US20130174582A1 - Cryogenic refrigerator and displacer - Google Patents
Cryogenic refrigerator and displacer Download PDFInfo
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- US20130174582A1 US20130174582A1 US13/709,275 US201213709275A US2013174582A1 US 20130174582 A1 US20130174582 A1 US 20130174582A1 US 201213709275 A US201213709275 A US 201213709275A US 2013174582 A1 US2013174582 A1 US 2013174582A1
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- displacer
- heat conducting
- conducting part
- cylinder
- cryogenic refrigerator
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
- F25B9/14—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the cycle used, e.g. Stirling cycle
Definitions
- the present invention relates to a cryogenic refrigerator that produces cryogenic temperatures by causing the Simon expansion using a high-pressure refrigerant gas fed from a compressor, and to a displacer used in the cryogenic refrigerator.
- the cryogenic refrigerator described in Japanese Laid-Open Patent Application No. 2011-17457 produces cold temperatures by causing a refrigerant gas in an expansion space to expand with the opening and closing of a valve while causing a displacer to reciprocate inside a cylinder.
- the refrigerant gas is fed into and discharged from the expansion space through a clearance between the displacer and the cylinder.
- the refrigerant gas exchanges heat with a cooling stage positioned on the peripheral side of the clearance and the expansion space, so that the cold temperatures produced by the refrigerant gas in the expansion space cool an object of cooling connected to the cooling stage.
- a cryogenic refrigerator includes a displacer including a body part and a heat conducting part, wherein a material of the heat conducting part has a higher thermal conductivity than the body part; a cylinder accommodating the displacer in such a manner as to allow the displacer to reciprocate in axial directions of the cylinder, wherein an expansion space is formed between the cylinder and a low temperature end of the displacer; a clearance channel formed between the displacer and the cylinder so as to allow a refrigerant gas to flow into the expansion space; and a cooling stage positioned adjacent to the expansion space, wherein the heat conducting part faces the cooling stage across the clearance channel.
- a displacer includes a body part; and a heat conducting part, wherein the heat conducting part is positioned at a low temperature end of the displacer, and a material of the heat conducting part has a higher thermal conductivity than the body part.
- FIG. 1 is a schematic diagram illustrating a cryogenic refrigerator and a displacer according to a first embodiment of the present invention
- FIG. 2 is a schematic diagram illustrating a cryogenic refrigerator and a displacer according to a second embodiment of the present invention
- FIG. 3 is a diagram illustrating a variation of a heat conducting part of the cryogenic refrigerator and the displacer according to the second embodiment
- FIG. 4 is a schematic diagram illustrating another variation of the heat conducting part of the cryogenic refrigerator and the displacer according to the second embodiment.
- FIG. 5 is a schematic diagram illustrating a two-stage cryogenic refrigerator according to a third embodiment of the present invention.
- Japanese Laid-Open Patent Application No. 2011-17457 describes a cryogenic refrigerator that produces cold temperatures by causing a refrigerant gas in an expansion space to expand with the opening and closing of a valve while causing a displacer to reciprocate inside a cylinder.
- the refrigerant gas that passes through the clearance exchanges heat only with the cooling stage positioned on the peripheral side of the clearance, thus making it difficult to ensure a sufficient substantial area for heat exchange.
- a cryogenic refrigerator and a displacer are provided that make it possible to more effectively ensure a sufficient substantial area for heat exchange.
- the heat conducting part transfers heat to a refrigerant gas that enters the clearance channel because of expansion.
- a cryogenic refrigerator 1 is, for example, a Gifford-McMahon (GM) refrigerator that uses helium gas as a refrigerant gas.
- the cryogenic refrigerator 1 includes a displacer 2 , a cylinder 4 , and a cooling stage 5 that has a bottomed cylinder (tube) shape.
- a clearance C (a clearance channel) and an expansion space 3 are formed between the displacer 2 and the cylinder 4 .
- the cooling stage 5 is adjacent to and encloses the expansion space 3 .
- the displacer 2 includes a body part 2 a and a heat conducting part 2 b.
- the heat conducting part 2 b is formed of a material that has a higher thermal conductivity than the body part 2 a.
- the heat conducting part 2 b faces the cooling stage 5 across the clearance C.
- the cooling stage 5 is formed of, for example, copper, aluminum, stainless steel or the like.
- the heat conducting part 2 b has a lower coefficient of thermal expansion than the body part 2 a.
- the heat conducting part 2 b includes an overlapping part 2 ba that overlaps the body part 2 a in the directions of strokes (stroke directions) of the displacer 2 (in which the displacer 2 reciprocates).
- the body part 2 a includes an overlapped part 2 a b that corresponds to the overlapping part 2 ba.
- the heat conducting part 2 b has a two-stage (stepped) columnar shape, and the overlapping part 2 ba is formed by the second (upper) columnar shape from the bottom in FIG. 1 .
- the overlapping part 2 ba includes first hole parts 2 bah, and the overlapped part 2 ab includes second hole parts 2 abh that correspond to the first hole parts 2 bah.
- the body part 2 a and the heat conducting part 2 b are connected by press-fit pins 6 (an insertion member) that are press-fit and inserted into both the second hole parts 2 abh and the first hole parts 2 bah.
- the press-fit pins 6 are provided at suitable points in a circumferential direction of the displacer 2 .
- a material that has a higher thermal conductivity than at least the body part 2 a, such as copper, aluminum, stainless steel or the like, is used for the heat conducting part 2 b.
- the press-fit pins 6 may be either Bakelite (phenol containing cloth) or stainless steel.
- the overlapping part 2 ba is fixed to the overlapped part 2 ab by press-fitting the press-fit pins 6 into the first hole parts 2 bah and the second hole parts 2 abh.
- the cylinder 4 accommodates the displacer 2 in such a manner as to allow the displacer 2 to reciprocate in the longitudinal directions of the cylinder 4 .
- stainless steel is used for the cylinder 4 in terms of strength, thermal conductivity, helium blocking capability, etc.
- a Scotch yoke mechanism (not graphically illustrated) that causes the displacer 2 to reciprocate is provided at a high-temperature end of the displacer 2 , so that the displacer 2 reciprocates along the axial directions of the cylinder 4 .
- the displacer 2 has a cylindrical peripheral (exterior circumferential) surface.
- the displacer 2 is filled with a regenerator material.
- the internal space of the displacer 2 forms a regenerator 7 .
- An upper flow rectifier 9 that rectifies (regulates) a flow of helium gas is provided on the upper end side, that is, the room temperature chamber 8 side, of the regenerator 7 .
- a lower flow rectifier 10 is provided on the lower end side of the regenerator 7 .
- An opening 11 through which a refrigerant gas flows from a room temperature chamber 8 into the displacer 2 is formed at the high temperature end of the displacer 2 .
- the room temperature chamber 8 which is a space defined by the cylinder 4 and the high temperature end of the displacer 2 , changes in volume with the reciprocation of the displacer 2 .
