JP2016163899A - Press die - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a press die which can form a press part having a U-shaped cross section by drawing without making a wrinkle prevention flange remain, reduces peculiar bending (warpage) remaining at a flange tip part being a product terminal, and can improve product accuracy.SOLUTION: A press die 10 comprises: an upper die 1 having a vertical wall part 11 whose lower part is opened, and formed into a U shape in a cross section, and a sidewall part 12; a lower punch 2 having a vertical wall part 21 which opposes the upper die, and is formed into a U-shape at a cross section, and a sidewall part 22; and a wrinkle prevention member 3 which adjoins the vertical wall part of the lower punch, and is energized to a die direction. The press die 10 performs drawing so that a flange tip part W11 of a raw material plate W0 intrudes into a clearance between the vertical wall parts of the upper die and the lower punch. On a wrinkle prevention surface 31 of the wrinkle prevention member, there is arranged an escape part 4 which separates from a wrinkle prevention face 13 of the upper die in the vicinity of the vertical wall part of the lower punch, and is formed in a recessed shape toward the vertical wall part of the lower punch 2.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a press die for forming a press part having a U-shaped cross section by drawing.

  For example, Patent Document 1 discloses a drawing apparatus (press die) that forms a pressed part having a U-shaped cross section by drawing. The drawing apparatus disclosed in Patent Document 1 includes a movable mold that can move up and down, a die provided on the movable mold, a fixed mold provided to face the movable mold, and a fixed mold corresponding to the die. And a wrinkle presser member provided corresponding to the die around the punch and biased in the die direction, at least one of the die and the wrinkle presser member, In the drawing apparatus, an inclined surface is formed in which a gap between the wrinkle holding member and the crease pressing member increases toward the center of the die.

In the above drawing apparatus, as the drawing process proceeds, the wrinkle presser flange is brought closer to the center of the die, and the wrinkle presser flange thickness increases as the applied amount increases. As the wrinkle presser flange thickness increases, the gap between the die and the wrinkle presser member increases toward the center of the die, so regardless of the amount of wrinkle presser flange that is pushed toward the center of the die, The gap between the outer end portion of the wrinkle holding flange and the die and the wrinkle holding member is always kept at a substantially constant minute gap. Accordingly, the wrinkle pressing flange is pressed by the die and the wrinkle pressing member while maintaining the slidability, so that the generation of wrinkles and cracks is suppressed.
However, in the above drawing forming apparatus, when the drawing process is completed, the wrinkle holding flange remains between the die and the wrinkle pressing member. Therefore, in the subsequent process, the wrinkle holding flange should be cut to fit the product shape. Alternatively, it is necessary to perform bending after cutting. For this reason, there is a problem in that the yield of the material is reduced, the number of processing steps after the drawing process is increased, and the production cost is increased.

JP-A-5-123773

  In order to cope with this problem, as shown in FIG. 13, the present inventors have an upper die 110 having a vertical wall portion 111 and a lateral wall portion 112 that are open at the bottom and formed in a U-shaped cross section, A lower die punch 120 having a vertical wall portion 121 and a horizontal wall portion 122 formed in a U-shaped cross section facing the upper die 110, and an upper portion disposed adjacent to the vertical wall portion 121 of the lower die punch 120. A pressing die that includes a wrinkle pressing member 130 biased in the die direction and draws the flange tip W1 so as to enter between the vertical wall portions of the upper die 110 and the lower punch 120 when drawing is completed. 100 were examined. According to the press die 100, with the upper die 110 and the wrinkle presser 130 sandwiching the flange tip W1 of the material plate W0 (FIG. 13A), the lower die punch 120 is placed at the center of the material plate. By pressing (FIG. 13B), pressing the flange tip W1 by the vertical wall portion 111 of the upper die 110 and the vertical wall portion 121 of the lower punch 120 at the bottom dead center (FIG. 13C). The press part W having a U-shaped cross section can be formed without leaving the wrinkle pressing flange between the upper die 110 and the wrinkle pressing member 130.

  However, in the press die 100, as shown in FIG. 14A, the flange tip W1 is bent into a curved shape by the die shoulder R portion 113 of the upper die 110 in the middle of the drawing process. As shown in FIG. 14 (B), it enters the gap between the vertical wall 111 of the upper die 110 and the vertical wall 121 of the lower punch 120. Therefore, even if the flange tip W1 bent into a curved shape is pressed by the vertical wall portion 111 of the upper die 110 and the vertical wall portion 121 of the lower die punch 120, the curved shape of the flange tip portion W1 is within the elastic range. However, it is difficult to bend the flange tip W1 back to a straight line. Therefore, a large bending wrinkle (warp) remains at the flange tip W1 serving as a product terminal, resulting in a problem that the product accuracy is lowered.

  The present invention has been made to solve the above-described problems, and can form a pressed part having a U-shaped cross section by drawing without leaving a wrinkle-pressing flange, and can remain on the front end of the flange serving as a product terminal. An object of the present invention is to provide a press die that can reduce bending wrinkles (warpage) and improve product accuracy.

