Abstract:
A bearing assembly includes a hub element or a housing element, the hub element or the housing element having at least one opening, at least one intermediate element mounted in the at least one opening, the at least one intermediate element including at least one wave-shaped or lug-shaped projection in contact with the hub element or the housing element, and a first bearing element press-fit in the at least one intermediate element and a second bearing element mounted in the at least one opening, the second bearing element being movable relative to the first bearing element.

Description:
CROSS-REFERENCE 
       [0001]    This application claims priority to German patent application no. 10 2015 202 720.1 filed on Feb. 16, 2015, the contents of which are fully incorporated herein by reference. 
       TECHNOLOGICAL FIELD 
       [0002]    The present disclosure is directed to a bearing assembly including a hub element or housing element with at least one opening for a bearing and at least one bearing element secured in the at least one opening by a press fit. 
       BACKGROUND 
       [0003]    Known bearing assemblies may include a housing element or a hub element that has at least one opening for receiving first and second bearing rings such that the second bearing ring is movable relative to the first bearing ring. These may be used, for example, as wheel hub bearing assemblies in motor vehicles. In such assemblies, the bearing outer ring is usually press fit in the at least one opening on the hub element. The bearing rings must be strong enough to withstand the forces to which they are subjected and are therefore generally made mostly of steel, in particular of rolling-element bearing steel (e.g., 100Cr6). In order to reduce weight, a lighter material, such as aluminum, is often used to form the hub element or housing element. 
         [0004]    The light weight of aluminum wheel hubs makes them desirable for wheel-bearing arrangements. A disadvantage of aluminum wheel hubs, however, is that aluminum has a substantially greater coefficient of thermal expansion as compared to that of steel. This means that it is difficult to design the connection or interface between steel parts and aluminum parts for all relevant temperature ranges. The different degrees of expansion may prove particularly troublesome at the press-fit junction between the hub element and the bearing outer ring. At high temperatures the fit between these elements can loosen, since the aluminum hub will expand more than the steel bearing ring. This may allow the bearing outer ring to shift or rotate in the hub, and such movement can damage the hub and/or the bearing. 
         [0005]    On the other hand, at low temperatures the aluminum hub strongly constricts the outer ring and may cause high contact stresses. This may cause the hub to crack or may deform the bearing ring, in particular on the raceway. 
         [0006]    It was therefore proposed in DE 10 2012 211 261 (family member of U.S. Pat. No. 8,961,028) to provide a specific design for a bearing assembly with a hub element or housing element and a rolling-element bearing outer ring press-fit in a receiving bore. In order to ensure a proper fit of the bearing ring at all operating temperatures, even with the use of different materials for the hub element or housing element and the bearing ring, the designs of the receiving bore and of the outer circumference of the outer ring are configured in a particular manner. Specifically, they are configured such that the radial press-fit between receiving bore and the outer ring is smaller in the region of the raceway than in the region outside the raceway. This can be achieved, for example, by the varying the diameter of the receiving bore or of the outer ring over its axial length. 
         [0007]    However, a disadvantage of this conventional approach is that forming the axial extensions of the receiving bore or outer ring with varying diameters is very expensive, and in addition each element must be individually manufactured. Such bearing assemblies are thus very cost-intensive. 
       SUMMARY 
       [0008]    One aspect of the present disclosure is therefore to provide a bearing assembly, in particular for a wheel hub bearing, that is simple to manufacture and that allows for improved mounting of the bearing ring in a housing element or hub element even when the housing element/hub element and bearing ring are formed from materials with different properties. 
         [0009]    The present disclosure relates to a bearing assembly including a housing element or hub element that includes at least one opening for a bearing including a first bearing element and a second bearing element movable relative to a first bearing element. The first bearing element is press-fit in the opening. In order to ensure a proper fit of the bearing element in the housing element or hub element even when the housing element or hub element and the bearing element are made of different materials and over a range of operating temperatures, an intermediate element is disposed in the opening, and the first bearing element is received in the intermediate element with press-fit. The intermediate element allows a different press-fit between the intermediate element and the opening and between the bearing ring and the intermediate element. In this manner, the bearing elements can be mounted on or in the opening on the housing element or hub element under the optimal conditions for them. In order to further improve the connection between intermediate element and opening, the intermediate element may include at least one projection that can enter into operative connection with the opening. The projection is preferably wave-shaped and/or lug-shaped. The friction of the intermediate element in the opening can thereby be increased such that radial and axial movement of the intermediate element in the opening is made more difficult or prevented. 
         [0010]    According to a further exemplary embodiment it is preferred that the projection engage into a recess formed in the opening. Radial and axial movement of the intermediate element in the opening is thereby further made more difficult or prevented. 
         [0011]    According to one further advantageous exemplary embodiment, the housing element or hub element is formed from a first material, in particular aluminum, having a first coefficient of thermal expansion, and the intermediate element is made from a second material, in particular steel, having a second coefficient of thermal expansion different from that of the first coefficient of thermal expansion. A bearing assembly can thereby be provided in which light metal is preferably used for the hub element or housing element, while at the same time rolling-element bearing steel, which is preferred for its superior strength, can be used for the bearing rings. As a result a bearing assembly can be manufactured that is both lightweight and that satisfies the stipulated strength requirements. The intermediate elements between the bearing ring and the hub or housing element help ensure that the different materials of these elements do not directly affect one another. 
         [0012]    According to a further advantageous exemplary embodiment, the intermediate element and the bearing element received therein are formed from materials having similar or identical coefficients of thermal expansion or are formed from the same material. This helps ensure that the press-fit between the intermediate element and the bearing element remains essentially constant over a large range of operating temperatures, such as occurs in particular in wheel hub bearing assemblies. This in turn makes it possible that even at high temperatures the bearing element does not loosen from the intermediate element or that the intermediate element is not deformed at very low temperatures. 
         [0013]    The intermediate element itself can be press-fit in the housing element or hub element, or it can be directly cast into the material of the housing element or hub element. Of course it is also possible with a plurality of intermediate elements disposed on the bearing housing to attach the intermediate elements to the housing element or the hub element using different attachment methods. However, press fitting the intermediate element in the opening of the housing element or hub element is particularly advantageous. For example, the intermediate element can be received in the opening with a very tight press-fit, so that even at very high temperatures the intermediate element does not loosen significantly. Such a tight press-fit would not be possible for the bearing element itself, since it could deform the precisely prepared raceway or sliding surface of the bearing ring. 
         [0014]    The bearing assembly may be a component of a wheel hub bearing assembly and include a first opening and a second opening axially spaced from each other, and first and second rolling element bearings press-fit into the openings. The rolling-element bearings preferably each include an outer ring and an inner ring, and at least one of the outer rings is press-fit in the intermediate element, the intermediate element being disposed in at least one of the openings formed on the hub element. Using the intermediate element of the present disclosure, thermal influences on the hub element and on the outer ring can be decoupled from each other in a simple and cost-effective manner. 
         [0015]    Further advantages and advantageous embodiments are defined in the description, the drawings, and the claims. 
         [0016]    In the following aspects of the disclosure are described in more detail with reference to the exemplary embodiments depicted in the Figures. Here the exemplary embodiments illustrated are of a purely exemplary nature and are not intended to establish the scope of the application. This scope is defined solely by the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is a schematic, sectional, side elevational view of a first exemplary embodiment of a bearing assembly according to the disclosure. 
           [0018]      FIG. 2  is a schematic, sectional, side elevational view of a second exemplary embodiment of a bearing assembly according to the disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    In the following, identical or functionally equivalent elements are designated by the same reference numbers. 
         [0020]    In  FIG. 1  a wheel bearing  1  is depicted in radial cross-section as a preferred exemplary embodiment of the disclosure. Only the components relevant to the description of the exemplary embodiment are depicted and described. The wheel bearing  1  comprises a hub element  2  for attaching a rim to a wheel bearing  1 . First and second openings  4 ,  6  are formed in the hub element  2 , and these first and second openings  4 ,  6  are configured to receive first and second rolling-element bearings  8 ,  10 , respectively. The rolling-element bearings  8 ,  10  rotatably support the wheel bearing  1  on a wheel axis (not shown), and each includes an outer ring  12 ,  14 , rolling elements  16 ,  18 , cages,  20 ,  22 , and an inner ring  24 ,  26 . The inner rings  24 ,  26  have different bore diameters, and the smaller inner ring  24  is disposed behind the larger inner ring  26  with respect to the insertion direction of the wheel axis. 
         [0021]    The rolling-element bearings  8  and  10  are axially spaced from each other, and a connecting piece  28  is disposed between the rolling element bearings  8 ,  10  that is in contact with the inner rings  24 ,  26  of the rolling element bearings and that fixes the axial spacing of the rolling-element bearings  8 ,  10  with respect to each other. The connecting piece  28  is preferably sleeve-shaped so that the wheel axis can pass therethrough. The bore diameter of the connecting piece  28  is chosen such that at radially circulating contact points  30 ,  32  with the inner rings  24 ,  26  it has essentially the same respective bore diameter as the adjacent inner ring  24 ,  26 . It can optionally be respectively embodied smaller or larger. 
         [0022]    Furthermore,  FIG. 1  shows intermediate elements  34 ,  36  disposed between the outer rings  12 ,  14  and the openings  4 ,  6 . The outer rings  12 ,  14  are in turn press-fit in these intermediate elements  34 ,  36 . The intermediate elements  34 ,  36  serve to compensate for the influence of the different coefficients of thermal expansion of the hub element  2  and the outer rings  12 ,  14 , and the intermediate elements  24 ,  26  may comprise rings or be ring-shaped. 
