Loop Heat Pipe

Abstract

To provide a loop type heat pipe that can improve heat dissipation performance.SOLUTION: A loop type heat pipe 10 comprises: an evaporator for vaporizing working fluid; a condenser 13 for liquefying the working fluid; a liquid pipe connecting the evaporator and the condenser 13; a vapor pipe connecting the evaporator and the condenser 13; and a loop-shaped flow passage 15 through which the working fluid flows. The condenser 13 has a structure in which metal layers 31, 32, and 33 are laminated. The metal layer 31 that is an outer metal layer comprises: an inner surface 31A joined to the metal layer 32 that is an inner metal layer; and an outer surface 31B provided on the side opposite to the inner surface 31A in a thickness direction of the metal layer 32. The metal layer 31 comprises one or a plurality of concave parts 40 provided in the outer surface 31B. The concave parts 40 are provided so as not to overlap with the flow passage 15 in a planar view.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] Conventionally, heat pipes that transport heat by utilizing a phase change of a working fluid have been proposed as devices for cooling heat-generating components of semiconductor devices (e.g., CPUs) mounted on electronic devices (see, for example, Patent Documents 1 and 2).

[0003] As an example of a heat pipe, a loop-type heat pipe is known, which includes an evaporator that vaporizes a working fluid by heat from a heat generating component, and a condenser that cools and liquefies the vaporized working fluid, and in which the evaporator and the condenser are connected by a liquid pipe and a vapor pipe that form a loop-shaped flow path. In the loop-type heat pipe, the working fluid flows in one direction through the loop-shaped flow path. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6291000 [Patent Document 2] Patent No. 6400240 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above-mentioned loop heat pipe, improvement in heat dissipation performance is desired, and there is still room for improvement in this regard. [Means for solving the problem]

[0006] According to one aspect of the present invention, there is provided an electrical refrigeration system having an evaporator that vaporizes a working fluid, a condenser that liquefies the working fluid, a liquid pipe connecting the evaporator and the condenser, a vapor pipe connecting the evaporator and the condenser, and a loop-shaped flow path through which the working fluid flows, wherein at least one structure of the evaporator, the condenser, the liquid pipe, and the vapor pipe has a first outer metal layer, a second outer metal layer, and a single or multiple inner metal layers provided between the first outer metal layer and the second outer metal layer, the first outer metal layer has a first inner surface joined to the inner metal layer, and a first outer surface provided on the opposite side to the first inner surface in a thickness direction of the first outer metal layer, and the first outer metal layer has one or more first recesses provided on the first outer surface, and the first recesses are provided so as not to overlap the flow path in a plan view. the second outer metal layer has a second inner surface joined to the inner metal layer and a second outer surface provided on the opposite side to the second inner surface in a thickness direction of the second outer metal layer, the second outer metal layer has one or more second recesses provided on the second outer surface, and the second recesses are provided so as not to overlap the flow path in a plan view. There are. Effect of the Invention

[0007] Advantageous Effects of Invention According to one aspect of the present invention, an effect of improving heat dissipation is achieved. [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic plan view showing a loop heat pipe according to an embodiment; [Diagram 2] FIG. 2 is a schematic cross-sectional view (cross-sectional view taken along line 2-2 in FIG. 1) illustrating a condenser according to one embodiment. [Diagram 3] 1 is a schematic cross-sectional view (cross-sectional view taken along line 3-3 in FIG. 1) illustrating a loop heat pipe according to an embodiment. [Figure 4] 1(a) to 1(d) are schematic cross-sectional views showing a manufacturing method of a loop heat pipe according to one embodiment. [Diagram 5] 1(a) to 1(d) are schematic cross-sectional views showing a manufacturing method of a loop heat pipe according to one embodiment. [Figure 6] 5(a) and 5(b) are schematic cross-sectional views showing a manufacturing method of a loop heat pipe according to one embodiment. [Figure 7] FIG. 11 is a schematic cross-sectional view showing a modified example of a loop heat pipe. [Figure 8] FIG. 11 is a schematic cross-sectional view showing a modified example of a loop heat pipe. [Figure 9] FIG. 11 is a schematic cross-sectional view showing a modified example of a loop heat pipe. [Figure 10] FIG. 11 is a schematic plan view showing a modified loop heat pipe. [Figure 11] FIG. 11 is a schematic plan view showing a modified loop heat pipe. [Figure 12] FIG. 11 is a schematic plan view showing a modified loop heat pipe. [Figure 13] FIG. 11 is a schematic plan view showing a modified loop heat pipe. [Figure 14] FIG. 11 is a schematic plan view showing a modified loop heat pipe. [Figure 15] FIG. 11 is a schematic plan view showing a modified loop heat pipe. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment will be described with reference to the accompanying drawings. In addition, for convenience, the attached drawings may show characteristic parts in an enlarged manner to make the characteristics easier to understand, and the dimensional ratios of each component may differ from one drawing to another. In addition, in the cross-sectional views, in order to make the cross-sectional structure of each component easier to understand, the hatching of some components is shown as a matte pattern, and the hatching of some components is omitted. In each drawing, XYZ axes perpendicular to each other are illustrated. In the following description, for convenience, the direction extending along the X axis is referred to as the X-axis direction, the direction extending along the Y axis is referred to as the Y-axis direction, and the direction extending along the Z axis is referred to as the Z-axis direction. In this specification, the term "planar view" refers to viewing an object from a vertical direction (here, the Z-axis direction) such as in FIG. 2, and the term "planar shape" refers to the shape of an object viewed from a vertical direction such as in FIG. 2.

