WO2019009019A1

WO2019009019A1 - Cryogenic refrigerator

Info

Publication number: WO2019009019A1
Application number: PCT/JP2018/022244
Authority: WO
Inventors: 乾包; 名堯許
Original assignee: 住友重機械工業株式会社
Priority date: 2017-07-07
Filing date: 2018-06-11
Publication date: 2019-01-10

Abstract

A cryogenic refrigerator 10 comprising: an expansion chamber 34; a cooling stage 26 thermally coupled to the expansion chamber 34, said cooling stage 26 comprising a first heat transfer block 28 having a surface exposed to the expansion chamber 34 and a first heat exchange surface 46 arranged on the outside of the expansion chamber 34, and a second heat transfer block 30 having a second heat exchange surface 48 facing the first heat exchange surface 46; a refrigerant supply opening 64 installed in the cooling stage 26 on the outside of the expansion chamber 34; a refrigerant discharge opening 66 installed in the cooling stage 26 on the outside of the expansion chamber 34; and a refrigerant passage 68 fluidically separated from the expansion chamber 34, said refrigerant passage 68 being formed between the first heat transfer block 28 and the second heat transfer block 30 such that the refrigerant flows along the first heat exchange surface 46 and the second heat exchange surface 48 from the refrigerant supply opening 64 to the refrigerant discharge opening 66.

Description

Cryogenic refrigerator

The present invention relates to a cryogenic refrigerator.

Cryogenic refrigerators, represented by Gifford-McMahon (GM) refrigerators, have a cooling stage thermally coupled to an expansion chamber of a working gas. By properly synchronizing the expansion chamber volume change and the pressure change, the cryogenic refrigerator can cool the cooling stage to a desired cryogenic temperature. The objects to be cooled are thermally coupled to the cooling stage and cooled by the cooling stage. Such a cooling stage is also provided to other cryogenic refrigerators such as Stirling refrigerator and pulse tube refrigerator.

JP 2001-248930 A Unexamined-Japanese-Patent No. 10-122683

Cryogenic refrigerators are often used to cool various refrigerant fluids (hereinafter also referred to as refrigerants) such as liquid nitrogen, gaseous or liquid helium. Cooled refrigerants are used to cool various devices that require a low temperature environment, such as superconducting devices and instrumentation. In one typical arrangement, a refrigerant tube for flowing the refrigerant is joined to the outer surface of the cooling stage of the cryogenic refrigerator by joining means such as welding or brazing and thermally coupled to the cooling stage. The cooling pipe cools the refrigerant pipe, and the refrigerant pipe cools the refrigerant. The bonding state of the refrigerant pipe and the outer surface of the cooling stage affects the cooling performance of the refrigerant by the cryogenic refrigerator. Since the joint failure of the refrigerant pipe generates a large thermal resistance between the refrigerant pipe and the cooling stage, the refrigerant becomes difficult to cool.

One of the exemplary objects of an aspect of the present invention is to provide a technique for improving the cooling performance of a cryogenic refrigerator.

According to an aspect of the present invention, the cryogenic refrigerator is an expansion chamber and a cooling stage thermally coupled to the expansion chamber, the cryogenic refrigerator being disposed outside the expansion chamber and the exposed surface to the expansion chamber. A first heat transfer block having a first heat exchange surface, and a second heat transfer block having a second heat exchange surface facing the first heat exchange surface, and the outside of the expansion chamber A refrigerant supply port installed in the cooling stage, a refrigerant discharge port installed outside the expansion chamber and installed in the cooling stage, and a refrigerant passage fluidly isolated from the expansion chamber, Forming between the first heat transfer block and the second heat transfer block such that the refrigerant flows along the first heat exchange surface and the second heat exchange surface from the refrigerant supply port to the refrigerant discharge port And a refrigerant passage.

It is to be noted that any combination of the above-described constituent elements, or one in which the constituent elements and expressions of the present invention are mutually replaced among methods, apparatuses, systems, etc. is also effective as an aspect of the present invention.

An object of the present invention is to provide a technique for improving the cooling performance of a cryogenic refrigerator.

It is a figure showing roughly the cryogenic refrigerator concerning a 1st embodiment. FIG. 2 is a schematic view showing an AA cross section of the cryogenic refrigerator shown in FIG. 1; It is the schematic which shows the other example of the 1st heat-transfer block which concerns on 1st Embodiment. It is the schematic which shows the other example of the cooling stage which concerns on 1st Embodiment. It is a figure showing roughly the important section of the cryogenic refrigerator concerning a 2nd embodiment. FIG. 6 is a schematic view showing a cross section BB of the cryogenic refrigerator shown in FIG. 5; It is a figure showing roughly the important section of the cryogenic refrigerator concerning a 3rd embodiment. It is a figure showing roughly the important section of the cryogenic refrigerator concerning a 4th embodiment. FIG. 9 is a schematic view showing a cross section CC of the cryogenic refrigerator shown in FIG. 8; FIG. 10A and FIG. 10B are schematic views showing another example of the communication passage in the cryogenic refrigerator according to the fourth embodiment. It is a figure showing roughly other examples of the cryogenic refrigerator concerning a 4th embodiment. It is a figure showing roughly other examples of the cryogenic refrigerator concerning a 4th embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the description, the same elements will be denoted by the same reference signs, and overlapping descriptions will be omitted as appropriate. Further, the configurations described below are exemplifications and do not limit the scope of the present invention. Further, in the drawings referred to in the following description, the size and thickness of each component are for convenience of description, and do not necessarily indicate actual dimensions and ratios.

First Embodiment
FIG. 1 is a view schematically showing a cryogenic refrigerator 10 according to the first embodiment. FIG. 2 is a schematic view showing an AA cross section of the cryogenic refrigerator 10 shown in FIG.

The cryogenic refrigerator 10 includes a compressor 12 that compresses a working gas (e.g., helium gas) and a cold head 14 that cools the working gas by adiabatic expansion. The compressor 12 has a compressor discharge port 12a and a compressor suction port 12b. The cold head 14 is also called an expander. The illustrated cryogenic refrigerator 10 is a single-stage GM refrigerator.

As described in detail later, the compressor 12 supplies a high pressure (PH) working gas from the compressor discharge port 12 a to the cold head 14. The cold head 14 is provided with a regenerator 15 for precooling the working gas. The precooled working gas is further cooled by expansion in the cold head 14. The working gas is recovered through the regenerator 15 to the compressor suction port 12b. The working gas cools the regenerator 15 as it passes through the regenerator 15. The compressor 12 compresses the recovered low pressure (PL) working gas and supplies it to the cold head 14 again. Generally, both high pressure (PH) and low pressure (PL) are much higher than atmospheric pressure. Typically, the high pressure (PH) is for example 2 to 3 MPa and the low pressure (PL) is for example 0.5 to 1.5 MPa.

The cold head 14 includes a displacer 20 capable of reciprocating in an axial direction (vertical direction in FIG. 1 and indicated by an arrow C), a cylinder 22 accommodating the displacer 20, and a displacer drive mechanism 16. The displacer drive mechanism 16 comprises a connecting rod 24 coaxially connected to the displacer 20. The cylinder 22 is configured as part of a pressure vessel for working gas.

