Cryocooler, rotary valve assembly of cryocooler, and valve stator of rotary valve for cryocooler

Abstract

A cryocooler includes a housing and a rotary valve that is accommodated in the housing. The rotary valve includes a valve rotor and a valve stator. The valve stator is disposed adjacent to the valve rotor and is non-rotatably supported on the housing by a plurality of anti-rotation members.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This is a bypass continuation of International PCT Application No. PCT / JP2025 / 003780, filed on Feb. 5, 2025, which claims priority to Japanese Patent Application No. 2024-045498, filed on Mar. 21, 2024, which are incorporated by reference herein in their entirety.BACKGROUNDTechnical Field

[0002] Certain embodiments of the present invention relate to a cryocooler, a rotary valve assembly of a cryocooler, and a valve stator of a rotary valve for a cryocooler.Description of Related Art

[0003] A cryocooler typified by a Gifford-McMahon (GM) cryocooler generates cold by repeating a refrigeration cycle in which a volume change and a pressure change of an expansion chamber of a working gas (also referred to as a refrigerant gas) are appropriately synchronized. Therefore, the cryocooler includes a valve for controlling a pressure of the working gas, for example, a rotary valve. Such a pressure control valve can also be mounted on other cryocoolers such as a pulse tube cryocooler.SUMMARY

[0004] One or more embodiments provide a cryocooler including: a housing; and a rotary valve that is accommodated in the housing. The rotary valve includes a valve rotor and a valve stator. The valve stator is disposed adjacent to the valve rotor and is non-rotatably supported on the housing by a plurality of anti-rotation members.

[0005] One or more embodiments provide a rotary valve assembly of a cryocooler, the rotary valve assembly including: a valve rotor; and a valve stator disposed adjacent to the valve rotor and non-rotatably supported on a housing of the cryocooler by a plurality of anti-rotation members.

[0006] One or more embodiments provide a valve stator of a rotary valve for a cryocooler, the valve stator including: a first end surface adjacent to a valve rotor of the rotary valve for the cryocooler; and a second end surface facing an opposite side from the first end surface, in which the second end surface has a plurality of pin holes each configured to receive an anti-rotation pin.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIG. 1 is a diagram schematically showing a cryocooler according to an embodiment;

[0008] FIG. 2 is a diagram schematically showing the cryocooler according to the embodiment;

[0009] FIG. 3 is a diagram schematically showing the cryocooler according to the embodiment;

[0010] FIG. 4 is a diagram schematically showing an exploded perspective view of a main part of a drive unit of a cold head, according to the embodiment;

[0011] FIGS. 5A and 5B are diagrams schematically showing a valve stator of a rotary valve and anti-rotation members thereof, according to the embodiment; and

[0012] FIG. 6 is a diagram schematically showing a valve stator of a rotary valve and an anti-rotation member thereof, according to a comparative example.DETAILED DESCRIPTION

[0013] In an existing configuration, a rotary valve of a cryocooler 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 by using one fixing pin. When the valve rotor rotates and slides against the valve stator, a frictional force acting on the valve stator from the valve rotor causes a rotational torque around the fixing pin to act on the valve stator, and this rotational torque may cause a specific portion of the valve stator to be pressed against the housing. Such a localized load on the valve stator acts over a long term with long-term operation of the cryocooler, which may result in deterioration of the valve stator or the fixing pin.

[0014] It is desirable to improve long-term reliability of a cryocooler.

[0015] Hereinafter, an embodiment for implementing the present invention will be described in detail with reference to drawings. In the description and the drawings, the same reference numerals will be assigned to the same or equivalent components, members, and processes, and overlapping descriptions will be omitted as appropriate. The scale or shape of each part that is shown in the drawings is conveniently set for ease of description and is not limitedly interpreted unless otherwise specified. The embodiment is merely an example and does not limit the scope of the present invention in any way. All of features described in the embodiment and combinations thereof are not necessarily essential to the invention.

