JPH11193994A - Flat heat pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flat heat pipe with superior heat transportation capability. SOLUTION: In a flat heat pipe 1 where fluid with a condensation property is encapsulated as an operating fluid to the inside of a hollow flat container 2 being made of metal where a flat heating part 20 opposes the flat radiating part 21, the container 2 is formed by a sectronally recessed main body 3 with an opening width being equal to or more than a depth and a sealing plate 4 for sealing the opening part of the body part 3. Also, a support 8 for connecting the inner surface of a part opposing the sealing plate 4 out of the body part 3 to the inner surface of the sealing plate 4 is integrally formed on the sealing plate 4. Furthermore, a porous layer 9 for generating capillary pressure is formed on the entire inner surface of the container 2 including the surface of the support 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 transporting heat as latent heat of a working fluid, and more particularly to a flat heat pipe in which a container has a hollow flat shape.

[0002]

2. Description of the Related Art As is well known, a flat heat pipe forms a closed space inside a container having a hollow flat plate structure, and a condensable gas is formed in the space by removing non-condensable gas such as air. Is sealed as a working fluid. In this type of heat pipe, the surface becomes flat, so the contact area with the heat exchange target is increased, and there is an advantage that heat transfer performance or heat exchange performance is improved, but the internal pressure of the container becomes vacuum pressure There is a problem that the wall surface of the container is liable to bend when not in operation. Therefore, it is necessary to take some measures to maintain the expected container configuration.

As one example, a hollow flat-plate-shaped container is conventionally formed by a main body having a concave cross-sectional shape having an opening width equal to or greater than a depth, and an upper plate closing the opening of the main body. There is a flat heat pipe having a configuration in which a wick made of a thermal spray coating is provided in the entire area and a screen mesh is arranged along the thermal spray coating. That is,
This flat heat pipe is configured to prevent the upper plate and the portion of the main body portion facing the upper plate from being bent by the elastic force of the screen mesh.

Therefore, in this flat heat pipe, the working fluid vapor is radiated and condensed on the inner surface of the upper plate by operating the lower side of the bottom of the main body as a heating unit. The working fluid in the liquid phase is retained without being dripped from the upper plate by the thermal spray coating and the capillary pressure of the screen mesh, and is returned to the evaporating portion on the bottom inner surface through the side wall of the main body, and is heated again to evaporate. I do.

[0005]

However, in the above-mentioned conventional flat heat pipe, the surface tension of the screen mesh due to the hydraulic fluid penetrating into the joint acts on the screen mesh, so that the screen mesh is not placed between the screen mesh and the inner surface of the container. In some cases, the working fluid vapor may remain shielded.
In addition, in this type of heat pipe, since the opening cross-sectional area of the container is small and the evaporating part and the condensing part are close to each other, the pressure difference between the evaporating part and the condensing part tends to be small. As a result, in the above-mentioned conventional flat heat pipe,
The heat transfer cycle of the working fluid was not performed normally, and the heat transfer ability was inferior.

The present invention has been made in view of the above circumstances, and has as its object to provide a flat heat pipe having excellent heat transport ability.

[0007]

As a means for solving the above-mentioned problems, the present invention relates to a hollow flat metal container in which a flat heating section and a flat heat radiating section are opposed to each other. In a flat heat pipe filled with a condensable fluid as a working fluid in a degassed state, a main body having a concave cross section having an opening width equal to or greater than a depth, and a sealing plate for sealing the opening of the main body By this, while the container is formed, a column connecting the inner surface of the portion of the main body facing the sealing plate and the inner surface of the sealing plate is integrally formed with the sealing plate, Furthermore, a porous layer that generates capillary pressure is formed on the entire inner surface of the container including the surface of the column.

According to the flat heat pipe of the present invention,
For example, when the lower side of the main body is operated as a heating unit in a posture where the sealing plate is arranged above the main body, the vapor of the working fluid flows toward the lower sealing plate side of the internal pressure, and the Heat is deprived (dissipates heat) on the inner surface and condenses. Most of the working fluid that has returned to the liquid phase moves from the inner surface of the sealing plate to the base end side of the column due to capillary pressure generated in the porous layer, and moves toward the distal end side on the surface of the column, Further, it is heated and evaporated while being diffused over a wide area on the inner surface of the bottom.

That is, the columns serve as a liquid return path, and most of the working fluid is directly supplied to the evaporator. In addition, since the working fluid is spread on the surface of the evaporator in a thin film state, so-called good wettability is obtained, the effective area of the evaporator is increased. Further, since the inside of the container is configured as an open space without a shield, and the pressure difference between the evaporating section and the condensing section is largely maintained, the heat transport cycle by the working fluid is actively performed. As a result, a high heat transport capability can be obtained.

