Patent Publication Number: US-2020282442-A1

Title: Molding device

Description:
TECHNICAL FIELD 
     The present invention relates to a forming device. 
     BACKGROUND ART 
     There are many types of aircraft components that configure an aircraft, and in a case where a desired shape is obtained by press forming an aluminum alloy plate, it is necessary to prepare various types of forming dies. As one method of press forming, there is a method in which a forming target material is placed on a male forming die, and the forming target material is pressed by a rubber bag pressurized by a liquid such as oil instead of a female die (rubber forming press). For rubber forming press, it need only prepare the male die as the forming die, and thus rubber forming press is suitable for the production of many kinds in small quantities of aircraft components and the like. 
     On the other hand, there is also known a technique of forming a forming target material by using an electromagnetic forming device instead of rubber forming press. In electromagnetic forming, a large current is caused to instantaneously flow through the electromagnetic coil, thereby generating an induced current on a surface of the forming target material arranged along the electromagnetic coil. As a result, an electromagnetic force acts on the surface of the forming target material, and the forming target material moves toward the forming die and is pressed against the forming die. 
     PTL 1 discloses that a thin plate is formed into a desired shape by an electromagnetic forming device, and PTL 2 discloses that an electromagnetic force is applied to a predetermined portion of a hollow material in multiple stages by an electromagnetic plastic working method to perform a forming process. 
     CITATION LIST 
     Patent Literature 
     [PTL 1] Japanese Unexamined Patent Application Publication No. 2007-296553 
     [PTL 2] Japanese Unexamined Patent Application Publication No. 6-23442 
     SUMMARY OF INVENTION 
     Technical Problem 
     In the rubber forming press, the bag pressurized by a liquid presses the forming target material via a rubber plate, and thus the force is not distributed to the entire forming target material, the formation amount is insufficient, and the shape accuracy is not high. Accordingly, a product obtained by forming may have a defective shape or may require a shape correction work. Since the shape correction work is performed by forming a plurality of times or processing by manual operation, there is a problem that time and labor are required. Further, such as a case where a flange with an outwardly projected curved surface (a shrinkage flange) is formed, depending on the formed shape, a compressive force acts on the forming target material at the time of press forming, so that unnecessary wrinkles may occur. 
     The present invention is made in view of the above-described circumstances, and an object thereof is to provide a forming device capable of accurately performing press forming on a forming target material. 
     Solution to Problem 
     According to an aspect of the present invention, there is provided a forming device including an electromagnetic coil, a fluid having conductivity and installed on one surface side of a forming target material along the forming target material, and a forming die installed on the other surface side of the forming target material and formed so as to impart a formed shape to the forming target material, in which an electromagnetic force generated by the electromagnetic coil is caused to act on the fluid so that the fluid presses the forming target material against to the forming die. 
     According to this configuration, the fluid having conductivity is installed on one surface side of a forming target material along the forming target material and the forming die is installed on the other surface side of the forming target material. When a current is caused to instantaneously flow through the electromagnetic coil, an induced current is generated in the fluid having conductivity, and the electromagnetic force acts on the fluid. Then, the fluid moves toward the forming die, and the fluid presses the forming target material against the forming die. Therefore, the forming die imparts a formed shape to the forming target material. By generating the electromagnetic force in the fluid, a larger pressing force can be generated in a short time as compared with a case where the forming target material is pressed against the forming die by only a fluid pressure of the fluid. The forming target material is formed at a high speed with a large pressing force by using the electromagnetic force, and thus forming can be performed with high accuracy and the spring back amount is reduced. As a result, the strain correction work after forming can be reduced. 
     In the above aspect, the fluid may be a metal powder, a liquid in which a metal powder is dispersed, or a liquefied metal. 
     In the above aspect, the fluid may be accommodated in a bag-shaped member. 
     Advantageous Effects of Invention 
     According to the present invention, it is possible to accurately perform press forming on a forming target material. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a longitudinal sectional view showing a forming device according to an embodiment of the present invention. 
         FIG. 2  is a longitudinal sectional view showing a forming device according to an embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, a forming device  1  according to an embodiment of the present invention will be described with reference to  FIGS. 1 and 2 . 
     The forming device  1  according to the embodiment is a device that imparts a formed shape to a plate-shaped material  50  which is, for example, a forming target material made of an aluminum alloy by using a forming die  4 . A formed member  60  formed by the forming device  1  is used for aircraft components and the like. 
     As shown in  FIG. 1 , the forming device  1  according to the embodiment includes an electromagnetic coil  2 , a power supply unit  3  that supplies a current to the electromagnetic coil  2 , the forming die  4 , and the like. The forming device  1  generates an induced current to a conductive material by the electromagnetic coil  2  and causes an electromagnetic force to act, similarly to generally known electromagnetic forming. The operating conditions and the like of the forming device  1  can be set in the same manner as in usual electromagnetic forming. 
     The electromagnetic coil  2  is arranged outside a forming surface of the forming die  4 . For example, the electromagnetic coil  2  is arranged along the surface of the forming die  4  as shown in  FIG. 1 . The electromagnetic coil  2  may have a cylindrical shape for example, and the forming die  4  may be arranged inside the electromagnetic coil  2 . 
     A large current is supplied from the power supply unit  3  to the electromagnetic coil  2 . As shown in  FIG. 1 , a power supply circuit  5  includes a circuit in which a capacitor  6  is installed in parallel with the electromagnetic coil  2  and a switch  7  is installed between a connection point between the power supply unit  3  and the capacitor  6  and the electromagnetic coil  2 . In this configuration, when the switch  7  is open, an electric charge is charged from the power supply unit  3  to the capacitor  6  through an electric resistance  8 . Then, by closing the switch  7  and discharging an electric charge charged in the capacitor  6 , a large current to the electromagnetic coil  2  is generated. 
     A fluid  10  is a material having conductivity and fluidity. The fluid  10  is accommodated in a rubber bag  11 , for example. The fluid  10  is, for example, a metal powder or a liquid in which a metal powder is dispersed. The metal powder is, for example, an iron powder. The liquid is oil, for example, and fluidity and rust prevention are ensured. In the liquid in which a metal powder is dispersed, a ratio of the metal powder to the liquid is preferably 50% by mass or more, and if possible, 75% by mass or more. Although there is a possibility that a load pressure at the time of forming is reduced, even in a case where the material has a value smaller than the above described example, it can be applied as the fluid  10  as long as forming can be performed by the material. Further, the fluid  10  may be a low melting point metal. A low melting point metal is, for example, lead or tin. By setting an environment of the forming device  1  to an environment with equal to or more than the melting point of the fluid  10  which is a low melting point metal, the fluid  10  can be used in a fluidized and liquefied state. 
     The fluid  10  is placed on one surface side of the plate-shaped material  50  which is the forming target material, and the forming die  4  is installed on the other surface side of the plate-shaped material  50  with the plate-shaped material  50  interposed therebetween. 
     By causing a large current to instantaneously flow through the electromagnetic coil  2 , an induced current is generated on the surface of the fluid  10  arranged along the electromagnetic coil  2 . As a result, an electromagnetic force acts on the fluid  10 , the fluid  10  moves toward the forming die  4 , and the fluid  10  and the plate-shaped material  50  are pressed against the forming die  4 . 
     Before forming, the plate-shaped material  50  which is the forming target material is placed on the forming surface of the forming die  4 . The forming die  4  is a male die and imparts the formed shape to the plate-shaped material  50 . 
     In the forming method using the forming device  1  according to the embodiment, first, the plate-shaped material  50  is placed on the forming surface of the forming die  4  as shown in  FIG. 1 . Furthermore, the fluid  10  is placed on an upper surface of the plate-shaped material  50  placed on the forming die  4 . 
     Next, a current is supplied to the electromagnetic coil  2 . As a result, an induced current is generated on the surface of the fluid  10  and an electromagnetic force acts on the fluid  10 , so that the fluid  10  moves toward the forming die  4 , and the fluid  10  presses the plate-shaped material  50  against the forming die  4 . At this time, the fluidity of the fluid  10  decreases, and the fluid  10  can strongly press the plate-shaped material  50 . Thereby, as shown in  FIG. 2 , the plate-shaped material  50  is formed along the forming die  4  to form the formed member  60 . After pressing the plate-shaped material  50  for a predetermined time, the supply of a current is cut off, whereby the action of the electromagnetic force on the fluid  10  can be stopped. Accordingly, fluidity of the fluid  10  is restored. 
     As described above, according to the forming device  1  according to the embodiment, by generating the electromagnetic force in the fluid  10 , a larger pressing force can be generated in a short time as compared with a related rubber forming press in which the plate-shaped material is pressed against the forming die by only a fluid pressure of the fluid. 
     Stated another way, the plate-shaped material  50  is formed at a high speed with a large pressing force by using the electromagnetic force acting on the fluid  10 , and thus the plate-shaped material can be formed in a shape along the forming die  4  with high accuracy and the spring back amount is reduced in the resulting formed member  60 . In particular, in the case of an aluminum alloy, it is a material having a higher breaking elongation as the strain rate becomes higher, and has a great effect of reducing the spring back amount by being formed at a high speed. Therefore, since the insufficiency of the formation amount of the formed member  60  is unlikely to occur, the strain correction work after forming can also be reduced. In addition, since forming can be accurately performed, the formed member  60  can be formed without generating unnecessary wrinkles even in a case of forming a flange (a shrinkage flange) having an outwardly projected curved surface. A magnesium alloy (such as AZ80) is known as a material having a higher breaking elongation as the strain rate increases, in addition to an aluminum alloy, and an effect of reducing the spring back amount can be obtained. 
     In the above embodiment, the case where the formed member  60  is formed for the first time from the unprocessed plate-shaped material  50  has been described, but the present invention is not limited thereto. For example, the present invention can be applied to a case where the forming die  4  is pressed against the processed formed member  60  to correct the shape of the formed member  60 . 
     REFERENCE SIGNS LIST 
     
         
         
           
               1 : forming device 
               2 : electromagnetic coil 
               3 : power supply unit 
               4 : forming die 
               5 : power supply circuit 
               6 : capacitor 
               7 : switch 
               8 : electric resistance 
               10 : fluid 
               11 : bag 
               50 : plate-shaped material 
               60 : formed member