JPH11257772A - Cryogenic refrigerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optimize an intermediate pressure to improve the ability in a cryogenic refrigerator which reciprocally moves a displacer due to the pressure difference between a high/low pressure and intermediate pressure of an operating gas to generate a cold gas at a cryogenic level. SOLUTION: In a cylinder 2 a displacer 22 is provided to form expansion chambers 30, 31, a slack piston 17 is provided to form a lower pressure chamber 20, an intermediate pressure chamber 8 communicating with the lower pressure chamber 20 through an orifice 21 is formed, a high pressure communicating passage 45 is provided between the intermediate pressure chamber 8 and motor chamber 6 to introduce a high pressure operating gas in the intermediate pressure chamber 8 and has an opening-variable flow rate control valve CV, and a low pressure communicating chamber 48 is provided between the intermediate pressure chamber 8 and low pressure passage 13 to exhaust the operating gas from the intermediate pressure chamber 8 and formed to exhaust the operating gas at specified flow rate from the intermediate pressure chamber 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cryogenic refrigerator in which a working gas such as helium is expanded by reciprocating a displacer (replacer) to generate a cryogenic level of refrigeration, and in particular, to improve its performance. Belongs to the technical field.

[0002]

2. Description of the Related Art Conventionally, a cryogenic refrigerator is provided with a displacer for partitioning an expansion chamber in a cylinder.
A GM (Gifford McMahon) refrigerator is known which expands a high-pressure working gas supplied to the expansion chamber in accordance with the reciprocation of the displacer to generate cryogenic cooling.

[0003] In this type of cryogenic refrigerator, a mechanically driven GM in which a displacer is connected to a motor via a crankshaft and the displacer is reciprocated by the operation of the motor.
There is a refrigerator. For example, Japanese Patent Application Laid-Open No. Hei 6-300378
In this publication, a valve body that slides on and opens and closes a valve plate that rotates integrally with a crankshaft is rotatable from the outside, and the relative position of the valve body with respect to the valve plate is changed. It has been proposed that the timing of supplying the high-pressure working gas to the expansion chamber in the inside and the timing of discharging the low-pressure working gas expanded in the expansion chamber are linked and made variable.

On the other hand, as shown in FIG. 7, an intermediate pressure chamber (a) set at an intermediate pressure of a high and low pressure working gas is provided, and the pressure of the intermediate pressure chamber (a) and the pressure of the expansion chamber (b) are increased. There is also known a GM refrigerator of a gas pressure drive type (modified Solvay type) in which a piston (c) is reciprocated together with a displacer (d) by a pressure difference from a gas pressure of a working gas to be supplied and exhausted.

[0005]

The above-mentioned gas-pressure-driven G
In the M refrigerator, a capillary tube (e) is provided for the purpose of setting the pressure of the intermediate pressure chamber (a) to the intermediate pressure of the high and low pressure working gas. One end of the capillary tube (e) communicates with the intermediate pressure chamber (a), and the other end has a gas flow path through which high-pressure and low-pressure working gas supplied and exhausted to the expansion chamber (b) flows.
(f). And the capillary tube
By supplying a small amount of high pressure working gas to the intermediate pressure chamber (a) via (e) or discharging the working gas from the intermediate pressure chamber (a),
An intermediate pressure is set.

However, in that case, in one cycle of the reciprocation of the displacer (d), the expansion chamber in the cylinder (g) is provided.
(b) High-pressure supply state for supplying high-pressure working gas to the expansion chamber
When the ratio of (b) to the low-pressure discharge state in which the working gas is discharged is changed, the behavior of the displacer (d) is affected accordingly, and a problem arises in that the performance of the refrigerator cannot be improved due to the poor behavior. For example, when the ratio of the low pressure discharge state is made larger than that of the high pressure supply state,
A relatively large amount of the working gas (a) is discharged to the low pressure side, and the pressure in the intermediate pressure chamber (a) decreases, and the displacer (d) does not move at full stroke, making it difficult to move on the low temperature side and becoming It becomes easy to move, and it is biased to the normal temperature side. On the other hand, if the ratio of the low-pressure discharge state is made smaller than that of the high-pressure supply state, a relatively large amount of high-pressure working gas is supplied to the intermediate pressure chamber (a) and the pressure in the intermediate pressure chamber (a) increases. The displacer (d) is difficult to move at the room temperature and moves with a stroke biased toward the low temperature.

Further, the stroke position of the displacer (d) fluctuates due to individual differences between the refrigerators, making it difficult to optimize the stroke position, and causing a problem that the performance of the refrigerator varies.
Specifically, the piston (c) and the like are provided with a seal member for preventing leakage of the working gas. However, there are individual differences in the seal member, the piston (c), and the like, and the leakage amount of the working gas differs from one refrigerator to another. For this reason, the displacer (d)
, The displacer (d) does not move at full stroke, and the cryogenic refrigerator cannot exhibit its full capacity.

