JP4874318B2 - Superconducting bearing - Google Patents

Description

  The present invention relates to a superconducting bearing used in a power storage flywheel, a high-speed rotating device, or the like.

  A superconducting bearing uses a pinning effect between a superconductor and a magnet, and has a function of stably floating and rotating an object without contact without contact. The positional relationship between the superconductor and the magnet in the superconducting bearing mainly includes an axial bearing type arrangement and a radial bearing type arrangement. As shown in FIG. 22, in the axial bearing type arrangement, the superconductor and the magnet face each other in the axial direction. On the other hand, as shown in FIG. 23, in the radial bearing type arrangement, the superconductor and the magnet face each other in the radial direction.

  A large oxide superconductor made in a single crystal form is used for the superconducting bearing. However, single-crystal oxide superconductors have anisotropy due to crystal orientation, and are parallel to the crystal c-axis and perpendicular to the crystal c-axis, that is, the crystal a-axis and b-axis. The superconducting characteristics differ greatly between the direction parallel to the ab plane to be formed. As a result, the levitation force varies greatly depending on the orientation of the crystal orientation of the superconductor relative to the magnet. Conventionally, in order to increase the levitation force, it was common to use a crystal arrangement in which the c-axis of the superconductor is directed toward the magnet, that is, the c-axis of the superconductor is perpendicular to the surface of the magnet. . That is, in the axial bearing type arrangement, the c-axis of the superconductor is axially oriented in the axial direction, and in the radial bearing type arrangement, the c-axis of the superconductor is radial oriented in the radial direction.

  In the axial bearing type arrangement, it is possible to orient the c-axis of the entire superconductor constituting the bearing in the axial direction. However, in the radial bearing type arrangement, it is not possible with a single crystal to radially orient the c-axis of the superconductor constituting the bearing over the entire circumference of the bearing. Therefore, as shown in FIG. 24, as a conventional technique, several samples are manufactured, each is processed into a fan shape, and they are combined to form a superconductor constituting one bearing, and individual bearings are constituted. A technique is employed in which the c-axis of the element member is radially oriented. At this time, the method of joining the individual fan-shaped members is to physically join the individual members by simply storing them in the cooling container, or to bond them together with an adhesive when they are stored in the cooling container. It is only fixed.

JP-A-8-284957

  However, when the superconductor of the superconducting bearing is manufactured by the method as shown in FIG. 24, the individual element members are merely physically coupled, and the superconducting current does not flow at the boundary between the element members. In addition, strictly speaking, the portion where the c-axis of each element member is radially oriented is only the center portion of the element member, and the deviation between the c-axis and the radial direction increases as the distance from the center portion increases. Therefore, in order to improve the degree of orientation of the c-axis of the superconductor as a whole bearing in the radial direction, the number of element members is increased, but conversely, no superconducting current flows. The number of boundaries between element members will also increase. Therefore, in the radial bearing type arrangement, the conventional method has the contradictory properties of improving the crystal orientation of the entire bearing and reducing the number of boundary surfaces where the superconducting current does not flow. There was a problem that it was difficult to improve the levitation force.

  Further, even in the axial bearing type arrangement, when the bearing size is increased, it is difficult to produce a single crystal superconductor as a single body, and thus a plurality of superconductors are combined. In this case as well, there is a problem that it is difficult to improve the levitation force because the superconducting current does not flow between the individual superconductors.

  An object of the present invention is to provide a superconducting bearing that achieves high levitation force in an axial bearing type arrangement in which the superconductor and the magnet are axially opposed in order to solve the above problems.

The superconducting bearing of this reference example is an axial type superconducting bearing in which the superconductor and the magnet face each other in the axial direction, and the superconductor constituting the superconducting bearing has a plurality of single crystal regions inside, The superconducting bearing is characterized in that the c-axis of each single crystal region in the superconductor is oriented in the axial direction of the bearing.

A first superconducting bearing according to the present invention is an axial type superconducting bearing in which a superconductor and a magnet face each other in the axial direction. The superconductor constituting the superconducting bearing is composed of a plurality of element members. A superconducting bearing characterized in that a laminated structure is formed in the axial direction, and the position of the boundary surface between the element members is shifted for each adjacent layer, and the c-axis of the single crystal region faces the axial direction of the bearing. is there.
Second superconducting bearing according to the invention are the first superconducting bearing according to the invention, wherein the thickness of the layer closest to the magnet of the superconductor having a layered structure is 5mm or less.

