JP2017148847A - Press forming die - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a press forming die capable of forming a corner flange part in one step, preventing stretch flange crack by suppressing localization of strain at or near the center of a corner caused by elongation deformation, and improving both quality and productivity.SOLUTION: A press forming die 1 capable of forming a corner flange portion 42 standing from an inner end edge 43 of an inward corner portion 41 comprises a die 2 having a die corner portion 21 and a punch 3 having a punch corner portion 31. The punch corner portion has a contour shape having a recess 32c between two arc-shaped projections 32a and 32b on both sides of a corner center C1 on a tip surface 33 of a stroke direction X, and in the contour shape of a cross section in parallel with the tip surface, the more away the cross section is from the tip surface, the smaller the projections are, and the two aic-shaped projections are close to each other to converge into an outward corner shape.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a press mold for extending and flange-forming a flange portion standing from an edge of a corner portion.

  In recent years, aluminum alloy plates have been applied to automobile parts in order to reduce vehicle weight. For example, when a flange portion is formed in a glass opening for a sunroof as an automobile part, a vertical wall-shaped flange portion along a rectangular hole is generally formed by rectangular burring. The aluminum alloy plate is preliminarily provided with a rectangular hole by punching or cutting, and by pushing a rectangular punch larger than the rectangular hole, the hole edge of the rectangular hole is pushed and bent in the punch traveling direction to form a flange portion. .

  In that case, since an aluminum alloy plate is inferior in stretch flangeability compared with a mild steel plate, the stretch flange crack in a corner part tends to become a problem. For example, in the case of a rectangular hole, the hole edge at the straight side is a simple flange forming that is bent in the direction of punch movement, but the blank edge of the corner edge is stretched in a direction perpendicular to the direction of punch movement. It becomes stretch flange molding that can be pushed and bent. Therefore, the corner radius and the flange length are limited at the corner portion.

  On the other hand, various techniques for preventing stretch flange cracking have been studied in press molding with stretch flange molding. For example, in Patent Document 1, a step of specifying the position of a flange portion that undergoes an extension deformation more than a preset value as a maximum extension flange deformation portion, and a plate thickness direction with respect to both sides or one side of the specified maximum extension flange deformation portion. And a pre-deformation step of forming a deformed pre-deformation portion, and after forming the pre-deformation portion, a method of performing a flange forming process as a final forming step is disclosed.

Japanese Patent Laying-Open No. 2015-139783

  However, in the method described in Patent Document 1, in the pre-deformation step, the pre-deformation portion is greatly deformed on the plate edge side, and the cross-section line length increase amount in the pre-deformation step is set to be equal to or less than the cross-section line length increase amount in the molded product However, a specific forming method therefor is not shown. In addition, a plurality of processes including a pre-deformation process and a final molding process are required, which is disadvantageous from the viewpoint of equipment cost and productivity. Furthermore, since it is difficult to form an aluminum alloy plate as compared with a steel plate, there is a problem that the desired forming cannot be performed by the above method.

  The present invention has been made in view of such a background, and a corner flange portion with stretch flange molding can be molded in one step, and strain flange localization is suppressed to prevent stretch flange cracking. It is possible to provide a press mold that can achieve both quality and productivity.

One aspect of the present invention is a press mold that can mold a corner flange portion standing up from an inner edge of an inward corner portion,
A die having a die corner portion along the inward corner portion, and a punch having a punch corner portion cooperating with the die corner portion;
The punch corner portion is composed of two arc-shaped convex portions arranged on both sides of the corner center on the front end surface in the relative stroke direction of the punch and a concave portion formed between the two arc-shaped convex portions. Has a contour shape,
The contour shape of the cross section parallel to the tip surface is a press mold in which the concave portion becomes smaller and the two arc-shaped convex portions approach and converge to an outward corner shape as the cross section moves away from the tip surface. is there.

  In the press mold, the tip surface of the punch corner has a contour shape consisting of two arc-shaped convex portions and a concave portion between them, so that the punch moves relative to the die by holding the blank sheet between the die and the blank holder. When doing so, first, the two arc-shaped convex portions first come into contact with the blank sheet on both sides of the corner center. Moreover, since the recessed part between two arc-shaped convex parts becomes so small that it leaves | separates in a stroke direction from a front end surface, the area | region contact | abutted with a blank sheet | seat gradually spreads to a corner center as press molding progresses. Therefore, when the punch corner portion advances while expanding the inner edge of the inward corner portion of the blank sheet, the portion corresponding to the corner center of the blank sheet is not initially formed, and the portions at both ends of the corner are Molded by two arc-shaped protrusions.

