JP2765044B2 - Cryogenic support structure - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a support structure in which a cryogenic member is supported by a room-temperature member via a support. Such a support structure is mainly used when the inner tank of the cryostat is stably fixed in the outer tank.

[Conventional technology]

The cryostat, which houses superconducting equipment such as superconducting magnets, has a heat transfer path between the inner tank and the outer tank that is a vacuum vessel, in order to maintain high insulation between the inner tank and the outer tank, which is the same temperature as the stored refrigerant during use. When the connecting member is absolutely necessary from the viewpoint of the support stability of the inner tank, a strut with good heat insulation and a small heat transfer area is bridged between the outer tank and the inner tank. A method of supporting is adopted.

The conventional strut used for this support structure is, for example,
As disclosed in JP 63-126474, an integral support seat is provided at the end, and this seat is bolted to an object to be connected.

[Problems to be solved by the invention]

In the cryostat, a heat insulating layer other than the vacuum layer, for example, a radiation shield, a cooling pipe, a multilayer heat insulating material, and the like are provided between the inner and outer tanks for the purpose of enhancing the heat insulating effect.

The struts will penetrate these insulation layers,
Therefore, when bolting the pillars, make holes in these heat-insulating layers to enable assembly work such as bolting, or assemble the heat-insulating layers avoiding the pillars after bolting. It becomes necessary.

However, the former method of unnecessarily increasing the hole size deteriorates the heat insulating property.On the other hand, when assembling the heat insulating layer while avoiding the columns, the number of columns is increased, particularly when the number of steps is increased and the work becomes complicated. There is a problem.

[Means for solving the problem]

In order to solve the above problems, in the support structure of the present invention, a mounting seat is provided on the cryogenic member side, and the mounting seat and the support are formed of materials having different coefficients of thermal expansion and fitted to each other. The part is brought into an interference-fit state by the difference in heat shrinkage at the operating temperature of the cryogenic member.

[Action]

FIG. 2 shows measured data on the correlation between the fiber winding direction of a CFRP (carbon fiber reinforced plastic) cylinder and the coefficient of thermal expansion. Now, when a cylinder having a fiber winding angle of 45 ° is used as a column, the thermal expansion coefficient of the column becomes almost zero.

On the other hand, if the mounting seat is made of SUS304, its thermal expansion coefficient will be
It is 9.8 × 10 ^-6 .

Therefore, now, if the support made of each of the above materials and the mounting seat are fitted together at room temperature with zero clearance, and then the cryogenic member is cooled to the operating temperature, for example, 4.2K, the mounting seat is also reduced to 4.2K. Since the temperature drops, the amount of shrinkage of 9.8 × 10 ⁻⁶ × 269K = 0.26% serves as a tightening margin of the fitting portion, so that a strong fastening is performed without using a bolt.

In addition, since the fitting with zero clearance can be performed by lightly press fitting,
Even if the pillar insertion hole provided in the heat insulating layer or the like is made the minimum size, there is no problem in assembling.

〔Example〕

FIG. 1 shows an example of a support structure of the present invention. In the figure, 1 is a wall of a liquid helium container, 2 is a wall of a vacuum container surrounding 1, 3 is a multilayer heat insulating material layer along the outer surface of 1, and 4 is a liquid disposed so as to surround 1 in the vacuum layer Nitrogen shielding layer, 4a is a column insertion hole provided in 4, 5 is a SUS304 mounting seat welded to the outer surface of 1, 6 is a CFRP hollow column with a fiber winding angle of 45 °, 7 is the same material as 5 A mounting seat 8 is formed and fixed to 2 with bolts 9, and 8 is an O-ring that hermetically seals around 9. Both the mounting seats 5 and 7 in the figure have cylindrical portions 5a and 7a. The former cylindrical portion 5a has an inner diameter equal to the outer diameter of 6 and is press-fitted into 6 at normal temperature. On the other hand, the latter cylindrical portion 7a
Is machined slightly larger than the inner diameter of 6 and fitted inside 6 by cold fitting. In this way, when 5 and 5 are cooled to liquid helium temperature (4.2K), 5a
Contracts to tighten 6, and a sufficient joining force is generated at the fitting portion between the two. In addition, since the temperature of 7 becomes approximately normal temperature during use, the interference caused by the cooling fit between 7a and 6 is almost maintained.

