JP2017166563A - Superconductive bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a large-sized superconductive bearing excellent in floating stability and capable of being simply manufactured.SOLUTION: A superconductive bearing is configured such that a magnet part comprising a permanent magnet or electromagnet and a superconductive bulk body are opposite to each other. The superconductive bulk body includes a multicrystal superconductive bulk body, and a monocrystal superconductive bulk body fixed to a side surface of the multicrystal superconductive bulk body. The multicrystal superconductive bulk body is arranged on a surface opposite to the magnet part in the superconductive bulk body.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a superconducting bearing using a superconducting bulk body.

  By using the pinning effect of magnetic flux, bulk superconductors can be combined with permanent magnets and electromagnets to achieve stable levitation on magnets without a complicated feedback control system. Therefore, application as a non-contact bearing is expected. Hereinafter, a bearing using such a bulk superconductor is referred to as a superconducting bearing. Superconducting bearings allow stable and non-contact levitation, so clean bearings that do not generate dust in clean rooms, ultra-low-loss bearings for flywheel power storage devices, and cryogenic temperatures mounted on space satellites It has been proposed to apply to bearings for detection devices that operate in the above.

A superconducting bulk body used for a superconducting bearing is preferably a superconducting bulk body having a high critical temperature (T _c ) and a high critical current density (J _c ) in a magnetic field. RE-Ba-Cu-O based oxide superconductor (RE is one or more elements selected from Y or a rare earth element) is the critical temperature T _c of but high as about 90K, the general preparation of oxides The bulk body produced by the sintering method is a polycrystalline superconducting bulk body composed of a large number of crystal grains. If superconductive bulk body is a polycrystal, the crystal grain boundaries to inhibit superconducting current, the critical current density J _c is a 1.0 × 10 3 ^{A /} cm ² or less at 77K, which is a low value.

On the other hand, Bi-Sr-Ca-Cu- O based oxide superconductor critical temperature T _c of the high order of 110K, bulk body made by sintering method is a general preparation of oxides can likewise It is a polycrystalline superconducting bulk material. Therefore, if the superconducting bulk body is a polycrystalline, since the grain boundaries to inhibit superconducting current, the critical current density _{J c} is a 1.0 × ¹⁰ 3 A / cm ² or less at 77K, which is a low value. In addition, the Mg—B-based metal superconductor has a low critical temperature _Tc of about 40 K, although the degree of crystal grain boundaries hindering the superconducting current is smaller than that of the oxide superconductor.

Although it is difficult to produce a single-crystal bulk body having no grain boundary using these superconductors, for example, as disclosed in Patent Document 1, a single crystal-like bulk body is obtained by applying a melt crystal growth process. A superconducting bulk body having a structure in which RE ₂ BaCuO ₅ is finely dispersed in RE ₁ Ba ₂ Cu ₃ O _y (y is the amount of oxygen, 6.8 ≦ y ≦ 7.1) can be obtained. Such superconducting bulk body, 77K, exhibits high characteristics even in a magnetic field of the critical current density _{J c} is 1.0 × ¹⁰ 4 A / cm ² or more at 1T. When the critical current density _Jc is high, the pinning force with respect to the magnetic flux is strong, and stable levitation, which is the greatest feature of the superconducting bearing, is easily realized. Therefore, the superconducting bearing, considered critical temperature T _c and the critical current and density J _c is higher single crystalline RE-Ba-Cu-O-based oxide superconductive bulk body is suitable, applications using the same Development is progressing. As application development progresses, larger superconducting bearings have been demanded.

  As described above, the oxide superconducting bulk body having a strong pinning force is in a single crystal form, but it is difficult to increase the size of a single crystal sample. For example, the maximum length of a superconducting bulk body that can be single-crystallized is currently available. Is about 150 mm. Therefore, when producing a large superconducting bearing exceeding the maximum length that can be crystallized, a single bearing is formed by combining a plurality of superconducting bulk bodies. Since non-contact support is possible even if a plurality of superconducting bulk bodies are used, the bearing loss of the superconducting bearing is sufficiently small compared to a contact-type mechanical bearing. However, for applications that require very low bearing loss, such as flywheel power storage devices, even slight magnetic field disturbances at the joints between individual superconducting bulk bodies can cause bearing loss. Further reduction is required

  Therefore, Patent Document 2 proposes a bearing structure in which superconducting bulk bodies as individual element members form a laminated structure, and the position of the boundary surface between the element members is shifted for each adjacent layer. That is, by superposing the superconducting bulk bodies constituting the bearings so-called bricks, it is possible to reduce the slight magnetic field disturbance at the joints between the individual superconducting bulk bodies and to further reduce the bearing loss. Further, Patent Document 3 proposes a bearing structure configured such that the joint surface of each superconducting bulk body is not orthogonal to any one of the surfaces in contact with the joint surface. That is, by making the joint surfaces of the superconducting bulk bodies constituting the bearings oblique, it is possible to reduce the slight magnetic field disturbance at the joints between the individual superconducting bulk bodies and to further reduce the bearing loss. it can.

Japanese Examined Patent Publication No. 4-40289 JP 2001-248642 A Japanese Patent Laid-Open No. 2004-039949

  As described above, making individual superconducting bulk bodies brickwork or slanting the joint surfaces are effective means for realizing a superconducting bearing that is large and has a small bearing loss. However, building individual superconducting bulk bodies into brickwork or slanting the joint surface requires not only the production and processing of individual superconducting bulk bodies with high accuracy, but also the use of individual superconducting bulk bodies. When assembling the bearing, it is necessary to carry out with high accuracy, and there is a problem that it takes much time and effort.

