Stamping method and device for forming outer panel of automobile

Abstract

The present invention relates to a method for stamping an outer panel for an automobile, which uses a punch (3), a die (5) and a blank holder (7) to stamp a metal blank (51) into an outer panel for an automobile (61) having a characteristic line (63) and panel surfaces (65a) and (63b). The method comprises the following steps: arranging an elastic body (9) protruding toward the die (5) side more than the punch side forming surface (3c) and placing the elastic body on the punch (3) side; (9) is brought into contact with a metal blank (51); and a step of performing stamping while bringing the elastomer (9) into contact with the metal blank (51) to form a characteristic line at the lower dead point of the forming, wherein the amount of protrusion of the elastomer (9) from the forming surface (3c) on the punch side is set so that the elastomer (9) is brought into contact with the metal blank (51) before the ridge line portion (3a) of the punch (3) abuts against the metal blank (51) and the metal blank (51) undergoes plastic deformation.

Description

Technical Field

[0001] The present invention relates to a press forming method and press forming device for an automotive outer panel, and press forming is performed on an automotive outer panel formed with a character line. In the present invention, the so-called metal sheet refers to a sheet composed of various metals such as stainless steel, aluminum, magnesium, etc., including a hot-rolled sheet, a cold-rolled sheet, or a surface treated steel sheet obtained by surface treatment (electro galvanized, hot-dip galvanized, organic coating treatment, etc.) of a steel sheet. Background Art

[0002] From the viewpoint of improving the designability and tension rigidity of automobiles, many automobile outer panels used in door outers, front fenders, or rear fenders have character lines added to their outer surfaces. Character lines are usually applied by pressing a metal blank (blank) against the ridgeline of a punch provided in a press forming tool and clamping it with the valley line of the die. In recent years, in order to further improve the designability of automobiles, it has been required to apply sharp character lines (i.e., the curvature of the ridgeline is large (the curvature radius is small)).

[0003] However, in such press forming, when the tension of the metal blank generated in the middle of forming is unbalanced, the metal blank may slide in the direction of greater tension, and the ridgeline of the punch may contact a portion other than the portion to which the characteristic line should be applied, thereby generating a linear pattern. Such a linear pattern remains even after coating, resulting in a poor appearance called skid line of the outer panel. This skid line is particularly significant when a punch having a ridgeline formed at the front end by an arc with a small cross-sectional radius is used for press forming to impart a sharp characteristic line, and thus becomes a major factor hindering the improvement of the design of the automobile.

[0004] So far, several technologies have been proposed for applying characteristic lines to suppress the generation of such linear patterns. For example, Patent Document 1 discloses the following stamping method: by providing an auxiliary cross-sectional shape in forming of a design recess in a die and a blank holder to clamp the periphery of the blank, the central portion of the blank is pre-bent and deformed into a forming surface along the punch, and then the punch is used to form the design surface. Patent Document 2 discloses the following method: a suction port is formed on the stamping surface of the linear convex portion provided with the forming characteristic line, and a suction device that performs suction from the suction port through a gas flow path is used to adsorb the metal plate to the stamping surface to perform press forming, thereby suppressing the movement of the metal plate and preventing line deviation. Patent document 3 discloses the following technology: after a blank is formed once using a punch angle and a cushion pad, deep drawing and stretch forming are performed while the punch is lowered, thereby preventing line deviation from occurring at the portion of the metal blank abutted by the punch angle. Patent document 4 discloses the following technology: when manufacturing a stamped product having a ridge portion, a first stamping process of forming an intermediate shape (pre-forming shape) and a second stamping process of further forming the intermediate shape are performed to eliminate line deviation and obtain a high-quality stamped product. Patent document 5 discloses a technology for alleviating bending in the early stage of forming by forming the punch ridge portion into an elastic body.

[0005] Prior art literature

[0006] Patent Literature

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

[0008] Patent Document 2: Japanese Patent Application Publication 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 Summary of the invention

[0012] Problems to be solved by the invention

[0013] However, the following problems exist in the technologies disclosed in Patent Documents 1 to 5. In the technology disclosed in Patent Document 1, the deformation caused by the die and blank holder provided with the auxiliary cross-sectional shape is not restrained by the punch, and can only restrain the two ends of the blank corresponding to the concave part of the design, so the bending deformation is limited to a straight line shape. In the technology disclosed in Patent Document 2, a suction device that is not used in ordinary stamping is required, and the shape of the suction port may be transferred to the surface of the formed product. In the technology disclosed in Patent Document 3, since the final product shape is partially formed in the middle of the forming, it is possible to generate surface strain between the unfinished forming part. In the technology disclosed in Patent Document 4, the mold for forming the intermediate shape is different from the mold for forming the target shape, and the number of processes such as mold replacement increases. In the technology disclosed in Patent Document 5, since the convex side of the ridge portion is formed by an elastomer, the ridge portion may not be formed according to the target shape.

[0014] The present invention is completed to solve the above-mentioned problems, and its purpose is to provide a stamping forming method and stamping forming device for an automobile outer panel, which prevents line deviation (skid line) without increasing the man-hours of stamping forming and forms a target characteristic line.

[0015] Technical solutions to solve problems

[0016] The method for stamping an outer panel for an automobile involved in the present invention uses a punch having a ridge portion, a die having a valley portion opposite to the punch, and a blank holder opposite to the end of the die to stamp a metal blank into an outer panel for an automobile having a characteristic line formed by the ridge portion and the valley portion and a panel surface (panel surface) continuous on both sides of the characteristic line, wherein an elastic body is provided on the punch, and the elastic body forms the panel surface in a manner of abutting separately from a portion of the metal blank corresponding to the characteristic line, and the elastic body protrudes further toward the die side than the forming surface (forming surface) on the punch side, and the stamping method includes the following steps: an elastic body abutting step, in a state in which the two ends of the metal blank are clamped by the die and the blank holder, the die is relatively moved toward the punch side, so that the abutting surface (contact surface) of the protruding elastic body faces) abut against the metal blank; and a characteristic line forming step, while keeping the abutting surface of the protruding elastic body in abutment with the metal blank, the die is further moved relative to the punch side, the elastomer is deformed to be flush with the punch side forming surface at the forming bottom dead center, and the characteristic line is formed by the ridge line portion and the valley line portion, and the protrusion amount of the elastomer from the punch side forming surface is set to make the elastomer abut against the metal blank before the ridge line portion of the punch abuts against the metal blank and the metal blank undergoes plasticity deformation.

[0017] In the above press forming method, the elastic body is provided on the punch side via a movable device, the movable device is movable in the press forming direction, and pressurizes and supports the elastic body toward the die side.

[0018] In the above press forming method, the elastic body is in contact with a portion of the metal blank on the side where tension is smaller during the press forming process, among portions on both sides of a portion of the metal blank on which the ridgeline of the punch is in contact.

[0019] In the above press forming method, the elastic body is in contact with a portion of the metal blank on the side where tension is greater during the press forming process, among portions on both sides of a portion of the metal blank where the ridgeline of the punch is in contact.