In order to achieve the above object, the press die according to the present invention has the following configuration.
(1) A die having a vertical wall portion and a horizontal wall portion that are open at the top or bottom and formed in a U-shaped cross section, and a vertical wall portion and a horizontal wall that are formed in a U-shaped cross section facing the die And a wrinkle pressing member that is arranged adjacent to the vertical wall portion of the punch and is biased in the die direction, and when the drawing process is completed, the flange tip of the blank plate is connected to the die and the punch. A press die that is drawn so as to enter between the vertical wall portions,
The wrinkle pressing surface of the wrinkle pressing member is provided with a relief portion formed in a concave shape toward the vertical wall portion of the punch and spaced from the wrinkle pressing surface of the die in the vicinity of the vertical wall portion of the punch. It is characterized by.

In the present invention, the wrinkle pressing surface of the wrinkle pressing member is provided with a relief portion that is formed in a concave shape toward the vertical wall portion of the punch, in the vicinity of the vertical wall portion of the punch, spaced from the wrinkle pressing surface of the die. Therefore, at the initial stage of drawing, the flange end of the blank plate that was narrowly pressed between the wrinkle holding surface of the die and the wrinkle holding surface of the wrinkle holding member starts from the wrinkle holding surface of the die. It can be separated and enter the escape portion. Therefore, the flange tip portion can enter between the vertical wall portions of the die and the punch while rotating along the vertical wall portion of the punch with the die shoulder R portion as a fulcrum. As a result, the flange tip portion is not easily bent into a curved shape by the die shoulder R portion, and when the flange tip portion is narrowly pressed between the vertical wall portions of the die and the punch, the flange tip portion can be easily bent back in a straight line. Become.
Further, the flange tip portion enters between the vertical wall portions of the die and the punch while rotating along the vertical wall portion of the punch with the die shoulder R portion serving as a fulcrum. Therefore, the tensile stress remaining after the completion of drawing can be greatly reduced. As a result, it is possible to make it difficult to cause bending wrinkles (warping) due to the die shoulder R portion at the flange tip portion.
Therefore, according to the present invention, a pressed part having a U-shaped cross section can be formed by drawing without leaving a wrinkle holding flange, and bending wrinkles (warping) remaining at the end of the flange serving as a product terminal can be reduced. It is possible to provide a press die that can improve product accuracy.

(2) In the press die described in (1),
The relief portion is formed to be recessed stepwise with respect to the wrinkle pressing surface of the wrinkle pressing member.

  In the present invention, since the relief portion is formed so as to be recessed stepwise with respect to the wrinkle holding surface of the wrinkle holding member, when the flange tip portion is separated from the wrinkle holding surface of the die, the outer edge of the flange tip portion and It is easy to avoid interference with the escape part. Therefore, the vertical end portion of the die and the punch is rotated while the flange end portion is rotated along the vertical wall portion of the punch with the shoulder portion of the die shoulder as a fulcrum, without receiving warp deformation based on interference with the relief portion. You can get in between. As a result, the flange tip is hardly bent into a curved shape by the die shoulder R and the relief portion, and when the flange tip is narrowed between the vertical wall portions of the die and the punch, the flange tip is further straightened. It becomes easy to bend back into a shape.

(3) In the press die described in (1) or (2),
The relief portion is formed so as to be separated from the die pressing surface of the die from a position at least 5 mm away from the contact point between the die pressing surface and the die shoulder R portion.

  In the present invention, the relief portion is formed so as to be separated from the wrinkle pressing surface of the die from a position at least 5 mm away from the contact between the wrinkle pressing surface of the die and the die shoulder R portion. The portion can enter between the vertical wall portions of the die and the punch while holding the linear flange of at least 5 mm and rotating along the vertical wall portion of the punch with the die shoulder R portion as a fulcrum. Therefore, when the flange tip portion is narrowed between the vertical wall portions of the die and the punch, a linear flange of at least 5 mm or more becomes wrinkles, and the flange tip portion is more easily bent back in a straight line. As a result, a bending wrinkle (warp) due to the die shoulder R portion can be made more unlikely to occur at the flange tip portion.

(4) In the press die described in any one of (1) to (3),
The punch is characterized in that a shelf that intersects with the vertical wall portion of the punch and faces the wrinkle pressing surface of the die is formed.

  In the present invention, the punch is formed with a shelf portion that intersects with the vertical wall portion of the punch and faces the wrinkle pressing surface of the die, so that the relief portion is separated from the wrinkle pressing surface of the die from the middle stage of the drawing process. It is possible to form a pressed part having a hat-shaped flange on the outer edge of the U-shaped cross section by pressing the flange end portion that has entered into the die by the wrinkle pressing surface of the die and the shelf portion of the punch. Therefore, the shape of the flange tip is frozen by forming a hat-shaped flange on the outer edge, and bending wrinkles (warping) remaining at the flange tip can be further reduced. As a result, product accuracy can be further improved.

  According to the present invention, a press part having a U-shaped cross-section can be formed by drawing without leaving a wrinkle holding flange, reducing bending wrinkles (warping) remaining at the end of the flange serving as a product terminal, A press die capable of improving accuracy can be provided.