         [0023]    This arrangement is particularly advantageous if the hub element  2  and the outer rings  12 ,  14  are comprised of different materials. Thus, for example, it is preferable to manufacture the hub element  2  from a light metal, such as aluminum, in order to reduce the total weight of the wheel hub. However, aluminum is itself not a suitable material for forming the outer bearing rings  12 ,  14 , because of the high strength required for bearing rings. The bearing rings  12 ,  14 ;  24 ,  16  are therefore usually manufactured from rolling-element bearing steel (e.g., 100Cr6). Disadvantageously, however, the coefficients of thermal expansion of aluminum and of the rolling-element bearing steel differ significantly; aluminum expands approximately twice as much as steel does per degree of temperature change. Since the wheel bearings may be operated over a temperature range of −40° to 180° C., this difference in coefficients of thermal expansion is not negligible. This in turn makes it very difficult to design the connection or interface between the steel parts and the aluminum parts for all relevant temperature ranges. Thus at high temperatures the fit of the bearing rings  12 ,  14  mounted directly in the openings  4 ,  6  can loosen, while at low temperatures the aluminum of the hub element can contract so much that very high contact stresses arise. However, in the present disclosure, this problem is addressed by providing the intermediate elements  34 ,  36  in the openings  4 ,  6  in order to compensate for these differences. The intermediate elements  34 ,  36  are preferably manufactured from steel. Alternatively the intermediate elements  34 ,  36  can also be manufactured from a material that has a coefficient of thermal expansion similar to that of the of the material from which the outer rings  12 ,  14  are manufactured. The force of the press-fit between the outer rings  12 ,  14  and the intermediate elements  34 ,  36  thereby remains substantially constant over the entire operating temperature range so that damage to the bearing due to overtensioning or loosening of the bearing is prevented. 
         [0024]    The intermediate elements  34 ,  36  in turn can be press-fit in the openings  4 ,  6  of the hub element  2 . The press-fit between the intermediate elements  34 ,  36  and the openings  4 ,  6  can also be very tight because temperature-related contractions of the hub element  2  will not substantially affect the bearing outer rings  12 ,  14 . As used herein “very tight” refers to a press-fit that is too tight for mounting a bearing outer ring directly in a hole in a hub or housing. 
         [0025]    As shown in the enlarged detail in  FIG. 1 , the intermediate elements  34 ,  36  can include a ribbing  40  on their edges  38  facing the hub element  2 , which ribbing  40  enters into operative connection with the opening  4 ,  6  and tightens the press-fit of the intermediate element  34 ,  36  in the opening  4 ,  6 . Here the ribbing  40  can grab into the material of the hub element such that the friction between the intermediate elements  34 ,  36  and the openings  4 ,  6  is increased. In this manner, even at high operating temperatures, the intermediate elements  34 ,  36  are disposed in the openings  4 ,  6  such that they are captive and do not rotate. 
         [0026]    As an alternative,  FIG. 2  shows the intermediate elements  34 ,  36  can also be cast into the hub element  2  during the manufacturing process. As the detail in  FIG. 2  illustrates, lug-shaped projections can be formed on the radially outer edge of the intermediate elements  34 ,  36 , which lug-shaped projections engage into complementarily designed indentations  44 ,  46  in the openings  4 ,  6 . Even with large temperature fluctuations the intermediate elements  34 ,  36  can be radially and axially secured in the openings  4 ,  6 . 
         [0027]    In addition, elements (not depicted) can also be disposed on the outer edge  48  of the hub element  2 , which elements prevent a thermal expansion of the hub element  2 . These elements can also be introduced into the hub element  2  with press-fit or by casting-in. 
         [0028]    Overall, using the disclosed intermediate elements  34 ,  36  a bearing assembly can be provided that is very simple to manufacture and that provides a uniform preload in the bearing. In addition, the bearing outer ring cannot loosen from its seat, which may significantly increase the service life of the bearing. 
         [0029]    Representative, non-limiting examples of the present invention were described above in detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Furthermore, each of the additional features and teachings disclosed above may be utilized separately or in conjunction with other features and teachings to provide improved bearing assemblies. 
         [0030]    Moreover, combinations of features and steps disclosed in the above detailed description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe representative examples of the invention. Furthermore, various features of the above-described representative examples, as well as the various independent and dependent claims below, may be combined in ways that are not specifically and explicitly enumerated in order to provide additional useful embodiments of the present teachings. 
         [0031]    All features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter, independent of the compositions of the features in the embodiments and/or the claims. In addition, all value ranges or indications of groups of entities are intended to disclose every possible intermediate value or intermediate entity for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter. 
       REFERENCE NUMBER LIST 
       [0032]      1  Wheel bearing 
         [0033]      2  Hub element 
         [0034]      4 ,  6  Opening 
         [0035]      8 ,  10  Rolling-element bearing 
         [0036]      12 ,  14  Outer ring 
         [0037]      16 ,  18  Rolling elements 
         [0038]      20 ,  22  Rolling-element bearing cage 
         [0039]      24 ,  26  Inner ring 
         [0040]      28  Connecting sleeve 
         [0041]      30 ,  32  Connecting points between connecting sleeve and inner rings 
         [0042]      34 ,  36  Intermediate element 
         [0043]      38  Outer edge of the intermediate element 
         [0044]      40  Ribbing 
         [0045]      42  Lug-shaped projections 
         [0046]      44 ,  46  Indentations in the openings 
         [0047]      48  Outer edge of the hub element