Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D19/00—Flanging or other edge treatment, e.g. of tubes
  • B21D19/08—Flanging or other edge treatment, e.g. of tubes by single or successive action of pressing tools, e.g. vice jaws
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
  • B21D22/20—Deep-drawing
  • B21D22/22—Deep-drawing with devices for holding the edge of the blanks
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D19/00—Flanging or other edge treatment, e.g. of tubes
  • B21D19/08—Flanging or other edge treatment, e.g. of tubes by single or successive action of pressing tools, e.g. vice jaws
  • B21D19/088—Flanging or other edge treatment, e.g. of tubes by single or successive action of pressing tools, e.g. vice jaws for flanging holes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D53/00—Making other particular articles
  • B21D53/88—Making other particular articles other parts for vehicles, e.g. cowlings, mudguards

Definitions

• the present disclosure relates to a production method of a press formed product and a press forming apparatus.
• Press formed products are used, for example, for structural members for automobiles.
• Such a press formed product is produced by subjecting a blank to press forming by using a punch and a die. The blank is pushed toward the die by the punch and formed into a desired shape.
• Patent Literature 1 discloses a production method of a press formed product in which a pad is used in addition to the punch and the die.
• curved surfaces are included in a side surface of the punch and a side surface of the die that cooperates with the punch.
• the die is moved relative to the punch along the side surface of the punch. In this way, a press formed product is formed from the blank.
• Patent Literature 2 also discloses a production method of a press formed product in which a punch, a die, and a pad are used.
• the edge of the upper surface of the punch has a shape including a dent in the center in plane view.
• the die has a shape corresponding to the punch.
• a blank placed on the upper surface of the punch is held by the pad and a bead is formed in the blank. Thereafter, the blank is bent by the punch and the die, so that a press formed product is formed.
• the edge of the die closer to the punch includes a curved portion.
• the curved portion is a portion that is curved and protrudes toward the punch in plane view of the die.
• the portion of the blank drawn toward the curved portion is stretched in the extending direction of the curved portion.
• cracks may be generated in the blank.
• An object of the present disclosure is to reduce the occurrence of blank cracking in producing a press formed product.
• a production method of a press formed product includes: clamping a blank between a die and a blank holder; and pushing the blank by a punch in a press direction.
• an edge of the die closer to the punch includes a curved portion that is curved and protrudes toward the punch and that extends with a radius of curvature of less than 400 mm.
• a distance between an edge of the blank holder closer to the punch and the edge of the die closer to the punch varies along the edge of the die, the distance being on a perpendicular to an extending direction of the edge of the die.
• the distance is smallest at the curved portion.
• the occurrence of blank cracking can be reduced.
• FIG. 17 is a diagram of a punch 91 and a die 92 used in typical press forming, which are projected onto a plane perpendicular to the press direction.
• the punch 91 and the die 92 are used to perform press forming, the blank is drawn toward an edge 921 of the die 92 closer to the punch 91.
• the edge 921 of the die 92 includes a curved portion 921a and straight portions 921b provided on opposite sides of the curved portion 921a when viewed from the press direction, a portion drawn toward the curved portion 921a in the blank is stretched in the extending direction of the curved portion 921a as indicated by double-headed arrows A2 in FIG. 17 .
• the dashed lines in FIG. 17 are examples of isopachic lines of the blank during press forming.
• the isopachic line is a line connecting locations of an equal sheet thickness in the blank during press forming. In FIG. 17 , it is indicated that the thicker the isopachic line is, the thicker the sheet thickness of the blank is at the position.
• One way of reducing the blank cracking includes applying a compressive stress in the sheet thickness direction of the blank.
• applying a compressive stress to the blank in the sheet thickness direction to reduce the blank cracking is referred to as a novel developed method.
• the present inventors have conceived of applying the novel developed method in the case in which an edge of the die closer to the punch includes a curved portion and completed a production method of a press formed product according to embodiments.
• the production method of a press formed product includes: clamping a blank between a die and a blank holder; and pushing the blank by a punch in the press direction.
• the edge of the die closer to the punch includes a curved portion that is curved and protrudes toward the punch and that extends with a radius of curvature of less than 400 mm.
• a distance between the edge of the blank holder closer to the punch and the edge of the die closer to the punch varies along the edge of the die, the distance being on a perpendicular to the extending direction of the edge of the die.
• the distance is smallest at the curved portion.
• the sheet thickness of the blank becomes thinner in press forming as the blank is drawn toward the curved portion.
• the distance between the edge of the blank holder closer to the punch and the edge of the die closer to the punch is smallest at the curved portion.
• the portion drawn toward the curved portion in the blank namely, a sheet-thickness-reduced portion can be clamped with the die and the blank holder up to the vicinity of the curved portion, so that a compressive stress can be applied to the sheet-thickness-reduced portion in the sheet thickness direction up to the vicinity of the curved portion. Accordingly, in producing a press formed product, it is possible to reduce the occurrence of blank cracking.
• the distance between the edge of the blank holder closer to the punch and the edge of the die closer to the punch varies along the extending direction of the edge of the die. More specifically, on the edge of the die, there is a location in the curved portion, at which the distance to the edge of the blank holder is smallest, and the distance to the edge of the blank holder increases away from the location. Consequently, during press forming, the blank is pressed by the die and the blank holder up to the vicinity of the edge of the die at the location at which the distance between the edge of the blank holder and the edge of the die is smallest, while the blank is not pressed up to the vicinity of the edge of the die at a location adjacent to the location. In this way, it is possible to cause a material to flow in the sheet-thickness-reduced portion of the blank during press forming and to mitigate a reduction in sheet thickness in the blank. Accordingly, it is possible to further reduce the occurrence of blank cracking.
