JP2006120828A - Superconducting coil and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a superconducting coil effectively prevented from the generation of quenching in a superconducting line by reducing separation or breakage between a filler, for filling the gap between the superconducting line and an insulating sheet. <P>SOLUTION: The superconducting coil comprises a superconducting line 3 wound across a plurality of layers, insulating sheets 4, 5 interposed between respective layers of the superconducting line 3 and consisting of an electrically insulating resin sheet, and an adhesive resin 6 filled between the superconducting line 3 and the insulating sheets 4, 5. Easy adhesion treatment is applied on the surface of the insulating sheets 4, 5. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a superconducting coil having a structure in which a periphery of a superconducting wire wound over a plurality of layers is filled and fixed with an adhesive resin, and a method of manufacturing the same.

  In a conventional superconducting coil, while winding a superconducting wire over a plurality of layers around a winding frame, an insulating sheet is interposed between the superconducting wire and the winding frame, and between each layer of the superconducting wire, and the superconducting wire There is a configuration in which an insulating resin such as an epoxy resin adhesive is filled between the insulating sheets and integrated.

  Here, the insulating sheet described above prevents the superconducting wires overlapping in the radial direction from falling into the depressions between the wires and causing the winding state to become misaligned, and is sufficient between the layers of the superconducting wires and the winding frame. It is provided to ensure electrical insulation. As the insulating sheet in this case, conventionally, an electrically insulating resin sheet made of polyester, polyethylene, or the like, which is relatively inexpensive, has been used.

  The reason why the space between the superconducting wire and the insulating sheet is filled with the adhesive resin is to prevent so-called quenching, which is a phenomenon that the superconducting state of the superconducting wire is destroyed. That is, when the superconducting coil is cooled, a cooling stress is generated due to the difference in thermal contraction of the constituent members, and when the superconducting coil is excited, an electromagnetic stress is generated. At this time, if the superconducting wire easily moves due to these stresses, the superconducting wire locally becomes above the critical temperature and quenches due to the heat generated by the mechanical movement, so the superconducting wire does not move easily. It is firmly fixed with an adhesive resin.

  On the other hand, in the prior art, instead of filling the space between the superconducting wire and the insulating sheet with an adhesive resin, an adhesive film is applied to the surface of the superconducting wire, and the superconducting wire is bonded to the insulating sheet or the winding frame by this adhesive film. There has also been proposed one that suppresses the occurrence of quenching by suppressing the movement of the superconducting wire by fixing (see, for example, Patent Document 1).

JP-A-10-125527 (2-3 pages, FIG. 1)

  By the way, in the conventional configuration in which the space between the superconducting wire and the insulating sheet is filled with the adhesive resin, even if the adhesive strength at the interface between the superconducting wire and the filler is large, the space between the insulating sheet and the adhesive resin is large. The adhesive strength of is small. Therefore, when the above-described cooling stress or electromagnetic stress occurs, the interface between the two peels off or cracks occur, and the heat generated at that time is transmitted to the surface of the superconducting wire close to the insulating sheet, and the superconducting wire is easily quenched. There's a problem.

  Moreover, although the thing of the prior art described in patent document 1 has a cooling passage between the superconducting wire and the insulating sheet, the cooling capacity for the superconducting wire is improved, but the superconducting wire and the insulating sheet The fixing strength of the entire superconducting coil is weak as much as the gap is not filled with the adhesive resin, and the superconducting wire easily moves and quenches easily when cooling stress or electromagnetic stress occurs. In addition, even if an adhesive coating is applied to the surface of the superconducting wire, the adhesive strength between the insulating sheet and the insulating sheet is not high, so when cooling stress or electromagnetic stress occurs, the adhesive coating and the insulating sheet The interface between them is easily peeled off. For this reason, quenching of the superconducting wire cannot be sufficiently suppressed only by securing a cooling passage around the superconducting wire and improving the cooling ability.

  The present invention has been made in order to solve the above-described problems. In the case where the space between the superconducting wire and the insulating sheet is filled with an adhesive resin, the adhesive strength between the insulating sheet and the adhesive resin is significantly larger than the conventional one. Therefore, the superconducting coil is manufactured so that the superconducting wire does not move easily even when cooling stress or electromagnetic stress is generated, it is difficult to cause quenching, and it can be realized at a relatively low cost. It aims to provide a method.

