ROLLING BEARING

Abstract

A rolling bearing having an inner ring, an outer ring and a plurality of rolling elements being arranged between the inner ring and the outer ring is provided. The inner ring and the outer ring each include a raceway for the plurality of rolling elements. Each raceway encompasses the plurality of rolling elements symmetrically. The rolling bearing further includes an asymmetric cage being arranged between the inner ring and the outer ring for holding the rolling elements. The rolling bearing is lubricated by a lubricant being arranged on each axial side of the plurality of rolling elements. The raceways are offset in the same axial direction from the axial center of the inner ring and the outer ring such that the shear rate acting on the lubricant is equal on each axial side of the rolling bearing.

Claims

1. A rolling bearing comprising: an inner ring, an outer ring, and a plurality of rolling elements being arranged between the inner ring and the outer ring, wherein the inner ring and the outer ring each comprise a raceway for the plurality of rolling elements, wherein each raceway encompasses the plurality of rolling elements symmetrically, wherein the rolling bearing further comprises an asymmetric cage being arranged between the inner ring and the outer ring for holding the rolling elements, wherein the rolling bearing is lubricated by a lubricant being arranged on each axial side of the plurality of rolling elements, and wherein the raceways are offset in the same axial direction from the axial center of the inner ring and the outer ring such that the shear rate acting on the lubricant is equal on each axial side of the rolling bearing.

2. The rolling bearing according to claim 1, wherein the cage is a snap-type cage and comprises a backbone side and a pronged side.

3. The rolling bearing according to claim 1, further comprising sealing elements that are arranged at both axial ends of the rolling bearing.

4. The rolling bearing according to claim 1, wherein the volume defined between the inner ring, the outer ring, the backbone side of the cage and one sealing element is equal to the volume defined between the inner ring, the outer ring, the rolling elements and the other sealing element.

5. The rolling bearing according to claim 1, wherein the distance between the backbone side of the cage and one sealing element is equal to the distance between the rolling elements and the other sealing element.

6. The rolling bearing according to claim 1, wherein the raceways are offset in the same axial direction from the axial center of the inner ring and the outer ring such that the shear rate acting on the lubricant at each point of the space defined between the inner ring, the outer ring, the backbone side of the cage and one sealing element is equal to the shear rate acting on the lubricant at each point of the space defined between the inner ring, the outer ring, the rolling elements and the other sealing element.

7. The rolling bearing according to claim 1, wherein the cage comprises a polymer material.

8. The rolling bearing according to claim 1, wherein the rolling bearing is a ball bearing and the rolling elements are balls.

9. The rolling bearing according to claim 8, wherein the ball bearing is a deep groove ball bearing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Further preferred embodiments are defined in the dependent claims as well as in the description and the figures. Thereby, elements described or shown in combination with other elements may be present alone or in combination with other elements without departing from the scope of protection.

[0041] At least one of the embodiments of the present invention is accurately represented by this application's drawings which are relied on to illustrate such embodiment(s) to scale and the drawings are relied on to illustrate the relative size, proportions, and positioning of the individual components of the present invention accurately relative to each other and relative to the overall embodiment(s). Those of ordinary skill in the art will appreciate from this disclosure that the present invention is not limited to the scaled drawings and that the illustrated proportions, scale, and relative positioning can be varied without departing from the scope of the present invention as set forth in the broadest descriptions set forth in any portion of the originally filed specification and/or drawings. In the following, preferred embodiments of the invention are described in relation to the drawings, wherein the drawings are exemplarily only, and are not intended to limit the scope of protection. The scope of protection is defined by the accompanied claims, only.

[0042] The figures show:

[0043] FIG. 1: a cross sectional view of a rolling bearing according to the prior art;

[0044] FIG. 2: a cross sectional view of a cage for a rolling bearing; and

[0045] FIG. 3: a cross sectional view of a rolling bearing according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0046] Those of ordinary skill in the art will appreciate from this disclosure that when a range is provided such as (for example) an angle/distance/number/weight/volume/spacing being between one (1 of the appropriate unit) and ten (10 of the appropriate units) that specific support is provided by the specification to identify any number within the range as being disclosed for use with a preferred embodiment. For example, the recitation of a percentage of copper between one percent (1%) and twenty percent (20%) provides specific support for a preferred embodiment having two point three percent (2.3%) copper even if not separately listed herein and thus provides support for claiming a preferred embodiment having two point three percent (2.3%) copper. By way of an additional example, a recitation in the claims and/or in portions of an element moving along an arcuate path by at least twenty (20°) degrees, provides specific literal support for any angle greater than twenty (20°) degrees, such as twenty-three (23°) degrees, thirty (30°) degrees, thirty-three-point five (33.5) degrees, forty-five (45°) degrees, fifty-two (52°) degrees, or the like and thus provides support for claiming a preferred embodiment with the element moving along the arcuate path thirty-three-point five (33.5°) degrees. In the following same or similar functioning elements are indicated with the same reference numerals.

[0047] FIG. 1 shows a rolling bearing 1 of the prior art. In this exemplary illustration, the rolling bearing 1 is a ball bearing having balls. However, it should be noted that the bearing 1 may also be any other kind of rolling bearing, for example a roller bearing.

[0048] The ball bearing 1 comprises an inner ring 2, an outer ring 4 and a plurality of balls 6 being arranged between the inner ring 2 and the outer ring 4. The balls 6 are hold by an asymmetric cage 8.

[0049] The cage 8 may be a snap-type, in particular ball-guided, cage having a backbone side 18 and a pronged side 20 (see FIG. 2). The backbone side 18 of the cage 8 is arranged at the axially left side 24 of the bearing 1, wherein the pronged side 20 is directed towards the axially right side 26 of the bearing 1 and is arranged in between the balls 6. The pronged arrangement forms pockets 22 in which the balls 6 may be snapped in.

[0050] Each ring 2, 4 comprises a raceway 10, 12 which encompass the balls 6 in a symmetrical way. As can be seen, the raceways 10, 12 are arranged symmetrically in the axial direction with respect to an axial center X of the bearing 1. Seal elements 14, 16 are arranged on both axial sides 24, 26 of the bearing 1.

[0051] When the bearing 1 is filled with lubricant, in particular grease, the lubricant may be exposed to different strains, i.e., shear rates, on both axial sides 24, 26 of the bearing 1. As the bearing 1 is non-symmetric, due to the asymmetric cage 8 having a backbone side and a pronged side, the shear rates left and right will be different and therefore there are different grease viscosities left and right. Different shear rates occur, as on one side 26 of the bearing 1, the grease is sheared between the surfaces of the balls 6 and a sealing element 14 and, on the other side 24 of the bearing 1, the grease is sheared between the cage 8 and the sealing element 16. As explained above, the shear rate depends on the gap between the rotating plates (i.e., balls 6 and sealing element 14 or cage 8 and sealing element 16), and therefore the shear rate is higher on the side 24 of the backbone side of the cage 8.

[0052] Different shear rates and thus different grease viscosities will induce a transverse flow from left 24 to right 26. Such a transverse flow leads to an increased mechanical degradation of the grease due to the above-mentioned over-rolling of the grease by the balls 6.

[0053] On order to overcome these negative effects, in particular to reduce the transverse flow and to reduce the negative effect on the lubricant, the rolling bearing 1 as shown in FIG. 3 has raceways 10, 12 which are offset in the same axial direction from the axial center X of the inner ring 2 and the outer ring 4 such that the shear rates on both sides 24, 26 of the rolling bearing 1 are equal.

[0054] It should be noted that, although the illustrated bearing 1 is a ball bearing, the bearing 1 may also be any other kind of rolling bearing, for example a roller bearing, having any kind of rolling elements, for example rollers. For the sake of convenience, the ball bearing 1 will be described but the description and explanations may also apply to any other kind of rolling bearing.

[0055] The offset of the raceways 10, 12 is such that the shear rate acting on the lubricant is equal on each side 24, 26 of the rolling bearing 1. Equal shear rates on both axial sides 24, 26 of the bearing 1 lead to equal viscosities despite of the asymmetric cage 8 and thus to a reduced transverse flow of the lubricant. Hence, the degradation of the lubricant may be reduced compared to conventional rolling bearings.

[0056] The offset of the raceways 10, 12 and the equal shear rates may be achieved according to different considerations. Some of them will be described in the following.

[0057] According to one example, equal shear rates on both sides 24, 26 of the rolling bearing 1 may be achieved by making the volume being defined between the inner ring 2, the outer ring 4, the backbone side 18 of the cage 8 and one sealing element 16 equal to the volume defined between the inner ring 2, the outer ring 4, the balls 6 and the other sealing element 14. Equal volumes on each side 24, 26 of the bearing 1 leads to, at least substantially, equal shear rates on both axial sides 24, 26 of the rolling bearing 1.

[0058] Alternatively, equal shear rates on both axial sides 24, 26 of the bearing 1 may be achieved by making the distance h.sub.l between the backbone side 18 of the cage 8 and one sealing element 16 equal to the distance h.sub.r between the balls 8 and the other sealing element 16.

[0059] As explained above, the shear rate depends on the gap between the rotating plates between which the lubricant or grease is arranged. Thus, in a conventional bearing like the rolling bearing of FIG. 1, the shear rate is higher on the side of the backbone side 18 of the cage 8, where the distance h.sub.l from the cage 8 to the sealing element 14 is smaller than the distance h.sub.r from the balls 6 to the sealing element 16.

[0060] Thus, by making the distance h.sub.l between the backbone side 18 of the cage 8 and the sealing element 14 equal to the distance h.sub.r between the balls 8 and the sealing element 16, as shown in FIG. 3, the shear rates may also be made equal on both axial sides 24, 26 of the bearing 1.

[0061] Another, more complex approach is to calculate the shear rate {dot over (γ)}(P.sub.l) acting on the lubricant at each point P.sub.l of the space 24 defined between the inner ring 2, the outer ring 4, the backbone side 18 of the cage 8 and the sealing element 16 and the shear rate {dot over (γ)}(P.sub.r) acting on the lubricant at each point P.sub.r of the space 26 defined between the inner ring 2, the outer ring 4, the balls 6 and the sealing element 14. The position and offset of the raceways 10, 12 may then be determined such that the shear rate {dot over (γ)}(P.sub.l) at each point P.sub.l is equal to the shear rate {dot over (γ)}(P.sub.r) at each point P.sub.r. This means that the shear rate for one specific point P.sub.l on the left side 24 is equal to the shear rate for the corresponding point P.sub.r on the right side 26. Thus, in contrast to look at the shear rate on the left 24 and right 26 side as a whole, the shear rate may be considered in this case in a very detailed way.

[0062] It should be noted that, although the backbone side 18 is shown to be on the axially left side, the overall arrangement of the bearing 1 may also be inverted, i.e., the backbone side 18 may be on the axially right side 26.

[0063] In summary, independent of the specific design configurations as explained above based on illustrative examples, the raceways 10, 12 are offset to the axial center X of the bearing 1 so that the shear rates acting on the lubricant are made equal on both sides 24, 26 of the bearing 1. Equal shear rates reduce the transverse flow and thus the mechanical degradation of the lubricant, as explained above.