JPS6053838B2 - Manufacturing method of double tube heat pipe for rotating shaft - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a double-tube heat pipe used for a rotating shaft of a rotating electric machine or the like.

Generally, during operation of a rotating electrical machine, the insulation of the windings may break down 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 tubes that enclose them are made of copper or aluminum. However, when used as a rotating shaft, metals with high mechanical strength are used to withstand the rotational moment. It has a double-tube structure in which the outer tube is an outer tube and the inner tube, which is made into a heat pipe, is inserted inside. Conventionally, as shown in FIG. 1, a method for manufacturing a double tube heat pipe for a rotating shaft involves opening a hole 2 along the axial direction from one end of a metal rod 1 made of a material with high mechanical strength. A cylindrical outer tube 3 is formed.

Next, the inner surface of this hole 2 and the inner tube 4 which has been made into a heat pipe in advance.
After coating the surface of the heat conductive filler 5, the inner tube 4 is inserted into the outer tube 3 as shown in FIG. 2 to manufacture a double tube heat pipe 6 for a rotating shaft. . However, since this method inserts and fixes the inner tube 4 into the outer tube 3, it is necessary to strictly control the machining accuracy of both at the joint surface. A gap is created between the two, increasing the thermal resistance at the joint surface and deteriorating the performance as a heat vibrator.

Moreover, since the filler 5 filled in this gap deteriorates over time, there are drawbacks such as a decrease in thermal conductivity over time. As a result of various studies in view of the above points, the present invention has been developed as a double-tube heat exchanger for rotating shafts, which improves the adhesion between the inner tube and the outer tube, improves heat transfer characteristics, and improves workability. He discovered a method for manufacturing vibrators.

That is, the method of the present invention involves forming an inner tube by joining a disk-shaped cap to one end of a cylindrical metal tube with both ends open and a disk-shaped cap having an injection capillary to the other end. The interior is degassed, and then a working fluid is injected through the injection capillary tube to form a heat vibrator.The inner tube that has been converted into a heat vibrator is then inserted into an outer tube made of a cylindrical metal tube to form a composite. The feature is that the body is reduced in size and the outer tube and inner tube are brought into close contact with each other.

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

Figures 3 to 7 illustrate the method of the present invention step by step.

As shown in FIG. 3, a disk-shaped cap 8 is attached to one end of a cylindrical metal tube 7 with both ends open, and a disk-shaped key cap 10 with an injection capillary 9 attached to the other end is welded. ,
An inner tube 4 is formed. The material constituting the inner tube 4 is selected in consideration of compatibility with the hydraulic fluid to be sealed. For example, copper is used when the hydraulic fluid is water, and copper or aluminum is selected when the hydraulic fluid is fluorocarbon. use Next, the injection tube 9 of the inner tube 4 is connected to a vacuum pump (not shown) to degas the inside, and then the working fluid 11 is injected, and the injection tube 9 is immediately sealed and heated as shown in FIG. Make it into a vibe.

Next, the inner tube 4 made into a heat vibrator is inserted into the outer tube 3 made of a cylindrical metal tube 12 to form a composite body 13, as shown in FIG.

In this case, the cylindrical metal tube 12 serving as the outer tube 3 is made of a material with high mechanical strength such as iron, stainless steel, or aluminum alloy. Next, as shown in FIG. 6, this composite body 13 is passed through a swaging die 14 and reduced from one end side to another, so that the outer tube 3 and the inner tube 4 are brought into close contact with each other, as shown in FIG. A double tube heat vibrator 6 for a rotating shaft is manufactured.

Note that the reduction processing method is not limited to the swaging processing as mentioned above, but also the die drawing method in which the material is passed through a die,
Any method may be used, such as a method using a mandrel mill.

Although the outer tube 3 and the inner tube 4 that have been reduced and joined in this manner can achieve good adhesion, an air gap 16 may be formed on the adhesion surface 15 as shown in Fig. 8, which may increase the thermal resistance. .

This is because fine irregularities 17 are generated on the surfaces of the outer tube 3 and inner tube 4 during machining, and when the shrinking process is performed, the concave and convex portions 1 of the contact surface 15 are
This is because air is trapped in 7 and an air gap 16 is created. Therefore, by reducing the gap between the outer tube 3 and the inner tube 4 of the composite body 13 while deaerating it, a perfect contact surface 15 without an air gap 16 can be obtained as shown in FIG. Therefore, it is more preferable. Note that the present invention is not limited to the above-mentioned method, but the surface of the inner tube 4 which has been made into a heat vibrator,
It is also possible to apply a thin layer of thermally conductive filler 5 in advance, insert it into the outer tube 3, and then shrink it to form a close contact surface 15 without an air gap 16.

In this case, as the thermally conductive filler 5 to be applied, for example, grease mixed with metal powder such as alumina powder or an epoxy resin adhesive is used. This method uses outer tube 3 and inner tube 4.
Since the filler 5 is reduced and bonded by plastic deformation, it is sufficient to apply the filler 5 thinly enough to fill the minute unevenness 17. Therefore, there is almost no effect of deterioration over time as in the conventional method, and a good thermal effect is achieved. Conductive properties can be maintained.

Further, in the above embodiment, a cylindrical metal tube 7 serving as the inner tube 4 was used with a smooth inner surface, but a tube with an inner groove 7a as shown in FIG. 10 may also be used.

By using the internally grooved tube 7a in this way, when used as a rotating shaft, the internal working fluid 11 is made uniform in the circumferential direction by the action of centrifugal force and the winding action by the groove 18, and is also made uniform in the longitudinal direction. The smoothing action of the working fluid 11 along the line promotes the return of the working fluid 11 to the heating section side, and a good heat transfer action can be performed. Further, in this internally grooved tube 7a, the narrower the width of the groove portion 18, the greater the capillary force, but on the other hand, there is a problem that it becomes difficult to process the groove.

