Patent Application
20150030453
The present invention relates to the field of rolling-element bearing arrangements, and more specifically to a bearing assembly for supporting and axially locating a rotating shaft, such as a wind turbine rotor shaft, which assembly comprises a toroidal roller bearing arrangement which allows for self-aligning capability in combination with at least partial unconstrained axial displacement, and a thrust bearing arrangement.
The present invention also relates to a method for manufacturing a bearing assembly for supporting a shaft, which assembly comprises a toroidal bearing arrangement.
During high torque transfer and high load applications comprising a rotating shaft in space-limited housings, such as a rotor shaft of a wind turbine, the rotating shaft is commonly supported by a spherical roller bearing which has a spherical geometry allowing for self-alignment of the shaft during operation. By self-alignment, the angular alignment of the rotational axis of the rotating shaft may change in relation to the bearing such that angular movements of the shaft in relation to a housing is permitted. During operation, in order to provide suitable operation and to reduce wear and damage to connected and/or surrounding equipment, such as gear boxes, etc, the axial movement of the rotating shaft must be restricted by the spherical roller bearing. Any excessive axial play may considerably reduce the life time of the application arrangement.
In order to provide suitable and durable axial locating function of the spherical roller bearing, the size and radial dimension of the spherical geometry of the spherical roller bearing is increased which increases the contact angles between the rollers and raceway in relation to the axis of the rotating shaft. Furthermore, the required spherical geometry of the spherical bearing is further increased by the required radial dimension of the rotating shaft which must be design to withstand the required torque level of the application.
Hence, known solutions involving a self-aligning and axially locating spherical roller bearing suffer from overdesigning in relation to e.g. radial load bearing capacity. Also, in order to provide sufficient axial load bearing function, known solutions entail non-compact designs with large bearings which occupy valuable space. Furthermore, designing with large bearings sizes leads to high material cost and high bearing mass which limits the operational efficiency by e.g. increasing the rotational inertia of the arrangement.
In view of the above-mentioned and other drawbacks of the prior art, a general object of the present invention is to provide an improved bearing assembly and method for manufacturing such bearing assembly.
These and other objects are met by the subject matters provided in the independent claims. Preferred embodiments of the invention are presented in the dependent claims.
According to a first aspect thereof, the present invention relates to a bearing assembly for supporting a shaft, comprising a toroidal roller bearing arrangement comprising a first set of rolling elements formed of toroidal roller elements, which roller elements are arranged in a first row and interposed between an inner ring comprising a first inner raceway and a first outer ring comprising a first outer raceway, wherein the first inner and outer raceways are in contact with the roller elements and are arranged to cooperate with the roller elements to allow for axial and angular displacement between the inner ring and the first outer ring. The bearing assembly further comprises a first thrust bearing arrangement comprising a second set of rolling elements arranged in a second row, which rolling elements are in contact with and arranged to cooperate with a second inner raceway and a second outer raceway for supporting axial loads and for restricting axial movement of the shaft in relation to the first outer ring.
The invention is based on the realization by the inventors that an improved and more compact bearing assembly for rotatably supporting and axially locating, at least in a first axial direction, a rotatable shaft is realized by forming a bearing unit comprising a toroidal roller bearing arrangement having a geometrical design which is inherently arranged to enable and allow for self-alignment and unconstrained axial displacement, in combination with a thrust bearing arrangement for supporting axial loads and restricting axial movements of the shaft.
This solution is advantageous in that it enables a compact design which allows for angular misalignment, has a more compact cross section and which may support increased or same radial and axial loads, while reducing the required installation space and reducing the weight of the bearing arrangement. Hence, the solution according to the present invention save space, weight and production costs while allowing the same or improved performance. Also, the rotational inertia of the bearing arrangement is decreased allowing for more efficient operation.
Furthermore, the design of the rollers and raceways of the toroidal roller bearing arrangement which enable relative self-alignment and unconstrained axial displacement between the rollers and raceways, also enable self-guiding operation of the rollers in relation to the raceway. Hence, during operation, when the shaft experience angular misalignment, while the thrust bearing arrangement restricts axial movements of the shaft, the rollers of the toroidal bearing adapt a position in relation to the raceways of the toroidal roller arrangement such that the internal loads are evenly distributed over the at least a portion of the roller axial length and raceways. In turn, lower internal loads reduces the friction of the bearing assembly which leads to reduced power loss of applications arranged with the bearing assembly, such as a wind turbine application. Also, the solution is advantageous in that internal loads are separated between the toroidal and thrust bearing arrangements which leads to that the internal contact loads between the members of the bearing assembly are reduced.
The bearing assembly further improves the limitation of axial displacement of the rotating shaft during operation which increases life time of the arrangement and life time and performance of devices operatively connected to the rotating shaft, such as a gear box, generator, turbine, etc.
