Patent Application
20130315736
The invention relates to an assembly comprising a connection for the rotor hub of a wind turbine of a wind power plant whose rotor rotation axis points approximately in the direction of the wind during operation, for the purpose of absorbing all the forces and torques occurring there, and comprising at least one rotor bearing or main bearing for diverting axial and radial forces and tilting moments into a load-bearing structure of the wind power plant, further comprising a device for extracting the rotational energy from the rotor hub of the wind turbine in the form of a single-stage planetary gear mechanism, which is integrated with the rotor bearing or main bearing and whose planet gears are mounted on a planet gear carrier and simultaneously mesh with a sun gear and a ring gear, and comprising a generator which is or can be connected to the output side of the planetary gear mechanism and operates to convert the rotational energy into electrical energy.
An assembly of the above species is disclosed in WO 02/14690 A1 and the related DE 01 954 251 T1. Described therein is a drive assembly for a wind turbine, having a structure that carries a rotor hub and having a main bearing, a single-stage planetary gear mechanism and a generator. There, however, the outer ring of the main bearing is connected to or suitable for connection to a wind turbine rotor hub. Since the inner ring consequently has to be fixed to a load-bearing structure of the gondola or the like and thus is not available to transmit torques, an additional structure is necessary for tapping (drive) torques and must be connected to the rotor hub. Taken altogether, therefore, the result is a very elaborate design that also renders maintenance difficult.
From the disadvantages of the described prior art comes the problem initiating the invention, to further develop an assembly of the above species to be connected to the rotor hub of a wind turbine of a wind power plant in order to absorb the forces and torques arising there, in such a way that the drive power developed by the wind is separated from the other forces and torques by the simplest means and can ultimately be converted into electrical energy. In addition, the assembly to be provided should be as maintenance-friendly as possible, so that maintenance can be performed even on hard-to-access wind power plants—located, for example, on mountains or in the offshore region of the ocean—without auxiliary equipment, particularly without a crane.
This problem is solved by the fact that the inner ring of a rotor bearing or main bearing of the wind power plant has at one end face a connection surface for connection to the rotor hub of the wind power plant, has at its outer face one or more raceways for rolling elements that simultaneously roll along one or more raceways of the outer ring, and is provided at its inner face with a fully circumferential set of teeth from which the rotational energy is tapped.
The inner ring of the rotor bearing or main bearing thus becomes a sort of “shunt” for redirecting forces and torques: while axial and radial forces and tilting moments are diverted via the outer ring into a load-bearing structure of the wind power plant, the rotational energy of the hub can be tapped via the internal teeth of the inner ring. Only one design part is needed for this purpose, so the number of components is minimized and the susceptibility to failure is therefore also reduced to a minimum. In addition, connected gear mechanisms can easily be maintained from the back, i.e., from the rear area of the gondola, and even removed from the back if necessary, i.e. without the need to demount the rotor hub from the inner ring of the main bearing or rotor bearing. Such maintenance and/or repair work thus can be performed without a crane.
It has proven advantageous for the inner ring of the rotor bearing or main bearing to comprise, at its end face facing the rotor hub, particularly at its connection surface located there, connecting elements for attaching the rotor hub, preferably in the form of coronally distributed fastening bores, particularly in the form of coronally distributed blind bores with an internal thread. The rotor hub can be connected thereto by means of a corresponding number of screws, threaded bolts or the like, sufficiently firmly so that it will remain anchored securely to the bearing even during strong gusts of wind.
It is within the scope of the invention that the raceways provided on the inner ring for rolling elements running therealong and its circumferential teeth and/or its connecting elements for attaching the rotor hub are formed by machining or shaping a common base body. As a result of this measure, all the forces from the rotor hub are absorbed in a single base body, and thus, with no internal parts that are subject to play, are separated into axial and radial forces and tilting moments that are to be braced against, on the one hand, and the drive torque that is to be tapped, on the other. Since, due to the lack of any parts that move in relation to one another, there can be no play or other relative movement, such an inner ring is nearly wear-free.
