JPH07274563A - Superconducting levitation device - Google Patents

Abstract

PURPOSE:To provide a non-contact levitation device, which requires no complicate controller, cost of which is reduced and which has high damping characteristics and utilizes superconduction. CONSTITUTION:In a superconducting levitation device, a levitated body 1 is formed by using a magnet 2, and a superconductive material 3 or a conductive material 4 having a damping function and a superconductive material 5 having a levitation function and a high Jc are arranged onto a fixing section 6 at places oppositely faced to the levitated body 1. When the levitated body 1 is vibrated, the low-Jc superconductive material 3 or the conductive material 4 having high electrical conductivity absorbs vibrational energy as thermal energy, and damps vibrations.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact levitation device utilizing a superconducting phenomenon, for example, a bearing device for a turbo molecular pump or a flywheel for power storage, a non-contact transfer device in a semiconductor manufacturing process, The present invention relates to a superconducting levitation device that can be used as a vibration isolation device.

[0002]

2. Description of the Related Art In industrial equipment such as turbo electronic pumps, flywheels, conveyors, anti-vibration equipments, etc., there is an increasing demand for equipments such as high efficiency, high speed, long life, low noise and cleanliness. There is. In order to meet this demand, a non-contact levitation device is desired, and a device using an electromagnet is currently being developed. However, the non-contact levitation device using the electromagnet has a problem that the structure is complicated and the cost is high in order to stably hold the levitation body in a non-contact state. That is, a precise and responsive sensor for accurately measuring the position of the floating body, and a responsive controller for controlling the energization of the electromagnet based on the signal from the sensor are required. The structure is complicated and the cost is high. Therefore, the spread of control-type non-contact levitation devices using electromagnets is limited.

In order to solve the problems of the non-contact levitation device using an electromagnet, a non-contact levitation device utilizing a superconducting phenomenon has been proposed. For example, as for the superconducting magnetic bearing, there is JP-A-63-243523. Among non-contact levitation devices using superconductivity, those utilizing the strong pinning effect hold the levitation body stable by pinning the magnetic lines of force from the magnet by the superconductor. That is,
When the levitating body is out of equilibrium, the magnetic force lines are pinned and the restoring force acts to try to return to the original position. As described above, the non-contact levitation device using superconductivity is expected to realize a non-contact levitation device that has a simple structure and is inexpensive.

[0004]

As described above, the non-contact levitation device utilizing superconductivity can realize stable levitation without requiring a complicated control circuit. However, when the levitation body deviates from the equilibrium state, the restoring force tries to return to the original position, but since it floats without contact, the levitation body does not stop immediately at the equilibrium position, There is a problem of shaking for hours. In order to realize a superconducting levitation device, it is necessary to suppress vibrations at this equilibrium position.
For example, if the levitation body vibrates at the equilibrium point for a long time in a transfer device, a vibration isolation device, etc., the positioning accuracy will deteriorate. Further, in the bearing device, when the number of rotations reaches the natural frequency, the vibration phenomenon increases due to the resonance phenomenon, and the rotation axis comes off.

The mechanism for damping the vibration as described above is called damping, and sufficiently large damping is necessary for non-contact floating application. In a non-contact levitation device using an electromagnet, an electronic control device not only stably levitates the levitation body, but also imparts high damping characteristics to the device. As a result, the control device becomes more complicated and more expensive. Even in a non-contact levitation device using superconductivity, it is possible to add damping characteristics with a complicated control device. However, the characteristic of the superconducting non-contact levitation device that the structure is simple and inexpensive is lost.

The present invention solves the above problems,
It is an object of the present invention to provide a non-contact levitation device that does not require a complicated control device, is inexpensive, and uses superconductivity that has high damping characteristics.

[0007]

The superconducting levitation apparatus of the present invention contains a material having a damping function in order to solve the above-mentioned problems. That is, (1) in a levitation device including a superconducting material and a magnet, a material having a damping function is integrated with the superconducting material, (2) in (1), a damping function. A superconducting levitation device, characterized in that a superconducting material is used as a material having (3)
In (1), a superconducting levitation device, characterized in that a conductive material is used as a material having a damping function,
(4) A superconducting levitation device according to (1), wherein a superconducting material and a conductive material are used as the material having a damping function.

Here, in the superconducting levitation apparatus, the term "integral" means the relative position of the superconducting material having a high critical current density (Jc) responsible for the levitation function and the material having the dyneping function when the position of the levitation body changes. It means that the relationship does not change.

