Wind turbine bearings

Abstract

The invention relates to a bearing arrangement for a wind turbine. A bearing arrangement for a wind turbine (1) comprises: a bearing (9, 10) having an outer ring (12) and an inner ring (13) and a lubricating fluid provided between the two rings (12, 13); and at least one sealing device (18) arranged at each side of the bearing (9, 10) for sealing a gap (17) between the outer ring (12) and the inner ring (13), whereby each sealing device (18) is fixed to one ring (12, 13) and contacts the other ring (12, 13) by means of a flexible lip-shaped sealing element (20), wherein a pressure device (21) is provided for at least temporarily providing a gas overpressure (33) in the sealed gap (17) in order to increase the contact load of the lip-shaped sealing element (20) with the rings (12, 13).

Description

Technical Field

[0001] The present invention relates to a bearing device for a wind turbine, the bearing device comprising: a bearing having an outer ring and an inner ring and a lubricating fluid provided between the two rings; and at least one sealing device, which is arranged at each side of the bearing for sealing a gap between the outer ring and the inner ring, whereby each sealing device is fixed to one ring and contacts the other ring with a flexible lip-shaped sealing element. Background Art

[0002] As is known, a wind turbine comprises a tower and a nacelle fixed to the top of the tower. A hub is arranged at the nacelle, to which several rotor blades are attached. As is known, the hub rotates when the turbine blades interact with the incoming wind and drive a generator to generate electricity. Such a wind turbine comprises several rotating elements, which are arranged in corresponding bearings. One example is the main bearing of the generator at a direct drive wind turbine, another example is the blade bearing, by which the rotor blades whose pitch can be changed are attached to the hub.

[0003] Each bearing comprises an inner ring and an outer ring and roller elements, such as tapered rollers or balls rolling on two rings separated in radial direction by a gap. In the gap, a lubricating fluid, such as a glue or liquid grease or fluid, is arranged to lubricate the roller elements and, accordingly, the raceways of the rings. In order to avoid leakage of the lubricating fluid from the gap, each bearing is sealed by a corresponding sealing device, which seals the gap on both axial sides of the bearing so as to provide a closed, sealed gap for blocking lubricant. Each sealing device comprises an attachment portion, by which the sealing device is attached to one ring, such as a non-rotating ring. It also comprises at least one flexible lip-shaped sealing element, which contacts another ring, such as a rotating ring. These sealing devices are usually annular rubber seals, which, since the bearing has a diameter of several meters, have a corresponding length of several meters, such as up to ten meters or more.

[0004] When the wind turbine is in operation, the bearings are subject to high axial and radial loads, which may vary significantly during operation when the operating conditions change. These loads will subject the bearings to deformations, especially between the inner ring and the outer ring, which may move relative to each other. This deformation movement has a negative impact on the sealing performance, since the gap width and, since the sealing device is fixed to a ring, the contact of the lip-shaped sealing element with the corresponding contact surface of the ring may also change. As a result, increased leakage occurs due to the unevenness of the contact load of the lip-shaped sealing element with the ring.

[0005] To address this problem, the geometry of the sealing arrangement has been adapted to provide a more even lip load distribution. However, some leakage may still occur. The problem is also still prominent at bearings that still have older seal types that do not have any improved lip geometry. The only option to avoid any excessive leakage is to replace the seal with a new one. This process is very time consuming and expensive and may also increase the risk of introducing contamination into the bearing and, thereby, the risk of pre-major bearing failure due to hard particle indentation. Summary of the invention

[0006] It is therefore an object of the present invention to provide an improved bearing arrangement for a wind turbine.

[0007] To solve this problem, the present invention proposes a bearing device as mentioned above, characterized in that a pressure device is provided for at least temporarily providing a gas overpressure in the sealed gap to increase the contact load between the lip seal element and the ring.

