spherical roller bearing

Abstract

A spherical roller bearing (1), in particular for supporting a wind turbine main shaft, is disclosed, comprising: at least one outer ring (4) and one inner ring (6), wherein the inner ring (6) has a diameter of at least 499 mm, two sets of barrel rollers (8) rolling on raceways formed on the outer and inner rings (4, 6), and at least one cage (2) configured to retain the barrel rollers (8), wherein the at least one cage (2) comprises: at least one axial inner cage ring (10) extending in a circumferential direction of the spherical roller bearing (1), a first axial outer cage ring (12-1) spaced apart from the at least one axial inner cage ring (10) on a first axial side and connected to it by several cage webs (14), thereby forming closed pockets (16), each pocket (16) being configured toto accommodate a single barrel roller (8) of the first set of barrel rollers, and a second axial outer cage ring (12-2) which is spaced apart from the at least one axial inner cage ring (10) on a second axial side opposite the first axial side and is connected to it by several cage webs (14) thereby forming closed pockets (16), each pocket (16) being configured to accommodate a single barrel roller (8) of the second set of barrel rollers (8), wherein at least one cage web (14) has a radial curvature (30) to curve the cage web (14) in the radial direction along the axial direction.

Description

Technical Field of the InventionThe present invention relates to a spherical roller bearing. Moreover, the present invention relates to a bearing arrangement comprising a spherical roller bearing.BACKGROUND OF THE INVENTIONRolling bearings are common mechanical components for many different applications. There are various types of rolling bearings designed to meet different requirements. Depending on the conditions of the specific application, i.e., the degree of load, the rotational speed, the temperature, etc., there are various types of suitable rolling bearings.One common type of bearing is a spherical roller bearing. The bearing is configured to receive large radial loads and axial loads, and is also configured to receive deflection of a shaft supported by the bearings, i.e., the bearing rings may be relatively misaligned. Therefore, such bearings are particularly suitable for more sophisticated industrial applications such as machines in wind turbines and the like.In most demanding industrial applications for spherical roller bearings, most bearing failures are usually associated with increased wear. One reason for the occurrence of increased wear may be a displacement of the barrel rollers in a cage retaining the barrel rollers during operation of the spherical roller bearing. For example, the cage webs may shift in a radial direction with respect to the barrel rollers due to cage play and gravity and / or cage deformations under load. This radial displacement may entail an increased risk of so-called edge running, wherein the barrel roller may scraper along an edge of the cage retaining the roller. Contact between an edge of the cage and a running surface of the barrel roller may reduce or even damage the lubricating film on the barrel roller, which may then lead to increased wear of the barrel roller and / or the cage and consequently to a shortened service life of the spherical roller bearing.It is therefore an object of the present invention to provide a spherical roller bearing having an extended life.Summary of the InventionThis object is achieved by a spherical roller bearing according to claim 1.A spherical roller bearing is provided below. The spherical roller bearing may be used for supporting a wind turbine main shaft.The spherical roller bearing includes at least an outer ring and an inner ring, two sets of barrel rollers rolling on raceways formed in the outer and inner rings, and at least one cage configured to retain the rollers. The inner ring has a bore with a diameter of at least 499 mm, preferably at least 699 mm and particularly preferably at least 899 mm. The bore may be configured to receive a component of another machine, for example a shaft of a wind turbine.In particular, the barrel roller may have a roller length equal to or even greater than 1.2 times the roller diameter.The inner ring may be formed with flanges or without flanges on an axially inner side and / or an axially outer side. If the inner ring is provided with flanges, flanges can be used as guide flanges for the rolling elements. Moreover, they can also serve as retaining flanges to prevent the rollers from falling out of the bearings.The at least one cage includes at least one axial inner cage ring extending in a circumferential direction of the bearing, a first axial outer cage ring spaced apart from the at least one axial inner cage ring on a first axial side and connected thereto by a plurality of cage webs, thereby forming closed pockets, each pocket configured to receive a single barrel roll of the first set of rolls, and a second axial outer cage ring spaced apart from the at least one axial inner cage ring on a second axial side opposite the first axial side and connected thereto by a plurality of cage webs, thereby forming closed pockets, each pocket configured to receive a single barrel roll of the second set of rolls.In order to extend the service life of the spherical roller bearing, at