Patent Application
20150369290
This application claims priority to German patent application no. 10 2014 212 076.4 filed on Jun. 24, 2014, the contents of which are fully incorporated herein by reference.
The present disclosure relates to a bearing cage for a rolling-element bearing, in particular for a tapered roller bearing. The bearing cage includes at least one first ring element and one second ring element that are connected to each other via at least one bridge. The first and second ring elements are configured to receive at least one rolling element between them and to hold the at least one rolling element axially, and the at least one bridge is designed to hold the at least one rolling element circumferentially.
Rolling-element bearings, in particular tapered roller bearings, usually include a bearing outer ring and a bearing inner ring. Rolling elements are disposed between these rings to permit relative movement between the outer ring and the inner ring. The rolling-element bearing can be a full-complement bearing, that is, a bearing in which the rolling elements contact one another directly, or the bearing may include a bearing cage that axially and circumferentially secures and separates the rolling elements. Advantageously, bearing cages can simplify the assembly of a rolling-element bearing.
The rolling elements themselves can be, for example, spherical, cylindrical, toroidal, or conical. Rolling-element bearings that include conical rolling elements, so-called tapered roller bearings, also have a retaining flange and a guide flange attached to the inner ring or to the outer ring to help axially stabilize the rolling elements.
In order to reduce friction between the elements of a rolling-element bearing that are movable against one another, it is further known to provide a lubricant in the rolling-element bearing. Especially in tapered roller bearings such a lubricant helpfully reduces the friction produced by the rolling elements rubbing against the retaining flange or guide flange.
However a problem with such tapered roller bearings is that the lubricant is transported by the tapered rollers from their smaller diameter ends towards their larger diameter ends, and from there transported out of the bearing. The lubricant thereafter collects in static regions and is no longer available for lubricating the rolling elements.
It will be appreciated that, starting at a certain distance from the rolling elements, the force with which the lubricant adheres to the static parts of the bearing is greater than the shear force of the lubricant. Therefore, the lubricant can only be removed from the static regions by a particularly high operating temperature or by a physical shock. This can disadvantageously lead to too little lubricant or no lubricant at all being available on the rolling elements, in particular in the region of the retaining flange, leading to insufficient lubrication in these locations. This insufficient lubrication in turn leads to an undesirable temperature increase and thus also to excessive wear and a reduced service life of the rolling-element bearing elements.
The object of the present disclosure is therefore to provide a rolling-element bearing, in particular a tapered roller bearing, which provides an improved lubricant retention.
According to the disclosure, a bearing cage for a rolling-element bearing, in particular for a tapered roller bearing, is provided, which includes at least a first ring element and a second ring element connected to one another via at least one bridge. The first and the second ring elements are configured to receive at least one rolling element between them and to hold the at least one rolling element axially, while the at least one bridge is configured to hold the rolling element circumferentially and to space it from an adjacent rolling element. Bearing cages of this type are usually configured such that pairs of adjacent bridges form a receiving pocket for a rolling element, and the pocket has a circumferential width between the adjacent bridges and an axial length between the ring elements.
In order to improve lubricant retention in the rolling-element bearing, the disclosed bearing cage includes a flange on at least the first ring element, which flange extends at least partially radially outward over (when the rolling element bearing is oriented with the first ring element above the second ring element) or beyond a radially outer surface of the bridge. This radially-outward-extending flange also defines a volume for the lubricant in a further spacing from a rolling-element end side, in which volume the lubricant is retained and impeded from being pumped outwardly. In a rolling-element bearing provided with such a bearing cage, the lubricant can thereby be retained on the rolling elements, and the amount of lubricant that comes to rest in static regions is reduced. It is particularly advantageous if the flange extends only radially outward but not radially inward, so that its radially inner side extends up to a radially inner surface of the bridge because such a configuration does not impede access of the lubricant to the rolling elements.
Advantageously, the flange may extend radially outward from a location axially outside the outer ring of the rolling-element bearing. In this case, the outer ring can be made to be axially shorter than a conventional outer ring.
According to a further advantageous exemplary embodiment the flange and the ring element are integrally formed. This is particularly advantageous if the cage is injection-molded from a material, in particular plastic, since then the inventive flange and the cage can be formed in one work step.
