JP2012229879A - Flat heat pipe and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flat heat pipe and a method for manufacturing the same including a wick improved in recirculation characteristic without reducing an area in which a working fluid in the wick is vaporized.SOLUTION: The flat heat pipe 5 transporting heat by the working fluid heated to vaporize and radiating heat to condense includes: a flat container 3 with the working fluid filled; and the wick 4 formed by bundling a large number of thin wires. The wick 4 is fixed by being sintered to one flat surface in the container 3 over the whole length of the container 3 in a longitudinal direction so as to be piled up and raised. The vaporized working fluid flows between the wick 4 fixed to one flat surface and the other flat surface in the container 3.

Description

  The present invention relates to a heat pipe configured to transport heat by a working fluid enclosed in a container, and in particular, a wick for generating a capillary force for returning the working fluid to an evaporation unit is configured by a thin wire bundle, Moreover, the present invention relates to a heat pipe configured in a flat shape as a whole and a manufacturing method thereof.

  A heat pipe basically encloses a fluid that evaporates and condenses in a target temperature range, such as water or alcohol, as a working fluid inside a container (container) from which non-condensable gas such as air has been deaerated. Further, a wick for generating a capillary force for refluxing the liquid phase working fluid is provided inside the container. Therefore, in the heat pipe, the working fluid receives heat from the outside and evaporates, and the vapor flows toward a low pressure portion and then dissipates heat and condenses. As a result, the working fluid transports heat by its latent heat. The condensed working fluid penetrates into the wick. On the other hand, since the capillary force due to the wick is generated at the location where evaporation occurs, the working fluid that has permeated the wick is returned to the location where evaporation occurs due to the capillary force.

  As described above, in the heat pipe, a vapor flow is generated between the evaporation portion where heat is transferred from the outside and the heat dissipation portion where the working fluid radiates heat to the outside, and a liquid flow is generated in the opposite direction. As a result, heat is transported. Therefore, in order to improve the heat transport capability or reduce the thermal resistance, it is preferable to generate the vapor flow and the liquid flow smoothly and sufficiently. In addition, heat pipes are used for various purposes, and may be used, for example, for cooling in electronic equipment. In such cases, heat pipes are reduced in size and weight in accordance with downsizing of electronic elements and circuits. It is desirable.

  Thus, various techniques for securing a flow path for a vapor flow, improving the reflux characteristics of the working fluid, and further reducing the size have been developed. The heat pipe described in Patent Document 1 is a flat heat pipe flattened by crushing the pipe, and a core material having a cutout portion is inserted into the pipe to cut the pipe from the inner wall surface of the pipe. The space formed by the notch is filled with metal powder, heated to form a wick that is sintered metal powder and fixed to the inner wall of the pipe, and then only the core material is piped And then flattened by crushing the pipe so that the wick fixed to the inner wall surface contacts the other inner wall surface facing the inner wall surface fixing the wick. Therefore, according to the heat pipe described in Patent Document 1, capillary force is generated between the wick and the other inner wall surface, and the working fluid can be recirculated by the capillary force and the capillary force of the wick. It is said that transportation can be strengthened.

JP 2011-43320 A

  As described in Patent Document 1, the vapor space is bisected in the inner wall surface of the flattened container, that is, in a state where the other inner wall surface and the wick obtained by sintering the metal powder are in contact with each other, Two narrow vapor spaces will result. Therefore, the steam space cannot be effectively used, for example, the flow velocity of the working fluid vapor is increased in the narrow steam space, and the heat transport capability may be reduced. In addition, the wick made of sintered metal powder has a larger flow resistance of the working fluid because the continuous working fluid recirculation path is not formed compared to the case where the thin wire bundle is used as the wick. In a heat pipe, there is a possibility that it is disadvantageous for improving the reflux characteristics of the working fluid.

  The present invention has been made paying attention to the above technical problem, and a flat heat pipe having a wick with improved reflux characteristics without reducing the area where the working fluid in the wick is vaporized, and its manufacture It is intended to provide a method.

  In order to achieve the above object, the invention of claim 1 is a flat heat pipe that transports heat by a working fluid that is heated to evaporate and dissipates heat to condense. The container includes an enclosed container and a wick in which a number of thin wires are bundled, and the wick is baked in a state of rising in a mountain-like manner on one flat surface inside the container over the entire length in the longitudinal direction of the container. The evaporated working fluid is configured to flow between the wick fixed to one flat surface of the wick and the other flat surface inside the container. It is.

  A second aspect of the present invention is the flat heat pipe according to the first aspect of the present invention, wherein at least one thin wire in the wick intersects with a plurality of other thin wires.

  According to a third aspect of the present invention, in the first or second aspect of the invention, the shortest distance between the wick fixed to the one flat surface and the other flat surface is a distance that allows the evaporated working fluid to flow. It is a flat heat pipe characterized by being.

  The invention of claim 4 is the invention of any one of claims 1 to 3, wherein the shape of the cross section of the wick fixed to the flat surface perpendicular to the longitudinal direction of the container is a rectangular shape and a flat semicircular shape. It is a flat type heat pipe characterized by including any one of these.

