Patent Application
20200102939
The following relates to a bearing arrangement for a wind turbine, to a wind turbine and to a method for manufacturing the bearing arrangement.
In wind turbines, bearing arrangements are used to support, for example, the main shaft connecting the rotor to the generator. The main shaft is subjected to substantial loads during the operation or the wind turbine. For this reason, main shafts typically have a diameter of 1 m and larger.
Prior art bearing arrangements typically have one of two configurations explained hereinafter.
According to a first configuration, the two bearings supporting the main shaft are housed in separate bearing housings. Each bearing housing is bolted to the bed frame inside the nacelle of the wind turbine.
According to a second configuration, the two bearings supporting the main shaft are housed in a single housing. The single housing is bolted to the bed frame.
Disadvantages associated with the first configuration are that it is weak in bending around a horizontal axis running at right angles with respect to the axis of rotation of the main shaft. The second configuration is disadvantageous in that it is difficult to access the bearings and corresponding seals, for example, for maintenance purposes.
An aspect relates to an improved bearing arrangement, an improved wind turbine and an improved method for manufacturing a bearing arrangement.
Accordingly, a bearing arrangement for a wind turbine is provided. The bearing arrangement comprises a bed frame, a support structure mounted to the bed frame, a shaft, bearings supporting the shaft rotatably around a shaft axis, and bearing housings supporting one of the bearings respectively, wherein the bearing housings are mounted to opposite faces of the support structure, the faces facing in the axial direction with respect to the shaft axis.
By providing the support structure, the stiffness in bending about a horizontal axis perpendicular to the shaft axis is increased. The stiffness of the bearing arrangement is in particular enhanced by connecting the bearings to each other by use of the support structure, and connecting the support structure to the bed frame to thus form a single unit. Said single unit transfers, preferably, all rotor bending loads to the bed frame.
Having the bearing housings mounted on the axial faces of the support structure also allows for a more uniform support of the bearing housings, the support being distributed around the entire circumference of each bearing housing or at least a portion thereof instead of the traditional point support.
At the same time, due to the bearing housings being mounted on the axial faces of the support structure, the bearings and corresponding seals are easily accessible. This simplifies assembly and serviceability, in particular, replacement of bearing seals.
Preferably, the support structure is mounted to the bed frame by a plurality of bolts.
The shaft can have, for example, a diameter larger than 1 m.
The bearings may be configured as roller bearings or sliding bearings. Spherical bearings are preferable.
For example, two or more bearings are provided. For example, one of the bearings is a fixed bearing and the other bearing is a floating bearing.
The shaft axis may be orientated horizontally or substantially horizontally. This is to include deviations of up to 20° from the horizontal axis.
The faces of the support structure are, preferably, ring-shaped. The ring has a circular shape, preferably. Preferably, the bearing housings each lie directly against a respective face. Bolts fastening the bearing housing may extend through a respective bearing housing into a corresponding face.
In other embodiments, the bolts are fastened at locations adjacent to a respective face. Such locations may be formed as threaded holes arranged on a circular line. Said circular line has a diameter, for example, larger than the outer parameter of the corresponding face.
The bearing housings may be exclusively connected to the bed frame via the support structure. That is to say that any flow of forces from the bearing housings to the bed frame runs via the support structure. There is no other connection between the bearing housings and the bed frame.
A wind turbine is an apparatus to convert the wind's kinetic energy into electrical energy. The wind turbine comprises, for example, a rotor having one or more blades, a nacelle comprising the bearing arrangement and a tower holding, at its top end, the nacelle.
According to an embodiment, the faces are arranged at opposite ends of the support structure.
This makes access to the bearing housings, and therefore to the bearings even more easy.
According to a further embodiment, the faces face away from a geometric center of the support structure.
The geometric center can be determined, for example, when looking at a cross-section through the support structure along the shaft axis. The geometric center can be the point in which a first and a second line of symmetry intersect. The first line of symmetry is, for example, colinear with the shaft axis. The second line of symmetry is, for example, a line orientated perpendicularly with respect to the shaft axis.
According to a further embodiment, the bearing housings are bolted to the faces, preferably with bolts extending parallel to the shaft axis.
Such bolts are easy to access, for example when doing maintenance work on the bearings.
According to a further embodiment, the shaft extends through the support structure.
For example, the shaft will connect the rotor of the wind turbine with a generator of the wind turbine. The support structure being arranged between the rotor and the generators will therefore only extend along the shaft for a portion of the shaft's total length.
