JP2831809B2 - Cryogenic refrigeration equipment - Google Patents

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial application field) The present invention relates to a cryogenic refrigerator having a regenerative refrigerator as a main refrigerator.

(Prior Art) There are various types of cryogenic refrigerators. Among these, there is a regenerative cryogenic refrigerator represented by a Gifford McMahon refrigerator. This regenerative cryogenic refrigerator, for example, a two-stage expansion type Gifford McMahon refrigerator (hereinafter abbreviated as a GM refrigerator) is configured as shown in FIG.

That is, this 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 piston housed in the cylinder 11 so as to be reciprocally movable, that is, a displacer 12 formed of a heat insulating material, and a motor that supplies power required for the reciprocating movement to the displacer 12. It is composed of thirteen.

The cylinder 11 includes a large-diameter first cylinder 14 and a small-diameter second cylinder 15 coaxially connected to the first cylinder 14. First cylinder 14 and second cylinder
15 is usually formed of a thin stainless steel plate or the like.
The first cooling stage 16 is constituted by the boundary wall between the first cylinder 14 and the second cylinder 15, and the second cylinder
15 second wall at lower temperature than first cooling stage 16 at the tip wall
The step cooling stage 17 is constituted.

The displacer 12 includes 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 connected to a connecting mechanism 20.
Are connected in the axial direction.

A fluid passage 21 for forming a regenerator is formed in the first displacer 18 in the axial direction. The fluid passage 21 accommodates a regenerator material 22 made of copper mesh or the like.

A fluid passage 23 is formed in the second displacer 19 in the axial direction to constitute a final stage regenerator, and the fluid passage 23 accommodates a regenerator material 24 formed of spherical lead. .

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 second
A seal device 2 is provided between the cylinder 15 and the inner peripheral surface.
5, 26 are installed.

The upper end of the first displacer 18 in the figure is a connecting rod 31,
Motor 13 via scotch yoke or crankshaft 32
Is connected to the rotating shaft. Therefore, when the motor 13 rotates, the displacer 12 reciprocates in the direction shown by the solid arrow 33 in the figure in synchronization with this rotation.

An inlet 34 and an outlet 35 for the refrigerant gas are provided in the upper part of the side wall of the first cylinder 14, and the inlet 34 and the outlet 35 are connected to the refrigerant gas guide / discharge system 2. The refrigerant gas guide / discharge system 2 constitutes a helium gas circulation system passing through the cylinder 11, and the discharge port 35 includes a low-pressure valve 36, a compressor 37, and a high-pressure valve.
It is connected to the inlet 34 via 38. That is, the refrigerant gas guide / discharge system 2 compresses helium gas of low pressure (about 5 atm) to high pressure (about 18 atm) by the compressor 37 and sends it into the cylinder 11. And the low pressure valve 36,
The high-pressure valve 38 is controlled to open and close in a relationship described later in relation to the reciprocation of the displacer 12.

The operation of the refrigerator will be briefly described as follows.

In this refrigerator, a portion where cold occurs, that is, a portion provided for a cooling surface is a first cooling stage 16 and a second cooling stage 17.

When the motor 13 starts rotating, the displacer 12 reciprocates between a bottom dead center, which is the lowermost point in the figure, and a top dead center, which is the uppermost point in the figure. When the displacer 12 is at the bottom dead center, the high pressure valve 38 opens and high pressure helium gas flows into the cold head 1. Next, the displacer 12 moves to the top dead center. As described above, 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, 26 is installed. For this reason, when the displacer 12 moves to the top dead center, the high-pressure helium gas is supplied to the fluid passage 21 formed in the first displacer 18 and the fluid passage formed in the second displacer 19.
23, a one-stage expansion chamber 39 formed between the first displacer 18 and the second displacer 19 and a two-stage expansion chamber formed between the second displacer 19 and the tip wall of the second cylinder 15. Flows to 40. Along with this flow, the high-pressure helium gas is cooled by the cold storage materials 22 and 24,
The high-pressure helium gas flowing into the two-stage expansion chamber 39 is at a 50K level, and the high-pressure helium gas flowing into the two-stage expansion chamber 40 is
Cooled to 15 levels.

Here, the high pressure valve 38 closes and the low pressure valve 36 opens. When the low-pressure valve 36 is thus opened, the inside of the first-stage expansion chamber 39 and the inside of the two-stage expansion chamber 39
The high-pressure helium gas in the 40 expands and generates cold. By this cold, the first cooling stage 16 and the second cooling stage 17 are further cooled to a lower temperature. Then, when the displacer 12 moves to the bottom dead center again, 1
Helium gas in the step expansion chamber 39 and the two-step expansion chamber 40 is eliminated. The expanded helium gas cools the cold storage materials 24 and 22 while passing through the fluid passages 23 and 21, and is discharged at normal temperature. Hereinafter, the above-described cycle is repeated to perform the refrigeration operation.

