JP2002081875A - Flat heat pipe and its machining method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flat heat pipe, and its machining method, in which deformation or positional shift of a wick can be minimized even when the heat pipe is deformed. SOLUTION: In the flat heat pipe provided with a groove wick on the inner wall of a container having flat cross-section, at least one auxiliary linear wick extending in the axial direction is provided on each inner inside of the flat cross-section in the lateral direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for preventing performance deterioration due to thinning of a flat heat pipe, and a processing method excellent in deformation processing such as bending.

[0002]

2. Description of the Related Art Heat pipes are used to cool main components of portable electronic devices such as notebook personal computers.
In recent years, despite the increase in power consumption by increasing the drive frequency for improving the performance of the electronic device,
The demand for thinner and lighter is remarkable, and to fulfill this demand,
The heat pipe has been required to be thinner and more versatile than ever before without reducing the heat transport amount.

[0003]

However, in the conventional general-purpose heat pipe, mainly, the entire inner wall of the main body has a groove / groove.
Because of the wick or mesh wick, it has been difficult to obtain a flattened heat pipe having a thickness of 1.5 mm or less and having a heat transfer rate of 10 W or more, which is required in recent years.

[0004] The reason is that in order to maintain a heat transfer amount of 10 W or more, the groove wick groove depth and the mesh wick thickness are usually required to be about 0.15 mm, and the container thickness is required to be about 0.3 mm. Then, the height of the steam passage is about 0.6 mm, so the working steam flow of the heat pipe
This is because the limit at which the refluxing hydraulic fluid is scattered comes earlier.

[0005] The above-mentioned scattering limit problem is inevitably caused by a groove wick having an inverted trapezoidal cross section. On the other hand, in the mesh wick, the wick is easily loosened due to flattening, and a problem arises in that the steam wick is deformed due to buckling of the wick due to bending, thereby blocking the steam passage.

The basic structure of a heat pipe that solves the problems of these conventional general-purpose heat pipes has already been disclosed by the applicant in Japanese Patent No. 3045491 and Japanese Patent Publication No. 2000-039276.
By arranging the wick in the flat heat pipe in the vicinity of the center in the width direction in the container cavity, the present invention invents and provides a method capable of maintaining a practical heat transfer amount and enabling a heat pipe having a thickness of less than 1 mm.

[0007] The heat pipe proposed above was mainly intended to perform flattening of a container before the heat pipe was completed. However, the present invention has been further developed and the heat pipe of the above-mentioned application has been developed. After completing the heat pipe with the wick arrangement according to the excellent structure straight as it is, it can be bent or bent and flattened,
The heat pipe structure greatly contributes to cost reduction.

A general heat pipe structure has a container having good heat conductivity, such as copper or aluminum, and a wick such as a mesh on the inner wall of the container. The operation fluid is injected into the container several tens% of its volume. When heat is applied to one end of the heat pipe, the hydraulic fluid in that portion absorbs heat and evaporates, and the vapor is vaporized at the other end. Where the vapor dissipates heat and condenses into a liquid. The liquid will cycle through the wick and return to the heated section.

Here, when the amount of heat applied is large, the working liquid evaporates too much, and a large amount of heat can be transferred to the condensation part. As the number increases, the heat transport amount of the heat pipe increases.

However, when the heat pipe is deformed,
The wick in the container causes buckling or misalignment, so that a sufficient steam passage cannot be secured, and at the same time, the working fluid easily accumulates in the deformed portion of the wick, so that reflux to the heating unit is prevented.

[0011] Therefore, the shape of the wick of the heat pipe becomes insufficient even after the heat pipe is bent or flattened to arbitrarily route the inside of various electronic devices. However, there is a problem that the heat transport effect cannot be obtained.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a flat heat pipe capable of minimizing the deformation and displacement of a wick even when the heat pipe is deformed, and a method of processing the same.

[0013]

Means for Solving the Problems To solve the above problems, the present invention uses the following means. That is,
The heat pipe according to claim 1, wherein the inner wall of the container has a groove wick, and the cross section of the container is a flat heat pipe. Is a flat heat pipe in which at least one is disposed.

According to a second aspect of the present invention, the groove wick has a groove depth of 0.12 mm to 0.17 mm, and the groove has an average width of 0.1 m.
m to 0.2 mm, the auxiliary wick has a wire diameter of 0.1 mm to 0.6 mm
It is the flat heat pipe of claim 1.

According to a third aspect of the present invention, at least two linear auxiliary wicks are fixed at substantially opposite positions inside a tubular container having a groove wick on the inner wall,
A heat pipe is completed by filling an appropriate amount of the working fluid, and then deforming processing such as bending is performed as necessary, so that the flat heat pipe is crushed so that the auxiliary wicks are positioned on both sides of the flat cross section.

According to a fourth aspect of the present invention, there is provided the flat heat pipe processing method according to the third aspect, wherein the linear wick is bitten into the groove wick by press working and fixed.

[0017]

The heat pipe has a groove wick on the inner wall of the container and a flat cross section of the container. At least two linear auxiliary wicks extending in the axial direction are provided on both inner sides in the width direction of the flat cross section. By using a single flat heat pipe, the return of the working fluid in the center of the container, which is the main steam passage, is diverted to both sides by the auxiliary wick, greatly improving the scattering limit.

The groove wick has a groove depth of 0.12.
2. An auxiliary wick having a wire diameter of 0.1 mm to 0.6 mm, an average width of the groove is 0.1 mm to 0.2 mm, and an auxiliary wick having a wire diameter of 0.1 mm to 0.6 mm.
In the experiment conducted by the applicant, excellent characteristics were obtained when the flat heat pipe was used.

The above processing can be facilitated by fixing the linear wick by pressing it into the groove wick.

[0020]

FIG. 1 is a sectional view of a flat heat pipe 100 according to an embodiment of the present invention. In FIG. 1, a flat heat pipe 100 has a groove depth of 0.15 mm and a width of 0.14 mm on the inner wall of a flat container 1 made of copper having a width of about 7 mm and a thickness of about 1.5 mm.
The groove wick 2 is composed of about 50 grooves at a uniform pitch, and the auxiliary wick 3 made of a copper wire having an outer diameter of 0.4 mm extending in the axial direction is provided on both inner sides in the flat width direction. .

The inside of the flat heat pipe 100 is
Although not shown, water, which is a working liquid enough to completely fill the groove wick 2 under reduced pressure, is sealed. Therefore, when the total thickness including the groove height of the container 1 is 0.45 mm, the space height serving as the steam passage is 0.6 mm.

Next, the operation of the flat heat pipe 100 will be described in detail. When the entire flat heat pipe 100 is placed so that the flat surface is horizontal and there is no significant temperature difference between the parts, the hydraulic fluid fills the entire lower groove wick 2 and is still substantially evenly distributed in the axial direction. However, since there is a linear wick serving as the auxiliary wick 3 at the end in the width direction, the hydraulic fluid that originally fills the groove wick in the upper flat portion is relatively large in the vicinity of the linear wick 3. Are gathering.

From this static state, the flat heat pipe 1
When one of the axial directions of 00 is heated, the amount of hydraulic fluid near the flat central portion of the heated portion is small, so evaporation starts immediately and the other of the unheated low-temperature portion in the axial direction as well as in the width direction. At the same time, it cools and condenses to return to a liquid.

In response to the increase in the evaporation pressure due to the heating, the capillary pressure is increased, and the condensed liquid is returned to the heated portion, thereby forming one of the heating section and the other of the condensing section. As long as there is a temperature difference, heat transfer takes place actively.

When the heating heat amount is sequentially increased as described above, if only the groove wick 2 is used, the working fluid near the center of the flat portion of the heating portion becomes dry out due to a shortage of the reflux working fluid corresponding to the evaporation amount. However, since the reflux of the hydraulic fluid near the linear wick 3 is sufficient, the level of the hydraulic fluid in the width direction has a pan-bottom distribution.

Also, the distribution of the working fluid in the width direction until it reaches the unheated condensing portion in the axial direction has a pot-bottomed distribution almost similarly to the above-mentioned heating portion. The reason is that the groove wick 2 and the linear wick 3 are configured to be substantially parallel to the axial direction, and the balance in the width direction of the steam pressure and the capillary pressure of the heating unit does not change to an appropriate length in the axial direction. It is thought that it is.

As a result, even if the steam pressure in the vicinity of the flat central portion, which is the main steam passage, increases, the amount of the working fluid in the vicinity of the flat portion is small. Is very narrow at 0.6 mm, but the heat transport amount when there is no linear wick 3 is about 3 W to 1
It is greatly improved to about 0W.

The wire diameter and the number of the linear wicks 3 are not particularly limited. However, the thicker and larger the wicks, the larger the wick amount. Groove wick 2 is a heat pipe that has a large thermal resistance due to poor start-up characteristics that require a large amount of heat and a cause of turbid flow in the axial direction.
Groove depth of 0.12 mm to 0.17, average groove width of 0.1 mm to 0.2 mm,
On the other hand, it was confirmed that excellent characteristics were exhibited when the linear wick had a wire diameter of 0.1 mm to 0.6 mm. The wire diameter of the linear wick 3 is best bundled with several thin wires, and the thick wire is best with a single wire.

Next, a processing method for arranging the linear auxiliary wicks 3 on both inner sides of the flat heat pipe 100 will be described. As a general-purpose processing method, after the container 1 having the groove wick 2 is flattened as shown in FIG. 1, the linear auxiliary wick 3 is processed into a deformed closed loop shape shown in FIG. When the flat heat pipe 100 is completed, the flat heat pipe 100 is completed. However, it is troublesome to put containers having various shapes other than the round shape into the heat pipe manufacturing process.
The problem of displacement of the linear wick 3 due to bending after completion cannot be avoided.

Therefore, the processing method of the present invention relates to a method of processing a heat pipe having a linear auxiliary wick 3 that can withstand bending and flattening after completion of the heat pipe. FIG. 1 shows a method of fixing a linear auxiliary wick 3.

In FIG. 2, the inside of a container 1 having a groove wick 2 having an outer diameter of 5 mm has a groove 1 having an elliptical cross section.
The linear wick 3 is inserted by holding the core 10 with the linear wick 3 shown in FIG. 5 up and down, and pressed by pressing the press jigs 20 and 21 at a position opposed to the groove 11. 3 is fixed by biting into the groove 4 of the groove wick 2 as shown in FIG.

Thereafter, when the core 10 is removed from the container 1, the container 1 having a slightly elliptical cross section in FIG. 4 is obtained. Needless to say, the dimensional difference between the outer shape of the core 10 and the inner diameter of the container is not so large that a cross section with less deformation can be obtained. The heat pipe 200 is completed.

The completed heat pipe 200 having a substantially circular cross section shown in FIG. 6 is arbitrarily bent in accordance with a customer's request. However, the fixing position of the linear wick 3 is in the direction in which a press mark remains. Processing can be performed without mistake in the direction of flattening, and the linear wick 3 can be bent while being fixed to the container 1.

Next, the bent heat pipe 200 shown in FIG. 6 is pressed into the flat cross section shown in FIG.
0 is completed. If the flatness of the flattening process is large, as shown in FIG. 8, the groove 4 of the groove wick 2 on the flat side surface that bites the linear wick 3 is made narrower than usual by the flattening process. The wick 3 falls out of the biting groove 4, but the linear wick 3 does not largely move from the vicinity of the side surface because the shape before the insertion of the linear wick 3 is a closed loop shape as shown in FIG.

The setting for dropping the linear wick 3 is as follows.
It is preferable that the entire circumference works effectively as a wick function.
Whether or not the metal wick falls off can be selected based on the relationship between the groove width of the groove wick 2 and the wire diameter of the linear wick 3 and the flattening ratio. As another fixing method, there is a method of partially welding.

[0036]

As described in detail above, according to the present invention, in order to realize the demand for thin and light weight while securing the heat transport ability, various bent bent thin heat pipes and groove wicks are used. By additionally arranging the linear wick 3 at a specific location in a general-purpose container having the same, it is possible to provide the heat pipe in an inexpensive and easy manner without changing the conventional heat pipe processing method.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a flat heat pipe according to an embodiment of the present invention.

FIG. 2 shows a method for processing a heat pipe of the present invention.

FIG. 3 is a partially enlarged view of a groove and an auxiliary wick during a container press.

FIG. 4 shows the state of the container after the stroke of FIG. 2;

FIG. 5 shows a side view of the auxiliary wick.

FIG. 6 shows an initial completed drawing of the heat pipe of the present invention.

FIG. 7 shows a completed drawing of the heat pipe of the present invention.

FIG. 8 shows a partially enlarged view of the groove wick of the present invention.

[Explanation of symbols]

 In the drawings, the same reference numerals indicate the same or corresponding parts. DESCRIPTION OF SYMBOLS 1 Container 2 Groove wick 3 Auxiliary wick 4 Groove 10 Core 11 Groove 20, 21 Press jig 100, 200 Flat heat pipe

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[Procedure amendment]

[Submission date] October 11, 2000 (2000.10.
11)

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Fig. 7

[Correction method] Change

[Correction contents]

FIG. 7

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) H01L 23/427 H05K 7/20 R H05K 7/20 H01L 23/46 B

Claims (4)

[Claims] 1. A heat pipe having a groove wick on an inner wall of a container and having a flat cross section of the container, and a linear auxiliary wick extending in the axial direction is provided on both inner sides in the width direction of the flat cross section. At least one flat heat pipe. 2. The groove wick has a groove depth of 0.12 mm or less.
2. The flat heat pipe according to claim 1, wherein the diameter of the groove is 0.17 mm, the average width of the groove is 0.1 mm to 0.2 mm, and the auxiliary wick has a wire diameter of 0.1 mm to 0.6 mm. 3. A heat pipe is completed by fixing at least two linear auxiliary wicks at substantially opposite positions inside a tubular container having a groove wick on the inner wall, and then filling an appropriate amount of hydraulic fluid. A method of processing a flat heat pipe which is deformed by bending or the like as necessary and crushed so that the auxiliary wick is positioned on both sides of the flat cross section. 4. The method for processing a flat heat pipe according to claim 3, wherein the linear wick is fixed to the groove wick by being bitten by press working.