Stamping method and device for automobile outer panel

Abstract

The present invention relates to a method for stamping an automobile outer panel, wherein a metal blank (101) is stamped into an automobile outer panel (111) having a characteristic line (113), a panel face (115), and a panel face (117), and comprises: moving a die (5) relative to a punch (3) to form a panel face (117), a punch side elastic body (9) and a formed panel face (115) protruding from a punch side forming face (3c). The invention relates to a step of bringing a die side elastic body (11) protruding from a die side forming surface (5b) into contact with a metal blank (101); and a step of moving the die (5) relative to the punch (3) side to a forming lower dead point while keeping the punch side elastic body (9) and the die side elastic body (11) in contact with the metal blank (101) to thereby flatten the punch side elastic body (9) and the die side elastic body (11) and stamp out an automobile outer panel (111).

Description

Technical Field

[0001] The present invention relates to a press forming method and apparatus for press forming a metal sheet into an automobile outer panel having a character line formed thereon. In the present invention, the metal sheet refers to a sheet composed of various metals, such as stainless steel, aluminum, and magnesium, typified by hot-rolled steel sheet, cold-rolled steel sheet, or surface-treated steel sheet subjected to surface treatment (electrogalvanization, hot-dip galvanizing, organic coating treatment, etc.). Background Art

[0002] For automotive exterior panels used in vehicle door outers, front fenders, and rear fenders, character lines are often applied to their exterior surfaces to enhance the vehicle's designability and tensile rigidity. Character lines are typically applied by pressing a metal blank against the ridgeline of a punch provided in a stamping die and clamping it with the valley line of the die. In recent years, in particular, there has been a demand for sharp character lines (i.e., ridgelines with large curvature (small curvature radius)) to further enhance vehicle design.

[0003] However, during this type of stamping, the punch's ridgeline sometimes contacts a portion other than the portion intended for character lines, creating a linear pattern. This linear pattern can remain even after coating, resulting in an appearance defect known as "line deviation" of the outer panel. This linear deviation is particularly noticeable when stamping using a punch with a small-radius arc-shaped ridgeline tip to create a clear character line, hindering improvements in vehicle design.

[0004] Some techniques have been proposed so far for suppressing the occurrence of such linear patterns and providing character lines.

[0005] For example, Patent Document 1 discloses a method in which a forming auxiliary cross-sectional shape having a design recess portion is provided in a die and a blank holder to clamp the periphery of the blank, thereby pre-bending and deforming the central portion of the blank along the forming surface of the punch, and then forming the design surface using the punch. Patent Document 2 discloses a method in which a suction port is formed on a stamping surface having a linear convex portion having a forming characteristic line, and a suction device that sucks from the suction port through a gas flow path is used to cause a metal sheet to adhere to the stamping surface for stamping, thereby suppressing the movement of the metal sheet and preventing skid line. Patent Document 3 discloses a technique in which, after a material is primarily formed using a punch angle and a cushion pad, deep drawing and stretch forming are performed while the punch is lowered, thereby preventing linear deviation from occurring at the portion of the metal material contacted by the punch angle.

[0006] Patent document 4 discloses the following technology: when manufacturing a stamped part having a ridge portion, a first stamping process of forming an intermediate shape (preforming shape) and a second stamping process of further forming the intermediate shape are performed to eliminate line deviation and obtain a high-quality stamped part. Patent document 5 discloses the following technology: an elastic body is provided at the front end of the punch to suppress the bending tendency (bending tendency) caused by the initial contact of the punch, and the generated bending tendency is suppressed from moving from the characteristic line, thereby suppressing the line deviation when the characteristic line is formed. Patent document 6 discloses the following technology: a die pad composed of an elastic body and the front end of the punch are used to form a characteristic line on the blank, and the characteristic line to be formed is constrained by the above-mentioned die pad and the above-mentioned punch, and is kept unchanged through the parts other than the characteristic line formed by the die and the punch. Patent Document 7 discloses a technique in which a plate-shaped workpiece is pressed against a lower die having a convex R portion having a molding characteristic line. After the workpiece is held in contact with the convex R portion, a press pad is brought into contact with the workpiece near the convex R portion to suppress slippage of the workpiece.

[0007] Patent Document 1: Japanese Patent No. 5876786

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2015-199102

[0009] Patent Document 3: Japanese Patent Publication No. 63-58652

[0010] Patent Document 4: Japanese Patent No. 5959702

[0011] Patent Document 5: Japanese Patent Application Publication No. 2018-103249

[0012] Patent Document 6: Japanese Patent Application Publication No. 2018-158351

[0013] Patent Document 7: Japanese Patent Application Laid-Open No. 2018-183786

[0014] However, the techniques disclosed in Patent Documents 1 to 7 have the following problems.

[0015] In the technology disclosed in patent document 1, for the deformation caused by the die and blank holder provided with the auxiliary forming cross-sectional shape, since there is no restriction of the punch, only the two ends of the blank corresponding to the designed recess can be constrained, so the bending deformation is limited to a straight line shape. In the technology disclosed in patent document 2, there is the following problem: a suction device that is not used in ordinary stamping is required, and in addition, the shape of the suction port is transferred to the surface of the molded part. In the technology disclosed in patent document 3, there is the following problem: since the final product shape is partially formed during the forming process, surface strain (surface deflection) is generated between the forming incomplete portion (forming incomplete portion).

[0016] In the technology disclosed in Patent Document 4, the die for forming the intermediate shape is different from the die for forming the target shape, and the number of processes such as die replacement increases, which becomes a problem. In the technology disclosed in Patent Document 5, there is the following problem: since the convex side of the ridge portion is formed by an elastomer, it is not formed according to the shape of the ridge portion. In the technology disclosed in Patent Document 6, there is the following problem: since the characteristic line is formed by a die pad composed of an elastomer, the characteristic line cannot be formed into the target shape when multiple characteristic lines are close. In the technology disclosed in Patent Document 7, there is the following problem: in the case of a complex surface shape, it is impossible to set the appropriate time for the pressing pad to abut against the workpiece, and abutment marks (defective) are generated on the workpiece due to the pressing pad. Summary of the Invention

[0017] The present invention has been made in view of the above-mentioned problems, and an object thereof is to provide a stamping method and a stamping apparatus for an automobile outer panel that prevents line deviation and forms a target character line without increasing the man-hours for stamping.

[0018] The present invention relates to a method for stamping an outer panel for an automobile, wherein a punch, a die opposed to the punch, and a blank holder opposed to an end of the die are used to stamp a metal blank into an outer panel for an automobile having a character line and panel faces continuous on both sides thereof, wherein the punch comprises: a ridge portion for forming the character line; a punch-side forming surface portion for forming the panel face; and a punch-side elastic body supported so as to protrude further toward the die than the punch-side forming surface portion so as to be able to abut against a character-line equivalent portion in the metal blank along the character-line equivalent portion. the portion on both sides of the metal blank having a larger tension during stamping, the portion corresponding to the characteristic line being separated from the portion corresponding to the characteristic line, the die comprising: a valley portion for forming the characteristic line in cooperation with the ridge portion; a die-side forming surface portion for forming the panel surface portion; and a die-side elastic body supported to protrude further toward the punch than the die-side forming surface portion so as to abut against and press against a portion on both sides of the metal blank having a smaller tension during stamping, the portion corresponding to the characteristic line being separated from the portion corresponding to the characteristic line. The method for stamping an automobile outer panel comprises: an elastic body contact step in which the die is relatively moved toward the punch while both ends of the metal blank are clamped by the die and the blank holder, so that the punch-side elastic body and the die-side elastic body respectively abut against the metal blank;and a stamping forming step, in which the punch side elastic body and the die side elastic body are kept in contact with the metal blank and the die is moved relatively toward the punch side to the forming lower dead point to stamp out the above-mentioned automobile outer panel formed by the above-mentioned ridge line portion and the above-mentioned valley line portion. The protrusion amount of the punch side elastic body from the above-mentioned punch side forming surface portion is set as follows: in the above-mentioned elastic body contact step, before the above-mentioned ridge line portion of the above-mentioned punch contacts the above-mentioned metal blank, the above-mentioned punch side elastic body contacts the above-mentioned metal blank and is flush with the above-mentioned punch side forming surface portion at the forming lower dead point. The protrusion amount of the die side elastic body from the above-mentioned die side forming surface portion is set as follows: in the above-mentioned elastic body contact step, before the above-mentioned ridge line portion of the above-mentioned punch contacts the above-mentioned metal blank to plastically deform the above-mentioned metal blank. Before the stamping step, the die-side elastic body is in contact with the metal blank, and the friction force imparted by the product of the load of the die-side elastic body pressing the metal blank in the stamping step and the friction coefficient between the die-side elastic body and the metal blank is greater than the absolute value of the difference between the tensions acting on both sides of the portion corresponding to the characteristic line.

