JP3318217B2 - Superconducting magnet and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting magnet and a method for manufacturing the same, and more particularly, to a method for controlling mechanical disturbance of a superconducting magnet using a superconducting coil which exhibits a superconducting phenomenon in liquid helium (LHe) which is a cryogenic refrigerant. A superconducting magnet suitable for one that is firmly supported and fixed via a spacer fitting so as to prevent relative slippage due to vibration or the like in the superconducting coil housed in the inner tank in order to prevent slip heat generation which is one of the causes,
And its manufacturing method.

[0002]

2. Description of the Related Art A superconducting material which exhibits a superconducting phenomenon when cooled by LHe, such as an Nb-Ti wire, is generally made of copper (Cu) or (Al) having high thermal conductivity (stabilizing material).
By embedding a large number of ultrafine wires, it is used as a multiconductor composite superconductor. This superconductor is wound in multiple layers and generally impregnated with epoxy as an adhesive to produce, for example, a superconducting coil integrated in a race track shape.

When this superconducting coil is used as a superconducting magnet, a technique described in, for example, Japanese Patent Application Laid-Open No. 57-48206 is conventionally known.

A conventional superconducting magnet will be described below with reference to the drawings. FIG. 9 is a plan view showing the structure of a conventional superconducting magnet, FIG. 10 is a sectional view taken along the line CC 'of a portion for supporting and fixing a superconducting coil in an inner tank, and FIG. 11 is a side view thereof.

In FIGS. 9 to 11, 1 is a superconducting coil, 2 is an inner tank, 3 is an insulating material, 4a and 4b are spacers, 5 is a bolt, and 6 is a cavity. That is, the superconducting magnet according to the prior art has a superconducting coil 1 formed in a race track shape, as shown in FIGS. It is configured so as to be electrically insulated and supported and fixed via an insulating material 3 arranged at a predetermined interval and a spacer metal member 4a, 4b divided into two parts. Then, the spacer fittings 4a, 4
b is elastically deformed in the direction of the self-electromagnetic force of the superconducting coil 1 and is firmly fixed to the superconducting coil 1 by bolts 5.

Thus, in the prior art, when a current is supplied to the superconducting coil 1, the superconducting coil 1 tends to deform by its own electromagnetic force, but the spacers 4a and 4b are moved in the direction of the self-electromagnetic force of the superconducting coil 1. Since the superconducting coil 1 is elastically deformed and fixed to the superconducting coil 1 by the bolt 5, an effect that the superconducting coil 1 can be prevented from being deformed and moved can be obtained.

[0007]

SUMMARY OF THE INVENTION
No consideration is given to the difference in heat shrinkage between the materials constituting the superconducting magnet, that is, the superconducting coil 1, the insulating material 3, and the spacers 4a, 4b. There is a problem that a gap is generated between the insulating members 3 or between the insulating member 3 and the spacers 4a and 4b.

This is because Cu, Nb-T is used as a constituent material.
Since the superconducting coil 1 using i, epoxy, and insulating material and the insulating material 3 have a larger heat shrinkage than the inner bath 2 and the spacer fittings 4a and 4b, which are generally formed of stainless steel, they are cooled to the operating temperature LHe. Then, between the superconducting coil 1 and the insulating material 3 or between the insulating material 3 and the spacer 4
This is because a gap is created between the holes a and 4b.

This will be described below. FIG. 12 is a view for explaining the measurement results of the heat shrinkage of the material forming the superconducting coil 1. This figure shows the measurement of heat shrinkage during cooling of a superconducting coil 1 having a cross section of 40 × 75 mm, a spacer 4a, 4b made of stainless steel, an inner tank 2 and an aluminum for reference, with an insulating material 3 interposed therebetween. The results are shown.

As can be understood from this figure, the amount of heat shrinkage of the superconducting coil 1 up to the operating temperature is larger than that of the spacers 4a, 4b made of stainless steel or the inner tank 2, so that the spacers 4a, 4b, Alternatively, the gap between the insulating material 3 and the surface of the superconducting coil 1 is 0, but when the operating temperature is reached, about 75000 × 0.07 / 100 = 5.
This results in a gap of 3 μm.