The present invention has been made in view of the above point, and an object thereof is to reciprocate the displacer by the differential pressure between the high and low pressures of the working gas and the intermediate pressure as described above, and An object of the present invention is to improve the performance of a cryogenic refrigerator by optimizing the behavior of the displacer by optimizing the intermediate pressure in the cryogenic refrigerator that generates a level of cold.

[0009]

The present invention provides an intermediate pressure chamber (8).
Adjustable the flow rate of the working gas flowing into or out of the
The pressure in the intermediate pressure chamber (8) can be set to a predetermined value.

More specifically, a first solution taken by the present invention is a cylinder to which high-pressure or low-pressure working gas is supplied and exhausted.
(2) and a displacer member (17, 22) for forming an expansion chamber (30, 31) and a pressure chamber (20) inside the cylinder (2).
And an intermediate pressure chamber (8) set to the intermediate pressure of the high and low pressure working gas and communicating with the pressure chamber (20), and the gas pressure and pressure of the working gas supplied and exhausted to and from the cylinder (2). Room (20)
Displacer member (17,22)
Reciprocates to supply and exhaust the working gas to and from the expansion chambers (30, 31), and to expand the high-pressure working gas supplied to the expansion chambers (30, 31) to generate cryogenic refrigeration at the cryogenic level. Machine. Then, the high-pressure working gas is supplied to the intermediate pressure chamber.
(8) and a low-pressure communication passage (48) for discharging a predetermined flow of working gas in the intermediate pressure chamber (8).
And the intermediate pressure chamber (8) provided in the high pressure communication passage (45).
Variable flow control valve (CV) that adjusts the flow rate of the working gas flowing through the high-pressure communication passage (45) so that the pressure becomes a predetermined intermediate pressure.
Are provided.

[0011] The second solution taken by the present invention is:
Cylinder to which high or low pressure working gas is supplied and exhausted (2)
And an expansion chamber (30, 31) and a pressure chamber (2) inside the cylinder (2).
0) and a displacer member (17, 22) for forming
An intermediate pressure chamber (8) which is set at an intermediate pressure between the high and low pressure working gases and communicates with the pressure chamber (20);
The displacer member (17, 22) reciprocates due to the pressure difference between the gas pressure of the working gas supplied and exhausted to (2) and the pressure of the pressure chamber (20), and the working gas flows into the expansion chambers (30, 31). It is assumed that a cryogenic refrigerator that supplies and exhausts air and generates cryogenic-level cold by expansion of high-pressure working gas supplied to the expansion chambers (30, 31). A high-pressure communication path (45) for introducing a predetermined flow of high-pressure working gas to the intermediate pressure chamber (8); a low-pressure communication path (48) for discharging the working gas in the intermediate pressure chamber (8); And a variable opening flow control valve (CV) for adjusting the flow rate of the working gas flowing through the low pressure communication passage (48) so that the intermediate pressure chamber (8) has a predetermined intermediate pressure. It is.

Further, a third solution taken by the present invention is:
In the first or second solution, the high-pressure working gas is supplied from only the high-pressure communication passage (45) to the intermediate pressure chamber (8), and the working gas in the intermediate pressure chamber (8) is supplied to the low-pressure communication passage (45). 48) only so as to be discharged to the outside of the cryogenic refrigerator (R).

-Operation- In the first solution, the expansion chamber (30, 30) in the cylinder (2) is used.
31) The high pressure supply state for supplying high pressure working gas to the
(30, 31) is switched to a low pressure discharge state in which the working gas is discharged, and the pressure difference between the gas pressure of the expansion chamber (30, 31) and the pressure chamber (20) communicating with the intermediate pressure chamber (8) is changed. This causes the displacer members (17, 22) to reciprocate in the cylinder (2).

At this time, the flow control valve (C
V) flows into the intermediate pressure chamber (8) from the high-pressure communication passage (45) while the working gas flows at a predetermined flow rate through the low-pressure communication passage (48). Emitted from 8). Thus, the intermediate pressure chamber (8) is maintained at a predetermined intermediate pressure. Further, since the opening of the flow control valve (CV) is variable, the opening of the flow control valve (CV) is adjusted to change the flow rate of the working gas flowing through the high-pressure communication passage (45), and the intermediate pressure chamber ( 8) Adjust the intermediate pressure to a predetermined value.

[0015] In the second solution, a cylinder is provided.
The expansion chamber (30, 31) switches between a high-pressure supply state in which high-pressure working gas is supplied to the expansion chamber (30, 31) and a low-pressure discharge state in which the working gas in the expansion chamber (30, 31) is discharged. , 31) and the gas pressure between the pressure chamber (20) communicating with the intermediate pressure chamber (8) causes the displacer members (17, 22) to reciprocate in the cylinder (2).

