JP4804221B2 - Superconducting magnet device - Google Patents

Description

  The present invention relates to a superconducting magnet device used in a magnetically levitated railway, and more particularly to a radiant heat shield plate for an inner tank containing a superconducting coil.

  In a superconducting magnet device used in a conventional magnetic levitation railway, a radiant heat shield plate using a reinforced plastic material (CFRP) in which carbon fiber is impregnated with resin as a material that is lightweight, has high electrical resistance, and high thermal conductivity. (For example, refer to Patent Document 1).

Japanese Patent Laid-Open No. 6-232461 (2nd page)

  In the conventional superconducting magnet device, the temperature distribution of the radiant heat shield plate is kept uniform by mainly improving the thermal conductivity, and the amount of heat penetration into the inner tank is reduced. That is, the temperature distribution of the liquid nitrogen (LN2) cooling pipe, the metal heat shield plate, and the CFRP heat shield plate constituting the radiant heat shield plate is made uniform.

  However, in order to ensure rigidity and heat conduction, the difference between the thermal expansion coefficient of the CFRP heat shield plate and the LN2 cooling pipe in which an alloy such as aluminum or copper is used and the metal heat shield plate is significant, and the superconducting magnet When the device was cooled to cryogenic temperature, it was necessary to pay attention to the thermal stress resulting from the differential thermal expansion.

  The present invention has been made to solve the above-described problems, and improves the reliability of the superconducting magnet device by bringing the thermal expansion coefficient of the CFRP heat shield plate closer to the thermal expansion coefficient of the LN2 cooling pipe. For the purpose.

The superconducting magnet device according to the present invention includes a superconducting coil, an inner tank that houses the superconducting coil at a cryogenic temperature, a cooling pipe that encloses liquid nitrogen for indirectly cooling the inner tank, and the cooling In the superconducting magnet apparatus including a piping and a radiant heat shield plate that covers the inner tank and suppresses heat intrusion, the radiant heat shield plate includes a first prepreg sheet and a second fiber oriented at ± 60 degrees . Ri consists of carbon fiber reinforced plastic formed by laminating a prepreg sheet, said first prepreg sheet, the elastic modulus than said second prepreg sheet, the thermal conductivity are both large, the second prepreg sheet It is characterized by being laminated on the outside .

  According to the present invention, the difference in thermal expansion of the LN2 cooling pipe, the metal heat shield plate, and the CFRP heat shield plate constituting the radiant heat shield plate is reduced, and the reliability against thermal stress during cooling of the superconducting magnet device is improved. Can do.

Embodiment FIG. 1 is a schematic diagram of a magnetically levitated railway to which a superconducting magnet apparatus of the present invention is applied.
In FIG. 1, the superconducting magnet device 1 is attached to both sides of a carriage 3 of a vehicle 2 and electromagnetically acts with a ground coil 5 installed on a U-shaped guideway 4 so that the vehicle 2 floats. ing.

FIG. 2 is a cross-sectional view of the superconducting magnet device of the present invention.
In FIG. 2, the superconducting magnet device 1 is filled with a coolant such as liquid helium in an inner tank 7 that houses a superconducting coil 6 and cooled, and further, a radiant heat shield plate 8 is used to suppress heat intrusion from the outside. The tank 7 is covered and bonded and supported by a load supporting material 10 to an outer tank 9 whose inside is vacuum insulated.

  This radiant heat shield plate 8 is a reinforced plastic material (hereinafter referred to as CFRP) in which carbon fiber is impregnated with resin as a material having a light weight, high electrical resistance, and high thermal conductivity for the purpose of suppressing eddy current heat generation due to vibration in a magnetic field. (Abbreviated).

  FIG. 3 shows the configuration of the radiant heat shield plate 8. In FIG. 3, a CFRP heat shield plate 11 constituting the entire surface of the radiant heat shield plate 8 is provided with a metal cooling pipe 12 filled with a coolant such as liquid nitrogen, and a metal heat shield such as Al. It is cooled via the plate 13 so that the temperature distribution is uniform.

  The cooling pipe 12 and the metal heat shield plate 13 are fixed by welding or the like, and the metal heat shield plate 13 and the CFRP heat shield plate 11 are joined by riveting. Thermal stress occurs when there is a large difference in the linear expansion coefficient.

  The linear expansion coefficient of the cooling pipe 12 made of copper or aluminum alloy and the metal heat shield plate 13 is 10-25 ppm / K, and the difference from the linear expansion coefficient of the CFRP heat shield plate 11 of −1 ppm / K is remarkable. Thus, thermal stress is generated every time the superconducting magnet device 1 is cooled and heated, and there is a possibility that particularly severe portions of the thermal stress occur in the joint portion of the cooling pipe 12.

  Therefore, for example, as shown in FIG. 4, as the CFRP heat shield plate 11, the first prepreg sheet 14 made of carbon fiber having an elastic modulus of 850 GPa or more and a thermal conductivity of 300 W / m · K or more is formed on the outside and elastic on the inside. Second prepreg sheets 15 made of carbon fibers having a rate of less than 850 GPa and a thermal conductivity of less than 300 W / m · K were laminated with a fiber orientation angle (θ) of ± θ, and molded and processed.

  FIG. 5 shows the relationship between the fiber orientation angle and the linear expansion coefficient of the CFRP heat shield plate 11 laminated, molded and processed as described above. As a result, it can be seen that the linear expansion coefficient of the heat shield plate 11 made of CFRP increases as the fiber orientation angle approaches 90 degrees.

On the other hand, FIG. 6 shows the relationship between the fiber orientation angle and the elastic modulus of the CFRP heat shield plate 11 laminated, molded and processed as described above. In CFRP laminated at each fiber orientation angle (± 45 to 75 degrees), (1) θ = 0 degree (pipe direction), (2) θ = 45 degrees, (3) θ = 90 degrees in three directions of elastic modulus Is shown.
As a result, in (3), the elastic modulus increases as the fiber orientation angle approaches 90 degrees, but in (1) and (2), the elastic modulus decreases as the fiber orientation angle approaches 90 degrees, and the fiber orientation If the angle exceeds 60 degrees, the CFRP heat shield plate 11 cannot secure the same rigidity (10 GPa) as the conventional one.

  From the above results, the first prepreg sheet 14 and the second prepreg sheet 15 are laminated at a fiber orientation angle of 60 degrees, and molded and processed, so that the conventional prepreg sheet 14 is aligned in all directions (1) to (3). The CFRP heat shield plate 11 having a linear expansion coefficient of 10 ppm / K which is substantially equal to that of the cooling pipe 12 can be obtained.

  For example, when the superconducting magnet device is cooled to a very low temperature, the cooling pipe 12 and the CFRP heat shield plate 11 are at −196 ° C., and the heat shrinkage that occurs between the cooling pipe 12 and the conventional CFRP heat shield plate 11. Although the difference was 0.00424, the heat shrinkage difference generated between the cooling pipe 12 and the CFRP heat shield plate 11 of the present embodiment is 0.00178, and the heat shrinkage difference is reduced to the conventional CFRP heat shield. Compared to the case of using a plate, it can be reduced by about 60%, and the generated thermal stress can also be reduced by about 60%.

  In addition, the superconducting magnet device is returned to room temperature for maintenance and inspection, and after the completion, the same heat is applied between the cooling pipe 12 and the CFRP heat shield plate 11 every time the cooling / heating process is performed. Although stress was generated, the thermal stress repeatedly generated can be reduced by about 60% by using the CFRP heat shield plate 11 of this embodiment.

  As described above, in the present embodiment, the second prepreg sheets 15 are oriented and laminated one layer at a time. However, according to the composite rule, there is no characteristic difference when laminated in line symmetry. If the second prepreg sheet 15 having a thickness (fiber density) twice or three times that of the first prepreg sheet 14 is oriented and laminated, the same CFRP heat shield plate 11 is used. Work efficiency can be improved.

As described above, the superconducting magnet device according to the embodiment of the present invention has the same rigidity as the conventional one, and has a linear expansion coefficient substantially equal to that of the cooling pipe 12 and the metal heat shield plate 13, so that Even when it is cooled and heated, the thermal stress generated at each joint surface is alleviated and the reliability can be improved.

1 is a schematic sectional view of a magnetically levitated railway according to an embodiment of the present invention. It is sectional drawing of the superconducting magnet apparatus of embodiment of this invention. It is a block diagram of the radiation heat shield board of embodiment of this invention. It is a block diagram of the heat shield board made from CFRP of embodiment of this invention. It is the figure which showed the relationship between the fiber orientation angle of the CFRP heat shield board of embodiment of this invention, and a linear expansion coefficient. It is the figure which showed the relationship between the fiber orientation angle and elastic modulus of the CFRP heat shield board of embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Superconducting magnet apparatus, 2 Vehicle, 3 cart, 4 Guide way, 5 Ground coil, 6 Superconducting coil, 7 Inner tank, 8 Radiation heat shield board, 9 Outer tank, 10 Load support material, 11 CFRP heat shield board, 12 Cooling Piping, 13 metal heat shield plate, 14 first prepreg sheet, 15 second prepreg sheet.

Claims (2)

A superconducting coil;
An inner tank for storing the superconducting coil at a cryogenic temperature;
A cooling pipe enclosing liquid nitrogen for indirectly cooling the inner tank;
In the superconducting magnet device provided with the cooling pipe and the radiant heat shield plate that covers the inner tank and suppresses heat intrusion,
The radiant heat shield plate is
Ri from ± 60 ° to the first prepreg sheet and carbon fiber reinforced plastic formed by laminating a second prepreg sheets fiber orientation formed,
The first prepreg sheet is
The superconducting magnet apparatus , wherein both the elastic modulus and the thermal conductivity are larger than those of the second prepreg sheet, and are laminated on the outer side of the second prepreg sheet . Radiant heat shield plate
A first prepreg sheet made of carbon fiber having an elastic modulus of 850 GPa or more and a thermal conductivity of 300 W / m · K or more is laminated on the outside;
A second prepreg sheet made of carbon fiber having an elastic modulus of less than 850 GPa and a thermal conductivity of less than 300 W / m · K is made of a carbon fiber reinforced plastic laminated and processed inside. The superconducting magnet device according to 1.

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