Heat pipe

Abstract

Provided is a heat pipe that can enhance the efficiency of reflux of a working fluid, and thus has excellent heat transport characteristics.　A heat pipe 1 includes, in a container 2 which has an internal space S having a working fluid F sealed therein: an evaporation unit 3 that evaporates a liquid-phase working fluid FL to cause phase-change to a gas-phase working fluid Fg; a condensation unit 4 that is disposed at a position separated from the evaporation unit 3, and that condenses the gas-phase working fluid Fg to cause phase-change to a liquid-phase working fluid FL; and an intermediate unit 5 that is positioned between the evaporation unit 3 and the condensation unit 4. The heat pipe has: a first sintered body layer 6 that is made of a sintered body of a first copper powder and that is formed in a specific region on an inner peripheral surface 2a of the container 2 when viewed in a cross section in the evaporation unit 3; and a second sintered body layer 7 that is made of a sintered body of a second copper powder having an average particle diameter larger than that of the first copper powder and that is formed annularly over the entire inner peripheral surface 2a of the container 2 in a state of having the first sintered body layer 6 interposed between the second sintered body layer and the inner peripheral surface 2a of the container 2.

Description

heat pipe

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

[0002] The amount of heat generated by electronic components such as semiconductor elements mounted in recent electric and electronic devices, including laptops, digital cameras, and mobile phones, tends to increase due to the high density of mounting that accompanies the advancement of functionality. Therefore, it is important to adopt a configuration that can cool electronic components efficiently. For example, a method using a heat pipe can be used to cool electronic components.

[0003] Here, a heat pipe generally includes a tubular vessel (container) having an internal space in which a working fluid is sealed. The tubular vessel has an evaporator at one end that evaporates the liquid-phase working fluid to change it to a gas-phase working fluid, and a condenser at the other end that condenses the gas-phase working fluid to change it to a liquid-phase working fluid. The working fluid that has changed from liquid to gas in the evaporator flows from the evaporator to the condenser. The working fluid that has changed from gas to liquid in the condenser flows from the condenser to the evaporator. In this way, a circulating flow is formed between the evaporator and condenser within the tubular vessel due to the reflux of the working fluid, thereby transferring heat between the evaporator and condenser within the tubular vessel.

[0004] For example, Patent Document 1 describes a conventional heat pipe comprising a pipe body having a sealed hollow portion, a porous metal layer disposed in contact with the inner circumferential surface of the pipe body, and a working fluid sealed within the pipe body, wherein the porous metal layer has a first porous portion partitioned in the circumferential direction and a second porous portion having a lower porosity than the first porous portion. In this heat pipe, the liquid phase working fluid is transported mainly by the first porous portion, and heat exchange between the pipe body and the working fluid is achieved mainly by the second porous portion.

[0005] Japanese Patent Application Laid-Open No. 2003-148886

[0006] In the heat pipe described in Patent Document 1, the working fluid changes phase from liquid to gas in the second porous portion, but in order to cope with the ever-increasing heat generation of electronic devices, it is necessary to efficiently circulate a larger amount of working fluid. Here, while it is possible to increase the efficiency of the reflux of the working fluid by increasing the thickness of the second porous portion, this narrows the hollow portion through which the gas-phase working fluid flows, and therefore actually reduces the heat transport characteristics of the heat pipe.

[0007] SUMMARY OF THE INVENTION An object of the present invention is to provide a heat pipe that can increase the efficiency of reflux of a working fluid, thereby providing excellent heat transport properties.

[0008] To achieve the above object, the gist of the present invention is as follows: (1) A heat pipe including a container having an internal space filled with a working fluid, an evaporator section for evaporating the liquid working fluid to change its phase to a gaseous working fluid, a condenser section disposed at a position spaced apart from the evaporator section for condensing the gaseous working fluid to change its phase to a liquid working fluid, and an intermediate section located between the evaporator section and the condenser section, the heat pipe having, as viewed in cross section of the heat pipe at the evaporator section, a first sintered body layer made of a sintered body of a first copper powder and formed in a specific region on an inner circumferential surface of the container, and a second sintered body layer made of a sintered body of a second copper powder having an average particle size larger than that of the first copper powder and formed in an annular shape over the entire inner circumferential surface of the container with the first sintered body layer interposed between the first sintered body layer and the inner circumferential surface of the container. (2) The heat pipe according to (1), wherein, when viewed in a longitudinal cross section including the longitudinal direction of the heat pipe, the length of the first sintered body layer is longer than the longitudinal dimension of the evaporation section, and the length of the second sintered body layer is longer than the length of the first sintered body layer. (3) The heat pipe according to (2), wherein the second sintered body layer terminates at a position in the intermediate section. (4) The heat pipe according to (3), wherein the liquid-phase working fluid that has undergone a phase change in the condensation section flows toward the evaporation section by capillary force through an internal void of the second sintered body layer located in the intermediate section, and flows from the second sintered body layer toward the first sintered body layer through a contact interface between the outer circumferential surface of the second sintered body layer and the inner circumferential surface of the first sintered body layer. (5) The heat pipe according to any one of (1) to (4), wherein the specific region includes a region of the inner circumferential surface of the container that faces the heating element. (6) The heat pipe according to any one of (1) to (5), wherein the inner circumferential surface of the container is formed with a plurality of grooves extending along the longitudinal direction of the container. (7) The heat pipe according to (6), wherein the first sintered body layer is also filled into the grooves located in the specific region.(8) A heat pipe described in (6) or (7) above, in which the second sintered body layer substantially separates the vapor flow of the gas-phase working fluid that has undergone a phase change in the evaporator section from the liquid flow of the liquid-phase working fluid that has undergone a phase change in the condenser section, and the liquid flow is divided into a path that passes through the multiple grooves and a path that passes through the internal voids of the second sintered body layer.

[0009] According to the present invention, it is possible to improve the efficiency of reflux of the working fluid, thereby providing a heat pipe with excellent heat transport properties.

[0010] FIG. 1 is a diagram showing the internal structure of the heat pipe of the first embodiment, in which FIG. 1(a) is a longitudinal cross-sectional view, and FIG. 1(b) is a cross-sectional view of FIG. 1(a). Ａ -I Ａ FIG. 1(c) is a cross-sectional view of the I-thickness portion of FIG. 1(a). Ｂ -I Ｂ Fig. 2 is a cross-sectional view of the heat pipe of Fig. 1, illustrating the flow of working fluid that occurs inside the heat pipe during operation. Fig. 3 is a diagram showing the internal structure of a heat pipe of a second embodiment, with Fig. 3(a) being a longitudinal cross-sectional view and Fig. 3(b) being a cross-sectional view of Fig. 3(a) in section II of Fig. 3(a). Ａ -II Ａ FIG. 3(c) is a cross-sectional view taken along line II of FIG. 3(a). Ｂ -II Ｂ 4A and 4B are cross-sectional views showing the internal structures of the heat pipes of the present invention and the comparative example, where Fig. 4A is a cross-sectional view of the heat pipe of the present invention, and Fig. 4B is a cross-sectional view of the heat pipe of the comparative example.

