JPH04324919A - Manufacture of helical coil - Google Patents

Abstract

PURPOSE:To easily-manufacture a highly strong helical coil having high conductivity and high dimentional accuracy. CONSTITUTION:A flat-square type wire-drawn conductor 13 is spirally wound on a cylindrical body 16, and after the wire-drawn conductor 13 and the cylindrical body 16 have been coupled into one body, the above-mentioned wound conductor 17 is machined, and a helical coil 22 is manufactured.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

[Industrial Application Field] The present invention relates to a method for manufacturing a normally conductive helical coil for generating a strong magnetic field, and in particular a method for manufacturing a helical coil having high strength, high conductivity, large size, and high dimensional accuracy. Regarding.

0002

[Prior Art] In a nuclear fusion device, the magnetic field strength required to confine the generated plasma is 10 to 20
It is expected that the magnetic field will exceed Tesla's, and there is an urgent need to develop a coil made of electrically conductive material that can withstand such a strong magnetic field. Various nuclear fusion devices to date use coils made of normally conducting conductors (copper wires), which consume enormous amounts of power. For this reason, it is essential to develop coils using superconducting wires that consume no power.

By the way, in order to develop high-performance superconducting conductors that can withstand strong magnetic fields, various types of conductors are developed and put into a strong magnetic field generator, and critical current density (Jc), upper critical magnetic field, AC loss, etc. need to be investigated.

The strong magnetic field generator described above is generally constructed by arranging a superconducting magnet coil 2 concentrically outside a water-cooled magnet coil 1, as shown in FIG. At the center 3 of the magnetic field of the water-cooled magnet coil 1, the sum of the magnetic fields generated by both magnet coils 1 and 2 becomes maximum,
For example, a strong magnetic field of 30 Tesla or more can be generated.

There are three types of water-cooled magnet coil 1: a polyhelix type, a bitter type, and a monohelix type, and the present invention relates to a method for manufacturing a polyhelix type coil.

[0006] Polyhelix type coils are made by combining a plurality of single-layer helical coils made of rectangular wire in a concentric ring shape.
This is a multilayer helical coil in which each single layer coil is electrically connected in parallel and in series. Generally, a structure is adopted in which cooling water is allowed to flow into the gaps between adjacent layers for cooling. Assuming that the multilayer helical coils are independently supported, the circumferential tensile stress generated in each coil is proportional to the product of current density, coil radius, and magnetic field. Therefore, the conductor of the helical coil is required to have as much strength in the circumferential direction as possible, especially a conductor with high yield strength and high electrical conductivity; for example, Cu or a Cu alloy is used.

That is, in a hybrid magnet, when trying to obtain a strong magnetic field of, for example, 40 to 50 Tesla, the stress in the circumferential direction acting on the water-cooled magnet becomes extremely high, so the proof stress of the helical coil conductor is 45 kg/m.
m2 or more must be satisfied. For further compactness, a conductivity of 90% (IACS) or higher is required.

Conventionally, such a helical coil conductor is
For example, they were manufactured using the steps shown in FIGS. 8(a), (b), (c), and (d). That is, a rectangular drawn wire 5 is obtained by cold drawing from a rod-shaped copper 4 made of pure copper or a copper alloy, and a wound helical coil conductor 7 is formed by winding the wire helically around a cylindrical body 6 using a winding machine. Ru. Then, when the winding restraint with the cylindrical body 6 is released, a helical coil conductor 8 which is spring-backed due to free expansion is obtained.