[0020] The punching device for the automobile outer panel of the present invention uses a punch having a ridge portion, a die having a valley portion opposite to the punch, and a blank holder opposite to the end of the die to punch a metal blank into an automobile outer panel having a characteristic line formed by the ridge portion and the valley portion and panel face portions continuous on both sides of the characteristic line, wherein the punch has a punch side forming face portion for respectively forming the panel face portions on both sides, and an elastic body is provided on either side of the punch side forming face portion. The elastic body protrudes further toward the die side than the punch side forming surface so as to be able to abut against the metal blank plate separately from the portion of the metal blank plate abutting against the ridge portion of the punch, and the elastic body can be deformed until the abutting surface abutting against the metal blank plate is flush with the punch side forming surface, and the protrusion amount of the elastic body from the punch side forming surface is set so that the elastic body abuts against the metal blank plate before the ridge portion of the punch abuts against the metal blank plate and the metal blank plate is plastically deformed.

[0021] In the above press forming device, the elastic body is provided on the punch side via a movable body, the movable body is movable in the press forming direction, and pressurizes and supports the elastic body toward the die side.

[0022] In the above-mentioned stamping forming device, the elastic body is arranged on the punch side forming surface in a manner of abutting against the part on both sides of the part where the ridgeline part of the punch abuts in the metal blank, which part has a smaller tension during the stamping forming process.

[0023] In the above-mentioned stamping forming device, the elastic body is arranged on the punch side forming surface in a manner of abutting against the part on both sides of the part where the ridgeline part of the punch abuts in the metal blank, which part has greater tension during the stamping forming process.

[0024] Effects of the Invention

[0025] According to the present invention, by making the elastic body protrude from the forming surface of the punch side and abut against the metal blank while performing stamping, the portion of the metal blank abutting against the ridge portion of the punch and the abutting surface of the elastic body is gradually bent and deformed to form a gentle shape, and by forming a characteristic line at the lower dead point of the forming, the initial bending mark (initial bending fold) of the metal blank caused by the ridge portion of the punch can be prevented, thereby making it possible to stamp the outer panel for an automobile formed with a characteristic line in a manner that reduces line deviation. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a diagram for explaining a press-forming apparatus for an automobile outer panel according to the first embodiment of the present invention.

[0027] Figure 2 It is a figure explaining the press-forming method of the automobile outer panel concerning Embodiment 1 of this invention.

[0028] Figure 3 It is a diagram for explaining another form of the press forming apparatus and press forming method of the automobile outer panel according to the first embodiment of the present invention.

[0029] Figure 4 It is a diagram for explaining a press-forming apparatus for an automobile outer panel according to a second embodiment of the present invention.

[0030] Figure 5 It is a diagram for explaining a press-forming method of an automobile outer panel according to a second embodiment of the present invention.

[0031] Figure 6 It is a diagram for explaining another form of the press forming apparatus and press forming method of the automobile outer panel according to the second embodiment of the present invention.

[0032] Figure 7 The present invention is a diagram for explaining a conventional press-forming apparatus and press-forming method for an automobile outer panel and line deviation generated during the press-forming process.

[0033] Figure 8 This is a diagram showing the results of the cross-sectional shape of the outer plate panel obtained by press forming analysis in the example.

[0034] Fig. 9 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. DETAILED DESCRIPTION

[0035] Before describing the press forming method and press forming apparatus for automobile outer panel according to the first and second embodiments of the present invention, line deviation occurring during press forming of an automobile outer panel having a character line will be described.

[0036] <Reasons for line deviation>

[0037] As an example, Figure 7 As shown in (d), the automobile outer panel 61 used as the object of the present invention has a characteristic line 63 and panel surfaces 65a and 65b continuous on both sides of the characteristic line 63, and is deep-drawn in the following manner using a stamping forming device 41, wherein the stamping forming device 41 comprises: a punch 43 having a ridge portion 43a extending in the front and back directions of the paper surface; a die 45 having a valley portion 45a extending in the front and back directions of the paper surface; and a pressure ring 47 opposite to the two end portions of the die 45.

[0038] First, if Figure 7 As shown in (a), the end portions 51a and 51b of the metal blank 51 are clamped by the die 45 and the blank holder 47, respectively. Then, while maintaining the clamped state, as shown in FIG. Figure 7 As shown in (b) to (d), the die 45 and the blank holder 47 are relatively moved toward the punch 43 until the lower dead point of the forming process, thereby stamping and forming an automobile outer panel 61 having a characteristic line 63 formed by the ridge line portion 43a of the punch 43 and the valley line portion 45a of the die 45.

[0039] When the die 45 is relatively moved toward the punch 43 during the press forming process, first, the ridgeline 43a of the punch 43 abuts against the metal blank 51, generating an initial bend ( Figure 7 (b)). Then, in the process of deep drawing by the die 45 and the punch 43, tension is generated in the metal blank 51 in the direction toward the end 51a side and the end 51b side respectively with the initial bending mark as the boundary ( Figure 7 (b), (c)).

[0040] Due to the distances from the initial bending mark to the end 51a and the end 51b, the panel surface 65a and the panel surface 65b ( Figure 7 (d)) The difference in angle relative to the stamping direction and the resulting difference in the depth in the forming direction from the ridge 43a to the end 51a and the end 51b causes a difference in the tension generated in the metal blank 51 as described above, with the initial bending mark as the boundary.

[0041] For example, when the acute angle between the panel face 65a and the panel face 65b is set as θa and the acute angle between the panel face 65b and the panel face 65b is set as θb, as in the stamping of the outer plate 61 for an automobile, when the angle θb of the panel face 65b with respect to the stamping direction is smaller than the angle θa of the panel face 65a (refer to Figure 7 (d) During the press forming process, the tension generated on the end 51b side (portion 55b) of the metal blank 51 becomes larger than the tension generated on the end 51a side (portion 55a) of the metal blank 51 ( Figure 7 (b), (c)).

[0042] When a tension difference occurs with the initial bending mark as a boundary as described above, slipping occurs in the metal blank 51 toward the side with greater tension, and the initial bending mark shifts toward the end portion 51b with greater tension ( Figure 7 (c)). In addition, the initial bending mark is crushed by the punch 43 and the die 45 at the lower dead point of the forming, resulting in a linear pattern, i.e., line deviation ( Figure 7 (d)).

[0043] Thus, the main cause of the line deviation in the automobile outer panel 61 formed with the character line 63 is the imbalance of the tension generated in the metal blank 51 during the deep drawing process. As mentioned above, as a main cause of the imbalance of the tension, there can be cited the difference in the forming depth at the two ends 51a and 51b of the metal blank 51 due to the difference in each distance or angle from the position where the ridge line portion 43a of the punch 43 abuts to the end 51a and the end 51b of the metal blank 51.

[0044] That is, when the forming depths at both ends 51a and 51b of the metal blank 51 are different, the tension generated on the end 51b side with a larger forming depth during deep drawing becomes larger, and line deviation occurs due to the tension difference with the side with a smaller forming depth.

[0045] Next, the press forming method and press forming apparatus of the automobile outer panel member according to the first and second embodiments of the present invention are described. In the following description, the same reference numerals as those described above are used to mark parts having the same functions to avoid duplication of description.

[0046] [Implementation Method 1]

[0047] <Press forming device>

[0048] The stamping forming device 1 for an automobile outer panel member according to the first embodiment (hereinafter referred to as the "stamping forming device 1") is as follows: Figure 1 and Figure 2 As shown in the example, a metal blank 51 is press-formed into an automobile outer panel 61 ( Figure 2 (d)), and comprises a punch 3, a die 5, a blank holder 7 and an elastic body 9.

[0049] In the first embodiment, the outer panel 61 ( Figure 2 (d) As above Figure 7 As shown, the angle θb of the panel surface 65b relative to the stamping direction is smaller than the angle θa of the panel surface 65a relative to the stamping direction. During the stamping process, the tension generated on the end 51b side (portion 55b) is greater than the tension generated on the end 51a side (portion 55a) with the portion abutted by the ridge portion 3a of the punch 3 as the boundary ( Figure 2 ).

[0050] like Figure 1 and Figure 2As shown, the punch 3 has a ridgeline portion 3a, punch side forming surface portions 3b and 3c located on both sides of the ridgeline portion 3a, and a groove portion 3d. The ridgeline portion 3a is a portion that forms a characteristic line 63 ( Figure 2 (d)) components. The punch side forming surfaces 3b and 3c respectively form the panel surfaces 65a and 65b ( Figure 2 (d)). The groove 3d is formed in a concave shape on the punch side forming surface 3c and is provided with an elastic body 9. In addition, it is preferable that the boundary of the groove 3d on the ridge 3a side is separated from the ridge 3a by 10% or more of the length of the punch side forming surface 3c.

[0051] The punch 5 has a valley line portion 5a, and die side forming surface portions 5b and 5c that are continuous on both sides of the valley line portion 5a. The valley line portion 5a cooperates with the ridge line portion 3a of the punch 3 to form a characteristic line 63 ( Figure 2 (d)). The die-side forming surfaces 5b and 5c cooperate with the punch-side forming surfaces 3b and 3c to form the panel surfaces 65a and 65b, respectively. Figure 2 (d)).

[0052] Here, the punch side forming surface 3b and the die side forming surface 5b form the portion 55a on the side where the tension acting on the metal blank plate 51 is small during the stamping process into the panel surface 65a. On the other hand, the punch side forming surface 3c and the die side forming surface 5c form the portion 55b on the side where the tension acting on the metal blank plate 51 is large during the stamping process into the panel surface 65b.

[0053] The blank holder 7 is disposed opposite to both end portions of the die 5 , and cooperates with the die 5 to clamp the end portions 51 a and 51 b of the metal blank plate 51 .

[0054] The elastic body 9 is arranged in the groove portion 3d of the punch 3 so that it can abut along the portion 53 at a position separated from the portion 53 of the metal blank 51 corresponding to the characteristic line 63, and is arranged at the bottom of the groove portion 3d in a manner that allows it to deform (contract in the stamping direction) until it protrudes further toward the die 5 side than the punch side forming surface 3c and until the abutting surface 9a abutting against the metal blank 51 is flush with the punch side forming surface 3c.

[0055] The protrusion amount of the elastic body 9 from the punch side forming surface 3c is set so that when the die 5 is relatively moved toward the punch 3 side, the abutment surface 9a abuts against the metal blank plate 51 before the portion of the metal blank plate 51 that contacts the ridge line portion 3a of the punch 3 undergoes plastic deformation.

[0056] Furthermore, the elastic body 9 only needs to have such hardness and shape that the bending shape of the metal blank 51 formed by the ridge line portion 3a is smooth when the elastic body 9 protrudes from the punch side forming surface portion 3c before the forming bottom dead point and contacts the metal blank 51, and the elastic body 9 can be deformed along the mold shape (shape of the punch side forming surface portion 3c) at the forming bottom dead point. As a specific material of such an elastic body 9, a rubber material or a polyurethane material having a Shore hardness of 40 to 100 HS can be exemplified.

[0057] <Press forming method>

[0058] Regarding the press forming method of the automobile outer plate panel 61 according to the first embodiment, Figure 1 The stamping forming device 1 shown in the example Figure 2 A case where an automobile outer panel 61 having a character line 63 formed by press forming as shown will be described.

[0059] The press forming method of the automobile outer panel according to the first embodiment uses a Figure 1 The punching forming device 1 shown in FIG. 1 includes a punch 3, a die 5, a blank holder 7 and an elastic body 9. Figure 2 As shown in the figure, the automobile outer panel 61 is stamped and formed into a characteristic line 63 and panel surfaces 65a and 65b continuous on both sides of the characteristic line 63. The stamping method includes: an elastic body abutment step, in which the die 5 is relatively moved toward the punch 3 side so that the elastomer 9 abuts against the metal blank 51; and a characteristic line forming step, in which the elastomer 9 is crushed at the lower dead point of the forming to form the characteristic line 63 using the ridge line portion 3a of the punch 3 and the valley line portion 5a of the die 5.

[0060] Here, as described above, the elastic body 9 is provided in the groove portion 3d formed to the punch side forming surface portion 3c, protrudes further toward the die 5 side than the punch side forming surface portion 3c, and is provided at the bottom of the groove portion 3d in a manner that can be deformed (contracted in the stamping direction) until the contact surface portion 9a contacting the metal blank plate 51 is flush with the punch side forming surface portion 3c, so that it can contact at a position separated from the portion 53 corresponding to the characteristic line 63 of the metal blank plate 51. The elastic body contact step and the characteristic line forming step described above are described below.

[0061] 《Elastic body contact step》

[0062] The elastic body abutment step is a step of relatively moving the die 5 and the blank holder 7 toward the punch 3 side while the end portions 51a and 51b of the metal blank plate 51 are respectively clamped by the die 5 and the blank holder 7, so that the abutment surface 9a of the elastic body 9 protruding more than the punch side forming surface 3c of the punch 3 abuts against the metal blank plate 51.

[0063] The protrusion amount of the elastic body 9 from the punch side forming surface 3c is set so that when the die 5 is moved relatively toward the punch 3 side, the abutting surface 9a of the elastic body 9 abuts against the metal blank plate 51 before the ridge line portion 3a of the punch 3 abuts against the metal blank plate 51 and causes the metal blank plate 51 to undergo plastic deformation, and can be deformed (contracted in the stamping direction) at the lower dead point of the forming until it is flush with the punch side forming surface 3c.

[0064] Plastic deformation of the metal blank 51 caused by the ridge 3 a can be determined to occur when the strain of a portion of the metal blank 51 abutting against the ridge 3 a exceeds the strain ε0 calculated by the following equation (1), for example.

[0065] ε0=t / 2R…(1)

[0066] Here, R is the radius of curvature of the curve of the characteristic line 63 , and t is the thickness of the metal blank 51 .

[0067] In addition, the protrusion amount of the elastic body 9 may be set so that the contact surface 9a of the elastic body 9 contacts the metal blank plate 51 before the ridge line portion 3a of the punch 3. The contact surface 9a of the elastic body 9 can be reliably contacted with the metal blank plate 51 before the ridge line portion 3a of the punch 3 contacts the metal blank plate 51 and plastic deformation of the metal blank plate 51 occurs. As a result, after the deviation of the metal blank plate 51 caused by the difference in tension between the end portions 51a and the end portions 51b on both sides of the metal blank plate 51 ends, plastic deformation can occur at the ridge line portion 3a, thereby preventing line deviation.

[0068] 《Character line forming step》

[0069] The characteristic line forming step is as follows: while keeping the abutting surface 9a of the elastic body 9 protruding more than the punch side forming surface 3c in abutment with the punch 3 side of the metal blank 51, the die 5 is further moved relative to the punch 3 side, and at the lower dead point of the forming, the abutting surface 9a of the elastic body 9 is crushed and deformed to be flush with the punch side forming surface 3c, and the characteristic line 63 is formed by the ridge line portion 3a of the punch 3 and the valley line portion 5a of the die 5.

[0070] Furthermore, at the forming lower dead point, the punch side forming surface 3b cooperates with the die side forming surface 5b to form the panel surface 65a, and the flush punch side forming surface 3c and the abutting surface 9a cooperate with the die side forming surface 5c to form the panel surface 65b.

[0071] <Reasons for preventing line deviation>

[0072] The following is based on Figure 2 The reason why the automobile outer panel 61 can be press-formed while preventing line deviation by the press-forming method and press-forming apparatus 1 of the automobile outer panel 61 according to the first embodiment is described below.

[0073] First, the contact surface 9a of the elastic body 9 protruding from the punch side forming surface 3c contacts the metal blank 51 ( Figure 2 (a)~(b)).

[0074] Next, the die 5 is relatively moved toward the punch 3 while the contact surface 9a is kept in contact with the punch 3 side of the metal blank 51, and the ridge 3a of the punch 3 contacts the metal blank 51 ( Figure 2 (c) During this period, the metal blank plate 51 slips due to the difference in tension between the end 51a side and the end 51b side of the metal blank plate 51.

[0075] At this time, when the die 5 is relatively moved toward the punch 3 side while the contact surface 9a of the elastic body 9 is kept in contact with the metal blank 51, the elastic body 9 is deformed as the press forming progresses. Therefore, the portion of the metal blank 51 that contacts the ridge portion 3a and the elastic body 9 is gradually bent and deformed to a gentle shape, which can prevent the generation of initial bending marks caused by plastic deformation. In addition, when plastic deformation starts, the metal blank 51 is clamped by the elastic body 9 and the die-side forming surface 5c and is not easily offset.

[0076] Therefore, even if the tension difference (refer to Figure 7 ) causes the portion in contact with the ridge portion 3a and the elastic body 9 to move toward the end portion 51b with greater tension, and is clamped by the die side forming surface 5b and the punch side forming surface 3b at the lower dead point of forming, thereby preventing the generation of initial bending marks in the metal blank 51. Therefore, the automobile outer panel 61 with the characteristic line 63 can be stamped and formed without causing line deviation.

[0077] In the first embodiment, the elastic body 9 is preferably placed in contact with the metal blank 51 at a position away from the portion 53 corresponding to the characteristic line 63. This is to facilitate supporting the metal blank 51 by the elastic body 9 before the ridgeline portion 3a of the punch 3 contacts the metal blank 51. Figure 2 As in the illustrated automobile outer panel 61 , the portion 53 corresponding to the character line 63 may be brought into contact with the portion 55 b corresponding to the panel surface 65 b .

[0078] <Other methods>

[0079] The stamping forming method and stamping forming device 1 according to the first embodiment are as follows: Figure 2 As shown, the elastic body 9 protruding beyond the punch side forming surface 3c is brought into contact with the portion 55b on the side where the tension is greater in the metal blank 51 during the stamping process, so that the bending deformation caused by the ridge portion 3a becomes a gentle shape, and the elastic body 9 is crushed at the lower dead point of the forming to form a characteristic line 63.

[0080] However, as another embodiment of the present invention, Figure 3 As shown, a press forming device 11 may be used in which the elastic body 15 protruding from the punch-side forming surface portion 13 b is brought into contact with a portion 55 a on the side where the tension of the metal blank 51 is small during the press forming process.

[0081] like Figure 3 As shown in FIG. 1 , the stamping forming device 11 includes a punch 13, a die 5, a blank holder 7, and an elastic body 15. The die 5 and the blank holder 7 in the constituent elements of the stamping forming device 11 are similar to the stamping forming device 1 ( Figure 1 and Figure 2 ) are the same, so the punch 13 and the elastic body 15 are described below.

[0082] The punch 13 has a ridge portion 13a, punch-side forming surface portions 13b and 13c that are continuous on both sides of the ridge portion 13a, and a groove portion 13d that is formed in a concave shape in the punch-side forming surface portion 13b.

[0083] The ridge line 13a cooperates with the valley line 5a of the die 5 to form a characteristic line 63 ( Figure 3 (d)). The punch side forming surface 13b forms the portion 55a on the side where the tension acting on the metal blank 51 is small during the stamping process into the panel surface 65a. On the other hand, the punch side forming surface 13c forms the portion 55b on the side where the tension acting on the metal blank 51 is large during the stamping process into the panel surface 65b.

[0084] The groove 13d is formed in a concave shape on the punch side forming surface 13b and is provided with an elastic body 15. The boundary of the groove 13d on the ridge 13a side is preferably separated from the ridge 13a by 10% or more of the length of the punch side forming surface 13b.

[0085] The elastic body 15 is arranged in the groove portion 13d formed on the punch side forming surface portion 13b, so that it can abut along the portion 53 at a position separated from the portion 53 of the metal blank 51 corresponding to the characteristic line 63. The elastic body 15 protrudes further toward the die 5 than the punch side forming surface portion 13b, and is supported at the bottom of the groove portion 13d in a manner that can be deformed until the abutting surface portion 15a abutting against the metal blank 51 is flush with the punch side forming surface portion 13b.

[0086] In the stamping forming of the automobile outer plate panel 61 using such a stamping forming device 11, first, while the end portions 51a and 51b of the metal blank 51 are respectively clamped by the die 5 and the blank holder 7, the die 5 is relatively moved toward the punch 13 side, so that the abutting surface portion 15a of the elastic body 15 protruding from the punch side forming surface portion 13b of the punch 13 abuts against the metal blank 51 (elastic body abutting step, Figure 3 (a)~(b)).

[0087] Here, the amount of protrusion of the elastic body 15 from the punch side forming surface 13b is set so that when the die 5 is relatively moved toward the punch 13 side, the abutting surface 15a of the elastic body 15 abuts against the metal blank plate 51 before the ridge line 13a of the punch 13 abuts and plastically deforms the metal blank plate 51. Thus, even if a tension difference occurs between the end portions 51a and 51b on both sides of the metal blank plate 51, the displacement of the metal blank plate 51 is advanced before the plastic deformation of the metal blank plate 51 due to the ridge line 13a occurs.

[0088] The protrusion amount of the elastic body 15 from the punch side forming surface 13b is set so that when the die 5 is moved relatively toward the punch 13 side, the abutting surface 15a of the elastic body 15 abuts against the metal blank plate 51 before the ridge line portion 13a of the punch 13 abuts against the metal blank plate 51 and causes the metal blank plate 51 to undergo plastic deformation, and can be deformed until it is flush with the punch side forming surface 13b at the lower dead point of the forming.

