Abstract:
A heat sink comprises a plurality of fins that may be positioned in a plurality of orientations relative to a heat-generating electronic component to which the heat sink is thermally coupled. A controller may be used to detect an elevated processor temperature and to activate a drive member to automatically adjust the orientation of fins on the heat sink. The fins may be moved and aligned with an air flow made over the heat sink. The adjustable-fin heat sink affords added flexibility in arranging a processor or other heat-generating electronic component on a circuit board. The orientation or position of the heat sink fins may also be automatically changed in response to a change in the air flow direction as manifested by a rise in the temperature of the heat sink or the heat-generating member.

Description:
BACKGROUND 
     Field of the Invention 
     The present invention relates to heat sinks for removing heat from heat-generating electronic components used in computers. 
     Background of the Related Art 
     Computer systems require removal of heat from heat-generating electronic components such as processors. Heat-generating electronic components are generally coupled to a generally planar host card such as a circuit board having a series of electronic contacts along an edge to facilitate electronic engagement between the host card and a motherboard. Electrical current and data are routed to the heat-generating electronic component through the motherboard and through the electronic contacts on the circuit board. Heat generated by the electronic component may be transferred by conduction to a heat sink. A plurality of fins may be coupled to the heat sink to dissipate heat to surrounding air within the computer chassis. Air flow within the chassis may be provided by air movers such as fans installed within a computer chassis, a server rack or within a server room. Air movers are generally fixed and may be coupled to a controller to vary the speed of the air mover as needed to provide sufficient air flow to cool electronic components. 
     Fins on a heat sink efficiently dissipate heat to a surrounding air flow when the fins are generally aligned with the air flow. For this reason, air movers are generally positioned to draw air into an inlet end of a chassis, server rack or server room, and heat sinks are generally positioned within a chassis to align the fins with the anticipated air flow. However, the direction of air flow within a computer chassis, server rack or server room can change direction. For example, if a computer chassis or server rack has multiple air movers disposed in a row or array, the failure of one or more air movers will change the direction of air flow across heat sink fins disposed within the computer chassis or server rack. As a result, the efficiency of the heat sink will decrease due to the misalignment of the air flow across the fins of the heat sink. As another example, obstructions such as expansion cards, circuit boards or even articles inadvertently placed near an air inlet or outlet of the chassis or rack can disrupt and change the direction of air flow across a heat sink, thereby resulting in a dramatic loss of heat sink efficiency due to misaligned air flow across the fins. 
     BRIEF SUMMARY 
     One embodiment of the present invention provides a heat sink comprising a base having a first face to engage a heat-generating electronic device and a second face, a rotary member having a first face to support a plurality of fins and a second face to engage the second face of the base, wherein the rotary member is rotatably received on the base, and a drive member coupled to the rotary member to rotate the rotary member relative to the base in response to a control signal. 
     Another embodiment of the invention provides a computer program product including computer usable program code embodied on a computer usable storage medium, the computer program product comprising a computer usable program code for receiving a signal from a temperature sensor coupled to a heat sink, and computer usable program code for activating a drive member to rotate a rotary member of the heat sink to minimize the temperature of heat sink, wherein the minimum temperature of the heat sink is minimized in response to aligning fins on the rotary member of the heat sink with air flow across the heat sink. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a plan view of a circuit board disposed within a computer chassis to support a processor coupled to an embodiment of a heat sink of the present invention with a plurality of orientable fins aligned with an air flow drawn through the computer chassis by a set of fans. 
         FIG. 2  is a plan view of the processor and an embodiment of a heat sink of  FIG. 1  after the direction of the air flow through the computer chassis changes due to a fan failure. 
         FIG. 3  is a section view of an embodiment of a heat sink having fins that may be adjusted to align with a changed air flow. 
         FIG. 4  is the section view of the heat sink of  FIG. 3  after the fins are rotated to align with the changed air flow illustrated in  FIG. 2 . 
         FIG. 5  is the plan view of  FIG. 2  after the fins are rotated to align with the changed air flow as illustrated in  FIG. 4 . 
