JP2018079491A - Press molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a press molding method for a press-molded article which keeps the top plate part curved, has a vertical wall part shrunk by being continuously molded from the top plate part to undergo flange deformation, and makes the vertical wall part form a projected part the seat face of which is flat and extends in a height direction of the vertical wall part.SOLUTION: A press molding method of this invention, which makes a vertical wall part 5 form a projected part 7 the seat face 9 of which is flat and extends in a height direction of the vertical wall part 5 when a press-molded article 1 which keeps the top plate part 3 curved, has a vertical wall part 5 shrunk by being continuously molded from the top plate part 3 to undergo flange deformation is molded, includes: a grooved blank molding step of molding grooved blanks 41 where a plurality of lower projection grooved parts 43 extending in a direction corresponding to the height direction of the vertical wall part 5 are formed in a part corresponding to the vertical wall part 5 in a blank 31 at predetermined intervals; and a vertical wall molding step of molding the vertical wall part 5 which form projected parts 7 between the plurality of lower projection grooved parts 43 formed by using a punch 13 and a die 15.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a press molding method, and more particularly, to a press molding method of a press molded product that is press-molded in response to shrinkage flange deformation.

When press-molding a press-molded product having a vertical wall part that is bent and bends and is deformed by flange bending, the vertical wall part is formed by in-plane compression deformation, and the amount of compression deformation moves away from the bending ridge line. It gets bigger. For example, when the top plate portion is press-molded into a convexly curved part, if the ridge line between the top plate portion and the vertical wall portion is curved, the vertical wall portion is further compressed and deformed as it is separated from the top plate portion.
And there is a problem that wrinkles are generated in the vertical wall portion of the press-molded product that has been subjected to such compressive deformation, and particularly when high-tensile steel plates are used, the generation of wrinkles becomes significant. The defective shape of the press-formed product becomes a problem. Therefore, it is necessary to take measures to suppress the generation of wrinkles due to compression deformation in the vertical wall surface during the molding process.

Conventionally, it has been generally practiced to suppress the generation of wrinkles by forming an uneven portion on the vertical wall portion from the in-plane to the plate end (Non-Patent Document 1).
In addition, in Patent Document 1, in a press-formed body having a vertical wall surface having a curvature and a flange surface below the vertical wall surface, a convex bead sticking out in a convex shape is applied to the vertical wall surface, and the convex shape A press working method that suppresses wrinkle generation by providing a concave bead recessed in a concave shape on the flange surface directly under the bead is disclosed.
Further, in Patent Document 2, in the formation of a metal product having a U-shaped or C-shaped cross-sectional shape, a convex portion is formed at a position corresponding to a convex curved portion in the longitudinal direction of the vertical wall portion of the product. A multi-stage press molding method in which a shape emboss is provided is disclosed.

JP 2010-115674 A JP 2008-12570 A

Edition of Steel Sheet Forming Technology Study Group, “Press Forming Difficulty Handbook”, 3rd edition, Nikkan Kogyo Shimbun, April 2007, p.283-284

  Non-Patent Document 1 and Patent Document 1 disclose a technique for forming a convex bead as described above on a curved vertical wall, but a press-formed product having such a vertical wall has a U-shaped cross section. When welding with other parts in the shape, the seat surface of the convex bead may be used as the joint surface. In such a case, avoid wrinkles on the seat surface of the convex bead. Therefore, it is required to absorb the surplus of wrinkle material and to mold the flatness of the seating surface of the convex bead.

  However, according to the technique disclosed in Patent Document 1, when a die having a bending blade (die) having a recess along the shape of the convex bead of the punch is used, The blank is bent and deformed into the shape of a convex bead at the concave part, but it is crushed flat at the bottom dead center of the molding, but the bending wrinkles remain, so that it can be elastically restored when the press-molded product is taken out of the mold, or pushed flat. Since it cannot be crushed, there is a problem that a wrinkle shape is generated on the seating surface, the surface accuracy is poor, and the flatness of the seating surface of the convex bead is lowered.

  In addition, the technique disclosed in Patent Document 2 provides a difference in the line length of the material end by providing a convex emboss at a position corresponding to the curved portion with respect to the vertical wall curved in a convex shape in the longitudinal direction. However, there is no disclosure or suggestion about flattening the seating surface of the convex emboss, and there is a technique disclosed in Patent Document 1. Similarly, there is a problem that wrinkles generated on the embossed seating surface can be suppressed and high flatness cannot be formed.

