JPH07335427A - Superconductive coil - Google Patents

Abstract

PURPOSE:To manufacture a superconductive coil having high performance and stability by a method wherein the bobbin thereof is composed of an organic fiber having negative expansion coefficient as well as a fiber plastics integrally molded with a resin. CONSTITUTION:Within a superconductive coil wound around a tubular or columnar bobbin comprising a combination of an organic fiber having a negative expansion coefficient and a carbon fiber as well as a fiber reinforced plastics integrally molded with a resin. Otherwise, the organic fiber having the negative expansion coefficient is a high powerful, high elastic modulus polyethylene fiber or furthermore, the organic fiber and the carbon fiber are alternately wound around the bobbin making + or -40-90 deg. angle with the axial direction to be integrally molded with a resin. Through these procedures, the superconductive coil in the less training times and the maximum current value having the stability and high performance can be manufactured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting coil which is cooled to an extremely low temperature and used.

[0002]

2. Description of the Related Art In a superconducting coil device, a superconducting conductor is wound around a winding frame, and layer coil elements in which the superconducting conductor is wound along a spiral groove formed between layers with a spacer or engraved on the outer peripheral surface are sequentially formed. Concentric layers are formed. Conventionally, a metal such as aluminum or glass fiber reinforced plastic is used as the reel.

[0003]

Although there are various uses of the superconducting coil, increasing the current density of the superconducting wire is extremely important for improving the performance of the coil itself. And, this largely depends on the stability of the superconducting wire wound around the bobbin. The physical stability of the superconducting wire wound around the bobbin is closely related to the electrical stability of the superconducting coil itself. Usually, the reel is made of metal such as stainless steel or aluminum, or glass fiber reinforced plastic (G
FRP) is used, but when they are wound at room temperature and cooled to liquid nitrogen (LNT) or liquid helium temperature (LHeT), both shrink greatly in the circumferential direction of the bobbin and shrink slightly in the axial direction. On the other hand, when the superconducting wire is excited at a very low temperature, the superconducting wire expands in the circumferential direction due to the repulsive force resulting from the Lorentz force, and the winding moves away from the winding frame. Further, when the temperature becomes extremely low in the axial direction, the size of the superconducting wire changes more than the small amount in the axial direction of the winding frame due to the large contraction caused by the positive expansion in the vertical direction. These two movements combine to cause microscopic mutual movements between the superconducting wires, causing a disturbance due to frictional heat generation on the surface and causing the superconducting coil to be quenched. Further, in the case of stainless steel or aluminum frame, since it is conductive, Joule heat is generated due to eddy current, especially in an alternating current, so that it becomes unstable.

In order to improve the coil performance, a large diameter,
It is necessary to make the superconducting wire long and secure the length of the superconducting wire. On the other hand, in order to use the cryogenic measurement with LHeT, it is necessary to reduce the thickness of the coil bobbin itself and reduce the heat capacity of the coil bobbin itself.
It is important for improving cooling efficiency. On the other hand, for the coil, when the superconducting wire is wound around the winding frame, it is necessary to apply a certain tension in advance to suppress the movement of the superconducting wire. It can be said that the higher the tension is to a certain limit, the higher the effect of suppressing the wire rod and the higher the quenching resistance. Considering this and the technological trend of large diameter thinning of the reel, it is important that the reel itself has high rigidity. If a material with low compressive strength and elastic modulus is used as the material forming this reel, it will be deformed over time due to high pre-tension during coil making, and strain characteristics from room temperature to cryogenic temperature will be repeated. This causes a disadvantage that the coil characteristics change depending on the cycle and the coil characteristics change. The present invention has been made to solve the above problems,
The purpose is to obtain a high-performance and stable superconducting coil.

[0005]

DISCLOSURE OF THE INVENTION The present invention relates to a cryogenic superconducting coil in which a superconducting wire is wound around a cylindrical or columnar winding frame, wherein the winding frame has a negative expansion coefficient of an organic fiber and a carbon fiber. The superconducting coil is characterized in that it is made of a combination of the above and is made of a fiber reinforced plastic obtained by integrally molding the resin and the resin.

