Press molding method, press molding device, and molding method

Abstract

To provide a press molding method capable of suppressing springing-back while suppressing complication of a process.SOLUTION: This press molding method using a press molding device 1A comprises a specific bending step S2 of bending an oblique wall part 812 in a prescribed rotational direction while applying, to the tip surface 812b of the oblique wall part 812, end pressure which is a force of a direction in which the plate length of the oblique wall part 812 equivalent to the length of the oblique wall part 812 from a top plate 811 to the tip surface 812b of the oblique wall part 812 contracts in a state where the top plate 811 is fixed for a spare molding 81 provided with the top plate 811 and the oblique wall part 812 inclined in the prescribed rotational direction with respect to the top plate 811.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to a press molding method, a press molding apparatus, and a molding method. [Background technology]

[0002] As a press forming method, for example, JP 2014-4618 A discloses a method for manufacturing a formed product having a U-shaped cross section by bending. This press forming method includes a press bending process in which a die is lowered to bend the metal material while the metal material is pressed by a punch and a pad, and a push bending process in which the die is moved diagonally downward in a direction approaching the punch after the press bending process to bend the metal material. The push bending process is performed while the width direction tip of the metal material is in contact with the vertical wall of the die. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-4618 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the above processing method does not realize the suppression of springback of bending, which is a problem in plate bending, for example. In press forming including bending, suppression of springback of bending has been desired for some time. The object of the present invention is to provide a press forming method, a press forming device, and a forming method that can suppress springback of bending while suppressing the complication of the process. [Means for solving the problem]

[0005] The press molding method of the present invention is a press molding method using a press molding apparatus, and includes a specific bending process in which, with the top plate portion fixed, a pre-formed product having a top plate portion and an inclined wall portion inclined in a predetermined rotational direction relative to the top plate portion is bent in the predetermined rotational direction while applying a compressive force to the tip face of the inclined wall portion, which is a force in a direction that reduces the plate length of the inclined wall portion, which corresponds to the length of the inclined wall portion from the top plate portion to the tip face of the inclined wall portion.

[0006] The press molding apparatus of the present invention is a press molding apparatus that molds a press-molded product having a top plate portion, a shoulder R portion curved from the top plate portion, and a vertical wall portion continuing from the top plate portion via the shoulder R portion from a preliminary formed product having a top plate portion and an inclined wall portion inclined with respect to the top plate portion, and the press molding apparatus is equipped with: a mold member having a top surface corresponding to the top plate portion, a shoulder surface corresponding to the shoulder R portion, and a side wall surface corresponding to the vertical wall portion; a pressing member arranged on one side of the top plate in a predetermined direction so as to face the top surface; a butting member facing the side wall surface and corresponding to the vertical wall portion; and a drive device that moves the butting member in a direction intersecting the predetermined direction, wherein a protrusion that protrudes toward the mold member is formed at a position of the butting member corresponding to the tip position of the vertical wall portion, and the protrusion is formed so that a pressing surface, which is the surface on one side of the protrusion in the predetermined direction, abuts against the tip surface of the inclined wall portion when the inclined wall portion is bent to mold the shoulder R portion and the vertical wall portion.

[0007] The forming method of the present invention is a forming method for bending a sheet material using a forming device, in which the forming device applies a compressive force to the sheet material in a direction (reduction direction) that reduces the sheet length of the sheet material, while bending the sheet material in a predetermined rotational direction so that the rotation axis of bending extends in a direction intersecting the reduction direction of the sheet material. Effect of the Invention

[0008] According to the press forming method of the present invention, by bending the inclined wall portion while applying a compressive force to the tip surface of the inclined wall portion, the compressive stress in the compressive stress region (inner part of the bend) increases and the tensile stress in the tensile stress region (outer part of the bend) decreases in the stress distribution of the bent portion of the inclined wall portion. By decreasing the tensile stress, the bending moment generated in the bent portion of the inclined wall portion decreases, and the amount of springback also decreases. In other words, according to the press forming method of the present invention, springback is suppressed. In addition, by performing "bending" and "application of compressive force" to the inclined wall portion simultaneously (in one process), the complication of the process can be suppressed. In addition, according to the press forming device of the present invention, since the protruding portion is configured to abut the tip surface of the inclined wall portion during bending, it is possible to execute the specific bending process. Therefore, the same effect as the above method is exerted.

[0009] According to the forming method of the present invention, the non-uniform stress distribution in a plate caused by bending can be made closer to a uniform stress distribution, and the occurrence of springback can be suppressed. [Brief description of the drawings]

[0010] [Figure 1] 1 is a conceptual diagram of a plate material, a preform, and a press-formed product according to an embodiment of the present invention. [Diagram 2] 2 is a flowchart of a press molding method according to the present embodiment. [Diagram 3] FIG. 2 is a configuration diagram of a press forming apparatus (pre-bending process) according to the present embodiment. [Figure 4] 4 is a conceptual diagram for explaining the movement of the press forming apparatus (pre-bending process) of the present embodiment. FIG. [Diagram 5] 4 is a conceptual diagram for explaining the movement of the press forming apparatus (pre-bending process) of the present embodiment. FIG. [Figure 6] FIG. 2 is a configuration diagram of a press forming apparatus (specific bending process) according to the present embodiment. [Figure 7] 2 is a partially enlarged conceptual diagram of the press forming apparatus (specific bending process) of the present embodiment. FIG. [Figure 8]4 is a conceptual diagram for explaining the movement of the press forming apparatus (specific bending process) of the present embodiment. FIG. [Figure 9] 2 is a partially enlarged conceptual diagram of the press forming apparatus (specific bending process) of the present embodiment. FIG. [Figure 10] 4 is a conceptual diagram for explaining the movement of the press forming apparatus (specific bending process) of the present embodiment. FIG. [Figure 11] FIG. 11 is a conceptual diagram of a modified embodiment of the press forming apparatus of the present embodiment. [Figure 12] FIG. 11 is a conceptual diagram of a modified embodiment of the press forming apparatus of the present embodiment. [Figure 13] FIG. 11 is a conceptual diagram of another example of the preform of the present embodiment. [Figure 14] 4 is a conceptual diagram for explaining the movement of the press forming apparatus (pre-bending process) of the present embodiment. FIG. [Figure 15] FIG. 1 is a conceptual diagram for explaining a stress state of a conventional press-formed product. [Figure 16] FIG. 2 is a conceptual diagram for explaining a stress state of the press-formed product of the present embodiment. [Figure 17] 4 is a conceptual diagram for explaining deformation of the press-formed product of the present embodiment. FIG. [Figure 18] FIG. 4 is a plan view showing an example of the shape of a plate material used in the present embodiment. [Figure 19] FIG. 1 is a conceptual diagram for explaining the present embodiment. [Figure 20] FIG. 2 is a perspective view showing an example of a press-formed product according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, as a mode for carrying out the present invention, a press molding apparatus 1A and a press molding method according to an embodiment of the present invention will be described in detail with reference to the drawings. In addition to the following examples, the present invention can be carried out in various forms with various modifications and improvements based on the knowledge of those skilled in the art.

