JP2735653B2 - Superconducting rotating assembly - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a superconducting rotary assembly, and more particularly to a superconducting bearing using a type II superconductor.
The United States Government has certain licenses from the United States National Science Foundation and has general license to use the invention.

BACKGROUND OF THE INVENTION It is known that conventional bearings for high speed rotating equipment are susceptible to wear, noise, vibration and heat generation problems. Until recently, practical magnetic bearings were either permanent magnet or electromagnetic feedback types. Permanent magnet bearings have inherent static instability and need to be stabilized to at least one degree of freedom via non-magnetic means, such as a rotating coupling. Feedback-based magnetic bearings require sophisticated position sensors and electronics to achieve stability.

The prior art seeks to improve magnetic bearing technology by considering superconducting properties. For example, by maintaining a bearing member and / or a rotating member or both in a class I superconducting state, a magnetic force is obtained therebetween and a required levitation is obtained. Type I superconductors exhibit complete diamagnetism up to the critical applied magnetic field,
At the critical point, the superconductivity disappears and the magnetization intensity of the sample sharply increases. Examples of Class I superconducting bearings are found in U.S. Pat. No. 3,493,274 to Ms. et al. And U.S. Pat.
To obtain stability in this type of device, the bearing structure is typically a mechanical rotating support (eg, of a back hold) or a dish or other enclosed superconductor, which minimizes weight. And limited lateral stability (see M3 et al.).

Recently, various new ceramic compositions have been discovered that exhibit superconductivity at higher temperatures than liquid nitrogen. These new superconductors are Class II materials with high critical magnetic fields, typically above 30-35 Tesla. Class I superconductors may be said to have "excluded" magnetic flux from within. On the other hand, the type II superconductor is capable of transmitting magnetic flux inside a large number of lines of magnetic force. Under such circumstances, circulation of superconducting current is established in the type II superconductor. These in turn generate a substantial magnetic field, causing a magnet pinned above the surface of the superconductor to have a position pinning effect.

An advantage with respect to potential energy obtained from the levitated superconducting bearing is that a rotational speed of 10,000 rpm can be obtained. Prior art suggests immersing the entire device in liquid helium / nitrogen to achieve such a rate, but is impractical. The prior art seems to want to avoid as much as possible the need for exquisite rotor balancing with "rigid suspension". Further, it seems that the external rotation stabilizing means should be omitted if possible.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a superconducting rotating assembly that exhibits stable lateral, vertical and axial buoyancy while rotating at high speed.

It is another object of the present invention to provide a simple and inexpensive superconducting rotating assembly that performs high-speed stable rotation.

It is yet another object of the present invention to provide a soft-suspension superconducting rotary assembly that allows the rotor to have significant imbalance.

SUMMARY OF THE INVENTION In accordance with the above objects, a non-contact soft suspension superconducting rotating assembly is disclosed that includes a rotating member that stably floats without being supported. This assembly is
It includes first and second bearing means which are made of a material exhibiting class II superconductivity and are appropriately arranged facing each other. The rotating member attached to the opposing bearing means has magnet means at both ends. The shaft connecting the north and south poles of each magnet means is collinear with the rotation axis of the rotating member.
Means are provided for maintaining the bearing means at or below the critical superconducting temperature. Further, means for rotating the rotating member are provided. In this manner, each magnet means is levitated by the magnetic field and is stably rotated at the non-contact position, and the magnetic pinning effect is produced by the incorporated bearing means.

 The present invention will be described with reference to the accompanying drawings showing an embodiment.

(Embodiment) In FIG. 1, the rotor 10 is
And 18 are fitted into holes 12 and 14. Each bearing block 16 and 18 is mounted on a copper or aluminum bearing stand 20 and immersed in a cryogenic liquid such as liquid nitrogen. Four coils 22, 24 and 26 (one not shown) drive the four coils to rotate the rotor 10.

Each bearing block 16 and 18 is composed of a material that exhibits Type II superconductivity when maintained at a temperature below its critical temperature. The preferred material for bearing blocks 16 and 18 is a YBa ₂ Cu ₃ Ox ceramic composite. In addition, a composite exhibiting Type II superconductivity based on thallium, bismuth or other ceramics can be used. The preferred material for the bearing pedestal 20 is a 60/63 aluminum alloy.

FIG. 2 shows a cross section of the rotor 10. The rotor 10 has two levitating magnets 30 and 32, preferably cylindrical, whose north / south poles are aligned with the centerline 34 of the rotor 10.
The third magnet 36 has a polar axis oriented perpendicular to the center line 34,
A magnetic field is generated, and the rotor 10 can be rotated by the field coils 22, 24, 26, and the like. The magnets 30 and 32 are held in place via hollow cylinders 40 and 42 combined with a long cylinder 44. Cylinders 40, 42, and 44 are constructed from a suitable non-magnetic material that provides sufficient strength to maintain a stable shape as rotor 10 rotates at high speeds. For example, polycarbonate and other similar polymeric materials may be used as the non-magnetic material. Magnet 30 and
32 is preferably formed from samarium cobalt and exhibits a linear dipole as shown in FIG. In addition, a rare earth magnet, for example, a magnet based on Nd, B, or Fe may be used. Similarly, the magnet 36 may be made of a rare earth material or other suitable permanent magnet material. It is preferred that the rotor 10 be balanced as much as possible about its center line, but no special balancing operation is required at high speeds, primarily due to the "soft suspension" performed by the bearing blocks 16 and 18. In other words, this suspension allows some wobble without damaging the equipment.

