JP2008311526A - Superconductive coil, and quench prevention method of superconductive coil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a superconductive coil capable of preventing occurrence of a quench phenomenon without strongly constraining a superconductive wire. <P>SOLUTION: This super conductive coil is structured to be excited at an ultralow temperature, and provided with: a winding frame 10 including a cylindrical shaft part 11, and a pair of flange parts 12 and 13 extended in a radially-outer direction from both axial ends of the shaft part 11; a superconductive wire 20 spirally wound around the outer periphery of the shaft part 11, and impregnated with a resin in its wound state; and a reinforcing material 50 connected to both the pair of flange parts 12 and 13 at least at an ultralow temperature, and restraining the pair of flange parts 12 and 13 from coming close to each other by thermal contraction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a superconducting coil excited at a cryogenic temperature and a method for preventing quenching of a superconducting coil, and in particular, is configured by spirally winding a superconducting wire around a substantially cylindrical winding frame having flange portions at both axial ends. The present invention relates to a superconducting coil and a method for preventing quenching of a superconducting coil.

  Conventionally, a superconducting coil that generates a strong magnetic field spirally winds a superconducting wire around a winding frame having a cylindrical shaft portion and a flange portion extending radially outward from both axial ends of the shaft portion. And is excited by energization in a state of being cooled to a very low temperature (about 4.2 K or less).

  In such a superconducting coil in an excited state, an attempt is made to expand the superconducting wire (in this case, a collection of superconducting wires in a wound state) in the radial direction of the superconducting coil by the interaction between the energizing current and the magnetic field generated by itself. The hoop force that acts on the superconducting wire. Thereby, since the superconducting wire is slightly displaced, there is a disadvantage that frictional heat is generated at the displaced portion and a quench phenomenon may occur.

In order to solve the above inconvenience, for example, a technique as disclosed in Patent Document 1 has been proposed. In this patent document 1, the axial pressure (axial pressure) applied to the superconducting wire is increased to strongly restrain the superconducting wire, thereby preventing the superconducting wire from being displaced minutely and preventing the occurrence of the quench phenomenon. It is out.
JP-A-5-182819

  By the way, in a structure like the said patent document 1, in order to acquire sufficient quenching prevention effect, the big restraint force with respect to a superconducting wire is required. However, there are structural and technical limitations in the means for applying a large restraining force to such a superconducting wire. In addition, an excessively large restraining force is not preferable for a superconducting wire.

  The present invention has been made to solve the above-described problems, and provides a superconducting coil and a superconducting coil quench prevention method capable of preventing the occurrence of a quench phenomenon without strongly constraining the superconducting wire. The purpose is to provide.

  In achieving the above object, the inventors of the present application have conceived not to increase the restraining force on the superconducting wire but to suppress the restraining force. In other words, conventionally, it is possible to reduce the probability that the superconducting wire is displaced by a strong restraining force, but in the unlikely event that the superconducting wire is slightly displaced for some reason, the superconducting wire is accompanied by the displacement by the amount restrained by a large force. The frictional heat generated in the process increases and is likely to be quenched. On the other hand, if the restraining force on the superconducting wire is suppressed, the frictional heat generated at that time is small even if the superconducting wire is slightly displaced, and the quenching phenomenon starting from the minute displacement hardly occurs.

  The superconducting coil of the present invention made from such a viewpoint is a superconducting coil excited at a cryogenic temperature, and extends in a radially outward direction from a cylindrical shaft portion and both axial ends of the shaft portion. A winding frame including a pair of flange portions, a superconducting wire spirally wound around the outer periphery of the shaft portion and impregnated in the impregnated material in the wound state, and the pair of flange portions at least at an extremely low temperature And a reinforcing material that suppresses the pair of flange portions from approaching each other due to thermal contraction.

  In addition, the “connection” in the present invention is not only a state in which the flange portion and the reinforcing material are in direct contact with each other and exerting a force directly, but both exert forces indirectly through other members. Also includes state.

  In the superconducting coil of the present invention, as described above, the reinforcing material connected to the pair of flange portions is configured to suppress the pair of flange portions from approaching each other at an extremely low temperature. The axial pressure (axial pressure) applied to the superconducting wire by approaching each other can be reduced by the reinforcing material. As a result, the restraining force on the superconducting wire can be weakened, so that even if the superconducting wire is slightly displaced, the frictional heat generated at that time can be reduced, and a quenching phenomenon starting from the minute displacement of the superconducting wire occurs. Can be difficult. Therefore, it is possible to prevent the quench phenomenon from occurring without strongly restraining the superconducting wire.

  In addition, as described above, by using the superconducting wire impregnated in the impregnated material in the wound state, local displacement of the superconducting wire can be suppressed, and thus the superconducting wire is partially displaced slightly. The occurrence of a quenching phenomenon starting from can be suppressed in advance. Examples of the impregnating material include resin and water (ice).

  In the superconducting coil according to claim 1, preferably, the reinforcing material has a thermal contraction rate smaller than or equal to the thermal contraction rate of the winding frame (claim 2).

