JP2006189232A - Heat transfer pipe for heat pipe, and heat pipe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat transfer pipe for a heat pipe and the heat pipe having high cooling performance even when it is used in a state of minus angle, and capable of being manufactured without using a separated member such as a wick. <P>SOLUTION: This heat transfer pipe used as the heat pipe by sealing operating fluid in the pipe, comprises a number of first fins 3 formed on an inner peripheral face of the heat transfer pipe, at least one second fin 4 formed between the first fins 3 and having a height lower than the first fin 3, and a projecting portion 5 formed on a slant face 4b of the second fin 4. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heat pipe for heat pipe and a heat pipe, and more particularly to a heat pipe for heat pipe and a heat pipe used for cooling a CPU (Central Processing Unit) of an electronic device.

  In recent years, as represented by a personal computer, in particular, a notebook personal computer (hereinafter referred to as a notebook personal computer), the amount of heat generated by the CPU is increasing as the performance of the CPU increases. The CPU is provided with a cooling device for cooling a malfunction such as a decrease in arithmetic processing capability when the temperature becomes high due to heat generation.

  Note that the cooling device provided in the notebook personal computer is desired to be as small as possible in view of the installation space, and the cooling device 100 having the configuration illustrated in FIG. 8A is widely used. Yes. The cooling device 100 mainly includes a heat pipe 101, a heat radiating plate 103, and a small fan 102. The heat pipe 101 is a pipe in which a minute groove is formed and a certain amount of hydraulic fluid is sealed under reduced pressure. One end of the heat pipe 101 is brought into contact with a heating element such as the CPU 104 to absorb the heat, and the other end is absorbed. Is absorbed by cooling by a small fan 102 or the like.

  That is, as shown in FIG. 7, the working fluid 8 enclosed in the heat pipe 10 is heated and vaporized at the contact portion (heating unit (evaporating unit 12)) of the heat pipe 10 with the heating element, and vaporized. As a result, the heat of the heating element is absorbed. Then, the vaporized working fluid 8 is cooled and condensed by the heat radiating portion (heat radiation portion (condensing portion 11)) at the other end of the heat pipe 10, and becomes the working fluid 8 again. Capillary force is generated in the hydraulic fluid 8 that has been returned to liquid by the condensing unit 11 due to the grooves formed in the heat pipe 10. Then, the hydraulic fluid 8 is refluxed to the evaporation unit 12 by this capillary force. As described above, the heat pipe 10 repeatedly evaporates and condenses the working fluid 8 in the sealed heat pipe 10, and the continuous heat transport from the evaporation unit 12 to the condensation unit 11 can be performed by refluxing the heat pipe 10. It can be done.

  In the future, development of the heat pipe 10 with more excellent cooling performance is desired in order to further improve the performance of the CPU and the like. The cooling performance can be expressed by using the heat transfer coefficient and the maximum heat transport amount as an index. The heat transfer rate represents how quickly heat can be transferred from the evaporation unit 12 to the condensation unit 11, and the maximum heat transport amount is how many watts (W) when the temperature of the evaporation unit 12 rises. It is an index that indicates whether the amount of heat can be transmitted.

  Based on such a request, for example, Patent Document 1 discloses a self-excited vibration type heat pipe heat transfer tube in which a number of fine fins continuous in the length direction are formed on the inner surface of a metal thin tube (in Patent Document 1, self-excited Has been proposed). Further, the ratio of fin height to tube inner diameter (fin height / tube inner diameter) is 0.01 to 0.35, and the ratio of fin number to tube inner diameter (fin number / tube inner diameter) is 3 to 25. Or the fin lead angle of the fin with respect to the tube axis is preferably 0 to 20 °. Further, according to the self-excited vibration heat pipe for heat pipe having the above structure, the inner surface of the pipe is wetted by the capillary force generated between the fins, and stable heat transport performance (corresponding to the maximum heat transport amount in the present invention). It is described that can be maintained.

  Patent Document 2 proposes an internally grooved heat transfer tube which is not a heat transfer tube for heat pipes but is applied to a heat exchanger characterized by fins formed on the inner surface of the tube. In the heat transfer tube with an inner surface groove of Patent Document 2, a high fin having a predetermined height is formed in a spiral shape on the inner surface of the tube main body, and one or a plurality of lower fins than the high fin are interposed between the high fins. A low fin is formed, and the height of the low fin is 1/15 to 1/5 of the height of the high fin. Further, it is described that the height of the high fin is preferably 0.1 to 0.3 mm, or the twist angle of the high fin with respect to the tube axis (corresponding to the fin lead angle) is preferably 15 to 35 °. Yes. And according to the inner surface grooved heat transfer tube, the condensation heat transfer rate and the evaporation heat transfer rate are improved in a well-balanced manner, and the heat transfer performance is improved without increasing the pressure loss in the tube and the mass of the heat transfer tube. It is stated that it can be done.