  According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the container has the wick placed in contact with and biased to the inner wall surface of the pipe and sintered in that state. The flat heat pipe is formed by crushing so that the inner wall surface to which the wick is fixed becomes a flat surface.

  A sixth aspect of the present invention is the flat heat pipe according to any one of the first to fifth aspects, wherein the thin wire includes one of a copper wire and a carbon fiber.

  The invention of claim 7 is a method of manufacturing a flat heat pipe that transports heat by a working fluid that is heated to evaporate and dissipates heat to condense, and a wick forming step of bundling a plurality of thin wires to form a wick; Thereafter, the wick is placed in contact with and biased to the inner wall surface over the entire length of the pipe, and the wick is fixed to the inner wall surface over the entire length of the pipe by sintering in that state. And a flattening step of flattening the pipe by crushing the pipe so that the inner wall surface to which the wick is fixed becomes a flat surface. .

  The invention of claim 8 is the method of manufacturing a flat heat pipe according to the invention of claim 7, wherein at least one fine wire in the wick intersects with other multiple fine wires. .

  The invention of claim 9 is the invention of claim 7, wherein in the sintering step, the wick and a cylindrical spacer formed with a holding portion for holding the wick are both inserted into the pipe. By placing the wick in contact with and biasing the inner wall surface of the pipe over the entire length of the pipe, and firing the pipe with the wick and the spacer inserted into the pipe. And a step of pulling out only the spacer from the pipe after the wick is fixed to the wall surface.

  The invention of claim 10 is the invention according to any one of claims 7 to 9, wherein the shortest distance between the wick fixed to the flat surface and the other flat surface facing the flat surface is the evaporated A flat heat pipe manufacturing method characterized in that a working fluid can flow.

  The invention of claim 11 is the invention according to any one of claims 7 to 10, wherein the cross section of the wick fixed to the flat surface perpendicular to the longitudinal direction of the flattened pipe has a rectangular shape and a flat shape. It is a manufacturing method of the flat type heat pipe characterized by including any one of semicircle shape.

  A twelfth aspect of the present invention is the method for producing a flat heat pipe according to any one of the seventh to eleventh aspects, wherein the thin wire includes one of a copper wire and a carbon fiber.

  According to the first aspect of the present invention, since the wick is constituted by a thin wire bundle in which thin wires are bundled, the effective capillary radius at the meniscus generated when the working fluid permeates is reduced, and as a result, the liquid-phase working fluid is reduced. A large capillary force for refluxing can be obtained. In addition to this, since the density difference of the fine wires in the longitudinal direction of the wick and the change in the void ratio between the fine wires are suppressed, a smoothly continuous working fluid reflux path is formed between the fine wires. As a result, the working fluid The flow resistance can be reduced. In addition, since the wick is fixed to one flat surface of the flat container in a raised state, the contact area between the wick and the one flat surface can be increased. In other words, since the liquid-phase working fluid can be spread over the width direction of the one flat surface, there is no limitation on the place where heat is input in the width direction of the container. In addition, since the working fluid evaporated between the wick and the other flat surface can flow, a capillary force is generated between the wick and the other flat surface, so that the wick surface becomes liquid. It is possible to avoid or suppress the covering with the phase working fluid. That is, it is possible to avoid or suppress the reduction of the area for evaporating the working fluid in the wick by covering the surface of the wick with the liquid-phase working fluid. In addition to this, the space for the evaporated working fluid to flow is reduced by the capillary force being generated at a place other than the wick and the working fluid in the liquid phase is refluxed. As a result, the flow of the evaporated working fluid is reduced. Can be avoided or suppressed in advance. As a result, the evaporation area of the liquid-phase working fluid is increased, the reflux characteristic of the liquid-phase working fluid is improved, and the flow of the evaporated working fluid is smoothed. As a result, the heat transport characteristics can be improved. Furthermore, since the wick is configured by bundling a large number of thin wires and does not require a member for binding, the outer diameter of the wick as a whole can be reduced, so that when the container is flattened, its thickness Can be made thinner than before. In other words, excellent heat transport characteristics can be ensured even when configured flat. Moreover, the wick is fixed to the inner wall surface of the container over its entire length. In order to fix it, it is sufficient to sinter and fix the wick inserted in the container, and the manufacturability is good. In addition to this, even if the container is deformed such as bending, the wick fixed inside it deforms following the container, so the position of the wick shifts and contacts the inner wall surface of the container. Accordingly, a situation in which a closed space is generated inside the container and the flow of the evaporated working fluid is obstructed can be avoided or suppressed in advance, and a steam flow path along the wick can be reliably ensured.

  According to the invention of claim 2, in addition to the same effect as that of the invention of claim 1, since at least one thin line in the wick intersects with another thin line, in other words, at least one Since the thin wires and other thin wires are twisted relatively gently, members for bundling the thin wires are unnecessary, so the number of necessary parts as a heat pipe can be reduced, and in the container The flow of the liquid-phase working fluid and the evaporated working fluid is hardly inhibited. In addition to this, by making at least one fine line intersect with many other fine lines, the density difference of fine lines in the longitudinal direction of the wick and the void ratio between the fine lines can be adjusted. As a result, a smoothly continuous working fluid reflux path is formed between the thin wires, and the flow resistance of the working fluid can be reduced.

