JP4030933B2 - Electromagnetic expansion coil - Google Patents

Description

  The present invention relates to an electromagnetic tube forming coil used for electromagnetic forming a metal tube or the like.

  Electromagnetic tube expansion forms a strong magnetic field in a very short time by instantly discharging the electric charge stored at a high voltage to the energizing coil and forming a strong magnetic field in an extremely short time. This is a technology that receives a strong expansion force by the pressure and is pressed against the outer mold.

  Electromagnetic tube expansion is suitable for forming aluminum alloys, which are good electrical conductors, and is used for processing such as forming grooves in aluminum alloy tubes or joining aluminum alloy tubes together. In addition, application of electromagnetic tube expansion forming is being studied for processing of bending the end of an aluminum alloy tube, processing of a large amount of deformation such as caulking of a large diameter tube, and processing of a high-strength material. For example, application to processing or caulking of frame materials such as vehicles, automobiles, and motorcycles is being studied.

  Conventionally, the coils used for these electromagnetic tube expansion moldings have a structure in which a conducting wire having a circular cross section is wound around an axis made of an insulating resin (Japanese Patent Laid-Open No. 55-42140: Patent Document 1). .

  FIG. 3 is a perspective view showing a conventional electromagnetic tube expansion forming method. A cylindrical aluminum alloy work 11 is inserted into an outer mold 12 in which a circular hole is provided by combining a split mold having a semicircular cut, and an electromagnetic tube expansion coil 13 is inserted into the work 11. Then, an electromagnetic force is applied from the coil 13 to the work 11, the work 11 is expanded toward the outer mold 12 by the repulsive force of the magnetic field, and the outer surface of the work 11 is formed by the outer mold 12.

  In this case, in order to insert the coil 13 into the work 11 from one end of the work 11, both ends of the conductor are arranged at the end (base end side) of the coil 13 which is not the insertion tip, and the terminal 14 is connected thereto. Is provided to connect to the lead wire for external connection. For this reason, as shown in FIGS. 4A and 4B, the inner conductor 15 of the coil 13 reaches the distal end portion from the proximal end portion through the inner space 16 of the axial center of the coil 13 and is bent at the distal end portion. Are arranged around the shaft surface 17 and wound around the shaft center to return to the base end portion. 4A and 4B are perpendicular to each other in section line. At this time, in order to avoid that the repulsive force received by the conductor at the time of workpiece forming is concentrated on a part, the tip portion 18 is routed so that the bending radius of the conductor 15 is as large as possible. For example, in a conventional coil for expanding an electromagnetic tube, as shown in FIG. 4A, the conductor 15 is bent in a semicircular arc shape at the tip 18 (Japanese Patent Laid-Open No. 6-238356: Patent Document 2). ).

JP-A-55-42140 JP-A-6-238356

  However, in this prior art, in the cross section shown in FIG. 4 (a), the conductor 15 is curved in a semicircular arc shape at the tip 18 of the coil 13, but on the axial center surface 17 of the coil, this half The conductor 15 that is curved in an arc shape and is turned back toward the coil base end portion is bent at an angle of 90 ° toward the circumferential direction of the axis. For this reason, in the prior art, there are still places where the bending radius is small. In particular, in a small-diameter coil, the bending radius is further reduced with respect to the diameter of the conductor.

  When the bending radius is small in this way, the electromagnetic repulsion force is concentrated at this portion, and there is a problem that the electromagnetic tube expansion forming coil is easily broken when repeatedly used.

  Further, when a conductor having a hollow cross section is used in order to obtain a cooling effect, the hollow portion may be crushed if the bending radius is small during handling, and the cooling effect may not be obtained satisfactorily.

  Furthermore, in the conventional coil structure, since an extra length was required for the handling of the conducting wire at the end, there was a problem that the length that could be formed relative to the entire length of the coil was short. Alternatively, the extra length for this run requires extra conductors and resin, which unnecessarily increases the weight of the coil.

  The present invention has been made in view of such problems, and there is no portion where the bending radius of the conductor is small, and even when used repeatedly, damage due to concentration of electromagnetic repulsion is difficult to occur, and it is lighter and has a smaller volume. An object of the present invention is to provide an electromagnetic tube forming coil.

The coil for electromagnetic tube expansion molding according to the present invention is wound around a cylindrical shaft center and a peripheral surface of the shaft center from the coil base end side, and moves to the inside of the shaft center on the coil tip end side. An electromagnetic tube forming coil having a conductor led to the coil base end side through the inside of the core, wherein the conductor bends in the longitudinal direction of the axis from the peripheral surface of the axis at the coil tip. Instead, the shaft center is inserted through the hole provided in the shaft center, enters the shaft center, curves in the shaft center, and extends in the direction toward the coil base end, so that the shaft of the conductor The curved portion inside the core is in contact with the inner surface of the shaft center at a position closer to the coil base end than the hole .