• the distance between the edge of the blank holder and the edge of the die expands further away from the curved portion.
• the novel developed method to the entire portion drawn toward the curved portion in the blank and to facilitate a material inflow to the portion. That is, the distance between the edge of the blank holder and the curved portion on the edge of the die is smaller than the distance between the edge of the blank holder and other portions on the edge of the die, and therefore, it is possible to apply a compressive stress by the die and the blank holder to the entire portion drawn toward the curved portion in the blank in the sheet thickness direction up to the vicinity of the curved portion.
• the distance between the edge of the blank holder and other portions than the curved portion on the edge of the die becomes larger further away from the curved portion, and therefore, on opposite sides of the curved portion, the blank is not pressed up to the vicinity of the edge of the die. Accordingly, it is possible to facilitate a material inflow to the portion drawn toward the curved portion in the blank.
• the edge of the die closer to the punch when viewed from the press direction, may consist only of the curved portion. In this case, when viewed from the press direction, the distance between the edge of the blank holder closer to the punch and the edge of the die closer to the punch may be largest at the end portion of the curved portion.
• a line length of a portion on the edge of the blank holder closer to the punch, at which the distance to the edge of the die closer to the punch is smallest may be 0.5 times or more to 2.5 times or less the line length of the curved portion.
• the press forming apparatus includes a punch, a die, and a blank holder.
• the edge of the die closer to the punch includes a curved portion that is curved and protrudes toward the punch and that extends with a radius of curvature of less than 400 mm.
• a distance between the edge of the blank holder closer to the punch and the edge of the die closer to the punch varies along the edge of the die, the distance being on a perpendicular to the extending direction of the edge of the die.
• the distance is smallest at the curved portion.
• the distance between the edge of the blank holder closer to the punch and the edge of the die closer to the punch may become larger further away from the curved portion.
• the edge of the die closer to the punch when viewed from the press direction, may consist only of the curved portion. In this case, when viewed from the press direction, the distance between the edge of the blank holder closer to the punch and the edge of the die closer to the punch may be largest at the end portion of the curved portion. (Seventh configuration)
• a line length of a portion on the edge of the blank holder closer to the punch, at which the distance to the edge of the die closer to the punch is smallest may be 0.5 times or more to 2.5 times or less the line length of the curved portion.
• FIG. 1 is a schematic perspective view of a press forming apparatus 100 according to a first embodiment.
• the press forming apparatus 100 includes a punch 10, a die 20, and a blank holder 30. While FIG. 1 illustrates a die 20 only on one side with respect to an imaginary line CL, dies 20 may be disposed on opposite sides of the punch 10. These dies 20 may be separate or formed integrally with each other. In the embodiment, a space between the dies 20 may be referred to as a die cavity.
• the blank holder 30 is provided for each of the dies 20 correspondingly.
• the punch 10 and the blank holder 30 are configured to be movable relative to the die 20 in a press direction P.
• the punch 10 and the blank holder 30 may be moved in the press direction P or the die 20 may be moved in the press direction P, for example, by a drive mechanism (not illustrated) such as a fluid pressure cylinder.
• the blank holder 30 is movable relative to the punch 10 in the press direction P, for example, by a drive mechanism (not illustrated) such as a cushion.
• the press direction P is, but not particularly limited to, the vertical direction, for example. When the press direction P is the vertical direction, it is easy to place a blank 200 ( FIG. 4A ) described later between the punch 10 and the die 20.
• FIG. 2 is a cross-sectional view of the press forming apparatus 100 illustrated in FIG. 1 .
• the cross section of the press forming apparatus 100 is a section of the press forming apparatus 100 cut in a plane that is parallel to the press direction P and perpendicular to the longitudinal direction of the punch 10.
• the direction perpendicular to the press direction P on the cross section of the press forming apparatus 100 is referred to as the width direction of the press forming apparatus 100.
• FIG. 2 illustrates the portion of the press forming apparatus 100 only on one side with respect to the imaginary line CL.
• the imaginary line CL is, for example, the center line in the width direction of the press forming apparatus 100.
• the punch 10 includes a punch top surface 11, a punch shoulder 12, and a punch side surface 13.
• the punch top surface 11 is a surface intersecting with the press direction P.
• the punch top surface 11 may be perpendicular to the press direction P.
• the punch top surface 11 extends substantially in the width direction.
• the punch shoulder 12 is continuous with the end portion of the punch top surface 11.
• the punch shoulder 12 has, for example, substantially an arc shape. The reason is that if the punch shoulder 12 is sharp, there is a risk of cutting the blank 200 ( FIG. 4A ) with the punch shoulder 12 during press forming.
• the radius of curvature of the punch shoulder 12 may be 1.0 mm or more.
• the punch side surface 13 is connected to the punch top surface 11 via the punch shoulder 12.
• the punch side surface 13 When viewed in the cross section of the press forming apparatus 100, the punch side surface 13 extends from the punch shoulder 12 in the press direction P. When viewed in the cross section of the press forming apparatus 100, the punch side surface 13 may be parallel to the press direction P or may be oblique with respect to the press direction P.
