JPH0468266A - Cryogenic refrigerating machine - Google Patents

Abstract

PURPOSE:To maintain the refrigerating capacity by a method wherein the changeover of high and low pressure gas refrigerant supplies to a cylinder is done by a changeover valve and the gas pressure for driving the changeover valve is changed and supplied by a valve motor. CONSTITUTION:In an expansion device 2, the high pressure gas supplied from a compressor 1 is adiabatically expanded in expansion chambers 12 and 13 in a cylinder 3 by the reciprocating motion of a displacer 10 to generate cold of a cryogenic level. A pressure changeover device 51 is provided with a gas supply-discharge port 57 communicating with a pressure chamber 37, high and low pressure gas ports 53 and 54 respectively connected to the delivery and suction port sides of the compressor 1, a valve 62 which switches the communication state of the gas ports, and a valve motor 61. When the valve 62 is switched by the valve motor 61 at specified timings, the delivery and suction ports of the compressor 1 are alternately communicated to the gas supply discharge port 57. Together with the switching operation of the valve 62, a changeover valve 32 alternatively communicates either a high pressure gas inlet 28 or a low pressure gas outlet 29 to a gas supply discharge chamber 11 so that the gas is supplied to and discharged from either the gas supply discharge chamber 11 or the expansion chambers 12 and 13.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention reciprocates a displacer within the cylinder of an expander using gas pressure, and by adiabatic expansion of refrigerant gas accompanying the reciprocating movement of the displacer, the refrigerant gas can be heated to a cryogenic level. This relates to a cryogenic refrigerator that generates cold.

(Prior Art) Conventionally, as this type of cryogenic refrigerator, a gas pressure driven GM refrigerator having a refrigerant cycle of a GM (Gifford-McMahon) cycle has been known. The expander of this refrigerator includes a cylinder, a displacer and a slack piston that are reciprocally disposed within the cylinder, and an expansion chamber is defined at the tip of the cylinder by the displacer. It communicates with the space on the base end side of the cylinder via the inner flow generator.

The slack piston is arranged on the proximal end side of the cylinder so as to partition the proximal space into a gas supply/discharge chamber and an intermediate pressure chamber,
The displacer is engaged with the displacer at a predetermined stroke interval. The intermediate pressure chamber is communicated with the surge volume, while the gas supply/discharge chamber is communicated with a high pressure gas inlet and a low pressure gas outlet connected to the discharge side and suction side of the compressor, respectively. By periodically switching the supply and discharge of refrigerant gas to and from the gas supply and discharge chamber or the expansion chamber, the slack piston is moved by the differential pressure between the gas supply and discharge chamber and the intermediate pressure chamber, causing the displacer to reciprocate. The expansion of the refrigerant gas in the expansion chamber due to the reciprocating movement of the refrigerant generates cold in the cylinder around the expansion chamber.

When switching the supply and discharge of the gas, there are two main types: those that use electric actuators such as motors and solenoid valves, and those that use fluctuations in gas pressure in an expander as shown in Japanese Patent Application Laid-Open No. 190665/1983. It can be divided into those that are made to do so.

Incidentally, in recent years, superconducting quantum interference devices (Super
conduitive Quantull Interr
erence device (hereinafter abbreviated as 5QUID) is attracting attention. By connecting a magnetic flux input circuit consisting of a superconducting coil to this 5QUID, a gradiometer can be created that can maintain n1 constant of extremely weak magnetic flux, such as the magnetic field associated with a minute current flowing inside a living body or the magnetic field from a minute magnet inside the body. Obtainable.

However, in order to cool this 5QUID to the operating temperature level, when using a gas pressure-driven GM refrigerator with the above-mentioned electric actuator, the refrigerator has an actuator that generates magnetic flux, such as a motor or solenoid valve. Therefore, there is a problem in that the magnetic flux from this actuator is detected as harmful noise, and the measurement accuracy is reduced.

Conventionally, in order to reduce the influence of the valve motor, the valve and valve motor in the expander were separated from the cylinder part, and the valve motor assembly and cylinder assembly were connected via piping, thereby connecting the valve motor to a 5QUID, that is, cylinder. A separate type that is placed away from the tip to reduce harmful noise caused by magnetic flux from the valve motor has been proposed (for example, in 1988).
The meeting held from 8.18 to 8.19 “5th Int.
ernatlonal Cryocooler Con
1’erence” American paper “Develops
ent or A Hybrid GifTord-M
c+gahon Joule-Thoapson Ba
5ed Neuromagnetometer, Cry
osquid') 0 (Problem to be Solved by the Invention) However, in such a separate expander in which the valve motor is separated from the cylinder part, there is a pressure loss of refrigerant gas in the refrigerant pipe that connects the two. Therefore, compared to an integrated type, for example, as shown in Fig. 6, it is unavoidable that the so-called Pv indicated capacity decreases by the pressure loss and the refrigerating capacity decreases, and the load on the compressor also decreases. increase

In addition, with an integrated expander, high and low pressure gas is circulated between the compressor and the compression heat taken by the gas at the cold end of the cylinder is released while the gas returns to the compressor, which is a problem. However, in a separate expander such as the one described above, the amount of refrigerant gas circulating between the compressor and the compressor decreases, and as a result, the compression heat is not sufficiently dissipated and accumulates in the room-temperature part of the cylinder assembly. That will happen. This retention of heat heats the surge volume located at the base end of the cylinder, increasing the gas pressure inside it and reducing the differential pressure between the intermediate pressure and high pressure, allowing smooth movement of the slack piston and displacer. This causes troubles such as lengthening the cool-down time and reducing the refrigeration capacity during steady operation after the cool-down.

