US20170010026A1 - Stirling cryocooler - Google Patents
Stirling cryocooler Download PDFInfo
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- US20170010026A1 US20170010026A1 US15/270,017 US201615270017A US2017010026A1 US 20170010026 A1 US20170010026 A1 US 20170010026A1 US 201615270017 A US201615270017 A US 201615270017A US 2017010026 A1 US2017010026 A1 US 2017010026A1
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- Prior art keywords
- displacer
- convection control
- convection
- gas
- stirling cryocooler
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- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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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
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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
- F25B2309/00—Gas cycle refrigeration machines
- F25B2309/001—Gas cycle refrigeration machines with a linear configuration or a linear motor
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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
- F25B2309/00—Gas cycle refrigeration machines
- F25B2309/003—Gas cycle refrigeration machines characterised by construction or composition of the regenerator
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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
- F25B2309/00—Gas cycle refrigeration machines
- F25B2309/14—Compression machines, plants or systems characterised by the cycle used
- F25B2309/1428—Control of a Stirling refrigeration machine
Abstract
In a Stirling cryocooler, a displacer includes an internal space which is filled with gas. The displacer is reciprocatably accommodated in the expander main body. The displacer accommodates in the internal space one or more convection control plates, for controlling gas convection to a minimum. The one or more convection control plates are disposed along a line intersecting the displacer's longitudinal axis. At least one of the convection control plates divides the internal space into first and second sub-chambers, and includes an opening through which the sub-chambers communicate. The at least one of the convection control plates includes a convection control wall provided in the opening.
Description
- Priority is claimed to Japanese Patent Application No. 2014-062411, filed Mar. 25, 2014, and International Patent Application No. PCT/JP/2015/058178, filed Mar. 19, 2015, the entire content of which is incorporated herein by reference.
- Technical Field
- Certain embodiments of the present invention relate to cryocoolers, and particularly, to Stirling cryocoolers.
- Description of Related Art
- In the related art, in a Stirling cryocooler, a displacer may be shaped in a hollow form so as to accommodate a gas. In this case, it is well-known that heat loss arises due to heat transfer owing to convecting of gas inside the displacer. Accordingly, in order to control from gas convecting, technology whereby a cotton-like heat insulator, a strip-like heat insulator, or a powder-form heat insulator is accommodated in the displacer is known.
- One embodiment of the present invention affords a Stirling cryocooler comprising a displacer having a longitudinally extending gas-filled internal space, an expander main body reciprocatably accommodating the displacer, and at least one convection control plate for controlling gas convection to a minimum, accommodated in the displacer internal space, disposed along a line intersecting the longitudinal axis of the displacer.
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FIG. 1 is a view schematically showing a Stirling cryocooler according to an embodiment of the present invention. -
FIG. 2 is a view schematically showing an expander of the Stirling cryocooler according to the embodiment of the present invention. -
FIGS. 3A and 3B are views schematically showing an example of an accommodation position of a convection control plate according to the embodiment. -
FIG. 4 is a schematic view showing an internal configuration of a displacer according to another embodiment. -
FIG. 5 is a view schematically showing an expander of a Stirling cryocooler according to another embodiment of the present invention. -
FIG. 6 is a view schematically showing an expander of a Stirling cryocooler according to still another embodiment of the present invention. -
FIG. 7 is a view schematically showing an expander of a Stirling cryocooler according to still another embodiment of the present invention. - It is desirable to provide a technology which more appropriately controls convection of gas inside a displacer.
- In addition, arbitrary combinations of the above-described components, or components or expression of the present invention may be replaced by each other in methods, devices, systems, or the like, and these replacements are also included in aspects of the present invention.
- According to the present invention, it is possible to provide a technology which more appropriately controls convection of gas inside a displacer.
- During an operation of a Stirling cryocooler, a displacer reciprocates. Accordingly, in a case where a member which controls convection of gas inside the displacer is used, preferably, the member is fixed to the displacer. However, for example, if a cotton-like heat insulator, a strip-like heat insulator, or a powder-form heat insulator is used as the gas-convection control member, it is difficult to fix the member to the inner portion of the displacer. If the gas-convection control member cannot be fixed to the displacer, gas convection inside the displacer may not be appropriately controlled. In some cases, when the displacer reciprocates, the gas-convection control members collide with the inner wall of the displacer, or collide with each other, and thus noise may occur. Accordingly, a Stirling cryocooler according to an embodiment of the present invention uses a platelike member as the gas-convection control member.
- Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In descriptions, the same reference numerals are assigned to the same elements, and overlapping descriptions thereof are omitted. In addition, configurations described below are exemplified, and do not limit the scope of the present invention.
