Abstract:
An air bearing assembly includes a split bearing with a first portion and a second portion configured to join and form a female tapered section with distal ends of a larger diameter than a joining central portion. A shaft with a male section including distal ends of a larger diameter than a central portion mates with the female tapered section formed by the joined split bearing. In order to provide adequate lubrication, support, and cooling, one or more an passages in the split bearing fluidly communicates a supply of pressurized air to the shaft. The air pressure provides a cushion of air for the shaft to float on during operation.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims a benefit of priority based on Provisional Patent Application No. 61/862,397 filed Aug. 5, 2013, the entire contents of which are hereby expressly incorporated by reference into the present application. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates in general to the field of turbochargers. More particularly, the present invention relates to lubrication of turbochargers. 
         [0004]    2. Discussion of the Related Art 
         [0005]    Internal combustion engines operate as an pumps. That is to say, they draw in air, combine it with fuel, and produce energy. This energy is realized as power when the air-fuel mixture is ignited. Afterward, the waste created by the combustion is expelled. All of this is typically accomplished in four strokes of the pistons. 
         [0006]    As internal combustion engines are not perfectly efficient, there is always an amount of wasted energy that is expelled with the exhaust. Turbochargers harness some of the wasted energy by fitting more air into the engine&#39;s combustion chambers, which may then be combined with more fuel, and creates a greater amount of power. The turbocharger accomplishes this task by compressing the air molecules so that the air the engine draws in is more dense. 
         [0007]    A turbocharger uses the hot, expanding exhaust gases leaving the engine after combustion. These gases are routed directly to the turbine wheel side of the turbocharger to make it rotate. That turbine wheel is connected by a shaft to a compressor wheel. As the turbine wheel spins faster and faster, it causes the compressor wheel, and shaft, to also spin quickly. The rotation of the compressor wheel pulls in ambient air and compresses it before pumping it into the engine&#39;s combustion chambers. The compressor wheel, shaft, and turbine rotate at speeds up to 150,000 rpm. 
         [0008]    Fluid bearings are commonly required within the turbocharger to prevent failure of the shaft at such high rotation speeds. The fluid bearings support the shaft on a layer of oil that is pumped around the shaft, cooling it and preventing friction. The fluid bearings typically employ a bronze material, forming a journal surrounding the shaft. In recent times, ball bearings have become more prevalent. Use of ceramics and high temperature alloys has made ball bearings more prevalent in turbochargers. Ball bearings reduce the contact area the shaft and bearing have, reducing friction. As there still is an element of friction, oil is commonly used as a lubricant for any turbocharger, regardless of the bearing type. 
         [0009]    Some systems utilize a sealed oil to lubricate the turbocharger. More commonly, the engine&#39;s oil ,system is plumbed into the turbocharger&#39;s bearings to provide lubrication. Oil is commonly used as oil technology provides a low-cost friction reducing material that can withstand the temperatures and pressures of exhaust gases produced by an internal combustion chamber and withstand rotational speeds up to 150,000 rpm. 
         [0010]    The use of oil is not, however, without its drawbacks. The shaft still comes in contact with the bearings, even if they are ball bearings. Oil&#39;s lubrication properties break down after use and exposure to the harsh environments of an internal combustion engine. This requires repeated maintenance of draining and filtering the oil. Oil is also an expensive commodity that has risen in price over recent decades. 
         [0011]    What is therefore needed is an improved lubrication device that can withstand the volatile environments a turbocharger produces, while offering proper cooling and lubrication to a turbocharger&#39;s bearings. An additional need is for a turbocharger bearing that further reduces the friction a shaft is subjected to. Lastly, the lubrication would preferably be renewable, low cost, and readily available to all turbo-charging enthusiasts. 
       SUMMARY AND OBJECTS OF THE INVENTION 
       [0012]    The preferred embodiments disclosed herein relate to lubrication and cooling of a turbocharger&#39;s shaft. Pressurized air may be supplied to a split bearing through air passages. The shaft may then ride on a cushion of air without making any contact on frictional surfaces within the turbocharger&#39;s cartridge. 
         [0013]    An air bearing assembly may include a split bearing with a first portion and a second portion configured to join and form a female tapered section with distal ends of a larger diameter than a joining central portion. A shaft with a male section including distal ends of a larger diameter than a central portion may mate with the female tapered section formed by the joined split bearing. In order to provide adequate lubrication, support, and cooling, a plurality of air passages in the split bearing may fluidly communicate a supply of pressurized air to the shaft. The air pressure provides a cushion of air for the shaft to float on during operation. 
         [0014]    The air bearing may further include a bearing housing with a first spring chamber configured to receive a first spring. The first spring applies a pressure to the first portion of the split bearing against the male section of the shaft. A second spring chamber may also be provided in the bearing housing and configured to receive a second spring. The second spring may apply a pressure to the second portion of the split bearing against the male section of the shaft. 
         [0015]    The bearing housing may include a first half configured to removably attach to a second half encasing the split bearing and the shaft in a central portion of the housing. 
         [0016]    These and other aspects and objects of the present invention will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following description, while indicating preferred embodiments of the present invention, is given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0017]    A clear conception of the advantages and features constituting the present invention, and of the construction and operation of typical mechanisms provided with the present invention, will become more readily apparent by referring to the exemplary, and therefore non-limiting, embodiments illustrated in the drawings accompanying and forming a part of this specification, wherein like reference numerals designate the same elements in the several views, and in which: 
           [0018]      FIG. 1  illustrates an isometric view of a turbocharger air bearing housing according to the preferred embodiment; 
           [0019]      FIG. 2  illustrates cross sectional view of the bearing housing along section A-A according to  FIG. 4 ; 
           [0020]      FIG. 3  illustrates a cross sectional view along section  13 - 13  according to  FIG. 4 ; 
           [0021]      FIG. 4  illustrates an end view showing hidden lines of a bearing assembly within the bearing housing of  FIG. 1 ; 
           [0022]      FIG. 5  illustrates an isometric view of the air bearing and shaft of the air bearing housing in  FIG. 1 ; and 
           [0023]      FIG. 6  illustrates a side, end, and section view along section A-A of the air bearing within the bearing housing of  FIG. 1   
       
    
    
       [0024]    In describing the preferred embodiment of the invention which is illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, it is not intended that the invention be limited to the specific terms so selected and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar purpose. For example, the words “connected”, “attached”, or terms similar thereto are often used. They are not limited to direct connection but include connection through other elements where such connection is recognized as being equivalent by those skilled in the art. 
       DETAILED DESCRIPTION OF EMBODIMENTS 
       [0025]    The present invention and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments described in detail in the following description. 
         [0026]    The inventive air hearing utilizes a split bearing to provide a cushion of pressurized air to a turbocharger&#39;s shaft. The air pressure cools the shaft and provides for a near-frictionless journal. 
         [0027]    Beginning with  FIG. 1 , a turbocharger cartridge  8  is shown with the inventive air bearing assembly. Externally, the cartridge  8  appears similar to a conventional turbocharger except for an inlet fitting  28  protruding from the side of a housing second half  16 . Air inlet fitting  28  provides access to the air bearing assembly, described in  FIGS. 2-6 , through one or more air inlets  30 . A housing  12  is split into two halves, a housing first half  14  and the housing second half  16 . The split housing  12  provides access to the internals of the cartridge  8 , specifically the air bearing assembly. Housing fasteners  18  hold the respective housing halves  14 ,  16  together, sealing the air bearing assembly within. Extending through the central aids of the housing  12  is a shaft  10  that may support a compressor wheel (not pictured) on the compressor side  24  and also a turbine (not pictured) on the turbine side  20 . A. back plate  26  provides a sealing surface for a compressor housing (not pictured) which may be machined to match the particular compressor wheel used. The back plate  26  may be sized to any standard size to accommodate any compressor wheel and compressor housing combination. On the turbine side  20 , a heat shield  22  is provided to help shield away heat from exhaust gases that pass through the turbine. Just as with the compressor side  24 , the turbine side  20  may accommodate any turbine wheel and turbine housing combination. The compressor housing and turbine housings may attach to the cartridge  8  with any known attachment means including, but not limited to, snap rings, bolts, band clamps, and v-band fasteners. 
         [0028]    Moving on to  FIG. 2 , a cross sectional view of the cartridge  8  is shown about section line A-A, which is referenced in  FIG. 4 . The section bisects the cartridge  8  into two equal halves. In operation, pressurized air is supplied to air inlet fitting  28 . Pressurized air may originate from any source, but is preferably supplied by an air compressor (not pictured) mounted in or proximate the engine bay. The air compressor may be powered by the engine through electric energy generated by an alternator, a battery, or directly off the crankshaft of the engine. 
         [0029]    The pressurized air enters the air inlet fitting  28  and travels through an orifice in a second spring chamber  38 . The pressurized air then passes through a series of split bearing air passages  44  and surrounds the shaft taper section  50 . Similarly, an additional air outlet fitting  32  may also supply pressurized air through a first bearing insert  46  and through the split bearing an passages  44  of the split bearing  34 . A first bearing spring  40  is retained in a first spring chamber  36  and a second bearing spring  42  is retained in a second spring chamber  38 . The first and second bearing springs  40 ,  42  exert pressure against the split bearing  34  to push the split bearing first half  52  and the split bearing second half  58  against the shaft taper section  50  of the shaft  10 , see  FIG. 6 . Once sufficient air pressure is built up, the air pressure between the shaft taper section  50  and the split bearing  34  pushes the split bearing  34  away from the shaft taper section  50 . At this point, the shaft is supported on a cushion of air, producing near-zero friction. When the air pressure falls below the sufficient amount, the first bearing spring  40  and second bearing spring  42  push the split bearing  34  against the shaft taper section  50  to provide support to the shaft. Preferably, whenever the engine is operating at sufficient loads to rotate the shaft  10 , the air compressor is supplying sufficient air pressure to the split bearing  34  to produce a cushion of air, preventing any rotational contact between the shaft  10  and the split bearing  34 . Some rotational contact between the shaft  10  and the split bearing  34  may occur during start up and shut down of the engine, however the split bearing  34  may be constructed out of a material such as oil impregnated brass or any other known bearing material that can withstand this type of friction. 
         [0030]    Transitioning to  FIGS. 3 and 4 , a cross sectional view of the cartridge  8  is shown about section line B-B in  FIG. 3  (referenced in  FIG. 4 ), while  FIG. 4  shows a side view of the cartridge  8  from the compressor side  24 . The housing  12  is disassembled in this view by removing housing fasteners  18 , see  FIG. 1 , and exposing the housing fastener holes  54 . The housing first half  14  is essentially a mirror image of the housing second half  16 , see  FIG. 4 , except the housing fastener holes  54  on the housing second half  16  are counter bored for fastener heads. 
         [0031]    The split bearing first half  52  includes distal ends  64  and a central portion  62 . A female taper  60  is formed in the split bearing first half  52  and receives the shaft taper section  50  of the shaft  10 . The split bearing second half  58  is similarly shaped and rests in the housing second half  16 , as shown in  FIG. 4 . The split bearing first and second halves  52 ,  58  are formed such that the female taper  60  includes distal ends  64  that are of a larger diameter than the central portion  62 . The shaft taper section  50  is also formed with a similar taper, and fits within the female taper of the split bearing first half  52  and split bearing second half  58  when the housing  12  is assembled. 
         [0032]    As mentioned with respect to  FIG. 1 , the back plate  26  may support a compressor housing while a compressor wheel may be attached to the compressor side  24  of the shaft  10 . Similarly, a turbine housing may be attached to the turbine side  20  of the housing and a turbine may be attached to the turbine side  20  of the shaft  10  to complete the turbocharger assembly. 
         [0033]    The split bearing  34 , the housing  12 , and the entire air bearing assembly is shown in phantom. The shaft  10  is supported about the central axis of the housing  12 . The split bearing first half  52  and split bearing second half  58  are pressed against the shaft  10  by the first bearing spring  40  and the second bearing spring  42 , respectively. When the split bearing first half  52  and split bearing second half  58  are joined together within the housing first half  14  and the housing second half  16 , a gap  74  remains between the respective split bearing halves  52 ,  58 . 
         [0034]    While the air inlet fitting  28  and air outlet fitting  32  may provide pressurized air to the split bearing first half  52  and split bearing second half  58  any combination of air outlet  76  and air inlets  30  may be used to supply pressurized air or to bleed out pressurized air and control pressure with a regulator. Additionally, any style of air fitting may be used as the air outlet fitting  32  and air inlet fitting  30 . The fittings may also include any amount of air inlets  30  and air outlets  76 . 
         [0035]      FIG. 5  shows the shaft  10  and the split bearing  34  removed from the housing  12 . The split bearing first half  52  is symmetrical and a mirror image of the split bearing second half  58 . On one side of each split bearing half a split bearing air inlet/outlet  66  allows for air to both enter and exit the female taper  60  through split bearing air passages  44 . As previously mentioned, the air passages  44  provide a pathway for pressurized air to be supplied to the distal ends  64  and central portion  62  of the female taper  60  of the split bearing  34 . The pressurized air supports the shaft taper section  50  of the shaft  10  which in turn floats the shaft on a cushion of air while the shaft rotates in operation. The shaft taper section  50  and the female taper  60  of the split bearing  34  prevents axial movement of the shaft  10 . Typically, a thrust bearing is needed for turbocharger shafts for any axial forces. The dual taper on the distal ends of the split bearing provide axial forces in both directions to effectively cancel out any axial forces and ensure the shaft  10  remains in place. 
         [0036]    Moving on to  FIG. 6 , the sides and end of the split bearing first half  52  is shown. Note that the split bearing second half  58  is essentially the same as the split bearing first half  52 . The air inlet/outlet side  68  shows the split bearing air inlet/outlet  66  and the female taper  60  is shown in phantom. It can be seen that the split bearing air passages  44  are angled such that they are normal to the female taper  60  surface. Looking at the female taper side  70 , the distal ends  64 , central portion  62 , and split bearing air passages  44  are shown. The distal ends  64  of the female taper  60  are preferably of a larger diameter than the central portion  62 . While the shape of the taper may vary to include any shape, a dual tapered design provides axial stability, as previously discussed. 
         [0037]    Looking at the distal side of the split bearing first half  52  a recess  72  is included on the surface of the split bearing first half  52 . This recess from the vertical allows for expansion of the split bearing  34  as temperature rises and prevents the split bearing first half  52  from binding against the split bearing second half  58 . The split bearing air inlet/outlet  66  provides a path for pressurized air to flow through the split bearing passages  44  and into the central portion  62  of the female taper  60  to support, cool, and lubricate the shaft  10 . 
         [0038]    Although the best mode contemplated by the inventors of carrying out the present invention is disclosed above, practice of the present invention is not limited thereto. It will be manifest that various additions, modifications and rearrangements of the features of the present invention may be made without deviating from the spirit and scope of the underlying inventive concept. 
         [0039]    Moreover, the individual components need not be formed in the disclosed shapes, or assembled in the disclosed configuration, but could be provided in virtually any shape, and assembled in virtually any configuration. Furthermore, all the disclosed features of each disclosed embodiment can be combined with, or substituted for, the disclosed features of every other disclosed embodiment except where such features are mutually exclusive. 
         [0040]    It is intended that the appended claims cover all such additions, modifications and rearrangements. Expedient embodiments of the present invention are differentiated by the appended claims.