The displacer drive mechanism 16 can adopt various known configurations. For example, in the case of a motor driven GM refrigerator, the displacer drive mechanism 16 includes a scotch yoke mechanism and a motor. The displacer 20 is mechanically connected to the motor via the connecting rod 24 and the scotch yoke mechanism and driven by the motor. In the case of a gas-driven GM refrigerator, the displacer 20 is connected to the displacer drive piston via a connecting rod 24 and is driven by the gas pressure acting on the displacer drive piston.

The axial reciprocation of the displacer 20 is guided by the cylinder 22. Typically, the displacer 20 and the cylinder 22 are each an axially extending cylindrical member, the inner diameter of the cylinder 22 corresponding to or slightly larger than the outer diameter of the displacer 20. The central axes of the displacer 20 and the cylinder 22 correspond to the central axis 92 of the cryogenic refrigerator 10 (see FIG. 2). The connecting rod 24 is smaller in diameter than the displacer 20.

The cylinder 22 is partitioned by the displacer 20 into an expansion chamber 34 and a room temperature chamber 36. The expansion chamber 34 defines an expansion space for the working gas of the cryogenic refrigerator 10. The displacer 20 forms an expansion chamber 34 with the cylinder 22 at one axial end, and forms a room temperature chamber 36 with the cylinder 22 at the other axial end. The expansion chamber 34 is disposed on the bottom dead center LP side, and the room temperature chamber 36 is disposed on the top dead center UP side. The connecting rod 24 extends through the room temperature chamber 36 to the upper lid of the displacer 20.

The cold head 14 is provided with a cooling stage 26 fixed to the cylinder 22 so as to enclose the expansion chamber 34. Cooling stage 26 is thermally coupled to expansion chamber 34. The cooling stage 26 is joined to the cylinder 22 by brazing or welding, for example. The details of the cooling stage 26 will be described later.

The regenerator 15 is built in the displacer 20. The displacer 20 has an inlet channel 40 in the upper lid thereof, which connects the regenerator 15 to the room temperature chamber 36. Further, the displacer 20 has an outlet flow passage 42 communicating the regenerator 15 with the expansion chamber 34 in the cylindrical portion thereof. Alternatively, the outlet channel 42 may be provided in the lower lid of the displacer 20. In addition, the regenerator 15 includes an inlet retainer 41 inscribed in the upper lid portion, an outlet retainer 43 inscribed in the lower lid portion, and a regenerator material sandwiched between the two retainers. In FIG. 1, the cool storage material is illustrated as a dotted area sandwiched by the inlet retainer 41 and the outlet retainer 43. The cold storage material may be, for example, a copper wire mesh. The retainer may be a wire mesh coarser than the regenerator material.

A seal portion 44 is provided between the displacer 20 and the cylinder 22. The seal portion 44 is, for example, a slipper seal, and is attached to the cylindrical portion or the upper lid portion of the displacer 20. Since the clearance between the displacer 20 and the cylinder 22 is sealed by the seal portion 44, there is no direct gas flow between the room temperature chamber 36 and the expansion chamber 34 (that is, the gas flow bypassing the regenerator 15).

As the displacer 20 moves axially, the expansion chamber 34 and the room temperature chamber 36 complementarily increase or decrease in volume. That is, when the displacer 20 moves downward, the expansion chamber 34 narrows and the room temperature chamber 36 widens. The reverse is also true.

The working gas flows from the room temperature chamber 36 into the regenerator 15 through the inlet channel 40. More precisely, the working gas flows from the inlet channel 40 into the regenerator 15 through the inlet retainer 41. The working gas flows from the regenerator 15 into the expansion chamber 34 via the outlet retainer 43 and the outlet channel 42. When the working gas returns from the expansion chamber 34 to the room temperature chamber 36, it passes the reverse path. That is, the working gas returns from the expansion chamber 34 to the room temperature chamber 36 through the outlet channel 42, the regenerator 15, and the inlet channel 40. The working gas that bypasses the regenerator 15 and tries to flow through the clearance is shut off by the seal portion 44.

Further, the cryogenic refrigerator 10 includes a working gas circuit 52 connecting the compressor 12 to the cold head 14. The working gas circuit 52 comprises a valve unit 54 configured to control the pressure of the expansion chamber 34. The valve unit 54 has an intake on-off valve V1 and an exhaust on-off valve V2. The valve unit 54 can adopt various known configurations such as a rotary valve system.

When the intake on-off valve V1 is open, the exhaust on-off valve V2 is closed. A high pressure working gas is supplied to the cylinder 22 from the compressor discharge port 12a through the intake on-off valve V1. On the other hand, when the exhaust on / off valve V2 is open, the intake on / off valve V1 is closed. Working gas is recovered from the cylinder 22 to the compressor suction port 12b through the exhaust on-off valve V2, and the cylinder 22 is depressurized. The intake on-off valve V1 and the exhaust on-off valve V2 may be temporarily closed together. Thus, the cylinders 22 are alternately connected to the compressor discharge port 12a and the compressor suction port 12b.

An exemplary operation of the cryogenic refrigerator 10 is described. At some point in the working gas supply process, the displacer 20 is located in the cylinder 22 at the bottom dead center LP. At the same time, or when the intake valve is opened at a timing shifted slightly, high-pressure working gas is supplied from the compressor 12 to the cylinder 22. The working gas is supplied to the expansion chamber 34 while being cooled by the regenerator 15.

When the expansion chamber 34 is filled with the high pressure working gas, the intake on-off valve V1 is closed. At this time, the displacer 20 is located in the cylinder 22 at the top dead center UP. At the same time or when the exhaust on-off valve V2 is opened at a timing shifted slightly, the working gas of the expansion chamber 34 is decompressed and expanded. The expansion brings the working gas to a low temperature and absorbs heat from the cooling stage 26.

The displacer 20 moves toward the bottom dead center LP, and the volume of the expansion chamber 34 decreases. The working gas in the expansion chamber 34 cools the regenerator material while passing through the regenerator 15, and is recovered by the compressor 12. The above steps constitute one cycle, and the cryogenic refrigerator 10 cools the cooling stage 26 to a desired cryogenic temperature by repeating this cooling cycle.

The cooling stage 26 includes a first heat transfer block 28 and a second heat transfer block 30. The cylinder 22, the first heat transfer block 28, and the second heat transfer block 30 are axially arranged in this order of description. The cylinder 22 extends in the axial direction from the first heat transfer block 28. The cooling stage 26 is formed in a cylindrical shape slightly larger in diameter than the cylinder 22. The first heat transfer block 28 and the second heat transfer block 30 are formed in combination to form a cylindrical shape.

The first heat transfer block 28 and the second heat transfer block 30 are formed of, for example, a metal or other heat conductive material having a relatively high thermal conductivity, such as copper. The first heat transfer block 28 and the second heat transfer block 30 are typically formed of the same material, but may be formed of different materials. The first heat transfer block 28 is formed, for example, by machining such as cutting from a block of material. Similarly, the second heat transfer block 30 is also formed by machining, such as cutting, from a block of material.

The first heat transfer block 28 is disposed to surround the expansion chamber 34 and is thermally coupled to the expansion chamber 34. The first heat transfer block 28 forms an expansion chamber 34 with the displacer bottom 20 a. The first heat transfer block 28 has an exposed surface to the expansion chamber 34, and the exposed surface includes an expansion chamber bottom surface 34a opposite to the displacer bottom 20a. The expansion chamber bottom surface 34 a forms a plane substantially perpendicular to the central axis 92 of the cryogenic refrigerator 10. The first heat transfer block 28 includes a first heat exchange surface 46 disposed outside the expansion chamber 34. The first heat exchange surface 46 is directed in the axial direction opposite to the expansion chamber bottom surface 34 a.

