Thermal switch and thermal switch device

Abstract

A thermal switch (100) is provided with a high-temperature-side heat transfer element (110) and a low-temperature-side heat transfer element (120) disposed facing the high-temperature-side heat transfer element (110) with an air gap (130) therebetween. One of the high-temperature-side heat transfer element (110) and the low-temperature-side heat transfer element (120) is provided with a first base part (111) and a column part (112) extending from the first base part (111). The other of the high-temperature-side heat transfer element (110) and the low-temperature-side heat transfer element (120) is provided with a second base section (121) facing the column section (112), and a tube section (122) extending from the second base section (121) so as to surround the column section (112). The thermal switch (100) is further provided with a connecting cylinder (140) which connects the cylinder part (122) to the first base part (111) so as to isolate the air gap (130) from the surrounding environment, and which is formed of a heat insulating material.

Description

Technical Field

[0001] The invention relates to a thermal switch and a thermal switch device using the thermal switch. Background Art

[0002] For example, in a cryogenic device such as a superconducting magnet device that operates at a very low temperature, initial cooling is performed from an initial temperature such as room temperature to a target cooling temperature when the device is started. The use of a cryogenic device such as a superconducting magnet that provides a high magnetic field can only be achieved after the initial cooling is completed. Therefore, it is desirable that the time required for the initial cooling is as short as possible.

[0003] In order to perform ultra-low temperature cooling, ultra-low temperature devices generally use a two-stage ultra-low temperature refrigerator such as a Gifford-McMahon (GM) refrigerator. The second stage of the ultra-low temperature refrigerator, which cools to a lower temperature, cools the ultra-low temperature device's cooled object such as a superconducting coil, and the first stage of the ultra-low temperature refrigerator, which cools to a higher temperature than the second stage, cools the first stage's cooled object such as a radiation shielding member used to reduce the input heat to the second stage's cooled object. Since the first stage has a larger refrigeration capacity, the first stage's cooled object can be initially cooled in a shorter time. However, the second stage's refrigeration capacity is generally much smaller than that of the first stage, so the initial cooling of the second stage's cooled object often takes longer time than the first stage. In particular, in an ultra-low temperature device having a large superconducting coil, for example, the time required for initial cooling may sometimes become quite long.

[0004] In order to speed up the cooling speed and complete the initial cooling in a short time, it is proposed to set a thermal switch between the cooled objects of the first stage and the second stage. As an exemplary thermal switch, there is known a structure in which two heat transfer surfaces that do not contact each other are set in a container sealed with gas. When the temperature of the heat transfer surface is higher than the boiling point of the gas, the two heat transfer surfaces are thermally connected through heat exchange through the gas, and the thermal switch is turned on. If the heat transfer surface is cooled and its temperature becomes lower than the boiling point of the gas, the gap between the two heat transfer surfaces becomes a vacuum due to the condensation of the gas, and due to vacuum insulation, the thermal connection is released and the thermal switch is closed.

[0005] By providing a thermal switch between the first stage and the second stage of the objects to be cooled, the first stage and the second stage of the objects to be cooled are thermally connected by the thermal switch at a high temperature such as room temperature, and not only the second stage of the ultra-low temperature refrigerator can be used, but also the first stage can be used to quickly cool the second stage of the objects to be cooled. In this way, the time required for initial cooling can be shortened. At ultra-low temperatures, the thermal switch is switched to the closed state, the thermal connection between the first stage and the second stage is cut off, and the first stage and the second stage of the objects to be cooled can be cooled to the target cooling temperature respectively.

[0006] Previous technical literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 9-166365 Summary of the invention

[0009] Technical problem to be solved by the invention

[0010] For efficient heat transfer under the open state, it is expected that the areas of the two heat transfer surfaces of the thermal switch are respectively as large as possible. At the same time or as an alternative, it is expected that the thermal switch can reliably cut off the thermal connection when closed.

[0011] An exemplary object of one embodiment of the present invention is to provide a new thermal switch suitable for a cryogenic device and a thermal switch device using the thermal switch.

[0012] Means for solving technical problems

[0013] According to one embodiment of the present invention, a thermal switch includes a high-temperature side heat transfer element and a low-temperature side heat transfer element disposed opposite to the high-temperature side heat transfer element with an air gap therebetween. One of the high-temperature side heat transfer element and the low-temperature side heat transfer element includes a first base and a column extending from the first base. The other of the high-temperature side heat transfer element and the low-temperature side heat transfer element includes a second base opposite to the column and a cylinder extending from the second base in a manner of surrounding the column. The thermal switch also includes a connecting cylinder that connects the cylinder to the first base to isolate the air gap from the surrounding environment and is formed of an insulating material.

[0014] According to one embodiment of the present invention, the thermal switch includes a high-temperature side heat transfer element, a low-temperature side heat transfer element arranged opposite to the high-temperature side heat transfer element with an air gap therebetween, and a getter material thermally connected to the low-temperature side heat transfer element and capable of absorbing gas from the air gap.

[0015] According to one embodiment of the present invention, a thermal switch device includes a plurality of thermal switches connected in series. Each of the plurality of thermal switches includes a high temperature side heat transfer element and a low temperature side heat transfer element disposed opposite to the high temperature side heat transfer element via an air gap.

[0016] Effects of the Invention

[0017] According to the present invention, a new thermal switch suitable for a cryogenic device and a thermal switch device using the thermal switch can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 (a) is a diagram schematically showing a cryogenic device according to one embodiment, Figure 1 (b) is a diagram schematically showing a cryogenic refrigerator according to one embodiment.

[0019] Figure 2It is a schematic cross-sectional view showing an exemplary structure of the thermal switch according to the embodiment in more detail.

[0020] Figure 3 Schematic diagram showing a thermal switch according to a modification.

[0021] Figure 4 (a) and Figure 4 (b) is a schematic diagram showing a thermal switch according to a modification example.

[0022] Figure 5 Schematic diagram showing a thermal switch according to a modification.

[0023] Figure 6 Schematic diagram showing a thermal switch according to a modification.

[0024] Figure 7 Schematic diagram showing a thermal switch according to a modification.

[0025] Figure 8 Schematic diagram showing a thermal switch device according to an embodiment.