According to the configuration of the superconducting bearing of this reference example , since the superconducting current flows also at the boundary between the plurality of single crystal regions in which the superconductor is present, the physical coupling is not performed at all. As compared with the conventional example, the levitation force is improved.
According to the configuration of the first superconducting bearing according to the present invention, the superconductor of the adjacent layer exists at the position of the boundary surface where the superconductors are merely physically coupled. It works to reduce the effect of weakening the general connection. For this reason, the levitation force is improved as compared with the conventional example in which the superconductor does not have a laminated structure.
The reason for limiting the thickness of the layer closest to the magnet of the superconductor having a laminated structure to 5 mm or less in the second superconducting bearing according to the present invention will be described. The present inventors investigated the relationship between the thickness of the superconductor and the levitation force.When the thickness of the superconductor is 5 mm or less, the levitation force increases as the sample thickness increases, but the sample thickness exceeds 5 mm. I found that the levitation force was almost constant as the value increased. That is, if the thickness of the layer closest to the magnet is larger than 5 mm, the effect of making the superconductor a laminated structure becomes very small. Therefore, the thickness of the layer closest to the superconductor magnet having a laminated structure is limited to 5 mm or less.

The superconductor used in the present invention is not particularly limited as long as it can exhibit a pinning effect, but a superconductor having a strong pinning force is preferable. The superconductor used in this example is called a QMG material. The RE ₂ BaCuO ₅ phase is finely dispersed in a single-crystal REBa ₂ Cu ₃ O _x phase (RE is Y or a rare earth element and a combination thereof). It is an oxide-based superconductor that has a strong pinning power at liquid nitrogen temperature (patent registration number 1869884). The magnet used in the present invention is preferably a permanent magnet because the bearing structure is simplified, but may be an electromagnet or a superconducting magnet. Since the levitation force increases as the magnetic flux density on the surface facing the superconductor increases, when using a permanent magnet, a material having a high surface magnetic flux density, such as a rare earth-based permanent magnet, for example, Nd-Fe-B A permanent magnet such as Pr-Fe-B or Sm-Co is desirable.

  According to the superconducting bearing of the present invention, a high levitation force can be provided by the axial bearing type arrangement in which the superconductor and the permanent magnet face each other in the axial direction, so that it is possible to realize a superconducting bearing used for a power storage flywheel or a high-speed rotating device. Can increase the sex.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
1A and 1B are schematic views showing one embodiment of a superconducting bearing, where FIG. 1A is a perspective view and FIG. 1B is a cross-sectional view. In FIG. 1, in the radial bearing type arrangement in which the superconductor and the permanent magnet face each other in the radial direction, the c-axis direction of the superconductor faces the axial direction of the bearing, not the radial direction of the bearing. Although a cooling system for cooling the superconductor is not shown in FIG. 1, the superconductor is housed in a cooling container and cooled by a refrigerant such as liquid nitrogen or cooled by a refrigerator.

  As shown in Fig. 2 (a), as a superconductor of the reference example, a Y-type oxide superconductor with an outer diameter of 46 mm, an inner diameter of 15 mm, and a height of 20 mm with the c-axis facing the axial direction of the ring. A shape sample was prepared, and as a superconductor of the conventional example, as shown in Fig. 2 (b), four fan-shaped samples of the Y-type oxide superconductor with the central portion facing the radial direction were used as a reference example. Were combined in a ring shape of the same size as the above, and the levitation force was measured and compared for each. The levitation force is measured by cooling the superconductor fixed to the storage jig with liquid nitrogen in a ring-shaped magnet. After the superconductor has cooled sufficiently, the distance between the superconductor and the permanent magnet is measured. I went away.

  FIG. 3 shows an example of measurement of the levitation force characteristic curve. As the distance between the superconductor and the permanent magnet increased, the levitation force increased rapidly at first and then gradually decreased after taking the maximum value. Here, the maximum value of the levitation force is simply called the levitation force. The levitation force of the conventional example of FIG. 2B was 122 N, whereas the levitation force of the superconductor of the reference example of FIG. 2A was 148 N.

