Abstract:
A tandem roller bearing assembly is provided that combines a tapered roller bearing with an angular contact ball bearing, yielding high load capacity with improved efficiency. A one-piece outer ring contains an outer tapered roller raceway and an outer angular contact ball raceway and can support an axial load in a single direction. A one-piece inner ring contains an inner tapered roller raceway and an inner angular contact ball raceway and can support an axial load in a single direction. Various rib configurations are implemented on the inner tapered roller raceway to achieve multiple friction and axial load support options.

Description:
TECHNICAL FIELD 
       [0001]    Example aspects described herein relate to rolling element bearing assemblies, particularly of bearings that are used in vehicle drivetrains that require high efficiency and minimal packaging space. 
       BACKGROUND 
       [0002]    Given the fuel economy goals of future passenger vehicles, friction and weight reduction are of high importance to automotive engineers. The drivetrain of an automobile consists of multiple arrays of gears and bearings to transfer the rotary motion of the internal combustion engine to the rotary motion of the wheels. The efficiency of the drivetrain has evolved very rapidly in recent years due in large part to improved designs of transmissions, transfer cases and differential units. The design of rolling element bearings has played a vital role in this efficiency gain and will continue to evolve with the innovations of drivetrain technology. 
         [0003]    Rolling element bearing assemblies are typically circular in shape, and generally comprise of rolling elements, normally contained by a cage, disposed between inner and outer raceways. Rolling elements take many forms, including spherical balls, cylindrical rollers, needle rollers, or various other configurations, such as cone-shaped tapered rollers or barrel-shaped spherical rollers. Cages are often used to contain the rolling elements and guide them throughout the rotating motion of the bearing, but are not a necessity in some configurations. The material of a cage can vary from steel to plastic, depending on the application, duty cycle, along with noise and weight requirements. 
         [0004]    The type of bearing used for a particular application depends on multiple factors including the load, load direction, required stiffness, and speed. Angular contact ball bearings are known and are able to withstand combined radial and axial loads. One or two rows of balls are possible in a single bearing unit and various arrangements of multiple angular contact ball bearings are possible to address the needs of the application. Referring to  FIG. 11 , a cross-sectional view of a prior art angular contact ball bearing  200  is shown. Angular contact ball bearing  200  contains an inner ring  214 , an outer ring  211 , balls  212 , and a ball cage  213 . The inner ring  214  contains an inner ball raceway  219  with an axial shoulder  217 ; the outer ring  211  contains an outer ball raceway  218  with an axial shoulder  215 . In addition to the inherent radial load capability of a ball bearing, the presence of the respective axial shoulders  217 ,  215  provides axial load capability in the directions shown in  FIG. 11 . In general, angular contact ball bearings provide a low-friction solution for drivetrain applications due to a rolling interface that is maintained between the balls  212  and respective inner and outer raceways  219 ,  218 , including axial shoulders  217 ,  215 , when subjected to radial or axial load conditions. However, the load capacity of angular contact ball bearings is relatively low compared to other bearing types. 
         [0005]    Like angular contact ball bearings, tapered roller bearings are known and are also able to withstand combined radial and axial loads, but, for a given bearing envelope size, have a significantly higher load capacity than angular contact ball bearings. Referring to  FIG. 10 , a cross-sectional view of a prior art tapered roller bearing  100  is shown that rotates about a central axis  113 . Tapered roller bearing  100  contains an inner ring  104 , an outer ring  101 , tapered rollers  102  and a tapered roller cage  103 . The inner ring  104  contains an inner tapered roller raceway  108  with a small diameter end  112  and a large diameter end  111 ; a rib  106  is present at the small diameter end  112  and a rib  105  is present at the large diameter end  111 . The outer ring  101  contains an outer tapered roller raceway  107  with a small diameter end  110  and a large diameter end  109 . The design of tapered roller bearings is such that the inner raceway  108  and outer raceway  107  are angled with respect to the central axis  113  of the tapered roller bearing  100 . For a given width of envelope space, the angled inner and outer raceways  108 ,  107  increase the amount of line contact with the tapered rollers  102  which increases the load capacity of the tapered roller bearing  100 . The rib  106  on the small diameter end  112  of the inner raceway  108  is present to retain the tapered rollers  102  on the inner raceway  108 . The rib  105  on the large diameter end  111  of the inner raceway  108  serves as a thrust interface for the tapered rollers  102 . However, the friction that results from this sliding interface exceeds that of the rolling interface between the balls and axial shoulders of an angular contact ball bearing. 
         [0006]    For drivetrain applications, tapered roller bearings offer high load capacity while sacrificing efficiency. A bearing solution is required that maintains the load capacity of a tapered roller bearing while lowering the inherent friction. 
       SUMMARY OF THE INVENTION 
       [0007]    A bearing assembly that combines a tapered roller bearing with an angular contact ball bearing is disclosed. This combination of rolling elements within a single bearing assembly blends the positive attributes of each bearing type to achieve an increased load capacity while minimizing friction. The bearing assembly includes a one-piece outer ring, a one-piece inner ring, tapered rollers, balls, a tapered roller cage and an angular contact ball cage. The outer ring includes an outer tapered roller raceway and an outer angular contact ball raceway with an axial shoulder. The inner ring includes an inner tapered roller raceway and an inner angular contact ball raceway with an axial shoulder. Different aspects of the outer and inner rings include different angular orientations of the tapered roller raceways together with different locations of the axial shoulders of the angular contact ball raceways. Further aspects include an axial rib placed on either or both ends of the tapered roller raceway of the inner ring that can provide tapered roller containment or a thrust interface for the tapered rollers. The aspects that include a rib as a thrust interface on the tapered roller raceway of the inner ring can facilitate a design characteristic where the axial load is partially supported by the rib interface with the tapered rollers and the respective inner and outer ring axial shoulder interfaces with the angular contact balls. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0008]    The above mentioned and other features and advantages of the embodiments described herein, and the manner of attaining them, will become apparent and better understood by reference to the following descriptions of multiple example embodiments in conjunction with the accompanying drawings. A brief description of the drawings now follows. 
           [0009]      FIG. 1  is a perspective view of a first example embodiment of a tandem tapered roller and angular contact ball bearing assembly. 
           [0010]      FIG. 2  is a cross-sectional view of the bearing of  FIG. 1 . 
           [0011]      FIG. 3  is a cross-sectional view of a second example embodiment of a tandem tapered roller and angular contact ball bearing assembly. 
           [0012]      FIG. 4  is a cross-sectional view of a third example embodiment of a tandem tapered roller and angular contact ball bearing assembly. 
           [0013]      FIG. 5  is a cross-sectional view of a fourth example embodiment of a tandem tapered roller and angular contact ball bearing assembly. 
           [0014]      FIG. 6  is a cross-sectional view of a fifth example embodiment of a tandem tapered roller and angular contact ball bearing assembly. 
           [0015]      FIG. 7  is a cross-sectional view of a sixth example embodiment of a tandem tapered roller and angular contact ball bearing assembly. 
           [0016]      FIG. 8  is a cross-sectional view of a seventh example embodiment of a tandem tapered roller and angular contact ball bearing assembly. 
           [0017]      FIG. 9  is a cross-sectional view of an eighth example embodiment of a tandem tapered roller and angular contact ball bearing assembly. 
           [0018]      FIG. 10  is a cross-sectional view of a prior art tapered roller bearing assembly. 
           [0019]      FIG. 11  is a cross-sectional view of a prior art angular contact ball bearing assembly. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    Identically labeled elements appearing in different figures refer to the same elements but may not be referenced in the description for all figures. The exemplification set out herein illustrates at least one embodiment, in at least one form, and such exemplification is not to be construed as limiting the scope of the claims in any manner. A radially inward direction is from an outer radial surface of the outer raceway, toward the central axis or radial center of the outer raceway. Conversely, a radial outward direction indicates the direction from the central axis or radial center of the outer raceway toward the outer surface. Axially refers to directions along a diametric central axis. The words “left” and “right” designate directions in the drawings to which reference is made. 
