Patent Publication Number: US-2023148290-A1

Title: Rotating assembly, in particular for guiding a motor vehicle wheel

Description:
TECHNICAL FIELD OF THE INVENTION 
     The invention relates to a rotating assembly, and in particular to a rotating assembly suitable for guiding a wheel, in particular a drive wheel, of a motor vehicle. 
     STATE OF THE PRIOR ART 
     A motor vehicle drive wheel assembly, once mounted on the vehicle, generally comprises a fixed subassembly intended to be secured to a suspension element of the vehicle and comprising a first outer raceway and a second outer raceway defining an axis of rotation; a rotating subassembly, capable of rotating relative to the fixed member about the axis of rotation, and comprising a wheel hub, a transmission bowl, a first inner raceway located opposite the first outer raceway, a second inner raceway located opposite the second outer raceway; and balls, forming a first row of balls between the first outer raceway and the first inner raceway and a second row of balls between the second outer raceway and the second inner raceway. The wheel hub has an attachment interface for a wheel rim and a brake disc. The assembly therefore typically has a stack of technical functions, arranged along the axis of rotation from the inside to the outside of the vehicle: transmission of torque, attachment to the suspension of the vehicle, guidance in rotation, braking and rolling, which requires a large size in the axial direction, that is to say, transverse in the coordinate system of the vehicle. 
     It has been proposed in document FR 3,052,104 to shrink an inner bearing race for the second inner raceway onto the transmission bowl, which makes it possible to reduce the axial size for a given distance between the two rows of balls, while increasing the pitch diameter of the row of balls located on the inside of the vehicle. Insofar as the payload and the camber stiffness are increasing functions of the distance between the two rows of balls and of the pitch diameter of the rows of balls, this architecture provides a solution for reconciling reduced axial bulk and good performance in terms of payload and camber stiffness. 
     Electric and hybrid vehicle powertrains often turn out to be bulkier than combustion engine powertrains in the width direction of the vehicle at the drive wheels, which leads to shortening of the transverse drive shafts. This shortening is undesirable because it leads to greater deflection angles in the transmission joints during movements of the wheel relative to the chassis. In this context, any measure making it possible to increase the space available for the transverse transmission shafts, even slightly, is desirable. There is therefore an increased need for compactness of drive wheel assemblies in the axial direction, which does not come at the expense of performance, in particular in terms of payload and rigidity. 
     DISCLOSURE OF THE INVENTION 
     The invention aims to provide a rotating assembly, for example for guiding a motor vehicle drive wheel, which combines axial compactness, high payload and a good level of camber stiffness. 
     To do this, proposed according to a first aspect of the invention is a rotating assembly, comprising:
         an outer subassembly comprising a first annular outer raceway and a second annular outer raceway centered on a common axis of rotation;   an inner subassembly comprising a first inner bearing race on which a first inner raceway is formed, the first inner raceway having a raceway bottom diameter DI 1 , and a second inner bearing race on which a second inner raceway is formed, the second inner raceway having a raceway bottom diameter DI 2  larger than the raceway bottom diameter DI 1  of the first inner raceway, the second inner bearing race and the first inner bearing race being fixed relative to each other; and   balls forming a first row of balls capable of rolling on the first outer raceway and the first inner raceway and a second row of balls capable of rolling on the second outer raceway and the second inner raceway for guiding the outer subassembly and the inner subassembly relative to each other in rotation about the axis of rotation, the balls of the first row of balls having a diameter DC 1 , a first pitch plane containing the centers of the balls of the first row of balls being located at a non-zero distance L from a second pitch plane containing the centers of the balls of the second row of balls;       

     According to the invention, the second inner bearing race has an outer diameter (ϕ), measured in a section plane perpendicular to the axis of rotation and located between the first pitch plane and the second pitch plane, at a measurement distance DM from the first pitch plane, which is greater than a given threshold value VS, where: 
     
       
         
           
             { 
             
               
                 
                   
                     DM 
                     = 
                     
                       1.25 
                       ⨯ 
                       
                         
                           DC 
                           ⁢ 
                           1 
                         
                         2 
                       
                     
                   
                 
               
               
                 
