WO2021188328A1

WO2021188328A1 - Roller bearing with axially-fixed, rotatable rib flange

Info

Publication number: WO2021188328A1
Application number: PCT/US2021/021619
Authority: WO
Inventors: Xiaolan Ai; Ryan Evans; Don MEANOR; Brian Berg
Original assignee: The Timken Company
Priority date: 2020-03-20
Filing date: 2021-03-10
Publication date: 2021-09-23

Abstract

A bearing includes an inner ring having first and second raceways, an outer ring having a raceway, a first row of rolling elements positioned to roll on the first raceway of the inner ring and the raceway of the outer ring, and a second row of rolling elements positioned to roll on the second raceway of the inner ring and the raceway of the outer ring. A cage maintains relative spacing of the first row and the second row of rolling elements. A rib ring is positioned between the first and second raceways of the inner ring, the rib ring being rotatable relative to the inner ring and axially constrained relative to the inner ring.

Description

ROLLER BEARING WITH AXIALLY-FIXED, ROTATABLE RIB FLANGE

RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 62/992,251 filed March 20, 2020, the entire content of which is hereby incorporated by reference herein.

BACKGROUND

[0002] The present disclosure relates to bearings.

[0003] Spherical roller bearings are used in applications such as wind turbine gear boxes where shaft misalignment is unavoidable. Spherical bearings can cany a heavy radial load and an appreciable amount of thrust load. A typical configuration of a double-row spherical roller bearing is shown in Fig. 1, and is comprised of an inner ring 10, an outer ring 20, two sets of barrel-shaped rollers 30, and a single or double cage 40 that retains and separates each of the rollers 30 in the annular space between the inner and outer rings 10, 20 when assembled. To provide positive guidance to the rollers 30, a fully floating ring or rib flange 15 is often installed between the two rows of rollers 30. For spherical roller bearings with symmetric rollers, the floating ring 15 does not bear any appreciable amount of axial load from rollers 30. Thus, the rib flange 15 is allowed to float in the axial direction.

[0004] To improve axial loading capacity, asymmetric rollers are used in spherical roller bearings. These rollers have a tapered, barrel-shaped roller body with a large diameter end and a small diameter end. Rollers are arranged in two rows with their larger diameter ends facing each other. Under heavy thrust load, rollers in one of the two rows tend to move axially toward their large-diameter end, away from their intended design position. To ensure that rollers are properly seated against the rib flange, and thus reduce the amount of roller axial movement, which often results in an undesirable amount of raceway wear, a fixed rib flange has been used on the inner ring and positioned between the two raceways as an integral formation on the inner ring. The rib flange has two concaved conical guiding faces for receiving the axial inboard ends of the two rows of asymmetric rollers.

[0005] With this fixed, integrally-formed rib flange, sliding and spinning motions occur between roller ends and the guiding faces of rib flange. This leads to increased frictional torque and power loss of the bearing. Testing has clearly demonstrated this adverse effect. Furthermore, producing a fixed, integrally-formed rib flange between the two curved raceways on the inner ring imposes a great manufacturing challenge. It not only requires additional machining operations, but also greatly restricts manufacturing options that can be economically applied to curved raceways.

SUMMARY

[0006] In one aspect, a bearing includes an inner ring having first and second raceways, an outer ring having a raceway, a first row of rolling elements positioned to roll on the first raceway of the inner ring and the raceway of the outer ring, and a second row of rolling elements positioned to roll on the second raceway of the inner ring and the raceway of the outer ring. A cage maintains relative spacing of the first row and the second row of rolling elements. A rib ring is positioned between the first and second raceways of the inner ring, the rib ring being rotatable relative to the inner ring and axially constrained relative to the inner ring.

[0007] Other aspects of the disclosure will become apparent by consideration of the detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Fig. 1 is a section view of a prior art spherical roller bearing.

[0009] Fig. 2 is an exploded view of a spherical roller bearing embodying the disclosure.

[0010] Fig. 3 is a section view of the inner ring and assembled flange ring of the bearing of Fig. 2.

[0011] Fig. 4 is an enlarged section view similar to Fig. 3 illustrating the flange ring retaining pins inserted and exploded.

[0012] Fig. 5 is a partial section view illustrating an alternative flange ring arrangement.

[0013] Fig. 6 is a partial section view taken at an axial end of the flange ring illustrating an alternative flange ring and retention arrangement.

[0014] Fig. 7 is a partial section view illustrating another alternative flange ring arrangement. [0015] Fig. 8 is a partial section view illustrating yet another alternative flange ring arrangement.

DETAILED DESCRIPTION

[0016] Before any embodiments of the disclosure are explained in detail, it is to be understood that the disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The disclosure is capable of other embodiments and of being practiced or of being carried out in various ways.

[0017] This disclosure relates to roller bearings, in general, and to roller bearings with asymmetric rollers and floating rib flanges in particular. While the drawings and description are directed to a spherical roller bearing as one example, the disclosure also contemplates any multi-row bearing in which there is an opposing-load bearing central flange/rib/ring upon which rolling elements abut or contact during operation. This is true for asymmetric spherical bearings, and is also true for tapered double inner ring (TDI) bearings. One desire is to reduce, as much as possible, bearing frictional torque and power losses by eliminating the sliding motion of the rollers. Another desire is to reduce manufacturing costs.

[0018] Referring to Fig. 2, a spherical roller bearing 95 with asymmetrical rollers and a rotatable flange ring is shown, the bearing 95 includes an inner ring 100 with first and second inner conical concaved raceways 110, 120, an outer ring 200 having a spherical outer raceway 210, a first set of tapered, barrel-shaped rolling elements or rollers 300 arranged in a first row, a second set of tapered, barrel-shaped rol ling elements or rollers 350 arranged in a second row, a first cage 400 for retaining and spacing the first set of rollers 300 in the first row, and a second cage 450 for retaining and spacing the second set of rollers 350 in the second row. In other embodi ments, the cage can be one piece that retains both sets of rol lers 300, 350. Also in other embodiments, the outer ring may be formed from two parts, each defining a portion of the outer raceway, which need not be spherical.

[0019] Referring to Figs. 2-4, the inner ring sub-assembly includes the inner ring 100 and a rib ring or rib flange 130. The inner ring 100 has a land 125 (see Fig. 2) between the first and second raceways 110, 120. A set of apertures or through holes 170 are machined radially through the land 125 at circumferential intervals. In other embodiments, the holes 170 need not be through holes, but instead could be blind holes formed into the land 125. The number and spacing of the holes 170 can vary. In one embodiment, there can be two or more holes that are substantially evenly spaced around the circumference of the inner ring 100 to facilitate adequate load balancing around the inner ring 100. The rib ring 130 is a separate part from the inner ring 100 and from the cages 400, 450, and has an outer cylindrical surface 133, an inner cylindrical surface 134, and first and second guiding faces 140, 150, which are the axially oppositely-facing outer surfaces of the rib flange 130. The inner cylindrical surface 134 of the rib ring 130 contains an annular groove 135 that extends circumferentially about the entire inner surface 134. The rib ring 130 is sized and configured to be positioned over the land 125 of the inner ring 100.

[0020] A set of retaining pins 160 is provided and inserted into some or all of the holes 170 on the inner ring 100. The pins 160 are sized and configured to fit tightly within the holes 170 and to extend radially outwardly beyond the radially outer-most surface of land 125 lor extending into the groove 135 of the rib ring 130 (see Figs. 2 and 3). The diameter and axial placement of the pins 160 are designed relati ve to the axial width of the groove 135 to provide enough clearance between the pins 160 and the groove 135 so that when assembled, the rib ring 130 is free to rotate about the bearing axis 98 with respect to the inner ring 100, but is constrained axially to be substantially immovable in the direction of the bearing axis 98. While the holes 170 and pins 160 are illustrated as being circular in cross section, other hole and pin cross sections can also be used. For example, star-shaped, oval, rectangular, or other cross-sectional shapes can be used. In addition, some holes 170, if through holes, may not receive pins 160, but instead may be left open to facilitate lubricant flow in the bearing 98.

[0021] It should be understood that the clearance (and tolerances) may allow for a negligible amount of axial movement of the rib ring 130, but such movement would be small enough so that axial movement of the rollers 300, 350 would still be suitably constrained by the rib ring 130. Slight clearance is needed to permit smooth rotation of the rib ring 130. As those of skill in the art of bearing design will understand, the amount of permissible axial movement of the rib ring 130 also depends upon the design and size of the bearing 98 and can vary from zero or nearly zero millimeters at the lower end, to two or three millimeters at the upper end. The term “axially constrained” or the like as used herein and in the appended claims means that there is structure designed to provide a definite limit or extent on axial movement, while still accounting for this small amount of permissible axial movement. [0022] When the bearing 95 is fully assembled and set into operation under an applied load, the rollers 300 in the first row are urged to move axially so that their roller-ends are firmly seated against or abutting the first guiding face 140 of the rib flange. Similarly, the rollers 350 in the second row are urged to abut the second guiding face 150 of the rib ring 130. Sliding and spinning motions occur at the contact locations between the large roller- ends 320, 370 (see Fig. 2) and the rib ring’s guiding faces 140, 150. The rib ring 130 can rotate with the rollers 300, 350, but is constrained axially to limit the axial movement of the rollers 300, 350 in the direction of the rib ring 130.

[0023] With a prior art rib flange that is fixed with the inner ring, the frictional torque reflected on the inner ring or the outer ring due to roller-end and rib face contact of a single roller is,

where R_° is the effective radius of the outer raceway; D is the effective diameter of the roller; h is the roller-end and rib contact height, measured from the rolling line of the inner raceway to the center of the contact ellipse; m_i is a fictional moment with respect to the centroid of the contact ellipse and Ff is the friction force at the contact. The total rib torque of the bearing is obtained by summation of the contributions of all rollers in the bearing.

[0024] By providing a rotatable rib flange or rib ring 130 to the spherical roller bearing 95, the current disclosure effectively reduces bearing torque. This is explained in detail below. During operation, the frictional moments exerted on the rib ring guiding faces 140,

150 from the roller ends 320, 370 drive the rib ring 130 rotationally as the rollers 300, 350 orbit around the inner ring 100. Theses frictional moments are balanced by a friction moment generated by the friction force Ff, which is now acting in the opposite direction. The frictional torque reflected on the inner ring 100 or the outer ring 200 generated by the roller- end and rib ring contact of a single roller is expressed as,

where Ri is the effective radius of the inner raceway 1 10, 120.

[0025] As one can appreciate from equation (1), the rib torque for a bearing with a fixed rib flange has two components. The first component is characterized by m_i, representing frictional torque due to spin motion, and the second component is characterized by hFf which represents frictional torque associated with sliding. For most cases, the first and second components are comparable. The benefit of the current disclosure for employing a rotatable rib flange or rib ring in a tapered, barrel-shaped spherical roller bearing can be seen clearly from the equation (2) in comparison with equation (1). In equation (2), the component associated with sliding motion is absent. in addition, the frictional torque associated with spinning motion is reduced by a factor of Ri/(R_i+h), which renders increasing the contact height h desirable. In practice, it is recommended that h > 0.2D . Bearings with a rotatable rib flange or rib ring according to the disclosure will have noticeable reduction in rib torque (T_flo) as compared to the rib torque (T_fix) for fixed rib bearings,

[0026] Additionally, for bearings with a fixed rib flange, the frictional force Ft at the roller-end and flange contact has the tendency to cause negative skew of the roller whi ch, by definition, drives the roller toward the rib flange with increased contact stress. In contrast, with the rotatable rib flange or rib ring 130, the frictional force F_f at the roller-end and flange contact has changed its direction, which tends to cause a positive roller skewing angle, driving the roller aw ay from the flange with reduced contact stress, and thus, reduced friction.

[0027] The current disclosure provides other tangible benefits. For example, the rib ring 130 allows the bearing 95 to be operated at higher operating speeds due to reduced friction at roller-end and rib ring 130 contacts, extending its applicability.

[0028] The current disclosure also provides manufacturing advantages. Since the rib flange 130 can be made as a separate piece, the undesirable interference between guiding faces and raceways during the machining of an integral rib flange is eliminated. The concaved conical raceways on the rib-less inner ring 100 can be machined by more effective manufacturing means, such as plug grinding or conjugant-grinding. These manufacturing processes not only save processing time, but also maintain high precision. The inner rings 100 can be machined from stock material wdth thinner sections, resulting in direct material savings. Similarly, the guiding faces 140, 150 of the rib flange 130 can be machined by simpler means without restrictions imposed by inner raceways 110, 120. It opens the opportunity for various profiles, engineering textures or coatings to be put on the rib flanges 130 to improve bearing performance. Different materials can be used for the rib flange 130 to achieve various desired operation or cost objectives. 3D printing technology may also be used as an alternative means to produce the rib flange 130 with the inclusion of the retaining features, such as the groove 135 mentioned above, and optional lubrication holes or channels for enhanced lubrication between the rib flange 130 and the inner ring 100.

[0029] To further reduce bearing frictional torque, the guiding faces 140, 150 may be profiled specifically to produce a circular contact footprint at the contact between the roller- ends 320, 370 and the rib faces 140, 150. For comparable contact stress, this footprint would produce a smaller frictional moment m_i, and thus results in lower bearing torque according to equation (2).

[0030] Another performance enhancement is to further reduce bearing frictional torque by adding a low friction coating on the guiding faces 140, 150 of the rib flange 130. This reduces rtn, and thus bearing torque. Some examples of coatings include conventional solid lubricant coatings (e.g., dichalcoginides like WS2 and MoS2, graphite, Polytetrafluoroethylene (PTFE), and soft metal coatings (such as lead, silver, and gold)), hard wear-resistant coatings such as diamond like carbon (DLC) and composites or nanocomposites thereof (such as tungsten-incorporated DLC, titanium-incorporated DLC, and silicon-incorporated DLC, for example), polymer-based coatings, ceramic based coatings, and composites (including multi-layer architectures) of these general classes of coatings.

[0031] Yet another performance enhancement is to produce an engineered surface texture, such as pores and boss-like asperities, on the frictional interfaces between the rib flange 130 and the roller ends 320, 370, and between the rib flange 130 and the land 125 of the inner ring 100.

[0032] One of the cost-saving enhancements is to use different materials for the rib flange 130. Since the stress at the contact between roller-end 320, 370 and flange guiding face 140, 150 is relatively low, and sliding motion is reduced or eliminated by the rotatable rib flange 130, low friction and low-cost materials can be used. These materials include powder-metals, and even plastics. Creating this dissimilar material pair between the rotating rib ring 130 and the inner ring 100 and rollers 300, 350 may also reduce friction and increase wear resistance. For example, the rotating rib ring 130 may be fabricated from a different type of steel than the rest of the bearing assembly, or it may be made from an aluminum or titanium containing metal alloy, for example. The rib ring 130 may also be made from a non-metal such as a carbon-carbon composite material, a polymer, or a ceramic or composites thereof.

[0033] Another cost-saving enhancement is to use a circular-section ring 130 made from wire to reduce manufacturing cost.

[0034] Yet another cost-saving enhancement is to use a rectangular-section ring to reduce manufacturing cost and at the same time to produce a circular contact footprint for reducing bearing rib torque.

[0035] Other means for axially retaining the rotatable rib ring are also possible, in one example shown in Fig. 5, a ridge 500 is formed on the land 505 of the inner ring 510 and extends radially outwardly from the land 505. The rib ring 530 is made of two axially separable pieces or components 535, 540. When assembled, the halves of the two-piece rib flange 530 forms a slot or groove for engaging the ridge 500 on the inner ring 510. Alternatively, the rib flange could be made from a split ring with a groove at the inner cylindrical surface. This arrangement would look similar to that shown in Fig. 5 except that the two halves of the split ring would not be separate pieces. The split rib ring could be snapped on to the inner ring.

[0036] Furthermore, as shown in Fig. 6, the rib ring or flange 630 could have two or more circumferential segments 635, 640 secured onto the inner ring 610. A wrapping band 645 is provided to secure these segments 635, 640 in place on the inner ring 610. The cross-section of the rib flange segments 635, 640 and the axial retention could be the same as illustrated with the rib ring 130 or the rib ring 530 (or see below regarding rib ring 830).

[0037] In another example shown in Fig. 7, an inwardly-extending ridge or projection 705 is formed on the bore of the rib ring 730. The projection 705 can be annular, or can include discrete projections spaced circumferentially. The projection(s) 705 can be integral with the rib ring 730, or can be separate pieces (e.g., one or more pins extending through the rib ring 730). The inner ring 710 is made from two axially separable pieces 715, 720. When assembled, the two-piece inner ring 710 forms an annular slot or groove at the centerline of the land 725 for engaging the inwardly-extending ridge 705 of the rib ring 730.

[0038] In another example shown in Fig. 8, an annular groove 805 is formed on the land segments 835, 840, as in Fig. 6, each having inwardly-extending ridges or projections 845 that engage the groove 805 on the inner ring 810. The projections 845 can be annular, or can include discrete projections spaced circumferentially. A wrapping band 850 can secure the segments 835, 840 on the inner ring 810.

[0039] Various aspects of the disclosure are set forth in the following claims.

Claims

CLAIMS What is claimed is:

1. A bearing comprising: an inner ring having first and second raceways; an outer ring having a raceway; a first row' of rolling elements positioned to roll on the first raceway of the inner ring and the racew'ay of the outer ring; a second row of roiling elements positioned to roll on the second raceway of the inner ring and the raceway of the outer ring; a cage maintaining relative spacing of the first row' and the second row_' of rolling elements; and a rib ring positioned between the first and second raceways of the inner ring, the rib ring being rotatable relative to the inner ring and axially constrained relative to the inner ring.

2. The bearing of claim 1, wherein the inner ring includes a land separating the first and second raceways, and wherein the rib ring is positioned on the land.

3. The bearing of claim 2, wherein the land includes a plurality of circumferentially spaced apertures formed therein, wherein the bearing further includes a plurality of pins positioned in the respective plurality of apertures and extending radially outwardly from an outer surface of the land, and wherein the rib ring includes an annular groove extending about an inner surface of the rib ring for receiving the pins, the engagement of the pins in the annular groove permitting rotation of the rib ring relative to the inner ring while axially constraining the rib ring relative to the inner ring.

4. The bearing of claim 3, wherein the apertures are through holes extending entirely through the inner ring.

5. The bearing of claim 2, wherein the land includes a ridge extending radially outwardly from an outer surface of the land, and wherein the rib ring defines first and second components that together define an annular groove receiving the ridge.

6. The bearing of claim 5, wherein the first and second components of the rib ring are separate pieces.

7. The bearing of claim 5, wherein the first and second components of the rib ring are portions of a split ring.

8. The bearing of claim 2, wherein the rib ring is formed from multiple circumferential segments secured together on the inner ring by a wrapping band.

9. The bearing of claim 2, wherein the inner ring includes an annular groove formed in the land, and wherein the rib ring includes a projection received in the annular groove.

10. The bearing of claim 9, wherein the rib ring is one piece.

11. The bearing of claim 9, wherein the inner ring includes two pieces and the annular groove is defined at an interface of the two pieces.

12. The bearing of claim 9, wherein the projection is an annular projection.

13. The bearing of claim, 9 wherein the projection includes a plurality of discrete projections.

14. The bearing of claim 9, wherein the rib ring is multiple pieces, each having a projection received in the annular groove.

15. The bearing of claim 14, wherein a wrapping band secures the multiple pieces of the rib ring together about the inner ring.

16. The bearing of claim 1 , wherein the cage includes two pieces.

17. The bearing of claim 1, wherein the bearing is a spherical roller bearing with the raceway of the outer ring being a spherical raceway, and wherein the first and second rows of rolling elements include tapered, barrel-shaped rollers.

18. The bearing of claim 17, wherein the tapered, barrel-shaped rollers are asymmetrical.

19. The bearing of claim 1, wherein the rolling elements in the first row abut a first guiding face of the rib ring and the rolling elements in the second row abut a second guiding face of the rib ring.

20. The bearing of claim 19, wherein the first and second guiding faces are profiled to produce a circular contact footprint at a contact location between the respective ends of the rollers and the rib guiding faces.

21. The bearing of claim 19, wherein the first and second guiding faces include a low friction coating.

22. The bearing of claim 1 , wherein the rib ring is made from a different material than the inner ring.

23. A bearing comprising: an inner ring having first and second raceways; an outer ring having a raceway; a first row' of rolling elements positioned to roll on the first raceway of the inner ring and the raceway of the outer ring; a second row of rolling elements positioned to roll on the second raceway of the inner ring and the raceway of the outer ring; a cage maintaining relative spacing of the first row and the second row' of rolling elements; and a rib ring positioned between the first and second raceways of the inner ring, the rib ring being rotatable relative to the inner ring and axially constrained relative to the inner ring; wherein the inner ring includes a land separating the first and second raceways, and wherein the rib ring is positioned on the land; and wherein the rolling elements in the first row abut a first guiding face of the rib ring and the rolling elements in the second row abut a second guiding face of the rib ring.