Abstract:
A rolling bearing includes a bottom ring, a top ring having a skirt with at least one radial protrusion, and a plurality of rolling elements disposed between the rings. A seal is radially disposed between the top and bottom rings and includes an annular radial rib, the rib being positioned axially above the radial protrusion of the top ring skirt so as to interfere diametrically with the radial protrusion and configured to frictionally contact the skirt to attach the seal to the top ring, and a retainer configured to axially retain the bottom ring relative to the top ring. A suspension thrust bearing device includes the rolling bearing and a support element for the rolling bearing forming bearing means for a spring, and a suspension strut for a motor vehicle includes the suspension thrust bearing device.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to European patent application no. 10305109.0, filed on Feb. 3, 2010, which is incorporated fully herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to the field of rolling bearing adapted to the suspension thrust bearing devices used in particular on motor vehicles in the suspension struts of the steered road wheels. 
         [0003]    The invention relates more particularly to a rolling bearing comprising a top ring and a bottom ring between which are positioned a seal and rolling elements, for example balls or rollers. The top and bottom rings may be mounted in contact with bottom and top bearing or support pieces, such as covers or cups. The top and bottom cups form a housing for the rings of the rolling bearing and provide the interface between said rings and the neighboring elements. 
         [0004]    A suspension thrust bearing device is positioned in the top part of the suspension strut between the bodywork of the vehicle and a suspension spring. The spring is fitted around a damping piston rod, the end of which is linked to the bodywork of the vehicle through an elastic block that filters the vibrations. The suspension spring axially bears, directly or indirectly, on the bottom cup. The top cup is fixed relative to the bodywork of the vehicle. 
         [0005]    The rolling bearing makes it possible to transmit axial forces between the suspension spring and the bodywork of the vehicle, while allowing a rotation movement between the bottom cup and the filtering elastic block. This relative angular movement derives from a steer angle of the steered road wheels of the vehicle and/or the compression of the suspension spring. 
         [0006]    For more detail, it is possible for example to refer to the French patent application FR-A1-2 688 836. 
         [0007]    French patent application FR-A1-2 617 252 also discloses such a rolling bearing adapted to a suspension thrust bearing device. The disclosed rolling bearing comprises a bottom ring, a top ring and a seal disposed radially between said rings and adapted to axially retain the bottom ring relative to the top ring. 
         [0008]    To fix the seal to the top ring, cut-out windows are formed on an external skirt of the top ring during stamping of said ring and external clipping sections are also foreseen on the seal to cooperate with said windows. This prevents the seal from moving both axially and radially between the rings. 
         [0009]    To this end, French patent application FR-A1-2 816 550 discloses a top ring having an external skirt comprising bosses which are created by the displacement of metal material radially inwards. External sections of the seal may be clipped onto said bosses to block the seal between the two rings. 
         [0010]    In both two latter prior art documents, during the rolling bearing assembly, the seal must be angularly oriented or indexed relative to the top ring before mounting. In fact, these designs of seals each use external clipping sections to mate with the associated cut-out windows or bosses of the top ring. This leads to an increase of the assembly time as well as the overall cost of the rolling bearing. 
       SUMMARY OF THE INVENTION 
       [0011]    One aim of the present invention is therefore to overcome the drawbacks of the prior as discussed above, particularly the necessity of orienting/indexing the seal relative to the top ring. 
         [0012]    It is a particular object of the present invention to provide a rolling bearing, particularly adapted to a suspension thrust bearing device, which is simple to assembly and economic, while guaranteeing an efficient sealing to prevent the ingress of moisture, dust and other foreign matter into the bearing. 
         [0013]    In one embodiment, the rolling bearing comprises a bottom ring, a top ring, at least one row of rolling elements mounted between the rings, and a seal radially disposed between said rings. The seal includes an annular radial rib, the rib being positioned above the radial protrusion of the top ring skirt so as to interfere diametrically with the radial protrusion and configured to frictionally contact the skirt to attach the seal to the top ring, and a retainer configured to axially retain the bottom ring relative to the top ring. 
         [0014]    The seal has a relatively simple structure and can easily be mounted between the two rings of the rolling bearing because there is no need to angularly orient the seal relative to the top ring during the rolling bearing assembly due to the annular structure of the radial rib and to the frictional contact between said rib and the skirt, which prevents rotation of the seal after mounting. 
         [0015]    Additionally, with such a circumferentially continuous rib extending radially, the seal has an improved static sealing with the top ring due to the external contact between said rib and the skirt of the top ring over 360°. “Static sealing” means the sealing made between two parts that do not move relative to one another. 
         [0016]    In one embodiment, the skirt of the top ring extends axially. 
         [0017]    Preferably, the external diameter of the annular radial rib of the seal in a free state is greater than the internal diameter of the skirt of the top ring so as to create an interference fit between said seal and said skirt. 
         [0018]    In one embodiment, the seal includes an annular top radial surface in contact with a radial portion of the top ring to provide a further static sealing with said top ring. The contacting surfaces between the seal and the top ring are thus increased in order to have a better static sealing effect of the seal. 
         [0019]    In a preferred embodiment, the seal comprises a chamfer in the form of a frustoconical surface disposed between the top radial surface and the annular radial rib. 
         [0020]    In one embodiment, the skirt of the top ring comprises a plurality of radial protrusions spaced apart from one another in the circumferential direction. Alternatively, the skirt of the top ring comprises an annular radial protrusion. The radial protrusion(s) of the top ring may be obtained by deforming the skirt of the top ring axially. 
         [0021]    The seal may also comprise an annular bottom radial surface radially offset outwards relative to the axially retaining means. 
         [0022]    In one embodiment, the rolling bearing further comprises a cage configured to maintain a circumferential spacing between the rolling elements. The cage preferably has at least two extensions each frictionally contacting the bottom ring and the top ring. The cage is distinct from the seal disposed radially between the rings. 
         [0023]    In one embodiment, the axially retainer includes an annular lip coming into friction contact with the bottom ring. 
         [0024]    According to another aspect, it is proposed a suspension thrust bearing device comprising a rolling bearing as previously defined and a support element for the rolling bearing forming bearing means for a spring. 
         [0025]    According to a further aspect, it is proposed a suspension strut for a motor vehicle comprising a suspension thrust bearing device as previously defined. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0026]    The present invention and its advantages will be more readily understood by studying the detailed description of one specific embodiment, which constitutes a non-limiting example of the present invention, and illustrated by the appended drawings on which: 
           [0027]      FIG. 1  is a view in axial section of a rolling bearing according to an example of the invention, 
           [0028]      FIG. 2  is a part section on a larger scale of  FIG. 1 , 
           [0029]      FIG. 3  is a part section of a top ring of the rolling bearing of  FIG. 1 , 
           [0030]      FIG. 4  is an under view of the top ring of  FIG. 3 , and 
           [0031]      FIG. 5  is an upper view of a seal of the rolling bearing of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0032]    As illustrated on  FIGS. 1 to 3 , an example of rolling bearing  10 , with an axis  12 , comprises a top ring  14  and a bottom ring  16 , between which is mounted a row of rolling elements  18 , which in this case are balls. The rolling bearing  10  also comprises a seal  20  radially disposed between the rings  14 ,  16 . A cage  22  is also provided between the rings so as to maintain an even circumferential spacing between the rolling elements  18 . 
         [0033]    The top ring  14  and the bottom ring  16  are made of a thin metal sheet, which has been stamped or rolled so as to define toroidal tracks or raceways for the rolling elements  18  between the two rings  14 ,  16 . 
         [0034]    The top ring  14  includes an annular radial portion  14   a  with an external annular axial skirt  14   b  of small thickness and of large diameter at this end, opposite to the rolling element  18 , and extending axially downward. A small-diameter edge of the radial portion  14   a  is extended towards the inside and downward by a toroidal portion  14   c . The concave external surface of the toroidal portion  14   c  forms the track or raceway for the rolling elements  18 . The bottom end of the toroidal portion  14   c  is extended radially inwards and axially downward by a short frustoconical portion  14   d.    
         [0035]    The top ring  14  also comprises a plurality of radial protuberances or protrusions  14   e  provided on the internal bore of the external axial skirt  14   b , in the vicinity of its bottom end. The protrusions  14   e  are directed radially towards the inside and are evenly spaced relative to one another in the circumferential direction, i.e., the protrusions  14   e  are circumferentially spaced. Each protrusion  14   e  preferably forms a hook directed radially towards the inside, towards the bottom ring  16 . In this example, the top ring  14  includes twelve protrusions  14   e.    
         [0036]    The protrusions  14   e  are preferably formed by axially deforming partly the bottom end of the axial skirt  14   b  with an appropriate tool in order to create local deformations of material which extend radially inwards. It is relatively easier to stamp bosses or protrusions  14   a  by deforming the skirt  14   b  axially rather than by forming radial deformations in the metal part. Additionally, the process for creating the protrusions  14   e  is relatively inexpensive since it is done during the stamping process of the top ring  14 . 
         [0037]    The bottom ring  16  includes an annular radial portion  16   a  extending radially opposite from the radial portion  14   a  of the top ring. The radial portion  16   a  extends generally towards the outside and upwardly by a toroidal portion  16   b . The concave internal surface of the toroidal portion  16   b  forms the track or raceway for the rolling elements  18 . The bottom ring  16  also includes a cylindrical portion  16   c  extending axially downward a small-diameter edge of the radial portion  16   a  and providing with a radially folded edge  16   d  at its end. The toroidal portion  16   b  of the bottom ring  16  and the external axial skirt  14   b  of the top ring  14  are separated radially from one another by an annular space  24  in which the seal  20  is mounted. 
         [0038]    The seal  20  is preferably of one-piece construction and may be formed of a plastic or polymeric material by molding, for example polyamide (PA), polytetrafluoroethylene (PTFE), or natural or synthetic rubber. The seal  20  has an annular shape and includes an annular axial skirt or portion  30  and an annular lip  32  projecting radially inward from an axial bottom edge of the axial portion  30 . The axial portion  30  and the lip  32  apply respectively a static sealing with the top ring  14  and a dynamic sealing with the bottom ring  16 . 
         [0039]    The axial portion  30  is delimited axially by two opposite annular radial surfaces  30   a ,  30   b . The top radial surface  30   a  bears against a bottom surface of the radial portion  14   a  of the top ring  14  and forms a static sealing with the ring over 360°, i.e., about substantially the entire perimeter of the ring  14 . The contact between the top radial surface  30   a  and the bottom surface of the radial portion  14   a  is located radially near the axial skirt  14   b . The bottom radial surface  30   b  is approximately situated in a radial plane containing the bottom end surface of the axial skirt  14   b  of the top ring. 
         [0040]    The axial portion  30  comprises an annular rib  34  extending radially outwards, towards the axial skirt  14   b  of the top ring  14 . An annular outer surface  34   a  of the rib  34  frictionally contacts the internal bore of the external axial skirt  14   b  of the top ring  14 . Therefore, the annular rib  34  forms an external static sealing contact with the top ring  14  over 360° (i.e., about the entire perimeter of the ring  14 ). 
         [0041]    The seal  20  is rotationally coupled or attached with the top ring  14  due mainly to the frictional contact forces between the annular rib  34  and the axial skirt  14   b . Preferably, the diameter of the outer surface  34   a  of the annular rib  34 , in a free state, is greater than the internal diameter of the bore of the external axial skirt  14   b  such that the seal  20  and the skirt  14   b  are coupled by an interference fit. The interference fit prevents rotation of the seal  20  relative to the top ring  14 . Additionally, the interference fit between the outer surface  34   a  of the annular rib  34  and the axial skirt  14   b  enhances the efficiency of the static sealing between these two elements. The annular rib  34  is adapted to form a means for fixing or attaching the seal  20  to the top ring  14  in the circumferential direction. 
         [0042]    The annular rib  34  is also adapted to cooperate with the radial protrusions  14   e  of the skirt  14  of the top ring  14  to serve as a retainer for axially retaining the seal relative to the top ring  14 . An annular bottom radial surface  34   b  of the rib  34  bears against the top surfaces of the radial protrusions  14   e  of the skirt  14 . The external diameter of the radial rib  34  is greater than the inner diameter of the radial protrusions  14   e  so that a diametrical interference exists between the seal  20  and the top ring  14  to prevent an axial displacement of said seal  20  downward. The annular rib  34  therefore forms an axial retention means interacting with a complementary axial retention means of the top ring  14  and axially positioned above the latter. The seal  20  is locked in axial direction downward and upward respectively by the radial protrusions  14   e  and the radial portion  14   a  of the top ring  14 . Axial narrow passageways are formed between the internal edges of the radial protrusions  14   e  and the axial portion  30  of the seal. 