The second heat transfer block 30 is disposed adjacent to the first heat transfer block 28 and thermally coupled to the expansion chamber 34 via the first heat transfer block 28. The second heat transfer block 30 is joined to the first heat transfer block 28 by brazing or welding, for example. The outer peripheral portion of the second heat transfer block 30 is joined to the outer peripheral portion of the first heat transfer block 28. The second heat transfer block 30 is disposed outside the expansion chamber 34 and has no exposed surface to the expansion chamber 34. The second heat transfer block 30 includes a second heat exchange surface 48 facing the first heat exchange surface 46.

The cryogenic refrigerator 10 includes a refrigerant circuit 60 for flowing a refrigerant. The refrigerant circuit 60 is fluidly isolated from the working gas circuit 52. The refrigerant circuit 60 is provided as a separate system from the working gas circuit 52, and both are separated. The refrigerant flowing through the refrigerant circuit 60 is not mixed with the working gas flowing through the working gas circuit 52. The refrigerant may be the same kind as the working gas (for example, helium gas). The refrigerant may be different (e.g., liquid nitrogen) from the working gas. In any case, the pressure of the refrigerant in the refrigerant circuit 60 is generally lower than the pressure of the working gas in the working gas circuit 52, for example, about atmospheric pressure.

The refrigerant circuit 60 includes a refrigerant pump 62, a refrigerant supply port 64, a refrigerant discharge port 66, and a refrigerant passage 68.

The refrigerant pump 62 is provided to circulate the refrigerant in the refrigerant circuit 60. The refrigerant pump 62 is connected to the refrigerant supply port 64 and the refrigerant discharge port 66 so as to deliver the refrigerant discharged from the refrigerant discharge port 66 to the refrigerant supply port 64. The discharge port of the refrigerant pump 62 is connected to the refrigerant supply port 64 by a refrigerant supply pipe 63a, and the recovery port of the refrigerant pump 62 is connected to the refrigerant discharge port 66 by a refrigerant discharge pipe 63b. The refrigerant pump 62, the refrigerant supply pipe 63a, and the refrigerant discharge pipe 63b may not be considered to constitute a part of the cryogenic refrigerator 10. The refrigerant supply pipe 63 a and the refrigerant discharge pipe 63 b may be manufactured by a manufacturer different from the manufacturer of the cryogenic refrigerator 10 and may be prepared by the user of the cryogenic refrigerator 10.

The refrigerant supply port 64 and the refrigerant discharge port 66 are disposed on the outer surface of the cooling stage 26 as a part of the cryogenic refrigerator 10. Therefore, the refrigerant supply port 64 and the refrigerant discharge port 66 are disposed outside the expansion chamber 34. The refrigerant supply port 64 is provided with a refrigerant inflow hole 64 a which allows the refrigerant to flow into the cooling stage 26, specifically to the refrigerant passage 68. The refrigerant inflow hole 64 a connects the refrigerant supply pipe 63 a to the refrigerant passage 68. The refrigerant discharge port 66 includes a refrigerant outflow hole 66 a which causes the refrigerant to flow out from the inside of the cooling stage 26, specifically, from the refrigerant passage 68. The refrigerant outflow hole 66a connects the refrigerant passage 68 to the refrigerant discharge pipe 63b. The refrigerant is supplied from the refrigerant pump 62 to the refrigerant passage 68 through the refrigerant supply port 64. In addition, the refrigerant is discharged from the refrigerant passage 68 to the refrigerant pump 62 through the refrigerant outlet 66.

Although the positions and the number of the refrigerant supply ports 64 on the outer surface of the cooling stage 26 are arbitrary, a plurality of refrigerant supply ports 64 are arranged at equal intervals in the circumferential direction on the outer peripheral surface of the cooling stage 26 here. The refrigerant supply port 64 is provided at the boundary between the first heat transfer block 28 and the second heat transfer block 30, but is not limited thereto. The refrigerant supply port 64 may be one. Although one refrigerant | coolant discharge port 66 is provided in the end surface center part of the 2nd heat-transfer block 30 on the opposite side to the 2nd heat exchange surface 48, it is not restricted to this. A plurality of refrigerant outlets 66 may be provided.

The refrigerant passage 68 is fluidly isolated from the expansion chamber 34. The refrigerant passage 68 is formed inside the cooling stage 26 and penetrates the cooling stage 26. In the cooling stage 26, the refrigerant passage 68 and the expansion chamber 34 are separated from each other. The working gas does not flow into the refrigerant passage 68 from the expansion chamber 34. The refrigerant does not leak from the refrigerant passage 68 to the expansion chamber 34.

The refrigerant passage 68 has a first heat transfer block 28 and a second heat transfer block 30 so that the refrigerant flows from the refrigerant supply port 64 to the refrigerant discharge port 66 along the first heat exchange surface 46 and the second heat exchange surface 48. It is formed between. The refrigerant passage 68 is formed between the first heat exchange surface 46 and the second heat exchange surface 48.

A heat exchanger 72 for cooling the object 70 is provided between the refrigerant pump 62 and the refrigerant supply port 64. The heat exchanger 72 is connected to the middle of the refrigerant supply pipe 63a. The heat exchanger 72 may be connected to the middle of the refrigerant discharge pipe 63 b between the refrigerant discharge port 66 and the refrigerant pump 62. The object 70 is thermally connected to the heat exchanger 72. By flowing the cooled refrigerant to the heat exchanger 72, the object 70 is cooled.

The distance between the first heat exchange surface 46 of the first heat transfer block 28 and the second heat exchange surface 48 of the second heat transfer block 30 is constant. The flow passage width of the refrigerant passage 68 is constant throughout the refrigerant passage 68. However, this is not essential, and as will be described later, the distance between the first heat exchange surface 46 and the second heat exchange surface 48 may be different depending on the place.

The first heat exchange surface 46 includes a first base surface 74 and at least one first fin 76 extending from the first base surface 74. The first base surface 74 forms a plane substantially parallel to the expansion chamber bottom surface 34a, and is axially opposite to the expansion chamber bottom surface 34a. The first base surface 74 can also be referred to as the upper surface of the refrigerant passage 68. The first fin 76 comprises a first fin tip 76a. The first heat transfer block 28 includes one first fin 76, but may include a plurality of first fins 76. The outer peripheral portion of the first heat transfer block 28 can also be regarded as another first fin 76.

The second heat exchange surface 48 includes a second base surface 78 and at least one second fin 80 extending from the second base surface 78. The second base surface 78 forms a plane substantially parallel to the first base surface 74. The second base surface 78 can also be referred to as the lower surface of the refrigerant passage 68. The second fin 80 extends along the first fin 76. The second fin 80 includes a second fin tip 80a. The second heat transfer block 30 includes two second fins 80, but the number of second fins 80 may be one, or three or more.

The second base surface 78 forms a recess for receiving the first fin 76 between two adjacent second fins 80. Further, in the case where the plurality of first fins 76 are provided in the first heat transfer block 28, the first base surface 74 has a recess for receiving the second fin 80 between two adjacent first fins 76. Form.

The first fin tip 76a is disposed closer to the second base surface 78 than the second fin tip 80a. The second fin tip 80a is disposed closer to the first base surface 74 than the first fin tip 76a. Thus, the first fins 76 are inserted between two adjacent second fins 80 so that the first fins 76 and the second fins 80 are alternately arranged. Thus, a meandering refrigerant passage 68 is formed.

