JP2009056491A - Press shaping method and press device for aluminum alloy plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a press shaping method for aluminum alloy plates capable of shaping large sized panels of shapes which are hardly shaped. <P>SOLUTION: In the method for press shaping the aluminum alloy plate 30 to a shaped product panel 1, a first punch 11 and a separatedly movable second panel 15 are provided and the following steps a to c are carried out in series. In a step a, the second punch 15 is displaced toward a dice 22 side in advance and the plate 30 is shaped by the first punch 11 and the dice while bringing the second punch 15 into contact with the noncontact outer peripheral sites 5, 6 of the plate 30. In a step b, the second punch 15 is displaced so as to maintain the distance between the second punch 15 and margin forming faces of the dice 22 while holding the contacting condition of the second punch 15 and the noncontact outer peripheral sites 5, 6 of the plate 30 along with the progression of the shaping. In the step c, the noncontact outer peripheral sites 5, 6 of the plate 30 are shaped by the margin forming faces of the second punch 15 and the dice 22 before the first punch 11 reaches the position of a press lower dead point. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a press forming method of an aluminum alloy plate that makes it possible to form a large-sized panel that is difficult to be formed, such as an automobile body outer panel. Hereinafter, aluminum is also referred to as Al.

  As is well known, steel (steel plate) is used for the outer panel (outer plate) and inner panel (inner plate) of panel structures such as automobile hoods (bonnets), fenders, doors, luggage (trunk lids), and roofs. Instead of panels, aluminum alloy panels are also used. These aluminum alloy panels are panel molded products (press molded products: simply referred to as panels hereinafter) in which aluminum alloy plates (blanks, panel molding material plates) are press-molded with a mold, as with steel plates. ing.

  Among them, outer panels such as hoods, luggages, and trunk lids are particularly difficult to press due to the diversification of automobile (panel) designs in recent years. This is because the formability of the aluminum alloy plate is inferior to that of the steel plate and the shape of the outer panel itself.

  An example of the trunk lid outer panel is shown in FIG. As shown in FIG. 15, the trunk lid outer panel 1 includes at least two ridge lines (ridges) 2 extending in the vehicle body width direction and surrounding the ridge lines 2 at the center (top) of the panel. Long (broad) curved surface portions (or convex peripheral edge portions, contour portions) 3 and 4. The ridgeline portion 2 often has a semicircular (curved) character line in plan view as shown in FIG. 15 in terms of the design of the vehicle body. In FIG. 15, reference numeral 9 denotes a license seat (concave portion) on which the license plate is mounted.

  When the trunk lid outer panel 1 having such a semicircular arc-shaped large ridge line portion is manufactured by being stretched and formed from an aluminum alloy plate, which is a forming material plate, by a press device, particularly on the molding surface of the molded product panel. Wrinkles are likely to occur. That is, as in a press-formed product panel shown in FIG.

  The occurrence of such wrinkles is a particular problem when a product shape such as a trunk lid outer panel 1 having a large semicircular arc-shaped ridgeline portion 2 is formed by overhanging. This is because the ridgeline portion 2 pulls the material plate non-uniformly, and a surplus due to material inflow tends to occur, and the material plate part at the end does not contact the punch until near the bottom dead center (hereinafter referred to as non-contact outer peripheral part) This is because it can be freely deformed. Such a problem of wrinkles is a problem peculiar to a molded product panel having the non-contact outer peripheral portion. That is, such a wrinkle generation problem is unlikely to occur in an ordinary flat panel molded product that does not have such a non-contact outer peripheral portion or is not in the shape of the ridge line portion 2 or the curved surface portions 3 and 4.

  When a trunk lid outer panel 1 is stretched and formed by a press device, a normal method will be described with reference to FIGS. FIG. 16A is a perspective view showing a deformed state of the aluminum alloy plate in the middle of pressing, and FIG. 16B is a cross-sectional view of the pressing device and the aluminum alloy plate in section B of FIG. Usually, the die 22 and the blank holder (wrinkle pressing member) 20 sandwich the peripheral edge 31 of the aluminum alloy plate 30, and the die 22 is directed toward the punch 11 fixed on the bolster (base) 21. The aluminum alloy plate 30 is formed by relatively moving (lowering). At this time, in the aluminum alloy plate 30 being formed, the portions of the plates 33 and 34 between the top portion 32 corresponding to the ridge line portion 2 of the trunk lid outer panel and the peripheral portion 31 sandwiched by the blank holder 20 are the trunk lid outer panel. Corresponds to the curved surface portions 3 and 4.

  In the panel in the middle of molding shown in FIG. 16 (a), the cross-section A at the center of the product has a substantially arc-shaped ridgeline, so that the top of the cross-section A is higher than the cross-section B at a position off the product center. It has become. In other words, the line length lA (lA ') of the cross section A is longer than the line length lB (lB') of the cross section B, and a line length difference is generated between the cross sections A and B. As described above, when a difference in line length occurs between two adjacent cross sections, a non-uniform tensile force is likely to act as described above, and a surplus is likely to occur. Furthermore, since there is a difference in the molding height of the cross section A in the center of the product and the molding height of the outer periphery of the product, the non-contact outer peripheral portion is generated in which the material plate portion at the end does not contact the punch until near bottom dead center . Since this non-contact outer peripheral portion is freely deformed, as described above, wrinkles are likely to occur in X shown in the figure.

  As countermeasures against this, as shown in FIG. 17 partially showing the cross section of the press device, the surplus forming portions 19 and 26 are provided on the inner side of the blank holder 20, and the tension associated with surplus molding is applied to the plate 30. The method of acting is generally. That is, by providing this surplus on the periphery of the plate 30, the plate 30 comes into contact with the mold forming the surplus portion from the early stage of press molding, and tension is applied when forming the surplus. Methods for preventing wrinkle generation are widely used.

  In addition to this, when press-molding an aluminum alloy hood outer panel having a large bent portion at the end, it is expected that a recess that will cause wrinkles will be generated before or when wrinkle pressing starts. It has also been proposed to previously mold the center portion of the molding surface (see, for example, Patent Document 1). In this method, the height of the panel (product) molding surface of the punch is set higher than the upper surface of the wrinkle pressing member by a predetermined dimension, and the center of the molding surface of the plate is molded in advance.

