JPS6115358B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a double tube heat pipe used for a rotating shaft of a rotating electrical machine, etc., and a method for manufacturing the same.

Generally, during operation of a rotating electrical machine, the insulation of the windings may be destroyed due to heat generation due to energy loss occurring in the rotor and stator. For this reason, various studies have been conducted on forming the rotating shaft with a heat pipe that has excellent thermal conductivity.Especially in the miniaturization of rotating electric machines, it is possible to form the rotating shaft with a heat pipe and cool it from inside the winding. is essential.

Heat pipes mainly use water or fluorocarbons as their working fluid, so the metal tube that encloses them is made of copper or aluminum. However, when used as a rotating shaft, a mechanical material such as iron or aluminum alloy is used to withstand the rotational moment. A double-tube structure is adopted in which a strong metal tube is used as the outer tube, and a heat pipe is inserted inside this tube as the inner tube.

Conventionally, as shown in FIG. 1, a method for manufacturing a double-tube heat pipe for a rotating shaft involves opening a hole 2 at one end of a metal rod 1 made of iron or aluminum alloy, etc., and forming a cylindrical outer tube. form 3.
In addition to this, a cylindrical metal tube 4 with open ends
An inner tube 8 is formed by welding a disk-shaped cap 5 at one end and a disk-shaped cap 7 with an injection capillary 6 at the other end. Liquid 9 is sealed to form a heat pipe. Next, after applying a thermally conductive filler 10 to the surface of this heat pipe-shaped inner tube 8 and the inner peripheral surface of the outer tube 3, the inner tube 8 is inserted into the outer tube 3 as shown in FIG. A double tube heat pipe 11 for a rotating shaft was manufactured by inserting the heat pipe into a rotating shaft.

However, since this method inserts the inner tube 8 shaped into a heat pipe into the outer tube 3, it is necessary to strictly control the machining accuracy of both at the joint surface.
Furthermore, since the insertion method is used, a gap is inevitably created between the two, which increases the thermal resistance at the joint surface and deteriorates the performance as a heat pipe. Further, since the filler 10 filled in the gap between the two deteriorates over time, the heat conduction characteristics deteriorate over time. In addition, since the outer peripheries of the caps 5 and 7 joined to both ends of the cylindrical metal tube 4, which will become the inner tube 8, are joined by welding, the area of the welded part 12 is large.
When a large internal pressure is applied to the heat pipe 11 while it is in operation, there are drawbacks such as steam leaking from pinholes in the welded portion 12 and cracks occurring.

In view of the above, the present invention has been developed as a result of various researches, and has developed a rotating shaft that is easy to process, has high adhesion between the inner tube and outer tube, has excellent heat conduction characteristics, and has excellent pressure resistance. We have discovered a double-tube heat pipe for industrial use and a method for manufacturing the same.

That is, the present invention includes an inner tube formed by sealing a hydraulic fluid inside a cylindrical metal tube whose both ends are sealed by drawing, and a tube that is inserted into the inner tube and whose joint surfaces are tightly bonded by plastic deformation. The first aspect is a double-tube heat pipe for a rotating shaft formed of a cylindrical metal tube and an outer tube.

Furthermore, the present invention processes the openings at both ends of a cylindrical metal tube by spinning or swaging to form a cap portion having a small hole at one end and a cap portion having an injection capillary tube at the other end, and then The hole is sealed to form an inner tube, and then this inner tube is inserted into an outer tube made of a cylindrical metal tube, and then hydraulic pressure is applied from the injection capillary to expand the inner tube and bring the inner and outer tubes into close contact. , After that, the inside of the inner tube is cleaned and degassed, a working fluid is injected, and the injection capillary is then sealed to seal the inside. This is the gist of Section 2.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

3 to 7 sequentially show the steps of manufacturing a double tube heat pipe for a rotating shaft by the method of the present invention.

As shown in FIG. 3, a cylindrical metal tube 4 made of copper, aluminum, or the like and open at both ends is prepared. The material of this cylindrical metal tube 4 is selected in consideration of compatibility with the hydraulic fluid 9 to be sealed. For example, copper is selected when the hydraulic fluid 9 is water, and copper or aluminum is selected when the hydraulic fluid 9 is fluorocarbon. Use.

The openings at both ends of this cylindrical metal tube 4 are spun or swaged to form a small hole at one end.
3, and an injection capillary 6 at the other end.
The cap portions 15 having the following shapes are each drawn and formed.

Next, a small hole 13 inevitably formed in the center of one cap portion 14 by spinning or swaging is welded and sealed as shown in FIG. Further, if the length of the injection capillary 6 formed in the other cap portion 15 is short, another capillary tube 6a may be joined. The inner tube 8 thus formed is inserted into the outer tube 3 with both ends open, as shown in FIG. This outer tube 3 is made of iron, stainless steel,
It is formed of a metal tube 16 made of a material with high mechanical strength such as an aluminum alloy.

