JP4237791B2 - Manufacturing method of regenerator material - Google Patents

Description

  The present invention relates to a method for manufacturing a regenerator material, and more particularly to a method for manufacturing a regenerator material capable of exhibiting a significant refrigerating capacity over a long period in a cryogenic temperature region of 10K or less.

  In recent years, the development of superconducting technology has been remarkable, and the development of compact and high-performance refrigerators has become indispensable as the field of application expands. Such small refrigerators are required to be lightweight, small and have high thermal efficiency, and are being put to practical use in various application fields.

  For example, in superconducting MRI apparatuses, cryopumps, and the like, refrigerators using a refrigeration cycle such as the Gifford-McMahon (GM) method or the Stirling method are used. High-performance refrigerators are also essential for magnetic levitation trains. Furthermore, recently, high-performance refrigerators are also used in superconducting power storage devices (SMES) and single-crystal pulling devices in a magnetic field for producing high-quality silicon wafers.

  In such a refrigerator, a working medium such as compressed He gas flows in one direction in the regenerator filled with the regenerator material, supplies the heat energy to the regenerator material, and the operation expanded here. The medium flows in the opposite direction and receives heat energy from the cold storage material. As the recuperation effect in such a process becomes better, the thermal efficiency in the working medium cycle is improved, and a lower temperature can be realized.

  Conventionally, Cu, Pb, etc. have been mainly used as the regenerator material used in the refrigerator as described above. However, such a regenerator material has a remarkably small specific heat at an extremely low temperature of 20K or less, so that the above-described recuperation effect does not function sufficiently, and the regenerator material is operated every cycle at a very low temperature when operating in a refrigerator. Sufficient heat energy cannot be stored, and the working medium cannot receive sufficient heat energy from the cold storage material. As a result, there has been a problem that a refrigerator incorporating a regenerator filled with the regenerator material cannot reach an extremely low temperature.

Therefore, recently, in order to improve the recuperative characteristics at the cryogenic temperature of the regenerator and realize a refrigeration temperature closer to absolute zero, it has a maximum value of volume specific heat particularly in an extremely low temperature region of 20K or less, and Magnetic regenerators mainly composed of intermetallic compounds composed of rare earth elements and transition metal elements such as Er ₃ Ni, ErNi, and HoCu ₂ having large values are used. By using such a magnetic regenerator material for a GM refrigerator, refrigeration at 4K is realized.
JP-A-6-159828 JP-A-5-203274

  However, the application of the refrigerator as described above to various systems has been studied more specifically, and technical demands for cooling a large-scale cooling object in a stable state for a long period of time have increased. There is a need for further improvements in refrigeration capacity.

  The magnetic regenerator material is generally processed into spherical particles having a diameter of about 0.1 to 0.5 mm in order to efficiently promote heat exchange with a working medium such as He gas. As shown in FIG. The inside of the regenerator 1 is filled with high density and used. However, during the operation of the refrigerator, vibrations and impacts due to the reciprocating motion of the regenerator 1 repeatedly act on the particulate magnetic regenerator material 2. Further, complicated hydrodynamic stress due to the high-pressure He gas passing through the inside of the regenerator 1 also acts on the magnetic regenerator material particles.

  For this reason, the particulate magnetic regenerator material 2 filled at a high density at the beginning of the operation of the refrigerator is likely to generate a gap 3 between the particles as the operation time elapses, and the He gas flow path is formed. There has been a problem that the refrigerating capacity is lowered due to a change or a non-uniform flow of He gas. In addition, there is a problem in that the performance of the refrigerator is adversely affected by the fact that fine powder generated by friction between the regenerator particles is mixed into the seal portion of the refrigerator and damages the seal portion at an early stage.

  In order to solve the above problems, for example, while trying to limit the particle size range of magnetic regenerator particles to be used narrowly and to increase the sphericity, an attempt was made to increase the sphericity, but this led to a significant increase in cost from an industrial standpoint. Can only be achieved, and cannot be a realistic solution. Therefore, for example, as shown in JP-A-5-203274, a method of sintering magnetic regenerator particles and stably fixing gaps between the particles has been proposed.

  However, according to this method, a gap is easily generated between the outer periphery of the sintered magnetic regenerator material and the inner periphery of the regenerator, and the He gas easily leaks through the gap, and is stable for a long time. It was difficult to ensure the refrigerating performance. In addition, the sintered magnetic regenerator material is brittle, so it is difficult to finish with high dimensional accuracy due to mechanical finishing, and fine defects are likely to occur due to the processing. In any case, stable refrigeration performance is maintained for a long time. There was a difficult point.

  In addition, an attempt has been made to seal with an adhesive or the like in order to fill the gap, but there is a difficulty in that the sealing process is complicated and the manufacturing cost increases.

  The present invention has been made to solve the above-described problems, and provides a method for producing a regenerator material capable of stably exhibiting a remarkable refrigerating capacity over a long period of time, particularly in a cryogenic region. With the goal.

  In order to achieve the above-mentioned object, the present inventors prepare cold storage materials having various fixed structures and fill them in the regenerator of the refrigerator, and the fixed structure has the refrigerating capacity of the refrigerator, the life of the regenerator material, The effect on durability was compared by experiments.

  As a result, especially when the magnetic regenerator particles are sintered in a state where the inside of the cylindrical metal is filled and the fixed structure is formed by integrating the particles and the particles with the cylindrical metal, the gaps between the regenerator particles are reduced. A regenerator that is stabilized and has no gap between the magnetic regenerator material and the regenerator, and that can effectively prevent He gas leakage is realized, and a refrigerator that exhibits stable refrigerating performance over a long period of time can be obtained. There was found. The present invention has been completed based on the above findings.

