Patent Publication Number: US-2007116397-A1

Title: Unitized bearing assembly and method of assembling the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      Not Applicable.  
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH  
      Not Applicable.  
     BACKGROUND OF THE INVENTION  
      This invention relates in general to bearings and more particularly to a unitized bearing assembly and method of assembling the same.  
      Automobiles and light trucks of current manufacture contain many components that are acquired in packaged form from outside suppliers. The packaged components reduce the time required to assemble automotive vehicles and further improve the quality of the vehicles by eliminating critical adjustments from the assembly line. So called “wheel ends” represent one type of packaged component that has facilitated the assembly of automotive vehicles.  
      The typical wheel end has a housing that is bolted against a steering knuckle or other suspension upright, a hub provided with a flange to which a road wheel is attached and also a spindle that projects from the flange into the housing, and an antifriction bearing located between the housing and the hub spindle to enable the hub to rotate in the housing with minimal friction. In an advanced form of the wheel end the inboard end of the spindle is formed over the end of the bearing to permanently unitize the wheel end.  
      Actually, the bearing has rolling elements, such as tapered rollers, organized in two rows and raceways along which the rolling elements roll. The raceways and rolling elements of the outboard row are oriented opposite to the raceways and rolling elements of the inboard to enable the bearing to transfer thrust loads in both axial directions as well as radial loads. Moreover, the inner raceway for inboard row, that is to say the raceway that is around the spindle at the inboard end of the spindle, is on a race that is formed separately from the hub spindle, so the axial position of this race determines the setting for the entire bearing, and that setting should preferably provide a light preload in the bearing. Once the inboard inner race is installed over the spindle, the end for the spindle is deformed outwardly against the end of the race to permanently capture the bearing, at least in the unitized form of the wheel end. In order for the inboard inner race to assume the correct position on the hub spindle and thereby provide the bearing with the correct setting, that inner race must be machined with considerable precision. This consumes time and increases the cost of the wheel end.  
      U.S. Pat. No. 6,443,622 discloses a rotary forming process for upsetting the end of the hub spindle to utilize a wheel end, but requires a precisely machined inner race.  
      U.S. Pat. No. 6,532,666 discloses a more sophisticated process, that also requires precision machining. U.S. Pat. No. 6,460,423 discloses a process for verifying preload in the unified bearing, but requires complex equipment and a long cycle time. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       FIG. 1  is a sectional view of a bearing assembly in the form of a wheel end assembled in accordance with the present invention;  
       FIG. 2  is an elevational view of a rotary forming machine used to assemble the wheel end;  
       FIGS. 3A , B, C, D are fragmentary sectional views, in sequence, showing the steps of assembling the wheel end;  
       FIG. 4  illustrates circlips that may be used for the spacer in the wheel end;  
       FIG. 5  illustrates collapsible sleeves that may be used for the spacer in the wheel end;  
       FIG. 6  is a sectional view of a modified wheel end;  
       FIG. 7  is a fragmentary sectional view of another modified wheel end that utilizes angular contact ball bearings;  
       FIG. 8  is a fragmentary sectional view of still another modified wheel end that utilizes angular contact ball bearings.  
       FIG. 9  is a sectional view of another modified wheel end that further has the capacity to monitor angular velocity;  
       FIG. 10  shows fragmentary sectional views of the elongated spacers suitable for the modified wheel end of  FIG. 9 , both before and after deformation between opposing crushing surfaces; and  
       FIG. 11  shows fragmentary sectional views of spacers formed integral with a backing element that is in turn formed integral with the hub spindle. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      Referring to the drawings, a wheel end A ( FIG. 1 ), which is in essence a bearing assembly, couples a road wheel R to a suspension system component S of an automobile, and enables the road wheel B to rotate about an axis X and to transfer both radial loads and thrust loads in both axial directions between the wheel B and suspension system component S. If the road wheel R steers the vehicle, the suspension system component S takes the form of a steering knuckle. If it does not steer, the suspension system component S is a simple suspension upright. The wheel end A includes a housing  2  that is bolted to the suspension system component S and provides an outer member, a hub  4  that provides an inner member to which the road wheel B is attached, and a bearing  6  located between the housing  2  and hub  4  to enable the latter to rotate with respect to the former about the axis X with minimal friction. The wheel end A is unitized permanently with its bearing  6  in a slight preload.  
      The housing  2 , which is formed from high carbon steel, preferably as a forging, includes ( FIG. 1 ) a generally cylindrical body  10 , which is tubular, and a triangular or rectangular flange  12  projecting radially from the body  10  generally midway between the ends of the body  10 . The inboard segment of the body  10  is received in the suspension system component C such that the flange  12  comes against the component S, to which the flange  12  is secured with bolts  14 . Thus, the wheel end A is attached to the suspension system component C at the flange  12  of its housing  2 .  