By the way, such a superconducting magnet exerts its own electromagnetic force in a fixed direction, but is not used in a completely stationary state, and its direction cannot be determined due to vibration of a building to be installed, an earthquake or the like. When vibration or the like acts, the superconducting coil 1 may be displaced and moved in all directions.

FIG. 13 is a diagram for explaining the result of vibration analysis during running acting on the superconducting coil of the superconducting magnet for a magnetic levitation train. As can be seen from the vibration analysis example shown in FIG. It will be easily displaced and moved by the vibration from. As described above, the prior art is used to dispose between the superconducting coil 1 and the insulating material 3 or the insulating material 3.
There is a problem that a gap is formed between the superconducting coil 1 and the spacer fittings 4a and 4b, so that the superconducting coil 1 becomes higher than a critical temperature due to frictional heat generated by displacement movement of the superconducting coil 1 and a quench is generated.

The present invention has been made in view of the above points,
The purpose is to support and fix the superconducting coil to the inner tank via an insulating material and a spacer.
It is an object of the present invention to provide a superconducting magnet which eliminates displacement movement caused by a difference in heat shrinkage between materials constituting the superconducting magnet, thereby not generating frictional heat and causing no quench, and a method of manufacturing the same.

[0014]

According to the present invention, in order to achieve the above object , the inner tank is formed of a material having a heat shrinkage equivalent to or larger than that of the spacer metal fitting and the superconducting coil, or the spacer metal fitting, A superconducting magnet in which both the inner tanks are formed of a material having a higher heat shrinkage than the superconducting coil,
Alternatively, the spacer is formed of a material having a larger heat shrinkage than that of the superconducting coil and the inner bath, an insulating material is provided on the outer periphery of the superconducting coil main body, and the spacer metal is pressed on the insulating material by two, and the spacer is pressed. The facing surface of the spacer is welded in a state where a compressive load is applied to the spacer, and then the inner tank is divided into two so that a compressive elastic strain larger than the heat shrinkage strain difference between the spacer and the inner tank is maintained. And a method of manufacturing a superconducting magnet formed by welding the opposing surface of the inner tank while pressing.

That is, since the spacer fitting surrounding the superconducting coil has a larger heat shrinkage than the superconducting coil, it is more firmly fixed at the operating temperature than at room temperature. However, since a gap is created between the inner tank and the space fitting due to the contraction of the space fitting, the inner tank is pressed and welded and fixed while elastic deformation larger than the thermal contraction difference between the two is applied to the spacer fitting. By doing so, it is possible to prevent the superconducting coil from deforming and moving even when mechanical force such as vibration with undetermined direction is applied, and therefore, it is possible to suppress frictional heat generation due to slip, and as a result, the superconducting coil Quench can be prevented.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to embodiments of the drawings.

A first embodiment of the present invention will be described with reference to FIGS. The basic configuration of the present invention is shown in FIGS.
This is almost the same as the case of the conventional example described above, and is configured by supporting the race-track-shaped superconducting coil 1 in the inner tank 2.

FIG. 1 is a cutaway perspective view of a main part of a portion for supporting a racetrack-shaped superconducting coil 1 on an inner tank 2, and FIG.
Spacer fitting 4 for supporting and fixing superconducting coil 1 to inner tank 2
FIG. FIG. 3 shows the material characteristics of the stress and strain of the constituent materials of the superconducting coil 1.

The superconducting coil 1 according to the first embodiment of the present invention shown in FIGS. 1 to 3 has a superconductor in which a large number of ultrafine Nb-Ti wires are embedded in copper (Cu) as a stabilizing material between layers. It is manufactured by impregnating with epoxy resin and forming it into a race track shape while being fixed by a mold so that the cross section in the length direction becomes substantially rectangular via the insulating material 3 of glass cloth. The insulating material 3 surrounding the surface of the superconducting coil 1 was made of a material having poor thermal conductivity and high abrasion resistance.