• the die 20 includes a pressing surface 21, a die shoulder 22, and a die side surface 23.
• the pressing surface 21 of the die 20 is, for example, a flat surface substantially perpendicular to the press direction P.
• the die shoulder 22 is continuous with the end portion of the pressing surface 21 closer to the punch 10.
• the die shoulder 22 has, for example, substantially an arc shape. The reason is that if the die shoulder 22 is sharp, there is a risk of cutting the blank 200 ( FIG. 4A ) with the die shoulder 22 during press forming.
• the radius of curvature of the die shoulder 22 may be 1.0 mm or more.
• the die side surface 23 is connected to the pressing surface 21 via the die shoulder 22. When viewed in the cross section of the press forming apparatus 100, the die side surface 23 extends from the die shoulder 22 in the press direction P.
• the die side surface 23 has a shape corresponding to the punch side surface 13.
• the blank holder 30 is disposed to the outside of the punch 10 in the width direction of the press forming apparatus 100. In addition, the blank holder 30 is disposed such that it faces the die 20 in the press direction P.
• the blank holder 30 includes a pressing surface 31, a holder shoulder 32, and a holder side surface 33.
• the pressing surface 31 of the blank holder 30 faces the pressing surface 21 of the die 20 in the press direction P.
• the pressing surface 31 is, for example, a flat surface substantially perpendicular to the press direction P.
• the holder shoulder 32 is continuous with the end portion of the pressing surface 31 closer to the punch 10.
• the holder side surface 33 is connected to the pressing surface 31 via the holder shoulder 32.
• the holder side surface 33 extends from the holder shoulder 32 in the press direction P.
• the holder side surface 33 faces the punch side surface 13 in the width direction of the press forming apparatus 100.
• the press forming apparatus 100 may have a symmetrical shape with respect to the width center line CL when viewed in cross section, it may have an asymmetrical shape with respect to the width center line CL.
• FIG. 3 is a diagram schematically illustrating a relationship among the punch 10, the die 20, and the blank holder 30 when viewed from the press direction P.
• FIG. 3 is a schematic view illustrating the punch 10, the die 20, and the blank holder 30 as projected onto a plane perpendicular to the press direction P.
• FIG. 3 illustrates an edge 24 of the die 20 in a solid line and an edge 34 of the blank holder 30 in a dashed line.
• the blank holder 30 is hatched.
• an edge 14 of the punch 10 is indicated in a dash-dot line.
• the edge 14 of the punch 10 in FIG. 3 corresponds to the punch side surface 13 in the same plane as the pressing surface 21 of the die 20.
• the edge 14 of the punch 10 closer to the die 20 extends along the edge 24 of the die 20 closer to the punch 10.
• the edge 24 of the die is a die shoulder 22.
• the edge 14 of the punch 10 has a shape corresponding to the edge 24 of the die 20.
• the edge 14 of the punch 10 is substantially parallel to the edge 24 of the die 20 as a whole.
• the clearance between the edge 14 of the punch 10 and the edge 24 of the die 20 when viewed from the press direction P is equal to or larger than the sheet thickness of the blank, which is a starting material for press forming, such that relative movement between the punch 10 and the die 20 in the press direction P is not impeded.
• the edge 24 of the die 20 includes a curved portion 241 and straight portions 242 and 243.
• the curved portion 241 When viewed from the press direction P, the curved portion 241 is curved and protrudes toward the punch 10. When viewed from the press direction P, the curved portion 241 extends with a radius of curvature of less than 400 mm.
• the curved portion 241 may have a constant radius of curvature or may vary in terms of the radius of curvature.
• the radius of curvature when viewed from the press direction P, for each of points arranged at an interval of 5.0 mm on the edge 24 of the die 20, the radius of curvature is measured for an arc that passes through three points including the point and neighboring points on opposite sides, and a section with the radius of curvature of less than 400 mm is considered as the curved portion 241 and a section with the radius of curvature of 400 mm or more as a non-curved portion (straight portion).
• the straight portions 242 and 243 are provided to be continuous with opposite ends of the curved portion 241. When viewed from the press direction P, the straight portions 242 and 243 extend such that they diverge from each other from the curved portion 241 further away from the curved portion 241. The straight portions 242 and 243 may be located on tangential lines on opposite ends of the curved portion 241 when viewed from the press direction P.
• the blank holder 30 is provided such that, for example, it corresponds to only a part of the region of the edge 24 of the die 20.
• the blank holder 30 When viewed from the press direction P, the blank holder 30 is disposed at a position corresponding to the curved portion 241 of the edge 24 of the die 20.
• the blank holder 30 when viewed from the press direction P, the blank holder 30 has a shape that substantially tapers toward the punch 10. In the example illustrated in FIG. 3 , the blank holder 30 has a generally triangular shape when viewed from the press direction P.
• a distance C between the edge 34 of the blank holder 30 closer to the punch 10 and the edge 24 of the die 20 varies along the edge 24 of the die 20. That is, the distance C between the edge 34 of the blank holder 30 and the edge 24 of the die 20 is not constant over the entire length of the edge 34 of the blank holder 30.
• the distance C on a perpendicular to the extending direction of the edge 24 of the die 20 when viewed from the press direction P is a distance between the edge 34 of the blank holder 30 and the edge 24 of the die 20.