[0009]

[Problems to be Solved by the Invention] However, according to the conventional winding method, the helical coil conductor is made of pure copper or precipitation hardening copper alloys such as Cu-Cr, Cu-C.
Even when molded with r-Zr alloy, the 0.2% yield strength is 40 kg.
/mm 2 , which is insufficient in terms of strength. In addition, when alumina dispersion-strengthened copper is used, it has sufficient strength and electrical properties, but the outer periphery of the coil conductor is subjected to tensile stress and the inner periphery is subjected to compressive stress due to winding, as shown in Figure 9. At the outer periphery, the coil conductor contracts in the thickness direction and expands in the circumferential direction, forming a trapezoidal cross-sectional shape. Therefore, between each turn of the conductor 8a, 8b, 8c,
The surface pressure of the insulator inserted into the ... may locally become extremely high, causing breakdown of the insulator. Furthermore, since the magnitude of the surface pressure is non-uniform, bending deformation occurs in the coil, which may cause the coil to buckle due to the compressive magnetic field in the axial direction of the coil, resulting in destruction of the entire coil.

Therefore, in order to correct this trapezoidal deformation by machining, each turn is fixed with a low melting point material 10, such as an alloy of lead, zinc, etc., as shown in FIG.
Even if machined, it is difficult to process accurately because the rigidity and strength of the fixed part are low. Furthermore, even if the machining core 9 for machining inserted into the diameter expanded by the spring and the respective turns 8a, 8b, 8c, etc. are bonded with adhesive, the strength required for machining can be obtained. There are problems such as the inability to form coils using the wire winding method, and there are limits to forming coils using the wire winding method, making it particularly unsuitable for forming large coils.

Furthermore, in the wire winding method, the amount of springback of the coil is large, and it is difficult to obtain a coil with the designed inner and outer diameter dimensions. In particular, it is difficult to prevent large differences in diameter between the start of winding and the middle or end of the winding due to springback, and even if you try to finish the inner and outer diameters by machining, the internal residual stress caused by winding is large, resulting in machining deformation. There was a major problem in that it was extremely difficult to finish it to a predetermined size. Furthermore, in order to increase the dimensional accuracy, a large machining allowance for the conductor must be taken, which has the drawback of lowering the yield of materials and increasing the number of machining steps.

The present invention has been made in order to solve the above problems, and provides a helical coil that can easily obtain a helical coil that has higher strength, higher conductivity, and also has higher dimensional accuracy. The purpose of the present invention is to provide a method for manufacturing a coil. [Structure of the invention]

[0013]

[Means for Solving the Problems] In order to achieve the above object, a method for manufacturing a helical coil according to a first aspect of the present invention is to spirally wind a drawn wire conductor having a rectangular cross-sectional shape around a cylindrical body. After joining the cylindrical body together, the wound conductor is machined to form a spiral conductor.

[0014] Furthermore, in the method for manufacturing a helical coil according to the second aspect of the present invention, a drawn wire conductor having a rectangular cross section is spirally wound around a cylindrical body, and in a fixed state, the wound conductor and the cylinder are simultaneously annealed at a high temperature. After heating, the wrapped conductor is removed from the cylinder and machined to form a helical conductor.

[0015]

[Operation] According to the method for manufacturing a helical coil according to the first invention, since the long drawn wire conductor is wound around the cylindrical body and joined together, not only the sides between the coil turns of the conductor but also the side surfaces of the conductor are Since the inner peripheral side and the cylindrical body are integrated, it is possible to finish the cross-sectional shape of the conductor, which has been deformed by winding, into a uniform rectangular cross-section by machining. This makes it possible to prevent bending buckling of the coil and destruction of the insulating material between each turn.

Further, according to the method for manufacturing a helical coil according to the second aspect of the invention, since the long drawn wire conductor is heated at high temperature while being wound around the cylindrical body, the residual stress caused by the winding almost disappears. The amount of springback caused by residual stress becomes extremely small, making it easy to manufacture a helical coil that takes into account the amount of springback, and improving the dimensional accuracy of the coil's inner and outer diameters.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings.