[0026] Explanation of symbols:

[0027] 100-thermal switch, 110-high temperature side heat transfer element, 111-first base, 112-column, 120-low temperature side heat transfer element, 121-second base, 122-cylinder, 130-air gap, 140-connecting tube, 150-intake material, 152-intake chamber, 170-covering, 200-thermal switch device. DETAILED DESCRIPTION

[0028] Hereinafter, the method for implementing the present invention will be described in detail with reference to the accompanying drawings. In the description and the accompanying drawings, the same or equivalent components, parts, and processes are marked with the same symbols, and repeated descriptions are appropriately omitted. In each of the drawings, for the convenience of description, the proportions or shapes of each part are appropriately set, and unless otherwise specifically stated, they are not interpreted as limiting. The implementation methods are examples and do not limit the scope of the present invention in any way. All the features or combinations thereof described in the implementation methods are not necessarily the essence of the invention.

[0029] Figure 1 (a) is a diagram schematically showing a cryogenic device 10 according to an embodiment. The cryogenic device 10 is configured to cool a superconducting coil 12 as an example of a cooled object from room temperature to a cryogenic temperature, and to maintain the superconducting coil 12 at a cryogenic temperature during use.

[0030] The superconducting coil 12 can be mounted on a strong magnetic field utilization device as a magnetic field source for, for example, a single crystal pulling device, an NMR system, an MRI system, an accelerator such as a cyclotron, a high energy physics system such as a nuclear fusion system, or other strong magnetic field utilization equipment (not shown), thereby generating a strong magnetic field required by the equipment. The superconducting coil 12 is configured to generate a strong magnetic field by passing electricity through the superconducting coil 12 in a state of being cooled to an ultra-low temperature below the superconducting transition temperature.

[0031] The cryogenic device 10 includes a cryogenic refrigerator 20, a vacuum container 30, and a radiation shield 40. In this embodiment, the cryogenic device 10 is configured as a conduction cooling type in which the superconducting coil 12 is directly cooled by the cryogenic refrigerator 20, rather than an immersion cooling type in which the superconducting coil 12 is immersed in a cryogenic liquid refrigerant such as liquid helium for cooling. The cryogenic refrigerator 20 is thermally connected to the superconducting coil 12 to cool the superconducting coil 12 by conduction cooling.

[0032] In addition, Figure 1 In (a), one cryogenic refrigerator 20 is shown as an example, but when the superconducting coil 12 is large, for example, the cryogenic device 10 may include a plurality of cryogenic refrigerators 20 for cooling the same object to be cooled as needed.

[0033] The cryogenic refrigerator 20 includes a cooling stage 22 for cooling an object by conduction cooling, more specifically, a first cooling stage 22a and a second cooling stage 22b. The cryogenic refrigerator 20 is disposed in a vacuum container 30, and the first cooling stage 22a and the second cooling stage 22b are disposed in the vacuum container 30. As an example, the cryogenic refrigerator 20 is a two-stage Gifford-McMahon refrigerator.

[0034] The cryogenic refrigerator 20 includes a compressor (not shown) of a working gas (e.g., helium) and an expander also called a cold head. The compressor and the expander constitute a refrigeration cycle of the cryogenic refrigerator 20, whereby the first cooling stage 22a and the second cooling stage 22b are cooled to the desired ultra-low temperature, respectively. The first cooling stage 22a is cooled to a first cooling temperature, e.g., 30K to 80K, and the second cooling stage 22b is cooled to a second cooling temperature, e.g., 3K to 20K, which is lower than the first cooling temperature. The second cooling temperature is a temperature lower than the superconducting transition temperature of the superconducting coil 12. The first cooling stage 22a and the second cooling stage 22b are formed of, for example, a metal material such as copper (e.g., pure copper, the same below) or other materials having a high thermal conductivity.

[0035] The vacuum container 30 is configured to isolate a vacuum region 32 from the external environment 14. The vacuum region 32 is confined within the vacuum container 30. The vacuum container 30 may be, for example, a cryostat. The superconducting coil 12, the cooling stage 22 of the cryogenic refrigerator 20, and the radiation shield 40 are disposed in the vacuum region 32 and are vacuum-insulated from the external environment 14.

[0036] The radiation shield 40 is thermally connected to the first cooling stage 22a and is cooled to the first cooling temperature. The radiation shield 40 is directly mounted on the first cooling stage 22a and is thermally connected to the first cooling stage 22a. Alternatively, the radiation shield 40 can also be mounted on the first cooling stage 22a via a flexible or rigid heat transfer component. The radiation shield 40 is configured to surround the superconducting coil 12 cooled to the second cooling temperature, the second cooling stage 22b of the cryogenic refrigerator 20, and other low-temperature components, and can thermally protect these low-temperature components from external radiant heat. The radiation shield 40 is formed of, for example, a metal material such as copper or other material having a high thermal conductivity.

[0037] The superconducting coil 12 is thermally connected to the second cooling stage 22b via a heat transfer component 50. The heat transfer component 50 is formed of, for example, a metal material such as copper or other material having a high thermal conductivity, and connects the superconducting coil 12 to the second cooling stage 22b. The heat transfer component 50 may be flexible to allow relative displacement between the superconducting coil 12 and the second cooling stage 22b and connect them in this way, or may be a rigid component that rigidly connects the superconducting coil 12 and the second cooling stage 22b. The heat transfer component 50 is formed of, for example, a metal material such as copper or other material having a high thermal conductivity.

[0038] In the example shown in the figure, the heat transfer member 50 is fixed to the bottom surface of the second cooling stage 22b, but it can also be fixed to other parts such as the side surface or the upper surface of the second cooling stage 22b. Similarly, the heat transfer member 50 is fixed to the bottom surface of the superconducting coil 12, for example, but it can also be fixed to other parts such as the side surface or the upper surface of the superconducting coil 12.

[0039] In this embodiment, the cryogenic device 10 includes a thermal switch 100 for thermally connecting or disconnecting the superconducting coil 12 and the radiation shield 40. The details will be described later. The thermal switch 100 includes a high-temperature side heat transfer element 110 and a low-temperature side heat transfer element 120 that are arranged opposite to each other with an air gap 130 interposed therebetween. The thermal switch 100 constitutes an airtight container that seals the working gas in the air gap 130.

