Patent Publication Number: US-2016245340-A1

Title: Centrifugal disk as a pre-seal for a wheel bearing

Description:
BACKGROUND 
     The invention relates to a seal arrangement of a wheel bearing, which is inserted between a first bearing part and a second bearing part of the wheel bearing. Here the seal arrangement comprises a pre-seal embodied as a centrifugal disk, together with a seal set comprising sealing lips and a reinforcement. The reinforcement of the seal set is connected to the first, torsionally fixed bearing part and at least partially enclosed by an elastic sealing material, which forms a radially defined socket. The pre-seal fixed to the second bearing part is embodied as a centrifugal disk and forms a catch groove, and engages with a degree of play in the socket formed by the sealing material. A radial edge of the centrifugal disk running here maintains a seal gap in relation to the seal set. 
     Seal arrangements with rubbing seal contacts of sealing lips and non-rubbing sealing lips for sealing off antifriction bearings are known from a variety of applications in wheel bearings for vehicles. 
     JP 2003-56577 A discloses a seal for a wheel bearing in which the outer ring, as first bearing part, is sealed off from the wheel flange, as second bearing part. The wheel bearing seal encloses a centrifugal plate, which rests both axially and radially on the wheel hub and the wheel flange. In the fitted state axial sealing lips are supported by rubbing seal contacts against the centrifugal plate. The sealing lips are assigned to a carrier, which is fixed to a radial inner side of the outer ring. DE 10 2009 052 311 A1 discloses a wheel bearing, the flange-side centrifugal disk of which forms axial faces for a rubbing seal contact of two axial sealing lips. On the wheel flange side, the fixing area of the centrifugal disk in a transitional area forms a radially extending portion. 
     SUMMARY 
     The object of the invention is to create an effective seal arrangement for wheel bearings which is easy to assemble and cost-effective to manufacture. 
     This object is achieved by a seal arrangement having the features of the invention. Advantageous developments of the invention are described below. 
     The construction of the seal arrangement according to the invention comprises a pre-seal constructed in one piece as a centrifugal disk, which is fixed in position on a radially oriented annual flange of the second, rotatable bearing part of the wheel bearing by a radial leg. Together with the seal set of the seal arrangement the pre-seal forms a seal labyrinth having a defined inlet gap, wherein a radial edge of the centrifugal disk runs while maintaining a seal gap in relation to the seal set. According to the design concept of the seal arrangement according to the invention, the sealing lips are not supported on the centrifugal disk and the pre-seal but directly on the rotating bearing part. Consequently, in contrast to known, existing solutions, a centrifugal disk of a non-corroding material can advantageously be dispensed with. The invention affords a further cost advantage, since this obviates the need for any sealing, for example by means of a sealing compound, for a seal gap occurring between the annular flange of the rotating bearing part and the leg of the centrifugal disk. Moreover, the invention advantageously allows the creation of a low-friction torque (LFT) seal arrangement. In addition, the invention affords scope for enlarging a transition radius between the radially oriented flange and the axially running portion of the rotating second bearing part, in order to improve the component rigidity of the second bearing part connected to the vehicle wheel. At the same time, it is thereby advantageously possible to achieve a compact, robust bearing construction. The invention makes it possible to increase both the service life and the sealing efficiency of a seal arrangement based on sealing lips and a centrifugal disk, without forfeiting any advantages of the known, conventional seal arrangements. 
     According to a preferred development of the invention a centrifugal disk having a U-shaped cross sectional profile is provided. Here the radial leg of the centrifugal disk runs parallel to the associated edge, which together laterally define the catch groove. Alternatively, according to the invention the centrifugal disk may have a Z-shaped cross sectional profile, wherein the radial leg is oriented in opposition to the edge of the centrifugal disk. In the fitted state of the centrifugal disk having the Z-shaped cross sectional profile, the catch groove is defined by the radial annular flange of the second bearing part and the edge of the centrifugal disk. 
     In order to form a seal labyrinth of the seal arrangement, the edge of the centrifugal disk, whilst maintaining a seal gap, engages in an axial socket of the seal set. Here the socket is defined radially by a projection and sealing lips formed from the elastic sealing material. 
     In order to ensure a durable positional fixing of the centrifugal disk on the annular flange of the rotatable, second bearing part, the radial leg of the centrifugal disk may be fixed to the annular flange by a cohesive material connection, especially by an adhesive bond. A further possibility that presents itself is to fix the leg to the annular flange by positive interlock in order to center and fix the centrifugal disk. For this purpose, for example, the centrifugal disk may be fitted into a step or recess of the radially oriented annular flange of the second, rotatable bearing part. In the case of an alternative, positively interlocking fixing, the annular flange of the second, rotatable bearing part locally comprises at least one projecting formed attachment, which engages in a corresponding formation of the leg of the centrifugal disk. In order to ensure a durable bond between the annular flange and the centrifugal disk, it is also possible, where necessary, to fix the centrifugal disk to the annular flange by a combined cohesive material and positively interlocking connection. 
     In order to ensure a durable bond of the seal set, its reinforcement non-positively and externally encloses an end portion of the first bearing part with an angled leg, forming a sleeve portion. This measure serves to fix the reinforcement in its fitted position and at the same time to fix the seal set in relation to the first bearing part, which may also be referred to as an outer bearing ring. 
     The seal arrangement according to the invention also makes provision for coating the reinforcement of the seal set with a sealing material on one side, in at least some areas. The angled leg of the reinforcement forming a sleeve portion is preferably fully enclosed by the elastic sealing material. In particular, an elastomer, which serves to form protruding, elastic sealing lips and/or projections, is provided as elastic sealing material. A first, largely axially oriented projection formed from the sealing material overlaps the catch groove on the opening side and is taken up to an annular gap on the annular flange of the first bearing part. The seal set includes multiple sealing lips or projections, positioned beneath the centrifugal disk and likewise formed from the sealing material, which are oriented for rubbing contact or non-contact with the second bearing part, advantageously with a radial offset in relation to the projection. A sealing lip running largely axially, to which a non-rubbing sealing lip is assigned on both sides, is preferably supported on the radial flange of the second bearing part. A radially oriented sealing lip is led up to a gap dimension on an axially running portion of the second bearing part. A further non-rubbing sealing lip is positioned between the centrifugal disk and the rubbing sealing lip. At the end this sealing lip has a fold pointing towards the centrifugal disk, thereby forming a collecting channel. 
     According to a preferred development the centrifugal disk and the reinforcement are produced from a metallic material. As an alternative to a rustproof material, a sheet steel may be used, for example, the surfaces of which are treated or coated. In addition, a centrifugal disk comprised of plastics may be used, or a sheet-metal ring or a cylindrical steel sleeve, on to which a plastic leg is molded, may be used as centrifugal disk. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features of the invention emerge from the following description and from the drawings, in which exemplary embodiments of the invention are represented. The embodiments represented show examples of how the seal arrangement according to the invention can be configured. They do not conclusively limit the invention, which is not confined to these exemplary embodiments. In the drawings: 
         FIG. 1  shows a first embodiment of a seal arrangement according to the invention in connection with a wheel bearing; 
         FIG. 2  shows a second embodiment of a seal arrangement according to the invention; 
         FIG. 3  shows a third embodiment of a seal arrangement according to the invention; 
         FIG. 4  shows a fourth embodiment of a seal arrangement according to the invention; and 
         FIG. 5  shows a fifth embodiment of a seal arrangement according to the invention; 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a detail of a wheel bearing  1  embodied as an antifriction bearing and illustrates the construction of a seal arrangement  2  on the wheel side. The wheel bearing  1  comprises a first bearing part  3 , an outer, fixedly positioned bearing ring, which in the fitted state is connected to a wheel carrier (not shown). Rolling elements  4  are guided on the outside on the bearing part  3  and on the inside on a second bearing part  5 , an inner bearing ring, which is integrally connected to a radially oriented annular flange  6 . The seal arrangement  2  comprises a seal set  7 , assigned to the first bearing part  3 , and as pre-seal a frictionless centrifugal disk  8 . The centrifugal disk  8  forming a seal labyrinth  9  together with the seal set  7  has a U-shaped cross sectional profile. A cohesive material connection, for example adhesive bonding, serves to fix the position of a circumferential leg  10  of the centrifugal disk  8  on the radially oriented annular flange  6 . An externally open catch groove  12  of the centrifugal disk  8  is axially defined by the leg  10  and an edge  11 . To form the seal labyrinth  9 , the edge  11  of the centrifugal disk  8 , while maintaining a seal gap  13 , engages in an axial socket  15  of the seal set  7 , which is defined radially by a projection  17  and a sealing lip  18 . The projection  17  and the sealing lip  18  are correspondingly formed from an elastic sealing material  16 , which covers a reinforcement  14  of the seal set  7  at least to a limited degree. To fix the reinforcement  14  and consequently the seal set  7 , an angled portion  21  of the reinforcement  14  locally encloses an external contour of the first bearing part  1 . The projection  17 , offset at the end, largely covers an opening of the catch groove  12  of the centrifugal disk  8  and is led up to an annular gap  19  at the leg  10  of the centrifugal disk  8 . In service, the centrifugal disk  8  serves to deflect both water and dirt particles radially, so as to keep these away from the seal gap  13  of the seal labyrinth  9 . The sealing lip  18  forms a collecting channel  20  downstream of the catch groove  12  of the centrifugal disk  8 , the channel being fixed, unlike the catch groove  12 , which rotates in operation. A liquid entering the collecting channel  20 , for example, passes unimpeded, under gravitational force, in a vertical direction to the lowest zone of the collecting channel  20 , and thence to the inside of the centrifugal disk  8 . Under centrifugal force the liquid is then delivered radially outwards by the rotating centrifugal disk  8  via the seal gap  13 . The sealing lip  18  forms the first lip of a seal arrangement of the seal set  7  comprising a total of three elastic sealing lips, which are correspondingly formed from the sealing material  16 . The middle, axially running sealing lip  22  is supported by the annular flange  6  through rubbing contact on an inner radius  24 . The other non-rubbing sealing lip  23  is oriented radially inwards. To sum up, the invention relates to a seal arrangement  2 , in which in service, the centrifugal disk  8  serves to deflect both water and dirt particles radially so as to keep these away from the seal gap  13  of the seal labyrinth  9 . 
       FIG. 2  to  FIG. 5  illustrate alternative embodiments of seal arrangements according to the invention, the same reference numerals being used for corresponding components. The following descriptions are substantially confined to configurations that deviate from the exemplary embodiment in  FIG. 1 . 
     According to  FIG. 2  the annular flange  6   a  adjoining the inner radius  24  forms a circumferential step  25 , on which the centrifugal disk  8  is supported. A defined fitting position of the centrifugal disk  8  can thereby be achieved. In order to avoid a sharp-edged transition, a rounded transition  31  to the annular flange  25  adjoins the step  25 .  FIG. 3  shows the annular flange  6   b , which encloses a recess  30 , into which the leg  10  of the centrifugal disk  8  is fitted with a positive interlock. The annular flange  6   c  according to  FIG. 4  forms an axially projecting formed attachment  26 , which engages by positive interlock in a corresponding formation  27  of the leg  10   a  of the centrifugal disk  8   a .  FIG. 5  shows the centrifugal disk  8   b , in which the edge  11   a  and the leg  10   b  are radially oriented in opposite directions. The seal set  7   a  further comprises a total of four sealing lips. Complementing the construction according to the exemplary embodiments in  FIG. 1  to  FIG. 4 ,  FIG. 5  shows two non-rubbing, largely axially oriented sealing lips  18   a ,  28 , which each form a collecting channel  20   a ,  29 . The catch groove  12   a  of the centrifugal disk  8   b  here is axially defined by the edge  11   a  and the annular flange  6 . 
     LIST OF REFERENCE NUMERALS 
     
         
           1  wheel bearing 
           2  seal arrangement 
           3  bearing part (first) 
           4  rolling element 
           5  bearing part (second) 
           6  annular flange 
           6   a  annular flange 
           6   b  annular flange 
           6   c  annular flange 
           7  seal set 
           7   a  seal set 
           8  centrifugal disk 
           8   a  centrifugal disk 
           8   b  centrifugal disk 
           9  seal labyrinth 
           10  leg 
           10   a  leg 
           10   b  leg 
           11  edge 
           11   a  edge 
           12  catch groove 
           12   a  catch groove 
           13  seal gap 
           14  reinforcement 
           15  socket 
           16  sealing material 
           17  projection 
           18  sealing lip 
           18   a  sealing lip 
           19  annular gap 
           20  collecting channel 
           20   a  collecting channel 
           21  portion 
           22  sealing lip 
           23  sealing lip 
           24  inner radius 
           25  step 
           26  formed attachment 
           27  formation 
           28  sealing lip 
           29  collecting channel 
           30  recess 
           31  transition