Cryogenic Equipment

Abstract

To improve a guide structure for guiding movements of a cold head with respect to a cold head storage sleeve.SOLUTION: A cryogenic device 10 comprises a sleeve 50, a cold head 22 and a guide structure 70. The guide structure 70 includes: a guide part which provided in a sleeve side flange 52; and a guided part which is provided in a cold head side flange 26 and guided by the guide part. A clearance in a lateral direction vertical to a movement direction of the cold head side flange 26 is provided between the guide part and the guided part. The clearance of the guide structure 70 is determined so as to prevent contacts of a single-step cooling stage 30, a double-step cooling stage 34 and the sleeve 50 caused by an inclination of the guided part with respect to the guide part, the inclination occurring while the single-step cooling stage 30 and the double-step cooling stage 34 of the cold head 22 are respectively separated from a single-step heat transfer stage 56 and a double-step heat transfer stage 60 of the sleeve 50.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to cryogenic devices. [Background technology]

[0002] It is known that a mounting structure with a sleeve is used to mount a cryogenic refrigerator in a cryogenic vacuum vessel such as a cryostat. An object to be cooled, such as a superconducting coil, is accommodated in the cryogenic vacuum vessel and is in thermal contact with an end of the sleeve. The cold head of the cryogenic refrigerator is mounted inside the sleeve and cools the object to be cooled via the sleeve.

[0003] During long-term operation of the cryogenic refrigerator, periodic maintenance of the cryogenic refrigerator may be required. An operator can slightly lift the cold head from the sleeve, thereby releasing the thermal contact between the cold head and the sleeve, and perform maintenance on the cold head. The cold head is heated to a temperature suitable for maintenance work, such as room temperature, and is re-cooled after the work is completed. By releasing the thermal contact, the object to be cooled can be kept at a low temperature. There is no need to heat and re-cool the object to be cooled for maintenance of the cryogenic refrigerator. Therefore, the time required for re-cooling the object to be cooled can be shortened compared to when the object to be cooled is heated to room temperature together with the cryogenic refrigerator and maintenance is performed on the cryogenic refrigerator, and the time required for maintenance can be shortened. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2005-123313 A Summary of the Invention [Problem to be solved by the invention]

[0005] The inventors of the present invention have intensively studied the above-mentioned cryogenic device and have come to recognize the following problems. A guide structure is provided to guide the movement of the cold head relative to the cold head receiving sleeve. The guide structure has some clearance between a guide portion and a guided portion. When the cold head is lifted from the sleeve to release thermal contact, this clearance can cause the cold head to tilt relative to the sleeve. Due to the tilt, the cooling stage at the end of the cold head can come into contact with the sleeve, which may be undesirable in some cases. In addition, when the cold head is pressed against the sleeve, an unbalanced load can act on the cold head. Deformation of the cold head that can occur due to the unbalanced load can affect the flow of refrigerant gas in the cold head, reducing the refrigeration capacity of the cold head.

[0006] SUMMARY OF THE PRESENT EMBODIMENT One exemplary object of an aspect of the present invention is to provide an improvement to a guide structure that guides movement of a coldhead relative to a coldhead receiving sleeve. [Means for solving the problem]

[0007] According to an aspect of the present invention, a cryogenic device includes a cold head accommodating sleeve including a sleeve flange, a first heat transfer stage, and a second heat transfer stage, a cold head flange, a first cooling stage, and a second cooling stage cooled to a lower temperature than the first cooling stage, the first cooling stage and the second cooling stage being provided with a cold head that comes into contact with or separates from the first heat transfer stage and the second heat transfer stage by movement of the cold head flange relative to the sleeve flange, and a guide structure that guides movement of the cold head flange relative to the sleeve flange. The guide structure includes a guide portion provided on the sleeve flange and a guided portion provided on the cold head flange and guided by the guide portion, and has a lateral clearance between the guide portion and the guided portion perpendicular to the movement direction of the cold head flange. The clearance of the guide structure is determined so as to prevent contact between the first and second cooling stages and the cold head accommodating sleeve due to inclination of the guided portion relative to the guide portion that occurs when the first and second cooling stages are separated from the first and second heat transfer stages, respectively.

[0008] According to an aspect of the present invention, a cryogenic device includes a cold head housing sleeve including a sleeve flange, a first heat transfer stage, and a second heat transfer stage, a cold head flange, a first cooling stage, and a second cooling stage cooled to a lower temperature than the first cooling stage, the first cooling stage and the second cooling stage being brought into contact with or separated from the first heat transfer stage and the second heat transfer stage by movement of the cold head flange relative to the sleeve flange, and a guide structure for guiding movement of the cold head flange relative to the sleeve flange. The guide structure includes a guide portion provided on the sleeve flange and a guided portion provided on the cold head flange and guided by the guide portion, and has a lateral clearance between the guide portion and the guided portion perpendicular to the movement direction of the cold head flange. The cold head includes a two-stage cylinder connecting the first cooling stage to the second cooling stage, and a two-stage displacer accommodated in the two-stage cylinder so as to be movable relative to the two-stage cylinder. The clearance of the guide structure is determined so that the lateral gap between the second-stage cylinder and the second-stage displacer does not exceed the allowable upper limit of the gap under the unbalanced load acting on the cold head side flange when the second-stage cooling stage is pressed against the second-stage heat transfer stage. Effect of the Invention

[0009] Advantageous Effects of Invention The present invention provides an improvement to the guide structure that guides movement of the coldhead relative to the coldhead receiving sleeve. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing a schematic diagram of a cryogenic device according to an embodiment; [Diagram 2] FIG. 1 is a diagram showing a schematic diagram of a cryogenic device according to an embodiment; [Diagram 3] FIG. 2 is a top view illustrating a schematic diagram of a cold head of a cryogenic refrigerator according to an embodiment. [Figure 4]FIG. 2 is a diagram illustrating a guide structure provided in a cryogenic device according to an embodiment. [Diagram 5] 11A and 11B are schematic diagrams illustrating an inclination that may occur in a guide structure according to the embodiment. [Figure 6] 6(a) and 6(b) are schematic diagrams illustrating an exemplary configuration of a two-stage cooling stage of a cold head according to an embodiment. [Figure 7] 7(a) and 7(b) are schematic diagrams showing an exemplary shape of a first cooling stage of a cold head according to an embodiment. [Figure 8] 5 is a schematic diagram showing an unbalanced load that may act on the cold head in the embodiment. FIG. [Figure 9] 9(a) and 9(b) are diagrams illustrating a schematic diagram of another example of a guide structure according to the embodiment. [Figure 10] 10(a) and 10(b) are diagrams illustrating a schematic diagram of another example of a guide structure according to an embodiment. [Figure 11] 11A and 11B are diagrams illustrating another example of a guide structure according to an embodiment of the present invention. [Figure 12] 11A and 11B are diagrams illustrating another example of a guide structure according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the embodiments for carrying out the present invention will be described in detail with reference to the drawings. In the description and drawings, the same or equivalent components, members, and processes are given the same reference numerals, and duplicated descriptions are omitted as appropriate. The scale and shape of each part shown in the drawings are set for convenience in order to facilitate the description, and are not to be interpreted as being limiting unless otherwise specified. The embodiments are merely examples, and do not limit the scope of the present invention in any way. All features and combinations thereof described in the embodiments are not necessarily essential to the invention.

[0012] Fig. 1 and Fig. 2 are schematic diagrams showing a cryogenic device according to an embodiment. Fig. 1 shows a state in which an object to be cooled in the cryogenic device is thermally coupled to a cold head of a cryogenic refrigerator provided in the cryogenic device, and Fig. 2 shows a state in which the cold head and the object to be cooled are thermally released due to movement of the cold head. Fig. 3 is a top view schematic diagram showing the cold head of the cryogenic refrigerator according to an embodiment. Fig. 4 is a schematic diagram showing a guide structure provided in the cryogenic device according to an embodiment.

[0013] The cryogenic device 10 is installed in a vacuum vessel 12, also called a cryostat, and is used as a cooling source that provides a cryogenic environment within the vacuum vessel 12. A cooled object 14 that is cooled by the cryogenic device 10 is placed within the vacuum vessel 12. The cryogenic device 10, together with the vacuum vessel 12 and the cooled object 14, may constitute a part of cryogenic application equipment. The cryogenic application equipment may be, for example, a single crystal pulling device, an NMR system, an MRI system, an accelerator such as a cyclotron, a high-energy physics system such as a nuclear fusion system, or other high magnetic field application equipment, in which case the cooled object 14 may be a superconducting coil.

[0014] The cryogenic device 10 includes a cryogenic refrigerator 20 having a cold head 22 and a compressor 24, and a cold head accommodation sleeve (hereinafter also simply referred to as a sleeve) 50. The sleeve 50 is installed in the vacuum vessel 12 so as to be combined with the vacuum vessel 12 to define a vacuum region 13 within the vacuum vessel 12. The cold head 22 is attached to the sleeve 50 while being inserted into the sleeve 50. An airtight region 18 isolated from an ambient environment 16 is formed between the cold head 22 and the sleeve 50. The ambient environment 16 is, for example, an atmospheric pressure environment at room temperature. The airtight region 18 may be evacuated to a vacuum.

[0015] The compressor 24 of the cryogenic refrigerator 20 is provided to circulate a working gas (e.g., helium gas) through the cryogenic refrigerator 20. The compressor 24 is disposed in the ambient environment 16. The compressor 24 is configured to supply a high-pressure working gas to the cold head 22, and to recover from the cold head 22 the low-pressure working gas that has been decompressed by adiabatic expansion in an expansion space within the cold head 22, and to re-pressurize the working gas.

[0016] The cryogenic refrigerator 20 is, for example, a two-stage Gifford-McMahon (GM) refrigerator. Thus, the cold head 22 includes a cold head flange 26, a first stage cylinder 28, a first stage cooling stage 30, a second stage cylinder 32, and a second stage cooling stage 34. These components of the cold head 22 are arranged in this order along the central axis of the cold head 22. The cold head flange 26 is disposed in the ambient environment 16, and the first stage cylinder 28, the first stage cooling stage 30, the second stage cylinder 32, and the second stage cooling stage 34 are disposed in the airtight region 18.

[0017] The first-stage cylinder 28 connects the cold head side flange 26 to the first-stage cooling stage 30, and the second-stage cylinder 32 connects the first-stage cooling stage 30 to the second-stage cooling stage 34. Typically, the first-stage cylinder 28 and the second-stage cylinder 32 are hollow cylindrical members extending coaxially with the central axis of the cold head 22, and the first-stage cylinder 28 has a larger diameter than the second-stage cylinder 32. The cold head side flange 26, the first-stage cylinder 28, and the second-stage cylinder 32 are formed of a metal such as stainless steel.

[0018] The first-stage cooling stage 30 is fixed to an end of the first-stage cylinder 28 on the axially opposite side to the cold head side flange 26, and its axial length is shorter than that of the first-stage cylinder 28. The second-stage cooling stage 34 is fixed to an end of the second-stage cylinder 32 on the axially opposite side to the first-stage cooling stage 30, and its axial length is shorter than that of the second-stage cylinder 32. The first-stage cooling stage 30 and the second-stage cooling stage 34 typically have a cylindrical outer shape coaxial with the central axis of the cold head 22, and the first-stage cooling stage 30 has a larger diameter than the second-stage cooling stage 34. The first-stage cooling stage 30 and the second-stage cooling stage 34 are formed of a highly thermally conductive metal such as copper (e.g., pure copper) or other thermally conductive material. The thermal conductivity of the thermally conductive material forming the cooling stage is higher than that of the material forming the cylinder.

[0019] The cold head 22 further includes a single-stage displacer 36 and a two-stage displacer 38 connected to each other at their ends, and a drive unit 40 for axially driving these displacers.

[0020] The first-stage displacer 36 and the second-stage displacer 38 extend coaxially with the central axis of the cold head 22, and are arranged axially movably in the first-stage cylinder 28 and the second-stage cylinder 32, respectively. A regenerator material is built in the first-stage displacer 36 and the second-stage displacer 38. A first-stage expansion space for the working gas is formed between the first-stage displacer 36 and the first-stage cooling stage 30 in the first-stage cylinder 28, and a two-stage expansion space for the working gas is formed between the second-stage displacer 38 and the second-stage cooling stage 34 in the second-stage cylinder 32.

[0021] The driving unit 40 includes an electric motor that outputs rotation, and a motion conversion mechanism, such as a Scotch yoke mechanism, that converts the rotation into linear reciprocating motion. This motion conversion mechanism is connected to the single-stage displacer 36 on the axially opposite side to the two-stage displacer 38. Thus, by driving the electric motor, the single-stage displacer 36 and the two-stage displacer 38 can be reciprocated in the axial direction via the motion conversion mechanism.

[0022] The drive unit 40 also includes a built-in valve for controlling the pressure of the expansion space. The pressure control valve is configured to alternately switch between supplying high-pressure working gas from the compressor 24 to the expansion space via the regenerator material and recovering low-pressure working gas from the expansion space to the compressor 24 via the regenerator material. The drive unit 40 is configured to appropriately synchronize the volume change of the expansion space caused by the axial reciprocating motion of the first-stage displacer 36 and the second-stage displacer 38 with the pressure change of the expansion space caused by the pressure control valve. By such an operation of the cryogenic refrigerator 20, the first-stage cooling stage 30 is cooled to a first cooling temperature, for example, 30K to 80K, and the second-stage cooling stage 34 is cooled to a second cooling temperature, for example, 3K to 20K, which is lower than the first cooling temperature.

[0023] The drive unit 40 is disposed in the ambient environment 16 together with the cold head side flange 26, and is fixed to the cold head side flange 26 on the opposite side to the first stage cylinder 28 by fastening members (not shown) such as bolts. When performing maintenance on the cryogenic refrigerator 20, the drive unit 40 can be released from the cold head side flange 26. This allows the first stage displacer 36 and the second stage displacer 38 to be pulled out from the first stage cylinder 28 and the second stage cylinder 32, respectively, and the drive unit 40 can be removed from the cold head 22 together with the first stage displacer 36 and the second stage displacer 38.

[0024] When the cryogenic refrigerator 20 is of a two-stage type, the sleeve 50 is also configured of a two-stage type correspondingly. Thus, the sleeve 50 includes a sleeve-side flange 52, a first-stage sleeve body 54, a first-stage heat transfer stage 56, a second-stage sleeve body 58, and a second-stage heat transfer stage 60. These components of the sleeve 50 are arranged along the central axis of the cold head 22 in the order described above.

[0025] The first-stage sleeve body 54 connects the sleeve-side flange 52 to the first-stage heat transfer stage 56, and the second-stage sleeve body 58 connects the first-stage heat transfer stage 56 to the second-stage heat transfer stage 60. The first-stage sleeve body 54 and the second-stage sleeve body 58 are hollow cylindrical members extending coaxially with the central axis of the cold head 22, and the first-stage sleeve body 54 has a larger diameter than the second-stage sleeve body 58. The sleeve-side flange 52, the first-stage sleeve body 54 and the first-stage heat transfer stage 56 are formed of a metal such as stainless steel.

[0026] The first-stage sleeve body 54 and the second-stage sleeve body 58 are disposed so as to surround the first-stage cylinder 28 and the second-stage cylinder 32, respectively. The diameter of the first-stage sleeve body 54 is somewhat larger than the diameter of the first-stage cylinder 28, and there is a gap between the first-stage sleeve body 54 and the first-stage cylinder 28, so they do not come into contact with each other. Similarly, the diameter of the second-stage sleeve body 58 is somewhat larger than the diameter of the second-stage cylinder 32, and there is a gap between the second-stage sleeve body 58 and the second-stage cylinder 32, so they do not come into contact with each other.

[0027] The first-stage heat transfer stage 56 is fixed to an end of the first-stage sleeve body 54 on the axially opposite side to the sleeve-side flange 52, and the second-stage heat transfer stage 60 is fixed to an end of the second-stage sleeve body 58 on the axially opposite side to the first-stage heat transfer stage 56. A through opening is formed in the center of the first-stage heat transfer stage 56, connecting the internal space of the first-stage sleeve body 54 to the internal space of the second-stage sleeve body 58. The second-stage cylinder 32 and the second-stage cooling stage 34 of the cold head 22 are inserted into the internal space of the second-stage sleeve body 58 from this opening. The first-stage heat transfer stage 56 and the second-stage heat transfer stage 60 are formed of a highly heat-conductive metal such as copper (e.g., pure copper) or other heat-conductive material. The thermal conductivity of the heat-conductive material forming the heat transfer stage is higher than that of the material forming the sleeve body.

[0028] The first heat transfer stage 56 is thermally coupled to the first cooling stage 30 through physical contact therewith. The second heat transfer stage 60 is thermally coupled to the second cooling stage 34 through physical contact therewith. In this embodiment, the contact surface between the heat transfer stage and the cooling stage is a flat surface. However, the cooling stage may have a non-flat surface such as a tapered surface, an inclined surface, or an uneven surface, and the heat transfer stage may have a non-flat surface corresponding to the non-flat surface. The heat transfer stage and the cooling stage may be in direct contact with each other, or may be in thermal contact with each other through a soft intervening layer, such as an indium sheet, that contributes to good heat transfer.

[0029] An object to be cooled other than the object to be cooled 14 (for example, a heat shield surrounding the object to be cooled 14) is attached to the outer surface of the first-stage heat transfer stage 56 exposed to the vacuum region 13, or is thermally coupled to the object to be cooled via an appropriate heat transfer member. Thus, when the first-stage cooling stage 30 is in contact with the first-stage heat transfer stage 56, the object to be cooled in the first stage can be cooled to a first cooling temperature by the first-stage cooling stage 30 via the first-stage heat transfer stage 56. Also, the object to be cooled 14 is attached to the outer surface of the second-stage heat transfer stage 60 exposed to the vacuum region 13, or is thermally coupled to the object to be cooled via an appropriate heat transfer member. Thus, when the second-stage cooling stage 34 is in contact with the second-stage heat transfer stage 60, the object to be cooled 14 can be cooled to a second cooling temperature by the second-stage cooling stage 34 via the second-stage heat transfer stage 60.

[0030] The sleeve side flange 52 is disposed in the surrounding environment 16 and is coupled to the cold head side flange 26. As an example, the sleeve side flange 52 is fixed to an opening formed in the top plate of the vacuum vessel 12, and the first-stage sleeve body 54 and the second-stage sleeve body 58 extend from this opening into the vacuum vessel 12. Thus, the cold head 22 is installed in the vacuum vessel 12 with its central axis parallel to the vertical direction, with the drive unit 40 facing upward and the cooling stage facing downward. However, the installation orientation of the cold head 22 is not limited to this vertical orientation, and it may be installed in other orientations such as horizontal or oblique. The sleeve 50 may be formed on any surface of the vacuum vessel 12, such as the side or bottom surface.

[0031] As an exemplary configuration, the sleeve side flange 52 includes an annular first flange 52a to which the cold head side flange 26 is attached, an annular second flange 52b fixed to the vacuum vessel 12, and a cylindrical outer tubular portion 52c connecting the first flange 52a and the second flange 52b. The first flange 52a, the second flange 52b, and the outer tubular portion 52c are arranged coaxially with the central axis of the cold head 22. The second flange 52b extends radially outward from an end of the first-stage sleeve body 54, the outer tubular portion 52c extends from the second flange 52b in the axially opposite direction to the first-stage sleeve body 54, and the first flange 52a extends radially outward from an end of the outer tubular portion 52c in the axially opposite direction to the second flange 52b.

[0032] The cold head side flange 26 is a combination of two flanges, namely, a main flange 42 and a transition flange 44. The main flange 42 extends radially outward from an end of the first-stage cylinder 28 on the axially opposite side to the first-stage cooling stage 30. The main flange 42 may be formed integrally with the first-stage cylinder 28.

[0033] The transition flange 44 is fixed to the main flange 42 and combined with the sleeve-side flange 52 to form an airtight region 18 between the sleeve 50 and the cold head 22. The transition flange 44 has an annular flange portion 44a and a cylindrical inner tube portion 44b. The flange portion 44a is fixed to the lower surface of the main flange 42 (the surface axially opposite to the drive portion 40) by a fastening member (not shown) such as a bolt, and faces the first flange 52a of the sleeve-side flange 52 with a gap in the axial direction. The inner tube portion 44b extends from the inner periphery of the flange portion 44a to the axially opposite side to the main flange 42, and is inserted into the outer tube portion 52c of the sleeve-side flange 52. The inner tube portion 44b surrounds the upper end portion of the first-stage cylinder 28.

[0034] The outer cylinder portion 52c of the sleeve side flange 52 is disposed adjacent to the outer side of the inner cylinder portion 44b of the transition flange 44. The diameter of the outer cylinder portion 52c is, for example, several mm larger than the diameter of the inner cylinder portion 44b, and there is a gap between the inner peripheral surface of the outer cylinder portion 52c and the outer peripheral surface of the inner cylinder portion 44b, so that they do not contact each other. A seal member 46 for maintaining the airtightness of the airtight region 18 is disposed between the outer cylinder portion 52c and the inner cylinder portion 44b. The seal member 46 is, for example, a seal member such as an O-ring disposed in a circumferential groove formed in the inner cylinder portion 44b. In the illustrated example, the seal member 46 is attached to the inner cylinder portion 44b, but may be attached to the outer cylinder portion 52c.

[0035] The cryogenic device 10 also includes a guide structure 70 that guides the movement of the cold head side flange 26 relative to the sleeve side flange 52. As shown in Fig. 3, the guide structures 70 are provided at multiple locations, four locations in this example, on the cold head side flange 26. The guide structures 70 may be disposed at equal angular intervals (e.g., every 90 degrees) in the circumferential direction on the cold head side flange 26 so as to surround the drive unit 40 of the cold head 22.

[0036] The guide structure 70 includes a guide portion provided on the sleeve side flange 52, and a guided portion provided on the cold head side flange 26 and guided by the guide portion. In this embodiment, a guide pin 72 is provided on the sleeve side flange 52 as the guide portion. Also, a guide hole 74 into which the guide pin 72 is inserted is provided on the cold head side flange 26 as the guided portion.

[0037] 4, the guide pin 72 is a cylindrical protrusion that is erected on the first flange 52a of the sleeve side flange 52 and extends toward the cold head side flange 26. The guide hole 74 is a circular through hole into which the guide pin 72 is inserted, and is provided in the transition flange 44 in this embodiment.

[0038] The guide structure 70 has a lateral clearance d perpendicular to the direction of movement of the cold head side flange 26. G between the guide pin 72 and the guide hole 74. That is, the clearance d G is a radial gap between the guide pin 72 and the guide hole 74, the diameter of the guide pin 72 is φG, and the diameter of the guide hole 74 is φG m When expressed as d G =(φG m -φG) / 2.

[0039] In this embodiment, the clearance d of the guide structure 70 G may be smaller than the clearance C1 in the seal member 46, i.e., the radial gap between the inner cylindrical portion 44b of the transition flange 44 and the outer cylindrical portion 52c of the sleeve-side flange 52. According to a typical O-ring design, the crush rate of the O-ring is selected, for example, from the range of 8% to 30%. Therefore, when the seal member 46 is an O-ring, if the thickness of the O-ring is, for example, 3 mm, the clearance C1 is selected from the range of 0.24 mm to 0.9 mm. The clearance d of the guide structure 70 G may be smaller than a selected clearance C1 (eg, 0.9 mm).

[0040] In this way, even if the transition flange 44 is misaligned from the central axis of the cold head 22 and the seal member 46 is locally deformed, the flange portion 44a of the transition flange 44 will come into contact with the guide pin 72 in the guide hole 74 before the inner cylindrical portion 44b of the transition flange 44 comes into contact with the outer cylindrical portion 52c of the sleeve-side flange 52. In this way, the guide structure 70 can function as a mechanical stopper against radial displacement of the cold head 22 that accompanies deformation of the seal member 46.

[0041] The main flange 42 is formed with a through hole 76 that is continuous with the guide hole 74 in the axial direction. The guide pin 72 is inserted from the guide hole 74 into the through hole 76. In this embodiment, a lateral clearance C2 formed between the main flange 42 and the guide pin 72, i.e., a radial gap between the guide pin 72 and the through hole 76, is smaller than the clearance d of the guide structure 70. G Greater than.

[0042] In this way, it is easy to align the central axis determined by the multiple guide structures 70 with the center of the seal member 46. If the guide holes 74 were provided in the main flange 42, on the other hand, there would be a disadvantage that the central axis determined by the guide structures 70 could be misaligned from the center of the seal member 46 due to an assembly error between the main flange 42 and the transition flange 44.

[0043] Note that, when assembly errors can be sufficiently reduced by accurately assembling the main flange 42 and the transition flange 44, the guide hole 74 may be provided in the main flange 42. In this case, the through hole formed in the transition flange 44 into which the guide pin 72 is inserted may have a larger diameter than the guide hole 74 of the main flange 42. Alternatively, the through hole of the transition flange 44 and the guide hole 74 of the main flange 42 may have the same diameter.

[0044] To assist in accurate assembly of the main flange 42 and the transition flange 44, the cold head side flange 26 may be provided with an alignment structure 78. As an example of the alignment structure 78, as shown in Fig. 4, a protrusion provided on the outermost periphery of the flange portion 44a of the transition flange 44 may engage with the outer periphery of the main flange 42. By fitting the main flange 42 into this protrusion of the transition flange 44 during assembly, the centers of the main flange 42 and the transition flange 44 can be easily aligned.

[0045] 3, flange fastening members 48 such as bolts are provided at a plurality of locations on the cold head side flange 26 so as to surround the drive unit 40 of the cold head 22. The flange fastening members 48 are screwed into bolt holes in the sleeve side flange 52 through insertion holes or cutouts formed in the cold head side flange 26, and can fasten the cold head side flange 26 and the sleeve side flange 52 together. When the flange fastening members 48 are released from the fastening, the cold head side flange 26 becomes movable in the axial direction along the guide structure 70 relative to the sleeve side flange 52.

[0046] As an exemplary arrangement, the flange fastening member 48 may be arranged on the cold head side flange 26 on the same circumference as the guide structure 70, or at least one flange fastening member 48 (two in the illustrated example) may be provided between circumferentially adjacent guide structures 70. Although not shown in Fig. 3 for simplicity, the cold head side flange 26 is also provided with a fastening member for fastening the main flange 42 and the transition flange 44.

[0047] In the cryogenic device 10 according to the embodiment, as described below, the first cooling stage 30 and the second cooling stage 34 come into contact with or are separated from the first heat transfer stage 56 and the second heat transfer stage 60, respectively, by movement of the cold head side flange 26 relative to the sleeve side flange 52.

[0048] When the time arrives when maintenance of the cryogenic refrigerator 20 is permitted, the cooling operation of the cryogenic refrigerator 20 is stopped. At this time, as shown in FIG. 1, the first cooling stage 30 is in physical and thermal contact with the first heat transfer stage 56, and the second cooling stage 34 is in physical and thermal contact with the second heat transfer stage 60.

[0049] First, the flange fastening member 48 is removed by an operator, and the cold head side flange 26 and the sleeve side flange 52 are released from the fastening. The cold head side flange 26 is lifted from the sleeve side flange 52 along the guide structure 70, and the cold head 22 is lifted from the sleeve 50. This lifting height L C is about several mm, for example, about 2 to 3 mm. As shown in Fig. 2, the first cooling stage 30 and the second cooling stage 34 are separated from the first heat transfer stage 56 and the second heat transfer stage 60, respectively, and thermal contact is released. A seal member 46 is provided between the cold head side flange 26 and the sleeve side flange 52, so that the isolation of the airtight region 18 from the surrounding environment 16 is maintained. The temperature of the cold head 22 can be raised while the object to be cooled 14 is maintained at a low temperature.

[0050] Maintenance of the cryogenic refrigerator 20 is performed. The drive unit 40 of the cold head 22 is removed from the cold head 22 together with the first-stage displacer 36 and the second-stage displacer 38. The first-stage cylinder 28, the first-stage cooling stage 30, the second-stage cylinder 32, and the second-stage cooling stage 34 are still installed in the sleeve 50. Then, the drive unit and displacer that have been maintained (or are new) are attached to the cold head 22. Then, the cooling operation of the cryogenic refrigerator 20 is resumed.

[0051] Thereafter, the cold head flange 26 is pressed into the sleeve flange 52 along the guide structure 70, and the first and second cooling stages 30 and 34 are again brought into contact with the first and second heat transfer stages 56 and 60, respectively. The cold head flange 26 and the sleeve flange 52 are again fastened by the flange fastening members 48, and the first and second cooling stages 30 and 34 are pressed against the first and second heat transfer stages 56 and 60, respectively, and are again in thermal contact with each other, as shown in FIG.

[0052] 5 is a schematic diagram showing an inclination that may occur in the guide structure 70 according to the embodiment. As described above, the guide structure 70 has a clearance d between the guide pin 72 of the sleeve side flange 52 and the guide hole 74 of the cold head side flange 26. G Therefore, when the cold head side flange 26 is lifted from the sleeve side flange 52, the guide hole 74 can be inclined with respect to the guide pin 72. When the guide hole 74 is inclined to the maximum, the inclination angle θ is expressed as follows: θ=tan -1 (2d G / L G )

[0053] Here, L G represents the length of the guide structure 70 and represents the depth of the guide hole 74 provided in the cold head side flange 26. When the guide hole 74 is formed in the flange portion 44a of the transition flange 44 as in the above example, the length L of the guide structure 70 is G corresponds to the thickness of the flange portion 44a of the transition flange 44.

[0054] In this way, if the guide structure 70 is tilted when the cold head side flange 26 is lifted from the sleeve side flange 52, the cold head 22 will be tilted with respect to the sleeve 50. If the tilt angle is large, the cold head 22 may contact or collide with the sleeve 50, which may cause inconvenience. For example, if a temperature sensor is provided on the cooling stage of the cold head 22, wiring to the temperature sensor is arranged around the cold head 22, and when the cold head 22 contacts the sleeve 50, such wiring may be pinched between them and damaged. If another sensor is arranged in the airtight region 18, there may be a similar risk of damage. In addition, the cooling stage of the cold head 22 has a contact interface that contacts the heat transfer stage of the sleeve 50, and this contact interface may be damaged when the cold head 22 contacts the sleeve 50. It is desirable to avoid such concerns.

[0055] In this embodiment, the clearance d of the guide structure 70 is set to prevent contact between the first and second cooling stages 30 and 34 and the sleeve 50 due to the inclination of the guide hole 74 relative to the guide pin 72, which occurs when the first and second cooling stages 30 and 34 are spaced apart from the first and second heat transfer stages 56 and 60, respectively. G is set forth.

[0056] According to the inventor's study, one of the areas with a high risk of contact or collision due to tilting in the guide structure 70 is the two-stage cooling stage 34 and the two-stage sleeve body 58. Therefore, the clearance d of the guide structure 70 is set so that the amount of lateral movement of the two-stage cooling stage 34 due to the tilting of the guide hole 74 relative to the guide pin 72 does not exceed the lateral distance between the two-stage cooling stage 34 and the two-stage sleeve body 58. G may be defined.

[0057] The maximum horizontal movement of the two-stage cooling stage 34 is L R sinθ, where L Rcorresponds to the axial length of the cold head 22, and is the distance from the lower surface of the main flange 42 of the cold head 22 to the end surface of the two-stage cooling stage 34 (the contact surface with the two-stage heat transfer stage 60). As described above, the inclination angle θ is expressed as θ=tan -1 (2d G / L G ).

[0058] In addition, L R =L A +L B As shown in Figure 2, L A corresponds to the length of the two-stage cylinder 32, and is the distance from the end face of the first-stage cooling stage 30 (the contact face with the first-stage heat transfer stage 56) to the end face of the second-stage cooling stage 34. B corresponds to the length of the first-stage cylinder 28, and is the distance from the lower surface of the main flange 42 of the cold head 22 to the end surface of the first-stage cooling stage 30.

[0059] The lateral distance between the two-stage cooling stage 34 and the two-stage sleeve body 58 is (D s -D h2 ) / 2, where D h2 is the outer diameter of the two-stage cooling stage 34, D s represents the inside diameter of the two-stage sleeve body 58.

[0060] Therefore, the clearance d of the guide structure 70 G may be determined so that the following equation (1) is satisfied. L R sin(tan -1 (2d G / L G ))<(D s -D h2 ) / twenty one)

[0061] 6(a) and 6(b) are schematic diagrams showing an exemplary shape of the two-stage cooling stage 34 of the cold head 22 according to the embodiment. As shown in FIG. 6(a), the two-stage cooling stage 34 may have a cylindrical shape with an outer diameter that is constant in the axial direction. In this case, in a cold head 22 that is generally readily available (for example, a 4KGM refrigerator manufactured by Sumitomo Heavy Industries, Ltd.), the outer diameter D h2 6(b), the second-stage cooling stage 34 may have a flange portion at its end, and this flange portion has a larger diameter than other portions of the second-stage cooling stage 34. In this case, in a cold head 22 that is generally readily available (for example, a 4KGM refrigerator manufactured by Sumitomo Heavy Industries, Ltd.), the outer diameter D h2 (i.e., the diameter of the flange portion) is 64 mm. Therefore, the outer diameter D h2 typically ranges from 46mm to 64mm.

[0062] In addition, the inner diameter D of the two-stage sleeve body 58 s From the viewpoint of reducing the amount of heat input to the second-stage cooling stage 34 due to thermal conduction through the two-stage sleeve body 58, it is not desirable for the inner diameter D of the two-stage sleeve body 58 to be excessively large. s may be smaller than the outer diameter of the first cooling stage 30 of the cold head 22. The outer diameter of the first cooling stage 30 is typically 90 mm. s may be selected from the range of 50 mm to 90 mm. Therefore, the lateral distance (D s -D h2 ) / 2 can be in the range of 2 mm to 22 mm.

[0063] Length L of guide structure 70 G The axial length L of the cold head 22 may be selected from the range of, for example, 5 mm to 50 mm, and may be selected from the range of, for example, 10 mm to 15 mm. R may be selected, for example, from the range of 360 mm to 440 mm.

[0064] (D s -D h2 ) / 2 is 22 mm, and the axial length L of the cold head 22 is R Considering an example where the length L of the guide structure 70 is 392.5 mm, G When the clearance d of the guide structure 70 that satisfies the above formula (1) is 10 mm, G The length L of the guide structure 70 is about 0.25 mm or less. G For example, if the clearance d of the guide structure 70 is 12 mm, G If the length L of the guide structure 70 is about 0.3 mm or less, the above formula (1) is satisfied. G For example, if the clearance d of the guide structure 70 is 13 mm, G If the length L of the guide structure 70 is about 0.35 mm or less, the above formula (1) is satisfied. G When the clearance d of the guide structure 70 is 15 mm, G If is approximately 0.4 mm or less, the above formula (1) is satisfied.

[0065] In this way, the clearance d of the guide structure 70 G The upper limit of the distance can be determined based on the above formula (1). This makes it possible to prevent contact between the two-stage cooling stage 34 and the two-stage sleeve body 58 caused by the inclination of the guide hole 74 relative to the guide pin 72 that occurs when the cold head 22 is lifted up from the sleeve 50.

[0066] According to the inventor's study, another part with a high risk of contact or collision due to tilting in the guide structure 70 is the first-stage cooling stage 30 and the first-stage heat transfer stage 56. Therefore, the amount of downward movement of the edge portion 30a of the first-stage cooling stage 30 due to the tilting of the guide hole 74 relative to the guide pin 72 is equal to the lift height L of the cold head side flange 26 relative to the sleeve side flange 52. C The clearance L of the guide structure 70 must not exceed G may be defined.

[0067] 7(a) and 7(b) are schematic diagrams showing an exemplary shape of the first cooling stage 30 of the cold head 22 according to the embodiment. As shown in FIG. 7(a), the first cooling stage 30 may have a cylindrical shape with an outer diameter that is constant in the axial direction. In this case, in a cold head 22 that is generally readily available (for example, a 4KGM refrigerator manufactured by Sumitomo Heavy Industries, Ltd.), the outer diameter D h1 is 90mm.

[0068] 7(b), the first cooling stage 30 may have a flange portion in the axial middle portion, and this flange portion has a larger diameter than other portions of the first cooling stage 30. In this case, in a cold head 22 that is generally readily available (for example, a 4KGM refrigerator manufactured by Sumitomo Heavy Industries, Ltd.), the outer diameter D h1 (i.e. the diameter of the flange part) is often around 125 mm.

[0069] The amount of downward movement of the edge portion 30a of the first-stage cooling stage 30 due to the inclination of the guide hole 74 relative to the guide pin 72 is (D h1 / 2)sinθ+L B cosθ-L B Therefore, the clearance d of the guide structure 70 can be expressed as G may be determined so that the following equation (2) is satisfied. (D h1 / 2)sinθ+L B cosθ-L B <L C (2) Here, the inclination angle θ is, as described above, θ=tan -1 (2d G / L G ).

[0070] As an example, the lifting height L C 2 mm, the length of the first cylinder 28 L B 192.5 mm, the outer diameter D of the first cooling stage 30 h1 Considering an example where the length L of the guide structure 70 is 125 mm, GWhen the clearance d of the guide structure 70 that satisfies the above formula (2) is 10 mm, G The length L of the guide structure 70 is about 0.15 mm or less. G When the clearance d of the guide structure 70 is 15 mm, G If is approximately 0.25 mm or less, the above formula (2) is satisfied.

[0071] In this way, the clearance d of the guide structure 70 G The upper limit of the distance can be determined based on the above formula (2). This makes it possible to prevent contact between the first cooling stage 30 and the first heat transfer stage 56 due to the inclination of the guide hole 74 relative to the guide pin 72 that occurs when the cold head 22 is lifted from the sleeve 50.

[0072] The clearance d of the guide structure 70 from the viewpoint of allowing the guide hole 74 to slide relative to the guide pin 72 is G A lower limit may be set for the clearance d of the guide structure 70. G may for example be greater than 0.01 mm (or such as 0.04 mm, or such as 0.06 mm).

[0073] However, unlike the case where the cold head 22 is lifted from the sleeve 50, when the cold head 22 is pressed against the sleeve 50, the cooling stage of the cold head 22 is in close contact with the heat transfer stage of the sleeve 50, so that the cold head 22 does not come into contact with or collide with the sleeve 50 due to the inclination of the cold head 22 as described above. However, according to the study by the present inventor, there is another concern caused by an unbalanced load that may act on the cold head side flange 26 when the cold head 22 is pressed against the sleeve 50. The unbalanced load may cause the cold head 22 to deform, and the gap between the second-stage cylinder 32 and the second-stage displacer 38 may expand locally. If this happens, the working gas flow in the second-stage cylinder 32, which should normally pass through the regenerator material in the second-stage displacer 38, may bypass the regenerator material and pass through this gap, which may reduce the second-stage refrigeration capacity of the cold head 22.

[0074] Therefore, in order to prevent the lateral gap between the second-stage cylinder 32 and the second-stage displacer 38 from exceeding the allowable upper limit of the gap under the unbalanced load acting on the cold head side flange 26 when the second-stage cooling stage 34 is pressed against the second-stage heat transfer stage 60, the clearance d G may be defined.

[0075] Fig. 8 is a schematic diagram showing an unbalanced load that may act on the cold head 22 according to the embodiment. The deformation of the cold head 22 due to the unbalanced lateral load W acting on the cold head side flange 26 can be estimated using a beam model with the two-stage cooling stage 34 as a fixed end, as shown in Fig. 8.

[0076] The allowable upper limit of the gap between the two-stage cylinder 32 and the two-stage displacer 38 is dA. max The initial value of the gap between the two-stage cylinder 32 and the two-stage displacer 38 is d i The lateral displacement of the end of the first-stage cylinder 28 (the upper end of the second-stage cylinder 32) due to the offset load W is δ A When expressed as δ A +d i ≦dA max It is sufficient if the following holds true.

[0077] Based on the beam model in Fig. 8, δ B =Xδ A Here, δ B represents the lateral displacement of the cold head side flange 26 due to the unbalanced load W. The Young's modulus E of the first-stage cylinder 28 and the second-stage cylinder 32 are equal, and the second moment of area I of a cylinder with an outer diameter D and an inner diameter d is I=1 / 64×π×(D 4 -d 4 ), the coefficient X is X=(2β+6αβ+6α 2 β+2α 3 ) / (2β+3αβ), where α=L B / L A , β=I B / I A =(Φ B 4 -φ B 4 ) / (Φ A4 -φ A 4 ), and Φ A and φ A are the outer and inner diameters of the two-stage cylinder 32, and Φ B and φ B are the outer and inner diameters of the first-stage cylinder 28.

[0078] The cold head side flange 26 has a maximum clearance d G Since the horizontal displacement is only δB≦d G (=(φG m -φG) / 2).

[0079] Therefore, the clearance d of the guide structure 70 G may be determined so that the following equation (3) is satisfied. d G / X+di≦dAmax (3)

[0080] It is known that in order to prevent the working gas of the cryogenic refrigerator 20 from flowing linearly in the axial direction through the gap between the second-stage cylinder 32 and the second-stage displacer 38, it is preferable to set the gap to 0.03 mm or less. Therefore, the allowable upper limit of the gap between the second-stage cylinder 32 and the second-stage displacer 38 is set to dA max can be set to 0.03 mm. Also, the initial gap value is d i As a typical example of the length L of the first-stage cylinder 28 and the second-stage cylinder 32 of a commonly available cold head 22 (for example, a 4KGM refrigerator manufactured by Sumitomo Heavy Industries, Ltd.), B , L A , outer diameter Φ B , Φ A , inner diameter φ B , φ A Based on the above formula (3), φG m -φG(=2d G ) is approximately 0.1 mm.

[0081] In this way, the clearance d of the guide structure 70 GThe upper limit value of can be determined based on the above formula (3). This makes it possible to prevent a decrease in the refrigeration capacity of the cold head 22 due to an unbalanced load that may act on the cold head 22 when pressed.

[0082] 9(a) and 9(b) are diagrams that show another example of the guide structure 70 according to the embodiment. Fig. 9(a) shows a state in which the cold head side flange 26 is pressed against the sleeve side flange 52, and Fig. 9(b) shows a state in which the cold head side flange 26 is lifted up from the sleeve side flange 52. That is, in Fig. 9(a), the first-stage cooling stage 30 and the second-stage cooling stage 34 are in contact with the first-stage heat transfer stage 56 and the second-stage heat transfer stage 60, respectively, and in Fig. 9(b), the first-stage cooling stage 30 and the second-stage cooling stage 34 are separated from the first-stage heat transfer stage 56 and the second-stage heat transfer stage 60, respectively.

[0083] The guide structure 70 has a tapered guide pin 72 in the sleeve side flange 52, and the guide pin 72 has a large diameter at its base portion fixed to the sleeve side flange 52 and a smaller diameter at its tip portion. A guide hole 74 in the cold head side flange 26 into which the guide pin 72 is inserted has a constant inner diameter.

[0084] Therefore, as shown in the figure, when the guide hole 74 is pushed in to the base of the guide pin 72, the clearance of the guide structure 70 is a first size d G1 When the guide hole 74 is raised to the tip of the guide pin 72, the clearance of the guide structure 70 is a second size d G2 and a first magnitude d G1 is the second magnitude d G2 Less than.

[0085] In this manner, when the cold head side flange 26 is pressed against the sleeve side flange 52, i.e., when the first-stage cooling stage 30 and the second-stage cooling stage 34 are in contact with and pressed against the first-stage heat transfer stage 56 and the second-stage heat transfer stage 60, respectively, the guide structure 70 can act as a mechanical stopper against radial displacement of the cold head 22 due to deformation of the sealing member 46.

[0086] 10(a) and 10(b) are schematic diagrams showing another example of the guide structure 70 according to the embodiment. Fig. 10(a) shows a state in which the cold head side flange 26 is pressed against the sleeve side flange 52, and Fig. 10(b) shows a state in which the cold head side flange 26 is lifted up from the sleeve side flange 52.

[0087] In this example, a guide pin 72 is provided on the cold head side flange 26 as a guided portion, and a guide hole 74 into which the guide pin 72 is inserted is provided on the sleeve side flange 52 as a guide portion. The guide pin 72 has a constant diameter in the axial direction, and is inserted into the guide hole 74. The guide hole 74 has a tapered hole shape, and its inner diameter is small deep inside the guide hole 74 and larger at the entrance.

[0088] Therefore, as shown in the figure, when the guide pin 72 is pushed deep into the guide hole 74, the clearance of the guide structure 70 is a first size d G1 When the guide pin 72 is raised to the entrance of the guide hole 74, the clearance of the guide structure 70 is a second magnitude d G2 and a first magnitude d G1 is the second magnitude d G2 Less than.

[0089] Even in this manner, as in the above-described example, when the cold head side flange 26 is pressed against the sleeve side flange 52, i.e., when the first-stage cooling stage 30 and the second-stage cooling stage 34 are in contact with and pressed against the first-stage heat transfer stage 56 and the second-stage heat transfer stage 60, respectively, the guide structure 70 can act as a mechanical stopper against radial displacement of the cold head 22 due to deformation of the sealing member 46.

[0090] In the guide structure 70 shown in FIGS. 9 and 10, the first magnitude d of clearance of the guide structure 70 G1 may be determined so that the above formula (3) is satisfied. In addition, the second magnitude d G2 may be determined so that the above formula (1) or (2) is satisfied.

[0091] FIG. 11 is a diagram showing a schematic diagram of another example of the guide structure 70 according to the embodiment. In FIG. 11, a top view of the cold head 22 is shown as in FIG. 3. In this example, the guide structure 70 has a guide pin 72 as a guide portion provided on the sleeve side flange 52, and an outer peripheral surface 26a of the cold head side flange 26 as a guided portion. When the cold head side flange 26 moves in the axial direction of the cold head 22 relative to the sleeve side flange 52, the outer peripheral surface 26a of the cold head side flange 26 is guided along the guide pin 72. Therefore, the cold head side flange 26 is not provided with a guide hole into which the guide pin 72 is inserted. A clearance d is provided between the outer peripheral surface 26a of the cold head side flange 26 and the guide pin 72. G The clearance d of the guide structure 70 is G may be determined such that any of the above equations (1), (2), or (3) is satisfied.

[0092] FIG. 12 is a diagram showing a schematic diagram of another example of a guide structure 70 according to an embodiment. The guide structure 70 has an inner peripheral surface of the sleeve-side flange 52 as a guide portion, and a guide ring 80 provided on the inner cylindrical portion 44b of the transition flange 44 as a guided portion. In this example, the guide ring 80 is provided on the upper side of the seal member 46, but it may be provided on the lower side of the seal member 46. When the transition flange 44 moves in the axial direction of the cold head 22 relative to the sleeve-side flange 52, the guide ring 80 is guided along the inner peripheral surface of the sleeve-side flange 52. A clearance d is provided between the guide ring 80 and the inner peripheral surface of the sleeve-side flange 52. G The clearance d of the guide structure 70 is G may be determined such that any of the above equations (1), (2), or (3) is satisfied.

[0093] The present invention has been described above based on examples. It will be understood by those skilled in the art that the present invention is not limited to the above-described embodiments, that various design changes are possible, that various modifications are possible, and that such modifications are also within the scope of the present invention. Various features described in relation to one embodiment can also be applied to other embodiments. A new embodiment resulting from a combination has the combined effects of each of the combined embodiments.

[0094] In the above embodiment, the cryocooler 20 is a two-stage GM cryocooler, but the cryocooler 20 may be a pulse tube cryocooler, a Stirling cryocooler, or any other type of cryocooler.

[0095] The present invention has been described using specific terms based on the embodiments, but the embodiments merely show one aspect of the principles and applications of the present invention, and many modifications and changes in arrangement are permitted to the embodiments without departing from the spirit of the present invention as defined in the claims.

[0096] The embodiment of the present invention can also be expressed as follows.

[0097] 1. A cold head housing sleeve including a sleeve side flange, a first heat transfer stage, and a second heat transfer stage; a cold head including a cold head side flange, a first cooling stage, and a second cooling stage cooled to a temperature lower than that of the first cooling stage, the first cooling stage and the second cooling stage being brought into contact with or separated from the first heat transfer stage and the second heat transfer stage, respectively, by movement of the cold head side flange relative to the sleeve side flange; a guide structure for guiding movement of the cold head side flange relative to the sleeve side flange, the guide structure comprising a guide portion provided on the sleeve side flange and a guided portion provided on the cold head side flange and guided by the guide portion, the guide structure having a lateral clearance between the guide portion and the guided portion perpendicular to the movement direction of the cold head side flange, a guide portion that is inclined relative to the guide portion when the first-stage cooling stage and the second-stage cooling stage are spaced apart from the first-stage heat transfer stage and the second-stage heat transfer stage, respectively, and the guided portion is inclined relative to the guide portion, thereby preventing contact between the first-stage cooling stage and the second-stage cooling stage and the cold head accommodating sleeve.

[0098] 2. The cold head housing sleeve includes a two-stage sleeve body that connects the first heat transfer stage to the second heat transfer stage; The cryogenic device described in embodiment 1, characterized in that the clearance of the guide structure is determined so that the lateral movement of the two-stage cooling stage due to the inclination of the guided portion relative to the guide portion does not exceed the lateral distance between the two-stage cooling stage and the two-stage sleeve body.

[0099] 3. A cryogenic device as described in embodiment 1 or 2, characterized in that the clearance of the guide structure is determined so that the amount of downward movement of the edge portion of the first-stage cooling stage due to the inclination of the guided portion relative to the guide portion does not exceed the lift height of the cold head side flange relative to the sleeve side flange.

[0100] 4. A cold head accommodating sleeve including a sleeve side flange, a first heat transfer stage, and a second heat transfer stage; a cold head including a cold head side flange, a first cooling stage, and a second cooling stage cooled to a temperature lower than that of the first cooling stage, the first cooling stage and the second cooling stage being brought into contact with or separated from the first heat transfer stage and the second heat transfer stage, respectively, by movement of the cold head side flange relative to the sleeve side flange; a guide structure for guiding movement of the cold head side flange relative to the sleeve side flange, the guide structure comprising a guide portion provided on the sleeve side flange and a guided portion provided on the cold head side flange and guided by the guide portion, the guide structure having a lateral clearance between the guide portion and the guided portion perpendicular to the movement direction of the cold head side flange, the cold head includes a two-stage cylinder that connects the first-stage cooling stage to the second-stage cooling stage, and a two-stage displacer that is accommodated in the two-stage cylinder and is movable relative to the two-stage cylinder; a clearance of the guide structure is determined so that the lateral gap between the two-stage cylinder and the two-stage displacer does not exceed an allowable upper limit of the gap under an unbalanced load acting on the cold head side flange when the two-stage cooling stage is pressed against the two-stage heat transfer stage.

[0101] 5. The cold head side flange comprises a main flange and a transition flange fixed to the main flange and combined with the sleeve side flange to form an airtight region isolated from the ambient environment between the cold head accommodating sleeve and the cold head; 5. The cryogenic device according to any one of the first to fourth embodiments, wherein the guided portion is provided on the transition flange.

[0102] 6. A cryogenic device as described in embodiment 5, characterized in that the lateral clearance formed between the main flange and the guide portion is larger than the clearance of the guide structure.

[0103] 7. A cryogenic device described in any one of embodiments 1 to 6, characterized in that the clearance of the guide structure has a first magnitude when the first-stage cooling stage and the second-stage cooling stage are in contact with the first-stage heat transfer stage and the second-stage heat transfer stage, respectively, and has a second magnitude when the first-stage cooling stage and the second-stage cooling stage are spaced apart from the first-stage heat transfer stage and the second-stage heat transfer stage, respectively, and the first magnitude is smaller than the second magnitude.

[0104] 8. A cryogenic apparatus according to any one of embodiments 1 to 7, wherein the guide portion has a guide pin, and the guided portion has a guide hole into which the guide pin is inserted. [Explanation of symbols]

[0105] 10 cryogenic device, 16 ambient environment, 18 airtight area, 22 cold head, 26 cold head side flange, 30 first cooling stage, 32 second cylinder, 34 second cooling stage, 38 second displacer, 42 main flange, 44 transition flange, 50 sleeve, 52 sleeve side flange, 56 first heat transfer stage, 60 second heat transfer stage, 70 guide structure, 72 guide pin, 74 guide hole.

Claims

1. a cold head housing sleeve including a sleeve side flange, a first heat transfer stage, and a second heat transfer stage; a cold head including a cold head side flange, a first cooling stage, and a second cooling stage cooled to a temperature lower than that of the first cooling stage, the first cooling stage and the second cooling stage being brought into contact with or separated from the first heat transfer stage and the second heat transfer stage, respectively, by movement of the cold head side flange relative to the sleeve side flange; a guide structure for guiding movement of the cold head side flange relative to the sleeve side flange, the guide structure comprising a guide portion provided on the sleeve side flange and a guided portion provided on the cold head side flange and guided by the guide portion, the guide structure having a lateral clearance between the guide portion and the guided portion perpendicular to the movement direction of the cold head side flange, the cold head includes a two-stage cylinder that connects the first-stage cooling stage to the second-stage cooling stage, and a two-stage displacer that is accommodated in the two-stage cylinder and is movable relative to the two-stage cylinder; a clearance of the guide structure is determined so that the lateral gap between the two-stage cylinder and the two-stage displacer does not exceed an allowable upper limit of the gap under an unbalanced load acting on the cold head side flange when the two-stage cooling stage is pressed against the two-stage heat transfer stage.

2. the cold head side flange comprises a main flange and a transition flange fixed to the main flange and combined with the sleeve side flange to form an airtight region isolated from an ambient environment between the cold head accommodating sleeve and the cold head; The cryogenic device according to claim 1 , wherein the guided portion is provided on the transition flange.

3. 3. The cryogenic device of claim 2, wherein the lateral clearance formed between the main flange and the guide portion is greater than the clearance of the guide structure.

4. 4. The cryogenic device according to claim 1, wherein the clearance of the guide structure has a first magnitude when the first-stage cooling stage and the second-stage cooling stage are in contact with the first-stage heat transfer stage and the second-stage heat transfer stage, respectively, and has a second magnitude when the first-stage cooling stage and the second-stage cooling stage are spaced apart from the first-stage heat transfer stage and the second-stage heat transfer stage, respectively, and the first magnitude is smaller than the second magnitude.

5. 5. The cryogenic device according to claim 1, wherein the guide portion has a guide pin, and the guided portion has a guide hole into which the guide pin is inserted.

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