Abstract:
A heat dissipation device includes a fin unit ( 50 ), and at least a heat pipe ( 30 ) including an evaporating section (32) and at least a condensing section ( 34 ) extending through the fin unit. The fin unit includes a plurality of fins stacked together. Each fin comprises a wavy and a V-shaped section ( 52,53 ) and a planar section ( 54 ) therebetween. The wavy and V-shaped sections of the fins can guide an airflow flowing into the fin unit to smoothly flow therethrough, and prevent escape of the airflow from lateral directions of the fin unit. Furthermore, the wavy and V-shaped sections increase the heat dissipation area of the fins and strengthen the fins.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to a heat dissipation device, and particularly to a heat dissipation device for a heat generating electronic device.  
       DESCRIPTION OF RELATED ART  
       [0002]     As computer technology continues to advance, electronic components such as central processing units (CPUs) of computers are being made to provide faster operational speeds and greater functional capabilities. When a CPU operates at high speed in a computer enclosure, its temperature can increase greatly. It is desirable to dissipate the generated heat quickly; thus, a heat dissipation device is often attached on the CPU to efficiently remove the heat generated thereby.  
         [0003]      FIG. 6  shows a conventional heat dissipation device  1 . The heat dissipation device  1  comprises a fin unit  2 , a heat pipe  4  extending through the fin unit  2 , and a cooling fan (not shown) for generating an airflow. The fin unit  2  includes a plurality of fins stacked together. Each fin is planar and parallel to each other. A flow channel  3  is formed between two adjacent fins. Each fin defines two through holes therein. The heat pipe  4  is U-shaped. The heat pipe  4  includes an evaporating section for thermally connecting with the CPU and two condensing sections extending upwardly from two opposite ends of the evaporating section, respectively. The condensing sections extend in the through holes of the fins of the fin unit  2  and thermally connect with the fins. The cooling fan is arranged at a front side of the fin unit  2 , facing the flow channels  3  thereof.  
         [0004]     During operation of the heat dissipation device  1 , the working fluid of the heat pipe  4  absorbs the heat generated by the CPU and evaporates into vapor. The vapor moves from the evaporating section to the condensing sections to dissipate the heat to the fins of the fin unit  2 . The airflow generated by the cooling fan flows through the flow channels  3  to exchange heat with the fins. Then the heat is dissipated to surrounding environment by the airflow. Thus, heat dissipation of the heat generating device is accomplished.  
         [0005]     For enhancing the heat dissipation effectiveness of this heat dissipation device  1 , a heat dissipation area of the fin unit  2  needs to be increased. One way to increase the heat dissipation area of the fin unit is to reduce the spacing distance of the adjacent fins so that the fin unit can accommodate more fins. However, this way will increase the weight of the heat dissipation device, which is disadvantageous in view of lightweight requirement of electronic products. Another way is to increase the size of each fin. This way will increase both the weight and size of the heat dissipation device, which is disadvantageous in view of compact requirement of the electronic products. On the other hand, for the planar shape of the fins, a part of the airflow generated by the cooling fan escapes from the fin unit from lateral sides thereof before the airflow reaches a side of the fin unit opposite the cooling fan. This causes the airflow not able to have a sufficient heat exchange with the fins. Therefore, the airflow cannot be sufficiently utilized to dissipate heat absorbed by the fin unit from the heat-generating electronic device. Accordingly, heat dissipation effectiveness of the conventional heat dissipation device  1  is not totally satisfied. Finally, the planar configuration of the fins makes the fins too weak to withstand an impact force acting on the fins by the airflow. The airflow can cause the fins to vibrate and generate noise.  
         [0006]     What is needed, therefore, is a heat dissipation device having a high heat dissipation effectiveness by generating an airflow toward a fin unit without lose of the airflow before the airflow sufficiently contacts with fins of the fin unit, and without increasing the size and weigh of the fin unit.  