                   
                     VS 
                     = 
                     
                       sup 
                       ⁡ 
                       ( 
                       
                         
                           
                             1.1 
                             ⨯ 
                             DI 
                           
                           ⁢ 
                           1 
                         
                         ; 
                         
                           
                             DI 
                             ⁢ 
                             1 
                           
                           + 
                           
                             
                               DC 
                               ⁢ 
                               1 
                             
                             2 
                           
                         
                       
                       ) 
                     
                   
                 
               
             
           
         
       
     
     These dimensional characteristics reflect the fact that the second inner bearing race carrying the second inner raceway is close to the first raceway and has a significant thickness near the first raceway, giving the inner subassembly a high stiffness and the rotating assembly a satisfactory axial compactness. 
     Preferably, the second inner bearing race comprises an axial end face facing axially toward the first pitch plane, axially bearing against a bearing face of the first inner bearing race, the axial end face being positioned in a transverse plane situated between the first pitch plane and the second pitch plane, at a distance D from the first pitch plane, preferably less than half the diameter DC 1  of the balls of the first row of balls. Preferably, the axial end face is planar. It has an outside diameter that is preferably equal or substantially equal to that of the bearing face. The outer diameter of the axial end face is preferably greater than or equal to the raceway bottom diameter DI 1 . In practice, it is below the threshold value VS. In section in a plane containing the axis of rotation, the outer surface of the second inner bearing race, in the portion located between the axial end face and the section plane PC, is concave and the distance from a current point of this outer surface of the second inner bearing race to the axis of rotation increases continuously when the current point moves away from the axial end face and approaches the section plane PC. 
     For good control of the positioning of the balls of the first row of balls during mounting of the assembly or in use, a first one-piece bearing cage is preferably provided, the first one-piece bearing cage comprising a ring defining a reference axis of the first bearing cage and retaining claws distributed around the periphery of the ring to delimit the cells for housing the balls of the first row of balls. 
     The second inner bearing race occupies a volume in the immediate vicinity of the first raceway, which leaves little room to accommodate a cage whose ring would be located between the first pitch plane and the second pitch plane. Preferably, the ring is therefore positioned on one side of the first pitch plane opposite the second pitch plane, the retaining claws projecting from the ring in the direction of the second pitch plane by crossing the first pitch plane, the retaining claws having a free distal end, the cells each being delimited by two adjacent retaining claws among the retaining claws of the first one-piece cage and by a portion of the ring connecting the two adjacent retaining claws. The first cage then has no ring located between the first pitch plane and the second pitch plane close to the second inner bearing race. More space can be allocated for the second inner bearing race, to increase its outside diameter in the area between the axial end face and the section plane PC. 
     Preferably, the cells are enveloping, the claws enclosing the balls to prevent them from escaping during assembly. According to one embodiment, the two adjacent retaining claws for each of the cells each comprise a concave retaining guide facet facing the ball housed in the cell, the retaining guide facets preferably being located at least partially inside a first pitch cylinder having as its base a first pitch circle passing through the centers of the balls of the first row of balls and centered on the axis of rotation, the retaining guide facets preferably lying at least partially between the first pitch plane and the second pitch plane. Preferably, the ring portion connecting the two adjacent retaining claws comprises an end guide facet facing the ball housed in the cell, the end guide facet preferably being located at least partially radially outside the first pitch cylinder 
     According to a first variant, the first bearing cage further comprises additional claws distributed around the periphery of the ring, each of the additional claws being associated with one of the retaining claws and having a free distal end located radially outside and opposite the associated retaining claw. Preferably, the two additional claws associated with the two adjacent retaining claws, for each of the cells, each comprise an additional concave guide facet facing the ball housed in the cell, the additional guide facets being located at least partially outside the first pitch cylinder and at least partially between the first pitch plane and the second pitch plane. 
     According to a second variant, it is provided that for each of the cells, the two adjacent retaining claws each comprise an additional concave guide facet facing the ball housed in the cell, the additional guide facets being located at least partially outside the first pitch cylinder and at least partially between the first pitch plane and the second pitch plane. 
