JP6375266B2 - Electromagnetic forming coil and manufacturing method of bumper stay for automobile using the same - Google Patents

Description

  The present invention relates to an electromagnetic forming coil capable of expanding and contracting a metal element pipe having a substantially elliptical cross-sectional shape and a substantially rectangular cross-sectional shape, respectively, and a method for manufacturing a bumper stay for an automobile using the same.

  Application of electromagnetic forming to various fields such as tube forming and plate forming has been studied. In recent years, a technique for manufacturing a member (for example, a front bumper stay for an automobile) having a rectangular cross section by expanding an aluminum alloy tube by electromagnetic forming has also been disclosed (see Patent Document 1).

  In the electromagnetic forming described in Patent Document 1, a cylindrical electromagnetic forming coil in which a conductor wire is spirally wound and an aluminum alloy element tube having a substantially rectangular cross section preliminarily shaped into a special shape are adopted. Has been.

JP 2014-73502 A

  Originally, if an automobile front bumper stay with a rectangular cross-section shape is manufactured by electromagnetic forming, an aluminum alloy element tube having a substantially rectangular cross-section shape is simply expanded by using an electromagnetic forming coil with a substantially rectangular column shape. I want to do it.

  However, the winding portion of the electromagnetic forming coil is formed by winding a conductor wire spirally around the axis of the electromagnetic forming coil. There was a restriction that it had to be almost a perfect circle.

  Therefore, in order to manufacture a front bumper stay for automobiles having a rectangular cross-section shape using an electromagnetically formed coil having a substantially circular plan view of such a winding portion, trial and error are repeated and the cross-sectional shape is made special. There was a problem that an aluminum alloy element tube having a substantially rectangular cross-sectional shape pre-shaped into a shape had to be prepared.

  Such a problem can be said to be the same for a metal element tube when a member having a substantially elliptical cross-sectional shape is manufactured using an electromagnetically formed coil having a substantially circular shape in a plan view of the winding portion.

  An object of the present invention is to produce a sufficiently durable electromagnetic forming coil capable of expanding and contracting a metal element pipe having a substantially elliptical cross-sectional shape and a substantially rectangular cross-sectional shape, respectively, and a bumper stay for an automobile using the same. It is to provide a method.

In order to achieve this object, the electromagnetic formed coil according to the first invention is:
Electromagnetic forming coil having a substantially elliptical column shape for expanding and forming a metal element tube having a substantially elliptical cross-sectional shape, or a cylindrical electromagnetic forming coil having a substantially elliptical hole for forming the metal element tube by contraction forming Because
The winding portions of these electromagnetic molded coils have a cross-sectional shape of a circle, a square or a circle having a hollow portion, or any one conductor wire in a square spiral around the axis of each electromagnetic molded coil. It is wound around
The cross-sectional shapes of the winding portions in the direction perpendicular to the axis are substantially elliptical, and the dimensions of these substantially elliptical shapes are a major axis a ₁ (mm) and a minor axis b ₁ (mm), respectively.
A planar view thickness t ₁ (mm) of each conductor wire satisfies the following formula (1), and is an electromagnetically formed coil.

An electromagnetically formed coil according to the second invention is
A substantially rectangular column-shaped electromagnetic forming coil for expanding and forming a metal element tube having a substantially rectangular cross-sectional shape, or a cylindrical electromagnetic forming coil having a substantially rectangular hole for forming the metal element tube by contraction Because
Each of the winding portions of the electromagnetic molded coils has a circular cross section, a square or a circle having a hollow portion, or any one conductor wire out of a square orbits around the axis of each electromagnetic molded coil. However, it is wound so as to proceed in a direction parallel to the axial direction,
The cross-sectional shapes in the direction perpendicular to the axis of the winding part are each substantially rectangular, and the dimensions of these substantially rectangular shapes are a ₂ (mm) for the long side and b ₂ (mm) for the short side,
The thickness t ₂ (mm) in plan view of each conductor wire satisfies the following formula (2), and is an electromagnetically formed coil.