Increasing the diameter of the refrigerant piping in order to ensure a large refrigerating capacity makes it easier for the heat of compression mentioned above to accumulate, while making it thinner causes the paradoxical problem of increasing pressure loss. Selection of pipe diameter is also important.

On the other hand, in refrigerators that utilize fluctuations in gas pressure in the expander,
As far as the material of the moving parts is concerned, there is no need to worry about electromagnetic noise, but on the other hand, the structure of the gas flow path and valve arrangement is extremely complicated, and reliability during long-term continuous operation is low. It is difficult to say that it is practical as disassembly and reassembly becomes complicated.

The present invention has been made in view of the above points, and its purpose is to improve the refrigerant piping that connects the valve motor to the cylinder portion by adding certain improvements to the above-mentioned actuator-driven expander. The objective is to stabilize the reciprocating motion of the displacer and secure the refrigerating capacity by eliminating the pressure loss of the gas caused by the heat exchanger and the influence of heating on the surge volume.

(Means for Solving the Problem) In order to achieve the above object, in the invention of claim (1), in the expander, high pressure and low pressure refrigerant gas are supplied and discharged to and from the cylinder using a gas pressure-driven switching valve. The gas pressure for driving this switching valve is switched and supplied by a valve motor separate from the expander.

Specifically, as shown in Fig. WS1 or Fig. 4, this invention includes a compressor (1) that compresses refrigerant gas to generate high-pressure gas, and a displacer (3) fitted into a cylinder (3). 10), and by reciprocating the displacer (10), the high-pressure gas supplied from the compressor (1) is adiabatically expanded in the expansion chambers (12) and (13) in the cylinder (3) and brought to a cryogenic temperature. Expansion machine that generates a level of coldness (2)
The above expander (2)
has the following configuration.

That is, the expander (2) includes the expansion chamber (12),
(13), and the high pressure gas inlet (28) and low pressure gas outlet (29) are inflated by switching the gas pressure to the pressure chamber (37). A switching valve (32) switches to selectively communicate with the chambers (12) and (13).
).

Then, the high pressure gas inlet (28) is connected to the compressor (1).
) via a high pressure pipe (91),
The low pressure gas outlet (29) is connected to the suction side of the compressor (1) via a low pressure pipe (92).

Pressure switching means (51) that periodically switches the gas pressure for the pressure chamber (37) of the expander (2) to high pressure or low pressure.
is arranged separately from the expander (2), and the pressure switching means (51) includes a gas supply/discharge port (57) communicating with the pressure chamber (37) via a connecting pipe (93); The above compressor (1
) and a high pressure gas port (53) and a low pressure gas port (54) respectively connected to the discharge side and suction side of the gas supply/discharge port (57). Valve (62) that switches communication between
and a valve motor (61) that switches and drives the valve (62) at a predetermined timing.

In the invention of claim (2), in the structure of the invention of claim (1), the pressure switching means is a linear motor compressor instead of the valve means using a valve motor.

That is, in this invention, as shown in FIG.
3) a piston (75) that is reciprocably disposed within the cylinder (73) and forms a compression chamber (74) that communicates with the pressure chamber (37) via a communication pipe (93); It is characterized by comprising a linear motor (76) that reciprocates a piston (75).

(Function) With the above configuration, in the invention of claim (1), the valve (62) in the pressure switching means (51) is controlled by the valve motor (
61) at a predetermined timing, the discharge side and suction side of the compressor (1) are alternately switched to the gas supply/discharge port (5).
7). This gas supply/exhaust port (57) is connected to the connecting pipe (
93), the gas pressure in the pressure chamber (37) increases or decreases as the valve (62) is switched. This pressure chamber (37
) The switching valve (32
) is switched to selectively communicate the high pressure gas inlet (28) and the low pressure gas outlet (29) with the gas supply and discharge chamber (11), and thereby the gas supply and discharge chamber (11) or the expansion chamber ( Gas is supplied to and discharged from 12) and (13).

In this invention, the valve motor (61) is used to switch between high and low pressure, but since it is the switching valve (32) in the expander (2) that switches based on this high and low pressure, the valve motor (61) the cylinder (3) low temperature end, that is 5
It can be installed with sufficient performance from QUID etc., and magnetic noise for 5QUID etc. can be reduced.

In addition, the structure is such that the switching valve (32) is switched by the valve (62) driven by the valve motor (61), and the expander (2
) and compressor (1) are high pressure and low pressure piping (91), (9
2), the flow of refrigerant gas between the compressor (1) and expander (2) is equivalent to that of an integrated type in which the valve motor (61) is not separated. Therefore, as in a separate refrigerator where the valve section is separated from the cylinder section and the two are connected via refrigerant piping, the refrigerating capacity may decrease due to gas pressure loss in the refrigerant piping, or compression 11 (1)
It is possible to avoid an increase in the load on the cylinder (3) or an adverse effect on the reciprocating motion of the displacer (10) due to retention of compression heat at the normal temperature end of the cylinder (3).

