JPS60177606A - Manufacture of superconductive electromagnet coil - Google Patents

Abstract

PURPOSE:To obtain a superconductive electromagnet coil having superior insulating performance, cooling performance, adhesion strength and cryoresistive performance by a method wherein when the superconducting coil is to be fixed on the surface of a cooling body interposing an insulating layer between them, a multiplex insulating layer consisting of a polyimide film, glass reinforced plastics and a heat-sensitive adhesive film is used as the insulating layer. CONSTITUTION:An adhesive resin layer 12 is applied on the inside surface of a cooling body 2, and a superconductive coil 4 is fixed thereon interposing a composite sheet 11 between them. At this construction, as the core material of the composite sheet 11, a polyimide film 6 processed to have rough surfaces according to a sand blast is used, and glass reinforced plastic sheets 7 are adhered to both the surfaces of the film thereof interposing epoxy resin adhesives 8 between them. Moreover a heat-sensitive adhesive layer 9 is adhered to the side to face with the cooling body 2, and an adhesion checking sheet 10 is sticked thereon. The composite sheet 11 is constructed in such a way, and when the adhesive layer 9 side is to be sticked to the cooling body 2 interposing butted parts 11A, 11B between them, sticking is performed by peeling off the sheet 10. Accordingly, the sheet 11 having no void, etc. can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a method for manufacturing an indirect cooling superconducting electromagnetic coil used for detecting particles in high-energy physics.

[Prior art and its problems']

This type of superconducting electromagnetic coil has several meters in diameter and length, and generally consists of a cylindrical cooling body with a cooling pipe fixed to the outer circumference for passing a cooling medium such as liquefied helium, and An indirect cooling type electromagnetic coil is used, which consists of a single-layer inner-wound superconducting coil that is tightly wound around the inner circumferential surface.The coil electrically insulates the cooling body and the coil and conducts a large current. In order to mechanically strengthen the coil and the cooling body, an insulating layer containing an adhesive resin is interposed between the coil and the cooling body to fix and integrate the two. Therefore, the coil is cooled through the insulating layer, so the insulating layer is required to have high insulation performance and adhesive strength, as well as good thermal conductivity and the ability to withstand severe cooling cycles. It is said to have cryogenic resistance and heat cycle resistance that do not deteriorate.

FIG. 1 is a schematic cross-sectional view of an inner-wound superconducting electromagnetic coil.

In the figure, reference numeral 2 denotes a cylindrical cooling body made of a good thermal conductor such as aluminum or copper, and a cooling pipe 5 is welded to the outer peripheral surface of the cooling body. 3 is an insulating layer containing an adhesive resin applied to the inner peripheral surface of the cooling body 2, and 4 is an inwardly wound superconducting coil, which is a superconducting wire formed into a rectangular cross section by a snare conductor such as aluminum or copper and coated with insulation. is tightly wound around the insulating layer 3 while applying force in the tangential direction of the cylinder. The thus formed superconducting electromagnetic coil 1 is loaded into a heat curing furnace at a predetermined temperature with distributed loads indicated by arrows in the figure being applied by an axial pressure device and a radial pressure device (not shown). By heating and curing the adhesive resin applied to the insulating layer, the cooling body 2 and the inner-wound superconducting coil 4 are firmly bonded and integrated via the insulating layer 3.

In the superconducting electromagnetic coil formed as described above,
When the coil is a large coil with a diameter and length of several meters, the voltage required to flow a large current in the coil is several thousand volts, so the insulation between the four superconducting coils and the cooling body 2 is required. is expected to withstand the above voltage. Furthermore, based on the weak point theory, the breakdown voltage of an insulator decreases in inverse proportion to the increase in the area of the insulator, so for large coils such as those mentioned above, the breakdown voltage generally measured as a material is I can see something.

Conventionally, glass-reinforced plastic laminates have been used as an insulating material that can withstand such voltages. It was used by gluing two layers of laminate together. However, due to the high rigidity of the laminate, it is difficult to adhere it to the inner circumferential surface of the cylindrical cooling body without any gaps, and the highly viscous adhesive prevents the trapped air bubbles from forming on the coil. It is difficult to drive out even if pressing force is applied through the insulating layer, and the thermal conductivity of the insulating layer formed in this way is deteriorated due to the serial intervening of the thermal resistance of the thick insulating layer and the thermal resistance of the void. However, there is a problem in that it becomes difficult to indirectly cool the superconducting coil 4 to a predetermined temperature near zero absolute temperature. In addition, voids remain where the laminates butt each other, and the insulation strength of these areas is low, so even if the butts of different layers are stacked with their butts offset from each other, the withstand voltage value will drop by almost a fraction. There were drawbacks.