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FIG. 1 is a view schematically showing a Stirlingcryocooler 10 according to an embodiment of the present invention. The Stirling cryocooler 10 includes acompressor 11, aconnection pipe 12, and anexpander 13. - The
compressor 11 includes acompressor case 14. Thecompressor case 14 is a pressure container which is configured so as to airtightly hold a high-pressure working gas. For example, the working gas is helium gas. In addition, thecompressor 11 includes a compressor unit which is accommodated in thecompressor case 14. The compressor unit includes a compressor piston and a compressor cylinder, with one of either the compressor piston or the compressor cylinder being amovable member 15 that is configured so as to reciprocate in thecompressor case 14, and the other of the two is a stationary member that is fixed to thecompressor case 14. The compressor unit includes a drive source for driving themovable member 15 with respect to thecompressor case 14 in a direction along a center axis of themovable member 15. Thecompressor 11 includes asupport portion 16 which supports themovable member 15 to thecompressor case 14 such that themovable member 15 can reciprocate. Themovable member 15 vibrates with respect to thecompressor case 14 and the stationary member at predetermined amplitude and frequency. The volume of the working gas inside thecompressor 11 vibrates at specific amplitude and frequency. - A working gas chamber is formed between the compressor piston and the compressor cylinder. The working gas chamber is connected to one end of the
connection pipe 12 through a communication path which is formed in the above-described stationary member andcompressor case 14. The other end of theconnection pipe 12 is connected to the working gas chamber of theexpander 13. The working gas chamber of thecompressor 11 is connected to the working gas chamber of theexpander 13 by theconnection pipe 12. - As described below with reference to
FIG. 2 , theexpander 13 includes an expandermain body 20, adisplacer 22, and asupport portion 40. -
FIG. 2 is a view schematically showing theexpander 13 according to the embodiment of the present invention.FIG. 2 shows an outline of an internal structure of theexpander 13. - The
expander 13 includes the expandermain body 20 and thedisplacer 22. The expandermain body 20 is a pressure container which is configured so as to airtightly hold a high-pressure working gas. Thedisplacer 22 is a movable member which is configured so as to reciprocate in the expandermain body 20. In addition, theexpander 13 includes at least onesupport portion 40 which supports thedisplacer 22 to the expandermain body 20 such that thedisplacer 22 can reciprocate. - The expander
main body 20 includes afirst compartment 24 and asecond compartment 26. Thefirst compartment 24 includes anexpansion space 28 of a working gas which is formed between the expandermain body 20 and thedisplacer 22. Acooling stage 29 for cooling an object is provided on the portion of the expandermain body 20 adjacent to theexpansion space 28. Thesecond compartment 26 is configured so as to support thedisplacer 22 to the expandermain body 20 viaelastic members 30. - The
second compartment 26 is adjacent to thefirst compartment 24 in a reciprocation direction (shown by arrow C inFIG. 2 ) of thedisplacer 22. Aseal portion 25 is provided between thesecond compartment 26 and thefirst compartment 24, and thus, thesecond compartment 26 is separated from thefirst compartment 24. Accordingly, pressure variation of a working gas in thefirst compartment 24 is not transmitted to thesecond compartment 26, or a pressure of the working gas in thesecond compartment 26 is less influenced by the pressure variation of the working gas in thefirst compartment 24. In addition, gas which has the same kind as that of the working gas is enclosed in thesecond compartment 26 such that the pressure of thesecond compartment 26 is the same as an average pressure of the working gas supplied to thecompressor 11. - The
displacer 22 includes a displacermain body 32 which is accommodated in thefirst compartment 24, and adisplacer rod 34. Thedisplacer rod 34 is a shaft portion which is thinner than the displacermain body 32. Thedisplacer 22 has a center axis which is parallel to the reciprocation direction of thedisplacer 22, and the displacermain body 32 and thedisplacer rod 34 are provided so as to be coaxial with the center axis of thedisplacer 22. Thedisplacer 22 includes an internal space, and is filled with gas which has the same kind as that of the working gas. In addition, thedisplacer 22 includes one or moreconvection control plate 42 for controlling convection of gas. In addition, details of thedisplacer 22 will be described below. - The
displacer rod 34 extends from the displacermain body 32 to thesecond compartment 26 through theseal portion 25. Thedisplacer rod 34 is supported by the expandermain body 20 in thesecond compartment 26 such that thedisplacer 22 can reciprocate. For example, the above-describedseal portion 25 may be a rod seal which is formed between thedisplacer rod 34 and the expandermain body 20. - The
first compartment 24 forms a cylinder portion which surrounds the displacermain body 32. Theexpansion space 28 is formed between the bottom surface of the cylinder portion and the end surface of the displacermain body 32. Theexpansion space 28 is formed on a side opposite to a joint portion between the displacermain body 32 and thedisplacer rod 34 in the reciprocation direction of thedisplacer 22. Agas space 36 which is connected to theconnection pipe 12 is formed between the joint portion and theseal portion 25. - A