  The present invention has been made to solve the above-described problems, the top plate portion is curved, and has a vertical wall portion that is continuously formed from the top plate portion and becomes a shrinkage flange deformation, When forming a press-molded product in which the vertical wall portion has a flat seat surface and a convex shape portion extending in the height direction of the vertical wall portion is formed, the occurrence of wrinkles on the seat surface of the convex shape portion is suppressed. Then, it aims at providing the press molding method which can shape | mold the flatness of this seat surface highly.

(1) In the press molding method according to the present invention, when a top plate portion is curved and a press molded product having a vertical wall portion which is continuously formed from the top plate portion and is subjected to shrinkage flange deformation, Is formed in the vertical wall portion in the height direction of the vertical wall portion in the height direction of the vertical wall portion. Using a grooved blank forming step for forming a grooved blank in which a plurality of groove-shaped portions extending in a corresponding direction are formed at a predetermined interval, and using the punch and the die, the protrusions are formed between the plurality of groove-shaped portions. And a vertical wall forming step for forming the vertical wall portion on which the shape portion is formed.

(2) The groove according to (1), wherein the groove-shaped portion formed in the grooved blank forming step is convex in a direction opposite to the convex direction of the convex-shaped portion formed on the vertical wall portion. It is a shape part.

  In the present invention, when forming a press-molded product having a vertical wall portion that is curved from the top plate portion and is continuously formed from the top plate portion to form a flange deformation, the vertical wall portion has a flat seating surface. A convex shape portion extending in the height direction is formed in the vertical wall portion, and a groove shape extending in a direction corresponding to the height direction of the vertical wall portion in a portion corresponding to the vertical wall portion in the blank The groove-shaped blank forming step for forming a grooved blank having a plurality of portions formed at predetermined intervals, and the convex-shaped portion is formed between the plurality of formed groove-shaped portions using a punch and a die. A vertical wall forming step for forming the vertical wall portion, thereby concentrating bending deformation in the groove shape portion in the forming process, and suppressing the occurrence of wrinkles on the seat surface of the convex shape portion, and the seat surface A press-formed product with high flatness can be obtained.

It is explanatory drawing explaining the press molding method which concerns on embodiment of this invention. It is explanatory drawing explaining the press molded product made into a shaping | molding object in embodiment of this invention. It is explanatory drawing explaining the conventional press-molding metal mold | die which shape | molds the press-molded product made into shaping | molding object in embodiment of this invention. It is a figure which shows the analysis result of the deformation | transformation behavior of the blank in the process shape | molded by the conventional press molding method. It is a figure which shows the shape of the press-molded article which concerns on embodiment of this invention, and the grooved blank in which the downward convex groove shape part was shape | molded. It is a figure which shows the analysis result of the deformation | transformation behavior of the grooved blank in which the downward convex groove shape part was formed in the process of shape | molding a press molded product with the press molding method which concerns on embodiment of this invention. It is explanatory drawing explaining the press molding method using the grooved blank which shape | molded the upward convex groove shape part as another aspect of embodiment of this invention. It is a figure which shows the analysis result of the deformation | transformation behavior of the grooved blank in which the upward convex groove shape part was shape | molded in the process in which a press molded product is shape | molded with the press molding method which concerns on embodiment of this invention. In the Example of this invention, it is explanatory drawing explaining the evaluation item for evaluating generation | occurrence | production of the wrinkle in the seat surface of the convex-shaped part of a press-formed product. In a present Example, it is a graph which shows the analysis result of the curvature radius in the formation process of the site | part corresponded to the lower end of the convex-shaped part of the press-molded product shape | molded by the conventional press molding method (comparative example). In a present Example, it is a figure of the analysis result which shows the influence of the vertical wall shaping | molding height with respect to wrinkle generation | occurrence | production in the seat surface of the convex-shaped part of the press-molded product shape | molded by the conventional press-molding method as a comparative example. In a present Example, it is a figure of the analysis result which shows the influence of the seat surface height of a convex-shaped part with respect to wrinkle generation | occurrence | production in the seat surface of the convex-shaped part of the press-molded product shape | molded by the conventional press molding method as a comparative example. In a present Example, it is a figure which shows the evaluation result of the wrinkle generation | occurrence | production in the seat surface of the convex-shaped part of the press-molded product shape | molded by the press-molding method which concerns on this invention as an invention example.

  Prior to explaining the press molding method according to the embodiment of the present invention, first, the press molded product 1 to be molded in the present invention will be described.