At this time, a predetermined flow rate of the high-pressure working gas flows through the high-pressure communication passage (45) and flows into the intermediate pressure chamber (8), while being controlled to a predetermined flow rate by the flow control valve (CV) of the low-pressure communication passage (48). The adjusted working gas is discharged from the intermediate pressure chamber (8). Thus, the intermediate pressure chamber (8) is maintained at a predetermined intermediate pressure. Also, since the opening of the flow control valve (CV) is variable, the opening of the flow control valve (CV) is adjusted to change the flow rate of the working gas flowing through the low-pressure communication passage (48), and the intermediate pressure chamber ( 8) Adjust the intermediate pressure to a predetermined value.

In the third solution, the intermediate pressure chamber is provided.
Supply of working gas to (8) is performed only through the high-pressure communication passage (45), and discharge of working gas from the intermediate-pressure chamber (8) is performed only through the low-pressure communication passage (48). Therefore, part of the high-pressure working gas sucked into the cylinder (2) for supplying to the expansion chambers (30, 31) does not flow into the intermediate pressure chamber (8).

[0018]

Therefore, according to the above-described means, by adjusting the opening of the flow regulating valve (CV) provided in the high-pressure communication passage (45) or the low-pressure communication passage (48), the intermediate pressure chamber is adjusted. (8)
Intermediate pressure can be adjusted. For this reason, even if the ratio between the high pressure supply state and the low pressure discharge state in one cycle of the reciprocating movement of the displacer member (17, 22) is changed, the intermediate pressure in the intermediate pressure chamber (8) is kept constant. be able to. Therefore, the pressure chamber (2) communicating with the intermediate pressure chamber (8)
0) can be kept constant, and the behavior of the displacer members (17, 22) in the cylinder (2) can be optimized. As a result, the cryogenic refrigerator (R) can exhibit sufficient performance.

Further, the intermediate pressure in the intermediate pressure chamber (8) can be set in accordance with the individual difference of each refrigerator, and the behavior of the displacer members (17, 22) in the cylinder (2) is optimized. be able to. As a result, the cryogenic refrigerator (R) can reliably exhibit sufficient performance regardless of individual differences between the refrigerators.

In particular, according to the third solution, the intermediate pressure chamber (8) is passed only through the high pressure communication passage (45) and the low pressure communication passage (48).
Supply and exhaust of working gas to Therefore, as described above, even when the ratio between the high-pressure supply state and the low-pressure discharge state is changed, the intermediate pressure in the intermediate pressure chamber (8) can be more reliably kept constant. Therefore, the intermediate pressure chamber
The pressure in the pressure chamber (20) communicating with (8) can be maintained constant, and the cylinder of the displacer member (17, 22)
(2) The behavior within can be optimized. As a result, the cryogenic refrigerator (R) can exhibit sufficient performance.

Conventionally, a part of the high-pressure working gas sucked into the cylinder to be supplied to the expansion chamber is led to the intermediate pressure chamber, and the intermediate pressure chamber is maintained at the intermediate pressure. That is, a part of the high-pressure working gas which is expanded and subjected to cold generation is used to maintain the intermediate pressure chamber at the intermediate pressure. For this reason,
There is a problem that the amount of high-pressure working gas provided for the generation of cold is reduced, and the capacity of the refrigerator is not sufficiently exhibited.

On the other hand, according to the above solution,
The intermediate pressure chamber (8) is maintained at the intermediate pressure without part of the high pressure working gas sucked into the cylinder (2) to supply to the expansion chambers (30, 31) flows into the intermediate pressure chamber (8) can do. That is, it is not necessary to flow a part of the high-pressure working gas for generating cold by expanding into the intermediate pressure chamber (8).
For this reason, the intermediate pressure chamber (8) can be maintained at the intermediate pressure without reducing the amount of high-pressure working gas to be provided for the generation of cold. As a result, the cryogenic refrigerator (R) can be sufficiently exhibited.

[0023]

Embodiment 1 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the overall configuration of a cryogenic refrigerator (R) according to Embodiment 1 of the present invention.
High pressure helium gas (working gas) by reciprocating the displacer (22) with helium gas pressure in the cylinder (2)
And a gas pressure driven GM cycle (Gifford McMahon Cycle) expander.

That is, the cryogenic refrigerator (R) is air-tightly connected to an upper surface of the motor head (1) and a lower large-diameter portion (2a). Small diameter part (2b)
And a two-stage large- and small-stage cylinder (2).
A high-pressure gas inlet (4) and a low-pressure gas outlet (5) located above the high-pressure gas inlet (4) are formed on the side of the motor head (1), and the high-pressure gas inlet (4) is connected to a compressor (not shown) (not shown). The low pressure gas outlet (5) is connected to the discharge side of the compressor via a low pressure pipe (5a) to the suction side of the compressor.

