Patent Publication Number: US-2018030988-A1

Title: Bearings for a turbocharger

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This patent application claims the benefit of, and priority to, U.S. Provisional Patent Application Ser. No. 62/114,632, filed Feb. 11, 2015, the disclosure of which is expressly incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to support of a turbocharger shaft in a housing and, in particular, the use of bearings to support the shaft. 
     BACKGROUND 
     Some turbochargers may operate at rotational speeds of up to 350,000 rpm in certain applications. Low-friction bearings and adequate support of the shaft lead to efficient operation and long operational life of the turbocharger. It is therefore desirable to design turbocharger bearings to achieve the dual goals of high stability and low friction. 
     SUMMARY 
     The present invention may comprise one or more of the features recited in the attached claims, and/or one or more of the following features and combinations thereof. In a first example aspect, a turbocharger may comprise a turbocharger housing, a turbocharger shaft received within the turbocharger housing, a turbine wheel affixed to the turbocharger shaft at or adjacent to a first end thereof, a compressor wheel affixed to the turbocharger shaft at or adjacent to a second end thereof, the second end opposite the first end, a first bearing received on the turbocharger shaft between the turbine wheel and the compressor wheel, and a second bearing received on the turbocharger shaft between the first bearing and the compressor wheel. One of the first and second bearings may be floating relative to the turbocharger shaft and affixed to the turbocharger housing, and the other of the first and second bearings may be floating relative to the turbocharger shaft and floating relative to the turbocharger housing. 
     A second example aspect includes the subject matter of the first example aspect, and wherein the turbocharger housing defines therein a first boss and a second boss, the first bearing disposed in the first boss and the second bearing disposed in the second boss, the one of the first and second bearings affixed to the housing being prevented from rotating relative to the respective one of the first and second bosses. 
     A third example aspect includes the subject matter of the second example aspect, and wherein the turbocharger housing defines a turbine housing portion defining the first boss therein and a compressor housing portion coupled to the turbine housing portion and defining the second boss therein. 
     A fourth example aspect includes the subject matter of any of the first-third example aspects, and further comprises an electric machine having a rotor affixed to the turbocharger shaft between the first and second bearings. 
     A fifth example aspect includes the subject matter of the fourth example aspect, and wherein the electric machine includes a stator coupled to the rotor and mounted within the turbocharger housing. 
     A sixth example aspect includes the subject matter of any of the first-fifth example aspects, and wherein the second end of the turbocharger is threaded, and further comprising a threaded nut configured to engage the threaded second end of the turbocharger shaft to secure the compressor wheel to the turbocharger shaft. 
     A seventh example aspect includes the subject matter of any of the first-fifth example aspects, and wherein the compressor wheel is one of press fit onto the turbocharger shaft and welded to the turbocharger shaft. 
     An eighth example aspect includes the subject matter of any of the first-fifth and seventh aspects, and wherein the turbine wheel is one of press fit onto the turbocharger shaft and welded to the turbocharger shaft. 
     A ninth example aspect includes the subject matter of any of the first-eighth example aspects, and wherein the first and second bearings each define an inside diameter, and wherein the inside diameter of the first bearing is greater than the inside diameter of the second bearing. 
     A tenth example aspect includes the subject matter of either of the second and third example aspects, and wherein the first and second bosses are each concentrically formed. 
     In an eleventh example aspect, a turbocharger may comprise a turbocharger housing defining first and second bosses therein, a turbocharger shaft received within the turbocharger housing, a turbine wheel affixed to the turbocharger shaft at or adjacent to a first end thereof, a compressor wheel affixed to the turbocharger shaft at or adjacent to a second end thereof, the second end opposite the first end, a first bearing received on the turbocharger shaft between the turbine wheel and the compressor wheel and disposed in the first boss, and a second bearing received on the turbocharger shaft between the first bearing and the compressor wheel and disposed in the second boss. One of the first and second bearings may be freely rotatable relative to both the turbocharger shaft and the respective one of the first and second bosses, and the other of the first and second bearings may be affixed to the turbocharger housing such that the turbocharger shaft freely rotatable relative to the other of the first and second bearings but the other of the first and second bearings is prevented from rotating relative to the respective one of the first and second bosses. 
     A twelfth example aspect includes the subject matter of the eleventh example aspect, and may further comprise an electric machine having a rotor affixed to the turbocharger shaft between the first and second bearings. 
     A thirteenth example aspect includes the subject matter of the twelfth example aspect, and wherein the electric machine includes a stator coupled to the rotor and mounted within the turbocharger housing. 
     A fourteenth example aspect includes the subject matter of either of the twelfth and thirteenth aspects, and wherein the turbocharger housing comprises a turbine housing portion defining the first boss therein, a compressor housing portion defining the second boss therein and an electric machine housing portion having the electric machine mounted therein, the turbine housing portion and the compressor housing portion each coupled to the electric machine housing portion. 
     A fifteenth example aspect includes the subject matter of any of the eleventh-fourteenth example aspects, and wherein the first and second bearings each define an inside diameter, and wherein the inside diameter of the first bearing is greater than the inside diameter of the second bearing. 
     In a sixteenth example aspect, a turbocharger may comprise a turbocharger housing defining first and second bosses therein, a turbocharger shaft received within the turbocharger housing, a turbine wheel affixed to the turbocharger shaft at or adjacent to a first end thereof, a compressor wheel affixed to the turbocharger shaft at or adjacent to a second end thereof, the second end opposite the first end, a first bearing received on the turbocharger shaft between the turbine wheel and the compressor wheel and disposed in the first boss, the first bearing freely rotatable relative to both the turbocharger shaft and the first boss, and a second bearing received on the turbocharger shaft between the first bearing and the compressor wheel and disposed in the second boss, the second bearing secured to the turbocharger housing such that the turbocharger shaft is freely rotatable relative to the second bearing but the second bearing is prevented from rotating relative to the second boss. 
     A seventeenth example aspect includes the subject matter of the sixteenth example aspect, and may further comprise an electric machine having a rotor affixed to the turbocharger shaft between the first and second bearings. 
     An eighteenth example aspect includes the subject matter of the seventeenth example aspect, and wherein the turbocharger housing comprises a turbine housing portion defining the first boss therein, a compressor housing portion defining the second boss therein and an electric machine housing portion having the electric machine mounted therein, the turbine housing portion and the compressor housing portion each coupled to the electric machine housing portion. 
     A nineteenth example aspect includes the subject matter of any of the sixteenth-eighteenth example aspects, and wherein the first and second bearings each define an inside diameter, and wherein the inside diameter of the first bearing is greater than the inside diameter of the second bearing. 
     A twentieth example aspect includes the subject matter of any of the sixteenth-nineteenth example aspects, and wherein the first and second bosses are each concentrically formed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       This disclosure is illustrated by way of example and not by way of limitation in the accompanying figures. Where considered appropriate, reference labels have been repeated among the figures to indicate corresponding or analogous elements. 
         FIG. 1  is a cross-sectional view of a prior-art, electronically-controlled turbocharger (ECT) that includes a high-speed electric machine. 
         FIG. 2  is an exploded view of an embodiment of a turbocharger shaft and bearing arrangement that may be implemented in a turbocharger generally, and in particular, in an ECT such as that illustrated in  FIG. 1 . 
         FIG. 3  is an exploded view of an embodiment of a turbocharger shaft bearing arrangement configured to be secured to a housing of a turbocharger. 
         FIG. 4  is an assembled view of the turbocharger shaft bearing arrangement of  FIG. 3  shown secured to the turbocharger housing. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     While the concepts of the present disclosure are susceptible to various modifications and alternative forms, specific exemplary embodiments thereof have been shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit the concepts of the present disclosure to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives consistent with the present disclosure and the appended claims. 
     References in the specification to “one embodiment”, “an embodiment”, “an example embodiment”, etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases may or may not necessarily refer to the same embodiment. Further, when a particular feature, structure, process, process step or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, process, process step or characteristic in connection with other embodiments whether or not explicitly described. Further still, it is contemplated that any single feature, structure, process, process step or characteristic disclosed herein may be combined with any one or more other disclosed feature, structure, process, process step or characteristic, whether or not explicitly described, and that no limitations on the types and/or number of such combinations should therefore be inferred. 
