JP3588644B2 - Regenerator refrigerator - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a regenerator refrigerator, and more particularly to a regenerator refrigerator in which a displacer is reciprocally driven in a cylinder, and a refrigerant gas expands in an expansion chamber defined at a low temperature end in the cylinder to generate heat.
[0002]
[Prior art]
Gifford McMahon (GM) cycle refrigerators, (reverse) Stirling cycle refrigerators and the like are known as regenerator refrigerators using a refrigerant gas such as helium and containing a regenerator material. When a clean vacuum is to be obtained by a sputtering device for manufacturing semiconductor devices, a cryopump is used. In recent years, a GM refrigerator has been used as a cryopump refrigerator. Of course, the GM refrigerator is not limited to a cryopump and can be used for various purposes. Hereinafter, the configuration of the GM refrigerator will be described.
[0003]
A displacer is inserted in the cylinder. An expansion chamber is defined at the cold end of the cylinder and a cavity is defined at the hot end. A gas passage is provided in the displacer, and the gas passage is filled with a cold storage material. The gas flow path in the displacer communicates with the expansion chamber and the cavity on the high-temperature end side. A drive mechanism reciprocates the displacer in the axial direction of the cylinder.
[0004]
A helium gas supply system supplies helium gas to the high-temperature end side cavity and recovers helium gas from the cavity. The supply and recovery of the helium gas are performed in synchronization with the reciprocating drive of the displacer. When the helium gas is supplied to the cavity on the high temperature end side, the helium gas is introduced into the expansion chamber through the gas flow path in the displacer. Helium gas in the expansion chamber is recovered to the helium gas supply system through the same path.
[0005]
A seal mechanism for preventing leakage of helium gas is provided in a gap between the cylinder and the displacer. When the reciprocating motion of the displacer and the supply and recovery of the helium gas are repeated, heat is absorbed in the expansion chamber. When the cooled helium gas is recovered from the expansion chamber, the cold storage material in the displacer is cooled. When helium gas is introduced into the expansion chamber, the regenerator cools the helium gas.
[0006]
Due to the failure of the sealing mechanism between the cylinder and the displacer, the desired refrigerating capacity may not be exhibited. Japanese Patent No. 2659684 discloses an invention relating to a refrigerator capable of preventing a decrease in refrigeration capacity due to a failure of a sealing mechanism. In the invention disclosed in Japanese Patent No. 2659684, a spiral groove is provided on the outer peripheral surface of the displacer instead of providing a seal mechanism.
[0007]
Helium gas that has branched from the regular gas flow path in the displacer and has flowed into the gap between the cylinder and the displacer flows along the spiral groove. The helium gas flowing along the spiral groove passes through a longer path than when flowing in parallel with the cylinder axis, so that sufficient heat exchange with the displacer can be performed. Therefore, heat loss due to helium gas flowing in the gap between the cylinder and the displacer can be reduced.
[0008]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a regenerator having a groove formed on the outer peripheral surface of a displacer, which can further increase the refrigerating capacity and can be easily manufactured.
[0009]
According to one aspect of the present invention, a cylinder, a displacer disposed in the cylinder so as to be able to reciprocate in the axial direction of the cylinder, and defining an expansion chamber at one end in the cylinder, and a metal cylinder; A coating formed on the outer peripheral surface of the cylinder, wherein the cylinder and the coating have a smaller coefficient of friction when the coating and the cylinder are in contact with each other than a coefficient of friction when the cylinder and the cylinder are in direct contact with each other. A displacer made of a material having a smaller coefficient of friction, a main gas flow path for supplying a refrigerant gas into the expansion chamber and recovering the refrigerant gas from the expansion chamber; A cold storage material disposed on at least a portion of the auxiliary gas flow path connecting both ends of the outer peripheral surface of the displacer, wherein the auxiliary gas flow path includes a groove formed on the outer peripheral surface of the displacer, At least one of the grooves There along the direction intersecting with the axial direction of the displacer, the groove may have a with said auxiliary gas passage that reaches deeper than the outer peripheral surface or outer peripheral surface of the metal cylinder of the displacer A regenerative refrigerator having a heat conductivity of the cylinder larger than a heat conductivity of the coating is provided.
[0010]
Since the groove is formed on the outer peripheral surface of the displacer, the gas branched from the main gas flow path having the regenerator and flowing through the gap between the displacer and the cylinder flows along the groove. The groove is formed to include a groove along a direction intersecting the axial direction of the displacer so that the gas flowing in the groove actively exchanges heat with the displacer and the cylinder.