[0010] In the flat heat pipe of the present invention, the same substantially rigid post as the sealing plate is used.
Since the sealing plate and the main body are supported from the inside, even when the heat pipe is not operating and the internal pressure is a vacuum pressure, the container does not depress in a direction in which the heating unit and the heat radiation unit approach. The desired hollow flat plate shape can be maintained.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a C mounted on a personal computer will be described.
A specific example in which the flat heat pipe of the present invention is applied to cooling a PU will be described with reference to FIGS. In the flat heat pipe 1, a container 2 is configured by a hollow flat closed metal container including a main body 3 and a sealing plate 4. A working fluid (not shown) is sealed in the container 2 in a vacuum degassed state.

More specifically, the main body 3 is composed of a bottom wall 5 made of a rectangular plate-like body, and flat side walls 6 rising from four sides (edges) of the bottom wall 4. Cup-shaped member. The height of each side wall 6 is set smaller than both the length and the width of the bottom wall 5. That is, the main body 3 has an opening width equal to or greater than its depth. A plurality of parallel grooves 7 are formed on the upper surface of the bottom wall 5. On the other hand, the lower surface of the bottom wall 5 forms a flat surface. In addition,
Each groove 7 is only required to generate capillary pressure, and is not limited to the illustrated rectangular cross section. For example, a V-shaped cross section or a U-shaped cross section may be employed.

A fitting portion 10 having a step having a right-angled cross section is formed on the inner surface of each edge of the side wall portion 6. The fitting portion 10 is a portion into which the sealing plate 4 is fitted and attached. Then, the main body 3 excluding the fitting portion 10
Is provided with a thermal spray coating 9 of a predetermined thickness on the entire inner surface, that is, on the surfaces of the side walls 6 and the bottom wall 5 and the groove.

The thermal spray coating 9 has a porous structure having pores between thermal spray particles bonded to each other, and generates a large capillary pressure. Therefore, this thermal spray coating 9 corresponds to the porous layer of the present invention. As the thermal spray particles, particles having a smaller particle size than the opening width of each groove 7 are employed so as not to fill the internal space of each groove 7.

The thermal spray coating 9 can be easily formed by, for example, performing plasma spraying or gas spraying before assembling the main body 3 and the sealing plate 4. That is, since the spraying process can be performed in the open space, the operability of the spraying torch is good,
Alternatively, there are advantages that heat does not accumulate and that cleaning is easy. Further, as the thermal spraying material, a different metal or ceramic or a cermet obtained by mixing them may be used as long as it is excellent in thermal conductivity and heat resistance. A material that does not dissolve even when it is brought into contact with the working fluid over the entire area is adopted.

On the other hand, the sealing plate 4 is a metal plate having a size that matches the fitting portion 10 in a plan view. The lower surface in FIG. 2 of the sealing plate 4 forms a flat surface. On the other hand, on the upper surface of the sealing plate 4 in FIG. 2, for example, a plurality of prism-shaped columns 8 each having a side substantially equal to the opening width of the groove 7 are provided. The base end 15 of these columns 8
Are formed integrally with the sealing plate 4. Therefore, each support 8 is made of a substantially rigid body such as copper. Further, as an example, these columns 8 are arranged so that every four columns and three columns in FIG. 2 are shifted from each other in the horizontal direction. Further, the thermal spray coating 9 is provided on the entire surface of the surface of each column 8 and the upper surface of the sealing plate 4 in FIG. Is formed. The thermal spray coating 9 has the same composition as that of the main body 3. Therefore, it corresponds to the porous layer of the present invention.

As shown in FIG. 3, the sealing plate 4 is tightly fitted into the fitting portion 10 in a direction in which the tip 14 of the column 8 faces the bottom wall 5. That is, the sealing plate 4 is assembled to the main body 3 in a state where the opening formed by the upper edge of each side wall 6 is closed. Then, the sealing plate 4 and the main body 3
Is sealed by welding. In addition,
The distal end portion 14 of each column 8 is brought into contact with the bottom wall portion 5 in a state shifted in the lateral direction in FIG. 3 so as to cover a part of the opening of each groove 7.

The flat heat pipe 1 having the above structure
3 is supported on a circuit board 13 by a holder 12 with the lower surface of the bottom wall portion 5 being in close contact with the upper surface of the CPU 11, as shown in FIG. Therefore, the lower surface of the bottom wall portion 5 is the heating portion 20, whereas the upper surface of the sealing plate 4 is the heat radiating portion 21.

Next, the operation of the above specific example will be described. When the CPU 11 generates heat by energization due to the use of the personal computer, the heat is transmitted to the main body 3 of the flat heat pipe 1, and the working fluid stored at the bottom of the container 2 is heated and evaporated. Therefore, the bottom wall 5 of the main body 3 and each groove 7 become the evaporator 16.

The working fluid that has turned into steam flows upward through the gap between the columns 8 at a low pressure and temperature, and
The heat is removed from the inner surface of the sealing plate 4, condensed, and penetrates into the thermal spray coating 9. Therefore, the inner surface of the sealing plate 4 becomes the condensing portion 17. Note that the released heat is radiated from the outer surface of the sealing plate 4 to the internal space of the personal computer case, and as a result, the CP
U11 is cooled.

The condensed working fluid is held on the inner surface of the sealing plate 4 by capillary pressure generated in the gap between the spray particles. Most of the working fluid moves toward the base end 15 of the support 8, moves toward the distal end 14 while spreading the wall surface of the support 8 in a thin film shape, and moves toward the bottom 14 of the main body 3. 5 and each groove 7. In addition, a part of the working fluid moves from the inner surface of the sealing plate 4 while spreading in a thin film form on each side surface, and returns to the evaporator 16. That is, since the plurality of columns 8 function as a direct liquid recirculation path from the condenser 17 to the evaporator, a necessary and sufficient amount of working fluid is reliably supplied to the evaporator 16.

The working fluid returned to the bottom of the container 2 is
While penetrating into the thermal spray coating 9 and entering each groove 7, it moves in the surface direction of the bottom wall portion 5 by the capillary pressure generated in the gap between the thermal spray particles, and along the groove 7 in the depth direction in FIG. Moving. As a result, almost the entire area of the bottom of the container 2 acts as the effective area of the evaporating section 16.

As described above, in the flat heat pipe 1 having the above-described structure, the working fluid is directly supplied from the vertically opposed condensing portion 17 to the evaporating portion 16 through the support 8, and the working fluid is also supplied. Since the heat is dispersed over a wide range of the evaporator 16, the heat transport capability can be improved. In addition, the space between the evaporating section 16 and the condensing section 17 is configured as an open space without a shield, and the pressure difference between the evaporating section 16 and the condensing section 17 is large. And the heat transport ability is improved from this point.

Further, according to the flat heat pipe 1 having the above-described structure, the sealing plate 4 and the main body 3, both of which are formed of a flat body, are supported from inside by the plurality of columns 8, so that the inside of the container 2 is Even in a state where the pressure is in a vacuum state, that is, in a non-operating state, particularly, the sealing plate 4 and the bottom wall 5 do not bend, and the container 2 can be maintained in an intended shape. In addition, each support 8
Are made of the same material as the sealing plate 4 and are arranged at a sufficient distance from each other, so that the heat transport action by the working fluid is not hindered at all.

In the above specific example, a sprayed coating is exemplified as the porous layer. However, the present invention is not limited to the above specific example. The thing sintered on the inner surface can be mentioned. Further, in the above specific example, the present invention is applied to cooling of a CPU, but may be applied to cooling of an electronic device for a server, for example. Further, in the above specific example, a step is provided at the edge of each side wall portion, and the sealing plate is fitted here. However, the present invention is not limited to the above specific example. The edge portion may be bent in a direction parallel to the bottom wall portion to form a flange portion, and a container having a configuration in which a sealing plate is adhered to the flange portion may be used.

[0026]

As described above, according to the present invention, a main body having a concave cross-sectional shape having an opening width equal to or greater than a depth is provided.
With a sealing plate that seals the opening of the main body, a hollow plate-shaped container is formed, and a column connecting the inner surface of the portion of the main body facing the sealing plate and the inner surface of the sealing plate is formed. , Formed integrally with the sealing plate, and further formed with a porous layer on the entire inner surface of the container including the surface of the column, so that the working fluid in the condensing section is directly supplied to the evaporating section via the column. In addition, since the heat transfer cycle of the working fluid is actively performed by a large pressure difference between the evaporator and the condenser, the heat transfer capacity can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a main body.

FIG. 2 is a schematic diagram showing a sealing plate and a support.

FIG. 3 is a schematic diagram showing a state in which a flat heat pipe is attached to a CPU.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Flat heat pipe, 2 ... Container, 3 ... Body part, 4 ... Sealing plate, 7 ... Groove, 8 ... Prop, 9 ...
Thermal spray coating, 10 ... fitting part, 14 ... tip part, 15 ...
Base end portion, 20: heating portion, 21: heat radiation portion.

Claims (1)

[Claims] 1. A flat heat pipe in which a condensable fluid is sealed as a working fluid in a degassed state inside a hollow flat metal container in which a flat heating section and a flat heat radiating section face each other. The container is formed by a main body having a concave cross-sectional shape having an opening width equal to or greater than the depth, and a sealing plate for sealing the opening of the main body, and the main body is opposed to the sealing plate in the main body. A column connecting the inner surface of the portion to be formed and the inner surface of the sealing plate is formed integrally with the sealing plate, and further, a porous layer that generates capillary pressure over the entire inner surface of the container including the surface of the column. A flat plate heat pipe, characterized in that a heat pipe is formed.