It is a perspective view of the press component drawn by the press die concerning the embodiment of the present invention. FIG. 2 is a cross-sectional view (bottom dead center state) corresponding to the AA cross section of the press part shown in FIG. 1 in the press die according to the embodiment of the present invention. FIG. 3 is a detailed cross-sectional view (a state during drawing) of a relief portion in the press die shown in FIG. 2. FIG. 3 is a cross-sectional view of the press die shown in FIG. 2 in the middle of drawing (initial stage). FIG. 3 is a cross-sectional view of the press mold shown in FIG. 2 in the middle of drawing (mid-processing). FIG. 3 is a cross-sectional view of the press die shown in FIG. 2 in a state during drawing (processing end). It is explanatory drawing of the stress analysis result (60 mm rise from a bottom dead center) in the press die shown in FIG. It is explanatory drawing of the stress analysis result (40 mm rise from a bottom dead center) in the press die shown in FIG. It is explanatory drawing of the stress analysis result (25 mm rise from a bottom dead center) in the press die shown in FIG. It is explanatory drawing of the stress analysis result (bottom dead center) in the press die shown in FIG. It is explanatory drawing of the curvature amount analysis result of the side plate in the press components after mold release. FIG. 2 is a modification of the press die shown in FIG. 2, (A) shows a state during drawing (initial stage of machining), (B) shows a state during drawing (mid stage of machining), and (C) shows completion of drawing. Indicates the state. It is a press die examined by the present inventors, (A) shows a state during drawing (material gripping), (B) shows a state during drawing (middle processing), and (C) shows completion of drawing. Indicates the state. FIG. 14 is a cross-sectional view illustrating a phenomenon in which bending wrinkles (warping) remain at the flange tip portion due to the die shoulder R portion in the press die shown in FIG. 13. (A) shows a state in which the flange tip is bent into a curved shape by the die shoulder R portion of the upper die, and (B) shows the flange tip at the vertical wall portion of the upper die and the vertical wall of the lower die punch. Even if it presses by a part, the curved shape of the flange front-end | tip part shows the state which deform | transforms within an elastic region.

  Next, a press die according to an embodiment of the present invention will be described in detail with reference to the drawings. First, the structure of a press part drawn by the press die according to the present embodiment will be described, and then the structure of the press die and the material inflow operation during drawing will be described. Next, the CAE analysis result of the stress distribution and the side plate warpage amount in the press part drawn by the press die will be described. Finally, a modification of the press die according to this embodiment will be described.

<Structure of pressed parts>
First, the structure of a pressed part drawn by the press die according to the present embodiment will be described with reference to FIG. FIG. 1 shows a perspective view of a pressed part drawn by a press die according to an embodiment of the present invention.

  As shown in FIG. 1, this press part W is a long reinforcing part having a substantially U-shaped cross section formed by a top plate W20 formed horizontally and a side plate W10 formed vertically. . The internal angle of the intersection W30 where the side plate W10 and the top plate W20 intersect is about 90 to 95 °. The side plate W10 is formed with a substantially constant width dimension from the intersection W30 to the outer edge W14 of the flange tip W11. The outer edge W14 of the flange tip portion W11 constitutes a product terminal except for the portion indicated by the virtual line W141. A portion indicated by an imaginary line W141 is cut by a drawing process after the press part W is drawn. The side plate W10 is formed in a substantially linear shape in the longitudinal direction and the vertical direction, and a convex or concave reinforcing bead W13 extending in the vertical direction is appropriately formed in a part thereof.

  The top plate W20 is formed in a substantially linear shape in the longitudinal direction and the width direction, but a broken line W21 is formed at an intermediate position in the longitudinal direction, and is bent with the broken line W21 as a boundary. A convex or concave reinforcing bead W22 extending in the width direction is appropriately formed on a part of the top plate W20. A material plate W0 (see FIG. 2) of the press part W is a cold-rolled steel plate having a thickness of about 1 to 2 mm. The tensile strength of the material plate W0 is, for example, about 490 to 590 MPa. In addition, since the side plate W10 of this press part W is plate-matched with the to-be-reinforced part which is not shown in figure, the request | requirement of the surface position accuracy in the flange front-end | tip part W11 is high especially.

<Press die structure>
Next, the structure of the press mold will be described with reference to FIGS. FIG. 2 is a cross-sectional view (bottom dead center state) corresponding to the AA cross section of the press part shown in FIG. 1 in the press die according to the embodiment of the present invention. FIG. 3 shows a detailed cross-sectional view (a state during drawing) of the relief portion in the press die shown in FIG.

  As shown in FIGS. 2 and 3, the press die 10 includes an upper die (die) 1 having a vertical wall portion 11 and a horizontal wall portion 12 that are open at the bottom and formed in a U-shaped cross section, and A lower punch 2 having a vertical wall portion 21 and a lateral wall portion 22 formed in a U-shaped cross section so as to face the upper die 1 and adjacent to the vertical wall portion 21 of the lower punch 2 And the wrinkle pressing member 3 urged in the die direction, and when the drawing process is completed, the flange tip W11 of the blank plate W0 is the vertical wall portions 11 and 21 between the upper die 1 and the lower punch 2. This is a press die that draws in between.

  The upper die 1 is fastened to a ram of a press machine (not shown) and moves up and down in the direction of arrow P. At the lower end of the upper die 1, a wrinkle pressing surface 13 extending outside the vertical wall portion 11 is formed horizontally. The wrinkle pressing surface 13 of the upper die 1 is formed in a range in which both end portions in the width direction of the material plate W0 are pressed. A die shoulder R portion 14 is formed at the intersection between the vertical wall portion 11 and the wrinkle pressing surface 13 of the upper die 1. The die shoulder R portion 14 is formed substantially parallel to the left and right in the longitudinal direction. The corner R dimension of the die shoulder R portion 14 is about 3 to 5 mm.

