Heat pipe and method for manufacturing heat pipe

Abstract

To provide a heat pipe which can diffuse heat up to an end part and a method for manufacturing the heat pipe.SOLUTION: A heat pipe 1 includes work fluid enclosed in an inner space surrounded by an inner wall face, and has a groove part 5 as a wick on the inner wall face (an inner wall face 11b, an inner wall face 21b). The groove part 5 is composed of a plurality of micro grooves 6. The heat pipe includes: a cylindrical body part 2 including a first member 10 having the groove part 5 in a longitudinal direction and a second member 20 arranged along the longitudinal direction of the first member 10; and sealing members 3, 4 arranged at a longitudinal end part of the body part 2. The first member 10 and the second member 20 are bonded together in the longitudinal direction with the groove part 5 facing inward, and the end part of the body part 2 and the sealing members 3, 4 are bonded.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a heat pipe and a method for manufacturing a heat pipe. [Background technology]

[0002] A known heat pipe has a working fluid sealed in a decompressed container, and uses the evaporation of the working fluid in the heat absorption section, the movement of the evaporated working fluid to the heat dissipation section, the condensation of the working fluid in the heat dissipation section, and the movement of the condensed working fluid back to the heat absorption section to diffuse heat from the heat absorption section.The heat pipe has a groove-like capillary structure (wick) inside the container, and the condensed liquid working fluid is moved by the wick from the heat dissipation section to the heat absorption section.

[0003] Patent Document 1 discloses a heat pipe circuit board in which two plates, at least one of which has a recess formed therein to serve as a flow path for the working fluid, are joined by friction stir welding. Patent Document 1 also discloses that at least one of the plates has an injection port through which the working fluid is injected into the flow path for the working fluid. After the plates are joined, the working fluid is injected through the injection port, which is then sealed, and the working flow path is sealed in a vacuum state. In this way, Patent Document 1 discloses a heat pipe manufactured having an internal space through which the working fluid circulates. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-329379 Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, two metal plates are joined by forming a recess in a plate material by machining. By performing a cutting process on the center of the plate material, a recess can be formed, which is a space surrounded by the bottom of the plate material and a wall portion where an injection port is provided. In this case, when attempting to form a groove portion as a wick in the recess, it is difficult to form the groove portion throughout the entire recess, including near the edge, because it is difficult for a tool to access the area near the wall. Since no groove portion is provided near the edge of the recess, the working fluid cannot be circulated by the recess near the edge, resulting in a problem of insufficient heat diffusion to the end of the heat pipe.

[0006] From this viewpoint, an object of the present invention is to provide a heat pipe that can diffuse heat to the ends. [Means for solving the problem]

[0007] That is, the above-mentioned problems of the present invention are solved by the following configuration.

[0008] (1) A heat pipe in which a working fluid is sealed in an internal space surrounded by an inner wall surface, and which has a groove portion on the inner wall surface as a wick, the groove portion being composed of a plurality of microgrooves, and which comprises a first member having the groove portion in the longitudinal direction and a second member arranged along the longitudinal direction of the first member, a cylindrical main body portion, and a sealing member arranged at the longitudinal end of the main body portion, wherein the first member and the second member are joined in the longitudinal direction with the groove portion facing inward, and the end of the main body portion and the sealing member are joined.

[0009] (2) The heat pipe according to (1), wherein the first member has the groove portion in an area including an end portion in the longitudinal direction.

[0010] (3) The heat pipe according to (1), wherein the first member has the groove portion over the entire longitudinal direction.

[0011] (4) The heat pipe described in (1) has a thin cylindrical shape and includes a first wall portion and a second wall portion arranged opposite each other across the internal space and having a flat outer surface, and the joint between the first member and the second member is provided on the first wall portion or the second wall portion.

[0012] (5) The heat pipe according to (4), wherein the first wall portion has the groove portion therein, the first wall portion being one of the main surfaces, and the second wall portion being the other main surface.

[0013] (6) The heat pipe according to (5), wherein the second wall portion has the groove portion therein as a wick.

[0014] (7) The groove provided in the first wall portion or the second wall portion and the groove provided in the sealing member are arranged in an intersecting direction. (5) The heat pipe according to (5).

[0015] (8) The microgrooves of the groove portion provided in the first wall portion or the second wall portion and the microgrooves of the groove portion provided in the sealing member are arranged continuously. (5) The heat pipe according to (5).

[0016] (9) A heat pipe as described in (6), in which the microgrooves of the groove portions provided in the first wall portion and the second wall portion and the microgrooves of the groove portions provided in the sealing member are arranged continuously.

[0017] (10) The heat pipe according to (1), wherein the sealing member has a wick on its inner wall surface.

[0018] (11) The heat pipe according to (1), wherein the sealing member has the groove portion as a wick on its inner wall surface.

[0019] (12) The heat pipe according to (11), wherein the sealing member has two or more rows of the grooves that intersect with each other.

[0020] (13) The main body has a bottomless cylindrical shape with both ends open, and the sealing member is joined to both ends of the main body. The heat pipe according to (1).

[0021] (14) The main body has a bottom at one end and is cylindrical with the other end open. The sealing member is joined to the other end of the main body. The heat pipe according to (1).

[0022] (15) A heat pipe as described in (1), wherein the first member and the second member are L-shaped in cross section, the sealing member is rectangular in front view, and a first butt joint is formed where one end of the L-shape of the first member and the other end of the L-shape of the second member are joined, and a second butt joint is formed where the other end of the L-shape of the first member and one end of the L-shape of the second member are joined, and the main body is rectangular tubular and has the end portion formed in a rectangular shape, and a third butt joint is formed where the end of the main body and the sealing member are joined.

[0023] (16) A heat pipe as described in (15), wherein the first member has a first step portion along the longitudinal direction at one end of the L-shape, the second member has a second step portion along the longitudinal direction at one end of the L-shape, the first step portion of the first member and the other end of the L-shape of the second member are joined at the first butt portion, and the other end of the L-shape of the first member and the second step portion of the second member are joined at the second butt portion.

[0024] (17) A heat pipe as described in (1), wherein one of the first member and the second member has a support portion that stands upright along the longitudinal direction from the inner wall surface of the one member toward the other member, and the tip of the support portion is in contact with the other member in the internal space of the main body portion.

[0025] (18) The heat pipe according to (1), having a plurality of the internal spaces that are independent of each other, and the plurality of internal spaces are arranged in parallel in the longitudinal direction.

[0026] (19) The heat pipe according to (1), having a plurality of the internal spaces that are independent of each other, and the plurality of the internal spaces are arranged in series in the longitudinal direction.

[0027] (20) The heat pipe according to (1), wherein the groove portion has the microgrooves with a groove width of 0.2 to 0.6 mm.

[0028] (21) The heat pipe according to (1), wherein the groove portion has the microgrooves having a groove width of 0.2 to 0.6 mm and the microgrooves having a groove width of 0.8 to 1.5 mm.

[0029] (22) The heat pipe according to (1), wherein the first member has fins integrally formed on the outside.

[0030] (23) The heat pipe according to (1), wherein the first member has fins integrally formed on the outside at the longitudinal end.

[0031] (24) The heat pipe according to (1), wherein the sealing member has fins formed on the outside.

[0032] (25) The heat pipe according to (1), wherein the sealing member has a fastening portion for fastening to another adjacent sealing member.

[0033] (26) The heat pipe according to (1), further comprising a connecting member for connecting adjacent other sealing members to each other.

[0034] (27) A heat pipe as described in (1), having one main surface formed along the longitudinal direction and another main surface opposite the one main surface, and having a flat surface portion on the outside of at least one of the first member, the second member, and the sealing member as a surface other than the main surface.

[0035] (28) A method for manufacturing a heat pipe in which a working fluid is sealed in an internal space surrounded by an inner wall surface and which has grooves on the inner wall surface as wicks, comprising the steps of: a preparation step of forming a plurality of microgrooves along the longitudinal direction of a base material to prepare a first member having the grooves and a second member corresponding to the first member; a combination step of combining the first member and the second member with the grooves facing inward to form a cylindrical main body having an open end in the longitudinal direction, and combining the end of the main body with the sealing member; a joining step of joining the first member, the second member, and the sealing member to form an intermediate member; and a sealing step of injecting a working fluid into the intermediate member and then sealing the intermediate member.

[0036] (29) A method for manufacturing a heat pipe according to (28), wherein in the preparation step, the base material is cut using a multi-cutter having multiple stacked disc cutters to form the multiple microgrooves.

[0037] (30) A method for manufacturing a heat pipe described in (28), wherein the sealing member has a pipe hole connecting the inside and outside of the intermediate member and a pipe connected to the outside of the pipe hole, and in the sealing process, the pipe hole is sealed while drawing a vacuum through the pipe.

[0038] (31) The method for manufacturing a heat pipe according to (28), wherein the first member or the second member has a through hole communicating the inside and outside of the intermediate member, the sealing member has a sealing passage communicating with the through hole and communicating the inside and outside of the intermediate member, and in the sealing step, a vacuum sealing member having a pipe hole passing through it is positioned at a position where the pipe hole communicates with the through hole, and the sealing passage is sealed while drawing a vacuum through the pipe hole in a state where the pipe hole, the through hole, and the sealing passage are connected.

[0039] (32) A method for manufacturing a heat pipe described in (28), wherein the sealing member has a pipe hole connecting the inside and outside of the intermediate member and a pipe connected to the outside of the pipe hole, and in the sealing process, the pipe hole is sealed while injecting high-pressure gas through the pipe.

[0040] (33) The method for manufacturing a heat pipe according to (28), wherein in the preparation step, the base material is formed by extrusion or press processing.

[0041] (34) A method for manufacturing a heat pipe as described in (28), wherein in the preparation process, the base material is formed to have a first step portion along the longitudinal direction, and in the joining process, the first step portion of the first member and the end portion of the second member are joined in a state where the first step portion and the end portion are butted together.

[0042] (35) The method for manufacturing a heat pipe according to (28), wherein in the joining step, the first member and the second member are joined by micro FSW or laser welding. [Effects of the Invention]

[0043] According to the heat pipe and the method for manufacturing the heat pipe of the present invention, it is possible to provide a heat pipe that can diffuse heat to the ends. [Brief explanation of the drawings]

[0044] [Figure 1] 1 is a perspective view showing a heat pipe according to a first embodiment of the present invention; [Figure 2] FIG. 2 is a cross-sectional view taken along the line II-II in FIG. [Figure 3] 1 is an exploded perspective view of a heat pipe according to a first embodiment of the present invention; [Figure 4] 3A to 3C are diagrams illustrating preparation steps in a method for manufacturing a heat pipe according to a first embodiment of the present invention. [Figure 5] FIG. 3 is a front view showing an assembling step (main body forming step) of the manufacturing method of the heat pipe according to the first embodiment of the present invention. [Figure 6] FIG. 3 is a plan view showing an assembling step (sealing member butting step) of the manufacturing method of the heat pipe according to the first embodiment of the present invention. [Figure 7] FIG. 2 is a plan view showing a first joining step (first step) of the method for manufacturing a heat pipe according to the first embodiment of the present invention. [Figure 8] FIG. 3 is a cross-sectional view showing a first joining step (first butting portion in the first step) in the method for manufacturing a heat pipe according to the first embodiment of the present invention. [Figure 9] FIG. 3 is a cross-sectional view showing a first joining step (a fourth butting portion in the first step) in the method for manufacturing a heat pipe according to the first embodiment of the present invention. [Figure 10] FIG. 3 is a plan view showing a first joining step (second step) of the manufacturing method of the heat pipe according to the first embodiment of the present invention. [Figure 11] FIG. 3 is a cross-sectional view showing a first joining step (a third butting portion in a second step) in the method for manufacturing a heat pipe according to the first embodiment of the present invention. [Figure 12] 4 is a side view showing a second joining step in the manufacturing method of the heat pipe according to the first embodiment of the present invention. FIG. [Figure 13] FIG. 3 is a plan view showing a sealing step in the method for manufacturing a heat pipe according to the first embodiment of the present invention. [Figure 14] FIG. 4 is a plan view showing a first modified example of the method for manufacturing a heat pipe according to the first embodiment of the present invention. [Figure 15]FIG. 10 is a plan view showing a first joining step of a second modified example of the method for manufacturing a heat pipe according to the first embodiment of the present invention. [Figure 16A] FIG. 10 is a plan view showing a second joining step of a second modified example of the method for manufacturing a heat pipe according to the first embodiment of the present invention. [Figure 16B] FIG. 10 is a side view showing a second joining step of a second modified example of the method for manufacturing a heat pipe according to the first embodiment of the present invention. [Figure 17] FIG. 4 is an exploded perspective view of a heat pipe according to a second embodiment of the present invention. [Figure 18] FIG. 10 is a front view showing an assembling step (main body forming step) of the manufacturing method of the heat pipe according to the second embodiment of the present invention. [Figure 19] FIG. 10 is a plan view showing an assembling step (sealing member butting step) of the method for manufacturing a heat pipe according to a second embodiment of the present invention. [Figure 20] 5 is a schematic diagram showing a first joining step in a method for manufacturing a heat pipe according to a second embodiment of the present invention. FIG. [Figure 21] 5 is a schematic diagram showing a second joining step in the method for manufacturing a heat pipe according to the second embodiment of the present invention. FIG. [Figure 22] 5 is a schematic diagram showing a third joining step in the method for manufacturing a heat pipe according to the second embodiment of the present invention. FIG. [Figure 23] 10 is a cross-sectional view showing a third joining step in the method for manufacturing a heat pipe according to the second embodiment of the present invention. FIG. [Figure 24] 10 is a schematic diagram showing a first joining step of a first modified example of the manufacturing method of the heat pipe according to the second embodiment of the present invention. FIG. [Figure 25] 10 is a schematic diagram showing a second joining step of a first modified example of the manufacturing method of a heat pipe according to the second embodiment of the present invention. FIG. [Figure 26] 10 is a schematic diagram showing a third joining step of a first modified example of the method for manufacturing a heat pipe according to the second embodiment of the present invention. FIG. [Figure 27] FIG. 10 is a plan view showing a second modified example of the method for manufacturing a heat pipe according to the second embodiment of the present invention. [Figure 28]FIG. 10 is an exploded perspective view of a heat pipe according to a third embodiment of the present invention. [Figure 29] FIG. 10 is a front view showing an assembling step (main body forming step) of the manufacturing method of the heat pipe according to the third embodiment of the present invention. [Figure 30] FIG. 10 is a plan view showing an assembling step (sealing member butting step) of the manufacturing method of the heat pipe according to the third embodiment of the present invention. [Figure 31] FIG. 10 is a plan view showing a joining step in a manufacturing method of a heat pipe according to a third embodiment of the present invention. [Figure 32] FIG. 10 is an exploded perspective view of a heat pipe according to a fourth embodiment of the present invention. [Figure 33] FIG. 10 is a plan view showing a joining step in a manufacturing method of a heat pipe according to a fourth embodiment of the present invention. [Figure 34] FIG. 34 is a cross-sectional view taken along the arrows in FIG. 33. [Figure 35] FIG. 10 is a plan view showing a process of friction stirring the sealing passage of the heat pipe according to the fourth embodiment of the present invention. [Figure 36] FIG. 10 is a side view of a heat pipe according to a fifth embodiment of the present invention. [Figure 37] FIG. 10 is a perspective view showing a sealing member of a heat pipe according to a sixth embodiment of the present invention. [Figure 38] FIG. 13 is a perspective view showing a first modified example of a sealing member of a heat pipe according to a sixth embodiment of the present invention. [Figure 39] FIG. 10 is a side cross-sectional view showing a second modified example of the heat pipe according to the sixth embodiment of the present invention. [Figure 40] FIG. 10 is a side cross-sectional view showing a third modified example of the heat pipe according to the sixth embodiment of the present invention. [Figure 41] FIG. 10 is a side view showing a heat pipe according to a seventh embodiment of the present invention. [Figure 42] FIG. 13 is a side view showing a first modified example of the heat pipe according to the seventh embodiment of the present invention. [Figure 43] FIG. 13 is a side view showing a second modified example of the heat pipe according to the seventh embodiment of the present invention. [Figure 44]FIG. 13 is a side view showing a third modified example of the heat pipe according to the seventh embodiment of the present invention. [Figure 45] 1A and 1B are plan views illustrating an example and a comparative example of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0045] Embodiments of the present invention will be described with reference to the drawings as appropriate. The present invention is not limited to the following embodiments. Furthermore, the components in each embodiment can be combined in part or in whole as appropriate. In the following description, "front surface" refers to the surface opposite to the "rear surface." In this specification, a numerical range expressed by "to" means "greater than or equal to" or "less than or equal to," and is intended to include both ends of the numerical range.

