JP2007003034A - Cooling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve structural strength and cooling performance of a closed container. <P>SOLUTION: A plurality of heat pipes 4 transporting heat as latent heat of working fluid 3 are arranged in the closed container 2 in an uprising state, a plurality of flat fins 5 are arranged in parallel with each other at prescribed intervals at closed end portions 4A of the heat pipes 4, a support 8 is mounted for supporting a wick 7A (wick 7B) mounted on an inner surface of at least one of an upper surface portion 2B and a lower surface portion 2A opposite to each other in the closed container 2, between the upper surface portion 2B and the lower surface portion 2A, hole portions 10 penetrating through opening end portions 4B of the heat pipes 4 are formed on the upper surface portion 2B, the hole portions 10 are held by the opening end portions 4B, and the opening end portions 4B of the heat pipes 4 are connected with the wick 7A (wick 7B) at an upper surface portion 2B side or a lower surface portion 2A side. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  In the present invention, a condensable fluid that evaporates or condenses according to the state of heat input or heat dissipation is enclosed as a working fluid inside a hollow flat airtight container, and the capillary pressure is reduced by wetting with the working fluid. The present invention relates to a cooling device in which a wick to be generated is provided inside a sealed container.

  Conventionally, a cooling device including a heat pipe or a heat sink that transports heat as latent heat of a working fluid is widely known. In this type of cooling device, the working fluid evaporated into a vapor phase transports heat by flowing to the condensing part on the low temperature / low pressure side, and after the heat transport, a wick provided inside the heat pipe. The condensed liquid phase working fluid is recirculated to the evaporation section (heat input section) by the capillary pressure due to.

  The wick is, in essence, for generating capillary pressure, so that the so-called wettability with the working fluid is good, and the effective capillary radius at the meniscus formed on the liquid surface of the liquid-phase working fluid. Is preferably as small as possible. In general, porous sintered bodies (porous bodies), ultrafine wire bundles, and the like are employed as wicks. Among these wicks, the wick using a porous sintered body has a smaller opening area than the wick using another structure different from the porous sintered body, so it is generated. The capillary pressure to be obtained, that is, the pumping force for the liquid phase working fluid is large. Further, since this wick can be formed in a sheet shape, it has been adopted in a heat pipe called a vapor chamber such as a flat plate type which has been attracting attention recently.

  This heat pipe forms a space sealed by a hollow flat plate container (sealed container), and a non-condensable gas such as air is degassed in the space as a working fluid. It is a thing. 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.

  On the other hand, since the heat pipe has a configuration in which only a condensable fluid is sealed in the space portion, the working fluid is condensed in a non-operating state or a cooling state without heat input from the outside, so that the space portion has a high interior. It becomes a vacuum state. On the other hand, if there is a large amount of heat input from the outside, the working fluid evaporates and increases its volume, so that the internal pressure in the space increases. For this reason, in flat heat pipes, the rigidity of the parts with large surface areas on the upper and lower surfaces is low, so that the upper and lower surfaces are recessed during non-operation and manufacturing, or conversely, the upper and lower surfaces expand during operation. Deformation may occur.

  In order to eliminate such inconvenience, in the invention described in Patent Document 1, a plurality of support columns (columnar portions) are erected integrally in a thin container having an open upper end portion, and function as a wick. A porous film is formed inside the container by thermal spraying, and after the opening of the container is sealed, the air such as air is vacuum degassed and a condensable fluid such as water is used as a working fluid. A sealed heat pipe is proposed.

  Further, a heat sink having a structure that dissipates heat to the atmosphere from the outer peripheral surface of the heat pipe and the surface of the flat fin (radiation fin) is known, and an example of this heat sink is described in Patent Document 2.

The heat sink described in Patent Document 2 is a tower-type heat sink having a structure in which a heat transfer member such as a support is erected on a base portion and a flat fin is attached to the heat transfer member. Since a large number of flat fins can be provided by being fitted to the member, there are few restrictions on the number and the heat radiation area. In order to further increase the heat radiation amount, it is preferable to perform forced cooling by blowing air toward the flat fins. For example, when a tower-type heat sink is attached to the inside of the housing, a blower (fan) for feeding into the gap between the flat fins is located at a predetermined position inside the housing or a flat plate in the tower-type heat sink. It is attached at a position where cooling air flows in or out in a direction substantially perpendicular to the arrangement direction of the fins.
JP-A-11-287578 Japanese Patent Laid-Open No. 7-263601

  By the way, in such a cooling device including a heat pipe or a heat sink, a lower surface portion and an upper surface portion having a large area are connected to each other by a plurality of support columns, and therefore the lower surface portion or the upper surface portion due to a decrease in internal pressure. It is possible to prevent depression deformation and bulge deformation of the lower surface portion or the upper surface portion due to an increase in internal pressure during operation. However, the lower surface portion and the upper surface portion connected to these columns are formed of a thin flat plate portion and have low rigidity, and therefore, when an electronic component including an electronic element such as a CPU is mounted on or closely adhered to a heat pipe. There is a possibility that the central portion of these upper surface portion and lower surface portion is deformed by the pressing force.

  Further, in the upper surface portion or the lower surface portion of the sealed container, only the heat conduction through the support column occurs at the portion where the support column is joined, so that the heat transport by the evaporation / condensation of the working fluid is not used. For example, due to the recent demand for miniaturization, when an electronic component to be radiated is configured as a smaller chip and becomes as small as the cross-sectional area of the column, the chip is transferred from the chip to the column via the upper surface or the lower surface. Since heat is transferred, heat transfer by the working fluid is hindered. For this reason, the entire apparatus has poor cooling performance such as heat transport capability or heat dissipation performance.

  Furthermore, in the tower type heat sink described above, a large number of flat fins are arranged on the base portion, so that the heat radiation area can be increased. However, when a tower-type heat sink is disposed inside a housing such as an electronic device having a limited space for placement, the placement of electronic components within the housing is limited. Therefore, there is a possibility that a necessary space cannot be ensured in terms of cooling performance. Moreover, if the entire tower type heat sink is made compact in order to solve this problem, the flat fins and the base part must be made compact. For this reason, there is a possibility that the rigidity of the heat sink is lowered or the cooling performance cannot be ensured.

  The present invention has been made by paying attention to the above technical problem, and an object of the present invention is to provide a cooling device capable of improving the structural strength and cooling performance of a sealed container.

  In order to achieve the above object, the invention of claim 1 is characterized in that a condensable fluid that evaporates or condenses in accordance with the state of heat input or heat dissipation is enclosed as a working fluid inside a hollow flat airtight container. A cooling device in which a wick that generates capillary pressure by being wetted by the working fluid is provided inside the sealed container, and a plurality of heat pipes that transport heat to the sealed container as latent heat of the working fluid Are arranged in a standing state, and a plurality of flat fins are arranged in parallel with each other at a predetermined interval at the closed end of the heat pipe, and at least one of the upper surface portion and the lower surface portion facing each other in the sealed container A support for supporting the wick provided on the inner surface between the upper surface portion and the lower surface portion is disposed, and the opening end portion of the heat pipe penetrates the upper surface portion. A hole is formed, the hole is held by the opening end of the heat pipe, and the opening end of the heat pipe is joined to the wick on the upper surface side or the lower surface side. The cooling device is characterized.

  The invention of claim 2 is an apparatus characterized in that the opening end portion of the heat pipe in the invention of claim 1 is joined to the hole portion so as to be able to transfer heat.

  According to the first aspect of the present invention, the wick supports the wick between the upper surface portion and the lower surface portion, and the hole formed in the upper surface portion is held by the open end portion of the heat pipe, and the upper surface portion. Since the opening end of the heat pipe is joined to the wick on the side or the lower surface side, the wick can be reliably fixed inside the sealed container. Also, with this structure, the rigidity at a predetermined location where the bending moment in the sealed container increases is increased, so that even when a pressing force is applied to the sealed container, for example, when the electronic components are brought into close contact, the deformation of the sealed container is ensured. Can be prevented. Therefore, the entire apparatus can be made compact without reducing the rigidity of the sealed container. Furthermore, since a plurality of open end portions of the heat pipe are joined to the wick, a large amount of liquid-phase working fluid can be evaporated on the inner surface side of the joint portion between the open end portion of the heat pipe and the wick. . Therefore, since the circulating flow of the working fluid is promoted as the entire apparatus, the cooling performance can be improved.

  According to the invention of claim 2, since the opening end portion of the heat pipe is joined to the hole portion of the upper surface portion so as to be able to transfer heat, the heat of the sealed container body can be efficiently transported to the heat pipe. . Therefore, since the heat capacity of the entire apparatus is increased, the cooling performance can be further improved.

  The best mode for carrying out the present invention will be described below. In the cooling device according to the present invention, a condensable fluid that evaporates or condenses in accordance with a state of heat input or heat dissipation is enclosed as a working fluid in a hollow flat airtight container and wetted with the working fluid. A wick for generating capillary pressure is provided inside the sealed container. More specifically, as shown in FIG. 1, in the cooling device 1, a plurality of cylindrical heats that transport heat as latent heat of the working fluid 3 to the sealed container 2 (a vapor chamber that is a kind of flat plate heat pipe). The pipe 4 is arranged in an upright state, and a plurality of flat fins (radiating fins) 5 are arranged in parallel to each other at a closed end 4A of the heat pipe 4 at a predetermined interval. Further, inside the sealed container 2, the wicks 7A and 7B provided on the inner surfaces of the lower surface portion 2A and the upper surface portion 2B facing each other (in the thickness direction of the lower surface portion 2A or the upper surface portion 2B) in the sealed container 2 are provided. Is disposed between the lower surface portion 2A and the upper surface portion 2B.

  The sealed container 2 is a thin rectangular parallelepiped made of a metal having high thermal conductivity such as copper, and the lower surface portion 2A and the upper surface portion 2B of the sealed container 2 are formed in a rectangular shape. An open end 4B of the heat pipe 4 is joined to each wick 7A, 7B on the lower surface 2A side and the upper surface 2B side. A predetermined electronic component 11 is attached to the lower surface portion 2A, and a hole 10 is formed in the upper surface portion 2B so as to penetrate the opening end portion 4B. The hole 10 is joined to the opening end 4B so as to be able to transfer heat and is held by the opening end 4B. Further, the hole 10 is formed at a location where the bending moment in the upper surface portion 2B increases, and the rigidity at that location is high. For example, even when a pressing force is applied to the lower surface portion 2A when the electronic component 11 is brought into close contact with the lower surface portion 2A, the deformation of the lower surface portion 2A can be reliably prevented. As a result, the entire cooling device 1 can be made compact without reducing the rigidity of the sealed container 2.

  Here, the wick 7A attached to the lower surface portion 2A will be described. When the wick 7A is wetted by the liquid-phase working fluid 3, a meniscus is generated in the wick 7A on the lower surface portion 2A side, and a capillary pressure inversely proportional to the effective capillary radius at the meniscus is generated. The wick 7A is formed so that its effective capillary radius is small. For example, a porous sintered body or a net-like body (as an example, # 200) made of fine particles (as an example, copper particles having a particle size of 25 to 100 μm) is used. Mesh).

  The wick 7B attached to the upper surface portion 2B is formed with a so-called flow path in which the liquid-phase working fluid 3 that has condensed and permeated flows, and the flow path of the liquid-phase working fluid 3 flows. Is formed smoothly. Further, the wick 7B is formed in a shape in which a gap portion serving as a flow path has as wide an opening area as possible or is connected as linearly as possible. (As an example, # 100 mesh) or a material particle having a relatively larger diameter than the wick 7A (as an example, a copper particle having a particle size of 75 to 250 μm), a porous sintered body, or a narrow groove (as an example, 0.1 mm width × 0.1 mm depth). That is, in this specific example, the wick 7A is configured to generate a large capillary pressure, and the wick 7B is configured to have a low flow resistance with respect to the liquid-phase working fluid 3.

  Furthermore, the support | pillar 8 is a column-shaped structure extended in the column shape, and the both end surfaces are flat. In addition, the height of the support | pillar 8 is set to the same dimension as the width | variety between the lower surface part 2A and the upper surface part 2B. This support | pillar 8 can be formed using the same material as the airtight container 2, and may be formed by appropriate methods, such as forge molding (processing) and casting by a press.

  Next, the operation of the cooling device in the present invention will be specifically described. First, heat generated in the electronic component 11 is transmitted to the lower surface portion 2A. Therefore, the lower surface portion 2 </ b> A becomes a heat input portion of the cooling device 1. Next, the heat transmitted to the lower surface portion 2A is transmitted to the liquid-phase working fluid 3 penetrating the wick 7A, and the working fluid 3 evaporates. In this state, the liquid-phase working fluid 3 on the inner surface side of the joint portion between the opening end 4B and the wick 7A evaporates.