Inside the motor head (1), a motor chamber (6) communicating with the high-pressure gas inlet (4) and a motor chamber (6)
The mounting hole (7), which consists of a vertical through hole that is located at the upper side of the inside and whose internal space communicates with the motor chamber (6) at the lower end, and the substantially annular space located around the mounting hole (7). And an intermediate pressure chamber (8).

A valve stem (9) constituting a closing member at the lower end (base end) of the cylinder (2) is fitted into a boundary portion of the motor head (1) with the cylinder (2). The valve stem (9) is formed to have a diameter smaller than the inner diameter of the valve seat portion (9a) hermetically fitted in the mounting hole (7) and the large diameter portion (2a) of the cylinder (2). The large diameter portion (2a) includes a piston support portion (9b) protruding concentrically in the lower portion and a flange portion (9c) constituting an upper wall of the intermediate pressure chamber (8). ) And the wall of the mounting hole (7), the space between the high-pressure gas inlet (4) and the motor chamber
A valve chamber (10) communicating through (6) is formed.

FIGS. 4 and 5 show the valve stem (9).
As shown in FIG. 2, the first gas passage is formed such that the lower half thereof is bifurcated and communicates the valve chamber (10) into the cylinder (2).
(12), one end of which communicates with the first gas flow path (12) through a low pressure port (37) of a rotary valve (35), which will be described later, and the other end of which is connected to the low pressure gas outlet (5). (1)
A second gas flow path (14) communicating through a low-pressure passage (13) formed through is formed through. Both gas flow paths (12, 1
In the second gas flow path (14), the valve stem (9) branches off at the lower surface of the valve seat (9a) of the valve stem (9) facing the valve chamber (10). One gas channel
In (12, 12), openings are provided at symmetrical positions with respect to the second gas flow path (14).

On the other hand, a slack piston (17) as a displacer member and a displacer (22) are provided inside the cylinder (2).

The slack piston (17) is formed in a substantially inverted cup shape having a bottom wall, and has a large diameter portion (2) of the cylinder (2).
a) At the lower end, the slack piston (17) has its inner surface facing the piston support (9b) of the valve stem (9).
Are externally fitted so as to be able to reciprocate while being slid and guided. Although not shown, seals for preventing the flow of the working gas are provided at the sliding contact portions between the slack piston (17), the cylinder (2) and the piston support (9b). The upper pressure chamber (29) is formed above the cylinder (2) by the slack piston (17).
Lower pressure chambers (20) are formed at the inner and lower ends, respectively, and the lower pressure chamber (20) is always communicated with an intermediate pressure chamber (8) in the motor head (1) via an orifice (21). ing. Therefore, the lower pressure chamber (20) is set at an intermediate pressure between the high pressure and the low pressure helium gas, and this lower pressure chamber (2) is
The slack piston (17) reciprocates with the displacer (22) due to the pressure difference between the respective gas pressures of the pressure chamber (0) and the upper pressure chamber (29). Above slack piston (17)
A large diameter center hole (18) is formed through the center of the bottom wall,
A plurality of communication holes (19, 19,...) Communicating the inside and outside of the piston (17) are formed in the peripheral corner.

The displacer (22) is reciprocally fitted to the cylinder (2). This displacer (22) has a large-diameter hermetically sealed cylindrical portion (22a) that slides in substantially the upper half of the large-diameter portion (2a) of the cylinder (2).
2a) Small diameter part of cylinder (2)
(2b) a closed cylindrical small diameter portion (22b) that slides inside. The displacer (22) is provided above the upper pressure chamber (29), while the first-stage expansion chamber (30) is provided above the large-diameter portion (22a) and is provided above the small-diameter portion (22b). The second-stage expansion chambers (31) are respectively defined.
The space inside the large-diameter portion (22a) of the displacer (22) is always communicated with the first-stage expansion chamber (30) through a communication hole (23). A first-stage regenerator (24) composed of a regenerative heat exchanger is fitted. The space in the small-diameter portion (22b) of the displacer (22) is connected to the first-stage expansion chamber (30) through a communication hole (25).
(31) through a communication hole (26), and a second-stage regenerator (27) similar to the first-stage regenerator (24) is provided in the space inside the small-diameter portion (22b) of the displacer. Fitted.

The large diameter portion of the displacer (22)
(22a) At the lower end, a tubular locking piece (33) is formed integrally with the upper pressure chamber (29) to communicate the space inside the large diameter portion (22a) with the upper pressure chamber (29). The lower part of the locking piece (33) passes through the center hole (18) of the bottom wall of the slack piston (17) and the piston (17).
It extends inside by a predetermined size, and the piston (17)
A flange-shaped engaging portion (33a) engaging with the bottom wall is formed integrally. When the slack piston (17) rises and moves up by a predetermined stroke, the slack piston (17) and the displacer (22) move upward.
The displacer (22) is driven by the slack piston (17) and starts moving upward, while the slack piston (17) moves downward while the piston (17) descends by a predetermined stroke. Lower surface and locking piece (33)
The displacer (22) is driven by the piston (17) to start descending. That is, the displacer (22) is configured to follow the slack piston (17) with a delay of a predetermined stroke.