Here, if a polycrystalline superconducting bulk body is used, a superconducting bulk body for a large bearing can be manufactured relatively easily. As described above, the multi-critical current density J _c of crystalline bulk superconductor is low, since the pinning force also weak against the magnetic flux, if limited to small weight that can be floatingly supported, superconducting be polycrystalline shaped superconducting bulk It is considered applicable to bearings. However, the weak pinning force means that the stable supporting force in the lateral direction perpendicular to the flying direction of the superconducting bulk body is also weak. That is, even if a superconducting bearing is configured using only a polycrystalline superconducting bulk material, there is a problem that stable floating in the lateral direction cannot be obtained.

On the other hand, an oxide superconductor such as single crystal RE ₁ Ba ₂ Cu ₃ O _y has a large specific gravity of about 6.5 to 7 g / cm ^3, so that it is much heavier in the case of a large bearing. There was also a problem.

  Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide a new and improved large superconducting bearing that is excellent in floating stability and can be easily manufactured. For the purpose.

  Another object of the present invention is to provide a superconducting bearing that can be made lighter than before in one embodiment of the present invention.

Superconducting bearings using the superconducting bulk material of the present invention are as follows.
(1) In a superconducting bearing configured such that a magnet portion made of a permanent magnet or an electromagnet and a superconducting bulk body are opposed to each other, the superconducting bulk body includes a polycrystalline superconducting bulk body and the polycrystalline superconducting bulk body. A single-crystal superconducting bulk body fixed to a side surface of the superconducting bulk body, wherein the polycrystalline superconducting bulk body is disposed on a surface of the superconducting bulk body facing the magnet portion. Superconducting bearing.
(2) The superconducting bearing according to (1), wherein the single-crystal superconducting bulk body is further fixed to a bottom surface of the polycrystalline superconducting bulk body.
(3) The single-crystal superconducting bulk body is RE ₁ Ba ₂ Cu ₃ O _y (RE is one or more elements selected from the group consisting of Y and rare earth elements, and y is the amount of oxygen. The superconducting bearing according to (1) or (2), comprising an oxide superconducting bulk body in which RE ₂ BaCuO ₅ is dispersed in 6.8 ≦ y ≦ 7.1).
(4) The polycrystalline superconducting bulk is a polycrystalline oxide superconducting bulk made of RE, Ba, Cu, or O, or a polycrystalline oxide superconducting bulk made of Bi, Sr, Ca, Cu, or O. The superconducting bearing according to any one of (1) to (3), wherein the superconducting bearing is any one of a body and a polycrystalline metal bulk superconductor composed of Mg and B.
(5) The superconducting bearing according to any one of (1) to (4), wherein the maximum length of the polycrystalline superconducting bulk body is 150 mm or more.

  As described above, according to the present invention, it is possible to provide a large superconducting bearing that is excellent in floating stability and can be easily manufactured. Further, as another object of the present invention, in one embodiment of the present invention, a superconducting bearing that can be made lighter than before can be provided.

It is explanatory drawing which shows an example of the general structure of the rotary body using a superconducting bearing. It is explanatory drawing which shows the other example of the general structure of the rotary body using a superconducting bearing. It is a conceptual diagram which shows the general structure of a superconducting bearing. It is a conceptual diagram which shows the structure of the superconducting bearing which concerns on the 1st Embodiment of this invention. It is a conceptual diagram which shows the structure of the superconducting bearing which concerns on the 2nd Embodiment of this invention. It is a schematic plan view which shows another aspect of the superconducting bulk body which concerns on the same embodiment. It is a schematic plan view which shows the aspect of the superconducting bulk body of the superconducting bearing which concerns on the 3rd Embodiment of this invention. It is a schematic sectional drawing which shows the structure of the superconducting bearing which concerns on the 4th Embodiment of this invention. It is a schematic sectional drawing which shows the structure of the superconducting bearing which concerns on the 5th Embodiment of this invention. It is a schematic sectional drawing which shows the structure of the superconducting bearing which concerns on the 6th Embodiment of this invention.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  First, the structure of a general superconducting bearing will be described with reference to FIGS. 1A to 1C. 1A and 1B show a general structure of a rotating body using a superconducting bearing. The upper view of FIG. 1A is a side view, and the lower view is a bottom view. The upper view of FIG. 1B is a cross-sectional view taken along the line AA in the lower view, and the lower view is a bottom view. In addition, although the following description is related with the structure of a general superconducting bearing, the superconducting bulk body which concerns on this invention mentioned later can also be applied to such a bearing structure.

  In the structure 10 shown in FIG. 1A, superconducting bearings 11 and 15 are provided at both ends of the rotating shaft 14 of the rotating body 12. In the structure 10, the rotating body 12 is levitated and supported by superconducting bearings 11 and 15 at both ends. In FIG. 1A, the superconducting bearings 11 and 15 are attached to both ends of the rotating shaft 14, but depending on the weight and stability of the rotating body 12, the superconducting bearings 11 and 15 are either the upper end or the lower end of the rotating shaft 14. It may be attached to either one. In general, the superconducting bearing 11 attached to the upper end often uses suction levitation due to the pinning effect of magnetic flux, and the superconducting bearing 15 attached to the lower end often uses repulsive levitation due to the pinning effect of magnetic flux.

