JP2018027567A - Press mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a press mold capable of molding a corner flange portion in a single process and capable of combining quality with productivity.SOLUTION: A press mold 1 can mold a corner flange portion and a pair of side flange portions extending on its opposite sides on a blank sheet 4 having an inward corner portion 41. The press mold 1 comprises a die 2 having a die corner portion 21 for molding the inward corner portion 41 and a pair of die side portions 22 for molding the pair of side flange portions, and a punch 3 having a punch corner portion 31 that cooperates with the die corner portion 21 and the pair of die side portion 22, and a pair of punch side portion 32. The punch corner portion 31 has a corner groove portion 6 at a position where a side end surface crosses with a tip surface 33. The corner groove portion 6 is shaped so as to decrease in groove width as it moves away from the tip surface 33 and converges to a corner center on the side end surface.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 edge of the hole on the right side is simply flange-formed so that it is pushed and bent in the direction of punch movement, but the edge of the hole in the corner is pushed and bent while being stretched in the direction perpendicular to the direction of movement of the punch. It becomes the stretch flange molding. 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 is a press mold that can form an inward corner flange portion with stretch flange molding and side flange portions on both sides of the inward corner flange portion in one process, and can achieve both quality and productivity. Is to provide.

One aspect of the present invention is a press mold capable of forming a corner flange portion standing from an inner edge of the inward corner portion and a pair of side flange portions extending on both sides of the blank sheet having an inward corner portion. There,
A die having a die corner portion for forming the inward corner portion and a pair of die side portions for forming the pair of side flange portions, and a punch corner that cooperates with the die corner portion and the pair of die side portions. A punch having a portion and a pair of punch side portions,
The punch corner portion has a corner groove portion at a portion where the tip end surface and the side end surface in the relative stroke direction of the punch intersect,
The corner groove portion is in a press mold having a shape in which the groove width becomes narrower as the distance from the tip end surface in the stroke direction and converges at the corner center on the side end surface.

  Since the press mold has a corner groove at the punch corner, when the punch moves relative to the die, the side flange is first formed by the punch side and the die side. The corner flange portion has a shape in which the groove width of the punch shoulder portion of the corner groove portion becomes narrower and converges to the corner center as it moves away from the tip surface in the stroke direction, so it is molded from the side closer to the side flange portion. Is done. That is, on both sides of the corner center, both ends of the punch shoulder first come into contact with the blank sheet, and the region in contact with the blank sheet gradually expands toward the corner center as press molding proceeds.

  Therefore, when the punch advances while pushing the inner end edge of the inward corner portion of the blank sheet and both sides thereof, a portion corresponding to the corner center of the blank sheet is not initially formed. Thereafter, as the groove width of the corner groove portion becomes narrower, the forming region is expanded and finally the corner center is formed. In the series of steps, the inward corner portion is pushed and bent in the advancing direction of the punch while moving from the side flange side to the corner center side.

  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 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 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 perspective view which shows the principal part structure of the punch which comprises the press molding die in Embodiment 1. FIG. FIG. 3 is a plan view, a perspective view, and a side view of a main part of a punch including a punch corner portion in the first embodiment. The top view which shows the outline shape of the principal part in the front end surface of a punch in Embodiment 1, and the outline shape change in a cross section parallel to a front end surface. The perspective view which shows schematic structure of the principal part of the press mold in Embodiment 2. FIG. The perspective view which shows the principal part structure of the punch in Embodiment 2. FIG. The principal part perspective view which shows the other example of a shape of the punch in Embodiment 1,2. The perspective view which shows schematic structure of the principal part of the press mold in Embodiment 3. FIG. The perspective view which shows the principal part structure of the punch in Embodiment 3. FIG. FIG. 9 is a plan view, a perspective view, and a side view of a main part of a punch including a punch corner portion in Embodiment 3. The perspective view which shows schematic structure of the principal part of the press mold in Embodiment 4. FIG. The top view, perspective view, and side view of the principal part of a punch including a punch corner part in Embodiment 4. The principal part expansion perspective view which shows the state from a shaping | molding start of punch and a blank sheet to completion in an Example. The principal part expanded sectional view which shows the shaping | molding state of the blank sheet in the corner center of a punch accompanying the stroke of a punch in an Example, and the position of R stop. The principal part enlarged view for demonstrating the state at the time of stretch flange molding of the blank sheet in an Example compared with the past. The principal part enlarged view for demonstrating the state at the time of stretch flange molding of the blank sheet in an Example compared with the past.

