JPH0653036A - Thermal insulant for low temperature - Google Patents

Abstract

PURPOSE:To obtain thermal insulant for low temperature wherein the strength of a drawn member is improved and drastic breakdown behavior hardly occurs, by constituting a rod of a retaining member as compound material wherein the center is a drawn member of A-FRP (alumina fiber reinforced plastic), and the outer periphery is covered by winding a cloth of C-FRP (carbon fiber reinforced plastic). CONSTITUTION:Cloth 6 of C-FPR is wound around a round rod 5 of a drawn member of A-FRP. The center drawn member 5 of A-FRP is formed by drawing out alumina fiber and forming a rod while epoxy resin is made matrix, and the cloth 6 wherein carbon fiber is knitted into orthogonal cross is wound around the rod. Thereby the stress in the radius direction and the circumsference derection which is generated when the rod is compressed is borne by the C-FRP cloth, so that the strength becomes large and the unloading behavior at the time of breakdown gently changes. Hence thermal insulant wherein thermal insulation properties and strength at a low temperature are improved can be obtained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a heat insulating material for a superconducting magnet device.

[0002]

2. Description of the Related Art A superconducting magnet device for driving, guiding, and propulsing a vehicle used in a linear motor car or the like contains a superconducting coil together with a refrigerant in a low-temperature inner tank container. In order to maintain it, the inside of the container is vacuum-insulated so that it is suspended and held by a supporting device. At this time, the inner vessel container supporting device in the outer vessel for hanging is required to have a heat insulating property in order to prevent heat from entering from the outside, and further needs mechanical strength to support the electromagnetic force of the coil.

As described above, a large load is applied to the heat insulating support device of the superconducting coil, and at the same time, heat insulation from ambient temperature ranging from 4K to room temperature must be measured.

Therefore, C-FRP (carbon fiber reinforced plastic), which has a high strength at low temperature and a small thermal conductivity, has been conventionally used as a material for the supporting device.

By the way, FRP (fiber reinforced plastic)
The thermal conductivity of is from 4K to 40K according to the characteristic diagram (Fig. 4).
Up to C-FRP (carbon fiber reinforced plastic), 40
It can be seen that the thermal conductivity of G-FRP (glass fiber reinforced plastic) is small from K to 300K.

Therefore, conventionally, as shown in FIG. 3, an inner tank 1 containing a superconducting coil cooled to 4K with a liquid helium refrigerant, and a radiation shield plate having the outside of the inner tank cooled to 77K with liquid nitrogen are used. The support structure for the inner tank of the superconducting magnet, which consists of the outer tank 2 which is covered and housed, is composed of a thin cylinder 3 made of C-FRP on the inner tank side and a solid round bar 4 made of G-FRP on the outer tank side. It has a double structure of support. But such a 2
Since the double structure is complicated and various problems in design, manufacturing, and quality are likely to occur, a simpler structure is desired.

[0007]

By the way, as can be seen from FIG. 4, A-FRP (alumina fiber reinforced plastic) is used.
Has a low thermal conductivity in the entire range of 4K to 300K. Therefore, using A-FRP, the above supporting structure (in the case of Fig. 3)
However, there are the following strength problems.

Alumina fibers are relatively easily broken when fibers are piled up and woven. In other words, the strength when pulling the fibers themselves is high, but when the fibers rub against each other, they are brittle. Therefore, a unidirectionally drawn material of alumina fiber is used as the load supporting rod. However, when the load is supported in the compression direction, buckling of the fiber easily occurs.

The object of the present invention is to obtain a heat-insulating support material that solves the above-mentioned drawbacks.

[0010]

[Means for Solving the Problems] A rod of a supporting material is made of an A-FRP drawn material at the center thereof and a composite material in which the outer periphery of the rod is covered with a cloth of C-FRP.

[0011]

With this construction, the strength of the drawn material is improved, and a dramatic fracture behavior occurs, which is annoying.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described based on the embodiments shown in FIGS.

A-FRP (alumina fiber reinforced plastic)
It is configured by winding a cross 6 made of C-FRP around a round bar 5 made of a drawn material.

As the center drawing material 5 of A-FRP, alumina fibers are used as a rod having a drawing diameter of 14 mm while using an epoxy resin as a matrix, and a 1 mm thick cloth 6 woven with carbon fibers into an orthogonal cloth is wound. In this way, the C-FRP cloth bears the radial and circumferential stresses that occur when the rod is compressed. As a result, in the case of the same size configuration, the strength of the product of the present invention is larger than that of the conventional C-FRP or G-FRP, and the unloading behavior at the time of breakage changes gently.

FIG. 2 shows the load vs. flexural relationship characteristics of the rod of the present invention having such a structure and the rod of the conventional structure in the compression fracture test.

Even when the C-FRP cloth is wound around the C-FRP drawing material, the contact pressure at the interface is higher in the present invention in which the cloth is wound around the A-FRP drawing material. This is due to the difference in linear expansion coefficient between the two. Therefore, the latter which is the product of the present invention has a slightly higher strength.

By using the heat insulating support material according to the present invention as described above, the support device is simplified and the performance is improved.

[0018]

According to the present invention, a heat insulating material having improved heat insulating properties and strength at a lower temperature than before can be obtained, and a superconducting magnet having improved reliability can be obtained.

[Brief description of drawings]

FIG. 1A is a sectional front view and FIG. 1B is a top view of a heat insulating material according to the present invention.

FIG. 2 is a load-deflection characteristic curve between a heat insulating material according to the present invention and a conventional product,

FIG. 3 is a front sectional view of a conventional heat insulating support device,

FIG. 4 is a characteristic curve diagram of various fiber reinforced plastics.

[Explanation of symbols]

 1 ... Inner tank 2 ... Outer tank 5 ... A-FRP drawing material 6 ... C-FRP cloth

Claims (1)

[Claims] 1. A low temperature heat insulating material comprising a C-FRP (carbon fiber reinforced plastic) cloth wound around an A-FRP (alumina fiber reinforced plastic) extraction rod.