Abstract:
A cooling device for electronic devices is built comprising at least two fan sinks thermally coupled together such that when one fan sink fails, the remaining fan sinks are able to compensate for the failed fan sink. Optionally, the remaining fan sinks may be controlled to speed up upon detection of a failure, increasing their cooling capacity to compensate for the failed fan sink. Also optionally, a thermal coupling device such as heat pipes may be used as part of the thermal coupling between the fan sinks to increase the cooling efficiency of the remaining fan sinks to the device or devices closest to the failed fan sink. Also optionally, the thermal coupling device may be configured to allow some flexibility in the cooling device assembly allowing for the cooling of non-coplanar electronic devices.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to the field of heat sinks and more specifically to the field of fan sink designs with redundancy.  
       BACKGROUND OF THE INVENTION  
       [0002]     Modern electronic devices, such as microprocessors, not only generate large amounts of heat during operation, but are also temperature sensitive. Most integrated circuits run at slower speeds as temperature increases, and also failure mechanisms such as electromigration increase as temperature increases. Thus, the art of cooling electronic devices to a temperature within their operating range is critical to the proper operation of computers and other large electronic devices.  
         [0003]     One common configuration used for cooling electronic devices is the fan sink. A fan sink is created by constructing a heat sink substantially surrounding a fan, configured such that when the fan is operating it creates substantial airflow over the heat sink. Often the fan sink is attached to an electronic device such as a microprocessor through the use of a heat spreader. This heat spreader allows the heat generated by the microprocessor to spread evenly to the fan sink without the creation of substantial hot spots.  
         [0004]     However one problem inherent with fan sinks is that since they typically are only used where their cooling capacity is necessary, if the fan fails, the electronic device will overheat, sometimes catastrophically.  
       SUMMARY OF THE INVENTION  
       [0005]     A cooling device for electronic devices is built comprising at least two fan sinks thermally coupled together such that when one fan sink fails, the remaining fan sinks are able to compensate for the failed fan sink. Optionally, the remaining fan sinks may be controlled to speed up upon detection of a failure, increasing their cooling capacity to compensate for the failed fan sink. Also optionally, a thermal coupling device such as heat pipes may be used as part of the thermal coupling between the fan sinks to increase the cooling efficiency of the remaining fan sinks to the device or devices closest to the failed fan sink. Also optionally, the thermal coupling device may be configured to allow some flexibility in the cooling device assembly allowing for the cooling of non-coplanar electronic devices.  
         [0006]     Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]      FIG. 1  is a front view of a redundant fan sink design including heat pipes according to the present invention configured to cool a single electronic device.  
         [0008]      FIG. 2  is a front view of a redundant fan sink design including heat pipes and a double fan sink according to the present invention configured to cool multiple electronic devices.  
         [0009]      FIG. 3  is a front view of a redundant fan sink design including flexible heat pipes according to the present invention configured to cool multiple electronic devices.  
     
    
     DETAILED DESCRIPTION  
       [0010]      FIG. 1  is a front view of a redundant fan sink design including heat pipes according to the present invention configured to cool a single electronic device. In this example embodiment of the present invention a heat sink is built including two fan sinks. Other embodiments of the present invention may include any number of additional fan sinks to the two shown in  FIG. 1 . An electronic device  104  that generates heat is thermally and mechanically coupled to a heat spreader  100 . In this example embodiment of the present invention, the heat spreader  100  includes at least one heat pipe  102  to increase the efficiency of the heat spreader  100  in eliminating hot spots over the electronic device  104 . Other embodiments of the present invention may not require the use of heat pipes. A first fan sink  106  comprising a first heat sink  112  surrounding a first fan is thermally and mechanically coupled to the heat spreader  100 . The first fan includes a first motor  108  and first fan blades  110 . A second fan sink  114  comprising a second heat sink  120  surrounding a second fan is also thermally and mechanically coupled to the heat spreader  100 . The second fan includes a second motor  116  and second fan blades  118 . In this example embodiment of the present invention, a single fan sink is sufficient to cool the electronic device  104 , however two fan sinks are used for greater cooling. When one fan sink fails, the remaining fan sink is sufficient to keep the temperature of the electronic device  104  within design limits.  
         [0011]      FIG. 2  is a front view of a redundant fan sink design including heat pipes and a double fan sink according to the present invention configured to cool multiple electronic devices. In this example embodiment of the present invention a heat sink is built including a double fan sink. Those of skill in the art will recognize that a wide variety of fan sinks with multiple fans may be build within the scope of the present invention. While this embodiment of the present invention shows a double fan sink, any number of fans may be used within a single surrounding heat sink within the scope of the present invention. Other embodiments of the present invention may include any number of additional fan sinks to the single double fan sink shown in  FIG. 2 . A first electronic device  200  and a second electronic device  202  that generate heat are thermally and mechanically coupled to a heat spreader  100 . Those of skill in the art will recognize that heat spreaders may be made out of a wide variety of materials, including aluminum and copper, within the scope of the present invention. In this example embodiment of the present invention, the heat spreader  100  includes at least one heat pipe  102  to increase the efficiency of the heat spreader  100  in eliminating hot spots over the electronic devices  200 ,  202 . Other embodiments of the present invention may not require the use of heat pipes, or may use other equivalent thermally conductive devices. A double fan sink  106  comprising a double wide heat sink  112  surrounding a first fan and a second fan is thermally and mechanically coupled to the heat spreader  100 . The first fan includes a first motor  108  and first fan blades  110 . The second fan includes a second motor  116  and second fan blades  118 . In this example embodiment of the present invention, a single fan is sufficient to cool the electronic devices  200 ,  202 , however two fans are used for greater cooling. When one fan fails, the remaining fan is sufficient to keep the temperature of the electronic devices  200 ,  202  within design limits.  
