JPH01268521A - Metallic vacuum double structure and manufacture thereof - Google Patents

Abstract

PURPOSE:To require no getter nor getter holding fitting by covering the surface of an internal wall with an activated copper foil, interposing activated titanium or zirconium between the surface of the internal wall and the copper foil, thereby, obtaining a vacuum double structure made of metal excellent in heat insulation property at low cost and completely evacuating the inner space container in a short time. CONSTITUTION:A metallic vacuum double structure forms a double wall structure consisting of an internal wall 3 and an external wall 2 to evacuate a space between the internal wall 3 and the external wall 2 and seal the space. The surface of the internal wall 3 is covered by activated copper foil 3a and activated titanium or zirconium 3b is interposed between the surface of the internal wall 3 and the copper foil 3a. Hydrogen gas remaining in a vacuum space between the internal wall 3 and the external wall 2 or gas isolated from the internal wall 3 or the external wall 2 is absorbed by the activated copper foil 3a covering the surface of the internal wall 3 and nitrogen is absorbed by the titanium or the zirconium 3b interposed between the surface of the internal wall 3 and the copper foil 3a, so that the vacuum space is maintained to a high vacuum state to maintain the heat insulation property. Since the titanium or the zirconium 3b is interposed between surface of the internal wall 3 and the copper foil 3a, a holding member is not completely required.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a metal vacuum double structure such as a thermos flask or a double vacuum pipe, and a method for manufacturing the same.

(Prior art) In order to improve the heat retention of a double-walled vacuum container made of metal, such as a vacuum double-walled container such as a thermos bottle, it is necessary to increase the degree of vacuum between the inner container and the outer container, and to It is important to block radiant heat transfer to the container.

In order to increase the degree of vacuum, it is necessary not only to increase the evacuation processing capacity and seal to a high vacuum, but also to prevent the escape of the occluded gas from the outer surface of the inner container or the inner surface of the outer container after sealing. Especially necessary. For this reason, conventional methods include degreasing the outer surface of the inner container and the inner surface of the outer container and then pickling with nitric-hydrofluoric acid, etc., heating in a furnace during exhaust treatment to exhaust the occluded gas along with air, and using a getter. There is a method of adsorbing the occluded gas that is released from the metal surface, but all of these methods are commonly used.

In addition, as a method for preventing radiation heat transfer, conventional methods include forming a plating layer on at least the outer surface of the inner container by electrolytic plating or silver mirror reaction, or the method described in Japanese Patent Laid-Open No. 61-3111.
As shown in Publication No. 1, there is a method of covering the outer surface of the inner container with a thin plate of copper or aluminum.

On the other hand, there are two methods for vacuum containment after vacuum evacuation: a method in which a closing member is soldered to the exhaust port formed on the bottom of the outer container to close it (hereinafter referred to as the "brazing method"); There is a method in which a tip tube for use is pinched off (hereinafter referred to as the tip tube method).

In the pre-fertilization soldering method, if 7lux is used to solder the closing member, gas will flow into the vacuum space of both the inner and outer containers, reducing the degree of vacuum, so it is necessary to solder without using flux. For this reason, for example, in the case of a stainless steel vacuum double container, the surface is lathed at a high temperature of 7 degrees, and nickel solder etc.
A filler metal must be used that has a melting point of . Moreover, when stainless steel is heated to a high temperature or cooled from a high temperature, it must be heated within a certain temperature range (generally about 450 to 80°C).
Solute carbon precipitates as carbide at temperatures of 50°C) and becomes sensitized, making intergranular corrosion more likely to occur and reducing corrosion resistance.
Evacuation treatment and brazing are performed at the above temperature, 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 chip tube method does not use brazing material,
Temperature below the sensitization zone, i.e. 400-450°C
A vacuum evacuation process is being performed.

By the way, during the vacuum evacuation process, it is necessary to heat the double container in order to clean the metal surface and release the occluded gas, but heating during the evacuation process oxidizes the plating surface, etc.
Conventionally, before heating, preliminary evacuation is performed to a higher vacuum than 1X10-'' Torr (1,33 Pa), and in the brazing method,
The temperature is 0 to 950°C, and the chip tube method is heated to 400 to 450°C.

The above-described methods of increasing the degree of vacuum, preventing radiation heat transfer, and vacuum confinement methods are also applied to the manufacture of vacuum double pipes used for water supply pipes for freezing prevention and the like.