      The hub  4 , which is also formed from high-carbon steel, preferably as a forging, includes ( FIG. 1 ) a spindle  20 , which extends through the tubular body  10  of the housing  2 , and a flange  22  that is formed integral with the spindle  20  at the outboard end of the spindle  20 . The flange  22  is fitted with lug bolts  24  over which lug nuts  26  thread to secure a brake disk  28  and the road wheel B to the hub  4 .  
      The spindle  20  merges with the flange  22  at an enlarged region  30  that leads out to a cylindrical bearing seat  34  that in turn leads out to a formed end  36 . The formed end  36  is directed outwardly away from the axis X and provides an inside face  38  that is squared off with respect to the axis X and is presented toward the enlarged region  30 .  
      The bearing  6  lies between the spindle  20  of the hub  4  and the housing  2  and enables the hub  4  to rotate relative to the housing  2  about the axis X. It includes (FIG.  1 ) two outer raceways  40  and  42  formed on the interior surface of the tubular body  10  for the housing  2 , the former being outboard and the latter being inboard. The two raceways  40  and  42  taper downwardly toward each other so that they have their least diameters where they are closest, generally midway between the ends of the housing  2 . Along the raceways  40  and  42  the housing  2  is hardened by induction heating and quenching. Apart from the two outer raceways  40  and  52 , the bearing  6  also includes an inner raceway  44  and thrust rib  46  that are on the enlarged region  30  of the spindle  20 . The raceway  44  lies at the outboard position and faces the outboard outer raceway  40 , tapering in the same direction downwardly to the center of the housing  2 . The thrust rib  46  extends along the large end of the raceway  44 . Both along the raceway  44  and the thrust rib  46  the hub is case hardened by induction heating and quenching. Beyond the opposite small end of the raceway  44 , the bearing  6  has a shoulder  48  that faces away from the flange  22 . It is presented toward the inside face  38  of the formed end  36  and enables the end of the enlarged region  30  to serve as a backing element.  
      The bearing  6  also includes ( FIG. 1 ) an initially separate inner race in the form of a cone  50  that fits over the bearing seat  34  of the spindle  20  with an interference fit. It is preferably formed from case hardened bearing steel and includes a raceway  52  that is presented outwardly toward the inboard outer raceway  42  on the housing  2  and tapers in the same direction, downwardly toward the middle of the housing  2 . At the large end of its raceway  52  the cone  50  has a thrust rib  54  that leads out to a back face  56  that is squared off with respect to the axis X. At the small end of its raceway  52  the cone  50  has a retaining rib  58  that leads out to a cone front face  60  that is also squared off with respect to the axis X.  
      Completing the bearing  6  are rolling elements in the form of tapered rollers  62  organized in two rows, one located between and contacting the outboard raceways  40  and  44  and the other located between and contacting the inboard raceways  42  and  52 .  
      The rollers  62  of each row are on apex. Thus, the conical envelopes in which the outboard raceways  42  and  46  and outboard rollers  62  lie have their apices at a common point along the axis, and likewise the conical envelopes in which the inboard raceways  42  and  50  and the inboard rollers  62  lie have their apices at another common point along the axis X. The rollers  62  of each row are separated by a cage  64  that maintains the proper spacing between the rollers  62  and further retains them in place around their respective inner raceways  44  and  52  in the absence of the housing  2 .  
      The cone  50  fits over the bearing seat  34  of the spindle  20  with an interference fit and there lies captured between the enlarged region  30  of the spindle  20  and the formed end  36  of the spindle  20 . Indeed, its back face  56  bears against the inside face  38  of the formed end  36 , while its front face  60  is presented toward, yet spaced from, the shoulder  48  at the end of the enlarged region  30  of the spindle  20 .  
      Preferably, the space between the shoulder  48  and the back face  56  of the cone  50  is occupied by a collapsed spacer  66  that bears against both and extends circumferentially around essentially the entire bearing seat  34 . The spacer  66  is preferably formed from a soft metal. In any event, the substance from which the spacer  66  is formed together with its configuration are such that the spacer  66 , when compressed between the shoulder  32  of the spindle  20  and the front face  60  of the cone  50 , will plastically deform under a force less than that required to plastically deform either the enlarged region  30  of the hub spindle  20  or the cone  50 .  