- a pipe common to supply and discharge (a supply and discharge common pipe) is connected to the room temperature chamber 8 . Further, a seal 15 is attached between part of the displacer 2 on the high temperature end side and the cylinder 4 .
- Openings 16 that introduce a refrigerant gas into the expansion space 3 via the clearance C are formed at a low temperature end of the displacer 2 .
- the expansion space 3 which is a space defined by the cylinder 4 and the displacer 2 , changes in volume with the reciprocation of the displacer 2 .
- the cooling stage 5 which is thermally coupled to an object of cooling, is placed at a position corresponding to the expansion space 3 on the periphery and the bottom of the cylinder 4 .
- the cooling stage 5 is cooled by a refrigerant gas that passes through the clearance C.
- FIG. 1 illustrates the cryogenic refrigerator 1 in operation. Therefore, because of slight contraction of the body part 2 a due to low temperature, the body part 2 a and the heat conducting part 2 b are equal in outside diameter. However, at normal temperature (5° C. to 35° C.), the outside diameter of the heat conducting part 2 b is slightly smaller than the outside diameter of the body part 2 a.
- the displacer 2 is positioned at its bottom dead center inside the cylinder 4 .
- the supply valve 13 is opened at the same time with or slightly before or after that point of time, high-pressure helium gas is supplied into the cylinder 4 through the supply valve 13 and the supply and discharge common pipe, and flows into the regenerator 7 inside the displacer 2 through the opening 11 positioned at the top (high temperature end) of the displacer 2 .
- the high-pressure helium gas that has flown into the regenerator 7 is supplied into the expansion space 3 through the openings 16 , positioned in a lower part of the displacer 2 , and the clearance C while being cooled by the regenerator material.
- the expansion space 3 is filled with the high-pressure helium gas, and the supply valve 13 is closed.
- the displacer 2 is positioned at its top dead center inside the cylinder 4 .
- the return valve 14 is opened at the same time with or slightly before or after that point, the pressure of the helium (refrigerant) gas inside the expansion space 3 is reduced, so that the helium gas expands.
- the helium gas inside the expansion space 3 whose temperature has been lowered because of its expansion, absorbs the heat of the cooling stage 5 through the clearance C.
- the displacer 2 moves toward the bottom dead center, so that the volume of the expansion space 3 is reduced.
- the helium gas inside the expansion space 3 is returned to the intake side of the compressor 12 through the clearance C, the openings 16 , the regenerator 7 , and the opening 11 .
- the regenerator material is cooled by the refrigerant gas (helium gas).
- the cryogenic refrigerator 1 cools the cooling stage 5 by repeating this cooling cycle.
- the heat conducting part 2 b constantly faces the cooling stage 5 across the clearance C. Heat that enters from the cooling stage 5 also enters the heat conducting part 2 b via the helium gas in the clearance C. Therefore, when the low-temperature helium gas generated in the expansion space 3 passes through the clearance C, heat exchange is performed not only between the helium gas and the cooling stage 5 but also between the helium gas and the heat conducting part 2 b. As a result, it is possible to increase a substantial area for heat exchange (heat exchange area) between the cooling stage 5 and the low-temperature helium gas.
- the heat that has entered the heat conducting part 2 b is further transferred through the inside of the heat conducting part 2 b toward the expansion space 3 . Therefore, it is possible to further improve heat exchange efficiency by configuring the heat conducting part 2 b so that the heat conducting part 2 b comes into contact with the low-temperature helium gas inside the expansion space 3 .
- the cryogenic refrigerator 1 and the displacer 2 of the first embodiment it is possible to cause the heat conducting part 2 b as well to effectively contribute to heat exchange, compared with the conventional displacer, so that it is possible to increase a substantial heat exchange area.
- the above-described flow (transfer) of heat generated inside the heat conducting part 2 b makes it possible to further improve heat exchange efficiency. That is, it is possible to reduce the temperature difference of the cooling stage 5 in a vertical direction in FIG. 1 . In particular, it is possible to reduce the temperature difference in the case of providing an object of cooling below the cooling stage 5 .
- the part contracts with a decrease in temperature because of a relatively high coefficient of thermal expansion of Bakelite, so that a part corresponding to the overlapping part 2 ba may come off a part corresponding to the overlapped part 2 ab.
- the overlapping part 2 ba which has a lower coefficient of thermal expansion than the body part 2 a, is provided inside (on the inner circumference side of) the overlapped part 2 ab of the body part 2 a.
- the heat conducting part 2 b also contributes to heat exchange, thereby increasing a substantial heat exchange area. Therefore, even when the cooling stage 5 and the clearance C are reduced in length in the axial directions (the moving directions of the displacer 2 ) compared with the conventional displacer, it is possible to obtain a desired refrigerating capacity. As a result, it is possible to reduce channel resistance and pressure loss in the clearance C, so that it is possible to increase the refrigeration efficiency of the cryogenic refrigerator 1 . Further, reduction in the volume of the clearance C leads to a decrease in dead volume that does not contribute to generation of cold temperatures. This may be expected to reduce a pressure difference between a high pressure and a low pressure during one cycle due to dead volume.
- the overlapping part 2 ba and the overlapped part 2 ab may form a screw part so as to be screwed to each other.
- the overlapping part 2 ba and the overlapped part 2 ab may be screwed to each other with their respective threaded parts mating with each other. This allows the body part 2 a and the heat conducting part 2 b to be more easily attached to and detached from each other.
- a squeezing force is exerted on the overlapping part 2 ba of the heat conducting part 2 b.
- FIG. 2 is a schematic diagram illustrating a cryogenic refrigerator 21 and a displacer 22 according to a second embodiment.
- the same elements as those of the first embodiment of FIG. 1 are referred to by the same reference numerals, and a description is basically given of differences from the first embodiment.
- the displacer 22 includes a body part 22 a and a heat conducting part 22 b.
- the heat conducting part 22 b has a tubular shape, and the entire heat conducting part 22 b forms an overlapping part 22 ba that overlaps the body part 22 a in the stroke directions of the displacer 22 .
- a portion of the body part 22 a that is positioned on the low temperature side of the openings 16 (that is, below the openings 16 in FIG. 2 ) has a smaller diameter than a portion of the body part 22 a that is positioned on the high temperature side of the openings 16 (that is, above the openings 16 in FIG. 2 ).
- This smaller-diameter portion of the body part 22 a forms an overlapped part 22 ab that corresponds to the overlapping part 22 ba.
- the overlapping part 22 ba includes first hole parts 22 bah, and the overlapped part 22 ab includes second hole parts 22 abh that correspond to the first hole parts 22 bah.
- the body part 22 a and the heat conducting part 22 b are connected by press-fit pins 26 (an insertion member) that are press-fit and inserted into both the second hole parts 22 abh and the first hole parts 22 bah.
- press-fit pins 26 may be either Bakelite (phenol containing cloth) or stainless steel.
