Abstract:
The invention concerns a vehicle thrust bearing comprising a rolling bearing forming a stop element ( 8 ), a support spring retainer ( 11 ), and an elastic support block ( 2 ), the rolling bearing including an upper race ( 12 ) arranged in an annular upper cap ( 16 ) forming a contact surface between said upper race ( 12 ) and the elastic block ( 2 ), a lower race ( 13 ). The device comprises an annular lower cap ( 17 ) forming a contact surface between the lower race ( 13 ) and the support spring retainer ( 11 ). The caps ( 16, 17 ) comprise each a thick portion ( 18, 22 ) and a thin portion ( 19, 23 ), the thin portion ( 19, 23 ) being located axially opposite the thick portion ( 22, 18 ) of the other cap, the lower ( 13 ) and upper ( 12 ) races being urged to be pressed on the thick portions ( 22, 18 ) of the lower ( 17 ) and upper ( 16 ) caps forming a rolling bearing with oblique contact.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of suspension thrust bearingthrust bearings used, in particular, in motor vehicles on the telescopic suspension struts of the steered wheels. 
     2. Description of the Relevant Art 
     A suspension thrust bearing usually includes an upper race and a lower race between which are placed rolling elements, in the form of balls or rollers. 
     A suspension thrust bearing is usually placed at the top of the suspension strut between a lower metal cup that also acts as a seat for a suspension spring, and an upper element secured to the vehicle body. The spring of the suspension device is installed around the rod of the damper piston whose end is secured to an elastic support block. The suspension thrust bearing allows a rotating motion between the spring cup, able to rotate, and the elastic support block that is attached to the vehicle body. The relative angular movement between the spring cup and the elastic block is the result of a turning of the steered wheel and/or the compression of the suspension spring. 
     The suspension thrust bearing also transmits the axial loads between the spring and the vehicle body. 
     From document FR 2,779,096, a suspension thrust bearing device is known in which the rolling bearing includes an upper race placed inside a cap in contact with the elastic support block and a lower race in direct contact with the cup. The rolling bearing includes a cage fitted with sealing lips to seal the bearing. 
     However, the bearing seal thus obtained is not satisfactory. Specifically, the suspension thrust rolling bearings are situated under the vehicle body and in the near vicinity of the wheels which, particularly during rainy weather, splash pollutants likely to enter the bearing. 
     Pollution of the bearing by external elements may, in the long run, adversely affect the operation of the bearing. 
     SUMMARY 
     Described herein is a suspension thrust rolling bearing that is very tightly sealed while remaining axially and radially compact. 
     In one embodiment, a suspension thrust rolling bearing capable of transmitting both axial and radial loads while correctly distributing the loads is described. 
     Finally, a suspension thrust rolling bearing with a high degree of imperviousness that may easily be assembled, cannot be dismantled and is cheap to fabricate is also described. 
     A vehicle suspension thrust bearing device is of the type including an angular contact rolling bearing forming a thrust bearing, a cup for a spring, and an elastic support block, the rolling bearing being placed between the cup and the elastic support block secured to the vehicle chassis. The rolling bearing includes an upper race placed inside an upper annular cap forming an interface between said upper race and the elastic block with which the upper cap is in contact, a lower race, and rolling elements placed between raceways of the upper and lower races. The suspension thrust bearing device includes an annular lower cap forming an interface between the lower race and the cup with which the lower cap is in contact. The lower and upper caps each include a thick portion and a thin portion, the thin portion of one cap being situated axially opposite the thick portion of the other cap, the lower and upper races bearing against the thick portions of the lower and upper caps thereby forming an angular contact rolling bearing. 
     The placing of a thick portion opposite a thin portion makes it possible to produce an angular contact rolling bearing of reduced axial and radial bulk. The particular shape of the caps including a thick portion and a thin portion provides a good distribution of the loads from a cap to the cup or from a cap to the elastic support block while facilitating the formation on the caps of sealing means and/or the placing of separate seals, to protect the suspension thrust rolling bearing effectively. 
     Advantageously, one race has an external diameter substantially equal to the internal diameter of the other race, so that the lower and upper races may be obtained from one and the same blank to reduce their fabrication cost. With such a race configuration, it is easy to obtain an angular contact rolling bearing with good operational qualities. 
     The ratio between the internal diameter of one outer race and the external diameter of the other race lies between 1 and 1.05. Depending on the orientation of the rolling bearing angular contact, the upper race is the race with the larger average diameter, or the lower race is the race with the larger average diameter. 
