WO2008066127A1

WO2008066127A1 - Refrigerating machine

Info

Publication number: WO2008066127A1
Application number: PCT/JP2007/073089
Authority: WO
Inventors: Junpei Yuyama; Shuichi Yamasaki; Mitsuki Terashima; Taku Komuro
Original assignee: Ulvac, Inc.
Priority date: 2006-11-30
Filing date: 2007-11-29
Publication date: 2008-06-05
Also published as: KR101121232B1; KR20090085641A; EP2090850A1; CN101542219A; EP2090850B1; TW200839162A; CN101542219B; JPWO2008066127A1; EP2090850A4; US20100031693A1; TWI395916B

Abstract

A refrigerating machine is provided with a cooling stage for cooling a cooling object; a He condensation section whereupon the cooling object is placed; a reservoir which communicates with the He condensation section and is filled with He gas; and a heat transfer buffer member which is arranged between the cooling stage and the He condensation section and is composed of a material having a thermal conductivity lower than that of the He condensation section.

Description

Specification

refrigerator

Technical field

[0001] The present invention relates to a refrigerator.

Background art

[0002] GM refrigerators are used for measuring sample physical properties in a cryogenic environment near 4K, measuring various physical quantities using sensors that utilize the cryogenic environment, and the like. This refrigerator cools non-cooled materials to extremely low temperatures by repeatedly compressing and expanding (refrigeration cycle) a refrigerant gas such as He gas. However, due to the pulsation of the heat flow caused by the above-described refrigeration cycle, a temperature amplitude is generated on the placement surface of the object to be cooled. In order to cool the object to be cooled stably, it is desired to reduce this temperature amplitude.

[0003] Patent Document 1 discloses a regenerator that houses helium gas or helium gas and liquid helium, a compressed helium gas supply unit, and the cold accumulator provided in a cooling unit to which an object to be cooled is attached. An ultra-low temperature refrigerator including a helium gas introducing / exhausting means for connecting a gas is disclosed!

Patent Document 2 discloses a cryogenic temperature provided with a helium gas introduction pipe for introducing a necessary amount of helium gas at room temperature, a capacitor chamber for liquefying helium gas, and a liquid helium chamber for storing liquefied liquid helium. A temperature damper is disclosed.

Patent Document 1: Japanese Patent No. 2773793

Patent Document 2: Japanese Patent Application Laid-Open No. 2004-76955

Disclosure of the invention

Problems to be solved by the invention

However, since the temperature amplitude in the cryogenic refrigerator of Patent Document 1 is about 30 mK, further reduction of the temperature amplitude is desired.

On the other hand, the cryogenic temperature damper of Patent Document 2 has a complicated structure, and since the heat transfer path from the coolant is long and non-axisymmetric, cooling may be uneven and unstable.

[0005] The present invention has been made in order to solve the above-described problems, and includes a placement surface for an object to be cooled. The purpose of the present invention is to provide a refrigerator that can reduce the temperature amplitude of the product and that can cool the object to be cooled uniformly and stably.

Means for solving the problem

[0006] In order to solve the above problems, the present invention employs the following means. That is, the refrigerator of the present invention includes a cooling stage for cooling an object to be cooled; a He condensing unit on which the object to be cooled is mounted; a reservoir filled with He gas that communicates with the He condensing unit; And a heat transfer buffer made of a material having a lower thermal conductivity than that of the He condensing unit, which is disposed between the cooling stage and the He condensing unit.

According to this configuration, the pulsating power of heat flow caused by the refrigeration cycle of the refrigerator is absorbed by the evaporation and condensation (phase transition) of He in the He condensation section. At this time, since the heat transfer buffer acts as a heat flow restricting mechanism, transmission of temperature amplitude in the cooling stage is suppressed. As a result, the temperature amplitude on the placement surface of the object to be cooled can be reduced. In addition, since the cooling stage, the heat transfer buffer material, the He condensing portion, and the object to be cooled are continuously arranged coaxially, the object to be cooled can be uniformly and stably cooled.

[0007] The He condensing part may be made of a material having a thermal conductivity of 200 W / (m * K) or more at a temperature in the vicinity of 4K.

According to this configuration, the force S can efficiently cool the object to be cooled P with the liquid He condensed in the He condensing unit.

[0008] The heat transfer buffer may be made of a material having a thermal conductivity of less than 100 W / (m.K) at a temperature in the vicinity of 4K.

According to this configuration, transmission of temperature amplitude in the cooling stage can be reliably prevented.

[0009] The volume of the He condensing part may be not less than lOcc and not more than lOOcc.

According to this configuration, while ensuring the storage volume of the liquid He necessary for cooling the object to be cooled,

The He condensing part can be made compact.

[0010] The volume of the reservoir may be not less than 5 times and not more than 100 times the volume of the He condensing part.

According to this configuration, while ensuring the storage capacity of He gas necessary for cooling the object to be cooled, The server can be made compact.

[0011] The pressure of the He gas filled in the reservoir is 0. IMPa or more at room temperature.

Even below OMPa! / ヽ.

According to this configuration, even if the refrigerator is stopped and the liquid He in the He condensing part evaporates, it is possible to prevent the reservoir and the He condensing part from becoming high pressure.

[0012] Fins may be erected on the inner surface of the He condensation section.

In addition, a porous structure may be attached to the inner surface of the He condensation unit.

According to these configurations, since the contact area between the inner surface of the He condensing unit and the liquid He is increased, the object to be cooled placed on the He condensing unit can be efficiently cooled.

[0013] Concavities and convexities may be formed on a contact surface between the heat-transfer buffer material and the cooling stage or the He condensation unit.

According to this configuration, the contact area between the heat transfer buffer material and the cooling stage or the He condensing portion is reduced, so that transmission of temperature amplitude in the cooling stage is suppressed. As a result, the temperature amplitude on the placement surface of the object to be cooled can be reduced.

[0014] A temperature sensor and a heater mounted on the He condensing unit; and a control unit that drives the heater based on a measurement result of the temperature sensor may be further provided.

According to this configuration, when the temperature of the He condensing unit falls below a predetermined value, the heater can be driven to return the temperature of the He condensing unit to the predetermined value. Therefore, the temperature amplitude on the mounting surface of the object to be cooled can be reduced.

The invention's effect

[0015] According to the present invention, the provision of the heat transfer buffer prevents the temperature amplitude from being transmitted in the cooling stage, and as a result, it is possible to reduce the temperature amplitude on the placement surface of the object to be cooled. . In addition, since the cooling stage, the heat transfer buffer, the He condensing part, and the object to be cooled are continuously arranged coaxially, the object to be cooled can be uniformly and stably cooled.

Brief Description of Drawings

FIG. 1 is a schematic configuration diagram of a refrigerator according to a first embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the temperature of the second cooling stage and the temperature amplitude.

FIG. 3 is a graph showing the relationship between the volume ratio of liquid He and the temperature amplitude in the He condensation section. It is.

FIG. 4 is a graph showing the relationship between the temperature of the second cooling stage and the refrigerating capacity.

FIG. 5 is a graph showing the relationship between the cooling time and the temperature of the second cooling stage.

FIG. 6 is a schematic configuration diagram in the vicinity of a He condensing part of a refrigerator according to a second embodiment of the present invention.

FIG. 7 is a schematic configuration diagram in the vicinity of a He condensing part of a refrigerator according to a third embodiment of the present invention.

FIG. 8 is a schematic configuration diagram in the vicinity of a He condensing unit of a refrigerator according to a fourth embodiment of the present invention.

FIG. 9 is a schematic configuration diagram in the vicinity of a He condensing unit of a refrigerator according to a fifth embodiment of the present invention.

Explanation of symbols

[0017] 1 Refrigerator

14 Second cooling stage (cooling stage)

16 Heat transfer buffer

18 Concavity and convexity

20 He condensation section

30 reservoir

40 Object to be cooled

50 He gas

62 Control unit

64 temperature sensor

66 Heater

222 1st fin

224 2nd fin

322 Porous structure

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings. (First embodiment)

FIG. 1 is a schematic configuration diagram of a refrigerator according to the first embodiment of the present invention. The refrigerator 1 according to the present embodiment includes a second cooling stage 14 that cools the object 40 to be cooled, a He condensing unit 20 on which the object 40 to be cooled is mounted, and a He gas 50 that communicates with the He condensing unit 20. And a heat transfer buffer 16 made of a material having a lower thermal conductivity than that of the He condensation section 20 disposed between the second cooling stage 14 and the He condensation section 20, It is equipped with.

