JP2015059683A - Heat pipe and heat pipe manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat pipe and a heat pipe manufacturing method, capable of improving refrigerant transportability.SOLUTION: A heat pipe includes: a passage 1 absorbing heat from an outside by a gas-liquid phase change in refrigerant flowing inside; a wide portion 6 formed by increasing a width of the passage 1 along a downstream end edge of the passage 1, an internal surface exhibiting hydrophobic property; and a stepped surface 6a constituting a part of the wide portion 6 and formed into a planar shape crossing an internal surface of the passage 1. The heat pipe also includes a hydrophilic film 4 exhibiting hydrophilic property and covering an internal surface 1a of the passage 1 upstream of a line of crossing between the internal surface 1a of the passage 1 and the stepped surface 6a.

Description

  The present case relates to a heat pipe and a method for manufacturing the heat pipe.

  Conventionally, a heat pipe in which a volatile refrigerant is sealed inside a pipe is known. This heat pipe is a heat exchange device that performs heat transport using absorption and release of latent heat due to evaporation and condensation (gas-liquid phase change) of refrigerant. In recent years, low-loss heat pipes whose apparent thermal conductivity is more than 1000 times that of metals have been developed.

  If the internal structure of the heat pipe is classified according to its function, the evaporation pipe, the vapor phase moving section, the condensing section, and the liquid phase moving section are provided in the heat pipe in the order in which the refrigerant flows. The evaporation unit is a part that absorbs heat from the outside and vaporizes the liquid refrigerant, and the gas phase moving unit is a passage for supplying the gas refrigerant to the condensing unit. The condensing part is a part that radiates heat to the outside and liquefies the gaseous refrigerant, and the liquid phase moving part is a passage for supplying the liquid refrigerant to the evaporating part. A capillary channel is provided in the liquid phase transfer part and the evaporation part. As a result, the refrigerant is transported by capillary action and circulates in the heat pipe.

  By the way, the magnitude of the capillary force acting on the refrigerant moving along the surface of the capillary is proportional to the cosine of the contact angle between the refrigerant and the capillary surface. Therefore, in order to improve the circulation of the refrigerant in the heat pipe, it has been proposed to increase the wettability inside the capillary as compared with the outside of the capillary. For example, it has been studied that the surface of the portion through which the liquid refrigerant passes is subjected to a hydrophilization treatment and the surface of the portion through which the gas refrigerant passes is subjected to a hydrophobization treatment (see Patent Document 1). With such a configuration, the capillary force that can be generated inside the capillary tube is increased, or the decrease in the capillary force is suppressed, and the circulation of the refrigerant is improved.

Special Table 2006-526128

  However, in the conventional heat pipe and its manufacturing method, it is difficult to appropriately set the boundary between the hydrophilic surface and the hydrophobic surface due to construction errors when performing the hydrophilic treatment and the hydrophobic treatment. It may not always coincide with the edge. In particular, when the capillary is miniaturized to increase the capillary force, the deviation between the boundary between the hydrophilic surface and the hydrophobic surface and the edge of the capillary tends to increase. Due to the mismatch between the shape of the capillary and the wettability, there is a problem that the transportability of the refrigerant in the capillary is lowered or the transportability of the refrigerant is hindered.

For example, when the hydrophobic surface protrudes from the outside to the inside of the capillary, the capillary force generated on the hydrophobic surface acts in a direction to weaken the capillary force generated on the hydrophilic surface. Thereby, the total capillary force that can be generated inside the capillary tube is reduced, and the transportability of the refrigerant is lowered.
Further, when the hydrophilic surface protrudes from the inside of the capillary toward the outside, the refrigerant tends to spread out to the outside of the capillary, and the liquid refrigerant tends to stay at the outlet end of the capillary. Such stagnation of the refrigerant becomes a factor that hinders the transportability and circulation of the refrigerant.

One of the purposes of the present case has been devised in view of such a problem, and is to improve the transportability of the refrigerant in the heat pipe.
In addition, the present invention is not limited to the above-described purpose, and is an operational effect derived from each configuration shown in “Mode for Carrying Out the Invention” to be described later. Can be positioned as a purpose.

  The disclosed heat pipe includes a passage that absorbs heat from the outside due to a gas-liquid phase change of the refrigerant flowing inside, a widened portion that widens the passage along the outer edge of the downstream end of the passage, and an inner surface is hydrophobic. A step surface formed in a planar shape that forms part of the widened portion and intersects the inner surface of the passage. Moreover, it has a hydrophilic film and has a hydrophilic film that covers the inner surface of the passage on the upstream side of the intersection line between the inner surface of the passage and the step surface.

  According to the disclosed technology, the transportability of the refrigerant in the heat pipe can be improved.

It is a figure which illustrates the composition of the heat pipe concerning an embodiment. It is a figure which expands and shows the principal part of the heat pipe of FIG. It is a perspective view which illustrates the shape of the evaporation part in the heat pipe of FIG. It is sectional drawing of the downstream end in the channel | path formed in the evaporation part of FIG. (A), (b) is sectional drawing of the downstream end of a channel | path. It is a flowchart which illustrates the manufacture procedure of the heat pipe of FIG. (A) is a top view of the passage forming member in the manufacturing process, (b) is a cross-sectional view taken along line AA of (a), (c) is a cross-sectional view taken along line BB of (a), and (d) is a cross-sectional view of (a). It is CC sectional drawing. (A) is a top view of the channel | path formation member in a manufacture process, (b) is DD sectional drawing of (a), (c) is EE sectional drawing of (a). It is a figure for demonstrating the plasma processing to a channel | path formation member, (a) is a conceptual diagram of an ion milling apparatus, (b) is a top view of a channel | path formation member, (c) is FF cross section of (b). (D) is a GG cross-sectional view of (b). It is sectional drawing for demonstrating the state of the refrigerant | coolant which flows in the inside of a channel | path, (a), (b) shows the state in the conventional heat pipe, (c), (d) shows the state in the heat pipe of FIG. Show. (A)-(e) is sectional drawing which shows the modification of the downstream end shape of a channel | path.