Each row of rolling elements may, according to an exemplifying embodiment, form a row of aligned rolling elements which extend and roll circumferentially around the inner ring, or their respective inner rings, and around the shaft, during operation, in an annular configuration.
According to an exemplifying embodiment, the first set of rolling elements, being formed of toroidal roller elements, are slightly crowned symmetrical rollers having a convex shape in the axial direction, wherein the first inner and/or outer raceway of the toroidal roller bearing arrangement is/are concave and adapted to cooperate with the convex shape of the first set of the toroidal rolling elements, and is/are further situated symmetrically about the bearing centre in the axial direction.
According to an exemplifying embodiment, the second inner raceway of the first thrust bearing arrangement is arranged in the inner ring. Thereby, inner ring of the bearing assembly is shared by the first and second set of rolling element. In other words, the inner ring of the toroidal bearing arrangement and the inner ring of the thrust bearing arrangement are integrated with each other which allows for a more robust and durable bearing assembly having a compact design. Also, mounting and incorporation into existing space of compact application designs are facilitated. During operation, the shared inner ring, which also may form a shaft washer, improves the internal forces transfer/distribution and load bearing capacity of both radial and axial loads.
According to an exemplifying embodiment, the second outer raceway is arranged in a second outer ring, wherein the second outer ring is connected to the first outer ring via a support structure. Hence, support structure is arranged to support the first outer ring in relation to the second outer ring. The support structure may advantageously be configured to control the position of the second outer ring cooperating with the second set of rolling elements in relation to the first outer ring, such that bearing assembly allows for misalignment but restricts the axial displacement of the shaft in relation to the inner ring. Also, the support structure provides a suitable support for operatively coupling the first and second rings in relation to each other during operation, and/or in relation to a housing of the application.
According to an exemplifying embodiment, the bearing assembly further comprises a second thrust bearing arrangement comprising a third set of rolling elements arranged in a third row, which rolling elements are in contact with and arranged to cooperate with a third inner raceway and a third outer raceway for supporting axial loads. By providing a first and second thrust bearing arrangement, the bearing assembly may advantageously be used for supporting axial loads and for restricting axial movements of the shaft in both axial directions in relation to the axis of the shaft. For example, according to an embodiment, the first and second thrust bearing are arrangements on opposite axial ends of the toroidal roller bearing arrangement. Hence, three sets of rolling elements which are arranged in annular essentially coaxial rows, which are separated in the axial direction, are provided.
According to an exemplifying embodiment, the third inner raceway of the second thrust bearing arrangement is arranged in the inner ring. By providing also the third raceway on the same inner ring as the toroidal roller bearing arrangement, a more compact and versatile bearing assembly capable of supporting radial and axial loads, wherein the forces are transferred through and supported by one inner ring, is provided. Also, the integration of several raceways of separate bearing arrangements for supporting loads in different directions is advantageous in that the loads are distributed in one ring having larger uniform and continuous body compared to providing the raceways on separate inner rings.
According to an exemplifying embodiment, the third raceway is arranged in a third outer ring, wherein the third outer ring is connected to the first outer ring via the support structure, wherein the third outer ring is connected to the first outer ring via the support structure. Hence, a bearing assembly comprising three separated outer rings, one for each one of the toroidal roller bearing arrangement and the first and second thrust bearing arrangement, is provided, wherein the outer rings are operatively supported, connected and/or at least partially restricted from relative movement in the axial direction in relation to each other by a common support structure.
According to an exemplifying embodiment, the second outer ring is movable in relation to the first outer ring in a radial direction in relation to the radial direction of the first outer ring, or in relation to the shaft. This is advantageous in that the ability of the bearing assembly to allow for misalignment of the shaft during operation is improved. For example, the design of the support structure enables the second outer ring to displace or translate in a radial direction in relation to a center axis of first outer ring during misalignment of the shaft, while restricting the axial movements of the shaft in the first axial direction.
According to an exemplifying embodiment, the second and third outer rings are movable in relation to the first outer ring in the radial direction of the first outer ring, or in relation to the radial direction of the shaft. This is advantageous in that the ability of the bearing assembly to allow for misalignment of the shaft during operation is improved. For example, the design of the support structure enables the second and third outer ring to displace or translate in a radial direction in relation to a center axis of the first outer ring during misalignment of the shaft, while restricting the axial movements of the shaft in the first axial direction, and in the opposite axial direction.
The support structure may also, according to various exemplifying embodiments, be arranged to provided relative displacement between the first and second outer rings or between the first, second and third outer rings, in other directions, such as in the axial or intermediate tilted directions. For example, the support structure may comprises an outer ring slide surfaces, wherein the second and/or third outer rings are arranged to abut the slide surface in the axial direction and slide against, and in relation to, the slide surface in the radial direction. The slide surface may also be tilted in relation to the radial direction of the first outer ring, for example in a direction anywhere between 0,01 and 5 degrees, or between 0,05 and 3 degrees. Hence, suitable displacement movement between any one of the second and third outer rings in relation to the first outer ring may be provided, wherein the angle is adapted to the dimensions of the toroidal roller bearing and the predicted, or actual, misalignment permitted by the bearing assembly.
According to an exemplifying embodiment, a contact angle of at least one of the thrust, or axial, bearing arrangements of the bearing assembly exceeds 20 degrees, or 25 degrees, or 35 degrees, or 45 degrees. The contact angle a of the thrust bearing may for example be defined as the angle between a line joining the points of contact of the rolling elements and associated raceways in the radial plane, along which the load is transmitted from one raceway to another, and a line perpendicular to the bearing axis. According to an exemplifying embodiment, at least 25%, or 50%, 75% or 90% of the roller-contacting surfaces between the rolling elements of at least one of the thrust bearing arrangements and the corresponding inner and/or outer raceway which is operative during operation, has a contact angle that exceed the limit according to any one of the previous embodiments.
According to an exemplifying embodiment, at least one or each thrust bearing arrangement is formed of a spherical roller thrust bearing, a tapered roller bearing, a cylindrical roller thrust bearing, a thrust ball bearing, an angular contact ball bearing, or a combination of the two or more of these bearing types. For example, the first and second thrust bearing arrangement may be formed of different bearing types with different rolling element and raceways designs, such as according to the characteristics of any one of exemplified bearing types described above.
According to an exemplifying embodiment, the second outer raceway of the first thrust bearing arrangement is arranged in the first outer ring. Thereby a more compact and efficient outer integrated outer ring configuration comprising both the first and second outer raceway is provided.
According to an exemplifying embodiment, the bearing assembly further comprises a second thrust bearing arrangement comprising a third set of rolling elements arranged in a third row, which rolling elements are in contact with and arranged to cooperate with a third inner raceway and a third outer raceway for supporting axial loads, wherein the third outer raceway of the second thrust bearing arrangement is arranged in the first outer ring. Hence, the first and second thrust bearing arrangements are configured in back-to-back arrangement which is more stiff which reduces the permitted misalignment.
According to a further aspect thereof, the present invention relates to the use of the bearing assembly according to any aspect or embodiment the present invention for supporting radial and axial forces of a shaft.
According to a further aspect thereof, the present invention relates to a wind turbine arrangement comprising a rotor shaft supporting wind turbine blades, which rotor shaft is supported by the bearing assembly according to any aspect or embodiment the present invention. For example, the bearing assembly forms the main bearing of a wind turbine application for supporting the wind turbine rotor shaft in relation to a nacelle housing, or corresponding structure.
According to a further aspect thereof, the present invention relates to a method for manufacturing a bearing assembly for supporting a shaft, which method comprises:
The method is advantageous in that an improved bearing assembly is provided which is more compact and has enhanced performance in terms of friction and internal load/stress distribution which increase operational life time and/or allows for reduced size and material savings. The method is further advantageous in similar manner as described in relation to any other aspect or embodiment of the present invention, and the manufacturing may be realized in an improved manner. For example, mounting and integration of the bearing assembly in various applications may be achieved without damaging the rings and roller elements. Also, the assembly may be performed more time efficient using less steps and by utilizing improved and more time efficient tools and machinery.
Generally, other objectives, features, and advantages of the present invention will appear from the following detailed disclosure, from the attached dependent claims as well as from the drawings are equally possible within the scope of the invention.
Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, wherein:
It is noted that the drawings are not true to scale, and, as is readily appreciated by a person skilled in the art, dimensions other than those illustrated in the drawings are equally possible within the scope of the invention. It is also to be noted that some details in the drawings may be exaggerated in comparison with other details. Furthermore, some of the drawings have been simplified by removing some details relating to the rotational symmetry of the bearing assembly.
In the drawings, similar, or equal elements are referred to by equal reference numerals. If not stated or illustrated otherwise, the described embodiments are arranged in a similar or corresponding manner.
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According to exemplifying embodiments, the shaft is support by a 3-point or 2-point suspension/support configuration comprising, in addition to the bearing arrangement 61, additional non-locating and/or locating bearings. The additional bearings may e.g. be located integrated with and/or adjacent to the gear box.
It should be noted that the invention has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims. For example, bearing assembly may also used with and/or integrated with other applications comprising rotating shafts, such as gear boxes, propeller/impeller/turbine shafts, hub units, such as wheel or rotational hub units, process applications, construction applications, construction vehicle solutions, drive train applications, actuator applications comprising rotatable members/shafts, etc., or combinations.
It is further noted that, 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. A single apparatus or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain features or method steps are recited in mutually different dependent claims does not indicate that a combination of these features or steps cannot be used to advantage
| Number | Date | Country | Kind |
|---|---|---|---|
| 1200103.8 | Feb 2012 | SE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/SE2013/000024 | 2/18/2013 | WO | 00 |
