view of the manufacturing apparatus shown in FIG. 4, showing a state in which a blank is being pressed. 6 is an enlarged view of a part of the cross section shown in FIG. 5. FIG. 7 is an enlarged view of a part of the cross section shown in FIG. 6. FIG. 5 is a diagram schematically showing a part of the outer shape of the pad shown in FIG. 4. FIG. FIG. 2 is a diagram for explaining the effects of the method for manufacturing a press-formed body according to an embodiment of the present invention, and is a locally enlarged and simplified perspective view of an inwardly curved portion of the press-formed body. . FIG. 2 is a diagram for explaining the effects of the method for manufacturing a press-formed body according to an embodiment of the present invention, and is a locally enlarged and simplified perspective view of a saddle-shaped portion of the press-formed body. FIG. 2 is an exploded perspective view of a press molded body manufacturing apparatus used in a press molded body manufacturing method according to a comparative example of the present invention. FIG. 13 is an enlarged view showing a part of the cross section of the manufacturing apparatus shown in FIG. 12 when a blank is being pressed. 13 is a diagram schematically showing a part of the outer shape of the pad shown in FIG. 12. FIG. It is a figure which shows the result of the simulation calculated on the premise of the manufacturing method of a comparative example, Comprising: It is a top view of the press molded object which shows wall thickness by light and shade. FIG. 3 is a diagram showing the results of a simulation calculated based on the manufacturing method of a comparative example, and is a side view of a press-formed body in which the wall thickness is shown in shading. It is a figure which shows the result of the simulation calculated based on the manufacturing method of an Example, Comprising: It is a top view of the press molded object which shows the wall thickness by light and shade. FIG. 2 is a diagram showing the results of a simulation calculated based on the manufacturing method of the example, and is a side view of a press-formed body in which the wall thickness is shown in shading.

Hereinafter, a method for manufacturing a press molded body 30 according to an embodiment of the present invention will be described with reference to FIGS. 1 to 11. In this manufacturing method, a press molded body 30 is manufactured from a blank B using a manufacturing apparatus 10.

(Press molded body 30)
In explaining the method for manufacturing the press-formed body 30, first, the press-formed body 30 manufactured by this manufacturing method will be described.

As shown in FIGS. 1 to 3, the press-formed body 30 is a so-called front side member. The shape of the press molded body 30 is a channel shape. In the press-formed body 30, the length in the length direction X is longer than the length in the width direction Y. The press molded body 30 is open toward one side in the height direction Z.

The press molded body 30 includes a first wall 31, a second wall 32, a ridgeline portion 33, and a flange 34.
The first wall 31 has a generally rectangular shape when viewed from its normal direction. The first wall 31 forms the bottom surface of a channel-shaped groove formed by the press-formed body 30 .
Note that the length of the first wall 31 in the longitudinal direction X is, for example, 640 mm or more and 960 mm or less. The length of the first wall 31 in the width direction Y is, for example, 70 mm or more and 180 mm or less. The thickness of the first wall 31 is, for example, 0.8 mm or more and 2.0 mm or less. The tensile strength of the first wall 31 is, for example, 780 MPa or more and 1470 MPa or less.

The second wall 32 extends in a direction crossing the first wall 31. The second wall 32 is disposed at the edge of the first wall 31 in the width direction Y with a ridgeline portion 33 interposed therebetween. Two second walls 32 are provided sandwiching the first wall 31 in the width direction Y. The second wall 32 extends in the height direction Z of the press molded body 30. The second wall 32 forms a groove side surface of the channel shape.

The ridgeline portions 33 are provided at both end edges of the first wall 31 in the width direction Y, respectively. Each ridgeline portion 33 connects the second wall 32 and the first wall 31. The ridgeline portion 33 extends in the length direction X. The ridgeline portion 33 forms a curve when viewed in a cross section perpendicular to the length direction X (a cross section along the width direction Y). The curve formed by the ridgeline portion 33 is convex toward the outside of the press-formed body 30.
The flange 34 protrudes from the second wall 32 in the width direction Y. The flange 34 is provided at an edge of each second wall 32 located on the opposite side to the ridgeline portion 33 along the height direction Z. The flange 34 extends in the length direction X along the edge of each second wall 32.