       SUMMARY OF INVENTION  
       [0007]     According to a preferred embodiment of the present invention, a heat dissipation device comprises a fin unit and at least a heat pipe. The heat pipe comprises an evaporating section and a condensing section extending through the fin unit. The fin unit comprises a plurality of fins stacked together. Each fin comprises two planar sections and a wavy section between the two planar sections. Two V-shaped sections extend laterally outwardly from the planar sections, respectively. By the wavy section and the V-shaped sections, the fins of the fin unit can have an increased heat dissipation area and enhanced strength. Furthermore, the wavy sections and the V-shaped sections of the fins can prevent an airflow through the fin units to escaped from the fin unit from lateral sides thereof. Thus, the fin unit can have a sufficient heat exchange with the airflow to thereby effectively dissipate the heat of the fin unit absorbed from a heat generating device to surrounding environment.  
         [0008]     Other advantages and novel features of the present invention will be drawn from the following detailed description of the preferred embodiment of the present invention with attached drawings, in which: 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0009]      FIG. 1  is an assembled, isometric view of a heat dissipation device in accordance with a preferred embodiment of the present invention;  
         [0010]      FIG. 2  is an exploded view of the heat dissipation device of  FIG. 1 ;  
         [0011]      FIG. 3  is an exploded, isometric view of a base of the heat dissipation device viewed from a bottom aspect;  
         [0012]      FIG. 4  is an isometric view of a fin unit, with two fins thereof being separated, of the heat dissipation device shown in  FIG. 1 ;  
         [0013]      FIG. 5  is an enlarged isometric view of one of the separate fins of the fin unit shown in  FIG. 4 ; and  
         [0014]      FIG. 6  is a cross-sectional view of a conventional heat dissipation device. 
     
    
     DETAILED DESCRIPTION  
       [0015]     Referring to  FIGS. 1-2 , a heat dissipation device according to a preferred embodiment of the present invention comprises a base  10 , a fin unit  50 , and three heat pipes  30  connecting the base  10  and the fin unit  50 .  
         [0016]     The base  10  is rectangle-shaped and comprises a bottom wall  12  and a cover  14  mounted on the bottom wall  12 . A space is defined between the bottom wall  12  and the cover  14 .  
         [0017]     Referring to  FIG. 3 , the bottom wall  12  is made of a flat metal plate (for example, a copper plate) and has a bottom surface  122  for thermally contacting with a heat generating device, such as a CPU (not shown). Four circular holes  120  are respectively defined in four corners of the bottom wall  12 . The cover  14  comprises four poles  140  extending downwardly from a bottom side thereof corresponding to the circular holes  120  of the bottom wall  12 . A concave  144  is defined in a lower portion of the cover  14 . A pair of openings  142  is defined through the cover  14  near two opposite lateral sides thereof, respectively. The two openings  142  communicate with the concave  144 . The concave  144  is located between the two openings  142 .  
         [0018]     Particularly referring to  FIGS. 1-2 , each heat pipe  30  is generally U-shaped and comprises an evaporating section  32  and two condensing sections  34  extending upwardly from two opposite ends of the evaporating section  32 , respectively. A working fluid (not shown) is received in the heat pipe  30  as a heat carrier when undergoing a phase transition between liquid state and vaporous state. A structure of the heat pipe  30  is well known by those skilled in the art; thus, a detailed explanation thereof is omitted herefrom.  
         [0019]     Referring to  FIGS. 4-5 , the fin unit  50  comprises a plurality of fins horizontally stacked together. A flow channel  70  is formed between two neighboring fins. Each fin comprises a middle wavy section  52 , two V-shaped sections  53  located beside two lateral sides of the wavy section  52 , respectively, two planar sections  54  each located between the wavy section  52  and a corresponding V-shaped section  53 , and two edge sections  55  each extending laterally outwardly from a corresponding V-shaped section  53 .  
         [0020]     The wavy section  52  is consisted of a plurality of continuous serrations. Each serration defines an included angel of about 60 degrees. The two planar sections  54  extend outwardly from two opposite sides of the wavy section  52 . Each planar section  54  defines three through holes  540  for extension of the condensing sections  34  of the heat pipes  30 , respectively. A flange  542  extends upwardly from an outer periphery of each of the through holes  540 .  