[0011] Next, heat pipes according to some embodiments of the present invention will be described below.

[0012] First Embodiment FIG. 1 shows the internal structure of a heat pipe according to a first embodiment, with FIG. 1(a) being a longitudinal cross-sectional view and FIG. 1(b) being a cross-sectional view of FIG. 1(a). Ａ -I Ａ FIG. 1(c) is a cross-sectional view of the I-thickness portion of FIG. 1(a). Ｂ -I Ｂ2 is a cross-sectional view illustrating the flow of working fluid that occurs inside the heat pipe of FIG. 1 during operation.

[0013] The heat pipe 1 is a heat pipe in which a liquid phase working fluid F is introduced into a container 2 having an internal space S in which the working fluid F is sealed. Ｌ is evaporated to form a gas phase working fluid F ｇ and a vaporizer 3 for converting the vapor phase working fluid F into a gas phase working fluid F. ｇ is condensed to form a liquid phase working fluid F Ｌ and an intermediate section 5 located between the evaporation section 3 and the condenser section 4. When viewed in cross section at the evaporation section 3, the heat pipe 1 has a first sintered body layer 6 made of a sintered body of a first copper powder and formed in a specific region on the inner circumferential surface 2 a of the container 2, and a second sintered body layer 7 made of a sintered body of a second copper powder having an average particle size larger than that of the first copper powder and formed in an annular shape over the entire inner circumferential surface 2 a of the container 2 with the first sintered body layer 6 interposed between the first sintered body layer 6 and the inner circumferential surface 2 a of the container 2.

[0014] In this heat pipe 1, a second sintered body layer 7 formed from a second copper powder having an average particle size larger than that of the first copper powder is laminated on an inner surface 6 a of a first sintered body layer 6 formed from a first copper powder, and thus a liquid-phase working fluid F flows through voids inside the second sintered body layer 7. Ｌ is supplied to the first sintered body layer 6, and the liquid phase working fluid F reaches the inner circumferential surface 6a of the first sintered body layer 6 and the voids formed therein. Ｌ As heat is transferred to the first sintered body layer 6, the liquid phase working fluid F Ｌ is evaporated to form gas phase working fluid F ｇ This allows heat exchange between the portion of the evaporation section 3 where the first sintered body layer 6 is formed and the working fluid F. Therefore, the heat transferred to the portion of the evaporation section 3 where the first sintered body layer 6 is formed is transferred to the gas-phase working fluid F. ｇIn particular, when the evaporator 3 of the heat pipe 1 is viewed in a cross section perpendicular to the longitudinal direction X, the first sintered body layer 6 is formed in a specific region that is a part of the inner circumferential surface 2a of the container 2, and the second sintered body layer 7 is formed in an annular shape over the entire inner circumferential surface 2a of the container 2. As a result, the entire surface of the first sintered body layer 6 is covered with the liquid-phase working fluid F. Ｌ The first sintered body layer 6 is covered with the second sintered body layer 7 through which the liquid-phase working fluid F flows, and the contact area between the first sintered body layer 6 and the second sintered body layer 7 is increased, so that the liquid-phase working fluid F flows over a wider area of ​​the inner circumferential surface 6a of the first sintered body layer 6. Ｌ is supplied, it is possible to promote the reflux of the working fluid F. At the same time, since the area of ​​the part where reflux takes place, i.e., the area where the second sintered body layer 7 is stacked, becomes larger relative to the area where the first sintered body layer 6 is stacked on the inner peripheral surface 2a of the container 2, it is possible to increase the efficiency of reflux of the working fluid F.

[0015] In this way, in this heat pipe 1, the liquid phase working fluid F Ｌ Since the working fluid can be circulated, the efficiency of the circulating working fluid can be increased, thereby providing a heat pipe with excellent heat transport properties.

[0016] 1 and 2 includes a container 2 having an internal space S in which a working fluid F is sealed. In FIGS. 1 and 2, a tubular vessel is shown as an example of the container 2.

[0017] Here, the shape of the container 2 extending in the longitudinal direction X is not particularly limited, and may be a straight line as shown in FIG. 1( a) or a curved shape such as an L-shape or a U-shape. The outer contour shape of the container 2 when cut perpendicular to the longitudinal direction X is not particularly limited, and may be a substantially circular shape as shown in FIGS. 1( b) and 1(c) or a flattened shape or a polygonal shape such as a square. The thickness of the container 2 is not particularly limited, but may be, for example, in the range of 0.05 mm to 1.0 mm. The outer diameter of the container 2 is not particularly limited, but is preferably in the range of 5 mm to 20 mm when the container 2 has the substantially circular outer contour shape shown in FIGS. 1( b) and 1(c).

[0018] The material of the container 2 is not particularly limited. In particular, when an aqueous liquid is used as the working fluid F, it is preferable to use a metal material from the viewpoint of improving wettability with the working fluid F. In particular, copper, copper alloys, etc. can be used for the container 2 in terms of excellent thermal conductivity. Furthermore, aluminum, aluminum alloys, etc. can be used for the container 2 in terms of lightweighting. Furthermore, stainless steel, etc. can be used for the container 2 in terms of high strength. Furthermore, depending on the usage situation, tin, tin alloys, titanium, titanium alloys, nickel, nickel alloys, etc. may also be used for the container 2.

[0019] [Configuration of Evaporation Section, Condenser Section, and Intermediate Section] The heat pipe 1 is configured to supply a liquid-phase working fluid F Ｌ is evaporated to form a gas phase working fluid F ｇ and a vaporizer 3 for converting the vapor phase working fluid F into a gas phase working fluid F. ｇ is condensed to form a liquid phase working fluid F ＬThe container 2 includes a condenser section 4 that changes the phase of the evaporator 3 to a phase change of 1 / 2, and an intermediate section 5 that is located between the evaporator section 3 and the condenser section 4. Here, the evaporator section 3, the condenser section 4, and the intermediate section 5 can each be provided at a portion along the longitudinal direction X of the container 2, as shown in FIG. 1( a). The container 2 shown in FIG. 1( a) has the evaporator section 3 at one end portion, the condenser section 4 at the other end portion, and the intermediate section 5 between the evaporator section 3 and the condenser section 4, and is configured as a sealed tube.