The refrigerator 1 mainly includes a compressor 4, a main body 2, and a cooling unit 15. The compressor 4 compresses low-pressure He gas supplied from the low-pressure pipe 8 into high-pressure He gas, and supplies it to the high-pressure pipe 6. The main body 2 continuously switches the connection between the high pressure pipe 6 and the low pressure pipe 8 and the He gas flow path in the cooling section 15 described below by the power of a motor or the like.

A cooling unit 15 is provided continuously to the main body unit 2. The cooling unit 15 is disposed inside the vacuum chamber 10 maintained in a vacuum environment, and generates cold by the expansion of He gas flowing through the inside. The cooling unit 15 is provided with a first cooling unit 11, a first cooling stage 12, a second cooling unit 13 and a second cooling stage 14 in this order. The first cooling part 11 and the second cooling part 13 are formed in a columnar shape, and the first cooling stage 12 and the second cooling stage 14 are formed in a disk shape and are arranged coaxially. A He gas flow path (not shown) is formed inside the cooling unit 15. The high-pressure He gas supplied to the He gas flow path undergoes endothermic expansion at the second cooling stage 14 and changes to low-pressure He gas.

A heat transfer buffer 16 is provided between the lower surface of the second cooling stage 14 and the He condensing unit 20 described later. The heat transfer buffer 16 is formed in a plate shape having a diameter of about several tens of mm and a thickness of about 2 mm, for example. The heat transfer buffer 16 is made of a stainless material or the like whose thermal conductivity at a temperature in the vicinity of 4K is lower than that of the He condensing unit 20 described later. In particular, if the heat transfer buffer 16 is made of a material having a thermal conductivity of less than 100 W / (mK) at a temperature in the vicinity of 4 K, the temperature amplitude of the second cooling stage 14 is transmitted to the He condensation unit 20. The power S can be suppressed.

In addition, In foil or the like is applied to both surfaces of the heat transfer buffer 16 to increase the thermal contact property, and the second cooling stage 14, the heat transfer buffer 16 and the He condensing unit 20 are fastened.

[0022] On the lower surface of the heat transfer buffer 16, a He condensing unit 20 on which the object to be cooled 40 is placed is provided. The The He condensing unit 20 is made of a material such as Cu, Ag, or A1 whose thermal conductivity at a temperature in the vicinity of 4K is higher than that of the heat transfer buffer 16 described above. In this embodiment, the He condensing part 20 is formed of oxygen-free copper. In particular, if the He condensing unit 20 is made of a material having a thermal conductivity of 200 W / (mK) or higher at a temperature in the vicinity of 4K, the liquid 40 condensed in the He condensing unit 20 efficiently cools the object 40 to be cooled. can do.

[0023] The He condensing unit 20 is formed in a cylindrical shape with both ends sealed, and can store liquid He therein. If the volume of the He condensing part 20 is not less than lOcc and not more than lOOcc, the He condensing part 20 can be made compact while ensuring the storage capacity of the liquid He necessary for cooling the object 40 to be cooled. In this embodiment, the volume of the He condensing part 20 is set to 40 cc.

A table 41 is disposed on the lower surface of the He condensing unit 20. The lower surface of the table 41 is a cooling position where the 1S object 40 is placed. The table 41 is made of a material having the same physical properties as the He condensing unit 20. In the present embodiment, an In foil or the like is applied between the He condensing unit 20 and the table 41, and between the table 41 and the object to be cooled 40, and the He condensing unit 20 and the table 41 are fastened. Yes. Note that the object to be cooled 40 without providing the table 41 may be applied to the He condensing unit 20 in good thermal contact.

[0024] The second cooling stage 14, the heat transfer buffer 16, the He condensing unit 20, and the object to be cooled 40 of the cooling unit 15 described above constitute a heat transfer channel from the object to be cooled. In the present embodiment, it is possible to shorten the distance of the heat transfer flow path by arranging these continuously in a coaxial manner. As a result, the cooling loss can be reduced, and the object to be cooled 40 can be efficiently cooled to the target temperature in a short time. In addition, the heat transfer flow path can be axisymmetric, and the entire object to be cooled 40 can be cooled uniformly and stably.

A narrow tube 32 extends from the He condensing unit 20 and is always connected to a reservoir 30 disposed outside the vacuum chamber 10. The volume of the reservoir 30 is preferably 5 to 100 times the volume of the He condensing unit 20. In this embodiment, the volume of the reservoir 30 is set to 3250 cc. As a result, the reservoir 30 can be made compact while ensuring the storage capacity of the He gas necessary for cooling the object 40 to be cooled.

[0026] The interior of the reservoir 30 is filled with He gas. The pressure of the He gas 0. IMPa or more 1. Desirably OMPa or less. In this embodiment, the reservoir 30 is filled with He gas 50 having a pressure of 0.4 MPa at room temperature. Thus, even if the refrigerator 1 is stopped and the liquid He52 in the He condensing unit 20 evaporates, the reservoir 30 does not become a high pressure. A heat anchor 34 for exchanging heat with the first cooling stage 12 is formed in the middle portion of the narrow tube 32! /.

Next, the operation of the refrigerator 1 according to this embodiment will be described. As described above, the high-pressure He gas supplied from the compressor 4 to the cooling unit 15 undergoes endothermic expansion in the second cooling stage 14 and changes to low-pressure He gas. The main body 2 continuously switches the connection between the high pressure pipe 6 and the low pressure pipe 8 and the He gas flow path of the cooling section 15. Thereby, compression and expansion (refrigeration cycle) of He gas are repeated, and the temperature of the second cooling stage 14 becomes extremely low.

[0028] A He condensing unit 20 is provided below the second cooling stage 14. Second cooling stage

When the He condensing unit 20 is cooled by 14, the He gas inside the He condensing unit 20 is condensed and liquefied to generate liquid He 52. In the present embodiment, the liquid He is generated so that the volume ratio with respect to the He condensing unit 20 is 30% or less (for example, about 20%).

By the way, due to the pulsation of the heat flow caused by the above-described refrigeration cycle, a temperature amplitude is generated in the second cooling stage 14. However, in this embodiment, the pulsation of the heat flow caused by the refrigeration cycle is absorbed by the evaporation and condensation (phase transition) of He. Therefore, a temperature amplitude equivalent to that of the second cooling stage 14 is not generated in the He condensing unit 20, and the temperature amplitude of the He condensing unit 20 becomes small.

Moreover, in the present embodiment, the heat transfer buffer 16 made of a material is provided between the second cooling stage 14 and the He condensing unit 20 and has a lower thermal conductivity than that of the He condensing unit 20. ! / Since the heat transfer buffer 16 acts as a heat flow restricting mechanism, it is possible to suppress the temperature amplitude force e transmitted to the condensing unit 20 in the second cooling stage 14. Therefore, the temperature amplitude on the mounting surface of the object to be cooled can be reduced.

FIG. 2 is a graph showing the relationship between the temperature of the second cooling stage and the temperature amplitude. Here, the temperature amplitude was measured for three types of device configurations. Specifically, (1) the temperature amplitude (diamond plot) of the He condensing unit 20 when the second cooling stage 14, the heat transfer buffer 16 and the He condensing unit 20 are provided as in the present embodiment, and (2 ) Second cooling without heat transfer buffer 16 The temperature amplitude (triangular plot) of the He condensation unit 20 when the stage 14 and the He condensation unit 20 are provided, and (3) the second cooling stage 14 when the heat transfer buffer 16 and the He condensation unit 20 are not provided. Temperature amplitude (round plot) was measured. The horizontal axis indicates the temperature at the cooling position (temperature amplitude measurement position) where the object is placed. The volume of the reservoir 30 was set to 3 250 cc, the filling pressure of the He gas into the reservoir 30 was set to 0.4 MPa, and the volume ratio of the liquid He inside the He condensing unit 20 was set to 20%.

As a result, the magnitude of the temperature amplitude of each device configuration was in the order of (3)> (2)> (1). Note that the higher the temperature at the cooling position, the greater the difference in temperature amplitude between each device configuration. In the configuration of (1), when the temperature at the cooling position was 4.2K, the temperature amplitude of the He condensing unit 20 was suppressed to ± 9mK. From the above measurement results, (3) Compared to the device configuration with only the second cooling stage 14, (2) The device configuration with the addition of the He condensing unit 20 significantly reduces the temperature amplitude, and (1) Heat transfer It was confirmed that the temperature amplitude was further reduced in the system configuration with the buffer material 16 and the He condensing unit 20 added compared to (2).

FIG. 3 is a graph showing the relationship between the volume ratio of liquid He and the temperature amplitude in the He condensation section. Here, (1) the temperature amplitude when the heat transfer buffer material is provided (diamond plot) as in the present embodiment, and (2) the temperature amplitude when the heat transfer buffer material is not provided (triangle plot). It was measured . The volume of Rizzano 30 was set to 3250cc, the maximum filling pressure of He gas into the reservoir 30 was set to 0 · 48 MPa, and the temperature at the cooling position was set to 4.2K.

As a result, regardless of the volume ratio of liquid He, the magnitude of the temperature amplitude was (2)> (1). In addition, the temperature amplitude increased when there was no liquid He, but the temperature amplitude decreased when liquid He existed even a little. Further, in (1), in the case of the volume fractional force% to 30% of the liquid He, the temperature amplitude of the He condensation unit 20 was suppressed to ± 9 mK in all cases. From the above, it was confirmed that even a small amount of liquid He has the effect of greatly reducing the temperature amplitude.

By the way, in this embodiment, since the heat conductivity is lower than that of the He condensing unit 20 and the heat transfer buffer material 16 is provided, it is considered that the refrigerating capacity of the refrigerator decreases. Therefore, the inventor of the present application investigated a difference in refrigerating capacity depending on the presence or absence of the heat transfer buffer 16.

Fig. 4 is a graph showing the relationship between the temperature at the cooling position and the refrigeration capacity at the cooling position. . Here, (1) the refrigerating capacity (diamond plot) when the heat transfer buffer 16 is provided as in the present embodiment, and (2) the refrigerating capacity (square plot) when the heat transfer buffer is not provided. It was measured. The volume ratio of liquid He inside the He condensing unit 20 was set to 20%.

As a result, regardless of the temperature at the cooling position, the rate of decrease in refrigeration capacity with the heat transfer buffer 16 was about 25%. Therefore, it was confirmed that the loss of refrigeration capacity can be suppressed to several tens of percent.

[0036] In this embodiment, since the heat conductivity is lower than that of the He condensing unit 20 and the heat transfer buffer 16 is provided, it is considered that the cooling time increases. Therefore, the inventor of the present application investigated the difference in cooling time depending on the presence or absence of the heat transfer buffer 16.

FIG. 5 is a graph showing the relationship between the cooling time and the temperature at the cooling position. Here, (1) the temperature at the cooling position when the heat transfer buffer material is provided (solid line) as in this embodiment, and (2) the temperature at the cooling position when the heat transfer buffer material is not provided (square) Plot). As a result, it was confirmed that there was almost no difference in cooling time depending on the presence or absence of the heat transfer buffer 16.

[0037] As described in detail above, the refrigerator according to the present embodiment (see FIG. 1) is configured such that the He condensing unit 20 on which the object to be cooled 40 is placed is placed between the He cooling unit 20 and the second cooling stage 14. The heat transfer buffer 16 made of a material having a lower thermal conductivity than the condensing unit 20 is provided. According to this configuration, the pulsation power of heat flow caused by the refrigeration cycle of the refrigerator 1 is absorbed by the evaporation and condensation (phase transition) of He in the He condensing unit 20. At that time, since the heat transfer buffer 16 acts as a heat flow restricting mechanism, the transmission of the temperature amplitude in the second cooling stage 14 is suppressed, and as a result, the temperature amplitude on the mounting surface of the object 40 to be cooled is reduced. be able to. In addition, since the second cooling stage 14, the heat transfer buffer 16, the He condensing section 20, and the object to be cooled 40 are continuously arranged coaxially, the heat transfer flow path from the object to be cooled is axisymmetric and has a short distance. Become. Therefore, uniform and stable cooling of the object to be cooled 40 becomes possible.

[0038] Further, in the present embodiment, it is possible to suppress the volume ratio of the liquid He52 in the He condensing unit 20 to 30% or less. Therefore, the reservoir 30 filled with the He gas 50 can be downsized. Further, the filling pressure of the He gas 50 to the reservoir 30 at room temperature can be lowered. As a result, even if the refrigerator 1 is stopped and the liquid He52 in the He condensing unit 20 is vaporized, the reservoir 30 and the He condensing unit can be prevented from becoming high pressure. [0039] (Second Embodiment)

Next, a refrigerator according to the second embodiment of the present invention will be described.

FIG. 6 is a schematic configuration diagram in the vicinity of the He condensing unit of the refrigerator according to the present embodiment. In the refrigerator according to the present embodiment, fins 222 and 224 force S are erected on the inner surfaces 221 and 223 of the He condensing unit 220. Note that detailed description of portions having the same configuration as in the first embodiment is omitted.

A He condensing unit 220 is disposed between the second cooling stage 14 and the object 40 to be cooled.

The He condensing unit 220 is a cylindrical hollow container made of a material such as Cu, Ag, or A1, and the inside thereof is filled with He gas 50. When the He condensing unit 220 is cooled by the second cooling stage 14, the He gas is condensed and the liquid He52 is generated. The object to be cooled 40 is cooled by the liquid He52.

[0041] On the inner surface of the He condensing unit 220, a plurality of fins 222, 224 forces S are installed. Each of the fins 222 and 224 is preferably made of a material having high thermal conductivity, like the He condensing unit 220. The fins 222 and 224 may be formed integrally with the He condensing unit 220, or may be formed separately and fixed to the He condensing unit 220.

The first fin 222 is formed from the bottom surface 221 of the He condensing unit 220 toward the ceiling surface 223. This makes it possible to increase the contact area between the inner surface of the He condensing unit 220 and the liquid He52. Therefore, the force S can efficiently cool the object 40 to be cooled placed on the He condensing unit 220.

The second fin 224 is formed from the ceiling surface 223 to the bottom surface 221 of the He condensing unit 220. As a result, the contact area between the inner surface of the He condensing unit 220 and the He gas 50 can be increased. Therefore, it is measured by the power that efficiently cools and condenses the He gas 50 inside the He condensing unit 220.

[0043] (Third embodiment)

Next, a refrigerator according to a third embodiment of the present invention will be described.

FIG. 7 is a schematic configuration diagram in the vicinity of the He condensing unit of the refrigerator according to the present embodiment. In the refrigerator according to the present embodiment, a porous structure 322 is attached to the inner surface of the He condensing unit 320. Note that the detailed description of the same parts as in the first embodiment will be given. I will omit the description.

[0044] A porous structure 322 is attached to the inner surface of the He condensation section 320. The porous structure 322 is made of a mesh, a foam metal, a sintered metal, or the like. The porous structure 322 may be filled in the entire inner side of the He condensing part 320 or may be filled only in a part.

The porous structure 322 is attached to the inner surface of the He condensing portion 320 with an adhesive or the like so as to keep a good thermal contact with the inner surface of the He condensing portion 320.

[0045] By providing the porous structure 322, it becomes possible to increase the contact area between the inner surface of the He condensation section 320 and the liquid He52. Therefore, the object to be cooled 40 placed on the He condensing unit 320 can be efficiently cooled. Further, by providing the porous structure 322, the contact area between the inner surface of the He condensing section 320 and the He gas 50 can be increased. Therefore, the He gas 50 inside the He condensing section 320 can be efficiently cooled and condensed.

[0046] (Fourth embodiment)

Next, a refrigerator according to a fourth embodiment of the present invention will be described.

FIG. 8 is a schematic configuration diagram in the vicinity of the He condensing unit of the refrigerator according to the present embodiment. In the refrigerator according to the present embodiment, unevenness 18 is formed on the contact surface of the heat transfer buffer 16 with the second cooling stage 14. Note that detailed description of portions having the same configuration as in the first embodiment is omitted.

[0047] The heat transfer buffer 16 has a low thermal conductivity! /, And is made of a stainless material or the like! Concavities and convexities 18 are formed on the contact surface with the second cooling stage 14. The irregularities 18 may be formed regularly or irregularly (randomly). The unevenness 18 may be formed in a pyramid shape so as to be in point contact with the second cooling stage 14, or the unevenness 18 may be formed in a frustum shape so as to be in surface contact with the second cooling stage 14. Further, the projections and recesses 18 may be formed in a triangular shape so as to be in line contact with the second cooling stage 14, and the projections and depressions 18 may be formed in a trapezoidal shape in cross section so as to be in surface contact with the second cooling stage 14.

In the present embodiment, since the unevenness 18 is formed on the contact surface of the heat transfer buffer material 16 with the second cooling stage 14, the contact area between the heat transfer buffer material 16 and the second cooling stage 14 is reduced. . As a result, compared to the case where the heat transfer buffer 16 and the second cooling stage 14 are in full contact with each other. Since the heat flow throttling function is strengthened, it is possible to suppress the temperature amplitude in the second cooling stage 14 from being transmitted to the He condensation unit 420. Therefore, it is possible to reduce the temperature amplitude on the surface on which the object to be cooled is placed.

In this embodiment, the unevenness 18 is formed on the contact surface of the heat transfer buffer 16 with the second cooling stage 14. However, the unevenness is formed on the contact surface of the second cooling stage 14 with the heat transfer buffer 16. May be. In addition, unevenness may be formed on the contact surface of the heat transfer buffer material 16 with the He condensing portion 420, or unevenness may be formed on the contact surface of the He condensing portion 420 with the heat transfer buffer material 16. That is, it is only necessary that irregularities be formed on the contact surface between the second cooling stage 14 or the He condensing section 420 and the heat transfer buffer material 16. In any case, it is possible to suppress the temperature amplitude in the second cooling stage 14 from being transmitted to the He condensing unit 420. Accordingly, it is possible to reduce the temperature amplitude on the surface on which the object to be cooled is placed.

[0050] (Fifth embodiment)

Next, a refrigerator according to a fifth embodiment of the present invention will be described.

FIG. 9 is a schematic configuration diagram in the vicinity of the He condensing unit of the refrigerator according to the present embodiment. The refrigerator according to the present embodiment includes a temperature sensor 64 and a heater 66 attached to the He condensing unit 520, and a control unit 62 that drives the heater 66 based on the measurement result of the temperature sensor 64. . Note that detailed description of portions having the same configuration as in the first embodiment is omitted.

In the present embodiment, the temperature sensor 64 is mounted in the vicinity of the placement surface of the object 40 to be cooled in the He condensing unit 520. The He condensing unit 520 is provided with a heater 66 equipped with a heating wire or the like. These temperature sensor 64 and heater 66 are connected to the control unit 62. The control unit 62 drives the heater 66 based on the measurement result of the temperature sensor 64. That is, the output signal of the temperature sensor 64 is converted into the drive current of the heater 66, and the feedback current is passed through the heater 66, so that the temperature pulsation caused by the heat generation is controlled to be minimized.

Specifically, first, the set temperature of the mounting surface of the object to be cooled 40 is compared with the measured temperature of the temperature sensor 64. When the measured temperature falls below the set temperature, the He condensing unit 520 is heated by driving the heater. As a result, the temperature of the mounting surface of the object to be cooled 40 is raised to the set temperature. It becomes possible to return at a time. Therefore, the temperature amplitude on the placement surface of the object to be cooled 40 can be reduced.

[0052] The technical scope of the present invention is not limited to the above-described embodiments, but includes those in which various modifications are made to the above-described embodiments without departing from the spirit of the present invention. That is, the specific materials and configurations described in the embodiments are merely examples, and can be changed as appropriate.

Industrial applicability

[0053] It is possible to provide a refrigerator that can reduce the temperature amplitude on the surface on which the object to be cooled is placed and can cool the object to be cooled uniformly and stably.

Claims

The scope of the claims

[1] a cooling stage for cooling an object to be cooled;

A He condensing unit on which the object to be cooled is placed;

A reservoir filled with He gas that communicates with the He condensation section;

A heat transfer buffer material, which is disposed between the cooling stage and the He condensing unit, and has a lower thermal conductivity than the He condensing unit!

A freezer comprising the above.

[2] The refrigerator according to claim 1, wherein the He condensing part is made of a material having a thermal conductivity of 200 W / (m.K) or more at a temperature in the vicinity of 4K.

[3] The refrigerator according to claim 1, wherein the heat transfer buffer material is made of a material having a thermal conductivity of less than 100 W / (m-K) at a temperature in the vicinity of 4K.

[4] The refrigerator according to claim 1, wherein the volume of the He condensing part is not less than lOcc and not more than lOOcc.

[5] The refrigerator according to claim 1, wherein the volume of the reservoir is not less than 5 times and not more than 100 times the volume of the He condensation unit.

[6] The pressure of the He gas filled in the reservoir is 0. IMPa or more at room temperature 1.

The refrigerator according to claim 1, wherein the refrigerator is OMPa or less.

7. The refrigerator according to claim 1, wherein fins are erected on the inner surface of the He condensation section.

8. The refrigerator according to claim 1, wherein a porous structure is attached to the inner surface of the He condensation section.

[9] The refrigerator according to claim 1, wherein unevenness is formed on a contact surface between the heat transfer buffer material and the cooling stage or the He condensing unit.

[10] a temperature sensor and a heater attached to the He condensation section;

The refrigerator according to claim 1, further comprising: a control unit that drives the heater based on a measurement result of the temperature sensor.