Abstract:
A bearing assembly comprises an outer ring and an inner ring radially inward of the outer ring and cooperating therewith to form a roller volume. The inner ring has opposed faces including slots extending axially and circumferentially spaced. The slots extends axially to openings into the opposed axial faces and communicate with partial circumferential slots in the inner circumferential surface and in fluid communication with the roller volume through passages in the inner ring. A first plurality of the axial slots has a radial depth increasing from a first of the axial faces to the respective partial circumferential slot. A second plurality of the axial slots has a radial depth increasing from the second of the axial faces to the respective partial circumferential slot. Bearing elements are in the roller volume rollingly disposed against the outer ring and the inner ring.

Description:
TECHNICAL FIELD 
       [0001]    The application relates generally to bearing assemblies and, more particularly, to an inner ring for such an assembly. 
       BACKGROUND OF THE ART 
       [0002]    To reduce wear on bearing assemblies such as those used in gas turbine engines, lubricating fluid such as oil is typically used to keep them cool and lubricate them. In particular, some of these bearing may be high-speed bearings, whereby adequate lubricating may increase their durability. Lubricating fluid (i.e., lubricant such as may be delivered by being channeled under the bearing, for example through circular axial slots formed on an inside surface of an inner ring of the bearing assembly, with radial holes extending through the inner ring to intersect the axial slots. The axial slots may be provided with an angle relative to a rotational axis of the component supported by the bearing, to enhance flow of the lubricant to the radial holes. However, because of the angulation of axial slots, the bearing has an orientation, and it is misoriented, the angulation of the axial slots may hamper the flow of lubricant to the radial holes. 
       SUMMARY 
       [0003]    In one aspect, there is provided a bearing assembly comprising: an outer ring defining a central axis of rotation for the bearing assembly; an inner ring disposed radially inwardly of the outer ring and cooperating therewith to form a roller volume, the inner ring having opposed axial faces and including axial slots formed in, extending axially along and circumferentially spaced around an inner circumferential surface, each said axial slots extending axially toopenings into the opposed axial faces of the inner ring and communicating with a respective partial circumferential slot defined in the inner circumferential surface and being in fluid communication with the roller volume through a respective passage in the inner ring, a first plurality of the axial slots having a radial depth increasing from a first of the axial faces to at least the respective partial circumferential slot, and a second plurality of the axial slots having a radial depth increasing from the second of the axial faces to at least the respective partial circumferential slot; and bearing elements in the roller volume rollingly disposed against an inner circumferential surface of the outer ring and an outer circumferential surface of the inner ring, the bearing elements allowing relative rotational motion between the outer ring and the inner ring. 
         [0004]    In another aspect of the present disclosure, there is provided an inner ring of a bearing assembly comprising a ring body configured to be disposed radially inwardly of an outer ring of the bearing assembly and cooperating therewith to form a roller volume configured for receiving roller bearing elements allowing relative rotational motion between the outer ring and the inner ring, the inner ring having opposed axial faces and including axial slots formed in, extending axially along and circumferentially spaced around an inner circumferential surface of the ring body, each said axial slots extending axially to openings into the opposed axial faces of the inner ring and communicating with a respective partial circumferential slot defined in the inner circumferential surface and being in fluid communication with the roller volume through a respective passage in the inner ring, a first plurality of the axial slots having a radial depth increasing from a first of the axial faces to at least the respective partial circumferential slot, and a second plurality of the axial slots having a radial depth increasing from the second of the axial faces to at least the respective partial circumferential slot. 
         [0005]    In yet another aspect of the present disclosure, there is provided a method of lubricating a bearing assembly comprising: circulating a lubricating fluid axially and radially outwardly along a first plurality of axial slots in an inner surface of an inner ring of the bearing assembly to distally-located partial circumferential slots in the inner ring; and circulating the lubricating fluid axially and radially inwardly along a second plurality of axial slots in the inner surface of the inner ring of the bearing assembly to proximally-located partial circumferential slots in the inner ring. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0006]    Reference is now made to the accompanying figures in which: 
           [0007]      FIG. 1  is a schematic front view of a bearing assembly in accordance with a particular embodiment; 
           [0008]      FIG. 2  is a schematic cross-sectional side view of the bearing assembly of  FIG. 1 ; 
           [0009]      FIG. 3  is a schematic tridimensional view of a cross-section of part of an inner ring of the bearing assembly of  FIG. 1 ; 
           [0010]      FIG. 4  is a cross-sectional view of part of the inner ring of  FIG. 3  showing a first axial slot; and 
           [0011]      FIG. 5  is a cross-sectional view of part of the inner ring of  FIG. 3  showing a second axial slot. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    Referring to  FIGS. 1-2 , a bearing assembly  10  in accordance with a particular embodiment is shown. According to an embodiment, the bearing assembly  10  is a high speed bearing, in that it may rotate in excess of 2.0 MDN (bearing bore diameter in millimeters times speed in rpm divided by one million), although it may be used in bearing assemblies operating at lesser speeds. The bearing assembly  10  generally includes concentric inner and outer rings  12 ,  14  respectively defining complementary inner and outer races  16 ,  18 , in which a plurality of bearing elements  20  retained by a cage member  22  are received to allow relative rotation between the inner and outer rings  12 ,  14 . In the embodiments shown, the bearing elements  20  are roller bearings, but it is understood that other adequate types of bearing elements can alternately be used, such as for example ball bearings and tapered bearings. The cage member  22  is received between the inner and outer rings  12 ,  14  and equally spaces the bearing elements  20  apart such that each bearing element  20  rotates around the inner and outer races  16 ,  18  without contacting the other bearing elements  20 . 
