Abstract:
A cooling apparatus for heat generating devices such as semiconductor chips comprises a parallel disk fan in the middle of a set of heat sink fins. The parallel disk fan has radial elements placed between the disks to efficiently create air flow without turbulence. Cooling efficiency is further enhanced when heat dissipation through the parallel disks of the fan is introduced.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to cooling devices for devices that generate heat such as semiconductor chips, and particularly, to an apparatus that improves the capability and reliability of cooling devices for semiconductor chips. The invention is in the field of heat transfer and cooling of semiconductor chips used in computers and telecommunication equipment. 
   2. Description of the Prior Art 
   As the power of semiconductor chips increases, more efficient cooling device for semiconductor chips is therefore required. Current known cooling solutions have drawbacks in providing an adequate cooling to chips in small spaces and, drawbacks in lowering acoustic noise. For instance, U.S. Pat. Nos. 5,297,617, 5,309,983, and 5,445,215 each describe methods of using miniature “muffin fans” with multi-bladed propellers that drive cooling air toward heat collector fins at the periphery. These muffins fans tend to be nosier because the air is stirred up and pushed to the heat collector fins. U.S. Pat. No. 5,419,679 teaches a method using parallel disks to create air flow to draw air through an opening in an attached chassis for cooling electronic devices. U.S. Pat. No. 5,335,143 teaches a method using parallel disks between fins of a heat exchanger to provide cooling of chips. The arrangement is rather bulky, however, with only a small portion of a disk pumping air at any given time. U.S. Pat. No. 5,794,687 teaches a method of placing parallel disks in close fitting slots formed in a heat conducting housing. Methods of ducting incoming and outgoing air are additionally described. 
   U.S. Pat. No. 5,388,958 describes a “bladeless impeller” consisting of a plurality of disks and introduces a mechanism to transfer heat to the impeller shaft. However, the device needs to be positioned adjacent to an element to provide a complimentary surface to the disks to define a space in which pressure drop would occur on the operation of the impeller. U.S. Pat. No. 6,503,067 teaches a method using parallel disks to create laminar air flow for intake into an Internal combustion engine. 
   It would be highly desirable to provide a cooling apparatus for heat generating devices such as semiconductor chip devices that obviates the aforementioned deficiencies in the prior art. 
   SUMMARY OF THE INVENTION 
   The present invention relates to a cooling apparatus for heat generating devices such as semiconductor chips and devices, e.g., in computers and telecommunications equipment. 
   The apparatus includes a plurality of parallel disks that rotate at the center of a set of heat transfer fins and periodic radial elements placed between disks to generate air flow more efficiently while maintaining the air stream less turbulent. The air leaving the edge of the parallel disks as the disks rotate is more easily directed into the surrounding heat transfer fins. This arrangement of rotating disks creates air flow more efficiently. Furthermore, an array of heat pipes carrying heat from the source to the rotating disks increases the surface area of heat dissipation, leading to more efficient cooling. Additionally provided is a mechanism of transferring heat from a heat generating device to the rotating disks. 
   Thus, according to the invention, there is provided a cooling apparatus comprising: a fan means for creating a smooth, less turbulent air flow including a plurality of disk fan elements spaced apart in a stack configuration and adapted for rotation to create an air flow; multiple heat sink means surrounding the plurality of disk fan elements; a heat distribution means for receiving heat generated from a heat generating device; and, a plurality of heat pipe elements communicating with the heat distribution means and the multiple heat sinks, the heat distribution means and heat pipe elements transferring heat from a heat generating device for distribution to the heat sinks, wherein the plurality of disk fan elements are rotated to create efficient air flow in an outward direction such that heat is uniformly eliminated from the surrounding multiple heat sink means. 
   In a further embodiment, the cooling apparatus further comprises a heat transfer means for transferring additional heat from the heat distribution block to one or more of the plurality of disk fan elements. 
