JP2013142479A - Cryogenic refrigerator and displacer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cryogenic refrigerator and a displacer capable of more effectively securing a sufficient substantial area for heat exchange.SOLUTION: A cryogenic refrigerator 1 includes: a displacer 2; a cylinder 4 for housing the displacer 2 so as to be movable in an axial direction, and forming an expansion space 3 between the cylinder and a low temperature end of the displacer 2; a clearance channel C formed between the displacer 2 and the cylinder 4 so as to allow a refrigerant gas to flow into the expansion space 3; and a cooling stage 5 positioned adjacently to the expansion space 3. The displacer 2 includes: a body part 2a; and a heat conducting part 2b constituted of a material having a higher heat conductivity than the body part 2a. The heat conducting part 2b faces the cooling stage 5 across the clearance channel C.

Description

  The present invention relates to a cryogenic refrigerator that uses a high-pressure refrigerant gas supplied from a compression device to generate Simon expansion to generate cryogenic cooling and a displacer used in the cryogenic refrigerator.

  There exists a thing of patent document 1 as a cryogenic refrigerator, for example. In this cryogenic refrigerator, while the displacer reciprocates inside the cylinder, the refrigerant gas in the expansion space is expanded by opening and closing the valve to generate cold. The refrigerant gas is supplied to and discharged from the expansion space through the clearance between the displacer and the cylinder. The cooling of the refrigerant gas generated in the expansion space causes the object to be cooled connected to the cooling stage to be frozen by exchanging heat between the cooling stage and the refrigerant gas positioned on the outer peripheral side of the clearance and expansion space.

JP 2011-17457 A

  However, in the technique described in Patent Document 1, heat exchange is performed between the gas passing through the clearance and the cooling stage located on the outer peripheral side of the clearance. Therefore, it is difficult to sufficiently secure a substantial heat exchange area. It is an object of the present invention to provide a cryogenic refrigerator and a displacer that can effectively ensure a substantial heat exchange area more effectively.

In order to solve the above problems, the cryogenic refrigerator according to the present invention is:
A displacer,
A cylinder that accommodates the displacer movably in the axial direction and forms an expansion space between the displacer and a low temperature end;
A clearance channel formed between the displacer and the cylinder, for circulating a refrigerant gas into the expansion space;
A cooling stage located adjacent to the expansion space,
The displacer includes a main body part and a heat conduction part made of a material having a higher thermal conductivity than the main body part,
The heat conducting part is opposed to the cooling stage via the clearance flow path.

  Here, the thermal conduction part may have a lower linear expansion coefficient than the main body part, and the thermal conduction part has an overlapping part overlapping with the main body part in a stroke direction of the displacer, The part may have an overlapped part corresponding to the overlapping part. Moreover, the said heat conductive part is good also as having a bottomed cylinder shape, and the said heat conductive part is good also as having a slit which becomes a cylinder shape and becomes discontinuous in the circumferential direction.

  Further, the overlapping portion and the overlapped portion may constitute a screw portion, the overlapping portion has a first hole portion, and the overlapped portion corresponds to the first hole portion. The main body part and the heat conducting part may be connected by an insertion member inserted into both the second hole part and the first hole part. In addition, the heat conducting part may be copper, aluminum, or stainless steel.

In order to solve the above problems, the displacer according to the present invention is:
It is a displacer having a low temperature end, and includes a main body part and a heat conduction part which is located on the low temperature end side and made of a material having a higher thermal conductivity than the main body part. Here, the outer diameter of the heat conducting part may be smaller than the outer diameter of the main body part at room temperature.

  According to the cryogenic refrigerator and the displacer of the present invention, heat enters the heat conducting part from the cooling stage through the clearance channel on the outer peripheral side of the displacer, and enters the refrigerant gas entering the clearance channel by expansion. On the other hand, the heat conduction part carries heat, reduces the temperature difference of the cooling stage, increases the substantial heat exchange area contributing to heat exchange, and increases the heat exchange efficiency.

It is a schematic diagram shown about one Embodiment of the cryogenic refrigerator 1 and the displacer 2 of Example 1 which concern on this invention. It is a schematic diagram shown about one Embodiment of the cryogenic refrigerator 2 and the displacer 22 of Example 2 which concern on this invention. FIG. 10 is a schematic diagram showing a modification of the heat conducting section 22b of the cryogenic refrigerator 1 and the displacer 22 of the second embodiment. FIG. 10 is a schematic diagram showing a modification of the heat conducting section 22b of the cryogenic refrigerator 1 and the displacer 22 of the second embodiment. It is a schematic diagram shown about one Embodiment of the two-stage cryogenic refrigerator 31 of Example 3 which concerns on this invention.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings.

  The cryogenic refrigerator 1 of the first embodiment is, for example, a Gifford McMahon (GM) type refrigerator that uses helium gas as a refrigerant gas. The cryogenic refrigerator 1 includes a displacer 2, a cylinder 4 that forms a clearance C and an expansion space 3 between the displacer 2, and a bottomed cylindrical cooling stage that is positioned adjacent to and enclosing the expansion space 3. 5, the displacer 2 includes a main body 2a and a heat conducting portion 2b made of a material having a higher thermal conductivity than the main body 2a. The heat conducting portion 2b provides clearance C (clearance flow path) to the cooling stage 5. Opposite through. The cooling stage 5 is made of, for example, copper, aluminum, stainless steel or the like.

  Here, it is assumed that the heat conducting portion 2b has a lower linear expansion coefficient than the main body portion 2a, and the heat conducting portion 2b has an overlapping portion 2ba that overlaps the main body portion 2a in the stroke direction of the displacer 2, and the main body portion 2a. Has an overlapped portion 2ab corresponding to the overlap portion 2ba. In the first embodiment, the heat conducting portion 2b has a two-stage cylindrical shape, and the overlapping portion 2ba is formed in a second-stage cylindrical shape as viewed from the bottom in FIG.

  Furthermore, the overlapping part 2ba has a first hole part 2bah, and the overlapped part 2ab has a second hole part 2abh corresponding to the first hole part 2bah. The main body portion 2a and the heat conducting portion 2b are connected by a press-fit pin 6 (insertion portion) that is press-fitted and inserted into both the second hole portion 2abh and the first hole portion 2bah. The press-fit pins 6 are provided at appropriate locations in the circumferential direction. For the heat conduction part 2b, for example, a material having a higher thermal conductivity than at least the main body part 2a, such as copper, aluminum, or stainless steel, is used. The press-fit pin 6 may be either bakelite (phenol with cloth) or stainless steel. The overlapping portion 2ba is fixed to the overlapped portion 2ab by press-fitting the press-fit pin 6 into the first hole portion 2bah and the second hole portion 2abh.

  The cylinder 4 accommodates the displacer 2 so as to be reciprocally movable in the longitudinal direction. For example, stainless steel is used for the cylinder 4 from the viewpoints of strength, thermal conductivity, helium blocking ability, and the like.

  A scotch yoke mechanism (not shown) that reciprocates the displacer 2 is provided at the high temperature end of the displacer 2, and the displacer 2 reciprocates along the axial direction of the cylinder 4.

  The displacer 2 has a cylindrical outer peripheral surface, and the inside of the displacer 2 is filled with a cold storage material. The internal volume of the displacer 2 constitutes the regenerator 7. An upper rectifier 9 that rectifies the flow of helium gas is provided on the upper end side of the regenerator 7, that is, the room temperature chamber 8 side, and a lower rectifier 10 is provided on the lower end side of the regenerator 7.

  An opening 11 through which refrigerant gas flows from the room temperature chamber 8 to the displacer 2 is formed at the high temperature end of the displacer 2. The room temperature chamber 8 is a space formed by the high temperature end of the cylinder 4 and the displacer 2, and the volume changes as the displacer 2 reciprocates.

  The room temperature chamber 8 is connected to a common supply / exhaust pipe among the pipes connecting the intake and exhaust systems including the compressor 12, the supply valve 13, and the return valve 14. Further, a seal 15 is mounted between the portion from the high temperature end of the displacer 2 and the cylinder 4.

  At the low temperature end of the displacer 2, an opening 16 for introducing the refrigerant gas into the expansion space 3 through the clearance C is formed. The expansion space 3 is a space formed by the cylinder 4 and the displacer 2, and the volume changes as the displacer 2 reciprocates. A cooling stage 5 that is thermally connected to the object to be cooled is disposed at a position corresponding to the expansion space 3 on the outer periphery and bottom of the cylinder 4, and the cooling stage 5 is cooled by the refrigerant gas passing through the clearance C.

  For the main body 2a of the displacer 2, for example, bakelite (phenol in cloth) or the like is used from the viewpoint of specific gravity, strength, thermal conductivity, and the like. The cold storage material is constituted by, for example, a wire mesh. FIG. 1 shows a state where the cryogenic refrigerator 1 is in operation. For this reason, the outer diameters of both of the body portions 2a become the same due to a slight contraction of the main body portion 2a due to the low temperature. However, at normal temperature, the outer diameter of the heat conducting portion 2b is slightly smaller than the outer diameter of the main body portion 2a. .

  Next, the operation of the refrigerator will be described. At a certain point in the refrigerant gas supply process, the displacer 2 is located at the bottom dead center of the cylinder 4. When the supply valve 13 is opened at the same time or at a slightly shifted timing, high-pressure helium gas is supplied into the cylinder 4 from the supply / discharge common pipe via the supply valve 13, and the opening 11 located above the displacer 2. To the regenerator 7 inside the displacer 2. The high-pressure helium gas that has flowed into the regenerator 7 is supplied to the expansion space 3 through the opening 16 and the clearance C located at the lower portion of the displacer 2 while being cooled by the regenerator material.

  In this way, the expansion space 3 is filled with high-pressure helium gas, and the supply valve 13 is closed. At this time, the displacer 2 is located at the top dead center in the cylinder 4. When the return valve 14 is opened at the same time or slightly shifted timing, the refrigerant gas in the expansion space 3 is decompressed and expanded. The helium gas in the expansion space 3 that has become low temperature due to expansion absorbs the heat of the cooling stage 5 through the clearance C.

  The displacer 2 moves toward the bottom dead center, and the volume of the expansion space 3 decreases. The helium gas in the expansion space 3 is returned to the suction side of the compressor 12 through the clearance C, the opening 16, the regenerator 7, and the opening 11. At that time, the regenerator material is cooled by the refrigerant gas. This process is defined as one cycle, and the refrigerator cools the cooling stage 5 by repeating this cooling cycle.

  In the cryogenic refrigerator 1 and the displacer 2 according to the first embodiment, the heat conducting unit 2b always faces the cooling stage 5 via the clearance C. The heat entering from the cooling stage enters the heat conducting portion 2b via the helium gas present in the clearance C. Therefore, when the low-temperature helium gas generated in the expansion space 3 passes through the clearance C, in addition to the heat exchange between the helium gas and the cooling stage 5, the heat between the helium gas and the heat conducting unit 2b. Exchanges are also made. Thereby, the substantial heat exchange area between the cooling stage 5 and the low-temperature helium gas can be increased.

  Further, the heat that has entered the heat conducting unit 2 b is further transmitted toward the expansion space 3 through the inside of the heat conducting unit 2 b. Therefore, if the heat conduction part 2b is configured so that the heat conduction part 2b and the low-temperature helium gas in the expansion space 3 are in contact with each other, the heat exchange efficiency can be further improved.

  On the other hand, in a conventional displacer in which the heat conducting portion 2b is not provided, that is, the portion corresponding to the heat conducting portion 2b is made of bakelite, the heat exchange between helium gas and bakelite is very small and substantially There is no heat exchange. Therefore, when the low-temperature helium gas generated in the expansion space 3 passes through the clearance C, it is performed only by heat exchange between the helium gas and the cooling stage 5.

  As described above, according to the cryogenic refrigerator 1 and the displacer 2 of the first embodiment, compared to the conventional displacer, the heat conduction part 2b can also contribute to heat exchange more effectively. The exchange area can be increased. Further, the heat exchange efficiency can be further improved by the flow of heat generated inside the heat conducting portion 2b described above. That is, the temperature difference in the vertical direction of the cooling stage 5 in FIG. 1 can also be reduced, and in particular, the temperature difference when the object to be cooled is installed below the cooling stage 5 can be reduced.

  In addition, when bakelite is used in a portion corresponding to the heat exchange unit 2b as in the case of a conventional displacer, the bakelite has a relatively high linear expansion coefficient. There is a risk of coming off. On the other hand. In the cryogenic refrigerator 1 and the displacer 2 of the first embodiment, an overlapping portion 2ba having a larger linear expansion coefficient than the main body portion 2a is disposed on the inner peripheral side of the overlapped portion 2ab of the main body portion 2a. Therefore, when the overlapped portion 2ab of the main body portion 2a is cooled and contracts, a force that tightens the overlapped portion 2ba of the heat conducting portion 2b works and it is possible to prevent the overlapped portion 2ba from coming off.

  Moreover, according to the cryogenic refrigerator 1 and the displacer 2 of the first embodiment, the heat conduction part 2b also contributes to the heat exchange, thereby increasing the substantial heat exchange area. Therefore, it is possible to obtain a desired refrigeration capacity even if the length of the cooling stage 5 and the clearance C in the axial direction (displacer moving direction) is made shorter than that of the conventional displacer. Thereby, the channel resistance and pressure loss in the clearance C can be reduced, and the refrigeration efficiency of the refrigerator can be increased. In addition, reducing the volume of the clearance C leads to a reduction in dead volume that does not contribute to the occurrence of cold. Thereby, it can also be expected to suppress a reduction in the pressure difference between the high pressure and the low pressure in one cycle due to the dead volume.

  The overlapping portion 2ba and the overlapped portion 2ab may constitute a screw portion and be connected by screwing. According to this, desorption | detachment | attachment with the main-body part 2a and the heat conductive part 2b can be made easier. Even in this case, when the overlapped portion 2ab of the main body portion 2a is cooled and contracted, a force that tightens the overlapped portion 2ba of the heat conducting portion 2b works to further prevent the overlapping portion 2ba from coming off. it can.

  In the first embodiment described above, the heat conducting portion 2b has a cylindrical shape, but may have a cylindrical shape as described below. FIG. 2 is a schematic diagram showing the cryogenic refrigerator 21 and the displacer 22 of the second embodiment. In addition, about the component which is common in Example 1 of FIG. 1, the same code | symbol is attached | subjected and a difference is mainly demonstrated.

  In the displacer 22 of the second embodiment, the heat conducting portion 22b has a cylindrical shape, and the entire heat conducting portion 22b forms an overlapping portion 22ba that overlaps the main body portion 22a in the stroke direction. The portion located on the low temperature side (lower side in FIG. 2) of the opening 16 of the main body 22a has a smaller diameter than the portion located on the high temperature side (upper side) of the opening 16. This small diameter portion constitutes an overlapped portion 22ab corresponding to the overlap portion 22ba.

  The overlapping portion 22ba has a first hole portion 22bah, and the overlapped portion 22ab has a second hole portion 22abh corresponding to the first hole portion 22bah. The main body 2a and the heat exchange part 2b are connected by a press-fit pin 26 (insertion part) that is press-fitted and inserted into both the second hole 22abh and the first hole 22bah. As in the first embodiment, a material having a higher thermal conductivity than at least the main body portion 2a is used for the heat conduction portion 22b, such as copper, aluminum, and stainless steel. The press-fit pin 26 may be either bakelite (phenol with cloth) or stainless steel. By inserting the press-fit pin 26 into the first hole portion 22bah and the second hole portion 22abh, the overlapping portion 22ba is fixed to the overlapping portion 22ab.

  Also by the cryogenic refrigerator 21 and the displacer 22 of the second embodiment, the heat exchange area can be increased by contributing the heat conduction part 22b to the heat exchange as in the first embodiment. In addition, in the second embodiment, as compared with the first embodiment, the heat conducting portion 22b is disposed only on the outer peripheral side of the displacer 22 that contributes to heat exchange. Therefore, compared with Example 1, the volume and mass of the heat conduction part 22b can be made small, and the mass of the whole displacer 22 which is a movable part can be made small.

  In the presence of a magnetic field, when the heat conducting portion 22b, which is a conductor, reciprocates, an eddy current is generated, thereby generating heat, that is, copper loss. In the form of the present Example 2, since the volume of the heat conduction part 22b is comparatively small, generation | occurrence | production of a copper loss can also be suppressed according to it.

  In addition, since the heat conducting portion 22b can be made of standard pipe material, the cost can be reduced as compared with the first embodiment.

  As described above, it can be expected to suppress the occurrence of copper loss by reducing the volume of the conductor, but the occurrence of copper loss can also be suppressed by suppressing the generation of eddy current by devising the shape. For example, FIG. 3 is obtained by providing slits S that are discontinuous in the circumferential direction in the cylindrical heat conducting portion 22b shown in FIG. According to such a configuration, it is possible to prevent an eddy current from continuing to flow particularly in the circumferential direction, so that the occurrence of copper loss can be more effectively suppressed.

  Moreover, as shown in FIG. 4, the heat conductive part 22b can also be made into a bottomed cylindrical shape. By making the heat conduction part 22b into a bottomed cylindrical shape, the heat that has entered the heat exchange part 2b from the cooling stage 5 is heat exchanged between the bottom part of the heat conduction part 22b and the expansion space. Thereby, compared with the refrigerator of FIG. 2, cooling efficiency can be improved.

  In Examples 1 and 2 described above, the refrigerator is a single-stage type, but can be applied to a two-stage type as described below. FIG. 5 is a schematic diagram showing the cryogenic refrigerator 31 and the displacer 32 of the third embodiment.

  The cryogenic refrigerator 31 of the third embodiment is, for example, a Gifford McMahon (GM) type refrigerator that uses helium gas as the refrigerant gas, as in the first and second embodiments. As shown in FIG. 5, the cryogenic refrigerator 31 includes a first displacer 32 and a second displacer 36 connected to the first displacer 32 in the longitudinal direction. For example, as shown in FIG. 5, the first displacer 32 and the second displacer are connected via a pin 33, a connector 34, and a pin 35.

  The first cylinder 37 and the second cylinder 38 are integrally formed, and the low temperature end of the first cylinder 37 and the high temperature end of the second cylinder 38 are connected at the bottom of the first cylinder 37. The second cylinder 38 is formed coaxially with the first cylinder 37 and is a cylindrical member having a smaller diameter than the first cylinder 37. The first cylinder 37 accommodates the first displacer 32 so as to be reciprocally movable in the longitudinal direction, and the second cylinder 38 accommodates the second displacer 36 so as to be reciprocally movable in the longitudinal direction.

  For example, stainless steel is used for the first cylinder 37 and the second cylinder 38 in consideration of strength, thermal conductivity, helium blocking ability, and the like. The second displacer 36 forms a film of a wear-resistant resin such as a fluororesin on the outer peripheral surface of a metal cylinder such as stainless steel.

  A high temperature end of the first cylinder 37 is provided with a scotch yoke mechanism (not shown) for reciprocatingly driving the first displacer 32 and the second displacer 36. The first displacer 32 and the second displacer 36 are respectively the first cylinder 37, It reciprocates along the second cylinder 38.

  The first displacer 32 has a cylindrical outer peripheral surface, and the first displacer 32 is filled with a first cool storage material. The internal volume of the first displacer 32 functions as the first regenerator 39. A rectifier 40 is installed above the first regenerator 39, and a rectifier 41 is installed below the first regenerator 39. A first opening 42 through which refrigerant gas flows from the room temperature chamber 39 to the first displacer 32 is formed at the high temperature end of the first displacer 32. The room temperature chamber 39 is a space formed by the first cylinder 37 and the high temperature end of the first displacer 32, and the volume changes as the first displacer 32 reciprocates. The room temperature chamber 39 is connected to a common supply / exhaust pipe among the pipes connecting the intake and exhaust systems including the compressor 43, the supply valve 44, and the return valve 45. Further, a seal 46 is mounted between the portion of the first displacer 32 from the high temperature end and the first cylinder 37.

  At the low temperature end of the first displacer 32, a second opening 48 for introducing the refrigerant gas into the first expansion space 47 via the first clearance C1 is formed. The first expansion space 47 is a space formed by the first cylinder 37 and the first displacer 32, and the volume changes as the first displacer 32 reciprocates. A first cooling stage 49 that is thermally connected to an object to be cooled (not shown) is disposed at a position corresponding to the first expansion space 47 on the outer periphery of the first cylinder 37. The first cooling stage 49 has a first clearance. Cooled by the refrigerant gas passing through C1.

  The second displacer 36 has a cylindrical outer peripheral surface, and the second displacer 36 is filled with a second cool storage material. The internal volume of the second displacer 36 constitutes the second regenerator 50. The first expansion space 47 and the high temperature end of the second displacer 36 are communicated with each other through a communication path (not shown). Refrigerant gas flows from the first expansion space 47 to the second regenerator 50 through this communication path.

  At the low temperature end of the second displacer 36, a third opening 52 for allowing the refrigerant gas to flow through the second expansion space 51 via the second clearance C2 is formed. The second expansion space 51 is a space formed by the second cylinder 38 and the second displacer 36, and the volume changes as the second displacer 36 reciprocates. The second clearance C2 is formed by the low temperature end portion of the second cylinder 38 and the second displacer 36. The second clearance C2 is between the second displacer 36 and the second cylinder 38 having a spiral groove, which will be described later. It is configured to be larger than the clearance.

  A second cooling stage 53 thermally connected to the object to be cooled is disposed at a position corresponding to the second expansion space 51 on the outer periphery of the second cylinder 38, and the second cooling stage 53 has a second clearance C2. Cooled by the passing refrigerant gas.

  For the first displacer 32, for example, phenol with cloth is used from the viewpoint of specific gravity, strength, thermal conductivity, and the like. A 1st cool storage material is comprised, for example with a wire mesh. Moreover, the 2nd cool storage material is comprised, for example by pinching cool storage materials, such as a lead ball, with a felt and a metal net in an axial direction.

  Further, on the outer peripheral surface of the second displacer 36, there is formed a spiral groove 53 that has a starting end that communicates with the second expansion space 51 via the second clearance C2 and extends spirally toward the first expansion space 47. .

  Also in the third embodiment, both the first displacer 32 and the second displacer 36 include heat transfer portions 32b and 36b at the cold end. Both have a two-stage cylindrical shape. The heat transfer part 32 b is fixed to the main body part 32 a by a press-fit pin 54, and the heat transfer part 36 b is fixed to the main body part 36 a by a press-fit pin 55. Also in the third embodiment, for the reasons described in the first and second embodiments, the substantial heat exchange area can be increased in both the first cooling stage 49 and the second cooling stage 53, and the cooling efficiency can be increased.

  Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and substitutions are made to the above-described embodiments without departing from the scope of the present invention. be able to.

  For example, in the cryogenic refrigerator described above, the case where the number of stages is one and two is shown, but the number of stages can be appropriately selected to be three or the like. Moreover, although embodiment demonstrated the example whose cryogenic refrigerator is a GM refrigerator, it is not restricted to this. For example, the present invention can be applied to any refrigerator equipped with a displacer, such as a Stirling refrigerator or a Solvay refrigerator.

  The present invention increases the heat exchange efficiency by effectively increasing the heat exchange area that substantially contributes to the heat exchange through the side clearance without increasing the length of the cooling stage in the axial direction. Thus, the efficiency of freezing can be increased. Therefore, it can be applied to various cryogenic refrigerators.

DESCRIPTION OF SYMBOLS 1 Cryogenic refrigerator 2 Displacer 2a Main-body part 2ab Overlapping part 2abh 2nd hole 2b Heat conduction part 2ba Overlapping part 2bah 1st hole 3 Expansion space 4 Cylinder 5 Cooling stage 6 Press-fit pin (insertion part)
7 Regenerator 8 Room temperature chamber 9 Rectifier 10 Rectifier 11 Opening 12 Compressor 13 Supply valve 14 Return valve 15 Seal 16 Opening

Claims (10)

A displacer,
A cylinder that accommodates the displacer movably in the axial direction and forms an expansion space between the displacer and a low temperature end;
A clearance channel formed between the displacer and the cylinder, for circulating a refrigerant gas into the expansion space;
A cooling stage located adjacent to the expansion space,
The displacer includes a main body part and a heat conduction part made of a material having a higher thermal conductivity than the main body part,
The cryogenic refrigerator, wherein the heat conducting portion faces the cooling stage via the clearance flow path.   The cryogenic refrigerator according to claim 1, wherein the heat conducting unit has a lower linear expansion coefficient than the main body.   The said heat conduction part has the duplication part which overlaps with the stroke direction of the said displacer with respect to the said main-body part, The said main-body part has a to-be-duplicated part corresponding to the said duplication part, The cryogenic refrigerator described in 1.   The cryogenic refrigerator according to claim 3, wherein the heat conducting portion has a bottomed cylindrical shape.   The cryogenic refrigerator according to any one of claims 1 to 3, wherein the heat conducting portion has a cylindrical shape and has slits that are discontinuous in the circumferential direction.   The cryogenic refrigerator according to claim 4 or 5, wherein the overlapping portion and the overlapped portion constitute a screw portion.   The overlapping part has a first hole part, the overlapped part has a second hole part corresponding to the first hole part, and the main body part and the heat conducting part are the second hole part and The cryogenic refrigerator according to any one of claims 3 to 6, wherein the cryogenic refrigerator is connected by an insertion member inserted into both of the first hole portions.   The cryogenic refrigerator according to any one of claims 1 to 7, wherein the heat conducting unit is one of copper, aluminum, and stainless steel.   A displacer having a low temperature end, comprising a main body part and a heat conduction part which is located on the low temperature end side and is made of a material having a higher thermal conductivity than the main body part.   The displacer according to claim 9, wherein an outer diameter of the heat conducting portion is smaller than an outer diameter of the main body portion at room temperature.

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