- the cryogenic refrigerator 21 and the displacer 22 of the second embodiment it is possible to increase a heat exchange area by causing the heat conducting part 22 b to contribute to heat exchange as in the first embodiment.
- the heat conducting part 22 b is placed only on the peripheral (outer circumferential) side of the displacer 22 , which contributes to heat exchange compared with the first embodiment. Therefore, it is possible to reduce the volume and mass of the heat conducting part 22 b compared with the volume and mass of the heat conducting part 2 b of the first embodiment, and thus to reduce the mass of the entire displacer 22 , which is a movable part, compared with the mass of the displacer 2 of the first embodiment.
- the reciprocation of the heat conducting part 22 b which is a conductor, under the presence of a magnetic field generates eddy current, which causes heat generation, that is, copper loss.
- the volume of the heat conducting part 22 b is relatively small. Therefore, it is possible to control generation of copper loss accordingly.
- the heat conducting part 22 b may be formed of a standardized tubular material. Therefore, it is possible to reduce cost compared with the first embodiment.
- FIG. 3 illustrates a variation of the tubular heat conducting part 22 b illustrated in FIG. 2 , where a slit S is formed to make the heat conducting part 22 b discontinuous in its circumferential directions.
- (a) is a plan view and (b) is a side view of the variation of the heat conducting part 22 b. According to this configuration, it is possible to prevent eddy current from continuously flowing in the circumferential directions in particular, so that it is possible to control generation of copper loss more effectively.
- FIG. 4 illustrates another variation of the heat conducting part 22 b.
- the heat conducting part 22 b may have a bottomed tube shape.
- the heat conducting part 22 b of a bottomed tube shape causes heat that has entered the heat conducting part 22 b from the cooling stage 5 to be exchanged between a bottom part 22 b b of the heat conducting part 22 b and the expansion space 3 .
- FIG. 5 is a schematic diagram illustrating a cryogenic refrigerator 31 and first and second displacers 32 and 36 according to a third embodiment.
- the cryogenic refrigerator 31 is a Gifford-McMahon (GM) refrigerator using helium gas as a refrigerant gas.
- the cryogenic refrigerator 31 includes the first displacer 32 and the second displacer 36 .
- the second displacer 36 is connected to the first displacer 32 in a longitudinal direction of the second displacer 36 .
- the first displacer 32 and the second displacer 36 are connected via, for example, a pin 33 , a connector 34 , and a pin 35 .
- a first cylinder 37 and a second cylinder 38 are formed as a unit. A low temperature end of the first cylinder 37 and a high temperature end of the second cylinder 38 are connected at the bottom of the first cylinder 37 .
- the second cylinder 38 is coaxial with the first cylinder 37 , and is a cylindrical member that has a smaller diameter than the first cylinder 37 .
- the first cylinder 37 accommodates the first displacer 32 in such a manner as to allow the first displacer 32 to reciprocate in the longitudinal directions of the first cylinder 37 .
- the second cylinder 38 accommodates the second displacer 36 in such a manner as to allow the second displacer 36 to reciprocate in the longitudinal directions of the second cylinder 38 .
- the second displacer 36 has a coating of an abrasion resistant resin such as fluororesin on the peripheral (exterior circumferential) surface of its metallic cylinder of, for example, stainless steel.
- a Scotch yoke mechanism (not graphically illustrated) that causes the first displacer 32 and the second displacer 36 to reciprocate is provided at a high-temperature end of the first cylinder 37 , so that the first displacer 32 and the second displacer 36 reciprocate along the first cylinder 37 and the second cylinder 38 , respectively.
- the first displacer 32 has a cylindrical peripheral (exterior circumferential) surface.
- the first displacer 32 is filled with a first regenerator material.
- the internal space of the first displacer 32 serves as a first regenerator 39 .
- a flow rectifier 40 and a flow rectifier 41 are provided on and under the first regenerator 39 .
- a first opening 42 through which a refrigerant gas flows from a room temperature chamber 69 into the first displacer 32 is formed at a high temperature end of the first displacer 32 .
- the room temperature chamber 69 which is a space defined by the first cylinder 37 and the high temperature end of the first displacer 32 , changes in volume with the reciprocation of the first displacer 32 .
- a pipe common to supply and discharge (a supply and discharge common pipe) is connected to the room temperature chamber 69 . Further, a seal 46 is attached between part of the first displacer 32 on the high temperature end side and the first cylinder 37 .
- Second openings 48 that introduce a refrigerant gas into a first expansion space 47 via a first clearance C 1 (a clearance channel) are formed at a low temperature end of the first displacer 32 .
- the first expansion space 47 which is a space defined by the first cylinder 37 and the first displacer 32 , changes in volume with the reciprocation of the first displacer 32 .
- a first cooling stage 49 which is thermally coupled to an object of cooling (not graphically illustrated), is placed at a position corresponding to the first expansion space 47 on the periphery of the first cylinder 37 .
- the first cooling stage 49 is cooled by a refrigerant gas that passes through the first clearance C 1 .
- the second displacer 36 has a cylindrical peripheral (exterior circumferential) surface.
- the second displacer 36 is filled with a second regenerator material.
- the internal space of the second displacer 36 serves as a second regenerator 50 .
- the first expansion space 47 and a high temperature end of the second displacer 36 are connected by a communicating passage (not graphically illustrated).
- a refrigerant gas flows from the first expansion space 47 into the second regenerator 50 through this communicating passage.
- a third opening 52 that introduces a refrigerant gas into a second expansion space 51 via a second clearance C 2 (a clearance channel) is formed at a low temperature end of the second displacer 36 .
- the second expansion space 51 which is a space defined by the second cylinder 38 and the second displacer 36 , changes in volume with the reciprocation of the second displacer 36 .
- the second clearance C 2 is defined by a low temperature end part of the second cylinder 38 and the second displacer 36 .
- the second clearance C 2 is larger than a clearance between the second displacer 36 having a helical groove 63 as described below and the second cylinder 38 .
- a second cooling stage 53 which is thermally coupled to an object of cooling (not graphically illustrated), is placed at a position corresponding to the second expansion space 51 on the periphery of the second cylinder 38 .
- the second cooling stage 53 is cooled by a refrigerant gas that passes through the second clearance C 2 .
- the first displacer 32 includes a body part 32 a and a heat conducting part 32 b.
- the heat conducting part 32 b is formed of a material that has a higher thermal conductivity than the body part 32 a.
- Bakelite phenol containing cloth
- the heat conducting part 32 b has a lower coefficient of thermal expansion than the body part 32 a.
- the heat conducting part 32 b includes an overlapping part 32 ba that overlaps the body part 32 a in the directions of strokes (stroke directions) of the first displacer 32 .
- the body part 32 a includes an overlapped part 32 ab that corresponds to the overlapping part 32 ba.
- the second displacer 36 includes a body part 36 a and a heat conducting part 36 b.
