JP2015123490A - Drawing method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drawing method and device which hardly cause thickness lightening and a crack by making a compressive stress field in an acting place of tensile stress of a material being drawn in drawing with a comparatively simple and low cost constitution.SOLUTION: A drawing device comprises a punch 20, a die 40 for storing the punch 20 and executing drawing, and a wrinkle pressing-down mechanism 30 for pressing down a plate-like blank 10 in the substantially parallel direction to the die 40 while the blank 10 is subjected to the drawing by the punch 20 and the die 40, and executes the drawing by moving either one of the punch 20 and the die 40 in the press direction. The drawing device comprises a pressurization mechanism 100 for pressurizing an end surface of the blank 10 toward the punch 20 from a direction substantially orthogonal to the press direction, and executes the drawing while pressurizing the blank 10 toward the punch 20 from the direction substantially orthogonal to the press direction.

Description

  The present invention relates to a drawing method and a drawing device.

  In general drawing today, regardless of the product shape, for example, as described in Patent Document 1, punch 2, die 1, plate press (wrinkle press) 4 against blank (material) 3 Is formed (see FIG. 16A).

JP 2009-90318 A

  Here, in the rectangular tube drawing as shown in FIG. 16B, a large tensile stress acts on the material at the four corners R (four corners) 2R of the punch 2, so that it is shown at the left end of FIG. Such material cracking and thinning are likely to occur, and the radius R of the corner R (four corners) 2R, the shoulder R (shoulder radius) 2r and the shoulder R portion Rd of the die 1 can be reduced and the drawing depth can be reduced. There is a fact that it is difficult to deepen.

  This is because the material receives a forming load at the shoulder R portion 2r and the corner R portion 2R of the punch 2 during forming and withstands the tensile stress generated by the forming load with the material characteristic value of the material itself. If it becomes impossible, it is thought that thinning (a phenomenon in which the thickness is reduced by pulling the wall thickness) occurs and progresses to cracking.

  On the other hand, in drawing forming, in order to reduce flesh thinning and increase the drawing depth, for example, there is a method of increasing the number of drawing (drawing to a predetermined depth in a plurality of times), etc. Although it is conceivable, it has disadvantages such as longer molding time, increased process layout, and higher mold cost.

  As a result, the inventors have conducted various studies, investigations, researches, experiments, etc., and as a result, without reducing the above-mentioned drawbacks, the reduction of the thinning and the drawing depth can be reduced. I have come up with new ideas and techniques that can be deepened.

  In other words, in draw forming, the cause of thinning and cracking is thought to be the tensile stress applied to the material. Therefore, if a compressive stress field can be created at the location where the tensile stress of the material during forming acts, the thinning of the material will occur. It is considered possible to reduce cracks and cracks.

  The present invention has been made on the basis of such a new idea, and in a draw forming, a compressive stress field is created at a place where a tensile stress of a material being formed acts in a draw forming while being a relatively simple and low-cost configuration. Thus, an object of the present invention is to provide a drawing method and apparatus that are unlikely to cause thinning or cracking.

For this reason, the drawing apparatus according to the present invention is
A punch, a die for accommodating the punch and performing drawing, and a wrinkle pressing mechanism that presses the blank in a direction substantially parallel to the die when the plate-like blank is drawn by the punch and the die. A drawing apparatus that performs drawing by moving one of the punch and die in the pressing direction,
A pressurization mechanism that pressurizes the end face of the blank from the direction substantially orthogonal to the press direction toward the punch, and performing drawing while pressing the blank from the direction approximately orthogonal to the press direction toward the punch. .

  The drawing apparatus according to the present invention may be characterized in that the pressure applied to the blank by the pressure mechanism is performed at least on the generating portion of the shrink flange.

  In the drawing apparatus according to the present invention, the pressure applied to the blank by the pressurizing mechanism pressurizes the push plate that contacts the flange end surface of the blank by a fluid pressure cylinder mechanism or a combination of a spring mechanism and a cam mechanism. It can be characterized by that.

In addition, the drawing method according to the present invention includes:
Using a punch, a die for containing the punch for drawing, and a wrinkle holding mechanism, the plate and blank are pressed in a direction substantially parallel to the die, and the drawing is performed by the punch and the die. In the drawing method to be performed,
One of the punch and the die is moved in the press direction, and the drawing is performed while pressurizing the blank from the direction substantially orthogonal to the press direction toward the punch.

  In the drawing method according to the present invention, it is possible to apply pressure to the blank at least to the generating portion of the shrinkage flange.

  In the drawing method according to the present invention, pressurization to the blank is performed by pressurizing a push plate that contacts the flange end surface of the blank by a fluid pressure cylinder mechanism or a combination of a spring mechanism and a cam mechanism. Can be characterized.