[0012] The press forming method of the present embodiment is a method for forming a press-formed product 9 from a plate material 80 through a preform 81 using a press forming device, as shown in FIG. 1. The plate material 80 can also be called a plate-shaped metal material or workpiece. The preform 81 includes a top plate portion 811 and an inclined wall portion 812 inclined in a predetermined rotation direction with respect to the top plate portion 811. The inclined wall portion 812 can also be called a portion that curves and continues from the top plate portion 811. The inclined wall portion 812 includes a curved portion (also called a "bent portion") and a straight portion from a viewpoint seen along the rotation axis in the predetermined rotation direction (i.e., the viewpoint of FIG. 1). The "plate length of the inclined wall portion 812" corresponds to the length of the inclined wall portion 812 from the top plate portion 811 to the tip surface 812b of the inclined wall portion 812, as shown in FIG. 1. The plate length of the inclined wall portion 812 can also be said to be the longitudinal length of the inclined wall portion 812 when viewed along the rotation axis in a predetermined rotation direction (the perspective of FIG. 1). The preformed product 81 can also be said to be an intermediate formed product. The press-formed product 9 has a top plate portion 811, a shoulder R portion 92 curved from the top plate portion 811, and a vertical wall portion 93 continuing from the top plate portion 811 via the shoulder R portion 92. Note that the top plate portion of the preformed product 81 and the top plate portion of the press-formed product 9 are portions in the same position, and therefore will be described as "top plate portion 811" in the description.

[0013] The angle (obtuse angle) between the top plate portion 811 and the inclined wall portion 812 is larger than the angle (e.g., 90 degrees) between the top plate portion 811 and the vertical wall portion 93. In other words, the bending angle (acute angle) of the inclined wall portion 812 with respect to the top plate portion 811 is smaller than the bending angle (e.g., 90 degrees) of the vertical wall portion 93 with respect to the top plate portion 811. As described above, in the press forming method of this embodiment, the press forming apparatus preliminarily applies bending to the plate material 80 to form the preliminarily formed product 81, and further applies special bending (a specific bending process to be described later) to the preliminarily formed product 81 to form the press-formed product 9. As shown in FIG. 2, the press forming method of this embodiment includes a preliminary bending process S1 and a specific bending process S2.

[0014] (Pre-bending process) As shown in Fig. 3, the press forming apparatus 1 used in the preliminary bending process S1 includes a drive unit 10, a punch 2, a die 3, a pressing member 4, and a support unit 5. The punch 2 is configured to be movable in the vertical direction by the drive unit 10. The drive unit 10 is controlled by a control device (not shown) configured by, for example, a computer or an ECU. The punch 2 includes, as a processing surface (lower surface), a top surface 2y corresponding to the top plate portion 811, and shoulder surfaces 2z located on the left and right of the top surface 2y and corresponding to the inclined wall portion 812.

[0015] The die 3 is disposed so as to face the punch 2. The die 3 is disposed below the punch 2. The die 3 is composed of two die members 31 and 32. Each of the die members 31 and 32 has an inclined surface 3a formed thereon corresponding to the inclined wall portion 812. The inclined surface 3a is disposed so as to face a shoulder surface 2z of the punch 2.

[0016] The pressing member 4 is disposed so as to face the top surface 2y of the punch 2. The pressing member 4 is disposed below the punch 2. The pressing member 4 is disposed between the two die members 31, 32. The processing surface (upper surface) of the pressing member 4 corresponds to the top plate portion 811. The pressing member 4 can be said to be a portion on which the plate material 80 is placed before the preliminary bending process S1 is performed.

[0017] The support device 5 is a device that supports the pressing member 4. The support device 5 is disposed below the pressing member 4. The support device 5 supports the pressing member 4 so that it can move downward. The support device 5 applies an upward force in response to the downward movement of the pressing member 4. The support device 5 is configured to include, for example, a fluid cylinder such as an air cylinder or a hydraulic cylinder, or a spring. When the support device 5 is, for example, a spring, the spring directly or indirectly abuts against the pressing member 4 and applies an upward force to the pressing member 4 in response to the downward movement of the pressing member 4 according to the amount of compression and spring constant of the spring.

[0018] As shown in FIG. 3, in the preliminary bending process S1, the plate material 80 is placed on the pressing member 4. The plate material 80 extends above both inclined surfaces 3a. Then, as shown in FIG. 4, the driving device 10 moves the punch 2 downward, and the top surface 2y comes into contact with the plate material 80. The plate material 80 is sandwiched between the punch 2 and the pressing member 4. Then, as shown in FIG. 5, the driving device 10 moves the punch 2 downward together with the plate material 80 and the pressing member 4 while receiving the force of the support device 5. As the punch 2 moves downward, the center part of the plate material 80 moves downward. As a result, as the punch 2 moves downward, the left and right ends of the plate material 80 are bent so as to follow the inclined surfaces 3a.

[0019] Finally, the left and right ends of the plate material 80 are sandwiched between the shoulder surface 2z and the inclined surface 3a of the punch 2 to form the inclined wall portion 812 of the preformed product 81. The left and right central portion of the plate material 80 is sandwiched between the top surface 2y of the punch 2 and the pressing member 4 to form the top plate portion 811 of the preformed product 81. The inclined wall portion 812 of the preformed product 81 is inclined in a predetermined rotation direction with respect to the top plate portion 811. In this embodiment, the inclined wall portion 812 on the left side of the preformed product 81 is inclined clockwise with respect to the top plate portion 811. Also, the inclined wall portion 812 on the right side of the preformed product 81 is inclined counterclockwise with respect to the top plate portion 811.

[0020] In this way, the pre-bending process S1 is a process in which the plate material 80 is bent in a predetermined rotation direction by the press forming apparatus 1 to form a preformed product 81. In the pre-bending process S1, the plate material 80 is bent in the predetermined rotation direction so that the bending angle of the plate material 80 is less than 90°, that is, so that the bending angle is an acute angle (0<bending angle<90°).

[0021] (Specific bending process) 6, the press forming apparatus 1A used in the specific bending process S2 includes a driving device 10A, a punch (corresponding to a "die member") 2A, a pressing member 4A, supporting devices 51 and 52, cam sliders (corresponding to a "butting member") 71 and 72, and cam drivers 73 and 74. The punch 2A is connected to a supporting member 11 via the supporting device 51. The punch 2A is disposed between the cam drivers 73 and 74.

[0022] 6 and 7, the punch 2A includes a body 21A and shoulders 22A formed on the left and right sides of the body 21A. The right shoulder 22A bulges rightward from the right side surface of the lower end of the body 21A. The left shoulder 22A bulges leftward from the left side surface of the lower end of the body 21A. Each shoulder 22A protrudes from the lower end of the body 21A.

[0023] The punch 2A has, as processing surfaces, a top surface 2a corresponding to the top plate portion 811 of the press-formed product 9, a shoulder surface 2b corresponding to the shoulder R portion 92 of the press-formed product 9, and a side wall surface 2c corresponding to the vertical wall portion 93 of the press-formed product 9. The punch 2A has one top surface 2a, a pair of shoulder surfaces 2b, and a pair of side wall surfaces 2c. The top surface 2a is the lower surface of the main body portion 21A. The top surface 2a is formed in a shape corresponding to the top plate portion 811.

[0024] One shoulder surface 2b is formed continuously from the left end of the top surface 2a, and the other shoulder surface 2b is formed continuously from the right end of the top surface 2a. Each shoulder surface 2b is formed by the surface of the lower end of the corresponding shoulder portion 22A, i.e., the curved portion of the lower end of the shoulder portion 22A. Each shoulder surface 2b is formed in a curved shape corresponding to the shoulder R portion 92. Each side wall surface 2c is formed by the side surface of the corresponding shoulder portion 22A. Each side wall surface 2c is formed in a planar shape corresponding to the vertical wall portion 93. The right side wall surface 2c is the side surface of the right shoulder portion 22A and extends upward continuously from the right shoulder surface 2b. The left side wall surface 2c is the side surface of the left shoulder portion 22A and extends upward continuously from the left shoulder surface 2b.

[0025] Each shoulder 22A protrudes from a side surface at the lower end of the main body 21A. Therefore, on each of the left and right side surfaces of the punch 2A, the shoulder 22A and the main body 21A form a relief portion 20. On each side surface of the punch 2A, a portion recessed toward the center (i.e., relief portion 20) is formed at a position corresponding to the protrusion 70 (above the side wall surface 2c).

[0026] The pressing member 4A is disposed so as to face the punch 2A. The pressing member 4A is disposed below the punch 2A. The pressing member 4A is disposed between the cam sliders 71 and 72. The processing surface (upper surface) of the pressing member 4 is formed into a shape corresponding to the top plate portion 811. The pressing member 4A can be said to be a portion on which the preform 81 is placed before the specific bending process S2 is performed.

[0027] The support device 51 is disposed between the punch 2A and the support member 11, and supports the punch 2A so as to be movable upward. The support device 51 includes, for example, a spring or a fluid cylinder. When the punch 2A approaches the support member 11, the support device 51 applies a force to the punch 2A so as to prevent the approach. That is, when the punch 2A attempts to move upward relative to the support member 11, the support device 51 applies a downward force (for example, a spring force) to the punch 2A. Like the support devices 5 and 51, the support device 52 also includes, for example, a spring or a fluid cylinder. The support device 52 supports the pressing member 4A so as to be movable downward.

[0028] The cam sliders 71 and 72 are disposed opposite to each other. The cam slider 71 is disposed on the right side of the pressing member 4A, and the cam slider 72 is disposed on the left side of the pressing member 4A. Each of the cam sliders 71 and 72 is formed with an inclined surface 7a.

[0029] Each cam driver 73, 74 is a member for moving the corresponding cam slider 71, 72. Each cam driver 73, 74 is disposed above the corresponding cam slider 71, 72 so as to be movable in the up and down direction. The cam drivers 73, 74 are connected to the support member 11. The cam driver 73 corresponds to the cam slider 71, and is disposed on the right side of the punch 2A. The cam driver 74 corresponds to the cam slider 72, and is disposed on the left side of the punch 2A. Each cam driver 73, 74 is formed with an inclined surface 7b corresponding to the inclined surface 7a.

[0030] With its own inclined surface 7a in contact with the inclined surface 7b of the cam driver 73, the cam slider 71 moves in a direction approaching the pressing member 4A (to the left) as the cam driver 73 moves downward. With its own inclined surface 7a in contact with the inclined surface 7b of the cam driver 74, the cam slider 72 moves in a direction approaching the pressing member 4A (to the right) as the cam driver 74 moves downward.

[0031] The cam slider 71 is provided with a spring (not shown) that biases the cam slider 71 in a direction (rightward) away from the pressing member 4A. Similarly, the cam slider 72 is provided with a spring (not shown) that biases the cam slider 72 in a direction (leftward) away from the pressing member 4A. Each cam driver 73, 74 overcomes the force of the spring to move the corresponding cam slider 71, 72. When the abutment state with the cam drivers 73, 74 is released, the cam sliders 71, 72 move in a direction away from each other toward the initial position. When the cam sliders 71, 72 are not abutting against the cam drivers 73, 74, the spring returns the cam sliders 71, 72 to their predetermined initial positions. Note that the biasing force applied to the cam sliders 71, 72 is not limited to a spring, and may be other biasing members or biasing devices.

[0032] As shown in FIG. 6 and FIG. 7, the side surfaces 71a, 72a of the cam sliders 71, 72 on the punch 2A side are formed with abutment surfaces 7z corresponding to the shoulder portion 22A of the punch 2A. The butt surfaces 7z are formed to correspond to the shoulder R portion 92 and the vertical wall portion 93 of the press-molded product 9. The butt surfaces 7z are recessed (concave) from the side surfaces of the cam sliders 71, 72. The side surfaces 71a, 72a are formed with protruding portions 70 protruding toward the punch 2A side at positions (upper ends in FIG. 6) adjacent to the butt surfaces 7z. In other words, the protruding portions 70 protruding toward the opposing cam sliders 71, 72 are formed at positions adjacent to the ends (upper ends) of the ends of the butt surfaces 7z opposite to the shoulder R portion 92. The protruding portions 70 are formed at positions of the corresponding side surfaces 71a, 72a corresponding to the tip positions of the vertical wall portions 93 of the press-molded product 9. It can be said that the abutment surface 7z and the protrusion 70 form recesses in the side surfaces 71a, 72a of the cam sliders 71, 72.

