Abstract:
A cooling system for providing rapid and uniform cooling of a variety of objects. The cooling system utilizes a fan that cooperates with a heat sink to provide an active heat sink. Additionally, the arrangement of the heat sink and the fan provide a relatively uniform and linear airflow over the heat sink to provide uniform cooling.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to cooling systems for facilitating the removal of heat from a variety of objects, and particularly to a technique that utilizes a combined heat sink and fan.  
         BACKGROUND OF THE INVENTION  
         [0002]    In a variety of products and applications, it is beneficial to remove heat from certain objects or areas. For example, electronic devices, such as computers, servers, cameras, projectors, etc. often have heat producing components, such as processors or other microchips that generate heat. To ensure the desired operation and life of the component or overall device, it often is necessary or beneficial to cool such components.  
           [0003]    Many types of heat sinks have been used to facilitate the removal of heat from a given object. Heat sinks often include a plurality of fins that increase the rate at which heat is transferred from the object and dissipated to the environment. In some applications, fans are used to circulate air in the vicinity of the heat sink to promote a greater rate of heat transfer from the heat sink to the surrounding environment.  
           [0004]    Additionally, active heat sinks have been employed that utilize an axial fan dedicated to a specific heat sink. The axial fan is mounted to the heat sink or proximate the heat sink for providing a dedicated airflow over the heat sink. In a typical embodiment, an axial fan is mounted proximate the distal ends of heat transfer fins and air is directed along the heat transfer fins towards the base of the heat sink.  
           [0005]    However, whether this particular arrangement or others are used, existing active heat sinks are subject to a variety of problems that inhibit desired removal of heat. For example, axial fans are susceptible to backpressure. When backpressure builds, the airflow effectively stops. This reduction or stoppage of airflow is problematic, because increases in the amount of heat removed from the heat sink is directly related to the velocity of the air flow induced by the fan. Additionally, axial fans expel air in a circular or twisting motion due to the rotational movement of fan blades that extend radially outward from a center axis or hub. This arrangement leaves a “dead zone” extending axially outward from the hub, e.g. along the axis, of the fan. The air expelled by the fan blades moves in the circular or twisting motion around this dead zone.  
           [0006]    When the fan is positioned adjacent the heat transfer fins of a heat sink, this dead zone often is disposed generally at the center of the heat sink which typically is the area of greatest heat generation. Also, the circulating or twisting air tends to move laterally against the heat transfer fins. The fins interrupt or stall the movement of the air creating stagnant air between the heat transfer fins. Furthermore, the airflow tends to take the path of least resistance which is outward through the sides of the fins rather than to the center surface of the heat sink. Whether due to backpressure, outflow of air, occurrence of the dead zone or blockage of the circulating airflow by the heat transfer fins, reduced or stalled airflow across the heat sink base and heat transfer fins substantially inhibits the removal of heat from a given object.  
           [0007]    Another problem with certain types of fans, such as axial fans is the acoustical output, i.e., noise. As the flow capacity requirements increase, to combat backpressure for example, the noise output can rise to unacceptable levels.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention features a technique that utilizes an active heat sink which may be combined with a variety of components or incorporated in a variety of devices. The technique utilizes a fan, such as a blower fan, in a manner that promotes a high velocity airflow across a heat sink. In one example, a blower fan is combined with a heat sink such that the heat sink acts as what would otherwise be the base of the blower housing. Thus, the heat sink is positioned generally at the area of highest air velocity in the blower fan prior to experiencing a reduction in velocity when the air is expelled from the blower fan housing. This embodiment and others can be combined with a variety of components, such as processors or other heat generating devices, that are utilized in many types of products.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    The invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and:  
         [0010]    [0010]FIG. 1 is a front view of an exemplary device utilizing an active heat sink, according to one embodiment of the present invention;  
         [0011]    [0011]FIG. 2 is a perspective view of a fan mounted to a heat sink, according to one embodiment of the present invention;  
         [0012]    [0012]FIG. 3 is a front view of the device illustrated in FIG. 2;  
         [0013]    [0013]FIG. 3A illustrates an alternate embodiment of the device in FIG. 3;  
         [0014]    [0014]FIG. 4 is a side view of the device illustrated in FIG. 2;  
         [0015]    [0015]FIG. 5 is an exploded perspective view of the device illustrated in FIG. 2;  
         [0016]    [0016]FIG. 6 is a cross-sectional view taken generally along line  6 - 6  of FIG. 3; and  
         [0017]    [0017]FIG. 7 is an isometric view of the device illustrated in FIG. 2 mounted to an exemplary object for placement in an exemplary device, such as that illustrated in FIG. 1; and  
         [0018]    [0018]FIG. 7A illustrates an alternate embodiment of the device in FIG. 7. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]    Referring generally to FIG. 1, an exemplary device  10  is illustrated according to one embodiment of the present invention. Device  10  can be any of a variety of devices having a component  12  that requires or benefits from a cooling system  14 . An exemplary component  12  is a heat-generating component, such as a processor or other “chip” that generate heat and benefit from or require removal of that heat. However, the heat generating component may be of a variety of other types that benefit from the removal of heat via cooling system  14 .  
         [0020]    Similarly, device  10  represents a variety of devices that have components which require or benefit from the removal of heat. For example, device  10  may comprise an electronic device. Such electronic devices include computers, servers, projectors, cameras and a variety of other devices. In the devices listed, integrated circuits are often used and the resultant heat needs to be removed. Cooling system  14  promotes the uniform and rapid removal of heat from such components and devices.  
         [0021]    Referring generally to FIGS. 2, 3,  3 A and  4 , an exemplary cooling system  14  is illustrated. In this embodiment, cooling system  14  comprises a heat sink  20  coupled to a fan  22  able to output a generally linear airflow, represented by reference numeral  24 . An exemplary fan  22  is a blower fan, and fan  22  will be referred to as a blower fan throughout this description. Alternative styles of blower fan  22  are illustrated in FIGS. 3 and 3A. However, it should be realized that other types of fans able to output an appropriate linear airflow may be utilized.  
         [0022]    An exemplary heat sink  20  includes a base  26  and a plurality of projections  28  for dissipating heat from base  26 . Generally, base  26  abuts component  12 , e.g. a heat generating component, such that heat is transferred through base  26  and along projections  28  for greater transfer or dissipation of heat to the surrounding environment. In the illustrated embodiment, projections  28  comprise a plurality of heat transfer fins  30  separated by a plurality of channels  32 . Channels  32  may serve as airflow passages that direct the generally linear airflow  24  along heat transfer fins  30  to facilitate greater cooling. As discussed above, the higher the velocity of linear airflow  24  along heat sink  20  the greater the amount of heat that is removed from heat sink  20 . When a relatively high velocity airflow flows along the substantial surface area created by heat transfer fins  30  of heat sink  20 , large amounts of heat are rapidly dissipated to the surrounding environment. In the specific embodiment illustrated, heat sink  20  also includes a pair of outer walls  34  that generally extend from base  26  to facilitate the coupling of fan  22  to heat sink  20 .  
         [0023]    Blower fan  22  comprises a housing  36  and a fan cage  38  (see also FIG. 5). Blower fan  22  also includes a motor  40  coupled to fan cage  38  to rotate fan cage  38  within housing  36 , as with conventional blower fans. (In the embodiment illustrated in FIG. 3A, motor  40  is used to rotate a pair of fan cages  38 .)  
         [0024]    The exemplary housing  36  includes a main housing portion  42  defining a curved inner surface  44  along which fan cage  38  moves during rotation. Housing  36  also includes an outlet  46  and an inlet  48 . When fan cage  38  is rotated by motor  40 , air is drawn in through inlet  48 , accelerated along curved inner surface  44  and expelled through outlet  46 , as best illustrated in the cross-sectional view of FIG. 6. Effectively, fan cage  38  moves air towards and through outlet  46  creating a lower pressure area in the center of the fan cage causing air to move into housing  36  through inlet  48 , as represented by arrow  50 . (In the embodiment illustrated in FIG. 3A, air is drawn in through a pair of opposed inlets  48  and expelled through outlet  46 .)  
         [0025]    Because of the design of fan cage  38  and fan housing  36 , blower fan  22  is not susceptible to stoppage of outflow due to pressure buildup as described above with respect to axial-style fans. Additionally, the generally linear airflow  24  is substantially free of a centralized dead zone, as with axial fans, thereby allowing a more uniform airflow along heat sink  20 , e.g. through flow passages  32  and along heat transfer fins  30 . Furthermore, the linear flow is oriented generally parallel with the heat transfer fins  30 , avoiding the stoppage that otherwise occurs when air is circulated into the side of a heat transfer fin. Also, the maximum velocity of air is along the base surface of the heat sink, which tends to be the highest source of heat.  
         [0026]    As best illustrated in FIG. 5, an exemplary fan cage  38  comprises a plurality of fan blades  52 . Fan blades  52  generally are arranged parallel with each other in a circular pattern designed for rotation within and along curved inner surface  44  of housing  36 . Thus, as fan cage  38  is rotated, the substantially parallel fan blades  52  move air along curved inner surface  44  until expelled through outlet  46 . In this embodiment, each fan blade  52  has a generally curved cross-section  54 , as best illustrated in FIG. 6. It should be noted that the curvature of fan blades  52  can be changed to, for example, the inverse of the curvature illustrated. Additionally, fan blades  52  are held in place by an end ring  56  and an end plate  57 . In this embodiment, fan blades  52  extend between end ring  56  and end plate  57 , however, a variety of other mounting systems may be used, including a central ring from which each fan blade  52  extends in opposite directions or a pair of end rings.  
         [0027]    Although housing  36  may be disposed for cooperation with heat sink  20  in a variety of positions and according to a variety of methods, the figures illustrate one way of taking advantage of the airflow generated by fan cage  38 . As illustrated, the exemplary housing  36  includes an open base region  58  to permit placement of housing  36  over heat sink  20  and heat transfer fins  30 . In a conventional blower fan, housing  36  would include a solid base portion disposed to fill the opening  58  for conducting airflow out of the housing through an outlet, such as outlet  46 . It is along this base region that the outflowing air experiences its highest velocities. Once the air is moved through an outlet, such as outlet  46 , the velocity slows.  
         [0028]    Accordingly, the exemplary embodiment illustrated uses heat sink  20  to fill open base region  58 . This deployment allows the heat sink to effectively form the base portion of housing  36  such that the highest velocity airflow produced by blower fan  22  occurs across heat sink  20  and, in this embodiment, along heat transfer fins  30 . High velocity airflow across heat transfer fins  30 , of course, permits substantially greater heat removal for a given capacity fan. Efficient use of the output airflow, permits selection of a lower capacity/lower power fan than would otherwise be required for a given application thus also reducing acoustical output.  
         [0029]    One way of utilizing the high velocity airflow along the base or bottom of housing  36  (see FIG. 6) is to form a recessed region  60  in heat sink  20  to accommodate fan cage  38 . In one embodiment, recessed region  60  is formed by forming a cutout section  62  in each of a plurality of the heat transfer fins  30 . The cutouts  62  may be arcuate to provide the overall recessed region  60  with a curvature generally matching the perimeter curvature of fan cage  38 . However, other forms and shapes may be used to prepare cutout  62  and recessed region  60 .  
         [0030]    By way of example, recessed region  60  may be located such that heat transfer fins  30  have a greater reach or degree of extension proximate outlet  46 . These raised or extended portions  64  typically extend along fan cage  38  to fill outlet  46 , as best illustrated in FIGS. 3, 5 and  6 .  
         [0031]    As best shown in FIGS. 2, 4 and  5 , housing  36  may be designed with engagement features  66  designed to engage outer walls  34  of heat sink  20 . Engagement features  66  may be held to outer walls  34  by a variety of mechanisms, including adhesives, welds, clips or other methods of fastening. In this manner, fan cage  38  is disposed intermediate heat sink  20  and housing  36 .  
         [0032]    When fan cage  38  is rotated by motor  40 , inflowing air  50  is drawn through inlet  48  and pushed or moved along curved inner surface  44  by fan blades  52 . The air is continually accelerated along curved inner surface  44  and into contact with heat sink  20  which is a continuation from surface  44 . In this example, the air is moved along air passages  32  through heat transfer fins  30  until it is expelled through outlet  46 , as best illustrated in FIG. 6.  
         [0033]    Although heat transfer fins  30  are disposed within the maximum velocity area of blower fan  22 , other heat sink designs also can be employed. For example, heat transfer fins  30  can be designed to extend from outlet  46 , be adjacent outlet  46 , coupled to outlet  46  via an enclosed tube, extended along curved inner surface  44 , etc. Additionally, a variety of other heat transfer projections and elements can be utilized to facilitate the removal of heat.  
         [0034]    Referring generally to FIG. 7, an exemplary use of cooling system  14  can be explained. In this embodiment, the cooling system is connected to a heat generating component (generally referred to as component  12 ), such as a processor  70 . Processor  70  tends to produce the greatest heat, i.e., have the highest heat zone, at a central location  72 . Base  26  of heat sink  20  is mounted against an upper surface  74  of processor  70  such that heat zone  72  and at least a substantial portion of the upper surface  74  are disposed in cooperation with base  26 . Typically, a lower surface of base  26  is disposed in abutting engagement with upper surface  74  to facilitate a high degree of heat transfer from processor  70  to heat sink  20 . For example, a contact surface can be formed across a die, a portion of the upper surface of processor  70  or across all of the upper surface of processor  70 .  
         [0035]    During operation of processor  70 , heat is generated and conductively transferred to base  26  of heat sink  20 . The heat energy is then transferred from base  26  through heat transfer fins  30  which provide substantial surface area through which the heat may be dissipated to the surrounding air. By operating blower fan  22 , a high velocity airflow is continually moved past the surfaces of fins  30  and across the surface of base  26  for rapid removal of heat. Because of the uniform and linear airflow  24  through heat transfer fins  30 , substantial removal of heat occurs throughout the heat sink and therefore across the extent of the contact surface between the heat sink  20  and processor  70 . In other words, no dead zone exists in the vicinity of high heat zone  72  of processor  70 . As discussed above, a variety of other heated or heat generating components can benefit from the rapid and uniform removal of heat as afforded by cooling system  14 .  
         [0036]    As illustrated best in FIG. 7A, airflow can be supplied to blower  22  from a variety of desired locations via an appropriate airflow duct  80 . Duct  80  allows air to be drawn from a remote location within a chassis or from a location outside the chassis housing processor  70 .  
         [0037]    Similarly, an outflow duct  82  can be used to direct the airflow expelled through outlet  46  to a desired location away from blower  22 . The use of one or both air ducts  80 ,  82  can permit greater flexibility in the location of blower fan  22  and heat sink  20 .  
         [0038]    It will be understood that the foregoing description is of exemplary embodiments of this invention, and that the invention is not limited to the specific forms shown. For example, the materials utilized to construct the heat sink and the blower fan may vary; the size and design of the cooling system may be adjusted according to the design and application of components and/or devices in which the cooling system is utilized; the arrangement of the heat sink and fan can be adjusted and their relative positions can be changed; other types of fans able to provide a generally uniform, linear airflow may be utilized; and the cooling system may be used in combination with a variety of components and devices. These and other modifications may be made in the design and arrangement of the elements without departing from the scope of the invention as expressed in the appended claims.