[0046] [1. First embodiment] [1-1. Heat pipe configuration] As shown in FIG. 1, the heat pipe 1 according to the first embodiment is composed of a main body 2 and sealing members 3 and 4. The heat pipe 1 is a device that cools a heat generating element (not shown) placed inside by circulating a working fluid through its internal space. The heat pipe 1 is a flat heat pipe that is rectangular in plan view and rectangular in cross section. The heat pipe 1 is a thin flat heat pipe (vapor chamber) with a height that is relatively small compared to its length in the longitudinal direction and width in the lateral direction in plan view.

[0047] The heat pipe 1 is formed by joining the main body 2 and the sealing members 3 and 4 together by friction stir welding. The joining method is not limited to friction stir welding. For example, micro FSW, laser welding, or the like may be used for joining, or a combination of multiple joining methods may be used. The main body 2 and the sealing members 3 and 4 may be made of any metal that can be joined by friction stir welding (aluminum, aluminum alloy, magnesium, magnesium alloy, copper, copper alloy, titanium, titanium alloy, etc.), but in this embodiment they are made of an aluminum alloy.

[0048] The main body 2 has a rectangular shape in a plan view, and is a rectangular (square) cylinder with open ends 7 and 8 on both sides in the longitudinal direction, and has an open bottom. As shown in FIG. 2, the inside of the main body 2 is a rectangular hollow portion. In this embodiment, the main body 2 is a cylinder with an open bottom and open ends, but it may also be a cylinder with a closed bottom and only one open end. In this embodiment, the main body 2 is formed by combining two members, a first member 10 and a second member 20.

[0049] As shown in FIG. 3 , the first member 10 has an L-shape in a front view. The first member 10 has an L-shape in a cross-sectional view perpendicular to the longitudinal direction. The first member 10 includes a first wall portion 11 and a first side wall portion 12. In a cross-sectional view perpendicular to the longitudinal direction of the first member 10, the first wall portion 11 and the first side wall portion 12 are arranged to have a substantially right-angled positional relationship. In a cross-sectional view perpendicular to the longitudinal direction of the first member 10, the first wall portion 11 is longer than the first side wall portion 12. The first wall portion 11 is a plate-like member having a rectangular shape in a plan view. The first wall portion 11 includes an end surface 11a that abuts against the second member 20, an inner wall surface 11b that faces the second member 20, an outer wall surface 11c that contacts the heating element, and an end surface 11d that abuts against the sealing members 3 and 4. A groove portion 5 is formed in the inner wall surface 11b. The groove portion 5 is composed of a plurality of microgrooves 6 formed along the longitudinal direction of the heat pipe 1.

[0050] The microgrooves 6 are recessed from the inner wall surface 11b toward the outer wall surface 11c and have a groove-like shape. The shape of the microgrooves 6 can be appropriately set depending on the heating element to be cooled. The groove portions 5 are formed in an area including the longitudinal ends of the inner wall surface 11b. In other words, the groove portions 5 are formed over the entire longitudinal length of the inner wall surface 11b. The outer wall surface 11c is a flat surface that serves as the main surface (first main surface) on which the heating element is arranged.

[0051] The groove width of the microgrooves 6 may be set appropriately, for example, 0.1 to 2.0 mm, preferably 0.2 to 1.5 mm, more preferably 0.3 to 1 mm, even more preferably 0.4 to 0.8 mm, and particularly preferably 0.5 to 0.6 mm. The groove width of the microgrooves 6 constituting the groove portion 5 may be constant, or microgrooves 6 of multiple groove widths may be combined. When microgrooves 6 of multiple groove widths are combined, microgrooves 6 of multiple groove widths may be arranged in the longitudinal direction of the heat pipe 1, or microgrooves 6 of multiple groove widths may be arranged in the lateral direction of the heat pipe 1. When combining microgrooves 6 with multiple groove widths, it is preferable to combine microgrooves 6 with groove widths of 0.7 mm or less and microgrooves 6 with groove widths of 0.7 mm or more, more preferably to combine microgrooves 6 with groove widths of 0.6 mm or less and microgrooves 6 with groove widths of 0.8 mm or more, even more preferably to combine microgrooves 6 with groove widths of 0.5 mm or less and microgrooves 6 with groove widths of 0.9 mm or more, and particularly preferably to combine microgrooves 6 with groove widths of 0.4 mm or less and microgrooves 6 with groove widths of 1 mm or more. For example, the groove portion 5 may be provided by combining microgrooves 6 with groove widths of 0.2 to 0.6 mm and microgrooves 6 with groove widths of 0.8 mm to 1.5 mm.

[0052] The first side wall portion 12 is a portion that stands substantially vertically from an end portion in the width direction of the first wall portion 11. The first side wall portion 12 has an end surface 12a, an inner wall surface 12b, an outer wall surface 12c, and an end surface 12d. A first step portion 13 is formed on the end surface 12a of the first side wall portion 12 along the longitudinal direction. The first step portion 13 is composed of a first step bottom surface 13a that bends down from the inner wall surface of the first wall portion 11, and a first step side surface 13b that rises from the first step bottom surface 13a and bends down from the end surface 12a of the first side wall portion 12. The first step bottom surface 13a is formed at a position one step below the end surface 12a. The first step side surface 13b is formed at a position one step below the inner wall surface of the first wall portion 11. The inner wall surface 12b is a surface that faces the second member 20. The outer wall surface 12c is the surface opposite to the inner wall surface 12b. A heating element may be disposed on the outer wall surface 12c. The end surfaces 12d are end portions formed on both longitudinal sides and are surfaces that come into contact with the sealing members 30 and 40.

[0053] The second member 20 has an L-shape in a front view. The second member 20 has an L-shape in a cross-sectional view perpendicular to the longitudinal direction. The second member 20 includes a second wall portion 21 and a second side wall portion 22. In a cross-sectional view perpendicular to the longitudinal direction of the second member 20, the second wall portion 21 and the second side wall portion 22 are arranged to have a substantially right-angled positional relationship. In a cross-sectional view perpendicular to the longitudinal direction of the second member 20, the second wall portion 21 has a shape longer than the second side wall portion 22. The second wall portion 21 is a plate-like member having a rectangular shape in a plan view. The second wall portion 21 includes an end surface 21a that abuts against the first member 10, an inner wall surface 21b that faces the first member 10, an outer wall surface 21c that contacts the heating element, and end surfaces 21d and 21e that abut against the sealing members 3 and 4, respectively. Groove portions 5 are formed on the inner wall surface 21b. The groove portions 5 are composed of a plurality of microgrooves 6 formed along the longitudinal direction of the heat pipe 1. The groove portions 5 are formed in an area including the longitudinal ends of the inner wall surface 21b. In other words, the groove portions 5 are formed over the entire longitudinal length of the inner wall surface 21b. The outer wall surface 21c is a flat surface that serves as the main surface (second main surface) on which the heat generating element is arranged.

[0054] The second side wall portion 22 is a portion extending from an end portion of the second wall portion 21 in the width direction. The second side wall portion 22 includes an end surface 22a, an inner wall surface 22b, an outer wall surface 22c, and an end surface 22d. A second step portion 23 is formed on the end surface 22a of the second side wall portion 22 along the longitudinal direction. The second step portion 23 is composed of a second step bottom surface 23a that bends down from the inner wall surface 21b of the second wall portion 21, and a second step side surface 23b that rises from the second step bottom surface 23a and is located one step below the inner wall surface 21b of the second wall portion 21. The second step bottom surface 23a is located one step above the end surface 22a. The inner wall surface 22b is the surface facing the first member 10. The outer wall surface 12c is the surface opposite the inner wall surface 22b. A heating element may be disposed on the outer wall surface 22c. The end faces 22d are end faces formed on both sides in the longitudinal direction and are surfaces that come into contact with the sealing members 30, 40. Although the first member 10 and the second member 20 in the first embodiment are formed to have the same shape, they may have different shapes as long as they can be combined to form the cylindrical main body 2 having open ends 7, 8.

[0055] As shown in FIGS. 1 and 3 , the sealing members 3 and 4 have a rectangular (quadrilateral) shape in front view and are members that seal the openings 7a and 8a at both ends of the main body 2, respectively. The sealing member 3 includes a sealing wall 31 and an insertion portion 32. The sealing wall 31 is a rectangular plate-like portion. The sealing wall 31 includes a front surface 31a, a back surface 31b, and side surfaces 31c and 31d. The left-right and height dimensions of the sealing wall 31 are approximately the same as the left-right and height dimensions of the end 8 of the main body 2. The insertion portion 32 is formed continuously from the sealing wall 31 and is inserted into the opening 8a (see FIG. 11 ) of the main body 2. The left-right and height dimensions of the insertion portion 32 are approximately the same as the left-right and height dimensions of the opening 8a (see FIG. 11 ) of the main body 2. The shapes of the sealing members 3 and 4 can be changed as appropriate according to the application and the shape of the end of the main body 2.

[0056] The sealing member 4 includes a sealing wall portion 41, an insertion portion 42, a protrusion 43, a pipe 44, and a pipe hole 45. The sealing wall portion 41 is a plate-like portion having a rectangular (quadrilateral) shape. The sealing wall portion 41 includes a front surface 41a, a back surface 41b, and side surfaces 41c and 41d. The left-right and height dimensions of the sealing wall portion 41 are approximately the same as the left-right and height dimensions of the end portion 7 of the main body portion 2. The insertion portion 42 is formed continuously from the sealing wall portion 41 and is inserted into the opening 7a of the main body portion 2 (see FIG. 9). The left-right and height dimensions of the insertion portion 42 are approximately the same as the left-right and height dimensions of the opening 7a of the main body portion 2. The protrusion 43 is a portion that protrudes from the center of the sealing wall portion 41 and protrudes in the opposite direction (outward) from the insertion portion 42. The dimensions of the protruding portion 43 in the left-right and height directions are smaller than those of the sealing wall portion 41. The pipe 44 is cylindrical and protrudes further outward from the protruding portion 43. The pipe hole 45 is a through-hole that communicates with the sealing wall portion 41, the insertion portion 42, the protruding portion 43, and the pipe 44, and connects the inside and outside of the main body portion 2.

[0057] [1-2. Heat pipe manufacturing method] Next, a method for manufacturing the heat pipe according to this embodiment will be described. The method for manufacturing the heat pipe according to this embodiment includes a preparation step, an assembly step, a joining step, and a sealing step.

[0058] <Preparation process> The preparation step is a step of preparing the first member 10, the second member 20, and the sealing members 3 and 4. There are no particular limitations on the manufacturing method of the raw materials for the first member 10, the second member 20, and the sealing members 3 and 4, but they can be formed by, for example, extrusion, pressing, casting, forging, cutting, etc. The first member 10 and the second member 20 are preferably formed by extrusion so as to be elongated in the longitudinal direction and formed into a uniform cross-sectional shape, but may also be formed by forging or casting depending on the size. Furthermore, the sealing members 3 and 4 are preferably formed by casting and cutting so as to be formed into a shape that can be combined by being inserted into the first member 10 and the second member 20.

[0059] In the preparation step, as shown in FIG. 4, a multi-cutter M is used to form multiple microgrooves 6 along the longitudinal direction on the inner wall surface 11b of the first wall portion 11 of the raw material for the first member 10. The multi-cutter M includes a shaft portion Ma and multiple disk cutters Mb stacked on the shaft portion Ma with gaps between them. The microgrooves 6 are preferably formed up to the end portions, and more preferably formed over the entire area from one end to the other in the longitudinal direction. In the preparation step, microgrooves 6 are also formed in the second member 20 in the same manner as for the first member 10.

[0060] <Combination process> The assembling process is a process of assembling the first member 10, the second member 20, and the sealing members 3 and 4. The assembling process includes a main body forming process and a sealing member butting process. As shown in FIG. 5, the main body forming process is a process of assembling the first member 10 and the second member 20 to form the cylindrical main body 2.

[0061] In the main body forming process, the first step bottom surface 13a of the first member 10 is opposed to the inner wall surface 21b of the second member 20, and the second step bottom surface 23a of the second member 20 is opposed to the inner wall surface 11b of the first member 10. As a result, the first step side surface 13b is butted against the end surface 21a of the second wall portion 21 to form a first butting portion J1. Furthermore, the second step side surface 23b of the second step portion 23 is butted against the end surface 11a of the first wall portion 11 to form a second butting portion J2. In other words, the first butting portion J1 is formed by butting the first step portion 13 provided at one end of the first member 10 against the other end of the second member 20. Furthermore, the second butting portion J2 is formed by butting the second step portion 23 provided at one end of the second member 20 against the other end of the first member 10. As a result, the end face 12a of the first side wall portion 12 and the outer wall surface 21c of the second wall portion 21 are flush with each other. In addition, the end face 22a of the second side wall portion 22 and the outer wall surface 11c of the first wall portion 11 are flush with each other. The first butting portion J1 and the second butting portion J2 are formed along the longitudinal direction of the main body portion 2.

[0062] 6, 9, and 11, the sealing member butting process is a process of inserting the insertion portion 32 of the sealing member 3 and the insertion portion 42 of the sealing member 4 into the openings 7a, 8a of both end portions 7, 8 of the main body portion 2 to attach the sealing members 3, 4 to the main body portion 2. One end portion 8 of the main body portion 2 is butted against the sealing wall portion 31 to form a third butt portion J3. Furthermore, the other end portion 7 of the main body portion 2 is butted against the sealing wall portion 41 to form a fourth butt portion J4. The third butt portion J3 and the fourth butt portion J4 are formed over the entire circumferential direction of the main body portion 2.

[0063] <Joining process> The joining process is a process of joining the first butt portion J1, the second butt portion J2, the third butt portion J3, and the fourth butt portion J4. In this embodiment, as shown in FIGS. 6 to 12, a rotary tool F is used to friction stir weld the first butt portion J1, the second butt portion J2, the third butt portion J3, and the fourth butt portion J4. The joining process includes a clamping process, a first joining process, and a second joining process. The clamping process is a process of fixing the main body portion 2 and the sealing members 3 and 4 using clamps (not shown) to prevent them from moving.

[0064] As shown in Fig. 8, the rotary tool F is composed of a connecting portion F1 and a stirring pin F2. The rotary tool F is made of, for example, tool steel. The connecting portion F1 is a portion that is connected to the rotating shaft of a friction stirring device (not shown). The connecting portion F1 is cylindrical and has a screw hole (not shown) formed therein for fastening a bolt.

[0065] The stirring pin F2 hangs down from the connecting portion F1 and is coaxial with the connecting portion F1. The stirring pin F2 tapers as it moves away from the connecting portion F1. The tip of the stirring pin F2 is perpendicular to the central axis of rotation C and has a flat surface.

[0066] A spiral groove is engraved on the outer circumferential surface of the stirring pin F2. In this embodiment, in order to rotate the rotary tool F clockwise, the spiral groove is formed counterclockwise from the base end to the tip. In other words, the spiral groove is formed counterclockwise when viewed from above when tracing the spiral groove from the base end to the tip.

[0067] When rotating the rotary tool F counterclockwise, it is preferable to form the spiral groove clockwise from the base end to the tip. In other words, in this case, the spiral groove is formed clockwise as viewed from above when tracing the spiral groove from the base end to the tip. By setting the spiral groove in this manner, the metal that has plastically fluidized during friction stirring is guided by the spiral groove to the tip side of the stirring pin F2. This makes it possible to reduce the amount of metal that spills out of the metal members to be joined (the main body 2 and the sealing members 3, 4).