  In addition, the structure 20 shown in FIG. 1B has a configuration in which the rotating body 22 is supported by levitation by a superconducting bearing 21 attached to the rotating body 22. In the structure 20 of FIG. 1B, a ring-shaped superconducting bearing 21 is provided on one surface of a disk-shaped rotating body 22. When the rotating body 22 has a flat structure, the superconducting bearing 21 is directly attached to the rotating body 22 as shown in FIG. The structure 10 as shown in FIG. 1A can be considered to be suitable for a flywheel power storage device and the like because the rotating body 12 can be enlarged independently of the bearing portion. Since the superconducting bearing 21 having the structure as shown in FIG. 1B can mount a wafer and an observation device on the rotating body 22, it can be used for a device such as a spin coater in a clean room or an observation device mounted on a space satellite. It is considered suitable.

  FIG. 1C is a conceptual diagram of the structure of the superconducting bearing 30. The superconducting bearing 30 mainly includes a magnet part 31 and a superconducting bulk body part 32. The magnet unit 31 includes a permanent magnet or an electromagnet serving as a magnetic flux source and a portion for fixing and holding the magnet. The magnet unit 31 may be either a permanent magnet or an electromagnet, but the permanent magnet does not need to be connected to an external power source, so that the structure becomes simple. The superconducting bulk body portion 32 includes a superconducting bulk body that exhibits a pinning effect on the magnetic flux lines generated from the magnet portion 31, and a cooling container that fixes and holds the superconducting bulk body. The superconducting bulk body is cooled by a separately provided cooling mechanism. Is done. The cooling vessel that fixes and holds the superconducting bulk body is manufactured using a material with high thermal conductivity such as copper or aluminum in order to increase cooling efficiency. Vacuum grease or epoxy resin is used between the superconducting bulk body and the cooling vessel. The thermal contact property can be further enhanced by applying a coating or the like or inserting an indium sheet or the like to improve the adhesion.

  Such a superconducting bearing is installed in a vacuum atmosphere. However, a rare helium gas or the like that does not increase the windage loss, for example, 10 Pa or less may be introduced. Although omitted in FIGS. 1A and 1B, since the superconducting bearing before cooling does not have a levitation support function, a separate mechanism for holding the rotating body is required until the superconducting bulk body is sufficiently cooled. It is. Furthermore, in the example of FIGS. 1A to 1C, the magnet portion and the superconducting bulk body portion are shown in the same size, but it is not always necessary to have the same size, and the respective sizes of the magnet portion and the superconducting bulk body portion are used.・ It can be determined by design according to the purpose. For example, since the magnetic flux generated from the magnet portion tends to spread, when the magnetic flux from the magnet portion is to be used more effectively, the size of the superconducting bulk body portion may be made larger than the size of the magnet portion. In the example of FIG. 1C, the magnet portion 31 is shown on the upper side and the superconducting bulk body portion 32 is shown on the lower side. However, if the magnetic pinning effect is used, the reverse structure is also possible.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. In the present invention, the maximum length of the polycrystalline superconducting bulk body disposed on the surface facing the magnet portion is, for example, a disk or ring shape as in the first to fifth embodiments described later. In the case of a superconducting bulk body, the outer diameter is the maximum length, and in the case of a rectangular superconducting bulk body such as a linear bearing as in the sixth embodiment, the length of the diagonal line is the maximum length. .

(First embodiment)
FIG. 2 is a conceptual diagram showing an example of the superconducting bearing 100A in the first embodiment of the present invention. The upper view of FIG. 2 is a cross-sectional view taken along the line BB of the lower view, and the lower view is a bottom view. A superconducting bearing 100A shown in FIG. 2 includes a magnet part 110A of a superconducting bearing made of a permanent magnet or an electromagnet, and a superconducting bulk body 120A arranged so as to include a part facing the magnet part 110A. The magnet part 110A and the superconducting bulk body 120A are both formed in a ring shape. The superconducting bulk body 120 </ b> A includes a polycrystalline superconducting bulk body 121 disposed on the inner peripheral side, and a single crystalline superconducting bulk body 123 disposed on the outer periphery of the polycrystalline superconducting bulk body 121. Polycrystalline superconducting bulk body 121 is arranged to face magnet portion 110A.

  Since the superconducting bulk body on the surface facing the magnet portion 110A is the polycrystalline superconducting bulk body 121, it can be easily and integrally manufactured even in a large size compared to the single-crystal superconducting bulk body 123. In the case of an integral superconducting bulk body, since there is no joint between the superconducting bulk bodies as element members, it is possible to eliminate a bearing loss factor due to magnetic field disturbance caused by the joint portion. As a result, a super-low-loss bearing inherent in a superconducting bearing can be realized. Further, by disposing a single-crystal superconducting bulk body 123 having a strong pinning force on the outer peripheral portion of the polycrystalline superconducting bulk body 121, a bearing can be provided only by the polycrystalline superconducting bulk body 121 having a weak pinning force. Compared to the case where it is configured, the floating stability in the horizontal direction can be remarkably enhanced. The single-crystal superconducting bulk body 123 is for enhancing the levitation stability, and therefore does not need to be integrated unlike the polycrystalline superconducting bulk body 121. For example, the single-crystal superconducting bulk body 123 shown in FIG. 2 is composed of eight element members having the same size in the circumferential direction. Furthermore, since it is sufficient that the levitation stability can be enhanced, the single crystal superconducting bulk body 123 may be thin in the radial direction.