     It is advantageous to provide means for stacking the cages for storage thereof before mounting the drive wheel assembly on an assembly line. To this end, provision can be made for the ring of the first bearing cage to further comprise a planar annular stacking face axially facing away from the retaining claws, and a centering bearing having a symmetry of revolution about the reference axis of the first bearing cage, the first bearing cage further comprising planar facets facing axially away from the annular stacking face, superimposed with the planar annular stacking face seen in orthogonal projection in a stacking plane containing the planar annular stacking face, and centering facets, turned radially opposite the centering bearing, so that, seen in orthogonal projection on the stacking plane, the centering facets face the centering bearing. The cages can thus be stacked while remaining centered, without the risk of them clinging to each other. 
     For good control of the positioning of the balls of the second row of balls during mounting of the assembly or in use, a second one-piece bearing cage is preferably provided comprising a ring defining a reference axis of the second bearing cage and retaining claws distributed around the periphery of the ring of the second bearing cage to delimit the cells for housing the balls of the second row of balls. 
     The second inner bearing race and the outer bearing race occupy a volume between the first pitch plane and the second pitch plane and in the immediate vicinity of the second raceway, which leaves little room to accommodate a cage whose ring would be located between the first pitch plane and the second pitch plane. Preferably, provision is therefore made for the ring of the second bearing cage to be positioned on a side of the second pitch plane opposite the first pitch plane, the retaining claws of the second bearing cage projecting from the ring of the second bearing cage toward the first pitch plane by crossing the second pitch plane, the retaining claws of the second bearing cage having a free distal end, the cells each being delimited by two adjacent retaining claws among the retaining claws of the second bearing cage and by a portion of the ring connecting the two adjacent retaining claws. The second cage then has no ring situated between the first pitch plane and the second pitch plane. More space can be allocated to the second inner bearing race, to increase its outer diameter, as well as to the outer bearing race to decrease its inner diameter between the first pitch plane and the second pitch plane. 
     According to a particularly advantageous embodiment, the balls forming the first row of balls have a ball diameter DC 1  less than or equal to a ball diameter DC 2  of the balls forming the second row of balls. The increased diameter of the balls of the second row makes it possible to reduce the distance between the two rows of balls, which limits the bending in the second inner bearing race, and therefore the risks of separation between the parts of the inner subassembly. The outer raceways are preferably enveloping in the axial direction, in the sense that they each have a raceway bottom, located in an intermediate axial position between the axial ends of the raceway. 
     According to one embodiment, the second inner bearing race is shrunk on a shrink-fit bearing of the first inner bearing race. Alternatively, the first inner bearing race and the second inner bearing race can be shrunk onto a common solid or hollow part. 
     The second inner bearing race is preferably a solid metal part, made for example from steel. Likewise, the first inner bearing race is preferably a solid metal part, made for example from steel. 
     The rotating assembly as described above is particularly suitable for guiding a vehicle wheel, in particular a drive wheel. According to one embodiment, the outer subassembly constitutes a fixed subassembly of a motor vehicle drive wheel guide, and the inner subassembly constitutes a rotating subassembly of the motor vehicle drive wheel guide, capable of rotating with respect to the fixed subassembly about the axis of rotation, the rotating subassembly comprising a wheel hub comprising a flange provided with an interface for attaching a wheel rim or a brake disc, the attachment flange forming a mounting face of the wheel rim or of the brake disc facing axially in a direction of disassembly of the wheel rim or of the brake disc, the direction of disassembly being parallel to the axis of rotation, the first inner bearing race being constituted by the wheel hub or shrunk on the wheel hub, the second inner bearing race being shrunk on a shrink-fit bearing of the wheel hub. 
     The first raceways and the first row of balls are intended, once the assembly has been integrated into the vehicle, to be further from a longitudinal median vertical plane of the vehicle than the second raceways and the second row of balls. 
     According to one embodiment, the rotating subassembly further comprises a transmission bowl, the inner bearing race bearing against the transmission bowl at an annular contact interface extending at least in a radial direction relative to the axis of rotation. Preferably, the annular contact interface is positioned at least partially, and preferably completely, between the first pitch plane and the second pitch plane, which contributes to the great compactness of the rotating assembly. 
     The second inner bearing race has a specific geometry, which makes it possible to position the second inner raceway radially outside the first inner raceway, and to house part of the transmission bowl, including the annular bearing surface, in a recess formed by the inner bearing race. 
     Preferably, the wheel hub is a solid one-piece metal part, which contributes to greater rigidity of the assembly. Alternatively, the hub can be a solid one-piece bi-material part, for example a steel/aluminum or steel/composite material combination. 
     Where appropriate, the rotating subassembly further comprises a brake disc bearing on the mounting face, a wheel rim bearing on the brake disc and elements for attaching the wheel rim and the brake disc to the attachment flange. 
    