[0011]
For this reason, when the branched gas flows from the high temperature side to the low temperature side, it is more cooled than when it flows directly in the axial direction. Conversely, when the branched gas flows from the low temperature side to the high temperature side, it cools the displacer and the cylinder more. . Further, since the groove reaches the outer peripheral surface of the metal cylinder or a position deeper than the outer peripheral surface, the heat exchange efficiency can be improved. Therefore, heat loss due to the branch gas can be reduced.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows a basic configuration of a regenerative refrigerator according to an embodiment of the present invention. A cylindrical displacer 2 is inserted into the cylinder 1. The cylinder 1 is formed of a rigid material having low thermal conductivity and high airtightness, for example, stainless steel or the like. The side wall of the displacer 2 is composed of a stainless steel cylinder 2a and a resin coating 2b formed on the outer peripheral surface thereof. On the outer peripheral surface of the displacer 2, one or a plurality of spiral grooves 4 connecting the upper surface and the lower surface are formed. The spiral groove 4 reaches the surface of the stainless steel cylinder 2a or a position deeper than the surface. That is, the stainless steel cylinder 2 a is exposed at the bottom surface of the groove 4.
[0013]
A gas passage 3 is formed inside the displacer 2. The gas flow path 3 is filled with a cold storage material 5 having a high heat capacity at an operating temperature. An expansion chamber 6 is defined between the displacer 2 and one end (the lower end in FIG. 1) of the cylinder 1.
[0014]
Refrigerant gas supplied into the cylinder 1 from the upper end of the cylinder 1 is introduced into the expansion chamber 6 through the gas passage 3 in the displacer 2. Some of the refrigerant gas branches off from the gas flow path 3 and flows through a gap between the displacer 2 and the cylinder 1. This gas flows downward along the spiral groove 4 provided on the outer peripheral surface of the displacer while exchanging heat with the surfaces of the displacer 2 and the cylinder 1 and is introduced into the expansion chamber 6.
[0015]
When the refrigerant gas expands, heat is generated, and when the refrigerant gas is recovered upward, the refrigerant gas flows through the refrigerant gas passage 3 and cools the cold storage material 5 at that time. As described above, a part of the refrigerant gas flows upward in the spiral groove 4 while cooling the displacer 2 and the surface of the cylinder 1, and merges with the refrigerant gas flowing through the gas flow path 3.
[0016]
When the refrigerant gas flows along the spiral groove 4, the flow of the refrigerant gas between the surface of the displacer 2 or the cylinder 1 and the refrigerant gas is smaller than when the refrigerant gas flows linearly in the axial direction in the gap between the displacer 2 and the cylinder 1. Many heat exchanges can take place between them. Furthermore, since the stainless steel cylinder 2a is exposed on the inner surface of the groove 4, more heat exchange is performed than when the groove 4 is formed only in the resin coating 2b.
[0017]
In a conventional regenerative refrigerator, a seal mechanism has been used to reduce the amount of refrigerant gas flowing through a gap between a displacer and a cylinder. However, it is extremely difficult to achieve the airtightness, and it is considered that the sealing performance becomes unstable and the cooling temperature increases or fluctuates.
[0018]
In the present embodiment, it is not necessary to use a sealing mechanism in the low-temperature portion, so that the above-described deterioration hardly occurs. Hereinafter, an embodiment of the present invention will be described using a two-stage GM refrigerator schematically shown in FIG. 2 as an example.
[0019]
FIG. 2 schematically illustrates a configuration example of a GM refrigerator according to the embodiment. The GM refrigerator of the embodiment has a two-stage configuration and is suitable for obtaining an extremely low temperature of about several K to 20K.
[0020]
The gas compressor 10 compresses helium gas to about 20 kgf / cm ² and supplies high-pressure helium gas. The high-pressure helium gas is supplied to the high-temperature end cavity of the first-stage cylinder 11 via the intake valve V1 and the gas flow path 16. The second stage cylinder 12 is connected to the low temperature end of the first stage cylinder 11.
[0021]
A first-stage displacer 13 and a second-stage displacer 14 that are connected to each other are accommodated in the first-stage cylinder 11 and the second-stage cylinder 12, respectively. A scotch yoke S is led out from the high temperature end of the first stage cylinder 11. The scotch yoke S is connected to a driving motor M via a crank mechanism 15.