[0033] The driving device 10A is a device that moves at least one of the punch 2A and the pressing member 4A in a vertical direction (a predetermined direction) and moves the cam sliders 71, 72 in a left-right direction (a direction intersecting the predetermined direction). The driving device 10A of this embodiment is a device that moves the support member 11 in a vertical direction. The driving device 10A moves the support member 11 in a vertical direction, thereby moving the punch 2A in a vertical direction and moving the cam sliders 71, 72 in a left-right direction. The driving device 10A is configured to execute the specific bending process S2.

[0034] 6, before the specific bending step S2 is performed, the preform 81 is placed on the pressing member 4A so that the inclined wall portion 812 is located on the punch 2A side (above) with respect to the top plate portion 811. The top plate portion 811 is placed on the pressing member 4A, and the inclined wall portion 812 is in a floating state.

[0035] As shown in Fig. 8, the driving device 10A moves the punch 2A downward, bringing the punch 2A into contact with the preformed product 81. The punch 2A moves downward while pressing the preformed product 81 and the pressing member 4A. When the pressing member 4A reaches its lowest point, the supporting device 51 contracts and the punch 2A does not move downward even if the supporting member 11 moves downward. That is, in this state, the preformed product 81 is positioned. In this example, when the preformed product 81 is positioned, the cam sliders 71, 72 are not in contact with the inclined wall portion 812.

[0036] As the support member 11 moves downward, the cam drivers 73, 74 also move downward. Each cam driver 73, 74 comes into contact with the corresponding cam slider 71, 72 and moves the corresponding cam slider 71, 72 in a direction approaching the preformed product 81. As shown in Fig. 8, with the preformed product 81 positioned, the shoulder portion 22A of the punch 2A faces the abutment surfaces 7z of the cam sliders 71, 72, and the relief portion 20 of the punch 2A faces the protrusions 70 of the cam sliders 71, 72.

[0037] As the cam sliders 71, 72 move further, the tip end 812a of the inclined wall portion 812 comes into contact with the abutment surface 7z and is bent along the abutment surface 7z toward the protrusion 70. As shown in Fig. 9, as the cam sliders 71, 72 move, the tip end surface 812b of the inclined wall portion 812 comes into contact with the pressing surface 70a located on the abutment surface 7z side of the protrusion 70.

[0038] In this state, when the cam sliders 71 and 72 approach the punch 2A, the inclined wall portion 812 is bent, and the tip surface 812b of the inclined wall portion 812 tries to move upward, but the pressing surface 70a prevents the movement. In other words, the tip surface 812b of the inclined wall portion 812 is pressed downward by the pressing surface 70a of the protruding portion 70. In this way, when the inclined wall portion 812 is bent, a force is applied to the tip surface 812b of the inclined wall portion 812 in a direction that reduces the plate length of the inclined wall portion 812 (downward in this example). This force is called a "compressive force." When the inclined wall portion 812 is bent, a pressing force (i.e., a compressive force) is applied to the tip surface 812b of the inclined wall portion 812 in a direction perpendicular to the tip surface 812b of the inclined wall portion 812. The average pressure applied to the tip surface 812b is called an "end pressure."

[0039] The compressive force can be said to be a force in a direction perpendicular to the tip surface 812b of the inclined wall portion 812. Alternatively, the compressive force can be said to be a force on the plate length direction compressing side of the tip portion 812a of the inclined wall portion 812. Hereinafter, the formed inclined wall portion 812 (e.g., the shoulder R portion 92 and the vertical wall portion 93) is also referred to as a "flange."

[0040] For example, while bending the inclined wall portion 812, a compressive force that generates a yield stress in the bent portion of the inclined wall portion 812 is applied to the tip surface 812b. As a result, for example, as shown in FIG. 20, at the tip portion 812a of the stretch flange, the thickness of the inclined wall portion 812 is suppressed from being reduced by bending. Unlike a shrink flange or a straight flange, the tip portion (tip portion 812a) of the stretch flange is prone to a reduction in thickness due to bending. However, according to this method, the thickness reduction of the tip portion 812a is suppressed. In the specific bending step S2, the press forming apparatus 1A bends the inclined wall portion 812 while applying a compressive force that generates yield to the tip surface 812b, thereby bending the inclined wall portion 812 in a predetermined rotation direction while suppressing a reduction in the thickness of the inclined wall portion 812 in the stretch flange. Even when the compressive force is smaller than the force corresponding to the yield, the tensile stress in the circumferential direction of the stretch flange is lowered, and the occurrence of necking is delayed. In addition, the application of compressive force can suppress the progression of voids and cracks. Bending increases the plate thickness in the contracted flange and linear bend, creating a compressive stress field in the plate length direction. This reduces the circumferential compressive stress in the contracted flange, suppressing shape deformation. Elastic recovery occurs in the plate length direction, but no significant dimensional differences occur. Straight bending causes elastic recovery in the plate length direction, but no significant dimensional differences occur.

[0041] Regardless of the shape of the flange, such as a stretch flange, a contraction flange, or a straight flange, the plate length of the inclined wall portion 812 (flange) is actually reduced by bending the inclined wall portion 812 while applying a yield stress in the compressive direction to the bent portion of the inclined wall portion 812. In this case, the plate length of the press-formed product 9 becomes smaller than the plate length of the preformed product 81. In other words, the plate material 80 or the preformed product 81 is provided with a compression allowance according to the target shape of the press-formed product 9 (see FIG. 18).

[0042] 10, the preform 81 is finally sandwiched between the cam sliders 71, 72, the punch 2A, and the pressing member 4A to become the press-formed product 9. At this time, the protruding portions 70 of the cam sliders 71, 72 are inserted into the corresponding relief portions 20 of the punch 2A.

