Abstract:
An exemplary bearing and locating pin system for a turbocharger includes a locating pin including a shaft, a head and an aperture and a bearing having a central axis and including an internal bore to receive a shaft extending between a compressor wheel and a turbine wheel, the internal bore including a plurality of axial grooves, the bearing including a locating pin aperture substantially equidistant from axial ends of the bearing for engaging the locating pin to prevent rotation of the bearing within a bearing case bore, the bearing further including a plurality of lubricant inlets, each inlet extending between an outer surface of the bearing and one of the axial grooves at an angle non-orthogonal to the central axis. Other exemplary technologies are also disclosed.

Description:
FIELD OF THE INVENTION  
       [0001]     Subject matter disclosed herein relates generally to bearings for turbochargers and, in particular, to bearings that include passages for flow of lubricant to and from a bore of the bearing.  
       BACKGROUND  
       [0002]     Exhaust gas driven turbochargers include a rotating shaft carrying a turbine wheel and a compressor wheel, which is rotatably supported within a center housing by one or more lubricated bearings (e.g., oil lubricated). The turbine wheel is driven by the exhaust gas at high rotational speeds, often well in excess of 100,000 RPM, to drive the compressor wheel to provide boosted charge air for use by an internal combustion engine.  
         [0003]     With respect to lubrication of various bearing surfaces, one approach relies on two distinct lubricant galleries machined in a turbocharger center housing that allow lubricant to flow to radial bearing journals. While this approach provides for reasonable bearing power losses, production issues exist related to machining, deburring, cleaning and quality control of the center housing. Another approach relies on a single lubricant gallery machined in a turbocharger center housing. The single gallery allows lubricant to flow to radial bearing outer journals and bore journals where flow is outward toward the bearing ends only.  
         [0004]     The latter single gallery approach is reasonably low cost with respect to machining and related processes for production of the center housing but the bearing power losses are can be high.  
         [0005]     A need exists for technology that strikes an appropriate balance between production related costs and performance. As described herein, various exemplary technologies aim to address this need and others needs.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]     A more complete understanding of the various methods, devices, systems, arrangements, etc., described herein, and equivalents thereof, may be had by reference to the following detailed description when taken in conjunction with the accompanying drawings wherein:  
         [0007]      FIG. 1  is a perspective view of an exemplary system that includes an exemplary locating pin and an exemplary bearing.  
         [0008]      FIG. 2  is a cross-sectional view of an exemplary turbocharger center housing suitable for use with the exemplary system of  FIG. 1 .  
         [0009]      FIG. 3  is a cross-sectional view of an exemplary arrangement that includes the exemplary system of  FIG. 1  and the exemplary center housing of  FIG. 2 .  
         [0010]      FIG. 4  is another cross-sectional view of the exemplary arrangement of  FIG. 3 .  
         [0011]      FIGS. 5A, 5B  and  5 C are a series of views of an exemplary bearing.  
         [0012]      FIGS. 6A, 6B ,  6 C and  6 D are a series of views of the exemplary bearing of  FIGS. 5A, 5B  and  5 C.  
         [0013]      FIG. 7  is a cross-sectional view of an exemplary locating pin. 
     
    
     DETAILED DESCRIPTION  
       [0014]     Various exemplary methods, devices, systems, arrangements, etc., disclosed herein address issues related to technology associated with turbochargers. Turbochargers are frequently utilized to increase the output of an internal combustion engine. A turbocharger generally acts to extract energy from the exhaust gas and to provide energy to intake air, which may be combined with fuel to form combustion gas. A turbocharger may include a variable geometry mechanism, for example, with features such as those associated with commercially available variable geometry turbochargers (VGTs), such as, but not limited to, the GARRETT® VNT™ and AVNT™ turbochargers, which use multiple adjustable nozzle vanes to control the flow of exhaust across a turbine.  
         [0015]      FIG. 1  shows an exemplary system  100  that includes a locating pin  110  and a bearing  120 . The exemplary locating pin  110  acts generally as an anti-rotation component or mechanism and it includes a shaft  112  and a head  116  and an aperture defined by an inner shaft surface  114  and an inner head surface  116  of the pin  110 . The aperture provides a passage for flow of lubricant, as described further below. In this example, the inner head surface  116  has a hexagonal shape to receive, for example, a hex wrench. Other shapes may be used as appropriate. In general, the pin  110  includes a feature that allows for rotation or positioning of the pin  110 . Other examples may include anti-rotation mechanisms that differ from the specific example shown; however, in general, an exemplary bearing includes a feature or a mechanism that allows for drainage of lubricant from the bore region of a bearing to a drain of a center housing, as described further below.  
         [0016]     The exemplary bearing  120  includes a variety of features. Importantly, the bearing  120  includes a pin aperture  130  defined by a wall of the bearing  120 . The exemplary system  100  provides for reception of at least a portion of the shaft  112  of the pin  110  by the pin aperture  130  of the bearing  120 . The cooperative nature of the pin  110  and the bearing  120  is described in more detail with respect to a center housing of  FIG. 2 .  