[0068] In this embodiment, the rotary tool F is attached to a friction stirring apparatus that is movable in the horizontal and vertical directions. The rotary tool F may also be attached to a robot arm having a rotation drive means such as a spindle unit at its tip.

[0069] <First joining process> 7, in the first joining step, friction stir welding is performed on the first butt portion J1, the third butt portion J3, and the fourth butt portion J4 exposed on the front and back surfaces of the main body portion 2 and the sealing members 3, 4. The first joining step includes a first step in which friction stir welding is performed from a start position SP1 to an end position EP1 shown in Fig. 7, and a second step in which friction stir welding is performed from a start position SP2 to an end position EP2 shown in Fig. 10.

[0070] In the first step, friction stir welding is performed from the start position SP1 to the end position EP1 via intermediate positions S1 and S2. The start position SP1 is set on the first butt portion J1. The intermediate position S1 is set at the position where the first butt portion J1 and the fourth butt portion J4 intersect. That is, the intermediate position S1 is set at the position of the corner formed by the end face 21a and the end face 21d of the second wall portion 21. The end position EP1 is set at a position on the surface of the sealing wall portion 41 of the sealing member 4 opposite the intermediate position S1, which is located on the end face 21a side of the second wall portion 21, in a plan view, close to the second side wall portion 22 and spaced from the fourth butt portion J4. The intermediate position S2 is set on the fourth butt portion J4 and near the end position EP1. The intermediate position S2 is set to a position close to the outer wall surface 22c of the second side wall portion 22 so that the plasticized region W1 formed by friction stir welding of the fourth butt portion J4 in the first step and the plasticized region W6 formed by friction stir welding of the fourth butt portion J4 in the second step described below can be partially overlapped.

[0071] In the first step, the rotated rotary tool F is inserted into the start position SP1 and moved along the first butt portion J1 toward the intermediate position S1. When the rotary tool F reaches the intermediate position S1, the welding direction is changed, and the rotary tool F is moved along the fourth butt portion J4 toward the intermediate position S2. When the rotary tool F reaches the intermediate position S2, the welding direction is changed, and the rotary tool F is moved on the sealing wall portion 41 toward the end position EP1. After passing through the intermediate positions S1 and S2, the rotary tool F is removed from the sealing member 4 when it reaches the end position EP1. A plasticized region (welded portion) W1 is formed along the movement trajectory of the rotary tool F. As shown in FIGS. 8 and 9, friction stir welding is performed with the base end side of the stirring pin F2 exposed. In the first step, the insertion depth of the rotary tool F into the first butt portion J1 and the fourth butt portion J4 may be set as appropriate. In this embodiment, however, it is set to approximately half the thickness of the second wall portion 21 or the height of the first step side surface 13b. As an example, if the thickness of the second wall portion 21 or the height of the first step side surface 13b is 3 mm, the insertion depth of the rotary tool F is set to 1.5 mm. The conditions of the rotary tool F may be set appropriately, but for example, the rotation speed is set to 9800 rpm and the feed rate is set to 300 mm / min.

[0072] As shown in Fig. 8, at the first butting portion J1, the plasticized region W1 or the stirring pin F2 may be set to reach the first step bottom surface 13a. Also, as shown in Fig. 9, at the fourth butting portion J4, the plasticized region W1 or the stirring pin F2 may be set to reach the insertion portion 42. This can further improve watertightness, airtightness, and joining strength.

[0073] In the second step, as shown in FIG. 10 , friction stir welding is performed from a start position SP2 to an end position EP2 via intermediate positions S3 and S4. The start position SP2 is set on the first butt portion J1 and on the plasticized region W1. The intermediate position S3 is set at a position where the first butt portion J1 and the third butt portion J3 intersect. That is, the intermediate position S3 is set at a corner formed by the end faces 21a and 21e of the second wall portion 21. The end position EP2 is set at a position on the surface of the sealing wall portion 31 of the sealing member 3 opposite the intermediate position S3, which is located on the end face 21a side of the second wall portion 21, in a plan view, proximate to the second side wall portion 22, and spaced from the third butt portion J3. The intermediate position S4 is set on the third butt portion J3 and near the end position EP2. The intermediate position S4 is set to a position close to the outer wall surface 22c of the second side wall portion 22 so that the plasticized region W2 formed by friction stir welding of the third butt portion J3 in the first step and the plasticized region W7 formed by friction stir welding of the third butt portion J3 in the second step described below can be partially overlapped.

[0074] In the second process, the rotated rotary tool F is inserted into the start position SP2 and moved along the first butt joint J1 toward the intermediate position S3. When the rotary tool F reaches the intermediate position S3, the welding direction is changed and the rotary tool F is moved along the third butt joint J3 toward the intermediate position S4. When the rotary tool F reaches the intermediate position S4, the welding direction is changed and the rotary tool F is moved on the sealing wall 31 toward the end position EP2. After passing through the intermediate positions S3 and S4, the rotary tool F is removed from the sealing member 3 when it reaches the end position EP2. A plasticized region W2 is formed along the movement trajectory of the rotary tool F. As shown in FIG. 11, the insertion depth of the rotary tool F can be set appropriately in the same manner as in the first process. At the first butt joint J1, the plasticized region W1 and the plasticized region W2 partially overlap. The welding conditions for the second process (insertion depth, rotation speed, feed rate, etc.) are set in the same manner as in the first process.

[0075] In the first joining step, friction stir welding is also performed on the second butt portion J2 (see FIG. 5), the third butt portion J3, and the fourth butt portion J4 exposed on the back surfaces of the main body portion 2 and the sealing members 3 and 4. The back surfaces are subjected to the same process as the front surfaces, so a description thereof will be omitted.

[0076] <Second joining process> As shown in Figure 12, the second joining process is a process of joining the portions of the third butt portion J3 and the fourth butt portion J4 that are exposed on both side surfaces of the main body portion 2. Tab material T is placed on both sides (vertical direction) of each of the third butt portion J3 and the fourth butt portion J4. The tab material T has a rectangular parallelepiped shape. The tab material T is positioned so that the end faces of the tab material T are flush with the side surfaces of the main body portion 2 and the sealing members 3, 4.

[0077] In the second joining process, the rotary tool F is inserted into a start position SP3 set on the tab material T and moved along the third butt joint J3 toward an end position EP3 set on the opposite tab material T. A plasticized region W5 is formed in the movement trajectory of the rotary tool F.

[0078] Similarly, in the second joining step, the rotary tool F is inserted into a start position SP4 set on the tab material T, and is moved along the fourth butt portion J4 toward an end position EP4 set on the opposite tab material T. A plasticized region W6 is formed in the movement trajectory of the rotary tool F.

[0079] As shown in FIG. 13, in the second joining process, the insertion depth of the rotary tool F is set so that the plasticized region W6 overlaps with the plasticized region W1 exposed on the front side and the plasticized region W1 exposed on the back side, respectively. While the insertion depth may be set as appropriate, it is more preferable to set the plasticized region W6 so that it reaches the first butting portion J1. This allows the plasticized regions W1, W1 to be friction-stirred again, further improving watertightness, airtightness, and joining strength. Furthermore, as shown in FIG. 12, the insertion depth of the rotary tool F is also set so that the plasticized region W5 formed at the third butting portion J3 overlaps with the plasticized region W2 exposed on the front side and the plasticized region W2 exposed on the back side, respectively.

[0080] In the second joining process, although not specifically illustrated, portions of the third butt portion J3 and the fourth butt portion J4 exposed on the opposite side of the main body portion 2 are also joined. As shown in FIG. 1 , the opposite side of the third butt portion J3 and the opposite side of the fourth butt portion J4 are also friction-stir-welded in the same manner, thereby forming a plasticized region W7 and a plasticized region W8, respectively. As shown in FIG. 13 , in the second joining process, the insertion depth of the rotary tool F is set so that the plasticized region W8 overlaps with the plasticized region W1 exposed on the front side and the plasticized region W1 exposed on the back side, respectively. While the insertion depth may be set as appropriate, it is more preferable to set the plasticized region W8 so that it reaches the second butt portion J2. This again friction-stirs the plasticized regions W1 and W1, thereby further improving watertightness, airtightness, and joining strength.

[0081] In the second joining step, the insertion depth of the rotary tool F is set so that the plasticized region W7 overlaps with the plasticized region W2 exposed on the front side and the plasticized region W2 exposed on the back side. While the insertion depth may be set as appropriate, it is more preferable to set the plasticized region W7 so that it reaches the second butting portion J2. This again causes the plasticized regions W2, W2 to be friction-stirred, further improving watertightness, airtightness, and joining strength. After the second joining step is completed, the tab material T is removed. Through the first joining step and the second joining step, the main body portion 2 and the sealing members 3 and 4 are friction stir joined to form an intermediate member.

[0082] <Sealing process> As shown in FIG. 13, the sealing process involves injecting a working fluid into the intermediate member and then sealing the intermediate member. In the sealing process, the working fluid is injected into the intermediate member, frozen, and then a rotary tool F is used to perform friction stirring on the protruding portion 43 while drawing a vacuum, thereby sealing the pipe hole 45. In the sealing process, the rotating rotary tool F is inserted at a start position SP5 set on one end of the protruding portion 43 and moved toward an end position EP5. A plasticized region W9 is formed along the movement trajectory of the rotary tool F. The insertion depth of the rotary tool F is set so that the pipe hole 45 is divided by the plasticized region W9. Since the pipe hole 45 is divided, the interior of the heat pipe 1 is placed in a low vacuum state. The heat pipe 1 is formed through the above process. Examples of working fluids that can be used include pure water, methanol, ethanol, acetone, and mixtures thereof.

[0083] [1-3. Action and Effects] Conventionally, in manufacturing a flat heat pipe, a recess is formed in at least one plate to serve as a flow path for the working fluid, a wick is formed in the recess, and then the plates are stacked with the recess facing inward, and the plates are joined around their peripheries to seal the recess. The recess can be formed by machining, bending, forging, etc. When forming a recess by machining, cutting the center of a plate material allows for the formation of a recess surrounded by a bottom portion of the plate material and a wall portion extending from the periphery of the bottom portion. In this case, it is necessary to avoid contact between the tool and the wall portion when forming a groove as a wick within the recess. For example, when attempting to form a groove by cutting the bottom portion of the plate material using a rotating circular saw blade, the circular saw blade cannot approach the outer periphery near the wall portion, making it difficult to form a groove throughout the entire recess, including near the edges. The lack of grooves near the edges of the recess prevents the working fluid from circulating near the edges, resulting in insufficient heat diffusion to the ends of the heat pipe. Furthermore, when forming a recess by bending or forging, it is difficult to achieve dimensional accuracy in the plate material after the recess formation process. In addition, tubular heat pipes, which are made of pipes with internal wicks, have also been known. In tubular heat pipes, the internal space is sealed by swaging the pipe ends and then welding them, or by heating and stretching the pipe ends and then welding them. In this case, the quality of the welds can be unstable, and the stretching of the ends can reduce the wall thickness, resulting in a decrease in strength.

[0084] In this embodiment, the first member 10, which has a longitudinal groove, and the second member 20 are joined together longitudinally to form the cylindrical main body 2 with open ends 7 and 8. The ends 7 and 8 of the main body 2 are joined to the sealing members 3 and 4 to form the heat pipe 1. Thus, the first member 10 and the second member 20 have shapes that allow the ends of the main body 2 to be open, i.e., the ends 7 and 8 of the first member 10 and the second member 20 are open. Therefore, for example, when forming the grooves 5 in the first member 10 and the second member 20 using the multi-cutter M, the grooves 5 as wicks can be formed all the way to the ends of the first member 10 and the second member 20. This allows the working fluid to circulate throughout the entire heat pipe 1, including the portions corresponding to the ends of the first member 10 and the second member 20, via the grooves 5, thereby improving cooling performance.

[0085] In this embodiment, the groove portion 5 is formed by a plurality of microgrooves 6 sandwiched between the first side wall portion 12 and the second side wall portion 22 extending from the inner wall surfaces 11b and 21b. This allows heat applied to the outer wall surfaces 11c and 21c of the first and second members 10 and 20, which are located opposite the inner wall surfaces 11b and 21b, to be transferred directly to the inner wall surfaces 11b and 21b, and then to the working fluid flowing through the microgrooves 6, thereby efficiently transferring and diffusing the heat. This improves cooling performance compared to a heat pipe that uses a porous metal wick or a mesh-like metal wick.

[0086] In addition, in this embodiment, the first member 10 and the second member 20, whose ends 7 and 8 are open, can be formed by, for example, extrusion (extrusion molding). This makes it possible to improve the dimensional accuracy of the first member 10 and the second member 20 compared to when recesses are formed by bending or forging, and a heat pipe with excellent dimensional accuracy can be provided. In addition, in this embodiment, the first member 10 and the second member 20 have the same shape and size, which improves productivity.

[0087] In addition, in this embodiment, grooves 5 are formed in an area including the longitudinal ends of the first member 10, or grooves 5 are formed throughout the entire longitudinal direction of the first member 10, so that heat can be diffused to the ends via the grooves 5.

[0088] In this embodiment, the main body 2 has a thin, cylindrical shape and includes a first wall 11 and a second wall 21, which are arranged opposite each other across an internal space and have flat outer wall surfaces 11c, 21c. The joints between the first member 10 and the second member 20 are provided on the first wall 11 and the second wall 21, which are arranged opposite each other across the internal space. This eliminates the need to provide flanges or other components for joining the first member 10 and the second member 20 in a manner that protrudes outward beyond the walls that are arranged opposite each other across the internal space. Therefore, the effective area of ​​the heat pipe 1, which is the sum of the area of ​​the portion of the heat pipe 1 that has an internal space through which the working fluid flows and contributes to cooling, and the area of ​​the portion of the heat pipe 1 that is provided for joining components and does not contribute to cooling, such as the flanges, can be increased.

[0089] Furthermore, in this embodiment, since the main body 2 has planar outer wall surfaces 11c, 21c, when a flat surface facing a heat-generating element is provided, the outer wall surfaces 11c, 21c of two or more heat pipes 1,1 can be arranged so that they contact the flat surface of the heat-generating element, thereby sandwiching the heat-generating element between the heat pipes 1,1, thereby further improving cooling efficiency. Furthermore, in this embodiment, since the main body 2 has planar outer wall surfaces 11c, 21c, when a flat surface facing a heat-generating element is provided, the outer wall surfaces 11c, 21c of the heat pipe 1 can be arranged so that they contact the flat surface of the heat-generating element, thereby sandwiching the heat pipe 1 between the heat-generating elements, thereby further improving cooling efficiency. Furthermore, in this embodiment, since the main body 2 has planar outer wall surfaces 11c, 21c, when a flat surface facing a heat-generating element is provided, the outer wall surfaces 11c, 21c of two or more heat pipes 1,1 can be arranged so that they contact the flat surface of the heat-generating element, thereby sandwiching the heat pipe 1 between the heat pipes 1,1, thereby further improving cooling efficiency. Furthermore, in this embodiment, since the main body 2 has flat outer wall surfaces 11c, 21c, when the heating elements have opposing flat surfaces, the outer wall surfaces 11c, 21c of the multiple heat pipes 1 are in contact with the corresponding flat surfaces of the multiple heating elements, and the heat pipes 1 and the heating elements are arranged alternately, thereby further improving the cooling efficiency.

[0090] Moreover, the first wall portion 11 has a groove portion 5 inside (inner wall surface 11b), with the outer wall surface 11c of the first wall portion 11 being one main surface and the outer wall surface 21c of the second wall portion 21 being the other main surface. Thus, by providing the groove portion 5 in the first wall portion 11, heat received from a heating element that contacts the outer wall surface 11c of the first wall portion 11 can be efficiently dissipated via the groove portion 5. Further, the second wall portion 21 has a groove portion 5 inside (inner wall surface 21b), with the outer wall surface 21c of the second wall portion 21 being one main surface and the outer wall surface 11c of the first wall portion 11 being the other main surface. Thus, by providing the groove portion 5 in the second wall portion 21, heat received from a heating element that is in contact with the outer wall surface 21c of the second wall portion 21 can be efficiently dissipated via the groove portion 5.