[0089] Next, the die 5 is further moved relatively toward the punch 13 side while the contact surface 15a of the elastic body 15 protruding from the punch side forming surface 13b is kept in contact with the punch 13 side of the metal blank 51, and the contact surface 15a of the elastic body 15 is crushed to be flush with the punch side forming surface 13b at the forming lower dead point, and the characteristic line 63 is formed by the ridge line portion 13a of the punch 13 and the valley line portion 5a of the die 5 (characteristic line forming step, Figure 3 (c)~ Figure 3 (d)).

[0090] In this way, even if the stamping is performed by making the elastic body 15 protruding from the punch side forming surface 13b abut against the part 55a on the side with less tension in the metal blank 51, the elastic body 15 deforms as the stamping progresses, and thus the part abutting against the ridge line part 13a and the elastic body 15 gradually deforms to make the bending shape gentle, which can prevent the generation of the initial bending mark caused by plastic deformation. In addition, when the plastic deformation caused by the ridge line part 13a of the punch 13 starts, the metal blank 51 is clamped by the abutting surface 15a of the elastic body 15 and the die side forming surface 5b, and is not easily offset.

[0091] Thus, even if the metal blank 51 slips on the end portion 51 b side with high tension during the press forming process, the automobile outer panel 61 having the character line 63 can be press formed without causing line deviation.

[0092] In addition, the elastomer 15 that abuts the portion 55a on the side of the end portion 51a with low tension only needs to have the following hardness and shape: when it protrudes beyond the punch side forming surface 3b before the forming lower dead point and abuts against the metal blank 51, the curved shape of the metal blank 51 formed by the ridge portion 3a becomes a gentle shape, and it can be deformed along the mold shape (the shape of the punch side forming surface 13b) at the forming lower dead point. Examples include rubber materials or polyurethane materials with a Shore hardness of 40 to 100 HS.

[0093] [Implementation Method 2]

[0094] <Press forming device>

[0095] The stamping device 21 for the automobile outer panel according to the second embodiment (hereinafter referred to as the "stamping device 21") is as follows: Figure 4 and Figure 5 As shown as an example, a metal blank 51 is stamped into an automobile outer panel 61 having a characteristic line 63 and panel surfaces 65a and 65b continuous on both sides of the characteristic line 63, and is equipped with a punch 23, a die 5, a retaining ring 7, an elastic body 25 and a movable body 27.

[0096] The die 5 and the blank holder 7 are the same as those of the press forming device 1 according to the first embodiment described above, and therefore the punch 23 , the elastic body 25 , and the movable body 27 will be described below.

[0097] The punch 23 has a ridgeline portion 23a, punch side forming surface portions 23b and 23c continuous on both sides of the ridgeline portion 23a, and a groove portion 23d formed in a concave shape on the punch side forming surface portion 23c, similarly to the punch 3 of the stamping forming device 1 involved in the above-mentioned first embodiment.

[0098] The ridge line 23a cooperates with the valley line 5a of the die 5 to form a characteristic line 63 ( Figure 5 (d)). The punch side forming surface portions 23b and 23c cooperate with the die side forming surface portions 5b and 5c to form the panel surface portions 65a and 65b, respectively. Figure 5 (d)).

[0099] The punch side forming surface 23b forms the portion 55a on the end 51a side where the tension acting on the metal blank 51 during the stamping process is small into the panel surface 65a. On the other hand, the punch side forming surface 23c forms the portion 55b on the end 51b side where the tension acting on the metal blank 51 during the stamping process is large into the panel surface 65b.

[0100] The groove 23d is formed in a concave shape on the punch side forming surface 23c and is provided with an elastic body 25 and a movable body 27. The boundary of the groove 23d on the ridge 23a side is preferably separated from the ridge 23a by 10% or more of the length of the punch side forming surface 23c.

[0101] The elastic body 25 is provided in the groove portion 3d of the punch side forming surface portion 23c so as to be able to abut and support along the portion 53 at a position separated from the portion 53 corresponding to the characteristic line 63 of the metal blank plate 51, protrude further toward the die 5 than the punch side forming surface portion 23c, and is provided in the groove portion 23d so as to be able to deform (contract in the stamping direction) until the abutting surface portion 25a abutting against the metal blank plate 51 is flush with the punch side forming surface portion 23c. In addition, the elastic body 25 is supported at the bottom of the groove portion 23d via the movable body 27.

[0102] The movable body 27 is supported in the groove 23d so that the elastic body 25 can be pressurized toward the die 5 so that the elastic body 25 abuts against the metal blank 51. The movable body 27 includes a pad 27a on which the elastic body 25 is mounted and which can move along the stamping direction, and a pressure source 27b that applies pressure to the pad 27a. Here, as the pressure source 27b, a gas cushion or polyurethane can be exemplified.

[0103] In the press forming device 21 according to the second embodiment, the amount of protrusion of the elastic body 25 from the punch side forming surface 23c is set so that when the die 5 is relatively moved toward the punch 23 side, the abutting surface 25a abuts against the metal blank 51 before the portion of the metal blank 51 that contacts the ridge portion 23a of the punch 23 is plastically deformed. Even if a tension difference occurs between the end portions 51a and the end portions 51b on both sides of the metal blank 51, the displacement of the metal blank 51 is promoted before the plastic deformation of the metal blank 51 caused by the ridge portion 23a begins. In addition, when the plastic deformation begins, the metal blank 51 is clamped by the elastic body 25 and the die side forming surface 5c and is not easily displaced.

[0104] In addition, the elastic body 25 only needs to have the following hardness and shape: before the lower dead point of the forming, the elastic body 25 abuts against the metal blank plate 51 in a state protruding from the punch side forming surface 23c, so as to make the bending shape of the metal blank plate 51 formed by the ridge line 23a gentle, and can be deformed along the mold shape (shape of the punch side forming surface 23c) at the lower dead point of the forming. As a specific material of such an elastic body 25, a rubber material or a polyurethane material with a Shore hardness of 40 to 100 HS can be exemplified.

[0105] Moreover, the movable body 27 sets the pressure of the pressure source 27b that pressurizes the elastic body 25 toward the die 5 side so that the elastic body 25 that is crushed during the stamping process is pressed back to the bottom side (bottom side) of the groove portion 23d, and the abutment surface 25a of the elastic body 25 that is crushed and deformed (contracted) at the lower dead point of the forming is flush with the forming surface 23c on the punch side.

[0106] <Press forming method>

[0107] Regarding the press forming method of the automobile outer plate panel 61 according to the second embodiment, Figure 4 The stamping forming device 21 shown in the example, stamping forming Figure 5 A case of an automobile outer panel 61 having a character line 63 shown in (d) will be described.

[0108] The press forming method of the automobile outer plate panel 61 according to the second embodiment is as follows: Figure 4 and Figure 5 As shown, a stamping device 21 including a punch 23, a die 5, a blank holder 7, an elastic body 25 and a movable body 27 is used to stamp out an automotive outer panel 61 having a characteristic line 63 and panel surfaces 65a and 65b continuous on both sides of the characteristic line 63. The stamping method includes: an elastic body abutment step, in which the die 5 is relatively moved toward the punch 23 so that the elastic body 25 abuts against the metal blank 51; and a characteristic line forming step, in which the elastic body 25 is crushed at the lower dead point of the forming and the characteristic line 63 is formed using the ridge line portion 23a of the punch 23 and the valley line portion 5a of the die 5.

