Abstract:
A thermal compensation element which has an inner ring, an outer ring, and a washer. The washer is arranged within the inner ring and the outer ring is mounted over the inner ring, encapsulating the washer, which can be a split wave spring. The inner ring and the outer ring each have retention features to ensure they are retained relative to each other. The thermal compensation, which is positioned between a housing or a shaft, can account for variations in loading and/or temperature that may occur to a bearing and a shaft system when the shaft and an associated component are made of different materials and have different coefficients of thermal expansion by ensuring a proper axial preload is maintained on the bearing.

Description:
This application claims the priority U.S. 61/437,189 filed Jan. 28, 2011 which is incorporated by reference herein. 
    
    
     FIELD OF INVENTION 
     The present invention relates generally to bearings and more particularly to a thermal compensation element which accounts for thermal changes that may occur in applications utilizing bearings or the like that require axial preload for proper functionality. 
     BACKGROUND OF THE INVENTION 
     The use of an elastomeric material to compensate for thermal expansion and contraction of components which have dissimilar materials and are used in conjunction with each other are known, see, for example, U.S. Pat. No. 5,028,152. Such an arrangement includes inserting an elastomer into a cavity within a machined outer ring of a bearing, bonding an elastomer to a metallic backing, or encapsulating an elastomer within two cups which are snapped into a cavity in an outer ring or an inner ring. However, there are various drawbacks to such arrangements. For example, such arrangements can affect the load carrying capability of the bearing. The bonding of an elastomer to a metallic backing is an especially costly process. Moreover, encapsulated design with two cups requires a special profiled elastomer which is difficult to assemble and the elastomer increases the tolerance stack-up. Additionally, the encapsulated design requires shimming on an individual basis when trying to achieve a desired preload at the application assembly. Further, many elastomeric materials are compressible and cannot withstand variation in temperature cycles. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a thermal compensation element, which is positioned between a bearing and a shoulder of a housing or a shaft and can account for high loads and extreme variations of temperature that may occur to a bearing and shaft system when the shaft and an associated housing for a transmission, gearbox, axle or the like are comprised of different materials and have different coefficients of thermal expansion (e.g., sheet metal shaft and an aluminum housing). Due to the differences of materials and different coefficients of thermal expansion, the rates of expansion and contraction can vary causing a wide variation in bearing preload over a range of temperatures. This variation can lead to an increased preload, an increased frictional torque, and/or a loss of preload, which in turn can lead to a reduction in the life of the bearing and noise. 
     The present invention, which is inexpensive and relatively easy to manufacture and assemble, compensates for the potential loading and thermal changes without affecting the bearing&#39;s load carrying capacity by maintaining a preload force on the bearing regardless of the size of the components surrounding the bearing. Through expansion and compression, the thermal compensating element ensures shaft system stiffness and aids in maintaining the life of the bearing. Further, the thermal compensation element reduces axial tolerance stack-up with the only variation being due to the wall thickness of the cup formed by the inner ring and the outer ring. 
     It should be noted that the present invention can be used in conjunction with various types of bearings including, but not limited to angular contact ball bearings, tandem ball bearings, tapered roller bearings. 
     Broadly, the present invention can be defined as a thermal compensation element, which can comprise an inner ring, an outer ring, and a washer, which can be arranged within a channel of the inner ring with the outer ring being mounted over the inner ring, encapsulating the washer. 
     The washer can be a split wave spring. 
     The inner ring can have a U-shaped cross-section with a first wall extending from a first end of a base and a second wall extending in a same direction as the first wall from a second end of the base. The first flange and the second flange of the inner ring can each have an inner face and an outer face. Also, the outer ring can have a U-shaped cross-section with a first wall extending from a first end of a base and a second wall extending in a same direction as the first wall from a second end of the base. The first flange and the second flange of the outer ring can each have an inner face and an outer face. 
     The inner ring can have a first channel in which the washer is arranged and the outer ring can have a second channel. 