  Hereinafter, an embodiment relating to a heat pipe and a method for manufacturing the heat pipe will be described with reference to the drawings. However, the embodiment described below is merely an example, and there is no intention of excluding various modifications and technical applications that are not explicitly described in the embodiment. That is, the present embodiment can be implemented with various modifications (combining the embodiments and each modification) without departing from the spirit of the present embodiment.

[1. heat pipe]
A heat pipe 10 in which a volatile liquid refrigerant is sealed inside a metal tube is illustrated in FIG. The heat pipe 10 is a loop heat pipe (loop heat pipe) in which a tubular path through which a refrigerant flows is formed. Specific examples of the refrigerant include working fluids such as water, ethanol, and alternative chlorofluorocarbon. Inside the heat pipe 10, an evaporation unit 11, a gas phase moving unit 12, a condensing unit 13, and a liquid phase moving unit 14 are provided in the order in which the refrigerant flows.

  The evaporation unit 11 is a part that absorbs heat from the external heat source 15 and vaporizes the liquid refrigerant, and the gas phase moving unit 12 is a passage for supplying the gas refrigerant to the condensing unit 13. The condensing unit 13 is a part that radiates heat to the outside and liquefies the gaseous refrigerant, and the liquid phase moving unit 14 is a passage for supplying the liquid refrigerant to the evaporation unit 11.

As shown in FIG. 2, a plurality of passages 1 (fine channels) formed in a capillary shape are provided inside the evaporation unit 11. For example, the liquid refrigerant absorbs heat and vaporizes in the process of passing through the passage 1. Further, the liquid refrigerant wets and spreads in the portion where the refrigerant is vaporized, and the liquid refrigerant on the liquid phase moving unit 14 side is replenished into the passage 1 of the evaporation unit 11. On the other hand, the vaporized refrigerant moves from the evaporation unit 11 to the gas phase moving unit 12 and is supplied to the condensing unit 13 side. Through these series of operations, refrigerant circulation utilizing capillary action is achieved.
Hereinafter, the inner surface of the passage 1 is referred to as an inner surface 1a, and the surface on which the opening on the downstream side of the passage 1 is formed (the surface serving as the inner surface of the gas phase moving unit 12) is referred to as an end surface 1b.

[2. Aisle structure]
The structure of the exit end of the passage 1 is illustrated in FIG. Here, the inside of the evaporation part 11 in which the several channel | path 1 was formed is shown partially. The passage 1 is formed by bonding together two passage forming members 7 having concave grooves 7a formed on the surface. For example, a concave groove 7a having a rectangular cross-sectional shape is engraved on each passage forming member 7 and bonded so that the engraved surfaces of the concave groove 7a face each other. The groove width of the concave groove 7a is, for example, about 0.1 [mm]. The pitch between the concave grooves 7a (distance to the adjacent concave grooves 7a) is about 0.1 [mm], and the respective concave grooves 7a are arranged in parallel to each other.

  The cross-sectional shape of the downstream end of the passage 1 is illustrated in FIG. The passage forming member 7 includes a base material 2, a hydrophobic film 3, and a hydrophilic film 4. The base material 2 is a plate-like member that is the basis of the passage forming member 7, and is formed of, for example, synthetic resin, glass, fiber reinforced plastic, metal, or the like. On one surface of the substrate 2, a groove 2a corresponding to the concave groove 7a is formed. As a method for forming the groove 2a, for example, sand blasting or etching (dry etching, wet etching, optical etching, etc.) can be applied, or mechanical cutting and removal may be performed.

  Hydrophobic membrane 3 (hydrophobic layer, hydrophobic part) is a coating layer formed of a hydrophobic substance. For example, a fluororesin such as PTFE (Poly-tetra-fluoro-ethylene) or FEP (Fluorinated Ethylene Propylene) is used. It is formed by vapor deposition on the surface of the substrate 2. The hydrophobic film 3 is formed at least on the inner surface 1a of the passage 1 (the inner surface of the groove 2a), and preferably on the end surface 1b (base material end surface 2b) where the downstream end (exit side) opening of the passage 1 is formed. Is also formed. Of these, the portion where the hydrophobic film 3 is exposed on the surface of the passage 1 is a portion other than the inner surface 1a of the passage 1, as shown in FIG. On the inner surface 1 a of the passage 1, the hydrophobic film 3 is formed below the hydrophilic film 4.

The film thickness T ₁ of the hydrophobic film 3 is set according to a margin for forming a cutting portion 6 described later. This is because as the film thickness T ₁ of the hydrophobic film 3 is increased, a margin for forming a cutting portion 6 described later increases. In the present embodiment, the film thickness T ₁ of the hydrophobic film 3 is set to about 1000 [nm] (about 1 [μm]). Note that it is possible to make the thickness T ₁ of the hydrophobic film 3 thinner in consideration of only imparting hydrophobic characteristics to the surface of the end face 1 b where the hydrophobic film 3 is exposed. On the other hand, in the present embodiment, the film thickness T ₁ of the hydrophobic film 3 is set slightly thick in consideration of the workability of the cutting part 6 and the like.