The rotor bearing or main bearing is preferably configured as a multi-row ball bearing, conical bearing, barrel roller bearing, roller bearing and/or needle bearing. Mixed forms thereof are also encompassed, i.e., bearings with rows of different rolling elements, although an embodiment in the form of a multi-row rolling bearing having only one kind of rolling element is preferred. Whereas ball bearings may be able to get along with few rows of rolling elements, the other rolling-element geometries offer advantages under extreme airflow conditions, such as, for example, hurricane gusts, when the wind turbine is attacked by considerable forces that can be diverted safely only if the mounting system is extremely stable. It is advantageous here that the load-carrying capacity of a bearing that features linear contact, particularly a roller bearing, is generally higher than the load-carrying capacity of a comparable ball bearing having nearly punctiform contact areas. Linear contact generally occurs with rolling elements that have a clear axis of rotation, i.e., that are rotationally symmetrical, but not spherical. It is not critically important, in this regard, whether the diameter of a rolling element changes along the longitudinal direction of its axis of rotation, as in the case of barrel roller bearings or conical bearings, or whether it does not, as in the case of roller bearings or needle bearings.
The invention further provides that the inner ring of the rotor bearing or main bearing is configured as a so-called nose ring, with a fully circumferential flange at its outer face. Such a nose—i.e., a fully circumferential flange—is capable of transmitting particularly strong axial forces and tilting moments.
The invention can be developed further by disposing running surfaces for one or more rows of rolling elements at the peripheral and/or end face(s) of the fully circumferential flange. Rolling elements running along the two end faces of the flange preferably serve both to transmit axial compressive forces in both directions and to transmit tilting moments, while rolling elements running along a peripheral face transmit radial forces.
If the outer ring of the rotor bearing or main bearing is divided into a hub-side subring and a generator-side subring, then such a bearing is particularly easy to assemble, since the two subrings of the outer ring can be moved apart for the insertion of the inner ring.
Additional advantages are gained if the gap between the inner and the outer ring of the rotor bearing or main bearing is sealed, particularly in the region of the nose-side subring. This prevents the escape of a lubricant—preferably grease—and also the ingress of dirt and other particles. It also serves to keep out rain that would otherwise wash out any grease from inside.
Particularly simple construction is achieved if the fully circumferential set of teeth at the inner face of the inner ring of the rotor bearing or main bearing simultaneously forms the ring gear of the planetary gear mechanism, since, as a result of this measure, the inner ring of the rotor bearing or main bearing simultaneously becomes a component of the planetary gear mechanism.
It has proven worthwhile for all the components of the inventive assembly, including all the connected output drive elements, such as the gear mechanism, generator, brake, etc., to be located in the axial direction behind the connection surface of the inner ring. None of the components of the inventive assembly then extend into or even near the rotor hub, so if the hub has to be demounted, there is no danger to the gear parts or other parts of the inventive assembly. These are protected against damage, for example from collisions with the rotor hub hanging from a crane or the like, by the front connection surface of the inner ring.
The invention further provides that the planetary gear mechanism does not protrude in the radial direction beyond the rotor bearing or main bearing. As a result of this measure, the rotor bearing or main bearing has a maximum diameter that roughly corresponds to the hub diameter of the wind turbine and thus is also of the same order of magnitude as the cross section of the gondola in the front region, and it can therefore, if necessary, be demounted and pushed aside, i.e., into the center of the gondola.
The planetary gear mechanism can be disposed radially inside the rotor bearing or main bearing. This results in optimum use of space, thus making it possible to reduce the overall size of the gondola under some circumstances.
Particular advantages can be gained if the inner ring of the rotor bearing or main bearing is connected at its end face facing the rotor hub to at least one hub-side plate of approximately circular extent, whose outer diameter is equal to or less than the diameter of the rotor bearing or main bearing, preferably equal to or less than the outer diameter of the inner ring. This plate, on the one hand, protects the parts of the inventive assembly located behind it, for example the parts of a gear mechanism, and, on the other hand, can guide and/or stabilize such parts.
Affixed to the hub-side plate, there can be a bearing bushing to which the sun gear of the planetary gear mechanism can be mounted. This is a simple method of mounting the sun gear of a planetary gear mechanism stationarily amid the gear mechanism.
