JPH0285652A - cryogenic refrigerator - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a cryogenic refrigerator that generates cold by expanding refrigerant gas through reciprocating movement of a displacer within a cylinder. This invention relates to an improved technology for a type of displacer that has a built-in regenerator that stores a portion of the cooled temperature.

(Prior Art) Conventionally, as a cryogenic refrigerator having an expansion machine that expands high-pressure refrigerant gas in a cylinder to generate cold, for example, as disclosed in Japanese Patent Application Laid-Open No. 58-214758, etc. A compressor that compresses helium gas as a refrigerant gas and an expander that expands the compressed gas are connected in a closed circuit by high-pressure piping and low-pressure piping,
The switching valve in the expander allows the high-pressure and low-pressure pipes to communicate alternately into the cylinder of the expander, and in response to the switching operation of the switching valve, a slack piston is reciprocated within the cylinder, and the piston reciprocates the displacer. BACKGROUND ART A so-called improved Solvay cycle helium refrigerator is known that generates cold by driving and expanding helium gas. Also,
In addition, a GM cycle (Gifford-McMahon cycle) in which the displacer is directly driven by gas pressure without using a slack piston is also well known.

In such a refrigerator, as the refrigerant gas expands adiabatically in the cylinder expansion chamber, its temperature decreases and cold occurs. Usually, in order to make the expander more compact, a regenerator is built into the displacer, which consists of a large number of metal regenerators such as lead balls and copper nets housed in a container. During the exhaust stroke, the refrigerant gas, whose temperature has dropped due to the temperature drop, is discharged from the expansion chamber of the cylinder, and the refrigerant gas is discharged through the regenerator in the displacer, and a portion of the cold is stored in the regenerator as it passes through the regenerator. Next, in the intake stroke for supplying refrigerant gas to the expansion chamber in the cylinder, the refrigerant gas reaching the expansion chamber is supplied through the regenerator, and the gas temperature is lowered by heat exchange with the regenerator. By repeating the exhaust stroke, the temperature is gradually increased to cryogenic levels.

(Problem to be Solved by the Invention) Generally, when a metal placed in a magnetic field moves, a loop of induced electromotive current is generated within the metal, and the larger the range of this loop, the smaller the induced current. There is a phenomenon in which the fluctuation of the magnetic field increases as the magnetic field increases. Therefore, as the displacer reciprocates, the regenerator material in the regenerator inside the displacer moves in a magnetic field such as earth's magnetism, and an induced current flows in the regenerator. That is, the movement of the displacer generates a loop of induced electromotive current in each of the regenerator materials in the regenerator. Then, since the stray electromotive currents cancel each other out between adjacent cold storage materials, the induced electromotive current remains as a loop passing through the cold storage materials located on the outer periphery of the cold storage material aggregate, and as a result, the induced current loop The range becomes larger.

For this reason, 5QUID (superconducting quantum interferometer; 5u
per conducting Quantum In
terrerence device) etc. to a cryogenic level by the cryogenic refrigerator for its operation, the 5QUID etc. may erroneously detect the induced magnetic field due to the loop of induced electromotive current generated in the regenerator, and the There was a problem in that the noise increased and had a negative effect on the operational reliability of the 5QUID and the like. For this reason, the above 5Q
Currently, liquid helium is used to cool UIDs and the like.

The present invention has been made in view of the above points, and its purpose is to perform a predetermined treatment on the metal regenerator material in the regenerator of the cryogenic refrigerator described above, thereby reducing the amount of heat generated as the displacer moves. By suppressing the size of the induced electromotive current loop and reducing its induced magnetic field, 5QUID
The purpose is to enable cooling by a refrigerator while ensuring operational reliability.

(Means for Solving the Problem) In order to achieve the above object, the solution of the present invention is to coat the surface of the metal cold storage material in the cold storage device with a thin oxide film, resin, etc. This blocks the induced electromotive current from flowing to other cold storage materials.

That is, the present invention, as shown in FIGS. 1 and 3,
As described above, the cylinder (5) and the displacer (18) that is fitted in the cylinder (5) so as to be reciprocally movable and that defines the expansion chambers (20) and (21) in the cylinder (5). By reciprocating the displacer (18), the refrigerant gas supplied from the compressor is transferred to the expansion chamber (18).
20) and (21) to lower the temperature, and the refrigerant gas whose temperature has been lowered is sent to the displacer (
The premise is a cryogenic refrigerator that stores cold by passing it through the built-in regenerators (28) and (29).

The regenerators (28) and (29) are the containers (30
) contains a large number of metal cold storage materials (31), (34), and the surfaces of the cold storage materials (31), (34) are coated with a coating film (3) having heat conductivity, heat storage properties, and non-conductivity.
2).