regenerator 38 is attached to the lateral surface of the cylinder portion of the expandermain body 20 such as to be located along the outer periphery of the displacermain body 32. More specifically, theregenerator 38 is provided in the lateral surface of the cylinder portion of the expandermain body 20 such as to be located in a cylindrical region having the longitudinal axis of thedisplacer 22 as its center axis, along the outer peripheral portion of the displacermain body 32. For example, theregenerator 38 has a laminated structure of metal meshes. A working gas between theexpansion space 28 and thegas space 36 can flow through theregenerator 38. - A water-cooled
heat exchanger 37 is provided between the regenerator 38 and thegas space 36. The water-cooledheat exchanger 37 performs heat exchange by which the working gas supplied to thecompressor 11 is cooled and heat of the working gas is discharged to the outside of theexpander 13. Moreover, a low-temperature heat exchanger 39 is attached to a portion between the regenerator 38 and thecooling stage 29. - The
expander 13 supports thedisplacer 22 in the expandermain body 20 at a plurality of different positions in the reciprocation direction of thedisplacer 22 such that thedisplacer 22 can reciprocate. Accordingly, theexpander 13 includes twosupport portions 40. The twosupport portions 40 are provided in thesecond compartment 26. Therefore, it is possible to prevent thedisplacer 22 from being inclined to the center axis. - Each
support portion 40 includes the above-describedelastic member 30. Theelastic member 30 is disposed between thedisplacer rod 34 and the expandermain body 20 so as to apply an elastic restoring force to thedisplacer 22 when thedisplacer 22 is displaced from a neutral position. Accordingly, thedisplacer 22 reciprocates at a natural frequency which is determined by a spring constant of theelastic member 30, a spring constant due to the pressure of the working gas, and mass of thedisplacer 22. Thedisplacer rod 34 is fixed to theelastic members 30 via elasticmember attachment portions 51. - For example, the
elastic member 30 is a spring mechanism which includes at least one leaf spring. The leaf spring is a spring which is referred to as a flexure spring, is flexible in the reciprocation direction of thedisplacer 22, and is rigid in the direction perpendicular to the reciprocation direction. - For example, the leaf spring is disclosed in Japanese Unexamined Patent Application Publication No. 2008-215440. The entire content of this related art document is incorporated herein by reference. Accordingly, the
elastic member 30 allows the movement of thedisplacer 22 in the direction along the center axis, but prevents the movement thereof in the direction orthogonal to the direction along the center axis. - In this way, a vibration system including the
displacer 22 and theelastic members 30 is configured. This vibration system is configured such that thedisplacer 22 is vibrated at the same frequency as that of the vibration of themovable member 15 of thecompressor 11 so as to have a phase difference with respect to the vibration of themovable member 15. Thedisplacer 22 is driven by pulsation of the working gas pressure generated by the vibration of themovable member 15 of thecompressor 11. - A reverse Stirling cycle is formed between the
expansion space 28 and the working gas chamber of thecompressor 11 by the reciprocation of thedisplacer 22 and themovable member 15 of thecompressor 11. In this way, the cooling stage adjacent to theexpansion space 28 is cooled and theStirling cryocooler 10 can cool the object. - Next, the
displacer 22 will be described in more detail. - As described above, the
displacer 22 according to the present embodiment is hollow, and has the internal space which is filled with gas which has the same kind as that of the working gas. Since thedisplacer 22 is hollow, weight of thedisplacer 22 decreases, and weight of theStirling cryocooler 10 also decreases. In addition, the internal space of thedisplacer 22 is filled with the gas which has the same kind as that of the working gas, and thus, even when the gas inside thedisplacer 22 flows into thefirst compartment 24 or thesecond compartment 26 due to some reasons, it is possible to prevent the working gas from being contaminated. - Here, the internal space of the
displacer 22 is in a vacuum state, and thus, it is possible to prevent the gas inside thedisplacer 22 from flowing into thefirst compartment 24 or thesecond compartment 26. In this case, if the internal space of thedisplacer 22 and thefirst compartment 24 or thesecond compartment 26 communicate with each other due to some reasons, the working gas flows into the internal space of thedisplacer 22, and thus, the working gas contributing cooling decreases. Accordingly, preferably, the internal space of thedisplacer 22 is filled with the gas which has the same kind as that of the working gas. - Cooling generated by the
expansion space 28 is accumulated in theregenerator 38. Accordingly, the temperature of the end portion on the side of theregenerator 38 which is in thermal contact with the low-temperature heat exchanger 39 is lower than the end portion on the side of theregenerator 38 which is in thermal contact with the water-cooledheat exchanger 37. Hereinafter, in the present specification, the end portion on the side of theregenerator 38 which is in thermal contact with the low-temperature heat exchanger 39 is referred to as a “low-temperature end,” and the end portion on the side of theregenerator 38 which is in thermal contact with the water-cooledheat exchanger 37 is referred to as a “high-temperature end.” Similarly, the tip portion of thedisplacer 22 facing theexpansion space 28 is referred to as a “low-temperature end,” and the base end portion facing the gas space 36 (that is, compression space) is referred to as a “high-temperature end.” - During an operation of the
Stirling cryocooler 10, a temperature gradient in which a temperature decreases from the high-temperature end to the low-temperature end is generated in theregenerator 38. As shown inFIG. 2 , theregenerator 38 is provided in the expandermain body 20 so as to be positioned at a cylindrical predetermined region which has the longitudinal axis of thedisplacer 22 as a center axis in the outer peripheral portion of thedisplacer 22. In addition, the range in the reciprocation of thedisplacer 22, that is, a stroke length of thedisplacer 22 is shorter than that of theregenerator 38. Accordingly, in thedisplacer 22, a region which is in contact with the vicinity of the low-temperature end of theregenerator 38 and a region which is in contact with the vicinity of the high-temperature end of theregenerator 38 exist. For convenience of description, the position of thedisplacer 22 which is in thermal contact with theregenerator 38 may be referred to as a “position corresponding to theregenerator 38.” The “position corresponding to theregenerator 38” may be referred to as a “position of thedisplacer 22 facing theregenerator 38.” - As a result, in the gas which fills the internal space of the
displacer 22, a temperature difference between the gas existing on the low-temperature end side of thedisplacer 22 and the gas existing on the high-temperature end side of thedisplacer 22 is generated. The reason why the temperature difference occurs is because the gas existing on the low-temperature end side of thedisplacer 22 is cooled by the low-temperature end of theregenerator 38 or theexpansion space 28. - The
expander 13 according to the embodiment may be installed such that the direction (the reciprocation direction of the displacer 22) in which the longitudinal axis of thedisplacer 22 extends is set to a horizontal direction, that is, a direction intersecting the gravity. In this case, in general, since weight of a low-temperature gas is heavier than weight of a high-temperature gas, convention is generated in which the low-temperature gas flows to the lower portion of the internal space of thedisplacer 22, and the high-temperature gas flows to the upper portion of the internal space. Accordingly, in the gas which fills the internal space of thedisplacer 22, a temperature gradient is generated in the direction intersecting the longitudinal axis of thedisplacer 22. More specifically, in the gas which fills the internal space of thedisplacer 22, the temperature of the gas existing on the lower side with respect to the gravity is lower than the temperature of the gas existing on the upper side. - Hereinafter, the
expander 13 according to the embodiment has the assumption that the direction in which the longitudinal axis of thedisplacer 22 extends is the horizontal direction. Accordingly, the direction of the gravity is the direction intersecting the longitudinal axis of thedisplacer 22. - Since the temperature gradient is generated in the gravity direction in the gas which fills the internal space of the
displacer 22, the temperature gradient is generated in the gravity direction in theregenerator 38 which surrounds the outer periphery of thedisplacer 22. That is, the temperature on the side of theregenerator 38 existing on the lower side with respect to the gravity is lower than the temperature on the side of theregenerator 38 existing on the upper side. The low-temperature end of theregenerator 38 is in thermal contact with the low-temperature heat exchanger 39 so as to perform heat exchange. However, according to a location, the temperature of the low-temperature end of theregenerator 38 is different from the temperature of the low-temperature heat exchanger 39, when the heat exchange is performed, heat loss is generated, and freezing performance of theStirling cryocooler 10 decreases. - In the
displacer 22 according to the embodiment, one or the plurality ofconvection control plates 42 which are disposed in the direction intersecting in the longitudinal axis of thedisplacer 22 are accommodated in the internal space of thedisplacer 22. Since the internal space of thedisplacer 22 is divided into a plurality of sub-chambers by theconvection control plates 42, it is possible to control gas convection to a minimum over the entire internal space. Preferably, theconvection control plates 42 are disposed along a line orthogonal to the longitudinal axis. - Preferably, the
convection control plate 42 is a member has low emissivity and has high heat transmissivity. For example, theconvection control plate 42 may be formed of an aluminum plate. Preferably, theconvection control plate 42 is in airtight contact with the inner wall of thedisplacer 22. In addition, theregenerator 38 existing on the lower side with respect to the gravity and theregenerator 38 existing on the upper side are thermally connected to each other via the walls of thedisplacer 22 and theconvection control plates 42. Accordingly, it is possible to decrease occurrence of the temperature gradient of theregenerator 38 in the gravity direction. -
FIGS. 3A to 3B are views for explaining accommodation positions ofconvection control plates 42 according to the embodiment. More specifically,FIG. 3A is a view showing an aspect in which thedisplacer 22 is positioned at a bottom dead center, andFIG. 3B is a view showing an aspect in which thedisplacer 22 is positioned at a top dead center. - As shown in
FIGS. 3A and 3B , a relative positional relationship between the regenerator 38 and theconvection control plate 42 is changed according to the reciprocation of thedisplacer 22. As shown inFIGS. 3A and 3B , aconvection control plate 42 a which is accommodated in the vicinity of the intermediate portion of the accommodation space of thedisplacer 22 exists at the “position corresponding to theregenerator 38” even when thedisplacer 22 reciprocates. Meanwhile, aconvection control plate 42 b, which is accommodated in the side closer to the high-temperature end than theconvection control plate 42 a in the accommodation space of thedisplacer 22, is deviated from the “position corresponding to theregenerator 38” according to the position of thedisplacer 22. - For example, as shown in
FIG. 3B , when thedisplacer 22 is positioned at the top dead center, theconvection control plate 42 b exists at the “position corresponding to theregenerator 38.” However, as shown inFIG. 3A , when thedisplacer 22 is positioned at the bottom dead center, theconvection control plate 42 b is deviated from the “position corresponding to theregenerator 38” and is positioned at the “position corresponding to the water-cooledheat exchanger 37.” - As described above, since the
regenerator 38 existing on the lower side with respect to the gravity is thermally connected to theregenerator 38 existing on the upper side by theconvection control plates 42, it is possible to decrease occurrence of the temperature gradient of theregenerator 38 in the gravity direction. Accordingly, preferably, theconvection control plate 42 is provided at the “position corresponding to theregenerator 38” even when thedisplacer 22 reciprocates. InFIGS. 3A and 3B , preferably, theconvection control plate 42 is not accommodated in the position of theconvection control plate 42 b, and is accommodated in the position of theconvection control plate 42 a. - In this way, the
convection control plates 42 are provided in the internal space of thedisplacer 22, and thus, it is possible to decrease the convection of the gas which fills the internal space, and it is possible to decrease occurrence of the temperature gradient of the gas in the gravity direction. As a result, it is possible to decrease occurrence of the temperature gradient of theregenerator 38 in the gravity direction. In addition, theregenerator 38 existing on the lower side and theregenerator 38 existing on the upper side in the gravity direction are thermally connected to each other via theconnection prevention plates 42. Accordingly, this contributes a decrease of the temperature gradient of theregenerator 38 which is generated in the gravity direction. Therefore, a predetermined effect can be obtained if thedisplacer 22 has only oneconvection control plate 42. However, as shown inFIG. 2 , if the plurality ofconvection control plates 42 are provided, it is possible to more effectively prevent occurrence of the temperature gradient of theregenerator 38 generated in the gravity direction. - Since the internal space of the
displacer 22 is divided by one or the plurality ofconvection control plates 42, it is possible to decrease the convection of the gas which fills the internal space. However, even when the internal space of thedisplacer 22 is divided into a plurality of sub-chambers by theconvection control plates 42, gas still exist in each sub-chamber. Accordingly, even when the internal space of thedisplacer 22 is divided by theconvection control plates 42, it is difficult to completely prevent the heat loss generated due to the convection of the gas. In addition, the heat of the gas which fills the internal space is transmitted to theregenerator 38, the temperature of theregenerator 38 increase, and heat loss may occur. - Here, in addition to the
convection control plate 42, a filling gas-convection control member may be accommodated in the internal space of thedisplacer 22. -
FIG. 4 is a schematic view showing an internal configuration of thedisplacer 22 according to another embodiment. In thedisplacer 22 shown inFIG. 4 , in addition to theconvection control plates 42, fillingmembers 43 for minimizing gas convection are accommodated in the internal space. Here, each of the fillingmembers 43 is held in the internal space so as to be interposed between theconvection control plates 42. Hereinafter, portions overlapping those of the internal configuration of thedisplacer 22 shown inFIG. 2 are described so as to be appropriately omitted or simplified. - As shown in
FIG. 4 , a portion between twoconvection control plates 42 different from each other is filled with the fillingmember 43, and thus, gas inside a sub-chamber divided by theconvection control plates 42 decreases. The gas itself decreases, and thus, it is possible to prevent heat loss due to the gas convecting. - Here, a ratio of the filling
member 43 occupying the internal space of thedisplacer 22 is greater than a ratio of theconvection control plate 42 occupying the internal space of thedisplacer 22. Accordingly, in order to prevent an increase in the weight of thedisplacer 22, the fillingmember 43 is configured such that specific weight of the fillingmember 43 decreases. Specifically, the fillingmember 43 may be realized by a fibrous member or a net-like member. In addition, for example, since the inside of thedisplacer 22 may have a low temperature such as approximately 70K, the fillingmember 43 is configured of a material in which low temperature brittle fracture is not easily generated. Specifically, the fillingmember 43 can be realized using a synthetic resin polymer such as a fluorine-based resin or aramid resin, pumice stone (pumice), or the like. In order to prevent radiation, an aluminum tape may be bonded to, or an aluminum film may be sputter-deposited onto, the surface of the fillingmember 43. - In the
displacer 22 shown inFIG. 4 , the plurality of fillingmembers 43 are spread so as to be in contact with theconvection control plates 42 and the inner walls of the displacer, and thus, a laminated structure having multiple layers is obtained. In this way, the laminated structure is configured by the fillingmembers 43, and thus, it is possible to decrease heat conduction from the fillingmembers 43 to theregenerator 38. - As described above, one
convection control plate 42 or each of the plurality ofconvection control plates 42 is a partition plate which extends along a plane intersecting the longitudinal axis direction C of thedisplacer 22, preferably, along a plane orthogonal to the longitudinal axis direction C. The partition plates divide the internal space of thedisplacer 22 into sub-chambers. Each of the sub-chambers may have air-tightness. The plate operates as a thermal bridge which is thermally cross-linked to the internal space of thedisplacer 22. The partition plate forms a thermal cross-link in the internal space of thedisplacer 22 from one side wall of thedisplacer 22 to other side wall thereof in the direction (for example, gravity direction) intersecting the longitudinal axis direction C. In addition, the gravity direction G is exemplified inFIG. 5 . - The disposition of one or the plurality of
convection control plates 42, particularly, the position of theconvection control plate 42 in the longitudinal axis direction C of thedisplacer 22 and a gap between theconvection control plates 42 may be variously set. For example, as shown inFIGS. 3A and 3B , one of twoconvection control plates 42 is positioned at an intermediate-temperature portion of thedisplacer 22, and the other thereof is positioned at a high-temperature portion of thedisplacer 22. In addition, as shown inFIGS. 2 and 4 , theconvection control plates 42 are arranged with equal gaps in the longitudinal axis direction C of thedisplacer 22. That is, the gaps between theconvection control plates 42 have the same width as each other in the longitudinal axis direction C. - However, the
convection control plates 42 may be disposed at locations different from those of the above-described embodiment. For example, theconvection control plates 42 may be disposed with unequal gaps. As shown inFIG. 5 , theconvection control plates 42 may be densely arranged on theexpansion space 28 side in the longitudinal axis direction C of thedisplacer 22. Accordingly, theconvection control plates 42 may be sparsely arranged on thegas space 36 side. For example, the minimum gap between theconvection control plates 42 in the longitudinal axis direction C is a half or less of the maximum gap therebetween. - At least three (five in
FIG. 5 )convection control plates 42 are accommodated in the internal space of thedisplacer 22. Theconvection control plates 42 includes a first plate which is positioned on theexpansion space 28 side, a second plate which is positioned at the intermediate portion, and a third plate which is positioned on thegas space 36 side. The three partition plates are disposed so as to be adjacent to each other in the longitudinal axis direction C. A first sub-chamber is formed between the first plate and the second plate, and a second sub-chamber is formed between the second plate and the third plate. - A width W1 of the first sub-chamber in the longitudinal axis direction C is narrower than a width W2 of the second sub-chamber. A gap between the first plate and another plate (or tip portion of the displacer 22) adjacent to the
expansion space 28 side may be the same as the width W1 of the first sub-chamber, or may be narrower than the width W1. A gap between the third plate and another plate (or base end portion of the displacer 22) adjacent to thegas space 36 side may be the same as the width W2 of the second sub-chamber, or may be wider than the width W2. - Alternatively, two
convection control plates 42 may be accommodated in the internal space of thedisplacer 22. Contrary to the embodiment shown inFIGS. 3A and 3B , one of the twoconvection control plates 42 may be positioned at the intermediate-temperature portion of thedisplacer 22, and the other thereof may be positioned at the low-temperature portion of thedisplacer 22. In this case, a first sub-chamber is formed between the firstconvection control plate 42 on the expansion-space 28 side and the tip portion of thedisplacer 22, and a second sub-chamber is formed between the first and secondconvection control plates 42. The width of the first sub-chamber in the longitudinal axis direction C is narrower than the width of the second sub-chamber. - According to the embodiment shown in
FIG. 5 , it is possible to densely divide the internal space of thedisplacer 22 on the expansion-space 28 side in the longitudinal axis direction C. In this way, it is possible to more effectively control convection in the low-temperature portion. Accordingly, it is possible to prevent freezing performance from deteriorating due to convecting of the gas inside thedisplacer 22. - Particularly, since heat capacity is small in the low-temperature portion, the low-temperature portion is easily subjected to adverse effects due to the convection such as a temperature increase due to inflow of a high-temperature gas. In addition, the temperature gradient of a low-temperature portion of the
regenerator 38 of the shownStirling cryocooler 10 in the longitudinal axis direction C is steeper than the temperature gradient of a high-temperature portion thereof (a temperature difference per unit length of the low-temperature end in the axial direction is greater than a temperature difference per unit length of the high-temperature end). Accordingly, the convection is easily generated in the low-temperature portion. Since theconvection control plates 42 are densely arranged on the low-temperature portion, and thus, it is possible to cope with the phenomenon in which the convection is easily generated in the low-temperature portion. - In general, convection is generated due to a posture of the
expander 13 of the Stirling cryocooler installed at the site, particularly, a horizontal disposition (installation in which the longitudinal axis direction C is the horizontal direction) of theexpander 13. According to the present embodiment, since deterioration in freezing performance due to convection is prevented, it is possible to install the Stirling cryocooler not only at a horizontal posture but also at an arbitrary posture. - In addition, similarly to the embodiment described with reference to
