Abstract:
A cooling assembly includes a housing supporting a nozzle for directing cooling air over an electronic component. A casing rotatably supports a shaft, which in turn, supports a compressor, an expander, and an electric motor, for circulating air and delivering the cooling air to the nozzle. The assembly is distinguished by air bearings supporting the shaft in the casing on a thin film of air, thereby maintaining a contaminate free housing.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The subject invention relates to a cooling assembly for cooling an electronic component with direct air. 
   2. Description of the Prior Art 
   The operating speed of computers is constantly being improved to create faster computers. With this, comes increased heat generation and a need to effectively dissipate that heat. 
   Heat exchangers and heat sink assemblies have been used that apply natural or forced convection cooling methods to dissipate heat from electronic devices that are highly concentrated heat sources such as microprocessors and computer chips. The most common method of cooling computer chips has been direct air cooling, which is adequate for the moderate thermal load generated by the chip. These heat exchangers typically use air to directly remove heat from the electronic devices; however air has a relatively low heat capacity. Thus, liquid-cooled units called LCUs employing a cold plate in conjunction with high heat capacity fluids have been used to remove heat from these types of heat sources. Although LCUs are satisfactory for moderate heat flux, increasing computing speeds have required more effective heat sink assemblies. 
   Accordingly, thermosiphon cooling units (TCUs) have been used for cooling electronic devices having a high heat flux. A typical TCU absorbs heat generated by the electronic device by vaporizing the working fluid housed on the boiler plate of the unit. The boiling of the working fluid constitutes a phase change from liquid-to-vapor state and as such the working fluid of the TCU is considered to be a two-phase fluid. The vapor generated during boiling of the working fluid is then transferred to a condenser, where it is liquefied by the process of film condensation over the condensing surface of the TCU. The heat is rejected into a stream of air flowing through a tube running through the condenser or flowing over fins extending from the condenser. Alternatively, a second refrigerant can flow through the tube increasing the cooling efficiency. The condensed liquid is returned back to the boiler plate by gravity to continue the boiling-condensing cycle. 
   In recent years the generation of higher thermal load is being handled by improving the chip design such that even with higher computing speeds the chip does not generate large amounts of heat. Thus, chip cooling can be handled by air cooling without having to resort to LCUs or TCUs. Although the prior art dissipates heat from electronic devices, as computing speeds increase, there is a continuing need for cooling assemblies having more efficient or alternative heat transfer capabilities as compared to the conventional electronic cooling assemblies. 
   SUMMARY OF THE INVENTION AND ADVANTAGES 
   The invention provides a cooling assembly for cooling an electronic component with direct air. The assembly includes a housing and at least one electronic component disposed in the housing. A nozzle is supported in the housing and directs cooling air over the electronic component. An open air cycle cooling unit is disposed in the housing and supplies the cooling air to the nozzle. The cooling unit includes a casing and a compressor rotatably supported by the casing for moving air. The assembly is distinguished by having air bearings that support the compressor in the casing on a thin film of air, thereby maintaining a contaminate free housing. 
   Accordingly, the subject invention provides an enhanced air cooling assembly. The open air cycle cooling unit is housed inside the computer case or housing, and enhances the cooling efficiency. With no oil introduced into the air stream, the open air cycle cooling unit is ideal for cooling electronic components. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
       FIG. 1  is a perspective view of the subject invention; 
       FIG. 2  is an schematic view of air being directed over an electronic chip in the subject invention; 
       FIG. 3  is a perspective view of a casing utilized for the air cycle cooling unit in the subject invention; 
       FIG. 4  is a side view of a thrust bearing utilized in the subject invention; 
       FIG. 5  is an exploded view of a thrust bearing utilized in the subject invention; 
       FIG. 6  is an exploded view of a journal bearing utilized in the subject invention; 
       FIG. 7  is a fragmentary end view partially broken away and in cross section of the journal bearing shown in  FIG. 6 ; and 
       FIG. 8  is a schematic of the air cycle cooling unit utilized in the subject invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, a cooling assembly  20  is generally shown for cooling an electronic component with direct air in  FIGS. 1-4 . 
   The subject invention comprises a housing  22  generally indicated which has a generally rectangular periphery that defines four corners  24 ,  26  (only the first and second of the four corners are numbered). The housing  22  is typically made of metal, but may be any other material known in the art. The housing  22  includes a housing bottom  28  and a housing top  30  with spaced and parallel side walls  32 ,  34 . The side walls  32 ,  34  are solid and extend between the housing bottom  28  and the housing top  30 . The housing  22  further includes opposite housing ends  36  and a longitudinal housing axis  38 . The housing bottom  28 , the side walls  32 ,  34 , and the housing top  30  extend axially between the housing ends  36  to define an air entrance  40  at one of the housing ends  36  and an air exit  42  at the other of the housing ends  36 . The air entrance  40  and air exit  42  allow for the flow of air through the housing  22 . 
   An entrance plate  44  is disposed at the air entrance  40 . The entrance plate  44  has a plurality of entrance apertures  46  for the flow of air through the air entrance  40 . The air entrance  40  is typically made of metal, but may be any other material known in the art. 
   An exit plate  48  is disposed at the air exit  42 . The exit plate  48  has a plurality of exit apertures  50  for the flow of air through the air exit  42 . The air exit  42  is typically made of metal, but may be any other material known in the art. 
   A first electronics box  52  is disposed at a first corner  24  adjacent a first side wall  32  and the air entrance  40  for providing electric signals to the assembly  20 . A second electronics box  54  is disposed at a second corner  26  adjacent the first side wall  32  and the air exit  42  for providing electric signals to the assembly  20 . 
   The assembly  20  further includes a plurality of electronic components disposed within the housing  22 . The electronic components including a mother board  56  disposed on the housing bottom  28 , a plurality of circuits  58  disposed on the mother board  56 , and a plurality of electronic chips  60  disposed on the mother board  56 . A plurality of cold plates  62  having a plurality of heat transfer fins  64  are disposed on the chips  60 . 
   The assembly  20  further includes an open air cycle cooling unit  66  generally indicated that is disposed in the housing  22  for cooling the air that cools the electronic components. The cooling unit  66  includes a plurality of fans  68  that are disposed side-by-side between the second electronics box  54  and a second side wall  34 . The fans  68  are parallel to the exit plate  48  and move air through the exit apertures  50  in the exit plate  48 . 
   The cooling unit  66  includes a heat exchanger  70  for cooling air. The heat exchanger  70  is disposed between and parallel to the plurality of fans  68  and the exit plate  48 . The heat exchanger  70  includes a heat exchanger inlet  72  and a heat exchanger outlet  74  for the flow of hot compressed air through the heat exchanger  70 . The cooling unit  66  further includes a casing  76  generally indicated having opposite casing ends  78  and a casing axis  80  extending parallel to the housing axis  38 . The casing  76  is supported on the housing bottom  28  between the plurality of fans  68  and the air entrance  40 . A shaft  82  is rotatably supported along the casing axis  80  between the casing ends  78 . 
   A compressor  84  is mounted on the shaft  82  at the one of the casing ends  78  nearer the air entrance  40 . The compressor  84  has a compressor inlet  86  and a compressor outlet  88  for establishing the flow of air through the heat exchanger  70 . An expander  90  is mounted on the shaft  82  at the one of the casing ends  78  nearer the air exit  42 . The expander  90  reduces the pressure of air that flows through the expander  90  and rotates the shaft  82 . The expander  90  has an expander inlet  92  and an expander outlet  94  for the flow of air through the expander  90 . An electric motor  96  rotates the shaft  82  and is disposed in the casing  76  between the compressor  84  and the expander  90 . 
   The cooling unit  66  further includes a nozzle  98  that distributes air over the cold plates  62 . The nozzle  98  includes a nozzle inlet  100  and a plurality of nozzle outlets  102  disposed over the cold plates  62 . 
   A first air tube  104  interconnects the compressor outlet  88  to the heat exchanger inlet  72  for the flow of air therebetween. A second air tube  106  interconnects the heat exchanger outlet  74  to the expander inlet  92  for the flow of air therebetween. A third air tube  108  interconnects the expander outlet  94  to the nozzle inlet  100  for the flow of air therebetween. 
   The subject invention is distinguished by air bearings  110 ,  112  that support the shaft  82  on a thin film of air and thus maintain a contaminate free air stream. The air bearings  110 ,  112  are self-actuated hydrodynamic air bearings  110 ,  112  and require no source of compressed air. The air bearings  110 ,  112  include a plurality of journal bearings  110  that support the radial load of the shaft  82  and a plurality of thrust bearings  112  that support the axial load of the shaft  82 . 
   As air enters the compressor inlet  86  air is compressed. The volume of the compressed air is reduced and the temperature increases. The hot compressed air exits the compressor outlet  88  into the first air tube  104  where it flows to the heat exchanger inlet  72 . The hot compressed air flows through the heat exchanger  70  where it is cooled by the fans  68 . The fans  68  move air through a plurality of spaced fins on the heat exchanger  70 . The cooled air exits the heat exchanger  70  through the heat exchanger outlet  74  into the second air tube  106  where it flows to the expander inlet  92 . The volume of the cooled air is expanded and the temperature of the cooled air is further reduced. The cooled air exits the expander outlet  94  into the third air tube  108  where it moves to the nozzle inlet  100 . The cooled air is distributed over the electronic component by the nozzle outlet  102  that is placed over the electronic component to be cooled. 
   The subject invention may include a water separator, which is generally located at the heat exchanger outlet  74 . The need of a water separator can be eliminated by controlling the temperature of the air coming out of the expander  90  just above the dew point temperature of the air entering the compressor  84 . The temperature can be controlled through the use of a controls system that monitors the temperature of the air exiting the expander  90 . 
   While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.