  In order to achieve the above object, the present invention provides a superconducting wire wound over a plurality of layers, an insulating sheet made of an electrically insulating resin sheet interposed between the layers of the superconducting wire, and the superconducting wire. In a superconducting coil including an adhesive resin filled between an insulating sheet and the insulating sheet, the surface of the insulating sheet is subjected to a surface treatment for improving adhesion (that is, easy adhesion treatment).

  According to the present invention, since the insulating sheet subjected to the easy adhesion treatment is interposed between the layers of the superconducting wire, when the space between the superconducting wire and the insulating sheet is filled with the adhesive resin, the insulating sheet is bonded. The adhesive strength between the functional resins can be significantly increased as compared with the conventional case. For this reason, even when cooling stress or electromagnetic stress is generated, peeling or cracking at the interface between the adhesive resin and the insulating sheet does not occur. Therefore, heat is not transmitted to the surface of the superconducting wire close to the insulating sheet, and quenching of the superconducting wire can be sufficiently suppressed.

Embodiment 1 FIG.
1 is a cross-sectional view of a superconducting coil according to Embodiment 1 of the present invention, and FIG. 2 is an enlarged cross-sectional view showing a part of the superconducting coil.

  The superconducting coil 1 according to the first embodiment includes a thread-wound cylindrical winding frame 2 made of stainless steel or the like. And the superconducting wire 3 is wound by the outer periphery of the trunk | drum of this winding frame 2 over several layers. As the superconducting wire 3 in this case, for example, a wire such as NbTi, Nb3Sn or the like is used, and an insulating coating (not shown) is formed on the surface thereof in advance. Insulating sheets 4 and 5 are interposed between the winding frame 2 and the superconducting wire 3 and between each layer of the superconducting wire 3. Further, an adhesive resin 6 such as an epoxy resin adhesive is filled between the superconducting wire 3 and the insulating sheets 4 and 5.

  As a feature of Embodiment 1, the insulating sheets 4 and 5 are made of a resin sheet made of polyolefin resin such as polyethylene, polyester, polyethylene terephthalate (PET) or the like and having a thickness of about several hundred μm. The both surfaces are subjected to easy adhesion treatment for improving adhesion. As a specific easy-adhesion process, in the first embodiment, a corona discharge process is performed in which a resin sheet is passed through an electric field where a corona discharge occurs to modify the surface molecules to have affinity with other resins. ing.

  As described above, the superconducting coil 1 of the first embodiment has the insulating sheets 4 and 5 subjected to the easy adhesion treatment between the winding frame 2 and the superconducting wire 3 and between each layer of the superconducting wire 3. Therefore, when the gap between the superconducting wire 3 and the insulating sheets 4 and 5 is filled with the adhesive resin 6, the adhesive strength between the insulating sheets 4 and 5 and the adhesive resin 6 can be significantly increased as compared with the prior art. . Therefore, even when cooling stress or electromagnetic stress is generated, peeling or cracking at the interface between the adhesive resin 6 and the insulating sheets 4 and 5 does not occur, so that the surface of the superconducting wire 3 close to the insulating sheets 4 and 5 is not formed. Heat generation is not transmitted, and quenching of the superconducting wire 3 can be sufficiently suppressed.

  When the superconducting coil 1 having this configuration is manufactured, first, the insulating sheet 5 that has been subjected to the easy adhesion treatment is applied to the surface of the winding frame 2 on which the superconducting wire is wound. In the case of the first embodiment, the insulating sheet 5 is subjected to easy adhesion treatment on both surfaces, but the surface facing the winding frame 2 may not necessarily be subjected to easy adhesion treatment.

  Next, the superconducting wire 3 is wound over a plurality of layers around the outer periphery of the body 2 of the winding frame 2 on which the insulating sheet 5 has been applied. At that time, the insulating sheet 4 that has been subjected to easy adhesion treatment on both surfaces is provided between the layers of the superconducting wire 3. Intervene. Thereafter, an adhesive resin 6 such as an epoxy resin adhesive is filled in the gap between the superconducting wire 3 and the insulating sheets 4 and 5 by, for example, a vacuum impregnation method and cured.

  According to the method of manufacturing the superconducting coil 1, the manufacturing procedure is basically the same as the conventional one, except that the insulating sheets 4 and 5 subjected to the easy adhesion treatment are used. Generation of quenching can be effectively prevented, and a complicated method such as welding the insulating sheets 4 and 5 and the adhesive resin 6 is not required. Therefore, the superconducting coil 1 having desired characteristics can be manufactured at a relatively low cost.