Furthermore, the pressure switching means (51) outside the expander (2) switches the gas pressure in the pressure chamber (37) of the expander (2), and this gas pressure drives the switching valve (32). 2) only needs to be provided with a gas pressure switching valve (32), and the valve structure within the expander (2) becomes extremely simple.

In the invention of claim (a), since the pressure switching means (71) is constituted by a linear motor compressor, as the linear motor (76) operates, the piston (75) moves into the cylinder (
73) at a predetermined period, and the gas pressure within the compression chamber (74) changes in height. Since this compression chamber (74) communicates with the pressure chamber (37) of the expander (2) via the connecting pipe (93), the reciprocating movement of the piston (75) causes
The switching valve (32) of the expander (2) is connected to the high pressure gas inlet (2).
8) and the low-pressure gas outlet (29) are switched to selectively communicate with the gas supply/discharge chamber (11), and gas supply to the gas supply/discharge chamber (11) or the expansion chambers (12) and (13) is switched. Evacuation takes place. Therefore, the same effects as described above can be obtained in this invention as well.

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

FIG. 1 shows a gas pressure driven GM according to a first embodiment of the present invention.
The overall configuration of a type cryogenic refrigerator is shown. This refrigerator is used as a precooling refrigerator for a JT refrigerator that uses Joule-Thomson expansion of helium gas (refrigerant gas).
A refrigerator cools the 5QUID (not shown) to cryogenic levels. In the figure, (1) is a compressor that compresses helium gas as a refrigerant gas to generate high-pressure gas, and (2) is a compressor that adiabatically expands the high-pressure gas supplied from compressor (1) to reach a cryogenic level. It is an expansion machine that generates cold.

The expander (2) includes a bottomed cylindrical cylinder (3),
It has a lid member (21) that airtightly closes the proximal end side opening of the cylinder (3). The cylinder (3) is formed in a two-stage structure with a large diameter part (3a) on the base end side and a small diameter part (3b) continuous to the tip of the large diameter part (3a).
At the lower end of 3a) there is a first stage heat station (4) maintained at a temperature level of, for example, 55-60 degrees, and at the lower end of the small diameter section (3b) there is a A second stage heat station (5) maintained at a low temperature level, e.g.
Heat is transferred from 5) to pre-cool the helium gas in the JT refrigerator (not shown).

A slack piston (7) is disposed inside the upper end of the large diameter portion (3a) of the cylinder (3) and defines an intermediate pressure chamber (6) inside the large diameter portion (3a). The slack piston (7) is approximately cup-shaped with a bottom wall, and the upper end of its inner circumference is connected to the protrusion (2) of the valve stem (22), which will be described later.
2a) The lower end of the outer circumference is in airtight sliding contact with the inner circumference of the large diameter portion (3a) of the cylinder (3). Also,
There is a center hole (8) in the center of the bottom wall of the slack piston (7).
However, a plurality of communication holes (9), (9), . . . are formed through the corners of the bottom wall to communicate the inside and outside of the piston (7).

Further, a displacer (10) is fitted into the cylinder (3) so as to be able to reciprocate. This displacer (1
0) is a large diameter part (10a) arranged to be airtightly slidable in the large diameter part (3a) of the cylinder (3), and the large diameter part (10a) of the cylinder (3).
Continuing with the tip of a), the small diameter part (3b) of the cylinder (3)
It has a two-stage structure, consisting of a small diameter part (10b) arranged so as to be airtightly slidable.
A sealed space is formed inside each of 0b),
With this displacer (10), the space inside the cylinder (3) is divided into a gas supply/discharge chamber (11) surrounded by the upper end of the displacer (10) and the slack piston (7), and a large diameter part (10a) of the displacer (10). ) and the large diameter part (3a) of the cylinder (3), and corresponds to the first stage heat station (4).
), a second stage expansion chamber (13) surrounded by the tip of the small diameter part (10b) of the displacer (10) and the tip of the small diameter part (3b) of the cylinder (3), and corresponding to the second stage heat station (5). It is divided into.

Further, at the lower end of the large diameter part (10a) of the displacer (10), there is a communication hole (14) that constantly communicates the sealed space inside the large diameter part (10a) with the first stage expansion chamber (12).
is formed. Further, at the upper end of the small diameter part (10b), there is a communication hole (15), (15) that always communicates the space inside the small diameter part (10b) with the first stage expansion chamber (12), and at the lower end, there is a communication hole (15) that always communicates the space inside the small diameter part (10b) with the first stage expansion chamber (12). Communication holes (16), (16) are formed, respectively, to constantly communicate with the second stage expansion chamber (13).

Furthermore, the large diameter portion (10a) of the displacer (10)
) A tubular locking piece (17) that communicates the space inside the large diameter portion (10a) with the gas supply/discharge chamber (11) is integrally provided at the upper end, and the locking piece (17) is connected to the slack. Piston (7)
It extends into the piston (7) by a predetermined dimension through the center hole (8) of the bottom wall, and is integrally provided with a flange-like locking part (17a) that engages with the bottom wall of the piston (7) at its upper end. When the slack piston (7) moves upward, when the piston (7) rises by a predetermined stroke, the bottom wall of the slack piston (7) engages with the locking portion (17a) of the locking piece (17).
The displacer (10) is driven by the piston (7) to start rising.
0) is moved to follow the piston (7) with a delay of a predetermined stroke.

The large diameter portion (10a) of the displacer (10)
) is the first stage regenerator (18) (regenerator), and the small diameter part (10b) is the second stage regenerator (18) (regenerator) in the sealed space.
A stage regenerator (19) is fitted respectively.

Each of these regenerators (18), (19) is a regenerator type heat exchanger. Specifically, the first stage regenerator (18) has a large number of disk-shaped copper meshes stacked together as a cold storage material in a closed space.
In the second stage regenerator (19), a large number of lead balls (lead shots) having a predetermined diameter are filled and sealed as a cold storage material in the space, and the mesh of these meshes and the gaps between the lead balls are used as gas passages. The cold heat of the helium gas flowing through this gas passage is stored in the mesh and each lead bulb. That is, the displacer (10) is connected to the cylinder (3).
) during the intake stroke, the mesh and lead bulb whose temperature has dropped to a cryogenic level in the previous exhaust stroke are transferred from the gas supply and exhaust chamber (11) to the first and second stage expansion chambers (12), (
13), and the gas is cooled to near cryogenic levels by heat exchange between the two. On the other hand, when the displacer (10) is in the downward exhaust stroke, the mesh and a lead ball, and the mesh and the lead ball are cooled again to near cryogenic levels by heat exchange between the two.

On the other hand, the lid member (21) includes a valve stem (22) that closes the opening of the cylinder (3), and a valve stem (22) that closes the opening of the cylinder (3).
2) and a valve case (27) connected to the upper side. The valve stem (22) has a cylindrical protrusion (22a) that protrudes concentrically within the cylinder (3) at a predetermined distance from the inner wall thereof. In addition, the valve stem (22
) has a protrusion (22
a) A gas flow path (23) penetrating to the lower surface (gas supply/discharge chamber (11)) and a surge volume (24) of a predetermined volume are formed. The gas flow path (23) is always in communication with the surge volume (24) via a communication path (25) with a small passage cross-sectional area, and this communication path (25) allows the intermediate portion of the surge volume (24) to I try to set the pressure to an appropriate value. Also, surge volume (24)
is in constant communication with the intermediate pressure chamber (6) via the orifice (26).

The upper surface of the valve case (27) has a high pressure gas inlet (2
8) and a low pressure gas outlet (29) are opened in line at a predetermined interval, and a high pressure gas inlet (28) is connected to a high pressure pipe (91).
to the discharge port of the compressor (1) via the low pressure gas outlet (
29) are respectively connected to the suction side of the compressor (1) via low pressure pipes (92). The valve case (27) constitutes a part of the switching valve (32), and the switching valve (32) connects the high pressure gas inlet (28) and the low pressure gas outlet (29) to the gas supply and discharge chamber (11). ) are selectively communicated.

That is, a cylindrical space (33) extending from the high pressure gas inlet (28) to the low pressure gas outlet (29) is formed in the valve case (27), and the space (33)
The lower ends of a high-pressure gas outlet (28) and a low-pressure gas outlet (29) are opened at the upper wall surface of the gas chamber. On the other hand, space (33)
There are two ports (34) with the same diameter as the high pressure gas inlet (28) and low pressure gas outlet (29) on the lower wall surface of the (3
5) are opened vertically corresponding to the high pressure gas inlet (28) and the low pressure gas outlet (29), respectively, and these ports (
34) and (35) are joined together in the valve case (27) and then communicated with the gas flow path (23) of the valve stem (22). A spool (36) is slidably inserted into the space (33), and the spool (36) is slidably inserted into the space (33).
6), the space (33) is divided into a pressure chamber (37) on the right side and a spring chamber (38) on the left side in the figure. spool(
36), a flow path (39) is formed vertically through it.

In addition, a spring (40) that biases the spool (36) to the right side in the figure is housed in the spring chamber (38).
36), the high pressure gas inlet (28) of the flow path (39)
) or switching the communication to the low pressure gas outlet (29),
As shown by the solid line in the figure, when the pressure rises in the pressure chamber (37) and the spool (36) moves to the high pressure position at the left end against the biasing force of the spring (40), the high pressure gas flows through the flow path (39). Match the inlet (28) with the high pressure gas population (2
8) and the corresponding boat (34) in the channel (39)
On the other hand, when the pressure in the pressure chamber (37) decreases and the spool (36) moves to the right end low pressure position due to the biasing force of the spring (40), the flow path (39) is connected to the low pressure gas outlet (29). Low pressure gas outlet (29)
and the corresponding boat (35) are communicated via a channel (39).

The spring chamber (38) and the high pressure pipe (91) are connected by a pipe (42) equipped with an intermediate pressure regulating valve (41).
The spring chamber (38) and the low pressure pipe (92) are connected to each other by a pipe (44) equipped with an intermediate pressure regulating valve (43), and these regulating valves (41) and (43) communicate with each other. The gas pressure at (38) is adjusted.

A valve motor assembly (51) serves as a pressure switching means for periodically switching the gas pressure in the pressure chamber (37) of the expander (2) to high pressure or low pressure.
) is located separately from the

This valve motor assembly (51) is composed of a bottomed cylindrical valve housing (52) whose upper end is closed, and a valve stem (56) which airtightly closes the lower end opening of the housing (52). It has a closed cylindrical shape, and the high pressure pipe (91) is attached to the side wall of the valve housing (52).
), that is, the high pressure gas port 1 (53) connected to the discharge side of the compressor (1), and the low pressure pipe (92), that is, the compressor (
A low pressure gas port (54) connected to the suction side of 1) is opened. Further, a gas supply/discharge port (57) is opened at the lower end of the valve stem (56).
7) is connected to the pressure chamber (37) of the expander (2) via a connecting pipe (93). Valve housing (5
2) is formed with a valve chamber (55) that communicates with the high pressure gas port (53), and this valve chamber (55)
The upper surface of the valve stem (56) is facing.

The valve stem (56) has a first gas passage (58) whose upper half is branched into two and communicates the valve chamber (55) with the gas supply/discharge port (57), and a first gas flow passage (58) whose upper half is divided into two and communicates the valve chamber (55) with the gas supply/discharge port (57). 1 gas flow path (58) via a low pressure boat (64) of a valve disc (62) to be described later, and the other end is connected to the low pressure gas port (54) formed in the valve housing (52). A second gas flow path (60
) are formed through it. Both gas channels (58).

(60) is a valve stem (56) as shown in FIG.
) At the upper surface, the valve chamber (55) is located at the center of the valve stem in the second gas flow path (60), and the second gas flow path (58) is located in the two branched portions of the first gas flow path (58). The openings are respectively symmetrical with respect to the opening of the flow path (60).

Further, a valve disc (62) as a switching valve is disposed in the valve chamber (55) and is rotated at a predetermined period by a valve motor (61).
62), the valve chamber (55) communicating with the high pressure gas port (53) and the low pressure gas port 1- (54
) are alternately communicated with the gas supply/discharge port (57).

Specifically, the valve disc (62) is slidably connected to the output shaft (61a) of the valve motor (61). In addition, the top surface of the valve disc (62) and the motor (
A spring (65) is compressed between the valve chamber (55) and the spring force of the spring (65).
), the lower surface of the valve disk (62) is pressed against the upper surface of the valve stem (56) with a constant pressing force. In addition, as shown in FIG. 3, a pair of high-pressure boats (63), (63) are cut into the lower surface of the valve disk (62) by a predetermined length from the radially opposing outer peripheral edges toward the center. and the high-pressure bows (63) and (63) are arranged at an angular interval of approximately 90'' in the rotational direction of the valve disc (62), and are arranged from the center of the lower surface of the valve disc (62) toward the vicinity of the outer periphery. Low pressure port (
64) is formed. And the valve motor (6
1), when the valve disc (62) rotates and performs a switching operation while pressing its lower surface against the upper surface of the valve stem (56), the high pressure gas port (53) Or low pressure gas port (
54) are alternately communicated with the gas supply/discharge port (57) at a predetermined timing.

By switching the valve disc (62) in the valve motor assembly (51), the pressure chamber (37) of the expander (2) receives high pressure gas from the high pressure gas port (53) or from the low pressure gas port (54). The spool (36) of the switching valve (32) is moved by applying low pressure gas alternately, and the valve disc (62) is moved as shown in FIG. 2(a).
A first gas flow path (5) in which the inner ends of the high pressure ports (63), (63) on the lower surface open to the upper surface of the valve stem (56), respectively.
8), the pressure chamber (37) of the expander (2)
), move the spool (36) to the high pressure position on the left end in the diagram, and connect the high pressure gas inlet (28) of the expander (2) to the flow path (39) of the spool (36) and the gas flow path. The gas supply/discharge chamber (11), first and second stage expansion chambers (12) and (13) in the cylinder (3) are communicated with each other through the passage (23). ), the slack piston (7) and the displacer (10) driven by the piston (7) are raised.

On the other hand, as shown in FIG. 2(b), the valve stem (56
) When the outer end of the low pressure port (64), which is in constant communication at the center with the second gas flow path (60) opened on the top surface, matches the first gas flow path (58), the spring (40) is attached. The force moves the spool (36) to the low pressure position on the right side in the figure, and the chambers (11) to (13) in the cylinder (3) are connected to the first gas flow path (58) and the flow path of the spool (36). (39
) to the low pressure gas outlet (29) to connect each chamber (
By discharging the helium gas filled in 11) to (13) to the low pressure gas outlet (29), the slack piston (7) and the displacer (10) are lowered, and as the displacer (10) moves downward, the helium gas is discharged to the low pressure gas outlet (29). Expansion chamber (1
It is configured to generate cold in each heat station (4), (5) by the expansion of helium gas in (2), (13).

