JP2008188659A - Press molding die and press molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a press forming technology capable of realizing the excellent shape accuracy of a product. <P>SOLUTION: The holding force in the initial forming stage is set to be FF1 of a medium value, the holding force in the middle forming stage is set to be FF2 of a small value, and the holding force in the final forming stage is set to be FF3 of a large value, respectively, preventing a product from being in a wrinkle area or a crack area. In the final forming stage, the elongation of a blank is very small, and any crack is not formed even when the holding force is increased. The shape accuracy of the formed product can be enhanced by weakening the holding force of a movable bead in the middle forming stage. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a press forming technique for drawing a thin metal plate.

  A press-molded product can be obtained by placing a blank material on a die having a molding recess and allowing the molding projection of the punch to enter the molding recess. At this time, if the peripheral edge portion of the blank material is suppressed by the blank holder, a beautiful molded product free from wrinkles can be obtained. However, it is desirable to adjust the pressing force in accordance with the progress of the press, that is, the progress of the drawing process, rather than simply suppressing the peripheral edge of the blank material.

2. Description of the Related Art Conventionally, a press apparatus that can adjust the holding force is known (see, for example, Patent Document 1).
JP-A-9-29349 (abstract)

Patent document 1 is demonstrated based on the following figure.
FIG. 9 is a diagram for explaining the basic configuration of a conventional press apparatus. With reference to FIG. 9, the [Summary] of Patent Document 2 states that “[Solution] Wrinkle prevention is a blank holder alone or a blank holder. And the fixed bead 103 (added 100 to distinguish the reference numerals of the embodiment to make a three-digit reference. The same applies hereinafter) to prevent the cracks 120 of the material 111 from occurring during the molding of the variable point bead 105 There is a description of “a drawing method and apparatus using a variable bead, which is performed by applying a point-like effect to an appropriate part in an arbitrary partial period.”

  However, due to the presence of the variable point bead 105, the fixed bead 103 must be disposed outside. When the fixed bead 103 is arranged outside, when cutting the edge after molding, the cutting margin becomes large and the yield deteriorates.

  Further, since the variable point bead 105 is on the inner side, the fixed bead 103 that plays the role of preventing wrinkles is disposed on the outer side. The blank material flows in along with the press while receiving the restraining action of the fixed bead 103. Since the fixed bead 103 is on the outside, a large distance is generated between the fixed bead 103 and the molded portion. As this distance increases, wrinkles tend to occur between these distances.

  That is, the conventional technique shown in FIG. 9 has a problem in yield and wrinkle control.

  It is an object of the present invention to provide a press molding technique that has a good yield and can easily control wrinkles.

The invention according to claim 1 includes a die provided with a molding recess, a blank holder that presses the peripheral edge of the blank material against the peripheral edge of the die, and a punch provided with a molding convex that enters the molding recess. In the press mold,
The blank holder includes a fixed bead whose pressing force does not change during pressing and a movable bead whose pressing force changes during pressing,
The fixed bead is arranged closer to the forming convex portion than the movable bead.

The invention according to claim 2 is a press molding method, and when the blank material is drawn by the press molding die according to claim 1, a large restraining force that strongly restrains the peripheral portion of the blank material, and the blank During setting between the small restraining force that weakly restrains the peripheral edge of the blank material so that the material flows into the molding concave portion side, and the small restraining force and the large restraining force so as not to cause wrinkles during molding. A degree of restraining force can be obtained by controlling the position of the movable bead,
In the initial stage of molding, molding is performed while suppressing the blank material with the above-mentioned moderate suppression force. In the middle period of molding, molding is performed while suppressing the blank material with the above-mentioned small suppression force. It is characterized by carrying out the molding while suppressing the material.

In the invention which concerns on Claim 1, the fixed bead was arrange | positioned inside and the movable bead was arrange | positioned outside. Since the fixed bead is disposed on the inner side, when cutting the edge after molding, the cutting margin is reduced and the yield is improved.
Moreover, since a fixed bead exists inside, a fixed bead and a formation part approach. As a result, wrinkles are less likely to occur and a molded product having a good shape can be obtained.