  As the superconductor of the reference example in FIG. 2A is an integral superconductor, it is desirable that the superconductor is an integral sample without any break in the circumferential direction and the axial direction. However, as the size of the superconducting bearing increases, it becomes difficult to produce a single-crystal sample as a single piece. Even in that case, several superconductors are combined, but the same effect can be obtained by orienting the c-axis of each superconductor in the axial direction of the bearing. As a method of combination, depending on the size of the superconductor required for the bearing, as shown in FIG. 4 (a), samples having no discontinuities in the circumferential direction may be stacked in the axial direction, or as shown in FIG. 4 (b). Thus, samples that are not cut in the axial direction may be combined in the circumferential direction, or several samples may be combined in both the axial direction and the circumferential direction as shown in FIG.

  FIG. 5 is a schematic view showing an embodiment of a superconducting bearing. In FIG. 5, the permanent magnet is not shown, but it is assumed to be in the radial direction as in FIG. In FIG. 5, the superconductors constituting the superconducting bearing are integrated, and there are four single-crystal regions in the sample, and the c-axis of each single-crystal region faces the radial direction. ing.

  As a superconductor of the reference example, a ring-shaped sample of an Y-type oxide superconductor having an outer diameter of 46 mm, an inner diameter of 15 mm, and a height of 20 mm with the c-axis facing the radial direction as shown in FIG. 5 was prepared. . In order to form four single-crystal regions in a monolithic sample, as shown in FIG. 6, when the sample was produced, crystal growth was performed using four seed crystals. In addition, by making the c-axis direction of each seed crystal the radial direction, the c-axis of each single crystal region could also be oriented in the radial direction. The levitation force of this sample was measured and found to be 165N. On the other hand, the levitation force of the conventional superconductor shown on the right side of FIG.

  FIG. 6 shows a case where four single crystal regions are included in one sample. However, as shown in FIG. 7, the effect is also examined in the case where six single crystal regions are included in one sample. I tried. As a superconductor of a reference example, a ring-shaped sample of an Y-type oxide superconductor having an outer diameter of 46 mm, an inner diameter of 15 mm, and a height of 20 mm with the c-axis facing the radial direction is shown in FIG. It was prepared using six seed crystals with the c-axis directed in the radial direction. For comparison, a ring oxide of the same size as that of the reference example was used by using six Y-shaped oxide superconductors with a c-axis facing the radial direction at the center as shown in FIG. What was fixed to the combination storage jig was prepared. The levitation force of the reference sample was 172N, and the levitation force of the comparative example was 138N.

  As shown in FIG. 9, the effect was examined also in the case where three single crystal regions were included in one sample. As a superconductor of the reference example, a ring-shaped sample of an Y-type oxide superconductor having an outer diameter of 46 mm, an inner diameter of 15 mm, and a height of 20 mm with the c-axis facing the radial direction is shown in FIG. Three seed crystals with the c-axis directed in the radial direction were used. For comparison, using a Y-type oxide superconductor as shown in FIG. 10 and using three fan-shaped samples with the c-axis facing the radial direction at the center, the ring shape has the same size as the reference example. What was fixed to the combination storage jig was prepared. The levitation force of the sample of the reference example was 126N, and the levitation force of the comparative example was 119N.

  In the case where four single crystal regions are included in one sample as shown in FIG. 6, the angle formed between the adjacent single crystal regions in the c-axis direction is 90 °. In the example of FIG. 6, the levitation force is improved from 122N to 165N and 43N. In addition, in the case where six single crystal regions are included in one sample as shown in FIG. 7, the angle formed between the adjacent single crystal regions in the c-axis direction is 60 °. In the example of FIG. 7, the levitation force is improved from 138N to 172N and 34N. On the other hand, when three single crystal regions are included in one sample as shown in FIG. 9, the angle formed by the adjacent single crystal regions in the c-axis direction is 120 °. In the example of FIG. 9, the levitation force is improved from 119N to 126N by 7N, but the effect of improving the levitation force is small compared to the cases of FIGS. Therefore, in order to increase the effect of improving the levitation force, it is desirable that the angle formed by the c-axis direction between adjacent single crystal regions be 90 ° or less.

  In the reference examples described so far, a manufacturing process using a plurality of seed crystals was performed at the time of sample preparation in order to manufacture a plurality of single crystal regions in one superconductor. is not. An example of another manufacturing process is shown in FIG. FIG. 11 shows a manufacturing process in which a fan-shaped superconductor is prepared in advance and a post-treatment for superconducting them is performed to form one sample.

  In the method of FIG. 11, as a post-processing step for superconducting bonding, the main body is made of a Y-based oxide superconductor having a crystal growth temperature of 1000 ° C., and a Yb-based oxide superconductor having a crystal growth temperature of 900 ° C. therebetween. In the state of inserting, the heating was performed to 900 ° C. or higher, and the temperature was gradually cooled to about 900 ° C. That is, the process was performed using a superconductor having a low crystal growth temperature as solder and bonding the superconductor having a high crystal growth temperature. In this manufacturing process, a ring-shaped sample having an outer diameter of 46 mm, an inner diameter of 15 mm, and a height of 20 mm was manufactured, and the flying force was measured to be 145N. On the other hand, the levitation force of the conventional superconductor shown on the right side of FIG.

  In the reference examples described so far, the superconductor constituting the bearing is an integral superconductor. However, as the size of the superconducting bearing increases, it becomes difficult to produce an integral sample. In that case, several superconductors are combined. As shown in FIG. 12, a plurality of single crystal regions are provided inside each superconductor, and the c-axis of each single crystal region is A similar effect can be obtained by directing in the radial direction of the bearing.

  FIG. 13 is a schematic view showing an embodiment of a superconducting bearing. In FIG. 13, the permanent magnet is not shown, but it is assumed to be in the radial direction as in FIG. In FIG. 13, the superconductor constituting the superconducting bearing has a brick structure in the radial direction in a brick shape. FIG. 14 is a schematic view showing an embodiment of a superconducting bearing. In FIG. 14, the permanent magnet is not shown, but the permanent magnet is assumed to be in the radial direction, and the thickness of the layer closest to the permanent magnet is thin.

  In order to investigate the effect of the thickness of the layer closest to the permanent magnet, the levitating force of a Y-based oxide superconductor with an outer diameter of 46 mm and a height of 20 m, and with the ring radial thickness changed. As a result, the results as shown in FIG. 15 were obtained. From FIG. 15, it can be seen that the levitation force becomes substantially constant when the thickness in the radial direction is greater than 5 mm. Therefore, when the superconductor has a laminated structure, the effect of improving the levitation force is small even if the thickness of the layer closest to the permanent magnet is larger than 5 mm.

  As a superconductor of the reference example, a ring-shaped sample with an outer diameter of 46 mm, an inner diameter of 15 mm, and a height of 20 mm with a c-axis facing the radial direction as shown in FIG. did. The laminated structure in the radial direction was two layers, the thickness of the layer closest to the permanent magnet was 3 mm, the thickness of the second layer was 12.5 mm, and the number of circumferential divisions was four. The levitation force of the sample of the reference example was measured and found to be 146N. On the other hand, the levitation force of the conventional superconductor shown on the right side of FIG. In the reference example, the c-axis of the superconductor was oriented in the radial direction. However, when the c-axis of the superconductor is oriented in the axial direction, the same effect can be obtained by using a laminated structure. Can do.

FIG. 16 is a schematic view showing one reference form of a superconducting bearing based on this reference example . In FIG. 16, the superconductor constituting the superconducting bearing is an integrated body, and the sample has four single crystal regions in the sample. In this case, because of the axial bearing type arrangement, the c-axis of each single crystal region is oriented in the axial direction.

In order to investigate the above effect, the superconductor of this reference example is a Y-based oxide superconductor having an outer diameter of 46 mm, an inner diameter of 15 mm, and a height of 15 mm with the c-axis facing the axial direction as shown in FIG. A disk-shaped sample of the object was prepared. In order to form four single-crystal regions in a monolithic sample, as shown in FIG. 17, when the sample was produced, crystal growth was performed using four seed crystals. In addition, by setting the direction of the c-axis of each seed crystal to the axial direction, the c-axis of each single crystal region could also be oriented in the axial direction. For comparison, a ring-shaped sample of the same size as this reference example with the c-axis facing the axial direction is divided into four parts with a Y-based oxide superconductor as shown in FIG. What was fixed to the jig was prepared.

