CN114001091A

CN114001091A - Self-aligning roller bearing

Info

Publication number: CN114001091A
Application number: CN202010729769.2A
Authority: CN
Inventors: 阿敏·埃亚迪; 陈慧; 马库斯·卢夫
Original assignee: SKF AB
Current assignee: SKF AB
Priority date: 2020-07-27
Filing date: 2020-07-27
Publication date: 2022-02-01
Also published as: WO2022023152A1

Abstract

The present disclosure relates to a self-aligning roller bearing (1) comprising an inner ring (2), an outer ring (3) and at least one row (41, 42) of roller elements (4) between the inner ring (2) and the outer ring (3). The self-aligning roller bearing further comprises a cage (5), the cage (5) comprising a first cage section (51) formed as a ring and a plurality of distributed cage cavity bars (52), the plurality of distributed cage cavity bars (52) protruding axially outwards from an axial side face (6) of the first cage section (51) thereby defining a plurality of cage cavity cells (7) for the roller elements (4). The side face (6) of the cage (5) further comprises one or more projections (8), the one or more projections (8) being adapted to abut a region of an axial end face (9) of the respective roller element (4), respectively. Said area comprising at least the radial centre (40) of the roller element (4).

Description

Self-aligning roller bearing

Technical Field

The present disclosure relates to self-aligning roller bearings (self-aligning roller bearings).

Background

Self-aligning roller bearings are known for their ability to handle demanding applications where loads are high and shaft deflection (/ skew) may also occur. By using rollers instead of balls, a large load can be borne. Furthermore, the ability to center the core (i.e., the ability to relatively misalign the inner and outer races of the bearing) protects the bearing from internal stresses caused by shaft deflection, and therefore the service life of the bearing is generally not adversely affected by such deflection.

Self-aligning roller bearings come in different types, wherein one of the most common types is a spherical roller bearing, which comprises two rows of symmetrical rollers, a common spherical outer raceway and two inner raceways inclined at a certain angle to the bearing axis, and the center point of the sphere where the outer raceway is located at the bearing axis. Another example of a self-aligning roller bearing is the well-known spherical roller bearing with two rows of asymmetric rollers, and yet another example is the well-known toroidal roller bearing comprising one row of rollers, wherein the bearing is able to accommodate both shaft deflection and axial shaft displacement.

Self-aligning roller bearings, such as spherical roller bearings, typically include one or two cages (e.g., a window-type or fork-type cage) for holding roller elements interposed between an inner and an outer bearing ring. Furthermore, self-aligning roller bearings typically also include guide rings (e.g., floating guide rings) or center-fixed flanges (e.g., ribs) or ribs to prevent excessive movement of unloaded roller elements in the axial direction toward the center of the bearing. By blocking (/ arresting) the axial movement of the unloaded rollers, the rollers are prevented from being squeezed between the raceways as they re-enter the loading zone, resulting in friction and ultimately bearing failure. For example, the floating guide ring is typically centered on the center of the inner race or cage.

However, during use of the bearing and/or during implementation of known guide rings, flanges and/or ribs, friction between different components within the self-aligning roller bearing may cause component wear and further cause noise, such as rattling noise (rattling noise), to be generated, which is undesirable for many applications (e.g., applications involving fans and/or elevators).

Therefore, there is room for improvement in order to reduce noise generated by the self-aligning roller bearing.

Disclosure of Invention

It is therefore an object of the present disclosure to provide a self-aligning roller bearing which overcomes or ameliorates, at least to some extent, at least some of the disadvantages of the prior art, or which provides a useful alternative.

This object is achieved by a self-aligning roller bearing according to claim 1. Embodiments are set forth in the appended claims, in the following description, and in the accompanying drawings.

Accordingly, the present disclosure relates to a self-aligning roller bearing comprising an inner ring, an outer ring and at least one row of roller elements between the inner ring and the outer ring. The bearing has a cage comprising a ring-formed (ring-formed) first cage portion and a plurality of distributed cage pocket bars (distributed cage pocket bars) projecting axially (axially) outwardly from an axial side of the first cage portion, thereby defining a plurality of cage pockets for the roller elements. The side face of the first cage portion formed as a ring comprises one or more protrusions adapted (/ adapted) to abut respectively a region of an axial end face of a respective roller element, said region comprising at least a radial center of said roller element.

