US20110048682A1

US20110048682A1 - Heat dissipation device

Info

Publication number: US20110048682A1
Application number: US12/620,571
Authority: US
Inventors: Fang-Xiang Yu; Jer-Haur Kuo
Original assignee: Fuzhun Precision Industry Shenzhen Co Ltd; Foxconn Technology Co Ltd
Current assignee: Fuzhun Precision Industry Shenzhen Co Ltd; Foxconn Technology Co Ltd
Priority date: 2009-08-31
Filing date: 2009-11-17
Publication date: 2011-03-03
Also published as: CN102003903A; CN102003903B

Abstract

A heat dissipation device includes a heat pipe and a heat sink. The heat sink defines a through hole with a diameter slightly smaller then an outer diameter of the heat pipe. The heat pipe is fixedly engaging in the through hole of the heat sink via interference fit. The heat pipe includes a tube defining an interspace therein, a first wick formed on an inner surface of the tube, working fluid received in the interspace of the tube, and a retaining structure. The retaining structure is received in the interspace of the tube and abuts the first wick of the tube to enhance a rigidity of the tube. A second wick is formed on an outer surface of the retaining structure and connects with the first wick of the tube.

Description

BACKGROUND

1. Technical Field
The disclosure generally relates to heat dissipation devices, and more particularly to a heat dissipation device incorporating an improved heat pipe.
2. Description of Related Art
With the continuing development of electronics technology, electronic components such as central processing units (CPUs) used in computers are generating more and more heat which is required to be dissipated immediately. A heat dissipation device is usually adopted for cooling the electronic component.
Typically, a heat dissipation device includes a heat pipe and a fin-type heat sink. The heat pipe includes a sealed tube, a wick structure attaching to an inner surface of the tube, and working fluid received in the tube. One end of the heat pipe forms an evaporation end and attaches to an electronic component to absorb heat therefrom, and an opposite end of the heat pipe forms a condensation end and extends through the heat sink to transfer the heat of the electronic component to the heat sink for further dissipation. Usually, the condensation end of the heat pipe is inserted into the heat sink by way of interference fit, therefore the condensing end of the heat pipe can be maintained in intimate contact with the heat sink. Thus the heat of the electronic component can be timely transferred from the condensation end of the heat pipe to the heat sink.
However, in many cases, the tube of the heat pipe may deform during assembly of the heat pipe into the heat sink, and thus the wick structure attached on the tube may be damaged or destroyed. For example, narrow gaps are usually formed between the tube and the wick structure. It is well known that, in the heat pipe, the wick structure not only provides a capillary force for drawing condensed working fluid from the condensation end back to the evaporation end, but also provides a heat transfer path between the tube and the working fluid contained in the tube. Therefore, if the wick structure is damaged or destroyed, a heat transfer capability of the heat pipe may be greatly impaired. Accordingly, a heat dissipation efficiency of the heat dissipation device is reduced.
For the foregoing reasons, therefore, there is a need in the art for a heat dissipation device incorporating a heat pipe which can overcome the limitations described.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an assembled, isometric view of a heat dissipation device in accordance with a first embodiment.

FIG. 2 is an exploded view of a heat pipe of the heat dissipation device of FIG. 1.

FIG. 3 is an assembled view of the heat pipe of FIG. 2, but with two end caps thereof being omitted.

FIG. 4 is a schematic view of a wick structure of a heat pipe according to a second embodiment.

FIG. 5 shows a wick structure according to a third embodiment.

FIG. 6 shows a wick structure according to a fourth embodiment.

FIG. 7 shows a wick structure according to a fifth embodiment.