The first fins 76 and the second fins 80 extend in the axial direction. Thus, the first fins 76 and the second fins 80 have fin heights in the axial direction. The height (distance from the first base surface 74 to the first fin tip 76a) H1 of the first fin 76 is larger than the distance G1 between the first base surface 74 and the second fin tip 80a. The height (distance from the second base surface 78 to the second fin tip 80a) H2 of the second fin 80 is larger than the distance G2 between the second base surface 78 and the first fin tip 76a. The height H1 of the first fin 76 and the height H2 of the second fin 80 are equal. If desired, the height H1 and the height H2 may be different. The distance G1 between the first base surface 74 and the second fin tip 80a and the distance G2 between the second base surface 78 and the first fin tip 76a are equal. The intervals G1 and G2 may be different.

The refrigerant passage 68 includes a first cross passage 82, a second cross passage 84, and an inter-fin passage 86. The first transverse passage 82 is formed between the first fin tip 76 a and the second base surface 78 so that the coolant traverses the first fin 76. The second transverse passage 84 is formed between the second fin tip 80 a and the first base surface 74 so that the refrigerant traverses the second fin 80. The inter-fin passage 86 is formed between the first fin 76 and the second fin 80. The inter-fin passage 86 communicates the first transverse passage 82 with the second transverse passage 84.

A plurality of inter-fin passages 86 are formed. One inter-fin passage 86 is formed between one of the two adjacent second fins 80 and the first fin 76, and another inter-fin passage 86 between the other second fin 80 and the first fin 76. Is formed. The two inter-fin passages 86 are in communication by the first cross passage 82. As shown in FIG. 2, the widths W1, W2, W3 of the inter-fin passages 86 are equal. The widths W1, W2, and W3 may be equal to the above-described intervals G1 and G2.

As shown in FIG. 1, the refrigerant flows along the first fin tip 76 a by the coolant flowing through the first transverse passage 82. The refrigerant flows through the second transverse passage 84, so that the refrigerant traverses the second fin 80 along the second fin tip 80a. The inter-fin passage 86 guides the refrigerant from the first transverse passage 82 to the second transverse passage 84 or from the second transverse passage 84 to the first transverse passage 82.

The second heat transfer block 30, as shown in FIG. 2, forms a concentric ring structure 90 in which the second fin 80 is combined with the first fin 76 to be coaxially arranged with the central axis 92 of the cryogenic refrigerator 10. To be fixed to the first heat transfer block 28. Most cryogenic refrigerators 10 have a generally axisymmetric structure. Therefore, the concentric ring structure 90 is easy to apply to the cryogenic refrigerator 10 as compared to other structures.

The first fins 76 have a ring shape centered on the central axis 92 of the cryogenic refrigerator 10. The second fins 80 also have a ring shape centered on the central axis 92 of the cryogenic refrigerator 10. However, the second fin 80 has a diameter different from that of the first fin 76. The first and

second fins

76 and 80 extend circumferentially around the central axis 92 of the cryogenic refrigerator 10.

The first fins 76 and the second fins 80 have a fin thickness in the radial direction of the cryogenic refrigerator 10 and a fin length in the circumferential direction. In the case of a ring shape, the fin length corresponds to the circumferential length of the ring. The fin height and fin length are greater than the fin thickness. Also, the fin length is larger than the fin height. Conversely, the fin length may be smaller than the fin height.

The concentric ring structure 90 has an inner portion of the cooling stage 26 so that the fin height direction, fin thickness direction, and fin length direction coincide with the axial direction, radial direction, and circumferential direction of the cryogenic refrigerator 10, respectively. Provided in However, the arrangement of such concentric ring structure 90 is not essential. The concentric ring structure 90 may be arranged at any position and orientation inside the cooling stage 26, in which case the fin height direction, the fin thickness direction, and the fin length direction of the cryogenic refrigerator 10 are It does not necessarily coincide with the axial direction, the radial direction, and the circumferential direction.

The first fin 76 and the second fin 80 are continuous all around. Therefore, the first transverse passage 82, the second transverse passage 84, and the inter-fin passage 86 are also continuous along the entire circumference. That is, the first fin tip 76a is separated from the second base surface 78 all around. The second fin tip 80a is spaced from the first base surface 74 all around. In addition, the first fins 76 and the second fins 80 are separated from each other over the entire circumference.

However, the first transverse passage 82 may be divided into a plurality of sections by the first fin tip 76 a being in partial contact with the second base surface 78. The second transverse passage 84 may be divided into a plurality of sections by the second fin tip 80 a being in partial contact with the first base surface 74. Similarly, the inter-fin passage 86 may be divided into a plurality of areas by partial contact between the first fin 76 and the second fin 80. Thus, the first cross passage 82, the second cross passage 84, and the inter-fin passage 86 may be circumferentially divided, for example.

The first fins 76 and the second fins 80 may be circumferentially divided. The gap between the segments of the divided first fins 76 (or the second fins 80) may be part of the coolant passage 68. One of the second fins 80 is formed on the central axis 92 of the cryogenic refrigerator 10, and the second fins 80 have a rod-like shape. The first fins 76 may be formed on the central axis 92 of the cryogenic refrigerator 10 and have a rod-like shape.

In addition, the refrigerant passage 68 includes an outlet passage 88 communicating the refrigerant outlet 66 with the refrigerant passage 68. The outlet passage 88 extends through the second heat transfer block 30 along the central axis 92 of the cryogenic refrigerator 10. Since the second fin 80 is formed on the central axis 92 of the cryogenic refrigerator 10, the outlet passage 88 penetrates the second fin 80 in its height direction, and the second transverse passage 84 is the refrigerant outlet hole 66a. Connected to When the first fin 76 is formed on the central axis 92 of the cryogenic refrigerator 10, the outlet passage 88 is a second base facing the first fin 76 disposed on the central axis 92. The surface 78 may penetrate the second heat transfer block 30 and be connected to the refrigerant outlet 66.

The refrigerant supply port 64 is disposed on the cooling stage 26 so as to supply the refrigerant to the outer peripheral portion of the concentric ring structure 90. The refrigerant passage 68 is configured to guide the refrigerant from the outer periphery of the concentric ring structure 90 to the center of the concentric ring structure 90. The refrigerant discharge port 66 is disposed on the cooling stage 26 so as to discharge the refrigerant from the center of the concentric ring structure 90.

As described above, the refrigerant passage 68 is configured to allow the refrigerant to flow radially from the outer peripheral portion to the central portion of the cooling stage 26. The refrigerant flows from the refrigerant supply port 64 into the outer periphery of the concentric ring structure 90, and the second cross passage 84, the inter fin passage 86, the first cross passage 82, the inter fin passage 86, the second cross passage 84, the outlet passage It flows vertically and horizontally to 88. Thus, the refrigerant is discharged from the center of the concentric ring structure 90 to the refrigerant outlet 66. The direction in which the refrigerant flows is indicated by arrows in FIG. 1 for the purpose of understanding.

The refrigerant passage 68 acts as a heat exchanger integrated with the cooling stage 26 for cooling the refrigerant by the cooling stage 26. The refrigerant flow in the refrigerant passage 68 contacts the first heat exchange surface 46 and is cooled by heat exchange with the first heat exchange surface 46. In addition, the refrigerant flow in the refrigerant passage 68 contacts the second heat exchange surface 48 and is cooled by heat exchange with the second heat exchange surface 48.