         [0021]     The V-shaped sections  53  extend outwardly from two opposite sides of the planar sections  54 , respectively. Each of the V-shaped section  53  defines an included angel of approximate 120 degrees.  
         [0022]     The two edge sections  55  are arranged at two opposite sides of each of the fins. Each edge section  55  comprises a pair of latches  56  bent downwardly from a lateral edge thereof and defines a pair latching notches  58  in the lateral edge located corresponding to the latches  56 , respectively. When stacked together, the fins are arranged horizontally parallel to each other. The flanges  542  of each fin abuts against a bottom face of the planar sections  54  of a neighboring upper fin, whereas the latches  56  of each fin fit in corresponding notches  58  defined in a neighboring lower fin. Thus the fins stacked together and space a distance with each other to define the flow channels  70  therebetween.  
         [0023]     The wavy and V-shaped sections  52 ,  53  of the fins are made by stamping a flat metal sheet. The wavy and V-shaped sections  52 ,  53  have a thickness which is smaller than that of the planar sections and edge sections  54 ,  55 . Thus, the weight of the fins does not increase, while the heat dissipation area of the fins increases and each fin can have a stronger structure to withstand vibration caused by a forced airflow through the fins. Thus, noise due to vibration of the fins can be lowered.  
         [0024]     When assembly, the heat pipes  30  are mounted to the cover  14  by extending the condensing sections  34  of the heat pipes  30  through the openings  142  of the cover  14  from a bottom thereof. Then, each pole  140  of the cover  14  enters into and is fixed in a corresponding circular hole  120  of the bottom wall  12  by soldering. Thus the cover  14  and the bottom wall  12  together define the space for receiving the evaporating sections  32  of the heat pipes  30 . Alternatively, the poles  140  can be fixed in the circular holes  120  by other mechanical connection method; for example, the poles  140  are interferingly engaged in the circular holes  120 .  
         [0025]     The evaporating sections  32  of the heat pipes  30  are received in the space of the base  10  and thermally contact with an upper surface of the bottom wall  12 . Each condensing section  34  of the heat pipe  30  extends through a corresponding opening  142  of the cover  14  and into a corresponding through hole  540  of the fin unit  50 . The evaporating sections  32  are soldered to the base  10  and the condensing sections  34  are soldered to the flanges  542 . Thus the heat dissipation device is assembled together. A cooling fan (not shown) is arranged at a front side of the fin unit  50 , facing the flow channels  70  of the fin unit  50 . Therefore, when the cooling fan is operated, a forced airflow can flow through the flow channels  70 .  
         [0026]     During operation of the heat dissipation device, the working fluid of the heat pipes  30  absorbs the heat generated by the heat generating device and evaporates into vapor. The vapor moves from the evaporating sections  32  to the condensing sections  34  to dissipate the heat to the fin unit  50 . The airflow generated by the cooling fan flows through the flow channels  70  of the fin unit  50  and exchanges heat with the fins. Thus the heat is dissipated to surrounding environment. The vapor cools and condenses at the condensing sections  34  and then returns to the evaporating sections  32 . Thus, heat dissipation of the heat generating device is accomplished.  
         [0027]     In the present invention, when the airflow flows through the fin unit  50 , the wavy and V-shaped sections  52 ,  53  of the fin unit  50  can guide the airflow to more smoothly flow through the flow channels  70  of the fin unit  50  from the front side to a rear side thereof. The loss or escape of the airflow from the lateral edges of the fin unit  50  is significantly reduced. Thus the airflow can be sufficiently utilized to exchange heat with the fins. One the other hand, the area of these wavy and V-shaped sections  52 ,  53  of the fins is larger than that of the planar fins of the prior art. Thus the heat dissipation area of the heat dissipation device of the present invention is increased. Therefore, the heat dissipation effectiveness of the heat dissipation device of the present invention is improved.  
         [0028]     It is understood that the invention may be embodied in other forms without departing from the spirit thereof. Thus, the present example and embodiment are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein.