JPH02309159A - Manufacture of cold accumulation material and ultra-low temperature refrigerator - Google Patents

Abstract

PURPOSE:To prevent cold heat accumulation material of magnetic material from generating any fine powders by a method wherein after the cold heat accumulation material of the magnetic material is formed into a predetermined size by crushing the magnetic material, corners of the material are removed after mixing. CONSTITUTION:After melting operation, cold heat accumulation material 24 of magnetic material is crushed and selected to a proper size (100 to 500mum) by a sieve or the like so as to form fine magnetic particles. The magnetic particles under this state have several find projections of which angle is less than 30 deg. ranging from several tens mum to several mum. Then, the projection corners 41a placed at the surface of the cold heat material 24 of magnetic material are removed by a mixing operation after crushing of the magnetic material. Accordingly, if the cold heat accumulation material 24 of magnetic material is applied, the projections are prevented from being crushed. With such an arrangement as above, it is possible to prevent the find powder form being generated from the cold heat accumulation material 24 of the magnetic material during an operation of a refrigerator, from adhering the seal, reducing a refrigerating performance, scratching a valve and damaging a compressor.

Description

DETAILED DESCRIPTION OF THE INVENTION [Objective of the Invention (Field of Industrial Application)] The present invention relates to a cryogenic refrigerator, and particularly to a regenerator refrigerator.

(Prior Art) Among cryogenic refrigerators, there are various types of regenerator refrigerators with regenerators, such as Gifford-McMahon (GM) refrigerators and Stirling refrigerators.
The configuration of the refrigerator is shown in Figure 3.

This GM refrigerator can be broadly divided into cold head 1.
and a refrigerant gas introduction and discharge system 2. To the Cold Rad 1 includes a closed cylinder 11, a displacer 12 housed in the cylinder so as to be able to reciprocate, and a displacer 1 disposed in a room communicating with the cylinder 11.
2 provides the necessary power for reciprocating motion.

The cylinder 11 includes a large-diameter first cylinder 14 and a small-diameter second cylinder 15 coaxially connected to the first cylinder 14.
It is made up of. Then, the first cylinder 14 and the second cylinder
A first stage 16 is formed as a cooling surface at the boundary part with the cylinder 15, and a first stage 16 is formed at the tip wall part of the cylinder 15.
A second stage 17 having a lower temperature than the second stage 16 is configured.

The displacer 12 includes a first displacer 18 that reciprocates within the first cylinder 14 and a second displacer 19 that reciprocates within the second cylinder 15. 1st
The displacer 18 and the second displacer 19 are connected in the axial direction by a connecting member 20. Inside the first displacer 18, a fluid passage 2 extending in the axial direction is provided.
1 is formed to constitute a first regenerator 35, and a regenerator material 22 formed of copper mesh or the like is accommodated in the first regenerator 35. Similarly, a fluid passage 23 extending in the axial direction is formed inside the second displacer 19.
A second regenerator 36 is configured.

Inside the second regenerator 36, there is a regenerator material 2 made of balls such as lead.
4 is accommodated. A seal 1 is provided between the outer circumferential surface of the first displacer 18 and the inner circumferential surface of the first cylinder 14 and between the outer circumferential surface of the second 'i' displacer 19 and the inner circumferential surface of the second cylinder 15, respectively. Pictures 25 and 26 are installed.

The upper end of the first display υ18 in the figure is connected to the connecting rod 27.
, is connected to the rotating shaft of the motor 13 via a Scotch choke or crankshaft 28.

Therefore, when the rotating shaft of the motor 13 rotates, the displacer 12 reciprocates in synchronization with this rotation as shown by the solid line arrow 29 in the figure.