By flowing the refrigerant thus cooled to the heat exchanger 72, the object 70 can be cooled. The refrigerant heated by heat exchange with the object 70 is recooled by the cooling stage 26 by flowing through the refrigerant passage 68. The recooled refrigerant is again used to cool the object 70.

According to the cryogenic refrigerator 10 according to the first embodiment, the heat exchanger for cooling the refrigerant is integrated in the inside of the cooling stage 26. More specifically, the refrigerant passage 68 includes the first heat exchange surface 46 and the refrigerant passage 68 so that the refrigerant flows from the refrigerant supply port 64 to the refrigerant discharge port 66 along the first heat exchange surface 46 and the second heat exchange surface 48. It is formed between the second heat exchange surface 48. By integrating the heat exchanger in this manner, thermal contact between the cryogenic refrigerator 10 and the refrigerant can be made even more reliably as compared with the external heat exchange configuration in which the refrigerant pipe is joined to the outer surface of the conventional cooling stage. Can be Therefore, the cryogenic refrigerator 10 can cool the refrigerant more efficiently.

In the cryogenic refrigerator 10, a serpentine refrigerant passage 68 is formed by a combination of the first fins 76 and the second fins 80. The contact area between the refrigerant and the heat exchange surface can be increased as compared to the case where two opposing heat exchange surfaces are both flat without providing such a fin. Thus, the cryogenic refrigerator 10 has an improved heat exchange efficiency.

In addition, when the cryogenic refrigerator 10 has a generally axisymmetric structure, the temperature at the central portion is slightly lower than that at the outer peripheral portion of the cooling stage 26. The refrigerant supply port 64 is disposed at the outer peripheral portion of the cooling stage 26, and the refrigerant discharge port 66 is disposed at the central portion of the cooling stage 26. The temperature of the refrigerant at the refrigerant supply port 64 is relatively high because the refrigerant is heated by the object 70. By disposing the refrigerant supply port 64 at a relatively high temperature site in the cooling stage 26, the temperature difference between the refrigerant at the refrigerant supply port 64 and the cooling stage 26 can be reduced. The smaller the temperature difference, the higher the heat exchange efficiency. This also helps to improve the heat exchange efficiency of the cryogenic refrigerator 10.

FIG. 3 is a schematic view showing another example of the first heat transfer block 28 according to the first embodiment. In the above-mentioned embodiment, although the 1st heat transfer block 28 is formed from a block of material, the present invention is not limited to this. The first heat transfer block 28 may be formed of a plurality of sub blocks. A plurality of sub blocks may be joined by brazing or welding to form the first heat transfer block 28. Similarly, the second heat transfer block 30 may be formed of a plurality of sub blocks.

As shown in FIG. 3, the first heat transfer block 28 includes an expansion chamber forming sub block 28 a and a first fin sub block 28 b. An expansion chamber bottom surface 34a is provided in the expansion chamber forming sub-block 28a, and a first fin 76 is provided in the first fin sub block 28b. The first fin sub block 28 b is bonded to the expansion chamber forming sub block 28 a via a bonding layer 94 such as a brazing layer. The expansion chamber forming sub block 28a has a flat bonding surface 94a, and the first fin sub block 28b has a flat bonding surface 94b, and these two

bonding surfaces

94a and 94b are bonded by the bonding layer 94. There is. The bonding surfaces 94a, 94b may be flat surfaces parallel to the expansion chamber bottom surface 34a. Such bonding between flat surfaces is easier to perform stronger bonding than when a conventional external heat exchanger is bonded to the outer surface of the cooling stage.

Also in the bonding of the first heat transfer block 28 and the second heat transfer block 30, it is preferable to be bonded at a flat bonding surface. Therefore, the outer peripheral portion of the first heat transfer block 28 is an annular flat surface, and the outer peripheral portion of the second heat transfer block 30 is also an annular flat surface, and these two annular flat surfaces are joined by brazing or welding It is also good.

FIG. 4 is a schematic view showing another example of the cooling stage 26 according to the first embodiment. As illustrated, the distance between the first heat exchange surface 46 and the second heat exchange surface 48 in the outer peripheral portion of the concentric ring structure 90 is the same as that in the central portion of the concentric ring structure 90. The distance between the heat exchange surfaces 48 may be smaller.

As in the embodiment shown in FIG. 2, when the distance between the first heat exchange surface 46 and the second heat exchange surface 48 is uniform, the cross-sectional area of the inter-fin passage 86 (perpendicular to the central axis 92) The area of the cross section by the plane becomes larger toward the outer periphery of the concentric ring structure 90. This is because the diameter of the inter-fin passage 86 located outside is larger than that of the inter-fin passage 86 located inside the concentric ring-like structure 90. The larger the flow path cross-sectional area, the smaller the flow path resistance. That is, in the concentric ring-like structure 90 shown in FIG. 2, the flow path resistance at the outer peripheral portion is relatively small, and the flow path resistance at the central portion is relatively large. The more uniform flow path resistance results in better heat exchange efficiency in the concentric ring structure 90.

Further, as one evaluation index of the heat exchanger, the ratio of heat exchange amount to pressure loss (= heat exchange amount / pressure loss) is considered. This evaluation index indicates that the performance of the heat exchanger is good when the value is large. Since the temperature difference between the refrigerant and the cooling stage 26 is large near the refrigerant supply port 64, the amount of heat exchange is large. Therefore, even if the flow path is narrow in the vicinity of the refrigerant supply port 64 and the pressure loss is large, this evaluation index has a certain size. On the other hand, since the refrigerant is already cooled near the refrigerant outlet 66, the temperature difference between the refrigerant and the cooling stage 26 is small, and hence the amount of heat exchange is also small. Therefore, if the pressure loss is large in the vicinity of the refrigerant outlet 66, the above-mentioned evaluation index becomes significantly small, which is not desirable.

Thus, as shown in FIG. 4, the refrigerant passage 68 is relatively narrow at the outer periphery of the concentric ring structure 90, and the refrigerant passage 68 is relatively wide at the center of the concentric ring structure 90. The width W 1 of the outer inter-fin passage 86 is narrower than the width W 2 of the middle inter-fin passage 86. Further, the width W2 of the middle inter-fin passage 86 is narrower than the width W3 of the inner inter-fin passage 86. In this way, both the flow path resistance in the refrigerant passage 68 and the evaluation index can be made more uniform.

In the first embodiment, as described above, the first transverse passage 82 and the second transverse passage 84 are formed all around the concentric ring structure 90, and the refrigerant flow in the inter-fin passage 86 is induced in the fin height direction. ing. However, the present invention is not limited to this. Such an example is described next.

Second Embodiment
FIG. 5 is a view schematically showing the main part of the cryogenic refrigerator 10 according to the second embodiment. 6 is a schematic view showing a cross section BB of the cryogenic refrigerator 10 shown in FIG. The cooling stage 26 and its surrounding structure are shown in FIG. 5 and the concentric ring 90 is shown in FIG. The cryogenic refrigerator 10 according to the second embodiment is different from the first embodiment in the refrigerant passage 68.

The first transverse passage 82 is locally formed between the first fin tip 76 a and the second base surface 78, and the second transverse passage 84 is between the second fin tip 80 a and the first base surface 74. It is formed locally. One first transverse passage 82 is formed in one first fin 76, and one second transverse passage 84 is formed in one second fin 80.