[0008] The invention proposes to provide a certain gas overpressure in the sealed gap at least temporarily, preferably permanently. This gas overpressure acts on the flexible lip-shaped sealing elements of the two sealing devices and, as a result, increases the contact load of the lip-shaped sealing elements, so that the lip-shaped sealing elements are pressed into stronger contact with the rings than without the contact load or contact pressure of the overpressure. As a result, the sealing performance can be significantly improved and, even when higher loads are applied to the bearing, resulting in greater deformations of the bearing, the gap is still sealed due to the improved contact of the sealing element with the rings, even if the rings move relative to each other. Due to the gas overpressure and the increased contact load, the lip-shaped sealing elements can follow the deformation and, as a result, can maintain the sealing contact. This ensures an improved gap sealing, so that the leakage over time can be significantly reduced.

[0009] A further advantage of the improved bearing arrangement is that the sealing performance of already installed older sealing types with a simpler lip design can also be improved, since due to the gas overpressure the contact load of these conventional or corresponding unimproved sealing arrangements or corresponding lip elements can also be increased, resulting in better sealing performance.

[0010] As mentioned, the invention proposes to provide a gas overpressure in the sealed gap. This is achieved by pressing the gas into the gap, which is a sealed and almost gastight space, which is sealed radially by two rings and axially by the at least two sealing devices. Since it is of course possible to press a specific gas into the sealed gap, which may be free of any moisture etc., i.e. nitrogen, it is preferred to simply use air as the pressurized gas. Therefore, the pressure device is preferably suitable for providing an air overpressure in the sealed gap, so that no specific gas is used that needs to be provided in a corresponding gas tank.

[0011] In another embodiment of the invention, at least one pressure sensor is provided for measuring the gas pressure in the gap, the pressure sensor communicating with the control device of the pressure device. The control device controls at least the pressurization process by controlling a corresponding pressurization device, which presses gas or respectively air into the sealed gap. In order to monitor the gas pressure in the gap, at least one pressure sensor is provided, which measures the gas pressure in the gap. Based on the sensor information, the control can then control the corresponding pressurization device in order to increase the pressure if necessary and control the overpressure to be in a certain pressure interval.

[0012] The pressure device may comprise at least one controllable pump, which is in communication with the sealed gap, for increasing the gas pressure in the sealed gap. A simple pump, i.e. a compressor, is sufficient to provide the gas overpressure, the pump or a corresponding compressor being connected to the gap via a corresponding pipe. The operation of the pump or the corresponding compressor is controlled by a corresponding control device, so that the gas overpressure can be precisely controlled, in particular when a pressure sensor for monitoring the gas pressure is provided.

[0013] The pump is preferably connected to the sealed gap via a tube and at least one valve, which allows the gas in the gap to be pumped, but prevents a return gas flow from the gap to the pump. Therefore, the valve is preferably a simple check valve, which is sufficient to provide a corresponding gas flow in the gap, but prevents a return flow.

[0014] Another embodiment of the present invention proposes that the pressure device includes at least one pressure relief valve connected to the sealed gap for releasing pressure when reaching a set maximum pressure. The gas pressure in the gap can be increased by pumping action. As a safety device, a pressure relief valve is provided, which opens and thus allows the release of the overpressure when the overpressure reaches or exceeds the maximum pressure. Therefore, when the pressure device or the corresponding pump increases the overpressure, the overpressure will not actually exceed the set maximum pressure, because when the maximum pressure value is reached, the pressure relief valve will automatically open. Integrating the pressure relief valve (pressure relief value) is a safety measure, which, for example, in combination with a pressure sensor, helps to avoid a pressure rise exceeding a certain maximum value, which will be harmful to the gap seal.

[0015] The pressure relief valve may be a mechanically adjustable valve, which allows adjustment of the maximum pressure at which the valve opens. In an alternative, the pressure relief valve may also be a controllable solenoid valve, which is preferably controlled by the control device controlling the pressure device.

[0016] The pressure relief valve is preferably connected to a leakage pipe for conveying the leaking lubricating fluid via the pipe to a lubricating fluid collecting device when the pressure relief valve is open. When this maximum pressure is reached and the pressure relief valve is open, a certain amount of lubricating fluid will simultaneously leave the gap via the pressure relief valve. In order to avoid an uncontrolled exit of the lubricating fluid, the pressure relief valve is connected to a leakage pipe, via which the leaking fluid is conveyed by a pipe to a leaking fluid collecting device. This allows collecting the leaking fluid, even if the amount of fluid is small. The collecting device can be a simple container in which the fluid is collected, which is emptied from time to time.

[0017] Over time, the overpressure can be maintained at a constant level. The control device controls the pressure device or a corresponding pump to keep the overpressure at a certain value, respectively in a certain pressure interval. This ensures that a continuously increasing contact load is placed on the lip sealing element and thus on the sealing contact with the ring.

[0018] In a preferred alternative, the pressure device is adapted to gradually increase the gas pressure over time until a maximum pressure is reached. According to this embodiment, a constant gas pressure is not provided, but a variable gas pressure is provided, which is gradually or correspondingly increased at several pressure levels until a maximum pressure value or a corresponding level is reached. When the maximum pressure value or a corresponding level is reached, for example, a pressure relief valve is opened for a certain time, for example, so that the overpressure is controlled to be reduced to a lower level, so that the overpressure in the gap can be gradually increased again. The time for the release valve to be opened can be controlled by the control device in response to the pressure measurement result of the pressure sensor. When the sensor measures that a defined lower pressure value is reached, the control device will close the pressure relief valve again, and a new cycle begins. Even if such a pressure relief value is not provided, after reaching the maximum pressure value or a corresponding level, the gas pressure will also decrease over time, because the sealed gap is not completely airtight, resulting in a certain pressure drop over time. When the pressure is reduced to a certain pressure value or a corresponding level again, a new step-like increase cycle can begin. An advantage of applying a non-constant overpressure and thus a varying pressure on the sealing lip is that the wear of the seal is reduced, which increases the service life of the seal.

[0019] The purpose of the gas overpressure in the sealed gap is to increase the load placed on the corresponding lip-shaped sealing element and, therefore, to increase the contact load or contact force with which the sealing element contacts or presses against the corresponding ring. In order to ensure that each sealing element contacts the ring with a certain contact load even without the application of an overpressure, each sealing device therefore preferably comprises at least one lip-shaped sealing element, which is urged into contact with the ring by means of one or more spring elements. As mentioned, each sealing element, which is usually made of an elastic polymer or a corresponding rubber or the like, comprises at least one spring element, which urges the sealing lip into contact with the ring. The spring element can be a separate spring element attached to the sealing device. In an alternative, the spring element can also be incorporated in or respectively embedded in the sealing device.

[0020] In a first embodiment, the spring element can be a circular spring extending around the perimeter of the lip element, in particular an annular helical spring. The spring element in this embodiment is a separate element attached to the seal. As already mentioned, the length of the circular sealing device is noteworthy, due to the diameter of the bearing, it can have a length of several meters, even up to ten meters or more. Therefore, the spring element or the corresponding annular helical spring is also very long. It has been shown that the longer the sealing device or the corresponding spring element or annular helical spring is, the lower the pressure applied by the spring element on the sealing lip, and the local pressure seen along the perimeter is also uneven in some way. Therefore, the spring element provides a certain basic load, which is increased by the overpressure provided by the pressure device.

[0021] In an alternative to a separate circular spring element or a corresponding annular helical spring, the corresponding sealing device may also include a circular spring element having a plurality of longitudinal spring rods extending axially along the lip-shaped sealing element. In this embodiment, in which the sealing element is preferably integrated or correspondingly embedded in a matrix of a material or a corresponding sealing device material, the spring element comprises a greater number of longitudinal spring rods extending axially along the lip-shaped sealing element. These spring rods may be realized by corresponding grooves arranged at the spring element. A large number of spring rods provide a higher basic load, which is evenly distributed around the periphery because each spring rod is a separate small spring. In addition, in this embodiment, the basic contact load provided by the spring element is significantly increased by the overpressure achieved in the sealed gap according to the invention.

[0022] In addition to the bearing arrangement of the invention, the invention also relates to a wind turbine comprising at least one bearing arrangement as mentioned above. The bearing arrangement may be a main bearing, or respectively comprise a main bearing of a direct drive wind turbine, or may be or comprise a corresponding blade bearing. The enumeration of corresponding bearings that may be part of the bearing arrangement is not exhaustive, since other bearings that present leakage problems in operation may also be part of the bearing arrangement of the wind turbine.

[0023] Finally, the invention relates to a method for reducing the amount of leakage fluid leaking from a bearing of a wind turbine, the bearing comprising an outer ring and an inner ring and a lubricating fluid provided between the two rings, wherein the gap between the two rings is sealed by at least two sealing devices, whereby each sealing device is fixed to one ring and contacts the other ring by means of a flexible lip-shaped sealing element. The method is characterized in that a gas overpressure is applied at least temporarily in the sealed gap by means of a pressure device in order to increase the contact load of the lip-shaped sealing element with the rings.

[0024] The pressure may be continuously increased so that a constant overpressure value or level is maintained. In an alternative, the pressure may rise gradually over time until a maximum pressure is reached. The maximum pressure may then be automatically reduced again, for example by a pressure relief valve, which opens when the maximum pressure is reached so that a new step-by-step pressurization cycle can begin. In an alternative, the high pressure may also decrease over time due to some air leakage from the gap of a not completely airtight seal.

[0025] To provide the gas overpressure, preferably air overpressure, a pump may be used, which is controlled by a control device. The control device may communicate with a pressure sensor measuring the gas pressure in the gap, so that the pump may be controlled based on the sensor information.

[0026] As already mentioned, the pressure relief valve can open when the maximum pressure in the sealed gap is reached. When the valve is open, a small amount of lubricating fluid will leak from the gap through the valve. The leaking fluid is preferably collected in a lubricating fluid collecting device, to which it is led via a pipe, which is attached to the corresponding pressure relief valve, or respectively, the corresponding pressure relief valve is integrated into the pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. However, the accompanying drawings are only schematic diagrams designed for illustrative purposes only and do not limit the present invention. The accompanying drawings show:

[0028] Figure 1 A schematic diagram of a wind turbine according to the present invention is shown,

[0029] Figure 2 The front view shows the principle diagram of the bearing device of the present invention.

[0030] Figure 3 The cross-section through a portion of the bearing shows Figure 2 Schematic diagram of the bearing device,

[0031] Figure 4 a schematic diagram showing a section through a sealing device of a first type,

[0032] Figure 5 A schematic diagram of a second type of sealing device is shown in perspective, and

[0033] Figure 6 A diagram is shown which shows the operation of the pump as a first curve and the pressure in the gap as a second curve over time. DETAILED DESCRIPTION

[0034] Figure 1 A wind turbine 1 is shown, comprising a tower 2 and 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 is known, a rotor 7 comprising the hub 5 and the rotor blades 6 rotates in operation and drives a rotor 8 of the generator 4. The rotating arrangement or respectively the rotor 8 is attached to a bearing 9, such as a main bearing in a direct drive wind turbine.

[0035] Another rotating component is each rotor blade 6, which can rotate relative to the hub for changing the pitch. In addition, each rotor blade 6 is attached to a bearing 10, allowing this rotation.

[0036] Figure 1It is only a simple schematic diagram, which shows that there are several large bearings 9, 10 at the wind turbine 1, which support corresponding large devices and can be part of the bearing device of the present invention disclosed in detail below. The bearings 9, 10 shown are only for illustration purposes. Of course, other larger bearings of the wind turbine 1 can also be part of such a bearing device.

[0037] As is known, each bearing 9, 10 comprises an inner ring and an outer ring. One ring is fixed, while the other ring is fixed to the rotating part. Both rings have raceways on which corresponding roller elements such as rollers, tapered rollers, balls or the like roll. Since lubrication is necessary, a lubricating fluid, such as grease or oil of sufficient viscosity, is provided in the gap between the two rings where the roller elements and the raceways are located. The gap is sealed to both axial sides by corresponding sealing means in order to keep the lubricating fluid in the gap.

