JP2011226743A - Flat heat pipe - Google Patents

Abstract

A flat type heat pipe having excellent heat transport characteristics is provided.
A working fluid that heats, evaporates, dissipates heat, and condenses is enclosed in a container 4 and generates a capillary force that recirculates the liquid working fluid at a location where the working fluid evaporates. In the flat heat pipe 10 in which 5 is provided in the container 4 and the container 4 is formed in a thin hollow structure, the wick 5 is connected to the container 5 with a large number of fine wires 1 bound at both ends. Is inserted into the inside of the container 5 and has a configuration in which an intermediate portion in the longitudinal direction of the ultrafine wire bundle 2 is expanded along the inner surface of the container 5, and the ultrafine wire bundle 2 expanded along the inner surface of the container 5 is A vapor channel 6 is formed around the extra-fine wire bundle 2 fixed to the inner surface of the container 4 by sintering, and the working fluid vapor flows around the extra-fine wire bundle 2 fixed to the inner surface of the container 4.
[Selection] Figure 1

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, And it is related with the heat pipe comprised by the flat shape as a whole.

  The basic structure of a heat pipe is a working fluid filled with a fluid that evaporates and condenses in a target temperature range, such as water or alcohol, in a container (container) from which non-condensable gas such as air is degassed In addition, 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 have been developed for securing a flow path for the vapor flow, improving the reflux characteristics of the hydraulic fluid, and further reducing the size, for example, increasing the capillary force for refluxing the hydraulic fluid. Therefore, a wick is formed by bundling a large number of thin wires made of copper, carbon, etc., and examples thereof are described in Patent Document 1, Patent Document 2, or Patent Document 3. That is, the capillary force increases as the effective capillary radius at the meniscus formed at the liquid level of the working fluid decreases, so if the wicks are formed by bundling the thin wires, the distance between the thin wires is reduced and a large capillary force is obtained. Can do. In addition to this, since the flow path of the hydraulic fluid formed between the thin wires is smoothly continuous, the flow resistance against the hydraulic fluid is relatively small, and in this respect also, the hydraulic fluid reflux characteristics are improved. To do.

  In this way, in a wick composed of a bundle of fine wires, a flow path for the working fluid is formed between the fine wires, so that the fine wires are generally bound to the extent that they are bundled without bonding using an adhesive or the like. Is. For example, in the heat pipe described in Patent Document 1, a thin wire bundle is arranged inside a helical member such as a coil spring, and the thin wire bundle is bound by the helical member. Further, in the heat pipe described in Patent Document 2, a plate material in which a concave portion is formed in a groove shape is arranged inside the pipe, and a thin wire bundle is arranged inside the concave portion, so that the thin wires are not scattered. is doing. Furthermore, Patent Document 3 describes a configuration in which a stranded wire is made using a number of extra fine wires as strands and inserted into the inside of the groove tube. That is, in the configuration described in Patent Document 1 or Patent Document 2, a coil spring or a plate material is used to bind the thin wires, whereas in the configuration described in Patent Document 3, twisting is performed. Thus, the bundled state of the extra fine wires is maintained.

  On the other hand, Patent Document 4 describes a technique for securing a working fluid vapor channel. The heat pipe described in Patent Document 4 is a flat heat pipe that is thinned by crushing the pipe. The wire mesh wick is so-called vertically attached to the inside of the container, and the wire mesh wick is attached to the container by seam welding. Fixed and configured. Therefore, even when this heat pipe is bent, the wick bends along the container, the wick contacts the inner wall surface on the inner peripheral side in the direction of the bending radius, and thereby the steam flow path is closed. This has been prevented.

  Then, as described in Patent Document 1, Patent Document 2, or Patent Document 4 described above, flattening is conventionally performed by crushing the heat pipe in the radial direction. The described heat pipe has a thickness of 1.5 mm or less. Furthermore, Patent Document 5 describes a heat pipe whose thickness can be 1 mm or less.

JP 2004-53186 A JP 2000-74579 A JP 2003-247791 A JP 2001-204889 A JP-A-11-173777

  As described in Patent Document 1 and Patent Document 2, when a coil spring or the plate material is used as a binding tool, the thickness or outer diameter of the entire wick is increased accordingly, so that the flat heat pipe is made thinner. It will be disadvantageous. On the other hand, as described in Patent Document 3, in the configuration in which the bundling state is maintained by twisting, the outer diameter of the wick is reduced by the amount not using the bundling tool. Therefore, Patent Document 4 or Patent Document 5 is used. Is advantageous when the heat pipe is flattened.

  However, when a thin wire bundle is used as a wick, it will be placed along the entire length of the container, so that a sufficient steam flow path can be secured even when deformation such as bending is applied. It is preferable to fix the wick as described in Patent Document 2 and Patent Document 4. However, as described in Patent Document 2, if the thin wire bundle is accommodated in the recess formed in the plate material, the plate material not only increases the number of parts, but also causes the flat heat pipe to be thick. Become. Further, as described in Patent Document 4, if the wick is joined to the inner surface of the container by seam welding, there is a possibility that an extremely difficult operation is required or a special manufacturing method may be employed.

  The present invention has been made paying attention to the above technical problem, and an object of the present invention is to provide a flat heat pipe excellent in heat transport characteristics.

  In order to achieve the above object, according to the present invention, the working fluid that is heated, evaporates, dissipates heat and condenses is enclosed in the container, and the working fluid evaporates. In a flat heat pipe in which a wick for generating a capillary force for refluxing the working fluid in a liquid phase is provided inside the container, and the container is formed in a thin hollow structure, the wick is bound at both ends. A plurality of extra fine wires are inserted into the container, and the intermediate portion in the longitudinal direction of the extra fine wire bundle is extended along the inner surface of the container, and is extended along the inner surface of the container. A vapor flow path is formed in which the fine wire bundle is fixed to the inner surface of the container by sintering, and the working fluid vapor flows around the fine wire bundle fixed to the inner surface of the container. And it is characterized in that it is.

  The invention according to claim 2 is the flat heat pipe according to claim 1, wherein the container is flattened by crushing a pipe having a circular cross section in the radial direction.

  Further, the invention of claim 3 is the invention according to claim 2, wherein the pipe is crushed in a state in which the bundle of fine wires formed by arranging the fine wires in a straight line is inserted along the longitudinal direction thereof. It is a flat heat pipe characterized by being flattened.

  And, the invention of claim 4 is the invention of claim 2 or 3, wherein the extra fine wire bundle is inserted into the horizontally installed pipe, and the pipe is crushed and flattened. The flat heat pipe is heated from the outside of the pipe and sintered on the inner surface of the heat pipe.

  According to this invention, the ultrafine wire bundle formed by binding both ends of a large number of ultrafine wires is provided along the inner peripheral surface of the container with the intermediate portion expanded, and the ultrafine wires are sintered. Since it is fixed to the container, the effective capillary radius at the meniscus generated by the working fluid penetrating into the micro wire bundle is reduced, and as a result, a large capillary force for refluxing the liquid-phase working fluid can be obtained. it can. Furthermore, since a smoothly continuous working fluid reflux path is formed between the thin wires, the flow resistance of the working fluid is reduced. Further, since the fine wires are bundled and the both ends thereof are bundled to form a fine wire bundle, the fine wires can be made into one bundle, so that the flow of the liquid phase working fluid and working fluid vapor in the container is hindered. It becomes difficult. As a result, the reflux characteristic of the liquid phase working fluid is improved, and the flow of the working fluid is smoothed, whereby the heat transport characteristic of the entire heat pipe can be improved.

  In addition, after inserting the above-mentioned ultrafine wire bundle into the above-mentioned pipe, a flat heat pipe can be formed by crushing the pipe in the radial direction, and the ultrafine wire bundle is then heated by heating from the outside of the pipe. Can be sintered into pipes. As a result, the flow path of the liquid phase working fluid and the steam passage formed by ultrafine wire bundles can be formed in the flat heat pipe, so that the reflux characteristics of the working fluid can be improved and the operation can be performed. By smoothing the fluid flow, the heat transport characteristics of the entire heat pipe can be improved.