Further, a method has been proposed in which an aluminum alloy plate is press-formed on an automobile hood outer panel having a large bent portion and a contour line connecting the bent portion and the panel main body portion being curved toward the front of the panel main body. (For example, see Patent Document 2). In this method, among the portions corresponding to the bent portion of the plate end portion, the portion corresponding to the wrinkle pressing surface at the time of press molding has a shape adapted to the wrinkle pressing member surface shape at the time of press molding. This is a method in which the end portion of the aluminum alloy plate is bent in advance to form a bent portion, and then press-molded while wrinkling and including a portion corresponding to the wrinkle pressing surface of the bent portion. It has also been proposed that the end portion of the aluminum alloy plate is bent in advance by a divided punch that moves independently of the punch portion for forming the panel body.
JP 2001-58218 A Japanese Patent Laid-Open No. 2004-188445

  A general wrinkle generation prevention method for forming the surplus portion formed around the above-described material plate, that is, in FIG. The method of adding cannot exert the effect of suppressing wrinkles sufficiently. That is, in this method, since the surplus forming portion 19 that contributes to surplus molding is integrally formed with the punch 11, surplus molding is not started unless the punch 11 is sufficiently close to the die 22. For this reason, in this method, the mold and the material plate do not contact in the vicinity of the product end until relatively late in the molding, and the free deformation of the non-contact outer peripheral portion leading to wrinkle generation cannot be restricted. Further, since the contact timing between the material plate and the mold is in the later stage of molding, the tension at the initial stage of molding which is important in suppressing wrinkles is not generated, and the effect of suppressing wrinkles cannot be fully exhibited.

  On the other hand, from the first half of the molding, if it is attempted to obtain a deformation restraint or a tension effect on the material plate by bringing the surplus mold into contact with the material plate, the surplus portion provided on the punch 11 is provided. It is necessary to extremely increase the height of the convex portion of the meat forming portion 19 and the depth of the concave portion of the surplus portion forming portion 26 provided on the die. However, in such a case, an extremely deep surplus is formed in the peripheral portion of the plate 30 near the bottom dead center of the forming, and an excessive tension acts on the plate 30. For this reason, in the trunk lid outer panel or the like targeted by the present invention, the tendency of the plate thickness reduction of the portion corresponding to the ridgeline portion 2 or the surplus portion 15 of the outer panel becomes larger, and in some cases, the plate breaks. There is a fear.

  Thus, in the trunk lid outer panel or the like targeted by the present invention, if the surplus thickness necessary for preventing wrinkles is provided, the tendency of this reduction in plate thickness becomes so large that it cannot be ignored, Cracks at the surplus portion 15 and the like are likely to occur. Therefore, the general wrinkle generation preventing method for forming the surplus portion formed around the material plate cannot achieve both wrinkle generation prevention and crack generation prevention.

  In addition, the method of Patent Document 1 is effective for suppressing wrinkles in the case of a panel in which the contour of the panel ridge line portion 2 is not a semicircular arc shape (curved shape) but a substantially straight line. However, for the trunk lid outer panel as the object of the present invention, there is still the non-contact outer peripheral part that leads to the generation of wrinkles. The prevention effect is thin. Furthermore, the method of Patent Document 2 is unique in that the ridgeline portion 2 in the trunk lid outer panel is formed by bending the plate in the front-rear direction (vehicle body longitudinal direction) with a divided punch. However, it is difficult to set the bending conditions in the longitudinal direction of the plate and the design conditions of the divided punch, and there is a problem that is not practical in this respect.

  In addition, as a molding method using such a divided punch, there is a “calling molding method” that is widely used for preventing cracks. This is because a locally movable part is provided in the panel body molding part (for example, the central part) on the punch side, and the blank is pushed up by this locally movable punch part, so that the material from the periphery into the mold can be formed. It increases the inflow and prevents cracking. However, with this crack prevention method, it is impossible to achieve both the prevention of wrinkles and the prevention of cracks in the trunk lid outer panel and the like targeted by the present invention. That is, since the amount of material flowing into the mold is increased by the local movable punch portion, the remainder of the blank, that is, the punch forming the central portion of the panel and the non-contact outer periphery that does not contact the bottom dead center. On the contrary, the part becomes larger, and the molded panel is more likely to be wrinkled.

  On the other hand, while these molding problems still remain, needs for application of aluminum alloy plates such as Al-Mg-Si (6000 series), which have excellent bake hardness and recyclability, and high strength to automobile body outer panels Are increasing due to the need for vehicle weight reduction and energy absorption to enhance vehicle safety to protect the global environment.

  The present invention aims to provide a press forming method for an aluminum alloy plate that can form a large-sized panel that is difficult to form, such as an outer panel of an automobile body such as a trunk lid outer panel, by paying attention to such circumstances. It is.

In order to achieve the above object, the gist of the press forming method of the aluminum alloy plate of the present invention is to provide a non-contact outer peripheral portion that does not contact the punch for forming the central portion of the panel to the vicinity of the bottom dead center of the punch. A method of press-molding an aluminum alloy plate on a molded product panel having a first punch for molding a central portion of the panel and the non-contact outer peripheral portion that can be separately displaced with respect to the first punch A second punch for forming the surplus portion provided outside the die and a die having a shape corresponding to the second punch are provided, and the blank holder provided on the outer periphery of the die is used to sandwich the outer periphery of the aluminum alloy plate. Then, the first and second punches and the die are relatively moved, and the first and second punches are interlocked to press the aluminum alloy plate. Upon is to perform the following a~c steps in order.
a. First, the second punch is preliminarily displaced to the die side as compared to the relative position with respect to the first punch at the press bottom dead center. An aluminum alloy plate corresponding to the center portion of the panel is formed by the first punch and the die while being in contact with the non-contact outer peripheral equivalent portion.
b, Next, the contact state between the second punch and the non-contact outer peripheral portion is maintained with respect to the proximity of the first punch and the die as the molding of a proceeds. The second punch is displaced so as to maintain the distance between the second punch and the surplus surface of the die.
c, and with the progress of the molding of b, the second punch reaches the position at the press bottom dead center before the first punch reaches the position at the press bottom dead center. The punch is displaced to the die side, and the non-contact outer peripheral portion is formed by the second punch and the surplus surface of the die in the vicinity of the press bottom dead center of the first punch. .

  In order to achieve the above object, a preferred embodiment of the press forming method of the aluminum alloy sheet of the present invention is that the displacement operation of the second punch is performed by a gas spring provided in the second punch. Further, the time when the second punch reaches the position at the press bottom dead center is set to be 10 mm to 45 mm before the first punch reaches the press bottom dead center.

  In the present invention, as described in the above gist, at least one or more second punches that can be displaced separately from the first punch that molds the central part of the panel are used. The first feature is to make contact with the non-contact outer peripheral portion on the outer side (outer peripheral portion) and further to mold.