DETAILED DESCRIPTION

Referring to FIG. 1, a heat dissipation device according to a first embodiment includes a heat sink 10 and a heat pipe 20.
The heat sink 10 overall has a substantially rectangular configuration. The heat sink 10 includes a main body 12, and a plurality of dissipation fins 14 extending outwardly generally away from a middle of the heat sink 10. The main body 12 is a quadrangular prism, and defines an approximately rectangular top surface, an opposite rectangular bottom surface, and four rectangular side surfaces between the top surface and the bottom surface. A through hole 124 extends through the main body 12 along an axial direction of the main body 12 from the bottom surface to the top surface of the main body 12. The through hole 124 is substantially located at a center of the main body 12. A cross section of the through hole 124 is circular.
Four ribs 16 extend outwardly from four corners of the main body 12, respectively, i.e., from junctions of the four side surfaces of the main body 12. The dissipation fins 14 are formed at all four lateral sides of the main body 12. Each dissipation fin 14 is plate-shaped. The dissipation fins 14 at each lateral side of the main body 12 are located between two neighboring ribs 16, and have outer ends coplanar with outer ends of the two neighboring ribs 16. The dissipation fins 14 at left and right lateral sides of the main body 12 are parallel to each other, while perpendicular to the left and the right lateral sides of the heat sink 10. The dissipation fins 14 at front and rear lateral sides of the main body 12 are parallel to each other, while perpendicular to the front and rear lateral sides of the heat sink 10. Thus, the dissipation fins 14 at the left and right lateral sides of the main body 12 are perpendicular to the dissipation fins 14 at the front and rear lateral sides of the main body 12.
In this embodiment, the heat pipe 20 is a round-type heat pipe 20, and has an outer diameter slightly larger than a diameter of the through hole 124 of the main body 12 of the heat sink 10. Referring also to FIGS. 2 and 3, the heat pipe 20 includes a tube 26, a bottom cap 22, a top cap 24, working fluid (not shown), and a retaining structure 28. The tube 26, the bottom cap 22 and the top cap 24 cooperatively form a sealed interspace 268 in the heat pipe 20, the sealed interspace 268 receiving the working fluid and the retaining structure 28 therein.
The tube 26 is cylindrical. An outer diameter of the tube 26 is slightly larger than the diameter of the through hole 124 of the main body 12 of the heat sink 10. A first wick 260 is provided on an entire inner surface of the tube 26, in the form of a layer. The first wick 260 is for providing a capillary force to draw back condensed working fluid. Both of the bottom cap 22 and the top cap 24 are disk-shaped. A diameter of each of the bottom cap 22 and the top cap 24 is equal to the outer diameter of the tube 26. The bottom cap 22 and the top cap 24 respectively couple to a bottom end 262 and a top end 264 of the tube 26, thereby forming the interspace 268. The bottom cap 22 has a planar-shaped bottom surface 222 and an opposite top surface. A third wick 220 is provided on the top surface of the bottom cap 22, in the form of a layer. The top cap 24 has a top surface 240 and an opposite bottom surface. An annular protrusion 242 extends upwardly from a center of the top surface 240 of the top cap 24. An aperture (not shown) extends through the top cap 24 and communicates with the protrusion 242.
In this embodiment, the retaining structure 28 includes two plates 282, 284. The two plates 282, 284 are substantially the same as each other. Each of the plates 282, 284 is elongated, rectangular and thin. A width of each plate 282, 284 is substantially the same as an inner diameter of the tube 26, and a length of each plate 282, 284 is a little shorter than a length of the tube 26 in an axial direction of the tube 26. The two plates 282, 284 perpendicularly cross each other, and thus the retaining structure 28 has a profile like a cross. A second wick 280 is formed on an outer surface of each plate 282, 284, in the form of a layer. In this embodiment, the first wick 260 of the tube 26, the third wick 220 of the bottom cap 22, and the second wick 280 of the retaining structure 28 are sintered powder. Alternatively, the wicks 260, 220, 280 of the tube 26, the bottom cap 22, and the retaining structure 28 can be screen mesh or fine grooves. The wicks 260, 220, 280 of the tube 26, the bottom cap 22, and the retaining structure 28 can all be of the same type, or can be of different types.
When the heat dissipation device is assembled, the retaining structure 28 is arranged in the tube 26 with a bottom end thereof being at the same level as the bottom end 262 of the tube 26. Since the width of each plate 282, 284 of the retaining structure 28 is approximately the same as the inner diameter of the tube 26, each of the two plates 282, 284 abuts the first wick 260 of the tube 26 at opposite two lateral edges thereof. Accordingly, the second wick 280 on the retaining structure 28 is connected to the first wick 260 of the tube 26. The bottom cap 22 is coupled to the bottom end 262 of the tube 26 and is fixed onto the tube 26 by soldering. The third wick 220 on the bottom cap 22 is thus connected to the first wick 260 of the tube 26 and the second wick 280 of the retaining structure 28. Similarly, the top cap 24 is coupled and fixed onto the top end 264 of the tube 26 by soldering. Since the retaining structure 28 is shorter than the tube 26, the top cap 24 spaces a distance from a top end of the retaining structure 28.
