JP4808683B2 - Stabilizing method of magnetic bearing using high temperature superconducting bulk body and magnetic bearing thereof - Google Patents

Description

  The present invention relates to a method for stabilizing a magnetic bearing using a high-temperature superconducting bulk body and the magnetic bearing.

  Conventionally, in a magnetic bearing using a superconducting bulk body, there is a problem that the magnetic levitation characteristics of the superconducting bulk body deteriorate with time. When this phenomenon occurs, a phenomenon occurs in which the rotating shaft descends (see Patent Document 1 and Non-Patent Document 1 below).

  Further, according to the following Non-Patent Document 2, the magnetic field experienced during rotation, for example, the high temperature superconducting bulk body is displaced in the left-right direction, so that the magnetic field experienced when the high temperature superconducting bulk body makes one rotation varies. Rotation loss may occur due to the above, and the levitation force may change.

  In the former, the preload method is called a preload method, in which a load larger than the bearing burden load is applied in advance to promote magnetic flux creep, thereby reducing the amount of magnetic flux creep under normal operating load and suppressing shaft descent. A method has been proposed. The same effect as the preload method can be achieved by setting the cooling temperature to a value lower than the critical temperature of the high-temperature superconducting bulk body and higher than the normal operating temperature, applying a load and magnetic field, and then cooling to the normal operating temperature. A method called a supercooling method is proposed.

  FIG. 14 is a cross-sectional view showing an example of a conventional thrust magnetic bearing.

  A high-temperature superconducting bulk body 102 is applied to the rotating shaft 101, and a magnetic generator is arranged on the fixed side in order to apply an electromagnetic force as a levitation force or a guiding force of the bearing to the high-temperature superconducting bulk body 102. Reference numeral 105 denotes a refrigerant in which the high-temperature superconducting bulk body 102 is immersed.

  This represents a magnetic bearing that supports a load in the thrust direction by the high-temperature superconducting bulk body 102, and the radial support of the rotating shaft 101 is omitted. As the electromagnet 103, a solenoid type coil 104 is used. The magnitude of the electromagnetic force acting between the electromagnet 103 and the high temperature superconducting bulk body 102 is a magnetic force field obtained by multiplying the magnitude of the magnetic field where the high temperature superconducting bulk body 102 is placed and the rate of change of the magnetic field at that location. It can be expressed by an index.

Here, the electromagnetic force superconductor bulk body is generated for (axially) F _Z will be described.

F _z = {(π ² R _d ⁴ ) / [L _cyl (R _d , t)]} × [(B _z ) (∂B _z / ∂z)
Here, L _cyl is the self-inductance of the superconducting shield current flowing in the superconducting bulk body, R _d is the radius of the superconducting bulk body, t is the thickness of the superconducting bulk body, and (π ² R _d ⁴ ) / [L _cyl ( R _d , t)] is a form factor of the superconducting bulk body. B _z is the magnetic field in the axial direction of the space where the superconducting bulk body is placed, ∂B _z / ∂z is the magnetic field gradient (axial direction), and B _z (∂B _z / ∂z) is the magnetic force field (axial direction) ) Is an index representing the magnetic field distribution of the superconducting coil. That is, the magnitude of the electromagnetic force acting between the electromagnet and the superconducting bulk body can be expressed by the shape of the superconducting bulk body and the magnetic force field.

  In the figure, the magnetic field distribution is indicated by a solid curve, and the magnetic force field distribution is indicated by a broken line. These curves represent the Z direction component on the center line of the rotating shaft 101. When used for the purpose of supporting the levitation force, the magnetic force field increases as the high-temperature superconducting bulk body 102 goes down as described above. Therefore, the position where the electromagnetic force that becomes the levitation force increases is selected accordingly. In this case, if the magnetic levitation characteristics of the high-temperature superconducting bulk body 102 are temporally deteriorated or there is a rotational loss, the high-temperature superconducting bulk body 102 supporting the rotating shaft 101 tends to fall, and the magnetic force increases accordingly. Therefore, the levitation force is increased. Therefore, it is possible to keep almost the same position in a short time. However, if time deterioration or rotation loss progresses due to long-time operation, the load applied to the bearing suddenly becomes unsupported when the degree of deterioration of the high-temperature superconducting bulk body 102 does not balance with the increase in the magnetic force field, and rotation There is a risk that the shaft 101 may fall off instantaneously.

