JP2549861Y2 - Regenerator for cryogenic refrigerator - Google Patents

Description

[Detailed description of the invention]

[0001]

The present invention relates to a cryogenic refrigerator.
In particular, it relates to a regenerator for a cryogenic refrigerator. In recent years, Gifford McMahon refrigerators, Stirling refrigerators, and the like have been widely used as small cryogenic refrigerators. The performance of these cryogenic refrigerators largely depends on the performance of the regenerator.

[0002]

2. Description of the Related Art In a Gifford-McMahon type refrigerator or a Stirling type refrigerator, a displacer is disposed in a cylinder, and the displacer reciprocates to form an expansion space having a variable volume at one end of the cylinder.

When a working gas such as helium gas expands in the expansion space, freezing occurs and the temperature of the working gas decreases. When the cooled gas passes through the displacer, it cools the regenerator material disposed in the displacer.

Next, when the working gas is introduced into the expansion space, the working gas is precooled by the regenerator material when passing through the displacer. The achievement temperature of refrigeration by the next adiabatic expansion is determined by the degree of precooling of the working gas.

[0005] Therefore, the regenerator storing the regenerator material is
It is desirable to have a sufficiently high heat capacity at the operating temperature and high heat exchange efficiency with the passing working gas.

[0006] In this regard, the same applies to the Stirling type refrigerator in which the compressor itself generates fluctuating gas pressure, and the Gifford McMahon type refrigerator in which the valve generates fluctuating gas pressure.

Incidentally, in a regenerator in which a cylindrical regenerator is filled with a granular regenerator material, it is known that there is a flow velocity distribution in the radial direction as disclosed in Japanese Unexamined Patent Publication (Kokai) No. 3-129257 and the 48th Autumn Meeting of the 1992 Low Temperature Engineering and Superconductivity Society of Japan. B1-13.

FIG. 3 reproduces an example of a radial velocity distribution from Japanese Patent Application Laid-Open No. 3-129257. In the figure, the horizontal axis shows the position in the radial direction, and the vertical axis shows the flow velocity. As is clear from the figure, the flow velocity changes slightly at the center, but the flow velocity increases rapidly near the inner wall of the cylindrical container.

[0009] Such a flow velocity distribution requires an excessive heat exchange performance for the cold storage material at the high flow velocity portion, and makes full use of the heat exchange performance for the cold storage material at the low flow velocity portion. You can't do it. In each case,
The refrigeration performance of the refrigerator is limited.

[0010] In order to equalize the flow velocity distribution in the radial direction in the cylindrical vessel, a proposal is made to insert a coaxial partition to change the particle diameter of the cold storage material inside and outside, or to alternate the cold storage material and mesh in the axial direction. Proposals for stacking have been made.

[0011]

If the flow velocity distribution occurs in the regenerator, the performance of the regenerator material cannot be fully utilized. In order to make the flow velocity distribution uniform by the conventional technique, the structure inside the regenerator becomes complicated.

An object of the present invention is to provide a regenerator for a cryogenic refrigerator which can make the flow velocity distribution uniform with a simple structure.

[0013]

SUMMARY OF THE INVENTION A regenerator for a cryogenic refrigerator according to the present invention comprises a cylindrical container, a layer of an adhesive applied on an inner side wall of the cylindrical container, and The filled particulate cold storage material, the particulate cold storage material disposed closest to the inner side wall of the cylindrical container, has a particulate cold storage material at least partially embedded in the layer of adhesive.

[0014]

The present inventor has considered the cause of the flow velocity distribution as shown in FIG. FIG. 4 schematically shows the distribution of the cold storage material 5 in the vicinity of the inner wall of the cylindrical container 3 of the regenerator. The cold storage material 5 had a spherical shape.

The inner wall of the cylindrical container 3 has a substantially flat surface, whereas the surface of the spherical regenerator 5 has a remarkably small radius of curvature. In order to accommodate as much cold storage material as possible in the cold storage material storage space of the cool storage device, the spherical cold storage material 5
It will take a structure close to the densest structure. At this time, the inner wall of the cylindrical container 3 exists to limit the distribution of the spherical cold storage material on the side.

Therefore, in the area A near the inner wall of the cylindrical container, compared with the central area B in which the spherical cool storage material is almost densely packed, in a space where one cool storage material cannot be completely accommodated, the cool storage material is used. A void portion is generated, and the filling rate of the cold storage material is significantly reduced (the void ratio is increased).

As described above, in the vicinity of the inner wall of the cylindrical container of the regenerator, a region A where the refrigerating material filling rate is extremely low occurs. In this region A, since the resistance to the flow of the working gas is significantly reduced, it is considered that the flow velocity is increased as shown in FIG.

According to the invention, a layer of adhesive is applied on the inner side wall of the cylindrical container, and the granular cold storage material located closest to this side wall is at least partially embedded in the layer of adhesive. ing.

As a result, the gap is crushed in the region A shown in FIG. Therefore, it is considered that a substantially uniform flow velocity can be obtained over the entire radial direction.

[0020]

FIG. 2 shows a Gifford model according to an embodiment of the present invention.
1 shows a configuration example of a McMahon refrigerator.

The Gifford McMahon type refrigerator includes a cold head 1 and a refrigerant gas introduction / discharge system 2 roughly divided. The cold head 1 includes a closed cylinder 11,
It has a displacer 12 reciprocally housed in the cylinder 11 and a motor 13 for providing the displacer 12 with a driving force required for reciprocation.

The cylinder 11 includes a large-diameter first cylinder 14 arranged on the upper side in the figure and a small-diameter second cylinder 15 coaxially connected to the lower side of the first cylinder 14. A first stage 16 as a cooling surface is constituted by a boundary wall portion between the first cylinder 14 and the second cylinder 15, and a second stage 17 having a lower temperature than the first stage is constituted by a tip wall portion of the cylinder 15.

The displacer 12 includes a first cylinder 14
A first displacer 18 reciprocating in the inside and a second displacer 19 reciprocating in the second cylinder 15 are connected in the axial direction by a connecting member 20.

A fluid passage 21 extending in the axial direction is formed inside the first displacer 18, and a cold storage material 22 formed of a copper mesh or the like is accommodated in the fluid passage 21.

A fluid passage 23 extending in the axial direction is also formed inside the second displacer 19, and the cold storage material 5 formed of a lead ball or the like is accommodated in the fluid passage 23.

The distance between the outer peripheral surface of the first displacer 18 and the inner peripheral surface of the first cylinder 14 and the distance between the outer peripheral surface of the second displacer 19 and the inner peripheral surface of the second cylinder 15
Sealing mechanisms 25 and 26 are mounted respectively.

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

In the upper part of the side wall of the first cylinder 14, an inlet 34 and an outlet 35 for the refrigerant gas are provided. These inlet 34 and outlet 35 are connected to the refrigerant gas inlet / outlet system 2.

The refrigerant gas introduction / discharge system 2 forms a helium gas circulation system via a cylinder 11. That is, the outlet 35 is connected to the inlet 34 via the low-pressure valve 36, the compressor 37, and the high-pressure valve 38.

For example, the refrigerant gas introduction / discharge system 2 has a capacity of about 5
The low-pressure helium gas is compressed to a high pressure of about 18 atm by the compressor 37 and sent into the cylinder 18. Low pressure valve 36,
The opening and closing of the high-pressure valve 38 is controlled in a predetermined phase relationship in relation to the reciprocation of the displacer 12.

When the motor 13 starts rotating, the displacer 12 starts reciprocating. When the displacer 12 is located at the lowest position in the drawing, the high-pressure valve 38 opens and high-pressure helium gas flows into the cold head 1.

Next, the displacer 12 moves upward. Since the seal mechanisms 25 and 26 are mounted between the displacer 12 and the inner wall of the cylinder, high-pressure helium gas is supplied to the fluid passage 21 in the first displacer 18 and the fluid in the second displacer 19 as the displacer moves. It flows to the first-stage expansion chamber 39 and the second-stage expansion chamber 40 through the passage 23. With this flow, the high-pressure helium gas is cooled by the cold storage materials 22 and 5.

Here, the high pressure valve 38 is closed and the low pressure valve 36 is opened. When the low-pressure valve 36 is opened, the high-pressure helium gas in the cylinder 11 is discharged, and the high-pressure helium gas accommodated in the first-stage expansion chamber 39 and the second-stage expansion chamber 40 expands to generate cold. The first stage 16 and the second stage 17 are cooled by this cold.

Next, the displacer 12 moves from the upper side to the lower side again, and accordingly, the helium gas in the first-stage expansion chamber 39 and the second-stage expansion chamber 40 is removed. While the cooled helium gas passes through the fluid passages 21 and 23,
It is warmed by the cold storage materials 22 and 24 and discharged at normal temperature. At this time, the cold storage materials 22 and 24 are cooled by low-temperature helium gas.

Thereafter, this cycle is repeated, and the refrigeration operation is performed. This type of refrigerator is used, for example, for cooling a superconducting magnet, for cooling an infrared sensor, and for cooling a cryopump.

In the Stirling refrigerator,
The low pressure valve 36 and the high pressure valve 38 are omitted, and the compressor 37 directly generates the fluctuating helium gas pressure, and supplies the fluctuating helium gas pressure to the cold head 1.

In this embodiment, an adhesive layer 4 a is formed on the inner wall of the fluid passage 23 of the second displacer 19. FIG. 1 shows an enlarged part of the second displacer. As shown in FIG. 1A, the second displacer 1
The adhesive layer 4 is applied on the inner peripheral surface of the cylindrical container 3 of No. 9. The fluid passage 23 is defined by the inner peripheral surface of the adhesive layer 4.

As shown in FIG. 1B, the fluid passage 23 in the second displacer 19 is filled with the spherical cold storage material 5 formed of lead particles or the like. The filling of the spherical cold storage material 5 is performed before the adhesive layer 4 solidifies.

For this reason, the cold storage material 5 penetrates into the adhesive layer 4, and in the vicinity of the inner peripheral surface of the cylindrical container 3, the outermost spherical cold storage material in which the adhesive layer 4 a is disposed near the inner wall. 5 to be embedded. In this state, the adhesive layer 4
a is solidified.

In the configuration of the regenerator as shown in FIG. 1B, a spherical regenerator 5 and a cylindrical container 3 of a displacer are provided.
Since the adhesive layer 4a is disposed so as to partially embed the spherical cold storage material 5 between itself and the inner wall, a region A having a low filling factor near the inner wall of the cylindrical container as shown in FIG. 4 is excluded. .
Therefore, the filling rate of the cold storage material 5 in the fluid passage 23 becomes substantially uniform, and a uniform flow velocity is realized.

In FIG. 1 (B), the space between the outside of the spherical cold storage material 5 and the inner wall of the cylindrical container 3 is completely occupied by the adhesive layer 4a. However, the thickness of the adhesive layer 4a is not strict.

For example, compared to the state shown in FIG.
Even if the thickness of a is somewhat thin or thick, the effect of eliminating the space near the inner peripheral surface of the cylindrical container 3 where the refrigerating material filling rate is extremely low is the same.

The spherical cold storage material 5 has a diameter of, for example, 0.2 to 0.2.
It has a size of about 0.4 mm. The thickness of the adhesive layer 4 a with the cold storage material 5 filled therein may be about half the diameter of the cold storage material 5. Therefore, the reduced volume of the fluid passage 23 is small compared to the total volume of the fluid passage 23 due to the presence of the adhesive layer 4a.

According to this embodiment, a substantially uniform flow velocity distribution can be obtained only by applying an adhesive having a predetermined thickness on the inner wall of the cylindrical container before filling the cold storage material, and the performance of the cold storage material is maximized. It is possible to pull out.

The present invention has been described with reference to the embodiment.
The present invention is not limited to these. For example, 2
Although the configuration of the stage displacer has been described, the present invention may be applied to a single stage displacer. The present invention can be applied not only to the second stage of the two-stage displacer but also to the first and second stages.

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

[0047]

[Effects of the Invention] As described above, according to the present invention,
The flow velocity distribution in the fluid passage in the regenerator can be made uniform with a simple configuration.

Since the flow velocity distribution can be made uniform, the performance of the cold storage material can be maximized.

[Brief description of the drawings]

FIG. 1 is an enlarged schematic cross-sectional view of a regenerator according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view schematically illustrating a configuration of a Gifford-McMahon refrigerator according to an embodiment of the present invention.

FIG. 3 is a graph showing a radial flow velocity distribution in a fluid passage in a conventional regenerator.

FIG. 4 is a conceptual diagram for explaining the consideration of the present inventors.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cold head 2 Refrigerant gas introduction / discharge system 3 Cylindrical container 4 Adhesive layer 5 Spherical cold storage material 11 Cylinder 12 Displacer 13 Motor 14 1st cylinder 15 2nd cylinder 16 1st stage 17 2nd stage 18 1st displacer 19th 2 displacer 21, 23 fluid passage 22 cold storage material

Claims (1)

(57) [Scope of request for utility model registration] 1. A cylindrical container, a layer of an adhesive applied on an inner side wall of the cylindrical container, and a granular cold storage material filled in the cylindrical container, the inner side wall of the cylindrical container A cold regenerator having a granular regenerator material disposed closest to the adhesive layer at least partially embedded in the layer of adhesive.