Method for manufacturing press-molded article, die set, and door inner panel

Abstract

This method for manufacturing a press-molded article (90) comprises a preparation step, a first molding step, and a second molding step. In the preparation step, a blank (30) is prepared. In the first molding step, pressing is performed on the blank (30) to form a first region (90A), and an intermediate molded article (40) is obtained. The first region (90A) includes, from the press-molded article (90), at least part of an inner vertical wall (92) and a portion of a top plate (91) that is adjacent to at least part of the inner vertical wall (92). In the second molding step, pressing is performed on the intermediate molded article (40) in a state in which the first region (90A) is held, and a second region (90B) is molded. The second region (90B) is the portion of the press-molded article (90) other than the first region (90A).

Description

Manufacturing method of press-molded product, die set and door inner panel

[0001] The present disclosure relates to a method for manufacturing a press-formed product, more specifically, to a method for manufacturing a press-formed product including a top plate, an inner vertical wall connected to the top plate, and a plurality of vertical wall portions connected to each other via corner portions. The present disclosure also relates to a die set, more specifically, to a die set used for manufacturing a press-formed product including a top plate, an inner vertical wall connected to the top plate, and a plurality of vertical wall portions connected to each other via corner portions. The present disclosure also relates to an automobile door inner panel.

[0002] In the automotive field, there is an increasing demand for crashworthiness, and structures that can ensure interior space for occupant protection in the event of a collision are required. Possible collision types for automobiles include side collisions, frontal collisions, and rear collisions. To ensure crashworthiness, automobile side doors are required to absorb the impact of a collision and suppress excessive deformation toward the interior of the vehicle. Furthermore, automobiles are also required to reduce the weight of their bodies to improve fuel efficiency. Therefore, side doors are required to achieve both crashworthiness and lightweight design.

[0003] The inner door panel of a side door functions as an impact absorbing member in frontal and rear collisions, and supports other impact absorbing members in side collisions. Forming the inner door panel from a high-strength material is thought to be effective in achieving both impact resistance and weight reduction, as it leads to thinner door inner panels and lighter weight for other parts.

[0004] Patent Document 1 discloses a press-forming method for automobile door panels and the like. The forming method in Patent Document 1 includes a first draw forming step and a second draw forming step. In the first draw forming step, an upper die including a movable die and a fixed die is lowered to form a portion with a shallow drawing depth. In the second draw forming step, from the state after the first draw forming step, the movable die is displaced relative to the fixed die to cause the fixed die to protrude downward, to form a portion with a deep drawing depth.

[0005] JP 2015-066584 A

[0006] A press-formed product such as a door inner panel includes, for example, a top plate and a vertical wall connected to the top plate. The vertical wall may include multiple vertical wall portions connected to each other via corner portions. For example, when manufacturing such a press-formed product using the press forming method described in Patent Document 1, cracks may occur. In Patent Document 1, the first and second draw forming processes are performed as a single process using the same mold, which tends to increase the forming load on the blank and make the press-formed product more susceptible to cracks. When a press-formed product is manufactured using a high-strength blank, cracks are particularly likely to occur.

[0007] An object of the present disclosure is to provide a method for manufacturing a press-formed product that can suppress the occurrence of cracks.

[0008] A manufacturing method according to the present disclosure is a method for manufacturing a press-formed product. The press-formed product includes a top plate and an inner vertical wall. The inner vertical wall is connected to the top plate. The inner vertical wall includes a plurality of vertical wall portions. The plurality of vertical wall portions are connected to each other via corner portions. The manufacturing method includes a preparation step, a first forming step, and a second forming step. In the preparation step, a blank is prepared. In the first forming step, the blank is press-formed to form a first region to obtain an intermediate formed product. The first region includes at least a portion of the inner vertical wall and a portion of the top plate adjacent to at least a portion of the inner vertical wall of the press-formed product. In the second forming step, the intermediate formed product is press-formed while holding the first region to form a second region. The second region is a portion of the press-formed product other than the first region.

[0009] According to the method for manufacturing a press-molded product according to the present disclosure, the occurrence of cracks can be suppressed.

[0010] FIG. 1 is a top view of a press-formed product according to an embodiment. FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1. FIG. 3 is a cross-sectional view schematically showing a mold set according to an embodiment. FIG. 4 is a cross-sectional view schematically showing a mold set according to an embodiment. FIG. 5 is a schematic diagram for explaining a preparation step. FIG. 6A is a schematic diagram for explaining a first molding step. FIG. 6B is a schematic diagram for explaining a first molding step. FIG. 6C is a schematic diagram for explaining a first molding step. FIG. 6D is a schematic diagram for explaining a first molding step. FIG. 7A is a schematic diagram for explaining a second molding step. FIG. 7B is a schematic diagram for explaining a second molding step. FIG. 7C is a schematic diagram for explaining a second molding step. FIG. 8 is a cross-sectional view schematically showing a mold set according to an embodiment. FIG. 9 is a cross-sectional view schematically showing a mold set according to an embodiment. FIG. 10 is a cross-sectional view schematically showing a mold set according to a modified example of the embodiment.

[0011] A manufacturing method according to an embodiment is a method for manufacturing a press-formed product. The press-formed product includes a top plate and an inner vertical wall. The inner vertical wall is connected to the top plate. The inner vertical wall includes a plurality of vertical wall portions. The plurality of vertical wall portions are connected to each other via corner portions. The manufacturing method includes a preparation step, a first forming step, and a second forming step. In the preparation step, a blank is prepared. In the first forming step, the blank is press-formed to form a first region, thereby obtaining an intermediate formed product. The first region includes at least a portion of the inner vertical wall and a portion of the top plate adjacent to at least a portion of the inner vertical wall, of the press-formed product. In the second forming step, the intermediate formed product is press-formed while holding the first region, thereby forming a second region. The second region is a portion of the press-formed product other than the first region (first configuration).

[0012] In the manufacturing method according to the first aspect, a blank prepared in a preparation step is formed in two steps, a first forming step and a second forming step. Specifically, in the first forming step, the blank is press-formed to form a first region, which is a part of the press-formed product. In the second forming step, the intermediate product obtained in the first forming step is press-formed while holding the first region so as to substantially maintain the shape of the first region, thereby forming a second region, which is a part of the press-formed product other than the first region. By separately performing the first forming step to form the first region and the second forming step to form the second region, the forming load in the press working can be distributed compared to when the press-formed product is formed in a single step. This can reduce the occurrence of cracks when manufacturing a press-formed product having a corner portion on the inner vertical wall.

[0013] The first region formed in the first forming step includes at least a portion of the inner vertical wall of the press-formed product and a portion of the top plate adjacent to at least a portion of the inner vertical wall. The second region is located, for example, outside the first region. Since the second region is not completely formed in the first forming step, the first region can be formed by flowing material from the second region side toward the first region side. Furthermore, if the second region is located outside the first region, the second forming step can also be formed by flowing material from outside the second region toward the second region side. In this way, because material can be appropriately flowed during the forming of the first and second regions, the occurrence of cracks due to localized material shortages during the production of the press-formed product can be suppressed.

[0014] In the manufacturing method according to the first configuration, the first forming step may include preforming at least a portion of the blank that will become the second region (second configuration). Furthermore, in the manufacturing method according to the second configuration, the first forming step may include preforming the entire portion of the blank that will become the second region (third configuration).

[0015] In the second or third configuration, in the first forming step, at least a portion or all of the portion of the blank that will become the second region is preformed. This reduces the forming load in the second forming step. For example, when manufacturing a press-formed product in which a relatively difficult-to-form portion is widely present in the second region, it is possible that the forming load in the second forming step will be excessively large compared to the forming load in the first forming step. Even in such a case, by preforming the second region in the first forming step, the forming load in the second forming step can be reduced, and the forming load can be well distributed between the first and second forming steps.

[0016] In the manufacturing method according to any one of the first to third configurations, the first region may include a portion of the inner vertical wall that has the greatest height (fourth configuration).

[0017] In the fourth configuration, the first region includes the part of the inner vertical wall that has the greatest height. That is, the part of the press-formed product that is likely to be subjected to a relatively large forming load is formed in the first forming step. This makes it easier to distribute the forming load between the first and second forming steps.