  As a result, when the aluminum punch plate is formed in cooperation with the die by the first punch, it is possible to restrain wrinkle deformation of the end portion of the material plate and to apply tension to the material plate.

  At this time, b, with respect to the proximity of the first punch and the die as the molding proceeds, the contact state between the second punch and the non-contact outer peripheral portion is maintained, A second feature is that the second punch is displaced so as to maintain a distance between the second punch and the surplus surface of the die.

  Thus, the excessive lifting of the aluminum alloy plate (the non-contact outer peripheral equivalent portion) to the die side (upward) by the second punch is prevented.

  Further, by this, c, the portion corresponding to the non-contact outer periphery can be formed by the second punch and the surplus forming surface of the die in the vicinity of the press bottom dead center of the first punch. As a result, at the position near the press bottom dead center of the first punch, the tension from the die face is transmitted to the material aluminum alloy plate corresponding to the central portion of the panel, and the amount of wrinkles generated is suppressed.

  As a result, the non-contact outer peripheral portion even in the case where the protruding height of the ridge line in FIG. 16 is high and the line length difference between the cross sections A and B is large as in the trunk lid outer panel targeted by the present invention. Thus, tension can be applied over the entire region of the plate (panel being formed). For this reason, the suppression effect can be exhibited also about the wrinkles which generate | occur | produce from the comparatively initial stage of shaping | molding.

  In addition, in the present invention, in addition to the effect of wrinkle suppression described above (function of restraining the material plate and applying tension by the second punch), it is possible to prevent the product (molded panel) from being broken by the second punch. It also has an effect. That is, since the second punch comes into contact with the material plate (non-contact outer peripheral portion) from an early stage of the molding process by the first punch, it is possible to perform deformation restraint and tensioning of the material plate. On the other hand, at the press bottom dead center, the relative position of the second punch with respect to the die moves toward the punch side as compared to during press molding. As a result, the height of the surplus is reduced, and there is an effect that the tension is not excessively increased in the vicinity of the bottom dead center of the press that is easily broken.

  In other words, in the present invention, from the first half of the molding process that determines whether or not wrinkles occur, the deformation of the material plate portion corresponding to the curved surface portions (3, 4) surrounding the ridge line of the panel to be molded is restrained, Sufficient tension can be applied to the plate. As a result, wrinkles are prevented from occurring in the first half of the molding process, and the tension level can be controlled below a certain value in the second half of the molding process, so that the material is extremely reduced in thickness near the bottom dead center and breaks. Can be prevented.

  As described above, according to the present invention, it is possible to achieve both the prevention of wrinkles and the prevention of cracks in the difficult molding, and it is an aluminum alloy automobile body outer panel such as a trunk lid outer panel, and is a large-sized panel that is difficult to form. Even so, molding becomes possible.

  Hereinafter, more specific embodiments of the present invention will be described in detail.

(Press machine)
Specific embodiments of the press apparatus used in the present invention will be described with reference to FIGS. FIG. 2 shows an upper die (die: FIG. 2 shows only a peripheral portion from which the central portion corresponding to the center of the molded product is removed) 22, a lower punch first punch 11, second punch 15, and blank holder (wrinkle). A mode in which the pressing member 20 is combined is shown.

(Lower mold)
FIG. 3 shows only the lower die, and includes a first punch (main body punch) 11 and a second punch (divided punch) 15 that is divided from the first punch 11 and moves independently (displaces). The mode which combined these is shown. The upper surfaces of the punches 11 and 15 each have a product forming surface that is engaged with a molding forming surface at the center of the die 22 as an upper die.

  That is, the 1st punch 11 shape | molds the center part of a shaping | molding panel (raw material board) as a main body punch. Specifically, as partially shown in a perspective view in FIG. 4, the first punch 11 serves as a product formation surface of a target trunk lid outer panel or the like as a ridge line portion (2 in FIG. 15) at the center of the panel. And the plane portions 13 and 14 forming the plane portions (3 and 4 in FIG. 15) surrounding the ridge line portion 12 of the panel. Moreover, it has the formation surface a which forms the license seat 9 to which the number plate shown in FIG. 15, which is unique to the trunk lid outer panel, is mounted.

  In addition, the second punch 15 is a divided punch, separately from the first punch 11 that molds the central portion of the panel. The portion that does not come into contact with the punch 11) contacts or further proceeds, and this non-contact outer peripheral portion is positively formed. Specifically, the second punch 15 is an abbreviated arrangement arranged around the first punch 11 as a product forming surface (extra-wall forming surface described later) as partially shown in a perspective view in FIG. It has an annular shape. In addition, the molding punch may be divided into these first and second punches, but in any case, the second punch 15 is interlocked with the first punch 11. Are configured to be separately displaceable.

  However, the peripheral shape (contour) and the number of the second punch 15 should be determined according to the peripheral shape (contour) of the first punch 11, and are not necessarily circular or one as shown in FIG. 5. Not only that. In this respect, for example, a partial annular shape including a plurality of punches or parts (parts) partially surrounding the first punch 11 may be used.

  FIG. 8 is a perspective view showing a state in which the punches 11 and 15 are attached to the punches 11 and 15 on a bolster. The punch 11 is rigidly attached on the bolster. On the other hand, the second punch 15 is coupled to the bolster via gas springs 18 and the like arranged in a necessary number at necessary portions, and sinks downward when a compression force is applied to the second punch 15 from above. It has become. As another embodiment, a plurality of second punches 15 are provided as described above, and each of the second punches 15 can be moved forward and backward (movable up and down) individually with respect to the upper die via a drive device such as a separate hydraulic pressure. It may be configured. In order to precisely control the displacement of the second punch 15 according to each molding step of the present invention by interlocking the second punch 15 with the first punch 11 as in the present invention, The gas spring 18 and the like are optimal in terms of mechanism.

(Upper type)
On the other hand, as shown in a perspective view in FIG. 6, the upper die 22 has a central portion corresponding to the center of the molded product and wrinkle pressing surfaces 23 and 23. Further, as shown in a perspective view in FIG. 7, the blank holder (wrinkle pressing member) 20 has 24 and 24 wrinkle pressing surfaces, respectively. The blank holder 20 is held by a cushion pin (not shown), and an upward force generated by a hydraulic mechanism below the press device is transmitted to the blank holder 20 via the cushion pin, and the blank holder 20 is used as a wrinkle holding force. Used to hold

  More specifically, the die 22 is attached to a slide (not shown) connected to the lifting device. A product forming surface 22 a is formed on the lower surface of the die 22. Further, frame-shaped wrinkle pressing surfaces 23, 23 are formed on the outermost peripheral portion of the die 22 at positions facing the wrinkle pressing surfaces 24, 24 of the lower mold blank holder 20.