FIGS. 2 to 4 , in the embodiment shown inFIG. 5 , theconvection control plates 42 are positioned at the “positions corresponding to theregenerator 38.” During the reciprocation of thedisplacer 22, theconvection control plates 42 are always positioned at a columnar region which is surrounded by theregenerator 38. Alternatively, at least oneconvection control plate 42 may be deviated from the “position corresponding to theregenerator 38.” At least oneconvection control plate 42 may be positioned outside the columnar region in at least a portion of the reciprocation of thedisplacer 22. For example, theconvection control plate 42 which is disposed (that is, is positioned on the lowest temperature side) adjacent to the tip portion of thedisplacer 22 may be positioned at the “position corresponding to the low-temperature heat exchanger 39 or thecooling stage 29” when thedisplacer 22 is positioned at the bottom dead center. - The
displacer 22 becomes heavy as the number of theconvection control plates 42 increases. In a case where a decrease in weight of thedisplacer 22 is important, theconvection control plate 42 may be provided on only theexpansion space 28 side in thedisplacer 22. In this case, a relatively wide cavity is formed on thegas space 36 side in thedisplacer 22. The fillingmembers 43 may be accommodated in this cavity. - According to an embodiment, each of the
convection control plate 42 may have anopening 44. Theopening 44 of theconvection control plate 42 allows the first sub-chamber of the internal space of thedisplacer 22 adjacent to the first side of theconvection control plate 42 to communicate with the second sub-chamber of the internal space of thedisplacer 22 adjacent to the second side of theconvection control plate 42. Theopening 44 is a degassing hole which is provided so as to easily evacuate thedisplacer 22. For example, when theexpander 13 of the Stirling cryocooler is manufactured, the evacuation is performed so as to discharge air from the internal space of thedisplacer 22. After the evacuation is performed, the internal space of thedisplacer 22 is filled with the working gas of the Stirling cryocooler. In this way, theopening 44 may be provided on at least oneconvection control plate 42. - While the
opening 44 is advantageous in manufacturing of theexpander 13, theopening 44 may be a passage in convection of gas between the sub-chambers when theexpander 13 is used. Particularly, this phenomenon significantly occurs in a case where theopenings 44 in theconvection control plates 42 are linearly arranged. - Accordingly, as shown in
FIG. 6 , at least oneconvection control plate 42 may include aconvection control wall 46 that is provided on theopening 44. Eachconvection control plate 42 includes theopening 44 at the center thereof. Theconvection control wall 46 extends from the outer periphery of theopening 44 to both sides in the axial direction of theconvection control plate 42. Theconvection control wall 46 may extend from theopening 44 to one side in the axial direction. In this way, side walls surrounding theopening 44 discontinuously extend along the center axis of thedisplacer 22. In a case where theopening 44 is circular, theconvection control wall 46 is a cylinder. For example, an axial gap D between oneconvection control wall 46 and anotherconvection control wall 46 adjacent to the oneconvection control wall 46 is within a range of ¼ to ¾ of the axial gap W between theconvection control plates 42, and preferably, is ½ of the axial gap W. In this way, side walls are provided on theopening 44, and thus, it is possible to effectively control convection of gas between sub-chambers through theopening 44. - Instead of the
convection control wall 46, as shown inFIG. 7 ,adjacent openings 44 may be displaced relative to each other. That is, theopening 44 in oneconvection control plate 42 and theopening 44 in anotherconvection control plate 42 adjacent to the oneconvection control plate 42 may be positioned in locations different from each other in the plane intersecting the longitudinal axis of the displacer 22 (for example, the plane orthogonal to the longitudinal axis). Accordingly, it is possible to effectively control convection of gas between sub-chambers through theopening 44. Particularly, this off-set disposition of the openingportions 44 is effective for the case where theconvection control plates 42 are densely arranged in the axial direction as the embodiment described with reference toFIG. 5 . In addition, in some embodiments, a combination of the off-set disposition of the openingportions 44 and theconvection control walls 46 may be used. - As described above, according to the
Stirling cryocooler 10 of the present invention, it is possible to more appropriately control convection of gas in thedisplacer 22. Accordingly, it is possible to prevent deterioration in freezing performance due to convection of gas in thedisplacer 22. - It should be understood that the invention is not limited to the above-described embodiment, but may be modified into various forms on the basis of the spirit of the invention. Additionally, the modifications are included in the scope of the invention.
Claims (10)
1. A Stirling cryocooler comprising:
a displacer having a longitudinally extending gas-filled internal space;
an expander main body reciprocatably accommodating the displacer; and
at least one convection control plate for controlling gas convection to a minimum, accommodated in the displacer internal space, disposed along a line intersecting the displacer's longitudinal axis; wherein
the at least one convection control plate divides the displacer internal space into first and second sub-chambers, includes an opening through which the first sub-chamber communicates with the second sub-chamber, and includes a convection control wall provided on the opening.
2. The Stirling cryocooler according to claim 1 , further comprising:
a regenerator contained in the expander main body such as to be located outer peripherally along the displacer, in a predetermined cylindrical region having the longitudinal axis of the displacer as its center axis, wherein the at least one convection control plate is provided such as to be positioned, even when the displacer reciprocates, in a location corresponding to the predetermined cylindrical region in which the regenerator is positioned.
3. The Stirling cryocooler according to claim 1 , wherein the displacer accommodates a plurality of the convection control plates.
4. The Stirling cryocooler according to claim 1 , wherein the at least one convection control plate is in thermal contact with an inner wall of the displacer.
5. The Stirling cryocooler according to claim 1 , wherein:
the displacer further includes a gas-convection minimizing filling member; and
the at least one convection control plate retains the filling member.
6. The Stirling cryocooler according to claim 5 , wherein the filling member is composed of a synthetic resin polymer.
7. The Stirling cryocooler according to claim 5 , wherein the filling member is either fibrous or reticular.
8. The Stirling cryocooler according to claim 1 , wherein:
the expander main body is configured to form an expansion space between the displacer and the expander main body, and to form a compression space between the displacer and the expander main body on a side thereof longitudinally opposite from the expansion space in the axial orientation of the displacer; and
the displacer in its internal space accommodates a plurality of the convection control plates, densely arranged on the expansion-space side of the displacer and sparsely arranged on the compression-space side of the displacer along its longitudinal axis.
9. The Stirling cryocooler according to claim 1 , comprising at least two of the convection control plates, each having a sub-chamber communicating opening, wherein the sub-chamber communicating openings of adjacent convection control plates are displaced relative to each other in a plane intersecting the longitudinal axis of the displacer.
10. The Stirling cryocooler according to claim 1 , wherein the convection control wall extends outer peripherally from the opening in at least one sideward direction along the longitudinal axis of the displacer.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
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JP2014062411 | 2014-03-25 | ||
JP2014-062411 | 2014-03-25 | ||
PCT/JP2015/058178 WO2015146761A1 (en) | 2014-03-25 | 2015-03-19 | Stirling freezer |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
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PCT/JP2015/058178 Continuation WO2015146761A1 (en) | 2014-03-25 | 2015-03-19 | Stirling freezer |
Publications (1)
Publication Number | Publication Date |
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US20170010026A1 true US20170010026A1 (en) | 2017-01-12 |
Family
ID=54195282
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US15/270,017 Abandoned US20170010026A1 (en) | 2014-03-25 | 2016-09-20 | Stirling cryocooler |
Country Status (4)
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US (1) | US20170010026A1 (en) |
JP (1) | JP6490054B2 (en) |
CN (1) | CN106164605B (en) |
WO (1) | WO2015146761A1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US11209192B2 (en) * | 2019-07-29 | 2021-12-28 | Cryo Tech Ltd. | Cryogenic Stirling refrigerator with a pneumatic expander |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
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JP6951889B2 (en) * | 2017-07-07 | 2021-10-20 | 住友重機械工業株式会社 | Magnetic shield structure of cryogenic refrigerators and cryogenic refrigerators |
CN108168135A (en) * | 2018-02-21 | 2018-06-15 | 杨厚成 | A kind of acoustic energy refrigeration machine and its expansion piston |
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JPH09152214A (en) * | 1995-11-30 | 1997-06-10 | Sanyo Electric Co Ltd | Piston for external combustion engine |
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- 2015-03-19 JP JP2016510280A patent/JP6490054B2/en active Active
- 2015-03-19 WO PCT/JP2015/058178 patent/WO2015146761A1/en active Application Filing
- 2015-03-19 CN CN201580015949.1A patent/CN106164605B/en not_active Expired - Fee Related
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2016
- 2016-09-20 US US15/270,017 patent/US20170010026A1/en not_active Abandoned
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US4345437A (en) * | 1980-07-14 | 1982-08-24 | Mechanical Technology Incorporated | Stirling engine control system |
US4945726A (en) * | 1989-08-23 | 1990-08-07 | Sunpower, Inc. | Leaky gas spring valve for preventing piston overstroke in a free piston stirling engine |
US6475935B1 (en) * | 1999-07-09 | 2002-11-05 | Irie Kouken Co., Ltd | Regenerator and regenerative material used therein |
US20090217658A1 (en) * | 2008-02-28 | 2009-09-03 | Andreas Fiedler | Method for Centering Reciprocating Bodies and Structures Manufactured Therewith |
US8615993B2 (en) * | 2009-09-10 | 2013-12-31 | Global Cooling, Inc. | Bearing support system for free-piston stirling machines |
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US11209192B2 (en) * | 2019-07-29 | 2021-12-28 | Cryo Tech Ltd. | Cryogenic Stirling refrigerator with a pneumatic expander |
Also Published As
Publication number | Publication date |
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CN106164605B (en) | 2018-08-14 |
CN106164605A (en) | 2016-11-23 |
JP6490054B2 (en) | 2019-03-27 |
WO2015146761A1 (en) | 2015-10-01 |
JPWO2015146761A1 (en) | 2017-04-13 |
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