JP2845724B2 - Regenerator for cryogenic refrigerator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a regenerator for a cryogenic refrigerator, and more particularly, to a regenerator without using a Joule Thomson (JT) valve.
The present invention relates to a regenerator for a cryogenic refrigerator capable of achieving a cryogenic temperature of 0K or less.

[0002]

2. Description of the Related Art Stirling refrigerators, Gifford McMahon (GM) refrigerators and the like are known as cryogenic refrigerators.

In a Stirling refrigerator, a pulsating working gas pressure is generated by a compressor, and a displacer is reciprocated in the expander with a phase shift of 1/4 with respect to pressure fluctuation. A regenerator is provided in the displacer, and causes heat exchange between the working gas cooled by adiabatic expansion and the high-temperature high-pressure gas.

The GM refrigerator has valves on the high and low pressure sides of the compressor, adiabatically expands the working gas supplied to the expander at a high pressure, and recovers the working gas at a low pressure. Similar to the Stirling refrigerator, a displacer is provided in the expander, and a regenerator is provided in the displacer. In order to realize a lower temperature, a two-stage displacer (regenerator) is used.

[0005] As a cold storage material for refrigerators, the specific heat is high.
Copper and lead, which are easy to handle, are used. In order to increase the heat exchange rate, these metals are made spherical or wire mesh to increase the surface area, and are supported by a felt-like support material or a punching metal provided with a large number of through holes.

However, metals having a high specific heat at a relatively high temperature, such as copper and lead, have an extremely small specific heat in a temperature region of 10 K or less (hereinafter, referred to as a “cryogenic region”). Therefore, even if these regenerator materials are used, it is difficult to generate an extremely low temperature of 10K or less with a refrigerator including only a compressor and an expander using the regenerator material.

In order to obtain a very low temperature, conventionally, a configuration has been used in which a JT valve is used and the working gas supplied to the JT valve is cooled by a GM refrigerator or the like. In recent years, by using a regenerator material made of a magnetic intermetallic compound such as Er ₃ Ni for the second-stage regenerator of a two-stage GM refrigerator, a temperature lower than the liquid helium temperature (4.2 K) is generated. Became possible. This is because such a magnetic regenerator has a large specific heat due to a magnetic phase transition in an extremely low temperature region. For example, ErRh shows a very large specific heat peak near 4K. However, ErRh is very expensive and is difficult to put to practical use.

However, the specific heat of Er ₃ Ni is very small in a low temperature range as compared with the specific heat of helium as a refrigerant, and thus cannot be said to have a sufficient heat capacity for performing heat exchange with helium. Actually, even with a GM refrigerator using Er ₃ Ni, the refrigeration capacity actually achieved at 4.2 K is only 1 W or less. Therefore, in order to further improve the refrigerating capacity, a regenerator having a higher specific heat in an extremely low temperature region is desired.

The magnetic regenerator material has a large specific heat peak near the temperature at which the magnetic phase transition occurs. Therefore, a proposal has been made to stack magnetic regenerator materials having specific heat peaks at different temperatures in the regenerator in accordance with the temperature distribution of the regenerator.
The regenerator having such a structure is hereinafter referred to as a “stacked” regenerator.

However, in the cryogenic region, especially at 4.2K
Laminated regenerators that can improve the refrigeration capacity in the field have not yet been put to practical use.

[0011]

The cryogenic temperature range, especially
A regenerator capable of sufficiently improving the refrigerating capacity near 2K has not yet been developed.

An object of the present invention is to provide a cryogenic temperature region, particularly 4.2.
An object of the present invention is to provide a regenerator for a cryogenic refrigerator having a sufficient refrigerating capacity near K.

[0013]

SUMMARY OF THE INVENTION A regenerator for a cryogenic refrigerator according to the present invention has a configuration including two or more types of regenerator materials having different specific heat characteristics stacked in a temperature distribution direction. regenerator material is _{Er 1-x R x Ni 1} -yz Co y M z ( wherein, R is Dy, Ho, Gd, Tm or mixtures thereof, M is Mn, Cu, Al, Sb, Sn or mixtures thereof, 0 ≦ x ≦ 0.3, 0 <y ≦ 0.2, 0 ≦ z ≦
0.3, 0 <(1-yz) <1) as a main component.

[0014]

[Effect] Er _1-x R _x Ni _1-yz Co _y M _z (R is D
y, Ho, Gd, Tm or a mixture thereof, M is M
n, Cu, Al, Sb, or a mixture thereof, 0 ≦ x
≦ 0.3, 0 <y ≦ 0.2, 0 ≦ z ≦ 0.3, 0 <(1
-Yz) <1) the main component of the magnetic intermetallic compound is
The specific heat in the cryogenic region, especially around 4.2 to 12K, is large,
The refrigeration capacity of the cryogenic refrigerator can be greatly improved.