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

During cool-down, the 5QUID is gradually cooled to a low temperature level as the GM refrigerator and JT refrigerator operate.
After the temperature of the 5QUID drops to the cryogenic level (approximately 4K), the refrigerator shifts to a steady operating state, and in that state, the
QUID is activated.

That is, to explain in detail the operation of the above GM refrigerator,
The spool of the switching valve (32) in the expander (2)
36) is in the closed position. Further, it is assumed that the pressure inside the cylinder (3) is low and the slack piston (7) and the displacer (10) are at the lower end position. In this state, the valve disc (62) is rotated by the drive of the valve motor (61) of the valve motor assembly (51), and the high pressure boat (63) is rotated as shown in FIG. 2(a).
, (63) coincide with the first gas flow path (58) on the upper surface of the valve stem (56), and the valve disc (62) opens to the high pressure side. Along with this, from the compressor (1) to the high pressure gas port (
The high-pressure helium gas supplied to the valve chamber (55) of the valve motor assembly (51) via the high-pressure ports (63), (6) of the valve disc (62)
B) and the gas supply/discharge port (5) via the first gas flow path (58).
7), and is introduced from this gas supply/discharge port (57) into the pressure chamber (37) of the expander (2) via the connecting pipe (93). This rise in gas pressure in the pressure chamber (37) causes the spool (36) to move to the left in FIG.
9) matches the high-pressure gas inlet (28) and the port (34) to communicate them, and accordingly, the high-pressure gas inlet (28)
The gas passes through the gas flow path (23) to the slack piston (
7) Introduced into the lower gas supply/discharge chamber (11).

Further, this gas is distributed from the gas supply/discharge chamber (11) to each regenerator (18) of the displacer (10).

(19) and then each expansion chamber (12), (13)
This regenerator (18), (19
), it is cooled by heat exchange with the copper mesh and lead bulbs that have been cooled in the previous exhaust stroke.

In addition, the intermediate pressure chamber (6) above the slack piston (7)
) is the surge volume (2
4), so the pressure is kept at a constant and appropriate value. Therefore, when high-pressure helium gas is introduced into the gas supply/discharge chamber (11), the internal pressure becomes higher than that of the intermediate pressure chamber (6), and the compartments (6),' (1
1) The piston (7) rises due to the pressure difference between the two. When the piston (7) moves up by a predetermined stroke, the bottom wall of the piston (7) and the displacer (10
) The displacer (10) engages with the locking piece (17) at the upper end, and the displacer (10) moves the piston (7) with a delay in response to pressure changes.
The upward movement of this displacer (10) causes the expansion chambers (12), (13) below it to
is further filled with high pressure gas (intake stroke).

After this, the valve disc (62) rotates 90'' and closes, but the displacer (10) continues to rise due to inertia, and as a result, the air in the gas supply/discharge chamber (11) above the displacer (10) increases. Helium gas enters the first and second stage expansion chambers (12).

Move to (13).

After the displacer (10) reaches the upper end position, the valve disc (62) rotates further 90'', and the low pressure port (64) is moved to the first position as shown in FIG. 2(b).
The valve disc (62) opens to the low pressure side in line with the gas flow path (58), and with this valve opening, the switching valve (32)
The pressure chamber (37) of the spool (36) and the spring (
40) moves to the right in Fig. 1 and is positioned at a low pressure position, and its flow path (39) is connected to the low pressure gas outlet (2).
9) and port (35) to communicate them. As the switching valve (32) opens to the low pressure side, each expansion chamber (12), (13) below the displacer (10)
The helium gas in ) undergoes Simon expansion, and this expansion of helium gas generates cooling (expansion stroke).

This extremely low-temperature helium gas passes through the glue generators (19) and (18) in the displacer (1o), contrary to the gas introduction process, and passes through the gas supply and discharge chamber (1o).
1) return within - while regenerator (19);
(18) While cooling the copper mesh and lead bulb inside, it is heated to room temperature.

This room temperature helium gas is then stored in the gas supply and exhaust chamber (11
) is returned to the low-pressure gas outlet (29) via the gas flow path (23), and from there is sucked into the compressor (1) via the low-pressure pipe (92). With this gas discharge, the gas pressure in the gas supply and discharge chamber (11) decreases and becomes lower than that in the intermediate pressure chamber (6), and both chambers (6),
Due to the pressure difference at (11), the slab piston (7)
is lowered and the bottom wall of this piston (7) comes into contact with the upper surface of the displacer (10).
) is pressed down and the downward movement of the displacer (10) causes the gas in the expansion chambers (12), (13) to be further discharged to the outside of the expander (2) (exhaust stroke).

Next, the valve disc (62) rotates 90'' and closes, and thereafter the displacer (1o) continues to descend to the lowering end position, and the gas in the expansion chambers (12) and (13) is exhausted, returning to the initial state. .With the above, one cycle of the operation of expansion 8! (2) is completed, and the same operation as above is repeated.As a result of this repetition, the two-stage heat stations (4) and (5) of the cylinder (3) are gradually heated. cooled to
The helium gas in the JT refrigerator that receives cold air from both heat stations (4) and (5) is cooled.