     In an embodiment, the upper and lower caps define an internal space in which the upper and lower races are located, the upper and lower caps including sealing means to seal the internal space. The lower cap cooperates with the upper cap to form an internal space in which the rolling bearing of the suspension thrust bearing device lies and is thus protected. The means of sealing the upper and lower caps interact to ensure that the bearing is protected against the ingress of external pollutants. 
     In one embodiment, a cap including a skirt extending axially toward the other cap and radially limiting the internal space, while forming a narrow sealing passage with the other cap. The presence of the skirt radially encloses, at the inner or outer periphery, the internal space defined between the upper and lower caps. The skirt forms a sealing means cooperating with the other cap to seal the internal space by means of a narrow radial and/or axial passage. 
     One cap includes means of axial retention with the other cap. This produces a compact assembly that cannot be dismantled and may be easily handled without the risk of being accidentally dismantled by an operator. 
     In one embodiment, one cap includes a radially elastic lip extending toward a skirt of the other cap thereby forming a narrow passage and interacting with a radial flange of the skirt to allow an axial motion in one direction while preventing an inverse axial motion. The lip interacts with the skirt to produce a means of sealing the internal space. The skirt interacts with the radial flange to produce a means of axial retention between the upper cap and the lower cap. The skirt therefore performs a dual function of axial retention and of sealing, capable of being produced at low cost and of allowing easy assembly of the suspension thrust rolling bearing and ensuring that the suspension thrust rolling bearing cannot be accidentally dismantled. 
     To further improve the sealing of the rolling bearing, the suspension thrust bearing device may include a seal placed on one cap, for example in an annular rib, and having a lip in contact with a radial portion of the race placed on the other cap, or with the other cap. If necessary, each cap may include a seal interacting with the race placed on the other cap or directly with the other cap. Hence, a seal provides improved imperviousness, the means of sealing between the upper and lower caps providing additional sealing. 
     Advantageously, a seal is injection overmolded onto one cap or dual injection molded at the same time as the cap. 
     Another embodiment relates to a method of fabricating a rolling bearing including a lower race and an upper race, in which, in a thin annular cup, two annular races provided with toroidal portions are formed, these portions having surfaces with, in cross section, a concave profile, said surfaces being suitable for forming raceways, one race having an internal diameter substantially equal to the external diameter of the other race, the races being connected, the races are separated, and the recess radius of at least one race and/or the internal diameter of the larger diameter race is reduced. 
     This fabrication method can easily be applied to a suspension thrust bearing device: the races are secured with lower and upper annular cups, rolling elements are placed between the races to form a suspension rollingbearing, the bearing is placed between a cup of a spring and an elastic support block secured to the vehicle chassis, the upper cap forming an interface between said upper race and the elastic block with which it is placed in contact, the lower cap forming an interface between the lower race and the cup with which it is placed in contact, each cap including a thick portion and a thin portion, the thin portion of one cap being situated axially opposite the thick portion of the other cap, the lower and upper races bearing against the thick portions of the lower and upper caps thereby forming an angular contact rolling bearing. The races easily enable the fabrication of an angular contact rolling bearing that may take axial and radial loads. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention and its advantages will be better understood by studying the detailed description of some embodiments taken as nonlimiting examples and illustrated by the appended drawings wherein: 
         FIG. 1  is a view in axial section of a suspension thrust bearing device in the assembled state; 
         FIG. 2  is a view of the suspension thrust bearing according to  FIG. 1 ; 
         FIG. 3  is a variant of a suspension thrust bearing according to  FIG. 2 ; and 
         FIGS. 4 to 6  illustrate a method of fabricating two races used in the suspension thrust rolling bearing according to  FIGS. 1 to 3 . 
     
    
    
     While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the drawing and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present invention as defined by the appended claims. 
     DETAILED DESCRIPTION 
     In  FIG. 1 , a damper includes a cylinder, not shown, in which a piston can slide whose rod  1  is linked at its top end to an elastic support block  2  which bears against an element of the chassis  3  forming a seat while being secured to the latter. The elastic support block  2  includes an internal annular link element  4  made up of two portions  4   a  and  4   b  onto which the end of the damper piston rod  1  is mounted by means of a nut  5 , an annular external link element  6  used for securing to the chassis  3 , an annular upper cup  7  acting as a seat for the thrust bearing  8 , a rubber block  9  bonded to the surface of these three parts and forming a link between the latter with filtration of vibrations. 
     The external linking element  6  is attached to the chassis  3 , for example by screwing or bolting. The upper cup  7  is placed axially on the internal linking element  4 , but is of greater diameter. Also shown is the suspension spring  10  the top of which bears against a lower annular cup  11  which, in turn, bears against the thrust bearing  8 . 