  Moreover, the electromagnetic molded coil which concerns on 3rd invention is the electromagnetic molded coil which concerns on the 1st or 2nd invention, The said conductor strand is a good conductor, It is characterized by the above-mentioned.

Moreover, the manufacturing method of the bumper stay for automobiles according to the fourth invention is as follows:
Using the substantially elliptical columnar electromagnetic forming coil according to the first invention or the substantially rectangular columnar electromagnetic forming coil according to the second invention, an aluminum alloy element tube having a substantially elliptical cross sectional shape or a substantially rectangular cross sectional shape is respectively expanded. This is a method for manufacturing a bumper stay for an automobile.

The electromagnetic molded coil according to the first invention is:
Electromagnetic forming coil having a substantially elliptical column shape for expanding and forming a metal element tube having a substantially elliptical cross-sectional shape, or a cylindrical electromagnetic forming coil having a substantially elliptical hole for forming the metal element tube by contraction forming Because
The winding portions of these electromagnetic molded coils have a cross-sectional shape of a circle, a square or a circle having a hollow portion, or any one conductor wire in a square spiral around the axis of each electromagnetic molded coil. It is wound around
The cross-sectional shapes of the winding portions in the direction perpendicular to the axis are substantially elliptical, and the dimensions of these substantially elliptical shapes are a major axis a ₁ (mm) and a minor axis b ₁ (mm), respectively.
Since the thickness t ₁ (mm) in plan view of each conductor wire satisfies the above formula (1),
To provide an electromagnetically formed coil having sufficient durability (the maximum Mises stress σ ₁ acting on the winding portion does not exceed the yield point) capable of expanding and contracting a metal element tube having a substantially elliptical cross section. it can.

An electromagnetically formed coil according to the second invention is
A substantially rectangular column-shaped electromagnetic forming coil for expanding and forming a metal element tube having a substantially rectangular cross-sectional shape, or a cylindrical electromagnetic forming coil having a substantially rectangular hole for forming the metal element tube by contraction Because
Each of the winding portions of the electromagnetic molded coils has a circular cross section, a square or a circle having a hollow portion, or any one conductor wire out of a square orbits around the axis of each electromagnetic molded coil. However, it is wound so as to proceed in a direction parallel to the axial direction,
The cross-sectional shapes in the direction perpendicular to the axis of the winding part are each substantially rectangular, and the dimensions of these substantially rectangular shapes are a ₂ (mm) for the long side and b ₂ (mm) for the short side,
Since the thickness t ₂ (mm) in plan view of each conductor wire satisfies the above formula (2),
To provide an electromagnetic forming coil having sufficient durability (the maximum Mises stress σ ₂ acting on the winding portion does not exceed the yield point) capable of expanding and contracting a metal element tube having a substantially rectangular cross section. it can.

Moreover, the manufacturing method of the bumper stay for automobiles according to the fourth invention is as follows:
Using the substantially elliptical columnar electromagnetic forming coil according to the first invention or the substantially rectangular columnar electromagnetic forming coil according to the second invention, an aluminum alloy element tube having a substantially elliptical cross sectional shape or a substantially rectangular cross sectional shape is respectively expanded. Because it is a feature characterized by
There is no need to prepare a substantially elliptical or rectangular shaped aluminum alloy tube that has been pre-shaped into a special shape through repeated trial and error, and has a simple elliptical or rectangular shape. It is possible to manufacture an automobile bumper stay having an elliptical cross-sectional shape or a rectangular cross-sectional shape by directly using a shaped aluminum alloy tube.

BRIEF DESCRIPTION OF THE DRAWINGS It is an elliptical columnar electromagnetic forming coil of Embodiment 1 of this invention, (a) is a top view, (b) is an elevation view. In electromagnetic forming coil of the elliptic cylinder shape, a contour diagram in plan view the thickness t ₁ of the conductor wire which is calculated from the equation based on the major axis a ₁ and minor axis b _{1 (1).} It is an elliptical cylindrical electromagnetic forming coil of Embodiment 2 of this invention, (a) is a top view, (b) is an elevation view. It is an oblong cylindrical electromagnetic forming coil of Embodiment 3 of the present invention, (a) is a top view and (b) is an elevation. It is a long cylindrical electromagnetic forming coil of Embodiment 4 of the present invention, (a) is a top view and (b) is an elevation. It is an electromagnetic forming coil of the rectangular column shape of Embodiment 5 of the present invention, (a) is a top view and (b) is an elevation. It is another rectangular column-shaped electromagnetic forming coil of Embodiment 6 of this invention, (a) is a top view, (b) is an elevation view. It is another rectangular column-shaped electromagnetic forming coil of Embodiment 7 of this invention, (a) is a top view, (b) is an elevation view.

(Embodiment 1)
1A and 1B show an elliptic cylindrical electromagnetic molding coil according to Embodiment 1 of the present invention, in which FIG. 1A is a plan view and FIG. 1B is an elevational view.

  In FIG. 1, 11 is a conductor element made of pure copper having a quadrangular cross-sectional shape, 12 is an insulating reinforcing material for impregnating the FRP resin around the conductor element wire 11 to reinforce the gap, and 13 is electromagnetic forming. This is a winding portion spirally wound around the axis of an FRP bobbin (not shown) of the coil 14. The elliptical columnar electromagnetic forming coil 14 includes a winding portion 13 and an insulating reinforcing material 12.

  The inventors of the present invention do not use an aluminum alloy element tube having a substantially rectangular cross-sectional shape whose cross-sectional shape is pre-shaped into a special shape, but an aluminum alloy element tube having a simple rectangular cross-sectional shape. Was used to study whether a bumper stay for automobiles with a rectangular cross-section could be obtained simply by expanding the tube with an electromagnetic forming coil having a rectangular column shape.

  To that end, from the viewpoint of durability performance, commercially available general-purpose structural analysis software ABAQUS is used to determine the cause of the necessity of using a cylindrical electromagnetic forming coil (not shown) so far. The stress behavior when a directional distributed load was applied was investigated by comparing with the case of the elliptically shaped electromagnetic coil 14 shown in FIG.

  For example, the cross-sectional shape in the direction perpendicular to the axis of the winding portion of the cylindrical electromagnetic molded coil is 160 mm in diameter, and an internal pressure of 5 MPa is applied to a circular cross section of the conductor wire in the winding portion having a thickness of 6 mm in plan view. In this case, the stress was uniformly distributed in the cross section, and the maximum Mises stress was about 60 MPa.

On the other hand, the cross-sectional shape in the direction orthogonal to the axis of the winding portion 13 of the elliptical cylindrical electromagnetic forming coil 14 shown in FIG. 1 is an ellipse having a major axis a ₁ of 160 mm and a minor axis b ₁ of 120 mm. When the internal pressure 5 MPa is applied to an elliptical cross section having a thickness t ₁ of 6 mm in plan view of the conductor wire 11 in the portion 13, the stress changes so as to be unevenly distributed in the cross section, and the tip of the major axis a ₁ The maximum Mises stress σ ₁ was about 597 MPa at the portion {the position indicated by the symbol A shown in Fig. 1 (a)}. In addition, the stress distribution linearly changed in the direction of the thickness t _{1 in} plan view of the conductor wire 11 in the vicinity of the distal end portion (symbol A) of the major axis a ₁ . In other words, the reason why such an elliptical columnar electromagnetic molded coil 14 is damaged in a short life (a problem that causes a problem from the viewpoint of durability) is that the bending around the tip portion (symbol A) of the long diameter a ₁ is very high. It was found that the conductor wire 11 exceeded the yield point due to the stress and was plastically deformed.

Accordingly, then, even if elliptical, the shape of the electromagnetic forming coil 14, the maximum Mises stress sigma ₁ at the tip portion of the long diameter a ₁ {code points A shown in FIG. 1 (a)} of the winding portion 13 yield We examined in more detail where the conditions that do not exceed the point are.

