JP2002062071A - Flat plate type heat pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat pipe excellent in strength and heat transporting characteristics. SOLUTION: In the flat plate type heat pipe, in which only substantially condensable fluid is sealed into a flat plate type sealed vessel 1, the flat plate type sealed vessel 1 is provided in the same with a block 8, connecting both of flat plate units opposed to each other in the direction of thickness of the same, while the surface contacted with one flat plate unit of the block 8 is provided with fine grooves 9 and at least one end of the fine grooves 9 is opened at the outer peripheral surface of the block 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat pipe for transferring heat as latent heat of vaporization of a working fluid, and more particularly to a flat heat pipe in which a container has a flat shape.

[0002]

2. Description of the Related Art A flat heat pipe has a closed space formed by a container having a hollow flat plate structure, and a condensable fluid is supplied with a working fluid while a non-condensable gas such as air is degassed in the space. It is what was enclosed as. This type of flat heat pipe has a flat surface, which increases the contact area with the heat exchange target, resulting in improved heat transfer or heat exchange performance, and also used as a cooling means. In this case, there is an advantage that a wide heat radiation area can be secured.

That is, the heat pipe evaporates the working fluid in the container by heat transmitted from the outside,
After the steam flows to a place where the temperature and pressure are low, the steam is radiated to the outside and condensed, thereby transferring heat as latent heat of evaporation of the working fluid. Therefore, if a heating element such as an electronic component is attached to one surface such as a bottom portion of a container having a hollow flat plate structure and the other surface facing the surface is a heat radiation surface, the heat generated by the heating element is generated by the one side. As a result, the working fluid in contact with the one surface is heated and evaporated. On the other hand, when the other surface is exposed to outside air and cooled by air, the working fluid that has been heated and evaporated flows to the other surface side, contacts the other surface, condenses, and radiates heat. . As described above, since both the transfer of heat to the working fluid and the transfer of heat from the working fluid vapor occur on the wide surface of the container, when cooling the steam heating element, the cooling performance is low. improves.

[0004] Such a cooling function or heat transport action is generated by a circulating flow accompanied by evaporation and condensation of the working fluid. Therefore, in order to generate the heat transport function most efficiently, the heat input from the object to be cooled is generated at a point where the distance from all the points where the working fluid vapor radiates and condenses is almost equal. Is preferred. Specifically, it is preferable that a heating element such as an electronic component is brought into close contact with the center of the one surface.

[0005] However, in a flat heat pipe having a hollow flat container, the bending moment at the central portion of one surface is large, and the strength is low. Therefore, if a heating element to be cooled is pressed against the portion to be in close contact, the flat-type heat pipe is deformed, and a depression is generated particularly in the central portion of the one surface, which hinders the possibility of the heat pipe. In addition to this, there is a gap in the contact portion with the heating element, which causes a problem that the thermal resistance is increased and the cooling function is reduced.

Accordingly, for example, Japanese Patent Application Laid-Open No. H11-287578.
In the invention described in the publication, while a plurality of columnar portions are integrally erected inside a thin container having an open upper end,
A porous film that functions as a wick is formed by thermal spraying inside the container, and the opening of the container is then sealed. Has been proposed as a flat heat pipe in which is sealed as a working fluid.

[0007]

In the plate-shaped heat pipe described in the above-mentioned publication, the surface on which the object to be cooled is brought into close contact is supported by a column disposed on the inner surface side, so that the surface is deformed. Can be prevented or suppressed. In general, such a support may be provided at the center of a flat closed container, but it is necessary to increase the thickness or increase the number of the support to secure a certain strength. Further, it is preferable that the container, which is a flat closed container, is formed of a thin material in order to reduce the heat capacity thereof and also reduce the thermal resistance between the container and the working fluid. In order to prevent local deformation, it is necessary to increase the number of columns.

The struts are arranged between the opposing surfaces constituting the container and are brought into close contact with the respective surfaces. Therefore, the struts are in contact with the surfaces where the working fluid evaporates and condenses. The portion that is being covered is hidden from the working fluid and does not function as a portion for evaporating or condensing the working fluid. That is, by providing pillars,
Although the strength of the container is improved, the circulating flow or reflux of the working fluid is hindered, and there is a possibility that the heat transport capacity or the cooling function is reduced.

The present invention has been made in view of the above technical problems, and has as its object to provide a flat plate heat pipe which is excellent in both strength and thermal characteristics. .

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a block for supporting a surface to be contacted with a heat exchange object such as an electronic component from the inside, and the block includes a block. It is characterized by having a function as a wick. Specifically, the invention according to claim 1 is a flat plate heat pipe in which substantially only a condensable fluid is sealed in a flat closed container, wherein the flat closed container has: A block connecting the flat plate portions facing each other in the thickness direction is provided, and a narrow groove is provided on a surface of the block that contacts the one flat plate portion, and at least one end of the narrow groove is formed in the block. This is a flat heat pipe characterized by being opened on the outer surface.

Therefore, according to the first aspect of the present invention, since a block formed in a predetermined shape is provided at the center of the inner surface of the flat closed container, the bending moment is minimized when an external load is applied. The enlarged portion is supported from the inside by the block, and as a result, the strength of the flat closed container can be increased.
The central portion of the flat closed container is a portion having excellent thermal characteristics as a heat pipe, and an object to be cooled, for example, is brought into close contact with this portion. Therefore, the heat input to the location where the block is disposed increases, and it is necessary to actively return the working fluid to this portion and evaporate it. In the flat heat pipe according to the present invention, the block has a narrow groove formed therein, and the liquid-phase working fluid flows into the central portion of the block, that is, a portion having excellent thermal characteristics due to the capillary pressure generated in the narrow groove. Actively reflux,
And evaporates. Therefore, according to the present invention, it is possible to obtain a flat plate heat pipe having excellent strength and heat transport ability.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a specific example of a flat heat pipe according to the present invention will be described with reference to the drawings. First, the structure of the container (container) 1 will be described. In FIG. 1, the upper lid 2 is a thin plate made of a metal having good heat conductivity such as copper, and is formed in a rectangular shape in the example shown in the drawing. ing. The inner surface 3 of the upper lid 2 has a flat rectangular shape. Further, a main body 4 made of the same material as the upper lid 2 is provided.

The main body 4 has a bottom wall 5 made of a rectangular flat plate conforming to the shape of the upper lid 2, and flat side walls rising from four sides (edges) of the bottom wall 5. And a member having a concave cross-sectional shape constituted by the portion 6. Each side wall 6 has a constant height, and the bottom wall 5
Is set smaller than both the length and width.
That is, the main body 4 has an opening width equal to or greater than its depth. The inner surface and the outer surface of the bottom wall 5 are both flat surfaces. Further, a fitting portion 7 having a step having a right-angle cross section is formed on the inner surface side of each edge portion of the side wall portion 6. The fitting portion 7 is a portion into which the upper lid 2 is fitted and attached.

A block 8 is provided substantially at the center of the inner surface of the bottom wall 5. This block 8
It is made of the same material as the main body 4 and has a rectangular column shape. Also, the thickness of the block 8 is determined by the inner surface 3 of the upper lid 2 and the bottom wall 5.
, That is, the same depth as the inner depth of the container 1. Further, both top surfaces of the block 8 are formed as flat surfaces, and a narrow groove 9 is formed in the surface of the container 1 facing the heating side.

The narrow grooves 9 have a triangular cross-sectional shape, and are formed in large numbers so as to extend to both ends of the block 8 and open. Further, the narrow groove 9 generates a capillary pressure during operation to improve the recirculation of a working fluid, which will be described later.