- the heat conducting part 36 b is formed of a material that has a higher thermal conductivity than the body part 36 a.
- Bakelite phenol containing cloth
- the heat conducting part 36 b has a lower coefficient of thermal expansion than the body part 36 a.
- the heat conducting part 36 b includes an overlapping part 36 ba that overlaps the body part 36 a in the directions of strokes (stroke directions) of the second displacer 36 .
- the body part 36 a includes an overlapped part 36 ab that corresponds to the overlapping part 36 ba.
- the first regenerator material is formed of, for example, a wire mesh.
- the second regenerator material is formed by holding a regenerator material such as lead spheres with felt and a wire mesh in the axial directions.
- the helical groove 63 is formed on the peripheral (exterior circumferential) surface of the second displacer 36 .
- the helical groove 36 has a starting end communicating with the second expansion space 51 through the second clearance C 2 , and helically extends toward the first expansion space 47 .
- the first displacer 32 and the second displacer 36 include the heat conducting part 32 b and the heat conducting part 36 b at their respective cold (low) temperature ends. Both the heat conducting part 32 b and the heat conducting part 36 b have a two-stage (stepped) columnar shape.
- the heat conducting part 32 b is fixed to the body part 32 a with press-fit pins 54 .
- the heat conducting part 36 b is fixed to the body part 36 a with press-fit pins 55 .
- the number of stages may be suitably selected, and may be, for example, three.
- embodiments of the present invention are not limited to the GM refrigerator, and may be applied to any refrigerators having a displacer, such as Stirling refrigerators and Solvay cycle refrigerators.
- the present invention it is possible to improve the refrigeration efficiency of a cryogenic refrigerator by improving its heat exchange efficiency by effectively increasing a heat exchange area that substantially contributes to heat exchange through a side clearance without increasing the length of a cooling stage in the axial directions of the cryogenic refrigerator. Accordingly, embodiments of the present invention may be applied to various kinds of cryogenic refrigerators.
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Abstract
A cryogenic refrigerator includes a displacer including a body part and a heat conducting part, wherein the material of the heat conducting part has a higher thermal conductivity than the body part; a cylinder accommodating the displacer in such a manner as to allow the displacer to reciprocate in the axial directions of the cylinder, wherein an expansion space is formed between the cylinder and a low temperature end of the displacer; a clearance channel formed between the displacer and the cylinder so as to allow a refrigerant gas to flow into the expansion space; and a cooling stage positioned adjacent to the expansion space. The heat conducting part faces the cooling stage across the clearance channel.
Description
- This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2012-001627, filed on Jan. 6, 2012, the entire contents of which are incorporated herein by reference.
- 1. Field of the Invention
- The present invention relates to a cryogenic refrigerator that produces cryogenic temperatures by causing the Simon expansion using a high-pressure refrigerant gas fed from a compressor, and to a displacer used in the cryogenic refrigerator.
- 2. Description of the Related Art
- For example, the cryogenic refrigerator described in Japanese Laid-Open Patent Application No. 2011-17457 produces cold temperatures by causing a refrigerant gas in an expansion space to expand with the opening and closing of a valve while causing a displacer to reciprocate inside a cylinder. The refrigerant gas is fed into and discharged from the expansion space through a clearance between the displacer and the cylinder. The refrigerant gas exchanges heat with a cooling stage positioned on the peripheral side of the clearance and the expansion space, so that the cold temperatures produced by the refrigerant gas in the expansion space cool an object of cooling connected to the cooling stage.
- According to an aspect of the present invention, a cryogenic refrigerator includes a displacer including a body part and a heat conducting part, wherein a material of the heat conducting part has a higher thermal conductivity than the body part; a cylinder accommodating the displacer in such a manner as to allow the displacer to reciprocate in axial directions of the cylinder, wherein an expansion space is formed between the cylinder and a low temperature end of the displacer; a clearance channel formed between the displacer and the cylinder so as to allow a refrigerant gas to flow into the expansion space; and a cooling stage positioned adjacent to the expansion space, wherein the heat conducting part faces the cooling stage across the clearance channel.
- According to an aspect of the present invention, a displacer includes a body part; and a heat conducting part, wherein the heat conducting part is positioned at a low temperature end of the displacer, and a material of the heat conducting part has a higher thermal conductivity than the body part.
- The object and advantages of the embodiments will be realized and attained by means of the elements and combinations particularly pointed out in the claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and not restrictive of the invention.
- Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings, in which:
-
FIG. 1 is a schematic diagram illustrating a cryogenic refrigerator and a displacer according to a first embodiment of the present invention; -
FIG. 2 is a schematic diagram illustrating a cryogenic refrigerator and a displacer according to a second embodiment of the present invention; -
FIG. 3 is a diagram illustrating a variation of a heat conducting part of the cryogenic refrigerator and the displacer according to the second embodiment; -
FIG. 4 is a schematic diagram illustrating another variation of the heat conducting part of the cryogenic refrigerator and the displacer according to the second embodiment; and -
FIG. 5 is a schematic diagram illustrating a two-stage cryogenic refrigerator according to a third embodiment of the present invention. - As described above, Japanese Laid-Open Patent Application No. 2011-17457 describes a cryogenic refrigerator that produces cold temperatures by causing a refrigerant gas in an expansion space to expand with the opening and closing of a valve while causing a displacer to reciprocate inside a cylinder. However, according to the technique described in Japanese Laid-Open Patent Application No. 2011-17457, the refrigerant gas that passes through the clearance exchanges heat only with the cooling stage positioned on the peripheral side of the clearance, thus making it difficult to ensure a sufficient substantial area for heat exchange.
- According to an aspect of the present invention, a cryogenic refrigerator and a displacer are provided that make it possible to more effectively ensure a sufficient substantial area for heat exchange.
- In a cryogenic refrigerator and a displacer according to an aspect of the present invention, heat enters a heat conducting part from a cooling stage through a clearance channel on the periphery of the displacer. The heat conducting part transfers heat to a refrigerant gas that enters the clearance channel because of expansion. As a result, the temperature difference of the cooling stage is reduced, and a substantial heat exchange area that contributes to heat exchange increases, so that it is possible to improve heat exchange efficiency.
- A description is given below, with reference to the accompanying drawings, of embodiments of the present invention.