The negative expansion organic fibers used in the present invention are high-strength, high-modulus fibers such as polyethylene, aramid, polyarylate (wholly aromatic polyester), and P.
Fibers of BZ polymer (polybenzbisoxazole, polybenzbisthiazole, etc.) may be mentioned, with polyethylene fibers being particularly preferred. All of these fibers have the peculiar property that they expand as the temperature decreases, and because they have a much lower specific gravity than glass fibers,
It is possible to obtain a reinforcing fiber having a high specific strength, a high specific elastic modulus and a light weight.

On the other hand, all of these organic fibers have the common drawback that they have extremely low compression, bending, and properties as compared with inorganic fibers such as metal and ceramics. However, although the inorganic fibers are excellent in compression and bending properties, both show only positive expansion properties. On the other hand, carbon fiber has a small negative expansion property, is excellent in compression and bending characteristics, and has a small specific gravity. Therefore, in the present invention, by using a fiber reinforced plastic in which these organic fibers and carbon fibers are combined, it is possible to obtain a reel having excellent compression resistance and bending characteristics without impairing the negative expansion property of the organic fibers.

Further, in order to satisfy many physical properties as a reel, it is possible to mix two or more kinds of the organic negative expansion fibers mentioned above, or it is possible to mix and use a part of the positive expansion fibers. . Examples of the positive expansion fibers include ceramic fibers such as glass, alumina, silica, zirconia, titania, silicon carbide and silicon nitride, and metal fibers such as aluminum, copper and stainless steel. The carbon fiber may be either PAN-based or pitch-based, and a wide range of carbon fibers can be used. The volume ratio of the organic negative expansion fiber to the carbon fiber is 80/20 to 20/80, preferably 70/30 to.
A range of 30/70 is preferred. If the amount of carbon fibers is less than 30, the effect of improving the compression characteristics will be small, and if the amount of organic fibers is less than 30, the negative expansion will be small.

Next, the dimensional change will be described in detail. All of these organic negative expansion fibers and carbon fibers have a unique property that they have a negative expansion coefficient (expand when temperature is lowered from room temperature). However, there is a large difference in the characteristics between organic fibers and carbon fibers, the former shows a large value,
The latter has a negative expansion coefficient close to zero.

On the other hand, the matrix resin exhibits a positive expansion, but a cylinder or a cylinder formed by winding filaments of these fibers can have a large negative expansion coefficient in the circumferential direction and a positive expansion coefficient in the axial direction. it can. The matrix used here is epoxy resin, unsaturated polyester resin,
Although vinyl ester resin, urethane resin, urethane acrylate resin and the like can be used, epoxy resin is particularly preferable. Each of these matrix resins shows positive expansion, but using these fibers showing negative expansion, the filaments are wound by changing the winding angle, and the dimensional change with temperature of a molded cylinder or cylinder is shown in FIG. As shown, depending on the winding angle, a large negative expansion coefficient in the circumferential direction and a positive expansion in the axial direction can be obtained by appropriately selecting it.
The negative expansion in the circumferential direction is much higher than the negative expansion coefficient of the fiber itself. Orientation angle is ± 40 with respect to the axial direction
A range of ˜90 degrees is suitable, but a range of ± 47 to ± 85 degrees is desirable. If the angle is less than ± 40 degrees, the positive expansion in the circumferential direction (contracting as the temperature becomes lower) increases. On the other hand, GFRP
In this case, since both the glass fiber and the matrix resin have positive expansion, only the characteristic of normal expansion, which is found in ordinary materials, can be obtained regardless of the winding angle. Therefore, the superconducting coil using the reel according to the present invention can be a high-performance coil that is stable, has high quench resistance, and has a large current density. When GFRP is used as a bobbin of a superconducting coil, the biggest problem is that the coil is easily quenched due to loosening of the superconducting wire accompanying a large contraction in the circumferential direction.

In the present invention, when a high-strength, high-modulus organic negative expansion fiber such as polyethylene, aramid, polyarylate, or PBZ polymer is combined with a carbon fiber excellent in compression resistance and bending characteristics, a fiber molded product is obtained. ± 40 relative to the axis
A stable and high-performance superconducting coil that can be easily trained and has a high maximum current value by using a fiber reinforced plastic integrally molded with winding resin to form an angle of ± 90 degrees from the degree It is provided. As a method for mixing the organic fibers and the carbon fibers, one or more kinds of the organic fibers and the carbon fibers are uniformly mixed and wound in a yarn unit, and a yarn in which the organic fibers and the carbon fibers are uniformly mixed in a filament unit is wound. It is possible to use any method such as a method of winding, a method of alternately laminating organic fibers and carbon fibers and winding. The most effective method is to uniformly mix the organic fiber and the carbon fiber with a filament or a yarn and wind them. In this case, the mixing ratio may be changed by changing the number of filaments of the organic fibers and the carbon fibers, or the ratio of both wound fibers, for example, one carbon fiber for every two organic fibers.
It can be appropriately set by winding at a ratio of a book. Examples of the molding method include a filament winding method or a tape winding method in which the present fiber is wound around a mandrel while impregnating a thread-shaped or tape-shaped fiber with a matrix resin.