  If comprised in this way, at the time of cooling, a reinforcing material will not heat-shrink larger than a winding frame. When a reinforcing material having a thermal contraction rate equal to the thermal contraction rate of the reel is used, the amount of thermal contraction in the axial direction of the reinforcing member becomes equal to the thermal contraction amount in the axial direction of the reel. If a load is applied to the pair of flange portions in a state of separating them from each other at a normal temperature, the reinforcing material is stretched against the thermal contraction in the axial direction of the reel at an extremely low temperature. Can do. Thereby, since the force of the direction which mutually separates can be made to act on a pair of flange part, the approach of a pair of flange part can be suppressed under a cryogenic temperature by a reinforcing material.

  On the other hand, when a reinforcing material having a thermal contraction rate smaller than the thermal contraction rate of the reel is used, the axial thermal contraction amount of the reinforcing member is smaller than the axial thermal contraction amount of the reel. For this reason, for example, if the reinforcing material is connected to the pair of flange portions in a state of applying a load in the direction away from each other to the pair of flange portions at room temperature, the thermal contraction in the axial direction of the reel at an extremely low temperature. Since the reinforcing material can be sufficiently stretched, it is possible to sufficiently apply a force in a direction away from each other to the pair of flange portions. Thereby, the approach of a pair of flange parts can be fully suppressed under a cryogenic temperature by a reinforcing material.

  Further, when a reinforcing material having a thermal contraction rate smaller than the thermal contraction rate of the reel is used, for example, the reinforcing material is connected to the flange part in a state where no load is applied to the pair of flange parts at room temperature. However, since the reinforcing material can be stretched against the thermal contraction in the axial direction of the reel at an extremely low temperature, forces in a direction away from each other can be applied to the pair of flange portions. Thereby, the approach of a pair of flange parts can be easily suppressed under the cryogenic temperature by the reinforcing material.

  The superconducting coil according to claim 1 or 2, wherein a support member is provided on the outer side in the axial direction of the flange portion so as to project radially outward from at least one of the flange portions, and supports the winding frame. The flange portion may be fixed to the support member, and the reinforcing member may be connected to the support member at a radially outer position of the flange portion.

  When configured in this way, the support member provided on the outer side in the axial direction of the reel is effectively used to support the reel, and the pair of flange portions are prevented from approaching each other at an extremely low temperature. Can do.

  The superconducting coil according to any one of claims 1 to 3, wherein the flange portion includes an outer edge portion located on a radially outer side of a winding region of the superconducting wire, and the reinforcing member includes the outer edge portion. It may be configured to be coupled to the inner side in the axial direction (claim 4).

  When comprised in this way, a reinforcement material can press a flange part directly from radial inside, and the force of a separation direction can be made to act on a flange part under cryogenic temperature. Thereby, it becomes possible to suppress the approach of flange parts by a simple structure, without requiring the fixing tool for fixing a flange part and a reinforcing material separately.

  In the superconducting coil according to any one of claims 1 to 4, preferably, the reinforcing member is formed in a cylindrical shape, and the flange portion has a posture in which an axial direction thereof coincides with an axial direction of the winding frame. (Claim 5).

  If comprised in this way, since the intensity | strength with respect to the compressive force of the axial direction of a cylindrical reinforcement material is higher compared with the case where a plate-shaped reinforcement material is connected with a pair of flange part, for example, a cylindrical reinforcement material Thus, the approach of the pair of flange portions can be more efficiently suppressed at an extremely low temperature.

  Further, the quenching prevention method for a superconducting coil according to the present invention is a quenching prevention method for a superconducting coil excited at a cryogenic temperature, and extends from a cylindrical shaft portion and both axial ends of the shaft portion radially outward. A step of preparing a winding frame including a pair of flange portions to be provided; a step of spirally winding a superconducting wire around the outer periphery of the shaft; and the superconducting wire wound around the shaft as an impregnating material. A step of impregnating; a step of forming a coil body by connecting a reinforcing material to the pair of flange portions; and cooling the coil body to a cryogenic temperature, and the pair of flange portions by thermal contraction at a cryogenic temperature. And a step of suppressing the approach to each other by the reinforcing material.

  In this superconducting coil quench prevention method, as described above, the reinforcing material connected to the pair of flange portions suppresses the pair of flange portions from approaching each other at an extremely low temperature. The axial pressure (axial pressure) applied to the superconducting wire when the parts approach each other can be reduced by the reinforcing material. As a result, the restraining force on the superconducting wire can be weakened, so that even if the superconducting wire is slightly displaced, the frictional heat generated at that time can be reduced, and a quenching phenomenon starting from the minute displacement of the superconducting wire occurs. Can be difficult. Therefore, it is possible to prevent the quench phenomenon from occurring without strongly restraining the superconducting wire.

  Further, as described above, by impregnating the impregnated material with the wound superconducting wire, local displacement of the superconducting wire can be suppressed, so that the superconducting wire is partially displaced slightly. The occurrence of the quenching phenomenon can be suppressed in advance.

