Wind turbine

The invention relates to a wind turbine comprising a nacelle with at least one main bearing tilted with its rotation axis towards the horizontal axis and comprising an inner ring and an outer ring.

A wind turbine usually comprises a tower with a nacelle at its top. A rotor is arranged at the nacelle, which rotor com prises a hub, to which one or more rotor blades, usually three rotor blades, are fixed interacting with the wind. The rotation of the hub respectively the rotor runs an electric generator. The rotor is arranged in at least one main bear ing, which comprises an inner ring, which is usually station ary, and an outer ring, which is connected to the rotor and which rotates relative to the inner ring. It is though also known, especially in relation to geared wind turbines, to have the rotor connected to the inner ring of the main bear ing and where the outer ring is stationary. Traditionally wind turbines use a roller bearing as a main bearing but new and large multi Megawatt wind turbines may find it beneficial to use a slide bearing as a main bearing. A slide bearing needs a liquid lubrication and a good sealing to avoid leak age, which nevertheless still occurs.

It is an object of the invention to provide a wind turbine with an improved lubrication.

For solving the problem the invention proposes a wind turbine comprising a nacelle with at least one main bearing tilted with its rotation axis towards the horizontal axis and com prising an inner ring and an outer ring, whereby the main bearing is a slide bearing and the inner ring is stationary while the outer ring rotates around the inner ring, with the main bearing being lubricated with a lubrication fluid, and with the outer ring comprising a first and a second sealing means arranged at both sides of the outer ring for sealing to the inner ring and extending around the outer ring, whereby the first sealing means is due to the tilt of the main bear ing lower than the second sealing means, whereby a stationary leakage lubrication fluid collection means is provided adja cent to the first sealing means adapted for collecting lubri cation fluid leaking from the first and the second sealing means, whereby the outer ring is provided with one or more axial bores connecting a leakage lubrication fluid collection area adjacent to the second sealing means to the leakage lu brication fluid collection means and wherein each sealing means comprises a groove accommodating a sealing element and a sealing element carrier ring having a fold and a clamp ring attached to the carrier ring closing the fold to build the groove and clamping the sealing means in the groove.

The invention proposes a wind turbine with a lubrication sys tem using a lubrication fluid, preferably oil, for lubricat ing the main bearing, which is a slide bearing, and with the possibility to collect any leakage and to return the leakage back to the lubrication circuit. This is possible, as the ro tating outer ring, which is preferably a one-piece-ring made of one single part, is provided with a first and a second sealing means, which are arranged on both sides of the outer rotating ring extending around the whole circumference of the outer ring. The sealing means are arranged to provide a good sealing towards the stationary inner ring. Nevertheless some leakage may occur. This leakage is collected. For collecting the leakage a stationary leakage lubrication fluid collection means is provided adjacent to the first sealing means. This stationary lubrication fluid collection means is adapted to collect the lubrication fluid leaking through both sealings. As the first sealing means is adjacent to the stationary lu brication fluid collection means, this leakage amount can easily be collected. As mentioned, a second sealing means is arranged on the other side of the outer ring. For collecting any leakage a leakage lubrication fluid collection area is provided adjacent to this second sealing means, which leakage lubrication collection area is preferably provided as rotat ing with the outer ring respectively the second sealing means. So any lubrication fluid leaking through the second sealing means will be collected in this leakage lubrication fluid collection area.

For transferring the collected leakage fluid the outer ring is provided with one or preferably more axial bores acting as rotating channels, which bores connect the leakage lubrica tion fluid collection area to the leakage lubrication fluid collection means arranged at the other bearing side, so that the leakage fluid can flow from one side of the bearing to the other side of the bearing. This flow is promoted by the fact that the main bearing and thus the rotor etc. is slight ly tilted towards the horizontal axis. The tilt angle usually is about 5 - 10°. Due to the slight tilt of the main bearing one side of the bearing is lower than the other side of the bearing. According to the invention the first bearing side, to which the first sealing means is arranged, is the lower bearing side, while the opposite second bearing side, to which the second sealing means is arranged, is the higher bearing side. As also the rings are tilted, and as the bore or the bores provided in the rotating outer ring connecting the leakage lubrication fluid collecting area with the leak age fluid lubrication fluid collecting means are parallel to the axis of rotation of the bearing, also the one or the sev eral axial bores are tilted, so that there is a permanent in cline from the leakage lubrication fluid collection area to the leakage lubrication fluid collection means, which incline promotes the flow of the leakage fluid from the collection area to the collection means.