  FIG. 15 shows an example of a rotation experiment of a high-temperature superconducting bulk body that simulates the prior art. In FIG. 15, G indicates the coil current, H indicates the levitation force, and I indicates the rotational speed. This is because a high-temperature superconducting bulk body is arranged as a rotating body, and in a magnetic bearing in which a superconducting coil is applied to the stationary side, the high-temperature superconducting bulk body is rotated at 1000 rpm with a levitation force of approximately 2.5 kN generated. The change in levitation force for 10 minutes is monitored. FIG. 16 shows an enlarged display of the change in levitation force among the results of the simulation test of the prior art. In FIG. 16, J indicates the levitation force, and K indicates the rotational speed.

In FIG. 16, the levitation force gradually decreases from the point A where the high-temperature superconducting bulk body starts rotating to the point B where rotation stops. At point B where the rotation is stopped, the levitation force is constant. Although this experiment is a result simulating rotational loss, even if this decrease in levitation force is due to creep, it shows almost the same tendency.
JP 2004-197767 A Interim evaluation report of "Flywheel power storage superconducting bearing technology research and development" New Energy and Industrial Technology Development Organization, National Institute of Advanced Industrial Science and Technology Technical Evaluation Committee August 2003 "Rotational characteristics of superconducting magnetic bearings", Hiroshi Kiyono et al., 15th MAGDA Conference in Kiryu, Proceedings of Conferences on Electromagnetic Phenomena and Electromagnetic Forces, AEM Society of Japan, November 1, 2006

  As described above, in the magnetic bearing using the high-temperature superconducting bulk body, there is a problem that the magnetic levitation characteristics of the high-temperature superconducting bulk body deteriorate with time. When this phenomenon occurs, the rotating shaft descends. Further, the magnetic field exposure during rotation, for example, displacement of the high-temperature superconducting bulk body in the left-right direction causes a rotational loss due to fluctuations in the magnetic field experienced when the high-temperature superconducting bulk body makes one rotation. There is also a problem that power is reduced.

  In addition, a magnetic bearing that uses a high-temperature superconducting bulk body on its rotating shaft and has a magnet generator on the fixed side that acts on the high-temperature superconducting bulk body to act on the high-temperature superconducting bulk body. However, the shaft does not almost drop, but if time degradation or rotation loss progresses due to long-term operation, the bearing is suddenly loaded when the degree of deterioration of the high-temperature superconducting bulk body does not balance with the increase in the magnetic force field. The load can no longer be supported, and the rotating shaft may drop instantaneously. This phenomenon is an unstable behavior that can lead to the destruction of the rotating shaft and is very dangerous.

  In view of the above situation, the present invention provides a magnetic bearing that uses a high-temperature superconducting bulk body. Even if there is a temporal deterioration in the magnetic levitation characteristics of the high-temperature superconducting bulk body or rotational loss, the magnetic bearing stability does not vary. It is an object of the present invention to provide a method and a magnetic bearing thereof.

In order to achieve the above object, the present invention provides
[1] In a magnetic bearing stabilization method using a high-temperature superconducting bulk body, magnetism is generated by incorporating a high-temperature superconducting bulk body into the rotating shaft and applying an electromagnetic force as a levitation force or guide force to the high-temperature superconducting bulk body By arranging the device on the fixed side and adjusting the electromagnetic force generated by this magnetism generator, even if the magnetic levitation characteristics of the high-temperature superconducting bulk body deteriorate over time or the rotation loss occurs, the bearing capacity varies. It is characterized by not generating it.

  [2] In the method for stabilizing a magnetic bearing using the high-temperature superconducting bulk body described in [1] above, a magnetic generator arranged on the fixed side by detecting a burden load of the magnetic bearing and using the information The magnetic bearing is adjusted to stabilize the magnetic bearing.

  [3] In the method for stabilizing a magnetic bearing using the high-temperature superconducting bulk material according to [1] or [2], the magnetism generator is made of an electromagnet.

  [4] In the method for stabilizing a magnetic bearing using the high-temperature superconducting bulk material according to [3], the electromagnet includes a coil made of a superconducting material.