  According to the invention of claim 3, in addition to the same effect as that of the invention of claim 1 or 2, the evaporated working fluid is caused to flow even at the shortest distance between the wick and the other flat surface. It is configured to be able to. Therefore, there is no capillary force between them. As a result, the steam flow path along the wick can be reliably ensured.

  According to the invention of claim 4, in addition to the effect similar to the effect of any one of the inventions of claims 1 to 3, the shape of the cross section of the wick is rectangular in the longitudinal direction of the container, that is, perpendicular to the longitudinal direction of the wick. Alternatively, it is formed in a flat semicircular shape. Therefore, a wick can be arranged along a flat container.

  According to the invention of claim 5, in addition to the effect similar to the effect of any one of claims 1 to 4, the pipe is crushed in a state where the wick is fixed by sintering inside the pipe having a circular cross section. Therefore, manufacturability is good.

  According to invention of Claim 6, in addition to the effect similar to the effect by the invention of any one of Claims 1 thru | or 5, both a copper wire and carbon fiber can be used for a wick.

  According to the invention of claim 7, after forming a wick by bundling a large number of thin wires, the wick is brought into contact with the inside of the pipe and arranged in a biased manner and fixed inside the pipe by firing, and thereafter The wick is fixed to a flat surface by crushing the pipe. For this reason, the wick configured as described above and fixed inside the container suppresses the difference in fine wire density in the longitudinal direction and the change in the void ratio between the fine wires, that is, smoothly between the fine wires. Therefore, the flow resistance of the working fluid can be reduced. In addition, when the pipe is crushed so that the inner wall surface of the pipe to which the wick is fixed becomes a flat surface, both ends of the exposed surface of the wick exposed to the inner space side of the pipe are pulled along with the deformation of the pipe. While deforming so as to be extended, the central portion rises like a mountain on the inner space side. In other words, for example, along with the deformation of the pipe, the portion that has been arc-shaped along the inner wall surface of the pipe until then becomes a flat surface, and is exposed to the inner space side of the pipe until then, and is flat or almost flat. The part that has become an arc shape. As a result, since the wick is fixed to one flat surface of the flat container in a state of rising in a mountain shape, the contact area between the wick and the one flat surface can be increased. In other words, since the liquid-phase working fluid can be spread over the width direction of the one flat surface, there is no limitation on the place where heat is input in the width direction of the container. In addition, since the working fluid evaporated between the wick and the other flat surface can flow, no capillary force is generated between them. As a result, the steam flow path can be reliably ensured. In other words, it is possible to avoid or suppress the reduction of the area for evaporating the working fluid in the wick by covering the surface of the wick with the liquid-phase working fluid. As a result, the evaporation area of the liquid-phase working fluid and the reflux characteristics of the liquid-phase working fluid are improved, and the flow of the evaporated working fluid is smoothed to improve the heat transport characteristics of the entire heat pipe. Can be made. Furthermore, since the wick is configured by bundling a large number of thin wires and does not require a member for binding, the outer diameter of the wick as a whole can be reduced, so that when the container is flattened, its thickness Can be made thinner than before. In other words, excellent heat transport characteristics can be ensured even when configured flat. Moreover, the wick is fixed to the inner wall surface of the container over its entire length. In order to fix it, it is sufficient to sinter and fix the wick inserted in the container, and the manufacturability is good. In addition to this, even if the container is deformed such as bending, the wick fixed inside it deforms following the container, so the position of the wick shifts and contacts the inner wall surface of the container. Accordingly, a situation in which a closed space is generated inside the container and the flow of the evaporated working fluid is obstructed can be avoided or suppressed in advance, and a steam flow path along the wick can be reliably ensured.

  According to the invention of claim 8, in addition to the same effect as that of the invention of claim 7, at least one fine line in the wick intersects with another fine line, in other words, at least one Since the thin wires and other thin wires are twisted relatively gently, members for bundling the thin wires are unnecessary, so the number of necessary parts as a heat pipe can be reduced, and in the container The flow of the liquid-phase working fluid and the evaporated working fluid is hardly inhibited. In addition to this, by making at least one fine line intersect with many other fine lines, the density difference of fine lines in the longitudinal direction of the wick and the void ratio between the fine lines can be adjusted. As a result, a smoothly continuous working fluid reflux path is formed between the thin wires, and the flow resistance of the working fluid can be reduced.

  According to the invention of claim 9, in addition to the effect similar to the effect of the invention of claim 7, the thin wires bundled together with the spacer are inserted into the pipe and sintered in that state, and thereafter only the spacer is attached. It is configured to pull out from the pipe and then crush the pipe. Therefore, it is possible to easily insert the thin wires bundled with the pipe.

  According to the invention of claim 10, in addition to the effect similar to the effect of any of the inventions of claims 7 to 9, the working fluid evaporated even at the shortest distance between the wick and the other flat surface It is comprised so that can be made to flow. Therefore, there is no capillary force between them. As a result, the steam flow path along the wick can be reliably ensured.