In the invention which concerns on Claim 2, since it shape | molds in the initial stage of shaping | molding, suppressing a blank material with a moderate suppression force, generation | occurrence | production of a flaw can be prevented. In the middle of molding, since the molding is performed while suppressing the blank material with a small suppression force, the occurrence of cracks can be prevented. At the end of molding, molding is carried out while suppressing the blank material with a large holding force, so that the shape of the molded product can be adjusted well.
That is, according to the present invention, the shape accuracy of the molded product is improved by weakening the holding force of the movable bead in the middle of molding.

The best mode for carrying out the present invention will be described below with reference to the accompanying drawings. The drawings are viewed in the direction of the reference numerals.
FIG. 1 is a plan view of a punch and a blank holder in a press molding die according to the present invention, and a punch 11 of the press molding die 10 includes molding convex portions 12 and 12. And the blank holder 20 is arrange | positioned so that the punch 11 may be enclosed.

  The blank holder 20 includes first beads 21, 21, 21, 21, which are called fixed beads, and a first blank holder 23 having a first holder surface 22 which is a flat-shaped surface of a mouth shape, The first blank holder 23 includes second blank holders 25, 25, 25 accommodated so as to be movable in the front and back direction of the drawing.

The second blank holder 25 has a second bead 26 called a movable bead and a second holder surface 27 which is an I-shaped flat surface. The second bead 26 is provided on the molding convex portion 12 side, that is, on the inner side than the second holder surface 27.
That is, the second bead 26 is provided at the edge of the second blank holder 25 so as to be closer to the molding convex portion 12 than the second holder surface 27.

  Since the blank holder 20 is divided into the first flank holder 23 and the second blank holder 25, it is not necessary to incorporate the second bead 26 in the first blank holder 23. As a result, the press molding die 10 can have a simple structure.

  2 is a cross-sectional view taken along line 2-2 of FIG. 1, and includes a die 29 having a molding recess 28, a blank holder 20 that presses the peripheral edge of the blank material 30 against the peripheral edge of the die 29, and a molding recess 28. In a press molding die 10 including a punch 11 having a molding convex portion 12 to be entered, a blank holder 20 includes a first bead 21 and a first holder surface 22 and includes a first bead 21 during pressing. The first holder surface 22 includes a first blank holder 23 that presses the blank 30 against the die 29 with a constant holding force, a second bead 26, and a second holder surface 27, and the holding force that changes during pressing. The second blank holder 25 presses the blank material 30 against the die 29. The die 29 has a pad 32 that elastically presses the second holder surface 27 through the blank material 30. To have.

The pad 32 includes a pad main body 34 having a pressing protrusion 33 at the lower portion and an elastic body 35 provided on the pad main body 34. The protrusion 33 and the pad main body 34 are blocks made of hard cast iron or cast steel.
The elastic body 35 is urethane rubber or a spring. When a large upward external force acts on the protrusion 33, the elastic body 35 contracts and the pad body 34 rises. When the upward external force decreases, the elastic body 35 extends and the pad main body 34 descends. Therefore, the protrusion 33 moves up and down according to the upward external force.

  The second blank holder 25 is driven by a cam driver mechanism 37 described below. The cam driver mechanism 37 includes an inclined surface 38 provided at the bottom of the second blank holder 25, a taper member 39 that is in contact with the inclined surface 38 and is movable to the left and right in the drawing, and the taper member 39 on the left side of the figure. A compression spring 41 extending from the first blank holder 23 to the taper member 39 for biasing, and a driver cam 42 attached to the side surface of the punch 11 for driving the taper member 39 to the right in the drawing. The driver cam 42 includes a first peak 43 protruding rightward in the drawing, a second peak 44 higher than the first peak 43, and a valley 45 provided between these peaks 43, 44.

The operation of the press molding die having the above configuration will be described below.
The process in which the punch 11 relatively moves from the top dead center to the bottom dead center will be described in three stages, that is, the initial stage of molding, the middle stage of molding, and the last stage of molding.

