JPH08313094A - Cold storage type refrigerator - Google Patents

Abstract

PURPOSE: To provide a cold storage type refrigerator capable of improving the refrigerating capacity of a cooler disposed at the final stage. CONSTITUTION: In a cold storage type refrigerating machine which employs the type of a plurality of expansion stages by providing a plurality of stages of cold storage units, a final cooler 52 for generating the lowest temperature constitutes a pulse tube refrigerating machine, and the high-temperature end of the tube 67 in a pulse tube refrigerating machine is extended substantially to an ambient temperature part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a regenerator having a plurality of stages of regenerators and adopting a multistage expansion system.

[0002]

2. Description of the Related Art As is well known, most of the superconducting magnet devices currently in practical use employ an immersion cooling method in which a superconducting coil and a cryogenic refrigerant represented by liquid helium are housed together in a heat insulating container. In addition, the system uses a cryogenic refrigerator to cool the thermal shield provided in the heat insulating layer of the heat insulating container. Further, recently, a refrigerator direct cooling type superconducting magnet device in which a superconducting coil housed in a heat insulating container is directly cooled by a cryogenic refrigerator is being put into practical use. In many of such superconducting magnet devices, a regenerator is used as a cryogenic refrigerator because of its small size and achieving a sufficiently low ultimate temperature.

[0003] Such a regenerator is usually equipped with a plurality of regenerators and adopts a multi-stage expansion system, and alternately introduces high-pressure gas into the entire cooling system and alternately discharges gas from the entire cooling system. The normal temperature part is equipped with a gas control system. A typical example is a regenerator with a Gifford-McMahon refrigeration cycle.

FIG. 4 shows a schematic structure of a two-stage expansion regenerator with a Gifford-McMahon refrigeration cycle. This refrigerator comprises a cold head 1 for cooling helium gas and a gas control system 2, for example.

In the cold head 1, a displacer 12 formed of a heat insulating material is reciprocally housed in a closed cylinder 11. The cylinder 11 is composed of a large-diameter first cylinder 14 and a small-diameter second cylinder 15 coaxially connected to the first cylinder 14. The first cylinder 14 and the second cylinder 15 are usually formed of a thin stainless steel plate or the like.

First and second cooling stages 16 and 17 are provided in the first and second cylinders 14 and 15, respectively. That is, the head wall portion of the first cylinder 14 is provided with the first cooling stage 16 that expands the compressed refrigerant gas to generate cold, and the second cylinder 1
Second, which expands the compressed refrigerant gas in the head wall portion of No. 5 to generate colder temperature lower than that of the first-stage cooling stage 16
A cooling stage 17 is provided.

The displacer 12 includes a first cylinder 14
The first displacer 18 reciprocates inside and the second displacer 19 reciprocates inside the second cylinder 15. The first displacer 18 and the second displacer 19 are axially connected by a connecting mechanism 20.

A fluid passage 21 for constituting a first-stage regenerator is formed in the first displacer 18 in the axial direction, and the fluid passage 21 has a mesh-shaped regenerator made of copper, for example. A material 22 is contained. Similarly, a fluid passage 23 for forming a second-stage (final-stage) regenerator is formed inside the second displacer 19, and the fluid passage 23 is made of, for example, lead or Er.
_A regenerator material 24 such as a magnetic regenerator material that utilizes anomalous magnetic specific heat associated with a magnetic phase transition such as Ni is housed.

A sealing device 25 is provided between the upper outer peripheral surface of the first displacer 18 and the inner peripheral surface of the first cylinder 14, and between the outer peripheral surface of the second displacer 19 and the inner peripheral surface of the second cylinder 15, respectively. , 26 are attached.

The upper end of the first displacer 18 is connected to the rotary shaft of the motor 13 via a connecting rod 31, a Scotch yoke, a crank shaft 32, or the like. Therefore, when the motor 13 rotates, the displacer 12 reciprocates in synchronization with this rotation as indicated by a solid arrow 33 in the figure.

A helium gas inlet 34 and an outlet 35 are provided on the upper side wall of the first cylinder 14, and the inlet 34 and the outlet 35 are connected to the gas control system 2.

In the gas control system 2, the discharge port 35 is connected to the low pressure valve 3
6, inlet 34 through compressor 37, high pressure valve 38
Connected to The low-pressure valve 36 and the high-pressure valve 38 are controlled to open and close in synchronization with the rotation of the motor 13 in a relationship described later. The gas control system 2 constitutes a helium gas circulation system passing through the cylinder 11. That is, low pressure (about 8
The operation of compressing the helium gas (atm) to a high pressure (about 20 atm) by the compressor 37 and sending it into the cylinder 11 and the operation of exhausting the helium gas in the cylinder 11 are alternately performed. Incidentally, reference numeral 41 in the figure denotes the outer wall of the heat insulating container to which the refrigerator is attached.

The freezing operation of the regenerator having the above structure will be briefly described as follows. Generation of cold is performed in the first cooling stage 16 and the second cooling stage 17. The first cooling stage 16 is cooled to about 30K in an ideal state where there is no heat load. The second cooling stage 17 is cooled to about 8K when lead is used as the regenerator material 24 and to about 4K when a magnetic regenerator material such as Er ₃ Ni is used. Therefore, the temperature between the upper and lower ends of the first displacer 18 (30
A temperature gradient from 0K to 30K occurs, and between the upper and lower ends of the second displacer 19 is 30K to 8K (4K).
A temperature gradient up to occurs. Of course, the temperatures of the first and second cooling stages 16 and 17 change depending on the heat load.

When the motor 13 starts rotating, the displacer 12 reciprocates between the bottom dead center (top point in the figure) and the top dead center (bottom point in the figure). When the displacer 12 reaches the top dead center, the high pressure valve 38 opens, the high pressure helium gas flows into the cold head 1, and then the displacer 12
Moves to bottom dead center.

As described above, a seal is provided between the outer peripheral surface of the first displacer 18 and the inner peripheral surface of the first cylinder 14, and between the outer peripheral surface of the second displacer 19 and the inner peripheral surface of the second cylinder 15, respectively. Since the devices 25 and 26 are mounted, when the displacer 12 moves toward the bottom dead center, the high-pressure helium gas passes through the fluid passage 21 formed in the first displacer 18 and the fluid passage 23 formed in the second displacer 19. The first stage expansion chamber 39 formed between the first displacer 18 and the head wall of the first cylinder 14, the second displacer 19 and the second cylinder 15.
Flow into the second-stage expansion chamber 40 formed between the second head and the head wall. Along with this flow, the high-pressure helium gas is cooled by the regenerator materials 22, 24, the high-pressure helium gas that has flowed into the first-stage expansion chamber 39 reaches approximately 30K, and the high-pressure helium gas that has flowed into the second-stage expansion chamber 40. Is 8K
Cooled to a degree.

When the displacer 12 reaches the bottom dead center, the high pressure valve 38 is closed and the low pressure valve 36 is opened. When the low pressure valve 36 is opened in this way, the high pressure helium gas in the first stage expansion chamber 39 and the second stage expansion chamber 40 adiabatically expands to generate cold. This cold causes the first cooling stage 1
6 absorbs heat from the outside, and the second cooling stage 17 also absorbs heat from the outside. Then, when the displacer 12 moves to the top dead center again, the low temperature helium gas in the first-stage expansion chamber 39 and the second-stage expansion chamber 40 passes through the fluid passages 21 and 23 accordingly. Regenerator material 2 when passing
Cool 2, 24. Helium gas whose temperature has risen
It is discharged from the cold head 1 to the compressor 37 via the low pressure valve 36.

