JP4568170B2 - Method for producing cryogenic regenerator material and method for producing cryogenic regenerator - Google Patents

Description

The present invention relates to a method for producing a refrigerator or the like cryogenic for cold storage material that are used in, and a method of manufacturing a cryogenic regenerator.

  In recent years, the development of superconducting technology has been remarkable, and as the field of application has expanded, the development of small, high-performance refrigerators has become indispensable. Such refrigerators are required to be lightweight, small and have high thermal efficiency. For example, in superconducting MRI apparatuses, cryopumps, and the like, refrigerators using refrigeration cycles such as the Gifford-McMahon method (GM method) and the Stirling method are used. In addition, a high-performance refrigerator is indispensable for a magnetic levitation train, and a high-performance refrigerator is also used in some single crystal pulling devices and the like.

  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 expands here. The medium flows in the opposite direction and repeats the cycle of receiving thermal energy from the cold storage material. As the recuperation effect is improved in such a process, the thermal efficiency of 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. However, since the specific heat of such a cold storage material becomes extremely small at an extremely low temperature of 20K or less, the above-described recuperation effect does not sufficiently function, and it has been difficult to realize an extremely low temperature. Therefore, recently, in order to realize a temperature close to absolute zero, Er—Ni-based intermetallic compounds such as Er ₃ Ni, ErNi, ErNi _{2 and the} like that exhibit a large specific heat in a cryogenic temperature range (see Patent Document 1) and ErRh The use of magnetic regenerator materials such as RRh-based intermetallic compounds (R: Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, etc.) (see Patent Document 2) has been studied.
JP-A-1-310269 JP 51-52378

  By the way, in the operating state of the refrigerator as described above, a gap between the regenerators filled in the regenerator is formed so that the working medium such as He gas is high-pressure and high-speed and the direction of the flow is frequently changed. pass. For this reason, various forces including mechanical vibration are applied to the cold storage material. In addition, when the refrigerator is mounted on, for example, a magnetic levitation train or an artificial satellite, a large acceleration acts on the cold storage material.

In this way, various forces act on the regenerator material, whereas the above-described magnetic regenerator material made of an intermetallic compound such as Er ₃ Ni or ErRh is generally a brittle material. It has a problem that it tends to be pulverized due to mechanical vibration and acceleration. The generated fine powder has an adverse effect on the performance of the regenerator by, for example, hindering the gas seal, and consequently reduces the capacity of the refrigerator.

The present invention relates to a method for producing a cryogenic regenerator material having excellent mechanical properties against mechanical vibration, acceleration, etc. with excellent reproducibility, and a refrigerating performance excellent over a long period of time. It aims at providing the manufacturing method of the regenerator for cryogenic temperature which enabled it to exhibit.

The method for producing a cryogenic regenerator material according to one aspect of the present invention is a cryogenic regenerator material comprising magnetic regenerator particles,
The magnetic regenerator material particles are represented by L ² / 4πA, where L is the perimeter of the projected image of each magnetic regenerator material particle constituting the magnetic regenerator material particle, and A is the actual area of the projected image. Of the magnetic regenerator particles that are shape-classified so that the ratio of the magnetic regenerator particles with a shape factor R exceeding 1.5 is 5% or less and that constitute the magnetic regenerator particles, the magnetic regenerator particles maximum acceleration is a the production process for extremely low temperature cold accumulating material ratio of the magnetic cold accumulating material particles is not more than 1% by weight to break when applying 1 × 10 ⁶ times the simple harmonic oscillation of 300m / s ^2, below ( a step of producing magnetic regenerator particles satisfying the conditions of a) to (d), extracting a certain amount of magnetic regenerator particles from the magnetic regenerator particles, and maximizing a population of these extracted magnetic regenerator particles a step of measuring the ratio of particles to break when the acceleration is added 1 × 10 ⁶ times the simple harmonic oscillation of 300m / s ^2, the The step of selecting the magnetic regenerator material particles having a particle ratio of 1% by weight or less that breaks when vibration is applied, and the perimeter of the projected images of the individual magnetic regenerator material particles constituting the magnetic regenerator material particles. L, where the actual area of the projected image is A, the magnetic regenerator material particles such that the ratio of the magnetic regenerator material particles having a shape factor R represented by L ² / 4πA of more than 1.5 is 5% or less. And a step of classifying the body.
(A) The carbon content of the magnetic regenerator material particles constituting the magnetic regenerator material particles is 0.1% by weight or less.
(B) The nitrogen content of the magnetic regenerator material particles constituting the magnetic regenerator material granule is 0.3% by weight or less.
(C) 70% by weight or more of the magnetic regenerator material particles constituting the magnetic regenerator material particles have a particle size in the range of 0.01 to 3.0 mm.
(D) General formula: RM _z (wherein R is at least one selected from Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb) R represents a rare earth element, M represents at least one metal element selected from Ni, Co, Cu, Ag, Al and Ru, and z represents a number in the range of 0.001 to 9.0, or a general formula: RRh (wherein R represents a rare earth element represented by Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb. Containing intermetallic compounds