That is, the method for producing a regenerator material according to the present invention is a method for producing a regenerator material that sinters particulate magnetic regenerator materials filled inside a cylindrical metal, bonds them together, and integrates them with the cylindrical metal. In the above, the surface roughness of at least a part of the inner wall of the cylindrical metal with which the magnetic regenerator particles come into contact is 30 μm or more on the basis of the maximum height (Ry), and the cylindrical metal is made of stainless steel, Sintering of the particulate magnetic regenerator material filled in the cylindrical metal by adjusting the ratio of the magnetic regenerator particles having a particle size of 10 μm or more and 5 mm or less in the particulate magnetic regenerator material to be 70% weight or more. Is carried out in a vacuum, in an inert gas atmosphere, or in a reducing gas atmosphere .

Moreover, in the manufacturing method of the said cool storage material, it is preferable that the adhesive agent which coat | covers the said particulate magnetic cool storage material is an epoxy resin.

  Furthermore, the method for producing a regenerator material according to the present invention is the method for producing a regenerator material in which the particulate magnetic regenerator material filled in the cylindrical metal is mutually coupled and integrated with the cylindrical metal. The surface of the magnetic regenerator material is coated with a low melting point metal having a melting point lower than that of the regenerator material or an alloy thereof in a thickness of 1 to 50 μm and liquid phase sintered.

  In the method for producing a regenerator material, it is preferable to use at least one metal selected from Pb, In, Sn, Ga, and Zn as a low melting point metal that covers the particulate magnetic regenerator material.

  Moreover, the manufacturing method of the cool storage material which concerns on this invention sinters the particulate magnetic cool storage material with which the inside of the cylindrical metal was filled, it was mutually connected, and manufacture of the cool storage material integrated with a cylindrical metal The method is characterized in that the surface roughness of at least a part of the inner wall of the cylindrical metal with which the magnetic regenerator material particles come into contact is 30 μm or more on the basis of the maximum height (Ry).

  Furthermore, the manufacturing method of the regenerator material according to the present invention is a method for manufacturing a regenerator material that sinters and combines the particulate magnetic regenerator material filled in the cylindrical metal and integrates it with the cylindrical metal. In the method, an annular groove or an annular projection is formed on the inner wall of the cylindrical metal.

  Moreover, the manufacturing method of the cool storage material which concerns on this invention sinters the particulate magnetic cool storage material with which the inside of the cylindrical metal was filled, it was mutually connected, and manufacture of the cool storage material integrated with a cylindrical metal In the method, unevenness is formed on the inner wall of the cylindrical metal.

  Furthermore, the manufacturing method of the regenerator material according to the present invention is a method for manufacturing a regenerator material that sinters and combines the particulate magnetic regenerator material filled in the cylindrical metal and integrates it with the cylindrical metal. In the method, the inner wall is tapered so that the cross-sectional area of the cylindrical metal is enlarged or reduced in the axial direction.

  Moreover, the manufacturing method of the cool storage material which concerns on this invention sinters the particulate magnetic cool storage material with which the inside of the cylindrical metal was filled, it was mutually connected, and manufacture of the cool storage material integrated with a cylindrical metal In the method, after placing or applying a brazing material in the form of a foil or a paste on the inner wall of the cylindrical metal, the cylindrical metal is filled with a particulate magnetic regenerator material and sintered. .

  The regenerator material obtained in the present invention is sintered in a state in which the particulate magnetic regenerator material is filled in the inside of the cylindrical metal, bonds the magnetic regenerator material particles to each other, and combines the cylindrical metal and the magnetic regenerator material. It is characterized by being integrated.

  Further, the surface of the particulate magnetic regenerator material may be covered with a low melting point metal having an melting point lower than that of the magnetic regenerator material or an alloy thereof. As the low melting point metal, at least one metal selected from Pb, In, Sn, Ga and Zn may be used. The surface of the particulate magnetic cold storage material may be covered with an adhesive.

  Furthermore, the surface roughness of at least a part of the inner wall of the cylindrical metal with which the magnetic regenerator particles come into contact is preferably 30 μm or more on the basis of the maximum height (Ry). An annular groove or an annular protrusion may be formed on the inner wall of the cylindrical metal. Furthermore, the same effect can be obtained by forming irregularities on the inner wall of the cylindrical metal. Further, the inner wall may be tapered so that the cross-sectional area of the cylindrical metal expands or contracts in the axial direction. Furthermore, it is good to join the sintered magnetic regenerator material and the cylindrical metal which covers the outer peripheral part by brazing. The cylindrical metal may be formed of stainless steel.

  The magnetic regenerator material is preferably an antiferromagnetic material.

The particulate magnetic regenerator material constituting the regenerator material used in the present invention is, for example, a general formula RMz (where R component is Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy). , Er, Tm, and Yb, and the M component is Ag, Cu, Au, Al, Ga, In, Ge, Sn, Sb, Bi, Ni, Pd, Pt, Zn, It is at least one metal element selected from Co, Rh, Ir, Mn, Fe, Ru, Cr, Mo, W, V, Nb, Ta, Ti, Zr and Hf, and z is 0.001 to 9. And a rare earth element simple substance such as an intermetallic compound containing a rare earth element or Nd. In particular, HoCu ₂ , Er ₃ Ni, ErNi, and ErN _0.9 Co _0.1 are preferable because they have a large specific heat in a very low temperature region.

  The magnetic material having the above composition is used as magnetic regenerator particles after being processed into a particle shape by a mechanical pulverization method or an atomization method. The shape of the magnetic regenerator material particles may be any shape such as an indefinite shape or a spherical shape.