[0091] In this embodiment, the second wall portion 21 has grooves 5 inside (on the inner wall surface 21b) as a wick. That is, by providing the grooves 5 not only on the first wall portion 11 but also on the second wall portion 21, it is possible to efficiently dissipate heat received from a heat generating element that is in contact with the second wall portion 21. The grooves 5 may be provided on at least one of the inner wall surfaces that constitute the main body portion 2.

[0092] In this embodiment, the main body 2 has a cylindrical shape with no bottom, with both ends 7 and 8 open, and sealing members 3 and 4 are respectively joined to both ends 7 and 8 of the main body 2. This increases the strength of the heat pipe 1. Note that the main body 2 may also have a cylindrical shape with a bottom at one end and an open end at the other.

[0093] In this embodiment, the first member 10 and the second member 20 are L-shaped in cross section, and the sealing members 3 and 4 are rectangular in front view. A first butting portion J1 is joined where one end of the L-shape of the first member 10 and the other end of the L-shape of the second member 20 are butted together. A second butting portion J2 is joined where the other end of the L-shape of the first member 10 and one end of the L-shape of the second member 20 are butted together. Furthermore, the main body 2 is rectangular tubular and has a rectangular end portion. A third butting portion J3 and a fourth butting portion J4 are joined where the end of the main body 2 and the sealing members 3 and 4 are butted together. Since the first member 10 is L-shaped and composed of the first wall portion 11 and the first side wall portion 12, the groove portion 5 can be formed using the multi-cutter M not only on the inner wall surface 11b of the first wall portion 11 but also on the inner wall surface 12b of the first side wall portion 12. Furthermore, since the second member 20 is L-shaped and made up of the second wall portion 21 and the second side wall portion 22, it becomes possible to form the groove portion 5 using the multi-cutter M not only on the inner wall surface 21b of the second wall portion 21 but also on the inner wall surface 22b of the second side wall portion 22. Furthermore, in this embodiment, the number of joints can be reduced compared to when the main body is formed using four plate materials, thereby improving production efficiency. Furthermore, when the first member 10 and the second member 20 are L-shaped, this is suitable when the heat pipe 1 has a certain thickness.

[0094] In this embodiment, the first member 10 has a first step portion 13 at one end of the L-shape along the longitudinal direction, and the second member 20 has a second step portion 23 at one end of the L-shape along the longitudinal direction. A first butting portion J1 is joined where the first step portion 13 of the first member 10 and the other end (end face 21 a) of the L-shape of the second member 20 are butted together, and a second butting portion J2 is joined where the other end (end face 11 a) of the L-shape of the first member 10 and the second step portion 23 of the second member 20 are butted together. By forming the first step portion 13 and the second step portion 23 in this way, it is possible to increase the stability of assembly and make joining easier.

[0095] In this embodiment, the groove portion 5 has microgrooves 6 with a groove width of 0.2 to 0.6 mm. This allows for efficient diffusion of the working fluid by capillary action. Alternatively, the groove portion 5 may be configured to have microgrooves 6 with a groove width of 0.2 to 0.6 mm and microgrooves 6 with a groove width of 0.8 to 1.5 mm. Under conditions where the pressure in the internal space is low, microgrooves with narrow groove widths facilitate the flow of liquefied working fluid, while under conditions where the pressure in the internal space is high, microgrooves with wide groove widths facilitate the flow of liquefied working fluid. Therefore, by providing multiple microgrooves 6 with different groove widths, it is possible to provide the function of allowing the working fluid to flow appropriately in accordance with the pressures of multiple internal spaces.

[0096] In this embodiment, the heat pipe has one main surface (first wall portion 11) formed along the longitudinal direction and the other main surface (second wall portion 21) facing the one main surface, and has planar flat portions (first side wall portion 12, second side wall portion 22, sealing wall portions 31, 41) on the outside of at least one of the first member 10, the second member 20, and the sealing members 3, 4 as surfaces other than the first wall portion 11 and the second wall portion 21. In this way, by having multiple flat surfaces, the heat pipe can be made to stand on its own in any direction, thereby expanding its applications.

[0097] The method for manufacturing a heat pipe according to this embodiment includes the following steps: a preparation step of forming a plurality of microgrooves 6 along the longitudinal direction of a preformed material to prepare a first member 10 and a second member 20 corresponding to the first member 10, a combination step of assembling the first member 10 and the second member 20 with the grooves 5 facing inward to form a cylindrical main body 2 with an open longitudinal end, and assembling the end of the main body 2 with sealing members 3 and 4, a joining step of joining the first member 10, the second member 20, and the sealing members 3 and 4 to form an intermediate member, and a sealing step of injecting a working fluid into the intermediate member and then sealing the intermediate member. This allows the working fluid to circulate throughout the entire heat pipe 1, including the portions corresponding to the ends of the first member 10 and the second member 20, via the grooves 5, thereby improving cooling performance.

[0098] In the preparation process, a multi-cutter M, which is made up of multiple stacked disk cutters Mb, is used to cut the base material to form multiple microgrooves 6. Therefore, by changing the number, thickness, and spacing of the disk cutters Mb, the number, width, and spacing of the microgrooves 6 can be easily changed.

[0099] In the sealing process, the pipe hole 45 is sealed while drawing a vacuum through the pipe 44. This allows the heat pipe 1 to be easily evacuated. In the sealing process, a working gas (working fluid) may be used instead of the working liquid, and the pipe hole 45 may be sealed while injecting high-pressure gas through the pipe 44. Examples of gases that can be used include helium, nitrogen, methane, ammonia, chlorofluorocarbons, alternative chlorofluorocarbons, and mixtures thereof.

[0100] Furthermore, since the preform is formed by extrusion or press working in the preparation process, the first member 10 and the second member 20 can be easily formed. At this time, the preform with open ends can be formed by extrusion or press working. The first and second members with open ends can be formed by forming microgrooves in this preform. Then, by combining these first and second members, a cylindrical main body with open longitudinal ends can be formed. Furthermore, forming the preform by extrusion or press working allows for higher dimensional accuracy compared to forming a recess for the internal space of the heat pipe by bending or forging.

[0101] Furthermore, in the preparation step, a base material having a first step portion 13 along the longitudinal direction is formed, and in the joining step, the first step portion 13 and the end portion (end face 21 a) of the second member 20 are joined together in a state where the first step portion 13 of the first member 10 and the end portion (end face 21 a) of the second member 20 are butted against each other. This makes it easy to position the first member 10 and the second member 20, and allows joining to be performed in a state where the first member 10 and the second member 20 are stably held.

[0102] Furthermore, in the joining process, the first member 10 and the second member 20 are joined by micro FSW or laser welding, so that the first member 10 and the second member 20 can be easily joined even if the width of the joining portion between them is narrow.

[0103] The end position of the joining process may be set on the third butt portion J3 and the fourth butt portion J4, but in this case, perforations are formed on the third butt portion J3 and the fourth butt portion J4, which is likely to affect the watertightness and airtightness. In this regard, in this embodiment, the end positions EP1 and EP2 of the joining process are set on the sealing members 3 and 4, so that perforations are formed in the sealing members 3 and 4. This makes it less likely that the perforations will affect the watertightness and airtightness.

[0104] Furthermore, in this embodiment, all exposed butt joints can be friction stir welded in the joining process. That is, according to this embodiment, in addition to the first butt joint J1 and the second butt joint J2, the entire circumferential direction of the third butt joint J3 and the fourth butt joint J4 can be friction stir welded. This improves airtightness, watertightness, and joint strength. Furthermore, by using the tab material T in the second joining process, it is possible to easily friction stir weld even portions with short joining distances, such as the side surfaces of the main body portion 2, over their entire lengths. Furthermore, by overlapping the plasticized regions W1 and W2, it is possible to improve airtightness, watertightness, and joint strength. Furthermore, by overlapping the plasticized regions W1 and W2 with the plasticized regions W5 to W8, it is possible to improve airtightness, watertightness, and joint strength.

[0105] [1-4.Other] The first embodiment of the present invention has been described above. In the first embodiment described above, a tab material T is placed on both sides of each of the third butt portion J3 and the fourth butt portion J4 of one main body portion 2. Then, a case has been exemplified in which a rotary tool is inserted into a start position SP3, SP4 set on the tab material T, passes through the third butt portion J3 and the fourth butt portion J4, and is moved toward an end position EP3, EP4 set on the opposite tab material T to perform friction stir welding. When performing friction stir welding of the third butt portion J3 and the fourth butt portion J4, in the second joining step shown in FIG. 12 , multiple main body portions 2 and sealing members 3, 4 may be arranged (stacked) so that the outer wall surface 11c of each main body portion 2 contacts the adjacent outer wall surface 21c, and tab materials T may be placed on both sides of each of the third butt portion J3 and the fourth butt portion J4 of the main body portions 2 located at both ends. Then, a rotary tool may be inserted into start positions SP3, SP4 set on the tab material T, and the rotary tool may be moved through the third butt portion J3 and the fourth butt portion J4 of the aligned main body portions 2 toward end positions EP3, EP4 set on the opposite tab material T, thereby performing friction stir welding on multiple bodies at once. This makes it possible to continuously perform friction stir welding on the third butt portion J3 and the fourth butt portion J4 of the multiple main body portions, thereby improving joining efficiency and reducing manufacturing costs.

[0106] In the first embodiment, the groove portion 5 is formed of a plurality of microgrooves 6 parallel to the longitudinal direction. However, for example, the groove portion 5 may be formed of a plurality of microgrooves 6 parallel to the longitudinal direction and a microgroove parallel to the lateral direction. In this case, the microgrooves parallel to the lateral direction may be provided only at the longitudinal ends of the inner wall surfaces 11b and 21b. This allows the working fluid accumulated at the ends to move not only in the longitudinal direction but also in the lateral direction.

[0107] Furthermore, in this embodiment, the main body 2 is formed of the L-shaped first member 10 and second member 20, but other shapes are also possible. For example, the first member may have a concave cross section (a square-shaped bracket, a U-shaped bracket with approximately right-angled corners), and the second member may be plate-shaped. In this case, the joint (plasticized region) between the first and second members is provided in the second wall portion. Also, for example, the first member may have an H-shaped cross section, and the second member (+third member) may be plate-shaped. Also, for example, four plate-shaped members may be combined.

[0108] [2. First Modification of First Embodiment] Next, a first modified example of the first embodiment will be described. In the first modified example, the joining path in the joining process is different from that in the first embodiment. In the joining process of this embodiment, a first joining process and a second joining process are performed. The second joining process is the same as in the first embodiment, so a description thereof will be omitted.

[0109] 14, in the first joining step of the heat pipe manufacturing method according to the first modified example, a rotary tool F is used to perform friction stir welding on the surface sides of the main body 2 and the sealing members 3 and 4 from a start position SP11 to an end position EP11. The start position SP11 is set on the surface of the sealing member 3 on the opposite side from the first butt portion J1. The end position EP11 is set on the surface of the sealing member 4 on the opposite side from the first butt portion J1. Furthermore, in the first joining step, intermediate positions S11, S12, S13, and S14 are set.

[0110] The intermediate position S11 is set near the start position SP11 in the third butting portion J3. The intermediate position S12 is set at a position where the first butting portion J1 and the third butting portion J3 intersect. The intermediate position S13 is set at a position where the first butting portion J1 and the fourth butting portion J4 intersect. The intermediate position S14 is set near the end position EP11 in the fourth butting portion J4.

[0111] In this joining process, the rotary tool F is inserted into the start position SP11, and friction stir welding is performed in a single stroke in the order of the start position SP11, intermediate positions S11, S12, S13, S14, and end position EP11. In the first joining process, friction stir welding is performed on the back sides of the main body 2 and the sealing members 3 and 4 in the same manner as on the front sides.

[0112] In the first embodiment, the first joining step was performed in two steps, but according to this modification, it can be performed in one step, thereby shortening the manufacturing time. Furthermore, by providing the intermediate positions S13 and S15, friction stir welding can be performed up to the end sides of the third butt portion J3 and the fourth butt portion J4, which makes it easier to overlap the plasticized region formed in the first joining step and the plasticized region formed in the second joining step.

[0113] 3. Second Modification of First Embodiment Next, a second modified example of the first embodiment will be described. The second modified example differs from the first embodiment in the joining path in the joining step. The joining step of this embodiment includes a first joining step and a second joining step.

[0114] 15, in the first joining step, friction stir welding is performed on the front surface sides of the main body portion 2 and the sealing members 3, 4 from a start position SP21 to an end position EP21 using a rotary tool F. The start position SP21 is set on an extension of the first butt portion J1 on the front surface of the sealing member 3, and is located to the left of the third butt portion J3 (toward the sealing member 3) in a planar view. The end position EP21 is set on an extension of the first butt portion J1 on the front surface of the sealing member 4, and is located to the right of the fourth butt portion J4 (toward the sealing member 4) in a planar view. In the first joining step, friction stir welding is performed on the rear surface sides of the main body portion 2 and the sealing members 3, 4 in the same way as on the front surface sides.

[0115] In the second joining process of this modified example, as shown in FIGS. 16A and 16B, the third butt portion J3 and the fourth butt portion J4 are joined by laser welding along the circumferential direction. In the second joining process, a start position SP31 is set on the third butt portion J3. An end position EP31 is set at a position on the third butt portion J3 spaced from the start position SP31 on the side where the laser advances. In the second joining process, a start position SP41 is set on the fourth butt portion J4. An end position EP41 is set at a position on the fourth butt portion J4 spaced from the start position SP41 on the side where the laser advances. In the laser welding, the torch of the laser welding device is moved relative to the main body portion 2 and the sealing members 3 and 4, and welding is performed so that the weld marks overlap at each butt portion.

[0116] As in this modified example, friction stir welding using a rotary tool F may be combined with laser welding. Laser welding has a greater degree of freedom in the range and angle of movement than a friction stir welding machine, making it easy to perform circumferential welding and the like.

[0117] [4. Second Embodiment] Next, a second embodiment of the present invention will be described with reference to Figures 17 to 23. As shown in Figure 17, a heat pipe 1A according to the second embodiment includes a main body 2A and sealing members 3 and 4. The heat pipe 1A according to the second embodiment differs from the first embodiment in the shape of the first member 10A and the shape of the second member 20A. The heat pipe 1A according to the second embodiment is also thinner and wider than the first embodiment. The second embodiment will be described mainly with reference to the differences from the first embodiment.

[0118] As shown in Figures 17 and 18, the first member 10A includes a first wall portion 111, first side wall portions 112, 112, and a support portion 113. The first wall portion 111 is a plate-shaped member. The first wall portion 111 includes an inner wall surface 111b that faces the second member 20A and an outer wall surface 111c that contacts the heating element. A groove portion 5 consisting of a plurality of microgrooves 6 is formed on the inner wall surface 111b. The first side wall portion 112 stands from both edge portions in the width direction of the first wall portion 111 and is formed along the entire length in the longitudinal direction. The first side wall portions 112, 112 are portions on which the second member 20A is placed.

[0119] The support portion 113 is formed along the longitudinal direction at the center of the width direction of the first wall portion 111 and divides the internal space. The height position of the end face (tip portion) 113a of the support portion 113 is approximately the same as the height position of the end faces 112a, 112a of the first side wall portions 112, 112. The longitudinal length of the support portion 113 is slightly shorter than that of the first wall portion 111. That is, as shown in FIG. 19 , the longitudinal length of the support portion 113 is set so that a small gap is formed between the sealing members 3, 4 and the support portion 113 when the sealing members 3, 4 are attached. This allows the working fluid to be injected into the interior of the intermediate member during the sealing process. For this reason, the gap between the sealing members 3, 4 and the support portion 113 is preferably at least 0.1 mm.

[0120] 17, the second member 20A is a plate-shaped member placed on the first member 10A. The second member 20A has an inner wall surface 121b facing the first member 10A and an outer wall surface 121c in contact with the heating element. A groove 5 is formed in the inner wall surface 121b.

[0121] Next, a description will be given of a method for manufacturing the heat pipe 1A according to the second embodiment. The method for manufacturing the heat pipe according to the second embodiment includes a preparation step, an assembly step, a joining step, and a sealing step.

[0122] As shown in FIG. 17, the preparation step is a step of forming the first member 10A, the second member 20A, and the sealing members 3 and 4. The first member 10A, the second member 20A, and the sealing members 3 and 4 can be manufactured by, for example, extrusion, pressing, casting, forging, cutting, etc. The first member 10A and the second member 20A are preferably formed by extrusion so as to be elongated in the longitudinal direction and have a constant cross-sectional shape, but may also be formed by forging or casting depending on the size. Furthermore, the sealing members 3 and 4 are preferably formed by casting or cutting so as to be formed into a shape that can be combined by being inserted into the first member 10A and the second member 20A. Furthermore, grooves 5 are formed on the inner wall surface 111b of the first member 10A and the inner wall surface 121b of the second member 20A.

[0123] The combining step includes a main body forming step and a sealing member butting step. The main body forming step is a step of forming the main body 2A by placing the second member 20A on the first member 10A, as shown in Fig. 18. In the main body forming step, the second member 20A is placed on the end faces 112a, 112a of the first side wall 112 and the end face 113a of the support member 113. The end faces 112a, 112a of the first side wall 112 and the inner wall surface 121b of the second member 20A are butted (overlapped) together to form first butting portions J11, J11.

[0124] 19, the sealing member butting process is a process in which the insertion portion 32 of the sealing member 3 and the insertion portion 42 of the sealing member 4 are inserted into both ends of the main body portion 2A to attach the sealing members 3 and 4 to the main body portion 2A. One end of the main body portion 2A is butted against the sealing wall portion 31 to form a third butt portion J3. The other end of the main body portion 2A is butted against the sealing wall portion 41 to form a fourth butt portion J4. The third butt portion J3 and the fourth butt portion J4 are formed over the entire circumferential direction of the main body portion 2A.

[0125] The joining process is a process of joining the first butt portions J11, J11, the third butt portion J3, and the fourth butt portion J4. In this embodiment, as shown in FIGS. 20 to 23, the joining process is a process of friction stir welding the first butt portions J11, J11, the third butt portion J3, and the fourth butt portion J4 using a rotary tool F. The joining process includes a first joining process performed on the front side of the main body portion 2A and the sealing members 3, 4 as shown in FIG. 20, a second joining process performed on the back side of the main body portion 2A and the sealing members 3, 4 as shown in FIG. 21, and a third joining process performed on the back side of the main body portion 2A and the sealing members 3, 4. Note that in FIGS. 20 to 23, the lengths of the sealing members 3, 4 are drawn larger than actual size for ease of explanation.

[0126] In the first joining step, friction stir welding is performed from a start position SP51 to an end position EP51 via intermediate positions S51, S52, S53, S54, and S51, as shown in Fig. 20. In other words, in the first joining step, friction stir welding is performed in the order of the first butt portion J11 and the fourth butt portion J4 on one side, and the first butt portion J11 and the third butt portion J3 on the other side.

[0127] The start position SP51 and the end position EP51 are set on the surface of the sealing member 3 on an extension line of one of the first butt portions J11. The intermediate position S51 is set at a position where one of the first butt portions J11 and the third butt portion J3 intersect. The intermediate position S52 is set at a position where one of the first butt portions J11 and the fourth butt portion J4 intersect. The intermediate position S53 is set at a position where the other of the first butt portion J11 and the fourth butt portion J4 intersect. The intermediate position S54 is set at a position where the other of the first butt portion J11 and the third butt portion J3 intersect. Note that in FIG. 20, for convenience of drawing, the start position SP51 and the end position EP51 are illustrated at different positions, and the path from the start position SP51 to the intermediate position S51 and the path from the intermediate position S51 to the end position EP51 are illustrated at different positions. The start position SP51 and the end position EP51 are set at the same position, and the path from the start position SP51 to the intermediate position S51 and the path from the intermediate position S51 to the end position EP51 are set at the same position.

[0128] In the first joining process, the rotary tool F is inserted into a start position SP51, and is moved to intermediate positions S51, S52, S53, S54, S51, and an end position EP51 in that order. A plasticized region W21 is formed on the movement trajectory of the rotary tool F (see FIG. 23). The insertion depth of the rotary tool F in the first joining process may be set as appropriate, but in the first joining process, the insertion depth is changed for each section.

[0129] The insertion depth from the start position SP51 to the intermediate position S52 and from the intermediate position S53 to the intermediate position S54 is set to a position where the tip of the stirring pin F2 reaches the end face 112a of the first side wall portion 112. In other words, the stirring pin F2 is inserted deeper than the thickness of the second member 20A, and preferably inserted to a depth of about 1.1 times the thickness of the second member 20A. This allows the overlapping portions of the first butting portions J11, J11 formed by overlapping the end faces 112a, 112a of the first side wall portion 112 and the inner wall surface 121b of the second member 20A to be joined and sealed.

[0130] The insertion depth from intermediate position S52 to intermediate position S53, the insertion depth from intermediate position S54 to intermediate position S51, and the insertion depth from intermediate position S51 to end position EP51 are preferably inserted to a depth of about 0.8 times the thickness of second member 20A. This allows the butted portions of third butt portion J3 formed by butting one end of main body portion 2A against sealing wall portion 31 and fourth butt portion J4 formed by butting the other end of main body portion 2A against sealing wall portion 41 to be joined and sealed.

[0131] For example, in the present embodiment, when the height dimension of the first side wall portion 112 is set to 4 mm and the thickness of the second member 20A is set to 2 mm, the insertion depth from the start position SP51 to the intermediate position S52 is set to 2.2 mm. The insertion depth from the intermediate position S52 to the intermediate position S53 is set to 1.5 mm, the insertion depth from the intermediate position S53 to the intermediate position S54 is set to 2.2 mm, and the insertion depth from the intermediate position S54 to the end position EP51 is set to 1.5 mm.

[0132] 21, friction stir welding is performed on the rear surfaces of the main body portion 2A and the sealing members 3 and 4 from a start position SP52 via intermediate positions S55 and S56 to an end position EP52. Also, in the second joining process, friction stir welding is performed on the rear surfaces of the main body portion 2A and the sealing members 3 and 4 from a start position SP53 via intermediate positions S57 and S58 to an end position EP53.

[0133] The start position SP52 is set on the back surface 31b of the sealing wall 31, on the upper side of the sealing member 3 (the side close to the side surface 31c of the sealing wall 31). The end position EP52 is set on the back surface 31b of the sealing wall 31, on the lower side of the sealing member 3 (the side close to the side surface 31d of the sealing wall 31). The intermediate position S55 is set on the back surface 31b of the sealing member 3, at a position where the first butt portion J11 on the upper side (the side close to the side surface 31c of the sealing wall 31) and the third butt portion J3 intersect. The intermediate position S56 is set on the back surface 31b of the sealing member 3, at a position where the first butt portion J11 on the lower side (the side close to the side surface 31d of the sealing wall 31) and the third butt portion J3 intersect.

[0134] The start position SP53 is set on the back surface 41b of the sealing wall portion 41, on the lower side of the sealing member 4 (the side close to the side surface 41d of the sealing wall portion 41). The end position EP53 is set on the back surface 41b of the sealing wall portion 41, on the upper side of the sealing member 4 (the side close to the side surface 41c of the sealing wall portion 41). The intermediate position S57 is set on the back surface 41b of the sealing wall portion 41, at a position where the first abutting portion J11 on the lower side (the side close to the side surface 41d of the sealing wall portion 41) and the fourth abutting portion J4 intersect. The intermediate position S58 is set on the back surface 41b of the sealing wall portion 41, at a position where the first abutting portion J11 on the upper side (the side close to the side surface 41c of the sealing wall portion 41) and the fourth abutting portion J4 intersect.

[0135] In the second joining step, the rotary tool F is inserted into the start position SP52, and is moved to the intermediate positions S55, S56, and the end position EP52 in this order. In the second joining step, the rotation tool F is inserted into the start position SP53, and then moved to the intermediate positions S57 and S58 and the end position EP53 in that order.

[0136] In the second joining process, the insertion depth of the rotary tool F is set so that the third butt portion J3 and the fourth butt portion J4 are friction stir welded. The insertion depth of the rotary tool F from the start position SP52 to the end position EP52 may be approximately the same as that for joining the butt portions on the front side, and is preferably inserted to a depth of approximately 0.8 times the thickness of the second member 20A. This allows the third butt portion J3 and the fourth butt portion J4 to be welded and sealed. The insertion depth of the rotary tool F may be set as appropriate, but in this embodiment it is set to, for example, 1.5 mm.

[0137] In the third joining step, as shown in Fig. 22, friction stir welding is performed on the four corners on the back side of the main body portion 2A and the sealing members 3 and 4. For ease of explanation, the plasticized regions formed in the second joining step are not shown in Fig. 22. In the third joining step, friction stir welding is performed using a rotary tool F from a start position SP54 to an end position EP54, from a start position SP55 to an end position EP55, from a start position SP56 to an end position EP56, and from a start position SP57 to an end position EP57.

[0138] The start position, end position, and intermediate position of the plasticized region from start position SP54 to end position EP54 and the plasticized region from start position SP55 to end position EP55 formed in the third joining process are set at positions where they intersect with the plasticized region from intermediate position S55 to intermediate position S56 formed in the second joining process. Furthermore, the start position, end position, and intermediate position of the plasticized region from start position SP56 to end position EP56 and the plasticized region from start position SP57 to end position EP57 formed in the third joining process are set at positions where they intersect with the plasticized region from intermediate position S57 to intermediate position S58 formed in the second joining process. This allows friction stir welding to be performed without leaving any unjoined portion between the plasticized region formed in the second joining process and the plasticized region formed in the third joining process.

[0139] The start position SP54 is set at a corner (upper left corner in FIG. 22) of the outer wall surface 111c of the first member 10A, and is located farther from the side surface 31c of the sealing wall 31 than the plasticized region formed in the second joining process from the start position SP52 to the intermediate position S55. The start position SP55 is set at a corner (lower left corner in FIG. 22) of the outer wall surface 111c of the first member 10A, and is located farther from the side surface 31c of the sealing wall 31 than the plasticized region formed in the second joining process from the intermediate position S56 to the end position EP52. The start position SP56 is set at a corner (upper right corner in FIG. 22) of the outer wall surface 111c of the first member 10A, and is located farther from the side surface 41c of the sealing wall 41 than the plasticized region formed in the second joining process from the intermediate position S58 to the end position EP53. The start position SP57 is set at a corner of the outer wall surface 111c of the first member 10A (the lower right corner in Figure 22), and on a side farther away from the side portion 41d of the sealing wall portion 41 than the plasticized region formed in the second joining process from the start position SP53 to the intermediate position S57.

[0140] The end position EP54 is set to face the start position SP54 across the third butt portion J3 on the back surface 31b of the sealing wall portion 31 and is farther from the side surface 31c of the sealing wall portion 31 than the plasticized region from the start position SP52 to the intermediate position S55 formed in the second joining step. The end position EP55 is set to face the start position SP55 across the third butt portion J3 on the back surface 31b of the sealing wall portion 31 and is farther from the side surface 31d of the sealing wall portion 31 than the plasticized region from the intermediate position S56 to the end position EP52 formed in the second joining step. The end position EP56 is set to face the start position SP56 across the fourth butt portion J4 on the back surface 41b of the sealing wall portion 41 and is farther from the side surface 41c of the sealing wall portion 41 than the plasticized region from the intermediate position S58 to the end position EP53 formed in the second joining step. The end position EP57 is set on the back surface 41b of the sealing wall portion 41, opposite the start position SP57 across the fourth butt portion J4, and is further away from the side portion 41d of the sealing wall portion 41 than the plasticized region from the start position SP53 to the intermediate position S57 formed in the second joining process.

[0141] In the third joining step, the rotary tool F is inserted into start positions SP54, SP55, SP56, and SP57, respectively, and moved to end positions EP54, EP55, EP56, and EP57. The rotary tool F is inserted from start positions SP54, SP55, SP56, and SP57 to end positions EP54, EP55, EP56, and EP57 to a position where the tip of the stirring pin F2 reaches the portion of the inner wall surface 121b of the second member 20A that overlaps with the end surface 112a of the first side wall portion 112. In other words, the rotary tool F is inserted deeper than the thickness of the first side wall portion 112, preferably to a depth of approximately 1.05 times the thickness of the first side wall portion 112. This allows the overlapping portions of the ends of the first butt portions J11, J11 formed by the overlapping of the inner wall surface 121b of the second member 20A and the end surface 112a of the first side wall portion 112 to be joined and sealed. The insertion depth of the rotary tool F in the third joining step may be set as appropriate, but in this embodiment it is set to, for example, 4.1 mm.

[0142] FIG. 23 is a cross-sectional view showing a third joining step in the method for manufacturing a heat pipe according to the second embodiment. As shown in FIG. 23, by performing the first joining step, plasticized regions W21, W21 are formed on the surface sides of the main body portion 2A and the sealing members 3, 4. In the second embodiment, the rotary tool F is inserted at the start position SP57 and moved to the end position EP57. The insertion depth is set so that the stirring pin F2 of the rotary tool F reaches the second member 20A. In the third joining step, a plasticized region W22 is formed along the movement trajectory of the rotary tool F. In the third joining step, the stirring pin F2 of the rotary tool F reaches the plasticized region W21, so that the tip of the plasticized region W21 can be friction stir welded again. Friction stir welding is also performed between the start position SP54 and the end position EP54, between the start position SP55 and the end position EP55, and between the start position SP56 and the end position EP56 in the same manner as between the start position SP57 and the end position EP57.

[0143] Finally, a sealing step is performed. The sealing step is the same as that in the first embodiment, and therefore a description thereof will be omitted. By performing the sealing step, the heat pipe 1A can be placed in a low vacuum state.

[0144] As described above, the heat pipe 1A according to the second embodiment includes the support portion 113 that stands in the longitudinal direction from the inner wall surface 111b of one member (the first member 10A) toward the other member (the second member 20A), and the end surface 113a is in contact with the other member (the second member 20A). As a result, the second member 20A is supported by the support portion 113, thereby increasing the strength of the heat pipe 1A.

[0145] Furthermore, since the support portion 113 is formed, the internal space can be divided into multiple spaces. In other words, multiple internal spaces can be arranged in parallel in the longitudinal direction. By dividing the internal space in this way, the position where the working fluid flows can be adjusted depending on the application of the heat pipe 1A and the position of the heating element. Furthermore, by performing the first bonding process, the second bonding process, and the third bonding process, the watertightness, airtightness, and strength of the heat pipe 1A can be improved.

[0146] Furthermore, because the heat pipe 1A of this embodiment is thinner than that of the first embodiment, it is difficult to perform friction stir welding on the side surfaces, as in the second joining step of the first embodiment. In this regard, by performing the third joining step shown in FIG. 22, the entire heights of the third butt joint J3 and the fourth butt joint J4 are sealed with plasticized regions W21, W22. In other words, simply by performing friction stir welding on the front and back sides of the main body 2A and the sealing members 3, 4, the watertightness and airtightness of the heat pipe 1A can be improved.

[0147] 5. First Modification of Second Embodiment Next, a first modification of the second embodiment will be described. In the method for manufacturing a heat pipe according to the first modification, the joining paths in the joining step are different from those in the second embodiment. The following describes the differences from the second embodiment.

[0148] As shown in Fig. 24, the joining process of this modified example is a process of friction stir welding the first butt portions J11, J11, the third butt portion J3, and the fourth butt portion J4 as shown in Figs. 24 to 26. The joining process includes a first joining process performed on the front surface sides of the main body portion 2A and the sealing members 3, 4 as shown in Fig. 24, a second joining process performed on the front surface sides of the main body portion 2A and the sealing members 3, 4 as shown in Fig. 25, and a third joining process performed on the back surface sides of the main body portion 2A and the sealing members 3, 4 as shown in Fig. 26.

[0149] 24, friction stir welding is performed from a start position SP61 to an end position EP61 via intermediate positions S61 and S62. The start position SP61 is set on the surface 31a of the sealing wall 31, on an extension of the first butting portion J11 on the upper side of the sealing member 3 (the side close to the side surface 31d of the sealing wall 31) and at a position spaced apart from the third butting portion J3. The intermediate position S61 is set at a position where the first butting portion J1 and the third butting portion J3 on the upper side of the sealing member 3 (the side close to the side surface 31d of the sealing wall 31) intersect. The intermediate position S62 is set at a position where the first butting portion J1 and the third butting portion J3 on the lower side of the sealing member 3 (the side close to the side surface 31c of the sealing wall 31) intersect. The end position EP61 is set on the surface 31a of the sealing wall portion 31, on an extension of the first butt portion J11 on the lower side (the side close to the side portion 31c of the sealing wall portion 31), and at a position spaced apart from the third butt portion J3. In the first joining process, the rotation tool F is inserted into the start position SP61, and is moved to the intermediate positions S61, S62, and the end position EP61 in this order.

[0150] 24, friction stir welding is performed from a start position SP62 to an end position EP62 via intermediate positions S63 and S64. The start position SP62 is set on the surface 41a of the sealing wall 41, on an extension of the first butting portion J11 on the lower side (the side close to the side surface 41c of the sealing wall 41) and at a position spaced apart from the fourth butting portion J4. The intermediate position S63 is set at a position where the first butting portion J11 on the lower side (the side close to the side surface 41c of the sealing wall 41) and the fourth butting portion J4 intersect. The intermediate position S64 is set at a position where the first butting portion J11 on the upper side (the side close to the side surface 41d of the sealing wall 41) and the fourth butting portion J4 intersect. The end position EP62 is set on the surface 41a of the sealing wall portion 41, on an extension of the first butt portion J11 on the upper side (the side close to the side portion 41d of the sealing wall portion 41), and at a position away from the fourth butt portion J4. In the first joining process, the rotation tool F is inserted into the start position SP62, and is moved to the intermediate positions S63, S64, and the end position EP62 in this order.

[0151] The insertion depth from the start position SP61 to the end position EP61 and from the start position SP62 to the end position EP62 is preferably about 0.8 times the thickness of the second member 20A. This allows the third butt portion J3 and the fourth butt portion J4 to be joined and sealed. The insertion depth of the rotary tool F may be set as appropriate, but in this embodiment it is set to, for example, 1.5 mm.

[0152] 25, in the second joining step, friction stir welding is performed on the front surface sides of the main body portion 2A and the sealing members 3, 4 from a start position SP63 to an end position EP63 and from a start position SP64 to an end position EP64. For ease of explanation, the plasticized regions in the first joining step are not depicted in FIG.

[0153] The start position SP63 is set at a position on the surface 31a of the sealing wall 31 away from the third butt portion J3 and below the start position SP61 set in the first joining step (the side away from the side portion 31d of the sealing wall 31). The end position EP63 is set at a position on the surface 41a of the sealing wall 41 away from the fourth butt portion J4 and below the end position EP62 set in the first joining step (the side away from the side portion 41d of the sealing wall 41). The start position SP64 is set at a position on the surface 41a of the sealing wall 41 away from the fourth butt portion J4 and above the start position SP62 set in the first joining step (the side away from the side portion 41c of the sealing wall 41). The end position EP64 is set on the surface 31a of the sealing wall portion 31, at a position away from the third butt portion J3, and above the end position EP61 set in the first joining process (the side away from the side wall portion c of the sealing wall portion 31).

[0154] The start position, end position, and intermediate position of the plasticized region from start position SP63 to end position EP63 formed in the second joining process are set at positions where the plasticized region from intermediate position S61 to intermediate position S62 formed in the first joining process and the plasticized region from intermediate position S63 to intermediate position S64 intersect. Furthermore, the start position, end position, and intermediate position of the plasticized region from start position SP64 to end position EP64 formed in the second joining process are set at positions where the plasticized region from intermediate position S61 to intermediate position S62 formed in the first joining process and the plasticized region from intermediate position S63 to intermediate position S64 intersect. This allows friction stir welding to be performed without leaving any unjoined portion between the plasticized region formed in the first joining process and the plasticized region formed in the second joining process.

[0155] The insertion depth from the start position SP63 to the end position EP63 and from the start position SP64 to the end position EP64 is such that the tip of the stirring pin F2 reaches the end surface 112a of the first side wall portion 112. In other words, the insertion depth is deeper than the thickness of the second member 20A. Furthermore, when friction stir welding the first butt portions J11, J11, the insertion depth is such that the plasticized region formed on the front side in the second joining process and the plasticized region formed on the back side in the third joining process partially overlap in the thickness direction of the main body portion 2A and the sealing members 3, 4. It is preferable that the insertion depth in the second joining process and the insertion depth in the third joining process be approximately 0.52 times the combined thickness of the first member 10A and the second member 20A. This allows the overlapping portions of the first butt portions J11, J11 to be welded and sealed from both sides. In the second joining step, the insertion depth from the start position SP63 to the end position EP63 and the insertion depth from the start position SP64 to the end position EP64 may be set appropriately, but in this embodiment, they are set to, for example, 3.1 mm.

[0156] In the third joining step, as shown in Fig. 26, friction stir welding is performed on the back surface sides of the main body portion 2A and the sealing members 3 and 4. In the third joining step, as shown in Fig. 26, friction stir welding is performed on the four corners on the back surface sides of the main body portion 2A and the sealing members 3 and 4, and the third butt portion J3 and the fourth butt portion J4. Since the third joining step is partially common to the second joining step (see Fig. 21) and the third joining step (see Fig. 22) of the second embodiment, the common parts are denoted by the same reference numerals and their description is omitted, and only the different parts will be described.

[0157] The insertion depths from start position SP54 to end position EP54, from start position SP55 to end position EP55, from start position SP56 to end position EP56, and from start position SP57 to end position EP57 are set so that the plasticized region formed from the front side in the second joining process and the plasticized region formed from the back side in the third joining process partially overlap in the thickness direction of the main body portion 2A and the sealing members 3, 4. It is preferable to insert the rotary tool F to approximately 0.52 times the combined thickness of the first member 10A and the second member 20A in the second joining process and the third joining process, respectively. This allows the overlapping portions of the first butt portions J11, J11 to be joined and sealed from both sides. The insertion depth of the rotary tool F in the third joining process can be set as appropriate; in this embodiment, it is set to, for example, 3.1 mm.

[0158] As in this modified example, the movement route of the rotary tool F is not limited to that described in the second embodiment, and may be set as appropriate. In this modified example, effects substantially equivalent to those of the second embodiment can be achieved.

[0159] 6. Second Modification of Second Embodiment Next, a second modification of the second embodiment will be described. As shown in Fig. 27, the heat pipe 1A differs from the second embodiment in the orientation of the support portion 113. Note that Fig. 27 depicts the first member 10A and sealing members 4, 4, but omits the second member 20A.

[0160] The heat pipe 1A includes a main body 2A and sealing members 4, 4. The support members 113 are formed in a direction perpendicular to the longitudinal direction. In other words, independent internal spaces may be arranged in series in the longitudinal direction. This allows the shape, arrangement, size, etc. of the internal spaces to be changed to match the shape of the heat source.

[0161] 7. Third Embodiment Next, a third embodiment will be described with reference to FIGS. 28 to 31. As shown in FIG. 28, a heat pipe 1B according to the third embodiment includes a main body 2B and sealing members 3 and 4. This heat pipe 1B differs from the second embodiment in that two support portions 113 are formed on the first wall portion 111 of the first member 10B. Three or more support portions 113 may be formed. This embodiment is thinner and wider than the second embodiment. The other configurations are similar to those of the second embodiment, and therefore description thereof will be omitted. Although grooves are not shown in FIG. 28, grooves are formed on the inner wall surface 111b of the first wall portion 111 and the inner wall surface 121b of the second member 20B, as in the previous embodiment.

[0162] Next, a method for manufacturing the heat pipe 1B according to the third embodiment will be described. The method for manufacturing the heat pipe according to the third embodiment includes a preparation step, an assembly step, a joining step, and a sealing step.

[0163] As shown in FIG. 28, the preparation process is a process of forming the first member 10B, the second member 20B, and the sealing members 3 and 4. The first member 10B, the second member 20B, and the sealing members 3 and 4 can be manufactured by, for example, extrusion, pressing, casting, forging, cutting, or the like. The first member 10B and the second member 20B are preferably formed by extrusion so as to be elongated in the longitudinal direction and have a uniform cross-sectional shape. Depending on the size, they may also be formed by forging or casting. Furthermore, the sealing members 3 and 4 are preferably formed by casting or cutting so as to be shaped so as to be inserted into the first member 10B and the second member 20B and combined with each other. Furthermore, grooves 5 are formed on the inner wall surface 111b of the first member 10B and the inner wall surface 121b of the second member 20B. The formation of the grooves 5 is the same as in the first embodiment, and therefore a description thereof will be omitted.

[0164] The assembling process includes a main body forming process and a sealing member butting process. The main body forming process is a process in which the second member 20B is placed on the first member 10B to form the main body 2B, as shown in FIG. 29. The main body 2B has a bottomless cylindrical shape with both longitudinal ends open. In the sealing member butting process, sealing members 3 and 4 are attached to both ends of the main body 2B and butted together, as shown in FIG.

[0165] 29 and 30, in the assembling step, the end faces 112a, 112a of the first side wall portion 112 of the first member 10B and the inner wall surface 121b of the second member 20B are respectively butted (overlapped) to form first butt joints J21, J21. In addition, both ends of the main body 2B are respectively butted against the sealing members 3, 4 to form third butt joints J3 and fourth butt joints J4.

[0166] The joining process is a process of friction stir welding the first member 10B, the second member 20B, and the sealing members 3 and 4 together using a rotary tool. In the joining process, as shown in FIG. 31 , the rotary tool F is moved in the order of a start position SP51, intermediate positions S51, S52, S53, S54, and S51, and an end position EP51. This causes the first butting portions J21, J21, the third butting portion J3, and the fourth butting portion J4 to be friction stir welded. Note that, for convenience of drawing, the start position SP51 and the end position EP51 are shown in different positions in FIG. 31 , but the start position SP51 and the end position EP51 are actually set to the same position.

[0167] 29, in this embodiment, for example, the height dimension of the first side wall portion 112 is set to 2 mm and the thickness of the second member 20B is set to 1 mm, and therefore the insertion depth of the rotary tool F is set to 1.5 mm so that the stirring pin F2 reaches the first side wall portion 112. In the joining process, the insertion depth of the rotary tool F may be changed in the circumferential direction, but in this embodiment, the insertion depth is kept constant.

[0168] As described above, the heat pipe 1B according to the third embodiment has a plurality of support portions 113, and the support portions 113 support the second member 20B. This allows the strength of the heat pipe 1B to be increased even if the heat pipe 1B is made thin. Furthermore, according to this embodiment, the plurality of support portions 113 allows the internal space to be divided into a plurality of sections.

[0169] Furthermore, because the heat pipe 1B is thin, the first butting portions J21, J21, the third butting portion J3, and the fourth butting portion J4 are joined by simply moving the rotary tool F around the second member 20B once, ensuring watertightness and airtightness. This shortens the manufacturing process and makes it easy to manufacture the heat pipe 1B.

[0170] 8. Fourth Embodiment Next, a fourth embodiment will be described with reference to Figures 32 to 35. As shown in Figure 32, a heat pipe 1C according to the fourth embodiment includes a main body 2C formed by combining a first member 10C and a second member 20C, and sealing members 30C and 40C.

[0171] The first member 10C includes a first wall portion 111, first side walls 112, 112, a support portion 113, and mounting portions 114, 114. The first member 10C is formed to be slightly longer in the longitudinal direction than the first member 10A of the second embodiment (see FIG. 17). That is, the mounting portions 114, 114 on which parts of the sealing members 30C, 40C (insertion portions 32C, 42C) are to be mounted are formed at the longitudinal ends of the first member 10C.

[0172] The second member 20C is a plate-shaped member placed on the first member 10C. The second member 20C has an outer wall surface 121c that contacts the heat source, an inner wall surface 121b that faces the first member 10A, and a through-hole 120c that penetrates the second member 20C in the plate thickness direction. The through-hole 120c is provided at an end of the second member 20C in the longitudinal direction. The second member 20C is formed to have a larger longitudinal dimension than the first member 10C. In other words, the longitudinal dimension of the second member 20C is approximately the same as the length from the end of the sealing member 30C to the end of the sealing member 40C when the sealing members 30C and 40C are attached to the first member 10C.

[0173] The sealing member 30C is an L-shaped member in side view. The sealing member 30C includes a sealing wall portion 31C, an insertion portion 32C, and a encapsulation flow path 33C. The sealing wall portion 31C is a rectangular plate-like portion. The left-right and height dimensions of the sealing wall portion 31C are substantially the same as the left-right and height dimensions of the first member 10C. The insertion portion 32C is formed continuously from the sealing wall portion 31C and is a portion that is placed on the placement portion 114 of the first member 10C. The height dimension of the insertion portion 32C is smaller than that of the sealing wall portion 31C. The height dimension of the insertion portion 32C is substantially the same as the height dimensions of the first side walls 112, 112 and the support portion 113. The encapsulation flow path 33C is cut out so as to be recessed from the end of the insertion portion 32C toward the sealing wall portion 31C. When the second member 20C of the main body 2C and the sealing member 30C are combined, the confinement passage 33C communicates with the through-hole 120c and is a portion that connects the inside and outside of the heat pipe 1C (intermediate member). The sealing member 40C has the same configuration as the sealing member 30C except that it does not have the confinement passage 33C.

[0174] Next, a method for manufacturing the heat pipe 1C according to the fourth embodiment will be described. The method for manufacturing the heat pipe according to the fourth embodiment includes a preparation step, an assembly step, a joining step, and a sealing step.

[0175] 32, the preparation step is a step of forming a first member 10C, a second member 20C, and sealing members 30C, 40C. The method of forming the grooves is the same as in the first embodiment, so a description thereof will be omitted.

[0176] The combining process includes a main body forming process and a sealing member butting process. The main body forming process is a process of forming the main body 2C by placing the second member 20C on the first member 10C. In the main body forming process, the second member 20C is placed on the end faces 112a, 112a of the first side wall 112 and the end face (tip) 113a of the support member 113. The end faces 112a, 112a of the first side wall 112 and the inner wall surface 121b of the second member 20A are butted (overlapped) to form first butting portions J31, J31 (see FIG. 33). The first butting portions J31 are formed along the longitudinal direction on both sides in the width direction.

[0177] As shown in Fig. 33, the sealing member butting step is a step of placing the insertion portion 32C of the sealing member 30C and the insertion portion 42C of the sealing member 40C on the mounting portions 114 at both ends of the main body portion 2C and butting the sealing members 30C, 40C against both ends of the main body portion 2C. As shown in Fig. 33, the end face of the sealing wall portion 31C and the end face of the first wall portion 111 of the first member 10C are butted together to form a third butt portion J3. Similarly, as shown in Figs. 32 and 33, the end face of the sealing wall portion 41C and the end face of the first wall portion 111 of the first member 10C are butted together to form a fourth butt portion J4.

[0178] 32, the surface of the insertion portion 32C is flush with the end surface 112a of the first side wall portion 112. Furthermore, the surface of the insertion portion 42C is flush with the end surface 112a of the first side wall portion 112.