The hydrophilic film 4 (hydrophilic layer) is a coating layer formed of a hydrophilic substance, and is formed, for example, by depositing an oxide such as silicon dioxide or titanium dioxide on the surface of the hydrophobic film 3. The hydrophilic film 4 is formed on the inner surface 1a of the passage 1 and is not formed on the end surface 1b. In addition, as shown in FIG. 4, the inner surface 1 a of the passage 1 becomes the exposed surface of the hydrophilic film 4.
Thickness T ₂ of the hydrophilic film 4 is, for example, about 10 [nm]. This film thickness T ₂ is set to a thickness necessary and sufficient for imparting hydrophilic characteristics to the inner surface 1 a of the passage 1, for example. That is, the hydrophobic film 3 is formed to be slightly thicker than the functionally desirable thickness, while the hydrophilic film 4 is formed to have a desirable functional thickness. Incidentally, the larger the thickness T ₂ of the hydrophilic film 4, the cutting depth when forming the cutting unit 6 to be described later (removal depth) increases.

  As shown in FIG. 4, a cutting portion 6 (widening portion) is provided on the end surface 1 b where the exit of the passage 1 is formed. The cutting part 6 is a part where the internal dimension of the passage 1 is widened (expanded, expanded, expanded) along the outer edge (outer edge of the downstream end) of the opening on the outlet side of the passage 1 over the entire circumference of the outer edge. It is. A portion having hydrophobicity is provided on the inner surface of the cutting portion 6. This hydrophobic portion is formed from the inner surface of the cutting portion 6 (widened portion) to the lower layer of the hydrophilic film 4 on the inner surface 1 a of the passage 1.

  As a method for forming the cutting portion 6, for example, as will be described later, physical cutting, chemical decomposition, removal, or the like can be considered. Alternatively, the shape of the hydrophobic film 3 may be molded so that the shape of the outer edge of the opening end is a step shape (chamfered chamfered shape). In any case, on the end face 1b on the outlet side of the passage 1, the portion formed so as to widen the passage 1 is the cutting portion 6, and there is no intention to exclude the portion formed through a forming method other than cutting.

  The cutting part 6 of the present embodiment has a step surface 6a and an extended surface 6b. The step surface 6 a is a planar portion that inclines in the direction of expanding the passage 1 and intersects the inner surface 1 a of the passage 1. In the example shown in FIG. 4, the step surface 6 a is planar and the inclination angle with respect to the passage 1 is approximately 90 °, and intersects the inner surface 1 a of the passage 1 substantially perpendicularly. As shown in FIG. 5A, the hydrophobic film 3 is exposed on the step surface 6a. Further, the end portion Y (three-dimensional end side) on the inner surface 1 a side of the passage 1 in the surface of the step surface 6 a coincides with the end portion (end side) of the hydrophilic film 4. That is, the boundary between the hydrophobic film 3 and the hydrophilic film 4 coincides with the intersecting position between the inner surface 1a of the passage 1 and the step surface 6a.

Strictly speaking, the boundary between the hydrophobic film 3 and the hydrophilic film 4 is a position indicated by a point X in FIG. That is, the boundary between the hydrophobic film 3 and the hydrophilic film 4 in FIG. 5A is the dimension corresponding to the film thickness T ₂ of the hydrophilic film 4 from the intersection position of the inner surface 1a of the passage 1 and the step surface 6a. The position is shifted downward from the inner surface 1 a of the passage 1. On the other hand, in FIG. 5 (a), (b) , the thickness T ₂ of the hydrophilic film 4 is deformed, it is extremely thick representation than the actual state. Thickness T ₂ of the hydrophilic film 4, since in practice sufficiently thin, the position of the point X can be considered a match at intersections between the inner surface 1a and the step surface 6a of the passage 1.

The extended surface 6b is a planar portion that connects the step surface 6a and the end surface 1b. In the example shown in FIG. 4, the expansion surface 6 b is arranged in parallel to the inner surface 1 a of the passage 1. As shown in FIG. 5 (a), the hydrophobic film 3 is exposed on the surface of the extended surface 6b. The surface gradient and surface shape of the extended surface 6b can be arbitrarily set.
Here, regarding the dimension of the cutting part 6, the width dimension of the passage 1 (the vertical dimension in FIG. 5A) expanded by the step surface 6 a is referred to as the height H of the cutting part 6. In addition, the dimension in the flow path direction (the dimension in the left-right direction in FIG. 5A) of the portion expanded by the step surface 6a is referred to as the width W of the cutting portion 6.

In the cutting part 6 of this embodiment, the height H and the width W are smaller than the value (T ₁ + T ₂ ) obtained by adding the film thickness T ₁ of the hydrophobic film 3 and the film thickness T ₂ of the hydrophilic film 4, respectively. Set to a value. If the height H is less than the added value (T ₁ + T ₂ ) of the film thickness, the substrate 2 is prevented from being exposed on the surface of the cutting portion 6 regardless of the width W. Similarly, if the width W is less than the added value (T ₁ + T ₂ ) of the film thickness, the base material 2 is prevented from being exposed on the surface of the cutting portion 6 regardless of the height H. Therefore, the surface exposure of the base material 2 is more reliably prevented by these double dimension settings.

