JPS61134592A - Manufacture of heat pipe - Google Patents

Abstract

PURPOSE:To provide the manufacture of a heat pipe, the welded part and pressed part or the sealed part of which has enough strength against breakdown, by a method wherein processes to introduce heat transfer medium in the pipe and the like are applied after the interior of the pipe is evacuated until the predetermined degree of vacuum is reached. CONSTITUTION:Firstly, a heat pipe 8 is connected with an exhauster by means of a vacuum hose 9 in order to start to evacuate, Fig. (1). Secondly, a certain measured amount of preliminarily treated water is sucked in the heat pipe 8 held under vacuum state in order to perfectly degas the residual gas dissolved in the water under vacuum and, after that, to seal it. Thirdly, the heat pipe 8 is pressed with the clamp 3 consisting o two steps of clamps or the upper step clamp 10 and lower step clamp 11 of a press, Fig. (4). Fourthly, a copper pipe extending above the upper step clamp 10 is cut off with knives. The upper end part of the heat pipe is welded by tungsten inert gas welding process under the condition that the pressing with the lower step clamp 11 is kept on being applied, Fig. (7). Finally, the portion ranging from the tip of the welded part 6 to the lower end of the pressed part 5 is made into a bent part by being bent along the axis of the pipe into a U-shape, a semi-circular shape, a chevron shape or the like, Fig. (9).

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a heat pipe manufacturing method 8, in particular, after reducing the pressure inside the heat pipe container and sealing in a heat transfer liquid,
The present invention relates to a method for manufacturing a heat pipe, which is completed by sealing the heat pipe.

[Prior art]

In recent years, heat pipes have been increasingly used in relatively high temperature ranges. A relatively high temperature range refers to a temperature of 100"C or higher, but water is used as a heat transfer liquid for a relatively high temperature range because there is a problem of thermal decomposition on the heat transfer liquid side and there are no stable substances in organic heat transfer liquids. Water is absolutely stable against thermal decomposition, but on the other hand, due to its high critical temperature, a pressure corresponding to the saturated vapor pressure is generated in the heat pipe. When used in a heating device, if the heat pipe is heated without any load, the temperature inside the heat pipe reaches 270°C, and at that time an internal pressure of 564/csi is generated.Therefore, the sealed part of the heat pipe is resistant to high temperatures and high pressures. It must have sufficient reliability.That is, arc welding, such as tungsten inert gas welding (hereinafter referred to as TIG
Welding is the cheapest and easiest method in terms of equipment.

However, as mentioned above, the sealing part consisting of the welded part and the pressurized part is often damaged due to high temperature and high pressure.

When sealing a heat medium liquid in a heat pipe, there are cases in which evacuation is not necessary at the time of sealing and cases in which evacuation is necessary, and the conventional process is shown in FIGS. 3 and 4.

fil If there is no need to vacuum, use ta+ in Figure 3.
(As shown in bl and fcl, the heat transfer liquid is injected from the injection device 1 into the pipe 2, the tip of the pipe 2 is crushed by the clamp 3 of the pressurizer, the upper part is cut off, and the tip is filled with Ti.
g Perform welding 4.

(2) If it is necessary to vacuum, see Figure 4 (1), fb
), (c) As shown in Jζ, inject the heat transfer liquid, evacuate the pipe 2, and continue to evacuate the pipe 1.
The pipe 2 is crushed by the clamp 3 of the pressure machine, the crushed upper part is cut, and a 71g weld 4 is performed on the cut surface.

[Problem that the invention seeks to solve]

However, in the conventional process as shown in FIG. As shown in the figure, cracks occur in the welded part 6 and it eventually breaks.

In addition, especially when it is necessary to create a vacuum, it is necessary to apply a large pressure to the pressurizing part 5 of the heat pipe 8 using the clamp 3 of the pressurizing machine. When both ends are damaged and the pressurizing part 5 is pushed and expanded by large internal pressure, cracks are generated at both ends of the pressurizing part 5, making it easy to break.

The present invention was made in view of the above-mentioned drawbacks, and it is an object of the present invention to provide a method for manufacturing a heat pipe having sufficient strength against destruction of the welded portion and pressurized portion, that is, the sealing portion.

[Means for solving problems]

The present invention is intended to solve the above-mentioned problems, and the details thereof will be explained below based on FIGS. 1 and 2.

The present invention includes the steps of evacuating the internal gas of a pipe (8) with one end closed from the other end, and introducing a heat medium into the pipe (8) after reaching a predetermined degree of vacuum, and while continuing the evacuation. Clamp the other end of the pipe (8) in two stages (1o), (1
1) and place the pipe (8) on the upper clamp (10).
), and the process of removing the upper clamp (10) and pressurizing the pipe (11) with the lower clamp (11).
8) Arc welding the tip and the welded part (6)
and a pipe (8) to the sealing part (7) consisting of the pressurizing part (5).
A- consists of a process of bending around the axis.
The invention is characterized by a method for producing dopaibu.