Then working fluid is injected into the tube 26 via the protrusion 242 and the aperture of the top cap 24. Finally, air is evacuated from the tube 26, and the protrusion 242 is sealed to form the heat pipe 20. The sealed interspace 268 formed in the heat pipe 20 between the top cap 24, the bottom cap 22 and the tube 26 is separated into four channels 266 by the two plates 282, 284 of the retaining structure 28 received in the interspace 268. In this embodiment, the four channels 266 are the same as each other. Each of the channels 266 extends along the axial direction of the tube 26, and communicates the other channels 266 over the top end of the retaining structure 28.
When assembling the heat pipe 20 to the heat sink 10, the heat pipe 20 is vertically inserted into the through hole 124 of the heat sink 10 until the bottom surface of the bottom cap 22 of the heat pipe 20 is at the same level as the bottom surface of the heat sink 10. Since the heat pipe 20 has the retaining structure 28 arranged therein, a rigidity of the tube 26 of the heat pipe 20 is enhanced. That is, the tube 26 of the heat pipe 20 resists deformation during assembly even though the outer diameter of the heat pipe 20 is slightly larger than the diameter of the through hole 124 of the heat sink 10. Thus damage to or destruction of the first wick 260 of the tube 26 of the heat pipe 20 is avoided.
During operation of the heat dissipation device, the bottom surface of the bottom cap 22 of the heat pipe 20 attaches to an electronic component tightly to absorb heat therefrom, and thereby rapidly transfers the heat to the working fluid in the heat pipe 20. The working fluid vaporizes immediately and flows upwardly along the channels 266 to dissipate the heat to the heat sink 10. Since the first wick 260 on the tube 26 of the heat pipe 20 is intact and fully functional, the first wick 260 not only can provide a capillary force for drawing condensed working fluid back to a bottom of the heat pipe 20, but also can provide a heat transfer path between the tube 26 and the working fluid. In addition, the second wick 280 on the retaining structure 28 also can provide a capillary force for drawing back condensed working fluid. Therefore, the heat of the electronic component can be timely transferred to the heat sink 10 by the heat pipe 20.
FIG. 4 shows a retaining structure 28 a according to a second embodiment. In this embodiment, the retaining structure 28 a includes four plates, i.e., a first plate 284, a second plate 282, a third plate 286 and a fourth plate 288. A wick 280 in the form of a layer is provided on an outer surface of each of the four plates 282, 284, 286, 288. The first plate 284 and second plate 282 are the same as the two plates 282, 284 of the retaining structure 28 of the first embodiment. The third plate 286 and the fourth plate 288 are identical to each other. The third plate 286 and the fourth plate 288 are arranged at opposite sides of the first plate 284, and are equidistantly spaced from the first plate 284. Both the third plate 286 and the fourth plate 288 perpendicularly cross the second plate 282. Thus the first plate 284, the third plate 286 and the fourth plate 288 are parallel to each other, and all are perpendicular to the second plate 282.
A length of each of the third plate 286 and the fourth plate 288 is the same as that of the first plate 284 and the second plate 282, i.e., the four plates 282, 284, 286, 288 have the same length. A width of each of the third plate 286 and the fourth plate 288 is less than that of each of the first plate 284 and the second plate 282. Lateral edges of the first plate 284, the second plate 282, the third plate 286 and the fourth plate 288 are located on an imaginary cylinder, which has a diameter approximately the same as the inner diameter of the tube 26. Thus when the retaining structure 28 a is assembled into the tube 26 of the heat pipe 20, lateral edges of all of the four plates 282, 284, 286, 288 attach to the first wick 260 of the tube 26 to enhance the rigidity of the tube 26. The interspace 268 of the heat pipe 20 is thus separated into eight channels 266 a by the four plates 282, 284, 286, 288, for vaporized working fluid flowing upwardly in order to dissipate heat.
FIG. 5 shows a retaining structure 28 b according to a third embodiment. In this embodiment, the retaining structure 28 b includes a hollow core 281, and a plurality of supporting fins 282 b extending radially from an outer circumferential surface of the core 281. Similar to the previous embodiment, a wick 280 in the form of a layer is provided on an outer surface of each supporting fin 282 b, and on the outer circumferential surface of the core 281. In addition, an additional wick 285 is arranged inside the core 281, for providing an additional path for condensed working fluid to flow back to the bottom of the heat pipe 20. The core 281 has an outer diameter smaller than the inner diameter of the tube 26. The supporting fins 282 b are identical to each other, and are evenly angularly spaced from each other around the outer surface of the core 281. Each supporting fin 282 b is rectangular. Lateral edges of the supporting fins 282 b are located on an imaginary cylinder, which has a diameter substantially the same as the inner diameter of the tube 26. In this embodiment, there are eight supporting fins 282 b formed around the core 281. When the retaining structure 28 b is assembled into the tube 26, all of the eight supporting fins 282 b abut the tube 26, and eight channels 266 b are defined in the heat pipe 20 between neighboring supporting fins 282 b for moving of vaporized working fluid.
FIG. 6 shows a retaining structure 28 c according to a fourth embodiment. The retaining structure 28 c of this embodiment includes a core 281 c and a plurality of supporting fins 282 c. A wick 280 in the form of a layer is provided on an outer surface of each of the supporting fins 282 c, and on an outer circumferential surface of the core 281 c. The core 281 c is hollow, and is in the shape of a frustum of a circular cone. An outer diameter of the core 281 c gradually decreases from bottom to top; and an inner diameter of the core 281 c gradually decreases from bottom to top, corresponding to the outer diameter. Thus the core 281 c defines a passage 283 c therein, with a diameter of the passage 283 c gradually decreasing from bottom to top. A maximum outer diameter of the core 281 c at the bottom is substantially the same as the inner diameter of the tube 26.
The supporting fins 282 c are formed on the outer circumferential surface of the core 281 c, and are identical to each other. Each supporting fin 282 c is triangular. A with of the supporting fin 282 c as measured in a radial direction gradually decreases from top to bottom. A lateral edge of each supporting fin 282 c is vertical. When the retaining structure 28 c is assembled into the tube 26, the lateral edges of all of the supporting fins 282 c abut the tube 26 to enhance the rigidity of the tube 26. In addition, since the core 281 c at the bottom end has the outer diameter approximately equal to the inner diameter of the tube 26, the bottom end of the core 281 c can also abut the tube 26. The passage 283 c in the core 281 c acts as a convergent channel for moving of vaporized working fluid. Thus the vaporized working fluid flowing in the passage 283 c of the core 281 c and the condensed wording fluid flowing in the wick 280 on the retaining structure 28 c and in the first wick 260 on the tube 26 are isolated from each other by the core 281 c, and interaction between the vaporized working fluid and condensed wording fluid is avoided. Accordingly, a heat transfer capability of the heat pipe 20 with the retaining structure 28 c is enhanced.
FIG. 7 shows a retaining structure 28 d according to a fifth embodiment. The retaining structure 28 d of this embodiment includes a hollow core 281 d, and a plurality of supporting fins 282 d around the core 281 d. A wick 280 in the form of a layer is provided on an outer surface of each supporting fin 282 d, and on an outer circumferential surface of the core 281 d. In this embodiment, the core 281 d includes an upper portion 287 d and a lower portion 289 d. The lower portion 289 d of the core 281 d has an outer diameter gradually decreasing from bottom to top, while the upper portion 287 d of the core 281 d has a uniform outer diameter. A maximum outer diameter of the lower portion 289 d of the core 281 d is at the bottom of the core 281 d, and is substantially equal to the inner diameter of the tube 26. A minimum outer diameter of the lower portion 289 d of the core 281 d is at a top of the lower portion 289 d of the core 281 d, and is larger than the diameter of the upper portion 287 d of the core 281 d. A generally annular, horizontal step 285 d is formed at the top of the lower portion 289 d of the core 281 d. The step 285 d surrounds and adjoins an outer periphery of a bottom of the upper portion 287 d of the core 281 d.
The supporting fins 282 d are identical to each other. A lateral edge of each supporting fin 282 d is vertical. All of the lateral edges of the supporting fins 282 d are located on an imaginary cylinder, which has a diameter approximately the same as the inner diameter of the tube 26. Each supporting fin 282 d includes an upper section 29 extending radially and outwardly from the upper portion 287 d of the core 281 d, and a lower section 30 extending radially and outwardly from the lower portion 289 d of the core 281 d. The upper section 29 of each supporting fin 282 d is rectangular, while the lower section 30 of each supporting fin 282 d is triangular. When the retaining structure 28 d is assembled into the tube 26, lateral edges of the supporting fins 282 d abut the first wick 260 of the tube 26 to enhance the rigidity of the tube 26. The bottom end of the core 281 d abuts the tube 26, and the hollow core 281 d defines a channel 283 d therein for moving of vaporized working fluid.
It is to be understood, however, that even though numerous characteristics and advantages of various embodiments have been set forth in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

Claims

1. A heat dissipation device, comprising:

a heat sink defining a through hole therein; and

a heat pipe having an outer diameter slightly larger than a diameter of the through hole of the heat sink and being fixedly engaging in the through hole via interference fit, the heat pipe comprising a tube defining an interspace therein, a first wick formed on an inner surface of the tube, working fluid received in the interspace of the tube, and a retaining structure received in the interspace of the tube and abutting the first wick on the tube to enhance a rigidity of the tube, and a second wick being formed on an outer surface of the retaining structure.

2. The heat dissipation device of claim 1, wherein the heat sink comprises a main body and a plurality of dissipation fins, the main body being a quadrangular prism, the through hole being defined in a center of the main body, the plurality of dissipation fins extending generally away from a middle of the main body.

3. The heat dissipation device of claim 2, wherein four ribs respectively extend from four corners of the main body, the dissipation fins at each lateral side of the main body are perpendicular to that lateral side of the main body and are located between two corresponding neighboring ribs, and outer ends of the dissipation fins at each lateral side of the main body and outer ends of the two corresponding neighboring ribs are coplanar.

4. The heat dissipation device of claim 1, wherein the retaining structure comprises two plates perpendicularly crossing each other, lateral edges of each plate abutting the first wick, the interspace of the tube being separated into four axial channels by the retaining structure, and the second wick being formed on an outer surface of each plate.

5. The heat dissipation device of claim 1, wherein the retaining structure comprises four plates, one of the four plates perpendicularly crossing the other three plates, lateral edges of each plate abutting the first wick, the interspace of the tube thereby being separated into eight axial channels by the retaining structure, the second wick being formed on an outer surface of each plate.

6. The heat dissipation device of claim 1, wherein the retaining structure comprises a hollow core and a plurality of supporting fins extending from an outer circumferential surface of the core, lateral edges of each of the supporting fins abutting the first wick, the second wick being formed on an outer surface of each supporting fin and the outer circumferential surface of the core.

7. The heat dissipation device of claim 6, wherein the core has a uniform outer diameter smaller than an inner diameter of the tube, each supporting fin being rectangular, a third wick being arranged in the core for providing a path for condensed working fluid to flow back to a vaporizing region of the interspace, and a channel being defined between each two neighboring supporting fins for moving of vaporized working fluid.

8. The heat dissipation device of claim 6, wherein the core has an outer diameter gradually decreasing from bottom to top, a maximum outer diameter of the core being substantially equal to an inner diameter of the tube, each supporting fin being triangular, a channel being defined inside the core for moving of vaporized working fluid.

