JPH06238356A - Coil for electromagnetic forming - Google Patents

Abstract

(57) [Summary] [Purpose] An object of the present invention is to provide a coil for electromagnetic forming having a long life by avoiding the accumulation of Joule heat generated during operation. According to the electromagnetic forming coil of the present invention, a hollow conductor 13 having a hollow portion 12 therein is wound in a coil shape to form an electromagnetic coil portion 16, and the hollow conductor 1
3, the cooling medium can be circulated through the hollow portion 12 from both end portions 14a and 14b of the cooling medium 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic forming coil used for electromagnetic forming of various metal materials.

[0002]

2. Description of the Related Art In electromagnetic forming, an electromagnetic force is applied to a material by applying a momentary strong magnetic field to a coil to perform plastic working. Specifically, electric forming stored in a capacitor of an electromagnetic forming apparatus is performed. Electromagnetic force is generated by applying energy to the coil as a shocking current of 10 kA or more.

Conventionally, coils used for electromagnetic forming are
"Plasticity and processing" vol. 23, No. 255 (198
2) 328 or “Japan Industrial Technology Promotion Association technical data” N
o. 131 (1983), etc., a solid copper wire such as a round shape or a rectangular shape is wound around a shaft core made of an insulating resin, and a similar insulating resin is also applied to the space between the copper wires. It is manufactured by filling.

[0004]

However, in the electromagnetic forming coil as described above, the thermal conductivity of the insulating resin is poor, so that the joule generated in the copper wire by the impressing large current is shocked. Heat accumulates inside the coil,
There was the inconvenience of raising the coil temperature. As a result, there is a problem in that the difference in the coefficient of thermal expansion between the copper wire and the insulating resin creates a gap at the boundary between the two, resulting in poor insulation of the coil, expansion of the outer diameter, etc., and shortening the life of the coil. . Further, such a problem is more remarkable as the electric energy stored in the capacitor is larger, that is, the electromagnetic force given to the material is larger, and the coil life is remarkably reduced particularly when molding a high-strength material. Further, even when the same coil is used for continuous molding at regular intervals, heat is likely to be accumulated because the molding is performed next before the generated Joule heat is cooled, which causes the above-mentioned problems. It was

The present invention is intended to solve the above problems and to provide a long-life electromagnetic forming coil by avoiding the accumulation of Joule heat generated during operation.

[0006]

In order to achieve the above object, the electromagnetic forming coil of the present invention has a hollow portion (1) inside.
The hollow conductive wire (13) having 2) is wound in a coil to form an electromagnetic coil portion (16), and the hollow portion (14a) (14b) is connected to the hollow portion (14). It is characterized in that the cooling medium can be circulated around 12).

The material of the hollow conducting wire (13) is not particularly limited, but copper or copper alloy is preferably used because of its excellent electrical conductivity, and particularly excellent in mechanical strength and heat resistance. And chromium copper is preferred. In addition, the hollow conductor (1
The cross-sectional shape of the outer periphery of 3) is generally circular or rectangular, but is not limited to these. In addition, the hollow part (1
The cross-sectional shape of 3) is not limited to a general circular shape or a square shape, but may be a modified cross-sectional shape in order to enhance cooling efficiency. However, it is desirable that the wall thickness of the hollow conductor (13) be equal to or larger than the skin depth of a large current flowing through the conductor (13).

As the cooling medium to be circulated in the hollow conductor (13), water, alcohol, liquid such as liquid nitrogen,
A gas such as N ₂ or He can be used and is not particularly limited. However, in terms of cooling efficiency, it is advantageous to use a liquid.

Further, the structure of the electric circuit (20) for applying a large current to the electromagnetic coil portion (16) is not particularly limited and may be the one used in conventional electromagnetic molding.

In the electromagnetic forming coil of the present invention, the shape of the electromagnetic coil portion (16) is not particularly limited, and the shape of the material to be molded is not particularly limited. For example, the cylindrically wound electromagnetic coil portion (16) may be inserted into a raw tube to be used as a coil for pipe expansion molding, or the raw material tube may be placed in the cylindrically wound electromagnetic coil portion (16). It can also be inserted and used as a coil for shrink tube formation. Furthermore, the electromagnetic coil portion (16) wound in a planar spiral shape can be brought close to the base plate and used as a flat plate forming coil. In addition, a bobbin or the like is used as a shaft core for facilitating the production of the electromagnetic coil (16), and an insulator portion having a required shape is provided around the electromagnetic coil (16) for facilitating the electromagnetic forming work. A configuration that supplements the shape retention of the electromagnetic coil (16) may be added as appropriate.

[0011]

In the coil for electromagnetic forming of the present invention, the electromagnetic coil portion (16) has a hollow conductor (1) having a hollow portion (12) therein.
3) is wound in a coil shape, and a cooling medium is circulated from both ends (14a) (14b) of the hollow conducting wire (13) around the hollow portion (12) to thereby form an electromagnetic coil portion (16). ) Can be in a cooled state. When a large current is momentarily applied to the electromagnetic coil portion (16) in such a cooled state of the electromagnetic coil portion (16),
Although a strong magnetic field is generated to make the moldable state and Joule heat is generated, the electromagnetic coil portion (16) is rapidly cooled by heat exchange by the cooling medium circulating in the hollow portion (12).

[0012]

Next, a specific embodiment of the electromagnetic forming coil of the present invention will be described with reference to the drawings.

FIG. 1 is a partial cross-sectional view schematically showing a coil used for pipe expansion forming, in which a solenoid-shaped electromagnetic forming coil (11) is inserted and arranged in a raw pipe (1). It is in the state of being

In the electromagnetic forming coil (11),
A hollow conductor (13) having a circular hollow portion (12) at the center in cross section is arranged around a cylindrical shaft core (15) made of an insulating resin, leaving one end portion (14a), from the right side of the drawing. The electromagnetic coil portion (16) is formed by spirally winding to the left, and the winding end portion (14 ') is bent so that the other end portion (14b) is a hole () formed in the shaft core (15). 17) is guided to the outside of the shaft core (15), and both ends (14a) (14b) of the hollow conductor (13) are connected to the shaft core (15).
Protruding from. Both ends (14a) (14b) of the hollow conductor (13) projecting from the shaft core (15) are respectively connection pieces (18a) (18b) made of an insulating resin.
A communicating end (19) communicating with the hollow portion (12) via
a) (19b) and the electric circuit (2) for applying a large current to the electromagnetic coil part (16) by closing the hollow part (12).
It is bifurcated into the closed ends (21a) and (21b) connected to (0). On the other hand, a glass tape (22) is wound around the outer circumference of the hollow conductor (13) wound around the shaft core (15), and an insulating resin is further provided between the glass tape (22) and the shaft core (15). An insulator part (23) is provided so as to bury not only the space between the filled and wound hollow conductors (13) but also the end portion (14 ') of the hollow conductors (13), and as a whole, a columnar shape. Shaped electromagnetic forming coil (11) is formed.

In the present embodiment, the hollow conductor (13)
Is made of chromium copper and has an outer diameter of 3 mm and an inner diameter of 1 mm, and the shaft core (15) and the connecting piece (18a) are used.
Both (18b) are made of epoxy resin. Further, the insulator part (23) is made of an epoxy-based VBI resin and is a liquid VBI that is cured by mixing a curing agent.
The resin is formed by pouring the resin into the space surrounded by the glass tape (22) and allowing it to stand for a predetermined time to cure.

In the electromagnetic forming coil (11),
Circulation cooling water is introduced from one communication end (19a) of the hollow conductor (13) to circulate through the hollow portion (12) of the hollow conductor (13) and discharged from the other communication end (19b) to produce an electromagnetic coil. Allow the part (16) to cool. Then, when the switch (24) of the electric circuit (21) connected to the closed ends (21a) (21b) of the hollow conducting wire (13) is closed, the electric charge charged in the capacitor (25) is discharged, and the electromagnetic coil part is released. A momentary strong magnetic field is generated in (16) and an induced current flows in the surface layer of the inner peripheral portion of the shell tube (1), and a repulsive force is generated between this induced current and the current flowing in the electromagnetic coil section (16). Acts,
The raw pipe (11) is subjected to plastic deformation that expands in the radial direction and is formed. At this time, Joule heat is generated in the electromagnetic coil portion (16), but the hollow portion (1
Heat is rapidly exchanged by the cooling water flowing through 2) to cool the electromagnetic coil part (16), and heat is stored in the electromagnetic coil part (16), the surrounding insulator part (23), and the shaft core (15). There is no. In the electric circuit (20) of FIG. 1, the power supply for charging the capacitor (25) and its associated circuit are not shown.

Next, the aforementioned electromagnetic forming coil according to the present invention (hereinafter abbreviated as the present embodiment) and the conventional electromagnetic forming coil having no cooling ability (hereinafter abbreviated as the conventional example) are provided. A continuous operation was performed under the same conditions, and a comparative experiment was performed on the heat generation. As the conventional example used in the experiment, a wire manufactured in the same manner as this example was used except that a solid wire was used as the conductive wire. In the comparative experiment, the coil was supplied with electric energy of 8 kJ once, the coil was continuously operated every 120 seconds, and the temperature of the electromagnetic coil portion was measured from the top of the glass tape as the coil outer surface temperature for each shot. As a result, the relationship between the number of shots and the temperature change on the coil outer surface was obtained as shown in FIG.

As shown in FIG. 2, in this embodiment, the temperature before the operation was 26 ° C., and the temperature was about 32 at the fifth shot.
Although the temperature slightly increased to 0 ° C, the temperature gradually increased thereafter, and after reaching about 34 ° C at the 15th shot, the temperature was not increased even after operating over 50 shots. On the other hand, in the conventional example, the temperature was rapidly increased every time shots were repeated, the temperature reached 54 ° C. at the 28th shot, and peeling occurred in the insulator part, so that the experiment could not be continued thereafter. Therefore, it is clear that the electromagnetic forming coil according to the present invention has a much longer life than the conventional one.

In the present embodiment, the hollow portion (12)
Uses a hollow conductor wire (13) having a circular cross section, but in order to improve the cooling efficiency by increasing the internal surface area, the fin-shaped protrusion (35) protruding into the hollow portion (32) as shown in FIG. 3 is used. Alternatively, a hollow conductor wire (33) having a cross-section may be used. Further, the outer peripheral shape is not limited to the circular cross section, and a polygonal shape may be used.

[0020]

As described above, in the coil for electromagnetic forming of the present invention, the electromagnetic coil portion is formed by winding a hollow conductor wire having a hollow portion inside in a coil shape, and both end portions of this hollow conductor wire. It is possible to bring the electromagnetic coil portion into a cooled state by circulating the cooling medium around the hollow portion. In this cooling state, when a large current is instantaneously applied to the electromagnetic coil portion, a strong magnetic field is generated so that the magnetic material is in a moldable state and Joule heat is generated. To be cooled.

Therefore, in the electromagnetic forming coil of the present invention, the Joule heat generated by the operation of the electromagnetic forming coil is promptly eliminated, and the temperature rise of the electromagnetic coil portion and its peripheral portion due to heat accumulation is avoided. Prevents coil insulation failure and outer diameter expansion due to temperature rise,
The life of the coil can be extended as compared with the conventional product.
In addition, such a life prolonging effect of the coil is remarkable in the molding of a high-strength material in which a large amount of heat is generated and in the continuous molding in which heat is easily accumulated.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of an electromagnetic forming coil for pipe expansion in an embodiment of the present invention.

FIG. 2 is a graph showing a comparison result of the electromagnetic forming coils of the present example and the conventional example.

FIG. 3 is a cross-sectional view of a hollow conductor according to another example.

[Explanation of symbols]

 12 ... Hollow part 13 ... Hollow conductor 14a ... Both ends (one end) 14b ... Both ends (other end) 16 ... Electromagnetic coil part

Claims (1)

[Claims] 1. An electromagnetic coil portion (16) is formed by winding a hollow conductor wire (13) having a hollow portion (12) inside, and both ends (14a) of the hollow conductor wire (13). ) (14b), a cooling medium can be circulated around the hollow portion (12), and an electromagnetic forming coil.