  The lower die punch 2 is fastened to a bolster of a press machine (not shown) and receives the press load of the upper die 1. A punch shoulder R portion 23 is formed at the intersection of the vertical wall portion 21 and the horizontal wall portion 22 of the lower punch 2. The punch shoulder R portion 23 is pressed by the concave R portion of the upper die 1 at the bottom dead center. The corner R dimension of the punch shoulder R portion 23 is about 5 to 6 mm. The lower punch 2 is formed with a cushion hole 24 through which the cushion pin 5 that moves in the direction of the arrow Q is inserted. The cushion pin 5 pushes up the wrinkle pressing member 3 to at least the height of the lateral wall portion 22 of the lower punch 2. A plurality of cushion holes 24 are formed adjacent to the vertical wall portion 21 of the lower punch 2 and are equally spaced in the longitudinal direction.

  The wrinkle pressing member 3 is a substantially plate-like body in which wrinkle pressing surfaces 31 that press both ends in the width direction of the material plate W0 are formed in a horizontal shape in cooperation with the wrinkle pressing surface 13 of the upper die 1. The wrinkle pressing surface 31 of the wrinkle pressing member 3 is recessed in the vicinity of the vertical wall portion 21 of the lower die punch 2 away from the wrinkle pressing surface 13 of the upper die 1 in the vicinity of the vertical wall portion 21 of the lower die punch 2. The relief portion 4 is formed. The relief portion 4 is formed so as to be recessed stepwise with respect to the wrinkle pressing surface 31 of the wrinkle pressing member 3. Specifically, the relief portion 4 includes an inclined portion 41 formed at an inclination angle of about 30 to 60 ° inward of the wrinkle holding surface 31 of the wrinkle holding member 3 and a wrinkle of the wrinkle holding member 3. And a parallel portion 42 formed substantially parallel to the pressing surface 31. The parallel portion 42 is formed up to the profile surface 32 facing the vertical wall portion 21 of the lower punch 2 of the wrinkle pressing member 3.

  More specifically, as for the cross-sectional dimension of the relief portion 4, for example, the horizontal distance L1 is about 15 to 20 mm, and the vertical distance L3 is about 10 to 15 mm. Further, the relief portion 4 is separated from the wrinkle pressing surface 13 of the upper die 1 from a position at least 5 mm away from the contact point between the wrinkle pressing surface 13 of the upper die 1 and the die shoulder R portion 14. Preferably it is formed. For example, the distance L2 from the contact point between the wrinkle pressing surface 13 of the upper die 1 and the die shoulder R portion 14 to the intersection of the inclined portion 41 of the relief portion 4 and the wrinkle pressing surface 31 of the wrinkle pressing member 3 is 5 mm or more. It is good to form so that it becomes.

<Material inflow operation during drawing with a press die>
Next, the inflow operation of the material plate during the drawing process by the press die will be described with reference to FIGS. FIG. 4 shows a cross-sectional view of the press mold shown in FIG. 2 in the middle of drawing (initial stage). FIG. 5 shows a cross-sectional view of the press mold shown in FIG. FIG. 6 shows a cross-sectional view of the press die shown in FIG.

  As shown in FIG. 4, when the upper die 1 is lowered while the wrinkle holding surface 13 of the upper die 1 and the wrinkle holding surface 31 of the wrinkle holding member 3 narrow the both ends in the width direction of the blank, In the initial stage of processing, the lateral wall portion 22 of the lower punch 2 presses the center portion in the width direction of the material plate (corresponding to the top plate W20) upward, so that both end portions in the width direction of the material plate (corresponding to the side plate W10). Flows into the gap between the vertical wall 11 of the upper die 1 and the vertical wall 21 of the lower punch 2. At this time, the flange tip W11 positioned on the outer edge side in the width direction of the material plate is narrowly pressed by the wrinkle pressing surface 13 of the upper die 1 and the wrinkle pressing surface 31 of the wrinkle pressing member 3, and the width direction of the material plate An outward tensile load is acting. Therefore, the material plate W12 flowing into the gap between the vertical wall portion 11 of the upper die 1 and the vertical wall portion 21 of the lower die punch 2 is bent from the vertical direction to the horizontal direction by the die shoulder R portion 14.

  However, the wrinkle pressing surface 31 of the wrinkle pressing member 3 is spaced from the wrinkle pressing surface 13 of the upper die 1 toward the vertical wall portion 21 of the lower die punch 2 in the vicinity of the vertical wall portion 21 of the lower die punch 2. The relief part 4 (41, 42) formed in the shape of a dent is formed. Therefore, the material plate W12 passing through the die shoulder R portion 14 is slightly separated from the wrinkle pressing surface 13 of the upper die 1 and escapes in the direction of the relief portion 4, while the vertical wall portion 11 and the lower die of the upper die 1 are escaped. It flows into the gap with the vertical wall portion 21 of the punch 2. In this case, the distance G at which the material plate W12 is separated from the wrinkle pressing surface 13 of the upper die 1 is equal to or less than the plate thickness of the material plate W12 (for example, 10 to 20% of the plate thickness). The R dimension R2 is larger than the corner R dimension R1 of the die shoulder R portion 14, and the relief portion 4 is formed on the wrinkle pressing surface 31 of the wrinkle pressing member 3, so that the material plate that passes through the die shoulder R portion 14 is formed. W12 easily flows into the gap between the vertical wall portion 11 of the upper die 1 and the vertical wall portion 21 of the lower die 2.