Further, the spacer 4 is made of, for example, high-strength aluminum (A5083P) having a larger heat shrinkage than the superconducting coil 1.
−32H-10T), and as shown in FIG.
a and 4b are formed into an L-shape. On the other hand, the inner tank 2 is formed of, for example, stainless steel and divided into 2a and 2b in the axial direction of the coil at the center thereof. The method for assembling a superconducting magnet according to the first embodiment of the present invention is as follows. First, an L-shaped two-piece spacer metal fitting 4a, 4b
Are pressed and arranged, and the two are united by welding to fix the superconducting coil 1. Thereafter, the inner tanks 2a and 2b divided into two are pressed and joined by welding. In addition,
A cavity 6 is formed in the two-piece spacer metal fittings 4a and 4b so as to allow LHe, which is a refrigerant, to flow in the inner tank 2, and a cavity 6 is formed in an axial direction in a corner portion of a welding surface between the two-piece spacer metal fittings 4a and 4b. It has such a structure.

Here, the basis of the selection criteria for the constituent materials of the superconducting coil 1 will be described with reference to FIGS.
Naturally, when assembling with any of the components,
And the stress state within the yield stress in the operating state during LHe.

As shown in FIG. 12, the heat shrinkage of the constituent material selected in this embodiment is determined by the following equation: high tensile aluminum (Young's modulus E = 70 GPa) of the spacer 4> superconducting coil 1 (1
10MPa)> Stainless steel of inner tank 2 (E = 200GP)
The order is a). Therefore, for example, even when assembled with no pressing force at normal temperature, the superconducting coil 1 and the spacer 4 are firmly fixed at the operating temperature of LHe. That is, (0.11-0.07) / 100 × 700 is used for the high-strength aluminum spacer 4.
This means that a stress of 00 = 28 MPa has been generated. On the other hand, a gap is created between the spacer 4 and the inner tank 2. In order to prevent the formation of a gap, a compression stress of 0.11%, which corresponds to a heat shrinkage difference of 0.11% between the two when the inner tank 2 is welded.
It is necessary to apply 11/100 × 70000 = 77 MPa to the spacer 4. Therefore, the spacer fitting 4
Is made of high-tensile aluminum, the 0.2% yield stress σy must be 77 MPa or more in order to prevent gaps from forming between the constituent members at the LHe temperature. Furthermore, assuming that the self-electromagnetic force when a current flows through the superconducting magnet and the vibration stress during operation are ± 30 MPa, it is necessary to select a material having a 0.2% yield stress σy = 107 MPa or more.

The material of the spacer 4 according to the present invention includes:
As shown in FIG. 3, 0.2% yield stress σy = 210 MPa
High tensile aluminum (A5083P-32H-10T)
This condition is fully satisfied. Therefore, the pressing force at the time of welding the inner tank 2 is set to 107 to 210 M as a stress generated in the spacer fitting 4 in consideration of the self electromagnetic force and the vibration stress.
It suffices to set it to Pa or less.

When the spacer 4 according to the present invention is made of high-strength aluminum from conventional stainless steel and a superconducting magnet is applied to a magnetic levitation train, about 80 kg per vehicle.
This has the effect of reducing weight. Even if frictional heat is generated due to slippage between the insulating material 3 and the spacer 4, the frictional heat of the high-tensile aluminum is about 1000 times larger than that of stainless steel at the LHe temperature. From the superconducting coil 1
Intrusion into the main body can be significantly prevented, and there is also an effect that instantaneous quench can be prevented.

The high-strength aluminum (A5083P-
32H-10T), as shown in FIG. 3, has a yield stress equivalent to that of stainless steel, which is the material of the inner tank 2 conventionally used. Therefore, as a modification of the first embodiment of the present invention, the material of the spacer 4 and the inner tank 2 may be made of high-strength aluminum (A5083P-32H-10T). In this case, there is no stress relaxation due to a difference in heat shrinkage between the spacer fitting 4 and the constituent material of the inner tank 2 when the operating temperature reaches the LHe temperature. Only the force and the vibration stress need to be considered. Therefore, the pressing force at the time of welding the inner tank 2 may be 30 MPa or more as the stress generated in the spacer 4.

