Patent Publication Number: US-2018045243-A1

Title: Encapsulated axial bearing assembly having an internal damping layer

Description:
FIELD OF INVENTION 
     The present invention relates to an encapsulated bearing assembly, and, more particularly, to an encapsulated bearing assembly having an internal damping layer. 
     BACKGROUND 
     Axial roller bearings are used in various applications, including automotive assemblies such as drivetrain and suspension components, to distribute loads and allow for relative rotation. These include thrust bearings, which are positioned adjacent to a component in order to carry an axial load exerted by that component. Thrust and other axial roller bearings are often encapsulated in that they include a plurality of rollers enclosed by an opposing pair of washers. The rollers are positioned in a cage and directly contact races formed by inner surfaces of the washers. While this is a typical bearing configuration, it may be less than ideal in certain situations because the direct contact between all components allows the bearing to transmit vibration from one side to the other, and to adjacent components, fairly easily. For example, a typical thrust bearing may transmit vibration to a transmission case, which may then lead to undesirable noise being produced from the case. 
     Excessive vibration can be inhibited by preventing surface defects in the rollers and races of the bearings. However, ensuring that all components are made without even minor defects is cost prohibitive and generally not feasible. Another potential solution is to include an external damping layer between the bearing and the adjacent component, such as in the configuration described in U.S. Patent Application No. 2011/0182542. A drawback of the external damping layer, however, is that it may wear due to rotation of the bearing relative to the adjacent component. 
     It would therefore be desirable to provide an axial roller bearing which addresses the problem of edge loading and other drawbacks of the prior art. 
     SUMMARY 
     In one aspect, the present disclosure is directed to an axial roller bearing assembly. The axial roller bearing assembly includes a first axial washer including a first race surface and a second axial washer including a thrust surface. The first axial washer and the second axial washer form a housing space. The axial roller bearing assembly also includes a third axial washer disposed in the housing space between the first axial washer and the second axial washer and including a second race surface. The axial roller bearing assembly further includes a bearing element disposed in the housing space and which includes a cage and a plurality of rollers in contact with the first race surface and the second race surface. The axial roller bearing assembly also includes a damping layer disposed in the housing space and in contact with the second axial washer and the third axial washer. The damping layer inhibits vibration from transferring between the third axial washer and the second axial washer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING(S) 
       The foregoing Summary and the following detailed description will be better understood when read in conjunction with the appended drawings, which illustrate a preferred embodiment of the invention. In the drawings: 
         FIG. 1  is a cross-sectional view of an axial roller bearing including an internal damping layer. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
       FIG. 1  depicts an axial roller bearing assembly  10 . In an exemplary embodiment, the axial roller bearing assembly  10  is positioned adjacent to a part of a transmission case  100  and used as a thrust bearing. It should be understood, however, that the axial roller bearing assembly  10  may be used in other environments, such as adjacent to other components that are particularly susceptible to generating excessive noise when vibrated. The axial roller bearing assembly  10  (“bearing assembly  10 ”) includes a first axial washer  12 , a second axial washer  14 , a third axial washer  16 , a bearing element  18 , and a damping layer  20 . 
     The first axial washer  12  includes a circumferentially extending body  22  which includes an axial flange  24  and a radial flange  26 . The axial flange  24  extends axially and forms an enclosing surface  28 . The radial flange  26  is directly connected to and extends in an outward-radial direction from the axial flange  24 . The radial flange  26  defines an outer thrust surface  30  and an inner race surface  32  (i.e. a first race surface). In an exemplary embodiment, the axial flange  24  and radial flange  26  form an L-shaped cross-section, with the axial flange  24  extending in a first axial direction (e.g., toward the transmission case  100 ) at a radially-inner section of the bearing assembly  10 . 
     The second axial washer  14  includes a second circumferentially extending body  34  which includes an axial flange  36  and a radial flange  38 . The axial flange  36  extends axially and forms an enclosing surface  40 . The radial flange  38  is directly connected to and extends in an inward radial direction from the axial flange  36 . The radial flange  38  defines an outer thrust surface  42  which, in an exemplary embodiment, is in contact with the transmission case  100 . The radial flange also includes an inner surface  44 . In an exemplary embodiment, the axial flange  36  and the radial flange  38  form an L-shaped cross-section, with the axial flange  36  extending in a second axial direction, which is opposite to the first axial direction (e.g., away from the transmission case  100 ) at a radially-outer section of the bearing assembly  10 . 
     As shown in  FIG. 1 , the first axial washer  12  and the second axial washer  14  are positioned to form a housing space  46  for receiving the third axial washer  16 , the bearing element  18 , and the damping layer  20 . For example, the L-shaped first and second washers  12 ,  14  are positioned such that the housing space  46  is formed axially between the inner race surface  32  and the inner surface  44 , and radially between the enclosing surface  28  and the enclosing surface  40 . 
     The third axial washer  16  is positioned in the housing space  46 , between the bearing element  18  and the damping layer  20 , and includes a race surface  48  (i.e., a second race surface) and a damping surface  50 . 
     The bearing element  18  is preferably an axial needle roller arrangement, although other types of bearing elements are possible. In an exemplary embodiment, the bearing element  18  includes a plurality of rollers  52  which are spaced apart circumferentially from one another by a cage  54 . The rollers  52  and cage  54  may be preassembled as a cage and roller assembly that includes the rollers  52  located in pockets in the cage  54 , which is preferably stamped from sheet metal. The rollers  52  are located in at least some of the pockets and roll against the inner race surface  32  of the first axial washer  12  on one side and the race surface  48  of the third axial washer  16  on the opposite side. A lubricant may be positioned in between the race surfaces  32 ,  48  and the rollers  52 . An axial force exerted on the bearing assembly  10  may help to maintain the rollers  52  in contact with the race surfaces  32 ,  48 , which may help to ensure proper operation of the bearing assembly  10 . 
     In order to connect the components of the bearing assembly  10 , the first axial washer  12  and the second axial washer  14  preferably include interlocking features. For example, the first axial washer  12  and the second axial washer may include punch-in tabs  56  which overlap and/or are inserted into opposing portions of the cage  54 . This interlocking connection retains the bearing element  18  within the first axial washer  12  and the second axial washer  14 . Alternative means for interconnecting the components include external fasteners, an overlap of interlocking features on the axial washers themselves etc. 
     The damping layer  20  is positioned between and in contact with the inner surface  44  and the damping surface  50 . The damping layer  20  is made of a vibration-reducing material which isolates the bearing element  18  from the second axial washer  14  and the transmission case  100 . For example, the damping layer  20  may be formed from a polymer material having good sound and vibration damping qualities. Examples of materials that may be used for damping layer  20  include nitrile butadiene rubber (NRB), fluoroelastomers which contain vinylidene fluoride monomers, and acrylic. The damping layer  20  may include a hardness of approximately 50-75 durometer. In some embodiments, the damping layer  20  may include a thin steel core coated with a damping material, such as one of the materials listed above. 
     In an exemplary embodiment, the damping layer  20  is formed to be a flat ring-shaped component. For example, the damping layer  20  may include an axial thickness that is much less than a radial length (i.e., the radial dimension of the cross-section of the damping layer  20  shown in  FIG. 1 ). In this way, the damping layer  20  does not dramatically increase an overall thickness of the axial roller bearing assembly  10 . This can be further addressed by forming associated thicknesses of the first, second, and third axial washers  12 ,  14 ,  16  to be smaller than a typical axial roller bearing assembly, and, in some embodiments, smaller than the thickness of the damping layer  20 . 
     Moreover, the damping layer  20  is formed to be in surface contact with the second and third axial washers  14 ,  16 . For example, the opposing surfaces of the damping layer  20  may be in surface contact with the inner surface  44  and the damping surface  50 . In some embodiments, in order to sufficiently decouple the second and third axial washers  14 ,  16 , the damping layer  20  may contact at least 80% of a surface area of the inner surface  44  and the damping surface  50 . 
     In use, the damping layer  20  inhibits the transfer of vibration from the third axial washer  16  to the second axial washer  14  and the adjacent transmission case  100  (and vice versa). In this way any vibration produced by the bearing element  16  (or another component in contact with the first axial washer  12 ) will be inhibited from causing the transmission case  100  to vibrate, thereby reducing the potential for the transmission case  100  to produce excessive noise and/or be damaged. Similarly, any vibration originating in the transmission case  100  (or other component in contact with the thrust surface  30 ) will not transfer through the bearing assembly  10 . 
     Further, the interlocking connection with the cage  54  insures that the first and second axial washers  12 ,  14  remain decoupled from each other in terms of vibration-transmission. Vibration that occurs due to the rollers  52  will primarily be localized to the first and third axial washer  12 ,  16 , and does not transfer easily through the cage  54 . Therefore, despite the close positioning and interconnection of an encapsulated bearing, the disclosed configuration nevertheless allows such a bearing to inhibit the transfer of vibration from one side to another. In this way, such encapsulated bearings may be used in conjunction with components (i.e., transmission case  100 ) that are susceptible to vibration and/or on which vibration has a negative effect. 
     Having thus described various embodiments of the present bearing assembly  10  in detail, it is to be appreciated and will be apparent to those skilled in the art that many physical changes, only a few of which are exemplified in the detailed description above, could be made in the assembly without altering the inventive concepts and principles embodied therein. For example, in some embodiments, the components may be reversed, with the third axial washer  16  and the damping layer  20  positioned on an axially-outer side of the bearing element  18  and the second axial washer  14  defining a race surface in contact with the rollers  52 . Moreover, the axial flanges  24 ,  36  may be reversed, with the axial flange  24  forming a radial-outer support surface and the axial flange  36  forming a radial-inner support surface. 
     The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore to be embraced therein. 
     PARTS LIST 
     
         
         
           
               10 . Axial Roller Bearing Assembly 
               12 . First Axial Washer 
               14 . Second Axial Washer 
               16 . Third Axial Washer 
               18 . Bearing Element 
               20 . Damping Layer 
               22 . Body 
               24 . Axial Flange 
               26 . Radial Flange 
               28 . Enclosing Surface 
               30 . Thrust Surface 
               32 . Race Surface 
               34 . Body 
               36 . Axial Flange 
               38 . Radial Flange 
               40 . Enclosing Surface 
               42 . Thrust Surface 
               44 . Inner Surface 
               46 . Housing Space 
               48 . Race Surface 
               50 . Damping Surface 
               52 . Roller 
               54 . Cage 
               56 . Punch-in Tab 
               100 . Transmission Case