JP4058831B2 - Superconducting magnetic bearing - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a superconducting magnetic bearing applied to, for example, a fluid machine or a machine tool that requires high-speed rotation, or a power storage device that converts surplus power into rotational kinetic energy of a flywheel and stores it. More specifically, the present invention relates to a superconducting magnetic bearing that uses a superconductor and a permanent magnet to float and support a rotating body in a non-contact state with respect to a fixed portion.
[0002]
[Prior art]
This type of superconducting magnetic bearing includes a superconductor portion provided on the fixed portion side and a permanent magnet portion provided on the rotating body side so as to face the superconductor portion. The superconductor portion includes a cooling container in which a cooling fluid such as liquid nitrogen is circulated, and a superconductor disposed in the cooling container. The permanent magnet portion includes a permanent magnet disposed so as to face the superconductor via the wall of the cooling container. In order to increase the magnetic levitation force by the superconducting magnetic bearing, it is necessary to make the distance between the superconductor and the permanent magnet as small as possible. For this reason, conventionally, the distance between the permanent magnet and the wall of the cooling container facing the permanent magnet is made as small as possible, the thickness of the wall is made as small as possible, and the superconductor is disposed so as to be in close contact with the inner surface of the wall. Yes. And the superconductor is cooled with the cooling fluid which distribute | circulates between surfaces other than the surface at the side of the permanent magnet of a superconductor, and the wall of a cooling container.
[0003]
By the way, in the superconducting magnetic bearing as described above, the surface of the superconductor undergoes a magnetic field change as the permanent magnet rotates together with the rotating body. This is caused by uneven magnetic flux density of the permanent magnet and change of magnetic flux density due to rotational shake of the rotating body. This magnetic field change changes the shielding current of the superconductor and causes an AC loss on the surface of the superconductor. As a result, the superconductor generates heat. However, since the surface of the superconductor on the permanent magnet side is in close contact with the wall of the cooling vessel and cannot be directly cooled with the cooling fluid, the heat generated by the superconductor cannot be removed, and the temperature of the superconductor rises slightly. To do. For this reason, the critical current density of a superconductor falls and the magnetic force of a superconductor will fall. As a result, the magnetic levitation force, which is a characteristic of the superconducting magnetic bearing, is reduced, and the rotation loss is increased.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide a superconducting magnetic bearing capable of solving the above problems and effectively cooling a superconductor to prevent a decrease in magnetic levitation force.
[0005]
[Means for Solving the Problems and Effects of the Invention]
A superconducting magnetic bearing according to the present invention is a superconducting magnetic bearing that supports a rotating part by floating in a non-contact state with respect to a fixed part, the superconducting part provided on the fixed part side, and the superconductor part. And a permanent magnet portion provided on the rotating body side so as to face the ring, and the superconductor portion includes an annular cooling vessel in which a cooling fluid is circulated, and an annular shape disposed in the cooling vessel. A superconducting magnetic bearing comprising an annular permanent magnet disposed so that the permanent magnet portion faces the superconductor through a wall of the cooling vessel. A cooling fluid circulation space through which a cooling fluid passes is formed between both circumferential surfaces and both end surfaces and the wall of the cooling vessel facing them, and the superconductor is disposed in the cooling fluid circulation space with respect to the cooling vessel. Radial direction It is characterized in that the spring-like spacing member for holding is provided.
[0006]
Nearly the entire surface of the superconductor is directly cooled by the cooling fluid passing through the cooling fluid circulation space formed between the entire surface of the annular superconductor and the wall of the cooling container facing them . For this reason, heat generation of the superconductor can be prevented, and a decrease in magnetic levitation force and an increase in rotation loss can be suppressed.
[0007]
In addition, the space holding member can reliably hold the superconductor with respect to the cooling container and form a cooling fluid circulation space between the cooling container and the wall .
[0008]
Interval holding member are those spring-like having appropriate elasticity. As a spring-like spacing members, for example, ring shaped into corrugated and thin cylinder Ru is used.
[0009]
When the spring-like spacing member is used, the vibration of the rotating body at the critical speed can be suppressed by the damping effect. In addition, the spacing member can absorb the difference in thermal shrinkage between the cooling container and the superconductor.
[0013]
For example, the superconductor portion includes a plurality of cooling containers arranged side by side in the axial direction of the rotating body, and superconductors arranged in the cooling containers.
[0014]
In order to increase the magnetic levitation force in a large superconducting magnetic bearing, the superconductor portion and the permanent magnet portion must be elongated in the axial direction. However, in that case, the superconductor becomes vertically long and is difficult to mold. In addition, the cooling container is also vertically long and has a large volume, which makes it difficult to cool the superconductor.