Thus, instead of initially having the roller elements rub against a large surface associated with the guide ring or central rib/flange, the roller elements first contact the sides of the cage through a protrusion at the center of the roller elements. This enables the roller elements to abut in the event that the tangential velocity of the roller elements is zero or substantially zero during use of the bearing. Thus, the sliding contact is reduced in terms of both the relative speed of the contact surface and the abutment surface. This has the benefit of reducing noise, friction and component wear, thus potentially extending component life, and also in turn reducing noise due to future wear.

Alternatively, the projection and/or the first cage portion are further adapted (/ adapted for) (adaptedfor) to guide the respective roller element to an axial position. Since the one or more protrusions and/or the first cage portion may also optionally be adapted to guide the respective roller element to an axial position, the protrusions and/or the first cage portion may completely prevent the roller element from moving in the axial direction towards the center of the bearing. Thus, guiding of the roller elements may be provided by means of the protrusions and/or the first cage portion, thereby eliminating or at least reducing the need for guide rings, flanges and/or ribs, which are typically used for guiding roller elements between two roller rows. Thus, the introduced roller bearing may potentially be provided without guide rings, flanges and/or ribs. The benefits of reducing the guide ring or flange and/or ribs are primarily to provide fewer components and/or surfaces that may provide rattle or generate noise from rubbing against each other. Furthermore, a bearing with lower weight and fewer components is provided, which makes the bearing easier to assemble (without a guide ring) and/or manufacture (with reduced ribs). Furthermore, the space previously used by the guide ring or the center rib may instead be provided with grease, thereby enhancing the lubrication characteristics (/ properties) and performance of the bearing.

Alternatively, the outer ring has an outer ring raceway with an average surface roughness equal to or less than 0.25 Ra. Further alternatively, the inner ring has an inner ring raceway with an average surface roughness equal to or less than 0.25 Ra. A raceway is the surface of a roller in rolling contact with a (bearing) ring.

Surface roughness may help, for example, guide the rollers and/or enhance lubrication, but also help to generate noise. The advantage of having a Ra value equal to or less than 0.25Ra is to reduce noise generated during operation.

Surface roughness (also referred to as surface profile Ra) is a measure of surface finish (surface finish). It is topography (/ terrain) on a scale (scale) that can be considered as "texture" on a surface. The profile roughness (Ra) may be extracted as a line passing through a certain region. Ra is calculated as the "roughness average" of the surface of the peaks and valleys measured on a microscopic scale. Surface roughness is a quantitative calculation of the relative roughness of a linear profile or area, expressed as a single numerical parameter (Ra). Ra (μm) is used to assess the roughness amplitude on the profile, i.e. the irregularities inherent in the production process (e.g. from cutting tools (/ cutting tools) or abrasive grits).

Alternatively, the outer ring raceway has a peak waviness (peak waviness) equal to or less than 90 μ r. Further alternatively, the inner ring 2 raceway has a peak waviness equal to or less than 90 μ r.

For example, waviness is used to describe how a roller or bearing ring deviates from its desired shape/profile. The waviness of the assembly can be due to vibration, chatter (chatter) or working deflection during assembly processing and/or strain in the material and contributes to noise when the mating surfaces deviate from the desired shape.

Waviness is a defect of the roller element and raceway surface, which extends over the entire length of the circumference (strained out). In other words, it is the shape deviation (form deviation) of the rollers, Inner Ring (IR) and Outer Ring (OR) from the ideal geometry (perfect circle) that is caused during the manufacturing process.

Waviness can be measured in different parameters and in different units. "Peak waviness" (Peakwaviness) is a measure (/ measurement) representing the highest deviation from a reference (e.g., a nominal circle). Waviness can also be measured in "microns" (μm) specifying deviations from, for example, a nominal circle.

The "Waviness length" (measured) is measured in "micro radians" (μ r), specifying the length of the curve with the angle. The "Peak waviness length" is a parameter for measuring the maximum length of a curve or wave having a certain angle, i.e., in radians.

Alternatively, the roller raceway of the self-aligning roller bearing has a peak corrugation length equal to or less than 80 μ r. The benefit of having roller raceways with peak corrugation lengths equal to or less than 80 μ r is to reduce noise generated during operation.

Alternatively, the self-aligning roller bearing is a sealed roller bearing. By "sealed" bearing is meant a bearing having seals on both sides of the bearing. The benefit of having the bearings sealed on both sides is that the noise generated is contained within the bearings making them quieter. In addition, the seal also prevents debris from entering the interior of the bearing and causing vibration and noise.

Alternatively, the sealed self-aligning roller bearing further comprises a lubricant, such as oil or grease. The seal prevents lubricant (such as grease or oil) from leaking to the outside, which has several benefits, for example, enhancing the lubrication performance of the bearing and preventing the lubricant from leaking out to affect the surrounding environment and/or machinery. An additional benefit of having the seal contain lubricant (such as grease) inside the bearing is that it helps to further reduce noise and vibration.

Alternatively, the sealed self-aligning roller bearing has a grease filling level of greater than 30%. Typically, sealed bearings may have a grease fill level of up to 30% to achieve maximum benefit in terms of lubrication performance and reduced friction, while preventing "over-lubrication" and/or grease leakage during operation due to increased pressure inside the bearing and/or expansion of the grease due to temperature rise. It has been found that having a fat fill level greater than 30% helps to reduce the level of noise generated while maintaining leakage of fat at an acceptable level.

Alternatively, the sealed self-aligning roller bearing has a grease filling level between 35% and 45%. This has proven to be a useful interval when testing for noise generation and comparing it to the amount of grease leakage to achieve an acceptable level of grease leakage. The benefit of a grease fill level of 35% to 45% is that noise generation can be minimised whilst still keeping grease leakage at an acceptable level.

Alternatively, the self-aligning roller bearing comprises a grease with solid lubricant particles. It has been found that solid lubricant particles can keep the metal surfaces of the bearing at a greater distance from each other than normal grease. The benefit of having grease with solid lubricant particles is to reduce noise generated during operation.

Alternatively, the solid lubricant comprises 3 vol% to 5 vol% of the grease. Alternatively, the solid lubricant is at least partially one of molybdenum disulfide and/or graphite. Alternatively, the size of the particles is controlled and kept uniform to achieve better noise reduction performance. Alternatively, the graphite particles are between 0.04mm and 0.06mm in size. Alternatively, the molybdenum disulphide particles have a size between 4 μm and 6 μm.

Alternatively, the self-aligning roller bearing (1) is a double row self-aligning roller bearing having two rows of roller elements, such as a spherical double row bearing.

According to a second aspect, the object is achieved by an elevator traction motor comprising a self-aligning roller bearing according to any embodiment of the self-aligning roller bearing as disclosed herein. A benefit of equipping an elevator traction motor with a self-aligning roller bearing according to any embodiment of the present disclosure is to reduce noise and vibration. Reducing noise and vibration is particularly important in elevator applications because they are located in rooms where people can also live or work. Furthermore, for elevator applications, this is particularly appreciated as producing confidence in the reliability and quality of the equipment used by the elevator passengers.

Drawings

The disclosure is described in more detail below by way of further non-limiting embodiments illustrated on the basis of the accompanying drawings.

In the drawings:

fig. 1 illustrates a three-dimensional cross-sectional view of an exemplary bearing according to an embodiment of the present disclosure.

Fig. 2 shows a cage according to an embodiment of the present disclosure.

Detailed Description

Non-limiting embodiments of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which presently preferred embodiments of the disclosure are shown. This disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Like reference numerals refer to like elements throughout.

Hereinafter, an improved and/or alternative self-aligning roller bearing will be disclosed according to embodiments herein relating to self-aligning roller bearings.

Referring now to the drawings, and in particular to fig. 1, fig. 1 depicts a schematic three-dimensional cross-sectional view of an exemplary self-aligning roller bearing 1 according to an embodiment of the present disclosure.

The self-aligning roller bearing 1 comprises an inner bearing ring 2, an outer bearing ring 3 and at least one row 41, 42 of roller elements 4 between the inner bearing ring 2 and the outer bearing ring 3. The roller bearing 1 further comprises a cage 5, as shown in fig. 2, the cage 5 comprising a first cage part 51 formed as a ring and a plurality of distributed cage pocket bars (cage pocket bars) 52, the plurality of distributed cage pocket bars 52 protruding axially outwards from the axial side 6 of the first cage part 51, thereby defining a plurality of cage pocket cells 7 for the roller elements 4.

Alternatively, as shown in exemplary fig. 2, the cage 5 may further include second cage segments 53 formed as rings in parallel with the first ring segments 51 in the axial direction, as is known in the art, the second cage segments 53 connecting the ends of the cage cavity bars 52 together in the axial direction. Thereby, the second cage portion 53 contributes to retaining the roller elements 4 within the cage pockets 7 and also limits axial movement of the roller elements 4 within the cage pockets 7 towards the outside of the self-aligning roller bearing 1, for example.

Alternatively, as shown in exemplary fig. 1, the self-aligning roller bearing 1 may be a double row self-aligning roller bearing, such as a spherical double row bearing, having two rows 41, 42 of roller elements 4. Further alternatively, the spherical double row bearing may be free of guide rings (/ guide rings), flanges (/ ribs) and/or ribs. Still further alternatively, the self-aligning roller bearing 1 may be adapted for rotational speeds above a threshold orbital speed (threshold orbital speed) at which the roller elements 4 are subjected to centrifugal forces exceeding the force of gravity.

Alternatively, the self-aligning roller bearing 1 may have any dimensions suitable for the intended application. Further alternatively, the self-aligning roller bearing 1 may have an outer ring 3 having a diameter of 200mm or less. Still further alternatively, the self-aligning roller bearing 1 may have an inner ring 2 with a diameter between 100mm and 120 mm. In one example, the bearing has a combination of an outer ring 3 having a diameter of 200mm or less and an inner ring 2 having a diameter between 100mm and 120 mm. The diameter dimension refers to the distance measured from the radial center of the bearing 1 to the radially outer surface of the respective ring 2, 3.

Furthermore, the expression "roller bearing" may potentially refer to a "spherical roller bearing" and/or a "spherical double bearing". The inner bearing ring 2 may take any dimensions considered feasible and may be represented by any known inner ring suitable for self-aligning roller bearings, such as spherical double row bearings, and the inner bearing ring 2 also comprises any known suitable material. The inner bearing ring 2 may thus, as shown in exemplary fig. 1, comprise at its radial outer periphery two axially adjacent raceways, each in the form of a truncated spherical surface, wherein the roller elements 4 of the same row 41, 42 may roll on only one of the raceways of the inner ring 2. Correspondingly, the outer bearing ring 3 may be represented by any known outer ring suitable for self-aligning roller bearings (such as spherical double bearings) and also comprising any known suitable material. Thus, as shown in exemplary fig. 1, the outer ring 3 may comprise at its radially inner periphery a raceway in the form of a truncated sphere on which the roller elements 4 may roll. Both the inner bearing ring 2 and the outer bearing ring 3 can rotate around the axis of symmetry of the self-aligning roller bearing 1.

In this context, the terms "axial" or "in axial direction" may refer to a direction parallel to the axis of symmetry of the roller bearing 1, the roller elements 4 and/or the cage 5 (if applicable), while the terms "radial" or "in radial direction" may refer to a direction perpendicular to the axis of symmetry of the bearing 1, the roller elements 4 and/or the cage 5 (if applicable).

The roller elements 4 may be represented by any known rollers suitable for self-aligning roller bearings, such as spherical double row bearings, and also comprise any known suitable material.

For example, as shown in exemplary fig. 1, the roller elements 4 can be arranged in two axially adjacent rows 41, 42. The expression "roller element" may refer to a "roller" and/or a "substantially cylindrical roller" as well as a "spherical roller element" according to examples of embodiments herein.

The cage 5, which similarly may have any size considered feasible, may be represented by any known roller bearing cage suitable for self-aligning roller bearings, such as spherical double row bearings, except for the additional features discussed herein, for example, the cage 5 may be a window type (window type) or a fork type (prog type) cage. The cage 5 may be guided internally, alternatively, for example, the cage 5 may be guided externally or guided by the roller elements 4. The expression "cage" may refer to a "roller bearing cage", whereas the phrase "cage comprising" according to an example may refer to a "cage for holding and/or guiding roller elements, said cage comprising". Furthermore, the expression "ring-formed" first cage part/second cage part may refer to "annular" and/or "circular" first cage part/second cage part, while the cage "part" may refer to the cage "core". According to an example, a "first cage portion" may refer to an "inner cage portion" and/or an "inner portion". "distributed" cage pocket bars may refer to "evenly distributed" cage pocket bars, and "projecting outward in the axial direction" may refer to "projecting outward substantially in the axial direction". Furthermore, the phrase "a plurality of cage pockets for roller elements" may refer to "a plurality of evenly distributed cage pockets for roller elements" and/or "a plurality of cage pockets for roller elements such that a respective cage pocket is provided for each respective roller element of at least one row of roller elements".

According to the introduced concept (/ idea), the side face 6 of the first cage portion 51 of the cage 5 comprises one or more protrusions 8, the one or more protrusions 8 being adapted to abut a region of the axial end face 9 of the respective roller element 4, respectively, which region comprises at least the radial center 40 of the roller element 4. Thereby, at least during use of the bearing 1 and/or during axial displacement of the roller elements 4 and/or skewing (/ deflection/tilting) of the roller elements 4, at least a first protrusion 8 protruding from the side surface 6 of the cage 5 facing the roller elements 4 abuts an end 9 (such as an inner end) of the roller elements 4 at a contact area at and/or around the rotational axis of the roller elements 4. Accordingly, the roller elements 4 are in contact with the side faces 6 of the cage 5 by means of the protrusions 8 at the centers 40 of the roller elements 4, whereby abutment with the roller elements 4 can be ensured during use of the bearing 1 when the tangential velocity (tandenitialvelocity) of the roller elements 4 is zero or substantially zero. Thus, sliding contact with the roller elements 4 and subsequent wear of the components may be avoided or at least kept to a minimum, thereby potentially extending the lifetime of the components.

Furthermore, optionally, one or more protrusions 8 and/or the first cage portion 51 may also be adapted to guide the respective roller element 4 to the correct axial position. Thereby, the protrusion 8 and/or the first cage portion 51 may prevent the roller elements 4 from moving in axial direction towards the center of the bearing 1, and thus guidance of the roller elements 4 may be provided by means of the protrusion 8 and/or the first cage portion 51, thereby eliminating or at least reducing the need for guide rings, flanges (flanges) and/or ribs for guiding the roller elements between two roller rows, as typically comprised in prior art bearings, such as spherical double row bearings. Therefore, the introduced rolling bearing 1 may potentially be provided without guide rings, flanges and/or ribs, thereby potentially enabling a reduction in the weight and/or cost of the roller bearing, and/or noise, such as rattling noise (rattle), generated during use of the roller bearing.

For example, the first cage portion 51 may be designed to drive the respective roller element 4 back to the correct axial position by including similarities in known guide ring, flange and/or rib geometries. For example, the distance between the first cage portion 51 and the inner ring 2 may be adapted to match known guide ring, flange and/or rib structures such that the first cage portion 51 acts as a first portion contacting the inner ring 2, thus acting as an inner ring centering roller guide. The term "correct" axial position may refer to an "optimal", "desired" and/or "predeterminable" axial position, whereas the expression "guiding the respective roller elements to the correct axial position" may refer to "guiding the respective roller elements to the correct axial position at least during use of the self-aligning roller bearing" and/or "guiding the respective roller elements to the correct axial position at least during axial displacement of the roller elements and/or tilting (deviating/skewing) of the roller elements".

Alternatively, one or more projections 8 may be distributed along the side 6, such that a respective projection 8 is provided for each cage pocket 7.

The protrusion 8 may have any size and/or shape deemed feasible to abut with the area of the end face 9 of the roller element 4, including the radial center 40 of the roller element 4, at least during use of the bearing 1 and/or during axial displacement of the roller element 4 and/or deflection of the roller element 4. Similarly, the area of the roller element end face 9 may have any size deemed feasible, for example ranging from a radius of less than one millimeter up to a radius of several hundred millimeters, and/or ranging from a radius of less than one percent of the radius of the roller element 4 up to 50 percent of the radius of the roller element 4. In a similar manner, the end faces 9 of the roller elements 4 (substantially perpendicular to the axis of rotation of the roller elements 4) may take any size and/or shape deemed feasible. According to an example, the end face 9 may be flat. Alternatively, for example, the end surface may be dome-shaped (dome), concave, or the like.

The expression side "face" may refer to a side "surface" and "side" face may refer to an "outer" face. On the other hand, according to an example, "protrusion" may mean "bump" and/or "bump", and "abutment" may mean "contact". According to an example, the phrase "adapted to abut respectively" may mean "adapted to abut respectively at least during use of the self-aligning roller bearing" and/or "adapted to abut respectively at least during axial displacement of the roller elements and/or tilting (deviating/skewing) of the roller elements". The expression "area" of an axial end surface may refer to an "area", "contact area" and/or "portion" of the axial end surface, while the end "surface" may refer to an end "surface". The "radial center" of a roller element may refer to the "substantially radial center" of the roller element, and may also refer to the "axis" and/or "axis of rotation" of the roller element.

Alternatively, one or more protrusions 8 may each have a shape without edges. Thereby, since no edge protrudes from the side surface 6 of the first holder part 51, the component wear can be limited. Further alternatively, one or more of the protrusions 8 may each have a truncated spherical shape. The expression "edge" may refer to a "sharp edge", whereas "truncated sphere" may refer to a "dome".

Furthermore, as an alternative, the one or more projections 8 can each extend in the normal direction over a maximum extension of at least 0.5% of the diameter of the roller element 4 (preferably over at least 1% of the roller diameter d). Thereby, the protrusion elongation is sufficiently large not to allow the bottom part (i.e. the corner of the cage pocket 7) to interfere with the end face 9 of the roller element. The expression "elongation" may refer to "height", while according to an example "normal direction" may refer to "axial direction". On the other hand, "axial length" may refer to "width".

At least a portion of the cage 5 and/or one or more of the projections 8 may be made of a metallic material such as steel, cast iron or brass. Alternatively, at least a portion of the cage 5 and/or one or more of the protrusions 8 may comprise a polymeric material. Thus, the protrusions 8 and/or the cage 5 may comprise, in whole or in part, materials commonly used in cages known in the art, such as PA66 and/or PEEK. Additionally or alternatively, at least a portion of the cage 5 and/or one or more protrusions 8 may be made of a synthetic material and/or a composite material comprising a polymer.

Alternatively, the one or more projections 8 together with the first holder part 51 and/or the holder 5 may form a single whole (/ single body). Thereby, the protrusion 8 may be integrated with at least the first holder part 51 in a single piece, thereby enabling a smaller number of components and/or a smaller complexity.

Alternatively, the bearing outer ring 3 has an outer ring 3 raceway, the outer ring 3 raceway having an average surface roughness equal to or less than 0.25 Ra. Further alternatively, the inner ring 2 also has an inner ring 2 raceway, the inner ring 2 raceway having an average surface roughness equal to or less than 0.25 Ra.

Raceway means the surface of the roller in rolling contact with the (bearing) ring. Surface roughness may help, for example, guide the rollers and/or enhance lubrication, but also help to generate noise. The advantage of having a Ra value equal to or less than 0.25Ra is to reduce noise generated during operation. The "pattern" of surface roughness may be evenly distributed, for example with lines along the raceway direction from a honing (honing) operation, when viewed in an enlarged view. Alternatively, the pattern may be a shallow cross pattern, resulting in better lubrication performance.

Alternatively, the raceway of the outer ring 3 has a peak wavinesslength (peak wavinesslength) equal to or less than 90 μ r. Waviness is used to describe how, for example, the rollers 4 or (bearing) rings 2, 3 deviate from their desired shape/profile. In most applications, the waviness on the bearing 1 assembly will result in high vibration levels. The waviness of the assembly may be due to vibration, chatter or work deflection during processing of the assembly and/or strain in the material, and contributes to noise generation when the mating surfaces deviate from the desired shape. Further alternatively, the inner ring 2 raceway has a peak corrugation length equal to or less than 90 μ r.

Waviness can be measured in different parameters and in different units. "Peak waviness" is a measure representing the highest deviation from a reference shape (e.g., a nominal circle). Measurements may be made in "microns" (μm) to specify deviations from a nominal shape (e.g., a nominal circle). The "peak corrugation length" can be measured in "micro radians" (μ r) to specify the length of the maximum curve with a certain angle. The advantage of having the peak corrugation length of the raceway of the outer ring 3 equal to or less than 90 μ r is to reduce noise generated during operation.

Alternatively, the self-aligning roller bearing 1 has the roller 4 raceways, and the roller 4 raceways have a peak corrugation length equal to or less than 80 μ r, which further reduces noise generated during operation.

As an alternative, the self-aligning roller bearing 1 can be a sealed roller bearing (seals not shown in fig. 1 and 2). By "sealed" bearing 1 is meant a bearing 1 having seals on both sides of the bearing 1. This controls the noise generated inside the bearing 1, making the bearing 1 quieter. Furthermore, the seal also prevents debris from entering the interior of the bearing 1 causing vibration, noise and ultimately failure of the bearing 1.

Alternatively, the sealed self-aligning roller bearing 1 further comprises a lubricant, such as oil or grease. The seal prevents lubricant from leaking to the outside, which has many benefits, such as enhancing the lubrication performance of the bearing and preventing lubricant from leaking to affect the surrounding environment and/or machinery. An additional benefit of having the seal contain lubricant (such as grease) inside the bearing is that the grease further helps to mitigate noise and vibration.

Alternatively, the sealed self-aligning roller bearing 1 has a grease filling level of more than 30%. Typically, a sealed bearing may be shipped with a grease fill level of up to 30% of pre-injected (/ pre-greased), as this may be all the grease that the bearing will require, as the re-lubrication interval may be longer than the expected life of the bearing. Excessive grease fill volume in the bearing (over-lubrication) will cause the rotating bearing elements to initially agitate the grease, pushing it aside, causing energy loss and temperature rise. This may lead to accelerated wear of the rolling elements, which in turn may lead to failure of the assembly.

Furthermore, the leaked grease may affect the surrounding machinery and/or area in a negative way. It has been found that having a grease fill level greater than 30% helps to reduce the level of noise generated while keeping the negative effects of over lubrication (grease) and grease leakage at acceptable levels.

Alternatively, the sealed self-aligning roller bearing 1 has a grease filling level between 35% and 45%. This has proven to be a useful interval when testing for noise generation and comparing it to the amount of grease leakage to achieve an acceptable level of grease leakage. The benefit of having a grease fill level of 35% to 45% is that noise generation can be minimized while still maintaining grease leakage at an acceptable level for various specifications. In one example, the bearing has a combination of an outer ring 3 having a diameter of 200mm or less and an inner ring 2 having a diameter of between 100mm and 120mm, as measured between the radial centre of the bearing 1 and the radially outer surface of the rings 2, 3. Further alternatively, the lipid fill level is between 37% and 43%. Still further alternatively, the fat fill level is 39% to 41%. Still further alternatively, the fat fill level is about 40%.

