ROLLING BEARING

Abstract

A rolling bearing (1) includes an outer ring (2), an inner ring (4), and a plurality of rolling elements (6) arranged between the outer and inner ring (2, 4). The rolling bearing (1) is provided with lubricant. The outer ring (2) has an outer contact width (b.sub.o) between the outer ring (2) and the rolling elements (6). The inner ring (4) has an inner contact width (b.sub.i) between the inner ring (4) and the rolling elements (6). A ratio =b.sub.i/b.sub.o between the inner and outer contact width (b.sub.i, b.sub.o) is larger than 1.65 or a ratio =b.sub.i/b.sub.o between the inner and outer contact width (b.sub.i, b.sub.o) is larger than 0.97 and smaller than 1.06 or a ratio =b.sub.i/b.sub.o between the inner and outer contact width (b.sub.i, b.sub.o) is smaller than 0.68.

Claims

1. A rolling bearing comprising: an outer ring; an inner ring; lubricant; and a plurality of rolling elements arranged between the outer and inner rings; wherein the outer ring has an outer contact width between the outer ring and the rolling elements, and the inner ring has an inner contact width between the inner ring and the rolling elements, a ratio between the inner and outer contact widths being larger than 1.65, or larger than 0.97 and smaller than 1.06, or smaller than 0.68.

2. The rolling bearing according to claim 1, wherein a viscosity value of the lubricant is larger than 10 mm.sup.2/s at 40 C., preferably larger than 15 mm.sup.2/s at 40 C.

3. The rolling element according to claim 1, wherein the ratio between the inner and outer contact width is smaller than 1.8.

4. The rolling bearing according to claim 1, wherein the lubricant is an oil-based lubricant.

5. The rolling bearing according to claim 4, wherein the oil-based lubricant includes mineral oil, ester oil, diester oil, olefin oil and/or a combination thereof.

6. The rolling bearing according to claim 1, wherein the lubricant includes an additive.

7. The rolling bearing according to claim 6, wherein the additive includes lithium soap, a barium salt, urea and/or a combination thereof.

8. The rolling bearing according to claim 1, wherein the rolling bearing is a ball bearing.

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

10. The rolling element according to claim 2, wherein the ratio between the inner and outer contact width is smaller than 1.8.

11. The rolling bearing according to claim 10, wherein the lubricant is an oil-based lubricant.

12. The rolling bearing according to claim 11, wherein the oil-based lubricant includes mineral oil, ester oil, diester oil, olefin oil and/or a combination thereof.

13. The rolling bearing according to claim 12, wherein the oil-based lubricant includes an additive.

14. The rolling bearing according to claim 13, wherein the additive includes lithium soap, a barium salt, urea and/or a combination thereof.

15. The rolling bearing according to claim 14, wherein the rolling bearing is a ball bearing.

16. The rolling bearing according to claim 15, wherein the ball bearing is a deep groove ball bearing or an angular contact ball bearing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] 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.

The Figures Show:

[0015] FIG. 1: a schematic cross section of a rolling bearing according to an embodiment of the invention, and

[0016] FIG. 2: an overview at which ratios (p between an inner contact width and an outer contact width hooting noise is expected to occur.

[0017] In the following same or similar functioning elements are indicated with the same reference numerals.

DETAILED DESCRIPTION

[0018] FIG. 1 shows a cross section of a rolling bearing 1. The rolling bearing 1 is a ball bearing, such as deep groove ball bearing or an angular contact ball bearing. The rolling bearing 1 has an outer ring 2, an inner ring 4, and a plurality of rolling elements 6, in this case balls, arranged between the outer and inner ring 2, 4. The inner ring 4 and the outer ring 2 are rotatable relative to each other. For example, the inner ring 4 may be the rotating ring, while the outer ring 2 is fixed or the outer ring 2 may be the rotating ring, while the inner ring 4 is fixed.

[0019] To reduce wear and facilitate a rotation of the rolling bearing 1, the rolling bearing 1 is provided with a lubricant. Preferably, a viscosity value of the lubricant may be larger than 10 mm.sup.2/s at 40 C. The lubricant may be an oil-based lubricant, wherein the oil may be a mineral oil, an ester oil, a diester oil, an olefin oil and/or a combination thereof. Furthermore, the lubricant may include an additive, particularly a thickening additive. For example, the additive may be lithium soap, a barium salt, urea and/or a combination thereof. Preferably, the lubricant has a working temperature range between 40 C. and 150 C.

[0020] One of the purposes of the lubricant is to reduce friction between surfaces in mutual contact, such as a contact between the rolling elements and a raceway provided on the inner and outer bearing ring 2, 4. As mentioned above, the contact width is related to the groove radius r of the respective bearing ring, the ball diameter D, and depends further on other bearing parameters, such as the pitch diameter, the clearance and/or the load. The ratio between the contact width of the inner ring b.sub.i and the contact width of the outer ring b.sub.o, namely =b.sub.i/b.sub.o, can be designed by means of choosing the groove radii of the inner ring r.sub.i and the outer ring r.sub.o, respectively, relative to the ball diameter D. For the rotational speeds when hooting noise occurs, the centrifugal load of the rolling elements is small compared to the static load. In that case the ratio hardly depends on the load and is thus in fact a bearing design parameter.

[0021] As can be seen from FIG. 2, there are ratios =b.sub.i/b.sub.o between the inner and outer contact width b.sub.i, b.sub.o at which no hooting noise occurs and ratios at which hooting noise does occur. The inventors have surprisingly found that hooting noise can be reduced or even eliminated independent of the conditions in which the rolling bearing 1 is used by setting the ratio =b.sub.i/b.sub.o between the inner and outer contact width b.sub.i/b.sub.o such that the ratio is larger than 1.65 or such that the ratio b.sub.i/b.sub.o is larger than 0.97 and smaller than 1.06 or such that the ratio b.sub.i/b.sub.o is smaller than 0.68. Preferably, the ratio b.sub.i/b.sub.o may be smaller than 1.8. This has the further advantage that the frictional torque of the bearing is reduced and/or a wear on the bearing rings and/or rolling elements may be reduced.

[0022] In summary, by adjusting the groove radii of the inner and outer ring of the bearing such that a certain ratio between the inner and outer contact width =b.sub.i/b.sub.o is fulfilled allows to reduce or even eliminate hooting noise in a simple and cost-efficient manner since no special attention has to be given to other contributing factors such as the lubricant and/or the machine design, and the like. Using a different lubricant as a solution may have a negative impact on other performance parameters, such as bearing life. These negative side effects can be prevented by using the invention instead.

REFERENCE NUMERALS

[0023] 1 rolling bearing [0024] 2 outer ring [0025] 4 inner ring [0026] 6 rolling element [0027] r.sub.o groove radius of the outer ring [0028] r.sub.i groove radius of the inner ring [0029] D ball diameter [0030] b.sub.o outer contact width [0031] b.sub.i inner contact width