FIG. 1 shows a process diagram for explaining a first embodiment of the method for manufacturing a helical coil according to the present invention. In the first example, as shown in FIG. 1(a), a rod-shaped copper elongation 12 is prepared in which alumina dispersion-strengthened copper is formed into a circular rod shape using alumina particles 11 using copper as a reinforcing material as a matrix. Next, this rod-shaped copper elongation 12 is cold-drawn to form a long rectangular drawn wire conductor 1 as shown in FIG. 1(b).
form 3.

Next, a wax foil 14 is placed on one surface of this rectangular drawn wire conductor 13 as shown in FIG. 1(c), and spot welds 15 are performed at a plurality of points using a spot welder. The conductor 13' with the wax foil 14 thus obtained is spirally wound at a constant pitch while applying a predetermined tension on the outer periphery of the cylindrical body 16 as shown in FIG. 1(d) using a coil winding machine. A wrapped conductor 17 is obtained by winding the conductor 17 into a shape and fixing both ends with fixing fittings 18.

Next, after degreasing and cleaning impurities and dirt adhering to the cylindrical body 16 and the wrapped conductor 17, etc., as shown in FIG.
As shown in FIG. 2, the inner peripheral side of the wrapped conductor 17 is integrally joined to the cylindrical body 16 by placing it in a heating furnace 19 and heating it at a temperature of 650 to 850° C. with a heater 20. After taking these out from the heating furnace 19 and cooling them,
f), each turn 17a of the wrapped conductor 17,
17b, . . . , 17f are machined using a cutting tool 21, the cross-sectional shape deformed by winding is finished into a rectangular shape, and then the outer periphery of the wound conductor and the inner periphery side where the cylindrical body 16 is attached are finished, and a cylindrical shape is formed. By removing the body 16, a helical coil 22 as shown in FIG. 1(g) is obtained.

If a helical coil is manufactured by the process described in the above embodiment, the rectangular drawn wire conductor 13 with a smaller cross-sectional area is formed by cold working from the rod-shaped copper elongation 12, so that the tensile strength characteristics are improved and at the same time , the conductor can have any cross-sectional shape. In addition, the helical coil 22
The height and diameter of the conductor can be freely selected.
By using the long drawn wire conductor 13, it is possible to manufacture a large-sized, high-strength helical coil.

FIG. 2 shows the amount of change in the cross section of the coil conductor when the rectangular drawn wire conductor 13 is wound around the cylindrical body 16. It represents the amount of shrinkage on the outer circumference side and the amount of swelling on the inner circumference side. Since the amount of deformation of a coil conductor increases in proportion to the thickness of the conductor and inversely proportional to the diameter of the coil, it is possible to absorb this amount of deformation by changing the thickness of the insulator inserted between each turn. It's not easy. Therefore, the coil conductor side must be processed so that the surface between each turn contacts the insulator uniformly.

[0023] Also, the conductor 1 wound around the cylindrical body 16
By heating 7, the wrapped conductor 17 and the cylindrical body 1
In order for the brazing agent 14 between the two parts to be in a liquid phase and to bond the two parts, it is necessary to prevent a gap from forming between the two parts due to thermal expansion. For this purpose, a material is used for the cylindrical body 16 whose coefficient of linear expansion is slightly larger than that of the coil conductor in a high temperature state. For example, JIS SUS304.

[0024] The wax foil may be any Cu-Ag type material that is inert at high temperatures or can be used in vacuum, but if the heating temperature conditions are particularly limited, the amount of Ag may be adjusted. or those to which other elements are added. Further, in order to improve the bondability, one method is to plate the surface of the cylindrical body with Ni or the like in advance.

When a coil conductor is heated, the strength characteristics improved by cold working generally disappear, but the alumina dispersion strengthened copper used in this example is characterized by a small decrease in strength. 0 of conductor material in each process
．． The measured values of 2% proof stress and electrical conductivity are shown in the table below.