     The inner ring and the outer ring can be movable axially relative to each other. 
     The outer face of the first wall of the inner ring can have a first protrusion which is contactable with the inner face of the first wall of the outer ring and the outer face of the second wall of the inner ring can have a second protrusion which is contactable with the inner face of the second wall of the outer ring. Also, the first wall of the outer ring can be bent inward and can be contactable with the outer face of the first wall of the inner ring and the second wall of the outer ring can be bent inward and can be contactable with the outer face of the second wall of the inner ring. 
     Also, the first wall of the inner ring can be bent outward and can be contactable with the inner face of the first wall of the outer ring and the second wall of the inner ring can be beat outward and can be contactable with the inner face of the second wall of the outer ring. Also, the first wall of the outer ring can be bent inward and can be contactable with the outer face of the first wall of the inner ring and the second wall of the outer ring can be beat inward and can be contactable with the outer face of the second wall of the inner ring. 
     Alternatively, a first tab can protrude outward from the outer face of the first wall of the inner ring, near a first end region and a groove can extend along the outer face of the first wall of the inner ring up to the first tab and a second tab can protrude outward from the outer face of the second wall, near a second end region and a groove can extend along the outer face of the second wall of the inner ring up to the second tab. Also, a third tab can protrude outward from the inner face of the first wall of the outer ring, near a first end region and a groove can extend along the inner face of the first wall of the outer ring up to the third tab, and a fourth tab can protrude outward from the inner face of the second wall of the outer ring, near a second end region and a groove can extend along the inner face of the second wall of the outer ring up to the fourth tab such that the first tab of the inner ring can be in sliding contact with the groove of the first wall, the second tab can be in sliding contact with the groove of the second wall of the outer ring, the third tab of the outer ring can be in sliding contact with the groove of the first wall of the inner ring and the fourth tab of the outer ring can be in sliding contact with the groove of the second wall of the inner ring. 
     Further, a first wall of the inner ring can have a first lip protruding outward from the outer face of the first wall which can be in sliding contact with the inner face of the first wall of the outer ring and the second wall of the inner ring can have a second lip protruding outward from the outer face of the second wall which can be in sliding contact with the inner face of the second wall of the outer ring. Also, the first wall of the outer ring can have a third lip protruding inward from the inner face of the first wall which can be in sliding contact with the outer face of the first wall of the inner ring and the second wall of the outer ring can have a fourth lip protruding inward from the inner face of the second wall which can be in sliding contact with the outer face of the second wall of the inner ring. 
     The first wall and the second wall of the inner ring can be a predetermined length, providing a positive stop to protect the washer from plastic deformation. 
     The thermal compensation element can be positioned between a housing/shaft system shoulder and a bearing. 
     The bearing can be a tandem hall bearing, an angular contact hall bearing, or a tapered roller bearing. 
     The bearing can be preloaded axially through the thermal compensation element, compressing the washer at a position between fully free and a positive stop. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be further understood and appreciated by reading the following description in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a partial cross-sectional view of a thermal compensation element of the present invention in contact with an outer ring of a bearing; 
         FIG. 2  is a partial cross-sectional view of the thermal compensation element of the present invention in contact with an inner ring of a bearing; 
         FIG. 3  is a cross-sectional view of a thermal compensation element of the present invention in contact with an outer ring of a bearing; 
         FIG. 4  is a perspective view of a wave spring of the present invention; 
         FIG. 5  is a further perspective view of the wave spring of the present invention; 
         FIG. 6  is an axial view of an inner ring and the wave spring of the present invention; 
         FIG. 7  is a cross-sectional view of a first embodiment of the thermal compensation element of the present invention; 
         FIG. 8  is a cross-sectional view of a second embodiment of the thermal compensation element of the present invention; 
         FIG. 9  is a cross-sectional view of a third embodiment of the thermal compensation element of the present invention; and 
         FIG. 10  is a cross-sectional view of a fourth embodiment of the thermal compensation element of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1-3  illustrate a thermal compensation element  10  positioned against a bearing  12 . Typically, the thermal compensation element  10  is arranged between the bearing  12  and a housing/shaft system shoulder (not shown) to maintain proper preload even when the housing/shaft system is composed of dissimilar materials by expanding and compressing. 