[0019] The present invention relates to a stamping method for an automobile outer panel, wherein a punch, a die opposed to the punch, and a blank holder opposed to an end of the die are used to stamp a metal blank into an automobile outer panel having a characteristic line and a panel surface portion (panel surface portion) continuous on both sides thereof, wherein the punch has: a ridge portion for forming the characteristic line; a punch side forming surface portion for forming the panel surface portion; and a punch side elastic body supported to protrude further toward the die side than the punch side forming surface portion so as to be able to abut against a position separated from the characteristic line corresponding portion in a portion of the metal blank on the side where tension is smaller during stamping among portions of the metal blank sandwiching the characteristic line corresponding portion along the characteristic line corresponding portion, the characteristic line corresponding portion being equivalent to the characteristic line, and the die having: a valley portion for cooperating with the ridge portion to form the characteristic line; a die side forming surface portion for forming the panel surface portion; and a die side elastic body supported to protrude further toward the punch side than the die side forming surface portion so as to be able to The punch and die side elastic bodies are respectively in contact with the metal blank plate, and the punch and die side elastic bodies are respectively in contact with the metal blank plate. The die-side elastic body is configured to be pressed and formed into the automobile outer panel having the characteristic line formed by the ridge line portion and the valley line portion, wherein the protrusion amount of the punch-side elastic body from the punch-side forming surface portion is set so that: before the ridge line portion of the punch abuts the metal blank, the punch-side elastic body abuts the metal blank and is coplanar with the punch-side forming surface portion at the forming bottom dead center, and the protrusion amount of the die-side elastic body from the die-side forming surface portion is set so that: in the elastic body abutting step, before the ridge line portion of the punch abuts the metal blank to plastically deform the metal blank, the die-side elastic body abuts the metal blank, and the friction force given by the product of the load on the die-side elastic body pressing the metal blank in the stamping step and the friction coefficient between the die-side elastic body and the metal blank becomes greater than the absolute value of the difference between the tensions acting on both sides of the portion corresponding to the characteristic line.

[0020] The punch-side elastic body is preferably provided on the punch side via a punch-side movable body. The punch-side movable body is movable in a punching direction and pressurizes and supports the punch-side elastic body toward the die side.

[0021] The die-side elastic body is preferably provided on the die side via a die-side movable body that is movable in the stamping direction and pressurizes and supports the die-side elastic body toward the punch.

[0022] The punching device for an automobile outer panel according to the present invention uses a punch, a die opposite to the punch, and a blank holder opposite to the end of the die to stamp a metal blank into an automobile outer panel having a characteristic line and panel faces continuous on both sides thereof, wherein the punch has: a ridge portion for forming the characteristic line; a punch-side forming face for forming the panel face; and a punch-side elastic body supported to protrude toward the die side more than the punch-side forming face so as to abut against a position separated from the characteristic line corresponding portion in a portion of the metal blank sandwiched between the two sides of the characteristic line corresponding portion and on a side where tension is greater during the stamping process, the characteristic line corresponding portion being equivalent to the characteristic line, the die having: a valley portion for cooperating with the ridge portion to form the characteristic line; a die-side forming face for forming the panel face; and the die-side elastic body supported to protrude toward the punch side more than the die-side forming face so as to abut against the metal blank along the characteristic line corresponding portion. The punch side elastic body is pressed at a position separated from the corresponding part of the above-mentioned characteristic line in the part on the side with small tension in the stamping process, and the protrusion amount of the above-mentioned punch side elastic body from the above-mentioned punch side forming surface is set as follows: when the above-mentioned die is relatively moved toward the above-mentioned punch side, before the above-mentioned ridge line part of the above-mentioned punch abuts against the above-mentioned metal blank, and is coplanar with the above-mentioned punch side forming surface at the bottom dead point of the forming, and the above-mentioned die side elastic body The protrusion amount from the die side forming surface portion is set so that when the die is relatively moved toward the punch side, before the ridge portion of the punch abuts against the metal blank to plastically deform the metal blank, the die side elastic body abuts against the metal blank, and the friction force imparted by the product of the load of the die side elastic body pressing the metal blank and the friction coefficient of the die side elastic body and the metal blank becomes greater than the absolute value of the difference in tension between the portions acting on both sides of the portion corresponding to the characteristic line.

[0023] The present invention relates to a stamping device for an automobile outer panel, which uses a punch, a die opposed to the punch, and a blank holder opposed to the end of the die to stamp a metal blank into an automobile outer panel having a characteristic line and panel faces continuous on both sides thereof, wherein the punch has: a ridge portion for forming the characteristic line; a punch-side forming face portion for forming the panel face portion; and a punch-side elastic body supported so as to protrude further toward the die than the punch-side forming face portion so as to be able to abut against the portion corresponding to the characteristic line. The punching die is provided with a groove portion for forming the grooves of the punch and the grooves of the grooves, and the grooves are provided on the grooves of the punch and the grooves of the grooves. The protrusion amount from the above-mentioned die side forming surface portion is set so that when the above-mentioned die is relatively moved toward the above-mentioned punch side, before the above-mentioned ridge portion of the above-mentioned punch abuts against the above-mentioned metal blank to plastically deform the above-mentioned metal blank, the above-mentioned die side elastic body abuts against the above-mentioned metal blank, and the friction force given by the product of the load of the above-mentioned die side elastic body pressing the above-mentioned metal blank and the friction coefficient between the die side elastic body and the above-mentioned metal blank becomes greater than the absolute value of the difference between the tensions acting on the parts on both sides of the corresponding part of the above-mentioned characteristic line.

[0024] It is preferable that the punch-side elastic body is provided on the punch side via a punch-side movable body that is movable in the punching direction and pressurizes and supports the punch-side elastic body toward the die side.

[0025] The die-side elastic body is preferably provided on the die side via a die-side movable body that is movable in the stamping direction and pressurizes and supports the die-side elastic body toward the punch.

[0026] According to the present invention, in a process of press-forming a metal blank into an automobile outer panel having a characteristic line formed by the ridge line and the valley line and panel face portions continuous on both sides thereof using a punch having a ridge line portion, a die having a valley line portion opposed to the punch, and a blank holder opposed to the end of the die, the punch side elastic body protruding from the punch side forming face portion can be brought into contact with and supported at a position of the metal blank separated from a portion corresponding to the characteristic line, thereby preventing the initial bending mark of the metal blank caused by the ridge line portion of the punch. The die side elastic body protruding from the die side forming surface is pressed at a position opposite to the punch side elastic body and separated from the characteristic line equivalent portion, so that the friction force between the die side elastic body protruding from the die side forming surface and the metal blank is greater than the tension difference acting on both sides of the metal blank with the characteristic line equivalent portion clamped therebetween, thereby preventing the movement of the metal blank caused by the tension difference, reducing line deviation, and stamping out an automobile outer panel with a characteristic line. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 These are views for explaining the structure of a press-forming method and press-forming apparatus for an automobile outer panel according to the first embodiment of the present invention.

[0028] Figure 2 This is a diagram illustrating the load P applied to the metal blank by the flattened die-side elastic body and the tensions F1 and F2 generated in the metal blank during the stamping process of the automotive outer panel stamping method and stamping apparatus according to embodiment 1 of the present invention.

[0029] Figure 3 These are views for explaining the structure of a press-forming method and press-forming apparatus for an automobile outer panel according to another aspect of the first embodiment of the present invention.

[0030] Figure 4 These are views for explaining the structure of a press-forming method and press-forming apparatus for an automobile outer panel according to a second embodiment of the present invention.

[0031] Figure 5 These are views for explaining the structure of a press-forming method and press-forming apparatus for an automobile outer panel according to another aspect of the second embodiment of the present invention.

[0032] Figure 6 These are diagrams explaining the arrangement when evaluating the shape and line deviation of the outer plate panel to be formed in the examples and the panel face portion of the outer plate panel.

[0033] Figure 7This is a diagram showing the results of the cross-sectional shape of the outer plate panel obtained by press forming analysis in the examples.

[0034] Figure 8 This is a diagram showing the results of the evaluation value Δs of the surface strain of the outer plate panel obtained by the press forming analysis in the examples.

[0035] Figure 9 These are diagrams explaining a conventional automobile outer panel press forming method, the operation of a press forming apparatus, and line deviations generated during the press forming process. DETAILED DESCRIPTION

[0036] Before describing the stamping method and stamping apparatus for automobile outer panels according to the first and second embodiments of the present invention, line deviation occurring during stamping of automobile outer panels having character lines will be described.

[0037] <Reasons for line deviation>

[0038] As an example, Figure 9 As shown in (d), the automobile outer panel 111, which is the object of the present invention, has a characteristic line 113 and a panel face 115 and a panel face 117 continuous on both sides thereof, and is deep-drawn as follows using a stamping forming device 51 having a punch 53 having a ridge portion 53a extending in the front and back directions of the paper, a die 55 having a valley portion 55a extending in the front and back directions of the paper, and a blank retainer 57 opposite to the two end portions of the die 55.

[0039] First, if Figure 9 As shown in (a), the end portion 101a and the end portion 101b of the metal blank 101 are clamped by the die 55 and the blank holder 57, respectively. Figure 9 As shown in (a) to (d), the die 55 and the blank retainer 57 are moved relative to the punch 53 side to the lower dead point of the forming while maintaining the state of clamping the metal blank 101, and the automobile outer panel 111 with the characteristic line 113 formed by the ridge line portion 53a of the punch 53 and the valley line portion 55a of the die 55 is stamped.

[0040] In the stamping process, if the die 55 is relatively moved toward the punch 53, first, the ridge 53a of the punch 53 abuts against the metal blank 101, and an initial bend ( Figure 9 Then, during the process of deep drawing by the die 55 and the punch 53, tension is generated in the metal blank 101 in the directions toward the end 101a and the end 101b, respectively, with the initial bending mark as the boundary ( Figure 9 (b), (c)).