[0020] 1(a), the evaporation section 3 is formed at one end of the container 2 and has a function of receiving (absorbing) heat from a thermally connected heating element 9. Specifically, the evaporation section 3 is, for example, as shown in FIG. Ｌ is evaporated to form a gas phase working fluid F ｇ By changing the phase of the fuel to the fuel, the fuel absorbs the heat received from the heating element 9 as latent heat of evaporation.

[0021] In the evaporation section 3, heat generated from the heating element 9 is transferred to the first sintered body layer 6 through the container 2, and further transferred from the first sintered body layer 6 to the second sintered body layer 7. On the other hand, as shown in FIG. 2, the liquid phase working fluid F supplied from the condenser section 4 to the evaporation section 3 is Ｌ is supplied from the second sintered body layer 7 to the first sintered body layer 6 in the evaporation section 3. Therefore, the liquid phase working fluid F Ｌ Gas phase working fluid F ｇ The phase change to the liquid phase of the working fluid F in the first sintered body layer 6 mainly occurs in the first sintered body layer 6, but may occur partly in the second sintered body layer 7. Ｌ The vapor phase working fluid F produced by evaporation of ｇ moves into the internal space S through the voids formed inside the second sintered body layer 7.

[0022] The condenser 4 is disposed at a position separated from the evaporator 3, and in FIG. 1, for example, is disposed at the other end of the container 2. The condenser 4 converts the gas-phase working fluid F, which has undergone a phase change in the evaporator 3 and has been transported, into the gas-phase working fluid F. ｇ The condenser 4 has a function of dissipating the latent heat of vaporization of the working fluid F by a heat exchanger (not shown). ｇ is condensed to form a liquid phase working fluid F ＬThe heat transported as the latent heat of condensation of the working fluid F is released to the outside of the heat pipe 1.

[0023] [Configuration of the first sintered layer] The first sintered layer 6 is made of a sintered body of a first copper powder, and is a sintered body layer formed in a specific region on the inner circumferential surface 2a of the container 2 when viewed in a cross section perpendicular to the longitudinal direction X of the heat pipe 1 in the evaporation section 3. The first sintered layer 6 is made of a sintered body of a first copper powder having a smaller average particle size than the second sintered layer 7 described later, and therefore has a smaller average particle size than the second sintered layer 7. Ｌ The gap through which the liquid phase working fluid F can flow is small. Ｌ The flow rate of the working fluid F is slow. In addition, since the first sintered body layer 6 is adjacent to the inner circumferential surface 3a of the evaporation section 3 of the container 2, the temperature of the first sintered body layer 6 is likely to become relatively high. Therefore, the flow of the working fluid F in the first sintered body layer 6 is similar to the flow of the working fluid F in the liquid phase supplied from the inner circumferential surface 6a side and penetrating into the first sintered body layer 6, as shown in FIG. Ｌ and the flow of the liquid-phase working fluid F that has penetrated into the first sintered body layer 6. Ｌ The gas phase working fluid F flows from the inside of the first sintered body layer 6 through the inner peripheral surface 6 a toward the internal space S. ｇ By using such a first sintered body layer 6, heat received (absorbed) from a heat generating element (not shown) thermally connected to the container 2 is transferred to the first sintered body layer 6, and most of the heat is retained on a specific region of the inner circumferential surface 2 a of the container 2, and the liquid phase working fluid F Ｌ The specific region of the inner circumferential surface 2 a of the container 2 can be a region including the region of the inner circumferential surface 2 a that constitutes the portion of the container 2 facing the heating element 9.

[0024] As shown in FIG. 1( a), the first sintered body layer 6 is provided at least in the evaporation section 3. By providing such a first sintered body layer 6 in the evaporation section 3, the liquid phase working fluid F in the evaporation section 3 can be Ｌ Since the evaporation of the working fluid F is promoted, the heat received from the heating element 9 thermally connected to the evaporation section 3 can be absorbed by a larger amount of the working fluid F as latent heat of evaporation.

[0025] Here, the length L of the first sintered body layer 6 １ is the longitudinal dimension L of the evaporator 3 when viewed in a vertical cross section including the longitudinal direction X of the heat pipe 1. ０ As a result, the first sintered body layer 6 is provided adjacent to both the inner circumferential surface 3a of the evaporation section 3 and the inner circumferential surface 5a of the intermediate section 5. In this way, the length L of the first sintered body layer 6 is preferably longer than １ By configuring the first sintered body layer 6 as described above, heat directed from the heating element 9 toward the intermediate portion 5 can be conducted to the first sintered body layer 6 and absorbed by the working fluid F. In particular, from the viewpoint of efficiently absorbing heat directed from the heating element 9 toward the intermediate portion 5 into the working fluid F, it is more preferable that the first sintered body layer 6 is disposed at least in a region of the inner circumferential surface 2a of the container 2 that forms a portion facing the heating element 9, and in regions of the inner circumferential surface 2a of the container 2 adjacent to both sides of that region, when viewed in vertical cross section. On the other hand, the disposition length L of the first sintered body layer 6 １ The upper limit of the thickness is preferably 150 mm or less, from the viewpoint of facilitating the production of the first sintered body layer 6 by the production method described later.

[0026] Furthermore, when viewed in a cross section perpendicular to the longitudinal direction X of the heat pipe 1, it is preferable that the length of the portion of the inner circumferential surface 2a of the container 2 where the first sintered body layer 6 is disposed is longer than the region of the inner circumferential surface 2a that constitutes the portion facing the heating element 9. In particular, it is more preferable that the first sintered body layer 6 is disposed at least in the region of the inner circumferential surface 2a of the container 2 that constitutes the portion facing the heating element 9 and in regions on the inner circumferential surface 2a of the container 2 adjacent to both sides of that region when viewed in cross section. By configuring the first sintered body layer 6 in this manner, heat transferred from the heating element 9 to the container 2 can be efficiently conducted to the first sintered body layer 6 and absorbed by the working fluid F.

[0027] In this specification, the inner peripheral surface refers to the surface along the wall surface on the side of the internal space S. In addition, the outer peripheral surface refers to the surface along the wall surface on the side away from the internal space S. In addition, the longitudinal dimension L of the evaporation section 3 ０ can be the size of the heating element 9 thermally connected to the heat pipe 1 along the longitudinal direction X of the heat pipe 1.