     The thermal compensation element  10  includes an inner ring  14 , an outer ring  16 , and a washer or split wave spring  18 . The inner ring  14  has a U-shaped cross-section with a first wall  20  extending from a first end of a base  22  and a second wall  24  extending in a same direction as the first wall  20  from a second end of the base  22 . Similarly, the outer ring  16  has a U-shaped cross-section with a first wall  26  extending from a first end of a base  28  and a second wall  30  extending in a same direction as the first wall  26  from a second end of the base  28 . The wave spring  18  is arranged within a channel formed by the walls  20 ,  24  and the base  22  of the inner ring  14 . The outer ring  16  is then mounted, i.e. pressed over the inner ring  14 , encapsulating the wave spring  18 . The inner ring  14  and the outer ring  16  are movable axially relative to each other, but are retained by the interaction of the walls  20 ,  24 ,  26 ,  30 . Such retention features can include formed tabs, staked tabs, machined tabs, grooves, cutouts, and the like or any combination of retention features. Also, the lengths of the walls  20 ,  24  of the inner ring  14  are predetermined so as to provide a positive stop to protect the wave spring  18  from plastic deformation. 
     As shown, the bearing  12  has an outer ring  32 , an inner ring  34 , roller bodies  36  which are arranged between the outer ring  32  and the inner ring  34 , and a cage  38 . The bearing  12  can be, for example, a tandem ball bearing, an angular contact ball bearing, a tapered roller bearing or the like. 
       FIGS. 4 and 5  show views of the wave spring  18  removed from the channel of the inner ring  14 . The wave spring  18  applies a preload force to the bearing  12 , and compensates for axial displacement of the housing/shaft system as the system is heated and cooled. For example, the distance between a shoulder of an aluminum housing and a shoulder of a steel shaft disposed in the housing can vary with change in temperature. In a system without a thermal compensating element, maintaining preload for the bearing  12  at high temperatures often results in excessive preload as the system contracts at low temperatures. Excessive preload can increase friction in the bearing  12 , thereby decreasing its performance. 
     The thermal compensating element  10  uses the wave spring  18  to maintain a relatively consistent preload force on the bearing  12  as the housing/shaft system displaces at high and low temperatures. That is, the expansion and contraction of the housing/shaft system is compensated by deflection of the wave spring, with relatively minor differences in bearing preload at the various operating temperatures. The load-deflection characteristic of the wave spring is such that the spring force is somewhat constant for large changes in deflection. 
       FIG. 6  is an axial view depicting only the inner ring  14  and the wave spring  18  (outer ring  16  removed for clarity). As shown, the wave spring  18  is not continuous, but rather has a gap  40 . The gap  40  allows the wave spring to deflect axially while maintaining a relatively constant diameter. 
       FIGS. 7-10  show a cross-section of various embodiments  100 ,  200 ,  300 ,  400  of the thermal compensation element  10 . 
       FIG. 7  shows a first embodiment of the thermal compensation element  100 . As shown, a first wall  102  of the inner ring  104 , which has a U-Shaped cross-section, has a first protrusion  106  and a second wall  108  of the inner ring  104  has a second protrusion  110 . The first protrusion  106  is in sliding contact with an inner face of a first wall  112  of an outer ring  114  and the second protrusion  110  is in sliding contact with an inner face of a second wall  116  of the outer ring  114 . Also, the first wall  112  of the outer ring  114 , which has U-Shaped cross-section, is bent inward and is in sliding contact with an outer face of the first wall  102  of the inner ring  104  and the second wall  116  of the outer ring  114  is bent inward and is in sliding contact with an outer face of the second wall  110  of the inner ring  104 . The configuration allows for axial movement of the inner ring  104  and the outer ring  114  to maintain a proper preload while ensuring the inner ring  104  and the outer ring  114  do not axially separate. 
       FIG. 8  shows a second embodiment of the thermal compensation element  200 . As shown, a first wall  202  of an inner ring  204 , which has U-Shaped cross-section, is bent outward and is in sliding contact with an inner face of a first wall  206  of an outer ring  208  and a second wall  210  of the inner ring  204  is bent outward and is in sliding contact with an inner face of a second wall  212  of the outer ring  208 . Similarly, the first wall  206  of the outer ring  208 , which also has a U-Shaped cross-section, is bent inward and is in sliding contact with an outer face of the first wall  202  of the inner ring  204  and the second wall  212  of the outer ring  208  is bent inward and is in sliding contact with an outer face of the second wall  219  of the inner ring  204 . The configuration allows for axial movement of the inner ring  204  and the outer ring  208  to maintain a proper preload while ensuring the inner ring  204  and the outer ring  208  do not axially separate. 
       FIG. 9  shows a third embodiment of the thermal compensation element  300 . As shown, a groove  302  extends along an outer face of a first wall  304  of an inner ring  306 , which has a U-Shaped cross-section, up to a first tab  308  which protrudes outward, toward a first wall  310  of an outer ring  312  and a groove  314  extends along an outer face of a second wall  316  of the inner ring  306 , up to a second tab  318  which protrudes outward, toward a second wall  320  of the outer ring  312 . Similarly, a groove  322  extends along an inner face of the first wall  310  of the outer ring  312 , which also has a U-Shaped cross-section, up to a third tab  324  which protrudes inward, toward the first wall  304  of the inner ring  306  and a groove  326  extends along an inner face of the second wall  320  of the outer ring  312 , up to a fourth tab  328  which protrudes inward, toward the second wall  316  of the inner ring  306 . The first tab  308  and the second tab  318  are each in sliding contact with the grooves  322 ,  326 , respectively, of outer ring  312  and the third tab  324  and the fourth tab  328  are each in sliding contact with the grooves  302 ,  314 , respectively, of the inner ring  306 . The configuration allows for axial movement of the inner ring  306  and the outer ring  312  along the grooves  302 ,  314 ,  322 ,  326  to maintain a proper preload while ensuring the inner ring  306  and the outer ring  312  do not axially separate. 
     Finally,  FIG. 10  shows a fourth embodiment of the thermal compensation element  400 . As shown, a first wall  402  of an inner ring  404 , which has a U-Shaped cross-section, has a first lip  406  that extends outward and is in sliding contact with an inner face of a first wall  408  of an outer ring  410  and a second wall  412  of the inner ring  404  has a second lip  414  that extends outward and is in sliding contact with an inner face of a second wall  416  of the outer ring  410 . The first wall  408  of the outer ring  410 , which also has a U-Shaped cross-section, has a third lip  418  that extends inward and is in sliding contact with an outer face of the first wall  402  of the inner ring  404 , and the second wall  412  of the outer ring  410  has a fourth lip  420  that extends inward and is in sliding contact with an outer face of the second wall  412  of the inner ring  404 . The configuration allows for axial movement of the inner ring  404  and the outer ring  410  to maintain a proper preload while ensuring the inner ring  404  and the outer ring  410  do not aerially separate. 
     The present invention has been described with reference to a preferred embodiment. It should be understood that the scope of the present invention is defined by the claims and is not intended to be limited to the specific embodiment disclosed herein. 