It is a figure which shows typically the process of manufacturing the wick in the heat pipe which concerns on this invention. It is sectional drawing of the round heat pipe which is an intermediate product in the manufacture process of the flat type heat pipe which concerns on this invention. It is a figure which shows the cross-sectional shape of an example of the flat type heat pipe which concerns on this invention. It is a figure which shows the cross-sectional shape of the other example of the flat type heat pipe which concerns on this invention. It is a top view which shows the shape of each heat pipe in the characteristic test about an Example and a comparative example. It is a figure for demonstrating the method of the characteristic test about an Example and a comparative example. It is a graph which shows the result of having measured the relationship between the heat gain and heat resistance about the 1st and 2nd heat pipe. It is a graph which shows the result of having measured the relationship between the amount of heat inputs and thermal resistance about the 3rd heat pipe. It is a graph which shows the result of having measured the relationship between each number of thin wires, and each thermal resistance. It is a top view which shows the shape of the heat pipe used for the test which determines the optimal number of thin wires.

  Next, the present invention will be described more specifically. The present invention is a heat pipe characterized by the structure of the wick. Specifically, the wick of the heat pipe according to the present invention is configured by a large number of thin wires that are bundled by binding both ends. 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.

  In this invention, the wick formed by binding both ends of the thin wire bundle is disposed inside the container and fixed by sintering, and then 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 surface of the container.

  The wick constructed by binding both ends of the thin wire bundle described above is fixed to the inner surface of this 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.

  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, alcohol, or alternative chlorofluorocarbon is 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, and since the wick is fixed to the inner surface of the container by sintering, the steam flow path is secured even if deformation such as bending is applied to the heat pipe. The working fluid vapor flows sufficiently and sufficiently, and the heat transport characteristics as a heat pipe are improved.

  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. In other words, when evaporating from the working fluid, the meniscus formed between the wick thin wires decreases, so that a capillary force is generated, and the liquid phase working fluid is returned to the evaporating part side using the capillary force as a pumping force. To do. And since a larger capillary force is generated when the gap between the thin wires is small, so-called reflux characteristics are improved. Further, the thin wire constituting the wick is continuous over its entire length, and there are no places where the fine wire bundle is tightened at the place where the condensed working fluid flows although the ends are bound. Therefore, the so-called reflux path formed between them also has a smoothly continuous linear shape, and therefore the resistance to the flow of the liquid-phase working fluid is small, and the reflux characteristics are also good in this respect. And, since the wick is fixed by sintering, if a bundle of thin wires is inserted into the pipe as a wick and heated from the outside, the wick can be fixed over its entire length, and the work is easy to make. Will be better.

  Next, an example of a heat pipe according to the present invention will be described together with a manufacturing method. First, a large number of thin wires 1 having a predetermined length as wicks are bundled as shown in FIG. Specifically, the thin wire 1 is a copper wire having a direct connection of about 0.05 mm, and a predetermined number of wires are bundled. The number of bundles of the thin wires 1 may be determined from the outer diameter of the heat pipe and the thickness when the flat shape is used. For example, when the outer diameter of the heat pipe is 5 mm and processed to a thickness of 1 mm, 250 is used. Bundle the thin wires 1 of the book. Further, when the thickness is 1 mm to 2 mm, the number of the thin wires 1 bundled is about 200 to 800. Next, as shown in FIG. 1B, the thin wire bundle 2 is bound or tied with other thin wires or a binding member 3 and then pulled in both end directions. Note that the means for binding or binding here is not limited to this, and it is only necessary that the bundled thin wires 1 can be bound, so both ends may be bonded and fixed. By doing so, the thin wires 1 are maintained in a straight line and in a state of being bound to each other. In addition, when the thin wire | line 1 is what was wound by the coil, since a bending wrinkle may remain | survive by a residual stress, it heat-processes and makes it linear.

  On the other hand, a pipe having a wall thickness of 0.3 mm and an outer diameter of 3.0 to 6.0 mm subjected to cleaning such as degreasing is prepared, and this is cut into a predetermined length. When a copper wire is used as the wick 5, a copper pipe is used as the container 4. Then, swaging is performed on one end of the container 4. Thereafter, the thin wire bundle 2 is inserted into the container 4 as a wick 5. At this time, the inserted thin wire bundle 2 is linearly installed on the lower surface of the container 4 due to gravity, and the thin wire bundle 2 spreads along the inner peripheral surface of the container 4. That is, as shown in FIG. 2, the cross-sectional shape of the thin wire bundle is substantially rectangular. And the edge part by the side of the swaging process of the container 4 is welded and sealed. That is, so-called bottom swaging and bottom welding are performed.

  Next, swaging processing (that is, top swaging processing) is performed on the other end of the container 4. By doing so, a substantial container 4 is produced. And this container 4 is sent and heated to a heating furnace (not shown), maintaining substantially horizontal. When the container 4 and the wick 5 are made of copper, the heating temperature is about 1000 ° C., whereby the wick 5 is sintered and fixed to the inner surface of the container 4 over its entire length. At the same time, the copper wires may be sintered and joined together.

  After the container 4 to which the wick 5 is fixed is taken out from the heating furnace and cooled, liquid injection is performed using the nozzle-like portion formed by performing the top swaging process. That is, the working fluid is injected into the container 4. In that case, it is necessary to deaerate non-condensable gas such as air from the container 4, and 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.

  The round pipe type heat pipe manufactured in this way is crushed in the radial direction to obtain a flat type heat pipe 10. In that case, in order to obtain the linear flat heat pipe 10, the round pipe heat pipe is crushed as it is to be flattened. On the other hand, in order to obtain the bent or bent flat heat pipe 10, the round pipe heat pipe is bent or bent into a predetermined shape and then flattened by being crushed in the radial direction. Even in the case of bending or bending in this way, the wick 5 made of a bundle of thin wires is sintered and fixed to the inner surface of the container 4, so that it deforms in accordance with the deformation of the container 4, and as a result, the wick 5 is secured.

  Since the flat heat pipe 10 according to the present invention binds and bonds both ends to bind the thin wire bundle 2 to form the wick 5, the outer diameter of the binding portion of the thin wire bundle 2 is not increased. Since the wick 5 is fixed to the inner surface of the container 4 by sintering, the steam channel 6 can be reliably secured. For example, as shown in a cross-sectional view in FIG. 3, the wick 5 in the heat pipe 10 is configured by binding both ends in a state where a large number of fine wires 1 are bundled as described above. The container 4 is formed in a hollow flat shape, and a working fluid such as water is sealed therein. The container 4 can be produced by, for example, crushing a copper pipe in the radial direction. In the example shown in FIG. 3, a large number of narrow grooves 11 along the axial direction are formed on the inner peripheral surface of the container 4. These narrow grooves 11 function as wicks, and the contact area between the working fluid and the container 4 is expanded by these narrow grooves 11.

  And the wick 5 is arrange | positioned in the center part of the width direction in the flat container 4 and the wick 5 is arrange | positioned on the so-called lower surface of the container 4, and is fixed to this surface over the whole length by sintering. Yes. Therefore, since there is no inclusion between the wick 5 and the inner surface of the container 4 and both are in direct contact with each other, the thickness of the heat pipe 10 as a whole is reduced accordingly. Further, in the inside of the container 4, a hollow portion formed on both the left and right sides around the wick 5 and the upper side of the wick 5 serves as a flow path 6 for the working fluid vapor. The so-called steam flow path 6 is naturally formed as expected by the fact that the container 4 and the wick 5 are linear in the manufacturing stage of the heat pipe. Further, when the container 4 (that is, the heat pipe) is bent, the wick 5 is disposed along the container 4 and is fixed, so that it deforms in accordance with the deformation of the container 4. In other words, since the wick 5 does not come into contact with the inner surface of the bent container 4 on the inner peripheral side, the steam flow path 6 is ensured as originally manufactured, and as a result, the flow of the working fluid vapor is hindered. There is nothing to do.