The sun gear of the planetary gear mechanism can further be connected to the generator in order to drive it. Owing to its small number of teeth, the sun gear generally rotates faster than the driven unit of the planetary gear mechanism; consequently, the sun gear is particularly well suited to transmit this rapid rotation to the generator of the wind power plant.
If the planet gear carrier of the planetary gear mechanism is fixed to the chassis, frame or housing of the gondola of the wind power plant, then the rotation speed nSo of the driving sun gear is greater than the rotation speed nHo of the driven ring gear by the tooth count ratio zHo/zSo of the ring gear to the sun gear:
n
So
=n
Ho
·z
Ho
/z
So,
although in the opposite direction of rotation.
To fix the planet gear carrier, the latter can be disposed at, particularly fixed to, at least one generator-side plate, which in turn is disposed at that end face of the rotor bearing or main bearing which faces away from the rotor hub. A plate can also easily transmit relatively large torques in its plane and is therefore ideally suited for fixing the planet gear carrier in place.
The generator-side plate preferably is or can be connected to the outer ring of the rotor bearing or main bearing. These are both non-rotating parts, so they can be interconnected to form a subassembly.
A further advantage of the invention is that one, a plurality of, or preferably all of the planet gears are configured as one-piece and undivided. In this way, the planet gears can occupy the entire width between the hub-side and the generator-side plate, thus minimizing compressive stress on the tooth flanks.
It has proven particularly worthwhile for the planetary gear mechanism to have a transmission ratio T=nHo·nSo, between the rotation speed nHo of the ring gear and the rotation speed nSo of the sun gear, which is within a range of 1:1.5 to 1:20, preferably a transmission ratio within a range of 1:2 to 1:12, particularly a transmission ratio within a range of 1:4 to 1:7, the rotation speed of the generator-side output drive being greater than the hub-side input rotation speed.
It is within the scope of the invention that the diameter of a planet gear is at least half the diameter of the sun gear, preferably at least exactly the same, particularly at least one and a half times the diameter of the sun gear.
The generator should not protrude in the radial direction beyond the rotor bearing or main bearing. If the outer diameter of the generator is approximately equal to the outer diameter of the rotor bearing or main bearing, the two parts can be moved around either individually or together inside the gondola, for example for purposes of cleaning, maintenance or repair.
The invention recommends disposing, particularly fixing, the stator of the generator at the generator-side plate of the main bearing or rotor bearing and/or at its outer ring. During operation, these parts are all anchored rotationally fixedly to the gondola support structure and can therefore be connected to one another without problems. They can thus, for example, be transported as a common assembly.
Because the generator rotor is connected to the sun gear of the planetary gear mechanism, it can be driven with maximal speed.
The invention is further optimized if a connection piece, preferably configured as a reducing piece, is provided between the rotor of the generator and the sun gear of the planetary gear mechanism. The purpose of this reducing piece is to compensate for the difference between the diameter of the generator rotor and the generally smaller diameter of the sun gear of the planetary gear mechanism.
A seal that can be provided between the connection piece or the sun gear, on the one hand, and the bushing or shaft guiding it, on the other hand, serves to keep any lubricant coming from the region of the bearing and/or the planetary gear mechanism away from the generator.
According to an advantageous further development of the invention, the connection piece, particularly the reducing piece, is coupled to, connected to or integrated with a support bearing. The purpose of this support bearing is to additionally stabilize the relatively fast-rotating generator rotor, and thus to rigorously counteract any potential imbalance.
The support bearing can be configured as a rolling bearing, so that the friction losses caused by it are minimal.
A particularly stable arrangement is obtained if the counter ring of the support bearing is fixed to or integrated with the connection piece at the generator-side plate of the rotor bearing or main bearing.
The rotor of the generator is preferably configured as disk-shaped, preferably circular-ring-shaped. In this case, the radial extent of a cross section through the rotor is preferably greater than its axial extent. With dimensioning of this kind, optimum use can be made of the space available in a gondola. Where appropriate, two or more such disk rotors can be arranged one behind the other in the axial direction to increase the power of the generator.
The generator can be equipped with permanent magnets. These are particularly suitable for being attached to or built into a disk rotor. In particular, magnetic plates can be attached to and/or embedded in the disk rotor for this purpose. The magnetic poles of these magnets are preferably located on their approximately planar end faces, facing the air gap.
With a disk rotor, an also disk-shaped air gap is formed between rotor and stator, the rotor preferably being located between two stator disks. To the extent that—as the invention also provides—the magnetic field generated by the magnets of the disk rotor passes through the air gap approximately perpendicular to the base thereof, the magnetic field will have an approximately axial course in relation to its axis of rotation. The generator is then an axial field generator, also commonly referred to as an axial generator.
It has been found that a particularly stable arrangement is obtained if the generator's stator embraces its rotor radially outwardly. The two stator disks are thus connected outwardly by a sort of yoke and thereby stabilize each other. Preferably applied to or inserted in the stator disks are electrical coils that embrace the magnetic flux from the rotor magnets to varying degrees, depending on the rotational position of the rotor, such that an electrical voltage, particularly an alternating voltage, is induced in these electrical coils. This voltage can, for example, be rectified and then reconverted to an alternating voltage with an oscillating frequency of 50 Hz, which can then be fed into a power grid.
Should the generator have channels for a preferably fluid cooling and/or temperature control medium, then this medium can be cooled actively. The necessary cooling systems can also be disposed in the gondola of the wind power plant.
The invention is further distinguished by a central passage through the generator and/or the planetary gear mechanism, for cables or the like. For example, control lines for the drives serving to adjust the pitch angle of the rotor blades can be led through this passage, for example with the aid of slip rings or other rotational decoupling means.
The assembly according to the invention can be fixed to or integrated with a preferably cast or welded support structure, which simultaneously serves as the load-bearing structure of the gondola and/or is connected to or integrated with an azimuth bearing for pivoting the gondola. An arrangement that is particularly simple statically is obtained in this way. The support structure can transmit the wind pressure force, for example by means of lateral diagonal struts, directly to a baseplate of the gondola, from which it is then relayed to the nacelle bearing of the wind power plant.
Finally, it is within the teaching of the invention that one or more fastening elements are provided at the end face, facing the hub, of a structure supporting the assembly according to the invention, in order to fix the hub of the wind turbine temporarily to the support structure during the removal or installation of the assembly according to the invention. These fastening elements must be strong enough to support the entire hub of the wind turbine, including all the blades. The main bearing or rotor bearing or an assembly connected thereto can then be inspected, maintained or repaired. The bearing is then reinstalled, and once the inventive fastening elements are released, the wind turbine is again able to rotate freely.
Additional features, details, advantages and effects based on the invention will become apparent from the following description of a preferred embodiment of the invention and by reference to the drawing. Therein:
The wind power plant 1 illustrated in the drawing is designed to be particularly maintenance-friendly. A nacelle bearing 3 illustrated only schematically in
Whereas one ring of this nacelle bearing 3 is fixed to the top side of the tower 2, the other ring can thus be pivoted about the tower axis 4. It is driven, for this purpose, by a motor (not shown), whose housing is, for example, attached to the tower 2, and whose pinion, for example, meshes with a set of teeth on the pivotable ring.
Bearing against the pivotable ring of the nacelle bearing 3 is a top plate or frame 5 of a support structure 6 that is able to pivot about the tower axis 4. This support structure 6 can further comprise a back wall 7 and a baseplate 8 with an opening for the tower 2. Side wall plates 9 connect the baseplate 8, the back wall 7 and the top plate or frame 5 to one another and thus lend sufficient rigidity to the support structure 6.
At their respective sides approximately opposite the back wall 7, the baseplate 8, the side wall plates 9 and the top plate or frame 5 are prolonged to an approximately circular mouth 10.
The entire space behind this mouth 10 is surrounded by a casing 11, which for aerodynamic reasons has a gently curving shape and is intended to keep wind and weather out of the inner chamber serving as the nacelle or gondola 12, which can be reached by maintenance personnel via a stairway or ladder 13 inside the tower 2 and upper egress openings 14 in the wall of the tower 2.