         [0013]    Referring more particularly to  FIG. 2 , the outer ring  14  has a ring body that is centered on a central axis X of the bearing assembly  10 , with the outer race  18  being defined on an inner surface  24  thereof around its circumference. Although not shown in  FIG. 2 , the inner surface  24  may be at the same diameter as the outer race  18 . The inner ring  12  may also be centered on the central axis X of the bearing assembly  10 , with the inner race  16  being defined on an outer surface  26  thereof around its circumference. The outer surface  26  of the inner ring  12  includes two annular shoulders  28  also extending around its circumference, with the inner race  16  being defined between the shoulders  28 . 
         [0014]    Referring to  FIGS. 2-5 , the inner surface  30  of the inner ring  12  includes a plurality of axial slots  32  and partial circumferential slots  34  defined therein. In the figures, the axial slots  32  may be shown as  32 A and  32 B, while slots  34  may be illustrated as  34 A,  34 B,  34 C and  34 D, while being concurrently referred to as slots  32  and  34  for simplicity. 
         [0015]    The axial slots  32  have a length L A  ( FIGS. 2, 4 and 5 ) defined along the axial direction of the bearing assembly  10 , a width W A  ( FIG. 3 ) defined along the circumferential direction, and a radial depth D A  ( FIGS. 4 and 5 ) defined along the radial direction. In the embodiment shown in  FIG. 2 , the axial slots  32  are regularly spaced apart around the circumference of the inner ring  12 , and each axial slot  32  extends straight across the inner surface  30  from a first axial face  36  to a second axial face  38  of the inner ring  12 . For example, the slots  32  alternate between in a  32 A- 32 B- 32 A- 32 B- . . . sequence. All the axial slots  32  may have a same width W A . Other configurations are also possible. 
         [0016]    As can be seen more clearly in  FIGS. 3-5 , the axial slots  32  have a cross-section defining a flat bottom wall  40 . In the embodiment shown, the axial slots  32  have a rectangular cross-section, and are defined with a depth D A  varying across their length L A . As shown in  FIGS. 4 and 5 , the axial slots  32  are angled relative to a rotational axis of the bearing assembly  10 , shown as central axis X in  FIG. 1 . In  FIG. 4 , the axial slot  32 A is angled such that the depth D A  increases from the second axial face  38  to the first axial face  36 . The depth D A  may increase in linear fashion, as in  FIG. 4 , from face to face or at least to the respective circumferential slot  34 . However, other depth variations may be present, for example by way of an arcuate shape to the bottom wall  40 . Likewise, in  FIG. 5 , the axial slot  32 B is angled such that the depth D A  increases from the first axial face  36  to the second axial face  38 . Again, the depth D A  may increase in linear fashion, as in  FIG. 5 . However, other depth variations may be present, for example by way of an arcuate shape to the bottom wall  40 . The variation in depth D A  in the slots  32 A and  32 B may be the same, such that the slots  32 A and  32 B are mirror images of one another. The depth variation D A , when linear, may be depicted by angle θ having an angle of 1° 15′±0° 15′, as an example, relative to the central axis X. The arrangement of slots  32 A and  32 B is such that the partial circumferential slots  34  are located at the deeper portion of the slots  32 . Therefore, taking the example of  FIG. 4 , if pressurized lubricant is fed to the axial slot  32 A via the second axial face  38 , centrifugal forces on the lubricant will collaborate with the favorable angle θ to assist in directing the lubricant to the partial circumferential slot  34 A, distally located. If, alternatively, pressurized lubricant is fed to the axial slot  32 A via the first axial face  36 , the proximity between the first axial face  36  and the partial circumferential slot  34 A is such that the pressure of the lubricant will direct it to the partial circumferential slot  34 A, proximally located, in spite of the unfavorable angle θ. The same action may occur if the partial circumferential slot is of the  34 B kind. Now taking the example of  FIG. 5 , if pressurized lubricant is fed to the axial slot  32 B via the first axial face  36 , centrifugal forces on the lubricant will collaborate with the favorable angle θ to assist in directing the lubricant to the partial circumferential slot  34 D, distally located. If pressurized lubricant is fed to the axial slot  32 B via the second axial face  38 , the proximity between the second axial face  38  and the partial circumferential slot  34 D is such that the pressure of the lubricant will direct it to the partial circumferential slot  34 D, proximally located, in spite of the unfavorable angle θ. The same action may occur if the partial circumferential slot is of the  34 C kind. Therefore, by having slots  32 A and  32 B in the inner ring  12 , for instance in the alternating sequence  32 A- 32 B- 32 A- 32 B-etc or in any other sequence, allows the inner ring  12  to be reversible, i.e., not to have an orientation. The inner ring  12  may also be symmetrical, for example in the case of the alternating sequence  32 A- 32 B- 32 A- 32 B-etc. 
         [0017]    As observed in  FIGS. 2-5 , the partial circumferential slots  34  are off-centered relative to the axial dimension. However, some if not all of the circumferential slots  34  may be substantially centered in the axial dimension. When off-centered, as in  FIGS. 2-5 , the partial circumferential slots  34  may be located in the half portion of the inner ring  12  in which the slots  32 A and  32 B are deeper, as explained in detail above for  FIGS. 4 and 5 . The slots  34 A and  34 D, as explained below, are substantially closer to the first end  36  and to the second end  38 , respectively, than to the second end  38  and to the first end  36 , respectively. 
         [0018]    The partial circumferential slots  34  have a length L C  ( FIG. 2 ) defined along the circumferential direction of the bearing assembly  10 , a width W C  defined along the axial direction, and a depth D C  defined along the radial direction. The partial circumferential slots  34  may have a depth D C  varying across their length, defined by an arcuate bottom wall  42  (e.g., circular) having a center of curvature offset from the central axis X of the bearing assembly  10  and a smaller radius than that of the inner surface  30  of the inner ring  12 . The partial circumferential slots  34  may also have a rectangular cross-section defined perpendicularly to their length L C . Each partial circumferential slot  34  extends circumferentially across and in fluid communication with a respective one of the axial slots  32 , around a portion of the circumference greater than that of the respective axial slot  32  such as to extend circumferentially therefrom, i.e. the length L C  of each partial circumferential slot  34  is greater than the width W A  of the corresponding axial slot  32 . In the embodiment shown, all the partial circumferential slots  34  have a same length L C  and have a same maximum depth D C . Alternately, partial circumferential slots  34  with different geometries from one another may be provided. 
         [0019]    The partial circumferential slots  34  may be disposed into four sets: first and second sets  34 A,  34 B closer to the first axial face  36  of the inner ring  12 , axially offset from one another with the first set  34 A being closest to the first axial face  36 , and third and fourth sets  34 C,  34 D closer to the second axial face  38  of the inner ring  12 , axially offset from one another with the fourth set  34 D being closest to the second axial face  38 . In the embodiment shown, each set  34 A,  34 B,  34 C,  34 D includes the same number of partial circumferential slots  34 , and the slots  34  are equally spaced apart circumferentially and disposed such as to alternate between the four sets  34 A,  34 B,  34 C,  34 D around the circumference of the inner ring  12 , i.e. the partial circumferential slots  34  from the four sets  34 A,  34 B,  34 C,  34 D are staggered. The axial distance between the partial circumferential slots  34 A and the first axial face  36  of the inner ring  12  and the axial distance between the partial circumferential slots  34 D and the second axial face  38  of the inner ring  12  may be the same. The axial distance between the partial circumferential slots  34 B and the first axial face  36  of the inner ring  12  and the axial distance between the partial circumferential slots  34 C and the second axial face  38  of the inner ring  12  may be the same. Other configurations are of course possible. In the particular embodiment shown, each set A, B, C, D includes four partial circumferential slots  34  for a total of sixteen partial circumferential slots  34 , and sixteen axial slots  32  are provided; alternately, more or less slots  32 ,  34  may be provided. 
         [0020]    The axial and partial circumferential slots  32 ,  34  extend radially into the inner ring  12  without penetrating the outer surface  26  and the inner race  16  defined therein. Each axial slot  32  extends radially into the inner ring  12  a distance less than that of the corresponding partial circumferential slot  34 , i.e. the depth D A  of the axial slots  32  is smaller than the maximum depth D C  of the partial circumferential slots  34 . 