  [5] In the magnetic bearing using the high-temperature superconducting bulk body, the high-temperature superconducting bulk body incorporated in the rotating shaft and the high-temperature superconducting bulk body are arranged on the fixed side so that the electromagnetic force as a levitation force and a guiding force acts on the high-temperature superconducting bulk body. It is characterized by comprising a magnetic generator and electromagnetic force adjusting means for adjusting the electromagnetic force generated by the magnetic generator.

  [6] In the magnetic bearing using the high-temperature superconducting bulk body described in [5] above, the load detecting means for detecting the load applied to the magnetic bearing and the information on the load detecting means are arranged on the fixed side. Electromagnetic force adjusting means for adjusting the magnetic field of the magnetism generator is provided.

  [7] In the magnetic bearing using the high-temperature superconducting bulk material according to [5] or [6], the magnetic generator is an electromagnet.

  [8] In the magnetic bearing using the high-temperature superconducting bulk body according to [5] or [6], the electromagnet includes a coil made of a superconducting material.

  [9] In the magnetic bearing using the high-temperature superconducting bulk material described in [5] above, a load detector used for control for preventing electromagnetic force deterioration of the superconducting magnetic bearing is separated from the magnetic field generator of the superconducting magnetic bearing. In order to detect only the change in load, it is provided separately.

  [10] In the magnetic bearing using the high-temperature superconducting bulk body described in [9] above, a thrust bearing is installed in a load detection unit including the load detector, and a cantilever made of a cantilever is interposed through the thrust bearing. It is characterized in that a load change in the vertical direction of the rotating body is detected by detecting the bending.

  [11] In the magnetic bearing using the high-temperature superconducting bulk body according to [9] above, the rotating body is supported without contacting the rotating body by using a magnetic support for a load detection unit including the load detector. It is characterized in that a change in load in the vertical direction is detected.

  [12] In the magnetic bearing using the high-temperature superconducting bulk body described in [11] above, an attraction force by a permanent magnet and a magnetic material is used for magnetic support of a load detection unit including the load detector. And

  According to the present invention, it is possible to provide a stable magnetic bearing in which the bearing capacity does not fluctuate even if the magnetic levitation characteristic of the high-temperature superconducting bulk body is temporally deteriorated or rotational loss occurs.

  In addition, it solves the problem that the load detection accuracy decreases when the rotating body supported by the magnetic bearing is enlarged, and the electromagnetic force of the electromagnetic force is not affected by the magnitude of the electromagnetic force supporting the rotating body. Changes can be detected.

  The method of stabilizing a magnetic bearing using the high-temperature superconducting bulk body according to the present invention includes the generation of magnetism for incorporating a high-temperature superconducting bulk body into a rotating shaft and applying an electromagnetic force as a levitation force or a guiding force to the high-temperature superconducting bulk body. By arranging the device on the fixed side and adjusting the electromagnetic force generated by this magnetism generator, even if the magnetic levitation characteristics of the high-temperature superconducting bulk body deteriorate over time or the rotation loss occurs, the bearing capacity varies. It was made not to make it occur.

  Hereinafter, embodiments of the present invention will be described in detail.

  FIG. 1 is a schematic view showing a magnetic bearing using a high-temperature superconducting bulk body according to a first embodiment of the present invention.

  In this figure, 1 is a pedestal, 2 is an electric motor / generator (M / G) composed of a rotor 2A and an armature 2B arranged on the gantry 1, and 3 is an electric motor / generator (M / G) 2 thereof. The rotating shaft 4 is suspended from the high temperature superconducting bulk body 4 incorporated in the rotating shaft 3, 4A is a vacuum heat insulating container, 4B is a refrigerant in which the high temperature superconducting bulk body 4 is immersed, and 5 is a magnetic generation arranged on the fixed side. An electromagnet as a device, 5A is a coil of the electromagnet 5, 6 is an electromagnet frame, 7 is a flywheel disposed at the lower end of the rotating shaft in the electromagnet frame 6, 8 is a load detector disposed below the electromagnet 5, Reference numeral 9 denotes a first radial bearing, 10 denotes a second radial bearing, and 11 denotes a backup thrust bearing.

  As described above, the high-temperature superconducting bulk body 4 is incorporated in the rotating shaft 3 and the electromagnet 5 as a magnetism generator is arranged on the fixed side in order to cause the levitation force and guiding force of the bearing to act on the high-temperature superconducting bulk body 4. The magnetic bearing will be described as an example.