(Function) With the above configuration, in the present invention, when the refrigerator is operated, as the displacer (18) reciprocates within the cylinder (5), the regenerator (28) built in the displacer (18) , each cold storage material (31) in (29), (
34) An induced electromotive current is generated. And this cold storage material (
Since the surfaces of 31) and (34) are covered with a non-conductive coating film (32), the cold storage material (31)
, (34) are blocked by the coating film (32), and each cold storage material (31),
(34) adjoining cold storage material (31),
(34), and the large loop of induced electromotive current is cut off.

As a result, the induced magnetic field due to the loop of induced electromotive current is suppressed, and the adverse effect on the 5QUID etc. is suppressed, thereby making it possible to cool the 5QUID etc. with a refrigerator.

Moreover, since the coating film (32) formed on the surface of the cold storage material (31), (34) has heat conductivity and heat storage property, the cold storage property of the cold storage material (31), (34) itself is reduced. The cold storage capacity of the cold storage devices (28) and (29) can be ensured.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 3 shows an embodiment in which the present invention is applied to a helium refrigerator with an improved Solvay cycle, and (1) is an expander that expands helium gas as a refrigerant gas compressed by a compressor not shown. The expander (1) is connected to the compressor by high-pressure and low-pressure gas piping (none of which are shown) to form a closed circuit.

The expander (1) includes a valve housing (4) having a high pressure gas outlet (2) to which the high pressure gas pipe is connected and a low pressure gas outlet (3) to which the low pressure gas pipe is connected; ) is integrally and airtightly joined to the bottom of the
The cylinder (5) has a two-stage structure consisting of an upper large diameter part (5a) and a lower small diameter part (5b), and the inside of the valve housing (4) is connected to the high pressure gas port (2). A motor chamber (6) that communicates with the motor chamber (6), a vertical through hole (7) that communicates with the motor chamber (6), and a surge volume chamber (9) that communicates with the low pressure gas outlet (3) via an auxiliary orifice (8). ) are formed.

Further, a valve stem (10) constituting the upper closed end of the cylinder (5) is fitted into the joint between the valve housing (4) and the cylinder (5).
10) is a valve seat part (10a) hermetically fitted into the through hole (7) of the valve housing (4); (5a) Hanging part (lob) hanging from the inner upper part
A space surrounded by the upper surface of the valve seat portion (10a) and the wall surface of the through hole (7) allows a valve chamber (1) to communicate with the high pressure gas pipe via the motor chamber (6).
1) is formed. In addition, the above valve stem (10
) has two branch channels (12a) and (1
2a), which communicates the valve chamber (11) with the inside of the cylinder (5);
), and the other end is connected to the low pressure gas outlet (3) through the valve housing (4).
A second gas flow path (13) communicating with the second gas flow path (13) via a communication path (14) formed in the second gas flow path (12) is formed through the second gas flow path (13).
(13) is connected to the valve chamber (11) on the upper surface of the valve stem (10), and in the second gas flow path (13), the first gas flow path (12) is located at the center of the valve stem (10).
The branch flow paths (12a) and (12a) are opened at positions symmetrical to the opening of the second gas flow path (13).

On the other hand, a drive space (
A roughly cup-shaped slack piston (1G) that defines a section of the valve stem (15) has its upper end inner surface connected to the valve stem (10).
The driving space (15) is fitted into the drooping part (tab) of the valve housing (4) so as to be reciprocally movable in an airtight sliding state, and the orifice (17) is connected to the surge volume chamber (9) in the valve housing (4). We are in constant communication via.

The slack piston (16) has a bottom wall (lea), and a center hole (IGb) and a communication hole (l[ic) that communicate between the inside and outside of the piston (16) are formed through the bottom wall (1 (ia)). has been done.

Furthermore, a displacer (18) is provided in the cylinder (5).
) are fitted to allow reciprocating movement. The disblazer (
18) includes a closed cylindrical large diameter part (18a) that slides inside the lower half of the large diameter part (5a) of the cylinder (5), and a large diameter part (
18a) It consists of a closed cylindrical small diameter part (18b) that is integrally formed at the lower end and slides inside the small diameter part (5b) of the cylinder (5), and this displacer (18) allows the slack piston (16) to be moved downwardly. The inner space of the cylinder (5) is divided into an intermediate chamber (19), a first stage expansion chamber (20), and a second stage expansion chamber (21) in order from the top. Through a communication hole (not shown), the space within the large diameter portion (18a) of the displacer (18) is connected to the first stage expansion chamber (20).
The space within the small diameter section (tab) is constantly communicated with the first and second stage expansion chambers (20) and (21).