         [0017]     The exemplary bearing  120  is a single piece bearing having an internal bore and integral thrust surfaces on opposing ends. The bearing  120  has a central surface  122  that extends axially between two beveled surfaces  123 ,  123 ′ which, in turn, border journal surfaces  124 ,  124 ′, respectively. In general, the radius of the central surface  122  is less than the radius of a journal surface.  
         [0018]     The internal bore of the exemplary bearing  120  includes bore surfaces  125 ,  125 ′. In the example of  FIG. 1 , each of the internal journal surfaces  125 ,  125 ′ includes four axial grooves, which are labeled  126 ,  126 ′,  126 ″,  126 ′″ and  127 ,  127 ′,  127 ″,  127 ′″, respectively. In general, the axial length of the bore surface  125  is approximately equal to the axial length of the journal surface  124  and the axial length of the bore surface  125 ′ is approximately equal to the axial length of the journal surface  124 ′.  
         [0019]     The exemplary bearing  120  further includes four lubricant inlets on each of the two beveled surfaces  123 ,  123 ′. The four lubricant inlets associated with the beveled surface  123  are labeled  128 ,  128 ′,  128 ″,  128 ′″ and the four other lubricant inlets associated with the beveled surface  123 ′ are labeled  132 ,  132 ′,  132 ″,  132 ′″. These inlets are spaced at approximately 90° intervals and each inlet extends from a respective beveled surfaces  123 ,  123 ′ to a respective axial grooves  126 - 126 ′″,  127 - 127 ′″, for example, at a relative angle of approximately 30° to a central axis of the bearing  120 .  
         [0020]     With respect to lubricant, the inlets receive lubricant and allow such lubricant to flow to a respective axial groove. The axial grooves allow for lubricant distribution along the bore surfaces  125 ,  125 ′. The internal bore of the bearing  120  may receive a shaft whereby the lubricant provides a film between the bore surfaces  125 ,  125 ′ and the shaft. In such an exemplary arrangement, lubricant flows to the lubricant inlets  128 - 128 ′″,  132 - 132 ′″, to the grooves  128 - 128 ′″, 1, and then to a drain via one or more paths, as described in more detail with respect to  FIG. 2 . The axial grooves  126 - 126 ′″,  127 - 127 ′″ additionally provide an enhancement in rotordynamics by improving resistance to subsynchronous shaft motion through reduction of lubricant whirl encountered in lightly loaded bearing conditions.  
         [0021]      FIG. 2  shows an exemplary housing  200  having a compressor end  202  and a turbine end  204 . In this example, the housing  200  is a center housing of a turbocharger assembly and the housing  200  includes a bearing case bore  210  and a boss  220  with an aperture  224  for receiving the exemplary locating pin  110  such that the pin  110  extends into the bearing case bore  210  substantially centrally in the bore  210 . In such a manner, the exemplary bearing  120  may be constrained from rotating in the bearing case bore  210  of the center housing  200  by the pin  110  inserted through the aperture  224  in boss  220 .  
         [0022]     In general, once arranged in conjunction with the housing  200 , the bearing  120  is semi-floating with symmetrical freedom of movement from end to end due to the centrally located pin  110  thereby optimizing the effectiveness of the lubricant-film (e.g., oil-film) damper in the clearance between the bearing outer diameter (e.g., journal surfaces  124 ,  124 ′) and the case bore  210 . Lubricant for the bearing is supplied through an inlet  206  of the housing  200  and lubricant may exit the housing  200  via an exit  208 .  
         [0023]      FIG. 3  shows a cross-section of an exemplary assembly  300  that includes the exemplary pin  110 , the exemplary bearing  120 , the exemplary housing  200  and a shaft  310 . The exemplary assembly  300  provides entry of lubricant to the bearing via the inlet  206  of the housing  200  and for three lubricant flow paths A, B, C to the exit  208  of the housing  200  (see, e.g.,  FIG. 2 ). Path A is via the aperture of the pin  110  while paths B and C are via film ends where the lubricant film exists between the shaft  310  and the bore surfaces  125 ,  125 ′ of the bearing  120 . The shaft  310 , which extends through the bore of the bearing  120  may include a relieved portion that promotes lubricant flow between the shaft  310  and the bearing  120 . The shaft  310  may be a single piece or a multipiece shaft.  
         [0024]      FIG. 4  shows another cross-sectional view of the exemplary assembly  300  of  FIG. 3 . In this example, the relieved portion of the shaft  310  creates a substantially central annular chamber in the bore of the bearing  120 . Lubricant may flow into this chamber and drain from the chamber via the aperture of the locating pin  110 . For example, lubricant may flow into the chamber from an end of the film located between a bore surface  125  and a shaft surface or via an axial groove  126 ′″. Also shown in  FIG. 4 , is a chamber formed by the housing  200  and at least in part by the outer central surface  122  of the bearing  120  that at least partially surrounds the outer central surface  122  of the bearing  120 . Lubricant entering the housing  200  via the inlet  206  flows to this chamber and to the various inlets  128 - 128 ′″,  132 - 132 ′″ of the bearing  120 .  
