Wind turbine with a bearing unit for an elongated rotor blade

Abstract

Wind turbine with a bearing unit (1; 1') as a blade bearing for the rotatable connection of an elongated rotor blade (2) to a rotor hub (3) comprising the bearing unit (1; 1'): - at least two axially offset raceways (22, 23, 37) with rotating rolling elements (24, 25), which connect to two annular connecting elements (13, 14; 13', 14') rotatable relative to each other, for indirect or direct connection to the rear end (5) of the rotor blade (2) on the one hand and to the rotor hub (3) on the other hand, wherein - the annular connecting elements (13, 14; 13', 14') have opposite end faces (15, 16) which serve as connection surfaces to the rotor hub (3) on the one hand and to the respective rotor blade (2) on the other hand, and - between the two connecting elements (13, 14; 13', 14') an annular gap is formed, sealed in the area of ​​the two connecting surfaces, wherein - the rolling elements (24, 25) of two axially offset raceways (22, 23, 37) have an approximately cylindrical shape, each with a cylindrical surface (26) that is rotationally symmetric to exactly one axis of rotation (31), wherein - these rolling elements (24, 25) are aligned such that their respective axes of rotation (31) are aligned approximately perpendicular to exactly one longitudinal axis of the respective rotor blade (2), and wherein a projecting, circumferential nose (21; 21') is provided on the outer surface of a connecting element (14; 13') facing the other connecting element (13; 14'), wherein the two annular side surfaces (22, 23) of the nose (21; 21') serve as running surfaces for the approximately cylindrical rolling elements (24, 25) of each row of rolling elements, wherein the rolling elements (24, 25) roll without play between the side surfaces (22, 23) of the nose (21) on the one hand and the side surfaces (37) of a circumferential recess (36) of approximately rectangular cross-section provided on an outer or inner surface of the connecting element (13, 14), and where - the rotor blade (2) is designed as a shell surface (4) surrounding an inner cavity, which transitions at the rear end (5) of the rotor blade (2) into a cylindrical shell shape up to a flat, rear connection surface (6), wherein blind holes (7) are provided which, on the one hand, lead to each anchoring body (8) made of a hard material inserted into the rotor blade (2), in which they continue as internal threaded holes, and which, on the other hand, correspond with ring-shaped distributed through holes (17) in the respective connection element (13, 13') in terms of number, diameter and orientation such that they are aligned and thereby allow the insertion of each stud bolt (19), and - a hydraulic cylinder or a drive unit (47) which, irrespective of whether the wind turbine is in operation or not, or whether the wind turbine is stationary or not, or whether the rotor blades need to be adjusted or not, continuously and periodically rotates the rotor blade (2) relative to the rotor hub (3) about its longitudinal axis.

Description

[0001] The invention is directed to a wind turbine with a bearing unit for an elongated rotor blade, with two mutually rotatable, annular elements for indirect or direct connection to a rotor blade hub on the one hand and to the rotor blade on the other hand and with at least two axially offset raceways with rotating rolling elements of approximately cylindrical shape, ie, each with a lateral surface that is rotationally symmetrical to exactly one axis of rotation (cylindrical, conical, needle or barrel shape), wherein for the complete absorption of the tilting moment resulting from the wind pressure on the rotor blade and on the bearing unit and if necessary for the absorption of further forces (blade weight, centrifugal force etc.) and other moments (for example due to the temporary inclination of a blade relative to the vertical), two axially offset raceways arranged between the two connecting elements and comprising rotating rolling elements of approximately cylindrical shape serve to absorb these moments, said rolling elements being aligned such that their axes of rotation are directed approximately radially, i.e. approximately perpendicularly, with respect to the longitudinal axis of the respective rotor blade. During operation of a wind turbine with at least one such rotor blade bearing, the respective rotor blade(s) is / are constantly rotated about its / their longitudinal axis(es).

[0002] Wind turbines – and thus particularly their rotor diameters – are becoming ever larger. Accordingly, the stress on all support and bearing units is also increasing. This also applies to the blade bearings, which are used to adjust the blade pitch and allow adaptation to different wind speeds, both for optimal power control and in the form of storm wind shutdown. The greatest stress here is the tilting moment, which the wind load concentrated in the center of pressure (Cp, approximately midway along the rotor blade length) exerts on the blade bearings. With regard to this tilting moment, the blade bearings are to be considered the pivot point, and due to the considerable lever arm, the wind load results in very high bending stress on the blade root and blade bearings.The bending moments at the blade bearings are therefore far more difficult to handle than at the rotor bearings as a whole, because the bending moments generated by the rotor blades, which are mounted offset from each other by the same angle of rotation, largely compensate for each other. Furthermore, the rotor of a wind turbine is constantly rotating during torque application, so the rolling elements there are in motion and no localized permanent loads are to be feared, unlike the rotor blade bearings, which are usually only rotated to adjust the rotor blade pitch when the average wind speed changes noticeably—which is rather rare.

[0003] DE 37 32 730 A1 discloses a trunnion bearing for the rotor blades of wind turbines. In one embodiment, two bearing units are disclosed, spaced apart in the axial direction relative to the axis of rotation, each consisting of an angular contact bearing, a cylindrical roller bearing, and a needle bearing. The cylindrical roller bearing transmits radial forces and the needle bearing transmits axial forces from an outer ring unit to the outer ring of the angular contact bearing, whose inner ring transmits these forces jointly to the hub. To cope with the considerable tilting moments resulting from the wind load, two bearing units are provided. Since each such bearing unit comprises an axial bearing and a radial bearing, each tilting moment or root bending moment resulting from the wind load generates a pair of opposing radial forces (one radial force at each radial bearing) and a pair of opposing axial forces (one at each axial bearing).Since the tilting or root bending moment is distributed among forces of a comparable magnitude at all four bearing locations due to the geometric distances between the bearings, all radial and axial bearings must be designed for comparatively high loads. To reduce these loads to a tolerable level, a minimum distance must be maintained between the two bearing units, necessitating their separation. However, the use of two bearing units with a total of four bearing locations, all of which must be designed for high loads, entails increased design effort, especially since each bearing requires a separate inner and outer ring as a raceway.

[0004] US 3,652,141 relates to a bearing unit comprising two axially offset raceways with rotating rolling elements, wherein two mutually rotatable, annular elements are arranged for the indirect or direct connection of the parts to be supported, the rolling elements of two axially offset raceways having an approximately cylindrical shape, i.e. each having a lateral surface that is rotationally symmetrical to exactly one axis of rotation, and wherein these rolling elements are aligned such that their axes of rotation are directed approximately radially, i.e. approximately perpendicularly, with respect to the longitudinal axis of the respective part to be supported. A similar arrangement is shown in DE 39 09 664 C1.

[0005] DE 123 805 A and DE 37 32 730 A1 concern wind turbines, but do not show a rotor blade.

[0006] DE 956 390 B shows a rotor blade, but no details of the bearing arrangement. Instead, a rotary bearing on a shaft located upstream of the actual rotor blade is illustrated. Further technical background is DE 101 40 793 A1, DE 36 09 781 A1 DE 3 1 04 097 C2, DE 34 23 433 C2, US 4 573 811 A, US 4 463 995 A, US 4 422 697 A, CA 2 536 058 A1, DE 197 39 164 A1, EP 1 286 048 A1, US 3 652 141 A EP 1 259 741 B1, DE 20 11 141 A1, DE 26 48 144 A1, EP 0 238 725 A2, DE 3 0 09 922 A1, EP 1 286 048 A1 can be found.

[0007] Erich Hau: “Windturbines”, Springer Verlag, pages 138-139, 228-234, 330, 457-459: In Fig. Section 8.15 on page 234 shows a rotor blade bearing arrangement with angular contact cylinder and crossed roller bearings. Section 7.5 shows rotor blades made of fiber-reinforced composite materials. Fig. 7.14 on page 202 shows a typical rotor blade design. The rotor blade shown has a shell surface surrounding an inner cavity, which at the rear end of the rotor blade transitions into a cylindrical shell-shaped profile until it reaches a flat, rear connection surface. Section 7.7 on page 207 shows a cross-bolt connection, shown in the Fig. 7.20. The rear connection surface is provided with holes that lead to an anchoring body made of a hard material inserted into the rotor blade, where they continue as internally threaded holes. Fig. Figure 7.22 shows that the holes are arranged in a ring pattern. According to Section 15.2.2 on pages 457 to 459, the angle of attack of the rotor blades is adjusted accordingly during rotation to further increase the efficiency of the wind turbine.

[0008] Erich Hau: “Wind turbines: Basics, technology, application, economic efficiency”, 2nd edition, Springer Verlag, pages 1, 2, 81-83, 198-209, 232-235, shows in Fig. 8.15, that the rolling elements of the two axially offset raceways are aligned such that their axes of rotation are directed radially and perpendicularly with respect to the longitudinal axis of the rotor blade in question. Fig. Figure 8.15 also shows that the two connecting elements are arranged concentrically within each other and that the holes are also arranged in a ring shape. Fig. Figure 8.15 shows that the annular gap between the connecting elements is sealed, and that the inner connecting element has a protruding nose facing the other connecting element. The nose serves as a running surface for the two rows of rolling bearings.

[0009] In Fig. 8.15, the raceways run along flat circular surfaces perpendicular to the longitudinal axis of the rotor blade, and a third bearing location is arranged between the two raceways and between the outer surfaces of the connecting elements. This third bearing location has rolling elements with an axis of rotation parallel to the longitudinal axis of the rotor blade. These rolling elements are smaller than the rolling elements of the other bearings. This document lists theoretical possibilities for using certain bearing types and disregards the disadvantages of individual bearing types. It describes that multi-row cylindrical roller bearings, although they allow for high moment loads, are complex and expensive; whereas a similar load capacity can be achieved at significantly lower cost with ball bearings.

[0010] EP 1 398 499 A1 relates to a wind turbine with a rotor and three rotor blades attached to the rotor. The rotor blades are each made of a fiber-reinforced composite material and have a blade profile shape that is tubular in the area of ​​a rotor blade connection for attachment to the rotor. In the area of ​​the rotor blade connection, the rotor has a flange section provided with through-holes. Blind holes aligned with the through-holes are arranged in the lateral surface of the rotor blade. The blind holes lead to an anchoring body inserted into the rotor blade. The blind holes and the through-holes are each arranged in a ring-like manner.

[0011] WO 20 0 1 / 426 47 A2, DE 3 1 04 097 C2, DE 34 23 433 C2, US 4 573 811 A, US 4 463 995 A, US 4 422 697 A relate to the use of anchoring elements, blind holes and through holes for fastening a rotor blade to a rotor unit.

[0012] US 3 81 488 A shows filler material in the annular gap between the two bearing parts.

[0013] Dubbel's "Handbook for Mechanical Engineering," 20th edition, Springer Verlag, pages G80 to G106, covers, among other things, rolling elements with transition areas or crowns, and rolling elements with rounded end faces in the chapter "Rolling Bearings," pages G80 to G84. The guide ribs should allow only the smallest possible axial play and be as tightly constructed as possible. Fig. 2 on page G80 and Fig. 4 on page G81, spacers are known which are arranged between the rolling elements.

[0014] DE 42 02 098 A1 relates to a bearing with hollow rolling elements, wherein the rolling elements are connected to one another by connecting elements engaging at the end face and are integrated into a cage.

[0015] The disadvantages of the described prior art give rise to the problem initiating the invention of creating a rotor blade bearing for wind turbines which can permanently meet the special requirements of such components, in particular the much higher tilting moment under strong wind loads than, for example, on the rotor bearings, and can withstand the relatively difficult load case with a long operating time.

[0016] This problem is solved in a generic wind turbine with a bearing unit by the features of patent claim 1. Here, two ring-shaped elements which can be rotated relative to one another are provided for direct or indirect connection to the rotor blade hub on the one hand and to a rotor blade on the other; wherein the rolling elements of two axially offset raceways have an approximately cylindrical shape, i.e. each with a shell surface which is rotationally symmetrical to exactly one axis of rotation (cylindrical, conical, needle or barrel shape); and wherein in order to fully absorb the tilting moment resulting from the wind pressure on the rotor blade and acting on the bearing unit (and if necessary to absorb other forces such as blade weight, centrifugal force, etc., and / or moments, e.g.due to the temporary inclination of a rotor blade relative to the vertical), two raceways arranged between the two connecting elements and axially offset from one another with rotating rolling elements of approximately cylindrical shape serve, these rolling elements being aligned in such a way that their axes of rotation are directed approximately radially, i.e. approximately perpendicularly, with respect to the longitudinal axis of the rotor blade in question.

[0017] Due to the alignment of the longitudinal axes of these rolling elements, they do not transmit any radial forces, but only axial forces. The two pairs of raceways for the rolling elements are arranged on the two mutually rotatable connecting elements in such a way that one row of rolling elements can transmit axial compressive forces in one direction, while the other row can transmit the same compressive forces diametrically opposite and in the opposite direction along the common axis of rotation. This arrangement is based on the fact that a rotor blade also has a considerable diameter of, for example, 2 m to 3 m, with the pivot points on the blade bearing for the tilting moment resulting from the wind load being located approximately on a line passing through the central longitudinal axis of the rotor blade and running perpendicular to the rotor axis. It is therefore not necessary to provide two additional radial bearings.In addition, the strong tilting moment triggered by the wind results in a bending moment at the root of the rotor blade around these pivot points or around their connecting line, which manifests itself as axial tensile forces in the areas of the blade bearing offset by 90° from the line defining the pivot points or - on the opposite side - as axial compressive forces. These axial forces are absorbed by the two bearing points according to the invention. The tilting moment generated by the wind pressure is supported exclusively by an axial force couple. This prevents the creation of radial forces that would expand the bearing rings radially and complicate sealing. This advantage is achieved precisely by omitting a pair of radial bearings. Furthermore, thanks to the invention, it is possible to dispense with angular contact bearings even on the blade bearings, which are rarely adjusted and therefore very unfavorable in terms of load. Furthermore, no axle journal is required.Since the tilting moment is completely supported by the axial force couple, a second bearing unit is not required, which significantly reduces the number of parts and thus also the vulnerability of the bearing unit; the design is extremely compact, and mutual adjustment of several bearing points is no longer necessary.

[0018] As the two connecting elements are arranged concentrically within each other, the two bearing points, which are offset from each other in the axial direction, both find space between the connecting elements.

[0019] It has proven advantageous for the two connecting elements to each have mounting holes arranged in a ring. These can be threaded blind holes or, preferably, through holes for screws, bolts, or similar components that are screwed into or anchored to a rotor blade or the rotor hub.

[0020] According to the invention, opposite end faces of the annular connecting elements serve as connecting surfaces to the rotor blade hub on the one hand and to the respective rotor blade on the other. This allows the bearing unit to be inserted between these two components.

[0021] Since the annular gap between the two connecting elements is sealed in the area of ​​the two connecting surfaces, the rolling elements run in a space completely sealed off from the environment. This protects them from the influence of, for example, salty and thus corrosive sea air, prevents dust penetration, and retains grease or other lubricants in the area of ​​the rolling elements.

[0022] Further advantages arise from the fact that at least one connecting element has at least one projecting, circumferentially extending nose on the shell side facing the other connecting element. An axial force can be introduced into the respective connecting element via its side surfaces.

[0023] Continuing this inventive concept, it can also be provided that the axial extension of the nose corresponds to the axial distance between the rolling elements of the two bearings. This makes it possible to use or design the two annular side surfaces of the nose as a running surface for the approximately cylindrical rolling elements of each bearing location.

[0024] The invention proposes that the raceways for the approximately cylindrical rolling elements run along approximately flat circular ring surfaces, which are traversed approximately perpendicularly by the longitudinal axis of the respective rotor blade. Flat surfaces are easier to manufacture than curved surfaces; on the other hand, the bearings in question only transmit axial forces in the invention, so there is no need to provide the raceways with a curvature or to construct them at a (large) angle, e.g., on the order of approximately 45°, to the longitudinal axis of the respective rotor blade, as is the case with double angular contact roller bearings.

[0025] The bearing according to the invention preferably has at least one third bearing point, which is inserted between two mutually facing lateral surfaces of the two connecting elements. In contrast to the previously described bearings, the latter is responsible for transferring the wind pressure, also associated with the wind load, from the respective rotor blade to the rotor hub. Although the load on the bearing caused by the wind force itself is significantly lower than the load caused by the tilting moment resulting from the wind load, it cannot be neglected because the bearings according to the invention, with their approximately cylindrical rolling elements, cannot transmit radial forces. Instead, the additional bearing serves this purpose.

[0026] The invention prefers an arrangement in which the third bearing location is located between the two raceways for approximately cylindrical rolling elements, which are aligned such that their rotational axes are oriented approximately radially with respect to the longitudinal axis of the respective rotor blade. The result is a very space-saving design, as the third or additional bearing location is placed axially between the first two, particularly in the region of a nose between the first two bearings.

[0027] The third bearing location can also be designed as a rolling bearing to ensure the smoothest possible rotor blade adjustment, with the rotational axes of its rolling elements being approximately parallel to the longitudinal axis of the rotor blade. On the other hand, since the forces to be transmitted by the third bearing are lower than those of the first two described, a rolling element of the third bearing can have a smaller volume than a rolling element of one of the bearings with the rolling elements oriented approximately radially with the rotational axis relative to the longitudinal axis of the rotor blade.

[0028] On the other hand, it is also possible to design the third bearing point as a plain bearing. Since this bearing is subjected to comparatively low forces, it also does not generate significant frictional forces.

[0029] A further consequence of the lower load on the third or additional bearing point is that the effective width of the raceway or sliding surface of a bearing point which is inserted between two mutually facing lateral surfaces of the two connecting elements can be dimensioned smaller than the effective width of a raceway which comes into contact with a rolling element whose axis of rotation is directed approximately radially with respect to the longitudinal axis of the rotor blade in question.

[0030] In order to facilitate the assembly of the two annular connecting elements together with the rolling elements arranged between them and, if necessary, spacers or rolling element cages, the invention recommends that a connecting element be designed in a manner divided along a plane oriented approximately perpendicular to the longitudinal axis of the rotor blade, so that the two halves can be removed from each other for inserting the rolling elements.

[0031] In order to ensure that the rolling elements are aligned parallel to the raceways with as little jamming as possible, especially under load, the cross-section of the raceways provided for the insertion of rolling elements is designed in such a way that, at least in some regions, it does not correspond to the longitudinal section of a rolling element to be inserted there, but is preferably narrower in the axial direction and is thus preloaded against the rolling elements. If the raceway then widens - on the one hand under the influence of the rolling elements themselves, but on the other hand possibly also under load - it still rests positively on the rolling elements so that they cannot jam. For this purpose, the axial extent of the cross-section of the raceways provided for the insertion of rolling elements is selected to be smaller, at least in some regions, than the diameter of the corresponding section of a rolling element.

[0032] To increase the service life of the bearing according to the invention, the rolling elements, whose rotational axes are directed approximately radially with respect to the longitudinal axis of the respective rotor blade, should have at least one cambered transition area between the outer surface and at least one adjacent end face, i.e., a flattened or rounded portion. This tolerates edge pressure against the raceway during elastic deformation of the bearing unit during operation, by ensuring a sufficient contact area with the raceways in the area of ​​the rounded transition.

[0033] Another measure for reducing wear in the bearing arrangement according to the invention consists in the rolling elements, whose rotational axes are directed approximately radially with respect to the longitudinal axis of the respective rotor blade, having at least one dome-shaped end face. This increases the sliding surface area because the radially outer end faces of a rolling element slide along the inside of the connecting element there and are therefore subject to only minimal wear. In this sense, it is advantageous if the radius of curvature of the dome-shaped end face is approximately equal to or smaller than the radius of the inside of the outer ring.

[0034] Increasing the elasticity of the rolling elements also reduces wear, as they can then elastically yield at least to a limited extent under high loads and thus high elastic deformation of the bearing unit and then spring back without permanent deformation. Elasticity is increased, for example, by designing the rolling elements as hollow bodies, whose axes of rotation are aligned approximately radially with respect to the longitudinal axis of the rotor blade in question. This can be achieved, for example, by coaxial drilling along their axis of rotation. The elasticity can be precisely adjusted depending on the thickness of the bore or the remaining shell.

[0035] Such cavities can be used to guide adjacent hollow rolling elements together using end-face connecting elements, thus maintaining a defined distance between them. These connecting elements engage, at least partially, in the cavities of the rolling elements. In the simplest case, they can, for example, take the form of C-shaped clamps, the ends of which engage in a central or coaxial bore of two adjacent roller- or roughly cylindrical-shaped rolling elements.

[0036] Such connecting elements, in turn, offer the possibility of being combined to form one or more cages or cage segments. Such cage segments, for example, extend only over a limited central angle and not over the entire circumference of a row of rolling elements, and / or they encompass the rolling elements on their inner or outer end faces, or on both sides.

[0037] Alternatively, a spacer can be inserted between adjacent rolling elements, each with a radial cross-section that is smaller than or equal to the radial cross-section of a rolling element. In this case, the rolling elements themselves can be longer and thus designed with a maximum volume, allowing greater forces to be transmitted, since no space is lost for a cage within a specified installation space.

[0038] In a first embodiment of the invention, no toothing is provided on any connecting element; in this case, the rotor blade adjustment is carried out by means of a hydraulic cylinder that is pivoted on the rotor blade eccentrically to its longitudinal axis and supported on the rotor hub, or vice versa.

[0039] Otherwise, for the purpose of rotor blade adjustment, a toothing is also provided on a connecting element, preferably on the inside of the inner ring, for engagement of a toothed output element of a drive motor, e.g. a pinion.

[0040] A constant, i.e., uninterrupted (small) rotation of the rotor blades supports the rotor blade bearing system according to the invention by allowing the lubricating film between the rolling elements and the running surfaces to continuously regenerate, thus preventing temporary dry running. This is especially true in the case where the blade pitch angle hardly changes under constant wind conditions, and the blade bearings thus remain in one position.Even with such a quasi-constant blade pitch angle, adverse raceway wear can occur in the blade bearings, since when the rotor blade passes the tower, a tilting moment load acts on the stationary (non-rotating) blade bearings due to aerodynamic suction and pressure. Without the method according to the invention, this load would eliminate the lubricating film between the rolling elements and the raceway and then raceway damage would occur due to so-called "false brinelling", i.e. degeneration of the raceway due to high Hertzian pressure of the rolling elements on the raceways) as a result of changing loads repeatedly acting on the rolling bearing, which quickly lead to the displacement of the lubricating film when the rolling bearing is at a standstill.

[0041] This so-called "false brinelling" occurs when the wind turbine is shut down for whatever reason, e.g., during maintenance / repair work or during a storm, and the rotor and blades slowly rotate freely ("freewheeling") without generating electrical energy. In this case, too, the application of the method according to the invention during wind turbine downtime can prevent or prevent raceway damage caused by false brinelling.

[0042] A further advantage of the method according to the invention is the prevention of raceway wear caused by so-called "fretting corrosion". This occurs due to elastic deformation of the bearing unit / its connecting structure and the resulting sliding movement of the rolling elements in the direction of their longitudinal axis and thus along the raceway. The method according to the invention always ensures a rolling movement of the rolling elements and thus the build-up of the necessary lubricating film between the rolling elements and the running surfaces, even when the rolling elements are exposed to adverse sliding movements along their longitudinal axis. This applies regardless of whether the wind turbine is in operation or not, or whether the rotor blades need to be adjusted or not, as long as the constant, i.e. uninterrupted (small) adjustment of the rotor blades is advantageously carried out.

[0043] The constant rotation is achieved by controlling the motor or cylinder for the rotor blade pitch. It is advisable to impose a periodic movement as the constant rotation, because the resulting oscillating movement of a rotor blade results in a particularly favorable lubricant film buildup between the rolling elements and the raceways.

[0044] The invention can be optimized by ensuring that the period of the oscillating rotation of the rotor blade corresponds to the rotational period of the wind turbine. This achieves a mutual equalization of the loads caused by the different rotor blades, thus minimizing the resulting structural load. On the other hand, when the wind turbine is stationary (e.g., during calm conditions), the periodic movement should continue. In the lower speed range of the wind turbine, this may require decoupling the periodic adjustment from the speed of the wind turbine, for example, such that a minimum adjustment frequency is never undercut. This minimum adjustment frequency can be continued during the start-up of the wind turbine until an angular position synchronous with the angular position of the wind turbine is finally achieved, in order to subsequently adjust the angle of attack to this angular position of the wind turbine.

[0045] During the periodic rotation of a rotor blade, its angle of attack oscillates between two extreme values. Mutual compensation of different deflections of the various rotor blades can be achieved if the maximum of the periodic angle of attack deflection for all rotor blades is reached at a given angle of rotation of the respective rotor blade around the rotor axis. Such a roughly sinusoidal deflection, for example, with three rotor blades, results in the periodic deviations of neighboring rotor blades from the mean value differing from each other by 120° at any given time, or generally, i.e., with n rotor blades, by 360° / n.

[0046] Very good results can be achieved if the extremes of the periodic angle of attack deflection are reached approximately at the highest and lowest points of the rotor blade. The rotor blade angle at the highest point should correspond to a higher wind speed, while the angle at the lowest point should correspond to a lower wind speed. Indeed, wind speed is naturally greater at increasing altitude than at ground level.

[0047] Optimization of the individual blade pitch angle is achieved when the amplitude of the periodic deflection of the rotor blade pitch angle depends on the wind speed, which increases with altitude, e.g., is approximately proportional to it. With such a control system, care should be taken to ensure that the amplitude of the deflection does not fall below a lower limit, even when the wind speed or the difference between the wind speeds in the upper and lower areas of the wind turbine approaches zero (e.g., in absolute calm).

[0048] Finally, it is in accordance with the teaching of the invention that the mean value between the extreme values ​​of the twist depends on the wind speed. As before, the mean value of the rotor blade angle of attack is used to achieve optimal adaptation of the rotor blade position to the specific wind conditions. By preferably selecting the previously statically set rotor blade angle of attack as the mean value, optimal conditions are achieved for each individual rotor blade.

[0049] Further features, properties, advantages, and effects based on the invention will become apparent from the following description of some preferred embodiments of the invention and from the drawings. Herein: Fig. 1 a section through a rotor blade bearing unit according to the invention in installed state, partially broken away; Fig. 2 the blade bearing unit Fig. 1 in dismantled condition, also demolished; Fig. 3 a view of the outer surface of a rolling element of the blade bearing unit from the Fig. 1 and Fig. 2; and Fig. 4 one of the Fig. 1 corresponding view of a modified embodiment of the invention.

[0050] A blade bearing 1 according to the invention is used in wind turbines and serves there for the rotatable connection of a rotor blade 2 to the rotor hub 3,

[0051] The rotor blade 2 is typically made of fiber composite material and is designed like a wing. To save weight, the rotor blade 2 is formed as a shell surface 4 surrounding an inner cavity, which at the rear end 5 of the rotor blade 2 transitions into a cylindrical shell-shaped profile with a diameter of, for example, approximately 2 m to 3 m. Accordingly, the flat rear connection surface 6 has a circular outline. In this connection surface 6 are blind holes 7 arranged in a ring, each of which leads to an anchoring body 8 made of a hard material, e.g., iron, inserted into the rotor blade 2. The blind holes 7 continue in the anchoring bodies 8 as internally threaded holes.

[0052] The rotor hub 3 has a rigid bulge 9 with a flat, circular connecting surface 10 for each rotor blade 2, which surrounds a circular opening 11. These connecting surfaces 10 also contain blind holes 12 arranged in a ring shape, which are provided with an internal thread.

[0053] In the illustrated embodiment, the inner diameter of such a circular opening 11 is larger than the outer diameter of the rotor blade 2 at its rear end 5. Between the two connecting surfaces 6, 10 is the bearing unit 1, which has two annular, concentric, and mutually rotatable connecting elements 13, 14. Each of the two opposite end faces 15, 16 of these connecting elements 13, 14 rests fully against a respective connecting surface 6, 10.

[0054] For the secure connection of the connecting elements 13, 14 to the rotor blade 2 on the one hand and the rotor hub 3 on the other hand, through-bores 17, 18 arranged in a ring shape are provided in each of the two connecting elements 13, 14. The through-bores 17 of the inner connecting element 13 correspond in terms of number, diameter, and orientation with the blind holes 7 in the connecting surface 6 of the rotor blade 2 such that each through-bore 17 is aligned with each blind hole 7, allowing the insertion of a stud bolt 19. Once all nuts on the stud bolts 19 are firmly tightened, the inner ring 13 is firmly connected to the rear end 5 of the rotor blade 2, preferably such that the central axis of the inner ring 13 is aligned with the longitudinal axis of the rotor blade 2.

[0055] The through holes 18 of the outer connecting element 14 correspond in number, diameter, and orientation to the blind holes 12 in the connecting surface 10 of the rotor hub 3 such that each through hole 18 is aligned with each blind hole 12 and allows the insertion of a stud bolt 20. Once all nuts on the stud bolts 20 are firmly tightened, the outer ring 14 is firmly connected to the recess 9 of the rotor hub 3.

[0056] The further details of the storage unit 1 are easier to see on the illustration according to Fig. 2. Clearly visible is a circumferential, collar-shaped nose 21 with an approximately rectangular cross-section arranged on the inside of the outer connecting element 14. The circular side surfaces 22, 23 of this nose 21 serve as running surfaces for a row of rolling elements 24, 25, respectively.

[0057] Such a rolling element 24, 25 is in Fig. 3 is shown in isolation. One can see the approximately cylindrical shape with a cylindrical outer surface 26 in the central region and the cambered, i.e. rounded, transitions 27, 28 into the end faces 29, 30. All rolling elements 24, 25 are oriented such that their longitudinal axes 31 run radially to the longitudinal axis of the rotor blade 2. Accordingly, each rolling element 24, 25 has a radially outer end face 29 and a radially inner end face 30. The outer end face 29 is convexly curved outwards, specifically in a dome-shaped manner. The radius of curvature of this dome-shaped elevation corresponds approximately to the inner diameter of the outer ring 14 laterally next to the nose 21 or axially offset relative to it, or is slightly smaller than the latter. Therefore, in the area of ​​the circumference 27 of this end face, there is no contact with the inside of the outer ring 14 and therefore no friction.For this purpose, additional circumferential recesses 32 can be provided at the relevant locations on the outer ring 14.

[0058] The radial extension of the nose 21 relative to the bearing rotation axis corresponds approximately to the length of a rolling element 24, 25. In the inner end face 33 of the nose 21, a raceway 34 in the form of a groove-shaped recess is provided for another bearing location 35, which is preferably also constructed in the manner of a cylindrical roller bearing. The width of this raceway 34 is smaller than the width of the raceways 22, 23 of the other two bearing locations 24, 25.

[0059] The radially inner connecting element 13 has a circumferential recess 36 of approximately rectangular cross-section on its outer side. While the depth of this recess 36 corresponds approximately to the length of a rolling element 24, 25, its width results from the sum of the diameters of a rolling element 24 of the upper bearing point facing the rotor blade 2 and a rolling element 25 of the lower bearing point facing the rotor hub 3, plus the axial extent of the nose 21 located between them. If this condition is met as precisely as possible, the rolling elements 24, 25 roll without play between the side surfaces 22, 23 of the nose 21 on the one hand and the side surfaces 37 of the recess 36 on the other.

[0060] The depression 36 is delimited laterally and in the axial direction by a collar-shaped nose 38, 39 projecting radially outwards. Between these and the corresponding areas of the inner side of the outer ring there is an annular sealing element 40, 41.

[0061] The inner ring 13 is divided into two halves, an upper 43 and a lower 44, along a center plane 42 through which the bearing rotation axis passes perpendicularly. These halves 43, 44 are separated from each other during assembly of the blade bearing 1 and are reassembled only after the rolling elements 24, 25, and 35 have been inserted and secured to each other by means of axially directed screws 45. One of the two halves 43, 44 also contains the radially inner running surface for the third bearing position 35.

[0062] The rolling elements 24, 25, 35 of each rolling bearing are kept at a distance by inserted spacer elements or by cages.

[0063] The rolling elements 24, 25, whose longitudinal or rotational axes 31 are oriented radially with respect to the bearing rotation axis, primarily serve to transmit relatively high tilting or blade root bending moments caused by wind pressure on the rotor blade 2. The smaller rolling elements 35 transfer the wind pressure from the rotor blade 2 to the blade hub 3.

[0064] In this embodiment, a change in the rotor blade pitch angle is achieved, for example, by a hydraulic cylinder that is hinged to the rotor blade 2 on the one hand and the rotor hub 3 on the other. This cylinder is preferably continuously adjusted so that the rolling elements 24, 25, 35 are constantly moving, thereby maintaining the lubricating film covering them.

[0065] In Fig.Figure 4 shows another bearing unit 1' with an alternative mechanism for changing the rotor blade pitch angle. For this purpose, an internal toothing 46 is provided on the inside of the inner ring 13'. A drive unit 47 is secured on the housing side in the recess 11 of the bulge 9 of the rotor hub 3, while an output pinion 48 meshes with the internal toothing 46. This rotates the inner ring 13' and, with it, the rotor blade 2 relative to the rotor hub 3. The drive unit 47 can consist of a motor 49, a downstream gear 50, and a brake 51. Preferably, the motor 49 is also constantly adjusted in order to maintain the lubricating film on the rolling elements 24, 25, 35.In order to avoid having to assemble the ring carrying the internal toothing 46 from several parts, which would entail additional adjustment problems, in this embodiment 1' the subdivision 42' is provided on the outer ring 14' and not on the inner ring 13'; accordingly, the central nose 21' is located on the outside of the inner ring 13' instead of on the inside of the outer ring 14'.

[0066] The invention allows for a number of further modifications; for example, the inner ring 13 can be fixed to the rotor hub 3 and the outer ring 14 to the rotor blade 2. The rings 13, 14 can be offset from one another in the axial direction or have different axial extensions. Some or all of the through holes 17, 18 can be replaced by blind holes.

[0067] The outer ring 14 attached to the hub 3 may have a depression 36 if, conversely, the inner ring 13 has a nose 21.

[0068] The outer ring 14 could have an external toothing similar to that of the inner ring 13', 46 and be connected to the rotor blade 2 if, conversely, the inner ring 13 were connected to the rotor hub 3.

[0069] The ring 44 could be connected to the rotor blade 2 if, conversely, ring 43 served as a support surface for the nut of the stud bolt 19.

[0070] Instead of the studs 19, 20, screws, especially machine screws, could be used.

Claims

[1] Wind turbine with a bearing unit (1; 1') as a blade bearing for the rotatable connection of an elongated rotor blade (2) to a rotor hub (3), the bearing unit (1; 1') comprising: - at least two axially offset raceways (22, 23, 37) with rotating rolling elements (24, 25), which have two mutually rotatable, annular connecting elements (13, 14; 13', 14') for indirect or direct connection to the rear end (5) of the respective rotor blade (2) on the one hand and to the rotor hub (3) on the other hand, wherein - the annular connecting elements (13, 14; 13', 14') have mutually opposite end faces (15, 16) which serve as connecting surfaces to the rotor hub (3) on the one hand and to the relevant rotor blade (2) on the other hand, and - an annular gap sealed in the area of ​​the two connection surfaces is formed between the two connection elements (13, 14; 13', 14'), wherein - the rolling elements (24, 25) of two axially offset raceways (22, 23, 37) have an approximately cylindrical shape, each with a lateral surface (26) which is rotationally symmetrical to exactly one axis of rotation (31), wherein - these rolling elements (24, 25) are aligned such that their respective axes of rotation (31) are aligned approximately perpendicular to exactly one longitudinal axis of the respective rotor blade (2), and wherein a projecting, circumferentially extending nose (21; 21') is provided on the shell side of a connecting element (14; 13') facing the other connecting element (13; 14'), wherein the two annular side surfaces (22, 23) of the nose (21; 21') serve as a running surface for the approximately cylindrical rolling elements (24, 25) of each row of rolling elements, wherein the rolling elements (24, 25) are arranged without play between the side surfaces (22, 23) of the nose (21) on the one hand and the side surfaces (37) of a circumferential depression (36) of approximately rectangular cross-section provided on an outer surface or inner surface of the connecting element (13, 14) roll off, and where - the rotor blade (2) is designed as a shell surface (4) surrounding an inner cavity, which at the rear end (5) of the rotor blade (2) merges into a cylindrical shell-shaped profile up to a flat, rear connection surface (6), wherein blind holes (7) are provided, which on the one hand lead to an anchoring body (8) made of a hard material inserted into the rotor blade (2), in which they continue as internally threaded holes, and which on the other hand correspond with through holes (17) distributed in a ring shape in the respective connection element (13, 13') in terms of number, diameter and orientation in such a way that they are aligned and thus allow the insertion of a stud bolt (19) in each case, and - a hydraulic cylinder or a drive unit (47) which constantly and periodically rotates the rotor blade (2) relative to the rotor hub (3) about its longitudinal axis, regardless of whether the wind turbine is in operation or not, or whether the wind turbine is stationary or not, or whether the rotor blades need to be adjusted or not. [2] Wind turbine with a bearing unit according to claim 1, characterized by that the two connecting elements (13, 14; 13', 14') are arranged concentrically within one another. [3] Rotor blade bearing unit according to claim 1 or 2, characterized by that the two connecting elements (13, 14; 13', 14') each have fastening bores (17, 18) arranged in a ring shape. [4] Rotor blade bearing unit according to one of the preceding claims, characterized bythat the mutually opposite end faces (15, 16) of the annular connecting elements (13, 14; 13', 14') serve as connecting surfaces to the rotor hub (3) on the one hand and to the relevant rotor blade (2) on the other hand, either directly or via intermediate rings, plates or the like. [5] Wind turbine with a bearing unit according to claim 1, characterized by that the annular gap between the two connecting elements (13, 14; 13', 14') is sealed (40, 41) in the area between a rolling element raceway and the nearest connecting surface (15, 16). [6] Wind turbine with a bearing unit according to claim 1, characterized by that the raceways (22, 23, 37) for the approximately cylindrical rolling elements (24, 25) run along approximately flat circular ring surfaces which are penetrated approximately perpendicularly by the longitudinal axis of the respective rotor blade (2). [7] Wind turbine with a bearing unit according to one of the preceding claims, characterized byat least one third bearing point (35) which is inserted between two mutually facing lateral surfaces (33) of the two connecting elements (13, 14; 13', 14'). [8] Wind turbine with a bearing unit according to claim 1, characterized by that the third bearing point (35) is located between the two raceways for approximately cylindrical rolling elements (24, 25) which are aligned such that their axes of rotation (31) are oriented approximately radially, i.e. approximately perpendicularly, with respect to the longitudinal axis of the rotor blade (2) in question. [9] Wind turbine with a bearing unit according to claim 7 or 8, characterized by that the third bearing point (35) is also designed as a rolling bearing. [10] Wind turbine with a bearing unit according to claim 9, characterized by that the rotation axis (31) of the rolling elements (35) of the third bearing point is oriented approximately parallel to the longitudinal axis of the rotor blade (2). [11] Wind turbine with a bearing unit according to claim 5 or 1, characterized by that a rolling element (35) of the third bearing point has a smaller volume than a rolling element (24, 25) whose axis of rotation (31) is oriented approximately radially, i.e. approximately perpendicularly, to the longitudinal axis of the rotor blade (2). [12] Wind turbine with a bearing unit according to claim 7 or 8 characterized by that the third bearing point (35) is designed as a plain bearing. [13] Wind turbine with a bearing unit according to one of claims 7 to 12, characterized bythat the effective width of the raceway (22, 23, 37) which comes into contact with a rolling element (24, 25) whose axis of rotation (31) is directed approximately radially, i.e. approximately perpendicularly, with respect to the longitudinal axis of the rotor blade (2) in question, is greater than the effective width of the raceway or sliding track (34) of a bearing point (35) which is inserted between two mutually facing lateral surfaces (33) of the two connecting elements (13, 14; 13', 14'). [14] Wind turbine with a bearing unit according to one of the preceding claims, characterized by that a connecting element (13; 14') is divided along a plane (42) oriented approximately perpendicular to the longitudinal axis of the rotor blade (2). [15] Wind turbine with a bearing unit according to one of the preceding claims, characterized bythat the transition region(s) (27, 28) between the lateral surface and one or both end faces of those rolling elements (24, 25) whose axes of rotation (31) are directed approximately radially, i.e. approximately perpendicularly, with respect to the longitudinal axis of the rotor blade (2) in question, is / are cambered. [16] Wind turbine with a bearing unit according to one of the preceding claims, characterized by that the rolling elements (24, 25), whose axes of rotation (31) are directed approximately radially, i.e. approximately perpendicularly, with respect to the longitudinal axis of the rotor blade (2) in question, are designed as hollow bodies. [17] Wind turbine with a bearing unit according to claim 16, characterized by that adjacent hollow rolling elements (24, 25) are connected to one another by end-face connecting elements which engage at least partially in the cavities of the rolling elements (24, 25). [18] Wind turbine with a bearing unit according to one of the preceding claims, characterized bythat the rolling elements (24, 25) are separated by a cage. [19] Wind turbine with a bearing unit according to one of the preceding claims, characterized by that the rolling elements (24, 25), whose axes of rotation (31) are directed approximately radially, i.e. approximately perpendicularly, with respect to the longitudinal axis of the rotor blade (2) in question, have at least one dome-shaped curved end face (29). [20] Wind turbine with a bearing unit according to claim 19, characterized by that the radius of curvature of the dome-shaped end face (29) corresponds approximately to the radius of the inside of the outer ring (14). [21] Wind turbine with a bearing unit according to one of the preceding claims, characterized by that between adjacent rolling elements (24, 25) a spacer is inserted, the radial longitudinal section of which is smaller than the radial longitudinal section of a rolling element (24, 25) or the same size as that. [22] Wind turbine with a bearing unit according to one of the preceding claims, characterized by that no toothing is provided on any connecting element (13, 14). [23] Wind turbine with a bearing unit according to one of claims 1 to 21, characterized by that a toothing (46) is provided on a connecting element (13', 14'). [24] Wind turbine with a bearing unit according to claim 23, characterized by that the toothing (46) is provided on the inside of the inner ring (13').

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