• the distance C is a distance from the edge 34 of the blank holder 30 to the edge 24 of the die 20 in a normal direction to the curved portion 241 or in a perpendicular direction to the straight portions 242 and 243 when viewed from the press direction P.
• a perpendicular to the extending direction of the edge 24 of the die 20 refers to a perpendicular or a normal to the edge of the die shoulder 22 ( FIG. 2 ) closer to the punch 10 when viewed from the press direction P.
• the perpendicular to the extending direction of the edge 24 of the die 20 generally coincides with the direction in which the blank is drawn toward the die cavity when the blank is formed by using the press forming apparatus 100 ( FIG. 1 and FIG. 2 ).
• the edge 34 of the blank holder 30 is the edge of the holder shoulder 32 ( FIG. 2 ) closer to the punch 10 when viewed from the press direction P.
• the distance C between the edge 34 of the blank holder 30 and the edge 24 of the die 20 is smallest at the curved portion 241. That is, drawing a perpendicular to the edge 24 of the die 20 by selecting a position on the edge 24 of the die 20, at which the distance to the edge 34 of the blank holder 30 is smallest, when viewed from the press direction P, the perpendicular will pass through the curved portion 241.
• a minimum value of the distance C is smaller than the clearance between the edge 14 of the punch 10 and the edge 24 of the die 20.
• the minimum value of the distance C may be 0 mm.
• the edge 34 of the blank holder 30 and the edge 24 of the die 20 overlap at a location at which the edge 34 of the blank holder 30 is closest to the edge 24 of the die 20, and at other locations, the edge 24 of the die 20 is disposed on a punch 10 side with respect to the edge 34 of the blank holder 30.
• the minimum value of the distance C is larger than 0 mm, when viewed from the press direction P, the entire edge 34 of the blank holder 30 is disposed on the opposite side of the punch 10 with respect to the edge 24 of the die 20.
• a line length of a portion at which the distance C to the edge 24 of the die 20 on the edge 34 of the blank holder 30 is smallest can be, for example, 0.5 times or more to 2.5 times or less the line length of the curved portion 241.
• the line length of the curved portion 241, namely, the length in the extending direction of the curved portion 241 can be a product of an included angle ⁇ (rad) and the radius of curvature of the curved portion 241.
• the included angle ⁇ is an angle formed between tangential lines on opposite sides of the curved portion 241 when viewed from the press direction P.
• the included angle ⁇ may be 1/3 ⁇ (rad) or more to 2/3 ⁇ (rad) or less.
• the radius of curvature of the curved portion 241 can be, for example, an average value of values of the radius of curvature measured at an interval of 5.0 mm as described above.
• the distance C between the edge 34 of the blank holder 30 and the edge 24 of the die 20 is smallest at the apex of the curved portion 241 protruding toward the punch 10.
• the distance C between the edge 34 of the blank holder 30 and the edge 24 of the die 20 becomes larger further away from the apex of the curved portion 241. That is, the distance C varies within the range of the curved portion 241.
• the distance C between the edge 34 of the blank holder 30 and the edge 24 of the die 20 is even larger along the straight portions 242 and 243 on opposite sides of the curved portion 241.
• the distance C becomes larger further away from the curved portion 241.
• the blank 200 is first prepared to produce a press formed product.
• the blank 200 can be obtained, for example, by subjecting a rolled steel sheet to blanking.
• the blank 200 is formed, for example, in an expanded shape of an intended press formed product.
• Such an expanded shape of an intended press formed product can be obtained, for example, by using a function of deriving a blank shape before being formed from a shape of a formed product from finite element analysis software for analyzing press forming.
• the blank 200 may be a steel sheet.
• the blank 200 is preferably a high tensile strength steel sheet.
• the tensile strength of the blank 200 is, for example, 440 MPa or more.
• the tensile strength of the blank 200 may be 590 MPa or more, or may be 780 MPa or more.
• the tensile strength of the blank 200 may be 980 MPa or more, may be 1180 MPa or more, or may be 1300 MPa or more.
• the sheet thickness of the blank 200 may be, for example, 0.4 mm or more to 6.0 mm or less, or may be 1.0 mm or more to 4.0 mm or less.
• the production method of a press formed product includes: clamping the blank 200 with the die 20 and the blank holder 30; and pushing the blank 200 by the punch 10 in the press direction P.
• the blank 200 is first disposed between the punch 10/the blank holder 30 and the die 20.
• the blank 200 is placed on the punch top surface 11 and the pressing surface 31 of the blank holder 30.
• the blank 200 may be placed on the pressing surface 21 ( FIG. 2 ) of the die 20.
• the blank holder 30 and the die 20 are brought close relative to each other in the press direction P to clamp and hold the blank 200 between the pressing surface 21 of the die 20 and the pressing surface 31 of the blank holder 30.
• the die 20 and the punch 10 are brought close relative to each other in the press direction P with the blank 200 being clamped between the die 20 and the blank holder 30.
• the blank 200 is pushed toward the die 20 (die cavity) by the punch 10.
• the blank 200 is drawn toward the die cavity.
• the direction in which the blank 200 is drawn is indicated by an arrow D.
• pushing by the punch 10 (forming) is completed after the blank 200 is completely pulled out from between the die 20 and the blank holder 30.
• the forming may be considered complete while a part of the blank 200 is still clamped between the die 20 and the blank holder 30.
• the press formed product 300 includes a top plate 301, a ridge portion 302, and a flange 303.