FIG. 1 shows an example of a concrete structure of the present invention.
As shown in FIG. 5, a levitation body is formed by using a magnet, and a superconducting material having a high Jc and a material having a damping function are arranged on the fixed portion side at a position facing the levitation body. When the material having a damping function is arranged between the magnet and the high Jc superconducting material, the change in the magnetic field due to the vibration of the magnet can be more sensitively sensed, so that the damping characteristic is enhanced. On the contrary, as shown in FIG. 2, the levitation body may be formed of a high Jc superconducting material and a material having a damping function, and the magnet may be arranged on the fixed portion side at a position facing them. The floating body is, for example, a rotating shaft in the bearing device, a transport vehicle in the transport device, and a vibration isolation table in the vibration isolation device.

In the superconducting levitating apparatus of the present invention, the levitating function is carried out by the superconducting material having a high Jc, that is, a high levitating force. As a high Jc superconducting material, for example, a single crystal R such as Japanese Patent Application No. 63-261607 can be used.
There is an oxide superconducting material in which RE ₂ BaCuO ₅ is dispersed in an EBa ₂ Cu ₃ O _7-x phase (RE is a rare earth element and a combination thereof) (QMG material). As a material having a damping function, a superconducting material having a low Jc or a conductive material having a high electric conductivity is effective.

[0011]

In the superconducting levitation device of the present invention, when the levitation body is displaced from the equilibrium position for some reason and the levitation body vibrates, the magnetic field changes at the position of the material having the damping function. The vibration energy at the equilibrium point of the levitating body is absorbed as thermal energy by these materials having a damping function, and the vibration is damped.

When the material having a damping function is a low Jc superconducting material, the magnetic flux in the superconductor moves along with the vibration of the levitation body, resulting in energy loss, and the vibration energy of the levitation body is absorbed as thermal energy, thereby vibrating the vibration body. Dampen the vibration of.

When the material having a damping function is a conductive material, an eddy current is generated in the conductive material due to the vibration of the levitation body, energy loss occurs, and the vibration energy of the levitation body is absorbed as heat energy. Damps the vibration of the levitating body.

Energy loss in a superconducting material is
This is due to the movement of the magnetic flux quantum existing in the superconductor. Magnetic flux flow resistance ρf, which is a measure of the ease of movement of the magnetic flux of the superconductor
Is given by ρf = (H / Hc2) ρn where H is the strength of the magnetic field at the position of the superconductor, the upper critical magnetic field of the Hc2 superconductor, and ρn is the electrical resistance of the superconductor in the normal conducting state.

Therefore, in order to improve the damping characteristics, a material having a large Hc2 and a small ρn is desirable.
Materials having a large Hc2 include Y-based, Bi-based, Tl-based, and Hg-based oxide superconducting materials. Furthermore, the ease of movement of the magnetic flux in the superconductor depends on the critical current density Jc.
Also related to. When the Jc of the superconductor is large, the force for stopping the movement of the magnetic flux is large, so that the displacement of the magnetic flux in the superconductor is smaller than that of the one having a small Jc. Since the total energy loss is proportional to the volume, J
Higher damping will be achieved for materials with smaller c. Therefore, Y system or Bi system or T system
A material having a lower Jc and an l-based or Hg-based oxide superconducting material is more suitable as a high damping material. A low Jc superconducting material has a small levitation force and is not suitable for a superconducting non-contact levitation device. However, based on a completely opposite idea, a low Jc superconducting material is used as a high damping material. The superconducting material Jc, which has a levitating function, has a Jc of 10,000 A / cm, assuming that a weight of several Kg is levitated.
It is desirable that the number exceeds ² , but conversely, it is desirable that the superconducting material having a damping function has a small Jc. Since the Jc of an oxide superconducting material produced by a sintering method, which is a standard method for producing oxides, generally does not exceed 1000 A / cm ² , a sintered body that is easy to produce is used as a damping material. Considering the use, Jc of the superconducting material having a damping function is preferably 1000 A / cm ² or less.

On the other hand, the energy loss in the conductive material is caused by Joule heat due to the eddy current flowing in the conductive material due to electromagnetic induction. The loss due to such an eddy current becomes larger in a material having a higher electric conductivity, that is, a lower electric resistivity. Therefore, a metal material having an electrical resistivity of 10 ⁻⁸ Ωm or less, such as copper or silver, is suitable as the high damping material. Since such a metal material having high electric conductivity such as copper or silver can be used as a material for a non-contact floating device, it is useful for simplifying the structure of the entire device.