[0022]
The first-stage displacer 13 and the second-stage displacer 14 each have a space filled with cold storage materials 17 and 18, and have gas flow paths 23a, 23b, 24a, and 24b connecting the internal space and the outside. Have. A first-stage expansion chamber 21 is defined on the low-temperature end side of the first-stage cylinder 11, and a second-stage expansion chamber 22 is defined on the low-temperature end side of the second-stage cylinder 12. The gas flow path 23 a connects the cavity on the high-temperature end side of the first-stage cylinder 11 to the space in the first-stage displacer 13. The gas passage 23 b connects the space inside the first-stage displacer 13 and the first-stage expansion chamber 21. The gas passage 24 a connects the first-stage expansion chamber 21 to a space in the second-stage displacer 14. The gas passage 24 b connects the space inside the second-stage displacer 14 and the second-stage expansion chamber 22. The gas flow paths 23a, 23b, 24a and 24b are functionally described for explaining the flow of the refrigerant gas, and are different from the actual structure.
[0023]
Usually, the first-stage cylinder 11 and the second-stage cylinder 12 are formed of a stainless steel (for example, SUS304) having sufficient strength, low thermal conductivity, and sufficient helium gas shielding ability.
[0024]
The first-stage displacer 13 is made of cloth-containing phenol (bakelite) having low specific gravity, sufficient abrasion resistance, relatively high strength, and low thermal conductivity. As described with reference to FIG. 1, the second stage displacer 14 includes a stainless steel cylinder, a resin coating formed on the outer peripheral surface thereof, and a spiral groove.
[0025]
FIG. 3 shows a detailed cross-sectional view of the second-stage displacer 14. On the outer peripheral surface of the stainless steel cylinder 39, a coating 40 of phenol containing cloth having a thickness of about 0.5 mm is formed. Both ends of the cylinder 39 are open. For example, when the inner diameter of the second stage cylinder shown in FIG. 2 is 35 mm, the outer diameter of the coating 40 is 35 mm, and the inner diameter of the cylinder 39 is 30 mm. The axial length of the displacer is, for example, about 200 mm.
[0026]
A lid 31 made of cloth-containing phenol or the like is inserted and adhered to the lower end of the cylinder 39. A wire mesh 32 is disposed thereon, and a felt plug 33 is disposed thereon. The felt plug 33 is filled with the regenerator 18 made of, for example, lead balls. A felt plug 34 is arranged on the cold storage material 18, and a punching metal 35 is arranged on the felt plug 34. The lid 41 closes the upper end of the cylinder 39, and fixes the punching metal 35. A coupling mechanism 36 for coupling to the first-stage displacer 13 shown in FIG.
[0027]
An opening 37 that forms a gas flow path is provided on a side wall of the cylinder 39 at a position corresponding to the height of the wire mesh 32. A single spiral groove 38 connecting the position of the opening 37 and the upper end is formed on the outer peripheral surface of the cylinder 39 above the opening 37. This groove has a width of about 2 mm, a depth of about 1 mm, and a pitch of about 4 mm, for example. Since the thickness of the coating 40 is about 0.5 mm, the depth of the groove 38 reaches the cylinder 39 made of stainless steel.
[0028]
The coating 40 is not formed on the outer peripheral surface of the cylinder 39 below the opening 37. Therefore, a gap is formed between the cylinder 39 and the second-stage cylinder 12 in a portion below the opening 37. This gap serves as a gas flow path connecting the inside of the cylinder 39 and the expansion chamber 22 shown in FIG.
[0029]
The gap between the outer peripheral surface of the coating 40 and the inner peripheral surface of the second-stage cylinder 12 is preferably 0.01 mm or more in order to stably drive the displacer back and forth. It is preferably 0.03 mm or less in order to prevent the water from flowing to the outside.
[0030]
In addition, other materials, for example, a magnetic regenerator, may be used as the regenerator 18 instead of lead. By using a magnetic regenerator material having a large specific heat in an extremely low temperature region, the refrigerating capacity can be increased.
[0031]
Next, the operation of the GM refrigerator shown in FIG. 2 will be described. High-pressure helium gas supplied from the gas compressor 10 via the intake valve V1 is supplied into the first-stage cylinder 11 via the gas passage 16. Further, the gas is introduced into the first-stage expansion chamber 21 through the gas passage 23a, the space in the first-stage displacer 13, and the gas passage 23b.