     Returning to  FIG. 7 , outer ring  114  includes outer base  118 . Outer wall  112  extends from outer base  118  in direction D 1 . Outer wall  112  includes distal end  120 . Distal end  120  is opposite outer base  118  in direction D 1 . Distal end  120  is bent in direction D 2  orthogonal to direction D 1 . Outer wall  116  extends from outer base  118  in direction D 1 . Outer wall  116  includes distal end  124 . Distal end  124  is opposite outer base  118  in direction D 1 . Distal end  120  is bent in direction D 3  opposite direction D 2 . 
     Inner ring  104  includes inner base  128 . Inner wall  102  extends from inner base  128  in direction D 4 , opposite direction Dl. Inner wall  102  includes outer face  130  with portion  132 . Protrusion  106  extends from portion  132  in direction D 3 . Outer face  130  includes portion  134  extending beyond protrusion  106  in direction D 4 . Inner wall  108  extends from inner base  128  in direction D 4 . Inner wall  108  includes outer face  136  with portion  138 . Protrusion  110  extends from portion  138  in direction D 2 . Outer face  136  includes portion  140  extending beyond protrusion  110  in direction D 4 . 
     Returning to  FIG. 8 , outer ring  208  includes outer base  214 . Outer wall  206  extends from outer base  214  in direction D 1 . Outer wall  206  includes distal end  216 . Distal end  216  is opposite outer base  214  in direction D 1 . Distal end  216  is bent in direction D 2 . Outer wall  212  extends from outer base  214  in direction D 1 . Outer wall  212  includes distal end  220 . Distal end  220  is opposite outer base  206  in direction D 1 . Distal end  220  is bent in direction D 3 . 
     Inner ring  204  includes inner base  224 . Inner wall  202  extends from inner base  224  in direction D 4 . Inner wall  202  includes distal end  226  opposite base  224  in direction D 4 . Distal end  226  is bent in direction D 3 . Inner wall  210  extends from inner base  224  in direction D 4 . Inner wall  210  includes distal end  230  opposite base  224  in direction D 4 . Distal end  230  is bent in direction D 2 . 
     Reference Characters 
     
         
           10  Thermal Compensation Element 
           12  Bearing 
           14  Inner Ring 
           16  Outer Ring 
           18  Washer or Split Wave Spring 
           20  First Wall of the Inner Ring 
           22  Base of the Inner Ring 
           24  Second Wall of the Inner Ring 
           26  First Wall of the Outer Ring 
           28  Base of the Outer Ring 
           30  Second Wall of the Outer Ring 
           32  Outer Ring of the Bearing 
           34  Inner Ring of the Bearing 
           36  Roller Bodies 
           38  Cage 
           40  Gap of the Washer or Split Wave Spring 
           100  Thermal Compensation Element 
           102  First Wall of the Inner Ring 
           104  inner Ring 
           106  First Protrusion of the inner Ring 
           108  Second Wall of the Inner Ring 
           110  Second Protrusion of the Inner Ring 
           112  First Wall of the Outer Ring 
           114  Outer Ring 
           116  Second Wall of the Outer Ring 
           200  Thermal Compensation Element 
           202  First Wall of the inner Ring 
           204  Inner Ring 
           206  First Wall of the Outer Ring 
           208  Outer Ring 
           210  Second Wall of the Inner Ring 
           212  Second Wall of the Outer Ring 
           300  Thermal Compensation Element 
           302  Groove 
           304  First Wall of the Inner Ring 
           306  inner Ring 
           308  First Tab 
           310  First Wall of the Outer Ring 
           312  Outer Ring 
           314  Groove 
           316  Second Wall of the Inner Ring 
           318  Second Tab 
           320  Second Wall of the Outer Ring 
           322  Groove 
           324  Third Tab 
           326  Groove 
           328  Fourth Tab 
           400  Thermal Compensation Element 
           402  First Wall of the Inner Ring 
           404  inner Ring 
           406  First Lip 
           408  First Wall of the Outer Ring 
           410  Outer Ring 
           412  Second Wall of the Inner Ring 
           414  Second Lip 
           416  Second Wail of the Outer Ring 
           418  Third Lip 
           420  Fourth Lip