The invention advantageously allows to use a lubrication flu id for lubricating a slide bearing. As it is a fluid, it al lows for lubrication of all contact points during operation, all surfaces are wetted by the lubrication fluid and are therefore corrosion protected during operation and even dur ing standstill, even a long standstill. Due to its fluid character it is possible to circulate the lubrication fluid in a lubrication circuit by means of at least one pump allow ing to transport the lubrication fluid to any points of need, so that it is easily possible to supply the lubrication fluid to distinct points of the main bearing, where a good lubrica tion is necessary, from where the lubrication fluid then dis tributes within the whole main bearing.

While the wind turbine, which may be a direct drive wind tur bine with a single bearing or a gear wind turbine, may com prise only one single main bearing, the wind turbine may also comprise a two-bearing system with the outer ring rotating around the stationary inner ring. The inventive leakage fluid collection and distribution system also allows for an excel lent lubrication of the two-bearing system, which is a double slide bearing system.

As mentioned, a rotating leakage lubrication fluid collection area is provided at the rotating outer ring respectively the outer ring system. This leakage lubrication fluid collection area is preferably a collection groove extending around the outer ring, so that any leakage fluid leaking at any point at the circumference of the outer ring respectively the second sealing means can be collected in the circular groove. The leakage fluid usually collects at the low side of the rotat ing groove respectively at the lowest point, as it is fluid and as the rotational speed is not very high. Even if only one axial bore or channel with a certain diameter is provid ed, this rotating bore passes through the leakage fluid sump and takes some leakage fluid which flows to the other bearing side. Preferably certainly several bores connecting the leak age lubrication fluid collection area with the leakage fluid connection means are provided, which bores are preferably equally distributed around the circumference of the outer ring. This ensures that the leakage fluid is transported from one bearing side to the other side almost all the time, as there is a number of connection bores rotating through the leakage fluid sump, into which bores the fluid can flow. As these several bores are preferably equally distributed, there is almost a constant fluid flow.

As mentioned, the collected lubrication fluid leaking from both the first and the second sealing means is collected in a collection means arranged stationary adjacent to the first sealing means. This leakage lubrication fluid collection means is preferably arranged at the stationary inner ring, which is very close to the outer ring respectively the first sealing means, so that any fluid leaking from the first seal ing means can almost directly be collected in the collection means. This collection means is preferably a collector ring extending around the main bearing, which ring as mentioned is preferably arranged at the stationary inner ring. In an al ternative it may certainly also be fixed to any other sta tionary support means, as long it is adjacent respectively very close to the first sealing means. The collector ring al lows the collection of the leakage fluid not only at the low est point of the circumference but also along the whole 360° rotation of the outer ring during which some leakage fluid max exit especially the bores.

A drip edge ring may be arranged at the outer ring extending to or into the leakage lubrication fluid collection means, especially the collector ring. This drip edge ring bridges any axial distance between the first sealing means and the collection means respectively the collector ring, so that no leakage fluid can flow anywhere else than into the collector ring. It drips from the drip edge of the drip edge ring into the collection means respectively the collector ring, which may have a certain collection groove or the like.

Each sealing means is adapted to provide a proper sealing be tween the rotating outer ring, to which it is fixed, and the stationary inner ring. Each sealing means preferably compris es a groove accommodating a sealing element, which is for ex ample a lip seal element having one or more lips extending from a sealing element basis towards the inner ring, along which the sealing element respectively the sealing lip(s) slide. This sealing element is accommodated in a groove of the sealing means, so that it is easy to be arranged at the sealing means respectively installed.