         [0021]    Referring to  FIG. 1 , a first embodiment of a tandem tapered roller and angular contact ball bearing assembly  10  is shown that rotates about central axis  12 . Referring now to  FIG. 2 , a cross-sectional view of the tandem tapered roller and angular contact ball bearing assembly  10  is shown that includes an outer ring  14 , an inner ring  16 , tapered rollers  20 , a tapered roller cage  24 , balls  18 , and a ball cage  22 . The outer ring  14  contains an outer angular contact ball raceway  15  with an axial shoulder  25 , and an outer tapered roller raceway  13 . The outer tapered roller raceway  13  has a small diameter end  27  and a large diameter end  28 . The inner ring  16  contains an inner angular contact ball raceway  19  with an axial shoulder  26 , and an inner tapered roller raceway  21 . The inner tapered roller raceway  21  has a small diameter end  29  and a large diameter end  30 . A rib  17  is present on the small diameter end  29  and a rib  11  is present on the large diameter end  30  of the inner tapered roller raceway  21 . The rib  17  on the small diameter end  29  is present to retain the rollers on the raceway, while the rib  11  on the large diameter end  30  is present to function as a potential thrust interface for the tapered rollers  20 . A single row of balls  18  is present on the right hand side, while a single row of tapered rollers  20  is present on the left hand side. With the orientation shown in  FIG. 2 , the bearing is able to withstand radial loads in addition to an axial load that acts from right to left on the inner ring or an axial load that acts from left to right on the outer ring. This is evident by the orientation of the tapered rollers  20  (increasing diameter from left to right) and the location of the axial shoulder  26  on the inner ball raceway  19  and the axial shoulder  25  on the outer ball raceway  15 . The axial design load direction can be reversed by merely installing the bearing such that tapered rollers  20  are on the right side and the balls are on the left relative to the tandem tapered roller and angular contact ball bearing assembly  10  shown in  FIG. 2 . As is typical for angular contact ball bearings and tapered roller ball bearings, adjustment of axial clearance upon installation is recommended to compensate for the effects of interference fits and thermal expansion of the bearing components, shafts and housings to ensure optimum bearing performance. For the tandem tapered roller and angular contact ball bearing assembly  10  shown in  FIG. 2 , the axial clearance can be set by either moving the inner ring  16  or outer ring  14  axially relative to the other ring to obtain the desired clearance. In most applications it is desired to eliminate all axial clearance upon installation, even to the extent that the balls or tapered rollers are slightly pre-loaded, representing a “negative clearance” condition. The design of the tandem tapered roller and angular contact ball bearing assembly  10  of  FIG. 2  allows the bearing designer to potentially tune the distribution of axial load support between the balls  18  with the axial shoulder  25  of the outer ring  14  and the axial shoulder  26  of the inner ring  16  along with the tapered rollers  20  and the rib  11  on the large diameter end  30  of the inner tapered roller raceway  21  of the inner ring  16 . Axial clearance between the balls  18  and their respective axial shoulders  25 ,  26  versus axial clearance between the tapered rollers  20  and rib  11  can be adjusted in the design to either partially support the axial load between these interfaces (the total axial load is divided equally or unequally between interfaces of an amount greater than 0% but less than 100%), or such that either the balls  18  or tapered rollers  20  support 100% of the axial load. In an effort to reduce bearing friction, a designer could adjust the axial clearances such that the balls  18  would support most of the applied axial load, as rolling friction between the balls  18  and their respective axial shoulders  25 ,  26  is less than the sliding friction between the tapered rollers  20  and the rib  11 . 
         [0022]    Referring to  FIG. 3 , a second example embodiment of a tandem tapered roller and angular contact ball bearing assembly  10 ′ is shown that includes an inner ring  16 ′ which does not have a rib at the large diameter end  30  of the inner tapered roller raceway  21 . With the orientation shown in  FIG. 3 , the bearing is able to withstand radial loads in addition to an axial load that acts from right to left on the inner ring  16 ′ or an axial load that acts from left to right on the outer ring  14 . Axial clearance is set by either moving the inner ring  16 ′ or outer ring  14  axially relative to the other ring; however, due to the absence of the aforementioned rib, for this second embodiment the axial clearance is always a function of axial clearance between the balls  18  and their respective axial shoulders  25 ,  26  on the outer ring  14  and the inner ring  16 ′. 
         [0023]    Referring to  FIG. 4 , a third example embodiment of a tandem tapered roller and angular contact ball bearing assembly  10 ″ is shown that includes an inner ring  16 ″ which does not have a rib  11  at the small diameter end  29  of the inner tapered roller raceway  21 , but does have a rib at the large diameter end  30  of the inner tapered roller raceway  21 . With the orientation shown in  FIG. 4 , the bearing is able to withstand radial loads in addition to an axial load that acts from right to left on the inner ring  16 ″ or an axial load that acts from left to right on the outer ring  14 . The axial load direction that the bearing can withstand can be reversed by merely installing the bearing such that the tapered rollers  20  are on the right side and the balls  18  are on the left compared to the configuration shown in  FIG. 4 . Axial clearance is set by either moving the inner ring  16 ″ or outer ring  14  axially relative to the other ring. The design of this bearing allows the bearing designer to potentially tune the distribution of the axial load support between the balls  18  and tapered rollers  20  as described for the first example embodiment in  FIGS. 1 and 2 . 
         [0024]    Referring to  FIG. 5 , a fourth example embodiment of a tandem tapered roller and angular contact ball bearing assembly  10 ′″ is shown that includes an inner ring  16 ′″ which does not have rib at the small diameter end  29  of the inner tapered roller raceway  21  or the large diameter end  30  of the inner tapered roller raceway  21 . A single row of balls  18  is present on the right hand side, while a single row of tapered rollers  20  is present on the left hand side. With the orientation shown in  FIG. 5 , this bearing is able to withstand radial loads in addition to an axial load that acts from right to left on the inner ring  16 ′″ or an axial load that acts from left to right on the outer ring  14 . The axial load direction that the bearing can withstand can be reversed by merely installing the bearing such that tapered rollers  20  are on the right side and the balls  18  are on the left compared to the configuration shown in  FIG. 5 . As in the previous example embodiments, the axial clearance is set by either moving the inner ring  16 ′″ or outer ring  14  axially relative to the other ring; however, due to the absence of a rib to serve as a thrust interface for tapered rollers  20 , for this fourth example embodiment the axial clearance is always a function of the clearance between the balls  18  and their respective axial shoulders  25 ,  26  on the outer ring  14  and the inner ring  16 ′″. 
         [0025]    Referring to  FIG. 6 , a fifth example embodiment of a tandem tapered roller and angular contact ball bearing assembly  40  is shown. The tandem tapered roller and angular contact ball bearing assembly  40  includes an outer ring  44 , an inner ring  46 , tapered rollers  20 , a tapered roller cage  54 , balls  18 , and a ball cage  52 . The outer ring  44  contains an outer angular contact ball raceway  45  with an axial shoulder  55 , and an outer tapered roller raceway  43 . The outer tapered roller raceway  43  has a small diameter end  57  and a large diameter end  58 . The inner ring  46  contains an inner angular contact ball raceway  49  with an axial shoulder  56 , and an inner tapered roller raceway  51 . The inner tapered roller raceway  51  has a small diameter end  59  and a large diameter end  60 . A rib  47  is present on the small diameter end  59  and a rib  41  is present on the large diameter end  60  of the inner tapered roller raceway  51 . The rib  47  on the small diameter end  59  is present to retain the rollers on the raceway, while the rib  41  on the large diameter end  60  is present to function as a potential thrust interface for the tapered rollers  20 . A single row of balls  18  is present on the right hand side, while a single row of tapered rollers  20  is present on the left hand side. With the orientation shown in  FIG. 6 , this bearing is able to withstand radial loads in addition to an axial load that acts from left to right on the inner ring  46  or an axial load that acts from right to left on the outer ring  44 . This is evident by the orientation of the tapered rollers  20  (increasing diameter from right to left) and the location of the axial shoulder  56  on the inner ball raceway  49  and the axial shoulder  55  on the outer ball raceway  45 . The axial design load direction can be reversed by merely installing the bearing such that tapered rollers  20  are on the right side and the balls  18  are on the left compared to configuration shown in  FIG. 6 . The design of this bearing allows the bearing designer to potentially tune the distribution of the axial load support between the balls  18  and the axial shoulder  55  of the outer ring  44  and the axial shoulder  56  of the inner ring  46  along with the tapered rollers  20  and the rib  41  on the large diameter end  60  of the inner tapered roller raceway  51  of the inner ring  46 . Axial clearance between the balls  18  and their respective axial shoulders  55 ,  56  versus axial clearance between the tapered rollers  20  and rib  41  can be adjusted in the design to fulfill partial support of the axial load between these interfaces (the total axial load is divided equally or unequally between interfaces of an amount greater than 0% but less than 100%), or such that either the balls  18  or tapered rollers  20  support 100% of the axial load. In an effort to reduce bearing friction, a designer could adjust the axial clearances such that the balls  18  would support most of the applied axial load, as rolling friction between the balls  18  and their respective shoulders  55 ,  56  is less than the sliding friction between the tapered rollers  20  and the rib  41 . 
         [0026]    Referring to  FIG. 7 , a sixth example embodiment of a tandem tapered roller and angular contact ball bearing assembly  40 ′ is shown that includes an inner ring  46 ′ which does not have a rib at the small diameter end  59  of the inner tapered roller raceway  51 . A single row of balls  18  is present on the right hand side, while a single row of tapered rollers  20  is present on the left hand side. With the orientation shown in  FIG. 7 , this bearing is able to withstand radial loads in addition to an axial load that acts from left to right on the inner ring  46 ′ or an axial load that acts from right to left on the outer ring  44 . The axial load direction that the bearing can withstand can be reversed by merely installing the bearing such that the tapered rollers  20  are on the right side and the balls  18  are on the left compared to the configuration shown in  FIG. 7 . The design of this bearing allows the bearing designer to potentially tune the distribution of the axial load support between the balls  18  and tapered rollers  20  as described for the fifth example embodiment in  FIG. 6 . 
         [0027]    Referring to  FIG. 8 , a seventh example embodiment of a tandem tapered roller and angular contact ball bearing assembly  40 ″ is shown that includes an inner ring  46 ″ which does not have a rib on the large diameter end  60  of the inner tapered roller raceway  51 , but does have a rib  47  on the small diameter end  59  of the inner tapered roller raceway  51 . With the orientation shown in  FIG. 8 , the bearing is able to withstand radial loads in addition to an axial load that acts from left to right on the inner ring  46 ″ or an axial load that acts from right to left on the outer ring  44 . The axial load direction that the bearing can withstand can be reversed by merely installing the bearing such that the tapered rollers  20  are on the right side and the balls  18  are on the left compared to the configuration shown in  FIG. 8 . Axial clearance is set by either moving the inner ring  46 ″ or outer ring  44  axially relative to the other ring; however, due to the absence of a rib to serve as a thrust interface for tapered rollers  20 , for this seventh example embodiment the axial clearance is always a function of the clearance between the balls  18  and their respective axial shoulders  55 ,  56  on the outer ring  44  and the inner ring  46 ″. 
         [0028]    Referring to  FIG. 9 , an eighth example embodiment of a tandem tapered roller and angular contact ball bearing assembly  40 ′″ is shown that includes an inner ring  46 ′″ which does not have a rib on the large diameter end  60  of the inner tapered roller raceway  51  or on the small diameter end  59  of the inner tapered roller raceway  51 . A single row of balls  18  is present on the right hand side, while a single row of tapered rollers  20  is present on the left hand side. With the orientation shown in  FIG. 9 , this bearing is able to withstand radial loads in addition to an axial load that acts from left to right on the inner ring  46 ′″ or an axial load that acts from right to left on the outer ring  44 . The axial load direction that the bearing can withstand can be reversed by merely installing the bearing such that tapered rollers  20  are on the right side and the balls  18  are on the left compared to the configuration shown in  FIG. 9 . As in the previous example embodiments, the axial clearance is set by either moving the inner ring  46 ′″ or outer ring  44  axially relative to the other ring; however, due to the absence of a rib to serve as a thrust interface for tapered rollers  20 , for this eighth example embodiment the axial clearance is always a function of the clearance between the balls  18  and their respective axial shoulders  55 ,  56  on the outer ring  44  and the inner ring  46 ′″. 
         [0029]    For all example embodiments, if additional tapered roller retention is needed, known retention methods may be used. For example, U.S. Pat. No. 8,783,966 describes an arrangement where a tapered roller cage contains projections that interface with a rim on an inner ring to retain the cage and tapered rollers. 
         [0030]    In the foregoing description, example embodiments are described. The specification and drawings are accordingly to be regarded in an illustrative rather than in a restrictive sense. It will, however, be evident that various modifications and changes may be made thereto, without departing from the broader spirit and scope of the present invention. 
         [0031]    In addition, it should be understood that the figures illustrated in the attachments, which highlight the functionality and advantages of the example embodiments, are presented for example purposes only. The architecture or construction of example embodiments described herein is sufficiently flexible and configurable, such that it may be utilized (and navigated) in ways other than that shown in the accompanying figures. For example, while all of the bearing embodiments can support axial loads in one direction, they may be arranged in pairs in such a way to increase axial load capacity in a single direction, or in the traditional “X” or “0” configurations to support axial loads in both directions. 
         [0032]    Although example embodiments have been described herein, many additional modifications and variations would be apparent to those skilled in the art. It is therefore to be understood that this invention may be practiced otherwise than as specifically described. Thus, the present example embodiments should be considered in all respects as illustrative and not restrictive.