  According to the invention of claim 11, in addition to the effect similar to the effect of any of the inventions of claims 7 to 10, the cross-sectional shape of the wick is rectangular in the longitudinal direction of the container, that is, perpendicular to the longitudinal direction of the wick. Alternatively, it is formed in a flat semicircular shape. Therefore, a wick can be arranged along a flat container.

  According to the invention of claim 12, in addition to the effect similar to the effect of any one of claims 7 to 11, any of copper wire and carbon fiber can be used for the wick.

It is a figure which shows the cross-sectional shape of an example of the process which manufactures the other flat heat pipe which concerns on this invention, and the flat heat pipe which concerns on this invention. It is a figure which shows the cross-sectional shape of the process of manufacturing the other flat type heat pipe which concerns on this invention, and the other example of the flat type heat pipe which concerns on this invention. It is a figure which shows typically the fine wire bundle made to function as a wick in the flat type heat pipe concerning this invention. It is a figure for demonstrating the method of the characteristic test about an Example and a comparative example. It is another figure for demonstrating the method of the characteristic test about an Example and a comparative example. It is another figure for demonstrating the method of the characteristic test about an Example and a comparative example.

  Next, the present invention will be specifically described. This invention is a heat pipe characterized by the structure of the wick. The wick of the heat pipe according to the present invention is constituted by a large number of thin wires that are bundled without using a binding tool. The fine wire may be any wire that has excellent wettability with a working fluid sealed inside the container, such as a metal wire such as copper or carbon fiber. More specifically, in the wick of the heat pipe according to the present invention, at least one thin line or many of the bundled thin lines intersect with other many thin lines. That is, it is twisted relatively gently. This is to adjust the density of the fine wires in the longitudinal direction of the wick or the gap between the fine wires for generating the capillary force, and to prevent the bundle of fine wires from being scattered. Therefore, a thin wire that maintains the shape after being crossed is preferable, and a thin metal wire such as a copper wire is preferable.

  In the present invention, for example, a wick configured by bundling a plurality of thin wires as described above is arranged on one inner wall surface of the container, and therefore, the wick and another inner wall facing the one inner wall surface are arranged. A gap is formed between the inner wall surface. The wick is fixed to the one inner wall surface by sintering. That is, in this invention, a space | gap is ensured between the wick fixed to the inner wall surface, and the other inner wall surface facing the inner wall surface to which the wick was fixed. Thereafter, the working fluid is sealed inside the container. The container is basically an airtight hollow container, and a hollow pipe is used for a heat pipe used for transporting heat between locations apart from each other. Since it is necessary to transfer heat between the inside and the outside of the container, the container is preferably made of a material having high thermal conductivity, and for example, a copper tube is preferably used. Further, a narrow groove that serves as a flow path for the working fluid and causes capillary action may be formed on the inner wall surface of the container.

  The wick configured as described above is fixed to the inner wall surface of the container. Specifically, the wick is heated to a predetermined temperature in a state where the wick is disposed inside the container, thereby causing sintering between the wick and the container and joining them together. A so-called surplus space excluding the wick inside the container serves as a steam flow path through which the working fluid steam flows. Here, the predetermined temperature is, for example, a temperature before and after the melting point of copper when a thin wire or a container is formed of copper, and more specifically, a temperature slightly lower than the melting point temperature. Yes, when these are heated to that temperature, adjacent fine wires or containers and fine wires in contact with them are combined.

  On the other hand, the working fluid is a fluid that heats and evaporates, dissipates heat and condenses, thereby transporting heat in the form of latent heat, and is appropriately selected according to the temperature at which the heat pipe is used. For example, water, alcohols such as methanol and ethanol, ammonia, and alternative chlorofluorocarbon are used as the working fluid. The working fluid is sealed inside the container in a state where non-condensable gas such as air is deaerated from the inside of the container.

  Therefore, in the heat pipe according to the present invention, when heat is applied to a part of the container and the other part is cooled, the working fluid is heated and evaporated, and the steam flows toward a place where the temperature and pressure are low. Then, it dissipates heat and condenses. The steam flow path is a flow path along the wick. In the present invention, the wick is disposed and fixed on the inner wall surface of a part of the container, and therefore a part of the container that fixes the wick. A steam flow path is also secured between the other inner wall surface facing the inner wall surface and the wick. In addition, since the wick is fixed by sintering, a steam flow path is secured even if deformation such as bending is applied to the heat pipe. As a result, the working fluid vapor flows sufficiently and sufficiently, and the heat transport characteristics as a heat pipe are improved. In addition, as described above, a steam flow path is ensured between the wick and the other inner wall surface, in other words, no capillary force is generated between the wick and the other inner wall surface. As a result of the flow of the working fluid condensed between the two, the surface of the wick disposed on the side where the working fluid is heated is prevented or suppressed from being covered with the condensed working fluid. An evaporation area is secured.