Each sealing means comprises a sealing element carrier ring having a fold and a clamp ring attached to the carrier ring closing the fold to build the groove and clamping the sealing means in the groove. Each sealing means therefore consists of two parts, i.e. the sealing element carrier with the fold and a clamp ring closing the fold to build the groove. The width of the sealing element is a little bit larger than the width of the groove, so that the sealing means is clamped when the groove is closed.

As already mentioned, the leakage lubrication fluid area is preferably as close as possible to the second sealing means and preferably realised as a collection groove extending around the circumference of the outer ring. In a preferred embodiment the clamp ring of the second sealing means com prises the leakage lubrication fluid area, especially the collection groove. The collection area respectively the col lection groove is integrated in the second sealing means com prising the sealing element carrier and the clamp ring. It is directly integrated in the clamp ring, so that any leakage fluid leaking from the very close sealing element can direct ly be collected in the collection groove.

For avoiding any collected leakage fluid again leaking from the leakage lubrication fluid collection area respectively the collection groove, a sealing element like a sealing lip is arranged at the clamp ring sealing the collection groove to the inner ring. This sealing lip seals the collection groove on the other side of the groove, so that any leakage fluid collected in the groove remains in the groove until it is guided away via the axial bores to the leakage fluid col lection means on the other side of the main bearing. As mentioned above, the sealing means preferably comprises the sealing element carrier and the clamp ring, closed to which respectively integrated into which the leakage lubrica tion fluid collection area is realised, preferably in form of the groove. According to another embodiment of the invention the at least one axial bore respectively each axial bore com municates with the leakage lubrication fluid collection area, especially the groove, and extends from the clamp ring through the sealing element carrier ring of the second seal ing means, the outer ring and through the sealing element carrier and the clamp ring of the first sealing means and is open to the leakage lubrication fluid collection means. Each axial bore which connects the leakage lubrication fluid col lection area with the leakage lubrication fluid collection means comprises several bore sections, which together realise the complete axial bore connecting the collection area to the connection means. The bore sections are realised in the clamp ring and the carrier ring of the second sealing means, in the outer ring and in the element carrier and the clamp ring of the first sealing means. The or each axial bore is open on both ends. On the side of the second sealing means it is open to the collection area respectively the collection groove, and on the side of the first sealing means it is open to the collection means respectively the collector ring. As all re spective bore sections are realised on the same radius of all ring components, it is only necessary to adjust the separate parts and to align the bore sections, so that the respective axial bore is realised. Especially when the axial bores are equally distanced around the circumference the alignment is simple.

The clamp ring and the element carrier ring are preferably fixed to the outer ring by means of several bolt connections, which are preferably equally distributed around the circum ference of the outer ring. Also the fixation of the respec tive parts is realised with equally distanced bolt connec tions. For example a bolt connection follows each axial bore or the like. Nevertheless the spacing may also be different. In this circumstance it is also possible to fix the sealing element carrier with first bolt connections to the side of the outer ring and the clamp ring with the second bolt con nections either to the sealing element carrier or also to the outer ring side.

As each sealing means is a two-piece device sealing or col lecting a fluid it is preferable when at least one sealing ring is arranged each between the clamp ring and the element carrier ring and the element carrier ring and the outer ring, which sealing rings are arranged in respective grooves. With these sealing rings a radial tight connection of the clamp ring to the element carrier ring and of the element carrier ring to the outer ring is realised. It is possible to provide the groove in only one of the adjacent pieces, or it is also possible that both are provided with respective parts which complement to the final groove.

As already mentioned the inventive main bearing is preferably automatically lubricated. For realising such an automatic lu brication the wind turbine preferably comprises an automatic lubrication arrangement with a lubrication circuit with a pump for circulating the lubrication fluid, to which lubrica tion circuit the leakage lubrication fluid collection means, especially the collector ring is connected. This lubrication arrangement allows for automatically providing the lubrica tion fluid to the points of need at or in the one or two main bearings, i.e. one or two slide bearings. As the leakage lu brication fluid collection means, especially the collector ring is connected to the lubrication circuit, also any leak age fluid is recirculated in the lubrication circuit and therefore not lost. So the amount of lubrication fluid in the circuit remains constant over a long time. Maintenance can be reduced regarding any refill of lubrication fluid or the like.