- A
cryogenic refrigerator 1 according to a first embodiment is, for example, a Gifford-McMahon (GM) refrigerator that uses helium gas as a refrigerant gas. Thecryogenic refrigerator 1 includes adisplacer 2, acylinder 4, and acooling stage 5 that has a bottomed cylinder (tube) shape. A clearance C (a clearance channel) and anexpansion space 3 are formed between thedisplacer 2 and thecylinder 4. Thecooling stage 5 is adjacent to and encloses theexpansion space 3. Thedisplacer 2 includes abody part 2 a and aheat conducting part 2 b. Theheat conducting part 2 b is formed of a material that has a higher thermal conductivity than thebody part 2 a. Theheat conducting part 2 b faces thecooling stage 5 across the clearance C. Thecooling stage 5 is formed of, for example, copper, aluminum, stainless steel or the like. - Here, the
heat conducting part 2 b has a lower coefficient of thermal expansion than thebody part 2 a. Theheat conducting part 2 b includes an overlappingpart 2 ba that overlaps thebody part 2 a in the directions of strokes (stroke directions) of the displacer 2 (in which the displacer 2 reciprocates). Thebody part 2 a includes an overlappedpart 2 a b that corresponds to the overlappingpart 2 ba. In the first embodiment, theheat conducting part 2 b has a two-stage (stepped) columnar shape, and the overlappingpart 2 ba is formed by the second (upper) columnar shape from the bottom inFIG. 1 . - The overlapping
part 2 ba includesfirst hole parts 2 bah, and the overlappedpart 2 ab includessecond hole parts 2 abh that correspond to thefirst hole parts 2 bah. Thebody part 2 a and theheat conducting part 2 b are connected by press-fit pins 6 (an insertion member) that are press-fit and inserted into both thesecond hole parts 2 abh and thefirst hole parts 2 bah. The press-fit pins 6 are provided at suitable points in a circumferential direction of thedisplacer 2. A material that has a higher thermal conductivity than at least thebody part 2 a, such as copper, aluminum, stainless steel or the like, is used for theheat conducting part 2 b. The press-fit pins 6 may be either Bakelite (phenol containing cloth) or stainless steel. The overlappingpart 2 ba is fixed to the overlappedpart 2 ab by press-fitting the press-fit pins 6 into thefirst hole parts 2 bah and thesecond hole parts 2 abh. - The
cylinder 4 accommodates thedisplacer 2 in such a manner as to allow thedisplacer 2 to reciprocate in the longitudinal directions of thecylinder 4. For example, stainless steel is used for thecylinder 4 in terms of strength, thermal conductivity, helium blocking capability, etc. - A Scotch yoke mechanism (not graphically illustrated) that causes the
displacer 2 to reciprocate is provided at a high-temperature end of thedisplacer 2, so that thedisplacer 2 reciprocates along the axial directions of thecylinder 4. - The
displacer 2 has a cylindrical peripheral (exterior circumferential) surface. Thedisplacer 2 is filled with a regenerator material. The internal space of thedisplacer 2 forms aregenerator 7. Anupper flow rectifier 9 that rectifies (regulates) a flow of helium gas is provided on the upper end side, that is, theroom temperature chamber 8 side, of theregenerator 7. Alower flow rectifier 10 is provided on the lower end side of theregenerator 7. - An
opening 11 through which a refrigerant gas flows from aroom temperature chamber 8 into thedisplacer 2 is formed at the high temperature end of thedisplacer 2. Theroom temperature chamber 8, which is a space defined by thecylinder 4 and the high temperature end of thedisplacer 2, changes in volume with the reciprocation of thedisplacer 2. - Of the various pipes that interconnect a
compressor 12, asupply valve 13, and areturn valve 14, which form a intake and outlet system, a pipe common to supply and discharge (a supply and discharge common pipe) is connected to theroom temperature chamber 8. Further, aseal 15 is attached between part of thedisplacer 2 on the high temperature end side and thecylinder 4. -
Openings 16 that introduce a refrigerant gas into theexpansion space 3 via the clearance C are formed at a low temperature end of thedisplacer 2. Theexpansion space 3, which is a space defined by thecylinder 4 and thedisplacer 2, changes in volume with the reciprocation of thedisplacer 2. Thecooling stage 5, which is thermally coupled to an object of cooling, is placed at a position corresponding to theexpansion space 3 on the periphery and the bottom of thecylinder 4. Thecooling stage 5 is cooled by a refrigerant gas that passes through the clearance C. - For example, Bakelite (phenol containing cloth) is used for the
body part 2 a of thedisplacer 2 in view of specific gravity, strength, thermal conductivity, etc. The regenerator material is formed of, for example, a wire mesh.FIG. 1 illustrates thecryogenic refrigerator 1 in operation. Therefore, because of slight contraction of thebody part 2 a due to low temperature, thebody part 2 a and theheat conducting part 2 b are equal in outside diameter. However, at normal temperature (5° C. to 35° C.), the outside diameter of theheat conducting part 2 b is slightly smaller than the outside diameter of thebody part 2 a. - Next, a description is given of an operation of the
cryogenic refrigerator 1. At some point of time during a refrigerant gas supply process, thedisplacer 2 is positioned at its bottom dead center inside thecylinder 4. When thesupply valve 13 is opened at the same time with or slightly before or after that point of time, high-pressure helium gas is supplied into thecylinder 4 through thesupply valve 13 and the supply and discharge common pipe, and flows into theregenerator 7 inside thedisplacer 2 through theopening 11 positioned at the top (high temperature end) of thedisplacer 2. The high-pressure helium gas that has flown into theregenerator 7 is supplied into theexpansion space 3 through theopenings 16, positioned in a lower part of thedisplacer 2, and the clearance C while being cooled by the regenerator material. - Thus, the
expansion space 3 is filled with the high-pressure helium gas, and thesupply valve 13 is closed. At this point, thedisplacer 2 is positioned at its top dead center inside thecylinder 4. When thereturn valve 14 is opened at the same time with or slightly before or after that point, the pressure of the helium (refrigerant) gas inside theexpansion space 3 is reduced, so that the helium gas expands. The helium gas inside theexpansion space 3, whose temperature has been lowered because of its expansion, absorbs the heat of thecooling stage 5 through the clearance C. - The
displacer 2 moves toward the bottom dead center, so that the volume of theexpansion space 3 is reduced. The helium gas inside theexpansion space 3 is returned to the intake side of thecompressor 12 through the clearance C, theopenings 16, theregenerator 7, and theopening 11. During this process, the regenerator material is cooled by the refrigerant gas (helium gas). Letting this process be one cycle, thecryogenic refrigerator 1 cools thecooling stage 5 by repeating this cooling cycle. - According to the
cryogenic refrigerator 1 and thedisplacer 2 of the first embodiment, theheat conducting part 2 b constantly faces thecooling stage 5 across the clearance C. Heat that enters from thecooling stage 5 also enters theheat conducting part 2 b via the helium gas in the clearance C. Therefore, when the low-temperature helium gas generated in theexpansion space 3 passes through the clearance C, heat exchange is performed not only between the helium gas and thecooling stage 5 but also between the helium gas and theheat conducting part 2 b. As a result, it is possible to increase a substantial area for heat exchange (heat exchange area) between the coolingstage 5 and the low-temperature helium gas. - Further, the heat that has entered the
heat conducting part 2 b is further transferred through the inside of theheat conducting part 2 b toward theexpansion space 3. Therefore, it is possible to further improve heat exchange efficiency by configuring theheat conducting part 2 b so that theheat conducting part 2 b comes into contact with the low-temperature helium gas inside theexpansion space 3. - In contrast, according to a configuration without the