Whereas the tower 2 of the wind power plant 1 is stationary and the gondola 12 is able to pivot in the azimuthal direction on a vertical axis 4, the wind turbine 15 per se has an additional degree of freedom of movement, namely that of a rotation on a second axis 16, which extends away from the tower axis 4 in an approximately horizontal direction in the region of the gondola 12. The wind turbine 15 itself consists of a hub 17 from which a plurality of wings or blades 18 extend in an approximately radial direction, in relation to the hub axis 16. These blades 18, finally, are each mounted to the hub 17, in a respective blade bearing, so that they are able to rotate about their longitudinal axis, for example in order to adjust their pitch as a function of wind speed.
As will be explained further below, the hub 17 is mounted to the support structure 6, rotatably about its hub axis 16, by means of an assembly 19 according to the invention, which is illustrated enlarged in
This assembly 19 includes several functional units, specifically the actual main bearing or rotor bearing 20, a gear mechanism 21, particularly a step-up gear mechanism, and a generator 22.
Disposed at the side of this assembly 19 facing the hub 17 is the main bearing 20, which comprises two mutually concentric rings, an outer ring 23 and an inner ring 24.
The main bearing 20 is implemented as a rolling bearing, particularly as a roller bearing. As can be seen from
The gap 25 between the outer ring 23 and the inner ring 24 is preferably sealed in the region of the hub-side gap opening. This can be effected by means of one or more fully circumferential seals 37. This seal or these seals can be (partially) covered and held in place by, for example, a ring 39 fixed, for example screwed, to the hub-side end face 38 of the outer ring 23.
The outer, i.e., hub-side, end face 40 of the inner ring 24 serves as a connection surface for the hub 17. Located in this connection surface or end face 40 are a plurality of coronally arranged fastening means, preferably fastening bores, particularly blind bores with an internal thread, for screw-fastening the hub 17 of the wind turbine 15. By means of screws 41 inserted therein, the hub 17 is pressed against the connection surface 40 of the inner ring 24 and is lockingly, preferably friction-lockingly, fixed there.
Radially inside the connection surface 40—in relation to the hub axis 16—the outer ring 23 is provided with a recess 42 bounded by a planar, annular end-face portion 43 and by a concavely curved, hollow-cylindrical portion 44. Located in the planar end-face portion 43 are coronally distributed fastening bores 45 for screwing tight a hub-side cover plate 46 provided with a central opening 47.
The rim of this opening 47 is surrounded coronally by a plurality of fastening bores 48, to which is fixedly screwed a bushing 49 that extends from the cover plate 46 all the way through the main bearing 20. A toothed wheel 51 is mounted on this bushing 49—preferably by means of one or more rolling bearings 50—so as to be able to rotate about the hub axis 16. The toothed wheel 51 simultaneously forms the drive shaft of the gear mechanism 21.
The inner face of the inner ring 24 of the main bearing 20 is provided with a fully circumferential set of teeth 52, which transmit the rotational drive power from the wind turbine 15 to the gear mechanism 21.
Whereas the toothed wheel 51 serves as the sun gear of the gear mechanism 21 configured in the manner of a planetary gear mechanism, the fully circumferential set of teeth 52 at the inner face of the inner ring 24 of the main bearing 20 simultaneously forms its ring gear. The ring gear 52 has a much larger diameter than the sun gear 51. Disposed in the radial space between the sun gear 51 and the ring gear 52 is a plurality of toothed planet gears 53, each of which meshes with the sun gear 51 and the ring gear 52. The planet gears preferably have a larger diameter than the sun gear 51. For this reason, the number of planet gears 53 is limited to six at the most, preferably five or less, particularly four or less, for example three.
The planet gears 53 are preferably mounted to a common cage or planet gear carrier 54. This has the shape of a plate, which is fixed to the generator-side end face of outer ring 23, preferably via bores 55 that are aligned with the bores 34 in the outer ring 23, particularly in its subrings 27, 28, and are collectively engaged end to end by a respective fastening screw 35.
The generator-side plate 54 serving as the planet gear carrier also has a central opening, through which an end-face region 56 of the sun gear 51 is prolonged or at least accessible and serves as the output of the planetary gear mechanism 21.
Immediately adjacent the far side of the plate 54 serving as the planet gear carrier is the generator 22. This has an approximately disk-shaped form and is configured as an axial field generator.
Its stator 57 is fixed in the generator housing 58, which in turn has bores 59 that pass between its two end faces and are aligned on the one side with bores 55 in plate 54 and on the other side with bores 34 in outer ring 23. These bores 34, 55, 59 are collectively engaged from end to end by fastening screws 35, such that all these elements of the assembly 19—i.e., main bearing 20, gear mechanism 21 or planet gear carrier plate 54 and generator 22—can be fixed collectively to the support structure 6. Naturally, it would also be possible first to connect these parts to one another with fastening means specifically for that purpose and then fix them collectively to the support structure 6 with other fastening means, or first to connect the main bearing 20 to the support structure 6 and then fix the gear plate 54 and/or the generator 22 to the main bearing 20.
In contrast, the rotor 60 of the generator 22 is rotationally fixedly connected via a reducing piece 61 to the end-face region 56 of the sun gear 51, for example by means of axially parallel screw connections 62. The reducing piece 61 is necessary because the rotor 60 is preferably configured as annular, with an inner diameter that is generally greater than the outer diameter of the sun gear 51. The reducing piece 61 can further be braced against the generator-side plate 54 by means of an additional bearing 63, preferably by means of a rolling bearing, particularly by means of a ball bearing. This purpose is served, for example, by an outer ring of bearing 63, which, for its part, is attached to the generator-side plate 54. Additional seals 64 can further be provided in the region of the reducing piece 61, to ensure that lubricant cannot find its way from the main bearing 20 or out of the gear mechanism 21 into the generator 22.
The rotor 60 is preferably fixed to the reducing piece 61 by means of screw connections 65 coronally distributed along its inner rim 66 and extending parallel to the hub axis 16. Radially outside these fastening means, the disk-shaped rotor 60 is equipped with permanent magnets having magnet poles on their flat sides, such that an approximately axial magnetic field is established in the gap between the stator 57 and the rotor 60. To allow both end faces of the rotor 60 to be utilized, the stator 57 embraces the rotor 60 at its outer periphery. The stator 57 thus has an approximately U-shaped geometry in cross section. The two legs of this U-shaped stator cross sectional geometry each correspond to a respective circular ring 67, which extends next to the rotor disk 60 at a scant axial distance therefrom. Each of these two circular rings 67 is occupied by coils in which, when the rotor 60 turns, a voltage is induced by the respective embraced magnetic field, which varies during a rotation, and this voltage can then be tapped and—after electrical transformation, where appropriate—fed into a power grid.
As can be appreciated from the drawing, all the components of the assembly 19 according to the invention are centerless, so it is possible, for example, to lead cables or the like through a central opening and on into the hub 17, and thus, for example, to control the drives of the blade bearings and/or to supply them with current, for example via slip rings.
As can be seen, this connection is embodied in the form of releasable screw connections 41 that can be released as necessary, for example in order to maintain, repair or even replace the components of the assembly 19 according to the invention.
So that the wind turbine 15 does not drop out in this case, and also so that it does not have to be lowered with a crane, additional fastening means 68 are provided at the hub 17, specifically for fixing the hub 17, including the blades 18, directly to the support structure 6. These fastening 68 are located radially farther outward than the screw connections 41 in relation to the hub axis 16. Whereas the screw connections 41 are preferably located inside the hub 17, the additional fastening means 68 are preferably located outside the hub 17. They can optionally be disposed in a fully circumferential flange 69 of the hub 17 or in individual radial extensions of the hub 17. The additional fastening means 68 are preferably bores arranged approximately parallel to the hub axis 16 in a fully circumferential flange 69 of the hub 17, which, at least in a given rotational position of the hub 17 or wind turbine 15, are exactly aligned each with a respective bore 70 in the support structure 6 and enable the hub 17 to be fixed temporarily to the support structure 6 by means of screws 71. Where appropriate, interposed spacer elements 72 in the manner of washers serve to maintain a suitable distance between the hub 17 and the support structure 6.
Finally,
The most striking difference with respect to wind power plant 1 is that the ring of the nacelle bearing 3′ that is not fixed to the tower 2 is anchored, not in the region of the top of the gondola 12′, but in the region of the bottom thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2010 049 023.7 | Oct 2010 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP11/05068 | 10/11/2011 | WO | 00 | 8/6/2013 |