[0010] (Overall configuration of the loop heat pipe 10) 1 is housed in a mobile electronic device M1 such as a smartphone, a tablet terminal, etc. The loop heat pipe 10 has an evaporator 11, a vapor pipe 12, a condenser 13, and a liquid pipe 14.

[0011] The evaporator 11 and the condenser 13 are connected by a steam pipe 12 and a liquid pipe 14. The evaporator 11 has a function of vaporizing the working fluid C to generate steam Cv. The steam Cv generated in the evaporator 11 is sent to the condenser 13 via the steam pipe 12. The condenser 13 has a function of liquefying the steam Cv of the working fluid C. The liquefied working fluid C is sent to the evaporator 11 via the liquid pipe 14. The steam pipe 12 and the liquid pipe 14 form a loop-shaped flow path 15 through which the working fluid C or the steam Cv flows.

[0012] The steam pipe 12 is formed, for example, in a long pipe body. The liquid pipe 14 is formed, for example, in a long pipe body. In this embodiment, the steam pipe 12 and the liquid pipe 14 are, for example, equal in lengthwise dimension (i.e., length). The length of the steam pipe 12 and the length of the liquid pipe 14 may be different from each other. For example, the length of the steam pipe 12 may be shorter than the length of the liquid pipe 14. Here, the "length direction" of the evaporator 11, the steam pipe 12, the condenser 13, and the liquid pipe 14 in this specification refers to the direction that coincides with the direction in which the working fluid C or the steam Cv flows in each member (see the arrow in the figure). In addition, in this specification, "equal" includes the case where they are exactly equal, as well as the case where there is some difference between the objects to be compared due to the influence of dimensional tolerances, etc.

[0013] (Configuration of evaporator 11) The evaporator 11 is fixed in close contact with a heat-generating component (not shown). The working fluid C in the evaporator 11 is vaporized by the heat generated by the heat-generating component, and steam Cv is generated. A thermal interface material (TIM) may be interposed between the evaporator 11 and the heat-generating component. The thermal interface material reduces the contact thermal resistance between the heat-generating component and the evaporator 11, and facilitates the transfer of heat from the heat-generating component to the evaporator 11.

[0014] (Configuration of steam pipe 12) The steam pipe 12 has, for example, a pair of pipe walls 12w provided on both sides in a width direction perpendicular to the length direction of the steam pipe 12 in a plan view, and a flow path 12r provided between the pair of pipe walls 12w. The flow path 12r communicates with the internal space of the evaporator 11. The flow path 12r is a part of a loop-shaped flow path 15. Steam Cv generated in the evaporator 11 is guided to the condenser 13 via the steam pipe 12.

[0015] (Configuration of condenser 13) The condenser 13 has, for example, a heat dissipation plate 13p with an increased area for heat dissipation, and a flow path 13r provided inside the heat dissipation plate 13p. The flow path 13r has a flow path r1 communicating with the flow path 12r and extending in the Y-axis direction, a flow path r2 bending from the flow path r1 and extending in the X-axis direction, and a flow path r3 bending from the flow path r2 and extending in the Y-axis direction. The flow path 13r (flow paths r1 to r3) is a part of a loop-shaped flow path 15. The condenser 13 has pipe walls 13w provided on both sides of the flow path 13r, that is, the direction perpendicular to the length direction of the flow paths r1 to r3 in a plan view. The steam Cv guided through the steam pipe 12 is liquefied in the condenser 13.

[0016] (Configuration of liquid pipe 14) The liquid pipe 14 has, for example, a pair of pipe walls 14w provided on both sides in a width direction perpendicular to the length direction of the liquid pipe 14 in a plan view, and a flow path 14r provided between the pair of pipe walls 14w. The flow path 14r communicates with a flow path 13r (specifically, flow path r3) of the condenser 13 and also communicates with the internal space of the evaporator 11. The flow path 14r is a part of a loop-shaped flow path 15. The working fluid C liquefied in the condenser 13 is guided to the evaporator 11 through the liquid pipe 14.

[0017] (Configuration of loop heat pipe 10) In the loop heat pipe 10, heat generated in the heat generating components is transferred to the condenser 13 and dissipated in the condenser 13. This cools the heat generating components and suppresses the temperature rise of the heat generating components.

[0018] Here, it is preferable to use a fluid with high vapor pressure and large latent heat of vaporization as the working fluid C. By using such a working fluid C, the heat-generating components can be efficiently cooled by the latent heat of vaporization. As the working fluid C, for example, ammonia, water, fluorocarbon, alcohol, acetone, etc. can be used.

[0019] (Specific structure of condenser 13) Fig. 2 shows a cross section of the condenser 13 taken along line 2-2 in Fig. 1. This cross section is a plane perpendicular to the flow direction of the working fluid C in the condenser 13. Specifically, the cross section shown in Fig. 2 is a cross section of the condenser 13 cut along a YZ plane perpendicular to the length direction of the flow path r2. Fig. 3 shows a cross section of the loop heat pipe 10 taken along line 3-3 in Fig. 1. This cross section is a cross section of the condenser 13 cut along an XZ plane extending parallel to the flow path r2.

[0020] 2, the condenser 13 has a structure in which, for example, three metal layers 31, 32, and 33 are laminated. In other words, the condenser 13 has a structure in which the metal layer 32 serving as the inner metal layer is laminated between the metal layers 31 and 33 serving as a pair of outer metal layers. The inner metal layer of the condenser 13 in this embodiment is composed of only one metal layer 32.

[0021] Each of the metal layers 31-33 is, for example, a copper (Cu) layer having excellent thermal conductivity. The metal layers 31-33 are directly bonded to each other by solid-phase bonding such as diffusion bonding, pressure welding, friction welding, and ultrasonic bonding. In FIG. 2, the metal layers 31-33 are distinguished by solid lines for easy understanding. For example, when the metal layers 31-33 are integrated by diffusion bonding, the interfaces of the metal layers 31-33 may disappear, and the boundaries may not be clear. Here, solid-phase bonding is a method in which the objects to be bonded are heated in a solid phase (solid) state to soften them without melting them, and are further heated to cause plastic deformation to bond them. The metal layers 31-33 are not limited to copper layers, and may be formed of stainless steel layers, aluminum layers, magnesium alloy layers, or the like. In addition, some of the metal layers 31-33 may be made of a material different from that of the other metal layers. The thickness of each of the metal layers 31 to 33 may be, for example, about 50 μm to 200 μm. Note that some of the metal layers 31 to 33 may have a different thickness from the other metal layers, or all of the metal layers may have a different thickness from each other.

[0022] The condenser 13 is made of metal layers 31 to 33 stacked in the Z-axis direction, and has a flow passage 13r and a pair of tube walls 13w provided on both sides of the flow passage 13r in the Y-axis direction. (Configuration of metal layer 32) The metal layer 32 is laminated between the metal layer 31 and the metal layer 33. The upper surface of the metal layer 32 is bonded to the metal layer 31. The lower surface of the metal layer 32 is bonded to the metal layer 33. The metal layer 32 has a through hole 32X penetrating the metal layer 32 in the thickness direction, and a pair of pipe walls 32w provided on both sides of the through hole 32X in the Y-axis direction. The through hole 32X constitutes a flow path 13r.

[0023] (Configuration of Metal Layer 31) The metal layer 31 is laminated on the upper surface of the metal layer 32. The metal layer 31 has an inner surface 31A (here, the lower surface) joined to the metal layer 32, and an outer surface 31B (here, the upper surface) provided on the opposite side to the inner surface 31A in the thickness direction of the metal layer 31 (here, the Z-axis direction). The metal layer 31 has a tube wall 31w provided at a position overlapping the tube wall 32w in a plan view, and an upper wall 31u provided at a position overlapping the flow path 13r in a plan view. The inner surface 31A of the tube wall 31w is joined to the upper surface of the tube wall 32w. The upper wall 31u is provided between a pair of tube walls 31w. The inner surface 31A of the upper wall 31u is exposed to the flow path 13r. In other words, the upper wall 31u constitutes the flow path 13r.

[0024] The metal layer 31 has one or more recesses 40 provided on the outer surface 31B. The recesses 40 are provided so as not to overlap the flow path 15, specifically the flow path 13r, in a plan view. The recesses 40 are provided on the outer surface 31B of the pipe wall 31w. The recesses 40 are provided, for example, on both of the pair of pipe walls 31w. Each recess 40 is not provided on the outer surface 31B of the upper wall 31u. Each recess 40 is formed, for example, so as to recess from the outer surface 31B of the metal layer 31 to the middle part of the metal layer 31 in the thickness direction. Each recess 40 is formed, for example, so as to extend from the outer surface 31B of the metal layer 31 to the middle part of the metal layer 31 in the thickness direction.

[0025] As shown in FIG. 3, the metal layer 31 has a plurality of recesses 40 arranged side by side along one direction (here, the X-axis direction) of a planar direction perpendicular to the thickness direction of the metal layer 31. The plurality of recesses 40 are arranged, for example, along the X-axis direction at a predetermined interval. As shown in FIG. 1, in the condenser 13, a plurality of recesses 40 are arranged side by side along the X-axis direction on both sides of the flow path 13r (specifically, the flow path r2) in the Y-axis direction. Each recess 40 extends, for example, along the Y-axis direction. As shown in FIG. 2, each recess 40 extends along the planar direction (here, the Y-axis direction) of the outer surface 31B of the metal layer 31. Each recess 40 is provided, for example, away from the outer surface 31C of the metal layer 31. Also, each recess 40 is provided, for example, away from the inner wall surface of the through hole 32X in the Y-axis direction. That is, each recess 40 is provided only in the middle part of the outer surface 31B of the tube wall 31w in the Y-axis direction.

[0026] As shown in Figs. 2 and 3, the inner wall surface of each recess 40 is formed to extend perpendicularly to the outer surface 31B, for example. The inner wall surface of each recess 40 is formed to be a plane extending along the Z-axis direction, for example. The bottom surface of each recess 40 is formed to be a plane parallel to the outer surface 31B, for example. The bottom surface of each recess 40 is formed to be a plane extending parallel to the XY plane, for example. The inner wall surface of each recess 40 may be tapered so as to widen from the bottom surface side toward the opening side.

[0027] (Configuration of metal layer 33) As shown in FIG. 2, the metal layer 33 is laminated on the lower surface of the metal layer 32. The metal layer 33 has an inner surface 33A (here, the upper surface) joined to the metal layer 32, and an outer surface 33B (here, the lower surface) provided on the opposite side to the inner surface 33A in the thickness direction of the metal layer 33 (here, the Z-axis direction). The metal layer 33 has a pipe wall 33w provided at a position overlapping the pipe wall 32w in a plan view, and a lower wall 33d provided at a position overlapping the flow path 13r in a plan view. The inner surface 33A of the pipe wall 33w is joined to the lower surface of the pipe wall 32w. The lower wall 33d is provided between a pair of pipe walls 33w. The inner surface 33A of the lower wall 33d is exposed to the flow path 13r. In other words, the lower wall 33d constitutes the flow path 13r.