heat conducting part 2 b, that is, according to the conventional displacer where a part corresponding to theheat conducting part 2 b is formed of Bakelite, the heat exchange between helium gas and Bakelite is so limited that no substantial heat exchange is performed. Therefore, when low-temperature helium gas generated in an expansion space passes through a clearance, heat exchange is performed only between the helium gas and a cooling stage. - Thus, according to the
cryogenic refrigerator 1 and thedisplacer 2 of the first embodiment, it is possible to cause theheat conducting part 2 b as well to effectively contribute to heat exchange, compared with the conventional displacer, so that it is possible to increase a substantial heat exchange area. Further, the above-described flow (transfer) of heat generated inside theheat conducting part 2 b makes it possible to further improve heat exchange efficiency. That is, it is possible to reduce the temperature difference of thecooling stage 5 in a vertical direction inFIG. 1 . In particular, it is possible to reduce the temperature difference in the case of providing an object of cooling below thecooling stage 5. - Further, when Bakelite is used for a part corresponding to the
heat conducting part 2 b as in the conventional displacer, the part contracts with a decrease in temperature because of a relatively high coefficient of thermal expansion of Bakelite, so that a part corresponding to the overlappingpart 2 ba may come off a part corresponding to theoverlapped part 2 ab. In contrast, according thecryogenic refrigerator 1 and thedisplacer 2 of the first embodiment, the overlappingpart 2 ba, which has a lower coefficient of thermal expansion than thebody part 2 a, is provided inside (on the inner circumference side of) the overlappedpart 2 ab of thebody part 2 a. Therefore, when theoverlapped part 2 ab of thebody part 2 a is cooled to contract, a squeezing force is exerted on the overlappingpart 2 ba of theheat conducting part 2 b, so that it is possible to prevent the overlappingpart 2 ba from coming off theoverlapped part 2 ab. - Further, according to the
cryogenic refrigerator 1 and thedisplacer 2 of the first embodiment, theheat conducting part 2 b also contributes to heat exchange, thereby increasing a substantial heat exchange area. Therefore, even when thecooling stage 5 and the clearance C are reduced in length in the axial directions (the moving directions of the displacer 2) compared with the conventional displacer, it is possible to obtain a desired refrigerating capacity. As a result, it is possible to reduce channel resistance and pressure loss in the clearance C, so that it is possible to increase the refrigeration efficiency of thecryogenic refrigerator 1. Further, reduction in the volume of the clearance C leads to a decrease in dead volume that does not contribute to generation of cold temperatures. This may be expected to reduce a pressure difference between a high pressure and a low pressure during one cycle due to dead volume. - The overlapping
part 2 ba and theoverlapped part 2 ab may form a screw part so as to be screwed to each other. For example, the overlappingpart 2 ba and theoverlapped part 2 ab may be screwed to each other with their respective threaded parts mating with each other. This allows thebody part 2 a and theheat conducting part 2 b to be more easily attached to and detached from each other. In this case as well, when theoverlapped part 2 ab of thebody part 2 a is cooled to contract, a squeezing force is exerted on the overlappingpart 2 ba of theheat conducting part 2 b. Thus, it is possible to further prevent the overlappingpart 2 ba from coming off theoverlapped part 2 ab. - In the above-described first embodiment, the
heat conducting part 2 b has a columnar shape, while theheat conducting part 2 b may have a tubular shape as described below.FIG. 2 is a schematic diagram illustrating acryogenic refrigerator 21 and adisplacer 22 according to a second embodiment. InFIG. 2 , the same elements as those of the first embodiment ofFIG. 1 are referred to by the same reference numerals, and a description is basically given of differences from the first embodiment. - According to the second embodiment, the
displacer 22 includes abody part 22 a and aheat conducting part 22 b. Theheat conducting part 22 b has a tubular shape, and the entireheat conducting part 22 b forms an overlappingpart 22 ba that overlaps thebody part 22 a in the stroke directions of thedisplacer 22. A portion of thebody part 22 a that is positioned on the low temperature side of the openings 16 (that is, below theopenings 16 inFIG. 2 ) has a smaller diameter than a portion of thebody part 22 a that is positioned on the high temperature side of the openings 16 (that is, above theopenings 16 inFIG. 2 ). This smaller-diameter portion of thebody part 22 a forms anoverlapped part 22 ab that corresponds to the overlappingpart 22 ba. - The overlapping
part 22 ba includesfirst hole parts 22 bah, and theoverlapped part 22 ab includessecond hole parts 22 abh that correspond to thefirst hole parts 22 bah. Thebody part 22 a and theheat conducting part 22 b are connected by press-fit pins 26 (an insertion member) that are press-fit and inserted into both thesecond hole parts 22 abh and thefirst hole parts 22 bah. Like in the first embodiment, a material that has a higher thermal conductivity than at least thebody part 22 a, such as copper, aluminum, stainless steel or the like, is used for theheat conducting part 22 b. In this embodiment as well, the press-fit pins 26 may be either Bakelite (phenol containing cloth) or stainless steel. The overlappingpart 22 ba is fixed to theoverlapped part 22 ab by inserting the press-fit pins 26 into thefirst hole parts 22 bah and thesecond hole parts 22 abh. - According to the
cryogenic refrigerator 21 and thedisplacer 22 of the second embodiment as well, it is possible to increase a heat exchange area by causing theheat conducting part 22 b to contribute to heat exchange as in the first embodiment. In addition, in the second embodiment, theheat conducting part 22 b is placed only on the peripheral (outer circumferential) side of thedisplacer 22, which contributes to heat exchange compared with the first embodiment. Therefore, it is possible to reduce the volume and mass of theheat conducting part 22 b compared with the volume and mass of theheat conducting part 2 b of the first embodiment, and thus to reduce the mass of theentire displacer 22, which is a movable part, compared with the mass of thedisplacer 2 of the first embodiment. - Further, the reciprocation of the
heat conducting part 22 b, which is a conductor, under the presence of a magnetic field generates eddy current, which causes heat generation, that is, copper loss. According to the second embodiment, the volume of theheat conducting part 22 b is relatively small. Therefore, it is possible to control generation of copper loss accordingly. - Further, the
heat conducting part 22 b may be formed of a standardized tubular material. Therefore, it is possible to reduce cost compared with the first embodiment. - As described above, the generation of copper loss is expected to be controlled by reducing the volume of a conductor, while the generation of copper loss may also be controlled by controlling generation of eddy current by designing a shape. For example,
FIG. 3 illustrates a variation of the tubularheat conducting part 22 b illustrated inFIG. 2 , where a slit S is formed to make theheat conducting part 22 b discontinuous in its circumferential directions. InFIG. 3 , (a) is a plan view and (b) is a side view of the variation of theheat conducting part 22 b. According to this configuration, it is possible to prevent eddy current from continuously flowing in the circumferential directions in particular, so that it is possible to control generation of copper loss more effectively. - Further,
FIG. 4 illustrates another variation of theheat conducting part 22 b. As illustrated inFIG. 4 , theheat conducting part 22 b may have a bottomed tube shape. Theheat conducting part 22 b of a bottomed tube shape causes heat that has entered theheat conducting part 22 b from thecooling stage 5 to be exchanged between abottom part 22 b b of theheat conducting part 22 b and theexpansion space 3. As a result, it is possible to increase cooling efficiency compared with thecryogenic refrigerator 21 ofFIG. 2 . - In the above-described first and second embodiments, single-stage refrigerators are illustrated, while an embodiment of the present invention may also be applied to a two-stage refrigerator as described below.