     This disclosure is directed to a bearing arrangement for supporting a rotatable turbocharger shaft in, and relative to, a turbocharger housing. It will be understood that the bearing concepts illustrated and described herein are applicable to any conventional turbocharger including, for example, but not limited to, fixed geometry turbochargers, variable geometry turbochargers, so-called electronically controlled turbochargers (ECT) having one or more electric machines coupled thereto for controlling turbocharger rotational speed, and other conventional turbo-machinery. As will be described in detail with reference to  FIGS. 2-4 , the bearing arrangement that is the subject of this disclosure may be implemented in any such conventional turbocharger, and one example such turbocharger is the conventional ECT  10  illustrated in cross-section in  FIG. 1 . 
     Referring to  FIG. 1 , the illustrated ECT  10  has a turbocharger shaft  12  to which a turbine wheel  14  is affixed, e.g., by welding or other conventional turbine wheel affixing structure(s) and/or technique(s), at one end thereof. At an opposite end of the shaft  12  a compressor wheel  16  is affixed. In one embodiment, the compressor end of the turbocharger shaft  12  is threaded, and a complementarily threaded nut is advanced onto the shaft  12  to affix the compressor wheel  16  to the shaft  12 . In alternative embodiments, other conventional structures and/or techniques may be used to affix the compressor wheel  16  to the shaft  12 , examples of which include, but are not limited to, welding, press-fitting, or the like. 
     The turbocharger shaft  12  is supported by a pair of bearings  18  and  28 , and each bearing  18 ,  28  is disposed in a boss or cradle  20 ,  30  respectively formed in the turbocharger housing. In the illustrated embodiment, the bearing  18  is disposed in the boss or cradle  20  in a turbine housing portion  24  of the turbocharger housing, and the bearing  28  is disposed in the boss or cradle  30  in a compressor housing portion  26  of the turbocharger housing. In some embodiments, the bosses or cradles  20 ,  30  are concentrically machined, although in alternate embodiments only one or neither may be concentrically machined. 
     In the illustrated embodiment, the outer diameter of the turbocharger shaft  12  is greater in a region  12 A about which the bearing  18  is disposed than in the region  12 B about which the bearing  28  is disposed. In this embodiment, the inner diameter of the bearing  18  is thus greater than that of the bearing  28 , although it will be understood that in alternate embodiments the outer diameters of the shaft regions  12 A,  12 B, and therefore the inner diameters of the bearings  18 ,  28 , may be the same or the outer diameter of the shaft region  12 B/inner diameter of the bearing  28  may be greater than that of the outer diameter of the shaft region  12 A/inner diameter of the bearing  18 . 
     An electric machine  32 , e.g. an electrically-controlled motor or motor/generator, includes a rotor  34  affixed to the turbocharger shaft  12  between the bearings  18 ,  28  such that the rotor  34  rotates with the shaft  12 . A stator  36  is operatively coupled to the rotor  34 , and the electric machine  32  is disposed within an electric machine housing portion  22  of the turbocharger housing. In the illustrated embodiment, the turbocharger housing is thus made up of three housing portions; the turbine housing portion  24 , the compressor housing portion  26 , and the electric machine housing portion  22 . The turbine housing portion  24  and the compressor housing portion  26  are each illustratively affixed to the electric machine housing portion  22  in a conventional manner. Those skilled in the art will recognize that depending on the location of the splits between housing portions, the bosses  22  and  24  may be included in other housing portions of turbocharger  10 , and that the embodiment illustrated in  FIG. 1  is merely one non-limiting example thereof. 
     Referring now to  FIG. 2 , a partially exploded view is shown of a turbocharger shaft  46  including an embodiment of a bearing arrangement carried thereby. In the illustrated embodiment, a turbine wheel  40  is affixed to shaft  46  at or adjacent to one end thereof, e.g., by welding or other conventional fixation structure(s) and/or technique(s) such as a splined engagement, pressed collar, press fit, or the like. A bearing  42  is slidably received on and over the shaft  46  adjacent to the turbine wheel  40 . In the illustrated embodiment, the bearing  42  is a fully-floating bearing; i.e., the bearing is not affixed to either the shaft  46  or the turbocharger housing, but rather is freely rotatable about the shaft  46  as well as within the boss or cradle  20  of the turbocharger housing. In one embodiment, oil or other lubricant is provided between bearing  42  and the boss  29  (not shown in  FIG. 2  but shown in  FIG. 1 ) as well as between the shaft  46  and the bearing  42 . In any case, the bearing  42  is free to rotate relative to both the boss or cradle  20  and the shaft  46 . Because the bearing  42  is freely floating, however, the bearing  42  illustratively rotates a lower rotational speed than that of the turbocharger shaft  46 . 
     In the embodiment illustrated in  FIG. 2 , a rotor  44  of an electric machine is affixed to the shaft  46  by any conventional structure(s) and/or technique(s), e.g., such as a press fit, welding, threads, a nut or other structure pressing the rotor  44  into a shoulder or conical section of the shaft  46 , a splined engagement, pressed collar, keyed engagement, and/or the like. A plate  50  having an opening defined therethrough is received on and over the turbocharger shaft  46  at an opposite end thereof, and another bearing  52  is, in turn, likewise received on and over the shaft  46  with the plate  50  positioned between the rotor  44  and the bearing  52 . A thrust bearing assembly is then received on and over the turbocharger shaft  46  between the bearing  52  and the end of the shaft  46 . In the illustrated embodiment, the thrust bearing assembly illustratively includes, in order of proximity to the bearing  52 , a thrust bearing washer  54 , a thrust bearing  56 , a thrust bearing sealing plate  58 , a compressor seal  60  and piston ring seals  62 . A compressor wheel  64  is then affixed to the shaft  46  at or adjacent to the opposite end thereof, i.e., the end of the shaft  46  that is opposite to the end at which the turbine wheel  40  is affixed. In the illustrated embodiment, the opposite end of the turbocharger shaft  46  is provided with threads  68 , and the compressor wheel  64  is affixed to the shaft by advancing a complementarily threaded nut  66  along the threads  68  such that the nut  66  engages the shaft  46  to secure the compressor wheel  64  thereto. In alternate embodiments, the compressor wheel  64  may be affixed to the shaft  46  via one or more other conventional fixation structure(s) and/or technique(s) such as welding, splined engagement, pressed collar, press fit, or the like. 
     In one embodiment, the bearing  52  illustratively defines one or more slots, channels or indentations therein, and the plate  50  illustratively defines one or more complementarily configured teeth, tangs or protrusions which engage the one or more slots, channels or indentations defined in the bearing  52  when the plate  50  and bearing  52  are received on the shaft  46  to prevent the bearing  52  from rotating relative to the plate  50 . In some alternative embodiments, the plate  50  may defined the one or more slots, channels or indentations and the bearing may define the one or more teeth, tangs or protrusions. In any case, the plate  50  further illustratively defines one or more passageways or openings therethrough sized to receive conventional fixation members, e.g., screws, bolts, etc., therethrough. With the plate  50  and bearing  52  received on the shaft  46 , the one or more slots, channels or indentations defined in the bearing  52  align with and engage the one or more corresponding teeth, tangs or protrusions defined in the plate  50 , and the one or more openings or passageways defined through the plate  50  align with corresponding openings or passageways defined in the compressor housing portion  26  (and/or the electric machine housing portion  22 ) of the turbocharger housing. One or more conventional fixation members are passed through the openings or passageways defined through the plate  50  and into engagement with the aligned openings or passageways defined in the compressor housing portion  26  to secure the plate  50  and the bearing  52  to the turbocharger housing such that the bearing  52  and plate  50  are prevented from rotating relative to the turbocharger housing. In this manner, the bearing  152  is said to be “pinned” to the compressor housing portion  26  such that the bearing  152  cannot rotate relative to the turbocharger housing. 
