JPH06318514A - Superconducting coil device - Google Patents

Abstract

PURPOSE:To provide a high-performance and stable superconducting coil by using a fiber material for a winding frame and fiber reinforced plastics which are molded in one body with a wound resin so that the roving of a negative expansion fiber, the melting point of which is a specific temperature or higher, makes the angle of a specific range with respect to the axis. CONSTITUTION:The winding frame for a superconductive wire is a fiber reinforced plastics molded in one body with a wound resin so that the roving of a fiber molding which has a high strength and a high elastic rate of aramid, polyarylate, carbon and the like and a negative expansion rate, the melting point of which is 160 deg. or higher, has an angle of from + or -40 deg. to + or -80 deg. with respect to the axis thereof. Thereby, the stable and high-performance superconducting coil which is easy in the operation of training and high in the maximum current value can be obtained.

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, a metal such as aluminum or glass fiber reinforced plastic (GFRP) is used as the reel, but these are wound at room temperature and liquid nitrogen (LN
T) or when cooled to 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, the superconducting wire expands in the circumferential direction due to the repulsive force derived from the Lorentz force when excited at a very low temperature,
The winding will move away from the bobbin. 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 an aluminum frame, since it is conductive, Joule heat is generated due to an eddy current, especially in an alternating current, so that it becomes unstable. The present invention has been made to solve the above problems, and an object thereof is to obtain a high-performance and stable superconducting coil.

[0004]

SUMMARY OF THE INVENTION The present invention is a superconducting coil device in which a superconducting wire is wound around a cylindrical or columnar winding frame and used at extremely low temperatures, and the winding frame has a melting point of 16 as a fibrous material.
Roving of negative expansion fiber above 0 ℃ is ± 40 with respect to the axis
A superconducting coil device, which is made of a fiber-reinforced plastic integrally molded with a winding resin so that an angle of ± 80 degrees is formed.

The melting point used in the present invention is 160.
Negative expansion above ℃ (expands as the temperature decreases) is a high-strength, high-modulus fiber such as aramid, polyarylate (wholly aromatic polyester), PBZ polymer (polybenzbisoxazole, polybenzbisthiazole, etc. ) And dendritic cones such as carbon. Since all of these fibers have the unique property of expanding as the temperature becomes lower and have a much lower specific gravity than glass fibers, it is necessary to obtain a reinforcing fiber that has a high specific strength and a high specific elastic modulus and is light. You can Where the melting point is 160 ° C
For example, the following polyethylene fibers have not only restrictions on the molding conditions of the resin that is the matrix, but also restrictions on the curing conditions of the resin impregnation step after winding the superconducting conductor,
A superconducting coil with excellent performance cannot be obtained. Also, in order to satisfy all of the many physical properties as a reel,
Two or more kinds of negative expansion fibers can be mixed, or a part of the positive expansion fibers can be mixed and used. Examples of the positive expansion fibers include seamix fibers such as glass, alumina, silica, zirconia, titania, silicon carbide and silicon nitride, and metal fibers such as aluminum, copper and stainless steel.

Next, regarding the dimensional change, all of these negative expansion fibers have a peculiar property that they have a negative expansion coefficient (elongate when the temperature is lowered from room temperature). On the other hand, the matrix resin exhibits positive expansion, but a cylinder or column formed by winding a filament of these fibers can have a large negative expansion coefficient in the circumferential direction and a positive expansion coefficient in the axial direction. As the matrix used here, an epoxy resin, an unsaturated polyester resin, a vinyl ester resin, a urethane resin, a urethane acrylate resin or the like can be used, but an epoxy resin is particularly preferable. All of these matrix resins exhibit positive expansion, but by using these fibers exhibiting negative expansion, the filament is wound by changing the winding angle, and the dimensional change of the molded cylinder or cylinder is as shown in FIG. 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. The orientation angle is preferably ± 40 to ± 80 degrees with respect to the axial direction, but is preferably ± 47 to ± 75 degrees. If the angle is less than ± 40 degrees, the positive expansion in the circumferential direction (contracting as the temperature becomes lower) increases, and if the angle exceeds ± 80 degrees, the thermal stress generated inside the molded product increases and cracks easily occur. Be stable. On the other hand, in the case of GFRP, since both glass fiber and matrix resin have positive expansion, only the characteristic of normal expansion, which is a characteristic of ordinary materials, can be obtained regardless of the winding angle. Therefore, the superconducting coil using the winding frame made of this 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, the aramid, polyarylate, carbon, etc. are integrated with the winding resin so as to form an angle of ± 40 ° to ± 80 ° with respect to the axis of the fiber molding having high strength, high elastic modulus and negative expansion coefficient. (EN) A superconducting coil which is stable and has a high maximum current value, which can be easily trained by using a molded fiber-reinforced plastic as a winding frame.

Examples of the molding method include a filament winding method or a tape winding method in which the present fiber is impregnated with a matrix resin in a thread or tape shape and wound around a mandrel. The mixing ratio of the fibers and the matrix resin in the composite material is preferably 35 to 85%, more preferably 40 to 70% as the volume fraction (Vf) of the fibers. When the Vf of the fiber is less than 35%, the reinforcing effect of the fiber is not exhibited, and when it exceeds 85%, it is difficult to impregnate the matrix resin and the mechanical properties of the composite material are deteriorated, which is not preferable.

[0008]

EXAMPLES Cylindrical fiber reinforced plastics (FRP) made of negative expansion fibers of the present invention were prepared as follows. As negative expansion fibers, aramid fibers (Japanese aramid fibers, Twaron HM), polyarylate fibers (Kuraray, Vectran), carbon fibers (Toray, HT), and glass fibers for comparison were used. A total of 7 types of cylindrical FRPs of Examples 4 to 7 were prepared by the filament winding method. Epoxy resin was used as the matrix, and a uniform mixed resin dope was prepared by the following formulation. 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
Hardened and molded by hr, the volume of the conical cone is 65%, the outer diameter is 100.
A molded body having a size of mm × 500 mm and a wall thickness of 5 mm was obtained. A flange made of GFRP was adhered to each of the cylinders thus obtained to obtain a coil winding frame. 1.2mmφ to this
After winding 5 layers of the superconducting conductor of 10 kg with a tension of 10 kg, impregnating the above-mentioned epoxy resin for sheet winding,
The superconducting coil was completed by heat curing at 100 ° C. for 4 hours and further at 130 ° C. for 3 hours. The results of these evaluations are shown in Table 1.

[0009]

[Table 1]

(Coefficient of thermal expansion) A strain gauge was attached to the outer peripheral surface of the winding frame, and then immersed in liquid N2 to measure dimensional changes in the circumferential direction and the axial direction. (Crack resistance) Each pipe is placed in liquid He from room temperature, held for 30 minutes, then pulled up and visually observed. The order of higher crack resistance was ◯>△> ×. (Quench current) The superconducting coil device was immersed in liquid He and the quench current was measured. The results are shown by the maximum current density reached by repeated training and the number of trainings at that time.

[0011]

According to the present invention, it is possible to provide a stable and high-performance superconducting coil which requires a small number of trainings and 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.

Claims (1)

[Claims] 1. A superconducting coil device in which a superconducting wire is wound around a cylindrical or columnar winding frame and used at a cryogenic temperature, wherein the winding frame has a roving of negative expansion fiber having a melting point of 160.degree. A superconducting coil device comprising a fiber reinforced plastic integrally molded with a winding resin so that an angle of ± 40 degrees to ± 80 degrees is obtained.