least one cage web has a radial curvature in order to curve the cage web in the radial direction along the axial direction. In particular, the radial curvature can be concave with respect to a pitch circle diameter.The term "pitch circle diameter" can describe the diameter along which the centers of the barrel rollers move during operation.Providing at least one cage web with the radial curvature can have the advantage that it can be avoided that the barrel roller scrapings along an edge of the at least one cage web if a contact point between the barrel roller and the cage web moves in the radial direction due to the spherical profiling of the roller. In particular, barrel rollers can have a spherical raceway, wherein the roller diameter is maximum in the roller center and decreases along the roller axis. The radial curvature of the cage webs can ensure that the contact point of the barrel rollers can always have the same distance from the edges of the cage webs.More specifically, in a case where the cage has straight cage bars, a contact point between the roller and the cage bar would change with respect to the axial position. This may be due to the fact that the barrel roller has an axial clearance in the cage pocket. For this reason, the contact point between the cage web and the roller need not always be at the maximum diameter of the barrel roller. In particular, an axial movement of the barrel roller can also shift the contact point between the cage web and the barrel roller. Due to the crowning of the raceway of the barrel roller, the contact point may tend to move non-linearly or in a straight line. In particular, the contact point may tend to approach the pitch circle diameter. Therefore, providing the at least one cage web with the radial curvature may allow the cage web to further adapt to a movement of contact between the roller and the cage web. This may also allow to ensure that the contact point lies on a surface of the cage and not on an edge, even if additional radial play is added and / or cage deformations occur.In particular, it may be that the movement of the contact point closer to the ends of the cage webs is sometimes not completely covered by a cage web which is formed in a straight line. Thus, providing the at least one cage web with the radial curvature may have the additional advantage of reducing the risk of the contact point moving closer to a radial edge.Preferably, more than one cage web with the radial curvature can be provided. In particular, all of the cage webs forming the pockets for receiving the first and / or second set of barrel rollers may have a radial curvature to curve the cage web in the radial direction along the axial direction.According to a further embodiment, a circumferential side surface of each cage web can be provided with a single contact region in the axial direction.For example, the circumferential side surface of each cage rib may be provided with an opening between the cage rib and the roller along the axial direction. This oscillation may determine a movement of the contact point between the cage web and the barrel roller during operation of the spherical roller bearing. The oscillation, which is the radius at the cage web divided by the crowning radius of the roller, can be between 100% and 104%. This can lead to a reduction in the contact stresses compared to a straight cage web.According to a further embodiment, a circumferential side surface of each cage web in the axial direction may be provided with at least two contact regions configured to contact the roller.Preferably, the at least two contact areas can be located next to the side surfaces of the roller. The presence of at least two contact areas can reduce the roller skew. In addition, at least two contact regions may have the advantage that a voltage on the at least one cage can be reduced. In particular, if a contact point between the roller and the cage web is as close as possible to the cage rings, a bending moment of the cage web can be reduced, which leads to a lower stress within the at least one cage.According to a further embodiment, a radius of the radial curvature is adapted to a crowning radius of the drum rollers. In particular, the radius of the radial curvature on an outer radial side surface of the cage web can be between 0.7 and 6 times the crowning radius of the drum rollers, preferably between 1.5 and 4 times the crowning radius of the drum rollers, and particularly preferably between 2 and 3 times the crowning radius of the drum rollers.In particular, an optimum ratio can depend on a position of the cage webs in the radial direction relative to a pitch circle diameter of the spherical roller bearing. The radius of the radial curvature can be smaller if the cage webs are positioned closer to the pitch circle diameter. The more the cage webs can deviate from the pitch circle diameter, the larger the radius of the radial curvature can be.According to a further embodiment, at least one pocket is defined by a cage web on a first circumferential side and a second cage web on a second circumferential side with respect to the first circumferential side, wherein each of the first cage web and the second cage web has a contact surface for contacting a barrel roller, wherein the contact surfaces of the first and the second cage web are at least partially inclined such that