  In this electromagnetic pipe expanding coil, when the radius of the peripheral surface around which the conductor of the shaft center is wound is R1, and the inner diameter of the shaft center is R2, 0.5 ≦ (R2 / R1) ≦ 0.95. It is preferable that

  According to the present invention, since the conductor is wound and arranged on the shaft center so that the distortion of the conductor is reduced, even if the coil for electromagnetic tube expansion molding is used repeatedly, it is not easily damaged, and the coil end Since the conductor can be wound, a lightweight and small coil for electromagnetic tube expansion molding can be obtained.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. FIG. 1 is a view showing a coil for forming an electromagnetic tube according to an embodiment of the present invention. The insulating cylindrical shaft center 1 is provided with a flange portion 1 a at the coil tip, and a conductor 2 is wound around the peripheral surface of the shaft center 1. The conductor 2 is introduced from the peripheral surface of the shaft center 1 into the shaft center 1 through a hole 3 provided in the shaft center 1. In this case, the conductor 2 has a slightly smaller radius than the winding radius on the peripheral surface of the shaft 1 and passes through the hole 3 of the shaft 1 to enter the shaft center. 1 is not bent in the longitudinal direction. The conductor 2 is smoothly curved inside the shaft center, and its extending direction is directed to the base end side of the shaft center 1, passes through the center portion (center line 5) of the shaft center 1, and then the coil base end portion. Led to the side. In this case, the curved portion 101 of the conductor inside the shaft center is in contact with the inner surface of the shaft center. Thereby, the bending part 101 can be bent with the maximum curvature radius inside the shaft center. The conductor 2 wound around the peripheral surface of the shaft center 1 is electrically separated from each other and fixed by filling the peripheral surface with an insulating resin 4.

  In the coil for electromagnetic pipe expansion formed as described above, the conductor 2 enters the inside of the shaft center on the peripheral surface of the shaft center 1 at the coil tip, so that the conductor 2 is slightly inside the winding radius. It only deforms to have a small radius and does not bend at 90 ° as in the prior art. Further, since there is a large internal space in the radial direction and the axial direction of the axial center 1 inside the axial center, the conductor 2 can be curved with a large curvature radius in this portion. In this case, the conductor 2 is twisted while moving in the winding direction on the circumferential surface of the shaft center, that is, the circumferential direction of the shaft center 1 and the axial direction, and reaches the center (center line 5) of the shaft center 1. However, the center of curvature is always located closer to the base end side than the conductor introduction portion into the shaft center where the hole 3 is provided. In other words, the conductor 2 does not exist inside the shaft center at the position of the hole 3 at the coil tip portion, that is, at the coil tip side from the conductor introduction portion into the shaft center, and is always coiled from the conductor introduction portion. Since it exists on the base end side, the bending radius of the conductor 2 has a large degree of freedom and can be made extremely large.

  For this reason, in this embodiment, when the coil is used, the electromagnetic repulsion force is not concentrated, and fatigue damage of the conductor 2 can be prevented. Moreover, when using a hollow conductor as the conductor 2, it can prevent that a hollow part is crushed at the time of handling of a conductor.

  Further, as described above, since the conductor 2 exists on the coil base end side with respect to the portion where the hole 3 at the coil tip is located, the distance (extra part) between the tip of the axis 1 and the hole 3 is small. It is short, and therefore the electromagnetic tube-expanded coil can be reduced in weight and size.

  In the present invention, when the radius of the peripheral surface around which the conductor 2 of the axis 1 is wound is R1, and the inner diameter of the axis 1 is R2, 0.5 ≦ (R2 / R1) ≦ 0.95. Is preferred. When R2 / R1 is smaller than 0.5, the bending radius of the conductor 2 necessary for handling becomes small. Further, if R2 / R1 exceeds 0.95, the distance between the conductor 2 passing through the inside of the shaft center 1 and the conductor 2 wound around the circumferential surface of the shaft center 1 becomes too close. By repeated use, the resin 4 filled in the shaft center and the tube is easily damaged, and the strength is lowered. For this reason, it is preferable that 0.5 ≦ (R2 / R1) ≦ 0.95.

  In addition, in order to increase the insulation inside the shaft center and to suppress the vibration of the conductor, the final product is filled with an insulating resin, but when the coil diameter is large or the conductor size is sufficient for the input energy In the case where it has, the insulating resin is not filled and it may remain hollow. Further, only the curved portion 101 of the conductor 2 can be made hollow. Furthermore, the conductor used for this coil is not limited to a circular cross section, and may be either a square cross section or a circular or square hollow cross section.

It is sectional drawing which shows the coil for electromagnetic tube expansion shaping | molding which concerns on embodiment of this invention. Similarly, it is a figure which shows the conductor wound around the axial center surrounding surface of the coil for electromagnetic tube expansion shaping | molding of this embodiment. It is a figure which shows the conventional electromagnetic pipe expansion forming method. It is a figure which shows the conventional coil for electromagnetic tube forming.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1; Shaft center 2; Conductor 3; Hole 4; Insulating resin 5; Center line of shaft center 11; Workpiece 12; Outer mold 13;

Claims (2)

A cylindrical shaft center, and is wound around the peripheral surface of the shaft center from the coil base end side, moves to the inside of the shaft center on the coil tip end side, passes through the inside of the shaft center, and then the coil base end side In the coil for electromagnetic tube expansion molding, the conductor is connected to the coil tip through a hole provided in the shaft center without bending from the circumferential surface of the shaft center in the longitudinal direction of the shaft center. Inserted into the shaft center through the shaft center, bent inside the shaft center and directed to the coil base end side, and the curved portion inside the shaft center of the conductor is more coiled than the hole. A coil for electromagnetic tube expansion molding, wherein the coil is in contact with the inner surface of the shaft center at a position on the base end side . When the radius of the peripheral surface around which the conductor of the shaft is wound is R1, and the inner diameter of the shaft is R2, 0.5 ≦ (R2 / R1) ≦ 0.95. Item 2. The coil for electromagnetic tube expansion molding according to Item 1.

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