  According to the superconducting coil and the method for preventing quenching of a superconducting coil according to the present invention, the reinforcing material connected to the pair of flange portions suppresses the pair of flange portions from approaching each other at an extremely low temperature. The axial pressure (axial pressure) applied to the superconducting wire when the flange portions of each other approach each other can be reduced by the reinforcing material. As a result, the restraining force on the superconducting wire can be weakened, so that even if the superconducting wire is slightly displaced, the frictional heat generated at that time can be reduced, and a quenching phenomenon starting from the minute displacement of the superconducting wire occurs. Can be difficult. Therefore, it is possible to prevent the quench phenomenon from occurring without strongly restraining the superconducting wire.

  In addition, by impregnating the impregnated material with the wound superconducting wire, local displacement of the superconducting wire can be suppressed, so that the quench phenomenon starting from the minute displacement of the superconducting wire partially occurs. Occurrence can be suppressed in advance.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a front sectional view showing the overall configuration of the superconducting coil according to the first embodiment of the present invention, and FIG. 2 is a top view of the superconducting coil shown in FIG. FIG. 3 is a front sectional view showing a state during the assembly of the superconducting coil shown in FIG. First, with reference to FIGS. 1-3, the whole structure of the superconducting coil by 1st Embodiment of this invention is demonstrated.

  The superconducting coil of this embodiment is provided in a superconducting magnet apparatus such as an MRI apparatus or NMR apparatus, and is configured to be excited by energization in a state cooled to a very low temperature (about 4.2 K or less). Has been. As shown in FIG. 1, the superconducting coil includes a winding frame 10 made of aluminum, a superconducting wire 20 made of NbTi, a base plate 30 and a top plate 40 made of stainless steel (SUS). The base plate 30 and the top plate 40 correspond to the “support member” of the present invention.

  The reel 10 includes a cylindrical shaft portion 11 and a pair of flange portions 12 and 13 provided so as to extend radially outward from both axial ends of the shaft portion 11. The shaft portion 11 is a portion around which the superconducting wire 20 is wound. A magnetic field region (not shown) formed by the superconducting coil is located on the inner diameter side of the shaft portion 11. In the flange portions 12 and 13, end portions on the inner diameter side of the flange portions 12 and 13 are connected to an axial end portion of the shaft portion 11, respectively. These flange portions 12 and 13 have a function of regulating the end position in the axial direction of the superconducting wire 20 wound around the shaft portion 11.

The superconducting wire 20 is wound around the outer periphery of the shaft portion 11 in a spiral shape (or a solenoid shape). Further, the superconducting wire 20 is configured to be impregnated with an impregnating material such as resin or water (ice) in a state of being wound around the shaft portion 11, and thereby the local area of the superconducting wire 20 in a wound state. Is suppressed. In addition, the superconducting wire 20 of this embodiment has shown the aggregate | assembly of the superconducting wire in a winding state. Further, examples of the material of the superconducting wire 20 include Nb ₃ Sn and Nb ₃ Al other than the NbTi.

  The base plate 30 and the top plate 40 are for supporting the winding frame 10. The constituent materials of these plates 30 and 40 may be materials other than the stainless steel as long as they are difficult to deform. The base plate 30 is formed in a flat plate shape, and is disposed on one end (the lower end in FIG. 1) in the axial direction of the reel 10 so as to protrude outward in the radial direction from the outer peripheral edge of the flange portion 13. The flange portion 13 is fixed to the base plate 30 with a plurality of bolts 61 in a state where the lower surface thereof is in surface contact with the upper surface of the base plate 30. Further, the flange portion 13 is fixed to the base plate 30 by a plurality of bolts 61 at a substantially intermediate portion in the radial direction.

  The top plate 40 is formed in a flat plate shape, and is disposed on the other end (upper end in FIG. 1) in the axial direction of the reel 10 in a posture of projecting radially outward from the outer peripheral edge of the flange portion 12. Yes. The flange portion 12 is fixed to the top plate 40 by a plurality of sets of bolts 62 and nuts 63 at a substantially intermediate portion in the radial direction. The bolt 62 is fixedly embedded in the flange portion 12 and is inserted through a through hole (not shown) of the top plate 40. A nut 63 is screwed into a projecting tip of the bolt 62 above the top plate 40 and tightened. By rotating in the direction, the flange portion 12 and the top plate 40 are configured to be fixed.

  In the present embodiment, the attachment of the flange portion 13 to the base plate 30 is performed prior to the attachment of the flange portion 12 to the top plate 40.

  The pair of plates 30 and 40 are formed with holes 31 and 41 at positions corresponding to the shaft 11 respectively. These holes 31 and 41 function as openings for the magnetic field region on the inner diameter side of the shaft 11.

  Here, the superconducting coil of 1st Embodiment is provided with the reinforcing material 50 which consists of stainless steel (SUS), as shown in FIG. 1 and FIG. The reinforcing member 50 is formed in a cylindrical shape having an inner diameter larger than the outer diameter of the flange portions 12 and 13, and the pair of plates 30 in a posture in which the axial direction of the reinforcing member 50 coincides with the axial direction of the winding frame 10. , 40 is interposed. Specifically, the upper end portion 51 of the reinforcing member 50 is fixed to the top plate 40 with bolts 64, and the lower end portion 52 of the reinforcing member 50 is fixed to the base plate 30 with bolts 65. In addition, you may attach the reinforcing material 50 to the plates 30 and 40 by welding etc., for example.