In this examination, the maximum Mises stress σ ₁ was calculated using the above-mentioned general-purpose structural analysis software ABAQUS under a combination of shapes under the following 80 conditions.

Winding portion 13 has a minor axis b ₁ of 4 levels of 50, 100, 150, and 200 mm, and a major axis a ₁ of 5 levels greater than the minor axis b _{1 of} 0 (ie, perfect circle), 25, 50, 75, and 100 mm, respectively. The maximum Mises stress σ ₁ is calculated with a combination of 80 conditions in which the thickness t ₁ of the conductor wire 11 in the winding portion 13 is changed in four levels of 3, 6, 9, and 12 mm, respectively. It was. As a premise of this calculation, similarly to the case described above, an electromagnetic force is assumed and fixed when an internal pressure p ₁ = 5 MPa is applied to the elliptical cross section. The 80 Analysis of the results of calculation by combination of the shape of conditions, the maximum von Mises stress sigma ₁ at the tip portion of the long diameter a ₁ {code points A shown in FIG. 1 (a)} of the winding portion _13, the long diameter a ₁ , minor b _1, the relationship between the viewed thickness t ₁ and the internal pressure P ₁ of the conductor element wire 11 was found to be expressed by the following formula (A1).
Here, a ₀ = b ₀ and t ₀ are internal pressures p ₀ (this is, for example, an aluminum alloy base tube as a workpiece) on the circular cross section in a plan view of a winding portion of a cylindrical electromagnetic forming coil. The maximum Mises stress σ ₀ generated in the winding portion when an electromagnetic force necessary for electromagnetic tube forming is applied is a value under reference conditions that do not exceed the yield point, and a ₀ = b ₀ , t The unit of ₀ is mm. The definitions of a ₀ = b ₀ and t ₀ are as follows.
a ₀ = b ₀ : Diameter in a plan view of a winding portion of a cylindrical electromagnetic forming coil
t ₀ : Thickness in plan view of a rectangular conductor wire having the same cross-sectional shape as that of the conductor wire 11 in the winding part of the cylindrical electromagnetic forming coil

Further, p ₁ / p ₀ in the above formula (A1) varies depending on the size and material strength of the workpiece (metal base tube) to be subjected to electromagnetic forming. Normal thin-walled tube yield condition (that is, internal pressure (electromagnetic force) required for yielding a metal tube ≥ proof strength of the metal tube x thickness of the metal tube / radius of the cross-section of the metal tube ), The electromagnetic force required for plastic deformation of the workpiece (metal blank) is inversely proportional to the radius of the workpiece (metal blank). Therefore, it can be estimated that p ₁ / p ₀ is also inversely proportional to the diameter of the winding portion of the electromagnetic forming coil in plan view. Therefore, the following formula (B1) is established.

The above formula (B1) are substituted into the formula _{(A1), σ 1 / σ} 0 = 1 (i.e., the maximum Mises stress sigma ₁ to be equal to the maximum Mises stress sigma ₀ reference conditions not exceeding the yield _point) In addition, by solving a quadratic equation for t ₁ , the elliptical columnar electromagnetic forming coil 14 shown in FIG. 1 has sufficient durability (the maximum Mises stress σ ₁ acting on the winding portion 13 exceeds the yield point) No) The following formula (C1) that can calculate the planar view thickness t ₁ of the conductor wire 11 in the winding portion 13 is obtained.

The diameter a ₀ = b ₀ = 90 mm in a plan view of a winding portion of a cylindrical electromagnetic forming coil (reference condition) that is currently used and has sufficient durability, and the thickness t ₀ in a plan view of a conductor wire Substituting = 2 mm into the above formula (C1) and rearranging gives the following formula (1).

