JP2012071338A - Press molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of performing molding without causing breakage at a corner part at a low cost, in press molding wherein a material is made to flow in from a bottom face to a vertical wall part.SOLUTION: A plurality of fragile parts (hole parts 12) are previously formed in a region corresponding to the bottom face 3 of a blank 10. By setting the number, position and form of the fragile parts appropriately, flow rate A of the material of the bottom face 3 flowing in the direction orthogonal to an outer edge 4 toward a straight part 9 is so controlled as to be larger than flow rate B of the material of the bottom face flowing in the direction orthogonal to the outer edge 4 toward the corner part 8, so that the material of the straight part 9 is fed to the corner part 8.

Description

  The present invention relates to a press forming method by drawing, and more particularly to a press forming method for extending a vertical wall portion by allowing a material to flow into the vertical wall portion from a bottom surface.

  The press forming by drawing is a method of forming a predetermined shape while pressing a blank material and stretching a vertical wall portion. For example, Patent Document 1 discloses a method of preventing the occurrence of wrinkles and cracks by adjusting the bead shape and the like to control the inflow amount of the material. Patent Document 2 discloses a method of preventing the occurrence of wrinkles and cracks by adjusting the holder pressure of the blank material to control the inflow amount of the material.

Japanese Patent Laid-Open No. 10-202326 JP 2002-86219 A

  In press molding by drawing, the vertical wall is usually stretched while the material is introduced from the outer region of the vertical wall. However, for example, when the vertical wall portion is doubled like a back door inner of an automobile (refer to the vertical wall portion 5 and the vertical wall portion 7 in FIG. 2), the material from the outer region to the outer vertical wall portion However, since the material flow from the outer region is inhibited by the outer vertical wall portion, it is difficult to flow the material from the outer region to the inner vertical wall portion. For this reason, the inner vertical wall portion is stretched while the material flows in from the inner region (bottom surface 3) of the vertical wall portion.

  In this way, in the press molding in which the material flows into the vertical wall portion from the bottom surface, when the outer edge 102 of the bottom surface 101 is composed of the corner portion 103 and the straight portion 105 as shown in FIG. 14, as shown in FIG. In the vicinity of the straight portion 105, the material is not stretched in the extending direction of the outer edge 102 and is pulled in a direction orthogonal to the outer edge 102 (L1 = L1 ′), but the material is extended in the vicinity of the corner portion 103 of the bottom surface 101. Since it is pulled in the direction perpendicular to the outer edge 102 while being stretched in the present direction, breakage is likely to occur (L2 <L2 ′). For this reason, the bottom face 101 could not be sufficiently stretched, and only a product with a small drawing depth (height of the vertical wall portion) could be formed.

  Further, as described above, in the vicinity of the straight portion 105 of the bottom surface 101, the material moves in a direction perpendicular to the outer edge 102, and thus the flow resistance of the material is small. On the other hand, in the vicinity of the corner portion 103 of the bottom surface 101, the material is pulled in the direction orthogonal to the outer edge 102 while being stretched in the extending direction of the outer edge 102, so that the flow resistance of the material in the direction orthogonal to the outer edge 102 is relatively large. . As described above, the flow resistance of the material in the direction orthogonal to the outer edge 102 is different between the vicinity of the straight line portion 105 and the corner portion 103, so that the flow amount in the same direction becomes non-uniform. In this case, for example, by providing a bead on the bottom surface 101 (see Patent Document 1) or adjusting a holder pressure (see Patent Document 2), the material flow in the straight portion 105 is regulated, and the material flow in the bottom surface 101 is performed. It is also possible to make the amount uniform. However, even if the amount of flow of the material is made uniform, the situation in which the material is pulled in the extending direction of the outer edge 102 in the vicinity of the corner portion 103 does not change, so that breakage in the vicinity of the corner portion 103 cannot be prevented. Rather, the flow of the material from the bottom surface 101 to the vertical wall portion 104 is reduced by preventing the flow of the material in the straight portion 105 by the bead or the holder pressure, and the vertical wall portion 104 may be broken.

  Further, when controlling the flow of the material on the bottom surface by means of a bead, it is necessary to provide a holder for pressing the bottom surface from both sides and form the bead on this holder. Moreover, when controlling the flow of the material on the bottom surface by the holder pressure, it is necessary to provide a plurality of holders that hold the bottom surface from both sides and control the pressure of each holder. In any case, since it is necessary to provide a holder for pressing the bottom surface separately from the blank holder that holds the end of the blank material, the apparatus cost is increased. In particular, when controlling the material flow with the holder pressure, it is inevitable that the holder pressure slightly changes with each press molding, so it is difficult to press mold under stable conditions, which may cause variations in quality. is there.

  In the press molding in which the material flows into the vertical wall portion from the bottom surface, the present invention can be molded even with a product with a deep drawing depth without causing breakage in the corner portion or the vertical wall portion. It aims to provide a method that can be produced.

  In order to achieve the above object, the present invention provides a product having a bottom surface having a corner portion having a larger curvature than other regions in a part of the outer edge and a vertical wall portion rising from the outer edge of the bottom surface. This is a press molding method in which the material of the bottom surface is caused to flow into the vertical wall portion by drawing the material, and a plurality of weakened portions are formed in advance in a region corresponding to the bottom surface of the blank material, thereby The flow of the material is controlled so that the material in the vicinity of the straight line portion wraps around the corner portion.

  As described above, in the press molding method according to the present invention, when the material of the bottom surface is caused to flow into the vertical wall portion and the molding is performed, the material near the straight portion of the bottom surface is made to wrap around the corner portion at the time of press molding. It is possible to sufficiently supply the material to prevent breakage at the corner (see FIG. 10).

  Incidentally, in the press molding of the product shown in FIG. 14, in the latter half of the press (immediately before the press is completed), the outer edge 102 of the bottom surface 101 is almost completely bent to prevent the flow of the material. It is very difficult to get around. Therefore, it is desirable to supply the material from the straight portion on the bottom surface to the corner portion as described above at the initial stage of pressing. Therefore, in the press molding method of the present invention, a plurality of fragile portions are formed in advance in a region corresponding to the bottom surface of the blank material, and the number, position, and shape of the fragile portions are appropriately set, so that the material on the bottom surface To control the flow rate. In this way, it is possible to stretch the bottom surface in the initial stage of pressing by forming the fragile portion and promoting the flow of the material, rather than hindering the flow of the material by the bead or the holder pressure. Further, by controlling the flow of the material on the bottom surface by forming the fragile portion, it is not necessary to provide a holder for pressing the bottom surface, so that an increase in device cost can be avoided. Furthermore, by controlling the flow of the material not at the holder pressure but at the fragile portion on the bottom surface, it is possible to produce under stable molding conditions if only the specifications of the fragile portion on the bottom surface are determined.

  In the above press molding method, by forming a plurality of fragile portions in the region corresponding to the bottom surface of the blank material in advance, the corner is more than the amount of flow of the material on the bottom surface that flows in the direction perpendicular to the outer edge toward the corner portion. It is possible to control so that the amount of flow of the material on the bottom surface that flows in the direction orthogonal to the outer edge toward the region other than the portion increases. In this way, instead of equalizing the flow amount of the material in the corner portion and other regions (for example, the straight portion), the material of the straight portion is circulated into the corner portion by intentionally expanding the difference in the flow amount. be able to.

  The fragile portion may be anything that reduces the tensile strength of the blank material, for example, a hole or slit that penetrates the blank material, or a thin wall formed by partially removing the surface of the blank material by machining or the like It can consist of parts.

  As described above, according to the press molding method according to the present invention, by forming a fragile portion on the bottom surface and causing the material near the straight portion on the bottom surface to flow toward the corner portion, the corner portion and the vertical wall portion It prevents breakage and can be molded even for products with deep drawing depth. In addition, since the holder for sandwiching the bottom surface can be omitted, the apparatus cost can be reduced, and production can be performed under stable conditions regardless of the holder pressure.

It is a front view of a back door inner. It is sectional drawing in the XX line of FIG. It is sectional drawing in the YY line | wire of FIG. It is a top view of the blank material used for the press molding method which concerns on embodiment of this invention. It is sectional drawing of the press molding die of a back door inner. It is sectional drawing which shows the mode of press molding using the metal mold | die of FIG. It is sectional drawing which shows the mode of press molding using the metal mold | die of FIG. It is sectional drawing which shows the mode of press molding using the metal mold | die of FIG. It is an expanded sectional view of FIG. It is a top view of the blank material 10 of the state of FIG. It is a top view near a hole. It is a top view of the blank material used for the press molding method which concerns on other embodiment. It is a top view which shows the state which extended the blank material of FIG. 12 by drawing. It is a perspective view of the workpiece | work which has a corner part in the outer edge of a bottom face. It is a top view of the corner vicinity at the time of press-molding the workpiece | work of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  In the present embodiment, a method for press-molding a back door inner 1 of an automobile as shown in FIGS. The back door inner 1 is formed by drawing a flat blank material, and includes a bottom surface 3 having a window hole 2 on which glass is mounted and an outer side of the outer edge 4 of the bottom surface 3 (see FIG. 2). An annular vertical wall portion 5 rising upward (left side in FIG. 3), a flat portion 6 extending outward from an inner side end of the vertical wall portion 5, and an outer side from the outer edge of the flat portion 6 (downward in FIG. 2) , And a vertical wall portion 7 rising on the right side of FIG. A corner portion 8 having a larger curvature than other regions is formed in a part of the outer edge 4 of the bottom surface 3, and the outer edge 4 of the bottom surface 3 in the illustrated example has a substantially rectangular shape including a straight portion 9 and a corner portion 8. is doing.

  Hereinafter, a press molding method according to an embodiment of the present invention will be described. First, prior to press molding, as shown in FIG. 4, in the blank material 10, a region corresponding to the bottom surface 3 of the molded product (back door inner 1), particularly a region 11 corresponding to the window hole 2 (indicated by a dotted line). The hole 12 as a plurality of weak parts is formed. In the illustrated example, the hole 12 having an elliptical shape or an elongated track shape is provided.

  The press molding according to the present embodiment is performed using a mold shown in FIG. This mold includes a punch 20 that is a fixed side, a die 30 that is a movable side, and a blank holder 40 that sandwiches an end portion of the blank material 10. The punch 20 is provided with a vertical wall portion 5, a flat portion 6, and a convex portion 21 for forming the vertical wall portion 7 of the back door inner 1. The die 30 is provided with a concave portion 31 in which the convex portion 21 is fitted to form the vertical wall portion 5, the flat portion 6, and the vertical wall portion 7, and a molding surface 32 for molding the bottom surface 3 on the blank material 10. It is done. The blank holder 40 includes a lower holder 41 provided to be movable up and down with respect to the punch 20 and an upper holder 42 provided to be movable up and down with respect to the die 30. The configuration of the mold is not limited to the above. For example, the upper mold holder 42 may be provided integrally with the die 30.

  First, as shown in FIG. 6, the die 30 and the upper holder 42 are lowered with the blank 10 placed on the fixed punch 20 and the lower holder 41. Then, the entire circumference of the end portion of the blank 10 is sandwiched and fixed by the upper holder 42 and the lower holder 41.

  When the die 30 and the upper holder 42 are further lowered, as shown in FIG. 7, the convex portion 21 of the punch 20 and the concave portion 31 of the die 30 start to be fitted. At this time, the outer vertical wall portion 7 begins to be molded, and the molding surface 32 of the die 30 is pressed against the blank material 10 and stretched, and the bottom surface 3 begins to be molded.

  When the die 30 and the upper holder 42 are further lowered, the inner vertical wall portion 5 starts to be molded as shown in FIG. Specifically, as shown in an enlarged view in FIG. 9, the vertical wall portion 5 is stretched while the material flows into the vertical wall portion 5 from the bottom surface 3. At this time, as shown in FIG. 10, a plurality of hole portions 12 are formed in advance in a region 11 corresponding to the window hole 2 spaced inward from the outer edge 4 in the bottom surface 3 of the blank material 10. To the outside is promoted, and the material easily flows into the vertical wall portion 5. In particular, the material of the bottom surface 3 that flows in the direction orthogonal to the outer edge 4 toward the straight portion 9 (the white arrow in FIG. The flow amount of A) is controlled to be larger than the flow amount of the material of the bottom surface 3 (shown by the white arrow B in FIG. 10) that flows in the direction orthogonal to the outer edge 4 toward the corner portion 8. ing. In the illustrated example, the number, position, and number of the plurality of hole portions 12 are set so that the tensile strength in the vertical direction and the left-right direction in the drawing passing through the center portion of the bottom surface 3 is weaker than the tensile strength in the diagonal direction of the bottom surface 3. The shape is set. In this way, the flow of the material toward the straight portion 9 is promoted, and the flow of the material toward the corner portion 8 is relatively restricted, so that the material of the bottom surface 3 is cornered from the straight portion 9 near the outer edge 4. It turns around toward the part 8 (refer to the chain line arrow in FIG. 9). Thereby, the material is sufficiently supplied to the corner portion 8 and breakage at the corner portion 8 can be prevented.

  Further, since the plurality of hole portions 12 are provided as described above, the elongation of the bottom surface 3 is promoted, so that the bending angle of the outer edge 4 of the bottom surface 3 is small (see FIG. 9), that is, the material of the bottom surface 3 Since the material can sufficiently flow from the straight line portion 9 to the corner portion 8 before the flow is restricted by the outer edge 4, the breakage at the corner portion 8 can be reliably prevented.

  Further, as shown in FIG. 10, by making the plurality of hole portions 12 non-circular (in the illustrated example, an oval shape or an elongated track shape), the effect of promoting the elongation of the bottom surface 3 by each hole portion 12 is made anisotropic. You can have it. For example, as shown in FIG. 11, when one elliptical hole 12 is provided in the rectangular area P, the tensile strength of the rectangular area P in the long side direction C of the elliptical hole 12 is the short side direction. It becomes larger than the tensile strength of the rectangular region P in D. Thus, by giving anisotropy to the shape of each hole 12, the degree of design freedom when a plurality of such holes 12 are combined is widened, and the flow amount of the material of the bottom surface 3 can be easily controlled.

  As described above, by controlling the flow of the material of the bottom surface 3 with the plurality of holes 12, it is possible to omit the holder that moves up and down with respect to the punch 20 and the die 30 and sandwiches the bottom surface 3 from above and below. The cost of the device (mold) can be reduced. Further, as long as the predetermined number, position, and shape of the hole portions 12 are formed in the blank member 10, press molding can be performed under stable conditions, so that the quality can be stabilized.

  Moreover, the inflow of the material from the flat part 6 to the vertical wall part 5 can be suppressed by flowing the material into the vertical wall part 5 from the bottom surface 3 as described above. For this reason, the stretch amount of the flat part 6 becomes small, and the smoothness fall by generation | occurrence | production of wrinkles etc. can be prevented. The flat portion 6 may function as a hermetic seal surface when the back door of the automobile is closed. Even in this case, the sealing property can be improved by increasing the smoothness of the flat portion 6 as described above. .

  Then, the die 30 and the upper holder 42 are further lowered, and the bottom surface 3, the inner vertical wall portion 5, the flat portion 6, and the outer vertical wall portion 7 are sandwiched between the die 30 and the punch 20 to perform press molding. Is completed (not shown). Then, the back door inner 1 shown in FIG. 1 is completed by removing an unnecessary part (the window hole 2 and the outer area | region of a product) among the molded products taken out from the metal mold | die.

  The present invention is not limited to the above embodiment. For example, a slit 13 as shown in FIG. 12 can be provided as a weakened portion provided in a region corresponding to the bottom surface 3 of the blank material 10. Specifically, slits 13 extending in a direction parallel to the straight line portion 9 of the outer edge 4 of the bottom surface 3 are formed inside the straight line portions 9 at positions avoiding diagonal lines of the bottom surface 3. When this blank material 10 is press-molded, the bottom surface 3 is stretched, and each slit 13 spreads in a direction orthogonal to each linear portion 9 as shown in FIG. Thereby, the flow of the material toward the straight portion 9 on the bottom surface 3 is promoted (white arrow A), and the flow of the material toward the corner portion 8 is relatively regulated (white arrow B). As a result, the material flows from the straight line portion 9 toward the corner portion 8 (dashed line arrow), and breakage at the corner portion 8 is prevented.

  In the above embodiment, the holder for sandwiching the bottom surface from above and below is omitted. However, this is not necessarily omitted. A holder for controlling the flow may be provided. However, since it is necessary to sufficiently stretch the bottom surface 3 to prevent breakage at the corner portion 8 in the initial stage of pressing, the holder preferably holds the bottom surface 3 in the latter half of the press (just before mold clamping).

  The product to which the press molding method according to the present invention can be applied is not limited to the back door inner 1, but any product that has a corner portion on the outer edge of the bottom surface and flows the material from the bottom surface to the vertical wall portion. Other parts are also applicable.

DESCRIPTION OF SYMBOLS 1 Back door inner 2 Window hole 3 Bottom face 4 Outer edge 5 Vertical wall part 6 Flat part 7 Vertical wall part 8 Corner part 9 Straight line part 10 Blank material 11 Area | region 12 equivalent to a window hole (fragile part)
13 Slit (fragile part)
20 Punch 21 Convex 30 Die 31 Concave 32 Molding Surface 40 Blank Holder 41 Lower Holder 42 Upper Holder

Claims (2)

A product having a bottom surface with a corner portion with a larger curvature than other regions at a part of the outer edge and a vertical wall portion rising from the outer edge of the bottom surface is subjected to drawing processing on the blank material so that the material on the bottom surface becomes a vertical wall. A press molding method of molding while flowing into a part,
A press molding method for controlling the flow of a material so that a material in the vicinity of the straight line portion of the bottom surface wraps around the corner portion by forming a plurality of fragile portions in a region corresponding to the bottom surface of the blank material in advance.   By forming a plurality of fragile portions in the region corresponding to the bottom surface of the blank material in advance, the amount of flow of the bottom surface material flowing in the direction perpendicular to the outer edge toward the corner portion is directed toward the region other than the corner portion. 2. The press molding method according to claim 1, wherein the amount of flow of the bottom surface material flowing in a direction orthogonal to the outer edge is controlled to be increased.

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