[0109] Here, as described above, the elastic body 25 is provided in the groove portion 23d formed to the punch side forming surface portion 23c, protrudes further toward the die 5 side than the punch side forming surface portion 23c, and is supported at the bottom of the groove portion 23d in a manner that allows deformation (contraction) until the contact surface portion 25a contacting the metal blank plate 51 is flush with the punch side forming surface portion 23c, so as to be able to contact along the portion 53 at a position separated from the portion 53 corresponding to the characteristic line 63 of the metal blank plate 51. The elastic body contact step and the characteristic line forming step described above are described below.

[0110] Elastic body contact step

[0111] The elastic body abutment step is a step of moving the die 5 relative to the punch 23 side while the end portions 51a and 51b of the metal blank plate 51 are respectively clamped by the die 5 and the blank holder 7, so that the abutment surface 25a of the elastic body 25 protruding more than the punch side forming surface 23c of the punch 23 abuts against the metal blank plate 51.

[0112] The protrusion amount of the elastic body 25 from the punch side forming surface 23c is set so that when the die 5 is relatively moved toward the punch 23 side, the abutting surface 25a of the elastic body 25 abuts against the metal blank plate 51 before the ridge line portion 23a of the punch 23 abuts and causes plastic deformation of the metal blank plate 51.

[0113] The plastic deformation of the metal blank 51 caused by the ridge 23 a may be determined to occur when, for example, the strain of the portion of the metal blank 51 that contacts the ridge 23 a exceeds the strain ε0 calculated by the above formula (1).

[0114] 《Characteristic line formation steps》

[0115] The characteristic line forming step is as follows: while making the abutting surface 25a of the elastic body 25 abut against the punch 23 side of the metal blank 51 to make the curved shape formed by the ridge line portion 23a smooth, the die 5 is further moved relative to the punch 23 side to the forming lower dead point. At the forming lower dead point, the abutting surface 25a of the elastic body 25 is crushed to be flush with the punch side forming surface 23c, and the characteristic line 63 is formed by the ridge line portion 23a of the punch 23 and the valley line portion 5a of the die 5.

[0116] In the characteristic line forming step, when the die 5 is moved relative to the punch 23 side, the elastic body 25 which is pressurized and supported by the pressure source 27b of the movable body 27 toward the die 5 side is crushed and deformed (contracted), and is pressed back to the bottom side of the groove portion 23d together with the pad 27a of the movable body 27.

[0117] Furthermore, at the lower dead point of forming, the panel face 65a is formed by the punch side forming face 23b and the die side forming face 5b, and the panel face 65b is formed by the punch side forming face 23c and the abutting face 25a and the die side forming face 5c which are crushed by the elastic body 25 to become flush.

[0118] <Effects>

[0119] The effects of the stamping method and the stamping device 21 according to the second embodiment are as follows. Figure 5As shown, when the die 5 is relatively moved toward the punch 23 side while the elastic body 25 supported by the movable body 27 at the bottom of the groove portion 23d of the punch side forming surface 23c is brought into contact with the metal blank 51, the portion of the metal blank 51 that abuts against the ridge portion 23a of the punch 23 and the abutting surface 25a of the elastic body 25 is gradually bent and deformed into a gentle shape, thereby preventing the occurrence of initial bending marks caused by plastic deformation.

[0120] Therefore, similar to the above-mentioned present embodiment 1, even during the stamping process, due to the tension difference between the end 51a side and the end 51b side of the metal blank 51, the part abutting against the ridge portion 23a and the elastic body 25 moves toward the end 51b side with greater tension, and is clamped by the die side forming surface 5b and the punch side forming surface 23c at the lower dead point of the forming, thereby preventing the initial bending mark from being generated in the metal blank 51. Therefore, the automobile outer panel 61 with the characteristic line 63 can be stamped and formed without generating a line offset on the panel surface 65b.

[0121] Moreover, since the elastomer 25 is pressurized and supported toward the die 5 side by the pressure source 27b of the movable body 27, even if the elastomer 25 is deformed (contracted) due to the relative movement of the die 5 toward the punch 23 side, the elastomer 25 can be abutted against the metal blank 51 and supported while the elastomer 25 is kept pressurized toward the die 5 side.

[0122] Here, compared with the above-mentioned present embodiment 1, in the present embodiment 2, in addition to the change of the material, shape and size of the elastomer 25, by adjusting the pressure of the pressure source 27b supporting the elastomer 25, the freedom of stamping can be increased so that the bending deformation of the part of the metal blank 51 that abuts against the ridge portion 23a and the abutting surface portion 25a of the elastomer 25 can be made into a gentle shape.

[0123] <Other methods>

[0124] The stamping method and stamping device 21 of the automobile outer panel 61 involved in the above-mentioned present embodiment 2 pressurize the elastic body 25 at the portion 55b on the side with greater tension in the metal blank plate 51 supported by the movable body 27 toward the die 5 side so that the elastic body 25 abuts against the metal blank plate 51, and at the same time move the die 5 relatively toward the punch 23 side, and form a characteristic line 63 at the lower dead point of the forming by the ridge line portion 23a of the punch 23 and the valley line portion 5a of the die 5.

[0125] However, as another embodiment of the present invention, Figure 6 As shown, a press forming device 31 may be used in which the elastic body 35 supported by the movable body 37 is brought into contact with a portion 55 a on the side where the tension is small in the metal blank plate 51 .

[0126] like Figure 6 As shown, the stamping device 31 has a punch 33, a die 5, a blank holder 7, an elastic body 35 and a movable body 37. The die 5 and the blank holder 7 are the same as the die 5 and the blank holder 7 of the stamping device 1 described above, so the punch 33, the elastic body 35 and the movable body 37 are described below.

[0127] The punch 33 has a ridge portion 33a, punch-side molding surface portions 33b and 33c that are continuous on both sides of the ridge portion 33a, and a groove portion 33d that is formed in a concave shape in the punch-side molding surface portion 33b.

[0128] The ridge line 33a cooperates with the valley line 5a of the die 5 to form a characteristic line 63 ( Figure 6 (d)). The punch side forming surface 33b forms the portion 55a on the side where the tension acting on the metal blank 51 is small during the stamping process into the panel surface 65a. On the other hand, the punch side forming surface 33c forms the portion 55b on the side where the tension acting on the metal blank 51 is large during the stamping process into the panel surface 65b.

[0129] The groove 33d is formed in a concave shape on the punch side forming surface 33b and is provided with an elastic body 35 and a movable body 37. The boundary of the groove 33d on the ridge 33a side is preferably separated from the ridge 33a by 10% or more of the length of the punch side forming surface 33b.

