JP2008173678A - Press forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain higher-accuracy press formed products by stabilizing forming load during press forming. <P>SOLUTION: A press forming apparatus includes cushion members 42 which are provided so as to be housed in hole parts 40 of a cushion plate 36, also brought into contact with the lower end parts of cushion pins 38 and with which forming load produced in the beginning of forming is absorbed. The cushion member 42 includes a single body 52, a first piston 56a and a second piston 56b which are arranged in series in the chamber of the body 52, a first pressure chamber 62a in which air for pressing the first piston 56a is supplied and a second pressure chamber 62b in which air for pressing the second piston 56b is supplied. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a press forming apparatus capable of drawing a flat thin steel plate into a desired shape.

  A large number of press-formed products obtained by press-forming thin steel plates with a press machine are used for automobile bodies. For example, in a press machine that press-forms parts of a desired shape, a thin steel plate is set between a movable die and a fixed die, and is generated when the thin steel plate is pressed by the respective forming parts of the movable die and the fixed die. There is a case where a cushion device is provided in order to buffer the impact.

  With respect to this type of press molding cushion device, for example, in Patent Document 1, a die cushion lifted by a cushion cylinder is disposed on the lower side of the lower die, and a cushion pin extends from the die cushion to the upper portion of the lower die. In addition, it is described that a structure in which a cushion pad is attached to the upper end of the cushion pin is generally employed, and cushion pressure generated in the die cushion is transmitted to the cushion pad as it is through the cushion pin. .

  Further, Patent Document 1 discloses that a hydraulic cylinder is newly provided below the cushion pin that supports the cushion pad, and the cushion load for each cushion pin is controlled by the hydraulic cylinder.

Japanese Utility Model Publication No. 62-20711

  However, in the technical idea disclosed in Patent Document 1, since the cushion load is controlled using a hydraulic cylinder, there is a concern that the fluidity of the pressure oil may be reduced due to the viscous resistance. There is a demand from the industry to control each cushion load with higher accuracy.

  The present invention has been made in view of the above points, and an object thereof is to provide a press molding apparatus that can stabilize a molding load at the time of press molding and obtain a press molding product with higher accuracy. And

In order to achieve the above object, the present invention is an apparatus that performs press molding by applying a pressing force to a molding material with a punch that is relatively displaced and movable between an upper mold and a lower mold,
A blank holder provided to surround the lower mold;
A plurality of cushion pins for supporting the blank holder;
A cushion plate and a cushion pad provided on the lower side of the lower mold,
A cushion cylinder for supporting the cushion pad;
A cushion member that is accommodated in the hole of the cushion plate and is in contact with the lower end of the cushion pin, and absorbs a molding load generated in the initial stage of molding;
With
The cushion member is provided between a single body, a first piston and a second piston arranged in series in the body of the body, and the first piston and the second piston. A first pressure chamber supplied with air for pressing one piston, and a second pressure chamber provided on a lower side of the second piston and supplied with air for pressing the second piston. To do.

  In this case, the air pressure in the second pressure chamber may be set larger than the air pressure in the first pressure chamber.

  According to the present invention, first, the impact load (vibration) generated when the punch and the lower die are in contact is transmitted to the cushion member via the blank holder and the cushion pin. At this time, the first piston, which is in contact with the lower end portions of the plurality of cushion pins and is given a predetermined pressure upward by the air supplied to the first pressure chamber, resists the predetermined pressure. Accordingly, the first buffering action is exerted by displacing downward, and the low load component of the molding load is suitably absorbed by the first buffering action. When the first piston is displaced to provide a buffering action, the second piston is not applied with an impact load and is in a substantially stationary state.

  Subsequently, a first buffering action is performed by the first piston, so that the first piston is displaced downward and comes into contact with the second piston, and the second piston b is moved downward. Press. While the first piston and the second piston are kept in contact with each other, a second piston to which a predetermined receiving pressure is applied upward by air supplied to the second pressure chamber is a first piston and The secondary buffering action is exhibited by the displacement toward the lower side integrally with the predetermined receiving pressure, and the medium load component of the molding load is suitably absorbed by the secondary buffering action.

