JPH024172A - Cryogenic cooling device - Google Patents

Abstract

PURPOSE:To separate a shield from a refrigerator mechanically and prevent the vibration of said refrigerator from being directly transmitted to a vacuum vessel by producing a vacuum chamber different from a vacuum layer of a vacuum vessel around a support member, pulling out the end of said support member to an ambient temperature section, and providing a buffer, such as bellows between said refrigerator and vacuum vessel. CONSTITUTION:When it is necessary to replace an O ring or the like, loosen studs 17 and 18, which serve as a connection member 19 and move upward those which are integrated with a refrigerator 1, a cylinder 13, and a low temperature generation section and remove the low temperature generation section from a heat conductor 15. Then, a second bellows 21 which is a second buffer as well as a refrigerator's airtightness holding member is elongated, thereby preventing a vacuum state in a vacuum chamber 22 from being broken. When the refrigerator 11, the cylinder 13, and the low temperature generation section 14 are disassembled for repair, remove a bolt 29 and a nut 30 and the aforesaid members 11, 13 and 14 from a support member 5, then start the work. The refrigerator 11 is fixed with a shield 4 while a vacuum vessel 2 is connected in such a manner that no vibration of the refrigerator may be transmitted, maintaining the vacuum state by way of a first bellows which is a first buffer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a cooling device for maintaining a superconducting magnet such as a nuclear magnetic resonance imaging diagnostic apparatus at an extremely low temperature for a long period of time.

(Prior Art) Conventionally, as a means of holding a refrigerant for as long as possible to maintain a superconducting magnet at a low temperature, a shield called a heat shield or a protective shield is provided between an outer vacuum container and an inner refrigerant container. A method was used to actively cool this shield using a refrigerator. - In terms of design, the refrigerator uses a 0M cycle, a Solvay cycle, etc., and is operated by reciprocating a regenerator or a piston housed in a cylinder.

Such refrigerators are inevitably subject to mechanical wear and require periodic repair. More specifically, it is necessary to replace the O-ring etc. inside the refrigerator cylinder.
For this purpose, it is necessary to heat the chiller to room temperature. In order to perform this operation without raising the temperature of the entire cooling device, there is a method described in Japanese Patent Laid-Open No. 60-69540. This method mechanically separates the fitting part between the refrigerator and the shield without breaking the vacuum.
It is characterized by being able to heat the refrigerator and perform maintenance work such as replacing the O-ring without heating the shield.

(Problem to be Solved by the Invention) However, with the conventional latter detachable means, the contact pressure between the fitting part of the refrigerator and the shield during operation is small, so thermal contact is insufficient and the shield and refrigerator Compared to the former method, which firmly connects the shield to the machine, heat transfer is significantly worse, and due to its thermal resistance, the shield temperature increases significantly.
The amount of refrigerant evaporation increases.

On the other hand, with the conventional former means, when fixing the refrigerator,
This method has the disadvantage that the refrigerator must be supported in a vacuum container, and the influence of vibrations of the refrigerator on the entire device cannot be suppressed.

In the present invention, when repairing a refrigerator, the shield and the refrigerator can be mechanically separated without raising the temperature of the entire cryogenic cooling device, and normally the shield and refrigerator are solid. combined with.

It is an object of the present invention to provide a cryogenic cooling device which has good thermal contact between the two and further prevents the vibrations of the refrigerator from being directly transmitted to the vacuum container.

[Structure of the invention]

(Means for Solving the Problem) In order to achieve the above object, in the present invention, a support for supporting the refrigerator is fixed to the shield, and the periphery of the support is separated from the vacuum layer of the vacuum container. This is a vacuum chamber, and by pulling out the end of this support to the room temperature section, the refrigerator and the shield can be joined and separated from each other at the room temperature.

In addition, a buffer member such as a bellows is provided between the refrigerator and the vacuum container to prevent the vibrations of the refrigerator from being transmitted to the vacuum container.Furthermore, in order to reduce contact resistance, the shield and the low temperature generation part of the refrigerator are A highly elastic thermal conductor is interposed on the contact surface.

(Function) The support body is firmly fixed to the shield, and the upper end of the support body is pulled out to the room temperature part, so that the work of connecting and separating the refrigerator and the shield can be reliably performed in the room temperature part,
In addition, since a buffer member such as a bellows is disposed between the end of the support and the vacuum container, it is possible to suppress factors that adversely affect the diagnostic apparatus, such as vibrations of the refrigerator.