[0038] In operation, when the rotor 7 rotates and drives the rotor 8 of the generator 4, high axial and radial loads are placed on each respective bearing 9, 10. These loads may vary over time due to changing operating conditions, such as changes in wind direction, strength of the blowing wind, etc. These loads cause certain deformations of the respective bearings 9, 10, especially with regard to the position of the rings relative to each other. They may shift relative to each other, especially in the radial direction, resulting in changes in the gap geometry or the respective local gap widths. This may lead to sealing problems and to an increased leakage rate of the lubricating fluid.

[0039] In order to solve this problem, the present invention proposes a bearing device 11, the principle of which is shown in Figure 2 and Figure 3 Shown in. Figure 2 A front view of one of the bearings 9, 10 is shown, and Figure 3 A principle cross-sectional view of a bearing 9 , 10 is shown.

[0040] The bearings 9, 10 comprise 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. Thus, a gap 17 is achieved between the two rings 12, 13, which gap 17 is sealed on both axial ends by respective sealing means 18, which are for example fixed to the fixed inner ring 13 and sealed to the outer ring 12 by contact. Each sealing means 18 comprises a fixing portion 19, by which the sealing means 18 is fixed to the inner ring 13, and a lip-shaped sealing element 20, which contacts the outer ring 12 with a certain contact load.

[0041] Since the geometry of the gap 17 may change due to high, varying loads, the sealing contact may be negatively affected. In order to solve this problem, the bearing device of the invention comprises a pressure device 21, which comprises a pump 22, i.e. a compressor, which is connected via a pipe 23 to a radial inlet hole 24, which is arranged in the inner ring 13 and opens into the gap 17. A valve 25 is provided, which is preferably a simple non-return valve, which allows compressed air to flow from the pump 22 through the pipe 23 to the gap 17 and which blocks a return flow, so that an overpressure can be established or maintained in the sealed gap 17.

[0042] The control device 26 is arranged for controlling the operation of the pump 22. The control device 26 is preferably in communication with a pressure sensor 27 for preferably constantly measuring the gas pressure or respectively air pressure in the gap 17 so that the operation of the pump 22 can be controlled based on the sensor information.

[0043] The pressure device 21 further comprises a pressure relief valve 28 connected to a radial hole 29 in the inner ring 13, which also opens into the gap 17. The pressure relief valve 28 can be an adjustable mechanical valve, which is adjustable with respect to the air pressure acting thereon for opening the pressure relief valve 28, so that a certain maximum overpressure value can be adjusted, which is the pressure value for opening the pressure relief valve 28. It can also be a solenoid valve, which can be controlled by the control device 26. Since this is only an option, the corresponding control lines are in Figure 2 Indicated by dotted line.

[0044] The function of the pressure relief valve 28 is to open when a certain overpressure value or level is reached, in order to avoid an undesired rise in overpressure to an amount that could be harmful to the sealing device 12. The pressure relief valve 28 is therefore a safety device.

[0045] Since the gap 17 is open when the pressure relief valve 28 is opened, a certain amount of lubricating fluid, even a small amount, will escape from the gap 17 together with the gas or air. In order to collect the leakage fluid, a leakage pipe 30 is connected to the pressure relief valve 28, which conveys the leakage fluid through a pipe to a leakage fluid collection device 31, such as a container or the like.

[0046] In operation of the wind turbine 1, a certain different overpressure can be established in the sealed gap 17 by controlling the pump 22. This overpressure increases the contact load or the corresponding contact force at which the respective sealing element 20 contacts or presses against the ring 12. This increased sealing or contact pressure ensures a tight sealing of the gap 17 even when high loads or highly varying loads are applied to the respective bearings 9, 10, resulting in the above-mentioned deformations in which the rings 12, 13 are displaced relative to each other, thereby changing the geometry of the gap 17. This deformation can be compensated because the lip element 20 is still in contact with the ring 12 due to the increased pressure or the corresponding contact force, so that a tight seal is maintained.

[0047] Figure 4 and Figure 5 Two embodiments of sealing devices 12 that may be used are shown. Figure 4 A sealing device made of an elastic polymer is shown, which has a conventional design, comprising a fixed part 19 to which a lip-shaped sealing element 20 is attached. A spring element 32, such as a Garter spring, extending around the entire circumference of the lip-shaped element 20, urges the sealing element 20 radially into sealing contact with the corresponding ring. The circumference of the sealing element 20 is large, which can reach ten meters or more. Therefore, the circular spring element 32 is also very long, resulting in a reduced spring force, which in turn results in an uneven forced distribution around the circumference. This may lead to the above-mentioned problems.

