Heat pipe

Abstract

A heat pipe includes a container in which a working fluid is sealed; and a wick accommodated in the container, in which an evaporation portion, a condensation portion, and an intermediate portion provided between the evaporation portion and the condensation portion are provided at different positions in a longitudinal direction of the container, in a transverse cross section orthogonal to the longitudinal direction, a shape of the wick in the intermediate portion is different from a shape of the wick in the evaporation portion and the condensation portion, and in the evaporation portion and the condensation portion, the wick has an annular shape and includes a thin wall portion and a thick wall portion having a thickness larger than a thickness of the thin wall portion.

Description

TECHNICAL FIELD

[0001] The present invention relates to a heat pipe.

[0002] Priority is claimed on Japanese Patent Application No. 2023-054784, filed March 30, 2023, the content of which is incorporated herein by reference.BACKGROUND ART

[0003] A heat pipe as disclosed in Patent Document 1 has been known in the related art. The heat pipe includes a container in which a working fluid is sealed, and a wick disposed in the container. The wick is provided to return the working fluid in the liquid phase from the condensation portion to the evaporation portion. In Patent Document 1, the thickness of the wick changes in the longitudinal direction of the heat pipe.Citation ListPatent Document

[0004] Patent Document 1: United States Patent No. 7520315SUMMARY OF INVENTIONTechnical Problem

[0005] In the configuration of Patent Document 1, the thickness of the wick is constant in a cross section orthogonal to the longitudinal direction of the container. By making the thickness of the wick constant, a flow resistance of the working fluid in the wick can be made uniform in the circumferential direction, but in this case, a thermal resistance due to the thickness of the wick may increase.

[0006] The present invention has been made in consideration of such circumstances, and an object of the present invention is to provide a heat pipe capable of achieving both reduction of a flow resistance of a working fluid in a wick and reduction of a thermal resistance of the wick.Solution to Problem

[0007] In order to solve the above-described problem, according to an aspect 1 of the present invention, there is provided a heat pipe including a container in which a working fluid is sealed, and a wick accommodated in the container, in which an evaporation portion, a condensation portion, and an intermediate portion provided between the evaporation portion and the condensation portion are provided at different positions in a longitudinal direction of the container, in a transverse cross section orthogonal to the longitudinal direction, a shape of the wick in the intermediate portion is different from a shape of the wick in the evaporation portion and the condensation portion, and in the evaporation portion and the condensation portion, the wick has an annular shape and includes a thin wall portion and a thick wall portion having a thickness larger than a thickness of the thin wall portion.

[0008] In this configuration, since the thermal resistance in the thin wall portion of the wick is small and the flow resistance in the thick wall portion of the wick is small, reflux performance of the working fluid can be improved. As a result, the amount of heat transport and the distance of heat transport in the heat pipe can be increased.

[0009] In addition, according to an aspect 2 of the present invention, in the heat pipe of the aspect 1, in the evaporation portion and the condensation portion, a thickness of the wick gradually changes along a circumferential direction.

[0010] In addition, according to an aspect 3 of the present invention, in the heat pipe of the aspect 1 or 2, in one transverse cross section, the number of valley portions in which a thickness of the wick turns from decrease to increase in a circumferential direction is two, and the number of peak portions in which the thickness of the wick turns from increase to decrease in the circumferential direction is two.

[0011] In addition, according to an aspect 4 of the present invention, in the heat pipe of any one of the aspects 1 to 3, a center of an internal space of the wick and a central axis of the heat pipe are provided at different positions.