[0028] The first sintered body layer 6 is preferably formed of a sintered body of the first copper powder and is made of a porous material different from the bulk material. By forming the first sintered body layer 6 from a porous material, the surface area of ​​the first sintered body layer 6 is increased, so that the liquid-phase working fluid F Ｌ In addition, by forming the first sintered layer 6 from a sintered body of copper powder, it is possible to improve wettability with the working fluid F and increase thermal conductivity.

[0029] The average particle size (average primary particle size) of the first copper powder is not particularly limited, but may be, for example, in the range of 0.01 μm to 200 μm. The average particle size in this specification is the particle size at 50% of the volume-based integrated value in the particle size distribution measured by a laser diffraction / scattering particle size distribution measurement method. The thickness of the first sintered body layer 6 is not particularly limited, but may be, for example, in the range of 0.1 mm to 1 mm.

[0030] [Configuration of the second sintered body layer] The second sintered body layer 7 is made of a sintered body of a second copper powder having a larger average particle size than the first copper powder, and is a sintered body layer formed in a ring shape over the entire inner circumferential surface 2a of the container 2, with the first sintered body layer 6 interposed between the second sintered body layer 7 and the inner circumferential surface 2a of the container 2, when viewed in a cross section perpendicular to the longitudinal direction X of the heat pipe 1 in the evaporation section 3. Here, the second sintered body layer 7 is layered on the inner circumferential surface 6a of the first sintered body layer 6, and is also layered on the inner circumferential surface 2a of the container 2 on which the first sintered body layer 6 is not layered, and these are positioned so as to extend continuously. Since the second sintered body layer 7 is made of a sintered body of the second copper powder having a larger average particle size than the first sintered body layer 6, large voids are formed inside, and these voids serve as a space for the liquid-phase working fluid F Ｌ In order to form a flow path in which the liquid phase working fluid F Ｌ The second sintered body layer 7 is also a portion where the temperature is less likely to become high than the first sintered body layer 6. Therefore, when viewed in a cross section perpendicular to the longitudinal direction X of the heat pipe 1, the flow of the working fluid F inside the second sintered body layer 7 is the same as that of the liquid phase working fluid F supplied from the condenser 4 as shown in FIG. ＬThe flow of the working fluid F in the gas phase generated mainly in the first sintered body layer 6 along the inner peripheral surface 2a of the container. ｇ The main flow is toward the internal space S.

[0031] Length L of the second sintered body layer ２ is the length L of the first sintered body layer 6 when viewed in a vertical cross section including the longitudinal direction X of the heat pipe 1 as shown in FIG. １ In this case, the second sintered body layer 7 extends continuously from the inner peripheral surface 6a of the first sintered body layer 6 in the evaporation section 3 to the inner peripheral surface 5a of the intermediate section 5. As a result, the liquid-phase working fluid F sucked up by the second sintered body layer 7 at the inner peripheral surface 5a of the intermediate section 5 is Ｌ is smoothly supplied to the inner peripheral surface 6a of the first sintered body layer 6 through the voids formed inside the second sintered body layer 7, so that the liquid phase working fluid F Ｌ In addition, the liquid phase working fluid F Ｌ flows from the inner circumferential surface 5a of the intermediate portion 5 toward the tip of the evaporation portion 3 along the longitudinal direction X of the container through the gap formed inside the second sintered body layer 7, so that the liquid phase working fluid F Ｌ and the gas phase working fluid F passing through the internal space S. ｇ The working fluid F in the liquid phase is allowed to flow over a wider area of ​​the inner peripheral surface 6a of the first sintered body layer 6 in the evaporation section 3. Ｌ can be supplied.

[0032] Here, when viewed in a longitudinal cross section including the longitudinal direction X of the heat pipe 1, the flow of the working fluid F inside the second sintered body layer 7 is as follows: Ｌ The flow of the working fluid F in the gas phase generated in the first sintered body layer 6 flows toward the tip of the evaporator 3 along the longitudinal direction X of the container. ｇ The main flow is toward the internal space S.

[0033] In particular, it is preferable that the second sintered body layer 7 terminates at any position in the intermediate portion 5. In this case, the second sintered body layer 7 extends so as to be in contact with both the inner circumferential surface 6a of the first sintered body layer 6 and the inner circumferential surface 5a of the intermediate portion 5. Furthermore, the second sintered body layer 7 has both an outer circumferential surface 7b located on the inner circumferential surface 6a of the first sintered body layer 6 and an outer circumferential surface 7b' located on the inner circumferential surface 5a of the intermediate portion 5 of the container 2. On the other hand, it is preferable that the second sintered body layer 7 does not contact the condenser portion 4, from the viewpoint of lowering the temperature of the condenser portion 4 and promoting condensation of the working fluid F.

[0034] Here, the liquid-phase working fluid F that has undergone a phase change in the condenser 4 Ｌ is preferably configured so that the working fluid F flows toward the evaporation section 3 by capillary force through the internal voids of the second sintered body layer 7 located in the intermediate section 5, and flows from the second sintered body layer 7 toward the first sintered body layer 6 through the contact interface between the outer peripheral surface 7b of the second sintered body layer 7 and the inner peripheral surface 6a of the first sintered body layer 6. By configuring the second sintered body layer 7 in this way, the working fluid F in the liquid phase can be Ｌ is transported from the inner peripheral surface 5a of the intermediate portion 5 along the second sintered body layer 7 extending in the longitudinal direction X of the container 2 to the portion in contact with the first sintered body layer 6, and is evaporated from a wider area of ​​the first sintered body layer 6. As a result, the liquid-phase working fluid F Ｌ By efficiently evaporating the heat, the thermal resistance of the heat pipe 1 can be reduced.

[0035] The second sintered body layer 7 is provided on the inner peripheral surface 2 a of the container 2 and is configured to supply the liquid-phase working fluid F Ｌ The second sintered body layer 7 is configured so that the liquid flow of the working fluid F in the gas phase, which has undergone a phase change in the evaporation section 3, flows at least in the internal voids of the second sintered body layer 7. ｇ and the liquid-phase working fluid F that has undergone a phase change in the condenser 4. Ｌ It is preferable that the second sintered body layer 7 is configured to be substantially isolated from the liquid flow of the liquid phase working fluid F. Ｌ and the gas phase working fluid F passing through the internal space S. ｇ The working fluid F in the vapor phase in the evaporation section 3 and the intermediate section 5 is contacted with the ｇ This makes it difficult for unintended condensation to occur.

