Abstract:
A wheel bearing useful for automobiles includes an axle shaft and an axle tube around the shaft, inner and outer bearing races defined respectively at the outer periphery of the shaft and the inner periphery of the tube. A circumferential row of balls and a circumferential set of rollers disposed axially apart between the inner and outer bearing races to form a ball bearing and a roller bearing, in parallel, for supporting the axle shaft within the axle tube.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a 35 U.S.C. §§371 national phase conversion of PCT/IB2008/001532, filed Mar. 7, 2008, which claims priority of U.S. Provisional Application No. 60/894,032, filed Mar. 9, 2007, the disclosure of which is incorporated by reference herein. The PCT International Application was published in the English language. 
    
    
     BACKGROUND OF THE DISCLOSURE 
     1. Field of the Disclosure 
     The present disclosure relates to an improved support bearing for use, for example, for supporting the wheel end of an automobile axle. 
     2. Background Art 
     A bearing for an automotive axle performs several functions. It supports both radial and axial loads, including the weight of the vehicle and the additional wheel loads due to vehicle cornering. It transmits torque from the differential to the wheel. In particular, it is desirable to keep the torque as low as possible. 
     DE 80 14 137, DE 67 52 038, JP 62-210102, DE 29 07 342, DE 10 45 737, and DE 96 84 32 disclose ball bearing and cylindrical or needle roller bearing arrangements of background interest. However, none of these references discloses the automotive wheel end support bearing described herein. 
     SUMMARY 
     The bearing design for an automotive axle proposed herein combines a ball bearing and a roller bearing arrayed axially and located between an axle and a tube around the axle. Several benefits may be obtained. 
     A rear axle provided with such a bearing may be easier and cheaper to assemble than axles with bearings in the prior art. Unlike known bearings, a clamp load is not required across the bearing. Clamp load is required, for example, when using a known single-row taper (unitized) concept. 
     Also, a “C” clip is usually required in the differential at the axle when a conventional cylindrical bearing is used around the axle. With the disclosed bearing, the “C” clip conventionally required in the differential is eliminated. Also, a cylindrical roller bearing may have excessive axial play, which is particularly undesirable for a wheel speed sensor. The new bearing has less axial play. 
     The bearing herein may have improved axial rigidity and spindle stiffness. Thus, brake judder is reduced. This may lead to better brake response and improved disk brake wear being achieved. 
     The bearing may have higher efficiency (less bearing torque loss) than a conventional unitized taper. There is no sliding friction between the rolling elements and the side face. 
     The disclosed bearing may have the potential to reduce overall system cost. For example, an oil seal can be integrated into the bearing. It is possible to “seal the bearing for life” and move the oil seals to the ends of the differential, thus saving gear oil. The number of components in the system may be reduced as well. 
     According to various embodiments, an automobile wheel bearing may comprise the following components. There is an axle shaft connected to a wheel hub. An axle tube encircles a part of the shaft and is radially spaced out from the shaft. Inner and outer bearing races are formed respectively outside the axle and inside the tube and are opposed to each other. A set of rollers in a circumferential row toward the hub and a set of balls in another circumferential row further from the axle hub are disposed between and contact the inner and outer bearing races to form a ball bearing and a roller bearing, in parallel planes, for supporting the axle shaft within the axle tube. 
     The inner and outer raceways on the surfaces of the races may be conventionally configured for two-, three-, or four-point or angular contact with the balls of the ball bearing. 
     One or more seals and/or a cover plate may be positioned axially for enclosing the inner and outer bearing races and particularly for enclosing the ball and roller bearings. 
     The inner race of at least the roller bearing, or of both the roller bearing and the ball bearing, may be provided by portions of the axle shaft. 
     Other features and advantages will become apparent from the following description which refers to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partial cross-sectional view showing a first embodiment of the disclosed bearing. 
         FIG. 2  is a partial cross-sectional view showing a second embodiment of the disclosed bearing. 
         FIG. 3  is a partial cross-sectional view showing a third embodiment of the disclosed bearing. 
         FIG. 4  is a partial cross-sectional view showing a fourth embodiment of the disclosed bearing. 
         FIG. 5  shows a fifth embodiment, including an arrangement for mounting the bearing on an axle. 
         FIG. 6  shows four possible raceway configurations for the ball bearing portion of the disclosed bearing. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     All of the disclosed embodiments of the wheel end support bearing comprise a common core of components, and redundant descriptions of the various common components will be omitted. 
     Referring to the embodiments in all of  FIGS. 1-5 , an automobile wheel hub  10  is typically formed integrally with or attached to an axle shaft  12 . The axle shaft  12  is surrounded concentrically by an axle tube  14  spaced outward radially from the shaft. That tube may be at or part of the vehicle body or other part that does not move with the axle. A distal end  24  of the axle tube  14  is disposed substantially adjacent to but spaced away from the wheel hub  10 . The distal end  24  is considered to be “distal” in the sense of being distal from the automobile differential, which is not shown, but which would be located away from the hub  10  past the right-hand side of each of the respective Figures. This mutual arrangement of the wheel hub  10 , axle shaft  12  and axle tube  14  is well known to the art. 
     Also seen in  FIGS. 1-5  are embodiments of a wheel bearing providing mutual or relative rotation of the axle shaft  12  and the axle tube  14 . For this purpose, there are provided a circumferential row of rollers  16  and a corresponding roller cage  18  for the roller row and a short axial distance away, a circumferential row of balls  20  and a corresponding ball cage  22  for the row of balls. The rows  16  and  20  extend circumferentially in the radial space between the axle shaft and the axle tube. Together with respective bearing races, described below, the rollers  16  form a roller bearing and the balls  20  form a ball bearing which are disposed close together axially inside the distal end  24  of the axle tube. 
     Embodiment 1 
     In the first embodiment  FIG. 1 , an inner bearing race  30  comprises a cylindrical bearing ring mounted concentrically and securely around the periphery of the axle shaft  12  adjacent or substantially adjacent to the wheel hub  10 . The inner race is secured at a distal end by a shoulder  32  formed between the wheel hub  10  and the axle shaft  12  and is secured at a proximal end by a snap ring  34  which engages the shaft  12 , for example in a groove provided for that purpose. 
     The outer race  36  on the other hand comprises a cylindrical ring secured at a proximal end to the interior of the axle tube  14  by a shoulder  38  formed in the axle tube  14  and at a distal end by a snap ring  40  which engages the axle tube  14 , for example in a groove therein. The inner and outer races are opposed. 
     Appropriately indented or grooved raceways  31  and  37  are formed respectively in the inner and outer races for accommodating the row of balls  20 . The bearing rollers  16  are cylindrical and engage the raceways. No indentation is provided for the cylinders in the raceways. 
     No sealing elements are integrated into the bearing in this embodiment. The bearing may be lubricated by differential oil. Suitable seal elements external to the bearing may be provided. 
     Embodiment 2 
     In the second embodiment in  FIG. 2 , sealing elements  50  and  52  are positioned into the bearing between the distal and proximal ends, respectively, of the inner race  30  and the outer race  36  and axially outward of the rows of rollers and balls. By these sealing elements, the bearing between the sealing elements can be one that is “sealed for life” with no additional need for outside lubrication. 
     An annular cover plate  54  is fastened near the radially outward edge of the plate by a plurality of bolts  56  which in turn are secured to one or more flanges  58  extending radially outwardly from the axle tube  14 . At its radially inward end, the cover plate  54  secures the distal end  60  of the outer bearing race  36 . Moreover, the cover plate  54  extends radially inward as close as is practicable to the distal end of the inner race  30 , i.e., to the shoulder  32  and to the wheel hub  10 , in order to block the entry of contaminants into the bearing. 
     Embodiment 3 
     In the third embodiment in  FIG. 3 , an extended shoulder  70  formed in the axle shaft  12  extends in the proximal direction from the wheel hub  10  far enough to serve as the inner race of the more distal row of roller bearings. The same shoulder  70  also secures the distal end of the inner race  72  which accommodates the balls  20  of the ball bearing. 
     In this example, one oil seal  50  is integrated into one end of the bearing. The bearing may be lubricated by gear oil from the differential. 
     Embodiment 4 
     In the fourth embodiment in  FIG. 4 , an extended shoulder  76  formed in the axle shaft  12  extends far enough in the proximal direction to serve as the inner race for both the ball bearing and the roller bearing. Otherwise, this embodiment may be identical to or may have the same elements as the third embodiment. 
     Embodiment 5 
       FIG. 5  shows the fifth embodiment, which is similar to  FIG. 2 , but has additional features configured for mounting the bearing on an axle. In this example, the wheel hub  10   a  is not integral with the axle shaft  12  as in the other embodiments. Instead, the wheel hub has a cylindrical portion  10   b  that extends in the proximal direction (toward the right in the Figure). The axle shaft  12   a  is substantially constant in diameter. It is threaded at its distal end  12   b . The end  12   b  is passed through the cylindrical portion  10   b  of the hub  10   a  and is secured to the wheel hub  10   a  by a nut  78  tightened on the thread at end  12   b.    
     The outer race  36   a  has one or more radially extending flanges  36   b . This flange or these flanges  36   b  are fastened by bolts  56  to corresponding flange or flanges  58   a  extending radially from the axle tube  14   a.    
     A cover plate may also be provided, as in the second embodiment. 
     In this embodiment, the wheel hub  10   a , the axle shaft  12   a , the bearing ( 30 ,  36   a  and related components), and the axle tube  14   a  are separable components, which may simplify both the assembly process and repairs when needed. 
       FIG. 6  shows ball raceway configurations which may be used with any of the foregoing embodiments. As shown, the raceways may be configured so as to provide (a) two-point, (b) three-point, (c) four-point, or (d) angular contact between the balls and the raceway. 
     U.S. Pat. No. 5,927,867 and DE 197 13 333 C2 disclose a snap ring (securing sleeve 6) that may be used as either or both of the snap rings  34  and  40  in the disclosed embodiments. 
     Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited not by the specific disclosure herein, but only by the appended claims.