[0012] In addition, according to an aspect 5 of the present invention, in the heat pipe of any one of the aspects 1 to 4, a thickness of the wick in a circumferential direction is uniform in the intermediate portion.Advantageous Effects of Invention

[0013] According to the above-described aspects of the present invention, it is possible to provide a heat pipe that can achieve both reduction of a flow resistance of a working fluid in a wick and reduction of a thermal resistance of the wick.BRIEF DESCRIPTION OF DRAWINGS

[0014] [FIG. 1] A side view of a heat pipe according to a first embodiment. [FIG. 2] A cross-sectional view taken along line II-II of the heat pipe shown in FIG. 1 is a transverse cross-sectional view of an evaporation portion. [FIG. 3] A cross-sectional view taken along line III-III of the heat pipe shown in FIG. 1 is a transverse cross-sectional view of an intermediate portion. [FIG. 4] A transverse cross-sectional view of an evaporation portion of a heat pipe according to a second embodiment. [FIG. 5] A transverse cross-sectional view of an evaporation portion of a heat pipe according to a third embodiment. [FIG. 6] A transverse cross-sectional view of a heat pipe according to a modification example of the first to third embodiments. [FIG. 7] A transverse cross-sectional view of the heat pipe according to another modification example of the first to third embodiments. DESCRIPTION OF EMBODIMENTS(First Embodiment)

[0015] Hereinafter, a configuration of a heat pipe 1 of the present embodiment will be described with reference to the drawings.

[0016] As shown in FIGS. 1, 2, and 3, the heat pipe 1 includes a wick 20 and a container 30. The container 30 has an elongated shape that extends in one direction. The wick 20 is accommodated in the container 30. A working fluid (not shown) is sealed in the container 30.

[0017] The heat pipe 1 is, for example, a heat transfer element that receives heat from heat source 110 and that transfers the heat by using latent heat of a working fluid enclosed in the container 30.(Direction Definition)

[0018] In the present specification, a direction in which the container 30 extends is simply referred to as a longitudinal direction X. In addition, a cross section of the container 30 orthogonal to the longitudinal direction X is referred to as a transverse cross section. In addition, in a transverse cross-sectional view orthogonal to the longitudinal direction X of the container 30, a direction orthogonal to the central axis O is referred to as a radial direction, and a direction of movement around the central axis O is referred to as a circumferential direction.

[0019] As shown in FIG. 1, the container 30 has both ends in the longitudinal direction X sealed. As shown in FIGS. 2 and 3, the container 30 is a cylindrical hollow container. The container 30 has an inner peripheral surface 31 facing the radially inner side and an outer peripheral surface 32 facing the radially outer side.

[0020] The material of the container 30 can be appropriately selected depending on conditions such as a type of the working fluid and the operating temperature. For example, the container 30 is formed of a metal such as copper, steel, or aluminum. In particular, in a case of using a metal material having high thermal conductivity such as copper or aluminum, it is possible to enhance the heat transportability or heat diffusivity. In the present embodiment, a copper tube is used as the container 30.

[0021] In the longitudinal direction X, an inner diameter and an outer diameter of the container 30 are substantially constant. In the end parts 1a and 1b of the heat pipe 1 in the longitudinal direction X, the outer diameter of the container 30 may gradually decrease toward the end surface.

[0022] A working fluid is sealed inside the container 30. The working fluid is a well-known heat transfer medium capable of undergoing a phase change, and undergoes the phase change between a liquid phase and a gas phase in the container 30. As the working fluid, for example, water, alcohol, ammonia, CFC substitutes, and the like can be adopted. The type of the working fluid may be appropriately changed according to a temperature range of heat transported by the heat pipe 1 and an amount of the heat transport. In the present specification, in some cases, the working fluid in the liquid phase is referred to as "working liquid", and the working fluid in the gas phase is referred to as "vapor". In addition, in a case where the liquid phase and the gas phase are not particularly distinguished, the working fluid is simply referred to as the working fluid.

[0023] The wick 20 is disposed in the container 30. In the longitudinal direction X, the wick 20 extends over the entire length of the container 30.

[0024] The wick 20 is formed in an annular shape along the inner peripheral surface 31 of the container 30, for example, as shown in FIGS. 2 and 3. The wick 20 covers the entire inner peripheral surface 31 of the container 30. The wick 20 may not be formed in a part of the region of the inner peripheral surface 31 of the container 30 in the circumferential direction. For example, the wick 20 formed in an annular shape may have a C-shape in a transverse cross section.