  In addition, in cooperation with the second punch 15 at positions corresponding to the surplus forming surfaces 16 and 17 of the lower second punch 15 of the die 22, Surplus forming surfaces 22b and 22c for molding the surplus portions 35 and 36 on the outer edge side are provided.

  As the feature of the present invention, the relative position of the second punch 15 with respect to the first punch 11 at the start of press molding is set in advance on the die 22 side compared to the relative position at the press bottom dead center. The mode of displacing is also preferable from the top of the equipment. In such an embodiment, as the molding progresses and the die 22 moves downward and the gap between the first punch 11 and the die 22 becomes smaller, the second punch 15 is brought into contact with the plate. Molding is performed while moving downward while maintaining. Such a molding mode is possible by combining a movable mold and a die cushion, and can be achieved with a relatively simple mold configuration, which is preferable in terms of equipment.

  On the other hand, when a mechanism for independently controlling the displacement of the second punch 15 is provided for the first punch 11, the press apparatus becomes complicated in terms of equipment, but more positively the material plate It is suitable for press-molding a product (molded panel) that is more difficult to mold (prone to wrinkles and breakage).

  In addition, the said non-contact outer peripheral part said by this invention has both the meaning of the non-contact outer peripheral part in the shape | molded panel, and the non-contact outer peripheral part in the aluminum alloy plate which is a shaping | molding material corresponding to this. In the present invention, these are appropriately used.

  Further, in the present invention, the range in which the first punch 11 is formed may include not only the central portion of the panel but also the vicinity of the central portion and the necessary portions around the central portion. Therefore, the expression of the first punch 11 for forming the central portion of the panel is the first punch 11 for forming only the central portion of the panel or the vicinity of the central portion of the panel and the periphery of the central portion. Meaning.

(Press molding method)
Next, referring to FIGS. 1A, 1B, 1C, and 1D, which are cross-sectional views of a press apparatus premised on such a configuration, the press forming method of the aluminum alloy plate of the present invention will be concretely described. I will explain it.

  1 is premised on that the lower punch 11 is fixed to the bolster 21 and does not move, and the upper die 22 is moved downward (indicated by a downward arrow). Is. In this respect, the lower punch 11 side may be raised, and the point is that the punch 11 and the die 22 may move relatively.

FIG. 1 (a):
Fig.1 (a) shows the state before the shaping | molding start by punch which set the aluminum alloy plate 30 to the press apparatus. In FIG. 1A, the outermost peripheral edge 31 of the plate 30 is appropriately wrinkled by the wrinkle pressing surfaces 23, 23 located in the peripheral portion of the die 22 and the wrinkle pressing surfaces 24, 24 of the blank holder 20. It is pinched by force. This wrinkle holding force may be in a range used in press forming of a normal aluminum alloy plate. Here, the blank holder 20 is held at the upper limit position by the cushion pin 25 before the aluminum alloy plate 30 is set.

FIG. 1 (b):
FIG. 1B shows a state where the die 22 is lowered to a position 65 mm above the bottom dead center position of the molding. As the die 22 descends, the blank holder 20 is in a state where the aluminum alloy plate 30 is sandwiched by the cooperation of the wrinkle pressing surface 24 that is a part of the blank holder 20 and the wrinkle pressing surface 23 that is positioned around the die 22. Continue to sink.

  FIG. 1B shows a state in which the second punch 15 starts to contact the surplus portions 35 and 36 of the plate as the first punch 11 starts to be formed. Here, the surplus portions 35 and 36 of the plate are non-contact outer peripheral portions of the above-described plate, and are portions that do not contact the first punch 11 until near the bottom dead center of the panel. And the surplus parts 35 and 36 of a board are the further outer edge sides of the plane parts 33 and 34 corresponding to the surplus parts 5 and 6 of the molded article panel mentioned later.

(Process a)
In order to start the contact of the second punch 15 with the surplus portions 35 and 36 of the plate as the molding of the first punch 11 shown in FIG. The second punch 15 is displaced in advance toward the die 22 as compared with the relative position with respect to the first punch 11 at the press bottom dead center. Thus, when forming the ridge line portion corresponding portion 32 (2) which is the center portion of the plate 30 by the first punch 11 and the die 22, the second punch is the non-contact outer peripheral equivalent portion of the plate 30. It ensures contact with the surplus parts 35, 36 of the plate.

  In the example of FIG. 1b, the second punch 15 is floated in advance by the gas spring 18 from the bolster 21, and the contact of the second punch 15 is performed at the initial stage where molding with the first punch 11 starts. Like to start.

  As the process a, if the second punch 15 is not displaced in advance toward the die 22 as compared with the relative position with respect to the first punch 11 at the press bottom dead center, the molding by the first punch 11 is performed. In the early stage of the process, the second punch 15 cannot be brought into contact with the surplus portions 35 and 36 of the plate, which are the non-contact peripheral portions. For this reason, wrinkle deformation at the end of the material plate 30 is restricted, and tension cannot be applied to the material plate 30.

  Here, if the timing of contact with each non-contact outer peripheral part is controlled independently using each of the plurality of second punches 15, depending on the shape of the product, the material plate for each place in the product The tension applied to 30 can be finely controlled. In order to maximize this effect, the second punch 15 is provided in a portion corresponding to the surplus portions 35 and 36 of the plate provided around the product.

  Note that the timing of the start of contact of the second punch 15 with the surplus portions 35, 36 of the plate is only at the initial stage of molding the first punch 11 (early stage of the molding process by the first punch). Prior to the molding of the first punch 11, at the same time as the molding of the first punch 11, or after the molding of the first punch 11. The contact timing between the second punch 15 and the surplus portions 35 and 36 of the material plate is conveniently selected according to the tension applied to the product to be molded.

(Forming the plate with the first punch)
In FIG. 1B, as described above, the first punch 11 is in a state where the forming of the ridge line portion corresponding portion 32 (2) which is the central portion of the plate 30 is started. After the state of FIG. 1B, the die 22 continues to descend toward the first punch 11, and the first punch 11 forms the plate 30. That is, the product forming surfaces 12, 13, and 14 of the first punch 11 cooperate with the product forming surface 22a of the die, and the ridge line portion 2 (corresponding portion 32 of the plate) at the center of the panel and the ridge line of this panel The flat portions 3 and 4 (corresponding portions 33 and 34 of the plate) surrounding the portion 2 are formed.

  At this time, as described above, the second punch 15 that is in contact with the surplus portions 35 and 36 of the plate 30 is relatively displaced toward the die 22, and is formed by the first punch 11. The plate 30 is in contact with the surplus forming surfaces 16 and 17 of the second punch 15 at two contact points. That is, when forming with the first punch 11, the plate 30 functions to apply tension from the periphery to the portion 32 corresponding to the ridge line portion 2 at the center of the panel.

  As a result, when the first punch 11 forms the aluminum alloy plate 30 in cooperation with the die 22, a tension is applied from the periphery to the portion 32 corresponding to the curved surface portions 3 and 4 of the panel in the plate 30. It becomes possible to mold while giving and restraining.

  Moreover, by adjusting the position and degree of contact of each surplus portion 35, 36 of the plate 30 by the second punch 15, as in the trunk lid outer panel targeted by the present invention, in FIG. Even when the line length difference between the cross sections A and B of the plate 30 to which the tension is to be applied is large, the tension can be applied over the entire panel.

  For this reason, even if the line length difference between the cross sections A and B of the plate 30 is large, when the first punch 11 or the die 22 is formed, the non-contact outer peripheral portion is eliminated, and the trunk lid outer panel Wrinkles are less likely to occur in the portions corresponding to the flat portions 3 and 4.

FIG. 1 (c):
In FIG. 1C, the molding proceeds after the state of FIG. 1B, and then the die 22 moves (lowers) toward the first punch 11 to a position 30 mm above the molding bottom dead center. Indicates the state. FIG. 1C shows a state in which the second punch 15 does not move downward and the plate surplus portions (the non-contact outer peripheral portions) 35 and 36 are sandwiched by the second punch 15.

(Process b)
However, at this stage, as the step b, simply bringing the second punch 15 into contact with the surplus plate portions (the non-contact outer peripheral portion) 35, 36 eliminates the non-contact outer peripheral portion, This is important for constraining wrinkle deformation at the end of the plate and exerting an effect of controlling the tension applied to the material plate. That is, the distance between the second punch 15 and the die surplus surface 22b, 22c is maintained, and the second punch 15 is displaced while the second punch 15 is brought into contact with the plate surplus portions 35, 36. This is very important. That is, it is important that the second punch is brought into contact with the material in the first half of the molding process where wrinkles tend to occur, and it is important to apply a predetermined tension of the material. It is not necessary to sandwich the non-contact outer peripheral portion) 35, 36.

  In other words, from this contact state, it is desirable that pressure is further applied to the surplus portions 35 and 36 of the plate 30 by the second punch 15 so that the surplus portions 35 and 36 are not held firmly. If the surplus portions (the non-contact outer peripheral portions) 35 and 36 are firmly held by the second punch 15 and the die 22 in the middle of the molding, the tension from the die face is excessive in the vicinity of the bottom dead center. The inner portions of the meat portions 35 and 36 are not applied, and the wrinkles are difficult to erase. Furthermore, when the plate surplus portions 35 and 36 are sandwiched in the middle of molding, the second punch 15 is excessively displaced toward the die 22, and in the initial stage of the molding process by the first punch 11, The second punch 15 raises the surplus portions 35 and 36 of the plate 30 to the die 22 side (upward), and there is a problem that wrinkles increase due to an increase in the surplus amount.

  This state will be described with reference to FIGS. 12, 13, and 14. FIG. FIG. 12 is a partially enlarged cross-sectional view of the vicinity of the apex only on the right side of the product in the state shown in FIG. On the other hand, FIG. 13 shows a partially enlarged cross-sectional view of the vicinity of the apex only on the right side of the product in the state of FIG. It is a comparative example which shows the state which the 2nd punch 15 has hold | maintained the raw material 30 completely. That is, in FIG. 13, the second punch 15 completely holds the material 30 between the surplus forming surface 16 and the surplus forming surface 22 b of the die 22 in the middle of molding. It is a comparative example which shows a state.

  FIG. 14 shows a cross section taken along line A of FIG. As shown in FIG. 14, when the material plate 30 as shown in FIG. 13 is formed by the second punch 15, the center portion is formed with respect to the bottom dead center shape 14 that is the molding surface of the first punch 11. The side plate 30 is lifted by the height H to the die 22 side (upward), the line length L is longer than the line length L ′ of the shape 14 at the bottom dead center, and the remainder Will increase. And it can be said that the amount of excess meat increases as H increases.

  As a control for preventing this, the second punch 15 does not firmly hold the surplus portions 35 and 36 of the plate 30 as shown in FIG. 12, which shows the state of FIG. The state is desirable. In this FIG. 12, while maintaining the space | interval of the 2nd punch 15 and die surplus formation surface 22b, 22c (not shown), and making the 2nd punch 15 contact the board surplus part 35,36, The state of the said FIG.1 (c) which displaces the 2nd punch 15 is shown.

  Thus, by the above-described step b, the surplus portions of the second punch 15 and the plate 30 (the non-existing portion described above) are brought into close proximity to each other as the molding of the first punch 11 and the die 22 proceeds. The second punch 15 is displaced so as to maintain the distance between the second punch 15 and the surplus surface 22b, 22c of the die while maintaining the contact state with the contact outer circumference equivalent portions 35, 36). Let Accordingly, the second punch 15 is excessively displaced toward the die 22, and the aluminum alloy plate 30 (the non-contact outer peripheral portion) is excessively lifted by the second punch 15 toward the die 22 (upward). Is prevented.

  Further, as a process c described later, the surplus surplus of the plate 30 is formed by the second punch 15 and surplus surface forming surfaces 22b and 22c of the die 22 in the vicinity of the press bottom dead center of the first punch 11. The portion (the non-contact outer peripheral equivalent portions 35, 36) can be molded. As a result, at the position near the press bottom dead center of the first punch 11, the tension from the die face is transmitted to the material aluminum alloy plate 30 corresponding to the center of the panel, and the amount of wrinkles generated is suppressed.

(Descent of second punch)
In order to maintain the contact state between the second punch 15 and each surplus portion of the plate 30 (the non-contact outer peripheral equivalent portions 35 and 36), the surplus forming surfaces 22b and 22c of the second punch 15 and the die are formed. The second punch is displaced while maintaining the interval. If the distance between the second punch 15 and the surplus forming surfaces 22b and 22c of the die cannot be maintained, the molding proceeds excessively or the contact with the plate is interrupted and the restraint state of the plate is released.