Furthermore, the large diameter portion (18a) of the displacer (18)
) A tubular locking piece (22) that communicates the space within the large diameter portion (L8a) with the intermediate chamber (19) is integrally provided at the upper end, and the locking piece (22) is connected to the slack piston. Bottom wall (
The piston (16a) passes through the center hole (16b) of the piston (16a).
) A flange-shaped locking part (22a) that extends inside by a predetermined length and engages with the piston bottom wall (16a) at its upper end.
are integrally formed, and when the slack piston (16) moves upward, when the piston (16) rises by a predetermined stroke, the bottom wall (lea) and the locking part (22a) of the locking piece (22) By engaging with the displacer (18
) is driven by the piston (16) to start rising, that is, the displacer (18) is moved to follow the piston (16) with a delay of a predetermined stroke.

In addition, the valve chamber (11) of the valve housing (4)
Inside is a valve motor (23) placed in the motor chamber (6).
A rotary valve (24) is provided as a switching valve that is rotatably driven by the rotary valve (24), and the switching operation of the rotary valve (24) causes the high-pressure gas pipe, that is, the valve chamber (11) that communicates with the high-pressure gas pipe, and the low-pressure gas pipe In other words, the communication passage (14) communicating with the low pressure gas pipe is connected to the cylinder (5).
), the intermediate chamber (■9), the first and second stage expansion chambers (20)
, (21) are alternately communicated.

That is, the rotary valve (24) is non-rotatably but slidably connected to the output shaft (23a) of the valve motor (23). Further, a spring (25) is compressed between the upper surface of the valve (24) and the motor (23), and the spring force of this spring (25) and the valve chamber (1
1), the lower surface of the rotary valve (24) is pressed against the upper surface of the valve stem (10) with a constant pressing force.

On the other hand, a pair of high-pressure boats (2B) are formed by cutting a predetermined length toward the center from the radially opposing outer peripheral edges of the lower surface of the low-pressure valve (24).

(26) and the high pressure port (2G) are arranged at an angular interval of approximately 90'' from (28) in the rotational direction of the rotary valve (24), extending from the center of the lower surface of the valve (24) near the outer periphery. A low-pressure port (27) is formed by cutting out in the diametrical direction.Then, when the valve motor (23) is driven, the low-pressure valve (24) presses its lower surface against the upper surface of the valve stem (lO). When rotating and switching, the slack piston (16) and displacer (18) reciprocate within the cylinder (5) according to the switching operation of the low-return valve (24), and the high pressure port (2B) on the lower surface of the valve (24) ) and (2B) respectively match the first gas flow path (12) opening on the upper surface of the valve stem (10), the valve chamber (1
1) to the intermediate chamber (19) in the cylinder (5) via the high pressure boat (26), (2B) and the first gas flow path (12).
The slack piston (1a
) and raise the displacer (18) driven by the piston (16). On the other hand, the valve stem (1
0) When the outer end of the low-pressure boat (27), which is in constant communication at the center with the second gas flow path (13) opened on the top surface, matches the first gas flow path (12), the cylinder (5) Each chamber (19) to (21) inside is connected to a first gas passage (12), a low pressure port (27), a second gas passage (13) and a communication passage (
(1) The slack piston (
16) and the displacer (18), and as the displacer (18) moves downward, the expansion chamber (20)
, (21) is configured to generate refrigeration by expansion of helium gas within.

Furthermore, the large diameter portion (18a) of the displacer (18)
), the first stage regenerator (28) is located in the space inside the small diameter part (
A second stage regenerator (29) is fitted in the space inside 18b), and these regenerators (2B) and (29) have the same configuration and are both regenerator type heat exchangers. Each of the regenerators (28) and (29) includes a large number of lead balls (31) having a predetermined diameter as a regenerator inside a cylindrical container (30).
, (31), ... (lead shot) are filled and sealed, and the gap between these lead balls (31), (31) is used as a gas passage, and the cold heat of the helium gas flowing through this gas passage is transferred. It is stored in each lead bulb (31). That is, when the displacer (18) is in the intake stroke rising inside the cylinder (5), the lead balls (31), (H), . . . whose temperature has dropped to an extremely low temperature level in the previous exhaust stroke
from the intermediate chamber (19) to the first or second stage regenerator (20),
(21) by contacting it with room temperature helium gas,
Heat exchange between the two cools the gas to near cryogenic levels. On the other hand, when the displacer (18) is in the downward exhaust stroke, the helium gas whose temperature has dropped to an extremely low temperature level due to expansion in each expansion chamber (20), (21) is discharged out of the cylinder (5). (31).

(31), . . . and is configured to cool the lead balls (31), (31), .

As a feature of the present invention, as shown in enlarged detail in FIG. 1, the surface of each lead ball (31) is coated with, for example, an oxide film or a resin coating such as Teflon, polyester, polyurethane, etc., to improve heat conductivity, heat storage, It is covered with a non-conductive coating film (32). Specifically, when a Teflon film is used as this coating film (32), its various characteristics at each temperature level are as shown in the table below, and according to this, the thickness of the coating film (32) is several μm or less. is preferred.

Next, the operation of the above embodiment will be explained.

The operation of the refrigerator is basically the same as in a normal fight.

That is, first, the cylinder (5) in the expander (1)
When the internal pressure is low and the slack piston (16) and displacer (18) are at the lower end position, the high pressure boat ( 2B),
(2G) is the first gas flow path (
12), the rotary valve (24) opens to the high pressure side. Along with this, high pressure helium gas at room temperature, which is being supplied from the compressor to the valve chamber (11) via the high pressure gas piping and the motor chamber (6) of the expander (1), is transferred to the high pressure port of the rotary valve (24). (2B), (20) and the first
The gas is introduced into the intermediate chamber (19) below the slack piston (16) via the gas flow path (12). Further, this gas is passed from the intermediate chamber (19) through each of the regenerators (28) and (29) of the displacer (18), and sequentially through each expansion chamber (20) and the displacer (18).
(21), and this regenerator (28), (
29), which has been cooled during the previous exhaust stroke (
31), (31), etc., it is cooled to near the cryogenic temperature level. In addition, the above piston (16
) The piston (I6) rises due to the pressure difference between the upper drive space (15) and the lower intermediate chamber (19). and,
When the upward stroke of the piston (16) reaches a predetermined value, the bottom wall (16a) of the piston ([6) and the locking piece (22) at the upper end of the displacer (18) engage with each other. ) is pulled up by the piston (16) with a delay in response to the pressure change, and the upward movement of the displacer (18) causes the expansion chamber (20) below it to rise.
, (21) is further filled with high pressure gas (intake stroke).

After this, when the above-mentioned low-pressure valve (24) closes, the displacer (18) continues to rise due to inertia.
Along with this, the intermediate chamber (1) below the displacer (18)
Helium gas in the first and second stage expansion chambers (20)
, move to (21).

After the displacer (18) reaches the rising end position, the low pressure boat (27) of the rotary valve (24) matches the first gas flow path (12) on the upper surface of the valve stem (10), and the valve (24) ) opens to the low pressure side, and with this opening, each expansion chamber (20
), (21) undergoes Simon expansion, and this expansion of helium gas generates cooling (expansion stroke).

This extremely low-temperature helium gas is transferred to the regenerator (28) in the displacer (1B), contrary to when the gas was introduced.
), return to the intermediate chamber (I9) through (29),
Meanwhile, the lead bulb (31) inside the regenerator (28) and (29)
, (31).

It can heat itself to room temperature while cooling it to an extremely low temperature level. This helium gas at room temperature is further transferred to the first gas flow path (12) together with the gas in the intermediate chamber (19).
, low pressure boat (27) of valve (24), communication passage (14)
) is discharged to the outside of the expander ([), flows through the low-pressure gas piping to the compressor, and is sucked into it. With this gas discharge, the gas pressure in the intermediate chamber (19) decreases, and the slack piston (1
6) descends, and the bottom q (tea
) comes into contact with the upper surface of the displacer (18), the displacer (18) is pressed and lowered, and the downward movement of the displacer (18) causes the expansion chamber (20),
(21) is further discharged to the outside of the expander (1) (exhaust stroke).

Next, the rotary valve (24) closes, but even after this, the displacer (18) descends to the lower end position, the gas in the expansion chambers (20), (21) is exhausted, and the displacer (18) returns to its initial state. With the above, one cycle of the operation of the expander (1) is completed, and the same operation as described above is repeated thereafter.

Then, the displacer (18) is connected to the cylinder (5).
As shown in FIG. 2, a regenerator (28) built into the displacer (18) moves back and forth within the displacer (18).

Lead ball (31) in (29), (31),...(
As the cold storage material) moves in a magnetic field such as the earth's magnetism, the lead ball (
31), (31), . . . an induced electromotive current is generated.

