JP2008264838A - Press mold and press molding method - Google Patents

Abstract

[PROBLEMS] To eliminate the twisting of a product during molding without modifying the mold when molding a long and hat-shaped molded product having a right-angle cross section, which is extremely advantageous in terms of cost. A press mold and a press molding method are provided.
Before forming a blank material B by a punch 12 and a die 11, the punch 12 is displaced with respect to the die 11 to form a gap G between the mold and the blank material B, and the blank material B Is moved toward the outside of the mold by the moving means 20, and the residual stress generated in the molding process and the bending moment accompanying the release of the residual stress are eliminated during the molding, and the complex twist generated in the molded product is eliminated. It is characterized by preventing.
[Selection] Figure 2

Description

  The present invention relates to a press mold and a press molding method for press-molding a long molded product without twisting.

  For example, long automobile parts such as side members and pillar parts have recently been used high-tensile steel sheets in order to demand safety and light weight. Due to the nature of high-strength steel sheets, elastic recovery phenomena such as springback and torsion appear remarkably, and it is not easy to ensure dimensional accuracy.

  Therefore, conventionally, there are a correction method by restructuring and coining, and a method of offsetting by prospective molding by overbending. For example, in the methods by overbending disclosed in Patent Documents 1 and 2 below, the one having a U-shaped cross section perpendicular to the axis is formed, and the side plate is erected on the side of the main body substrate located at the center of the molded product. However, the side plate is over-bended in consideration of the spring back at the molding position of the side plate with respect to the main body substrate so that the side plate has a predetermined dimensional accuracy after molding.

  In the case of molding a U-shaped cross section perpendicular to the axis, since the bent portions are only on both sides, molding by overbending is relatively easy. However, when molding a product with a cross section perpendicular to the axis, the bent part is not only on both sides of the main board, but also between the flange part that extends integrally from the side plate. The elastic recovery phenomenon is complicated and its correction is complicated and not easy.

  In general, a draw molding method is used for forming a long, hat-shaped cross section perpendicular to the axis, while pressing both sides of the blank while restraining it with a crease presser. In the draw molding process, a large curvature is used. Residual stress in the compression direction is generated on the flange surface, and residual stress is generated on the flange surface with a small curvature. When the mold is released after molding, the residual stress is released and a bending moment is generated inside the molded product. Twisting occurs, and the twist of the side plate portion is also added to this.

In order to prevent such complicated twisting, there is a method in which a twist is offset when a mold is manufactured in advance so as to be deformed in a direction opposite to the twisting direction and then released after molding. However, in this method, since the mold needs to be corrected a plurality of times, the mold cost increases, which is disadvantageous in cost.
Japanese Unexamined Patent Application Publication No. 2004-9129 (see claim 1 and FIGS. 1 and 2). Japanese Patent Application Laid-Open No. 2004-195535 (see abstract, claim 1 and FIG. 1).

  The present invention was made in order to solve the problems associated with the prior art, and when forming a molded product having a long and hat-shaped cross section perpendicular to the axis, it is possible to perform molding without correcting the mold. Another object of the present invention is to provide a press die and a press molding method that are extremely advantageous in terms of cost and that can eliminate the twist of the product.

  A press die according to the present invention includes a pair of dies that are relatively close to each other, a blank holder that holds an edge of a blank material installed between the dies between either one of the two dies, A press mold for forming a molded product having a hat-shaped cross section, wherein one mold is moved toward and away from the other mold before the blank material is processed by the two molds. A gap is formed between the tip of the one mold and the blank facing the tip with a predetermined amount of displacement, and the flange of the blank held by the blank holder is moved outward of the mold. It has a moving means to move toward.

  In the press molding method according to the present invention, when a blank material is press-molded by a pair of molds that are relatively close to and away from each other, an edge of the blank material is held in a state of being sandwiched between one of the two molds and a blank holder. A press molding method for molding a hat-shaped molded product, wherein one mold is shifted in the proximity and separation direction with respect to the other mold before the molding of the blank material by the two molds is completed. After forming a gap between the tip of the mold and the blank facing the tip, the flange of the blank held by the blank holder is moved outward of the mold by the moving means. It is characterized by press-molding with both the molds while moving.