         FIG. 6  is a section view of an alternate embodiment of a heat sink having fins that may be adjusted to align with a changed air flow. 
     
    
    
     DETAILED DESCRIPTION 
     One embodiment of the present invention provides a heat sink having a drive member, a base and a rotary member to support a plurality of air-cooled fins. The rotary member is rotatably disposed on the base adapted to engage a heat-generating electronic device, such as a processor, disposed within a computer chassis. The drive member may be activated to rotate the rotary member to align the fins with an air flow within the computer chassis to remove heat generated by the processor by way of dissipation from the fins. 
     Embodiments of the heat sink may further comprise a temperature sensor coupled to at least one of the base and the rotary member to generate a signal corresponding to the temperature of the base or the rotary member. The temperature signal is communicated to a controller that activates the drive member to rotate the rotary member and thereby align the fins on the rotary member with an air flow within the chassis. 
     Alternate embodiments of the heat sink comprise a drive member activatable by a controller that receives a signal from a temperature sensor disposed on, in or adjacent to the heat-generating electronic device. For example, the temperature sensor may be included within a chip package having one or more processors. The signal from the temperature sensor to the controller corresponds to the temperature of the heat-generating electronic device. Activation of the drive member rotates the rotary member to align the fins with an air flow through the computer chassis to improve heat-dissipation capacity of the heat sink. 
     Embodiments of the heat sink may comprise a thermally conductive material disposed intermediate the base and the rotary member to promote conductive heat transfer from the base to the rotary member for dissipation of heat from the fins. The thermally conductive material may further provide lubrication to promote smooth rotation of the rotary member on the base. The thermally conductive material may comprise, for example, liquid metal or thermal grease. 
     Embodiments of the heat sink may comprise a gear disposed on the rotary member to engage a drive gear on a drive member coupled to the base, the processor, the circuit board on which the processor is secured or to the chassis. The drive member, upon activation, rotates the drive gear to counter-rotate the rotary member on the base to align the fins thereon with an air flow within the computer chassis. A low-conductivity bracket may be used to limit heat-transfer from the base or processor to the drive motor. A low-conductivity bracket may comprise an insulating material, such as ceramic, or it may comprise a thin-walled member having a very small cross-section to limit heat transfer. 
     Alternate embodiments of the heat sink may comprise a drive member coupled to the rotary member to rotate a drive gear that engages a stationary gear disposed on the base. The reaction force applied to the rotary member through the drive motor and bracket cause the rotary member to rotate relative to the base to align the fins on the rotary member with an air flow within the computer chassis. 
     A computer program product according to one embodiment of the invention includes computer usable program code embodied on a computer usable storage medium, where the computer program product comprises computer usable program code for receiving a signal from a temperature sensor coupled to a heat sink, and computer usable program code for activating a drive member to rotate a rotary member of the heat sink to minimize the temperature of heat sink. The temperature of the heat sink is minimized in response to aligning fins on the rotary member of the heat sink with air flow across the heat sink. 
     The computer program product may be executed by a controller, which may be a service processor such as a baseboard management controller (BMC) or an integrated management module (IMM). In a first option, the computer program product may further comprise computer usable program code for comparing the signal from the temperature sensor to a predetermined value; and computer usable program code for activating the drive member if the signal exceeds the predetermined value. According to this method, the rotary member remains stationary until a temperature deviation is detected. 
     In a second option, the computer program product may further comprise computer usable program code that determines a position or orientation of the rotary member and fins that produces the minimum heat sink temperature. Optionally, the temperature at each position of the rotary member and fins is measured which the heat-generating device is under a comparable workload. Where the heat-generating device is a processor, the workload of the processor may be controlled or at least monitored to assure that temperature differences between positions of the rotary member are not attributed to alignment/misaligned of the fins and airflow, when in fact the workload has changed. 