Further, the shape of the cutting part 6 is set according to the wettability of the hydrophobic film 3. Here, as shown in FIG. 5 (b), the contact angle of the hydrophobic film 3 with the liquid refrigerant is θ [rad] (0 ≦ θ ≦ π), and the inner surface 1a of the passage 1 and the step surface 6a are formed. The angle is set to φ [rad] (0 ≦ θ ≦ π). The width W and the height H of the cutting part 6 are set so as to satisfy the relationship of the following formula 1. With such a setting, even when the refrigerant transmitted through the passage 1 reaches the intersection of the inner surface 1a and the step surface 6a, the contact between the refrigerant and the expansion surface 6b is prevented. Note that since the film thickness T ₂ of the hydrophilic film 4 is sufficiently smaller than the height H, it may be considered that T ₂ = 0.

[3. Production method]
FIG. 6 is a flowchart illustrating a manufacturing process for forming the passage 1 of the evaporation unit 11 built in the heat pipe 10.

In step A10 (hydrophobic film lamination step), the hydrophobic film 3 is formed on the surface of the substrate 2. As a method for forming the hydrophobic film 3, it is possible to apply a method such as vacuum deposition, sputtering, or plasma polymerization. For example, when vacuum deposition is used, the base material 2 is placed inside the vacuum chamber of the film forming apparatus, and the inside of the vacuum chamber is decompressed. In addition, the hydrophobic film 3 is formed by heating and evaporating the fluororesin in a vacuum chamber and adhering it to the surface of the substrate 2.
The hydrophobic film 3 is formed so as to cover the entire surface of the substrate 2. However, when forming the cutting part 6, the hydrophobic film 3 should just be formed in both the end surface 1b in which the exit of the channel | path 1 was formed, and the inner surface 1a of the channel | path 1. FIG.

In step A20 (hydrophilic film lamination step), the hydrophilic film 4 is formed on the surface of the substrate 2 on which the hydrophobic film 3 is formed. Similarly to the method of forming the hydrophobic film 3, the method of forming the hydrophilic film 4 can be applied with a method such as vacuum deposition, sputtering, or plasma polymerization. The hydrophilic film 4 is formed so as to cover the entire surface of the hydrophobic film 3. The hydrophilic film 4 may be formed on at least the hydrophobic film 3 on the inner surface 1 a of the passage 1, but may be laminated on the entire surface of the substrate 2.
7A to 7D are diagrams illustrating the passage forming member 7 at the time when Step A20 is completed. Here, the surface of the substrate 2 is covered with the hydrophobic film 3, and the surface is further covered with the hydrophilic film 4.

  In step A30 (protective layer coating step), at least a resist mask 5 that covers a portion corresponding to the inner surface 1a of the passage 1 is formed. The resist mask 5 functions as a protective layer for protecting the hydrophilic film 4 from plasma processing in the next step. In the present embodiment, all the hydrophilic films 4 except the portion whose distance from the end surface 1b is less than the predetermined dimension V in the top view of the passage forming member 7 is protected by the resist mask 5 regardless of the inside or outside of the groove 7a. . The masking range in this embodiment is illustrated in FIGS. Thereby, the joint surface 7b in the two channel | path formation members 7 bonded together by a next process is also protected.

  Further, the range in which the resist mask 5 is formed on the inner surface 1a of the passage 1 is set to avoid the bent surface 1c as shown in FIG. The bent surface 1 c is a curved surface that connects the inner surface 1 a and the end surface 1 b of the passage 1, and is formed so as to surround the entire circumference of the passage 1 along the outer edge of the downstream end of the passage 1. The tip position of the resist mask 5 indicated by reference numeral 5a in FIG. 8C coincides with the intersecting position of the step surface 6a formed in the subsequent process and the inner surface 1a of the passage 1.

  As a specific method for forming the resist mask 5, a dry film resist (DFR) is attached to the passage forming member 7 for exposure and development, a method for immersing the passage forming member 7 in a liquid resist, or spin coating. Techniques etc. are applicable. DFR is an example of a resist mask (photoresist) having photosensitivity, and includes a negative photoresist that exposes a portion to be cured, a positive photoresist that exposes a portion that is not cured, and the like.

  In the case of using a negative DFR, the DFR in the masking range is denatured and cured by sticking the DFR to the entire passage forming member 7 with a roller and exposing the masking range with ultraviolet rays or the like. The film thickness of DFR is, for example, about 10 [μm] (10000 [nm]). Note that the resist mask 5 is intended to protect the hydrophilic film 4 from the plasma treatment, and therefore the DFR film thickness may be set further thicker. In addition, the film thickness may be different depending on the attachment site, or the film thickness may vary. The film thickness of the resist mask 5 may not be uniform.

For aligning the masking range, for example, a mask aligner is used. In this case, it is preferable to adjust the position to be masked using an optical microscope while confirming the shape of the passage 1 and the position of the end face 1b through the glass mask. In the present embodiment, the distance from the tip position 5a of the resist mask 5 to the end face 1b is less than the added value (T ₁ + T ₂ ) of the film thickness T ₁ of the hydrophobic film 3 and the film thickness T ₂ of the hydrophilic film 4. Set to a value. Thereby, the width W of the cutting part 6 formed in the next step is less than the added value (T ₁ + T ₂ ).

  Thereafter, if the unexposed portion of DFR is removed by development with a weak alkaline solvent, a resist mask 5 for protecting a desired position is completed. When a positive DFR is used instead of a negative DFR, the exposure range may be reversed from that in the above case.

  In step A40 (cutting portion forming step), the cutting portion 6 is formed on the passage forming member 7 on which the resist mask 5 has been applied. Here, the cutting portion 6 is cut along the edge of the exit of the passage 1 by, for example, plasma processing using the ion milling device 16. In this step, as shown in FIG. 9A, the surface of the passage forming member 7 is irradiated with an accelerated ion beam 8. As a result, the surface of the passage forming member 7 is mechanically polished by ions, and the hydrophobic film 3 and the hydrophilic film 4 at portions not protected by the resist mask 5 are physically removed (physical etching). Moreover, when the hydrophilic film | membrane 4 is formed in the end surface 1b, this is also removed collectively.