  As described above, the flat heat pipe 10 according to the present invention shown in FIG. 3 includes the wick 5 that is bundled by bundling both ends of the thin wire 1 so that the heat pipe 10 can be made thin. In addition to the fact that the capillary force by the wick 5 is strong and a smooth continuous fluid return path can be secured between the thin wires, the flow of the working fluid vapor can be achieved even when deformation such as bending is applied. Since the path 6 can be secured, the heat transport capability can be increased compared to the conventional case.

  In the present invention, when the heat pipe is formed in a flat shape, the wick 5 is arranged so as to be biased to either the left or right as shown in FIG. 4 in addition to the central portion in the width direction of the container 4. May be. Even if it is a case where it is such a structure, the performance substantially equivalent to the heat pipe 10 of the structure shown in said FIG. 3 can be acquired.

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

(Example)
As the wick 5, a thin wire bundle 2 formed by binding both ends of the thin wire 1 with another thin wire 3 is inserted into the pipe, and a heat pipe is produced by the method described above. The flat heat pipe 10 was crushed to a thickness. The wick 5 was disposed in the center of the container 4 in the width direction, and was fixed and integrated with the container 4 by sintering.

(Comparative Example 1)
The bundled fine wires 1 were produced in the same manner as in the above example except that the wick 5 formed by twisting and bundling the fine wires 1 over the entire length thereof was used.

  The flat heat pipe 10 of the above-described embodiment and comparative example has three types of shapes as shown in FIG. 5, that is, a linear shape having a total length of 130 mm, a width of 7.43 mm, and a thickness of 1 mm shown in FIG. A flat heat pipe (first heat pipe), a flat heat pipe (second heat pipe) having a total length of 130 mm, a width of 7.43 mm, a thickness of 1 mm, and a bending angle of 135 degrees shown in FIG. And a flat heat pipe (third heat pipe) having a total length of 175 mm, a width of 8.5 mm, a thickness of 2 mm, and a bending angle of 90 degrees as shown in FIG.

(Test method)
As shown in FIG. 6, one end of the heat pipe 10 to be tested is brought into contact with the surface (30 mm × 30 mm) of the electric heater 15, and the other end of the heat pipe 10 is connected to the heat radiating plate 16 (40 mm × 40 mm). ) Was placed in contact with the top surface. Further, a space between the electric heater 15 and the heat radiating plate 16 is a heat insulating part. One end of the heat pipe 10 is heated by energizing the electric heater 15, the amount of electric power (heat input Q), the temperature Te at the contact point P <b> 1 between the electric heater 15 and the heat pipe 10, The temperature Tc of the other end P2 was measured. From these measurement data, the heat resistance (° C./W) for each heat pipe and the maximum heat input (W) within a range where no so-called dry out occurs were obtained. The thermal resistance R was determined as (R = (Te−Tc) / Q). FIG. 7 shows the test results of the first and second heat pipes, and FIG. 8 shows the test results of the third heat pipe.

  From the above test results, evaluation can be made as follows. First, in the first heat pipe, the maximum heat input amount in Comparative Example 1 is 6 W, whereas in the Example, the heat input is 8 W, and in the second heat pipe, the maximum heat input amount in Comparative Example 1 is 6 W. On the other hand, the example is 7 W, and in the third heat pipe, the maximum heat input of Comparative Example 1 is 18 W, whereas the example is 20 W. Therefore, the Example has a higher maximum heat input. . In addition, the thermal resistance of the first and second heat pipe examples is 1 ° C./W or less regardless of the shape of the heat pipe, whereas the second heat pipe is comparative example 1 in particular. In Comparative Example 1, the thermal resistance is about 1.5 ° C./W, or in the third heat pipe, the thermal resistance of the example is 0.35 ° C./W. Since the thermal resistance is 0.4 ° C./W, the thermal resistance is lower in the example. From these results, it can be seen that, as a method of forming the wick 5, it is desirable to bind the thin wires 1 and bind both ends. This is presumed that when the working fluid flows from the condensing part to the evaporation part, the flow resistance is lower than that of Comparative Example 1 because the thin lines 1 are formed in a straight line and parallel to each other in the flow direction. it can.

