Cryogenic refrigerator compressor

Abstract

To achieve miniaturization while mounting a gas spring on a compressor of a cryogenic refrigerator.SOLUTION: A compressor 12 of a cryogenic refrigerator 10 includes a compressor housing 20, and a compressor piston 24 and a compressor cylinder 26 arranged in the compressor housing 20 and forming a compression chamber 22 of refrigerant gas of the cryogenic refrigerator 10 therebetween. One of the compressor piston 24 and the compressor cylinder 26 is a movable body supported by the compressor housing 20 so as to be vibrated, and the other of the compressor piston 24 and the compressor cylinder 26 is fixed to the compressor housing 20. The movable body has a gas spring chamber 32 therein.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a compressor suitable for a cryogenic refrigerator, such as a Stirling type cryogenic refrigerator.

Background Art

[0002] Conventionally, Stirling type cryogenic refrigerators, such as Stirling refrigerators and Stirling type pulse tube refrigerators, are known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As one measure for miniaturizing a Stirling type cryogenic refrigerator, it is conceivable to increase the operating frequency of the refrigerator, that is, the resonance frequency of a vibrating body (piston or cylinder) vibrating in the compressor. For this purpose, generally, it is necessary to increase the spring constant of a mechanical spring such as a leaf spring that supports the vibrating body. However, there are design difficulties in achieving both this and miniaturization. This is because miniaturization reduces the installation space for the mechanical spring and also requires miniaturization of the spring itself. When trying to ensure a large spring constant, stress concentration is likely to occur in the spring.

[0005] Therefore, it has been proposed to add a gas spring acting on the vibrating body and increase the spring constant by the sum of the gas spring and the mechanical spring. However, adding a gas spring requires a corresponding volume, which may also go against the miniaturization of the cryogenic refrigerator.

[0006] One exemplary object of an aspect of the present invention is to enable miniaturization while mounting a gas spring on a compressor of a cryogenic refrigerator. [Means for solving the problem]

[0007] According to one aspect of the present invention, the compressor of a cryogenic refrigerator comprises a compressor housing and a compressor piston and a compressor cylinder disposed in the compressor housing and forming a compression chamber for the refrigerant gas of the cryogenic refrigerator between them. One of the compressor piston and the compressor cylinder is a movable body vibrably supported in the compressor housing, and the other of the compressor piston and the compressor cylinder is fixed to the compressor housing. The movable body has a gas spring chamber inside. [Effects of the Invention]

[0008] According to the present invention, it is possible to miniaturize a cryogenic refrigerator while incorporating a gas spring into the compressor of the cryogenic refrigerator. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram showing a cryogenic refrigerator according to an embodiment. [Figure 2] This diagram schematically shows a compressor for a cryogenic refrigerator in a modified configuration. [Figure 3] This diagram schematically shows a compressor for a cryogenic refrigerator according to another embodiment. [Modes for carrying out the invention]

[0010] The embodiments for carrying out the present invention will be described in detail below with reference to the drawings. In the description and drawings, identical or equivalent components, members, and processes are denoted by the same reference numerals, and redundant descriptions will be omitted as appropriate. The scale and shape of the illustrated parts are set for convenience to facilitate the explanation and are not to be interpreted restrictively unless otherwise specified. The embodiments are illustrative and do not limit the scope of the present invention in any way. Not all features or combinations thereof described in the embodiments are necessarily essential to the invention.

[0011] Figure 1 is a schematic diagram showing a cryogenic refrigerator 10 according to an embodiment. In this embodiment, the cryogenic refrigerator 10 is a single-stage Stirling refrigerator and comprises a compressor 12, a connecting pipe 14, and an expander 16, also called a cold head.

[0012] The compressor 12 is configured, for example, as a so-called opposed two-cylinder linear compressor having two compressor units arranged coaxially opposite each other. The compressor 12 comprises a compressor housing 20, a compressor piston 24 and a compressor cylinder 26 arranged in the compressor housing 20 and forming a compression chamber 22 for the refrigerant gas of the cryogenic refrigerator 10 between them, and a compressor motor 28 that drives the compressor 12. The two compressor units are combined and share a common compressor housing 20.

[0013] The refrigerant gas (also called the working gas) used in the cryogenic refrigerator 10 is typically helium gas. However, it is not limited to helium, and other suitable gases can also be used as the refrigerant gas. The refrigerant gas is filled and sealed inside the cryogenic refrigerator 10.

[0014] In the compressor 12, the compressor housing 20 is a pressure vessel that airtightly holds refrigerant gas at a pressure higher than the ambient pressure, and the refrigerant gas is sealed inside the compressor housing 20. A refrigerant gas chamber 30 is also formed inside the compressor housing 20, separated from the compression chamber 22. While the compression chamber 22 is connected to the expander 16 via a connecting pipe 14, the refrigerant gas chamber 30 is a closed space within the compressor housing 20. The pressure in the refrigerant gas chamber 30 roughly coincides with the refrigerant gas sealing pressure, or in other words, the intermediate pressure of the pressure fluctuations in the compression chamber 22.

[0015] In this embodiment, the compressor 12 is of the movable cylinder type. Therefore, the compressor cylinder 26 is a movable body (vibrating body) that is vibrably supported in the compressor housing 20, and the compressor piston 24 is fixed to the compressor housing 20. The compressor cylinder 26 divides the internal volume of the compressor housing 20 into a compression chamber 22 and a refrigerant gas chamber 30. The compression chamber 22 is connected to the connecting pipe 14 through a gas passage formed in the compressor piston 24.

[0016] The compressor cylinder 26 and the compressor piston 24 are arranged coaxially, with the compressor piston 24 inserted into the compressor cylinder 26. Both the compressor cylinder 26 and the compressor piston 24 are elongated in the axial direction (left-right direction in Figure 1). The direction of vibration of the compressor cylinder 26 coincides with the axial direction of the compressor cylinder 26 and the compressor piston 24.

[0017] The compressor cylinder 26 has a gas spring chamber 32 inside it. The gas spring chamber 32 is formed between the gas spring chamber piston 34 and the gas spring chamber cylinder 36 and is separated from the refrigerant gas chamber 30. The gas spring chamber piston 34 and the gas spring chamber cylinder 36 are located in the refrigerant gas chamber 30 on the side of the compressor cylinder 26 opposite the compressor piston 24.

[0018] The gas spring chamber piston 34 is fixed to the compressor housing 20. While the compressor piston 24 is located in the axial center of the compressor housing 20, the gas spring chamber piston 34 is located at the axial end of the compressor housing 20. The gas spring chamber piston 34 may be integrally formed with the compressor housing 20.

[0019] The gas spring chamber cylinder 36 is fixed to the compressor cylinder 26 on the opposite side from the compressor piston 24. The gas spring chamber cylinder 36 is located within the compressor housing 20 and is fixed to the compressor cylinder 26. and Both are movable. The gas spring chamber cylinder 36 faces away from the compressor cylinder 26, and the gas spring chamber piston 34 is inserted inside it. Piston 34And the gas spring chamber cylinder 36 is arranged coaxially with the compressor piston 24 and the compressor cylinder 26. The gas spring chamber cylinder 36 may be integrally formed with the compressor cylinder 26.

[0020] When the compressor 12 is driven, the pressure in the gas spring chamber 32 fluctuates, but the pressure in the gas spring chamber 32 when the compressor 12 is not operating is equal to the pressure in the refrigerant gas chamber 30. The gas spring chamber 32 may communicate with the refrigerant gas chamber 30 through the clearance between the gas spring chamber piston 34 and the gas spring chamber cylinder 36.

[0021] The compressor motor 28 is configured to vibrate the compressor cylinder 26 upon its drive to generate pressure vibration of the refrigerant gas in the compression chamber 22. The compressor motor 28 is attached to the compressor housing 20 and is arranged in the refrigerant gas chamber 30.

[0022] The compressor motor 28 is, as an example, a magnetically movable linear vibration actuator. The compressor motor 28 has an inner yoke 28a, a permanent magnet 28b, a coil 28c, an outer yoke 28d, and a yoke support 28e. Thus, the movable part of the compressor motor 28 is constituted by the permanent magnet 28b, and the stationary part of the compressor motor 28 is constituted by the inner yoke 28a, the coil 28c, the outer yoke 28d, and the yoke support 28e.

