Abstract:
A rolling-element bearing assembly includes an inner race and an outer race and a plurality of rolling elements between inner and outer races, the rolling elements being mounted in pockets between axial bridges of a cage having first and second axial side rings. One or both of the side rings has at least one corrugated surface, and the corrugations project axially and/or radially.

Description:
CROSS-REFERENCE 
       [0001]    This application claims priority to German patent application no. 10 2016 211 906.0, filed on Jun. 30, 2016, the contents of which are fully incorporated herein by reference. 
       TECHNOLOGICAL FIELD 
       [0002]    The present invention relates to a rolling-element bearing assembly, in particular for a crankshaft bearing assembly, in particular for a connecting-rod- and/or main-shaft-bearing assembly of the crankshaft. 
       BACKGROUND 
       [0003]    Sliding bearings and/or rolling-element bearings are usually used in crankshaft bearing assemblies. The pin of the crankshaft is bounded here by two crankshaft cheeks such that the bearing assembly is not only bordered over its radial inner and radially outer race surface, but also axially by the crankshaft cheeks. With use of a roller bearing this limited installation space can lead, among other things, to problems with lubricant supply. Thus, for example, the installation space allows only limited possibilities to deliver the oil supplied for the required lubricating film in the rolling-element bearing from inside via the housing raceway outward into a motor housing receiving the crankshaft. In order to counteract this problem it has been proposed, for example, in DE 10 2010 055 090 A1, to provide lubricant channels that allow lubricant to pass through the rolling-element bearing. 
         [0004]    However, it is disadvantageous with this prior art that while lubricant can be guided to the bearing, a lubricant exchange is only possible to a limited extent since at least some lubricant remains static in the bearing. 
       SUMMARY 
       [0005]    An aspect of the present disclosure is therefore to provide a rolling-element bearing assembly that ensures the passage of lubricant even with limited installation spaces, which occur, for example, in a crankshaft bearing assembly. 
         [0006]    In the following a rolling-element assembly having a radially inner race surface and a radially outer race surface is disclosed, wherein the race surfaces are disposed spaced with respect to each other and include rolling elements between them that roll on the race surfaces. These rolling elements are in turn received in a cage, which includes at least two side rings that are spaced from each other via bridges. Here the bridges form pockets between themselves that receive the rolling elements spaced from one another and guide them. Furthermore, the radially inner surface is disposed on a first component and the radially outer surface on a second component. Here the race surfaces can be formed integral with the first or second component; however it is also possible to form the race surfaces on separate bearing rings that are received by the respective component. A mixed form is also possible wherein one component includes the race surface directly and the other component includes a bearing ring. In addition, the rolling-element bearing assembly is bordered axially by side walls of at least one of the components, which side walls extend radially beyond the race surfaces. A very limited installation space for the rolling-element bearing thereby arises, as is common, for example, with crankshaft bearing assemblies, in particular with a connecting-rod- and/or main-shaft-bearing assembly of the crankshaft. However, other application cases are of course also comprised by the disclosure. 
         [0007]    As one exemplary embodiment shows, the rolling-element bearing assembly is configured as a connecting-rod bearing assembly, wherein the first component is a crankpin of a crankshaft disposed between two crankshaft cheeks, and the second component is a connecting rod eye of a connecting rod, or a housing connection in the engine block. 
         [0008]    Furthermore the crankshaft cheeks of the crankshaft extend axially on both sides of the connecting rod radially outward beyond the outer race surface provided by the connecting rod eye or the housing. 
         [0009]    In order to improve the supply of lubricant in such a rolling-element bearing it is proposed to form at least one of the side rings of the cage at least partially corrugated or undulated. During operation of the rolling-element bearing assembly this corrugation or undulation ensures that lubricant is moved over the sequence of corrugation peaks and corrugation valleys in the rolling-element bearing, with the result that no static lubricant accumulation can occur in the rolling-element bearing. Due to the continually tapering spaces between the corrugations in operation, a hydrodynamic effect arises that leads to an uplift or even separation of the surfaces of the cage and the race surface on the outer raceway and a reduction of the friction and a movement of the lubricant in the rolling-element bearing. In turn the passage of the lubricant through the rolling-element bearing can be improved, and a lubricant accumulation in the bearing can be avoided. In addition a further friction reduction is possible due to pressure reduction. 