[0040] As an example, as shown in the figure, the high temperature side heat transfer element 110 is mounted on the radiation shield 40, the low temperature side heat transfer element 120 is mounted on the superconducting coil 12, and the thermal switch 100 directly connects the superconducting coil 12 and the radiation shield 40. Alternatively, the high temperature side heat transfer element 110 can be mounted on the first cooling stage 22a or the radiation shield 40 via a heat transfer component, and the low temperature side heat transfer element 120 can be mounted on the second cooling stage 22b, the superconducting coil 12, or the heat transfer component 50 via a heat transfer component. The thermal switch 100 can connect any portion cooled to the first cooling temperature and any portion cooled to the second cooling temperature.

[0041] When the temperature of the high-temperature side heat transfer element 110 and the low-temperature side heat transfer element 120 is higher than the switching temperature, the thermal switch 100 can thermally connect the high-temperature side and the low-temperature side through the heat transfer between the heat transfer elements of the working gas in the air gap 130. This is the on state of the thermal switch 100. The switching temperature of the thermal switch 100 is equivalent to the boiling point of the sealed working gas. The air gap 130 is an extremely narrow gap for good heat transfer. The size of the air gap 130 (the shortest distance between the high-temperature side heat transfer element 110 and the low-temperature side heat transfer element 120) can be within 5 mm or within 2 mm, for example.

[0042] Furthermore, when the temperature of at least one of the high-temperature side heat transfer element 110 and the low-temperature side heat transfer element 120 (usually the low-temperature side heat transfer element 120) is lower than the switching temperature, the thermal switch 100 disconnects the thermal connection between the high-temperature side and the low-temperature side. This is because the working gas in the air gap 130 condenses at least on the surface of the low-temperature side heat transfer element 120, and the air gap 130 becomes a vacuum, and the high-temperature side heat transfer element 110 and the low-temperature side heat transfer element 120 are vacuum-insulated via the air gap 130. This is the closed state of the thermal switch 100.

[0043] The cryogenic device 10 according to the embodiment operates as follows. When the cryogenic refrigerator 20 is started, the first cooling stage 22a of the cryogenic refrigerator 20 is cooled to the first cooling temperature, and the second cooling stage 22b is cooled to the second cooling temperature. The radiation shield 40 is cooled to the first cooling temperature by the first cooling stage 22a, and the superconducting coil 12 is cooled to the second cooling temperature by the second cooling stage 22b. By energizing the superconducting coil 12 from a power source not shown in the figure, the superconducting coil 12 can generate a strong magnetic field. Thus, the cryogenic device 10 can be operated.

[0044] Connecting a portion of the first cooling temperature such as the radiation shield 40 and a portion of the second cooling temperature such as the superconducting coil 12 by a thermal switch 100 is beneficial to the initial cooling when the ultra-low temperature device 10 is started. In the initial cooling, the ultra-low temperature refrigerator 20 is cooled from the ambient temperature (e.g., room temperature) to the target ultra-low temperature. Therefore, at the beginning of the initial cooling, the thermal switch 100 is turned on, and the radiation shield 40 and the superconducting coil 12 are thermally connected. Generally speaking, the refrigeration capacity in the first cooling stage 22a of the ultra-low temperature refrigerator 20 is greater than the refrigeration capacity in the second cooling stage 22b, so the refrigeration capacity of the first cooling stage 22a can be used in the cooling assistance of the superconducting coil 12 based on the second cooling stage 22b. Thus, the required time for initial cooling can be shortened.

[0045] Then, cooling is performed, and when the superconducting coil 12 is cooled to a temperature lower than the switching temperature of the thermal switch 100, the thermal switch 100 is switched off, and the thermal connection between the radiation shield 40 and the superconducting coil 12 is cut off. The radiation shield 40 is maintained at the first cooling temperature by the first cooling stage 22a, while the superconducting coil 12 is further cooled by the second cooling stage 22b and finally cooled to the second cooling temperature.

[0046] Figure 1 (b) is a diagram schematically showing a cryogenic refrigerator 20 according to one embodiment. Figure 1 In (a), the case where the thermal switch 100 is connected to the radiation shield 40 and the superconducting coil 12 is described as an example. Figure 1 As shown in (b) of FIG. 1 , the thermal switch 100 may be connected to the first cooling stage 22 a and the second cooling stage 22 b of the cryogenic refrigerator 20 .

[0047] And, in Figure 1 (a) and Figure 1 In (b), the case where one thermal switch 100 is provided is described as an example, but the present invention is not limited thereto. For example, the cryogenic device 10 may include a plurality of thermal switches 100, each of which may be connected to a portion of the first cooling temperature such as the radiation shield 40 and a portion of the second cooling temperature such as the superconducting coil 12. Furthermore, the cryogenic refrigerator 20 may include a plurality of thermal switches 100, each of which may be connected to the first cooling stage 22a and the second cooling stage 22b.

[0048] Figure 2 is shown in more detail Figure 1 (a) and Figure 1 (b) is a schematic cross-sectional view of an exemplary structure of the thermal switch 100. Figure 21 shows a longitudinal section including the central axis of the thermal switch 100. As described above, the thermal switch 100 includes a high temperature side heat transfer element 110 and a low temperature side heat transfer element 120 disposed opposite to the high temperature side heat transfer element 110 via an air gap 130. For example, the thermal switch 100 may have a substantially cylindrical shape extending along the central axis thereof.

[0049] The high temperature side heat transfer element 110 includes a first base portion 111 and a column portion 112 extending from the first base portion 111. The first base portion 111 and the first member 61 (for example, Figure 1 The first base 111 may be thermally connected to the radiation shield 40 or the first cooling stage 22a shown in (a). The first base 111 may have, for example, a roughly disc-shaped shape, and is fixed to the first component 61 by bringing its circular end face into contact with the surface of the first component 61. The column 112 is arranged inside the thermal switch 100. The column 112 may have, for example, a cylindrical shape. The column 112 extends coaxially with the first base 111 along the central axis of the thermal switch 100 from the first base 111 on the side opposite to the first component 61. The column 112 may be formed integrally with the first base 111, or may be prepared separately from the first base 111 and joined to the first base 111.

[0050] The low temperature side heat transfer element 120 includes a second base portion 121 and a cylindrical portion 122 extending from the second base portion 121. The second base portion 121 and the second member 62 (for example, Figure 1 The second base 121 may be thermally connected to the superconducting coil 12 or the second cooling stage 22b shown in (a). The second base 121 may have, for example, a roughly disc-shaped shape, and is fixed to the second component 62 by bringing its circular end face into contact with the surface of the second component 62. The barrel 122 may have, for example, a cylindrical shape. The barrel 122 extends coaxially with the second base 121 along the central axis of the thermal switch 100 from the second base 121 on the side opposite to the second component 62. The barrel 122 may be formed integrally with the second base 121, or may be prepared separately from the second base 121 and joined to the second base 121.

[0051] The low-temperature-side heat transfer element 120 is configured to accommodate the high-temperature-side heat transfer element 110 therein. The column 112 of the high-temperature-side heat transfer element 110 is inserted into the cavity of the cylinder 122 of the low-temperature-side heat transfer element 120. The second base 121 of the low-temperature-side heat transfer element 120 faces the column 112 of the high-temperature-side heat transfer element 110, and the cylinder 122 of the low-temperature-side heat transfer element 120 surrounds the column 112 of the high-temperature-side heat transfer element 110. The column 112 of the high-temperature-side heat transfer element 110 is separated from the second base 121 and the cylinder 122 of the low-temperature-side heat transfer element 120 by an air gap 130, and has no physical contact. The cylinder 122 of the low-temperature-side heat transfer element 120 is disposed on the side opposite to the second base 121 and close to the first base 111 of the high-temperature-side heat transfer element 110.

[0052] In this way, when the high temperature side heat transfer element 110 has the column part 112 and the low temperature side heat transfer element 120 has the cylinder part 122, the volume of the low temperature side heat transfer element 120 can be reduced compared with the high temperature side heat transfer element 110. The small volume of the low temperature side heat transfer element 120 reduces the heat load on the second cooling stage 22b of the ultra-low temperature refrigerator 20, thereby (for example, Figure 3 example) may be advantageous.

[0053] In addition, the thermal switch 100 includes a connecting tube 140, which together with the high-temperature side heat transfer element 110 and the low-temperature side heat transfer element 120 forms an airtight container for sealing the working gas of the thermal switch 100. The connecting tube 140 connects the high-temperature side heat transfer element 110 and the low-temperature side heat transfer element 120, and more specifically, separates the air gap 130 from the surrounding environment (for example, Figure 1 The connecting tube 140 is, for example, cylindrical in shape and extends coaxially with the first base 111 and the tube 122 along the central axis of the thermal switch 100. The connecting tube 140, the high-temperature side heat transfer element 110, and the low-temperature side heat transfer element 120 can be joined, for example, by brazing, bonding, or other appropriate joining methods.

[0054] The axial length of the connecting tube 140 can be much shorter than the axial length of the thermal switch 100, for example, less than half or less than 1 / 3 of the total axial length of the thermal switch 100. As an example, the connecting tube 140 can have a ring shape (e.g., a circular ring shape) with an axial length shorter than the diameter, rather than a tube.

[0055] In a conventional heat switch design, a tube member serving as the outer shell of the heat switch extends substantially over the entire length of the heat switch in the axial direction, and two heat transfer bodies separated from each other are connected by the tube member. Figure 5The diameter of the heat transfer body is smaller than the diameter of the cylinder member by an amount corresponding to the radial gap, and as a result, the surface area of ​​the heat transfer body also decreases in accordance with the diameter, which may cause the heat transfer performance of the thermal switch to decrease.

[0056] In contrast, in this embodiment, the connecting tube 140 is connected in series with the tube portion 122 of the low temperature side heat transfer element 120 in the axial direction. There is no radial gap between the connecting tube 140 and the tube portion 122. The diameter of the tube portion 122 is the same as the diameter of the thermal switch 100, which can make the surface area of ​​the tube portion 122 wider. Compared with the previous design, this can improve the heat transfer performance of the thermal switch 100.

[0057] The high-temperature side heat transfer element 110 and the low-temperature side heat transfer element 120 are formed of metal materials such as copper or other materials with high thermal conductivity, similar to other heat transfer components in the ultra-low temperature device 10. In addition, the high-temperature side heat transfer element 110 and the low-temperature side heat transfer element 120 are usually formed of the same material, but can also be formed of different materials.

[0058] The connecting tube 140 is formed of a material having a lower thermal conductivity than the high-temperature side heat transfer element 110 and the low-temperature side heat transfer element 120, such as a heat insulating material. Here, the heat insulating material may be a material having a thermal conductivity of, for example, 1 / 10 or less of the thermal conductivity of the high heat conductive material forming the high-temperature side heat transfer element 110 (or the low-temperature side heat transfer element 120). The connecting tube 140 may also be formed of, for example, stainless steel or glass fiber reinforced plastic (GFRP) or other plastic materials. Thus, when the thermal switch 100 is closed, heat intrusion from the high-temperature side heat transfer element 110 to the low-temperature side heat transfer element 120 through the connecting tube 140 can be prevented or minimized.

[0059] Compared with the high heat conductivity material forming the heat transfer element, the material forming the connecting tube 140 is generally high in strength, so as shown in the figure, the wall thickness of the connecting tube 140 can be thinner than the wall thickness of the tube portion 122 of the heat transfer element. Such thinning of the connecting tube 140 helps to suppress the heat intrusion from the high-temperature side heat transfer element 110 to the low-temperature side heat transfer element 120 through the connecting tube 140.

[0060] The working gas sealed in the thermal switch 100 is selected so that the switching temperature of the thermal switch 100 is lower than the first cooling temperature of the ultra-low temperature refrigerator 20 and higher than the second cooling temperature. As described above, the switching temperature of the thermal switch 100 is equivalent to the boiling point of the sealed working gas. Therefore, the working gas sealed in the thermal switch 100 can be, for example, neon (about 27.1K). Alternatively, the working gas can also be hydrogen (about 20.4K) or helium (about 4.2K). Here, the boiling points of each gas type at atmospheric pressure are marked in brackets. For example, when neon is sealed as a working gas in the thermal switch 100 at atmospheric pressure, the switching temperature of the thermal switch 100 can be about 27.1K. The working gas can also be sealed in the thermal switch 100 at a pressure higher than the atmospheric pressure (for example, within 5 atmospheres or within 10 atmospheres). By adjusting the sealing pressure of the working gas, the switching temperature of the thermal switch 100 can be adjusted.

[0061] In addition, the working gas may also be a mixed gas, for example, a mixed gas containing at least one of neon, hydrogen and helium. The mixed gas may contain a diluent gas such as nitrogen, argon or air. By adjusting the composition of the mixed gas, the switching temperature of the thermal switch 100 can be adjusted.

[0062] Optionally, the thermal switch 100 may include a getter material 150 that is thermally connected to the low temperature side heat transfer element 120 and can absorb gas from the air gap 130. The getter material 150 may be, for example, activated carbon or other porous materials or other adsorbent materials that have the ability to absorb the working gas of the thermal switch 100 at ultra-low temperatures (i.e., temperatures below the switching temperature of the thermal switch 100, such as the second cooling temperature). The getter material 150 is disposed on the surface of the low temperature side heat transfer element 120 in an appropriate manner so that it can be cooled by the low temperature side heat transfer element 120.

[0063] Ideally, when the thermal switch 100 is cooled to a temperature lower than its switching temperature, as described above, the working gas condenses inside the thermal switch 100, the air gap 130 becomes a vacuum, and the thermal switch 100 is closed. However, in reality, some working gas may remain in the air gap 130. Such residual gas may cause heat transfer between the high-temperature side heat transfer element 110 and the low-temperature side heat transfer element 120. Undesirably, heat intrusion from the high-temperature side heat transfer element 110 to the low-temperature side heat transfer element 120 through the thermal switch 100 that should be closed may not be ignored.

[0064] On the other hand, by providing the getter material 150 in the thermal switch 100 to absorb the residual gas, the vacuum degree of the air gap 130 can be further increased. Therefore, the thermal connection can be cut off more reliably when the thermal switch 100 is in the closed state.

[0065] The getter material 150 is disposed on the low-temperature side heat transfer element 120 and faces the air gap 130. Thus, the getter material 150 is exposed to the residual gas that may exist in the air gap 130 and can efficiently adsorb the residual gas. Furthermore, by directly cooling the getter material 150 with the low-temperature side heat transfer element 120, the temperature of the getter material 150 can be quickly reduced. Thus, the thermal switch 100 can be quickly switched to off, and a thermal switch 100 with excellent responsiveness can be provided.

[0066] In the example shown in the figure, the getter material 150 is disposed on the surface of the second base 121 of the low-temperature-side heat transfer element 120 that faces the column 112 of the high-temperature-side heat transfer element 110. Alternatively or in addition, the getter material 150 may be disposed in other ways on the low-temperature-side heat transfer element 120. For example, the getter material 150 may be disposed on the inner surface of the cylinder 122 that faces the circumferential surface of the column 112.

[0067] The thermal switch 100 is a so-called single-gap (1-gap) type thermal switch. That is, the thermal switch 100 has only one set of column 112 and cylinder 122, so the air gap 130 is the only air gap of the thermal switch 100 formed between the column 112 and the cylinder 122. The single-gap type thermal switch has the advantage of being easy to manufacture and assemble compared to the multi-gap type described later.

[0068] In reference Figure 2 In the exemplary thermal switch 100 described above, the high temperature side heat transfer element 110 has a convex shape, and the low temperature side heat transfer element 120 has a concave shape to accommodate the high temperature side heat transfer element 110. However, as an alternative, in any embodiment described in this specification, as shown in FIG. Figure 3 As described later, the high-temperature-side heat transfer element 110 may have a concave shape, and the low-temperature-side heat transfer element 120 may have a corresponding convex shape.

[0069] Figure 3 The thermal switch 100 includes a high temperature side heat transfer element 110 and a low temperature side heat transfer element 120 disposed opposite to the high temperature side heat transfer element 110 via an air gap 130. The high temperature side heat transfer element 110 and the low temperature side heat transfer element 120 are connected by a connecting tube 140.

[0070] like Figure 3 As shown, the low-temperature side heat transfer element 120 may include a first base 123 and a column 124 extending from the first base 123. The high-temperature side heat transfer element 110 may include a second base 113 facing the column 124 and a cylinder 114 extending from the second base 113 to surround the column 124. The cylinder 114 is connected to the first base 123 via a connecting cylinder 140. Even so, a single-gap type thermal switch can be provided.

[0071] Optionally, a getter material 150 may be provided on the thermal switch 100. For example, the getter material 150 is provided on the front end surface of the column 124 of the low temperature side heat transfer element 120. The getter material 150 may be provided on the circumference of the column 124 of the low temperature side heat transfer element 120.

[0072] Figure 4 (a) and Figure 4 (b) is a schematic diagram showing a thermal switch 100 according to a modified example. The thermal switch 100 includes a high-temperature side heat transfer element 110 and a low-temperature side heat transfer element 120 disposed opposite to the high-temperature side heat transfer element 110 via an air gap 130. The high-temperature side heat transfer element 110 has a convex shape, and the low-temperature side heat transfer element 120 has a concave shape for accommodating the high-temperature side heat transfer element 110. The high-temperature side heat transfer element 110 and the low-temperature side heat transfer element 120 are connected by a connecting tube 140. The thermal switch 100 is a single-gap type thermal switch.

[0073] like Figure 4 As shown in (a), the thermal switch 100 includes an air intake chamber 152 having an air intake material 150 therein. The air intake chamber 152 is accommodated in the low-temperature side heat transfer element 120, for example, in the second base 121 of the low-temperature side heat transfer element 120. The second base 121 has a recessed portion on the end surface facing the outside of the thermal switch 100 which is the side opposite to the high-temperature side heat transfer element 110, and the air intake chamber 152 is arranged in the recessed portion. When the low-temperature side heat transfer element 120 is mounted on the second component 62, the air intake chamber 152 does not interfere with the second component 62, which is advantageous.

[0074] The suction chamber 152 is connected to the air gap 130 through an internal passage 154 in the thermal switch 100. The internal passage 154 is formed in the low temperature side heat transfer element 120. As an example, the internal passage 154 may be a through hole penetrating the second base portion 121 on the central axis of the thermal switch 100. Therefore, the residual gas in the air gap 130 can enter the suction chamber 152 through the internal passage 154 and be adsorbed by the getter material 150.

[0075] like Figure 4 As shown in (b), the thermal switch 100 includes an air suction chamber 152 having an air suction material 150 therein. The air suction chamber 152 is arranged outside the thermal switch 100 and is connected to the air gap 130 through an external passage 156. The air suction chamber 152 is accommodated within the axial direction of the thermal switch 100, so when the thermal switch 100 is mounted on the first component 61 and the second component 62, the air suction chamber 152 can avoid interference with these components.

[0076] The air intake chamber 152 is a container for accommodating the air intake material 150, and the external channel 156 can be a pipe connecting the air intake chamber 152 to the thermal switch 100. The air intake chamber 152 is thermally connected to the low-temperature side heat transfer element 120 via the external channel 156. In order to efficiently cool the air intake material 150, the air intake chamber 152 and the external channel 156 are formed of metal materials such as copper or other materials with high thermal conductivity. As an example, one end of the external channel 156 is installed in the air intake chamber 152, and the other end is installed in the cylinder 122 of the low-temperature side heat transfer element 120. The residual gas in the air gap 130 can enter the air intake chamber 152 through the external channel 156 and be adsorbed on the air intake material 150.

[0077] A heater or other thermostat 158 ​​may be additionally provided in the air intake chamber 152. At this time, by operating the thermostat 158 ​​to heat the air intake material 150, the adsorbed working gas can be released from the air intake material 150 into the air gap 130. In order to efficiently heat the air intake material 150 using the thermostat 158, the air intake chamber 152 and the external passage 156 may be formed of a metal material having a low thermal conductivity such as stainless steel. In addition, by stopping the thermostat 158 ​​and cooling the air intake material 150 using the low temperature side heat transfer element 120, the working gas can be adsorbed on the air intake material 150 again. Thus, the switch of the thermal switch 100 can be switched independently of the cooling action of the ultra-low temperature refrigerator 20.

[0078] When the thermal switch 100 is disposed in the ultra-low temperature device 10, various other devices may be disposed around the thermal switch 100. Figure 4 As schematically shown by the dotted line in (b), a predetermined settable area 160 can be set in the thermal switch 100 .

[0079] Figure 2 and Figure 4 The thermal switch 100 having a built-in getter material 150 according to the embodiment (a) of Figure 4 Compared with the thermal switch 100 having the external air intake chamber 152 according to the embodiment (b), the diameters of the high temperature side heat transfer element 110 and the low temperature side heat transfer element 120 can be increased. Figure 4 In the embodiment (b), in order to accommodate the thermal switch 100 in the settable area 160, the diameters of the high-temperature side heat transfer element 110 and the low-temperature side heat transfer element 120 have to be reduced by an amount corresponding to the external suction chamber 152. The heat transfer area of ​​the high-temperature side heat transfer element 110 and the low-temperature side heat transfer element 120 of the thermal switch 100 increases or decreases in accordance with the diameter. Therefore, the thermal switch 100 with the built-in suction material 150 has the following advantage: relative to the size (volume) of a certain settable area 160, a relatively large area of ​​the heat transfer element can be ensured in the high-temperature side heat transfer element 110.

[0080] Figure 5 1 is a schematic diagram showing a thermal switch 100 according to a modified example. The thermal switch 100 includes a high-temperature side heat transfer element 110 and a low-temperature side heat transfer element 120 disposed opposite to the high-temperature side heat transfer element 110 via an air gap 130. The high-temperature side heat transfer element 110 has a convex shape, and the low-temperature side heat transfer element 120 has a concave shape for receiving the high-temperature side heat transfer element 110. The high-temperature side heat transfer element 110 and the low-temperature side heat transfer element 120 are connected by a connecting tube 140. The thermal switch 100 is a single-gap type thermal switch.

[0081] exist Figure 5 In the heat switch 100 shown, the connecting tube 140 is relatively long and extends substantially over the entire length of the heat switch in the axial direction. The connecting tube 140 connects the first base 111 of the high-temperature side heat transfer element 110 to the second base 121 of the low-temperature side heat transfer element 120. The cylinder 122 of the low-temperature side heat transfer element 120 is arranged radially inward relative to the connecting tube 140, and a radial gap 162 is formed between the connecting tube 140 and the cylinder 122. The column 112 of the high-temperature side heat transfer element 110 is inserted into the cylinder 122 of the low-temperature side heat transfer element 120, and an air gap 130 is formed between the column 112 and the cylinder 122.

[0082] Similar to the above-mentioned embodiment, the thermal switch 100 may include a getter material 150 that is thermally connected to the low-temperature side heat transfer element 120 and can absorb gas from the air gap 130. The getter material 150 is disposed on the low-temperature side heat transfer element 120 facing the air gap 130. For example, the getter material 150 may be disposed on the surface of the second base 121 of the low-temperature side heat transfer element 120 that faces the column 112 of the high-temperature side heat transfer element 110. Alternatively or simultaneously, the getter material 150 may also be disposed on other surfaces of the low-temperature side heat transfer element 120, for example, the end portion of the cylinder 122 of the low-temperature side heat transfer element 120.

[0083] Figure 6 Schematic diagram showing a thermal switch 100 according to a modification. The thermal switch 100 includes a high temperature side heat transfer element 110 and a low temperature side heat transfer element 120 disposed opposite to the high temperature side heat transfer element 110 with an air gap 130 interposed therebetween. Figure 6 The illustrated thermal switch 100 is a multi-gap type thermal switch having a plurality of air gaps 130. The multi-gap type thermal switch is advantageous in that the heat transfer area can be easily increased compared to the single-gap type thermal switch.

[0084] The high temperature side heat transfer element 110 includes a first base portion 111 and a column portion 112 extending from the first base portion 111. Figure 2Unlike the embodiment shown in the figure, the column 112 is hollow. The low temperature side heat transfer element 120 includes a second base 121 and a cylinder 122 extending from the second base 121. Figure 2 Unlike the illustrated embodiment, a shaft portion 126 extending from the second base portion 121 coaxially with the cylindrical portion 122 is formed in the cylindrical portion 122. The connecting cylinder 140 connects the cylindrical portion 122 to the first base portion 111.

[0085] The low-temperature side heat transfer element 120 is configured to accommodate the high-temperature side heat transfer element 110 inside. The column 112 of the high-temperature side heat transfer element 110 is inserted into the cavity in the cylinder 122 of the low-temperature side heat transfer element 120. At this time, the shaft 126 of the low-temperature side heat transfer element 120 is inserted into the hollow portion of the column 112. As a result, an air gap 130 is formed inside the column 112 of the high-temperature side heat transfer element 110, and another air gap 130 is formed outside the column 112. The high-temperature side heat transfer element 110 and the low-temperature side heat transfer element 120 are separated by these air gaps 130 and have no physical contact.