The method for manufacturing a cryogenic regenerator according to one aspect of the present invention includes a regenerator container and magnetic regenerator material particles filled in the regenerator container, and each of the magnetic regenerator material particles constituting the magnetic regenerator material particles. When the perimeter of the projected image is L and the actual area of the projected image is A, the magnetic regenerator material particles have a ratio of the magnetic regenerator material particles having a shape factor R expressed by L ² / 4πA exceeding 1.5. Of the magnetic regenerator material particles that are classified so as to be 5% or less and constitute the magnetic regenerator material particles, a single vibration with a maximum acceleration of 300 m / s ² is applied to the magnetic regenerator material particles 1 × 10 ^A method for producing a cryogenic regenerator comprising a cryogenic regenerator material in which the ratio of the magnetic regenerator particles that breaks when applied ^six times is 1% by weight or less, comprising the following (a) to (d a step of preparing a satisfying magnetic regenerator material granular material), a certain amount of the magnetic cold accumulating material particles from the magnetic regenerator material granules Extracting the steps of maximum acceleration the population of these extracted magnetic regenerator material particles measuring the ratio of particles destroyed when added 1 × 10 ⁶ times the simple harmonic oscillation of 300 meters / s ^2, the single vibration added A step of selecting the magnetic regenerator material particles having a particle ratio of 1% by weight or less, and a perimeter of the projected image of the magnetic regenerator material particles constituting the magnetic regenerator material particles, L, Assuming that the actual area of the projected image is A, the magnetic regenerator material particles are shaped so that the ratio of the magnetic regenerator material particles having a shape factor R represented by L ² / 4πA exceeding 1.5 is 5% or less. The ratio of the particles to be destroyed when the simple vibrations that have been classified and shape classified are applied is 1% by weight or less, and the ratio of the magnetic regenerator material particles having the shape factor R exceeding 1.5 is 5 A step of filling a regenerator container with the magnetic regenerator material particles that are less than or equal to% to produce a regenerator. It is characterized by having.
(A) The carbon content of the magnetic regenerator material particles constituting the magnetic regenerator material particles is 0.1% by weight or less.
(B) The nitrogen content of the magnetic regenerator material particles constituting the magnetic regenerator material granule is 0.3% by weight or less.
(C) 70% by weight or more of the magnetic regenerator material particles constituting the magnetic regenerator material particles have a particle size in the range of 0.01 to 3.0 mm.
(D) General formula: RM _z (wherein R is at least one selected from Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb) R represents a rare earth element, M represents at least one metal element selected from Ni, Co, Cu, Ag, Al and Ru, and z represents a number in the range of 0.001 to 9.0, or a general formula: RRh (wherein R represents a rare earth element represented by Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb. Containing intermetallic compounds

According to the onset bright, it can be obtained with good reproducibility excellent mechanical properties with respect to mechanical vibration and acceleration, and the like. Therefore, very low-temperature regenerator using such very low temperature for the cold storage material, more can be maintained over a long period of time with good reproducibility excellent refrigeration performance according to the refrigerator.

Hereinafter, modes for carrying out the present invention will be described. The cryogenic regenerator material according to one embodiment of the present invention comprises a magnetic regenerator material particle, that is, an aggregate (group) of magnetic regenerator particles. Examples of the magnetic regenerator material used in the present invention include, for example, the general formula: RM _z (1)
(Wherein R is at least one rare earth element selected from Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb, and M is Ni, Represents at least one metal element selected from Co, Cu, Ag, Al and Ru, and z represents a number in the range of 0.001 to 9.0 (the same applies hereinafter).
Intermetallic compounds containing rare earth elements represented by
General formula: RRh (2)
The intermetallic compound containing the rare earth element represented by these is mentioned.

  The magnetic regenerator material particles as described above can make the gas flow smoother as their particle diameters become uniform and the shape is closer to a spherical shape. Therefore, it is preferable that 70% by weight or more of the magnetic regenerator material particles (total particles) is composed of magnetic regenerator particles having a particle size in the range of 0.01 to 3.0 mm. When the particle diameter of the magnetic regenerator material particles is less than 0.01 mm, the packing density becomes too high, and the risk of increasing the pressure loss of a working medium such as helium increases. On the other hand, when the particle diameter exceeds 3.0 mm, the heat transfer area between the magnetic regenerator material particles and the working medium is reduced, and the heat transfer efficiency is lowered. Therefore, when such particles exceed 30% by weight of the magnetic regenerator material particles, there is a risk of causing a decrease in regenerator performance. A more preferable particle diameter is in the range of 0.05 to 2.0 mm, and further preferably in the range of 0.1 to 0.5 mm. The ratio of particles having a particle size in the range of 0.01 to 3.0 mm in the magnetic regenerator material granule is more preferably 80% by weight or more, and still more preferably 90% by weight or more.

The cryogenic regenerator material of the present invention is a magnetic regenerator particle that breaks when a single vibration having a maximum acceleration of 300 m / s ² is applied to the group of magnetic regenerator particles as described above 1 × 10 ⁶ times. The magnetic regenerator material particles having a ratio of 1% by weight or less. In the present invention, the magnetic strength of each magnetic regenerator material particle is intricately related to the amount of nitrogen and carbon as impurities, the cooling rate in the solidification process, the metal structure, the shape, etc. Focusing on the mechanical strength as a group of magnetic regenerator material particles in which is generated.

By measuring the ratio of such magnetic regenerator particles, that is, the percentage of particles that break when a single vibration with a maximum acceleration of 300 m / s ² is applied to the magnetic regenerator particles 1 × 10 ⁶ times, It becomes possible to evaluate the reliability with respect to the mechanical strength of the particles. A method for producing a cryogenic regenerator material according to an embodiment of the present invention extracts a certain amount of magnetic regenerator particles from magnetic regenerator particles, and a maximum acceleration of 300 m / s in the group of these extracted magnetic regenerator particles. ^{A step} of measuring a ratio of particles to be broken when the single vibration of ² is applied 1 × 10 ⁶ times, and selecting a magnetic regenerator material particle having a ratio of the particles to be broken at this time of 1% by weight or less.

In other words, if the ratio of the particles that break when 1 × 10 ⁶ times a single vibration with a maximum acceleration of 300 m / s ² is applied to the magnetic regenerator material granules is 1% by weight or less, the magnetic regenerator material production lot Furthermore, even if the production conditions are different, there are almost no magnetic regenerator particles that are pulverized due to mechanical vibration during operation of the refrigerator or acceleration due to the movement of the system in which the refrigerator is mounted. Therefore, by using magnetic regenerator material particles having such mechanical characteristics, it is possible to prevent the occurrence of gas seal obstruction or the like in the refrigerator. The ratio of magnetic regenerator particles that breaks when a single vibration with a maximum acceleration of 300 m / s ² is applied 1 × 10 ⁶ times to the magnetic regenerator material particles is more preferably 0.5% by weight or less, and still more preferably 0.1 wt% or less.

Here, when the maximum acceleration in the vibration test (acceleration test) is less than 300 m / s ² , most of the magnetic regenerator material particles are not broken, and thus the reliability cannot be evaluated. In addition, if the number of times that a single vibration with a maximum acceleration of 300 m / s ² is applied to the magnetic regenerator material particles is less than 1 × 10 ⁶ times, it acts on the magnetic regenerator material particles due to the movement of the system in which the refrigerator is mounted. Sufficient practical reliability cannot be evaluated for acceleration and the like. In the present invention, the conditions of the vibration test described above are important, and by setting the maximum acceleration of single vibration and the number of vibrations to the above-described values, it is possible to evaluate the reliability of the magnetic regenerator particles for actual use conditions for the first time. It becomes possible. The reliability evaluation of magnetic regenerator particles is performed when a single vibration with a maximum acceleration of 400 m / s ² is applied 1 × 10 ⁶ times, or a single vibration with a maximum acceleration of 300 m / s ² is applied 1 × 10 ⁷ times. It is more preferable that the ratio of the magnetic regenerator particles to be destroyed is 1% by weight or less.

The reliability evaluation test (vibration test) of the magnetic regenerator material particles described above is performed as follows. First, a certain amount of magnetic regenerator particles are randomly extracted for each production lot from magnetic regenerator particles having a particle size and the like within a specified range. Next, the extracted magnetic regenerator material particles are filled into a cylindrical container 1 for vibration test as shown in FIG. 1, and a single vibration having a maximum acceleration of 300 m / s ² is applied 1 × 10 ⁶ times. Anodized or the like is used as the material of the cylindrical container 1 for vibration test. After the vibration test, the broken magnetic regenerator material particles are selected by sieving, shape classification, etc., and the weight thereof is measured to evaluate the reliability of the magnetic regenerator material particles as a group.