<Press-formed product>
As shown in FIG. 2, the press-molded product 1 to be molded in the present embodiment has a top plate portion 3 that is curved upward and convex in a side view along the longitudinal direction of the press-molded product 1. It has a U-shaped cross-sectional shape having a vertical wall portion 5 that is continuously formed from the portion 3 and forms a deformed flange, and in the vertical wall portion 5, the seating surface 9 is flat and has a height from the lower end of the vertical wall portion 5. The convex-shaped part 7 extended in the direction is formed.

Conventionally, as shown in FIG. 3A, for example, the press-formed product 1 forms the vertical wall portion 5 in cooperation with the punch 13 having the punch-side vertical wall forming surface portion 19 and the punch-side vertical wall forming surface portion 19. The die 15 having the die-side vertical wall forming surface portion 21 and the pad 17 for pressing the portion corresponding to the top plate portion 3 in the blank 31 are molded using the press-molding die 11, and the vertical wall portion 5 is formed. In order to form the convex portion 7, a convex shape forming portion 25 is formed on the punch side vertical wall forming surface portion 19, and a concave portion 27 is formed on the die side vertical wall forming surface portion 21.
Note that the press-molding die 11 and the press-molded product 1 shown in FIG. 3 show only the portion in the width direction 1/2.

  The convex portion 7 is formed on the vertical wall portion 5 in order to suppress the occurrence of wrinkles on the vertical wall portion 5 due to shrinkage flange deformation in the molding process. When joining, since the seating surface 9 of the convex-shaped part 7 is used as a joining surface with other components, it is necessary to form the seating surface 9 flatly. However, when the press-molded product 1 is molded using the press-molding die 11, wrinkles are generated on the seating surface 9 of the convex portion 7, and the flatness is deteriorated, which causes a problem when joining with other components. There was a case.

  Here, the reason why wrinkles occur on the seating surface 9 of the convex portion 7 is subjected to press molding analysis in the process of molding the press molded product 1 using the press molding die 11 shown in FIG. This will be described below based on the analysis result of the deformation behavior of the blank 31 in the molding process shown in FIG. In FIG. 4, the punch 13, the pad 17, and the blank 31 are shown without displaying the die 15 (see FIG. 3) in order to make the deformation of the blank 31 easier to see.

  When the press-molded product 1 is press-molded using the press-molding die 11, when the die 15 is moved relative to the punch 13 while the upper surface of the blank 31 is pressed by the pad 17, the bending blade R of the die 15 is moved. The portion 23 (see FIG. 3A) contacts the surface of the blank 31.

  Here, the die-side vertical wall molding surface portion 21 is formed with a concave portion 27 that forms the convex-shaped portion 7 in the vertical wall portion 5 and a convex portion 29 that protrudes toward the punch 13 between the concave portions 27. The surface of the die-side vertical wall molding surface portion 21 has an uneven shape, and this uneven shape continues to the bending blade R portion 23 (see FIG. 3A).

  Therefore, when the bending blade R portion 23 of the die 15 comes into contact with the surface of the blank 31, first, the convex portion 29 of the bending blade R portion 23 is formed on the surface of the blank 31. It abuts as a part to be molded.

  When the die 15 is further moved relative to the punch 13 side, even if the convex portion 29 comes into contact with the surface of the blank 31 in the die-side vertical wall molding surface portion 21, the molding starts (for example, as shown in FIG. 4C). Since the seat surface portion 60) and the recess 27 do not come into contact with each other (for example, the seat surface portion 61 in FIG. 4C), the blank 31 undergoes plastic bending and deforms into a wave shape (FIGS. 4B to 4D). The part enclosed with the ellipse of the middle broken line, FIG.4 (d-2)).

  Such a wave-like deformation in the blank 31 is deformed into a concavo-convex shape in the concave portion 27 of the die 15 and the convex shape forming portion 25 of the punch 13 in the vicinity of the molding bottom dead center (FIG. 4 (e)). At the bottom dead center of the molding (FIG. 4 (f)), the concave portion 27 of the die 15 and the convex shape forming portion 25 of the punch 13 are pressed and crushed. Even then, the plastic bending deformation cannot be completely eliminated, and bending folds remain.

As a result, when the press-molded product 1 is taken out from the press-molding die 11 due to the bending wrinkles, it is elastically recovered or is not flatly crushed, so that wrinkles occur on the seating surface 9 of the convex portion 7. Therefore, it becomes difficult to form it flat.
Furthermore, the flatness at the portion where the bending folds remain after undergoing plastic bending deformation decreases as the bending radius of curvature decreases, and this tendency is particularly remarkable in high-tensile steel sheets.