• the side edge of the top plate 301 is provided with a portion that is depressed inward in the width direction.
• the top plate 301 is formed such that the width of the center portion in the longitudinal direction is smaller than the width of each of opposite end portions in the longitudinal direction. That is, the top plate 301 is formed in a shape that is indented inward in the center portion in the longitudinal direction in plane view.
• the top plate 301 may have a flat shape as a whole, or may have a concave or convex shape in a part thereof.
• the top plate 301 may have a through hole formed therein.
• a ridge portion 302 is provided continuously on the side edge in the width direction of the top plate 301.
• the flange 303 is connected to the side edge of the top plate 301 via the ridge portion 302.
• the flange 303 is continuous with the ridge portion 302 and provided in a standing manner from the top plate 301.
• the ridge portion 302 and the flange 303 extend along the side edge of the top plate 301.
• the tensile strength of the press formed product 300 is, for example, 440 MPa or more.
• the tensile strength of the press formed product 300 may be 590 MPa or more, or may be 780 MPa or more.
• the tensile strength of the press formed product 300 may be 980 MPa or more, may be 1180 MPa or more, or may be 1300 MPa or more.
• the sheet thickness of the press formed product 300 may be, for example, 0.4 mm or more to 6.0 mm or less, or may be 1.0 mm or more to 4.0 mm or less.
• the press formed product 300 can be used, for example, for automobile components.
• the press formed product 300 may be a body component, a chassis component, or a panel component of an automobile.
• the body components include, for example, a side sill, a roof siderail, a front pillar, a center pillar, a lock pillar, a kick reinforce, and a side member.
• the chassis components are, for example, arm components or link components for suspensions.
• the arm components or the link components include, for example, a sub-frame, a lower arm, an upper arm, and a trailing arm.
• the panel components include a door inner panel, a side panel, a floor panel, and the like.
• machining marks such as impressions or scratches are left at a location locally held by the blank holder 30 of the press formed product 300. These machining marks do not adversary affect the mechanical properties of the press formed product. For example, in the press formed product 300 in FIG. 4E , machining marks are left on the back side, which is not exposed in the figure of the flange 303.
• the embodiment relates to the novel developed method of applying a compressive stress by the blank holder 30 to the sheet-thickness-reduced portion occurring in the blank 200 when draw forming is performed by using the die 20 that includes the curved portion 241 on the edge 24 closer to the punch 10 to reduce cracking in the blank 200.
• the blank 200 when the blank 200 is subjected to forming by pushing it into the die cavity by the punch 10, the blank 200 is drawn toward the curved portion 241 provided on the edge 24 of the die 20 closer to the punch 10.
• the portion of the blank 200 drawn toward the curved portion 241 is stretched in the extending direction of the curved portion 241 as it is drawn in the curved portion 241, so that the sheet thickness thereof is reduced.
• the press forming apparatus 100 is configured such that, when viewed from the press direction P, the distance C between the edge 34 of the blank holder 30 closer to the punch 10 and the edge 24 of the die 20 closer to the punch 10 is smallest at the curved portion 241. Accordingly, it is possible to apply a compressive stress in the sheet thickness direction to a portion of the blank 200, which is drawn toward the curved portion 241 so that a reduction in sheet thickness occurs, by clamping it up to the vicinity of the curved portion 241 between the die 20 and the blank holder 30. In this way, it is possible to reduce the occurrence of cracking in the blank 200 in the production of the press formed product 300.
• the blank 200 is formed into the press formed product 300, the blank 200 drawn toward the curved portion 241 is pressed by the die 20 and the blank holder 30 up to the vicinity of the curved portion 241.
• the periphery of the sheet-thickness-reduced portion in the blank 200 is pressed by the die 20 and the blank holder 30, a material flows in the sheet-thickness-reduced portion in the blank 200 and a reduction in sheet thickness in the blank 200 can be mitigated.
• the distance C between the edge 34 of the blank holder 30 and the edge 24 of the die 20 is designed to vary in the extending direction of the edge 24 of the die 20. That is, when viewed from the press direction P, the edge 34 of the blank holder 30 extends along the edge 24 of the die 20 but is not parallel to the edge 24 of the die 20. When viewed from the press direction P, the distance C between the edge 34 of the blank holder 30 and the edge 24 of the die 20 is smallest at a part of the curved portion 241 and larger in other portions.
• the blank 200 is pressed by the die 20 and the blank holder 30 up to the vicinity of the edge 24 of the die 20 at a location at which the distance C is smallest, while the blank 200 is not pressed up to the vicinity of the edge 24 of the die 20 at adjacent locations to the location. Accordingly, it is possible both to apply a compressive stress to the sheet-thickness-reduced portion in the blank 200 in the sheet thickness direction and to cause material flow. Accordingly, when the edge 24 closer to the punch 10 is subjected to draw forming by using the die 20 that includes the curved portion 241, it is possible to reduce the occurrence of cracking in the blank 200.
• the edge 24 of the die 20 and the edge 34 of the blank holder 30 may be brought closest to each other at the portion at which a reduction in sheet thickness is severe.
• the distance C between the edge 34 of the blank holder 30 and the edge 24 of the die 20 can be smallest at the apex of the curved portion 241 protruding toward the punch 10.