9. The heat dissipation device of claim 6, wherein the core comprises an upper portion and a lower portion, the lower portion having an outer diameter gradually decreasing from bottom to top, the upper portion having a uniform outer diameter being not larger than a minimum outer diameter of the lower portion, a maximum outer diameter of the lower portion being approximately the same as an inner diameter of the tube, a channel being defined in the core for moving of vaporized working fluid, each supporting fin comprising an upper section being rectangular and a lower section being triangular.

10. The heat dissipation device of claim 9, wherein the outer diameter of the upper portion of the core is smaller than the minimum diameter of the lower portion of the core, a generally annular step being formed at a top of the lower portion of the core, the step adjoining an outer periphery of a bottom of the upper portion of the core.

11. The heat dissipation device of claim 1, wherein the tube of the heat pipe is open at two opposite ends thereof, two caps being fixed onto the two opposite ends of the tube to seal the tube, the retaining structure having a length in an axial direction smaller than that of the tube, the retaining structure attaching to one of the two caps and spaced a distance from the other one of the two caps, a third wick being formed on the one of the two caps and connecting with the first wick and the second wick.

12. A heat pipe comprising:

a tube defining an interspace therein;

a first wick formed on an inner surface of the tube;

working fluid received in the interspace of the tube; and

a retaining structure received in the interspace of the tube and abutting the first wick of the tube to enhance a rigidity of the tube, and a second wick being formed on an outer surface of the retaining structure and connecting with the first wick of the tube.

13. The heat dissipation device of claim 12, wherein the retaining structure comprises two plates perpendicularly crossing each other, lateral edges of each plate abutting the first wick, the interspace of the tube being separated into four axial channels by the retaining structure, and the second wick being formed on an outer surface of each plate.

14. The heat dissipation device of claim 12, wherein the retaining structure comprises four plates, one of the four plates perpendicularly crossing the other three plates, lateral edges of each plate abutting the first wick, the interspace of the tube thereby being separated into eight axial channels by the retaining structure, the second wick being formed on an outer surface of each plate.

15. The heat dissipation device of claim 12, wherein the retaining structure comprises a hollow core and a plurality of supporting fins extending from an outer circumferential surface of the core, lateral edges of each of the supporting fins abutting the first wick, the second wick being formed on an outer surface of each supporting fin and the outer circumferential surface of the core.

16. The heat dissipation device of claim 15, wherein the core has a uniform outer diameter smaller than an inner diameter of the tube, each supporting fin being rectangular, a third wick being arranged in the core for providing a path for condensed working fluid to flow back to a vaporizing region of the interspace, and a channel being defined between each two neighboring supporting fins for moving of vaporized working fluid.

17. The heat dissipation device of claim 15, wherein the core has an outer diameter gradually decreasing from bottom to top, a maximum outer diameter of the core being substantially equal to an inner diameter of the tube, each supporting fin being triangular, a channel being defined inside the hollow core for moving of vaporized working fluid.

18. The heat dissipation device of claim 15, wherein the core comprises an upper portion and a lower portion, the lower portion having an outer diameter gradually decreasing from bottom to top, the upper portion having a uniform outer diameter being not larger than a minimum outer diameter of the lower portion, a maximum outer diameter of the lower portion being approximately the same as an inner diameter of the tube, a channel being defined in the core for moving of vaporized working fluid, each supporting fin comprising an upper section being rectangular and a lower section being triangular.

19. The heat dissipation device of claim 18, wherein the outer diameter of the upper portion of the core is smaller than the minimum diameter of the lower portion of the core, a generally annular step being formed at a top of the lower portion of the core, the step adjoining and an outer periphery of a bottom of the upper portion of the core.

20. The heat dissipation device of claim 12, wherein the tube of the heat pipe is open at two opposite end thereof, two caps being fixed onto the two opposite ends of the tube to seal the tube, the retaining structure having a length in an axial direction smaller than that of the tube, the retaining structure attaching to one of the two caps and spaced a distance from the other one of the two caps, a third wick being formed on the one of the two caps and connecting with the first wick and the second wick.