[0026]

[Table 1]

[0027] By forming the rectangular drawn conductor in this way, the yield strength is greatly improved, but the electrical conductivity is lowered. However, even when the coil conductor is heated, its yield strength decreases only to an intermediate value between that of the rod-shaped copper elongation 12 and the drawn wire conductor 13, indicating that it has sufficient strength as a conductor. It can also be seen that the electrical conductivity increases by about 3% by heating, and the characteristics are improved. That is, even if high-temperature heat treatment is performed, cold working has the advantage that the effect of improving strength is fully utilized, and the electrical properties are improved more than after cold working.

In the above embodiment, the surface of the cylindrical body remains smooth, but in order to facilitate winding of the coil conductor,
The same effect can be obtained by providing a guide groove for coil winding on the surface of the cylindrical body and spot welding a wax foil to the bottom of the groove. Further, in the above embodiments, a brazing agent that is used in an inert gas atmosphere is used, but a brazing agent that can be bonded by heating in the atmosphere may also be used.

Furthermore, substantially the same effect as described above can be obtained by wrapping a brazing agent around the gap between the coil winding guide groove and the coil conductor and heating it. Alternatively, diffusion bonding may be performed by adjusting the heating temperature and time without using a brazing agent.

Next, a second embodiment of the method for manufacturing a helical coil according to the present invention will be described with reference to FIG. In the second embodiment, as shown in FIG. 3(a), a rod-shaped copper elongation 24 is prepared by forming alumina dispersion-strengthened copper into a rod shape in which alumina particles 23 as a reinforcing material are dispersed in copper used as a matrix. do. Next, this rod-shaped drawn copper wire 24 is cold-formed to form a long rectangular drawn copper wire 25 shown in FIG. 3(b). Here, it is also possible to use ceramic or metal fine particles, short fibers, whiskers, etc. as the reinforcing material.

As shown in FIG. 3(c), the rectangular drawn conductor 25 thus obtained is wound around a cylindrical body 26 while applying a predetermined tension using a coil winding machine, and the starting end of the conductor is and the terminal end portions are fixed with fixing fittings 27 to obtain a helical coil conductor 28 in a wound state.

Next, the cylindrical body 26 and the helical coil conductor 28
After degreasing and purifying the impurities and dirt attached to the
As shown in d), it is placed in the heat treatment furnace 29 while being wrapped around the cylindrical body 26, and heated to a temperature of 700 to 900
By heating and annealing at a temperature of 0° C. for 1 to 3 hours, the residual stress in the coil conductor 25 due to the winding process is eliminated. After that, even if the fixing fitting 27 fixed to the cylindrical body 28 is removed, a helical coil conductor 31 with a small amount of springback can be obtained. The machining of the helical conductor 31 is as follows:
After the heating annealing treatment, the inner peripheral portion is subjected to the annealing after being removed from the cylindrical body 26.

When the rectangular drawn wire conductor shown in FIG. 3(b) is used, the thickness of the outer periphery of the drawn wire conductor wound around the cylindrical body 26 decreases as shown in FIG. A cross-sectional deformation occurs that increases. Therefore, in the process of obtaining a wire-drawn conductor in advance, a modified cross section in the opposite direction to the cross-sectional deformation described above, that is, the outer peripheral part of the coil conductor is made thicker and the inner peripheral part is made thinner, as shown in FIG. A trapezoidal drawn wire 32 is formed. When this conductor is wound around the cylindrical body 26, a helical coil conductor 33 having a rectangular cross section is obtained as shown in FIG. 5(b).

According to the second embodiment, the rectangular drawn wire conductor 22 having a smaller cross-sectional area is obtained by cold working the rod-shaped copper wire 24, so that the tensile strength characteristics are improved and at the same time, it is possible to form an arbitrary shape. Since it is possible to make the conductor cross-sectional shape, the height and diameter of the helical coil conductor 31 can be arbitrarily set, and a large-sized helical coil with high strength can be manufactured.