[0028] The metal layer 33 has one or more recesses 50 provided on the outer surface 33B. The recesses 50 are provided so as not to overlap the flow path 15, specifically the flow path 13r, in a plan view. The recesses 50 are provided on the outer surface 33B of the pipe wall 33w. The recesses 50 are provided, for example, on both of the pair of pipe walls 33w. Each recess 50 is not provided on the outer surface 33B of the lower wall 33d. Each recess 50 is formed, for example, so as to recess from the outer surface 33B of the metal layer 33 to the middle part of the metal layer 33 in the thickness direction. Each recess 50 is formed, for example, so as to extend from the outer surface 33B of the metal layer 33 to the middle part of the metal layer 33 in the thickness direction.

[0029] As shown in FIG. 3, the metal layer 33 has a plurality of recesses 50 arranged side by side along one direction (here, the X-axis direction) in a planar direction perpendicular to the thickness direction of the metal layer 33. The plurality of recesses 50 are arranged, for example, at a predetermined interval along the X-axis direction. For example, each recess 50 is arranged so as not to overlap with the recess 40 in a plan view. For example, each recess 50 is arranged so as not to overlap with the entire recess 40 in a plan view. The plurality of recesses 50 are arranged at intervals along the X-axis direction so as not to overlap with the recess 40. The width dimension of each recess 50 along the X-axis direction is equal to the width dimension of each recess 40 along the X-axis direction, for example. For example, the interval between two recesses 50 adjacent to each other in the X-axis direction is greater than the width dimension of each recess 40, 50.

[0030] 1, in the condenser 13, a plurality of recesses 50 are arranged side by side along the X-axis direction on both sides of the Y-axis direction of a flow path 13r (specifically, flow path r2). Each recess 50 extends, for example, along the Y-axis direction. Each recess 50 extends, for example, parallel to each recess 40. The length dimension along the Y-axis direction of each recess 50 is, for example, equal to the length dimension along the Y-axis direction of the recess 40 adjacent thereto in the X-axis direction.

[0031] 2, each recess 50 is provided, for example, away from the outer surface 33C of the metal layer 33. Also, each recess 50 is provided, for example, away from the inner wall surface of the through hole 32X in the Y-axis direction. That is, each recess 50 is provided only in a middle portion in the Y-axis direction of the outer surface 33B of the pipe wall 33w.

[0032] As shown in Figs. 2 and 3, the inner wall surface of each recess 50 is formed to extend perpendicularly to the outer surface 33B, for example. The inner wall surface of each recess 50 is formed to be a plane extending along the Z-axis direction, for example. The bottom surface of each recess 50 is formed to be a plane parallel to the outer surface 33B, for example. The bottom surface of each recess 50 is formed to be a plane extending parallel to the XY plane, for example. The inner wall surface of each recess 50 may be formed to be tapered so as to widen from the bottom surface side toward the opening side.

[0033] (Specific structure of flow path 13r) 2, the flow path 13r is formed by a through hole 32X of the metal layer 32. The flow path 13r is formed by a space surrounded by the inner wall surface of the through hole 32X, the inner surface 31A of the upper wall 31u, and the inner surface 33A of the lower wall 33d.

[0034] (Specific structure of pipe wall 13w) Each tube wall 13w is composed of, for example, a tube wall 31w of the metal layer 31, a tube wall 32w of the metal layer 32, and a tube wall 33w of the metal layer 33.

[0035] (Configuration of steam pipe 12) 3, the steam pipe 12 is formed by stacking three metal layers 31 to 33, similar to the condenser 13. For example, in the steam pipe 12, a through hole 32Y is formed penetrating the metal layer 32, which is an inner metal layer, in the thickness direction, to form a flow path 12r. The steam pipe 12 has a pair of pipe walls 12w provided on both sides in the width direction (here, the X-axis direction) perpendicular to the length direction (here, the Y-axis direction) of the steam pipe 12. For example, no hole or groove is formed in each pipe wall 12w.

[0036] (Configuration of liquid pipe 14) The liquid pipe 14 is formed by stacking three metal layers 31 to 33, similarly to the condenser 13. In the liquid pipe 14, a through hole 32Z is ​​formed penetrating the metal layer 32, which is the inner metal layer, in the thickness direction, to form a flow path 14r. The liquid pipe 14 has a pair of pipe walls 14w provided on both sides in the width direction (here, the X-axis direction) perpendicular to the length direction (here, the Y-axis direction) of the liquid pipe 14. For example, no hole or groove is formed in each pipe wall 14w. The liquid pipe 14 may have, for example, a porous body. The porous body is configured to have, for example, a first bottomed hole recessed from the upper surface of the metal layer 32, which is the inner metal layer, a second bottomed hole recessed from the lower surface of the metal layer 32, and pores formed by partially communicating the first bottomed hole and the second bottomed hole. The porous body, for example, guides the working fluid C liquefied in the condenser 13 to the evaporator 11 (see FIG. 1) by the capillary force generated in the porous body. Although not shown, the liquid pipe 14 is provided with an inlet for injecting the working fluid C (see FIG. 1). However, the inlet is closed with a sealing member, and the inside of the loop heat pipe 10 is kept airtight.

[0037] (Configuration of evaporator 11) The evaporator 11 shown in Fig. 1 is formed by laminating three metal layers 31 to 33 (see Fig. 3) in the same manner as the steam pipe 12, the condenser 13, and the liquid pipe 14 shown in Fig. 3. The evaporator 11 may have a porous body, for example, in the same manner as the liquid pipe 14. For example, in the evaporator 11, the porous body provided in the evaporator 11 is formed in a comb-like shape. In the evaporator 11, a space is formed in the region where the porous body is not provided.

[0038] In this manner, the loop heat pipe 10 is constructed by stacking three metal layers 31 to 33 (see Figs. 2 and 3). The number of stacked metal layers is not limited to three, and may be four or more.

[0039] (Function of the loop heat pipe 10) Next, the operation of the loop heat pipe 10 will be described. The loop heat pipe 10 has an evaporator 11 that vaporizes the working fluid C, a vapor pipe 12 that flows the vaporized working fluid C (i.e., vapor Cv) into a condenser 13, a condenser 13 that liquefies the vapor Cv, and a liquid pipe 14 that flows the liquefied working fluid C into the evaporator 11. The vapor Cv generated in the evaporator 11 due to heat from a heat-generating component is guided to the condenser 13 through the vapor pipe 12. The vapor Cv is liquefied in the condenser 13. That is, the heat generated in the heat-generating component is dissipated in the condenser 13. This cools the heat-generating component, suppressing a rise in temperature of the heat-generating component.

[0040] 2 and 3, in the condenser 13, a recess 40 is provided on the outer surface 31B of the metal layer 31, which is the outer metal layer, and a recess 50 is provided on the outer surface 33B of the metal layer 33, which is the outer metal layer. This allows the surface area of ​​the outer surfaces 31B, 33B of the metal layers 31, 33 to be increased compared to when the recesses 40, 50 are not provided. Therefore, the surface area of ​​the metal layers 31, 33 that can come into contact with the outside air can be increased compared to when the recesses 40, 50 are not provided, and the amount of heat exchange with the outside air can be increased. As a result, the efficiency of heat exchange in the condenser 13, that is, the heat dissipation, can be improved.

[0041] In this embodiment, metal layer 31 is an example of a first outer metal layer, metal layer 32 is an example of an inner metal layer, and metal layer 33 is an example of a second outer metal layer. Furthermore, inner surface 31A is an example of a first inner surface, outer surface 31B is an example of a first outer surface, inner surface 33A is an example of a second inner surface, and outer surface 33B is an example of a second outer surface. Furthermore, recess 40 is an example of a first recess, and recess 50 is an example of a second recess.

[0042] (Method of manufacturing the loop heat pipe 10) Next, a method for manufacturing the loop heat pipe 10 will be described. First, in the step shown in Fig. 4(a), a flat metal sheet 71 is prepared. The metal sheet 71 is a member that will eventually become the metal layer 31 (see Fig. 3). The metal sheet 71 is made of, for example, copper, stainless steel, aluminum, magnesium alloy, etc. The thickness of the metal sheet 71 can be, for example, about 50 µm to 200 µm.

[0043] Subsequently, a resist layer 72 is formed on the upper surface of the metal sheet 71, and a resist layer 73 is formed on the lower surface of the metal sheet 71. As the resist layers 72 and 73, for example, a photosensitive dry film resist or the like can be used.

[0044] 4(b), the resist layer 72 is exposed and developed to form an opening 72X that selectively exposes the upper surface of the metal sheet 71. The opening 72X is formed to correspond to the recess 40 shown in FIG.

[0045] 4(c), the metal sheet 71 exposed in the opening 72X is etched from the upper surface side of the metal sheet 71. As a result, a recess 40 is formed on the upper surface of the metal sheet 71. The recess 40 can be formed, for example, by wet etching the metal sheet 71 using the resist layers 72 and 73 as an etching mask. When copper is used as the material of the metal sheet 71, an aqueous ferric chloride solution or an aqueous cupric chloride solution can be used as the etching solution.

[0046] Next, the resist layers 72 and 73 are stripped off with a stripping liquid, thereby forming the metal layer 31 having the recesses 40 on the outer surface 31B, as shown in FIG. 5(a), a flat metal sheet 74 is prepared. The metal sheet 74 is a member that will eventually become the metal layer 32 (see FIG. 3). The metal sheet 74 is made of, for example, copper, stainless steel, aluminum, magnesium alloy, etc. The thickness of the metal sheet 74 can be, for example, about 50 μm to 200 μm.

[0047] Subsequently, a resist layer 75 is formed on the upper surface of the metal sheet 74, and a resist layer 76 is formed on the lower surface of the metal sheet 74. As the resist layers 75 and 76, for example, a photosensitive dry film resist or the like can be used.

[0048] Next, in the step shown in FIG. 5(b), the resist layer 75 is exposed and developed to form openings 75Y, 75Z that selectively expose the upper surface of the metal sheet 74. Similarly, the resist layer 76 is exposed and developed to form openings 76Y, 76Z that selectively expose the lower surface of the metal sheet 74. The openings 75Y, 76Y are formed to correspond to the through hole 32Y shown in FIG. 3. The openings 75Z, 76Z are formed to correspond to the through hole 32Z shown in FIG. 3. The openings 75Y and 76Y are provided at positions that overlap each other in a plan view. The openings 75Z and 76Z are provided at positions that overlap each other in a plan view.

[0049] Next, in the step shown in FIG. 5(c), the metal sheet 74 exposed from the resist layers 75, 76 is etched from both the top and bottom of the metal sheet 74. The openings 75Y, 76Y form the through hole 32Y in the metal sheet 74. The openings 75Z, 76Z form the through hole 32Z in the metal sheet 74. The through holes 32Y, 32Z can be formed, for example, by wet etching the metal sheet 74 using the resist layers 75, 76 as an etching mask. When copper is used as the material of the metal sheet 74, an aqueous solution of ferric chloride or an aqueous solution of cupric chloride can be used as the etching solution. Although not shown, the through hole 32X (see FIG. 2) can be formed in the same manner as the through holes 32Y, 32Z.