  However, the flow of the working medium such as helium gas flowing in the regenerator filled and sintered with the magnetic regenerator material particles is made smooth, the heat exchange efficiency between the working medium and the regenerator material is increased, and the heat exchange function is provided. In order to maintain it stably, the magnetic regenerator material particles may be composed of spherical magnetic particles having a uniform particle size. Specifically, the magnetic regenerator material particles having a ratio of the major axis to the minor axis (aspect ratio) of 5 or less and a particle size of 10 μm or more and 5 mm or less with respect to all the magnetic particles constituting the magnetic regenerator material particles. It is preferable to adjust the ratio so that the ratio becomes 70% by weight or more.

  The particle size of the magnetic regenerator particles is a factor that greatly affects the strength of the particles, the cooling function of the refrigerator, and the heat transfer characteristics. If the particle size is less than 10 μm, the density when filling the regenerator increases. Thus, the passage resistance (pressure loss) of He gas, which is a cooling medium, rapidly increases, and is entrained by the circulating He gas and enters the compressor to quickly wear components and the like.

  On the other hand, when the particle size exceeds 5 mm, the crystal structure of the granule is segregated and becomes brittle, and the heat transfer area between the magnetic particles and the He gas as the cooling medium is reduced, so that the heat transfer efficiency is remarkably increased. May decrease. Moreover, when such coarse particle | grains exceed 30 weight%, there exists a possibility of causing the fall of cold storage performance. Therefore, the average particle diameter is set to 10 μm or more and 5 mm or less, more preferably in the range of 30 μm to 1.0 mm, and further preferably 50 μm or more and 0.3 mm or less. Further, in order to sufficiently exhibit the cooling function and strength practically, the particle size of the particles is at least 70% by weight, preferably 80% by weight or more, more preferably 90% or more, based on the whole magnetic regenerator material particles. It is preferable to occupy.

  The ratio of the major axis to the minor axis (aspect ratio) of the magnetic regenerator material particles is set to 5 or less, preferably 3 or less, more preferably 2 or less, and still more preferably 1.3 or less. The aspect ratio of the magnetic regenerator material particles greatly affects the strength of the particles and the packing density and uniformity when filling the regenerator. When the aspect ratio exceeds 5, the magnetic regenerator material has a mechanical effect. It becomes difficult for the material particles to easily deform and break, and it becomes difficult to uniformly and densely fill the regenerator so that the voids are uniform. When such particles exceed 30% by weight of the total magnetic regenerator material particles, There is a risk of lowering the cold storage efficiency.

  Here, the particle size variation of the magnetic regenerator material particles prepared by the molten metal quenching method and the variation of the ratio of the major axis to the minor axis are greatly reduced as compared with the case of preparing by the conventional plasma spray method. The ratio of outside magnetic regenerator particles is small. Also, even when variations occur, they can be classified and used as appropriate. In this case, among all the magnetic regenerator particles filled in the regenerator, the ratio of the magnetic particles having an aspect ratio within the above range is 70% or more, preferably 80% or more, and more preferably 90% or more. It can be a cold storage material that can withstand practical use.

  In addition, by setting the average crystal grain size of magnetic regenerator material particles prepared by the molten metal quenching method to 0.5 mm or less, or by making at least a part of the metal structure amorphous, magnetism with extremely high strength and long life Particles can be formed.

  The surface roughness of the magnetic regenerator material particles is a factor that greatly affects the mechanical strength, the cooling characteristics, the passage resistance of the cooling medium, the regenerator efficiency, and the like. Generally, the maximum height Ry of the irregularities defined by JIS B0601 is 10 μm. In the following, it is desirable to set it to 5 μm or less, more preferably 2 μm or less. These surface roughnesses can be measured with a scanning tunneling microscope (STM roughness meter).

  When the surface roughness exceeds 10 μm Ry, microcracks that are the starting point of destruction are likely to occur in the particles, the passage resistance of the cooling medium increases, the load on the compressor increases, and particularly between the filled magnetic particles A contact area increases, the movement of the cold heat between magnetic particles becomes large, and cold storage efficiency will fall.

  Further, the ratio of the magnetic regenerator material particles having a micro defect having a length of 10 μm or more that affects the mechanical strength of the magnetic regenerator material particles is 30% or less, preferably 10% or less, more preferably 10% or less. It is desirable in practice.

  The manufacturing method of magnetic regenerator particles as described above is not particularly limited, and various general-purpose alloy particle manufacturing methods can be applied. For example, a method (melting and quenching method) in which a molten metal having a predetermined composition is dispersed and rapidly solidified at the same time in accordance with a centrifugal spraying method, a gas atomizing method, a rotating electrode method, or the like can be applied. Various mechanical grinding methods can also be applied.

  In particular, when magnetic regenerator particles made of an antiferromagnetic material are formed, even when used as a regenerator material for a refrigerator for a superconducting system, there is an effect that it is less affected by the leakage magnetic field from the superconducting magnet. can get.

  The cylindrical metal filled with the magnetic regenerator particles prepared as described above is integrated with the sintered regenerator particles to provide high processing accuracy to the regenerator material, and protects the sintered regenerator particles and is high It exerts the effect of increasing the durability of the entire cold storage material by imparting rigidity. The constituent material of the cylindrical metal is not particularly limited, and stainless steel, tungsten (W), molybdenum (Mo) having a melting point higher than that of the regenerator particles by 300 ° C. or more and less deformation at the sintering temperature. ), And alloy materials thereof. In particular, it is preferable to use stainless steel that is inexpensive, excellent in workability, has a relatively low thermal conductivity in a cryogenic region, and has a large cold storage effect.

  The regenerator material of the present invention is manufactured, for example, by the following method. That is, after filling the cylindrical metal with a predetermined amount of magnetic regenerator material particles, a lid made of a material that does not react with the magnetic regenerator material, such as quartz glass, is attached to the upper and lower openings. It is manufactured by performing a heat sintering process in a state. In order to prevent oxidation of the magnetic regenerator material during sintering, the sintering operation is preferably performed in a vacuum, an inert gas atmosphere, or a reducing gas atmosphere.

  In addition, in order to increase the bonding strength between the outer peripheral portion of the sintered magnetic regenerator material particles and the cylindrical metal, and to increase the durability of the entire regenerator material, at least a part of the inner wall of the cylindrical metal that the magnetic regenerator material particles contact It is effective to set the surface roughness to 30 μm or more on the basis of the maximum height (Ry). The surface roughness is preferably 50 μm or more, and more preferably 100 μm or more.

  Instead of providing the surface roughness, for example, as shown in FIGS. 3 to 5, an annular groove 7 a, an annular protrusion 7 b, and irregularities 8 are formed on the inner walls of the cylindrical metals 5 a, 5 b, 5 c, respectively, or threaded By processing, irregularities may be formed, or irregular rough surfaces may be formed. Furthermore, as shown in FIG. 6, by forming a tapered surface 9 on the inner wall so that the cross-sectional area of the cylindrical metal 5 d expands or contracts in the axial direction, the sintered magnetic regenerator material 4 is moved in the axial direction. They can be restrained, and both can increase the rigidity of the entire cold storage material.

  Further, as a means for further increasing the bonding strength between the sintered magnetic regenerator particles and the cylindrical metal, as shown in FIG. 2, between the outer peripheral portion of the sintered body of the magnetic regenerator particles 4 and the inner wall of the cylindrical metal 5. The brazing filler metal layer 6 may be formed integrally. This brazing material layer 6 is formed by the following method, for example. That is, it is formed by filling or sintering magnetic regenerator particles after placing or applying a foil-like or paste-like brazing material on the inner wall surface of the cylindrical metal 5. The brazing material to be used is not particularly limited, but a brazing material suitable for the sintering temperature is used.

  The surface of the particulate magnetic regenerator material is covered with a low melting point metal having a melting point lower than that of the magnetic regenerator material such as Pb, In, Sn, Ga, Zn, or an alloy thereof, and then filled into the cylindrical metal. It is also possible to sinter the regenerator particles and the cylindrical metal and simultaneously integrate them by liquid-phase sintering the magnetic regenerator particles through these low melting point metals.

  The thickness of the low melting point metal that covers the surface of the magnetic regenerator material is preferably 1 to 50 μm. If it is less than 1 μm, the bonding strength between the magnetic regenerator particles through the low melting point metal becomes insufficient, which is not preferable. On the other hand, if it exceeds 50 μm, the volume ratio of the low melting point metal in the entire regenerator material increases, and the apparent specific heat of the entire regenerator material decreases, which is not preferable. In addition, when it exceeds 50 μm, during the liquid phase sintering via the low melting point metal, the excessive low melting point metal closes the gap between the magnetic regenerator particles, increasing the flow resistance of helium gas, As a result, the performance of the regenerator is reduced. The thickness of the low melting point metal is more preferably 3 to 40 μm, and further preferably 5 to 30 μm.

  Since the low melting point metal as described above acts as a bonding agent that increases the bonding strength between particles and between the particles and the cylindrical metal during sintering, it is possible to increase the rigidity and durability of the entire regenerator material. Among the various low melting point metals and alloys, Pb having a large specific heat in the low temperature region and high cold storage efficiency is particularly preferable.

  Also, after coating the surface of the particulate magnetic regenerator material with an adhesive such as an epoxy resin, it is filled into a cylindrical metal, and the magnetic regenerator material particles are bonded together with an adhesive, and at the same time, the regenerator particle and the cylindrical metal It is also possible to bond them together. The adhesive is not particularly limited, but an epoxy resin is preferable as an adhesive exhibiting sufficient adhesive strength at an extremely low temperature.

  Also, a coupling agent can be added to improve the surface of the regenerator particles and improve the adhesion. In that case, it is preferable to add 0.05 to 2 wt% of the coupling agent with respect to the weight of the regenerator particles.

  Here, the epoxy resin is preferably a liquid resin that easily forms a uniform resin film on the surface of the regenerator particles. The coating amount of the epoxy resin is preferably 0.1 to 5 wt% with respect to the weight of the cold storage material particles. If it is less than 0.1 wt%, the adhesive strength between the magnetic regenerator particles becomes insufficient, which is not preferable. On the other hand, when it exceeds 5 wt%, the excessive adhesive plugs the gaps between the magnetic regenerator particles, thereby increasing the flow resistance of the helium gas, and consequently reducing the performance of the regenerator. A more preferable range of the coating amount of the adhesive is 0.5 to 4 wt%.

  As shown in FIGS. 1 and 2, the cylindrical metal integrated with the magnetic regenerator material is inserted into the regenerator and used, but the cylindrical metal itself can be used as a regenerator (cold regenerator cylinder). It is.

  It is also possible to integrate the magnetic regenerator material after processing it into a cylindrical metal shape so that it can be used as it is. Moreover, after integrating with a magnetic cool storage material, a dimension finishing process can be given and it can also be used as it is as a cool storage.

  According to the regenerator material according to the above configuration, since the magnetic regenerator material particles are sintered in a state in which the particles are filled in the cylindrical metal, and the particles are integrated with each other and the particles and the cylindrical metal, the regenerator material A gap between the particles is stabilized, and a gap between the magnetic regenerator and the regenerator is eliminated, thereby realizing a regenerator that can effectively prevent He gas leakage. Moreover, since the sintered body of magnetic regenerator material particles is protected and reinforced by the cylindrical metal, a regenerator material having a large rigidity as the whole regenerator material and excellent in durability can be obtained. Then, by providing the regenerator material in the regenerator of the final cooling stage of the refrigerating machine, a refrigerating machine having a high refrigerating capacity in a low temperature region and capable of maintaining a stable refrigerating performance over a long period of time is provided. Can do.

  In addition, it is possible to firmly fix the magnetic regenerator particles by sintering, it is possible to use magnetic particles with low sphericity, and it is possible to widen the particle size range of the magnetic particles. Therefore, the raw material yield is greatly improved, and an industrially inexpensive regenerator can be provided.

  The MRI apparatus, the cryopump, the superconducting magnet for the magnetic levitation train, and the magnetic field application type single crystal pulling apparatus all use the refrigerator as described above because the refrigerator performance affects the performance of each device. The MRI apparatus, cryopump, magnetic levitation train superconducting magnet, and magnetic field application type single crystal pulling apparatus of the present invention can all exhibit excellent performance over a long period of time.

  According to the method for producing a regenerator material according to the present invention, the magnetic regenerator material particles are sintered in a state where the particles are filled in the inside of the cylindrical metal, and the fixed structure is obtained by integrating the particles with each other and the particles and the cylindrical metal. In addition, the gap between the regenerator particles can be stabilized, and the gap between the magnetic regenerator and the regenerator can be eliminated, thereby realizing a regenerator that can effectively prevent He gas leakage. Moreover, since the sintered body of magnetic regenerator material particles is protected and reinforced by the cylindrical metal, a regenerator material having a large rigidity as the whole regenerator material and excellent in durability can be obtained. Then, by providing the regenerator material in the regenerator of the final cooling stage of the refrigerating machine, a refrigerating machine having a high refrigerating capacity in a low temperature region and capable of maintaining a stable refrigerating performance over a long period of time is provided. Can do.

  In addition, it is possible to firmly fix the magnetic regenerator particles by sintering, it is possible to use magnetic particles with low sphericity, and it is possible to widen the particle size range of the magnetic particles. Therefore, the raw material yield is greatly improved, and an industrially inexpensive regenerator can be provided.

  The MRI apparatus, the cryopump, the superconducting magnet for the magnetic levitation train, and the magnetic field application type single crystal pulling apparatus all use the refrigerator as described above because the refrigerator performance affects the performance of each device. The MRI apparatus, cryopump, magnetic levitation train superconducting magnet, and magnetic field application type single crystal pulling apparatus can all exhibit excellent performance over a long period of time.

  Next, embodiments of the present invention will be specifically described based on the following examples.

[Example 1]
A mother alloy having a composition of HoCu ₂ was prepared by blending Ho and Cu metal raw materials and using a high frequency melting method. The mother alloy is melted at about 1350 K, and the obtained alloy melt is dropped on a disk rotating at a speed of 1 × 10 ⁴ rpm in an Ar atmosphere having a pressure of 90 KPa to rapidly cool and solidify the magnetic particles. Was made. From the obtained magnetic particles, particles having an aspect ratio of 1.2 or less were classified and then sieved to prepare magnetic regenerator particles for Example 1 consisting of spherical magnetic particles having a particle size of 105 to 250 μm. . When the sphericity of the obtained magnetic regenerator material particles was evaluated by image analysis, particles having an aspect ratio of 0.9 or more were 87% by weight.

  Next, the obtained magnetic regenerator material particles were filled into a cylindrical metal made of stainless steel (SUS304) having an outer diameter of 34 mm, an inner diameter of 30 mm, and a length of 150 mm, and heated and sintered in a vacuum at a temperature of 860 ° C. for 3 hours. . Further, by correcting the thermal deformation caused by the heat sintering process by machining, a cold storage material 19 according to Example 1 in which the magnetic cold storage material 4 and the cylindrical metal 5 were integrated as shown in FIG. 1 was prepared. .

  On the other hand, in order to evaluate the characteristics of the regenerator material 19 prepared as described above, a two-stage expansion GM refrigerator as shown in FIG. 7 was prepared. A two-stage GM refrigerator 10 shown in FIG. 7 shows an embodiment of the refrigerator used in the present invention. A two-stage GM refrigerator 10 shown in FIG. 7 includes a vacuum vessel 13 in which a large-diameter first cylinder 11 and a small-diameter second cylinder 12 connected coaxially to the first cylinder 11 are installed. Have. A first regenerator 14 is disposed in the first cylinder 11 so as to be able to reciprocate, and a second regenerator 15 is disposed in the second cylinder 12 so as to be capable of reciprocating. Seal rings 16 and 17 are disposed between the first cylinder 11 and the first regenerator 14, and between the second cylinder 12 and the second regenerator 15, respectively.

  The first regenerator 14 accommodates a first regenerator material 18 such as Cu mesh. On the low sound side of the second regenerator 15, the cryogenic regenerator material of the present invention is accommodated as the second regenerator material 19. The first regenerator 14 and the second regenerator 15 each have a passage for a working medium such as He gas provided in a gap between the first regenerator 18 and the cryogenic regenerator 19.

  A first expansion chamber 20 is provided between the first regenerator 14 and the second regenerator 15. A second expansion chamber 21 is provided between the second regenerator 15 and the tip wall of the second cylinder 12. A first cooling stage 22 is formed at the bottom of the first expansion chamber 20, and a second cooling stage 23 having a temperature lower than that of the first cooling stage 22 is formed at the bottom of the second expansion chamber 21.

  A high-pressure working medium (for example, He gas) is supplied from the compressor 24 to the two-stage GM refrigerator 10 as described above. The supplied working medium passes between the first regenerators 18 accommodated in the first regenerator 14, reaches the first expansion chamber 20, and is further stored in the second regenerator 15. (Second cool storage material) 19 passes through and reaches the second expansion chamber 21. At this time, the working medium is cooled by supplying heat energy to the regenerator materials 18 and 19. The working medium that has passed between the regenerators 18 and 19 expands in the expansion chambers 20 and 21 to generate cold, and the cooling stages 22 and 23 are cooled. The expanded working medium flows in the opposite direction between the regenerator materials 18 and 19. The working medium is discharged after receiving thermal energy from each of the cold storage materials 18 and 19. As the recuperating effect is improved in such a process, the thermal efficiency of the working medium cycle is improved, and an even lower temperature is realized.

  Then, the regenerator material according to Example 1 prepared as described above is filled in the second-stage regenerator of the above-described two-stage expansion GM refrigerator, the refrigerator according to Example 1 is assembled, and the refrigeration test is performed. The refrigeration capacity after 3000 hours of continuous operation was measured.

  As a result, the refrigerating capacity at 4.2 K was 521 mW. The refrigerating capacity after 3000 hours of continuous operation was also stable at 518 mW. Furthermore, when the regenerator material 19 was taken out from the second regenerator 15 and observed after continuous operation, damage such as cracks and uneven distribution were not observed in the magnetic regenerator material particles 4.

  The refrigeration capacity in this example was defined as a heat load when a heat load was applied to the second cooling stage by the heater during the operation of the refrigerator and the temperature increase of the second cooling stage stopped at 4.2K.

[Example 2]
An Er ₃ Ni master alloy was prepared by a high frequency melting method, and this mother alloy was mechanically pulverized, and then magnetic regenerator particles having a particle size of 150 to 250 μm were prepared by sieving.

Next, the regenerator particles are filled to a height corresponding to half the length of a cylindrical metal made of stainless steel (SUS304) having an outer diameter of 34 mm, an inner diameter of 30 mm, and a length of 150 mm. Then, a heat sintering process was performed for 3 hours. Furthermore, after correcting the thermal deformation caused by the heat treatment by machining, HoCu ₂ spherical particles (particle size: 150 to 250 μm) are filled in a portion corresponding to the remaining half length, and the cold storage according to the second embodiment A material was prepared.

  The cold storage material was loaded into the second stage regenerator 15 of the two-stage expansion GM refrigerator as in Example 1 and the refrigeration test was performed. As a result, the refrigerating capacity at 4.2 K was a high value of 842 mW. Obtained. In addition, the refrigerating capacity after continuous operation for 3000 hours was 838 mW and stable performance was obtained. Moreover, when the cold storage material was taken out and observed after continuous operation, damage to the magnetic cold storage material was not observed.

[Comparative Example 1]
Heat sintering treatment under the same conditions as in Example 1 with the HoCu ₂ magnetic regenerator particles prepared in Example 1 filled in a quartz glass mold with an inner diameter of 30.5 mm in consideration of shrinkage at a height of 5 mm And 30 disk-shaped magnetic regenerator materials were produced. As a result of carrying out a refrigeration test by loading these disk-shaped magnetic regenerator materials in the second stage regenerator of a two-stage expansion GM refrigerator, the refrigerating capacity at 4.2 K is as low as 318 mW. Value.

[Comparative Example 2]
The Er ₃ Ni magnetic regenerator material particles prepared in Example 2 were filled in the second stage regenerator 15 of the two-stage expansion GM refrigerator 10 shown in FIG. 7 without sintering, and the refrigeration according to Comparative Example 2 was performed. The machine was assembled and a refrigeration test was conducted to measure the refrigeration capacity after continuous operation for 3000 hours.

As a result, the initial value of the refrigeration capacity at 4.2 K was 840 mW, but the refrigeration capacity after 3000 hours of continuous operation decreased to 413 mW. When the refrigerator after the continuous operation was disassembled, it was observed that the refrigerated regenerator material Er ₃ Ni adhered to the seal.

[Example 3]
The HoCu ₂ spherical magnetic regenerator particles prepared in Example 1 were barrel-plated to coat the particle surfaces with Pb having a thickness of about 7 μm. The magnetic regenerator material particles are filled into a SUS304 cylindrical metal in the same manner as in Example 1, and subjected to a heat sintering process at a temperature of 370 ° C. for 2 hours in a hydrogen atmosphere, and further machined to a predetermined size. A cold storage material according to Example 3 was obtained. This cold storage material was loaded into the second stage cold storage 15 of the two-stage expansion GM refrigerator similarly to Example 1, and the refrigeration test was carried out.

  As a result, 516 mW was obtained as the refrigerating capacity at 4.2K. In addition, the refrigerating capacity after continuous operation for 3000 hours was 507 mW, and a stable refrigerating performance was obtained. Furthermore, although the cold storage material was taken out and observed after continuous operation, damage to the magnetic cold storage material particles was not observed.

[Example 4]
A screw having a thread height of 0.2 mm and a screw pitch of 1 mm was formed on the inner wall of the cylindrical metal made of SUS304 used in Example 1. Then, the spherical magnetic regenerator material particles of HoCu ₂ prepared in Example 1 are filled into the cylindrical metal, heat-sintered at a temperature of 860 ° C. for 3 hours in vacuum, and further machined to a predetermined size. Thus, a cold storage material according to Example 4 was obtained. This cold storage material was loaded into the second stage cold storage 15 of the two-stage expansion GM refrigerator similarly to Example 1, and the refrigeration test was carried out.

  As a result, 505 mW was obtained as the refrigerating capacity at 4.2K. Moreover, the refrigerating capacity after continuous operation for 3000 hours was 501 mW, and a stable refrigerating performance was obtained. Furthermore, although the cold storage material was taken out and observed after continuous operation, damage to the magnetic cold storage material particles was not observed.

[Example 5]
A 30 μm-thick silver brazing foil (Cu 28 wt% -Ag 72 wt%) was attached to the inner wall of the SUS304 cylindrical metal used in Example 1. This cylindrical metal was filled with the spherical magnetic regenerator particles of HoCu ₂ prepared in Example 1, and heat-sintered at a temperature of 860 ° C. for 3 hours in a vacuum, and further machined to a predetermined size. A cold storage material according to Example 5 was obtained. This cold storage material was loaded into the second stage cold storage 15 of the two-stage expansion GM refrigerator similarly to Example 1, and the refrigeration test was carried out.

  As a result, 508 mW was obtained as the refrigerating capacity at 4.2K. In addition, the refrigerating capacity after continuous operation for 3000 hours was 502 mW and a stable refrigerating performance was obtained. Furthermore, although the cold storage material was taken out and observed after continuous operation, damage to the magnetic cold storage material particles was not observed.

[Example 6]
0.2 wt% titanate coupling agent (Ajinomoto KK Preneact) was added to and mixed with the spherical magnetic regenerator material particles of HoCu ₂ prepared in Example 1. Next, epoxy resin (Stycast 1266) was added and mixed with 2 wt% of the regenerator particles. The magnetic regenerator material particles were filled in a cylindrical metal made of SUS304 in the same manner as in Example 1, cured for 8 hours at room temperature, and further cured for 2 hours at 95 ° C. This cold storage material was loaded into the second stage regenerator of the two-stage expansion type GM refrigerator as in Example 1 to conduct a refrigeration test.

  As a result, 507 mW was obtained as the refrigerating capacity at 4.2K. In addition, the refrigerating capacity after continuous operation for 3000 hours was 502 mW and a stable refrigerating performance was obtained. Furthermore, although the cold storage material was taken out and observed after continuous operation, damage to the cold storage material particles was not observed.

  As is clear from the results shown in the above examples and comparative examples, the refrigerator using the regenerator material of each example obtained by sintering or curing the regenerator material particles filled in a cylindrical metal In each case, it was confirmed that the refrigerating capacity in the low temperature region was greatly improved as compared with the comparative example. Furthermore, in the refrigerator using the regenerator material according to each example, since the rigidity, mechanical strength, durability of the regenerator material is increased, there is little deterioration, and the decrease in the refrigerating capacity is small even after long-term continuous operation, It was found that a stable refrigeration capacity can be maintained.

  Next, examples of a superconducting MRI apparatus using a regenerative refrigerator according to the present invention, a superconducting magnet for a magnetic levitation train, a cryopump, and a magnetic field application type single crystal pulling apparatus will be described.

  FIG. 8 is a cross-sectional view showing a schematic configuration of a superconducting MRI apparatus to which the present invention is applied. A superconducting MRI apparatus 30 shown in FIG. 8 includes a superconducting static magnetic field coil 31 that applies a spatially uniform and temporally stable static magnetic field to a human body, and a correction coil that is not shown to correct nonuniformity of the generated magnetic field. A gradient magnetic field coil 32 that applies a magnetic field gradient to the measurement region, a radio wave transmission / reception probe 33, and the like. In addition, as described above, the regenerative refrigerator 34 according to the present invention is used for cooling the superconducting static magnetic field coil 31. In the figure, 35 is a cryostat, and 36 is a radiation heat shield.

  In the superconducting MRI apparatus 30 using the regenerative refrigerator 34 according to the present invention, the operating temperature of the superconducting static magnetic field coil 31 can be assured stably over a long period of time. A stable static magnetic field can be obtained over a long period of time. Therefore, the performance of the superconducting MRI apparatus 30 can be exhibited stably over a long period of time.

  FIG. 9 is a perspective view showing a schematic configuration of a main part of a superconducting magnet for a magnetic levitation train using a regenerative refrigerator according to the present invention, and shows a portion of a superconducting magnet 40 for a magnetic levitation train. A superconducting magnet 40 for a magnetic levitation train shown in FIG. 9 includes a superconducting coil 41, a liquid helium tank 42 for cooling the superconducting coil 41, a liquid nitrogen tank 43 for preventing volatilization of the liquid helium tank, and a regenerative type according to the present invention. It is comprised by the refrigerator 44 grade | etc.,. In the figure, 45 is a laminated heat insulating material, 46 is a power lead, and 47 is a permanent current switch.

  In the superconducting magnet 40 for a magnetically levitated train using the regenerative refrigerator 44 according to the present invention, the operating temperature of the superconducting coil 41 can be assured stably over a long period of time. A necessary magnetic field can be stably obtained over a long period of time. In particular, the superconducting magnet 40 for a magnetic levitation train acts on acceleration, but the regenerative refrigerator 44 according to the present invention can maintain excellent refrigeration capacity over a long period of time even when acceleration acts, so that the magnetic field strength, etc. Greatly contribute to the long-term stabilization of Therefore, the magnetic levitation train using such a superconducting magnet 40 can exhibit its reliability over a long period of time.

  FIG. 10 is a cross-sectional view showing a schematic configuration of a cryopump using the regenerative refrigerator according to the present invention. A cryopump 50 shown in FIG. 10 includes a cryopanel 51 that condenses or adsorbs gas molecules, a regenerative refrigerator 52 according to the present invention that cools the cryopanel 51 to a predetermined cryogenic temperature, and a shield provided therebetween. 53, a baffle 54 provided at the intake port, and a ring 55 for changing the exhaust speed of argon, nitrogen, hydrogen or the like.

  In the cryopump 50 using the regenerative refrigerator 52 according to the present invention, the operating temperature of the cryopanel 51 can be stably guaranteed over a long period of time. Therefore, the performance of the cryopump 50 can be exhibited stably over a long period of time.

  FIG. 11 is a perspective view showing a schematic configuration of a magnetic field application type single crystal pulling apparatus using a regenerative refrigerator according to the present invention. A magnetic field application type single crystal pulling device 60 shown in FIG. 11 includes a raw material melting crucible, a heater, a single crystal pulling unit 61 having a single crystal pulling mechanism, a superconducting coil 62 for applying a static magnetic field to the raw material melt, and It is constituted by an elevating mechanism 63 of the single crystal pulling unit 61 or the like. Then, as described above, the regenerative refrigerator 64 according to the present invention is used for cooling the superconducting coil 62. In the figure, 65 is a current lead, 66 is a heat shield plate, and 67 is a helium vessel.

  In the magnetic field application type single crystal pulling apparatus 60 using the regenerative refrigerator 64 according to the present invention, the operating temperature of the superconducting coil 62 can be stably guaranteed over a long period of time. A good magnetic field that suppresses the convection can be obtained over a long period of time. Therefore, the performance of the magnetic field application type single crystal pulling apparatus 60 can be exhibited stably over a long period of time.

Sectional drawing which shows one Example of the cool storage material formed with the manufacturing method of the cool storage material which concerns on this invention. Sectional drawing which shows the other Example of the cool storage material formed with the manufacturing method of the cool storage material which concerns on this invention. Sectional drawing which shows the other Example of the cool storage material formed with the manufacturing method of the cool storage material which concerns on this invention. Sectional drawing which shows the other Example of the cool storage material formed with the manufacturing method of the cool storage material which concerns on this invention. Sectional drawing which shows the other Example of the cool storage material formed with the manufacturing method of the cool storage material which concerns on this invention. Sectional drawing which shows the other Example of the cool storage material formed with the manufacturing method of the cool storage material which concerns on this invention. Sectional drawing which shows the principal part structure of the cool storage type refrigerator (GM refrigerator) used by this invention. Sectional drawing which shows schematic structure of the superconducting MRI apparatus used by this invention. The perspective view which shows the principal part schematic structure of the superconducting magnet (for magnetic levitation train) used by this invention. Sectional drawing which shows schematic structure of the cryopump used by this invention. The perspective view which shows the principal part schematic structure of the magnetic field application type single crystal pulling apparatus used by this invention. Sectional drawing of the regenerator filled with the conventional magnetic regenerator material particle.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Regenerator 2 Magnetic regenerator material 3 Crevice 4 Magnetic regenerator material 5, 5a Cylindrical metal (SUS)
6 Brazing material layer 7a Annular groove 7b Annular projection 8 Unevenness 9 Tapered surface 10 GM refrigerator (cool storage type refrigerator)
11 First cylinder 12 Second cylinder 13 Vacuum vessel 14 First regenerator 15 Second regenerator 16, 17 Seal ring 18 First heat storage material 19, 19a, 19b, 19c, 19d, 19e Second heat storage material (for cryogenic use) Cold storage material)
20 First expansion chamber 21 Second expansion chamber 22 First cooling stage 23 Second cooling stage 24 Compressor 30 Superconducting MRI apparatus 31 Superconducting static magnetic field coil 32 Gradient magnetic field coil 33 Radio wave transmitting / receiving probe 34 Cold storage refrigerator 35 Cryostat 36 Radiation Insulation shield 40 Superconducting magnet (magnet)
41 Superconducting coil 42 Liquid helium tank 43 Liquid nitrogen tank 44 Regenerative refrigerator 45 Laminated insulation 46 Power lead 47 Permanent current switch 50 Cryopump 51 Cryopanel 52 Regenerative refrigerator 53 Shield 54 Baffle 55 Ring 60 Magnetic field applied single crystal Pulling device 61 Single crystal pulling unit 62 Superconducting coil 63 Lifting mechanism 64 Cold storage refrigerator 65 Current lead 66 Heat shield plate 67 Helium container

Claims (7)

In the method for producing a regenerator material, in which a particulate magnetic regenerator material filled in a cylindrical metal is sintered and bonded to each other and integrated with the tubular metal, the cylindrical regenerator material particles are in contact with each other The surface roughness of at least a part of the inner wall of the metal is 30 μm or more on the basis of the maximum height (Ry), and the cylindrical metal is made of stainless steel, while the particle size in the particulate magnetic regenerator is 10 μm or more. The ratio of magnetic regenerator material particles of 5 mm or less is adjusted to be 70% weight or more, and sintering of the particulate magnetic regenerator material filled in the cylindrical metal is performed in vacuum, in an inert gas atmosphere, or a reducing gas. The manufacturing method of the cool storage material characterized by implementing in an atmosphere . 2. The method for producing a regenerator material according to claim 1, wherein a surface of the particulate magnetic regenerator material is coated with a low melting point metal having a melting point lower than that of the regenerator material or an alloy thereof at a thickness of 1 to 50 [mu] m, and liquid phase firing is performed. The manufacturing method of the cool storage material characterized by making it tie. 2. The method for manufacturing a regenerator material according to claim 1, wherein at least one metal selected from Pb, In, Sn, Ga and Zn is used as a low melting point metal for covering the particulate magnetic regenerator material. The manufacturing method of the cool storage material. The manufacturing method of the cool storage material of Claim 1 WHEREIN: An annular groove or an annular protrusion is formed in the inner wall of the said cylindrical metal, The manufacturing method of the cool storage material characterized by the above-mentioned. The manufacturing method of the cool storage material of Claim 1 WHEREIN: The unevenness | corrugation was formed in the inner wall of the said cylindrical metal. 2. The method of manufacturing a regenerator material according to claim 1, wherein an inner wall is formed in a tapered shape so that a cross-sectional area of the cylindrical metal expands or contracts in the axial direction, and the cylindrical metal has a maximum other than the end portion in the axial direction. The manufacturing method of the cool storage material characterized by having an internal diameter. 2. The method of manufacturing a regenerator material according to claim 1, wherein a foil-like or paste-like brazing material is disposed or applied to the inner wall of the cylindrical metal, and then the inside of the cylindrical metal is filled with a particulate magnetic regenerator material. A method for producing a regenerator material, characterized by sintering.

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