In general, regarding the degree of vacuum, the pressure is 10-3To
rr or more is low vacuum, 10-"I 0-3Torr range is high vacuum, 10-"
'-10-4Torr range ultra-high vacuum, 10-4Torr
Since the vacuum below rr is called an ultra-ultra-high vacuum, this also applies in this specification.

(Problem to be solved by the invention) However, as in the prior art,
When preliminary evacuation is performed to a higher vacuum, air, which is a convective heat transfer medium, becomes diluted, and the heat transfer between the outer container and the inner container becomes extremely poor. For this reason, even if the inner container is heated after preliminary evacuation, there is a significant delay compared to the outer container, which directly receives the heating and furnace heat of the inner container, resulting in long evacuation processing times and insufficient degassing from the outer surface of the inner container. Therefore, the occluded gas remaining after vacuum confinement is liberated, the degree of vacuum decreases, the heat insulation properties change over time, and the heat retention properties gradually decrease.

Therefore, conventionally, a getter has been used to adsorb the occluded gas liberated after vacuum confinement.

The use of such a getter is essential for perfecting heat retention, but on the other hand, it has the problem of increasing the cost of materials such as the original getter and getter holding fittings.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a metal vacuum double structure that has excellent heat insulation properties and is inexpensive, and that degasses from the inner container in a short evacuation process time. It is an object of the present invention to provide a method for manufacturing a metal vacuum double structure that can be carried out satisfactorily and eliminates the need for an original getter and getter holding fittings.

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

Therefore, the present invention first focuses on the relationship between the degree of vacuum and the heat insulation property.It is well known that an extremely excellent heat insulation property can be obtained under a high vacuum of 1 X 1 O-4 Torr or less. The change in the degree of vacuum is lO-"10-"
Focusing on the fact that Torr changes to tJ between order (7) (see Thermal Engineering Materials edited by the Japan Society of Mechanical Engineers), we focused on the fact that under vacuum, where thermal insulation does not appear significantly and heat conductivity is good to some extent, that is, IO-” It was decided that heating and degassing would be performed in a low vacuum of the order of Torr or higher.

Furthermore, in order to have the copper foil coated on the outer surface of the inner container effectively exhibit a gas absorption function, that is, a getter function, in addition to its original radiation heat transfer prevention function, the copper foil is activated during the vacuum evacuation process. In addition to effectively degassing, titanium or zirconium absorbs gases that cannot be absorbed by copper foil.

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

Therefore, the present inventors conducted an analysis of the gases released when the copper foil is activated, taking into account that copper and hydrogen are chemically adsorbed, and obtained the following results.

When a copper foil is housed in a stainless steel chamber and activated while heating and exhausting, mainly water vapor (H2) is released from the copper foil.
O), carbon dioxide (COz), -carbon oxide (CO) were released, and hydrogen (N7) was slightly released. here,
The water vapor (H2O) released is 120°0.240°
Three peaks were observed at C and 370°C, and the peak at 120°C was physically adsorbed on the surface of the copper foil.
The peaks at 240° C. and 370° C. are considered to be caused by a combination of oxygen (0) that was bonded to copper (Cu) in the form of CuO or Cu2O and diffused hydrogen (H). Carbon dioxide (CO2) and -carbon oxide (CO) are 240
Two peaks at 400° C. and 400° C. were observed, and it is thought that oxygen (0) bonded to copper (Cu) and diffused carbon (C) bonded on the surface. In addition, hydrogen (N2
) is considered to be what remained in the form of water vapor (H2O) and was released as is.

In addition, the hydrogen released by activation of this copper foil (approximately 12 g) (including that released in the form of N2
Hydrogen (equivalent to 5t-707 made by S, P, A, about 0.5 g) is released when activated.

Furthermore, when copper foil is forcibly oxidized in air, the probability of collision between hydrogen (H) and oxygen (0) on its surface increases when it is activated, so hydrogen (N2) is more likely to be released in the form of water vapor (N20). It has been confirmed that no damage remains due to oxidation.

In addition, the present inventors took into account that nitrogen, which is not chemically adsorbed even when physically adsorbed with copper, is chemically adsorbed with titanium or zirconium, and as a result of analyzing the released gas when titanium foil is activated, we found that hydrogen ( The peak of hydrogen is about 700°C1 nitrogen (
The peak of N,) was about 400°C. In addition, as a result of analyzing the gas released during activation of zirconium foil, we found that hydrogen (
N2) and nitrogen (N2) peaks are both approximately 300°
It was C. Furthermore, nitrogen (approximately 0.8 g) of titanium foil (
N2) absorption capacity is the same as that of the general getter material (approximately 0.5g
It has also been confirmed that the absorption capacity for nitrogen (N, ) is equivalent to that of In addition, conventionally commercially available titanium getters are activated at 700° C. or higher to absorb hydrogen (N2) more effectively than nitrogen (N), and are used as high-temperature getters.