  As shown in FIG. 3, the cutting portion 6 is provided over the entire periphery of the opening along the edge of the outlet of the passage 1. Therefore, when the ion milling device 16 in which the irradiation direction of the ion beam 8 is fixed in one direction is used, it is preferable to rotate the passage forming member 7 while being inclined with respect to the irradiation direction of the ion beam 8. . For example, as shown in FIG. 9A, the normal line K of the plate surface (for example, the bonding surface 7b) of the passage forming member 7 is inclined with respect to the irradiation direction of the ion beam 8, and the normal line K is set as the central axis. As a whole, the entire passage forming member 7 is rotated.

  Accordingly, as shown in FIGS. 9B to 9D, the irradiation direction of the ion beam 8 with respect to the surface of the passage forming member 7 can be changed like precession, and the entire inner surface 1a of the passage 1 can be changed. Can be cut. The incident angle of the ion beam 8 with respect to the joint surface 7b of the passage forming member 7 changes according to the inclination angle κ of the normal K with respect to the ion beam irradiation direction and the rotation angle ψ of the passage forming member 7. For example, if the inclination angle κ is set within a range of about π / 6 to π / 4 [rad], the groove is generally recessed during one rotation of the passage forming member 7 although it depends on the shape and depth of the groove 7a. The entire inner surface of 7a can be irradiated with the ion beam 8. In addition, the ion beam 8 is applied not only to the inside of the groove 7a of the passage forming member 7 as shown in FIG. 9 (d) but also to the end face 1b of the passage 1 as shown in FIG. 9 (c). Therefore, when the hydrophilic film 4 is formed on the end face 1b, it is removed in this step.

The cutting direction of the member by the ion milling device 16 depends on the irradiation direction of the ion beam 8, and the cutting depth (removal depth) of the member is proportional to the irradiation time of the ion beam 8. Therefore, the cutting depth can be controlled by adjusting the irradiation time of the ion beam 8. Alternatively, the cutting depth can be controlled by correcting the irradiation time of the ion beam 8 according to the inclination angle and rotation speed of the passage forming member 7 with respect to the ion beam 8. In the present embodiment, the irradiation time of the ion beam 8 is set so that the height H of the cutting part 6 is less than the above added value (T ₁ + T ₂ ).

In step A50 (protective layer removing step), the resist mask 5 formed in step A30 is removed. In this step, for example, the passage forming member 7 is washed with a strong alkaline solvent, and the DFR is peeled and removed. Thereby, the channel | path formation member 7 in which the edge part structure as shown in FIG. 4 was formed in the exit side of the channel | path 1 is completed.
Then, in step A60 (bonding process), as shown in FIG. 3, the two channel | path formation members 7 are bonded together. Thereby, the inner wall surface is covered with the hydrophilic film 4, and the passage 1 formed so that the boundary between the hydrophobic film 3 and the hydrophilic film 4 coincides with the intersecting position between the inner surface 1a and the step surface 6a is completed. The completed component is built in, for example, a heat pipe 10 having a structure as shown in FIG.

[4. Action]
The state of the refrigerant in the conventional heat pipe is illustrated in FIGS. 10 (a) and 10 (b), and the state of the refrigerant in the heat pipe 10 is illustrated in FIGS. 10 (c) and 10 (d).
In FIG. 10A, the hydrophilic film 4 is formed on the inner surface 1a of the passage 1, and the hydrophobic film 3 protrudes from the outside (end surface 1b side) of the passage 1 toward the inside. The broken line in the figure indicates the liquid level in a state where the liquid refrigerant is filled along the hydrophilic film 4 in the passage 1. Here, it is assumed that the liquid refrigerant expands due to the temperature rise of the evaporation unit 11, and the liquid level of the liquid refrigerant moves to the downstream side to the position indicated by the solid line. At this time, the liquid refrigerant acts between the liquid refrigerant and the hydrophobic film 3 in a direction in which the liquid refrigerant is pushed back to the inlet side of the passage 1 as indicated by a black arrow in FIG. Therefore, the total capillary force that can be generated in the passage 1 is reduced, and the transportability of the refrigerant is lowered.

  In FIG. 10B, the hydrophilic film 4 protrudes from the inner surface 1a of the passage 1 to the end surface 1b, and the hydrophilic film 4 is formed to expand in the diameter increasing direction. The broken line in the figure indicates the liquid level in a state where the liquid refrigerant is filled along the hydrophilic film 4 on the inner surface 1 a of the passage 1. In this case, when the liquid refrigerant expands, the liquid refrigerant wets and spreads along the hydrophilic film 4 on the end face 1 b side and stays at the downstream end of the passage 1. As shown by the solid line in the figure, the retention state of the liquid refrigerant is a mountain shape with an expanded base at the end face 1b. At this time, the capillary force acting between the liquid refrigerant and the hydrophilic film 4 on the end face 1b acts in the direction along the end face 1b as shown by the black arrow in FIG. The capillary force in the direction along the inner surface 1a is not increased. Further, if the end surface 1b is cooler than the inner surface 1a of the passage 1, the vaporization efficiency of the liquid refrigerant staying at the downstream end of the passage 1 is lowered. As a result, the transportability and circulation of the liquid refrigerant are hindered.