[0179] As shown in Fig. 33, the joining process involves friction stir welding by moving the rotary tool F from a start position SP51, which is set on the outer wall surface 121c of the second member 20C closer to the sealing member 30C than the third butt portion J3, to intermediate positions S81, S82, S54, S53, S52, S51, and an end position EP51 in this order. For ease of illustration, in Fig. 33, the start position SP51 and the end position EP51 are shown in different positions, and the path from the start position SP51 to the intermediate position S51 and the path from the intermediate position S51 to the end position EP51 are shown in different positions. The start position SP51 and the end position EP51 are set in the same position, and the path from the start position SP51 to the intermediate position S51 and the path from the intermediate position S51 to the end position EP51 are set in the same position.

[0180] The intermediate positions S81 and S82 are set at positions on the outer wall surface 121c of the second member 20C that correspond to opposite ends of the encapsulation flow path 33C. From the intermediate positions S81 to S82, the movement route is set so as to follow the periphery of the encapsulation flow path 33C. The other positions are the same as those in the first joining step of the second embodiment (see FIG. 20). The insertion depth of the rotary tool F in the joining step may be set as appropriate, but in this embodiment, it is set so that the tip of the stirring pin F2 reaches the first side wall portion 112 and also the insertion portions 32C and 42C.

[0181] In the joining step, although not specifically shown in the drawings, friction stir welding is performed on the third butt portion J3 and the fourth butt portion J4 from the rear surface sides of the main body portion 2C and the sealing members 30C, 40C in the same manner as in the second embodiment, for example, to form an intermediate member in which the main body portion 2C and the sealing members 30C, 40C are integrated by friction stir welding.

[0182] As shown in FIG. 34, the sealing process is a process of creating a low vacuum state in the intermediate member using a vacuum sealing member V. The vacuum sealing member V includes a cylindrical base V1, a pipe V2 protruding upward from the base V1, and a pipe hole V3 penetrating the base V1 and the pipe V2. When drawing a vacuum, the vacuum sealing member V is positioned so that it communicates with the through-hole 120c of the second member 20C, thereby creating a state in which the pipe hole V3, the through-hole 120c, and the sealing flow path 33C are in communication. In this state, vacuuming is performed to create a vacuum in the internal space of the intermediate member. To prevent the vacuum sealing member V from moving, the base V1 may be fixed to the second member 20C with an adhesive or the like. Furthermore, when drawing a vacuum, an adhesive or the like may be applied to the third butting portion J3 to ensure airtightness.

[0183] After the evacuation is completed, as shown in FIG. 35, the rotating rotary tool F is moved from a start position SP91 to an end position EP91 around the vacuum sealing member V. The start position SP91 and the end position EP91 are set to positions on both sides of the second member 20C, straddling the sealing passage 33C. Then, with the main body 2C and the sealing member 30C combined, the rotary tool F is moved from the start position SP91 to the end position EP91 so as to pass through the sealing passage 33C on the first member 10C side (right side in the figure) with respect to the through hole 120c. By moving the rotary tool F, the sealing passage 33C is divided at the plasticized region formed by friction stir welding, thereby sealing the sealing passage 33C. This allows the heat pipe 1C to be evacuated.

[0184] According to the fourth embodiment described above, the first member 10C or the second member 20C has the through hole 120c connecting the inside and outside of the intermediate member, and the sealing member 30C or 40C has the sealing passage 33C connecting the inside and outside of the intermediate member through the through hole 120c. In the sealing process, a vacuum sealing member V having a pipe hole V3 passing therethrough is positioned so that the pipe hole V3 communicates with the through hole 120c. With the pipe hole V3, the through hole 120c, and the sealing passage 33C communicating with each other, a vacuum is drawn through the pipe hole V3 to seal the sealing passage. This eliminates the need to provide a pipe for drawing a vacuum in the sealing member and only requires the preparation of an external pipe (vacuum sealing member V), thereby reducing costs and improving the design flexibility of the sealing member.

[0185] 9. Fifth Embodiment Next, a fifth embodiment will be described. Fig. 36 is a schematic diagram showing a heat pipe 1D according to the fifth embodiment. The heat pipe 1D includes a main body 2D and sealing members 3D and 4D. Like the heat pipe 1, the heat pipe 1D is a thin, flat heat pipe (vapor chamber). The heat pipe 1D has a heating element H disposed at one longitudinal end (sealing member 4), and a plurality of fins 50 integrally formed as heat dissipators at the other longitudinal end (sealing member 3). The plurality of fins 50 stand perpendicular to the sealing member 3. The fins 50 may be integrally formed by, for example, extrusion processing, or may be formed by cutting. The heat pipe 1D has a groove (not shown) formed inside along the longitudinal direction.

[0186] As described above, the heat pipe 1D according to the fifth embodiment has a plurality of fins 50 extending from the other end. This allows heat generated from the heat-generating element H at one end to be transferred through the heat pipe 1D to the fins 50 at the other end, where it can be dissipated. This allows localized heat generated by the heat-generating element H to be dissipated at a more distant location through the heat pipe 1D. Furthermore, the heat pipe 1D can be formed thin, which allows for space savings compared to cylindrical heat pipes with circular cross sections. This improves cooling efficiency and increases design flexibility. The fins 50 may also be provided extending from the main body 2D.

[0187] 10. Sixth Embodiment Next, a sixth embodiment will be described. As shown in FIG. 37, a sealing member 3A according to the sixth embodiment differs from the first embodiment in that a groove portion 5A having a plurality of microgrooves 6A functioning as a wick is formed on the inner wall surface of the insertion portion 32. The microgrooves 6A are formed along the height direction of the insertion portion 32. For example, when the sealing member 3A is used in the first embodiment, the arrangement direction of the opposing microgrooves 6, 6 (see FIG. 2) is the same as the arrangement direction of the microgrooves 6A. That is, the microgrooves 6, 6 provided on the inner wall surfaces 11b, 21b are formed along the longitudinal direction of the heat pipe 1, while the microgrooves 6A are formed along the same plane as the microgrooves 6, 6.

[0188] As described above, the sealing member 3A according to the sixth embodiment includes the grooves 5A as wicks on the inner wall surface of the insertion portion 32. This allows the working fluid to flow smoothly in the thickness direction of the main body 2. For example, consider a case where a heat pipe having grooves 5 extending in the longitudinal direction of the heat pipe 1 is arranged horizontally, and the grooves 5A in the sealing member 3A are arranged vertically, with the heat source located at the top of the heat pipe and the working fluid accumulating at the bottom. In this case, the condensed working fluid can be transported to the upper heat source by the grooves 5A. That is, the grooves 5A allow the working fluid to flow horizontally, and also allow the working fluid to flow vertically (height direction).

[0189] In this embodiment, the microgrooves 6A are provided so as to extend in the height direction, but they may also be provided so as to extend in the horizontal direction. That is, the microgrooves 6 shown in the first embodiment and the microgrooves provided in the sealing member 3A may be formed so as to intersect. Furthermore, in this embodiment, multiple microgrooves 6A are provided in the sealing member 3A, but multiple microgrooves 6A may also be provided in the sealing member 4.

[0190] 11. First Modification of Sixth Embodiment Next, a first modified example of the sixth embodiment will be described. As shown in Fig. 38, a sealing member 3B according to the first modified example of the sixth embodiment has a plurality of microgrooves 6A functioning as a wick on the inner wall surface of the insertion portion 32, as well as a plurality of microgrooves 6B formed in a direction intersecting the microgrooves 6A. In other words, the sealing member 3B has two or more rows of grooves (microgrooves 6A, microgrooves 6B) that intersect with each other. This allows the working fluid to flow in two directions corresponding to the orientation of the microgrooves 6A and the microgrooves 6B.

[0191] For example, if a heat pipe having grooves in the longitudinal direction of the main body is arranged so that the longitudinal direction is horizontal, the intersecting grooves 5B allow the working fluid to flow not only vertically but also horizontally (or even when rotated 90 degrees), which increases the flexibility of installation and design.

[0192] In this modification, a plurality of microgrooves 6B are provided in the sealing member 3B, but a plurality of microgrooves 6B may be provided in the sealing member 4.

[0193] 12. Second Modification of Sixth Embodiment Next, a second modification of the sixth embodiment will be described. As shown in FIG. 39, in this second modification, the sealing members 3C and 4C have a solid hemispherical shape and a dome-shaped outer periphery. The sealing members 3C and 4C have a groove 5A on the inner wall surface of the insertion portion 32, which has a plurality of microgrooves 6A functioning as a wick. The microgrooves 6A on the sealing members 3C and 4C are arranged in the same direction as the microgrooves 6 formed on the first wall portion 11 and the second wall portion 21. That is, the microgrooves 6, 6 on the inner wall surfaces 11b and 21b are formed along the longitudinal direction of the heat pipe 1, while the microgrooves 6A are formed along the same plane as the microgrooves 6, 6. Furthermore, the microgrooves 6 and 6A on the first member 10 are formed in a continuous positional relationship, and the microgrooves 6 and 6A on the second member 20 are also formed in a continuous positional relationship. That is, a continuous microgroove is formed around the inner wall surface of the main body 2. In other words, the recesses of the microgrooves 6, 6 and the microgroove 6A are connected to each other, allowing the working fluid to flow between the groove portion 5 and the groove portion 5A.

[0194] This allows the working fluid to flow continuously through the microgrooves 6 formed in the first wall portion 11 and the second wall portion 21 and the microgrooves 6A formed in the sealing members 3C and 4C. For example, consider a case where a heat pipe having grooves 5 extending in the longitudinal direction of the heat pipe 1 is arranged horizontally, the grooves 5A of the sealing member 3A are arranged vertically, and the heat source is located on the second member 20, which is the upper part of the heat pipe. In this case, the working fluid accumulated in the lower first member 10 can flow from the microgrooves 6 of the first member 10 to the microgrooves 6A of the sealing members 3C and 4C, and then from the microgrooves 6A of the sealing members 3C and 4C to the microgrooves 6 of the second member 20, continuously through the microgrooves. In this way, when the heat source is located at the upper part of the heat pipe 1 and the working fluid accumulates at the lower part, the condensed working fluid can be transported from the lower part to the upper heat source side. This facilitates improving cooling efficiency.

[0195] In this embodiment, the microgrooves 6A formed in the sealing members 3C and 4C are continuous with the microgrooves 6 formed in the first wall portion 11 and the second wall portion 21. However, the microgrooves 6A may be arranged so as to be continuous with either the microgrooves 6 of the first wall portion 11 or the microgrooves 6 of the second wall portion 21. For example, when the microgrooves 6A formed in the sealing member 3C are arranged so as to be continuous with the microgrooves 6 formed in the first wall portion 11, the working fluid accumulated in the first member 10 can flow from the microgrooves 6 of the first member 10 to the microgrooves 6A of the sealing members 3C and 4C. In this case, when the heat source is located on the side surface of the heat pipe 1 where the sealing members 3C and 4C are located and the working fluid accumulates at the bottom, the condensed working fluid can be transported from the bottom to the heat source side at the top of the side surface.

[0196] 13. Third Modification of Sixth Embodiment Next, a third modified example of the sixth embodiment will be described. As shown in FIG. 40, in the third modified example, the sealing members 3D and 4D have a hollow hemispherical shape and a dome-shaped outer periphery. Furthermore, the sealing members 3D and 4D do not have insertion portions, and the end faces of the sealing members 3D and 4D are butted against the end face of the main body 2 to form a heat pipe. Microgrooves 6A may be formed on the curved inner wall surfaces of the sealing members 3D and 4D. In this case, the sixth embodiment, the first modified example of the sixth embodiment, and the second modified example of the sixth embodiment may be applied to the microgrooves 6A.

[0197] 14. Seventh Embodiment Next, a cooling device 100 using a heat pipe 1 will be described. As shown in FIG. 41, the cooling device 100 includes a pair of heat pipes 1, 1. The battery pack R has a thin box shape and is a heat generating body that generates heat. The pair of heat pipes 1, 1 are arranged on opposite flat surfaces of the battery pack R, with the battery pack R sandwiched between them.

[0198] As described above, the cooling device 100 according to the seventh embodiment is configured to include a pair of heat pipes 1, 1. According to the seventh embodiment, it is possible to cool the battery pack R, which is a heat generating body, from both sides, thereby improving the cooling efficiency.

[0199] In the seventh embodiment, the battery pack R is arranged in a positional relationship in which both sides of the battery pack R are sandwiched between a pair of heat pipes 1, 1. However, a plurality of battery packs R and a plurality of heat pipes 1 may be arranged. That is, a plurality of battery packs R and heat pipes 1 may be arranged alternately. In this case, it is preferable that both sides of the battery pack R are sandwiched between a pair of heat pipes 1, 1. That is, it is preferable that the heat pipe 1 is arranged on the outside of the battery pack R that is arranged outermost among the plurality of battery packs R. This allows the battery pack R to be cooled by the heat pipes 1, 1 that sandwich the battery pack R while the plurality of battery packs R are arranged in parallel. Therefore, it is possible to increase the energy density of the battery pack R and also to cool it.

[0200] 15. First Modification of Seventh Embodiment Next, a first modification of the seventh embodiment will be described. As shown in FIG. 42 , a cooling device 100A of the first modification has a plurality of fins 51 formed on the outer side surfaces 4a of the sealing members 3, 4 of the heat pipes 1, 1. Providing the fins 51 on the sealing members 3, 4 can improve heat dissipation performance. While the fins 51 are provided on the side surfaces 4a of the sealing members 3, 4 in this embodiment, the fins 51 may be formed on the ends (end surfaces) 4b of the sealing members 3, 4, or on the main body 2. For example, the main body 2 (first member 10 and second member 20) may have the fins 51 integrally formed on the outside. Furthermore, the main body 2 (first member 10 and second member 20) may have the fins 51 integrally formed on the outside at the longitudinal ends (end surfaces). Furthermore, the fins 51 may be joined to the sealing members by brazing or the like, or may be formed by cutting a single blank. The fins 51 may also function as fastening portions 52, which will be described later.

[0201] 16. Second Modification of Seventh Embodiment Next, a second modification of the seventh embodiment will be described. As shown in FIG. 43 , a cooling device 100B of the second modification includes fastening portions 52 outside the sealing members 3, 4 of the heat pipes 1, 1 for fastening adjacent sealing members to each other. The fastening portions 52 have holes through which bolts B are inserted. The fastening portions 52 of adjacent heat pipes 1, 1 are overlapped and fastened with bolts B and nuts N, thereby firmly fixing the adjacent heat pipes 1, 1 to each other. According to the cooling device 100B, by arranging multiple battery packs R side by side in the short direction and connecting them with the fastening portions 52, the multiple battery packs R can be easily unitized and efficiently cooled. Furthermore, even if a force that pushes apart the heat pipes 1, 1 sandwiching the battery pack R due to a battery pack R deforming (expanding), the heat pipes 1, 1 are fastened to each other by the fastening portions 52, thereby restricting the distance between the heat pipes 1, 1 to be constant, thereby suppressing deformation of the battery pack R. The fastening portions 52 may also function as fins 51.

[0202] 17. Third Modification of Seventh Embodiment Next, a third modification of the seventh embodiment will be described. As shown in FIG. 44 , a cooling device 100C of the third modification includes a connecting member 53 for connecting the sealing members 3, 4 of the heat pipes 1, 1 to each other. The connecting member 53 includes multiple holding portions 54 that sandwich and hold the heat pipes 1. In the third modification, the holding portions 54 clamp both longitudinal ends of the heat pipes 1 to secure adjacent heat pipes 1, 1. The spacing between the holding portions 54 can be appropriately adjusted depending on the size of the battery packs R. According to the cooling device 100C, multiple battery packs R are arranged side by side in the lateral direction and sandwiched between the holding portions 54, thereby easily unitizing the multiple battery packs R and efficiently cooling them. Furthermore, even if a force that pushes apart the heat pipes 1, 1 sandwiching the battery pack R due to the battery pack R deforming (expanding), the heat pipes 1, 1 are connected to each other by the holding portions 54, thereby restricting the spacing between the heat pipes 1, 1 to a constant value, thereby suppressing deformation of the battery pack R.

[0203] [18. Note] The following notes are included in the above description. (1) A heat pipe in which a working fluid is sealed in an internal space surrounded by an inner wall surface and a groove portion serving as a wick is formed on the inner wall surface, The groove portion is composed of a plurality of microgrooves, a cylindrical main body portion including a first member having the groove portion in a longitudinal direction and a second member arranged along the longitudinal direction of the first member; a sealing member disposed at an end of the main body in the longitudinal direction, The first member and the second member are joined in a longitudinal direction with the groove portion facing inward, and an end portion of the main body portion and the sealing member are joined. A heat pipe characterized by: (2) The heat pipe according to (1), wherein the first member has the groove portion in an area including an end portion in the longitudinal direction. (3) The heat pipe according to (1) or (2), wherein the first member has the groove portion over the entire length thereof. (4) The main body has a first wall and a second wall, which are arranged opposite each other across the internal space and have flat outer surfaces, and has a thin cylindrical shape. The heat pipe according to any one of (1) to (3), wherein a joint between the first member and the second member is provided on the first wall portion or the second wall portion. (5) The first wall portion has the groove portion therein, and an outer wall surface of the first wall portion serves as one main surface, and an outer wall surface of the second wall portion serves as the other main surface. (4) The heat pipe according to (4). (6) The heat pipe according to (5), wherein the second wall portion has the groove portion therein as a wick. (7) The heat pipe according to (5), wherein the groove provided in the first wall portion or the second wall portion and the groove provided in the sealing member are arranged in an intersecting direction. (8) The heat pipe according to (5), wherein the microgrooves of the groove portion provided in the first wall portion or the second wall portion and the microgrooves of the groove portion provided in the sealing member are arranged continuously. (9) The microgrooves of the grooves provided in the first wall portion and the second wall portion and the microgrooves of the grooves provided in the sealing member are arranged continuously. (6) The heat pipe according to (6). (10) The heat pipe according to any one of (1) to (6), wherein the sealing member has a wick on an inner wall surface. (11) The heat pipe according to any one of (1) to (6), wherein the sealing member has the groove portion as a wick on an inner wall surface. (12) The heat pipe according to (11), wherein the sealing member has two or more rows of the grooves that intersect with each other. (13) A heat pipe according to any one of (1) to (12), wherein the main body has a bottomless cylindrical shape with both ends open, and the sealing members are joined to both ends of the main body. (14) A heat pipe described in any one of (1) to (12), wherein the main body portion has a bottomed cylindrical shape with a bottom at one of both ends and an open end at the other, and the sealing member is joined to the other end of the main body portion. (15) A heat pipe according to any one of (1) to (14), wherein the first member and the second member are L-shaped in cross section, the sealing member is rectangular in front view, and a first butt joint is formed where one end of the L-shape of the first member and the other end of the L-shape of the second member are joined, and a second butt joint is formed where the other end of the L-shape of the first member and one end of the L-shape of the second member are joined, and the main body is rectangular tubular, and the end portion is formed in a rectangular shape, and a third butt joint is formed where the end of the main body and the sealing member are joined. (16) The first member has a first step portion at one end of the L-shape along the longitudinal direction, the second member has a second step portion at one end of the L-shape along the longitudinal direction, the first step portion of the first member and the other end of the L-shape of the second member are butted together at the first butting portion, and The heat pipe according to (15), wherein the other end of the L-shape of the first member and the second step portion of the second member are joined at the second butting portion. (17) One of the first member and the second member has a support portion that stands upright from the inner wall surface of the one member toward the other member along the longitudinal direction, The heat pipe according to any one of (1) to (14), wherein the support portion has a tip end that contacts the other member in the internal space of the main body portion. (18) The heat pipe according to any one of (1) to (14), which has a plurality of the internal spaces that are independent of each other, and the plurality of internal spaces are arranged in parallel in the longitudinal direction. (19) The heat pipe according to any one of (1) to (14), which has a plurality of the internal spaces that are independent of each other, and the plurality of internal spaces are arranged in series in the longitudinal direction. (20) The heat pipe according to any one of (1) to (19), wherein the groove portion has the microgrooves with a groove width of 0.2 to 0.6 mm. (21) The heat pipe according to any one of (1) to (19), wherein the groove portion has the microgrooves having a groove width of 0.2 to 0.6 mm and the microgrooves having a groove width of 0.8 to 1.5 mm. (22) The heat pipe according to any one of (1) to (21), wherein the first member has fins integrally formed on the outside thereof. (23) The heat pipe according to any one of (1) to (21), wherein the first member has fins integrally formed on the outside at longitudinal ends thereof. (24) The heat pipe according to any one of (1) to (23), wherein the sealing member has fins formed on the outside. (25) The heat pipe according to any one of (1) to (23), wherein the sealing member has a fastening portion for fastening to another adjacent sealing member. (26) The heat pipe according to any one of (1) to (23), further comprising a connecting member for connecting adjacent other sealing members to each other. (27) A heat pipe as described in (1), having one main surface formed along the longitudinal direction and another main surface opposite the one main surface, and having a flat surface portion on the outside of at least one of the first member, the second member, and the sealing member as a surface other than the main surface. (28) A method for manufacturing a heat pipe in which a working fluid is sealed in an internal space surrounded by an inner wall surface and a groove portion serving as a wick is formed on the inner wall surface, a preparation step of forming a plurality of microgrooves along the longitudinal direction of a preform to prepare a first member having the grooved portions and a second member corresponding to the first member; an assembling process of assembling the first member and the second member with the groove portion facing inward to form a cylindrical main body portion having an open end in the longitudinal direction, and assembling the end of the main body portion with a sealing member; a joining step of joining the first member, the second member, and the sealing member to form an intermediate member; a sealing step of sealing the intermediate member after injecting a working fluid into the interior of the intermediate member. (29) In the preparation step, the base material is cut using a multi-cutter having a plurality of stacked disc cutters to form the plurality of microgrooves. (28) A method for manufacturing a heat pipe according to (28). (30) The sealing member has a pipe hole that connects the inside and outside of the intermediate member, and a pipe that is connected to the outside of the pipe hole, In the sealing step, the pipe hole is sealed while drawing a vacuum through the pipe. A method for manufacturing a heat pipe according to (28) or (29). (31) The first member or the second member has a through hole that communicates the inside and the outside of the intermediate member, the sealing member has a sealing flow path communicating with the through hole and communicating the inside and outside of the intermediate member, (28) or (29), wherein in the sealing step, a vacuum sealing member having a pipe hole passing through it is placed at a position where the pipe hole communicates with the through hole, and the sealing flow path is sealed while drawing a vacuum through the pipe hole in a state where the pipe hole, the through hole, and the sealing flow path are in communication. (32) The sealing member has a pipe hole that connects the inside and outside of the intermediate member, and a pipe that is connected to the outside of the pipe hole, The method for manufacturing a heat pipe according to (28) or (29), wherein in the sealing step, the pipe hole is sealed while injecting high-pressure gas through the pipe. (33) The method for manufacturing a heat pipe according to any one of (28) to (32), wherein in the preparation step, the base material is formed by extrusion or press working. (34) A method for manufacturing a heat pipe described in any one of (28) to (32), wherein in the preparation process, the base material is formed to have a first step portion along the longitudinal direction, and in the joining process, the first step portion of the first member and the end of the second member are joined in a state where the first step portion and the end are butted together. (35) The method for manufacturing a heat pipe according to any one of (28) to (34), wherein in the joining step, the first member and the second member are joined by micro FSW or laser welding. [Example]

[0204] Next, an example of the present invention will be described. As shown in Figure 45, the heat pipe 1 of the example and the heat pipe 201 of the reference example, which contained acetone as the working fluid, were immersed in a water bath at 50°C, and after 48 seconds, the heat transfer was observed using thermography. The heat pipe 1 of the example and the heat pipe 201 of the reference example were provided with a groove 5 in the longitudinal direction. Both the heat pipe 1 of the example and the heat pipe 201 of the reference example were positioned with their longitudinal direction vertical, with their lower portions immersed in the water bath.

[0205] The heat pipe 1 of the example has the same configuration as the first embodiment and is maintained in a high vacuum state. On the other hand, the heat pipe 201 of the reference example is the same as the example except that it is not maintained in a vacuum state. As shown in Figure 45, with the heat pipe 1, it can be seen that heat (dark shading) is transferred throughout the entire heat pipe. On the other hand, with the heat pipe 201 that is not maintained in a vacuum state, it can be seen that almost no heat transfer occurs. This confirms that the heat pipe 1 is capable of diffusing heat all the way to the ends. [Explanation of symbols]

[0206] 1 heat pipe 2 Main body 3 Sealing member 4 Sealing member 5 Groove 6 Micro Groove 10 First member 11 First wall 11a End face 11b Inner wall surface (inner wall surface) 11c External wall surface 12 First side wall part 20 Second member 21 Second wall section 21a End face 21b Inner wall surface (inner wall surface) 21c External wall surface 22 Second side wall part

Claims

1. A heat pipe in which a working fluid is sealed in an internal space surrounded by an inner wall surface, and a groove portion serving as a wick is formed on the inner wall surface, The groove portion is composed of a plurality of microgrooves, a cylindrical main body portion including a first member having the groove portion in a longitudinal direction and a second member arranged along the longitudinal direction of the first member; a sealing member disposed at an end of the main body in the longitudinal direction, The first member and the second member are joined in the longitudinal direction with the groove portion facing inward, and an end portion of the main body portion and the sealing member are joined. A heat pipe characterized by:

2. The first member has the groove portion in a region including an end portion in the longitudinal direction. The heat pipe of claim 1 .

3. The first member has the groove portion over the entire longitudinal direction. The heat pipe of claim 1 .

4. The main body portion has a thin cylindrical shape and includes a first wall portion and a second wall portion, the first wall portion and the second wall portion having a flat outer surface and arranged opposite each other across the internal space, a joint portion between the first member and the second member is provided on the first wall portion or the second wall portion; The heat pipe of claim 1 .

5. the first wall portion has the groove portion therein, The outer wall surface of the first wall portion is one main surface, and the outer wall surface of the second wall portion is the other main surface. The heat pipe according to claim 4.

6. The second wall portion has the groove portion therein as a wick. The heat pipe according to claim 5.

7. The groove provided in the first wall portion or the second wall portion and the groove provided in the sealing member are arranged in an intersecting direction. The heat pipe according to claim 5.

8. the microgrooves of the groove portion provided in the first wall portion or the second wall portion and the microgrooves of the groove portion provided in the sealing member are arranged continuously. The heat pipe according to claim 5 .

9. the microgrooves of the groove portions provided in the first wall portion and the second wall portion and the microgrooves of the groove portions provided in the sealing member are arranged continuously; The heat pipe according to claim 6.

10. The sealing member has a wick on its inner wall surface. The heat pipe of claim 1 .

11. The sealing member has the groove portion as a wick on an inner wall surface. The heat pipe of claim 1 .

12. The sealing member has two or more rows of the grooves that intersect with each other. The heat pipe of claim 11.

13. The main body has a bottomless cylindrical shape with both ends open, The sealing members are bonded to both ends of the main body. The heat pipe of claim 1 .

14. The main body has a cylindrical shape with a bottom at one end and an open end at the other end, The sealing member is joined to the other end of the main body. The heat pipe of claim 1 .

15. The first member and the second member have an L-shape in cross section, The sealing member has a rectangular shape when viewed from the front, a first butt portion where one end of the L-shape of the first member and the other end of the L-shape of the second member are butted together is joined; a second butt portion where the other end of the L-shape of the first member and one end of the L-shape of the second member are butted together is joined; The main body has a rectangular tubular shape, and the end portion is formed in a rectangular shape. a third butt portion where the end portion of the main body portion and the sealing member are butted together is joined; The heat pipe of claim 1 .

16. the first member has a first step portion at one end of the L-shape along the longitudinal direction, the second member has a second step portion at one end of the L-shape along the longitudinal direction, the first step portion of the first member and the other end of the L-shape of the second member are butted together at the first butting portion, and the other end of the L-shape of the first member and the second step portion of the second member are butted together to form the second butt portion, The heat pipe of claim 15.

17. one of the first member and the second member has a support portion erected along a longitudinal direction from the inner wall surface of the one member toward the other member, The support portion has a tip end that contacts the other member in the internal space of the main body portion. The heat pipe of claim 1 .

18. a plurality of the internal spaces that are independent of each other; The plurality of internal spaces are arranged in parallel with each other in the longitudinal direction. The heat pipe of claim 1 .

19. a plurality of the internal spaces that are independent of each other; The plurality of internal spaces are arranged in series in the longitudinal direction. The heat pipe of claim 1 .

20. The groove portion has the microgroove having a groove width of 0.2 to 0.6 mm. The heat pipe of claim 1 .

21. The groove portion has the microgroove having a groove width of 0.2 to 0.6 mm and the microgroove having a groove width of 0.8 to 1.5 mm. The heat pipe of claim 1 .

22. The first member has fins integrally formed on the outside. The heat pipe of claim 1 .

23. The first member has fins integrally formed on the outside at the longitudinal end portions thereof. The heat pipe of claim 1 .

24. The sealing member has fins formed on the outside. The heat pipe of claim 1 .

25. The sealing member has a fastening portion for fastening to another adjacent sealing member. The heat pipe of claim 1 .

26. a connecting member for connecting adjacent other sealing members to each other; The heat pipe of claim 1 .

27. The substrate has one main surface formed along the longitudinal direction and another main surface facing the one main surface, a flat surface portion is provided on the outside of at least one of the first member, the second member, and the sealing member as a surface other than the main surface; The heat pipe of claim 1 .

28. A method for manufacturing a heat pipe in which a working fluid is sealed in an internal space surrounded by an inner wall surface and a groove portion serving as a wick is formed on the inner wall surface, a preparation step of forming a plurality of microgrooves along the longitudinal direction of a preform to prepare a first member having the grooved portions and a second member corresponding to the first member; an assembling process of assembling the first member and the second member with the groove portion facing inward to form a cylindrical main body portion having an open end in the longitudinal direction, and assembling the end of the main body portion with a sealing member; a joining step of joining the first member, the second member, and the sealing member to form an intermediate member; and a sealing step of sealing the intermediate member after injecting a hydraulic fluid into the intermediate member. A method for manufacturing a heat pipe.

29. In the preparation step, the base material is cut using a multi-cutter having a plurality of stacked disc cutters to form the plurality of microgrooves.

29. A method for manufacturing the heat pipe of claim 28.

30. the sealing member has a pipe hole that communicates the inside and outside of the intermediate member, and a pipe that is connected to the outside of the pipe hole, In the sealing step, the pipe hole is sealed while drawing a vacuum through the pipe.

29. A method for manufacturing the heat pipe of claim 28.

31. the first member or the second member has a through hole communicating the inside and the outside of the intermediate member, the sealing member has a sealing flow path communicating with the through hole and communicating the inside and outside of the intermediate member, In the sealing step, a vacuum sealing member having a pipe hole passing therethrough is disposed at a position where the pipe hole communicates with the through hole, and the sealing flow path is sealed while drawing a vacuum through the pipe hole in a state where the pipe hole, the through hole, and the sealing flow path are in communication with each other.

29. A method for manufacturing the heat pipe of claim 28.

32. the sealing member has a pipe hole that communicates the inside and outside of the intermediate member, and a pipe that is connected to the outside of the pipe hole, In the sealing step, the pipe hole is sealed while injecting high-pressure gas through the pipe.

29. A method for manufacturing the heat pipe of claim 28.

33. In the preparation step, the base material is formed by extrusion or press working.

29. A method for manufacturing the heat pipe of claim 28.

34. In the preparation step, the base material is formed to have a first step portion along a longitudinal direction; In the joining step, the first step portion of the first member and the end portion of the second member are joined together in a state where the first step portion and the end portion are butted against each other.

29. A method for manufacturing the heat pipe of claim 28.

35. In the joining step, the first member and the second member are joined by micro FSW or laser welding.

29. A method for manufacturing the heat pipe of claim 28.

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