  Here, the density (filling rate) at which the vibration test container is filled with the magnetic regenerator material particles depends complicatedly on the shape and particle size distribution of the magnetic regenerator material particles. A free space in which the magnetic regenerator material particles can move around exists in the container, and the vibration resistance characteristics of the magnetic regenerator material particles cannot be accurately evaluated. On the other hand, if the filling rate is set too high, it is necessary to push the magnetic cold storage material particles into the test container, and the possibility of destruction by the compressive force at that time increases. Therefore, it is necessary to test by changing the filling rate widely. That is, in the present invention, the ratio of the magnetic regenerator material particles broken by the vibration test was tested by varying the filling rate for one lot, and among them, the ratio of the broken magnetic regenerator particles was the lowest value. Shall be adopted as the measured value.

The cryogenic regenerator material of the present invention is not particularly limited to its composition or shape as long as it satisfies the reliability evaluation test (vibration test) described above, but it depends on mechanical vibration, acceleration, etc. It is desirable that the following conditions are satisfied with respect to the impurity concentration and shape in the particles that cause particle destruction.
(A) In the state processed into the particle shape, the amount of nitrogen as an impurity in the magnetic regenerator material particles is set to 0.3% by weight or less.
(B) The amount of carbon as an impurity in the magnetic regenerator material particles is 0.1% by weight or less in a state of being processed into a particle shape.
(C) When the perimeter of the projected image of each particle constituting the magnetic regenerator material granule is L and the actual area of the projected image is A, the shape factor R represented by L ² / 4πA is greater than 1.5. The abundance ratio is 5% or less.

  That is, nitrogen and carbon as impurities in the magnetic regenerator material particles cause rare earth nitrides and rare earth carbides to precipitate at the crystal grain boundaries of the magnetic regenerator material represented by the above-described formulas (1) and (2). It becomes a factor of lowering the mechanical strength of the regenerator particles. In other words, by reducing the amounts of nitrogen and carbon, good mechanical strength can be stably obtained, and the reliability evaluation test (vibration test) can be satisfied with good reproducibility. For these reasons, the amount of nitrogen as an impurity in the magnetic regenerator material particles is preferably 0.3% by weight or less, and the carbon amount is preferably 0.1% by weight or less. The amount of nitrogen as an impurity is more preferably 0.1% by weight or less, and still more preferably 0.05% by weight or less. The amount of carbon as an impurity is more preferably 0.05% by weight or less, and further preferably 0.02% by weight or less.

  In addition, the shape of the magnetic regenerator material particles is preferably spherical as described above, and the higher the sphericity and the smoother the surface, the smoother the gas flow, and the magnetic regenerator material particles can be machined. It is possible to suppress extreme stress concentration when mechanical vibration or the like is applied. Thereby, the mechanical strength as a group of magnetic cold storage material particles can be increased. That is, particles having a complicated surface shape such as the presence of protrusions on the particle surface tend to cause stress concentration when the magnetic regenerator material particles are subjected to force, which adversely affects the mechanical strength of the magnetic regenerator material particles. Effect.

Therefore, the presence of particles having a shape factor R expressed by L ² / 4πA exceeding 1.5, where L is the perimeter of the projected image of each particle constituting the magnetic regenerator grain and A is the actual area of the projected image. The ratio is preferably 5% or less. That is, it is preferable to classify the magnetic regenerator particles so that the ratio of magnetic regenerator particles having a shape factor R exceeding 1.5 is 5% or less. The shape factor R is preferably evaluated by, for example, randomly extracting 100 or more particles for each production lot of magnetic regenerator material granules, and processing these images. If the number of extracted particles is too small, the shape factor R of the entire magnetic regenerator material granule may not be accurately evaluated.

  The above-described shape factor R takes a large value (large partial deformity) even when particles having a high sphericity as a whole shape are present on the surface. On the other hand, if the surface is relatively smooth, the shape factor R has a low value even for particles having a somewhat low sphericity. As described above, the shape factor R tends to have a larger value as particles having protrusions on the surface thereof. That is, the small shape factor R means that the particle surface is relatively smooth (small partial deformity), and is an effective parameter for evaluating the partial shape of the particle. Therefore, the mechanical strength of the magnetic regenerator material particles can be improved by setting the ratio of particles having a shape factor R exceeding 1.5 to 5% or less. The abundance ratio of particles having a shape factor R exceeding 1.5 is more preferably 2% or less, and further preferably 1% or less. Further, the abundance ratio of particles having a shape factor R exceeding 1.3 is preferably 15% or less. The abundance ratio of particles having a shape factor R exceeding 1.3 is more preferably 10% or less, and further preferably 5% or less.

  The manufacturing method of the magnetic regenerator material granule as described above is not particularly limited, and various manufacturing methods can be applied. For example, it is possible to apply a method in which a molten metal having a predetermined composition is rapidly cooled and solidified by a centrifugal spraying method, a gas atomizing method, a rotating electrode method, or the like. At this time, the amount of nitrogen and the amount of carbon in the magnetic regenerator particles can be reduced by using high-purity raw materials or reducing the amount of impurity gas in the atmosphere when rapidly solidifying. Further, for example, by performing shape classification by optimization of manufacturing conditions, a gradient vibration method, or the like, a magnetic regenerator material granule having an abundance ratio of particles having a shape factor R exceeding 1.5 can be obtained at 5% or less.

The cryogenic regenerator material of this embodiment is filled in a regenerator container to constitute a cryogenic regenerator, and the cryogenic regenerator is used in a refrigerator. In other words, the refrigerator is a cryogenic regenerator material filled in a regenerator container, when the magnetic regenerator material granule having the above-mentioned mechanical characteristics, that is, when a single vibration with a maximum acceleration of 300 m / s ² is applied 1 × 10 ⁶ times A regenerator using a magnetic regenerator material granule in which the ratio of particles to be destroyed is 1% by weight or less is provided.

  As described above, the cryogenic regenerator material used in the refrigerator includes magnetic regenerator particles that are pulverized due to mechanical vibration during operation of the refrigerator and acceleration due to the movement of the system in which the refrigerator is mounted, as described above. Since there is almost no obstruction of the gas seal of the refrigerator or the like is not caused. Accordingly, it is possible to maintain the refrigeration performance stably for a long time. The MRI apparatus, the cryopump, the magnetic levitation train, and the magnetic field application type single crystal pulling apparatus all have an MRI apparatus that uses a refrigerator as described above because the refrigerator performance affects the performance of each apparatus. The cryopump, the magnetic levitation train, and the magnetic field application type single crystal pulling device can all exhibit excellent performance over a long period of time.

  Next, specific examples of the present invention and evaluation results thereof will be described.

Example 1 and Comparative Example 1
First, an Er ₃ Ni mother alloy was prepared by high frequency melting. This Er3Ni master alloy was melted at about 1263 K, and this molten metal was dropped on a rotating disk in an Ar atmosphere (pressure = about 80 kPa) and rapidly solidified. The obtained granules were classified and sieved, and 1 kg of spherical particles having a particle size of 180 to 250 μm were selected. This process was repeated to obtain 10 lots of spherical Er ₃ Ni particles.

Next, the 10 Er ₃ Ni particles extracted at random from the spherical Er ₃ Ni particles of lots, vibration test container shown in FIGS 1 1 (D = 15mm, h = 14mm) was packed into a A single vibration with a maximum acceleration of 300 m / s ² was applied 1 × 10 ⁶ times using a vibration tester. Each granule after the test was appropriately classified and sieved, and the ratio of the broken spherical Er ₃ Ni particles was determined. Table 1 shows the ratio of broken particles (breakage rate) for each lot. As apparent from Table 1, the spherical Er ₃ Ni particles of samples No 1 to No 8 correspond to Example 1, and the spherical Er ₃ Ni particles of Samples No 9 to No 10 correspond to Comparative Example 1.

Here, the filling rate of Er ₃ Ni particles into the vibration test container 1 was changed in the range of 55 to 66%, and the lowest breaking rate was defined as the breaking rate of the lot. FIG. 2 shows the relationship between the filling rate of the spherical Er ₃ Ni particles of sample No1 into the vibration test container and the fracture rate by the vibration test. In FIG. 2, since the destruction rate is 0 (below the detection limit) at a filling rate of 63.7%, this value is the destruction rate of this lot. In addition, the test was not performed at a filling rate higher than that.

Each of the lots of magnetic regenerator material spherical particles made of Er ₃ Ni described above is filled in a regenerator at a filling rate of 63.5 to 63.8% to produce regenerators, and these regenerators are shown in FIG. A refrigeration test was conducted by incorporating each of the two-stage regenerators (second regenerator 15) into a stage-type GM refrigerator. The results are also shown in Table 1.

As is clear from Table 1, a refrigerator using a magnetic regenerator granule that has a particle ratio of 1% by weight or less when a single vibration with a maximum acceleration of 300 m / s ² is applied 1 × 10 ⁶ times. It can be seen that both can maintain excellent refrigeration capacity over a long period of time.

  The two-stage GM refrigerator 10 shown in FIG. 3 includes a large-diameter first cylinder 11 and a small-diameter second cylinder 12 that is coaxially connected to the first cylinder 11. A vacuum vessel 13 is provided. 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. In 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 the 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. Further, 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 and reaches the first expansion chamber 20, and further, the pole accommodated in the second regenerator 15. It passes between the low-temperature regenerator material (second regenerator material) 19 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 cold storage materials 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 recuperation effect is improved in such a process, the thermal efficiency of the working medium cycle is improved, and an even lower temperature is realized.