Therefore, the inventor forms a groove shape portion in advance between the portion corresponding to the seating surface 9 of the convex portion 7 in the blank 31 and concentrates the plastic bending deformation on the groove shape portion in the molding process. This has led to the idea of reducing the deformation of the blank 31 in a wavy shape during the forming process and forming the flatness high without causing wrinkles on the seating surface 9 of the convex portion 7.
The present invention has been made based on such an idea, and the contents thereof will be specifically described below.

<Press molding method>
Next, the press molding method according to the embodiment of the present invention will be described.
As shown in FIG. 2, the press molding method according to the present embodiment is a press molding having a vertical wall portion 5 in which the top plate portion 3 is curved and is continuously formed from the top plate portion 3 so as to be contracted and deformed into a flange. When the product 1 is molded, the seat surface 9 is flat and the convex wall portion 7 is formed on the vertical wall portion 5 extending in the height direction from the lower end of the vertical wall portion 5. As shown in FIG. A grooved blank 41 in which a plurality of downward convex groove-shaped portions 43 extending in a direction corresponding to the height direction from the lower end of the vertical wall portion 5 is formed at a predetermined interval is formed in a portion corresponding to the vertical wall portion 5 in 31. Using a grooved blank forming step (FIG. 1 (a)) and a press molding die 11 having a punch 13, a die 15 and a pad 17, a convex shape is formed between a plurality of downward convex groove-shaped portions 43 formed. The vertical wall forming step for forming the vertical wall portion 5 so that the portion 7 is formed (FIG. 1B) It is those with a.
Hereafter, each said process is demonstrated in detail.

≪Grooved blank forming process≫
The grooved blank forming step is performed, for example, in the parts a to d (see FIG. 5A) corresponding to the vertical wall portion 5 in the blank 31 from the lower end of the vertical wall portion 5 as shown in FIG. A grooved blank 41 in which a plurality of convex lower convex groove-shaped portions 43a to 43d are formed at a predetermined interval downward (in a direction opposite to the convex shape of the convex shaped portion 7) as a groove-shaped portion extending in a direction corresponding to the height direction. In forming the grooved blank 41, for example, as shown in FIG. 1 (a), upper molds each having a lower convex groove shape forming portion 47a and 49a for forming a lower convex groove shape portion 43, respectively. A preforming mold 45 comprising 47 and a lower mold 49 can be used.

  Here, the X, Y, and Z axes in FIG. 5A are the longitudinal direction, the width direction, and the height direction of the press-formed product 1, respectively. In FIG. 5, the press-formed product 1 has a half portion in the width direction.

  In addition, the grooved blank 41 shown in FIG. 5B is formed by forming the lower convex groove-shaped portions 43a to 43d at portions a to d corresponding to the centers of the convex portions 7a to 7e formed on the vertical wall portion 5. The X coordinates of the downward convex groove-shaped portions 43a to 43d are defined based on the X coordinates of the parts a to d.

  Furthermore, the downward convex groove-shaped portions 43 a to 43 d are concave shapes having a length of 75 mm, a width of 7 mm, and a depth of 3 mm, and the depth of the downward convex groove-shaped portions 43 a to 43 d at the tip side 10 mm is from the surface of the blank 31. It is set so as to gradually change to the bottom surfaces of the downward convex groove-shaped portions 43a to 43d. However, the groove-shaped part formed in the blank in the present invention is not limited to the above dimensions, and the dimension of the groove-shaped part can be appropriately set.

≪Vertical wall forming process≫
In the vertical wall forming step, as shown in FIG. 1B, a grooved blank 41 is formed by a press molding die 11 having a punch 13, a die 15 and a pad 17, and the grooved blank forming is performed. The vertical wall part 5 in which the convex part 7 is formed between the plurality of downward convex groove part 43 formed in the process is formed.

  In the press-formed product 1 shown in FIG. 5A, convex portions 7b to 7d are formed between the downward convex groove-shaped portions 43a to 43d (FIG. 5B).

  Deformation behavior of the grooved blank 41 obtained by the press forming analysis in the process of forming the press-formed product 1 by the press forming method according to the present embodiment will be described below based on the analysis result shown in FIG. In FIG. 6, in order to make the deformation of the grooved blank 41 easier to see, the punch 13, the pad 17, and the grooved blank 41 are shown without displaying the die 15 (see FIG. 3).