Most of the first fin tips 76a are in contact with the second base surface 78, and the first fin tips 76a have a single recess at a specific site in the circumferential direction, and this recess forms a first cross passage 82. Most of the second fin tip 80a is in contact with the first base surface 74, and the second fin tip 80a has a single recess at a specific location in the circumferential direction, and the recess forms a second cross passage 84.

The arrangement of the first transverse passage 82 and the second transverse passage 84 is determined such that the refrigerant flow in the inter-fin passage 86 is directed in a direction at an angle to the fin height direction. The first transverse passage 82 and the second transverse passage 84 are disposed at circumferentially different places. More specifically, the first cross passage 82 and the second cross passage 84 are disposed opposite to each other with respect to the central axis 92. Therefore, the refrigerant flow in the inter-fin passage 86 is induced in a direction oblique to or circumferentially with respect to the fin height direction (i.e., the axial direction).

Only one refrigerant supply port 64 is provided.

For the purpose of understanding, in FIGS. 5 and 6, the directions in which the refrigerant flows are indicated by arrows, and the corresponding arrows in FIGS. 5 and 6 have the same reference numerals D1 to D4. The refrigerant flows from the refrigerant supply port 64 through the outer first cross passage 82 into the outer inter-fin passage 86 (arrow D1). The refrigerant bifurcates from the outer inter-fin passage 86, flows half a circumference, joins (arrow E1), and flows from the outer second cross passage 84 into the middle inter-fin passage 86 (arrow D2). The refrigerant branches into the middle inter-fin passage 86 again to flow half a circumference, merges (arrow E2), and flows from the inner first cross passage 82 into the inner inter-fin passage 86 (arrow D3). The refrigerant branches again to the inner inter-fin passage 86 and flows half a circumference respectively to join (arrow E3), and from the inner second cross passage 84 to exit the refrigerant outlet 66 through the outlet passage 88 (arrow D4) ).

According to the second embodiment, the refrigerant flow in the inter-fin passage 86 is induced in a direction making an angle with the fin height direction. The refrigerant flow in the inter-fin passage 86 is generally directed in the circumferential direction. The refrigerant passage 68 is longer than in the case where the refrigerant flow in the inter-fin passage 86 is induced in the fin height direction as in the first embodiment. In this way, the contact area between the refrigerant and the heat exchange surface can be increased, so that the heat exchange efficiency of the cryogenic refrigerator 10 is improved.

It should also be noted that the first transverse passage 82 and the second transverse passage 84 are disposed at different locations in the fin height direction. The first cross passage 82 is located below, whereas the second cross passage 84 is located above. Therefore, the flow passage length from the first transverse passage 82 to the second transverse passage 84 is longer than when the first transverse passage 82 and the second transverse passage 84 are at the same height. This also helps to increase the contact area between the refrigerant and the heat exchange surface.

Further, one refrigerant supply port 64 and one refrigerant discharge port 66 also help to make the refrigerant passage 68 longer.

In addition, the position and number of the 1st crossing passage 82 and the 2nd crossing passage 84 are arbitrary. For example, one first fin 76 may be provided with a plurality of first transverse passages 82. The plurality of first transverse passages 82 may be circumferentially equiangularly spaced. Similarly, a plurality of second transverse passages 84 may be provided in one second fin 80. The plurality of second transverse passages 84 may be provided at equal angular intervals in the circumferential direction.

Third Embodiment
FIG. 7 is a view schematically showing the main part of the cryogenic refrigerator 10 according to the third embodiment.

The expansion chamber bottom surface 34 a includes a ring-shaped convex portion 96 coaxially disposed with the displacer 20. Also, the displacer bottom 20 a includes a ring-shaped recess 98 that receives the ring-shaped protrusion 96. Thus, the fin type heat exchanger may be provided not only in the refrigerant passage 68 but also in the expansion chamber 34. Since the heat exchange area between the working gas of the cryogenic refrigerator 10 and the cooling stage 26 is increased, the heat exchange efficiency of the cryogenic refrigerator 10 is improved.

In addition, the ring-shaped convex portion 96 is hollow so as to receive the second fin 80 from the side opposite to the expansion chamber bottom surface 34 a. In this way, the thermal coupling between the expansion chamber 34 and the refrigerant passage 68 can be further improved. Further, since the second fin 80 can be accommodated in the ring-shaped convex portion 96, the axial length of the cooling stage 26 can be shortened.

In other words, the displacer 20 is provided with a displacer bottom fin 100 extending toward the expansion chamber bottom 34 a. The first heat transfer block 28 is formed with a cavity 102 which is formed on the expansion chamber bottom surface 34 a to receive the displacer bottom fin 100 and which makes the first fin 76 hollow. In this way, the thermal coupling between the expansion chamber 34 and the refrigerant passage 68 can be further improved. In addition, since the displacer bottom fin 100 can be accommodated in the hollow portion 102 of the first fin 76, the axial length of the cooling stage 26 can be shortened.

Fourth Embodiment
FIG. 8 is a view schematically showing the main part of the cryogenic refrigerator 10 according to the fourth embodiment. FIG. 9 is a schematic view showing a cross section CC of the cryogenic refrigerator 10 shown in FIG. In each of the embodiments described above, the refrigerant passage 68 has a single hierarchy, but is not limited to this.

The refrigerant passage 68 is divided into a plurality of layers. The plurality of layers are arranged at different locations in the axial direction. The plurality of layers are connected to one another so that the refrigerant flows in order. The individual layers can also be referred to as sub-passages in the sense that they form part of the coolant passage 68.

As shown in FIG. 8, the refrigerant passage 68 is divided into a first level 104 and a second level 106. In the cooling stage 26, the first level 104 is disposed at the axially lower portion, and the second level 106 is disposed at the axially upper portion. Thus, the first layer 104 and the second layer 106 are axially adjacent to each other.

The second heat transfer block 30 of the cooling stage 26 is disposed to surround the first heat transfer block 28. The second heat transfer block 30 includes a second heat transfer block bottom portion 30a and a second heat transfer block side cylindrical portion 30b. The second heat transfer block bottom portion 30a is axially adjacent to the first heat transfer block 28, and the second heat transfer block side cylindrical portion 30b extends axially upward from the second heat transfer block bottom portion 30a. The whole circumference of the heat block 28 is enclosed.

The refrigerant supply port 64 is installed in the second heat transfer block side cylindrical portion 30 b so as to supply the refrigerant to the second layer 106 of the refrigerant passage 68. The second level 106 is formed between the first heat exchange surface 46 and the second heat exchange surface 48. More specifically, the second layer 106 is a circumferential flow passage formed between the outer peripheral surface of the first heat transfer block 28 and the inner peripheral surface of the second heat transfer block side cylindrical portion 30 b. The first level 104 of the refrigerant passage 68 is formed between the first heat transfer block 28 and the second heat transfer block bottom 30 a. As an example, the first hierarchical level 104 is a serpentine flow path formed by opposing fins as in the second embodiment described above. The first hierarchical layer 104 may be a serpentine channel as in the first embodiment or the third embodiment. The refrigerant discharge port 66 is disposed at the second heat transfer block bottom 30 a so as to discharge the refrigerant from the first floor 104.