Example 2 and Comparative Example 2
A HoCu ₂ master alloy was prepared by high frequency melting. This HoCu ₂ master alloy was melted at about 1323 K, and this molten metal was dropped on a rotating disk in an Ar atmosphere (pressure = about 80 kPa) and rapidly solidified. The obtained granules were sieved and the particle size was adjusted in the range of 180 to 250 μm, and then shape classification was carried out by the gradient vibration plate method, and 1 kg of spherical granules were selected. Such a process was performed several times to obtain 5 lots of spherical HoCu ₂ particles. Here, the sphericity of each lot was changed by adjusting the shape classification conditions such as the inclination angle and the vibration intensity.

Next, 300 particles are randomly extracted from these 5 lots of spherical HoCu ₂ particles, the perimeter L of the projected image of each particle and the actual area A of the projected image are measured by image processing, and L ² The shape factor R expressed by / 4πA was evaluated. A vibration test was performed on each lot in the same manner as in Example 1 to determine the ratio of the broken spherical HoCu ₂ particles. Table 2 shows the shape factor R for each lot and the fracture rate of the particles by the vibration test. As is clear from Table 2, each spherical HoCu ₂ particle of Samples No 1 to No 4 corresponds to Example 2, and the spherical HoCu ₂ particle of Sample No 5 corresponds to Comparative Example 2.

After filling the above-mentioned magnetic regenerator material spherical particles of each of the above-mentioned HoCu ₂ with a filling rate of 63.5 to 64.0% on the low temperature side 1/2 of the regenerator, and with the Pb sphere on the high temperature side 1/2 As in Example 1, a two-stage GM refrigerator was incorporated as a second-stage regenerator, and the same refrigeration test as in Example 1 was performed. The results are also shown in Table 2.

As is clear from Table 2, a refrigerator using a magnetic regenerator granule that has a particle ratio of 1% by weight or less when a single vibration with a maximum acceleration of 300 m / s ² is applied 1 × 10 ⁶ times. It can be seen that both can maintain excellent refrigeration capacity over a long period of time.

Example 3 and Comparative Example 3
An ErNi _0.9 Co _0.1 master alloy was prepared by high frequency melting. This ErNi _0.9 Co _0.1 master alloy was melted at about 1523 K, and this molten metal was dropped on a rotating disk in an Ar atmosphere (pressure = about 80 kPa) and rapidly solidified. The obtained granules were appropriately classified and sieved, and 1 kg of spherical granules having a particle size of 180 to 250 were selected. Such a process was performed several times to obtain 5 lots of spherical ErNi _0.9 Co _0.1 particles.

Here, the amount of impurities in the spherical particles differs because the raw material lot when producing the master alloy, the degree of vacuum of the atmosphere during high-frequency melting, the impurity gas concentration during the rapid solidification process, and the like are different. Table 3 shows the amounts of nitrogen and carbon in the spherical particles. These five lots of spherical ErNi _0.9 Co _0.1 particles were subjected to a vibration test in the same manner as in Example 1 to determine the ratio of the broken spherical ErNi _0.9 Co _0.1 particles. Table 3 shows the amount of nitrogen and carbon for each lot, and the particle destruction rate by the vibration test. As is clear from Table 3, each spherical ErNi _0.9 Co _0.1 particle of Samples No. 1 to No. 4 corresponds to Example 3, and the spherical ErNi _0.9 Co _0.1 particle of Sample No. 5 corresponds to Comparative Example 3.

Each lot of magnetic regenerator material spherical particles made of ErNi _0.9 Co _0.1 described above is filled in the cold storage ½ of the cold storage container at a filling rate of 63.4-64.0%, and the high temperature ½ is filled with Pb spheres. After that, as in Example 1, it was incorporated into a two-stage GM refrigerator as a second-stage regenerator, and a refrigeration test was conducted in the same manner as in Example 1. The results are also shown in Table 3.

As is clear from Table 3, a refrigerator using a magnetic regenerator material granule in which the ratio of particles that breaks when a single vibration with a maximum acceleration of 300 m / s ² is applied 1 × 10 ⁶ times is 1% by weight or less. It can be seen that both can maintain excellent refrigeration capacity over a long period of time.

Example 4 and Comparative Example 4
ErNi mother alloy, Er ₃ Co mother alloy, ErCu mother alloy, and Ho ₂ Al mother alloy were prepared by high frequency melting. Each of these master alloys was melted at about 1493 K, and these molten metals were dropped on a rotating disk in an Ar atmosphere (pressure = about 80 kPa) and rapidly solidified. Each of the obtained granules was appropriately classified and sieved, and 1 kg of spherical granules having a particle diameter of 180 to 250 μm were selected. Such a process was performed several times to obtain 5 lots of spherical particles each.

  For each lot of these spherical particles, a vibration test was performed in the same manner as in Example 1 to measure the fracture rate. The lot with the lowest fracture rate (Example) and the lot with the highest fracture rate (Comparative Example) Was selected respectively. For each of these lots, the shape factor R was measured and the nitrogen and carbon were analyzed. These results are shown in Table 4.

Each magnetic regenerator material spherical particle described above was incorporated into a refrigerator as follows. First, spherical particles of magnetic regenerator material made of ErNi are filled in the low temperature side 1/2 of the cold storage container at a filling rate of 63.2 to 64.0%, respectively, and Er ₃ Co, ErCu, or Ho ₂ Al on the high temperature side 1/2. After filling the magnetic regenerator material spherical particles composed of 63.0% to 64.1% with each other, it is incorporated in the two-stage GM refrigerator as the second-stage regenerator in the same manner as in Example 1 and frozen in the same manner as in Example 1. A test was conducted. The results are also shown in Table 4.

  Next, configuration examples of the MRI apparatus, the magnetic levitation train, the cryopump, and the magnetic field application type single crystal pulling apparatus will be described.

  FIG. 4 is a diagram showing a schematic configuration of a superconducting MRI apparatus to which the present invention is applied. The superconducting MRI apparatus 30 shown in FIG. 1 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. The refrigerator 34 as described above 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 above-described refrigerator 34, the operating temperature of the superconducting static magnetic field coil 31 can be stably assured over a long period of time, and therefore a spatially uniform and temporally stable static magnetic field is long. Can be obtained over a period of time. Therefore, the performance of the superconducting MRI apparatus 30 can be stably exhibited over a long period of time.

  FIG. 5 is a diagram showing a schematic configuration of a main part of a magnetic levitation train to which the present invention is applied, 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 the figure includes a superconducting coil 41, a liquid helium tank 42 for cooling the superconducting coil 41, a liquid nitrogen tank 43 for preventing the liquid helium from being volatilized, a refrigerator 44, and the like. It is configured. 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 refrigerator 44, the operating temperature of the superconducting coil 41 can be stably ensured over a long period of time, so that the magnetic field necessary for the magnetic levitation and propulsion of the train can be stabilized over a long period of time. Can be obtained. In particular, the superconducting magnet 40 for a magnetic levitation train acts on acceleration, but the refrigerator 44 can maintain excellent refrigeration capacity over a long period of time even when acceleration acts, thus greatly contributing to long-term stabilization of magnetic field strength and the like. . Therefore, the magnetic levitation train using such a superconducting magnet 40 can exhibit its reliability over a long period of time.

  FIG. 6 is a diagram showing a schematic configuration of a cryopump to which the present invention is applied. A cryopump 50 shown in the figure includes a cryopanel 51 that condenses or adsorbs gas molecules, a refrigerator 52 that cools the cryopanel 51 to a predetermined cryogenic temperature, a shield 53 provided therebetween, and a suction port. Baffle 54, and a ring 55 for changing the exhaust speed of argon, nitrogen, hydrogen or the like. The cryopump 50 using the refrigerator 52 can guarantee the operating temperature of the cryopanel 51 stably over a long period of time. Therefore, the performance of the cryopump 50 can be exhibited stably over a long period of time.

  FIG. 7 is a diagram showing a schematic configuration of a magnetic field application type single crystal pulling apparatus to which the present invention is applied. A single-crystal pulling apparatus 60 for applying a magnetic field shown in the figure includes a raw crystal 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, It is constituted by an elevating mechanism 63 of the single crystal pulling unit 61 or the like. The refrigerator 64 as described above 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 refrigerator 64, the operating temperature of the superconducting coil 62 can be stably ensured over a long period of time, so that a good magnetic field that suppresses convection of the single crystal raw material melt can be obtained. It 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 stably exhibited over a long period of time.

It is sectional drawing which shows an example of the container for a vibration test used for the reliability evaluation test of the magnetic cool storage material granule of this invention. It is a figure which shows the relationship between the filling rate to the container for a vibration test of the magnetic regenerator material granule by one Example of this invention, and the ratio of the particle | grains destroyed by the vibration test. It is a figure which shows the principal part structure of the GM refrigerator produced by one Example of this invention. It is a figure which shows schematic structure of the superconducting MRI apparatus by this invention. It is a figure which shows the principal part schematic structure of the magnetic levitation train by this invention. It is a figure which shows schematic structure of the cryopump by this invention. It is a figure which shows the principal part schematic structure of the magnetic field application type single crystal pulling apparatus by this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Cylindrical container for vibration tests, 10 ... GM refrigerator, 14, 15 ... Regenerator, 19 ... 2nd cool storage material (cold storage material for cryogenic temperature).