[0041] The tension generated in the metal blank 101 is determined by the distances from the initial bending mark to the end 101a and the end 101b, the panel surface 115 and the panel surface 117 ( Figure 9 The difference in the angle of (d) relative to the stamping direction or the difference in the forming depth from the ridge 53a to the end 101a and the end 101b caused by them produces a difference with the initial bending mark as the boundary.

[0042] For example, the acute angle between the line drawn from the ridge line 53a of the punch 53 in the press forming direction and the panel surface 115 is θ a , let the acute angle with the panel surface 117 be θ b , at an angle θ on the panel face 117 b smaller than the angle θ of the panel surface 115 a In the case of (refer to Figure 9 (d)), and the tension generated on the end 101b side (portion 107) during the stamping process is greater than the tension generated on the end 101a side (portion 105) in the metal blank 101 ( Figure 9 (b), (c)).

[0043] Furthermore, if a tension difference occurs at the initial bending mark as described above, the metal blank 101 slides toward the side with greater tension, and the initial bending mark shifts toward the end portion 101b with greater tension ( Figure 9 (c)). Furthermore, the initial bending mark is destroyed by the punch 53 and the die 55 at the bottom dead point of the forming, resulting in a linear pattern, i.e., line deviation ( Figure 9 (d)).

[0044] As described above, the imbalance in tension generated in the metal blank 101 during the deep drawing process contributes to line deviation in the automotive outer panel 111 formed with the character line 113. Furthermore, as mentioned above, one example of a factor causing the imbalance in tension is the difference in forming depth at the ends 101a and 101b of the metal blank 101, caused by differences in distance and angle between the point where the ridgeline 53a of the punch 53 abuts and the ends 101a and 101b of the metal blank 101.

[0045] That is, when the forming depths are different between the end 101a side and the end 101b side of the metal blank 101, the tension generated on the end 101b side where the forming depth is greater during the deep drawing process becomes greater, and due to the tension difference with the end 101a side where the forming depth is smaller, the metal blank 101 slides toward the end 101b side, resulting in line deviation.

[0046] Next, the stamping method and stamping apparatus for automobile outer panels according to Embodiments 1 and 2 of the present invention will be described. In the following description, components having the same or corresponding functions are denoted by the same reference numerals to avoid duplication.

[0047] [Implementation Method 1]

[0048] <Stamping device>

[0049] As an example, Figure 1 As shown, the stamping forming device 1 for an automobile outer panel involved in this embodiment 1 (hereinafter referred to as "stamping forming device 1") stamps a metal blank 101 into an automobile outer panel having a characteristic line 113 and a panel face 115 and a panel face 117 continuous on both sides thereof, and is equipped with a punch 3, a die 5, a blank retainer 7, a punch side elastomer 9 and a die side elastomer 11.

[0050] here, Figure 1 (a) shows the state before molding begins. Figure 1 (b) shows the state where the punch side elastic body 9 and the die side elastic body 11 are in contact with the metal blank 101. Figure 1 (c) shows the state where the metal blank 101 is supported by the punch side elastic body 9. Figure 1 (d) shows the state where the metal blank 101 is pressed by the die side elastic body 11. Figure 1 (e) shows the state at the bottom dead point of molding.

[0051] In addition, as mentioned above Figure 9 As shown, in the first embodiment, the outer panel 111 ( Figure 1 (e)) During the stamping process, the tension generated on the end 101b side with the characteristic line equivalent portion 103 in the metal blank 101 as the boundary is greater than the tension generated on the end 101a side (refer to Figure 2 ).

[0052] Punch

[0053] like Figure 1 As shown, the punch 3 includes a ridge portion 3a, a punch-side molding surface portion 3b and a punch-side molding surface portion 3c located on both sides of the ridge portion 3a, and a groove portion 3d.

[0054] The ridge portion 3a forms a characteristic line 113 ( Figure 1 (e)).

[0055] The punch side forming surface portion 3b and the punch side forming surface portion 3c form the panel surface portion 115 and the panel surface portion 117 respectively ( Figure 1(e)). The punch side forming surface 3b forms the portion 105 on the side where the tension acting on the metal blank 101 is small during the stamping process into a panel surface 115 ( Figure 1 On the other hand, the punch side forming surface 3c forms the portion 107 on the side where the tension acting on the metal blank 101 is large during the stamping process into a panel surface 117 ( Figure 1 (e)).

[0056] The groove portion 3 d is formed in a concave shape in the punch-side molding surface portion 3 c , and the punch-side elastic body 9 is provided therein.

[0057] "die"

[0058] like Figure 1 As shown, the die 5 includes a valley line portion 5a, a die side molding surface portion 5b and a die side molding surface portion 5c that are continuous on both sides of the valley line portion 5a, and a groove portion 5d.

[0059] The valley line portion 5 a cooperates with the ridge line portion 3 a of the punch 3 to form a character line 113 .

[0060] The die-side molding surface portion 5 b cooperates with the punch-side molding surface portion 3 b to mold the panel surface portion 115 , and the die-side molding surface portion 5 c cooperates with the punch-side molding surface portion 3 c to mold the panel surface portion 117 .

[0061] The die-side forming surface 5b forms a portion 105 on the side where the tension acting on the metal blank 101 during the stamping process is small, into a panel surface 115. On the other hand, the die-side forming surface 5c forms a portion 107 on the side where the tension acting on the metal blank 101 during the stamping process is large, into a panel surface 117.

[0062] The groove portion 5d is formed in a concave shape in the die-side molding surface portion 5b, and the die-side elastic body 11 is placed therein.

[0063] 《Blank Retainer》

[0064] like Figure 1 As shown, the blank holder 7 is arranged to face both ends of the die 5 , and cooperates with the die 5 to clamp the end portions 101 a and 101 b of the metal blank 101 .

[0065] 《Punch side elastic body》

[0066] like Figure 1As shown, the punch side elastic body 9 is arranged in the groove portion 3d so as to protrude toward the die 5 side more than the punch side forming surface portion 3c, so that it can abut against the position 105 on both sides of the characteristic line equivalent portion 103 corresponding to the characteristic line 113 in the metal blank 101 along the characteristic line equivalent portion 103 and the position separated from the characteristic line equivalent portion 103 in the portion 107 on the side with greater tension during the stamping process, and has a punch side abutting surface portion 9a abutting against the metal blank 101.

[0067] The protrusion amount of the punch side elastic body 9 from the punch side forming surface 3c is set so that when the die 5 is moved relative to the punch 3 side, the punch side abutting surface 9a of the punch side elastic body 9 abuts against the metal blank 101 before the ridge line portion 3a of the punch 3 abuts against the metal blank 101.

[0068] Furthermore, the punch side elastic body 9 has the following features: the punch side elastic body 9 protrudes from the punch side forming surface portion 3c to the forming bottom dead point and contacts and supports the metal blank 101, so that the bending shape of the metal blank 101 caused by the ridge line portion 3a is smoothed, and the punch side elastic body 9 has the following features: Figure 1 The punch side elastic body 9 can be deformed along the mold shape (the shape of the punch side molding surface 3c) at (e), that is, the punch side abutting surface 9a can be deformed (contracted in the stamping direction) to a hardness and shape that is coplanar with the punch side molding surface 3c. Specific materials for such a punch side elastic body 9 include rubber materials or urethane materials with a Shore hardness of 40 to 100 HS.

[0069] 《Elastomer on the die side》

[0070] The die side elastic body 11 is set to protrude further toward the punch 3 side than the die side forming surface 5b, so that it can abut against the position separated from the characteristic line equivalent portion 103 in the metal blank 101 along the characteristic line equivalent portion 103 and the position of the portion 105 on the side with smaller tension during the stamping process in the portion 107 to press, and has a die side abutting surface 11a abutting against the metal blank 101.

[0071] The amount by which the die-side elastic body 11 protrudes from the die-side forming surface portion 5b is set so that, when the die 5 is relatively moved toward the punch 3, the die-side contact surface portion 11a contacts the metal blank 101 before the ridge portion 3a of the punch 3 contacts the metal blank 101 and plastically deforms the metal blank 101. Furthermore, the amount of protrusion is set so that the frictional force between the die-side elastic body 11 and the metal blank 101, which is the product of the load pressing the portion 105 of the metal blank 101 due to contraction of the die-side elastic body 11, which has been flattened during the press-forming process, and the coefficient of friction between the die-side elastic body 11 (die-side contact surface portion 11a) and the metal blank 101, becomes greater than the absolute value of the difference between the tensions acting on the portions 105 and 107 on both sides of the characteristic line corresponding portion 103.

[0072] Plastic deformation of the metal blank 101 caused by the ridge 3 a can be determined to occur, for example, when the strain at the portion of the metal blank 101 where the ridge 3 a contacts exceeds the strain ε0 calculated by the following equation (1).

[0073] ε0=t / 2R … (1)

[0074] Here, R is the radius of curvature of the curve of the characteristic line 113 , and t is the thickness of the metal blank 101 .

[0075] Furthermore, the friction force between the die-side elastic body 11 and the metal blank 101 satisfies the following formula (2).

[0076] |F1-F2|≤P×μ e … (2)

[0077] Here, as Figure 2 As shown, F1 and F2 are tensions acting on the portions 105 and 107 on both sides of the characteristic line corresponding portion 103, respectively, and P is the load that presses the metal blank 101 by the contraction of the die side elastic body 11 ( Figure 2 ), μ e It is the friction coefficient between the die-side elastic body 11 and the metal blank 101.

[0078] The load P can be calculated based on the shrinkage of the die side abutment surface 11a when it is flattened to be coplanar with the die side molding surface 5b. The shrinkage of the die side elastic body 11 is equal to the protrusion of the die side elastic body 11 from the die side molding surface 5b.

[0079] Friction coefficient μ e Alternatively, when a rubber material or a polyurethane material is used as the die-side elastic body 11 as described later, the friction coefficient μ eUsually μ e =0.1~0.3(lubricant), μ e ≈0.5~0.6 (dry), so these values ​​can also be used.

[0080] The difference in tension between the portions 105 and 107 on both sides of the characteristic line equivalent portion 103 during the stamping process (F1-F2 in formula (2)) can be determined in advance by an experiment in which the tension acting on the metal blank 101 during the actual stamping process into the automotive outer panel 111 is measured using a strain gauge, etc., or by a press forming analysis of the automotive outer panel 111 based on the finite element method (FEM), etc.

[0081] Furthermore, the die-side elastic body 11 may have a hardness and shape that allows it to deform along the mold shape (the shape of the die-side molding surface 5b) at the bottom dead center of the molding process. Specifically, it may be deformed (contracted in the molding direction) until the die-side contact surface 11a and the die-side molding surface 5b become flush with each other. Specific materials for such a die-side elastic body 11 include rubber or polyurethane materials having a Shore hardness of 40 to 100 HS.

[0082] <Stamping method>

[0083] like Figure 1 As shown, the stamping method of the automobile outer panel involved in this embodiment 1 uses a stamping device 1 equipped with a punch 3, a die 5, a blank retainer 7, a punch side elastic body 9 and a die side elastic body 11 to stamp a metal blank 101 into an automobile outer panel 111 having a characteristic line 113 and a panel face 115 and a panel face 117 continuous on both sides thereof, and has an elastic body abutment step and a stamping step.

[0084] As described above, the punch side elastic body 9 is arranged in the groove portion 3d so as to protrude further toward the die 5 side than the punch side forming surface portion 3c, so that it can abut against the position of the metal blank 101 at the portion 105 on both sides of the characteristic line equivalent portion 103 and the position of the portion 107 on the side with greater tension during the stamping process, which is separated from the characteristic line equivalent portion 103.

[0085] As described above, the die-side elastic body 11 is provided in the groove portion 5d so as to protrude further toward the punch 3 than the die-side forming surface portion 5b. This allows the die-side elastic body 11 to abut against the portions 105 on both sides of the metal blank 101 sandwiching the portion 103 corresponding to the characteristic line, and to press the portion 107 on the side where the tension is low during the stamping process, at a position separated from the portion 103 corresponding to the characteristic line. The following describes the elastic body abutment step and the stamping step.

[0086] Elastic body contact step

[0087] like Figure 1 As shown in (a) to (b), the elastic body abutment step is a step in which the die 5 is moved relative to the punch 3 side while the end 101a and the end 101b of the metal blank 101 are clamped by the die 5 and the blank retainer 7, so that the punch side abutment surface 9a of the punch side elastic body 9 and the die side abutment surface 11a of the die side elastic body 11 are respectively abutted against the metal blank 101.

[0088] The protrusion amount of the punch side elastic body 9 from the punch side forming surface 3c is set as follows: before the ridge portion 3a of the punch 3 abuts the metal blank 101, the punch side abutting surface 9a abuts the metal blank 101, and at the lower dead point of forming, the punch side abutting surface 9a and the punch side forming surface 3c are coplanar.

[0089] The amount of protrusion of the die-side elastic body 11 from the die-side forming surface 5b is set so that the die-side contact surface 11a contacts the metal blank 101 before plastic deformation occurs at the portion of the metal blank 101 abutted by the ridge 3a of the punch 3. At the bottom dead center of forming, the die-side contact surface 11a and the die-side forming surface 5b are flush. The plastic deformation of the metal blank 101 caused by the ridge 3a can be determined, for example, by the strain ε0 calculated using the aforementioned equation (1).

[0090] Furthermore, as shown in the above formula (2), the protrusion amount of the die side elastic body 11 is set to be: the load P generated by the shrinkage (deformation) of the die side elastic body 11 in the stamping direction in the stamping step following the elastic body abutment step and the friction coefficient μ between the die side elastic body 11 and the metal blank 101 e The friction force given by the product of the load P and the friction coefficient μ is greater than the absolute value |F1-F2| of the difference between the tensions F1 and F2 acting on the end 101a and end 101b sides respectively across the characteristic line corresponding portion 103 in the metal blank 101. e The absolute value of the difference between the tension |F1-F2| and the tension|F1-F2| only needs to satisfy the above-mentioned formula (2).

[0091] Stamping steps

[0092] like Figure 1 As shown in (b) to (e), the stamping forming step is a step of moving the die 5 relative to the punch 3 side to the forming lower dead point while keeping the punch side abutting surface 9a and the die side abutting surface 11a in abutment with the metal blank 101 to stamp out the automobile outer panel 111 having the characteristic line 113 formed by the ridge line portion 3a and the valley line portion 5a.

[0093] <Reasons for preventing line deviation>

[0094] The following is based on Figure 1 and Figure 2 The reason why the automobile outer panel 111 can be press-formed while preventing line deviation by the press-forming method and press-forming apparatus of the automobile outer panel according to the first embodiment will be described.

[0095] First, the die 5 moves relatively toward the punch 3 side, and the punch side contact surface 9a of the punch side elastic body 9 contacts the punch 3 side of the portion 107 in the metal blank 101 before the ridge line portion 3a of the punch 3. In addition, the die side contact surface 11a of the die side elastic body 11 contacts the die 5 side of the portion 105 ( Figure 1 (a)~(b)).

[0096] Next, when the die 5 is further moved relative to the punch 3, the punch side elastic body 9 deforms while contacting the portion 107 to support the portion 107, thereby gradually bending and deforming the metal blank 101 from the characteristic line corresponding portion 103 to the portion 107 to form a gentle shape ( Figure 1 (c)). Therefore, even if the ridge portion 3a contacts the metal blank 101, it is possible to prevent the generation of an initial bending mark caused by plastic deformation of the contacting portion.

[0097] On this basis, when the die 5 is further moved relative to the punch 3, the die side elastic body 11 contacts the portion 105 and deforms, pressing the portion 105 against the punch side forming surface portion 3b ( Figure 1 (d)).

[0098] At this time, when the ridge line portion 3a of the punch 3 contacts the metal blank 101, tensions F1 and F2 are generated in the metal blank 101 in directions toward the end 101a and the end 101b, respectively, with the characteristic line corresponding portion 103 as the boundary. Figure 2 There is a difference between the tension F1 on the end 101a side and the tension F2 on the end 101b side, so there is a concern that the metal blank 101 may slip from the end 101a side with low tension to the end 101b side with high tension (see Figure 9 ).

[0099] However, the friction between the die-side elastic body 11, which is pressed and flattened by the portion 105 on the side with less tension, and the metal blank 101 prevents the metal blank 101 from sliding toward the end portion 101a on the side with greater tension, thereby preventing the misalignment of the characteristic line corresponding portion 103 plastically deformed by the ridge portion 3a. Figure 1 (d)).

[0100] In this way, the punch side elastic body 9 can be used to alleviate the bending deformation from the characteristic line corresponding portion 103 to the portion 107, and the die side elastic body 11 can be used to prevent the metal blank 101 from sliding toward the end portion 101b with greater tension, so that the die 5 can be relatively moved to the forming bottom dead center ( Figure 1 (d)~(e)).

[0101] Moreover, at the bottom dead point of the forming, the characteristic line 113 is formed by the ridge line portion 3a of the punch 3 and the valley line portion 5a of the die 5, the punch side abutting surface portion 9a of the punch side elastic body 9 is deformed to be coplanar with the punch side forming surface portion 3c to form the panel surface portion 117, and the die side abutting surface portion 11a of the die side elastic body 11 is deformed to be coplanar with the die side forming surface portion 5b to form the panel surface portion 115 ( Figure 1 (e)).

[0102] As a result, the automobile outer panel 111 having the character line 113 formed therein can be punched and formed while preventing line deviation.

[0103] <Other methods>

[0104] In the stamping method and stamping apparatus for the automobile outer panel according to the first embodiment of the present invention, Figure 1 As shown, the punch-side elastic body 9 is supported by the bottom of the groove portion 3d, and the die-side elastic body 11 is supported by the bottom of the groove portion 5d.

[0105] Of course, as another embodiment of the present invention, Figure 3 As in the press forming device 21 shown as an example in FIG, the punch side elastic body 9 is provided in the groove portion 3d via the punch side movable body 23, and the die side elastic body 11 is provided in the groove portion 5d via the die side movable body 25.