[0025] The wick 20 has a large number of pores capable of generating a capillary force in the liquid phase working fluid. The pores are used as a liquid flow passage through which the working liquid flows, and are a reflux passage (hereinafter, referred to as a "flow passage") for refluxing the working liquid from the condensation portion 5 to the evaporation portion 4 described later. The working liquid in the flow passage flows in the longitudinal direction X and the circumferential direction due to the capillary force.

[0026] The wick 20 is formed by, for example, bundling a plurality of thin metal wires, for example, thin copper wires. The thin copper wire is a linear body extending in the longitudinal direction X of the container 30. The outer diameter of the thin copper wire is, for example, several µm to several hundred µm. A pore extending in the longitudinal direction X is formed between the thin copper wires. These pores are used as the above-described liquid flow passage. In addition, the working liquid moves between the pores extending in the longitudinal direction X, so that the working liquid also flows in the circumferential direction of the heat pipe 1.

[0027] The wick 20 is not limited to a fine metal wire, and may be a metal mesh (network body), a sintered body of metal powder, or the like, or may be a mixture of these.

[0028] Exemplary examples of the metal forming the wick 20 include copper, aluminum, stainless steel, and alloys thereof. The wick 20 is not limited to being formed of metal, and may be formed of a carbon material and the like. For example, the wick 20 may be formed of a thin carbon wire, a carbon mesh, and the like.

[0029] As shown in FIG. 1, the heat pipe 1 has a first end part 1a and a second end part 1b which are end parts of the container 30 in the longitudinal direction X. The heat pipe 1 has an evaporation portion 4 in which a working liquid evaporates to generate vapor, and a condensation portion 5 in which the vapor generated in the evaporation portion 4 is condensed to generate the working liquid. The evaporation portion 4 and the condensation portion 5 are provided at intervals in the longitudinal direction X. In the present embodiment, the evaporation portion 4 is provided at the first end part 1a of the container 30. The condensation portion 5 is provided at the second end part 1b of the container 30.

[0030] The heat pipe 1 has an intermediate portion 6 between the evaporation portion 4 and the condensation portion 5. In the present embodiment, the shape of the wick 20 in the intermediate portion 6 is different from the shape of the wick 20 in the evaporation portion 4 and the condensation portion 5. Hereinafter, the shape of the wick 20 in the evaporation portion 4, the condensation portion 5, and the intermediate portion 6 will be described with reference to FIGS. 2 and 3.

[0031] FIG. 2 is a transverse cross-sectional view of the evaporation portion 4 of the heat pipe 1.

[0032] In the transverse cross section, in the evaporation portion 4, the dimensions of the wick 20 in the radial direction are not constant in the circumferential direction. Hereinafter, the dimensions of the wick 20 in the radial direction will be simply referred to as the thickness of the wick 20.

[0033] In the evaporation portion 4, the wick 20 has a thin wall portion 20a and a thick wall portion 20b having a thickness larger than the thickness of the thin wall portion 20a. In the circumferential direction, the thin wall portion 20a and the thick wall portion 20b are alternately provided.

[0034] In the present embodiment, two thin wall portions 20a and two thick wall portions 20b are provided in the wick 20. In the transverse cross section, the thickness of the wick 20 is thinnest at a center portion of the thin wall portion 20a in the circumferential direction, and the thickness of the wick 20 is thickest at a center portion of the thick wall portion 20b in the circumferential direction. That is, in the transverse cross section, the center portion of the thin wall portion 20a in the circumferential direction is a valley portion 20a1 where the thickness of the wick 20 turns from decrease to increase in the circumferential direction, and the center portion of the thick wall portion 20b in the circumferential direction is a peak portion 20b1 where the thickness of the wick 20 turns from increase to decrease in the circumferential direction. In other words, it can be said that the wick 20 is provided with two valley portions 20a1 and two peak portions 20b1.