  FIG. 3 is an operation explanatory view at the initial stage of molding. As shown in FIG. 3A, for convenience, the punch 11 is fixed and the die 29 and the blank holder 20 are lowered. If the press slide stroke from the top dead center to the bottom dead center is 100%, the press slide stroke at the initial stage of molding is 0 to 60% (the slide height from the bottom dead center is 100 to 40%).

  At the initial stage of molding, the blank material 30 is pressed against the die 29 by the first blank holder 23. In addition, the taper member 39 is moved to the right by the first peak 43, and the second blank holder 25 is raised. Then, the blank material 30 is clamped (clamped) between the second holder surface 27 and the pad 32.

(B) is an enlarged view of part b of (a), and the blank material 30 is restrained by a constant restraining force F <b> 1 while being bent by the first bead 21 and the first holder surface 22.
Further, the second bead 26 bites into the blank material 30 moderately. It is assumed that the bead height is 0 at the position where the second bead 26 begins to bend the blank 30 upward (the position where the second bead 26 hits the lower surface of the blank 30), and the second bead 26 is Assuming that the bead height is 100% at the position where the ascending limit is reached, the bead height is set to 80 to 100% at a moderate bite.
Thus, the blank member 30 is restrained by the force F2 while being bent by the second bead 26.

Further, since the blank member 30 is sandwiched between the second holder surface 27 and the pad 32, the blank member 30 is restrained by the force F3.
As a result, the blank material 30 is restrained with a restraining force FF1 proportional to F1 + F2 + F3. This holding force FF1 corresponds to a binding force that does not cause wrinkles on the blank 30.

  FIG. 4 is an operation explanatory diagram in the middle of molding. As shown in FIG. 4A, the blank material 30 is pressed against the die 29 by the first blank holder 23 in the middle of molding. In addition, due to the valley 45, the taper member 39 moves to the left in the figure, and the second blank holder 25 is lowered. The press slide stroke in the middle of molding is 30% to 100% (the slide height from the bottom dead center is 70% to 0).

(B) is an enlarged view of part b of (a), and the blank material 30 is restrained by a constant restraining force F <b> 1 while being bent by the first bead 21 and the first holder surface 22.
Further, the second bead 26 slightly bites into the blank material 30. With a slight bite, the bead height is set to 10% to 80%. As a result, the blank 30 is restrained by the weak force f2 while being bent on a small scale by the second bead 26.

Further, since the blank member 30 is sandwiched between the second holder surface 27 and the pad 32, the blank member 30 is restrained by a weak force f3.
As a result, the blank material 30 is suppressed by the suppression force FF2 proportional to F1 + f2 + f3, but the suppression force FF2 is smaller than the suppression force FF1. Therefore, it is not hindered that the blank material 30 moves to the left in the figure. That is, the inflow phenomenon of the blank material 30 occurs.

  FIG. 5 is an explanatory diagram of the operation at the end of molding. As shown in FIG. 5A, the blank material 30 is pressed against the die 29 by the first blank holder 23 at the end of molding. In addition, the taper member 39 is greatly moved to the right in the figure by the second mountain 44, and the second blank holder 25 is largely raised. Then, the blank member 30 is strongly clamped (clamped) between the second holder surface 27 and the pad 32. The press slide stroke at the end of molding is 80% to 100% (the slide height from the bottom dead center is 20% to 0).

(B) is an enlarged view of part b of (a), and the blank material 30 is restrained by a constant restraining force F <b> 1 while being bent by the first bead 21 and the first holder surface 22.
Further, the second bead 26 bites into the blank member 30 strongly. With strong bite, the bead height is set to 90% to 100%. Thus, the blank member 30 is restrained by the force F4 while being strongly bent by the second bead 26.

Further, since the blank member 30 is sandwiched between the second holder surface 27 and the pad 32, the blank member 30 is restrained by the force F5.
As a result, the blank 30 is restrained by the restraining force FF3 proportional to F1 + F4 + F5, but F4 is larger than F2 and F5 is larger than F3. Be bound.