[0050] Next, the resist layers 75 and 76 are stripped off with a stripping liquid, thereby forming the metal layer 32 having the through holes 32Y and 32Z and the through hole 32X (see FIG. 2) as shown in FIG.

[0051] 6(a), a metal layer 33 having a recess 50 on an outer surface 33B is formed by a method similar to the steps shown in FIGS.

[0052] Next, in the step shown in FIG. 6(b), the stacked metal layers 31-33 are pressed while being heated to a predetermined temperature (for example, about 900° C.), thereby bonding the metal layers 31-33 by solid-state bonding. As a result, the metal layers 31, 32, and 33 adjacent in the stacking direction are directly bonded. At this time, the inner surface 31A (here, the lower surface) of the tube wall 31w and the upper surface of the tube wall 32w are directly bonded. Here, the through-hole 32X (see FIG. 2) and the recess 50 are not formed in the metal layers 31-33 in the portion overlapping the recess 40 in a plan view. Therefore, no space is formed in the metal layers 31-33 in the portion overlapping the recess 40 in a plan view. As a result, pressure can be appropriately applied to the inner surface 31A of the metal layer 31 and the upper surface of the metal layer 32 during pressing, and the inner surface 31A of the metal layer 31 and the upper surface of the metal layer 32 can be appropriately bonded. Similarly, the inner surface 33A (here, the upper surface) of the tube wall 33w and the lower surface of the tube wall 32w are directly joined. Here, in the metal layers 31-33, the through-holes 32X (see FIG. 2) and the recesses 40 are not formed in the portions overlapping the recesses 50 in a planar view. Therefore, in the metal layers 31-33, no space is formed in the portions overlapping the recesses 50 in a planar view. This allows suitable pressure to be applied to the inner surface 33A of the metal layer 33 and the lower surface of the metal layer 32 during pressing, and allows suitable joining of the inner surface 33A of the metal layer 33 and the lower surface of the metal layer 32.

[0053] The above-described steps form a structure in which the metal layers 31, 32, and 33 are laminated. Then, the loop heat pipe 10 having the evaporator 11, the steam pipe 12, the condenser 13, and the liquid pipe 14 shown in Fig. 1 is formed. After that, for example, the liquid pipe 14 is evacuated using a vacuum pump or the like, and the working fluid C is injected into the liquid pipe 14 from an injection port (not shown), and then the injection port is sealed.

[0054] Next, the effects of this embodiment will be described. (1) The recesses 40 are provided on the outer surface 31B of the metal layer 31, which is the outer metal layer. This allows the surface area of ​​the outer surface 31B of the metal layer 31 to be increased compared to when the recesses 40 are not provided. For example, by providing the recesses 40, the surface area of ​​the outer surface 31B of the metal layer 31 can be increased without increasing the planar shape of the condenser 13. Therefore, the surface area of ​​the metal layer 31 that can come into contact with the outside air can be increased compared to when the recesses 40 are not provided, and the amount of heat exchange with the outside air can be increased. As a result, the efficiency of heat exchange in the loop heat pipe 10, i.e., the heat dissipation performance, can be improved.

[0055] (2) The recesses 40 are provided so as not to overlap the flow passage 15 in a plan view. In other words, the recesses 40 are not provided in the metal layer 31 at the portion overlapping the flow passage 15 in a plan view, i.e., the outer surface 31B of the upper wall 31u. This makes it possible to prevent the upper wall 31u constituting the flow passage 15 from becoming thin, and to prevent a decrease in the rigidity of the upper wall 31u.

[0056] (3) The recesses 50 are provided on the outer surface 33B of the metal layer 33, which is the outer metal layer. This allows the surface area of ​​the outer surface 33B of the metal layer 33 to be increased compared to when the recesses 50 are not provided. For example, by providing the recesses 50, the surface area of ​​the outer surface 33B of the metal layer 33 can be increased without increasing the planar shape of the condenser 13. Therefore, the surface area of ​​the metal layer 33 that can come into contact with the outside air can be increased compared to when the recesses 50 are not provided, and the amount of heat exchanged with the outside air can be increased. As a result, the heat dissipation performance of the loop heat pipe 10 can be improved.

[0057] (4) The recesses 50 are provided so as not to overlap the flow passage 15 in a plan view. In other words, the recesses 50 are not provided in the metal layer 33 at the portion overlapping the flow passage 15 in a plan view, i.e., the outer surface 33B of the bottom wall 33d. This makes it possible to prevent the bottom wall 33d constituting the flow passage 15 from becoming thin, and to prevent a decrease in the rigidity of the bottom wall 33d.

[0058] (5) The recess 50 is provided so as not to overlap the recess 40 in plan view. In this configuration, the flow path 15 and the recess 50 are not formed in the metal layers 31-33 at the portion overlapping the recess 40 in plan view, and the flow path 15 and the recess 40 are not formed in the portion overlapping the recess 50 in plan view. Therefore, in the metal layers 31-33, no space is formed in the portion overlapping the recess 40 in plan view, and no space is formed in the portion overlapping the recess 50 in plan view. As a result, when pressing the metal layers 31-33 to be bonded to each other, pressure can be suitably applied to the inner surface 31A of the metal layer 31 and the upper surface of the metal layer 32, and pressure can be suitably applied to the inner surface 33A of the metal layer 33 and the lower surface of the metal layer 32. As a result, the inner surface 31A of the metal layer 31 and the upper surface of the metal layer 32 can be suitably bonded, and the inner surface 33A of the metal layer 33 and the lower surface of the metal layer 32 can be suitably bonded.

[0059] (6) The recess 40 is formed so as to recess from the outer surface 31B of the metal layer 31 to the middle part in the thickness direction of the metal layer 31. With this configuration, it is possible to preferably prevent a decrease in the rigidity of the metal layer 31 caused by the provision of the recess 40, compared to, for example, a case in which the recess 40 is formed so as to penetrate the metal layer 31 in the thickness direction. Therefore, it is possible to preferably prevent a decrease in the handleability of the metal layer 31 alone during the manufacturing process.

[0060] (7) The recess 40 is provided away from the outer surface 31C of the metal layer 31. With this configuration, a portion where the recess 40 is not formed, i.e., a portion that is not thinned, is provided between the outer surface 31C of the metal layer 31 and the recess 40. Therefore, when pressing to bond the metal layers 31 to 33 to each other, pressure can be suitably applied to the inner surface 31A of the metal layer 31 and the upper surface of the metal layer 32 in the portion between the outer surface 31C of the metal layer 31 and the recess 40. As a result, the inner surface 31A of the metal layer 31 and the upper surface of the metal layer 32 can be suitably bonded to each other.

[0061] (Other embodiments) The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

[0062] The cross-sectional shape of each of the recesses 40, 50 in the above embodiment is not particularly limited. For example, as shown in FIG. 7, the inner surface of each recess 40, 50 may be formed into a curved surface that is curved in an arc shape in a cross-sectional view. The inner surface of each recess 40, 50 may be formed into a concave shape having a semicircular or semi-elliptical cross-sectional shape. In this specification, the term "semicircular" refers not only to a semicircle obtained by dividing a perfect circle into two equal parts, but also to a shape having a longer or shorter arc than a semicircle. In addition, in this specification, the term "semi-elliptical" refers not only to a semi-ellipse obtained by dividing an ellipse into two equal parts, but also to a shape having a longer or shorter arc than a semi-ellipse. The inner surface of each recess 40, 50 in this modified example has a semi-elliptical cross-sectional shape. The radius of curvature of the bottom surface of the recess 40, 50 and the radius of curvature of the inner wall surface of the recess 40, 50 may be equal to each other or may be different from each other.

[0063] In the above embodiment, the recess 50 is provided so as not to overlap with the recess 40 in a plan view, but this is not limited to the above. For example, as shown in Fig. 8, the recess 50 may be provided so as to partially overlap the recess 40 in plan view. That is, a portion of the recess 50 in this modified example overlaps a portion of the recess 40 in plan view.

[0064] In the above embodiment, the recess 40 is formed to recess from the outer surface 31B of the metal layer 31 to the center of the metal layer 31 in the thickness direction, but the depth of the recess 40 is not limited to this. 9, the recess 40 may be formed so as to penetrate the metal layer 31 in the thickness direction. That is, the recess 40 may be formed as a through hole. With this configuration, the inner wall surface of the recess 40 exposed to the outside becomes larger in proportion to the depth of the recess 40, so that the surface area of ​​the metal layer 31 that can come into contact with the outside air can be increased. This can improve the heat dissipation performance of the condenser 13.

[0065] Similarly to the above embodiment, the recess 40 formed as a through hole is provided, for example, away from the outer surface 31C of the metal layer 31. Moreover, the recess 40 formed as a through hole is provided, for example, away from the inner wall surface of the through hole 32X in the Y-axis direction.

[0066] When the recesses 40 are formed as through holes, the handleability of the metal layer 31 alone during manufacturing is likely to decrease. For this reason, it is preferable to form the recesses 40 so as to penetrate the metal layer 31 in the thickness direction within a range in which the desired handleability can be maintained. For example, only some of the recesses 40 may be formed so as to penetrate the metal layer 31 in the thickness direction.

[0067] In the above embodiment, the recess 50 is formed to recess from the outer surface 33B of the metal layer 33 to the center in the thickness direction of the metal layer 33, but the depth of the recess 50 is not limited to this. 9, the recess 50 may be formed so as to penetrate the metal layer 33 in the thickness direction. That is, the recess 50 may be formed as a through hole. With this configuration, the inner wall surface of the recess 50 exposed to the outside increases in proportion to the depth of the recess 50, so that the surface area of ​​the metal layer 33 that can come into contact with the outside air can be increased. This can improve the heat dissipation performance of the condenser 13.

[0068] Similarly to the above embodiment, the recess 50 formed as a through hole is provided, for example, away from the outer surface 33C of the metal layer 33. Moreover, the recess 50 formed as a through hole is provided, for example, away from the inner wall surface of the through hole 32X in the Y-axis direction.

[0069] When the recess 50 is formed as a through hole, the handleability of the metal layer 33 alone during the manufacturing process is likely to decrease. For this reason, it is preferable to form the recess 50 so as to penetrate the metal layer 33 in the thickness direction within a range in which the desired handleability can be maintained.

[0070] In the above embodiment, the recesses 40, 50 are provided at positions away from the outer surface of the pipe wall 13w, but the present invention is not limited to this. For example, as shown in Fig. 10, each of the recesses 40, 50 may be formed to extend to the outer surface of the pipe wall 13w. In this case, each of the recesses 40, 50 is formed to open in the Y-axis direction, for example. That is, each of the recesses 40, 50 in this modification is formed in a notch shape.

[0071] The planar shape of each of the recesses 40, 50 in the above embodiment is not particularly limited. The planar shape of each of the recesses 40, 50 can be formed into any shape. For example, the planar shape of each of the recesses 40, 50 can be appropriately changed depending on the overall shape of the condenser 13, the direction in which the outside air flows, and the like.