[0032]
The helium gas introduced into the first-stage expansion chamber 21 further passes through the gas passage 24a, the space in the second-stage displacer 14, and the gas passage 24b into the second-stage expansion chamber 22. be introduced. Part of the helium gas flows along the spiral groove 38 in the gap between the second-stage cylinder 12 and the second-stage displacer 14.
[0033]
When the intake valve V1 is closed and the exhaust valve V2 is opened, the high-pressure helium gas in the second-stage cylinder 12 and the first-stage cylinder 11 reversely follows the same path as in the case of intake, and the gas flow path 16 , And is collected by the gas compressor 10 through the exhaust valve V2.
[0034]
During the operation of the GM refrigerator, the first-stage displacer 13 and the second-stage displacer 14 are reciprocated up and down by the rotation of the drive motor M as shown by arrows in the figure. When the first-stage displacer 13 and the second-stage displacer 14 move downward, the intake valve V1 opens, and high-pressure helium gas is supplied into the first-stage cylinder 11 and the second-stage cylinder 12.
[0035]
When the first-stage displacer 13 and the second-stage displacer 14 are moved upward by the driving motor M, the intake valve V1 is closed and the exhaust valve V2 is opened, and the helium gas is collected by the gas compressor 10. At this time, the pressure in the expansion chambers 21 and 22 in the first-stage cylinder 11 and the second-stage cylinder 12 becomes low.
[0036]
In the expansion chambers 21 and 22, heat is generated by expansion of the helium gas. The cooled helium gas passes through the spaces in the displacers 14 and 13 and cools the cold storage materials 18 and 17.
[0037]
The high-pressure helium gas supplied in the next intake step is supplied to the expansion chambers 21 and 22 while being cooled by the cold storage materials 17 and 18. As the cooled helium gas expands, cooling proceeds further. In a steady state, the expansion chamber 21 of the first stage cylinder 11 is maintained at a temperature of, for example, about 40K to 70K, and the temperature of the expansion chamber 22 of the second stage cylinder 12 is maintained at a temperature of about several K to 20K. Dripping.
[0038]
Since the stainless steel tube 39 is exposed on the inner surface of the spiral groove 38, the heat exchange efficiency between the cold storage material 18 in the displacer 14 and the helium gas flowing along the spiral groove 38 can be increased. This makes it possible to increase the refrigeration capacity.
[0039]
Near the low-temperature end of the first-stage cylinder, a first-stage heat station 19 is thermally coupled. Near the low-temperature end of the second-stage cylinder 12, a second-stage heat station 20 is thermally connected. Are combined.
[0040]
The first-stage heat station 19 is connected to, for example, a cryopanel or the like, and adsorbs gas molecules. Further, the second-stage heat station 20 is connected to an adsorption tower containing an adsorbent such as activated carbon, for example, and adsorbs residual gas molecules. The cryopump having such a configuration is used for forming a clean vacuum in a sputtering apparatus or the like.
[0041]
In the above embodiment, the coating 40 is formed of cloth-containing phenol, but may be formed of another material having high abrasion resistance and low frictional resistance. Examples of such a material include polyetheretherketone, polyamideimide, polyetherimide, polyimide, glass fiber reinforced epoxy, and polytetrafluoroethylene. Alternatively, ethylene tetrafluoride or the like may be used.
[0042]
Cloth-containing phenol is formed by winding a cloth around a tube and impregnating it with phenol. The thermoplastic resin is formed by baking the resin on the outer peripheral surface of the cylinder. The glass fiber reinforced epoxy is formed by wrapping a glass fiber cloth around the outer periphery of the cylinder and impregnating the cloth with the epoxy. The tetrafluoroethylene is formed by spraying and baking raw material powder on the outer peripheral surface of the cylinder.
[0043]
Further, in the above embodiment, the coating 40 is thinner than the depth of the spiral groove 38. Therefore, it is possible to shorten the time of the coating process of the coating 40 as compared with a case where the coating 40 is thickened and the spiral groove 38 is formed only inside the coating 40. Further, by making the coating 40 thinner, the cylinder 39 can be made thicker. This makes it possible to increase the filling amount of the cold storage material 18.