FIG. 2 is a plan view thickness t of the conductor wire 11 calculated by substituting the major axis a ₁ and the minor axis b ₁ into the above formula (1) in the elliptically cylindrical electromagnetic forming coil 14 shown in FIG. it is a contour diagram of _one. The meaning of FIG. 2 is that in the elliptical columnar electromagnetic forming coil 14 having the major axis a ₁ and the minor axis b ₁ , the planar thickness of the conductor wire 11 shown in the contour diagram is equal to or larger than the planar thickness t _1. If this is adopted, it is possible to realize an elliptically shaped electromagnetic coil 14 having sufficient durability (the maximum Mises stress σ ₁ acting on the winding portion 13 does not exceed the yield point).

In the present embodiment, the diameter a ₀ = b ₀ = 90 mm in plan view of the winding portion of the cylindrical electromagnetic molded coil and the thickness t ₀ = 2 mm in plan view of the conductor wire have sufficient durability. Although it was specifically adopted as a reference condition for having it, it is not necessarily limited to this, and a ₀ = b ₀ , t ₀ is a circular sectional view in a plan view of a winding portion of a cylindrical electromagnetic forming coil. It is sufficient if the maximum Mises stress σ ₀ generated in the winding portion when the internal pressure p ₀ is applied satisfies the reference condition that does not exceed the yield point.

  In the present embodiment, the case where the conductor wire 11 has a quadrangular cross-sectional shape has been described. However, the present invention is not necessarily limited to this, for example, a circle or a square having a hollow portion. It may have any one of the cross-sectional shapes. In the present embodiment, the case where the conductor element 11 is made of pure copper has been described. However, the present invention is not necessarily limited to this. For example, the conductor element 11 may be a good conductor having a high conductivity such as a copper alloy. That's fine.

  Further, in the present embodiment, the case of an elliptically shaped electromagnetic shaped coil has been described as an example. However, if it is based on the mechanism of the present invention, an elliptically shaped electromagnetic shaped coil (for details, see Embodiment 2 below). ), An electromagnetic molded coil having a long cylindrical shape (for details, see Embodiment 3 below), and an electromagnetic forming coil having a long cylindrical shape (for details, see Embodiment 4 below). In this case, it is only necessary to satisfy the above formula (1). In the present invention, the definition of a substantially elliptic cylinder shape is a generic name including an elliptic cylinder mathematically referred to, an elliptic cylinder close to the mathematical elliptic cylinder, and the long cylinder (see Embodiment 3 below). The definition of the substantially elliptic cylinder shape is a generic name including an elliptic cylinder mathematically referred to, an elliptic cylinder close to the mathematical elliptic cylinder, and the long cylinder (see Embodiment 4 described later).

  Further, if based on the mechanism of the present invention, a rectangular column-shaped electromagnetic formed coil (for details, see Embodiment 5 below), another rectangular column-shaped electromagnetic formed coil (for details, see Embodiment 6 below), and Furthermore, the present invention can be applied to another electromagnetic forming coil having a rectangular column shape (for details, refer to Embodiment 7 described later). Although not shown, the present invention can also be applied to a rectangular cylindrical electromagnetic forming coil. In these cases, it is only necessary to satisfy the above-described formula (2). In addition, in the present invention, the definition of the substantially rectangular column shape is described in a quadrangular column, a column with a rectangular cross section (see Embodiment 5 below), a column with a cross-sectional shape described in Embodiment 6 below, and Embodiment 7 below. It is a generic term that includes pillars with a cross-sectional shape. Further, the definition of the substantially rectangular tube shape is a generic name including a tube that penetrates from the solid defined in the substantially rectangular column shape.

In the ellipsoidal column-shaped electromagnetic forming coil 14 shown in FIG. 1, the planar view thickness t ₁ of a conductor element 11 made of pure copper having a major axis a ₁ of 150 mm, a minor axis b ₁ of 100 mm, and a quadrangular cross section is 10 mm, The winding length was 300 mm, and the conductor wire 11 was wound around an FRP bobbin. After winding, the gap was reinforced by impregnating with FRP resin 12 as an insulating reinforcing material. Using the electromagnetic column-shaped electromagnetic forming coil 14 manufactured in this manner, the electromagnetic of a 6000 series aluminum alloy extruded element tube as a metal element tube having a wall thickness of 3 mm, a major axis of 170 mm, a minor axis of 120 mm, and a length of 250 mm. Tube expansion was performed. The object subjected to electromagnetic tube expansion molding is a front bumper stay for automobiles. By this electromagnetic tube expansion molding, it was possible to form into a desired shape, and no abnormality was observed in the conductor wire of the electromagnetic forming coil, and it was confirmed that the material has durability sufficient for practical use. In the present embodiment, an example in which electromagnetic tube expansion molding is performed on an automobile front bumper stay having an elliptical cross-section shape using an ellipsoidal column-shaped electromagnetic forming coil has been described. Using a columnar electromagnetic forming coil, it is also possible to perform electromagnetic pipe expansion molding from a rectangular metal cross-section corresponding to the electromagnetic forming coil to a front bumper stay for automobiles having a rectangular cross section. Further, in the present embodiment, as a metal element tube to be subjected to electromagnetic forming, a description has been given by taking a 6000 series aluminum alloy as an example, but it is not necessarily limited to this, for example, other aluminum alloys, Copper alloy, magnesium alloy, gold, silver, platinum, etc. are also suitable. That is, a metal element tube having high conductivity and low relative permeability is more preferable.

(Embodiment 2)
FIGS. 3A and 3B are elliptic cylindrical electromagnetic forming coils according to the second embodiment of the present invention. FIG. 3A is a plan view and FIG. 3B is an elevation view.

In FIG. 3, 21 is a conductor wire, 22 is an FRP resin as an insulating reinforcing material, 23 is a winding portion, 24 is an elliptical cylindrical electromagnetic molding coil, and the elliptical cylindrical electromagnetic molding coil 24 is insulative. It consists of an FRP resin 22 as a reinforcing material and a winding part 23. Further, a ₁ is the major axis of the cross-sectional shape in the direction orthogonal to the axis of the winding part 23 of the electromagnetically formed coil 24 having an elliptical cylindrical shape, b ₁ is the minor axis, and t ₁ is the conductor wire 21 of the winding part 23. It is the thickness in plan view.

  If an elliptical cylindrical shaped electromagnetic forming coil 24 as shown in FIG. 3 is used, an electromagnetic contraction can be formed as it is from an elliptical cross sectional metal element tube corresponding to the electromagnetic forming coil 24 into a desired elliptical cross sectional shape. In addition, no abnormality is observed in the conductor wire 21 of the electromagnetic forming coil 24, and it has a durability performance sufficient for practical use.

(Embodiment 3)
4A and 4B show a long cylindrical electromagnetic forming coil according to Embodiment 3 of the present invention, in which FIG. 4A is a plan view and FIG. 4B is an elevation view.

In FIG. 4, 31 is a conductor wire, 32 is FRP resin as an insulating reinforcing material, 33 is a winding part, 34 is a long cylindrical electromagnetic forming coil, and the long cylindrical electromagnetic forming coil 34 is insulative. It consists of an FRP resin 32 as a reinforcing material and a winding part 33. In addition, a ₁ is a long diameter in a plan view of the winding portion 33 of the electromagnetic forming coil 34 having a long cylindrical shape, b ₁ is a short diameter thereof, and t ₁ is a plan view of the conductor wire 31 in the winding portion 33. Is the thickness.

  If an electromagnetic forming coil 34 having a long cylindrical shape as shown in FIG. 4 is used, an electromagnetic tube can be formed from a metal element tube having an elliptical cross section corresponding to the electromagnetic forming coil 34 into a desired elliptical cross sectional shape as it is. In addition, no abnormality is observed in the conductor wire 31 of the electromagnetic forming coil 34, and it has durability sufficient for practical use.

(Embodiment 4)
5A and 5B show a long cylindrical electromagnetic forming coil according to Embodiment 4 of the present invention, in which FIG. 5A is a plan view and FIG. 5B is an elevation view.

In FIG. 5, 41 is a conductor wire, 42 is an FRP resin as an insulating reinforcing material, 43 is a winding portion, 44 is a long cylindrical electromagnetic forming coil, and the long cylindrical electromagnetic forming coil 44 is insulative. It consists of an FRP resin 42 as a reinforcing material and a winding part 43. Further, a ₁ is the major axis of the cross-sectional shape in the direction perpendicular to the axis of the winding portion 43 of the electromagnetic forming coil 44 having a long cylindrical shape, b ₁ is the minor axis thereof, and t ₁ is the length of the conductor wire 41 in the winding portion 43. It is the thickness in plan view.

  If a long cylindrical electromagnetic forming coil 44 as shown in FIG. 5 is used, an electromagnetic constriction tube forming from an oblong cross-sectional metal element tube corresponding to the electromagnetic forming coil 44 to a desired oblong cross sectional shape as it is. And no abnormality is found in the conductor wire 41 of the electromagnetic forming coil 44, and it has durability sufficient for practical use.

(Embodiment 5)
6A and 6B are rectangular columnar electromagnetic molded coils according to the fifth embodiment of the present invention. FIG. 6A is a plan view and FIG. 6B is an elevation view.

In FIG. 6, 51 is a conductor wire, 52 is an FRP resin as an insulating reinforcing material, 53 is a winding portion, 54 is a rectangular column-shaped electromagnetic forming coil as a rectangular column shape, and rectangular column-shaped electromagnetic forming The coil 54 includes an FRP resin 52 as an insulating reinforcing material and a winding portion 53. Also, a ₂ long side 51b of the length of the direction perpendicular to the axis of the cross-sectional shape of the winding portion 53 of a rectangular prism shape of the electromagnetic forming coil 54, b ₂ is the length of the short sides 51a, t ₂ is wound This is the thickness of the conductor wire 51 in the line portion 53 in plan view.

Also in this embodiment, as described above, in order to be based on the mechanism of the present invention, the long diameter a ₁ and the short diameter b ₁ in the above formula (1) are read as the long side a ₂ and the short side b ₂ , respectively. This is established as is, and this is defined as the above equation (2).

  If a rectangular column-shaped electromagnetic forming coil 54 as shown in FIG. 6 is used, an electromagnetic tube expansion can be formed as it is from a rectangular metal section tube corresponding to the electromagnetic forming coil 54 into a desired rectangular sectional shape, and No abnormality is observed in the conductor wire 51 of the electromagnetic forming coil 54, and it has durability sufficient for practical use.

(Embodiment 6)
7A and 7B show another rectangular column-shaped electromagnetic forming coil according to Embodiment 6 of the present invention. FIG. 7A is a plan view and FIG. 7B is an elevation view.

In FIG. 7, 61 is a conductor wire, 62 is an FRP resin as an insulating reinforcing material, 63 is a winding portion, and 64 is another rectangular column-shaped electromagnetic forming coil. The electromagnetic forming coil 64 is an insulating reinforcing member. It consists of an FRP resin 62 as a material and a winding part 63. Further, a ₂ is the length of the long side 61 b of the cross-sectional shape in the direction perpendicular to the axis of the winding part 63 of the electromagnetic forming coil 64, b ₂ is the length of the short side 61 a, and t ₂ is the length of the winding part 63. This is the thickness of the conductor wire 61 in plan view.

Also in this embodiment, as described above, in order to be based on the mechanism of the present invention, the long diameter a ₁ and the short diameter b ₁ in the above formula (1) are read as the long side a ₂ and the short side b ₂ , respectively. This is established as is, and this is defined as the above equation (2).

  If an electromagnetic forming coil 64 as shown in FIG. 7 is used, an electromagnetic tube can be formed from a metal element tube having a cross-sectional shape corresponding to the electromagnetic forming coil 64 to a desired corresponding cross-sectional shape, and the electromagnetic forming coil. No abnormality was found in the 64 conductor wires 61, and the durability sufficient for practical use was obtained.

(Embodiment 7)
FIG. 8 shows still another rectangular columnar electromagnetic molded coil according to the seventh embodiment of the present invention, in which (a) is a plan view and (b) is an elevational view.

In FIG. 8, 71 is a conductor wire, 72 is an FRP resin as an insulating reinforcing material, 73 is a winding portion, and 74 is another rectangular column-shaped electromagnetic forming coil. This electromagnetic forming coil 74 is insulative. It is comprised from the FRP resin 72 and the coil | winding part 73 as a reinforcing material. Further, a ₂ is the length of the long side 71 b in a plan view of the winding portion 73 of the electromagnetic forming coil 74, b ₂ is the length of the short side 71 a, and t ₂ is a conductor wire in the winding portion 73. 71 is a thickness in plan view.

Also in this embodiment, as described above, in order to be based on the mechanism of the present invention, the long diameter a ₁ and the short diameter b ₁ in the above formula (1) are read as the long side a ₂ and the short side b ₂ , respectively. This is established as is, and this is defined as the above equation (2).

  If an electromagnetic forming coil 74 as shown in FIG. 8 is used, an electromagnetic tube can be formed from a metal element tube having a cross-sectional shape corresponding to the electromagnetic forming coil 74 to a desired corresponding cross-sectional shape, and the electromagnetic forming coil. No abnormality is observed in the conductor wire 71 of 74, and it has durability sufficient for practical use.

11, 21, 31, 41, 51, 61, 71 Conductor wire 12, 22, 32, 42, 52, 62, 72 FRP resin as an insulating reinforcing material 13, 23, 33, 43, 53, 63, 73 Winding part 14, 24, 34, 44, 54, 64, 74 Electromagnetic forming coil

Claims (4)

Electromagnetic forming coil having a substantially elliptical column shape for expanding and forming a metal element tube having a substantially elliptical cross-sectional shape, or a cylindrical electromagnetic forming coil having a substantially elliptical hole for forming the metal element tube by contraction forming Because
The winding portions of these electromagnetic molded coils have a cross-sectional shape of a circle, a square or a circle having a hollow portion, or any one conductor wire in a square spiral around the axis of each electromagnetic molded coil. It is wound around
The cross-sectional shapes of the winding portions in the direction perpendicular to the axis are substantially elliptical, and the dimensions of these substantially elliptical shapes are a major axis a ₁ (mm) and a minor axis b ₁ (mm), respectively.
A thickness t ₁ (mm) in plan view of each of the conductor wires satisfies the following formula (1).
A substantially rectangular column-shaped electromagnetic forming coil for expanding and forming a metal element tube having a substantially rectangular cross-sectional shape, or a cylindrical electromagnetic forming coil having a substantially rectangular hole for forming the metal element tube by contraction Because
Each of the winding portions of the electromagnetic molded coils has a circular cross section, a square or a circle having a hollow portion, or any one conductor wire out of a square orbits around the axis of each electromagnetic molded coil. However, it is wound so as to proceed in a direction parallel to the axial direction,
The cross-sectional shapes in the direction perpendicular to the axis of the winding part are each substantially rectangular, and the dimensions of these substantially rectangular shapes are a ₂ (mm) for the long side and b ₂ (mm) for the short side,
A thickness t ₂ (mm) in plan view of each of the conductor wires satisfies the following formula (2).
  The electromagnetic forming coil according to claim 1, wherein the conductor wire is a good conductor.   Using the substantially elliptical columnar electromagnetic forming coil according to claim 1 or the substantially rectangular columnar electromagnetic forming coil according to claim 2, an aluminum alloy element tube having a substantially elliptical cross-sectional shape or a substantially rectangular cross-sectional shape is respectively provided. A method of manufacturing a bumper stay for an automobile, characterized by performing pipe expansion molding.