The levitation force in the axial bearing type arrangement was measured by cooling the superconductor with liquid nitrogen and sufficiently cooling the superconductor, and then bringing the ring-shaped permanent magnet close to the superconductor. FIG. 19 shows an example of measurement of the levitation force characteristic curve. As the distance between the superconductor and the permanent magnet decreased, the levitation force gradually increased and reached a maximum when the permanent magnet contacted the superconductor. Here, the maximum value of the levitation force is simply called the levitation force. The levitation force of the sample of this reference example was 189N, and the levitation force of the comparative example was 161N. By this reference example, levitation force it was confirmed that improvement.

Figure 20 is a schematic diagram illustrating an embodiment of a superconducting bearing in accordance with the present onset bright. In FIG. 20, the superconductors constituting the superconducting bearing have a brick-like laminated structure. In this case, because of the axial bearing type arrangement, the c-axis of each superconductor forming the laminated structure is directed in the axial direction.

  In order to investigate the effect of the present invention, a Y-based oxide superconductor is used as the superconductor of the present embodiment, and a rectangular shape having a c-axis of 40 mm on one side and a height of 15 mm as shown in FIG. A shape sample was produced in a laminated structure. The axial laminated structure has two layers, the thickness of the layer closest to the permanent magnet is 3 mm, there is a bonding interface at the center, the thickness of the second layer is 12 mm, and the first layer is bonded to the first layer. The boundary position was shifted. For comparison, as shown in FIG. 21 (b), a rectangular sample having the same size as that of the present example in which the c-axis is directed in the axial direction is divided into two parts by simply joining them. I prepared what I did. The flying force of the sample of this example was 135 N, and the flying force of the comparative example was 109 N. It was confirmed that the levitation force was improved by the present invention.

  According to the superconducting bearing of the present embodiment, a high levitation force can be provided by the axial bearing type arrangement in which the superconductor and the permanent magnet face each other in the axial direction, thereby realizing a superconducting bearing used for a power storage flywheel or a high-speed rotating device. The possibility can be increased.

It is (a) perspective view and (b) sectional drawing of a superconducting bearing. It is a figure which shows (a) one reference example and its (b) comparative example of the superconductor of a superconducting bearing. It is a figure which shows the graph of an example of the measurement data of the floating force in radial bearing type | mold arrangement | positioning. (A), (b), (c) is a figure which shows another reference example of the superconductor of a superconducting bearing, respectively. It is a figure which shows one reference example of the superconductor of a superconducting bearing. It is a figure which shows an example of the preparation process of the superconductor of a superconducting bearing. It is a figure which shows an example of the manufacturing process of the superconductor which contains six single-crystal-like area | regions in one sample. It is a figure which shows the comparative example with respect to FIG. It is a figure which shows an example of the manufacturing process of the superconductor which contains three single-crystal-like area | regions in one sample. It is a figure which shows the comparative example with respect to FIG. It is a figure which shows another reference example of the preparation process of the superconductor of a superconducting bearing. It is a figure which shows another reference example of the superconductor of a superconducting bearing. It is a figure which shows one reference example of the superconductor of a superconducting bearing. It is a figure which shows one reference example of the superconductor of a superconducting bearing. It is a figure which shows the graph of the relationship between levitation force and the radial direction thickness of a superconductor. Is a diagram illustrating an outline of a superconducting bearing. Is a diagram showing an example of a manufacturing process of the superconductor superconducting bearing. It is a figure which shows the comparative example with respect to FIG. It is a figure which shows the graph of an example of the measurement data of the levitation force in an axial bearing type | mold arrangement | positioning. (A) a perspective view of a superconducting bearing in accordance with the present onset bright, a (b) cross-section. (A) an embodiment of a superconducting bearing in accordance with the present onset bright as is a diagram showing the (b) Comparative Example. It is (a) perspective view, (b) sectional drawing of the conventional axial superconducting bearing. It is the (a) perspective view and (b) sectional view of the conventional radial type superconducting bearing. It is a figure which shows the prior art example of the preparation process of the superconductor for radial bearings.

Claims (2)

In an axial superconducting bearing in which a superconductor and a magnet are opposed in the axial direction, the superconductor constituting the superconducting bearing is composed of a plurality of element members, and each element member forms a laminated structure in the axial direction. And the position of the boundary surface between element members shifts for every adjacent layer, and the c-axis of the single crystal region is oriented in the axial direction. The superconducting bearing according to claim 1 , wherein the thickness of the layer closest to the magnet of the superconductor having a laminated structure is 5 mm or less.

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