Heat dissipation device

A heat dissipation device (100) comprises a heat sink (10) and a fan (40) mounted on the heat sink (10). The heat sink (10) comprises a central core (12), a plurality of branches (122) radially extending outwardly from a periphery of the core (12) and a plurality of fins (14) extending from of the core (12) and the branches (122). The fan (40) comprises a plurality of blades (404). The branches (122) and the fins (14) extend and are oriented in a direction opposite to a rotation direction of the blades (404) of the fan (40).

BACKGROUND OF THE INVENTION

The present invention relates generally to a heat dissipation device, and more particularly to a heat sink with low heat resistance.

DESCRIPTION OF RELATED ART

Electronic devices such as central processing units (CPUs) generate a lot of heat during normal operation. If the heat generated by the electronic devices is not timely and properly dissipated, it can affect their operational stability and damage associated electronic devices. Thus the heat must be removed quickly and efficiently to ensure the normal operation of these electronic devices. A heat dissipation device is often attached to a top surface of the CPU to remove heat therefrom.

FIG. 6discloses a related heat dissipation device. The heat dissipation device includes a heat sink and a fan attached to a top portion of the heat sink. The heat sink includes a base contacting with the CPU and a plurality of fins upwardly extending from a top of the heat sink for facilitating heat convection. Blades of the fan revolve and create an axial airflow. The direction of such airflow is related to the orientation of the blades. When such air enters the heat sink, it strikes the straight fins, rebounds, and thus creates obstructing airflow. Additionally, part of the air emitted by the fan strikes a bottom portion of the base being relatively close to the CPU, rebounds back toward the fan and creates obstructing airflow. All this prevents air from entering the heat sink and exiting the heat sink, and thus reduces efficiency of forced heat convection. Thus the heat dissipation efficiency of the heat sink is reduced.

SUMMARY OF THE INVENTION

A heat dissipation device comprises a heat sink and a fan mounted on the heat sink. The heat sink comprises a central core, a plurality of branches radially extending outwardly from peripheries of the core, and a plurality of fins extending from the core and the branches. The fan comprises a plurality of blades. The branches and the fins extend and are oriented in a direction opposite to a rotational direction of the blades of the fan.

Other advantages and novel features of the present heat dissipation device will become more apparent from the following detailed description of preferred embodiment when taken in conjunction with the accompanying drawings, in which:

DETAILED DESCRIPTION OF THE INVENTION

As shown inFIG. 1, a heat dissipation device100in accordance with a preferred embodiment of the present heat dissipation device adapted to dissipate heat generated by an electrical component, such as a CPU (not shown) on a printed circuit board (not shown) comprises a heat sink10, four fasteners20, a fan bracket30and a fan40. The fan bracket30is employed to secure the fan40to a top surface of the heat sink10. The fan40includes a plurality of blades404. The combined heat sink10, fan bracket30and fan40are attached to the CPU by the four fasteners20.

The heat sink10has a cylindrical configuration and comprises a central core12with a shape similar to a cube and four curved symmetrical branches122radially extending outwardly from four vertical edges of the core12. The core12comprises four outer side surfaces (not labeled) separated by the branches122. Each branch122comprises an outer side surface (not labeled) and an inner side surface (not labeled). The four outer side surfaces of the core12and the side surfaces of the four branches122cooperatively define four regions. A plurality of curved fins14extend outwardly from side surfaces of the core12and the branches122. From a top-down view, the side surfaces of the core12and the branches122in each region are smoothly connected and form an inverse L-like projection. The fins14in different regions are oriented towards four different directions. In each region, the curved branches122and fins14extend and are oriented in a same direction, such as, for example, clockwise. The central core12comprises a top surface120and a bottom surface (not shown) configured for absorbing heat from the CPU. The core12has a central axis16as indicated by a dashed line inFIG. 1. The central axis16is oriented perpendicular to the top surface120of the core12. Point O shows a crossing point of the axis16and the top surface120, as well as a center of the top surface120. A first imaginary straight line OB is formed by joining point O and a crossing point B of each vertical edge of the core12and the top surface120corresponding to each branch122. Each branch122deviates from the corresponding line OB towards a same side as other branches122, such as the clockwise side of the line OB in the embodiment. Another second imaginary straight line BD is formed by joining the corresponding point B of each vertical edge and another adjacent crossing point D of the vertical edge on a counterclockwise side of each region and the top surface120. Each branch122deviates from the corresponding line BD towards the same side as for the line OB, such as the clockwise direction in the preferred embodiment. The fins14in the same region are spaced from each other by uniform intervals, thus defining a plurality of airflow passages142therebetween. Furthermore, the fins14deviate from the corresponding branch122located on the counterclockwise side in each region towards a same side as the branch122, such as the clockwise direction in the embodiment. In each region, the fins14extending from each side surface of the core12gradually become shorter along the curving direction of the adjacent branches122.

Four protrusions126extend outwardly from lower portions of the branches122. Each protrusion126is C-shaped and has a through hole128defined therein. The four fasteners20are adapted to engage in the through holes128, for facilitating an attachment of the heat sink10onto the printed circuit board. Two recesses127are symmetrically defined in a circumferential periphery of the heat sink10. In the embodiment the recesses127are defined in a middle level of the heat sink10, and are defined by cutting away outer ends of two symmetrical branches122and the fins14adjacent to the two symmetrical branches122.

