JPH0698109B2 - Metal vacuum double structure and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to a metal vacuum double structure such as a thermos and a vacuum double pipe, and a method for manufacturing the same.

(Prior Art) In order to improve the heat retaining property of a metallic vacuum double structure, for example, a vacuum double container such as a thermos bottle, increase the degree of vacuum between the inner container and the outer container and remove it from the inner container. It is important to block radiant heat transfer to the container.

In order to increase the degree of vacuum, it is not only possible to enhance the vacuum evacuation processing capability and seal it to a high vacuum, but also to prevent the release of stored gas from the outer surface of the inner container or the inner surface of the outer container after sealing. It is especially necessary. Therefore, conventionally, a method of degreasing the outer surface of the inner container and the inner surface of the outer container and further pickling with nitric hydrofluoric acid, a method of heating in a furnace during exhaust treatment to discharge the stored gas together with air, and a getter are used. There is a method of adsorbing the occluded gas which is released from the metal surface, but usually all of these methods are used.

Further, as a method of preventing radiant heat transfer, conventionally, at least a method of forming a plating layer on the outer surface of the inner container by electrolytic plating or silver mirror reaction, or as shown in JP-A-61-31111, the outer surface of the inner container There is a method of covering with a thin plate of copper or aluminum.

On the other hand, as a vacuum sealing method after the vacuum evacuation treatment, a method of brazing a closing member to an exhaust port formed on the bottom surface of the outer container (hereinafter referred to as a brazing method) and an exhaust gas provided on the bottom surface of the outer container. There is a method of sandwiching the tip tube for use (hereinafter referred to as the tip tube method).

In the above brazing method, when flux is used for brazing of the closing member, gas flows into the vacuum spaces of both the inner and outer containers to lower the degree of vacuum, so it is necessary to braze without using flux.

For this reason, for example, in a vacuum double container made of stainless steel, it is necessary to flush the surface thereof at a high temperature and use a brazing material having a melting point of about 900 to 1070 ° C. such as nickel brazing. Moreover, when stainless steel is heated to a high temperature or cooled from a high temperature, solid solution carbon is precipitated as a carbide in a certain temperature range (generally, about 450 to 850 ° C), and is sensitized to form grains. Since interphase corrosion is likely to occur and corrosion resistance is low, avoid the critical temperature range for sensitization.
When performing vacuum evacuation treatment and brazing at a temperature of 0 ° C. or higher, and when cooling from a high temperature, an inert gas must be supplied into the vacuum heating furnace for rapid cooling.

On the other hand, since the brazing material is not used in the tip tube method,
The vacuum exhaust treatment is performed at a temperature lower than the sensitization region, that is, 400 to 450 ° C.

By the way, during the vacuum evacuation process, it is necessary to heat the double container for cleaning the metal surface and releasing the occluded gas. However, if the heating is performed during the evacuation process, the plating surface or the like is oxidized. After pre-evacuating to a vacuum higher than × 10 ^-2 Torr (1.33 Pa), the brazing method raises the temperature to 850-950 ° C.
The tip tube method is designed to heat to 400 to 450 ° C.

The above method of increasing the degree of vacuum, the method of preventing radiant heat transfer, and the method of vacuum containment are also applied to the manufacture of a vacuum double pipe used as a water supply pipe for freeze prevention.

Generally, regarding the degree of vacuum, when the pressure is 10 ^-3 Torr or more, low vacuum, 10 ^-5 to 10 ^-3 Torr range are high vacuum, 10 ^-8 to 10 ^-5 Torr range are ultra high vacuum, 10 ^{Since -8} Torr or less is called an ultrahigh vacuum, it is also referred to in this specification.

(Problems to be Solved by the Invention) However, when pre-evacuating to a vacuum higher than 1 × 10 ^-2 Torr as in the conventional case, air which is a convective heat transfer medium is diluted, and a space between the outer container and the inner container is reduced. The heat transfer is extremely poor. Therefore, even if the inner container is heated after preliminary evacuation, the temperature rise of the inner container is significantly delayed compared to the outer container that receives the furnace heat directly.As a result, the vacuum evacuation process takes a long time and degassing from the outer surface of the inner container is insufficient. Therefore, the occluded gas remaining after the vacuum containment is released, the degree of vacuum is lowered, the heat insulating property is changed over time, and the temperature is gradually lowered.

Therefore, conventionally, a getter is used to adsorb the occluded gas liberated after the vacuum containment. The use of such a getter is indispensable for achieving perfect heat retention, but on the other hand, it has a problem that the material cost increases.

The above problem similarly occurs in the production of the vacuum double pipe.

The present invention has been made in view of such problems, and provides an excellent heat insulating property, and an inexpensive metal vacuum double structure and a method for manufacturing the same, further, from an inner wall in a short vacuum exhaust processing time. It is an object of the present invention to provide a method for producing a metal vacuum double structure capable of sufficiently degassing, stabilizing heat insulation and reducing the amount of getters or eliminating the need for getters. And

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention has an extremely excellent heat insulating property under a high vacuum of 1 × 10 ⁻⁴ Torr or less in the relationship between the degree of vacuum and the heat insulating property. Is well known in the art, but attention is paid to the fact that this change in adiabaticity changes abruptly when the vacuum degree is in the order of 10 ^-1 to 10 ^-3 Torr (see Material for Heat Transfer Engineering, edited by the Japan Society of Mechanical Engineers). The heat degassing is performed under a vacuum that does not show remarkable heat insulation and has a good heat transfer property, that is, in a low vacuum of the order of 10 ^-2 Torr or more.

Further, the copper foil coated on the outer surface of the inner container, in order to effectively exert a gas absorbing action other than the original radiation heat transfer preventing action, that is, a ketter action, by activating the copper foil during vacuum evacuation treatment, It is designed to effectively degas.

Generally, if a metal and a specific gas chemisorb at room temperature, the amount of the specific gas absorbed by the metal depends on the amount of released gas at the time of activation. Therefore, for example, if the copper foil can chemically adsorb a specific gas and the amount of released gas at the time of activation is equivalent to that of a general getter material, the copper foil can be expected to have a getter action similar to that of the getter material.

Therefore, in consideration of the fact that copper and hydrogen are chemically adsorbed, the present inventors analyzed the released gas when the copper foil was active, and obtained the following results.

When the copper foil is housed in a stainless steel chamber and activated while being heated and exhausted, water vapor (H
₂ O), carbon dioxide (CO ₂ ), carbon monoxide (CO) were released, and hydrogen (H ₂ ) was slightly released.

Here, the water vapor (H ₂ O) released is 120 ° C, 240 ° C and
Three peaks at 370 ℃ were observed, and the peak at 120 ℃ was physically adsorbed on the surface of the copper foil.
The peak at ° C is considered to be a combination of oxygen (O) bound to copper (Cu) in the form of CuO or Cu ₂ O and hydrogen (H) diffused. Carbon dioxide (CO ₃ ) and carbon monoxide (CO) have two peaks at 40 ℃ and 400 ℃,
It is considered that oxygen (O) bound to copper (Cu) and carbon (C) diffused are bound on the surface. Further, it is considered that hydrogen (H ₂ ) is released as it is without being released in the form of water vapor (H ₂ O).

In addition, hydrogen (H ₂ ) [including those released in the form of water vapor (H ₂ O)] released by the activation of this copper foil (about 12 g) is a standard getter material (SAES GETTERS SPA st
It was equivalent to or higher than hydrogen (H ₂ ) released at the time of activation of -707 equivalent, about 0.5 g).

In addition, the copper foil that has been forcedly oxidized in the air has a higher probability of collision between hydrogen (H) and oxygen (O) on its surface during activation, so hydrogen (H ₂ ) is converted into water vapor (H ₂ O). It has been confirmed that it is easily released and does not leave any damage due to oxidation.

The first invention is made based on the above insight,
In a metal vacuum double structure in which a double wall structure is formed by an inner wall and an outer wall, and the space between the inner wall and the outer wall is exhausted and vacuum-sealed, the vacuum surface is covered with an activated copper foil. It is a thing.

The second aspect of the present invention is a metal vacuum chamber in which an outer surface of an inner wall is covered with a copper foil, a double wall structure is formed by the inner wall and the outer wall, and a space between the inner wall and the outer wall is exhausted to be vacuum-sealed. In the manufacturing method of heavy structures, when exhausting the space between the inner wall and the outer wall, the copper foil should be heated to approximately 400 ° C.
It is heated and activated at the above temperature.

Furthermore, a third invention is a metal vacuum chamber in which the outer surface of the inner wall is covered with copper foil, a double wall structure is formed by the inner wall and the outer wall, and the space between the inner wall and the outer wall is exhausted to be vacuum-sealed. In the method for manufacturing a heavy structure, as shown in FIG. 1, in the first step I, pre-evacuation to a low vacuum of the order of 10 ^-2 Torr or more is performed, and in the second step II, the temperature is about 400 ° C. or more for a predetermined time. After heating and degassing, in the third step III, while maintaining the heating temperature, an evacuation process is performed to a high vacuum of the order of 10 ⁻⁴ Torr or less, and the fourth step IV encloses the vacuum. .

When the material of the inner wall or the outer wall is austenitic stainless steel such as SUS304, it is preferable to carry out the heat degassing at a temperature lower than or above the sensitization region of the stainless steel.

The vacuum sealing method can be either a conventional tip tube method or a brazing method. However, when the material of the inner wall or the outer wall is austenitic stainless steel, the tip tube method is a sensitized region of the stainless steel. The hot degassing should be performed at a lower temperature, and the brazing method should be performed at a temperature above the sensitization region.

In addition to the air, an inert gas such as nitrogen (N ₂ ) or argon (Ar) can be sealed in the space between the inner wall and the outer wall. However, in the case of air, the copper foil is oxidized by oxygen (O ₂ ) in the air, but the probability of collision between oxygen (O ₂ ) and hydrogen (H ₂ ) which is the main component of degassing increases. , And oxygen and hydrogen are easily combined to be released as water vapor (H ₂ O), which has the advantage of being economical from the viewpoint of activation.

(Operation) According to the configuration of the first invention, the gas remaining in the vacuum space between the inner wall and the outer wall or the gas released from the inner wall or the outer wall is absorbed by the activated copper foil covering the surface of the inner wall. Therefore, the vacuum space is maintained at a high vacuum and the heat insulating property is maintained.

On the other hand, according to the configuration of the second invention, the copper foil is heated to about 400 ° C. or more to release the stored gas and activated during the exhaust treatment between the inner wall and the outer wall. Then, this released gas is exhausted together with the free gas from the outer wall, but after the exhaust processing is finished, the copper foil acts as a getter and absorbs the residual gas released from the inner wall or the outer wall, so that the heat insulating property is maintained. It

Further, according to the configuration of the third invention, 10 ^{−2 in} the first step I
When pre-evacuating to a low vacuum of Torr order or more, the heat transfer between the inner wall and the outer wall is reduced and heat insulation occurs, but 10 ^-2
At the order of Torr, heat conductivity is not so badly impaired.

Therefore, when the temperature is raised to about 400 ° C. or higher in the second step II, the heat of the inner wall directly receiving the heat of the furnace is quickly transferred to the inner wall by radiation, conduction and convection, and the inner wall is heated in a short time. Therefore, the occluded gas is liberated from the wall surface of the inner wall as well as the outer wall, and the degassing is sufficiently performed in a short time. Further, as the inner wall is heated, the copper foil 6 is also heated and the stored gas is released and activated.

Then, in the third step III, if the exhaust process is performed to the order of 10 ⁻⁴ Torr or less, the free gas from the inner wall or the outer wall and the gas released from the copper foil are discharged to the outside together with the residual air.

After this exhausting process is completed, vacuum sealing is performed by the tip tube method or the brazing method in the fourth step IV, whereby a high vacuum vacuum double structure is obtained, and the copper foil acts as a getter and the inner wall Or absorb the residual gas released from the outer wall,
Thermal insulation is maintained.

When the inner wall or the outer wall is austenitic stainless steel such as SUS304 and vacuum sealing is performed by the tip tube method, by heating degassing at a temperature lower than the sensitization region of the stainless steel in the second step II, There is no risk of deterioration of corrosion resistance due to sensitization.

Further, when the inner wall or the outer wall is austenitic stainless steel and vacuum sealing is performed by a brazing method, heating degassing is performed at a temperature exceeding the sensitization region of the stainless steel in the second step II, As with the tip tube method, there is no risk of deterioration in corrosion resistance.

(Example) Next, the Example of this invention is described according to an accompanying drawing.

(1) Embodiment of the First Invention i) First Embodiment FIG. 4 shows a vacuum double container 1 for a thermos bottle according to the present invention.
An outer container 2 made of stainless steel, which was formed by dividing the upper part 2a and the lower part 2b into two parts, had a copper foil with an outer surface of 16.5μ and a weight of 12g.
Insert the inner container 3 made of stainless steel covered with a, join the inner container 3 and the part 2a of the outer container 2 at the part Y, and further join the upper part 2a and the lower part 2b of the outer container 2 at the part X. Then, it is formed into a double wall structure, and the tip tube 4 for exhaust is provided at the bottom of the outer container 2.

The central portion of the bottom outer surface of the inner container 3 facing the tip tube 4 is exposed without being covered with the copper foil 3a.

The space between the outer container 2 and the inner container 3 is vacuum-sealed by heating and exhausting it through the chip tube 4 and activating the copper foil 3a, and then sandwiching the chip tube 4 between them. ing.

In the vacuum double container 1 having the above structure, the gas that is not exhausted from the tip tube 4 during manufacturing and remains in the vacuum space 5 between the outer container 2 and the inner container 3, or the outer container 2 or the inner container after vacuum sealing The gas released from 3 is absorbed by the copper foil 3a by the getter action of the activated copper foil 3a. Therefore, the vacuum space 5 between the outer container 2 and the inner container 3 is maintained at a high vacuum, and the heat insulation is maintained.

ii) Second Embodiment FIGS. 5 and 6 show a double container 1a for a thermos bottle according to another embodiment of the present invention, in place of the tip tube 4 of the outer container 2 of the double container 1, An opening 4a is formed, and an exhaust port edge member 7 having an exhaust port 6 in the center is fitted and joined to the opening 4a,
An exhaust port closing member 8 is installed in the exhaust port 6 via a brazing material 9, and the space between the outer container 2 and the inner container 3 is heated and exhausted through an opening 4a, and then the brazing material 9 is melted. Let the opening
It is substantially the same except that it is vacuum-sealed by closing 4a with the exhaust port closing member 8, and corresponding parts are given the same numbers and their explanations are omitted.

In the vacuum double container 1a having the above configuration, since the copper foil 3a acts as a getter as in the first embodiment,
The vacuum space 5 between the outer container 2 and the inner container 3 is maintained in a high vacuum, and heat insulation is maintained.

iii) Third Embodiment FIG. 9 shows a vacuum double pipe used for a water supply pipe for freeze prevention, etc., and is roughly composed of a water supply pipe 10, an outer cylinder 11, and connecting members 13 and 14. .

The water supply pipe 10 is a stainless pipe having an inner diameter of 22 mm and a thickness of 1 mm, and a portion where the outer cylinder 11 is exteriorly covered is covered with a copper foil 10a. An appropriate spacer may be provided to keep the gap with the outer cylinder 11 constant and prevent thermal contact between the outer cylinder 11 and the water supply pipe 10 as much as possible. Outer cylinder
Reference numeral 11 denotes a stainless steel pipe having an inner diameter of 42 mm and a thickness of 1.2 mm, which is adapted to be installed on the water supply pipe 10, and a copper tip tube 12 is attached to the outer peripheral portion on the upstream side. Connection member 1
Reference numerals 3 and 14 are ring members having a U-shaped cross section formed of a stainless steel material, which are inserted into the water supply pipe 10 and welded all around the outer surface of the water supply pipe 10 and the end of the outer cylinder 11 to form the water supply pipe 10 and the outer cylinder. The space between 11 is covered.

Then, this space is heated and exhausted through the chip tube 12, and after activating the copper foil 10a, the chip tube 12 is
It is vacuum-sealed by sandwiching it.

Further, caps 15 and 16 made of stainless steel are attached to both ends of the outer cylinder 11 and outside of the connecting members 13 and 14, respectively, and sealing agents 17 and 17 are provided between the caps 15 and 16 and the connecting members 13 and 34, respectively. Each chip tube 12 is injected, and the tip tube 12 is covered with the downstream side of the cap 16 and another cap 18 and is appropriately sealed with a sealant or the like. As shown in the drawing, the tip tube 12 may be covered with the cap 9 and the inside thereof may be filled with the sealant 17.

In the vacuum double pipe configured as above, the copper foil 10a
Since, like the first embodiment, acts as a getter, the vacuum space 20 between the water supply pipe 10 and the outer cylinder 11 is maintained at a high vacuum, and the heat insulating property is maintained.

iv) Fourth Embodiment In the vacuum double pipe according to the third embodiment, instead of sandwiching the tip tube 12 and vacuum-sealing it, the second tube is used.
An opening was formed as in the example, and the opening was closed with a closing member and brazed.

Also in this case, the vacuum space 20 between the water supply pipe 10 and the outer cylinder 11 is maintained at a high vacuum by the getter action of the copper foil 10a, and the heat insulation is maintained.

(2) Embodiments of the second and third inventions Since the manufacturing method according to the second invention is a part of the steps of the manufacturing method according to the third invention, an embodiment of the manufacturing method according to the third invention will be described below. .

A. Manufacturing method of vacuum double container i) First embodiment To manufacture the vacuum double container 1 as shown in the first embodiment (FIG. 4) of the first invention, first, the outer container 2 and A double structure is formed with an inner container 3 whose outer surface is covered with a copper foil, and the double container 1 is placed in a heating furnace and the tip tube 4 is connected to a vacuum pump.

Then, as shown in FIG. 2, in the first step 21, the inner container 3
The space 5 between the outer container 2 and the outer container 2 is pre-evacuated to a low vacuum of 1 × 10 ^-2 Torr. At this time, since the outer surface of the bottom of the inner container 3 facing the tip tube 4 is not covered with the copper foil 3a, the copper foil 3a is not sucked up during the exhaust treatment.

In the second step 22 in this low vacuum state, heating is performed at 400 to 450 ° C. At this time, the outer container 2 directly heated by the furnace heat
The heat of the inner container 3 is generated by the radiant heat transfer, the heat transfer of the mouth portion Y, and the convective heat transfer performed through the residual gas in the space 5.
Be transmitted to. Although exhausted to a low vacuum of 1 × 10 ^-2 Torr in the first step 21, convective heat transfer due to residual gas in the space 5 becomes dominant at this degree of vacuum, and the outer container 2 to the inner container 3
The heat transfer to is not so bad. Therefore, the outer container 2
The heat of is quickly transferred to the inner container 3, and the inner container 3 is
The temperature is raised in about a minute. Therefore, not only the outer container 2 but also the outer surface of the inner container 3 is released into the occluded gas space 5 for sufficient degassing in a short time. Also, at the same time when the inner container 3 is heated, the copper foil 3a is also heated and activated,
Water vapor (H ₂ O), carbon dioxide (CO ₂ ), carbon monoxide (CO)
Etc. are released from the surface of the copper foil 3a.

Since the heating in the second step 22 is performed at a temperature lower than that of the sensitized region of stainless steel, there is no fear of deterioration of corrosion resistance due to sensitization.

Then, while maintaining the temperature of the second step 22, the gas is further evacuated in the third step 23 to obtain a high vacuum of 1 × 10 ⁻⁴ Torr. At this time, the residual gas in the space 5, the free gas from the inner container 3 or the outer container 2 and the gas released from the copper foil 3a are discharged to the outside through the chip tube 4.

Next, while maintaining this high vacuum state, it is cooled in the fourth step 24, and in the fifth step 25, the chip tube 4 is pinched off and vacuum sealed.

The vacuum double container manufactured by the above process is the second process.
At 22, the outer container 2 as well as the inner container 3 is sufficiently degassed, so that the stored gas is less released after the vacuum containment, and the heat insulation is stabilized.

Further, in the second step 22, hydrogen (H ₂ ) is activated by activating the copper foil 3a.
Since the copper foil 3a is released, the copper foil 3a such as vacuum containment has a gas absorbing function, that is, a gettering function. Therefore, the gas released from the inner container 3 or the outer container 2 after the vacuum sealing is absorbed by the copper foil 3a, and the heat insulating property does not deteriorate. Needless to say, the copper foil 3a has a function of preventing radiation heat transfer from the inner container 3a.

ii) Second Embodiment In order to manufacture the vacuum double container 1 as shown in the second embodiment (FIGS. 5 and 6) of the first invention, first, the double container 10 is inverted and As shown in FIG. 6, an annular corrugated brazing material 9 is installed on the outer peripheral edge of the exhaust port 6, and the exhaust port closing member 8 is placed on the brazing material 9 and then set in a vacuum heating furnace.

Then, as shown in FIG. 3, in the first step 31, 1 × 10 ^-2 To as in the first step 21 of the manufacturing method according to the first embodiment.
After pre-evacuating to a low vacuum of rr, heating to 850-950 ° C in the second step 32 to degas, and then 1 × 10 ^-4 Torr in the third step 33.
Evacuate to high vacuum. Next, when the temperature is raised to around 1000 ° C. in the fourth step 34 while maintaining the high vacuum state, the brazing filler metal 9 is melted and the exhaust port closing member 8 descends onto the exhaust port edge member 7 due to the action of gravity. Then, the exhaust port 6 is closed. Then, the fifth step 35
When it is rapidly cooled by, the brazing filler metal 9 is rapidly solidified, and the space between the exhaust port edge member 7 and the exhaust port closing member 8 is completely removed as shown in FIG. 5 while maintaining the space 5 between the inner and outer containers at a high vacuum. It is sealed.

In the manufacturing method according to the second embodiment, 1 × is used in the first step 31.
Since it was evacuated to a low vacuum of 10 ^-2 Torr,
Similar to the manufacturing method according to the embodiment, the heating degassing in the second step 32 is sufficiently performed in a short time, and
The vacuum exhaust processing time in the third step 33 can be shortened.

In addition, the copper foil 3a is activated by the heating in the second step 32, and the steam (H
_{Since 2} O) and the like are released, the copper foil 3a acts as a getter after being vacuum-sealed, the gas released from the inner container 3 or the outer container 2 is absorbed, and the heat insulating property is not deteriorated.

Further, in the second step 32, heating is performed at a temperature exceeding the sensitization region of the stainless steel and quenching is performed in the fifth step 35, so that the time period during which the stainless steel is exposed to the sensitization region is extremely short, and the sensitization reduces corrosion resistance. There is no fear.

In the above embodiment, 1 × 10 ⁻ in the first step 21, 31.
_Although pre-evacuation was performed to ₂ Torr, it is not limited to this value, and it is sufficient to evacuate to a low vacuum of the order of 10 ^-2 Torr to about 100 Torr. Also, the degree of vacuum in the third step 23, 33 is not limited to 1 × 10 ^-4 Torr, but 10 ^-4 Tor
A high vacuum region on the order of rr or less may be used.

iii) Confirmation test The present inventors conducted a test for confirming the heat retaining property of the stainless steel vacuum double container manufactured by the method according to the present invention.

In this heat retention test, under the conditions shown in Table 1, five stainless steel vacuum double containers manufactured by the method according to the present invention, each of which has an inner container covered with a copper foil having a different wall thickness, are provided in groups of five. It was used as a test sample.

For comparison with this, as a sample of a stainless steel vacuum double container manufactured by a conventional method, those shown in Table 2-1 and Table 2-2 were prepared.

No getter was used in any of the samples.

For each sample, initial: immediately after production, after 1 week of production at 95 ° C atmosphere, then 2 weeks of production (more 1 week), after being placed at 95 ° C atmosphere for 4 weeks of production (more 2 weeks) After placing in a 95 ° C atmosphere, in March after manufacturing (more February) After placing in a 95 ° C atmosphere, in April after manufacturing (more January) After placing in a 95 ° C atmosphere, In 6 steps, put hot water of 95 ℃ in the inner container 1 and 20 ℃
Thermal retention was tested by measuring the temperature of the hot water after 24 hours in the atmosphere.

Of these test results, those of the test sample of the present invention are shown in Table 3, and those of the conventional comparative sample are shown in FIGS. 7a to 7d and 8a.
Shown in Figures 8d. In Figures 7a to 7d and 8a to 8d, it is possible to know the temperature drop of hot water at 95 ° C after 24 hours of warming, that is, the magnitude of the 24-hour warming power, by checking the temperature curve. It is possible to know the decrease in the degree of vacuum due to aging, that is, the magnitude of the vacuum maintaining force, by the decreasing gradient of. Also, by comparing the figures for the same type of material, for example, A ₂ , A ₃ , and A ₄ , it is possible to know the influence of the length of the exhaust time during manufacturing.

The results of this test confirmed the following items regarding heat retention and exhaust time.

As is clear from the average value of each sample I and II in Table 3,
The vacuum holding power decreased by 1 ° C after 1 week in Sample I,
In II, the temperature decreases 0.8 ° C. after 1 week, further decreases 0.2 ° C. after 2 weeks, and tends to increase thereafter. Therefore, according to the method of the present invention, the vacuum maintaining force is flat and hardly decreases.

Further, since the temperature of Sample II is slightly higher than that of Sample I, it is shown that the thinner the copper foil, the better the heat retention for 24 hours in the initial stage. This is because the exhaust time of both is the same, the thinner the copper foil, the higher the degree of adhesion with the inner container 3 and the faster the absorption of heat, and the sufficient release of gas due to activation during vacuum exhaust processing. It is presumed that the gas absorption capacity after vacuum containment is high.

As is clear from a comparison between Sample I in Table 3 and Sample B _{3 in} FIG. 7c under the same conditions except for the exhaust method, the vacuum maintenance power of Sample I decreases by about 1 ° C. The vacuum maintaining power of B ₃ is reduced by about 3 ° C. after 2 weeks. Therefore, according to the method of the present invention, the vacuum maintaining power is improved as compared with the conventional method.

Further, while the peak of the bottom of the sample I the curve is after 1 week and after 2 weeks Sample A _3. Thus, the early peaks indicate that the release of the stored gas is small and / or the getter action of the copper foil is large.

As is clear from the comparison between sample I in Table 3 and sample B _{1 in} FIG. 7a, both have the same 24-hour heat retention, and
The vacuum maintaining power also tends to level off, but the evacuation time of sample I
50 (10 + 40) minutes, whereas sample B ₁ exhaust time is 10
0 minutes. Therefore, the method according to the present invention can shorten the exhaust time by 50 minutes as compared with the conventional method.

For the 7a view, second 7d figure, different from the present invention is intended for samples prepared by the manufacturing method, but there is a sample _{A 2 ~A 4, B 1 ~B} 4 covering the inner container with copper foil, The effect of the getter action of copper foil can be known. That is, a. The one in which the inner container is covered with copper foil is far superior to the others in terms of 24-hour heat retention and vacuum retention.

B. If the evacuation time is long, the vacuum maintenance power will level off and the degree of decrease will be small. Further, when the exhaust time is short, the vacuum maintaining power becomes unstable, and it tends to decrease until 2 weeks after manufacturing and then improve. This is because the degassing of the inner container or outer container and the wall surface of the copper foil is insufficient when the exhaust time is short, so the amount of stored gas released immediately after vacuum sealing is greater than the amount of gas absorbed by the copper foil as a getter. This is because the getter action is too large to catch up with, and if the occluded gas is subsequently desorbed, the getter action of the copper foil becomes predominant and gas absorption is accelerated.

Figure 8a, second 8d figure, although the present invention is intended for samples prepared by different manufacturing methods, the sample F ₂ ~F _4, G ₁ ~G
Since ₄ is intended to cover the inner container with aluminum foil, Sample A ₂ to A ₄ of the inner container shown in the 7a view, second 7d view covered with copper foil, B ₁ .about.B
By comparing with ₄ , it is possible to know the effect of the getter action of the copper foil. That is, a. For the same evacuation time, for example, sample B ₁ and
Comparing with sample B _{2 in} Fig. 8a, it is clear that the one with the inner container covered with copper foil has a better 24-hour heat retention than the one covered with aluminum foil, and the vacuum maintaining power is also stable. .

B. Samples C _{2 to} C ₄ and D _{2 to} D _{4 in} FIGS. 7a to 7d represent blank products (no plating or foil), and the tendency of recovery after one month was It is suggested that the gas absorption capacity of the outer container 2 is reversed with respect to the amount of gas, and the magnitude of the inclination thereafter indicates the magnitude of that amount.

Therefore, looking at the points of inversion and the magnitude of the inclination in the aluminum foils of FIGS. 8a to 8d, the samples C _{2 to} C ₄ and D _{2 to} D _{4 were} examined.
Therefore, it can be said that there is almost no activation of the aluminum foil under these conditions. The getter action of aluminum foil cannot be expected.

B. Example of Manufacturing Method of Vacuum Double Pipe To manufacture a vacuum double pipe as shown in FIG. 9, first, as shown in FIG. 10, a connecting member 13 is provided on the downstream side of the water supply pipe 10. Exterior with its U-shaped inner surface facing downstream,
The point indicated by the arrow A is welded on the entire circumference, the connecting member 14 is internally mounted at the upstream end of the outer cylinder 11 with its U-shaped inner surface facing the upstream side, and the point indicated by the arrow B is welded on the entire circumference.

Then, the outer surface of the water pipe 10 is covered with a copper foil 10a, and then,
The outer cylinder 11 is sheathed from the upstream side of the water absorption pipe 10, the points indicated by arrows C and D are welded all around, and the outer cylinder 11 is attached to the outside of the water pipe 10.
And a space surrounded by the connecting members 13 and 14 is formed. In addition,
When the outer pipe 11 is mounted on the water pipe 10, the tips of the water pipe 10 and the outer pipe 11 do not come into contact with the connecting members 14 and 13 up to near the final position, so that it can be easily performed without difficulty. Also,
The copper foil 10a provided on the outer surface of the water supply pipe 10 is not damaged.

Next, the heating and exhausting treatment and the vacuum sealing treatment of the space portion between the water pipe 10 and the outer cylinder 11 are performed. The method is the same as the method in the first embodiment of the vacuum double container, and its operation Since the effect is the same, the description is omitted.

In this manufacturing process, if the material is put into the furnace from room temperature and heated, the temperature of the outer cylinder 11 rises first, and then the water pipe.
Since the temperature of 10 rises later, the expansion amount of the outer cylinder 11 is large at the time of heating, and the outside and inside of the connecting members 13 and 14 are forced in the directions of arrows a and b in FIG. 9, respectively. It is transformed by receiving it.

On the contrary, if the cooling is started, the outer cylinder 11 is cooled faster than the water pipe 10, so that the contraction amount of the outer cylinder 11 is large at the time of cooling, and the connecting member 13 is conversely to the heating time. , 14 are deformed by receiving forces in the directions of arrows a'and b ', respectively.

As described above, the connecting members 13 and 14 receive forces in the opposite directions during heating and cooling, but the connecting members 13 and 14 are connected to the inner ring portion and the outer ring portion in the middle. Since the parts are substantially right angled and have a degree of freedom in both directions, no excessive stress is applied at the time of deformation and no damage occurs.

The present inventors also conducted a confirmation test on the vacuum double pipe, and as a result, kept the upper and lower portions of the antifreezing pipe in an atmosphere of 5 ° C. and kept a low temperature state of −30 ° C. between them. The result was that the water inside did not freeze for about 80 hours even when exposed.

(Effects of the Invention) As is apparent from the above description, according to the first invention, the vacuum space between the inner wall and the outer wall is kept at a high vacuum by the getter action of the activated copper foil, and the heat insulating property is maintained. In addition to being
The original getter material is reduced, and in some cases, it is unnecessary, resulting in an inexpensive product.

On the other hand, according to the second aspect of the invention, the copper foil covering the inner wall is heated during the exhaust treatment to release the stored gas and activate, so that the copper foil acts as a getter after the exhaust treatment, and the vacuum space between the inner wall and the outer wall is high. It is kept in a vacuum to maintain heat insulation,
The original getter material can be reduced and, in some cases, unnecessary.

Further, according to the third aspect of the present invention, before evacuating to a high vacuum, the inner container is quickly heated by heating under a low vacuum that does not impair the heat transfer property. The gas is supplied sufficiently and in a short time, the overall heating and exhausting treatment time is shortened, the manufacturing process can be shortened, and the heat insulating property is stabilized.

In addition, the copper foil covering the outer surface of the inner container is activated during heating and degassing, releasing the stored gas and acting as a getter after vacuum containment, so that a high degree of heat insulation is maintained and the original getter material is maintained. It is possible to reduce the cost, and in some cases, it is not necessary, and the material cost can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a manufacturing process by a method for manufacturing a metal vacuum double container according to the third invention, and FIGS. 2 and 3 are stainless steels by a tip tube method and a brazing method according to the third invention, respectively. FIG. 4 is a cross-sectional view of the double container according to the first invention manufactured by the tip tube method, and FIG. 5 is a first process manufactured by the brazing method. Sectional drawing of the double container according to the invention, FIG. 6 is a partially enlarged sectional view of FIG. 5, FIG.
FIGS. 7d and 8a to 8d are diagrams showing the test results regarding the heat retaining property of the vacuum double container manufactured by the conventional method, and FIG. 9 is the first invention manufactured by the tip tube method. FIG. 10 is a half cross-sectional view of the vacuum double pipe, and FIG. 10 is a half cross-sectional view showing a state in which the vacuum double pipe is being manufactured. 1 ... Double container, 2 ... Outer container, 3a ... Copper foil, 3 ... Inner container, 5 ... Space.

Claims (3)

[Claims] 1. A metal vacuum double structure in which a double wall structure is formed by an inner wall and an outer wall, and a space between the inner wall and the outer wall is exhausted to be vacuum-sealed, and the surface of the inner wall is activated. A metallic vacuum double structure characterized by being covered with a copper foil. 2. A metal vacuum double structure in which an outer surface of an inner wall is covered with a copper foil, a double wall structure is formed by the inner wall and the outer wall, and a space between the inner wall and the outer wall is exhausted to be vacuum-sealed. In the method for manufacturing a body, a method for manufacturing a metal vacuum double structure, characterized in that a copper foil is heated and activated at a temperature of about 400 ° C. or higher during exhaust treatment of a space between an inner wall and an outer wall. 3. A metal vacuum double structure in which the outer surface of the inner wall is covered with copper foil, a double wall structure is formed by the inner wall and the outer wall, and the space between the inner wall and the outer wall is exhausted to be vacuum-sealed. In the body manufacturing method, pre-evacuate to a low vacuum of the order of 10 ^-2 Torr or more,
After degassing by heating at a temperature above ℃ for a predetermined time,
A method for producing a metal vacuum double structure, which comprises subjecting the material to a high vacuum of the order of 10 ^-4 Torr or less and vacuum-sealing while maintaining the heating temperature.