an opening angle is formed, wherein the opening angle is preferably between 55° and 67°.According to a further embodiment, the cage webs are arranged at a position in a radial direction which is at least partially offset with respect to a pitch circle diameter. This may allow the dynamic bearing capacity of the spherical roller bearing to be increased.For example, the cage bars may be disposed at a distance from the raceway of the inner or outer ring in the radial direction corresponding to 10 to 40% of a diameter of a barrel roller and 60 to 90% of the diameter of the barrel roller, respectively. In particular, the cage webs can be arranged at least partially on a radially inner side of the pitch circle diameter.Disposing the cage bars at a position in a radial direction offset from a pitch circle diameter may allow a distance between two adjacent rollers to be reduced, so that it may be possible to increase the number of rollers in a set of rollers. Moreover, arranging the cage bars at a position in a radial direction offset from a pitch circle diameter may allow for increasing a width of the cage bar even at very small nominal roller distances. In particular, increasing the number of rollers in the set of rollers may have the advantage that the dynamic load bearing capacity of the spherical roller bearing may be increased without the need to adapt the outer ring and / or the inner ring of the bearing.According to a further embodiment, the at least one cage can be made of sheet metal.The use of sheet metal as the base material for the at least one cage may have the advantage of reducing the costs for the at least one cage.Alternatively, the cage can also be made from a cast material or be made from a solid material.According to a further embodiment, the pockets can be formed by pressing and embossing and / or milling.For example, it may be advantageous to produce the at least one cage from a flat sheet metal and to form the geometry of the at least one cage by bending and subsequently pressing the pockets or otherwise milling the pockets. The most cost-effective solution can consist in pressing or punching the pockets and then producing the contact surface by stamping, in particular in the case of a number of more than four cages.According to a further embodiment, the axial inner cage ring consists of two separate ring elements.Two separate cages may allow one set of rollers to have a different rotational speed than the other row. This can reduce the forces acting on each cage as compared to a cage coupling the two sets of rollers. Alternatively, the first and second cages may be separated from each other, but may also be arranged so close together that it may be possible for the first and second cages to support each other and yet be able to perform a relative movement.Preferably, a gap can be formed between the first and the second ring element of the axial inner cage ring.A gap between the first and second ring members of the cage axial inner ring may allow lubricant flow to the inner ring of the spherical roller bearing to be improved.According to a further embodiment, the axial inner cage ring comprises a first ring element and a second ring element which are fastened to each other.This may have the advantage that the at least one cage may be formed by two identical cages which are fastened to one another. This may allow a simpler manufacturing process for the at least one cage.According to a further aspect there is provided a bearing arrangement for a wind turbine main shaft, the bearing arrangement comprising at least one spherical roller bearing as described above.All features described above with respect to the spherical roller bearing apply-separately or in combination-to the spherical roller bearing used in the bearing arrangement.Further preferred embodiments are defined in the dependent claims as well as in the description and in the figures. Here, 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.Brief Description of the DrawingsPreferred embodiments of the invention will be described below with reference to the drawings, wherein the drawings are merely exemplary and are not intended to limit the scope of protection. The scope of protection is defined solely by the appended claims.The figures show: FIG. 1 : shows a schematic cross section of a spherical roller bearing according to one embodiment, FIG. 2 : shows a schematic perspective view of part of a cage of the spherical roller bearing according to the embodiment, FIG. 3 shows a schematic circumferential cross section of the cage, and FIG. 4 : shows a schematic cross section of a barrel roller at a maximum diameter of the barrel roller in a cage of the spherical roller bearing of FIG. 1.DETAILED DESCRIPTION OF THE INVENTIONIn the following, the same or similar functional elements are denoted by the same reference numerals.FIGS. 1, 2, 3 to 4 show a spherical roller bearing 1 for supporting a wind turbine main shaft and a part of a cage 2 of the spherical roller bearing 1.The spherical roller bearing 1 comprises an outer ring 4 and an inner ring 6, two sets of barrel rollers 8 rolling on raceways 9 formed on the outer ring 4 and on raceways 11 formed on the inner ring 6. The outer ring 4 comprises an opening 5 through which lubricant can be supplied to the spherical roller bearing 1. In particular, the outer ring can be stationary, while the inner ring can rotate about an axis of rotation A. Moreover, the inner ring 6 may be configured to be mounted on a main shaft of a wind turbine.In particular, the barrel roller 8 has a roller length 26 equal to or even greater than 1.2 times a maximum roller diameter Dw (FIG. 4 ).The inner ring 6 can be formed with flanges or without flanges on an axial inner side and / or an axial outer side. The spherical roller bearing shown in FIG. 1 is formed without flanges on both the axial inner side and the axial outer side of the inner ring 6.Furthermore, the spherical roller bearing comprises a cage 2 which is configured to retain both sets of barrel rollers 8. The cage 2 of the spherical roller bearing shown in FIG. 1 comprises a first cage element 2- 1 configured to retain the first set of barrel rollers 8 and a second cage element 2- 2 having an identical shape and being connected to each other to form the cage 2. FIG. 2 shows the first cage element 2- 1 in detail.Each cage element 2- 1, 2- 2 comprises an axial inner cage ring 10 which extends in a circumferential direction of the bearing, an axial outer cage ring 12 which is spaced axially from the axial inner cage ring 10 and is connected thereto by a plurality of cage webs 14, as a result of which closed pockets 16 are formed. Each pocket 16 is configured to receive a single barrel roll 8.The cage elements 2- 1, 2- 2 may be formed separately from each other, so that a gap may be formed between the cage elements 2- 1, 2- 2.As an alternative, the cage 2 may be integrally formed such that the cage 2 includes only a single axial inner cage ring 10 instead of two axial inner cage rings 10 secured together.The cage axial inner ring 10 has a flange member 18 radially outward and the cage axial outer ring 12 has a flange member 20 extending radially inward.Moreover, the cage bars 14 are disposed at a position offset from the radially inner side of a pitch circle diameter of the spherical roller bearing 1. The position preferably corresponds to 10 to 40% of the roller diameter Dw (FIG. 4 ) or 60 to 90% of the roller diameter Dw.Arranging the cage bars 14 offset from the pitch circle diameter may allow a minimum distance Dm between the raceways of two adjacent rollers 8 to be reduced, such that it may be possible to increase the number of rollers 8 used in a set of rollers 8. The minimum distance Dm is determined in a state where the barrel rollers 8 are equally spaced in the circumferential direction.In particular, a ratio Dm / Dw of the minimum distance in the circumferential direction between the raceways of two adjacent barrel rollers 8 of the first and / or of the second set of barrel rollers to the maximum roller diameter Dw is equal to or less than 0.11, preferably 0.09 and particularly preferably 0.075, if the barrel rollers 8 of the respective set of barrel rollers 8 are uniformly spaced apart in the circumferential direction.Alternatively or additionally, the minimum distance Dm in the circumferential direction between the raceways of two adjacent barrel rollers of the first and / or the second set of barrel rollers may be equal to or less than a value obtained by the equation: if the barrel rollers 8 of the respective set of rollers 8 are equally spaced in the circumferential direction, wherein P is the pitch circle diameter and Dw is the maximum roller diameter, wherein the millimeter values of P and Dw are to be used as dimensionless variables.As can be seen from FIG. 3, each cage web 14 has a concave radial curvature 30 in order to curve the cage web in the radial direction. In particular, the barrel rollers 8 can come into contact with the cage webs along a line 38 which is indicated by a dashed line in FIG. 3. The radial curvature 30 of the cage webs 14 is preferably selected such that the ideal contact line 38 has the same distance from the edges of the cage webs 14.The radius of the radial curvature 30 is adapted to a crowning radius of the barrel rollers 8. In particular, the radius of the radial curvature can be between 0.7 and 6 times the crowning radius of the drum rollers, preferably between 1.5 and 4 times the crowning radius of the drum rollers, and particularly preferably between 2 and 3 times the crowning radius of the drum rollers.Contact surfaces 24, which are formed on circumferential side surfaces 22 of the cage webs 14 and are configured for contacting the barrel roller 8 accommodated in a single pocket 16, are at least partially inclined such that an opening angle α is formed, as shown in FIG. 4. The opening angle α between the contact surfaces 24 is preferably between 55° and 67°.If the cage 2 is produced from a metal sheet in which the pockets 16 are formed by pressing and the contact surfaces 24 are formed by stamping, the stamping height 32 can depend on a thickness 34 of the cage web 14. In order to reduce the risk of edge running, contact between the barrel roller 8 and the contacting surface 24 may occur at a distance from the radially outer side surface 36 of the cage web 14 that corresponds to 20 to 45% of the cage web thickness 34, preferably 30 to 40% of the cage web thickness 34, in a position in which the roller 8 is pressed into the pockets 16. Line 38 in Figure 3 shows the ideal line of contact between the roller 8 and the contacting surface 24 at the position where the roller 8 is forced into the pocket 16 and the roller is moved axially within the cage pocket 16 within its cage pocket axial clearance, each contact point being tracked in the line 38.In summary, by providing the cage webs 14 with a radial curvature 30, the risk of the barrel rollers 8 coming into contact with an edge of the cage web 14 or even scraping along the edge of the cage web 14 can be reduced. Thus, the radial curvature 30 may allow for more reliable cage web contact with a reduced risk of edge running at the outer axial edges of the cage web 14. Since the likelihood of edge running can be at least reduced, the contact between the barrel roller 8 and the cage web 14 can be more stable. This may additionally allow to reduce an embossing height 32 and / or a cage web thickness 34 and / or allow for larger radial and axial cage pocket clearances, which may reduce the material and / or manufacturing costs of the cage 2 and thus of the spherical roller bearing 1. In addition, due to the more stable contact between the barrel roller 8 and the cage bar 14, the contact stresses may decrease.List of reference characters1 Spherical roller bearing 2 Cage 2- 1, 2- 2 Cage element 4 Outer ring 5 Opening 6 Inner ring 8 Barrel roller 9 Outer raceway 10 Axial inner cage ring 11 Inner raceway 12- 1, 12- 2 Axial outer cage ring 14 Cage web 16 Pocket 18 Flange element 20 Flange element 22 Circumferential surface 24 Contact surface 26 Roller length 30 Radial curvature 32 Stamping height 34 Cage web thickness 36 Outer radial side surface 38 Contact line α Opening angle Dw Roller diameter A Axis of rotation

Claims

Spherical roller bearing (1), in particular for supporting a wind turbine main shaft, comprising: at least one outer ring (4) and an inner ring (6), the inner ring (6) having a diameter of at least 499 mm, two sets of barrel rollers (8) rolling on raceways formed on the outer and inner rings (4, 6), and at least one cage (2) configured to retain the barrel rollers (8), the at least one cage (2) comprising: at least one axial inner cage ring (10) extending in a circumferential direction of the spherical roller bearing (1), a first axial outer cage ring (12-1) spaced apart from the at least one axial inner cage ring (10) on a first axial side and connected thereto by a plurality of cage webs (14), thereby forming closed pockets (16), each pocket (16) being configured to, a barrel roller (8) of the first set of barrel rollers and a second axial outer cage ring (12-2) spaced from the at least one axial inner cage ring (10) on a second axial side opposite the first axial side and connected thereto by a plurality of cage webs (14), thereby forming closed pockets (16), each pocket (16) being configured to receive a barrel roller (8) of the second set of barrel rollers (8), characterized in that at least one cage web (14) has a radial curvature (30) to curve the cage web (14) in the radial direction along the axial direction.Spherical roller bearing (1) according to claim 1, wherein the radial curvature (30) is concave with respect to a pitch circle diameter.Spherical roller bearing (1) according to claim 1 or 2, wherein a radius of the radial curvature (30) is adapted to a crowning radius of the barrel rollers (8).Spherical roller bearing (1) according to claim 3, wherein the radius of the radial curvature (30) is between 0.7 and 6 times the crowning radius of the barrel rollers (30), preferably between 1.5 and 4 times the crowning radius of the barrel rollers (30), and particularly preferably between 2 and 3 times the crowning radius of the barrel rollers (30).Spherical roller bearing (1) according to one of the preceding claims, wherein at least one pocket (16) is defined by a first cage web on a first circumferential side and a second cage web on a second circumferential side opposite the first circumferential side, wherein each of the first cage web and the second cage web has a contact surface for contacting a barrel roller (8), wherein the contact surfaces (24) of the first and the second cage web are at least partially inclined such that an opening angle (α) is formed, wherein the opening angle (α) is preferably between 55° and 67°.Spherical roller bearing (1) according to one of the preceding claims, wherein the at least one cage (2) is produced from a metal sheet.Spherical roller bearing (1) according to one of the preceding claims, wherein the cage webs (14) are arranged at least partially at a position in a radial direction which is offset with respect to a pitch circle diameter.Spherical roller bearing (1) according to Claim 7, wherein the cage webs (14) are arranged on a radially inner side of the pitch circle diameter.Spherical roller bearing (1) according to one of the preceding claims, wherein the axial inner cage ring (10) consists of two separate ring elements.Spherical roller bearing (1) according to claim 9, wherein a gap is formed between the first and the second ring element of the axial inner cage ring (10).Spherical roller bearing (1) according to any one of claims 1 to 8, wherein the axial inner cage ring (10) comprises a first ring element and a second ring element which are fixed to each other.A bearing arrangement for a wind turbine main shaft, the bearing arrangement comprising at least one spherical roller bearing (1) according to any of the preceding claims.

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