[0048] However, according to the invention, the radial force pressing the sealing element 20 against the ring 12 increases when a gas or air overpressure is provided in the gap 17. This overpressure is illustrated by the cloud symbol 33 and the arrow 34, which illustrates the radial overpressure acting on the radial lip-shaped sealing element 20. Obviously, due to this overpressure 33, and in combination with the spring element 32, the radial sealing force or contact load increases, so that any deformations can be compensated.

[0049] Figure 5 A second type of sealing element 12 is shown. It also has a fixed portion 19 and a lip-shaped sealing element 20, which extends radially from the fixed portion 19. Likewise, a spring element 32 is provided, which is preferably embedded in the elastic material of which the sealing device 12 is made, such as an elastic polymer or the like. Figure 4 The spring element 32 , which is a metal element like a spring element 32 or a corresponding annular helical spring, is provided with a number of slots 35 extending in axial and radial direction, so that a large number of corresponding longitudinal spring rods 36 are provided, which act as separate springs for providing the basic contact load.

[0050] By providing a gas or air overpressure as indicated by cloud symbol 33 , the contact load is increased again so that the lip seal element 20 is urged into contact with the ring with an increased load or force as indicated by arrow 34 .

[0051] Figure 6 An example of operation is shown in the form of a diagram having time shown on the horizontal axis, and operation of the pump 22 and corresponding pressure levels shown along the vertical axis.

[0052] Curve I shows the operation of the pump 22. As shown, the pump is not operated for most of the time. Only at different times t1, t2, ..., t6, t7, the pump is activated for a short time, for example 5-10 seconds, while the time interval t1-t2, t2-t3, etc. between each time is, for example, 30 minutes. This short operation is sufficient to raise the overpressure in the gap 17 from one level to another.

[0053] The corresponding overpressure is shown by curve II. Figure 6 In the first time interval between 0 - t1, the pressure in the gap 17 is at a first level P1. At time t1, the pump 22 is operated for a few seconds, causing the pressure to rise to a second level P2, as shown in curve II. This level is maintained during the next time period between t1 - t2. At t2, the pump is started again, causing the pressure to rise to a third level P3, which is maintained until time t3, when the pump is started again, causing the overpressure to rise to a level P4. This level P4 is already close to the maximum overpressure P that can exist in the gap 17. max , and the maximum overpressure P max The pressure relief valve 28 is adjusted so that when this maximum pressure level is reached, the pressure relief valve 28 will open. This is the case at time t4, when the pump 22 is started again, causing the overpressure to rise to or above the maximum pressure P. max This automatically opens the pressure relief valve 28, either due to its mechanical adjustment or due to the control of the control device 26, so that the overpressure is released. As curve II clearly shows, the pressure drops again to, for example, level P1. From now on, a new cycle begins, in which, at corresponding times t5, t6, t7, ..., the pressure is increased again stepwise by brief operation of the pump 22 until the maximum pressure P is reached again. max , and the pressure drops again as the pressure relief valve 28 opens again. In the case where the pressure relief valve 28 is a mechanical valve, it opens automatically, or in the case where it is a controllable solenoid valve, it opens through the control of the control device 26.

[0054] The control of the pump 22 may also be based on the measured pressure value transmitted from the pressure sensor 27. The control device 26 may control the operation of the pump 22 to increase the pressure until the corresponding pressure level P2, P3, P4 is reached, and will immediately stop the pump 22 when the pressure sensor 27 measures the corresponding pressure value.

[0055] In an alternative, the pressure may also be maintained at a constant higher level without step changes, the higher level being somewhere below the maximum pressure P max Preferably, the pressure sensor 27 continuously monitors the pressure as the control basis of the control device 26 controlling the pump 22. Once the pressure drops to a certain lower pressure value (mower pressure value), the pump 22 will start to immediately raise the pressure to the higher level again. This allows the pressure to be continuously maintained in the set pressure interval. Nevertheless, the pressure relief valve 28 as a safety device will still be opened when the pressure exceeds the maximum pressure P max Open in any case.

[0056] Although the present invention has been described in detail with reference to the preferred embodiments, the present invention is not limited to the disclosed examples, and those skilled in the art will be able to derive other variations from the disclosed examples without departing from the scope of the present invention.

Claims

1. A bearing device for a wind turbine (1), comprising: A bearing (9, 10) having an outer ring (12) and an inner ring (13) and a lubricating fluid provided between the two rings (12, 13); and at least one sealing device (18) arranged at each side of the bearing (9, 10) for sealing the gap (17) between the outer ring (12) and the inner ring (13), whereby each sealing device (18) is fixed to one ring (12, 13) and contacts the other ring (12, 13) by means of a flexible lip-shaped sealing element (20), characterised in that pressure means (21) are provided for at least temporarily providing a gas overpressure (33) in the sealed gap (17) in order to increase the contact load of the lip-shaped sealing element (20) with the rings (12, 13) on both sides of the bearing, The pressure device (21) comprises at least one controllable pump (22), and the pump (22) is connected to the sealed gap (17) to increase the gas pressure in the sealed gap (17).

2. The bearing device according to claim 1, characterized in that: The pressure device (21) is suitable for providing an air overpressure in the sealed gap (17).

3. The bearing device according to claim 1 or 2, characterized in that: At least one pressure sensor (27) is provided for measuring the gas pressure in the gap (17), the pressure sensor (27) communicating with a control device (26) of the pressure device (21).

4. The bearing device according to claim 1, characterized in that: The pump (22) is connected to the sealed gap (17) via a pipe (23) and at least one valve (25).

5. The bearing device according to claim 1, characterized in that: The pressure device (21) comprises at least one pressure relief valve (28) connected to the sealed gap (17) for releasing the pressure when a set maximum pressure is reached.

6. The bearing device according to claim 5, characterized in that: The pressure relief valve (28) is connected to a leakage pipe (30) for conveying leaked lubricating fluid to a lubricating fluid collecting device (31) through the pipe when the pressure relief valve (28) is opened.

7. The bearing device according to claim 1, characterized in that: The pressure device (21) is suitable for gradually increasing the gas pressure over time until a maximum pressure is reached.

8. The bearing device according to claim 3, characterized in that: The control device (26) is adapted to cyclically control the pump (22) to gradually increase the gas pressure.

9. The bearing device according to claim 1, characterized in that: Each sealing device (18) comprises at least one lip-shaped sealing element (20) which is urged into contact with the rings (12, 13) by means of one or more spring elements (34).

10. A wind turbine comprising at least one bearing device (11) according to any of the preceding claims.

11. A method for reducing the amount of leakage fluid leaking from a bearing (9, 10) of a wind turbine (1), the bearing (9, 10) comprising an outer ring and an inner ring (12, 13) and a lubricating fluid provided between the two rings (12, 13), wherein: The gap (17) between two rings (12, 13) is sealed by at least two sealing devices (18) at both sides of the bearing (9, 10), whereby each sealing device (18) is fixed to one ring (12, 13) and contacts the other ring (12, 13) by means of a flexible lip-shaped sealing element (20), characterised in that a gas overpressure (33) is applied at least temporarily in the sealed gap (17) by means of a pressure device (21) in order to increase the contact load of the lip-shaped sealing element (20) with the rings (12, 13) on both sides of the bearing, The pressure device (21) comprises at least one controllable pump (22), and the pump (22) is connected to the sealed gap (17) to increase the gas pressure in the sealed gap (17).

12. The method according to claim 11, characterized in that The gas pressure continues to increase, or the gas pressure gradually increases over time until a maximum pressure is reached.

13. The method according to claim 11 or 12, characterized in that: When the maximum pressure in the sealed gap (17) is reached, the pressure relief valve (28) opens and any lubricating fluid leaking from the gap (17) due to the opening of the pressure relief valve (28) is collected in a lubricating fluid collecting device (31).

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