BEARING ARRANGEMENT OF A WIND TURBINE

Abstract

Bearing arrangement of a wind turbine, including a bearing with an outer ring and an inner ring and a lubrication fluid provided between both rings, and at least one sealing means arranged at each side of the bearing for sealing the gap between the outer and the inner ring, whereby each sealing means is fixed to one ring and contacts the other ring with a flexible lip-like sealing element, wherein a pressure device for at least temporarily providing a gas overpressure in the sealed gap for increasing the contact load of the lip-like sealing element to the ring is provided.

Claims

1. A bearing arrangement of a wind turbine, comprising: a bearing with an outer ring and an inner ring and a lubrication fluid provided between the outer ring and the inner ring; at least one sealing means arranged at each side of the bearing for sealing a gap between the outer ring and the inner ring, wherein each of the at least one sealing means is fixed to one ring and contacts the other ring with a flexible lip-like sealing element; and a pressure device for at least temporarily providing a gas overpressure in the gap for increasing a contact load of the lip-like sealing element to the ring.

2. The bearing arrangement according to claim 1, wherein the pressure device is configured to provide an air overpressure in the gap.

3. The bearing arrangement according to claim 1, further comprising at least one pressure sensor measuring a gas pressure in the gap, the at least one pressure sensor communicates with a control device of the pressure device.

4. The bearing arrangement according to claim 1, wherein the pressure device comprises at least one controllable pump communicating with the gap for increasing a gas pressure in the gap.

5. The bearing according to claim 4, wherein the pump is connected to the sealed gap via a pipe and at least one valve.

6. The bearing arrangement according to claim 1, wherein the pressure device comprises at least one pressure relief valve connected to the gap for relieving pressure, when a set maximum pressure is reached.

7. The bearing arrangement according to claim 6, wherein the at least one pressure relief valve is connected to a leakage pipe for piping leaking lubrication fluid to a lubrication fluid collection means when the at least one pressure relief valve opens.

8. The bearing arrangement according to claim 1, wherein the pressure device is configured to stepwise raise a gas pressure over time until a maximum pressure is reached.

9. The bearing arrangement according to claim 3, wherein the control device is configured for cyclically controlling a pump to stepwise raise the gas pressure.

10. The bearing arrangement according to claim 1, wherein each of the at least one sealing means comprises at least one lip-like sealing element which is urged by means of one or more spring elements in contact with the ring.

11. A wind turbine, comprising at least one bearing arrangement according to claim 1.

12. A method for reducing an amount of leakage fluid leaking from a bearing of a wind turbine, the bearing comprising an outer ring and an inner ring and a lubrication fluid provided between both the outer ring and the inner ring, with a gap between both rings being sealed by at least two sealing means, whereby each of the at least two sealing means are fixed to one ring and contacts the other ring with a flexible lip-like sealing element, the method comprising: applying a gas overpressure in the gap at least temporarily by a pressure device for increasing a contact load of the lip-like sealing element to the ring.

13. The method according to claim 12, wherein a pressure is constantly increased, or that the pressure is stepwise raised over time until a maximum pressure is reached.

14. The method according to claim 12, wherein a pump controlled by a control device is used for providing the gas overpressure.

15. The method according to claim 12, wherein a pressure relief valve opens, when a maximum pressure in the gap is reached, and that any lubrication fluid leaking from the gap due to an opening of the pressure relief valve is collected in a lubrication fluid collection means.

Description

BRIEF DESCRIPTION

[0028] Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein:

[0029] FIG. 1 depicts a principle illustration of an inventive wind turbine;

[0030] FIG. 2 depicts a principle illustration of an inventive bearing arrangement in a front view;

[0031] FIG. 3 depicts a principle illustration of the bearing arrangement of FIG. 2 in a cross-section through a part of the bearing;

[0032] FIG. 4 depicts a principle illustration of a cross-section of a sealing means of a first type;

[0033] FIG. 5 depicts a principle illustration, in a perspective view, of a sealing means of a second type; and

[0034] FIG. 6 depicts a diagram showing the operation of the pump in a first curve and the pressure in the gap as a second curve over the time.

DETAILED DESCRIPTION

[0035] FIG. 1 shows a wind turbine 1, comprising a tower 2 in a nacelle 3 attached to the top of the tower 2. The nacelle comprises a generator 4, which is connected to a hub 5, to which respective rotor blades 6 are attached. As commonly known, the rotor 7 comprising the hub 5 and the rotor blade 6 rotates in operation and drives the rotor 8 of the generator 4. This rotative arrangement respectively the rotor 8 is attached to a bearing 9, e.g. a main bearing in a direct drive wind turbine.

[0036] Another rotating component is each rotor blade 6, which can be rotated relative to the hub for changing the pitch. Also, each rotor blade 6 is attached to a bearing 10 allowing this rotation.

[0037] FIG. 1 is only a simple principle illustration showing that there are several large bearing 9, 10 at the wind turbine 1, which bear respective large devices, and which can be part of an inventive bearing arrangement, which is disclosed in detail below. The shown bearings 9, 10 are only for illustration purpose. Certainly also other larger bearings of the wind turbine 1 may be part of such a bearing arrangement.

[0038] As commonly known, each bearing 9, 10 comprises an inner ring and an outer ring. One ring is stationary, while the other ring is fixed to the rotating component. Both rings have raceways, on which respective roller elements like rollers, tapered rollers, balls etc. roll. As a lubrication is necessary, a lubrication fluid like a sufficiently viscous grease or oil is provided in the gap between both rings, where the roller elements and raceways are. The gap is sealed to both axial sides by a respective sealing means in order to retain the lubrication fluid in the gap.

[0039] In operation, when the rotor 7 rotates and drives the rotor 8 of the generator 4, high axial and radial loads rest on each respective bearing 9, 10. These loads may vary over the time due to changing operation conditions like changes in the wind direction, in the strength of the blowing wind etc. The loads cause some deformation of the respective bearing 9, 10, especially regarding the position of the rings relative to each other. They may shift relative to each other especially in radial direction leading to a change of the gap geometry respectively the local gap width. This may lead to sealing problems and to an enhanced leakage rate of the lubrication fluid.

[0040] To address this problem the present invention proposes a bearing arrangement 11, a principle example of which is shown in FIGS. 2 and 3. FIG. 2 shows a front view of one of the bearings 9, 10, while FIG. 3 shows a principle cross-section of the bearing 9, 10.

[0041] The bearing 9, 10 comprises an outer ring 12 and an inner ring 13. Each ring has a raceway 14, 15, on which respective roller elements 16, here for example cylindrical rollers, roll. Therefore between both rings 12, 13 a gap 17 is realised, which is sealed on both axial ends by respective sealing means 18, which for example are fixed to the stationary inner ring 13 and seal by contact to the outer ring 12. Each sealing means 18 comprises a fixation part 19, by which it is fixed to the inner ring 13, and a lip-like sealing element 20, which contacts with a certain contact load to the outer ring 12.

[0042] As the geometry of the gap 17 may vary due to the high, changing loads, this sealing contact may be negatively influenced. To address this problem the inventive bearing arrangement comprises a pressure device 21 comprising a pump 22, i.e. a compressor, which is connected by a pipe 23 to a radial inlet bore 24 provided in the inner ring 13 and open to the gap 17. A valve 25 is provided, which is a simple non-return valve allowing the flow of compressed air from the pump 22 through the pipe 23 to the gap 17, and which blocks the return flow, so that an overpressure may be built up or maintained in the sealed gap 17.

[0043] A control device 26 is provided for controlling the operation of the pump 22. The control device 26 communicates with the pressure sensor 27 which is used for, constantly, measuring the gas respectively air pressure in the gap 17, so that the operation of the pump 22 may be controlled based on the sensor information.

[0044] The pressure device 21 further comprises a pressure relief valve 28, which is connected to a radial bore 29 in the inner ring 13, which bore is also open to the gap 17. This pressure relief valve 28 may be an adjustable mechanical valve, which can be adjusted in regard of the air pressure acting on it for opening the pressure relief valve 28, so that a certain maximum overpressure value may be adjusted, which is the pressure value for opening the pressure relief valve 28. It may also be an electromagnetic valve, which can be controlled by the control device 26. As this is only an option, a respective control line is dashed in FIG. 2.

[0045] The function of this pressure relief valve 28 is to open, when a certain overpressure value or level is reached in order to avoid an unwanted rise of the overpressure to amounts which may be harmful for the sealing means 12. The pressure relief value 28 therefore is a safety device.

[0046] As, when the pressure relief valve 28 opens, the gap 17 is open, a certain, even though small amount of lubrication fluid will, together with the gas or air, also escape from the gap 17. For collecting this leakage fluid, a leakage pipe 30 is connected to the pressure relief valve 28, which pipes the leakage fluid to a leakage fluid collection means 31 like a container or the like.

[0047] In operation of the wind turbine 1 a certain distinct overpressure can be built up in the sealed gap 17 by controlling the pump 22. This overpressure increases the contact load respectively the contact force by which the respective sealing element 20 contacts or presses against the ring 12. This enhanced sealing or contact pressure ensures also a tight sealing of the gap 17 even when high loads or high varying loads are applied to the respective bearing 9, 10 resulting in the above mentioned deformation of shifting of the rings 12, 13 relative to each other, changing the geometry of the gap 17. This deformation can be compensated, as due to the increased pressure respectively contact force the lip-like elements 20 are still in contact with the ring 12, so that the tight sealing is maintained.

[0048] FIGS. 4 and 5 show two embodiments of sealing means 12, which may be used. FIG. 4 shows a sealing means, made of an elastic polymer, having a usual design, comprising the fixation part 19, to which the lip-like sealing element 20 is attached. A spring element 32, like a Garter spring, which extends around the complete circumference of the lip-like element 20, forces the sealing element 20 radially in sealing contact to the respective ring. The circumference of the sealing element 20 is large, it may amount to ten or more meters. Therefore, also the circular spring element 32 is very long, resulting in a reduced spring force respectively an uneven forced distribution around the circumference. This may lead to the abovementioned problems.

[0049] But when, according to the present invention, the gas or air overpressure is provided within the gap 17, the radial force, which presses the sealing element 20 against the ring 12, is increased. The overpressure is shown by the cloud symbol 33 and the arrows 34 showing the radial overpressure force acting on the radial lip-like sealing element 20. It is obvious that due to this overpressure 33, and in combination with the spring element 32, the radial sealing force or contact load is increased, so that any deformation may be compensated.

[0050] FIG. 5 shows a sealing element 12 of a second type. It again has a fixation part 19 and a lip-like sealing element 20, which extends radially from the fixation part 19. Again, a spring element 32 is provided, which is embedded in the elastic material the sealing means 12 is made of, for example an elastic polymer etc. The spring element 32, which, like the spring element 32 respectively the Garter spring of FIG. 4, is a metal element, is provided with many slits 35 extending in the axial and radial direction, so that a large number of respective longitudinal spring bars 36 are provided, which act as separate springs for providing a basic contact load.

[0051] This contact load is again increased by providing the gas or air overpressure as symbolised by the cloud symbol 33, so that, as shown by the arrows 34, the lip-like sealing element 20 is urged in contact with the ring with an increased load or force.

[0052] FIG. 6 shows an operation example in form of a diagram with the time shown on the horizontal axis and the operation of the pump 22 and the respective pressure levels shown along the vertical axis.

[0053] The curve I shows the operation of the pump 22. As shown, the pump is most of the time not operating. Only at the distinct times t.sub.1, t.sub.2, . . . , t.sub.6, t.sub.7 the pump is started for a short time, for example 5-10 seconds, with a time gap between each time t.sub.1-t.sub.2, t.sub.2-t.sub.3, etc. of for example 30 minutes. This short time of operation is sufficient to raise the overpressure in the gap 17 from one level to another.

[0054] The respective overpressure is shown by the curve II. In FIG. 6 in the first time slot between 0-t.sub.1 the pressure in the gap 17 is on a first level P.sub.1. At the time t.sub.1 the pump 22 is in operation for some seconds raising the pressure to the second level P.sub.2 as shown in curve II. This level is maintained during the next period between t.sub.1-t.sub.2. At t.sub.2 the pump is again started raising the pressure to the third level P.sub.3, which is maintained until the time t.sub.3, when the pump again is started raising the overpressure to the level P.sub.4. The level P.sub.4 is already close to the maximum overpressure P.sub.max, which may be present in the gap 17, and which is adjusted in regard of the pressure relief valve 28, which will open when this maximum pressure level is reached. This is the case at the time t.sub.4, when the pump 22 is again started raising the overpressure to or above the maximum pressure P.sub.max. This will automatically open the pressure relief valve 28 either due to its mechanical adjustment or based on a control by the control device 26, so that the overpressure relieved. As the curve II clearly shows, the pressure drops again for example to the level P.sub.1. From now on a new cycle starts, where the pressure again is increased stepwise by the short operation of the pump 22 at the respective times t.sub.5, t.sub.6, t.sub.7, . . . , until the maximum pressure P.sub.max is reached again and the pressure drops again as the pressure relief valve 28 opens again. Either the pressure relief valve 28 opens automatically, in case it is a mechanical valve, or it opens by control of the control device 26, in case it is a controllable electromagnetic valve.

[0055] The control of the pump 22 may also be based on the measured pressure values delivered from the pressure sensor 27. The control device 26 may control the operation of the pump 22 to raise the pressure, until the respective pressure level P.sub.2, P.sub.3, P.sub.4 is reached and will immediately stop the pump 22, when the pressure sensor 27 measures the respective pressure value.

[0056] In an alternative the pressure may also be maintained on a constant higher level, which is somewhere below the maximum pressure P.sub.max, without a stepwise change. The pressure is constantly monitored by the pressure sensor 27 as a control basis for the control device 26 controlling the pump 22, which is started as soon as a pressure drop to a certain mower pressure value is measured to immediately raise the pressure again to the higher level. This allows to maintain the pressure constantly in a set pressure interval. Nevertheless, the pressure relief valve 28 as a safety device will open in any case the pressure exceed the maximum pressure P.sub.max.

[0057] Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.

[0058] For the sake of clarity, it is to be understood that the use of “a” or “an” throughout this application does not exclude a plurality, and “comprising” does not exclude other steps or elements.