FIG. 5 is a schematic diagram illustrating acryogenic refrigerator 31 and first and second displacers 32 and 36 according to a third embodiment. - Like the
cryogenic refrigerators cryogenic refrigerator 31 according to the third embodiment is a Gifford-McMahon (GM) refrigerator using helium gas as a refrigerant gas. As illustrated inFIG. 5 , thecryogenic refrigerator 31 includes thefirst displacer 32 and thesecond displacer 36. Thesecond displacer 36 is connected to thefirst displacer 32 in a longitudinal direction of thesecond displacer 36. As illustrated inFIG. 5 , thefirst displacer 32 and thesecond displacer 36 are connected via, for example, apin 33, aconnector 34, and apin 35. - A
first cylinder 37 and asecond cylinder 38 are formed as a unit. A low temperature end of thefirst cylinder 37 and a high temperature end of thesecond cylinder 38 are connected at the bottom of thefirst cylinder 37. Thesecond cylinder 38 is coaxial with thefirst cylinder 37, and is a cylindrical member that has a smaller diameter than thefirst cylinder 37. Thefirst cylinder 37 accommodates thefirst displacer 32 in such a manner as to allow thefirst displacer 32 to reciprocate in the longitudinal directions of thefirst cylinder 37. Thesecond cylinder 38 accommodates thesecond displacer 36 in such a manner as to allow thesecond displacer 36 to reciprocate in the longitudinal directions of thesecond cylinder 38. - For example, stainless steel is used for the
first cylinder 37 and thesecond cylinder 38 in consideration of strength, thermal conductivity, helium blocking capability, etc. Thesecond displacer 36 has a coating of an abrasion resistant resin such as fluororesin on the peripheral (exterior circumferential) surface of its metallic cylinder of, for example, stainless steel. - A Scotch yoke mechanism (not graphically illustrated) that causes the
first displacer 32 and thesecond displacer 36 to reciprocate is provided at a high-temperature end of thefirst cylinder 37, so that thefirst displacer 32 and thesecond displacer 36 reciprocate along thefirst cylinder 37 and thesecond cylinder 38, respectively. - The
first displacer 32 has a cylindrical peripheral (exterior circumferential) surface. Thefirst displacer 32 is filled with a first regenerator material. The internal space of thefirst displacer 32 serves as afirst regenerator 39. Aflow rectifier 40 and aflow rectifier 41 are provided on and under thefirst regenerator 39. Afirst opening 42 through which a refrigerant gas flows from aroom temperature chamber 69 into thefirst displacer 32 is formed at a high temperature end of thefirst displacer 32. Theroom temperature chamber 69, which is a space defined by thefirst cylinder 37 and the high temperature end of thefirst displacer 32, changes in volume with the reciprocation of thefirst displacer 32. Of the pipes that interconnect acompressor 43, asupply valve 44, and areturn valve 45, which form an intake and outlet system, a pipe common to supply and discharge (a supply and discharge common pipe) is connected to theroom temperature chamber 69. Further, aseal 46 is attached between part of thefirst displacer 32 on the high temperature end side and thefirst cylinder 37. -
Second openings 48 that introduce a refrigerant gas into afirst expansion space 47 via a first clearance C1 (a clearance channel) are formed at a low temperature end of thefirst displacer 32. Thefirst expansion space 47, which is a space defined by thefirst cylinder 37 and thefirst displacer 32, changes in volume with the reciprocation of thefirst displacer 32. Afirst cooling stage 49, which is thermally coupled to an object of cooling (not graphically illustrated), is placed at a position corresponding to thefirst expansion space 47 on the periphery of thefirst cylinder 37. Thefirst cooling stage 49 is cooled by a refrigerant gas that passes through the first clearance C1. - The
second displacer 36 has a cylindrical peripheral (exterior circumferential) surface. Thesecond displacer 36 is filled with a second regenerator material. The internal space of thesecond displacer 36 serves as asecond regenerator 50. Thefirst expansion space 47 and a high temperature end of thesecond displacer 36 are connected by a communicating passage (not graphically illustrated). A refrigerant gas flows from thefirst expansion space 47 into thesecond regenerator 50 through this communicating passage. - A
third opening 52 that introduces a refrigerant gas into asecond expansion space 51 via a second clearance C2 (a clearance channel) is formed at a low temperature end of thesecond displacer 36. Thesecond expansion space 51, which is a space defined by thesecond cylinder 38 and thesecond displacer 36, changes in volume with the reciprocation of thesecond displacer 36. The second clearance C2 is defined by a low temperature end part of thesecond cylinder 38 and thesecond displacer 36. The second clearance C2 is larger than a clearance between thesecond displacer 36 having ahelical groove 63 as described below and thesecond cylinder 38. - A
second cooling stage 53, which is thermally coupled to an object of cooling (not graphically illustrated), is placed at a position corresponding to thesecond expansion space 51 on the periphery of thesecond cylinder 38. Thesecond cooling stage 53 is cooled by a refrigerant gas that passes through the second clearance C2. - The
first displacer 32 includes abody part 32 a and aheat conducting part 32 b. Theheat conducting part 32 b is formed of a material that has a higher thermal conductivity than thebody part 32 a. For example, Bakelite (phenol containing cloth) is used for thebody part 32 a of thefirst displacer 32 in view of specific gravity, strength, thermal conductivity, etc. A material that has a higher thermal conductivity than at least thebody part 32 a, such as copper, aluminum, stainless steel or the like, is used for theheat conducting part 32 b. - The
heat conducting part 32 b has a lower coefficient of thermal expansion than thebody part 32 a. Theheat conducting part 32 b includes an overlappingpart 32 ba that overlaps thebody part 32 a in the directions of strokes (stroke directions) of thefirst displacer 32. Thebody part 32 a includes an overlappedpart 32 ab that corresponds to the overlappingpart 32 ba. - The
second displacer 36 includes abody part 36 a and aheat conducting part 36 b. Theheat conducting part 36 b is formed of a material that has a higher thermal conductivity than thebody part 36 a. For example, Bakelite (phenol containing cloth) is used for thebody part 36 a of thesecond displacer 36 in view of specific gravity, strength, thermal conductivity, etc. A material that has a higher thermal conductivity than at least thebody part 36 a, such as copper, aluminum, stainless steel or the like, is used for theheat conducting part 36 b. - The
heat conducting part 36 b has a lower coefficient of thermal expansion than thebody part 36 a. Theheat conducting part 36 b includes an overlappingpart 36 ba that overlaps thebody part 36 a in the directions of strokes (stroke directions) of thesecond displacer 36. Thebody part 36 a includes an overlappedpart 36 ab that corresponds to the overlappingpart 36 ba. - The first regenerator material is formed of, for example, a wire mesh. The second regenerator material is formed by holding a regenerator material such as lead spheres with felt and a wire mesh in the axial directions.
- The
helical groove 63 is formed on the peripheral (exterior circumferential) surface of thesecond displacer 36. Thehelical groove 36 has a starting end communicating with thesecond expansion space 51 through the second clearance C2, and helically extends toward thefirst expansion space 47. - According to the third embodiment as well, the
first displacer 32 and thesecond displacer 36 include theheat conducting part 32 b and theheat conducting part 36 b at their respective cold (low) temperature ends. Both theheat conducting part 32 b and theheat conducting part 36 b have a two-stage (stepped) columnar shape. Theheat conducting part 32 b is fixed to thebody part 32 a with press-fit pins 54. Theheat conducting part 36 b is fixed to thebody part 36 a with press-fit pins 55. According to the third embodiment as well, for the reasons stated above with respect to the first and the second embodiment, it is possible to improve cooling efficiency by increasing a substantial heat exchange area for each of thefirst cooling stage 49 and thesecond cooling stage 53. - All examples and conditional language provided herein are intended for pedagogical purposes of aiding the reader in understanding the invention and the concepts contributed by the inventors to further the art, and are not to be construed as limitations to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority or inferiority of the invention. Although one or more embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.
- For example, in the above-described embodiments, a description is given of the case where the number of stages of a cryogenic refrigerator is one or two. However, the number of stages may be suitably selected, and may be, for example, three. Further, in the above-described embodiments, a description is given of the case where the cryogenic refrigerator is a GM refrigerator. However, embodiments of the present invention are not limited to the GM refrigerator, and may be applied to any refrigerators having a displacer, such as Stirling refrigerators and Solvay cycle refrigerators.
- According to an aspect of the present invention, it is possible to improve the refrigeration efficiency of a cryogenic refrigerator by improving its heat exchange efficiency by effectively increasing a heat exchange area that substantially contributes to heat exchange through a side clearance without increasing the length of a cooling stage in the axial directions of the cryogenic refrigerator. Accordingly, embodiments of the present invention may be applied to various kinds of cryogenic refrigerators.
Claims (10)
1. A cryogenic refrigerator, comprising:
a displacer including a body part and a heat conducting part, wherein a material of the heat conducting part has a higher thermal conductivity than the body part;
a cylinder accommodating the displacer in such a manner as to allow the displacer to reciprocate in axial directions of the cylinder, wherein an expansion space is formed between the cylinder and a low temperature end of the displacer;
a clearance channel formed between the displacer and the cylinder so as to allow a refrigerant gas to flow into the expansion space; and
a cooling stage positioned adjacent to the expansion space,
wherein the heat conducting part faces the cooling stage across the clearance channel.
2. The cryogenic refrigerator as claimed in claim 1 , wherein the heat conducting part has a lower coefficient of thermal expansion than the body part.
3. The cryogenic refrigerator as claimed in claim 1 , wherein the heat conducting part includes an overlapping part that overlaps the body part in stroke directions of the displacer, and
the body part includes an overlapped part corresponding to the overlapping part.
4. The cryogenic refrigerator as claimed in claim 3 , wherein the heat conducting part has a bottomed tube shape.
5. The cryogenic refrigerator as claimed in claim 3 , wherein the overlapping part and the overlapped part form a screw part.
6. The cryogenic refrigerator as claimed in claim 3 , further comprising:
an insertion member inserted into a first hole part formed in the overlapping part and a second hole part formed in the overlapped part so as to connect the body part and the heat conducting part.
7. The cryogenic refrigerator as claimed in claim 1 , wherein the heat conducting part has a tubular shape with a slit that makes the heat conducting part discontinuous in a circumferential direction thereof.
8. The cryogenic refrigerator as claimed in claim 1 , wherein the material of the heat conducting part is selected from the group consisting of copper, aluminum, and stainless steel.
9. A displacer, comprising:
a body part; and
a heat conducting part,
wherein the heat conducting part is positioned at a low temperature end of the displacer, and
a material of the heat conducting part has a higher thermal conductivity than the body part.
10. The displacer as claimed in claim 9 , wherein an outside diameter of the heat conducting part is smaller than an outside diameter of the body part at normal temperature.
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US15/887,312 US20180156500A1 (en) | 2012-01-06 | 2018-02-02 | Cryogenic refrigerator and displacer |
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JP2012001627A JP5917153B2 (en) | 2012-01-06 | 2012-01-06 | Cryogenic refrigerator, displacer |
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US15/887,312 Division US20180156500A1 (en) | 2012-01-06 | 2018-02-02 | Cryogenic refrigerator and displacer |
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US13/709,275 Abandoned US20130174582A1 (en) | 2012-01-06 | 2012-12-10 | Cryogenic refrigerator and displacer |
US15/887,312 Abandoned US20180156500A1 (en) | 2012-01-06 | 2018-02-02 | Cryogenic refrigerator and displacer |
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US20160123631A1 (en) * | 2014-10-29 | 2016-05-05 | Sumitomo Heavy Industries, Ltd. | Cryogenic refrigerator |
US9841212B2 (en) | 2014-04-02 | 2017-12-12 | Sumitomo Heavy Industries, Ltd. | Cryogenic refrigerator |
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- 2012-01-06 JP JP2012001627A patent/JP5917153B2/en active Active
- 2012-12-10 US US13/709,275 patent/US20130174582A1/en not_active Abandoned
-
2013
- 2013-01-04 CN CN201310003022.9A patent/CN103196254B/en active Active
-
2018
- 2018-02-02 US US15/887,312 patent/US20180156500A1/en not_active Abandoned
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Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US9841212B2 (en) | 2014-04-02 | 2017-12-12 | Sumitomo Heavy Industries, Ltd. | Cryogenic refrigerator |
US20160123631A1 (en) * | 2014-10-29 | 2016-05-05 | Sumitomo Heavy Industries, Ltd. | Cryogenic refrigerator |
US9976779B2 (en) * | 2014-10-29 | 2018-05-22 | Sumitomo Heavy Industries, Ltd. | Cryogenic refrigerator |
Also Published As
Publication number | Publication date |
---|---|
JP2013142479A (en) | 2013-07-22 |
CN103196254B (en) | 2016-01-20 |
JP5917153B2 (en) | 2016-05-11 |
US20180156500A1 (en) | 2018-06-07 |
CN103196254A (en) | 2013-07-10 |
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