[0043] In this way, the specific bending process S2 is a process in which the press forming apparatus 1A bends the inclined wall portion 812 in a predetermined rotation direction while applying a compressive force to the tip surface 812b of the inclined wall portion 812. As an example, the specific bending process S2 is a process in which the inclined wall portion 812 is bent in a predetermined rotation direction while suppressing a decrease in the plate thickness of the inclined wall portion 812 or while increasing the plate thickness of the inclined wall portion 812 by applying a compressive force (a force that reaches the yield stress) to the tip surface 812b. The specific bending process S2 in this example is a process in which the inclined wall portion 812 is bent in a predetermined rotation direction while reducing the plate length of the inclined wall portion 812 by applying a compressive force (a force that reaches the yield stress) to the tip surface 812b.

[0044] (summary) The press forming method of this embodiment is a press forming method using a press forming apparatus 1A, and includes a specific bending step S2 in which a preform 81 having a top plate portion 811 and a slanted wall portion 812 slanted in a predetermined rotation direction with respect to the top plate portion 811 is bent in a predetermined rotation direction while applying a compressive force to a tip end surface 812b of the slanted wall portion 812 with the top plate portion 811 fixed. The compressive force may be a force that does not cause yielding in the plate material.

[0045] The press forming method of this embodiment includes a preliminary bending step S1 and a specific bending step S2. The preliminary bending step S1 is a step of bending a plate material 80 in a predetermined rotation direction to form a preformed product 81. The specific bending step S2 is a step of bending the inclined wall portion 812 in a predetermined rotation direction to form a shoulder R portion 92 and a vertical wall portion 93 while applying a compressive force to a tip end surface 812b of the inclined wall portion 812 with the top plate portion 811 fixed, in order to form a press-formed product 9 from the preformed product 81.

[0046] The press molding device 1A includes a die member 2A (e.g., punch 2A), a pressing member 4A, butting members 71 and 72 (e.g., cam sliders 71 and 72), and a driving device 10A. The die member 2A has a top surface 2a corresponding to the top plate portion 811, a shoulder surface 2b corresponding to the shoulder R portion 92, and a side wall surface 2c corresponding to the vertical wall portion 93. The pressing member 4A is disposed below the top surface 2a (on one side in a predetermined direction) so as to face the top surface 2a. The butting members 71 and 72 face the side wall surface 2c and correspond to the vertical wall portion 93. The driving device 10A moves the butting members 71 and 72 in the left-right direction (direction intersecting the predetermined direction). At a position of the butting members 71 and 72 corresponding to the tip position of the vertical wall portion 93, a protrusion 70 protruding toward the die member 2A is formed. In the specific bending process S2, with the top plate portion 811 of the preform 81 sandwiched between the top surface 2a and the pressing member 4A, and with the tip surface 812b of the inclined wall portion 812 abutting against the pressing surface 70a, which is the lower end surface (end surface on one side in a specified direction) of the protrusion 70, the driving device 10A moves the abutment members 71, 72 toward the side wall surface 2c.

[0047] A relief portion 20 into which the protruding portion 70 can enter is formed in a portion of the die member 2A corresponding to the protruding portion 70. In the specific bending process S2, with the top plate portion 811 of the preform 81 sandwiched between the top surface 2a and the pressing member 4A and with the tip surface 812b of the inclined wall portion 812 abutting against the pressing surface 70a of the protruding portion 70, the driving device 10A moves the abutting member 4A toward the side wall surface 2c, causing the protruding portion 70 to enter the relief portion 20.

[0048] In the press forming apparatus 1A of this embodiment, the protruding portion 70 is formed so that the pressing surface 70a comes into contact with the tip surface 812b of the inclined wall portion 812 when the inclined wall portion 812 is bent to form the shoulder R portion 92 and the vertical wall portion 93. The pressing surface 70a of the protruding portion 70 is formed so as to apply a force (i.e., a compressive force) to the tip surface 812b of the inclined wall portion 812 in a direction in which the plate length of the inclined wall portion 812 is reduced as the abutting members 71, 72 move (approach the die member 2A). The abutting members 71, 72 of this embodiment are cam sliders 71, 72 that move in conjunction with the movement of the cam drivers 73, 74.

[0049] (Transformation mode) The configuration of the press forming apparatus 1A used in the specific bending process S2 is not limited to the above embodiment, and may be configured as shown in FIG. 11. This press forming apparatus 1A also includes a die member 2A, a pressing member 4A, a butting member 71, and a driving device (not shown) for moving the pressing member 4A. FIG. 11(a) shows a state in which the top plate portion 811 of the preform 81 is sandwiched and fixed between the top surface 2a of the die member 2A and the pressing member 4A. FIG. 11(b) shows a state in which the butting member 71 moves leftward and the tip portion 812a of the inclined wall portion 812 abuts against the butting surface 7z. FIG. 11(c) shows a state in which the butting member 71 moves further leftward and the inclined wall portion 812 is bent and the tip surface 812b abuts against the pressing surface 70a of the protruding portion 70. Fig. 11(d) shows a state in which the abutting member 71 has moved further leftward, and end pressure has been applied to the tip end surface 812b, bending the inclined wall portion 812. Fig. 11(d) also shows a state in which the protrusion 70 has entered the relief portion 20, and the inclined wall portion 812 has been sandwiched between the shoulder surface 2b, the side wall surface 2c, and the abutting surface 7z, and has been deformed into the shoulder R portion 92 and the vertical wall portion 93.

[0050] The press forming apparatus 1A used in the specific bending process S2 may have a configuration as shown in Fig. 12. This press forming apparatus 1A also includes a die member 2A, a pressing member 4A, an abutting member 71, and a drive device (not shown) for moving the abutting member 71. In this example, the pressing member 4A includes, in addition to a top surface 41 corresponding to the top plate portion 811, a shoulder pressing surface 42 corresponding to at least a part of the shoulder R portion 92. When the abutting member 71 moves leftward, it also moves downward. That is, the abutting member 71 moves obliquely relative to the die member 2A.

[0051] In the example of FIG. 12, a compression allowance is provided in the plate material 80 or the preformed product 81 in consideration of the reduction in plate length due to the compressive force. In the press forming method of this embodiment, the inclined wall portion 812 is compressed while being bent, so that the plate material 80 or the preformed product 81 is formed into a target shape (shoulder R portion 92 and vertical wall portion 93). The plate length of the plate material 80 or the preformed product 81 includes a compression allowance corresponding to the compression amount (reduction amount) in the specific bending process S2, and is larger than the plate length of the target shape by the compression amount in the specific bending process S2. The two-dot chain arrow in FIG. 12 indicates the path of the tip surface 812b in the case of no compression, and the solid arrow indicates the path of the tip surface 812b in the case of compression. The reduction amount of the plate length corresponds to the compression allowance. Providing a compression allowance in the plate material 80 or the preformed product 81 in this way and bending the plate material 80 or the preformed product 81 while compressing it by the compression allowance can be applied to all embodiments of the present disclosure (for example, the embodiments of FIG. 6 to FIG. 11, FIG. 13, and FIG. 14). Providing a compression allowance for the plate length of the target shape, and bending the plate while compressing it by only the compression allowance to form the target shape is equivalent to bending the plate while generating yield stress in the plate material 80 or the preformed product 81 by compression.