Further, by making the support body airtight and configuring another vacuum chamber completely isolated from the vacuum vessel, it is possible to attach and detach the refrigerator including the cylinder without breaking the vacuum of the vacuum vessel. This means that even if the shock absorbing member, such as the bellows, which is relatively susceptible to damage, is damaged, the vacuum of the entire cooling device will not be broken, and the damage will be minimal. By making the connections between the buffer member, the refrigerator, and the support body removable, the buffer member can be easily replaced.

Furthermore, as described above, since the refrigerator and the shield can be mechanically and firmly joined, thermal contact between the shield and the refrigerator is significantly better than in the conventional attachment/detachment structure.

The pressure applied to the contact surface can be adjusted by changing the relative distance between the support and the refrigerator, and tightening can be achieved by interposing a shock absorbing member such as a spring or bellows at the part. In addition to being adjustable, it can sufficiently absorb the difference in the amount of thermal contraction between the cylinder of the refrigerator and the support, and there is little possibility of damaging the support or the refrigerator.

(Examples) Example 1 A first example of the present invention will be described below with reference to FIG. 1.

In Example 1, a refrigerant container (1) containing a cryogenic refrigerant is housed in a vacuum container (2), and a shield is placed between both containers (1) and (2) via a vacuum layer (3). (4)
will be placed. The lower end of the support body (5) is secured to the shield (4) with bolts (7) and nuts (8) while maintaining airtightness with an O-ring (6). The upper end of the support (5) is made to protrude outside the vacuum container (2) and is provided with an upper end flange (9).

The vacuum container (2) and the upper end flange (9) flexibly connect a first bellows (10), which is a first buffer member, to prevent the vacuum in the vacuum container (2) outside the support (5). Maintain vacuum in layer (3). The refrigerator (11) has a refrigerator flange (
12), and a low temperature generation section (14) is provided below it via a cylinder (13). Between the low temperature generation part (14) and the shield (4) are both (14) and 6 thermoelectric conductors (15) sandwiching a thermal conductor (15) with greater elasticity than (4).
) is provided, and a connecting member (19) consisting of a stud (17), a nut (18), etc. is provided to connect the refrigerator flange (12) and the refrigerator receiving flange (16). An O-ring (20) is provided between the refrigerator flange (12) and the refrigerator holder flange (16).
) and the refrigerator receiver are connected to the flange (16) with bolts (29) and nuts (30), and the upper end flange (9) of the support (5) and the refrigerator receiver are connected to each other between the flange (16) and the second
A second bellows (21), which serves as a buffer member and also serves as an airtight maintenance member for the refrigerator, is airtightly provided to form a vacuum chamber (22) inside the support (5).

Next, the operation of this first embodiment will be explained.

When replacing the sliding part of the refrigerator (11), that is, the O-ring (not shown), use the stud (19) that is the connecting member (19).
17) Loosen the nut (18) and move the integrated refrigerator (1), cylinder (13), and low-temperature generation part (14) upwards, and move the low-temperature generation part (14) to heat conduction. Body (1
5) Pull it away. At this time, the second bellows (21), which is a second buffer member and also serves as a refrigerator airtight member, extends, and the vacuum in the vacuum chamber (22) is not broken. Thereafter, the refrigerator (11) is heated to room temperature and maintenance work such as replacing the O-ring is performed. In addition, the refrigerator (11) and cylinder (13)
, when dismantling and repairing the low-temperature growth part (14), use the bolts (
29), remove the nut (30) and remove the member (11),
(13) and (14) will be extracted from the support (5) for work. In this case, the vacuum in the vacuum chamber (22) of the extracted part will be broken, but the vacuum in the large vacuum layer (3) outside the support (5) will not be broken, so it will be extremely difficult to draw the vacuum when restarting the operation. It can be done quickly. Since the lower end of the low temperature generation part (14) can be strongly pressed against the shield (4) via the highly elastic heat conductor, even if there is a change in the force, the pressing will not continue to a certain extent. The heat transfer is good, the amount of refrigerant evaporation is small, and highly efficient shield cooling is possible. Further, the refrigerator (11) is fixed to the shield (4), and the vacuum container (2) maintains the vacuum through the first bellows, which is the first buffer member, and prevents the vibrations of the refrigerator from being transmitted. Since the coupling is made such that there is no coupling, it is possible to provide a cryogenic cooling device that is superior mechanically and thermally compared to the conventional fitting method.