[0016] FIGS. 1 to 3 are diagrams schematically showing a cryocooler 10 according to the embodiment. FIG. 1 shows an appearance of the cryocooler 10. FIG. 2 shows an internal structure of a low-temperature section of the cryocooler 10, and FIG. 3 shows an internal structure of a drive unit. The cryocooler 10 is, for example, a two-stage type Gifford-McMahon (GM) cryocooler.

[0017] The cryocooler 10 includes a compressor 12 and an expander 14. The compressor 12 is configured to collect a working gas of the cryocooler 10 from the expander 14, pressurize the collected working gas, and supply the working gas to the expander 14 again. The compressor 12 and the expander 14 constitute a refrigeration cycle of the cryocooler 10, thereby enabling the cryocooler 10 to provide desired cryogenic cooling. The expander 14 is also often referred to as a cold head. The cold head is usually installed in a vacuum chamber (not shown) such that the low-temperature section is disposed inside the vacuum chamber and the drive unit is disposed in a surrounding environment (for example, a room temperature atmospheric pressure environment) outside the vacuum chamber, and the compressor 12 is disposed in the surrounding environment. The working gas is also called a refrigerant gas, and other suitable gases may be used although a helium gas is typically used. In order to facilitate understanding, a flow direction of the working gas is shown by an arrow in FIG. 1.

[0018] In general, a pressure of the working gas supplied from the compressor 12 to the expander 14 and a pressure of the working gas collected from the expander 14 to the compressor 12 are both considerably higher than the atmospheric pressure, and can be referred to as a first high pressure and a second high pressure, respectively. For convenience of description, the first high pressure and the second high pressure are 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, and is, for example, about 0.8 MPa. For better understanding, a direction in which the working gas flows is shown by an arrow.

[0019] The expander 14 includes a cold head cylinder 16, a displacer assembly (hereinafter, also simply referred to as a displacer) 18, and a cold head housing (hereinafter, also simply referred to as a housing) 20. The cold head cylinder 16 guides a linear reciprocating motion of the displacer 18, and forms an expansion chamber (32, 34) as an expansion space for the working gas between the displacer 18 and the cold head cylinder 16. The cold head cylinder 16 is fixed to the cold head housing 20. In this manner, a casing of the expander 14 is formed, and an airtight space for accommodating the displacer 18 is formed inside the cold head cylinder 16.

[0020] In the present specification, in order to describe a positional relationship between components of the cryocooler 10, for convenience of description, a side close to a top dead center of axial reciprocation of the displacer 18 will be referred to as “up”, and a side close to a bottom dead center will be referred to as “down”. The top dead center is a position of the displacer 18 at which the volume of the expansion space is maximized, and the bottom dead center is a position of the displacer 18 at which the volume of the expansion space is minimized. During an operation of the cryocooler 10, a temperature gradient occurs in which the temperature decreases from an upper side to a lower side, so that the upper side can also be referred to as a high temperature side and the lower side can also be referred to as a low temperature side.

[0021] The cold head cylinder 16 includes a first cylinder 16a and a second cylinder 16b. As an example, each of the first cylinder 16a and the second cylinder 16b is a member having a cylindrical shape, and the second cylinder 16b has a diameter smaller than that of the first cylinder 16a. The first cylinder 16a and the second cylinder 16b are coaxially disposed, and a lower end of the first cylinder 16a is rigidly connected to an upper end of the second cylinder 16b.

[0022] The displacer assembly 18 includes a first displacer 18a and a second displacer 18b that are connected to each other and that move integrally. As an example, each of the first displacer 18a and the second displacer 18b is a member having a cylindrical shape, and the second displacer 18b has a diameter smaller than that of the first displacer 18a. The first displacer 18a and the second displacer 18b are coaxially disposed.

[0023] 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 can reciprocate in the axial direction along the first cylinder 16a, and the second displacer 18b can reciprocate in the axial direction along the second cylinder 16b.

[0024] As shown in FIG. 2, the first displacer 18a accommodates a first regenerator 26. The first regenerator 26 is formed by filling a tubular main body of the first displacer 18a with a wire mesh of copper or other appropriate first regenerator materials. An upper lid portion and a lower lid portion of the first displacer 18a may be provided as separate members from the main body of the first displacer 18a, and the upper lid portion and the lower lid portion of the first displacer 18a may be fixed to the main body by any suitable method such as fastening or welding. In this manner, the first regenerator material may be accommodated in the first displacer 18a.

[0025] Similarly, the second displacer 18b accommodates a second regenerator 28. The second regenerator 28 is formed by filling a tubular main body of the second displacer 18b with a non-magnetic regenerator material such as bismuth, a magnetic regenerator material such as HoCu2, or other appropriate second regenerator materials. The second regenerator material may be formed into a granular shape. An upper lid portion and a lower lid portion of the second displacer 18b may be provided as separate members from the main body of the second displacer 18b, and the upper lid portion and the lower lid portion of the second displacer 18b may be fixed to the main body by any suitable method such as fastening or welding. In this manner, the second regenerator material may be accommodated in the second displacer 18b.

[0026] 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. In order to exchange heat with a desired object or medium to be cooled by the cryocooler 10, the expander 14 includes a first cooling stage 33 and a second cooling stage 35. The upper chamber 30 is formed between the upper lid portion of the first displacer 18a and an upper portion of the first cylinder 16a. The first expansion chamber 32 is formed between the lower lid portion of the first displacer 18a and the first cooling stage 33. The second expansion chamber 34 is formed between the lower lid portion of the second displacer 18b and the second cooling stage 35. The first cooling stage 33 is fixed to a lower portion of the first cylinder 16a to surround the first expansion chamber 32, and the second cooling stage 35 is fixed to a lower portion of the second cylinder 16b to surround the second expansion chamber 34.

[0027] The first regenerator 26 is connected to the upper chamber 30 through a working gas flow path 36a formed in the upper lid portion of the first displacer 18a, and is connected to the first expansion chamber 32 through a working gas flow path 36b formed in the lower lid portion of the first displacer 18a. The second regenerator 28 is connected to the first regenerator 26 through a working gas flow path 36c formed from the lower lid portion of the first displacer 18a to the upper lid portion of the second displacer 18b. In addition, the second regenerator 28 is connected to the second expansion chamber 34 through a working gas flow path 36d formed in the lower lid portion of the second displacer 18b.

[0028] A first seal 38a and a second seal 38b may be provided so that a working gas flow between the first expansion chamber 32, the second expansion chamber 34, and the upper chamber 30 is guided to the first regenerator 26 and the second regenerator 28 rather than to a clearance between the cold head cylinder 16 and the displacer 18. The first seal 38a may be mounted on the upper lid portion of the first displacer 18a so as to be disposed between the first displacer 18a and the first cylinder 16a. The second seal 38b may be mounted on the upper lid portion of the second displacer 18b so as to be disposed between the second displacer 18b and the second cylinder 16b.

[0029] As shown in FIG. 3, the cold head housing 20 is provided with an intake port 20a, which is an inlet for the working gas of the cryocooler 10 to the expander 14, and an exhaust port 20b, which is an outlet of the working gas from the expander 14. The intake port 20a is connected to a high-pressure side of the compressor 12, and the exhaust port 20b is connected to a low-pressure side of the compressor 12. The working gas is supplied from the intake port 20a to the expander 14, and is discharged from the exhaust port 20b to the compressor 12.

[0030] A drive unit of the cold head includes a cold head motor 40, a rotary valve 42, and a motion conversion mechanism 43. These components of the drive unit are accommodated 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.

[0031] The cold head motor 40 is provided in the expander 14 as a drive source of the displacer 18 and the rotary valve 42. The cold head motor 40 may be an appropriate electromagnetic motor, and may be configured to rotate a motor rotary shaft 40a at a constant rotational speed, or may be capable of variably controlling the rotational speed of the motor rotary shaft 40a.

[0032] The rotary valve 42 is configured to alternately connect the high-pressure side and the low-pressure side of the compressor 12 to the cold head cylinder 16 (that is, the upper chamber 30, the first expansion chamber 32, and the second expansion chamber 34), and to periodically switch the intake and the exhaust of the cold head cylinder 16.

[0033] 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 flow path formed such that an internal housing flow path 24 is alternately connected to the intake port 20a and the low-pressure gas chamber 22 of the cold head housing 20 by rotation of the valve rotor 42a relative to the valve stator 42b. The internal housing flow path 24 is formed in the cold head housing 20 and connects the rotary valve 42 to the upper chamber 30. Various known forms can be adopted for the internal valve flow path of the rotary valve 42, and will not be described in detail here.

[0034] As indicated by a one-dot chain line in FIG. 4, a rotation axis 42c of the valve rotor 42a is coaxial with the motor rotary shaft 40a. The valve rotor 42a may be supported on the cold head housing 20 to be rotatable around the rotation axis 42c by a valve support bearing 49 shown in FIG. 3.

[0035] The valve stator 42b includes a first end surface 50a that is adjacent to the valve rotor 42a, a second end surface 50b that faces an opposite side from the first end surface 50a, and a valve stator side surface 50c that connects the first end surface 50a and the second end surface 50b. The valve rotor 42a is in contact with the first end surface 50a of the valve stator 42b, while the cold head housing 20 is in contact with the second end surface 50b and the valve stator side surface 50c of the valve stator 42b.

[0036] In the illustrated example, the valve stator 42b has a cylindrical shape in which the first end surface 50a and the second end surface 50b have the same diameter; however, the configuration is not limited to this. For example, the second end surface 50b may have a smaller diameter than the first end surface 50a, and the valve stator 42b may have a stepped cylindrical shape having a step portion on the valve stator side surface 50c.

[0037] The valve stator 42b is fixed to the cold head housing 20. The valve stator 42b is non-rotatably supported on the cold head housing 20 by a plurality of anti-rotation members. As will be described below with reference to FIGS. 5A and 5B, the plurality of anti-rotation members include a plurality of anti-rotation pins 54, for example, a first anti-rotation pin 54a and a second anti-rotation pin 54b. The plurality of anti-rotation pins 54 are disposed on the second end surface 50b of the valve stator 42b.

[0038] When the valve rotor 42a rotates around the rotation axis 42c, the valve rotor 42a slides against the first end surface 50a of the valve stator 42b. In order to prevent the working gas from leaking from such a sliding surface between the valve rotor 42a and the valve stator 42b, the valve stator 42b is pressed toward the valve rotor 42a by using a differential pressure between the low-pressure gas chamber 22 and the internal flow path of the rotary valve 42. In addition, an elastic body 52, such as a spring for pressing the valve stator 42b toward the valve rotor 42a in a direction of the rotation axis 42c of the valve rotor 42a, may be interposed between the second end surface 50b of the valve stator 42b and the cold head housing 20. In addition, a sealing member 53 such as an O-ring may be interposed between the valve stator side surface 50c and the cold head housing 20.

[0039] The motion conversion mechanism 43 is configured to couple 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 the rotation into the linear reciprocation of the displacer 18. An example of the motion conversion mechanism 43 will be described below. One rotation of the motor rotary shaft 40a causes one reciprocation of the displacer 18 via the motion conversion mechanism 43, thereby periodically changing the volume of the expansion space for the working gas. Simultaneously, one rotation of the motor rotary shaft 40a causes one rotation around the rotation axis 42c of the rotary valve 42 via the motion conversion mechanism 43, thereby periodically changing the pressure of the expansion space for the working gas.

[0040] FIG. 4 is a diagram schematically showing an exploded perspective view of a main part of a drive unit of a cold head according to the embodiment. FIG. 4 shows the motor rotary shaft 40a and the 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 including 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.

[0041] The crank 44 is fixed to the motor rotary shaft 40a, and thus is coupled to the cold head motor 40. The crank 44 is accommodated in the cold head housing 20 together with the cold head motor 40. The crank 44 includes a crank pin 44a that extends toward the scotch yoke mechanism, on a side opposite to the motor rotary shaft 40a. The crank pin 44a extends parallel to the motor rotary shaft 40a at an eccentric position from the motor rotary shaft 40a.