  On the other hand, the condensed working fluid permeates into the wick and flows toward a portion where evaporation occurs using a gap between the thin wires constituting the wick as a flow path. That is, when the working fluid evaporates, the meniscus formed between the thin wick lines decreases, and accordingly, a capillary force is generated. The capillary force is used as a pumping force to bring the liquid-phase working fluid to the evaporation unit side. Reflux. And since a larger capillary force is generated when the gap between the thin wires is small, so-called reflux characteristics are improved. In addition, the thin wire constituting the wick is continuous over its entire length, and there are not only places where the thin wire bundle is fastened for bundling, but at least one thin wire is composed of many other wires. By crossing the fine wires, the gaps and density between the fine wires are adjusted to be constant or substantially constant in the longitudinal direction of the wick. Therefore, the so-called reflux path formed between the thin wires is also smoothly continuous, and therefore there is little resistance to the flow of the liquid phase working fluid, and the reflux characteristics are also good in this respect. In addition, since the wick is fixed by sintering, if the wick is inserted into the pipe and heated from the outside, the wick can be fixed to the pipe over its entire length, and the work is easy and the productivity is improved. Become good.

  Next, an example of a heat pipe according to the present invention will be described together with a manufacturing method. FIG. 3 schematically shows a bundle of thin wires formed from a large number of thin wires that function as a wick according to the present invention. First, at least one thin wire 1 intersects with another many thin wires 1. The thin wire bundle 2 is formed by bundling. This binds the thin wires 1 relatively gently, secures a space between the thin wires 1, and makes the porosity and density between the thin wires 1 constant or almost constant in the longitudinal direction of the bundled thin wires 1. This is because of the adjustment. The thin wire 1 is specifically a copper wire having a direct connection of about 0.05 mm, and bundles 600 to 700 wires. In addition, by twisting the thin wire bundle 2 around its central axis, the thin wires 1 can be bound to each other more strongly than the above configuration, and the state can be maintained.

  On the other hand, as shown in FIG. 1A, a pipe having a wall thickness of 0.3 mm and an outer diameter of 3.0 to 6.0 mm that has been cleaned such as degreasing is prepared and cut into a predetermined length. This is container 3. When a copper wire is used as the wick 4, a copper pipe is used as the container 3. Then, the thin wire bundle 2 is inserted into the container 3 as a wick 4.

  Although not shown in detail, as an example, the thin wire bundle 2 is inserted into the container 3 using a spacer. This spacer is for facilitating insertion of the thin wire bundle 2 into the inside of the container 3. Therefore, for example, when a round pipe is used as the container 3, the spacer is formed in a cylindrical shape, The outer diameter is formed to be the same as or substantially the same as the inner diameter of the container 3. A cutout portion formed by cutting out a part of the arc is formed on the outer peripheral surface of the spacer and in the axial length direction of the spacer over the entire length thereof. Then, the thin wire bundle 2 is inserted into the container 3 together with the spacer by holding the thin wire bundle 2 integrally with the spacer along the notch. In addition, the notch portion is formed into a shape along the shape of the thin wire bundle 2 packed in the space formed between this and the inner wall surface of the container 3, or the thin wire bundle is formed at a predetermined position in the container 3. In this invention, for example, the cross-sectional shape of the notch perpendicular to the axial direction of the spacer is formed in a semicircular shape or a curved rectangular shape. Yes. Therefore, the thin wire bundle 2 inserted together with the spacer is disposed along the inner wall surface of the container 3, that is, in a state biased to a part of the inner wall surface and over the entire length of the container 3. The shape of the cross section orthogonal to each other is a semicircular shape. And the wick 4 is formed by cut | disconnecting this thin wire bundle 2 to predetermined length. FIG. 2A shows an example in which the cross-sectional shape of the thin wire bundle 2 is a curved rectangular shape and is arranged so as to be biased to a part of the inner wall surface of the container 3. When the cross-sectional shape of the thin wire bundle 2 is formed as shown in FIG. 2A, a notch portion that is notched into a corresponding shape is formed in the spacer, and the spacer is used to make the above-described description. The thin wire bundle 2 may be inserted into the container 3 as described above.

  Next, the container 3 into which the thin wire bundle 2 is inserted together with the spacers as described above is sent to a heating furnace (not shown) while being kept substantially horizontal and heated. When the container 3 and the wick 4 are made of copper, the heating temperature is about 800 ° C. to 1000 ° C. Thus, the wick 4 is baked in a state where the wick 4 is biased to a part of the inner wall surface of the container 3 over its entire length. Tied and fixed. At the same time, adjacent copper wires are sintered and joined together.

  After the container 3 to which the wick 4 is fixed is taken out of the heating furnace and cooled, and the spacer is pulled out from the inside of the container 3, as shown in FIG. 1 (a) and FIG. The wick 4 formed along the shape is left in contact with the inner wall surface of the container 3.

  Next, swaging is performed on one end of the container 3, and the end is welded and sealed. That is, so-called bottom swaging and bottom welding are performed. In addition to these processes, swaging processing of the other end, that is, top swaging processing is performed. In this way, a substantial container 3 is produced.