The fan bracket30comprises a tubular frame300defining a central opening310therein. An annular flange320extends horizontally and outwardly from an upper edge of the frame300for supporting the fan40thereon. Four symmetrical ears322extend horizontally and outwardly from an outer edge of the flange320. A pin324and a latch326extend perpendicularly and upwardly from each ear322. The pin324and the latch326of each ear322are spaced from each other. Two symmetrical catches330extend downwardly from a lower edge of the frame300, for engaging in the recesses127to firmly secure the fan bracket30to the heat sink10. In the embodiment, the catches330are arranged below the two opposite ears322.

The fan40is mounted on the heat sink10with the help of the fan bracket30. The fan40has a substantially tubular housing400and a hub402received in the housing400. A plurality of blades404radially extend from the hub402. The housing400is provided with four pairs of tabs411,421extending outwardly and horizontally from upper and lower edges of the housing400. The tabs411each define a locating hole413therein. The holes413receive the pins324of the fan bracket30therein to position the fan40onto the fan bracket30in a horizontal direction. The tabs411are hooked by the latches326of the fan bracket30to hold the fan40on the fan bracket30in a vertical direction. The blades404of the fan40are configured to rotate in a direction opposite to the extension direction of the curved branches122and fins14, such as the counterclockwise direction in the preferred embodiment.

As shown inFIG. 2, in use, heat generated by the CPU is firstly conducted to the core12and the fins14of the heat sink10. During operation of the fan40, a large amount of cooling air is drawn into the housing400of the fan40and then toward the heat sink10via the opening310of the fan bracket30. Arrows show flow directions of airflow generated by the fan40, corresponding to a clockwise rotation direction of the blades404. The airflow enters the heat sink10within the airflow passages142and takes away heat from the core12and the fins14. Because the curved branches122and the fins14extend and are oriented in a direction opposite to the rotation direction of the blades404of the fan40, the airflow can be conducted into the core122more easily, allowing more airflow to impinge on the core122and the fins14. Thus, the heat on the heat sink10can be quickly transferred to the airflow and dissipated to the surroundings along with the airflow from the heat sink10.

Referring toFIG. 3, a heat dissipation device200in accordance with a second embodiment of the present heat dissipation device is illustrated. The heat dissipation device200comprises a heat sink10a, two clips20a, a fan bracket30and a fan40, and has a configuration similar to that of the first preferred embodiment. The heat sink10acomprises a central core12aand four branches122ahaving the same configuration as the corresponding ones of the first preferred embodiment. The main difference therebetween is that a plurality of fins14aextending from side surfaces of the core12aand the branches122aare straight. The fins14ain each region defined by the core12aand the branches122aare parallel to each other. The fins14ain different regions are perpendicular to the fins14ain the adjacent regions. Furthermore, the fins14adeviate from the corresponding branch122alocated on the counterclockwise side in each region towards a same side as the branch122a, such as the clockwise direction in the second embodiment. In each region, a protrusive portion152ais formed on an edge of one fin14a, being adjacent to the branch122a. The protrusive portion152aand the branch122acooperatively define a half-closed hole154aextending through from a top surface to a bottom surface of the heat sink10a. Two recesses127aare symmetrically defined in a circumferential periphery in the two opposite regions of the heat sink10a.

Each clip20acomprises a C-like base22a. Two self-tapping screws24aextending upwardly from respective ends of the base22aare adapted to engage in the half-closed holes154afrom the bottom surface of the heat sink10a. Thus the clips20aare attached to the heat sink10asecurely. Two ears222aextend outwardly from two side edges of the ends of the base22arespectively in a roughly horizontal direction. Each ear222adefines an aperture (not shown) for engaging with a fastener25aused to secure the clip20ato the printed circuit board.

It can be understood that the shape of the core12of the heat sink10can be prism-like, cylindrical, or parallelepiped, and is not limited to being cube-shaped. Referring toFIG. 4, a heat sink50of a heat dissipation device in accordance with a third embodiment of the present heat dissipation device is illustrated. Different from the heat sink10of the first preferred embodiment, the heat sink50comprises a central core52with a shape as a triangular prism and three straight branches522radially extending outwardly from and along three sides of the core52, respectively. Furthermore, each branch522deviates from an imaginary line formed by joining a center of the top surface520of the core52and a corresponding vertex of the central core52, towards a same side as other branches522, such as the clockwise direction side of the line in the third embodiment. A plurality of straight fins54extend outwardly from side surfaces of the core52and the branches522, and are divided into three regions oriented in three different directions. The fins54in each region defined by the core52and the branches522are parallel to each other. Furthermore, the fins54deviate from the corresponding branch522located on the counterclockwise side in each region towards a same side as the fins54in other regions, such as the clockwise direction in the third embodiment.

Referring toFIG. 5, a heat sink60of a heat dissipation device in accordance with a fourth embodiment of the present heat dissipation device is illustrated. The heat sink60has a configuration similar to the heat sink10of the first preferred embodiment. The main difference therebetween is that the heat sink60has a cylinder-like core62. Four branches622and a plurality of fins64extend out from a circumferential periphery (not labeled) of the core62in the same manner as that of the first preferred embodiment. Furthermore, the branches622can radially extend outwardly from the circumferential periphery of the core62in a tangential direction to the circumferential periphery of the core62.

It can be understood that the curving directions of the branches122,122a,522,622and the fins14,14a,54,64all extend and are oriented opposite to the rotation direction of the blades404of the fan40. Thus the airflow generated by the fan40can be conducted into the core12,12a,52,62more easily, allowing more airflow to impinge on the core12,12a,52,62and the fins14,14a,54,64. Therefore, the heat on the heat sink10,10a,50,60can be quickly transferred to the airflow and dissipated to the surroundings along with the airflow from the heat sink10,10a,50,60.