FIG. 6 compares the amount of coil back between conventional coil forming using a wire winding method and coil forming according to the second embodiment of the present invention. In the conventional unannealed method, the residual stress within the coil conductor exceeds the yield strength of the conductor.
The amount of springback is large at 5-15% of the coil diameter.
Furthermore, even with the same coil diameter, the amount of springback varies greatly. For this reason, it was difficult to manufacture a coil with the inner and outer diameters of the designed dimensions, but by providing the annealing process of the second embodiment, the residual stress in the conductor is reduced to the tensile strength equivalent at the maximum heating temperature, so the wrapped coil Since the amount of springback with respect to the diameter is within 1 to 2% and the variation thereof is small, it is extremely easy to predict the amount of springback and obtain a coil of a predetermined size.

Furthermore, even if the coil conductor is annealed as in the second embodiment, alumina dispersion-strengthened copper is characterized by a small decrease in strength, as in the first embodiment, so annealing at high temperatures is Even if the treatment is carried out, the strength improvement effect due to cold working is fully utilized, and the electrical properties are improved compared to after cold working.

In the second embodiment, the cylindrical body is heated and annealed with the coil conductor wound around it.
) By annealing the helical coil conductor after springback shown in ), the dimensional accuracy of subsequent machining can be improved by removing internal residual stress. In this case, as shown in FIG. 6, although it is not possible to suppress variations in diameter dimensions, mechanical and electrical properties similar to those of the first embodiment can be obtained.

In the first and second embodiments described above, alumina dispersion-strengthened copper or pure copper was used as the coil material, but the present invention also uses other coil materials such as short fibers and whiskers. A conductor made of an alloy mixed with particles or the like or a copper alloy may also be used. Furthermore, similar effects can be obtained by using silicon carbide, carbon, boron, organic matter, or metal as reinforcing fibers.

[0039]

[Effects of the Invention] As described above, the present invention provides a method for manufacturing a helical coil that can easily produce a helical coil having higher strength, higher conductivity, and higher dimensional accuracy. Can be provided.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing a first example for explaining the method for manufacturing a helical coil according to the present invention.

FIG. 2 is a curve diagram showing the amount of deformation of the conductor cross section due to winding in the same example.

FIG. 3 is a process diagram showing a second example for explaining the method for manufacturing a helical coil according to the present invention.

FIG. 4 is a diagram showing a deformed state of the cross section when a conductor with a rectangular cross section is wound around a cylindrical body in the same embodiment.

FIG. 5 is a diagram showing a drawn wire conductor with a trapezoidal irregular cross section and a state in which it is wound around a cylindrical body in the same embodiment.

FIG. 6 is a curve diagram showing a comparison of the amount of springback between the molding method in the same example and the conventional molding method.

FIG. 7 is an explanatory diagram of a hybrid magnet.

FIG. 8 is a process diagram for explaining a conventional helical coil manufacturing method.

9 is a diagram showing a deformed state of a conductor cross section in the coil conductor winding step of FIG. 8; FIG.

FIG. 10 is a diagram for explaining a conventional method of fixing the turns of each coil with a hardening agent.

[Explanation of symbols]

11... Alumina particles, 12... Rod-shaped copper elongation, 13... Rectangular wire drawing, 14... Brazing foil, 15... Spot weld, 16... Cylindrical body, 17... Wound conductor, 18...
Fixing fittings, 19... Heating furnace, 20... Heater, 21...
Cutting tool, 22...Helical coil.

Claims (2)

[Claims] 1. A wire drawn conductor having a rectangular cross section is spirally wound around a cylindrical body, the wire drawn conductor and the cylindrical body are integrally joined, and then the wound conductor is machined to obtain a spiral conductor. Features: Manufacturing method for helical coils. [Claim 2] A drawn wire conductor with a rectangular cross section is spirally wound around a cylindrical body, and in a fixed state, the wound conductor and the cylindrical body are simultaneously annealed and heated at a high temperature, and then the wound conductor is removed from the cylindrical body and machined. A method for manufacturing a helical coil, characterized by processing it to obtain a helical conductor.