         [0043]    The seal  20  also includes an annular chamfer  34   c  in the form of a frustoconical surface linking the outer surface  34   a  of the rib  34  and the top radial surface  30   a  of the axial portion  30 . The chamfer  34   c  is adapted to cooperate with the internal edges of the radial protrusions  14   e  of the top ring  14  when the seal  20  is mounted between said top ring and the bottom ring  16 . Specifically, the seal  20  is mounted between said rings with a simple axial pushing movement on the bottom radial surface  30   b . With the axial pushing movement, when the chamfer  34   c  bears against the internal edges of the radial protrusions  14   e , by virtue of the frustoconical form of said chamfer, the axial portion  30  is radially moved towards the bottom ring  16  until the ridge between the chamfer  34   c  and the outer surface  34   a  of the rib  34  reaches the internal edges of the radial protrusions  14   e . Then, the axial portion  30  partly recovers by elasticity its initial shape. The seal  20  is still axially pushed until the top radial surface  30   a  comes into contact with the bottom radial surface of radial portion  14   a  of the outer ring  14 . In this mounted position, the bottom radial surface  34   b  and the outer surface  34   a  of the rib  34  are respectively in frictional contact or engagement with the radial protrusions  14   e  and the skirt  14   b  of the top ring  14 . 
         [0044]    In the illustrated embodiment, the bottom surfaces of the protrusions  14   e  extend in a common radial plane. Alternatively, it may also be possible to foresee for these bottom surfaces an inclined form similar to the one of the chamfer  34   c  to ensure during the installation of the seal  20  inside the top ring  14 , a smooth and progressive radial deformation inwards of the axial portion  30  of the seal. To this end, some local recesses may be provided in the thickness of the axial portion to enhance its flexibility. 
         [0045]    The annular lip  32  extends obliquely downwards from the bottom edge of the axial portion  30  and is radially offset inwards relative to the bottom radial surface  30   b  of said portion. The lip  32  frictionally contacts the outer surface of the toroidal portion  16   b  of the bottom ring  16 . The lip  32  forms an internal dynamic sealing with the bottom ring  16 . 
         [0046]    The annular lip  32  is also functions as an axial retainer and is configured to axially retain the bottom ring  16  relative to the top ring  14  before the rolling bearing  10  is mounted into the suspension thrust bearing device. To this end, the inner diameter of the lip  32  is smaller than the outer diameter of the bottom ring  16 . 
         [0047]    As mentioned above, the seal  20  is preferably used to close or enclose the external space  24  delimited between the toroidal portion  16   b  of the bottom ring  16  and the external axial skirt  14   b  of the top ring  14 . In order to close the internal annular space delimited between the radial portion  16   a  of the bottom ring and the frustoconical portion  14   d  of the top ring, the cage  22  includes a lip having a first annular radial extension  22   a  which frictionally contacts the frustoconical portion  14   d  and a second annular axial extension  22   b  extending a small-diameter edge of said first radial extension and bearing against the bore of the cylindrical portion  16   c  of the bottom ring  16 . 
         [0048]    It should be noted that the embodiment illustrated and described was given merely by way of a non-limiting indicative example and that modifications and variations are possible within the scope of the invention. Thus, the invention applies not only to an angular contact ball bearing with a single row of balls but also to other types of rolling bearing, for example bearings having four points contacts and/or with double rows of balls, or with at least three rows of balls. 
         [0049]    It is easily understood that it could also be possible to use bearing with other types of rolling members such as rollers. Otherwise, in the illustrated embodiment, the protrusions of the top ring are spaced relative to one another in the circumferential direction. Alternatively, it may also be possible to form a circumferentially continuous protrusion or rib on the internal edge of the external axial skirt of the top ring to cooperate with the annular outer rib of the seal. 
         [0050]    The specific structure of the rib of the seal having a circumferentially continuous outer surface in friction contact with the skirt of the top ring permits to obtain a seal particularly easy to mount into the rolling bearing with a simple axial pushing movement without angular orientation. Additionally, the seal is fixed to the top ring without using an additional component.