Patent Publication Number: US-2011048682-A1

Title: Heat dissipation device

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.