JPH09170888A - Heat pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat pipe in which a wick is not deviated in a container even in the case of bending or collapsing. SOLUTION: In the heat pipe 4 having a wick, the wick is formed of a knitted assembly 10 made of many extrafine wires. A spiral member 3 wound spirally with a hollow part to open the gap of a predetermined interval is disposed along the lengthwise direction in the container 1 at both end sides of the container 1 in the lengthwise direction, and the wick is urged fixedly to the inner wall surface of the container 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat pipe which transfers heat input from the outside by latent heat of a working fluid.

[0002]

2. Description of the Related Art As is well known, a heat pipe is a vacuum degassed sealed metal pipe or the like inside a container.
A condensable fluid such as water or alcohol is enclosed as a working fluid, which operates when a temperature difference occurs,
The working fluid evaporated in the high temperature portion flows to the low temperature portion to radiate and condense, thereby performing heat transfer by the latent heat of the working fluid. Further, conventionally, a wick is laid on the inner wall surface of the container as an example of pump means for returning the liquid-phase working fluid to the evaporation portion.

An example of a conventional heat pipe using a wick is shown in FIG. 4, in which a wick 2 made up of a number of extra fine wires is arranged along the longitudinal direction inside a container 1 made of a closed metal pipe. Has been done. Further, the spiral member 3 wound in a hollow spiral shape so as to open a gap of a predetermined interval at least on both ends in the longitudinal direction of the container 1,
It is arranged inside the container 1 along its longitudinal direction,
The wick 2 is pressed and fixed to the inner wall surface of the container 1 by the spiral member 3. Further, the spiral member 3 is formed of an elastic material that produces an elastic force in the direction of increasing the winding radius.

In the heat pipe 4 having such a structure, when one end of the container 1 is heated, the working fluid attached to the wick 2 on the inner wall surface of the container 1 receives heat and evaporates.
The working fluid vapor flows into the hollow portion inside the spiral member 3 through the gap, and flows toward the other end of the container 1 where the internal pressure is low. Therefore, the inside of the spiral member 3 becomes a vapor flow path. Then, the flowing working fluid vapor escapes from the gap provided at the end of the spiral member 3 to the inner wall surface side of the container 1, where heat is taken and condensed.

The working fluid that has condensed to become a liquid phase again flows to the evaporation section side of the container 1 by the capillary pressure of the wick 2 and is evaporated again at the evaporation section. In that case,
Since the wick 2 that serves as a liquid flow path is arranged in the longitudinal direction of the container 1, and the effective capillary radius between the ultrafine wires forming the wick 2 is extremely small and the pumping action is large, even if top heat is used. Even in the mode, the working fluid surely flows back to the evaporator side. Moreover, since the vapor flow and the liquid flow do not interfere with each other, the scattering phenomenon does not occur. Therefore, heat transfer efficiency is improved.

If the spiral member 3 is made of an elastic material that produces an elastic force in the direction of increasing the winding radius,
Capillary pressure is generated along with the meniscus, so container 1
The working fluid efficiently circulates to the portion of the inner wall surface that becomes the evaporation portion, and the heat transporting power of the heat pipe 4 is further improved.

[0007]

However, when the heat pipe having the above structure is bent as shown in FIG. 4 (a), the portion not bent is shown in FIG. 4 (b).
As described above, the wicks are uniformly arranged, but in the bent portion, the expansion and contraction action occurs inside and outside the radius of curvature, and the spiral member is deformed inside the heat pipe. The spiral member exerts a force in a direction that repels the bending action when the initial state is maintained, so that a force is generated in a direction deviating from the center position, which is the normal position of the heat pipe. Then, the wick made of the ultrafine wire laid inside the heat pipe receives not only the pressing force that is normally received from the spiral member but also the repulsive force against the bending of the spiral member. Therefore, on the inner side with a small radius of curvature, a larger pressing force is applied than at the normal time, the ultrafine wire is moved to the outer side with a large radius of curvature, and the position of the spiral member moves inward. As a result, the wick is unevenly distributed as shown in FIG. 4C, and it is difficult to uniformly arrange the wicks. In other words, bending causes compression on the inner side of the radius of curvature and expansion on the outer side, which causes uneven distribution of the number of ultrafine wires to be wicks, and uneven distribution of wicks in the heat pipe. However, there is an inconvenience that the flow path resistance increases, the function of moving the working fluid from the condenser to the evaporator is affected, and the performance of the heat pipe deteriorates. In particular, in a micro heat pipe of a small size that controls the temperature of electronic devices such as IC, LSI, and VLSI, it is necessary to perform a complicated bending process according to the installation location. When the wick was laid in the longitudinal direction of and the bending process was performed, the performance deterioration of the heat pipe was remarkable.