     The controller may periodically or continuously take steps to assure that the heat sink fins are aligned with the airflow. This type of methodology may be preferred in environments where the air flow direction is known to periodically change. In such an environment, the controller may periodically activate the drive member to rotate the rotary member and fins of the heat sink from a first position to a second position. At each position, the controller receives a signal from the temperature sensor. Then, the controller may compare the temperature of the heat sink at the first position to the temperature of the heat sink at the second position. The controller then determines which position resulted in a lower temperature. The lower temperature indicates that the rotary member is positioned so that the fins are aligned with the air flow, since heat transfer is most efficient in that position. 
       FIG. 1  is a plan view of a circuit board  17  disposed within a computer chassis  10  to support a processor  11  coupled to a heat sink  12  with a plurality of fins  18  aligned with air flowing in the direction indicated by the adjacent arrow  13 . The cooling air is drawn through the chassis  10  by a set of air movers such as fans  14 . The direction of the air flow within the chassis may vary from location to location depending on factors including proximity to the fans  14 , fan speed and the proximity and size of obstructions. The direction of the air flowing within the computer chassis  10  in  FIG. 1  is indicated by the arrows  13 ,  15  and the direction of air flowing outside of the computer chassis  10  is indicated by arrows  16 . The direction of air flow indicated by the arrow  13  adjacent to the processor  11  and the adjacent arrows  15  to either side of the processor is generally congruent because the three fans  14  disposed within the chassis  10  are active, operating at approximately the same speed and generally uniformly spaced within the chassis  10 . 
       FIG. 2  is the plan view of the processor  11  and heat sink  12  of  FIG. 1  after the direction of the air flowing through the computer chassis  10  changes due to the failure of one of the three fans  14  illustrated in  FIG. 1 . The third (bottom) fan  14  from  FIG. 1  is omitted from  FIG. 2  to indicate two remaining operable fans  14 . The direction of the air flowing within the chassis  10  changes as a result of the failure of the third fan (not shown in  FIG. 2 ) and is in the directions as indicated by arrows  13 ,  15 ,  21 ,  22 ,  23 ,  24  within the chassis  10  and the directions of air flowing outside the chassis  10  is indicated by arrows  16 ,  19 . The direction of the air flow within the chassis  10  immediately upstream (and to the left in  FIG. 2 ) of the heat sink  12  is indicated by arrow  13 , which it will be noted is no longer substantially aligned with the fins  18  on the heat sink  12 . The direction of air flow indicated by the arrow  13  is instead flowing at an approach angle  20  of about 30 degrees at variance with alignment of the generally straight fins  18 . It will be understood that air-cooled fins, such as straight fins, flared fins and fin structures comprising interconnected, repeating air channels, will suffer a substantial loss in heat-dissipating efficiency where the direction of the air flow across or through the fins is at a substantial variance with the linear orientation of the fins as illustrated in  FIG. 2 . 
       FIG. 3  is a section view of an embodiment of a heat sink  12  of the present invention having a plurality of straight fins  18  in a generally parallel configuration that may be adjusted to align with a direction of an air flow that is at variance with an original position of the fins  18 . The embodiment of the heat sink  12  illustrated in  FIG. 3  comprises a base  38 , a rotary member  32  and a drive member  42 . The rotary member  32  comprises a retainer  30  with a retainer flange  34 , a gear  40  and a set of straight fins  18  extending in a generally parallel configuration. The retainer  30  is rotatably received against a first face  36  of the base  38  to couple the rotary member  32  to the base  38 . A thermally conductive material  50 , such as liquid metal or thermal grease, is disposed intermediate the retainer  30  and the base  38  to promote conductive heat transfer from the base  38  to the rotary member  32 . The base  38  comprises a first face  37  to engage a heat-generating electronic component (not shown) such as a processor. The base  38  further comprises a temperature sensor  52  to generate a signal  55  corresponding to the temperature of the base  38  to a controller  53 . The drive member  42  comprises a drive motor  54  coupled to a drive gear  44  positioned to engage and drive the gear  40  on the rotary member  32 . The drive member  42  is coupled to the base  38  using an insulated drive member bracket  57  to minimize heat transfer from the base  38  to the drive member  42 . 
     The controller  53 , upon receiving a signal  55  indicating an excessive temperature in the base  38 , generates an activating signal  56  to the drive motor  54  of the drive member  42 . The drive motor  54  receives the activating signal  56  and rotates the drive gear  44  to counter-rotate the gear  40  on the rotary member  32  to re-align the fins  18  thereon. 
       FIG. 4  is the section view of the heat sink of  FIG. 3  after the fins  18  and the rotary member  32  are rotated about 30 degrees counter-clockwise (if viewed from the plan view of  FIG. 2 ) relative to the base  38  to align the fins  18  with the changed air flow (see arrow  13  in  FIG. 2 ). The rotation of the retainer  30  on the rotary member  32  relative to the first face  36  of the base  38  does not impair conductive heat transfer from the base  38  to the fins  18  through the rotary member  32  because the thermally conductive material  50  continues to conduct heat from the base  38  to the rotary member  32 . The drive member  42  may be deactivated after rotation of the rotary member  32  by a predetermined angle or by the use of the temperature sensor  52  to generate a second signal  43  to the controller  53  to discontinue the activating signal  56  (or, alternately, to send a deactivating signal  56 ) to the drive member  42 . 
       FIG. 5  is the plan view of  FIG. 2  after the fins  18  on the heat sink  12  are rotated into general alignment with the new direction of air flow indicated by the arrow  13 . The direction of the air flow indicated by arrows  13 ,  15 ,  21 ,  22 ,  23 ,  24  within the chassis  10  and the direction of the air flow indicated by the arrows  16 ,  19 ,  28  outside the chassis  10  is generated by operation of the remaining two fans  14 . It will be understood that the fans  14  may operate at an increased fan speed to compensate for the loss of the adjacent fan (omitted from  FIG. 5 —see  FIG. 2 ). The actual directions of the air flow at various locations within and without the chassis  10  may vary with changes in the speed of the fans  14 , the temperature and density of the air, the dimensions of the chassis  10  and obstructions, but the arrows illustrated on  FIG. 5  illustrate a generally anticipated air flow pattern resulting from the operation of only two of the original three fans  14 . 
       FIG. 6  is a section view of an alternate embodiment of a heat sink having fins that may be adjusted to align with a changed air flow. The embodiment of the heat sink  12  illustrated in  FIG. 6  also comprises a base  38 , a rotary member  32  and a drive member  42 . The rotary member  32  comprises a retainer  30  with a retainer flange  34  and a set of straight fins  18  extending in a generally parallel configuration. The retainer  30  is rotatably received against a first face  36  of the base  38  to couple the rotary member  32  to the base  38 . A thermally conductive material  50 , such as liquid metal or thermal grease, is disposed intermediate the retainer  30  and the base  38  to promote conductive heat transfer from the base  38  to the rotary member  32 . The base  38  comprises a first face  37  to engage a heat-generating electronic component (not shown) such as a processor. The base  38  further comprises a gear  40 , a temperature sensor  52  to generate a signal  55  corresponding to the temperature of the base  38  to a controller  53 . The drive member  42  comprises a drive motor  54  coupled to a drive gear  44  positioned to engage the gear  40  on the rotary member  32 . The drive member  42  is coupled to the rotary member  32  (instead of the base  38 ) using an insulated drive member bracket  57  to minimize heat transfer from the rotary member  32  to the drive member  42 . 
     The controller  53 , upon receiving a signal  55  indicating an excessive temperature in the base  38 , generates an activating signal  56  to the drive motor  54  of the drive member  42 . The drive motor  54  receives the activating signal  56  and rotates the drive gear  44  which engages the stationary gear  40  on the base  38 . The reaction force within the motor  54 , the bracket  57  and the rotary member  32  to the torque generated by the motor  54  and applied to the gear  40  causes the rotary member  32  to rotate to re-align the fins  18  thereon. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, components and/or groups, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The terms “preferably,” “preferred,” “prefer,” “optionally,” “may,” and similar terms are used to indicate that an item, condition or step being referred to is an optional (not required) feature of the invention. 
     The corresponding structures, materials, acts, and equivalents of all means or steps plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but it is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. The embodiment was chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.