However, in this embodiment, the surface of each lead ball (31) is coated with a non-conductive coating film (32), so the induced electromotive current l generated in each lead ball (31) is reduced by the coating film (32). 32) and each lead ball (
31) and does not flow to the adjacent lead bulb (31), and if there is no coating film (32), the regenerator (2
8) and (29), a large loop of induced electromotive current (indicated by a dashed line in the figure) flowing in the circumferential direction is cut off. As a result, the induced magnetic field due to the induced electromotive current loop is suppressed with a simple structure, and the 5QU
Even if a refrigerator is used to cool the ID, etc., it will not have a negative effect on magnetic flux detection of the 5QUID, etc., and therefore the 5QUID
etc. can be cooled down by a refrigerator without any problem.

In addition, since the coating film (32) formed on the surface of each lead ball (3I) has heat conductivity and heat storage properties, the cold storage property of each lead ball (31) does not decrease, and the cold storage Good cold storage capacity of the containers (28) and (29) can be ensured.

Incidentally, in the research conducted by the present inventors, the degree of the magnetic field due to the current loop cut is as follows: (31), (31),
... are arranged so as to form a circle with radius R, it becomes r/R, and as in the above example, the lead ball (31), (
31), . . . are arranged to form a disk with radius R, then (r/R) becomes 2. Therefore, in the case of a regenerator in which lead balls (31) with a diameter of 0.3 mm are filled in a cylindrical container (30) with a diameter of 30 mm, the degree of magnetic field due to current loop cut is (r/R) 2- (
It can be suppressed to about 0.15/15)'-1/104.

In the above embodiment, a regenerator (
28).

Although (29) was used, it is also possible to use a regenerator containing other regenerator materials.

For example, as shown in Figure 4, a large number of copper nets (33), (3
3) When using a regenerator formed by laminating meshes in multiple stages, each copper mesh (33) has a large number of vertical and horizontal copper wires (34), (34), ...(cold storage). each surface of the material) is covered with a coating film (32),
As the displacer (18) moves, each copper wire (34)
The induced electromotive current I generated in is blocked by the coating film (32) and remains within each copper wire (34), and does not flow to the copper wires (34), (34), etc. that intersect or are parallel to each other. The copper wires (34) that are missing, intersect or parallel,
A large loop of induced electromotive current flowing in the circumferential direction of the entire regenerator via (34), . . . is cut off. Therefore, similarly to the above embodiment, the 5QUID and the like can be cooled by the refrigerator without any problem and without impeding the cold storage performance.

Furthermore, the present invention is of course applicable not only to helium refrigerators having the improved Solvay cycle as in the above embodiments, but also to refrigerators using refrigerant gases other than helium gas.

(Effects of the Invention) As explained above, according to the present invention, by coating the surfaces of many metal regenerators in the regenerator built in the displacer of a cryogenic refrigerator with a thin oxide film, resin, etc. The induced electromotive current generated in the cold storage material as the displacer moves is contained in each cold storage material, a large loop of induced current is cut with a simple structure, and the induced magnetic field due to the loop of induced current is suppressed, and 5QUID etc. Therefore, cooling of 5QUID etc. by a refrigerator can be realized.

[Brief explanation of the drawing]

The drawings show embodiments of the present invention; Fig. 1 is an enlarged sectional view of a lead bulb, Fig. 2 is a diagram illustrating the principle of breaking the loop of induced electromotive current in a regenerator, and Fig. 3 is a sectional view of an expander. be. FIG. 4 is a diagram corresponding to FIG. 2 showing another embodiment. (1)...Expansion machine, (5)...Cylinder, (te)
... slack piston, (18) ... displacer, (20), (21) ... expansion chamber, (28),
(29)...Regenerator, (30)...Container, (31
)...Lead ball (cool storage material), (32)...Coating film, (33)...Copper mesh, (34)...Copper wire (cold storage material). Patent applicant Daikin Industries, Ltd. Representative Patent attorney 1) Hiroshi (and 2 others) 28.
29 (1st drink) Tortoise figure 2

Claims (1)

[Claims] (1) A cylinder (5), an expansion chamber (20) fitted in the cylinder (5) so as to be able to reciprocate and
), (21), and the reciprocating movement of the displacer (18) transfers the refrigerant gas supplied from the compressor to the expansion chambers (20), (21).
21) In a cryogenic refrigerator in which the temperature is lowered by expanding the refrigerant gas within the refrigerant, and the refrigerant gas whose temperature has been lowered is stored by passing through regenerators (28) and (29) built in the displacer (18). , the regenerators (28), (29) contain a large number of metal regenerators (31), (34) in a container (30),
31) A cryogenic refrigerator characterized in that the surfaces of (34) are coated with a coating film (32) having heat conductivity, heat storage properties, and non-conductivity.