  According to the present invention, although it is a relatively simple and low-cost configuration, in draw forming, a compressive stress field is created in a place where tensile stress of a material being molded acts, thereby causing thinning and cracking. It is possible to provide a difficult drawing method and apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS (A) is a top view (figure seen from the press direction) which shows roughly an example of the drawing apparatus which concerns on one embodiment of this invention, (B) is front sectional drawing ((A) side) It is a sectional view (sectional view seen from the direction orthogonal to the press direction). (A) is a stress distribution diagram showing a simulation analysis result related to the drawing apparatus (method) according to the embodiment described above, and (B) is a plate thickness distribution diagram. It is a perspective view which shows the example of 1 structure of the die | dye utilized for the drawing apparatus which concerns on embodiment same as the above. It is a perspective view which shows one structural example of the die | dye and push plate (pressure plate) utilized for the drawing apparatus which concerns on embodiment same as the above. It is a perspective view which shows the setting state of the blank with respect to the die | dye, punch, push plate (pressurization plate), and blank holder of the drawing apparatus which concerns on embodiment same as the above. It is a perspective view which shows the state before the press by the push plate (pressure plate) to the blank in the drawing apparatus (drawing apparatus of FIG. 5) which concerns on embodiment same as the above. It is a perspective view which shows the pressurization state (before the drawing start by a punch) by the push plate (pressure plate) to a blank in the drawing apparatus (drawing apparatus of FIG. 5) which concerns on embodiment same as the above. Configuration examples and operational states ((A) to (D) of the die, punch, push plate (pressure plate), blank holder, and pressure mechanism (cam mechanism + gas spring mechanism) of the drawing apparatus according to the same embodiment. It is a front view which shows a mode that a process advances as it progresses to. Configuration examples and operation states of the die, punch, push plate (pressure plate), blank holder, pressure mechanism (hydraulic cylinder equipped with a pressure control device) of the drawing apparatus according to the same embodiment ((A) to) It is a front view which shows a mode that a process advances as it progresses to (D). It is an example (an example in the case of performing rectangular draw forming with a comparatively large aspect ratio) which shows the mode of the pressurization to the blank by the pressurization mechanism in the drawing molding apparatus (method) which concerns on embodiment same as the above. It is a schematic diagram explaining the shrinkage flange in drawing. It is an example (an example in the case of performing substantially square drawing with a comparatively small aspect ratio) which shows the mode of pressurization to the blank by the pressurization mechanism in the drawing apparatus (method) which concerns on embodiment same as the above. It is a perspective view which compares and compares the product which performed drawing (assist drawing) by actually changing the applied pressure with the drawing apparatus (method) which concerns on embodiment same as the above, and the conventional drawn product. (A) is a table | surface which shows each part plate | board thickness data of the product which performed drawing (assist drawing) by actually changing the applied pressure with the drawing apparatus (method) based on embodiment same as the above, (B) The data is graphed. It is a figure which shows the relationship between each part plate | board thickness data of the product which performed press forming (assist drawing) by actually changing the applied pressure with the drawing apparatus (method) based on embodiment same as above, and assist surface pressure. . (A) is a front view (figure seen from the direction orthogonal to a press direction) for demonstrating the conventional drawing, (B) is a top view (figure seen from the press direction).

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. The present invention is not limited to the embodiments described below.

  Here, as described above, the present inventors have conducted various examinations, investigations, researches, experiments, and the like, and as a result, in drawing, new thinning can be achieved and a new drawing depth can be increased. I came up with ideas and methods.

  In other words, in draw forming, the cause of thinning and cracking is thought to be the tensile stress applied to the material. Therefore, if a compressive stress field can be created at the location where the tensile stress of the material being processed acts, the thinning can occur. It is considered possible to reduce cracks and cracks.

  Therefore, if a mechanism for compressing from the end face (lateral) direction of the material at the time of draw forming is incorporated, and draw forming can be performed while creating a compressive stress field in the material, it is considered that draw forming with less fleshing can be performed.

  For this reason, aluminum, which is a difficult-to-work material, was selected as an experimental material, and a molding simulation and an experiment based on the simulation were conducted for the purpose of confirming formability in a rectangular tube drawing having a compressive stress field. Here, the contents of the forming simulation, the analysis results thereof, the contents of the experiment conducted based on the analysis results, and the experiment results of the compression stress and the product plate thickness will be described below.

<About molding simulation>
Using molding simulation, it was confirmed whether molding was possible or effective by drawing (hereinafter also referred to as assist drawing) on a blank (material) having a compressive stress field.

<Content of analysis>
The software used for this analysis is JSTAMP NV2.6 (manufactured by JSOL Corporation), and the conditions used for the analysis are as follows.
Blank mesh size: 0.75mm
Element type: Solid reduction integration (Thickness direction division 5 layers)
Material thickness: 4.0mm
Material database: Use of data in software (A3003-O material)

The mold structure used for the analysis is as shown in FIG.
In FIG. 1, only the structure of the portion in contact with the plate-like blank (material: material) 10 is extracted, but the punch 20 and the blank holder (wrinkle presser: material plate presser) 30 are arranged on the upper mold. In this structure, a die 40, a knockout (product extrusion device after molding) 50, and a push plate (pressure plate) 100 are disposed in the lower mold.
Here, the push plate (pressure plate) 100 constitutes a part of the pressure mechanism of the present invention.
If the push plate 100 is removed, the conventional rectangular tube diaphragm type is obtained.

  As the mechanism for the simulation analysis, the die 40 is fixed, the punch 20 moves toward the die 40, the pressing force by the blank holder 30 and the knockout 50 is set at 60 kN and 30 kN, respectively, and the blank holder 30 is blank ( The workpiece was set so that the pressing force was killer at a material plate thickness of 10 mm.

  In addition, the pair of push plates 100 arranged to face each other as the first point of the assist diaphragm acts on the punch 20 with a compression force (push plate force) of 19 kN on each side of the end face of the blank 10 before the start of molding. Further, when the punch 20 was operated 17 mm in the vertical direction in FIG. 1B, the compression force (push plate force) of the push plate 100 was set to zero.

  The reason why the compression force of the push plate 100 is set to 0 in the course of the molding process is that the pair of push plates 100 move in the direction of the punch 20, so that the push plate 100 contacts the punch 20 with a certain amount of movement. This is because the structure does not hold.

  In this simulation analysis, the wrinkle holding force is set to 6 times the normal. This is because the thickness of the flange portion 11 (the portion extending to the outside of the punch 20 in the blank 10 in FIGS. 1A and 5) due to the influence of the push plate 100 is increased. The reason for this is to increase the wrinkle pressing force and suppress the amount of increase in wall thickness as much as possible.

<Analysis results>
FIG. 2A shows a von Mises stress state (stress distribution diagram) of the material (blank 10) immediately after the punch 20 starts to move.
The color shading represents the stress distribution. The stress is lower as the color is darker and higher as it is lighter.
As shown in FIG. 2A, the push plate 100 pushes the end face of the blank 10 from the left and right sides of FIGS. 1A and 2A with a force of 19 kN. It can be seen that a stress field is generated toward each of the above.

  FIG. 2B shows the analysis result of the product (after drawing). In the analysis result of FIG. 2B, the neutral surface of the product (after drawing) is displayed as a shell element, and the color shading represents the thickness distribution. The plate thickness is thinner as the color is darker and thicker as it is lighter.

  From this analysis result, the plate thickness at the product corner was 3.16 mm, and the molding was completed with a plate thickness reduction rate of 20%. From this, it was confirmed that a good drawing with reduced occurrence of thinning and cracking was possible by drawing (assist drawing) while applying compression force (assist force).

<Experiment method>
The inventors of the present invention designed a mold based on the above-described molding simulation result, and tried an assist drawing experiment (actual drawing).

FIG. 3 shows a die 40 manufactured and used for the experiment.
As shown in FIG. 3, a recess (step) 41 is provided on the surface of the die 40 on the side where the blank 10 is placed. The depth of the recess 41 is slightly deeper than the thickness of the blank 10.

  As shown in FIG. 4, a pair of push plates (pressing plates) 100 arranged to face each other is accommodated in the recess 41, and the recess 41 serves as a guide for determining the moving direction of the push plate 100. It is configured.

Further, as shown in FIG. 5, a blank holder (plate holder, wrinkle holder) 30 that serves as a wrinkle holder is disposed above the die 40 during molding. By bringing them into contact with each other in the press direction (vertical direction), an effect of killer the wrinkle pressing force of the blank holder 30 can also be achieved.
The blank holder 30 is a wrinkle holding mechanism according to the present invention (when a plate-like blank placed on a die is drawn with a punch and a die, the blank is pressed in a direction substantially parallel to the die to suppress wrinkles. Equivalent to the mechanism for

Further, by making the thickness of the push plate 100 slightly smaller than the thickness of the blank 10, even if the push plate 100 is sandwiched between the die 40 and the blank holder 30, the wrinkle pressing force is exerted by the convex portion 42 of the die 40. Therefore, the push plate 100 is not subjected to a wrinkle pressing force, and an effect of ensuring the smooth movement (sliding) of the push plate 100 in the pressurizing direction (push direction) can be achieved.
However, the concave portion 41 and the convex portion 42 can be omitted.

  FIG. 5 shows a state in which the blank 10 is set. The blank 10 is set between the pair of push plates 100 shown in FIG. 4, and the shape of the push plate 100 is matched to the outer shape of the blank 10. Therefore, the push plate 100 can also have a role of positioning (locator) when the blank 10 is formed.

FIG. 6 shows a state where the blank holder 30 moves downward and contacts the die 40.
In the state of FIG. 6, since the cushion force is applied to the blank holder 30, a predetermined cushion force is applied as long as the punch 20 continues to descend.

  After the state of FIG. 6, the die 40 and the blank holder 30 are in contact with each other, and pressurization to the push plate 100 is started in a state where the blank holder 30 is applied with a wrinkle holding force. As shown in FIG. When 10 and the punch 20 come into contact with each other, the push plate 100 compresses the end face of the blank 10 with a predetermined pressing force, and in this state, drawing is started.

