Patent Application
20240203627
The present disclosure relates to a magnetic field generating device.
The present application claims priority to and the benefit of Japanese Patent Application No. 2021-071385 filed Apr. 20, 2021, the entire contents of which are incorporated herein by reference.
Conventionally, there are magnetic field generating devices that include a substantially C-shaped iron core and a pair of coils wound around a pair of ends of the iron core (for example, JP 2005-123084 A (PTL 1)).
PTL 1: JP 2005-123084 A
In such conventional magnetic field generating devices, in the case where superconducting coils are used as the coils, the superconducting coils need to be cooled. One conceivable cooling method is to store the entire iron core and pair of coils in a vacuum heat-insulation container. This, however, requires a large vacuum heat-insulation container.
It could therefore be helpful to provide a magnetic field generating device that can reduce the size of a vacuum heat-insulation container.
A magnetic field generating device according to the present disclosure comprises: an iron core; a pair of superconducting coils; and one or a pair of vacuum heat-insulation containers, wherein the iron core includes: a substantially C-shaped or substantially U-shaped yoke; and a pair of split iron core portions that are formed separately from the yoke, are located inside the yoke, and face each other with a work space therebetween, each of the pair of superconducting coils is wound around a different one of the pair of split iron core portions in a circumferential direction about an axis that is parallel to a direction in which the pair of split iron core portions face each other, a pair of split iron core coil assemblies each composed of the split iron core portion and the superconducting coil wound around the split iron core portion are stored in the one or pair of vacuum heat-insulation containers, and the yoke is located outside the one or pair of vacuum heat-insulation containers.
Preferably, in the magnetic field generating device according to the present disclosure, in at least one of the pair of split iron core coil assemblies, an outer circumferential surface of the split iron core portion has an annular stepped portion that faces the work space and is recessed toward an inner side in an orthogonal-to-axis direction, and the superconducting coil is wound around the stepped portion in the circumferential direction.
In the magnetic field generating device according to the present disclosure, in at least one of the pair of split iron core coil assemblies, an outer circumferential surface of the split iron core portion may have an annular groove, and the superconducting coil may be wound around the groove in the circumferential direction.
It is thus possible to provide a magnetic field generating device that can reduce the size of a vacuum heat-insulation container.
In the accompanying drawings:
A magnetic field generating device according to the present disclosure can be used for any purpose, such as a heating device for aluminum billets.
An embodiment of a magnetic field generating device according to the present disclosure will be described below, with reference to the drawings.
As illustrated in
The iron core 2 includes a yoke 21 and a pair of split iron core portions 22.
The yoke 21 contains iron, and is configured to pass magnetic flux. The yoke 21 is substantially C-shaped or substantially U-shaped (substantially C-shaped in the example in
The pair of split iron core portions 22 contain iron, and are configured to pass magnetic flux. The pair of split iron core portions 22 are formed separately from the yoke 21. The pair of split iron core portions 22 are located inside the yoke 21, and face each other with the workspace 6 therebetween. The work space 6 is an air gap.
Thus, the iron core 2 is substantially C-shaped.
In this specification, a direction parallel to an axis O that passes through the pair of split iron core portions 22 and extends in a direction in which the pair of split iron core portions 22 face each other is referred to as “axial direction AD”. The side closer to the work space 6 in the axial direction AD is referred to as “inner side in the axial direction ADI”, and the side farther from the work space 6 in the axial direction AD is referred to as “outer side in the axial direction ADO”. A direction perpendicular to the axial direction AD is referred to as “orthogonal-to-axis direction OD”. The side closer to the axis O in the orthogonal-to-axis direction OD is referred to as “inner side in the orthogonal-to-axis direction”, and the side farther from the axis O in the orthogonal-to-axis direction OD is referred to as “outer side in the orthogonal-to-axis direction”. In this specification, the circumferential direction about the axis O is also simply referred to as “circumferential direction”. The terms “outer circumferential side” and “inner circumferential side” respectively refer to the outer circumferential side and inner circumferential side with respect to the axis O, unless otherwise specified.
The pair of split iron core portions 22 and the pair of ends 21a of the yoke 21 face each other in the axial direction AD. The pair of split iron core portions 22 are located on the inner side in the axial direction ADI relative to the pair of ends 21a of the yoke 21. The surfaces of the pair of split iron core portions 22 on the outer side in the axial direction ADO face the pair of surfaces of the yoke 21 on the inner side in the axial direction ADI with a narrow gap therebetween.
