JP3967427B2 - Flat heat pipe - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heat pipe that transports heat as latent heat of a working fluid, and more particularly to a flat plate heat pipe in which a container has a hollow flat plate shape.
[0002]
[Prior art]
As is well known, a flat plate heat pipe forms a sealed space inside a hollow flat plate-shaped container, and a non-condensable gas such as air is degassed in the space. As enclosed. In this type of heat pipe, since the surface is flat, there is an advantage that the contact area with the heat exchange object is widened and heat transfer performance or heat exchange performance is improved.
[0003]
In general, this flat plate heat pipe is generally formed by extruding a metal material into a rectangular cross-section pipe shape, cutting it into a predetermined length, and sealing both ends of the cut piece with caps. The working fluid was sealed inside the sealed space formed in the above. A flat plate heat pipe having an alternative structure is described in JP-A-9-138083. This flat heat pipe forms a sealed container by sandwiching a flat brazing sheet between two aluminum plates facing each other provided with concave portions in close contact with each other inside each concave portion. Each is filled with a predetermined amount of working fluid in a vacuum deaerated state. In addition, a large number of narrow grooves are formed as wicks in each recess.
[0004]
[Problems to be solved by the invention]
However, in the above conventional flat plate heat pipe, since the opening cross-sectional area is small, the working fluid in the middle of refluxing scatters as the flow velocity of the working fluid vapor increases, and the amount of working fluid recirculated to the evaporation section There was a risk that the heat transport capacity would be low due to the lack of. In addition, since the capillary pressure obtained by the narrow groove wick is low, in the conventional flat plate heat pipe, when the heat flux increases, the pumping action with respect to the working fluid becomes insufficient. In this case, there was a possibility that a dry-out phenomenon in which the hydraulic fluid was insufficient occurred.
[0005]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a flat plate heat pipe having excellent heat transport capability even in a top heat pipe mode or in a state where the container is inclined.
[0006]
[Means for Solving the Problem and Action]
In order to achieve the above object, the present invention provides a flat plate heat pipe in which a condensable fluid is sealed as a working fluid in a vacuum degassed state inside a hollow flat container having a sealed structure. A groove portion connected to the condensing portion is formed on the inner surface of the container, and a porous layer generating capillary pressure covers the opening portion of the groove portion and does not fill the inner space of the groove portion. the mounting et been said porous layer is characterized in being formed by spraying the spray particles to the groove.
[0007]
Therefore, according to the heat pipe of the present invention, when heat is transmitted to a part of the container, the liquid phase working fluid is heated and evaporated on the inner surface. The working fluid vapor escapes from the internal space of the porous layer or the groove, and flows toward the other end having a low internal pressure, that is, the end serving as the condensing portion, where heat is taken away and condensed.
[0008]
The working fluid that has dissipated heat and has become a liquid phase again penetrates into the gaps between the pores of the porous layer and enters the internal space of the grooves that communicate with the gaps. These liquid-phase working fluids flow toward the evaporation portion of the container by capillary pressure generated in a large number of pores of the porous layer. In that case, the effective capillary radius of the pores of the porous layer acting as a wick is small and the pumping action is large. In addition, the liquid phase working fluid moving in the internal space of the groove is separated from the vapor flow by the porous layer. In addition, since the scattering phenomenon is unlikely to occur, for example, even in the top heat mode, the working fluid reliably recirculates to the evaporation portion side, and thus the heat transport capability is improved.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Next, a specific example in which the flat heat pipe of the present invention is applied to cooling a CPU mounted on a personal computer will be described with reference to FIGS. FIG. 1 is a schematic view showing the appearance of a flat plate heat pipe. In the flat plate heat pipe 1, a container 2 is constituted by a hollow flat plate-like sealed metal container composed of a bottom plate 3 and an upper member 4. A working fluid (not shown) is sealed inside the container 2 in a vacuum deaerated state.
[0010]
More specifically, the bottom plate 3 is made of a rectangular metal flat plate. As shown in FIGS. 2 and 3, as shown in FIG. 2 and FIG. Is formed over the length direction. The groove 5 may be any groove that can flow the liquid-phase working fluid. For example, a single groove having a large opening width and a deep depth may be employed. Above each groove 5, a sprayed coating (porous layer) 6 is provided so as to cover the opening of each groove 5.
[0011]
More specifically, the thermal spray coating 6 has a porous structure with pores between the thermal spray particles 7 bonded to each other, and generates a large capillary pressure. Further, as the thermal spray particles 7, particles having a particle diameter smaller than the opening width of each groove portion 5 are adopted, and are adhered to the upper surface portion of the bottom plate 3 without entering the inner space of the groove portion 5. Other examples of the porous layer include a porous structure obtained by sintering metal particles or ceramic particles.
[0012]
Such a thermal spray coating 6 can be easily formed, for example, by performing plasma spraying or gas spraying before assembling the bottom plate 3 and the upper member 4. That is, since the thermal spraying process can be carried out in the released space, there are advantages such as good operability of the thermal spraying torch and no heat generation. The thermal spray material may be a dissimilar metal or ceramic, or a cermet in which they are mixed as long as it has excellent thermal conductivity and heat resistance. In addition, attachment holes 9 are formed at the four corners of the bottom plate 3 for conducting a screw (not shown) for fixing the flat heat pipe 1.
[0013]
The upper member 4 includes a top plate 20 made of a rectangular metal plate, side plates 21 extending downward from the four edges of the top plate 20 in FIG. 2, and the edges of the side plates 21 in the same figure. It is a metal cup-shaped member comprised by the flange part 22 each extended in the horizontal direction. In addition, two reinforcing ribs 10 are formed on the top surface of the top plate 20 so as to protrude toward the bottom plate 3 over the length direction. The reinforcing rib 10 is provided as necessary in order to prevent deformation of the container 2 during operation of the heat pipe. For example, a dome shape, a cross shape or an oval shape is adopted in addition to the illustrated groove shape. You can also The upper member 4 is attached to the bottom plate 3 in a posture in which the groove portion 5 and the thermal spray coating 6 and the top plate 20 are opposed to each other by welding the edge portion of each flange portion 22 to the bottom plate 3.
[0014]
As shown in FIG. 4, the flat plate heat pipe 1 having the above-described configuration is installed inside a case 11 of a notebook computer. One end of the container 2 is disposed in close contact with the lower surface of the metal electronic shielding plate 12 provided on the back side of the keyboard (not shown) of the case 11. On the other hand, the other end portion of the container 2 is disposed on the upper surface portion of the CPU 13 so as to be able to exchange heat. In addition, since the electronic shielding plate 12 is disposed slightly higher than the CPU 13, the container 2 itself is inclined. The container 2 is attached to the case 11 with screws.
[0015]
Next, the operation of the present invention configured as described above will be described. When the CPU 13 generates heat as the personal computer is used, the heat is transmitted to the bottom plate 3 of the container 2 of the flat plate heat pipe 1. Since the liquid phase working fluid is pumped up from the other end portion by the capillary pressure generated in the pores of the thermal spray coating 6, the inner surface of the end portion is already in a wet state. To begin.
[0016]
That is, the working fluid is heated into steam inside the grooves 5 and in the gaps between the plurality of sprayed particles 7 and flows into the upper space, and at the end provided in the electromagnetic shielding plate 12 having a low internal pressure. The heat flows away and condenses on the inner wall surface of the container 2 including the sprayed coating 6. That is, the heat of the CPU 13 is transmitted to the electromagnetic shielding plate 12 through the working fluid. The heat is conducted through the electromagnetic shielding plate 12 and is dissipated from the surface to the internal space of the case 11. As a result, the CPU 13 is cooled.
[0017]
Therefore, the inner surface of the end portion disposed on the electromagnetic shielding plate 12 of the flat heat pipe 1 is the condensing portion 14, whereas the bottom surface portion of the inner surface of the end portion disposed on the CPU 13 side. Is the evaporation unit 15. The working fluid that has dissipated heat and is in a liquid phase is collected on the bottom plate 3 side of the container 2 and penetrates into the sprayed coating 6, and enters each groove portion 5. Since a capillary pressure is generated in the gap between the sprayed particles 7, the working fluid that has permeated the sprayed coating 6 flows toward the evaporation unit 15 located above.
[0018]
Moreover, since the internal space of each groove part 5 and the clearance gap between the spray particles 7 communicate with each other, and the capillary pressure of the sprayed film 6 acts on the liquid phase working fluid in each groove part 5, the sprayed film 6. The working fluid in each groove portion 5 flows toward the evaporation portion 15 together with the working fluid that has penetrated into the inside. In that case, the flow resistance is smaller than that of the thermal spray coating 6 because each groove portion 5 is configured without inclusions, in other words, as a space without cross-sectional deformation. As a result, a necessary and sufficient amount of working fluid is supplied to the evaporation unit 15.
[0019]
As described above, since the sprayed coating 6 and each groove portion 5 are formed along the longitudinal direction of the container 2, the liquid-phase working fluid flows back to the upper evaporation portion 15. Thus, the sprayed coating 6 and each groove part 5 of the container 2 serve as liquid flow paths, while the space above the sprayed coating 6 serves as a steam flow path. That is, each groove portion 5 is configured as an independent space separated from the steam flow path by the thermal spray coating 6, and the liquid-phase working fluid that has entered these groove portions 5 is directly in contact with the vapor flow that becomes the counter flow. Because it does not come into contact, the scattering phenomenon is unlikely to occur during reflux. Then, the working fluid supplied to the evaporation unit 15 is heated by the CPU 13 and evaporated again, and thereafter the same heat transport cycle as described above is continued. As a result, overheating of the CPU 13 is prevented.
[0020]
As described above, in the flat plate heat pipe 1, the wick is composed of a large number of fine spray particles 7, and in addition to a large so-called pumping force, each groove portion 5 separates the spray coating 6 from the steam flow. Since the structure is independent from the path and the liquid phase working fluid that passes through the groove 5 is less likely to scatter, it exhibits excellent heat transport capability even in the top heat mode or when the container 2 is tilted. Further, the cooling capacity for the CPU 13 can be improved as compared with the conventional case.
[0021]
In the above specific example, the configuration in which the groove portion and the thermal spray coating are provided only on the upper surface portion of the bottom plate is illustrated. However, the present invention is not limited to the above specific example, and the groove portion and the thermal spray coating are basically condensed. Therefore, it may be provided on the lower surface portion of the upper member, for example.
[0022]
【The invention's effect】
As is apparent from the above description, according to the present invention, the groove portion connected to the evaporation portion and the condensation portion is formed on the inner surface of the container, and the porous layer that generates capillary pressure covers the opening portion of the groove portion, and Since it is attached to the inner surface of the container without filling the inner space of the groove, the heat transport capability can be improved particularly in the top heat mode or in the state where the container is inclined.
[Brief description of the drawings]
FIG. 1 is a schematic view showing the appearance of a flat plate heat pipe according to the present invention.
FIG. 2 is a sectional view of the flat plate heat pipe.
FIG. 3 is a cross-sectional view showing a configuration of a groove and spray particles.
FIG. 4 is a schematic view showing a state in which a flat plate-like heat pipe is arranged in a personal computer.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Flat plate heat pipe, 2 ... Container, 5 ... Groove part, 6 ... Sprayed film, 7 ... Sprayed particle, 11 ... Case, 12 ... Electromagnetic shielding board, 13 ... CPU, 14 ... Condensing part, 15 ... Evaporating part.

Claims (1)

In a flat plate-shaped heat pipe in which a condensable fluid is sealed as a working fluid in a vacuum degassed state inside a hollow flat plate-shaped sealed structure container,
A groove portion connected to the evaporation portion and the condensation portion of the container is formed on the inner surface of the container, and a porous layer that generates capillary pressure covers the opening portion of the groove portion and does not fill the internal space of the groove portion in mounting et is the inner surface of the container, flat heat pipe, wherein the porous layer is formed by spraying the spray particles to the groove.

Images