Further, when a flat type heat pipe is made from a cylindrical heat pipe using the above ultrafine wire as a wick, the ultrafine wire is pressed in the direction of low pressing force during crushing. It is moved and causes a bias. As a result, as shown in FIG. 5, the ultrafine wire that becomes the wick is moved in a direction perpendicular to the crushing direction, and on the upper and lower surfaces that are subject to the crushing in FIG. It was arranged. As a result, the performance of the heat pipe has deteriorated.

The present invention has been made in view of the above circumstances. The wicks in the heat pipe are not biased even during bending and crushing, and the wicks are uniformly arranged and flow in the heat pipe is ensured. An object of the present invention is to provide a heat pipe in which the road resistance does not increase and the heat pipe performance does not deteriorate.

[0010]

In order to achieve the above object, the present invention relates to a heat pipe provided with a wick, in which a working fluid is enclosed in a container in a vacuum deaerated state. The wick is formed of a braided body composed of a large number of ultrafine wires, and a spiral member wound in a hollow spiral shape so as to open a gap at a predetermined interval at least at both longitudinal ends of the container is a container. It is characterized in that the wick is arranged inside along the longitudinal direction thereof, and the wick is pressed against and fixed to the inner wall surface of the container.

Further, since the wick is formed of a braided body made of ultrafine wires, when the wick is bent or crushed, the distance between the ultrafine wires constituting the braid changes, but the entire circumference of the container is changed. There is a wick, the wick is not biased in the container, and a uniform arrangement of wicks can be secured. Therefore, the flow resistance is not increased due to uneven distribution of the wick, and the circulation of the working fluid is not hindered.

That is, in the heat pipe of this invention,
When the one end is heated, the working energy in the heat pipe is warmed and evaporated by the heating energy. The working fluid vapor flows toward the end portion where the internal pressure of the container is low, that is, the end portion disposed on the heat radiation point side. Then, the working fluid vapor flowing to the end side where the internal pressure of the container is low releases heat and condenses.

The working fluid that has been condensed and turned into a liquid phase again flows toward the evaporation portion side of the container by the capillary pressure of the braid body that becomes the wick, and is evaporated again in the evaporation portion. In that case, since a braid having excellent elasticity is used for the wick that serves as the liquid flow path and is arranged over the longitudinal direction of the container, it is possible to arrange the wicks evenly even in a portion subjected to bending or crushing. The same action as that of the portion which is secured and is not processed is obtained, and the working fluid is surely returned to the evaporation portion side even in the top heat mode.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention is shown in FIG.
A description will be given based on FIG. Also in the heat pipe of this embodiment, the container 1 is formed by sealing a cylindrical pipe in the same manner as a conventionally known general heat pipe. The container 1 is filled with a predetermined amount of working fluid in a vacuum-deaerated state, and here, for example, a condensable fluid such as sodium is used. As the material for the pipe, pure copper, a copper alloy, or a metal such as aluminum or nickel, which has excellent thermal conductivity, is adopted.