Embodiment 2. FIG.
FIG. 3 is a cross-sectional view showing a part of the superconducting coil in the second embodiment, and the same reference numerals are given to the components corresponding to those in the first embodiment shown in FIGS.

  The superconducting coil according to the second embodiment is characterized in that the insulating sheet 5 is disposed between the winding 2 holding the superconducting wire 3 and the superconducting wire 3 wound around the superconducting wire 3 from the superconducting wire 3 side toward the winding frame 2 side. And the spacing sheet 7 having lower adhesive strength than the insulating sheet 5 is sequentially interposed.

  In the case of Embodiment 2, both surfaces of the insulating sheet 5 are subjected to easy adhesion treatment, but the surface on the side facing the winding frame 2 may not necessarily be subjected to easy adhesion treatment. In addition, as the separation sheet 7, a resin sheet that is the same material as the insulating sheet 5 and that has not been subjected to easy adhesion treatment can be applied. In this case, the insulating sheet 5 and the separation sheet 7 are made of the same material, which is easy to handle and convenient for cost reduction. In addition, as the separation sheet 7, a resin sheet such as Teflon (registered trademark) having low adhesiveness can be used.

  As described above, in the second embodiment, since the separation sheet 7 is interposed between the winding frame 7 and the insulating sheet 5, even if cooling stress or electromagnetic stress is applied to the superconducting wire 3, it is separated from the winding frame 7. Sliding easily occurs between the sheet 7 and the strain stress is released. For this reason, the superconducting wire 3 is not mechanically moved to generate heat. In addition, since heat generated by releasing the stress at that time is insulated by the separation sheet 7 and the insulating sheet 5, the heat is not transmitted to the surface of the superconducting wire 3. Therefore, quenching of the superconducting wire can be further suppressed than in the case of the first embodiment.

  Since other configurations and operational effects are the same as those in the first embodiment, detailed description thereof is omitted here. Also, the manufacturing method is the same as in the case of the first embodiment except that the separation sheet 7 is applied in advance before the insulating sheet 5 subjected to the easy adhesion treatment is applied to the outer periphery of the winding frame 2. Therefore, detailed description is omitted.

  In the first and second embodiments, the case where the corona discharge treatment is performed as the easy adhesion treatment of the insulating sheets 4 and 5 has been described. However, the easy adhesion treatment is limited to such a corona discharge treatment. Rather, for example, ultraviolet irradiation treatment that modifies the surface of the resin sheet by irradiating it with ultraviolet rays, or the surface of the resin sheet is blown with a gas flame while moving the resin sheet to bond oxygen or double bonds to surface molecules. It is possible to apply a frame process that causes the resin sheet to move, or a blast process that roughens the surface by irradiating the surface with fine particles while moving the resin sheet. Furthermore, it is also possible to combine a solvent treatment that removes impurities by washing the surface of the resin sheet in advance with a chlorine-based solvent or the like as a pretreatment for each treatment described above.

  Next, an experiment for confirming the bonding strength of the insulating sheet subjected to the easy-adhesion treatment used in the first and second embodiments and the quench suppression effect when the superconducting coil is configured using the insulating sheet was performed. Examples will be described.

Example 1.
This Example 1 investigated the adhesive strength of the insulating sheet which gave the corona discharge process as an easily bonding process.

As a sample to be measured, a sample in which the opposing surfaces of a pair of insulating sheets subjected to corona discharge treatment as an easy adhesion treatment were bonded with an epoxy resin adhesive to be an adhesive resin was used. In this case, the insulating sheet has a thickness of 100 μm and a width of 25 μm. In order to measure the adhesion strength of this sample, a so-called peeling test was performed in which a pair of insulating sheets adhered to each other was peeled off from each other. Table 1 shows the results of carrying out this peeling test and measuring the adhesive strength. For comparison, Table 1 also shows the results of performing a peeling test on an insulating sheet that has not been subjected to an easy adhesion treatment.

  As is apparent from Table 1, the insulating sheet made of polyester or polyethylene terephthalate that has not been subjected to easy adhesion treatment has a low adhesive strength of 4 N or less, whereas polyethylene terephthalate that has undergone easy adhesion treatment has a low value. It is understood that the resulting insulating sheet has an adhesive strength of 15 N or higher, and the adhesive strength is improved by a factor of 4 or more compared to the non-treated sheet.

Example 2
This Example 2 is an experiment for confirming the quench suppression effect in the case where a superconducting coil is configured using an insulating sheet subjected to easy adhesion treatment.

