JP2001336849A - Cold storage freezer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem with a prior art GM freezer in which it is difficult to obtain very low temperature of 2K or lower. SOLUTION: A cold storage freezer is provided, which comprises a cylinder and a displacer inserted into the cylinder, the displacer containing a cold storage member therein. As a working fluid use is made of that comprising He including 3He.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art The regenerative refrigerators include Gifford McMahon refrigerators (hereinafter abbreviated as "GM refrigerators").
There are a Stirling refrigerator, a pulse tube refrigerator and the like.

[0003] For example, when it is desired to obtain a clean vacuum with a sputtering apparatus for manufacturing semiconductor devices, a cryopump is used. In recent years, as a cryopump refrigerator,
A GM refrigerator is used. Of course, the GM refrigerator is not limited to a cryopump and can be used for various purposes.

[0004] The GM refrigerator includes a cylinder, a displacer inserted in the cylinder, and a cold storage material charged in the displacer.

[0005] The cylinder in the two-stage GM refrigerator is
It has two cylinder portions having different inner diameters. These two cylinder portions are continuous in the axial direction of the cylinder. One end of one of the cylinder portions (hereinafter, referred to as “first-stage cylinder portion”) is closed. The working fluid is supplied from the other cylinder section (hereinafter, referred to as “second cylinder section”). Usually, the inner diameter of the first-stage cylinder is smaller than the inner diameter of the second-stage cylinder.

A displacer is inserted into each of the first-stage cylinder portion and the second-stage cylinder portion. Each displacer is a cylindrical container-like member, and has openings formed at both ends in the longitudinal direction for communicating the internal space with the external space. A cool storage material is charged in the internal space of each displacer.

[0007] A displacer inserted into the first-stage cylinder portion (hereinafter, referred to as a "first displacer").
Forms a first expansion space with the closed end of the cylinder. The displacer inserted into the second-stage cylinder portion (hereinafter, referred to as “second displacer”) is provided with a second heat at the end of the second-stage cylinder portion on the side of the first-stage cylinder portion. Form an expansion space. First
The second displacer and the second displacer are connected to each other, and are disposed so as to be able to reciprocate in the axial direction of the cylinder.

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

As the working fluid, for example, helium is used. The working fluid is supplied into the cylinder when, for example, the first and second displacers are driven in a direction to narrow the first and second expansion spaces. The working fluid supplied into the cylinder is distributed to the internal space of the second displacer, the second expansion space, the internal space of the first displacer, and the first expansion space.

[0010] The working fluid in the cylinder is discharged out of the cylinder when the first and second displacers are driven in a direction to expand the first and second expansion spaces, for example.

[0011] With the expansion of the first and second expansion spaces, the working fluid expands in the first and second expansion spaces. The GM refrigerator is configured such that the expansion is adiabatic expansion, and obtains cold by utilizing the adiabatic expansion of the working fluid.

The working fluid, whose temperature has been lowered by the adiabatic expansion, cools the cold storage material inserted in the internal space of each of the first and second displacers.

By reciprocating the first and second displacers in the axial direction of the cylinder, adiabatic expansion of the working fluid repeatedly occurs in the first and second expansion spaces. As a result, the regenerator material in the first and second displacers is gradually cooled and eventually reaches a substantially constant temperature.

[0014] used as such as helium ⁴ (4 He) a working fluid, a three-stage type GM refrigerator using displacer magnetic regenerator material is charged into the inside, is known example cooling to 2.09K ing.

If a GM refrigerator is combined with a Joule Thomson (JT) valve mechanism, a very low temperature of the order of 1.8K can be obtained.

[0016]

The ultimate pressure of a cryopump, for example, can be significantly reduced because hydrogen can be exhausted when the cooling capacity of a refrigerator to be used is increased to, for example, about 3K. When the cooling capacity of the refrigerator is improved to, for example, about 2K, the pressure is expected to ^decrease more rapidly, and it is possible to achieve the ultimate pressure of 10 ^-12 Torr (about 7.5 × 10 ^-9 Pa). . If the ultimate pressure of the cryopump is reduced, it becomes easy to obtain a high-quality compound semiconductor thin film by, for example, a molecular beam epitaxy (MBE) apparatus.

