JPH04273956A - Stationary type magnetic refrigerating machine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention provides a cylindrical magnetic shield for repeating excitation and demagnetization processes between a superconducting coil for generating a strong magnetic field and a magnetic actuating body for generating cold.
In particular, the present invention relates to a static magnetic refrigerator that is applied to extremely low temperatures below liquid helium temperature.

0002

[Prior Art] In a conventional stationary magnetic refrigerator, a magnetic actuating body is fixedly placed in a strong magnetic field generated by a superconducting coil, and a current is passed through the electromagnet to generate a strong magnetic field, causing magnetic activation. By energizing the body and then interrupting the electromagnetic current,
A method of adiabatic demagnetization of a magnetic actuating body is widely known.

0003

[Problems to be Solved by the Invention] In conventional static magnetic refrigerators, in order to repeat the excitation/demagnetization process, it is necessary to repeatedly open and close a large current flowing through the superconducting coil. A large amount of Joule heat is generated in the lead wires between the two due to the large current, which is a major cause of reducing the thermal efficiency of magnetic refrigerators. Therefore, in order to reduce the internal resistance of the external power supply and lead wires as much as possible, the power supply device and wiring must be large-scale, which remains a practical problem to be solved.

The present inventors have already arranged a superconducting magnetic shield having a hollow portion for accommodating the magnetic working body between a superconducting coil and a magnetic working body so as to be able to move back and forth. We have proposed a stationary magnetic refrigerator that repeats the process of exposing a magnetic operating body to a strong magnetic field and excitation through reciprocating movement, and the process of being housed in the hollow part of the magnetic shield and demagnetized. Ganhei 2-305586). This method does not require any switching of current to the superconducting coils even when the refrigerator is operating, and can be used completely in persistent current mode, and the only mechanically moving part is the reciprocating mechanism that moves the magnetic shield back and forth. Therefore, it has the advantage of being highly energy efficient and compact in size compared to its refrigeration capacity.

However, even in the stationary magnetic refrigerator using the magnetic shield described above, since the magnetic shield is moved by cutting off the magnetic flux formed by the superconducting coil, a large force is required for reciprocating movement, and therefore the reciprocating mechanism is It had the disadvantage of being large.

Furthermore, a static magnetic refrigerator requires a thermal switch mechanism that efficiently transfers heat between a fixed magnetic operating body and a hot bath and a cold bath. A crystal column is reciprocatably attached to the tip of a copper thermal conductor connected to a small gas cooler, which is a heat bath, and the end surface of the crystal column and one end surface of the magnetic actuating body are made to closely face each other. It is known that the structure is In addition, as a low-temperature side heat switch connected to the cold bath side, a tube covering the magnetic actuating body communicates with the cold bath, and the working gas is convected between the surface of the magnetic actuating body and the inner surface of the cladding tube. There is a system in which droplets of the working gas generated by cooling of the magnetic working body are stored in a cold bath.

[0007] The above-mentioned heat switch, which uses a crystal column and a magnetic actuating body in close contact and separation, requires a separate reciprocating mechanism for the crystal column, and the above-mentioned heat pump method, which uses a tube covering the magnetic actuator, requires gas as a refrigerant and is not operated properly. The problem was that it was slow and had low efficiency.

In view of the above-mentioned problems, the present invention provides a stationary magnetic refrigerator in which a superconducting magnetic shield is interposed between a superconducting coil and a magnetic operating body, in which the reciprocating movement of the magnetic shield is By reducing the driving force as much as possible, and further providing a thermal switch mechanism that operates in conjunction with the reciprocating movement of the magnetic shield, there are fewer mechanically moving parts, and the thermal efficiency of the refrigerator is high, compared to its refrigerating capacity. The present invention aims to provide a small and compact stationary magnetic refrigerator.

[0009]

[Means for Solving the Problems] The magnetic refrigerator of the present invention has the following features:
This is a stationary magnetic refrigerator consisting of a superconducting coil that generates a strong magnetic field and a magnetic operating body placed in the hollow part of the superconducting coil.
The cylindrical superconducting magnetic shield is capable of reciprocating within a range inside from both opening surfaces of the hollow portion of the superconducting coil, and the magnetic operating body is housed in the hollow portion of the magnetic shield. By reciprocating the magnetic shield by a reciprocating mechanism, the magnetic operating body is accommodated in the hollow part of the magnetic shield and demagnetized, and the magnetic actuating body is extracted from the hollow part. The feature is that the process of being excited is repeated.

That is, the magnetic refrigerator of the present invention includes a superconducting solenoid coil that generates a strong magnetic field, a cylindrical superconducting magnetic shield, a magnetic operating body, and a reciprocating mechanism that reciprocates the magnetic shield. The magnetic shield is disposed within the hollow part of the solenoid coil so as to be able to reciprocate in the direction of the central axis of the hollow part,
At the same time, the magnetic actuating body is configured to be housed in the hollow part of the solenoid and fixed to the hollow part of the magnetic shield. And, by the reciprocating mechanism,
A process in which the magnetic actuating body separates from the hollow part of the magnetic shield and is excited in the strong magnetic field and generates heat, and a process in which the magnetic actuating body is housed in the hollow part of the magnetic shield and is demagnetized to cool the body. This is a stationary magnetic refrigerator that attempts to utilize the cold by repeating the process that occurs.

[0011] One end surface of the magnetic actuating body is connected to the high temperature liquid bath via a high temperature side heat switch mechanism for heat transfer, and the other end surface of the magnetic actuating body is connected to a low temperature side heat switch mechanism. It is interposed and connected to the low-temperature side bathtub for heat transfer. The high-temperature side heat switch has a crystal column movably attached to the copper tip connected to the heat bath as described above, and is configured by the close contact and separation of the end surface of the crystal column and the end surface of the magnetic actuating body. A heat switch is available. Similarly, the heat pump type described above can be used as the low temperature side heat switch.

In particular, in the present invention, the high-temperature side heat switch mechanism has a sealed end formed of a magnetic material that is connected to the high-temperature side liquid bath via an elastically biased bellows inside the sealed end. connected so that the hot side liquid circulates,
Further, the outer surface of the sealed end portion and the one end surface of the magnetic actuating body are arranged so as to face each other in close contact with each other.

[0013] Also, in the low temperature side heat switch mechanism, a sealed end formed of a superconductor, particularly a superconducting laminate, is connected to the low temperature side bath via a bellows having an elastic bias to the inside of the sealed end. They are connected so that the low-temperature side liquid circulates, and are arranged so that the outer surface of the sealed end and the other end surface of the magnetic actuating body face each other in close contact with each other. The bellows is adjusted to apply elastic force to the sealed end so as to bring the sealed end into close contact with the magnetic actuating body during the demagnetization process. Behind the superconductor plate, that is, in the vicinity of the superconductor plate in the opposite direction to the magnetic actuator, an annular magnetic shield is arranged to slightly reduce the magnetic field around the superconductor plate. is preferred.

Regarding other thermal switch mechanisms of the present invention,
The high-temperature side heat switch mechanism has a high-temperature side heat bath formed of a fluid bath, the high-temperature side fluid bath being sealed with a magnetic material to form a high-temperature side sealed end, and an outer surface of the high-temperature side sealed end. The high-temperature side sealed end is disposed close to the magnetic actuating body so that it can closely face the surface of the magnetic actuating body, and the low-temperature side heat switch mechanism is configured such that the low-temperature side heat bath is The fluid bath on the low temperature side is sealed with a non-magnetic thermal conductor to form a low temperature side sealed end, and the outer surface of the low temperature side sealed end is connected to the other side of the magnetic actuating body. The low-temperature side sealed end is arranged close to the magnetic actuating body so as to face the surface in close contact with the magnetic actuating body. Further, the magnetic actuating body is arranged to be movable back and forth via a heat insulating bearing fixed to a fixed member, and is connected to a heat insulating elastic body having one end fixed to the fixed member or the fixed side base of the bearing. In the degaussing process, the elastic member is elastically biased so as to come into close contact with the outer surface of the low-temperature sealed end. In this thermal switch mechanism, it is sufficient for the reciprocating amount of the magnetic operating body to be only about 1 mm to 1 cm, so a magnetic refrigerator using this thermal switch mechanism can still be called a stationary type.

Furthermore, a laminate or a wound body consisting of a thin film of magnetic material and a thin film of thermal conductor is preferably used as the magnetic actuating body.

[0016]

[Operation] A strong magnetic field is generated in the hollow part of the superconducting solenoid coil, and the magnetic actuating body fixed in the solenoid coil is excited. Even if the cylinder made of superconductor is in a strong magnetic field, the inside of the hollow part has a completely zero magnetic field, so it can be used as a magnetic shield, and the magnetic shield can be used inside the hollow part of the solenoid coil. If the hollow part is arranged to accommodate the magnetic actuating body, the magnetic actuating body is demagnetized. Next, when the magnetic shield is moved in parallel in the direction of the central axis of the solenoid coil so that the magnetic actuator is removed from the hollow portion of the magnetic shield, the magnetic actuator is excited. The magnetic shield is reciprocated by a reciprocating mechanism.
By reciprocating, the process of exciting and demagnetizing the magnetic operating body can be repeated. Superconducting coils are made of Nb-Ti alloy wire or Y1 Ba2 Cu3
A solenoid-shaped oxide copper coated wire is used after being cooled to below the superconducting transition temperature. In addition, the magnetic shield is used by forming the alloy or oxide into a cylindrical laminate with normal conductive copper or aluminum thin plates or foils, and cooling the laminate in the same way.

[0017] Even if the hollow part moves between the process of accommodating and detaching the magnetic actuating body, the magnetic shielding body remains located within the hollow part of the solenoid coil, and the opening of the hollow part of the solenoid coil It does not protrude or deviate outward from the surface. Since a generally uniform magnetic field is formed inside the hollow part of the solenoid coil, even if the superconductor, which is the magnetic shield, is moved in the uniform magnetic field in parallel to the direction of the lines of magnetic force, the superconductor will not be affected. Magnetic force does not work. Therefore, the driving force of the reciprocating mechanism for reciprocating the magnetic shield within the hollow portion of the solenoid coil is sufficient to be small.

The high-temperature side heat switch mechanism transfers the heat generated during the excitation process of the magnetic actuating body to the high-temperature side hot bath and releases it, and in the demagnetization process, the heat generated between the magnetic actuating body and the high-temperature side hot bath is transferred. It acts to block the transfer. The low-temperature side heat switch mechanism transfers the cold generated during the demagnetization process of the magnetic actuating body to the low-temperature side hot bath to cool the hot bath, and is thermally separate from the low-temperature side hot bath during the excitation process. It has the effect of blocking the

A thermal switch mechanism will be explained using an embodiment in which a high temperature side thermal switch mechanism and a low temperature side thermal switch mechanism of the present invention are integrated. In FIG. 5(A), the magnetic actuating body 2 is fixed in the protective tube 28 by a heat insulating member 27, and the magnetic body 2 is attached to the end of the hot bath 41 on the high temperature side via a bellows 43.
4 are connected to form a sealed end on the high temperature side, and the liquid in the hot bath 41 flows through the sealed end, and the outer surface of the magnetic body 44 at the tip of the sealed end is connected to the magnetic actuating body 2. Closely facing one end. When there is no magnetic field, the outer surface of the magnetic body 44 at the tip of the sealed end is separated from the magnetic actuating body 2 by the contraction force of the bellows 43, so that an appropriate gap G is created. A narrow gap G of about 1 mm is sufficient. On the other hand,
A superconducting laminate 53 is connected to the end of the hot bath 51 on the low temperature side via a bellows 52 to form a sealed end on the low temperature side, and the inside of the sealed end is normally filled with the hot bath 51 on the low temperature side. It is filled with gas from

The outer surface of the superconducting laminate 53 at the tip of the sealed end is arranged so as to be in close contact with the other end surface of the magnetic actuating body 2, and when there is no magnetic field, the superconducting laminate 53 is moved by the pressing force of the bellows 52. The outer surface of 53 is adjusted so as to be in contact with the magnetic actuating body 2.