The refrigerant passage 68 also has a communication passage 108 that connects the first level 104 and the second level 106. The communication passage 108 is formed between the outer peripheral surface of the first heat transfer block 28 and the inner peripheral surface of the second heat transfer block side cylindrical portion 30 b and extends in the axial direction from the first level 104 to the second level 106. ing. As shown in FIG. 9, the communication passage 108 is provided on the opposite side of the central axis 92 to the refrigerant supply port 64. For the sake of understanding, the refrigerant supply port 64 is shown in broken lines in FIG. As an example, the cross-sectional shape of the communication passage 108 is an elongated rectangle curved along the circumference, but is not limited thereto. The cross-sectional shape of the communication passage 108 may be circular, oval, or any other shape.

In this manner, the refrigerant passage 68 flows from the refrigerant supply port 64 to the refrigerant discharge port 66 along the first heat exchange surface 46 and the second heat exchange surface 48 so that the first heat transfer block 28 and the second heat transfer It is formed between the block 30. The refrigerant flows from the refrigerant supply port 64 into the second hierarchical layer 106, branches to the second hierarchical layer 106 for two hands, flows half a circumference around each other, joins, and flows into the communication passage 108. The refrigerant flows from the communication passage 108 into the first layer 104, passes through the outlet passage 88, and exits from the refrigerant outlet 66.

According to the fourth embodiment, the refrigerant passage 68 is divided into a plurality of layers in the axial direction. The plurality of layers are connected to one another so that the refrigerant flows in order. Thus, while the refrigerant passage 68 is accommodated in the bottom of the cooling stage 26 in the first to third embodiments, in the fourth embodiment, the refrigerant passage 68 can be expanded axially upward it can. Therefore, in the fourth embodiment, the flow passage length of the refrigerant passage 68 can be increased, and heat exchange between the refrigerant and the heat exchange surface can be promoted. Thus, the heat exchange efficiency of the cryogenic refrigerator 10 is improved.

In the above-described example, the refrigerant passage 68 has two layers, but is not limited thereto. The refrigerant passages 68 may be divided into three or more levels.

FIGS. 10A and 10B are schematic views showing another example of the communication passage 108 in the cryogenic refrigerator 10 according to the fourth embodiment. 10 (a) and 10 (b) show cross sections perpendicular to the central axis 92. FIG. Although in the embodiment described with reference to FIGS. 8 and 9 the communication passage 108 is provided at one place, it is not limited thereto.

As shown in FIG. 10 (a), a plurality of communication passages 108 may be provided. The plurality of communication paths 108 are formed between the first heat transfer block 28 and the second heat transfer block 30. The communication passage 108 may be a groove formed on the outer peripheral surface of the first heat transfer block 28 or may be a groove formed on the inner peripheral surface of the second heat transfer block 30. The communication passage 108 may be a through hole formed in either the first heat transfer block 28 or the second heat transfer block 30.

The plurality of communication paths 108 are arranged at equal angular intervals along a circumference centered on the central axis 92 except for the vicinity of the refrigerant supply port 64. As an example, seven communication passages 108 are disposed at 45 degree intervals, and one communication passage 108 is provided on the opposite side of the central shaft 92 to the coolant supply port 64. The flow passage cross-sectional areas (cross-sectional areas perpendicular to the axial direction) of the plurality of communication passages 108 are equal. The cross-sectional shape of the communication passage 108 is, for example, an elliptical shape, but is not limited thereto.

Further, as shown in FIG. 10 (b), the flow passage cross-sectional areas of the plurality of communication passages 108 may be different from one another. The flow passage cross-sectional area of the communication passage 108 may be smaller as it is closer to the refrigerant supply port 64 and larger as it is farther from the refrigerant supply port 64. Therefore, the communication passage 108 a provided on the opposite side of the central shaft 92 to the refrigerant supply port 64 has the largest flow passage cross-sectional area. In the case shown in FIG. 10A, the flow rate of the refrigerant passing through the communication passage 108 (for example, on the opposite side) far from the refrigerant supply port 64 is smaller than the flow rate of the refrigerant passing through the communication passage 108 near the refrigerant supply port 64. As a result, heat exchange in the communication passage 108 far from the refrigerant supply port 64 may be insufficient. According to the configuration shown in FIG. 10B, compared to the case shown in FIG. 10A, the flow rate of the refrigerant passing through the plurality of communication paths 108 can be made uniform, and the reams far from the refrigerant supply port 64 The heat exchange area in the passage 108 can be effectively utilized.

FIG. 11 is a view schematically showing another example of the cryogenic refrigerator 10 according to the fourth embodiment. In the embodiment described with reference to FIGS. 8 and 9, although the flow path cross-sectional areas of the refrigerant supply port 64 and the refrigerant discharge port 66 are equal, the present invention is not limited thereto.

The flow passage cross-sectional area A1 of the refrigerant inflow hole 64a of the refrigerant supply port 64 may be larger than the flow passage cross-sectional area A2 of the refrigerant outflow hole 66a of the refrigerant discharge port 66. When both the refrigerant inflow holes 64a and the refrigerant outflow holes 66a are circular, the diameter of the refrigerant inflow holes 64a may be larger than the diameter of the refrigerant outflow holes 66a. The refrigerant flowing from the refrigerant supply port 64 into the refrigerant passage 68 largely changes in flow direction when it enters the second layer 106 from the refrigerant inflow hole 64 a. That is, the refrigerant flowing in in the radial direction from the refrigerant inflow holes 64 a is bent in the circumferential direction in the second layer 106. Such a sudden change in the flow direction leads to an increase in flow path resistance. On the other hand, since the refrigerant flowing out from the refrigerant passage 68 to the refrigerant discharge port 66 linearly flows in the axial direction, the flow path resistance is relatively small.

Therefore, by making the flow passage cross sectional area A1 of the refrigerant supply port 64 larger than the flow passage cross sectional area A2 of the refrigerant discharge port 66, the flow passage resistance at the refrigerant supply port 64 is equal to the flow passage resistance at the refrigerant discharge port 66. Or can be smaller. Excessive flow path resistance at the refrigerant supply port 64 can be avoided. This helps to improve the heat exchange efficiency between the cooling stage 26 and the refrigerant.

Even when the refrigerant passage 68 does not have a plurality of layers as in the first to third embodiments, the cross-sectional area A1 of the refrigerant supply port 64 is the same as the flow path of the refrigerant outlet 66 in the same manner. It may be larger than the cross-sectional area A2.

FIG. 12 is a view schematically showing another example of the cryogenic refrigerator 10 according to the fourth embodiment. As shown in FIG. 12, the second level 106 of the refrigerant passage 68 may have a proximity area 110a and a remote area 110b. The proximity area 110a is an area closer to the communication passage 108 than the remote area 110b. The proximity area 110a and the remote area 110b form one flow path communicating with each other. The proximity area 110a is located axially below the second layer 106, and the remote area 110b is located axially upward.

The flow passage cross-sectional area (the cross-sectional area perpendicular to the circumferential direction) of the proximity region 110a is larger than the flow passage cross-sectional area of the remote region 110b. For example, the radial width of the proximity region 110a may be larger than the radial width of the remote region 110b. In this way, the flow passage cross-sectional area of the region where the flow of the refrigerant is easily concentrated is relatively large. In the case shown in FIG. 8, the flow rate of the refrigerant passing through the axially upper area far from the communication passage 108 in the second layer 106 is higher than the flow rate of the refrigerant flowing in the lower axial region near the communication path 108 in the second layer 106. As a result, heat exchange in the axially upper region far from the communication passage 108 may be insufficient. According to the configuration shown in FIG. 12, the flow passage cross-sectional area of the proximity region 110a where the flow of the refrigerant tends to be concentrated is relatively large. The heat exchange efficiency between the cooling stage 26 and the refrigerant in the vicinity of the communication passage 108 in the second layer 106 can be improved.