The press-formed body 30 is formed with an inwardly curved portion 30a and a saddle-shaped portion 30b.
As shown in FIG. 2, the inwardly curved portion 30a is a portion that is recessed toward the inside of the press-formed body 30 when viewed from the top of the press-formed body 30. A top view of the press-formed body 30 shows the first wall 31 on the side opposite to the side on which the second wall 32 is formed along the normal direction (the first wall 31 on the side opposite to the side on which the second wall 32 is formed along the normal direction of the first wall 31). This is the view from the opposite side of the second wall 32 with the wall 31 in between. In this embodiment, the inwardly curved portion 30a is formed by recessing one side edge of the first wall 31 in the width direction Y at one end of the press molded body 30 in the length direction X. ing.

The inwardly curved portion 30a includes an inwardly curved portion 31a of the first wall 31, an inwardly curved portion 32a of the second wall 32, and an inwardly curved portion 33a of the ridgeline portion 33. The inwardly curved portion 31a of the first wall 31 is a portion of the first wall 31 that curves in the width direction Y when the press molded body 30 is viewed from above. The inwardly curved portion 32a of the second wall 32 is a portion of the second wall 32 that is recessed toward the first wall 31 (inwardly curved portion 31a) when the press-formed body 30 is viewed from above. The inwardly curved portion 33a of the ridgeline portion 33 is a portion of the ridgeline portion 33 that is recessed toward the first wall 31 (inwardly curved portion 31a) when the press molded body 30 is viewed from above.

As shown in FIG. 3, the saddle-shaped portion 30b is a portion that is recessed toward the inside of the press-formed body 30 when the press-formed body 30 is viewed from the side. A side view of the press-formed body 30 shows the side opposite to the side where the first wall 31 is formed along the normal direction of the second wall 32 (the side where the second wall 32 is formed along the normal direction of the second wall 32). This is the view seen from the opposite side of the first wall 31 with In the present embodiment, the saddle-shaped portion 30b is formed by recessing a substantially central portion of the press-formed body 30 in the length direction X in the height direction Z.

The saddle-shaped portion 30b includes a saddle-shaped portion 32b of the second wall 32, a saddle-shaped portion 31b of the first wall 31, and a saddle-shaped portion 33b of the ridgeline portion 33. The saddle-shaped portion 32b of the second wall 32 is a portion of the first wall 31 that curves in the height direction Z when the press-formed body 30 is viewed from the side. The saddle-shaped portion 31b of the first wall 31 is a portion of the first wall 31 that is depressed toward the second wall 32 (saddle-shaped portion 32b) in a side view of the press-formed body 30. The saddle-shaped portion 33b of the ridgeline portion 33 is a portion of the ridgeline portion 33 that is depressed toward the second wall 32 (saddle-shaped portion 32b) in a side view of the press-formed body 30.

(Manufacturing equipment 10)
Next, the manufacturing apparatus 10 used in the above manufacturing method will be explained.

As shown in FIGS. 4 to 9, the manufacturing apparatus 10 includes a punch 11, a pad 12, and a die 13. Blank B is held between punch 11 and pad 12. With the blank B held as described above, the die 13 approaches the punch 11, and the blank B is pressed between the punch 11 and the die 13.

Note that hereinafter, the direction in which the punch 11 and the die 13 approach during press working will be referred to as a press direction Dz. The press direction Dz is the height direction Z in the press molded body 30 manufactured by this manufacturing apparatus 10. The punch 11 side along the press direction Dz is referred to as a first side Dz1, and the die 13 side is referred to as a second side Dz2.

In the illustrated example, the press direction Dz is a vertical direction, the first side Dz1 is downward, and the second side Dz2 is upward. That is, the punch 11 and the die 13 face each other in the vertical direction, and the punch 11 is located below the die 13. However, the first side Dz1 may be located above, that is, the punch 11 may be located above the die 13. Furthermore, the press direction Dz may be a horizontal direction, that is, the punch 11 and the die 13 may be horizontally opposed.