Further, Patent Document 3 proposes a heat pipe for heat pipe in which a wick is attached to the inner surface of the tube instead of processing fins on the inner surface of the tube. The heat pipe for heat pipe of Patent Document 3 (described as a small-diameter heat pipe in Patent Document 3) has a tube inner surface in a cross section orthogonal to the longitudinal direction of the tube (described as a pipe in Patent Document 3). A wick that is continuous in the longitudinal direction is provided in a state of being located on one side or both sides. This heat pipe heat transfer tube has a structure in which the wicks can be placed more concentrated without being dispersed inside the tube, so that capillary force is more efficiently generated between the wicks and the maximum heat transport amount is increased. It is written to do so. Moreover, as a wick, the wire, mesh, sintered metal porous material, etc. which consist of copper, silver, iron, stainless steel, glass etc. are illustrated.
JP 2003-302180 A (paragraphs 0004 to 0006, 0024 to 0026) JP 2002-350080 (paragraphs 0001, 0009 to 0011, 0022) JP-A-2-13395 (Page 2, upper left column, line 19 to upper right column, line 20; page 3, lower left column, lines 4 to 10)

  As shown in FIG. 7, the heat pipe is desirably used in a horizontal state in which the evaporation section 12 and the condensation section 11 of the heat pipe 10 are kept at the same height. However, as shown in FIG. 8B, a notebook personal computer or the like in which the heat pipe 101 (10) as shown in FIG. The heat pipe 101 (10) may be used in a negative angle state where the heat pipe 101 (10) is inclined at an angle β from the horizontal direction to the negative direction.

  Thus, when the heat pipe 10 is used in a minus angle state, when the heat pipe for heat pipe of Patent Document 1 is used as the heat pipe 10, the capillary force generated between the fins formed inside the pipe is reduced. Since the hydraulic fluid 8 is not so high as to be returned to the evaporator 12 at a higher position than the condenser 11, the return of the hydraulic fluid 8 to the evaporator 12 becomes worse (slower) and the cooling performance is deteriorated. was there. In addition, it has been studied to apply the fin shape described in Patent Document 2 as the shape of the fin formed on the inner surface of the pipe. However, the balance between the heat transfer coefficient and the heat transfer coefficient of the heat pipe can be improved. However, the improvement of the capillary force generated between the fins was not observed, and like the heat transfer pipe for heat pipe of Patent Document 1, the return of the working fluid 8 was poor and the cooling performance was lowered.

  Further, when the heat pipe heat transfer tube of Patent Document 3 is used as the heat pipe 10, the capillary force generated between the wicks is higher than the capillary force generated between the fins, so that Patent Document 1 and Patent Document 2 are used. However, the liquid return speed was not satisfactory as the liquid return speed of the heat pipe, and the cooling performance was not sufficient. And in the heat pipe for heat pipe of patent document 3, the operation | work which provides a wick in a pipe inner surface is complicated and high work cost compared with the operation | work which forms a fin in a pipe inner surface like patent document 1 and patent document 2. In addition, a material for forming the wick is required in addition to the tube, which increases the material cost. Therefore, there has been a problem that the manufacturing cost of the heat pipe for heat pipe becomes high.

  The present invention has been made in view of the above-mentioned problems, and has a superior cooling performance even when used in a minus angle state, and can be manufactured without using another member such as a wick. An object is to provide a heat transfer pipe and a heat pipe for a pipe.

  In order to solve the above-mentioned problems, the invention according to claim 1 is a heat transfer tube used as a heat pipe by enclosing a working fluid in a tube, and a first one formed on the inner peripheral surface of the heat transfer tube. For heat pipes, comprising: a fin; at least one second fin formed between the first fins; and a second fin having a height lower than that of the first fin; and a projecting portion formed on a slope of the second fin. It is configured as a heat transfer tube. According to the said structure, by forming a 2nd fin between 1st fins, the groove bottom width of a groove part becomes small, the capillary force of the hydraulic fluid condensed in a groove part becomes high, and a liquid return becomes quick. Further, by forming the projecting portion by processing the slope of the second fin, a narrow groove portion is formed between the projecting portion and the groove bottom portion, and the hydraulic fluid is condensed in this groove portion, The capillary force of the hydraulic fluid is increased and the liquid return is accelerated. Further, without attaching a wick or the like to the inner surface of the pipe as in a conventional heat pipe for heat pipes, the first and second fins processed on the inner surface of the pipe can increase the capillary force of the working fluid and accelerate the liquid return. it can.

  The invention according to claim 2 is for a heat pipe in which a second fin root radius ra formed at a root of the second fin is more than 0 mm and less than 0.04 mm in a cross section perpendicular to the axis of the heat transfer tube. It is configured as a heat transfer tube. According to the above configuration, by making the second fin root radius ra as small as possible, the length and amount of the protruding portion formed on the inclined surface of the second fin increase, and the protruding portion and the groove bottom portion The amount of hydraulic fluid that condenses between the two increases. Thereby, the capillary force of the hydraulic fluid is further increased, and the liquid return is accelerated.

  Moreover, in the invention according to claim 3, in the tube axis parallel section of the heat transfer tube, a first fin lead angle θ1 formed by the first fin and the tube axis is 0 ° or more and 30 ° or less, and The second fin lead angle θ2 formed by the second fin and the tube axis is configured as a heat pipe for heat pipe having the same as the first fin lead angle θ1. According to the above configuration, by defining the first fin lead angle θ1 and the second fin lead angle θ2 as low as possible, the distance between the condensing part and the evaporating part of the heat pipe is shortened. The return of the working fluid to the evaporation section is accelerated. Note that the first fin lead angle θ1 and the second fin lead angle θ2 being 0 ° indicate that the first fin and the second fin are parallel to the tube axis.

  According to a fourth aspect of the present invention, in the cross section orthogonal to the tube axis of the heat transfer tube, the first fin peak angle δ1 formed by both slopes of the first fin is 5 ° or more and 30 ° or less, and the first The second fin peak angle δ2 formed by both slopes of the two fins is configured as a heat transfer tube for a heat pipe having a angle of 5 ° to 30 °. According to the above-described configuration, the first fin peak angle δ1 and the second fin peak angle δ2 are defined within appropriate ranges, and the slopes of the first fin and the second fin are as perpendicular as possible to the groove bottom of the heat transfer tube. By forming, the capillary force of the working fluid condensed in the groove portion is further increased, and the liquid return is accelerated.

  The invention according to claim 5 is a heat in which the heat pipe for heat pipe according to any one of claims 1 to 4 is used, and a working fluid is sealed in the heat pipe for heat pipe under reduced pressure. It is configured as a pipe. According to the above configuration, since the heat pipe is produced using the heat pipe for heat pipe according to any one of claims 1 to 4, the capillary force of the working fluid in the heat pipe is increased, Liquid return is quicker.

  In the invention according to claim 6, the heat pipe for heat pipe is configured as a heat pipe having an elliptical shape or a semicircular shape in cross section perpendicular to the tube axis direction. According to the above configuration, by making the cross-sectional shape of the heat pipe for heat pipes into a predetermined shape, the contact area between the heat radiating body (for example, a heat radiating plate) and the heat generating body (for example, CPU) is increased, and the hydraulic fluid by heat radiation The condensation efficiency of the hydraulic fluid is increased, the evaporation efficiency of the hydraulic fluid due to heat generation (heating) is increased, and the liquid return is accelerated.

  Furthermore, invention of Claim 7 is comprised as a heat pipe whose said hydraulic fluid is water. According to the above configuration, by using water having a large surface tension as the working fluid, the capillary force of the working fluid is further increased and the liquid return is accelerated.

  According to the first to fourth aspects of the invention, even when used in a negative angle state, the hydraulic fluid returns quickly, so that the cooling performance, that is, the heat transfer rate and the maximum heat transport amount are excellent. Since a separate member such as a wick is not used, it is possible to provide a heat pipe for heat pipe that is inexpensive to manufacture. By setting the fin base radius ra of the second fin, the fin lead angles θ1 and θ2 of the first and second fins, and the fin peak angles δ1 and δ2 of the first and second fins within a predetermined range, the cooling performance is further improved. A more excellent heat transfer tube for heat pipe can be provided.

  According to the inventions of claims 5 to 7, even when used in a minus angle state, the liquid return of the working fluid is fast, so that the cooling performance, that is, the heat transfer rate and the maximum heat transport amount are excellent. Since a separate member such as a wick is not used, a heat pipe with a low manufacturing cost can be provided. In addition, the heat pipe which was further excellent in cooling performance can be provided by making the cross-sectional shape of the heat exchanger tube for heat pipes into a predetermined shape, or a hydraulic fluid being water.

Hereinafter, the best mode for carrying out the heat pipe for heat pipe and the heat pipe according to the present invention will be specifically described with reference to the drawings as appropriate.
In the drawings to be referred to, FIG. 1 (a) is a partial cross-sectional view in the tube axis direction of a heat transfer tube for heat pipes (note that the first fin and the second fin are simply shown by lines), and (b) is a tube. FIGS. 2A to 2C are main part enlarged perspective views showing other forms of the second fin, and FIGS. 3A to 3D are other forms of protruding parts. FIG. 4 is a partial cross-sectional view of the raw pipe and the grooved plug before rolling, and FIGS. 5A and 5B are partial cross-sections showing other forms of heat pipes for heat pipes. FIG. 6 and FIG. 6A are explanatory views showing the formation state of the meniscus of the hydraulic fluid formed in the groove, and FIG. 6B is an enlarged view of the main part of FIG.
Moreover, FIG. 7 is explanatory drawing for demonstrating the effect | action inside a heat pipe, FIG. 8 (a), (b) is a schematic diagram which shows an example of the usage pattern of a heat pipe.

<Heat pipe for heat pipe>
The heat transfer tube for heat pipe according to the present invention is a heat transfer tube used as a heat pipe by enclosing a working fluid in the tube, and its tube axis orthogonal section is substantially circular, preferably as described later, the cooling efficiency of the heat pipe Is configured to be elliptical or semicircular. The outer diameter of the tube (the longer diameter in the case of an ellipse) is 4 to 8 mm.

  As the heat transfer tube for heat pipe, copper and copper alloys, among which oxygen-free copper, low phosphorus deoxidized copper, and phosphorus deoxidized copper can be preferably used. Specifically, oxygen-free copper JIS H3300 C1020 can be suitably used. Further, it is more preferable to use these copper and copper alloy after tempering them into a soft material or a hard material. Furthermore, aluminum or the like can be suitably used in addition to copper as a metal having good heat conductivity.

  The manufacturing method of the heat pipe for heat pipe will be described later, but it is preferable to use a tube having an outer diameter of 8 to 13 mm as a dimension of the raw pipe before rolling for manufacturing the heat pipe for heat pipe. is there. If the outer diameter of the raw tube is less than 8 mm, the first and second fins, which will be described later when the heat transfer tube for heat pipe is manufactured, are small, so that the tool is lost during fin processing. Therefore, mass production tends to be difficult. Moreover, when the outer diameter of the raw tube exceeds 13 mm, the heat pipe for heat pipe to be manufactured becomes large, and it becomes difficult to manufacture a heat pipe for the purpose of space saving.

  The bottom wall thickness of the raw pipe before rolling for producing the heat pipe for heat pipe is preferably 0.25 mm to 0.60 mm. When the bottom wall thickness of the raw tube is less than 0.25 mm, when a heat transfer tube for a heat pipe is manufactured, the raw tube is likely to break, and it is difficult to process fins on the inner peripheral surface of the raw tube. . Further, if the bottom wall thickness of the raw tube exceeds 0.60 mm, the efficiency of fin workability tends to deteriorate, and the cooling performance tends to decrease.

As shown in FIGS. 1A and 1B, the heat pipe heat transfer tube 1 includes a first fin 3, a second fin 4, and a protruding portion 5. Each configuration will be described below.
(First fin)
A large number of first fins 3 are formed on the inner peripheral surface of the heat transfer tube 1 for heat pipes, and the number thereof is appropriately set in consideration of ease of fin processing and cooling performance. Further, the first fin 3 is composed of a peak summit curve portion 3a and a slope 3b smoothly connected thereto, and a flat (inner side) constituting this slope 3b and a part of the inner peripheral surface of the heat pipe 1 for heat pipe. Circumferential curvature curved surface) groove bottom portion 2a is formed so as to be smoothly connected with an arbitrary first fin root radius Ra. Further, the inner peripheral surface may be configured by smoothly connecting an arbitrary first fin root radius Ra and a second fin root radius ra described later without the groove bottom 2a. And in the pipe-axis orthogonal cross section of the heat transfer tube 1 for heat pipes, the first fin root radius Ra is preferably 0.04 to 0.12 mm. When the first fin root radius Ra is less than 0.04 mm, it is difficult to process the first fin on the inner peripheral surface of the tube, and the tube is easily broken and the tool (grooved plug) is easily lost. Further, when the first fin root radius Ra exceeds 0.12 mm, the first fin 3 becomes large and the heat pipe heat transfer tube 1 tends to be heavy.

  Further, in the tube axis parallel section of the heat transfer tube 1 for heat pipe, the first fin lead angle θ1 formed by the first fin 3 and the tube axis is preferably 0 ° or more and 30 ° or less, and preferably 0 ° or more and 10 °. The following is more preferable, and 0 ° to 5 ° is optimal. As shown in FIG. 1A, since the first fin 3 is formed so as to be nearly parallel to the tube axis direction by forming the first fin lead angle θ1 at a low angle, the heat pipe shown in FIG. 10, the length of the groove 2 (see FIG. 1B) that becomes the flow path of the hydraulic fluid 8 in the heat pipe 10, that is, the length of the groove 2 from the condenser 11 to the evaporator 12 is shortened. can do. As a result, the condensed working fluid 8 can be returned quickly, and the cooling performance can be improved.

  The first fin lead angle θ1 of 0 ° means that the first fin 3 is formed parallel to the tube axis, and the angle at which the first fin lead angle θ1 exceeds 0 ° is It means that the fin 3 is formed in a spiral shape with respect to the tube axis. When the first fin lead angle θ1 exceeds 30 °, the length of the groove 2 from the condensing unit 11 to the evaporation unit 12 in the heat pipe 10 becomes long, and the return of the working fluid 8 tends to be delayed.

  Further, it is preferable that the first fin peak angle δ1 formed by the both inclined surfaces 3b and 3b of the first fin 3 is 5 ° or more and 30 ° or less in the cross section orthogonal to the tube axis of the heat pipe 1 for heat pipe. The first fin peak angle δ1 also defines the angle between the slope 3b and the groove bottom 2a. The closer the slope 3b is to the vertical (the smaller the first fin peak angle δ1), the later forming a meniscus. The angle α increases, and the capillary force of the hydraulic fluid 8 condensed in the groove 2 formed by the inclined surface 3b and the groove bottom 2a increases (see FIGS. 6A and 6B). As a result, when the heat pipe 10 is used by being attached to, for example, a notebook computer, as shown in FIG. 8B, the posture of the notebook computer is inclined and the heat pipe 10 is in a negative angle state. However, the reduction in the return speed of the working fluid from the condensing unit 11 to the evaporation unit 12 is minimized by the high capillary force of the working fluid.

This can also be easily confirmed by observing the meniscus formed by the inclined surfaces of the fins and the working fluid 8 as shown in FIGS. 6 (a) and 6 (b) (the second in FIG. 6 (b)). Although the case of the inclined surface of the fin 4 has been described, the same applies to the inclined surface 3b of the first fin 3). The capillary force ΔP can be obtained by ΔP = (2σ · cos α) / w. In the ΔP equation, σ represents the surface tension, w represents the groove bottom width, and α represents the meniscus angle. Therefore, when the first fin peak angle δ1 is larger than 30 °, the capillary force acting on the hydraulic fluid 8 is reduced (the angle α forming the meniscus is reduced), and the cooling performance is likely to be lowered. On the other hand, if the first fin peak angle δ1 is less than 5 °, the moldability of the first fin 3 is deteriorated and mass production tends to be difficult.

  In addition, in the cross section perpendicular to the tube axis of the heat pipe 1 for heat pipe, the first fin height Ha of the first fin 3 is preferably 0.15 to 0.35 mm. If the first fin height Ha is less than 0.15 mm, the relative amount of the first fin 3 (groove portion 2) is insufficient, and the heat pipe 10 (the heat pipe 101 in the schematic diagram of the notebook type personal computer in FIG. 8A) The cooling performance is likely to deteriorate. On the other hand, if the first fin height Ha exceeds 0.35 mm, the first fin 3 to be molded becomes too high, and the moldability of the first fin 3 is easily deteriorated and the tool is easily damaged. The heat transfer tube 1 is likely to be difficult to manufacture.

(2nd fin)
At least one second fin 4 is formed between the first fins 3 and 3, and the number of the second fins 4 is not particularly limited. 5A shows a heat pipe for heat pipe 1a in which a plurality of second fins 4 are formed between the first fins 3, and FIG. 5B shows one second fin 4 between the first fins 3. The heat transfer tube 1b for heat pipes having the above is described.

  Similar to the first fin 3, the second fin 4 is composed of a peak curve portion 4 a and a slope 4 b smoothly connected thereto, and a part of the slope 4 b and the inner peripheral surface of the heat pipe 1 for heat pipe. Is formed so as to be smoothly connected to a flat (inner peripheral curvature curved surface) groove bottom 2a at an arbitrary second fin root radius ra. And in the pipe-axis orthogonal cross section of the heat transfer tube 1 for heat pipes, the second fin root radius ra is preferably greater than 0 mm and not greater than 0.04 mm. When the second fin root radius ra is 0 mm, it is difficult to process the first fin on the inner peripheral surface of the tube, and the tube is easily broken. Moreover, when the 2nd fin base radius ra exceeds 0.04 mm, formation of the protrusion part 5 mentioned later tends to become inadequate. As a result, the capillary force of the hydraulic fluid does not increase and the liquid return is unlikely to be accelerated.

  Further, the second fin lead angle θ2 formed between the second fin 4 and the tube axis in the cross section parallel to the tube axis of the heat transfer tube 1 for heat pipes is that the second fin 4 can be easily processed. It is preferably the same as the angle θ1. Further, in the cross section orthogonal to the tube axis of the heat pipe 1 for heat pipe, the second fin peak angle δ2 formed by the two inclined surfaces 4b, 4b of the second fin 4 is 5 ° for the same reason as the first fin peak angle δ1. It is preferably formed so as to be 30 ° or less, and more preferably the same as the first fin peak angle δ1 in that the second fin 4 can be easily processed. The second fin 4 is lower than the first fin 3, and the height (second fin height) ha is preferably 1/3 or less of the first fin height Ha. If the second fin height ha is higher than 1/3, the formation of the protruding portion 5 tends to be insufficient. The configuration of the protrusion 5 will be described later.

(Groove bottom width)
As shown in FIG. 1B and FIG. 5B, the groove portion 2 is formed between the first fin 3 and the second fin 4 by forming the first fin 3 and the second fin 4. Further, as shown in FIG. 5A, when a plurality of second fins 4 are formed between the first fins 3, the groove portions 2 are formed between the first fins 3 and the second fins 4. In addition, the groove 2 is formed between the second fins 4. The groove bottom widths w and w ′ of the groove 2 (groove bottom 2a) are preferably set to be 0.02 to 0.05 times the maximum inner diameter D of the heat pipe 1 for heat pipe. That is, it is preferable to set 0.02 ≦ (groove bottom width w, w ′ / maximum inner diameter D) ≦ 0.05. The maximum inner diameter D is the distance between the groove bottom portions 2a facing each other by 180 ° in the cross section perpendicular to the tube axis. The groove bottom width w between the first fin 3 and the second fin 4 and the groove bottom width w ′ between the second fins 4 are preferably the same width, but are set to different widths. Also good.

When the groove bottom widths w and w ′ are less than 0.02 times the maximum inner diameter D, the groove bottom widths w and w ′ are too narrow, so that the tool for forming the first fin 3 and the second fin 4 is used. Defects or the like are likely to occur, making it difficult to mass-produce the heat transfer tube 1 for heat pipes. On the other hand, when the groove bottom width w, w ′ exceeds 0.05 times the maximum inner diameter D, the groove portion 2 between the first fin 3 and the second fin 4 and the groove portion 2 between the second fins 4 are formed. The capillary force ΔP (see FIG. 6) acting on the condensing hydraulic fluid 8 is lowered, and the cooling performance is lowered.

(Protruding part)
As shown in FIG. 1B and FIGS. 2A to 2C, the protruding portion 5 is formed on the inclined surfaces 4b, 4b ′, 4b ″ of at least one side of the second fins 4, 4 ′, 4 ″. At least one is formed. At least a part of the protruding portion 5 is metal-line-connected or surface-connected to the inclined surfaces 4b, 4b ′, 4b ″ of the second fin 4. In addition, the shape of the protruding portion 5 is preferably a needle shape or a foil shape, but is not particularly limited in the present invention. A typical example of the protrusion 5 is schematically shown in FIGS. FIGS. 3A and 3B are examples of needle-like protrusions 5a and 5b. The protrusion 5a is formed in a conical shape, and the protrusion 5b is formed in a cylindrical shape. 3C and 3D are examples of the foil-like protrusions 5c and 5d. The protrusion 5c is formed in a rectangular prism shape, and the protrusion 5d is the width of the protrusion 5c. Is changed in the longitudinal direction. The protrusions 5 (5a to 5d) are formed from the slope 4b of the second fin 4 when processed, and the formation position, number, shape, etc. of the slope 4b are not particularly limited. Absent. Further, the adjustment of the outer diameter (width), length, shape, etc. of the protruding portion 5 is performed by adjusting the amount of reduction of the steel ball 9, the drawing speed of the raw tube 6, and the clearance c ( (See FIG. 4). FIG. 2B shows an example in which a plurality of projecting portions 5 and 5 are intermittently formed on the inclined surface 4b ′ of the second fin 4 ′ along the tube axis. FIG. 2C illustrates an example in which a plurality of protruding portions 5 and 5 are formed along the inclined surface 4b ″ of the second fin 4 ″.

  As shown in FIG. 6, the formation of the protruding portion 5 forms a narrow groove portion 2 ′ between the protruding portion 5 and the groove bottom portion 2 a, and the narrow groove portion 2 ′ also has this narrow groove portion 2 ′. The hydraulic fluid 8 is condensed. The condensed meniscus of the working fluid 8 also has a good shape due to the narrow width of the groove 2 ′, and the capillary force of the working fluid 8 is increased. As a result, the return of the working fluid 8 in the heat pipe 10 (see FIG. 7) is accelerated, and the cooling performance can be improved. Further, as shown in FIGS. 5A and 5B, the protruding portion 5 is formed on all the second fins 4, 4... Formed on the inner peripheral surfaces of the heat transfer tubes 1a, 1b. It is not necessary to form, and it should just be formed in at least one part of the 2nd fins 4, 4 ... formed in the internal peripheral surface.

<Method for producing heat transfer tube for heat pipe>
Next, a method for producing the heat pipe 1 for heat pipe will be described.
The first and second fins on the inner peripheral surface of the heat pipe for heat pipe can be formed by, for example, a rolling method. Specifically, as shown in FIG. 4, a grooved plug 7 having a groove shape corresponding to the first and second fins is inserted inside a raw pipe (copper pipe) 6 having a predetermined diameter. Then, the steel ball 9 is rotated on a planetary plane while being reduced from the outside of the raw tube 6. Then, by pulling out the raw tube 6 in the drawing direction, the grooved plug 7 is rotated, and first and second fins having a predetermined shape are continuously processed on the inner peripheral surface of the raw tube 6, and the heat pipe for heat pipe Is produced. The fin processing on the inner peripheral surface of the heat pipe for heat pipe may be performed not only by the ball rolling method but also by the roll rolling method. Moreover, it is not limited to a rolling method, For example, it can carry out also by a rolling method.

  Here, when the predetermined clearance c is provided between the inner peripheral surface of the element tube 6 and the grooved plug 7 and the rolling process is performed, the element tube 6 is distorted and formed by the grooved plug 7. A phase shift occurs in the fins, particularly the second fins. Due to this phase shift, the formed second fin is gnawed by the grooved plug 7, and the protruding portion described above is formed on the slope of the second fin. The clearance c is preferably 0.15 mm or more. When the clearance c is less than 0.15 mm, the degree of close contact between the raw tube 6 and the grooved plug 7 is increased, the grooved plug 7 is likely to be damaged, and heat transfer tubes for heat pipes are difficult to mass-produce.

  Also, the first and second groove depths Hb and hb, the first and second groove root radii Rb and rb, the first and second groove peak angles δ3 and δ4, the first and second groove leads of the grooved plug 7 are provided. Angles (not shown) and the like are the first and second fin heights Ha and ha, the first and second fin root radii Ra and ra, and the first and second fin peak angles of the heat pipe 1 for heat pipe. It is determined corresponding to δ1, δ2 and the first and second fin lead angles θ1, θ2 (see FIG. 1B).

<Production method of heat pipe>
Next, a method for manufacturing a heat pipe will be described.
After cutting the heat pipe for heat pipe to a predetermined length, one end thereof is sealed by TIG welding. After injecting a predetermined amount of hydraulic fluid into the heat pipe for heat pipe sealed on one side, the inside of the heat pipe for heat pipe is evacuated and kept at a reduced pressure, and the other end is sealed by TIG welding. Thus, it is possible to produce a heat pipe in which the inside of the pipe is close to a vacuum. The injection amount of the hydraulic fluid 8 is preferably about 20 to 35% of the internal volume of the evaporation unit 12 in consideration of the heat transfer rate and the maximum heat transfer amount (see FIG. 7). However, the injection amount is not limited to this. Further, as the hydraulic fluid, water, methyl alcohol, or the like is used. In particular, water (pure water) having a high surface tension and high capillary force is preferable, but the hydraulic fluid of the present invention is limited to water (pure water). Not what you want.

  As shown in FIG. 8, the heat pipe 101 (10) produced as described above can be suitably used for the cooling device 100 of the notebook personal computer. One end of the heat pipe 101 (10) is in contact with a heating element such as the CPU 104 as the evaporation unit 12 to absorb the heat of the part, and the other end is cooled as a condensing unit (radiation unit) 11 by the small fan 102 or the like. The Further, the heat pipe 101 (heat pipe for heat pipe) preferably has an elliptical shape or a semicircular shape in cross section perpendicular to the tube axis direction. By making the cross-sectional shape of the heat pipe 101 elliptical or semicircular, the contact area between the heat radiating body (for example, the heat radiating plate 103) and the heat generating body (for example, the CPU 104) is increased, and the condensing efficiency of the hydraulic fluid by heat radiation is high. At the same time, the evaporation efficiency of the hydraulic fluid due to heat absorption increases, and the hydraulic fluid returns faster. Furthermore, the heat pipe 101 cited as an embodiment of the present invention can be suitably used for other electronic devices such as desktop personal computers and various home appliances.

(A) is the fragmentary sectional view in the tube-axis direction of the heat exchanger tube for heat pipes concerning this invention, (b) is the fragmentary sectional view in a tube-axis orthogonal direction. (A)-(c) is a principal part expansion perspective view which shows the other form of the 2nd fin of the heat exchanger tube for heat pipes which concerns on this invention. (A)-(d) is a perspective view which shows typically the other form of the protrusion part of the heat exchanger tube for heat pipes which concerns on this invention. It is a fragmentary sectional view of a base pipe and a slotted plug before rolling processing in manufacture of a heat exchanger tube for heat pipe concerning the present invention. (A), (b) is a fragmentary sectional view which shows the other form of the heat exchanger tube for heat pipes which concerns on this invention. (A) is explanatory drawing which shows the formation condition of the meniscus of the hydraulic fluid formed in the groove part of the heat exchanger tube for heat pipes concerning this invention, (b) is a principal part enlarged view of (a). It is explanatory drawing for demonstrating the effect | action inside a heat pipe. (A), (b) is a schematic diagram which shows an example of the usage pattern of a heat pipe.

Explanation of symbols

1, 1a, 1b Heat pipe for heat pipe 3 First fin 3b Slope 4, 4′4 ″ Second fin 4b, 4b ′, 4b ″ Slope 5, 5a, 5b, 5c, 5d Projecting portion 8 Hydraulic fluid 10, 101 Heat pipe ra Second fin root radius θ1 First fin lead angle θ2 Second fin lead angle δ1 First fin peak angle δ2 Second fin peak angle

Claims (7)

  A heat transfer tube that is used as a heat pipe by enclosing a working fluid in a tube, and is formed between at least one first fin formed on the inner peripheral surface of the heat transfer tube and the first fin, A heat pipe for a heat pipe, comprising: a second fin having a height lower than that of the first fin; and a projecting portion formed on a slope of the second fin.   2. The heat pipe according to claim 1, wherein a second fin root radius ra formed at a root of the second fin is greater than 0 mm and equal to or less than 0.04 mm in a cross section perpendicular to the tube axis of the heat transfer tube. Heat transfer tube.   In a tube axis parallel section of the heat transfer tube, a first fin lead angle θ1 formed by the first fin and the tube axis is 0 ° or more and 30 ° or less, and a second fin formed by the second fin and the tube shaft. The heat transfer tube for a heat pipe according to claim 1 or 2, wherein a fin lead angle θ2 is the same as the first fin lead angle θ1.   In the cross section perpendicular to the tube axis of the heat transfer tube, the first fin peak angle δ1 formed by both slopes of the first fin is 5 ° or more and 30 ° or less, and the second fin peak formed by both slopes of the second fin. The heat transfer tube for a heat pipe according to any one of claims 1 to 3, wherein the angle δ2 is not less than 5 ° and not more than 30 °.   A heat pipe comprising the heat pipe for heat pipe according to any one of claims 1 to 4, wherein a working fluid is sealed under reduced pressure in the heat pipe for heat pipe.   6. The heat pipe according to claim 5, wherein the heat pipe for heat pipe has an elliptical shape or a semicircular shape in a cross section perpendicular to the tube axis direction. The heat pipe according to claim 5 or 6, wherein the hydraulic fluid is water.

Images