The first invention was made based on the above knowledge, and
In a metal vacuum double structure where an inner wall and an outer wall form a double wall structure, and the space between the inner and outer walls is evacuated and sealed in a vacuum, the surface of the inner wall is covered with activated copper foil. Additionally, activated titanium or zirconium is interposed between the inner wall surface and the copper foil.

Further, a 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 the space between the inner wall and the outer wall is evacuated and sealed in vacuum. The surface is covered with copper foil, and titanium or zirconium is interposed between the inner wall surface and the copper foil, and as shown in Figure 6, in the first step I, a low vacuum of the order of 1 O-'' Torr or higher is applied. After preliminary evacuation and degassing by heating at a temperature of approximately 400°C or higher for a predetermined time in the second step (2), a high vacuum of less than the order of lO-Torr is produced while maintaining the heating temperature in the third step (2). This is followed by evacuation treatment, followed by vacuum sealing in the fourth step (2).

As the titanium material or zirconium material, for example, titanium foil, titanium pellet, commercially available titanium getter, etc. can be used. Preference is given to using foil or zirconium foil. Further, when the material of the inner wall or the outer wall is austenitic stainless steel such as SU3304, it is preferable to carry out heating degassing at a temperature lower than or exceeding the sensitized region of the stainless steel.

As for the vacuum confinement method, either the conventional chip tube method or the soldering method can be used, but if the material of the inner or outer wall is austenitic stainless steel, the chip tube method is used because the sensitized region of the stainless steel Thermal degassing should be carried out at a lower temperature, and in brazing processes, the heating degassing should be carried out at a temperature above the sensitization region.

In addition to air, the space between the inner and outer walls contains nitrogen (N
2) An inert gas such as argon (Ar) can be sealed. However, in the case of air, oxygen in the air (0
□), the copper foil is oxidized, but as the probability of collision between oxygen (02) and hydrogen (H2), which is the main component of degassing, increases, oxygen and hydrogen combine to become water vapor (H20). It has the advantage of being easily released and being economical from the viewpoint of activation.

(Function) According to the configuration of the first invention, among 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, hydrogen (H8) is activated to cover the surface of the inner wall. Since nitrogen (N2) is absorbed by the copper foil and absorbed by the titanium or zirconium interposed between the inner wall surface and the copper foil, the vacuum space is kept at a high vacuum and its insulation properties are 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 invention, 1O-2T in the first step I
Preliminary evacuation to a low vacuum of the order of
On the order of O-'' Torr, the heat conductivity is not significantly impaired.

For this reason, in the second step (2), heating to approximately 400°C or higher
The heat of the outer wall that directly receives the furnace heat is radiation and conduction.

It is quickly transmitted to the inner wall by convection, and the temperature of the inner wall rises in a short time. Therefore, the stored gas is liberated from the wall surfaces of the inner wall as well as the outer wall, and degassing is carried out sufficiently and in a short time. Further, as the inner wall is heated, the copper foil and titanium or zirconium are also heated, and the occluded gas is released and activated.

Then, in the third step (3), when exhaust treatment is carried out to a pressure below the order of 10 -4 Torr, the free gas from the inner wall or the outer wall and the gas released from the copper foil, titanium or zirconium are discharged to the outside together with the residual air.

After completing this evacuation process, vacuum confinement is carried out using the chip tube method or soldering method in the fourth step (2), and a high vacuum vacuum double structure is obtained, and copper foil and titanium or zirconium are used as getters. Among the gases that act and remain in the vacuum space between the inner and outer walls, or the gases liberated from the inner or outer walls, hydrogen (H2) is absorbed by the copper foil,
Nitrogen (N2) is absorbed by titanium or zirconium to maintain thermal insulation.

If the inner or outer wall is made of austenitic stainless steel such as SUS 304 and vacuum confinement is performed using the chip tube method, in the second step , there is no risk of deterioration in corrosion resistance due to sensitization.

In addition, if the inner wall or outer wall is made of austenitic stainless steel and vacuum confinement is performed by the brazing method, in the second step As with the chip tube method, there is no risk of deterioration in corrosion resistance.