However, according to the method of the present invention, by increasing the area reduction rate in the reduction process, the groove 1 is reduced as shown in FIG.
8 can be formed narrower and deeper than that shown in FIG. Note that the method of the present invention is not limited to application to the rotating shaft of a rotating electrical machine, but can also be applied to the case where a rotating shaft used in a high-temperature section, such as a screw of an extruder, is formed using a heat vibrator.

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

The cylindrical metal tube 7 serving as the inner tube 4 in the embodiment has an outer diameter of 16 mm and a wall thickness of 0.7 mm. , using a copper tube with a length of 50-, a cap 8 made of a copper plate with an outer diameter of 14.6 Twtφ and a thickness of 1.5 wfn is attached to one end, and an outer diameter of 4.7=φ and a length of 10- to the other end. The caps 10 having the same shape as described above to which the thin tubes 9 were attached were joined together using silver solder to form the inner tubes 4.

Next, the inside of this inner tube 4 was degassed, water was injected as a working fluid 11 through an injection capillary 9, and then the tube was sealed off to be converted into a heat vibrator as shown in FIG. Next is the outer diameter of 407! A structural steel pipe with a diameter of φ and a wall thickness of 1 gm was used as the outer pipe 3, and the inner pipe 4, which had been made into a heat vibrator, was inserted inside the outer pipe 3. Next, this composite body 13 was swaged and reduced using a swaging die 14, and the outer tube 3 and the inner tube 4 were brought into close contact with each other to produce a double tube heat vibrator 6 for a rotating shaft. Regarding the thus obtained heat vibrator 6, the thermal resistance r at the contact surface 15 between the outer tube 3 and the inner tube 4 was measured; r=3X10-
It was confirmed that it had excellent heat transfer characteristics as low as 5°C h-d/Kcal.

Comparative Example As shown in Fig. 1, the diameter is 38WrIfiφ and the length is 600mm.
One end of the TnI1i carbon steel rod has an inner diameter of 17wnφ and a length of 5.
50w! The outer tube 3 is formed by opening the hole 2 of n.

Separately from this, an inner tube 4 made into a heat vibrator similar to that of the above embodiment was created. Next, filler 5 is applied to the surface of this inner tube 4.
After applying grease mixed with alumina powder as
A double-tube heat vibrator 6 for a rotating shaft as shown in FIG. 2 was created by inserting and fixing it into the outer tube 3. The thermal resistance r at the contact surface of the outer tube 3 and inner tube 4 of the thus obtained heat vibrator 6 was measured; r=7×10-3℃h-771'
ACal had inferior heat transfer properties compared to those of the present invention.

As explained above, according to the method for manufacturing a double-tube heat vibrator for a rotating shaft according to the present invention, after inserting the inner tube, which has been made into a heat vibrator, into the outer tube, the shrinking process is performed to bring the two into close contact with each other. Compared to a conventional structure bonded using a filler, the bonded surface has less thermal resistance and does not deteriorate over time, so it can exhibit excellent heat transfer characteristics.

Furthermore, the present invention has remarkable effects such as easier control of dimensional accuracy and superior workability compared to conventional methods.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing the state before the outer tube and inner tube are combined using the conventional method, Fig. 2 is a cross-sectional view showing a heat vibrator with a conventional structure, and Fig. 3 to Fig. 7 are sequential views showing the state before the outer tube and inner tube are combined using the method of the present invention. The steps are shown according to the process. Figure 3 is a cross-sectional view of the inner tube, Figure 4 is a cross-sectional view of the inner tube converted into a heat vibrator, Figure 5 is a cross-sectional view of the composite, and Figure 6 is a reduced scale of the composite. FIG. 7 is a cross-sectional view of the double-tube heat vibrator for a rotating shaft according to the present invention, and FIGS. 8 and 9 are enlarged views of the contact surface between the outer tube and the inner tube. 10 and 11 are cross-sectional views of a double-tube heat vibrator using internally grooved tubes. 3...Outer pipe, 4...Inner pipe, 5...
...Filler, 6...Heat vibe, 7,12...
...Metal tube, 8,10...Cap, 9...
... Injection tube, 11 ... Working fluid, 13 ...
... Complex, 14 ... Swaging dice, 1
5...Adhesion surface, 18...Groove portion.

Claims (1)

[Scope of Claims] 1. After forming an inner tube by joining a disk-shaped cap to one end of a cylindrical metal tube with open ends and a disk-shaped cap having an injection capillary to the other end, The inside is degassed, and then a working fluid is injected through the injection capillary to form a heat pipe.Then, this heat pipe-formed inner tube is inserted into an outer tube made of a cylindrical metal tube to form a composite. A method for manufacturing a double-tube heat pipe for a rotating shaft, characterized by reducing the body and bringing an outer tube and an inner tube into close contact. 2. The double tube heat for a rotating shaft according to claim 1, characterized in that the gap between the inside and outside of the composite body formed by inserting the inner tube into the outer tube is reduced while degassing. Method of manufacturing pipes. 3. The double tube heat for a rotating shaft according to claim 1 or 2, characterized in that a thermally conductive filler is applied to the outer periphery of the inner tube and then inserted into the outer tube. Method of manufacturing pipes. 4. A method for manufacturing a double-tube heat pipe for a rotating shaft according to claim 1, 2, or 3, characterized in that an inner grooved tube is used as the cylindrical metal tube serving as the inner tube.