JPH05338677A - Thermal extension-absorbing structure of vacuum heat-insulating box - Google Patents

Abstract

PURPOSE:To prevent an excess stress from being brought about in a membrane due to the thermal extension of the inner box of a vacuum heat-insulating box and increase the durability of vacuum heat-insulating box. CONSTITUTION:The end face of the opening side of a vacuum heat-insulating layer 13 between the outer box 11 and the inner box 12 is closely sealed with a membrane and a heat-insulating cover 17 is provided at the opening 16. A circular bend 18 is attached to be freely extensible to the superimposed part with the heat-insulating cover 17 at the wall body 15 of the opening in the inner box 12 in order to absorb the thermal expansion at the opening side of inner box 12 by means of the deformation of the membrane 14 and the bend 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal expansion / contraction structure for a vacuum insulation box which keeps the internal temperature constant, and in particular, the thermal expansion / contraction of a vacuum insulation box when the interior is hot and its thermal expansion is large. Regarding absorption structure.

[0002]

2. Description of the Related Art A conventional vacuum heat insulating box of this type is made of metal such as stainless steel and has a vacuum heat insulating layer 3 between an outer box 1 and an inner box 2 as shown in FIG. The end surface of the vacuum heat insulating layer 3 on the opening side is sealed with a membrane 4, and a heat insulating lid 7 with a flange is provided in the opening 6 formed by the opening wall body 5 of the inner box 2. The vacuum heat insulating layer 3 has a fibrous shape inside the vacuum state,
It is filled with a heat insulating material such as powder and keeps the internal temperature of the inner box 2 constant. At that time, for example, the thermal expansion and contraction generated in the inner box 2 due to the high temperature inside is absorbed by the rear side of the box body by the expansion and contraction of the inner side portion of the inner box 2, and the other half is the inner box 2 Is absorbed by the expansion and contraction of the opening-side portion and deformation of the membrane 4.

[0003]

However, in the conventional vacuum insulation box body described above, when the internal temperature is raised to a high temperature, the membrane 4 is formed by the two-dot chain line in FIG. 7 due to the thermal expansion of the opening side portion of the inner box 2. It deforms as shown, and excessive stress occurs at point A at the corner. Therefore, when heating and cooling are repeated, there is a problem that the membrane 4 is damaged and the vacuum of the vacuum heat insulating layer 3 is broken, and the life of the heating and cooling cycle is shortened.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to solve the above problems and to relieve the excessive stress generated in the membrane to prolong the life of the vacuum insulation box.

[0005]

In order to achieve the above object, the present invention has a vacuum heat insulating layer between an outer box and an inner box, and the opening side end surface of this vacuum heat insulating layer is sealed with a membrane, In a vacuum heat insulation box body provided with a heat insulation lid in the opening, in the portion of the wall of the opening of the inner box that overlaps with the heat insulation lid,
An annular curved portion protruding toward the vacuum heat insulating layer is provided so as to be expandable and contractible, and the ratio of the depth to the width of the curved portion is 1
It is / 4 or more and 1/2 or less.

[0006]

With this structure, when the internal temperature is raised to a high temperature, half of the thermal expansion of the inner box is absorbed by the deformation of the inner side portion of the inner box, and the other half is absorbed by the opening side portion of the inner box. It is thermally expanded and absorbed by the deformation of the membrane and the curved portion. In this way, half of the thermal expansion of the inner box is absorbed by the membrane and the curved portion, and the ratio of the depth and width of the curved portion is 1
Since it is set to / 4 or more and 1/2 or less, the stress generated in the curved portion and the stress generated in the membrane are substantially balanced and small, so both stresses are significantly reduced from the stress of the conventional membrane. , The life for repeated heating is extended. If the ratio is less than 1/4, the stress absorbing effect of the bending portion becomes weak, and if it exceeds 1/2, a larger stress than the membrane acts on the bending portion, and the bending portion is damaged. It will be easier. Since the curved portion is provided in a portion of the wall of the opening of the inner box that overlaps with the heat insulating lid, the curved portion has little influence on the end heat characteristics of the vacuum heat insulating layer.

[0007]

1 to 3 show an embodiment of the present invention. FIG. 1 is a cross-sectional view of a vacuum heat insulating box body to which the heat expansion and contraction absorbing structure of the present invention is applied. The vacuum heat insulation box body shown in this figure has the same kind of structure as the conventional one shown in FIG. 6, and has a vacuum heat insulation layer 13 between an outer box 11 and an inner box 12 made of metal such as stainless steel. An end face of the vacuum heat insulating layer 13 on the opening side is sealed with a membrane 14, and a flanged heat insulating lid 17 is provided in an opening 16 formed by an opening wall body 15 of the inner box 12.

A heat insulating lid 17 on the wall 15 at the opening of the inner box 12
An annular curved portion 18 projecting toward the vacuum heat insulating layer 13 is provided at an overlapping portion with the stretchable portion. As shown in FIG. 2, the curved portion 18 has a depth D formed to be 1/2 or less of the thickness T of the vacuum heat insulating layer 13, and has a depth D and a width W.
Is formed so that the ratio thereof to 1/4 to 1/2.
Further, as shown in FIG. 3, a rounded portion 19 having a radius of at least 10 mm is formed in the corner portion of the inner box 12 in the transverse section of the box body over the entire length including the opening wall body 15.

The vacuum heat insulating layer 13 is formed by filling a vacuumed inside with a heat insulating material such as fibrous or powdery material.
At the same time, the internal temperature of the inner box 12 is kept constant. In the vacuum insulation box body having such a structure, when the inner temperature of the inner box 12 is increased, half of the thermal expansion of the inner box 12 is absorbed by the deformation of the inner side portion of the inner box 12. The other half appears as thermal expansion of the opening side portion of the inner box 12, which is absorbed by the deformation of the membrane 14 and the curved portion 18. And
The maximum stress generated at the point A at the corner of the membrane 14 and the maximum stress generated at the point B at the skirt of the curved portion 18 due to these deformations is such that the ratio of the depth D of the curved portion 18 to the width W is 1/4. ~ 1/2
Balanced by limiting to. Since both stresses generated in the membrane 14 and the curved portion 18 are balanced as described above, both stresses are significantly reduced as compared with the stress of the conventional membrane. Moreover, since the rounded portions 19 are formed at the corners of the inner box 12, stress concentration at the corners is prevented. Therefore, the vacuum insulation box body has a significantly extended life for heating and cooling cycles, and the radius of the rounded portion 19 of the corner portion is 10 mm or more, which facilitates the forming process.

On the other hand, the curved portion 18 locally thins the thickness T of the vacuum heat insulating layer 13 at the deepest point P, but the curved portion 18 is formed in the central portion of the inner box 12 as in the comparative example of FIG. Since the temperature at the point P itself is lower than that in the case where it is provided and the depth D of the curved portion 18 is 1/2 or less of the thickness T of the vacuum heat insulating layer 13, the heat radiation loss from the curved portion 18 is reduced. Can be small.

In this embodiment, the membrane 14 is formed as one layer, but as another embodiment, as shown in FIG.
The membrane 14 may be formed to be expandable and contractible in a multi-layered bellows shape. Thereby, the stress of the membrane 14 can be further reduced.

In the above description, the case where the inner temperature of the inner box 12 is set to a high temperature has been described. However, even when the inner temperature is set to be lower than the outside temperature, the thermal expansion only changes to the thermal contraction, and the same as above. Produce the effect of.

Tables 1 and 2 show the results of comparison of stresses between the present invention and the conventional examples and the comparative examples, which were obtained by the present inventor by the FEM analysis method. Analysis conditions (common to Table 1 and Table 2) Material of vacuum insulation box SUS304 Internal size of inner box Width 1200 x Height 550 x Depth 160
0mm Membrane and wall thickness of opening 0.8mm Thickness of vacuum insulation layer 40mm Radius of radius of inner box corner 30mm Inner temperature of inner box 350 ℃ Outside temperature 20 ℃

[0014]

[Table 1] Table 1 shows a case where the membrane has a single layer, and a comparison is made between point A of the membrane of the present invention and point B of the curved portion (FIG. 2) when the stress at point A (FIG. 7) of the conventional example is 1. Indicates stress. As is apparent from Table 1, in the present invention, the stress of the membrane and the stress of the curved portion are balanced when D / W is 1/2, and both of these stresses are reduced to 69% of the stress of the conventional membrane. is doing. D / W is 1 /
When it is larger than 2, the stress of the curved portion becomes larger than the stress of the membrane, and the curved portion is easily damaged.

[0015]

[Table 2] Table 2 shows a case in which the membrane of the present invention was formed into a three-layer bellows shape (FIG. 4), and as a comparative example, a membrane having a three-layered bellows shape but omitting the curved portion of the present invention was analyzed. This Table 2 shows the comparative stresses at the points A and B of the curved portion of the membrane of the present invention when the stress at the point A of the comparative example membrane is 1. As can be seen from Table 2, in the present invention, the stress of the membrane and the stress of the curved portion are balanced when D / W is 1/4, and both of these stresses are reduced to about 70% of the stress of the comparative membrane. is doing. The stress of the comparative example membrane is reduced to 70% of the stress of the conventional example membrane.

[0016]

As described above, according to the present invention, half of the thermal expansion and contraction of the inner box can be absorbed by the deformation of the membrane and the curved portion, and the depth and width of the curved portion can be absorbed. By setting the ratio to be 1/4 or more and 1/2 or less, the stress generated in the curved portion and the stress generated in the membrane can be substantially balanced and reduced, so that the stress in both the deformed portions can be reduced in the conventional membrane. Can be significantly reduced. Therefore, the life of the vacuum insulation box body for heating and cooling cycles can be significantly extended. Since the curved portion is provided in a portion of the wall of the opening of the inner box that overlaps with the heat insulating lid, the heat radiation loss from the curved portion is small, and the influence on the heat insulating property of the vacuum heat insulating layer can be small.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a vacuum heat insulating box body to which a heat expansion and contraction absorbing structure of the present invention is applied.

FIG. 2 is a sectional view of a main part in FIG.

FIG. 3 is a sectional view taken along line III-III in FIG.

FIG. 4 is a sectional view of a main part of a vacuum heat insulating box body according to another embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a vacuum heat-insulating box body of a comparative example in which a curved portion is provided in the central portion of the inner box.

FIG. 6 is a cross-sectional view showing an example of a conventional vacuum insulation box body.

FIG. 7 is a partial cross-sectional view showing a functioning state of a membrane in a conventional vacuum heat insulating box.

[Explanation of symbols]

 11 Outer Box 12 Inner Box 13 Vacuum Insulation Layer 14 Membrane 15 Opening Wall 17 Heat Insulation Lid 18 Curved Section

Claims (1)

[Claims] 1. A vacuum heat insulating layer is provided between an outer box and an inner box,
The opening side end surface of this vacuum heat insulating layer is sealed with a membrane,
In a vacuum heat insulating box body having a heat insulating lid in an opening, an annular curved portion that bends toward the vacuum heat insulating layer is extendably provided at a portion of the wall of the opening of the inner box that overlaps with the heat insulating lid. At the same time, the heat expansion and contraction absorbing structure of the vacuum heat insulating box body, wherein the ratio of the depth to the width of the curved portion is set to 1/4 or more and 1/2 or less.