According to a further embodiment, a cross-section of the support structure, taken on a line perpendicular to the shaft axis, has a closed geometry. An example of a cross-section having a closed geometry is a ring shape or polygon shape. A circular ring shape may be preferable.
This configuration of the support structure increases bending stiffness further.
According to a further embodiment, the support structure has radial openings.
Such radial openings may reduce the weight of the support structure, while only marginally reducing its bending stiffness.
According to a further embodiment, the support structure is made from cast iron.
Thereby, the support structure is cheap to manufacture.
According to a further embodiment, the support structure is made from one piece, i.e. it is formed integrally.
Thus, the support structure is easy to manufacture and stiff. In other embodiments, the support structure may be made, for example, of two pieces, which are bolted together. For example, the two pieces may be formed as an upper and a lower casing, each casing having a semi-circular cross-section, for example.
According to a further embodiment, the bearing housings are made from steel.
For example, the bearing housings may be machined from a steel blank or made by forging. The steel may be a high alloy steel. Using such steel housings significantly reduces the risk of fretting and eliminates the need for sleeves, coatings etc.
According to a further embodiment, the support structure is connected to the bed frame by one or more feet. Preferably, the above-mentioned flow of forces goes through said feet.
According to a further embodiment, the bed frame is connected to a yaw bearing. Thereby, the bed frame is supported rotatably. For example, the yaw bearing may be in turn connected to a tower of the wind turbine.
According to a further aspect, a wind turbine comprising the bearing arrangement as described herein is provided.
According to an embodiment, the wind turbine comprises a rotor and a generator. The shaft of the bearing arrangement connects the rotor with the generator.
This includes arrangements where the shaft is coupled using a coupling, for example a shrink disc coupling, to a gearbox. The gearbox in turn may be connected to the generator by another shaft. Hence, the shaft may be connected to the generator directly or indirectly.
According to a further aspect, a method for manufacturing the bearing arrangement previously described, said method comprising
a) making the shaft stand with its shaft axis being orientated vertically, and
b) lowering the support structure over the shaft and mounting the bearings to the opposite faces of the support structure by the bearing housings.
According to an embodiment, prior to step b), the bearings are mounted to the vertically orientated shaft, in particular by heat-shrinking.
According to an embodiment, a first of the bearing housings is mounted to a lower one of the bearings, the support structure is lowered over the shaft onto the first of the bearing housings, a second of the bearing housings is mounted to an upper one of the bearings and/or the second of the bearing housings is mounted to the support structure.
In particular, the first of the bearing housings is mounted to a lower one of the bearings, thereafter the support structure is lowered over the shaft onto the first of the bearing housings, thereafter the second of the bearing housings is mounted to an upper one of the bearings and thereafter the second of the bearing housings is mounted to the support structure.
Embodiments presently described with regard to the bearing arrangement equally apply to the method for manufacturing said bearing arrangement, and vice versa.
Further possible implementations or alternative solutions of embodiments of the invention also encompass combinations—that are not explicitly mentioned herein—of features described above or below with regard to the embodiments. The person skilled in the art may also add individual or isolated aspects and features to the most basic form of embodiments of the invention.
Some of the embodiments will be described in detail, with references to the following Figures, wherein like designations denote like members, wherein:
The wind turbine 1 comprises a rotor 2 connected to a generator 38 arranged inside a nacelle 3. The nacelle 3 is arranged at the upper end of a tower 4 of the wind turbine 1.
The rotor 2 comprises, for example, three rotor blades 5. The rotor blades 5 are connected to a hub 6 of the wind turbine 1. Rotors 2 of this kind may have diameters ranging from, for example, 50 to 160 meters or even more. The rotor blades 5 are subjected to high wind loads. Accordingly, high loads act on a main shaft (not shown in
The main shaft 9 connects the hub 6 (see
The main shaft 9 may be configured as a hollow shaft and may comprise a flange 12 for connecting to the hub 6 (see
The bearing arrangement 7 further comprises a support structure 17 which is, for example, made of cast iron.
According to the embodiment and best seen in
The support structure 17 has a cross-section (taken along a line perpendicular to the shaft axis 8) which is of a circular ring shape, thus defining a hollow space 20 inside through which the main shaft 9 extends. A wall thickness t of the support structure 17 may vary, for example, along the shaft axis 8.
Also, the support structure 17 may comprise through holes in its walls to reduce weight. One such through hole is shown in
At its respective ends 18, 19, the support structure 17 has faces 22 and 23. The faces 22, 23 face in opposite directions denoted by x and −x along the shaft axis 8. The faces 22, 23 have a circular ring shape. The faces 22, 23 face away from geometric center G of the support structure 17. In the example, the geometric center G of the support structure 17 is at the intersection of lines of symmetry S1, S2 about which the support structure 17 is symmetric. The line S1 is coaxial with the shaft axis 8. The line S2 runs at right angles with respect to the line S1. The geometric center G may well be defined otherwise.
The support structure 7 further comprises bearing housings 24, 25. The bearing housings 24, 25 are made from steel, in particular high alloy steel. The bearing houses 24, 25 may be machined or forged. Each bearing housing 24, 25 supports a bearing 26, 27 inside.
The bearings 26, 27 may be formed as gliding bearings or roller element bearings, in particular spherical bearings. One bearing, for example the bearing 25, may be formed as a fixed bearing, whereas the other bearing, for example, the bearing 24, is formed as a floating bearing.
At least one of the bearing housings 24, 25 may comprise a shoulder 28 or other means to hold the bearing 26, 27 in place along the shaft axis 8. Therein, the bearing housings 24, 25 support a respective outer race 29 of each bearing 24, 25. A respective inner race 30 is fixed to the main shaft 9. The inner races 30 may be fixed to the main shaft 9 by, for example, heat shrinking, as explained in more detail with regard to
The bearing housing 24 is bolted to the face 22, and the bearing housing 25 is bolted to the face 23 of the support structure 17. For example, each bearing housing 24, 25 has a number of holes formed therein. The holes are, for example, spaced apart along a circular line C (when seen in a direction along the shaft axis 8—see
Returning now to
The shaft 9 thus runs for a portion of its length through the support structure 17, while being supported by the bearings 26, 27 at opposite ends of the support structure 17. Thus, when a bending moment is applied to the main shaft 9, the bearings 26, 27, the bearing housing 24, 25 and the support structure 17 form a stiff unit counter-acting said moment. All forces resulting from said moment are transferred via the feet 35, 36 of the support structure 17 into the bed frame 13. There is no single point support of the bearings 26, 27 directly at the bed frame 13. Thus, all forces need to flow through the feet 35, 36.
At the same time, the bearing housings 24, 25 and thus the bearings 26, 27 are easily accessible from the outside, for example, to do maintenance, such as replacing seals on the bearings 26, 27.
In a first step 100, the main shaft 9 is made to stand upright with its shaft axis 8 being orientated vertically. For example, in this position, the main shaft 9 stands on its flange 12 serving as a foot on a factory floor.
In a step 200, the bearings 26, 27 are each heated and then moved, from above, down along the shaft axis 8 into their respective locations. At those locations, the bearings 26, 27 cool down and are thus heat-shrunk onto the main shaft 9. To this end, the lower bearing 26 has a larger inner diameter than the upper bearing 27.
In a step 300, the bearing housing 24 is fitted to the lower bearing 26.
In a step 400, the support structure 17 is lowered from above (held there, for example, with a crane) down along the shaft axis 8 until the lower face 22 comes to lie against the bearing housing 24. For example, at this position, the lower bearing housing 24 is connected by the bolts 32 to the support structure 17 (step 500).
In a step 600, the upper bearing housing 25 is fitted to the upper bearing 27. At this time, the upper bearing housing 25 lies against the upper face 23 of the support structure 17. Thereafter, the upper bearing housing 25 is bolted by bolts 32 to the support structure 17 (step 700).
In a step 800, the unit made up of the main shaft 9, the support structure 17, the bearing housings 24, 25 and the bearings 26, 27 is turned into a horizontal position and lifted onto the bed frame 13. In this position, the feet 35, 36 of the support structure 17 are bolted by the bolts 37 to the bed frame 13. Thereafter, the coupling 10 is fitted to the main shaft 9. Then, the gearbox 11 is mounted on the bed frame 13 and connected to the coupling 10.
Although the invention has been illustrated and described in greater detail with reference to the preferred exemplary embodiment, the invention is not limited to the examples disclosed, and further variations can be inferred by a person skilled in the art, without departing from the scope of protection of the invention.
For the sake of clarity, it is to be understood that the use of “a” or “an” throughout this application does not exclude a plurality, and “comprising” does not exclude other steps or elements.