The valve chamber (1) of the motor head (1)
0), a high-pressure valve opening state for supplying high-pressure helium gas to the upper pressure chamber (29) and the first and second stage expansion chambers (30, 31) in the cylinder (2); (29) and both expansion chambers (30,3
A rotary valve (35) that alternately switches between a low pressure valve opening state for discharging helium gas and a valve motor (39) disposed in a motor chamber (6) is provided. Is driven to rotate. By the switching operation of the rotary valve (35), the high-pressure gas inlet (4), that is, the valve chamber (10) communicating with the high-pressure gas inlet (4),
The low pressure gas outlet (5), that is, the low pressure passage (13) communicating with the low pressure gas outlet (5) is connected to the upper pressure chamber (29) in the cylinder (2),
The first and second stage expansion chambers (30, 31) are configured to communicate alternately with each other.

That is, the output shaft (39a) of the valve motor (39) is integrally rotatably engaged with the center of the lower surface of the rotary valve (35). A spring (not shown) is contracted between the lower surface of the valve (35) and the motor (39), and the rotary force is generated by the spring force of the spring and the pressure of the high-pressure helium gas in the valve chamber (10). The upper surface of the valve (35) is pressed with a constant pressing force against the lower surface of the valve seat (9a) of the valve stem (9).

As shown in FIG. 3, the rotary valve (35)
The upper surface of the pair of high-pressure ports (3
6,36), and a rotary valve for the high pressure port (36,36).
In the direction of rotation of (35) (the direction indicated by the arrow in the figure), approximately 90
A low-pressure port (37) having a groove shape and having an end is formed, which is arranged at an angular interval of ° and is notched in the diameter direction from the center of the upper surface of the valve (35) to the vicinity of the outer peripheral edge. Then, the rotary valve (3) is driven by driving the valve motor (39).
5) is rotated with its upper surface pressed against the lower surface of the valve stem (9) to switch between open and closed.
Causes a pressure difference between the upper pressure chamber (29) and the lower pressure chamber (20), and this pressure difference causes the slack piston (17) and the displacer (22) to move to the cylinder (2).
It reciprocates inside.

That is, by the rotation of the rotary valve (35), as shown in FIG. 4, the high pressure ports (36, 36)
Of the valve seat (9) of the valve stem (9)
a) When it matches the two open ends of the first gas flow path (12) opening on the lower surface, the valve chamber (10) (that is, the high pressure gas inlet)
(4)) is connected to the upper pressure chamber (29) and the first and second stage expansion chambers (30, 31) through the high pressure ports (36, 36) and the first gas passage (12).
Communicate with In this state, high pressure helium gas is introduced and filled into each of the chambers (29 to 31), and a slack piston is formed by a difference in gas pressure between the high pressure upper pressure chamber (29) and the lower pressure chamber (20). Lower (17) with displacer (22).

On the other hand, as shown in FIG.
a) When both outer ends of the low-pressure port (37) constantly communicating with the second gas flow path (14) opened on the lower surface at the center coincide with both open ends of the first gas flow path (12), respectively. The upper pressure chamber
(29) and the first and second stage expansion chambers (30, 31) form a first gas passage (12), a low pressure port (37), a second gas passage (14), and a low pressure passage (13). Through to the low pressure gas outlet (5).
In this state, the helium gas filled in each of the chambers (29 to 31) is discharged to the low-pressure gas outlet (5) while expanding, and the low-pressure upper pressure chamber (29) and the lower pressure chamber The slack piston (1
7) is lifted together with the displacer (22), during which the helium gas passes through the low-pressure port (37) while expanding Simon and exits to the low-pressure gas outlet (5). The helium gas expands to generate a very low-temperature cold due to a temperature drop, and the cold causes a large-diameter portion (2a) of the cylinder (2) corresponding to the first-stage expansion chamber (30). The first heat station (41) to a predetermined temperature level and
(2b) The second heat station (42) at the tip (upper end) is configured to be cooled and held at a lower temperature level than the first heat station (41).

As a feature of the present invention, a high-pressure communication passage (45) and a low-pressure communication passage (48) are provided as shown in detail in FIG. The high-pressure communication path (45) is connected to the motor chamber (6).
The high pressure helium gas in the motor chamber (6) is led to the intermediate pressure chamber (8) by communicating with the pressure chamber (8). The high-pressure communication passage (45) is provided with a flow control valve (CV) having a variable opening, and the flow control valve (CV) controls the flow rate of the working gas flowing through the high-pressure communication passage (45). It is configured to be adjustable. On the other hand, the low-pressure communication passage (48) communicates with the intermediate-pressure chamber (8) and the low-pressure passage (13), and generates a predetermined flow resistance when the working gas flows through the low-pressure communication passage (48). Is formed. Thus, the low pressure communication passage (48) is configured to discharge a predetermined flow rate of the working gas from the intermediate pressure chamber (8) to the low pressure passage (13).

