A rolling-element bearing includes inner and outer rings, a cage with pockets disposed therebetween, and rolling elements respectively retained in the pockets. The cage has a guiding section extending along the axial length of the rolling elements. The distance between a radially-inner surface of the guiding section and the rotational axis of the bearing progressively decreases at least in sections along the axial direction of the rolling-element bearing from a point of the guiding section that is most distant from the rotational axis. A conveying section of the cage connects to that most-distant point and extends outside or away from the axial length of the rolling elements. The distance between a radially-inner surface of the conveying section and the rotational axis progressively decreases at least in sections in the axial direction away from the rolling elements. A lubricant collection channel is defined between the guiding section and the conveying section.

This application claims priority to German patent application no. 10 2013 203 828.3 filed on Mar. 6, 2013, the contents of which are incorporated herein by reference.

TECHNICAL FIELD

The invention relates to a rolling-element bearing comprising a bearing inner ring and a bearing outer ring, wherein rolling elements are disposed between the bearing rings, wherein the rolling elements are retained by a cage, wherein the cage has a guiding section that extends over the axial extension of the rolling elements and whose distance from an axis of rotation of the rolling-element bearing progressively changes at least in sections in the direction of the axis of rotation.

RELATED ART

Cages of the above-mentioned type are used for example in tapered roller bearings. The annular guiding section has receiving pockets for the rolling elements. Due to the arrangement and geometry of the tapered rollers, a radially, continuously-increasing extension of the guiding section progressively results along the axis of rotation. This has the consequence that, due to the centrifugal force during the operation of the bearing, a conveying of lubricant towards the largest cage diameter results. Accordingly, accumulation of lubricant, in particular lubricating grease, often occurs in the region of the largest cage diameter. This is true in particular in the case of sealed bearings. Without external influences, the lubricant remains there unused.

To date, this problem is addressed in that a sufficiently large quantity of lubricant is introduced into the bearing so that said space is filled with grease and the grease accumulated and unused there can be tolerated. Only due to special and fortuitous circumstances, such as vibrations or bearing stoppages, can possibly heated and liquefied lubricant grease again reach the region of the rolling contact and thus be usable.

SUMMARY

It is an object to design a rolling-element bearing in such a manner that the above-mentioned problem is reduced or eliminated. Accordingly, the lubricating properties by the lubricant should be improved, wherein the lubricant should be used more efficiently.

In particular, the temporal use of the lubricant should be able to be extended by more lubricant being able to come into use.

In a first aspect of the present teachings, a conveying section (retaining section) connects to the point of the guiding section of the cage that is most distant from the axis of rotation. The conveying section (retaining section) extends outside the axial extension of the rolling elements. The distance between the conveying section (radially inward or radially outward, or even both radially inward and radially outward) and the axis of rotation progressively decreases at least in sections in the direction of the axis of rotation away from the rolling elements, so that a collection channel is defined in the axial region between the guiding section and the conveying section. Pockets configured to receive the rolling elements are formed in the cage, and these pockets are bounded at the point of the guiding section that is most distant from the axis of rotation by a bounding surface facing towards the rolling elements, which bounding surface lies opposite an axial end side of the rolling element.

The bounding surface here lies opposite the end side of the rolling element, preferably while forming a gap. The gap preferably has a constant value over the radial extension; the gap thickness here preferably falls between 0.1 mm and 2.0 mm.

The conveying section is preferably formed cone-shaped. It can extend at an angle to the axis of rotation, which angle preferably falls between 10° and 30°.

The conveying section is preferably formed one-piece from the material of the cage.

The cage preferably has a substantially constant thickness. It is preferably comprised of a metal plate part, in particular of steel plate. However, it can also be provided that the cage is comprised of plastic.

The axial extension of the conveying section is preferably between 10% and 30% of the axial extension of the guiding section.

Tapered roller bearings are the preferred application of the proposed concept; but the inventive design can also be used, for example, in angular contact ball bearings.

In an advantageous manner, an improved lubrication of the rolling elements, in particular of the rolling elements, results with the use of the inventive concept.

In the proposed design the lubricant, in particular the lubricating grease, is available in increased quantity at the regions of the roller end side which are critical in terms of lubrication engineering, and also at the guide flange during rotation of the roller, which makes possible an improved lubrication.

Because the receiving pocket at the point of the guiding section that is most distant from the axis of rotation is bounded by a bounding surface facing towards the rolling element, which bounding surface lies opposite an axial end side of the rolling element—preferably forming a gap of constant size—it is achieved that grease that that contacts the radially inner side of the conveying section, as well as grease that contacts the radially outer side of the conveying section, is conveyed by the centrifugal force towards the end side of the rolling element and thus conveyed back into the region of the rolling elements.

Due to the formed collection- or accumulating-channel for lubricant, a faster lubricant film development can also be promoted at low speeds. This in turn allows the region of the mixed friction on the guide flange, and thus the heating of the bearing, to be reduced in an advantageous manner.

Said collection channel is formed on the inner side of the cage. However, the conical shape of the cage, and in particular of the cage conveying section (cage retaining section), forming in this respect on the outer side also has the advantageous result that, due to the cage rotation and the resulting centrifugal forces, even lubricant adhering on the outer side of the cage is conveyed back into the region of the rolling elements, and namely into the region of the roller end side, and the lubrication is thus improved.