It is optional to put a heat insulating material in the internal space of the column 6.

It is also optional to make 6 and 7 with an integral CFRP.
However, in this case, a metal plug into which the bolt 9 is screwed is buried in the metal plug 7, and the O-ring 8 is attached to the plug in order to stabilize the fastening and prevent airtight leakage.

FIG. 3 and FIG. 4 show an example of a cryostat made by using the support structure of the present invention. Figure 11
Is a helium container for storing superconducting magnet and liquid helium, 12 is a vacuum container, 13 is a port for passing current leads and helium transfer tubes, 14 is a vacuum port,
15 is a temporary support member. In addition, the same reference numerals as those in FIG. 1 indicate the same elements.

This cryostat is assembled as follows. That is, the multilayer heat insulating material layer 3 around the helium container 11,
After the liquid nitrogen shield layer 4 and the multilayer heat insulating material layer 3 ′ are arranged and fixed in this order, they are inserted into the inverted vacuum vessel 12. The temporary support member 15 supports the helium container 11 at this time. Next, the required number of mounting seats 5 are positioned and welded to the helium container 11 in advance, and the columns 6 are pressed into the cylindrical portions of the mounting seats from the outside of 3 '. A mounting seat 7 is mounted on the support 6 by cold fitting in advance.

After the above operation, the lid 12b (corresponding to 2 in FIG. 1) is hermetically sealed over the main body 12a of the container 12, and a predetermined distance (a distance equal to S in the figure) from the lid and the inner surface of the lid. Temporarily fasten the separated mounting seat 7 with the long bolt 16. After that, tighten the temporary fixing long bolt and the helium container 11
The object inside is lifted up to a position where the mounting seat 7 comes into close contact with the lid 12b away from the lid. Therefore, when the whole is turned upside down and the state shown in FIG. 3 is reached, the lid 12b and the mounting seat 7 are fastened again. Although illustration is omitted, between 7 and 12b and between 12a
An O-ring that seals around the fastening bolt is arranged between them.

〔effect〕

As described above, according to the present invention, the mounting seat for fitting the support is provided on the cryogenic member side, and the interference between the mounting seat and the support is made using the difference in heat shrinkage at the operating temperature of the support. For example, when used for a cryostat, it is possible to simplify the assembling work by connecting the support post after attaching the heat insulating material, and to provide the heat insulating material between the inner and outer layers required for this work. There is an effect that the heat insulating effect can be enhanced by making the support insertion hole as small as possible.

[Brief description of the drawings]

FIG. 1 shows an example of the support structure of the present invention, and FIG.
Graph showing the relationship between the fiber winding angle of RP and thermal expansion coefficient, FIG. 3 is a cross-sectional view showing an example of a cryostat using the same,
FIG. 4 is a reduced bottom view of the above. DESCRIPTION OF SYMBOLS 1 ... Liquid helium container wall, 2 ... Vacuum container wall, 3 ... Multilayer heat insulating material layer, 4 ... Liquid nitrogen shield layer, 4a ... Post insertion hole, 5, 7 ... Mounting seat , 5a, 7a ... cylindrical part, 6 ... pillar.

Claims (4)

(57) [Claims] In a supporting structure for supporting a cryogenic member with a room temperature member via a support, a mounting seat for fitting and connecting the support is provided on the cryogenic member side, and the mounting seat and the support are provided with a thermal expansion coefficient. A supporting structure for a cryogenic member, characterized in that the two fitting portions are made of different materials and the two fitting portions are brought into an interference-fit state due to a difference in heat shrinkage at a use temperature of the cryogenic member. 2. A mounting seat for fitting and connecting a support is provided on the room temperature member side, and the support is externally fitted on the cylindrical portion of the mounting seat on the room temperature member side, and the support is inserted inside the cylindrical portion of the installation seat on the cryogenic member side. The support structure for a cryogenic member according to claim 1, wherein the support structure is fitted. 3. The cryogenic member support structure according to claim 2, wherein each mounting seat is formed of stainless steel, and the support is formed of carbon fiber reinforced plastic. 4. The support structure for a cryogenic member according to claim 3, wherein said carbon fiber reinforced plastic support has a coefficient of thermal expansion of about 0.