[0130] The elastic body 35 is provided in the groove portion 33d of the punch side forming surface portion 33b so as to be able to abut and support along the portion 53 at a position separated from the portion 53 corresponding to the characteristic line 63 of the metal blank plate 51, and the elastic body 35 protrudes from the punch side forming surface portion 33b toward the die 5 side and is provided in the groove portion 33d so as to be able to deform (contract in the stamping direction) until the abutting surface portion 35a abutting against the metal blank plate 51 is flush with the punch side forming surface portion 33b. In addition, the elastic body 35 is supported at the bottom of the groove portion 33d via the movable body 37.

[0131] The movable body 37 supports the elastomer 35 at the bottom of the groove 33d so that the elastomer 35 can be pressurized toward the die 5 side so that the elastomer 35 abuts against the metal blank 51. The movable body 37 has a pad 37a on which the elastomer 25 is installed and can move along the stamping direction, and a pressure source 37b that applies pressure to the pad 37a.

[0132] Furthermore, the amount of protrusion of the elastic body 35 from the punch side forming surface portion 33b is set so that, when the die 5 is relatively moved toward the punch 33 side, the abutting surface portion 35a abuts against the metal blank plate 51 before the portion of the metal blank plate 51 that contacts the ridge portion 33a of the punch 33 is plastically deformed. Therefore, even if a tension difference occurs between the end portion 51a side and the end portion 51b side of the metal blank plate 51, the displacement of the metal blank plate 51 is advanced before the plastic deformation of the metal blank plate 51 due to the ridge portion 33a begins.

[0133] Furthermore, the movable body 37 sets the pressure of the pressure source 37b that pressurizes the elastic body 35 toward the die 5 side so that the elastic body 35 that is crushed during the stamping process is pressed back to the bottom side of the groove portion 33d, and the abutting surface 35a of the elastic body 35 that has been deformed (contracted) at the lower dead point of the forming is flush with the punch side forming surface 33c. Therefore, when the plastic deformation of the characteristic line 63 begins, the metal blank 51 is clamped by the elastic body 35 and the die side forming surface 5c and is not easily deviated.

[0134] In the stamping forming of the automobile outer plate panel 61 using such a stamping forming device 31, first, while the end portions 51a and 51b of the metal blank plate 51 are respectively clamped by the die 5 and the blank holder 7, the die 5 is relatively moved toward the punch 33 side, so that the abutting surface portion 35a of the elastic body 35 protruding from the punch side forming surface portion 33b of the punch 33 abuts against the metal blank plate 51 (elastic body abutting step, Figure 6 (a)~(b)).

[0135] Next, the die 5 is further moved relatively toward the punch 33 side while the contact surface 35a of the elastic body 35 pressed to the die 5 side is kept in contact with the metal blank 51. At the forming lower dead point, the contact surface 35a of the elastic body 35 is crushed to be flush with the punch side forming surface 35b, and the characteristic line 63 is formed by the ridge line 33a of the punch 33 and the valley line 5a of the die 5 (characteristic line forming step, Figure 6 (c)~(d)).

[0136] In this way, even if the stamping is performed by making the elastomer 35 protruding more than the punch side forming surface 33b abut against the portion 55a on the side with less tension in the metal blank 51, the elastomer 35 deforms as the stamping progresses, so that the portion abutting against the ridge portion 33a and the elastomer 35 gradually deforms into a gently curved shape, thereby preventing the occurrence of initial bending marks caused by plastic deformation.

[0137] Thus, even if the metal blank 51 slips on the end portion 51 b side with high tension during the press forming process, the automobile outer panel 61 having the character line 63 can be press formed without causing line deviation.

[0138] Furthermore, in other aspects of the second embodiment, in addition to changing the material of the elastic body 35, it is also possible to adjust the pressure of the pressure source 37b supporting the elastic body 35. Thus, compared with the first embodiment described above, it is possible to perform press forming with increased freedom for bending deformation of the portion of the metal blank 51 abutting against the ridge portion 33a and the abutting surface portion 35a of the elastic body 35 into a gentle shape.

[0139] [Example]

[0140] An example was performed to verify the effect of preventing line deviation when forming a character line by punching an automobile outer panel using the punching method and punching apparatus of the present invention, and this example will be described below.

[0141] In this embodiment, a stamping analysis is performed on an outer panel simulated with a characteristic line for an automobile by stamping the outer panel using the stamping method of the present invention, and whether line deviation occurs in the stamped outer panel is evaluated.

[0142] In the press forming analysis, a steel sheet SGCC-F having a thickness of 0.7 mm was used as a metal blank, and an outer plate panel (not shown) having a characteristic line and panel faces continuous on both sides thereof was used as an analysis object.

[0143] Here, the curvature radius R of the characteristic line is 3 mm, the angles of the panel face relative to the stamping direction are θa=85° and θb=65°, and regarding the width of the panel face (the length from the boundary with the characteristic line to the end), the width of the panel face with θa=85° is set to 500 mm, and the width of the panel face with θb=65° is set to 200 mm.

[0144] In this embodiment, as a conventional example, a process of deep drawing a metal blank into an outer panel using a punch, a die and a blank holder is performed (see Figure 7 )'s stamping forming analysis (press forminganalysis).

[0145] Furthermore, it was confirmed that a larger tension was generated during the press forming process on the panel face side with a smaller angle (θb=65°) than on the panel face side with a larger angle (θa=85°).

[0146] Next, as an example of the invention, a press forming device having a punch, a die, a blank holder and an elastic body is used, the elastic body is brought into contact with a position separated from a portion corresponding to a characteristic line in a metal blank, and a portion of the metal plate that is brought into contact with a ridge portion of the punch and a contact surface portion of the elastic body is gradually bent and deformed to form a gentle shape, and a deep drawing forming process is performed to form a characteristic line at a lower dead point of the forming process (refer to Figure 2 )’s stamping forming analysis.

[0147] The elastic body is provided in the groove of the punch side forming surface so as to protrude 5 mm from the punch side forming surface toward the die side, so as to be able to abut and press along the portion corresponding to the character line in the metal blank at a position separated from the portion.

[0148] Here, the protrusion amount of the elastic body from the punch side forming surface is set so that the abutting surface of the elastic body abuts against the metal blank before the ridgeline of the punch abuts against the metal blank and undergoes plastic deformation. In addition, in this stamping analysis, the material of the elastomer is hard urethane, and the elastic modulus of the elastomer is 253N / mm.

[0149] Figure 8 The results of the cross-sectional shape of the outer plate panel obtained by the stamping forming analysis are shown here. Figure 8 The cross-sectional shape is obtained by rotating the panel face on the side with a smaller angle relative to the stamping direction and is configured to be horizontal. The cross-sectional shape of the portion centered on the characteristic line of the outer plate panel obtained by stamping is enlarged and shown on a coordinate plane (coordinated plane) with the horizontal direction parallel to the panel face as the horizontal axis and the direction perpendicular to the panel face as the vertical axis.

[0150] according to Figure 8 Compared with the invention example, in the conventional example, a concave shape caused by line deviation was found on the panel surface on the side with greater tension per unit area ( Figure 8 The area enclosed by the dotted ellipse in the figure).

