JPH0698108B2 - 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 process, a method of brazing a closing member to an exhaust port formed on the bottom surface of the outer container to close it (hereinafter, referred to as a loose welding method) and a method of providing the bottom surface of the outer container are provided. There is a method of sandwiching an exhaust tip tube (hereinafter referred to as a 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 it is sensitized to cause intergranular corrosion. Is likely to occur and corrosion resistance is reduced, so avoid the dangerous temperature range for sensitization.
Perform vacuum exhaust treatment and brazing at a temperature of 850 ° C or higher,
In addition, 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 for increasing the degree of vacuum, the method for preventing radiant heat transfer, and the method for vacuum containment are also applied to the production 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 with time, and the heat retaining property 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 in order to complete heat retention, but on the other hand, there is a problem that the material cost of the original getter, getter holding metal fitting, etc. increases.

The present invention has been made in view of such problems, excellent thermal insulation, and to provide an inexpensive metal vacuum double structure, and degassing from the inner container in a short vacuum exhaust processing time. An object of the present invention is to provide a method for manufacturing a metal vacuum double structure, which is sufficiently performed and does not require an original getter or a getter holding metal fitting.

(Means for Solving the Problem) By the way, the gas released from the inner wall or the outer wall of the vacuum double structure contains a large amount of hydrogen and a small amount of nitrogen. Therefore, in order to increase the degree of vacuum of the vacuum double structure, it is necessary to absorb not only hydrogen but also nitrogen.

Therefore, according to the present invention, it is well known that, in the relationship between the degree of vacuum and the heat insulating property, extremely excellent heat insulating property can be obtained under a high vacuum of 1 × 10 ⁻⁴ Torr or less. Focusing on the fact that the degree of vacuum changes abruptly in the order of vacuum of 10 ^-1 to 10 ^-3 Torr (see Material for Heat Transfer Engineering, edited by the Japan Society of Mechanical Engineers), the heat insulation does not appear remarkably and the heat transfer The degassing was carried out by heating under a good vacuum, that is, in a low vacuum of the order of 10 ^-2 Torr or more.

Further, in the copper foil coated on the outer surface of the inner container, in addition to the original radiation heat transfer prevention effect, in order to effectively exert a gas absorption function, that is, a getter function, the copper foil is activated by evacuating during vacuum exhaust treatment. The gas is effectively degassed, and titanium or zirconium absorbs a gas that cannot be absorbed by the copper foil.

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 the same as 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 released water vapor (H ₂ O) has three peaks at 120 ° C, 240 ° C, and 370 ° C, and the 120 ° C peak was physically adsorbed on the surface of the copper foil. , 240 ℃ and 370 ℃ peaks are oxygen (O) bound to copper (Cu) in the form of CuO or Cu ₂ O.
It is considered that this is a combination of hydrogen (H) that has diffused with. Carbon dioxide (CO ₂ ) and carbon monoxide (CO)
Is observed to have two peaks at 240 ° C. and 400 ° C., and 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 that released in the form of water vapor (H ₂ O)) released by the activation of this copper foil (about 12 g) is used for general getter materials (SAES GETTERS SPA st
Equivalent to -707, about 0.5g) Hydrogen (H ₂ ) released during activation
Was equal to or higher than.

In addition, the copper foil that has been forcedly oxidized in air increases the probability of collision of hydrogen (H) and oxygen (O) on its surface during activation, so hydrogen (H ₂ ) is released in the form of water vapor (H ₂ O). It has been confirmed that it is easy to be damaged and does not leave damage due to oxidation.

Further, the present inventors considered that nitrogen, which is not chemically adsorbed even when physically adsorbed with copper, is chemically adsorbed if it is titanium or zirconium, and as a result of performing an emission gas analysis when the titanium foil is activated, hydrogen ( H ₂ ) peak is about 700 ℃, nitrogen (N ₂ )
Was about 400 ° C. Further, as a result of analysis of released gas during activation of the zirconium foil, the peaks of hydrogen (H ₂ ) and nitrogen (N ₂ ) were both about 300 ° C. Further, nitrogen (N ₂₎ absorption capacity of titanium foil (about 0.8 g) has also been confirmed that equivalent to the absorption capacity for nitrogen (N ₂₎ of the general of the getter material (about 0.5 g). Incidentally, a titanium getter commercially available in the past is activated at 700 ° C. or higher in order to effectively absorb hydrogen (H ₂ ) rather than nitrogen (N ₂ ), and is used as a high temperature getter.

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 to be vacuum-sealed, the inner wall surface is covered with activated copper foil. In addition, activated titanium or zirconium is interposed between the inner wall surface and the copper foil.

Further, the second invention is a method for manufacturing 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. While covering the surface with copper foil and interposing titanium or zirconium between the inner wall surface and the copper foil, as shown in FIG. 6, in the first step I, a preliminary vacuum of 10 ^-2 Torr or more was prepared. After evacuation and degassing by heating at a temperature of about 400 ° C. or higher for a predetermined time in the second step II, a high vacuum of the order of 10 ⁻⁴ Torr or less is maintained in the third step III while maintaining the heating temperature. Exhaust treatment is performed and vacuum sealing is performed in the fourth step.

As the titanium material or zirconium material, for example, a titanium foil, titanium pellets, or a commercially available titanium getter can be used if it is a titanium material, but a titanium getter holding part is unnecessary, and titanium is used in order to secure the surface area as much as possible. Preference is given to using foils or zirconium foils. Further, when the material of the inner wall or the outer wall is austenitic stainless steel such as SUS304, it is preferable to perform 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, hydrogen (H ₂ ) of the gas remaining in the vacuum space between the inner wall and the outer wall or the gas liberated from the inner wall or the outer wall is activated to cover the surface of the inner wall. Is absorbed by the copper foil, and nitrogen (N ₂ ) is absorbed by titanium or zirconium interposed between the inner wall surface and the copper foil, so that the vacuum space is kept at a high vacuum and the heat insulation is maintained. . Further, since titanium or zirconium is interposed between the inner wall surface and the copper foil, no holding member is required.

On the other hand, according to the second aspect of the present invention, when pre-evacuating to a low true vacuum of the order of 10 ^-2 Torr or more in the first step I, the heat transfer between the inner wall and the outer wall is reduced, and heat insulation occurs. 10 ^-2 Torr
In the order of, the heat conductivity is not so much impaired.

For this reason, the heat of the outer wall, which is heated to approximately 400 ° C. or higher in the second step II and directly receives 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 and titanium or zirconium are also heated, and the stored gas is released and activated.

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

After completion of this discharging process, vacuum sealing is performed by the tip tube method or the brazing method in the fourth step IV to obtain a high vacuum vacuum double structure, and copper foil and titanium or zirconium as a getter. Of the gas that acts and remains in the vacuum space between the inner and outer walls, or the gas released from the inner or outer wall, hydrogen (H ₂ ) is absorbed by the copper foil, and nitrogen (N ₂ ) is absorbed by titanium or zirconium. The 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.

i) Example of First Invention First Example FIG. 1 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.
Along with covering with a, a titanium foil 3b having a thickness of 25 μm and a weight of 0.8 g is rolled up, the inner container 3 made of stainless steel is inserted, the inner container 3 and the upper part 2a of the outer container 2 are joined at the mouth portion Y, and The upper part 2a and the lower part 2b of the outer container 2 are joined at the X portion to form a double wall structure, and the tip pipe 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.

Then, the space between the outer container 2 and the inner container 3 is heated and exhausted through the chip tube 4, and after activating the copper foil 3a and the titanium foil 3b, the chip tube 4 is sandwiched. It is vacuum-sealed.

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 Hydrogen (H ₂ ) in the gas released from 3 is a copper foil due to the getter action of the activated copper foil 3a.
It is absorbed by 3a. Further, nitrogen (N ₂ ) is absorbed by the titanium foil 3b by the getter action of the activated titanium foil 3b.
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.

Second Embodiment FIGS. 2 and 3 show a double container 1a for a thermos bottle according to an embodiment of the present invention. Instead of the tip tube 4 of the outer container 2 of the double container 1, an opening 4a is provided. An exhaust port edge member 7 having an exhaust port 6 in the center is fitted and joined to the opening 4a, and an exhaust port closing member 8 is installed on the exhaust port 6 via a brazing material 9 The space between the container 2 and the inner container 3 is heated and exhausted through the opening 4a, and then the brazing filler metal 9 is melted to form the opening 4a.
Are substantially the same except that they are vacuum-sealed by closing 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 structure, the copper foil 3a and the titanium foil 3b act as getters as in the first embodiment, so that the vacuum space 5 between the outer container 2 and the inner container 3 is formed.
Is kept in a high vacuum and the heat insulation is maintained.

Third Embodiment FIG. 4 shows a vacuum double pipe used as an antifreezing water supply pipe and the like, which 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 externally covered is covered with a copper foil 10a, and a titanium foil 10b is provided between the water supply pipe 10 and the copper foil 10a.
Is involved. 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. The outer cylinder 11 is a stainless steel pipe with an inner diameter of 42 mm and a thickness of 1.2 mm, which is designed to be fitted on the water supply pipe 10.
A copper tip tube 12 is attached to the outer peripheral portion on the upstream side. The connecting members 13 and 14 are ring members having a U-shaped cross section formed of a stainless 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. A space between the outer cylinders 11 is covered.

Then, this space is heated and exhausted through the chip tube 12, and after the copper foil 10a and the titanium foil 10b are activated, the chip tube 12 is sandwiched and vacuum-sealed.

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 14, 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 19 and the inside thereof may be filled with the sealant 17.

In the vacuum double pipe configured as above, the copper foil 10a
Since the titanium foil 10b and the titanium foil 10b act as a getter as in the first embodiment, the vacuum space 20 between the water supply pipe 10 and the outer cylinder 11 is kept at a high vacuum and the heat insulation is maintained.

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.

Even in this case, the vacuum space 20 between the water supply pipe 10 and the outer cylinder 11 is kept at a high vacuum by the gettering action of the copper foil 10a and the titanium foil 10b, and the heat insulating property is maintained.

ii) Example of the Second Invention First Example To manufacture the vacuum double container 1 as shown in FIG. 1, first, the outer container 2 and the outer surface are covered with the copper foil 3a and the titanium foil 3b. Is formed into a double-walled structure with the inner container 3 in which is wound, the double container 1 is put into a heating furnace, and the tip tube 4 is connected to a vacuum pump.

Then, as shown in FIG. 7, 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
Is transmitted to the inner container 3 by the radiant heat, the heat transfer of the mouth portion Y, and the convective heat transfer performed via the residual gas in the space 5. 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, the occluded gas is released into the space 5 from the outer surface of the outer container 2 as well as the outer surface of the inner container 3, so that degassing is sufficiently performed in a short time. Further, at the same time when the inner container 3 is heated, the copper foil 3a and the titanium foil 3b are also heated and activated, and steam (H ₂ O), nitrogen (N ₂ ), carbon dioxide (CO ₂ ), carbon monoxide ( CO) is released from the surfaces of the copper foil 3a and the titanium foil 3b.

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 released gas from the copper foil 3a or the titanium foil 3b are discharged to the outside through the tip 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.

In addition, in the second step 22, steam (H ₂
Hydrogen (H ₂ ) is released in the form of O), and nitrogen (N ₂ ) is released due to the activation of the titanium foil 3b, so the copper foil 3a and titanium foil 3b after vacuum containment absorb gas. It has an action, that is, a getter action. Therefore, the gas remaining in the space 5 after the vacuum containment, or the inner container 3 or the outer container 2
Hydrogen (H ₂ ) of the gas released from the is absorbed by the copper foil 3a and nitrogen (N ₂ ) is absorbed by the titanium foil 3b, so that 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. Also titanium foil
Since 3b is wrapped around the outer surface of the inner container 3 by the copper foil 3a, it does not fall off and no holding member is required.

Second Example In order to manufacture the vacuum double container 1a as shown in FIG. 2, first, the double container 1a is inverted, and as shown in FIG. Install brazing material 9 of
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. 8, 1 × 10 ⁻² Torr is used in the first step 31 as in the first step 21 of the manufacturing method according to the first embodiment.
Pre-evacuated to a low vacuum and heated to 850-950 ° C in the second step 32 to activate the copper foil 3a and the titanium foil 3b and degas, and then in the third step 33, 1 × 10 ^-4 Evacuate to high Torr vacuum. Next, while maintaining this high vacuum state, the fourth step 34
When heated to around 1000 ° C., the brazing filler metal 9 melts and the exhaust port closing member 8 descends onto the exhaust port edge member 7 due to the action of gravity to close the exhaust port 6. Then, when it is rapidly cooled in the fifth step 35, the brazing filler metal 9 is rapidly solidified, and the space 5 between the inner and outer containers is
While maintaining a high vacuum, the space between the exhaust port edge member 7 and the exhaust port closing member 8 is completely sealed as shown in FIG.

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.

Further, since the copper foil 3a and the titanium foil 3b are activated by the heating in the second step 32 and water vapor (H ₂ O), nitrogen (N ₂ ) and the like are released as in the manufacturing method according to the first embodiment. ,
The copper foil 3a and the titanium foil 3b act as getters after the vacuum sealing, and the residual gas in the space 5 and the gas released from the inner container 3 or the outer container 2 are 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 addition, in the first and second embodiments, preliminary evacuation to 1 × 10 ^-2 Torr was performed in the first steps 21 and 31, but the number is not limited to this value, and is in the order of 10 ^-2 Torr to about 100 Torr. It may be evacuated to a low vacuum. Also, the degree of vacuum in the third steps 23 and 33 is not limited to 1 × 10 ⁻⁴ Torr and may be in the high vacuum region of the order of 10 ⁻⁴ Torr or less.

Third Embodiment In order to manufacture a vacuum double pipe as shown in FIG. 4, first, as shown in FIG. 5, a connecting member 13 is provided on the downstream side of the water supply pipe 10 and its U-shaped inner surface is provided on the downstream side. Exterior,
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 supply pipe 10 is covered with the copper foil 10a, and the titanium foil 10b is wound between the copper foil 10a and the water supply pipe 10. Next, the outer cylinder 11 is sheathed from the upstream side of the water absorption pipe 10, and the points indicated by arrows C and D are welded all around to form the water supply pipe 10.
A space is formed on the outer side of the space surrounded by the outer cylinder 11 and the connecting members 13 and 14. In addition, when the outer cylinder 11 is mounted on the water supply pipe 10,
Since the tips of the water supply pipe 10 and the outer cylinder 11 do not come into contact with the connecting members 14 and 13, respectively, up to near the final position, they can be easily performed without difficulty. Also, copper foil provided on the outer surface of the water supply pipe 10.
It also does not damage 10a.

Next, the heating / exhausting process and the vacuum sealing process of the space between the water supply pipe 10 and the outer cylinder 11 are performed. The method is the same as the method in the first embodiment, and the operation and effect are also the same. Therefore, the description thereof will be omitted.

In this manufacturing process, when the material is put into the furnace from room temperature and heated, first, the temperature of the outer cylinder 11 rises, and then the temperature of the water supply pipe 10 rises later. The expansion amount of 11 is large, and the outside and the inside of the connecting members 13 and 14 are deformed by receiving forces in the directions of arrows a and b in FIG. 4, respectively.

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

In this way, the connecting members 13 and 14 receive forces in completely opposite directions during heating and cooling, but the connecting members 13 and 14
Since the intermediate connecting portion forms a substantially right angle with respect to the inner ring portion and the outer ring portion and has a degree of freedom in both directions, it is free from excessive stress during deformation and is not damaged.

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 second invention.

In this heat retention test, under the conditions shown in Table 1, a stainless steel vacuum double container manufactured by the method according to the present invention, in which the inner container was covered with copper foils having different wall thicknesses, and titanium foil was rolled up 5 samples each were used as test samples.

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, 4 weeks after 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. 9a to 9d and FIG.
Shown in Figures a-10d. 9a to 9d, 10a to 10d
In the figure, it is possible to know the temperature drop of 95 ° C hot water after 24 hours of warming, that is, the magnitude of the 24-hour heat retention, by the upper and lower sides of the temperature curve. You can know the magnitude of your strength. In addition, by comparing the figures of 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 by 0.8 ° C after 1 week, further decreases to 0.2 ° C or less after 2 weeks, and thereafter tends to increase. 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 of} FIG. 9c under the same conditions except for the exhaust method and titanium foil,
While the decrease in the vacuum maintaining power of Sample I is about 1 ° C,
The vacuum maintaining power of the sample 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, the bottom peak of the curve is after 1 week in the sample I, whereas it is after 2 weeks in the sample A ₃ . Thus, an early peak is due to less liberation of stored gas and / or
Alternatively, it shows that the getter action of the copper foil and the titanium foil is large.

As is clear from a comparison between sample I in Table 3 and sample B _{1 in} FIG. 9a, 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.

Since the 9a view, second 9d 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, It is possible to know the effect of the getter action of the copper foil. 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 worship time is short, the vacuum maintaining power becomes unstable, and it tends to decrease until 2 weeks after the production 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 large and the getter action cannot be followed up, and if the occluded gas is subsequently desorbed, the getter action of the copper foil becomes dominant and gas absorption is accelerated.

Figure 10a, second 10d figure, although the present invention is intended for samples prepared by different manufacturing methods, the sample F ₂ ~F _4, G ₁
~ G ₄ is the inner container covered with aluminum foil, so
Sample A ₂ to A ₄ of the inner vessel was covered with copper foil shown in FIGS., Second 9d FIG, B ₁
By comparing with ~ B 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
As is clear from a comparison with Sample B _{2 in} Fig. 10a, the one in which the inner container is 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. 9a to 9d 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 reversal and the magnitude of inclination in the aluminum foils of FIGS. 10a to 10d, the samples C _{2 to} C ₄ and D _{2 to} D were examined.
_Since it is not much different from ₄ , activation of aluminum foil under these conditions is
It can be said that it is rare. The getter action of aluminum foil cannot be expected.

On the other hand, the present inventors further conducted a confirmation test on a vacuum double pipe, and as a result, kept the upper and lower portions of the antifreezing pipe at an atmosphere of 5 ° C and kept a temperature of -30 ° C between them. The result shows that the water inside does not freeze for about 80 hours even when exposed to low temperature conditions.

(Effects of the Invention) As is clear from the above description, according to the first invention,
The activated copper foil and the gettering action of titanium or zirconium keep the vacuum space between the inner wall and the outer wall at a high vacuum and maintain the heat insulating property. Further, since the titanium material or the zirconium material is interposed between the copper foil and the inner wall, the titanium material or the zirconium material does not fall off and no holding member is required.

On the other hand, according to the second aspect of the invention, before exhausting to a high vacuum, the inner wall is quickly heated by heating under a low vacuum that does not impair the heat transfer property, so that degassing from the inner wall is particularly sufficient. In addition, it is performed in a short time, the heating and exhaust treatment time is shortened as a whole, the manufacturing process can be shortened, and the heat insulating property is stabilized.

Further, when heated and degassed, the copper foil covering the outer surface of the inner wall and titanium or zirconium are activated to release the occluded gas, which acts as a getter that absorbs hydrogen and nitrogen after vacuum containment, respectively, and therefore has a high degree of heat insulation. While being maintained, the original getter material and the metal fitting for holding the getter material can be eliminated, and the material cost can be reduced.

[Brief description of drawings]

FIG. 1 is a sectional view of a double container according to the present first invention manufactured by a tip tube method, and FIG. 2 is a sectional view of a double container according to the first invention manufactured by a brazing method. FIG. 4 is a partially enlarged sectional view of FIG. 2, FIG. 4 is a half sectional view of the vacuum double pipe according to the first invention manufactured by the tip tube method, and FIG. 5 is a state in the middle of manufacturing the vacuum double pipe. FIG. 6 is a half sectional view showing the manufacturing process of the metallic vacuum double structure according to the second aspect of the present invention, and FIGS. 7 and 8 are the tip tube method according to the second aspect of the present invention. , Fig. 9a to Fig. 9d, Fig. 10a to Fig. 10d showing the manufacturing process of a stainless steel vacuum double container by the brazing method.
The figure is a diagram showing a test result regarding heat retention of a vacuum double container manufactured by a conventional method. 1 ... double container, 2 ... outer container, 3a ... copper foil, 3b ... titanium foil, 3 ... inner container, 5 ... space.

Claims (2)

[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 in that it is covered with a copper foil and activated titanium or zirconium is interposed between the inner wall surface and the copper foil. 2. A method for manufacturing a metal vacuum double structure, wherein 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. While covering with copper foil, titanium or zirconium is interposed between the inner wall surface and copper foil, and the space between the inner wall and outer wall is pre-evacuated to a low vacuum of the order of 10 ^-2 Torr or more, approximately 400 ° C. After performing degassing by heating at the above temperature for a predetermined time, a metal vacuum characterized by exhausting to a high vacuum of the order of 10 ^-4 Torr or less while keeping the heating temperature and vacuum-sealing. Method for manufacturing double structure.