Spherical roller bearings with asymmetric cage pockets

Abstract

Disclosed is a spherical roller bearing (1), in particular for supporting a wind turbine main shaft, comprising at least one outer ring (4) and one inner ring (6), wherein the inner ring (6) has a bore with a diameter of at least 499 mm, two sets of spherical rollers (8) rolling on raceways formed on the outer and inner rings (4, 6), and at least one cage (2) configured to retain the spherical 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), and a second axial outer cage ring (12-2), each spaced apart from the at least one axial inner cage ring (10) on a first axial side and a second axial side and connected to it by a plurality of cage webs (14), thereby forming closed pockets (16).wherein each pocket (16) is adapted to receive a single spherical roller (8) and has an axial inner pocket side surface (40) and an axial outer pocket side surface (42) adapted to confine the spherical roller (8) in the axial direction, wherein each cage web (14) has an axially extending curvature in the circumferential direction, wherein the curvature is at least partially concave, and wherein in the axial direction a distance (30) between an apex (26) of the curvature and the axial inner pocket side surface (40) differs from a distance (28) between the apex (26) of the curvature and the axial outer pocket side surface (42).

Description

Technical field of the invention

[0001] The present invention relates to a spherical roller bearing. Furthermore, the present invention relates to a bearing arrangement comprising a spherical roller bearing. Background of the invention

[0002] Rolling bearings are common mechanical components used in many different applications. There are various types of rolling bearings designed to meet different requirements. Depending on the conditions of the specific application, such as the degree of load, rotational speed, temperature, etc., different types of rolling bearings are suitable.

[0003] A common bearing type is a spherical roller bearing, as described, for example, in German patent application DE 694 02 507 T2. This bearing is designed to withstand large radial and axial loads and is also designed to accommodate the deflection of a shaft supported by the bearings, meaning that the bearing rings can be relatively misaligned. Therefore, such bearings are particularly suitable for demanding industrial applications such as machinery in wind turbines and the like.

[0004] In most demanding industrial applications for spherical roller bearings, the majority of bearing failures are typically related to increased surface-initiating fatigue, such as wear. One cause of increased wear can be displacement of the barrel rollers within the cage, which can lead to undesired surface contact and / or increased stresses, particularly on the cage. Reducing these undesired contacts and / or stresses can extend the bearing's service life.

[0005] It is therefore an object of the present invention to provide a spherical roller bearing which has an extended service life. Brief description of the invention

[0006] This task is accomplished by a spherical roller bearing according to claim 1.

[0007] The following is a spherical roller bearing. The spherical roller bearing can be used to support a wind turbine main shaft.

[0008] The spherical roller bearing comprises at least one outer ring and one inner ring, two sets of barrel rollers rolling on raceways formed in the outer and inner rings, and at least one cage designed 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 designed to accommodate a component of another machine, for example, a shaft of a wind turbine.

[0009] The inner ring can be formed with or without flanges on an axial inner and / or an axial outer surface. If the inner ring is flanged, the flanges can serve as guide flanges for the rolling elements. They can also act as retaining flanges to prevent the rollers from falling out of the bearings.

[0010] The at least one cage comprises 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 to it by several cage webs, thereby forming closed pockets, each pocket being configured to receive a single barrel roller of the first set of rollers, and having an axial inner side surface and an axial outer side surface configured to confine the received barrel roller in the axial direction, 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 to it by several cage webs, thereby forming closed pockets, each pocket being configured toto accommodate a single barrel roller of the second set of rollers, and has an axial inner pocket side surface and an axial outer pocket side surface configured to constrain the accommodated barrel roller in the axial direction.

[0011] The axial inner pocket side surface and an axial outer pocket side surface can be formed by the axial inner and outer cage ring and / or an element connected to the axial inner and outer cage ring.