  By performing the top swaging process, a nozzle-like portion is formed at one end of the container 3, and liquid injection is performed using this. That is, the working fluid is injected into the container 3. In that case, it is necessary to deaerate non-condensable gas such as air from the container 3. Therefore, the injection is performed by injecting the working fluid after vacuum degassing, after injecting an excessive amount of working fluid, May be carried out by a conventionally known method such as a method of boiling non-condensable gas by boiling. And after crushing the part opened for liquid injection, it welds and seals. So-called top welding is performed.

  When a pipe having a circular cross section is used as the material of the container 3, the round pipe type heat pipe manufactured as described above is crushed in the radial direction to obtain a flat type heat pipe 5 having a thickness of 2.0 mm. Specifically, FIG. 1 (b) schematically shows a cross-sectional view of the heat pipe shown in FIG. 1 (a) and after flattening of the round pipe type heat pipe. FIG. 2B schematically shows a cross-sectional view of the heat pipe after flattening of the round pipe type heat pipe shown in FIG. When the pipe is crushed so that the inner wall surface to which the wick 4 is fixed becomes a flat surface, the arc-shaped portion of the wick 4 is extended in the example shown in FIG. And become flat. Contrary to this, in the wick 4, the portion that has been exposed to the inner space side of the pipe until then and has become flat or substantially flat becomes an arc shape. As a result, as shown in FIG. 1 (b), the wick 4 is in a state of rising in a mountain shape on the flat surface inside the container 3, and the wick 4 is fixed over the width direction of the flat surface. It becomes. Moreover, when making a pipe flat, it is made for the top part of the formed convex-shaped wick 4 not to contact the inner wall face of the container 3 which opposes this. This is to secure a surface area for vaporizing the working fluid in the wick 4 and to secure a vapor flow path inside the container 3. Therefore, the distance between them is, for example, that the evaporated working fluid is evaporated. It is a distance that can flow, or a distance that does not generate capillary force between them. As a result, the space formed by the inner wall surface of the container 3 and the wick 4 serves as the working fluid vapor channel 6.

  Further, as shown in FIG. 2A, when the curved rectangular wick 4 is disposed inside the container 3, when flattening is performed as described above, FIG. As in the example shown in FIG. 2, the shape of the wick 4 changes with the deformation of the container 3, and as a result, the shape of the wick 4 becomes rectangular as shown in FIG.

  On the other hand, when the flat heat pipe 5 that is bent or bent is formed, the wick 4 is fixed after the round pipe heat pipe is bent or bent into a predetermined shape, that is, after bending. The container 3 is crushed and flattened in the radial direction so that the inner wall surface is flat. Even when the flat heat pipe 5 curved or bent is formed as described above, the top of the convex wick 4 is prevented from coming into contact with the inner wall surface of the container 3 facing the flat wick 4 after flattening. . Therefore, a space formed by the inner wall surface of the container 3 and the wick 4 serves as a working fluid vapor flow path 6. In addition, since said wick 4 is being fixed to the inner wall surface of the container 3 by sintering, it deform | transforms according to the curve or bending of the container 3, and, as a result, the steam flow path 6 along the wick 4 is ensured. .

  As described above, in the flat heat pipe 5 according to the present invention shown in FIG. 1B and FIG. 2B, the wick 4 is configured by bundling a plurality of thin wires 1, so that the wick 4 As a result, the working fluid reflux path can be secured between the thin wires 1. Further, the wick 4 is fixed in a flat shape over the width direction of one flat surface of the hollow flat container 3, that is, the contact area between the wick 4 and the inner wall surface of the container 3 is expanded. Thus, the liquid-phase working fluid can be spread in the width direction of the container 3, and the place where heat is input in the width direction of the container is not limited. That is, in the width direction of the container 3, the area that can be thermally connected to the heat source with respect to the flat heat pipe according to the present invention can be expanded. In addition to this, even when deformation such as bending is applied to the container 3, the wick 4 is deformed in accordance with the deformation of the container 3, so that the flow path 6 for the working fluid vapor can be reliably ensured. In addition to these, since the working fluid vapor can flow between the wick 4 and the other flat surface opposite to the flat surface to which the wick 4 is fixed, there is a capillary force between them. By being generated and becoming a reflux path, it is possible to prevent the surface of the wick 4 from being covered with the liquid-phase working fluid. That is, in the wick 4, it is possible to secure an evaporation area for the working fluid to vaporize. As a result, the heat transport capability can be increased compared to the prior art.

  In addition, in the example mentioned above, you may use what is called a groove pipe by which many fine grooves along the axial direction were formed in the internal peripheral surface of the pipe used as the container 3. FIG. These narrow grooves function as the wick 4, and the contact area between the working fluid and the container 3 can be increased by using the groove tube as the container 3.

  Next, examples of the present invention will be described together with comparative examples.

Example 1
A wick 4 is formed by crossing and bundling at least one or many of the thin copper wires 1 having a diameter of 0.05 mm that are fed out from the material coil with the other many, and the wick 4 is axially arranged on the inner peripheral surface. As a container 3 in which a plurality of fine grooves along the direction are formed, it is inserted into a copper pipe having a wall thickness of 0.3 mm and an outer diameter of 4.0 mm by the above-described method, and fixed by sintering to be a round pipe type A heat pipe was prepared. As shown in FIG. 4, the heat pipe was bent at 90 ° in the central portion in the axial direction, and then crushed as described above to obtain a flat heat pipe 5. The size of each part after the processing is such that the total length of the flat heat pipe 5 is 160 mm, the thickness is 2.0 mm, the width of the container 3 is 8.7 mm, and the bent part is sandwiched between them. Was 57.0 mm, and the other length was 62.0 mm. Further, the bending radius (R) of the curved pipe was 18 mm, and water was used as the working fluid. In addition, the wick 4 was arrange | positioned in the center part in the width direction of the flattened container 3. FIG.

(Comparative Example 1)
A flat heat pipe 5 was produced in the same manner as in Example 1 except that the wick 4 used was a sintered wick 4 in which a copper powder having a particle size in the range of 80 μm to 200 μm was sintered.

(Comparative Example 2)
A wick in which a large number of thin copper wires are bundled as shown in the first embodiment, and then the thin wire bundle is twisted around the central axis, thereby binding the thin wire bundle more strongly than in the first embodiment. Configured. The wick was inserted into the container, and a round pipe type heat pipe was formed in the same manner as in Example 1 above. Then, it was crushed as it was in the radial direction of the container in the same manner as in Example 1 to obtain a flat heat pipe. Although not shown in detail, the flat heat pipe of Comparative Example 2 has a wick disposed at the center in the width direction of the flat container. It is sandwiched between the surfaces, and is fixed to these surfaces over the entire length by sintering. Other configurations were the same as those in the first embodiment.

(Test method 1)
As shown in FIG. 5A, one end of the flat heat pipe 5 to be tested is brought into contact with the surface (15 mm × 15 mm) of the electric heater 7 to form an evaporation section, and the other end of the heat pipe 5 Was brought into contact with the upper surface of an aluminum radiator plate 8 (50 mm × 50 mm × 1.5 mm) to form a condensing part. A heat insulating plate (not shown) was placed in contact with the lower surface of the heat radiating plate 8. FIG. 5B shows a top view of the configuration shown in FIG. 5A, and FIG. 5C shows a side view of the configuration shown in FIG. 5A. The electric heater 7 is energized at room temperature to heat the evaporation part of the heat pipe 5, the amount of electric power, that is, the heat input Q (W), the temperature Th at the contact point between the electric heater 7 and the heat pipe 5, The surface temperature Te of the evaporating part of the pipe 5, the surface temperature Tc of the condensing part of the heat pipe 5, and the surface temperature Ta of the central part of the heat pipe 5 were measured. This measurement was started after the temperature at each measurement point became constant with respect to the heat input, and the heat input was gradually increased. A K-type thermoelectric thermometer was used for temperature measurement. And from these measurement data, the heat resistance (° C./W) for each heat pipe and the maximum heat input (maximum heat transport amount) Q _MAX (W) at which so-called dry out occurs were determined. The results are shown in Table 1. The thermal resistance R was determined as (R = (Th−Tc) / Q). The amount of heat input that causes dryout is the amount of heat input at which the thermal resistance R increases rapidly when the amount of heat input Q is increased.

The results shown in Table 1 can be evaluated as follows. The maximum heat input Q _MAX (W) of the flat heat pipe 5 (Example 1) according to the present invention is 42 W, the maximum heat transport amount Q _MAX (W) of Comparative Example 1 is 37 W, and the maximum heat of Comparative Example 2 is The transport amount Q _MAX (W) was 34 W. From these results, the maximum heat transport amount of Example 1 using the wick 4 according to the present invention is about 5 W higher than that of Comparative Example 1 using the sintered wick, and Comparative Example 2 formed by strongly twisting the thin wire bundle. It was recognized that it was about 8 W higher. Further, the thermal resistance of Example 1 was 0.55 ° C./W, the thermal resistance of Comparative Example 1 was 0.57 ° C./W, and the thermal resistance of Comparative Example 2 was 0.84 ° C./W. From these results, it was confirmed that the thermal resistance of Example 1 was about 0.02 ° C./W lower than Comparative Example 1 and about 0.29 ° C./W lower than Comparative Example 2. Therefore, it was recognized that the flat heat pipe 5 (Example 1) according to the present invention exhibits excellent heat transport characteristics.

(Test method 2)
As shown in FIG. 6 (a), one end of the flat heat pipe 5 to be tested is brought into contact with the surface (20 mm × 10 mm) of the first electric heater 9 to form a first evaporator, and the heat The other end of the pipe 5 was brought into contact with the upper surface of the aluminum radiator plate 10 (50 mm × 50 mm × 1.5 mm) to form a condensing part. Further, the surface (10 mm × 10 mm) of the second electric heater 11 was brought into contact between the evaporation portion and the condensation portion of the heat pipe 5 to form a second evaporation portion. The distance between the first electric heater 9 and the second electric heater 11 was 50 mm. A direct current type blower fan (50 × 50 mm) 12 was attached to the heat radiating plate 10 to blow air. FIG. 6B shows a side view of the configuration shown in FIG. Specifically, by energizing the first electric heater 9 at room temperature, the first evaporation part is heated by a heat amount of 25 W, and by energizing the second electric heater 11, the second evaporation part is heated by a heat amount of 12 W. did. The blower fan 12 was blown toward the heat sink 10 by applying a DC voltage of 4V. And the amount of electric power, that is, the amount of heat input Q (W), the temperature Th1 at the contact point between the first electric heater 9 and the heat pipe 5, the temperature Th2 at the contact point between the second electric heater 11 and the heat pipe 5, The surface temperature Tc of the condensing part of the heat pipe 5 was measured. The results are shown in Table 2. This measurement was started after the temperature at each measurement point became constant with respect to the amount of heat input, as in Test Method 1 described above, and a K-type thermoelectric thermometer was used for temperature measurement at each measurement point. .