(Example) Next, embodiments of the present invention will be described with reference to the accompanying drawings.

i) First embodiment of the invention ■First embodiment Fig. 1 shows a vacuum double container l for a thermos flask according to the present invention.
A stainless steel outer container 2 is formed into two parts, an upper part 2a and a lower part 2b, and the outer surface has a thickness of 16.5μ2 and a weight of 1
It is covered with a 2g copper foil 3a, and the thickness is 25μ1 and the weight is 0.
Insert the stainless steel inner container 3 wrapped with 8g of titanium foil 3b, join the inner container 3 and the upper part 2a of the outer container 2 at the mouth Y, and then connect the upper part 2a and the lower part 2bf of the outer container 2.
They are joined at the tX portion to form a double wall structure, and a chip pipe 4 for exhaust is provided at the bottom of the outer container 2.

Note that the central part of the bottom outer surface of the inner container 3, which faces the chip tube 4, is not covered with the copper foil 3a and is exposed.

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. Contained in vacuum.

In the vacuum double container l having the above configuration, gas that is not exhausted from the chip tube 4 during manufacturing and remains in the vacuum space 5 between the outer container 2 and the inner container 3, or gas that remains in the vacuum space 5 between the outer container 2 and the inner container 3 after vacuum sealing. Among the gases liberated from the copper foil 3a, hydrogen (H2) is absorbed by the copper foil 3a due to the getter action of the activated copper foil 3a. Further, nitrogen (N, ) is absorbed into the titanium foil 3b by the getter action of the activated titanium foil 3b. For this reason, the vacuum space 5 between the outer container 2 and the inner container 3 is kept at a high vacuum, and its insulation properties are maintained.

■Second Embodiment FIGS. 2 and 3 show a double container 1a for a thermos flask according to another embodiment of the present invention, in which the tip tube 4 of the outer container 2 of the double container 1 is replaced with an opening. The opening 4a is formed by forming a portion 4a.
An exhaust port edge member 7 having an exhaust port 6 in the center is fitted and joined to the exhaust port 6, and an exhaust port closing member 8 is installed on the exhaust port 6 with a brazing material 9 interposed between the outer container 2 and the inner container 3. The space is substantially the same except that after heating and exhausting through the opening 4a, the brazing material 9 is melted and the opening 4a is closed with an exhaust port closing member 8 to seal it in vacuum. Corresponding parts are given the same numbers and explanations are omitted.

In the vacuum double container 1a having the above configuration, the copper foil 3
As in the first embodiment, the titanium foil 3b acts as a getter, so the vacuum space 5 between the outer container 2 and the inner container 3 is kept at a high vacuum and the heat insulation properties are maintained.

(3) Third Embodiment FIG. 4 shows a vacuum double pipe used as a water supply pipe for anti-freezing purposes, and is generally composed of a water supply pipe 10, an outer cylinder 11, and connecting members 13 and 14.

The water supply pipe IO is a stainless steel pipe with an inner diameter of 22 mm and a thickness of l+a+++, and the part where the outer cylinder 11 is sheathed is made of copper.
A titanium foil 10b is wrapped between the water supply pipe lO and the copper foil 10a.

Note that an appropriate spacer may be provided to maintain a constant gap with the outer cylinder 11 and to prevent thermal contact between the outer cylinder 11 and the water supply pipe 10 as much as possible. Outer cylinder 1
1 has an inner diameter of 42mm.

Water supply pipe lO with 1.2mm thick stainless steel pipe
A copper tip tube 12 is attached to the outer periphery on the upstream side.

The connecting members 13 and 14 are ring members made of stainless steel and having a U-shaped cross section, and are inserted into the water supply pipe 1O and welded all around to the outer surface of the water supply pipe 10 and the end of the outer cylinder 11, and are connected to the water supply pipe 10. The space between the outer cylinders 11 is covered.

Then, this space is heated and evacuated through the chip tube 12, and after activating the copper foil 10a and the titanium foil 10b, the chip tube 12 is sandwiched and sealed in a vacuum.

Further, caps 15.16 made of stainless steel are attached to both ends of the outer cylinder 11 and the outside of the connecting member 13.14, and a sealant 17.17 is applied between the caps 15.16 and the connecting member 13.14. While being injected, 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. In addition,
As shown, the tip tube 12 is covered with a cap 19,
A sealant 17 may be filled inside it.

