KR100785745B1 - Coolness storage unit and cryopump - Google Patents

Abstract

In addition to lead having a great environmental impact, there is provided a cold storage device and cryopump using a cold storage material that satisfies the requirements for the cold storage material (specific heat, thermal conductivity, processability, strength, hardness, chemical stability, low cost).

In the storage cooler 14 which accommodates the storage coolant 16 which heat-exchanged with helium gas in the inner passage through which helium gas which is refrigerant gas passes, the storage cooler 16 is Sn, Bi-Sn alloy. , Ag-Sn alloy, which is formed in a spherical shape, and a plurality of spherical coolant materials 16 are filled in the internal passage of the cooler 14.

Accumulator, cryopump

Description

Refrigerant and Cryopumps {COOLNESS STORAGE UNIT AND CRYOPUMP}

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a cryocooler containing a refrigerating material and a cryo pump provided with the refrigerating device, which serve to temporarily exchange heat with a helium gas, which is a refrigerant gas, to temporarily store heat. will be.

The cryopump is a pump that provides a low temperature surface in a vacuum vessel, and condenses or adsorbs gas molecules in the vessel to capture and exhaust the gas. In a method for forming a low temperature surface, a small helium refrigerator of a waste cycle is generally used.

The helium refrigeration machine is a cold storage refrigeration machine using helium gas as a refrigerant gas (working fluid), and sends a high-pressure helium gas to an expansion space in a low temperature part, where low temperature is obtained by adiabatic expansion of helium gas. A feature of the cold storage refrigerator is that it is provided with a heat exchanger called a cold storage refrigerator. The role of the cooler is to take the heat from the compressed high-pressure high-temperature helium gas flowing in one direction and to store the heat, and to cool the helium gas that is sent to the expansion space in advance, Give the helium gas a reserved heat so that cold helium gas is not released into the room temperature space.

In the cooler, a coolant to heat exchange with helium gas is accommodated. As the coolant, lead is used, which has a high thermal conductivity and a higher specific heat than other metals at a low temperature (below 30K) and is also cheaper. .

Alternatively, a magnetic material such as Er ₃ Ni, which has a higher specific heat than lead at cryogenic temperatures (5 K or less), may be used in a refrigerator having a high specification. See, for example, Patent Document 1 and Patent Document 2.

Patent Document 1: Japanese Patent Application Laid-Open No. 10-300251

Patent Document 2: Japanese Patent Application Laid-Open No. 2004-143341

Although lead has a higher specific heat at low temperature and is cheaper than other metals, lead is used in large quantities and with high purity to improve freezing performance, and has a high environmental impact, and requires recovery and proper treatment after use. , The handleability is bad.

Magnetic materials are very expensive. In addition, since the specific heat has a characteristic of having a large peak in the vicinity of the phase transition temperature, in the case of constituting the cold storage machine, various kinds of substances having specific heat peaks at different temperatures are selected in accordance with the temperature distribution in the cold storage machine. Since it is more effective to construct a storage cooler than using it alone, this also leads to a cost increase. In addition, the magnetic material is hardened by an intermetallic compound, resulting in poor workability.

Therefore, under such a background, in addition to lead having a large environmental impact, there is a demand for a heat storage material that satisfies the requirements for the heat storage material (specific heat, thermal conductivity, processability, strength, hardness, chemical stability, low cost), and the present invention. It is an object of the present invention to provide a cooler and a cryopump using such coolant.

The cold storage of the present invention is a cold storage in which a cold storage material for exchanging heat with the refrigerant gas is contained in an internal passage through which the refrigerant gas passes, wherein the cold storage material includes Sn, Bi-Sn alloy, and Ag-. It is characterized by consisting of any of Sn alloys.

Further, the cryopump according to the present invention is characterized by including a refrigerating machine in which a refrigerating material of Sn, Bi-Sn alloy or Ag-Sn alloy is accommodated in an internal passage through which the refrigerant gas passes.

Since the cool storage material which consists of said Sn, Bi-Sn alloy, and Ag-Sn alloy does not contain lead, the adverse influence to a human body and an environment is small, and handling is easy. It is also cheaper than magnetic materials. Furthermore, it is also excellent in workability, so that processing on a small spherical shape can be easily performed, for example, in order to improve the heat exchange efficiency with refrigerant gas.

1 is a schematic diagram of a cryopump according to an embodiment of the present invention.

2 is an explanatory view of the operation of the refrigerator in the cryo pump of FIG. 1.

3 is a graph showing the specific heat characteristics of various heat storage materials.