The above-described cycle is repeated to execute the refrigerating operation. This type of refrigerator is used as a cooling source for a thermal shield arranged inside a heat insulating container of a heat insulating container, a direct cooling of a superconducting coil, a cooling of an infrared sensor, and a cooling source of a cryosorption pump.

It has been pointed out that the conventional regenerator having the above structure has the following problems. That is, the sealing device 25 prevents the helium gas from flowing through the gap between the first cylinder 14 and the first displacer 18 between the room temperature portion and the first expansion chamber 39, and the sealing device 26 prevents Helium gas is prevented from flowing through the gap between the second cylinder 15 and the second displacer 19 between the stage expansion chamber 39 and the second stage expansion chamber 40. These sealing devices 25,
In No. 26, lubricating oil cannot be used to maintain the purity of helium gas (99.99%) and prevent malfunction due to freezing.

Here, the temperature in the first stage expansion chamber 39 is 30
K, if the temperature in the second expansion chamber 40 is 10 K as an example, if a leak occurs in the sealing device 26, it will be 3
0K helium gas enters the second stage expansion chamber 40 without contacting the regenerator material 24 in the second displacer 19,
On the contrary, 10 K of helium gas enters the first stage expansion chamber 39. As a result, the temperature of the first cooling stage 16 drops and the temperature of the second cooling stage 17 rises.

When a leak occurs in the sealing device 25, the same phenomenon occurs in the upper space of the first cylinder 14 and the first space.
It occurs between the stage expansion chamber 39 and the temperature of the first stage cooling stage 16 rises. However, since the sealing device 26 is located in the cryogenic portion, it is difficult to reduce leakage.
Since the amount of cold generated in the second cooling stage 17 is smaller than that in the second cooling stage 16, the influence thereof is very large.

[0021]

As described above, in the conventional regenerative refrigerator, since the sliding seal element is provided in the cryogenic portion, the refrigerating performance is significantly increased due to the leakage at the seal portion. It was deteriorated and it was essentially difficult to maintain stable refrigeration performance. Therefore, an object of the present invention is to provide a cold storage refrigerator capable of solving the above-mentioned problems.

[0022]

In order to achieve the above object, the present invention relates to a regenerator having a plurality of stages of regenerators and expanders, in which at least a final stage for generating a minimum temperature is an expander. And a high temperature end of the pulse tube extending substantially to a room temperature portion.

The phase control mechanism of the pulse tube refrigerator is preferably provided in the room temperature section. Further, it is preferable that a heat storage suppressing portion is formed by accommodating a regenerator material inside the high temperature end side of the pulse tube. Further, the high temperature end side of the pulse tube may be communicated with the phase control mechanism through a valve that opens and closes in conjunction with the operation of the phase control mechanism. Further, the high temperature end side of the pulse tube may be connected to at least one of a buffer tank provided at a room temperature portion and a gas introduction / exhaust portion in the first stage cooling portion of the regenerative refrigerator via a flow restricting element. . Furthermore, the refrigeration cycle of at least the first stage of the cold-storage refrigerator may be any one of the Gifford-McMahon refrigeration cycle, the Stirling refrigeration cycle, and the modified Solvay refrigeration cycle.

[0024]

The function of the final stage cooling unit in the cooling system is the pulse tube refrigerator. Pulse tube refrigerator
No sliding sealing elements are required either, since there are no moving parts. Therefore, it becomes possible to prevent the reduction of the refrigerating capacity caused by the presence of the sliding seal element.

Further, since the high temperature end of the pulse tube in the pulse tube refrigerator is located substantially at the room temperature portion, the phase control required in the pulse tube refrigerator, that is, the pressure change phase and the gas displacement is performed. A mechanism for providing a predetermined phase difference with the phase can be easily provided. That is, since the phase control mechanism of the pulse tube refrigerator is arranged in the room temperature portion, operability, ease of maintenance, reliability, etc. are improved.

[0026]

Embodiments will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a cold storage refrigerator according to an embodiment of the present invention. In this figure, the same functional parts as those in FIG. 4 are indicated by the same reference numerals. Therefore, detailed description of the overlapping portions will be omitted.