The invention further comprises a main bearing for a wind turbine according to the above detailed disclosure, compris- ing an inner ring and an outer ring, whereby the main bearing is a slide bearing and the inner ring is adapted to be sta tionary when mounted, while the outer ring is adapted to ro tate around the inner ring when mounted, with the main bear ing being lubricated with a lubrication fluid, and with the outer ring comprising a first and a second sealing means ar ranged at both sides of the outer ring for sealing to the in ner ring and extending around the outer ring, whereby an as sociated stationary leakage lubrication fluid collection means is provided to be arranged adjacent to the first seal ing means, which leakage lubrication collection means is adapted to collect lubrication fluid leaking from the first and the second sealing means, whereby the outer ring is pro vided with one or more axial bores connecting a leakage lu brication fluid collection area adjacent to the second seal ing means to the leakage lubrication fluid collection means and wherein each sealing means comprises a groove accommodat ing a sealing element and a sealing element carrier ring hav ing a fold and a clamp ring attached to the carrier ring closing the fold to build the groove and clamping the sealing means in the groove.

All features disclosed in regard of the inventive wind tur bine, which are directly or indirectly related to the main bearing, the main bearing setup, a main bearing part or the like are also relevant for the disclosure of the inventive main bearing itself, so that any of these features may also be claimed for the main bearing, as all these features have also inventive relevance.

Other objects and features of the present invention will be come apparent from the following detailed description consid ered in conjunction with the accompanying drawings. The draw ings, however, are only principle sketches designed solely for the purpose of illustration and do not limit the inven tion. The drawings show: Fig. 1 shows a principal perspective sketch of a wind tur bine,

Fig. 2 a principle sketch of the arrangement of the hub, the rotor and the main bearing,

Fig. 3 an enlarged sectional view of the main bearing,

Fig. 4 an enlarged perspective view of the main bearing side with the second sealing means,

Fig. 5 an enlarged perspective view of the main bearing side with the first sealing means, and

Fig. 6 a cross sectional view of the main bearing, in part, showing the fixation of the first and second sealing means to the outer ring.

Fig. 1 shows an inventive wind turbine 1, comprising a rotor 2 rotatably arranged at a nacelle 3, which is arranged on the top of a tower 4. The rotor 2 comprises three rotor blades 5 attached to a hub 6 as is commonly known. The rotor blades 5 interact with the wind making the rotor rotate. The rotor drives an electric generator, preferably a direct drive gen erator.

Fig. 2 shows an arrangement with the central elements of the wind turbine 1. It shows the hub 6 which is connected to a direct drive generator 7 comprising a rotor 8, which here is directly coupled to the hub 6, and further a stator 9. The stator 9 is stationary fixed to a main shaft 10.

The arrangement of hub 6 and rotor 8 is rotatable relative to the stationary shaft 10 respectively the stator 9. For bear ing the hub-rotor-arrangement a main bearing 11 is provided, which in the shown embodiment is a slide bearing 12 compris ing an outer ring 13, to which the hub-rotor-arrangement with the hub 6 and the rotor 8 is connected, so that, when the hub 6 rotates, also the outer ring 13 and the rotor 8 rotate. The main bearing 11 further comprises an inner ring 14 which is stationary and which is fixed to the main shaft 10.

As the main bearing 11 is a slide bearing 12 the rotating outer ring 13 is slidingly guided by axial and radial guiding or sliding pads or alternatively by tapered guiding or slid ing pads in a tapered sliding bearing. Fig. 2 shows front ax ial pads 15 and rear axial pads 16 for axially guiding the outer ring 13 and radial pads 17 for radially guiding the outer ring 13. The pads 15, 16 and 17 are stationary fixed to the stationary inner ring 14. A sliding pad (15, 16, 17) may comprise several components (not shown) e.g. an outer sliding part, a support part for attachment to a structure by bolts or similar, a tilting support part to ensure that the sliding pad is able to tilt and/or a resilient means like e.g. a spring to ensure a preloading of the sliding pad and the tilting support.

The axis of rotation of the rotor 2 and therefore also the axis of rotation of the main bearing 11 is slightly tilted relative to the horizontal plane or axis. Fig. 2 shows the tilt angle a, which the axis of rotation 18 of the main bearing 11 shows relative to the horizontal plane or axis 19. Therefore the main bearing 11 is slightly tilted, which is advantageous for a simple leakage lubrication fluid collec tion system, which will be explained in detail below.

As mentioned, the main bearing 11 is a slide bearing. This slide bearing needs to be lubricated by a lubrication fluid, which provides an extremely thin hydrodynamic fluid film be tween the sliding surfaces of the outer ring, which rotates, and the axial and radial pads 15, 16 and 17. It is therefore necessary to constantly provide enough lubrication fluid in this area, which can either be flooded or directly introduced respectively lubricated to respective bearing point or evacu ated bearing cavities etc. The lubrication system needs to maintain a permanent and constant lubrication amount in this area.

For providing a constant lubrication, an automatic lubrica tion arrangement 20 is provided, which is shown in principle in fig. 2. This lubrication arrangement comprises a reservoir 21 with the lubrication fluid 22, which is integrated in a lubrication circuit 23. The lubrication fluid 22 circulates in the circuit 23 with a pump 24 integrated in the circuit 23. The circuit 23 comprises one or more fluid pipes, which or at least some of which are guided to the main bearing 11 to emit the lubrication fluid 22 at one or several points to the main bearing 11 or to completely flood it. As fig. 2 fur ther shows, the lubrication arrangement 20 further comprises in the circuit 23 a redirection pipe which allows for redi recting any collected leakage lubrication fluid which leaks from the main bearing 11 and which is redirected in the cir cuit 23, which collection system is explained below.

Fig. 3 shows an enlarged partial view of the main bearing 11 respectively the slide bearing 12. The figure shows partly the outer ring 13 and the inner ring 14, and also the hub 6 which is in this embodiment attached to the outer ring 13. Fig. 3 shows a cross sectional view of the lower end of the main bearing 11.

The outer ring 13 is provided with a first sealing means 25 attached to the one respectively inner side of the outer ring 13 and with a second sealing means 26 attached to the other side of the outer ring 13. Each sealing means 25, 26 compris es a sealing element 27, 28, which slidingly contacts the ad jacent stationary surface of the inner ring 14. Each sealing element 27, 28 may comprises lips slidingly contacting the inner ring surface, which lips respectively detailed setup is not shown in the figure.

Each sealing means 25, 26 further comprises a sealing element carrier 29, 30 having a fold 31, 32. Furthermore each sealing means 25, 26 comprises a clamp ring 33, 34 attached to the element carrier 29, 30, which closes the fold 31 for building a respective groove 35, 36, in which the sealing element 27, 28 is arranged respectively clamped.

Both sealing means 25, 26 provide a good and tight sealing, nevertheless some leakage of the lubrication fluid 22 may oc cur. As mentioned this leakage lubrication fluid is collected and redirected to the lubrication circuit 23.

For collecting the leakage fluid leaking from the second sealing means 26 a leakage lubrication fluid collection area 37, which is realised as a circular groove 38 is realised in the clamp ring 34. This groove 38 is as close as possible to the sealing element 32, so that any lubrication fluid leaking from this sealing element 32 is collected in the groove 38.

This leakage lubrication fluid collection area 37 is connect ed to a leakage lubrication fluid collection means 39 real ised as a collector ring 40 extending around the main bear ing. This lubrication collecting means 39 respectively the collector ring 40 is stationary attached preferably to the inner ring 14, so that it is close to the first sealing means 25.

The collector ring 40 comprises a collection groove 41, where any leaking lubrication fluid is collected, which collection groove 41 is connected to the lubrication circuit 23 for re directing the collected leakage fluid.