  As shown in FIG. 6A, a grooved blank 41 is placed on the upper surface of the punch 13, and the die 15 (see FIG. 3A) is placed on the punch 13 side while the grooved blank 41 is pressed by the pad 17. As shown in FIG. 6 (b), the part continuous from the concave portion 27 of the die side vertical wall forming surface portion 21 in the bending blade R portion 23 (FIG. 3 (a)) does not come into contact. The part continuing from the convex portion 29 comes into contact with the surface of the grooved blank 41, and the deformation of the grooved blank 41 starts. At this time, the deformation of the grooved blank 41 concentrates on the downward convex groove shape portion 43, and the space between the downward convex groove shape portions 43 (for example, the seat surface portion 63 in FIG. 6C) is a conventional flat blank 31. 4 is maintained relatively flat compared to the seating surface portion 61 of FIG. 4C (see the portion surrounded by the dashed ellipse in FIGS. 6B and 6C).

  When the die 15 is further moved relative to the punch 13 side, as shown in FIG. 6D, the lower convex groove-shaped portion 43 of the grooved blank 41 is formed by the concave portion 27 of the die 15 and the convex shape forming portion 25 of the punch 13. The space is formed into a convex shape.

  In the process of relatively moving the die 15 to the molding bottom dead center (FIGS. 6 (e) to (f)), the downward convex groove-shaped portion 43 includes the punch side vertical wall molding surface portion 19 and the die side vertical wall molding surface portion 21. The press-molded product 1 in which the convex wall 7 is formed on the vertical wall 5 is molded at the bottom dead center (FIG. 6 (f)).

  Thus, according to the press molding method according to the present embodiment, it is possible to reduce the deformation of the blank 31 into a wave shape by concentrating the plastic bending deformation on the lower convex groove shape portion 43 during the molding, and the lower convex groove. Since the convex portion 7 can be formed while the space between the shape portions 43 is kept relatively flat, the occurrence of wrinkles on the seat surface 9 of the convex shape portion 7 is suppressed, and the flatness of the seat surface 9 is increased. can do.

  In the above description, the downward convex groove shape portions 43a to 43d shown in FIG. 5 are convex in the opposite direction to the convex shape of the convex shape portion 7 formed in the press-formed product 1, but according to the present invention. The groove-shaped portion formed in the blank in the grooved blank forming step does not limit the direction of the unevenness.

  That is, as another aspect of the press molding method according to the embodiment of the present invention, for example, as shown in FIG. 7, a grooved blank 51 in which an upward convex groove-shaped portion 53 having a convex shape upward is used. The press-formed product 1 may be molded.

  In this case, in the grooved blank forming step, as shown in FIG. 7A, from the upper mold 57 and the lower mold 59 respectively having the upper convex groove shape forming portions 57a and 59a forming the upper convex groove shape portion 53. As a groove-shaped portion extending in a direction corresponding to the height direction from the lower end of the vertical wall portion 5 at a portion corresponding to the vertical wall portion 5 in the blank 31, the pre-molding die 55 is formed. A grooved blank 51 is formed in which a plurality of convex upper convex groove-shaped portions 53 are formed at predetermined intervals in the same direction as the convex shape of the shape portion 7.

  Then, in the subsequent vertical wall forming step, as shown in FIG. 7B, a plurality of upward convex groove-shaped portions 53 are formed using the press-molding die 11 provided with the punch 13, the die 15, and the pad 17. The vertical wall part 5 in which the convex part 7 is formed is formed.

  Deformation behavior of the grooved blank 51 obtained by press forming analysis in the process of forming the press-formed product 1 using the grooved blank 51 will be described below based on the analysis result shown in FIG. In FIG. 8, the punch 13, the pad 17, and the grooved blank 51 are illustrated without displaying the die 15 (see FIG. 3) in order to make the deformation of the grooved blank 51 easier to see.

  As in the case of using the grooved blank 41 in which the above-described downward convex groove-shaped portion 43 is formed (FIG. 6), the die 15 is punched even in the case of using the grooved blank 51 in which the upward convex groove-shaped portion 53 is formed. In the process of bending the grooved blank 51 by relative movement to the side 13, the upper convex groove-shaped portion 53 comes into contact with the die 15 and the upper convex groove-shaped portion 53 is deformed somewhat concavely, Between the convex groove-shaped portions 53 (for example, the seat surface portion 65 in FIG. 8C) is kept relatively flat compared to the seat surface portion 61 in FIG. 4C using the conventional flat blank 31. It sag (the part surrounded by the dashed ellipse in FIG. 8B).

  Then, the die 15 is further moved relatively toward the bottom dead center, and the upward convex groove-shaped portion 53 is formed into a concave shape to form the vertical wall portion 5 (FIGS. 8C to 8F). ), And the plastic deformation between the upper convex groove-shaped portions 53 is reduced, and the convex-shaped portions 7 are molded while being kept relatively flat.

  As described above, even when the grooved blank 51 formed with the upper convex groove-shaped portion 53 is used, the blank 31 is deformed into a wave shape by concentrating the plastic bending deformation on the lower convex groove-shaped portion 43 during the molding. , And the occurrence of wrinkles on the seating surface 9 of the convex portion 7 can be suppressed, and the flatness of the seating surface 9 can be formed high.

  In addition, although the downward convex groove-shaped part 43 or the upward convex groove-shaped part 53 formed in the blank 31 is worried that bending wrinkles remain at the bottom dead center of the molding and wrinkles in the press-formed product 1. Since the portion corresponding to the downward convex groove shape portion 43 or the upward convex groove shape portion 53 in the press-formed product 1 is between the convex shape portions 7, even if wrinkles are generated, There is no problem because there is not.

  In the above description, the press-formed product 1 has a U-shaped cross-sectional shape. However, the press-formed product to be molded by the press molding method according to the present invention has a vertical wall portion that is deformed by shrinkage flange. As long as the flange portion is not provided at the lower end of the vertical wall portion, and may have an L-shaped cross section or a U-shaped cross section. Any press-formed product having a vertical wall portion may be used.

  Furthermore, the press-formed product 1 has a shape that is convexly convex upward in a side view. For example, the top plate portion that is curved in a convex shape in a side view in a plan view, or both in a plan view and a side view. In a press-molded product having a top plate portion curved in a convex shape, since the vertical wall portion continuously formed from these top plate portions shrinks and becomes flange deformation, the application object of the press molding method according to the present invention is Become.

Moreover, although the press-molded product 1 shown to Fig.5 (a) is a thing in which the five convex-shaped parts 7 were formed in the vertical wall part 5, the press molding method which concerns on this invention is with other components. As long as the joint surface can be secured, it is possible to suppress the molding load in press molding by not forming the convex portion for the portion where the large bending deformation (small curvature radius) does not occur in the vertical wall portion. What is necessary is just to set the number of convex-shaped parts suitably, and what is necessary is just to set according to the number of convex-shaped parts also about the groove-shaped part (down convex groove-shaped part 43 or the upper convex groove-shaped part 53) shape | molded in a blank. .
Furthermore, since the end of the press-formed product 1 is contracted and the flange deformation is small, wrinkles are unlikely to occur, and the groove-shaped portion (the lower convex groove-shaped portion 43 or the upper convex groove-shaped shape is formed with respect to the convex-shaped portion 7 formed at the end. It is sufficient if there is one adjacent portion 53).

  In the above description, the press-formed product 1 is formed in a state where the grooved blank 41 or 51 is pressed by the pad 17, but the press-molding method according to the present invention presses the grooved blank with the pad. This is not necessarily required.

Since verification for confirming the operational effects of the press molding method according to the present invention was performed, this will be described below.
In the present embodiment, press molding analysis and springback analysis are performed on the press molded product 1 shown in FIG. 2 as an analysis target, and the convex portion of the press molded product 1 is based on the analysis result of the press molded product 1 after springback. 7 generation of wrinkles on the seating surface 9 was evaluated.

The press-molded product 1 to be analyzed has a longitudinal wall length of 300 mm, a width of the top plate portion 3 and a curvature radius of curvature of 70 mm and 1000 mm, and a width of the seating surface 9 of the convex portion 7 of 25 mm. The height (height of the vertical wall portion 5) was changed from 40 mm to 65 mm, and the seat surface height of the convex portion 7 (height from the bottom surface of the convex shape to the seat surface (outside)) was changed in the range of 5 to 7 mm. The case was analyzed. In the analysis, the blank 31 was a steel plate having a tensile strength of 1180 MPa class and a plate thickness of 1.6 mm.
Then, finite element method analysis software LS-DYNA (manufactured by LSTC) was used for press molding analysis and springback analysis of the press molded product 1.

  In the present embodiment, in the press molding method according to the present invention, the case where the groove 41 is formed using the grooved blank 41 formed with the lower convex groove-shaped portion 43 is referred to as Invention Example 1 (see FIG. 1). The case where it shape | molded using the shape | molded blank 51 with a groove | channel was made into invention example 2 (refer FIG. 7). Furthermore, the case where it shape | molded using the blank 31 which does not shape | mold a groove shape part as a comparison object was made into the comparative example (refer FIG. 3).