In this embodiment, the valve motor assembly (51) is separated from the expander (2), and the valve motor (61) is separated from the cylinder (3).
1) The magnetic flux from 5QUID is suppressed from having an adverse effect as noise on the magnetic flux detection of 5QUID, and therefore the 5QUID is
It can be cooled down without any problem using a refrigerator.

In addition, by switching between high and low pressure of the valve disc (62) in the valve motor assembly (51), the expander (2
), and the expander (2) and compressor (1) are connected by high-pressure piping (91) and low-pressure piping (92), similar to conventional integrated refrigerators. Therefore, helium gas flows between the compressor (1) and the expander (2) in the same way as in an integrated refrigerator. Therefore, as in the case of separate refrigerators in which the valve section is separated from the cylinder section and the two are connected via refrigerant piping, the refrigerating capacity may decrease due to gas pressure loss in the refrigerant piping, or the compressor (1)
The load will not increase. Also, the cylinder (
3) The compression heat removed at the low temperature end of the cylinder (3) does not stop at the room temperature end, so the surge volume (24)
The gas pressure in the intermediate pressure chamber (6) set at 1 is prevented from increasing, and the differential pressure between the intermediate pressure and the high and low pressures is maintained appropriately.

Therefore, the reciprocating movement of the displacer (10) can be performed stably, the cool-down time of the refrigerator can be kept short, and the refrigerating capacity during steady operation can be increased.

Furthermore, the valve motor assembly (
51) switches the gas pressure in the pressure chamber (37) in the switching valve (32) of the expander (2), and this gas pressure drives the switching valve (32). Only the switching valve (32) is required, and the valve structure within the expander (2) can be extremely simplified.

(Other Embodiments) FIG. 4 shows a second embodiment. Note that the same parts as in FIG. 1 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

In this embodiment, a valve motor assembly (51') having the same configuration as the first embodiment is built into the compressor (1), and although not shown, its high pressure gas port is connected to the compressor (1).
1), the high pressure side is connected to the high pressure side, and the low pressure gas port is connected to the low pressure side.

Therefore, this embodiment can also provide the same effects as the first embodiment. In addition, since the valve motor assembly (51") is built into the compressor (1), the compressor (1) and expander (2) are connected through three pipes (9).
Only connections 1) to (93) are required, which has the advantage of simplifying the piping connection structure.

FIG. 5 shows a third embodiment (the same parts as in FIG. 2 are given the same reference numerals and detailed explanation thereof is omitted).

In this embodiment, in the configuration of the first embodiment, the valve motor assembly (51) is replaced with a linear motor compressor (
71).

The linear motor compression II (71) includes a closed casing (72), a cylinder (73) formed within the casing (72), and a reciprocatingly fitted cylinder (73). The compression chamber (74) is located inside the cylinder (73).
) and a piston (75) defining a section of the piston (7
A glue near motor (76
). This linear motor (76) has an annular permanent magnet (77) arranged around the cylinder (73), and this magnet (77) applies a magnetic field to a cylindrical gap concentric with the center of the cylinder (73). generate. A roughly cup-shaped bobbin (78) integrally fixed to the piston (75) at the center is arranged in the gap so as to be able to reciprocate, and a lead wire (79a ),
(79a) is wound with a coil (79) that is energized. Further, a coil spring (80) is provided between the outer bottom surface of the bobbin (78) (opposite side to the piston (75)) and the inner bottom surface of the casing (72) for elastically supporting the piston (75) so that the piston (75) can reciprocate. is installed, and by applying an alternating current of a predetermined frequency to the coil (79), the coil (79) and bobbin (78) are driven by the action of the magnetic field passing through the gap, and the piston (75) is moved into the cylinder ( 7
3), gas pressure is generated at a predetermined period in the compression chamber (74).

One end of a communication pipe (93) is connected to the compression chamber (74), and the other end communicates with the pressure chamber (37) of the switching valve (32) in the expander (2).
The switching valve (32) of the expander (2) is activated by the gas pressure of the expander (2).
) can be switched open and closed.

Therefore, for this example, the linear motor compressor (
71) With the operation of the linear motor (76), the piston (75) reciprocates within the cylinder (73) at a predetermined period;
The gas pressure within the compression chamber (74) changes in height. This compression chamber (74) communicates with the pressure chamber (37) of the expander (2) via the connecting pipe (93), so the piston (74) is connected to the pressure chamber (37) of the expander (2).
5), the switching valve (32) of the expander (2)
) is switched to selectively communicate the high pressure gas port (28) and the low pressure gas outlet (29) with the gas supply and discharge chamber (11), and the gas supply and discharge chamber (11) or the expansion chamber (12),
Gas is supplied and discharged to (13). Therefore, this embodiment also provides the same effects as the first embodiment.

Note that it is also possible to incorporate the linear motor compressor (71) into the compressor (1) as in the second embodiment.

Further, although each of the above embodiments is an example of cooling a 5QUID, the present invention can also be applied to the case of cooling a superconducting device in which magnetic flux from a motor is harmful.