* Explanation of Codes *

1: cryo pump 2: freezer unit

3: compressor 5: single stage cylinder

6: two-stage cylinder 7: shield

8: baffle 9: cryo panel

11: Displacer 12: Displacer

13: 1 stage cold storage 14: 2 stage cold storage

15: cold storage material 16: cold storage material

18: intake valve 19: discharge valve

21: One stage expansion space 22: Two stage expansion space

25: room temperature space 31: 1 stage heat load flange

32: 2-stage heat load flange

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described with reference to drawings.

1 shows a schematic diagram of a cryopump 1 according to an embodiment of the present invention. The cryopump 1 is equipped with the refrigerator unit 2, The refrigerator unit 2 is equipped with the compressor 3 and the large and small two-stage cylinders 5 and 6. As shown in FIG. Helium gas compressed at high pressure in the compressor (3) circulates in both cylinders (5, 6), and cools the expansion space formed in those cylinders (5, 6) to cryogenic temperatures, thereby accompanying the cylinders (5, 6) The shield 7, the baffle 8, and the cryopanel 9 provided in connection with each other are also cooled to cryogenic temperatures to condense gas molecules.

As shown in FIG. 2, two displacers 11 and 12 are accommodated in the cylinders 5 and 6. The displacers 11 and 12 are connected to the drive shaft of the motor 4 shown in FIG. 1 via the cam 17, and according to the drive rotation of the motor drive shaft, the two displacers 11 and 12 are integrated into a cylinder. It reciprocates inside (5, 6).

The first stage cold storage unit 13 is accommodated in the first stage displacer 11. The two stage cooler 14 is accommodated in the two stage displacer 12. The inside of the first stage cooler 13 is a passage through which helium gas, which is a refrigerant gas, passes, and a plurality of copper gold meshes are stacked in the passage as the coolant 15. The inside of the two-stage cooler 14 also serves as a passage through which helium gas passes, and a plurality of very small spheres are filled in the passage with the coolant 16. The cold storage material 16 of the two-stage cooler 14 is either Sn, a Bi-Sn alloy, or an Ag-Sn alloy.

In the first stage cylinder 5, a first stage heat load flange (1st stage) is formed on the outer wall of the first stage expansion space 21 formed between the end wall of the first stage cylinder 5 and the end wall of the first stage displacer 11. 31) is installed. The shield 7 and the baffle 8 shown in FIG. 1 are connected to the one-stage heat load flange 31, and the shields 7 and the baffle 8 are cooled when the one-stage expansion space 21 becomes cold. .

Inside the two-stage cylinder 6, a two-stage heat load flange is formed on the outer wall of the two-stage expansion space 22 formed between the single wall of the two-stage cylinder 6 and the single wall of the two-stage displacer 12. 32) is installed. The cryopanel 9 shown in FIG. 1 is connected to the two-stage heat load flange 32, and the cryopanel 9 is cooled when the two-stage expansion space 22 becomes low.

A suction valve 18 for supplying helium gas into the expansion spaces 21 and 22 in the compressor 3, and a discharge valve 9 for returning helium gas to the compressor 3 in the expansion spaces 21 and 22. Opening and closing is performed by the displacer 11 and 12 driving motor 4.

When the power supply of the refrigerator unit 2 is turned on, the opening and closing of the suction valve 18 and the discharge valve 19 and the reciprocating movement of the displacer 11 and 12 are repeated with the drive of the motor 4.

First, in the process (a) shown in FIG. 2, the discharge valve 19 is closed, the suction valve 18 is opened, and the high pressure helium gas discharged from the compressor 3 is discharged to the room temperature space of the first stage cylinder 5 ( 25).

Subsequently, the displacer 11, 12 is moved to the room temperature space 25 side as shown in FIG. 2 (b) with the suction valve 18 open. As a result, the helium gas in the room temperature space 25 moves to the expansion spaces 21 and 22 while being cooled by heat exchange with the cool storage materials 15 and 16 through the cool storage devices 13 and 14. This operation is performed while the suction valve 18 is opened to satisfy the isostatic pressure because the volume thereof contracts when helium gas passes through the coolers 3 and 4.

Subsequently, in step (c), the intake valve 18 is closed and the discharge valve 19 is opened to release the high pressure helium gas in the expansion spaces 21 and 22 to lower the pressure in the expansion spaces 21 and 22. In this process, the helium gas in the expansion spaces 21 and 22 is adiabaticly expanded to become a low-temperature gas at low temperature, so that the temperature of the expansion spaces 21 and 22 decreases, and through the heat load flanges 31 and 32, the shield ( 7), the baffle 8 and the cryopanel 9 are cooled.

Then, in step d, the displacers 11 and 12 are moved to the expansion spaces 21 and 22 with the discharge valve 19 open. As a result, the low-temperature helium gas remaining in the expansion spaces 21 and 22 moves to the room temperature space 25 through the coolers 13 and 14, and the helium gas exchanges heat with each of the cool storage materials 15 and 16. After the discharge, the discharge valve 19 is discharged. That is, the low-temperature helium gas in the expansion spaces 21 and 22 rises in temperature while cooling the accumulators 15 and 16 to cool the helium gas sucked in the next cycle, and then returns to room temperature. Is returned to the compressor (3). Then, the discharge valve 19 is closed, the intake valve 18 is opened, the operation of the first process (a) is completed, and one cycle ends.

In this embodiment, any of Sn, Bi-Sn alloy, and Ag-Sn alloy, which is a material that does not contain Pb, is used as the cold storage material 16 of the two-stage cold storage 14 arranged on the lower temperature side. have. As shown in the graph of FIG. 3, Sn has a specific heat smaller than Pb in the low temperature region (30K or less) using a cryopump. However, since the specific heat is smaller than that of Pb, the heat capacity of the regenerator material can be increased by increasing the capacity, thereby achieving a freezing capacity equivalent to that of the conventional Pb. In the region of 25 to 30K, Sn has a specific heat equivalent to that of some magnetic material (HoCu ₂ ). In the case of using a Bi-Sn alloy or an Ag-Sn alloy, when the content ratio of Bi or Ag to Sn is 50% or less, it has a specific heat equivalent to that of the Sn single body, and a refrigerating machine of equivalent performance Can be configured.

Thus, even if Sn, Bi-Sn alloy, and Ag-Sn alloy are used as a coolant instead of Pb, the freezing capability similar to the conventional one can be achieved. It is good just to change the refrigerating material accommodated in a refrigerating machine, without improving and adjusting to another component part, and the compatibility with the existing cryopump is high. In addition, since the appearance of the cryopump does not cause a change in appearance and a change in the mechanical structure, the maintainability is also good.

The heat storage material 16 may be composed of a plurality of spherical particles in order to smoothly flow the helium gas and increase the surface area to increase the heat exchange rate. The material of Sn, Bi-Sn alloy, and Ag-Sn alloy is not as hard and brittle as a magnetic material, and can be easily processed into spherical shape. If the diameter of each spherical particle is 1 mm or less, sufficient heat exchange with helium gas is possible. If each spherical particle becomes fine enough to become a powder form, it hinders the flow of helium gas. Therefore, the diameter of each spherical particle needs to be set to a size that allows a smooth flow of helium gas.

Next, Sn, Bi-Sn alloys and Ag-Sn alloys have less effect on human body and environment than lead, are easy to handle, and are cheaper than magnetic materials (price of about 1/18). Moreover, Sn, Bi-Sn alloys, and Ag-Sn alloys satisfy other conditions (thermal conductivity, chemical stability, strength, and hardness) as the cold storage material.

As mentioned above, although embodiment of this invention was described, of course, this invention is not limited to this, Various deformation | transformation are possible for it based on the technical idea of this invention.

The drive method of the displacers 11 and 12 is not limited to the motor driving method, but may be a gas pressure driving method using a pressure difference between the helium gas as the refrigerant gas, or a combination method of a motor and gas pressure driving.

In the above embodiment, an example in which a cooler is used in a Gifford McMahon type freezer is shown, but it can also be applied to a reverse stirling freezer, a pulse tube freezer, and a solvay freezer. In addition, such a refrigerator is not limited to being used in a cryopump, but can be used for cooling superconducting magnets and cryogenic sensors.

According to the cold storage device of the present invention, any one of Sn, Bi-Sn alloy, and Ag-Sn alloy is used as the coolant that performs heat exchange with the refrigerant gas. Inexpensive and excellent in handleability can be provided.

According to the cryopump according to the present invention, by using a refrigerating machine equipped with the above-mentioned refrigerating material in a refrigerating type freezer for forming a low temperature surface for condensing gas molecules, cumbersome handling, change in form and mechanical structure, and It is possible to provide a performance equivalent to the conventional one without requiring an increase in cost.

Claims (5)

In an accumulator, in which an accumulator that heat-exchanges with the refrigerant gas is accommodated in an internal passage through which refrigerant gas passes, The said cool storage material is an alloy containing Sn or at least either Bi or Ag which has Sn as a main component, The Bi content in the Bi-Sn alloy is greater than 0% and less than 50%, The content ratio of Ag in the Ag-Sn alloy is greater than 0% and 50% or less, characterized in that the cold storage. delete delete The method of claim 1, The accumulator is formed in a spherical shape, the plurality of spherical coolant is accommodated in the inner passage. A cryopump provided with the cooler of Claim 1 or 4.

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