[0036] The second sintered body layer 7 is made of a sintered body of a second copper powder, which is a porous material and has a larger average particle size than the first copper powder. As a result, the second sintered body layer 7 is filled with the liquid-phase working fluid F Ｌ Since pores through which the liquid phase working fluid F can pass are formed, Ｌ can be transported from the inner peripheral surface 5a of the intermediate portion 5 to the inner peripheral surface 6a of the first sintered body layer 6. In addition, by forming the second sintered body layer 7 from a sintered body of copper powder, it is possible to improve wettability with the working fluid F and increase thermal conductivity. Therefore, the second sintered body layer 7 has high thermal conductivity and can easily absorb the liquid phase working fluid F. Ｌ This allows the first sintered body layer 6, from which the sintered body 6 evaporates, to exhibit resistance to dry-out.

[0037] Here, the average particle size (average primary particle size) of the second copper powder constituting the second sintered body layer 7 is not particularly limited, but may be, for example, in the range of 100 μm to 500 μm. Furthermore, the ratio of the average particle size of the second copper powder to the average particle size of the first copper powder is not particularly limited, but may be, for example, in the range of 2 to 5. On the other hand, the thickness of the second sintered body layer 7 is not particularly limited, but may be, for example, in the range of 0.3 mm to 5 mm.

[0038] The area ratio of the second sintered body layer 7 to the total area of ​​the first sintered body layer 6 and the second sintered body layer 7 is preferably in the range of 50% to 90% when the evaporation section 3 is viewed in a cross section perpendicular to the longitudinal direction X of the heat pipe 1. By increasing the area ratio of the second sintered body layer 7 in this way, the liquid phase working fluid F passing through the inside of the second sintered body layer 7 can be reduced. Ｌ Since the flow rate of the working fluid F increases, the efficiency of the reflux of the working fluid F can be further improved.

[0039] [Operation Principle of Heat Pipe] Next, the operation principle of the heat pipe 1 will be described using the heat pipe 1 of the first embodiment shown in Figures 1 and 2. Here, the heat pipe 1 is configured to have a liquid-phase working fluid F Ｌ is sealed in the internal space S.

[0040] First, the liquid phase working fluid F Ｌis supplied to the portion of the inner circumferential surface 2a of the container 2 that is in contact with the second sintered body layer 7. Ｌ The supply means is not particularly limited. For example, the second sintered body layer 7 may be supplied with a liquid-phase working fluid F Ｌ By using the capillary force that occurs when the second sintered body layer 7 comes into contact with the liquid phase working fluid F Ｌ Since it is possible to supply the above, it is possible to make the occurrence of dry out less likely.

[0041] The liquid-phase working fluid F supplied to the portion of the inner circumferential surface 2a of the container 2 that is in contact with the second sintered body layer 7 Ｌ is configured so that at least a part of the working fluid F in the liquid phase is absorbed into the second sintered body layer 7 and flows into the internal voids of the second sintered body layer 7. In particular, when a plurality of grooves 8 are formed on the inner peripheral surface 2a of the container 2 as described later, the working fluid F in the liquid phase Ｌ The second sintered body layer 7 may be configured such that the liquid flow is divided into a path that passes through the plurality of grooves 8 and a path that passes through the internal voids of the second sintered body layer 7.

[0042] The liquid phase working fluid F absorbed in the second sintered body layer 7 Ｌ The working fluid F flows along the longitudinal direction X due to the capillary force of the second sintered body layer 7 and is absorbed by the first sintered body layer 6 over a wide area where the second sintered body layer 7 and the first sintered body layer 6 come into contact. On the other hand, the working fluid F that flows through the grooves 8 without being absorbed by the second sintered body layer 7 Ｌ is absorbed by the first sintered layer 6 or the second sintered layer 7 in the area where the groove 8 and the first sintered layer 6 or the second sintered layer 7 are close to each other.

[0043] Here, when the evaporation section 3 of the heat pipe 1 receives heat from the thermally connected heating element 9, the liquid phase working fluid F Ｌ On the surface of the first sintered body layer 6 to which the working fluid F in liquid phase is supplied, Ｌ is evaporated to form a gas phase working fluid F ｇ In particular, in the heat pipe 1, the liquid phase working fluid F is absorbed in the portion of the container 2 facing the heating element 9 and in the vicinity thereof. Ｌ The gas phase working fluid F ｇSince the phase change can be efficiently performed, the thermal resistance of the heat pipe 1 can be significantly reduced.

[0044] The vapor phase working fluid F that has absorbed heat in the evaporation section 3 ｇ flows through the vapor flow path, which is the internal space S of the container 2, from the evaporator (heat receiving section) 3 to the condenser (heat radiating section) 4 along the longitudinal direction X of the container 2, and the heat received from the heating element 9 is transported from the evaporator 3 to the condenser 4 via the intermediate section 5. At this time, the gas-phase working fluid F transported from the evaporator 3 to the condenser 4 via the intermediate section 5 is ｇ is the liquid phase working fluid F passing through the inside of the second sintered body layer 7. Ｌ Since it becomes difficult for the gas phase working fluid F ｇ This prevents the circulation flow of the working fluid F from being disturbed by a counter flow of the working fluid F. Therefore, the heat pipe 1 can achieve excellent heat transport characteristics.

[0045] Thereafter, the gas phase working fluid F transported to the condenser 4 ｇ is changed into a liquid phase in the condenser 4 by a heat exchanger (not shown). At this time, the heat of the transported heating element 9 is released to the outside of the heat pipe 1 as latent heat of condensation. Then, the liquid-phase working fluid F that has released heat in the condenser 4 and changed into a liquid phase is Ｌ is supplied to the inner circumferential surface 2a of the container 2 along the longitudinal direction X to the part of the inner circumferential surface 2a of the container 2 that is in contact with the second sintered body layer 7, thereby forming a circulating flow of working fluid between the evaporation section 3 and the condensation section 4.

[0046] Second Embodiment FIG. 3 is a diagram showing the internal structure of a heat pipe according to a second embodiment, in which FIG. 3(a) is a longitudinal cross-sectional view, and FIG. 3(b) is a cross-sectional view of FIG. 3(a). Ａ -II Ａ FIG. 3(c) is a cross-sectional view taken along line II of FIG. 3(a). Ｂ -II Ｂ 3 is a cross-sectional view taken along the line 3. Note that the components shown in Fig. 3 that are the same as those of the heat pipe 1 shown in Fig. 1 are denoted by the same reference numerals.

[0047] In the heat pipe 1 shown in the first embodiment, the inner circumferential surface 2a of the container 2 is configured as a smooth surface, but this is not limiting. For example, as in the heat pipe 1A shown in Fig. 3, the inner circumferential surface 2a of the container 2A may be formed with a plurality of grooves 8 extending along the longitudinal direction L of the container 2A. By providing such grooves 8, the liquid-phase working fluid F inside the heat pipe 1 can be easily Ｌ When transporting the liquid phase working fluid F Ｌ The capillary force can be exerted so that the liquid-phase working fluid F moves along the grooves 8 and the second sintered body layer 7 on the inner circumferential surface 2a of the container 2A. Ｌ The reverse operation capability means that the heat pipe can function even when the evaporator 3 is located higher than the condenser 4.

[0048] These grooves 8 preferably extend in the longitudinal direction X on the inner peripheral surface 2a from the condenser section 4 to the portion where the second sintered body layer 7 is located, and more preferably the grooves 8 extend continuously from the condenser section 4 to the evaporation section 3. This allows the liquid-phase working fluid F to flow smoothly from the condenser section 4 to the portion where the second sintered body layer 7 is located. Ｌ Since the transport of the working fluid F in the liquid phase is promoted, the working fluid F in the liquid phase is transported to the first sintered body layer 6 in the evaporation section 3 through the second sintered body layer 7. Ｌ In particular, by providing the grooves 8 that are continuous from the condenser section 4 to the evaporator section 3, the transport of the liquid-phase working fluid F Ｌ can be supplied to the first sintered body layer 6 located in the evaporation section 3 through both a path passing through the inside of the second sintered body layer 7 and a path passing through the grooves 8.

[0049] The container 2A having the groove 8 may be a grooved pipe in which the groove 8 extending in the longitudinal direction X of the container 2A is formed on the inner circumferential surface 2a of the container 2A. In particular, by configuring the container 2A as a grooved pipe, the liquid-phase working fluid F can be circulated throughout the entire length of the container 2A. Ｌ Therefore, when the heat pipe 1A is installed in the top heat position, that is, when the liquid phase working fluid FＬ Even if the evaporation section 3 downstream of the condenser section 4 and the intermediate section 5 is installed above the condenser section 4 and the intermediate section 5, the liquid phase working fluid F Ｌ This makes it easier to transport the goods.

[0050] The opening width of these grooves 8 is not particularly limited, but it is Ｌ From the viewpoint of promoting the transport of the particles, the thickness may be set to, for example, 0.1 mm to 1 mm.

[0051] The first sintered body layer 6A of the heat pipe 1A is preferably formed to fill the grooves 8 located in specific regions on the inner circumferential surface 2a of the container as well. That is, the first sintered body layer 6A is preferably formed to include the container 2A side of the imaginary inner circumferential surface 3b, which is a hypothetical case where the grooves 8 are not formed in the evaporation section 3 of the container. More preferably, the first sintered body layer 6A fills part or all of the grooves 8 in the longitudinal direction X. In particular, the first sintered body layer 6A is preferably formed to contact the bottom of the grooves 8, as shown in FIG. 3(b). This allows the liquid-phase working fluid F transported along the grooves 8 to flow smoothly. Ｌ However, when the working fluid F comes into contact with the first sintered body layer 6A, it is easily sucked up by the first sintered body layer 6A, and the working fluid F in the liquid phase Ｌ This can further promote evaporation of the solvent.

[0052] Here, as shown in Fig. 3(a), it is preferable that the inner peripheral surface of the first sintered body layer 6A is configured to be located closer to the central axis position M of the internal space S of the container 2A than the boundary surface position N, which is located in the intermediate portion 5 and where the part of the second sintered body layer 7A and the part of the inner peripheral surface 2a of the container 2A come into contact. This allows the liquid-phase working fluid F flowing through the second sintered body layer 7A to flow closer to the central axis position M of the internal space S of the container 2A. Ｌ At least a part of the flow of the working fluid F impinges on the first sintered body layer 6A, so that the working fluid F in the liquid phase flows from the second sintered body layer 7A to the first sintered body layer 6A. Ｌ This can promote the distribution of

[0053] The first sintered body layer 6A may also be configured such that a space of the groove 8 exists between the inner peripheral surface 2a of the container 2A and the outer peripheral surface 6b of the first sintered body layer 6A. This allows the liquid-phase working fluid F that has undergone a phase change in the condenser 4 to flow through the groove 8. Ｌ The liquid phase working fluid F can be more quickly moved through the grooves 8 to the position of the evaporation section 3 where the outer peripheral surface of the first sintered body layer 6A is present. As a result, the liquid phase working fluid F can be more quickly moved from the condensation section 4 to the evaporation section 3. Ｌ This can further promote the circulation of waste.

[0054] The second sintered body layer 7A of the heat pipe 1A is a gas-phase working fluid F that has undergone a phase change in the evaporation section 3. ｇ and the liquid-phase working fluid F that has undergone a phase change in the condenser 4. Ｌ and the liquid flow of the working fluid F Ｌ It is preferable that the liquid flow of the working fluid F is divided into a path passing through the plurality of grooves 8 and a path passing through the internal voids of the second sintered body layer 7A. This allows a larger amount of liquid-phase working fluid F to flow in the area where the second sintered body layer 7A and the grooves 8 are arranged. Ｌ Since the liquid phase working fluid F in this part can flow, Ｌ In addition, in the portion where the path passing through the plurality of grooves 8 and the path passing through the internal voids of the second sintered body layer 7 are formed in parallel, the liquid phase working fluid F Ｌ Since the liquid phase working fluid F in the intermediate section 5 and the evaporation section 3 is sucked up more strongly, Ｌ This increases the flow rate of the heat pipe 1, thereby further improving the heat transport characteristics of the heat pipe 1.

[0055] The average particle size (average primary particle size) of the second copper powder constituting the second sintered body layer 7A is not particularly limited, and may be in the range of 100 μm to 500 μm, similar to the above-mentioned heat pipe 1. On the other hand, the average particle size (average primary particle size) of the second copper powder constituting the second sintered body layer 7A is set to be equal to or larger than the diameter of the liquid-phase working fluid F formed in the grooves 8. Ｌ From the viewpoint of not obstructing the flow path of the groove 8, it is preferable that the groove width be larger than that of the groove 8.

[0056] The second sintered body layer 7A is formed in the grooves 8 by the liquid-phase working fluid F ＬFrom the viewpoint of not obstructing the flow path of the second sintered body layer 7A, it is preferable not to fill the grooves 8. Here, means for forming the second sintered body layer 7A so as not to fill the grooves 8 include a means for using, as the second copper powder, copper powder having a larger average particle size than the above-mentioned first copper powder, and a means for sintering the second copper powder by weakening the force applied to the copper powder when loading it into the container 2.