The single-crystal superconducting bulk body 123 used in the present embodiment is composed of a RE ₂ BaCuO ₅ phase (211 phase) having a diameter of 20 μm or less in a single-crystal RE ₁ Ba ₂ Cu ₃ O _7-x phase (123 phase), etc. It is sufficient that the non-superconducting phase represented by (2) has a dispersed structure, and a non-superconducting phase having a finely dispersed structure (hereinafter also referred to as “QMG material”) is preferable. Here, the term “single crystal” includes not only a perfect single crystal but also a defect having a defect that may be practically used such as a low-angle grain boundary. RE in the 123 phase and the 211 phase is a rare earth element composed of Y, La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Lu, and combinations thereof. The 123 phase containing La, Nd, Sm, Eu, and Gd deviates from the 1: 2: 3 stoichiometric composition, and Ba may be partially substituted at the RE site. In the 211 phase which is a non-superconducting phase, La and Nd are somewhat different from Y, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu, and the ratio of metal elements is non-stoichiometric. It is known that it has a theoretical composition or a different crystal structure. Such a single-crystal oxide superconducting bulk body 123 is not a sintering method, which is a general method for producing ceramics, but is heated to a melting temperature higher than a sintering temperature to be in a semi-molten state. After that, it is manufactured by a melt crystal growth method in which crystal growth is performed during slow cooling.

The fine dispersion of the 211 phase in the QMG material is extremely important from the viewpoint of improving the critical current density (J _c ). By adding a trace amount of at least one of Pt, Rh, or Ce, the grain growth of the 211 phase in the semi-molten state (a state composed of the 211 phase and the liquid phase) is suppressed, and as a result, the 211 phase in the material is reduced to about Refine to about 1 μm. The addition amount is Pt: 0.2 to 2.0% by mass, Rh: 0.01 to 0.5% by mass, Ce: 0.5 to 2.0 from the viewpoint of the amount at which the effect of miniaturization appears and the material cost. It is desirable that it is mass%. The added Pt, Rh, and Ce partially dissolve in the 123 phase. In addition, elements that could not be dissolved form a composite oxide with Ba and Cu and are scattered in the material. 211 phase ratio of 123 phase, in view of the critical current density _{J c} properties and mechanical strength, is desirably 5 to 35% by volume. Further, the material generally contains 5 to 20% by volume of voids (bubbles) of about 50 to 500 μm, and when Ag is added, 0 to about 1 to 500 μm of Ag or Ag compound is added depending on the addition amount. More than 25% by volume.

  Further, the oxygen deficiency (x) of the superconducting bulk body after crystal growth is about 0.5 to 0.8, and shows a temperature change in resistivity like a semiconductor or an insulating material. This is annealed in an oxygen atmosphere at 350 ° C. to 600 ° C. for about 100 hours by each RE system, so that oxygen is taken into the superconducting bulk body and the oxygen deficiency (x) is 0.2 or less, which is a good superconductivity. Show properties. At this time, a twin structure is formed in the superconducting phase. However, including this point, it is referred to as a single crystal here. In order to use an oxide superconducting bulk body as a superconducting bearing, the oxide superconducting bulk body after crystal growth is processed into a predetermined shape such as a disk shape, a square shape, a fan shape, or a tile shape, and the oxide superconductivity after processing. The bulk body is subjected to oxygen annealing.

  The polycrystalline superconducting bulk body 121 according to the present embodiment includes a polycrystalline oxide superconducting bulk body made of RE, Ba, and Cu, and a polycrystalline oxide superconducting bulk body made of Bi, Sr, Ca, and Cu. Or a polycrystalline metal superconducting bulk body made of Mg or B. The polycrystalline oxide superconducting bulk body made of RE, Ba, Cu and the polycrystalline oxide superconducting bulk body made of Bi, Sr, Ca, Cu are different from the above-described single-crystal oxide superconducting bulk body. There is no need to manufacture by the melt crystal growth method, and powders of initial raw materials such as constituent element oxides or carbonates are in a predetermined ratio (for example, RE: Ba: Cu = 1: 2: 3 in the case of RE system). In the case of Bi type, after mixing and calcination with Bi: Sr: Ca: Cu = 2: 2: 2: 3, etc., the molded body is sintered at a temperature of about 850 ° C. to 950 ° C. It is manufactured by. In this way, a polycrystalline oxide superconducting bulk body can be manufactured by a sintering method, which is a general manufacturing method of ceramics, and therefore, compared with a single crystal oxide superconducting bulk body that must be manufactured by melt crystal growth. And can be easily manufactured.

  In addition, a polycrystalline metal superconducting bulk body composed of Mg and B may be manufactured by sintering and molding a mixture of Mg powder and B powder in a ratio of 1: 2, but the melting point of Mg is The melting point of B is greatly different from 2076 ° C. at 650 ° C. For this reason, since Mg may vaporize and dissipate first in the sintering process, the composition may be shifted, so that the sintering is performed in a sealed state. In order to obtain a sintered body having a high density, means such as hot isostatic pressing (HIP) may be applied in the sintering process. The polycrystalline metal superconducting bulk body composed of Mg and B is a metal superconducting bulk body mainly composed of Mg and B, and is a carbon compound such as carbon or SiC, or an organic substance such as benzene or malic acid. An additive which becomes a pinning point such as may be included. Further, when a polycrystalline metal superconducting bulk body composed of Mg and B is used as the polycrystalline superconducting bulk body, the specific gravity of the polycrystalline metal superconducting bulk body composed of Mg and B is the oxide superconducting bulk body. Because it is lightweight with about one third to one fourth of its specific gravity, it is possible to reduce the weight even with large bearings.