  Next, as shown in FIG. 5, when the upper die 1 is further lowered, the flange of the material plate that has been narrowly pressed by the wrinkle pressing surface 13 of the upper die 1 and the wrinkle pressing surface 31 of the wrinkle pressing member 3. The distal end portion W11 moves away from the wrinkle pressing surface 13 of the upper die 1 and moves into the recessed space of the escape portion 4. Since the relief portion 4 is formed so as to be recessed stepwise with respect to the wrinkle holding surface 31 of the wrinkle holding member 3, the outer edge W14 of the flange tip portion W11 is less likely to interfere with the escape portion 4.

  For this reason, as shown in FIG. 6, the flange tip W11 is almost free from warping deformation based on interference with the escape portion 4, and follows the vertical wall portion 21 of the lower punch 2 with the die shoulder R portion 14 as a fulcrum. In this way, the upper die 1 and the lower punch 2 can enter between the vertical wall portions 11 and 21 while rotating. Therefore, the flange tip portion W11 is not easily bent into a curved shape by the die shoulder R portion 14. As a result, when the flange tip portion W11 is narrowly pressed between the vertical wall portions 11 and 21 of the upper die 1 and the lower die punch 2, the flange tip portion W11 is easily bent back linearly.

  The flange tip W11 rotates along the vertical wall portion 21 of the lower punch 2 with the die shoulder R portion 14 as a fulcrum, while the vertical wall portions 11, 21 of the upper die 1 and the lower punch 2 are rotated. Therefore, the tensile load due to the die shoulder R portion 14 is unlikely to act on the flange tip portion W11, and the tensile stress remaining after completion of drawing can be greatly reduced.

<Analytical results of stress distribution and warpage in pressed parts>
Next, the CAE analysis result of the stress distribution and the side plate warpage amount in the pressed part drawn by the press die will be described with reference to FIGS. FIG. 7 is an explanatory diagram of the stress analysis result (up by 60 mm from the bottom dead center) in the press die shown in FIG. FIG. 8 is an explanatory diagram of the stress analysis result (up 40 mm from the bottom dead center) in the press die shown in FIG. FIG. 9 shows an explanatory diagram of the stress analysis result (up 25 mm from the bottom dead center) in the press die shown in FIG. FIG. 10 is an explanatory view of the stress analysis result (bottom dead center) in the press die shown in FIG. FIG. 11 shows an explanatory diagram of the analysis result of the warpage amount of the side plate in the pressed part after mold release.

  FIGS. 7 to 10 show CAE stress analysis results in a pressed part (hereinafter referred to as “comparative example”) that is drawn by the press die 100 shown in FIG. 13 in FIG. 13A, and FIG. The CAE stress analysis result in the pressed part to be processed (hereinafter referred to as “the present embodiment”) is shown. Each CAE stress analysis result represents the stress distribution on the upper surface (outside of the plate) of the pressed part with contour lines and is displayed in six stages (P1 to P6) from the darker to the thinner dot density. Tensile stress is generated in the areas P1 to P3 where the dot density is high. In addition, compressive stress is generated in the P4 to P6 region where the dot density is low. In addition, the width dimension of the top plate and the side plate of the press parts is about 100 mm, and the material plate used is made of SPC590 and has a plate thickness of 1.6 mm. The cushion pressure is about 5 tons.

(Upper die rises 60mm above bottom dead center)
As shown in FIG. 7A, the strongest tensile stress P1 is distributed over substantially the entire region of the side plate of the comparative example. On the top plate of the comparative example, tensile stresses P1 and P2 and compressive stress P5 are repeatedly distributed in the width direction. In the wrinkle presser flange of the comparative example, the strongest compressive stress P6 is distributed in a strip shape along the die shoulder R portion, and the weak tensile stress P3 is distributed substantially uniformly along the wrinkle presser surface.

  On the other hand, as shown in FIG. 7B, in the side plate of this embodiment, a weak tensile stress P3 is distributed on the upper side near the punch shoulder R portion, and the strongest on the lower side near the die shoulder R portion. The tensile stress P1 is distributed. In the top plate of the present embodiment, the tensile stresses P1 and P2 at both ends in the width direction are distributed so as to gradually change to a weak tensile stress P3 or a weak compressive stress P4 toward the center in the width direction. In addition, the strongest compressive stress P6 is distributed in a band shape along the relief portion on the wrinkle presser flange of this embodiment, and the strongest tensile stress P1 is applied in a narrow range along the boundary line between the escape portion and the wrinkle presser surface. A weak compressive stress P4 is distributed along the wrinkle pressing surface outside the relief portion.

  From the above stress analysis results of FIGS. 7A and 7B, in the comparative example, the material plate is bent by the die shoulder R portion, whereby a strong tensile stress is generated in the entire side plate. On the other hand, in this example, when the material plate passes through the die shoulder R portion, the material plate is likely to flow into the vertical wall portion by bending in the direction of the relief portion, and the tensile stress of the side plate is relieved. It is considered a thing. Further, in this embodiment, since the material plate easily flows into the vertical wall portion, the stress change of the top plate is reduced as compared with the comparative example.

(Upper die rises 40mm above bottom dead center)
As shown in FIG. 8A, the strongest tensile stress P1 is distributed over substantially the entire region of the side plate of the comparative example. On the top plate of the comparative example, tensile stresses P1 and P2 and compressive stress P5 are repeatedly distributed in the width direction. In the wrinkle presser flange of the comparative example, the strongest compressive stress P6 is distributed in a strip shape along the die shoulder R portion, and the weak tensile stress P3 is distributed substantially uniformly along the wrinkle presser surface. The above points are substantially the same as those in FIG.

  On the other hand, as shown in FIG. 8B, in the side plate of this embodiment, weak tensile stresses P2 and P3 are distributed on the upper side near the punch shoulder R portion, and on the lower side near the die shoulder R portion. The strongest tensile stress P1 is distributed. As for the strongest tensile stress P1, the area | region has decreased compared with FIG.7 (B). In the top plate of the present embodiment, the tensile stresses P1 and P2 at both ends in the width direction are distributed so as to gradually change to a weak tensile stress P3 or a weak compressive stress P4 toward the center in the width direction. In addition, the strongest compressive stress P6 is distributed in a band shape along the relief portion on the wrinkle presser flange of this embodiment, and the strongest tensile stress P1 is applied in a narrow range along the boundary line between the escape portion and the wrinkle presser surface. A weak compressive stress P4 is distributed along the wrinkle pressing surface outside the relief portion. The above points are substantially the same as those in FIG.

  From the stress analysis results of FIGS. 8A and 8B described above, in the comparative example, the material plate is bent by the die shoulder R portion, so that strong tensile stress is still generated on the entire side plate. On the other hand, in this embodiment, when the material plate passes through the die shoulder R portion, the material plate is more likely to flow into the vertical wall portion by bending in the direction of the relief portion, and the tensile stress of the side plate is relieved. It is thought that it was done. It seems that the material plate is more likely to flow into the vertical wall because the presser area by the wrinkle presser surface has decreased.

(Upper die rises 25mm above bottom dead center)
As shown in FIG. 9A, the strongest tensile stress P1 is still distributed over substantially the entire region of the side plate of the comparative example. On the top plate of the comparative example, tensile stresses P1 and P2 and compressive stress P5 are repeatedly distributed in the width direction. In the wrinkle holding flange of the comparative example, the strongest compressive stress P6 is distributed in a band shape along the die shoulder R portion, and the weak compressive stress P4 is distributed in a band shape along the wrinkle pressing surface. Although the region of the compressive stress P4 due to the wrinkle pressing surface is narrow, it is considered that the tensile stress P1 of the side plate does not change because the influence of the tensile load by the die shoulder R portion is strong.

  On the other hand, as shown in FIG. 9B, in the side plate of this embodiment, weak tensile stresses P2 and P3 and weak compressive stress P4 are distributed on the upper side near the punch shoulder R portion, and the die shoulder R portion. The strongest tensile stress P1 is distributed on the lower side close to. The region of the strongest tensile stress P1 is further reduced as compared with FIG. In the top plate of the present embodiment, the tensile stresses P1 and P2 at both ends in the width direction are distributed so as to gradually change to a weak tensile stress P3 or a weak compressive stress P4 toward the center in the width direction. Further, since the wrinkle pressing flange of this embodiment is separated from the wrinkle pressing surface of the upper die and escapes to the relief portion, the strongest compressive stress P6 is relaxed to the medium compressive stress P5.

  From the stress analysis results of FIGS. 9A and 9B described above, in the comparative example, the material plate is bent by the die shoulder R portion, so that strong tensile stress is still generated on the entire side plate. On the other hand, in the present embodiment, it is considered that when the material plate escapes in the direction of the escape portion, it further flows into the vertical wall portion, and the tensile stress of the side plate is relaxed.

(Upper die is bottom dead center)
As shown in FIG. 10A, in the side plate of the comparative example, a region of a medium tensile stress P2 is partially generated in the vicinity of the end portion in the longitudinal direction, but the strongest tensile stress P1 is still many. Distributed in the area. The region of the strongest compressive stress P6 is distributed in a narrow strip at the flange tip of the side plate of the comparative example, and the region of the strongest tensile stress P1 is distributed in a narrow strip on the outer edge side. On the top plate of the comparative example, compressive stresses P6, P5, and P4 are distributed at narrow intervals in the width direction.

  On the other hand, as shown in FIG. 10 (B), the strongest tensile stress P1 is distributed only in the vicinity of the punch shoulder R portion on the side plate of this embodiment, and from the vicinity of the punch shoulder R portion to the flange tip portion. Compressive stresses P4 and P5 are distributed over a wide area. In the side plate of the present embodiment, the strongest tensile stress P1 is distributed in a band shape below the flange tip, and the region of the weak compressive stress P4 is distributed in a narrow band on the outer edge side. On the top plate of the present embodiment, compressive stresses P6, P5, and P4 are distributed at relatively wide intervals in the width direction.

  From the above stress analysis results of FIGS. 10A and 10B, in the comparative example, when the material plate is bent by the die shoulder R portion, a strong tensile stress is generated in most regions of the side plate. On the other hand, in this embodiment, it is considered that the material plate easily flows into the vertical wall portion by escaping in the direction of the escape portion, and the compressive stress of the side plate is increased. In the comparative example, strong compressive stress is distributed in a narrow band while strong tensile stress is widely distributed at the flange tip, whereas in this example, the flange tip is moderate or weak at the flange tip. Strong compressive stress is distributed in a band shape while compressive stress is widely distributed.