[0023] These components of the compressor motor 28 are arranged coaxially with the compressor cylinder 26 so as to surround the compressor cylinder 26. The compressor cylinder 26 is located on the central axis of the compressor 12, and from there, toward the outside in the radial direction, the inner yoke 28a, the permanent magnet 28b, the coil 28c, and the outer yoke 28d are arranged in this order. The inner yoke 28a and the outer yoke 28d are fixed to the yoke support 28e. The permanent magnet 28b is fixed to the compressor cylinder 26 so as to be arranged between the inner yoke 28a and the outer yoke 28d, and the compressor cylinder 26 is movable integrally with the permanent magnet 28b. The yoke support 28e is fixed to the compressor housing 20.

[0024] The outer yoke 28d and / or yoke support 28e may also be part of the compressor housing 20, for example, they may constitute part of the pressure partition of the compressor housing 20 that isolates the refrigerant gas chamber 30 from the surrounding environment.

[0025] The compressor cylinder 26 is connected to the compressor housing 20 via a support structure, such as a flexure bearing 38. The flexure bearing 38 comprises, for example, one or more leaf springs located in the refrigerant gas chamber 30, which are flexible in the direction of vibration of the compressor cylinder 26 (i.e., axially) and rigid in directions perpendicular to the direction of vibration (e.g., radially, circumferentially). Thus, the compressor cylinder 26 is elastically supported in the compressor housing 20 via the flexure bearing 38 so as to be displaceable in the axial direction while radial and circumferential displacement is restricted. In this embodiment, two flexure bearings 38 are provided for each compressor cylinder 26, with one flexure bearing 38 supporting the compressor cylinder 26 and the other supporting the gas spring chamber cylinder 36.

[0026] The connecting pipe 14 connects the compressor 12 to the expander 16. That is, the compressor 12 and the expander 16 are connected through the connecting pipe 14 so that refrigerant gas can flow bidirectionally between the compressor 12 and the expander 16. Therefore, pressure fluctuations of the refrigerant gas generated by the compressor 12 are transmitted to the expander 16 via the connecting pipe 14, thereby inducing pressure fluctuations within the expander 16. The connecting pipe 14 may be a flexible pipe or a rigid pipe.

[0027] The expander 16 may employ any known configuration as appropriate. Therefore, the specific internal configuration of the expander 16 will not be described in detail here.

[0028] In this configuration, when alternating current is supplied to the coil 28c of the compressor motor 28 in the compressor 12, an alternating magnetic field is generated around the coil 28c. The magnetic interaction between this magnetic field and the permanent magnet 28b drives the compressor cylinder 26 together with the permanent magnet 28b. That is, the compressor motor 28 causes the compressor cylinder 26 to vibrate in its longitudinal direction relative to the compressor housing 20. This causes the volume of the compression chamber 22 to increase or decrease oscillatingly, generating pressure oscillations of the refrigerant gas in the compression chamber 22. For example, the average pressure of the pressure oscillation may be on the order of megapascals, for example, in the range of about 1 to 3 MPa, the pressure amplitude may be in the range of about 0.5 to 1 MPa, for example, and the frequency may be in the range of about 50 to 60 Hz.

[0029] Pressure fluctuations of the refrigerant gas in the compression chamber 22 are transmitted to the expander 16 via the connecting pipe 14. A refrigeration cycle (for example, specifically an inverse Stirling cycle) is formed between the compressor 12 and the expander 16, and the cryogenic refrigerator 10 can provide cryogenic cooling.

[0030] In this embodiment, the compressor 12 is provided with a gas spring chamber 32. When the compressor 12 is driven by the compressor motor 28, the gas spring chamber 32 acts as a gas spring, with the refrigerant gas pressure inside acting on the compressor cylinder 26. The spring constant of the resonant system, with the compressor cylinder 26 as the vibrating body, is increased by the sum of this gas spring and the flexure bearing 38. This allows the resonant frequency to be increased, and thus the operating frequency of the cryogenic refrigerator 10 to be increased, while suppressing the increase in load on the flexure bearing 38. This means that the same cooling capacity can be achieved with a smaller refrigerator, thus contributing to the miniaturization of the cryogenic refrigerator 10.

[0031] Another design option for installing the gas spring is to add an additional gas spring chamber to the end of the compressor housing. In this case, the compressor housing would either be extended axially by the amount of the additional gas spring chamber, or a protrusion corresponding to the gas spring chamber would be formed at the end of the housing, which tends to lead to an increase in the size of the compressor housing.

[0032] In contrast, in this embodiment, the gas spring chamber 32 is located inside the compressor cylinder 26. This allows the gas spring chamber 32 to be incorporated into the compressor 12 while making effective use of the internal space and avoiding an increase in the size of the compressor housing 20.

[0033] Figure 2 is a schematic diagram showing a modified cryogenic refrigerator compressor 12. Similar to the embodiment described above, the compressor cylinder 26 has a gas spring chamber 32 inside it. The gas spring chamber 32 is formed between a gas spring chamber piston 34 fixed to the compressor housing 20 and a gas spring chamber cylinder 36 fixed to the compressor cylinder 26.

[0034] It is desirable that the spring constant of the gas spring chamber 32 be adjustable. Therefore, as shown in Figure 2, the gas spring chamber piston 34 is provided with a refrigerant gas passage 40 that connects the gas spring chamber 32 to the refrigerant gas chamber 30, and a flow regulator 42 may be provided in the refrigerant gas passage 40. The flow regulator 42 may be installed in the compressor housing 20. The flow regulator 42 may be, for example, a needle valve having a needle valve body 42a arranged in the refrigerant gas passage 40.

[0035] The flow regulator 42 may be operable from outside the compressor housing 20. For example, if the flow regulator 42 is a needle valve, the flow regulator 42 may be equipped with an operating part 42b, such as an adjustment screw, located on the outside of the compressor housing 20. By operating the operating part 42b from outside the compressor housing 20, the needle valve body 42a can be moved forward and backward within the refrigerant gas flow path 40, thereby adjusting the refrigerant gas flow rate in the refrigerant gas flow path 40.

[0036] The flow regulator 42 can be used to adjust the refrigerant gas flow rate in the refrigerant gas passage 40 when the volume of the gas spring chamber 32 increases or decreases due to vibration of the gas spring chamber cylinder 36, thereby adjusting the spring constant of the gas spring chamber 32. This changes the resonant frequency of the compressor cylinder 26 and, consequently, the operating frequency of the cryogenic refrigerator, thereby improving or optimizing the cooling capacity of the cryogenic refrigerator. The flow regulator 42 can be operated from outside the compressor housing 20, which is convenient for performing this adjustment work.

[0037] Figure 3 is a schematic diagram showing the compressor 12 of a cryogenic refrigerator 10 according to another embodiment. In the above-described embodiment, the case in which the compressor 12 is of the cylinder type was explained as an example, but as shown in Figure 3, the compressor 12 may be of the piston type. The gas spring chamber 32 may be applied to the piston type compressor 12.

[0038] The compressor 12 is configured as a so-called opposed two-cylinder linear compressor having two compressor units arranged coaxially opposite each other. The compressor 12 comprises a compressor housing 20, a compressor piston 24 and a compressor cylinder 26 arranged in the compressor housing 20 and forming a compression chamber 22 for the refrigerant gas of the cryogenic refrigerator 10 between them, and a compressor motor 28 that drives the compressor 12.

[0039] The compressor piston 24 is a movable body (vibrating body) that is vibrably supported in the compressor housing 20, and the compressor cylinder 26 is fixed to the compressor housing 20. The compressor cylinder 26 may be part of the compressor housing 20. A refrigerant gas chamber 30 is formed inside the compressor housing 20, separated from the compression chamber 22 by the compressor piston 24. The compression chamber 22 is connected to a connecting pipe 14.

[0040] The compressor piston 24 has a gas spring chamber 32 inside it. The gas spring chamber 32 is formed between the gas spring chamber piston 34 and the gas spring chamber cylinder 36 and is separated from the refrigerant gas chamber 30. The gas spring chamber piston 34 is fixed to the compressor housing 20. The gas spring chamber cylinder 36 is formed at the end of the compressor piston 24 on the opposite side from the compression chamber 22, and the gas spring chamber piston 34 is inserted into it.

[0041] The compressor motor 28 is mounted on the compressor housing 20 and positioned in the refrigerant gas chamber 30. Similar to the embodiments described above, the compressor motor 28 is, for example, a magnetically movable linear vibration actuator, having an inner yoke 28a, a permanent magnet 28b, a coil 28c, and an outer yoke 28d. The compressor piston 24 and the gas spring chamber cylinder 36 are connected to the compressor housing 20 via flexure bearings 38.

[0042] When the compressor 12 is driven by the compressor motor 28, the gas spring chamber 32 acts as a gas spring, with the internal refrigerant gas pressure acting on the vibrating compressor piston 24. In this way, as in the embodiment described above, it is possible to miniaturize the cryogenic refrigerator 10 while still incorporating a gas spring into the compressor 12 of the cryogenic refrigerator 10.

[0043] The present invention has been described above based on examples. Those skilled in the art will understand that the present invention is not limited to the above embodiments, that various design changes are possible, and that various modifications are possible, and that such modifications also fall within the scope of the present invention. Various features described in relation to one embodiment are applicable to other embodiments. New embodiments resulting from combinations will possess the combined effects of each of the embodiments combined.

[0044] In the embodiment shown in Figure 3, as in the embodiment in Figure 2, the gas spring chamber piston 34 is provided with a refrigerant gas passage 40 that connects the gas spring chamber 32 to the refrigerant gas chamber 30, and a flow regulator 42 may be provided in the refrigerant gas passage 40. The flow regulator 42 may be, for example, a needle valve having a needle valve body 42a arranged in the refrigerant gas passage 40. The flow regulator 42 may be operable from outside the compressor housing 20. For example, if the flow regulator 42 is a needle valve, the flow regulator 42 may be provided with an operating part 42b such as an adjustment screw provided on the outside of the compressor housing 20.

[0045] In the above-described embodiment, a single-stage Stirling-type cryogenic refrigerator is explained as an example. However, in some embodiments, the cryogenic refrigerator 10 can also be configured as a two-stage Stirling-type cryogenic refrigerator (i.e., a two-stage Stirling refrigerator, or a two-stage Stirling-type pulse tube refrigerator).

[0046] Although the present invention has been described using specific terms based on the embodiments, the embodiments only illustrate one aspect of the principle and application of the present invention, and many modifications and changes in arrangement are permitted in the embodiments, as long as they do not depart from the spirit of the present invention as defined in the claims. [Explanation of Symbols]

[0047] 10 Cryogenic refrigerator, 12 Compressor, 20 Compressor housing, 22 Compression chamber, 24 Compressor piston, 26 Compressor cylinder, 30 Refrigerant gas chamber, 32 Gas spring chamber, 34 Gas spring chamber piston, 36 Gas spring chamber cylinder, 40 Refrigerant gas flow path, 42 Flow regulator.

Claims

1. A compressor for a cryogenic refrigerator, Compressor housing and The compressor housing comprises a compressor piston and a compressor cylinder, which are arranged thereto and form a compression chamber for the refrigerant gas of the cryogenic refrigerator between them. One of the compressor piston and the compressor cylinder is a movable body that is vibrably supported in the compressor housing, and the other of the compressor piston and the compressor cylinder is fixed to the compressor housing. The compressor for a cryogenic refrigerator is characterized in that the movable body has a gas spring chamber inside, and when the compressor is driven, the gas spring chamber acts only as a gas spring through which the internal refrigerant gas pressure acts on the movable body.

2. The compressor housing includes a fixed gas spring chamber piston, The compressor for a cryogenic refrigerator according to claim 1, characterized in that the movable body comprises a gas spring chamber cylinder that forms the gas spring chamber between itself and the gas spring chamber piston.

3. A compressor for a cryogenic refrigerator, Compressor housing and The compressor housing comprises a compressor piston and a compressor cylinder, which are arranged thereto and form a compression chamber for the refrigerant gas of the cryogenic refrigerator between them. One of the compressor piston and the compressor cylinder is a movable body that is vibrably supported in the compressor housing, and the other of the compressor piston and the compressor cylinder is fixed to the compressor housing. The aforementioned movable body has a gas spring chamber inside, The compressor housing includes a fixed gas spring chamber piston, The movable body includes a gas spring chamber cylinder that forms the gas spring chamber between itself and the gas spring chamber piston. A refrigerant gas chamber is formed within the compressor housing, separated from the compression chamber. The gas spring chamber piston is provided with a refrigerant gas passage that connects the gas spring chamber to the refrigerant gas chamber. A compressor for a cryogenic refrigerator, characterized in that a flow regulator is provided in the refrigerant gas flow path.

4. The compressor for the cryogenic refrigerator according to claim 3, characterized in that the flow regulator can be operated from outside the compressor housing.

5. The compressor for a cryogenic refrigerator according to any one of claims 1 to 4, characterized in that the movable body is the compressor cylinder.

6. The compressor for a cryogenic refrigerator according to any one of claims 1 to 4, characterized in that the movable body is the compressor piston.

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