WO2019098128A1

WO2019098128A1 - Cryogenic refrigerator

Info

Publication number: WO2019098128A1
Application number: PCT/JP2018/041617
Authority: WO
Inventors: 名堯許; 乾包; 孝明森江
Original assignee: 住友重機械工業株式会社
Priority date: 2017-11-20
Filing date: 2018-11-09
Publication date: 2019-05-23
Also published as: JP2019095090A

Abstract

A cryogenic refrigerator 10 is provided with: a displacer 20 capable of reciprocating in an axial direction; a drive piston 22 capable of reciprocating in the axial direction; a drive shaft 24, one end of which is rigidly coupled to the displacer 20 and the other end of which is rigidly coupled to the drive piston 22; a displacer cylinder 26 housing the displacer 20 such that the displacer 20 can reciprocate in the axial direction; and a housing 27 provided with a removable housing cover 27a. The drive piston 22 is configured to place the housing 27 onto the displacer cylinder 26 independently or together with at least a part of the drive shaft 24 and to be attachable to and detachable from the displacer 20 with the housing cover 27a removed.

Description

Cryogenic refrigerator

The present invention relates to a cryogenic refrigerator.

Conventionally, GM (Gifford-McMahon) refrigerator is known as a representative example of a cryogenic refrigerator. GM refrigerators are roughly divided into two types, motor-driven and gas-driven, according to their drive sources. In the motor drive type, the displacer is mechanically connected to the motor and driven by the motor. In the gas drive type, the displacer is driven by gas pressure.

In a typical motor-driven GM refrigerator, the rotational motion output from the motor is converted into linear reciprocating motion by a drive mechanism such as a scotch yoke mechanism, whereby the displacer axially reciprocates in the cylinder. The lower end of the shaft extending from the scotch yoke mechanism to the displacer is fixed to the upper end of the displacer using an engagement pin. Typically, the displacer is located in the cylinder and the scotch yoke mechanism is located in the housing with the motor. The housing is fixed to the cylinder, so to speak, as a lid of the cylinder. The engagement pin is accommodated together with the displacer in the cylinder interior space closed by the housing in this way.

Patent No. 5575880 gazette

Generally, it is desirable to perform periodic maintenance on cryogenic refrigerators. The cryogenic refrigerator is disassembled to perform maintenance, and internal components are taken out.

For example, when disassembling the above-described typical GM refrigerator, an operator removes the engagement pin from the assembly of the displacer and the scotch yoke mechanism to release the pin engagement, and removes the scotch yoke mechanism from the displacer. The operator then removes the housing from the cylinder and removes the displacer from the cylinder. However, since the engagement pin is located in a closed space in the cylinder and out of reach of the operator, it is difficult to remove the engagement pin from the assembly of the displacer and the scotch yoke mechanism.

If it was possible to remove the housing from the cylinder in advance before starting the removal operation of the engagement pin, the closed cylinder internal space would be opened and the hand of the operator could be reached. Removal work of will be easier. However, in practice, the housing can not be completely removed from the cylinder without first removing the engagement pins and removing the scotch yoke mechanism from the displacer. Because the diameter of the shaft connecting the scotch yoke mechanism to the displacer is smaller than the diameter of the scotch yoke mechanism, the scotch yoke mechanism can not pass through the through hole of the housing for passing the shaft.

In an exemplary disassembly procedure, the housing is lifted from the cylinder to create a gap to the extent that the worker's hand or a working tool for removing the engagement pin can be inserted between the cylinder and the housing, and the worker The mating pin can be removed. However, removing the engagement pin while lifting the housing in that way is by no means an easy task. In particular, in the case of a large GM refrigerator, the total weight of a structure such as a housing to be lifted to create a gap can be quite large, for example, several tens of kg. It is difficult to lift by hand, and it takes time and effort to work, such as the need for lifting equipment such as a crane. Such problems can also occur in the disassembling operation of a gas-driven GM refrigerator.

In addition, the same decrease in workability may occur also in the assembly operation of the cryogenic refrigerator during the manufacture or maintenance of the cryogenic refrigerator.

One of the exemplary objects of an aspect of the present invention is to provide a cryogenic refrigerator having an internal structure that helps to facilitate the disassembly and assembly operations of the cryogenic refrigerator.

According to one aspect of the present invention, a cryogenic refrigerator is an axially reciprocable displacer, an axially reciprocable drive flange, and an axially extending drive shaft, said drive flange And a drive shaft having one end rigidly coupled to the displacer and the other end rigidly coupled to the drive flange so as to axially reciprocate the displacer axially reciprocate the displacer axially. A cylinder which can be accommodated, a removable housing lid, and a driving flange chamber which axially reciprocates the driving flange and which is open to the outside when the housing lid is removed, A housing removably secured to the cylinder, the drive flange being alone or as little as the drive shaft With a part, in a state where the housing is removed the placement vital the housing lid to the cylinder, and it is detachably attached to the displacer.

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.

According to the present invention, it is possible to provide a cryogenic refrigerator having an internal structure that helps make the disassembling and assembling operations of the cryogenic refrigerator easier.

It is a figure showing roughly the cryogenic refrigerator concerning a 1st embodiment. It is a flowchart which illustrates the decomposition | disassembly method of the cryogenic refrigerator which concerns on 1st Embodiment. FIG. 3 is a schematic view of the cryogenic refrigerator in one step of the decomposition method shown in FIG. 2; FIG. 3 is a schematic view of the cryogenic refrigerator in one step of the decomposition method shown in FIG. 2; FIG. 3 is a schematic view of the cryogenic refrigerator in one step of the decomposition method shown in FIG. 2; FIG. 3 is a schematic view of the cryogenic refrigerator in one step of the decomposition method shown in FIG. 2; It is the schematic which shows the cryogenic refrigerator concerning a comparative example. It is a figure showing roughly the cryogenic refrigerator concerning a 2nd embodiment. It is the schematic which shows 1 process of the decomposition | disassembly method of the cryogenic refrigerator which concerns on 2nd Embodiment. Fig.10 (a) to FIG.10 (c) is a figure which shows roughly the other example of the cryogenic refrigerator which concerns on 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.