   Still in a further embodiment, the plurality of disk fan elements may be mounted on a hollow shaft whereby a motor drive means for rotating the shaft is integrated in the shaft. Further, the hollow shaft is configured to include a plurality of air slots located along a length of the shaft for permitting air to pass through the shaft as the shaft rotates and exit the formed air gaps. Thus, further cooling efficiency is enhanced as heat is dissipated through the parallel disks of the fan. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The objects, features and advantages of the present invention will become apparent to one skilled in the art, in view of the following detailed description taken in combination with the attached drawings in which: 
       FIG. 1  depicts a three-dimensional (3-D) view of a cooling device with a parallel disk fan in the middle according to the invention; 
       FIG. 2(   a ) depicts a top view of the cooling device with a parallel disk fan of the invention, and,  FIG. 2(   b ) depicts a cross-sectional view of the cooling device when taken along section ‘A-A’ of  FIG. 2(   a ); 
       FIG. 3  depicts a 3-D view of an active cooling device according to a further embodiment of the invention 
       FIG. 4(   a ) depicts a top view of the cooling device with a parallel disk fan according to a further embodiment of the invention, and,  FIG. 4(   b ) depicts a cross-sectional view of the cooling device when taken along section ‘A-A’ of  FIG. 4(   a ); 
       FIGS. 5(   a ) and  5 ( b ) depict the detailed mounting of heat pipes to the parallel disks according to the embodiment of the invention depicted in  FIGS. 4(   a ),  4 ( b ); 
       FIGS. 6(   a ) and  6 ( b ) depict two different embodiments respectively, of the parallel disk fan in the cooling device with a flat parallel disk configuration as shown  FIG. 6(   a ) and a corrugated disk configuration as shown in  FIG. 6(   b ); and, 
       FIGS. 7(   a )- 7 ( c ) each depict an implementation of the parallel disk fan using a hollow shaft integrated with an electric motor according to the invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  depicts generally, the cooling device of the present invention. As shown in  FIG. 1 , the cooling device includes a plurality of ring-shaped heat sink fins  51  oriented parallel in a stacked configuration with a gap  57  between each ring-shaped heat sink fin, a plurality of circular disk fans  41  oriented parallel in a stacked configuration and coaxial with the plurality of ring-shaped heat sink fins  51 , the plurality of stacked circular disk fans  41  being mounted for rotation within the stacked plurality of circular heat sink fins  51  via a shaft under motor control  21 . As shown in  FIG. 1 , and described in greater detail herein, the plurality of heat sink fins  51  are in communication with a structure comprising heating pipe elements  33   a , . . . ,  33   d  interconnected with a heat distribution block  31  that receives and distributes heat generated by a semiconductor chip to the heat sink fins. Preferably, as shown in  FIG. 1 , the parallel circular disk fans  41  each include radial elements  43  between disks  41  in the middle of the set of circular parallel-stacked heat sink fins  51 . More specifically, the parallel disk fans include a plurality of disks  41  stacked in parallel on a shaft of an electric motor  21  and the disks  41  are separated by the radial elements  43  such that many air gaps are formed between disks  41 . When the parallel disks  41  are rotated by the electric motor  21 , a centrifugal force is generated that drives the air in the air gaps to move outward and, hence, a steady stream of less turbulent air is generated. Air comes into the fan from the both sides of fan inlets  42  provided near the center of the parallel disk unit  41  as shown in  FIGS. 1 and 2(   a ). 
   Particularly,  FIG. 2(   a ) depicts a top view of the cooling device with a parallel disk fan of the invention, and,  FIG. 2(   b ) depicts a cross-sectional view of the cooling device when taken along section ‘A-A’ of  FIG. 2(   a ). The cross-sectional view of  FIG. 2(   b ) particularly details the structure comprising the heating pipe elements, e.g., two elements  33   a ,  33   b , which are L-shaped and interconnect the heat distribution box  31  with the parallel-stacked heat sink fins  51 . Located above heat distribution block  31  is the motor  21  and the motor shaft  23  extending upward therefrom that rotatably support the parallel circular disk fans  41 . With more particularity, as shown in  FIG. 2(   a ), each parallel circular disk fan  41  is supported by arm members  44  which are mounted on the motor shaft  23 . The set of radial elements  43  is placed between disks  41  with three (3) shown in  FIGS. 1 and 2(   a ). It is understood however, that the number and the shape of the radial elements  43  as well as the spacing distance between disk fans  41  may vary. The diameter of the parallel disks may range anywhere from about 25 mm to 200 mm. The number of radial members separating two adjacent disks may range between three (3), as shown in the  FIG. 1 , to fifteen (15). The radial members can be straightly radial, forward inclined, or backward inclined. The shape of the radial members is preferred to be aerodynamically aligned with the air stream, and may include a circular (rounded) or elliptic shape. 