The inside of the protection tube 28 is always maintained at a high vacuum and the inside of the tube is in an adiabatic state.

In the state shown in FIG. 5(A), the magnetic actuating body 2
is in the demagnetization process, and the generated cold cools the superconducting laminate 5.
3 to cool the fluid in the hot bath on the low temperature side, but heat conduction to the high temperature side is blocked by the gap G.

FIG. 5(B) shows the excitation process. In this figure, a ring-shaped superconductor is formed on the outer peripheral surface of the protective tube 28 in the direction of the hot bath, which is higher than the inner surface of the superconducting laminate 53. The body 31 is fixed and arranged so as to slightly reduce the magnetic field near the superconducting laminate 53 during the excitation process. In the excitation process, the magnetic actuating body 2 is excited by the magnetic field lines 9, and the magnetic body 44 of the high-temperature side thermal switch is magnetized. Since the superconducting laminate 53 exhibits diamagnetic properties, it retreats in the direction in which the magnetic field is reduced by the annular superconductor 31 and creates a gap G between it and the magnetic actuating body, so that the heat generated by excitation is reduced to a high temperature. The magnetic actuating body 2 is cooled by moving only to the side heating bath 41.

Since this thermal switch mechanism can simultaneously control the magnetic field 9 that passes through the magnetic body 44, magnetic shield 2, and superconducting laminate 53 by reciprocating the magnetic shield, the thermal switch mechanism of the present invention has no There is no need for an operation unit, and the device operates properly by simply reciprocating the magnetic shield in conjunction with the repetition of the excitation/demagnetization process.

In the thermal switch shown in FIG.
The end of the high-temperature side heat bath 41 is sealed with a magnetic body 44, and the outer surface of the magnetic body 44 faces one end of the magnetic actuating body 2 in a close manner. Further, the tip of the low temperature side heat bath 51 is sealed with a heat conductor 64, and the outer surface of the heat conductor 64 is connected to the magnetic actuating body 2.
It faces the other end face in a close manner. As shown in FIG. 6(A), in the demagnetization process, one end of the ball bearing 6
Due to the pressing force of the bellows 43 whose other end is fixed to the magnetic actuating body 2 at the base of the magnetic actuating body 2, the magnetic actuating body 2 is in close contact with the outer surface of the thermal conductor 64 on the low temperature side. It is separated from the magnetic material 44 to form a gap G. Therefore, the cold generated during the demagnetization process is removed from the low temperature side heat bath 51.
will be cooled down.

In the excitation process, the magnetic body 44 as well as the magnetic actuator 2 are magnetized and attract each other, and on the other hand, a gap G is created between the outer surface of the heat conductor 64 on the low temperature side, so that the heat generated by the magnetic actuator 2 is reduced. is cooled by the high temperature side heat bath 41.

[0027] The magnetic actuator must efficiently transfer the generated heat and cold to the hot baths on the high temperature side and the cold side, respectively. From this point of view, Gd-Ga oxide garnet is
Advantageously, it has a high thermal conductivity, and it is possible to make garnet as a single crystal to reduce heat scattering and to form a silver coating on its outer surface to further increase the conductivity of the magnetic actuator. However, due to rapid changes in the magnetic field during the excitation/demagnetization process, eddy currents are generated in the silver film, generating a small amount of Joule heat, which reduces the thermal efficiency of the demagnetization process. Since the magnetic actuating body of the present invention is a laminate or a wound body consisting of a thin film of a magnetic material and a thin film of a good thermal conductor, the direction parallel to the surface of the thin film must be made to roughly match the direction of the magnetic lines of force. Ba,
Even if a thin silver film is used as a thin film of a good thermal conductor, it is possible to extremely reduce the generation of eddy currents on the film surface. At this time, if the direction of the surface of the thin film is made to roughly match the direction of the thermal switch, heat conduction from the magnetic body to the thermal switch will be improved. If such a laminated body or a wound body is used as a cylindrical magnetic actuating body, the direction parallel to the surface of the thin film is the central axis direction of the cylinder, and the central axis direction is the magnetic field line direction and the heat conduction direction. It becomes possible to arrange the magnetic actuators so that they coincide with each other, and heat conduction is not inhibited even if the height of the cylinder is made relatively large.