Further, as shown in FIGS. 1 (a) and 1 (b), a gap 9 having a predetermined interval is provided at both ends in the longitudinal direction of the heat pipe 4 at a substantially diametrical center position inside the container 1. A spiral member 3 wound in a hollow spiral shape to be opened is arranged along the longitudinal direction of the container 1, and the wick is pressed and fixed to the inner wall of the container 1. As the spiral member 3, for example, a tape material made of phosphor bronze is used. In this case, since the spiral member 3 made of phosphor bronze has a large elasticity in the winding radius direction, the wick is effectively fixed at a predetermined position.

As another example of the spiral member 3, there may be mentioned one in which copper or aluminum tape is wound in a circular shape, and in particular, a gap 9 is provided only at both end sides in the longitudinal direction thereof.

A wick is mounted on the outer peripheral surface of the spiral member 3 inside the container 1 along the longitudinal direction thereof. As an example, a braided body 10 composed of a large number of copper ultrafine wires is adopted in this wick. In this braided body 10, although the distance between the ultrafine wires constituting the braided body 10 changes even when bent and crushed, wicks are present over the entire circumference, and the heat pipe 4 is bent or crushed. Even if the above is applied, the wicks are not biased in the heat pipe, and the wicks can be arranged uniformly. That is, the unevenness of the wick in the processed portion does not occur, and the increase of the flow path resistance due to the uneven distribution of the wicks in the heat pipe does not occur, so that the inhibition of the recirculation ability of the working fluid can be prevented.

As is well known, the braided body 10 is provided as an example of a wick that distributes a working fluid to a wide range of the container 1 by a capillary pressure. Since the pipe has a circular cross section as described above, This braided body 10
The appearance of the is almost cylindrical. If the braided body 10 is made of carbon fiber coated with copper plating or copper oxide instead of copper wire, the weight can be reduced.

Next, as shown in FIG. 2, the heat pipe 4 of the present invention having the above-described structure is bent and heated at one end of the container 1 in a slightly inclined state. The operation when heated by the means 5 will be described. First, one end of the container 1 of the heat pipe 4 is heated and heated by the heating means 5 arranged at one end of the heat pipe 4 and serving as a heat source. Then, the working fluid inside the container 1 evaporates, flows into the space inside from the gap 9 of the spiral member 3, and flows toward the end portion where the internal pressure is low. Therefore, the inside of the spiral member 3 becomes a vapor flow path. The working fluid vapor further escapes from the gap 9 of the spiral member 3 to the outer peripheral side thereof on the other end side of the container 1 and is deprived of heat by the wall surface of the container 1 to be condensed. In other words, the heat generated by the heat source is released from this end.

In this case, the working fluid passes through the bent portion, but even in the bent portion, the wick is formed by the above-mentioned braided body 10, so that the wick shown in FIG. ), The wicks are uniformly arranged, the flow resistance in the heat pipe 4 does not increase due to uneven distribution of the wicks, and the circulation of the working fluid is not hindered. Therefore, the action as a flow path for the liquid-phase working fluid occurs in the same manner as in the portion other than the bent portion.

Then, the working fluid which has become a liquid phase again in the condensing portion 7 which is one end portion of the heat pipe 4 on the side where the internal pressure is low is sucked up by the braided body 10 serving as a wick,
It is carried to the evaporator 6 which is the other end on the one heat source side. That is, since the braided body 10 acts as a liquid flow path, even after the heat pipe 4 is bent, the wicks are uniformly arranged and the so-called pump force is large, and the braided body 10 is By being arranged in the container 1 in the longitudinal direction thereof, the working fluid surely flows back to the evaporation portion 6.

Further, in the heat pipe 4, since the central portion in the axial direction is supported from the inside by the spiral member, the vapor flow passage is sufficiently secured and the vapor flow passage and the liquid flow passage are separated. The braided body 10 is provided as a wick, and even when bending is performed, the distance between the ultrafine wires forming the braided body 10 changes between the outer circumference side and the inner circumference side of the radius of curvature, but over the entire circumference. The wick is present, and even in the bent portion, the braided body 10 serving as the wick is not biased and a uniform arrangement of the wick can be secured.