  On the other hand, the heat transferred from the lower surface portion 2A to the upper surface portion 2B is transmitted in the rising direction with a temperature difference. Since the opening end portion 4B and the hole portion 10 of the upper surface portion 2B are joined so as to be able to transfer heat, the heat of the upper surface portion 2B is transmitted to the flat fins 5 via the heat pipes 4. Since a plurality of the heat pipes 4 are arranged in the sealed container 2, a wide heat radiation area can be secured. Therefore, the heat capacity of the entire cooling device 1 is increased.

  Subsequently, when air is blown from a blower fan (not shown) toward the closed end portion 4A of the heat pipe 4, heat on the inner surface side of the open end portion 4B to which heat is transmitted is released. Since heat is generated at the closed end 4A, the pressure inside the closed end 4A is reduced. Therefore, the steam inside the heat pipe 4 moves to a place where the temperature and pressure inside the heat pipe 4 are low (the steam generated on the inner surface side of the opening end 4B is the inner surface side of the joint portion between the opening end 4B and the wick 7A) To flow).

  Thus, the heat of the closed end portion 4A and the upper surface portion 2B is taken to the outside, so that the inner surface side of the joint portion between the open end portion 4B and the wick 7A and the inside of the sealed container 2 (the lower surface portion 2A and the upper surface portion 2B) The gas-phase working fluid 3 existing in the space between the two is condensed and liquefied. The liquefied working fluid 3 present in the sealed container 2 penetrates into the wick 7B. When the liquid-phase working fluid 3 evaporates in the wick 7A, the meniscus in the wick 7A is lowered, so that a pumping force for pulling up the liquid-phase working fluid 3 by the capillary pressure corresponding to the effective capillary radius is generated.

  And since the flow path formed inside each wick 7A, 7B is connected and filled with the working fluid 3 of the liquid phase, the liquefied working fluid 3 existing inside the sealed container 2 is wicked. It is sucked to the lower surface portion 2A side by the pumping force of 7A. Thus, heat is transported as latent heat of the working fluid 3 as the working fluid 3 circulates and flows inside the heat pipe 4 by repeating evaporation and condensation.

  In this specific example, since a plurality of opening end portions 4B are joined to the wick 7A, a large amount of the liquid-phase working fluid 3 on the inner surface side of the joining portion between the opening end portion 4B and the wick 7A is evaporated. be able to. Therefore, since the circulating flow of the working fluid 3 is promoted as the entire cooling device 1, the cooling performance can be improved.

  In the above-described specific example, the wicks 7A and 7B are provided on the inner surfaces of the lower surface portion 2A and the upper surface portion 2B facing each other in the sealed container 2, respectively, but the wick of the present invention is in this specific example. It is not limited. In short, it is sufficient that a wick that generates capillary pressure by being wetted with the working fluid is provided inside the sealed container. For example, the wick is provided on at least one inner surface of the lower surface portion and the upper surface portion. Also good.

It is typical sectional drawing which shows one specific example of the cooling device in this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Cooling device, 2 ... Airtight container, 2A ... Lower surface part, 2B ... Upper surface part, 3 ... Working fluid, 4 ... Heat pipe, 4A ... Closed end part, 4B ... Opening end part, 5 ... Flat plate fin, 7A, 7B ... Wick, 8 ... Support, 10 ... Hole, 11 ... Electronic component.

Claims (2)

A condensable fluid that evaporates or condenses depending on the state of heat input or heat dissipation is enclosed as a working fluid inside a hollow flat airtight container, and a wick that generates capillary pressure by being moistened with the working fluid. A cooling device provided inside the sealed container,
A plurality of heat pipes that transport heat as latent heat of the working fluid are arranged in an upright state in the closed container, and a plurality of plate-like fins are arranged in parallel to each other at a closed end of the heat pipe at a predetermined interval. A support column that supports the wick provided between at least one of the upper surface portion and the lower surface portion facing each other in the sealed container is disposed between the upper surface portion and the lower surface portion, and the heat is disposed on the upper surface portion. A hole that penetrates the opening end of the pipe is formed, the hole is held by the opening end of the heat pipe, and the opening end of the heat pipe is formed on the wick on the upper surface side or the lower surface side. The cooling device characterized by being joined.   The cooling device according to claim 1, wherein an opening end portion of the heat pipe is joined to the hole portion so as to be able to transfer heat.

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