  This is an example of a power storage flywheel to which a magnetic bearing using the high-temperature superconducting bulk body 4 is applied in the thrust direction. A solenoid type is used for the electromagnet 5 as a magnetism generator. In order to describe the magnetic bearing in the thrust direction, the radial magnetic bearings 9 and 10 and the backup thrust bearing 11 are indicated by abbreviations.

  In the present invention, the load detector 8 disposed under the electromagnet 5 as the magnetism generator detects the bearing load borne by the magnetic bearing, and the electromagnet 5 as the magnetism generator does not change so that the load is not changed. Adjust the energization current value. Thereby, even if the magnetic levitation characteristics of the high-temperature superconducting bulk body 4 are temporally deteriorated or the rotation loss occurs, the generated force of the magnetic bearing is stable and the rotating shaft 3 does not drop.

  In contrast to the simulation experiments of the prior art shown in FIGS. 5 and 6, an experiment was conducted in which the energizing current value of the superconducting coil was changed and the levitation force was kept constant as an application example of the present invention.

  FIG. 2 is a diagram showing a result of a simulation experiment of the prior art and a simulation experiment result of an application example of the present invention. In FIG. 2, A is the levitation force with the control of the fixed coil of the present invention, B is the levitation force without the conventional control, and C is the rotational speed.

  FIG. 3 shows details of an application example of the present invention. In FIG. 3, D represents the levitation force, E represents the superconducting coil current, and F represents the superconducting coil voltage.

  In this embodiment, the decrease in the levitation force of the rotating shaft 3 is monitored, and the energizing current of the magnet coil 5A of the electromagnet 5 as the magnetism generator is adjusted from 30 seconds to 1 minute intervals. The place where the voltage rises is where the current is changed. In this way, the load change by the load detector 8 is monitored, and the levitation force of the rotary shaft 3 can be kept substantially constant by controlling the levitation force according to the change in the load.

  4 is a top view of a load detecting device for a magnetic bearing using a high-temperature superconducting bulk body according to a second embodiment of the present invention, FIG. 5 is a cross-sectional view taken along line AA in FIG. 4, and FIG. The figure which shows the cantilever in B sectional drawing, FIG. 7: is a figure which shows an example of the load detection apparatus provided in the cantilever.

  In these drawings, reference numeral 20 denotes a fixed portion, 21 denotes a rotating shaft of a rotating body, and 22 denotes a thrust bearing. The thrust bearing 22 includes a ball bearing assembly 24 including a ball and a cage, a housing washer 24a, an axial raceway. It is comprised with the board 24b. The shaft washer 24b is fitted to the structural part of the ring 23 fixed to the rotating shaft 21 of the rotating body. Reference numeral 25 denotes a cantilever (cantilever), and reference numeral 26 denotes a load detector disposed on the cantilever. This may be a strain gauge that detects the bending of the cantilever 25.

  As shown in FIG. 7, the load detector 26 has a 4-active gauge disposed at the root portion of the cantilever 25.

Here, in the strain amount ε _O = ε ₁ −ε ₂ + ε ₃ −ε ₄ , the absolute values of ε ₁ , ε ₂ , ε ₃ , ε ₄ are equal, ε ₁ and ε ₃ are tensile strains, ε ₂ and ε If the wires are connected so that ₄ becomes compressive strain, four times the amount of strain can be obtained in the case of 1 gauge.

  In this second embodiment, instead of detecting the bearing load borne by the magnetic bearing with the load detector 8 arranged under the electromagnet 5 as the magnetism generator as in the first embodiment described above, A thrust bearing 22 is attached to the load detector 26, and this fixed side is supported by a cantilever (cantilever) 25, and the load is detected by the bending stress. Since the thrust bearing 22 of the load detector 26 has a small burden load, there is an advantage that it does not become a large resistance.

  FIG. 8 is a cross-sectional view of a magnetic bearing load detection device using a high-temperature superconducting bulk body according to a third embodiment of the present invention, and FIG. 9 is a top view of FIG. FIG. 10 is a bottom view of FIG. 8 (a cross-sectional view of the state above the position AA), and FIG. 11 is a cross-sectional view of the state above the position BB of FIG. 12 is a sectional view taken along the line DD of FIG. 11, and FIG. 13 is a diagram showing the relationship between the distance (X) between the magnet and the iron plate and the attractive force (F).