[0015]
When a plurality of cooling containers are arranged in the axial direction as described above, it is not necessary to make each cooling container too large. For this reason, it is not necessary to make the superconductor vertically long, and its molding is easy. Further, the volume of each cooling container is not increased, and the superconductor can be effectively cooled. Further, since the entire superconductor portion is long in the axial direction, the magnetic levitation force is increased.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to a flywheel power storage device will be described with reference to the drawings.
[0017]
FIG. 1 shows a main part of the power storage device.
[0018]
As shown in FIG. 1, a vertical fixed shaft (2) is fixed at the center of the housing (1), and a vertical cylindrical rotating body (3) is disposed around the fixed shaft. The housing (1) has a substantially cylindrical shape, and the inside thereof is kept in a vacuum state in order to prevent windage damage. In FIG. 1, only the top and bottom walls of the housing (1) are shown. The housing (1) and the fixed shaft (2) constitute a fixed portion. A flywheel (4) for converting surplus electric power into rotational kinetic energy and storing it is provided on the outer periphery of the rotating body (3).
[0019]
Two sets of upper and lower superconductivity between the fixed shaft (2) and the rotating body (3) for non-contact support of the rotating body (3) in the axial direction (axial direction) and radial direction (radial direction) during operation A magnetic bearing (5) (6) and a built-in generator / motor (7) functioning as a generator when taking out electric power are provided as an electric motor for rotating the rotating body (3) at high speed when storing electric power. Hereinafter, the superconducting magnetic bearing is abbreviated as a superconducting bearing. The electric motor (7) includes a stator part (7a) provided on the fixed shaft (2) and a rotor part (7b) provided on the rotating body (3).
[0020]
Although not shown in the figure, two sets of upper and lower control type radial magnets are provided between the outer periphery of the rotating body (3) and the peripheral wall of the housing (1) to support the rotating body (3) in a radial non-contact manner during operation. A control type axial magnetic bearing is provided for supporting the rotating body (3) in a non-contact manner in the axial direction at the time of bearing and startup.
[0021]
On the bottom wall of the housing (1), there is a touchdown bearing (8) for mechanically supporting the lower part of the rotating body (3) when the superconducting bearing (5) (6) and the magnetic bearing are no longer supported. Is provided.
[0022]
An example of the configuration of the upper superconducting bearing (5) is shown in FIG. Since the upper and lower superconducting bearings (5) and (6) have the same configuration, the upper superconducting bearing (5) will be described below.
[0023]
The superconducting bearing (5) includes an annular superconductor portion (10) provided concentrically on the outer periphery of the fixed shaft (2), and a rotating body (3) so as to face the superconductor portion (10) in the radial direction. ) Of a permanent magnet portion (11) provided concentrically on the inner peripheral portion. The superconductor portion (10) is composed of two sets of upper and lower cooling units (10a) and (10b). The permanent magnet section (11) is composed of two sets of upper and lower permanent magnet units (11a) and (11b) respectively corresponding to the two sets of cooling units (10a) and (10b). A flange (14) is fixed to the outer periphery of the fixed shaft (2), and two sets of cooling units (10a) and (10b) are fixed side by side in the vertical direction, that is, in the axial direction. The flange (14) is preferably made of a non-magnetic material having thermal insulation properties, such as FRP (fiber reinforced plastics). Since the upper and lower cooling units (10a) and (10b) have the same configuration and the upper and lower permanent magnet units (11a) and (11b) have the same configuration, the upper cooling unit (10a) and the permanent magnet unit will be described below. (11a) will be described.
[0024]
A plurality of upper and lower annular permanent magnets (15) are arranged on the inner periphery of the rotating body (3) via a plurality of upper and lower annular iron yokes (16), thereby forming a permanent magnet unit (11a). For example, each permanent magnet (15) has magnetic poles at both ends in the axial direction, and the permanent magnets (15) adjacent to each other in the vertical direction are arranged so that the opposing magnetic poles have the same polarity, and the yoke (16) It becomes a magnetic pole. The permanent magnet (15) is arranged concentrically with the rotating body (3), and the magnetic flux distribution of the permanent magnet (15) around the rotation axis of the rotating body (3) is changed by the rotation of the rotating body (3). It is designed not to do so.
[0025]
The cooling unit (10a) includes an annular cooling vessel (cryostat) (17) through which a cooling fluid is circulated, and an annular second type superconductor (18) disposed in the vessel (17). . The cooling fluid is preferably a liquid, and in this example liquid nitrogen is used. The cooling container (17) is disposed concentrically with the fixed shaft (2). The container (17) is composed of an annular container body (19) whose upper surface is open and a lid (20) that closes the upper surface, and the container (17) has a rectangular cross-sectional shape passing through the axis. A space is formed. The container (17) is preferably made of a nonmagnetic material having thermal insulation properties, such as FRP. A bulging portion (19a) (20a) bulging radially inward is provided at one place in the circumferential direction of the container body (19) and the lid (20). A substantially annular protrusion (21) is integrally formed at the boundary between the inner peripheral wall (19b) and the bottom wall (19c) inside the container body (19), except for the portion corresponding to the bulging portion (19a). ing. Projections (22) are integrally formed at a plurality of locations that equally divide the boundary between the outer peripheral wall (19d) and the bottom wall (19c) in the container main body (19) in the circumferential direction. A substantially annular protrusion (23) is integrally formed on the inner surface of the lid (20) adjacent to the inner peripheral wall (19b) inner surface of the container body (19), except for the portion corresponding to the bulging portion (20a). Yes. Protrusions (24) are integrally formed at a plurality of locations that equally divide the inner surface of the lid (20) close to the inner surface of the outer peripheral wall (19d) of the container body (19) in the circumferential direction.
[0026]
The superconductor (18) has a vertical cylindrical shape. The inner diameter of the superconductor (18) is larger than the outer diameter of the inner peripheral wall (19b) of the container body (19), and the outer diameter of the superconductor (18) is slightly smaller than the inner diameter of the outer peripheral wall (19d) of the container body (19). . The superconductor (18) is concentrically arranged in the container (17), and the outer periphery of the superconductor (18) is the protrusion on the outer periphery side of the container body (19) (22) and the protrusion on the outer periphery side of the lid (20). (24) so that the superconductor (18) does not move in the axial direction. Between the outer peripheral surface of the superconductor (18) and the outer peripheral wall (19d) of the container body (19), and between the inner peripheral surface of the superconductor (18) and the inner peripheral wall (19b) of the container main body (19) In addition, cooling fluid circulation spaces (25) and (26) through which liquid nitrogen passes are formed.
[0027]
Dimension of the radial gap between the permanent magnet unit (11a) and the outer peripheral wall (19d) of the container body (19), the radial thickness of the outer peripheral wall (19d), and the radial gap of the outer circulation space (25) For example, 1 mm, 1 mm, and 0.5 mm, respectively. In the drawing, these are shown larger than the actual size.
[0028]
In each of the circulation spaces (25) and (26), interval holding members (27) and (28) for holding the superconductor (18) in the radial direction are provided. As shown in detail in FIG. 3, each holding member (27) (28) has a corrugated ridge (27b) extending over the entire height at a plurality of locations equally dividing the cylindrical base (27a) (28a) in the circumferential direction. (28b) is formed of a wavy ring formed integrally. These holding members (27) and (28) are preferably made of a nonmagnetic material having heat insulation properties such as FRP. The outer holding member (27) is sandwiched between the outer peripheral protrusion (22) of the container body (19) and the outer peripheral protrusion (24) of the lid (20) and is supported in the axial direction. The inner holding member (28) is sandwiched between the inner peripheral projection (21) of the container body (19) and the inner peripheral projection (23) of the lid (20), and is supported in the axial direction. Yes. In the outer holding member (27), the base (27a) is in close contact with the inner surface of the outer peripheral wall (19d) of the container body (19), and the top of the protrusion (27b) is in contact with the outer peripheral surface of the superconductor (18). . In the inner holding member (28), the base (28a) is in close contact with the inner surface of the inner peripheral wall (19b) of the container body (19), and the top of the protrusion (28b) is in contact with the inner peripheral surface of the superconductor (18). To do.
[0029]
The superconductor (18) is made of, for example, an yttrium-based superconductor such as YBa ₂ Cu ₃ O _{7-x, in} which normal conductive particles (Y ₂ BaCu) are uniformly mixed inside a bulk. In an environment where a superconducting state appears, it has the property of restricting the penetration of magnetic flux emitted from the permanent magnet (15). Then, the superconductor (18) is arranged as described above, so that the magnetic flux of the permanent magnet (15) is at a remote position where a predetermined amount of magnetic flux enters, and the rotation of the rotating body (3) causes the intrusion magnetic flux distribution to be distributed. It is placed at a position that does not change.
[0030]
The cooling fluid supply pipe (29) and the discharge pipe (30) are fixed in a penetrating manner to the bulging portion (20a) of the lid (20) of the container (17), and one end of the supply pipe (29) is connected to the container body ( 19) is located in the lower part in the bulging part (19a), and one end of the discharge pipe (30) is located in the upper part in the bulging part (19a). The other end sides of the supply pipe (29) and the discharge pipe (30) pass through the housing (1) and are connected to a cooling device (not shown). Then, by this cooling device, liquid nitrogen is circulated in the container (17) as follows, and the superconductor (18) is cooled by the liquid nitrogen filled in the container (17).
[0031]
The liquid nitrogen that has come out of the cooling device passes through the supply pipe (29) and enters the lower portion of the bulging portion (19a) of the container body (19) to fill the container (17). Then, the liquid nitrogen in the container (17) enters the discharge pipe (30) from the upper part in the bulging part (19a) and is returned to the cooling device. In the container (17), almost the entire surface of the superconductor (18) is directly cooled by liquid nitrogen passing through the space above and below the superconductor (18) and the flow space (26) (25) inside and outside the superconductor (18). Therefore, the superconductor (18) can be efficiently cooled. A part of the liquid nitrogen is vaporized while circulating in the container (17) to become nitrogen gas, and a part of the liquid nitrogen accumulates in the upper part of the container (17). However, when the lowest part of the layer of nitrogen gas falls to the height of the lower end of the discharge pipe (30), nitrogen gas enters the discharge pipe (30) and is discharged, so the nitrogen gas is discharged from the lower end of the discharge pipe (30). It does not collect downward. That is, the nitrogen gas only accumulates in a slight portion of the uppermost portion in the container (17) above the lower end of the discharge pipe (30). And since the lower end of the discharge pipe (30) is located at substantially the same height as the uppermost part of the superconductor (18), nitrogen gas does not accumulate around the superconductor (18). Therefore, only the liquid nitrogen is filled around the superconductor (18), and the superconductor (18) is always completely cooled by the liquid nitrogen, and a good superconducting state is obtained.
[0032]
In the lower cooling unit (10b) and the permanent magnet unit (11b), the same parts as those in the upper part are denoted by the same reference numerals. The container (17) of the lower cooling unit (10b) is concentrically fixed on the flange (14), and the container (17) of the upper cooling unit (10a) is concentrically fixed thereon. . Preferably, the bulging portions (19a) of the upper and lower container bodies (19) are arranged at symmetrical positions.
[0033]
In the lower superconducting bearing (6), the same parts as those of the upper superconducting bearing (5) are denoted by the same reference numerals. In the lower superconducting bearing (6), the supply pipe (29) and the discharge pipe (30) are passed through a hole (31) formed in the center of the fixed shaft (2), branched in the middle and led to the container (17). It has been.
[0034]
The above power storage device is activated as follows, for example.
[0035]
First, the radial magnetic bearing and the axial magnetic bearing are brought into an operating state, and the rotating body (1) is supported in a non-contact manner in the radial direction and the axial direction, and is floated to a predetermined operating position. Next, liquid nitrogen is supplied into the containers (17) of the respective superconducting bearings (5) and (6), and the superconductor (18) is cooled to a predetermined temperature and maintained in the superconducting state in which the type 2 superconducting state appears. To do. In this way, with the magnetic flux generated from the permanent magnet (15) invading the inside of the superconductor (18) located inside the permanent magnet (15), the superconductor (18) is cooled (magnetic field cooling) to obtain the second type. In the superconducting state, much of the magnetic flux that has entered the superconductor (18) is pinned at the pinning point inside the superconductor (18) as it is, and is restrained inside the superconductor (18). Next, the axial magnetic bearing is deactivated. As a result, the weight of the rotating body (3) is supported by the superconducting magnetic bearings (5) and (6), and the rotating body (3) is not moved to the operating position by the superconducting magnetic bearings (5) and (6) and the radial magnetic bearing. Since the contact is supported, the electric motor is driven to rotate the rotating body (3) at a high speed. At this time, the magnetic flux that has entered the superconductor (18) is not ideally a resistance that prevents rotation as long as the magnetic flux distribution is uniform and unchanged with respect to the rotational axis of the rotating body (3). .
[0036]
FIG. 4 shows a modification of the spacing member between the outer peripheral wall (19d) of the outer container body (19) and the superconductor (18). This holding member (32) uses a tolerance ring used for fastening the shaft and the housing and fixing the bearing ring of the rolling bearing with respect to the housing as it is, and the cylindrical base (32a) is used in the circumferential direction. A plurality of points equally divided into two are cut and raised inward to form a corrugated protrusion (32b) extending in the axial direction.
[0037]
FIG. 5 shows another modification of the spacing member. In this case, the spacing member (33) is formed of a thin cylinder with a small diameter. Shallow arc-shaped grooves (34) extending in the vertical direction are formed at a plurality of locations equally dividing the inner peripheral surface of the outer peripheral wall (19d) of the container main body (19) in the circumferential direction, and one of the holding members (33) is formed. The part is fitted into the groove (34), and the opposite part is in contact with the outer peripheral surface of the superconductor (18).
[0039]
In the case of FIG. 5, a spacing member (28) similar to the above can be provided in the inner cooling fluid circulation space (26). If the holding member (28) is not provided, it is not necessary to form the protrusion (21) in the container (17).
[0040]
The structure of each part of an electric power storage apparatus is not restricted to the thing of the said embodiment, It can change suitably.
[0041]
In the above embodiment, the two upper and lower superconducting bearings (5) and (6) support the upper and lower two portions of the rotating body (3). However, only one superconducting bearing may be provided.
[0042]
In the above embodiment, the superconducting bearings (5) and (6) are composed of two sets of upper and lower cooling units (10a) and (10b) and permanent magnet units (11a) and (11b). It may be composed of a cooling unit and a permanent magnet unit, or it may be composed of only one set of cooling unit and permanent magnet unit. Even when the superconductor portion of the superconducting bearing is divided into a plurality of upper and lower cooling units, the permanent magnet portion is not necessarily divided into a plurality of sets of cooling units.
[0043]
In the above embodiment, liquid nitrogen is used as the cooling fluid, but fluids other than liquid nitrogen can also be used.
[0044]
In the above embodiment, the superconductor portion (10) and the permanent magnet portion (11) are opposed to each other in the radial direction (horizontal direction). However, according to the present invention, the superconductor portion and the permanent magnet portion are in the axial direction (vertical direction). The present invention can also be applied to a superconducting magnetic bearing of the type opposite to.
[0045]
The superconducting magnetic bearing uses a type 1 superconductor that appears in the first type superconducting state by cooling, and rotates using the complete diamagnetic phenomenon (Meissner effect) in the first type superconducting state of the first type superconductor. Although there is one that supports the body in a non-contact manner, the present invention can also be applied to a superconducting magnetic bearing using such a first type superconductor.
[0046]
Furthermore, the superconducting magnetic bearing of the present invention can be used for devices other than the power storage device.
[Brief description of the drawings]
FIG. 1 is a schematic longitudinal sectional view of a main part of a power storage device showing an embodiment of the present invention.
FIG. 2 is a schematic longitudinal sectional view showing an enlarged portion of the upper superconducting magnetic bearing in FIG. 1;
3 is an enlarged horizontal sectional view showing a part of the upper superconducting magnetic bearing of FIG.
FIG. 4 is a perspective view showing a modified example of the spacing member.
FIG. 5 is a drawing corresponding to FIG. 3, showing another modification of the spacing member .
[Explanation of symbols]
(1) Housing
(2) Fixed shaft
(3) Rotating body
(5) (6) Superconducting magnetic bearing
(10) Superconductor part
(10a) (10b) Cooling unit
(11) Permanent magnet section
(11a) (11b) Permanent magnet unit
(15) Permanent magnet
(17) Cooling container
(18) Superconductor
(19) Container body
(19b) Inner wall
(19d) Perimeter wall
(25) (26) Cooling fluid distribution space
(27) (28) (32) (33 ) Spacing member

Claims (2)

A superconducting magnetic bearing for rotating and supporting a rotating body in a non-contact state with respect to a fixed portion, the superconductor portion provided on the fixed portion side, and the rotating body side so as to face the superconductor portion The superconductor portion includes an annular cooling container in which a cooling fluid is circulated, and an annular superconductor disposed in the cooling container, In the superconducting magnetic bearing provided with an annular permanent magnet disposed so that the permanent magnet portion faces the superconductor through the wall of the cooling vessel,
A cooling fluid circulation space through which a cooling fluid passes is formed between both the inner and outer peripheral surfaces and both end surfaces of the superconductor and the wall of the cooling vessel facing them, and the cooling fluid circulation space is provided with respect to the cooling vessel. A superconducting magnetic bearing is provided with a spring-like spacing member for holding the superconductor in the radial direction .   2. The superconducting device according to claim 1, wherein the superconductor portion includes a plurality of cooling containers arranged side by side in the axial direction of the rotating body, and superconductors respectively disposed in the cooling containers. Magnetic bearing.

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