  For this reason, for example, in the latter half of molding after FIG. 1B, as the molding progresses and the die 22 approaches the bottom dead center, the second punch 15 is interlocked with the die 22 to sandwich the plate 30. Lower in the state. That is, the die 22 in FIG. 1 (b) is formed by the surplus portion 35b formed on the plate 30 in cooperation with the surplus portion forming surfaces 22b and 22c and the surplus portion forming surfaces 16 and 17 of the second punch 15. After the state of movement (lowering) to a position where 36 is clamped, as the molding progresses and the die 22 approaches the bottom dead center, the second punch 15 is interlocked with the die 22 and the aluminum alloy plate 30 is clamped. Move it down in the same state. This lowering is performed by contracting the gas spring 18 that supports the second punch 15 by the lowering of the die 22.

  As a result, the function of applying (constraining) tension to the surplus portions 35 and 36 by the second punch 15 and the die 22 is maintained at a constant level. That is, as the molding progresses and the die 22 moves downward, and the gap between the first punch 11 and the die 22 becomes smaller, the second punch 15 is kept downward while maintaining contact with the plate. Forming while moving to This eliminates an unnecessary increase in tension in the latter half of the molding of the plates 33 and 34, and in this state, the latter half is molded by the first punch 11, and as shown in FIG. Finish the molding process. For this reason, it is possible to suppress the plate thickness reduction rate to the same level as in the normal overhang forming without greatly reducing the plate thickness.

  Of course, the movement of the second punch 15 is not only lowered, but depending on the molding conditions, in order to maintain the distance between the second punch 15 and the surplus forming surfaces 22b and 22c of the die, The second punch 15 may be raised in conjunction with the motor 22.

  Further, as described above, in FIG. 1C, it is not always necessary to completely hold the material 30 between the second punch 15 and the die 22. Rather, a predetermined distance is provided between the second punch 15 and the die 22. It is desirable that the clearance is provided, that is, the second punch 15 is simply in contact with the plate 30 or the clearance is provided. In such a state in which the second punch 15 is simply in contact with the plate or in a state in which the clearance is provided, the tension applied to the material plate is slightly smaller than in the case where the second punch 15 is completely clamped. However, since the second punch is in contact with the material plate 30, the deformation restraining effect of the material plate and the tension imparting effect due to the frictional resistance can be obtained, and as described above, the excess of the material due to the excessive lifting of the material The wrinkle can be further reduced by suppressing the increase and increasing the wrinkle suppressing effect by applying the tension near the bottom dead center.

  In order to obtain the above-described tension application function by surplus molding from the initial stage of molding without using a displacement operation such as the lowering operation of the second punch as described above, it is formed integrally with the punch as shown in FIG. In the surplus forming part 19 and the surplus forming part 26 of the die, as described above, the height of the surplus is particularly increased. However, in this method, since the forming depth in the surplus forming portions 26 and 19 becomes extremely deep near the bottom dead center of forming, excessive tension is applied to the aluminum alloy plate. Therefore, as described above, the plate thickness reduction rate is increased, which causes cracking of the plate being formed.

(Process c)
In the present invention, the first punch 11 is used as the process c until the molding shown in FIG. 1 (c) progresses to FIG. 1 (d) at the bottom dead center of molding, which is the final stage of the stretch molding described later. In the vicinity of the bottom dead center of the press, the surplus portions (the non-contact outer peripheral equivalent portions 35 and 36) of the plate 30 are formed by the second punch 15 and the surplus forming surfaces 22b and 22c of the die 22. . By this step c, the tension from the die face is transmitted to the blank 30 corresponding to the center of the panel at the position near the press bottom dead center of the first punch 11, and the amount of wrinkles generated is suppressed.

  For this purpose, the second punch 15 is positioned at the press bottom dead center before the first punch 11 reaches the position at the press bottom dead center with the progress of molding in FIG. The second punch 15 is displaced in advance to the die side so as to reach in advance. As a result, a portion corresponding to the non-contact outer periphery by the second punch 15 can be formed near the press bottom dead center of the first punch 11.

  If this molding cannot be performed, the material aluminum alloy in which the tension from the die face corresponds to the center of the panel at the position near the press bottom dead center of the first punch 11 in FIG. Since it is not transmitted to the plate, the amount of wrinkles is increased.

FIG. 1 (d):
FIG. 1D shows the final stage of overhang forming (the situation at the bottom dead center of forming). That is, in the panel molded product 1 shown in FIG. 1D, 2 is a ridge line portion 2 (corresponding portion 32 of the plate) at the center of the panel, and 3 and 4 are flat portions (corresponding portions of the plate) surrounding the ridge line portion 2. 33, 34). 5 and 6 are characteristic surplus portions (corresponding portions 35 and 36 of the plate) formed by the surplus surfacing surfaces 16 and 17 of the split punch 15 and surplus surfacing surfaces 22b and 22c of the die 22. : The non-contact outer peripheral portion).

  In FIG. 1 (d), the surplus surface 16 and 17 of the second punch 15 has a flat top surface, but this shape does not have to be flat, and the top surface has a substantially semicircular convex shape. It may be in shape. Moreover, you may provide an unevenness | corrugation or a level | step difference in the contact surface with the aluminum alloy plate of the 2nd punch 15. FIG. Furthermore, unevenness or a step corresponding to the unevenness or step may be provided on the surplus forming surfaces 22b and 22c (contact surfaces with the aluminum alloy plate) on the die 22 side corresponding thereto. By forming the plate part near the bottom dead center due to these irregularities or steps, it is expected that positive tension will be applied to the plate, surface distortion of the panel molded product will be eliminated, and shape accuracy will be improved. it can.

  The panel molded product stretched as described above is further trimmed to remove the surplus portions 5 and 6, the outermost peripheral portion, etc., and the trunk lid outer panel shown in FIG. Finished with aluminum alloy car body outer panel.

  In the present invention, as described above, it is possible to achieve both the prevention of wrinkles and the prevention of cracks during panel extension molding. As a result, it is possible to form even an aluminum alloy automobile body outer panel such as a trunk lid outer panel, which is difficult to form, such as a semi-arc-shaped character line at the ridge line portion of the panel. Become. Accordingly, the present invention is preferably applied to an aluminum alloy automobile body outer panel selected from a hood, a fender, a door, a trunk lid (luggage), a roof, and the like, which are representative examples of these large panels that are difficult to form.