-Operation- Next, the operation of the cryogenic refrigerator (R) will be described. First, when the pressure in the cylinder (2) in the refrigerator (R) is low, the slack piston (17) and the displacer (22)
The description of the operation will be started from the state in which is at the rising end position. The rotation of the rotary valve (35) driven by the valve motor (39) causes the high-pressure ports (36, 36) to open the valve stem (9).
The rotary valve (35) is brought into a high pressure open state in which the rotary valve (35) is opened to the high pressure side in accordance with both open ends of the first gas flow path (12) on the lower surface.

In this state, normal-temperature high-pressure helium gas supplied to the valve chamber (10) through the high-pressure gas inlet (4) of the refrigerator (R) and the motor chamber (6) is supplied to the rotary valve (35). ) And the first gas flow path (1
2) via the slack piston (17) above the upper pressure chamber (2
9). The high-pressure helium gas introduced into the upper pressure chamber (29) sequentially passes through the regenerators (24, 27) of the displacer (22) and fills the expansion chambers (30, 31). , 27) and is cooled by heat exchange.

Thereafter, when the gas pressure in the upper pressure chamber (29) above the slack piston (17) becomes higher than the lower pressure chamber (20) in communication with the intermediate pressure chamber (8), The piston (17) descends due to the pressure difference between the two pressure chambers (20, 29). When the lowering stroke of the piston (17) reaches a predetermined value, the lower surface of the bottom wall of the piston (17) engages with the locking portion (33a) of the locking piece (33) at the lower end of the displacer (22). The displacer (22) is then pulled down by the piston (17) with a delay to pressure changes. Then, the lowering movement of the displacer (22) further fills the expansion chambers (30, 31) above it with high-pressure gas.

Next, when the rotary valve (35) is closed, the displacer (22) further descends due to inertial force, and accordingly, the helium gas in the upper pressure chamber (29) above the displacer (22) expands. Move to room (30,31).

After the displacer (22) reaches the lower end position, the low pressure port (37) of the rotary valve (35) is connected to the open end of the first gas flow path (12) on the lower surface of the valve stem (9). Then, the valve (35) is in the low pressure open state in which it opens to the low pressure side. In this state, the helium gas in each of the expansion chambers (30, 31) above the displacer (22) undergoes Simon expansion, and the first heat station (41) reaches a predetermined temperature level due to a temperature drop accompanying the expansion of the gas. The second heat station (42) is cooled to a lower temperature level than the first heat station (41).

The helium gas, which has become low-temperature in the expansion chambers (30, 31), passes through the regenerators (24, 27) in the displacer (22) and reverses the time when the gas was introduced. (2
9) Returning to the inside, meanwhile, while cooling the regenerators (24, 27), it warms itself to room temperature. Then, the helium gas at normal temperature is further combined with the gas in the upper pressure chamber (29) in the first state.
The gas is discharged out of the refrigerator (R) through the gas passage (12), the low-pressure port (37) of the valve (35), and the low-pressure passage (13), and flows to the compressor through the low-pressure gas outlet (5). It is inhaled. Due to this gas discharge, the gas pressure in the upper pressure chamber (29) decreases, and the slack piston (29) is caused by the pressure difference between the gas pressure and the lower pressure chamber (20) communicating with the intermediate pressure chamber (8). 17) rises, and the upper surface of the bottom wall of this piston (17) is displacer (2
After contacting the lower surface of (2), the displacer (22) is pressed and rises, and as the displacer (22) moves upward, gas in the expansion chambers (30, 31) further flows out of the refrigerator (R). Is discharged.

Thereafter, the rotary valve (35) is closed, but thereafter, the displacer (22) moves up to the rising end position, and the gas in the expansion chambers (30, 31) is discharged to return to the initial state. Thus, one cycle of the operation of the displacer (22) is completed, and thereafter, the same operation as described above is repeated, and the temperature of each heat station (41, 42) gradually decreases toward the cryogenic temperature level.

In the cryogenic refrigerator (R), while the displacer (22) repeats the reciprocating operation as described above, the intermediate pressure chamber (8)
Is maintained at a predetermined intermediate pressure. That is, a constant flow of working gas flows from the motor chamber (6) into the intermediate pressure chamber (8) through the high pressure communication passage (45), while a constant flow of working gas flows through the low pressure communication passage (48). Low pressure passage (13) from pressure chamber (8)
Leaked to Therefore, the intermediate pressure chamber (8) is maintained at an intermediate pressure between the gas pressure of the high-pressure working gas and the gas pressure of the low-pressure working gas. The high-pressure communication passage (45) is provided with a flow control valve (CV) having a variable opening, and the flow control valve (CV) controls the flow rate of the working gas flowing into the intermediate pressure chamber (8). You. Therefore, by adjusting the opening of the flow control valve (CV), the intermediate pressure in the intermediate pressure chamber (8) is set to a predetermined value, and the behavior of the displacer (22) is optimized.