[0018] In the manufacturing method according to any one of the first to fourth configurations, the press-formed product may further include an outer vertical wall and a connecting portion. The outer vertical wall is located outside the inner vertical wall. The connecting portion connects the inner vertical wall to the outer vertical wall on the side opposite the top plate (fifth configuration).

[0019] In the manufacturing method according to the fifth configuration, the first region may include a top plate and an inner vertical wall (sixth configuration).

[0020] In the manufacturing method according to the fifth or sixth configuration, the second region may include an outer vertical wall. In this case, in the first forming step, preforming may be performed on at least a portion of the second region of the blank that will become the outer vertical wall (seventh configuration). By performing preforming on at least a portion of the portion that will become the outer vertical wall in the first forming step, the forming load in the second forming step can be reduced. This makes it possible to suppress the occurrence of cracks in the press-formed product, particularly in the outer vertical wall.

[0021] In the manufacturing method according to any one of the first to seventh configurations, the plurality of vertical wall portions may include two vertical wall portions and another vertical wall portion, the two vertical wall portions being arranged to face each other, and the other vertical wall portion being connected to each of the two vertical wall portions via a corner portion (an eighth configuration).

[0022] In the manufacturing method according to the eighth configuration, the first region may include two vertical wall portions and another vertical wall portion (ninth configuration).

[0023] In the manufacturing method according to the eighth configuration, the first region may include two vertical wall portions. In this case, the second region may include the other vertical wall portion (tenth configuration).

[0024] In a manufacturing method according to any one of the first to tenth configurations, in the first forming step, the first region may be formed by a die and a punch while the die and a pad clamp the outside of the part of the blank that will become the first region (eleventh configuration).

[0025] In the eleventh configuration, in the first forming step, a pad is used in addition to the punch and die. In this case, the forming of the first region in the first forming step is performed with the die and pad sandwiching the outside of the part of the blank that will become the first region. This prevents excessive material flow from the part of the blank sandwiched between the die and pad and the outside thereof to the first region, thereby preventing wrinkles from occurring in the first region, that part, and its vicinity.

[0026] In the manufacturing method according to any one of the first to eleventh configurations, in the second molding step, the second region may be molded using a die and a punch while the first region is held by a pad and a punch (twelfth configuration).

[0027] In the twelfth configuration, a pad is used in the second molding step in addition to the punch and die. In this case, the molding of the second region in the second molding step is performed while the first region is held by the pad and punch. Therefore, the second molding step can be performed without substantially deforming the first region molded in the first molding step. Furthermore, since the flow of material from the first region to the second region is suppressed, the occurrence of wrinkles due to excess material in the second region can also be suppressed.

[0028] In the manufacturing method according to any one of the first to twelfth configurations, in the second molding step, the second region may be molded using a die and a punch while the intermediate molded product is sandwiched between a die and a pad (a thirteenth configuration).

[0029] In the thirteenth configuration, in the second molding step, a pad is used in addition to the punch and die. In this case, molding of the second region in the second molding step is performed with the intermediate molded product sandwiched between the die and the pad. This prevents excessive material flow from the periphery of the portion of the intermediate molded product sandwiched between the die and the pad to the portion, thereby preventing wrinkles from occurring at or near the portion.

[0030] In the manufacturing method according to any one of the first to thirteenth configurations, in the second molding step, the intermediate molded product may be press-processed using a mold in which at least a portion of the molding surface is formed in a shape different from that of the press-molded product after molding, taking into account springback after demolding (fourteenth configuration).

[0031] In the fourteenth configuration, a die having a forming surface formed in consideration of springback after demolding, i.e., a so-called pre-determined die, is used in the second molding step. In this case, the shape of the press-formed product obtained after demolding approaches the target shape, thereby improving the shape accuracy of the press-formed product.

[0032] A die set according to an embodiment is used to manufacture a press-formed product. The press-formed product includes a top plate and an inner vertical wall. The inner vertical wall is connected to the top plate. The inner vertical wall includes a plurality of vertical wall portions. The plurality of vertical wall portions are connected to each other via corner portions. The die set includes a first punch, a first die, a second punch, and a second die. The first punch includes a first region molding surface shaped corresponding to the first region. The first region includes at least a portion of the inner vertical wall of the press-formed product and a portion of the top plate adjacent to at least a portion of the inner vertical wall. The first die is used in pairs with the first punch. The first die includes a first region molding surface shaped corresponding to the first region. The second punch includes a first region holding surface shaped corresponding to the first region and a second region molding surface shaped corresponding to the second region. The second region is a portion of the press-formed product other than the first region. The second die is used in pairs with the second punch (fifteenth configuration).

[0033] In a mold set of the 15th configuration, the second die can include a first region holding surface shaped corresponding to the first region and a second region molding surface shaped corresponding to the second region (16th configuration).

[0034] The die set of the fifteenth or sixteenth configuration may further include a first pad. The first pad is disposed outside the first punch and includes a first pad surface. In this case, the first die may include a first flange surface. The first flange surface corresponds to the first pad surface (seventeenth configuration).

[0035] The mold set of the fifteenth or seventeenth configuration may further include a second pad disposed inside the second die, the second pad including a first region support surface shaped to correspond to the first region (eighteenth configuration).

[0036] The die set according to any one of the fifteenth to eighteenth configurations may further include a third pad. The third pad is disposed outside the second punch and includes a third pad surface. In this case, the second die may include a second flange surface. The second flange surface corresponds to the third pad surface (nineteenth configuration).

[0037] The die set according to any one of the fifteenth to nineteenth configurations may further include a first blank holder. The first blank holder is disposed outside the first punch (twentieth configuration).

[0038] The die set according to any one of the fifteenth to twentieth configurations may further include a second blank holder. The second blank holder is disposed outside the second punch (twenty-first configuration).

[0039] An automobile door inner panel according to an embodiment includes a top plate and an inner vertical wall. The inner vertical wall is connected to the top plate. The inner vertical wall includes a plurality of vertical wall portions. The plurality of vertical wall portions are connected to each other via corner portions. The tensile strength of the steel plate constituting the door inner panel is 590 MPa or more (22nd configuration).

[0040] The door inner panel of the 22nd configuration further includes an outer vertical wall and a connecting portion. The outer vertical wall is located outside the inner vertical wall. The connecting portion connects the inner vertical wall to the outer vertical wall on the side opposite the top panel (23rd configuration).

[0041] In the door inner panel of the twenty-second or twenty-third configuration, the plurality of vertical wall portions may include a first vertical wall portion, a second vertical wall portion, and a third vertical wall portion. The second vertical wall portion is disposed opposite the first vertical wall portion. The third vertical wall portion is connected to each of the first vertical wall portion and the second vertical wall portion via a corner portion (a twenty-fourth configuration).

[0042] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, the same or equivalent components are designated by the same reference numerals, and the same description will not be repeated.

[0043] [Configuration of Press-Formed Product] Fig. 1 is a top view of a press-formed product 90 according to this embodiment. Fig. 2 is a cross-sectional view taken along line II-II in Fig. 1 . The press-formed product 90 is, for example, an inner door panel of an automobile. First, referring to Fig. 1 , the press-formed product 90 includes a top plate 91 and an inner vertical wall 92. In this embodiment, the press-formed product 90 further includes an outer vertical wall 93 and a connecting portion 94. The press-formed product 90 may further include a flange 95.

[0044] The inner vertical wall 92 is connected to the top plate 91. The inner vertical wall 92 includes a plurality of vertical wall portions 921, 922, and 923. The plurality of vertical wall portions 921, 922, and 923 are connected to each other via corner portions 921a and 923a.

[0045] In this embodiment, the inner vertical wall 92 has a substantially U-shape in a top view of the press-formed product 90. More specifically, in the inner vertical wall 92, two vertical wall portions 921, 923 are arranged to face each other. The other vertical wall portion 922 extends so as to intersect with the vertical wall portions 921, 923 in a top view of the press-formed product 90. The vertical wall portion 922 is connected to each of the vertical wall portions 921, 923 via corner portions 921a, 923a. That is, one end of the vertical wall portion 922 is connected to the vertical wall portion 921 via the corner portion 921a. The other end of the vertical wall portion 922 is connected to the vertical wall portion 923 via the corner portion 923a.