Next, the outer tube 3 and inner tube 8 combined in this way are
As shown in FIG. 6, presser jigs 19 and 20 are provided with protrusions 18 having an outer diameter slightly smaller than the inner diameter of the outer tube 3 so as to be inserted into a cylindrical presser jig 17 and further clamped from both ends. is inserted to securely support the outer tube 3 and inner tube 8. In addition, an insertion hole 21 is formed in one of the presser jigs 20, and the injection thin tube 6 is inserted through the insertion hole 21.

Next, the coupling 23 of the hydraulic hose 22 is connected to the tip of the injection thin tube 6, and a hydraulic medium 24 such as water or oil is press-fitted to apply hydraulic pressure, expanding the inner tube 8 from the inside and connecting it to the inner tube 3. The outer tube 8 is brought into close contact by plastic deformation. As the hydraulic medium 24 used to generate this hydraulic pressure, it is necessary to use water or oil that can be easily removed and cleaned prior to sealing in the hydraulic fluid 9. For example, when sealing water as the hydraulic fluid 9, , it is preferable to use clean water as the hydraulic medium 24.

Although good adhesion can be obtained between the outer tube 3 and the inner tube 8 which have been expanded and joined in this way, as shown in FIG. 8, an air gap 26 may be formed on the adhesion surface 25, resulting in an increase in thermal resistance. This is the outer tube 3 and inner tube 8.
This is because fine irregularities 27 are formed on the surface of the tube during processing, and air is trapped in the irregularities 27 on the joint surface during tube expansion, creating an air gap 26. Therefore, by expanding the gap between the outer tube 3 and the inner tube 8 while deaerating the tube, it is possible to obtain a complete contact surface 25 without an air gap 26 as shown in FIG. 9, which is more preferable.

Next, the hydraulic medium 24 press-fitted into the inner tube 8 is removed to clean the inside, and the presser jigs 17, 1
Remove 9 and 20. Next, the injection capillary 6 is connected to a vacuum pump (not shown) to degas the inside of the inner tube 8, and then
After injecting the working fluid 9 such as water or Freon,
The injection capillary tube 6 is sealed to seal the inside to create a double-tube heat pipe 11 for a rotary shaft as shown in FIG.

Note that the present invention is not limited to the above-mentioned method, and the surface of the inner tube 8 is coated with a thin layer of thermally conductive filler 10 in advance, and then inserted into the outer tube 3, and then expanded to form the air gap 26. A method of forming the adhesion surface 25 without any rough edges may also be used. In this case, the thermally conductive filler 10 to be applied
For example, grease mixed with metal powder such as alumina powder or epoxy resin adhesive is used.

In this method, since the outer tube 3 and the inner tube 8 are joined by tube expansion, the filler 10 can be applied thinly enough to fill the uneven parts 27, so there is almost no effect of deterioration over time unlike in the conventional method. Good heat transfer properties can be maintained.

Further, in the above embodiment, the cylindrical metal tube 4 is the inner tube 8.
Although a tube with a smooth inner surface was used as the tube, a tube with a grooved inner surface may also be used. By using the internally grooved tube in this way, when used as a rotating shaft, the internal working fluid 9 is made uniform in the circumferential direction by the action of centrifugal force and the rolling action of the groove, and the working fluid 9 is made uniform along the longitudinal direction. The smoothing effect of the liquid 9 promotes the return of the working liquid 9 to the heating section side, thereby providing good heat conduction. Further, in the above embodiment, a cylindrical metal tube 16 with both ends open was used as the outer tube 3, but if the outer diameter of the rotating shaft is large and a commercially available thick-walled tube cannot be obtained, a tube as shown in Fig. 1 may be used. Alternatively, a metal rod 1 having a hole 2 formed at one end by machining may be used.

Note that the present invention is not limited to application to a rotating shaft of a rotating electrical machine, but can also be applied to a case where a rotating shaft used in a high temperature section such as a screw of an extruder is formed of a heat pipe.

Next, specific examples of the present invention will be described.

Example: The outer diameter of the cylindrical metal tube 4 that becomes the inner tube 8 is 48 mm.
Using a copper tube with a diameter of 2 mm and a length of 600 mm, both ends of the tube were spun to form a cap part 14 with a small hole 13 at one end and a length of 8 mm in outer diameter and length at the other end, as shown in Fig. 3. Cap parts 15 each having a 10 mm injection capillary 6 are drawn. Next, the small hole 13 is welded and sealed, and the injection tube 6 has an outer diameter of 8 mm.
An inner tube 8 is formed by joining another thin tube 6a made of a copper tube with a diameter of 190 mm and a length of 190 mm.

Next, a structural steel pipe with an outer diameter of 70 mmφ and a wall thickness of 10 mm is used as the outer pipe 3, and after inserting the inner pipe 8 inside this pipe, hold it with the holding jigs 17, 19, 2 as shown in FIG.
0, and while evacuating the gap between the outer tube 3 and the inner tube 8, water pressure is applied from the injection capillary 6 to expand the inner tube 8, giving it plastic deformation and bringing it into close contact with the outer tube 3. Next, after removing the pressurized water and cleaning the inside, the holding jigs 17, 19, and 20 are removed, and water is injected as the working fluid 9 while degassing the inside of the inner tube 8. The thin tube 6 was sealed to create a double-tube heat pipe 11 for a rotating shaft as shown in FIG.

