JP2003021414A - Cold storage type refrigeration machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that a cryogenic temperature of 2K or lower is hard to attain by the conventional cold storage type refrigeration machine. SOLUTION: A cold storage material made of GdAlO3 is packed in a displacer on the low temperature end side, and helium containing<3> He is used as a working fluid, for constituting the cold storage type refrigeration machine having a plurality of the displacers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold storage refrigerator, and more particularly to a cold storage refrigerator including a cylinder, a displacer inserted in the cylinder, and a cold storage material loaded in the displacer. .

[0002]

2. Description of the Related Art Gifford-McMahon refrigerators (hereinafter abbreviated as "GM refrigerators") are examples of cold storage refrigerators.
There are Stirling refrigerators, pulse tube refrigerators, and the like.

A cryopump is used to obtain a clean vacuum in a sputtering apparatus for manufacturing a semiconductor device, for example. As a refrigerator for this cryopump,
A GM refrigerator is used. Of course, the GM refrigerator is not limited to the cryopump and can be used for various purposes.

The GM refrigerator comprises a compressor and a cold head for expanding the working fluid supplied from the compressor to obtain cold. The cold head has a cylinder having a high temperature end and a low temperature end defined therein, and a displacer inserted into the cylinder and reciprocating.

For example, a cylinder in a two-stage GM refrigerator has two cylinder parts having different inner diameters.
These two cylinder parts are continuous in the axial direction of the cylinder. The inner diameter of the cylinder portion formed on the high temperature end side of the cylinder (hereinafter, this cylinder portion is referred to as “first cylinder portion”) is equal to the inner diameter of the cylinder portion formed on the low temperature end side (hereinafter, referred to as “second cylinder portion”) It is larger than the inner diameter of the cylinder part.

A displacer is inserted into each of the first cylinder portion and the second cylinder portion. Each displacer has a cylindrical container and a regenerator material loaded therein, and an opening for communicating the internal space and the external space of the cylindrical container is provided at both ends in the longitudinal direction of the cylindrical container. Is formed.

The displacer (hereinafter referred to as "first displacer") inserted in the first cylinder portion is the second displacer.
It reciprocates in the axial direction of the cylinder while leaving the first expansion space between the cylinder and the cylinder. A displacer inserted in the second cylinder portion (hereinafter, referred to as a "second displacer") is connected to the first displacer, and a second expansion space is left between the displacer and the low temperature end of the cylinder, and a shaft of the cylinder. Reciprocates in the direction.

In order to operate the GM refrigerator, it is necessary to supply the working fluid from the high temperature end of the cylinder into the cylinder at a predetermined timing and to discharge the working fluid supplied into the cylinder to the outside of the cylinder at a predetermined timing. There is.

Helium, for example, is used as the working fluid. For example, the first and second expansion spaces are narrowest when the working fluid is supplied into the cylinder, and the first and second expansion spaces are the largest when the working fluid is discharged to the outside of the cylinder.

The working fluid supplied into the cylinder is the first
It is distributed inside the displacer, the first expansion space, the inside of the second displacer and the second expansion space. When the working fluid is exhausted from the first and second expansion spaces, these first
And expansion of the working fluid occurs in the second expansion space. Due to this expansion, the temperatures in the first and second expansion spaces decrease.

By reciprocating the first and second displacers in the axial direction of the cylinder and supplying and discharging the working fluid under a predetermined phase difference from the reciprocating cycle, the first and second expansions are performed. The temperature in the space can be lowered to a predetermined temperature. The working fluid whose temperature has dropped due to expansion cools the regenerator material loaded inside each of the first and second displacers. As a result, the regenerator materials in the first and second displacers are gradually cooled, and eventually reach a substantially constant temperature.

For example, a three-stage GM refrigerator using a displacer in which a magnetic regenerator material is loaded using helium ( ⁴ He) having a mass number of 4 as a working fluid is 2.09.
An example of cooling to K is known.

By combining the GM refrigerator and the Joule Thomson (JT) valve mechanism, it is possible to obtain a cryogenic temperature of the order of 1.8K.

[0014]

For example, the ultimate pressure of the cryopump is significantly lowered because hydrogen can be exhausted when the cooling capacity of the refrigerator used is improved to, for example, 3K. If the cooling capacity of the refrigerator improves to around 2K, for example, it is expected that the pressure will drop even more rapidly. 10 ^-12 Torr (about 1.33 × 10 ^-10 P
There is a possibility that the ultimate pressure of a) can be realized. If the ultimate pressure of the cryopump is lowered, it becomes easy to obtain a high-quality compound semiconductor thin film by, for example, a molecular beam epitaxy (MBE) device.