The relationship between the holding forces FF1 to FF3 described above and the press stroke can be summarized as shown in FIG.
FIG. 6 is a graph showing the relationship between the holding force and the press stroke. The horizontal axis is the press stroke, and from the start of molding to the end of molding, it is divided into the initial stage of molding, the middle stage of molding, and the end of molding. These molding initial period, middle molding period, and final molding period (length along the horizontal axis) are determined by the shape of the driver cam 42 described with reference to FIG.

  By the way, if the restraining force is insufficient at the initial stage of molding, the blank material excessively flows and wrinkles are generated. This area is shown in the graph as a “wrinkle area”. In addition, since the drawing process is actively performed during the middle of the molding, if the holding force is large, the blank material is insufficiently flown and cracks occur in the blank material. This region is clearly indicated in the graph as a “crack region”.

  In the present invention, the holding force at the initial stage of molding is set to a moderate FF1, the holding force at the middle stage of molding is set to a small FF2, and the holding force at the end of molding is set to a large FF3, so that It was possible to prevent it from entering the crack area. In addition, since the elongation in the blank material is slight at the end of molding, there is no fear of cracking even if the holding force is increased.

3 to 5 described the setting of the holding force based on the cross-sectional views. Next, the operation based on the plan view will be described.
FIG. 7 is an explanatory diagram of the operation of FIG. 1, and at the initial stage of molding, as shown in FIG. 7A, the second bead 21, 21, 21, 21 and the first holder surface 22 are restrained by the second Since a moderate restraining action of the beads 26, 26, 26 and the second holder surfaces 27, 27, 27 is added, the peripheral edge of the blank is restrained with a moderate restraining force as indicated by six arrows. Can do. The drawing process at the initial stage of molding can be carried out while suppressing wrinkles.

  In the middle stage of molding, as shown in (b), since the restraining action of the first beads 21, 21, 21, 21 and the first holder surface 22 is mainly, a small restraint as shown by two arrows. Press the edge of the blank with force. That is, in the drawing process in the middle stage of molding, inflow of material is promoted to prevent the occurrence of cracks, and the blank material is sandwiched between the second holder surfaces 27, 27, 27 to suppress generation of wrinkles. If the peripheral edge of the blank material is not constrained, wrinkles are generated, and therefore the action of the second holder surfaces 27, 27, 27 is important.

  At the final stage of molding, as shown in (c), the pressing action of the first beads 21, 21, 21, 21 and the first holder surface 22 indicated by two arrows is indicated by four white arrows. Since a large restraining action of the second beads 26, 26, 26 and the second holder surfaces 27, 27, 27 is added, the peripheral edge of the blank can be restrained with a large restraining force. Thus, the final shape adjustment of the molded product is performed, and a molded product having a good shape can be obtained.

Next, the relationship between the yield of the blank material and the position of the bead is examined.
As shown in FIG. 5B, it is necessary to continue pressing the blank 30 with the second bead 26 even at the end of molding. Therefore, the size of the blank material 30 prepared before forming is determined in consideration of the position of the second bead 26. That is, as the second bead 26 moves to the right in the drawing, the blank 30 becomes larger and the yield becomes worse.
As shown in FIG. 5B, if the second bead 26 is provided on the left edge of the second blank holder 20, the blank material 30 can be minimized, and the yield can be improved. .

  Next, in order to prepare for the case where the die needs to be divided for reasons such as adopting a movable bead, the division position is examined.

  FIG. 8 is an explanatory diagram when the die is divided. As shown in FIG. 8A, the dividing portion 48 is set at the left (or right) position of the bead 47, and the first die 51 and the second die are arranged. Suppose that it is divided into 52. The lower surfaces of the first die 51 and the second die 52 need to be flush with each other. However, there is inevitably a step between the lower surface of the first die 51 and the lower surface of the second die 52. This level difference causes the blank material 30 to be wrinkled or burnt. Therefore, (a) cannot be adopted.

  Therefore, as shown in (b), the dividing portion 48 is provided in the concave portion 53 corresponding to the bead 47. Since the concave portion 53 is a curved surface, the degree of contact with the blank material 30 becomes gentle. Therefore, even if there is a step between the first die 51 and the second die 52, there is no problem. The dividing unit 48 may be anywhere as long as it is in the section V.

  FIG. 4C is a reprint of FIG. 4B, and when the pad 32 is present, the pad 32 can move up and down and does not adversely affect the blank material 30. Therefore, the dividing portion 48 between the pad 32 and the die 29 can be set at a portion corresponding to the concave portion 53 corresponding to the second bead 26 and the second holder surface 27 as indicated by the section W. .

  That is, it is recommended that the die dividing portion 48 such as a die be provided in the concave portion 53 or the convex portion related to the bead 47. If the pad 32 is present, the range may be expanded.

Next, based on FIG.1 and FIG.2, the positional relationship of the 1st bead 21 and the 2nd bead 26 is demonstrated.
As shown in FIG. 1, the first beads 21, 21, 21, 21 substantially surround the punch 11. On the other hand, the second beads 26, 26, 26 partially surround the punch 11. The first beads 21, 21, 21, 21 contribute to the determination of the shape of the molded product by suppressing the blank material with a constant holding force from the initial molding stage to the final molding stage.

The first beads 21, 21, 21, and 21 that are important in this manner affect the shape control as they are closer to the punch 11. Therefore, in the present invention, the first beads 21, 21, 21, 21 that are more stable than the second beads 26, 26, 26 having a large variation factor are brought closer to the punch 11.
That is, the first beads 21, 21, 21, 21 are arranged on the inner side, and the second beads 26, 26, 26 are arranged on the outer side.

  As a result, the second blank holders 25, 25, 25 can be provided in the first blank holder 20 having the first beads 21, 21, 21, 21. That is, as shown in FIG. 2, liners 53 and 54 are attached to the first blank holder 20, and the second blank holder 25 can be guided by the liners 53 and 54 so as to be movable up and down.

  The means for raising and lowering the second blank holder 25 including the second bead 26 is a hydraulic cylinder capable of controlling the pressing force or a mechanical cylinder driven by a servo motor, in addition to the cam driver mechanism described in the embodiment. There may be.

  The present invention is suitable for a press-molding die and a press-molding method for drawing a high-tensile steel blank.

It is a top view of a punch and a blank holder among press molds concerning the present invention. FIG. 2 is a sectional view taken along line 2-2 of FIG. It is operation | movement explanatory drawing of the shaping | molding initial stage. It is operation | movement explanatory drawing of the shaping | molding middle stage. It is an operation explanatory view at the end of molding. It is a graph which shows the relationship between restraining force and a press stroke. FIG. 2 is an operation explanatory diagram of FIG. 1. It is explanatory drawing in the case of dividing | segmenting die | dye. It is a figure explaining the basic composition of the conventional press apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Metal mold | die for press molding, 11 ... Punch, 12 ... Molding convex part, 20 ... Blank holder, 21 ... Fixed bead (1st bead), 26 ... Movable bead (2nd bead), 28 ... Molding recessed part, 29 ... Die, 30 ... Blank material, FF1 ... Medium restraining force, FF2 ... Small restraining force, FF3 ... Big restraining force.

Claims (2)

In a die for press molding comprising a die having a molding recess, a blank holder for pressing the peripheral edge of the blank material to the peripheral edge of the die, and a punch having a molding convex to enter the molding recess,
The blank holder includes a fixed bead whose pressing force does not change during pressing and a movable bead whose pressing force changes during pressing,
A press-molding die, wherein the fixed bead is disposed closer to the molding convex portion than the movable bead. When the blank material is drawn by the press molding die according to claim 1, a large restraining force that strongly restrains the peripheral portion of the blank material and the blank material so that the blank material flows into the molding concave portion side. The position of the movable bead is controlled by a small restraining force that restrains the peripheral portion weakly and a moderate restraining force that is set between the small restraining force and the large restraining force so as not to wrinkle during molding. So that you can get
In the initial stage of molding, molding is performed while suppressing the blank material with the above-mentioned moderate suppression force. In the middle period of molding, molding is performed while suppressing the blank material with the above-mentioned small suppression force. A press molding method characterized in that molding is performed while suppressing materials.

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