         [0021]    Referring to  FIGS. 2-3 , the inner ring  12  also includes a plurality of radial holes  44 ,  46  defined therethrough, with one radial hole  44 ,  46  extending from each partial circumferential slot  34  in fluid communication therewith. The radial holes  44 ,  46  have a length L R  ( FIG. 3 ) defined along the radial direction. Each radial hole  44 ,  46  is circumferentially offset with respect to the axial slot  32  crossing the partial circumferential slot  34  in which the radial hole  44 ,  46  is defined, i.e. the radial hole  44 ,  46  is located in the portion of the partial circumferential slot  34  extending from the axial slot  32 . 
         [0022]    The radial holes  44 ,  46  are defined as shoulder radial holes or race radial holes depending on their position. Referring particularly to  FIG. 3 , each partial circumferential slot  34 A and  34 D has a shoulder radial hole  44  extending from the surface of its bottom wall  42 , the shoulder radial holes  44  extending through the inner ring  12  to the outer surface  26  along one of the shoulders  28  bordering the inner race  16 . The shoulder radial holes  44  feed the lubricating fluid to the cage piloting surface at the shoulder  28 . In a particular embodiment, the shoulder radial holes  44  are positioned such as to be overlapped by the cage member  22  in any position thereof when the bearing elements  20  are received within the inner race  16 . 
         [0023]    Moreover, each partial circumferential slot  34 B and  34 C has a race radial hole  46  extending from the surface of its bottom wall  42 , the race radial holes  46  extending through the inner ring  12  to a corner of the inner race  16 . In the embodiment shown, a circumferential groove  48  is defined along each corner of the inner race  16 , and the race radial holes  46  extend to the respective one of these two grooves  48 . The race radial holes  46  provide lubricating fluid directly to the bearing element  20  and the inner race contact interface. 
         [0024]    In a particular embodiment, all the radial holes  44 ,  46  have the same diameter, and have a constant diameter across their length L R , i.e. from the communication with the corresponding partial circumferential slot  34  to the communication with the surface of the shoulder  28  or with the corner of the inner race  16 . In a particular embodiment, the radial holes  44 ,  46  include a same number of the race radial holes  46  and of the shoulder radial holes  44 . 
         [0025]    The partial circumferential slots  34 , axial slots  32 , and radial holes  44 ,  46  function together as a series of fluid passages to deliver lubricating fluid to the bearing assembly  10 . Once the inner ring  12  has been mounted to a shaft, lubricating fluid is circulated to the inner ring  12 , for example from a radial scoop or an axial scoop depending on the space available for the bearing assembly  10 . The lubricating fluid is first circulated axially along the inner surface  30  of the inner ring  12  following a plurality of distinct first paths defined by the axial slots  32 , then from these first paths following a plurality of distinct second paths defined by the partial circumferential slots  34 . The lubricating fluid is then circulated radially from the partial circumferential slots  34 A and  34 D through the inner ring  12  directly to the shoulders  28  receiving the cage member  22 , through the shoulder radial holes  44 , and radially from the partial circumferential slots  34 B and  34 C through the inner ring  12  directly to the corners of the inner race  16 , through the race radial holes  46 . 
         [0026]    Therefore, a method of lubricating a bearing assembly comprises circulating a lubricating fluid axially and radially outwardly along a first set of the axial slots  32 A in the inner surface of the inner ring  12  of the bearing assembly  10  to distally-located partial circumferential slots  34 A,  34 B in the inner ring  12 , and simultaneously circulating the lubricating fluid axially and radially inwardly along a second set of the axial slots  32 B in the inner surface of the inner ring  12  of the bearing assembly  10  to proximally-located partial circumferential slots  34 C,  34 D in the inner ring  12 . The lubricating fluid, in a pressurized condition, may be received solely at the axial face  38  of the inner ring  12 . Circulating the lubricating fluid axially and radially outwardly comprises circulating the lubricating fluid at an angle of 1° 15′±0° 15′ outward relative to a rotational axis of the bearing assembly. Circulating the lubricating fluid axially and radially inwardly comprises circulating the lubricating fluid at an angle of 1° 15′±0° 15′ toward a rotational axis of the bearing assembly. Circulating the lubricating fluid comprises circulating the lubricating fluid in an equal number of the first set of the axial slots than the second set of the axial slots. 
         [0027]    The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the embodiments described without departing from the scope of the invention disclosed. For example, the bearing assembly  10  is used as a high speed bearing to support the compressor shaft or the turbine shaft of a gas turbine engine. The axial slots  32  may not extend all the way to the distal axial faces  36  or  38 , but would be extend only to the related distal partial circumferential slots  34 , although this would impact the reversibility of the inner ring  12 . Still other modifications which fall within the scope of the present invention will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the appended claims.