  In the press mold, the shoulder radius Rps of the punch shoulder portion where the corner groove portion or the tip end surface and the side end surface intersect, and the groove shoulder portion where the corner groove portion and the tip end surface intersect. The shoulder radius Rgs is preferably in a relationship of Rps ≦ Rgs, and preferably Rgs ≦ 30 mm. In this case, when the molding region is expanded from the side flange portion to the corner flange portion, the effect of suppressing an increase in strain at both end portions of the corner groove portion is enhanced.

  It is preferable that the thickness t of the blank sheet and the flange length Ls at both end portions of the inward corner portion have a relationship of t ≦ Rps ≦ Ls. In this case, the rise to the flange shape at the time of molding can be performed more favorably.

  Moreover, it is preferable that the position where the said punch shoulder part and the said groove shoulder part cross | intersect in the said front end surface exists in the boundary part of the said punch corner part and the said punch side part in the said side end surface, or its outer side. In this case, the combination with the shoulder radius Rgs and the groove depth D increases the effect of suppressing strain localization. The boundary portion between the punch corner portion and the punch side portion includes the position of the R stop that becomes both ends of the punch corner portion and the vicinity thereof.

  The corner groove portion preferably has a ratio D / W of the groove depth D in the stroke direction to the groove width W in the tip end surface is larger than 0.25. In this case, the effect of suppressing the localization of strain and reducing the maximum principal strain is further enhanced.

  Moreover, it is preferable that the said corner groove part is a shape which has a pair of inclined surface. Thereby, it becomes a shape which leaves | separates from a front end surface in a stroke direction, so that it goes to a corner center from the punch side part side, and since progress of press molding is delayed, the effect which suppresses the distortion in a corner center is high.

  Further, as the blank sheet for providing the inward corner portion, various metal plates can be adopted. However, preferably, an aluminum alloy plate or a steel plate is used, and stretch flange forming by the press forming die is favorably performed. The

  The die may have a rectangular cylinder hole, and the punch may have a substantially rectangular block shape along the rectangular cylinder hole. That is, the punch may be configured to include the substantially rectangular tip surface and the corner groove portions at four corners thereof. In this case, the so-called rectangular burring process can be performed more stably than before, and both the quality and productivity when forming the flange portion in the rectangular hole can be easily realized.

(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 and a punch 3, and a blank sheet 4 having an inward corner portion 41 is disposed between the die 2 and the punch 3 so as to face inward. A corner flange portion Fc standing from the inner end edge 43 of the corner portion 41 and a pair of side flange portions Fs extending on both sides thereof are formed. The side flange portion Fs rises from the inner edge 43 of the pair of side portions 42 extending on both sides of the inward corner portion 41 and forms the flange portion F together with the corner flange portion Fc.

  The die 2 has a die corner portion 21 along the R-shaped inward corner portion 41 and a pair of die side portions 22 along a pair of straight side portions 42. The punch 3 has a punch corner portion 31 and a pair of punch side portions 32 that cooperate with the die corner portion 21 and the pair of die side portions 22, respectively. 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 side portions 42 at both ends thereof are press-molded into a desired flange shape. Here, although the side part 42 is made into the shape of a straight side, other shapes, for example, at least one part may be a curved shape. The same applies to the die side portion 22 and the punch side portion 32.

  The press mold 1 forms a flange portion F having at least one corner flange portion Fc on the blank sheet 4, and the blank sheet 4 has at least one inward corner portion 41. 3 and 4 are examples of the blank sheet 4, and a part of the mold 1 that molds a ¼ shape thereof (for example, a shape defined by dotted lines in FIGS. 3 and 4) is shown in FIG. It is shown in FIG. The blank sheet 4 has four inward corner portions 41 having the same shape at four corners of a rectangular hole 4A formed through the central portion.