[0035] The thickness of the wick 20 gradually increases from the valley portion 20a1 toward the peak portion 20b1. Therefore, in the transverse cross section, the inner peripheral surface 21 of the wick 20 is a curved surface.

[0036] The two thin wall portions 20a face each other in the radial direction with the central axis O interposed therebetween. A direction in which a center portion of the two thin wall portions 20a is penetrated through the central axis O is defined as an A axis direction. The two thick wall portions 20b face each other in the radial direction with respect to the central axis O. A direction in which a center portion of the two thick wall portions 20b is penetrated through the central axis O is defined as a B axis direction. The A axis direction and the B axis direction are orthogonal to each other.

[0037] Since the thin wall portion 20a and the thick wall portion 20b of the wick 20 are disposed as described above, in the present embodiment, the internal space 11 of the wick 20 has an elliptical shape in a transverse cross section with the A axis as a major axis and the B axis as a minor axis. In addition, the center of the ellipse at which the A axis and the B axis intersect each other coincides with the central axis O.

[0038] The A axis direction and the B axis direction may not be orthogonal to each other. Further, the number of the thin wall portions 20a and the thick wall portions 20b in one transverse cross section is not limited to two, and may be one, or three or more. In the present embodiment, the example in which a position of the center portion of the thin wall portion 20a in the circumferential direction and a position of the valley portion 20a1 coincide with each other has been described, but the center portion of the thin wall portion 20a in the circumferential direction and the valley portion 20a1 may be provided at positions different from each other. Similarly, the position of the center portion of the thick wall portion 20b in the circumferential direction and the position of the peak portion 20b1 may be provided at different positions. In addition, in one transverse cross section, the number of the valley portions 20a1 and the peak portions 20b1 is not limited to two, and may be one, or three or more.

[0039] The shape of the internal space 11 in the transverse cross section is not limited to an elliptical shape, and may be a circular shape, the shape in which a plurality of ellipses are combined, or a polygonal shape, corresponding to the number, arrangement, and shape of the thin wall portion 20a and the thick wall portion 20b.

[0040] FIG. 3 is a transverse cross-sectional view of the intermediate portion 6 of the heat pipe 1. The shape of the wick 20 in the intermediate portion 6 is different from the shape of the wick 20 in the evaporation portion 4. In the intermediate portion 6, the thickness of the wick 20 is constant in the circumferential direction. That is, the internal space 11 in the transverse cross section has a circular shape.

[0041] In the present embodiment, the thickness of the wick 20 of the intermediate portion 6 is larger than the maximum thickness of the wick 20 of the evaporation portion 4 (that is, the thickness of the peak portion 20b1). The thickness of the wick 20 of the intermediate portion 6 may be the same as the maximum thickness of the wick 20 of the evaporation portion 4. The thickness of the wick 20 of the intermediate portion 6 may be smaller than the maximum thickness of the wick 20 of the evaporation portion 4 and may be larger than the minimum thickness of the wick 20 (that is, the thickness of the valley portion 20a1).

[0042] In the present embodiment, the shape of the wick 20 in the transverse cross section of the condensation portion 5 is the same as the shape of the evaporation portion 4. Therefore, a detailed description will be omitted. The shape of the evaporation portion 4 in the transverse cross section and the shape of the wick 20 in the condensation portion 5 may be different from each other. For example, in the condensation portion 5, the minimum thickness of the thin wall portion 20a and the maximum thickness of the thick wall portion 20b may be different from those of the evaporation portion 4.

[0043] As described above, since the shape of the wick 20 in the transverse cross section is different in the intermediate portion 6 with respect to the evaporation portion 4 and the condensation portion 5, the thickness of the wick 20 gradually changes in at least a part along the longitudinal direction X.[Heat Transport Cycle by Heat Pipe 1]

[0044] Next, the action of the heat pipe 1 configured as described above will be described.

[0045] As shown in FIG. 1, a heat transport device 100 includes a heat pipe 1, a heat source 110, and a cooling portion 120.

[0046] The heat source 110 is in direct or indirect contact with the evaporation portion 4 of the heat pipe 1. The heat source 110 heats the container 30 of a portion corresponding to the evaporation portion 4. The heat source 110 is, for example, an electronic component (for example, a CPU or the like) of an electronic device.

[0047] The cooling portion 120 is in direct or indirect contact with the condensation portion 5 in the heat pipe 1. The cooling portion 120 cools the container 30 of a portion corresponding to the condensation portion 5. The cooling portion 120 is, for example, a heat dissipation structure such as a heat sink.

[0048] A heat conductive member (not shown) may be provided between the heat source 110 and the container 30 and between the cooling portion 120 and the container 30. The heat conductive member may be, for example, a grease layer.

[0049] In a case where the heat pipe 1 is heated by the heat source 110, in the evaporation portion 4, the working liquid permeating the flow passage of the wick 20 is heated and evaporated to form vapor.

[0050] The vapor generated in the evaporation portion 4 flows through the internal space 11 toward the condensation portion 5 having a lower pressure and temperature than those in the evaporation portion 4. In the condensation portion 5, a part of the vapor is condensed to be the working liquid by cooling the heat pipe 1 with the cooling portion 120. The working liquid generated in the condensation portion 5 permeates into the flow passage of the wick 20.

[0051] The working liquid liquefied in the condensation portion 5 flows in the flow passage of the wick 20 and is refluxed to the evaporation portion 4 through the intermediate portion 6 from the condensation portion 5.

[0052] Here, as shown in FIG. 1, the heat pipe 1 is disposed such that the A axis direction intersects the heat source 110 and the cooling portion 120.

[0053] In this case, in the evaporation portion 4, one thin wall portion 20a of the wick 20 is disposed at a portion closest to the heat source 110. Since the wick 20 of the thin wall portion 20a is thinner than that of the thick wall portion 20b and the thermal resistance of the thin wall portion 20a is smaller than that of the thick wall portion 20b, the heat generated by the heat source 110 can be efficiently transferred toward the inside of the heat pipe 1. That is, in the thin wall portion 20a, the working liquid can be efficiently evaporated. Further, thick wall portions 20b are provided on both sides of the thin wall portion 20a in the circumferential direction.

[0054] In the thick wall portion 20b, the wick 20 is thicker than the thin wall portion 20a, and thus the flow resistance of the working liquid is smaller. Therefore, the working liquid moving from the condensation portion 5 can smoothly move through the thick wall portion 20b having smaller flow resistance, and the working liquid can be efficiently supplied from the thick wall portion 20b to the thin wall portion 20a where a large amount of the working liquid evaporates.

[0055] In addition, in the condensation portion 5, one thin wall portion 20a of the wick 20 is disposed at a portion closest to the cooling portion 120. Since the wick 20 of the thin wall portion 20a is thinner than that of the thick wall portion 20b and the thermal resistance of the thin wall portion 20a is smaller than that of the thick wall portion 20b, the heat can be efficiently transferred from the inside of the heat pipe 1 to the cooling portion 120. That is, in the thin wall portion 20a, the vapor can be efficiently subjected to a phase change to the working liquid in the liquid phase. In the two thick wall portions 20b that sandwich the thin wall portion 20a in the circumferential direction, the wick 20 is thicker than the thin wall portion 20a, so that the flow resistance of the working liquid is smaller. Therefore, the working liquid liquefied in the thin wall portion 20a can be smoothly moved toward the thick wall portion 20b.

[0056] In addition, in a case where the working liquid liquefied in the condensation portion 5 flows in the flow passage of the wick 20 and is returned to the evaporation portion 4 from the intermediate portion 6, the thickness of the wick 20 gradually changes along the longitudinal direction X. Therefore, the working liquid can be smoothly moved. Further, in the intermediate portion 6, since the thickness of the wick 20 is uniform over the entire circumference in the circumferential direction, the flow resistance of the working liquid is small, and the working liquid can be suitably moved from the condensation portion 5 to the evaporation portion 4.

[0057] By circulating the working fluid in the heat pipe 1 including the wick 20 in which the thin wall portion 20a and the thick wall portion 20b are formed, the heat from the heat source 110 can be efficiently transported to the cooling portion 120.

[0058] As described above, a heat pipe 1 includes a container 30 in which a working fluid is sealed, and a wick 20 accommodated in the container 30, in which an evaporation portion 4, a condensation portion 5, and an intermediate portion 6 provided between the evaporation portion 4 and the condensation portion 5 are provided at different positions along a longitudinal direction X of the container 30, in a transverse cross section orthogonal to the longitudinal direction X, a shape of the wick 20 in the intermediate portion 6 is different from a shape of the wick 20 in the evaporation portion 4 and the condensation portion 5, and in the evaporation portion 4 and the condensation portion 5, the wick 20 has an annular shape and includes a thin wall portion 20a and a thick wall portion 20b having a thickness larger than a thickness of the thin wall portion 20a.

[0059] In the wick 20 of the present embodiment, since the thermal resistance in the thin wall portion 20a is small and the flow resistance in the thick wall portion 20b is small, both the reduction of the flow resistance of the working fluid in the wick 20 and the reduction of the thermal resistance of the wick 20 can be achieved. Therefore, the reflux performance of the working fluid can be improved. As a result, the amount of heat transport and the distance of heat transport in the heat pipe 1 can be increased.

[0060] In addition, in the evaporation portion 4 and the condensation portion 5, the thickness of the wick 20 gradually changes along the circumferential direction.

[0061] Accordingly, since the flow resistance of the working liquid can be reduced, the working liquid can be smoothly moved from the thick wall portion 20b to the thin wall portion 20a in the evaporation portion 4 and from the thin wall portion 20a to the thick wall portion 20b in the condensation portion 5.

[0062] In addition, in one transverse cross section, the number of the valley portions 20a1 where the thickness of the wick 20 turns from decrease to increase in the circumferential direction is two, and the number of the peak portions 20b1 where the thickness of the wick 20 turns from increase to decrease in the circumferential direction is two.

[0063] As a result, the thin wall portion 20a can be suitably disposed with respect to the heat source 110 and the cooling portion 120 in order to efficiently perform heat transport.

[0064] In addition, in the intermediate portion 6, the thickness of the wick 20 in the circumferential direction is uniform.

[0065] Accordingly, since the flow resistance of the working liquid in the intermediate portion 6 can be reduced, the working liquid can be smoothly moved from the condensation portion 5 to the evaporation portion 4.<Second Embodiment>

[0066] Next, a second embodiment according to the present invention will be described, but the basic configuration is the same as the configuration of the first embodiment. Therefore, the same configurations are denoted by the same reference signs, the description thereof will be omitted, and only a difference will be described.

[0067] FIG. 4 shows a heat pipe 1 according to the second embodiment. In the present embodiment, the heat pipe 1 is different from the heat pipe 1 of the first embodiment in that the shape of the internal space 11 in the evaporation portion 4 and the condensation portion 5 of the heat pipe 1 is not an elliptical shape.

[0068] FIG. 4 is a transverse cross-sectional view of the evaporation portion 4 of the heat pipe 1 according to the second embodiment. Since the transverse cross section of the condensation portion 5 of the heat pipe 1 according to the second embodiment is also the same as that of FIG. 4, the illustration thereof will be omitted.