In the vacuum double pipe with the above configuration, copper 'f3
10a and titanium foil lOb are the same as in the first embodiment,
In order to act as a getter, the water supply pipe lO and the outer cylinder 1
The vacuum space 20 between the parts 1 and 1 is kept at a high vacuum and maintains heat insulation.

■Fourth Embodiment In the vacuum double pipe according to the third embodiment, instead of sandwiching the chip tube 12 and sealing it in vacuum, an opening is formed as in the second embodiment, and the opening is closed. It was closed with a closing member and soldered.

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 due to the getter action of the copper foil 10a and the titanium foil 10b, and the insulation is maintained.

ii) Second Embodiment of the Invention First Embodiment In order to manufacture the vacuum double container l as shown in FIG. 3b is formed into a double-walled structure with the inner container 3, and the double-walled container 1 is placed in a heating furnace and the chip tube 4 is connected to a vacuum pump.

Then, as shown in FIG. 7, in a first step 21, the space 5 between the inner container 3 and the outer container 2 is preliminarily evacuated to
Create a low vacuum of O-"I"orr. At this time, since the bottom outer surface of the inner container 3 facing the chip tube 4 is not covered with the copper foil 3a, the copper foil 3a is not sucked up during the exhaust process.

In the second step 22 in this low vacuum state, 400 to 450
Heat to °C. At this time, the heat of the outer container 2 heated by directly receiving the furnace heat is transferred to the inner container 3 by radiation heat, heat conduction through the mouth Y, and convective heat transfer via the residual gas in the space 5. Conveyed. In the first step 21 l X l O-2
Although the space is evacuated to a low vacuum of Torr, convective heat transfer by the residual gas in the space 5 becomes dominant at this level of vacuum, and the heat transfer from the outer container 2 to the inner container 3 is not significantly impaired.

Therefore, the heat of the outer container 2 is quickly transferred to the inner container 3, and the temperature of the inner container 3 rises in about 10 to 20 minutes.

Therefore, the stored gas is liberated into the space 5 from the outer surface of the inner container 3 as well as the outer container 2, and degassing is carried out sufficiently and in a short time. Furthermore, at the same time as this inner container 3 is heated, the copper foil 3a and titanium foil 3b are also heated and activated, producing water vapor (HzO), nitrogen (N2), carbon dioxide (CO
z), -carbon oxide (CO), etc. are present in the copper foil 3a and titanium foil 3
emitted from the surface of b.

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

Then, while maintaining the temperature of this second step 22, the third step
In step 23, the gas is further evacuated to create a high vacuum of lXl0-'TO. The released gas is exhausted to the outside through the tip tube 4.

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

In the vacuum double container manufactured by the above process, gas is sufficiently degassed not only from the outer container 2 but also from the inner container 3 in the second step 22, so that there is little release of occluded gas after vacuum sealing. , the insulation is stabilized.

In addition, in the second step 22, hydrogen (N3) etc. are released in the form of water vapor by activation of the copper foil 3a, and nitrogen (N2) is released by activation of the titanium foil 3b, so the vacuum The copper foil 3a and titanium foil 3b after being sealed have a gas absorption function, that is, a getter function. Therefore, the gas remaining in the space 5 after vacuum confinement or the inner container 3
Or out of the gas liberated from the outer container 2, hydrogen (N7
) is absorbed by the copper foil 3a, and nitrogen (N2) is absorbed by the titanium foil 3b.
Since it is absorbed by

It goes without saying that this copper foil 3a has the effect of preventing radiation heat transfer from the inner container 3a.

Further, since the titanium foil 3b is wrapped around the outer surface of the inner container 3 by the copper foil 3a, it will not fall off and no holding member is required.

■Second Embodiment To manufacture the double vacuum container 1a as shown in FIG. Install the corrugated brazing material 9,
After the exhaust port closing member 8 is placed on the brazing filler metal 9, it is set in a vacuum heating furnace.

Then, as shown in FIG. 8, in a first step 31, the first
Similar to the first step 21 of the manufacturing method according to the example, I
Preliminarily evacuate to a low vacuum of I O-” Torr, and perform the second step 3.
After heating the copper foil 3a and the titanium foil 3b to 850 to 950°C in step 2 and degassing them,
In step 33, the vacuum is evacuated to a high vacuum of lXlO-'Tor.Next, while maintaining this high vacuum state, a fourth step 34 is carried out.
When heated to around 10.degree. 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. Next, the fifth step 35
When rapidly cooled, the brazing filler metal 9 rapidly solidifies, and the gap between the exhaust port edge member 7 and the exhaust port closing member 8 is completely closed, as shown in FIG. 5, while maintaining the space 5 between the inner and outer containers at a high vacuum. sealed.