[0052] Thus, as one of the techniques disclosed herein, in the specific bending process S2, a compressive force is applied to the tip surface 812b of the inclined wall portion 812 so that the average pressure (end pressure) applied to the tip surface 812b of the inclined wall portion 812 reaches the yield stress of the inclined wall portion 812. Also, the preform 81 is provided with a compression allowance to be compressed by the compressive force, and the plate length of the inclined wall portion 812 before the specific bending process S2 is performed is greater than the plate length of the inclined wall portion 812 (the shoulder R portion 92 and the vertical wall portion 93) after the specific bending process S2 is performed. In this embodiment, the plate material 80 is provided with a compression allowance to be compressed by the compressive force, and the plate length of the inclined wall portion 812 is greater than the plate lengths of the shoulder R portion 92 and the vertical wall portion 93.

[0053] 13, in the preliminary bending process S1, the tip 812a of the inclined wall portion 812 may be bent in a predetermined rotation direction so that the tip surface 812b faces the pressing surface 70a of the protruding portion 70, i.e., so that the tip surface 812b faces the direction of the pressing surface 70a. This process is called an end bending process. The pressing surface 70a and the tip surface 812b face each other in the vertical direction (predetermined direction). In this way, the shape of the inclined wall portion 812 may be changed according to the shape of the vertical wall portion 93, etc. (the shape of the stretch flange), for example. In the preliminary bending process S1, the press forming device bends the tip 812a of the inclined wall portion 812 in a predetermined rotation direction so that the tip surface 812b of the inclined wall portion 812 faces downward (the other side of the predetermined direction).

[0054] As an example of the end bending process, as shown in FIG. 14, a press forming apparatus 1B is a press forming apparatus 1 in which the die 3 is replaced with a die 3B. The die 3B includes die members 31B and 32B. Each die member 31B and 32B includes a side surface 3b extending upward from the inclined surface 3a. In the end bending process, press forming is performed so that the tip 812a of the inclined wall portion 812 is sandwiched between the side surface 3b of each die member 31B and 32B and the side surface of the punch 2. That is, when the preliminary bending step S1 is performed, the end bending process is also performed at the same time. As a result, both ends of the plate material 80 are bent in a predetermined rotation direction to become the inclined wall portion 812, and the tip 812a of the inclined wall portion 812 is further bent in a predetermined rotation direction. In the example of FIG. 14, the tip 812a of the inclined wall portion 812 extends along the side surface of the punch 2. According to the end bending process, the pressing surface 70a of the protruding portion 70 and the tip surface 812b of the inclined wall portion 812 are likely to come into contact with each other during the specific bending step S2, and the compressive force can be applied to the tip surface 812b more efficiently. The punch may be replaced in conjunction with the replacement of the die.

[0055] (Effects of this embodiment) According to the press forming method of this embodiment, by bending the inclined wall portion 812 while applying a compressive force to the tip surface 812b of the inclined wall portion 812, the compressive stress in the compressive stress region (inner part of the bend) increases and the tensile stress in the tensile stress region (outer part of the bend) decreases in the stress distribution of the bent portion of the inclined wall portion 812. By decreasing the tensile stress, the bending moment generated in the bent portion of the inclined wall portion 812 decreases, and the amount of springback also decreases. That is, according to the press forming method of this embodiment, springback is suppressed. In addition, by performing "bending" and "application of compressive force" to the inclined wall portion 812 simultaneously (in one process), it is possible to suppress the process from becoming complicated. In addition, according to the press forming apparatus 1A of this embodiment, since the protruding portion 70 is configured to abut against the tip surface 812b of the inclined wall portion 812 during bending, it is possible to execute the specific bending process S2. Therefore, the same effect as the above method is exerted.

[0056] Furthermore, when the compressive force is a force corresponding to the yield stress of the inclined wall portion 812 (in other words, when the end pressure reaches the yield stress), bending is performed while suppressing a decrease in the plate thickness of the inclined wall portion 812 due to bending or while increasing the plate thickness of the inclined wall portion 812. For this reason, the occurrence of necking is slower than in conventional forming methods. Even if necking occurs, the fracture strain increases due to the increase in compressive stress within the plate, improving formability. In other words, even if necking occurs, voids are prevented from becoming larger and cracks are prevented from progressing, and the occurrence of cracks can be delayed. Hereinafter, the compressive force corresponding to the yield stress is also referred to as the "yield compressive force."

[0057] According to the specific bending process S2 in which a yield compressive force is applied to the tip end surface 812b, the shoulder R portion 92 is plastically compressed, and the stress that was non-uniform in the plate during bending deformation approaches a uniform compressive stress. Even when the load is removed, the stress decreases uniformly, and the residual stress is reduced. Therefore, springback is suppressed. In theory, the residual stress approaches 0 when the load is removed.

[0058] When a plate material is bent without applying a compressive force as in the conventional method, as shown in FIG. 15, the stress distribution in the plate is such that tensile stress is distributed on the outer side of the bend and compressive stress is distributed on the inner side of the bend. When the plate material is loaded by the press forming device 1A (i.e., before unloading), a moment M according to the stress distribution is applied to the plate material. When this load is removed, a moment in the opposite direction to the moment M is applied, and springback occurs. On the other hand, when the plate material is bent while applying a yield compressive force to the plate material, theoretically, compressive stress is distributed on the outer side of the bend of the plate material as well, and compressive stress is distributed in all regions, as shown in FIG. 16. As a result, even after unloading, the straight line showing the stress distribution in the stress state in FIG. 16 simply moves toward the central dotted line, and no moment is generated, and no springback occurs. When the end pressure (average pressure applied to the tip surface 812b) becomes the yield stress, theoretically, springback becomes 0. In addition, even if the compressive force is smaller than the yield compressive force, the tensile stress in the bent outer part in FIG. 15 can be reduced, and the moment M can be reduced. That is, in this case, the springback after unloading is smaller than when no compressive force is applied during bending. The compression allowance is not necessary. In this way, by bending the plate material while applying a compressive force to a predetermined end face of the plate material, the stress distribution in the bent outer part can be brought closer to the compression side, and springback can be suppressed. According to this embodiment, the uneven stress distribution in the plate caused by bending can be brought closer to a uniform stress distribution. The state of uniform stress distribution can be said to be a state in which compressive stress is distributed in all areas of the bent part (from the inner peripheral edge to the outer peripheral edge), as shown in FIG. 16, for example. In other words, the state of uniform stress distribution can be said to be a state in which the stress distribution in the bent part is all compressive stress (a state in which no tensile stress is generated). Note that FIG. 17 can also be referred to for the effect of this embodiment.

[0059] Also, as shown in FIG. 18, the shape of the plate material (80) before bending may be curved. In this example, the right end of the plate material bulges to the right, and the left end of the plate material is recessed to the right. It is also assumed that a plate material with such a shape is bent in a predetermined rotation direction (the rotation axis extends in the front-rear direction). For example, wrinkles are relatively likely to occur in a contraction flange, and cracks are relatively likely to occur in an expansion flange (see FIG. 20). However, according to this embodiment, even if the plate material has a complex shape, wrinkles and cracks can be suppressed by bending the plate material while applying a compressive force. In the example of FIG. 18, as shown by the dotted line, a compression allowance is provided with respect to the plate material's plate length (left-right direction). The dimensions represented by the dotted line are the actual dimensions of the press-formed product. By bending the plate material while compressing it as in this embodiment, not only springback but also wrinkles and cracks can be suppressed even if the plate material has a complex shape.

[0060] Thus, according to the press forming method of this embodiment, it is possible to suppress cracks and springback. It is also possible to suppress jutting out, twisting of the top plate portion 811, and shrinkage flange wrinkles caused by bending. Furthermore, by applying a yield compressive force to the end face of the plate material, the unevenness of the end face is smoothed. According to this embodiment, it is possible to suppress cracks (fracture), suppress springback from bending, suppress wrinkles, improve the end face properties, and improve forming accuracy. According to the press forming method and press forming apparatus 1A of this embodiment, it is possible to suppress springback, suppress twisting of the top plate portion, suppress wrinkles, suppress cracks, and reduce residual stress while suppressing the process from becoming complicated.

[0061] (others) The present invention is not limited to the above embodiment. For example, the die member 2A may not have the relief portion 20. For example, in the specific bending process S2, the press molding device may be configured so that the vertical wall portion 93 is formed at the position where the protrusion 70 abuts against the die member 2A or at the position immediately before the abutment. However, as in the above embodiment, the presence of the relief portion 20 allows the inclined wall portion 812 (vertical wall portion 93) to be more reliably sandwiched between the die member 2A and the abutment members 71 and 72, and the molding accuracy of the vertical wall portion 93 can be improved.

[0062] The arrangement of the mold and the like of the device in this embodiment may be reversed. The multiple members that come into contact with the object to be formed during press forming may be appropriately called mold members (punch, die, pad, etc.). The present invention can also accommodate more complex product shapes. The vertical wall portion 93 is also called a flange. For example, the top plate portions 811 and 91 may be formed with a groove shape or an uneven shape. According to the press forming method or press forming device of the present invention, metal vehicle parts, such as lower arms, axle beams, and interior parts, can also be manufactured with high accuracy. The present invention can be applied to all types of bending. The forming using the mold of this embodiment may also be called closed bending or closed cam bending. The press forming method of the present invention may also include a process of bending (cam bending) the tip of the preform 81 while applying pressure in a closed space. The press forming method of this embodiment may be called an end pressure closed cam bending method. The direction indicating the thickness of the plate may be called the plate thickness direction, and the direction perpendicular to the plate thickness direction may be called the plate length direction.

[0063] The technology of the present disclosure can also be described as follows. The forming method of the present disclosure is a forming method for bending a plate material (e.g., 80, 81) using a forming device, characterized in that the forming device bends the plate material in a predetermined rotation direction so that the rotation axis of bending extends in a direction intersecting the reduction direction of the plate material (direction of the compressive force) while applying a compressive force to the plate material in a direction that reduces the plate length of the plate material. This makes it possible to make the non-uniform stress generated in the plate material due to bending plastic deformation closer to a uniform compressive stress, and to suppress springback, etc., as described above. As shown in FIG. 19, the rotation axis (virtual straight line) indicating the rotation center in the predetermined rotation direction extends in a direction intersecting the reduction direction (which can also be said to be the compression direction). In other words, the center line of the bending of the plate material extends in a direction intersecting the reduction direction. The plate length can be said to be the length in a direction perpendicular to the plate thickness direction of the plate material. In addition, the forming device is not limited to a press forming device, and may be, for example, a device using a robot arm or the like. For example, a robot arm may grip the plate material and bend it while reducing the plate length. In this manner, various forming devices may bend the plate material in a predetermined rotational direction while reducing the plate length of the plate material by compressive force corresponding to yield. By bending the plate material while reducing the plate length, i.e., while applying compressive yield stress to the plate material, it is possible to more reliably bring the non-uniform stress distribution in the plate caused by bending closer to a uniform stress distribution. This makes it possible to precisely suppress the occurrence of springback.

[0064] The technology of the present disclosure can also be described as follows. The method of the present disclosure is a forming method for bending a plate material (e.g., 80, 81) using a forming device, characterized in that the forming device bends the plate material in a predetermined rotation direction so that the rotation axis of bending extends in a direction intersecting the compression direction while applying a compressive force (i.e., yield compressive force) to a predetermined end face (e.g., tip face 812b) of the plate material in a compressive direction in which the plate length of the plate material is reduced and which generates a yield stress in the plate material. This also produces the same effect as above. Note that the predetermined end face of the plate material is not limited to tip face 812b.

[0065] The technology of the present disclosure can also be described as follows. The method of the present disclosure is a forming method using a forming device to bend a plate material, characterized in that the forming device bends the plate material in a predetermined rotation direction while applying a force to the plate material in a direction that reduces the plate length so that non-uniform stress generated in the plate material by bending plastic deformation approaches uniform compressive stress (first embodiment). In the forming method of the first embodiment, the forming device bends the plate material in the predetermined rotation direction while applying a compressive force that causes yielding to a predetermined end face of the plate material (second embodiment). In the forming method of the first or second embodiment, the plate material is a preform having a top plate portion and an inclined wall portion inclined in the predetermined rotation direction with respect to the top plate portion, and the forming device bends the inclined wall portion in the predetermined rotation direction while applying a force to a tip face of the inclined wall portion in a direction that reduces the plate length of the inclined wall portion with the top plate portion fixed. [Explanation of symbols]

[0066] Reference Signs List: 1A...press molding device, 10A...drive device, 2A...punch (die member), 20...relief portion, 2a...top surface, 2b...shoulder surface, 2c...side wall surface, 70...protrusion, 70a...pressing surface, 71, 72...cam slider (abutment member), 4A...holding member, 80...plate material, 81...preliminary formed product, 811...top plate portion, 812...inclined wall portion, 812a...tip portion, 812b...tip surface, 9...press molded product, 92...shoulder R portion, 93...vertical wall portion.

Claims

1. A press molding method using a press molding apparatus, The method includes a specific bending process for bending a preform having a top plate portion and an inclined wall portion inclined in a predetermined rotation direction with respect to the top plate portion, while applying a compressive force to a tip surface of the inclined wall portion in a direction in which a plate length of the inclined wall portion corresponding to a length of the inclined wall portion from the top plate portion to a tip surface of the inclined wall portion is reduced, while the top plate portion is fixed. Press molding method.

2. a pre-bending step of bending a plate material in the predetermined rotation direction to form the pre-formed product; a specific bending process in which, in a state in which the top plate portion is fixed, the inclined wall portion is bent in the predetermined rotation direction while applying the compressive force to a tip surface of the inclined wall portion to form the shoulder R portion and the vertical wall portion, in order to form a press-formed product from the preformed product, the press-formed product having the top plate portion, a shoulder R portion curved from the top plate portion, and a vertical wall portion continuing from the top plate portion via the shoulder R portion; The press molding method according to claim 1 , comprising:

3. The press molding apparatus is a die member having a top surface corresponding to the top plate portion, a shoulder surface corresponding to the shoulder R portion, and a side wall surface corresponding to the vertical wall portion; A pressing member disposed on one side of the top surface in a predetermined direction so as to face the top surface; abutting member facing the side wall surface and corresponding to the vertical wall portion; A drive device that moves the abutment member in a direction intersecting the predetermined direction; Equipped with A protrusion protruding toward the die member is formed at a position of the abutting member corresponding to a tip position of the vertical wall portion, In the specific bending process, a pressing member for pressing the top plate portion of the preform between the top surface and the pressing member, and a tip surface of the inclined wall portion is in contact with a pressing surface that is a surface on one side of the protrusion in the predetermined direction, the driving device moves the abutting member toward the side wall surface. The press molding method according to claim 2.

4. A relief portion into which the protrusion can enter is formed in a portion of the mold member corresponding to the protrusion, In the specific bending process, In a state in which the top plate portion of the preform is sandwiched between the top surface and the pressing member and in a state in which the tip surface of the inclined wall portion is in contact with the pressing surface of the protruding portion, the driving device moves the abutting member toward the side wall surface, and causes the protruding portion to enter the relief portion. The press molding method according to claim 3.

5. In the pre-bending step, a tip end portion of the inclined wall portion is bent in the predetermined rotation direction so that a tip end surface of the inclined wall portion faces the other side of the predetermined direction. The press molding method according to claim 3.

6. In the specific bending process, the compressive force is applied to the tip surface of the inclined wall portion such that an average pressure applied to the tip surface of the inclined wall portion reaches a yield stress of the inclined wall portion. The press molding method according to any one of claims 1 to 5.

7. The preform is provided with a compression allowance that is compressed by the compression force, The plate length of the inclined wall portion before the specific bending process is performed is greater than the plate length of the inclined wall portion after the specific bending process is performed. The press molding method according to claim 1 .

8. The plate material is provided with a compression allowance that is compressed by the compression force, The plate length of the inclined wall portion is greater than the plate lengths of the shoulder R portion and the vertical wall portion. The press molding method according to any one of claims 2 to 5.

9. A press molding apparatus for molding a press-formed product from a preform having a top plate portion and an inclined wall portion inclined relative to the top plate portion, the press-formed product including a top plate portion, a shoulder R portion curved from the top plate portion, and a vertical wall portion continuing from the top plate portion via the shoulder R portion, a die member having a top surface corresponding to the top plate portion, a shoulder surface corresponding to the shoulder R portion, and a side wall surface corresponding to the vertical wall portion; A pressing member disposed on one side of the top surface in a predetermined direction so as to face the top surface; abutting member facing the side wall surface and corresponding to the vertical wall portion; A drive device that moves the abutment member in a direction intersecting the predetermined direction; Equipped with A protrusion protruding toward the die member is formed at a position of the abutting member corresponding to a tip position of the vertical wall portion, The protrusion is formed such that, when the inclined wall portion is bent to form the shoulder R portion and the vertical wall portion, a pressing surface which is a surface on one side of the protrusion in the predetermined direction comes into contact with a tip surface of the inclined wall portion. Press forming equipment.

10. The drive device is a pressing member is moved toward the side wall surface while the top plate portion of the preform is sandwiched between the top surface and the pressing member and while a tip surface of the inclined wall portion is in contact with the pressing surface of the protruding portion; The pressing surface of the protrusion is formed to apply a force to the tip surface of the inclined wall portion in a direction in which a plate length of the inclined wall portion, which corresponds to the length of the inclined wall portion from the top plate portion to the tip surface of the inclined wall portion, is reduced in accordance with the movement of the abutting member. The press forming apparatus according to claim 9.

11. a relief portion into which the protrusion can enter is formed in a portion of the die member corresponding to the protrusion, The drive device is a pressing member for pressing the top plate portion of the preform between the top surface and the pressing member and a tip end surface of the inclined wall portion in contact with the pressing surface of the protruding portion, the pressing member is moved toward the side wall surface, and the protruding portion is caused to enter the relief portion. The press forming apparatus according to claim 10.

12. The abutting member is a cam slider that moves in conjunction with the movement of the cam driver. The press molding apparatus according to any one of claims 9 to 11.

13. A forming method for bending a plate material using a forming device, comprising: The forming device applies a compressive force to the plate material in a direction to reduce the plate length of the plate material, while bending the plate material in a predetermined rotation direction so that a rotation axis of bending extends in a direction intersecting the reduction direction of the plate material. Molding method.

14. The forming device bends the plate material in the predetermined rotation direction while reducing the plate length of the plate material by the compressive force corresponding to yield. The molding method according to claim 13.

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