         [0012]      FIG. 3  is a front view of a redundant fan sink design including flexible heat pipes according to the present invention configured to cool multiple electronic devices. In this example embodiment of the present invention a heat sink is built including two fan sinks. Other embodiments of the present invention may include any number of additional fan sinks to the two shown in  FIG. 3 . A first electronic device  300  and a second electronic device  302  that generate heat are thermally and mechanically coupled to a first heat spreader  304 , and a second heat spreader  306  respectively. The first and second heat spreaders  304 ,  306  include at least one heat pipe  308  thermally coupling the first and second heat spreaders  304 ,  306 . A first fan sink  310  comprising a first heat sink  312  surrounding a first fan is thermally and mechanically coupled to the first heat spreader  304 . The first fan includes a first motor  316  and first fan blades  314 . A second fan sink  318  comprising a second heat sink  320  surrounding a second fan is thermally and mechanically coupled to the second heat spreader  306 . The second fan includes a second motor  324  and second fan blades  322 . In this example embodiment of the present invention, a single fan sink is sufficient to cool the electronic devices  300 ,  302 , however since the two electronic devices are non-coplanar two separate heat spreaders are used. These two heat spreaders are thermally coupled with a thermal coupling device  308  such that when one fan sink fails, the remaining fan sink is sufficient to keep the temperature of the electronic devices  300 ,  302  within design limits by transferring heat from the heat spreader of the failed fan sink to the heat spreader of the working fan sink. In this example embodiment of the present invention a heat pipe is shown as the thermal coupling device  308 , however, many other thermal coupling devices such as carbon fiber, a heat conducting fabric, copper straps or braids, or other equivalent thermally conductive materials. In some example embodiments of the present invention, one or more fans may remain idle until a fan failure is detected, and only activated at that time.  
         [0013]     In this example embodiment of the present invention a controller  326  is included to control fan speed of the fan sinks. A first fan detector  328  is used to detect proper operation of the first fan sink  310  and a second fan detector  330  is used to detect proper operation of the second fan sink  318 . Those of skill in the art will recognize that there are numerous ways to detect proper operation of the fans. Thermocouples may be used to detect rising temperatures in the heat sinks. Some fans include fan speed outputs that may be used to determine proper operation of the fans, and also to determine fan speed. Even something as simple as a switch that is pushed to one state by the airflow of a properly operating fan, and releases to a second state when the airflow is insufficient may be used to detect proper fan operation. In the present invention, “fan detector” is used as a generic term to describe any device capable of detecting failure of a fan.  
         [0014]     In this example embodiment of the present invention, the controller  326  includes a first output  336  configured to control the fan speed of the first fan, and a second output  338  configured to control the fan speed of the second fan. The controller  326  receives fan failure information from the first fan detector  328  through a first input  332  and the second fan detector  330  through a second input  334 . When one of the fans fails the controller  326  uses the fan failure information to raise the fan speed of the working fans to compensate for the failure. Also note that this controller  326  and its associated hardware may be used in embodiments similar to those shown in  FIGS. 1 and 2  if desired.  
         [0015]      FIG. 4  is a flow chart of a method for cooling heat-generating devices according to the present invention. The method starts at a step  400 . At a step  402 , at least one heat spreader is provided. At a step  404 , the heat-spreaders are thermally coupled to heat generating devices. At a step  406 , at least two fan sinks or at least one double fan sink are provided. At a step  408 , the fan sinks are thermally coupled to the heat spreaders. At an optional step  410 , a thermal coupling device, such as a heat pipe or copper braid, is provided. At an optional step  412 , the thermal coupling device is thermally coupled to the heat spreaders. At an optional step  414 , a fan detector is provided for each fan. At an optional step  416 , a controller similar to that of  FIG. 3  is provided. At an optional step  418 , the controller checks the fan detectors for evidence of fan failures. At an optional decision step  420 , if no failures are detected control returns to step  418 . If a failure is detected, at an optional step  422 , power to the failed fan is turned off, and in an optional step  424  the speed of the remaining working fans is increased or idle fans are activated. Optionally, at this point control may be returned to step  418  or the method ends at a finish step  426 .  
         [0016]     The foregoing description of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and other modifications and variations may be possible in light of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and various modifications as are suited to the particular use contemplated. It is intended that the appended claims be construed to include other alternative embodiments of the invention except insofar as limited by the prior art.