Patent Publication Number: US-2007119566-A1

Title: Heat dissipation device

Description:
FIELD OF THE INVENTION  
      The present invention relates generally to a heat dissipation device, and more particularly to a heat dissipation device used for dissipating heat generated by an electronic device.  
     DESCRIPTION OF RELATED ART  
      With advancement of computer technology, electronic devices operate rapidly. It is well known that the more rapidly the electronic devices operate, the more heat they generate. If the heat is not dissipated duly, the stability of the operation of the electronic devices will be impacted severely. Generally, in order to ensure the electronic device to run normally, a heat dissipation device is used to dissipate the heat generated by the electronic device.  
      Conventionally, a heat dissipation device comprises a heat sink which has a base and a plurality of fins arranged on the base. The fins each being a flat sheet are parallel to and spaced from each other. Therefore, pluralities of passages are defined between the fins for airflow passing therethrough. Usually, the heat dissipation device further comprises a fan located at a side of the heat sink for providing forced airflow to the heat sink. Generally, the fan has a central hub region which is confronted to a middle portion of fins of the heat sink, and a peripheral fan blade region which is confronted to side portions of the fins of the heat sink. When the fan works, the hub region produces a small quantity and low pressure of airflow to the middle portion of the fins, while the blade region produces a large quantity and high pressure of airflow to the side portions of the fins. Therefore, the middle portion of the fins has a very limited amount of airflow passing therethrough, while the side portions of the fins have an excessive amount of airflow passing therethrough. That is to say, the amounts of airflow distribute on the fins unevenly due to a configuration of the fan. Due to such uneven airflow distribution the middle portion of the fins always has too much heat accumulated therein, which can not dissipated away effectively. Accordingly, the heat dissipation capacity of the conventional heat dissipation device is not optimal. It is necessary to improve the heat dissipation capacity of the conventional heat dissipation device.  
      What is needed, therefore, is a heat dissipation device having improved heat dissipation capacity.  
     SUMMARY OF INVENTION  
      A heat dissipation device in accordance with a preferred embodiment of the present invention comprises a fin set comprising a plurality of fins assembled together and a fan located beside the fin set. Pluralities of passages are defined between the fins. The fan faces the passages. Each fin has two spaced flaps extending from a main body thereof and dividing the main body generally into upper, middle and lower portions. The two flaps have middle sections extending parallel to each other, and end sections extending away from each other whereby the end sections of the flaps located close to the fan form a converging inlet facing the fan, and the end sections of the flaps located distant from the fan form a diverging outlet opposing the fan. The inlets and outlets are used for guiding an airflow generated by the fan to flow through the middle portions of the fins. The fan confronts to the passages and the converging inlets of the middle portions of the fins of the fin set. By such design, a larger amount of airflow can be guided by the converging inlets to flow into the middle portions of the fins and by the diverging outlets to leave the middle portions of the fins.  
      Other advantages and novel features will become more apparent from the following detailed description of preferred embodiments when taken in conjunction with the accompanying drawings, in which: 
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       FIG. 1  is an exploded, isometric view of a heat dissipation device in accordance with a preferred embodiment of the present invention;  
       FIG. 2  shows a fin of the heat dissipation device of  FIG. 1 ; and  
       FIG. 3  is a assembled view of  FIG. 1 . 
    
    
     DETAILED DESCRIPTION  
      Referring to  FIG. 1 , a heat dissipation device in accordance with a preferred embodiment of the present invention comprises a heat sink having a base  10  and a fin set  30  on the base  10 , two heat pipes  50  connecting the base  10  and the fin set  30 , and a fan unit  70  mounted beside the fin set  30 .  
      The base  10  comprises a substantially rectangular heat receiver  100 , and four fixing legs  110  extending outwardly from four corners of the heat receiver  100 . The heat receiver  100  has a good heat conductivity. A top face of the heat receiver  100  defines therein two parallel grooves  101  each with a semicircular cross-section. A bottom face of the heat receiver  100  is flat for thermally contacting a heat generating electronic device (not shown) mounted on a printed circuit board (not shown). Each of the fixing legs  110  defines a fixing hole  111  in a distal end thereof for fixing the heat dissipation device to the printed circuit board.  
      Referring also to  FIG. 2 , the fin set  30  comprises a plurality fins  300  assembled together. Each fin  300  comprises a main body  310 , a first flange  320  perpendicularly extending from a top edge of the main body  310 , and a second flange  330  perpendicularly extending from a bottom edge of the main body  310 . The bottom edge of the main body  310  defines two semicircular cutouts  331  therein. The cutouts  331  are located corresponding to the grooves  101  of the heat receiver  100 . Two spaced flaps  311  are stamped from the main body  310  substantially along a direction parallel to the two flanges  320 ,  330 , whereby two slits  314  are defined in the main body  310  of the fin  300  adjacent to the flaps  311  respectively. The two flaps  311  divide the main body  310  into three portions: two side portions (i.e., upper and lower portions)  312  respectively between the flanges  320 ,  330  and the corresponding flaps  311 , and a middle portion  313  between the two flaps  311 . Each of the flaps  311  has a middle section (not labeled), a front end section (not labeled) and a rear end section (not labeled). The middle sections are parallel to each other. The front end sections extend from the middle sections in directions away from each other. The rear end sections extend from the middle sections in directions away from each other. The front end sections of the flaps  311  form a converging entrance  315  for the middle portion  313 . The rear end sections form a diverging exit  316  for the middle portion  313 . Two holes  317  are defined in the main body  310 , one of which is located between the two flaps  311 , and another of which is located above an upper one of the two flips  311 . In assembly, the flanges  320 ,  330  of each fin  300  abut the top and bottom edges of the main body  310  of an adjacent fin  300  respectively. The cutouts  331  of the fins  300  corporately define two slots  332  each with a semicircular cross-section. The holes  317  of the body  100  of the fins  300  corporately define two through channels  318  extending through the fin set  30  for receiving the heat pipes  50 . Pluralities of air passages (not labeled) are defined between the fins  300  and extend from front sides to rear sides thereof.  
      Each of the two heat pipes  50  is U-shaped, and comprises a first heat transfer section (i.e., evaporating section)  510 , a second heat transfer section (i.e., condensing section)  520  parallel to the first heat transfer section  510 , and a middle section connecting with the first and second heat transfer sections  510 ,  520  at ends thereof. A round corner is formed at each joint of the first, middle and second sections  510 ,  530 ,  520 .  
      The fan unit  70  comprises a fan  71  and a fan bracket  73  for fixing the fan  71  to the fin set  30 . The fan  71  comprises a hub  710  and a plurality of fan blades  720  radially extends from the hub  710 . The bracket  73  comprises four interconnecting walls (not labeled) having fixing members (not labeled) formed thereon.  
      Referring also to  FIG. 3 , in assembly, the fin set  30  is combined to the heat receiver  100  of the base  10  by conventional means such as soldering, adhering and so on. The second flanges  330  of the fins  100  thermally contact with the top face of the heat receiver  100 . The first heat transfer sections  510  of the two heat pipes  50  are thermally received in two passages (not labeled) corporately defined by the two grooves  101  of the heat receiver  100  and the two slots  332  of the fin set  30 . The second heat transfer sections  330  of the heat pipes  50  are respectively thermally received in the two through channels  318  of the fin set  30 . The fan unit  70  is attached to a front side of the fin set  30  via the fixing members of the bracket  73  engaged with the fin set  30  and the base  10 . The fan  71  faces the air passages between the fins  300  and the entrances  315  of the middle portions  313  of the fins  300  of the fin set  30 .  
      In use, the heat receiver  100  of the base  10  absorbs heat generated by the heat generating electronic device (not shown) with which the heat receiver  100  contacts. The heat in the heat receiver  100  is then transferred to a bottom portion of the fin set  30  and the first heat transfer sections  510  of the heat pipes  50 . The heat in the first heat transfer sections  510  of the heat pipes  50  is subsequently transferred to the second heat transfer sections  520  via the middle sections  530  of the heat pipes  50 , and then reaches the fins  300 . The heat in the fin set  30  is dissipated to ambient air duly under the action of an airflow generated by the fan  71 .  
      According to the preferred embodiment of the present invention, each of the fins  300  of the fin set  30  is divided to three portions by the two flaps  311 . The middle portion  313  has the converging entrance  315  confronted to the fan  71 ; therefore, a large portion of the airflow generated by the fan  71  is collected by the front end sections of the flaps  311  to enter the middle portions  314  of the fins  300  to remove heat in the middle portions  313 . Furthermore, due to the diverging exits  316 , the hot air in the middle portions  313  of the fins  300  can quickly leave the middle portions  313 . Therefore, in comparison with the conventional heat dissipation devices, the fins  300  of the present invention can distribute the airflow from the fan  71  on the fins  300  more evenly. The heat in the middle portions  313  of the fins  300  can be dissipated to the ambient air more duly and quickly. Thus, heat dissipation capacity of the heat dissipation device in accordance with the present invention is improved. The heat dissipation capacity of the heat dissipation device in accordance with the present invention is further improved by the provision of the slits  314 , which enable neighboring air channels to communicate with each other. Accordingly, the heat on the fin set  30  can leave the fin set  30  not only along a front-to-rear direction, but also along a lateral direction of the fin set  30 .  
      It is believed that the present embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the invention.