This cold storage type refrigerator adopts a two-stage expansion type and is composed of a cold head 1a and a gas control system 2a. Although the gas control system 2 can be arranged inside the cold head 1a, it is drawn outside the cold head 1a in FIG. 1 for convenience of explanation.

The cold head 1a includes a first stage cooling section 51.
And a second-stage cooling section 52 connected in series to this. The first-stage cooling unit 51 employs the same Gifford-McMahon refrigeration cycle as shown in FIG. 4, and the second-stage cooling unit 52 employs a pulse tube refrigeration cycle.

The second stage cooling section 52 is constructed as follows. That is, the cylinder 1 is attached to the head wall of the cylinder 14.
4 is connected to one end side of the pipe 61, and the other end side of the pipe 61 is connected to one connection port of the second stage regenerator 62. The second-stage regenerator 62 includes a container 63 formed of a heat insulating material, and Er ₃ N contained in the container 63.
and a magnetic regenerator material 64 that utilizes anomalous magnetic specific heat associated with the magnetic phase transition. The other connection port of the second-stage regenerator 62 is connected to the second-stage cooling stage 6
It is connected to one end side of a pulse tube 67 via a heat absorption tube 66 that constitutes the No. 5.

The pulse tube 67 has a diameter larger than that of the heat absorbing tube 66 and is parallel to the axial center line of the cylinder 14.
A pulse tube main body 68 extending upward to the same level as that of the stage cooling stage 16, and a diameter smaller than the pulse tube main body 68, one end of which communicates with the upper end of the pulse tube main body 68 and the other end of which is a heat insulating container. And a thin tube 69 that extends to the outside, that is, to a room temperature portion. The boundary between the pulse tube body 68 and the thin tube 69 is thermally connected to the first cooling stage 16 via the heat conducting member 70. Further, a regenerator material 71 made of lead particles or the like is housed in the thin tube 69, and the pulse tube main body 6 is kept from the room temperature portion.
The heat is prevented from entering the inside of No. 8.

On the other hand, the gas control system 2a connects the discharge port 35 to the introduction port 34 via the low pressure valve 36, the compressor 37 and the high pressure valve 38, and further, the gas discharge end of the compressor 37 via the auxiliary high pressure valve 72. It is connected to the end of the thin tube 69 protruding to the room temperature portion, and the gas suction end of the compressor 37 is connected to the end of the thin tube 69 protruding to the room temperature portion via the auxiliary low pressure valve 73. The low pressure valve 3
6. The high-pressure valve 38 synchronizes with the rotation of the motor 13 and the volume of the first expansion chamber formed in the cylinder 14 (volume change 0
.About.Vmax), the opening / closing control is performed in the relationship shown in FIG. In addition, the auxiliary high pressure valve 72 and the auxiliary low pressure valve 73
Is for setting a predetermined phase difference between the pressure change phase and the gas displacement phase in the pulse tube refrigerator constituting the second stage cooling unit 52, and is synchronized with the rotation of the motor 13. Similarly, the opening / closing control is performed in the relationship shown in FIG.

Next, the operation of the regenerator having the above-described structure will be described. The generation of cold in the first cooling stage 16 of the first cooling unit 51 is due to the Gifford-McMahon refrigeration cycle as in the conventional one shown in FIG.

On the other hand, the generation of cold in the second cooling stage 65 of the second cooling section 52 is due to the pulse tube refrigeration cycle using the pulse tube 67 as an expander. That is, cold is generated at the low temperature end of the pulse tube 67, that is, at the boundary with the heat absorbing tube 66 by the high and low pressure pressure waves created in the cold head 1 a by opening and closing the low pressure valve 36 and the high pressure valve 38.