     The upper cup  7  includes a radial portion  7   a  and a cylindrical axial portion  7   b  extending from the larger diameter portion of the radial portion  7   a . The upper surface of the radial portion  7   a  and the external surface of the cylindrical portion  7   b  are in contact with the rubber block  9  of the elastic support block  2 . 
     The lower cup  11  includes a recess  11   a  in which the end of the spring  10  rests, a radial portion  11   b  extending radially inward from the recess  11   a  and a cylindrical portion  11   c  extending axially toward the upper cup  7   a  from the free inner edge of the radial portion  11   b.    
     The suspension thrust bearing  8 , more clearly visible in  FIG. 2 , includes an upper race  12  and a lower race  13 , between which are housed rolling elements  14 , balls in this instance, retained circumferentially, regularly spaced by a cage  15  of synthetic material. The upper race  12  and lower race  13  are formed of steel plate by cutting and pressing. 
     The upper race  12  includes a toroidal portion  12   a  having in cross section an internal concave quarter circle profile suitable for forming a toric raceway for balls, said toroidal portion  12   a  being extended outward by a radial portion  12   b , extending from one lower edge of the toroidal portion  12   a.    
     The lower race  13  includes a toroidal portion  13   a  having in cross section an internal concave quarter circle profile suitable for forming a toric raceway for balls, said toroidal portion  13   a  being extended inward by a radial portion  13   b , extending from one upper edge of the toroidal portion  13   a . The internal diameter of the upper race  12  is substantially equal to the external diameter of the lower race  13 . 
     The suspension thrust bearing  8  includes an upper annular cap  16  and a lower annular cap  17  of synthetic material such as a glass-fiber-filled polyamide. The upper cap  16  includes a first portion and a second portion wherein the first portion has a thickness that is greater than the second portion. The upper cap  16  includes a thick peripheral portion (e.g., a first portion)  18  extended radially inward by a thin radial portion (e.g., a second portion)  19  of lesser thickness, from the top of the thick portion  18 . 
     The thick portion  18  includes a radial surface  18   b  oriented toward the lower cap  17  and a toroidal internal surface  18   a  with, in cross section, a concave profile oriented toward the lower cap  17  and radially inward, the internal surface  18   a  connecting the thick portion  18  to the thin portion  19 . The thick portion  18  is of a thickness that reduces radially inward. The upper cap  16  comprises an upper radial surface  16   a  and an external cylindrical surface  16   b  that are connected by a rounded bevel  16   c.    
     The upper cap  16  includes an internal skirt  20  extending axially toward the lower cap  17  from the area of lesser diameter of the thin portion  19 . The cap  16  also includes an external skirt  21  extending axially toward the lower cap  17  from the area of greater diameter of the thick portion  18 . 
     The thick portion  18  is of a shape that mates with the upper race  12 , the convex external surface of the toroidal portion  12   a  bearing against the toroidal internal surface  18   a  of the thick portion  18 , and the substantially radial portion  12   b  projecting over the radial surface  18   b  of the thick portion  18 . 
     The lower cap  17  includes a first portion and a second portion wherein the first portion has a thickness that is greater than the second portion. The lower cap  17  includes a thick portion (e.g., a first portion)  22  of lesser diameter extended radially outward and from a lower edge of the thick portion  22 , via a thin radial portion (e.g., a second portion)  23  of lesser thickness. The thick portion  22  includes an external surface  22   a  with, in cross section, a concave profile oriented outward, the external surface  22   a  connecting the thick portion  22  to the thinner portion  23 . The thick portion  22  is of a thickness that reduces radially toward the outside. The lower cap  17  includes a lower radial surface  17   a  and a cylindrical internal surface  17   b  which are connected by a rounded bevel  17   c.    
     The thick portion  22  is of a shape that mates with the lower race  13 , the concave profile internal surface of the toroidal portion  13   a  bearing against the external surface  22   a  of the thick portion, the radial portion  13   b  slightly overlapping the thick portion  22  of the lower cap  17 . 
     The lower cap  17  includes an annular rib  24  extending axially toward the upper cap  16  from the thick portion  22 . The diameter of the annular rib  24  is greater than the diameter of the internal cylindrical surface  17   b , while being less than the diameter of the lesser diameter area of the external surface  22   a . The lower cap  17  includes a radial surface  22   b  situated between the cylindrical surface  17   b  and the annular rib  24 , and a radial surface  22   c  situated between the annular rib  24  and the top edge of the external surface  22   a . The radial portion  13   b  of the lower race  13  overlaps the radial surface  22   c  coming radially close to the annular rib  24 . 