Example 2 A second example shown in FIG. 2 includes a support (5) and a shield (
4) is fixed at the welded portion (24). The refrigerator receiver, which is the main part of the second buffer member, has a flange (16).
sleeve (25) with spring (27) and stud (17)
), and the sleeve (25) slides on the inner circumferential surface of the support body (5) via an O-ring (28) to enable vertical movement. In addition, the sleeve (25) with flange (16) for the refrigeration gutter holder must be secured with bolts (29) to prevent it from falling under its own weight.
It is connected to the refrigerator flange (12) with a nut (30).

The heat conductor (13) is a refrigerator (11), a cylinder (13)
The heat conductor (13) is pressed against the shield (4) by the weight of the low temperature generation part (14) and the like and by the spring (27). The rest is the same as in Example 1.

In this way, the spring (27) attached to the stud (17) can absorb the difference in thermal contraction caused by the difference in material and length between the refrigerator (11) and the support (5), and the pressure support by increasing (5) or refrigerator (1)
1) There is less possibility of damage. Conversely, even if the pressure decreases due to the difference in the amount of thermal contraction between the support (5) and the refrigerator (11), it also has the effect of alleviating this decrease. The other effects are similar to those of the first embodiment.

In addition, in the present invention, in order to further improve the thermal contact between the low temperature generation part (14) and the shield (4), each contact surface is plated with silver,
Gold plating, indium coating, etc. may be used.The structure of the contact surface may include parallel flat plates, tapered surfaces, etc.
It may have an uneven surface or the like. Furthermore, in each of the above embodiments, the low-temperature generating section (14) is shown as having a single stage, but when the low-temperature generating section (14) is provided in multiple stages with multiple shields, the next stage of the refrigerator may be The amount of thermal contraction of the cylinder and the corresponding amount of thermal contraction of the support may be made similar, or an elastic body may be interposed between the refrigerator and the shield or on the support.

〔Effect of the invention〕

As explained above, according to the present invention, in a cryogenic cooling device used for nuclear magnetic resonance imaging diagnostic equipment, etc., mechanical and thermal attachment and detachment of the refrigerator, which requires periodic repair, can heat the entire device. Not only is it possible, but even if the refrigerator, cylinder, and low-temperature generator are removed from the support, only the inside of the support will break the vacuum. It is easy to operate and can suppress the effect of the vibration of the refrigerator on the vacuum container, and during normal operation, the shield and the low temperature generation part of the refrigerator sandwich and press the highly elastic heat conductor. Because the structure is mechanically and thermally strongly connected, it is possible to provide a cryogenic refrigeration system that is significantly superior to conventional structures.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are longitudinal sectional views showing different embodiments of the present invention. 1... Refrigerant container 2... Vacuum container 3.
...Vacuum layer 4...Shield 5...
・Support body 9...Top end flange 10・
...First bellows 11, which is the first buffer member...Freezer 12...Freezer flange 13.
... Cylinder 14 ... Low temperature generation section 15
...Thermal conductor 16...Freezer gutter holder is flange 19...Joining member 22...Vacuum chamber 25...Sleeve 27 which is a member for maintaining airtightness of the refrigerator...
・Spring agent who is the second buffer member Patent attorney Norihiro Ogo! Figure 11 Figure 2

Claims (1)

[Claims] a refrigerant container for storing a cryogenic refrigerant; a vacuum container for storing the refrigerant container; a shield disposed between the refrigerant container and the vacuum container via a vacuum layer; a first support that protrudes outside the vacuum container and has an upper end flange; and a first support that flexibly connects the upper end flange and the vacuum container to maintain the vacuum of the vacuum layer outside the support.
A refrigerator having a buffer member, a low temperature generation part with a cylinder inserted into the support body, a refrigerator flange that attaches the refrigerator to the support body, and a refrigerator sandwiched between the tip of the low temperature generation part and the shield from both sandwich parts. A highly elastic heat conductor, a connecting member that pressurizes the heat conductor and connects the refrigerator flange and the support flange, and maintains airtightness between the upper end flange of the support and the refrigerator flange to prevent axial displacement. A refrigerator airtight maintenance member that follows and forms a vacuum chamber separate from the vacuum layer, and a second buffer member that can maintain the vacuum of the vacuum chamber and separate the low temperature generation part from the thermal conductor. A cryogenic cooling device featuring: