Main bearing for a wind turbine

Abstract

A main bearing for a wind turbine (1), comprising a stationary ring (14) and a rotating ring (13) to be coupled to a rotor (2), wherein the main bearing (11) is a fluid film bearing (12), the fluid film bearing (12) comprising a plurality of bearing units (15, 16) arranged at the stationary ring (14) around the perimeter on both sides of the rotating ring (13) for radially and axially supporting the rotating ring (13), and the fluid film bearing (12) further comprising a load measuring arrangement (31) for determining measurement data which is a measure of the load applied to at least one of the axial or radial bearing units (15, 16, 17) or placed thereon.

Description

Technical Field

[0001] The present invention relates to a main bearing for a wind turbine, which main bearing comprises a stationary ring and a rotating ring to be coupled to a rotor. Background Art

[0002] As is well known, a wind turbine comprises a rotor which comprises a hub having one or more rotor blades, typically three rotor blades, attached thereto. The hub is connected to a main bearing arranged at a nacelle. The main bearing comprises a stationary ring and a rotating ring coupled to the rotor. The hub is also coupled to a generator. Wind interacts with the rotor blades such that the rotor rotates and drives the generator. As mentioned, for example, the main bearing, which may be a single bearing or a double bearing system relative to a two-bearing system, is responsible for providing a rotational arrangement of the rotor relative to a fixed part, such as a main beam or a shaft and a related floor support arranged in the nacelle. Thus, the loads of the rotor are borne by the main bearing and ultimately transmitted via the main bearing to the fixed part of the arrangement.

[0003] Considering the loads to be borne, the main bearing is typically a roller bearing, such as a double-row tapered roller bearing, which is used, for example, in a direct drive wind turbine, but can also be used in a turbine having a gear connection between the rotor and the generator. In a rotor bearing, the roller elements roll on corresponding running surfaces of an inner ring and an outer ring. The size or the corresponding setting of the roller bearing is selected in particular to meet mechanical requirements in order to bear the rotor loads, which may also vary during operation due to operating conditions. Since the layout of the roller bearing is very robust in this situation, the bearing is very heavy and expensive and has poor scalability. Summary of the Invention

[0004] An object of the present invention is to provide an improved main bearing for a wind turbine.

[0005] To solve this problem, the present invention proposes a main bearing for a wind turbine, which main bearing comprises a stationary ring and a rotating ring to be coupled to a rotor. The main bearing is a fluid film bearing comprising a plurality of bearing units. These bearing units may in particular be radial bearing units, axial bearing units and / or tapered bearing units. These bearing units are arranged around the perimeter at the stationary ring on both sides of the rotating ring for radially and axially supporting the rotating ring. The main bearing further comprises a load measurement arrangement for determining measurement data which is a measure of the load applied to or placed on at least one of the bearing units.

[0006] The main bearing is a fluid film bearing and does not include any roller elements as in roller bearings. Instead, a thin fluid film is used as a hydrodynamic or hydrostatic sliding device. This fluid film exists between the respective sliding surfaces of the rotating ring and the bearing units arranged at the stationary ring. These bearing units can include: a radial bearing unit for radially guiding the rotating ring; and axial bearing units arranged on both sides of the stationary ring and facing the axial sliding surfaces of the rotating ring. Additionally, these bearing units can also include tapered bearing units. Generally, a tapered bearing is a bearing that can support axial as well as radial forces. In a tapered bearing, the inner and outer raceways are typically tapered sections. The respective tapered bearing units can additionally be formed tapered. A plurality of bearing units are arranged around the perimeter of the rotating ring. This type of main bearing is advantageous over roller bearings in that they are generally less heavy and less expensive while exhibiting enhanced bearing characteristics and improved scalability.

[0007] The main bearing also includes a load measurement arrangement adapted to determine measurement data that is a measure of the load applied to at least one of the axial or radial bearing units or placed thereon. Thus, the main bearing of the present invention is characterized by an integrated load measurement arrangement that allows for continuous measurement of the load applied to one or more main bearings of a wind turbine rotor during standstill as well as during its operation. A control device connected to or being part of the load management arrangement continuously receives the measurement data and processes them, and this data or the corresponding load information is relevant for various purposes. First, such loads are directly related to the aerodynamic loads on the turbine blades. Thus, the load measurement results can be used as an additional input to the wind turbine controller that determines pitch and yaw angle actuation and can accordingly control blade actuation. Additionally, it can also control the power output or other parameters that affect the turbine loads. Second, the measurement data can provide information regarding load shearing between the bearing units, which can include sliding pads that may be tilted. This load information can be used to continuously monitor the condition of the bearing units or the corresponding sliding pads as well as the bearing clearance between the bearing units and the rotating ring. Thus, it allows for wear or corresponding maintenance control.

[0008] As mentioned above, the load measurement arrangement may be adapted to measure load data applied to or placed on at least one of the radial or axial bearing units. Thus, for example, load information related to only one axial bearing unit or only one radial bearing unit may already provide a good information basis to be processed by the controller. However, the more measurement data available, the better the overall information about the load distribution and the like. Therefore, the measurement arrangement is preferably adapted to determine measurement data for at least one axial bearing unit and at least one radial bearing unit and preferably for all axial, radial and / or tapered bearing units. Preferably, measurement data for at least one axial bearing unit and at least one radial bearing unit are provided such that axial and radial load data are available and can be processed. However, since a plurality of axial and radial bearing units are provided around the perimeter, in the most complex embodiments of the present invention, measurement data for all axial and / or radial bearing units, preferably measurement data for all axial and radial bearing units, are obtained and provided such that the overall load distribution is continuously monitored and can be processed or taken into account accordingly when controlling any load-related device of the turbine.

[0009] The measurement arrangement may be a direct measurement arrangement for directly measuring data at the at least one bearing unit or respectively at a plurality or all bearing units. In this embodiment, the measurement arrangement or respectively one or more sensors forming part of the arrangement and measuring the load directly measure information data at the unit of the load. In an alternative, the measurement arrangement may be adapted to indirectly measure data remote from the at least one bearing unit. In this embodiment, the sensor or each sensor is not directly arranged at the bearing unit of the load, but is arranged remote therefrom such that the sensor measures data which are indirect measurement data or respective values, but which are also a very accurate measure of the actual load placed on the bearing unit.

[0010] If the measurement arrangement is a direct measurement arrangement, it may include at least one measuring device which is directly attached to the at least one bearing unit. In this direct measurement embodiment, at least one measuring device, i.e. the respective sensor or sensor device, is directly attached to the bearing unit of the load whose load is to be measured. If only one bearing unit is under surveillance, only that single bearing unit is provided with a measuring device or respective sensor. If more than one bearing unit is under surveillance, each bearing unit is provided with a separate measuring device or respective sensor.

[0011] In another embodiment of this alternative, the measuring device is or includes at least one strain gauge or at least one load sensor arranged at the support structure of the at least one bearing unit. The measuring device or the corresponding sensor or sensor device is a separate strain gauge or load sensor, which may, for example, include several strain gauges or an array of strain gauges, etc. However it is arranged, the measuring device is arranged or attached to the support structure of at least one or each bearing unit to be measured. The bearing unit typically includes a slide pad, which is attached to the support structure, through which the bearing unit is fixed to the fixed part of the main bearing or the corresponding fixed ring. The connection between the slide pad and the support structure can be a ball-and-socket joint, such that the pad can be slightly tilted relative to the support structure and thus relative to the fixed ring in order to follow any small movement or tilt of the rotatable ring on which the rotor load is placed. The load placed on the slide pad is directly transferred to the support structure, where the corresponding load can be measured using the measuring device.

[0012] If a ball-and-socket joint is used, which is only mentioned as an example for coupling the bearing pad to the support structure to allow a certain movement, the ball-and-socket joint includes a ball head provided at the bearing pad and a socket provided at the support structure, whereby the strain gauge or load sensor is mounted adjacent to the socket on the underside of the support structure. Since the ball-and-socket joint or the corresponding ball head engaged in the socket is the mechanical interface between the bearing or the slide pad and the support structure, the load is transferred across this interface, and thus, it can be precisely measured in the area of this interface.

[0013] In order to arrange the measuring device or the corresponding sensor such as a strain gauge or load sensor, the underside is preferably provided with a recess in which the measuring device is arranged.

[0014] As already mentioned, the measuring arrangement including the measuring device is adapted to measure load-related data at at least one bearing unit. In order to process the measurement data, the measuring device communicates with a controller adapted to process the data, which controller, for example, includes a corresponding CPU with a corresponding processing algorithm, etc. In embodiments where direct measurement of load data or load-related data is utilized, as explained above, the measuring device is preferably arranged at the at least one bearing unit, or if several or all bearing units are being inspected, at each individual bearing unit. Thus, a certain number of separate measuring devices, or corresponding sensors, such as strain gauges or load sensors, are integrated in the overall measuring arrangement. Each of these measuring devices communicates with a central controller of the measuring arrangement, which central controller is adapted to process all incoming measurement data based on its corresponding processing software. The controller is also adapted to output any relevant control information, which is necessary for directly controlling the corresponding device, or it is transmitted to another controller responsible for device control.

[0015] As mentioned above, an alternative embodiment discloses a main bearing having an indirect measurement arrangement. If such an indirect measurement arrangement is provided, the measurement arrangement includes at least one measuring device attached to a rotating ring. In this embodiment, the measuring device is not arranged at the bearing unit or the fixed ring, but at the rotating ring and thus rotates with the rotating ring. Accordingly, regardless of which load is to be measured, the measuring device moves along a corresponding number of axial or radial bearing units. During this movement, it passes each of the axially or radially arranged bearing units, such that a single measuring device can measure the load placed on each of the axial or radial bearing units it passes. This allows for the precise monitoring of the loads or the corresponding load distributions of all axial bearing units or all radial bearing units on one side using only one measuring device.

[0016] As mentioned, the measuring device is adapted to indirectly measure the load placed on the corresponding bearing unit. The outer ring is coupled to the inner ring or the corresponding axial and radial bearing units arranged at the inner ring via a lubricating fluid, which provides a thin hydrodynamic fluid film in the gap between the outer ring and each of the radial and axial bearing units or their respective bearings or sliding pads. As previously mentioned, each bearing unit includes a sliding pad preferably arranged at the support structure via a ball-and-socket connection, which has a ball head at the sliding pad and a socket at the support structure. Accordingly, the measuring device needs to be adapted to indirectly measure the measurement data by measuring any relevant data of the fluid in the gap between the outer ring and the corresponding bearing unit or its respective sliding pad. To allow for such measurement, the measuring device is or includes at least one pressure sensor arranged to and adapted to measure the fluid pressure of the lubricating fluid present in the gap between the rotating ring and the radial or axial bearing unit. Here, the measurement data is pressure data, which is the value of the high pressure of the lubricating fluid in the gap between the outer ring and the corresponding bearing unit. The pressure of the lubricating fluid in this gap depends on the overall load placed on the corresponding bearing unit. Accordingly, the measurement result of this fluid pressure is an accurate measurement value of the pressure placed on the corresponding bearing unit.

[0017] In order to arrange the pressure sensors at the rotating ring, depending on whether the load on the radial bearing unit or the axial bearing unit is to be measured, a radial hole or an axial hole is provided in the rotating ring, which hole opens towards the adjacent radial or axial bearing unit, and the at least one pressure sensor is arranged in the hole. Arranging the pressure sensor in the corresponding hole is simple because only a radial or axial hole needs to be drilled in the sliding surface of the rotating ring and the pressure sensor inserted. Since the hole opens towards the adjacent radial or axial bearing unit, the pressure sensor is directly exposed to the lubricating fluid pressure and thus the fluid pressure directly related to the load can be measured very precisely.

[0018] If the load on the axial bearing unit as well as the load on the radial bearing unit are to be measured as well, the rotating ring is provided with at least two holes, one opening towards the radial bearing unit and the other opening towards the axial bearing unit arranged at a ring side, where a separate pressure sensor is arranged in each hole. If only one axial hole is provided, only the axial bearing unit at one bearing side is load-measured. If the load on the bearing units at both axial bearing sides is to be measured, a third hole is provided which opens towards the opposite ring side and has a third pressure sensor inside. This three-sensor arrangement structure provides an overall load monitoring of each single bearing unit, which is a radial bearing unit or an axial bearing unit, using only three sensors. In this embodiment, the pressure sensor or all the corresponding pressure sensors are also coupled to a controller, as already mentioned above, which controller is adapted to process the delivered measurement data or the corresponding measured values and provide any relevant control information for further controlling any relevant turbine device. Furthermore, in this embodiment, the controller also includes a corresponding CPU with processing software.

[0019] Furthermore, the invention relates to a wind turbine which includes at least one main bearing as mentioned above. As is well known, the wind turbine includes a rotor which has a hub and rotor blades attached to the hub, and the hub is coupled to the rotor of a generator. As mentioned above, the rotor is coupled to the rotating ring of the main bearing of the invention.

[0020] Finally, the invention relates to a method for condition monitoring of the main bearing as described above and for controlling the wind turbine based on the determined measurement data. Description of the Drawings

[0021] Other objects and features of the invention will become apparent from the following detailed description considered in conjunction with the drawings. However, the drawings are only schematic diagrams designed for illustrative purposes only and do not limit the invention. The drawings show:

[0022] Figure 1 shows a schematic diagram of a wind turbine,

[0023] Figure 2 shows the arrangement of the hub, the generator rotor and the main bearing,

[0024] Figure 3 shows an enlarged partial cross-sectional view of the main bearing,

[0025] Figure 4 shows a bearing unit of a first embodiment having a measuring device in the form of a strain gauge,

[0026] Figure 5 shows a bearing unit of a second embodiment having a measuring device in the form of a load cell,

[0027] Figure 6 shows a cross-section of the main bearing having a measuring device in the form of a pressure sensor arranged in a rotating ring, and

[0028] Figure 7 shows the arrangement having another pressure sensor Figure 6 thereof. DETAILED DESCRIPTION

[0029] Figure 1 shows a wind turbine 1 according to the invention, which comprises a rotor 2 rotatably arranged in a nacelle 3, which nacelle 3 is arranged on top of a tower 4. The rotor 2 comprises three rotor blades 5 attached to a hub 6, as is well known. The rotor blades 5 interact with the wind, causing the rotor to rotate. The rotor drives a generator, which is preferably a direct drive generator.

[0030] Figure 2 shows the arrangement of the central elements of the wind turbine 1. It shows the hub 6, which is connected to a direct drive generator 7, which direct drive generator 7 comprises a rotor 8, which rotor 8 is here directly coupled to the hub 6, and which direct drive generator 7 further comprises a stator 9. The stator 9 is fixedly fixed to the main shaft 10.

[0031] The arrangement of the hub 6 and the rotor 8 is rotatable relative to the fixed main shaft 10 or the corresponding stator 9. To support this hub-rotor-arrangement, a main bearing 11 is provided, which in the illustrated embodiment is a sliding bearing 12, which sliding bearing 12 comprises a rotating ring, which rotating ring is here the outer ring 13, and the hub-rotor-arrangement having the hub 6 and the rotor 8 is connected to this outer ring 13 such that when the hub 6 rotates, the outer ring 13 and the rotor 8 also rotate. The main bearing 11 further comprises a fixed ring, which fixed ring is here the inner ring 14 fixed to the main shaft 10.

[0032] When the main bearing 11 is a sliding bearing 12, the rotating outer ring 13 is slidably guided relative to the fixed inner ring 14 by means of axial and radial guides or sliding pads. Alternatively, the rotating outer ring may be guided by means of a conical guide or sliding pad in a conical sliding bearing (not shown). Figure 2 A front axial bearing unit 15 and a rear axial bearing unit 16 for axially guiding the outer ring 13 and a radial bearing unit 17 for radially guiding the outer ring 13 are shown. The bearing units 15, 16 and 17 are fixedly secured to the fixed inner ring 14.

[0033] The axis of rotation of the rotor 2 and thus the axis of rotation of the main bearing 11 is slightly inclined relative to the horizontal plane or the horizontal axis. Figure 2 An inclination angle α is shown, which the axis of rotation 18 of the main bearing 11 makes relative to the horizontal plane or the horizontal axis 19. Thus, the main bearing 11 is slightly inclined.

[0034] As mentioned, the main bearing 11 is a sliding bearing. This sliding bearing needs to be lubricated by a lubricating fluid, which provides a very thin hydrodynamic fluid film between the sliding surfaces of the rotating outer ring and the axial and radial bearing units 15, 16 and 17. Therefore, it is necessary to continuously supply sufficient lubricating fluid in this area, which can be filled or directly introduced or correspondingly lubricated to the respective bearing points or emptied bearing cavities etc. The lubrication system needs to maintain a persistent and constant lubrication quantity in this area.

[0035] To provide constant lubrication, an automatic lubrication arrangement 20 is provided, which is shown in principle in Figure 2 The lubrication arrangement includes a reservoir 21 with a lubricating fluid 22, which is integrated in a lubrication circuit 23. The lubricating fluid 22 is circulated in the circuit 23 by means of a pump 24 integrated in the circuit 23. The circuit 23 includes one or more fluid pipes, at least some of which are guided to the main bearing 11 and discharge the lubricating fluid 22 at one or more points to the main bearing 11 or completely fill the main bearing 11.

[0036] Figure 3Shows an enlarged view of the main bearing 11 or the corresponding sliding bearing 12. Around the perimeter of the inner ring 14, a plurality of axial bearing units 15 are arranged adjacent to the left or outer side of the outer rotating ring 13, while the axial bearing units 16 are arranged adjacent to the inner or right side of the rotating ring 13. A certain clearance is provided between the bearing units 15, 16 and the surface of the rotating ring 13, and a fluid film exists in this clearance. Also as shown, the radial bearing unit 17 is arranged at the inner ring 14, and this radial bearing unit 17 radially guides the rotating ring 13. Here, a clearance is also provided between the inner surface of the rotating ring 13 and this radial bearing unit or their corresponding sliding or bearing pads, and in this clearance, the fluid film guides the rotating ring 13.

[0037] The main bearing 11 of the present invention is equipped with a load measuring arrangement structure, which is adapted to determine measurement data that is a measure of the load applied to at least one of the axial or radial bearing units 15, 16, 17 or placed thereon. This load measuring arrangement structure can be a direct measurement arrangement structure for directly measuring data at at least one or more bearing units. In a second embodiment, this measurement arrangement structure can be an indirect measurement arrangement structure, which is used to measure data as indirect data away from the at least one or more bearing units.

[0038] If this measurement arrangement structure is a direct measurement arrangement structure, then at least its measuring device is directly arranged at one or more axial bearing units 15, 16 or at least one or more radial bearing units 17. If this measurement arrangement structure is an indirect measurement arrangement structure, then it is arranged at the rotating ring 13. Different settings of this measurement arrangement structure will be explained in detail below.