  According to the first and sixth aspects of the present invention, before the blank material is formed by the mold, one mold is displaced with respect to the other mold to form a gap between the mold and the blank material. Since the moving means is moved toward the outside of the mold, the residual stress generated in the molding process and the bending moment accompanying the release of the residual stress can be eliminated during the molding, and the mold is corrected. Therefore, it is possible to prevent a complex twist occurring in the molded product, and to improve the quality of the molded product, and to obtain a press die that is extremely advantageous in terms of cost.

  In the inventions of claims 2 and 7, since the moving means converts the movement of one mold into the movement of the blank holder to the outside, the blank holder can be used without using an accessory device. The mold structure can be simplified.

  According to a third aspect of the present invention, the moving means includes a cam member provided in one mold and a collapse member disposed on a side portion of the other mold, and the cam of the cam member is provided on the collapse member. Because it has a cam part where the surface abuts and a holding part that holds the state where the blank material surface side of the blank holder abuts, the movement of one mold can be easily and smoothly moved to the outside of the blank holder. It can be converted and the type structure is simplified.

  The inventions of claims 4 and 8 use a punch and a die as the mold, and the moving means supports the lower end portion of the punch provided in a fixed position at the time of processing by the holding portion of the collapse member, and the processing is completed. Before the punch, the holding member moves away from the lower end of the punch due to the movement of the collapse member by the cam member provided on the die that is close to and away from the punch, and a predetermined gap is created between the tip of the punch and the blank material. Since the flange portion of the blank material is moved in the direction outside the mold by further movement of the collapse member, the material can be caused to flow back into each corner portion formed in the blank material, Flange parts without stress or bending moment can be molded smoothly without modifying the mold, improving the quality of the molded product.

  According to the fifth and ninth aspects of the present invention, when the urging means for urging the collapse member toward the inside of the mold is provided in the moving means, the press mold immediately after the completion of machining is brought into the state of the press mold. And formability and workability are greatly improved.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

  1A and 1B are schematic perspective views illustrating molded articles formed according to the present invention, and FIG. 2 is a schematic cross-sectional view illustrating a press die according to an embodiment of the present invention.

  First, as shown in FIGS. 1A and 1B, a molded product formed according to the present invention is a shaft such as a front side member W1 or a rear side member W2 that is a part of a frame of an automobile. A long object with a right-angled cross-section in which a side plate 2 is provided on both sides of the main body substrate 1 at a substantially right angle, a flange portion 3 is formed from the side plate 2 at a substantially right angle, and is deformed vertically and horizontally in the axial direction. It is. In the present specification, for convenience, the corner between both sides of the main board 1 and the side plate 2 is defined as the first shoulder K1, and the corner between the side plate 2 and the flange 3 is defined as the second shoulder K2. Called.

  In order to form such a molded product W (generic name for W1 and W2), a press die 10 as shown in FIG. 2 is used in this embodiment. Although the illustrated press die 10 has a die 11 and a punch 12, these are extended in a direction perpendicular to the paper surface so as to form a long object.

  The die 11 of the press die 10 is attached to a slider 13 that can be moved up and down by a drive source (not shown), and a recess 14 is formed in which a punch 12 enters and a blank material B is formed.

  The punch 12 is fixedly installed on the bolster 15. Here, “fixed to the position” does not mean that it is completely fixed, but means that it is installed so that it can move up and down somewhat.

  That is, the punch 12 can be moved up and down slightly with respect to the fixed bolster 15 by, for example, about several millimeters. More specifically, the punch 12 is fitted so that the leg portion 12b having a width M2 smaller than the width M1 of the molding portion 12a is suspended from the lower end portion and can move up and down in the through hole O provided in the bolster 15. Has been. However, a tapered portion 12c is formed between the molded portion 12a and the leg portion 12b, and the tapered portion 12c is placed in contact with a holding portion 24 of the moving means 20 described later.

  The contact between the taper portion 12c of the punch 12 and the holding portion 24 depends on the weight of the punch 12, but when contact with only the weight of the punch 12 is difficult, an elevating means (not shown) that hydraulically or cams the punch 12 is used. Alternatively, a spring member (not shown) that urges the punch 12 toward the bolster 15 may be provided between the punch 12 and the bolster 15.

  On both sides of the punch 12, there are provided a blank holder 17 supported by a cushion pin 16 protruding through the bolster 15, and a moving means 20 for moving the blank holder 17 together with the blank material B in the mold outward direction. ing.

  The blank holder 17 is provided to prevent so-called wrinkles, and sandwiches the blank material B with the die surface 11 a of the die 11 lowered by the slider 13.

  The moving means 20 displaces the punch 12 downward with respect to the die 11 before the processing of the blank material B by the die 11 and the punch 12 is completed, and a gap G is formed between the tip of the punch 12 and the blank material B. (Refer to FIG. 4B), and the blank material B is moved in the outward direction of the mold by utilizing the gap generated here to prevent wrinkling and twisting.

  The moving means 20 according to the present embodiment is suspended from both sides of the die 11, and the cam member 21 having a cam surface 21 a inclined with respect to the moving direction of the die 11, and the blank holder B together with the blank holder 17 in the outward direction of the die. A collapse member 22 to be moved and an urging means 23 for urging the collapse member 22 in the mold direction are provided.

  The collapse member 22 is a member having a substantially L-shaped cross section, and is positioned below the blank holder 17 to hold the blank holder 17 and to stand up and down the holding unit 24 for raising and lowering the punch 12. And a cam portion 25 having a cam surface 25a pressed by the cam surface 21a of the cam member 21 and moving the holding portion 24 outward of the mold. The holding portion 24 has a long hole 26 through which the cushion pin 16 is inserted.

  The holding portion 24 has an inner end portion 24 a that has been cut off in a tapered shape, and when the urging means 23 urges the collapse member 22 in the mold direction, the inner end portion 24 a contacts the tapered portion 12 c of the punch 12. The punch 12 is lifted, and when the collapse member 22 moves out of the mold by the pressing of the cam member 21, the holding of the punch 12 is released and the punch 12 is lowered.

  FIG. 3 is a graph showing a stress strain curve. In general, the relationship between stress and strain is as shown in FIG. The press molding is performed in the plastic region. In the stress-strain curve, when the position at a predetermined molding time is “X” and the applied pressure is solved after molding, the stress-strain curve from the point X is It does not return along the stress-strain curve (shown by a solid line) but returns along the hysteresis shown by a broken line. Therefore, the stress (Δσ) can be greatly reduced by removing a slight amount (Δε) of the strain at the point X.

  Here, if the movement of the material in the blank material B during press molding is observed, the material is stretched from the original state during pressurization. That is, the material of the blank material B flows out of the punch. From this state, press molding is temporarily interrupted, a gap G (see FIG. 4B) is formed between the punch and the die, and the flange portion 3 is displaced outward from the mold by the blank holder 17. In the first shoulder portion K1 at the leading end of the punch, and also in the second shoulder portion K1 corresponding to the base portion of the flange portion 3, the state is returned from the right angle state to the obtuse angle, and the material is compressed. That is, in the movement state of the material in the blank material B, the outflowed material is returned, so to speak, it flows back into the punch, and the stress generated in the blank material B is very slight movement of the blank material B, For example, it can be significantly reduced by a few millimeters, so that distortion can be eliminated, bending moment can be prevented, and twist can be prevented.

  Next, a press molding method will be described.

  4A is a half cross-sectional view showing a processing state at a predetermined molding time, FIG. 4B is a half cross-sectional view showing a state in which only the punch is lowered, and FIG. 4C is the moving means operated. It is a half sectional view showing a state.

  First, the blank material B is set between the punch 12 and the die 11, the slider 13 is lowered, and molding is started. At the start of molding, the tapered portion 12 c of the punch 12 is in a state of being supported by the inner end portion 24 a of the holding portion 24. Further, the both sides of the blank material B are started to be molded while being sandwiched between the lower surface 11 a of the die 11 and the upper surface 17 a of the blank holder 17.

  When the molding is performed until just before reaching the bottom dead center of the die 11, the blank material B has a shape in which the substrate 1 at the center corresponds to the front end 12 d of the punch 12 as shown in FIG. 4A. The side plates 2 are formed at substantially right angles on both sides, and the flange portion 3 is formed to extend from the side plates 2 at substantially right angles.

  When the die 11 reaches a position several millimeters above the bottom dead center, as shown in FIG. 4B, the cam surface 21a of the cam member 21 provided on the die 11 and the cam surface 25a of the collapse member 22 come into contact with each other. The member 22 moves in the direction out of the mold. In this way, if the operation of the die 11 is used and the vertical movement is converted into the lateral movement of the collapse member 22 by the cam, the molding can be performed without using the incidental equipment, the apparatus configuration is simplified, and the cost is advantageous. is there.

  When the collapse member 22 moves in the direction out of the mold, the holding portion 24 also moves in the same manner, the inner end portion 24a scraped off in a tapered shape and the tapered portion 12c of the punch 12 are separated, and the holding of the punch 12 is released. 12 begins to descend. In this case, the lowering speed of the die 11 is greatly reduced by the cam member 21 coming into contact with the cam surface 25a of the collapse member 22, and the molding is almost interrupted, but the punch 12 is also in the inner end 24a. It descends as the taper surface moves.

  When the taper portion 12c of the punch 12 is disengaged from the inner end portion 24a of the holding portion 24, only the punch 12 is lowered by a few millimeters but abruptly falls, and the lower portion of the punch 12 abuts on the bolster 15. In the upper part of the punch 12, a gap G is formed between the tip 12d of the punch 12 and the substrate 1 of the blank material B.

  When the die 11 is further lowered after the punch 12 is positioned at the lower end, the die 11 is blanked by contact between the cam surface 21a of the cam member 21 provided on the die 11 and the cam surface 25a of the collapse member 22. While the holder 17 is pressed against the holding portion 24 of the collapse member 22, the holder 17 moves in the direction outside the mold. By this movement, the flange portion 3 sandwiched between the blank holder 17 and the die 11 is also pulled out in the direction outside the mold. Thereby, in the front-end | tip part of the punch 12, it deform | transforms so that the blank material B may contact | abut to the front-end | tip part of the punch 12 by presence of the clearance gap G, and so-called surplus meat is absorbed, and only the length shown by (DELTA) t in FIG. The flange portion 3 is also pulled out of the mold.

  As described above, after the gap G is formed between the punch 12 and the die 11, when the blank holder 17 is moved in the direction outside the mold, the first shoulder K1 and the second shoulder K1 that are substantially perpendicular to each other where the blank material B is formed. The shoulder K2 is stretched to an obtuse angle, so that the material that has flowed out by the draw molding is returned and flows back into the punch, reducing the stress generated in the blank material B and removing the strain. This contributes to the prevention of bending moments and prevents the occurrence of twisting.

  Then, as shown in FIG. 4C, when the die 11 is lowered until reaching the bottom dead center, the molding is completed. When the molding is completed, the die 11 is raised, and accordingly, the urging means 23 of the moving means 20 that has been compressed by the collapse member 22 repels and moves the collapse member 22 toward the inside of the mold. The tip of the holding portion 24 enters the tapered surface of the punch 12, and the press die 10 is in the initial state.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims. For example, in the above-described embodiment, the die is close to and away from the fixed position punch, but this may be reversed, and not only the punch and the die but also the blank holder is provided. Various pairs of closely spaced molds may be used.

  INDUSTRIAL APPLICABILITY The present invention can be used for press molding for forming a long molded product without twisting.