The punch 11 includes a first convex portion 14. The first convex portion 14 supports the blank B. The first convex portion 14 protrudes from the punch 11 toward the second side Dz2. The first convex portion 14 is shorter in the second direction Dy than in the first direction Dx in a plan view of the first convex portion 14 from the press direction Dz. Note that both the first direction Dx and the second direction Dy are directions perpendicular to the press direction Dz. The first direction Dx and the second direction Dy are orthogonal to each other. The first direction Dx is the length direction X in the press molded body 30 manufactured by this manufacturing apparatus 10. The second direction Dy is the width direction Y in the press molded body 30 manufactured by the manufacturing apparatus 10.

The first convex portion 14 includes a top surface 14a and a side surface 14b. The top surface 14a faces the second side Dz2. The side surface 14b faces the second direction Dy. The first convex part 14 press-works the blank B between it and a second convex part 15 of the die 13, which will be described later.

The pad 12 presses the blank B between it and the top surface 14a of the first convex portion 14. The pad 12 includes a first surface 16 and a protrusion 17 (see FIGS. 7 to 9).
The first surface 16 presses a portion of the blank B that will become the first wall 31 . The first surface 16 faces the first side Dz1. The first surface 16 is shorter in the second direction Dy than in the first direction Dx. The blank B is sandwiched between the first surface 16 and the top surface 14a of the first convex portion 14.

The protrusion 17 presses at least a portion of the blank B that will become the ridgeline portion 33 of the inwardly curved portion 30a and the saddle-shaped portion 30b. The protrusion 17 is provided on at least one side edge of the first surface 16 in the second direction Dy. In a modification of the present embodiment, two protrusions 17 may be provided with the first surface 16 interposed in the second direction Dy.

When the protrusion 17 is viewed in cross section, the protrusion 17 (the surface of the protrusion 17) forms a curve that is convex toward the first side Dz1. The cross section is a cross section that crosses the first surface 16 and both protrusions 17. The cross section is a cross section perpendicular to the first direction Dx. The cross section is a cross section along the second direction Dy.

When the protrusion 17 is viewed in cross section, the radius of curvature of the curve formed by the protrusion 17 is, for example, 7.0 mm or less, preferably 5.0 mm or less, and more preferably 3.0 mm or less. The smaller the radius of curvature is, the easier it is to press the portion that will become the ridgeline portion 33 during press molding of the press-formed body 30 with the pad 12, and the easier it is to suppress the generation of wrinkles. However, the preferable range of the radius of curvature of the protrusion 17 also depends on the shape of the press-formed body 30, such as the radius of curvature of the ridgeline portion 33 and the inclination of the second wall 32.
Further, from the viewpoint of durability of the pad 12, it is preferable that the radius of curvature of the protrusion 17 is large to some extent. Therefore, the radius of curvature may be, for example, 0.5 mm or more, or 1.0 mm or more.

In the cross section including the punch 11, the pad 12, and the die 13, the end surface 18 of the pad 12 passes through the boundary 34 between the part of the punch 11 that contacts the second wall 32 and the part of the punch 11 that contacts the ridgeline part 33, Further, it is arranged at a position tangent to a straight line Lz parallel to the direction of relative movement between the punch 11 and the die 13, or closer to the first wall 31 than the straight line Lz. The first wall 31 forms the bottom surface of a channel-shaped groove formed by the press-formed body 30, and the second wall 32 is disposed at the edge of the first wall 31 in the width direction Y via a ridgeline portion 33.

In this embodiment, the direction of relative movement between the punch 11 and the die 13 is the direction in which the punch 11 and the die 13 approach, that is, the press direction Dz. In FIG. 8, it is shown that the pad 12 is arranged at a position tangent to the straight line Lz indicated by the broken line. That is, the end surface 18 of the pad 12 is arranged at a position where it touches the straight line Lz.