     The internal skirt  20  of the upper cap  16  extends axially close to the radial surface  22   b  thereby forming a narrow radial passage. The external skirt  20  surrounds the annular rib  24  thereby forming a narrow axial passage. Thus, the skirt  20  interacts with the annular rib  24  to form a narrow passage means of sealing between the lower cap  17  and the upper cap  16 . 
     The internal skirt  20  has an internal diameter substantially equal to the internal diameter of the thick portion  22  of the lower cap  17 . 
     The cap  17  includes a radially elastic lip  25 , extending obliquely outward from the surface of an annular flange  25   a  formed at the end of greater diameter of the portion of lesser thickness  23 , and coming into contact with or close to the internal surface of the external skirt  21  of the upper cap  16 . The lip  25  extends radially outward and axially on the opposite side to the upper cap  16 . The lip  25  makes it possible to produce a narrow passage or, where appropriate, a friction contact means of sealing between the upper cap  16  and lower cap  17 . 
     The external skirt  21  includes at its opposite axial end to the upper cap  16  an annular flange  26  extending radially inward. The annular flange  26  allows axial motion in one direction of the lip  25  of the lower cap  17  that deforms radially inward and prevents the lip  25  from moving axially in the opposite direction. Thus, the lower cap  17  may be secured axially to the upper cap  16 . The flange  26  includes a truncated cone shaped surface  26   a  facing away from the upper cap  16  facilitating the deformation of the lip  25  when the lower cap  17  is inserted in the upper cap  16 . The flange  26  includes a truncated cone shaped surface  26   b  facing toward the cap  16  against which surface the lip  25  bears if the lower cap  17  tends to move axially away from the upper cap  16 , preventing the lower cap  17  and upper cap  16  from moving axially apart. 
     The lip  25  has a dual function of sealing and of axial retention. The lip  25 , in a single piece with the lower cap  17 , may be easily obtained at the same time as the lower cap  17 . The lip  25  enables easy assembly and axial retention with axial play where necessary. 
     The suspension thrust bearing  8  includes a seal  27  including a heel  28  placed and attached in an annular slot  29  of the lower cap  17  and a lip  30  extending radially outward and axially toward the upper cap  16  and coming into friction contact with the radial portion  12   b  of the upper race. The heel  28  of the seal  27  is situated axially facing the rolling elements  14  surrounding the free edge of the toroidal portion  13   a  of the lower race  13 . 
     The use of an upper cap  16  and a lower cap  17  allows the formation of an interior space, delimited axially by the upper cap  16  and the lower cap  17  and radially by the inner skirt  20  and outer skirt  21 , in which space the races  12 ,  13  as well as the rolling elements  14  are placed. It is easy to seal off the interior space. 
     The caps  16 ,  17  forming an interface respectively between the upper cup  7  and the upper race  12 , and between the lower race  13  and the lower cup  11 , transmit and distribute the axial and radial loads between the upper cup  7  and lower cup  11 . Returning to  FIG. 1 , the upper cap  16  bears axially by its thick portion  18  and thin portion  19  against the annular portion  7   a  of the upper cup  7  and is in contact by its thick portion  18  with the cylindrical portion  7   b . The thick portion  18  transmits radial and axial loads to the upper cup  7 . The thin portion  19  transmits mainly axial loads to the upper cup  7 . Similarly, the lower cap  17  bears axially by its thick portion  22  and thin portion  23  against the annular portion  11   b  of the lower cup and bears radially, by its thick portion  22 , against the axial portion  11   c.    
     Where appropriate, the upper cap  16  may be placed in direct contact with the rubber block  9  without using the intermediate upper cup  7 . 
     The lip  25  interacting with the annular flange  26  forms a means of axial retention between the upper cap  16  and the lower cap  17  so as to obtain a suspension thrust bearing  8  that is easy to assemble and cannot be dismantled, so that it can be handled by an operator without risk of accidental dismantling. 
     To improve the sealing of the suspension thrust bearing  8 , and as shown in  FIG. 3 , a second seal  31  may be installed, this seal having a heel  32  arranged radially in the lesser diameter area of the thin portion  19 , attached in an annular slot  33  formed between the interior skirt  20  and an annular flange  19   a  of the portion of lesser thickness  19  of the upper cap  16 , and having a lip  34  extending obliquely, axially toward the lower cap  17  and radially outward and coming into friction contact with the radial portion  13   b  of the lower race  13 . Thus, the seals  31 ,  27  provide an effective seal, improving the sealing already provided by the sealing means of the upper cap  16  and lower cap  17 . 
     The presence of the thin portions  19 ,  23  extending radially and axially opposite the thick portions  22 ,  18  facilitates the attachment of the additional seals  31 ,  27 . 