Specifically, when the intermediate pressure in the intermediate pressure chamber (8) is lower than a predetermined value, the displacer (22) does not move at full stroke but moves closer to the normal temperature side (lower side in FIG. 1). In this case, the opening degree of the flow control valve (CV) is increased to increase the flow rate of the working gas flowing into the intermediate pressure chamber (8). Since the flow rate of the working gas discharged from the intermediate pressure chamber (8) is constant, the intermediate pressure in the intermediate pressure chamber (8) increases due to an increase in the flow rate of the working gas, and the displacer (22)
Moves with full stroke. Meanwhile, the intermediate pressure chamber
When the intermediate pressure in (8) is higher than a predetermined value, the displacer (22) moves closer to the lower temperature side (upper side in FIG. 1).
In this case, the opening of the flow control valve (CV) is reduced to reduce the flow rate of the working gas flowing into the intermediate pressure chamber (8). As a result, the intermediate pressure in the intermediate pressure chamber (8) decreases, and the displacer (22) moves with a full stroke.

According to the first embodiment, by adjusting the opening of the flow control valve (CV) provided in the high pressure communication passage (45), the pressure in the intermediate pressure chamber (8) can be reduced. The intermediate pressure can be adjusted. Therefore, even when the ratio of the high pressure supply state and the low pressure discharge state in one cycle of the reciprocating motion of the displacer (22) is changed, the intermediate pressure in the intermediate pressure chamber (8) can be maintained constant. . Therefore, the pressure in the lower pressure chamber (20) communicating with the intermediate pressure chamber (8) can be kept constant, and the behavior of the displacer (22) in the cylinder (2) can be optimized. As a result, the cryogenic refrigerator (R) can exhibit sufficient performance.

Further, the intermediate pressure in the intermediate pressure chamber (8) can be set according to the individual difference of each refrigerator, and the behavior of the displacer (22) in the cylinder (2) can be optimized. . As a result, the cryogenic refrigerator (R) can exhibit sufficient performance regardless of individual differences between the refrigerators.

In particular, the high-pressure communication passage (45) and the low-pressure communication passage (4)
The working gas is supplied to and exhausted from the intermediate pressure chamber (8) only through 8). Therefore, as described above, even when the ratio between the high-pressure supply state and the low-pressure discharge state is changed, the intermediate pressure in the intermediate pressure chamber (8) can be more reliably kept constant. Therefore, the pressure in the pressure chamber communicating with the intermediate pressure chamber (8) can be kept constant, and the displacer (22)
Behavior in the cylinder (2) can be optimized. As a result, the cryogenic refrigerator (R) can exhibit sufficient performance.

Further, by supplying all the high-pressure working gas sucked into the cylinder (2) to the expansion chambers (30, 31) and expanding the same, cold can be generated. For this reason, the intermediate pressure in the intermediate pressure chamber (8) can be maintained at a predetermined value without reducing the amount of the high-pressure working gas used to generate cold. As a result, the behavior of the displacer (22) can be optimized, and the cryogenic refrigerator (R) can be sufficiently exhibited.

Table 1 shows how the refrigeration capacity is improved when the intermediate pressure is adjusted. Table 1 below illustrates changes in refrigeration capacity when the intermediate pressure is adjusted for three types of cryogenic refrigerators (RA) to (RC).
Here, for the refrigerators (RA) and (RB),
(CV), the intermediate pressure is increased, and the refrigerator (R
For C), the opening of the flow control valve (CV) was reduced to lower the intermediate pressure. According to Table 1, in any of the refrigerators, both the capacity of the first heat station (41) (1st capacity) and the capacity of the second heat station (42) (2nd capacity) are the values before the adjustment of the intermediate pressure. It can be seen that the value after the adjustment is higher than that of the value.

[0053]

[Table 1]

[0054]

Second Embodiment A second embodiment of the present invention is different from the first embodiment in that a flow control valve is provided in the high-pressure communication passage (45). 48) is equipped with a flow control valve (CV). Further, in the present embodiment, the high-pressure communication path (45) is formed such that a predetermined flow resistance occurs when the working gas flows. Thus, the high-pressure communication passage (45) is configured to allow a predetermined flow rate of the working gas to flow from the motor chamber (6) into the intermediate pressure chamber (8). Other configurations are the same as in the first embodiment.

-Operating operation- The cryogenic refrigerator (R) of the present embodiment operates in the same manner as the refrigerator (R) of the first embodiment, and the flow rate at the time of adjusting the intermediate pressure of the intermediate pressure chamber (8). Only the operation of the control valve (CV) is different.
Hereinafter, the operation of the flow control valve (CV) when adjusting the intermediate pressure will be described.

When the intermediate pressure in the intermediate pressure chamber (8) is lower than a predetermined value, the displacer (22) does not move at full stroke but moves closer to the normal temperature side. In this case, the opening degree of the flow control valve (CV) is reduced to reduce the flow rate of the working gas discharged from the intermediate pressure chamber (8). Since the flow rate of the working gas flowing into the intermediate pressure chamber (8) is constant, the intermediate pressure in the intermediate pressure chamber (8) increases due to the decrease in the discharge amount of the working gas, and the displacer (22) moves at full stroke. become.
On the other hand, when the intermediate pressure in the intermediate pressure chamber (8) is higher than a predetermined value, the displacer (22) moves closer to the low temperature side. In this case, the opening degree of the flow control valve (CV) is increased to increase the flow rate of the working gas discharged from the intermediate pressure chamber (8). As a result, the intermediate pressure in the intermediate pressure chamber (8) decreases, and the displacer (22) moves with a full stroke.

In the present embodiment, as described above, the same effects as those obtained in the first embodiment can be obtained only by arranging the flow control valve (CV) and its operation.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a cryogenic refrigerator according to a first embodiment.

FIG. 2 is an enlarged sectional view showing a main part of the cryogenic refrigerator according to the first embodiment.

FIG. 3 is an enlarged perspective view of a rotary valve.

FIG. 4 is an enlarged sectional view showing a high-pressure valve opening state of the rotary valve.

FIG. 5 is an enlarged sectional view showing a low-pressure opening state of the rotary valve.

FIG. 6 is an enlarged sectional view showing a main part of the cryogenic refrigerator according to the second embodiment.

FIG. 7 is a side sectional view of a conventional GM refrigerator driven by gas pressure.

[Explanation of symbols]

 (2) Cylinder (8) Intermediate pressure chamber (17) Slack piston (displacer member) (20) Lower pressure chamber (22) Displacer (displacer member) (30) First stage expansion chamber (31) Second stage expansion chamber (45) High pressure communication passage (48) Low pressure communication passage (CV) Flow control valve (R) Cryogenic refrigerator

Claims (3)

[Claims] A cylinder (2) to which high-pressure or low-pressure working gas is supplied and exhausted, and an expansion chamber (30, 3) inside the cylinder (2).
Displacer member for forming a partition between 1) and pressure chamber (20)
(17,22), and an intermediate pressure chamber (8) set to an intermediate pressure between the high and low pressure working gases and communicating with the pressure chamber (20), and the working gas supplied to and exhausted from the cylinder (2). Gas pressure and pressure chamber
Due to the pressure difference from the pressure of (20), the displacer member (17, 2
2) reciprocates to supply and exhaust the working gas to and from the expansion chambers (30, 31), and expands the high-pressure working gas supplied to the expansion chambers (30, 31). In the low-temperature refrigerator, a high-pressure communication path (45) for guiding the high-pressure working gas to the intermediate pressure chamber (8)
A low-pressure communication path (48) for discharging a predetermined flow rate of working gas in the intermediate pressure chamber (8); and a high-pressure communication path (45) provided in the intermediate pressure chamber (8). Variable flow control valve (CV) that regulates the flow rate of the working gas flowing through the high-pressure communication passage (45) so that
And a cryogenic refrigerator comprising: 2. A cylinder (2) to which high-pressure or low-pressure working gas is supplied and exhausted, and a displacer member for partitioning an expansion chamber (30, 31) and a pressure chamber (20) inside the cylinder (2). (17,22), and an intermediate pressure chamber (8) set to an intermediate pressure between the high and low pressure working gases and communicating with the pressure chamber (20), and the working gas supplied to and exhausted from the cylinder (2). Gas pressure and pressure chamber
Due to the pressure difference from the pressure of (20), the displacer member (17, 2
2) reciprocates to supply and exhaust the working gas to and from the expansion chambers (30, 31), and expands the high-pressure working gas supplied to the expansion chambers (30, 31). In the low-temperature refrigerator, a high-pressure communication path (45) for introducing a predetermined flow of high-pressure working gas to the intermediate pressure chamber (8), and a low-pressure communication path (48) for discharging working gas in the intermediate pressure chamber (8), A variable-opening flow control valve (CV) provided in the low-pressure communication passage (48) for adjusting the flow rate of the working gas flowing through the low-pressure communication passage (48) so that the intermediate pressure chamber (8) has a predetermined intermediate pressure. )
And a cryogenic refrigerator comprising: 3. The cryogenic refrigerator according to claim 1, wherein the high-pressure working gas is supplied only from the high-pressure communication passage (45) to the intermediate-pressure chamber (8).
And the working gas in the intermediate pressure chamber (8) is discharged only from the low pressure communication passage (48) to the outside of the cryogenic refrigerator (R). Cryogenic refrigerator.