According to this embodiment, there is an effect that the superconducting magnet can be reduced in weight and the weight can be reduced by about 300 kg.

Further, as a combination of constituent materials of the superconducting magnet, the inner tank 2 may be made of high-strength aluminum and the spacer 4 may be made of stainless steel. In this case, since the superconducting coil 1 has a larger thermal shrinkage by 0.07% than the spacer metal member 4, it is necessary to perform welding while pressing the spacer metal member 4 in consideration of stress relaxation caused by the heat shrinkage.

FIG. 4 shows a second embodiment of the present invention. FIG.
In FIG. 1, the insulating material 3 is surrounded on the surface of the superconducting coil 1 more widely than the spacer 4 in the cross section BB 'of FIG. The spacer metal fittings 4 are provided with projections on both sides in the longitudinal direction of the contact end face with the insulating material 3 and are pressed and supported. Here, the height of the protrusion is set to a range where no gap is formed in the center of the spacer 4 when pressed. Since the superconducting coil 1 is formed by impregnation with a resin and surrounds the insulating material 3, the contact surface with the spacer 4 does not have the parallelism and squareness as machined.
Therefore, even when the pressing is performed on the machined flat surface of the spacer 4, the pressing cannot be performed with a uniform surface pressure, resulting in one end, and a minute gap may be generated at the end. According to this embodiment, both end surfaces of the spacer 4 can be reliably pressed and supported by the insulating material 3 at a high surface pressure, and even when a bending vibration load is applied to the superconducting coil 1, localization at the pressed end portion is possible. This has the effect of suppressing typical micro fretting slip.

FIG. 5 shows a modification of the second embodiment. In order to obtain the same effect, a slit is provided in the longitudinal direction in the spacer 4 to reduce the rigidity of this portion and increase the surface pressure on both sides. In this embodiment, in order to enhance the cooling effect of the slit portion, the through hole 7 through which the refrigerant can flow in the lateral direction is provided.

FIG. 6 shows a modification of the second embodiment. In the present embodiment, contrary to the second embodiment shown in FIG. 4, the insulating material 3 is made narrower than the width of the spacer 4 and the thickness of both sides of the insulating material 3 is increased, so that the contact surface is flat. Press with the spacer fitting 4. Here, the thickness of both sides of the insulating material 3 is
The range was such that no void could be formed in the center at the time of pressing. In addition, the insulating material 3 only needs to additionally wind a narrow tape-shaped fiber on both sides in a normal construction work, and has an effect of being able to be constructed more easily than machining the spacer fitting 4.

FIG. 7 shows a modification of the second embodiment.
As a place where fretting occurs, a contact surface between the inner tank 2 and the spacer 4 can be considered. Even if frictional heat is generated in this portion, the frictional heat is diffused into LHe, which is a refrigerant, and instantaneous quench of the superconducting coil does not occur, but quench occurs with an increase in the amount of evaporation of LHe. Therefore, as shown in FIG. 7, projections are provided on both sides of the contact surface of the spacer 4 on the inner tank 2 side. FIG. 8 shows an example experimentally verified that the effect of the present invention, that is, that micro-fretting sliding heat generation can be suppressed by supporting and fixing at a high surface pressure. As the load amplitude ΔP in the vibration test increases, the absorbed energy E of the pressing support increases, but the pressing force,
That is, it is understood that the higher the pressing surface pressure, the smaller the absorbed energy.

Next, a modification of the method for manufacturing a superconducting magnet shown in the first embodiment of the present invention will be described. In the first embodiment, the welding of the high-strength aluminum spacer fitting 4 and the stainless steel inner tank 2 was all performed at room temperature.

In this modification, first, at room temperature, the insulating material 3
And presses the L-shaped two-piece spacer metal fittings 4a and 4b via welding to fix the same to the superconducting coil 1 by welding. Thereafter, the superconducting coil 1 to which the spacer 4 is fixed by welding is temporarily fixed in the inner tanks 2a and 2b which are divided into two, and is immersed in a cryogenic refrigerant, for example, liquid nitrogen. Weld and fix in the pressed state. Then return to room temperature and incorporate into the product.

Here, the spacer 4 is attached to the superconducting coil 1.
May be applied with a slight pressing force that can set the spacer 4 at a predetermined position. When cooled to the operating temperature in this state, as can be seen from the heat shrinkage characteristics shown in FIG. 12, the spacer metal fitting 4 has (0.11-0.07) / 100.
× 70000 = stress of 28 MPa will be generated. Further, the pressing force when welding the inner tank 2 in a low temperature state is as follows.
Considering the self-electromagnetic force and the vibration stress, the stress generated in the spacer 4 was set to 30 MPa or more. When the temperature is returned to normal temperature after welding the inner tank 2, the spacer metal 4 is loaded with 107 MPa, which is obtained by adding the stress of 0.11 / 100 × 70000 = 77 MPa due to the thermal expansion of the spacer metal 4 and 30 MPa at the time of pressing. There is no problem because it is not more than the yield stress of tensile aluminum. According to this embodiment, since the pressing force can be controlled mechanically, the superconducting magnet can be manufactured in a state where a predetermined stress is surely applied.

[0035]

According to the superconducting magnet and the method of manufacturing the same of the present invention described above , the inner tank is formed of a material having a heat shrinkage equivalent to or larger than that of the spacer and the superconducting coil, or the spacer is provided. , And both the inner tank, a superconducting magnet formed of a material having a larger heat shrinkage than the superconducting coil, or the spacer metal fitting is the superconducting coil,
And a material having a larger heat shrinkage than that of the inner tank.
Pressing the divided spacers, welding the opposing surfaces of the spacers while applying a compressive load to the spacers,
Then, a method of manufacturing a superconducting magnet formed by welding the inner tank while pressing the inner tank divided into two so that a compressive elastic strain larger than the heat shrinkage strain difference between the spacer metal fitting and the inner tank is maintained. Since the spacer metal, the inner bath, or both of them, which surround the superconducting coil, have a larger heat shrinkage than the superconducting coil, they are more firmly fixed at the operating temperature than at room temperature. Even if the coil is supported and fixed to the inner tank via an insulating material and a spacer, there is no displacement movement due to the difference in heat shrinkage between the constituent materials, and thus no quench occurs because no frictional heat is generated. However, it is very effective for this type of superconducting magnet.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view showing an embodiment of a superconducting magnet of the present invention.

FIG. 2 is a sectional view taken along the line AA ′ of FIG.

FIG. 3 is a characteristic diagram showing a relationship between compressive stress and strain for explaining mechanical properties of a constituent material of the present invention.

FIG. 4 shows a second embodiment of the present invention, and is BB 'in FIG.
It is sectional drawing which follows a line.

FIG. 5 shows a modification of the second embodiment of the present invention.
It is sectional drawing which follows the B 'line.

FIG. 6 shows a modification of the second embodiment of the present invention.
It is sectional drawing which follows the B 'line.

FIG. 7 shows a modification of the second embodiment of the present invention.
It is sectional drawing which follows the B 'line.

FIG. 8 is a characteristic diagram showing the result of experimentally verifying the effect of the present invention.

FIG. 9 is a plan view showing a conventional superconducting magnet.

FIG. 10 is a sectional view taken along the line CC ′ of FIG. 9;

FIG. 11 is a side view of FIG. 10;

FIG. 12 is a characteristic diagram of a thermal shrinkage measurement result for explaining a thermal characteristic of a material forming the superconducting magnet.