As illustrated in
The superconducting coil 3 includes at least a coil body containing a superconductor. The coil body of the superconducting coil 3 is in a strip shape, for example. The superconducting coil 3 may further include, in addition to the coil body, a coil case that stores the coil body therein. The coil case is made of, for example, resin.
In the example in
The magnetic field generating device 1 includes a current supply unit (not illustrated) for supplying current (for example, direct current) to each superconducting coil 3.
Each split iron core portion 22 and the superconducting coil 3 wound around the split iron core portion 22 constitute a split iron core coil assembly 5. That is, the split iron core coil assembly 5 is composed of the split iron core portion 22 and the superconducting coil 3 wound around the split iron core portion 22. The magnetic field generating device 1 includes a pair of split iron core coil assemblies 5.
Each split iron core coil assembly 5 is stored in a corresponding vacuum heat-insulation container 4. The yoke 21 is located outside the pair of vacuum heat-insulation containers 4. The pair of vacuum heat-insulation containers 4 face each other in the axial direction AD with the work space 6 therebetween. As illustrated in
The magnetic field generating device 1 includes a refrigerator (not illustrated). The refrigerator cools the equipment inside each vacuum heat-insulation container 4. The vacuum heat-insulation container 4 is configured to keep the temperature of the internal equipment cooled by the refrigerator. The vacuum heat-insulation container 4 is thus configured to, together with the refrigerator, cool the split iron core coil assembly 5 and thus the superconducting coil 3 and maintain it at ultralow temperature. Specifically, the superconducting coil 3 is cooled until the superconductor becomes superconducting (i.e. until the electrical resistance reaches substantially zero).
It is preferable that the vacuum heat-insulation container 4 is not only evacuated but also has a laminated heat-insulation material on part or all of its walls. The laminated heat-insulation material is formed, for example, by laminating a plurality of metal vapor-deposited resin films and resin nets. Examples of the material forming the main body of the vacuum heat-insulation container 4 include austenitic stainless steel and composite glass fiber reinforced plastic (GFRP).
The vacuum heat-insulation container 4 may be configured to cool the split iron core coil assembly 5 and thus the superconducting coil 3 by any method other than the above, as long as the split iron core coil assembly 5 is stored therein.
In the magnetic field generating device 1 having the above-described structure, when the current supply unit (not illustrated) supplies current to each superconducting coil 3, magnetic flux passes through the iron core 2 (the yoke 21 and the pair of split iron core portions 22), and a strong magnetic field is generated in the work space 6.
The strong magnetic field generated in the work space 6 may be used for any purpose.
For example, the magnetic field generating device 1 may be used in a heating device for aluminum billets. In this case, the heating device includes, in addition to the magnetic field generating device 1, a motor for rotating the aluminum billet. A direct current is passed through each superconducting coil 3, as a result of which a strong DC magnetic field is generated in the work space 6. The aluminum billet is placed in the work space 6 such that the central axis of the aluminum billet will be perpendicular to the axial direction AD and also horizontal, and is rotated around the central axis of the aluminum billet by the motor. This is equivalent to applying an AC magnetic field to the aluminum billet, so that an induced current flows in the aluminum billet and the aluminum billet is heated.
The effects in this embodiment will be described below.
First, according to this embodiment, since the magnetic field generating device 1 includes the superconducting coils 3, a stronger magnetic field can be generated in the work space 6 than in the case where the magnetic field generating device 1 includes, for example, typical copper coils instead of the superconducting coils 3.
Moreover, according to this embodiment, since the magnetic field generating device 1 includes the iron core 2, a strong magnetic field can be generated while reducing the amount of superconductor used for the production of the superconducting coils 3 as compared with the case where the magnetic field generating device 1 does not include the iron core 2. Hence, the amount of superconductor can be reduced and consequently the cost can be reduced. Given that superconductors are usually expensive, superconductor reduction is highly effective in cost reduction.
Moreover, according to this embodiment, since the iron core 2 in the magnetic field generating device 1 includes the yoke 21, the magnetic circuit resistance can be reduced and the magnetic flux can be increased as compared with the case where the iron core 2 does not include the yoke 21.
Moreover, according to this embodiment, the iron core 2 is divided into the yoke 21 and the pair of split iron core portions 22, the split iron core coil assemblies 5 are stored in the respective vacuum heat-insulation containers 4, and the yoke 21 is located outside the pair of vacuum heat-insulation containers 4, as described above. This can reduce the size of the vacuum heat-insulation containers 4 as compared with the case where an undivided substantially C-shaped iron core and a pair of superconducting coils wound around a pair of ends of the iron core are entirely stored in a vacuum heat-insulation container. Hence, heat penetration from outside can be reduced, with it being possible to save energy.
In the case of using an undivided substantially C-shaped iron core, the size of the vacuum heat-insulation container may be able to be reduced by forming the vacuum heat-insulation container toroidally so as to store only each of a pair of superconducting coils surrounding the respective pair of ends of the iron core. In such a case, however, a wall of the vacuum heat-insulation container is located between the iron core and the superconducting coil, that is, the iron core and the superconducting coil are separated from each other. This causes an increase in the circumference of the superconducting coil and thus an increase in the amount of superconducting coil used, leading to an increase in cost. In addition, since leakage magnetic flux increases due to the separation between the core and the superconducting coil, the amount of superconductor that needs to be used increases, leading to an increase in cost. According to this embodiment, the superconducting coil 3 is wound directly around the iron core 2 (specifically, the split iron core portion 22), and thus the iron core 2 (specifically, the split iron core portion 22) and the superconducting coil 3 are in contact with each other with there being no distance therebetween. Therefore, the circumference of the superconducting coil 3 can be shortened and consequently the amount of superconductor can be reduced and the cost can be reduced as compared with the case where the vacuum heat-insulation container is toroidal as mentioned above. In addition, since the iron core 2 (specifically, the split iron core portion 22) and the superconducting coil 3 are in contact with each other with there being no distance therebetween, leakage magnetic flux can be reduced and consequently the amount of superconductor can be reduced and the cost can be reduced as compared with the case where the vacuum heat-insulation container is toroidal as mentioned above. Furthermore, since the iron core 2 (specifically, the split iron core portion 22) and the superconducting coil 3 are in contact with each other, the cool storage effect of the iron core 2 (specifically, the split iron core portion 22) can be utilized to suppress a temperature rise of the superconducting coil 3, so that the cooling load of the refrigerator can be reduced and the superconducting coil can be sufficiently cooled to enable effective use of superconductor capabilities, as compared with the case where the vacuum heat-insulation container is toroidal as mentioned above.
Moreover, according to this embodiment, in each split iron core coil assembly 5, the Lorentz force (black arrow in
In this embodiment, the magnetic field generating device 1 includes a support member 7 as a support structure for supporting the split iron core coil assembly 5 in the vacuum heat-insulation container 4, as illustrated in
The support structure for supporting the split iron core coil assembly 5 in the vacuum heat-insulation container 4 is not limited to such, and may be any structure.
In this embodiment, the magnetic field generating device 1 includes a spacer member 8 between the split iron core coil assembly 5 and each of the walls 42 and 43 of the vacuum heat-insulation container 4 on both sides in the axial direction AD, as illustrated in
For example, the spacer member 8 may be fixed to or integrally formed with the split iron core portion 22 of the split iron core coil assembly 5, and formed separately from and not fixed to the corresponding one of the walls 42 and 43 of the vacuum heat-insulation container 4 on both sides in the axial direction AD. Alternatively, the spacer member 8 may be formed separately from and not fixed to the split iron core coil assembly 5, and fixed to or integrally formed with the corresponding one of the walls 42 and 43 of the vacuum heat-insulation container 4 on both sides in the axial direction AD.
The spacer member 8 may be omitted.
In this embodiment, the outer circumferential surface 221 of the split iron core portion 22 in each of the pair of split iron core coil assemblies 5 has an annular stepped portion 2211, as illustrated in
Since the superconducting coil 3 and the split iron core portion 22 face each other in the axial direction AD in this way, the Lorentz force (black arrow in
The stepped portion 2211 is preferably provided in both of the pair of split iron core coil assemblies 5, but may be provided in only one of the pair of split iron core coil assemblies 5.
