Abstract:
A heat dissipation device includes a base, a heat-dissipation portion attached to the base, at least one heat pipe connecting the base and the heat-dissipation portion and a fan directly secured to the heat-dissipation portion. The heat-dissipation portion comprises a square, tubular housing having opposite front and rear end portions opening to surroundings and a plurality of fins extending inclinedly and inwardly from an inner circumferential periphery of the housing. The housing of the heat-dissipation portion is employed as a fan duct to guide an airflow generated by the fan through the fins; the inclined orientation of the fins facilitates the airflow to flow toward the inner circumferential periphery of the housing and lower parts of the fins adjacent the inner circumferential periphery, whereby the airflow can effectively take heat away from the heat-dissipation portion.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a heat dissipation device for removing heat from an electronic device, and more particularly to a heat dissipation device which can more effectively use an airflow generated by a fan to improve heat dissipation capacity thereof. 
   2. Description of Related Art 
   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 a high speed in a computer enclosure, its temperature is greatly increased. It is desired to dissipate the heat quickly, by using, for example, a heat dissipation device attached to the CPU in the enclosure. This allows the CPU and other electronic components in the enclosure to function within their normal operating temperature ranges, thereby assuring the quality of data management, storage and transfer. 
   Conventionally, a related heat dissipation device includes a heat sink and a fan. The heat sink can be mounted in contact with a CPU inside a computer. The fan is usually positioned on the heat sink and generates a high-pressured airflow blowing downwards into the heat sink, causing the heat to be dissipated into the surroundings. The heat sink comprises a cylinder-shaped central core and a plurality of fins radially extending outwardly from the central core. The fan is mounted above the heat sink via a fan bracket buckled to a top portion of the heat sink. The fan draws outside cooling air downwardly into the heat sink. Due to the fins being configured extending radially, airflow generated by the fan is dispersed out of the fins along various directions of the fins before reaching a bottom portion of the heat sink where large amounts of heat accumulate. Thus, the related heat dissipation device has a low heat-dissipating efficiency. In other situations, a fan duct can be mounted to the heat sink; thus, more airflow from the fan can be guided to the bottom portion of the heat sink. However, it is expensive to manufacture and mount the fan duct to the heat sink. 
   SUMMARY OF THE INVENTION 
   A heat dissipation device in accordance with a preferred embodiment of the present invention includes a base, a heat-dissipation portion attached to the base, at least one heat pipe connecting the base and the heat-dissipation portion and a fan directly secured to a front side of the heat-dissipation portion. The heat-dissipation portion comprises a housing having opposite front and rear end portions opening to surroundings and a plurality of fins extending inwardly from an inner circumferential periphery of the housing and cooperatively defining a through hole in a center portion of the heat-dissipation portion. The housing has a plurality of sidewalls. The fins are inclinedly extended from the sidewalls, respectively. The housing of the heat-dissipation portion encircles the fins and is employed as a fan duct to guide an airflow generated by the fan to flow through the fins. Due to the inclination of the fins, when the airflow flows through the fins, the airflow is guided by the fins to flow toward the sidewalls and lower parts of the fins which are located near the inner circumferential periphery of the housing, whereby the airflow can have a sufficient contact with the sidewalls and the lower parts of the fins where most of heat absorbed by the heat dissipation portion from an electronic component accumulates. 
   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 THE DRAWINGS 
     Many aspects of the present embodiments can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
       FIG. 1  is an assembled view of a heat dissipation device according to a preferred embodiment of the present invention; 
       FIG. 2  is an exploded view of  FIG. 1 ; 
       FIG. 3  is a view similar to  FIG. 1 , but from a different aspect, showing heat transfer paths of the heat dissipation device; and 
       FIG. 4  is an assembled view of  FIG. 2 , with a fan being separated, showing airflow paths of the heat dissipation device. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIG. 1 , a heat dissipation device in accordance with a preferred embodiment of the present invention, which is used for dissipating heat from an electronic component (not shown) mounted on an printed circuit board (not shown) is illustrated. The heat dissipation device comprises a heat sink  10 , two pairs of heat pipes  20  attached to two opposite lateral sides of the heat sink  10  and a fan  30  directly secured at a front side of the heat sink  10 . The heat dissipation device further comprises two locking members  40  engaging with the heat sink  10  to secure the heat dissipation device to the printed circuit board so that the heat sink  10  can have an intimate contact with the electronic component. 
   Referring to  FIGS. 1-2 , the heat sink  10  which is made of a thermally conductive material such as copper or aluminum, comprises a base  12  and a heat-dissipation portion  14  attached to the base  12 . The base  12  is substantially rectangular, and has a flat bottom surface (not labeled) for attaching to the electronic component and a flat top surface  120  opposing the flat bottom surface of the base  12 . The base  12  defines four parallel first grooves  122  in a center portion of the flat top surface  120  thereof, for receiving the heat pipes  20 . The base  12  further defines two undercuts  124  in two opposite sides of the flat bottom surface thereof to form two locking portions  126 , for fastening with the locking members  40 . The undercuts  124  are parallel to the first grooves  122 . Each locking portion  126  defines two locking holes (not shown) in a bottom surface thereof for fastening the locking members  40  to the locking portions  126 . 
   The heat-dissipation portion  14  comprises a housing  140  and a plurality of fins  160  integrally extending from an inner circumferential periphery of the housing  140  toward a center of the housing  140 . The housing  140  has a shape of a hollow square with opposite front and rear end portions opening to surroundings. Preferably, the heat-dissipation portion  14  is formed as a monolithic piece by aluminum extrusion. The housing  140  comprises four congruent rectangular sidewalls  1410  encircling the fins  160 , thus forming a fan duct around the fins  160 . Five parallel flanges  1420  are integrally formed on a center portion of an outer surface of each of opposite lateral sidewalls  1410  of the housing  140 . Four slots  1430  are therefore formed between the flanges  1420  on each of the lateral sidewalls  1410  of the housing  140 , for receiving the heat pipes  20  therein. Four arc-shaped parallel second grooves  1440  are defined in a bottom sidewall  1410  of the housing  140  and correspond to the first grooves  122  in the flat top surface  120  of the base  12 . The first and second grooves  122 ,  1440  cooperatively form four passages (not labeled) for accommodating the heat pipes  20  therein when the heat-dissipation portion  14  is mounted on the flat top surface  120  of the base  12 . Four screw holes  180  are defined in four corners of the front end portion of the housing  140 , for engaging with screws  80  to mount the fan  30  on the front end portion of the housing  140  of the heat-dissipation portion  14 . The fins  160  extend inwardly from inner surfaces of the four sidewalls  1410  of the housing  140  and cooperatively define a circular through hole  1600  through a center portion of the heat-dissipation portion  14  along a front-to-rear direction. The through hole  1600  is provided in line with a central hub of an impeller (not labeled) of the fan  30  for reducing a weight of the heat-dissipation portion  14 . The fan  30  generates almost no or a very low airflow pressure at the hub. The fins  160  are oriented inclinedly to their respective corresponding sidewalls  1410  of the housing  140 . The fins  160  have different extension lengths. The fins  160  are spaced from each other at uniform intervals; thus, a plurality of airflow passages (not labeled) are defined between the fins  160  for the airflow to flow therethrough. Four screws  80  are used to extend through holes  32  defined in four corners of the fan  30  and engage in the screw holes  180  of the front end portion of the housing  140  of the heat-dissipation portion  14 , thereby mounting the fan  30  to the front end portion of the housing  140  of the heat-dissipation portion  14 . 
   Each of the heat pipes  20  has a substantially L-shaped configuration. Each heat pipe  20  comprises a heat-receiving section  22  and a heat-discharging section  24  perpendicularly extending from an end of the heat-receiving section  22 . The heat-receiving sections  22  of the two pairs of heat pipes  20  are soldered in the corresponding passages formed by the first and second grooves  122 ,  1440  when the heat-dissipation portion  14  is mounted on the flat top surface  120  of the base  12  of the heat sink  10 . The heat-receiving sections  22  of each pair of the heat pipes  20  are spaced with each other in the passages. The heat-receiving sections  22  of one of the two pairs of heat pipes  20  are located adjacent to the heat-receiving sections  22  of the other of the two pairs of heat pipes  20 . The heat-discharging sections  24  of each pair of heat pipes  20  are respectively received in the spaced slots  1430  and thermally contact with the flanges  1420  and the outer surface of the lateral sidewalls  1410  of the housing  140  of the heat-dissipation portion  14 . 
   Each locking member  40  comprises a locking lever  42  engaging with the corresponding locking portion  126  of the base  12  and two legs  44  extending outwardly from opposite ends of the locking lever  42  and angled with the locking lever  42 . The locking lever  42  defines bores  420  therein. Screws  90  are used to extend through the bores  420  and engage in the locking holes in the base  12  to secure the locking members  40  to the bottom surfaces of the locking portions  126  of the base  12 . The legs  44  define four apertures  440  therein for four screws  100  (only one shown) to extend therethrough to engage in corresponding fixtures (not shown) under the printed circuit board to thereby mount the heat dissipation device to the printed circuit board. 
   In operation, referring to  FIG. 3 , heat transfer paths of the heat dissipation device are shown by arrows in  FIG. 3 . The base  12  of the heat sink  10  absorbs heat from the electronic component (not shown) and a major part of the heat is directly transferred to the heat-receiving sections  22  of the heat pipes  20 . A minor part of the heat is conducted upwardly to the fins  160  formed on an inner surface of a bottom sidewall  1410  of the housing  140  of the heat-dissipation portion  14 . The major part of the heat received in the heat-receiving sections  22  of the heat pipes  20  is transmitted to the lateral sidewalls  1410  of the housing  140  in contact with the heat-discharging sections  24  of the heat pipes  20  and then to the fins  160  via the four sidewalls  1410 . The heat from the base  12  of the heat sink  10  is transferred upwardly to the four sidewalls  1410  of the housing  140  and distributed over the fins  160 . 
   Referring to  FIG. 4 , airflow paths of the heat dissipation device are shown by arrows in  FIG. 4 . During operation of the fan  30 , a large amount of cooling air is drawn into the heat-dissipation portion  14 . The arrows show flow directions of the airflow generated by the fan  30 , wherein the fan  30  rotates counterclockwise as viewed from a front of the fan  30 . The fan  30  blows the airflow into the airflow passages defined between the fins  160  in a direction opposite to the extension directions of the fins  160  from the sidewalls  1410 , due to the inclination of the fins  160  relative to their respective sidewalls  1410 . The airflow is thus forced to flow outwardly along the airflow passages to reach the sidewalls  1410  before the airflow is forced to flow rearwards out of the heat-dissipation portion  14 . Accordingly, the airflow can have a sufficient contact with the inner surfaces of the sidewalls  1410  of the housing  140  where a large amount of heat accumulates and the lower part of each of the fins  160  which is located near the inner surface of a corresponding sidewall  1410  of the housing  140 . It is obvious that heat-dissipation efficiency of the heat dissipation device having the housing  140  is enhanced, compared with a heat dissipation device without the housing  140 . In addition, the housing  140  is integrally formed with the fins  160  and employed as a fan duct and a fan mounting bracket, so cost of the heat dissipation device is greatly reduced and manufacturing process of the heat dissipation device is timesaving and simple. 
   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.