In this embodiment, in order to increase the amount of cold generation in the second cooling stage 65 by providing a predetermined phase difference between the phase of pressure change in the pulse tube 67 and the displacement phase of gas. An auxiliary high-pressure valve 72 and an auxiliary low-pressure valve 73 for supplying and discharging high-pressure helium gas from the portion of the thin tube 69 protruding to the room temperature portion are provided. The auxiliary high pressure valve 72 and the auxiliary low pressure valve 73 are the displacer 1
Opening / closing control is performed in conjunction with the reciprocating movement of 8. Specifically, as shown in FIG. 2, the auxiliary high pressure valve 72 is controlled to open and close at a timing earlier than the high pressure valve 38, and the auxiliary low pressure valve 73 is controlled to open and close at a timing earlier than the low pressure valve 36. By such control, the amount of cold generation in the second cooling stage 65 can be increased.

Further, in this embodiment, in order to prevent the helium gas at room temperature from flowing into the pulse tube body 68 via the auxiliary high pressure valve 72, the regenerator material 71 is placed in the thin tube 69.
The cold storage material 71 suppresses heat invasion from the room temperature portion and allows helium gas having a temperature similar to that of the first cooling stage 16 to flow into the high temperature end of the pulse tube main body 68. .

As described above, in the regenerator of the present embodiment, the second-stage cooling unit 52 located at the final stage of the cooling system is a pulse tube refrigerator. The pulse tube refrigerator also does not require a sliding seal element since there are no moving parts. Therefore, it becomes possible to prevent the reduction of the refrigerating capacity caused by the presence of the sliding seal element.

Further, since the high temperature end of the pulse tube 67 in the pulse tube refrigerator is located substantially at the room temperature portion, the phase control mechanism required for the pulse tube refrigerator can be easily provided. Since the amount of cold generation in the pulse tube 67 can be increased, the refrigeration performance can be significantly improved. That is, by providing the phase control mechanism in the room temperature section, the operability, reliability, easiness of maintenance of the valve and the like are remarkably improved.

In the above embodiment, the heat conducting member 7
Although the temperature of the boundary portion between the pulse tube main body 68 and the thin tube 69 is set to almost the same temperature as that of the first stage cooling stage 16 by using 0, the heat conduction member 70 may be omitted.
Further, although the pulse tube 67 is composed of the large-diameter pulse tube main body 68 and the thin tube 69, the entire pulse tube has the same diameter, and the cool storage material is not accommodated.
The high temperature end may be projected to the room temperature portion and connected to the auxiliary high pressure valve and the auxiliary low pressure valve.

FIG. 3 shows a schematic structure of a cold storage type refrigerator according to another embodiment of the present invention. In this figure, the same functional portions as those in FIGS. 1 and 4 are indicated by the same reference numerals. Therefore, detailed description of the overlapping portions will be omitted.

The cold storage refrigerator according to this embodiment differs from that shown in FIG. 1 in the configuration of the phase control mechanism of the pulse tube refrigerator constituting the second stage cooling section 52. That is, the portion of the thin tube 69 projecting to the normal temperature portion is communicated with the gas introduction / exhaust portion of the first-stage cooling unit 51, that is, the upper space of the cylinder 14 via the flow rate adjusting valve 81, and the normal temperature is obtained via the orifice valve 82. It is communicated with a buffer tank 83 provided in the section.

By adopting such a configuration,
The second-stage cooling unit 52 is a double-inlet type pulse tube refrigerator, which makes it possible to increase the amount of cold generation. Therefore, the same effect as the embodiment shown in FIG. 1 can be exhibited.

In the present embodiment, the flow rate adjusting valve 81 and the orifice valve 82 may be replaced with a flow restricting element such as a thin tube having a flow resistance equivalent to these. Further, also in this embodiment, the heat conduction member 70 can be omitted. Further, although the pulse tube 67 is composed of the large diameter pulse tube main body 68 and the thin tube 69, the pulse tube 67 has the same diameter as a whole, and the high temperature end thereof is projected into the room temperature portion without accommodating the regenerator material. Let
It may be communicated with the upper space of the cylinder 14 and the buffer tank 83. Alternatively, only one of them may be connected.

