JPH0668417B2 - Cryogenic refrigerator - Google Patents

Description

The present invention relates to a cryogenic refrigerator, and more particularly to a cold storage refrigerator.

(Prior Art) Among cryogenic refrigerators, there are various types of regenerators having a regenerator, such as Gifford McMahon (GM) refrigerator and Stirling refrigerator. Among them, GM refrigerator The configuration of the machine is shown in FIG.

That is, this GM refrigerator is roughly divided into a cold head 1 and a refrigerant gas guide / discharge system 2. The cold head 1 includes a closed cylinder 11, a displacer 12 reciprocally housed in the cylinder 11, and a motor 13 arranged in a room communicating with the cylinder 11 to provide power required for the reciprocating motion of the displacer 12. It consists of and.

The cylinder 11 is composed of a large-diameter first cylinder 14 and a small-diameter second cylinder 15 coaxially connected to the first cylinder 14. And the first cylinder 14 and the second cylinder
The boundary wall portion with 15 constitutes a first stage 16 as a cooling surface, and the tip wall portion of the cylinder 15 constitutes a second stage 17 having a temperature lower than that of the first stage 16.

The displacer 12 is composed of a first displacer 18 that reciprocates in the first cylinder 14 and a second displacer 19 that reciprocates in the second cylinder 15. The first displacer 18 and the second displacer 19 are axially connected by a connecting member 20. A fluid passage 21 extending in the axial direction is formed inside the first displacer 18.
The regenerator 35 is configured, and the regenerator material 22 formed of a copper mesh or the like is accommodated in the first regenerator 35. Similarly,
A fluid passage 23 extending in the axial direction is also formed inside the second displacer 19, and constitutes a second regenerator 36.
In the second regenerator 36, a regenerator material 24 made of spheres or powder of lead, other metal, intermetallic compound or the like is housed. A seal mechanism is provided between the outer peripheral surface of the first displacer 18 and the inner peripheral surface of the first cylinder 14, and between the outer peripheral surface of the second displacer 19 and the inner peripheral surface of the second cylinder 15, respectively.
25,26 are installed.

The upper end of the first displacer 18 in the figure is connected to the rotating shaft of the motor 13 by disengaging the connecting rod 27, the Scotch yoke or the crankshaft 28. Therefore, when the rotation shaft of the motor 13 rotates, the displacer 12 reciprocates in synchronization with this rotation as indicated by the solid arrow 29 in the figure.

An inlet 30 and an outlet 31 for the refrigerant gas are provided on the upper side wall of the first cylinder 14, and the inlet 30 and the outlet 31 are connected to the refrigerant gas guide / discharge system 2. The refrigerant gas introduction / exhaust system 2 constitutes a helium gas circulation system via the cylinder 11, and the exhaust port 31 is connected to the inlet port 30 via the low pressure valve 32, the compressor 33, and the high pressure valve 34. There is.
That is, the refrigerant gas guide / exhaust system 2 compresses the low-pressure (about 6 atm) helium gas to a high-pressure (about 18 atm) by the compressor 33 and sends it into the cylinder 11. And low pressure valve
The opening and closing of the high pressure valve 32 and the high pressure valve 34 are controlled in the relationship described later in relation to the reciprocal movement of the displacer 12.

The operation of the refrigerator configured as described above will be briefly described as follows. In this refrigerator, where cold is generated,
That is, the portions provided for the cooling surface are the first stage 16 and the second stage 17. They cool to around 30K and 8K respectively when there is no heat load. Therefore, there is a temperature gradient from room temperature (300K) to 30K between the upper and lower ends of the first regenerator 35, and a temperature gradient from 30K to 8K 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 usually 30 to 80 K in the first stage 16, 2
It becomes about 8 to 20K on the multistage stage 17.

When the motor 13 starts rotating, the displacer 12 reciprocates between the top dead center and the bottom dead center. When the displacer 12 is at the bottom dead center, the high pressure valve 34 is opened and the high pressure helium gas flows into the cold head 1. Next, the displacer
12 moves to top dead center. As described above, the sealing mechanism 25, between the outer peripheral surface of the first displacer 18 and the inner peripheral surface of the first cylinder 14, and the outer peripheral surface of the second displacer 19 and the inner peripheral surface of the second cylinder 15, respectively. 26 is installed. Therefore, when the displacer 12 heads to the top dead center, the high-pressure helium gas is formed between the first displacer 18 and the second displacer 19 through the first regenerator 35 and the second regenerator 36. It flows into the first-stage expansion chamber 39 and the second-stage expansion chamber 40 formed between the second displacer 19 and the tip wall of the second cylinder 15. Along with this flow, the high-pressure helium gas is cooled by the regenerator materials 22 and 24, so that the high-pressure helium gas flowing into the first-stage expansion chamber 39 is 30K.
The high-pressure helium gas flowing into the second-stage expansion chamber 40 is cooled to about 8K. Here, the high pressure valve 34 is closed and the low pressure valve 32 is opened. When the low pressure valve 32 is opened in this way, the high pressure helium gas in the first expansion chamber 39 and the second expansion chamber 40 expands to generate cold. The first stage 16 by this cold
And the second stage 17 is cooled. Then, the displacer 12 moves to the bottom dead center again, and accordingly, the helium gas in the first expansion chamber 39 and the second expansion chamber 40 is removed. The expanded helium gas is warmed by the regenerator materials 22 and 24 while passing through the regenerators 35 and 36, and is discharged at room temperature. Hereinafter, the cycle described above is repeated to perform the refrigerating operation.