  Further, as shown in FIG. 3, the reinforcing member 50 is dimensioned so that its axial length is longer than the axial length of the winding frame 10 before the superconducting coil is assembled. For this reason, a predetermined gap (see FIG. 3) is formed between the flange portion 12 and the top plate 40 at a stage before bolting when the superconducting coil is assembled. The gap is gradually narrowed as the nut 63 is tightened, and finally the upper surface of the flange portion 12 and the lower surface of the top plate 40 are in surface contact as shown in FIG. Yes. Then, in the state after the bolt tightening, the reinforcement is performed so that the distance between the pair of flange portions 12 and 13 is larger than that before the bolt tightening, that is, the flange portions 12 and 13 are loaded in a direction away from each other. A material 50 is attached to the plates 30 and 40. As described above, in the present embodiment, in the assembled state of the superconducting coil, an axial compressive force is already applied to the reinforcing member 50 and an axially outward tensile force is applied to the pair of flange portions 12 and 13. The reinforcing member 50 is configured such that its axial thermal contraction rate is smaller than the axial thermal contraction rate of the winding frame 10. Thus, the pair of flange portions 12 and 13 function to sufficiently suppress the approach of each other due to thermal contraction at a cryogenic temperature.

  In addition, the structure of this embodiment mentioned above is a case where the reinforcing material 50 which consists of a material with a thermal contraction rate smaller than the thermal contraction rate of the winding frame 10 is used, and axial pressure is only in the difference of both thermal contraction rates. This is a configuration that is preferably employed when it is determined that the effect of reducing the size cannot be sufficiently obtained.

  On the other hand, when the reinforcing material 50 made of a material having a thermal contraction rate smaller than the thermal contraction rate of the winding frame 10 is used, the effect of reducing the axial pressure only by the difference between the two thermal contraction rates is sufficient. If it is determined that the configuration is obtained, a configuration different from the configuration of the above embodiment is employed. That is, the dimension is designed so that the axial length of the reinforcing member 50 is substantially equal to the axial length of the winding frame 10, and at the stage before the bolting at the time of assembling the superconducting coil, the flange portion 12 and the top plate 40 A configuration is adopted in which the reinforcing member 50 is attached to the plates 30 and 40 in a state where no load is applied to the pair of flange portions 12 and 13 in the assembled state of the superconducting coil so that a predetermined gap is not formed between them. Is done.

  Moreover, when the reinforcing material 50 made of a material having a thermal contraction rate equivalent to the thermal contraction rate of the winding frame 10 is used, it is essential to adopt the configuration of the above embodiment.

  As shown in FIG. 2, the flange portion 12 has a plurality of bolts 62 and nuts 63 arranged on a concentric circle centered on the axis R of the winding frame 10 and symmetrical with respect to the axis R. As shown, the top plate 40 is fixed. Although not shown, the bolt 61 has the same configuration as described above. Furthermore, in the present embodiment, the radially inner bolt 62 and the nut 63 and the radially outer bolt 64 are configured to be arranged on the same line passing through the axis R. Although not shown, the bolts 61 and 65 have the same configuration. For these reasons, the load in the separation direction applied to the flange portions 12 and 13 due to the reinforcement member 50 striking against the thermal contraction in the axial direction of the winding frame 10 is evenly applied to the flange portions 12 and 13. It comes to work.

  A quench prevention method for the superconducting coil having the above configuration will be described. First, the superconducting coil is assembled at room temperature. Specifically, a winding frame 10 made of aluminum including a cylindrical shaft portion 11 and a pair of flange portions 12 and 13 extending radially outward from both axial ends of the shaft portion 11 is prepared. Then, a superconducting wire 20 made of NbTi is wound around the outer periphery of the shaft portion 11 of the winding frame 10. Thereafter, the superconducting wire 20 wound around the shaft portion 11 of the winding frame 10 is impregnated with an impregnating material such as resin.

  Next, a base plate 30 and a top plate 40 for supporting the winding frame 10 and a reinforcing material 50 made of stainless steel are prepared. First, the winding frame 10 is fixed to the base plate 30. Specifically, a substantially intermediate portion in the radial direction of the flange portion 13 is fixed to the base plate 30 by the bolt 61. In this fixed state, the upper surface of the base plate 30 and the lower surface of the flange portion 13 are in surface contact.

  Next, the lower end portion 52 of the reinforcing member 50 is fixed to the base plate 30 with bolts 65, and the upper end portion 51 of the reinforcing member 50 is fixed to the top plate 40 with bolts 64. Then, the flange portion 12 is fixed to the top plate 40 using bolts 62 and nuts 63. Specifically, the bolt 62 embedded and fixed in a substantially intermediate portion in the radial direction of the flange portion 12 is inserted into a through hole (not shown) of the top plate 40, and the tip of the bolt 62 protrudes above the top plate 40. . Then, the nut 63 is screwed onto the tip of the bolt 62 and tightened. At this time, since the axial length of the reinforcing member 50 is longer than the axial length of the winding frame 10, in a state where the nut 63 is lightly tightened with respect to the bolt 62, the flange portion 12 and the top plate 40 are interposed. A gap (see FIG. 3) is formed.

