US20060243426A1

US20060243426A1 - Wick Structure of Heat Pipe

Info

Publication number: US20060243426A1
Application number: US11/459,435
Authority: US
Inventors: Hul-Chun Hsu
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-04-21
Filing date: 2006-07-24
Publication date: 2006-11-02

Abstract

A wick structure of a heat pipe, having a wick structure attached to an internal wall of a tubular member. The tubular member is fabricated from metal material with good conductive characteristics, and the wick member is formed of a metal mesh and a metal powder. The metal mesh is in the form of a ring attached to an internal wall of the tubular member, and the metal powder is embedded in the interstices of the metal mesh. The wick structure is attached to the internal wall of the tubular member by sintering, such that a wick structure with a villiform structure is formed. Thereby, the peeling or fracture tendency of the wick structure during the mechanical process of the heat pipe avoided. In addition, the axial rod used for the sintering process is not required, such that the cost is greatly reduced.

Description

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent application Ser. No. 10/828,275, filed on Apr. 21, 2004.

BACKGROUND OF THE INVENTION

The present invention relates in general to a wick structure of a heat pipe, and more particularly, to a heat pipe wick structure for dissipation of electronic devices.
FIGS. 1 and 2 illustrate a conventional wick structure of a heat pipe. FIG. 1 shows a mesh-type heat pipe having a tubular member 10 a and a screen mesh 20 a, and FIG. 2 shows a heat pipe including a sintered heat pipe having the tubular member 10 a and a sintered material 30a. The wick structure formed of the mesh 20 a or the sintered material 30 a serves as a medium for liquid flow induction. The mesh-type heat pipe winds the screen mesh 20 a around an axial rod to be inserted into the tubular member 10 a. When screen mesh 20 a is attached to the internal wall of the tubular member 10 a by the insertion of the axial rod, the axial rod is removed from the tubular member 10 a to form the mesh-type heat pipe. The sinter-type heat pipe uses an axial rod 31 a inserted into the tubular member 10 a. Powder-like sintered material 30 a is then poured into the tubular member 10 a. The tubular member 10 a is cooled down after sintering process, and the axial rod 31 a is removed from the tubular member 10 a to form the sinter-type heat pipe. In application, the heat pipes are configured according to specific structures of heat dissipation devices or heat sources. For example, the heat pipes may be configured with an L shape or a U shape, or configured into a flat tube or a tube having higher section and lower section, such that the heat pipes can be properly connected to the heat dissipation fins or heat source.
However, the above heat pipe wick structure suffers from the following disadvantages during fabrication or mechanical processes.
Firstly, the tubular member 10 a and the screen mesh 20 a are fabricated from different types of materials. When the heat pipe is forced to bend, the corners of the screen mesh 20 a are stretched to reduce the structure density thereof. The screen mesh 20 a may also peel from the internal wall of the tubular member 10 a during the bending process. Thereby, the capillary force of the screen mesh 20 a is reduced.
Secondly, the bending step frequently causes fracture of the sintered material 30 a . In addition, as the axial rod 31 a has to be inserted into and removed from one end of the tubular member 10 a, the insertion and removal of the axial rod 31 a inevitably removes a portion of the sintered material 30 a. Further, as the removal step is performed after the tubular member 10 is softened by an annealing process, the tubular member 10 a is easily deformed by the removal process.
Thirdly, it is not easy to position the axial rod 31 a at the axis of the tubular member 10 a during thermal fusion or condensation, such that uneven thickness of the wick structure is resulted.
Fourthly, when a heat pipe with a large gauge is fabricated, the volume and mass of the axial rod 31 a are consequently increased. Therefore, longer time is consumed for heating and cooling to cause more variations of the wick structure.
To resolve the problems caused by the conventional heat pipe as described above, with many years of experience in this field, a wick structure of a heat pipe has been developed as described as follows.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a wick structure of a heat pipe. A composite structure is formed to prevent the wick structure from being peeling or fractured during mechanical process performed on the heat pipe. Thereby, the heat absorption and conduction capability of the heat pipe is enhanced. Further, the axial rod used in sintering is not required any more. Therefore, the fabrication process is simplified, and the cost is reduced.
The wick structure provided by the present invention includes a wick structure attached to an internal wall of a tubular member. The tubular member is preferably fabricated from metal material with good conducting performance, and the wick structure includes a metal mesh and a metal powder. The metal mesh is in the form of an elongate circular ring attached to the internal wall of the tubular member, and particles of the metal powder are embedded in the interstices of the metal mesh. The wick structure is attached to the internal wall by sintering, such that a dense wick structure is formed.
These and other objectives of the present invention will become obvious to those of ordinary skill in the art after reading the following detailed description of preferred embodiments.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