• the distance C between the edge 34 of the blank holder 30 and the edge 24 of the die 20 becomes larger further away from the curved portion 241. In this way, it is possible both to hold the entire portion drawn toward the curved portion 241 in the blank 200 by the blank holder 30 up to the vicinity of the die cavity, closer than portions drawn in the straight portions 242 and 243, and to facilitate material inflow from the periphery of the portion drawn in the curved portion 241 to the portion.
• the line length of a portion at which the distance C to the edge 24 of the die 20 on the edge 34 of the blank holder 30 is smallest is 0.5 times or more to 2.5 times or less the line length of the curved portion 241. In this way, cracking in the blank 200 can effectively be reduced.
• FIG. 5 is a diagram relating to a press forming apparatus 100A according to a second embodiment and is a diagram schematically illustrating a relationship among the punch 10, the die 20, and a blank holder 30A when viewed from the press direction P.
• FIG. 5 is a schematic view illustrating the punch 10, the die 20, and the blank holder 30A as projected onto a plane perpendicular to the press direction P.
• FIG. 5 illustrates the edge 24 of the die 20 in a solid line and the edge 34 of the blank holder 30A in a dashed line.
• the blank holder 30A is hatched.
• the edge 14 of the punch 10 is indicated in a dash-dot line.
• the edge 14 of the punch 10 in FIG. 5 corresponds to the punch side surface 13 in the same plane as the pressing surface 21 of the die 20.
• the press forming apparatus 100A according to the embodiment has basically the same configuration as the press forming apparatus 100 according to the first embodiment ( FIG. 1 to FIG. 3 ). However, the press forming apparatus 100A according to the embodiment includes the blank holder 30A that is different from the press forming apparatus 100 according to first embodiment.
• the blank holder 30A is provided such that, for example, it corresponds to only a part of the region of the edge 24 of the die 20.
• the blank holder 30A is disposed at a position corresponding to the curved portion 241 of the edge 24 of the die 20.
• the distance C between edge 34 of the blank holder 30A closer to the punch 10 and the edge 24 of the die 20 closer to the punch 10 on a perpendicular to the extending direction of the edge 24 of the die 20 varies along the edge 24 of the die 20.
• the curved portion 241 of the edge 24 of the die 20 is substantially parallel to the edge 34 of the blank holder 30A. That is, within the range of the curved portion 241, the distance C between the edge 34 of the blank holder 30A and the edge 24 of the die 20 is substantially constant.
• the straight portions 242 and 243 of the edge 24 of the die 20, which are adjacent to the curved portion 241 are not parallel to the edge 34 of the blank holder 30A.
• the distance C between the edge 34 of the blank holder 30A and the straight portions 242 and 243 becomes larger further away from the curved portion 241.
• the distance C between the edge 34 of the blank holder 30A and the edge 24 of the die 20 is smallest at the curved portion 241 and is substantially constant over the entire curved portion 241. Accordingly, during press forming, the entire portion of the blank drawn in the curved portion 241 can be pressed by the die 20 and the blank holder 30A up to the vicinity of the edge 24 of the die 20. On the other hand, in the straight portions 242 and 243 adjacent to the curved portion 241, the distance C between the edge 34 of the blank holder 30A and the edge 24 of the die 20 expands further away from the curved portion 241.
• the portions in the blank drawn in the straight portions 242 and 243 are not pressed by the blank holder 30A in the vicinity of the edge 24 of the die 20. Accordingly, it is possible to facilitate material inflow from the portions in the blank drawn in the straight portions 242 and 243 to the portion drawn in the curved portion 241. As a result, when the edge 24 closer to the punch 10 is subjected to draw forming by using the die 20 that includes the curved portion 241, it is possible to reduce the occurrence of blank cracking.
• FIG. 6 is a perspective view schematically illustrating a press formed product 400 that is different from the press formed product 300 illustrated in FIG. 4E .
• the press formed product 400 is, for example, a suspension arm component of an automobile.
• the press formed product 400 includes a top plate 401, ridge portions 402, 403, and 404, and flanges 405, 406, and 407.
• the flange 405 is connected to an end edge of the top plate 401 via the ridge portion 402.
• the flange 406 is connected to another end edge of the top plate 401 via the ridge portion 403.
• the flange 407 is connected to still another end edge of the top plate 401 via the ridge portion 404.
• the flanges 405, 406, and 407 are continuous with the ridge portions 402, 403, and 404, respectively, and are provided in a standing manner from the top plate 401.
• FIG. 7 is a diagram relating to a press forming apparatus 100B for forming the press formed product 400 that includes such ridge portion 402 and flange 405.
• FIG. 7 is a diagram for the press forming apparatus 100B, schematically illustrating a relationship among a punch 10B, a die 20B, and a blank holder 30B when viewed from the press direction P.
• FIG. 7 illustrates the edge 24 of the die 20B in a solid line and the edge 34 of the blank holder 30B in a dashed line.
• the blank holder 30B is hatched.
• the edge 14 of the punch 10B is indicated in a dash-dot line.
• the edge 14 of the punch 10 in FIG. 7 corresponds to the punch side surface 13 in the same plane as the pressing surface 21 of the die 20.
• the edge 14 of the punch 10B closer to the die 20B extends along the edge 24 of the die 20B closer to the punch 10B.
• the edge 14 of the punch 10B has a shape corresponding to the edge 24 of the die 20B.
• the edge 24 of the die 20B consists only of the curved portion 241. That is, when viewed from the press direction P, the edge 24 of the die 20B is curved and protrudes toward the punch 10B as a whole and extends with a radius of curvature of less than 400 mm.
• the edge 24 of the die 20B may have a constant radius of curvature or may vary in terms of the radius of curvature.
• the distance C between the edge 34 of the blank holder 30B closer to the punch 10B and the edge 24 of the die 20B closer to the punch 10B is smaller near the center portion and larger near the end portion in the extending direction of the curved portion 241.
• the distance C may become wider gradually toward the end portion in the extending direction of the curved portion 241.
• the distance C is largest at the end portion in the extending direction of the curved portion 241.
• the distance C is smallest, for example, in the curved portion 241 at a portion in the blank at which a reduction in sheet thickness is considered to be severe during press forming.
• the edge 34 of the blank holder 30B is provided such that, for example, it corresponds to only a part of the edge 24 of the die 20B.
• the edge 24 of the die 20B is made up only of the curved portion 241 when viewed from the press direction P, when a perpendicular (normal) to the end portion of the curved portion 241 is drawn, the perpendicular may not intersect with the blank holder 30B.
• the distance C in the perpendicular direction of the curved portion 241 between the end portion of the curved portion 241 and the edge 34 of the blank holder 30B is infinite. Even in this case, it is considered that the distance C is largest at the end portion of the curved portion 241.
• the edge 24 of the die 20B and the edge 34 of the blank holder 30B can be brought closest to each other at the portion at which a reduction in sheet thickness is severe, so that it is possible both to apply a compressive stress in the sheet thickness direction to the portion at which a reduction in sheet thickness is severe and to facilitate material inflow. Accordingly, when draw forming is performed by using the die 20B in which the edge 24 closer to the punch 10B consists only of the curved portion 241, it is possible to reduce the occurrence of blank cracking.
• the blank holder 30B when viewed from the press direction P, has a substantially similar shape to the blank holder 30 ( FIG. 3 ) of the first embodiment. However, the blank holder 30B may have a similar shape to the blank holder 30A ( FIG. 5 ) of the second embodiment when viewed from the press direction P.
• the blank holder may have a shape such that, when viewed from the press direction P, the distance between the edge of the blank holder closer to the punch and the edge of the die closer to the punch varies along the edge of the die closer to the punch and is smallest at the curved portion.
• a blank holder 30C illustrated in FIG. 8 can be used.
• the blank holder 30C has a shape that generally tapers further away from the punch 10 when viewed from the press direction P.
• the distance C between the edge 34 of the blank holder 30C and the edge 24 of the die 20 is smallest at the curved portion 241 when viewed from the press direction P.
• the distance C becomes larger toward opposite end portions in the extending direction of the curved portion 241.
• the distance C becomes larger further away from the curved portion 241.
• a blank holder 30D illustrated in FIG. 9 can be used as well.
• the distance C between the edge 34 of the blank holder 30D and the edge 24 of the die 20 is smallest at the curved portion 241.
• the edge 34 of the blank holder 30D is substantially parallel to a center portion of the curved portion 241.
• the distance C between the edge 34 of the blank holder 30D and the edge 24 of the die 20 becomes larger further away from the curved portion 241.
• a blank holder 30E illustrated in FIG. 10 a blank holder 30F illustrated in FIG. 11 , or a blank holder 30G illustrated in FIG. 12 can be used as well.
• the edge 34 of each of the blank holders 30E, 30F, and 30G is substantially parallel to the entire curved portion 241.
• the distance C between the edge 34 of each of the blank holders 30E and 30F and the edge 24 of the die 20 is larger at the straight portions 242 and 243 than the curved portion 241.
• the distance C becomes larger further away from the curved portion 241.
• the distance C between the edge 34 of the blank holder 30G and the edge 24 of the die 20 rapidly increases (infinite) at certain points P1 and P2.
• the blank holders 30C to 30G can also be applied to the case in which, as in the third embodiment, the edge 24 of the die 20B closer to the punch 10B consists only of curved portion 241.
• the blank holders 30 and 30A to 30G may have a symmetrical shape with respect to the perpendicular (normal) at the apex of the curved portion 241 when viewed from the press direction P.
• the blank holders 30 and 30A to 30G may not necessarily have a symmetrical shape when viewed from the press direction P. It is enough that the edge 34 of each of the blank holders 30 and 30A to 30G is closest to the edge 24 of the die 20B in at least a part of the curved portion 241, and the edge 34 may not necessarily be closest to the edge 24 of the die 20 or the die 20B at the apex of the curved portion 241.
• a protruding portion 35 can be provided on a surface that faces the die 20 or the die 20B in the press direction P.
• an edge of the protruding portion 35 closer to the punch 10 when viewed from the press direction P can be considered as the edge 34 of the blank holder 30H.
• the protruding portion 35 has a similar shape to the blank holder 30 in the first embodiment when viewed from the press direction P.
• the shape of the protruding portion 35 is not limited thereto.
• the protruding portion 35 can have a similar shape to any of the blank holders 30A to 30G when viewed from the press direction P.
• the shapes of the blank holders 30 and 30A to 30G can be altered as needed depending on the shape of the edge of the die closer to the punch or a portion in the blank at which a reduction in sheet thickness is severe.
• a blank holder that has a rectangular shape or a trapezoidal shape when viewed from the press direction P can be used.
• the blank holder may have any shape such as a semicircular shape or a semi-elliptical shape when viewed from the press direction P.
• the blank holder is configured such that the edge of the blank holder closer to the punch and the edge of the die closer to the punch are brought closest to each other at a part or all of the curved portion when viewed from the press direction P.
• a plate may be installed on a holddown surface of a blank holder provided on the existing press forming apparatus.
• the edge of the blank holder closer to the punch faces the edge of the die closer to the punch substantially over the entire edge thereof, and the distance between the edge of the blank holder and the edge of the die is constant.
• a plate is installed on a holddown surface of the blank holder. In this way, the edge of the plate closer to the punch when viewed from the press direction can be considered as the edge of the blank holder.
• a protruding portion may be formed by shaving the holddown surface of the blank holder, or the like.
• the edge of the protruding portion formed on the holddown surface of the blank holder can be considered as the edge of the blank holder.
• the die 20 and the blank holder 30 may be provided only on one side of the punch 10 in the width direction of the press forming apparatus 100.
• the blank holder 30 is provided on one side of the punch 10 and any of the blank holders 30A to 30G may be provided on the other side.
• the number or positions of the blank holders can be altered as needed, for example, depending on the number or positions of the curved portions 241.
• the press forming apparatus according to the present disclosure for example, as illustrated in FIG.
• blank holders 41 and 42 that are separate from the blank holder 30E can be provided adjacently to the blank holder 30E, in which the edge 34 closer to the punch 10 is closest to the edge 24 of the die 20 closer to the punch 10 at the curved portion 241 when viewed from the press direction P.
• the blank holders 41 and 42 are provided next to the blank holder 30E when viewed from the press direction P. Even in this case, since the blank holder 30E is operative independent of the blank holders 41 and 42, a sheet-thickness-reduced portion in the blank 200 drawn toward the curved portion 241 of the edge 24 of the die 20 can be pressed by the blank holder 30E up to the vicinity of the curved portion 241.
• the blank holder 30E similar to the one in FIG. 10 is exemplified as blank holder for holding the blank 200 in which drawing toward the curved portion 241 occurs.
• the blank holders 41 and 42 that are separate therefrom can also be provided.
• the press forming apparatus 100 may further be provided with a pad 50 facing the punch 10 in the press direction P.
• the pad 50 can relatively approach the punch 10 in the press direction P and hold the blank 200 on the punch 10.
• the press forming apparatuses 100A and 100B according to other embodiments can be provided with the pad 50.
• the present inventors chose to express the length of a section (line length) that makes the distance smallest between the edge of the die closer to the punch and the edge of the blank holder closer to the punch when viewed from the press direction as a ratio relative to the extending length (line length) of the curved portion included on the edge of the die closer to the punch.
• the extending length (line length) of the curved portion was assumed to be a product of an angle formed between intersecting tangential lines of opposite end portions of the curved portion (included angle ⁇ (rad)) and the radius of curvature of the curved portion.
• ⁇ angle formed between intersecting tangential lines of opposite end portions of the curved portion
• the length of a section (line length) that makes the distance smallest between the edge of the die closer to the punch and the edge of the blank holder closer to the punch/the line length of the curved portion being smaller than 1.0 means that the edge of the die and the edge of the blank holder are closest to each other at a part of the curved portion.
• the length of a section (line length) that makes the distance smallest between the edge of the die closer to the punch and the edge of the blank holder closer to the punch/the line length of the curved portion being 1.0 means that the edge of the die and the edge of the blank holder are closest to each other over all the curved portion.
• the length of a section (line length) that makes the distance smallest between the edge of the die closer to the punch and the edge of the blank holder closer to the punch/the line length of the curved portion being more than 1.0 means that the edge of the die and the edge of the blank holder are closest to each other over all the curved portion and in part of the straight portions adjacent to the curved portion.
• the press forming analysis was conducted for the following cases: the case in which the edge of the blank is removed between the die and the blank holder to complete the forming; and the case in which the forming is completed with the edge of the blank kept clamped between the die and the blank holder. Furthermore, the analysis was conducted in cases in which the included angle ⁇ for the curved portion on the edge of the die when viewed from the press direction was 60°, 90°, and 120°.
• FIG. 18 shows analysis results when the blank is removed from between the die and the blank holder to complete the forming.
• FIG. 19 shows analysis results when the forming is completed with the blank kept clamped between the die and the blank holder.
• the damage values I were lower in the press forming according to the present disclosure than typical draw forming.
• the line length of a section (closest section) that makes the distance smallest between the edge of the die closer to the punch and the edge of the blank holder closer to the punch/the line length of the curved portion was 0.5 or more to 2.5 or less, the rate of reduction of the damage value I with respect to typical draw forming was significantly improved.
• the line length of a portion on the edge of the blank holder closer to the punch, at which the distance to the edge of the die closer to the punch is smallest, when viewed from the press direction is preferably 0.5 times or more to 2.5 times or less the line length of the curved portion provided on the edge of the die.

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• Shaping Metal By Deep-Drawing, Or The Like (AREA)

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• 2022
  • 2022-09-21 EP EP22959539.2A patent/EP4592001A4/de active Pending
  • 2022-09-21 CN CN202280100043.XA patent/CN119894619A/zh active Pending
  • 2022-09-21 JP JP2024548012A patent/JPWO2024062575A1/ja active Pending
  • 2022-09-21 WO PCT/JP2022/035261 patent/WO2024062575A1/ja not_active Ceased

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