On the other hand, it is also known that an insulating layer is formed using an insulating film such as a polyimide film. Polyimide film has excellent electrical insulation properties, as well as excellent heat and cold resistance, and is thinner and softer than glass-reinforced plastic laminates, so it is suitable for forming an insulating layer that adheres closely to the inner circumferential surface of a cylindrical cooling body. Since it can be formed relatively easily and the thickness of the insulating layer can be several times smaller than that of the laminated plate method, it has the advantage of providing excellent cooling performance. However, polyimide film has poor adhesion with adhesives such as epoxy resin,
In addition, since it is easily damaged mechanically, it has disadvantages such as damage to the insulating layer during coil winding of superconducting wire, and peeling of the insulating layer due to electromagnetic mechanical force acting on the coil.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned situation, and has a thin insulating layer, few voids and voids in the adhesive layer, and excellent insulating performance and thermal conductivity.

[Key points of the invention]

The present invention is directed to a method of manufacturing a superconducting electromagnetic coil in which a superconducting coil is fixed to the surface of the cooling body through an insulating layer, and a roughened polyimide film and a glass-reinforced plastic sheet are placed on the surface of the cooling body. A composite insulating layer is formed by laminating a composite sheet with a heat-sensitive adhesive layer (hereinafter referred to as a heat-sensitive adhesive film) that does not contain air bubbles on both sides of at least one side of the laminate, and then the composite insulating layer and the superconducting coil are stacked together. The above object is achieved by fixing the composite insulating layer or the superconducting coil through an adhesive resin layer applied to the surface of the superconducting coil.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 2 is a structural sectional view of the composite sheet used in the present invention. In the figure, a composite sheet 11 is a polyimide film 6 whose surface has been roughened by sandblasting or the like.
and a glass-reinforced plastic sheet 7 are firmly bonded, for example, with an epoxy resin adhesive layer 8 to form a composite insulating sheet, and a heat-sensitive adhesive film 9 is provided on at least one surface of the composite insulating sheet.
For example, it is applied by a transfer method, etc., and heat-sensitive adhesive 1
An anti-adhesion sheet 10 is attached to the surface of x9, which is removed when the composite sheet is used. The thickness of the polyimide film that mainly maintains the withstand voltage of the composite sheet 11 configured in this way can be selected in the range of 0.01 to 0.5 mm, and the thickness of the polyimide film that mainly maintains the withstand voltage can be selected from the range of 0.01 to 0.5 mm. Glass-reinforced plastic sheets, whose main purpose is to improve the adhesive properties of the sheet, are made by impregnating and curing a thin glass cloth with, for example, epoxy varnish, and it is suitable that the thickness is slightly thinner than that of polyimide film. ing.

The composite sheet constructed in this manner has appropriate flexibility, high voltage strength, and mechanical strength. The heat-sensitive adhesive film has a particularly important function in forming the insulating layer. That is, the heat-sensitive adhesive H9 is made of, for example, a semi-cured epoxy resin, and the degree of semi-curing is such that it has a moderate adhesive strength at room temperature, and when it is attached to, for example, a cylindrical cooling body, it maintains its state and is easily peeled off. It is semi-cured so that when pressure is applied to the adhesive layer through the coil, it has the function of forming a passage between the bonded surface and the remaining air to escape. The state of can be determined.

Moreover, when heated to a predetermined temperature, it melts and becomes fluid, and the excess adhesive resin containing air bubbles flows out of the insulating layer, resulting in an adhesive layer that does not contain any voids or air bubbles when heated and cured. A material having melting temperature characteristics and curing temperature characteristics such as those to be formed is used.

FIG. 3 is a schematic sectional view of an internally wound superconducting electromagnetic coil for explaining the manufacturing method of the present invention, and FIG. 4 is a partially enlarged view of the superconducting electromagnetic coil.

In FIG. 1, first, two layers of the composite sheet 11 configured as shown in FIG. The layer 30 and the superconducting coil 4 are fixed to each other via the adhesive resin layer 12 applied to the surface of the composite insulating layer 30 or the superconducting coil 4.

The adhesive resin layer 12 may be made of either a heat-cured resin or a room-temperature cured resin, and the heat-curing temperature of the heat-sensitive adhesive film 9 in the composite sheet 11 can be appropriately selected depending on the type of heat-sensitive adhesive. 9 and adhesive resin layer 12
The curing method may be either simultaneous heating curing or heating curing of the thermosensitive adhesive film 9 in advance and then heating or room temperature curing of the adhesive resin layer 12.

As shown in FIG. 4, the composite insulating layer 30 is made by abutting a plurality of composite sheets each having a width of, for example, 0.5 meters, so that the ends of adjacent sheets do not overlap each other, and forming the first layer. The abutting portions 11A and the abutting portions 11B of the second layer are attached so as to extend in the axial direction of the coil cylinder while being shifted in number and position in the circumferential direction of the coil cylinder so that they do not overlap. The composite insulating layer 30 is not limited to the above-mentioned two-layer configuration, and the sheets may be overlapped along the axial direction at multiple locations in the circumferential direction without providing the abutting portion, or It is also possible to wrap the composite sheet in a spiral manner in the circumferential direction.

Now, after applying an adhesive of an appropriate viscosity to the surface of the composite insulating layer 30 to form the adhesive resin layer 12, force is applied to the superconducting wire in the tangential direction of the cylinder so that a pressing force acts on the composite insulating layer 30. To explain in more detail, taking as an example the case where the coil 4 is formed by winding the thermosensitive adhesive film 9 and the adhesive resin layer 12 at the same time, the adhesive resin layer 12 plays the role of a lubricant. The superconducting wire can be wound more tightly around the composite insulating layer 30, and even if a distributed load is applied to the coil 4 in the axial direction, the composite insulating layer 30 will not be damaged due to the lubricating action. A predetermined surface pressure can be applied evenly between each winding of the coil 4. Next, when a radial pressing force is applied to the insulating layer through the coil 4, the adhesive of the adhesive resin layer 12 fills the gap between the coils and the coil can be firmly fixed.

The heat-sensitive adhesive layer 9 (see FIG. 2) in a semi-cured state gradually comes into close contact with the surface to be bonded by the pressing force, and at this time, residual air present between the heat-sensitive adhesive layer 9 and the surface to be bonded is expelled. At this time, a small gap extending in the axial direction of the coil between the abutted portions 11A and IIB of the sheets becomes a passage for the remaining air, and has the advantage of making it easier to expel the remaining air. Next, when the whole is placed in a heat-curing furnace and gradually heated to a predetermined temperature, the heat-sensitive adhesive film 9 flows when the melting temperature of the heat-sensitive adhesive is reached, and the excess heat-sensitive adhesive containing residual air is generated. At the same time, the adhesive flows out to the outside through the abutting portions 11A, IIB, etc., and the gap between the abutting portions is filled with the flowing heat-sensitive adhesive. Therefore, when the adhesive resin is heated and cured, there are few voids or voids in the resulting insulating layer, and therefore a superconducting electromagnetic coil with high insulation performance and heat transfer performance, and which is strongly integrated can be obtained.

According to the inventors' experimental studies, an insulating model with a thickness of 0.5 mm was made using the configuration shown in Figure 4 and the manufacturing method described above, and the breakdown voltage was calculated to obtain a value of 70 KV. . This value is more than twice the breakdown voltage achieved for a 1 mm thick insulation model using a conventional method using glass-reinforced plastic laminates, and it is clear that the thickness of the insulation layer can be significantly reduced compared to the conventional method. Became. The adhesive shear strength of the two was also compared, and the values were almost the same, approximately 3 kg/xi (at room temperature).

Note that the thermal expansion coefficient of the composite sheet constructed as shown in Figure 2 is approximately equal to that of aluminum over a wide temperature range, so when the heat absorber 2 and the protective conductor of the superconducting wire are constructed of aluminum, In this case, there is less thermal stress caused by cooling/heating cycles, and the adhesive strength of the insulating layer can be stably maintained even when the insulating layer is cooled to an extremely low temperature.