In the non-contact levitation device utilizing superconductivity, the idea that the vibration energy of the levitation body is absorbed by the thermal energy of the material is contrary to conventional wisdom. That is, a cooling device is required to develop the superconducting phenomenon, and absorption by the heat energy of the material has a risk of quenching the superconducting state into the normal conducting state. On the other hand, the inventor has noticed that the specific heat is sufficiently large at the liquid nitrogen temperature as compared with the liquid helium temperature, and by using an oxide superconducting material having a critical temperature higher than the liquid nitrogen temperature, the method of the present invention can be obtained. We were able to develop a superconducting non-contact levitation device with high damping characteristics.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 shows an embodiment of the superconducting levitation apparatus of the present invention. Example 1 is a case where a low Jc superconducting material 3 is used as a material having a damping function. In this superconducting levitation device, the levitation body 1 is formed by using the permanent magnets 2, and the low Jc superconducting material 3 and the high Jc superconducting material 5 are arranged on the fixed portion 6 side at the opposing positions of the levitation body. Has been done. The low Jc superconducting material 3 is placed on the high Jc superconducting material 5.

The high Jc superconducting material used in this embodiment is called a QMG material, and is a single crystal REBa ₂
An oxide superconducting material in which RE ₂ BaCuO ₅ is dispersed in a Cu ₃ O _7-x phase (RE is a rare earth element and a combination thereof), and has a strong pinning force at liquid nitrogen temperature (Japanese Patent Application No. 63-261607). Specifically, high Jc
The method for producing the superconducting material of is described below. First,
Yttrium (Y), barium (Ba), and copper (Cu) oxides are weighed in a ratio of 1.3: 1.7: 2.4, respectively, and platinum is added thereto in an amount of 0.5% by weight.

Next, the raw material powder is sufficiently kneaded and then calcined. Then, the calcined powder is molded and heat-treated in a temperature range of 900 to 1200 degrees Celsius to grow crystals.
Finally, by annealing in an oxygen atmosphere to add oxygen, a superconducting material having a critical temperature exceeding 90 ° C. can be manufactured. The final size of the superconducting material is 46 mm in diameter and 20 mm in thickness. The Jc of this material is 100 when the magnetic field is 1T at an absolute temperature of 77K when determined using a sample vibration type magnetization measuring device (VSM).
It is extremely high, exceeding 00 A / cm ² .

The low Jc superconducting material having a damping function used in this embodiment is a Y-based crystal. Specifically, a method for producing a low Jc superconducting material will be described below. First, yttrium (Y), barium (Ba), and copper (Cu) oxides are weighed in a ratio of 1: 2: 3, respectively. Next, this raw material powder is sufficiently kneaded and then calcined.
Then, the calcined powder is molded into a temperature range of 800 to 100 degrees Celsius.
Heat treatment is performed in a temperature range of 0 degree to crystallize. Finally, by annealing in an oxygen atmosphere and adding oxygen,
A superconducting material having a critical temperature exceeding 90 ° C. can be produced. The final size of the superconducting material has a diameter of 4
It has a thickness of 6 mm and a thickness of 3 mm. The Jc of this material is 1000 A / c at an absolute temperature of 77 K even in the vicinity of a zero magnetic field, when determined using a sample vibration type magnetization measuring device (VSM).
It is as low as m ² or less. Although a crystal of a Y-based oxide superconducting material was used because of the ease of production in this example, the same result can be obtained by using a single crystal sample with few defects, that is, with few pinning points, instead of the Y-based crystal. It goes without saying that it is effective. In addition, Bi-based or Tl-based or Hg
It is needless to say that the same effect can be obtained by using other oxide superconducting materials such as those of the series.

In order to investigate the effect of Example 1, the above QMG
Material and Y-based crystal integrated (Example 1) and QM
The levitation characteristics and the damping characteristics of the G material alone (comparative example) were measured and compared.

The floating characteristics are measured by the method described in JP-A-4-17228.
It was carried out based on the 0 method. Specifically, the measurement sample is immersed in liquid nitrogen in a container, and Sm with a surface magnetic field of 0.3 T
After the Co-based permanent magnet was attached to the rod, the crosshead was lowered at a speed of 5 mm / min, and the magnetic repulsion force was measured when the distance between the measurement sample and the permanent magnet was 0.1 mm. As a result, the repulsive force of the integrated QMG material of Example 1 and the Y-based crystal was 10.5 kg.
The repulsive force of the MG material alone was 12 kg.