    
     
       BRIEF DESCRIPTION OF FIGURES 
       Other features and advantages of the invention will come to light on reading the following disclosure, with reference to the appended figures. 
         FIG.  1    is a longitudinal sectional view of a rotating assembly for guiding a motor vehicle drive wheel according to a first embodiment of the invention. 
         FIG.  2    is an isometric view of a bearing cage of the rotating assembly of  FIG.  1   . 
         FIG.  3    illustrates two bearing cages similar to the cage of  FIG.  2   , stacked on top of each other before one of them is mounted in the assembly of  FIG.  1   . 
         FIG.  4    is a longitudinal sectional view of a rotating assembly for guiding a motor vehicle drive wheel according to a second embodiment of the invention. 
         FIG.  5    is an isometric view of a bearing cage as a variant of the bearing cage of  FIG.  2   , for a rotating assembly according to  FIG.  1    or according to  FIG.  4   . 
         FIG.  6    illustrates two bearing cages similar to the cage of  FIG.  5   , stacked on top of each other before one of them is mounted in the assembly of  FIG.  1    or of  FIG.  4   . 
         FIG.  7    is an isometric view of a bearing cage as a variant of the bearing cage of  FIG.  2   , for a rotating assembly according to  FIG.  1    or according to  FIG.  4   . 
         FIG.  8    illustrates two bearing cages similar to the cage of  FIG.  7   , stacked on top of each other before one of them is mounted in the assembly of  FIG.  1    or of  FIG.  4   . 
         FIG.  9    is an isometric view of a bearing cage as a variant of the bearing cage of  FIG.  2   , for a rotating assembly according to  FIG.  1    or according to  FIG.  4   . 
         FIG.  10    illustrates two bearing cages similar to the cage of  FIG.  9   , stacked on top of each other before one of them is mounted in the assembly of  FIG.  1    or of  FIG.  4   . 
     
    
    
     For greater clarity, identical or similar elements are identified by identical reference signs in all of the figures. 
     DETAILED DESCRIPTION OF EMBODIMENTS 
       FIG.  1    shows a rotating assembly for guiding a motor vehicle drive wheel  10 , comprising a fixed outer subassembly  12 , intended to be secured to a suspension member of a motor vehicle (not shown) and defining an axis of rotation  100 , an inner rotating subassembly  14 , capable of rotating about the axis of rotation  100  inside the fixed outer subassembly  12 , and guide balls  16 ,  18  between the rotating subassembly  14  and the fixed subassembly  12 . 
     The fixed outer subassembly  12  here is constituted by a one-piece solid metal outer race  20  on which a first outer raceway  22  and a second outer raceway  24 , coaxial, are formed that define the axis of rotation  100 . The outer race further comprises at least one attachment clamp  26  extending radially outward, in which bores (not shown in this figure) are formed for attaching the attachment clamp  26  to a suspension member, via attachment elements (not shown). 
     The inner rotating subassembly  14  comprises a wheel hub  30 , a transmission bowl  32 , an optional first inner bearing race  34 , and a second inner bearing race  36 . 
     The wheel hub  30  is a solid one-piece metal part, which comprises a flange  38  for attaching a drive wheel rim  40  and a brake disc  41 . The flange  38  has a face  42  bearing the brake disc  41 , and is provided with attachment bores  43 , allowing the insertion of attachment elements  143  of the rim  40  and of the brake disc  41 . 
     The wheel hub  30  also has a centering skirt  44  that projects axially with respect to the planar bearing face  42 , in a direction  200  of disassembly of the wheel rim  40  and of the brake disc  41 , and has a centering bearing  45 , preferably stepped, facing radially outward, comprising a first cylindrical portion for centering the wheel rim  40  and a second cylindrical portion, of equal or greater diameter, for centering the brake disc  41  during assembly. The centering bearing  45  is not necessarily intended to remain in contact with the rim  40  and the brake disc  41  after assembly. 
     The transmission bowl  32  is a solid one-piece metal part, which has a protruding end portion  46  and a flared middle portion  48  delimiting a cavity  50  of constant velocity joint. The protruding portion  46  of the transmission bowl  32  is preferably splined and mounted free, fitted or shrunk in a splined tubular cavity  47  of the wheel hub  30 , forming a splined contact interface. Furthermore,  FIG.  1    shows means for attaching the transmission bowl  32  and the wheel hub  30 , which for example implement a nut  188  screwed to a threaded end  190  of the protruding portion  46 , and bearing against a shoulder  84  of the wheel hub  30 . 
     The first inner bearing race  34  is shrink-fitted on a cylindrical shrink-fit bearing  52  of the wheel hub  30 , bearing axially against an annular shoulder  54  formed on the wheel hub  30 . A first inner raceway  56  is formed on the first inner bearing race  34  facing the first outer raceway  22 . 
     The second inner bearing race  36  is also shrunk on the cylindrical shrink-fit bearing  52  of the wheel hub  30 , with a transverse end face  57  bearing axially against a transverse face  59  of the first inner bearing race  34 . The second inner bearing race  36  has an annular abutment face  58 , here frustoconical but which may be flat, axially facing away from the first inner raceway  56 , and axially protruding relative to the wheel hub  30 , so as to bear against an annular bearing face  60  formed on the transmission bowl  32 . A second inner raceway  62  is formed on the second inner bearing race  36  opposite the second outer raceway  24 . The balls  16 ,  18  form, on the one hand, a first row of balls  16  that roll on the first outer raceway  22  and the first inner raceway  56  and, on the other hand, a second row of balls  18  that roll on the second outer raceway  24  and the second inner raceway  62 . 
     For the rest of the description, we will focus on certain remarkable dimensional characteristics of the assembly, which require some preliminary definitions. Thus, we note:
         PP 1 , the pitch plane where the pitch circle is located constituting the trajectory of the centers of the balls  16  of the first row of balls with nominal dimensions;   PP 2 , the pitch plane where the pitch circle is located constituting the trajectory of the centers of the balls  18  of the second row of balls with nominal dimensions;   DP 1 , the diameter of the pitch circle of the first row of balls  16 ;   DP 2 , the diameter of the pitch circle of the second row of balls  18 ;   CP 1 , a pitch cylinder centered on the axis of rotation  100  and having as its base the pitch circle of the first row of balls  16 ;   DC 1 , the diameter of the balls  16  of the first row of balls;   DC 2 , the diameter of the balls  18  of the second row of balls;   DI 1 , a raceway bottom diameter of the first inner raceway  56 , defined as the smallest diameter of the raceway  56 ;   DI 2 , a raceway bottom diameter of the second inner raceway  62 , defined as the smallest diameter of the raceway  62 ;   DE 1 , a raceway bottom diameter of the first outer raceway  22 , defined as the largest diameter of the outer raceway  22 ;   PB, a plane perpendicular to the axis of rotation  100  and tangent to the axial end face  57  of the second inner bearing race  36 ;   D, the distance between the plane PB and the first pitch plane PP 1 .       

     The first pitch plane PP 1  is located at a non-zero distance L from the second pitch plane PP 2 . Remarkably, the raceway bottom diameter DI 2  of the second inner raceway  62  is larger than the raceway bottom diameter DI 1  of the first inner raceway  56 , and preferably larger than the raceway bottom diameter DE 1  of the first outer raceway  22 . The second inner bearing race  36  therefore has a shape that flares out in the direction opposite the direction of disassembly, from the axial end face  57 , which makes it possible to accommodate part of the transmission bowl  32  inside the second inner bearing race  36 . The second inner bearing race  36  is housed in a cramped volume of generally frustoconical contour, between the outer bearing race  20  and the transmission bowl  32 . To give the second inner bearing race  36  a high stiffness, provision is made for the outer diameter of the inner bearing race  36 , measured radially with respect to the axis of rotation  100 , to increase rapidly as one moves away from the axial end face  57 . 
     This increase in diameter can be characterized by observing the outer diameter ϕ of the second inner bearing race  36  in a section plane PC perpendicular to the axis of rotation  100  and located between the first pitch plane PP 1  and the second pitch plane PP 2 , at a measurement distance DM from the first pitch plane PP 1  such that 
     