  Further, when comparing the first heat pipe and the second heat pipe formed by using the wick 5 of the embodiment, the maximum heat input and the heat resistance are almost the same. Therefore, in the wick 5 of the embodiment, It can be seen that even when the heat pipe is bent, the maximum heat input and the thermal resistance are not affected. This is presumably because the wick 5 does not move in the heat pipe even if the heat pipe is bent because the wick 5 is sintered after being placed on the heat pipe. That is, since the steam flow path 6 in the heat pipe is not closed, the flow of the steam and the working fluid can be made smooth.

Next, a test for determining the optimum number of thin wires 1 for forming the wick 5 of the flat heat pipe 10 according to the present invention was performed. That is, the wick 5 and the flat heat pipe 10 are formed using the thin wires 1 of each number (200, 250, 300, 350) in the same manner as in the above-described embodiment, Was placed in contact with the electric heater 15 and the other end in contact with the upper surface of the heat sink 16. Further, the number of non-defective products (non-defective product ratio) out of 15 heat pipes 10 each using the number of fine wires 1 forming the wick 5 was determined. FIG. 9 shows the thermal resistance for each number of fine wires 1 forming the wick 5, and Table 1 shows the average thermal resistance and the yield rate for each number of fine wires 1 forming the wick 5. In addition, as shown in FIG. 10, the test was performed by using a linear flat heat sink 10 having a total length of 100 mm, a width of 7.4 mm, and a thickness of 1.0 mm, and a heat input amount of the electric heater of 10 W.

  As can be seen from FIG. 9 and Table 1, when the number of the thin wires 1 forming the wick 5 is 250, the thermal resistance and the yield rate are better than when the wick 5 is formed with another number. I understand. That is, it can be seen that the number of fine wires 1 forming the wick 5 needs to be determined according to the flat heat pipe 10 to be formed.

  DESCRIPTION OF SYMBOLS 1 ... Fine wire, 2 ... Thin wire bundle, 3 ... Bundling member, 4 ... Container, 5 ... Wick, 6 ... Steam flow path, 10 ... Heat pipe, 11 ... Fine groove, 15 ... Electric heater, 16 ... Heat sink

Claims (4)

A working fluid that is heated to evaporate, dissipates heat and condenses is enclosed inside the container, and a wick that causes capillary force to recirculate the liquid-phase working fluid is generated inside the container at the location where the working fluid evaporates. In a flat heat pipe whose container is formed in a thin hollow structure,
The wick has a structure in which a large number of fine wires having both ends bound therein are inserted into the container, and an intermediate portion in the longitudinal direction of the fine wire bundle is expanded along the inner surface of the container, and A steam flow path in which a fine wire bundle expanded along the inner surface of the container is fixed to the inner surface of the container by sintering, and a vapor channel through which the working fluid vapor flows around the fine wire bundle fixed to the inner surface of the container. A flat heat pipe characterized by being formed.   The flat heat pipe according to claim 1, wherein the container is flattened by crushing a pipe having a circular cross section in the radial direction.   3. The pipe is flattened by being crushed and flattened in a state in which an extra fine wire bundle constituted by aligning the extra fine wires in a straight line is inserted along a longitudinal direction thereof. The flat heat pipe as described.   The fine wire bundle is inserted into the horizontally installed pipe, and after the pipe is crushed and flattened, it is heated from the outside of the pipe and sintered on the inner surface of the heat pipe. The flat heat pipe according to claim 2 or 3, wherein

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