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

[0018] For these reasons, it is desired to further improve the cooling capacity of the regenerative refrigerator.

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

[0020]

According to one aspect of the present invention, there is provided a cylinder having one end closed, and a first cylindrical container-shaped displacer inserted into the cylinder.
An opening formed at each of both ends in the longitudinal direction to communicate the internal space and the external space, and a cold storage material charged into the internal space, a first portion between the closed end of the cylinder and a first displacer that is reciprocally disposed while forming a first expansion space in the axial direction of the cylinder, a working fluid supplied into the cylinder, ³
A regenerative refrigerator including He and a working fluid composed of He is provided.

Here, “H containing ³ He” referred to in this specification is used.
e "means helium 3 ( ³ H
Another meaning helium (He) comprising e) only, ³ the He
Artificially higher than natural content
⁴ also refers to a mixture of He and ³ He.

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

For this reason, it is difficult to obtain an extremely low temperature of 2 K or less using a conventional regenerative refrigerator using ⁴ He as a working fluid alone.

On the other hand, for example, ³ He has a positive coefficient of thermal expansion up to a lower temperature range than ⁴ He. Thermal expansion coefficient of ³ He has a positive value over the high temperature side to the vicinity of 1K.

Therefore, by using a working fluid composed of He containing ³ He, it is possible to obtain a regenerative refrigerator having a higher cooling capacity than when using ⁴ He as a working fluid.

[0026]

FIG. 1 schematically shows the configuration of a regenerative refrigerator 100 according to an embodiment. This regenerative refrigerator 100 is a two-stage GM refrigerator in which an expander 50 includes a cylinder 1 and two displacers 10 and 20 inserted in the cylinder. The regenerative refrigerator 100 includes a compressor 60 in addition to the expander 50.

The cylinder 1 has two cylinder portions that are continuous in the axial direction, that is, a first-stage cylinder portion 1a and a second-stage cylinder portion 1b. In addition, a cooling stage 1c made of copper for closing one end of the first-stage cylinder portion 1b side is provided.

First-stage and second-stage cylinder portions 1
In (a) and (1b), the cross section in the direction orthogonal to the axis has an annular shape. These cylinder portions 1a and 1b are formed of a rigid material having low thermal conductivity such as stainless steel and high airtightness, and have different inner diameters.

In the illustrated cylinder 1, the first-stage cylinder portion 1a and the second-stage cylinder portion 1b are separate members, but these two cylinder portions 1a, 1b
Can also be integrally formed. One end of the cylinder 1 can be closed by a member other than the copper cooling stage 1c.

A radiation shield plate, not shown, is attached to the outside of the second-stage cylinder portion 1b. The radiation shield plate reduces radiation from the room temperature to the first-stage cylinder portion 1a.

The first displacer 10 includes a cylinder 1
The first expansion space 30 is formed between the first expansion space 30 and the closed end (the inner surface of the cooling stage 1c).
It is inserted into the cylinder part 1a of the stage.

The first displacer 10 includes a cylindrical portion 10a formed of, for example, a stainless steel tube and a resin layer fixed to the outer surface thereof, a lid member 10b fitted to one end of the cylindrical portion 10a, It is a cylindrical container-shaped member having a lid 10c fitted to the other end of the cylindrical portion 10a.

The outer circumference of the cylindrical portion 10a has a width of 1.5 mm,
Many grooves having a depth of 1 mm are formed. These grooves are spirally formed at a pitch of 3 mm and constitute one groove pattern 11.

An opening (a plurality of holes) 12a is formed at the end of the cylindrical portion 10a on the side where the lid 10b is fitted, and is formed at the end on the side where the lid 10c is fitted. Has an opening (a plurality of holes) 12b.

In the internal space of the first displacer 10, the magnetic cold storage material layers 1 are sequentially arranged from the first expansion space 30 side.
5 and lead (Pb) cold storage material layer 16 are formed.

The second displacer 20 forms the second expansion space 31 at the end of the second-stage cylinder portion 1b on the side of the first displacer 10 so that the second expansion space 31 is formed.
It is inserted into the cylinder part 1b of the stage.

The second displacer 20 includes, for example, a cylindrical portion 20a made of phenol resin containing cloth, a lid member 20b fitted to one end of the cylindrical portion 20a, and a lid member fitted to the other end of the cylindrical portion 20a. 20c. An opening (a plurality of holes) 22 is formed at the end of the cylindrical portion 20a on the side where the lid member 20b is fitted. The opening (a plurality of (three in total) holes) 23 is
Is formed.

In the internal space of the second displacer 20, a lead (Pb) cold storage material layer 25 is formed on the second expansion space 31 side, and a number of copper wire meshes 26 as a cold storage material are laminated thereon. ing.

A seal member 28 is provided on the outer periphery of the second displacer 20. This sealing member 28
The working fluid is prevented from flowing through the gap between the outer peripheral surface of the second displacer 20 and the inner peripheral surface of the second cylinder portion 1b.

First and second displacers 10, 2
0 are connected to each other by a connecting member 35. The displacer 20 is connected to the power chamber 4 via the connecting member 36.
0 is connected to the rotating shaft of the motor M arranged at zero.

The power chamber 40 is fixed on a flange 41 provided at one end of the cylinder 1. The motor M is
A power for reciprocating the first and second displacers 10 and 20 in the axial direction of the cylinder 1 is generated. The connecting member 36 has a function as a crank.

In the power chamber 40, two valves V1, V
2 is provided with a rotary valve device V provided with a rotary valve 2.
The rotary valve device V is supplied with power from, for example, the motor M described above.

A pipe 45 is connected to one end of each of the valves V1 and V2, and a working fluid supply pipe 61 or a working fluid recovery pipe 62 described later is connected to each other end. One end of the pipe 45 is connected to an opening 42 a formed at the bottom of the housing 42 that defines the power chamber 40.

When operating the regenerative refrigerator 100,
The working fluid is supplied into the expander 50 (cylinder 1) at a predetermined timing, and the working fluid supplied into the expander 50 (cylinder 1) is supplied at a predetermined timing.
(Cylinder 1) is discharged outside. Therefore, the regenerative refrigerator 100 during operation contains the working fluid.

The timing of supplying the working fluid into the cylinder 1 and the timing of discharging the working fluid outside the cylinder 1 can be controlled by, for example, a rotary valve device V.

As the working fluid, for example, approximately 15 to 2
³ He or ³ H pressurized to 0 kgf / cm ² G
A mixed gas of e gas and ⁴ He gas is used.

In the regenerative refrigerator 100, a compressor 60 for pressurizing (compressing) the working fluid is provided outside the expander 50.

The working fluid pressurized by the compressor 60 is supplied to a working fluid supply pipe 61 through a rotary valve device V (a valve V).
1) and is supplied into the cylinder 1 through an opening 42a formed in the housing 42 via a pipe 45.

The working fluid supplied into the cylinder 1 reaches the inside of the second displacer 20, the second expansion space 31, the first displacer 10, and the first expansion space 30.

The openings 12a, 12b, the internal space of the first displacer 10, the openings 22, 23, and the second
Each of the internal spaces of the displacers 20 serves as a flow path of the working fluid. The gap between the outer peripheral surface of the first displacer 10 and the inner peripheral surface of the first cylinder portion 1a also serves as a flow path for the working fluid.

The working fluid supplied into the cylinder 1 is discharged out of the cylinder 1 through the opening 42a,
5. Collected by the compressor 60 via the rotary valve device V (valve V2) and the working fluid collection pipe 62, and reused.

The illustrated expander 50 is configured so that the working fluid adiabatically expands in the first and second expansion spaces 30, 31 as the first and second expansion spaces 30, 31 expand. I have. The cylinder 1 is housed in a vacuum vessel (not shown).

The supply of the working fluid into the cylinder 1 and the discharge of the working fluid outside the cylinder 1 are performed under a predetermined phase difference with the reciprocating motion of the first and second displacers 10 and 20. First and second displacers 30, 3
By reciprocating the cylinder 1 repeatedly in the axial direction of the cylinder 1, adiabatic expansion of the working fluid repeatedly occurs in the first and second expansion spaces 30, 31.

As a result, the regenerative material in the first and second displacers 10 and 20 is gradually cooled to reach a substantially constant temperature. The temperature of the outer surface of the cylinder 1 is also substantially constant.

In order to measure the performance of the regenerative refrigerator 100, the following tests I to V were performed. The temperature reached at the low-temperature end in each of the first-stage and second-stage cylinder portions 1a and 1b when ³ He was used as the working fluid for Test I was measured. At this time, the specifications of the expander 50 and the compressor 60 were set to the following specifications (1) to (16), and the number of revolutions of the motor M in the power chamber 40 was variously changed within the range of 54 to 96 rpm.

The temperature reached when ⁴ He was used as the working fluid instead of ³ He was measured in the same manner. (1) First-stage cylinder portion 1a; inner diameter 25 mm, length (inner size) 165 mm (2) Second-stage cylinder portion 1b; inner diameter 52 mm, length (inner size) 191.5 mm (3) No. (1) Displacer 10; inner diameter 21 mm (4) Second displacer 20; inner diameter 38 mm (5) Magnetic regenerator layer 15; formed by HoCu ₂ spheres having a particle size of 0.2 to 0.5 mm and a total weight of 150 g (6) Lead (Pb) Cold storage material layer 16; particle size 0.4 to 0.48 m
m, formed by Pb spheres having a total weight of 150 g (7) Lead (Pb) regenerator material layer 25; particle size 0.4 to 0.48 m
(8) Copper wire mesh 26; 180 mesh, 450 sheets used (9) Reciprocating stroke of each displacer 10, 20; 20 mm (10) Opening / closing timing of valves V1, V2; Same timing as when the highest performance is obtained when ⁴ He is used as the working fluid. (11) Compressor 60; CKW2 manufactured by Sumitomo Heavy Industries, Ltd.
1 (However, the adsorber was changed to a smaller one in order to suppress the amount of ³ He used.) (12) Filling pressure of ³ He; 15.5 kgf / cm ² G (13) Filling pressure of ⁴ He; 17 kgf / cm ² G (14) Operating condition of compressor 60; power consumption is approximately 2.5 kW
(15) Thermal load on the first-stage cylinder portion 1a; none (16) Thermal load on the second-stage cylinder portion 1b; none The measurement results are shown in FIG. In FIG. 2, the lower two lines indicate the temperatures reached at the low-temperature end (cooling stage 1c) of the first-stage cylinder section 1a, and the upper two lines indicate the second-stage temperature.
It shows the temperature reached at the low-temperature end of the cylinder part 1b at the stage.

The temperature reached at the low-temperature end of the first-stage cylinder section 1a was measured using a germanium thermometer disposed outside the cylinder section 1a. The temperature reached at the low-temperature end of the second-stage cylinder portion 1b is determined by using a platinum-cobalt thermometer disposed outside the end of the second-stage cylinder portion 1b on the side of the first-stage cylinder portion 1a. It was measured.

As apparent from FIG. 2, ³ He and ⁴ He
Regardless of which He is used as the working fluid, as the rotation speed of the motor M decreases from 96 rpm to 54 rpm, the temperature reached at the low-temperature end of the first-stage cylinder portion 1a tends to decrease.

When ³ He is used as a working fluid,
Even when the rotation speed of the motor M is 96 rpm, the temperature reached at the low-temperature end of the first-stage cylinder portion 1a is 2.01K. When the rotation speed of the motor M is 54 rpm, 1.6
It drops to 5K. Extremely low temperatures of 2K or less can be obtained.

On the other hand, when ⁴ He is used as the working fluid, even if the rotation speed of the motor M is set to 54 rpm, the temperature reached at the low-temperature end of the first-stage cylinder section 1a is 2.3K, and 2K The following cryogenic temperatures could not be obtained. Although the rotational speed of the motor M was reduced below 54 rpm, the temperature reached at the low-temperature end of the first-stage cylinder portion 1a could not be reduced below 2.3K within the range tested. Test II In the same manner as in Test I, except that the rotation speed of the motor M was fixed at 60 rpm and the magnitude of the heat load applied to the first-stage cylinder portion 1a was variously changed, the first-stage cylinder portion 1a The relationship between the ultimate temperature at the low temperature end and the magnitude of the heat load was investigated. The results are shown in FIG.

The heat load on the first stage cylinder portion 1a is applied to the outer periphery of the cooling stage 1c by the manganin (trade name)
A wire was wrapped and generated using this as an electric heater.

As is apparent from FIG. 3, the cooling capacity of the regenerative refrigerator 100 can be increased by using ³ He as the working fluid, as compared with the case where ⁴ He is used as the working fluid.

When ³ He is used as the working fluid,
Even when the temperature at the low-temperature end of the first-stage cylinder section 1a is 2K, a cooling capacity of 53.9 mW can be obtained. When the temperature reached at the low-temperature end of the first-stage cylinder portion 1a is 4.2K, a cooling capacity of 820 mW is obtained.

[0064] On the other hand, when using a ⁴ He as the working fluid, the cooling capacity when the temperature reached the low temperature end and a 4.2K first stage of the cylinder portion 1a is 630MW, ³
20% or more lower than when He is used. Test III The test was conducted except that the magnetic regenerator material layer 15 was formed using the HoCu ₂ regenerator material and the NdInCu ₂ regenerator material, and the rotation speed of the motor M was fixed at 48 rpm or 60 rpm.
In the same manner as II, the cooling capacity of the regenerative refrigerator 100 was measured when ³ He was used as the working fluid and the ultimate temperature at the low-temperature end of the first-stage cylinder portion 1a was 2K.

The HoCu ₂ cold storage material used in forming the magnetic cold storage material layer 15 is a HoCu ₂ sphere having a particle size of 0.2 to 0.5 mm, and the NdInCu ₂ cold storage material has a size of 0.2 to 0. NdInCu ₂ pulverized powder of about 0.5 mm. NdInCu _{2 in} order from the first expansion space 30 side.
A layer of ground powder and a layer of HoCu ₂ spheres were formed. NdIn
The amounts of the Cu ₂ pulverized powder and HoCu ₂ spheres used are shown in (a)
The above measurement was performed for a total of three types of expanders 50 having the amounts shown in (c). (a) 25.8 g of NdInCu ₂ ground powder, 1 HoCu ₂ sphere
20 g (b) NdInCu ₂ powder 47.2 g, HoCu ₂ spheres 9
0 g (c) 72.3 g of NdInCu ₂ ground powder, 6 HoCu ₂ balls
0g The measurement results are shown in FIG. Also, for reference, the measurement results when the rotation speed of the motor M was set to 60 rpm, the ultimate temperature at the low-temperature end of the first-stage cylinder portion 1a was set to 2K using ³ He as the working fluid in Test II are shown in FIG. Also described in 4.

As is apparent from FIG. 4, the magnetic regenerator material layer 15 is formed using the HoCu ₂ regenerator material and the NdInCu ₂ regenerator material, so that the HoCu ₂ regenerator material alone forms the magnetic regenerator material layer 15. The cooling capacity of the regenerative refrigerator 100 at 2K can be higher than when it is formed. Test IV Except that the magnetic regenerator material layer 15 was formed using HoCu ₂ spheres having a particle diameter of 0.2 to 0.5 mm and NdInCu ₂ crushed powder having a size of about 0.2 to 0.5 mm, Similarly, the relationship between the ultimate temperature at the low temperature end of the first-stage cylinder portion 1a and the magnitude of the thermal load when ³ He was used as the working fluid was examined.

The amount of HoCu ₂ sphere used was 90 g, NdIn
The used amount of the pulverized Cu ₂ powder was 47.2 g, and the layer of the pulverized NdInCu ₂ powder and H
A layer of oCu ₂ spheres was formed.

FIG. 5 shows the results. FIG. 5 also shows the results of Test II when ³ He was used as the working fluid.

As shown in FIG. 5, the magnetic regenerator material layer 15 is formed by using the HoCu ₂ regenerator material and the NdInCu ₂ regenerator material, so that the magnetic regenerator material layer 15 is formed solely by the HoCu ₂ regenerator material. It is possible to increase the cooling capacity at a temperature lower than about 2.3K than when it is performed.

It is speculated that the reason why the combined use of the cold storage material made of HoCu ₂ and the cold storage material made of NdInCu ₂ improves the cooling capacity at a temperature lower than 2.3K is due to the difference in specific heat characteristics of these cold storage materials. Is done.

FIG. 6 shows the characteristics of the specific heat of volume of HoCu ₂ (intermetallic compound) and NdInCu ₂ (intermetallic compound).

As shown in the figure, HoCu ₂ has peaks of volume specific heat associated with magnetic transition at around 9K and around 7K. The peak of volume specific heat around 9K is due to the phase transition to the antiferromagnetic state, and the peak of volume specific heat around 7K is due to the transition of the magnetic structure. On the other hand, NdI
nCu ₂ has a peak of volume specific heat near 2K due to a phase transition to an antiferromagnetic state.

The volume specific heat of NdInCu ₂ is higher than that of HoCu ₂ at least at 2K. In at least 4～5K, towards the volume specific heat of HoCu ₂ is higher than the volume specific heat of NdInCu _2. Test V In the same manner as in Test I, except that the magnetic regenerator material layer 15 was formed in the same manner as in Test IV, the temperature reached at the low-temperature end of the first-stage cylinder portion 1a when ³ He was used as the working fluid. The relationship with the rotation speed of the motor M was examined.

As a result, the rotation speed of the motor M is set to 48 rpm
Or, at 54 rpm, the temperature reached at the low temperature end of the first stage cylinder portion 1a was the lowest at 1.64K.

The regenerative refrigerator according to the embodiments has been described above, but the present invention is not limited to these embodiments.

For example, the regenerative refrigerator according to the embodiment is a two-stage GM refrigerator, but may be a one-stage or three-stage or more multi-stage GM refrigerator or a Stirling refrigerator. You may.

Assuming that the number of stages in a multi-stage GM refrigerator of three or more stages is N, the cylinder in this GM refrigerator is
It has N cylinder portions that are continuous in the axial direction and have N inner diameters different from each other. One cylindrical container-shaped displacer is inserted into each of these cylinder parts. Each displacer includes a cold storage material charged in its internal space. A cylinder portion that is continuous with one closed end of the cylinder is a first-stage cylinder portion,
The inserted displacer inserted here is the first displacer. Each of the displacers inserted into the other cylinder part forms a thermal expansion space at the end of the cylinder part where the displacer is inserted on the first displacer side, and the displacer adjacent to the first displacer side forms a thermal expansion space. Be linked.

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

By using He containing ³ He as a working fluid, even when a groove pattern is not formed on the outer periphery of the displacer, it can be cooled to a lower temperature than a conventional regenerative refrigerator having the same structure. It is possible.

A working fluid made of He containing ³ He is particularly useful for obtaining an extremely low temperature of about 4 K or less.

In order to obtain an extremely low temperature of 2K or less, the first
Preferably, a first magnetic regenerator having a volume specific heat peak at 4K or less and a second magnetic regenerator having a volume specific heat peak at a temperature higher than 4K are preferably charged into the internal space of the displacer. It is preferable that a layer of the first magnetic regenerator is formed on the first expansion space side, and a second layer of the magnetic regenerator is formed thereon.

It is preferable that the volume specific heat of the first magnetic regenerator is higher than the volume specific heat of the second magnetic regenerator at least at 2K.

As a specific example of the first magnetic regenerator material, in addition to the above-described NdInCu ₂ , another magnetic regenerator material containing a rare earth metal element, for example, SmInCu _{2 and the} like can be mentioned.

Specific examples of the second magnetic regenerator include other magnetic regenerators containing rare earth metal elements, such as ErNi _0.9 Co _0.1 in addition to HoCu ₂ described above.

Instead of the lead (Pb) cold storage material 16 charged inside the first displacer 10, Er ₃ Ni, Er
A magnetic regenerator material such as _0.7 Ho _0.3 Ni may be used.
Instead of the copper wire mesh 26, a stainless steel wire mesh or the like can be used.

Except for the regenerator material having a wire mesh shape, the shape of the regenerator material may be irregular, such as pulverized powder, but it is more preferable that the regenerator material be spherical with a particle size of approximately 0.2 to 0.5 mm. preferable. Further, it may be formed into a pellet.

When a very low temperature of 2 K or less is to be obtained by using a mixture of ³ He and ⁴ He as a working fluid, 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, a regenerative refrigerator capable of obtaining an extremely low temperature of 2 K or less can be provided at a lower cost.

The cooling capacity of the regenerative refrigerator 100 shown in FIG. 1 depends on the installation angle. First expansion space 30
Is set to 0 ° when the expander 50 is installed so as to be positioned vertically below the second expansion space 31, and vice versa.
Assuming that the angle is 80 °, it is preferable to use it at 0 ° or 180 °. For example, when installed at 90 °, the cooling capacity may be reduced by 10% or more. However, an extremely low temperature of 2K or less can be obtained regardless of the installation angle.

It will be obvious to those skilled in the art that various changes, improvements, combinations, and the like can be made.

[0090]

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

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a regenerative 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 is a graph showing the results of Test IV.

FIG. 6 is a graph showing characteristics of volume specific heat of HoCu ₂ and NdInCu ₂ .

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Cylinder 10 ... 1st displacer 15
... magnetic cold storage material layer, 16, 25 ... lead cold storage material layer, 20 ...
2nd displacer, 26 ... copper wire mesh, 30 ... 1st
Expansion space, 31: second expansion space, 40: power chamber, 50: expander, 60: compressor, 100: regenerative refrigerator

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Alphonse de Barra Dotterbeek 8, Feldhofen Nuel-5501 BH, The Netherlands

Claims (8)

[Claims] 1. A cylinder having one end closed, and a first displacer having a cylindrical container shape inserted into the cylinder, the first displacer being formed at each of both ends in a longitudinal direction to communicate an internal space and an external space. An opening to be formed, and a regenerative material charged in the internal space, so as to be able to reciprocate in the axial direction of the cylinder while forming a first expansion space between the closed end of the cylinder. The first arranged
And a working fluid supplied into the cylinder, wherein ³ He
And a working fluid comprising He. 2. The regenerative refrigerator according to claim 1, wherein an atomic ratio of ³ He in the working fluid is 0.4 or more. 3. The cylinder according to claim 1, wherein the cylinder includes a first-stage cylinder portion connected to the closed end and a second-stage cylinder portion having an inner diameter larger than an inner diameter of the first-stage cylinder portion. And a second cylinder portion that is continuous in the axial direction of the cylinder from the first cylinder portion, wherein the first displacer is inserted into the first cylinder portion, Furthermore, a cylindrical container-shaped second displacer inserted into the second-stage cylinder portion, the opening portion being formed at each of both ends in the longitudinal direction to communicate an internal space and an external space, A regenerative material charged in the internal space, and a second thermal expansion space is formed at an end of the second-stage cylinder portion on the side of the first displacer portion; Connected second display Cold accumulation refrigerator as set forth in claim 1 or claim 2 including a p o. 4. The cold storage material charged in the first displacer has a peak of volume specific heat below 4K, and the first magnetic cold storage material charged in the first expansion space side. And a second having a peak of volume specific heat at a temperature higher than 4K.
The regenerative refrigerator according to any one of claims 1 to 3, further comprising a magnetic regenerator material. 5. The regenerative refrigerator according to claim 4, wherein the volume specific heat of the first magnetic regenerator is at least 2K higher than the volume specific heat of the second magnetic regenerator. 6. The method according to claim 1, wherein the first magnetic regenerator material is NdInCu _2.
, And the cold accumulation refrigerator of claim 4 or claim 5 wherein the second magnetic cold accumulating material is HoCu _2. 7. A cold storage material layer made of NdInCu ₂ , a cold storage material layer made of HoCu ₂ , and a lead cold storage material layer are formed in the internal space of the first displacer in this order from the first expansion space side. A regenerative refrigerator according to any one of claims 1 to 6. 8. An outer peripheral surface of the first displacer,
The regenerative refrigerator according to any one of claims 1 to 7, wherein a groove pattern including a groove along a direction intersecting with the axial direction of the first displacer is formed.