FIG. 13 is a diagram showing a vibration analysis result of a superconducting coil when a superconducting magnet is applied to a magnetic levitation train.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Superconducting coil, 2, 2a, 2b ... Inner tank, 3 ... Insulating material, 4, 4a, 4b ... Spacer fitting, 6 ... Cavity.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hidehiro Ejima 502 Kandamachi, Tsuchiura-shi, Ibaraki Pref. Machinery Research Laboratory, Hitachi, Ltd. Hitachi, Ltd., Hitachi Plant (72) Inventor Tadashi Sonobe 3-1-1, Sachimachi, Hitachi, Ibaraki Pref. Hitachi, Ltd. Inside Hitachi, Ltd. (72) Inventor Fumio Suzuki 3-1-1, Sachimachi, Hitachi, Ibaraki No. Hitachi, Ltd. Hitachi Plant (72) Inventor Hiroyuki Watanabe 3-1-1, Kochicho, Hitachi, Ibaraki Prefecture Hitachi, Ltd. Hitachi Plant (72) Inventor Motoaki Terai Name Station in Nakamura-ku, Nagoya-shi, Aichi Prefecture 1-4-1 Tokai Passenger Railway Co., Ltd. (72) Inventor Tetsu Inadama 1-4-1 Meieki Station, Nakamura-ku, Nagoya City, Aichi Prefecture Tokai Passenger (56) References JP-A-4-290405 (JP, A) JP-A-4-134808 (JP, A) JP-A-7-249511 (JP, A) JP-A-6-244027 (JP) , A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01F 6/00 H01F 6/06

Claims (7)

(57) [Claims] 1. A superconducting coil body formed by winding a superconductor in multiple layers, impregnating it with an adhesive, and integrating the superconducting coil body with an insulating material arranged at a predetermined interval on the outer periphery thereof and a spacer metal fitting. Is housed in the superconducting magnet, wherein a cryogenic refrigerant is held between the inner tank and the superconducting coil, wherein the inner tank comprises the spacer fitting and the superconducting coil.
Made of a material with the same or higher heat shrinkage
A superconducting magnet characterized in that: 2. A superconducting coil body formed by winding a superconductor in multiple layers, impregnating an adhesive with the superconducting coil, and integrating the superconducting coil main body with an insulating material disposed at a predetermined interval on the outer periphery thereof and a spacer. In the superconducting magnet, which is stored in the inner tank and the cryogenic refrigerant is held between the inner tank and the superconducting coil , both the spacer metal fitting and the inner tank are connected to the superconducting magnet.
It must be made of a material with a higher heat shrinkage than the coil.
And a superconducting magnet. 3. An end at which said insulating material and a spacer fitting come into contact with each other.
Surface and spacer metal that the inner tank and the spacer metal are in contact with
The superconducting coil has a structure in which both end faces of the
2. The method according to claim 1, wherein said inner tank is supported by pressing.
Is a superconducting magnet according to 2. 4. The inner tank is made of high-strength aluminum.
The superconducting magnet according to claim 1, wherein: 5. A high tension iron for both the spacer and the inner tank.
3. The device according to claim 2, wherein the device is made of luminium.
Superconducting magnet. 6. A multi-layered superconductor wound with an adhesive.
The outer periphery of the superconducting coil body
Via insulating material and spacers
It is stored in the inner tank, and the cryogenic refrigerant is placed between the inner tank and the superconducting coil.
In the method for manufacturing a superconducting magnet having
Pacer fitting is more heat shrink than the superconducting coil and inner tank
Formed of a material with a large size and divided into two parts on the insulating material
Presses the spacer bracket, and applies a compressive load to the spacer bracket.
Weld the opposing surface of the spacer bracket with
Larger than the heat shrinkage strain difference between the spacer fitting and the inner tank
The inner tank divided into two so that the compressive elastic strain is maintained
It is characterized in that the opposing surface of the inner tank is welded while pressed.
Manufacturing method of superconducting magnet. 7. The superconducting coil body is provided on the outer periphery of the superconducting coil body at normal temperature
Spacer bracket divided into two parts on the insulating material via the insulating material
Is pressed, and a compression load is applied to the spacer.
The opposed surface of the inner tank is welded.
A method for producing the superconducting magnet described in the above.