  In these drawings, 30 is a fixed portion, 31 is a base projecting from the fixed portion 30, 32 is a rotating shaft of a rotating body, 33 is a magnetic material ring fixed to the rotating shaft 32, and 34 is a plurality of neodymium magnets 35. A support 36 to be supported is a linear guide for fixing the position of the support 34 in the horizontal plane and allows a degree of freedom in the vertical direction. 37 is a support arranged on the base 31 and guided by the linear guide 36. It is a load detector that receives a load in the vertical direction of the body 34.

  In this embodiment, an attractive force by a permanent magnet (neodymium magnet 35) and iron (magnetic material ring 33) is used.

  By adopting a non-contact load transmission method using magnetism for the load detector 37, it becomes possible to eliminate the resistance at all.

  More specifically, ten neodymium magnets (Neo48) 35 having a diameter of 20 × 10 mm are arranged concentrically on the stationary ring as the support 34. In addition, since there is sufficient separation between the magnets, the magnetic forces do not interfere with each other. The rotating shaft 32 on the rotating body side is provided with a magnetic material ring 33, and the gap between the magnetic material ring 33 and the neodymium magnet 35 fixed to the stationary side ring (supporting body 34) is set to about 3 mm.

  As shown in FIG. 13, when the vertical axis represents the attractive force F and the horizontal axis represents the distance X between the magnet and the iron plate, a curve a is obtained (see Magnet Magnet NeoMag Communication August 2006 issue, page 1/2). ). As is clear from this, the attractive force with the magnetic material ring 33 per piece of the neodymium magnet 35 changes to about 9 to 5 kgf with a gap of 2 to 4 mm. Therefore, the spring constant of the magnetic support is about 2 kgf / mm. With 10 parallel springs, it is 20 kgf / mm. A load change of 2 kgf occurs with a displacement of 0.1 mm. By installing a small-capacity, high-accuracy load detector (load converter) 37 on the stationary ring (support 34), it is possible to detect a load change and detect an electromagnetic force change in a non-contact manner.

  Thus, in the present invention, in the conventional invention, the load detector that measures the electromagnetic force is separated from the fixed-side magnetic field generator, and the load detector that measures only the change in the electromagnetic force is installed. . Thereby, the change of the electromagnetic force can be detected accurately without being affected by the mass of the rotating body, that is, the magnitude of the electromagnetic force that supports the rotating body.

  In addition, this invention is not limited to the said Example, Based on the meaning of this invention, a various deformation | transformation is possible and these are not excluded from the scope of the present invention.

  The magnetic bearing using the high-temperature superconducting bulk body of the present invention can be used as a stable magnetic bearing in which the bearing capacity does not fluctuate even if the magnetic levitation characteristics of the high-temperature superconducting bulk body deteriorate with time or rotation loss.

It is a schematic diagram which shows the magnetic bearing using the high-temperature superconducting bulk body which shows 1st Example of this invention. It is a figure which shows together the simulation experiment result of the prior art, and the simulation experiment result of the example of application of this invention. It is a figure which shows the detail of the example of application of this invention. It is a top view of the load detection apparatus of the magnetic bearing using the high-temperature superconducting bulk body which shows 2nd Example of this invention. It is the sectional view on the AA line of FIG. It is a figure which shows the cantilever in the BB sectional drawing of FIG. It is a figure which shows an example of the load detection apparatus provided in the cantilever in the BB sectional drawing of FIG. It is sectional drawing of the load detection apparatus of the magnetic bearing using the high-temperature superconducting bulk body which shows 3rd Example of this invention. FIG. 9 is a top view of FIG. 8 (a cross-sectional view in a state where the lower side is seen from the position of the line CC). It is a bottom view of FIG. It is sectional drawing of the state which looked at the upper side from the BB line position of FIG. It is the DD sectional view taken on the line of FIG. It is a figure which shows the relationship between the distance of a magnet and an iron plate, and attractive force. It is sectional drawing which shows an example of the conventional thrust magnetic bearing. It is a figure which shows an example of the rotation experiment of the high temperature superconducting bulk body which simulated the prior art. It is a figure which shows the example of a result of the simulation experiment of a prior art (a levitation force change is enlarged and displayed).

Explanation of symbols

1 Stand 2 Motor / Generator (M / G)
2A Rotor 2B Armature 3 Rotating shaft 4 High temperature superconducting bulk body 4A Vacuum insulation container 4B Refrigerant 5 Electromagnet as magnetism generator 5A Magnet coil 6 Electromagnet mount 7 Flywheel 8 Load detector 9 First radial bearing 10 2nd Radial bearing 11 Backup thrust bearing 20, 30 Fixed portion 21, 32 Rotating shaft of rotating body 22 Thrust bearing 23, 33 Magnetic material ring 24 Ball bearing assembly 24a Housing washer 24b Shaft washer 25 Cantilever (cantilever)
26 A load detector disposed on the cantilever 31 A base projecting from the fixed portion 34 A support body supporting a plurality of neodymium magnets 35 Neodymium magnet 36 A linear guide fixed to the support body 37 A load detector

Claims (12)

  A high-temperature superconducting bulk body is incorporated in the rotating shaft, and a magnetic generator for applying an electromagnetic force as a levitation force or a guiding force to the high-temperature superconducting bulk body is disposed on the fixed side, and the electromagnetic force generated by the magnetic generator is Magnetic properties using a high-temperature superconducting bulk body are characterized in that, by adjusting, the magnetic levitation characteristics of the high-temperature superconducting bulk body are not deteriorated in bearing capacity even if temporal deterioration or rotation loss occurs. Bearing stabilization method.   2. The method of stabilizing a magnetic bearing using a high-temperature superconducting bulk body according to claim 1, wherein a load applied to the magnetic bearing is detected and the information is used to adjust the magnetic field of the magnetic generator disposed on the fixed side. A method for stabilizing a magnetic bearing using a high-temperature superconducting bulk body, characterized by stabilizing the magnetic bearing.   3. A method for stabilizing a magnetic bearing using a high-temperature superconducting bulk body according to claim 1, wherein the magnetic generator is made of an electromagnet.   4. The method for stabilizing a magnetic bearing using a high-temperature superconducting bulk body according to claim 3, wherein the electromagnet has a coil made of a superconducting material. In magnetic bearings using high-temperature superconducting bulk materials,
(A) a high-temperature superconducting bulk body incorporated in the rotating shaft;
(B) a magnetism generator arranged on the fixed side so that an electromagnetic force that acts as a levitating force or a guiding force acts on the high-temperature superconducting bulk body;
(C) A magnetic bearing using a high-temperature superconducting bulk body, comprising electromagnetic force adjusting means for adjusting an electromagnetic force generated by the magnetism generator.   6. A magnetic bearing using the high-temperature superconducting bulk body according to claim 5, wherein a load detecting means for detecting a burden load of the magnetic bearing, and a magnetic generator disposed on the fixed side using information of the load detecting means. A magnetic bearing using a high-temperature superconducting bulk body, comprising electromagnetic force adjusting means for adjusting a magnetic field.   7. A magnetic bearing using a high-temperature superconducting bulk body according to claim 5, wherein the magnetic generator is an electromagnet.   7. A magnetic bearing using a high-temperature superconducting bulk body according to claim 5, wherein the electromagnet includes a coil made of a superconducting material.   6. A magnetic bearing using a high-temperature superconducting bulk body according to claim 5, wherein a load detector used for control for preventing electromagnetic force deterioration of the superconducting magnetic bearing is separated from a magnetic field generator of the superconducting magnetic bearing, A magnetic bearing using a high-temperature superconducting bulk material, which is separately installed to detect only changes.   10. A magnetic bearing using a high-temperature superconducting bulk body according to claim 9, wherein a thrust bearing is installed in a load detecting section including the load detector, and bending of a cantilever made of a cantilever is detected via the thrust bearing. A magnetic bearing using a high-temperature superconducting bulk body, characterized in that the load change in the vertical direction of the rotating body is detected by the above.   The magnetic bearing using the high-temperature superconducting bulk body according to claim 9, wherein a magnetic body is used for a load detection unit including the load detector, and the vertical body supports the rotating body without contacting the rotating body. A magnetic bearing using a high-temperature superconducting bulk material, characterized in that it can detect a change in load.   12. A magnetic bearing using a high-temperature superconducting bulk body according to claim 11, wherein an attraction force by a permanent magnet and a magnetic material is used for magnetic support of a load detection unit including the load detector. Magnetic bearing using bulk material.

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