Alternatively, the self-aligning roller bearing 1 comprises a grease (not shown) with solid lubricant particles. It has been found that the solid lubricant particles keep the metal surfaces of the bearing at a greater distance from each other than normal grease. The benefit of having grease with solid lubricant particles is to reduce noise generated during operation.

Alternatively, the solid lubricant comprises 3 vol% to 5 vol% of the grease. Further alternatively, the solid lubricant is at least partially one of molybdenum disulfide and/or graphite. Alternatively, the size of the particles is controlled and kept uniform to achieve better noise reduction performance. Further alternatively, the graphite particles have a size of between 0.04mm and 0.06 mm. Further alternatively, the molybdenum disulfide particles are between 4 μm and 6 μm in size. In another example of embodiment, the grease comprises about 2% graphite particles of about 0.05mm and about 2% molybdenum disulfide (MoS) of about 4 μm to 6 μm₂D50) And (3) granules.

The self-aligning roller bearing 1 may be part of an elevator traction motor. A benefit of equipping an elevator traction motor with a self-aligning roller bearing 1 according to any embodiment of the present disclosure is to reduce noise and vibration. Noise and vibration reduction is particularly important in elevator applications because they are located in rooms where people can also live or work. Furthermore, for elevator applications, this is particularly appreciated as producing confidence in the reliability and quality of the equipment used by the elevator passengers.

Alternatively, the self-aligning roller bearing 1 has a radial play within the lower half of the "N sets" and the upper half of the "2 sets" with reference to the ISO play class (clearance class) in ISO 5753. This further secures the assembly and reduces noise and vibration.

The person skilled in the art realizes that the present disclosure by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. Further, it should be noted that the figures are not necessarily to scale and that the dimensions of some features may have been exaggerated for clarity. Instead, emphasis is placed upon illustrating the principles of the embodiments herein. In addition, in the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.

Claims

1. A self-aligning roller bearing (1) comprising:

an inner ring (2);

an outer ring (3);

at least one row (41, 42) of roller elements (4) interposed between the inner ring (2) and the outer ring (3); and

a cage (5) comprising a first cage section (51) formed as a ring and a plurality of distributed cage pocket bars (52), the plurality of distributed cage pocket bars (52) protruding axially outwards from an axial side face (6) of the first cage section (51) defining a plurality of cage pocket cells (7) for the roller elements (4),

wherein the side surface (6) comprises one or more protrusions (8), the one or more protrusions (8) being adapted to abut a region of an axial end surface (9) of the respective roller element (4), respectively, said region comprising at least a radial center (40) of the roller element (4).

2. Self-aligning roller bearing (1) according to claim 1, wherein the one or more protrusions (8) and/or the first cage portion (51) are further adapted to guide the respective roller element (4) to an axial position.

3. Self-aligning roller bearing (1) according to any of the preceding claims, characterized in that the outer ring raceway has an average surface roughness equal to or less than 0.25 Ra.

4. Self-aligning roller bearing (1) according to any one of the preceding claims, characterized in that the outer ring raceway has a peak corrugation length equal to or less than 90 μ r.

5. Self-aligning roller bearing (1) according to any one of the preceding claims, characterized in that the roller tracks have a peak corrugation length equal to or less than 80 μ r.

6. Self-aligning roller bearing (1) according to any of the preceding claims, characterized in that the self-aligning roller bearing (1) is a sealed roller bearing.

7. Self-aligning roller bearing (1) according to claim 6, characterized in that the self-aligning roller bearing (1) further comprises a grease, wherein the grease filling level is more than 30%, preferably between 35% and 45%.

8. Self-aligning roller bearing (1) according to any of the preceding claims, characterized in that the bearing further comprises a grease with solid lubricant particles, which are at least partly made of molybdenum disulphide and/or graphite.

9. Self-aligning roller bearing (1) according to any of the preceding claims, characterized in that the self-aligning roller bearing (1) is a double row self-aligning roller bearing, such as a spherical double row bearing, having two rows (41, 42) of roller elements (4).

10. An elevator traction motor comprising a self-aligning roller bearing (1) according to any one of the preceding claims.