  Here, in this embodiment, the nut 63 is strongly tightened with respect to the bolt 62 to displace the flange portion 12 toward the top plate 40 (see the arrow in FIG. 3), and the upper surface of the flange portion 12 and the top plate 40. The lower surface of the surface is brought into surface contact. Accordingly, the reinforcing member 50 is disposed between the plates 30 and 40 in a state where a load in a direction away from each other is applied to the pair of flange portions 12 and 13 at room temperature, and both the pair of flange portions 12 and 13 are provided. Connect to. As described above, the assembly of the superconducting coil is completed.

  When this superconducting coil is cooled to a very low temperature and energized to be excited, a hoop force in the radially outward direction acts on the superconducting wire 20 due to the interaction between the energized current and the magnetic field generated by itself. Thereby, the superconducting wire 20 swells in the radial direction.

  Moreover, when it cools to cryogenic temperature, the winding frame 10, the superconducting wire 20, and the reinforcing material 50 contract according to the thermal contraction rate of each constituent material. Here, in this embodiment, since the heat shrinkage rate of the reinforcing member 50 is configured to be smaller than the heat shrinkage rate of the reel 10, the amount of shrinkage in the axial direction of the reel 10 during cooling is It becomes larger than the shrinkage amount of the reinforcing member 50 in the axial direction.

  Then, due to the difference between the axial shrinkage of the reel 10 and the axial shrinkage of the reinforcing member 50, the reinforcing member 50 is stretched against the axial thermal shrinkage of the reel 10. An axial compressive force acts on the reinforcing member 50 at a low temperature, and an axially tensile force acts on the reel 10. As described above, the pair of flange portions 12 and 13 are pulled in the direction away from each other by the reinforcing member 50 via the plates 30 and 40, so that the flange portion 12 and 13 exert an axial pressure applied to the superconducting wire 20 ( (Axial pressure) decreases.

  In the first embodiment, as described above, the reinforcing member 50 connected to both the pair of flange portions 12 and 13 is configured to suppress the pair of flange portions 12 and 13 from approaching each other at an extremely low temperature. Therefore, the axial pressure (axial pressure) applied to the superconducting wire 20 when the pair of flange portions 12 and 13 approach each other can be reduced by the reinforcing member 50. Thereby, since the restraining force with respect to the superconducting wire 20 can be weakened, even if the superconducting wire 20 is slightly displaced, the frictional heat generated at that time can be reduced. Therefore, it is possible to make it difficult for a quench phenomenon to start from a minute displacement of the superconducting wire 20.

  Further, in the first embodiment, as described above, by using the superconducting wire 20 impregnated in the impregnated material in a wound state, local displacement of the superconducting wire 20 can be suppressed. It is possible to suppress the occurrence of a quench phenomenon starting from the fact that 20 is partially displaced slightly.

  In the first embodiment, as described above, the reinforcing member 50 is configured so that the thermal contraction rate of the reinforcing member 50 is smaller than the thermal shrinkage rate of the winding frame 10, so that the reinforcing member 50 is more than the winding frame 10 during cooling. The amount of heat shrinkage in the axial direction of the reinforcing member 50 is smaller than the amount of heat shrinkage in the axial direction of the reel 10. Accordingly, the reinforcing member 50 can be sufficiently stretched against the thermal contraction in the axial direction of the winding frame 10 at an extremely low temperature, and thus a force in a direction away from each other is sufficiently applied to the pair of flange portions 12 and 13. Can be made. Furthermore, in the first embodiment, as described above, by applying a load in a direction away from each other to the pair of flange portions 12 and 13 at room temperature before cooling, the flange portion is kept at a very low temperature. It acts so that the approach of 12,13 may be suppressed. From these things, the approach of a pair of flange parts 12 and 13 can fully be suppressed under cryogenic temperature, and the axial pressure added to the superconducting wire 20 can be made small enough.

  In the first embodiment, as described above, the pair of flange portions 12 and 13 are fixed to the corresponding plates 40 and 30, respectively, and the reinforcing member 50 is disposed at the position on the radially outer side of the winding frame 10 with the plate 12. , 13 so that the pair of plates 30 and 40 provided on both sides in the axial direction of the reel 10 are effectively used to support the reel 10, and a pair of flange portions are used at an extremely low temperature. It can suppress that 12, 13 approaches mutually.

  In the first embodiment, as described above, the cylindrical reinforcing member 50 is provided between the plates 30 and 40 in a posture in which the axial direction thereof coincides with the axial direction of the winding frame 10. Since the strength of the material 50 against the compressive force in the axial direction is relatively high, the cylindrical reinforcing material 50 can efficiently suppress the approach of the pair of flange portions 12 and 13 at an extremely low temperature.

  Moreover, in 1st Embodiment, since it was set as the structure which fixes the substantially intermediate | middle site | part of the radial direction of the flange parts 12 and 13 to the plates 40 and 30 as mentioned above, among the flange parts 12 and 13, of the winding frame 10 is used. A load in the separation direction can be applied to a portion relatively close to the shaft portion 11 that is greatly involved in the thermal contraction in the axial direction. Thereby, the axial pressure applied to the superconducting wire 20 can be reduced efficiently.