FIG. 1 is a view schematically showing a cryogenic refrigerator 10 according to a first embodiment.

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.

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.

The illustrated cold head 14 is single stage. However, the cold head 14 may be of a multistage type.

The cold head 14 is gas driven. Therefore, the cold head 14 includes an axially movable body 16 as a free piston driven by gas pressure, and a cold head pressure vessel 18 which is airtightly configured and accommodates the axially movable body 16. The cold head pressure vessel 18 axially reciprocably supports the axially movable body 16. Unlike a motor driven GM refrigerator, the cold head 14 does not have a motor for driving the axially movable body 16 and a coupling mechanism (for example, a scotch yoke mechanism).

The axially movable body 16 includes a displacer 20 capable of reciprocating in the axial direction (vertical direction in FIG. 1 and indicated by an arrow C), and a drive flange that is capable of reciprocating in the axial direction. The drive flange forms a drive piston 22 which drives the axial reciprocation of the displacer 20 by means of the acting gas pressure. The drive piston 22 is coupled to the displacer 20 to axially drive the displacer 20. The drive piston 22 is disposed coaxially with and axially separated from the displacer 20.

The axially movable body 16 also includes an axially extending drive shaft 24. The drive shaft 24 rigidly couples the displacer 20 to the drive piston 22 such that the displacer 20 axially reciprocates integrally with the drive piston 22. Drive shaft 24 also extends from displacer 20 to drive piston 22 coaxially with displacer 20 and drive piston 22. One axial end (lower end) of the drive shaft 24 is rigidly connected to the displacer 20, and the other axial end (upper end) of the drive shaft 24 is rigidly connected to the drive piston 22. Therefore, the displacer 20 reciprocates in the axial direction by the axial reciprocation of the drive piston 22.

The cold head pressure vessel 18 includes a displacer cylinder (also simply referred to as a cylinder) 26 that accommodates the displacer 20 in an axial reciprocating manner, and a housing 27 that accommodates the drive piston 22 in an axial reciprocating manner. And. The housing 27 is removably fixed to the displacer cylinder 26. The housing 27 includes a housing lid 27a and a piston cylinder 28 which is an example of a drive flange chamber. The housing lid 27 a is removable from the piston cylinder 28. The piston cylinder 28 axially reciprocates the drive piston 22 and is opened to the outside when the housing cover 27a is removed. The piston cylinder 28 is disposed coaxially with and axially adjacent to the displacer cylinder 26.

The drive piston 22 has smaller dimensions compared to the displacer 20. The axial length of the drive piston 22 is shorter than the axial length of the displacer 20, and the diameter of the drive piston 22 is smaller than the diameter of the displacer 20. The diameter of the drive shaft 24 is smaller than the diameter of the drive piston 22.

The volume of the piston cylinder 28 is smaller than the volume of the displacer cylinder 26. The axial length (inner dimension) of the piston cylinder 28 is shorter than the axial length of the displacer cylinder 26, and the inner diameter of the piston cylinder 28 is smaller than the inner diameter of the displacer cylinder 26.

The dimensional relationship between the drive piston 22 and the displacer 20 is not limited to that described above, and may be different therefrom. Similarly, the dimensional relationship between the piston cylinder 28 and the displacer cylinder 26 is not limited to that described above, and may be different therefrom.

The axial reciprocation of the displacer 20 is guided by the displacer cylinder 26. Typically, the displacer 20 and the displacer cylinder 26 are each an axially extending cylindrical member, the inner diameter of the displacer cylinder 26 corresponding to or slightly larger than the outer diameter of the displacer 20. Similarly, axial reciprocation of the drive piston 22 is guided by the piston cylinder 28. Typically, the drive piston 22 is an axially extending cylindrical member. The piston cylinder 28 is an axially extending cylindrical member, and the inner diameter of the piston cylinder 28 corresponds to the outer diameter of the drive piston 22 or is slightly larger.

Since the displacer 20 and the drive piston 22 are axially and rigidly connected by the drive shaft 24, the axial stroke of the drive piston 22 is equal to the axial stroke of the displacer 20, and both move integrally over the entire stroke. The position of the drive piston 22 relative to the displacer 20 remains unchanged during axial reciprocation of the axially movable body 16.

The housing 27 also comprises a shaft guide 30 connecting the displacer cylinder 26 to the piston cylinder 28. The shaft guide 30 extends from the displacer cylinder 26 to the piston cylinder 28 coaxially with the displacer cylinder 26 and the piston cylinder 28. A drive shaft 24 passes through the shaft guide 30. The shaft guide 30 is configured as a bearing for guiding the axial reciprocation of the drive shaft 24. Since the through hole of the shaft guide 30 is formed in accordance with the drive shaft 24, the diameter of the through hole is smaller than the diameter of the displacer 20 and smaller than the diameter of the drive piston 22.

The displacer cylinder 26 is airtightly connected to the piston cylinder 28 via the shaft guide 30. The shaft guide 30 is also a partition that separates the inner cavity of the displacer cylinder 26 (ie, the reciprocating space of the displacer 20) and the inner cavity of the piston cylinder 28 (ie, the reciprocating space of the drive piston 22). In addition, the housing lid 27a is airtightly attached to the piston cylinder 28. Thus, the cold head pressure vessel 18 is configured as a pressure vessel for working gas.