These polycrystalline shaped bulk superconductor 121, a low critical temperature T _c and the critical current density J _c, is a material which has been considered to be unsuitable for superconducting bearing conventionally when used alone. In fact, when liquid nitrogen having a boiling point of 77K, which is relatively well used in industry, is used as a refrigerant, the levitation force at that temperature (77K) is very small and impractical. However, since the superconducting properties improve as the temperature decreases, the bearings used in the cryogenic region below 40K are lower than the single-crystal superconducting bulk material with strong pinning force, but the number of practical levels. A levitation force of about kg can be secured.

  Further, even if the superconducting bulk body 120A is a large superconducting bearing having a maximum length of 150 mm or more of the superconducting bulk body disposed on the surface facing the magnet portion 110A, the polycrystalline superconducting bulk body 121 may be used. Thus, it can be manufactured relatively easily and integrally without any joint, and the bearing loss factor due to the disturbance of the magnetic field caused by the joint can be eliminated. However, even if the levitation force can be ensured in an extremely low temperature region of 40K or less, it is difficult to ensure sufficient levitation stability with the polycrystalline superconducting bulk body 121. Therefore, in order to compensate for the low floating stability of the polycrystalline superconducting bulk body 121, the single-crystal superconducting bulk body 123 having a strong pinning force is disposed on the outer periphery of the polycrystalline superconducting bulk body 121. . At that time, the single crystal superconducting bulk body 123 can be manufactured in a plurality of sizes that can be manufactured, and can be divided and arranged. In addition, the superconducting bulk body according to the present embodiment can have the same configuration even when the bearing structure of FIG. 1B is applied to the present invention.

(Second Embodiment)
FIG. 3 is a conceptual diagram showing a configuration of a superconducting bearing 100B according to the second embodiment of the present invention. In the superconducting bearing 100A shown in FIG. 2, the single-crystal superconducting bulk body 123 is disposed on the outer peripheral side of the polycrystalline superconducting bulk body 121, but the superconducting bearing 100B according to this embodiment is shown in FIG. As shown, a single crystal superconducting bulk body 123 is disposed on the inner peripheral side of the polycrystalline superconducting bulk body 121.

  For the stability in the lateral direction of the magnet part 110B levitated on the superconducting bulk body 120B (direction perpendicular to the levitating direction (Z direction) of the superconducting bulk body), that is, the magnet part 110A levitating. In order to prevent it from coming out of the superconducting bulk body 120B, it seems to be effective to dispose a single crystal superconducting bulk body 123 having a strong pinning force on the outer peripheral side. However, even if the single-crystal superconducting bulk body 123 is arranged on the inner peripheral side of the polycrystalline superconducting bulk body 121, the lateral stability can be secured in the same manner. By disposing the single-crystal superconducting bulk body 123 on the inner peripheral side of the polycrystalline superconducting bulk body 121, the single-crystal superconducting bulk body 123 is disposed on the outer peripheral side of the polycrystalline superconducting bulk body 121. As a result, the amount of single-crystal superconducting bulk material 123 used can be reduced. Since it is necessary to manufacture the single-crystal superconducting bulk body 123 by a melt crystal growth process, the fact that the amount used can be reduced can simplify the manufacture.

  Furthermore, by arranging the single crystal superconducting bulk body 123 on the inner peripheral side of the polycrystalline superconducting bulk body 121, the size of the single crystal superconducting bulk body 123 can be reduced. That is, even if the maximum length (here, the outer diameter) of the polycrystalline superconducting bulk body 121 arranged on the surface facing the magnet portion 110B in the superconducting bulk body 120B is 150 mm or more, it is arranged on the inner peripheral side. If the maximum length of the single-crystal superconducting bulk body 123 (in this case, the outer diameter) is less than 150 mm, the inner peripheral side of the polycrystalline superconducting bulk body 121 as in the superconducting bulk body 120C shown in FIG. The single-crystal superconducting bulk body 123 disposed on the substrate can also be integrated seamlessly without being divided.

(Third embodiment)
FIG. 5 is a schematic plan view showing an aspect of the superconducting bulk body 120D of the superconducting bearing according to the third embodiment of the present invention. The superconducting bearing according to the present embodiment is provided with a superconducting bulk body 120D shown in FIG. 5 instead of the superconducting bulk body 120A of the superconducting bearing 100A according to the first embodiment shown in FIG. In any of the superconducting bulk bodies 120A and 120D, the single-crystal superconducting bulk body 123 is arranged on the outer peripheral side of the polycrystalline superconducting bulk body 121, but the configuration of the single-crystal superconducting bulk body 123 is different. That is, the single-crystal superconducting bulk body 123 is configured by continuously arranging a plurality of element members in the first embodiment, but the element members are discretely arranged in the present embodiment. .

  The polycrystalline superconducting bulk body 121 facing the magnet part 110A needs to be continuously arranged in order to reduce the bearing loss to the utmost limit. However, the single crystal superconducting body having the function of lateral stability is required. The bulk body 123 is not necessarily arranged continuously. Therefore, as in the present embodiment, the element member is arranged discretely to form the single-crystal superconducting bulk body 123, so that the amount of the single-crystal superconducting bulk body 123 used is larger than the continuous arrangement. Can be reduced. Since it is necessary to manufacture the single-crystal superconducting bulk body 123 by a melt crystal growth process, the fact that the amount used can be reduced can simplify the manufacture. Note that the number of element members and how to arrange the single-crystal superconducting bulk bodies 123 in a discrete manner are not limited to the example shown in FIG.

(Fourth embodiment)
FIG. 6 is a schematic cross-sectional view showing a configuration of a superconducting bearing 100E according to the fourth embodiment of the present invention. Compared with the superconducting bulk body 120A of the superconducting bearing 100A according to the first embodiment shown in FIG. 2, the superconducting bearing 100E according to this embodiment has a bottom surface in addition to the outer peripheral side of the polycrystalline superconducting bulk body 121. The difference is that a single-crystal superconducting bulk body 125 is also arranged on the side.

  As described above, since the polycrystalline superconducting bulk body 121 has a weak pinning force, it needs to be cooled to an extremely low temperature region of 40K or less in order to obtain a practical levitation force. Therefore, in order to further improve the levitation force, it is effective to dispose the single crystalline superconducting bulk body 123 on the bottom surface side of the polycrystalline superconducting bulk body 121 like the superconducting bulk body 120E according to the present embodiment. Become. In this case, if the upper polycrystalline superconducting bulk body 121 facing the magnet portion 110E is thick, the effect of the single crystalline superconducting bulk body 125 disposed on the bottom surface side is lost, so the polycrystalline superconducting bulk body 121 is removed. The thickness is preferably 5 mm or less.

  In the case of a large bearing, it is difficult to integrally manufacture a single crystal superconducting bulk body. For this reason, the single-crystal superconducting bulk body 125 arranged on the bottom surface side of the polycrystalline superconducting bulk body 121 is configured by arranging a plurality of element members side by side, and there is a seam. However, the polycrystalline superconducting bulk body 121 exists on the joint between the element members of the single crystal superconducting bulk body 125. As a result, the joint between the element members of the single-crystal superconducting bulk body 125 does not cause an increase in bearing loss, and a super-low-loss bearing inherent in a superconducting bearing can be realized.

(Fifth embodiment)
FIG. 7 is a schematic cross-sectional view showing the configuration of a superconducting bearing 100F according to the fifth embodiment of the present invention. The superconducting bearing 100F according to the present embodiment has a single crystal shape on the outer peripheral side of the polycrystalline superconducting bulk body 121 as compared with the superconducting bulk body 120A of the superconducting bearing 100A according to the first embodiment shown in FIG. This is different in that the superconducting bulk body 123 is shifted in the flying direction.

  That is, as shown in FIG. 2, in the superconducting bulk body 120A according to the first embodiment, a polycrystalline superconducting bulk body 121 and a single-crystal superconducting bulk body 123 disposed on the outer peripheral side are provided. , They were arranged at the same height in the flying direction (Z direction). On the other hand, in the superconducting bulk body 120F according to the present embodiment, as shown in FIG. 7, the single-crystal superconducting bulk body 123 is positioned higher than the polycrystalline superconducting bulk body 121, that is, the magnet part 110F side. Is arranged. In this way, by arranging the single-crystal superconducting bulk body 123 having a strong pinning force on the magnet part 110F side relative to the polycrystalline superconducting bulk body 121, the movement of the magnet part 110F coming off the bearing is prevented. As a result, the force to return to the original position works more strongly, and the superconducting bearing 100F with better floating stability can be realized.

(Sixth embodiment)
FIG. 8 is a schematic cross-sectional view showing the configuration of a superconducting bearing 100G according to the sixth embodiment of the present invention. Although the said 1st-5th embodiment was related to the rotary bearing which supports a rotary body, the superconducting bearing 100G which concerns on this embodiment supports what moves to a linear direction, as shown in FIG. The present invention relates to a linear bearing. Even a linear bearing has the same basic structure as a rotary bearing.

  That is, the superconducting bearing 100G according to the present embodiment includes a linear magnet portion 110G and a linear superconducting bulk body 120G arranged so as to include a portion facing the magnet portion 110G. The superconducting bulk body 120G includes a polycrystalline superconducting bulk body 121 disposed at a position facing the magnet part 110G, and a single crystalline state disposed on both sides in the width direction (X direction) of the polycrystalline superconducting bulk body 121. Of the superconducting bulk bodies 123 and 125. In the case of the rotary bearing shown in the first to fifth embodiments, the single crystal superconducting bulk body 123 is at least one of the outer peripheral side and the inner peripheral side of the polycrystalline superconducting bulk body 121. However, in the case of the linear bearing according to the present embodiment, in order to ensure levitation stability, the single crystal superconducting bulk is always provided on both sides of the polycrystalline superconducting bulk body 121. It is necessary to arrange the bodies 123 and 125. The single-crystal superconducting bulk bodies 123 and 125 may be arranged continuously or discretely as in the case of the rotary bearing, and further on the bottom side of the polycrystalline superconducting bulk body 121 in order to improve the levitation force. You may arrange.

  In the future, even when a single-crystal superconducting bulk body having a maximum length exceeding 150 mm can be produced, a large superconducting bearing that can be easily produced according to the present invention can be provided. In one embodiment, the usefulness of the present invention remains the same in that a superconducting bearing that is lighter than before can be provided.

Example 1
In this example, the levitation stability was verified for a superconducting bearing in which a single-crystal superconducting bulk body was continuously arranged on the outer peripheral side of the polycrystalline superconducting bulk body shown in FIG.

  The superconducting bearing was manufactured as follows. First, commercially available powders of 99.9% by mass purity of yttrium (Y), barium (Ba), and copper (Cu), respectively, with a molar ratio of Y: Ba: Cu = 1: 2: 3. The weighed powder was sufficiently kneaded over 2 hours and then calcined at 1173K for 8 hours in the air. Next, the calcined powder is formed into a ring shape using a mold, and this formed body is sintered at 1173K for 8 hours, and is a ring-shaped polycrystalline oxide having an outer diameter of 150 mm, an inner diameter of 90 mm, and a height of 20 mm. A bulk superconductor was obtained.

  Next, commercially available powders of gadolinium (Gd), barium (Ba), and copper (Cu) having a purity of 99.9% by mass are respectively converted into Gd: Ba: Cu = 1.6: 2.3. : Weighed at a molar ratio of 3.3, and added 0.5% by mass of platinum and 10% by mass of silver thereto. The weighed powder was sufficiently kneaded over 2 hours and then calcined at 1173 K for 8 hours in the air. Next, the calcined powder was formed into a disk shape using a mold. The molded body was heated to 1423K to be in a molten state, held for 30 minutes, and then seeded in the middle of lowering the temperature, and a temperature region of 1278K to 1252K was gradually cooled over 100 hours to grow a crystal, having a diameter of 50 mm and a height of 20 mm. A single crystalline superconducting bulk body was obtained. The eight single-crystal superconducting bulk bodies having a diameter of 50 mm were processed into fan-shaped element members so as to be in contact with the outer periphery of the polycrystalline superconducting bulk body, and heat-treated at 723 K for 100 hours in an oxygen stream.

  Thereafter, the element member of the fan-shaped single crystal superconducting bulk body having a radial length of 10 mm is continuously provided in the circumferential direction on the outer periphery of the ring-shaped polycrystalline oxide superconducting bulk body having an outer diameter of 150 mm. A ring-shaped superconducting bulk body was formed. Then, the superconducting bulk body was combined with an Nd—Fe—B permanent magnet having an outer diameter of 140 mm, an inner diameter of 100 mm, and a height of 10 mm and a surface magnetic flux density of 0.4 T to produce a superconducting bearing. A rotation experiment was performed on the superconducting bearing thus manufactured. In the rotation experiment, rotation driving was performed by blowing compressed air to the air turbine provided in the magnet part in a state where the superconducting bulk body was cooled to 40K using a refrigerator. As a result, the superconducting bearing having the configuration of this example was able to rotate stably up to 1000 rpm.

  For comparison, first, a similar rotation test was performed using a superconducting bulk body composed of only a polycrystalline superconducting bulk body in which no single crystalline superconducting bulk body is disposed on the outer peripheral portion. As a result, it was confirmed that the magnet part was detached from the superconducting bearing during rotation, and the levitation stability was low.

  For another comparison, a ring-shaped oxide superconducting bulk body having an outer diameter of 150 mm on the surface facing the magnet portion was composed of a single crystal superconducting bulk body, and the same rotation test was performed. As a result, the superconducting bearing was able to rotate stably up to 1000 rpm. However, in the process of manufacturing a single-crystal oxide superconducting bulk body with a diameter of 150 mm by the melt crystal growth method, the temperature range of 1278 K to 1252 K was gradually cooled over 300 hours to grow the crystal, so that it sintered in 8 hours. Compared with the polycrystalline oxide superconducting bulk material made, the time required for the production was significantly increased. Furthermore, a polycrystalline superconducting bulk body could be manufactured by one-time sintering, but a single-crystal oxide superconducting bulk body having a diameter of 150 mm was large in size and was near the outer periphery during crystal growth. Nucleation from other than the seed crystal occurred and it was polycrystallized, so it could not be manufactured once. Actually, after the production was repeated twice, the single crystallization was succeeded for the third time.

  From the above results, by using the superconducting bearing having the structure of the present invention, it is possible to provide a large superconducting bearing that has excellent levitation stability and can be easily manufactured.

(Example 2)
In this example, the levitation stability was verified for a superconducting bearing in which an integral single crystal superconducting bulk body is arranged on the inner peripheral side of the polycrystalline superconducting bulk body shown in FIG.

  The superconducting bearing was manufactured as follows. First, magnesium (Mg) and boron (B) powders having a purity of 99.9% by mass were weighed at a molar ratio of Mg: B = 1: 2, and the weighed powder was sufficiently kneaded over 1 hour. . This mixed powder is put in a stainless steel mold and sealed, and the whole mold is put in an electric furnace and sintered at 1123 K for 6 hours, and is a ring-shaped polycrystalline superconductor having an outer diameter of 160 mm, an inner diameter of 110 mm, and a height of 15 mm. A bulk body was obtained. The polycrystalline metal superconducting bulk body made of Mg and B obtained here is also referred to as “Mg—B-based polycrystalline superconducting bulk body”.

Next, commercially available powders of gadolinium (Gd), barium (Ba), and copper (Cu) having a purity of 99.9% by mass are respectively converted into Gd: Ba: Cu = 2: 2.5: 3. The mixture was weighed at a molar ratio of 0.5, and 1% by mass of CeO ₂ and 15% by mass of silver were added thereto. The weighed powder was sufficiently kneaded over 2 hours and then calcined at 1173 K for 8 hours in the air. Next, the calcined powder was formed into a disk shape using a mold. This molded body was heated to 1423K to be melted and held for 30 minutes, and then seeded in the middle of temperature reduction, and the temperature range of 1278K to 1252K was gradually cooled over 200 hours to grow crystals, with a diameter of 110 mm and a height of 15 mm. A single crystalline superconducting bulk body was obtained. Then, this single-crystal superconducting bulk body was processed into a ring shape whose outer periphery was in contact with the inner periphery of the above-described polycrystalline superconducting bulk body, and was heat-treated at 723 K for 100 hours in an oxygen stream.

  Thereafter, a ring-shaped single-crystal superconducting bulk body having a radial length of 5 mm is arranged on the inner circumference of a ring-shaped polycrystalline superconducting bulk body having an outer diameter of 160 mm and an inner diameter of 110 mm. Formed. Then, the superconducting bulk body was combined with an Nd—Fe—B permanent magnet having an outer diameter of 150 mm, an inner diameter of 120 mm, and a height of 15 mm and a surface magnetic flux density of 0.5 T to produce a superconducting bearing. A rotation experiment was performed on the superconducting bearing thus manufactured. In the rotation experiment, rotation driving was performed by blowing compressed air to an air turbine provided with a magnet portion in a state where the superconducting bulk body was cooled to 20 K using an evaporation gas of liquid helium. As a result, the superconducting bearing having the configuration of this example was able to rotate stably up to 1000 rpm.

  For comparison, the same rotation test was performed using a superconducting bulk body composed of only a polycrystalline superconducting bulk body in which no single crystalline superconducting bulk body is disposed on the inner periphery. As a result, the magnet part was detached from the superconducting bearing during the rotation. From this, it was confirmed that when a superconducting bulk body composed only of a polycrystalline superconducting bulk body was used, the levitation stability was low.

  Since the ring-shaped superconducting bulk body having an outer diameter of 160 mm on the surface facing the magnet portion is large, it is difficult to manufacture only the single-crystal superconducting bulk body. However, from the above results, as shown in the examples of the present invention, the floating stability is excellent simply by providing a single-crystal superconducting bulk body on the inner peripheral side of a polycrystalline superconducting bulk body that can be easily manufactured. A large superconducting bearing that can be easily manufactured can be provided.

  Furthermore, a superconducting bulk body can be reduced in weight by manufacturing a polycrystalline superconducting bulk body with an Mg—B-based polycrystalline superconducting bulk body as in this embodiment. For example, when the polycrystalline superconducting bulk body of this example was manufactured using an oxide-based superconducting bulk body, the weight was 1030 g, whereas the Mg-B-based polycrystalline superconducting bulk body was When manufactured, the weight was 230 g, and the weight of the portion of the polycrystalline superconducting bulk body in the superconducting bearing could be reduced to about 1/4. In addition, in terms of the weight of the entire superconducting bulk body, the weight of the superconducting bulk body in which the single crystal oxide superconductor is disposed on the inner peripheral side and the polycrystalline oxide superconductor bulk body is disposed on the outer peripheral side is Although it was 1190 g, the weight of the superconducting bulk body was 390 g when the polycrystalline superconducting bulk body on the outer periphery side was a Mg-B-based polycrystalline superconducting bulk body as in this example. That is, the total weight of the superconducting bulk body in the superconducting bearing could be reduced to about 1/3. As a result, it is possible to provide a lighter and larger superconducting bearing by using a Mg-B polycrystalline superconducting bulk material having a specific gravity lighter than that of an oxide superconducting bulk material as a polycrystalline superconducting bulk material. It became clear.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

10, 20 Structure 11, 15, 21, 30 Superconducting bearing 12, 22 Rotating body 14 Rotating shaft 31 Magnet part 32 Superconducting bulk body part 100A, 100B, 100E, 100F, 100F Superconducting bearing 110A, 110B, 110E, 110F, 110G Magnet part 120A, 120B, 120C, 120D, 120E, 120F, 120G Superconducting bulk body 121 Polycrystalline superconducting bulk body 123, 125 Single crystalline superconducting bulk body

Claims (5)

In a superconducting bearing configured by facing a magnet portion made of a permanent magnet or an electromagnet and a superconducting bulk body,
The superconducting bulk body is:
A polycrystalline superconducting bulk body;
A single-crystal superconducting bulk body fixed to a side surface of the polycrystalline superconducting bulk body;
With
The superconducting bearing according to claim 1, wherein the polycrystalline superconducting bulk body is disposed on a surface of the superconducting bulk body facing the magnet portion.   The superconducting bearing according to claim 1, wherein the single-crystal superconducting bulk body is further fixed to a bottom surface of the polycrystalline superconducting bulk body. The single-crystal superconducting bulk material is RE ₁ Ba ₂ Cu ₃ O _y (RE is one or more elements selected from the group consisting of Y and rare earth elements, y is the amount of oxygen, and 6. The superconducting bearing according to claim 1 or 2, comprising an oxide superconducting bulk body in which RE ₂ BaCuO ₅ is dispersed in 8 ≦ y ≦ 7.1).   The polycrystalline superconducting bulk is a polycrystalline oxide superconducting bulk made of RE, Ba, Cu, O, a polycrystalline oxide superconducting bulk made of Bi, Sr, Ca, Cu, O, The superconducting bearing according to any one of claims 1 to 3, wherein the superconducting bearing is any one of a polycrystalline metal bulk superconductor composed of Mg and B. The superconducting bearing according to any one of claims 1 to 4, wherein a maximum length of the polycrystalline superconducting bulk body is 150 mm or more.

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