JPH04341694A - Structure of vacuum heat insulation box body - Google Patents

Abstract

PURPOSE:To improve the durability of a vacuum heat insulation box body against a repeated thermal stress. CONSTITUTION:A bend 19, increasing a thermal resistance in a direction for a membrane from the inside of an inner box 1 is formed in a membrane neighboring part of this inner box 1 in a vacuum insulation box body. A heat insulator 20 and a deformation checking member 21 limiting any deformation of the bend 19 to the fixed range are installed in an inner part of the bend 19. Accordingly, even if temperature in the inner box 1 goes up, the bend 19 checks any temperature rise in a membrane 5, making a stress in the membrane 5 smaller, whilethe deformation checking member 21 limit any deformation in the bend 19 to the extent of less than the specified value. With this constitution, service life in the box body it thus prolonged.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of a vacuum insulated box, and more particularly to the structure of a vacuum insulated box suitable for accommodating high temperature items.

0002

2. Description of the Related Art Conventional vacuum insulated boxes, for example as shown in FIG. A vacuum heat insulating layer 4 is formed between the outer box 1 and the outer box 2. In addition, the vacuum insulation layer 4
The end wall 6 of the inner box 1 and the opening side periphery of the outer box 2 are connected to each other by a membrane 5 that seals the inner box 1 and the outer box 2. A vacuum insulated container is constructed by covering a flange 7 provided on the open peripheral edge of the outer box 2 with a heat insulating lid 8. The vacuum heat insulating layer 4 is filled with a powder heat insulating material. The membrane 5 is made of a thin plate, and is designed to reduce heat radiation due to thermal conduction and maintain heat insulating properties.

0003

[Problems to be Solved by the Invention] However, when high-temperature items are housed in the conventional vacuum insulated box described above, the temperature of the inner box 1 rises and expands by a length Δl toward the membrane side, as shown in FIG. . In the illustrated end structure, deformation concentrates on the membrane 5, and a large stress is generated in the illustrated portion a.

The cause will be explained with reference to FIG. Inner box 1
expands toward the membrane side by Δl, and as a result, as shown in FIG.
As shown in (a), compressive stress and tensile stress due to bending are generated on the inner and outer surfaces of the membrane at section a in FIG. 10, respectively. Also, inner box 1 and membrane 5
As the expansion in the circumferential direction is restrained by the outer box 2, compressive stress is generated in the cross section of section a in FIG. 10, as shown in FIG. 11(b). Therefore, as shown in FIG. 11(c), a stress that is the sum of the stresses shown in FIG. do. As a result, if the inner box 1 is repeatedly heated and cooled, there is a risk that this part a will be damaged due to thermal stress, resulting in a problem that the life span, that is, the durability of the vacuum insulated box body will be reduced.

SUMMARY OF THE INVENTION It is an object of the present invention to solve these problems, alleviate the stress acting on the membrane, and improve the life of the vacuum insulation box.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present invention forms a double-structured box body having an opening on one side by an inner box and an outer box, and provides a space between the inner box and the outer box. In a vacuum insulated box body in which a vacuum insulating layer is formed on the inner box and the opening side periphery of the inner box and the outer box are connected by a membrane that seals this vacuum insulating layer, a membrane is applied from the inside to a portion of the inner box near the membrane. A curved portion that increases the thermal resistance of the inner box in the direction of

[0007]

[Operation] In the vacuum insulation box having the above structure, since a curved portion is formed in the inner box near the membrane, the heat transfer path in that portion becomes longer and the thermal resistance increases. Therefore, the temperature of the opening-side peripheral portion of the inner box and the membrane decreases, and the compressive stress (FIG. 11(b)) due to expansion of the inner box and membrane in the circumferential direction decreases. Further, since the deformation suppressing member is provided inside the curved portion, deformation of the curved portion is restricted, and the stress generated in the curved portion is equal to or lower than the stress generated in the membrane. As a result, the life of the vacuum insulation box against thermal stress is improved. Further, the heat insulating material inside the curved portion eliminates air gaps to prevent air convection, and also increases the thermal resistance of the heat bridge portion to reduce the amount of heat dissipated. Therefore, the insulation performance of the vacuum insulation box is improved.

[0008]

【Example】

(Example 1) As shown in FIGS. 1 and 2, the end wall 6 of the inner box 1 is provided with a curved portion 19 in the vicinity of the membrane to increase the thermal resistance in the direction from the inside of the inner box 1 toward the membrane. , are formed so as to protrude into the vacuum insulation layer 4. The inside of the curved part 19 is filled with a heat insulating material 20, and as shown in FIG. There is. Further, by providing a pressing member 22 such as a wire mesh on the curved portion 19, the heat insulating material 20 and the deformation suppressing member 21 are supported so that they do not escape from the curved portion 19. As the heat insulating material 20, rock wool, glass wool, ceramic wool, etc. are suitable. Further, the deformation suppressing member 21 is formed into a saddle-shaped frame as shown in FIG. 4(a), or in a block shape as shown in FIG. 4(b). The materials used include calcium silicate molded bodies and heat insulating casters, which have pressure resistance and a certain degree of heat insulation.

[0009] When high-temperature items are housed in the vacuum insulated box having the above structure, the temperature of the inner box 11 rises. At this time, the curved portion 19 extends the heat transfer path of the end wall 6, increasing its thermal resistance. Therefore, even if the temperature of the inner box 1 increases, the temperature of the opening-side peripheral portion of the end wall 6 and the membrane 5 decreases compared to the case where the curved portion 19 is not formed. Therefore, compressive stress (
(Fig. 11(b)) decreases.

Furthermore, a deformation suppressing member 2 is provided inside the curved portion 19.
1 is inserted, the expansion of the inner box 1 toward the membrane side due to temperature rise is caused by the curved portion 19 as shown in FIG.
is absorbed by the deformation amount ΔL of the membrane 5 and the deformation amount ΔM of the membrane 5. Therefore, the amount of deformation ΔM of the membrane 5 is the amount of deformation when the curved portion 19 is not formed, that is, Δl in FIG.
As a result, the bending stress (FIG. 11(a)) generated at the edge A due to the expansion of the inner box 1 is reduced. At the same time, by appropriately setting the allowable amount of deformation ΔL in the curved portion 19, the stress generated in the curved portion 19 can be limited to the same level as or less than the stress generated in the membrane 5. Note that, depending on the case, the deformation suppressing member 21 may be made thicker so that the amount of deformation ΔL is zero.

As a result of the above, the thermal stress generated in the vacuum insulated box is reduced, and the life of the vacuum insulated box against repeated thermal stress is improved. Further, the heat insulating material 20 filled inside the curved section 19 eliminates voids within the curved section 19 to prevent air convection, and also increases the thermal resistance of the heat bridge section to reduce the amount of heat dissipated. Therefore, it is also possible to improve the insulation performance of the vacuum insulation box.

Regarding the adiabatic boundary shown in the shaded area in FIG. 5, the length X of the curved portion 19 and the temperature TA of the edge A of the membrane 5
Figure 6 shows the results obtained by one-dimensional heat transfer calculation of the relationship between
This is shown in the graph below. However, in FIG. 5, the length of the end wall 6 of the inner box 1 is made equal to the length L of the membrane 5, the temperature TB of the inner part B of the end wall 6 is set to 300 °C, and the length of the membrane 5 is set equal to the length L of the membrane 5.
The temperature TC of the side edge C of the outer box was set to 0°C. As can be seen from FIG. 6, the length X of the curved portion 19 is the length L of the membrane 5.
, the temperature TA at the edge A is significantly reduced from 150° C. without the curved portion 19 to 100° C. As a result, compressive stress is generated at edge A (Fig. 11
(b)) decreases to about 2/3. Note that the curved portion 19
In order to make the length X of 2L or more, two or more curved portions 19 are formed to cope with this problem. (Example 2) As shown in FIG. 7, the curved portions 19 in Example 1 are formed at two locations on the end wall 6, and the length of the curved portions 19 is doubled. If this is the case, compressive stress will occur at the edge A of the membrane 5 (Fig. 11(b)).
It is possible to significantly reduce the amount of heat and improve the heat insulation performance. (Example 3) As shown in FIG. 8, the membrane 5 in Example 1 is made into a three-layer bellows structure to facilitate deformation. This causes thermal stress generated at edge A (Fig. 11
(c) ) can be reduced.

[0013]

As described above, according to the present invention, the curved portion is formed in the inner box near the membrane to increase the thermal resistance in the direction from the inside of the inner box to the membrane.
Even if the temperature of the inner box increases due to the contents, the temperature increase at the connection between the membrane and the inner box is suppressed, and the stress generated can be reduced. In addition, the deformation suppressing member provided inside the curved section limits the deformation of the curved section to a certain range and averages the stress generated in the curved section and membrane, so the stress generated in the curved section is limited to a certain value or less. Can be done. As a result of the above, the durability of the vacuum insulation box against thermal stress can be improved.

Furthermore, the heat insulating material provided inside the curved part eliminates voids and prevents air convection, and also increases the thermal resistance of the heat bridge part and reduces the amount of heat dissipation, which improves the heat insulation performance of the vacuum insulated box. can be improved.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a vacuum insulation box according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a main part in FIG. 1.

FIG. 3 is a sectional view of a modification of the portion shown in FIG. 2;

FIG. 4 is a perspective view of the deformation suppressing member in FIG. 3;

FIG. 5 is an explanatory diagram of an adiabatic boundary modeled for performing heat transfer calculations for the vacuum insulated box shown in FIG. 1;

6 is a graph showing the relationship between the length of the curved portion and the temperature of the membrane, which is determined by heat transfer calculation based on the model of FIG. 5. FIG.

FIG. 7 is a sectional view of essential parts of a vacuum insulation box according to another embodiment of the present invention.

FIG. 8 is a sectional view of a main part of a vacuum insulation box according to still another embodiment of the present invention.

FIG. 9 is a sectional view showing an example of a conventional vacuum insulation box.

10 is an enlarged sectional view showing the end structure of the conventional vacuum insulation box shown in FIG. 9. FIG.

FIG. 11 is an explanatory diagram of stress generated in a membrane in a conventional vacuum insulation box.

[Explanation of symbols]

1 Inner box 2 Outer box 3 Opening 4 Vacuum insulation layer 5 Membrane 19 Curved part 20 Insulation material 21 Deformation prevention member

Claims (1)

[Claims] [Claim 1] An inner box and an outer box form a double-structure box with an opening on one side, a vacuum insulation layer is formed between the inner box and the outer box, and this vacuum insulation layer is sealed. In a vacuum insulated box body in which the opening side peripheries of an inner box and an outer box are connected by a membrane, a curved portion is provided in a portion of the inner box near the membrane to increase the thermal resistance of the inner box in the direction from the inside to the membrane. 1. A structure of a vacuum insulation box body, characterized in that a heat insulating material and a deformable member for restricting deformation of this curved part to a certain range are provided inside the curved part.