Since the lubricant is now used more efficiently, a reduction in the amount of lubricant located in the bearing can also be envisaged. The advantage here—besides economic aspects—is a reduction of churning action, which in turn reduces the heating of the bearing. Thus the operating life of the lubricating grease can also be increased.

DETAILED DESCRIPTION OF THE INVENTION

InFIG. 1a rolling-element bearing1in the form of a double row tapered roller bearing is illustrated. Here the right-side bearing shows a design according to the prior art, while the left-side bearing is formed according to the invention. The bearing1has two bearing inner rings2and a bearing outer ring3present, between which are disposed tapered rollers4. The tapered rollers4are retained in a known manner by a cage5. The rolling-element bearing1has an axis of rotation a.

The right-side tapered roller bearing shows, as stated, the solution according to the prior art. It can be seen that the cage steadily increases in its diameter towards an end side of the tapered rollers4(i.e. towards the right). The lubricating grease for lubrication can flow away freely in the right axial end region of the cage5of the right-side tapered roller bearing and adversely accumulate in a “dead space.” During rotation of the bearing, the resulting centrifugal force has the adverse effect that the above-mentioned accumulation of grease in the “dead space” is promoted.

The present invention therefore provides a design as the left-side tapered roller bearing according toFIG. 1shows. The design of the cage5is decisive. Details of the cage5are clear in particular fromFIG. 2(in this Figure the cage5can be seen in radial section; the rolling element4is drawn with dash-dotted lines).

The cage has a known guiding section6as the central part, which guiding section6is provided with receiving pockets10for the tapered rollers4. The guiding section6has an axial extension c that is only slightly greater than the axial extension E of the rolling elements4. Furthermore it can be seen that, along the axis of rotation a, the guiding section6radially distances itself gradually from the axis of rotation a; the particular distance from the axis of rotation a is indicated by r. That is, there is a most-distant point7of the guiding section6from the axis of rotation a, which point7lies in the region of an end side of the tapered roller4.

It is now provided that a conveying section8connects to said most-distant point7of the guiding section6. This conveying section8extends outside the axial extension E of the rolling elements4. The distance r of this conveying section8from the axis of rotation a progressively decreases in the direction of the axis of rotation a away from the rolling elements4. Accordingly, a collection channel9for lubricant forms in the axial region between the guiding section6and the conveying section8.

As can further be seen, at the most distant point7of the guiding section8from the axis of rotation a, the receiving pocket10is bounded by a boundary surface11facing towards the rolling element4. This lies opposite the one axial end side12of the rolling element4. One can therefore say that the conical structure of the conveying section8reaches directly up to the end side12of the rolling element4. It can be recognized that a gap s is present between the boundary surface11and the end side12of the rolling element4.

In the exemplary embodiment, the conveying section8is formed—which however is not mandatory—as a cone-shaped structure. The cone section extends at a (cone) angle α to the axis of rotation a, which presently falls at approximately 20°. It should be noted that the conveying section8need not necessarily have a conical shape in the manner illustrated. It is also possible that the outer cone angle α1deviates from the inner cone angle α2.

As can be seen, the cage5—formed as a metal plate part or as a plastic part—has a constant thickness d.

For the axial extension b of the conveying section8, a value that falls at approximately 25% of the axial extension c of the guiding section6has been proven itself to be expedient.

The inventive design of the cage5thus employs an inwardly bent section (conveying section8) which begins at the largest diameter of the cage5. In this way, on the one hand grease conveyed to the radially-inner-lying surface of the cage is retained, and on the other hand grease which adheres to the cage5in the sealing region on the bend is conveyed back again towards the bearing raceway by the effect of the centrifugal force.

Due to this design of the conveying section8having the small gap s, which conveying section8reaches the end side12of the rolling element4, lubricant which adheres both radially inward and radially outward at the conveying section8is thus conveyed back to the region of the rolling element4.

The conical raceway of the bearing outer ring3extends axially—as can be seen inFIG. 1, left side—at least somewhat over the boundary surface11in the region of the conveying section8, so that flung-off grease is retained here and remains in the region of the rolling engagement of the bearing.

The position of the collection channel9can also be displaced somewhat farther to the right (inFIG. 2), so that the “bend,” i.e. the collection channel9, comes to lie in the region of the rolling element4. It only remains significant that the boundary surface11in the guiding section8reaches directly up to the end side12of the rolling element, in order to lead radially-outward- and radially-inward-adherent lubricant back to the rolling engagement by centrifugal force.

Usually—as in the exemplary embodiment according to FIG.2—it is provided that the collection channel9or the point7comes to lie precisely in the region of the end side12of the rolling element4. However it is also possible that the collection channel9or the point7comes to lie in the region of the axial extension of the rolling element4, i.e. further right inFIG. 2. The point7or the collection channel9then therefore lies in the region of the axial extension of the guiding section6.

REFERENCE NUMBER LIST

1Rolling-element bearing2Bearing inner ring3Bearing outer ring4Rolling elements5Cage6Guiding section7Point8Conveying section (retaining section)9Collection channel10Receiving pocket11Boundary surface12Axial end side of the rolling elementE Axial extension of the rolling elementa Axis of rotationb Axial extension of the conveying sectionc Axial extension of the guiding sectionr Distance from the axis of rotationd Thicknesss Gapα angleα1angleα2angle