JPH01289179A - Supporting means for cryogenic container - Google Patents

Abstract

PURPOSE:To inhibit a change of the lengths of the whole supporting means by a difference between a positive thermal expansion coefficient and a negative thermal expansion coefficient when the supporting means are cooled with pour of a cryogenic liquid in a cryogenic container and to maintain a good heat-insulating state by a method wherein the supporting means for the cryogenic container are respectively constituted as a series coupled body consisting of a supporting member having a positive thermal expansion coefficient and a supporting member having a negative thermal expansion coefficient. CONSTITUTION:Three pieces of supporting means A1 are tightened across 8 sets left and right and before and behind between end plates 2c on both sides of a liquid helium container 2 and the inner peripheral face of an outer cylinder 3b of a vacuum container 3 in a state that a constant space is held between the container 2 with a built-in superconducting magnet 1 and the container 3 and the container 2 is supported coaxially to the container 3 and conforming the axial centers of the containers to each other. This supporting means A1 is constituted of a supporting member 11 having a positive thermal expansion coefficient and a supporting member 12 having a negative thermal expansion coefficient, both of these supporting members 11 and 12 are coupled with each other in series by an intermediate joint 13 made of stainless steel and other end parts of both members 11 and 12 are respectively coupled with end part joints 14 and 15.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application This invention relates to a support for a cryogenic container containing liquid helium, liquid nitrogen, etc.

Such a cryogenic container is used, for example, to cool a superconducting magnet of a nuclear magnetic resonance tomography apparatus (NMR-CT).

B. Prior art This type of support connects the cryogenic container to other members (e.g., a vacuum container) °1. Heat enters the cryogenic container due to heat conduction from other members through the support. Conventionally, supports have been made of glass fiber reinforced plastic (GFRP), which has extremely low thermal conductivity, in order to prevent this as much as possible.

An example of a conventional support A0 is shown in FIG.

This support A0 is composed of a support member 41 made of GFRP and having a positive coefficient of thermal expansion, and two end joints 42 and 43 made of stainless steel that connect the support member 41 in series.

The support member 41 is made of FRP made by winding continuous glass fibers many times in a ring shape and hardening them with epoxy resin, etc., and has two mutually parallel straight parts 41a and two semicircular retaining parts at both ends. The portion 41b is integrated with the portion 41b.

A pin 44 is attached to each end of the end zigo points 42 and 43.
A pulley-shaped grooved ring 45 is rotatably supported via the . Each semicircular retaining portion 41b of the support member 41 is
It is rotatably engaged in a groove in a grooved ring 45 of the end joints 42, 43.

C0 Problem to be solved by the invention Glass fiber reinforced plastic has a relatively small coefficient of thermal expansion, but when a cryogenic container supported by a support made of glass fiber reinforced plastic reaches an extremely low temperature, it contracts and the support also collapses. It is cooled and shrunk from the cryogenic container.

For example, consider a case where a liquid helium container is suspended in a vacuum container at room temperature via a GFRP support A0 shown in FIG. Liquid helium is injected into the liquid helium container from room temperature (approximately 293 K), and the liquid helium container is heated to 4.2 K.
When cooled to (the boiling point of liquid helium), the shrinkage rate of the commonly used stainless steel liquid helium container is 0.30%, and the support tool is 4.2K to 293K.
It has a temperature distribution up to K, and the overall shrinkage rate is 0.1
~0.2%, but since there is no temperature change in the vacuum container, no shrinkage occurs.

In this way, the vacuum container does not shrink, but the liquid helium container and support do. Therefore, if the center positions of the vacuum container and liquid helium container do not change, a large tensile stress is applied to the support, causing the support to There was a risk that it would break.

In order to avoid this, the cross-sectional area of the supporting member 41 can be increased to increase the tensile stress resistance, but if the cross-sectional area is increased to increase the strength, the amount of heat conducted will increase and the heat insulation will be impaired. It is also necessary to reinforce other parts such as the end jigoine) 42 and 43.

Furthermore, due to contraction of the support and the liquid helium container, the center position of the liquid helium container deviates from a predetermined reference position before and after injection of liquid helium.

In particular, when the liquid helium container is used to cool the superconducting magnet of a nuclear magnetic resonance tomography device, the center position of the superconducting magnet itself may deviate from the reference position because the superconducting magnet is housed in the liquid helium container. , the uniformity of the central magnetic field deteriorates, resulting in deterioration of image quality and distortion of the image.

This invention was made in view of the above circumstances, and is designed to prevent the center position of a cryogenic container from shifting as much as possible before and after injecting a cryogenic liquid such as liquid helium into the cryogenic container, and to The purpose of the present invention is to provide a support for a cryogenic container with excellent breakage resistance.

01 Means for Solving the Problems In order to achieve the above object, the present invention has the following configuration.

That is, the cryogenic container support of the present invention is formed by connecting a support member with a positive coefficient of thermal expansion and a support member with a negative coefficient of thermal expansion in series at an appropriate length ratio.

The material of the support member having a positive coefficient of thermal expansion may be fiber-reinforced plastic or a metal material.
Further, the material of the support member having a negative coefficient of thermal expansion is fiber-reinforced plastic for boat fishing.

The number of support members with a positive coefficient of thermal expansion and the number of support members with a negative coefficient of thermal expansion are not limited, and each may be one or two or more.

E6 action The effects of the configuration of this invention are as follows.

When the support is cooled as a cryogenic liquid is injected into the cryogenic container, the support member with a positive coefficient of thermal expansion contracts, while the support member with a negative coefficient of thermal expansion expands.

Taking into account the temperature drop due to cooling, the length and number of support members with a positive coefficient of thermal expansion and the length and number of support members with a negative coefficient of thermal expansion can be appropriately set to reduce the length of the entire support. It is possible to sufficiently reduce the change in
It is also possible to set the overall coefficient of thermal expansion to any desired value.

This makes it possible to sufficiently reduce the tensile stress and compressive stress applied to the support itself, thereby avoiding breakage of the support. Further, the displacement of the center position of the cryogenic container before and after the cryogenic liquid is injected is also sufficiently small.

F. Embodiments Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

■Top! Figure 3 (A) is a longitudinal sectional front view showing a nuclear magnetic resonance tomography device (NMR-CT) as an example of the object to be used;
B) is a longitudinal side view thereof.

In this NMR-CT, the liquid helium container 2 containing the superconducting magnet 1 is an inner cylinder 2a.

It has a double cylindrical shape including an outer cylinder 2b and closed end plates 2C on both sides. The vacuum container 3 in which the liquid helium container 2 is hermetically sealed is also configured in a double cylindrical shape from an inner tube 3a, an outer tube 3b, and closed end plates 3C on both sides.

A liquid helium container 2 containing a superconducting magnet 1 and a vacuum container 3 are coaxial with each other.

The internal space of the vacuum container 3 serves as a patient insertion section S.

In order to support the liquid helium container 2 coaxially and with the axial center aligned with the vacuum container 3 while maintaining a space of a certain width between the liquid helium container 2 and the vacuum container 3, the liquid helium container 2 is Eight supports A are provided between the end plates 2C on both sides of the container 2 and the inner peripheral surface of the outer cylinder 3b of the vacuum container 3, and between the outer cylinder 3b of the vacuum container 3 and the outside of the liquid helium container 2. Four supports A1' are hung between the tubes 2b symmetrically in the left and right directions.

The supports A, , A, and ' are provided to prevent vibration in the vertical direction, horizontal direction, and axial direction, respectively, and to ensure that the center of the liquid helium container 2 and the center of the vacuum container 3 coincide.

Note that, as shown by the two-dot chain line, a double cylindrical heat shield 4 made of aluminum or the like with high thermal conductivity is usually placed between the liquid helium container 2 and the vacuum container 3 to close the liquid helium container 2. By covering with a heat shield 4, heat radiation from the outside to the liquid helium container 2 is blocked.

In FIG. 3, a -heavy heat shield is used, but it may be double or more, and these heat shields may be cooled with a refrigerator.

Figure 4 (A) is a nuclear magnetic resonance tomography device (NMR-CT).
) is a longitudinal sectional front view showing another example, and FIG. 4(B) is a longitudinal sectional side view thereof.

The NMR-CT shown in FIG. 4 has an inner cylinder 2a.

An inner cylinder 5a and an outer cylinder 5b are disposed on the outside of the liquid helium container 2, which has a double cylindrical shape including an outer cylinder 2b and closed end plates 2C on both sides, and has a built-in superconducting magnet 1.

A liquid nitrogen container 5 consisting of a closed end plate 5c is fitted over the container. A liquid helium container 2 and a liquid nitrogen container 5 are hermetically sealed inside a vacuum container 3 configured in a double cylindrical shape from an inner cylinder 3a, an outer cylinder 3b, and closed end plates 3c on both sides.

A liquid helium container 2 containing a superconducting magnet 1, a liquid nitrogen container 5, and a vacuum container 3 are coaxial with each other.

In order to support the liquid helium container 2 coaxially with respect to the liquid nitrogen container 5 while maintaining a certain space between the liquid helium container 2 and the liquid nitrogen container 5, End plate 2C and inner cylinder 5a of liquid nitrogen container 5
Eight supports A are passed symmetrically between the inner circumferential surface of the frame and the inner circumferential surface of the frame.

Incidentally, a support similar to the support AI' shown in FIG. 3 may be interposed.

In addition, in order to support the liquid nitrogen container 5 coaxially with respect to the vacuum container 3 while securing a space of a certain width between the liquid nitrogen container 5 and the vacuum container 3, both sides of the liquid nitrogen container 5 are provided. Eight supports A are provided between the end plate 5C and the inner peripheral surface of the outer cylinder 3b of the vacuum container 3, symmetrically in the left and right directions.

In addition, as shown by the two-dot chain line, when a double cylindrical heat shield 4 made of aluminum is arranged between the liquid nitrogen container 5 and the liquid helium container 2 to cover the liquid helium container 2 with the heat shield 4. There is also.

When assembling and starting up the cryogenic container, first, the liquid helium container 2. Liquid nitrogen container5. The center of the vacuum container 3 is aligned, the inside of the vacuum container 3 is evacuated, and then liquid nitrogen is injected into the liquid nitrogen container 5, and liquid nitrogen is also injected into the liquid helium container 2 for preliminary cooling. , liquid nitrogen is discharged from the liquid helium container 2 and liquid helium is injected into the liquid helium container 2 instead.

Next, the specific structure of the supports A1 and AI' will be explained based on FIG. 1.

These supports AI and Al' include a support member 11 with a positive coefficient of thermal expansion, a support member 12 with a negative coefficient of thermal expansion, and an intermediate joint 13 made of stainless steel that connects both support members 11 and 12 in series. and both supporting members ll.

12 and an end joint 14, 15 made of stainless steel connected to the other end side.

Pulley-shaped grooved rings 17 are rotatably supported at both ends of the intermediate joint 13 via pins 16, respectively. Further, a grooved ring 19 is rotatably supported at each end of the end joints 14, 15 via a pin 18.

The support member 11 having a positive coefficient of thermal expansion is made of GFRP (glass fiber reinforced plastic), which is made by winding continuous glass fiber many times in a long ring shape and solidifying it with epoxy resin or the like.
Two mutually parallel linear parts 11a and two semicircular retaining parts 11b at both ends are integrated.

The support member 12, which has a negative coefficient of thermal expansion, is made by winding continuous aromatic polyamide (aramid) fibers many times in a long ring shape and solidifying it with epoxy resin or the like, and has two mutually parallel linear parts 12a and , and two semicircular retaining portions 12b at both ends are integrated.

A preferred example of the aromatic polyamide fiber is Technora (registered trademark: manufactured by Kijin ■). The chemical name of this technora is copolyvaraphenylene 3-4'
It is oxydiphenylene terephthalide, and its chemical structure is shown in Figure 2.

This Technora also has a negative coefficient of thermal expansion, meaning that it contracts when heated and expands when cooled. Reinforced fiber made by hardening Technora with resin is abbreviated as TFRP.

GFRP and TFRP used in this example were prepared at room temperature (293K).
) to the boiling point of liquid nitrogen (77K), GFRP contracted and the shrinkage rate was 0.18%.
FRP was elongated and the elongation rate was 0.07%. In other words, the thermal expansion coefficient (linear expansion coefficient) of GFRP is +0.18%,
The coefficient of thermal expansion (coefficient of linear expansion) of TFRP is -0.07%.

Each semicircular retaining part 11b of the support member 11 made of GFRP with a positive coefficient of thermal expansion rotates in the groove of one grooved ring 17 of the intermediate joint 13 and the groove of the grooved ring 19 of the end joint 14. Each semicircular retaining portion 12b of the supporting member 12 made of TFRP and having a negative coefficient of thermal expansion is freely engaged with the groove of the other grooved ring 17 of the intermediate joint 13 and the grooved ring of the end joint 15. It is rotatably engaged in the groove 19.

Intermediate joint 13. End joint 14.15. The support when liquid helium is injected, taking into account the amount of contraction of the grooved ring 17.19, the temperature distribution in the length direction of the support A, and the coefficient of thermal expansion of both support members 11.12. The dimensions of both support members 11 and 12 are determined so that the total AI shrinkage is at an appropriate value, and the supports are not subject to tensile stress or loosening, and furthermore, the cryogenic container is not moved.

In addition, liquid helium container 2. The liquid nitrogen container 5° vacuum container 3 contracts radially and axially.

If the materials are the same, the amount of contraction is greatest in the liquid helium container 2, which has the lowest temperature. Considering this point, support A
Assuming that there is no expansion or contraction of 1, liquid helium container 2
may rise slightly.

In order to prevent this lifting, it is better for the support A+ to extend a little by an amount that cancels out the lifting. In this case, the supporting member 12 made of TFRP with a negative coefficient of thermal expansion may be set to be slightly longer.

As described above, even if the support A1 is cooled by injection of liquid helium, tensile stress or loosening does not occur in the support AI, and the liquid helium container 2. Liquid nitrogen container5. Each center position of the vacuum container 3 can be maintained at a predetermined reference position, and the center position of the superconducting magnet 1 in the liquid helium container 2 can be kept in a state of matching with the predetermined reference position.

That is, the uniformity of the central magnetic field can be maintained with high accuracy, and the liquid helium container 2.1 nitrogen container 5. The vacuum containers 3 are prevented from coming into contact with each other, and a good insulation state between the containers can be maintained.

Furthermore, the tensile stress and loosening applied to the support A1 itself can be made substantially zero, thereby avoiding breakage of the support A1. Further, it is not necessary to increase the cross-sectional area of the support member A in order to increase the tensile stress resistance, but rather the cross-sectional area of both support members 11 and 12 can be reduced to improve the heat insulation properties.

Department, 111 Next, a second embodiment will be described based on FIG. 5.

The support member 21 made of GFRP and having a positive coefficient of thermal expansion consists of one straight part 21a and ring parts 21b integrally formed at both ends of this straight part 21a, and each ring part 21b has a filler metal 21c. is fitted and fixed. Further, the supporting member 22 made of TFRP and having a negative coefficient of thermal expansion is also made of one linear portion 22a.
and ring portions 22b integrally formed at both ends of this straight portion 22a, each ring portion 22b has a filler metal 22c.
is fitted and fixed.

These support members 21 and 22 are also made of continuous fibers wound many times in a long ring shape, and have a straight portion 21a.

They are made to contact each other at 22a and hardened with epoxy resin or the like. The material of the fillers 21c and 22c is stainless steel.

The fillets 21c, 22c of both support members 21.22 are rotatably connected to the intermediate joint 23 via the pin 26, and the fillets 21c, 22c of both support members 21.22 are connected to the end joint 24.25C. 22c are rotatably connected via pins 28 to constitute a support At.

nth Ω1 square Next, a third embodiment will be described based on FIG. 6.

Support member 31 made of GFRP and having a positive coefficient of thermal expansion and TFR
The support member 32 made of P and having a negative coefficient of thermal expansion is configured in a rod shape,
Male screw portions 31a and 32a are formed at both ends of each. Both the intermediate joint 33 and the end joints 34 and 35, which are made of stainless steel, are rod-shaped, and female threaded portions 33a, 34a, and 35a are formed in each of them.

Connect each male threaded portion 31a of the support member 31 to the intermediate joint 33.
female threaded portion 33a of and female threaded portion 34 of end jig 34
a, and each male threaded portion 32 of the support member 32.
A is screwed into the female threaded portion 33a of the intermediate joint 33 and the female threaded portion 35a of the end joint 35 to form the support A.

In addition, in each of the above examples, a support member made of TFRP is used as a support member having a negative coefficient of thermal expansion, but the present invention is not limited to this, and other fiber-reinforced members having a negative coefficient of thermal expansion are used. It may also be made of plastic. Further, although a support member made of GFRP is mentioned as a support member having a positive coefficient of thermal expansion, the present invention is not limited thereto, and may be made of other fiber-reinforced plastics having a positive coefficient of thermal expansion. ,or,
Since the support member with a negative coefficient of thermal expansion is made of fiber-reinforced plastic and has heat insulating properties, the support member with a positive coefficient of thermal expansion may be made of metal.

G. Effect of invention According to this invention, the following effects are exhibited.

Since the support for the cryogenic container is constructed as a series connection of a supporting member with a positive coefficient of thermal expansion and a supporting member with a negative coefficient of thermal expansion, the When the support is cooled, while the support member with a positive coefficient of thermal expansion contracts, the support member with a negative coefficient of thermal expansion expands.
By subtracting the amount, changes in the length of the support as a whole can be suppressed.

Therefore, the tensile stress and compressive stress applied to the support itself can be sufficiently reduced to avoid breakage of the support. As a result, there is no need to increase the cross-sectional area of the support in order to increase the tensile stress resistance, and deterioration of heat insulation properties can be avoided. Further, it is possible to prevent the center position of the cryogenic container from being displaced by twisting force immediately after the cryogenic liquid is injected.

In addition, if the cryogenic container is used to cool the superconducting magnet of a nuclear magnetic resonance tomography device, the displacement of the center position of the superconducting magnet itself inside the cryogenic container is suppressed, so the uniformity of the central magnetic field is It can be maintained with high precision, and a good thermal insulation state can be maintained by preventing the cryogenic container from coming into contact with the external heat shield or the like.

[Brief explanation of the drawing]

1 to 4 relate to a first embodiment of the present invention, in which FIG. 1 is a front view of a partially broken support of a cryogenic container, FIG. 2 is a diagram showing the chemical structural formula of Technora, Figure 3 (A) shows a nuclear magnetic resonance tomography device (NM) as an example of a target for use.
3(B) is a longitudinal sectional front view showing the R-CT), FIG. 4(A) is a longitudinal sectional front view showing another example of the nuclear magnetic resonance tomography apparatus, and FIG. ) is its vertical side view. FIG. 5 is a partially cutaway front view of the cryogenic container support of the second embodiment, and FIG. 6 is a partially cutaway front view of the cryogenic container support of the third embodiment. FIG. 7 is a partially cutaway front view of a conventional support for a cryogenic container. 11, 21.31... Support member 12 with a positive coefficient of thermal expansion,
22.32...Supporting member with negative coefficient of thermal expansion Fig. 3 Fig. 4 Fig. 6 Fig. 7

Claims (1)

[Claims] (1) A support for a cryogenic container comprising a support member with a positive coefficient of thermal expansion and a support member with a negative coefficient of thermal expansion connected in series.