According to a further advantageous exemplary embodiment the flange and the ring element are formed separately. In this case the flange in particular can be attachable or connected in the course of assembly by interference-fit or by friction-fit or by welding or by snap-fit, to the ring element. This is particularly advantageous if pre-existing cages are to be fitted with the flange disclosed herein.
According to a further advantageous exemplary embodiment the flange may project into the inner region of the cage to improve lubricant retention in this location as well. Particularly in the plugged-on design of the flange this radially-inward extension can be formed simply by the plug-on edge. However, an inwardly-extending flange is also possible, of course, in the integral design.
According to a further advantageous exemplary embodiment the bearing cage includes at least one recess or opening between the flange and the ring element. This recess allows lubricant located in the outer region of the bearing cage, in particular in the vicinity of the outer ring of the bearing, to be pumped back towards the rolling elements, and in particular towards the bearing inner ring. Particularly good lubrication of the critical regions can thereby be ensured, particularly in the region of the retaining flange and/or of the guide flange.
It is particularly advantageous if the recess is located in the region of the to-be-received rolling elements. In this way lubricant can be guided back directly onto the rolling elements and via the rolling elements directly onto the points to be lubricated.
According to a further advantageous exemplary embodiment the first ring element has a first radius and the second ring element has a second radius, the first radius being larger than the second radius. Since this disclosed bearing cage may advantageously be used in tapered roller bearings that usually have ring elements with first and second different radiuses, and the lubrication problem primarily occurs on the ring element having the larger diameter, it would be sufficient to only provide the disclosed flange on the larger ring element. Materials and thus costs can thereby be saved. Of course it is possible to form an inventive flange on the smaller ring element, so that an innovative lubricant management can also be provided in this region.
According to a further advantageous exemplary embodiment the bearing cage is assembled from bearing cage segments, each bearing cage segment including at least one bridge and a first and a second ring-element segment. A flange as described herein can be disposed on at least one of the ring element segments. The cage can also include a cage segment including an inventive flange and a cage segment without an inventive flange. Likewise bearing cages formed one-piece can also have a complete flange or a partial flange.
A further aspect of the present disclosure relates to rolling-element bearings, in particular tapered roller bearings including an outer ring and an inner ring, between which rolling elements are disposed, which are received in a bearing cage as disclosed and described herein.
Further advantages and advantageous embodiments are defined in the dependent claims, the description, and the drawings.
In the following the disclosure is described in more detail with reference to the exemplary embodiments depicted in the drawings. Here the exemplary embodiments are purely exemplary in nature and are not intended to establish the scope of the invention. This scope is defined solely by the appended claims.
In the following, identical or functionally equivalent elements are designated by the same reference numerals.
Due to the conical shape of the rolling elements 6, a pumping effect of the lubricant occurs in a direction from the smaller diameter towards the larger diameter. The lubricant is thus pumped from the bearing interior 14 outward into an outer region 16 of the bearing 1 from which it can no longer be guided back onto the rolling element 6 and thus no longer participates in the lubrication process. This can lead to a high degree of wear of the elements of the bearing 1 that move against each other, in particular in the sliding friction region of the guide flange 10, since only an insufficient lubrication can be provided by the remaining amount of lubricant. In addition, lubricant aging is significantly increased because only a small amount of lubricant is actually involved in the lubricating process, and the continual shearing and reuse of this smaller volume of lubricant causes the lubricant to break down and wear out faster. Both factors influence and limit the bearing service life.
As can further be seen in
The dashed lines in
The flange 18 can be formed integrally with the ring element 22; however, it is also possible, as depicted in
With continued reference to
Using the disclosed flange 18 lubricant is advantageously prevented from escaping unimpeded in large amounts, from the region of the cage 8 to the static regions. The flange helps retain lubricant that is pumped towards the larger diameter ring so that it can be further used for lubricating the rolling elements 6. This increases the amount of lubricant available for lubrication in the region of the rolling elements which reduces lubricant aging by increased lubricant exchange and helps ensure that sufficient lubricant is provided to the regions to be lubricated, in particular in the region between the flanges 10 and 12 and the rolling elements 6. As a result, wear of the rolling-element bearing 1 can be reduced and its service life can be increased.
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.
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.
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102014212076.4 | Jun 2014 | DE | national |