For example, the critical current density in a superconducting magnet increases as the temperature of the superconducting magnet decreases. If the critical current density of the superconducting magnet increases, a larger magnetic field can be generated.

For these reasons, further improvement of the cooling capacity of the regenerator is desired.

An object of the present invention is to provide a regenerator having a relatively simple structure and capable of cooling to a lower temperature.

[0018]

According to one aspect of the present invention, there is provided a cylinder having a hot end and a cold end defined by:
A cylinder having a first cylinder part continuous from the high temperature end and a second cylinder part having an inner diameter smaller than the inner diameter of the first cylinder part and extending from the low temperature end to the high temperature end side; A first displacer that is inserted into a first cylinder part and is capable of reciprocating in the axial direction of the cylinder while leaving a first expansion space at the end of the first cylinder part on the side of the second cylinder part. And a first gas flow path from the space on the high temperature end side of the cylinder to the first expansion space via the inside in which the first cold storage material is loaded. A second displacer is inserted between the first displacer and the second cylinder portion, and a second gap is formed between the first displacer and the low temperature end.
A second displacer capable of reciprocating in the axial direction of the cylinder while leaving an expansion space, wherein a second regenerator material made of gadolinium aluminum oxide is loaded inside,
A second displacer having a second gas flow path from the first expansion space to the second expansion space via the inside filled with the second regenerator material, and a space on the high temperature end side of the cylinder. And a gas compressor for supplying a working fluid made of helium containing ³ He and recovering the working fluid from the space on the high temperature end side.

[0019] Here, the referred to herein as "helium containing ³ He", another meaning helium (He) containing only the mass number 3 helium ⁽³ He) except for unavoidable impurities, ³ It also means a mixture of ⁴ He and ³ He in which the content of He is artificially increased from the content in nature.

Conventionally used as a working fluid ⁴
When He is cooled to about 2.17 K under atmospheric pressure, it undergoes a phase transition to a superfluid state. The thermal expansion coefficient of ⁴ He that has undergone a phase transition to a superfluid state is zero or a negative value. Therefore,
It is theoretically not possible for the temperature to be further reduced by adiabatic thermal expansion.

For this reason, it is difficult to obtain a cryogenic temperature of 2 K or less by using the conventional regenerator with ⁴ He as a working fluid.

On the other hand, for example, the thermal expansion coefficient of ³ He is
It has a positive value from the high temperature side to around 1K.

Therefore, by using helium containing ³ He as the working fluid, it is possible to obtain a cold storage refrigerator having a lower ultimate temperature than when ⁴ He is used as the working fluid.

By using a gadolinium aluminum oxide regenerator material as a part of the regenerator material loaded in the second displacer, the reached temperature can be further lowered.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 schematically shows the structure of a cold storage refrigerator according to an embodiment. The illustrated regenerator 100
Is a cold head 5 that expands the working fluid to obtain cold
0, and a compressor 60 that supplies the working fluid to the cold head 50 and recovers the working fluid from the cold head 50.

The cold head 50 comprises a two-stage cylinder 1 having a high temperature end and a low temperature end defined therein, and first and second displacers 10, 30 inserted into the cylinder 1.
Have and.

The cylinder 1 has two cylinder portions which are continuous in the axial direction, that is, a first cylinder portion 1a and a second cylinder portion 1b. First and second cylinder part 1
Both a and 1b have a cylindrical shape, and are made of a rigid material such as stainless steel having a low thermal conductivity and a high airtightness. The inner diameter of the first cylinder portion 1a is larger than the inner diameter of the second cylinder portion 1b.

At one end (high temperature end) of the first cylinder portion 1a,
The top flange 3 is fixed. At one end of the second cylinder portion 1b on the side of the first cylinder portion 1a, a first cooling stage 5 made of a material having good thermal conductivity such as copper.
Is fixed, and the other end of the first cylinder portion 1a is connected to the first cooling stage 5. The other end (low temperature end) of the second cylinder portion 1b is closed by a second cooling stage 7 made of a material having good thermal conductivity such as copper.