[0057] <Other Embodiments> In the above-described embodiment, the container 2 extends toward one side of the evaporation section 3 and has one condenser section 4 and one intermediate section 5, but the present invention is not limited to this configuration. For example, the container 2 may extend from the evaporation section 3 in multiple directions, and the condenser sections 4 and intermediate sections 5 may be provided in multiple locations. In the heat pipe 1, the container 2 may extend from the evaporation section 3 in multiple directions, and the liquid-phase working fluid F may be condensed. Ｌ Even if the flow rate of the condenser 1 is increased, the heat received from the heating element 9 as latent heat of evaporation can be efficiently transferred to the plurality of condensation sections.

[0058] <Method for Manufacturing Heat Pipe> A specific example of a method for manufacturing a heat pipe will now be described.

[0059] The shape of the container 2, such as a tubular vessel, used in the heat pipe 1 can be appropriately selected from pipe, plate, foil, etc., depending on the shape of the heat pipe 1. Dirt and other contaminants adhering to the surface of the container 2 may lead to a decrease in the heat transfer capacity of the heat pipe, so it is preferable to clean it. Cleaning can be performed by a common method, such as solvent degreasing, electrolytic degreasing, etching, or oxidation treatment.

[0060] A core rod (e.g., a stainless steel core rod) having a shape that will serve as a mold for the first sintered body layer 6 is inserted into the center of the interior of this container 2, and then a first copper powder, which is the raw material for the first sintered body layer 6, is loaded into the gap formed between the inner circumferential surface 2a of the container 2 and the outer surface of the core rod. The loaded first copper powder is sintered to form the first sintered body layer 6. The core rod is pulled out and removed from the container 2 on which the first sintered body layer 6 has been formed. Here, from the viewpoint of providing the first sintered body layer 6 only in a specific region on the inner circumferential surface 2a of the container 2, the formed first sintered body layer 6 may be subjected to cutting or the like.

[0061] Next, a core rod (e.g., a stainless steel core rod) having a shape that will serve as a mold for the second sintered body layer 7 is inserted into the center of the interior of the container 2, and second copper powder, which is the raw material for the second sintered body layer 7, is filled into the gap formed between the inner surface of the container 2 and the outer surface of the core rod. The filled second copper powder is sintered to form the second sintered body layer 7. The core rod is pulled out and removed from the container 2 on which the second sintered body layer 7 has been formed.

[0062] Here, the sintering of the first and second copper powders, which are the raw materials for the first sintered body layer 6 and the second sintered body layer 7, may be carried out under conditions that are generally used, and is not particularly limited. Examples of sintering conditions include a mixture of hydrogen gas, a mixture of hydrogen gas and an inert gas (N ２ For example, the reduction can be carried out by performing a heat treatment in an atmosphere of a reducing gas such as a mixed gas containing Ar, He, or the like.

[0063] After the first sintered body layer 6 and the second sintered body layer 7 are formed in the container 2, only one end of the container 2 is sealed except for the other end, which is the sealing port, and the working fluid F is poured through the sealing port. After pouring the working fluid F, the inside of the container 2 is degassed by heat degassing, vacuum degassing, or the like to reduce the pressure. The sealing port is then sealed to produce the heat pipe 1.

[0064] The sealing method is not particularly limited, and examples thereof include TIG welding, resistance welding, pressure welding, and soldering. The first sealing (sealing only the other end) is a step performed to seal the area other than the area from which the internal gas escapes during subsequent evacuation, and the second sealing (sealing the filling port) is a step performed to seal the area from which the internal gas escapes during evacuation.

[0065] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, but includes all aspects encompassed by the concept of the present invention and the scope of the claims, and can be modified in various ways within the scope of the present invention.

[0066] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0067] (Example of the Invention) The heat pipe 1B of this example of the invention is an example of a cylindrical heat pipe 1 having the internal structure shown in Figure 1. A cylindrical tubular vessel having a length of 400 mm along the longitudinal direction X and a diameter (inner diameter) of 7 mm was used as the container 2. A stainless steel core rod having a shape that would form the first sintered body layer 6B was inserted into the center of the container 2, and copper powder (first copper powder) having an average particle size (average primary particle size) of 100 µm, which was the raw material for the first sintered body layer 6B, was filled into the gap formed between the inner surface of the grooved tube and the outer surface of the core rod. The container 2 filled with the first copper powder was then subjected to a heat treatment in a reducing gas atmosphere to sinter the copper powder, and the core rod was then pulled out and removed from the container 2. As a result, a first sintered body layer 6B made of a sintered copper body and having a thickness of 0.5 mm was formed in a specific region on the inner circumferential surface 2a of the container 2, more specifically, in a region having an area ratio of 67% of the entire area of ​​the inner circumferential surface 2a of the portion that becomes the evaporation section 3, including the entire region of the inner circumferential surface 2a that constitutes the portion facing the heating element 9. Here, when the portion that becomes the evaporation section 3 of the heat pipe 1B is viewed in a cross section perpendicular to the longitudinal direction X, the length of the region that constitutes the portion of the inner circumferential surface 2a of the container 2 that faces the heating element 9 was 50% of the entire length of the inner circumferential surface 2a, and the region where the first sintered body layer 6B was formed was arranged in the region of the inner circumferential surface 2a that constitutes the portion facing the heating element 9 and in regions on the inner circumferential surface 2a adjacent to the region so that the sizes of both regions were equal. The region of the inner circumferential surface 2a of the container 2 that faces the heating element 9 is set in a range from 15 mm to 55 mm from the tip of the container 2 on the evaporator 3 side when viewed in a vertical cross section including the longitudinal direction X of the heat pipe 1B, and the range from the tip of the evaporator 3 side to the 55 mm position is defined as the evaporator 3. Therefore, the longitudinal dimension L of the evaporator 3 is ０ The first sintered body layer 6B is provided in a range from the tip of the evaporator 3 to a position 60 mm from the longitudinal cross section of the heat pipe 1B including the longitudinal direction X. Therefore, the length L of the first sintered body layer 6B along the longitudinal direction X is １ is 60 mm.

[0068] Next, a stainless steel core rod having a shape that would become the mold for the second sintered body layer 7 was inserted into the center of the container 2, and copper powder (second copper powder) having an average particle size (average primary particle size) of 200 μm, which was the raw material for the second sintered body layer 7, was filled into the gap formed between the inner surface of the grooved tube and the outer surface of the core rod. Then, the container 2 filled with the second copper powder was subjected to a heat treatment in a reducing gas atmosphere to sinter the copper powder, and then the core rod was pulled out and removed from the container 2. As a result, from the tip of the container 2 on the evaporation section 3 side to the intermediate section 5, as shown in Figure 4 (a), with the first sintered body layer 6B partially interposed between the inner surface 2a of the container 2 and the second sintered body layer 7 made of a copper sintered body was formed on the entire inner surface 2a of the container 2 when viewed in a cross section perpendicular to the longitudinal direction X, with the second sintered body layer 7 having a length of 250 mm along the longitudinal direction X and an inner diameter of 5 mm (the thickness of the part where the first sintered body layer 6B is formed is 0.5 mm, and the thickness of the part where the first sintered body layer 6B is not formed is 1.0 mm).