The mixing ratio of the fibers and the matrix resin in the above composite material is 35 to 8 as the volume molecular weight (Vf) of the fibers.
5% is preferable, and 40 to 70% is more preferable. If the fiber Vf is less than 35%, the reinforcing effect of the fiber will not be exhibited, and if it exceeds 85%, it is difficult to impregnate the matrix resin and the mechanical properties of the composite material deteriorate, which is not preferable.

[0013]

EXAMPLE A cylindrical fiber reinforced plastic (FRP) comprising negative expansion fibers of the present invention was prepared as follows. As the organic negative expansion fiber, high-strength polyethylene fiber (Toyobo,
Dyneema SK60), aramid fiber (Japanese aramid fiber, Twaron HM), polyarylate fiber (Kuraray, Becton), etc., and carbon fiber (Toray, H
T) was prepared by uniformly mixing or alternately laminating the rovings with each other, and a total of eight types of cylindrical FRPs of Examples 1 to 5 and Comparative Examples 1 to 4 were prepared by the filament winding method. Epoxy resin was used as the matrix, and a uniform mixed resin dope was prepared in the following proportions. Epicoat-827 (Oilized shell) 100 Epicure YH-300 (Oilized shell) 80 EMI-24 (Oilized shell) 1 Next, various fibers were impregnated with an epoxy resin and wound around a mandrel to form a cylindrical shape. Next, while keeping it on the mandrel, 100 ° C x 2 hr, then 130 ° C x 3
Curing and molding with hr, fiber volume content 65%, outer diameter 100
A molded body having a size of mm × length of 500 mm and a wall thickness of 13 mm was obtained.
A flange made of GFRP was adhered to each of the cylinders thus obtained to obtain a coil winding frame. 1.2mm to this
A superconducting coil of φ was wound by one layer with a tension of 10 kg, and then a superconducting coil was completed. The results of these evaluations are shown in Table 1.

[0014]

[Table 1]

(Coefficient of thermal expansion) After attaching a strain gauge to the outer peripheral surface of the reel, the strain gauge was immersed in the liquid N2 and the dimensional changes in the circumferential direction and the axial direction were measured. (Quench current) The superconducting coil device was immersed in liquid He, and the quench current of the coil after continuous operation for 10,000 hours was measured. The results are shown by the maximum current density reached by repeated training and the number of trainings at that time. The superconducting critical current value used at this time was 1850.
It is A. (Compression characteristics) Length from each pipe in the x (tangential direction when viewed from the cross section of the pipe), y (longitudinal direction of the pipe), z (direction 90 ° to the x and y axes) direction is 5, 10, 5 mm. The rectangular parallelepiped was cut out and the compression characteristics were measured at room temperature at a speed of 1 mm / min in the x direction. From this, the compressive strength and the compressive elastic modulus were calculated.

[0016]

According to the present invention, it is possible to provide a stable and high-performance superconducting coil with a small number of trainings, a high maximum current value.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a winding angle and a coefficient of thermal expansion in various fibers.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location 7310-4F B29C 67/14 X

Claims (3)

[Claims] 1. In a superconducting coil for cryogenic use, wherein a superconducting wire is wound around a cylindrical or columnar winding frame, the winding frame is made of a combination of organic fibers and carbon fibers having a negative expansion coefficient, and this is combined with a resin. A superconducting coil made of fiber-reinforced plastic integrally molded. 2. An organic fiber having a negative expansion coefficient has high tenacity,
The superconducting coil according to claim 1, which is a high elastic modulus polyethylene fiber. 3. An organic fiber and a carbon fiber whose winding frame has a negative expansion coefficient are alternately ± 40 to the axial direction of the coil.
The superconducting coil according to claim 1, wherein the superconducting coil is wound at an angle of 90 degrees, and the resin and the resin are integrally molded.