[0042] The scotch yoke plate 45a is a rectangular plate-shaped member including a horizontally elongated window 47. The horizontally elongated window 47 extends in an axial direction of the cold head and in a direction perpendicular to the motor rotary shaft 40a. The crank pin bearing 46 is disposed to be rollable in the horizontally elongated window 47. The crank pin bearing 46 may be, for example, a roller bearing. An engagement hole 46a that engages with the crank pin 44a is formed in the center of the crank pin bearing 46, and the crank pin 44a penetrates the engagement hole 46a.

[0043] On a side opposite to the crank 44 with respect to the scotch yoke plate 45a, the valve rotor 42a of the rotary valve 42 is disposed with a center axis thereof aligned with the motor rotary shaft 40a, and a tip of the crank pin 44a penetrating the engagement hole 46a is fixed to the valve rotor 42a.

[0044] The upper rod 45b extends upward from the center of an upper frame of the scotch yoke plate 45a, the lower rod 45c extends downward from the center of a lower frame of the scotch yoke plate 45a, and these rods are coaxially disposed. The scotch yoke plate 45a and the upper rod 45b are accommodated in the low-pressure gas chamber 22, and the lower rod 45c penetrates the cold head housing 20 to extend into the cold head cylinder 16. A tip of the lower rod 45c is coupled to the displacer 18 inside the cold head cylinder 16.

[0045] 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 at its upper portion for receiving the upper rod 45b, and the first sliding bearing 48a is disposed in the recess to support the upper rod 45b to be slidable in the axial direction. In addition, 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 to be slidable in the axial direction. The second sliding bearing 48b is provided with a seal portion such as a slipper seal and a clearance seal, and is configured to be airtight, so that the low-pressure gas chamber 22 is isolated from the upper chamber 30. There is no direct gas circulation between the low-pressure gas chamber 22 and the upper chamber 30.

[0046] In the above-described configuration of the cryocooler 10, when the cold head motor 40 is driven, the motor rotary shaft 40a is rotated. The rotation is transmitted to the rotary valve 42 and the motion conversion mechanism 43. Due to the rotation of the motor rotary shaft 40a, the crank pin bearing 46 engaged with the crank pin 44a rotates to draw a circle. In this case, the crank pin bearing 46 reciprocates in the horizontally elongated window 47 of the scotch yoke plate 45a, and accordingly, 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 therewith.

[0047] In this way, synchronized volume fluctuation and pressure fluctuation are brought to the expansion space to configure the refrigeration cycle of the cryocooler 10, whereby the cryocooler 10 can provide 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 a range of about 10 K to about 100 K, or in a range of about 20 K to about 40 K. The second cooling temperature may be, for example, about 20 K or less, about 10 K or less, or in a range of about 1 K to about 4 K.

[0048] FIGS. 5A and 5B are diagrams schematically showing the valve stator 42b of the rotary valve 42 and an anti-rotation member thereof according to the embodiment. FIGS. 5A and 5B show the second end surface 50b of the valve stator 42b.

[0049] A plurality of pin holes 56 are formed in the second end surface 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, that is, a first anti-rotation pin 54a and a second anti-rotation pin 54b are disposed on the second end surface 50b. Therefore, the first anti-rotation pin 54a is disposed in one of two pin holes 56 formed in the second end surface 50b, and the second anti-rotation pin 54b is disposed in the other pin hole 56. The 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 the same diameter.

[0050] The pin holes 56 of the valve stator 42b are formed from the second end surface 50b to the inside of the valve stator 42b, but are not connected to other surfaces (for example, the first end surface 50a) of the valve stator 42b. In addition, the pin holes 56 are not connected to the internal valve flow path formed in the valve stator 42b.

[0051] In addition, an opening 58 is formed in a central portion of the second end surface 50b of the valve stator 42b, that is, at a position of the rotation axis 42c of the valve rotor 42a. The opening 58 penetrates the valve stator 42b from the second end surface 50b to the first end surface 50a, and is connected to the intake port 20a (see FIG. 3) on the second end surface 50b. Therefore, the opening 58 is formed in the valve stator 42b as an internal flow path of the valve stator 42b for guiding the high-pressure working gas from the intake port 20a to the valve rotor 42a. The elastic body 52 shown in FIG. 3 may be accommodated in the opening 58 and may be interposed between the valve stator 42b and the cold head housing 20.

[0052] A part (for example, half) of the anti-rotation pin 54 is fitted into the pin hole 56 of the second end surface 50b, and the remaining part (for example, the remaining half) of the anti-rotation pin 54 is fitted into a pin hole of the cold head housing 20, thereby fixing the valve stator 42b to the cold head housing 20 using 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 of the cold head housing 20 have a cylindrical hole shape having the same diameter as the anti-rotation pin 54.

[0053] At least one of the plurality of anti-rotation pins 54 may be disposed on one side with respect to the rotation axis 42c of the valve rotor 42a on the second end surface 50b of the valve stator 42b, and at least one other of the plurality of anti-rotation pins 54 may be disposed on the other side with respect to the rotation axis 42c of the valve rotor 42a on the second end surface 50b of the valve stator 42b.

[0054] In the illustrated example, the first anti-rotation pin 54a is disposed on one side with respect to the rotation axis 42c on the second end surface 50b, and the second anti-rotation pin 54b is disposed on the other side with respect to the rotation axis 42c on the second end surface 50b. That is, the first anti-rotation pin 54a and the second anti-rotation pin 54b are disposed on both sides of the rotation axis 42c on the second end surface 50b.

[0055] The plurality of anti-rotation pins 54 may be disposed symmetrically around the rotation axis 42c on the second end surface 50b. As an example, as shown by a one-dot chain line in FIG. 5A, the second anti-rotation pin 54b may be disposed on a straight line 60 perpendicular to the rotation axis 42c and extending 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 disposed at equal intervals (that is, at 180-degree intervals) around the rotation axis 42c on the second end surface 50b of the valve stator 42b.

[0056] Alternatively, as shown in FIG. 5B, the plurality of anti-rotation pins 54 may be disposed at unequal intervals around the rotation axis 42c on the second end surface 50b of the valve stator 42b. As a result, at least one of the plurality of anti-rotation pins 54 may be deviated from symmetrical disposition around the rotation axis 42c on the second end surface 50b. For example, the second anti-rotation pin 54b may be disposed at a position offset by a predetermined angle θ around the rotation axis 42c from the straight line 60 perpendicular to the rotation axis 42c and extending from the rotation axis 42c to the center of the first anti-rotation pin 54a. The predetermined angle θ may be selected from a range of more than 0 degrees and 20 degrees or less, more preferably selected from a range of 3 degrees or more and 15 degrees or less, and still more preferably selected from a range of 5 degrees or more and 10 degrees or less.

[0057] Such asymmetric disposition of the plurality of anti-rotation pins 54 is helpful for accurately attaching the valve stator 42b in the assembly operation of the cryocooler 10. The valve stator 42b needs to be attached to the cold head housing 20 in a correct direction so that it can be combined with the valve rotor 42a to form the internal valve flow path as designed. As shown in FIG. 5A, when the anti-rotation pins 54 are disposed symmetrically, it is also physically possible to attach the valve stator 42b to the cold head housing 20 in a direction opposite to the correct direction. Therefore, a worker is required to carefully perform the attachment operation so as not to attach the valve stator 42b in the wrong direction. On the other hand, as shown in FIG. 5B, when the anti-rotation pins 54 are disposed asymmetrically, the valve stator 42b is physically allowed to be attached only in the correct direction in design, and it is physically impossible to attach the valve stator 42b in another wrong direction. Therefore, it is possible to prevent an error in the assembly of the valve stator 42b.

[0058] FIG. 6 is a diagram schematically showing the valve stator 42b of the rotary valve 42 and an anti-rotation member thereof according to a comparative example. As described at the beginning of this specification, in the existing configuration, the valve stator 42b is fixed to the cold head housing 20 by using one fixing pin 62. When the valve rotor 42a rotates and slides against the valve stator 42b while the valve rotor 42a and the valve stator 42b are pressed against each other, the frictional force acting on the valve stator 42b from the valve rotor 42a can cause a rotational torque 64 around the fixing pin 62 to act on the valve stator 42b.