The shaft guide 30 is not essential to form a part of the housing 27 and may be a separate member from the housing 27. In that case, the cold head pressure vessel 18 may be composed of four members of a housing lid 27 a, a housing body, a shaft guide 30 and a displacer cylinder 26. The housing lid 27a, the housing body and the shaft guide 30 respectively define an upper wall, a side wall and a lower wall of the reciprocating space of the drive piston 22. Alternatively, the housing 27 may be composed of two parts, the shaft guide 30 and the remaining part including the housing lid 27a. The shaft guide 30 may also be part of the displacer cylinder 26.

A first seal 32 is provided between the drive shaft 24 and the shaft guide 30. The first seal portion 32 is mounted on either the drive shaft 24 or the shaft guide 30 and slides on the other of the drive shaft 24 or the shaft guide 30. The first seal portion 32 is formed of, for example, a seal member such as a slipper seal or an O-ring. Further, instead of the seal member, the gap between the drive shaft 24 and the shaft guide 30 may be made extremely small to function as a clearance seal. The piston cylinder 28 is airtightly configured with respect to the displacer cylinder 26 by the first seal portion 32. Thus, the piston cylinder 28 is fluidly isolated from the displacer cylinder 26 and no direct gas flow between the piston cylinder 28 and the displacer cylinder 26 occurs.

The displacer cylinder 26 is partitioned by the displacer 20 into an expansion chamber 34 and a room temperature chamber 36. The displacer 20 forms an expansion chamber 34 with the displacer cylinder 26 at one axial end, and forms a room temperature chamber 36 with the displacer cylinder 26 at the other axial end. The expansion chamber 34 is disposed on the bottom dead center LP1 side, and the room temperature chamber 36 is disposed on the top dead center UP1 side. Further, the cold head 14 is provided with a cooling stage 38 fixed to the displacer cylinder 26 so as to enclose the expansion chamber 34.

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 second seal portion 44 is provided between the displacer 20 and the displacer cylinder 26. The second 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 displacer cylinder 26 is sealed by the second 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 second seal portion 44.

The piston cylinder 28 is divided into two sections by the drive piston 22. The piston cylinder 28 includes a drive chamber 46 as a first section and a gas spring chamber 48 as a second section. The drive piston 22 forms a drive chamber 46 with the piston cylinder 28 at one axial end, and forms a gas spring chamber 48 with the piston cylinder 28 at the other axial end. When the drive piston 22 moves axially, the drive chamber 46 and the gas spring chamber 48 complementarily increase and decrease the volume. The pressure in the drive chamber 46 is controllable to drive the drive piston 22. The pressure of the gas spring chamber 48 fluctuates as the drive piston 22 moves.

The drive chamber 46 is disposed axially opposite to the displacer cylinder 26 with respect to the drive piston 22. The gas spring chamber 48 is disposed on the same side of the drive piston 22 in the axial direction as the displacer cylinder 26. In other words, the drive chamber 46 is disposed on the top dead center UP2 side, and the gas spring chamber 48 is disposed on the bottom dead center LP2 side. The upper surface of the drive piston 22 receives the gas pressure of the drive chamber 46, and the lower surface of the drive piston 22 receives the gas pressure of the gas spring chamber 48.

The drive shaft 24 extends from the lower surface of the drive piston 22 through the gas spring chamber 48 to the shaft guide 30. Further, the drive shaft 24 extends through the room temperature chamber 36 to the upper lid of the displacer 20. The gas spring chamber 48 is disposed on the same side as the drive shaft 24 with respect to the drive piston 22, and the drive chamber 46 is disposed on the opposite side of the drive shaft 24 with respect to the drive piston 22.

A third seal 50 is provided between the drive piston 22 and the piston cylinder 28. The third seal portion 50 is, for example, a clearance seal, and a slight radial clearance is formed between the drive piston 22 and the piston cylinder 28. The radial clearance substantially prevents the gas flow in the drive chamber 46 and the gas spring chamber 48 or acts as a flow path resistance to the gas flow in the drive chamber 46 and the gas spring chamber 48.

When the drive piston 22 moves downward, the gas spring chamber 48 narrows. At this time, the gas in the gas spring chamber 48 is compressed to increase the pressure. The pressure of the gas spring chamber 48 acts upward on the lower surface of the drive piston 22. Thus, the gas spring chamber 48 generates a gas spring force that resists the downward movement of the drive piston 22. Conversely, the gas spring chamber 48 expands when the drive piston 22 moves up. The pressure of the gas spring chamber 48 decreases, and the gas spring force acting on the drive piston 22 also decreases.

Similarly to the first seal portion 32, the third seal portion 50 may be formed of a seal member such as a slipper seal or an O-ring. In this case, the gas spring chamber 48 is sealed by the first seal portion 32 and the third seal portion 50.

Thus, the drive portion of the gas driven cold head 14 includes the drive piston 22 and the piston cylinder 28. The cold head 14 also includes a gas spring mechanism that acts on the drive piston 22 to relieve or prevent a collision or contact between the displacer 20 and the displacer cylinder 26.

The cold head 14 is installed at the site where it is used in the orientation shown. That is, the cold head 14 is installed vertically so that the displacer cylinder 26 is disposed vertically downward and the piston cylinder 28 vertically disposed. Thus, the cryogenic refrigerator 10 has the highest refrigeration capacity when installed with the cooling stage 38 oriented vertically downward. However, the arrangement of the cryogenic refrigerator 10 is not limited to this. On the contrary, the cold head 14 may be installed in a posture in which the cooling stage 38 is directed vertically upward. Alternatively, the coldhead 14 may be installed in a sideways or other orientation.

When the cold head 14 is installed with the cooling stage 38 oriented vertically downward, gravity acts downward as shown by the arrow D. Therefore, the weight of the axially movable body 16 acts to assist the downward driving force of the drive piston 22. A larger driving force acts on the drive piston 22 at the time of downward movement than at the time of upward movement. Thus, in a typical gas-powered GM refrigerator, collision or contact between the displacer and the displacer cylinder is likely to occur at the bottom dead center of the displacer.