(Aluminum alloy)
The aluminum alloy used in the present invention includes 3000 series, 5000 series, 6000 series, and 7000 series that are specified or included in AA to JIS standards according to required characteristics for panel use such as rigidity, strength, formability, and corrosion resistance. An aluminum alloy material selected from the above is appropriately selected. However, among these, it is widely used for aluminum alloy automobile body panels and the like, and in order to improve the bake hardness, 0.2% proof stress is stretched and formed with a high strength of 130 MPa or more, and there is a demand for improvement of the formability. It is suitable for application to a high Al—Mg—Si (6000) aluminum alloy plate.

  Examples of the present invention will be described below. Among aluminum alloys, a high-strength aluminum alloy plate made of AA6022-T4, which is more difficult to be stretched, was stretched and formed on the trunk lid outer panel 1 having the license seat 9 having the shape shown in FIG. The aluminum alloy plate had a substantially trapezoidal shape with a 0.2% yield strength of 173 MPa, a plate thickness of 1.0 mm, and a size of width: 1720 (1620) mm × length: 1450 mm.

  The molded trunk lid outer panel 1 has a product width in the vehicle width direction of 1250 mm, a height difference in the press direction of 117 mm, and a deviation in the direction perpendicular to the press of 86 mm and the apex of the product cross section in the center in the product width direction. And a flat surface portion 3 (length: about 460 mm) and 4 (length: about 467 mm) surrounding the ridge line portion 2. The ridge line portion 2 has a bending angle of about 90 DEG. The shape is such that

  The invention example uses the press device 10 (10MN hydraulic press device) provided (divided) with the second punch described in FIGS. 1 and 2 to 8 as the press device, and the steps a to c described above are performed. Using this, a stretch molding test was conducted. BHF was changed to 1000, 1300 and 1700 kN, respectively. In addition, the rust preventive cleaning oil for commercial steel plates was used for the lubricant in common.

Each invention example (invention examples 1 and 2 to be described later) performed characteristic steps a to c under the following conditions.
a, The second punch 15 was previously displaced by 30 mm toward the die 22 as compared to the relative position with respect to the first punch 11 at the press bottom dead center. Before the molding is started by the proximity of the first punch 11 and the die 22, the second punch 15 is previously applied to the plate 30 with respect to the surplus forming surfaces 16 and 17 of the second punch 15. Contact was made at two contact points. That is, the surplus portions 16 and 17 of the second punch 15 and the surplus portions 22b and 22c of the die 22 are brought into contact with the surplus portions of the plate 30 (the non-contact outer peripheral equivalent portions 35 and 36). Then, tension was applied from the periphery to the portion 32 corresponding to the ridge line portion 2 in the center of the panel.
b. Next, the second punch 15 is kept in contact with the plate 30 with respect to the proximity of each other as the first punch 11 and the die 22 are formed. The second punch was lowered (displaced) between 60 and 30 mm above the bottom dead center in order to keep the distance from the surplus surface of the die at 30 mm.
c. Furthermore, at the point of 30 mm above the bottom dead center, the second punch 15 reaches the press bottom dead center position, and in the vicinity of the press bottom dead center of the first punch 11, the second punch 15 and the die 22 are Each surplus portion of the plate 30 (the non-contact outer peripheral equivalent portions 35 and 36) was formed with the surplus-wall forming surfaces 22b and 22c.

  For comparison, only the movement timing of the second punch is changed, and the second punch 15 is not moved up to the point of 30 mm above the bottom dead center. The punch 11 was also molded under the conditions for forming the product portion. This molding result is shown as a conventional example in FIGS. 9, 10 and 11 to be described later in comparison with the invention example. Under the molding conditions of this conventional example, the plate surplus portions (the non-contact outer peripheral portions) 35 and 36 are substantially clamped by the second punch 15 as shown in FIGS. It will be molded.

(Difference in deformation)
FIG. 9 shows a deformed form of the plate (panel) being molded (wrinkle generation state of the panel molded product). FIG. 9 shows a deformed shape at a top dead center of 30 mm. The upper row shows a conventional example, the middle row shows Invention Example 1, and the lower row shows Invention Example 2. Inventive example 1 shown in the middle stage shows the second punch 15 in FIG. 12 and step b above (the second punch 15 is kept in contact with the plate 30 with the second punch 15 remaining in contact with the die). The second punch was lowered to maintain the distance from the meat forming surface) from 60 mm above the bottom dead center. In addition, in Invention Example 2 shown in the lower stage, the above-described FIG. 12 and the step b were performed from 30 mm above the bottom dead center, behind the Invention Example 1.

  In the conventional example in which the plate surplus portions 35 and 36 are almost sandwiched by the second punch 15 as shown in FIGS. 13 and 14 in the middle of the molding, as shown in the upper part of FIG. Thus, a large number of wrinkles were generated radially from the periphery of the central ridge line portion (corresponding to 2 in FIG. 15) where the height of the panel molded product was high, toward the surplus portion of the peripheral edge. On the other hand, in the invention examples 1 and 2, it can be seen that wrinkles are suppressed as compared with the conventional example. Furthermore, it is excellent in the smoothness of the surface of the final panel molded product and the shape accuracy including the ridge line character line. In addition, when the difference in the movement timing of the second punch 15 is compared, when the second punch 15 is moved from 60 mm above the bottom dead center in the process of FIG. The occurrence of excess meat wrinkles is reduced. Therefore, rather than completely holding the material 30 in the middle of molding by the second punch 15, it is preferable to proceed with molding with a certain clearance and to form a surplus portion near the bottom dead center. This proves more desirable for wrinkle control.

(Wrinkle height)
FIG. 10 shows the result of measuring the wrinkle height at the peripheral edge portion (FIG. 15) of the curved surface portion 3 where the wrinkle height becomes the largest in the molded product panel of this invention example and the conventional example with a three-dimensional shape measuring machine of the molded panel. (A), (b) and (c) respectively. 10 (b) and 10 (c), the horizontal axis X and the vertical axis Z are as shown on the molded panel of FIG. 10 (a) (the molded panel of FIG. 9). The distance in the direction orthogonal to the wrinkle and the vertical axis Z indicate the height in the perpendicular direction. FIG. 10B shows a case where BHF is relatively small as 1300 kN, and FIG. 10C shows a case where BHF is relatively large as 1700 kN. 10 (b) and 10 (c), the thin and thick line is the conventional example, the thin solid line is Invention Example 1, and the thick and dark solid line is Invention Example 2. Comparing under the same BHF conditions in FIG. 10B, it can be seen that the wrinkle height indicated by the height of the vertical axis Z is reduced to 1/2 of the conventional example in Invention Examples 1 and 2. Further, as shown in FIG. 10C, when BHF is increased to 1700 kN, it can be seen that, particularly in Invention Example 1, the wrinkle height is reduced to such an extent that clear irregularities (wrinkles) cannot be confirmed. In addition, in the example (conventional example) using the press device using the integrated punch 11 which is not provided with the second punch as described in FIG. 15, the conventional example (comparative example) in this test evaluation is used. Wrinkle height is higher than that.

(Thickness reduction rate)
The maximum thickness reduction rate at each of the two portions of the curved surface portions 3 and 4 (FIG. 15) of the invention product and the conventional molded product panel where the thickness reduction is greatest (the thickness reduction rate relative to the original thickness). ) The results are shown in FIG. In FIG. 11, the measurement positions 1 to 4 on the horizontal axis are illustrated on the molded panel illustrated in the upper left of FIG. 11 (the molded panel in FIG. 9 and corresponding to the curved surface portions 3 and 4 in FIG. 5). Corresponds to each measurement position marked with a circle (numbered with an arrow). In FIG. 11, the vertical axis indicates the plate thickness reduction rate, the black bar graph is the conventional example, and the shaded bar graph is the invention example 1. As can be seen from FIG. 11, when the BHF is 1000 kN, the thickness reduction rate is slightly larger in the invention example than in the conventional example. This is a proof that the above-described steps a to c of the present invention are effective for the molded product panel, and it can be seen that the tension rigidity of the molded product panel is improved. The plate thickness reduction rate at this level is significantly smaller than 20% of the upper limit plate thickness reduction rate at which cracking is likely to occur in the overhang forming of an aluminum alloy trunk lid outer panel, and is completely within the allowable range.

  From these Examples, the effect of suppressing wrinkles when molding a difficult-to-form panel by the molding method of the present invention is supported. In addition, in a present Example, the moldability improvement effect is supported about 6000 type | system | group with comparatively difficult shaping | molding. As a result, even when applied to an Al alloy plate of 3000 series having a formability equal to or less than that of the 6000 series or 5000 series, which is relatively easy to form, the formability is reliably improved. These Al alloys have different mechanical properties such as tensile strength, yield strength and elongation depending on the alloy composition and tempering (heat treatment) conditions. However, although the degree of wrinkle generation is different depending on the difference in mechanical properties, the wrinkle generation mechanism itself is common regardless of these mechanical properties. Therefore, the wrinkle suppression mechanism of the present invention is also effective in common with such a wrinkle generation mechanism.

  According to the present invention, there is provided a press forming method of an aluminum alloy plate, which is an automobile body outer panel such as a trunk lid outer panel, and which can form a large-sized panel having the non-contact outer peripheral portion and having a shape difficult to form. be able to. For this reason, the use of an aluminum alloy plate as a forming material is greatly expanded for use in an outer panel molded product such as an automobile, and the industrial value is great.

It is sectional drawing of the press apparatus which shows one embodiment of this invention shaping | molding method in steps. It is a perspective view which shows one embodiment of the metal mold | die which concerns on this invention. It is a perspective view which shows one embodiment of the metal mold | die which concerns on this invention. It is a perspective view which shows one embodiment of the punch which concerns on this invention. It is a perspective view showing one embodiment of a division punch concerning the present invention. It is a perspective view which shows one embodiment of the board presser concerning this invention. It is a perspective view which shows one embodiment of the board presser concerning this invention. It is a perspective view showing one embodiment of a division punch concerning the present invention. It is explanatory drawing which shows the analysis result of this invention shaping | molding method. It is explanatory drawing which shows the wrinkle height of this invention shaping | molding method. It is explanatory drawing which shows the plate | board thickness reduction | decrease rate of this invention shaping | molding method. It is the elements on larger scale of FIG.1 (C). It is the elements on larger scale which show the comparative example with respect to FIG. It is A sectional view taken on the line A of FIG. It is a perspective view which shows an example of a trunk lid outer panel. It is sectional drawing of the press apparatus which shows the conventional shaping | molding method. It is a fragmentary sectional view of the press apparatus which shows the conventional forming method.

Explanation of symbols

1: Trunk lid outer panel, 2: Ridge part, 3, 4: Plane part,
5, 6: Non-contact outer peripheral part of the molded product panel (remaining part of the molded product panel),
10: Press device, 11: First punch, 12: Punch ridge line part,
13, 14: punch plane portion, 15: second divided punch,
16, 17: surplus forming surface, 18: gas spring, 19, 26: surplus forming portion,
20: Blank holder, 21: Bolster, 22: Dice,
23, 24: Wrinkle holding surface, 25: Cushion pin, 30: Plate,
31: The outermost peripheral part of a board, 32: The ridgeline part 2 equivalent site | part of a board,
33, 34: flat plate portions 3, 4 corresponding portions of the plate,
35, 36: non-contact outer peripheral portion of the plate (the surplus portion of the plate),

Claims (3)

A method of press-molding an aluminum alloy plate on a molded product panel having a non-contact outer peripheral portion that does not come into contact with the punch that molds the central portion of the panel to the vicinity of the bottom dead center of the punch, A first punch that molds the central portion, a second punch that can be separately displaced with respect to the first punch, and that molds a surplus portion provided outside the non-contact outer peripheral portion, and corresponds to these. A die having a shape is provided, and the blank holder provided on the outer peripheral portion of the second punch sandwiches the outer peripheral portion of the aluminum alloy plate. Then, the first and second punches are relatively connected to the die. The first and second punches are interlocked with each other, and the following steps a to c are sequentially performed when the aluminum alloy plate is press-formed. Press molding method of the plate.
a. First, the second punch is preliminarily displaced to the die side as compared to the relative position with respect to the first punch at the press bottom dead center. An aluminum alloy plate corresponding to the center portion of the panel is formed by the first punch and the die while being in contact with the non-contact outer peripheral equivalent portion.
b, Next, the contact state between the second punch and the non-contact outer peripheral portion is maintained with respect to the proximity of the first punch and the die as the molding of a proceeds. The second punch is displaced so as to maintain the distance between the second punch and the surplus surface of the die.
c, and with the progress of the molding of b, the second punch reaches the position at the press bottom dead center before the first punch reaches the position at the press bottom dead center. The punch is displaced to the die side, and the non-contact outer peripheral portion is formed by the second punch and the surplus surface of the die in the vicinity of the press bottom dead center of the first punch. .   The aluminum alloy sheet press forming method according to claim 1, wherein the displacement operation of the second punch is performed by a gas spring provided in the second punch.   The aluminum alloy sheet press forming according to claim 1 or 2, wherein the time when the second punch reaches the position at the press bottom dead center is 10 mm to 45 mm before the first punch reaches the press bottom dead center. Method.

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