  The thickness of the push plate 100 that pushes the end face of the blank 10 is less than the thickness of the blank 10 and is thin. However, the push plate 100 is sandwiched between the die 40 and the blank holder 30, so that the push plate 100 undergoes deformation such as buckling. It will be used in a difficult state.

Here, as an example, the power of the push plate 100 that compresses the blank (material) 10 from the end face is, as shown in FIG. 8, a cam (CAM) mechanism 200 and a gas spring (GAS).
(SPRING) mechanism 300 is configured to be supplied by a mechanism.
Here, push plate 100, cam (CAM) mechanism 200, gas spring (GAS)
SPRING) mechanism 300 corresponds to an example of a pressurizing mechanism according to the present invention.
The gas spring mechanism includes a spring including a fluid spring that uses a fluid (a spring (or a damper) that uses a passage resistance such as an orifice of an incompressible liquid such as air or other gas or an incompressible liquid such as oil). It can be a mechanism. Furthermore, the present invention is not limited to this, and a spring mechanism made of an elastic body such as metal can be used.

  If the inflow speed of the flange portion 11 of the blank 10 during molding (the moving speed of the end face of the flange portion 11) is confirmed from the simulation result, it is not a constant speed. Thus, it is difficult to push the end surface 11 of the blank 10 while applying a predetermined compression force (assist force) to the push plate 100.

Therefore, the cam (CAM) mechanism 200 is combined with the gas spring (GAS SPRING) mechanism 300 to push out the cam (CAM) 201 according to the angle (position) so as to realize the compression force (assist force) by the push plate 100. Amount (cam travel) and gas spring (GAS)
SPRING) The stroke amount of the mechanism 300 is overlapped to approximate the inflow amount of the flange portion 11 of the blank 10.

Thereby, there is a gap between the inflow amount of the flange portion 11 of the blank 10 and the push-out amount (cam movement amount) of the cam (CAM) 201, and the gas spring (GAS
(SPRING) The compression force that acts on the end surface of the flange portion 11 of the blank 10 is prevented from becoming zero even if the compression force (assist force) decreases within the stroke of the mechanism 300.

As the gas spring (GAS SPRING) mechanism 300 used in the present embodiment, for example, GSC50-10 and GSC38-10 manufactured by MISUMI Corporation can be used. Here, the initial load and the maximum load are as follows. It was as follows.
GSC50-10: initial load 15000N, maximum load 27750N
GSC38-10: Initial load 7500N, maximum load 13500N

  Further, in design, the stroke amount of the gas spring mechanism 300 at the moment when the punch 20 contacts the blank 10 is 3.7 mm, and the compression force (assist force) at that time is 18700 N for GSC 50-10 and 9500 N for GSC 38-10. It becomes.

Further, by sandwiching a spacer such as a washer (WASHER) of about 5 mm between the cam follower (CAM FOLLER) 202 and the gas spring mechanism (GSC50-10) 300, the stroke amount of the gas spring mechanism 300 immediately before molding is 8.7 mm. Thus, the assist force can be 26300N.
In this experiment, the assist force was determined to be 3 patterns of 9500N, 18700N, and 26300N.

  As described above, the mold structure is not provided with the concave portion (step) 41 on the die 40 side, but provided with a concave portion (step) that accommodates and moves the push plate 100 on the lower surface side of the blank holder 30. As a configuration in which the blank 10 is placed in the step, it can be designed to be a killer for the plate thickness even when the die 40 and the blank holder 30 are in contact with each other.

In the present embodiment, the knockout 50 can be a movable type, and is configured such that the die cushion force of the die cushion installed on the lower side of the press acts in the molding direction (vertical direction). Can be done. By applying such a die cushion force, the bottom of the product can be formed flat.
Further, a gas spring (GAS) is used as a generation source (supply source) of the pressing force (wrinkle pressing force) of the blank holder 30.
SPRING) can be used.

In this embodiment, the punch is attached to the moving upper die, but may be attached to the lower die fixed on the bolster of the press. In that case, a recess (step) that accommodates and moves the push plate 100 is provided on the upper surface side of the blank holder, and the blank 10 on the lower die side and the die attached to the upper die are placed in the step. It can also be designed to be a killer for the plate thickness even in contact with the plate.
In this case, as a generation source (supply source) of the cushioning force of the knockout 50, a gas spring (GAS)
SPRING) can be used.
Moreover, the die cushion installed in the press lower side can be used for the generation source (supply source) of the pressing force (wrinkle pressing force) of the blank holder 30.

A pressurizing method (assist diaphragm) in the diaphragm mold structure as shown in FIG. 8 will be described.
(1) First, the punch 20 is moved toward the blank 10 in the press direction (downward), but before they come into contact with each other, the die 40 fixed to the lower mold and the movable blank holder 30 make the blank 10 is applied to the flange portion 11 of the blank 10 and then the cam follower 202 is moved approximately 90 ° to the press direction by the action of the cam 201 of the cam mechanism 200 interlocked with the movement of the punch 20. The gas cushion force corresponding to the amount of movement of the cam follower 202 is applied to the push plate 100 to pressurize (compress) the end surface of the flange portion 11 of the blank 10.

  (2) The gas spring mechanism 300 here is pre-filled with a gas of a predetermined pressure, and the force to pressurize (compress) the end face of the flange portion 11 of the blank 10 is the stroke of the gas spring of the gas spring mechanism 300. The punch 20 comes into contact with the blank 10 at the time when the stroke amount of the gas cushion that achieves the desired applied pressure (compression force) is reached, and the drawing is started.

(3) Thereafter, during drawing by the cam 201 having a cam profile (inclination angle etc.) determined in accordance with the inflow speed of the blank 10 into the die 40 (moving speed of the end face of the flange portion 11). Drawing (assist drawing) is performed while applying a predetermined pressure to the end face of the flange portion 11 of the blank 10.
In addition, it is comprised so that the pressurization (compression) of the push plate 100 may be stopped in the vicinity before the end surface of the flange part 11 of the blank 10 enters into the shoulder R part of the die 40.

Here, the reason why the gas spring mechanism 300 (gas cushion) is used is as follows.
(1) This is because the blank material is an aluminum alloy or the like, and the proof stress and tensile strength are lower than that of the steel material, so that the applied pressure can be reduced.

(2) Inflow into the die 40 of the flange portion 11 of the blank 10 at all timings so that a desired pressing force (compression force) can be applied to the end face of the flange portion 11 of the blank 10 by the push plate 100. Since it is difficult to form the cam inclination angle (cam profile) so that the speed (complexly changing) can be matched, the cam profile (cam inclination angle) is matched to some extent, and the flange portion of the blank 10 11 where the inflow speed into the die 40 does not match, it is compensated for within the stroke of the gas spring mechanism 300 (gas cushion), so that the applied pressure is prevented from becoming zero, and a certain amount of applied pressure (compressive force) This is to allow the blank 10 to act on the blank 10.

  The specification of the gas spring mechanism 300 this time is that the gas spring (gas cushion) strokes 5 mm with respect to the 10 mm gas spring (gas cushion) stroke. That is, when the cam follower 202 moves 5 mm, the punch 20 comes into contact with the blank 10 and drawing is started.

  As a result, even if the amount of movement of the cam follower 202 and the amount of inflow of the flange portion 11 of the blank 10 into the die 40 do not completely match, if the difference is within ± 5 mm, the applied pressure is Although it will fluctuate from the desired value, it can be avoided that it becomes zero.

(3) If pressure is applied by the push plate 100 only with the cam mechanism 200, the inflow speed of the flange portion 11 of the blank 10 into the die 40 changes in a complicated manner. It is assumed that a phenomenon in which the applied pressure becomes too large can occur, and there is a possibility that good molding cannot be performed. On the other hand, if the cam profile (cam inclination angle) of the cam 201 and the inflow speed of the flange portion 11 of the blank 10 do not match, there is a possibility that the applied pressure becomes zero. There is a risk that the product may be thinned or cracked. However, such a fear can be avoided by using the gas spring mechanism 300 (gas cushion).

Next, FIG. 9 shows an example in which the cam mechanism 200 and the gas spring mechanism 300 are omitted, a hydraulic cylinder mechanism (hydraulic control mechanism) 400 is employed, and the pressure can be arbitrarily controlled by the hydraulic cylinder. Show. The other configuration is the same as that of FIG.
The push plate 100 and the hydraulic cylinder mechanism 400 correspond to an example of a pressurizing mechanism according to the present invention. In addition, not only oil pressure but a fluid pressure cylinder mechanism (fluid pressure control mechanism) using fluid pressure such as air pressure or water pressure can be used.

Here, a pressurizing method in the drawing die structure having the configuration shown in FIG. 9 will be described.
(1) The punch 20 is moved in the press direction (downward) toward the blank 10, but before they come into contact with each other, the die 10 fixed to the lower mold and the movable blank holder 30 are used to move the blank 10. After the wrinkle pressing force is applied to the flange portion 11 of the blank 10 by sandwiching, the push plate 100 is pushed by the hydraulic cylinder of the hydraulic cylinder mechanism 400, and the flange portion of the blank 10 is oriented approximately 90 ° with respect to the press direction. The end face of 11 is pressurized (compressed).

(2) When the desired pressure (compression force) is reached, the punch 20 contacts the blank 10 and starts drawing.

(3) Thereafter, the hydraulic cylinder of the hydraulic cylinder mechanism 400 applies a predetermined pressure to the end surface of the flange portion 11 of the blank 10 in accordance with the flow rate of the blank 10 into the die 40 (the moving speed of the end surface of the flange portion 11). It is supposed to act. In addition, it is comprised so that the pressurization (compression) of the push plate 100 may be stopped in the vicinity before the end surface of the flange part 11 of the blank 10 enters into the shoulder R part of the die | dye 40.