  Since the sample to be measured is too large when using an actual superconducting coil, a box-shaped container having a winding vertical width of 40 mm, a winding thickness of 30 mm, and a depth of 100 mm is used as a simulation. A superconducting wire with an outer diameter of 1.4 mm is laminated and arranged in a container, and after interposing an insulating sheet between each layer, an epoxy resin adhesive is vacuum impregnated between the superconducting wire and the insulating sheet. Filled and cured. Then, this sample was cooled with liquid nitrogen, and the presence or absence of peeling or cracking of the insulating sheet interface inside the sample due to cooling stress was measured by acoustic emission (AE), and the change with time was examined. The result is shown in FIG.

  Here, the same figure (a) shows the measurement result of the sample applicable to this invention (henceforth this invention applicable sample) using the insulating sheet which consists of a polyethylene terephthalate which performed the corona discharge process, and the same figure (b). For comparison, each shows a measurement result of a sample corresponding to the conventional technique using an insulating sheet made of polyester not subjected to easy adhesion treatment (hereinafter referred to as a conventional corresponding sample).

  In the conventional sample shown in FIG. 4B, the AE generation count during initial cooling is 1330, whereas in the sample corresponding to the present invention shown in FIG. 4A, AE generation during initial cooling occurs. The count number is 245 counts, and the AE occurrence frequency of the sample corresponding to the present invention is 1/5 or less than that of the conventional sample. Further, in the conventional sample, 19 AEs occurred during the cooling holding period of about 5 days, whereas in the sample of the present invention, AE did not occur during the cooling holding period of about 13 days. It can be seen that no peeling or cracking occurs between the insulating sheet and the filler during the holding period.

  As described above, by using the insulating sheets 4 and 5 in which the superconducting coil is subjected to the easy adhesion treatment, the adhesive strength at the interface with the adhesive resin 6 is increased, so that peeling and cracking are less likely to occur. It is understood that the occurrence of quenching can be effectively prevented.

  Conventionally, a polyimide amide resin is commercially available as a resin sheet. Although this polyimide amide resin can obtain a relatively large adhesive strength with an adhesive resin such as an epoxy resin adhesive without particularly easy adhesion treatment, it is used in the first and second embodiments. Since it is much more expensive (price difference of about one digit) than the conventional polyolefin resin, it is not practically appropriate to use such a polyimide amide resin. When a polyolefin resin (for example, PET) is used as the material of the insulating sheets 4 and 5 as in the first and second embodiments, the price is only increased by several tens of percent even if the easy adhesion treatment is performed, so that it is practical. It is extremely useful.

It is sectional drawing which shows the superconducting coil in Embodiment 1 of this invention. It is sectional drawing which expands and shows a part of superconducting coil in Embodiment 1 of this invention. It is sectional drawing which shows a part of superconducting coil in Embodiment 2 of this invention. In the case where a superconducting coil is configured using an insulating sheet that has been subjected to easy adhesion treatment and an insulating sheet that has not been subjected to easy adhesion treatment, the temporal change in the frequency of occurrence of peeling and cracking of the insulating sheet was measured by acoustic emission (AE). It is a characteristic view which shows a result.

Explanation of symbols

  1 superconducting coil, 2 reel, 3 superconducting wire, 4,5 insulation sheet, 6 adhesive resin, 7 spacing sheet.

Claims (4)

A superconducting wire wound over a plurality of layers, an insulating sheet made of an electrically insulating resin sheet interposed between the layers of the superconducting wire, and an adhesive resin filled between the superconducting wire and the insulating sheet; A superconducting coil comprising the insulating sheet, wherein the insulating sheet is subjected to easy adhesion treatment on the surface thereof. A winding frame for holding the superconducting wire is provided, and between the superconducting wire and the winding frame, the insulating sheet and a separation sheet having a lower adhesive strength than the insulating sheet are sequentially provided from the superconducting wire side to the winding frame side. The superconducting coil according to claim 1, wherein the superconducting coil is interposed. The superconducting coil according to claim 1 or 2, wherein the resin sheet constituting the insulating sheet is a polyolefin-based material. After constructing an insulating sheet with easy adhesion treatment on the winding frame, the superconducting wire is wound on the insulating sheet over a plurality of layers, and the insulating sheet is subjected to easy adhesion treatment between the layers of the superconducting wire. A method of manufacturing a superconducting coil, wherein an adhesive resin is filled in a gap between the superconducting wire and the insulating sheet.

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