  After that, the two arc-shaped convex parts approach and converge to the outward corner shape, so that they are also molded at the center of the corner. Therefore, an increase in the line length of the flange portion is suppressed at the corner center and the vicinity thereof. As a result, strain localization is suppressed, and stretch flange cracking can be prevented. Therefore, the flange portion standing from the inner edge of the inward corner portion can be formed in one process, and a high-quality product can be manufactured with high productivity.

FIG. 3 is a perspective view illustrating a schematic structure of a main part of a press mold according to the first embodiment. The whole perspective view which shows the structure of the principal part of the punch which comprises the press molding die in Embodiment 1. FIG. The top view which shows the whole blank sheet | seat shape shape | molded with the press mold in Embodiment 1. FIG. The principal part enlarged plan view which shows the shape before and behind shaping | molding of the blank sheet shape | molded by the press molding die in Embodiment 1. FIG. The top view which shows the outline shape of the punch corner part in the front end surface of a punch in Embodiment 1, and the outline shape change of the punch corner part in the cross section parallel to a front end surface. FIG. 3 is a perspective view of a main part showing a positional relationship before forming a punch and a die constituting the press mold in Embodiment 1. The principal part perspective view for demonstrating the press molding method in Embodiment 1. FIG. The principal part expansion perspective view which shows the positional relationship before shaping | molding of a punch and a blank sheet in Example 1. FIG. The principal part expansion perspective view which shows the state in the middle of shaping | molding of a punch and a blank sheet in Example 1. FIG. The principal part expansion perspective view which shows the state after the completion of shaping | molding of a punch and a blank sheet in Example 1. FIG. The principal part expanded sectional view which shows the molding state of the blank sheet | seat in the corner center of a punch with Example 1 and the position of R stop in Example 1. FIG. The whole perspective view which shows the structure of the conventional punch in the comparative example 1. FIG. The principal part perspective view which shows the positional relationship before the shaping | molding of the conventional punch and a blank sheet in the comparative example 1. FIG. The principal part expansion perspective view which shows the state in the middle of shaping | molding of the conventional punch and blank sheet in the comparative example 1. FIG. The principal part expansion perspective view which shows the state in the middle of shaping | molding of the conventional punch and blank sheet in the comparative example 1. FIG. The principal part expanded sectional view which shows the molding state of the blank sheet | seat in the corner center of a punch with the stroke of a punch in the comparative example 1, and the position of R stop. The figure which shows the ratio with respect to the corner radius of a punch corner part in the corner | angular center of a punch in the Example and a comparative example, the corner radius, and the shoulder radius in the position of R stop.

  In the press mold, it is preferable that the punch shoulder portion, which is the portion where the tip end surface and the side end surface intersect, in the punch corner portion has a shoulder radius that is closer to the corner center. Thereby, it becomes the outline shape which a recessed part becomes small as progress of press molding, and the effect which suppresses distortion is high.

  Moreover, it is preferable that the shoulder radius in the R stop which is a corner both ends of the said punch corner part is 20% or less of the corner radius of the said inward corner part. In this case, press molding proceeds early in the vicinity of the R stop. Thereby, at the R stop where the strain becomes relatively small, stretch flange molding is actively performed, and an increase in strain can be prevented at the corner center and its vicinity, that is, strain localization can be suppressed.

  Further, the punch corner portion preferably has a shoulder radius at the corner center of 80% to 100% of the corner radius of the inward corner portion. In this case, the recess becomes larger at the corner center. This makes it possible to delay stretch flange molding at the corner center and suppress strain localization at the corner center and its vicinity by performing aggressive stretch flange molding before reaching the corner center. .

  Moreover, as a blank sheet which provides the said inward corner part, although a various metal plate is employable, especially in the case of an aluminum alloy plate, utilization of the said press mold is effective.

(Embodiment 1)
Next, Embodiment 1 according to the press mold will be described with reference to the drawings.
As shown in FIGS. 1 and 2, the press mold 1 includes a die 2 having a die corner portion 21 and a punch 3 having a punch corner portion 31 that cooperates with the die corner portion 21. A blank sheet 4 having an inward corner portion 41 is disposed between the die 2 and the punch 3. The press mold 1 is configured so that the punch 3 is moved relative to the die 2 with the direction perpendicular to the plate surface of the blank sheet 4 as the stroke direction X (that is, the vertical direction in the figure). The direction corner portion 41 and the right side portions 4S at both ends thereof are press-molded into a desired flange shape.

  1 and 2 show the main part of the press mold 1 of the blank sheet 4 having rectangular holes with four corners having an R shape. FIG. 3 is an example of the blank sheet 4, and a part of the mold 1 that molds the ¼ shape (for example, the shape defined by the dotted line in FIG. 3) is shown in FIGS. 1 and 2. . FIG. 4 is an enlarged view of one of the inward corner portions 41 of the blank sheet 4.

  As shown in FIGS. 3 and 4, the contour line of the die corner portion 21 (for example, indicated by a broken line in FIGS. 3 and 4) has a shape along the inward corner portion 41 of the blank sheet 4. By the press forming of the blank sheet 4, the inward corner portion 41 is bent at the position of the contour line of the die corner portion 21, and the corner flange portion 42 that rises with the bending position as the inner edge 43 is formed. The corner flange portion 42 rises in the stroke direction X from the ab plane including the a direction and the b direction which are the directions of the two sides of the blank sheet 4 and are orthogonal to each other. The inward corner portion 41 having such a corner flange portion 42 can constitute each corner portion of a rectangular opening portion in, for example, a glass opening portion for a vehicle sunroof.

  The blank sheet 4 may be made of a plate material made of a material other than the aluminum alloy, for example, a mild steel plate. The aluminum alloy plate is effective for reducing the weight, but the effect of applying the present invention is great because the stretch flangeability is inferior to that of a mild steel plate. The die 2 and the punch 3 of the press mold 1 can be made of a well-known steel material for dies.

  In FIG. 1, a block-shaped die 2 has a rectangular cylinder hole 2A that is substantially similar to a rectangular hole 4A (see, for example, FIG. 3) in which four corners of a blank sheet 4 are R-shaped and slightly larger than the rectangular hole 4A. Have. In the die 2, an inward corner portion constituting the cylindrical wall of the rectangular tube hole 2 </ b> A is a die corner portion 21 along the inward corner portion 41 of the blank sheet 4. The rectangular hole 4A of the blank sheet 4 is located inside the rectangular cylinder hole 2A. Further, a block-shaped punch 3 is arranged inside the rectangular tube hole 2A, and relative operation is possible with the axial direction of the rectangular tube hole 2A as the stroke direction X. In the punch 3, a punch corner portion 31 having an outward corner-shaped outer shape is disposed to face the die corner portion 21.

  A blank holder 5 on which the blank sheet 4 is placed is provided below the die 2 so as to be movable up and down. In the state before the press molding shown in the drawing, the blank sheet 4 is sandwiched between the die 2 and the blank holder 5, and a hole edge of a predetermined width along the rectangular hole 4 </ b> A protrudes inside the die 2, and punch 3 Is located above.

  In FIG. 2, the punch 3 has straight side portions 35 on both sides of the punch corner portion 31 formed on the tip surface 33 (that is, the upper surface in the drawing) 33 in the relative stroke direction X. The punch corner portion 31 has a contour shape including two arc-shaped convex portions 32a and 32b disposed on both sides of the corner center C1 and a concave portion 32c formed between the two arc-shaped convex portions 32a and 32b. Both end portions of the punch corner portion 31, that is, the boundaries between the two arc-shaped convex portions 32a and 32b and the straight side portion 35 are R stops C2 and C3, respectively. The punch 3 has a rectangular block shape along the rectangular tube hole 2A of the die 2, and a part of the punch 3 having one punch corner portion 31 is shown in the drawing.

  Specifically, as shown in FIG. 5, the punch corner portion 31 has a sectional shape parallel to the distal end surface 33, and the concave portion 32 c decreases as the distance from the distal end surface 33 decreases, and two arc-shaped convex portions 32 a, 32b becomes the shape which approaches. The two arc-shaped convex portions 32a and 32b are finally united and the concave portion 32c disappears and converges to a predetermined outward corner shape. The punch 3 has an outer shape similar to the rectangular cylindrical hole 2A of the die 2 from the cross section where the concave portion 32c disappears to the end surface opposite to the tip surface 33, and has a predetermined outward direction along the die corner portion 21. It has a corner shape.

  The punch 3 has a curved punch shoulder portion 3S where the tip end surface 33 and the side end surface 34 intersect, and the shoulder radius Rs of the punch shoulder portion 3S is constant at the straight side portion 35. In the punch corner portion 31, the shoulder radius Rs of the punch shoulder portion 3S changes smoothly toward the corner center C1, and the shoulder radius Rs increases toward the corner center C1. Preferably, the shoulder radius Rs gradually increases gradually from the R stops C2 and C3 of the punch corner portion 31 to the corner 1/4 (that is, the intermediate position between the R stops C2 and C3 and the corner center C1). From / 4 to the corner center C1, the shoulder radius Rs gradually increases so that the change becomes larger.

  As shown in FIG. 6, the die 2 has a curved die shoulder 2S. The die shoulder portion 2S includes a die corner portion 21 and right side portions 22 on both sides thereof, and the shoulder radius of the die shoulder portion 2S is constant. When the punch shoulder portion 3S moves relative to the die shoulder portion 2S, the punch corner portion 31 having a predetermined shoulder radius Rs and the die corner portion 21 cooperate with each other so that the inward corner portion of the blank sheet 4 is formed. 41 is a corner flange portion 42 having a desired corner flange shape. The relationship between the strain at the time of forming the corner flange portion 42 and the shoulder radius Rs of the punch shoulder portion 3S will be described later.

Next, a method for press-molding the blank sheet 4 using the press-molding die 1 having the above configuration will be described.
As shown in the upper diagram of FIG. 7, the punch 3 is disposed below the blank sheet 4, and the punch 3 is moved up and down with the vertical direction as the stroke direction X using a punch driving unit (not shown). When the punch 3 is raised, the punch shoulder 3S comes into contact with the hole edge of the blank sheet 4 positioned in the traveling direction on the front end surface. As shown in the lower part of FIG. 7, the punch shoulder 3 </ b> S pushes the rectangular hole 4 </ b> A of the blank sheet 4 as the punch 3 moves up. Along with this, the hole edge of the blank sheet 4 is bent along the die shoulder 2S (for example, see FIG. 6), and the flange 4F rising from the inner edge 43 at a predetermined height is formed. In the flange portion 4F, a corner flange portion 42 is formed in the inward corner portion 41 by the die corner portion 21 and the punch corner portion 31, and a straight side portion 22 of the die shoulder portion 2S and a straight portion of the punch shoulder portion 3S. The side portion 35 forms a straight-side flange portion 44 following the corner flange portion 42. In FIG. 7, the die 2 and the blank holder 5 are not shown.

  At this time, as indicated by the arrows in FIG. 4 described above, the corner flange portion 42 rises along the corner shape of the die corner portion 21 (for example, corner radius RcDie = 70 mm) while spreading in the circumferential direction. That is, before and after molding, the inward corner portion 41 of the blank sheet 4 that becomes the corner flange portion 42 is stretch flange molding in which the line length of the flange portion increases. When the inner end edge portion (for example, corner radius Rc Blank sheet = 70 mm) of the inward corner portion 41 before molding is stretched and flange molded, the corner radius Rc of the corner flange portion 42 after molding is small, and the flange length L It is confirmed that the larger the is, the greater the strain. The corner radius Rc is substantially equal to the corner radius RcDie of the die corner portion 21, and the flange length L is substantially equal to both end portions of the inward corner portion 41 and the flange length Ls of the right side portion 4S. The flange length Ls is represented by Lc / √2 (for example, 8√2 mm = 11.3 mm) with respect to the flange length Lc (for example, 16 mm) at the corner center.

  On the other hand, for example, when applied to an opening for a vehicle sunroof or the like, the corner flange portion 42 formed in the opening is desired to have a smaller corner radius R and a larger flange length L. ing. For this reason, there is a concern about cracking due to stretch flange molding, and it is required to reduce the strain due to stretch flange molding in the corner flange portion 42 as much as possible. This is particularly important for aluminum alloy sheets with poor stretch flange formability.

  Therefore, the punch corner portion 31 shown in FIG. 2 has two arc-shaped convex portions 32 a and 32 b on the R-stop C 2 and C 3 sides, and the concave portion 32 c therebetween does not contact the blank sheet 4. Since the two arc-shaped convex portions 32a and 32b approach each other as the press molding progresses while positively imparting elongation, the elongation at the corner center C1 can be suppressed. Thus, the distortion at the corner center C1 when the corner flange portion 42 is press-molded while the die corner portion 21 and the punch corner portion 31 cooperate to widen the hole edge of the rectangular hole 4A of the blank sheet 4. Can be suppressed.

  The contour shape formed by the two arc-shaped convex portions 32a and 32b and the concave portion 32c of the punch corner portion 31 is determined by the shoulder radius Rs of the punch shoulder portion 3S. Preferably, the strain can be further reduced by appropriately adjusting the shoulder radius Rs with respect to the corner radius Rc of the corner flange portion 42. For example, the ratio of the shoulder radius Rs at the R stops C2 and C3 of the punch corner portion 31 to the corner radius Rc (that is, Rs / Rc) is desirably 20% or less. As a result, the shoulder radius Rs becomes relatively small at the R stops C2 and C3 between the punch corner portion 31 and the straight side portion 35, and the corner flange portion 42 is extended in the circumferential direction at the same timing as the straight side portion 35. Can be launched while.

  Further, Rs / Rc at the corner center C1 of the punch corner portion 31 is preferably 80% to 100%. Thereby, in the vicinity of the corner center C1, the recessed part 32c becomes large according to the magnitude | size of the shoulder radius Rs, and the site | part by which the blank sheet | seat 4 is not shape | molded becomes wide. Moreover, the recessed part 32c becomes small gradually with progress of press molding, and can give a predetermined shape. Rs / Rc at the corner 1/4 of the punch corner portion 31 may be between R stops C2 and C3 and Rs / Rc at the corner center C1, and is preferably 40% to 60%.

Next, with respect to the embodiment in which the corner flange portion 42 is press-molded on the four inward corner portions 41 of the blank sheet 4 using the press mold 1 having the above-described configuration, the effect of suppressing the distortion generated in the corner flange portion 42 is reduced. evaluated.
(Example 1 to Example 8)
As the blank sheet 4, a plate material made of an aluminum alloy having a thickness of 1.2 mm (for example, 6000 series aluminum alloy) was used. The corner radius Rc of the corner flange portion 42 after molding was 70 mm, the flange length Lc at the corner center was 16 mm, and the flange length Ls of the R stop and the straight side portion 4S was 11.3 mm. In the punch 3, the Rs / Rc at the corner center C1 of the punch corner portion 31 is in the range of 80.2% to 98.4%, and the Rs / Rc in the corner 1/4 is in the range of 43.7% to 56.5%. Thus, the shape of the punch shoulder 3S was changed (that is, Example 1 to Example 8). Rs / Rc at the R stops C2 and C3 of the punch shoulder 3S was constant at 14.6%.

  When the blank sheet 4 is sandwiched between the die 2 and the blank holder 5 by the press molding method shown in FIG. 7 and the punch 3 is raised to form the flange portion 4F at the hole edge of the rectangular hole 4A. Then, the transition of the maximum principal strain in the molding process was examined. The maximum principal strain is obtained from the strain distribution generated in each part of the corner flange portion 42 as the punch 3 is raised by forming simulation using the finite element method, and the maximum value at the time of forming is set as the maximum principal strain ε1. Table 1 shows the relationship between Rs / Rc in each part and the maximum principal strain ε1 generated in the corner flange part 42 with respect to the punch 3 of Examples 1 to 8.

  8 to 10 show, as an example, a process of forming the corner flange portion 42 using the punch 3 of the first embodiment. In the state before molding shown in FIG. 8 (that is, the stroke amount = 0 mm), the tip surface 33 of the punch 3 exposed from the rectangular hole 4A of the blank sheet 4 has a recess in the vicinity of the corner center C1 of the inward corner portion 41. 32c is located. From this state, when the punch 3 ascends as shown in FIG. 9 (ie, stroke amount = 20 mm), the two arc-shaped convex portions 32a and 32b on both sides of the concave portion 32c come into contact with the blank sheet 4 and inward corners. The corner flange portion 42 is gradually raised on the portion 41.