     In the embodiment illustrated in  FIG. 3 , the radial surface  22   b  is formed at a level axially offset downward relative to the radial surface  22   c  such that the exterior skirt  21  is more extended axially, the annular rib  24  being less extended axially to allow the passage of the lip  34 , while retaining a narrow passage of dimensions similar to the embodiment illustrated before. 
     In the preceding embodiments, it is easy to obtain the upper cap  16  and lower cap  17  by molding. Advantageously, the seals  27 ,  31  may be overmolded directly onto the upper and lower caps  16 ,  17  or be fabricated by dual injection molding at the same time as said caps  16 ,  17 . 
     The external diameter of the lower race  13  is substantially equal to the internal diameter of the upper race  12 . This particular configuration means that the upper race  12  and lower race  13  may be obtained from one and the same blank, as illustrated in  FIGS. 4 to 6 . 
     In  FIG. 4 , an annular cup  35  made of thin sheet metal, formed for example by cutting and pressing, includes two future races  36 ,  37  connected together and separated symbolically in  FIG. 4  by lines  38 . The smaller diameter race  36  includes a toroidal portion  39 , whose exterior surface  39   a  has, in cross section, a concave profile substantially in a quarter circle, and a radial portion  40  extending inward from the area of lesser diameter of the toroidal portion  39 . 
     The race  37  extends from the opposite free edge of the race  36  to the radial portion  40 . The race  37  includes a toroidal portion  41  whose inner surface  41   a  has, in cross section, a concave profile substantially in a quarter circle and includes a radial portion  42  extending outward from the opposite free edge of the race  37  to the race  36 . 
     The concave profile surfaces  39   a ,  41   a  of the toroidal portions  39 ,  41  of the races  36 ,  37  are suitable for forming raceways for rolling elements of a suspension thrust rolling bearing, balls for example. 
     To obtain the lower and upper races, the races  36 ,  37  are separated, for example by means of a blanking punch to cut out the material of the cup  35  in a circle whose center passes through the axis of revolution of the cup  35  and which is delimited radially by the lines  38 . A race  36  is obtained of external diameter substantially equal to the internal diameter of the other race  37 . The surface with concave profile  39   a  has a recess radius R 1  indicated by a dotted circle  43 . 
       FIG. 6  illustrates the race  37  after an additional forming operation during which the radius of the recess of the race  37  is reduced to obtain a recess radius R 2  less than R 1 , indicated by a dotted circle  44 . In the same operation, the internal diameter of the race  37  may be slightly reduced so that the race  37  protrudes radially inward beyond the pitch radius of the rolling bearing formed using the race  37  to ensure that the free edge of the race  37  does not damage the rolling elements in the event of a high axial load. An identical operation may be performed on the race  36 . 
     Preferably, on the finished races, a recess radius R 2  of the race  37  should be identical to the recess radius of the race  36 , the two recess radii being slightly greater than the radius of the balls of the rolling bearing. Preferably, the ratio between the final internal diameter of the race  36  and the final external diameter of the race  37  is between 1 and 1.05. 
     Returning to  FIGS. 1 to 3 , and using the races  36  and  37  whose internal and external diameters have been modified to form the races  13  and  12 , the free end of the toroidal portion  12   a  of the upper race  12  and the free end of the toroidal portion  13   a  of the lower race  13  should not damage the rolling elements  14  in the event of the transmission of a major axial load by the suspension thrust bearing  8 . 
     The process of fabricating the suspension thrust bearing  8  allows the upper and lower races to be produced from one and the same blank which reduces the cost of fabricating the suspension thrust bearing. In addition, using a simple additional operation, the recess radius of the lower race and/or of the upper race is reduced and the correct behavior of the elements is ensured during the transmission of major axial loads. 
     A suspension thrust bearing may be obtained including two caps defining an interior space that is sealed by means of sealing of the caps interacting as well as by separate seals. The particular structure of the caps produces a rolling bearing of reduced axial bulk, facilitating the installation of separate seals. The suspension thrust bearing is able to transmit both axial and radial loads, the lower and upper caps providing a good distribution and a better transmission of the loads from the lower cup to the upper cup and vice-versa. 
     Further modifications and alternative embodiments of various aspects of the invention may be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the general manner of carrying out the invention. It is to be understood that the forms of the invention shown and described herein are to be taken as the presently preferred embodiments. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed, and certain features of the invention may be utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description to the invention. Changes may be made in the elements described herein without departing from the spirit and scope of the invention as described in the following claims. In addition, it is to be understood that features described herein independently may, in certain embodiments, be combined.