     In the exploded view illustrated in  FIG. 3  and in the assembled view illustrated in  FIG. 4 , a specific but non-limiting example of such a pinning arrangement is illustrated. In  FIGS. 3 and 4 , the turbocharger shaft  46  is omitted so as not to obscure the foregoing details of the plate  50 , bearing  52  and compressor housing portion  26 . In the illustrated embodiment, the plate  50  defines a pair of diametrically opposed teeth or tangs  70  each extending radially inwardly into a turbocharger shaft receiving opening defined centrally therethrough, and the bearing  52  defines a corresponding pair of diametrically opposed slots or channels  72  into an annular edge or rim thereof, wherein the teeth or tangs  70  and the slots or channels  72  are sized and configured such that the teeth or tangs  70  are received in the corresponding slots or channels  72  as illustrated in  FIG. 3  such that the bearing  52  is prevented from rotating relative to the plate  50 . 
     In the embodiment illustrated in  FIGS. 3 and 4 , the plate  50  further defines a pair of diametrically opposed openings or passageways  74  therethrough in the same plane as that of the turbocharger shaft receiving opening, and the compressor housing portion  26  likewise defines a pair of openings or passageways  76  therein which align with the openings or passageways  74 . Fixation members  78 , e.g., screws, are passed through the openings or passageways  74  and into engagement with the openings or passageways  76  to secure the plate  50  and bearing  52  to the compressor housing portion  26  such that the bearing  52  is prevented from rotating relative to the turbocharger housing. 
     In one embodiment, a thin layer of oil or other lubricant may be disposed between the bearing  52  and the boss  30  in the housing in which it is contained. In alternative embodiments, the bearing  52  may be fixed to the compressor housing portion  26  with no layer of oil or other lubricant disposed between the bearing  52  and the boss  30 . In any case, the bearing  52  is pinned to the turbocharger housing such that it doesn&#39;t rotate with respect to the turbocharger housing. 
     In the illustrated embodiment, the bearing  52  is a partially floating bearing; that is, the bearing is affixed to the turbocharger housing but is floating, i.e., freely rotatable, relative to and about the shaft  46 . In one embodiment, oil or other lubricant is provided between bearing  52  and the shaft  46 . In any case, the bearing  52  is pinned to the turbocharger housing such that it is prevented from rotating relative to the boss or cradle  30  of the compressor housing portion  30  but is free to rotate relative to the turbocharger shaft  46 . 
     In the illustrated embodiment, the bearing  42  is described as being freely floating with respect to the turbocharger shaft  46  and also with respect to the boss or cradle  20  of the turbocharger housing, and the bearing  52  is described as being pinned to the turbocharger housing but freely floating with respect to the turbocharger shaft  46 . As such, the turbine-side bearing  42  may rotate relative to the boss or cradle  20  of the turbocharger housing and also relative to the turbocharger shaft  46 , although because the bearing  42  is not affixed to the shaft  46  it generally will rotate at a lower rotational speed than that of the shaft  46 , particularly if oil or other lubricant is disposed therebetween. The compressor-side bearing  52 , on the other hand, is fixed relative to the boss  30  of the turbocharger housing because it is secured to the turbocharger housing by the plate  50 , but is floating with respect to the turbocharger shaft  46 . The bearing  52  may thus rotate relative to the turbocharger shaft  46  but is prevented from rotating relative to the turbocharger housing by the plate  50  which engages the bearing  52  and is affixed to the housing. 
     In alternative embodiments, the roles and structures of the bearings  42 ,  52  may be switched, i.e., the turbine side bearing  42  may be pinned to the turbocharger housing and floating with respect to the turbocharger shaft  46 , e.g., as described above with respect to the bearing  52 , and the compressor side bearing  52  may be freely floating, e.g., as described above with respect to the bearing  42 . 
     While the disclosure has been illustrated and described in detail in the drawings and foregoing description, such an illustration and description is to be considered as exemplary and not restrictive in character, it being understood that only illustrative embodiments have been shown and described and that all changes and modifications consistent with the disclosure and recited claims are desired to be protected.