[0046] The outer vertical wall 93 is located outside the inner vertical wall 92. The connecting portion 94 connects the inner vertical wall 92 to the outer vertical wall 93 on the side opposite to the top plate 91.

[0047] The outer vertical wall 93 may have a shape corresponding to the inner vertical wall 92 in a top view of the press-formed product 90. In the example of this embodiment, the outer vertical wall 93 corresponds to the inner vertical wall 92 and has a substantially U-shape in a top view of the press-formed product 90. The outer vertical wall 93 includes a plurality of vertical wall portions 931, 932, and 933 corresponding to the vertical wall portions 921, 922, and 923 of the inner vertical wall 92, respectively. The vertical wall portions 931 and 933 are arranged to face each other. The vertical wall portion 932 extends so as to intersect with the vertical wall portions 931 and 933 in a top view of the press-formed product 90. The vertical wall portion 932 is connected to the vertical wall portion 931 via a corner portion 931a. The vertical wall portion 932 is connected to the vertical wall portion 933 via a corner portion 933a.

[0048] The flange 95 is connected to the outer vertical wall 93 on the side opposite to the connecting portion 94. The flange 95 is provided continuously with the vertical wall portions 931, 932, and 933 of the outer vertical wall 93. The flange 95 is disposed on the outer side of the outer vertical wall 93. The flange 95 protrudes from the outer vertical wall 93 toward the outer periphery of the outer vertical wall 93.

[0049] Referring to FIG. 2 , the inner vertical wall 92 extends from the periphery of the top plate 91 toward the connecting portion 94 and the flange 95 in a cross-sectional view of the press-formed product 90. The inner vertical wall 92 extends in the vertical direction on the plane of FIG. 2 in the cross section of the press-formed product 90. When the length of the inner vertical wall 92 in the vertical direction on the plane of FIG. 2 is defined as the height of the inner vertical wall 92, the height of the inner vertical wall 92 may be constant or may vary overall. For example, the heights of the vertical wall portions 921, 922, and 923 ( FIG. 1 ) may be the same or different from one another. Furthermore, the heights of the vertical wall portions 921, 922, and 923 may be constant or may vary.

[0050] The outer vertical wall 93 extends in the vertical direction on the plane of FIG. 2 in the cross section of the press-formed product 90. The outer vertical wall 93 extends from the connection portion 94 toward the flange 95 in the cross section of the press-formed product 90. The outer vertical wall 93 creates a step between the connection portion 94 and the flange 95. In the cross section of the press-formed product 90, the outer vertical wall 93 may be parallel to the inner vertical wall 92 or may be inclined relative to the inner vertical wall 92. When the length of the outer vertical wall 93 in the vertical direction on the plane of FIG. 2 is defined as the height of the outer vertical wall 93, the height of the outer vertical wall 93 may be constant or may vary overall. For example, the heights of the vertical wall portions 931, 932, and 933 ( FIG. 1 ) may be the same or different from one another. Furthermore, the heights of the vertical wall portions 931, 932, and 933 may be constant or may vary.

[0051] Referring again to FIG. 1 , the press-formed product 90 includes a first region 90A and a second region 90B. The first region 90A includes at least a portion of the inner vertical wall 92 and a portion of the top plate 91 adjacent to the at least a portion of the inner vertical wall 92. When the height of the inner vertical wall 92 is not constant overall, the first region 90A may include the portion of the inner vertical wall 92 with the greatest height. In this embodiment, the first region 90A is a portion inside the connecting portion 94. Specifically, the first region 90A includes the top plate 91 and the inner vertical wall 92. That is, the first region 90A includes the entire top plate 91 and the entire inner vertical wall 92 adjacent to the top plate 91. The second region 90B is a portion of the press-formed product 90 other than the first region 90A. When the first region 90A includes the top plate 91 and the inner vertical wall 92, the second region 90B includes the outer vertical wall 93 and the connecting portion 94. That is, the second region 90B includes the entire outer vertical wall 93 and the entire connecting portion 94 adjacent to the outer vertical wall 93. In this case, the second region 90B is located outside the first region 90A. The second region 90B may further include a flange 95.

[0052] The press-formed product 90 is typically formed of a metal plate. The press-formed product 90 may be formed of a steel plate. The tensile strength of the steel plate constituting the press-formed product 90 is, for example, 590 MPa or more. The tensile strength of the steel plate constituting the press-formed product 90 may be 780 MPa or more, 980 MPa or more, or 1180 MPa or more.

[0053] [Configuration of Die Set] Figures 3 and 4 are cross-sectional views schematically showing the die set 1 according to this embodiment. The die set 1 is used to manufacture a press-molded product 90 (Figure 1). The die set 1 includes a first die 10 and a second die 20. The first die 10 and the second die 20 are attached to, for example, a known press device. The first die 10 and the second die 20 may be attached to different press devices, or may be attached to a common press device. For example, the first die 10 and the second die 20 may be attached to a transfer press device for use.

[0054] 3, the first mold 10 of the mold set 1 includes a punch 11 and a die 12. In this embodiment, the first mold 10 further includes a pad 13 and a blank holder 14.

[0055] The die 12 can move closer to and farther away from the punch 11. The die 12 is attached to, for example, a slide (not shown) of a press device and moves together with the slide. Alternatively, the punch 11 may be attached to the slide and move together with the slide. Hereinafter, the direction in which the punch 11 and the die 12 move closer to and farther away from each other may be referred to as the press direction P1. The press direction P1 is, for example, the vertical direction.

[0056] The punch 11 includes a punch top surface 111 , a punch side surface 112 , a punch flange surface 113 , and a punch shoulder 114 .

[0057] The punch top surface 111 intersects with the pressing direction P1. The punch top surface 111 may be substantially perpendicular to the pressing direction P1, but it does not have to be perpendicular. The punch top surface 111 may have a generally flat shape, or may have partial irregularities.

[0058] The punch side surface 112 is connected to the punch top surface 111 via a punch shoulder 114. When viewed in a cross section along the press direction P1, the punch side surface 112 extends from the punch top surface 111 toward the punch flange surface 113. When viewed in a cross section along the press direction P1, the punch side surface 112 may extend parallel to the press direction P1 or may be inclined with respect to the press direction P1.

[0059] The punch flange surface 113 is connected to the punch side surface 112 via a punch corner 115. The punch flange surface 113 extends outward from the punch side surface 112 (opposite the punch top surface 111). The punch flange surface 113 intersects with the pressing direction P1. The punch flange surface 113 may or may not be substantially perpendicular to the pressing direction P1.

[0060] The punch 11 includes a first region forming surface 11A. The first region forming surface 11A is a region of the forming surface of the punch 11 that has a shape corresponding to the first region 90A ( FIG. 1 ) of the press-formed product 90. The first region forming surface 11A includes at least a portion of the punch side surface 112 and a portion of the punch top surface 111 that is adjacent to at least that portion of the punch side surface 112. In the example of this embodiment, the first region forming surface 11A includes the punch top surface 111, the punch side surface 112, and the punch shoulder 114.

[0061] The die 12 includes a die bottom surface 121 , die sides 122 and 123 , die flange surfaces 124 and 125 , and die shoulders 126 and 127 .

[0062] Die bottom surface 121 is provided to correspond to punch top surface 111. When first mold 10 is in use, die bottom surface 121 faces punch top surface 111 in press direction P1. Die bottom surface 121 has a shape that corresponds to punch top surface 111.

[0063] The die side surface 122 is provided corresponding to the punch side surface 112. The die side surface 122 is connected to the die bottom surface 121 via a die corner 128. When viewed in a cross section along the press direction P1, the die side surface 122 extends from the die bottom surface 121 toward the die flange surface 124. When viewed in a cross section along the press direction P1, the die side surface 122 extends in a direction corresponding to the punch side surface 112.

[0064] The die flange surface 124 is connected to the die side surface 122 via a die shoulder 126. The die flange surface 124 extends outward from the die side surface 122 (opposite the die bottom surface 121). The die flange surface 124 intersects with the pressing direction P1. The die flange surface 124 may or may not be substantially perpendicular to the pressing direction P1.

[0065] The die side surface 123 is connected to the die flange surface 124 via a die corner 129. When viewed in a cross section along the press direction P1, the die side surface 123 extends from the die flange surface 124 toward the other die flange surface 125. When viewed in a cross section along the press direction P1, the die side surface 123 may extend parallel to the press direction P1 or may be inclined with respect to the press direction P1.

[0066] The die flange surface 125 is connected to the die side surface 123 via a die shoulder 127. The die flange surface 125 extends outward from the die side surface 123 (opposite the die flange surface 124). The die flange surface 125 intersects with the press direction P1. The die flange surface 125 may or may not be substantially perpendicular to the press direction P1. The die flange surface 125 is located on the punch 11 side of the die flange surface 124 in the press direction P1.

[0067] The die 12 includes a first region molding surface 12A having a shape corresponding to the first region 90A ( FIG. 1 ) of the press-molded product 90 ( FIG. 1 ). The first region molding surface 12A includes at least a portion of a die side surface 122 and a portion of a die bottom surface 121 adjacent to the at least a portion of the die side surface 122. In this embodiment example, the first region molding surface 12A includes the die bottom surface 121 and the die side surface 122. The first region molding surface 12A may further include a die shoulder 126.

[0068] The die 12 may further include a preforming surface 12B. The preforming surface 12B includes, for example, at least a portion of the die side surface 123 and a portion of the die flange surface 124 adjacent to the at least a portion of the die side surface 123. In this example embodiment, the preforming surface 12B includes the die side surface 123 and the die flange surface 124.

[0069] The pad 13 is disposed on the outside of the punch 11. The pad 13 is supported by a support member 15. The support member 15 is a member that is expandable and contractible in the pressing direction P1, and is formed, for example, by a spring or a fluid pressure cylinder. Operation of the support member 15 enables the pad 13 to move in the pressing direction P1.

[0070] The pad 13 includes pad surfaces 131 and 132 , pad side surfaces 133 , and a pad shoulder 134 .

[0071] The pad surface 131 is provided to correspond to the die flange surface 124. When the first mold 10 is in use, the pad surface 131 faces the die flange surface 124 in the pressing direction P1. The pad surface 131 has a shape that corresponds to the die flange surface 124.

[0072] The pad side surface 133 is provided corresponding to the die side surface 123. The pad side surface 133 is connected to the pad surface 131 via a pad shoulder 134. When viewed in a cross section along the press direction P1, the pad side surface 133 extends from the pad surface 131 toward the other pad surface 132. When viewed in a cross section along the press direction P1, the pad side surface 133 extends in a direction corresponding to the die side surface 123.

[0073] The pad surface 132 is provided to correspond to the die flange surface 125. The pad surface 132 is connected to the pad side surface 133 via a pad corner 135. The pad surface 132 extends outward from the pad side surface 133 (opposite the pad surface 131). The pad surface 132 intersects with the pressing direction P1. The pad surface 132 may or may not be substantially perpendicular to the pressing direction P1. The pad surface 132 is located on the opposite side of the pad surface 131 from the die 12 in the pressing direction P1.

[0074] The pad 13 may include a preformed surface 13A. The preformed surface 13A includes, for example, at least a portion of the pad side surface 133 and a portion of the pad surface 131 adjacent to the at least a portion of the pad side surface 133. In this example embodiment, the preformed surface 13A includes the pad side surface 133 and the pad surface 131.

[0075] The blank holder 14 is disposed outside the punch 11 and the pad 13. The blank holder 14 is supported by a support member 16. The support member 16 is a member that is expandable and contractible in the press direction P1, and is formed, for example, by a spring or a fluid pressure cylinder. Operation of the support member 16 enables the blank holder 14 to move in the press direction P1.

[0076] The blank holder 14 includes a holder surface 141. The holder surface 141 is provided to correspond to the die flange surface 125. When the first mold 10 is in use, the holder surface 141 faces the die flange surface 125 in the press direction P1. The holder surface 141 has a shape that corresponds to the die flange surface 125.

[0077] In this embodiment, the first region 90A of the press-formed product 90 includes three vertical wall portions 921, 922, and 923 ( FIG. 1 ). In this case, the pad 13 and the blank holder 14 may correspond to the vertical wall portions 921, 922, and 923 ( FIG. 1 ) and be formed so as to surround the punch 11 from three directions when viewed along the press direction P1. For example, the pad 13 and the blank holder 14 have a substantially U-shape when viewed along the press direction P1.

[0078] 4, the second mold 20 of the mold set 1 includes a punch 21 and a die 22. In this embodiment, the second mold 20 further includes pads 23 and 24 and a blank holder 25.

[0079] The die 22 can move closer to and farther away from the punch 21. The die 22 is attached to, for example, a slide (not shown) of a press device and moves together with the slide. Alternatively, the punch 21 may be attached to the slide and move together with the slide. Hereinafter, the direction in which the punch 21 and the die 22 move closer to and farther away from each other may be referred to as the press direction P2. The press direction P2 is, for example, the vertical direction.

[0080] The punch 21 includes a punch top surface 211 , punch side surfaces 212 and 213 , a punch flange surface 214 , and punch shoulders 215 and 216 .

[0081] The punch top surface 211 intersects with the pressing direction P2. The punch top surface 211 may be substantially perpendicular to the pressing direction P2, but it does not have to be perpendicular. The punch top surface 211 may have a flat shape as a whole, or may have partial unevenness.

[0082] The punch side surface 212 is connected to the punch top surface 211 via a punch shoulder 215. When viewed in a cross section along the press direction P2, the punch side surface 212 extends from the punch top surface 211 toward the punch flange surface 214. When viewed in a cross section along the press direction P2, the punch side surface 212 may extend parallel to the press direction P2 or may be inclined with respect to the press direction P2.

[0083] The punch flange surface 214 is connected to the punch side surface 212 via a punch corner 217. The punch flange surface 214 extends outward from the punch side surface 212 (opposite the punch top surface 211). The punch flange surface 214 intersects with the press direction P2. The punch flange surface 214 may or may not be substantially perpendicular to the press direction P2.

[0084] The punch side surface 213 is connected to the punch flange surface 214 via a punch shoulder 216. When viewed in a cross section along the press direction P2, the punch side surface 213 extends toward the opposite side to the punch flange surface 214. When viewed in a cross section along the press direction P2, the punch side surface 213 may extend parallel to the press direction P2 or may be inclined with respect to the press direction P2.

[0085] The punch 21 includes a first region holding surface 21A and a second region forming surface 21B. The first region holding surface 21A is a region of the forming surface of the punch 21 having a shape corresponding to the first region 90A ( FIG. 1 ) of the press-formed product 90. The second region forming surface 21B is a region of the forming surface of the punch 21 having a shape corresponding to the second region 90B ( FIG. 1 ) of the press-formed product 90. The first region holding surface 21A includes at least a portion of the punch side surface 212 and a portion of the punch top surface 211 adjacent to at least the portion of the punch side surface 212. In this embodiment, the first region holding surface 21A includes the punch top surface 211, the punch side surface 212, and a punch shoulder 215. The second region forming surface 21B includes the punch side surface 213, the punch flange surface 214, and the punch shoulder 216.

[0086] The die 22 includes a die bottom surface 221 , a die side surface 222 , a die flange surface 223 , and a die shoulder 224 .

[0087] The die bottom surface 221 is provided to correspond to the punch flange surface 214. When the second die 20 is in use, the die bottom surface 221 faces the punch flange surface 214 in the pressing direction P2. The die bottom surface 221 has a shape that corresponds to the punch flange surface 214.

[0088] The die side surface 222 is provided corresponding to the punch side surface 213. The die side surface 222 is connected to the die bottom surface 221 via a die corner 225. When viewed in a cross section along the press direction P2, the die side surface 222 extends from the die bottom surface 221 toward the die flange surface 223. When viewed in a cross section along the press direction P2, the die side surface 222 extends in a direction corresponding to the punch side surface 213.

[0089] The die flange surface 223 is connected to the die side surface 222 via a die shoulder 224. The die flange surface 223 extends outward from the die side surface 222 (opposite the die bottom surface 221). The die flange surface 223 intersects with the press direction P2. The die flange surface 223 may or may not be substantially perpendicular to the press direction P2. The die flange surface 223 is located on the punch 21 side of the die bottom surface 221 in the press direction P2.

[0090] The pad 23 is disposed inside the die 22. The pad 23 may be connected to the die 22 by a connecting member 26. The connecting member 26 is a member that is expandable and contractible in the pressing direction P2, and is configured, for example, by a spring or a fluid pressure cylinder. The pad 23 can be moved in the pressing direction P2 by actuation of the connecting member 26. The connecting member 26 may also be capable of fixing the positional relationship between the die 22 and the pad 23 at any timing.

[0091] The pad 23 includes pad surfaces 231 and 232 , a pad side surface 233 , and a pad shoulder 234 .

[0092] Pad surface 231 is provided to correspond to punch top surface 211. When second die 20 is in use, pad surface 231 faces punch top surface 211 in press direction P2. Pad surface 231 has a shape that corresponds to punch top surface 211.

[0093] The pad side surface 233 is provided corresponding to the punch side surface 212. The pad side surface 233 is connected to the pad surface 231 via a pad corner 235. When viewed in a cross section along the press direction P2, the pad side surface 233 extends from the pad surface 231 toward the other pad surface 232. When viewed in a cross section along the press direction P2, the pad side surface 233 extends in a direction corresponding to the punch side surface 212.

[0094] The pad surface 232 is provided to correspond to the punch flange surface 214. The pad surface 232 is connected to the pad side surface 233 via a pad shoulder 234. The pad surface 232 extends outward from the pad side surface 233 (opposite the pad surface 231). The pad surface 232 intersects with the press direction P2. The pad surface 232 may or may not be substantially perpendicular to the press direction P2.

[0095] The pad 23 includes a first region retaining surface 23A. The first region retaining surface 23A is a region of the molding surface of the pad 23 that has a shape corresponding to the first region 90A ( FIG. 1 ) of the press-molded product 90. The first region retaining surface 23A includes at least a portion of the pad side surface 233 and a portion of the pad surface 231 that is adjacent to at least the portion of the pad side surface 233. In this embodiment, the first region retaining surface 23A includes the pad surface 231 and the pad side surface 233. The first region retaining surface 23A may further include a pad shoulder 234.

[0096] The pad 24 is disposed on the outside of the punch 21. The pad 24 is supported by a support member 27. The support member 27 is a member that is expandable and contractible in the pressing direction P2, and is formed, for example, by a spring or a fluid pressure cylinder. The pad 24 can be moved in the pressing direction P2 by actuation of the support member 27. The support member 27 may also be capable of fixing the pad 24 at any position.

[0097] The pad 24 includes a pad surface 241. The pad surface 241 is provided to correspond to the die flange surface 223. When the second mold 20 is in use, the pad surface 241 faces the die flange surface 223 in the pressing direction P2. The pad surface 241 has a shape that corresponds to the die flange surface 223.

[0098] The blank holder 25 is disposed outside the punch 21 and the pad 24. The blank holder 25 is supported by a support member 28. The support member 28 is a member that is expandable and contractible in the press direction P2, and is formed, for example, by a spring or a fluid pressure cylinder. The blank holder 25 can be moved in the press direction P2 by actuation of the support member 28. The support member 28 may also be capable of fixing the blank holder 25 at any position.

[0099] The blank holder 25 includes a holder surface 251. The holder surface 251 is provided to correspond to the die flange surface 223. When the second mold 20 is in use, the holder surface 251 faces the die flange surface 223 in the press direction P2. The holder surface 251 has a shape that corresponds to the die flange surface 223.

[0100] The pad 24 and the blank holder 25 may be formed so as to surround the punch 21 from three directions when viewed along the press direction P2, similar to the pad 13 and the blank holder 14 (FIG. 3) of the first die 10. For example, the pad 24 and the blank holder 25 have a substantially U-shape when viewed along the press direction P2.

[0101] The forming surfaces of the punch 21 and the die 22 may have a shape different from that of the press-formed product 90 ( FIG. 1 ) after forming. The punch 21 and the die 22 may be so-called pre-formed dies. A pre-formed dies refers to a die in which at least a portion of the forming surface is formed in a shape different from that of the press-formed product 90 after forming, taking into account springback after demolding. The shape of the forming surface of the pre-formed dies and the target shape of the product (press-formed product 90) may differ by the expected amount of springback after demolding. When the punch 21 is a pre-formed dies, for example, the radius of curvature of the punch shoulders 215, 216 may be smaller than the target radius of curvature of the corresponding ridge line portion in the press-formed product 90 ( FIG. 1 ). The die 22 is a pre-formed dies with a shape corresponding to this punch 21. In addition to the punch 21 and the die 22, the other dies shown in FIGS. 3 and 4 may also be pre-formed dies. For example, the punch 11 and the die 12 may also be pre-formed dies. When the punch 11 is a projection die, for example, the radius of curvature of the punch shoulder 114 may be smaller than the target radius of curvature of the corresponding ridge line portion in the press-formed product 90. The die 12 is a projection die having a shape corresponding to this punch 11.

[0102] [Method for manufacturing press-formed product] Next, an example of a method for manufacturing the press-formed product 90 using the die set 1 will be described. This manufacturing method includes a preparation step, a first forming step, and a second forming step. In the manufacturing method according to this embodiment, the press-formed product 90 is formed, for example, in a cold state.

[0103] Referring to FIG. 5 , in the preparation step, a blank 30 is prepared. The blank 30 has a shape obtained by unfolding the press-formed product 90 ( FIG. 1 ). The blank 30 is a metal plate. The blank 30 is typically a steel plate. In this case, the blank 30 has a tensile strength of, for example, 590 MPa or more. The tensile strength of the blank 30 may be 780 MPa or more, 980 MPa or more, or 1180 MPa or more. The thickness of the blank 30 may be, for example, 0.10 mm or more and 1.30 mm or less. The thickness of the blank 30 is preferably 0.40 mm or more and 0.80 mm or less, and more preferably 0.50 mm or more and 0.65 mm or less.

[0104] 6A to 6D, the first forming step will be described. In the first forming step, the blank 30 is pressed to form a first region 90A of the press-formed product 90 (FIG. 1), thereby obtaining the intermediate formed product 40. In the first forming step, the first die 10 of the die set 1 is used.

[0105] 6A , in the first forming step, the punch 11, pad 13, and blank holder 14 are first separated from the die 12 in the press direction P1. For example, in a press device to which the first mold 10 is attached, the die 12 is positioned at the top dead center. In this state, the blank 30 is placed between the punch 11, pad 13, and blank holder 14 and the die 12. When the punch 11 is positioned below the die 12, the blank 30 is placed on the punch 11.

[0106] Next, as shown in Fig. 6B, the die 12 is moved relatively closer to the punch 11 in the pressing direction P1. This brings the die 12 into contact with the blank 30, and the blank 30 begins to deform. The blank 30 is first clamped between the die 12 and the blank holder 14. The die flange surface 125 and the holder surface 141 of the die 12 and the blank holder 14 come into contact with the blank 30, respectively.

[0107] When the die 12 is further moved closer to the punch 11 while the blank 30 is sandwiched between the die 12 and the blank holder 14, the blank 30 comes into contact with the pad 13, as shown in Fig. 6C. As a result, the blank 30 is sandwiched between the die 12 and the pad 13. In this embodiment, the blank 30 is sandwiched between the die flange surfaces 124, 125 and the die side surface 123, and the pad surfaces 131, 132 and the pad side surface 133.

[0108] 6D , when the die 12 is further moved closer to the punch 11 with the blank 30 sandwiched between the die 12, the pad 13, and the blank holder 14, the blank 30 is sandwiched between the punch 11 and the die 12. Specifically, the blank 30 is sandwiched between the punch top surface 111 and punch side surface 112 of the punch 11 and the die bottom surface 121 and die side surface 122 of the die 12. For example, when the die 12 reaches the bottom dead center of the press machine, the forming of the blank 30 by the first mold 10 is completed. This results in an intermediate formed product 40.

[0109] In the first forming step, the blank 30 is pressed to form a first region 90A of the press-formed product 90 ( FIG. 1 ). That is, the intermediate product 40 obtained in the first forming step includes the first region 90A. The first region 90A of the intermediate product 40 has substantially the same shape as the first region 90A in the final press-formed product 90.

[0110] The first region 90A is formed by the first region forming surface 11A of the punch 11 and the first region forming surface 12A of the die 12. In this embodiment, the first region 90A includes a top plate 91 and an inner vertical wall 92. The top plate 91 is formed by the punch top surface 111 of the first region forming surface 11A and the die bottom surface 121 of the first region forming surface 12A. The inner vertical wall 92 is formed by the punch side surface 112 of the first region forming surface 11A and the die side surface 122 of the first region forming surface 12A. In this embodiment, the first region 90A is formed with the die 12 and the pad 13 clamping the outside of the portion of the blank 30 that will become the first region 90A. Furthermore, when forming the first region 90A, the outside of the portion of the blank 30 that will become the first region 90A is also clamped by the die 12 and the blank holder 14. Specifically, the portion of the blank 30 that will become the second region 90B (Figure 1) of the press-formed product 90 is clamped between the die 12, the pad 13, and the blank holder 14, and a portion of the blank 30 is formed into the first region 90A by the punch 11 and the die 12.

[0111] In the first forming step, in addition to forming the first region 90A, a portion of the blank 30 that will become the second region 90B ( FIG. 1 ) may also be preformed. In this embodiment, the die flange surfaces 124, 125 and die side surface 123 of the die 12, together with the pad 13, preform the portion of the blank 30 outside the portion that will become the first region 90A. Specifically, in the first forming step, at least a portion of the portion of the second region 90B of the blank 30 that will become the outer vertical wall 93 ( FIG. 2 ) is preformed. The die 12 and the pad 13 are used for preforming. The portion of the blank 30 to be preformed is sandwiched between the preforming surface 12B of the die 12 and the preforming surface 13A of the pad 13. In the first forming step, preforming may be completed before forming of the first region 90A is completed.

[0112] Preforming may be performed on at least a portion of the blank 30 that will become the second region 90B, or on the entire portion of the blank 30 that will become the second region 90B. Preforming may not be performed in the first forming step. In that case, only the first region 90A is formed in the first forming step. That is, the portion of the blank 30 that will become the second region 90B is not substantially deformed in the first forming step. In this embodiment, the vertical wall portions 921, 922, and 923 ( FIG. 1 ) of the inner vertical wall 92 of the press-formed product 90 are all formed in the first forming step.

[0113] 7A to 7C, the second molding step will be described. In the second molding step, the intermediate molded product 40 is pressed while holding the first region 90A to form the second region 90B, thereby obtaining the press-molded product 90. In the second molding step, the second mold 20 of the mold set 1 is used.

[0114] In the second forming step, first, the punch 21, pad 24, and blank holder 25 are separated from the die 22 and pad 23 in the press direction P2. For example, in a press device to which the second mold 20 is attached, the die 22 and pad 23 are positioned at the top dead center. In this state, the intermediate formed product 40 is placed between the punch 21, pad 24, and blank holder 25 and the die 22 and pad 23. When the punch 21 is positioned below the die 22 and pad 23, the intermediate formed product 40 is placed on the punch 21.

[0115] 7B , the die 22 and the pad 23 are moved relatively closer to the punch 21 in the pressing direction P2. As a result, the pad 23 first comes into contact with the intermediate molded product 40. The intermediate molded product 40 is sandwiched between the punch 21 and the pad 23. More specifically, the first region 90A of the intermediate molded product 40 is sandwiched between the first region holding surface 21A of the punch 21 and the first region holding surface 23A of the pad 23. In other words, the first region 90A is held by the punch 21 and the pad 23.

[0116] When the die 22 is brought relatively close to the punch 21 while holding the first region 90A, the connecting member 26 contracts, causing the die 22 to move toward the punch 21 relative to the pad 23. As a result, as shown in Fig. 7C, the intermediate formed product 40 is sandwiched between the die 22, the pad 24, and the blank holder 25. Specifically, the intermediate formed product 40 is sandwiched between the die flange surface 223 of the die 22, the pad surface 241 of the pad 24, and the holder surface 251 of the blank holder 25. Thereafter, the die 22 reaches, for example, the bottom dead center of the press device.

[0117] At the bottom dead center of the press machine, the intermediate formed product 40 is sandwiched between the punch 21 and the die 22. Specifically, the intermediate formed product 40 is sandwiched between the punch side surface 213 and punch flange surface 214 of the punch 21 and the die bottom surface 221 and die side surface 222 of the die 22. In this way, the press-formed product 90 is obtained.

[0118] In the second molding step, the intermediate molded product 40 is pressed to form a second region 90B of the press-molded product 90. In this embodiment, the second region 90B is formed by the second region molding surface 21B of the punch 21 and the die bottom surface 221 and die side surface 222 of the die 22. Furthermore, the second region 90B may also be formed by the second region molding surface 21B of the punch 21 and the pad surface 232 of the pad 23. The second region 90B may also be formed by the pad 24 and the die flange surface 223 of the die 22. In the second molding step, the molding by the pad 24 and the die 22 may be completed before the molding by the punch 21 and the die 22 or the pad 23 is completed.

[0119] In this embodiment, the second region 90B includes an outer vertical wall 93 and a connecting portion 94. The outer vertical wall 93 is formed by the punch side surface 213 and the die side surface 222. The connecting portion 94 is formed by the punch flange surface 214, the die bottom surface 221, and the pad surface 232. In this embodiment, the second region 90B is formed in a state in which the first region 90A is held by the punch 21 and the pad 23.

[0120] In the second forming step, no substantial processing is performed on the first region 90A formed in the first forming step. In the second forming step, the first region 90A is held by the first region holding surface 21A of the punch 21 and the first region holding surface 23A of the pad 23 so as to maintain the formed shape in the first forming step. However, if it is expected that the shape of the first region 90A in the intermediate formed product 40 obtained in the first forming step will be slightly different from the target shape of the first region 90A in the press-formed product 90 due to the influence of springback or the like, the second forming step may include a final pressing step. That is, in the second forming step, the first region 90A may be final pressed by the first region holding surface 21A and the first region holding surface 23A. For example, the shape of the first region 90A is adjusted by pressing the first region 90A against the first region holding surface 21A of the punch 21 using the first region holding surface 23A of the pad 23.

[0121] After the second forming step, a trimming step and / or a hole-punching step may be performed as a finishing step. In the trimming step, for example, unnecessary portions outside the second region 90B are cut off. In the hole-punching step, for example, through holes are formed in the top plate 91, the inner vertical wall 92, and the outer vertical wall 93. Furthermore, if the shape of the press-formed product 90 obtained in the second forming step is slightly different from the final product shape due to the influence of springback or the like, a final pressing step may be performed after the second forming step.

[0122] (Effects) In the manufacturing method according to this embodiment, the blank 30 prepared in the preparation step is formed in two steps: a first forming step and a second forming step. Specifically, in the first forming step, the blank 30 is press-formed to form a first region 90A, which is a portion of the press-formed product 90. In the second forming step, the intermediate product 40 obtained in the first forming step is press-formed while holding the first region 90A so as to substantially maintain the shape of the first region 90A, thereby forming a second region 90B, which is the portion of the press-formed product 90 other than the first region 90A. By separately performing the first forming step for forming the first region 90A and the second forming step for forming the second region 90B in this manner, the forming load in the press working can be distributed compared to when the press-formed product 90 is formed in a single step. This reduces the occurrence of cracks when manufacturing the press-formed product 90 having corner portions 921a, 923a provided on the inner vertical wall 92.

[0123] The first region 90A formed in the first forming step includes at least a portion of the inner vertical wall 92 of the press-formed product 90 and a portion of the top plate 91 adjacent to the at least a portion of the inner vertical wall 92. The second region 90B is located outside the first region 90A. Because the second region 90B is not completely formed in the first forming step, the first region 90A can be formed by flowing material from the second region 90B side toward the first region 90A side. Furthermore, because the second region 90B is located outside the first region 90A, the second forming step can also be formed by flowing material from outside the second region 90B (the portion to be cut in the trimming step) toward the second region 90B side. In this way, the material can be appropriately flowed during the forming of the first region 90A and the second region 90B, thereby suppressing cracks due to localized material shortages during the production of the press-formed product 90.

[0124] The molding load for molding the second region 90B may be greater than the load for molding the first region 90A. Therefore, in the first molding step, at least a part or all of the portion of the blank 30 that will become the second region 90B may be preformed. The portion of the second region 90B that is preformed in the first molding step is formed into its final shape in the second molding step. Preforming the second region 90B in the first molding step reduces the molding load in the second molding step, and allows for good distribution of the molding load between the first and second molding steps.

[0125] In this embodiment, in the first forming step, preforming is performed on at least a portion of the second region 90B of the blank 30 that will become the outer vertical wall 93. This reduces the forming load in the second forming step, thereby suppressing the occurrence of cracks in the press-formed product 90, particularly in the outer vertical wall 93. In addition, a die 12 and a pad 13 are used for this preforming. The portion of the blank 30 that is preformed is sandwiched between the preforming surface 12B of the die 12 and the preforming surface 13A of the pad 13. In this way, preforming of the outer vertical wall 93 by the die 12 and the pad 13 in the first forming step suppresses the occurrence of wrinkles in the outer vertical wall 93 of the press-formed product 90 and its vicinity.

[0126] The forming load is likely to be relatively large in the part of the inner vertical wall 92 where the height is greatest because the deformation amount of the blank 30 during forming is large. Therefore, the first region 90A may include the part of the inner vertical wall 92 where the height is greatest. In this case, the forming of the part of the press-formed product 90 where the forming load is likely to be relatively large is performed in the first forming step. This makes it easier to distribute the forming load between the first forming step and the second forming step.

[0127] In the first forming step of this embodiment, in addition to the punch 11 and die 12, a pad 13 and a blank holder 14 are used. In this case, the forming of the first region 90A in the first forming step is performed with the die 12, pad 13, and blank holder 14 clamping the outside of the portion of the blank 30 that will become the first region 90A. The flow of material is reduced (optimized) in the area clamped by the die 12, pad 13, and blank holder 14. Excessive material flow from the area of ​​the blank 30 clamped by the die 12, pad 13, and blank holder 14 and the area outside the area to the first region 90A is suppressed, thereby suppressing the occurrence of wrinkles in the first region 90A, the area, and its vicinity.

[0128] Generally, when corner portions 921a, 923a are provided on the inner vertical wall 92 of the press-formed product 90, wrinkles are likely to occur at these corner portions 921a, 923a. Therefore, the pad 13 and the blank holder 14 may have a shape corresponding to the inner vertical wall 92 in the first region 90A. Specifically, the pad 13 and the blank holder 14 may have a substantially U-shape when viewed along the press direction P1. In this case, in the first forming step, the pad 13 and the blank holder 14 are also disposed outside the portions of the blank 30 that will become the corner portions 921a, 923a of the inner vertical wall 92. This prevents excessive material from flowing from the portions sandwiched between the die 12 and the pad 13 and the blank holder 14 and from the outside of those portions toward the inner vertical wall 92. Therefore, the occurrence of wrinkles due to excess material near the corner portions 921a, 923a can be suppressed.

[0129] In the second molding step of this embodiment, a pad 23 is used in addition to the punch 21 and die 22. In this case, the molding of the second region 90B in the second molding step is performed while the first region 90A is held by the pad 23 and punch 21. Therefore, the second molding step can be performed without substantially deforming the first region 90A molded in the first molding step. Furthermore, since the flow of material from the first region 90A to the second region 90B is suppressed, the occurrence of wrinkles due to excess material in the second region 90B can also be suppressed.

[0130] In this embodiment, the second forming step further includes a pad 24 and a blank holder 25. In this case, the second region 90B is formed by the die 22, punch 21, and pad 24. This forming is performed while the die 22 and blank holder 25 constrain the outer side of the portion of the intermediate formed product 40 that will become the second region 90B. This suppresses excessive material flow from the area held by the die 22 and blank holder 25 and its outer side to the second region 90B, thereby suppressing the occurrence of wrinkles in the second region 90B, the area, and its vicinity. As described above, the pad 23 and punch 21 hold the first region 90A, which also suppresses the flow of material from the first region 90A to the second region 90B, making it easier to suppress the occurrence of wrinkles, particularly in the second region 90B.

[0131] A temporary die may be used in the second forming step according to this embodiment. A temporary die may also be used in the first forming step. For example, in the first forming step and / or the second forming step, springback may occur after the first die 10 and / or the second die 20 are released. For example, springback may cause the inner vertical wall 92 of the press-formed product 90 to open or twist more than the target shape. In contrast, a temporary die is a die in which at least a portion of the forming surface is formed to have a shape different from the shape of the press-formed product 90 after forming, taking into account springback after release. Therefore, when the second die 20, which is a temporary die, is used in the second forming step, the shape of the press-formed product 90 can be made closer to the target shape when springback occurs. Similarly, when the first die 10, which is a temporary die, is used in the first forming step, a portion of the press-formed product 90 can be formed into a shape close to the target shape when springback occurs. Therefore, even when springback occurs, a press-formed product 90 close to the target shape can be obtained, thereby improving the shape accuracy of the press-formed product 90.

[0132] At the bottom dead center of the second forming step, the pad 24 and the blank holder 25 are maintained in a state where they are pressed toward the die 22. If the die 22 is simply returned to its initial position (top dead center), as shown in FIG. 8 , the connecting member 26 extends, causing the die 22 to move away from the pad 24 and the blank holder 25 in the press direction P2 while maintaining the position of the pad 23. In this case, the press-formed product 90 is sandwiched between the punch 21 and the pad 23 and pressed by the pad 24 and the blank holder 25. This may result in deformation of the press-formed product 90. Therefore, in the second mold 20, it is preferable that the die 22 and the pad 23 be configured so that their positional relationship in the press direction P2 can be fixed. For example, the connecting member 26 may be capable of fixing the positional relationship between the die 22 and the pad 23 at any timing. In this case, as shown in FIG. 9 , the pad 23 can be moved away from the punch 21, the pad 24, and the blank holder 25 together with the die 22 in the press direction P2 while the positional relationship between the die 22 and the pad 23 is fixed. As a result, the press-formed product 90 is not sandwiched between the punch 21 and the pad 23. Therefore, even if the support members 27, 28 extend as the die 22 moves, the press-formed product 90 is simply pushed up as a whole by the pad 24 and the blank holder 25, and deformation of the press-formed product 90 can be suppressed.

[0133] The second mold 20 may be configured so that movement of the pad 24 and the blank holder 25 in the press direction P2 is restricted. For example, the support members 27, 28 may be capable of fixing the pad 24 and the blank holder 25 at any desired positions. In this case, after the die 22 reaches the bottom dead center of the press machine, the positions of the pad 24 and the blank holder 25 may be fixed in that state. This prevents the pad 24 and the blank holder 25 from applying pressure to the press-formed product 90 when only the die 22 is returned to its initial position (top dead center). In other words, even if the positional relationship between the die 22 and the pad 23 is not fixed, the pad 24 and the blank holder 25 will not deform the press-formed product 90 when the second mold 20 is released.

[0134] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present disclosure.

[0135] In the above embodiment, in the first forming step, the blank 30 is formed into the intermediate formed product 40 using the pad 13 and the blank holder 14. However, in the first forming step, either or both of the pad 13 and the blank holder 14 may not be used. Also, in the above embodiment, in the second forming step, the intermediate formed product 40 is formed into the press-formed product 90 using the pads 23 and 34 and the blank holder 25. However, in the second forming step, one or more of the pads 23 and 34 and the blank holder 25 may not be used. When the pad 23 is not used, as shown in FIG. 10 , the die 22 includes a first-region holding surface 22A shaped corresponding to the first region 90A ( FIG. 1 ) and a second-region forming surface 22B shaped corresponding to the second region 90B ( FIG. 1 ). In this case, in the second forming step, the first region 90A formed in the first forming step is held by the punch 21 and the die 22, and the second region 90B is formed by the punch 21 and the die 22.