However, the conventional cryogenic refrigerator configured as described above has the following problems. That is,
As shown in FIG. 6, the lead filled in the second displacer 19 as the cold storage material 24 decreases in volume specific heat as the temperature decreases, and the heat capacity decreases. Therefore, the amount of heat exchange with helium gas is greatly reduced. On the other hand, helium gas has the property that the volume specific heat increases as the temperature decreases. Due to these properties, it is difficult for the conventional regenerative cryogenic refrigerator to lower the temperature of the second cooling stage 17 to 8K or less.

Therefore, in order to lower the minimum temperature reached by the second cooling stage 17, GdRh or GdEr having a higher specific heat than lead at low temperatures.
A refrigerator using Rh as the regenerator material 24 and a refrigerator having three or more regenerators and displacers are considered. However, even with the improved refrigerator, it has been difficult to exert a large refrigerating capacity particularly near the liquid helium temperature of 4.2 K.

Considering the characteristics of adiabatic expansion and cooling, it is advisable to operate at a low pressure level in order to obtain a large refrigeration capacity in a low temperature range of 10K or less. However, if the conventional refrigerator is operated at a low pressure, the pressure level in the upper cooling stage (the one-stage cooling stage in the two-stage GM refrigerator and the one-stage and two-stage cooling stages in the three-stage GM refrigerator) is also low. Become. On the upper side, that is, in the region where the temperature exceeds 10K, conversely, a higher pressure is preferable for improving the refrigerating capacity. Therefore, if the pressure on the upper stage also becomes lower as described above, the refrigerating capacity on the upper stage decreases, and the temperature on the upper stage rises, which causes a problem that the refrigerating capability on the lower temperature side is reduced.

(Problems to be Solved by the Invention) As described above, in the conventional regenerative cryogenic refrigerator,
In particular, there was a problem that a high refrigeration capacity could not be obtained in the vicinity of an industrially useful liquid helium temperature (4.2 K).

Therefore, the present invention provides a 4.2 K
It is an object of the present invention to provide a cryogenic refrigeration apparatus capable of greatly improving the refrigeration capacity in the vicinity.

[Means for Solving the Problems] In order to achieve the above object, in the cryogenic refrigeration apparatus according to claim 1, a cylinder, a displacer housed in the cylinder in a reciprocating manner, and A helium gas passage formed in the displacer; a plurality of regenerators formed in the reciprocating direction of the displacer by filling the helium gas passage with a regenerator; and adjacent regenerators interposed between the regenerators. A heat exchange stage having a helium gas passage connecting a vessel, a cryogenic refrigerator that generates compressed cold by sequentially passing compressed helium gas through each of the regenerators, and around the cylinder. A heat transfer member disposed so as to be able to exchange heat with the heat exchange stage,
Cooling means for cooling the heat transfer member.

The heat transfer member may be arranged at a position facing the peripheral surface of the heat exchange stage when the displacer reaches the bottom dead center so as to form a minimum expansion space between the heat transfer member and the cylinder. Good.

In order to achieve the above object, in the cryogenic refrigeration apparatus according to claim 3, an inner cylinder and an outer cylinder which are concentrically arranged so that an inner space and an outer annular space communicate with each other at a tip portion, A displacer which is accommodated reciprocally in the inner cylinder and forms a variable volume expansion space between the inner cylinder and the inner cylinder and the outer cylinder with a regenerator filled in a direction in which the outer cylinder extends. A heat exchange stage having a plurality of regenerators and a helium gas passage interposed between the regenerators and connecting adjacent regenerators is provided, and the compressed helium gas is sequentially passed through the regenerators. And a cryogenic refrigerator that expands in the expansion space to generate cold, and is arranged around the outer cylinder so as to be able to exchange heat with the heat exchange stage. It includes a heat member, and a cooling means for cooling the heat transfer member.

In order to achieve the above object, in the cryogenic refrigeration apparatus according to claim 4, a first cylinder and a second cylinder arranged in a leading end portion so as to communicate with each other, and can reciprocate in the second cylinder. And a plurality of displacers which are formed in the first cylinder and which are filled with a cold storage material in a direction in which the first cylinder extends. A regenerator,
A heat exchange stage provided with a helium gas passage interposed between these regenerators and connecting adjacent regenerators, wherein the compressed helium gas is sequentially passed through the regenerators and then expanded in the expansion space. A cryogenic refrigerator that generates cold by heating; a heat transfer member disposed around the second cylinder so as to be able to exchange heat with the heat exchange stage; and a cooling unit that cools the heat transfer member. .