  In FIG. 2, the punch 3 has a corner groove portion 6 at a portion where the tip end surface 33 (that is, the upper surface in the drawing) 33 and the side end surface 34 intersect in the relative stroke direction X in the punch corner portion 31. On the front end surface 33, a pair of straight side portions 35 are formed on both sides of the punch corner portion 31, and the corner groove portion 6 or the portion where the side side portion 35 of the front end surface 33 and the side end surface 34 intersect with each other is It becomes the punch shoulder 3S. Specifically, as shown in FIG. 5, the corner groove portion 6 has a shape in which the groove width becomes narrower as the distance from the distal end surface 33 in the stroke direction X and converges to the corner center C <b> 1. In the side end face 34, both end portions of the punch corner portion 31 having the R-shaped contour line are connected to the planar punch side portion 32, and the boundary positions between them are R stops C2 and C3, respectively. The detailed shape of the corner groove 6 will be described later.

  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, and a punch side portion 32 is disposed to face the die side portion 22. The die 2 has die shoulder portions 2S that cooperate with the punch shoulder portions 3S at the die corner portion 21 and the die side portions 22 on both sides thereof. The shoulder radius of the die shoulder 2S is constant.

  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. 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.

  As shown in FIGS. 3 and 4, the contour lines of the die corner portion 21 and the die side portion 22 connected thereto (for example, shown by broken lines in FIGS. 3 and 4) are the inward corner portions 41 of the blank sheet 4 and The shape is along the side portion 42. By the press forming of the blank sheet 4, the inward corner portion 41 and the side portion 42 are bent at the positions of the contour lines of the die corner portion 21 and the die side portion 22, and the corner flange portion that stands up with the bending position as the inner end edge 43. Fc and the side flange portion Fs are formed. In the inward corner portion 41, the flange length Ls at both ends is equal to the flange length Ls at the side portion 42, and the flange length Lc at the corner center is equal to or greater than the flange length Ls (that is, Ls). ≦ Lc). Specifically, the flange length Ls is expressed by (Lc / 2) × √2 with respect to the flange length Lc at the corner center C1.

  The corner flange portion Fc and the side flange portion Fs rise 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 (for example, see FIG. 2). Such a rectangular flange portion F composed of the corner flange portion Fc and the side flange portion Fs having a straight side constitutes each corner portion of the rectangular opening portion in, for example, a glass opening portion for a vehicle sunroof. Can do.

  The blank sheet 4 is comprised with steel plates, such as an aluminum alloy plate or a mild steel plate, for example. Of these, the aluminum alloy plate is effective in reducing the weight, and generally has an effect obtained by applying the present invention because the stretch flangeability is inferior to that of a mild steel plate. Therefore, the flange portion F having a relatively high height can be formed while suppressing distortion. The die 2 and the punch 3 of the press mold 1 can be made of a well-known steel material for dies.

  5 and FIG. 6, the punch 3 has a V-groove corner groove portion 6 including a pair of inclined surfaces 61 and 62 in the punch corner portion 31. The pair of inclined surfaces 61 and 62 have groove shoulders 6 </ b> S at portions where the inclined surfaces 61 and 62 intersect the tip surface 33 in the tip surface 33. The groove width W of the corner groove portion 6 is the largest at the tip surface 33. Specifically, as shown in FIG. 7, the corner groove portion 6 extends on a diagonal line passing through the corner center C <b> 1, and the groove width W in a cross section parallel to the front end surface 33 decreases as the distance from the front end surface 33 increases. At the same time, the pair of inclined surfaces 61 and 62 are close to each other. The pair of inclined surfaces 61 and 62 are finally united and the corner groove portion 6 disappears and converges to a predetermined outward corner shape. A groove valley portion 6 </ b> V is formed at a portion where the pair of inclined surfaces 61 and 62 of the corner groove portion 6 intersect.