The first displacer 10 is inserted into the first cylinder portion 1a, and is placed between the first displacer 10 and the second cylinder portion 1b.
It reciprocates in the axial direction of the cylinder 1 while leaving the expansion space S1. This first displacer 10 is, for example, a cylindrical container 11 made of cloth-containing phenol resin.
And a first regenerator material loaded in the cylindrical container 11 and function as a regenerator.

The cylindrical container 11 has a plurality of openings 11a penetrating the container wall facing the high temperature end of the cylinder 1 and a plurality of openings 11b penetrating the side wall at the end on the first expansion space S1 side. Have. Multiple openings 11a
The inner space of the first displacer 10 (cylindrical container 11) and the plurality of openings 11b make the space S3 on the high temperature end side in the cylinder 1 communicate with the first expansion space S1.
Of the gas flow path.

The first regenerator material loaded in the cylindrical container 11 is, for example, a lead (Pb) ball or a metal mesh (wire mesh). In the illustrated example, a predetermined amount of lead (Pb) balls 13 as a regenerator material is loaded on the second cylinder portion 1b side, and a predetermined amount of copper wire net 17 as a regenerator material is loaded on it via a partition material 15. ing.

The seal member 20 is the first displacer 1
It is provided on the outer periphery of 0. The seal member 20 prevents the working fluid from flowing through the gap between the outer peripheral surface of the first displacer 10 and the inner peripheral surface of the first cylinder portion 1a.

The second displacer 30 includes a connecting member 25.
Is connected to the bottom surface of the first displacer 10 and is inserted into the second cylinder part 1b, and the second expansion space S2 is left between the low temperature end closed by the second cooling stage 7 and the axial direction of the cylinder 1. Move back and forth. The second displacer 30 has, for example, a cylindrical container 31 made of a composite material having stainless steel and a resin layer adhered to the outer surface thereof, and a cool storage material loaded in the cylindrical container 31. And functions as a regenerator.

The cylindrical container 31 has a plurality of openings 31a penetrating the side wall at the end on the first cylinder portion 1a side and a plurality of openings penetrating the side wall at the end on the second expansion space S2 side. 31b. Multiple openings 3
1a, the inner space of the second displacer 30 (cylindrical container 31), and the plurality of openings 31b form the first expansion space S.
The 2nd gas flow path which connects 1 and the 2nd expansion space S2 is constituted.

The regenerator material loaded in the cylindrical container 31 includes a regenerator material made of gadolinium aluminum oxide, which is one type of magnetic regenerator material. In this example, crushed powder of GdAlO ₃ (hereinafter, referred to as “GdAlO ₃ cold storage material 33”) was used as the cold storage material made of gadolinium aluminum oxide.

A predetermined amount of this GdAlO ₃ regenerator material 33 is loaded into the second expansion space S2, and a HoCu ₂ regenerator material 35, which is one kind of magnetic regenerator material, is placed on the second regenerator space S2 through a partition member 34.
Is loaded in a predetermined amount, and a lead ball 37 as a regenerator material is further loaded in a predetermined amount through the partition member 36.

A groove having a width of 1.5 mm and a depth of 1 mm is formed on the outer peripheral surface of the second displacer 30, for example. The grooves are spirally formed, for example, at a pitch of 3 mm to form one groove pattern 38.

Incidentally, in FIG. 1, for convenience, the cylindrical container 11 and the cylindrical container 31 are drawn as one member. However, in reality, each of the cylindrical containers 11 and 31 has a plurality of members, for example, one tubular body and one open end of each of the two tubular ends, for convenience of loading the cold storage material therein. It is composed of two lid members that are fixed to each other.

The power chamber 40 is arranged on the top flange 3 with a space S3 formed between the power chamber 40 and the first displacer 10. The motor M is arranged in the power chamber 40, and the rotation shaft of the motor M and the first displacer 10 are connected via the crank 42. The motor M generates power for reciprocating the first displacer 10 and the second displacer 30 in the cylinder 1.

The compressor 60 includes a compressor body 65 for compressing the working fluid, and a cold head 50 from the compressor body 65.
Supply / exhaust means for controlling the supply of the working fluid to and the discharge of the working fluid from the cold head 50.

The illustrated regenerator 100 has a rotary valve device V as a supply / exhaust means. The rotary valve device V includes an intake valve V1 and an exhaust valve V2, is arranged in the power chamber 40, and receives power from the motor M, for example.