  Further, after the first and second pistons exert the first and second buffering actions, the molding load applied by the last stage of molding is transmitted to the cushion cylinder via the cushion pad, and the cushion The cylinder exhibits a third buffering action, and the third buffering action suitably absorbs a high load component of the molding load.

  As described above, in the present invention, the impact load (vibration) generated by the molding load at the initial stage of molding is absorbed (buffered) by the plurality of cushion members, so that the molding load at the time of press molding can be stabilized. A molded product having a precise dimensional accuracy can be obtained.

  In the present invention, the low load component of the molding load transmitted from the cushion pin is absorbed by the first piston, and then the first piston is displaced so that the first piston and the second piston come into contact with each other. While maintaining the state, the intermediate load component of the molding load is absorbed by the second piston, and further, the high load component of the molding load transmitted through the cushion pad is absorbed by the cushion cylinder. The molding load transmitted in this manner can be sequentially absorbed in time series for each different load component.

  By absorbing the impact load in the initial stage of molding by the first piston and the second piston of the cushion member, the molding load at the time of press molding can be stabilized, and a press molded product with higher accuracy can be obtained.

  Preferred embodiments of the press molding apparatus according to the present invention will be described below and described in detail with reference to the accompanying drawings.

  In FIG. 1, reference numeral 10 indicates a press molding apparatus according to an embodiment of the present invention. The press molding apparatus 10 includes a bolster 14 fixed on the die bed 12 via a fixing means (not shown), and a molding portion 18 that is fixed on the bolster 14 via an intermediate block 16 and has a convex section having a curved cross section. The lower die 20 having the above, the punch 24 having the concave portion with the curved cross section corresponding to the molding portion 18 of the lower die 20 provided so as to be movable up and down above the lower die 20, and the action of the press ram (not shown). An upper die 26 that is integrally displaced with the punch 24 is provided below.

  A bead forming convex portion 28 is formed on the flange portion adjacent to the forming portion 22 of the punch 24, while the upper mold is provided in a blank holder (described later) adjacent to the forming portion 18 of the lower mold 20. A bead forming concave portion 30 corresponding to the 26 bead forming convex portions 28 is formed. Between the bead-forming convex portion 28 and the bead-forming concave portion 30, a bead (not shown) is formed on the end side of the thin steel plate 32, which is a forming material, thereby suppressing excessive inflow of the material during forming. The occurrence of wrinkles and the like can be suitably prevented.

  The press molding apparatus 10 is provided on the lower side of the bolster 14, adjusts the length of a cushion pin, which will be described later, and suppresses vibration and noise in the early stage of molding, and the first cushion. After the cushion action is performed by the mechanism 34a, the thin steel plate 32 that is a forming material has a second cushion mechanism 34b that suppresses a load generated during press forming.

  The first cushion mechanism 34 a protrudes to the side of the lower mold 20 through the through hole of the bolster 14 and the cushion plate 36 disposed along the substantially horizontal direction below the bolster 14. A plurality of cushion pins 38 supported on a substantially vertical vertical direction are accommodated in a bottomed cylindrical hole 40 disposed in a plurality of strips on the upper surface of the cushion plate 36 (see FIG. 2). A plurality of cushion members 42 that respectively contact the lower ends of the cushion pins 38, and a blank holder 44 that is supported by the cushion pins 38, is adjacent to the side of the lower mold 20, and is disposed so as to surround the lower mold 20. And have.

  The second cushion mechanism 34b includes a plurality of cushion pads 46, which are disposed on the lower side of the cushion plate 36, and a plurality of piston rods 48a that integrally support the cushion plate 36 and the cushion pads 46, respectively. The cushion cylinder 48 is provided.

  In this case, under the driving action of the cushion cylinder 48, the cushion plate 36, the cushion pad 46, the cushion pin 38, and the blank holder 44 are provided so as to be displaceable in the vertical direction integrally with the piston rod 48a. The thin steel plate 32 which is a forming material is held by a predetermined holding force between the displaced holding surface of the blank holder 44 and the holding surface of the punch 24 (see FIG. 4).

  As shown in FIG. 3, the cushion member 42 has a substantially cylindrical shape, and a male screw portion 50 that fits a female screw portion formed on the inner wall of the bottomed cylindrical hole 40 of the cushion plate 36 is formed on the outer peripheral surface. A single body 52 formed, and a cover member 54 provided substantially flush with the upper surface of the cushion plate 36 and forming a closed chamber in the body 52 by closing one end of the body 52; The first piston 56a on the upper side and the second piston 56b on the lower side are arranged in series in the chamber of the body 52.

  On the lower surface of the cover member 54, a convex portion 54a that abuts on the first piston 56a is bulged. By providing this cover member 54, entry of dust such as chips into the interior of the body 52 is preferably prevented. Note that the shape of the cover member 54 is not limited to the shape shown in FIG. 3, and may be formed in another shape (not shown) with a reduced thickness along the vertical direction. It is also possible to prevent dust and the like from entering the interior of the body 52 by using a dust prevention mechanism (not shown) instead of the cover member 54.

  A set of O-rings 58 a and 58 b that perform a sealing function with the hole 40 of the cushion plate 36 are mounted on the outer peripheral surface of the body 52.

  On the inner wall surface of the body 52, an annular shoulder portion of the first piston 56a on the upper side comes into contact with the first stopper portion 60a for restricting upward displacement, and an annular shoulder portion of the second piston 56b on the lower side. A second stopper portion 60b that abuts and regulates upward displacement is provided (see FIGS. 2 and 3).

  The chamber in the body 52 includes a first pressure chamber 62a formed between the lower surface of the first piston 56a and the upper surface of the second piston 56b, the lower surface of the second piston 56b, and the hole 40 of the cushion plate 36. The second pressure chamber 62b is formed between the bottom surface and the second pressure chamber 62b. The cushion plate 36 communicates with the first pressure chamber 62a, communicates with the first pressure chamber 62a, supplies a predetermined pressure of air, and communicates with the second pressure chamber 62b. A second air supply port 64b that supplies air of a predetermined pressure to the second pressure chamber 62b is provided.

  In this case, the predetermined pressure of the air filled in the second pressure chamber 62b is set higher than the predetermined pressure of the air filled in the first pressure chamber 62a. Further, for example, nitrogen gas having a rust prevention effect may be used as the air supplied into the first pressure chamber 62a and the second pressure chamber 62b.

  The press molding apparatus 10 according to the embodiment of the present invention is basically configured as described above. Next, the operation and effects thereof will be described.

  First, as shown in FIG. 4, the cushion pin 38 and the blank holder 44 are integrally raised under the drive action of the cushion cylinder 48, and the thin steel plate 32 is held between the flange portion of the punch 24 and the blank holder 44. Is done. In the state where the thin steel plate 32 is held, the upper die 26 is integrally lowered under the driving action of a press ram (not shown), and the forming portion 22 of the punch 24 and the forming portion 18 of the lower die 20 come into contact with each other, thereby Draw forming (drawing forming) on the thin steel plate 32 is started.

  Further, at the final stage of molding immediately before the upper die 26 reaches the bottom dead center as the molding process proceeds, the bead-forming convex portion 28 provided on the flange portion of the punch 24 contacts the end side of the thin steel plate 32. Further, a part of the thin steel plate 32 is pushed into the bead forming concave portion 30 provided in the blank holder 44 corresponding to the bead forming convex portion 28 to form a bead, and the forming process is completed ( (See FIGS. 5 and 6).

  Thereafter, the upper die 26 ascends integrally with a press ram (not shown), a knockout (not shown) is activated, and the blank holder 44 is lowered and separated from the molded product, so that the released molded product is transported (not shown). Is transferred to the next process.

  Next, the effects of the first cushion mechanism 34a and the second cushion mechanism 34b during the molding step will be described in detail below.

  First, at the initial stage of molding when the molding part 22 of the punch 24 and the molding part 18 of the lower mold 20 are in contact, the impact load generated when the contact is made is transmitted to the cushion member 42 via the blank holder 44 and the cushion pin 38. (See FIG. 7). At this time, the first piston 56a, which is in contact with the lower end portions of the plurality of cushion pins 38 and is given a predetermined receiving pressure upward by the air supplied to the first pressure chamber 62a, is provided with the predetermined receiving force. The first buffering action is exerted by displacing the pressure downward against the pressure, and the low load component of the molding load is suitably absorbed by the first buffering action (see FIG. 8). When the first piston 56a is displaced to provide a buffering action, the second piston 56b is substantially stationary.

  As a result of the first buffering action being performed by the first piston 56a, the first piston 56a is slightly displaced downward and comes into contact with the upper surface of the second piston 56b so that the second piston 56b is moved downward. Press toward.

  Accordingly, the second piston 56b to which a predetermined receiving pressure is applied upward by the air supplied to the second pressure chamber 62b while maintaining the state in which the first piston 56a and the second piston 56b are in contact with each other. The second buffering action is exerted by displacing the first piston 56a integrally with the first receiving pressure against the predetermined receiving pressure, and the second buffering action exerts a medium load component of the molding load. It is suitably absorbed (see FIG. 9).

  Furthermore, after the buffering action is exerted by the first cushion mechanism 34a, the molding load applied by the end of molding is transmitted to the cushion cylinder 48 via the lower cushion pad 46 superimposed on the cushion plate 36, The cushion cylinder 48 exerts a third buffering action, and a high load component of the molding load is suitably absorbed by the third buffering action.

  As described above, in the present embodiment, the vibration generated by the molding load at the initial stage of molding is absorbed (buffered) by the plurality of cushion members 42, thereby stabilizing the molding load at the time of press molding and high accuracy. A molded product having a high dimensional accuracy can be obtained. In other words, it is possible to obtain a press molded product with higher accuracy by stabilizing the formability of the press.

  Further, in the present embodiment, the low load component of the molding load is absorbed due to the first buffering action due to the displacement of the first piston 56a against the air pressure in the first pressure chamber 62a. The second piston 56b and the first piston 56a are integrally displaced against the air pressure in the second pressure chamber 62b (the pressure is set higher than the air pressure in the first pressure chamber 62a). Due to the secondary buffer action, the medium load component of the molding load is absorbed, and finally, the high load component of the molding load is absorbed due to the third buffer action by the cushion cylinder 48.

  In the present embodiment, different load components from the initial molding stage to the final molding stage are gradually increased with the passage of time by the first to third buffering actions in which the load components of the molding load absorbed in this way are different. Can be absorbed into. Note that the load component of the molding load can be appropriately controlled by adjusting the pressures of the first pressure chamber 62a, the second pressure chamber 62b, and the cushion cylinder 48 by a pressure reducing valve (not shown).

  For example, in the comparative example shown by the broken line in FIG. 10, when the molding load transmitted from the cushion pin is absorbed only by a single cushion device (not shown), the punch molding portion is in contact with the lower mold molding portion. In the present embodiment shown by the solid line in FIG. 10, the peak load at the initial stage of molding is suitably absorbed while the molding load suddenly increases and adversely affects the molding material at the initial stage of molding. A stable load characteristic curve in which the molding load gradually increases corresponding to the displacement amount of the punch 24 can be obtained.

  Furthermore, in the present embodiment, even if the overall length along the axial direction of the plurality of cushion pins 38 becomes uneven due to manufacturing errors or wear due to long-term use, the above-described manufacturing may occur. Since the height difference of the plurality of cushion pins 38 due to errors and wear is absorbed by the first piston 56a (air pressure of the first pressure chamber 62a) with which the lower end of the cushion pin 38 abuts, it is a thin material that is a molding material. A forming load can be uniformly and uniformly applied to the steel plate 32. Even if the overall lengths of the plurality of cushion pins 38 along the axial direction are the same, if an assembly error or the like of the plurality of cushion pins 38 occurs when the apparatus is manufactured, The height difference of the cushion pin 38 can be suitably absorbed.

  Furthermore, in the present embodiment, the pressing load at the time of forming the bead can be stabilized, so that the alignment position accuracy between the bead forming convex portion 28 and the bead forming concave portion 30 (particularly, the position in the height direction). (Accuracy) is improved, and the bead shape can be molded with very high dimensional accuracy.

  In the present embodiment, the structure in which the two pistons of the first piston 56a and the second piston 56b are disposed on the cushion member 42 has been described, but the present invention is not limited to this, and two or more plural pistons are provided. The pistons may be arranged in multiple stages and in series, and a plurality of pressure chambers to which air is supplied corresponding to the number of pistons may be provided.

It is a longitudinal cross-sectional view which shows schematic structure of the press molding apparatus which concerns on embodiment of this invention. It is a perspective view of the cushion plate arrange | positioned in the cushion plate which comprises the press molding apparatus of FIG. 1, and its hole. It is a partially cutaway side view of the cushion member shown in FIG. It is a longitudinal cross-sectional view which shows the shaping | molding preparation state by which the thin steel plate which is a shaping | molding raw material was hold | maintained between the punch and blank holder of the press molding apparatus shown in FIG. It is a longitudinal cross-sectional view which shows the state which the upper mold | type and the punch fell integrally from the state shown in FIG. FIG. 6 is a longitudinal sectional view showing a state where the punch is further lowered from the state shown in FIG. 5 and the forming is completed. It is an enlarged longitudinal cross-sectional view which shows the state by which the cushion member was pressed by the molding load transmitted via the cushion pin. FIG. 8 is an enlarged longitudinal sectional view showing a state where the first piston is displaced downward by the molding load from the state shown in FIG. 7 and is in contact with the second piston. FIG. 9 is an enlarged longitudinal sectional view in which the first piston and the second piston are further displaced from the state shown in FIG. 8 while being displaced. It is a characteristic view which shows the relationship between the shaping | molding load and displacement amount in this Embodiment and a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Press molding apparatus 12 ... Die bed 14 ... Bolster 20 ... Lower mold 24 ... Punch 26 ... Upper mold 28 ... Convex part for bead forming 30 ... Concave part for bead forming 32 ... Thin steel plate 34a, 34b ... Cushion mechanism 36 ... Cushion plate 38 ... Cushion pin 40 ... Hole 42 ... Cushion member 44 ... Blank holder 46 ... Cushion pad 48 ... Cushion cylinder 52 ... Body 54 ... Cover member 56a, 56b ... Piston 60a, 60b ... Stopper part 62a, 62b ... Pressure chamber 64a, 64b ... Air supply port

Claims (3)

An apparatus that performs press molding by applying a pressing force to a molding material with a punch that relatively displaces and moves an upper mold and a lower mold,
A blank holder provided to surround the lower mold;
A plurality of cushion pins for supporting the blank holder;
A cushion plate and a cushion pad provided on the lower side of the lower mold,
A cushion cylinder for supporting the cushion pad;
A cushion member that is accommodated in the hole of the cushion plate and is in contact with the lower end of the cushion pin, and absorbs a molding load generated in the initial stage of molding;
With
The cushion member is provided between a single body, a first piston and a second piston arranged in series in a body of the body, and the first piston and the second piston. A first pressure chamber supplied with air for pressing one piston, and a second pressure chamber provided at a lower side of the second piston and supplied with air for pressing the second piston. Press forming equipment. The apparatus of claim 1.
An air pressure in the second pressure chamber is set to be larger than an air pressure in the first pressure chamber. The apparatus according to claim 1 or 2,
While the low load component of the molding load transmitted from the cushion pin is absorbed by the first piston, the first piston is subsequently displaced and the first piston and the second piston are kept in contact with each other. The press molding apparatus is characterized in that a medium load component of the molding load is absorbed by the second piston, and further, a high load component of the molding load transmitted through the cushion pad is absorbed by the cushion cylinder.

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