Next, as shown in FIG. 11, the analysis results of the warpage amount of the side plate in the pressed part after mold release are compared between the comparative example (A) indicated by the phantom line and the present example (B) indicated by the solid line. Here, in order to compare the bending wrinkles due to the die shoulder R portion at the flange front end portion W11, the cross section of the comparative example (A) is rotated counterclockwise so as to match the upper side of the side plate W10. .
In the comparative example (A), there is a large bending rod S2 that is bent horizontally outward from the position of the height H1 with respect to the lower end of the side plate W10. On the other hand, in the present embodiment (B), there are only a few bending ridges S1 that are bent horizontally outward from the position of the height H1 with respect to the tangent line, which is 1 / of the bending ridge S2 of the comparative example (A). 2 times or less.

  Here, the height H1 is about 30% of the total height H0 of the side plate W10, and corresponds to a change position of the stress distribution at the flange tip shown in FIG. That is, as shown in FIG. 10A, in the comparative example (A), strong tensile stress is widely distributed on the outer side of the flange tip portion, and strong compressive stress is distributed in a narrow band shape. Therefore, on the outer side of the flange tip, a contractive force based on tensile stress acts from above and below across a narrow band-like compressive stress location. As a result, in the comparative example (A), it seems that the bending ridge S2 that bends horizontally outward from the position of the height H1 is greatly generated.

  On the other hand, in this embodiment (B), as shown in FIG. 10 (B), a strong tensile stress is formed in a strip shape while a medium or weak compressive stress is widely distributed on the outer side of the flange tip. Distributed. Therefore, on the outer side of the flange tip W11, an extension force based on compressive stress acts from above and below across a strong strip-like tensile stress location. As a result, in this embodiment (B), the contraction force of the tensile stress location acts so that the extension force of the compression stress location cancels from the vertical direction, and the bending ridge S2 that bends horizontally outward can be greatly reduced. Seem.

  According to the above mechanism, in the comparative example (A), the bending ridge S2 due to the die shoulder R portion 14 remains largely in the region of the band-like strong compressive stress in the flange tip portion W11, whereas in this embodiment (B). The tensile stress due to the die shoulder R portion 14 when flowing into the vertical wall portion at the flange tip portion W11 remains, but it is considered that the bending fold S1 due to the die shoulder R portion 14 hardly remains.

  In addition, the springback amount S3 of the side plate W10 of this example (B) was about 10 mm. On the other hand, the spring back amount of the side plate W10 of the comparative example (A) was about 18 mm when measured by rotating the gap S4 of the top plate W20 clockwise so as to be zero. In this embodiment (B), the amount of spring back of the side plate W10 can also be greatly reduced. The reason why the springback amount of the side plate W10 can be greatly reduced is that, as shown in FIG. 4 to FIG. 6, the upper die and the lower die punch are formed by the material plate escaping in the direction of the relief portion from the initial stage of drawing. This is considered to be due to the fact that the compressive stress of the side plate W10 increased due to the inflow between the vertical wall portions of the side plate W10.

<Effect>
As described above, according to the press die 10 of the present embodiment, the wrinkle pressing surface 31 of the wrinkle pressing member 3 and the wrinkle pressing surface 13 of the upper die 1 near the vertical wall portion 21 of the lower die punch 2. Since the escape portion 4 is formed so as to be spaced and recessed toward the vertical wall portion 21 of the lower die punch 2, the wrinkle holding surface 13 of the upper die 1 and the wrinkle of the wrinkle holding member 3 are formed at the initial stage of drawing. The flange tip W11 of the blank plate W0 that has been narrowly pressed between the pressing surface 31 can be separated from the wrinkle pressing surface 13 of the upper die 1 and enter the escape portion 4 from the middle stage of drawing. Therefore, the flange tip portion W11 rotates along the vertical wall portion 21 of the lower punch 2 with the die shoulder R portion 14 as a fulcrum, while the vertical wall portions 11, 21 of the upper die 1 and the lower punch 2 are rotated. You can get in between. As a result, the flange tip portion W11 is hardly bent into a curved shape by the die shoulder R portion 14, and the flange tip portion W11 is narrowed between the vertical wall portions 11, 21 of the upper die 1 and the lower die punch 2. At this time, it becomes easier to bend the flange tip W11 linearly.

  The flange tip W11 rotates along the vertical wall portion 21 of the lower punch 2 with the die shoulder R portion 14 as a fulcrum, while the vertical wall portions 11, 21 of the upper die 1 and the lower punch 2 are rotated. Therefore, the tensile load due to the die shoulder R portion 14 is unlikely to act on the flange tip portion W11, and the tensile stress remaining after completion of drawing can be greatly reduced. As a result, a bending wrinkle (warp) S1 due to the die shoulder R portion 14 can be made difficult to occur at the flange tip portion W11.

  Therefore, according to the present embodiment, the press part W having a U-shaped cross section can be formed by drawing without leaving the wrinkle holding flange, and the bending wrinkles (warping) remaining on the flange tip W11 serving as a product terminal. A press die 10 that can reduce S1 and improve product accuracy can be provided.

  Further, according to the present embodiment, the relief portion 4 is formed so as to be recessed stepwise with respect to the wrinkle pressing surface 31 of the wrinkle pressing member 3, so that the flange tip portion W11 is the wrinkle pressing surface of the upper die 1. When separating from 13, it is easy to avoid the interference between the outer edge W14 of the flange tip W11 and the escape portion 4. Therefore, the flange tip W11 is hardly subjected to warping deformation due to interference with the escape portion 4, while rotating along the vertical wall portion 21 of the lower punch 2 with the die shoulder R portion 14 as a fulcrum. It is possible to enter between the vertical wall portions 11 and 21 of the mold die 1 and the lower mold punch 2. As a result, the flange tip portion W11 is hardly bent into a curved shape by the die shoulder R portion 14 and the relief portion 4, and the flange tip portion W11 is located between the vertical wall portions 11, 21 between the upper die 1 and the lower die punch 2. When the pressure is narrowed, it becomes easier to bend the flange tip W11 back into a straight line.

  Further, according to the present embodiment, the relief portion 4 is provided with the wrinkle presser of the upper die 1 from a position at least 5 mm away from the contact point between the wrinkle presser surface 13 of the upper die 1 and the die shoulder R portion 14. Since the flange tip W11 is formed so as to be separated from the surface 13, the flange tip W11 is held along the vertical wall 21 of the lower punch 2 with the die shoulder R 14 as a fulcrum while holding a linear flange of at least 5 mm or more. It is possible to enter between the vertical wall portions 11 and 21 of the upper die 1 and the lower die punch 2 while rotating. Therefore, when the flange tip portion W11 is narrowed between the vertical wall portions 11 and 21 of the upper die 1 and the lower die punch 2, a linear flange of at least 5 mm becomes a flange, and the flange tip portion W11 is further straightened. It becomes easy to bend back into a shape. As a result, a bending wrinkle (warp) S1 due to the die shoulder R portion 14 can be made more unlikely to occur at the flange tip portion W11.

<Modification>
The embodiment described above can be changed as appropriate without departing from the scope of the present invention.
For example, as shown in FIGS. 12A to 12C, the lower punch 2 </ b> B has a shelf 25 that intersects with the vertical wall 21 of the lower punch and faces the wrinkle pressing surface 13 of the upper die 1. May be formed. According to this press die 10B, the flange tip W11 that has been separated from the wrinkle pressing surface 13 of the upper die 1 and entered the relief portion 4 from the middle stage of the drawing process is used as the wrinkle pressing surface 13 of the upper die 1 and the lower die. By pressing with the shelf 25 of the punch 2B, it can be formed as a pressed part WW having a hat-shaped flange W11T on the outer edge of the U-shaped cross section. Therefore, the flange tip W11 is frozen by forming a hat-like flange W11T on the outer edge, and the bending wrinkles (warping) remaining at the flange tip W11 can be further reduced. As a result, product accuracy can be further improved. Note that the press die 10B of the modified example is basically the same as the press die 10 of the present embodiment except for the shelf portion 25, and therefore, common portions are denoted by the same reference numerals and description thereof is omitted. To do.

Further, for example, in the present embodiment, the vertical wall portion 21 of the lower mold punch 2 is formed in a straight line, but the vertical wall portion 21 of the lower mold punch 2 expects the amount of bending wrinkles (warping) of the flange tip portion W11. Thus, it can be formed in a shape bent in the opposite direction to the warp. By considering the amount of bending wrinkles (warping), the product accuracy of the flange tip W11 can be further improved.
In this embodiment, the die is an upper die and the punch is a lower die. However, the die may be turned upside down.

  INDUSTRIAL APPLICABILITY The present invention can be used as a press die for forming a press part having a U-shaped cross section by drawing.

1 Upper die (die)
2, 2B Lower punch (punch)
3 Wrinkle holding member 4 Relief part 5 Cushion pin 10, 10B Press mold 11, 21 Vertical wall part 12, 22 Horizontal wall part 13, 31 Wrinkle pressing surface 14 Die shoulder R part 23 Punch shoulder R part 25 Shelf part S1, S2 Bending bar (warp)
W, WW Press parts W0 Material plate W10 Side plate W20 Top plate W11 Flange tip

Claims (4)

A die having a vertical wall portion and a horizontal wall portion that are open at the top or bottom and formed in a U-shaped cross section, and a vertical wall portion and a horizontal wall portion that are formed in a U-shaped cross section facing the die. And a wrinkle holding member that is arranged adjacent to the vertical wall portion of the punch and is urged in the die direction, and when drawing is completed, the front end of the flange of the blank plate has a vertical position between the die and the punch. A press die that draws between the walls,
The wrinkle pressing surface of the wrinkle pressing member is provided with a relief portion formed in a concave shape toward the vertical wall portion of the punch and spaced from the wrinkle pressing surface of the die in the vicinity of the vertical wall portion of the punch. A press die characterized by. In the press die according to claim 1,
The press die, wherein the relief portion is formed to be recessed stepwise with respect to the wrinkle pressing surface of the wrinkle pressing member. In the press die according to claim 1 or 2,
The press portion is formed so as to be separated from the crease pressing surface of the die from a position separated from the contact point between the crease pressing surface of the die and the die shoulder R portion by at least 5 mm or more to the outside of the mold. Type. The press die according to any one of claims 1 to 3,
A press die characterized in that the punch is formed with a shelf that intersects with the vertical wall portion of the punch and faces the wrinkle pressing surface of the die.