A pipe 70 is connected to one end of each of the intake valve V1 and the exhaust valve V2. One end of the pipe 70 is connected to an intake / exhaust port 45a formed at the bottom of the housing 45 that defines the power chamber 40.

At the other end of the intake valve V1, the working fluid supply pipe 7 for receiving the compressed working fluid from the compressor body 65.
3 are connected. At the other end of the exhaust valve V2, a working fluid recovery pipe 7 is supplied with the working fluid discharged from the cylinder 1.
5 is connected.

The working fluid compressed by the compressor body 65 is
It is supplied from the intake / exhaust port 45a into the cylinder 1 through the working fluid supply pipe 73, the rotary valve device V (intake valve V1) and the pipe 70.

The working fluid supplied into the cylinder 1 is a space S3, each opening 11a, inside the first displacer 10 (cylindrical container 11), each opening 11b, the first expansion space S1,
Each opening 31a, second displacer 30 (cylindrical container 3
The second expansion space S3 is reached through the inside of 1) and through each opening 31b.

When the exhaust valve V2 is opened, the working fluid in the cylinder 1 is discharged to the outside of the cylinder 1 by following the route opposite to that at the time of introduction, and the compressor main body 65 is discharged through the exhaust valve V2 and the working fluid recovery pipe 75. Be recovered to.

The intake air is supplied so that the supply of the working fluid into the cylinder 1 and the recovery of the working fluid from the cylinder 1 are performed with the reciprocating motion of the first and second displacers 10 and 30 under a predetermined phase difference. It controls the operation of the valve V1 and the exhaust valve V2. As a result, the first cooling stage 5 and the second cooling stage 7 can be cooled.

As the working fluid, ³ He or ³ He is used.
And a mixture of ⁴ He and ⁴ He is used. This working fluid is, for example, 15 to 20 kgf / cm depending on the compressor body 65.
² G (“G” in the pressure unit means that the pressure indicated in this unit is a gauge pressure). By setting the atomic ratio of ³ He in the working fluid to approximately 0.4 or more, it becomes easy to obtain a cryogenic temperature of, for example, 4 K or less.

In order to evaluate the performance of the cold storage type refrigerator 100 according to the example, the following tests I to III were conducted. Test I The reaching temperature of each of the first cooling stage 5 and the second cooling stage 7 was measured using ³ He as a working fluid. At this time, the cold head 50 and the compressor body 6
The specifications of 5 are the specifications shown in (1) to (12) below, and (13) to
The regenerator was operated under the conditions shown in (17). (1) 1st cylinder part 1a; inner diameter 52mm, length (inner dimension)
191.5mm (2) 2nd cylinder part 1b; inner diameter 25mm, length (inner dimension)
165 mm (3) First displacer 10; inner diameter 38 mm (4) Second displacer 30; inner diameter 21 mm (5) Lead ball 13; particle size 0.4 to 0.48 mm, total amount 120
g (6) Copper wire mesh 17; 180 mesh, 450 sheets used (7) Regenerator material 33 made of GdAlO ₃ ; Grain size 0.2 to 0.5 m
Milled powder, total amount 47.3g (8) HoCu ₂ regenerator material 35; particle size 0.2-0.5mm
90 g (9) Lead ball 37; particle size 0.4 to 0.48 mm, total amount 150
g (10) Stroke of reciprocating motion of the first and second displacers 10, 30; 20 mm (11) Cycle of reciprocating motion of the first and second displacers 10, 30; 48-96 times / min (12) Compressor body 65; CK manufactured by Sumitomo Heavy Industries, Ltd.
W21 (However, in order to reduce the amount of ³ He used, change the adsorber to a smaller one) (13) Opening / closing timing of intake valve V1 and exhaust valve V2; highest performance is obtained when ⁴ He is used as the working fluid. (14) ³ He loading pressure; 15.3 kgf / cm ² G (15) Compressor body 65 operating conditions; power consumption is approximately 2.5
Conditions for kW (16) Heat load to the first cooling stage 5: None (17) Heat load to the second cooling stage 7: None For comparison, instead of the GdAlO ₃ regenerator material 33, Nd was used.
A cold storage refrigerator having the same configuration was manufactured except that a total amount of InCu ₂ cold storage material (crushed powder having a particle size of about 0.2 to 0.5 mm) was used in an amount of 47.2 g. It was measured.

The temperature reached by the first cooling stage 5 is
The temperature was measured using a platinum-cobalt thermometer arranged outside thereof, and the temperature reached by the second cooling stage 7 was measured using a germanium thermometer arranged outside thereof.