      The housing  2  and its ends contain seals  70  which close the ends of the bearing  6  and prevent contaminants from entering the bearing  6  while retaining a lubricant in the bearing  6 .  
      Initially, the hub  4  does not have the formed end  36  at the inboard end of its spindle  2 . Instead, it is manufactured with a deformable end  74  ( FIG. 3 ) that forms an extension of the bearing seat  34 , it having an outside diameter that is the same as the outside diameter of the bearing seat  34 . Thus, the outwardly presented surface of the deformable end  74  and the bearing seat  34  are indistinguishable. Moreover, as manufactured, the spacer  66  is somewhat thicker than the thickness it assumes in the completed wheel end A, that is to say its axial dimension is initially greater.  
      To assemble the wheel end A, the inboard row of rollers  62  is installed around the inboard inner raceway  44  that is on the enlarged region  30  of the hub spindle  20 , with those rollers  62  being retained by the cage  64  for the inboard row ( FIG. 3A ).  
      Likewise, the outboard seal  70  is fitted to the thrust rib  46  on the enlarged region  30 .  
      Thereupon, the housing  2  is passed over the spindle  20  and advanced to seat its outboard raceway  40  against the rollers  62  of the outboard row, which rollers  62  are also seated against the inner raceway  44  ( FIG. 3B ). Next the spacer  66  in its original configuration is installed over the spindle  20  and brought against the shoulder  48  on the enlarged region  30 . After the spacer  66  is in place the cone  50 , with its complement of outboard rollers  62  around its raceway  52 , is forced over the bearing seat  34  until its front face  60  comes against the spacer  66  ( FIG. 3B ). In this condition the deformable end  74  projects beyond the back face  56  of the cone  50 , and the bearing  6  possesses a good measure of end play. As such clearances exist within the bearing  6 .  
      Once the cone  50  is in place around the spindle  20 , the partially assembled wheel end A is brought to a rotary forming machine D ( FIG. 2 ) including a table  80  configured to support the hub  4  with its spindle  20  projecting away from the region support and a forming tool  82  having a contoured face that is presented toward the table  80 . The hub  4  seats against the table  80  such that it is held fast and cannot rotate relative to the table  80 . Yet the table  80  rotates under power about the axis X of the spindle  20 , thus rotating the entire hub  4 . The table  80  further has the capacity to translate to and fro along the axis X. The forming tool  82  rotates under power about an axis Y that is oblique to the axis X. The housing  2  is retained against rotation by a device  86  that measures torque transferred through the bearing  6  to the retained housing  2 . U.S. Pat. No. 6,443,622 discloses the forming machine D and its operation in more detail, and is incorporated in this disclosure by reference.  
      With the table  80  and the hub  4  rotating about the axis X, the hub  4  is advanced toward the forming tool  82  which also rotates. The advance brings the deformable end  74  against the contoured face  84  of the rotating forming tool  82  ( FIG. 3B ). The table  80  forces the deformable end  74  against the face  84 , and the face  84  deforms the end  74  outwardly away from the axis X ( FIG. 3C ). The deformation of the end  74  continues, bringing the end  74  over the back face  56  of the cone  50 . With continued advancement of the table  80 , the end  74  bears against the back face  56  of the cone  50  and drives the entire cone  50  toward the enlarged region  30  and flange  22  of the hub  4  ( FIG. 3D ). The spacer  66  resists the advance, but even so collapses under the force applied. But neither the shoulder  48  on the enlarged region  30  of the spindle  20 , nor the cone  50  are deformed. The resistance offered by the spacer  66  enables the deformable end  74  to transform into the formed end  36  with a large and flat contact area between the formed end  36  and the cone back face  56 , that is to say it provides the deformed end with the inside face  38  at which it bears against the cone back face  56 . The advancement of the table  80  continues slowly at this juncture, until the restraining device  86  that is coupled to the housing  2  measures a prescribed torque that correlates with a desired preload for the bearing  6 . At that time the advancement of the table  80  ceases, but the table  80  continues to rotate as does the forming tool  82 . In short, the process enters a dwell phase. If the torque remains at the prescribed magnitude during dwell phase, the table  80  is withdrawn, the wheel end A is removed from it, and the outboard seal  70  is installed on the housing  2 .  
      Actually, the wheel end A may be assembled without the spacer  66 . In that event, the space otherwise occupied by the spacer  66  becomes a void. The geometry of the tapered rollers  62  and the tapered raceways  40 ,  42  and  44 ,  52  that they contact prevent the front face  60  of the cone  50  from bearing against the shoulder  48  on the enlarged region  30  of the hub spindle  20 . The torque transferred from the rotating hub  4  through the tapered rollers  62  to the housing  2  and measured at the restraining device  86  determines when the formed end  36  on the spindle  20  has assumed the correct position. In other words, a prescribed torque, which is determine empirically, reflects a desired preload for the bearing  6 . The presence of the spacer  66 , however, facilitates establishing a good contact area between the back face  56  of the inboard cone  50  and the formed end  36 . Moreover, the spacer  66  imparts an extra measure of stiffness to the spindle  20  of the hub  4 , so that the spindle  20  will experience less flexure when heavy radial loads are transferred through the wheel end A.  
      The spacer  66  before deformation between the shoulder  48  and cone front face  60  may assume various configurations. It may take the form of a simple circlip  90  ( FIG. 4 ) having open ends or it may be a closed circlip  92  formed by welding its ends together. The circlips  90  and  92  may be formed from wire of circular cross section, square cross section, rectangular cross section, or polygonal cross section ( FIG. 4 ). Other cross-sectional configurations will suffice for the spacer  66 —indeed, there are infinite different shapes that will work. The wire may be ductile steel, aluminum, copper, brass, or any material that can be deformed. The spacer  66  may also take the form of a sleeve  94  ( FIG. 5 ) having flanges  96  at its ends and a cylindrical intervening section  98  which deforms outwardly when the flanges  96  are forced together under a compressive force applied through the shoulder  48  and the cone back face  56 . Likewise, the spacer  66  may take the form of a sleeve  100  ( FIG. 5 ) having axially directed ends  102  and intervening portion  104  that bows outwardly. When the ends  102  are forced together, the intervening portion  104  bows still farther outwardly. Indeed, any sleeve that will deform under a compressive load will suffice. Irrespective of the material from which any of the spacers  66  are formed, the spacer  66 , when subjected to a compressive force between the shoulder  48  and the cone front face  60  should undergo a plastic deformation before either the enlarged region  30 , including its shoulder  48 , and the cone  50  deform plastically.  
      In lieu of forming the outboard inner raceway  44  on an integral segment of the spindle  20 —basically a cone integrated into the spindle  20 —a modified wheel end B ( FIG. 6 ) has the outboard inner raceway  44  on a separate outboard cone  110 . To accommodate the cone  110 , the bearing seat  34  extends farther toward the hub flange  22  and terminates at a shoulder  112  located adjacent to the flange  22 . The outboard cone  110  fits over the extended bearing seat  34  with an interference fit and bears against the shoulder  112  at its back face  56 . The front face  60  of the outboard cone  110  functions as a backing element or shoulder against which the spacer  66  is collapsed and thus corresponds to the shoulder  48  on the enlarged region  30  of wheel end A.  
      In lieu of the tapered roller bearing  6  between the housing  2  and spindle  4 , another modified wheel end C ( FIG. 7 ) utilizes, angular contact ball bearings  120 . The wheel end C has arcuate outer raceways  122  in the housing  2 , an arcuate inner raceway  124  on the enlarged region  30  of the spindle  4 , an inboard inner race  126  having another arcuate inner raceway  128 , and balls  130  arranged in two rows around the inner raceways  124  and  128  and of course within the outer raceways  122 . The spacer  66  fits between the inboard race  126  and the shoulder  48  on the enlarged region  30 .  
      A wheel end D ( FIG. 8 ) has the inboard inner raceway  124  on a separate inner race  132 , in which event the bearing seat  34  need be extended to a shoulder  112 . The spacer  66  fits between the front faces of the two inner races  126  and  132 . Indeed, the end of the outboard race  132  forms a backing element or shoulder against which the spacer  66  is deformed.  
      The tapered outer raceways  40  and  42  may be on separate outer races, called cups, forced into the housing  2  or even on a single outer race called a double cup.  
      Likewise the arcuate outer raceways  122  may be on separate races fitted to the housing  2  or on a single outer race.  
      Still another modified wheel end E ( FIG. 9 ) has the capability of sensing the angular velocity of the hub  4  so as to facilitate the operation of an antilock brake system and a traction control system. To this end, the housing  2  is provided with a bore  140  that opens into its interior between the small ends of the tapered outer raceways  40 . The bore  140  lies oblique to the axis X and opens out of the housing  2  at a location that is slightly offset from that face of the flange  12  that is against the suspension system component S. The oblique bore  140  contains a sensor  142  having at its inner end a probe  144  that is presented toward and in close proximity to the peripheral surface of a target wheel  144  that rotates with the hub  4  between the small ends of the tapered rollers  62  or other rolling elements. The probe  144  produces an electrical signal that reflects the angular velocity of the target wheel  146  and the hub  4 .  