Regarding the thus obtained heat pipe 11, the thermal resistance r at the contact surface 25 between the outer tube 3 and the inner tube 8 was measured and found that r=2.5×10 ^-5 m ² h°C/
It was kaal.

Comparative Example As shown in FIG. 1, an outer tube 3 is formed by opening a hole 2 with an inner diameter of 50 mmφ and a length of 650 mm in one end of a carbon steel rod with a diameter of 70 mmφ and a length of 700 mm. In addition, one end of a copper tube with an outer diameter of 48 mmφ and a wall thickness of 2 mm has an outer diameter of 44 mm.
A cap 5 made of copper plate with mmφ and thickness of 4 mm is welded,
In addition, a similar cap 7 with an injection capillary 6 joined to the other end was welded to form an inner tube 8.
After deaerating the inside, water was sealed as a working fluid 9 to form a heat pipe. Next, grease mixed with alumina powder was applied as a filling 10 to the outer periphery of the inner tube 8, and then inserted into the outer tube 3 to create a double tube heat pipe 11 for a rotating shaft as shown in FIG. .

When the thermal resistance r at the contact surface between the outer tube 3 and the inner tube 8 of the heat pipe 11 thus obtained was measured, it was found to be r=2.7×10 ⁻³ m ² h° C./kaal.

As explained above, according to the present invention, since the outer tube and the inner tube are joined by plastic deformation, the thermal resistance at the bonded surface is lower than that of the conventional structure in which they are joined using a filler. Also, it has excellent heat transfer properties because it does not deteriorate over time. Furthermore, both ends of the inner tube are sealed by forming a cap part by drawing, so the stress distribution is more uniform compared to the conventional welded disk-shaped cap structure, which has a welded part at the part where the most stress is applied. Moreover, since the area of the welded portion is small, a double-pipe heat pipe for a rotating shaft with excellent pressure resistance can be obtained. Furthermore, according to the method of the present invention, since the outer tube and the inner tube are brought into close contact with each other and then formed into a heat pipe, it has remarkable effects such as easier control of dimensional accuracy and superior workability compared to conventional methods. It is something.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing the state before the outer tube and inner tube are combined according to the conventional method, Fig. 2 is a cross-sectional view showing a conventional double-tube heat pipe for a rotating shaft, and Figs. 3 to 7 3 and 4 are sectional views of the inner tube, FIG. 5 is a sectional view of the inner tube inserted into the outer tube, and FIG. 6 is a sectional view of the outer tube. A cross-sectional view showing a combination of a tube and an inner tube set in a holding jig, FIG. 7 is a cross-sectional view of a double-tube heat pipe for a rotating shaft according to the present invention, and FIGS. 8 and 9 are external views. FIG. 3 is an enlarged cross-sectional view showing a close contact surface between the tube and the inner tube. 3... Outer tube, 4... Metal tube, 5, 7... Cap, 6... Injection tube, 8... Inner tube, 9... Working fluid, 10... Filler, 11... Heat pipe, 12
...Welded part, 13...Small hole, 14,15...Cap part, 16...Metal tube, 17,19,20...
Holding jig, 24... Hydraulic medium, 25... Close contact surface,
27...Uneven portion.

Claims (1)

[Claims] 1. An inner tube formed by sealing a working fluid inside a cylindrical metal tube whose both ends are sealed by drawing, and this inner tube is inserted inside and the joint surface is formed by plastic deformation. A double-tube heat pipe for rotating shafts consisting of an outer tube made of closely-attached cylindrical metal tubes. 2. The double-tube heat pipe for a rotating shaft according to claim 1, wherein an inner grooved tube is used as the cylindrical metal tube serving as the inner tube. 3 Spinning or swaging the openings at both ends of a cylindrical metal tube to form a cap portion having a small hole at one end and a cap portion having an injection tube at the other end, and then sealing the small hole. Then, after inserting this inner tube into an outer tube made of a cylindrical metal tube, the inner tube is expanded by applying hydraulic pressure from the injection capillary while deaerating the gap between the inner and outer tubes. A double-tube heat for rotating shafts characterized by tightly fitting both the inner and outer tubes, then cleaning and deaerating the inside of the inner tube, injecting the working fluid, and then sealing off the injection capillary to seal the inside. Method of manufacturing pipes. 4. The method for manufacturing a double-tube heat pipe for a rotating shaft according to claim 3, characterized in that the inner tube is coated with a thermally conductive filler on the outer periphery and then inserted into the outer tube. 5. The method for manufacturing a double-pipe heat pipe for a rotating shaft according to claim 3 or 4, characterized in that an inner grooved tube is used as the cylindrical metal tube serving as the inner tube.