It is preferable that the cryogenic refrigerator and the cooling means employ one of a Gifford-McMahon cycle, a Stirling cycle, and a Vilmiya cycle.

Further, the cooling means may also serve to cool a heat shield plate disposed in the heat insulating layer of the cryostat.

(Operation) Since the heat exchange stage is provided between the adjacent regenerators, the helium gas flowing to the adjacent regenerator after passing through a certain regenerator is compared with the case where the heat exchange stage is not provided. Cooled to low temperature. Therefore, by selecting the temperature of the heat exchange stage, it is possible to select the operating conditions (pressure level, rotation speed, etc.) that are most suitable for the generation of cold in the low-temperature section, and improve the refrigerating capacity near 4.2K. It becomes possible.

(Example) Hereinafter, an example is described, referring to drawings.

FIG. 1 shows a cryogenic refrigeration apparatus according to one embodiment of the present invention.

This cryogenic refrigeration apparatus is roughly divided into a cryogenic refrigerator main body 51 and a refrigerator 52 for pre-cooling. The portion of the cryogenic refrigerator main body 51 and the refrigerator 52 located below the boundary wall 53 in the figure is disposed in the heat insulating layer.

The cryogenic refrigerator main body 51 is configured as follows. That is, a cylinder 61 formed of a thin stainless steel plate or the like.
And a displacer 62 housed in the cylinder 61 so as to be able to reciprocate freely.
And a high pressure valve 66, a low pressure valve 67, and a compressor 68 for guiding and discharging helium gas between the cylinder 61 and the motor 64.

The displacer 62 is formed by alternately and coaxially connecting cylindrical heat-insulating material blocks 69, 70, 71 and heat-exchange stages 72, 73 formed of a good heat conductive material into a cylindrical shape. I have. In each of the heat insulating blocks 69, 70, 71, fluid passages 74, 75, 76 extending in the axial direction are formed. Fluid passages 77 and 78 are formed in each of the heat exchange stages 72 and 73 so as to communicate the fluid passages 74, 75 and 76 in series to communicate the upper end side and the lower end side of the displacer 62. In the fluid passage 74, a cold storage material 79 formed of a copper mesh or the like is accommodated, and in the fluid passage 57, a cold storage material 80 formed of a lead ball or the like is accommodated. Contains a regenerator 81 made of, for example, Er ₃ Ni spheres having a large specific heat near 4.2K. In the figure, reference numeral 82 denotes a sealing mechanism for sealing between the displacer 62 and the cylinder 61.

As can be seen from the above configuration, this cryogenic refrigerator main body 51
Consists of a one-stage inflatable GM refrigerator. Therefore, in the cryogenic refrigerator main body 51, the tip wall 83 of the cylinder 61
An expansion chamber 90 is formed between the pressure chamber and the displacer 62, and the distal end wall 83 serves as a cooling stage.

On the other hand, the pre-cooling refrigerator 52 comprises a two-stage expansion type GM refrigerator shown in FIG. Therefore, in this figure, the same parts as those in FIG. 5 are denoted by the same reference numerals. Refrigerator 52
One ends of heat transfer members 84 and 85 are thermally connected to the first stage cooling stage 16 and the second stage cooling stage 17, respectively.
Heat transfer block 8 with thermal close contact on the outer peripheral surface of 1
Thermally connected to 6,87.

The heat transfer block 86 is provided so as to be located just outside the heat exchange stage 72 when the displacer 62 is at the bottom dead center which is the lowest point in the drawing.
87 is provided so as to be located just outside the heat exchange stage 73 when the displacer 62 is at the bottom dead center.

Next, the operation of the cryogenic refrigerator configured as described above will be described.

As described above, the cryogenic refrigerator main body 51 is constituted by a one-stage expansion type GM refrigerator. Therefore, the basic operation is the same as that of the refrigerator shown in FIG. The pre-cooling refrigerator 52 performs the same operation as the refrigerator shown in FIG.

When the pre-cooling refrigerator 52 is operated, the heat transfer block 86
The heat transfer block 87 is cooled down to about 8K. Now, assuming that the displacer 62 is at the bottom dead center, the heat exchange stage 72 is cooled to about 45K via the heat transfer block 86, and the heat exchange stage 73 is cooled to about 12K via the heat transfer block 87. .

When the displacer 62 is at the bottom dead center, the high-pressure valve 66 opens and high-pressure helium gas flows into the cylinder 61. next,
The displacer 62 moves to the top dead center. When the displacer 62 moves toward the top dead center, which is the highest point in the drawing, the high-pressure helium gas is filled with the cold storage material 79 filled in the fluid passage 74.
After cooling, the fluid flows to the fluid passage 77 formed in the heat exchange stage 72. Since the heat exchange stage 72 is cooled to about 45K as described above, the helium gas exiting the fluid passage 77 has a temperature of about 45K. The helium gas is further cooled to a lower temperature by the cold storage material 80 filled in the fluid passage 75, and then flows to the fluid passage 78 formed in the heat exchange stage 73. Since the heat exchange stage 73 is cooled to about 12K as described above, the fluid passage 78
The temperature of the helium gas exiting is about 12K. This helium gas is then used as a cold storage material filled in the fluid passage 76.
After being cooled to about 4.2K by 81, it flows into the expansion chamber 90.

Here, the high pressure valve 66 closes and the low pressure valve 67 opens. When the low-pressure valve 67 is opened in this way, the high-pressure helium gas in the expansion chamber 90 expands to generate cold. By this cold, the cooling stage 83 is further cooled to a lower temperature. When the displacer 62 moves to the bottom dead center again, the expansion chamber 90
The helium gas inside is removed by the reverse route. The expanded helium gas passes through the fluid passages 76, 75, 74 while the cold storage material 81, 8
0,79 is cooled and discharged at room temperature. Hereinafter, the above-described cycle is repeated to perform the refrigeration operation.

As can be seen from the above operation, in this cryogenic refrigerator, the high-pressure helium gas flowing through the so-called regenerator is cooled to a desired temperature by the heat exchange stages 72 and 73 at some point in the regenerator. Therefore, the temperature of the high-pressure helium gas flowing into the expansion chamber 90 can be lowered as compared with the case where the heat exchange stages 72 and 73 are not provided.

As described above, in the region of 10 K or less, the lower the pressure of the helium gas flowing into the expansion chamber 90, the higher the refrigerating capacity.
However, lowering the pressure lowers the refrigeration capacity in the upper stage, so that the temperature of the helium gas flowing into the expansion chamber 90 increases. As in this embodiment, heat exchange stages 72 and 73
Is arranged, the temperature of the helium gas flowing into the expansion chamber 90 can be controlled, and as a result, the pressure of the helium gas can be reduced. Therefore, 4.2K
A low pressure (for example, a high pressure of 10 atm and a low pressure of 2 atm) at which cold is sufficiently generated in the vicinity can be freely selected, and the refrigerating capacity in the vicinity of 4.2 K can be improved.

FIG. 2 shows an example in which the cryogenic refrigerator according to the present invention is actually incorporated in a cryostat.

The cryostat 100 includes an inner tank 101, an outer tank 102, a vacuum insulating tank 103 formed between the inner and outer tanks, and a vacuum insulating tank 1
It is composed of radiant heat shield plates 104 and 105 arranged in 03. Then, for example, the superconducting coil 1
06 and liquid helium 107 for cooling the same are stored.

In this example, the helium gas generated by the evaporation of liquid helium is recondensed in the cooling stage 83 of the cryogenic refrigerator 51, and the first cooling stage 16 and the second cooling stage 16 in the precooling refrigerator 52 are used. The radiant heat shield plates 104 and 105 are cooled by the cooling stage 17. The heat transfer blocks 86 and 87 fixed to the outer peripheral surface of the cylinder 61 are thermally connected to the radiant heat shield plates 104 and 105.

With such a configuration, the helium gas can be efficiently re-condensed in the cooling stage 83, and the pre-cooling refrigerator 52 can also be used for cooling the radiant heat shield plate, thereby simplifying the overall configuration. Can be.

The present invention is not limited to the embodiments described above. That is, in the above-described embodiment, the cool storage material and the heat exchange stage are incorporated in the displacer. However, as shown in FIG. 3, the cylinder 61a is formed in a double cylindrical shape, and the displacer 62a is disposed inside, The regenerator materials 79, 80, 81 and the heat exchange stages 72, 73 may be arranged outside, and the displacer 61a may be made independent. With such a configuration, the cooling stages 72 and 73 can be cooled without passing through a gap, so that efficiency can be improved. Further, as shown in FIG. 4, a cylinder 61b accommodating a displacer 62a and cold storage materials 79, 80, 81
Alternatively, the cylinders 61c accommodating the heat exchange stages 72 and 73 may be made independent, and these may be connected in series.

Also, in the above-described embodiment, the GM refrigerator is used for pre-cooling, but the heat transfer block, that is, the heat exchange stage is cooled by using a refrigerant such as liquid nitrogen or liquid oxygen without using the refrigerator. You may. In the above-described embodiment,
Although two heat exchange stages are provided, one or three or more heat exchange stages may be provided.

Further, in the above-described embodiment, the cryogenic refrigerator body and the refrigerator for pre-cooling are configured by a GM cycle refrigerator.
A cycle using another regenerator, such as a Stirling cycle or a Vilmiya cycle, may be used.

[Effects of the Invention] As described above, according to the present invention, the heat exchange stage is interposed between the heat accumulators and the helium gas flowing between the heat accumulators is forcibly cooled. Conditions can be freely selected, and as a result, the refrigerating capacity in the vicinity of 4.2K can be significantly improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a cryogenic refrigerator according to one embodiment of the present invention, FIG. 2 is a diagram showing an example in which the cryogenic refrigerator is incorporated in a cryostat, and FIGS. 3 and 4 are modified examples. FIG. 5 is a diagram illustrating the configuration of a conventional regenerative refrigerator, and FIG. 6 is a diagram illustrating the problems of the conventional refrigerator. 51 …… Cryogenic refrigerator, 52 …… Refrigerator for pre-cooling, 61,6
1a, 61b, 61c …… Cylinder, 62,62a …… Displacer,
72,73… Heat exchange stage, 79,80,81 …… Cool storage material, 83…
... Cooling stage, 86,87 ... Heat transfer block, 90 ... Expansion chamber.

Claims (7)

(57) [Claims] 1. A cylinder, a displacer accommodated reciprocally in the cylinder, a helium gas passage formed in the displacer, and a regenerative movement of the displacer by filling the helium gas passage with a regenerator material. A plurality of regenerators formed in the direction, and a heat exchange stage provided with a helium gas passage interposed between the regenerators and connecting adjacent regenerators, and the compressed helium gas is supplied to each of the regenerators. A cryogenic refrigerator that generates cold by expanding after passing sequentially, a heat transfer member disposed around the cylinder so as to be able to exchange heat with the heat exchange stage, and cooling means for cooling the heat transfer member. A cryogenic refrigeration apparatus, comprising: 2. The heat transfer member is disposed at a position facing a peripheral surface of the heat exchange stage when the displacer reaches a bottom dead center so as to form a minimum expansion space between the heat transfer member and the cylinder. The cryogenic refrigeration apparatus according to claim 1, wherein 3. An inner cylinder and an outer cylinder which are concentrically arranged so that an inner space and an outer annular space communicate with each other at a distal end portion, and are reciprocally housed in the inner cylinder and between the inner cylinder and the inner cylinder. A displacer forming a variable volume expansion space, a regenerator formed between the inner cylinder and the outer cylinder, and a plurality of regenerators formed in a direction in which the outer cylinder extends by interposing a regenerator between the inner cylinder and the outer cylinder. A heat exchange stage provided with a helium gas passage connected to and connected to an adjacent regenerator, wherein the compressed helium gas is sequentially passed through the regenerators and then expanded in the expansion space to generate cold. A low-temperature refrigerator; a heat transfer member arranged around the outer cylinder so as to be able to exchange heat with the heat exchange stage; and a cooling means for cooling the heat transfer member. Cryogenic refrigeration apparatus characterized by being Bei. 4. A volume between a first cylinder and a second cylinder, which are disposed in a leading end portion so as to communicate with each other, and is reciprocally housed in the second cylinder. A displacer forming a variable expansion space, and a plurality of regenerators formed by filling a regenerator material in the first cylinder and forming a plurality of regenerators in a direction in which the first cylinder extends.
A heat exchange stage provided with a helium gas passage interposed between these regenerators and connecting adjacent regenerators, wherein the compressed helium gas is sequentially passed through the regenerators and then expanded in the expansion space. A cryogenic refrigerator that generates cold by heating; a heat transfer member disposed around the second cylinder so as to be able to exchange heat with the heat exchange stage; and cooling means for cooling the heat transfer member. A cryogenic refrigeration apparatus characterized in that: 5. The cryogenic refrigerator according to claim 1, wherein any one of a Gifford McMahon cycle, a Stirling cycle, and a Vilmiya cycle is employed.
The cryogenic cooling device according to any one of claims 3 and 4. 6. The cryogenic system according to claim 1, wherein said cooling means also serves to cool a heat shield plate disposed in a heat insulating layer of the cryostat. Cooling system. 7. The cooling device according to claim 1, wherein said cooling means employs any one of a Gifford McMahon cycle, a Stirling cycle, and a Vilmiya cycle.
7. The cryogenic cooling device according to claim 6.