[For production]

FIG. 1 shows details of the manufacturing process of a heat pipe that requires evacuation according to the present invention.

First, the inner wall of the heat pipe 8 formed of a copper tube is thoroughly degreased and ultrasonically cleaned before being evacuated.
In addition, it is necessary to dry and remove any remaining degreasing solution or agent inside the heat pipe 8.

In step (1) of FIG. 1, the heat pipe 8 and an exhaust device (not shown) are connected with a vacuum hose 9, and evacuation is started. As for the vacuum evacuation device, a combination of an oil rotary pump and an oil diffusion pump is sufficient, and the maximum degree of vacuum is 10” Torr.
Any exhaust system that can achieve this is fine. In addition, the purity of the water used as the heat transfer fluid is determined by using distilled water to prevent corrosion of the copper heat pipe 8, and by purifying it with cation and anion exchange resin to remove salts, and by improving the electrical conductivity of the water. 5
It has been found that it is desirable to have a purity of μs (5 μU/cps) or less in terms of the lifespan of the heat pipe 7. Furthermore, it is necessary to remove the salts and simultaneously remove the gas dissolved in the water immediately before sealing the heat pipe. That is, the main components of pure water C and the gases contained therein are carbon dioxide gas and air components nitrogen and oxygen, and these gases are directly passed through the heat pipe 8.
When the heat pipe 8 is introduced and sealed, the dissolved gas separates at high temperatures and the heat transfer characteristics of the heat pipe 8 deteriorate. Therefore, in order to discharge the dissolved gas in the water, deaeration is performed for 10 minutes or more by boiling immediately before sealing, and as shown in step (2), a vacuum state is created by switching the valve of the liquid seal bag rIL (not shown). A fixed amount of pretreated water is sucked and sealed into the maintained heat pipe 8. Thereafter, in step (3), a valve is switched to exhaust the dissolved residual gas in the water inside the heat pipe 8. Connect the heat pipe 8 to the vacuum exhaust system to exhaust the air,
Completely vacuum degas the dissolved residual gas in the water. The degree of vacuum inside the heat pipe 8 is reduced to the level of vapor pressure determined by the pumping speed of the vacuum pump, water temperature and pressure, and is usually 1 to 5 To.
The equilibrium pressure is rr. If evacuation continues for a long time in this state, the water in the pipe 8 will evaporate, so monitor the vacuum pressure gauge and when the pressure reaches 1 to 5 Tore, proceed to step (4) and turn off the pressure machine. The heat pipe 8 is pressurized by the upper and lower clamps 3, and then the process (
As shown in 5), cut the copper pipe above the upper clamp 10 with a knife. In step (6), the upper clamp 10 must be opened and the vacuum level inside the heat pipe 8 must be maintained by applying surface pressure above a certain level using only the lower clamp 11.
Must be 1. To achieve this, a surface pressure greater than a certain level is required depending on the steel material, copper pipe diameter, wall thickness, clamp width, etc. That is, the vacuum retention property obtained by applying pressure with the lower clamp lliζ was checked by the helium leak test method,
In view of the performance retention of the heat pipe 8, a goal is set to limit the amount of air that enters due to leakage during working hours, the leak rate is set to 10-7 atn'cc/sea or less, and the wall thickness of the copper tube to be crushed is determined. As a result, in the case of the heat pipe 8 made of copper pipe (dephosphorized copper 0 material), it is necessary to pressurize the upper and lower clamps 10 and 11 with a clamp interval of 85% or less of twice the original wall thickness. There is. For example, the wall thickness is 0.89
．． If n/ln, 2X0.89XO, 85-1,51
It is necessary to set the clamp interval so that m/I is 11 or less. By this procedure, the degree of vacuum within the heat pipe 8 is maintained within a range that does not substantially cause problems during the operations of steps (4) to (6). In step (7) Iζ, the upper end of the heat pipe is welded by 71 g while continuing to apply pressure using the lower clamp 11. In order to provide internal pressure resistance to TIG welding, current control is necessary, and it is essential to perform current control called crater filler, which gradually reduces the current value according to the distance from the welding start point and the temperature rise pattern. , the tip of the welded part 6 is damaged and a uniform penetration margin cannot be ensured. In other words, if the weld margin is uneven, unevenness will occur on the welding surface, and stress will be concentrated in the area where the weld margin is least, and the generated internal pressure will cause the weld to break as shown in Figure 5. We have found that reliability can be dramatically improved by setting the current and welding speed so that welding is uniform and at the same time penetration is at least twice the wall thickness.Step (8)! Then, TIG welding is completed and the lower clamp 11 is released.In step (9), a U-shaped semicircle is formed along the pipe axis from the tip of the welded part 6 of the heat pipe 8 to the lower end of the pressurized part 5. By forming the bent portion in the shape of a shape or the shape of (), it is possible to prevent stress failure of the pressurizing part, that is, a large internal pressure is generated in the heat pipe 8, and the pressurizing part is prevented from expanding into an elliptical 1ζ shape due to the internal pressure. We have found that the ability to maintain the shape against deformation is dramatically improved.In order to prevent the heat pipe itself, excluding the welded part 6 and pressurized part 5, from breaking due to stress, the heat pipe must first be heated at the set temperature. If the thickness of the copper tube is set to withstand the tensile stress of the creep test at steam pressure (for example, 56 kg/crA at 270° C.), the tube will not break inside.