In the manufacturing method according to this second embodiment, in the first step 31, l
1. As in the manufacturing method according to the first embodiment, the second
The heating and degassing in step 32 can be carried out sufficiently and in a short time, and the evacuation treatment time in third step 33 can also be shortened.

Further, the heating in the second step 32 activates the copper foil 3a and the titanium foil 3b, and as in the manufacturing method according to the first embodiment, water vapor (H2O), nitrogen (N, ), etc. are released. The foil 3a and the titanium foil 3b act as a getter after 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, so that the heat insulation properties do not deteriorate.

Furthermore, since the stainless steel is heated at a temperature exceeding the sensitization region in the second step 32 and rapidly cooled in the fifth step 35, the time that the stainless steel is exposed to the sensitization region is significantly shortened.
There is no risk of deterioration of corrosion resistance due to sensitization.

In addition, the above-mentioned No. 1. In the second embodiment, the first step 21.31
Although the pre-evacuation was carried out to l X l O-" Torr, it is not limited to this value.
It is sufficient to evacuate to a low vacuum of the order of r to l 00 Torr. Further, the degree of vacuum in the third step 23.33 is not limited to l x 10-4 Torr, but may be in a high vacuum region of the order of I O-4 Torr or lower.

■Third Embodiment To manufacture a vacuum double pipe as shown in FIG. 4, first, as shown in FIG. The connecting member 14 is attached to the upstream end of the outer cylinder 11 with its U-shaped inner surface facing upstream, and the point indicated by arrow A is welded all around. Weld the entire circumference.

Then, cover the outer surface of the water supply pipe 1O with a copper foil 10a,
Titanium foil 10b is placed between this copper foil tOa and the water supply pipe 10.
Involve them. Next, the outer cylinder 11 is sheathed from the upstream side of the water suction pipe IO, and the point indicated by the arrow C1D is welded all around, and the outer cylinder 11 and the connecting member 13 are attached to the outside of the water supply pipe IO.
．． A space surrounded by 14 is formed. It should be noted that when mounting the outer cylinder 11 on the water supply pipe IO, the tip of the water supply vibrator 1O1 and the outer cylinder 11 do not come into contact with the connecting members 14, 13, respectively, until near the final position, so this can be done easily and without difficulty.

Further, the copper foil 10a provided on the outer surface of the water supply pipe IO will not be damaged.

Next, the space between the water supply pipe IO and the outer cylinder 11 is subjected to heating exhaust treatment and vacuum sealing treatment, but the method is the same as the method in the first embodiment, and the operation and effect are also the same. Therefore, the explanation will be omitted.

In this manufacturing process, when the outer cylinder 11 is placed in a furnace from room temperature and heated, the temperature of the outer cylinder 11 rises, and then the temperature of the water supply pipe 1O rises. 11 has a large expansion amount, and the connecting member 13
．． The outside and inside of 14 are deformed by receiving forces in the directions of arrows a and b in FIG. 4, respectively.

On the other hand, when the cooling is transferred, the outer cylinder 11 is cooled more than the water supply pipe ♀, so when cooling, the outer cylinder 11
The amount of shrinkage of the connecting member 13 is large, and contrary to the heating, the connecting member 13
．． 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.
．． 14, the intermediate connecting part is approximately perpendicular to the inner ring part and the outer ring part, and has a degree of freedom in both directions, so that it will not be damaged when it is deformed without being subjected to excessive stress. There isn't.

1ii) Confirmation Test The present inventors conducted a test to confirm the heat retention 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, stainless steel vacuum double containers manufactured by the method according to the present invention were used, the inner container was covered with copper foil having different wall thicknesses, and titanium foil was wrapped around the inner container. Five pieces of each were used as test samples.

Table 1. Test sample In addition, for comparison, a sample of a stainless steel vacuum double container manufactured by a conventional method was prepared as shown in Table 2-11.
The materials shown in Table 2-2 were prepared.

Table 2-2. Comparative sample (2) Note that no getter was used in any of the samples.