This type of refrigerator is used as a cooling source for a super electric magnet, an infrared sensor, or a cooling source for a cryopump.

Furthermore, by using a certain amount of a magnetic material such as Er3Ni, EuS, GdRh instead of lead as the regenerator material 24 in the second regenerator 36, the minimum temperature of the refrigerator can be lowered to a low temperature (10K or less). ) Can increase the refrigerating capacity. This is because as the temperature decreases, the specific heat of lead decreases, the ability to store heat as a regenerator material decreases, and the heat exchange efficiency as a regenerator greatly decreases. Therefore, by using a material having a larger specific heat than lead at a low temperature, it is possible to improve the cold storage efficiency, lower the minimum temperature, and improve the refrigerating capacity at the low temperature. For example, instead of lead in the second regenerator,
With Er3Ni, the minimum temperature drops from 8K to 5K, 10K
And the refrigerating capacity has improved from 3W to 5W.

However, the conventional refrigerator configured as described above has the following problems. That is, the second regenerator 36
When a magnetic material is used for a part or all of the storage material 24 in the above, it is processed into a spherical shape like lead or the first displacer.
It is very difficult to process it into a mesh like the regenerator material 22 inside 18. Therefore, normally, after crushing the bulk material after melting, it is sieved to a certain size (100-500 μm).
It is used as a cold storage material.
However, these pulverized materials have fine corners and protrusions of about several μm, and these corners are chipped off during operation of the refrigerator. The regenerator material 24 is covered with a mesh or the like at both ends to prevent it from spilling by the second displacer 19, but there is also a gap of about several tens of μm open in it, and the fine powder of the magnetic material does not escape together with the helium gas. Will end up. On the other hand, making the gaps between the lids such as meshes on both ends finer is not a good idea because it leads to an increase in the pressure loss of the helium gas. Further, the fine particles of the magnetic material discharged from the second regenerator 36 adhere to the seal 25, increasing the leak amount of the seal and significantly reducing the refrigerating capacity. Further, it passes through the first regenerator 35 and the valve 32 to reach the compressor 33, leading to clogging of the valve 32 and damage to the compressor 33.
As described above, when the magnetic body as it is conventionally pulverized is used as the regenerator material, there is a problem that the capacity of the refrigerator is lowered and the refrigerator is damaged.

(Problems to be Solved by the Invention) As described above, in the regenerator that uses the crushed magnetic material as the regenerator material, the crushed magnetic material generated during the operation of the refrigerator is crushed by the regenerator. However, there is a problem in that the refrigerating capacity of the refrigerator is deteriorated and the refrigerator is damaged.

Therefore, an object of the present invention is to provide a cryogenic refrigerator in which the magnetic regenerator material does not generate fine powder even when the refrigerator is operated, and thus does not deteriorate the refrigerating function.

[Structure of Invention]

(Means for Solving the Problems) The present invention relates to a cryogenic refrigerator that cools a compressed refrigerant gas using a regenerator and then expands it in a low temperature section to generate cold, in which the regenerator in the regenerator is stored. A plurality of particulate magnetic bodies are used as the material, the magnetic bodies are covered with another metal film, and the coated magnetic bodies are housed so as to be filled in the container of the regenerator in an independent state. To do.

(Function) Since the particulate magnetic material is covered with another metal film, one part of the magnetic material, such as fine corners, where the magnetic material is likely to fall off is fixed by the metal film. Due to this, the shape is rounded and the metal film serves as a lubricating layer or a cushion, which is less likely to be chipped due to the two effects of not receiving stress concentration.

(Example) Hereinafter, an example will be described 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 those in FIG. 5 are designated by the same reference numerals. Therefore, the description of the overlapping parts will be omitted.

The difference between the refrigerator according to this embodiment and the conventional refrigerator is that
It is in the magnetic material used for the regenerator material 24 in the second regenerator 36.

After the magnetic material M is melted, it is crushed and screened to a suitable size (100 to 500 μm). The magnetic body in this state has a large number of fine corners of several tens to several μm.

FIG. 3 shows the state of the magnetic material M after crushing and selection. These corners 41 are chipped and leak into the refrigerator during freezing operation. Therefore, by coating the magnetic material M with metal, these fine corners are covered with the metal film S.

This metal has a toughness superior to that of the magnetic body M, and it is desirable that the metal also has a thermal conductivity close to that of the magnetic body M, and one that is excellent in the workability of coating the magnetic body M.

For example, gold, silver, copper, nickel, molybdenum and the like.
The metal film S is formed by plating, vapor deposition or the like.

As shown in FIG. 1, a plurality of magnetic bodies M covered with the metal film S are housed in a second regenerator (container) 36. This accommodation is performed by filling the individual magnetic particles in an independent state, that is, by filling the inside of the container 36 to the extent that they make point contact with each other.

FIG. 2 (a) shows a state of the magnetic body M after mixing.
As shown in FIG. 2 (b), the fine corners 41 are wrapped by plating. When this magnetic material M is used as a regenerator material, fine particles of the magnetic material are spilled from the second regenerator 36 during operation and are sealed. It will not adhere to the and will not deteriorate the refrigeration performance. This is because the corner 41 is fixed by the metal film S, and the metal film S
This is because the corner 41 is rounded, and the metal film S serves as a lubricating layer or a cushion so that stress concentration is not performed and the lack of the corner 41 is prevented.

In Fig. 4, 100 hours have passed since the operation of the cryogenic refrigerator in which the magnetic material M was merely crushed and used as the regenerator material and the cryogenic refrigerator in which the magnetic material M plated after crushing was used as the regenerator material The freezing capacity curve at the time of doing is shown. The horizontal axis represents the temperature (K) of the second stage 17, and the vertical axis represents the heat load (W) applied to the second stage 17. Both of them had the same refrigerating capacity curves immediately after the start of the operation, but after 100 hours, there was a difference in the capacity as shown in FIG. The refrigerators of the examples of the present invention showed completely the same refrigerating capacity immediately after the start of operation. Further, when a disassembly survey was carried out after the operation, a crushed magnetic substance was adhered to the seal 26 in the refrigerator in which only the crushed magnetic substance M was used for the regenerator material 24, but in the refrigerator of the embodiment of the present invention, No such fines were found. Therefore, it is considered that the fine particles of the attached magnetic material increased the leak amount of the seal 26, and caused the reduction of the refrigerating capacity as shown in FIG.
The effect of using the plated magnetic material as a regenerator material can be understood.

In the embodiment described above, the structure of the refrigerator was a GM refrigerator, but not limited to the GM refrigerator, in a regenerative cryogenic refrigerator such as a Stirling refrigerator, an improved Solvay cycle refrigerator, a Billmiya refrigerator, etc. The present invention also applies. Further, the shape of the magnetic body is not limited to the granular shape, and the present invention is also applicable to magnetic bodies having other shapes such as powder, fibrous magnetic body (for example, mesh or the like), and porous.

[Advantages of the Invention] As described above, according to the present invention, it is possible to eliminate generation of fine powder from the magnetic material used as the cold storage material. Therefore, it is possible to prevent deterioration of the refrigerating capacity of the cryogenic refrigerator or damage thereof.

[Brief description of drawings]

FIG. 1 is a structural view showing a cryogenic refrigerator according to an embodiment of the present invention by locally cutting it out, and FIG. 2 (a) is an enlarged view of a magnetic regenerator material incorporated in the cryogenic refrigerator. The second view I saw
2B is a partially enlarged sectional view of FIG. 2A, FIG. 3 is an enlarged view of a conventional magnetic regenerator material, and FIG. 4 is a cryogenic refrigerator according to an embodiment of the present invention. FIG. 5 is a diagram showing the characteristics of the above in comparison with that of a conventional cryogenic refrigerator, and FIG. 5 is a configuration diagram of the conventional cryogenic refrigerator. 35 …… First regenerator 36 …… Second regenerator 24 …… Regenerator M …… Magnetic material

Claims (3)

[Claims] 1. A cryogenic refrigerator in which a compressed refrigerant gas is cooled using a regenerator and then expanded in a low temperature section to generate cold, and a particulate magnetic material is added to a regenerator material in the regenerator. A cryogenic refrigerator characterized in that a plurality of the magnetic bodies are coated with another metal film, and the coated magnetic bodies are housed in a container of a regenerator in an independent state. 2. The cryogenic refrigerator according to claim 1, wherein the metal film is formed of a metal having a toughness higher than that of the magnetic material. 3. The cryogenic refrigerator according to claim 1, wherein the metal film is formed of a metal having a thermal conductivity substantially equal to that of the magnetic material.