However, the cold head 14 is provided with a gas spring chamber 48. The gas stored in the gas spring chamber 48 is compressed when the drive piston 22 moves downward, and the pressure increases. Since this pressure acts in the opposite direction to gravity, the driving force acting on the drive piston 22 is reduced. The speed immediately before the drive piston 22 reaches the bottom dead center LP2 can be reduced.

In this way, contact or collision between the drive piston 22 and the piston cylinder 28 and / or the displacer 20 and the displacer cylinder 26 can be avoided. Alternatively, even if a collision occurs, the collision sound is suppressed because the collision energy is reduced by the decrease in speed of the drive piston 22.

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 is configured to create a pressure differential between the piston cylinder 28 (ie, the drive chamber 46) and the displacer cylinder 26 (ie, the expansion chamber 34 and / or the room temperature chamber 36). The pressure difference causes the axially movable body 16 to move in the axial direction. If the pressure of the displacer cylinder 26 with respect to the piston cylinder 28 is low, the drive piston 22 moves downward, and the displacer 20 also moves downward accordingly. Conversely, if the pressure of the displacer cylinder 26 with respect to the piston cylinder 28 is high, the drive piston 22 moves upward, and the displacer 20 also moves upward accordingly.

The working gas circuit 52 comprises a valve unit 54 configured to control the pressure differential between the expansion chamber 34 and the drive chamber 46. The valve unit 54 is attached to the housing lid 27a. Thus, the housing lid 27 a contacts the bottom plate of the valve unit 54. The valve unit 54 is connected to the compressor 12 by piping.

It is not essential that the housing lid 27a includes the valve unit 54, and the valve unit 54 is provided separately from the cold head 14 and is disposed outside the cold head pressure vessel 18, and the cold head 14 and piping are provided. It may be connected. In that case, the housing lid 27a may be a removable flat plate for closing the piston cylinder 28.

The valve unit 54 includes a main pressure switching valve 60 and a sub pressure switching valve 62. The main pressure switching valve 60 has a main intake on-off valve V1 and a main exhaust on-off valve V2. The auxiliary pressure switching valve 62 has an auxiliary intake on-off valve V3 and an auxiliary exhaust on-off valve V4.

The main pressure switching valve 60 is disposed in the main intake and exhaust flow path 64 connecting the compressor 12 to the room temperature chamber 36 of the cold head 14. The main intake and exhaust flow passage 64 is branched into a main intake passage 64 a and a main exhaust passage 64 b by the main pressure switching valve 60. The main intake on-off valve V1 is disposed in the main intake passage 64a, and connects the compressor discharge port 12a to the room temperature chamber 36. The main exhaust on-off valve V2 is disposed in the main exhaust passage 64b, and connects the compressor suction port 12b to the room temperature chamber 36.

The main pressure switching valve 60 is configured to selectively communicate the compressor discharge port 12 a or the compressor suction port 12 b with the room temperature chamber 36 of the displacer cylinder 26. In main pressure switching valve 60, main intake on-off valve V1 and main exhaust on-off valve V2 are opened exclusively. That is, simultaneous opening of the main intake on-off valve V1 and the main exhaust on-off valve V2 is prohibited. When the main intake on-off valve V1 is open, the main exhaust on-off valve V2 is closed. Working gas is supplied from the compressor discharge port 12 a to the displacer cylinder 26 through the main intake and exhaust flow path 64. On the other hand, when the main exhaust on-off valve V2 is open, the main intake on-off valve V1 is closed. Working gas is recovered from the displacer cylinder 26 through the main intake and exhaust flow path 64 to the compressor suction port 12 b. The main intake on-off valve V1 and the main exhaust on-off valve V2 may be temporarily closed together. Thus, the displacer cylinder 26 is alternately connected to the compressor discharge port 12a and the compressor suction port 12b.

The sub pressure switching valve 62 is disposed in the sub air suction and discharge flow path 66 connecting the compressor 12 to the drive chamber 46 of the piston cylinder 28. The auxiliary intake and exhaust flow passage 66 is branched into an auxiliary intake passage 66 a and an auxiliary exhaust passage 66 b by an auxiliary pressure switching valve 62. The auxiliary intake on-off valve V3 is disposed in the auxiliary intake passage 66a, and connects the compressor discharge port 12a to the drive chamber 46. The sub exhaust on-off valve V4 is disposed in the sub exhaust path 66b, and connects the compressor suction port 12b to the drive chamber 46.

The auxiliary pressure switching valve 62 is configured to selectively communicate the compressor discharge port 12 a or the compressor suction port 12 b with the drive chamber 46 of the piston cylinder 28. The auxiliary pressure switching valve 62 is configured such that the auxiliary intake on-off valve V3 and the auxiliary exhaust on-off valve V4 are opened exclusively. That is, the simultaneous opening of the auxiliary intake on-off valve V3 and the auxiliary exhaust on-off valve V4 is prohibited. When the auxiliary intake on-off valve V3 is open, the auxiliary exhaust on-off valve V4 is closed. The working gas is supplied from the compressor discharge port 12 a to the drive chamber 46 through the sub intake / exhaust flow path 66. On the other hand, when the secondary exhaust on-off valve V4 is open, the secondary intake on-off valve V3 is closed. The working gas is recovered from the drive chamber 46 through the sub intake / exhaust flow path 66 to the compressor suction port 12 b. In addition, the sub air intake on-off valve V3 and the sub exhaust on-off valve V4 may be temporarily closed together. Thus, the drive chamber 46 is alternately connected to the compressor discharge port 12a and the compressor suction port 12b.