[0012] In particular, the inventors observed that window-like cages in spherical roller bearings can tend to shift towards the inside of the bearing during operation. This can lead to increased wear of the at least one cage and / or the barrel rollers and / or to increased stresses in the at least one cage. Both increased wear and increased stresses can lead to a reduced service life of the spherical roller bearing.

[0013] To extend the service life of the spherical roller bearing, each cage web has an axially extending curvature in the circumferential direction, wherein the curvature is at least partially concave, and wherein, in the axial direction, the distance between a vertex of the curvature and the axial inner pocket side surface differs from the distance between the vertex of the curvature and the axial outer pocket side surface. For example, the difference between the distance between the vertex of the curvature and the axial inner pocket side surface and the distance between the vertex of the curvature and the axial outer pocket side surface can be 0.5 mm, preferably 1 mm.

[0014] Providing the cage web with a circumferential curvature such that the distance between the apex of the curvature and the axial inner pocket surface differs from the distance between the apex of the curvature and the axial outer pocket surface allows the barrel roller to be shifted within the cage pocket towards the outside of the spherical roller bearing. This can further compensate for axial displacement between the barrel roller and the cage due to gravity and / or the contact angle. This can reduce wear on the cage and / or barrel rollers, thereby extending the service life of the spherical roller bearing.

[0015] According to another embodiment, the distance between the apex of the curvature and the axial inner pocket side surface can be greater than the distance between the apex of the curvature and the axial outer pocket side surface.

[0016] This allows for a defined positional relationship between the at least one cage and the barrel roller, which can lead to reduced relative movement between the cage and the barrel roller. Reducing the relative movement between the cage and the barrel roller can decrease contact stresses on the at least one cage. More precisely, a minimum axial clearance should be maintained between the roller and the axial inner pocket side surface and the axial outer pocket side surface to avoid any unwanted interference between the cage and the barrel roller.Since the direction in which the cage can generally move is known, it may be possible to design the cage such that a surface of the cage most likely to come into contact with the barrel roller can already be configured as a contact surface, thus allowing any necessary tolerance compensation to be made on another surface. This can also make it possible to keep the overall tolerance deviations small.

[0017] According to another embodiment, the radius of the curvature can be adjusted so that it forms a curve with a crowning of the barrel roller.

[0018] In particular, a precisely defined contact position between the cage web and the barrel roller, achieved by adjusting the radius of the cage web's circumferential side surface in the axial direction to conform to the barrel roller's crown, can allow for improved contact between the cage web and the barrel roller. This can reduce contact stress between the barrel roller and the cage web.

[0019] In particular, the curvature can be between 100% and 104%, preferably between 100.5% and 103%. Furthermore, the curvature can be defined by the radius of curvature of the cage web divided by the radius of crown of the barrel roller.

[0020] In particular, a 100% sizing can be described as very tight, while a 104% sizing can be described as very loose. Furthermore, loose sizing can lead to increased contact stresses in a central position of the cage and may result in a smaller contact ellipse. Conversely, tighter sizing can lead to reduced contact stresses in the central position and may result in a larger contact ellipse.

[0021] According to a further embodiment, an external axial clearance between the axial outer pocket side surface and an outer axial side surface of the barrel roller is smaller than an internal axial clearance between the at least one axial inner pocket side surface and an inner axial side surface of the barrel roller.

[0022] A smaller external axial clearance between the axial outer pocket face and an outer axial face of the barrel roller, compared to the internal axial clearance between the axial inner pocket face and an inner axial face of the barrel roller, can lead to a more precisely defined spherical roller position in the pocket during operation. This can reduce the cage web contact stress during operation and can improve the overall operating behavior of the spherical roller bearing.

[0023] According to another embodiment, the cage webs are at least partially arranged in a position in a radial direction that is offset from the pitch circle diameter. This can allow the dynamic load rating of the spherical roller bearing to be increased.

[0024] The term "pitch circle diameter" can describe the diameter along which the centers of the barrel rollers move during operation.

[0025] For example, the cage webs can be arranged at a distance from the raceway of the inner or outer ring in the radial direction that corresponds to 10 to 40% of the diameter of a barrel roller or 60 to 90% of the diameter of the barrel roller.

[0026] Arranging the cage webs in a position radially offset at least partially from the pitch circle diameter can reduce the distance between two adjacent rollers, thus increasing the number of rollers in a set. Furthermore, this arrangement allows for an increase in the cage web width, even with a very small minimum roller spacing. In particular, increasing the number of rollers in the set offers the advantage of increasing the dynamic load rating of the spherical roller bearing without requiring modifications to the outer and / or inner rings.

[0027] According to another embodiment, the at least one cage can be made of sheet metal.

[0028] Using sheet metal as the base material for at least one cage can have the advantage of reducing the cost of the cage.

[0029] Alternatively, the cage can also be made from a cast material or machined from a solid piece of material.

[0030] According to another embodiment, the pockets can be formed by pressing and embossing and / or milling.

[0031] According to another embodiment, the axial inner cage ring consists of two separate ring elements.

[0032] Two separate cages can allow one set of rollers to have a different rotational speed than the other set. This can reduce the forces acting on each cage compared to a single cage coupling the two sets of rollers. Alternatively, the first and second cages can be separated from each other but positioned close enough that they may support each other while still being able to move relative to one another.

[0033] Preferably, a gap can be formed between the first and the second ring element of the axial inner cage ring.

[0034] A gap between the first and second ring elements of the axial inner cage ring can allow lubricant flow to the inner ring of the spherical roller bearing to be improved.

[0035] According to another embodiment, the axial inner cage ring comprises a first ring element and a second ring element which are attached to each other.

[0036] This can have the advantage that the at least one cage can be formed from two identical cages attached to each other. This can allow for a simpler manufacturing process for the at least one cage.

[0037] According to another aspect, a bearing arrangement is provided for a wind turbine main shaft, wherein the bearing arrangement includes at least one spherical roller bearing as described above.

[0038] All the characteristics described above in relation to the spherical roller bearing apply - separately or in combination - to the spherical roller bearing used in the bearing arrangement.

[0039] Further preferred embodiments are defined in the dependent claims, the description, and the figures. Elements described or shown in combination with other elements may be present alone or in combination with other elements without exceeding the scope of protection. Brief description of the drawings

[0040] Preferred embodiments of the invention are described below with reference to the drawings, which are merely exemplary and are not intended to limit the scope of protection. The scope of protection is defined exclusively by the accompanying claims.

[0041] The figures show: Fig. Figure 1 shows a schematic cross-section of a spherical roller bearing according to one embodiment. Fig. Figure 2 shows a schematic perspective view of part of a cage of the spherical roller bearing according to the embodiment, Fig. Figure 3 shows a schematic section along an axis of a barrel roller in a pocket of the cage of the spherical roller bearing. Fig. 1 and a line of contact between the barrel roller and the cage, Fig. 4: shows detail IV of Fig. 3 and Fig. 5: shows detail V of Fig. 3. Detailed description of the invention

[0042] In the following, identical or similar functional elements will be designated with the same reference symbols.

[0043] Fig. 1 and Fig. Figure 2 shows a spherical roller bearing 1 for supporting a wind turbine main shaft and part of a cage 2 of the spherical roller bearing 1.

[0044] The spherical roller bearing 1 comprises an outer ring 4 and an inner ring 6, and two sets of barrel rollers 8 that roll on raceways 9 formed on the outer ring 4 and on raceways 11 formed on the inner ring 6. The outer ring 4 includes an opening 5 through which lubricant can be supplied to the spherical roller bearing 1.

[0045] The inner ring 6 can be formed with or without flanges on an axial inner and / or an axial outer surface. The in Fig. The spherical roller bearing shown in Figure 1 is formed without flanges on both the axial inside and the axial outside of the inner ring 6.

[0046] Furthermore, the spherical roller bearing includes a cage 2 designed to retain both sets of barrel rollers 8. The cage 2 of the in Fig. The spherical roller bearing shown in Figure 1 comprises a first cage element 2-1, which is configured to retain the first set of barrel rollers 8, and a second cage element 2-2, which have an identical shape and are joined together to form the cage 2. Fig. Figure 2 shows the first cage element 2-1 in detail.

[0047] Alternatively, the cage 2 can be formed in one piece, so that the cage 2 comprises only a single axial inner cage ring 10 instead of two axial inner cage rings 10 that are attached to each other.

[0048] Alternatively, the cage elements 2-1, 2-2 can also be formed separately from each other, so that a gap is formed between the cage elements 2-1, 2-2.

[0049] Each cage element 2-1, 2-2 comprises an axial inner cage ring 10 extending in a circumferential direction of the bearing, an axial outer cage ring 12 spaced axially from the axial inner cage ring 10 and connected to it by several cage webs 14, thereby forming closed pockets 16. Each pocket 16 is configured to receive a single barrel roller 8 and has an axial inner pocket side surface (indicated by the dashed line 40) and an axial outer pocket side surface (indicated by the dashed line 42) configured to confine the received barrel roller 8 in the axial direction.

[0050] The axial inner cage ring 10 has a flange element 18 extending radially outwards, and the axial outer cage ring 12 has a flange element 20 extending radially inwards.

[0051] Furthermore, the cage webs 14 are at least partially arranged in a position that is at least partially offset from the radial inner side of a pitch circle diameter of the spherical roller bearing 1. Preferably, the position corresponds to 10 to 40% of the diameter of the barrel roller 8 used in the spherical roller bearing 1.

[0052] Arranging the cage webs 14 in an offset relative to the pitch circle diameter can reduce the minimum distance between the raceways of two adjacent rollers 8, thus making it possible to increase the number of rollers used in a set of rollers 8. The minimum distance Dm is determined in a state where the barrel rollers 8 are uniformly spaced in the circumferential direction.

[0053] In particular, the 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 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 rollers 8 are uniformly spaced in the circumferential direction.

[0054] 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 can be equal to or less than a value obtained by the following equation: Dm≤0.0064 mm⋅(ln(P⋅Dw+Dw))3 when the barrel rollers 8 of the respective set of rollers 8 are uniformly spaced in the circumferential direction, where P is the pitch circle diameter and Dw is the maximum roller diameter, where the millimeter values ​​of P and Dw are to be used as dimensionless variables.

[0055] Fig. Figure 3 shows a schematic section along an axis of the barrel roller 8 in the pocket 16 and a line of contact between the barrel roller 8 and the cage. Fig. 4 shows detail IV of Fig. 3 and Fig. 5 shows detail V of Fig. 3.

[0056] As from Fig. As can be seen in Figure 3, the cage web 14 has a concave curvature in the axial direction on a circumferential side surface 22. The curvature is shaped such that, in the axial direction, the distance 30 between a vertex 26 of the curvature and the axial inner pocket side surface 40 is greater than the distance 28 between the vertex 26 of the curvature and the axial outer pocket side surface 42. This results in an asymmetric cage pocket geometry.

[0057] A radius of curvature is adapted such that it forms a conformation with a crown of the barrel roller 8, wherein the conformation is between 100% and 104%, preferably between 100.5% and 103%.

[0058] As from Fig. 4 and Fig. 5 can be seen to be an external axial play 34 ( Fig.5) between the axial outer pocket side surface 42 and an outer axial side surface 38 of the barrel roller 8 smaller than an inner axial clearance 32 between the axial inner pocket side surface 40 and an inner axial side surface 36 of the barrel roller 8.

[0059] In summary, the geometry of the cage pocket 16 can be optimized by compensating for the axial displacement of the cage 2 due to gravity and the contact angle. This can result in a more precisely defined roller position within the pocket during operation. It can also allow for a tighter curvature of the side surface 22 of the cage web 14, which is designed to contact a surface of the barrel roller 8 held in the pocket 16. A tighter curvature can reduce the cage web contact stress during operation and can improve the overall operating characteristics of the spherical roller bearing. Reference symbol list 1 spherical roller bearing 2 cages 2-1, 2-2 cage element 4 outer ring 5 Opening 6 inner ring 8-ton roller 9 outer lane 10 axial inner cage ring 11 inner career 12-1, 12-2 axial outer cage ring 14 Cage bridge 16 bags 18 Flange element 20 Flange element 22 side surface 26 Vertex 28 Distance 30 Distance 32 internal axial play 34 external axial play 36 inner roller side surface 38 outer roller side surface 40 axial inner pocket side surface 42 axial outer pocket side surface

Claims

[1] Spherical roller bearings (1), in particular for supporting a wind turbine main shaft, comprising: at least one outer ring (4) and one inner ring (6), wherein the inner ring (6) has a bore with a diameter of at least 499 mm, two sets of barrel rollers (8) which roll 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 to it by several cage webs (14), thereby forming closed pockets (16), each pocket (16) being configured to receive a barrel roller (8) of the first set of barrel rollers (8), and having an axial inner pocket side surface (40) and an axial outer pocket side surface (42) configured to restrict the received barrel roller (8) in the axial direction, 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 receive a barrel roller (8) of the second set of barrel rollers (8), and having an axial inner pocket side surface (40) and, having an axial outer pocket side surface (42) which is configured to restrict the received barrel roller (8) in the axial direction, characterized by , that each cage web (14) has an axially extending curvature in the circumferential direction, wherein the curvature is at least partially concave, and wherein in the axial direction a distance (30) between a vertex (26) of the curvature and the axial inner pocket side surface (40) differs from a distance (28) between the vertex (26) of the curvature and the axial outer pocket side surface (42). [2] Spherical roller bearing (1) according to claim 1, wherein the distance (30) between the apex (26) of the curvature and the axial inner pocket side surface (40) is greater than the distance (28) between the apex (26) of the curvature and the axial outer pocket side surface (42). [3] Spherical roller bearing (1) according to claim 1 or 2, wherein a radius of curvature is adapted such that a conformity with a crowning of the barrel roller (8) is formed. [4] Spherical roller bearing (1) according to claim 3, wherein the conformity is between 100% and 104%. [5] Spherical roller bearing (1) according to one of the preceding claims, wherein an external axial clearance (34) between the axial outer pocket side surface (42) and an external axial side surface (38) of the barrel roller (8) is smaller than an internal axial clearance (32) between the at least one axial inner pocket side surface (40) and an internal axial side surface (36) of the barrel roller (8). [6] Spherical roller bearing (1) according to one of the preceding claims, wherein the cage webs (14) are arranged at a position in a radial direction which is offset to a pitch circle diameter. [7] Spherical roller bearing (1) according to claim 6, wherein the cage webs (14) are arranged on a radially inner side of the pitch circle diameter. [8] Spherical roller bearing (1) according to one of the preceding claims, wherein the axial inner cage ring (10) consists of two separate ring elements. [9] Spherical roller bearing (1) according to claim 8, wherein a gap is formed between the first and the second ring element of the axial inner cage ring (10). [10] Spherical roller bearing (1) according to any one of claims 1 to 7, wherein the axial inner cage ring (10) comprises a first ring element and a second ring element which are attached to each other. [11] Spherical roller bearing (1) according to one of the preceding claims, wherein the at least one cage (2) is made from a sheet metal plate. [12] Bearing arrangement for a wind turbine main shaft, wherein the bearing arrangement comprises at least one spherical roller bearing (1) according to one of the preceding claims.

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