  For each of the inventive examples 1 and 2 and the comparative example, the convexity of the press-formed product 1 is determined according to three items of (a) sheet thickness increase rate, (b) equivalent plastic strain, and (c) maximum curvature radius shown in FIG. Generation | occurrence | production of the wrinkle in the seat surface 9 of the shape part 7 was evaluated.

  The plate thickness increase rate represents an increase in the plate thickness of the press-formed product 1 on the basis of the plate thickness of the blank 31. In a portion where the plate thickness increase rate is large, the in-plane compressive load is large. It is thought that it is easy to buckle and it is easy to generate wrinkles.

  Equivalent plastic strain is a value obtained by converting the strain due to plastic deformation to a single axis equivalent, and in areas where the value of equivalent plastic strain is large, the amount of plastic deformation is large and bending wrinkles tend to remain, so wrinkles are likely to occur. It is done.

  The minimum bending radius is the minimum value of the curvature radius in the molding process when the shape of the portion corresponding to the lower end of the convex portion 7 at the center in the longitudinal direction of the press-formed product 1 in the blank 31 is represented by the curvature radius. It is considered that the smaller the radius, the larger the bending deformation in the molding process, and the more likely the wrinkles occur on the seating surface 9 of the convex portion 7.

  Since the validity of the evaluation of the occurrence of wrinkles according to the above three items was verified based on the results of comparative examples (FIGS. 10 to 12), this will be described first.

  FIG. 10 shows the analysis result of the radius of curvature of the portion corresponding to the lower end of the convex portion 7 in the molding process when the press-formed product 1 is molded without providing the groove-shaped portion in the blank 31.

  In FIG. 10, the horizontal axis represents the die stroke (mm) during the relative movement of the die 15 to the molding bottom dead center, and the vertical axis represents the convex shape formed in the longitudinal center of the vertical wall portion 5 of the press-formed product 1. It is a radius of curvature (mm) calculated from the shape of the end portion of the blank 31 at a portion corresponding to the lower end of the portion 7c (see FIG. 5). Here, the radius of curvature is a radius of a circle passing through three points, a point corresponding to the midpoint in the longitudinal direction at the lower end of the seating surface 9c of the convex portion 7c and points 1.5 mm apart on both sides thereof (FIG. 9 (d )reference).

  As shown in FIG. 10, the radius of curvature in the molding process sharply decreases near the die stroke of 40 mm where the die 15 comes into contact with the blank 31 and molding starts, and after the minimum value is shown around the die stroke of 80 mm, the molding is performed. It shows a tendency to increase again as the seating surface 9c of the convex portion 7c is formed flat toward the bottom dead center. From the results shown in FIG. 10, the minimum bending radius is determined to be 9 mm, which is the minimum value of the curvature radius in the molding process.

  In FIG. 11, the vertical wall forming height of the press-formed product 1 formed without providing the groove-shaped portion on the blank 31 is 40 mm (FIG. 11 (a)), 55 mm (FIG. 11 (b)), and 65 mm (FIG. 11 (FIG. 11). The analysis result of each wrinkle generation evaluation item (plate thickness increase rate distribution, equivalent plastic strain distribution and minimum bending radius) in the case of c)) is shown.

Similarly, in FIG. 12, the seat surface height of the convex portion 7 of the press-formed product 1 formed using the blank 31 that does not form the groove-shaped portion is 7 mm (FIG. 12A) and 5 mm (FIG. 12B The analysis result of each wrinkle occurrence evaluation item in the case of)) is shown.
11 and 12, the maximum value of the equivalent plastic strain on the seating surface 9c of the convex portion 7c is also shown.

  11 and 12, it was found that the minimum bending radius tends to decrease as the maximum value of the equivalent plastic strain increases. And, as the vertical wall molding height of the press-formed product 1 and the seating surface height of the convex part 7 are increased, wrinkles are more likely to occur on the seating surface 9 of the convex part 7, and therefore the maximum value of the equivalent plastic strain And it was suggested that the minimum bending radius can be used to evaluate the occurrence of wrinkles.

  Next, FIG. 13 shows the evaluation results of wrinkle generation (plate thickness increase rate distribution, equivalent plastic strain distribution and minimum bending radius) in the press-formed product obtained by the press-forming method according to the present invention. Here, FIG. 13A shows Invention Example 1 formed using a grooved blank 41 (see FIG. 1) formed by forming a downward convex groove-shaped portion 43 on the blank 31, and FIG. FIG. 13C shows the result of Invention Example 2 formed using the grooved blank 51 (see FIG. 7) formed with the upward convex groove-shaped portion 53, and FIG. 13C uses the blank 31 in which the groove-shaped portion is not formed. It is the result of the comparative example shape | molded.