The valve unit 54 may take the form of a rotary valve. That is, the valve unit 54 may be configured such that the valves V1 to V4 are properly switched by rotational sliding of the valve disc with respect to the valve body. In that case, the valve unit 54 may include a rotational drive source 56 for rotationally driving the valve unit 54 (for example, a valve disc). The rotational drive source 56 may be attached to the housing lid 27a. The rotational drive source 56 is, for example, a motor. However, the rotational drive source 56 is not connected to the axially movable body 16. The valve unit 54 may also include a control unit 58 that controls the valve unit 54. The controller 58 may control the rotational drive source 56.

In one embodiment, the valve unit 54 may include a plurality of individually controllable valves V1 to V4, and the control unit 58 may control the opening and closing of each of the valves V1 to V4. In this case, the valve unit 54 may not include the rotational drive source 56.

The valve unit 54 can adopt various known configurations.

In this embodiment, the drive piston 22 alone is configured to be removable from the displacer 20 with the housing 27 mounted on the displacer cylinder 26 and the housing cover 27a removed. That is, with the housing 27 mounted on the displacer cylinder 26 and the housing lid 27 a removed from the housing 27, the operator can attach the drive piston 22 to the drive shaft 24 and remove it from the drive shaft 24. . The operator can attach and detach the drive piston 22 to the displacer 20 by attaching and detaching the drive piston 22 to and from the drive shaft 24.

The drive shaft 24 has a shaft tip 24a. The shaft tip 24 a is an end of the drive shaft 24 axially opposite to the displacer 20, and axially protrudes from the main body of the drive shaft 24. The shaft tip 24 a is disposed in the piston cylinder 28 (specifically, the drive chamber 46) and axially extends coaxially with the drive shaft 24. The shaft tip 24 a has a smaller diameter than the main body of the drive shaft 24, and the shaft tip 24 a and the shaft main body can also be referred to as a small diameter portion and a large diameter portion of the drive shaft 24, respectively. In the illustrated example, a step is formed between the shaft tip 24a and the main body of the drive shaft 24, but this is not essential, and the shaft tip 24a has a small diameter continuously or stepwise from the shaft main body It may be tapered to be

The drive piston 22 has a shaft insertion hole shaped to engage with the shaft tip 24 a and is formed in a ring shape. Therefore, the shaft tip 24 a can be inserted into the shaft insertion hole of the drive piston 22. By inserting the shaft tip 24 a into the drive piston 22, the drive piston 22 engages with the shaft tip 24 a. Thus, the drive piston 22 is held in a fixed position at the end of the drive shaft 24 axially opposite to the displacer 20 in the piston cylinder 28. When the drive piston 22 is engaged with the shaft tip 24 a, a portion of the shaft tip 24 a protrudes from the top surface of the drive piston 22 and is located outside the drive piston 22.

The axially movable body 16 is provided with a fixing member 68 for detachably fixing the drive piston 22 to the drive shaft 24. The fixed member 68 is mounted on the axially movable body 16 so as to be operable by the operator through the opening of the housing 27 when the housing lid 27a is removed from the housing 27. The fixing member 68 is disposed in the drive chamber 46. When the housing lid 27a is removed from the housing 27, the drive chamber 46 is opened to the outside. The fixing member 68 is configured to be attachable to and detachable from the shaft tip 24 a, and is disposed on the upper surface of the drive piston 22.

The fixing member 68 is, for example, a nut, and is screwed to the shaft tip 24a. The fixing member 68 fastens the drive piston 22 by positive rotation around the axis of the fixing member 68 with respect to the drive shaft 24, and reverses fastening of the drive piston 22 by reverse rotation of the fixing member 68 with respect to the drive shaft 24. The drive piston 22 is sandwiched between the fixing member 68 and the drive shaft 24 and fixed to the drive shaft 24.

The fixing member 68 is not limited to a nut. The locking member 68 may be a bolt, a snap ring, a pin or any other locking member that removably secures the drive piston 22 to the drive shaft 24.

The displacer cylinder 26 comprises a cylinder flange 26a defining a cylinder top opening. The cylinder flange 26 a extends radially outward from the upper end in the axial direction of the displacer cylinder 26. The cylinder top opening is part of the room temperature chamber 36 and allows the displacer 20 to be taken in and out through the cylinder top opening when the housing 27 is removed from the displacer cylinder 26.

The housing 27 is removably fixed to the displacer cylinder 26 using a housing fastening member 70. The housing fastening member 70 secures the housing lid 27a to the housing 27 and secures the housing 27 to the cylinder flange 26a. The housing fastening member 70 is, for example, a bolt. Bolt holes pass through the housing lid 27 a and the housing 27, and bolts are inserted into the bolt holes to fix the housing lid 27 a and the housing 27 to the displacer cylinder 26. A separate fastening member may be used for fixing the housing lid 27 a to the housing 27 and for fixing the housing 27 to the displacer cylinder 26.

The housing lid 27 a and the housing 27 are formed with a through hole which is a part of the main intake and exhaust flow path 64. The through hole is a gas inlet / outlet corresponding to the end of the main intake / exhaust flow path 64, and the main pressure switching valve 60 is connected to the room temperature chamber 36 through this. Further, a through hole which is a part of the auxiliary air suction and discharge passage 66 is formed in the housing lid 27a. The through hole is a gas inlet / outlet corresponding to the end of the auxiliary air suction and discharge passage 66, and the auxiliary pressure switching valve 62 is connected to the drive chamber 46 through this.

An example of the operation of the cryogenic refrigerator 10 having the above configuration will be described. When the displacer 20 is at or near the bottom dead center LP1, the intake process of the cold head 14 is started. The main intake on-off valve V 1 is opened, and high pressure gas is supplied from the discharge port of the compressor 12 to the room temperature chamber 36 of the cold head 14. The gas is cooled while passing through the regenerator 15 and enters the expansion chamber 34.

Simultaneously with the opening of the main intake on-off valve V1, the sub exhaust on-off valve V4 is opened, and the drive chamber 46 of the piston cylinder 28 is connected to the suction port of the compressor 12. Thus, the drive chamber 46 is at a low pressure relative to the room temperature chamber 36 and the expansion chamber 34. The drive piston 22 moves from the bottom dead center LP2 toward the top dead center UP2.

The drive piston 22 and the displacer 20 also move from the bottom dead center LP1 toward the top dead center UP1. The main intake on-off valve V1 and the sub exhaust on-off valve V4 are closed. The drive piston 22 and the displacer 20 continue to move toward the top dead center UP1, UP2. Thus, the volume of the expansion chamber 34 is increased and filled with high pressure gas.

When the displacer 20 is at or near the top dead center UP1, the evacuation process of the cold head 14 is started. The main exhaust on-off valve V 2 is opened, and the cold head 14 is connected to the suction port of the compressor 12. The high pressure gas is expanded and cooled in the expansion chamber 34. The expanded gas is recovered by the compressor 12 through the room temperature chamber 36 while cooling the regenerator 15.

Simultaneously with the opening of the main exhaust on-off valve V2, the sub-intake on-off valve V3 is opened, and high pressure gas is supplied from the discharge port of the compressor 12 to the drive chamber 46 of the piston cylinder 28. Therefore, the driving chamber 46 has a high pressure with respect to the room temperature chamber 36 and the expansion chamber 34. The drive piston 22 moves from the top dead center UP2 toward the bottom dead center LP2.

The drive piston 22 and the displacer 20 also move from the top dead center UP1 toward the bottom dead center LP1. The main exhaust on-off valve V2 and the secondary intake on-off valve V3 are closed. The drive piston 22 and the displacer 20 continue to move toward the bottom dead center LP1, LP2. Thus, the volume of the expansion chamber 34 is reduced and the low pressure gas is exhausted.

The cold head 14 cools the cooling stage 38 by repeating such a cooling cycle (i.e., GM cycle). Thereby, the cryogenic refrigerator 10 can cool a superconducting device or other object (not shown) thermally coupled to the cooling stage 38.

The cryogenic refrigerator 10 is regularly maintained. Prior to maintenance, the cooling operation of the cryogenic refrigerator 10 is stopped. During shutdown, the cryogenic refrigerator 10 is disassembled and internal components such as the displacer 20 are taken out. Necessary maintenance operations such as inspection, repair, and replacement are performed on each component of the cryogenic refrigerator 10, and the cryogenic refrigerator 10 is reassembled. Thus, when the maintenance of the cryogenic refrigerator 10 is completed, the cooling operation of the cryogenic refrigerator 10 is resumed.

FIG. 2 is a flowchart illustrating the method of disassembling the cryogenic refrigerator 10 according to the first embodiment. 3 to 6 are schematic views showing the cryogenic refrigerator 10 in each step of the present decomposition method.

First, as shown in FIG. 3, the housing lid 27a is removed (S10 in FIG. 2). The operator removes the housing fastening member 70 and removes the housing lid 27 a from the housing 27. At this time, the housing 27 is mounted as it is on the cylinder flange 26a. The drive chamber 46 is opened to the outside by removing the housing lid 27a.

Next, as shown in FIG. 4, the fixing member 68 is removed (S12). Since the drive chamber 46 is opened to the outside and the fixing member 68 is in the drive chamber 46, the operator performs the removing operation of the fixing member 68 manually or using a suitable work tool. The operator releases the fixation of the drive piston 22 by the fixing member 68. When the fixing member 68 is a nut, the operator rotates the fixing member 68 about the axis in the loosening direction and removes it from the shaft tip 24 a. The fixing member 68 is taken out of the drive chamber 46.

As shown in FIG. 5, the drive piston 22 as a drive flange is removed (S14). As the fixing member 68 is removed, the operator removes the drive piston 22 from the drive shaft 24. The drive piston 22 is taken out of the drive chamber 46. Thus, the drive shaft 24 can pass through the shaft guide 30.

As shown in FIG. 6, the housing 27 is removed (S16). The operator lifts the housing 27 upward using a manual operation or a lifting device such as a crane, and removes the housing 27. Drive shaft 24 is withdrawn from housing 27. The drive piston 22 does not disturb the removal of the housing 27 since the drive piston 22 has already been removed.

The displacer 20 is removed from the displacer cylinder 26 (S18). Since the housing 27 has already been removed from the displacer cylinder 26 and the room temperature chamber 36 is open, the operator takes the displacer 20 out of the displacer cylinder 26 through the cylinder upper opening. Thus, the cryogenic refrigerator 10 is disassembled. The operator can do the reverse procedure when assembling the cryogenic refrigerator 10.

FIG. 7 is a schematic view showing a cryogenic refrigerator 10 'according to a comparative example. Unlike the cryogenic refrigerator 10 according to the embodiment, in the cryogenic refrigerator 10 ′, the drive piston 22 is non-removably fixed to the drive shaft 24. The cryogenic refrigerator 10 ′ does not have the fixing member 68. The lower end of the drive shaft 24 is fixed to the upper end of the displacer 20 using an engagement pin 72. The engagement pin 72 is accommodated in the internal space of the displacer cylinder 26 together with the displacer 20. Since the cylinder internal space is closed by the housing 27, the engagement pin 72 can not reach the operator's hand.

Even if the housing fastening member 70 is removed to lift the housing 27 in order to remove the engagement pin 72, the drive piston 22 can not pass through the shaft guide 30, and the housing 27 can not be removed. The operator can not immediately release the engagement between the housing 27 and the axially movable body 16.

Therefore, in disassembling work of the cryogenic refrigerator 10 'according to the comparative example, the worker must lift the housing 27 from the displacer cylinder 26 to create a gap, and the worker must remove the engagement pin 72 from the gap . However, especially when the cryogenic refrigerator 10 'is large, the lifting operation is not easy because the weight of the housing 27 can be, for example, several tens of kg. It is difficult to lift by hand, and it takes time and effort to work, such as the need for lifting equipment such as a crane.

According to the cryogenic refrigerator 10 according to the first embodiment, the operator can remove the drive piston 22 from the displacer 20 with the housing 27 mounted on the displacer cylinder 26 and the housing lid 27a removed. It is. With the housing 27 still mounted on the displacer cylinder 26, the operator can release the fixation of the drive piston 22 by the fixing member 68 through the opening of the housing 27 and remove the drive piston 22 from the drive shaft 24. Then, the operator can remove the housing 27 from the displacer cylinder 26. In addition, when assembling the cryogenic refrigerator 10, the worker can carry out in the reverse procedure.

Therefore, compared with the configuration in which the drive shaft 24 is pin-engaged with the displacer 20 in the internal space of the displacer cylinder 26 as in the comparative example, the cryogenic refrigerator 10 according to the first embodiment And the assembly operation becomes easy. The time required for work is reduced.

Further, the drive piston 22 is detachably fixed to the drive shaft 24 by a fixing member 68. The fixing member 68 can adopt an easily detachable structure such as a nut. This also helps to improve the workability.

When the housing lid 27 a is removed, the drive chamber 46 is opened to the outside, and the fixing member 68 is disposed in the drive chamber 46. Therefore, it is easier for the operator to operate the fixing member 68 than when the fixing member 68 is disposed at another place such as the gas spring chamber 48, for example.

In the above-mentioned embodiment, although cryogenic refrigerator 10 is a gas drive-type GM refrigerator, it is not restricted to this, but cryogenic refrigerator 10 may be a motor drive-type GM refrigerator .

FIG. 8 is a view schematically showing a cryogenic refrigerator 10 according to a second embodiment. The cryogenic refrigerator 10 is a motor driven GM refrigerator. Hereinafter, the cryogenic refrigerator 10 according to the second embodiment will be described focusing on a configuration different from the first embodiment, and the common configuration will be briefly described or omitted.

The axially movable body 16 of the cold head 14 includes an axially reciprocable displacer 20 and an axially reciprocable drive flange. The drive flange forms the yoke plate 74 of the scotch yoke mechanism. One axial end (lower end) of the drive shaft 24 is rigidly connected to the displacer 20, and the other axial end (upper end) of the drive shaft 24 is rigidly connected to the yoke plate 74. Therefore, the displacer 20 reciprocates in the axial direction by the axial reciprocation of the yoke plate 74. The yoke plate 74 is accommodated in a reciprocating space 76 of the yoke plate 74 which is an internal cavity of the housing 27.

The radial width of the yoke plate 74 is smaller than the diameter of the displacer 20. The diameter of the drive shaft 24 is smaller than the radial width of the yoke plate 74. Since the through hole of the shaft guide 30 is formed to match the drive shaft 24, the diameter of the through hole is smaller than the diameter of the displacer 20 and smaller than the radial width of the yoke plate 74.

The scotch yoke mechanism may be a well-known one, and an example thereof is described in, for example, Japanese Patent No. 5575880, and therefore will not be described in detail here. No. 5,575,880 is hereby incorporated by reference in its entirety.

The yoke plate 74 is configured to be removable from the displacer 20 in a state where the housing 27 is mounted on the displacer cylinder 26 and the housing lid 27a is removed together with a part of the drive shaft 24. To that end, the axially movable body 16 comprises a threaded connection 78 arranged on the drive shaft 24. The drive shaft 24 is divided into a shaft upper portion 24b on the yoke plate 74 side and a shaft lower portion 24c on the displacer 20 side, with the screw connection portion 78 as a boundary. The upper shaft portion 24 b is fixed to the yoke plate 74, and the lower shaft portion 24 c is fixed to the displacer 20. The housing lid 27a may be provided with another shaft guide 33.

FIG. 9 is a schematic view showing one step of the method of disassembling the cryogenic refrigerator 10 according to the second embodiment. FIG. 9 shows the housing lid 27a removed and the housing 27 mounted on the cylinder flange 26a. By removing the housing cover 27a, the reciprocating space 76 of the yoke plate 74 is opened to the outside.

The operator can remove the yoke plate 74 from the displacer 20 by operating the screw connection portion 78. The screw connection portion 78 fastens the yoke plate 74 by the positive rotation E around the axis of the yoke plate 74 with respect to the displacer 20, and disengages the yoke plate 74 by the reverse rotation F around the yoke plate 74 with respect to the displacer 20. The shaft upper portion 24b rotates with the yoke plate 74 relative to the shaft lower portion 24c, and the screw connection portion 78 can be tightened and released.

According to the cryogenic refrigerator 10 according to the second embodiment, the operator can detach the yoke plate 74 from the displacer 20 with the housing 27 placed on the displacer cylinder 26 and the housing lid 27a removed. It is. With the housing 27 still mounted on the displacer cylinder 26, the operator can release the fastening by the screw connection 78 through the opening of the housing 27 and remove the yoke plate 74 from the lower shaft 24c together with the upper shaft 24b. Then, the operator can remove the housing 27 from the displacer cylinder 26. In addition, when assembling the cryogenic refrigerator 10, the worker can carry out in the reverse procedure.

Therefore, compared with a configuration in which the drive shaft 24 is pin-engaged with the displacer 20 in the internal space of the displacer cylinder 26 as in the comparative example, the cryogenic refrigerator 10 according to the second embodiment performs disassembly work And the assembly operation becomes easy. The time required for work is reduced.

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.