  On the other hand, in the heat pipe 10, the cutting portion 6 is formed along the outer edge of the downstream end of the passage 1, and the step surface 6 a is formed in a planar shape that intersects the inner surface 1 a of the passage 1. That is, as shown in FIG. 10C, the hydrophilic film 4 is formed in the range from the inner surface 1a of the passage 1 to the position intersecting the step surface 6a. Therefore, as shown in FIG. 10A, the hydrophobic film 3 is not formed so as to protrude to the inner surface 1a of the passage 1, and a decrease in the transportability of the refrigerant is avoided.

  Moreover, the broken line in a figure shows the liquid level of the state with which the liquid refrigerant was filled along the hydrophilic film | membrane 4 of the channel | path 1. FIG. In this case, even if the liquid refrigerant expands, the hydrophobic film 3 is exposed on the surface of the step surface 6a, so that wetting and spreading of the liquid refrigerant is prevented. The retention shape of the liquid refrigerant is small as shown by the solid line in the figure. Therefore, compared with the case shown in FIG.10 (b), the volume of the liquid refrigerant which retains becomes small.

Further, when the liquid refrigerant expands, as shown in FIG. 10D, before the liquid refrigerant wets and spreads along the end surface 1b, the liquid refrigerant leaves the passage 1 due to surface tension and moves toward the gas phase moving unit 12 side. Scatter. At this time, as shown by the solid line in the figure, the liquid surface of the liquid refrigerant is formed at the intersection of the inner surface 1a of the passage 1 and the step surface 6a, and the liquid refrigerant is filled along the hydrophilic film 4 of the passage 1. It becomes a state. As a result, the transportability and circulation of the refrigerant are restored.
In addition, since the shape of the cutting part 6 is set according to the wettability (contact angle) of the hydrophobic film 3, contact between the staying liquid refrigerant and the expansion surface 6b is also prevented. The spherical liquid refrigerant ejected from the passage 1 is divided into smaller particles or vaporized inside the gas phase moving part 12.

[5. effect]
(1) In the heat pipe 10 described above, the cutting portion 6 is formed at the outer edge of the downstream end of the passage 1 formed inside the evaporation portion 11, and a planar step surface 6 a that intersects the inner surface 1 a of the passage 1 is provided. . Further, the hydrophilic film 4 is formed on the upstream side of the passage 1 with respect to the intersecting line between the inner surface 1 a and the step surface 6 a of the passage 1, and the hydrophobic film 3 is formed on the inner surface of the cutting portion 6. With such a structure, wetting and spreading of the liquid refrigerant in the vicinity of the outlet can be suppressed while maintaining the capillary action on the inner surface 1a of the passage 1. That is, it is possible to suppress a decrease in flow (fluidity) caused by wetting and spreading of the liquid refrigerant. Therefore, compared with the conventional heat pipe 10 in which wetting and spreading can occur, the transportability of the refrigerant can be improved.

  (2) In the heat pipe 10, as shown in FIG. 4, the hydrophobic film 3 is formed in the range from the inner surface 1 a of the passage 1 to the cutting portion 6, and the hydrophilic film 4 is formed on the inner surface 1 a of the passage 1. It is formed by laminating on the surface. With such a two-layer structure of the hydrophobic film 3 and the hydrophilic film 4, the cutting part 6 can be easily formed by removing the hydrophobic film 3 and the hydrophilic film 4 along the outer edge of the downstream end of the passage 1. For example, the shape of the cutting part 6 can be easily formed simply by performing a plasma treatment using the ion milling device 16 and physically cutting it. Therefore, the workability and workability of the passage shape that improves the transportability of the refrigerant can be improved.

(3) In the heat pipe 10 described above, the dimension of the step surface 6a in the width direction of the passage 1 (the direction perpendicular to the flow path direction of the passage 1), that is, the height H of the cutting portion 6 is the film thickness of the hydrophobic film 3. It is set to a value smaller than the value (T ₁ + T ₂ ) obtained by adding T ₁ and the film thickness T ₂ of the hydrophilic film 4. By such dimension setting, it is possible to prevent the base material 2 from being exposed on the surface of the extended surface 6b regardless of the width W of the cutting portion 6. That is, the hydrophobic film 3 can be exposed on the surface of the extended surface 6b, and wetting and spreading of the liquid refrigerant to the extended surface 6b can be suppressed.

(4) In the above heat pipe 10, the dimension of the cutting part 6 along the flow path direction of the passage 1, that is, the width W of the cutting part 6 is the film thickness T _{1 of the} hydrophobic film 3 and the film thickness T of the hydrophilic film 4. A value smaller than the value obtained by adding ₂ (T ₁ + T ₂ ) is set. By such dimension setting, it is possible to prevent the base material 2 from being exposed on the surface of the step surface 6a regardless of the height H of the cutting portion 6. That is, the hydrophobic film 3 can be exposed on the surface of the step surface 6a, and wetting and spreading of the liquid refrigerant on the step surface 6a can be suppressed.

  (5) In the heat pipe 10 described above, the width W and the height H of the cutting portion 6 are set so as to satisfy the relationship of the above formula 1. When the left side and the right side of Equation 1 coincide with each other, if the contact angle between the liquid refrigerant staying at the downstream end of the passage 1 and the hydrophobic film 3 on the step surface 6a is θ, the refrigerant and the expansion surface 6b come into contact with each other. . On the other hand, if the relationship of Formula 1 is satisfied, the liquid refrigerant and the expansion surface 6b do not contact each other. Therefore, wetting and spreading of the liquid refrigerant to the extended surface 6b can be suppressed.