Claims (2)

A cryogenic regenerator with magnetic regenerator particles,
The magnetic regenerator material particles are represented by L ² / 4πA, where L is the perimeter of the projected image of each magnetic regenerator material particle constituting the magnetic regenerator material particle, and A is the actual area of the projected image. Of the magnetic regenerator particles that are shape-classified so that the ratio of the magnetic regenerator particles with a shape factor R exceeding 1.5 is 5% or less and that constitute the magnetic regenerator particles, the magnetic regenerator particles A method for producing a cryogenic regenerator material in which the ratio of the magnetic regenerator material particles that break when a single vibration with a maximum acceleration of 300 m / s ² is applied 1 × 10 ⁶ times is 1% by weight or less,
A step of producing magnetic regenerator material particles satisfying the following conditions (a) to (d) ;
Extract a certain amount of magnetic regenerator particles from the magnetic regenerator particles and destroy them when a single vibration with a maximum acceleration of 300 m / s ² is applied to the group of extracted magnetic regenerator particles 1 × 10 ⁶ times Measuring the ratio of particles;
Selecting the magnetic regenerator material particles having a ratio of particles of 1% by weight or less that break when the simple vibration is applied;
The shape factor R represented by L ² / 4πA exceeds 1.5, where L is the perimeter of the projected image of each magnetic regenerator material particle constituting the magnetic regenerator material particle, and A is the actual area of the projected image. And a step of classifying the magnetic regenerator material particles so that the ratio of the magnetic regenerator material particles is 5% or less.
(A) The carbon content of the magnetic regenerator material particles constituting the magnetic regenerator material particles is 0.1% by weight or less.
(B) The nitrogen content of the magnetic regenerator material particles constituting the magnetic regenerator material granule is 0.3% by weight or less.
(C) 70% by weight or more of the magnetic regenerator material particles constituting the magnetic regenerator material particles have a particle size in the range of 0.01 to 3.0 mm.
(D) General formula: RM _z (wherein R is at least one selected from Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb) R represents a rare earth element, M represents at least one metal element selected from Ni, Co, Cu, Ag, Al and Ru, and z represents a number in the range of 0.001 to 9.0, or a general formula: RRh (wherein R represents a rare earth element represented by Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb. Containing intermetallic compounds A cold storage container,
The magnetic regenerator material particles filled in the regenerator container, when the perimeter of the projected image of the magnetic regenerator material particles constituting the magnetic regenerator material particles is L, and the actual area of the projected image is A, The magnetic regenerator particles are classified so that the ratio of the magnetic regenerator particles having a shape factor R expressed by L ² / 4πA of more than 1.5 is 5% or less, and constitute the magnetic regenerator particles The ratio of the magnetic regenerator material particles that break when the magnetic regenerator material particles are broken by applying a single vibration with a maximum acceleration of 300 m / s ² 1 × 10 ⁶ times to the magnetic regenerator material particles is 1% by weight or less. A method of manufacturing a cryogenic regenerator comprising a cryogenic regenerator material,
A step of producing magnetic regenerator material particles satisfying the following conditions (a) to (d) ;
Extract a certain amount of magnetic regenerator particles from the magnetic regenerator particles and destroy them when a single vibration with a maximum acceleration of 300 m / s ² is applied to the group of extracted magnetic regenerator particles 1 × 10 ⁶ times Measuring the ratio of particles;
Selecting the magnetic regenerator material particles having a ratio of particles of 1% by weight or less that break when the simple vibration is applied;
The shape factor R represented by L ² / 4πA exceeds 1.5, where L is the perimeter of the projected image of each magnetic regenerator material particle constituting the magnetic regenerator material particle, and A is the actual area of the projected image. A step of classifying the magnetic regenerator material particles so that the magnetic regenerator particle ratio is 5% or less;
The ratio of the particles to be destroyed when the single vibrations that have been selected and classified are applied is 1% by weight or less, and the ratio of the magnetic regenerator particles having the shape factor R exceeding 1.5 is 5% or less. And a step of filling a regenerator container with magnetic regenerator material particles to produce a regenerator, and a method for producing a cryogenic regenerator.
(A) The carbon content of the magnetic regenerator material particles constituting the magnetic regenerator material particles is 0.1% by weight or less.
(B) The nitrogen content of the magnetic regenerator material particles constituting the magnetic regenerator material granule is 0.3% by weight or less.
(C) 70% by weight or more of the magnetic regenerator material particles constituting the magnetic regenerator material particles have a particle size in the range of 0.01 to 3.0 mm.
(D) General formula: RM _z (wherein R is at least one selected from Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb) R represents a rare earth element, M represents at least one metal element selected from Ni, Co, Cu, Ag, Al and Ru, and z represents a number in the range of 0.001 to 9.0, or a general formula: RRh (wherein R represents a rare earth element represented by Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb. Containing intermetallic compounds

Images