  The punch 3 has an outer shape similar to the rectangular cylindrical hole 2A of the die 2 from the cross section where the corner groove portion 6 disappears to the end surface opposite to the tip end surface 33, and has a predetermined outside along the die corner portion 21. It has an orientation corner shape. In the punch 3, the corner groove portion 6 or a portion where the tip end surface 33 and the side end surface 34 intersect is a curved punch shoulder portion 3 </ b> S, and the shoulder radius Rps of the punch shoulder portion 3 </ b> S is constant here.

  The shoulder radius Rps of the punch shoulder 3S is set so as to satisfy the relationship of t ≦ Rps ≦ Ls, where t is the thickness of the blank sheet 5 and Ls is the flange length at both ends of the inward corner portion 41. Is done. By setting the shoulder radius Rps to be equal to or greater than the plate thickness t of the blank sheet 4 and equal to or less than the flange length Ls, the rise to the flange shape can be satisfactorily performed so that the inward corner portion 41 faces the corner center C1 side. , Can be pushed and bent in the advancing direction of the punch. Preferably, the relationship of t <Rps <Ls should be satisfied, and when the shoulder radius Rps is smaller, the rising position is closer to the die 2 and the molding is advanced while the sheet material flows toward the corner center C1 side. Can do.

  Further, the shoulder radius Rgs of the groove shoulder 6S, which is a portion where the corner groove 6 and the tip surface 33 intersect, and the shoulder radius Rps are in a relationship of Rps ≦ Rgs, and preferably Rgs ≦ 30 mm. In this case, when the molding region is expanded from the side flange portion Fs to the corner flange portion Fc, an effect of suppressing an increase in strain at both end portions of the corner groove portion 6 is enhanced. In this embodiment, for example, the shoulder radius Rps of the punch shoulder 3S, the shoulder radius Rgs of the groove shoulder 6S, and the valley radius Rgv of the groove valley 6V are equal (that is, Rps = Rgs = Rgv).

  Further, the position where the punch shoulder portion 3S and the groove shoulder portion 6S intersect on the front end surface 33 is preferably on the boundary portion between the punch corner portion 31 and the punch side portion 32 on the side end surface 34 or on the outer side. Here, the boundary portion includes R stops C2 and C3 that are boundary positions and positions in the vicinity thereof. That is, the connecting portions S1 and S2 between the punch shoulder portion 3S and the groove shoulder portion 6S shown in FIGS. 5 and 6 are located at or near the positions of the R stops C2 and C3 at both ends of the punch corner portion 31, or the R stops. It should be outside C2 and C3. In this case, it is possible to suppress local distortion from occurring in the connection portions S1 and S2 at the start of molding.

  In this embodiment, for example, the connecting portions S1 and S2 of the groove shoulder 6S are positioned outside the R stops C2 and C3. At this time, in FIG. 6, the corner groove portion 6 has a groove width W at the distal end surface 33 larger than the width W <b> 0 of the punch corner portion 31. Here, the width W <b> 0 of the punch corner portion 31 is a linear distance between lines obtained by projecting the R stops C <b> 2 and C <b> 3, which are both ends of the punch corner portion 31, onto the front end surface 33.

  In FIG. 6, the corner groove portion 6 preferably has a ratio D / W between the groove depth D in the stroke direction X and the groove width W in the tip surface 33 larger than 0.25. As the groove depth D increases, the punch 3 is pushed and bent toward the corner center C1 side from the side flange portion Fs side, thereby suppressing the localization of strain and reducing the maximum principal strain. Will increase. However, as the groove depth D increases, the stroke amount required for flange forming increases and the press mold 1 increases in size, so that, for example, the ratio D / W is smaller than 1.9. Preferably, the ratio D / W is set to be 0.9 or less. In this embodiment, for example, the groove depth D is set to be larger than 50% of the groove width W in the distal end surface 33. At this time, for example, the pair of inclined surfaces 61 and 62 of the corner groove portion 6 has an angle α with the distal end surface 33 in the range of 30 ° to 75 °, preferably in the range of 30 ° to 60 °. Is set.

(Embodiment 2)
In the first embodiment, an example in which the shoulder radius Rps of the punch shoulder 3S and the shoulder radius Rgs of the groove shoulder 6S have the same size is shown. However, as shown in the second embodiment in FIGS. Is set so as to satisfy the relationship of Rps <Rgs, the punch shoulder portion 3S of the punch side portion 32 and the punch shoulder portion 3S of the punch corner portion 31 are more smoothly connected. Thereby, it can further suppress that local distortion arises in these connection parts S1 and S2 at the time of a shaping | molding start. In the range of Rgs ≦ 30 mm, the greater the shoulder radius Rgs of the groove shoulder 6S, the greater the strain suppression effect. However, when Rgs exceeds 20 mm, the effect does not change significantly. Therefore, it is preferable to set appropriately within the range of Rgs ≦ 20 mm.

  Other configurations are the same as those of the first embodiment, and the same reference numerals are given and the description thereof is omitted. The same applies to the following embodiments. In the first and second embodiments, the corner groove portion 6 is continuously formed up to the punch corner portion 31 (not shown) located diagonally opposite to the punch corner portion 31 on the tip surface 33 of the punch 3. Has been. The same applies to the other two corner grooves 6 in the diagonal direction of the punch 3.

  Further, as in another shape example shown in FIG. 10, the corner groove portion 6 may be arranged for each punch corner portion 31 of the punch 3 and may be formed independently of the other punch corner portions 31. In this case, the corner groove part 6 can be made into the shape which has the vertical wall 63 which connects a pair of inclined surfaces 61 and 62 on the opposite side to the punch corner part 31, for example.

(Embodiment 3)
In the first embodiment, the corner groove portion 6 has an example in which the groove depth D in the stroke direction X is larger than 50% of the groove width W in the distal end surface 33. FIG. 11 to FIG. Of course, the groove depth D may be set to be smaller than 50% of the groove width W. In this example, the groove width W is larger than the width W0 of the punch corner portion 31 as in the first embodiment.

(Embodiment 4)
Alternatively, as shown in Embodiment 4 in FIGS. 14 and 15, the corner groove portion 6 has a groove depth D smaller than 50% of the groove width W, and the groove width W is a width W 0 of the punch corner portion 31. It can also be set to be smaller. In any case, as described above, the ratio D / W is set in a range larger than 0.25. However, when the groove width W is smaller than the width W0 of the punch corner portion 31, local distortion tends to occur at the connection portions S1 and S2 at the start of molding, and in order to avoid this, the punch shoulder portion 3S The shoulder radius Rps and the groove depth D of the corner groove 6 may be restricted. In addition, when the groove width W is significantly larger than the width W0 of the punch corner portion 41, the stroke amount necessary for flange forming becomes large, and the press mold 1 becomes large. Therefore, it is preferable that the ratio W / W0 with the width W0 of the punch corner portion 31 is in the range of 0.9 to 1.5.

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 FIG. 1, the blank sheet 4 is sandwiched between the die 2 and the blank holder 5, and the punch 3 is disposed inside the die 2. As shown in the upper diagram of FIG. 2, the punch 3 is positioned below the blank sheet 4 in a state before molding. From this state, when the punch 3 is moved up and down using the punch driving unit (not shown) with the vertical direction as the stroke direction X, the punch 3 moves relative to the die 2. When the punch 3 is raised, first, the leading end surface 33 and the punch shoulder 3S come into contact with the hole edge of the blank sheet 4 positioned in the traveling direction.

  As shown in the lower part of FIG. 2, 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 portion of the blank sheet 4 is bent along the die shoulder portion 2S, and a flange portion F rising from the inner end edge 43 at a predetermined height is formed. In the flange portion F, a corner flange portion Fc is formed in the inward corner portion 41 by the die corner portion 21 and the punch corner portion 31, and the corner flange portion Fc is formed by the die side portion 22 and the punch side portion 32. A subsequent straight side flange portion Fs is formed. In FIG. 2, the description of the die 2 and the blank holder 5 is omitted.