A threaded connection 78 may be disposed between the drive shaft 24 and the displacer 20, as shown in FIG. 10 (a). In the example shown in FIG. 8, the screw connection portion 78 is disposed in the reciprocating space 76 of the yoke plate 74, but as shown in FIG. 10, the screw connection portion 78 may be disposed in the room temperature chamber 36. . In this case, with the housing 27 placed on the displacer cylinder 26 and the housing cover 27 a removed, the operator can remove the yoke plate 74 from the displacer 20 along with the entire drive shaft 24.

Not only the motor driven GM refrigerator, the screw connection portion 78 is also applicable to a gas driven GM refrigerator. In that case, as shown in FIG. 10 (b), the screw connection 78 may be disposed between the drive piston 22 and the drive shaft 24. The screw connection portion 78 fastens the drive piston 22 by positive rotation around the axis of the drive piston 22 with respect to the displacer 20, and disengages the drive piston 22 by reverse rotation around the axis of the drive piston 22 with respect to the displacer 20. In this case, with the housing 27 placed on the displacer cylinder 26 and the housing lid 27a removed, the operator can remove the drive piston 22 alone from the displacer 20. Note that, also in the gas driven GM refrigerator, the screw connection portion 78 may be disposed on the drive shaft 24 or may be disposed between the drive shaft 24 and the displacer 20.

Further, the fixing member 68 is applicable not only to a gas driven GM refrigerator but also to a motor driven GM refrigerator. In that case, as shown in FIG. 10C, the fixing member 68 may be provided on the lower frame portion of the yoke plate 74 so as to detachably fix the yoke plate 74 to the drive shaft 24. In this case, with the housing 27 placed on the displacer cylinder 26 and the housing cover 27a removed, the operator can detachably attach the yoke plate 74 to the displacer 20 alone. Thus, it is not essential that the fixing member 68 be installed on the upper surface of the drive flange, and the fixing member 68 may be installed on the lower part of the drive flange.

Although the above-described embodiment has been described by taking the GM refrigerator as an example, the drive flange mounting structure according to the embodiment is also applicable to other cryogenic refrigerators such as a Solvay refrigerator.

Hereinafter, some embodiments of the present invention will be listed.

1. An axially reciprocable displacer,
An axially reciprocable drive flange,
An axially extending drive shaft having one end rigidly coupled to the displacer and the other end rigidly coupled to the drive flange such that the displacer axially reciprocates by axial reciprocation of the drive flange; Connected drive shaft,
A cylinder which accommodates the displacer so as to be axially reciprocable;
A removable housing lid and a drive flange chamber axially reciprocably accommodating the drive flange and open to the outside when the housing lid is removed, and removably fixed to the cylinder A housing, and
The drive flange may be configured to be removable from the displacer in a state in which the housing is mounted on the cylinder and the housing lid is removed alone or together with at least a part of the drive shaft. Cryogenic refrigerator.

2. The cryogenic refrigerator according to claim 1, further comprising a fixing member for detachably fixing the drive flange to the drive shaft.

3. The drive flange is disposed in the drive flange chamber so as to divide the drive flange chamber into a first section axially opposite to the displacer and a second section on the displacer side.
The first section of the drive flange chamber is open to the outside when the housing lid is removed,
The cryogenic refrigerator according to Embodiment 2, wherein the fixing member is disposed in the first section of the driving flange chamber.

4. The drive flange and the drive shaft are coupled such that the drive flange is fastened by positive rotation around the drive flange relative to the displacer while fastening the drive flange by reverse rotation around the drive flange relative to the displacer. The cryogenic refrigerator according to claim 1, further comprising a threaded connection disposed between, or on the drive shaft, or between the drive shaft and the displacer.

5. 5. The cryogenic refrigerator according to any one of the preceding embodiments, wherein the drive flange forms a drive piston that drives axial reciprocation of the displacer by the gas pressure acting thereon.

6. The cryogenic refrigerator according to any one of the above embodiments, wherein the drive flange forms a yoke plate of a scotch yoke mechanism.

10 cryogenic refrigerator, 20 displacers, 22 drive pistons, 24 drive shafts, 27 housings, 27a housing lids, 68 fixing members, 74 yoke plates, 78 screw connections.

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

Claims

An axially reciprocable displacer,
An axially reciprocable drive flange,
An axially extending drive shaft having one end rigidly coupled to the displacer and the other end rigidly coupled to the drive flange such that the displacer axially reciprocates by axial reciprocation of the drive flange; Connected drive shaft,
A cylinder which accommodates the displacer so as to be axially reciprocable;
A removable housing lid and a drive flange chamber axially reciprocably accommodating the drive flange and open to the outside when the housing lid is removed, and removably fixed to the cylinder A housing, and
The drive flange may be configured to be removable from the displacer in a state in which the housing is mounted on the cylinder and the housing lid is removed alone or together with at least a part of the drive shaft. Cryogenic refrigerator.
The cryogenic refrigerator according to claim 1, further comprising a fixing member for detachably fixing the drive flange to the drive shaft.
The drive flange is disposed in the drive flange chamber so as to divide the drive flange chamber into a first section axially opposite to the displacer and a second section on the displacer side.
The first section of the drive flange chamber is open to the outside when the housing lid is removed,
The cryogenic refrigerator according to claim 2, wherein the fixing member is disposed in the first section of the driving flange chamber.
The drive flange and the drive shaft are coupled such that the drive flange is fastened by positive rotation around the drive flange relative to the displacer while fastening the drive flange by reverse rotation around the drive flange relative to the displacer. The cryogenic refrigerator according to claim 1, further comprising a screw connection disposed between, or on the drive shaft, or between the drive shaft and the displacer.
5. A cryogenic refrigerator according to any one of the preceding claims, wherein the drive flange forms a drive piston which drives the axial reciprocation of the displacer by the gas pressure exerted.
The cryogenic refrigerator according to any one of claims 1 to 4, wherein the drive flange forms a yoke plate of a scotch yoke mechanism.