[0069] In the evaporation portion 4 and the condensation portion 5 of the heat pipe 1 according to the second embodiment, the thickness of the wick 20 in the thick wall portion 20b is uniform in the circumferential direction. In addition, in the thin wall portion 20a, the thickness of the center portion (valley portion 20a1) of the thin wall portion 20a in the circumferential direction is the thinnest, and gradually increases toward the thick wall portion 20b, and the thickness of the wick 20 is equal to the thickness of the thick wall portion 20b at the end part of the thin wall portion 20a in the circumferential direction. Therefore, in the present embodiment, the entire length of the thick wall portion 20b in the circumferential direction corresponds to the peak portion 20b1.

[0070] As a result, the shape of the internal space 11 is a shape in which an ellipse having the A axis direction as a major axis and a circle having the central axis O as a center are superimposed.

[0071] As described above, in the heat pipe 1 of the present embodiment, since the thickness of the thick wall portion 20b is constant in the evaporation portion 4 and the condensation portion 5, the flow resistance in the thick wall portion 20b can be further reduced.<Third Embodiment>

[0072] Next, a third embodiment according to the present invention will be described, but the basic configuration is the same as the configuration of the first embodiment. Therefore, the same configurations are denoted by the same reference signs, the description thereof will be omitted, and only a difference will be described.

[0073] FIG. 5 shows a heat pipe 1 according to the third embodiment. In the present embodiment, the heat pipe 1 is different from the heat pipe 1 of the first embodiment in that the number of each of the thin wall portion 20a and the thick wall portion 20b in the evaporation portion 4 and the condensation portion 5 of the heat pipe 1 is one. That is, it can also be said that the number of the valley portions 20a1 and the number of the peak portions 20b1 are each one.

[0074] FIG. 5 is a transverse cross-sectional view of the evaporation portion 4 of the heat pipe 1 according to the third embodiment. Since the transverse cross section of the condensation portion 5 of the heat pipe 1 according to the third embodiment is also the same as that of FIG. 5, the illustration thereof will be omitted.

[0075] As shown in FIG. 5, the internal space 11 of the wick 20 of the heat pipe 1 according to the third embodiment has a circular shape. The center O1 of the internal space 11 is provided at a position different from the central axis O of the heat pipe 1. Since the central axis O and the center O1 are different from each other, the thin wall portion 20a and the thick wall portion 20b of the wick 20 are formed.

[0076] For example, in the longitudinal direction X, the center O1 gradually approaches the central axis O from the end parts 1a and 1b of the heat pipe 1 toward the intermediate portion 6, and the center O1 and the central axis O may coincide with each other at a center portion of the heat pipe 1 in the longitudinal direction X.

[0077] In the heat pipe 1 of the present embodiment, in the heat transport device 100, the thin wall portion 20a of the evaporation portion 4 may be disposed to be close to the heat source 110, and the thin wall portion 20a of the condensation portion 5 may be disposed to be close to the cooling portion 120.

[0078] As described above, in the heat pipe 1 of the present embodiment, the center O1 of the internal space 11 of the wick 20 and the central axis O of the heat pipe 1 are provided at different positions.

[0079] Accordingly, since the cross sectional area of the thick wall portion 20b can be ensured to be larger, the working liquid can be transported more efficiently.

[0080] It should be noted that the technical scope of the present invention is not limited to the embodiments or examples described above, and various changes can be made without departing from the gist of the present invention.

[0081] For example, the wick 20 may include the thin wall portion 20a and the thick wall portion 20b in the entire length in the longitudinal direction X. In addition, the shape of the wick 20 in the intermediate portion 6 in the transverse cross section may be the same as the shape of the wick 20 in the evaporation portion 4 and the condensation portion 5.

[0082] In addition, the wick 20 may include the thin wall portion 20a and the thick wall portion 20b in at least one transverse cross section of the entire length of the heat pipe 1 in the longitudinal direction X. For example, only the evaporation portion 4 may have the thin wall portion 20a and the thick wall portion 20b, and the thickness of the wick 20 may be constant over the entire circumference of the intermediate portion 6 and the condensation portion 5. Only the condensation portion 5 has the thin wall portion 20a and the thick wall portion 20b, and the thickness of the wick 20 may be constant over the entire circumference of the intermediate portion 6 and the evaporation portion 4. In this case, the shape of the wick 20 of the intermediate portion 6 in the transverse cross section may be different from the shape of the wick 20 of at least one of the evaporation portion 4 or the condensation portion 5.