A refrigerant gas inlet 30 is provided at the upper side wall of the first cylinder 14.
and a discharge port 31 are provided, and these inlet port 30 and discharge port 31 are connected to the refrigerant gas introduction and discharge system 2. The refrigerant gas introduction and discharge system 2 constitutes a helium gas circulation system via the cylinder 11, and has a discharge port 31 connected to an inlet port 30 via a low pressure valve 32, a compressor 33, and a high pressure valve 34. There is. That is, this refrigerant gas introduction and discharge system 2
The compressor 3 supplies low pressure (approximately 6 atm) helium gas to the compressor 3.
3, it is compressed to high pressure (approximately 18 atm>) and sent into the cylinder 11. Then, a low pressure valve 32, a high pressure valve 34
The opening and closing of the displacer 12 is controlled in the following relationship with respect to the reciprocating movement of the displacer 12.

A brief explanation of the operation of the refrigerator configured as described above is as follows. In this refrigerator, the part that generates cold,
In other words, the portions serving as cooling surfaces are the first stage 16 and the second stage 16.
This is stage 17. These cool down to about 30° and 8°, respectively, when there is no heat load. Therefore, there is always m (300K> to 3 m) between the upper and lower ends of the first regenerator 35.
A temperature gradient is created from 0K to 0K, and a mlU gradient from 30K to 8K is created between the upper and lower ends of the second regenerator 36 in the figure.

However, this temperature changes depending on the heat load of each stage, and is usually 30 to 80K for the first stage 16, and 30 to 80K for the second stage 17.
It will be between 8 and 20.

When the motor 13 starts rotating, the displacer 12 reciprocates between the top dead center and the bottom dead center. Display υ12
When the cold head is at the bottom dead center, the high pressure valve 34 opens and high pressure helium gas flows into the cold head 1. Next, the display 12 moves to the dead center. As mentioned above, there are gaps between the outer circumferential surface of the first displacer 18 and the inner circumferential surface of the first cylinder 14 and between the outer circumferential surface of the second displacer 19 and the inner circumferential surface of the second cylinder 15. Seals 25 and 26 are installed. Therefore, when the displacer 12 moves toward the top dead center, the high-pressure gas passes through the fluid passage 23 to the fluid passage 21 formed in the first displacer 18 and the second displacer 19, A first-stage expansion chamber 39 is formed between the displacer 18 and the second displacer 19, and a two-stage expansion chamber 39 is formed between one second displacer and the tip wall of the second cylinder 15.
It flows into the stage expansion chamber 40. Along with this flow, the high-It helium gas is cooled by the cold storage material 22, 24, and eventually flows into the first-stage expansion chamber 39. The high-pressure helium gas that has flowed into the two-stage expansion chamber 40 is cooled down to 8KF?ft2.The high-pressure valve 34 is closed, and the low-pressure valve 32 is closed. When the low pressure valve 32 hears this, the high pressure helium gas in the first stage expansion chamber 39 and the second stage expansion chamber 40 expands and generates cold.This cold causes -C first stage 16 and second stage 17. is cooled to N1.Then, the displacer 12 moves to the bottom dead center again, and along with this, the helium gas in the first-stage expansion chamber 39 and the second-stage expansion chamber 40 is removed.The expanded helium gas Fluid passage 21.23
While passing through the inside, it is warmed by the cold storage materials 22 and 24, and is discharged at room temperature. Thereafter, the above-described cycle is repeated to perform the refrigeration operation. This type of refrigerator is used to cool superconducting magnets, infrared sensors, and as a cooling source for cryopumps.

Further, instead of lead as the regenerator material 24 in the second regenerator 36, some kind of magnetic material such as Er 3Ni, fEu S,
By using a considerable amount of Gd Rh, etc., the R of the refrigerator can be reduced.
It is possible to lower the low temperature section and increase the refrigeration capacity at low temperatures (below IOK). This is because as the temperature decreases, the specific heat of lead decreases, reducing its ability to store heat as a regenerator, and the heat exchange efficiency as a regenerator decreases significantly. Therefore, by using a material that has a higher specific heat than lead at low temperatures, it is possible to improve the cold storage efficiency, lower the minimum temperature, and improve the refrigerating capacity at low temperatures.

For example, when Er 3N is used instead of lead in the second regenerator, the minimum temperature drops from 8K to 5K, and the cooling capacity improves from 3W to 5W at 10°C.

However, the conventional refrigerator configured as described above has the following problems. That is, the second regenerator 3
When a magnetic material is used for part or all of the regenerator material 24 in the first displacer 18, it is very difficult to process it into a spherical shape like lead or into a mesh shape like the regenerator material 22 in the first displacer 18. It's difficult. Therefore, after pulverizing the melted bulk material, it is usually divided into 1-sized pieces using a sieve.
00 to -500 μm) is used as a cold storage material. However, these materials after pulverization have small corners and protrusions on the order of several micrometers, and these protrusions can chip and come off during operation of the refrigerator. The cold storage material 24 is covered with mesh etc. at both ends to prevent it from spilling over the second displacer 19, but there
There is a gap of about 1.5 ft., and fine powder of the magnetic material escapes along with the helium gas. It is not a good idea to narrow the gap between the lids such as meshes at both ends, as this will increase the pressure loss of the helium gas.

In addition, the fine powder of magnetic material coming out of the second regenerator 36 is removed from the seal 2.
5, increasing seal leakage and significantly reducing refrigeration capacity. In addition, the first regenerator 35, the valve 3
2 and reaches the compressor 33, leading to clogging of the valve 32 and damage to the compressor 33. As described above, when the as-pulverized magnetic tI body is used as a cold storage material, there is a problem that the capacity of the refrigerator is decreased and the refrigerator is damaged.

(Problems to be Solved by the Invention) As mentioned above, in a regenerator refrigerator that uses a magnetic material as a regenerator, fine particles of the magnetic material generated during operation of the refrigerant come out from the regenerator. However, there was a problem in that the refrigerating capacity of the refrigerating machine was reduced, and even the refrigerating machine was damaged.

Therefore, the present invention provides a vJ manufacturing method that allows a regenerator material made of a magnetic material to be formed into a shape that does not produce fine powder, and a cryogenic refrigerator using a regenerator material made of a magnetic material manufactured by this manufacturing method. The purpose is to

[Structure of the Invention] (Means for Solving the Problems) The present invention is directed to cooling compressed refrigerant gas using a regenerator and then expanding the compressed refrigerant gas in a low-temperature section to generate cold. FIl is a method for manufacturing a regenerator material made of a physical body, in which the regenerator material made of a magnetic material is formed into a predetermined size by crushing a magnetic material, and then mixed to remove corners.

In addition, after cooling the compressed refrigerant gas using a regenerator,
In a cryogenic refrigerator that generates cold by expanding in a low-temperature section, the cold storage material used in the cold storage device is a magnetic cold storage material made by the manufacturing method described above.

(Function) By mixing after crushing the magnetic material, magnetic material cold storage (Δ
The corners of the protrusions on the surface were excluded. Therefore, if this magnetic regenerator material is used, the protrusions are prevented from chipping and coming off. Therefore, it is possible to prevent fine powder from being generated from the magnetic regenerator material during operation of the refrigerator, adhering to the seal, deteriorating the refrigerating performance, damaging the valve, and damaging the compressor.

(Example) Examples will be described below with reference to the drawings.

FIG. 1 shows a refrigerator according to an embodiment of the present invention. In this figure, the same parts as in FIG. 5 are designated by the same reference numerals. Therefore, the explanation of m multiple parts will be omitted.

The difference between the refrigerator according to this embodiment and the conventional refrigerator is that
The problem lies in the shape and processing method of the magnetic material used for the regenerator material 24 in the second regenerator 35.

After the magnetic regenerator material is melted, it is pulverized and sorted into appropriate sizes (100 to 500 μm) using a sieve or the like to obtain magnetic particles. The magnetic grains in this state have many fine protrusions of several micrometers to several micrometers and angles of 30 degrees or less.

FIG. 3 shows the state of the magnetic particles 41A after crushing and sorting. If the protrusions 41a of the magnetic grains 41Δ are left as they are during the refrigeration operation, they will break off at the back and leak into the refrigerator.

According to experiments, all of these protrusions 41a with an angle of 30 degrees or less have fallen off after the freezing operation.

Therefore, by using magnetic particles without protrusions of 30 degrees or less as a regenerator, it is possible to prevent fine powder of the magnetic particles from leaking from the regenerator.

Magnetic particles without protrusions of 30 degrees or less can be produced by crushing and sorting the magnetic material and then mixing it in an organic solvent such as alcohol or an inert gas such as argon gas using a mixer or the like.

Figure 2 shows the state of the magnetic particles 4113 after mixing. As shown in FIG. 2, fine protrusions (removed by mixing) are produced. When these magnetic particles 41B are used as a cold storage material, fine particles of magnetic particles 4'lB spill out from the second cold storage device 36 during operation. This prevents it from sticking to seals and deteriorating refrigeration performance.

Figure 4 shows a cryogenic refrigerator in which magnetic particles 41A, which are simply pulverized magnetic substances, are used as a regenerator material, and a cryogenic refrigerator according to an embodiment of the present invention, in which magnetic particles 41B, which are pulverized and mixed, are used as a regenerator material. A refrigerating capacity curve after 100 hours has passed after the operation of the low temperature refrigerator is shown. The horizontal axis represents the temperature (K) of the second stage 17, and the vertical axis represents the thermal load (W) applied to the second stage 17. The refrigerating capacity curves of both cases were the same immediately after the start of operation, but after 100 hours there was a difference in capacity as shown in Figure 4. Regarding the refrigerator of the example of the present invention, it showed exactly the same refrigerating capacity as immediately after the start of operation.

In addition, when we conducted an operational erosive decomposition investigation, we found that the seal 2 of a refrigerator using only pulverized magnetic particles 41A as the regenerator material 24 was
Although fine powder of magnetic particles 41a was found adhering to No. 6, such fine powder was not observed in the refrigerator of "Embodiment of the Present Invention".

Therefore, it is thought that the adhering fine particles of magnetic particles increased the amount of leakage from the seal 26, causing a decrease in the refrigerating capacity as seen in Fig. 4. I can understand the effect of using it as a cold storage material.

In the above-mentioned embodiments, the Seizo refrigerator was a GM refrigerator, but it is not limited to the GM76 refrigerator, but can also be used as a Stirling refrigerator, an improved Solvay cycle refrigerator, or a regenerator type refrigerator such as Birmi (7 Refrigerator). The present invention is also applicable to low hm refrigerators.The shape of the magnetic material is not only granular but also powder,
It is equally applicable to fibrous magnetic materials (for example, mesh shapes) and other hard magnetic materials.

[Effects of the Invention] As described below, according to the present invention, it is possible to obtain a magnetic regenerator material that does not have corners that are easily broken during use, and it is also possible to obtain cryogenic refrigeration materials using the same. According to the machine, it is possible to prevent a decrease in refrigerating capacity or damage.

[Brief explanation of drawings]

Fig. 1 is a partially cutaway block diagram of a cryogenic refrigerator according to an embodiment of the present invention; 3rd enlarged view of
The figure is an enlarged view of the magnetic regenerator material before mixing.
FIG. 4 is a diagram showing the characteristics of the cryogenic refrigerator according to the embodiment of the present invention in comparison with a conventional cryogenic refrigerator, and FIG. 5 is a diagram showing the configuration of the conventional cryogenic refrigerator. 24... Cold storage material 41Δ... Magnetic material cold storage material 41B before mixing...
・Magnetic cold storage material 41a after mixing... corner

Claims (2)

[Claims] (1) After cooling the compressed refrigerant gas using a regenerator,
A method for manufacturing a magnetic regenerator material used in a regenerator of a cryogenic refrigerator that generates cold by expanding in a low-temperature section, wherein the magnetic regenerator material is made into a predetermined size by crushing the magnetic material. A method for producing a cold storage material, which is characterized in that the material is formed into a solid material and then mixed to remove the corners. (2) After cooling the compressed refrigerant gas using a regenerator,
A cryogenic refrigerator that generates cold by expanding in a low-temperature section, characterized in that the cold storage material used in the cold storage device is a magnetic cold storage material produced by the manufacturing method according to claim 1. refrigerator.