[0044]
In the above embodiment, the case where one spiral groove is formed on the outer peripheral surface of the displacer has been described, but the gas flowing through the gap between the cylinder and the displacer flows while sufficiently exchanging heat with the displacer. If so, the shape of the groove is not limited to one spiral, and may be another shape. For example, a plurality of spiral grooves may be provided like a double spiral structure. The spiral groove may be a wavy line or a zigzag line. A stepwise zigzag line may be formed by combining a straight line parallel to the axial direction of the displacer and a straight line perpendicular to the displacer. Two spirals in which the directions of rotation of the spirals are opposite to each other, or two or more spirals may be combined so that the spiral grooves intersect each other. A plurality of circumferential grooves may be formed in the circumferential direction of the outer peripheral surface, and a connection groove for connecting adjacent grooves to each other may be provided. At this time, it is preferable that connection grooves formed above and below the circumferential groove are provided at different positions on the circumference in order to make the gas flow path length as long as possible.
[0045]
As described above, by forming at least a part of the grooves formed on the outer peripheral surface of the displacer along the direction intersecting the axial direction of the displacer, when the gas flows parallel to the axial direction, In comparison, it will flow on a longer path. For this reason, it becomes possible to exchange heat more efficiently between the gas and the displacer.
[0046]
The cross section of the gas flow path formed on the outer peripheral surface of the displacer may be other shapes such as a rectangle, a triangle, and a semicircle.
[0047]
Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. For example, the present invention is not limited to a GM refrigerator, but can be applied to a refrigerator using a regenerator such as a Stirling refrigerator or a Solvay cycle refrigerator.
[0048]
Further, the configuration of the two-stage displacer has been described as an example, but the present invention is also applicable to a case where a one-stage or three-stage or more displacer is used. Further, in other configurations, the present invention can be applied to a regenerator using a displacer at a low temperature. It will be apparent to those skilled in the art that various changes, improvements, combinations, and the like can be made.
[0049]
【The invention's effect】
As described above, according to the present invention, the groove formed on the outer peripheral surface of the displacer reaches the metal cylinder below the coating film on the surface. Therefore, the heat exchange efficiency between the refrigerant gas flowing along the groove and the cold storage material filled in the displacer can be increased. Thereby, the refrigerating capacity can be improved.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a basic configuration of a refrigerator according to an embodiment of the present invention.
FIG. 2 is a schematic sectional view of a GM refrigerator according to an embodiment of the present invention.
FIG. 3 is a sectional view of a second stage displacer of the GM refrigerator according to the embodiment.
[Explanation of symbols]
Reference Signs List 1 cylinder 2 displacer 3 gas flow path 4 spiral groove 5 cold storage material 6 expansion chamber 10 gas compressor 11 first stage cylinder 12 second stage cylinder 13 first stage displacer 14 second stage displacer 15 crank mechanism 16 gas Flow paths 17, 18 Cold storage material 19, 20 Heat stations 21, 22 Expansion chambers 23, 24 Gas flow paths 31 Lid 32 Wire mesh 33, 34 Felt plug 35 Punching metal 36 Coupling mechanism 37 Opening 38 Spiral groove 39 Tube 40 Coating 41 Lid

Claims (2)

A cylinder,
A displacer disposed in the cylinder so as to be able to reciprocate in the axial direction of the cylinder, and defining an expansion chamber at one end in the cylinder, comprising a metal cylinder and a coating formed on an outer peripheral surface of the cylinder. Wherein the cylinder and the coating are made of a material such that the friction coefficient when the coating and the cylinder are in contact with each other is smaller than the friction coefficient when the cylinder and the cylinder are in direct contact with each other. Said displacer being formed;
A main gas flow path for supplying a refrigerant gas into the expansion chamber and recovering the refrigerant gas from the expansion chamber;
A cold storage material disposed at least in a part of the main gas flow path,
An auxiliary gas flow path connecting both ends of an outer peripheral surface of the displacer, wherein the auxiliary gas flow path includes a groove formed on an outer peripheral surface of the displacer, and at least a part of the groove is formed in an axial direction of the displacer. along the direction crossing the, groove is the reaches deeper than the outer peripheral surface or outer peripheral surface of the metal cylinder of the displacer possess an auxiliary gas passage, the thermal conductivity of the tube A regenerator having a degree greater than the thermal conductivity of the coating . The regenerator according to claim 1 , wherein the groove forming the auxiliary gas flow path includes a spiral portion.

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