[0059] In principle, it is impossible to suppress the rotation of the valve stator 42b with only one fixing pin 62. Therefore, a specific portion 66 (for example, a part of the valve stator side surface 50c) of the valve stator 42b may be pressed against the cold head housing 20 with a force corresponding to the rotational torque 64. Such a localized load on the valve stator 42b may act over a long term with long-term operation of the cryocooler 10. This may cause the fixing pin 62, or the pin hole of the valve stator 42b or the cold head housing 20 to gradually deform or deteriorate. Alternatively, an excessive load may be locally applied to the sealing member 53 (see FIG. 3) of the valve stator side surface 50c, which may deteriorate the sealing member 53. A decrease in the sealing performance of the sealing member 53 may cause a leakage of the working gas, which may reduce the refrigeration performance of the cryocooler 10. In addition, in the worst case, these components may be finally damaged.

[0060] On the other hand, according to the embodiment, the valve stator 42b of the rotary valve 42 is non-rotatably supported on the cold head housing 20 by the plurality of anti-rotation pins 54. The rotation of the valve stator 42b can be reliably restricted by the plurality of anti-rotation pins 54 against the frictional force acting on the valve stator 42b from the valve rotor 42a as the valve rotor 42a rotates. In addition, the load is distributed to the plurality of anti-rotation pins 54, so that the deformation and deterioration of the valve stator 42b and the anti-rotation pins 54 can be suppressed. In addition, the localized load on the valve stator side surface 50c of the valve stator 42b, for example, the sealing member 53 can also be reduced. Therefore, it is possible to improve the long-term reliability of the cryocooler 10.

[0061] In addition, according to the embodiment, the plurality of anti-rotation pins 54 include the first anti-rotation pin 54a that is disposed on one side with respect to the rotation axis 42c of the valve rotor 42a on the second end surface 50b of the valve stator 42b, and the second anti-rotation pin 54b that is disposed on the other side with respect to the rotation axis 42c on the second end surface 50b of the valve stator 42b. In this way, the length of the arms of the couple acting on the first anti-rotation pin 54a and the second anti-rotation pin 54b can be set long, and the load can be reduced.

[0062] The present invention has been described above based on the example. The present invention is not limited to the above embodiment, and various design changes can be made, and it would be understood by those skilled in the art that various modifications are possible and such modifications also fall within the scope of the present invention. Various features described in relation to a certain embodiment are also applicable to other embodiments. A new embodiment resulting from a combination possesses the effects of each of the embodiments to be combined.

[0063] In the above-described embodiment, a case where two anti-rotation pins 54 are used has been described as an example; however, the configuration is not limited to this, and the number of the anti-rotation pins 54 to be used is arbitrary. The valve stator 42b may be fixed to the cold head housing 20 by, for example, three or more anti-rotation pins 54.

[0064] In the above-described embodiment, a case where the plurality of anti-rotation pins 54 are disposed at equal distances from the rotation axis 42c on the second end surface 50b of the valve stator 42b has been described as an example, but instead, at least one anti-rotation pin 54 (for example, the first anti-rotation pin 54a) among the plurality of anti-rotation pins 54 may be disposed at a distance from the rotation axis 42c on the second end surface 50b of the valve stator 42b, the distance being different from a distance of at least one other anti-rotation pin 54 (for example, the second anti-rotation pin 54b) from the rotation axis 42c. Such a disposition of the plurality of anti-rotation pins 54 can also help to prevent erroneous attachment of the valve stator 42b in the assembly operation of the cryocooler 10.

[0065] In addition, the plurality of anti-rotation pins 54 do not necessarily need to have the same shape. At least one of the plurality of anti-rotation pins 54 may have a different shape from at least one other anti-rotation pin 54. Therefore, at least one anti-rotation pin 54 (for example, the first anti-rotation pin 54a) among the plurality of anti-rotation pins 54 may have a different length and / or a different thickness and / or a different cross-sectional shape from at least one other anti-rotation pin 54 (for example, the second anti-rotation pin 54b). Such a configuration can also help to prevent erroneous attachment of the valve stator 42b in the assembly operation of the cryocooler 10.

[0066] In the above-described embodiment, a case where the plurality of anti-rotation pins 54 are prepared and used as separate components from the valve stator 42b and the cold head housing 20 has been described as an example; however, this configuration is not essential. For example, at least one anti-rotation pin 54 among the plurality of anti-rotation pins 54 may be integrally formed with the valve stator 42b. At least one anti-rotation pin 54 among the plurality of anti-rotation pins 54 may be integrally formed with the cold head housing 20.

[0067] In the above-described embodiment, a case where the valve stator 42b is non-rotatably supported on the cold head housing 20 by the plurality of anti-rotation pins 54 has been described as an example; however, this configuration is not essential. The anti-rotation member is not limited to a pin. For example, the plurality of anti-rotation members 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 in the cold head housing 20 (or the valve stator 42b). The valve stator 42b may be non-rotatably supported on the cold head housing 20 by engagement between the protrusions and the recesses.

[0068] Hitherto, the embodiment has been described with reference to the two-stage type GM cryocooler. The present invention is not limited to this, and the anti-rotation structure according to the embodiment is applicable to a single-stage or multi-stage type GM cryocooler or another cryocooler including a rotary valve.

[0069] The present invention has been described above based on the example. The present invention is not limited to the above embodiment, and various design changes can be made, and it would be understood by those skilled in the art that various modifications are possible and such modifications also fall within the scope of the present invention.

[0070] The present invention can be used in the fields of a cryocooler, a rotary valve assembly of a cryocooler, and a valve stator of a rotary valve for a cryocooler.

[0071] It should be understood that the invention is not limited to the above-described embodiment, but may be modified into various forms on the basis of the spirit of the disclosure. Additionally, the modifications are included in the scope of the disclosure.

Claims

1. A cryocooler comprising:a housing; anda rotary valve that is accommodated in the housing and that includes a valve rotor and a valve stator, the valve stator disposed adjacent to the valve rotor and non-rotatably supported on the housing by a plurality of anti-rotation members.

2. The cryocooler according to claim 1,wherein the plurality of anti-rotation members include a plurality of anti-rotation pins.

3. The cryocooler according to claim 2,wherein the valve stator includes a first end surface adjacent to the valve rotor and a second end surface facing an opposite side from the first end surface, andthe plurality of anti-rotation pins are disposed on the second end surface of the valve stator.

4. The cryocooler according to claim 3,wherein the plurality of anti-rotation pins are disposed at unequal intervals around a rotation axis of the valve rotor on the second end surface of the valve stator.

5. The cryocooler according to claim 3,wherein the plurality of anti-rotation pins include a first anti-rotation pin that is disposed on a first side with respect to a rotation axis of the valve rotor on the second end surface of the valve stator, and a second anti-rotation pin that is disposed on a second side with respect to the rotation axis on the second end surface of the valve stator.

6. The cryocooler according to claim 5,wherein the second anti-rotation pin is disposed at a position offset by a predetermined angle around the rotation axis from a straight line perpendicular to the rotation axis and extending from the rotation axis to the first anti-rotation pin.

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

8. The cryocooler according to claim 3,wherein, on the second end surface of the valve stator, at least one anti-rotation pin among the plurality of anti-rotation pins is disposed at a distance from a rotation axis of the valve rotor that is different from a distance of at least one other anti-rotation pin from the rotation axis of the valve rotor, and / orat least one anti-rotation pin among the plurality of anti-rotation pins has a shape different from a shape of at least one other anti-rotation pin.

9. A rotary valve assembly of a cryocooler, the rotary valve assembly comprising:a valve rotor; anda valve stator disposed adjacent to the valve rotor and non-rotatably supported on a housing of the cryocooler by a plurality of anti-rotation members.

10. A valve stator of a rotary valve for a cryocooler, the valve stator comprising:a first end surface adjacent to a valve rotor of the rotary valve for the cryocooler; anda second end surface facing an opposite side from the first end surface,wherein the second end surface includes a plurality of pin holes each configured to receive an anti-rotation pin.

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