These as well as other features of the present invention will become more apparent upon reference to the drawings therein:
FIG. 1 shows a conventional heat pipe;
FIG. 2 shows another type of conventional heat pipe;
FIG. 3 shows a cross sectional view of a heat pipe in one embodiment of the present invention;
FIG. 4 shows a local enlargement of FIG. 3;
FIG. 5 shows another cross sectional view of a heat pipe in one embodiment of the present invention; and
FIG. 6 shows a cross sectional view of a heat pipe in another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.
Referring now to the drawings wherein the showings are for purpose of illustrating preferred embodiments of the present invention only, and not for purposes of limiting the same, FIG. 3 to FIG. 5 show a heat pipe in one embodiment of the present invention. As shown, the heat pipe includes a tubular member 10 and a wick structure 20.
The tubular member 10 is preferably fabricated from material such as copper that has good conducting characteristics. The tubular member 10 may be formed with various geometric cross sections. In this embodiment, the tubular member 10 has a circular cross section. The tubular member 10 has an open end 11, a close end 12, and an internal wall 13.
The wick structure 20 installed inside the tubular member 10 includes a metal mesh 21 and a metal powder 22. Both the metal mesh 21 and the metal powder 22 have a fusion (melting) point lower than that of the tubular member 10 to advantage the sintering process performed on the wick structure 20. The metal mesh 21 includes a plurality of longitudinal and traversal woven fibers, which is wound as a hollow cylinder to be put into the tubular member 10. An interstice 211 is formed between every two adjacent longitudinal and traversal woven fibers. The perimeter of the woven mesh 21 is slightly larger than an internal perimeter of the tubular member 10, such that the metal woven mesh 21 can be firmly attached to the internal wall 13 of the tubular member 10. Moreover, one end (front end) of the metal mesh 21 extends towards a bottom surface of the close end 12 of the tubular member 10 to improve the thermal conduction of the tubular member 10. The metal powder 22 includes particles with dimensions substantially smaller than the interstices 211 of the metal mesh 21, such that the metal powder 22 can penetrate and embed in the interstices 211 of the metal mesh 21. The fusion point of the metal powder 22 is lower than that of the metal mesh 21, such that the metal powder 22 dispersing over the metal mesh 21 can combine the metal mesh 21 integrally attached to the tubular member 10 during a sintering process.
To attach the wick structure 20, the metal mesh 21 is received in the tubular member 10 from the open end 12 thereof. The metal powder 22 is then poured into the tubular member 10. The tubular member 10 is then rotated to evenly distribute the metal powder 22 in the metal mesh 21. That is, some particles of the metal powder 22 penetrate the interstices 211 to contact the internal wall 13 of the tubular member 10, some embed in the metal mesh 21 and the others spread on metal mesh surface, as shown in FIG. 4 and 5. Therefore, when the sintering process is performed, some particles of the metal powder 22 are dispersed over the metal mesh 21 and the others are used to attach with metal mesh 21 to the internal wall 13 of the tubular member 10.
FIG. 6 shows a cross sectional view of a heat pipe in another embodiment of the present invention. In this embodiment, a support member 14 is disposed in the tubular member 10 after the wick structure 20 is formed in the tubular member 10. The support member 14 has a fusion point higher than that of the metal mesh 21 and the metal powder 22. The support member 14 can be in the form of a linear or plate spiral structure or an elastic plate curled as a roll. By the elastic force exerted from itself, the metal mesh 21 and the metal powder 22 are pressed against the internal wall 13 of the tubular member 10. Therefore, the metal mesh 21 will not shrink or curl during sintering process, and the wick structure 20 can be firmly attached to the internal wall 13.
Accordingly, the present invention has at least the following advantages:
The composite wick structure prevents the wick structure from peeling or being fractured during sintering or mechanical process.
The metal mesh and the metal powder are attached to the tubular member by sintering, such that the wick structure can be fabricated from composite materials. Therefore, there are more choices and less limitation in design and fabrication.
During the fabrication process, the axial rod used for the conventional heat pipe is not required. Therefore, the cost is reduced, and the quality is improved. In addition, the uneven thickness of the wick structure is avoided.
This disclosure provides exemplary embodiments of wick structure of a heat pipe. The scope of this disclosure is not limited by these exemplary embodiments. Numerous variations, whether explicitly provided for by the specification or implied by the specification, such as variations in shape, structure, dimension, type of material or manufacturing process may be implemented by one of skill in the art in view of this disclosure.

Claims

1. A heat pipe comprising:

a tubular member made of metal material; and

a wick structure installed inside the tubular member, comprising a metal mesh in form of a wound hollow cylinder to be attached to an internal wall of the tubular member and a metal powder dispersing over the metal mesh and the internal wall, such that some particles of the metal powder embedded in interstices of the metal mesh and spread on surface of the metal mesh and other particles of the metal powder penetrated the metal mesh through the interstices to combine the metal mesh integrally attached to the tubular member during a sintering process.

2. The heat pipe of claim 1, wherein the tubular member includes an open end and a close end, and the metal mesh extends towards an internal bottom surface of the close end.

3. The heat pipe of claim 1, wherein the tubular member has a fusion point higher than those of the metal mesh and the metal powder.

4. The heat pipe of claim 1, wherein the metal mesh has a perimeter slightly larger than an internal perimeter of tubular member.

5. The heat pipe of claim 1, wherein the metal powder has a fusion point lower than that of the metal mesh.

6. The heat pipe of claim 1, wherein the particles of the metal powder have a dimension substantially smaller than that of the interstices.

7. The heat pipe of claim 1, wherein the particles include a plurality of fine broken fibers.

8. The heat pipe of claim 1, further comprising a support member disposed in the tubular member to press the wick structure against the internal wall of the tubular member.

9. The heat pipe of claim 8, wherein the support member has a fusion point higher than those of the metal mesh and the metal powder.

10. The heat pipe of claim 8, wherein the support member includes a plate spiral structure.

11. The heat pipe of claim 8, wherein the support member includes a linear spiral structure.