  In addition, in the invention examples 1 and 2 and the comparative example shown in FIGS. 13A to 13C, when the vertical wall forming height of the press-formed product 1 is 40 mm and the seating surface height of the convex portion 7 is 7 mm. Is the result of Furthermore, in FIG. 13, the maximum value of the equivalent plastic strain in the seating surface 9c of the convex portion 7c is also shown.

When formed using the grooved blank 41 of Invention Example 1 (FIG. 13A), the maximum value of the equivalent plastic strain was 0.11 and the minimum bending radius was 21 mm. Moreover, the generation | occurrence | production of the wrinkle in the seat surface 9 of the convex-shaped part 7 was not seen.
Furthermore, when it shape | molded using the grooved blank 51 which is the invention example 2 (FIG.13 (b)), the maximum value of the equivalent plastic strain was 0.13, and the minimum bending radius was 16 mm. Moreover, the generation | occurrence | production of the wrinkle in the seat surface 9 of the convex-shaped part 7 was not seen.
On the other hand, when the blank 31 which is a comparative example is molded (FIG. 13C), the maximum value of the equivalent plastic strain is 0.17 and the minimum bending radius is 9 mm. Wrinkles were observed.

  Therefore, by forming the blank 31 using the grooved blank 41 or 51 formed with a groove-shaped portion, bending deformation at a portion corresponding to the lower end of the convex-shaped portion 7 in the molding process is suppressed, and the convex-shaped portion 7 It was shown that the generation of wrinkles on the seating surface 9 can be suppressed.

  Furthermore, when comparing the grooved blank 41 formed with the lower convex groove-shaped portion 43 and the grooved blank 51 formed with the upper convex groove-shaped portion 53, the grooved blank 41 formed with the lower convex groove-shaped portion 43 is used. In this case, the minimum bending radius in the molding process is increased to suppress bending deformation, and the maximum value of the equivalent plastic strain at the bottom dead center of the molding is reduced, so that wrinkles are generated on the seating surface 9c of the convex portion 7 It was suggested that can be further suppressed.

  As described above, according to the press molding method according to the present invention, a grooved blank in which a plurality of groove-shaped portions extending in the height direction of the vertical wall portion are formed at predetermined intervals in a portion corresponding to the vertical wall portion of the blank. And suppressing the occurrence of wrinkles on the seating surface of the convex portion by molding the vertical wall portion in which the convex portion is formed between the plurality of groove-shaped portions formed, It was proved that the flatness of the seating surface of the convex portion can be formed with a high degree.

DESCRIPTION OF SYMBOLS 1 Press-molded product 3 Top plate part 5 Vertical wall part 7 Convex-shaped part 9 Seat surface 11 Mold for press molding 13 Punch 15 Die 17 Pad 19 Punch side vertical wall molding surface part 21 Die side vertical wall molding surface part 23 Bending blade R part 25 Convex Forming Part 27 Die Concave 29 Die Convex 31 Blank 41 Grooved Blank 43 Down Convex Groove Part 45 Pre-molding Die 47 Upper Die 47a Down Convex Groove Shaped Part 49 Lower Die 49a Lower Convex Groove Shape Molded part 51 Grooved blank 53 Upper convex groove shaped part 55 Premolding mold 57 Upper mold 57a Upper convex groove shaped molded part 59 Lower mold 59a Upper convex groove shaped molded part 60 Seat surface part 61 Seat surface part 63 Seat surface part 65 Seat surface area

Claims (2)

When forming a press-molded product having a vertical wall portion that is curved and is continuously formed from the top plate portion and shrinks to form a flange, the seating surface is flat in the height direction of the vertical wall portion. A press molding method for forming an extending convex portion on the vertical wall portion,
A grooved blank forming step of forming a grooved blank in which a plurality of groove-shaped portions extending in a direction corresponding to the height direction of the vertical wall portion are formed at a predetermined interval in a portion corresponding to the vertical wall portion in the blank; ,
A press molding method comprising: a vertical wall forming step of forming the vertical wall portion in which the convex portion is formed between the plurality of groove-shaped portions using a punch and a die.   The groove-shaped portion formed in the grooved blank forming step is a groove-shaped portion that is convex in a direction opposite to the convex direction of the convex-shaped portion formed on the vertical wall portion. The press molding method as described.