(A) (B) is a schematic perspective view which illustrates the molded article shape | molded by this invention. It is a schematic sectional drawing which shows the press die concerning embodiment of this invention. FIG. 3 is a graph showing a stress strain curve. (A) is a half sectional view showing a processing state at a predetermined molding time point, (B) is a half sectional view showing a state where only the punch is lowered, and (C) is a half sectional view showing a state where the moving means is operated. It is.

Explanation of symbols

10 ... press mold,
11 ... Die,
12 ... Punch,
17 ... Blank holder 20 ... Moving means,
21 ... Cam member 21a ... Cam surface,
22 ... collapse member,
23 ... biasing means,
24 ... holding part,
25 ... Cam part,
B ... Blank material
G ... Gap.

Claims (9)

A pair of molds that are relatively close to and away from each other, and a blank holder that clamps an edge of a blank material placed between the two molds between one of the two molds, and has a hat-shaped cross section A press mold for molding a molded product,
Before the processing of the blank material by the two molds is completed, one mold is shifted by a predetermined amount in the approaching and separating direction with respect to the other mold so as to face the tip of the one mold and the tip. A press die comprising a moving means for forming a gap between the blank material and moving a flange portion of the blank material held by the blank holder toward the outside of the die.   2. The press die according to claim 1, wherein the moving means is configured to convert the movement of the other die into a movement of the blank holder in a direction outside the die. The moving means is
A cam member provided on the other mold and having a cam surface inclined with respect to a direction in which the other mold approaches and separates;
A cam portion that is disposed on a side portion of the one mold and abuts the cam surface of the cam member; and a holding portion that holds a state in which the anti-blank material surface side of the blank holder abuts, A collapse member that moves toward the outside of the mold by pressing against the cam portion;
The press die according to claim 2.   The one mold is a punch provided in a fixed position, and the other mold is a die that moves close to and away from the punch, and the moving means moves the lower end portion of the punch to the holding portion of the collapse member during processing. The holding portion is moved away from the lower end portion of the punch by the movement of the collapsing member by the cam member provided on the die that is close to and spaced from the punch before the processing is completed, and the tip of the punch The press die according to claim 3, wherein the gap is formed between a portion and the blank material.   The press die according to any one of claims 1 to 4, wherein the moving means includes urging means for urging the collapsing member toward the inside of the mold. When a blank material is press-molded by a pair of molds that are relatively close to and away from each other, the edge of the blank material is held between one of the two molds and a blank holder to form a cross-sectional hat-shaped molded product. A molding method,
Before the molding of the blank material by the two molds is completed, one mold is shifted in the approaching and separating direction with respect to the other mold, and the blank material is opposed to the tip portion of the one mold and the tip portion. Is formed between the two molds while the flange portion of the blank material sandwiched by the blank holder is moved toward the outside of the mold by the moving means. Press molding method.   In the movement of the blank material, the movement means converts the movement of the other mold into the movement of the blank holder to the outside of the mold, and is sandwiched between the blank holder and the other mold. The press molding method according to claim 6, wherein the blank holder is moved toward the outside of the mold together with the blank material. A punch that is fixed in position as the one mold, and a die that is close to and spaced from the punch as the other mold,
As the moving means, a cam member provided on the die and a cam portion which is disposed on a side portion of a punch provided in a fixed position and a cam surface of the cam member abuts on, and a holding for holding the blank holder By using the one that converts the movement of the die into the movement of the blank holder in the out-of-mold direction by cooperating with the collapse member having a portion,
During processing by the punch and die, the lower end portion of the punch is supported by the holding portion of the collapse member, and the punch is moved in the moving direction of the die by the movement of the holding portion accompanying the movement of the collapse member by the cam member. After slipping and generating a predetermined gap between the tip of the punch and the blank material, the flange portion of the blank material is moved outward from the mold by further movement of the collapse member. The press molding method according to claim 6 or 7, characterized in that.   The press forming method according to claim 6, wherein the moving means includes urging means that urges the collapse member to move inward of the mold.

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