The damping characteristic is that the sample to be measured is immersed in liquid nitrogen in a container and Ne-F with a surface magnetic field of 0.45 T is used.
While the eB-based permanent magnet was kept at a flying height of 3 mm, a force having a frequency of 0.2 to 200 Hz was applied to the rod to which the magnet was attached, and measurement and evaluation were performed based on the magnitude of shake. The damping coefficient was calculated from the magnitude of the shake when a frequency force causing resonance was applied. When the damping coefficient is large, the shake becomes small. As a result of the measurement, QMG of Example 1
The damping coefficient of the integrated material and the Y-based sintered body was 4.75 Ns / m, and the damping coefficient of only the QMG material of the comparative example was 1.54 Ns / m. With the method of the present invention, when the Y-based sintered body is made of a material having a damping function, the floating characteristics are almost the same as those without the Y-based sintered body, but the damping characteristics are improved by about 3 times. Therefore, it can be seen that it has a high levitation force and a high damping characteristic.

(Embodiment 2) Embodiment 2 is the same as FIG.
This is the case where the conductive material 4 having high electric conductivity is used as the material having the damping function. In this superconducting levitation device, a levitation body 1 is formed by using a permanent magnet 2, and a conductive material 4 having a high electric conductivity and a superconducting material 5 having a high Jc are fixed to a position where the levitation body 1 faces each other. It is located on the 6 side. The low Jc superconducting material 3 is placed on the high Jc superconducting material 5.

The high Jc superconducting material used in this example is called a QMG material, which is the same as that in Example 1. The conductive material having a damping function used in this example is a copper plate having a resistivity of 0.2 × 10 ⁻⁸ Ωm.
Its size is 46 mm in diameter and 3 mm in thickness.

In order to investigate the effect of the second embodiment, the above QMG
The levitation characteristics and damping characteristics were measured and compared for the one in which the material and the copper plate were integrated (Example 2) and the one for only the QMG material (Comparative Example). The method for measuring the floating characteristic and the damping characteristic is the same as in the first embodiment. Measurement results, Example 2
The repulsive force of the integrated QMG material and copper plate is 10
kg, the repulsive force of the QMG material of the comparative example is 12 k
It was g.

Further, the damping coefficient of the QMG material of Example 2 and the copper plate integrated with each other is 4.87 Ns / m.
The damping coefficient of only the QMG material of the comparative example is 1.5.
It was 4 Ns / m. With the method of the present invention, the copper plate made of a material having a damping function has almost the same levitation characteristics as those without a copper plate, but the damping characteristics are improved by about 3 times, and high levitation force is obtained. It can be seen that it has high damping characteristics.

In Embodiments 1 and 2, the permanent magnet is arranged on the floating body side and the superconducting material or the material having a damping function is arranged on the fixed side, as shown in FIG. It is needless to say that the same effect can be obtained even if the configuration is reversed.

In this embodiment, the magnet is Ne-Fe-B.
Although a system type or Sm-Co type permanent magnet was used, it goes without saying that a similar effect can be obtained with an electromagnet instead of the permanent magnet.

[0032]

INDUSTRIAL APPLICABILITY As described above, the present invention relates to a superconducting levitation device including a superconducting material having a low Jc or a conductive material having a high electric conductivity so as to improve damping characteristics. . If the superconducting levitation device of the present invention is used, it is possible to stably support the levitation body with a simple structure, and it is not necessary to perform complicated control like a non-contact levitation device using an electromagnet, and at a low cost. is there. Therefore, the present invention has broad technical fields.
Enables practical application of superconducting levitation equipment.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of a superconducting levitation device of the present invention.

FIG. 2 is a schematic configuration diagram showing another embodiment of the superconducting levitation device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Floating body, 2 ... Magnet, 3 ... Superconducting material with low critical current density, 4 ... Conductive material with high electrical conductivity, 5 ... Superconducting material with high critical current density, 6 ... Fixed part.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Mitsuru Morita 1618 Ida, Nakahara-ku, Kawasaki-shi, Kanagawa Nippon Steel Corporation Advanced Technology Research Laboratories

Claims (4)

[Claims] 1. A levitation device comprising a superconducting material and a magnet, wherein a material having a damping function is integrated with the superconducting levitation device. 2. The superconducting levitation apparatus according to claim 1, wherein a superconducting material is used as the material having the damping function. 3. The superconducting levitation apparatus according to claim 1, wherein a conductive material is used as the material having the damping function. 4. The superconducting levitation apparatus according to claim 1, wherein a superconducting material and a conductive material are used as the material having the damping function.