[0086] Similar to the above-mentioned embodiment, the thermal switch 100 may include a getter material 150 that is thermally connected to the low-temperature side heat transfer element 120 and can absorb gas from the air gap 130. The getter material 150 is disposed on the low-temperature side heat transfer element 120 facing the air gap 130. For example, the getter material 150 may be disposed on the surface of the shaft portion 126 of the low-temperature side heat transfer element 120 that faces the first base portion 111 of the high-temperature side heat transfer element 110. Alternatively or simultaneously, the getter material 150 may be disposed on the surface of the second base portion 121 of the low-temperature side heat transfer element 120 that faces the column portion 112 of the high-temperature side heat transfer element 110. Alternatively or simultaneously, the getter material 150 may be disposed on other surfaces of the low-temperature side heat transfer element 120.

[0087] exist Figure 6 In the embodiment, the column 112 of the high-temperature side heat transfer element 110 can also be regarded as a cylindrical heat transfer fin. Therefore, the high-temperature side heat transfer element 110 can have a cylindrical heat transfer fin extending toward the low-temperature side heat transfer element 120. In addition, the high-temperature side heat transfer element 110 can also have a plurality of coaxially arranged cylindrical fins. The low-temperature side heat transfer element 120 can have at least one cylindrical fin that is arranged differently from the plurality of cylindrical fins of the high-temperature side heat transfer element 110. In this way, a multi-gap type heat switch having more air gaps 130 can be formed.

[0088] Alternatively, the high-temperature-side heat transfer element 110 may include at least one plate-shaped or other shaped heat transfer fin extending toward the low-temperature-side heat transfer element 120, and the low-temperature-side heat transfer element 120 may include at least one heat transfer fin extending toward the high-temperature-side heat transfer element 110. The at least one heat transfer fin of the high-temperature-side heat transfer element 110 and the at least one heat transfer fin of the low-temperature-side heat transfer element 120 may be configured differently from each other to form a plurality of air gaps 130 in the thermal switch 100.

[0089] Figure 7 1 is a schematic diagram showing a thermal switch 100 according to a modified example. The thermal switch 100 includes a high-temperature side heat transfer element 110 and a low-temperature side heat transfer element 120 disposed opposite to the high-temperature side heat transfer element 110 via an air gap 130. The high-temperature side heat transfer element 110 has a convex shape, and the low-temperature side heat transfer element 120 has a concave shape for accommodating the high-temperature side heat transfer element 110. The high-temperature side heat transfer element 110 and the low-temperature side heat transfer element 120 are connected by a connecting tube 140. The thermal switch 100 is a single-gap type thermal switch.

[0090] like Figure 7 As shown, the thermal switch 100 includes a covering member 170 covering the outer circumference thereof. The covering member 170 covers the outer circumference of the cylinder portion 122 of the low-temperature side heat transfer element 120 and the connecting cylinder 140. Due to the thermal contraction accompanying the ultra-low temperature cooling, relative displacement occurs between the first component 61 and the second component 62, and as a result, there is a concern that a load (for example, a lateral load) may act on the thermal switch 100. The covering member 170 can help to strengthen the thermal switch 100 against such a load. In order to reduce the heat intrusion from the high-temperature side heat transfer element 110 to the low-temperature side heat transfer element 120 through the covering member 170, the covering member 170 can be formed of a heat insulating material.

[0091] Figure 8 1 is a schematic diagram showing a thermal switch device 200 according to an embodiment. The thermal switch device 200 includes a plurality of thermal switches (two thermal switches 100a and 100b in this example) connected in series. Each of the plurality of thermal switches includes a high-temperature side heat transfer element 110 and a low-temperature side heat transfer element 120 disposed opposite to the high-temperature side heat transfer element 110 via an air gap 130. The high-temperature side heat transfer element 110 has a convex shape, and the low-temperature side heat transfer element 120 has a concave shape for accommodating the high-temperature side heat transfer element 110. The high-temperature side heat transfer element 110 and the low-temperature side heat transfer element 120 are connected by a connecting tube 140.

[0092] like Figure 8 As shown, the high temperature side heat transfer element 110 of one of the two adjacent thermal switches 100a is thermally connected to the first member 61. The low temperature side heat transfer element 120 of the other of the two adjacent thermal switches 100b is thermally connected to the second member 62.

[0093] The low temperature side heat transfer element 120 of the high temperature side heat switch 100a and the high temperature side heat transfer element 110 of the low temperature side heat switch 100b may be integrated. The integrated heat transfer element is thermally connected to the second member 62 via the heat transfer member 180, for example.

[0094] Alternatively, the low temperature side heat transfer element 120 of the high temperature side heat switch 100a and the high temperature side heat transfer element 110 of the low temperature side heat switch 100b may be thermally connected to each other. In other words, each of the plurality of heat switches may be a heat switch 100 involved in any of the above-mentioned embodiments, and such heat switches 100 may be simply stacked in the axial direction. The low temperature side heat transfer element 120 of each heat switch 100 and the high temperature side heat transfer element 110 of the adjacent heat switch 100 are thermally connected to the second component 62.

[0095] When the thermal switch device 200 has a plurality of thermal switches connected in series, the thermal connection between the first component 61 and the second component 62 is cut off by closing any thermal switch. If any of the plurality of thermal switches fails to switch to the closed state due to some fault (e.g., physical contact between the high temperature side heat transfer element 110 and the low temperature side heat transfer element 120, the presence of excessive residual gas, etc.), the thermal switch device 200 can also cut off the thermal connection between the first component 61 and the second component 62 by any other thermal switch switching to the closed state normally. Therefore, compared with the single thermal switch 100, the thermal switch device 200 is advantageous in terms of robustness against faults.

[0096] Therefore, it is not necessary to provide the getter material 150 for each thermal switch of the thermal switch device 200. However, as in the above-mentioned embodiment, the getter material 150 may be provided for each thermal switch as indicated by the dotted line.

[0097] Consider the situation where the thermal switch device 200 is turned on. If the case where a single thermal switch 100 is set in a settable area of ​​a certain size is compared with the case where the thermal switch device 200 is set, the size of each thermal switch constituting the thermal switch device 200 is smaller than that of the single thermal switch 100, but the total heat transfer area becomes approximately the same. Therefore, it can be expected that the heat transfer performance in the single thermal switch 100 and the thermal switch device 200 is approximately the same. In addition, in the thermal switch device 200, the total axial length of the connecting tube 140 of each thermal switch is approximately the same as the axial length of the connecting tube 140 of the single thermal switch 100. Therefore, it can be expected that the thermal insulation performance in the single thermal switch 100 and the thermal switch device 200 is approximately the same.

[0098] The present invention has been described above based on the embodiments. It should be understood by those skilled in the art that the present invention is not limited to the above-mentioned embodiments, and various design changes can be made, and various modifications can be implemented, and such modifications are also within the scope of the present invention. The various features described in relation to one embodiment can also be applied to another embodiment. The new embodiment generated by the combination has the effects of each of the combined embodiments.

[0099] In the above-mentioned embodiment, the case where the cryogenic refrigerator 20 is a multi-stage Gifford-McMahon refrigerator is described as an example, but the present invention is not limited to this. The cryogenic refrigerator 20 may also be a pulse tube refrigerator, a Stirling refrigerator, or other types of multi-stage cryogenic refrigerators. The thermal switch 100 and the thermal switch device 200 involved in the embodiment can be applied to various cryogenic refrigerators 20 or cryogenic devices 10 equipped with the cryogenic refrigerator 20.

[0100] In the above-mentioned embodiment, the thermal switch 100 and the thermal switch device 200 are applied to a conduction cooling type cryogenic device 10 in which the object to be cooled is directly cooled by the cryogenic refrigerator 20. However, in one embodiment, the thermal switch 100 and the thermal switch device 200 can also be applied to an immersion cooling type cryogenic device in which the object to be cooled is immersed in a cryogenic refrigerant such as liquid helium for cooling.

[0101] According to the implementation mode, the present invention is described using specific words, but the implementation mode is only to illustrate one aspect of the principle and application of the present invention. In the implementation mode, various modifications or configuration changes are allowed without departing from the scope of the idea of ​​the present invention specified in the technical solution.

[0102] Industrial Applicability

[0103] The present invention can be applied to the field of a thermal switch and a thermal switch device using the thermal switch.

Claims

1. A thermal switch, characterized in that: have: High temperature side heat transfer elements; and The low temperature side heat transfer element is arranged to face the high temperature side heat transfer element with an air gap therebetween. One of the high-temperature-side heat transfer element and the low-temperature-side heat transfer element includes a first base portion and a column portion extending from the first base portion. The other of the high-temperature-side heat transfer element and the low-temperature-side heat transfer element includes a second base portion facing the column portion and a cylindrical portion extending from the second base portion so as to surround the column portion. The thermal switch further includes a connecting tube that connects the tube portion to the first base portion to isolate the air gap from the surrounding environment and is formed of a heat insulating material.

2. The thermal switch according to claim 1, characterized in that Also available: The getter material is thermally connected to the low-temperature side heat transfer element and can absorb gas from the air gap.

3. The thermal switch according to claim 2, characterized in that: The getter material is disposed on the low-temperature-side heat transfer element and faces the air gap.

4. The thermal switch according to claim 2, characterized in that: have: The getter chamber is connected to the air gap and has the getter material inside.

5. The thermal switch according to claim 4, characterized in that: The air intake chamber is accommodated in the low-temperature side heat transfer element.

6. The thermal switch according to claim 1, characterized in that: The thermal switch has only one set of the column and the cylinder. The air gap is the only air gap of the thermal switch formed between the column portion and the cylinder portion.

7. The thermal switch according to any one of claims 1 to 6, characterized in that: Also available: The covering member covers the outer peripheral surface of the thermal switch.

8. The thermal switch according to claim 1, characterized in that The axial length of the connecting tube is less than half of the entire axial length of the thermal switch.

9. A thermal switch, characterized in that: have: High temperature side heat transfer element; a low-temperature-side heat transfer element disposed opposite to the high-temperature-side heat transfer element with an air gap therebetween; and The getter material is thermally connected to the low-temperature side heat transfer element and can absorb gas from the air gap.

10. The thermal switch according to claim 9, characterized in that The getter material is disposed on the low-temperature-side heat transfer element and faces the air gap.

11. The thermal switch according to claim 9, characterized in that have: The getter chamber is connected to the air gap and has the getter material inside.

12. The thermal switch according to claim 11, characterized in that The air intake chamber is accommodated in the low-temperature side heat transfer element.

13. The thermal switch according to claim 9, characterized in that One of the high-temperature-side heat transfer element and the low-temperature-side heat transfer element includes a first base portion and a column portion extending from the first base portion. The other of the high-temperature-side heat transfer element and the low-temperature-side heat transfer element includes a second base portion facing the column portion and a cylindrical portion extending from the second base portion so as to surround the column portion. The thermal switch has only one set of the column and the cylinder. The air gap is the only air gap of the thermal switch formed between the column portion and the cylinder portion.

14. The thermal switch according to claim 13, characterized in that Also available: The connecting tube connects the tube portion to the first base portion to isolate the air gap from the surrounding environment and is formed of a heat insulating material.

15. The thermal switch according to any one of claims 9 to 14, characterized in that Also available: The covering member covers the outer peripheral surface of the thermal switch.

16. A thermal switch device, characterized in that: With multiple thermal switches connected in series, Each of the plurality of thermal switches comprises: High temperature side heat transfer elements; and The low-temperature-side heat transfer element is arranged to face the high-temperature-side heat transfer element with an air gap therebetween.

17. The thermal switch device according to claim 16, characterized in that: The plurality of thermal switches include two adjacent thermal switches, The low temperature side heat transfer element of the heat switch on the high temperature side of the two adjacent heat switches is integrated with the high temperature side heat transfer element of the heat switch on the low temperature side of the two adjacent heat switches.

18. The thermal switch device according to claim 16, characterized in that In each of the plurality of thermal switches, One of the high-temperature-side heat transfer element and the low-temperature-side heat transfer element includes a first base portion and a column portion extending from the first base portion. The other of the high-temperature-side heat transfer element and the low-temperature-side heat transfer element includes a second base portion facing the column portion and a cylindrical portion extending from the second base portion so as to surround the column portion. Each of the plurality of thermal switches further includes a connecting tube that connects the tube portion to the first base portion to isolate the air gap from the surrounding environment and is formed of a heat insulating material.

19. The thermal switch device according to any one of claims 16 to 18, characterized in that: Each of the plurality of thermal switches includes a getter material that is thermally connected to the low-temperature-side heat transfer element and that can adsorb gas from the air gap.

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