  In the first embodiment, the example in which the reinforcing material 10 made of stainless steel, which is longer in the axial direction than the aluminum winding frame 10, is provided between the plates 30 and 40 is not limited thereto. The axial length is configured to be substantially equal to the axial length of the winding frame 10, and the flange portion 12, 13 is in a state in which the reinforcing member 50 is unloaded against the pair of flange portions 12, 13 at room temperature. It may be interposed between them. Even in this configuration, the reinforcing member 50 is stretched against the thermal contraction in the axial direction of the reel 10 at an extremely low temperature, and a force in a direction away from each other is applied to the pair of flange portions 12 and 13. Therefore, the approach between the pair of flange portions 12 and 13 can be sufficiently suppressed. In this case, since the load in the separation direction is not applied to the flange portions 12 and 13 of the reel 10 before cooling, the life of the reel 10 can be extended.

  In the first embodiment, the aluminum shrink frame 10 and the stainless steel reinforcing member 50 are used so that the thermal shrinkage rate of the reinforcing member 50 is smaller than the thermal shrinkage rate of the reel 10. Although an example has been shown, the present invention is not limited to this, and the thermal contraction rate of the reinforcing member 50 can be determined by applying a load in a direction away from each other to the pair of flange portions 12 and 13 at room temperature before cooling. It is also possible to adopt a configuration in which the thermal contraction rate is 10 or more, for example, a configuration in which both are made of stainless steel. In the case of this configuration, the amount of heat shrinkage in the axial direction of the reinforcing material 50 becomes equal to the amount of heat shrinkage in the axial direction of the winding frame 10, so that the reinforcing material 50 is paired with the pair of flange portions 12, If the pair 13 is connected to the pair of flange portions 12 and 13 while applying a load in a direction away from each other, the reinforcing member 50 can be stretched against thermal contraction in the axial direction of the reel 10 at an extremely low temperature. . Thereby, since the force of the direction which mutually separates can be made to act on a pair of flange parts 12 and 13, the approach of a pair of flange parts 12 and 13 can be suppressed by the reinforcing material 50 under cryogenic temperature. In this case, the choice of the material of the reinforcing material 50 increases.

  Next, with reference to FIG. 4 and FIG. 5, the analysis experiment by the simulation performed in order to confirm the effect of 1st Embodiment mentioned above is demonstrated. In this experiment, a superconducting coil according to the example corresponding to the first embodiment (see FIG. 4) and a superconducting coil according to a comparative example corresponding to the prior art (see FIG. 5) are prepared, and the superconducting wire is used at an extremely low temperature. The axial stress generated at 20 was calculated by simulation.

  That is, as shown in FIG. 4, the superconducting coil of the embodiment includes an aluminum winding frame 10, a NbTi superconducting wire 20, and a reinforcing material 50 made of stainless steel, and the inner diameter of the shaft portion 11. The superconducting wire 20 wound around the shaft portion 11 has a diameter d1 of 500 mm, an outer diameter d2 of the shaft portion 11 of 530 mm, a distance d3 between the flange portions 12 and 13 of 600 mm, a thickness d4 of the flange portion 13 (12) of 15 mm. The outer diameter d5 is 650 mm, the inner diameter d11 of the reinforcing member 50 is 660 mm, and the outer diameter d12 of the reinforcing member 50 is 670 mm. In a state before the nut 63 is tightened during assembly, the gap d13 between the flange portion 12 and the top plate 40 is 0.5 mm.

  In the analysis experiment, the physical properties of aluminum, NbTi, and stainless steel were set as follows. The longitudinal elastic modulus of aluminum, which is a constituent material of the reel 10, was 75 GPa, and the average coefficient of thermal expansion was 0.000015. Further, the longitudinal elastic modulus of NbTi, which is a constituent material of the superconducting wire 20, was set to 80 GPa, and the average coefficient of thermal expansion was set to 0.00001. Further, the longitudinal elastic modulus of stainless steel, which is a constituent material of the reinforcing member 50, was 200 GPa, and the average coefficient of thermal expansion was 0.00001.

  Under the above conditions, the axial stress generated in the superconducting wire 20 is obtained when the temperature is cooled from 294.2 K to 4.2 K which is the liquid helium temperature.

  The axial stress is determined by the difference between the amount of heat shrinkage in the axial direction of the superconducting wire 20 and the amount of heat shrinkage in the axial direction of the winding frame 10, and is an axis applied from the winding frame 10 to the superconducting wire 20 at an extremely low temperature. Equal to directional pressure (axial pressure). Although a detailed description is omitted, a predetermined number of equations (here, 12) are established from the viewpoint of balance of forces of each member, and the axial stress σ1 generated in the superconducting wire 20 is calculated from these equations. Can be derived. Thereby, the analysis result that the axial direction stress σ1 due to the cooling of the superconducting coil according to the example was 0 MPa was obtained.

  On the other hand, as shown in FIG. 5, the superconducting coil of the comparative example includes an aluminum winding frame 110 and a NbTi superconducting wire 120 and does not include a reinforcing material as in the embodiment. In this superconducting coil, the inner diameter d21 of the shaft portion 111 is 500 mm, the outer diameter d22 of the shaft portion 111 is 530 mm, the distance d23 between the flange portions 112 and 113 is 600 mm, the thickness d24 of the flange portion 113 (112) is 15 mm, The dimension is set so that the outer diameter d25 of the superconducting wire 120 wound around the shaft portion 111 is 650 mm.

  Under the above conditions, the axial stress generated in the superconducting wire 120 is obtained when the temperature is cooled from 294.2 K to 4.2 K which is the liquid helium temperature.

  The axial stress is determined by the difference between the amount of thermal contraction in the axial direction of the superconducting wire 120 and the amount of thermal contraction in the axial direction of the winding frame 110, and is an axis applied to the superconducting wire 120 from the winding frame 110 at an extremely low temperature. Equal to directional pressure (axial pressure). And although detailed explanation is omitted, a predetermined number (here, 6) equations are established, and the axial stress σ2 generated in the superconducting wire 120 can be derived from these equations. Thereby, the analysis result that axial direction stress (sigma) 2 by cooling of the superconducting coil by an Example is 19.7 Mpa was obtained.

  Next, the relationship between the axial stress and frictional heat generated between the winding frame and the superconducting wire will be described. For example, the enthalpy required for a superconducting wire having a line width of 0.6 mm and a body ratio of 1.3 to rise in temperature from 4.2 K to 9 K, which is a quench temperature, is 0.01 J / m. When the friction coefficient μ between the winding frame and the superconducting wire is 1, and the distance ΔL moved during the friction is 10 μm, the frictional heat generated between the winding frame 10 and the superconducting wire 20 when the axial stress σ1 is 0 MPa. Is 0 J / m, which is smaller than 0.01 J / m, which is a value for causing the above-described quench. On the other hand, the frictional heat generated between the winding frame 110 and the superconducting wire 120 when the axial stress σ2 is 19.7 MPa is 0.12 J / m, which is larger than 0.01 J / m. From this, it is considered that the quench phenomenon occurs when the superconducting wire 120 is slightly displaced in the superconducting coil of the comparative example, but the quench phenomenon does not occur when the superconducting wire 20 is slightly displaced. Therefore, the effect of the superconducting coil of the first embodiment was confirmed by the simulation.

  A more specific example of the superconducting coil according to the first embodiment is shown in FIG. In this superconducting coil, an inner coil 71, an outer coil 72, a correction coil 73, and a shield coil 74 are arranged in this order in the radially outward direction, and a base plate 30 and a top plate 40 are provided at both axial ends of each coil. ing. The reinforcing member 50 is interposed between the correction coil 73 and the shield coil 74 between the plates 30 and 40.

(Second Embodiment)
FIG. 7 is a front sectional view showing the overall configuration of the superconducting coil according to the second embodiment of the present invention, and FIG. 8 is a front sectional view showing a state during the assembly of the superconducting coil shown in FIG. .

  Unlike the first embodiment, the superconducting coil of the second embodiment has a configuration in which the top plate 40 is omitted as shown in FIG. In addition, the structural member of the superconducting coil of 2nd Embodiment is formed with the same material as the corresponding structural member of the said 1st Embodiment.

  The upper flange portion 212 of the winding frame 210 extends radially outward from the lower flange portion 13, and the reinforcing member 250 is interposed between the flange portion 212 and the base plate 30. Yes. Specifically, the lower end portion 252 of the reinforcing member 250 is fixed to the base plate 30 by the bolt 65, and the upper end portion 251 of the reinforcing member 250 is in contact with the outer peripheral edge portion of the flange portion 212 from below with the bolt 66. It is fixed by.

  Further, a substantially intermediate portion in the radial direction of the flange portion 13 is fixed to the base plate 30 by a bolt 67 and a nut 68. This fixing structure is the same as the fixing structure of the flange portion 12 to the top plate 40 in the first embodiment. That is, as shown in FIG. 8, the reinforcing member 250 has an axial length longer than the length from the lower surface of the flange portion 212 of the winding frame 210 to the lower surface of the flange portion 13 in a state before the coil is assembled. Dimensionally designed to be long. For this reason, a predetermined gap (see FIG. 8) is formed between the flange portion 13 and the base plate 30 at the stage before the bolt tightening when the superconducting coil is assembled. The gap is gradually narrowed as the nut 68 is tightened, and the bottom surface of the flange portion 13 and the top surface of the base plate 30 are finally brought into surface contact with each other.

  Then, in the state after the bolt tightening, the reinforcement is performed in such a manner that the distance between the pair of flange portions 212 and 13 is larger than that before the bolt tightening, that is, the flange portions 212 and 13 are loaded in a direction away from each other. A material 250 is attached to the flange portion 212 and the base plate 30. Thus, in the assembled state of the superconducting coil, an axial compressive force is already applied to the reinforcing member 250 and an axially outward tensile force is applied to the pair of flange portions 212 and 13. The reinforcing member 250 is configured such that its axial thermal contraction rate is smaller than the axial thermal contraction rate of the winding frame 210, so that the axial contraction amount due to cooling is less than the winding frame 210. Accordingly, the pair of flange portions 212 and 13 function to suppress approaching each other due to thermal contraction at a cryogenic temperature.

  In 2nd Embodiment, it was set as the structure which connects the reinforcing material 250 from the axial direction inner side (lower side) to the outer edge part of the flange part 212 located in the radial direction outer side of the winding area | region of the superconducting wire 20 as mentioned above. Therefore, the reinforcing member 250 can directly press the flange portion 212 from the inside in the radial direction under a very low temperature, and can exert a force in the separation direction on the flange portions 212 and 13. Thereby, the approach of the flange parts 212 and 13 can be suppressed with a simple configuration without separately requiring a fixture for fixing the flange part and the reinforcing material.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes all modifications within the meaning and scope equivalent to the scope of claims for patent.

  For example, in the said embodiment, although the example for using a plate for supporting a winding frame and suppressing a pair of flange parts from approaching each other by a reinforcing material was shown, the present invention is not limited thereto, and there is no plate. In some cases, the reinforcing material may be inserted between the flange portions in such a posture as to be sandwiched between the pair of flange portions, thereby preventing the pair of flange portions from approaching each other. At this time, for example, if the reinforcing material is inserted between the flanges in a state of being cooled and contracted in advance before insertion, the amount of contraction of the reinforcing material at the time of cooling is reduced, and the difference in the amount of contraction from the reel is reduced. Since it can enlarge, the approach of a pair of flange part can fully be suppressed under cryogenic temperature.

  Further, as a modification, a pair of reinforcing material side flange portions extending in the radial direction are provided at both axial ends of the reinforcing material, and these reinforcing material side flange portions are respectively fixed to the flange portions of the winding frame. The structure which suppresses that a pair of flange part mutually approaches under low temperature may be sufficient.

  Further, the reinforcing material is composed of a plurality of plate materials, and the plate materials are respectively installed between the flange portions so as to partially bridge the outer peripheral edge portions of the pair of flange portions, The structure which suppresses that a pair of flange part mutually approaches under cryogenic temperature may be sufficient.

  Further, the superconducting magnet device provided with the superconducting coil of the present invention may be not only a superconducting magnet device using liquid helium as a refrigerant but also a refrigerant-free superconducting magnet device.

It is the front sectional view showing the whole superconducting coil composition by a 1st embodiment of the present invention. It is a top view of the superconducting coil shown in FIG. It is front sectional drawing which showed the state in the middle of the assembly of the superconducting coil shown in FIG. It is front sectional drawing which showed each dimension of the superconducting coil by the Example corresponding to 1st Embodiment. It is front sectional drawing which showed each dimension of the superconducting coil by the comparative example corresponding to a prior art. It is front sectional drawing which showed the other example of attachment of the reinforcing material by 1st Embodiment. It is front sectional drawing which showed the whole structure of the superconducting coil by 2nd Embodiment of this invention. It is front sectional drawing which showed the state in the middle of the assembly of the superconducting coil shown in FIG.

Explanation of symbols

10, 210 reel 11 shaft portion 12, 13, 212 flange portion 20 superconducting wire 30 base plate (support member)
40 Top plate (support member)
50,250 reinforcement

Claims (6)

A superconducting coil excited at a cryogenic temperature,
A winding frame including a cylindrical shaft portion and a pair of flange portions extending radially outward from both axial ends of the shaft portion;
A superconducting wire wound spirally around the outer periphery of the shaft, and impregnated with the impregnating material in the wound state;
A superconducting coil, comprising: a reinforcing member connected to the pair of flange portions at least at a cryogenic temperature and preventing the pair of flange portions from approaching each other due to thermal contraction.   The superconducting coil according to claim 1, wherein the reinforcing material has a thermal contraction rate smaller than or equal to the thermal contraction rate of the winding frame. A support member that is provided on the outer side in the axial direction of the flange portion in a posture that protrudes radially outward from at least one flange portion, and supports the winding frame;
The flange portion is fixed to the support member,
3. The superconducting coil according to claim 1, wherein the reinforcing member is connected to the support member at a position radially outside the flange portion. 4. The flange portion includes an outer edge portion located on the radially outer side of the winding region of the superconducting wire,
The superconducting coil according to any one of claims 1 to 3, wherein the reinforcing member is connected to the outer edge portion from the inner side in the axial direction.   5. The reinforcing member according to claim 1, wherein the reinforcing member is formed in a cylindrical shape, and is connected to the flange portion in a posture in which an axial direction thereof coincides with an axial direction of the winding frame. The superconducting coil described. A method for preventing quenching of a superconducting coil excited at a cryogenic temperature,
Preparing a winding frame including a cylindrical shaft portion and a pair of flange portions extending radially outward from both axial ends of the shaft portion;
A step of spirally winding a superconducting wire around the outer periphery of the shaft portion;
Impregnating an impregnating material with the superconducting wire wound around the shaft; and
Connecting a reinforcing material to the pair of flange portions to form a coil body;
A step of cooling the coil body to a cryogenic temperature and a step of suppressing the pair of flange portions from approaching each other by thermal contraction at a cryogenic temperature by the reinforcing material. Method.

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