[0083] In addition, as shown in FIGS. 6 and 7, the container 30 may have a rectangular shape in a transverse cross section. For example, the container 30 has a dimension in the B axis direction larger than a dimension in the A axis direction, and a surface area of a first surface 32a among the outer peripheral surfaces 32 of the container 30 facing the A axis direction is larger than a surface area of a second surface 32b facing the B axis direction. Since the thin wall portion 20a is provided on a first surface 32a side, the thermal resistance is lower than that of the second surface 32b. And the surface area of the first surface 32a is larger than that of the second surface 32b. Therefore, in a case where the heat source 110 and the cooling portion 120 are disposed on the first surface 32a, heat can be transported more efficiently.

[0084] In addition, as shown in FIG. 6, the internal space 11 may have an elliptical shape in which the A axis is a minor axis and the B axis is a major axis.

[0085] In addition, as shown in FIG. 7, the internal space 11 may have a rectangular shape. That is, in the transverse cross section, the thickness of the thin wall portion 20a may be uniform, and the thickness of the thick wall portion 20b larger than the thickness of the thin wall portion 20a may be uniform.

[0086] In addition, in FIG. 1, the example in which one thin wall portion 20a of the wick 20 is brought close to one heat source 110 has been described, but a plurality of heat sources 110 may be arranged corresponding to positions where a plurality of thin wall portions 20a are arranged. For example, two heat sources 110 facing each other in the A axis direction with the central axis O interposed therebetween may be arranged in the evaporation portion 4. The same applies to the number and arrangement of the cooling portions 120 in the condensation portion 5.

[0087] The entire circumference of the evaporation portion 4 may be covered with the heat source 110, or the entire circumference of the condensation portion 5 may be covered with the cooling portion 120.

[0088] In addition, it is possible to appropriately replace the constituent elements in the above-described embodiment with well-known constituent elements without departing from the scope of the present invention, and the above-described embodiment and modification examples may be appropriately combined.REFERENCE SIGNS LIST

[0089] 1 Heat pipe 4 Evaporation portion 5 Condensation portion 6 Intermediate portion 11 Internal space 20 Wick 20a Thin wall portion 20a1 Valley portion 20b Thick wall portion 20b1 Peak portion 30 Container X Longitudinal direction O Central axis O1 Center of internal space

Claims

1. A heat pipe comprising: a container in which a working fluid is sealed; and a wick accommodated in the container, wherein an evaporation portion, a condensation portion, and an intermediate portion provided between the evaporation portion and the condensation portion are provided at different positions in a longitudinal direction of the container, in a transverse cross section orthogonal to the longitudinal direction, a shape of the wick in the intermediate portion is different from a shape of the wick in the evaporation portion and the condensation portion, and in the evaporation portion and the condensation portion, the wick has an annular shape and includes a thin wall portion and a thick wall portion having a thickness larger than a thickness of the thin wall portion.

2. The heat pipe according to Claim 1, wherein in the evaporation portion and the condensation portion, a thickness of the wick gradually changes along a circumferential direction.

3. The heat pipe according to Claim 1 or 2, wherein in one transverse cross section, the number of valley portions in which a thickness of the wick turns from decrease to increase in a circumferential direction is two, and the number of peak portions in which the thickness of the wick turns from increase to decrease in the circumferential direction is two.

4. The heat pipe according to any one of Claims 1 to 3, wherein a center of an internal space of the wick and a central axis of the heat pipe are provided at different positions.

5. The heat pipe according to any one of Claims 1 to 4, wherein a thickness of the wick in a circumferential direction is uniform in the intermediate portion.

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