         [0010]    It is to be noted here in particular that the corrugations of the side surface are not separate lubricant grooves. Although the extension of lubricant grooves is sufficient for lubricant transport, their shape cannot however ensure the hydrodynamic effect provided by the corrugations. For this purpose a uniform corrugation is necessary whose shape can be described, for example, by a sine function. The difference between corrugation and groove consists in particular in the abrupt transition, typical for a groove, from an essentially smooth surface to a depression. However, this abrupt transition does not lead to a periodic tapering of the spaces, which is necessary for the desired hydrodynamic effect. 
         [0011]    According to a further advantageous exemplary embodiment the corrugation of the side ring is configured such that corrugation peaks rising from corrugation valleys rise essentially radially outward. A corrugation shape thereby arises on the outer diameter that serves in particular for lubricant guiding and makes possible a lubricant film on the contact surface between cage and component or cage and rolling elements. 
         [0012]    Here it is preferred in particular when the corrugation peaks are disposed in the region of the pockets, and the corrugation valleys are disposed in the region of the bridges of the cage. The lubricant can thereby be guided into the region out from which it can be delivered to the rolling elements. Here it has been shown in particular that the supplying of lubricant to the rolling elements functions particularly well when the radially outermost point of the corrugation peaks is disposed essentially in the region of the rolling-element center. Alternatively, however, the corrugation peak can also be disposed in the region of the bridges and the corrugation valleys can also be disposed in the region of the pockets. 
         [0013]    Alternatively or in addition to an axial corrugation a lateral corrugation shape can also be realized, wherein a corrugation of the side ring is configured such that corrugation peaks rising from corrugation valleys rise essentially axially outward. This lateral corrugation shape also favors the active lubricant distribution in the rolling-element bearing, with the result that the formation of static lubricant accumulations is also prevented. Here in particular an embodiment has also proven advantageous wherein two smooth annular, mutually concentrically configured regions are formed on the side ring, which regions function as slip surfaces of the bearing cage on the side walls of the surrounding component. The corrugation on the side surface here is preferably disposed concentric between the two slip surfaces. As a result, on the one hand, support at axially outer sides can be ensured, while on the other hand lubricant accumulations are prevented from forming in axially outer regions that could prevent lubricant from passing through the bearing. 
         [0014]    According to a further advantageous exemplary embodiment the cage is configured split and includes at least one first and one second cage segment that abut on each other at separating surfaces. Via this split design the bearing cage can be simply disposed on the first component. 
         [0015]    Here it is preferred in particular when the separating surfaces are configured complementary to each other, wherein one separating surface is configured concave and the complementary separating surface convex. Assembly inaccuracies can thereby be avoided and the two surfaces can be centered with respect to each other, so that the cage segments are configured optimally with respect to each other. 
         [0016]    Furthermore it is advantageous when the cage segments are unequally split. This means that one cage segment is configured larger than the other cage segment. Thus, for example, a 9/11 division is possible wherein 11 bridges of one segment face 9 bridges of the other segment. The unequal division also serves for a more precise pairing and an assembly securing. 
         [0017]    According to a further advantageous exemplary embodiment the rolling-element cage is manufactured from an injection-moldable plastic. Here the injection-moldable plastic can preferably include a fiber-reinforcement. Lightweight and easy-to-manufacture cages can be provided for mass production by injection molding. In addition, the above-described corrugation shape of the bearing cage supports the flow properties during injection molding, with the result that the repeatability and controlling of tolerances in the manufacturing process is increased. Moreover, the manufacturing via an injection-molding method makes possible a greater design freedom of the entire rolling-element bearing cage, with the result that the rolling properties and lubricant-guiding properties of the cage can be optimized. 
         [0018]    According to a further advantageous exemplary embodiment, injection points for the injection-molding manufacturing of the cage are disposed in a region of the cage that is subject to low mechanical loads. Here the position of the injection points is preferably chosen such that first the bridge and then the side rings are formed by the injection-molding method. Furthermore it is advantageous when the injection points are chosen such that in the highly loaded center of the cage segment a connecting seam is formed with a fiber entanglement. 
         [0019]    According to a further advantageous exemplary embodiment at least one lubricant groove is formed axially outside on at least one of the side rings, which lubricant groove extends radially and/or tangentially-radially. Using this lubricant groove lubricant can be transported from a bearing interior to the bearing exterior and/or a bearing outer side in the bearing interior. However, in order to prevent a lubricant accumulation in the rolling-element bearing, as mentioned above, the corrugations are formed on the bearing cage, which corrugations ensure a movement of the lubricant introduced into the bearing assembly. 
         [0020]    According to one further advantageous exemplary embodiment, at least one bridge of the cage has a tapering in the axial direction that is preferably disposed approximately in the center of the bridge. The rolling element received in the associated cage pocket is thereby substantially contacted by the bridge at its rolling-element ends, with the result that a skewing of the rolling element is prevented, but a sufficiently stable contact of the rolling element in the pocket remains ensured. The optionally formed radially directed long, parallel contact surfaces on the bridge also serve for an improved guiding of the rolling element in the pocket, wherein the bridge surfaces outside the contact surfaces are preferably formed so as to osculate about the rolling element. It is thereby ensured that the rolling element can vary radially in the pocket but does not reach a clamping state. The osculating design also improves the lubricant flow between rolling element and cage. Here furthermore the osculating bridge surfaces can optionally be formed outside the contact surfaces as so-called retaining lobes, which facilitate the installation of the rolling element into the pocket by a deflecting. 
         [0021]    For an optimized axial contact surface of the rolling element in the pocket it can furthermore be provided that the pocket has a recess at at least one inner side wall of one of the side rings at the level of the rolling-element center. A contact of the pocket with the rolling element at the centerpoint of the rolling element can thereby be avoided. The contact is thus carried in a defined manner in an outer region of the rolling element, whereby manufacturing tolerances and straightness tolerances are increased in the forming of the bearing cage without restricting the mobility of the rolling element in the pocket. Here it is furthermore advantageous when an edge transition to the side ring is formed free of burrs and/or rounded in order to apply the lubricating film onto the rolling-element surface and not shear it off. It is also advantageous to provide a larger radius in the pocket corners by these being designed occurring slightly recessed. 
         [0022]    A further aspect of the present disclosure relates to a bearing cage for a rolling-element bearing in limited spaces, as described above. 
         [0023]    Further advantages and advantageous embodiments are specified in the description, the drawings, and the claims. Here in particular the combinations of features specified in the description and in the drawings are purely exemplary, so that the features can also be present individually or combined in other ways. 
         [0024]    In the following the disclosure is described in more detail with reference to the exemplary embodiments depicted in the drawings. Here the exemplary embodiments and the combinations shown in the exemplary embodiments are purely exemplary and are not intended to define the scope of the disclosure. This scope is defined solely by the pending claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]      FIG. 1  is a schematic sectional view through a rolling-element bearing assembly. 
           [0026]      FIG. 2  is a schematic perspective view of a bearing-cage half-shell of a bearing cage for a rolling-element bearing assembly depicted in  FIG. 1 . 
           [0027]      FIG. 3  is a schematic perspective view of an alternatively designed bearing-cage half-shell. 
           [0028]      FIG. 4  is a schematic sectional view through the bearing-cage half-shell depicted in  FIG. 2  or  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    In the following, identical or functionally equivalent elements are designated by the same reference numbers. 
         [0030]      FIG. 1  shows a perspective sectional view through a rolling-element bearing assembly  1 , which in the depicted case is configured as a crankshaft bearing assembly. As can be seen in  FIG. 1  a rolling-element bearing  6  is disposed in a connecting rod eye  4  of a connecting rod  2  or in a housing  4  for a crankshaft. The rolling-element bearing  6  ensures a rolling of the connecting rod  2  or of the housing  4  along a crankshaft  8 . Here, as can be seen in  FIG. 1 , in the rolling-element bearing assembly  6  an outer raceway  12 , on which a rolling element  10  rolls, is formed over the connecting rod eye or housing  4 , while an inner raceway  14  is depicted over a crankpin  16  of the crankshaft  8 . The crankpin  16  is in turn disposed between two crankshaft cheeks  18 ,  20 , which extend axially beyond the outer race surface  12  of the connecting rod eye  4 . 
         [0031]    The installation space provided for the rolling-element bearing  6  is highly confined by the crankshaft cheeks  18 ,  20 . In addition, the rolling elements  10  are received in a bearing cage  22 , which further limits the installation space. The limited installation space and the bearing cage  22  thus prevent a lubricant ingress and a passing of lubricant into/through the rolling-element bearing  6 , with the result that additional measures must be taken in order to on the one hand, guide the lubricant into the rolling-element bearing  6  and on the other hand to ensure that the lubricant in the rolling-element bearing  6  does not remain static. 
