JP4194276B2 - Flat plate heat pipe - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flat plate heat pipe in which a working fluid that transports heat as latent heat and a container that contains a wick for refluxing the working fluid form a hollow flat plate shape.
[0002]
[Prior art]
Various electronic components built into electronic devices such as computers have inevitable internal resistance, so they generate heat when they are energized and operated, and as a result, their operation becomes unstable when the temperature rises above a certain level. Finally, malfunction will occur. Therefore, various devices for cooling electronic components have been developed. For example, a device that directly attaches a heat sink to an electronic component to increase the heat radiation area, a device that attaches a microfan to the heat sink and forcibly air-cools, etc. have been developed. Has been.
[0003]
These cooling devices have a structure that prevents the electronic component from being overheated by increasing the amount of heat released from the electronic component by increasing the substantial heat radiation area of the electronic component with a heat sink. Therefore, the air used for cooling is limited to the air around the electronic component. For this reason, when the internal volume of the housing in which the electronic component is accommodated is small, the internal temperature gradually rises and the electronic component cannot be sufficiently cooled.
[0004]
A typical example is a so-called mobile small-sized data processing device such as a mobile phone, and this type of device uses a housing with as small a volume as possible with emphasis on portability and transportability. Therefore, the space around the electronic component is extremely limited. Therefore, if heat is radiated around the electronic component, sufficient cooling cannot be performed due to the small heat capacity of the air in the housing. In other words, usable electronic components are limited by the cooling capacity of the cooler.
[0005]
Therefore, conventionally, a cooler has been developed that cools electronic components by dissipating heat to the outside air at locations away from heating elements such as electronic components. In this type of cooler, the electronic component that is the object to be cooled and the heat dissipating part are separated from each other, and therefore it is necessary to efficiently transfer heat between them. For this purpose, a heating element is brought into contact with a heat transfer plate having high thermal conductivity such as aluminum, and a heat sink is attached to the other part of the heat transfer plate. Moreover, in order to assist the heat conduction by the heat transfer plate, a heat pipe is arranged along the heat transfer plate.
[0006]
The heat pipe encloses a condensable fluid such as water or alcohol as a working fluid in a sealed container (container), evaporates the working fluid by external heat input, It is a heat transfer device configured to flow to a low-pressure part, to dissipate heat and to condense, and to recirculate the liquefied working fluid to a portion where evaporation occurs by capillary pressure or the like. Various types of containers can be used as necessary. For example, a flat plate heat pipe forms a space part sealed by a container with a hollow flat plate structure, and non-condensable such as air in the space part. A condensable fluid is sealed as a working fluid in a state where gas is deaerated. Since this type of heat pipe has a flat surface, the contact area with the heat exchange object is widened. As a result, heat transfer performance or heat exchange performance is improved, and when used as a means for cooling. Has an advantage that a large heat radiation area can be secured.
[0007]
Flat plate heat pipes are sometimes referred to as vapor chambers, and those used for mobile are particularly referred to as mobile vapor chambers. Therefore, according to the mobile vapor chamber, heat can be transported by the latent heat of vaporization of the working fluid. By arranging this along the heat transfer plate, the amount of heat transported from the electronic component to the heat sink is greatly increased. Thus, the electronic component can be cooled more efficiently.
[0008]
[Problems to be solved by the invention]
As described above, the heat generated in the electronic component is transferred to the heat dissipation mechanism through the cooling plate or directly to the heat pipe with excellent heat transport capability, and then radiated to a place away from the electronic component by the air flow. Therefore, the temperature rise of the electronic component can be suppressed.
[0009]
However, recently, since the performance improvement of electronic devices such as mobile computers has been remarkable, the performance of electronic components has also improved, and accordingly, the amount of heat generated by electronic components has also increased. For this reason, it is desired to further improve the heat dissipation of the flat plate heat pipe.
[0010]
In addition, due to miniaturization of electronic devices such as mobile computers, the space for mounting electronic components and the like has become a limited and narrow range. For this reason, it is strongly desired to reduce the size of the flat plate heat pipe without impairing the heat transport characteristics.
[0011]
The present invention has been made against the background described above, and an object of the present invention is to provide a compact flat plate heat pipe having high cooling efficiency.
[0012]
[Means for Solving the Problem and Action]
In order to achieve the above-mentioned object, the invention of claim 1 is a flat plate type heat in which a wick that constitutes a passage for generating a capillary force and flowing a working fluid by the capillary pressure is disposed in a hollow flat container. in the pipe, the effective capillary half diameter smaller heat input side, large sintered metal window Quick is arranged, and the cross-sectional area is large effective capillary flow to the flow path of the working fluid to the heat radiating portion of the capillary pressure with it radius greatly, capillary pressure due to it being located relatively small mesh window Quick is yet plate type heat pipe, wherein a flow path of the wick is in communication with each other.
[0013]
Therefore, according to the first aspect of the present invention, when heat is transmitted to the heat input section, the working fluid inside the container evaporates and the vapor flows toward the heat radiating section having a low temperature and pressure. Then, the heat of the working fluid is radiated by the heat radiating section, and the working fluid is condensed and liquefied. The liquefied working fluid is then refluxed to the heat input portion side by the capillary action of the wick. At that time, since the effective capillary radius of the wick on the heat input portion is small, and the effective capillary radius on the wick on the heat dissipation portion is large, the capillary pressure generated in the heat input portion becomes the capillary pressure generated in the heat dissipation portion. It becomes higher. That is, the pump pressure for sucking the liquid-phase working fluid increases. Since each wick communicates, the action of returning the liquid-phase working fluid condensed in the heat radiating portion is strengthened, in other words, the liquid-phase working fluid is reliably returned to the heat input portion side to heat pipe. As the heat transport capacity increases. Further, the flow path cross-sectional area of the wick on the heat radiating portion side is large, and the flow path resistance is relatively small. In this respect as well, the reflux characteristic of the liquid phase working fluid is improved and the characteristics as a heat pipe are improved.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Next, a description will be given with reference to the drawings. FIG. 1 is a perspective view showing a specific example of a flat plate heat pipe according to the invention of claim 1, and FIG. 2 is a cross-sectional view thereof. This flat plate heat pipe 1 encloses a condensable fluid such as water as a working fluid in a state in which a non-condensable gas such as air is deaerated in a hermetically sealed container (hollow sealed container) 2. Furthermore, the wick 3 having a smaller effective capillary radius is disposed on the heat input portion side, and the wick 4 having a larger effective capillary radius is disposed on the heat radiating portion side.
[0017]
The container 2 is formed in a rectangular parallelepiped, and the upper surface of the container 2 is formed in a rectangle. An electronic component 5 is attached to the vicinity of one end in the longitudinal direction, and serves as a heat input portion 6. A heat radiating fin 7 formed by folding a plate of aluminum or the like having a high thermal conductivity and good workability is installed at the opposite end of the heat input portion 6, and this portion is the heat radiating portion. It is set to 8. The radiating fins 7 installed in the radiating portion 8 are directly fixed to the outer surface of the container 2 by means such as soldering or brazing.
[0018]
The wick 3 arranged on the heat input section 6 side is mainly configured to increase the pump pressure for refluxing the liquid-phase working fluid. For this reason, the effective capillary radius is small, and accordingly Thus, the capillary pressure is increased. Specifically, it is made of a porous material such as sintered metal, or is formed by binding ultrafine wires such as metal fiber or carbon fiber.
[0019]
On the other hand, the wick 4 arranged on the side of the heat radiating part 8 is configured mainly to promote the return of the working fluid to the heat input part 6 side, and therefore the effective capillary radius is large, and accordingly In addition, the capillary pressure is low and the cross-sectional area through which the liquid-phase working fluid flows is widened. Specifically, a mesh material, a groove formed on the inner surface of the container 2, or a striated body thicker than an extra fine wire used in the wick 3 on the heat input section 6 side is bound.
[0020]
In the flat plate heat pipe 1, heat generated by the operation of the electronic component 5 is first transmitted to the heat input portion 6 of the container 2. Then, the working fluid such as water inside the heat input portion 6 is heated and evaporated by the transmitted heat, and the vapor flows inside the heat radiating portion 8. The heat transferred by the flow is transferred from the heat radiating portion 8 to the heat radiating fins 7, and is radiated to the outside and condensed. That is, the heat of the electronic component 5 is conveyed to the heat radiating portion 8 in the form of latent heat of the working fluid, and is further dissipated from the heat radiating fin 7 to the outside, thus cooling the electronic component 5.
[0021]
The wicks 3 and 4 are arranged in close contact with the inner surface of the container 2, whereas the heat dissipation and condensation of the working fluid occurs when the vapor contacts the wick 4 and the inner surface of the container 2. The condensed and liquefied working fluid penetrates into the wick 4. Further, since the wick 4 and the wick 3 on the heat input section 6 side communicate with each other, the liquid-phase working fluid that has permeated the wick 4 in the heat radiating section 8 is sucked by the capillary pressure generated on the heat input section 6 side. The
[0022]
In that case, the meniscus of the liquid phase working fluid is generated also in the wick 4 on the heat radiating unit 8 side, and a capillary pressure may be generated. However, the effective capillary radius in the wick 4 is large, and the capillary pressure is on the heat input unit 6 side. Therefore, the liquid phase working fluid is positively sucked to the heat input section 6 side. Moreover, since the cross-sectional area of the flow path formed by the wick 4 on the side of the heat radiating section 8 is wide and the flow path resistance is small, there is little pressure loss for refluxing the working fluid toward the heat input section 6 side, Also in this respect, the liquid-phase working fluid is positively recirculated to the heat input section 6 side.
[0023]
Therefore, in the above embodiment, two types of wicks having different structures of the wick 3 having a small effective capillary radius and the wick 4 having a small pressure loss are provided on the heat input portion 6 side in the container 2 and the heat dissipation portion 8 side. As a result, the capillary action works remarkably. Therefore, the reflux property of the working fluid sealed in the container 2 is improved, and the heat transport amount is increased.
[0024]
FIG. 3 is a plan view showing a specific example of the invention of claim 2. The flat plate heat pipe 9 shown here has an L-shaped container, is combined with the bent inner side surface, and is combined with a square-shaped microfan 10 in a plan view. In plan view, the square shape is larger than the square shape.
[0025]
That is, the flat plate heat pipe 9 encloses a condensable fluid such as water as a working fluid in a hermetically sealed container (hollow sealed container) 11 in a state where non-condensable gas such as air is degassed. In addition, a wick (not shown) is provided inside.
[0026]
The container 11 is formed in an L shape as described above. An electronic component 12 is attached to the vicinity of the tip of one side of the L-shape, and serves as a heat input portion 13. Near the tip of the other side, a heat radiating fin 14 formed by folding ninety nine plates such as aluminum having high thermal conductivity and good workability is provided as a heat radiating portion 15. The radiating fins 14 are directly fixed to the outer surface of the container 11 by means such as soldering.
[0027]
The micro fan 10 combined with the flat plate heat pipe 9 has a hollow flat plate-like housing in which the thickness (height) in the installed state is smaller than the height of the heat radiating portion 15 and a rotation housed in the housing. This is a so-called horizontal axial fan having a blade to be driven. 3, a suction port 16 having a circular opening is formed on the upper surface portion, and a discharge port 17 having a rectangular opening is formed on one side surface of the microfan 10 in FIG. ing. The opening width of the discharge port 17 is set to a length substantially equal to the length of one side of the L shape inside the container 11. That is, the air is blown in the radial direction on the rotating surface of the blade.
[0028]
In the microfan 10, the discharge port 17 is opposed to the side edge portion of each radiating fin 1. Further, both edges in the discharge direction of the discharge port 17 are aligned with both edges on the L-shaped inner side of the container 11.
[0029]
Accordingly, when the microfan 10 is driven, the internal air enters the inside of the microfan 10 from the suction port 16 and is supplied from the discharge port 17 toward the radiating fins 14, and between the radiating fins 14 and between the containers 11. It passes through the upper surface and is sent to the outside.
[0030]
In the configuration shown in FIG. 3, first, heat generated from the electronic component 12 is transmitted to the heat input portion 13 of the container 11. Along with this, a temperature difference occurs at both ends of the flat plate heat pipe 9, and the heat pipe operation is automatically started.
[0031]
That is, the working fluid sealed inside evaporates, and the vapor flows to a condensing part in the container 11 (not shown) having a low temperature to dissipate heat. In this way, heat transfer from the container 11 to the heat radiating fins 14 is favorably performed.
[0032]
The heat transmitted to the heat radiating fins 14 is transmitted to an air flow generated by blowing air from the microfan 10, and the high-temperature air flow is discharged to the outside. Note that the working fluid that has dissipated heat and flows down toward the evaporation section inside the container, and is evaporated again by the heat of the electronic component 12.
[0033]
Therefore, in the above structure, the flat plate heat pipe 9 is made L-shaped, and the square microfan 10 is provided in the space inside the L-shape of the flat plate heat pipe 9 to make the whole compact. Can do. Therefore, when it is installed in a limited space inside an electric device or the like, the degree of freedom in arrangement can be improved. Furthermore, since the space for arranging other parts can be increased in the limited space, the degree of freedom in design can be improved.
[0034]
In the above structure, the flat plate heat pipe 9 is L-shaped. However, the present invention is not limited to the above-described structure. For example, a part of the side surface matches the contour of the fan. And bend or bend. In other words, any shape that can hold and store the peripheral edge of the fan is acceptable. In addition, although the fan is the micro fan 10, this is not limited to the above, and the point is that the blowing direction may be a radial direction.
[0035]
【The invention's effect】
As described above, according to the first aspect of the present invention, the effective capillary radius of the wick on the heat input section is small, whereas the effective capillary radius of the wick on the heat dissipation section is large. The capillary pressure to be increased is higher than the capillary pressure generated in the heat radiating portion. That is, the pump pressure for sucking the liquid-phase working fluid increases. And since each wick is connected, the effect | action which circulates the working fluid of the liquid phase condensed by the thermal radiation part becomes strong. In other words, it is possible to improve the heat transport capability as a heat pipe by reliably and abundantly returning the liquid-phase working fluid to the heat input portion side. Furthermore, the flow path cross-sectional area of the wick on the heat radiating portion side is large, and the flow path resistance is relatively small. In this respect as well, the reflux characteristic of the liquid phase working fluid can be improved and the characteristics as a heat pipe can be improved. .
[Brief description of the drawings]
FIG. 1 is a perspective view showing a specific example of a flat plate heat pipe according to the invention of claim 1;
FIG. 2 is a cross-sectional view of the heat pipe shown in FIG.
FIG. 3 is a plan view showing a specific example of a flat plate type heat pipe according to the invention of claim 2;
[Explanation of symbols]
1, 9 ... flat plate heat pipe, 2, 11 ... container, 3, 4 ... wick,
6, 13 ... Heat input part, 8, 15 ... Heat radiation part, 10 ... Micro fan.

Claims (1)

In a flat plate-shaped heat pipe in which a wick that constitutes a passage for generating a capillary force and circulating a working fluid by the capillary pressure is disposed in a hollow flat container,
The heat input side effective capillary half size is small, large sintered metal wick is arranged, and the cross-sectional area of the flow to flow path of the working fluid to the heat radiating portion is large effective capillary radius greatly capillary pressure with it flat-plate heat pipe, characterized in that the capillary pressure due to it is arranged a relatively small mesh material wick are communicated further communicating flow path of the respective wick to each other.

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