The end surface 18 of the pad 12 may be arranged closer to the first wall 31 (inner side) than the straight line Lz. The first wall 31 side from the straight line Lz is the center side of the pad 12 in the cross section of the pad 12 (a cross section along both the second direction Dy and the press direction Dz). In FIG. 8, the right side of the end surface 18 of the pad 12 in the drawing is the first wall 31 side of the straight line Lz. For example, when the radius of curvature of the ridgeline portion 33 is 1, the end surface 18 of the pad 12 is arranged in a range between 0 and 4/5 from the straight line Lz toward the first wall 31 in the second direction Dy. 0 on the first wall 31 side from the straight line Lz is a position where the end surface 18 of the pad 12 touches the straight line Lz. By arranging the end surface 18 of the pad 12 in this manner, the protrusion 17 can reliably press the portion that will become the ridgeline portion 33.

The pad 12 is not placed outside the straight line Lz. The outer side is the side opposite to the first wall 31 side from the straight line Lz in the cross section of the pad 12 (cross section along the second direction Dy). In FIG. 8, the left side of the end surface 18 of the pad 12 in the drawing is outside the straight line Lz.

By disposing the pad 12 at a position in contact with the straight line Lz or closer to the first wall 31 than the straight line Lz, the die 13 including the second convex portion 15 described later can move along the press direction Dz.

The die 13 includes a second protrusion 15 . Two second convex portions 15 are provided at intervals in the second direction Dy. A recess 19 is provided between the two second protrusions 15 . Both of these second convex portions 15 and concave portions 19 are long in the first direction Dx.
During press molding of the press molded body 30, the pad 12 is placed in the recess 19. Pad 12 and die 13 are connected via elastic element 20. The elastic element 20 is elastically compressed and deformed when the pad 12 receives a compressive force from the punch 11 in the press direction Dz.

Each second convex portion 15 includes a top surface 15a and a side surface 15b. The top surface 15a faces the first side Dz1. The side surface 15b is formed on the concave portion 19 side of the top surface 15a and faces in the second direction Dy. The second convex portion 15 presses the blank B pressed by the pad 12 and punch 11. The second wall 32 is pressed by the side surface 15b of the die 13 and the side surface 14b of the punch 11.

(Production method)
Next, the manufacturing method will be explained.
As shown in FIGS. 5 to 9, in this manufacturing method, the first wall 31 and part of the ridgeline portion 33 of the blank B are pressed between the first convex portion 14 of the punch 11 and the pad 12. . That is, the pad 12 is pressed against a portion of the first wall 31 of the blank B and a portion of the ridgeline portion 33 of the blank B, respectively. While pressing the blank B between the punch 11 and the pad 12 in this manner, the die 13 is brought close to the punch 11 from the pad 12 side to press the blank B (pressing step). In the pressing step, at least a portion of the second wall 32 is molded while a portion of the ridgeline portion 33 of the blank B is pressed by the punch 11 and the pad 12 in the inwardly curved portion 30a. Through such a pressing process, the pad 12 presses a portion of the first wall 31 and the ridgeline portion 33 of the blank B. The second wall 32 is pressed by the die 13. Specifically, the side surface 15b of the die 13 presses against the second wall. With such a configuration, the blank can be effectively pressed and wrinkles can be suppressed.

In the pressing process, the pad 12 and the punch 11 press the blank B by coming close to each other with the blank B in between, and the die 13 and the punch 11 are pressed in the same direction as the pad 12 and the punch 11 approach. moves. As shown in FIGS. 5 to 9, the die 13 and punch 11 move in the press direction Dz. Thereby, the second wall 32 is pressed by the die 13 and the punch 11. Since the die 13 and the punch 11 move in the same direction as the pad 12 and the punch 11 to press the second wall 32, the pad 12 and the punch 11 for pressing the second wall 32 are close to each other. There is no need to move in a direction different from the direction in which the

In the pressing step, at least a portion of the portion that will become the ridgeline portion 33 is pressed with the pad 12, and at least a portion of the ridgeline portion 33 and at least a portion of the second wall 32 are formed in one step. Alternatively, in the press working, after forming the ridgeline part 33, at least a part of the second wall 32 is formed while a part of the ridgeline part 33 is pressed by the pad 12.

The pad 12 may be used from the start of forming the ridgeline part 33 and the second wall 32, or may be used from the middle of forming the ridgeline part 33 and the second wall 32. That is, the pad 12 does not need to be used at the start of forming the press-formed body 30. For example, after the die 13 contacts the blank B, the die 13 is moved toward the punch 11 by about 10% or less of the height of the press-formed body 30 or about several mm or less, and then the pad 12 is arranged as described above. You may.
Moreover, the pad 12 may be used from the start of molding of the second wall 32 to the completion of molding, or may be used until the middle of molding of the second wall 32. That is, the pad 12 may be removed from between the die 13 and the blank B during the molding of the second wall 32.

However, from the viewpoint of easily suppressing the occurrence of wrinkles in the inwardly curved portion 30a and the saddle-shaped portion 30b, from the start of forming the ridgeline portion 33 and the second wall 32 to the completion of forming, the pad 12 protects the ridgeline portion of the blank B. It is preferable to press a part of the portion 33. That is, it is preferable to move the die 13 from the top dead center to the bottom dead center with respect to the punch 11 while pressing the blank B with the punch 11 and the pad 12. At this time, the portion of the blank B that will become the second wall 32 is pressed by the top surface 15a of the second convex portion 15. Then, the second wall 32 is formed between the side surface 14b of the first convex portion 14 and the side surface 15b of the second convex portion 15.

Note that the top dead center is the position when the second convex portion 15 starts to contact the blank B (the position when forming the second wall 32 starts) in the process of the die 13 approaching the punch 11 in the press direction Dz. be. In addition, the bottom dead center is the position when the further approach between the die 13 and the punch 11 is regulated during the process of the die 13 approaching the punch 11 in the press direction Dz (the position when the forming of the second wall 32 is completed). ). At the bottom dead center, the second wall 32 has been completely formed between the first convex portion 14 and the second convex portion 15 . That is, the states shown in FIGS. 6 and 8 are states located between the top dead center and the bottom dead center (states in the middle of press forming), and at the bottom dead center, the state shown in FIG. And unlike the state shown in FIG. 8, the blank B and the punch 11 are in close contact with each other, and the die 13 is in close contact with the blank B.

In this embodiment, the punch 11 is located below the die 13 and the die 13 is lowered relative to the punch 11, so the die 13 at the bottom dead center is located below the die 13 at the top dead center. . However, when the punch 11 rises relative to the die 13, the die 13 at the bottom dead center and the die 13 at the top dead center are at the same position in the press direction Dz. Furthermore, when the punch 11 is located above the die 13 and the die 13 rises relative to the punch 11, the die 13 at the bottom dead center is located above the die 13 at the top dead center. do.

In addition, since the pad 12 is provided with the protrusion 17, the portion of the blank B that will become the ridgeline portion 33 can be effectively pressed.
Moreover, in this embodiment, when the protrusion 17 is viewed in cross section, the protrusion 17 forms a curve that is convex toward the first side Dz1. Therefore, by appropriately adjusting the curvature of this curve, the above-described pressing by the protrusion 17 can be made more effective. That is, as shown in FIG. 9, when the projection 17 has a large curvature and a small radius of curvature (the projection 17a shown in FIG. 9), and when the projection 17 has a small curvature and a large radius of curvature (the projection 17b shown in FIG. 9), In comparison, the portion of the blank B that will become the ridgeline portion 33 can be pressed (contacted) between the first convex portion 14 and the protrusion 17 over a wide range. When the radius of curvature of the protrusion 17 is 0.2 mm, 1 mm, 2 mm, and 3 mm, the pressing range of the ridge line part 33 (the ratio of the range in which the ridge line part 33 is pressed by the protrusion 17) is 84% and 57% of the ridge line part 33, respectively. Press %, 38%, 25%.

(effect)
The inventors of the present invention discovered the following matters regarding the occurrence of wrinkles in the manufacturing method of manufacturing the press-formed body 30 from the blank B.
(A) Wrinkles are likely to occur in the ridgeline portion 33 forming the inwardly curved portion 30a and the saddle-shaped portion 30b of the press-formed body 30, respectively.
(B) One of the causes of the above-mentioned wrinkles is that when forming the second wall 32 with the punch 11 and die 13, the inwardly curved portion 30a and saddle-shaped portion 30b of the press-formed body 30 shrink and deform. There is a phenomenon of bending.
(C) The above-mentioned deflection occurs when the blank B is stretched and flanged in the process of forming the second wall 32.
(D) In each of the inwardly curved portion 30a and the saddle-shaped portion 30b of the press-formed body 30, the second wall 32 is stretch flanged from the start to the end of forming.
(E) The above-mentioned deflection can be suppressed by molding at least a portion of the second wall 32 while pressing at least a portion of the portion of the blank B that will become the ridgeline portion 33 with the pad 12.

The above (D) will be explained in more detail.
In the inwardly curved portion 30a of the press-formed body 30, as shown in FIG. The portion becomes elongated and deformed along the inwardly curved portion 30a (reference numeral 112 in the figure). At this time, the amount of elongation deformation of the blank B in the portion that will become the second wall 32 increases as the press forming progresses, and increases as the press forming approaches the bottom dead center. That is, the further away from the portion that will become the first wall 31 out of the portion that will become the second wall 32, the greater the amount of elongation deformation will occur. On the other hand, material movement from the surroundings (reference numeral 113 in the figure) occurs in the portion of the inwardly curved portion 30a that will become the ridgeline portion 33 and the first wall 31. Compressive deformation caused by this material flow causes wrinkles to occur.

In addition, in the saddle-shaped part 30b of the press-formed body 30, as shown in FIG. 32 is pressed and bent by the top surface 15a of the second convex portion 15. At this time, the portion that will become the second wall 32 is stretched along the saddle-shaped portion 30b and deformed into a flange (numeral 122 in the figure). The amount of elongation deformation of the blank B in the portion that will become the second wall 32 increases as the press forming progresses, similar to the inwardly curved portion 30a, and increases as the press molding approaches the bottom dead center. That is, the farther away from the portion that will become the first wall 31 out of the portion that will become the second wall 32, the greater the amount of elongation deformation will occur. On the other hand, material movement from the surroundings (reference numeral 123 in the figure) occurs in the portion of the saddle-shaped portion 30b that will become the ridgeline portion 33 and the first wall 31. Compressive deformation caused by this material flow causes wrinkles to occur.

Having discovered the above, the inventors of the present application have discovered that while pressing the first wall 31 and part of the ridgeline part 33 of the blank B between the punch 11 and the pad 12, the punch 11 and the die 13 are pressed. The idea was to mold at least a portion of the second wall 32. Thereby, compressive deformation associated with the above-mentioned stretch flange deformation can be suppressed. Therefore, the generation of wrinkles in the inwardly curved portion 30a and the saddle-shaped portion 30b due to the compressive deformation can be suppressed. As a result, it is possible to suppress the occurrence of wrinkles and form a high-quality press-formed body 30.

Note that the technical scope of the present invention is not limited to the embodiments described above, and various changes can be made without departing from the spirit of the present invention.

The press molded body 30 manufactured by the above manufacturing method is not limited to a front side member.

In addition, without departing from the spirit of the present invention, the components in the embodiments described above may be replaced with well-known components as appropriate, and the modifications described above may be combined as appropriate.

Next, a verification test was conducted to verify the above effects.
In this verification test, simulations were performed regarding each manufacturing method of the example and the comparative example.
In each of the manufacturing methods of Examples and Comparative Examples, press molded bodies 30 shown in FIGS. 1 to 3 are manufactured.

In the manufacturing method according to the embodiment, a manufacturing apparatus 10 shown in FIGS. 4 to 11 is used.
In the manufacturing method according to the comparative example, a manufacturing apparatus 10A shown in FIGS. 12 to 14 is used. In the manufacturing apparatus 10A according to the comparative example, the pad 12 is different from that in the manufacturing apparatus 10 according to the example. In the manufacturing apparatus 10A according to the comparative example, the pad 12 includes the first surface 16 but does not include the protrusion 17.

In the manufacturing method according to the embodiment, as shown in FIGS. 3 to 8, a portion of the blank B that becomes the first wall 31 and a ridgeline portion of the blank B are formed between the punch 11 and the pad 12. 33 on the first wall 31 side, the die 13 is moved relative to the punch 11 from the top dead center to the bottom dead center.
In the manufacturing method according to the comparative example, as shown in FIG. 13, although the portion of the blank B that will become the first wall 31 is pressed between the punch 11 and the pad 12, the portion that will become the ridgeline portion 33 is not pressed. The die 13 is moved from the top dead center to the bottom dead center with respect to the punch 11.