[0069] After the first sintered body layer 6 and the second sintered body layer 7 were formed, only one end of the container 2 was sealed except for the inlet, and water, which was the liquid-phase working fluid F(L), was poured into the inlet. Next, the inside of the container 2 was evacuated to a reduced pressure, and then the inlet was sealed to produce the heat pipe 1.

[0070] 4(b), the heat pipe 10 of the comparative example was fabricated such that a first sintered body layer 6C made of a sintered copper body, having an arrangement length of 60 mm along the longitudinal direction X and a thickness of 0.5 mm, was formed on the entire inner peripheral surface 2a of the container 2. Other than that, the heat pipe 10 was fabricated to have the same configuration as the heat pipe of the present invention.

[0071] Here, Figure 4 is a cross-sectional view showing the internal structure of a heat pipe of an example of the present invention and a comparative example, where Figure 4(a) is a cross-sectional view of a heat pipe 1 of an example of the present invention, and Figure 4(b) is a cross-sectional view of a heat pipe 10 of the comparative example.

[0072] (Performance Evaluation) The performance of the heat pipe was evaluated under the following conditions. 1. A heater block (heat generating capacity 50 W to 250 W) was attached as a heating element to the outer surface of the evaporator (heat receiving section), which is one end of the heat pipe. 2. A heat exchanger was attached to the condenser (heat dissipation section), which is the other end of the heat pipe. 3. A heat insulating material was attached to the intermediate section between the evaporator and condenser sections to create an insulated section. 4. With the heat input to the evaporator section installed horizontally, the heat input was gradually increased from 50 W, and the magnitude of the heat input when the difference between the temperature of the heating element and the temperature of the condenser section was minimized was measured, and this measured heat input was defined as the maximum heat transport capacity Qmax (W). 5. The difference between the temperature of the heating element and the temperature of the condenser was measured, and the value divided by the heat input was defined as the thermal resistance (°C / W).

[0073] The results of the maximum heat transport quantity Qmax were expressed as a relative value when the comparative example in which the first sintered body layer 6 was formed on the entire inner peripheral surface 2a of the container 2 was used as the reference (index ratio 100). The results are shown in the "Relative value of maximum heat transport quantity" column of Table 1.

[0074]

[0075] As a result, the heat pipe 1 of the present invention had a relative value of the maximum heat transport capacity Qmax of 128 when the comparative example in which the first sintered body layer 6 was formed on the entire inner surface 2a of the container 2 was used as the reference (index ratio 100).

[0076] Therefore, the heat pipe 1 of the present invention had a larger relative value of the maximum heat transport quantity Qmax than the heat pipe 10 of the comparative example, and therefore was found to have high heat transport properties.

[0077] 1, 1A Heat pipe 2, 2A Container 2a Inner peripheral surface of container 3 Evaporation section 3a Inner peripheral surface of evaporation section of container 3b Virtual inner peripheral surface of evaporation section of container 4 Condenser section 5 Intermediate section 5a Inner peripheral surface of intermediate section of container 6, 6A First sintered body layer 6a Inner peripheral surface of first sintered body layer 6b Outer peripheral surface of first sintered body layer 7, 7A Second sintered body layer 7b Outer peripheral surface of second sintered body layer located on inner peripheral surface of first sintered body layer 7b' Outer peripheral surface of second sintered body layer located on inner peripheral surface of intermediate section of container 8 Groove 9 Heat generating element 10 Comparative heat pipe F Working fluid F Ｌ Liquid phase working fluid F ｇ Gas phase working fluid L ０ Evaporation section longitudinal dimension L １ Length of the first sintered layer: L ２ Disposition length of the second sintered body layer M: Position of the central axis of the internal space of the container N: Position of the boundary surface located in the middle where the second sintered body layer and the internal surface of the container meet S: Internal space X: Longitudinal direction of the container Y: Thickness direction of the container Z: Depth direction of the container

Claims

1. A heat pipe comprising a container having an internal space filled with a working fluid, an evaporator section for evaporating a liquid phase working fluid and changing its phase to a gas phase working fluid, a condenser section disposed at a position spaced apart from the evaporator section and condensing the gas phase working fluid and changing its phase to a liquid phase working fluid, and an intermediate section located between the evaporator section and the condenser section, wherein, when viewed in cross section of the heat pipe at the evaporator section, there are a first sintered body layer made of a sintered body of a first copper powder and formed in a specific area on the inner circumferential surface of the container, and a second sintered body layer made of a sintered body of a second copper powder having an average particle size larger than that of the first copper powder and formed in an annular shape over the entire inner circumferential surface of the container with the first sintered body layer interposed between the first sintered body layer and the inner circumferential surface of the container.

2. A heat pipe as described in claim 1, wherein, when viewed in a vertical cross section including the longitudinal direction of the heat pipe, the arrangement length of the first sintered body layer is longer than the longitudinal dimension of the evaporation section, and the arrangement length of the second sintered body layer is longer than the arrangement length of the first sintered body layer.

3. The heat pipe according to claim 2, wherein the second sintered layer terminates at any position in the intermediate portion.

4. A heat pipe as described in claim 3, wherein the liquid-phase working fluid that has undergone a phase change in the condensation section flows toward the evaporation section due to capillary force through the internal voids of the second sintered body layer located in the middle section, and flows from the second sintered body layer toward the first sintered body layer through the contact interface between the outer circumferential surface of the second sintered body layer and the inner circumferential surface of the first sintered body layer.

5. A heat pipe as claimed in claim 1, wherein said specific region includes a region of the inner circumferential surface of said container that constitutes a portion facing a heating element.

6. The heat pipe according to claim 1, wherein a plurality of grooves are formed on the inner peripheral surface of said container, said grooves extending along the longitudinal direction of said container.

7. The heat pipe according to claim 6, wherein the first sintered layer is also filled into the grooves located in the specific region.

8. A heat pipe as described in claim 6, wherein the second sintered layer substantially separates a vapor flow of the gas-phase working fluid that has undergone a phase change in the evaporator section from a liquid flow of the liquid-phase working fluid that has undergone a phase change in the condenser section, and the liquid flow is divided into a path that passes through the multiple grooves and a path that passes through internal voids in the second sintered layer.

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