[0136] In the above embodiment, the first region 90A includes the entire inner vertical wall 92. That is, all of the vertical wall portions 921, 922, and 923 of the inner vertical wall 92 of the press-formed product 90 are formed in the first forming step. However, some of the vertical wall portions 921, 922, and 923 may be formed in the first forming step, and the remaining portions may be formed in the second forming step. For example, the first region 90A may include the vertical wall portions 921 and 923, and the second region 90B may include the vertical wall portion 922. However, the first region 90A is not particularly limited, and may include at least a portion of the inner vertical wall 92 and a portion of the top plate 91 adjacent to the at least a portion of the inner vertical wall 92. In the first forming step and the second forming step, a mold set 1 (first mold 10 and second mold 20) having a shape corresponding to the arrangement and shape of the first region 90A and the second region 90B may be used.

[0137] In the example of the above embodiment, the press-formed product 90 includes an outer vertical wall 93, a connecting portion 94, and a flange 95 in addition to the top plate 91 and the inner vertical wall 92. However, the press-formed product 90 does not have to include all of the outer vertical wall 93, the connecting portion 94, and the flange 95. Moreover, the press-formed product 90 does not have to include only the flange 95 out of the outer vertical wall 93, the connecting portion 94, and the flange 95, or it does not have to include the outer vertical wall 93 or the flange 95.

[0138] In the above embodiment, the inner vertical wall 92 of the press-formed product 90 includes vertical wall portions 921, 922, and 923. However, the inner vertical wall 92 does not have to include the vertical wall portion 921 or the vertical wall portion 923. The inner vertical wall 92 may have a substantially L-shape in a top view of the press-formed product 90, with the vertical wall portions 921 and 922 connected to each other via a corner portion 921 a. Alternatively, the inner vertical wall 92 may have a substantially L-shape in a top view of the press-formed product 90, with the vertical wall portions 922 and 923 connected to each other via a corner portion 923 a. The shape of the press-formed product 90 is not limited to the example described in the above embodiment.

[0139] As described in the above embodiment, the first region 90A of the press-formed product 90 may include the part of the inner vertical wall 92 that has the greatest height. However, the first region 90A does not have to include the part of the inner vertical wall 92 that has the greatest height. The height of the inner vertical wall 92 is the dimension of the inner vertical wall 92 in the press direction P1 in the first forming step. The height direction of the inner vertical wall 92 substantially coincides with the up-down direction on the plane of FIG. 2 .

[0140] 90: Press-molded product 90A: First region 90B: Second region 91: Top plate 92: Inner vertical wall 921: Vertical wall portion (first vertical wall portion) 922: Vertical wall portion (second vertical wall portion) 923: Vertical wall portion (third vertical wall portion) 921a, 923a: Corner portion 93: Outer vertical wall 94: Connection portion 1: Die set 11: Punch (first punch) 11A: First region molding surface 12: Die (first die) 12A: First region molding surface 13: Pad (first pad) 14: Blank holder (first blank holder) 21: Punch (second punch) 21A: First region holding surface 21B: Second region molding surface 22: Die (second die) 22A: First region holding surface 22B: Second region molding surface 23: Pad (second pad) 23A: First region holding surface 24: Pad (third pad) 25: Blank holder (second blank holder) 30: Blank 40: Intermediate molded product

Claims

A method for manufacturing a press-formed product comprising: a top plate; and an inner vertical wall connected to the top plate, wherein the inner vertical wall includes a plurality of vertical wall portions connected to each other via corner portions, a preparation step of preparing a blank; a first forming step of forming a first region of the press-formed product, the first region including at least a portion of the inner vertical wall and a portion of the top plate adjacent to the at least a portion of the inner vertical wall, by pressing the blank to obtain an intermediate formed product; a second molding process in which the intermediate molded product is press-processed while holding the first region to form a second region, which is the portion of the press-molded product other than the first region. 　 The method of claim 1, In the first forming step, preforming is performed on at least a portion of the blank that will become the second region. 　 The manufacturing method according to claim 2, In the first forming step, a preforming process is performed on the entire portion of the blank that will become the second region. 　 The method of claim 1, The manufacturing method, wherein the first region includes a portion of the inner vertical wall that has the greatest height. 　 The method of claim 1, The manufacturing method, wherein the press-molded product further comprises an outer vertical wall located outside the inner vertical wall, and a connecting portion connecting the inner vertical wall to the outer vertical wall on the side opposite the top plate. 　 The manufacturing method according to claim 5, The manufacturing method, wherein the first region includes the top plate and the inner vertical wall. 　 The manufacturing method according to claim 5, the second region includes the outer vertical wall, In the first forming step, preforming is performed on at least a portion of the second region of the blank that will become the outer vertical wall. 　 The method of claim 1, A manufacturing method in which the plurality of vertical wall portions include two vertical wall portions arranged to face each other, and another vertical wall portion connected to each of the two vertical wall portions via the corner portion. 　 The manufacturing method according to claim 8, The manufacturing method, wherein the first region includes the two vertical wall portions and the other vertical wall portion. 　 The manufacturing method according to claim 8, the first region includes the two vertical wall portions, The second region includes the other vertical wall portion. 　 The method of claim 1, A manufacturing method in which, in the first forming step, the die and a pad clamp the outside of the part of the blank that will become the first region, and the die and a punch form the first region. 　 The method of claim 1, In the second molding step, the second region is molded by a die and the punch while the first region is held by a pad and a punch. 　 The method of claim 1, In the second molding step, the intermediate molded product is sandwiched between a die and a pad, and the second region is molded using the die and a punch. 　 The method of claim 1, In the second molding step, the intermediate molded product is press-processed using a mold in which at least a portion of the molding surface is formed to have a shape different from that of the press-molded product after molding, taking into account springback after demolding. 　 A die set used to manufacture a press-formed product, comprising: a top plate; and an inner vertical wall connected to the top plate, wherein the inner vertical wall includes a plurality of vertical wall portions connected to each other via corner portions, a first punch including a first region forming surface having a shape corresponding to a first region of the press-formed product including at least a portion of the inner vertical wall and a portion of the top plate adjacent to the at least a portion of the inner vertical wall; a first die used in combination with the first punch and including a first region forming surface having a shape corresponding to the first region; a second punch including a first region holding surface having a shape corresponding to the first region and a second region forming surface having a shape corresponding to a second region of the press-formed product other than the first region; a second die paired with the second punch.

16. The mold set according to claim 15, The second die includes a first region holding surface shaped to correspond to the first region and a second region molding surface shaped to correspond to the second region.

16. The mold set of claim 15, further comprising: a first pad disposed outside the first punch and including a first pad surface; The first die includes a first flange surface corresponding to the first pad surface.

16. The mold set of claim 15, further comprising: a mold set including a second pad disposed inside the second die and including a first region support surface shaped to correspond to the first region; 　 16. The mold set of claim 15, further comprising: a third pad disposed outside the second punch and including a third pad surface; The second die includes a second flange surface corresponding to the third pad surface.

16. The mold set of claim 15, further comprising: a die set including a first blank holder disposed outside the first punch; 　 16. The mold set of claim 15, further comprising: a die set including a second blank holder disposed outside the second punch; 　 An inner door panel of an automobile, The top plate and an inner vertical wall connected to the top plate and including a plurality of vertical wall portions connected to each other via corner portions; The door inner panel, wherein the steel plate constituting the door inner panel has a tensile strength of 590 MPa or more.

23. The door inner panel according to claim 22, further comprising: an outer vertical wall located outside the inner vertical wall; a connecting portion that connects the inner vertical wall to the outer vertical wall on the opposite side from the top plate.

23. The door inner panel according to claim 22, The plurality of vertical wall portions are A first vertical wall portion; a second vertical wall portion disposed opposite the first vertical wall portion; a third vertical wall portion connected to each of the first vertical wall portion and the second vertical wall portion via the corner portion.

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