[0106] here, Figure 3 (a) shows the state before molding begins. Figure 3 (b) shows the state where the punch side elastic body 9 and the die side elastic body 11 are in contact with the metal blank 101. Figure 3 (c) shows the state where the metal blank 101 is supported by the punch side elastic body 9. Figure 3 (d) shows the state where the metal blank 101 is pressed by the die side elastic body 11. Figure 3(e) shows the state at the bottom dead point of molding. Figure 3 Regarding the various parts constituting the stamping forming device 21, Figure 1 The same and corresponding parts of the stamping forming device 1 are marked as Figure 1 The same reference numerals as those in FIG.

[0107] like Figure 3 As shown, the punch-side movable body 23 supports the punch-side elastic body 9 by applying pressure to the die 5 side. It includes a pad 23a on which the punch-side elastic body 9 is mounted and can move in the stamping direction, and a pressure source 23b that applies pressure to the pad 23a. Here, the pressure source 23b can be exemplified by air pressure, hydraulic pressure, polyurethane, etc.

[0108] Furthermore, the punch side movable body 23 is set to a pressure of a pressure source 23b that pressurizes the punch side elastic body 9 toward the die 5 side so that Figure 3 The punch side elastic body 9 that is flattened during the stamping process shown in (b) to (e) is pressed back to the bottom side of the groove portion 3d and is at the bottom dead point of the forming process. Figure 3 As shown in (e), the punch-side contact surface portion 9a of the punch-side elastic body 9 that has been crushed and deformed (contracted) is flush with the punch-side molding surface portion 3c.

[0109] Here, the protrusion amount of the punch-side elastic body 9 supported by the punch-side movable body 23 from the punch-side molding surface portion 3 c is set to be the same as that in the above-mentioned first embodiment.

[0110] like Figure 3 As shown, the die-side movable body 25 supports the die-side elastic body 11 by applying pressure to the punch 3. The movable body 25 includes a pad 25a on which the die-side elastic body 11 is mounted and which is movable in the stamping direction, and a pressure source 25b that applies pressure to the pad 25a. Examples of the pressure source 25b include air pressure, hydraulic pressure, and polyurethane.

[0111] Furthermore, the die side movable body 25 is set to a pressure of a pressure source 25b that pressurizes the die side elastic body 11 toward the punch 3 side so that Figure 3 The die side elastic body 11 that is flattened during the stamping process shown in (b) to (e) is pressed back toward the bottom side of the groove portion 5d and is at the bottom dead point of the forming process. Figure 3 As shown in (e), the die-side contact surface portion 11a of the die-side elastic body 11 that has been crushed and deformed (contracted) is flush with the die-side molding surface portion 5b.

[0112] Here, as shown in the above formula (2), the protrusion amount of the die-side elastic body 11 supported by the die-side movable body 25 from the die-side forming surface portion 5b is set to the friction force (load P and friction coefficient μ) between the die-side elastic body 11 and the metal blank 101. e The product of the loads (|F1-F2|) is equal to or greater than the absolute value of the difference in tension between the two sides of the characteristic line corresponding portion 103. The load P is the load generated by the contraction of the flattened die-side elastic body 11.

[0113] The effects of the press-forming method and press-forming apparatus for an automobile outer panel according to another aspect of the first embodiment are as follows.

[0114] In other aspects of this embodiment 1, Figure 3 As shown, the punch side elastic body 9 is supported by being pressurized toward the die 5 side by the pressure source 23b of the punch side movable body 23. Figure 3 As shown in (b) to (d), even if the punch side elastic body 9 is deformed (contracted) due to the relative movement of the die 5 toward the punch 3 side, the punch side elastic body 9 can be kept pressurized toward the die 5 side so that the punch side elastic body 9 is in contact with the metal blank 101 for support.

[0115] Therefore, compared with the above-mentioned embodiment 1 (refer to Figure 1 ), in addition to changing the material, shape / size of the punch side elastic body 9, the pressure of the pressure source 23b supporting the punch side elastic body 9 is also adjusted, thereby increasing the freedom for performing stamping to make the bending deformation of the portion where the ridge portion 3a in the metal blank 101 and the punch side abutting surface portion 9a of the punch side elastic body 9 abut against each other into a gentle shape and prevent the generation of initial bending marks caused by the ridge portion 3a.

[0116] Furthermore, in other aspects of this embodiment 1, as Figure 3 As shown, the die-side elastic body 11 is supported by being pressurized toward the punch 3 by the pressure source 25b of the die-side movable body 25. Therefore, even when sufficient friction is not obtained between the die-side elastic body 11 and the metal blank 101, or when the tension difference (F1-F2) in the metal blank 101 increases before the load pressing the metal blank 101 due to contraction of the die-side elastic body 11 becomes sufficiently large, the pressure source 25b can be used to apply a further load to the pad 25a to which the die-side elastic body 11 is attached, thereby increasing the degree of freedom in adjusting the load of the die-side elastic body 11 pressing the metal blank 101 to prevent the metal blank 101 from slipping.

[0117] As described above, in the stamping method and stamping apparatus for an automobile outer panel according to another aspect of the first embodiment, the automobile outer panel 111 having the character line 113 formed therein can be stamped and formed more effectively while preventing line deviation.

[0118] In the first embodiment and other embodiments, the position where the metal blank 101 is pressed by the die-side elastic body 11 is as described above (see Figure 1 and Figure 3 ), so that the die side elastic body 11 is pressed along the position separated from the characteristic line equivalent portion 103 in the abutment portion 105 of the characteristic line equivalent portion 103.

[0119] Furthermore, the groove portion 5d is located at a position separated from the characteristic line corresponding portion 103 and is located on the die-side molding surface portion 5b that molds the relatively flat and less stressful panel surface portion 115. Therefore, there is no problem, as in the technique described in Patent Document 7, where the groove portion 5d is provided near the characteristic line corresponding portion 103, where the corner of the groove portion 5d abuts against the vicinity of the characteristic line corresponding portion 103, thereby generating linear flaws.

[0120] Furthermore, the groove portion 5d for accommodating the die-side elastic body 11 is preferably spaced apart from the valley portion 5a by a distance equal to or greater than 10% of the width of the die-side molding surface portion 5b at its corner on the characteristic line corresponding portion 103 side.

[0121] Similarly, in the first embodiment and other embodiments, regarding the position where the punch side elastic body 9 presses the metal blank 101, as described above, the punch side elastic body 9 is moved along the position ( Figure 1 and Figure 3 ).

[0122] Regarding this point, as in the technology described in Patent Document 7, if the punch side elastic body 9 is set near the characteristic line equivalent portion 103, then this vicinity is a position where the stress of the forming characteristic line 113 is high, so the corner (corner) of the groove portion 3d abuts against the characteristic line equivalent portion 103 and linear defects are easily generated.

[0123] In contrast, in the present embodiment 1 and other embodiments, as Figure 1 and Figure 3 As shown, the groove portion 3d is located at a position separated from the characteristic line corresponding portion 103 and is located on the punch-side forming surface portion 3b of the panel surface portion 117, which is relatively flat and has low stress. Therefore, the problem of linear defects described above, which would occur if the groove portion 3d is provided near the characteristic line corresponding portion 103, as in the technique described in Patent Document 7, does not occur.

[0124] Furthermore, the groove portion 3d for accommodating the punch-side elastic body 9 is preferably spaced apart from the ridge portion 3a by a distance equal to or greater than 10% of the width of the punch-side molding surface portion 3c at a corner on the characteristic line corresponding portion 103 side of the groove portion 3d.

[0125] Furthermore, according to the present embodiment 1 and other aspects, in the case Figure 1 and Figure 3 When the metal blank 101 is press-formed into the automobile outer panel 111 , the order in which the punch-side elastic body 9 and the die-side elastic body 11 are brought into contact with the metal blank 101 is not particularly limited.

[0126] Specifically, as long as the protrusion amount of the punch side elastic body 9 is set so that the punch side elastic body 9 abuts the metal blank plate 101 before the ridge line portion 3a of the punch 3 abuts the metal blank plate 101, and the protrusion amount of the die side elastic body 11 is set so that the die side elastic body 11 abuts the metal blank plate 101 before the ridge line portion 3a of the punch 3 abuts the metal blank plate 101 and plastic deformation occurs, it can be any one of the following: the punch side elastic body 9 abuts first, the die side elastic body 11 abuts first, or the punch side elastic body 9 and the die side elastic body 11 abut at the same time.

[0127] [Implementation Method 2]

[0128] like Figure 1 As shown, in the above-mentioned embodiment 1 of the present invention, during the process of stamping a metal blank 101 into an automobile outer panel 111, the punch side elastic body 9 is supported by abutting against a portion 107 on the side with greater tension clamping the characteristic line equivalent portion 103, and the die side elastic body 11 is pressed by abutting against a portion 105 on the side with less tension.

[0129] In contrast, Figure 4 As shown in the stamping forming device 31 as an example, the stamping forming device and stamping forming method of the automobile outer panel involved in embodiment 2 of the present invention, in the process of stamping the metal blank 101 into the automobile outer panel 111, the punch side elastic body 9 is abutted against the part 105 on the side with low tension in the metal blank 101 for support, and the die side elastic body 11 is abutted against the part 107 on the side with high tension in the metal blank 101 for pressing.

[0130] here, Figure 4 (a) shows the state before molding begins. Figure 4 (b) shows the state where the punch side elastic body 9 and the die side elastic body 11 are in contact with the metal blank 101. Figure 4 (c) shows the state where the metal blank 101 is supported by the punch side elastic body 9. Figure 4 (d) shows the state where the metal blank 101 is pressed by the die side elastic body 11. Figure 4(e) shows the state at the bottom dead point of molding. Figure 4 Regarding the various parts constituting the stamping forming device 31, Figure 1 The same and corresponding parts of the stamping forming device 1 are marked as Figure 1 The same reference numerals as those in FIG.

[0131] like Figure 4 As shown, the punch side elastic body 9 is provided in the groove portion 3 d so as to protrude toward the die 5 side from the punch side molding surface portion 3 b so as to be able to abut against a position of the portion 105 separated from the characteristic line corresponding portion 103 along the characteristic line corresponding portion 103 .

[0132] like Figure 4 As shown, the die-side elastic body 11 is provided in the groove portion 5d so as to protrude toward the punch 3 from the die-side molding surface portion 5c so as to be able to press along a position of the contact portion 107 of the characteristic line corresponding portion 103 that is separated from the characteristic line corresponding portion 103 .

[0133] The protrusion amount of the punch-side elastic body 9 from the punch-side molding surface portion 3 b and the protrusion amount of the die-side elastic body 11 from the die-side molding surface portion 5 c are set similarly to those in the first embodiment described above.

[0134] Furthermore, the stamping method of the automobile outer panel according to the second embodiment is similar to the Figure 1 The embodiment 1 shown is similar, as Figure 4 As shown, a stamping device 31 having a punch 3, a die 5, a blank retainer 7, a punch side elastomer 9 and a die side elastomer 11 is used to stamp a metal blank 101 into an automotive outer panel 111 having a characteristic line 113 and a panel face 115 and a panel face 117 continuous on both sides thereof, including an elastomer abutment step and a stamping step.

[0135] like Figure 4 As shown in (a) to (b), the elastic body abutment step is a step in which the die 5 is relatively moved toward the punch 3 side while the end portions 101a and 101b on both sides of the metal blank 101 are clamped by the die 5 and the blank retainer 7, so that the punch side abutment surface portion 9a of the punch side elastic body 9 and the die side abutment surface portion 11a of the die side elastic body 11 abut against the metal blank 101 respectively.

[0136] like Figure 4 As shown in (b) to (e), the stamping forming step is a step of moving the die 5 relative to the punch 3 side to the forming lower dead point while keeping the punch side abutting surface 9a and the die side abutting surface 11a in abutment with the metal blank 101 to stamp out the automobile outer panel 111 having the characteristic line 113 formed by the ridge line portion 3a and the valley line portion 5a.

[0137] <Reasons for preventing line deviation>

[0138] The following is mainly based on Figure 4 The reason why the automobile outer panel 111 can be punched while preventing line deviation by the punching method and punching apparatus of the automobile outer panel according to the second embodiment will be described.

[0139] First, the die 5 is relatively moved toward the punch 3 side, and the punch side elastic body 9 provided on the punch side forming surface portion 3b abuts against the punch 3 side of the portion 105 in the metal blank 101 before the ridge portion 3a of the punch 3, and the die side elastic body 11 provided on the die side forming surface portion 5c abuts against the die 5 side of the portion 107 ( Figure 4 (a)~(b)).

[0140] Next, if the die 5 is relatively moved toward the punch 3 while the punch side abutting surface portion 9a abuts against the punch 3 side of the portion 105 for support and the die side abutting surface portion 11a abuts against the portion 107 for pressing, the ridge portion 3a of the punch 3 abuts against the characteristic line corresponding portion 103 of the metal blank 101 ( Figure 4 (c)).

[0141] Next, if the die 5 is further moved relative to the punch 3, the punch-side elastic body 9 deforms as the press forming progresses. Therefore, the portion 103 corresponding to the characteristic line abutting the ridge 3a to the portion 105 abutting the punch-side elastic body 9 gradually bends and deforms into a gentle shape.

[0142] This can prevent the generation of initial bending marks due to plastic deformation when the front ridge line portion 3 a of the pressing portion 107 of the die-side elastic body 11 contacts the metal blank 101 .

[0143] In addition, when the die 5 is relatively moved further toward the punch 3, the die-side elastic body 11, which is pressed against the portion 107 on the side with greater tension, and the metal blank 101, are rubbed against each other, thereby preventing the metal blank 101 from sliding toward the end portion 101b with greater tension, and preventing the characteristic line corresponding portion 103 from being plastically deformed by the ridge portion 3a. Figure 4 (c)~(d)).

[0144] In this way, the punch side elastic body 9 can be used to alleviate the bending deformation from the characteristic line corresponding portion 103 to the portion 105, and the die side elastic body 11 can be used to prevent the metal blank 101 from sliding toward the end portion 101b with greater tension, so that the die 5 can be relatively moved to the forming bottom dead center ( Figure 4 (d)~(e)).

[0145] Moreover, at the bottom dead point of the forming, the characteristic line 113 is formed by the ridge line portion 3a of the punch 3 and the valley line portion 5a of the die 5, the punch side abutting surface portion 9a of the punch side elastic body 9 is deformed to be coplanar with the punch side forming surface portion 3b to form the panel surface portion 115, and the die side abutting surface portion 11a of the die side elastic body 11 is deformed to be coplanar with the die side forming surface portion 5c to form the panel surface portion 117 ( Figure 4 (e)).

[0146] As a result, the automobile outer panel 111 having the character line 113 formed therein can be press-formed while preventing line deviation.

[0147] <Other methods>

[0148] In the stamping method and stamping apparatus for the automobile outer panel according to the second embodiment of the present invention, Figure 4 As shown, the punch-side elastic body 9 is supported by the bottom of the groove 3d formed in the punch-side molding surface portion 3b, and the die-side elastic body 11 is supported by the bottom of the groove 5d formed in the die-side molding surface portion 5c.

[0149] Of course, as another method of this embodiment 2, Figure 5 As shown in the stamping forming device 41 as an example, the punch side elastic body 9 is supported at the bottom of the groove portion 3d via the punch side movable body 23, and the die side elastic body 11 is supported at the bottom of the groove portion 5d via the die side movable body 25.

[0150] here, Figure 5 (a) shows the state before molding begins. Figure 5 (b) shows the state where the punch side elastic body 9 and the die side elastic body 11 are in contact with the metal blank 101. Figure 5 (c) shows the state where the metal blank 101 is supported by the punch side elastic body 9. Figure 5 (d) shows the state where the metal blank 101 is pressed by the die side elastic body 11. Figure 5 (e) shows the state at the bottom dead point of molding. Figure 5 Regarding the various parts constituting the stamping forming device 41, Figure 1 The same and corresponding parts of the stamping forming device 1 are marked as Figure 1 The same reference numerals as those in FIG.

[0151] Moreover, in other aspects of this embodiment 2, the protrusion amount of the punch side elastic body 9 from the punch side molding surface 3b and the protrusion amount of the die side elastic body 11 from the die side molding surface 5c are respectively set to be the same as those in other aspects of the above-mentioned embodiment 1.

[0152] In this way, the punch side elastic body 9 is supported by the punch side movable body 23, thereby Figure 5 In the stamping process shown in (b) to (d), as in the other methods of the above-mentioned embodiment 1, the freedom for stamping can be increased to make the bending deformation of the part where the ridge portion 3a in the metal blank 101 and the punch side abutment surface portion 9a of the punch side elastic body 9 abut into a gentle shape to prevent the generation of initial bending marks.

[0153] Furthermore, the die side elastic body 11 is supported by the die side movable body 25, thereby Figure 5 In the press forming process shown in (b) to (e), similarly to the other aspects of the first embodiment, the degree of freedom in adjusting the load of the die-side elastic body 11 pressing the portion 107 to prevent the metal blank 101 from sliding is increased.

[0154] As described above, in the stamping method and stamping apparatus for an automobile outer panel according to another aspect of the second embodiment, the automobile outer panel 111 having the character line 113 formed therein can be stamped and formed more effectively while preventing line deviation.

[0155] In addition, the groove portion 3d ( Figure 4 and Figure 5 ) It is preferable that the corner of the groove portion 3d on the side of the characteristic line 113 is separated from the ridge portion 3a by a distance of 10% or more of the width of the punch side molding surface portion 3b. The groove portion 5d ( Figure 4 and Figure 5 The corner of the groove portion 5d on the characteristic line 113 side is preferably separated from the valley line portion 5a by a distance equal to or greater than 10% of the width of the die-side forming surface portion 5c. This eliminates the problem of the corner of the groove portion 3d or 5d abutting against the vicinity of the characteristic line corresponding portion 103, thereby generating linear defects, as in the technique described in Patent Document 7.

[0156] Furthermore, according to the stamping forming method and stamping forming device for automobile outer panel involved in this embodiment 2 and other embodiments, in the process of stamping the metal blank 101 into the automobile outer panel 111, as in the above-mentioned embodiment 1 and other embodiments, the order in which the punch side elastomer 9 and the die side elastomer 11 are brought into contact with the metal blank 101 is not particularly restricted.

[0157] Furthermore, in the present invention, the groove portion that accommodates the punch-side elastic body accommodates deformation of the punch-side elastic body during the stamping process, and therefore, the width of the groove portion needs to be previously made wider than the punch-side elastic body. Similarly, the groove portion that accommodates the die-side elastic body accommodates deformation of the die-side elastic body during the stamping process, and therefore, the width of the groove portion needs to be previously made wider than the die-side elastic body.

[0158] Example

[0159] An example was conducted to verify the effect of preventing line deviation when a character line is formed by stamping an automobile outer panel using the stamping method and stamping apparatus of the present invention. This will be described below.

[0160] In this example, a stamping analysis was performed on an automotive outer panel simulated with a characteristic line by stamping the outer panel using the stamping method of the present invention, and the presence of line deviation in the stamped outer panel was evaluated.

[0161] In the stamping analysis, SGCC-F steel plate with a thickness of 0.7 mm was used as the metal blank. Figure 6 The outer plate panel 121 shown has a characteristic line 123 and panel face portions 125 and 127 continuous on both sides thereof as an analysis object.

[0162] Here, the curvature radius of the characteristic line 123 is 3 mm, and the angles of the panel surface 125 and the panel surface 127 relative to the stamping direction are θ and θ, respectively. a =85° and θ b =65°, and the widths of the panel surface 125 and the panel surface 127 (the length from the boundary with the character line to the end) are both 50 mm.

[0163] In this embodiment, as a conventional example, a process of deep drawing a metal blank into an outer plate panel using a press forming device equipped with a punch, a die, and a blank holder was performed (see Figure 9 ) stamping analysis.

[0164] Furthermore, the b = 65°) and the panel face 127 side with a large angle (θ a =85°) during the press forming process of the panel face 125 side, the difference in tension is 202 kN.

[0165] Next, as an example of the invention, Figure 1 The stamping forming device 1 shown in FIG. 1 is provided with a punch 3, a die 5, a blank holder 7, a punch side elastic body 9 and a die side elastic body 11 to stamp a metal blank 101 into an outer plate panel 121 ( Figure 6 ) stamping analysis.

[0166] In this stamping analysis, the punch-side elastic body 9 protrudes from the punch-side forming surface 3c toward the die 5 and is provided in the groove portion 3d of the punch-side forming surface 3c. Furthermore, the punch-side elastic body 9 is set so as to abut against a position separated from the characteristic line equivalent portion 103 corresponding to the characteristic line 123 in a portion of the panel surface 127 having a small acute angle with the stamping direction (the boundary on the characteristic line equivalent portion 103 side of the groove portion 3d of the punch 3 is 10% of the width of the punch-side forming surface 3c). Here, the protrusion amount of the punch-side elastic body 9 from the punch-side forming surface 3c is set to 5 mm so that the punch-side abutting surface 9a abuts against the metal blank 101 before the ridge portion 3a of the punch 3 abuts against the metal blank 101.

[0167] On the other hand, the die side elastic body 11 protrudes from the die side forming surface 5b toward the punch 3 side and is provided in the groove portion 5d of the die side forming surface 5b. Furthermore, the die side elastic body 11 is pressed by contacting the position separated from the characteristic line corresponding portion 103 in the portion corresponding to the panel surface 125 that forms a large acute angle with the stamping forming direction (the boundary of the characteristic line corresponding portion 103 side of the groove portion 5d of the die 5 is a position of 10% of the width of the die side forming surface 5b) (refer to Figure 1 Here, the protrusion amount of the die side elastic body 11 from the die side molding surface portion 5b is based on the press molding process of the conventional example (refer to Figure 9 ) is set to 12 mm by taking into account the difference in tension (= 202 kN) acting on both sides of the characteristic line equivalent portion 103.

[0168] In addition, in this stamping analysis, the material of the punch side elastomer 9 and the die side elastomer 11 are both hard polyurethane, the friction coefficient of the punch side elastomer 9 and the die side elastomer 11 metal blank 101 are both 0.6, and the elastic modulus is 253N / mm.

[0169] Figure 7 The cross-sectional shape of the outer plate panel 121 obtained by the stamping analysis is shown in FIG. Figure 7 Yes Figure 6 As shown, the cross-sectional shape of the outer plate panel 121 is rotated so that the panel surface 127 on the side with a smaller angle relative to the stamping direction becomes horizontal, and the cross-sectional shape of the portion centered on the characteristic line 123 in the outer plate panel 121 is enlarged in a coordinate plane with the horizontal direction parallel to the panel surface 127 (= the width direction of the panel surface 127) as the horizontal axis and the direction perpendicular to the panel surface 127 (= the stamping direction) as the vertical axis.

[0170] according to Figure 7Compared with the invention example, in the conventional example, the concave and convex shapes caused by the line deviation are seen on the panel surface 127 on the side with greater tension per unit area (in Figure 7 (the area enclosed by the dotted ellipse in the figure).

[0171] Figure 8 9 shows the results of evaluating the surface strain of the outer plate panel 121 obtained by the stamping forming analysis. Figure 8 As mentioned above Figure 6 The graph shown is a graph having the horizontal coordinate of the panel surface 127 when the panel surface 127 on the side with the smaller acute angle relative to the stamping direction is horizontal as the horizontal axis and the evaluation value Δs of the surface strain at each horizontal position as the vertical axis.

[0172] Here, as described in the following known references, the evaluation value Δs of the surface strain is represented by the maximum / minimum difference between the peak heights of a tripod (with a fixed span L).

[0173] (Reference) Thin Steel Sheet Forming Technology Research Association, Stamping Difficulty Handbook, 4th Edition, "Chapter 5: Surface Shape Accuracy Poorness and Forming Difficulty Evaluation," pp. 218-221, Nikkan Kogyo Shimbun, (2017)

[0174] according to Figure 8 The difference between the maximum and minimum values ​​of the surface strain evaluation value Δs is 0.017 in the conventional example and 0.006 in the inventive example. This indicates that the surface strain of the panel surface 127 is reduced by abutting the punch-side elastic body 9 against the metal blank 101 to support it in a gently bent shape, and pressing the metal blank 101 with the die-side elastic body 11 to perform press forming.

[0175] As described above, according to the present invention, it has been confirmed that an automobile outer panel having a character line formed therein can be press-formed while preventing line deviation.

[0176] also, Figure 7 and Figure 8 This is the result of providing the punch-side elastic body 9 at the portion 107 on the side with greater tension and the die-side elastic body 11 at the portion 105 on the side with less tension in the metal blank 101, similarly to the first embodiment.

[0177] Of course, for the case where the punch side elastic body 9 is provided at the portion 105 on the side with smaller tension and the die side elastic body 11 is provided at the portion 107 on the side with larger tension ( Figure 4 ), the punch side elastic body 9 is supported by the punch side movable body 23 and the die side elastic body 11 is supported by the die side movable body 25 ( Figure 3 and Figure 5) were also subjected to stamping analysis. These results are omitted for space reasons, but in all cases, it was confirmed that the outer plate panel with the characteristic line could be stamped and formed without line deviation.

[0178] Industrial applicability

[0179] According to the present invention, it is possible to provide a stamping method and a stamping apparatus for an automobile outer panel that prevents line deviation and forms a target character line without increasing the man-hours for stamping.

[0180] Description of Reference Numerals

[0181] 1…stamping device; 3…punch; 3a…ridge; 3b…punch-side forming surface; 3c…punch-side forming surface; 3d…groove; 5…die; 5a…valley; 5b…die-side forming surface; 5c…die-side forming surface; 5d…groove; 7…blank holder; 9…punch-side elastic body; 9a…punch-side abutting surface; 11…die-side elastic body; 11a…die-side abutting surface; 21…stamping device; 23…punch-side movable body; 23a…pad; 23b…pressure source; 25…die-side movable body; 25a…pad; 25b…pressure source; 31 …stamping device; 41…stamping device; 51…stamping device (prior art); 53…punch; 53a…ridge portion; 55…die; 55a…valley portion; 57…blank retainer; 101…metal blank; 101a…end portion; 101b…end portion; 103…portion corresponding to characteristic line; 105…position; 107…position; 111…outer panel for automobile; 113…characteristic line; 115…panel face; 117…panel face; 121…outer panel (embodiment); 123…characteristic line; 125…panel face; 127…panel face.

Claims

1. A method for stamping an outer panel for an automobile, comprising: using a punch, a die opposed to the punch, and a blank holder opposed to an end of the die to stamp a metal blank into an outer panel for an automobile having a characteristic line and panel faces continuous on both sides thereof, wherein: The punch includes: a ridge portion forming the characteristic line; a punch side forming surface portion forming the panel surface portion; and a punch side elastic body supported to protrude further toward the die side than the punch side forming surface portion so as to be able to abut against a position separated from the characteristic line corresponding portion in a portion of the metal blank plate on the side where tension is greater during stamping and forming, among portions on both sides of the characteristic line corresponding portion, along the characteristic line corresponding portion, the characteristic line corresponding portion being equivalent to the characteristic line. The punching die comprises: a valley line portion that cooperates with the ridge line portion to form the characteristic line; a die side forming surface portion that forms the panel surface portion; and a die side elastic body that is supported to protrude further toward the punch than the die side forming surface portion so as to be able to press along the characteristic line corresponding portion against a position separated from the characteristic line corresponding portion in a portion on the side where tension is smaller during stamping and forming among portions of the metal blank sandwiching the characteristic line corresponding portion. The stamping method for the automobile outer panel comprises: an elastic body contacting step of relatively moving the die toward the punch while both ends of the metal blank are clamped by the die and the blank holder, thereby causing the punch-side elastic body and the die-side elastic body to contact the metal blank, respectively; and A stamping forming step, in which the punch side elastic body and the die side elastic body are kept in contact with the metal blank and the die is relatively moved toward the punch side to the forming bottom dead point to stamp out the automobile outer panel having the characteristic line formed by the ridge line portion and the valley line portion. The protrusion amount of the punch side elastic body from the punch side forming surface portion is set so that, in the elastic body contacting step, before the ridge portion of the punch contacts the metal blank, the punch side elastic body contacts the metal blank and is coplanar with the punch side forming surface portion at the forming bottom dead point. The protrusion amount of the die-side elastic body from the die-side forming surface is set as follows: in the elastic body abutment step, before the ridge portion of the punch abuts against the metal blank to plastically deform the metal blank, the die-side elastic body abuts against the metal blank, and the friction force given by the product of the load of the die-side elastic body pressing the metal blank in the stamping forming step and the friction coefficient of the die-side elastic body with the metal blank becomes greater than the absolute value of the difference in tension between the parts acting on both sides of the part corresponding to the characteristic line.

2. The method for stamping an automobile outer panel according to claim 1, wherein: The punch-side elastic body is provided on the punch side via a punch-side movable body. The punch-side movable body is movable in a punching direction and pressurizes and supports the punch-side elastic body toward the die side.

3. The method for stamping an automobile outer panel according to claim 1 or 2, wherein: The die-side elastic body is provided on the die side via a die-side movable body. The die-side movable body is movable in a stamping direction and pressurizes and supports the die-side elastic body toward the punch.

4. A method for stamping an outer panel for an automobile, comprising: using a punch, a die opposed to the punch, and a blank holder opposed to an end of the die to stamp a metal blank into an outer panel for an automobile having a characteristic line and panel faces continuous on both sides thereof, wherein: The punch includes: a ridge portion forming the characteristic line; a punch side forming surface portion forming the panel surface portion; and a punch side elastic body supported to protrude further toward the die side than the punch side forming surface portion so as to be able to abut against a position separated from the characteristic line corresponding portion in a portion of the metal blank plate on the side where tension is smaller during stamping among portions on both sides of the characteristic line corresponding portion, the characteristic line corresponding portion being equivalent to the characteristic line. The punching die comprises: a valley line portion that cooperates with the ridge line portion to form the characteristic line; a die side forming surface portion that forms the panel surface portion; and a die side elastic body that is supported to protrude further toward the punch than the die side forming surface portion so as to be able to press along the characteristic line corresponding portion against a position separated from the characteristic line corresponding portion in a portion on the side where tension is greater during stamping and forming among portions of the metal blank on both sides of the characteristic line corresponding portion. The stamping method for the automobile outer panel comprises: an elastic body contacting step of relatively moving the die toward the punch while both ends of the metal blank are clamped by the die and the blank holder, thereby causing the punch-side elastic body and the die-side elastic body to contact the metal blank, respectively; and A stamping forming step, in which the punch side elastic body and the die side elastic body are kept in contact with the metal blank and the die is relatively moved toward the punch side to the forming bottom dead point to stamp out the automobile outer panel having the characteristic line formed by the ridge line portion and the valley line portion. The protrusion amount of the punch side elastic body from the punch side forming surface portion is set so that: before the ridge portion of the punch abuts the metal blank, the punch side elastic body abuts the metal blank and is flush with the punch side forming surface portion at the forming bottom dead point. The protrusion amount of the die-side elastic body from the die-side forming surface is set as follows: in the elastic body abutment step, before the ridge portion of the punch abuts against the metal blank to plastically deform the metal blank, the die-side elastic body abuts against the metal blank, and the friction force given by the product of the load of the die-side elastic body pressing the metal blank in the stamping forming step and the friction coefficient of the die-side elastic body with the metal blank becomes greater than the absolute value of the difference in tension between the parts acting on both sides of the part corresponding to the characteristic line.

5. The method for stamping an automobile outer panel according to claim 4, wherein: The punch-side elastic body is provided on the punch side via a punch-side movable body. The punch-side movable body is movable in a punching direction and pressurizes and supports the punch-side elastic body toward the die side.

6. The method for stamping an automobile outer panel according to claim 4 or 5, wherein: The die-side elastic body is provided on the die side via a die-side movable body. The die-side movable body is movable in a stamping direction and pressurizes and supports the die-side elastic body toward the punch.

7. A stamping device for an automobile outer panel, which uses a punch, a die opposite to the punch, and a blank holder opposite to the end of the die to stamp a metal blank into an automobile outer panel having a characteristic line and panel faces continuous on both sides thereof, characterized in that: The punch includes: a ridge portion forming the characteristic line; a punch side forming surface portion forming the panel surface portion; and a punch side elastic body supported to protrude further toward the die side than the punch side forming surface portion so as to be able to abut against a position of the metal blank plate at a side where tension is greater in a stamping process among the portions on both sides of the portion corresponding to the characteristic line, the portion corresponding to the characteristic line corresponding to the characteristic line corresponding to the characteristic line, wherein the portion corresponding to the characteristic line corresponds to the characteristic line. The punching die comprises: a valley line portion that cooperates with the ridge line portion to form the characteristic line; a die side forming surface portion that forms the panel surface portion; and a die side elastic body that is supported to protrude further toward the punch than the die side forming surface portion so as to be able to press along the characteristic line corresponding portion against a position separated from the characteristic line corresponding portion in a portion on the side where tension is smaller during stamping and forming among portions of the metal blank sandwiching the characteristic line corresponding portion. The protrusion amount of the punch side elastic body from the punch side forming surface portion is set so that when the die is relatively moved toward the punch side, before the ridge portion of the punch abuts against the metal blank, the punch side elastic body abuts against the metal blank and becomes coplanar with the punch side forming surface portion at the forming bottom dead point. The protrusion amount of the die-side elastic body from the die-side forming surface portion is set so that when the die is relatively moved toward the punch side, before the ridge portion of the punch abuts against the metal blank to plastically deform the metal blank, the die-side elastic body abuts against the metal blank, and the friction force given by the product of the load of the die-side elastic body pressing the metal blank and the friction coefficient of the die-side elastic body and the metal blank becomes greater than the absolute value of the difference between the tensions acting on the parts on both sides of the portion corresponding to the characteristic line.

8. The press-forming device for automobile outer panel according to claim 7, characterized in that: The punch-side elastic body is provided on the punch side via a punch-side movable body. The punch-side movable body is movable in a punching direction and pressurizes and supports the punch-side elastic body toward the die side.

9. The press-forming device for automobile outer panel according to claim 7 or 8, characterized in that: The die-side elastic body is provided on the die side via a die-side movable body. The die-side movable body is movable in a stamping direction and pressurizes and supports the die-side elastic body toward the punch.

10. A stamping device for an automobile outer panel, which uses a punch, a die opposite to the punch, and a blank holder opposite to the end of the die to stamp a metal blank into an automobile outer panel having a characteristic line and panel faces continuous on both sides thereof, characterized in that: The punch includes: a ridge portion forming the characteristic line; a punch side forming surface portion forming the panel surface portion; and a punch side elastic body supported to protrude further toward the die side than the punch side forming surface portion so as to be able to abut against a position separated from the characteristic line corresponding portion in a portion of the metal blank plate on the side where tension is smaller during stamping among portions on both sides of the characteristic line corresponding portion, the characteristic line corresponding portion being equivalent to the characteristic line. The punching die comprises: a valley line portion that cooperates with the ridge line portion to form the characteristic line; a die side forming surface portion that forms the panel surface portion; and a die side elastic body that is supported to protrude further toward the punch than the die side forming surface portion so as to be able to press along the characteristic line corresponding portion against a position separated from the characteristic line corresponding portion in a portion on the side where tension is greater during stamping and forming among portions of the metal blank on both sides of the characteristic line corresponding portion. The protrusion amount of the punch side elastic body from the punch side forming surface portion is set so that when the die is relatively moved toward the punch side, before the ridge portion of the punch abuts against the metal blank, the punch side elastic body abuts against the metal blank and becomes coplanar with the punch side forming surface portion at the forming bottom dead point. The protrusion amount of the die-side elastic body from the die-side forming surface portion is set so that when the die is relatively moved toward the punch side, before the ridge portion of the punch abuts against the metal blank to plastically deform the metal blank, the die-side elastic body abuts against the metal blank, and the friction force given by the product of the load of the die-side elastic body pressing the metal blank and the friction coefficient of the die-side elastic body and the metal blank becomes greater than the absolute value of the difference between the tensions acting on the parts on both sides of the portion corresponding to the characteristic line.

11. The press-forming device for automobile outer panel according to claim 10, characterized in that: The punch-side elastic body is provided on the punch side via a punch-side movable body. The punch-side movable body is movable in a punching direction and pressurizes and supports the punch-side elastic body toward the die side.

12. The press-forming device for automobile outer panel according to claim 10 or 11, characterized in that: The die-side elastic body is provided on the die side via a die-side movable body. The die-side movable body is movable in a stamping direction and pressurizes and supports the die-side elastic body toward the punch.

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