[0039] Figure 4 Shows a bearing unit, which can be an axial bearing unit 15, 16 or a radial bearing unit, because the settings of these different bearing units are comparably the same. Each of the bearing units 15, 16, 17 includes a bearing pad 25, which has a sliding surface 26 that faces the sliding surface of the rotating ring 13 and contacts the fluid film. The bearing units 15, 16, 17 also include a support structure 27, and the bearing pad 25 is fixed to this support structure 27 by a ball-and-socket joint 18, which includes a ball head 29 arranged at the bearing pad 25 and a ball socket 30 arranged at the support structure 27, and the ball head 29 engages in the ball socket 30. This ball-and-socket joint 28 allows the bearing pad 25 to tilt relative to the fixed and immovable support structure 27, and this support structure 27 is fixed relative to the inner ring 14 or fixed to the inner ring 14.

[0040] A measuring arrangement structure 31 is provided, which is a direct measuring arrangement structure 32. It is adapted to directly measure the load placed on the bearing units 15, 16, 17 as a load measurement value. The direct measuring arrangement structure 32 includes a measuring device 33 here in the form of a strain gauge 34, which is arranged in a recess 35, and the recess 35 is provided near the ball-and-socket joint 28 at the bottom side of the support structure 27. The measuring device 33 is connected to a controller 36, which is part of the measuring arrangement structure 31, and the controller 36 is adapted to process the measurement data determined by the measuring device 33 and output control data, etc., for controlling other turbine devices.

[0041] As mentioned, a plurality of axial bearing units 15, 16 or radial bearing units 17 are distributed along the perimeter of the inner ring 14. Only one axial and / or radial bearing unit may be equipped with the direct measuring arrangement structure 32 or the corresponding measuring device 33, or preferably, several or all of the axial and radial bearing units 15, 16, 17 are each equipped with such a measuring device 33, where all the measuring devices 33 are connected to a common controller 36, such that the controller 36 receives the measured load data from all the measuring devices 33 or the corresponding strain gauges 34. This allows the controller 36 to fully monitor the overall load distribution of the rotor load placed on the main bearing 11 on all the axial and radial bearing units 15, 16, 17, and to monitor the load distribution over time. Based on this monitoring, the corresponding control data can be processed and provided, or the corresponding wear and maintenance surveyance, etc., can be carried out.

[0042] Figure 5 Another embodiment of the measuring arrangement structure 31 in the form of the direct measuring arrangement structure 32 is shown, which is used to directly measure the load placed on the axial or radial bearing units 15, 16, 17. The arrangement of the bearing units 15, 16, 17 is the same as that Figure 4 explained, with reference to the above description. In the Figure 5 embodiment shown, the measuring device 33 is a load sensor 37, which is attached to the bottom surface of the support structure 27, and the support structure 27 supports the bearing pad 25 via the ball-and-socket joint 28. The load sensor includes one or more load sensors, such as strain gauges arranged in an array or any other load or pressure sensor, and again outputs the corresponding measurement data to the controller 36 that processes the data.

[0043] In addition, in this embodiment, each bearing unit 15, 16, 17 for which load measurement should be performed is also equipped with a load sensor 37, and all the load sensors 37 are again connected to a common controller 36, which in this embodiment is also adapted to monitor the load distribution on all bearing units 15, 16, 17 integrated in the load measurement arrangement structure.

[0044] Although Figure 4 and Figure 5 show a direct load measurement arrangement structure 32, the main bearing can also be equipped with an indirect measurement arrangement structure. Figure 6 and Figure 7 show two embodiments.

[0045] Figure 6 A cross-sectional view of a main bearing 11 having an inner ring 14, an outer ring 13, and two radial bearing units 15, 16 is shown. In this embodiment, the rotating ring 13 is equipped with a measurement arrangement structure 31 in the form of an indirect measurement arrangement structure 38 here. The indirect load measurement arrangement structure 38 includes a measuring device 33 in the form of a pressure sensor 39, which in this embodiment is arranged in an axial hole 40 that opens into the bearing unit 16, which is arranged adjacent to the right side of the rotating ring 13 and fixed to the inner ring 14. The pressure sensor 39 is connected to a controller 36, which is adapted to process the measurement data provided by the pressure sensor 39.

[0046] Although Figure 6 only the pressure sensor 39 facing the bearing unit 16 is shown, a second pressure sensor 41 can of course also be provided, which is arranged in an axial hole 42 that faces the bearing unit 15 arranged on the other side of the rotating ring 13. The pressure sensor 41 and the hole 42 are only shown in dashed lines because they can also be arranged at another circumferential position like the first pressure sensor 39, and they can also be arranged in a straight line with the first pressure sensor 39.

[0047] The pressure sensors 39 and 41 (if given) are fluid pressure sensors or transducers that move with the rotating ring 13. Thus, they pass along their paths past each bearing unit 16 or 15 during one rotation. The pressure sensors 39, 41 or the corresponding fluid pressure transducers are adapted to measure the fluid pressure of the fluid film present in the gap 43 between the adjacent surfaces of the rotating ring 13 and the bearing pad 15 or, correspondingly, in the gap 44 between the adjacent surfaces of the rotating ring 13 and the bearing unit 15. These surfaces are separated due to the pressure formed in the fluid film, and the loads carried by each bearing unit 15, 16 or, correspondingly, their respective sliding pads 25 are directly related to the pressure magnitude. Due to the rotation of the pressure sensors 39, 41 along all the axial bearing units 15, 16, the fluid film pressure can be mapped circumferentially for each bearing unit 15, 16 or, correspondingly, for each sliding pad 25, where the controller 36 is adapted to determine the loads placed on each bearing unit 15, 16 or the corresponding sliding pad 25 based on the pressure values. Thus, a single pressure sensor 39 can provide information about the loads of all the circumferentially distributed bearing units 16, while a single pressure sensor 41 can provide information about the loads of all the circumferentially distributed bearing units 15.

[0048] Figure 7 An embodiment of the main bearing 11 is shown which Figure 6 is similar, having an outer rotating ring 13 and an inner fixed ring 14. Although not shown in this section, the radial bearing units 17 are attached to this inner fixed ring 14, where the sliding pads 25 of these radial bearing units 17 guide the rotating ring 13 in the radial direction. In addition, a gap is also provided here between the inner circumference of the rotating ring 13 and the adjacent surfaces of the adjacent sliding pads 25 of the radial bearing units 17. Also here, due to the pressure formed in the fluid film in this gap, the fluid film also separates the rotating ring 13 from the sliding surface 26, and the load carried by the inclined sliding surface 26 is directly related to the pressure magnitude.

[0049] In order to measure the fluid pressure as measurement data regarding the actual loads placed on the radial bearing units 17 or the corresponding radial pads 25, a pressure sensor 45 is arranged in a radial hole 46 that opens towards the radial bearing unit 17 or the corresponding radial sliding pad 25. This pressure sensor 45 again communicates with the controller 36, which is adapted to process the given load measurement data.

[0050] Of course, it is possible and advantageous to measure the load measurement data of all axial and radial bearing units 15, 16, 17, such that in a preferred embodiment, all three pressure sensors 39, 41 and 45 are arranged together with the controller 36 at the rotating ring 13. In this embodiment, all pressure sensors 39, 41 and 45 together with the common controller 36 are part of the measurement arrangement 31 in the form of an indirect measurement arrangement structure 38.

[0051] Although the invention has been described in detail with reference to preferred embodiments, the invention is not limited to the disclosed examples, and other variations can be obtained by those skilled in the art from the disclosed examples without departing from the scope of the invention.

Claims

1. A main bearing for a wind turbine (1), comprising a stationary ring (14) and a rotating ring (13) to be coupled to a rotor (2), wherein, The main bearing (11) is a fluid film bearing (12), the fluid film bearing (12) includes a plurality of bearing units, the plurality of bearing units include a radial bearing unit (17) and / or an axial bearing unit (15, 16), the bearing units are arranged around the perimeter of the fixed ring (14) on both sides of the rotating ring (13) for supporting the rotating ring (13), and the fluid film bearing (12) further includes a load measurement arrangement structure (31) for determining measurement data, the measurement data being a measure of the load applied to at least one of the bearing units (15, 16, 17). Wherein, the measurement arrangement structure (31) includes a direct measurement arrangement structure (32) for directly measuring the data at the at least one bearing unit (15, 16, 17). Wherein, the direct measurement arrangement structure (32) includes at least one measurement device (33), the at least one measurement device (33) being directly attached to the at least one bearing unit (15, 16, 17). Wherein, the measurement device (33) includes at least one strain gauge (34) or at least one load sensor (37). Wherein, the bearing units (15, 16, 17) include bearing pads (25) arranged at a support structure (27), through which the bearing units (15, 16, 17) are mounted to the fixed ring (14). Wherein, the bearing pad (25) is coupled to the support structure (27) by a ball and socket joint (28), the ball and socket joint (28) having a ball head (29) provided at the bearing pad (25) and a socket (30) provided at the support structure (27), whereby the strain gauge (34) or the load sensor (37) is mounted adjacent to the socket (30) on the bottom side of the support structure (27).

2. The main bearing according to claim 1, characterized in that, The measurement arrangement structure (31) is adapted to determine measurement data for at least one bearing unit (15, 16, 17).

3. The main bearing according to claim 1 or 2, characterized in that, The measurement arrangement structure (31) includes an indirect measurement arrangement structure (38) remote from the at least one bearing unit (15, 16, 17) for measuring the data as indirect data.

4. The main bearing according to claim 1 or 2, characterized in that, A recess (35) is provided in the bottom side, and the strain gauge (34) or the load sensor (37) is arranged in the recess (35).

5. The main bearing according to claim 3, characterized in that, The indirect measurement arrangement structure (38) includes at least one measurement device attached to the rotating ring (13).

6. The main bearing according to claim 5, characterized in that, The at least one measurement device attached to the rotating ring (13) includes at least one pressure sensor (39, 41, 45), the pressure sensors (39, 41, 45) being arranged for and adapted to measure the fluid pressure of the lubricating fluid present in the gaps (43, 44) between the rotating ring (13) and the bearing units (15, 16, 17).

7. The main bearing according to claim 6, characterized in that, Radial or axial holes (40, 42, 46) are provided in the rotating ring (13), the holes (40, 42, 46) opening towards adjacent bearing units (15, 16, 17), and at least one pressure sensor (39, 41, 45) is arranged in the holes (40, 42, 46).

8. The main bearing according to claim 7, characterized in that, The radial or axial holes (40, 42, 46) include two holes, one of the two holes opening towards the radial bearing unit (17), and the other hole opening towards the axial bearing units (15, 16) and being arranged at one ring side, with a separate pressure sensor (39, 41, 45) arranged in each of the two holes.

9. The main bearing according to claim 8, characterized in that, A third hole (40, 42, 46) opening towards the other ring side is provided, the third hole (40, 42, 46) having a third pressure sensor (39, 41, 45) therein.

10. The main bearing according to claim 1, characterized in that, The measuring arrangement (31) is adapted to determine measurement data for all bearing units (15, 16, 17).

11. The main bearing according to claim 1, wherein The plurality of bearing units further includes tapered bearing units.

12. The main bearing according to claim 11, characterized in that, Tapered holes are provided in the rotating ring (13), the holes opening towards the tapered bearing units, and at least one pressure sensor is arranged in the holes.

13. A wind turbine comprising at least one main bearing (11) according to any one of claims 1 to 12.

14. A method for condition monitoring of a main bearing and for controlling a wind turbine based on the determined measurement data, the main bearing being the main bearing (11) according to any one of claims 1 to 12.

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