(Effects of the Invention) As explained above, in the invention according to claim (1), for a gas pressure driven GM refrigerator, high pressure and low pressure refrigerant gases from the compressor are supplied to the cylinder expansion chamber of the expander. A gas pressure-driven switching valve for switching supply and discharge was provided, and a pressure switching means was provided outside the expander for switching the gas pressure to the pressure chamber of the switching valve using a valve motor. In addition, in the invention of claim 2, the pressure switching means is a linear motor compressor. Therefore, according to these inventions, the separation of the valve motor from the cylinder reduces the 5QUI.
In addition to eliminating the influence of magnetic noise on superconducting devices such as D, the compressor and expansion chamber can be connected using high-pressure and low-pressure piping, similar to an integrated refrigerator, reducing the pressure loss of refrigerant gas and the resulting compression. It is possible to avoid problems in the reciprocating movement of the displacer due to an increase in machine load and retention of compression heat at the room temperature end of the cylinder of the expander. Furthermore, compared to conventional gas pressure-driven refrigerators, the valve structure of the expander can be simplified, and excellent practical effects can be achieved.

[Brief explanation of drawings]

1 to 3 show a first embodiment of the present invention, in which FIG. 1 is a sectional view of the refrigerator, FIG. 2 is a plan view of the upper surface of the valve stem facing the valve chamber in the valve motor assembly, and FIG.
The figure is a plan view of the lower surface of the valve disk. Figure 4 is the second
1 is a schematic configuration diagram of a refrigerator according to an example. Figure 5 is the third
FIG. 2 is a diagram corresponding to FIG. 2 showing an embodiment. FIG. 6 is a diagram showing the PV indicating capacity of a conventional separate type refrigerator. (1) Compressor (2) Expander (3) Cylinder (6) Intermediate pressure chamber (7) Slack piston (10) Displacer (11) ...Gas supply and discharge chamber (18), (19)...Regenerator (21)
... Lid member (24) ... Surge volume (26) ... Orifice (28) ... High pressure gas inlet (29) ... Low pressure gas outlet (32) ... Switching valve (37)・・Pressure chamber (51), (51')... Valve motor assembly (pressure switching means) (53)・
...High pressure gas port (54) ...Low pressure gas port (57) ...Gas supply and discharge port (61) ...Valve motor (62) ...Valve disc (71) ...Linear motor compressor (73)...Cylinder (74)...Compression chamber (75)...Piston (76)...Linear motor (91)...High pressure piping (pressure switching means) (92)...Low pressure Piping (93)...Connection piping

Claims (2)

[Claims] (1) A compressor (1) that compresses refrigerant gas to generate high-pressure gas, and a displacer (10) inserted into the cylinder (3).
By reciprocating the displacer (10), the high pressure gas supplied from the compressor (1) is transferred to the cylinder (3).
) A cryogenic refrigerator comprising an expander (2) that generates cryogenic level cold by adiabatic expansion in expansion chambers (12) and (13) in ), the expander (2) are the expansion chambers (12), (13)
A high pressure gas inlet (28) and a low pressure gas outlet (
29) and the high-pressure gas inlet (28) and low-pressure gas outlet (2) by switching the gas pressure to the pressure chamber (37).
9) to the expansion chambers (12) and (13), and the high pressure gas inlet (28) is connected to the high pressure gas inlet (28) of the compressor (1). It is connected to the discharge side via a high pressure pipe (91), while the low pressure gas outlet (29) is connected to the suction side of the compressor (1) via a low pressure pipe (92). Pressure switching means (51) that periodically switches the gas pressure for the pressure chamber (37) to high pressure or low pressure
is arranged separately from the expander (2), and the pressure switching means (51) includes a gas supply/discharge port (57) communicating with the pressure chamber (37) via a connecting pipe (93); A high pressure gas port (53) and a low pressure gas port (5) connected to the discharge side and suction side of the compressor (1), respectively.
4), a valve (62) for switching communication between the high pressure gas port (53) and the low pressure gas port (54) with respect to the gas supply/discharge port (57), and switching and driving the valve (62) at a predetermined timing. A cryogenic refrigerator characterized by comprising a valve motor (61). (2) A compressor (1) that compresses refrigerant gas to generate high-pressure gas, and a displacer (10) fitted into the cylinder (3).
By reciprocating the displacer (10), the high pressure gas supplied from the compressor (1) is transferred to the cylinder (3).
) A cryogenic refrigerator comprising an expander (2) that generates cryogenic level cold by adiabatic expansion in expansion chambers (12) and (13) in ), the expander (2) are the expansion chambers (12), (13)
A high pressure gas inlet (28) and a low pressure gas outlet (
29) and the high-pressure gas inlet (28) and low-pressure gas outlet (2) by switching the gas pressure to the pressure chamber (37).
9) to the expansion chambers (12) and (13), and the high pressure gas inlet (28) is connected to the high pressure gas inlet (28) of the compressor (1). The low pressure gas outlet (29) is connected to the discharge side via the high pressure pipe (91), while the low pressure gas outlet (29) is connected to the suction side of the compressor (1) via the low pressure pipe (91).
2), the pressure switching means (71) is arranged to be able to reciprocate within the cylinder (73), and the pressure switching means (71) is connected to the pressure chamber (37) within the cylinder (73). A piston (7) forming a compression chamber (74) communicating with the piping (93)
5) and a linear motor (76) that reciprocates the piston (75).