The proximity area 110 a and the remote area 110 b may be provided only in the vicinity of the communication passage 108 in the second layer 106. Alternatively, the proximity area 110 a and the remote area 110 b may be provided on the entire second layer 106 (that is, around the entire circumference of the cooling stage 26).

Similarly, at least one level (e.g., the first level 104) of the refrigerant passages 68 may have the proximity area 110a and the remote area 110b. The heat exchange efficiency between the cooling stage 26 and the refrigerant in the vicinity of the communication passage 108 in at least one hierarchy (for example, the first hierarchy 104) of the refrigerant passage 68 can be improved.

The present invention has been described above based on the embodiments. It is understood by those skilled in the art that the present invention is not limited to the above embodiment, and various design changes are possible, and various modifications are possible, and such modifications are also within the scope of the present invention. It is a place.

The shapes of the first fins 76 and the second fins 80 are not limited to the ring shape. The fin shape may be a cylindrical or rectangular plate shape, or a rod shape.

It is not essential that the refrigerant passage 68 be serpentine. The first heat exchange surface 46 may not have the first fins 76. The second heat exchange surface 48 may not have the second fin 80. At least one of the first heat exchange surface 46 and the second heat exchange surface 48 may be a flat surface. Even in this case, heat exchange between the refrigerant and the heat exchange surface is possible.

The various embodiments described in connection with the first embodiment are also applicable to the second to fourth embodiments. For example, the heat transfer block configuration shown in FIG. 3 may be applied to the second to fourth embodiments. The configuration of the refrigerant passage 68 shown in FIG. 4 may be applied to the second to fourth embodiments. The hierarchical channel structure of the fourth embodiment may be applied to the first to third embodiments. The new embodiments resulting from the combination combine the effects of each of the combined embodiments.

The above-described embodiment has been described using the single-stage cryogenic refrigerator 10 as an example, but is applicable to the multistage cryogenic refrigerator 10 as well. Moreover, although the above-mentioned embodiment was described taking GM refrigerator as an example, it is applicable also to other cryogenic refrigerators, such as a Stirling refrigerator and a pulse tube refrigerator.

10 cryogenic refrigerator, 20 displacer, 26 cooling stage, 28 first heat transfer block, 30 second heat transfer block, 34 expansion chamber, 46 first heat exchange surface, 48 second heat exchange surface, 64 refrigerant supply port, 66 refrigerant outlet, 68 refrigerant passage, 74 first base surface, 76 first fin, 76a first fin tip, 78 second base surface, 80 second fin, 80a second fin tip, 82 first transverse passage, 84 Second transverse passage, 86 inter-fin passage, 90 concentric ring-shaped structure, 92 central axis, 96 ring-shaped convex portion, 98 ring-shaped concave portion, 104 first layer, 106 second layer.

The invention can be used in the field of cryogenic refrigerators.

Claims

An expansion chamber,
A cooling stage thermally coupled to the expansion chamber, the first heat transfer block including a surface exposed to the expansion chamber and a first heat exchange surface disposed outside the expansion chamber; A second heat transfer block comprising a second heat exchange surface facing the first heat exchange surface;
A refrigerant supply port installed outside the expansion chamber and on the cooling stage;
A refrigerant outlet provided outside the expansion chamber and installed on the cooling stage;
A refrigerant passage fluidly isolated from the expansion chamber, the first flow path of the refrigerant along the first heat exchange surface and the second heat exchange surface from the refrigerant supply port to the refrigerant discharge port; A cryogenic refrigerator, comprising: a refrigerant passage formed between a heat transfer block and the second heat transfer block.
The first heat exchange surface includes a first base surface and at least one first fin extending from the first base surface, and the first fin includes a first fin tip.
The second heat exchange surface includes a second base surface and at least one second fin extending from the second base surface along the first fin, and the second fin is a second fin. Equipped with a tip,
The first fin tip is disposed closer to the second base surface than the second fin tip, and the second fin tip is disposed closer to the first base surface than the first fin tip. And
The refrigerant passage is
A first transverse passage formed between the tip of the first fin and the second base surface such that the coolant traverses the first fin;
A second transverse passage formed between the tip of the second fin and the first base surface such that the coolant traverses the second fin;
The pole according to claim 1, further comprising an inter-fin passage formed between the first fin and the second fin so as to connect the first cross passage to the second cross passage. Low temperature refrigerator.
The first transverse passage is locally formed between the first fin tip and the second base surface, and the second transverse passage is between the second fin tip and the first base surface. Locally formed,
The arrangement of the first cross passage and the second cross passage may be determined such that the refrigerant flow in the inter-fin passage is guided in a direction making an angle with the fin height direction. Cryogenic refrigerator as described in.
It further comprises an axially reciprocable displacer that forms the expansion chamber with the cooling stage,
The exposed surface of the first heat transfer block to the expansion chamber includes a bottom surface of the expansion chamber including a ring-shaped convex portion coaxially disposed with the displacer, and the ring-shaped convex portion is a bottom surface of the expansion chamber And is hollow to receive the second fin from the opposite side,
The cryogenic refrigerator according to claim 2 or 3, wherein the displacer comprises a ring-shaped recess formed to receive the ring-shaped protrusion.
The first fin has a ring shape centered on the central axis of the cryogenic refrigerator,
The second fin has a ring shape having a diameter different from that of the first fin,
The second heat transfer block is formed such that the second fins form a concentric ring-like structure coaxially arranged with the central axis of the cryogenic refrigerator, in combination with the first fins. The cryogenic refrigerator according to any one of claims 2 to 4, which is fixed to
The refrigerant supply port is disposed on the cooling stage so as to supply the refrigerant to the outer peripheral portion of the concentric ring structure, and the refrigerant passage is arranged in the concentric ring shape from the outer peripheral portion of the concentric ring structure. 6. A system according to claim 5, characterized in that it is arranged to lead to a central part of the structure, said refrigerant outlet being arranged at said cooling stage to discharge said refrigerant from said central part of said concentric ring structure. Cryogenic refrigerator.
The distance between the first heat exchange surface and the second heat exchange surface in the outer peripheral portion of the concentric ring structure is the distance between the first heat exchange surface and the second heat exchange surface in the central portion of the concentric ring structure 7. A cryogenic refrigerator according to claim 5 or 6, characterized in that it is narrower.
The cryogenic refrigerator according to any one of claims 1 to 7, wherein the refrigerant passage is divided into a plurality of layers.
9. The cryogenic refrigerator according to claim 8, wherein the plurality of layers of the refrigerant passages are disposed at different locations in the axial direction, respectively, and are connected to each other so that the refrigerant flows in order.
The plurality of layers of the refrigerant passage have a first layer and a second layer axially adjacent to each other, and the refrigerant passage includes a plurality of communication paths connecting the first layer and the second layer. The cryogenic refrigerator according to claim 8 or 9, characterized in that it comprises:
11. The cryogenic refrigerator according to claim 10, wherein flow passage cross-sectional areas of the plurality of communication passages are different from one another.
The cryogenic refrigerator according to any one of claims 1 to 11, wherein the refrigerant supply port has a flow passage cross-sectional area larger than that of the refrigerant discharge port.