JP2018076987A - heat pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat pipe that can obtain good heat transport capacity even if it is thin, and a method for manufacturing the same.SOLUTION: A heat pipe 1 according to an aspect of the present invention comprises a flat container 10 within which working fluid is enclosed, and a wick 20 provided within the container 10. The wick 20 is a braid body 21 made by cylindrically braiding fibers. A vapor passage 30 for the working fluid is formed around the braid body 21. A liquid passage 31 for the working fluid is formed in a hollow part 212 surrounded by an inner peripheral surface 21a of the braid body 21.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a heat pipe and a manufacturing method thereof.

  In recent years, thinning of portable devices such as smartphones and tablet PCs has been remarkable, and a thin heat pipe is required in order to dissipate heat from a CPU or the like mounted on the portable device. As such a thin heat pipe, the following Patent Document 1 discloses a flat heat pipe having a thickness dimension of 1 mm or less. The heat pipe is composed of a first pipe, a second pipe having a relatively small diameter and a shorter length than the first pipe, and at least one second pipe substantially at the center of the first pipe. A heat pipe that is inserted and fixed, and in which a working fluid is put into a first pipe and an end thereof is sealed, and the first and second pipes are formed in a flat shape.

  The first pipe is formed of a cylindrical material having a hollow inside and is formed into a flat shape. The axial ends are respectively drawn and pressed, and a container is formed between both ends. The drawing portion serves as a working fluid inlet, and forms a sealing portion in the assembly process to seal the inside of the first pipe. As described above, the first pipe is flat, a groove (groove) is formed inside, and a second pipe having a length dimension less than the effective length of the container is embedded. The second pipe has a shape in which the internal space is crushed.

Japanese Patent Laid-Open No. 11-183069

  Since the heat pipe having the above-described structure has grooves formed over the entire circumference of the inner wall surface of the container, a liquid pool may be generated in the vapor flow path of the working fluid. In a thin heat pipe, the flow path area of the steam flow path is small, and when a liquid pool is generated in the steam flow path, the liquid is pushed to the low temperature part by the steam of the working fluid, and heat transport by the latent heat of the working fluid There is a problem that the ability is reduced.

  This invention is made | formed in view of the said problem, and it aims at provision of the heat pipe which can obtain favorable heat transport capability even if it is thin, and its manufacturing method.

  (1) A heat pipe according to an aspect of the present invention includes a flat container in which a working fluid is sealed, and a wick provided in the container, and the wick has a fiber-like shape. The working fluid vapor channel is formed around the braided body, and the working fluid liquid channel is formed in the cavity surrounded by the inner peripheral surface of the braided body. Has been.

(2) In the heat pipe described in the above (1), the inner wall surface of the container is formed smoothly, and the braided body has an outer peripheral surface in contact with the inner wall surface of the container, A second liquid flow path for the working fluid may be formed between the outer peripheral surface of the braided body and the inner wall surface of the container.
(3) In the heat pipe described in (1) or (2) above, a third liquid channel of the working fluid may be formed between the fibers of the braided body.

  (4) A method of manufacturing a heat pipe according to an aspect of the present invention includes a flat container in which a working fluid is enclosed, and a wick provided in the container, wherein the wick is a fiber A steam flow path for the working fluid is formed around the braided body, and a liquid flow of the working fluid is formed in a cavity surrounded by an inner peripheral surface of the braided body. A heat pipe manufacturing method in which a path is formed, the wick pressing step for pressing the wick flatly, the wick insertion step for inserting the flattened wick into the container, and A working fluid introduction step of introducing the working fluid into the container into which the wick is inserted; a container sealing step of sealing the container into which the working fluid has been introduced; and the sealed container ; And a container pressing process to press into a flat shape.

  (5) The heat pipe manufacturing method described in (4) above, wherein the wick inserted into the container is sintered after the wick insertion process and before the working fluid introduction process. You may have the sintering process fixed to.

  According to the above aspect of the present invention, it is possible to provide a heat pipe that can obtain a good heat transport capability even if it is thin, and a method for manufacturing the heat pipe.

It is a top view of the heat pipe which concerns on one Embodiment. It is arrow AA sectional drawing of the heat pipe shown in FIG. It is an external view of the wick concerning one embodiment. It is a schematic diagram of the braided body which comprises the wick which concerns on one Embodiment. It is a flowchart of the manufacturing method of the heat pipe which concerns on one Embodiment. It is explanatory drawing explaining the wick insertion process of the manufacturing method of the heat pipe which concerns on one Embodiment. It is (a) top view and (b) side view of the testing machine which evaluates the performance of the heat pipe concerning one embodiment. It is a graph which shows the test result by the testing machine shown in FIG.

  Hereinafter, a heat pipe and a manufacturing method thereof according to an embodiment of the present invention will be described with reference to the drawings. In the drawings, some portions are enlarged or omitted for convenience of explanation. In addition, the dimensional ratio of each component shown in the drawings is not always the same as the actual one.

FIG. 1 is a plan view of a heat pipe 1 according to an embodiment. FIG. 2 is a cross-sectional view of the heat pipe 1 shown in FIG.
The heat pipe 1 is a heat transport element that uses the latent heat of the working fluid. The heat pipe 1 includes a container 10 in which a working fluid is enclosed, and a wick 20 provided in the container 10.

  The working fluid is a heat transport medium made of a known phase change material, and changes in phase between the liquid phase and the gas phase in the container 10. For example, water (pure water), alcohol, ammonia, or the like can be employed as the working fluid. The working fluid may be described as “liquid” in the liquid phase and “vapor” in the gas phase. Further, when the liquid phase and the gas phase are not particularly distinguished, they may be described as working fluid. In the thin heat pipe 1 as in the present embodiment, it is preferable to employ water as the working fluid.

  As shown in FIG. 1, the container 10 is an airtight hollow container in which one end 11 and the other end 12 are closed. In the heat pipe 1 that is used for heat transport between locations separated from each other, a hollow pipe (pipe) is used for the container 10. Since the container 10 needs to transfer heat between the inside and the outside, the container 10 is preferably made of a material having high thermal conductivity, such as a metal tube such as a copper tube, an aluminum tube, or a stainless tube. It is preferable to be configured.

  As shown in FIG. 2, the container 10 is formed in a flat shape in which the dimension in the width direction (left and right direction in FIG. 2) is larger than the dimension in the thickness direction (up and down direction in FIG. 2). The cross-sectional shape of the container 10 is an oval shape having a pair of plane portions 13 parallel to each other and a pair of curved surface portions 14 connecting both ends thereof. The curved surface portion 14 is not limited to a semicircular shape, and may be a semi-elliptical shape or other curved convex shape.

  The wick 20 is fixed to the center of the container 10 in the width direction. Further, the wick 20 is in contact with the pair of plane portions 13 of the container 10. A gap is formed between the wick 20 and the pair of curved surface portions 14, and the gap serves as a vapor flow path 30 for the working fluid. As shown in FIG. 1, the wick 20 extends in the longitudinal direction of the container 10, and evaporates the working fluid evaporated on one side of the one end 11 and the other end 12 and condensed on the other side. Reflux to one side again.

FIG. 3 is an external view of the wick 20 according to the embodiment. FIG. 4 is a schematic diagram of a braided body 21 constituting the wick 20 according to an embodiment.
The wick 20 is a braided body 21 in which fibers 210 are knitted in a cylindrical shape. As shown in FIG. 3, the braided body 21 of the present embodiment is formed by knitting a fiber bundle 211 in which fibers 210 are bundled into a tubular shape. The fibers 210 bundled as the fiber bundle 211 are not twisted.

  As the fiber 210, for example, a metal wire such as copper, aluminum, or stainless steel, or a non-metal wire such as carbon fiber or glass fiber can be employed. In addition, since a metal wire has high heat conductivity, it can employ | adopt suitably as the fiber 210. FIG. In addition, it is preferable to select the fiber 210 that has excellent wettability in relation to the working fluid enclosed in the container 10. The fiber 210 of the present embodiment uses, for example, a copper wire having a diameter of about 0.05 mm, and several fibers are bundled to form a fiber bundle 211.

  As shown in FIG. 2, a working fluid liquid flow path 31 (first liquid flow path) is formed in the cavity 212 surrounded by the inner peripheral surface 21 a of the braided body 21. The thickness t5 of the cavity 212 is large enough to exert a capillary force that moves the liquid of the working fluid. The thickness t5 of the hollow portion 212 is, for example, about 0.05 mm, and in this embodiment, the thickness t5 is about the same as the diameter of the fiber 210. Further, the thickness t4 of the braided body 21 is larger than the thickness t5 of the hollow portion 212, and is, for example, about 2 to 3 times the diameter of the fiber 210.

  A thickness t3 of the internal space of the container 10 is large enough to accommodate the braided body 21 having the cavity 212. Moreover, the thickness t2 of the container 10 is smaller than the thickness t4 of the braided body 21, and is, for example, about 1.5 to 2.5 times the diameter of the fiber 210. The total thickness t1 of the heat pipe 1 is a size obtained by adding the thickness t2 of the container 10 and the thickness t3 of the internal space thereof, and is about 0.5 mm in this embodiment, for example.

  The braided body 21 has an outer peripheral surface 21 b that contacts the inner wall surface 10 a of the container 10. The inner wall surface 10a of the container 10 has no irregularities such as grooves and is formed smoothly. A second liquid flow path 32 for the working fluid is formed between the outer peripheral surface 21 b of the braided body 21 and the inner wall surface 10 a of the container 10. Since the braided body 21 of the present embodiment is in contact with each of the pair of flat surface portions 13, the second liquid channel 32 is formed in each of the contact portions. The second liquid channel 32 is formed by a gap (groove) formed by the intersection of the fiber bundle 211 and the fiber bundle 211 shown in FIG.

  Further, as shown in FIG. 2, a third liquid flow path 33 for working fluid is formed between the fibers 210 inside the braided body 21. Since the third liquid channel 33 is a gap between the fibers 210, the space is smaller than the second liquid channel 32 that is a gap between the fiber bundles 211. For this reason, the second liquid flow path 32 has a larger liquid transport capability than the third liquid flow path 33. Further, since the fiber bundle 211 is in contact with the inner wall surface 10a of the container 10 in the second liquid channel 32, the contact portion serves as a resistance to the flow of the liquid. For this reason, the first liquid flow path 31 that is the cavity portion 212 has a larger liquid transport capability than the second liquid flow path 32.

  As shown in FIG. 4, the fibers 210 (fiber bundle 211) of the braided body 21 are knitted at an acute angle α with respect to the flow direction of the liquid of the working fluid. The flow direction of the liquid in the present embodiment is a longitudinal direction along the center line L of the braided body 21. If the angle α is large, the liquid that moves through the gaps of the fibers 210 (fiber bundle 211) is difficult to move in the longitudinal direction (the resistance to the flow of the liquid increases), so the angle α is closer to 0 degrees. preferable. However, since the braided body 21 cannot be formed when the angle α is 0 degree, the angle α is set in the range of 5 to 20 degrees.

Next, the manufacturing method of the heat pipe 1 of the said structure is demonstrated.
FIG. 5 is a flowchart of a method for manufacturing the heat pipe 1 according to an embodiment. Drawing 6 is an explanatory view explaining wick insertion process S2 of a manufacturing method of heat pipe 1 concerning one embodiment.
In this method, as shown in FIG. 5, the heat pipe 1 is manufactured through the wick press step S1, the wick insertion step S2, the sintering step S3, the working fluid introduction step S4, the container sealing step S5, and the container press step S6. To do.

The wick press step S1 is a step of pressing the wick 20 into a flat shape.
In this step, first, a plurality of fibers 210 are bundled to form a fiber bundle 211. Next, dozens of fiber bundles 211 are prepared and set on a braiding machine. This braiding machine is for forming a braided body 21 by knitting fiber bundles 211 into a cylindrical shape, and the principle configuration thereof is as conventionally known. Once the tubular braided body 21 is formed by the braiding machine, the braided body 21 is then cut into a predetermined length to form the tubular wick 20. The wick 20 is pressed into a flat shape using a press.

The wick insertion step S <b> 2 is a step of inserting the flat wick 20 into the container 10.
In this step, first, a round pipe subjected to cleaning such as degreasing is prepared, and this is cut into a predetermined length to form a container 10. When the braided body 21 is constituted by a copper wire, it is preferable to use a copper pipe as the container 10. Next, as shown in FIG. 6, the wick 20 is inserted into the container 10 using a fixture 40. The fixture 40 has a notch 41 in which a part of the outer peripheral surface is cut flat, and the wick 20 is inserted into the container 10 in a state of being bent into a semicircular arc shape.

The sintering step S <b> 3 is a step of sintering the wick 20 inserted into the container 10 and fixing it to the container 10.
In this step, as shown in FIG. 6, the container 10 in which the wick 20 is inserted is sent to a heating furnace (not shown) while being kept substantially horizontal and heated. When the container 10 and the wick 20 are made of copper, the heating temperature is about 1000 ° C. By doing so, the wick 20 is sintered and fixed to the inner wall surface 10 a of the container 10.

The working fluid introduction step S4 is a step of introducing the working fluid into the container 10 in which the wick 20 is inserted.
In this step, first, the container 10 is removed from the heating furnace and cooled. Next, the fixture 40 inserted into the container 10 is taken out, and the other end portion 12 on the bottom side of the container 10 shown in FIG. 1 is swaged, and the end portion is welded and sealed. So-called bottom swaging and bottom welding are performed. Further, a swaging process, that is, a top swaging process is performed on the one end portion 11 on the top side of the container 10. And a working fluid is introduce | transduced from the one end part 11 of the container 10 restrict | squeezed by the top swaging process.

The container sealing step S5 is a step of sealing the container 10 into which the working fluid has been introduced.
In this step, the one end portion 11 of the container 10 which has been opened for introducing the working fluid is crushed and then welded and sealed. So-called top welding is performed. In addition, when introducing a working fluid from the one end 11 of the container 10, it is necessary to deaerate non-condensable gas such as air from the container 10, and therefore the injection is a method of injecting the working fluid after vacuum degassing A method known in the art, such as a method of injecting an excessive amount of working fluid and then boiling it to drive off non-condensable gas, may be used.

The container pressing step S6 is a step of pressing the sealed container 10 into a flat shape.
In this step, the round pipe type container 10 filled with the working fluid is crushed in the radial direction so as to have a flat shape. When the container 10 is crushed and flattened in the radial direction, the wick 20 inserted in a state of being bent into a semicircular arc shape becomes a flat shape shown in FIG.
As described above, the heat pipe 1 having the above-described configuration can be manufactured.

Next, the operation (action) of the heat pipe 1 will be described.
As shown in FIG. 1, when a temperature difference occurs between one end 11 and the other end 12 of the container 10, the working fluid is heated and evaporated in the high temperature portion (for example, the one end 11), and the container 10 The internal pressure also increases. The working fluid vapor generated in the high temperature part moves toward the low temperature part (the other end part 12) having a low temperature and pressure, and the heat in the high temperature part is transported to the low temperature part as latent heat of the steam. In the low temperature part, the vapor of the working fluid is condensed by heat dissipation. As shown in FIG. 2, a vapor flow path 30 of vapor, that is, a gas-phase working fluid, is secured around the wick 20 (braided body 21).

  The working fluid condensed in the low temperature part penetrates into the wick 20 and moves toward a place where the working fluid evaporates, that is, a high temperature part. Specifically, a part of the liquid that has penetrated into the wick 20 penetrates into the cavity 212 surrounded by the inner peripheral surface 21 a of the braided body 21, passes through the liquid flow path 31 formed in the cavity 212, and reaches the high-temperature part. Move towards Thus, in this embodiment, since the liquid flow path 31 is formed in the internal space of the braided body 21, and the liquid flow path 31 and the vapor | steam flow path 30 are separated, a liquid is made into a low-temperature part with a vapor | steam. It will not be washed away. For this reason, the heat transport capability of the heat pipe 1 is improved.

  In addition, since the wick 20 is the braided body 21 in which the fibers 210 are knitted into a cylindrical shape, the distribution of the fibers 210 in the cross section of the wick 20 is unlikely to be uneven even when pressed flat. For this reason, the cavity part 212 used as the liquid flow path 31 can be favorably formed in the inside of the wick 20, and the dispersion | variation in the heat transport capability of the heat pipe 1 can be suppressed. Moreover, since the thickness t5 of the cavity part 212 can be managed by pressing the wick 20 into a flat shape in advance before inserting the wick 20 into the container 10 as in this embodiment, the capillary force is easily exerted. . Further, as in this embodiment, when the sintering step S3 is performed, the fibers 210 are fixed to each other, and therefore, only the wick 20 is pressed in advance, compared with the case where the fibers 210 are pressed flat together with the container 10. It becomes easier to manage the thickness t5 of the cavity 212.

  The remaining portion of the liquid that has permeated the wick 20 is formed between the second liquid flow path 32 formed between the outer peripheral surface 21 b of the braided body 21 and the inner wall surface 10 a of the container 10 and the fibers 210 of the braided body 21. The third working fluid moves through the third liquid flow path 33 toward the high temperature portion. As described above, since the heat pipe 1 has three liquid flow paths for the working fluid, even if the heat pipe 1 is a thin heat pipe 1 in which a groove (groove) cannot be formed on the inner wall surface 10a of the container 10, Can be secured sufficiently. Further, in the second liquid channel 32 and the third liquid channel 33, as shown in FIG. 4, the fibers 210 (fiber bundles 211) are knitted at a small angle α with respect to the flow direction of the working fluid liquid. Therefore, the resistance of the liquid flow is small, and a good liquid transport capability can be obtained.

FIG. 7 is a (a) plan view and (b) side view of a testing machine for evaluating the performance of the heat pipe 1 according to an embodiment. FIG. 8 is a graph showing a test result obtained by the testing machine shown in FIG.
In order to evaluate the performance of the heat pipe 1, a tester as shown in FIG. 7 was created. In this testing machine, as shown in FIG. 7A, the heat pipe 1 is attached to the center in the width direction of the surface of the support plate 50, and faces the vicinity of one end of the heat pipe 1 on the back surface of the support plate 50. The heater 100 is attached to the position. And the sensors 51 and 52 were provided in the high temperature part and low temperature part of the heat pipe 1, and the performance of the heat pipe 1 was evaluated by thermal resistance.

  The thermal resistance is determined by (Te−Tc) / Q [° C./W]. Q [W] is the amount of heat applied to the unit time by the heater 100 (so-called heat input amount). Te [° C.] is the temperature detected by the sensor 51 (the temperature of the heater 100). Tc [° C.] is a temperature (outside air temperature) detected by the sensor 52. The amount of heat input is the amount of electric power when the heater 100 is an electric heater. The temperature Te is measured in a state where the amount of heat input from the heater 100 is balanced with the amount of heat released through the heat pipe 1 and reaches equilibrium. Therefore, the higher the heat transport capacity of the heat pipe 1, the smaller the thermal resistance.

  FIG. 8 also shows, as a comparative example, the test results of the wick 20 that is focused in a state where the fibers 210 are twisted together (so-called twist wick). When comparing the test results of the example of the present invention (heat pipe 1) shown in FIG. 8 and the comparative example, the average thermal resistance of the example was about 30% smaller than that of the comparative example. That is, it can be seen that the heat transport capability of the example is about 30% higher than that of the comparative example.

  Thus, according to the above-described embodiment, the flat container 10 in which the working fluid is sealed is provided, and the wick 20 provided in the container 10 is provided. The braided body 21 is knitted in a cylindrical shape. A working fluid vapor channel 30 is formed around the braided body 21, and the working fluid liquid is formed in a cavity 212 surrounded by the inner peripheral surface 21 a of the braided body 21. By adopting the heat pipe 1 in which the flow path 31 is formed, a good heat transport capability can be obtained even if it is thin.

  Although preferred embodiments of the present invention have been described and described above, it should be understood that these are exemplary of the present invention and should not be considered as limiting. Additions, omissions, substitutions, and other changes can be made without departing from the scope of the invention. Accordingly, the invention is not to be seen as limited by the foregoing description, but is limited by the scope of the claims.

For example, the cross-sectional shapes of the container 10 and the wick 20 are arbitrary. The cross-sectional shape of the container 10 and the wick 20 shown in FIG. 2 is an oval shape, but may be, for example, a quadrangle, another polygon, or an ellipse.
Further, the shape of the container 10 in the longitudinal direction is arbitrary, and the container 10 may be curved or bent into a predetermined shape.

  Further, the configuration of the container 10 is not particularly limited, and is not limited to a pipe (tube) molded into a cylindrical shape without a joint, but includes one or more members having various shapes such as a plate shape, a box shape, and a groove shape. It is possible to comprise by the combination of. Examples of the thickness of the thinned container 10 include 0.3 to 2.0 mm, for example.

Further, for example, the number, cross-sectional shape, dimensions, and the like of the fibers 210 constituting the wick 20 can be appropriately selected.
The number of wicks 20 accommodated in the container 10 may be 1 or 2 or more.

  In the heat pipe 1 shown in FIG. 2, the wick 20 is disposed at the center in the width direction of the flat container 10, but the wick 20 is disposed at one end of the container 10 in the width direction. Alternatively, they may be disposed at both ends of the container 10 in the width direction.

  In addition, the use of the heat pipe (heat transport element) of the present embodiment is not particularly limited, but as an example, a smartphone, a tablet terminal, a mobile phone, a personal computer, a server, a copier, a game machine, a multifunction device, a projector, an electronic device Examples include equipment, fuel cells, and satellites.

DESCRIPTION OF SYMBOLS 1 ... Heat pipe, 10 ... Container, 10a ... Inner wall surface, 20 ... Wick, 21 ... Braided body, 21a ... Inner peripheral surface, 21b ... Outer peripheral surface, 30 ... Steam flow path, 31 ... Liquid flow path (1st liquid Channel), 32 ... second liquid channel, 33 ... third liquid channel, 210 ... fiber, 211 ... fiber bundle, 212 ... cavity, S1 ... wick pressing step, S2 ... wick insertion step, S3 ... Sintering process, S4 ... Working fluid introduction process, S5 ... Container sealing process, S6 ... Container press process

The present invention relates to a heat pipe .

This invention is made | formed in view of the said problem, and it aims at provision of the heat pipe from which favorable heat transport capability is obtained even if it is thin.

According to the aspect of the present invention, it is possible to provide a heat pipe that can obtain a good heat transport capability even if it is thin.

Claims (5)

A flat container enclosing a working fluid;
A wick provided inside the container,
The wick is a braided body in which fibers are knitted into a cylindrical shape,
A steam flow path for the working fluid is formed around the braided body,
A heat pipe, wherein a liquid flow path of the working fluid is formed in a cavity surrounded by an inner peripheral surface of the braided body. The inner wall surface of the container is formed smoothly,
The braided body has an outer peripheral surface that contacts the inner wall surface of the container;
The heat pipe according to claim 1, wherein a second liquid flow path for the working fluid is formed between an outer peripheral surface of the braided body and an inner wall surface of the container.   The heat pipe according to claim 1 or 2, wherein a third liquid flow path of the working fluid is formed between fibers of the braided body. A flat container enclosing a working fluid;
A wick provided inside the container,
The wick is a braided body in which fibers are knitted into a cylindrical shape,
A steam flow path for the working fluid is formed around the braided body,
In the cavity surrounded by the inner peripheral surface of the braided body, a liquid flow path of the working fluid is formed,
A wick press step of pressing the wick flatly;
A wick insertion step of inserting the flattened wick into the container;
A working fluid introduction step for introducing the working fluid into the container in which the wick is inserted;
A container sealing step for sealing the container into which the working fluid has been introduced;
And a container pressing step of pressing the sealed container into a flat shape.   5. The method according to claim 4, further comprising a sintering step of sintering and fixing the wick inserted into the container after the wick insertion step and before the working fluid introduction step. Heat pipe manufacturing method.

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