       
         
           
             DM 
             = 
             
               1.25 
               ⨯ 
               
                 
                   DC 
                   ⁢ 
                   1 
                 
                 2 
               
             
           
         
       
     
     Characteristically, the outer diameter ϕ is greater than a threshold value VS, which is equal to the greater of two values corresponding respectively to 110% of the raceway bottom diameter DI 1  of the first inner raceway  56  and to the sum of the raceway bottom diameter DI 1  of the first inner raceway  56  and of the radius of the balls  16  of the first row of balls: 
     
       
         
           
             { 
             
               
                 
                   
                     ϕ 
                     &gt; 
                     VS 
                   
                 
               
               
                 
                   
                     VS 
                     = 
                     
                       sup 
                       ⁡ 
                       ( 
                       
                         
                           
                             1.1 
                             ⨯ 
                             DI 
                           
                           ⁢ 
                           1 
                         
                         ; 
                         
                           
                             DI 
                             ⁢ 
                             1 
                           
                           + 
                           
                             
                               DC 
                               ⁢ 
                               1 
                             
                             2 
                           
                         
                       
                       ) 
                     
                   
                 
               
             
           
         
       
     
     The plane PB, in which the contact interface between the axial end face  57  and the annular bearing face  59  is located, is preferably located between the first pitch plane PP 1  and the second pitch plane PP 2 , at a distance D from the first pitch plane PP 1  preferably less than half the diameter DC 1  of the balls  16  of the first row of balls. This positioning contributes to great axial compactness and excellent rigidity of the assembly  10 . 
     The balls  16  of the first row of balls are guided in the volume between the first inner raceway and the first outer raceway by a first one-piece bearing cage  70 , illustrated in detail in  FIG.  2   , comprising a ring  72  defining a reference axis  300  of the first cage  70  and retaining claws  74  distributed around the periphery of the ring  72  to delimit cells  76  for housing the balls  16  of the first row of balls. The reference axis  300  of the first bearing cage  70  is intended to coincide with the axis of rotation  100  when the rotating assembly  10  is in a reference position. 
     The rapid increase in the outer diameter of the second inner bearing race  36  in the immediate vicinity of the first inner raceway  56  results in a reduced volume to position the first bearing cage  70 . In order to maximize the volume available for the second inner bearing race  36  in the space located between the first pitch plane PP 1  and the second pitch plane PP 2 , provision is advantageously made for the ring  72  of the first bearing cage to be positioned on a side of the first pitch plane PP 1  opposite the second pitch plane PP 2 . The retaining claws  74  extend from the ring toward the second pitch plane PP 2  crossing the first pitch plane PP 1 . The first cage therefore has no ring located between the first pitch plane PP 1  and the second pitch plane PP 2 , so that the retaining claws  74  have a free distal end  78 . The cells  76  are each delimited by two adjacent retaining claws  74  among the retaining claws of the first bearing cage  70  and by a portion of the ring  72  connecting the two adjacent retaining claws  74 . 
     For each of the cells  76 , the two adjacent retaining claws  74  each comprise a concave retaining guide facet  80  facing the ball  16  housed in the cell  76 , and the ring portion  721  connecting the two adjacent retaining claws  74  comprises an end guide facet  82  facing the ball  16  housed in the cell. The end guide facet  82  is located at least partially radially on the outside of a first pitch cylinder CP 1  whose base is the pitch circle of the first row of balls  16  and centered on the axis of rotation  100 . The retaining guide facets  80  are located at least partially inside the first pitch cylinder CP 1  and at least partially between the first pitch plane PP 1  and the second pitch plane PP 2 . 