A method for manufacturing a laminate consisting of a magnetic thin film and a good thermal conductor thin film is, for example, to use a silver foil film as the good thermal conductor thin film, and to apply the magnetic thin film on the surface of the silver thin film. ,
For example, Gd--Ga oxide garnet is vacuum-deposited to obtain a silver-garnet thin layer, and a large number of these thin layers are laminated and heated under pressure to form a laminate. In addition, a layered band obtained by vapor-depositing the above garnet on a band-shaped silver foil is tightly wound,
It is heated and annealed to form a wound body.

[0029]

[Embodiment] An embodiment of the present invention will be explained based on the drawings. FIG. 1 shows a cross-sectional view of a static magnetic refrigerator having a cooling capacity below liquid helium temperature. A superconducting solenoid coil 1 is fixed in a heat insulating container 8 filled with liquid helium, and a cylindrical magnetic shield 3 is suspended in the hollow part of the solenoid coil 1 by a support rod 71 penetrating the upper lid 81 of the container 8. The support rod 71 is equipped with a lifting device (
(not shown) is attached, and the magnetic shield 3 is arranged so as to be movable up and down.

Further, a protection tube 28 is fixed to the lower surface of the upper lid 81 so as to pass through the hollow portion of the magnetic shield 3, and is suspended from the upper lid 81. The inner upper part of the protection tube 28 constitutes a high-temperature side liquid tank, and is filled with liquid helium through an opening 45 that allows liquid helium from the heat-insulating container 8 to circulate through convection. A sealed end 42 of the tank extends to an internal space sealed by a magnetic material 44 .

Below the protective tube 28, a cylindrical magnetic actuator 2 is held movably up and down by a heat insulating ball bearing 61, and below the magnetic actuator 2 is a base 62 of the bearing 61. One end of the bellows 43 is connected to the other end of the bellows 43, and an elastic force is always applied downward to the magnetic actuating body 2. The outer surface of the sealed end of the high temperature side liquid tank is disposed close to and facing the upper surface of the magnetic actuating body 2, thereby forming a high temperature side heat switch.

[0032] Also, at the bottom of the protection tube, there is a low temperature side liquid tank 5.
1 is fixed, and a heat conductor 64 is airtightly attached to the upper part of the low temperature side liquid tank 51, such that the upper surface of the heat conductor 64 faces the lower surface of the magnetic actuator 2 in a close manner. A low-temperature side thermal switch mechanism is configured in close proximity to each other. In addition, a heat transmission column 54 that transmits cold is provided on the lower surface of the heat conductor 64 and protrudes into the low temperature side liquid tank 51, and the low temperature side liquid tank 51 is provided with a thin tube 55 for supplying helium gas and a helium gas supply tube 55. A thin tube 56 for gas discharge is connected.

The inner lower part of the protection tube is maintained in a high vacuum, and the high temperature side heat switch mechanism, magnetic operating body 2, low temperature side heat switch mechanism, and low temperature side liquid tank 51 are in a vacuum insulated state.

The lower end of the magnetic shield 3 must be located at least at a higher position than the magnetic body 44 of the high-temperature side heat switch at the upper limit of the rise by the lifting device, and at the lower limit of the lower end of the magnetic shield 3. As shown in FIG. 2, the hollow part of the magnetic shield 3 is connected to the magnetic body 44 of the high temperature side thermal switch
It is necessary to be in a position where both the magnetic actuator 2 and the magnetic actuator 2 can be accommodated. Therefore, the height and movement distance of the magnetic shield are approximately determined based on the length between the magnetic body 44 and the magnetic actuating body 2. Furthermore, the superconducting coil 1 has a height (
The solenoid-like coil is such that the distance between the opening surfaces of the hollow part of the coil is larger than the sum of the height of the magnetic shield and the travel distance.

In this embodiment, the superconducting coil 1 has N
It is made by winding b-Ti alloy wire. The magnetic shield 3 is a laminate made up of a large number of Nb-Ti alloy foil circular plates and metal aluminum foil circular plates, and is cooled by liquid helium to be in a superconducting state.

The magnetic actuator 2 is a single-crystal column of Gd--Ga oxide garnet, and its outer peripheral surface is covered with a silver film layer 24 to improve heat conduction. However,
It may be omitted in order to prevent heat generation due to the generation of eddy currents during the excitation/demagnetization process. Further, the upper surface of the magnetic actuator 2 is coated with a silver film layer or a thin crystal plate. Similarly, Gd--Ga oxide garnet is used for the magnetic material 44 of the high-temperature side thermal switch. For the heat conductor 64, quartz is used, and a silver ring is preferably used.

FIG. 1 shows the excitation process of the present magnetic refrigerator. The magnetic shield 3 is at its upper limit due to the lifting device (not shown), and the magnetic actuator 2 is exposed to the strong magnetic field of the superconducting coil 1. It is in a state where it is excited and generates heat. The magnetic body 44 of the high-temperature side heat switch is similarly magnetized, and the magnetic actuating body 2 is attracted to the lower surface of the magnetic body 44 against the elastic force of the bellows 43 and is attached to the surface, so that the heat of the magnetic actuating body 2 is absorbed. is conducted through the magnetic body 44 and absorbed by the liquid helium in the sealed end 41 of the high temperature side liquid tank 41, and the magnetic actuating body 2 is cooled. On the other hand,
Since a gap G is formed between the good heat conductive disk 64 of the low temperature side heat switch and the lower surface of the magnetic actuating body 2, heat due to excitation is not conducted to the low temperature side liquid tank.

FIG. 2 shows how the magnetic shield 3 is moved by the lifting device.
shows the demagnetization process at the lower limit, but the magnetic actuator 2
is located in the hollow part of the magnetic shield and is demagnetized and emits cold air. Since the magnetic body 44 of the high-temperature side thermal switch is also demagnetized, the attractive force between it and the magnetic actuating body 2 is reduced, and therefore, it is pulled back by the elastic force of the bellows 43 to form a gap G on the upper surface of the magnetic actuating body. Therefore, there is no loss of cold water to the hot side liquid tank.

On the other hand, the heat conductor disk 6 of the low temperature side heat switch
4 does not interact with any lines of magnetic force, it comes into contact with the lower surface of the magnetic actuator 2 by the pushing force of the bellows 52, and the cold of the magnetic actuator 2 is conducted through the heat conductor disk 64 and the heat transfer column 54. Then, the helium gas in the liquid tank 51 on the low temperature side is cooled and liquefied, and liquid helium accumulates in the liquid tank.

[0040] By simply repeating the raising and lowering of the magnetic shield, the above excitation process and demagnetization process can be repeated, and the temperature of liquid helium in the low temperature side liquid tank can be lowered to below the equilibrium temperature of superfluid helium. , cryogenic temperatures can be utilized.

When used on a satellite in a zero-gravity state, superfluid helium floats in the form of droplets in the low-temperature side liquid tank 51, so the heat transfer coefficient with the heat transfer column 54 decreases. However, in this case, it is preferable to use a porous sintered body made of copper for the heat transfer column 54, and use the sintered body as a carrier that collects floating droplets.

FIG. 3 is a sectional view of the periphery of a low-temperature side fluid bath of a magnetic refrigerator mounted on an artificial satellite and used in outer space. The protective tube 28 penetrates the bottom wall of the vacuum insulated container 8 and is opened to outer space.The bottom of the fluid tank 51 is made of copper or silver, which has good thermal conductivity, and the outer surface 511 is made of copper or silver, which has good thermal conductivity. It is a flat surface, and an infrared imaging solid-state device is attached thereto. Since helium is used as the fluid and the temperature of the image sensor is maintained at 1 K or less, extremely good infrared images with little thermal noise can be obtained.

FIG. 4 shows that the magnetic actuators 2, 2' are used in two stages to control the strong magnetic field of the superconducting coil 1 by raising and lowering a single magnetic shield 3. 1 is a cross-sectional view of a tandem magnetic refrigerator that alternately repeats an excitation process and a demagnetization process. This embodiment is designed for producing and cooling liquid helium.

In FIG. 4, a small gas cooler is used for the high-temperature side heat bath 41, and the lower sealed end 42' is filled with liquid hydrogen at a temperature of 20 K during operation. A disk 44' made of a magnetic material DyAl2 is connected to the tip of 42' with a bellows 43' interposed therebetween. Upper D
The magnetic actuating body 2' of yAl2 is fixed to the protection tube 28, and the upper surface of the magnetic actuating body 2' is the disc 44' of the magnetic body.
The high-temperature side heat switch of the upper magnetic actuating body 2' is configured to face the upper magnetic actuating body 2'. The low-temperature side thermal switch of the upper magnetic actuating body 2' is constituted by a disk 44 made of magnetic Gd-Ga garnet connected via a thermal conductor 47 made of crystal, and the disk 44 is connected to the lower magnetic body 2'. It is arranged to face the upper surface of the actuating body 2 in a close manner.

The lower magnetic actuator 2 is made of a single crystal of Gd-Ga garnet, and is held on the inner surface of the protection tube 28 via a heat-insulating ball bearing 61 made of polyethylene so as to be movable up and down. , the upper surface is the above-mentioned magnetic disk 4
The lower surface of 4 faces the thermal conductor 64 sealing the end of the protective tube 28 in a close manner, and the lower surface of the thermal conductor 6
4 is immersed in the liquid helium bath described above to cool the liquid helium bath 51.

In the state shown in FIG. 4, the magnetic shield 3 is
Only the lower magnetic actuating body 2 is accommodated, and the upper magnetic actuating body 2' is in the excitation process, and the upper magnetic actuating body 2' and the magnetic body 44' are in close contact, and the heat generated is generated by the gas. Cooler 41
has been transferred to. On the other hand, the lower magnetic actuator 2 is in the demagnetization process, and the generated cold cools the helium bath 51. When the magnetic shield 3 is raised, the upper magnetic actuator 2' is demagnetized and generates cold, and the lower magnetic actuator 2, which is in the process of being excited, absorbs the heat generated and is cooled.

In this embodiment as well, the magnetic shield 3 at the upper and lower limits is completely housed within the hollow part of the superconducting coil 1, so the operation of raising and lowering the magnetic shield is extremely easy. .

[0048]

[Effects of the Invention] By implementing the magnetic refrigerator of the present invention, the following effects can be achieved.

By reciprocating the superconducting magnetic shield,
Since the superconducting coil is such that the excitation process and demagnetization process of the magnetic actuating body can be repeated, and the magnetic shielding body moves back and forth within the range of both openings of the hollow part of the superconducting coil, the reciprocating movement is required. The force may be extremely small, so
The reciprocating mechanism can be miniaturized and simplified, and as a result, a stationary magnetic refrigerator that has high energy efficiency and is small and compact compared to its refrigerating capacity can be obtained.

[0050] Both the high temperature side heat switch that transfers the heat generated by the magnetic actuating body to the high temperature side heat bath and the low temperature side heat switch that transfers the generated cold to the low temperature side heat bath, that is, the cold bath, excite and excite the magnetic actuating body. It operates accurately in response to only changes in the demagnetizing magnetic field, does not require any manual operation means, has few malfunctions, and can be constructed in a compact and simple manner. In particular, if the thermal switch and the magnetic operating body are housed in the hollow part of the reciprocating superconducting magnetic shield and are demagnetized,
Since the thermal switch can be activated only by reciprocating the magnetic shield, a static refrigerator using superconducting coils in persistent current mode can be constructed.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a magnetic refrigerator, showing that it is in the excitation process.

FIG. 2 is a cross-sectional view of the magnetic refrigerator during the demagnetization process.

FIG. 3 is a partial cross-sectional view of the low-temperature side heat bath of a magnetic refrigerator used in outer space.

FIG. 4 is a sectional view of a tandem magnetic refrigerator.