         [0032]    For this purpose a cage shape presented in  FIG. 2  is provided, wherein  FIG. 2  shows a perspective depiction of a cage half-shell  22 - 1 . Since usually in vehicles the crankshaft  8  is configured as a one-part component, the connecting rod  2  and the cage  22  must be configured multi-part, but at least two-part, for an assembly of the connecting rod/housing  2  and the connecting-rod- or main-bearing  1  and thus also for an assembly of the cage  22  on the crankpin  16  of the crankshaft  8 . The cage half-shell  22 - 1  depicted in  FIG. 2  is a half of such a split bearing cage  22  and comprises, exactly like its not-shown other bearing-cage half-shell, two side rings  24 ,  26 , which are spaced from each other by bridges  28 . As usual the bridges  28  form rolling-element receiving pockets  30 , wherein the rolling elements  10  are guided spaced from one another. 
         [0033]    In order to induce a lubricant movement in the rolling-element bearing  6  and to prevent static lubricant accumulations in an outer space  23  (see  FIG. 1 ) and the rolling-element receiving pocket  30  of the cage  22 , the side rings  24 ,  26  are configured corrugated or undulating as depicted in  FIG. 2 . Here on the one hand a corrugation  32  (or undulation) can be provided on a radially outer edge  33  of the bearing cage  22 , which corrugation  32  comprises corrugation peaks  34  and corrugation valleys  36 . Here the corrugation peaks  34  are preferably disposed in the region of the pockets  30 , and the corrugation valleys  36  are disposed in the region of the bridges  28 . A particularly good lubricant movement and lubricant guiding in the outer region  23 , in particular radially outward, can thereby be achieved. As can furthermore be seen from  FIG. 2 , here the radially outermost point of the corrugation peak  34  is disposed approximately in the center of the pocket  30  so that lubricant can be directly guided onto the rolling element. Due to the rhythmically (periodically) tapered spaces the corrugation  32  itself ensures that lubricant that is located in the rolling-element receiving pocket  30  or in the outer region  23  of the rolling-element bearing  6  is guided to the rolling elements  10 . Via a hydrodynamic effect the lubricant is thereby brought into a contact surface  50  (see  FIG. 1 ) between the corrugation peak  34  and the race surface  12 , and also brought out again, so that it also propagates toward rolling element  10 . It Lubricant can thereby be prevented from statically lingering in the rolling-element receiving pocket  30  or in the outer region  23  of the side rings  24 ,  26  where it can no longer be supplied to the lubrication circuit. 
         [0034]    Furthermore it is shown in  FIG. 2  that alternatively or, as here, additionally, corrugations or undulations can also be formed on the axial side surfaces  40  of the side rings  24 . Here in order to still form defined abutment surfaces for the bearing cage  22  on the crankshaft cheeks  18 ,  20 , the corrugation  42  is concentrically received between two smooth annular surfaces  44 ,  46  that serve as abutment surfaces of the bearing cage  22  on the surrounding side cheeks  18 ,  20  of the crankshaft  8 . This situation is in particular also to be seen in  FIG. 1 , wherein a section can be seen through a corrugation valley  48  of the corrugation  42 . As depicted in the sectional view, the concentric annular partial regions  44 ,  46  are formed as abutment surfaces of the bearing cage  22  on the crankshaft cheeks  18 ,  20 . 
         [0035]    At the same time it can clearly be seen in  FIG. 1  that lubricant that is located in the radially outer region  50  or the axial outer region  52  would remain as a static volume in the bearing cages  22  if the corrugations were not present. However, both in region  50  and in region  52  the corrugations  32 ,  42  ensure that the lubricant is periodically compressed between the corrugation  32  and the raceway  12 , or the corrugation  42  and the crankshaft cheeks  18 ,  20 , and thus is removed from its static accumulation. 
         [0036]      FIG. 2  further shows that radially, or as depicted in  FIG. 3 , radially-tangentially oriented lubricant grooves  54  can be provided that ensure a general inflow or outflow of lubricant to the rolling-element bearing  6 . Here in particular the radially-tangentially oriented groove  54  of  FIG. 3  can be oriented such that it is oriented corresponding to the direction of rotation in order to improve the inflow of lubricant into the bearing interior or the outflow from the bearing interior. Here it is again noted that the lubricant grooves specifically serve for an inflow and outflow of lubricant into/out of the rolling-element bearing  6 , but due to their design cannot ensure a dynamic mixing and movement of the lubricant. For this purpose the corrugations  32 ,  42  are provided on the radial outer edge  33  or the side surfaces of the cage  22 . 
         [0037]      FIG. 2  furthermore shows contact surfaces  56  of the bearing-cage half-shell  22 - 1 , with which the bearing-cage half-shell  22 - 1  abuts on the second bearing-cage half-shell (not depicted here). In order to provide a centric design and in order to be able to compensate manufacturing tolerances, in particular with a manufacturing of the cage from injection molding, it is provided to form the contact surfaces  56  of the cage segments connecting to each other complementary to each other, in particular concave-convex or convex-concave. The bearing-cage half-shells can thereby be easily centered and aligned with respect to each other. A slightly concave-concave formation on the bridge with slightly convex/elevated contact surfaces only via the side rings  24 ,  26  would also be possible. 
         [0038]      FIG. 4  shows a further detail in a sectional view through the bearing cage  22  in the circumferential direction. From this sectional view the bridge shape of the bridges  28  can be seen, which bridge shape is essentially parallel in a contact region  58  of the rolling element  10  and extends along radially. In contrast, in regions  60 ,  62  outside the contact surfaces  58  the bridge shape is adapted to the rolling elements  10  in a osculating manner in order to improve the lubricant guiding. Furthermore it can be seen in  FIG. 4  that the osculation  60  is configured as retaining lobes, with the result that the rolling elements  10  can be snapped-in into the bearing cage  22 . 
         [0039]    Advantageously the bearing cage  22  is formed as an injection-molded element, with the result that the corrugations  32 ,  42  can be formed easily. At the same time the corrugation shape of the bearing cage  22  supports the injection-molding method, since the corrugation shape influences the flow behavior of the injection-molding material. 
         [0040]    Overall, using the presented bearing cage a crankshaft bearing assembly, or, generally, a rolling-element bearing in a confined installation space is provided wherein an improved lubricant guiding is possible. Due to the corrugation shape formed on the rolling-element bearing cage a static lubricant accumulation is in particular counteracted in regions between the rolling-element cage and surrounding components. Here the corrugation shape ensures on the one hand a general movement of the lubricant and on the other hand a forming of lubricant films in contact surfaces between bearing cage and surrounding components. The lubrication is thus better implemented and even critical points can thus easily be lubricated. Furthermore, the corrugation shape makes possible a simple forming of the bearing cage as an injected-molded element, since the corrugation shape positively influences the flow behavior of the injection-molded material. Here it is preferred in particular to locate injection points in regions of the bearing cage that are subjected to low mechanical loads. In order to compensate for manufacturing tolerances, in particular with injection molding, with the design of the injection-molded cage as cage segments the connection surfaces between the cage segments can be formed complementary to each other, with the result that a simple centering and fitting of the cage halves results. Here it is advantageous in particular when this complementary design arises, for example, in the region of a convex-concave end side. Due to the optimized lubricating and the forming of the bearing cage from plastic the efficiency of the motor can furthermore be improved, with the result that a lower fuel requirement and less exhaust are produced. 
         [0041]    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 cages. 
         [0042]    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. 
         [0043]    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 
       [0044]      1  Rolling-element bearing assembly 
         [0045]      2  Connecting rod/housing 
         [0046]      4  Connecting rod eye/housing bore 
         [0047]      6  Rolling-element bearing 
         [0048]      8  Crankshaft 
         [0049]      10  Rolling element 
         [0050]      12  Outer race surface 
         [0051]      14  Inner race surface 
         [0052]      16  Crankpin 
         [0053]      18 ,  20  Crankshaft cheeks 
         [0054]      22  Bearing cage 
         [0055]      23  Outer region 
         [0056]      24 ,  26  Side rings 
         [0057]      28  Bridges 
         [0058]      30  Pockets 
         [0059]      32  Radial outer corrugation 
         [0060]      34  Corrugation peak 
         [0061]      36  Corrugation valley 
         [0062]      40  Side surface 
         [0063]      42  Lateral corrugation 
         [0064]      44 ,  46  Annular smooth contact surfaces 
         [0065]      48  Corrugation valley of the lateral corrugation 
         [0066]      50 ,  52  Lubricant receiving space 
         [0067]      54  Radial or radial-tangential lubricant grooves 
         [0068]      56  Contact surfaces between cage half-shells 
         [0069]      58  Contact surfaces between rolling element and bridge 
         [0070]      60 ,  62  Bridge surfaces