For transferring leakage fluid collected in the groove 38 several axial bores 42 are provided, which connect the leak age lubrication fluid collection area 37 to the leakage lu brication fluid collection means 39, therefore it connects the groove 38 to the collector ring 40. A number of parallel axial bores 42 are provided and distributed equally around the circumference of the outer ring 13. Each axial bore 42 is open to the groove 38 at the one end and open to the collec- tor ring 40 at the other end. It comprises several bore sec tions, as each axial bore 42 extends through the clamp ring 34, the sealing element carrier 30, the outer ring 13, the sealing element carrier 29 and the clamp ring 33 as fig. 3 clearly shows. All respective bore sections are in alignment, so that a fluid channel is built.

As the main bearing 11 is slightly tilted towards the hori zontal axis as shown by the axis of rotation 18 and the hori zontal axis 19 and the tilt angle a in fig. 3, and as there fore the right side of the main bearing with the first seal ing means 25 is, due to the tilt, somehow lower than the oth er side with the second sealing means 26, each axial bore 42 is also slightly tilted with a tilt angle a towards the hor izontal axis, so that a natural flow direction is realised and the lubrication fluid flows automatically from the groove 38 to the collector ring 40.

When exiting the respective axial bore 42 the lubrication fluid flows on a drip edge ring 43 fixed to the first sealing means 25, which drip edge ring 43 collects the fluid exiting the axial bore 42 and guides it to the collector ring 40. It axially extends into the collector ring 40 as fig. 3 clearly shows.

Not only the lubrication fluid leaking the second sealing means 26 is collected on the drip edge ring 43 and the carri er ring 40, but also the lubrication fluid leaking from the first sealing means 25. This leakage fluid directly flows on the drip edge ring 43 and from there directly to the collec tor ring 40.

The respective leakage fluid flow is shown in fig. 3 by the respective arrows.

The lubrication fluid is present in the inner of the main bearing 11, which is either flooded with the lubrication flu id respectively the oil, or the fluid is directly lubricated to certain points. The lubrication fluid is present in the areas 44, 45 of the main bearing 11, therefore on one side of each sealing means 25, 26, from where it leaks through the sealing means 25, 26 and is collected as explained above.

Fig. 4 shows in an enlarged perspective view the second seal ing means 26 with the sealing element carrier 30 and the clamp ring 34 with the groove 38. Attached to the clamp ring 34 is a sealing element 46 in form of a sealing lip which ex tends to the inner ring 14. This sealing element 46 provides a sealing on this side, so that any leakage lubrication fluid collected in the groove 38 remains in the groove 38 until it flows in the respective bore 42.

For fixing the element carrier 30 tightly to the inner ring 13 and for fixing the clamp ring 34 tightly to the element carrier 30, respective further sealing elements 47, 48 are arranged in respective grooves 49, 50 for example provided in the sealing element carrier 30 and the clamp ring 34 for ex ample. This allows for an axial sealing of this element con nection.

An enlarged view of the other bearing side showing the first sealing means 25 is shown in fig. 5. Also here respective sealing elements 51, 52 are arranged in respective grooves 53, 54, preferably again provided in the surfaces of the sealing element carrier 29 and the clamp ring 33.

Fig. 5 shows furthermore the attachment of the collector ring 40 to the stationary inner ring 14 and the overlap of the drip edge ring 43 over or into the collector ring 40 respec tively the collection groove 41, so that any leakage oil dripping from the drip edge of the drip edge ring 40 directly drips into this collection groove 41.

Fig. 6 shows a cross section view showing the fixation of the first and second sealing means 25, 26 to the outer ring 13. Each sealing element carrier 29, 30 is connected with first bolt connections 55, 56 to the outer ring 13. The outer ring 13 is provided with respective threaded bores, into which the bolt connections 55, 56, which are accommodated in respective through bores of the sealing element carrier 29, 30, are screwed.

The clamp rings 33, 34 and in addition, as a second fixation means, also the whole sealing means 25, 26 is fixed by re spective further bolt connections 57, 58, which engage a re- spective through bore in the clamp ring 33, 34 and the seal ing element carrier 29, 30 and extends into respective threaded bores in the outer ring, as shown in fig. 6.

Although the present invention has been described in detail with reference to the preferred embodiment, the present in vention is not limited by the disclosed examples from which the skilled person is able to derive other variations without departing from the scope of the invention.