[0072] For example, as shown in Fig. 11, each of the recesses 40, 50 may be formed to extend along the X-axis direction in the XY plane. In this case, for example, a plurality of recesses 40 are provided side by side along the Y-axis direction, and a plurality of recesses 50 are provided side by side along the Y-axis direction.

[0073] 12, each of the recesses 40, 50 may be formed to extend in a first direction that intersects with both the X-axis direction and the Y-axis direction in the XY plane. In this case, for example, a plurality of recesses 40 are provided side by side along a second direction that is perpendicular to the first direction in the XY plane, and a plurality of recesses 50 are provided side by side along the second direction.

[0074] For example, the planar shape of the recesses 40, 50 may be formed to be circular as shown in Fig. 13. In this modification, a plurality of recesses 40 are provided in a matrix on the XY plane, and a plurality of recesses 50 are provided in a matrix on the XY plane.

[0075] The shape of the flow passage 13r in the condenser 13 in the above embodiment is not particularly limited. 14, the flow path 13r may be formed to have a shape having a meandering portion r4 that meanders in the XY plane. The flow path 13r of this modification has a flow path r1 extending in the Y-axis direction, a meandering portion r4 that extends in the X-axis direction while meandering from an end of the flow path r1, and a flow path r3 that extends in the Y-axis direction from an end of the meandering portion r4. Even in this case, the recesses 40 and 50 are provided so as not to overlap with the flow path 13r in a plan view.

[0076] In the above embodiment, the recesses 40, 50 are provided in the tube wall 13w of the condenser 13, but the present invention is not limited to this. 15, recesses 40, 50 may be provided in a pipe wall 12w of a steam pipe 12. In this case, the recesses 40, 50 are provided so as not to overlap the flow path 15, specifically the flow path 12r, in a plan view.

[0077] Further, recesses 40, 50 may be provided in the pipe wall 14w of the liquid pipe 14. In this case, the recesses 40, 50 are provided so as not to overlap the flow passage 15, specifically the flow passage 14r, in a plan view.

[0078] In the modification shown in FIG. 15, the recesses 40, 50 provided in the tube wall 13w of the condenser 13 may be omitted. In the above embodiment, the recesses 40 may be formed in different shapes.

[0079] In the above embodiment, the recesses 50 may be formed in different shapes. In the above embodiment, the recesses 40 and 50 may be formed in different shapes.

[0080] In the above embodiment, the recess 50 may be omitted. In the above embodiment, the inner metal layer is configured with only a single metal layer 32. That is, the inner metal layer has a single-layer structure. However, this is not limiting. For example, the inner metal layer may have a laminated structure in which multiple metal layers are laminated. In this case, the inner metal layer is configured by laminating multiple metal layers between metal layer 31 and metal layer 33. [Explanation of symbols]

[0081] C Working fluid Cv Steam 10 Loop type heat pipe 11 Evaporator 12 Steam Pipe 12w tube wall 13 Condenser 13w tube wall 14 Liquid pipe 14w tube wall 12r, 13r, 14r, 15 flow path 31 Metal layer 31A Inner surface 31B External surface 31C External surface 32 Metal layer 33 Metal layer 33A Inner surface Outer surface of 33B Outer side surface of 33C Tube walls of 31w, 32w, 33w Through holes of 32X, 32Y, 32Z Recess 40 Recess 50

Claims

1. an evaporator for vaporizing the working fluid; a condenser for liquefying the working fluid; A liquid pipe connecting the evaporator and the condenser; a steam pipe connecting the evaporator and the condenser; A loop-shaped flow path through which the working fluid flows, At least one of the structures of the evaporator, the condenser, the liquid pipe, and the vapor pipe has a first outer metal layer, a second outer metal layer, and a single or multiple inner metal layers provided between the first outer metal layer and the second outer metal layer, the first outer metal layer has a first inner surface joined to the inner metal layer and a first outer surface provided on the opposite side to the first inner surface in a thickness direction of the first outer metal layer, the first outer metal layer has one or more first recesses provided on the first outer surface, The first recess is provided so as not to overlap with the flow path in a plan view, the second outer metal layer has a second inner surface joined to the inner metal layer and a second outer surface provided on the opposite side to the second inner surface in a thickness direction of the second outer metal layer, the second outer metal layer has one or more second recesses provided on the second outer surface, The second recess is provided so as not to overlap with the flow path in a plan view of the loop heat pipe.

2. The loop heat pipe according to claim 1 , wherein the second recess is provided so as not to overlap with the first recess in a plan view.

3. The loop heat pipe according to claim 1 or 2, wherein the first recess is formed so as to recess from the first outer surface to a middle portion in a thickness direction of the first outer metal layer.

4. The loop heat pipe according to claim 1 or 2, wherein the first recess is formed so as to penetrate the first outer metal layer in a thickness direction.

5. The loop heat pipe according to claim 1 , wherein the first recess is formed to extend in a planar direction of the first outer surface.

6. The loop heat pipe according to claim 1 , wherein the first recess is provided away from an outer surface of the first outer metal layer.

7. The loop heat pipe according to claim 1 , wherein the at least one structure is the condenser.

8. the first outer metal layer has the first recesses, The plurality of first recesses are arranged side by side in a predetermined direction, the second outer metal layer has the second recesses, The plurality of second recesses are arranged side by side in the predetermined direction, The loop heat pipe according to claim 1 , wherein the first recesses and the second recesses are arranged so as not to overlap each other in a plan view.

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