In each example described in this specification, in at least one of the pair of split iron core coil assemblies 5, the outer circumferential surface 31 of the superconducting coil 3 may be at the same position in the orthogonal-to-axis direction OD as the outer circumferential surface 221 of the split iron core portion 22 as illustrated in
In each example described in this specification, in at least one of the pair of split iron core coil assemblies 5, the outer circumferential surface 221 of the split iron core portion 22 may have a protrusion 2213 projecting to the outer circumferential side, and the stepped portion 2211 may be provided at the protrusion 2213, as illustrated in
In at least one of the pair of split iron core coil assemblies 5, the outer circumferential surface 221 of the split iron core portion 22 may have an annular groove 2212, as illustrated in
In this case as in the case where the superconducting coil 3 is wound around the stepped portion 2211 (
In this case, when the wall portion 222 of the split iron core portion 22 between the groove 2212 and the end surface 223 of the split iron core portion 22 on the inner side in the axial direction ADI is thinner in the axial direction AD, magnetic flux saturation is more likely to occur in the wall portion 222 during energization, so that a stronger magnetic field can be generated in the work space 6. From this viewpoint, the thickness of the wall portion 222 in the axial direction AD is preferably 3 mm or less. From the same viewpoint, the center of the groove 2212 in the axial direction AD is preferably located on the inner side in the axial direction ADI relative to the center of the split iron core portion 22 in the axial direction AD.
In at least one of the pair of split iron core coil assemblies 5, the superconducting coil 3 may be wound around the outer circumferential surface 221 of the split iron core portion 22 without unevenness such as the stepped portion 2211 or the groove 2212. In such a case, too, the Lorentz force acting on the superconducting coil 3 toward the outer side in the axial direction ADO and the electromagnetic force acting on the split iron core portion 22 toward the inner side in the axial direction ADI cancel each other out, as a result of which the force acting on the split iron core coil assembly 5 in the axial direction AD decreases. This makes it possible to simplify the support structure for supporting the split iron core coil assembly 5 in the vacuum heat-insulation container 4. This effect is, however, greater in the case where the superconducting coil 3 is wound around the stepped portion 2211 or groove 2212 of the outer circumferential surface 221 of the split iron core portion 22 as illustrated in
In each example described in this specification, in at least one of the pair of split iron core coil assemblies 5, the superconducting coil 3 may have a single-stage structure consisting of only one layer in the axial direction AD as illustrated in
In each example described in this specification, a cooling plate (not illustrated) may be applied to the surface of the split iron core coil assembly 5 on the inner side in the axial direction ADI (specifically, the end surface 223 of the split iron core portion 22 on the inner side in the axial direction ADI and/or the end surface of the superconducting coil 3 on the inner side in the axial direction ADI) inside the vacuum heat-insulation container 4. In this case, it is more preferable that the superconducting coil 3 and the cooling plate are in contact with each other. Hence, the superconducting coil 3 can be cooled more effectively.
The cooling plate may be omitted.
In each example described in this specification, the end 21a of the yoke 21 and the wall 43 of the vacuum heat-insulation container 4 on the outer side in the axial direction are preferably separated from each other as illustrated in
In each example described in this specification, the structures of the vacuum heat-insulation containers 4 and the split iron core coil assemblies 5 are preferably symmetric with respect to the center of the magnetic field generating device 1 in the axial direction AD, but may be asymmetric with respect to the center of the magnetic field generating device 1 in the axial direction AD.
In each example described in this specification, the magnetic field generating device 1 may include only one vacuum heat-insulation container 4. In this case, the pair of split iron core coil assemblies 5 are stored in the vacuum heat-insulation container 4, and the yoke 21 is located outside the vacuum heat-insulation container 4. In such a case, too, the size of the vacuum heat-insulation container 4 can be reduced as compared with the case where an undivided substantially C-shaped iron core and a pair of superconducting coils wound around a pair of ends of the iron core are entirely stored in a vacuum heat-insulation container.
For example, the vacuum heat-insulation container 4 in this case may have a structure in which the pair of vacuum heat-insulation containers 4 in the example in
The magnetic field generating device according to the present disclosure can be used for any purpose, such as a heating device for aluminum billets.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-071385 | Apr 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/015723 | 3/29/2022 | WO |