[0151] Fig. 9 The results of plane strain evaluation for the outer plate panel obtained through stamping forming analysis are shown. Fig. 9It is a graph with the horizontal coordinates of the panel component when the panel face on the side with a smaller angle relative to the stamping forming direction is configured horizontally as the horizontal axis and the evaluation value Δs of the plane strain at each horizontal position as the vertical axis. In addition, the evaluation value Δs of the plane strain is expressed by the maximum-minimum difference of the peak height based on the three-point gauge (fixed span (fixed span) L) as described in the well-known references shown below. (Reference) Thin Steel Sheet Forming Technology Research Association, Stamping Forming Difficulty Handbook 4th Edition, "Chapter 5 Poor Surface Shape Accuracy and Forming Difficulty Evaluation", pp.218-221, Nikkan Kogyo Shimbun, (2017).

[0152] according to Fig. 9 The difference between the maximum and minimum values ​​of the evaluation value Δs of the plane strain is 0.0102 in the conventional example, while it is 0.0039 in the inventive example. It can be seen that the plane strain of the panel surface is reduced by performing press forming in a manner that the ridgeline portion of the punch and the contact surface of the elastic body contact the metal blank so that the bending deformation becomes a gentle shape.

[0153] As described above, according to the present invention, it has been shown that an automobile outer panel having a character line formed therein can be press-formed while preventing line deviation.

[0154] Industrial Applicability

[0155] According to the present invention, a stamping method and a stamping device for an automobile outer panel can be provided, which are not limited by the bending deformation shape, neither damage the surface of the formed product nor produce plane strain, and prevent line deviation without increasing the stamping time, thereby forming the target characteristic line.

[0156] Description of symbols

[0157] 1 Stamping device

[0158] 3 Punch

[0159] 3a Ridge

[0160] 3b, 3c Punch side forming surface

[0161] 3d slot

[0162] 5. Die

[0163] 5a Valley line

[0164] 5b, 5c Die side forming surface

[0165] 7. Blanking ring

[0166] 9 Elastomer

[0167] 9a Contact with face

[0168] 11 Stamping device

[0169] 13 Punch

[0170] 13a Ridge

[0171] 13b, 13c Punch side forming surface

[0172] 13d Groove

[0173] 15 Elastomer

[0174] 15a Contact with face

[0175] 21. Stamping device

[0176] 23 Punch

[0177] 23a Ridge

[0178] 23b, 23c Punch side forming surface

[0179] 23d Groove

[0180] 25 Elastomer

[0181] 25a Abutting face

[0182] 27 Movable body

[0183] 27a Pad

[0184] 27b Stressors

[0185] 31. Stamping device

[0186] 33 Punch

[0187] 33a Ridge

[0188] 33b, 33c Punch side forming surface

[0189] 33d Groove

[0190] 35 Elastomer

[0191] 35a Abutment face

[0192] 37 Movable body

[0193] 37a Pad

[0194] 37b Stressors

[0195] 41 Stamping device

[0196] 43 Punch

[0197] 43a Ridge

[0198] 45 Die

[0199] 45a Valley line

[0200] 51 Metal blank

[0201] 53 parts

[0202] 55a, 55b

[0203] 61. Automobile outer panel

[0204] 63 Feature Line

[0205] 65a, 65b Panel face

Claims

1. A method for stamping an outer panel for an automobile, using a punch having a ridge portion, a die having a valley portion opposite to the punch, and a blank holder opposite to the end of the die, to stamp a metal blank into an outer panel for an automobile having a characteristic line formed by the ridge portion and the valley portion and panel face portions continuous on both sides of the characteristic line, wherein: The punch is provided with an elastic body made of a rubber material or a polyurethane material, the elastic body is formed to form the panel face portion in a manner of being separated from and abutting against a portion of the metal blank corresponding to the characteristic line, and the elastic body protrudes further toward the die side than the punch side forming face portion, The stamping forming method comprises the following steps: an elastic body abutting step, in which the abutting surface of the protruding elastic body does not abut against the metal blank without relatively moving the die toward the punch in a state where both ends of the metal blank are clamped by the die and the blank holder, and the abutting surface of the protruding elastic body abuts against the metal blank by relatively moving the die toward the punch; and a characteristic line forming step, wherein the die is further moved toward the punch side while the abutting surface of the protruding elastic body is kept in abutment with the metal blank, the elastic body is deformed to be flush with the punch side forming surface at the forming bottom dead point, and the characteristic line is formed by the ridge line portion and the valley line portion, The protrusion amount of the elastomer from the forming surface portion on the punch side is set so that the elastomer abuts against the metal blank before the ridge portion of the punch abuts against the metal blank to cause plastic deformation of the metal blank. When the ridge portion of the punch abuts against the metal blank, the metal blank between the portion abutted by the ridge portion and the end clamped by the die and the pressure ring is supported by the elastomer, so that the portion of the metal blank where the ridge portion and the elastomer abut is gradually bent and deformed to form a gentle shape, and the metal blank is clamped by the elastomer and the die when the plastic deformation of the metal blank begins.

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

3. The press forming method of the automobile outer panel according to claim 1 or 2, wherein: The elastic body abuts against a portion of the metal blank plate on a side where tension is small during press forming, among portions on both sides of a portion of the metal blank plate where the ridgeline of the punch abuts.

4. The press forming method of an automobile outer panel according to claim 1 or 2, wherein: The elastic body abuts against a portion of the metal blank plate on the side where tension is greater during press forming, among portions on both sides of a portion of the metal blank plate where the ridgeline of the punch abuts.

5. A stamping device for an automobile outer panel, using a punch having a ridge portion, a die facing the punch and having a valley portion, and a blank holder facing the end of the die, to stamp a metal blank into an automobile outer panel having a characteristic line formed by the ridge portion and the valley portion and panel faces continuous on both sides of the characteristic line, wherein: The punch has punch side forming surfaces for respectively forming the panel surfaces on both sides. An elastic body made of a rubber material or a polyurethane material is provided on either side of the punch side forming surface, the elastic body protruding further toward the die side than the punch side forming surface so as to be able to abut against the metal blank plate separately from the portion abutting against the ridgeline portion of the punch, and the elastic body can be deformed until the abutting surface abutting against the metal blank plate is flush with the punch side forming surface. The protrusion amount of the elastomer from the forming surface portion on the punch side is set so that the elastomer abuts against the metal blank before the ridge portion of the punch abuts against the metal blank to cause plastic deformation of the metal blank. When the ridge portion of the punch abuts against the metal blank, the metal blank between the portion abutted by the ridge portion and the end clamped by the die and the pressure ring is supported by the elastomer, so that the portion of the metal blank where the ridge portion and the elastomer abut is gradually bent and deformed to form a gentle shape, and the metal blank is clamped by the elastomer and the die when the plastic deformation of the metal blank begins.

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

7. The press-forming device for an automobile outer panel according to claim 5 or 6, wherein: The elastic body is provided on the punch side forming surface portion so as to abut against a portion on the side with smaller tension during press forming, among portions on both sides of a portion of the metal blank plate abutting against a ridgeline portion of the punch.

8. The press forming device for an automobile outer panel according to claim 5 or 6, wherein: The elastic body is provided on the punch side forming surface portion so as to abut against a portion on the side where tension is greater during press forming, among portions on both sides of a portion of the metal blank plate abutting against a ridgeline portion of the punch.

Images