The results of these measurements are shown in FIG. In FIG. 2, the upper two lines show the reached temperature of the first cooling stage 5, and the lower two lines show the reached temperature of the second cooling stage 7.

As is clear from the figure, in the cold storage type refrigerator using either the cold storage material 33 made of GdAlO _{3 or the} cold storage material made of NdInCu ₂ , the second cooling stage 7 is set to about 2K or lower than 2K. It was able to cool.

When the cycle of the reciprocating motion of the first to second displacers 10, 30 is 48 to 96 times / minute, the second cooling stage 7 is increased according to the lengthening of this cycle (reducing the number of reciprocating motions per minute). There is a tendency that the temperature reached by

For example, in the regenerator 100 using the GdAlO ₃ regenerator material 33, the reciprocating motion of the first and second displacers 10 and 30 of the second cooling stage 7 is set to 96 times / minute. The ultimate temperature is 2.02K,
If the cycle is set to 48 times / minute, the second cooling stage 7
The temperature reached is reduced to 1.49K.

If the cycle of the reciprocating motion of the first and second displacers 10 and 30 is made longer than 84 times / minute, GdAl
In the cold storage type refrigerator 100 using the cold storage material 33 made of O ₃ ,
Compared with a cold storage refrigerator using a cold storage material made of dInCu ₂ ,
The second cooling stage 7 can be cooled to a lower temperature. Test II The reciprocating cycle of the first and second displacers 10 and 30 was fixed at 60 times / min, and the magnitude of the heat load applied to the second cooling stage 7 was changed variously, and the other conditions were the same as in Test I. Then, the relationship between the temperature reached by the second cooling stage 7 and the magnitude of the heat load was examined. The results are shown in Fig. 3.

The heat load on the second cooling stage 7 is
A manganin (trademark) wire was wound around the outer periphery of the second cooling stage 7, and this was used as an electric heater.

As is apparent from FIG. 3, in the regenerator 100 using the GdAlO ₃ regenerator material 33, NdIn
The cooling capacity of the second cooling stage 7 is higher than that of a cold storage refrigerator using a cold storage material made of Cu ₂ . For example, even when a heat load of about 91.2 mW is applied to the second cooling stage 7,
The ultimate temperature of the second cooling stage 7 can be set to 2K. Test III The cycle of reciprocating motion of the first and second displacers 10 and 30 was variously changed between 48 to 66 times / minute, and the magnitude of the heat load applied to the second cooling stage 7 was variously adjusted. Similar to Test II, the relationship between the cooling capacity of the second cooling stage 7 at 2K and the cycle of the reciprocating motion of the first and second displacers 10 and 30 was investigated. The results are shown in Fig. 4.

As is apparent from FIG. 4, the regenerator 100 using the GdAlO ₃ regenerator material 33 has a high cooling capacity, and the reciprocating cycle of the first and second displacers 10 and 30 is long. At 48 to 66 times / minute, the ultimate temperature of the second cooling stage 7 can be maintained at 2K even if a thermal load of 90 mW or more is applied. This cooling capacity is NdI
It is about 1.6 times or 1.7 times that of a cold storage refrigerator using a cold storage material made of nCu ₂ .

The cooling capacity of the regenerator 100 using the GdAlO ₃ regenerator material 33 is such that when the reciprocating cycle of the first and second displacers 10 and 30 is 48 to 66 times / minute. Tends to increase as is shortened.

The reason why the cooling capacity of the cold storage type refrigerator 100 using the GdAlO ₃ cold storage material 33 is higher than that of the cold storage type refrigerator using the NdInCu ₂ cold storage material is that the specific heat characteristics of these cold storage materials are different. It is presumed to be in.

In FIG. 5, GdAlO ₃ , NdInCu ₂
The characteristic of the volume specific heat of (intermetallic compound) and HoCu ₂ (intermetallic compound) is shown.

As shown in the figure, NdInCu ₂ is 2K
Although there is a peak of volume specific heat associated with the phase transition to the antiferromagnetic state in the vicinity, this peak is relatively small and the value of volume specific heat itself is also small. On the other hand, the volume specific heat of GdAlO ₃ has an extremely large peak around 3.8 K due to the magnetic transition, and its value exceeds 0.9. GdA
The volume specific heat of 10 ₃ is at least 5 K or less,
Higher than NdInCu ₂ .