Further, in the embodiment shown in FIGS. 1 and 3,
Although the regenerator material such as the magnetic regenerator material 64 is directly accommodated in the container 63, the container accommodating the regenerator material is accommodated in the container 63,
You may interpose a sealing material between both containers. In this case, since the sealing material is stationary, the leak amount is small and the refrigerating performance is not affected.

In each of the above embodiments, the first stage cooling unit 5
Although the Gifford-McMahon refrigeration cycle is adopted in 1, the Stirling refrigeration cycle and the modified Solvay refrigeration cycle can be adopted in the cooling section other than the final stage. Further, in each of the above-described embodiments, the cooling system is configured by providing two stages of cooling units, but three or more stages may be provided.

[0045]

As described above, according to the present invention,
Since the final stage cooling unit is configured as a pulse tube refrigerator that has no moving parts at all, that is, it does not require a sliding seal element, it is possible to prevent the reduction of the refrigeration capacity caused by the presence of the sliding seal element, and Can be improved. Further, since the configuration is adopted in which the high temperature end of the pulse tube in the pulse tube refrigerator is located substantially at the room temperature portion, the phase control mechanism required in the pulse tube refrigerator can be easily provided, and the preferred phase difference Since the setting can be achieved, the refrigerating capacity can be further improved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a cold storage refrigerator according to an embodiment of the present invention.

FIG. 2 is a diagram showing opening / closing timings of a phase control valve incorporated in the refrigerator.

FIG. 3 is a schematic configuration diagram of a cold storage refrigerator according to another embodiment of the present invention.

FIG. 4 is a schematic configuration diagram of a conventional regenerative refrigerator.

[Explanation of symbols]

1a ... Cold head 2, 2a ... Gas control system 51 ... Gifford McMahon refrigeration cycle first stage cooling unit 52 ... Pulse tube refrigeration cycle second stage cooling unit 16 ... First cooling stage 62 ... Cold storage Container 64 ... Magnetic regenerator material 65 ... Second cooling stage 66 ... Endothermic tube 67 ... Pulse tube 68 ... Pulse tube body 69 ... Thin tube 71 ... Regenerator material 72 ... Auxiliary high pressure valve 73 ... Auxiliary low pressure valve 81 ... Flow control valve 82 ... Orifice valve 83 ... Buffer tank

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsuya Yoshino 1 Komukai Toshiba-cho, Kouki-ku, Kawasaki-shi, Kanagawa Incorporated Toshiba Research and Development Center

Claims (6)

[Claims] 1. A regenerator having a plurality of stages of regenerator and expander, wherein at least a final stage for generating a minimum temperature is composed of a pulse tube refrigerator having a pulse tube as an expander, The regenerator according to claim 1, wherein the high temperature end of the pulse tube extends substantially to a room temperature portion. 2. The regenerator according to claim 1, wherein a phase control mechanism of the pulse tube refrigerator is provided in a room temperature section. 3. The cold storage refrigerator according to claim 1, wherein the pulse tube has a heat storage suppression portion formed therein by storing a cold storage material inside the high temperature side. 4. The cool storage according to claim 2, wherein the high temperature end side of the pulse tube communicates with the phase control mechanism through a valve that opens and closes in conjunction with the operation of the phase control mechanism. Refrigerator. 5. The high temperature end side of the pulse tube communicates with at least one of a buffer tank provided at a room temperature part and a gas introduction / exhaust part in the first stage cooling part of the regenerative refrigerator via a flow restricting element. The cold storage refrigerator according to claim 1, wherein the refrigerator is a cold storage refrigerator. 6. At least the first stage of the regenerative refrigerator is
Gifford McMahon refrigeration cycle,
The regenerative refrigerator according to claim 1, which is configured as either a Stirling refrigeration cycle or a modified Solvay refrigeration cycle.