The results are shown in FIGS. 15 to 18. FIGS. 15 to 18 are diagrams showing the results of simulations calculated on the premise of each manufacturing method of the comparative example and the example, and are top and side views of the press-formed body in which the wall thickness is shown in shading. 15 and 16 are comparative examples. 17 and 18 are examples. 15 and 17 are top views. 16 and 18 are side views. In FIGS. 15 to 18, the smaller the wall thickness, the darker the color, and the larger the wall thickness, the lighter the color.

From this result, it was found that the press-formed body 30 of the example shown in FIGS. 17 and 18 was more effective in both the inwardly curved portion 30a and the saddle-shaped portion 30b than the press-formed body 30A of the comparative example shown in FIGS. 15 and 16. It is also confirmed that the area where the wall thickness is large (the area where the color is light) has become narrower. That is, it was confirmed that the flow of material toward the inwardly curved portion 30a and the saddle-shaped portion 30b was more suppressed in the example than in the comparative example.

According to the present invention, it is possible to suppress the occurrence of wrinkles during press molding. Therefore, the present invention has high industrial feasibility.

10 Manufacturing device 11 Punch 12 Pad 13 Die 14 First convex portion 14a Top surface 14b Side surface 15 Second convex portion 15a Top surface 15b Side surface 16 First surface 17 Protrusion 30 Press molded body 31 First wall 31b Saddle-shaped portion 32 Second Wall 33 Ridgeline B Blank

Claims (6)

a first wall, a second wall extending in a direction crossing the first wall, a ridgeline connecting the first wall and the second wall and forming a curve when viewed in cross section ; A method for manufacturing a press-formed body, comprising: an inwardly curved portion in which the second wall is recessed toward the first wall when viewed from the normal direction of the first wall,
A pressing step of press-working the blank by moving a die close to the punch side from the pad side while sandwiching and pressing the blank between a punch and a pad,
In the pressing step, at least a part of the second wall is molded while a part of the ridgeline part of the blank is pressed by the punch and the pad in the inwardly curved part. Production method. a first wall, a second wall extending in a direction crossing the first wall, a ridgeline connecting the first wall and the second wall and forming a curve when viewed in cross section ; A method for manufacturing a press-formed body, comprising: a saddle-shaped part in which the first wall is recessed toward the second wall when viewed from the normal direction of the second wall,
A pressing step of press-working the blank by moving a die close to the punch side from the pad side while sandwiching and pressing the blank between a punch and a pad,
In the pressing step, manufacturing a press-formed body by molding at least a part of the second wall while pressing a part of the ridgeline part of the blank with the punch and the pad in the saddle-shaped part. Method. In the pressing process, the pad and the punch press the blank by approaching each other with the blank in between, and the die and the punch press the blank in the same direction as the pad and the punch approach. The method for manufacturing a press-formed body according to claim 1 or 2, wherein the die and the punch press the second wall by moving the die and the punch. An apparatus for manufacturing a press-formed body, comprising a punch, a pad, and a die, and used in the method for manufacturing a press-formed body according to any one of claims 1 to 3,
The pad is
a first surface that presses a portion of the blank that will become the first wall;
An apparatus for manufacturing a press-formed body, comprising: a protrusion that is provided on a side edge of the first surface and presses a part of the ridgeline portion of the blank. 5. The press-formed body manufacturing apparatus according to claim 4, wherein the protrusion forms a curve convex toward the punch side in a cross section that crosses the first surface and the protrusion. In a cross section including the punch, the pad, and the die,
The end surface of the pad is a straight line that passes through a boundary between a portion of the punch that contacts the second wall and a portion of the punch that contacts the ridgeline, and that is parallel to the direction of relative movement between the punch and the die. The apparatus for producing a press-formed body according to claim 4 or 5, wherein the apparatus is disposed at a position in contact with or closer to the first wall than the straight line.

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