For example, ErNi _0.9 Co _0.1 or ErN
The specific heat of i _0.8 Co _0.2 is such that Er ₃ N
It has a specific heat peak about twice as large as i.

[0016]

FIG. 1 shows the configuration of a two-stage GM refrigerator according to an embodiment of the present invention. 1A is a cross-sectional view schematically illustrating a configuration of an expander, and FIG. 1B is a cross-sectional view schematically illustrating a configuration of a second-stage regenerator of the expander.

In FIG. 1A, a cylinder 11 has a large diameter portion and a small diameter portion, and a piston (displacer) 12 inserted into the cylinder 11 also has a large diameter portion and a small diameter portion adapted to the shape of the cylinder 11. With parts. In the piston 12, a first-stage regenerator 14 is accommodated in a large-diameter portion, and a second-stage regenerator 16 is accommodated in a small-diameter portion.

Between the cylinder 11 and the piston 12, a first expansion space 18 is defined at a large diameter portion, and a second expansion space 19 is defined at a small diameter portion. In addition, a seal 21 is arranged between the cylinder 11 and the piston 12 to form an airtight state.

The first-stage regenerator 14 contains, for example, a mesh-like regenerator made of a normal regenerator such as Cu or Pb. The second-stage regenerator 16 has a laminated structure as shown in an example in FIG.

As shown in FIG. 1B, the second stage regenerator 1
6 are upper and lower openings 2 in a bakelite container 23.
4 and 25 form a gas passage 26 continuous with the outside. In this gas passage 26, several wire meshes 31,
The felt 32 is filled and the cold storage material does not flow out from the lower opening 25.

On the felt 32, ErNi _0.9 Co
The low-temperature regenerator material 33 composed of _0.1 spherical particles, the felt 34, the second low-temperature regenerator material 35 formed of spherical particles of Er _0.5 Dy _0.5 Ni ₂ , the felt 36, and spherical particles of DyNi ₂ . The third low-temperature regenerative material 37 is filled in a laminated shape, and the upper surface thereof is covered with a felt 38 and a punching metal 39.

FIG. 2 shows the specific heat characteristics of the regenerator material of the second stage regenerator. FIG. 2A shows specific heat characteristics of Er _{1 -x} Dy _x Ni ₂ used for the second low-temperature cold storage material and the third low-temperature cold storage material, together with other compositions and specific heats of Pb and He. The specific heat characteristics of the conventionally used ErRh are also shown. The specific heat characteristic of the second low-temperature cold storage material 35 corresponds to the case of x = 0.5,
The specific heat characteristic of the third low-temperature cold storage material 37 corresponds to the case where x = 1.0.

As shown in the figure, at a temperature of about 20 K or lower, DyNi ₂ used for the third low-temperature regenerator material is Pb
Better than the specific heat. Er _0.5 Dy _0.5 Ni ₂ (x = 0.5) used for the second low-temperature cold storage material is 12.3.
It has a specific heat peak near K, and D
than yNi ₂ with good specific heat.

FIG. 2B shows specific heat characteristics of ErNi _0.9 Co _0.1 and related substances used for the lowest temperature regenerator material 33. The specific heat characteristic of ErNi _0.9 Co _0.1 is about 8K
From the vicinity, the temperature rises sharply toward the low temperature, and after the peak of the specific heat is drawn at around 6, 7 K, it decreases sharply toward the extremely low temperature.

When the composition of the cold storage material used as the lowest temperature cold storage material is changed to ErNi _0.8 Co _0.2 , the specific heat characteristic is further shifted to a lower temperature side. The characteristics of the specific heat characteristics of ErNi _x Co _1-x will become more apparent when compared with the specific heat characteristics of Er ₃ Ni and ErNi, which are conventionally proposed practical cryogenic cold storage materials. That is, the specific heat characteristic of ErNi is 10K.
It draws a sharp peak in the vicinity, but then falls sharply.

The specific heat characteristic of Er ₃ Ni shows a higher value than the specific heat of ErNi at a temperature higher than about 12K.
At around 6K, the specific heat is lower than that of ErNi, but at a lower temperature, the specific heat is almost the same as that of ErNi.

Therefore, when a single kind of regenerative material is used, when Er ₃ Ni is used, a specific heat characteristic better than Pb can be obtained in a low temperature region of approximately 30 K or less.
In a temperature region lower than about 6K, specific heat almost equal to that of ErNi can be obtained.

ErNi _0.9 Co _0.1 used in the above embodiment
Cold storage material is always E in the extremely low temperature range of about 8K or less.
It shows better specific heat characteristics than rNi or Er ₃ Ni. Compared with Er ₃ Ni, ErNi _0.9 Co _0.1 or ErNi in a very low temperature region of about 7.5 K or less.
The specific heat characteristic of _0.8 Co _0.2 shows a specific heat about twice as large as the specific heat of Er ₃ Ni.

Therefore, if the temperature of the working gas introduced into the lowest-temperature regenerator material is sufficiently cooled, the lowest-temperature regenerator material shows a remarkably large specific heat, and the working gas can be extremely efficiently cooled to a cryogenic temperature. it can.

As shown in FIG. 2A, the third low-temperature regenerative material and the second low-temperature regenerative material have a good specific heat in the vicinity of about 20 to 7K, and are cooled from the first-stage regenerator. Thus, the working gas supplied to the lowest temperature regenerator material can be cooled to about 7K or less.

When the working gas cooled to about 7K or less is received, since the lowest temperature regenerator material 33 has an extremely large specific heat, the working gas is efficiently cooled, for example, to 4.2K or less. Can also.

As described above, the E shown as an example
By using a cold storage material having a composition of rNi _x Co _1-x , a cold storage material having a good specific heat in an extremely low temperature region can be obtained. For this reason, in a refrigerator having a regenerator,
Extremely low temperatures can be easily realized.

It should be noted that ErNi _0.9 Co _0.1 and ErN
Although the explanation has been made by taking the cold storage material of i _0.8 Co _0.2 as an example, such specific heat characteristics are expressed by Er _{1 -x} R _x Ni _{1 -yz} Co _y M _z
(R is Dy, Ho, Gd, Tm or a mixture thereof,
M is Mm, Cu, Al, Sb, Sn, or a mixture thereof, provided that 0 ≦ x ≦ 0.3, 0 <y <1, 0 ≦ z ≦
It is considered that the same specific heat characteristics can be realized even at 0.3, 0 <(1-yz) <1).

With such a refrigerator using the cold storage material,
It is possible to replace the conventional refrigerator using Er ₃ Ni, and to use the refrigerator in equipment and facilities that had to be cooled by liquid helium because of the lack of the refrigerating capacity of the conventional refrigerator. Becomes For example, a cryogenic cooler can be used for cooling a superconducting electromagnet such as a linear motor, cooling a magnetic shield such as an MRI, and cooling an element such as a radio telescope.

The present invention has been described in connection with the preferred embodiments.
The present invention is not limited to these. For example,
It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[0036]

As described above, according to the present invention,
It is possible to provide a cryogenic refrigerator using a regenerator with an improved cooling capacity in a cryogenic region, particularly around 4.2K.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a two-stage GM refrigerator according to an embodiment of the present invention.

FIG. 2 is a graph showing specific heat characteristics of a cold storage material used in the GM refrigerator shown in FIG.

[Explanation of symbols]

 11 Cylinder 12 Piston 14 First-stage regenerator 16 Second-stage regenerator 18 First-stage expansion space 19 Second-stage expansion space 21 Seal 23 Container 24, 25 Opening 31 Wire mesh 32, 34, 36, 38 Felt 33, 35, 37 Cool storage material 39 Punched metal

──────────────────────────────────────────────────続 き Continuation of the front page (72) Atsushi Onishi 63-30 Yuyogaoka, Hiratsuka-shi, Kanagawa Sumitomo Heavy Industries, Ltd. Inside the Hiratsuka Laboratory (56) References JP-A-4-313648 (JP, A) JP-A-5-70768 (JP, A) JP-A-5-71816 (JP, A) JP-A-1-310269 (JP, A) JP-A-7-27434 (JP, A) (58) Fields investigated (Int) .Cl. ⁶ , DB name) F25B 9/00

Claims (2)

(57) [Claims] 1. A regenerator for a cryogenic refrigerator, comprising two or more types of regenerators stacked in a temperature distribution direction and having different specific heat characteristics, wherein the regenerator on the lowest temperature side is Er _{1. -x} R _x Ni _1-yz Co _y M _z (where R is D
y, Ho, Gd, Tm or a mixture thereof, M is M
n, Cu, Al, Sb, Sn or a mixture thereof, 0
≦ x ≦ 0.3, 0 <y ≦ 0.2, 0 ≦ z ≦ 0.3, 0 <
A regenerator for a cryogenic refrigerator having (1-yz) <1) as a main component. 2. The regenerator for a cryogenic refrigerator according to claim 1, wherein z = 0.