  At this time, as indicated by arrows in FIG. 4 described above, the corner flange portion Fc 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 Fc 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 Fc 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.

  On the other hand, for example, when applied to an opening for a vehicle sunroof or the like, the corner flange portion Fc 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 minimize the strain due to stretch flange molding in the corner flange portion Fc. This is particularly important for aluminum alloy sheets with poor stretch flange formability.

  On the other hand, the punch 3 shown in FIG. 2 has the corner groove portion 6 in the punch corner portion 31, and the punch shoulder portion 3 </ b> S between the both end portions does not contact the blank sheet 4. Since the groove width W is reduced and the both end portions gradually approach the corner groove portion 6 as the press molding progresses, the elongation at the corner center C1 can be suppressed. The shoulder radius Rps of the punch shoulder 3S is set within a predetermined range, the side flange portion Fs is quickly raised, and the shoulder radius Rgs, groove width W, groove depth D, etc. of the groove shoulder 6S are adjusted. Thus, the influence on the corner flange portion Fc is minimized. Thus, the distortion at the corner center C1 when the corner flange portion Fc 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.

Next, with respect to the embodiment in which the corner flange portion Fc 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 Fc is reduced. evaluated.
(Examples 1 to 23)
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 Fc after molding was set to 70 mm, and the flange length Lc of the corner center C1 was set to 16 mm. The flange length Ls of both end portions and the side portion 42 of the inward corner portion 41 that becomes the R stops C2 and C3 was set to 11.3 mm (that is, 8√2 mm = 11.3 mm). As shown in Table 1, in the punch 3, the shoulder radius Rps of the punch shoulder 3S and the shoulder radius Rgs of the groove shoulder 6S were changed in the range of 2 mm to 10 mm. At this time, shoulder radius Rps = shoulder radius Rgs was set. It should be noted that the trough radius Rgv = shoulder radius Rps of the trough 6V. Further, the ratio W / W0 between the groove width W at the front end surface 33 of the corner groove portion 6 and the width W0 of the punch corner portion 31 was set to be in the range of 1 to 1.5. The inclination angle α of the inclined surfaces 61 and 62 was changed in the range of 30 ° to 75 °.

  When the blank sheet 4 is sandwiched between the die 2 and the blank holder 5 by the press molding method shown in FIG. 2, the punch 3 is raised, and the flange portion 4F is formed 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 Fc as the punch 3 moves up by forming simulation using the finite element method, and the maximum value at the time of completion of forming is set as the maximum principal strain ε1. The results are also shown in Table 1.

(Comparative Example 1)
For comparison, the blank sheet 4 was press-molded in the same manner as in Example 1 except that the shape of the punch 3 was changed. A comparative punch having the same shape as the pan 3 was used except that the corner groove 6 was not provided. The configuration of the press mold 1 other than the punch was the same, the maximum principal strain ε1 when the flange portion F was formed on the blank sheet 4 was determined, and the results are also shown in Table 1.

(Comparative Examples 2 to 4)
For comparison, with respect to the shape of the punch 3 of Example 1, the shoulder radius Rps of the punch shoulder portion 3S was changed to 14 mm, and the blank sheet 4 was press-formed by the same method. At this time, shoulder radius Rps = shoulder radius Rgs, valley radius Rgv = shoulder radius Rps, and the ratio W / W0 to the width W0 of the punch corner portion 31 was set to be in the range of 1 to 1.5. Similarly, the maximum principal strain ε1 when the flange portion F was formed on the blank sheet 4 was determined, and the results are also shown in Table 1.

  As shown in Table 1, in Comparative Example 1 in which the punch 3 does not have the corner groove 6, the maximum principal strain ε 1 is 0.233, whereas in Examples 1 to 23 in which the punch 3 has the corner groove 6. The maximum principal strain ε1 is as small as 0.177 to 224. In Comparative Examples 2 to 4, where the shoulder radius Rps of the punch shoulder 3S is larger than the flange length Ls, the maximum principal strain ε1 is 0.240 to 245, which is larger than that of Comparative Example 1. As described above, when the shoulder radius Rps of the punch shoulder portion 3S is in a relationship of t ≦ Rps ≦ Ls with respect to the plate thickness t of the blank sheet 4 and the flange length Ls at both ends of the inward corner portion 41. It can be seen that good results can be obtained.

(Example 24 to Example 27)
As shown in Table 2, with respect to the shape of the punch 3 of Example 2, the shoulder radius Rgs of the groove shoulder was changed in the range of 2 mm to 30 mm. At this time, valley radius Rgv = shoulder radius Rps. The blank sheet 4 was press-formed by the same method, the maximum principal strain ε1 when the flange portion F was formed on the blank sheet 4 was determined, and the results are also shown in Table 2.

(Example 28 to Example 38)
As shown in Table 2, with respect to the shape of the punch 3 of Example 1, the shoulder of the punch shoulder 3S is set so that the ratio W / W0 to the width W0 of the punch corner 31 is 0.9 or 1.1. The radius Rps was changed in the range of 2 mm to 10 mm. At this time, shoulder radius Rps = Rgs and valley radius Rgv = shoulder radius Rps. The blank sheet 4 was press-formed by the same method, the maximum principal strain ε1 when the flange portion F was formed on the blank sheet 4 was determined, and the results are also shown in Table 2.

  As shown in Table 2, when the shoulder radius Rgs of the groove shoulder 6S is in a relationship of Rps ≦ Rgs and Rgs ≦ 30 mm with respect to the shoulder radius Rps of the punch shoulder 3S, the same effect can be obtained. . The same effect can be obtained when the ratio W / W0 between the groove width W and the width W0 of the punch corner portion 31 is 0.9 or 1.1.

  FIG. 16 shows, as an example, a process for forming the corner flange portion Fc using the punch 3 of the second embodiment. In the state before molding shown in the uppermost stage of FIG. 16 (that is, stroke amount = 0 mm), the corner center C1 of the inward corner portion 41 is formed on the tip surface 33 of the punch 3 exposed from the rectangular hole 4A of the blank sheet 4. The corner groove part 6 is located on both sides. When the punch 3 is lifted from this state (ie, stroke amount = 16 mm), the punch shoulder 3S is first connected to both ends of the corner groove 6 from the punch side part 32, that is, the connecting part S1 with the groove shoulder 6S, Up to S2 comes into contact with the blank sheet 4. Thereby, the side flange portion Fs gradually rises on the side portion 42.

  The punch shoulder 3 </ b> S is connected to the side part 35 having a straight side of the tip end surface 33, and comes into contact with the blank sheet 4 first at the punch side part 32, which is a portion having a relatively small strain. At this time, since the shoulder radius Rps of the punch shoulder portion 3S is set to be relatively small in a range larger than the plate thickness t, the side flange portion Fs rises quickly. Further, since the groove width W of the corner groove portion 6 is larger than the width W0, the punch shoulder portion 3S of the punch corner portion 31 is not in contact with the inward corner portion 41 of the blank sheet 4 at the beginning of molding. Therefore, the forming region shifts to the inward corner portion 41 side while suppressing the elongation at the inward corner portion 41.

  When the punch 3 further rises (that is, stroke amount = 48 mm, 80 mm), the groove width W of the corner groove portion 6 gradually decreases. Thereby, the area | region which contacts punch shoulder part 3S spreads to the inward corner part 41, and the corner flange part Fc rises gradually. When the corner center C1 rises to a position where the lower end of the punch shoulder 3S is exposed (ie, stroke amount = 122 mm), the corner flange portion Fc is completely formed.

  FIG. 17 schematically shows the forming process by the punch 3 of the second embodiment by comparing the corner center C1 of the punch corner portion 31 with the cross sections at the R stops C2 and C3 on both sides thereof. When molding is started from the state before molding shown in the uppermost stage in the drawing (that is, stroke amount = 0 mm, 16 mm), molding of the side flange portion Fs is started in the punch side portion 32 (not shown). Since the groove width W of the corner groove portion 6 is larger than the width W0, the punch shoulder portion 3S does not reach the R stops C2 and C3 in the punch corner portion 31. As the punch 3 rises (ie, stroke amount = 48 mm), the blank sheet 4 starts to be formed at the R stops C2 and C3, but at the corner center C1, the punch 3 and the blank sheet 4 are separated.

  After the corner flange portion Fc completely rises at the R stops C2 and C3 (that is, stroke amount = 80 mm), the punch 3 approaches the blank sheet 4 at the corner center C1. Thereafter, the punch 3 is further raised (that is, the stroke amount = 122 mm), the punch shoulder portion 3S raises the blank sheet 4, and the corner flange portion Fc is completely formed.

Thus, by having the corner groove portion 6 whose size changes in the stroke direction X at the punch corner portion 31 of the punch 3, the timing of coming into contact with the blank sheet 4 and rising to the flange shape can be controlled. Specifically, the punch shoulder portion 3S first raises the side flange portion Fs on the outside of the punch corner portion 31, and then the R stops C2, C3 serving as boundaries with the punch side portion 32 and the vicinity thereof are blanks. The sheet 4 comes into contact with the sheet 4 and the contact area expands toward the corner center C1. Here, in the conventional configuration that does not include the corner groove portion 6 (see, for example, the left diagram in FIG. 18), the R shape of the inward corner portion 41 of the blank sheet 4 extends from the radius _R0 along the inner edge 43 after molding. When changing to the radius R, it is considered that the sheet material flows outward and the line length of the corner center C1 is increased (for example, see the left figure of FIG. 19).

  On the other hand, by having the corner groove 6 in the punch 3 (see, for example, the right diagram in FIG. 18), a molding timing difference occurs, and the side flange portion Fs rises quickly so that the sheet material faces inward. It is considered that the increase in the line length of the corner center C1 can be suppressed (for example, see the right figure in FIG. 19).

  In the above embodiment, the case where the four corner flange portions Fc 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 Fc which stands up from the inner 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 molding die 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 5 Blank holder 6 Corner groove part 6S Groove shoulder part Fc Corner flange part Fs Side flange part

Claims (8)

In a blank sheet having an inward corner portion, a press mold capable of forming a corner flange portion rising from an inner end edge of the inward corner portion and a pair of side flange portions extending on both sides thereof,
A die having a die corner portion for forming the inward corner portion and a pair of die side portions for forming the pair of side flange portions, and a punch corner that cooperates with the die corner portion and the pair of die side portions. A punch having a portion and a pair of punch side portions,
The punch corner portion has a corner groove portion at a portion where the tip end surface and the side end surface in the relative stroke direction of the punch intersect,
The corner mold part has a shape in which the groove width becomes narrower as the distance from the tip end surface in the stroke direction becomes smaller and converges at the corner center on the side end surface.   The shoulder radius Rps of the punch shoulder portion where the corner groove portion or the tip end surface and the side end surface intersect, and the shoulder radius Rgs of the groove shoulder portion where the corner groove portion and the tip end surface intersect are Rps. The press-molding die according to claim 1, which is in a relationship of ≦ Rgs and Rgs ≦ 30 mm.   The press mold according to claim 2, wherein a thickness t of the blank sheet and a flange length Ls at both ends of the inward corner portion are in a relationship of t≤Rps≤Ls.   The position where the punch shoulder portion and the groove shoulder portion intersect on the front end surface is at the boundary portion between the punch corner portion and the punch side portion on the side end surface or outside the boundary portion. 2. A press mold according to item 1.   The press molding die according to any one of claims 1 to 4, wherein the corner groove portion has a ratio D / W of a groove depth D in a stroke direction and a groove width W in the tip end surface larger than 0.25. .   The said corner groove part is a press molding die of any one of Claims 1-5 which has a pair of opposing inclined surface.   The press-molding die according to any one of claims 1 to 6, wherein the blank sheet is made of an aluminum alloy plate or a steel plate.   The press die according to any one of claims 1 to 7, wherein the die has a rectangular tube hole, and the punch has a substantially rectangular block shape along the rectangular tube hole.