Although the above explanation was given only for the inner-wound superconducting electromagnetic coil, it is clear from the above description that it is also applicable to the outer-wound superconducting electromagnetic coil. Furthermore, this invention can also be applied to conductive magnet coils in which a superconducting coil is fixed to the circumferential surface of a cylindrical cooling body via an insulating layer. FIG. 5 shows a cross-sectional view of a pancake-shaped superconducting electromagnetic coil, and the same parts as in FIGS. 3 and 4 are denoted by the same symbols and explanations thereof will be omitted. In the case of a pancake shape or a saddle shape, it is clear that similar effects can be obtained by applying the present invention from the above description, although the coil winding work is slightly more necessary.

〔Effect of the invention〕

The present invention provides a method for manufacturing a superconducting electromagnetic coil in which a superconducting coil is fixed on the surface of a cooling body through an insulating layer. A composite insulating layer is formed by laminating a composite sheet coated with a heat-sensitive adhesive film that does not contain air bubbles on at least one surface of the laminate, and the composite insulating layer and a superconducting coil are further bonded together to form a composite insulating layer or a superconducting coil. It was rubbed so that it would be fixed through the adhesive resin layer applied to the surface.

As a result, first of all, by selecting a glass-reinforced plastic laminate due to the high insulation strength of the composite insulating layer, it becomes easier to attach it to the cooling body, saving labor. By almost completely discharging and releasing the adhesive, an adhesive layer is formed with fewer voids and bubbles that cannot be obtained with the conventional method of applying an adhesive and forming an insulating layer, resulting in improved cooling performance and adhesive strength. It is possible to obtain a high insulation layer. Furthermore, the composite sheet is constructed so that the easily damaged polyimide film is protected by a mechanically strong glass-reinforced plastic sheet, and an adhesive resin layer is interposed between the composite insulating layer and the superconducting coil during winding and By improving the slippage between the two during pressure tightening, damage to the composite insulating layer can be prevented, and the coil tightening force can be applied effectively. Furthermore, despite the structure of the insulating layer, which relies mainly on polyimide film for its voltage resistance,
Since the glass-reinforced plastic layer functions as an aggregate, its coefficient of thermal expansion is close to that of aluminum, generating less thermal stress even at extremely low temperatures, and the adhesive strength of the insulating layer can be stably maintained.

By combining the above effects, insulation performance and cooling performance are improved.

It is possible to provide a method for manufacturing a superconducting electromagnetic coil that has excellent adhesive strength, cryogenic resistance performance, and heat cycle resistance performance, and requires less insulation space.

[Brief explanation of drawings]

Figure 1 is a schematic cross-sectional view of an inner-wound superconducting electromagnetic coil, Figure 2
The figure is a cross-sectional view of the composite sheet used in the present invention, Figure 3 is a plan view of a superconducting electromagnetic coil explaining the manufacturing method of the present invention, Figure 4 is a partially enlarged cross-sectional view of Figure 3, and Figure 5 is a diagram of the present invention. FIG. 3 is a cross-sectional view of a pancake-shaped superconducting electromagnetic coil to which the invention is applied. l...Superconducting electromagnetic coil, 2...Cooling body, 3...
・Insulating layer, 4... Superconducting coil, 5... Cooling pipe, 6
... Polyimide film layer, 7 ... Glass reinforced plastic layer, 8 ... Adhesive layer, 9 ... Heat-sensitive adhesive film,
11... Composite sheet, 12... Adhesive resin layer, IIA
, IIB...butt portion, 30... composite insulating layer. Sai 1 Continuation of Z drawing page 1 0 Inventor Ike 1) Yuu @ Inventor Makoto Kudo @ Inventor Tokimitsu Fujio @ Inventor Haruo Ono [Ai] Inventor Yama 1) Mitsuru Tokyo Parts Industry Ward Futaba 2-9-15 Furukawa Electric Co., Ltd. Central Research Laboratory Tokyo Parts Ward Futaba 2-9-15 Furukawa Electric Co., Ltd.

Claims (1)

[Claims] 1) In a method for manufacturing a superconducting electromagnetic coil in which a superconducting coil is fixed on a cooling body surface via an insulating layer, at least one surface of a laminate of a polyimide film and a glass-reinforced plastic sheet is heat-sensitive on the cooling body surface. A composite insulating layer is formed by pasting composite sheets coated with adhesive films, and the composite insulating layer and the superconducting coil are fixed via an adhesive resin layer applied to the surface of the composite insulating layer or the superconducting coil. A method for manufacturing a superconducting electromagnetic coil, characterized by: