Cryogenic refrigerator, rotary valve structure of cryogenic refrigerator, and valve stator of rotary valve for cryogenic refrigerator

Abstract

A cryogenic refrigerator (10) is provided with a cold head housing (20) and a rotary valve (42) accommodated in the cold head housing (20). The rotary valve (42) is provided with: a valve rotor (42a); and a valve stator (42b) which is disposed adjacent to the valve rotor (42a), and which is unrotatably supported on the cold head housing (20) by means of a plurality of detents, for example, a plurality of detent pins (54).

Description

Cryogenic refrigerator, rotary valve structure of cryogenic refrigerator, and valve stator of rotary valve for cryogenic refrigerator

[0001] The present invention relates to a cryogenic refrigerator, a rotary valve structure for a cryogenic refrigerator, and a valve stator for a rotary valve for a cryogenic refrigerator.

[0002] Cryogenic refrigerators, such as the Gifford-McMahon (GM) refrigerator, generate cold by repeating a refrigeration cycle in which the volume change and pressure change in the expansion chamber of a working gas (also called a refrigerant gas) are appropriately synchronized. Therefore, cryogenic refrigerators are equipped with a valve, such as a rotary valve, to control the pressure of the working gas. Such pressure control valves can also be installed in other cryogenic refrigerators, such as pulse tube refrigerators.

[0003] Japanese Patent Application Laid-Open No. 2020-73841

[0004] In an existing configuration, a rotary valve of a cryogenic refrigerator includes a valve stator fixed to a housing and a valve rotor that rotates adjacent to the valve stator. The valve stator is fixed to the housing using a single fixing pin. When the valve rotor rotates and slides relative to the valve stator, frictional force acting from the valve rotor to the valve stator causes a rotational torque around the fixing pin to act on the valve stator, and this rotational torque can press a specific portion of the valve stator against the housing. Such localized load on the valve stator acts over the long term as the cryogenic refrigerator operates over a long period of time, which may result in deterioration of the valve stator or the fixing pin.

[0005] One exemplary object of certain aspects of the present invention is to improve the long-term reliability of cryogenic refrigerators.

[0006] According to one aspect of the present invention, a cryogenic refrigerator includes a housing and a rotary valve accommodated in the housing, the rotary valve including a valve rotor and a valve stator disposed adjacent to the valve rotor and supported non-rotatably on the housing by a plurality of detents.

[0007] According to one aspect of the present invention, a rotary valve structure for a cryogenic refrigerator includes a valve rotor and a valve stator disposed adjacent to the valve rotor and supported non-rotatably on a housing of the cryogenic refrigerator by a plurality of detents.

[0008] According to one aspect of the present invention, a valve stator for a rotary valve for a cryogenic refrigerator includes a first end face adjacent to the valve rotor of the rotary valve for a cryogenic refrigerator, and a second end face facing the opposite side from the first end face, the second end face having a plurality of pin holes in each of which a detent pin is disposed.

[0009] According to the present invention, the long-term reliability of a cryogenic refrigerator can be improved.

[0010] Fig. 5(a) and Fig. 5(b) are diagrams schematically showing a valve stator and a detent of a rotary valve according to an embodiment; Fig. 5(a) is a diagram schematically showing a cryogenic refrigerator according to an embodiment; Fig. 5(b) is a diagram schematically showing a cryogenic refrigerator according to an embodiment; Fig. 5(b) is a diagram schematically showing a valve stator and a detent of a rotary valve according to an embodiment; Fig. 5(b) is a diagram schematically showing a valve stator and a detent of a rotary valve according to a comparative example;

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the description and drawings, identical or equivalent components, parts, and processes are designated by the same reference numerals, and redundant explanations will be omitted as appropriate. The scale and shape of each part shown in the drawings are set for convenience to facilitate explanation, and should not be interpreted as 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] Figures 1 to 3 are diagrams that schematically show a cryogenic refrigerator 10 according to an embodiment. Figure 1 shows the external appearance of the cryogenic refrigerator 10. Figure 2 shows the internal structure of the low-temperature section of the cryogenic refrigerator 10, and Figure 3 shows the internal structure of the drive section. The cryogenic refrigerator 10 is, for example, a two-stage Gifford-McMahon (GM) refrigerator.

[0013] The cryogenic refrigerator 10 includes a compressor 12 and an expander 14. The compressor 12 is configured to recover the working gas of the cryogenic refrigerator 10 from the expander 14, increase the pressure of the recovered working gas, and then supply the working gas to the expander 14 again. The compressor 12 and the expander 14 form a refrigeration cycle of the cryogenic refrigerator 10, thereby enabling the cryogenic refrigerator 10 to provide the desired cryogenic cooling. The expander 14 is often referred to as a cold head. The cold head is typically installed in a vacuum vessel (not shown) with a low-temperature section disposed within the vacuum vessel and a drive section disposed in an ambient environment (e.g., room temperature and atmospheric pressure) outside the vacuum vessel, and the compressor 12 is disposed in the ambient environment. The working gas, also referred to as a refrigerant gas, is typically helium gas, although other suitable gases may be used. For ease of understanding, the flow direction of the working gas is indicated by arrows in FIG. 1.

[0014] Generally, the pressure of the working gas supplied from the compressor 12 to the expander 14 and the pressure of the working gas recovered from the expander 14 to the compressor 12 are both significantly higher than atmospheric pressure, and can be referred to as a first high pressure and a second high pressure, respectively. For ease of explanation, the first high pressure and the second high pressure are also simply referred to as a high pressure and a low pressure, respectively. Typically, the high pressure is, for example, 2 to 3 MPa. The low pressure is, for example, 0.5 to 1.5 MPa, e.g., approximately 0.8 MPa. For ease of understanding, the flow direction of the working gas is indicated by arrows.

[0015] The expander 14 includes a cold head cylinder 16, a displacer assembly (hereinafter sometimes simply referred to as a displacer) 18, and a cold head housing (hereinafter sometimes simply referred to as a housing) 20. The cold head cylinder 16 guides the linear reciprocating motion of the displacer 18, and forms expansion chambers (32, 34) between the cold head cylinder 16 and the displacer 18 as expansion spaces for the working gas. The cold head cylinder 16 is fixed to the cold head housing 20, thereby forming a housing for the expander 14, and an airtight space for accommodating the displacer 18 is formed within the cold head cylinder 16.

[0016] In this document, for convenience in explaining the positional relationship between the components of the cryogenic refrigerator 10, the side closer to the top dead center of the axial reciprocation of the displacer 18 will be referred to as "top" and the side closer to the bottom dead center will be referred to as "bottom." The top dead center is the position of the displacer 18 where the volume of the expansion space is maximum, and the bottom dead center is the position of the displacer 18 where the volume of the expansion space is minimum. During operation of the cryogenic refrigerator 10, a temperature gradient occurs in which the temperature decreases from top to bottom, so the top side can also be referred to as the high-temperature side and the bottom side as the low-temperature side.

[0017] The cold head cylinder 16 includes a first cylinder 16a and a second cylinder 16b. The first cylinder 16a and the second cylinder 16b are, for example, cylindrical members, and the second cylinder 16b has a smaller diameter than the first cylinder 16a. The first cylinder 16a and the second cylinder 16b are arranged coaxially, and the lower end of the first cylinder 16a is rigidly connected to the upper end of the second cylinder 16b.

[0018] The displacer assembly 18 includes a first displacer 18a and a second displacer 18b that are connected to each other and move together. The first displacer 18a and the second displacer 18b are, for example, cylindrical members, and the second displacer 18b has a smaller diameter than the first displacer 18a. The first displacer 18a and the second displacer 18b are arranged coaxially.

[0019] The first displacer 18a is accommodated in the first cylinder 16a, and the second displacer 18b is accommodated in the second cylinder 16b. The first displacer 18a is reciprocatingly movable in the axial direction along the first cylinder 16a, and the second displacer 18b is reciprocatingly movable in the axial direction along the second cylinder 16b.

[0020] 2, the first displacer 18a accommodates a first regenerator 26. The first regenerator 26 is formed by filling a cylindrical main body of the first displacer 18a with a first regenerator material, such as a wire mesh made of copper or other suitable material. The upper and lower covers of the first displacer 18a may be provided as separate members from the main body of the first displacer 18a, and the upper and lower covers of the first displacer 18a may be fixed to the main body by suitable means such as fastening or welding, thereby accommodating the first regenerator material in the first displacer 18a.

[0021] Similarly, the second displacer 18b accommodates a second regenerator 28. The second regenerator 28 is made of a non-magnetic regenerator material such as bismuth, HoCu, etc., housed in a cylindrical body of the second displacer 18b. ２ The second displacer 18b is formed by filling it with a magnetic regenerator material such as a refrigerant or other suitable second regenerator material. The second regenerator material may be formed in a granular form. The upper and lower lids of the second displacer 18b may be provided as separate members from the main body of the second displacer 18b, and the upper and lower lids of the second displacer 18b may be fixed to the main body by suitable means such as fastening or welding, thereby containing the second regenerator material in the second displacer 18b.

[0022] The displacer 18 forms an upper chamber 30, a first expansion chamber 32, and a second expansion chamber 34 inside the cold head cylinder 16. The expander 14 includes a first cooling stage 33 and a second cooling stage 35 for heat exchange with the desired object or medium to be cooled by the cryogenic refrigerator 10. The upper chamber 30 is formed between the upper cover of the first displacer 18a and the top of the first cylinder 16a. The first expansion chamber 32 is formed between the lower cover of the first displacer 18a and the first cooling stage 33. The second expansion chamber 34 is formed between the lower cover of the second displacer 18b and the second cooling stage 35. The first cooling stage 33 is fixed to the lower part of the first cylinder 16a to surround the first expansion chamber 32, and the second cooling stage 35 is fixed to the lower part of the second cylinder 16b to surround the second expansion chamber 34.

[0023] The first regenerator 26 is connected to the upper chamber 30 through a working gas passage 36a formed in the upper lid of the first displacer 18a, and is connected to the first expansion chamber 32 through a working gas passage 36b formed in the lower lid of the first displacer 18a. The second regenerator 28 is connected to the first regenerator 26 through a working gas passage 36c formed from the lower lid of the first displacer 18a to the upper lid of the second displacer 18b. The second regenerator 28 is also connected to the second expansion chamber 34 through a working gas passage 36d formed in the lower lid of the second displacer 18b.

[0024] A first seal 38a and a second seal 38b may be provided so that the flow of working gas between the first expansion chamber 32, the second expansion chamber 34, and the upper chamber 30 is directed to the first regenerator 26 and the second regenerator 28, rather than through the clearance between the cold head cylinder 16 and the displacer 18. The first seal 38a may be attached to the top cover of the first displacer 18a so as to be positioned between the first displacer 18a and the first cylinder 16a. The second seal 38b may be attached to the top cover of the second displacer 18b so as to be positioned between the second displacer 18b and the second cylinder 16b.

[0025] 3, the cold head housing 20 is provided with an intake port 20a, which is an inlet for the working gas of the cryogenic refrigerator 10 to the expander 14, and an exhaust port 20b, which is an outlet for the working gas from the expander 14. The intake port 20a is connected to the high-pressure side of the compressor 12, and the exhaust port 20b is connected to the low-pressure side of the compressor 12. The working gas is supplied from the intake port 20a to the expander 14 and discharged from the exhaust port 20b to the compressor 12.

[0026] The cold head drive unit includes a cold head motor 40, a rotary valve 42, and a motion conversion mechanism 43. These components of the drive unit are housed in a low-pressure gas chamber 22 defined inside the cold head housing 20. The low-pressure gas chamber 22 communicates with the low-pressure side of the compressor 12 through the exhaust port 20b. Therefore, the low-pressure gas chamber 22 is always maintained at a low pressure.

[0027] The cold head motor 40 is provided in the expander 14 as a drive source for the displacer 18 and the rotary valve 42. The cold head motor 40 may be an appropriate electromagnetic motor configured to rotate a motor shaft 40a at a constant rotational speed, or the rotational speed of the motor shaft 40a may be variably controlled.

[0028] The rotary valve 42 is configured to alternately connect the high-pressure side and low-pressure side of the compressor 12 to the cold head cylinder 16 (i.e., the upper chamber 30, the first expansion chamber 32, and the second expansion chamber 34) and periodically switch between intake and exhaust of the cold head cylinder 16.

[0029] More specifically, the rotary valve 42 includes a valve rotor 42a and a valve stator 42b disposed adjacent to the valve rotor 42a, and these two valve components have an internal valve passage formed therein such that rotation of the valve rotor 42a relative to the valve stator 42b alternately connects the internal housing passage 24 to the intake port 20a of the cold head housing 20 and the low-pressure gas chamber 22. The internal housing passage 24 is formed in the cold head housing 20 and connects the rotary valve 42 to the upper chamber 30. The internal valve passage of the rotary valve 42 can take various known forms and will not be described in detail here.

[0030] The rotation axis 42c of the valve rotor 42a is coaxial with the motor rotation axis 40a, as indicated by the dashed line in Fig. 4. The valve rotor 42a may be rotatably supported around the rotation axis 42c relative to the cold head housing 20 by a valve support bearing 49 shown in Fig. 3.

[0031] The valve stator 42b has a first end face 50a adjacent to the valve rotor 42a, a second end face 50b facing the opposite side to the first end face 50a, and a valve stator side face 50c connecting the first end face 50a and the second end face 50b. The valve rotor 42a contacts the first end face 50a of the valve stator 42b, while the cold head housing 20 contacts the second end face 50b and the valve stator side face 50c of the valve stator 42b.

[0032] In the illustrated example, the valve stator 42b has a cylindrical shape with the first end face 50a and the second end face 50b having the same diameter, but is not limited to this. For example, the second end face 50b may have a smaller diameter than the first end face 50a, and the valve stator 42b may have a stepped cylindrical shape with a step on the valve stator side face 50c.

[0033] The valve stator 42b is fixed to the cold head housing 20. The valve stator 42b is supported by a plurality of detents to prevent it from rotating on the cold head housing 20. As will be described later with reference to Figures 5(a) and 5(b), the plurality of detents include a plurality of detent pins 54, for example, a first detent pin 54a and a second detent pin 54b. The plurality of detent pins 54 are arranged on a second end surface 50b of the valve stator 42b.

[0034] When the valve rotor 42a rotates around the rotation axis 42c, it slides on a first end surface 50a of the valve stator 42b. To prevent leakage of working gas from the sliding surface between the valve rotor 42a and the valve stator 42b, the valve stator 42b is pressed toward the valve rotor 42a by utilizing the pressure difference between the low-pressure gas chamber 22 and the internal flow path of the rotary valve 42. An elastic body 52 such as a spring may be interposed between the second end surface 50b of the valve stator 42b and the cold head housing 20 to press the valve stator 42b toward the valve rotor 42a in the direction of the rotation axis 42c of the valve rotor 42a. A sealing member 53, such as an O-ring, may be sandwiched between the valve stator side surface 50c and the cold head housing 20.

[0035] The motion conversion mechanism 43 is configured to connect the cold head motor 40 to the rotary valve 42 and the displacer 18 so as to transmit the rotation of the motor rotary shaft 40a to the rotary valve 42 and convert it into linear reciprocating motion of the displacer 18. An example of the motion conversion mechanism 43 will be described later. One rotation of the motor rotary shaft 40a causes one reciprocating motion of the displacer 18 via the motion conversion mechanism 43, thereby periodically changing the volume of the expansion space for the working gas. At the same time, one rotation of the motor rotary shaft 40a causes one rotation of the rotary valve 42 about its rotation axis 42c via the motion conversion mechanism 43, thereby periodically changing the pressure in the expansion space for the working gas.

[0036] FIG. 4 is a schematic exploded perspective view of the main components of the cold head drive unit according to an embodiment. FIG. 4 shows a motor rotating shaft 40a and a motion conversion mechanism 43. In this embodiment, the motion conversion mechanism 43 includes a Scotch yoke mechanism. Therefore, as shown in FIGS. 3 and 4, the motion conversion mechanism 43 includes a crank 44 having a crank pin 44a, a Scotch yoke shaft 45, and a crank pin bearing 46. The Scotch yoke shaft 45 includes a Scotch yoke plate 45a, an upper rod 45b, and a lower rod 45c.

[0037] The crank 44 is fixed to the motor shaft 40a and is thereby connected to the cold head motor 40. The crank 44 is housed in the cold head housing 20 together with the cold head motor 40. The crank 44 has a crank pin 44a that extends toward the Scotch yoke mechanism on the side opposite the motor shaft 40a. The crank pin 44a extends parallel to the motor shaft 40a at a position eccentric from the motor shaft 40a.

[0038] The Scotch yoke plate 45a is a rectangular plate-like member having a horizontally elongated window 47. The horizontally elongated window 47 extends in the axial direction of the cold head and in a direction perpendicular to the motor rotary shaft 40a. A crankpin bearing 46 is rotatably disposed in this horizontally elongated window 47. The crankpin bearing 46 may be, for example, a roller bearing. An engagement hole 46a that engages with the crankpin 44a is formed in the center of the crankpin bearing 46, and the crankpin 44a passes through the engagement hole 46a.

[0039] On the opposite side of the scotch yoke plate 45a from the crank 44, the valve rotor 42a of the rotary valve 42 is arranged with its central axis aligned with the motor rotary shaft 40a, and the tip of the crank pin 44a, which passes through the engagement hole 46a, is fixed to the valve rotor 42a.

[0040] The upper rod 45b extends upward from the center of the upper frame of the Scotch yoke plate 45a, and the lower rod 45c extends downward from the center of the lower frame of the Scotch yoke plate 45a, and these rods are arranged coaxially. The Scotch yoke plate 45a and the upper rod 45b are housed in the low-pressure gas chamber 22, and the lower rod 45c extends through the cold head housing 20 into the cold head cylinder 16. The tip of the lower rod 45c is connected to the displacer 18 inside the cold head cylinder 16.

[0041] A first sliding bearing 48a is provided between the upper rod 45b and the cold head housing 20, and a second sliding bearing 48b is provided between the lower rod 45c and the cold head housing 20. The cold head housing 20 has a recess in its upper portion to receive the upper rod 45b. The first sliding bearing 48a is disposed in this recess and supports the upper rod 45b axially slidably. The second sliding bearing 48b is disposed in a through-hole of the cold head housing 20 through which the lower rod 45c passes and supports the lower rod 45c axially slidably. The second sliding bearing 48b is provided with a seal, such as a slipper seal or clearance seal, and is configured to be airtight, thereby isolating the low-pressure gas chamber 22 from the upper chamber 30. There is no direct gas communication between the low-pressure gas chamber 22 and the upper chamber 30.

[0042] In the above-described configuration of the cryocooler 10, when the cold head motor 40 is driven, the motor shaft 40a is rotated. The rotation is transmitted to the rotary valve 42 and the motion conversion mechanism 43. The rotation of the motor shaft 40a causes the crank pin bearing 46 engaged with the crank pin 44a to rotate in a circular motion. At this time, the crank pin bearing 46 reciprocates through the horizontally elongated window 47 of the Scotch yoke plate 45a, and the Scotch yoke shaft 45 and the displacer 18 reciprocate in the axial direction. In this way, the cold head motor 40 drives the axial reciprocation of the displacer 18 and rotates the rotary valve 42 in synchronization with this.

[0043] In this manner, synchronized volume fluctuations and pressure fluctuations are generated in the expansion space, forming a refrigeration cycle for the cryogenic refrigerator 10, thereby enabling the cryogenic refrigerator 10 to provide the desired cryogenic cooling. The first cooling stage 33 can be cooled to a first cooling temperature, and the second cooling stage 35 can be cooled to a second cooling temperature lower than the first cooling temperature. The first cooling temperature may be, for example, in the range of about 10 K to about 100 K, or in the range of about 20 K to about 40 K. The second cooling temperature may be, for example, about 20 K or less, or about 10 K or less, or about 1 K to about 4 K.

[0044] 5(a) and 5(b) are diagrams illustrating an embodiment of the valve stator 42b and its rotation stopper of the rotary valve 42. The second end surface 50b of the valve stator 42b is shown in FIG.

[0045] A plurality of pin holes 56 are formed in the second end face 50b. A corresponding anti-rotation pin 54 is disposed in each of the plurality of pin holes 56. In the illustrated example, two anti-rotation pins 54, i.e., a first anti-rotation pin 54a and a second anti-rotation pin 54b, are disposed in the second end face 50b. Therefore, the first anti-rotation pin 54a is disposed in one of the two pin holes 56 formed in the second end face 50b, and the second anti-rotation pin 54b is disposed in the other pin hole 56. These two anti-rotation pins 54 may have the same shape. Therefore, the first anti-rotation pin 54a and the second anti-rotation pin 54b may have the same length and diameter.

[0046] The pin hole 56 of the valve stator 42b is formed from the second end face 50b to the interior of the valve stator 42b, but is not connected to other surfaces of the valve stator 42b (e.g., the first end face 50a) or to the internal valve flow passage formed within the valve stator 42b.

[0047] An opening 58 is formed in the center of the second end face 50b of the valve stator 42b, i.e., at the position of the rotation axis 42c of the valve rotor 42a. The opening 58 penetrates the valve stator 42b from the second end face 50b to the first end face 50a and is connected to the intake port 20a (see FIG. 3) at the second end face 50b. Thus, the opening 58 is formed in the valve stator 42b as an internal flow path for guiding high-pressure working gas from the intake port 20a to the valve rotor 42a. An elastic body 52 shown in FIG. 3 may be housed in the opening 58 and sandwiched between the valve stator 42b and the cold head housing 20.

[0048] A part (e.g., half) of the anti-rotation pin 54 is fitted into the pin hole 56 in the second end face 50b, and the remaining part (e.g., the other half) of the anti-rotation pin 54 is fitted into the pin hole in the cold head housing 20, thereby fixing the valve stator 42b to the cold head housing 20 by the anti-rotation pin 54. The anti-rotation pin 54 has, for example, a cylindrical shape, and the pin hole 56 of the valve stator 42b and the pin hole in the cold head housing 20 have a cylindrical hole shape with the same diameter as the anti-rotation pin 54.

[0049] At least one of the multiple anti-rotation pins 54 may be arranged on one side of the rotation axis 42c of the valve rotor 42a on the second end face 50b of the valve stator 42b, and at least one other of the multiple anti-rotation pins 54 may be arranged on the other side of the rotation axis 42c of the valve rotor 42a on the second end face 50b of the valve stator 42b.

[0050] In the illustrated example, the first anti-rotation pin 54a is disposed on one side of the rotation shaft 42c on the second end face 50b, and the second anti-rotation pin 54b is disposed on the other side of the rotation shaft 42c on the second end face 50b. In other words, the first anti-rotation pin 54a and the second anti-rotation pin 54b are disposed on both sides of the rotation shaft 42c on the second end face 50b.

[0051] The multiple anti-rotation pins 54 may be arranged symmetrically around the rotation axis 42c on the second end surface 50b. As an example, as shown by the dashed line in Fig. 5(a), the second anti-rotation pin 54b may be arranged on a straight line 60 that is perpendicular to the rotation axis 42c and extends from the rotation axis 42c to the center of the first anti-rotation pin 54a. In this case, the first anti-rotation pin 54a and the second anti-rotation pin 54b are arranged at equal intervals (i.e., at 180-degree intervals) around the rotation axis 42c on the second end surface 50b of the valve stator 42b.

[0052] Alternatively, as shown in FIG. 5B , the multiple anti-rotation pins 54 may be arranged at unequal intervals around the rotation axis 42c on the second end face 50b of the valve stator 42b. This may result in at least one of the multiple anti-rotation pins 54 being deviated from a symmetrical arrangement around the rotation axis 42c on the second end face 50b. For example, the second anti-rotation pin 54b may be arranged at a predetermined angle θ around the rotation axis 42c from a line 60 that extends from the rotation axis 42c to the center of the first anti-rotation pin 54a and is perpendicular to the rotation axis 42c. The predetermined angle θ may be selected from a range of greater than 0 degrees and not more than 20 degrees, more preferably from a range of 3 degrees to 15 degrees, and even more preferably from a range of 5 degrees to 10 degrees.

[0053] This asymmetric arrangement of the multiple anti-rotation pins 54 facilitates accurate installation of the valve stator 42b during assembly of the cryogenic refrigerator 10. The valve stator 42b must be installed in the cold head housing 20 in the correct orientation so that it can be combined with the valve rotor 42a to form the designed internal valve flow path. When the anti-rotation pins 54 are symmetrically arranged, as shown in FIG. 5( a), it is physically possible to install the valve stator 42b in the cold head housing 20 in an orientation opposite to the correct orientation. Therefore, workers must carefully perform the installation work to avoid installing the valve stator 42b in the incorrect orientation. In contrast, when the anti-rotation pins 54 are asymmetrically arranged, as shown in FIG. 5( b), installation of the valve stator 42b is physically permitted only in the correct orientation as designed, and installation in any other incorrect orientation is physically impossible. This prevents incorrect assembly of the valve stator 42b.

[0054] 6 is a diagram illustrating a comparative example, which schematically shows a valve stator 42b of a rotary valve 42 and its rotation stopper. As mentioned at the beginning of this document, in the existing configuration, the valve stator 42b is fixed to the cold head housing 20 using a single fixing pin 62. When the valve rotor 42a and the valve stator 42b press against each other and the valve rotor 42a rotates and slides relative to the valve stator 42b, the frictional force acting from the valve rotor 42a to the valve stator 42b can cause a rotational torque 64 about the fixing pin 62 to act on the valve stator 42b.

[0055] In principle, it is impossible to prevent the valve stator 42b from rotating with only one fixing pin 62. Therefore, a specific portion 66 of the valve stator 42b (e.g., a portion of the valve stator side surface 50c) may be pressed against the cold head housing 20 with a force corresponding to the rotational torque 64. Such a local load on the valve stator 42b may act over the long term as the cryogenic refrigerator 10 operates over a long period of time. This may cause gradual deformation or deterioration of the fixing pin 62, the pin hole of the valve stator 42b, or the cold head housing 20. Alternatively, an excessive load may be locally applied to the seal member 53 (see FIG. 3 ) on the valve stator side surface 50c, causing the seal member 53 to deteriorate. A deterioration in the sealing performance of the seal member 53 may cause leakage of the working gas and reduce the refrigeration performance of the cryogenic refrigerator 10. In the worst case scenario, these components may eventually be damaged.

[0056] In contrast, according to the embodiment, the valve stator 42b of the rotary valve 42 is supported non-rotatably on the cold head housing 20 by a plurality of anti-rotation pins 54. The plurality of anti-rotation pins 54 can reliably restrict rotation of the valve stator 42b against the frictional force acting from the valve rotor 42a to the valve stator 42b as the valve rotor 42a rotates. Furthermore, because the load is distributed among the plurality of anti-rotation pins 54, deformation and deterioration of the valve stator 42b and the anti-rotation pins 54 can be suppressed. Furthermore, localized loads on the valve stator side surface 50c of the valve stator 42b, for example, on the seal member 53, can also be reduced. Therefore, the long-term reliability of the cryogenic refrigerator 10 can be improved.

[0057] Furthermore, according to this embodiment, the multiple anti-rotation pins 54 include a first anti-rotation pin 54a that is arranged on one side of the rotation shaft 42c of the valve rotor 42a on the second end face 50b of the valve stator 42b, and a second anti-rotation pin 54b that is arranged on the other side of the rotation shaft 42c on the second end face 50b of the valve stator 42b. This makes it possible to increase the length of the arm of the force couple acting on the first anti-rotation pin 54a and the second anti-rotation pin 54b, thereby reducing the load.

[0058] 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, and that various design changes and 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 created by combining embodiments will have the combined effects of the respective combined embodiments.

[0059] In the above embodiment, an example in which two anti-rotation pins 54 are used has been described, but this is not limiting and any number of anti-rotation pins 54 may be used. The valve stator 42b may be fixed to the cold head housing 20 by, for example, three or more anti-rotation pins 54.

[0060] In the above-described embodiment, the multiple anti-rotation pins 54 are arranged equidistantly from the rotation axis 42c on the second end face 50b of the valve stator 42b. Alternatively, at least one of the multiple anti-rotation pins 54 (e.g., the first anti-rotation pin 54a) may be arranged at a different distance from the rotation axis 42c on the second end face 50b of the valve stator 42b than the other at least one anti-rotation pin 54 (e.g., the second anti-rotation pin 54b). Arranging the multiple anti-rotation pins 54 in this manner can also help prevent incorrect installation of the valve stator 42b during assembly of the cryogenic refrigerator 10.

[0061] Furthermore, the multiple anti-rotation pins 54 do not necessarily have to have the same shape. At least one of the multiple anti-rotation pins 54 may have a different shape from at least one other anti-rotation pin 54. Thus, at least one of the multiple anti-rotation pins 54 (e.g., the first anti-rotation pin 54a) may have a different length, thickness, and / or cross-sectional shape from at least one other anti-rotation pin 54 (e.g., the second anti-rotation pin 54b). Such a configuration can also help prevent incorrect installation of the valve stator 42b during assembly of the cryogenic refrigerator 10.

[0062] In the above-described embodiment, an example has been described in which the multiple anti-rotation pins 54 are prepared and used as separate components from the valve stator 42b and the cold head housing 20, but this is not essential. For example, at least one of the multiple anti-rotation pins 54 may be integrally formed with the valve stator 42b. At least one of the multiple anti-rotation pins 54 may be integrally formed with the cold head housing 20.

[0063] In the above-described embodiment, the valve stator 42b is non-rotatably supported on the cold head housing 20 by a plurality of anti-rotation pins 54, but this is not essential. The anti-rotation pins are not limited to pins. For example, the multiple anti-rotation pins may include a plurality of protrusions formed on the valve stator 42b (or the cold head housing 20), and a corresponding plurality of recesses may be formed on the cold head housing 20 (or the valve stator 42b). The engagement between these protrusions and recesses may support the valve stator 42b non-rotatably on the cold head housing 20.

[0064] Although the embodiments have been described above with reference to a two-stage GM refrigerator, the present invention is not limited thereto, and the anti-rotation structure according to the embodiments can be applied to single-stage or multi-stage GM refrigerators, or other cryogenic refrigerators equipped with rotary valves.

[0065] 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, and that various design changes and modifications are possible, and that such modifications are also within the scope of the present invention.

[0066] INDUSTRIAL APPLICABILITY The present invention can be utilized in the fields of cryogenic refrigerators, rotary valve structures for cryogenic refrigerators, and valve stators for rotary valves for cryogenic refrigerators.

[0067] 10 cryogenic refrigerator, 42 rotary valve, 42a valve rotor, 42b valve stator, 42c rotating shaft, 50a first end surface, 50b second end surface, 54 anti-rotation pin, 54a first anti-rotation pin, 54b second anti-rotation pin, 56 pin hole, 60 straight line.

Claims

1. A cryogenic refrigerator comprising: a housing; and a rotary valve accommodated in the housing, the rotary valve comprising a valve rotor and a valve stator disposed adjacent to the valve rotor and supported non-rotatably on the housing by a plurality of detents.

2. The cryogenic refrigerator according to claim 1, wherein said plurality of detents comprises a plurality of detent pins.

3. The cryogenic refrigerator described in claim 2, characterized in that the valve stator has a first end face adjacent to the valve rotor and a second end face facing opposite to the first end face, and the multiple anti-rotation pins are arranged on the second end face of the valve stator.

4. The cryogenic refrigerator according to claim 3, wherein the plurality of anti-rotation pins are arranged at uneven intervals around the rotation axis of the valve rotor on the second end face of the valve stator.

5. The cryogenic refrigerator described in claim 3, characterized in that the plurality of anti-rotation pins comprise a first anti-rotation pin arranged on one side of the rotation axis of the valve rotor on the second end face of the valve stator, and a second anti-rotation pin arranged on the other side of the rotation axis on the second end face of the valve stator.

6. The cryogenic refrigerator described in claim 5, characterized in that the second anti-rotation pin is positioned around the rotation axis at a predetermined angle from a straight line extending from the rotation axis to the first anti-rotation pin and perpendicular to the rotation axis.

7. The cryogenic refrigerator according to claim 6, wherein the predetermined angle is selected from the range of more than 0 degrees and less than or equal to 20 degrees.

8. A cryogenic refrigerator as described in any one of claims 3 to 7, characterized in that at least one of the plurality of anti-rotation pins on the second end surface of the valve stator is positioned at a different distance from the rotation axis of the valve rotor than at least one other anti-rotation pin, and / or at least one of the plurality of anti-rotation pins has a different shape than at least one other anti-rotation pin.

9. A rotary valve structure for a cryogenic refrigerator, comprising: a valve rotor; and a valve stator disposed adjacent to the valve rotor and supported non-rotatably on a housing of the cryogenic refrigerator by a plurality of detents.

10. A valve stator for a rotary valve for a cryogenic refrigerator, comprising: a first end face adjacent to the valve rotor of the rotary valve for a cryogenic refrigerator; and a second end face facing the opposite side from the first end face, wherein the second end face has a plurality of pin holes, each of which has a detent pin disposed therein.

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