FIG. 4 shows another example of the block 8 in the flat heat pipe of the present invention. In FIG. 4, a large number of narrow grooves 9 formed in the block have a rectangular cross-sectional shape, extend to both ends of the block, and are open.

FIG. 5 shows still another example of the block 8 in the flat heat pipe of the present invention. In FIG. 5, a large number of narrow grooves 9 formed in the block have a cross-sectional shape including a circular cross-section and a slit having a rectangular cross-section, and extend to both ends of the block to open.

As described above, the block 8 supports the opposing surfaces sandwiching the block 8 from the inside, so that the deformation of the container 1 during operation or non-operation as the heat pipe is prevented. At the same time, when the working fluid in the liquid phase intrudes into the narrow groove 9 formed in the block 8, a meniscus of the working fluid is generated, and accordingly, a capillary pressure is generated. That is, the narrow groove 9 functions as a wick, and the recirculation of the working fluid toward the portion where the block 8 is provided is promoted.

The location where the recirculation of the working fluid is promoted in this manner is a location where heat input from the outside is easily transmitted to the working fluid, and is biased with respect to the other surface on which the working fluid vapor condenses. Is a part where the flow distance of the working fluid vapor can be equalized, and by promoting the reflux of the working fluid, the heat transport function as a heat pipe is enhanced. The working fluid in which the narrow groove 9 evaporates flows through the inside of the narrow groove 9 to the outer peripheral side of the block 8, and then flows to the upper lid 2 side to radiate heat and condense.

The flat plate type heat pipe container 1 according to the present invention is constructed by fixing and integrating the above-mentioned members. That is, the block 8 is fixed to the inner surface of the bottom wall 5 of the main body 4. For example, when the main body 4 is made of copper and the block 8 is also made of copper, by heating the block 8 to a predetermined temperature with the block 8 being placed on the inner surface of the bottom wall 5, both are sintered. It can be fixed and integrated.

Next, the upper lid 2 is fitted and mounted on the fitting portion 7 of the opening of the main body 4. The thickness of the block 8 is set to be the same as the depth inside the main body 4 (that is, the height between the inner surface 3 of the upper lid 2 and the inner surface of the bottom wall 5), and both top surfaces of the block 8. Is a flat surface, so that the top surface of the block 8 is in close contact with the inner surface 3 of the upper lid 2. Then, the upper lid 2, the main body 4 and the block 8 are joined by an appropriate means such as welding, brazing, or an adhesive.

FIGS. 2 and 3 show a partially cutaway plan view and a vertical sectional side view of the container 1 thus constructed.
Although not shown, a small-diameter pipe (nozzle) communicating with the inside is attached to a predetermined portion of the side wall 6 constituting the side surface of the container 1. This nozzle is used to make the inside of the flat closed container 1 a heat pipe.

Specifically, a non-condensable gas such as air is exhausted from the inside of the flat closed container 1 through a nozzle, and a condensable working fluid such as water is sealed. Thereafter, the nozzle is closed. As a method for exhausting such a non-condensable gas and enclosing it in the working fluid thereafter, for example, a conventionally known method such as a heating purge method, a vacuum pump method, and a gas liquefaction method can be employed.

Thus, a flat heat pipe is completed. Therefore, by attaching the block 8, the flat heat pipe prevents deformation of the upper lid 2 and the bottom wall 5 in the approaching direction during non-operation and during operation, and is formed in the block 8. Since the narrow grooves 9 function as wicks, the internal structure of the flat heat pipe can be simplified.

In the flat heat pipe according to the present invention described above, the narrow groove 9 of the block 8 attached inside the flat airtight container functions as a wick, and holds a liquid-phase working fluid. Therefore, for example, if a heating element such as a CPU (not shown) is attached to a location corresponding to a central portion of the outside of the bottom wall 5 as a heating section, and the upper lid 2 is used as a heat radiating section, the working fluid is supplied to the heating element. Is heated and evaporated by the heat, and the vapor flows inside the upper lid 2 as a heat radiating portion, and radiates heat to the outside to condense. That is, the working fluid transports heat mainly as its latent heat. The condensed and liquefied working fluid is dropped toward the inner surface of the bottom wall portion 5 and returns to the heat generating portion side. At the same time, due to the capillary action of the narrow groove 9 by the wick, it is dispersed on the entire surface of the bottom wall portion 5, especially on the heating portion.

As described above, according to the specific example of the flat plate heat pipe of the present invention, the vapor of the working fluid is cooled by the cooling unit (the upper lid in this embodiment) during operation, and the heat generating unit (the self-weight) by its own weight. In the present example, the fluid is supplied to the bottom wall 5 at the same time as it is dropped and supplied to the central portion of the bottom wall 5 through the narrow groove 9 having a wick function, so that the recirculation of the working fluid is improved. In addition, since the block 8 that connects the bottom wall portion and the upper lid is provided, it is possible to reliably prevent deformation of the container at the time of manufacturing, non-operation, or operation.

In the above-described specific example, an example of a rectangular flat heat pipe is shown. However, the present invention is not limited to the above specific example, and the present invention is not limited to the above-described flat type heat pipe. It can be applied to heat pipes. Further, in the present invention, the block may be formed integrally with the upper lid or may be processed and joined. Also, regardless of the shape of the block, it is preferable that both top surfaces are flat surfaces. Further, the shape of the narrow groove is not limited to the exemplified shape, but may be any as long as it functions as a wick. Further, the material of the block is not limited to metal, but may be any material having thermal conductivity such as ceramics and plastic.

[0028]

As described above, according to the present invention, since a block having a predetermined shape is provided at the center of the inner surface of the flat closed container, the bending moment is maximized. The part is supported from the inside and its strength is improved.As a result, even if high pressure when operating as a heat pipe or high vacuum pressure when not operating is generated, deformation of the container can be prevented and at the same time heat generation The container can be prevented from being deformed even when receiving a load due to the close contact of a body or the like.

Furthermore, since a heating element or the like is disposed in contact with the place where the block is provided, heat may be directly transmitted to the block, and as a result,
Since heat is stored in accordance with the capacity of the block, it is possible to prevent or suppress a rise in temperature when the amount of heat generated by the heating element suddenly increases.

A narrow groove is provided on the surface of the block, which is in contact with one of the flat portions facing in the thickness direction, inside the flat closed container, and the narrow groove functions as a wick. The recirculation of the working fluid can be improved. That is, since the block according to the present invention has both functions of a column and a wick, the strength of the flat closed container can be improved, and the circulating flow of the working fluid can be promoted to improve the heat transport ability.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a container in an example of a flat heat pipe according to the present invention.

FIG. 2 is a plan view showing an example of a flat heat pipe according to the present invention in which a part of an upper cover is cut away.

FIG. 3 is a vertical sectional side view showing an example of the flat plate heat pipe according to the present invention.

FIG. 4 is a cross-sectional view showing another example of the block provided inside the flat plate heat pipe according to the present invention.

FIG. 5 is a sectional view showing still another example of a block provided inside the flat plate heat pipe according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Container, 2 ... Top lid, 4 ... Body part, 8 ... Block, 9 ... Narrow groove.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Koichi Mashiko 1-5-1, Kiba, Koto-ku, Tokyo Inside Fujikura Co., Ltd. (72) Inventor Ivan Saucheck 1-5-1, Kiba 1-chome, Koto-ku, Tokyo Inside Fujikura

Claims (1)

[Claims] 1. A flat plate heat pipe in which substantially only a condensable fluid is sealed inside a flat closed container, wherein the flat plates facing each other in the thickness direction are formed inside the flat closed container. A block to be connected is provided, and a narrow groove is provided on a surface of the block that contacts the one flat plate portion, and at least one end of the narrow groove is open to an outer peripheral surface of the block. Flat plate heat pipe.