For each sample, ■ Initial stage: Immediately after production, ■ After being placed in a 95°C atmosphere for one week after production, ■ After being placed in a 95°C atmosphere for two weeks after production (an additional week from ■), ■ After being placed in a 95°C atmosphere for 4 weeks after manufacture (an additional 2 weeks from ■), ■ After being placed in a 95°C atmosphere in Manufacturing I & March (further February from ■), ■ Manufacturing (in April (■ Furthermore, after placing it in a 95°C atmosphere (January 1), in the 6 steps of , 95°C hot water was put into the inner container 1 and the temperature of the water was measured after 24 hours in a 20°C atmosphere. , tested for heat retention.

Among the 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 10a to 10d. Figures 9a to 9d,
In Figures 10a to 10d, the temperature drop after keeping hot water at 95°C for 24 hours, that is, the magnitude of the heat retention ability for 24 hours, can be determined by the top and bottom of the temperature curve, and the decreasing slope of the temperature curve indicates the vacuum due to aging. It is possible to know the decrease in the degree of vacuum maintenance, that is, the magnitude of the vacuum maintenance force. Also, the same type of material, for example A! , A3. By comparing each figure for A, it is possible to know the influence of the evacuation time during manufacturing.

(Hereafter, blank space) Table 3. Test Results Based on the test results, the following items regarding heat retention and exhaust time were confirmed.

■ As is clear from the average value of each sample I and ■ in Table 3, the vacuum maintaining force decreased by 1°C after one week for sample I, decreased by 0.8°C after one week for sample ■, and decreased by 0.8°C after one week for sample I. After a week, the temperature decreases by only 0.2°C, and thereafter it tends to rise.

Therefore, according to the method according to the present invention, the vacuum holding power remains constant and does not decrease at all.

In addition, since the temperature of sample ① was slightly higher than that of sample I, this indicates that the thinner the copper foil, the better the heat retention ability for 24 hours in the initial stage. This is because, considering that the evacuation time for both is the same, the thinner the copper foil is, the higher the adhesion to the inner container 3, the faster the heat absorption, and the more gas is released due to activation during the evacuation process. It is presumed that the gas absorption capacity after vacuum confinement is increased.

■ Comparing sample ■ in Table 3 with sample B in Figure 9c, which is under the same conditions except for the exhaust system and titanium foil, it is clear that the decrease in vacuum maintaining power of sample ■ is about 1'C. On the other hand, the vacuum maintaining power of sample B decreased by about 3°C after two weeks. Therefore, according to the method according to the present invention, the vacuum maintaining ability is improved compared to the conventional method.

Further, in Sample I, the bottom peak of the curve is after one week, whereas in Sample A, it is after two weeks.

In this way, the early peak indicates that the release of the stored gas is small and/or that the getter action of the copper foil and titanium foil is large.

■ As is clear from the comparison between sample ■ in Table 3 and sample B1 in Figure 9a, both have the same 24-hour heat retention ability, and the vacuum maintenance ability tends to remain the same, but sample I While the evacuation time is 50 (lo+40) minutes, the evacuation time of sample B1 is 100 minutes. Therefore, according to the method according to the present invention, the evacuation time can be reduced by 50 minutes compared to the conventional method.

■ Figures 9a to 9d are samples manufactured by a manufacturing method different from that of the present invention, but since there are samples A2 to A, , B, and B4 whose inner containers were covered with copper foil, You can see the effect of the getter action of the foil. That is, (a) those whose inner containers are covered with copper foil have much better heat retention ability for 24 hours and vacuum maintenance ability than other types.

However, if the evacuation time is long, the vacuum maintenance power remains flat and the degree of decrease is small. Furthermore, if the evacuation time is short, the vacuum maintenance power becomes unstable, tends to decrease for up to two weeks after manufacture, and then improves thereafter. This is because when the evacuation time is short, degassing of the inner or outer container and the walls of the copper foil is insufficient, so the amount of released gas released immediately after vacuum confinement is greater than the amount of gas absorbed by the copper foil as a getter. This is because the getter action cannot catch up with the large amount of gas, and if the occluded gas is subsequently released, the getter action of the copper foil becomes dominant and gas absorption is accelerated.

■ Figures 10a to 10d are samples manufactured by a manufacturing method different from the present invention, but this sample F
, ~F, ,G, ~G are inner containers covered with aluminum foil, so samples A2-A, , B, -, in which the inner containers shown in FIGS. 9a to 9d are covered with copper foil, are By comparing with B4, it is possible to know the effect of the getter action of the copper foil. That is, a. Comparing samples with the same evacuation time, for example, sample B in FIG. 9a and sample B in FIG. 10a,
As is clear, the inner container covered with copper foil has better heat retention for 24 hours than the inner container covered with aluminum foil, and has a more stable vacuum maintenance ability.

Mouth, Samples C2-C, D, ~D in Figures 9a to 9d,
indicates a blank product (no plating or foil), and the recovery trend after one month suggests that the gas absorption capacity of the outer container 2 has reversed with respect to the amount of free gas from the inner container 3. , then the magnitude of the slope suggests the magnitude of that quantity.

Therefore, if we look at the point of reversal and the magnitude of the inclination in the aluminum foils shown in Figures 10a to 10d, we can see that the samples C2 to
Since there is not much difference between C4 and D2 to D, it can be said that activation of the aluminum foil under these conditions is unlikely. The getter effect of aluminum foil cannot be expected.

On the other hand, the inventors further conducted confirmation tests on vacuum double pipes, and as a result, the upper and lower parts of the antifreeze pipe were kept in an atmosphere of 5 degrees Celsius, and the space between them was maintained at -30 degrees Celsius. The results showed that even when exposed to low temperature conditions of C., the water inside did not freeze for about 80 hours.

(Effect of the invention) As is clear from the above explanation, according to the first invention,
Due to the getter action of the activated copper foil and titanium or zirconium, the vacuum space between the inner wall and the outer wall is kept at a high vacuum and the insulation properties can be maintained. Also, since the titanium material or zirconium material is interposed between the copper foil and the inner wall, it will not fall off and no holding member or the like is required.

On the other hand, according to the second invention, the temperature of the inner wall is quickly raised by heating it in a low vacuum without impairing heat conductivity before evacuation to a high vacuum. is carried out sufficiently and in a short time, reducing the overall heating and exhaust treatment time and shortening the manufacturing process.
Stabilizes insulation.

In addition, the copper foil and titanium or zirconium that cover the outer surface of the inner wall are activated during heat degassing and release the stored gas, and after vacuum sealing, they act as getters to absorb hydrogen and nitrogen, respectively, resulting in a high degree of heat insulation. In addition, it is possible to eliminate the need for the original getter material and the metal fittings for holding the getter material, and it is possible to reduce material costs.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the double container according to the first invention manufactured by the chip tube method, FIG. 2 is a sectional view of the double container according to the first invention manufactured by the soldering method, and FIG. The figure is a partially enlarged sectional view of Figure 2, Figure 4 is a half-sectional view of the vacuum double pipe according to the first invention manufactured by the chip tube method, and Figure 5 is a state in the middle of manufacturing the vacuum double pipe. , FIG. 6 is a diagram showing the manufacturing process by the method for manufacturing a metal vacuum double structure according to the second invention, and FIGS. 7 and 8 are the chip tube method of the second invention, respectively. , Figures 9a to 9d, and 10a to 10d show the manufacturing process of a vacuum double container made of stainless steel by the brazing method, and relate to the heat retention of the vacuum double container manufactured by the conventional method. It is a figure showing a test result. l...Double container, 2...Outer container, 3a...
Copper foil, 3b...Titanium foil, 3...Inner container, 5.
··space. Patent applicant Zojirushi Mahobin Co., Ltd. Agent
People Patent Attorney Blue White 葆 Haka 1 Name 9 Q Diagram W 9 C Go Δ 3 Niunkubu Iku l Shikui 9bC! 1 ∆ range 9d machining - job cycle 100th drawing - Jindusu' 100th drawing cycle

Claims (2)

[Claims] (1) In a metal vacuum double structure in which an inner wall and an outer wall form a double wall structure, and the space between the inner and outer walls is evacuated and sealed in a vacuum, the surface of the inner wall is made of activated copper. A metal vacuum double structure characterized by being covered with foil and having activated titanium or zirconium interposed between the inner wall surface and the copper foil. (2) In a method for manufacturing a metal vacuum double structure in which an inner wall and an outer wall form a double wall structure, and the space between the inner wall and the outer wall is evacuated and sealed in a vacuum, the surface of the inner wall is coated with copper foil. At the same time, titanium or zirconium is interposed between the inner wall surface and the copper foil to reduce the space between the inner wall and the outer wall by 10^-^
Preliminarily evacuate to a low vacuum of the order of 2 Torr or more, and
After degassing by heating at a temperature of 00℃ or higher for a predetermined period of time, the heating temperature is maintained at 10^-^4Torr.
1. A method for manufacturing a metal vacuum double structure, characterized by evacuation treatment to a high vacuum of the order of magnitude or less and vacuum sealing.