  The punch shoulder 3S is a boundary between the straight side 35 and R stops C2 and C3, which are portions having relatively small strains. The punch shoulder 3S first comes into contact with the blank sheet 4 and the corner flange 42 is formed. At this time, the two arc-shaped convex portions 32a and 32b have small Rs / Rc on the R-stop C2 and C3 side, and Rs / Rc gradually and gradually increases toward the corner center C1. The contour lines of the arc-shaped convex portions 32a and 32b increase outward. Thereby, the area | region which contact | abuts two arc-shaped convex parts 32a and 32b spreads gradually. On the other hand, the corner center C1 corresponding to the recess 32c and the vicinity thereof are not in contact with the blank sheet 4.

  When the punch 3 further rises, the two arc-shaped convex portions 32a and 32b approach each other, and the concave portion 32c becomes smaller, so that the region to be molded spreads toward the corner center C1 side. As shown in FIG. 10, when the lower end of the punch shoulder 3 </ b> S is raised at the corner center C <b> 1 (that is, the stroke amount = 90 mm), the corner flange portion 42 is completely formed.

  FIG. 11 shows a comparison of the forming process by the punch 3 of Example 1 in the cross section at the corner center C1 and the R stops C2 and C3 on both sides thereof. In step S1 in the drawing (that is, stroke amount = 10 mm), the formation of the blank sheet 4 is started as the punch 3 rises at the R stops C2 and C3, but at the corner center C1, due to the recess 32c, The punch 3 and the blank sheet 4 are separated. In step S2 (ie, stroke amount = 30 mm) in the figure, the corner flange portion 42 rises at a substantially right angle at the R stops C2 and C3, but the punch 3 and the blank sheet 4 remain separated at the corner center C1. . However, the blank sheet 4 gradually rises along the die shoulder portion 2S of the die corner portion 21 also at the corner center C1 as the molding progresses at the R stops C2 and C3.

  In the step S3 (ie, stroke amount = 50 mm) in the drawing, the molding at the corner center C1 is proceeding. However, the concave portion 32c of the punch corner portion 31 is gradually reduced, so that the deformation of the blank sheet 4 is also gradually performed. proceed. As shown in step S4 (ie, stroke amount = 70 mm) in the figure, when the recess 32c reaches the upper end position of the corner flange portion 42, the molding is almost completed and the corner flange portion that stands up from the inner end edge 43 at a substantially right angle. 42 is formed.

  As described above, the shoulder radius Rs of the punch 3 is larger toward the corner center C1 side, and the recess 32c whose size changes in the stroke direction X is provided at the corner center C1, thereby controlling the timing of contact with the blank sheet 4. It becomes possible. Specifically, on the front end surface 33 side, the R stops C2, C3 and the vicinity thereof, which are the boundaries with the straight side portion 35 of the punch corner portion 31, contact the blank sheet 4, and contact with each other as the distance from the front end surface 33 increases. The area expands to the corner center C1 side. At that time, even if the flange forming is completed at the R stops C2 and C3, the flange forming is not completed at the corner center C1 and the vicinity thereof, and the flange forming is performed first because of the difference in molding timing. This contributes to an increase in the line length of the flange portion at the R stops C2, C3 and in the vicinity thereof. Thereafter, as the punch 3 rises, the molding area gradually expands toward the corner center C1, but by that time, the line length of the flange portion preferentially increases on the R-stop C2 and C3 side. An increase in the line length of the flange portion at the center C1 and the vicinity thereof is suppressed. As a result, it is considered that the strain can be suppressed from being localized at the corner center C1 and the vicinity thereof.

(Comparative Example 1)
For comparison, the blank sheet was press-molded in the same manner as in Example 1 except that the shape of the punch 3 was changed. As shown in FIG. 12, the punch 6 has a constant shoulder radius of the punch shoulder 6S, and Rs / Rc at the corner center C1, corner 1/4, R stop C2, and C3 of the punch corner 61 are all 14 .6%. The configuration of the press mold 1 other than the punch 6 was the same, the maximum principal strain ε1 when the corner flange portion 42 was formed on the blank sheet 4 was determined, and the results are also shown in Table 1.

  FIGS. 13 to 16 show the forming process of the corner flange portion 42 using the punch 6 of Comparative Example 1 and the cross section of each portion. When the punch 6 ascends as shown in FIGS. 14, 15, and 16 (ie, stroke amount = 8 mm, 16 mm) from the state before molding shown in FIG. 13 (ie, stroke amount = 0 mm), the punch corner portion Since the punch shoulder 6S of 61 is constant, the molding proceeds simultaneously at the corner center C1. In that case, the increase in the line length of the flange portion becomes particularly large at the corner center C1 and in the vicinity thereof.

  As shown in Table 1, in Comparative Example 1, Rs / Rc is constant at 14.6%, and the maximum principal strain ε1 is 0.233. On the other hand, in Example 1, the maximum principal strain ε1 is reduced to 0.209 by increasing Rs / Rc of each part of the corner flange portion 42 toward the corner center C1. Also in Examples 2 to 8, the maximum principal strain ε1 is 0.210 to 0.222, and the strain is suppressed more than in Comparative Example 1.

  In FIG. 17, Rs / Rc of each part of the corner flange part 42 in Examples 1 to 4 is shown in comparison with Rs / Rc of the corner flange part 42 of Comparative Example 1. In Examples 1 to 4, Rs / Rc at the R-stops C2 and C3 of the corner flange portion 42 is the same as that in Comparative Example 1 and is in the range of 20% or less. In the corner 1/4, Rs / Rc is 40. In the range of% to 60%, Rs / Rc is in the range of 80% to 100% at the corner center C1. Thus, preferably, when Rs / Rc increases from R stops C2 and C3 toward corner ¼ and corner center C1, and Rs / Rc in each part is within the above range, the comparison is performed. The distortion suppressing effect with respect to Example 1 is obtained.

  In the above-described embodiment, the case where the four corner flange portions 42 are formed in the rectangular hole having the four inward corner portions 41 has been described. However, the press mold 1 press-molds at least one inward corner portion 41. Anything to do. At this time, the blank sheet 4 is not limited to a hole-shaped opening such as a rectangular hole, and may be an opening having one or more inward corners 41 in a shape curved in the longitudinal direction. Good.

  Moreover, in the said embodiment, although the case where the corner flange part 42 which stands up from the inner edge edge was formed in the inward corner part provided in the glass opening part for vehicle sunroof was demonstrated, it does not restrict to this. . The press molding die 1 and the press molding method using the same according to the present invention can be applied to openings provided in various members for vehicles or other than vehicles, and the same effect can be obtained.

DESCRIPTION OF SYMBOLS 1 Press mold 2 Die 21 Die corner part 2S Die shoulder part 3 Punch 31 Punch corner part 3S Punch shoulder part 4 Blank sheet 41 Inward corner part 42 Corner flange part 5 Blank holder

Claims (5)

A press mold that can mold a corner flange that stands up from the inner edge of an inward corner,
A die having a die corner portion along the inward corner portion, and a punch having a punch corner portion cooperating with the die corner portion;
The punch corner portion is composed of two arc-shaped convex portions arranged on both sides of the corner center on the front end surface in the relative stroke direction of the punch and a concave portion formed between the two arc-shaped convex portions. Has a contour shape,
The contour shape of the cross section parallel to the tip surface is a press mold in which the concave portion becomes smaller and the two arc-shaped convex portions approach and converge to an outward corner shape as the cross section moves away from the tip surface.   2. The press mold according to claim 1, wherein a punch shoulder portion, which is a portion where the front end surface and the side end surface intersect, in the punch corner portion has a shoulder radius that is larger as it is closer to the center of the corner.   3. The press-molding die according to claim 1, wherein the punch corner portion has a shoulder radius at an R stop that is both ends of the corner, which is 20% or less of a corner radius of the inward corner portion.   The press-molding die according to any one of claims 1 to 3, wherein the punch corner portion has a shoulder radius at the corner center of 80% to 100% of a corner radius of the inward corner portion.   The press forming die according to any one of claims 1 to 4, wherein the blank sheet provided with the inward corner portion is made of an aluminum alloy plate.