     In this embodiment, the first bearing cage  70  further comprises additional claws  84  distributed around the periphery of the ring  72 , each of the additional claws  84  being associated with one of the retaining claws  74  and having a free distal end  86  located radially outside and facing the associated retaining claw  74 . For each of the cells, the two additional claws  84  associated with the two adjacent retaining claws  74  each comprise an additional concave guide facet  88  facing the ball  16  housed in the cell  76 , the additional guide facets  88  being located at least partially outside the first pitch cylinder CP 1  and at least partially between the first pitch plane PP 1  and the second pitch plane PP 2 . An enveloping cage  70  is thus produced, in the sense that the balls  16  cannot be inserted into the cells and can only be extracted therefrom by elastically deforming the retaining claws  74  or the additional claws  84 , or the retaining claws  74  and the additional claws  84  simultaneously. Thus, there is no risk of losing a ball during assembly. 
     The ring  72  of the first bearing cage  70  comprises a planar annular stacking face  722  axially facing away from the retaining claws  74 , and a centering bearing  724  having a symmetry of revolution about an axis of symmetry  300  of the first bearing cage  70 . The free ends  86  of the additional claws  84  face axially away from the planar annular stacking face  722 , superimposed with the planar annular stacking face  722  seen in orthogonal projection in a stacking plane containing the planar stacking face  722 . The retaining claws  74  in turn comprise centering facets  742 , facing radially away from the centering bearing  724 , so that, seen in orthogonal projection in the stacking plane, the centering facets  742  face the centering bearing  724 . Thus, when two bearing cages identical to the first one-piece bearing cage  70  are stacked on top of each other before they are mounted in the rotating assembly  10 , as illustrated in  FIGS.  3  and  6   , the free ends  86  of the additional claws  84  of a bearing cage  70  bear against the annular stacking face  722  of the adjacent bearing cage  70 , while the centering facets  742  come opposite the centering bearing  724 , which ensures controlled relative positioning of the two bearing cages  70  and prevents them from becoming inextricably entangled. 
     The balls  18  of the second row of balls are guided in the volume between the second inner raceway  62  and the second outer raceway  24  by a second one-piece bearing cage  90 , comprising a ring  92  defining a reference axis of the second cage and retaining claws  94  distributed around the periphery of the ring  92  to delimit cells for housing the balls  18  of the second row of balls. 
     In order to maximize the volume available for the second inner bearing race  36  and the outer bearing race  20  in the space located between the first pitch plane PP 1  and the second pitch plane PP 2 , the ring  92  is preferably positioned on a side of the second pitch plane PP 2  opposite the first pitch plane PP 1 . The retaining claws  94  protrude from the ring toward the first pitch plane PP 1  while crossing the second pitch plane PP 2 . The retaining claws  94  have a free distal end  98 , cells each being delimited by two adjacent retaining claws  94  among the retaining claws of the second bearing cage  90  and by a portion of the ring  92  connecting the two adjacent retaining claws  94 . The second bearing cage  90  moreover has essentially the same configuration as the first bearing cage  70 , naturally with dimensions adapted to the diameter of the balls  18  and to the pitch diameter of the second row of balls  18 . 
     The outer raceways  22 ,  24  formed on the outer bearing race  20  are enveloping in the axial direction, in the sense that they each have a raceway bottom  64 ,  66 , located in an intermediate position between the axial ends of the corresponding raceway  22 ,  24 . 
     In this embodiment, the balls forming the first row of balls  16  have a diameter DC 1  that is preferably less than or equal to the diameter DC 2  of the balls forming the second row of balls  18 . Choosing a relatively small diameter for the first row of balls  16  makes it possible to retain a sufficient axial thickness of the second inner bearing race  36  in the shrink-fit region on the wheel hub  30 , dose to the first row of balls  16 , and to bring together the pitch planes PP 1  and PP 2 . The choice of a larger diameter for the second row of balls  18  makes it possible to ensure good load resistance, while maintaining a relatively small distance between the two pitch planes PP 1  and PP 2 . 
     The embodiment of  FIG.  4    differs from that of  FIG.  1    in that the first inner raceway  56  is formed directly on the wheel hub  30 , which thus constitutes the first inner bearing race  34  and has a shrink-fit bearing  52  and a shoulder  159 . The second inner bearing race  36  is thus shrink-fitted on the shrink-fit bearing  52  and axially bears against the shoulder  159  of the wheel hub  30 , and against the annular bearing face  60  of the transmission bowl  32 . 
       FIGS.  5  to  6    show a variant of the first bearing cage  70 , intended to equip the rotating assembly for guiding a drive wheel of a motor vehicle  10  of  FIG.  1   , or of  FIG.  4   . The first bearing cage  70  of  FIGS.  5  and  6    differs from the preceding ones in particular by the positioning of the first stacking face  722 , which is set back with respect to an axial end of the ring  72  of the bearing cage  70 , and by positioning and centering facets  742 , which are formed on the additional claws  84 .  FIG.  6    in particular shows the cooperation between the centering facets  742  and the centering bearing  724 , and between the free ends  86  of the additional claws  84  and the annular stacking face  722  to allow stacking of the first bearing cages  70  on top of each other on an assembly line of the rotating assembly  10 . 
       FIGS.  7  to  8    show another variant of the first bearing cage  70 , intended to equip the rotating assembly for guiding a drive wheel of a motor vehicle  10  of  FIG.  1   , or of  FIG.  4   . The first bearing cage  70  of  FIGS.  7  and  8    differs from the previous ones in that it comprises only one set of solid retaining claws  74 , and no additional claws. The retaining claws  74  have retaining guide facets  80  that are intended to be located at least partially inside the first pitch cylinder CP 1  and at least partially between the first pitch plane PP 1  and the second pitch plane PP 2 , and additional guide facets  88  intended to be located at least partially outside the first pitch cylinder CP 1  and at least partially between the first pitch plane PP 1  and the second pitch plane PP 2 . An enveloping cage  70  is thus produced, in the sense that the balls  16  cannot be inserted into the cells and can only be extracted therefrom by elastically deforming the retaining claws  74 . In the embodiments of  FIGS.  5  to  8   , the balls  16  are mounted in the first bearing cage  70  by a movement having either a zero radial component or a radial component oriented toward the reference axis  300 . 
       FIGS.  9  to  10    show another variant of the first bearing cage  70 , intended to equip the rotating assembly for guiding a drive wheel of a motor vehicle  10  of  FIG.  1   , or of  FIG.  4   . The first bearing cage  70  of  FIGS.  9  and  10    differs from the previous ones in that it comprises only one set of hook-shaped retaining claws  74 , and no additional claws. The retaining claws  74  have retaining guide facets  80  that are intended to be located at least partially inside the first pitch cylinder CP 1  and at least partially between the first pitch plane PP 1  and the second pitch plane PP 2 , and additional guide facets  88  intended to be located at least partially outside the first pitch cylinder CP 1  and at least partially between the first pitch plane PP 1  and the second pitch plane PP 2 . An enveloping cage  70  is thus produced, in the sense that the balls  16  cannot be inserted into the cells and can only be extracted therefrom by elastically deforming the retaining claws  74 . This embodiment of the first bearing cage  70  differs from the previous ones also in that the balls  16  are mounted in the bearing cage  70  by a movement having a radial component going from the inside toward the outside of the bearing cage  70 . 
     In all embodiments, the second bearing cages  90  may be similar to the first bearing cages  70 . 
     Alternatively, the balls  16 ,  18  of the two rows of balls may have the same diameter. 
     As a variant, it is possible to provide a fixed subassembly in several parts, with a clamp  26  in one or more parts forming the attachment clamp to a suspension element of the vehicle, and two coaxial outer bearing races shrunk in this clamp. 
     It is emphasized that all the features, as they will come to light for a person skilled in the art from the present description, the drawings and the attached claims, may be combined with other features or groups of features disclosed here, even if concretely these features have only been described in relation to other determined features, both individually and in arbitrary combinations, provided that this has not been expressly excluded or that technical circumstances make such combinations impossible or devoid of meaning. 
     Throughout the text of the present application, “fixed subassembly” has been used to refer to a subassembly that constitutes a fixed coordinate system for the rotation of the movable subassembly. Those skilled in the art will have understood that this subassembly is itself required to move relative to the body of the vehicle, depending on the geometry of the suspension interposed between the body of the vehicle and the fixed subassembly.