  The results shown in Table 2 can be evaluated as follows. In the flat heat pipe 5 (Example 1) according to the present invention, the temperature of Th1 was 61.4 ° C., and the temperature of Th2 was 60.4 ° C. On the other hand, the temperature of Th1 in the flat heat pipe using the sintered wick (Comparative Example 1) was 64.9 ° C, and the temperature of Th2 was 61.4 ° C. The temperature of Th1 in the flat heat pipe (Comparative Example 2) using the wick in which the thin wire bundle is twisted was 69.6 ° C., and the temperature of Th2 was 61.4 ° C. From these results, it was recognized that the flat heat pipe 5 (Example 1) according to the present invention exhibits excellent heat transport characteristics.

  Therefore, the flat heat pipe 5 using the wick 4 according to the present invention shows a maximum heat transport amount higher than those of the comparative example 1 and the comparative example 2, and the heat resistance exhibits a low value, and has an excellent heat transport capability. It was confirmed that it has. Further, the flat heat pipe 5 using the wick 4 according to the present invention has a thickness as thin as about 2.0 mm, and therefore has excellent mountability to a small electronic device.

  DESCRIPTION OF SYMBOLS 1 ... Fine wire, 2 ... Fine wire bundle, 3 ... Container, 4 ... Wick, 5 ... Flat type heat pipe, 6 ... Steam flow path.

Claims (12)

In a flat heat pipe that transports heat by a working fluid that is heated to evaporate and radiates and condenses,
A container formed in a flat shape and filled with the working fluid;
With a wick that bundles many thin wires,
The wick is fixed to the one flat surface inside the container over the entire length in the longitudinal direction of the container by sintering in a state of rising in a mountain,
A flat type heat pipe, wherein the evaporated working fluid flows between the wick fixed to one flat surface and the other flat surface inside the container.   The flat heat pipe according to claim 1, wherein at least one thin wire in the wick intersects with many other thin wires.   3. The flat type according to claim 1, wherein the shortest distance between the wick fixed to the one flat surface and the other flat surface is a distance through which the evaporated working fluid can flow. heat pipe.   The shape of the cross section of the wick fixed to the flat surface orthogonal to the longitudinal direction of the container includes one of a rectangular shape and a flat semicircular shape. Flat heat pipe.   The container is arranged such that the wick is brought into contact with and biased to the inner wall surface of the pipe and the wick is fixed by sintering in that state so that the inner wall surface to which the wick is fixed becomes a flat surface. The flat heat pipe according to any one of claims 1 to 4, wherein the heat pipe is crushed and formed.   The flat heat pipe according to any one of claims 1 to 5, wherein the thin wire includes one of a copper wire and a carbon fiber. In a manufacturing method of a flat heat pipe that transports heat by a working fluid that is heated and evaporated and radiates and condenses,
A wick forming step of bundling a large number of thin wires to form a wick;
Thereafter, the wick is placed in contact with and biased to the inner wall surface over the entire length of the pipe, and the wick is fixed to the inner wall surface over the entire length of the pipe by sintering in that state. The ligation process;
And a flattening step for flattening the pipe by crushing the pipe so that the inner wall surface to which the wick is fixed becomes a flat surface.   8. The method of manufacturing a flat heat pipe according to claim 7, wherein at least one thin wire in the wick intersects with many other thin wires. In the sintering step, the wick and the inner wall surface of the pipe are extended over the entire length of the pipe by inserting both the wick and a cylindrical spacer having a holding portion for holding the wick into the pipe. An arrangement step of placing and contacting with a bias,
And a step of pulling out only the spacer from the pipe after fixing the wick to the inner wall surface by firing in a state where the spacer is inserted together with the wick inside the pipe. Item 8. A method for producing a flat heat pipe according to Item 7.   11. The shortest distance between the wick fixed to the flat surface and another flat surface opposite to the flat surface is a distance through which the evaporated working fluid can flow. The manufacturing method of the flat type heat pipe in any one.   The cross-sectional shape of the wick fixed to the flat surface perpendicular to the longitudinal direction of the flattened pipe includes one of a rectangular shape and a flat semicircular shape. A method for producing a flat heat pipe according to any one of 10.
The method for manufacturing a flat heat pipe according to any one of claims 7 to 11, wherein the thin wire includes one of a copper wire and a carbon fiber.

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