FIG. 5 is a partial cross-sectional view of a magnetic actuator and a thermal switch mechanism.

FIG. 6 is a partial cross-sectional view of a magnetic actuator and other thermal switch mechanisms.

[Explanation of symbols]

1 Superconducting coil 2 Magnetic working body 28 Protection tube 3 Magnetic shield 31 Annular superconductor 41 High temperature side fluid bath 43 Bellows 44 Magnetic disc 51 Low temperature side fluid bath 52 Bellows 53 Superconducting disk 54 Heat transfer column 55 Helium gas supply pipe 61 Insulating ball bearing 62 Insulating ball bearing base 71 Support rod for lifting and lowering the magnetic shield 64 Thermal conductor 8 Vacuum insulation container 83 Helium liquid level 9. Lines of magnetic force G Gap between heat switch

Claims (6)

[Claims] Claim 1: A stationary magnetic refrigerator comprising a superconducting coil that generates a strong magnetic field and a magnetic actuator disposed in a hollow part of the superconducting coil, in which a cylindrical superconducting member is provided in the hollow part of the superconducting coil. The magnetic shielding body is arranged so that it can reciprocate within a range inside from both opening surfaces of the hollow part of the superconducting coil, and the magnetic operating body can be accommodated in the hollow part of the magnetic shielding body, By reciprocating the magnetic shield by a reciprocating mechanism, the magnetic operating body is accommodated in the hollow part of the magnetic shield and demagnetized, and the process of being extracted from the hollow part and excited. A stationary magnetic refrigerator characterized by being designed to repeat. 2. The magnetic actuating body has one end surface connected to the high temperature side heat bath with a high temperature side heat switch mechanism interposed therebetween, and the other end surface of the magnetic actuating body having a low temperature side heat switch mechanism. 2. The magnetic refrigerator according to claim 1, wherein the magnetic refrigerator is connected to the low-temperature side heat bath through a heat bath. 3. In the high-temperature side heat switch mechanism, the high-temperature side heat bath is formed of a fluid bath, a bellows having an elastic biasing force is connected to the fluid bath, and the other end of the bellows is made airtight by a magnetic material. The sealed end is sealed to form a sealed end, and the sealed end is arranged close to the magnetic actuating body such that the outer surface of the sealed end closely faces the surface of the magnetic actuating body. The static magnetic refrigerator according to claim 2, characterized in that: 4. In the low-temperature side heat switch mechanism, the low-temperature side heat bath is formed of a fluid bath, a bellows having an elastic biasing force is connected to the fluid bath, and the other end of the bellows is airtightly connected by a superconductor. The sealed end is sealed to form a sealed end, and the sealed end is arranged close to the magnetic actuating body such that the outer surface of the sealed end closely faces the surface of the magnetic actuating body. The static magnetic refrigerator according to claim 2, characterized in that: 5. The high temperature side heat switch mechanism has a high temperature side heat bath formed of a fluid bath, the high temperature side fluid bath being sealed with a magnetic material to form a high temperature side sealed end, and the high temperature side The high-temperature side sealed end is disposed close to the magnetic actuating body such that the outer surface of the sealed end closely faces the surface of the magnetic actuating body, and the low-temperature side heat switch mechanism The heat bath is formed of a fluid bath, the fluid bath on the low temperature side is sealed with a non-magnetic material to form a low temperature side sealed end, and the outer surface of the low temperature side sealed end is the other surface of the magnetic actuating body. The low-temperature side sealed end is disposed close to the magnetic actuating body so as to closely face the magnetic actuating body, and the magnetic actuating body is movable back and forth via an insulating bearing fixed to the fixed member. and connected to an insulating elastic body having one end fixed to the fixed side base of the fixed member or the bearing, and in the degaussing process, the elastic body is in close contact with the outer surface of the low temperature side sealed end. The static magnetic refrigerator according to claim 2, wherein the static magnetic refrigerator is elastically biased. 6. The static magnetic refrigerator according to claim 1, wherein the magnetic operating body is a laminate or a wound body comprising a thin film of magnetic material and a thin film of thermal conductor.