   Further, as shown in  FIG. 2(   a ), the multiple heat sink fins  51  that form a ring have an inner diameter that is larger than the diameter of the rotating circular disk fans  41  leaving a small gap  49 , e.g., ranging between 0.05 mm to 5 mm, between the fans and the heat sink fins  51  such that the parallel disks  41  can be rotated freely to generate air streams which are forced to pass through the heat sink fin gaps  57  (shown in  FIG. 1) , that may range, for example, between 0.2 mm to 3 mm. The heat sink fins  51  are additionally separated by spacer elements  52   a ,  52   b  to result in gaps  57  and may be soldered, brazed, or glued to the corresponding spacer elements  52   a ,  52   b  which have heat pipe elements  33  inserted therein. The exemplary heat sink fins  51  in  FIG. 2(   b ) have four sections and each has its designated spacers and heat pipes labeled as  52   a ,  52   b ,  52   c ,  52   d , and  33   a ,  33   b ,  33   c ,  33   d , respectively, however, it should be understood that the number of the heat sink fins, spacers, and heat pipes may be varied and should not be limited to four (4) as shown in the figures. As mentioned, the lower end of each heat pipe  33  is inserted into the heat distribution block  31  that is to be placed on a heat generating semiconductor chip (not shown). 
   In operation, heat generated in the semiconductor chip are collected by heat distribution block  31  and transferred by the heat pipes  33  and distributed to the heat sink fins  51 . The air stream driven by the parallel disk fans  41  pass through the air gap  57  between the heat sink fins  51  and carry away the heat from the semiconductor chip. While the number of disk fans  41  may vary, i.e., are not limited to seven (7) fins as shown in  FIG. 2(   b ), the heat sink fin spacers  52  are stacked closely up along the heat pipes  33  such that heat can be distributed evenly to all the heat sink fins  51 . Preferably, the distance between adjacent disks may range between 0.2 mm to 3 mm and the distance between adjacent fins  51  additionally ranges from 0.2 mm to 3 mm. It is understood however, that the distance between adjacent disks does not have to match the distance between adjacent fins. 
   It should be understood that in accordance with each of the embodiments of the invention depicted herein, the amount of air flow generated by the parallel disk fan depends primarily upon the rotational speed of the disks, the diameter of the disks, the spacing between disks, and the number of the radial elements  43  between disks  41 . The range of the rotational speed may range between about 100 rpm to 10,000 rpm, for example. 
     FIG. 3  depicts a 3-D view of an active cooling device according to a further embodiment of the invention. Particularly, in the embodiment depicted in  FIG. 3 , the active cooling device of  FIG. 1  is provided with a heat transfer mechanism  110  attached to the parallel disk fan such that the disks are also used to dissipating heat to the air streams. The active cooling device has a set of parallel disks  41  coaxial therewith and functioning as a fan for the surrounding plurality of heat sink fins  51 . The parallel disks  41  are mounted on the shaft of an electric motor  21  that rotates the disks  41  to generate air streams. Air streams coming in from the top and bottom of the fan inlets  42  are driven out from the edge of the disks toward the heat sink fins  51  and will pass through the fin gaps  57 . The heat transfer mechanism  110  in the device includes heat pipes connecting with one or more of the parallel disks  41  to transfer heat to the connected discs while allowing them to rotate freely to generate air streams. 
   The details of the heat transfer mechanism  110  are now described herein with respect to  FIGS. 4(   a ) and  4 ( b ). Particularly,  FIG. 4(   a ) depicts a top view of the cooling device with a parallel disk fan according to a further embodiment of the invention, and,  FIG. 4(   b ) depicts a cross-sectional view of the cooling device when taken along section ‘A-A’ of  FIG. 4(   a ). It is understood that all elements except the heat transfer mechanism  110  are the same as included in the first embodiment described with respect to  FIGS. 1 and 2(   a )- 2 ( b ). The heat transfer mechanism  110  includes an outer stationary part comprising a fixed outer casing  12  and one inner cylindrical rotational part  11  located coaxially therewith that rotates with respect to the outer casing  12  that is hollowed for receiving heat from the heat distribution block  31 . Preferably, a cylindrical outer surface of the rotational part  11  is separated from the inner surface of the stationary part  12  by a narrow gap  17 , for example, ranging from about 0.01 mm to 1 mm. The cylindrical rotational part  11  is mounted on the shaft of the motor  21  such that the rotational part can be rotated freely within the stationary part  12 . The gap  17  is filled with thermally conductive lubricants such as Krytox lubricants from Dupont, or like equivalent, for conducting heat from the fixed outer casing to the rotating inner part. Suitable sealing mechanisms (not shown) are provided on the shaft of the rotational part  11  to protect the lubricants as is well known in the art. As further shown in  FIG. 4(   b ), there are two heat pipes  36   a  and  36   b  that connect between the fixed outer casing  12  and the heat distribution block  31  such that heat can be additionally transferred to the stationary part  12  from the heat distribution block  31 . It is understood that additional heat distribution pipes may communicate heat from the heat distribution block to the stationary part  12 . Further, heat transferred to the outer stationary part may then be transferred to the rotational part  11  through the intermediary of the thermally conductive lubricants. Heat is further transferred to the set of parallel disks  41  through the heat pipes  15   a ,  15   b  that are shown connecting the inner rotational part  11  to several disks  41  by suitable mounting means (such as shown herein with respect to  FIGS. 5(   a ) and  5 ( b )) and are rotatable therewith. Because of this heat transfer mechanism  110 , heat can now be distributed to the parallel disks and dissipated there while generating less turbulent air flows. 
     FIGS. 5(   a ) and  5 ( b ) depict alternate embodiments for mounting the heat pipes to the rotational disks  41 .  FIG. 5(   a ) particularly depicts the end portion of a heat pipe  15   b  that is bent at an upper end to lie in parallel to one of the disks near a radial member  43 . That portion of the heat pipe may be soldered, epoxied or otherwise equivalently attached to the disk  41  and the radial member  43  at location indicated as  46  in  FIG. 5(   a ). Additionally shown in  FIG. 5(   a ) is the attachment of a bent upper portion of heat pipe  15   a  attached between two disks in a gap  47  near radial member.  FIG. 5(   b ) illustrates another embodiment of the mounting method in which the end of the heat pipes,  315   a ,  315   b , and  315   c , are not bent. Rather, a solid metal extension  316  may be used to bridge the radial members  43  and the heat pipes as depicted in  FIG. 5(   b ). 
     FIG. 6  depicts two versions of the parallel disks, one is flat configuration as shown  FIG. 6(   a ) and the other is corrugated as shown in  FIG. 6(   b ). In the flat parallel disks version depicted in  FIG. 6(   a ), the disks are separated by the radial elements  43  between disks to create air gaps  47 . Air comes from the inlets  42  from both sides of the parallel disks. In the corrugated disks set depicted in  FIG. 6(   b ), the radial elements are not needed because of the corrugated nature of the disks  141 . Rather, the adjacent disks  141  are aligned in a way that the disks can be joined together at locations  149  and form air outlets  47  all around the disks. Thus, in the corrugated disk set, air comes from the inlets  142 . As shown in  FIG. 6(   b ), a trough  145  of the corrugated disk fan element is connected to a peak  146  of an immediately adjacent corrugated disk fan element to form the air channels  147  enabling a smooth air flow with less turbulence when the disk fans rotate. As shown in  FIG. 6(   b ), these air channels  147  are cone shaped. 
     FIGS. 7(   a )- 7 ( c ) depict another embodiment of the cooling device of the invention that utilizes a hollow shaft to hold the plurality of parallel disks with an electric motor integrated in the shaft with  FIG. 7(   c ) depicting a cross-sectional view of the cooling device when taken along section ‘A-A’ of  FIG. 7(   b ). As shown in  FIG. 7(   c ), each disk  241  of the parallel disk set is mounted on the hollow shaft  223  as indicated by disk mounting holes  246  where the disks  241  will anchor on the hollow shaft  223 . As further shown in  FIG. 7(   c ), at locations located between each disk anchor mount  246  of the shaft are air slots  248  that permit air to pass through the shaft. Returning to the exploded view of  FIG. 7(   a ), radial elements  243  are placed between the disks  241  as in the other embodiment described herein to form gaps  247  between each disks. In operation, as the shaft rotates, air will enter into the hollow shaft  223  from a top opening  242  ( FIG. 7(   a )), and pass through the air passing slots  248 , and will exit between disk gaps  247 . At one end of hollow shaft  223 , a magnetic ring  224  is provided that is supported by a shaft member  225 . The magnetic ring  224  has alternating magnetic poles (north and south) such that when an electric winding plate  221  is mounted beneath and energized, the magnetic ring  224  will be driven to rotate accordingly. The details of the windings in the electric winding plate  221  are not shown however, are similar to well-known brushless motor configurations. Control circuitry is provided that is similar to brushless motor devices as would be known to skilled artisans. 
   It is understood that the arrangement of rotating disks according to the invention, creates a more turbulent-free air flow, and accordingly increases heat transfer efficiencies. 
   While there has been shown and described what is considered to be preferred embodiments of the invention, it will, of course, be understood that various modifications and changes in form or detail could readily be made without departing from the spirit of the invention. It is therefore intended that the invention be not limited to the exact forms described and illustrated, but should be constructed to cover all modifications that may fall within the scope of the appended claims.