FIG. 2 shows the results of a creep test in the case where a bent portion was formed in the sealing portion 7 consisting of the tongue contact portion 6 and the pressurizing portion 5. As a result of performing a creep resistance test at 270°C on the case where the heat pipe 8 was subjected to the bending process (8) and the case (8) where the bending process was not performed, the internal pressure at 270°C was 56/cli1.
The sample survival rate after 1000 hours of generation was 100% for the sample with the bending process, while it was less than 10% for the sample without the bending process.

〔Effect of the invention〕

The present invention achieves the following effects with the above-described configuration.

l) Using 1 heat medium and distilled water, the distilled water is subjected to cation and anion exchange to make the electrical conductivity 5 μS or less, heated to 80°C or higher, degassed, introduced into the heat pipe, and heated to 80°C or higher. Since the inside of the heat pipe is evacuated at room temperature to remove residual gas in the water, it can be produced at a lower cost than a heat medium outside the water plate, and it also prevents corrosion of copper heat pipes and prevents deterioration of heat transfer characteristics, making them permanent. Quality can be guaranteed.

2) Since the wall thickness of the sealing part is pressurized to 85% or less of the wall thickness before pressurization using a two-stage clamp, the degree of vacuum during work is maintained within a range that does not cause problems and welding is easy. I can work.

3) The tip of the heat pipe is TIG welded with a crater filler that can control current, and the welded part is provided with a weld margin that is more than twice the thickness of the heat pipe, so a uniform weld margin can be formed and the internal pressure can be reduced. This prevents damage to the welded parts due to

4) Since the sealing part is bent around the pipe axis, the pressurizing part can be prevented from being destroyed or deformed by internal pressure.

Therefore, due to the effects of 1) to 4) above, high temperature
1. A heat pipe with extremely high reliability for high pressures can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing an embodiment of the present invention, FIG. 2 is a comparison diagram of the heat pipe according to the present invention and other samples, and FIGS. 3 and 4 are process diagrams showing a conventional embodiment. Figure 5 is a partial front view and side view showing deformation due to conventional stress concentration, Figure 6 is a sectional view showing fracture of a welded part due to stress concentration, and Figure 7
The figure is a cross-sectional view of a pressurizing part where stress is concentrated and a detailed view thereof. Explanation of symbols 1. Injection device 2. Pipe 3, pressurizer clamp 4. Tf welding 5, pressure section
6. Welding part 7, sealing part 8. Heat pipe 9 Vacuum hose 10. Upper clamp 11, lower clamp Kunihiko Wakabayashi, Kamodensha Figure 1 Figure 2 710 ripe @tlfl (hr) Figure 4 (a) (b) (c) Figure 5 Figure 6 Figure 7 1

Claims (1)

[Claims] 1. The process of evacuating the internal gas of a pipe from the other end with one end closed and introducing a heat medium into the pipe after reaching a predetermined degree of vacuum; A process of pressurizing the other end with a two-stage clamp and cutting the pipe above the upper stage clamp, a process of removing the upper stage clamp and arc welding the pressurized tip of the pipe while applying pressure with a lower stage clamp, and a process of arc welding the tip of the pressurized pipe, and a process of arc welding the tip of the pressurized pipe while applying pressure with a lower stage clamp. and a method for manufacturing a heat pipe, comprising the steps of bending the sealing part, which is a pressurizing part, around the pipe axis. 2. The heat medium is distilled water that undergoes positive and anion exchange to make the electrical conductivity 5 μs or less, heated to 80°C or higher, deaerated, introduced into the heat pipe, and vacuumed inside the heat pipe at room temperature. 2. The method of manufacturing a heat pipe according to claim 1, wherein the heat pipe is evacuated to remove residual gas in the water. 3. The method for manufacturing a heat pump according to claims 1 and 2, wherein the heat pipe is formed of a copper tube. 4. The method for manufacturing a heat pump according to claim 1, wherein the sealing portion is formed under pressure to have a wall thickness of 85% or less of the wall thickness before pressurization. 5. The method for manufacturing a heat pipe according to claim 1, wherein the arc welding is tungsten inert gas welding in which the tip of the heat pipe is a crater filler and is current controllable. 6. The method for manufacturing a heat pipe according to claims 1 and 3, wherein the welded portion has a penetration margin that is at least twice the thickness of the heat pipe.