      The target wheel  146  is carried by an extended spacer  150  that fits over the bearing seat  34  with a slight interference fit and lies snuggly between the shoulder  48  on the enlarged region  30  and the front face  60  of the inboard cone  50 . It has an annular body  152  provided with cylindrical exterior surface  154  over which the target wheel  144  fits again with an interference fit. One end of the body  152  provides a face that lies perpendicular to the axis X, and that end the body  152  bears against the shoulder  48 . At its other end the annular body  152  merges into a deformable portion  156  that is, at least, initially thinner than the body  152 . The deformable portion  156  bears against the front face  60  of the cone  50 , and is deformed as a consequence of the compressive force applied to the cone  50  as the deformable end  74  of the hub spindle  20  is converted into the formed end  36 . When the spacer  150  is compressed between the enlarged region  30  of the spindle  20  and the cone  50 , the deformable portion  156  of the spacer  150  should deform plastically before the enlarged region  30 , including its shoulder  48 , or the cone  50 , including its front face  60 , undergo any plastic deformation. Likewise, it should plastically deform before the annular body  152  of the spacer  150  deforms plastically.  
      The deformable portion  156  may in cross-section initially be trapezoidal with its smallest end presented away from the annular body  152  or it may be rectangular ( FIG. 10 ). Then again it may be T-shaped in cross-section and oriented such that the cross-piece of the T is spaced from the annular body  152  so that the leg of the T experiences the deformation when the collapsing force is applied. Also, the end of an otherwise rectangular deformable end  156  may be rounded. The deformable end  156  may also have a triangular cross-section with a rounded apex presented such that the force is applied at a rounded apex. Other cross-sectional configurations are available for the deformable portion  156 . Irrespective of its configuration, the deformable portion  156  should deform plastically before either the cone  50  or the enlarged region  30  of the spindle  4  deform plastically and likewise before the main body  152  deforms plastically.  
      Of course, an outboard cone  110  may be substituted for the enlarged portion  30  of the spindle  4 , with the front face  60  of that cone  110  serving as the shoulder.  48 , so that the spacer  140  is compressed between the front faces  60  of the two cones  50  and  110 .  
      In yet another modified wheel end F ( FIG. 11 ), which in most respects is the same as the wheel end A, a spacer  160  is formed as a integral part of the enlarged region  30  of the spindle  20 . The spacer  16  projects from the shoulder  48  of the enlarged region  30 . Beyond the shoulder  48  the spacer bears against the front face  60  of the inboard cone  50 . Being an integral part of the enlarged region  30 , the spacer  160  is formed from the same material as the hub  4 , which is high carbon steel. And while high carbon steel may be case hardened in a heat treatment, the hub  4  is only case hardened along the raceway  44  and thrust rib  46  of the enlarged region  30 . To this end, the enlarged region  30  is induction heated along the raceway  44  and thrust rib  46  and then quenched, thus, leaving the raceway  30  and thrust rib  46  harder than the remainder of the hub  4 . As a consequence, the spacer  160  will deform when subjected to a compressive face applied through the cone  50 . After all, the spacer  160  possesses less cross-sectional area than the shoulder  48  and backing element of the enlarged region  30 , which lie immediately behind it. Being either formed from high carbon steel that is through hardened or preferably from low carbon steel that is case carburized and then hardened at its exterior surfaces, including its front face  60 , the inboard cone  50  does not deform as the spacer  160  is crushed.  
      The spacer  160  may be initially, that is before deformation, directed axially essentially parallel to the axis X. When deformed, it tends to spread radially inwardly and outwardly. On the other hand, the spacer may be initially directed slightly outwardly from the shoulder  48 , somewhat oblique to the axis X. When deformed, it tends to spread both inwardly and outwardly, but perhaps farther outwardly than inwardly. Other configurations are available for the integral spacer  160 .  
      The races may also be those of deep groove ball bearings or spherical roller bearings, both of which have raceways that are inclined with respect to the axis X to carry thrust loads. Furthermore, the bearing  6  may assume a hybrid form including rolling elements of one configuration in the inboard row and rolling elements of another configuration in the outboard row. For example, the inboard row may contain tapered rollers and function as a single row tapered roller bearing and the outboard row may contain balls that function as a single row angular contact ball bearing, or vice versa.  
      The housing  2 , spindle  20 , and bearing  6  need not be part of a wheel end, but may serve other purposes where facilitation of rotation about an axis X is required. In other words, the bearing assembly embodied in the wheel end A may have other applications which could require modification of the housing  2  or spindle  4  or both.