         [0025]      FIGS. 5A, 5B  and  5 C show three views of the exemplary bearing  120 . A bottom view ( FIG. 5A ) of the bearing  120  indicates a dimension D O  for the locating pin aperture  130 . In this example, each beveled surface  123 ,  123 ′ includes four inlets  128 - 128 ′″,  132 - 132 ′″, respectively. A side view ( FIG. 5B ) of the exemplary bearing  120  illustrates the locating pin aperture  130 , which can receive the exemplary locating pin  110 . A cross-sectional view ( FIG. 5C ) of the exemplary bearing  120  illustrates the junctures between the inlets  128 ,  128 ′,  132 ,  132 ′ and the respective axial grooves  128 ,  128 ′,  127 ,  127 ′. These features allow for film formation between the bore surfaces  125 ,  125 ′ and, for example, the shaft  310 . The central portion of the bore includes a central surface  129  that can create a central bore chamber with an outer surface of a shaft. In various examples, the shaft  310  includes a relieved surface that acts to increase the volume of this bore chamber. Other examples may include a shaft of with a diameter substantially the same as a bore surface  125  or bore surface  125 ′ diameter. In various examples, the bore surfaces  125 ,  125 ′ have substantially similar diameters and the shaft  310  has slightly smaller diameters to thereby allow for formation of films between the bearing bore surfaces  125 ,  125 ′ and respective outer surfaces of the shaft  310 .  FIGS. 6A, 6B ,  6 C and  6 D show various views of an exemplary bearing  120 .  
         [0026]      FIG. 6A  shows cross-sectional view that includes inlets  132 - 132 ′″ and axial grooves  132 - 132 ′″. The substantially parabolic outline of the inlets  132 - 132 ′″ indicates that the inlets traverse the bearing wall at an angle. For example, a relative angle of approximately 20° to approximately 85° with respect to a central axis of the bearing and thereby the inlets may help to distribute lubricant axially outward with respect to a lubricant inlet of a center housing. As already mentioned, the inlets may be at an angle of approximately 30° with respect to a central axis of the bearing.  
         [0027]      FIG. 6B  shows an end view of the exemplary bearing  120  whereby dashed lines indicate approximate inlet paths from the beveled surface  123  to the axial grooves  126 - 126 ′″. The arrows represent the direction of the partial cross-sectional view of  FIG. 6C  of the exemplary bearing  120 .  FIG. 6D  shows a magnified view of the inlet  132 ″ with respect to the axial groove  126 ′″. The inlet includes a dimension D that is substantially constant between the beveled surface  123 ′ and the axial groove  126 ′″. Of course, the dimension or dimensions of an inlet may vary with respect to any dimension, for example, of a cylindrical coordinate system (r, Θ, z) where the (r, z) origin is along the central axis of the bearing. Similarly, the axial grooves may vary in dimension from those shown in the various examples.  FIG. 6D  also shows an angle φ between a centerline of the inlet  132 ′″ and a line parallel to the central axis of the bearing  120 .  
         [0028]      FIG. 7  shows the exemplary pin  110  having a shaft  112  and a head  116  and various dimensions, primarily associated with the shaft. As already mentioned, the head  116  may include one or more features that allow for rotation or positioning of the pin  110 . An inner dimension D I  allows for lubricant from the bearing bore chamber to exit the bearing. The outer dimension D O  allows for inserting of the pin  110  into the locating pin aperture of the bearing. Threads or other feature(s) (e.g., bayonet, etc.) may be included to allow for cooperation between the pin  110  and a bearing or a housing.  
         [0029]     As already mentioned, the single gallery feature acts to reduce production costs of the exemplary center housing. The exemplary bearings, locating pins, systems or assemblies described herein may use a center housing that includes more than a single gallery as a lubricant inlet.  
         [0030]     The exemplary locating pin provides for lubricant drainage. Of course, other features (e.g., additional openings in the bearing wall) may provide for lubricant drainage. In general, drainage via the locating pin or other suitable mechanism is facilitated by gravity wherein alignment of the locating pin is substantially along the direction of gravitational acceleration.  
         [0031]     In comparison with conventional locating pins and bearings, the exemplary bearing and locating pin system may include a locating pin and a locating pin aperture of larger dimension.  
         [0032]     An exemplary assembly can reduce “Windage” losses by providing a low pressure lubricant environment (e.g., on the order of atmospheric pressure) that thereby allows the rotating shaft to rotate more freely.  
         [0033]     An exemplary bearing optionally has an enlarged inner bore cavity when compared to a conventional bearing as to increase the volume and allow for better lubricant mobility. As already mentioned, an exemplary shaft may include one or more reliefs to increase bore chamber volume.  
         [0034]     An exemplary center housing optionally includes a larger locating pin aperture, for example, in a locating pin boss, when compared to a conventional center housing. As already explained, an exemplary locating pin includes a passage for draining lubricant. The cross-sectional flow area of the passage may be of a dimension such that the housing requires a larger aperture when compared to a locating pin without such a passage.