In FIGS. 2 and 3, if the assembly superconducting temperature shown in FIG.
Placing the rotor 10 in 12 and 14 induces a superconducting current in the wall of the bearing hole. These superconducting currents are indicated by arrows
It generates an electromagnetic repulsion force indicated by 50 and indicated by arrow 52.
These repelling forces operate to lift and restrain magnets 30 and 32 to a stable levitation position. The horizontal side walls and end walls of each bearing bore cooperate to create a balancing effect on the rotor magnet associated therewith by electromagnetic pinning forces. What is important is that the inner surface of each bearing hole shows no change in the polarity of the magnetic flux when the rotor 10 rotates.
This is important because it prevents applying a displacement torque to the rotating magnet that makes the rotor 10 unstable. In other words, even when rotating, the hole 12 experiences the north pole and the south pole one after another when the rotor 10 rotates, and if torque is generated by the disturbing magnetic field, the device is prevented from rotating at a desired high speed. become. As is clear from the test shown in FIG. 4, the repulsion generated by the type II superconducting material was found to be a mass-related phenomenon. Therefore,
As the thickness of the superconductor adjacent to each bearing hole increases, so will the resilience of the magnets near it. However, as is apparent from the above curve, no substantial increase in repulsion is observed at a thickness of about 5 mm or more. Therefore, the thickness t surrounding the bearing hole is at least in order to guarantee the rotor 10 the maximum repulsion.
Preferably, it is 5 mm. This determines the maximum mass of the rotor 10.

Although not shown, many different types of components are mounted on rotor 10 in normal use. For example, a polygon mirror is used which is used in combination with a laser beam to scan an appropriate target. Further, a small disk for storing optical data is mounted.

The provision of a conductive bearing stand 20 that supports the bearing blocks 16 and 18 keeps the superconducting fluid level substantially inaccessible to rotating components. In this way, the rotating member 10 and the upper portions of the bearing blocks 16 and 18 are mounted so as to be able to rotate at a very high speed in a vacuum. When the bearing pedestal 20 is immersed in liquid nitrogen, the bearing blocks 16 and 18 can obtain Type II superconducting properties, even if such immersion occurs substantially away from the bearing block. I understood.

FIGS. 5 to 7 show a schematic configuration of an apparatus for imparting rotational motion to the rotor 10. FIG. FIG. 5 shows a two-coil drive system in which the magnet 36 is rotated by applying an alternating current to one coil with respect to the other coil in a cosine function relationship. FIG. 6 shows a three-coil drive system in which the coils are arranged at 120 ° intervals and driven with a phase difference of 120 °. FIG. 7 shows a four-coil drive system, in which each coil is driven with a phase difference of 90 ° to generate a rotating magnetic field, causing the rotor 10 to rotate. Although the above-described rotating machine uses electromagnetic energy, the rotor 10 may be provided with teeth at its peripheral portion, or may be fitted with turbine blades and rotated using a high-pressure gas jet.

8A, 8B and 8C show a circular type II superconducting bearing mechanism 72. FIG. The mechanism 72 has orifices 73 at both ends of the rotor 10. As shown in the rotating assembly of FIG. 1, the rotor 10 has magnets 70 at both ends. In this configuration, the rotor / bearing assembly is operable regardless of the direction in which gravity (see FIG. 8C) is oriented. 9A and 9B show a modification of the bearing mechanism. In FIG. 9A, each magnet
Bearing stand 82 diverging from the center of bearing block 80
Is replaced by a ring magnet surrounding.
In FIG. 9B, each magnet 70 has been replaced by a magnet having a concave depression engaging a conical bearing pedestal emanating from bearing block 80.

Test Example Several pairs of YBa ₂ Cu ₃ Ox bearing blocks having a diameter of 1.5 cm are manufactured by sintering at 950 ° C. in the atmosphere. Each crystal was irregularly oriented and was post-annealed at 800 ° C. for 2 hours in pressurized oxygen (20 bar) in order to obtain a critical temperature Tc of 90 ° K. or higher for the sample.

Some bearing blocks have been adapted to have the shape shown in FIGS. The standard magnetic flux density at the surface of the superconductor below the levitating permanent magnet was measured using a Hall effect probe. When the permanent magnet dipole was parallel to the ceramic bearing surface, the standard surface flux measurement was on the order of 0.07 Tesla. The standard current signature indicated that the two superconducting eddy currents acted as superconductors near the two poles of each magnet. In addition, surface magnetic field measurements showed that the incomplete flux rejection effect, which is a typical type II superconductor, was observed during levitation.

Significant hysteretic behavior was observed with respect to rotor fly height. For small perturbations, the levitating rotor exhibited lateral and vertical stiffness. The rotor was rotated by a magnetic field generated near the coil. The effects of the alternating magnetic field and the flying height on the superconductor during rotation and non-rotation were not recognized. However, at low frequencies of 1 to 4 Hz, the alternating magnetic force excites the magnetic stiffness mode in a resonant state that sometimes drives the rotor out of the superconducting bearing pad. At high frequencies, the rotor speed and drive field frequency become fixed, resulting in a rotor speed of 1200 rp
m or more. Low frequency instability can be easily eliminated by exciting the rotor at a substantially resonant frequency and causing the rotor to move rapidly. It is assumed that the flux pinning effect causes a hysteresis effect on the magnetic force in the rotor. However, once in position, the rotor will maintain a stable position unless the rotor is pulled out by an external force.

It is to be understood that the above description has been modified only with respect to one embodiment of the present invention. The present invention can be variously modified by those skilled in the art without departing from the present invention. Accordingly, the present invention is intended to embrace all such modifications and improvements as fall within the scope of the appended claims.

[Brief description of the drawings]

FIG. 1 is an isometric perspective view of the superconducting rotary assembly of the present invention, FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 1, and FIG. 3 is a view of the type II superconductor bearing shown in FIG. FIG. 4 is a graph showing a change in repulsion force with respect to the thickness of the type II superconducting bearing, FIG. 5 is a diagram showing the principle of a two-coil driven superconducting rotary assembly, FIG. FIG. 7 is a diagram showing the principle of a coil-driven superconducting rotary assembly, FIG. 7 is a diagram showing the principle of a four-coil driven superconducting rotary assembly, FIG. 8A, FIG. 8B and FIG. FIGS. 9A and 9B are an exploded perspective view, a partial cross-sectional view, and an external perspective view of the bearing mechanism, respectively. FIGS. 9A and 9B show the second and third embodiments of the bearing mechanism of the superconducting rotary assembly. It is a partial sectional view. 10 ... Rotor, 12, 14 ... Hole, 16, 18 ... Bearing block, 20 ... Bearing stand, 22, 24, 26 ... Field coil, 30, 32 ... Levitated magnet, 36 ... Magnet , 40, 42, 44 ... hollow cylinder, 70 ... magnet, 72 ... bearing mechanism, 73 ... orifice, 80 ... bearing block, 82 ... bearing stand.

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-64-55038 (JP, A) JP-A-1-234618 (JP, A) JP-A-4-505569 (JP, A)

Claims (12)

(57) [Claims] 1. A first and a second bearing means comprising a material which exhibits a type II superconductivity by being maintained at or below a superconducting critical temperature, two bearings arranged along a common axis. A rotating member, each end of which is combined with the bearing means, a rotating member, and a polar axis mounted on each end of the rotating member so as to be co-linear with a common axis of the rotating member. Magnet means having a magnetic pole surface for each bearing means, means for maintaining the first and second bearing means at or below the superconducting critical temperature, and levitating and combining each magnet means Rotating means for rotating the rotating member at a stable non-contact position by a repelling magnetic field generated through the first and second bearing means. , The non-contact Rubber suspension superconducting rotating assembly. 2. The rotary assembly according to claim 1, wherein said rotating means further includes additional magnet means mounted within said rotating member, and coil means for interacting with said additional magnet means to rotate said rotating member. . 3. The method of claim 1, wherein the first and second bearing means comprise a semi-cylindrical shape having a hole with an open end, the hole receiving the end of the rotating member, and the rotating member being cylindrical. The rotation assembly according to the item. 4. The temperature maintaining means includes conductive bearing means coupled to the first and second bearing means, said bearing means forming a heat transfer path for cooling said bearing means to a superconducting temperature. 4. The rotating assembly according to claim 3, wherein: 5. The rotating assembly according to claim 3, wherein the material comprising the first and second bearing means has a thickness of at least 5 mm around the open end hole. 6. A rotary assembly according to claim 5, wherein said rotating means further includes additional magnet means mounted within said rotating member, and coil means for interacting with said additional magnet means to rotate said rotating member. . 7. The rotary assembly according to claim 1, wherein the first and second bearing means are cylindrical with orifices closed at one end, the bearing means surrounding the end of the rotating member. 8. The method of claim 1, wherein the first and second bearing means include bearing stands oriented in each orifice, and each magnet means engages with the bearing stand and is disposed in the orifice to rotate the rotating member. A rotating assembly according to claim 7. 9. The system of claim 1, wherein the first and second bearing means include a conical bearing rest orientated centrally within the orifice, each magnet means having a conical recess aligned with the conical bearing rest and a rotating member. The rotating assembly according to claim 7, wherein the rotating assembly is rotatable. 10. The rotating assembly according to claim 7, wherein said rotating means further includes additional magnet means mounted within said rotating member, and coil means for interacting with said additional magnet means to rotate said rotating member. . 11. The temperature maintaining means includes conductive bearing means coupled to the first and second bearing means, said bearing means forming a heat transfer path for cooling said bearing means to a superconducting temperature. 9. The rotating assembly according to claim 7, wherein: 12. The rotating assembly according to claim 11, wherein the material forming the first and second bearing means has a thickness around the orifice of at least 5 mm.