Therefore, the flow path resistance in the heat pipe 4 does not increase, and the ability to recirculate the working fluid can be maintained as in the bending portion. That is, the bending process does not deteriorate the performance of the heat pipe 4, and the same heat transfer characteristics as those before the bending process can be obtained.
Further, it is possible to obtain an excellent heat transport ability even in the operation in the top heat mode or in the inclined state, and it is possible to greatly improve the heat transfer efficiency as compared with the conventional general heat pipe.

Further, when a flat type heat pipe is produced from the cylindrical heat pipe 4 using the above braided body 10 for the wick, the sectional structure of the crushed portion is also shown in FIG. As described above, the braided body 10 serving as a wick is uniformly arranged on the outer peripheral surface of the spiral member 3, and is pressed and fixed to the inner wall surface of the container 1 by the spiral member 3 having a high elasticity in the winding radial direction. Even after being crushed, the braided body 10 to be the wick is not biased, the flow resistance is not increased due to the uneven distribution of the wick, and the recirculation ability of the working fluid is not hindered. Therefore, the performance of the heat pipe 4 is not deteriorated, and the heat transfer characteristics similar to those before the crushing process can be obtained.

Although the spiral member 3 is formed of elastic phosphor bronze in the above embodiment, the spiral member 3 is not limited to this, and the spiral member 3 is formed of another elastic material. May be.

[0026]

As is apparent from the above description, according to the present invention, a braid body composed of a large number of ultrafine wires is arranged inside the container as a wick along the longitudinal direction thereof. Since a spiral member that presses and fixes the braid body that becomes the wick against the inner wall surface of the container is provided, even if bending or crushing is performed, the distance between the ultrafine wires that form the braid body changes. However, wicks can exist all around. That is, the unevenness of the wicks does not occur in the processed portion, the uniform arrangement of the wicks can be secured, and the flow resistance in the heat pipe does not increase due to the uneven distribution of the wicks. That is, when laying the heat pipe, even if it is deformed according to the layout of the heat generating portion and the heat radiating portion, the recirculation ability of the working fluid is not hindered,
The performance of the heat pipe is not deteriorated, and the heat transfer characteristics similar to those before processing are obtained.

Further, since the spiral member for pressing and fixing the knitted body as a wick supports the central portion in the axial direction of the container from the inside, and the steam flow path is sufficiently secured, the flow of the working fluid steam is prevented. The heat pipe has no hindrance and is excellent in heat transport capability.

[Brief description of the drawings]

FIG. 1 is a partial structural view showing an internal structure of a heat pipe in an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a state where the heat pipe is bent and one end thereof is heated.

FIG. 3 is a sectional view showing a sectional structure when the heat pipe is crushed.

FIG. 4 is a structural view showing an internal structure and a cross section of a conventional heat pipe equipped with a wick and a cross section of a bent portion, wherein (a) is a partially cutaway side view and (b) is B of (a). −
B sectional drawing, (c) is CC sectional drawing of (a).

FIG. 5 is a cross-sectional view when the conventional heat pipe is crushed.

[Explanation of symbols]

1 ... container, 2 ... extra fine wire, 3 ... spiral member,
4 ... Heat pipe, 5 ... Heating means, 6 ... Evaporating section,
7 ... Condensing part, 8 ... Fixing member, 9 ... Gap, 10 ... Braided body.

Front page continuation (72) Inventor Koichi Masuko 1-5-1, Kiba, Koto-ku, Tokyo Inside Fujikura Ltd.

Claims (1)

[Claims] 1. A heat pipe provided with a working fluid in a vacuum degassed state inside a container, wherein the wick is formed by a braided body composed of a large number of fine wires, and at least A spiral member wound in a hollow spiral shape so as to open a gap at a predetermined interval on both longitudinal ends of the container is disposed inside the container along the longitudinal direction thereof, and the wick is attached to the inner wall surface of the container. A heat pipe characterized by being pressed and fixed.