Therefore, GdAlO _{3 is} used as the magnetic regenerator material.
The cooling capacity of the regenerator 100 using GdAlO is
It is estimated that the volumetric heat of HoCu ₂ has one peak at around 6.5K, which is higher than that of the cold storage refrigerator using NdInCu ₂ instead of _3.
It gradually decreases as the temperature becomes lower than the vicinity.

Although the cold storage type refrigerator according to the embodiments has been described above, the present invention is not limited to these embodiments.

For example, although the regenerator of the embodiment is a two-stage GM refrigerator, it may be a multi-stage GM refrigerator of three or more stages, or a Stirling refrigerator of two or more stages. May be.

Furthermore, a one-stage GM refrigerator or one
In a multi-stage Stirling refrigerator, a regenerator (displacer) in which a cold storage material made of gadolinium aluminum oxide is loaded on the low temperature end side is used, and a working fluid made of helium containing ³ He is used to reach the cooling stage. It is possible to lower the temperature.

In the case of constructing a three-stage GM or Stirling refrigerator, the first regenerator (first displacer) arranged on the high temperature end side and the second regenerator arranged on the low temperature end side are arranged.
In the regenerator (second displacer) and in the third regenerator (third displacer) arranged between them,
For example, the regenerator material can be loaded in the following manner. (1) First Regenerator (First Displacer) For example, similarly to the first displacer 10 in the regenerator 100 according to the embodiment, a lead ball is loaded on the low temperature end side and a copper wire mesh is loaded on the high temperature end side. It is also possible to load only a copper wire mesh. (2) Second Regenerator (Second Displacer) For example, similarly to the second displacer 30 in the regenerator 100 according to the embodiment, gadolinium aluminum oxide is loaded on the low temperature end side and HoCu ₂ is loaded on the high temperature end side. Ho
ErNi _0.9 Co _0.1 can be loaded instead of Cu ₂ .

In addition, gadolinium aluminum oxide, HoCu ₂ , and Er _0.7 Ho in this order from the low temperature end side.
Or loading _0.3 Ni, gadolinium aluminum oxide, can also be loaded ErNi _0.9 Co _0.1, and Er _0.7 Ho _0.3 Ni. (3) Third Regenerator (Third Displacer) Er _0.7 Ho _0.3 Ni or Er ₃ Ni or the like is loaded on the low temperature end side, and lead balls are loaded on the high temperature end side. It is also possible to load only lead balls.

The gadolinium aluminum oxide used as the regenerator material is not limited to the oxide represented by the formula GdAlO ₃ . The ratio of Gd atom and Al atom can be variously changed within the range of 10 to 20 at%. However, the total proportion of Gd atoms and Al atoms is preferably 40 at%.

In the second displacer 30 (see FIG. 1), a GdAlO ₃ regenerator material is loaded on the second cooling stage 7 side, and on top of that, HoCu _{2 has} a volume specific heat larger than GdAlO ₃ at 4 K or more. It is preferable to load the magnetic regenerator material. Instead of HoCu ₂ , for example ErNi
It is also possible to use _0.9 Co _0.1 , Er ₃ Ni, or the like.

The uppermost portion of the second displacer 30 (first
The regenerator material loaded on the displacer 10 side is not limited to lead balls, but Er ₃ Ni, Er _0.7 Ho _0.3 Ni
It is also possible to use a magnetic regenerator material such as.

In the regenerator according to the embodiment, three layers of regenerator material are loaded in the second displacer 30, and the gadolinium aluminum oxide is used in accordance with the temperature distribution in the second displacer 30 during operation. It is also possible to load only the regenerator material in the second displacer 30. It is also possible to load the regenerator material in two or four layers in the second displacer 30.

On the low temperature end side (first cooling stage 5 side) of the first displacer 10, the first cooling stage 5 is provided.
The magnetic regenerator material having the highest specific heat at that temperature can be loaded in accordance with the reached temperature of. At this time, it is desirable to stack and load a plurality of types of cold storage materials for each type,
Depending on the combination of the cold storage materials, it is also possible to mix and load them. Instead of the copper wire mesh 17 shown in FIG. 1, a stainless wire mesh or the like may be used.

The shape of the regenerator material, except for the regenerator material in the form of wire mesh, may be indefinite like crushed powder, but it is more preferable that it be spherical with a particle size of 0.2 to 0.5 mm. preferable. Further, it may be molded into pellets.

As described in the specification of Japanese Patent No. 2659684, by forming a groove pattern on the outer circumference of the displacer, the groove pattern including grooves along a direction intersecting the axial direction of the displacer. The cooling capacity and the stability of the cooling capacity can be improved. This groove pattern, as shown in FIG.
It is preferably formed on the outer periphery of the displacer 30.
However, formation of the groove pattern is not an essential requirement.

By using helium containing ³ He as the working fluid, even when the groove pattern is not formed on the outer circumference of the displacer, it can be cooled to a temperature lower than that of the conventional regenerator having the same structure. It is possible. Helium containing ³ He is particularly useful as a working fluid for obtaining a cryogenic temperature of about 4 K or less.

When a mixture of ³ He and ⁴ He is used as a working fluid to obtain a cryogenic temperature of 2 K or less, ³ H
it is considered preferable to e and the atomic ratio ³ the He / ⁴ He and ⁴ He in a generally 0.4 or more. ^{Since 3} He is expensive, by using a mixture of ³ He and ⁴ He, it will be possible to provide a regenerator with a cryogenic temperature of 2 K or less at a lower cost.

The cooling capacity of the regenerator 100 shown in FIG. 1 is not so remarkable, but has an installation angle dependency. When the installation angle when the cold head 50 is installed so that the second expansion space S2 is located vertically below the first expansion space S1 is 0 ° and the opposite is 180 °, the installation is performed at 0 ° or 180 °. It is preferable to use. For example, when installed at 90 °, the cooling capacity may decrease by 10% or more. However, it is possible to obtain a cryogenic temperature of 2K or less regardless of the installation angle.

It will be apparent to those skilled in the art that various other modifications, improvements, combinations and the like are possible.

[0080]

As described above, according to the present invention,
It is possible to provide a regenerator having a relatively simple structure and capable of cooling to a lower temperature.

[Brief description of drawings]

FIG. 1 is a schematic view showing a cold storage refrigerator according to an embodiment.

FIG. 2 is a graph showing the results of test I.

FIG. 3 is a graph showing the results of test II.

FIG. 4 is a graph showing the results of test III.

FIG. 5: GdAlO ₃ , NdInCu ₂ and HoCu
₃ is a graph showing the characteristic of volume specific heat of ₂ .

[Explanation of symbols]

1 ... Cylinder, 1a ... 1st cylinder part, 1b ... 2nd
Cylinder part, 5 ... First cooling stage, 7 ... Second cooling stage, 10 ... First displacer, 30 ... Second
Displacer, 33 ... GdAlO ₃ made regenerator material, 5
0 ... cold head, 60 ... compressor, 65 ... compressor body, 100 ... cooling type refrigerator.

Claims (4)

[Claims] 1. A cylinder in which a high temperature end and a low temperature end are defined, the first cylinder portion being continuous from the high temperature end,
A cylinder having an inner diameter smaller than that of the first cylinder portion and having a second cylinder portion extending from the low temperature end to the high temperature end side; and a first cylinder inserted into the first cylinder portion, A first displacer capable of reciprocating in the axial direction of the cylinder while leaving a first expansion space at the end of the second cylinder portion side inside the cylinder, the first cool storage material being loaded inside the cylinder. From the space on the high temperature end side of the first expansion space to the first expansion space via the interior filled with the first cold storage material
And a second displacer that is inserted into the second cylinder portion and is capable of reciprocating in the axial direction of the cylinder while leaving a second expansion space between the low temperature end and the first displacer. A second regenerator material made of gadolinium aluminum oxide is loaded inside, and the second regenerator space is passed from the first expansion space to the second expansion space via the interior where the second regenerator material is loaded. A second displacer having a gas flow path, and a gas compressor for supplying a working fluid made of helium containing ³ He to the space on the high temperature end side of the cylinder and recovering the working fluid from the space on the high temperature end side. Regenerative refrigerator with and. 2. The cold storage refrigerator according to claim 1, wherein the atomic ratio of ³ He in the working fluid is 0.4 or more. 3. The second cool storage material, the HoC, inside the second displacer, in order from the second expansion space side.
The cold storage refrigerator according to claim 1 or 2, which is loaded with a cold storage material made of u ₂ and a cold storage material made of lead. 4. A groove pattern formed on the outer peripheral surface of the second displacer, the groove pattern including grooves extending in a direction intersecting the axial direction of the second displacer. The regenerator according to any one of 1.