  In the drawing die structure having the configuration shown in FIG. 9, it is possible to apply a desired pressure (compression force) to the end face of the flange portion 11 of the blank 10 by controlling the pressure with the hydraulic cylinder mechanism 400. Even if the inflow speed of 10 (the moving speed of the end face of the flange portion 11) changes in a complicated manner, the end face of the flange portion 11 of the blank 10 can be favorably pressed.

Here, the pressurization location of the blank 10 in the assist aperture according to the present embodiment will be described.
In this Embodiment, the site | part (location) as shown in FIG. 10 is pressurized on the end surface of the flange part 11 of the blank 10.

  In FIG. 10, the part (location) to be pressurized is a position where the pressing force (compressive force) by the push plate 100 can be applied to a portion (corner R portion) that becomes a shrinking flange portion generated during drawing.

More specifically, in the drawing, a shrink flange is generated near the corner R portion of the die (see reference numeral 20R in FIG. 10). As shown in FIG. 11, the shrinking flange gathers material from the circumferential direction near the corner R portion of the punch (die) and shrinks (compresses) the material, but at the same time in the pressing direction (punch pushing direction). Elongation (tensile) occurs.
The shrinkage shown in FIG. 11 increases the thickness of the blank or generates wrinkles, but if this is suppressed by the wrinkle presser (blank holder), the frictional force (adhesion between the blank and the wrinkle presser (blank holder)) This is considered to increase the tensile stress in the pressing direction (punch pressing direction) and cause cracks and thinning of the blank.

  Therefore, in the present embodiment, the tensile stress is relaxed by supplying pressure (compression force) to the portion where such a contracted flange is generated by the push plate 100 and offsetting it with the tensile stress, so that the blank is formed. It is intended to suppress the occurrence of cracks and flesh thinning.

  That is, in the present embodiment, the portion (location) that presses the blank applies a pressing force (compression force) in a direction that opposes (cancels) the elongation (tensile stress) in the contracted flange portion that occurs during drawing. It is a part that can.

  FIG. 10 shows an example of a pressing method in the case of drawing with a rectangular punch 20, and the aspect ratio of the rectangle is about 1: 5. In this case, the short side portion of the punch (or die) where the contracted flange is generated is pushed in from the left and right (from the direction substantially perpendicular to the short side). Note that the pressing force of the push plate 100 is concentrated toward the R center of the corner R portion 20R of the punch 20 (the component of the compressive force toward the R center of the corner R portion 20R is in the circumferential direction of the corner R portion 20R). The end face shape of the flange portion 11 of the blank 10 can be formed in an arc shape.

  In FIG. 10, the vertical direction (long side portion) of the blank 10 is lower than the left and right direction (short side portion) when the material is gathered from the circumferential direction during the draw forming and the material is shrunk. Little increase in flange thickness. As a result, there is little increase in frictional force (degree of adhesion) between the blank and the wrinkle presser (blank holder), so there is little increase in tensile stress in the pressing direction (punch pressing direction). Therefore, when applying pressure (compression force) by the push plate 100 also in the vertical direction (long side portion) of the blank 10 in order to prevent the blank from cracking or fleshing, the left and right shorts that cause the shrinkage flange are generated. A pressing force smaller than the pressing force applied to the side portion is sufficient.

FIG. 12 shows an example of a pressurizing method when the aspect ratio of the punch is relatively small.
Since a contraction flange is generated at the corner R portion 20R of the punch 20, the portions (locations) to be pressed are pressurized from the four corner portions of the flange portion 11 of the blank 10 toward the four corner R portions 20R of the punch 20. The end face shape of the flange portion 11 of the blank 10 is an arc shape so that the pressing force of the push plate 100 is concentrated toward the R center of the corner R portion 20R of the punch 20 (in the corner R portion 20R). The end face shape of the flange portion 11 of the blank 10 can be formed in an arc shape so that a compressive force component toward the R center is generated over the circumferential direction of the corner R portion 20R.

Also in FIG. 12, there is a portion that does not pressurize the end face of the flange portion 11 of the blank 10 (an end portion substantially parallel to the side of the punch 20), but the degree of the material gathering from the circumferential direction to shrink the material. Is low, and the increase in the blank flange plate thickness is small.
As a result, there is little increase in the frictional force (adhesion degree) between the blank and the wrinkle presser (blank holder), so there is little increase in tensile stress in the press direction (punch indentation direction), and thinning and cracking occur during molding. The degree of occurrence is low. Therefore, in comparison with the necessity of pressing the end face of the flange portion 11 of the blank 10 from the four corner portions of the flange portion 11 of the blank 10 toward the four corner R portions 20R of the punch 20, the direction substantially orthogonal to each side. Therefore, it is not necessary to apply a compressive stress by pressing the end face of the flange portion 11 of the blank 10.

  In other words, according to the present embodiment, in a shape in which a portion that becomes a contracted flange portion occurs regardless of the shape of a square, cracks occur in normal drawing, and a reduction in thickness (thinning) occurs. In the case where large and good molding cannot be performed, by pressing the end face of the blank serving as the shrinking flange portion in a direction of approximately 90 degrees with respect to the press direction, cracking occurs or the plate thickness decreases (wall thickness It is possible to perform good drawing with a small amount of thinness.

  However, the pressurization location is not limited to this, and during drawing, the blank is pressed from the direction substantially perpendicular to the press direction of the punch 20 to apply a compressive stress, and the tensile force generated on the blank by the press As long as the stress can be reduced, the pressurizing location is not particularly limited. For example, a configuration in which pressure is applied over the entire circumference of the end surface of the flange portion 11 of the blank 10 may be employed.

<Experimental result>
Here, the experimental results will be described.
FIG. 13 shows products that have been subjected to conventional rectangular tube drawing and products that have been subjected to assist drawing by switching the assist force. From the left side of the figure, products subjected to conventional drawing, assist molding (assist force: 9500 N), assist molding (assist force: 18700 N), and assist molding (assist force: 26300 N) are displayed.

As shown at the left end in FIG. 13, in the conventional drawing, a large tensile stress was applied to the material at the four corner R portions 20R of the punch 20, and cracks occurred.
This is because the material is subjected to a molding load at the corner R portion 20R during molding, and the molding load becomes a tensile stress that cannot be withstood by the material property value of the material itself, leading to thinning and progressing to cracking. It is done.

  However, as shown in the second, third, and fourth (that is, the right end) from the left end in FIG. 13, assist drawing has a small assist force (9500 N) and a neck (partial thinning). It was possible to form without cracking, and it was confirmed that as the assist force (18700N, 26300N) was increased, the occurrence of necking was eliminated and good molding was possible.

  FIG. 14A shows the result of measuring the plate thickness at measurement point 1 and measurement point 2 in FIG. 13 with a point micrometer.

FIG. 14B shows the relationship between the GAS SPRING (assist force) shown in FIG. 14A and the plate thickness.
From FIG. 14B, it can be seen that as the assist force increases, the plate thickness of each measurement point increases. In other words. It has been found that the plate thickness reduction rate can be reduced as the assist force is increased, and that further reduction in the plate thickness may be suppressed by further increasing the assist force.

<Discussion>
FIG. 15 shows the relationship between the assist surface pressure and the plate thickness.
The assist surface pressure (MPa) is a value obtained by dividing the assist force (initial load) of the gas spring by the a-part cross-sectional area of the push plate 100 shown in FIG.

Moreover, the broken line in FIG. 15 has shown 0.2% yield strength (YP: (sigma) y) and tensile strength (TS: (sigma) _B ) of general A3003-O material.

First, regarding the relationship between the assist surface pressure and the product plate thickness, when the plate thickness at the measurement point 1 is compared between when the assist force 9500N (34.7 MPa) is applied and when the assist force 18700N (68.4 MPa) is applied. When the assist force 18700N is applied, the plate thickness is 0.4 mm thicker than when the assist force 9500N is applied.
Further, comparing the case where the assist force 26300N (96.3 MPa) is applied with the case where the assist force 18700N is applied, the case where the assist force 26300N is applied is more than the case where the assist force 18700N (68.4 MPa) is applied. Is 0.15 mm thick.

When the assist force exceeds the 0.2% proof stress of the material, the amount of increase in sheet thickness increases, and when the assist force is near the tensile strength, the increase amount tends to decrease. In other words, it was found that the larger the assist force, the better. However, there is a possibility that the assist force may be limited due to a change in the mold structure or the material size. Therefore, at least the assist surface pressure is (σy + σ _B ) / By setting it to 2 or more, it can be expected to exhibit a high effect.

  However, even if the assist surface pressure is 0.2% proof stress (σy) or less, a neck is generated but it can be molded. Therefore, it is proved that the assist force is small even if it is small.

  The material used this time is 0.2% proof stress and low tensile strength aluminum, but if a predetermined assist force is applied to the SPC material or SUS material, the effect of the assist drawing can be similarly exhibited. it is conceivable that.

  As described above, in this embodiment, for the purpose of confirming square tube drawability with a compressive stress field due to aluminum, which is a difficult-to-work steel material, analysis by molding simulation and actual mold production The assist aperture was reduced and the following could be obtained.

(1) The assist diaphragm could be analyzed by molding simulation.
(2) By forming a compressive stress field at a place where tensile stress is applied, it is possible to form well without cracking or thinning even under conditions where cracking or thinning occurs in conventional drawing. I was able to.
(3) Assist molding has made it possible to mold materials that cannot be molded by conventional methods.
(4) Reduction of the plate thickness of the product affects the assisting force, and it is effective to perform the assisting force with a magnitude of (σy + σ _B ) / 2 or more of the material.

As described above, the aluminum rectangular tube drawing is a material that is difficult to mold and easily stretches when a tensile stress is applied to a difficult-to-work material. However, because the tensile strength is low, the assist drawing is good. Gas spring (GAS)
SPRING) mechanism could be achieved.

  Regardless of the shape of the product, general drawing is performed by punching, dies, and wrinkle pressing. The blank 10 has a frictional force due to the wrinkle pressing force by the blank holder 30, and the shoulder 40 of the die 40 and the punch 20 at the shoulder R portion 20r. And a bending flange deformation force that is pulled into the die 40 while being compressed in the circumferential direction of the punch 20 (or the die 40). When these sum totals become large, it causes the thinning and cracking of the boundary R portion between the side wall portion and the bottom portion.

  In particular, in the special drawing with a corner R portion, a large shrinkage flange deformation occurs in the corner R portion 20R of the punch 20 and a large tensile stress is applied to the material, and the wall thickness of the boundary R portion between the side wall portion and the bottom portion is thinned. And cracking easily occurs.

  In the present invention, by pressing the end face of the flange in the shrinking direction in the material flow direction, the material flow from the flange portion is promoted to perform drawing in a compressive stress field. Even under conditions where thinning and cracking are likely to occur, it is possible to satisfactorily perform drawing while suppressing the occurrence of thinning and cracking.

  For this reason, according to the present invention, it is not necessary to divide the drawing into multiple times as in the prior art, so the number of processes can be reduced, the molding time is increased, the process layout is increased, Disadvantages such as increased mold costs can be eliminated.

As described above, the drawing method and apparatus according to the present embodiment are configured so that a die is formed when a punch, a die provided corresponding to the punch, and a plate-like blank are drawn by the punch and the die. And a wrinkle pressing mechanism that presses in a direction substantially parallel to the drawing, and a drawing apparatus that performs drawing by moving one of the punch and the die in the pressing direction,
A pressurization mechanism that pressurizes the end face of the blank from the direction substantially orthogonal to the press direction toward the punch, and performing drawing while pressing the blank from the direction approximately orthogonal to the press direction toward the punch. .

  Then, according to the drawing method and apparatus according to the present embodiment, during drawing, the blank is pressed from the direction substantially orthogonal to the pressing direction to apply a compressive stress, whereby the tensile force generated in the blank by the press is generated. The stress can be reduced (relaxed), and therefore, even under molding conditions that have been difficult in the past, the occurrence of cracking and thinning can be suppressed and good drawing can be performed.

  That is, according to the present embodiment, in the draw forming, a compressive stress field is created at the place where the tensile stress of the material being formed acts, while the structure is relatively simple and low cost. Thus, it is possible to provide a drawing method and apparatus that are unlikely to occur.

  Note that the present invention can be applied even when the die structure described in the present embodiment is disposed upside down (when the die is disposed on the upper die and the punch is disposed on the lower die). .

  The embodiment described above is merely an example for explaining the present invention, and it is needless to say that various modifications can be made without departing from the gist of the present invention.

10 Blank (plate material, material)
11 Flange part 20 Punch 30 Blank holder (corresponding to a part of the wrinkle holding mechanism)
40 dies
100 push plate (pressure plate) (equivalent to part of the pressure mechanism)
200 cam mechanism 300 gas spring mechanism (an example of a fluid spring mechanism and a spring mechanism)
400 Hydraulic cylinder mechanism (hydraulic control mechanism) (fluid pressure cylinder mechanism, fluid pressure control mechanism)

Claims (6)

A punch, a die for accommodating the punch and performing drawing, and a wrinkle pressing mechanism that presses the blank in a direction substantially parallel to the die when the plate-like blank is drawn by the punch and the die. A drawing apparatus that performs drawing by moving one of the punch and die in the pressing direction,
A pressurization mechanism that pressurizes the end face of the blank from the direction substantially orthogonal to the press direction toward the punch, and performing drawing while pressing the blank from the direction approximately orthogonal to the press direction toward the punch. Drawing molding equipment.   2. The drawing apparatus according to claim 1, wherein the pressure is applied to the blank by the pressure mechanism at least with respect to the generating portion of the shrink flange.   The pressurization to the blank by the pressurization mechanism is performed by pressurizing the push plate that contacts the flange end surface of the blank by a fluid pressure cylinder mechanism or a combination of a spring mechanism and a cam mechanism. The drawing apparatus according to claim 1 or 2. Using a punch, a die for containing the punch for drawing, and a wrinkle holding mechanism, the plate and blank are pressed in a direction substantially parallel to the die, and the drawing is performed by the punch and the die. In the drawing method to be performed,
One of the punch and the die is moved in the pressing direction, and the drawing is performed while the blank is pressed from the direction substantially orthogonal to the pressing direction toward the punch.   The drawing method according to claim 4, wherein the pressurization to the blank is performed at least on the generating portion of the shrink flange.   The pressurization to the blank is performed by pressurizing the push plate that contacts the flange end surface of the blank by a fluid pressure cylinder mechanism or a combination of a spring mechanism and a cam mechanism. The drawing method according to claim 5.