  (6) In the heat pipe 10, as shown in FIG. 4, the cross-sectional shape of the step surface 6 a of the cutting portion 6 is formed perpendicular to the inner surface 1 a of the passage 1, and the cross-sectional shape of the expansion surface 6 b is The passage 1 is formed in parallel to the inner surface 1a. As described above, by simplifying the shape setting of the cutting part 6, the machining and forming work of the cutting part 6 can be facilitated, and the workability and workability can be improved.

  (7) In the method for manufacturing the heat pipe 10, the hydrophobic film 3 is laminated on the inner surface 1 a of the passage 1, and the hydrophilic film 4 is formed on the hydrophobic film 3. Thereafter, the hydrophobic film 3 and the hydrophilic film 4 are cut along the outer edge of the downstream end of the passage 1 so that the step surface 6a is formed. Through these manufacturing steps, it is possible to form the cutting portion 6 in which the hydrophobic film 3 is exposed at the outer edge on the downstream side of the passage 1 while leaving the hydrophilic film 4 formed on the inner surface 1a of the passage 1 as it is. Thereby, the channel | path formation member 7 in which the wetting spread of the liquid refrigerant in the downstream end of the channel | path 1 was suppressed can be manufactured. Moreover, since the heat pipe 10 is manufactured using the passage forming member 7, the transportability and circulation of the refrigerant can be improved as compared with the conventional heat pipe 10, and the heat transport efficiency can be improved. it can.

  (8) In the manufacturing method of the heat pipe 10 described above, the resist mask 5 (protective layer) is formed on the hydrophilic film 4 before cutting the outer edge of the downstream end of the passage 1. Thereby, the boundary between the part to be cut and the part not to be cut can be set by the end side of the resist mask 5. For example, as shown in FIG. 8B, the intersection position between the step surface 6 a and the inner surface 1 a of the passage 1 can be set at the tip position 5 a of the resist mask 5. Therefore, the cutting accuracy of the cutting part 6 can be improved.

(9) In the manufacturing method of the heat pipe 10 described above, from the end face 1b of the passage 1 the distance to the tip position 5a of the resist mask 5, the thickness T ₂ of the film thickness T ₁ and the hydrophilic film 4 of the hydrophobic film 3 It is set to a value less than the addition value (T ₁ + T ₂ ). Thereby, the width W of the part to be cut (cutting part 6) can be made smaller than the added value (T ₁ + T ₂ ). Therefore, the base material 2 can be prevented from being exposed on the surface of the step surface 6a regardless of the height H of the cutting portion 6. That is, the hydrophobic film 3 can be exposed on the surface of the step surface 6a, and wetting and spreading of the liquid refrigerant on the step surface 6a can be suppressed.

(10) In the manufacturing method of the heat pipe 10 described above, the cutting depth (height H of the cutting portion 6) when cutting the hydrophobic film 3 and the hydrophilic film 4 along the outer edge of the downstream end of the passage 1 is as described above. Less than the added value (T ₁ + T ₂ ). Thereby, irrespective of the size of the width W of the cutting part 6, it can prevent that the base material 2 is exposed to the surface of the extended surface 6b. That is, the hydrophobic film 3 can be exposed on the surface of the extended surface 6b, and wetting and spreading of the liquid refrigerant to the extended surface 6b can be suppressed.

(11) In the manufacturing method of the heat pipe 10 described above, when DFR is used as the resist mask 5, the resist mask 5 can be easily formed by performing development processing of the photoresist. On the other hand, the resist mask 5 can be easily removed by performing a photoresist peeling process.
For example, as shown in FIG. 6, the resist mask 5 can be formed before the cutting portion 6 is formed, and the resist mask 5 can be removed after the cutting portion 6 is formed. Thus, the hydrophilic film | membrane 4 can be temporarily protected by using DFR with which formation and removal of a protective layer are easy. Therefore, the workability and workability of the passage forming member 7 can be improved, and as a result, the productivity of the heat pipe 10 can be improved.

[6. Modified example]
Regardless of an example of the disclosed embodiment, various modifications can be made without departing from the spirit of the present embodiment. Each structure and each process of this embodiment can be selected as needed, or may be combined suitably.

In the above-described embodiment, the step surface 6a of the cutting portion 6 is exemplified as a plane that is perpendicular to the inner surface 1a of the passage 1. However, the shape, surface gradient, curvature, etc. of the step surface 6a are shown here. It is not limited. The same applies to the extended surface 6b of the cutting part 6.
For example, as shown in FIG. 11 (a), in the cross section perpendicular to the inner surface 1a, the angle formed by the step surface 6a and the inner surface 1a may be formed at an acute angle, or conversely, it may be formed at an obtuse angle. Also good. Moreover, as shown in FIG.11 (b), the angle | corner which the extended surface 6b and the end surface 1b make may be formed in an acute angle, and you may form in an obtuse angle on the contrary. When the cutting part 6 is formed by cutting using the ion milling device 16, the cutting direction can be adjusted by changing the direction of the rotation axis of the passage forming member 7 to a direction different from the normal line K. is there.

  In the above-described embodiment, the step surface 6a and the extended surface 6b of the cutting portion 6 are illustrated as intersecting substantially vertically, but these surfaces may not be clearly separated. That is, as shown in FIG. 11C, the step surface 6a and the extended surface 6b may be connected by a bent surface. Moreover, as shown in FIG.11 (d), the expansion surface 6b may be formed in substantially the same planar shape as the level | step difference surface 6a. That is, the extended surface 6 b can be omitted, and at least the step surface 6 a only needs to be formed in the widened portion 6.

  Moreover, in the above-mentioned embodiment, the method of forming the cutting part 6 using the ion milling apparatus 16 was shown. On the other hand, as other physical cutting methods, micro cutting, micro grinding, and the like using a cutting tool formed of single crystal diamond or nano-polycrystalline diamond can be applied. Alternatively, micro electric discharge machining, micro laser machining, or the like may be applied. Various surface shapes of the step surface 6a and the extended surface 6b are conceivable depending on the processing method. For example, as shown in FIG. 11E, a curved surface shape or an uneven surface shape may be used. Note that, as described above, the method for forming the cutting portion 6 is not limited to cutting. For example, a method of chemically decomposing and removing may be applied, or the cutting portion 6 may be formed by shaping the shape of the hydrophobic film 3.

[7. Addendum]
The following additional notes are disclosed with respect to the above-described embodiments and modifications.
(Appendix 1)
A passage that absorbs heat from the outside by a gas-liquid phase change of the refrigerant flowing inside,
Widening the passage along the outer edge of the downstream end of the passage, a widened portion having hydrophobicity,
A stepped surface formed in a plane that forms part of the widened portion and intersects the inner surface of the passage;
A hydrophilic film that has hydrophilicity and covers the inner surface of the passage on the upstream side of the intersection line between the inner surface of the passage and the step surface;
A heat pipe characterized by comprising:

(Appendix 2)
The heat pipe according to claim 1, wherein the hydrophobic portion is formed from an inner surface of the widened portion to a lower layer of the hydrophilic film on the inner surface of the passage.

(Appendix 3)
The heat pipe according to appendix 1 or 2, wherein a dimension of the step surface in the width direction of the passage is less than a value obtained by adding a thickness of the hydrophilic film and a thickness of the hydrophobic portion.

(Appendix 4)
Any one of appendices 1 to 3, wherein the dimension of the widened portion in the flow path direction of the passage is less than the sum of the thickness of the hydrophilic film and the thickness of the hydrophobic portion. The heat pipe according to item.

(Appendix 5)
In the manufacturing method of the heat pipe provided with a passage that absorbs heat from the outside by the gas-liquid phase change of the refrigerant flowing inside,
Laminating a hydrophobic membrane having hydrophobicity inside the passage,
Laminating a hydrophilic film having hydrophilicity on the hydrophobic film inside the passage,
The hydrophilic film and a part of the hydrophobic film are removed in the direction of widening the passage along the outer edge of the downstream end of the passage so that a planar stepped surface intersecting the inner surface of the passage is formed. A method for manufacturing a heat pipe.

(Appendix 6)
The method for producing a heat pipe according to appendix 5, wherein the surface of the hydrophilic film is covered with a protective layer for protecting the hydrophilic film before the hydrophilic film and the hydrophobic film are removed.

(Appendix 7)
The protective layer is covered so that the distance from the outer edge of the downstream end of the passage to the edge of the protective layer is less than the sum of the thickness of the hydrophobic film and the thickness of the hydrophilic film. The manufacturing method of the heat pipe of Additional remark 6.

(Appendix 8)
The hydrophilic film and the hydrophobic film are removed so that the removal depth from the surface of the hydrophilic film is less than the sum of the thickness of the hydrophobic film and the thickness of the hydrophilic film, The method for manufacturing a heat pipe according to any one of appendices 5 to 7.

(Appendix 9)
While using a photoresist as the protective layer,
The method for manufacturing a heat pipe according to any one of appendices 5 to 8, wherein the photoresist is removed after removing the hydrophilic film and the hydrophobic film.

DESCRIPTION OF SYMBOLS 1 Passage 1a Inner surface 1b End surface 3 Hydrophobic film 4 Hydrophilic film 5 Resist mask (protective layer)
6 Cutting part (widening part)
6a Step surface 6b Expansion surface 7 Passage forming member 10 Heat pipe

Claims (6)

A passage that absorbs heat from the outside by a gas-liquid phase change of the refrigerant flowing inside,
Widening the passage along the outer edge of the downstream end of the passage, the widened portion whose inner surface is hydrophobic,
A stepped surface formed in a plane that forms part of the widened portion and intersects the inner surface of the passage;
A heat pipe having a hydrophilic property and having a hydrophilic film covering the inner surface of the passage on the upstream side of the intersection line between the inner surface of the passage and the step surface. The heat pipe according to claim 1, wherein the hydrophobic portion is formed from an inner surface of the widened portion to a lower layer of the hydrophilic film on the inner surface of the passage. 3. The heat pipe according to claim 1, wherein a dimension of the step surface in the width direction of the passage is less than a value obtained by adding a thickness of the hydrophilic film and a thickness of the hydrophobic portion. . The dimension of the said widening part about the flow direction of the said channel | path is less than the value which added the thickness of the said hydrophilic film, and the thickness of the said hydrophobic part, The any one of Claims 1-3 characterized by the above-mentioned. The heat pipe according to item 1. In the manufacturing method of the heat pipe provided with a passage that absorbs heat from the outside by the gas-liquid phase change of the refrigerant flowing inside,
Laminating a hydrophobic membrane having hydrophobicity inside the passage,
Laminating a hydrophilic film having hydrophilicity on the hydrophobic film inside the passage,
The hydrophilic film and a part of the hydrophobic film are removed in the direction of widening the passage along the outer edge of the downstream end of the passage so that a planar stepped surface intersecting the inner surface of the passage is formed. A method for manufacturing a heat pipe. 6. The method of manufacturing a heat pipe according to claim 5, wherein the surface of the hydrophilic film is covered with a protective layer that protects the hydrophilic film before removing the hydrophilic film and the hydrophobic film.

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