ROLLING BEARINGS WITH AN ULTRASONIC SENSOR ARRANGEMENT FOR MONITORING TRACK DAMAGE

Description

[0001] The present invention lies in the field of mechanical engineering. It relates to a rolling bearing. The invention is particularly advantageous in the field of wind turbine technology. The invention also relates to a wind turbine with a rolling bearing and to a method for monitoring a wind turbine.

[0002] According to current technology, rolling bearings are used, for example, in wind turbines, such as blade bearings. They comprise two rings that rotate relative to each other. Such rolling bearings advantageously allow the rotational movement of very large components. To implement these movements, very powerful drives and very high torques are necessary. The raceways of the rings, on which the rolling elements roll, can be damaged during operation. For most applications, minor damage is tolerable; however, damage may progress during operation to a state where the bearing can no longer rotate or safety is compromised. In such cases, the bearing must be replaced. Currently, damage detection is achieved, for example, by measuring the drive torques. With very large rolling bearings, the torque measurements must also be designed for very high torques due to the high frictional torques present.In contrast, the relative change in torque caused by damage in its early stages is initially very small and often even falls within the range of measurement uncertainties. Therefore, it is not possible to detect the damage clearly and early. Furthermore, it is known from the prior art to indirectly infer bearing wear damage from changes in bearing deformation under load during operation.

[0003] The detection of metal particles in regularly drawn grease samples is another method used in the prior art to indirectly make statements about the damage to the bearing inside.

[0004] All of the approaches to damage detection used so far have the disadvantage that damage is only detected unreliably and often no statement can be made about the nature or severity of the damage.

[0005] US 2018 / 180576 A1 discloses the features of the preamble of claim 1.

[0006] The object of the invention is therefore to at least partially solve the aforementioned problems and to enable early and accurate detection of damage. For example, it should make it possible to plan the replacement of the bearing in advance or to relieve the load on the bearing by intervening in the operating procedures, thereby extending the usable operating time.

[0007] According to the invention, this problem is solved by a rolling bearing according to claim 1 or by a method according to the dependent claim. Advantageous embodiments will become apparent from the dependent claims as well as from the following description and the figures.

[0008] Accordingly, a rolling bearing with an ultrasonic sensor arrangement for monitoring raceway damage is proposed.

[0009] The rolling bearing comprises an inner ring with an inner ring raceway, an outer ring with an outer ring raceway opposing the inner ring raceway, and rolling elements arranged between the inner ring and the outer ring, which roll on the inner ring raceway and the outer ring raceway opposing it.

[0010] The rolling bearing also includes at least one ultrasonic sensor arrangement.

[0011] The at least one ultrasonic sensor arrangement comprises, for example, one or more ultrasonic sensor arrangements arranged on the inner ring, configured to emit sound waves through a volume of the inner ring in the direction of the inner ring raceway and to receive sound waves reflected at the inner ring raceway.

[0012] Alternatively or additionally, the at least one ultrasonic sensor arrangement comprises one or more ultrasonic sensor arrangements arranged on the outer ring, configured to emit sound waves through a volume of the outer ring in the direction of the outer ring raceway and to receive sound waves reflected at the outer ring raceway.

[0013] The ultrasonic sensor arrays are configured to emit sound waves in the direction of the respective raceway. When the sound waves encounter an interface between two media, a portion of the sound waves is reflected and subsequently received. From this, conclusions can be drawn about the nature of the interface and / or the thickness of the material traversed. For the sound waves emitted into a bearing ring, the aforementioned interface between two media is located at the surface of the raceway (the first medium being, for example, the bearing steel, and the second medium being air and / or lubricant).When arranging the ultrasonic sensors, transmitters and receivers can be placed in the same location or next to each other, but they can also be positioned at locations far apart, as long as emission of sound waves to the area of ​​the track to be monitored and reception of the reflected sound waves is possible.

[0014] The ultrasonic sensor arrangement(s) located on the inner ring and / or the ultrasonic sensor arrangement(s) located on the outer ring can be configured to monitor the raceway condition and / or the material thickness of the ring on which they are located.

[0015] The one or more ultrasonic sensor arrays can each be arranged, for example, such that ultrasonic waves are introduced into the ring by means of a transmitter at a point facing away from the track of the respective ring, so that they propagate in the direction of the track and, in particular, in the direction of the area of ​​the track to be monitored. At an interface formed by the track to be monitored, the ultrasonic waves can be reflected, so that after the reflection they continue to propagate within the ring, towards the receiver of the ultrasonic sensor array, by which they are ultimately detected. Thus, the ultrasonic waves propagate continuously within the medium of the ring on which the ultrasonic sensor array is located, by which they are emitted and again detected.Any changes in the track path that may indicate damage are detected "from the inside" by the sound waves when the interface formed by the track changes accordingly, and a reflected signal detected by the receiver changes as a result.

[0016] The rolling bearing is a blade bearing for a wind turbine.

[0017] It could also be a bearing for a drilling machine, especially for a tunnel boring machine, or a bearing for a crane (not claimed).

[0018] The rolling bearing can have a diameter of, for example, at least 1m, 2m, 3m, 5m, or 6m. There is no upper limit to the bearing's diameter, and it can, for example, reach up to 10m.

[0019] Especially with such large rolling bearings from the aforementioned areas of mechanical engineering, large forces are at work which, as explained at the beginning, make it difficult to carry out an indirect measurement via moments, while on the other hand there is a particular need for reliable damage detection in order to ensure plant safety.

[0020] In one possible embodiment, the at least one ultrasonic sensor arrangement comprises two ultrasonic sensor arrangements located at radially opposite positions on the inner ring. Alternatively or additionally, it comprises two ultrasonic sensor arrangements located at radially opposite positions on the outer ring.

[0021] Depending on the bearing type, damage occurs in specific areas of the bearing that bear increased loads, which in typical cases are not evenly distributed around the circumference. For example, blade bearings of wind turbines, due to their orientation relative to the rotor blade and hub, have a tension side and a compression side where particularly high loads act. In such cases, for example, opposing ultrasonic sensor arrays can be positioned on the tension and compression sides.

[0022] The at least one ultrasonic sensor arrangement comprises at least 6 ultrasonic sensor arrangements arranged within a first circular arc of at most 70°, wherein the circular arc is located on the tension side or the compression side of the rolling bearing.

[0023] The at least one ultrasonic sensor arrangement can, for example, comprise at least 3, at least 4, or at least 5 ultrasonic sensor arrangements arranged within a first circular arc of at most 120°, at most 90°, or at most 70° (not claimed). The at least one ultrasonic sensor arrangement can comprise at least 6 ultrasonic sensor arrangements arranged within a first circular arc of at most 120° or at most 90° (not claimed).

[0024] This allows for precise monitoring of this circular arc, in which, for example, particularly high loads are acting. Additionally, at least 3, 4, 5, or 6 further ultrasonic sensor arrays can be arranged within a second circular arc of at most 120°, 90°, or 70°, with the second arc being radially opposite the first. These circular arcs can then be located, for example, on the tension side and / or compression side.

[0025] Several ultrasonic sensor arrays can be arranged, for example, at a distance of at least 3° and / or at most 5° or at most 10° or at most 15° or at most 20° or at most 30° from each other.

[0026] The inner ring and / or the outer ring may have teeth.

[0027] The at least one ultrasonic sensor arrangement can, for example, comprise at least one ultrasonic sensor arrangement located on an outer surface of the outer ring and / or on an inner surface of the inner ring. This can be provided, for example, in tapered roller bearings or ball bearings, particularly four-point contact bearings. The at least one ultrasonic sensor arrangement can also comprise at least one ultrasonic sensor arrangement located on a top or bottom surface of the inner ring and / or on a top or bottom surface of the outer ring. The latter configurations can be provided, in particular, in connection with roller bearings and / or ball bearings, especially certain four-point contact bearings, and / or when a toothed surface is provided on the outer or inner surface.

[0028] The at least one ultrasonic sensor arrangement can, for example, comprise at least one ultrasonic sensor arrangement configured to emit sound waves into an off-center area, particularly an edge region, of the inner or outer ring raceway and to receive sound waves reflected from there. Such off-center areas, which are axially displaced towards a top or bottom surface, are subject to particularly high compressive stress from the rolling elements and can therefore be especially susceptible to damage. This is particularly the case if they are located in a highly stressed area on the tension or compression side of the bearing.

[0029] According to the invention, the rolling bearing is a blade bearing of a wind turbine, for adjusting the blade pitch angle. The inner ring or the outer ring is designed to be connected to a hub of the wind turbine, and the other of the two rings is designed to support a rotor blade of the wind turbine and to rotate relative to the hub.

[0030] The rolling bearings described herein can, for example, have rolling elements designed as rollers. This includes, for example, the possibility of providing tapered rollers or cylindrical rollers. The rolling bearings can also, for example, have rolling elements designed as balls. The rolling bearings can, in particular, be designed as four-point contact bearings.

[0031] The application also relates to systems with rolling bearings. In particular, a wind turbine with a rolling bearing is presented. The wind turbine according to the application comprises a rolling bearing with the properties described herein, such as a rolling bearing according to one of the claims or a rolling bearing according to this description or the figures. The at least one ultrasonic sensor arrangement of the rolling bearing comprises, for example, at least one ultrasonic sensor arrangement arranged on a tension side of the rolling bearing and / or at least one ultrasonic sensor arrangement arranged on a compression side of the rolling bearing.

[0032] In the wind turbine, the rolling elements can be designed as rollers, and the at least one ultrasonic sensor arrangement can, in one embodiment, comprise at least one ultrasonic sensor arrangement located on a tension side or a compression side of the rolling bearing. In particular, it can be a roller bearing with cylindrical rollers, wherein the at least one ultrasonic sensor arrangement is located on the tension side, with one example having one or more ultrasonic sensor arrangements exclusively on the tension side and none on the compression side. Alternatively, it can be, for example, a roller bearing with tapered rollers, in which the at least one ultrasonic sensor arrangement is located on the compression side, with one example having one or more ultrasonic sensor arrangements exclusively on the compression side and none on the tension side.

[0033] In the wind turbine, the rolling elements can also be designed as spheres, wherein the at least one ultrasonic sensor arrangement in possible embodiments comprises at least one ultrasonic sensor arrangement that is arranged on a tension side of the rolling bearing and / or at least one ultrasonic sensor arrangement that is arranged on a compression side of the rolling bearing.

[0034] A method for monitoring a wind turbine is presented. The wind turbine to be monitored has a rolling bearing as described in this application, acting as a blade bearing. In this method, the inner raceway of the inner ring and / or the outer raceway of the outer ring are monitored by emitting sound waves into a volume within the respective ring. This occurs particularly during operation and / or while the rolling bearing is rotating. Damage that develops on the raceway over time affects the reflected sound waves. Material loss on the raceways due to operational stress causes a reduction in volume and irregularities at the volume interface. Both can be monitored qualitatively and quantitatively using the received sound waves. This allows for an assessment of the location and severity of the damage.

[0035] The method may include warnings or interventions in the operation of a system. Accordingly, a device comprising a rolling bearing according to the invention, in particular a wind turbine, may be equipped with a processing unit that receives and evaluates signals from one or more ultrasonic sensor arrangements and, for example, sends warning signals to a user and / or control signals to the device in order to intervene in the operation of the device and, for example, relieve the bearing or perform an emergency shutdown.

[0036] The invention is explained below using figures as an example.

[0037] It shows Fig. 1 a rolling bearing designed as a blade bearing of a wind turbine, with opposing ultrasonic sensor arrangements on an outer ring, Fig. 2 a rolling bearing with an ultrasonic sensor arrangement on the outer ring, Fig. 3 a rolling bearing with a plurality of ultrasonic sensor arrangements on the outer ring, Fig. 4 a rolling bearing with opposing ultrasonic sensor arrangements on an inner ring, Fig. 5 a rolling bearing with a plurality of ultrasonic sensor arrangements on the inner ring, Fig. 6 a rolling bearing with a plurality of ultrasonic sensor arrangements on the inner and outer rings, Fig. 7 a positioning of ultrasonic sensors on a compression side of a rolling bearing with spherical rolling elements, Fig. 8 a positioning of ultrasonic sensors on a tension side of a rolling bearing with spherical rolling elements, and Fig. 9 a positioning of ultrasonic sensors on a tension side of a rolling bearing with cylindrical rolling elements.

[0038] Fig. 1Figure 1 schematically shows a top view of a hub 7 of a wind turbine. A rotor blade 6 is arranged on the hub 7, the position of which is illustrated in a sectional view. The rotor blade 6 is supported by a blade bearing designed as a rolling bearing, which allows the blade pitch angle to be adjusted. For this purpose, the rolling bearing comprises an outer ring 4, which is connected to the hub 7 of the wind turbine, and an inner ring 3, which supports the rotor blade 6 and is designed to rotate with the rotor blade 6 relative to the hub 7.

[0039] The roller bearing has a diameter of approximately 6m.

[0040] It should be noted that in other designs the rotor blade 6 may also be connected to the outer ring 4 while the inner ring 3 is fixed to the hub 3. The inner ring 3 and / or the outer ring 4 may have toothed connections.

[0041] The rolling bearing comprises the inner ring 3, which has an inner ring raceway 3a, and the outer ring 4 with an outer ring raceway 4a opposite the inner ring raceway 3a. Rolling elements 5a are arranged between the inner ring 3 and the outer ring 4, which roll on the inner ring raceway 3a and the opposing outer ring raceway 4a. For further possible embodiments of the rolling bearing, reference is made in particular to Figure 7-9 referred.

[0042] According to the application, at least one ultrasonic sensor arrangement 1, 1' is arranged on the rolling bearing.

[0043] In the example of Fig. 1 The rolling bearing comprises two ultrasonic sensor arrangements 1, which are arranged on the outer ring 4, configured to emit sound waves through a volume of the outer ring 4 in the direction of the outer ring raceway 4a and to receive sound waves reflected at the outer ring raceway 4a.

[0044] The two ultrasonic sensor assemblies 1 are arranged at radially opposite positions on the outer ring 3. With regard to the in Fig. 1 The wind direction shown indicates that the right of the two ultrasonic sensor assemblies 1 is located on a tension side 8 of the rolling bearing, and the left of the two ultrasonic sensor assemblies 1 is located on a compression side 9 of the rolling bearing. In the Figure 1 Areas of particularly high stress on tension side 8 and compression side 9 are marked by dashed lines. The two ultrasonic sensor arrangements 1 from Fig. 1 This enables the monitoring of points that are particularly important for the safety of the wind turbine, in particular the monitoring of the outer ring track 4a of the outer ring 4. This monitoring takes place especially during the operation of the wind turbine, and especially while the rotor blade 6 is being rotated.

[0045] Fig. 2 shows a similar structure to the Fig. 1, wherein only a single ultrasonic sensor arrangement 1 is arranged on the outer ring 4, namely on the tension side 8. Alternatively, for example, only one ultrasonic sensor arrangement can be provided on the pressure side 9.

[0046] Fig. 3 Figure 1 shows a rolling bearing in which nine ultrasonic sensor arrays 1 are arranged on both the tension side 8 and the compression side 9, each within approximately a quarter circle, i.e., within about 90°. The nine ultrasonic sensor arrays 1 on the tension side 8 are radially opposite the nine sensor arrays 1 on the compression side. This enables particularly precise monitoring of both high-load areas.

[0047] Fig. 4Figure 1 shows a rolling bearing in which two ultrasonic sensor assemblies 1' are arranged at radially opposite points on the inner ring 3. These assemblies are configured to emit sound waves through a volume of the inner ring 3 in the direction of the inner ring raceway 3a and to receive sound waves reflected from the inner ring raceway 3a. The position of the rotor blade 6, which is connected to the inner ring 3, is indicated by dashed lines. One of the two ultrasonic devices 1' is arranged on a tension side 8 and the other on a compression side 9. This allows, in particular, the monitoring of damage at critical points of the inner ring raceway 3a.

[0048] Fig. 5 shows a similar structure to Fig. 4, wherein three ultrasonic sensor arrangements 1' are provided on both the tension side 8 and the compression side 9 for monitoring sections of the inner ring raceway 3a. The three ultrasonic sensor arrangements 1' on the tension side 8 and on the compression side 9 are each arranged within circular arcs of approximately 30°.

[0049] Fig. 6 Figure 1 shows an embodiment of the rolling bearing in which several ultrasonic sensor arrangements 1' are provided on both the inner ring 3 and the outer ring 4, for monitoring both volumes and thus sections of both raceways 3a, 4a. For each ring 3, 4, three ultrasonic sensor arrangements 1, 1' are arranged on the tension side 8 and three ultrasonic sensor arrangements 1' are arranged on the compression side 9.

[0050] In the case of rolling bearings compliant with the application, of course more than three ultrasonic sensor arrangements 1, 1' can be arranged on the tension side 8 and / or compression side 9 of each ring 3, 4.

[0051] Fig. 7 Figure 1 shows a section through the pressure side 9 of a rolling bearing, in which the rolling elements 5a, 5b are designed as balls. The inner ring 3 supports the rotor blade 6, and the outer ring 4 is connected to the hub 7. A prevailing wind flows from the left onto the rotor blade 6 and pushes the rotor blade upwards to the right.

[0052] The inner ring 3 has a first inner ring raceway 3a, and the outer ring 4 has a first outer ring raceway 4a belonging to the inner ring raceway 3a. First spherical rolling elements 5a roll on the first inner ring raceway 3a and the first outer ring raceway 4a.

[0053] Below the first raceways 3a, 4a, the inner ring 3 has a second inner ring raceway 3b and the outer ring 4 has a second outer ring raceway 4b complementary to the second inner ring raceway 3b. Second spherical rolling elements 5b roll on the second inner ring raceway 3b and the second outer ring raceway 4b.

[0054] The first inner ring track 3a, the first outer ring track 4a, the second inner ring track 3b, and the second outer ring track 4b are each monitored by means of ultrasonic sensor arrangements 1, 1'. For each of the tracks 3a, 3b, 4a, 4b, a separate ultrasonic sensor arrangement is provided, specifically configured for that track.

[0055] The ultrasonic sensor arrangements 1' of the inner ring 3 are arranged on an inner surface of the inner ring 3 and the ultrasonic sensor arrangements 1 of the outer ring 4 are arranged on an outer surface of the outer ring 4.

[0056] Due to the wind approaching from the left, which pushes the rotor blade 6 upwards to the right, the expected damage locations 2, where the raceways 3a, 3b, 4a, 4b are subject to particularly high stress, are eccentric, i.e., offset upwards or downwards along the bearing axis. Accordingly, the ultrasonic sensor assemblies 1, 1' are each configured to emit sound waves into these eccentric areas of the inner ring raceway 3a and the outer ring raceway 4a, where the expected damage locations 2 are located, and to receive sound waves reflected from these areas. Thus, the ultrasonic sensor assemblies 1', located on the inner ring 3, emit into eccentric raceway areas that are offset upwards, towards the rotor blade 6, and the ultrasonic sensor assemblies 1, located on the outer ring 4, emit into eccentric raceway areas that are offset downwards, away from the rotor blade 6.This allows for targeted monitoring of the areas of greatest stress.

[0057] Accordingly, for example, storage facilities for other devices or large equipment, such as a tunnel boring machine or a crane, may be set up to monitor areas of the bearing tracks that are critical for the respective device.

[0058] Fig. 8 shows the tension side 8 of the rolling bearing. Figure 7 , which is printed on page 9 Figure 7 radially opposite. Here too, the ultrasonic sensor arrangements 1, 1' emit into off-center edge regions. Since the wind hits the rotor blade from the right and thus pulls it to the left at the bearing location shown, the positions of the expected damage locations 2 are different compared to Figure 7Here, the opposite is true: The ultrasonic sensor arrangements 1', which are arranged on the inner ring 3, emit into off-center raceway areas that are offset downwards, away from the rotor blade 6, and the ultrasonic sensor arrangements 1, which are arranged on the outer ring 4, emit into off-center raceway areas that are offset upwards, towards the rotor blade 6.

[0059] Here, the ultrasonic sensor arrangements 1, 1' are again arranged on the outer surface of the outer ring 4 and on the inner surface of the inner ring 3. Depending on the available installation space, for example, an ultrasonic sensor arrangement of the inner ring can also be arranged on the underside of the inner ring and / or an ultrasonic sensor arrangement of the outer ring on the top side of the outer ring.

[0060] Fig. 9 shows a section through the tension side 8 of a rolling bearing with rolling elements 5a, 5b, 5c designed as rollers.

[0061] The inner ring 3 has a first inner ring raceway 3a, and the outer ring 4 has a first outer ring raceway 4a belonging to the first inner ring raceway 3a. First roller-shaped rolling elements 5a roll on the first inner ring raceway 3a and the first outer ring raceway 4a. The first outer ring raceway 4a and the first inner ring raceway 3a extend horizontally, each in a plane orthogonal to an axis of the rolling bearing, and the roller-shaped rolling elements 5a accordingly have axes that also extend orthogonally to the axis of the rolling bearing.

[0062] The inner ring 3 has a second inner ring raceway 3b, and the outer ring 4 has a second outer ring raceway 4b corresponding to the second inner ring raceway 3b. Second roller-shaped rolling elements 5b roll on the second inner ring raceway 3b and the second outer ring raceway 4b. The second raceways 3b, 4b and the axes of the second roller-shaped rolling elements 5b extend parallel to the axis of the rolling bearing.

[0063] The inner ring 3 has a third inner ring raceway 3c, and the outer ring 4 has a third outer ring raceway 4c corresponding to the third inner ring raceway 3c. Third roller-shaped rolling elements 5c roll on the third inner ring raceway 3c and the third outer ring raceway 4c. The third raceways 3c, 4c and the axes of the third roller-shaped rolling elements 5c extend orthogonally to the axis of the rolling bearing, as do the first raceways 3a, 4a and the first rolling elements 5a.

[0064] The first outer ring raceway 4a is monitored by means of ultrasonic sensor arrangements 1. Due to the wind approaching from the right, which pushes the rotor blade 6 upwards to the left, the tension of the rotor blade 6 exerts a stress, in particular on the first outer ring raceway 4a, by the first rolling elements 5a. In order to monitor the expected damage position 2 on the first outer ring raceway 4a, the rolling bearing on the tension side 8 shown comprises at least one ultrasonic sensor arrangement 1, which is arranged on the upper surface of the outer ring 4 facing the rotor blade 6 and emits sound waves in the direction of the first outer ring raceway to be monitored. Reference symbol list

[0065] 1, 1'Ultrasonic sensor 2Expected damage position 3Inner ring 3a, 3b, 3cInner ring raceway 4Outer ring 4a, 4b, 4cOuter ring raceway 5a, 5b, 5cRolling element 6Rotor blade 7Hub 8Load zone tension side 9Load zone compression side

Claims

1. A roller bearing, comprising: an inner ring (3) with an inner ring raceway (3a), an outer ring (4) with an outer ring raceway (4a) opposing the inner ring raceway (3a) and rolling elements (5a) arranged between the inner ring (3) and the outer ring (4), which roll on the inner ring raceway (3a) and the opposing outer ring raceway (4a), and at least one ultrasonic sensor arrangement (1, 1'), wherein the at least one ultrasonic sensor arrangement (1, 1') comprises one or more ultrasonic sensor arrangements (1') arranged on the inner ring (3), configured to emit sound waves through a volume of the inner ring (3) in the direction of the inner ring raceway (3a) and to receive sound waves reflected at the inner ring raceway (3a) and / or wherein the at least one ultrasonic sensor arrangement (1, 1') comprises one or more ultrasonic sensor arrangements (1) which are arranged on the outer ring (4), configured for emitting sound waves through a volume of the outer ring (4) in the direction of the outer ring raceway (4a) and for receiving sound waves reflected at the outer ring raceway (4a), characterized in that the roller bearing is a blade bearing of a wind turbine for adjusting a blade pitch angle, wherein the inner ring (3) or the outer ring (4) is configured to be connected to a hub (7) of the wind turbine and the other of the inner ring (3) and the outer ring (4) is configured to support a rotor blade (6) of the wind turbine and to rotate relative to the hub (7), and wherein the at least one ultrasonic sensor arrangement (1, 1') comprises at least 6 ultrasonic sensor arrangements (1, 1') which are arranged within a first circular arc of at most 70°, the circular arc being located on the tension side or on the compression side of the roller bearing.

2. The roller bearing according to claim 1, wherein the one or more ultrasonic sensor arrangements (1'), which are arranged on the inner ring (3), are configured for monitoring a condition of the inner ring raceway (3a) and / or for monitoring a material thickness of the inner ring (3) and / or wherein the one or more ultrasonic sensor arrangements (1), which are arranged on the outer ring (4), are configured for monitoring a condition of the outer ring raceway (4a) and / or for monitoring a material thickness of the outer ring (4).

3. The roller bearing according to one of the preceding claims, wherein a diameter of the roller bearing is at least 1m or at least 2m or at least 3m or at least 5m or at least 6m.

4. The roller bearing according to one of the preceding claims, wherein the at least one ultrasonic sensor arrangement (1, 1') comprises two ultrasonic sensor arrangements (1') which are arranged at radially opposite positions on the inner ring (3) and / or wherein the at least one ultrasonic sensor arrangement (1, 1') comprises two ultrasonic sensor arrangements (1) which are arranged at radially opposite positions on the outer ring (3).

5. The roller bearing according to one of the preceding claims, wherein several ultrasonic sensor arrangements are arranged at a distance of at least 3° and at most 5° from one another.

6. The roller bearing according to one of the preceding claims, wherein the at least one ultrasonic sensor arrangement (1, 1') additionally comprises at least 3 or at least 4 or at least 5 or at least 6 further ultrasonic sensor arrangements (1, 1'), which are arranged within a second circular arc of at most 120° or at most 90° or at most 70°, wherein in particular the second circular arc lies radially opposite the first circular arc.

7. The roller bearing according to one of the preceding claims, wherein the inner ring (3) and / or the outer ring (4) has a toothing.

8. The roller bearing according to one of the preceding claims, wherein the at least one ultrasonic sensor arrangement (1, 1') comprises at least one ultrasonic sensor arrangement (1, 1') which is arranged on an outer surface of the outer ring (4) and / or on an inner surface of the inner ring (3).

9. The roller bearing according to one of the preceding claims, wherein the at least one ultrasonic sensor arrangement (1, 1') comprises at least one ultrasonic sensor arrangement (1, 1') arranged on an upper side or a lower side of the inner ring (3) and / or on an upper side or a lower side of the outer ring (4).

10. The roller bearing according to one of the preceding claims, wherein the at least one ultrasonic sensor arrangement (1, 1') comprises at least one ultrasonic sensor arrangement (1, 1') which is configured to emit sound waves into an eccentric region, in particular into an edge region, of the inner ring raceway (3a) or the outer ring raceway (4a) and to receive sound waves reflected from there.

11. A wind turbine comprising a roller bearing according to one of the preceding claims, wherein the at least one ultrasonic sensor arrangement (1, 1') comprises at least one ultrasonic sensor arrangement (1, 1') arranged on a tension side (8) of the roller bearing and at least one ultrasonic sensor arrangement (1, 1') arranged on a compression side (9) of the roller bearing.

12. The wind turbine according to claim 11, wherein the rolling elements (5) are designed as rollers and the at least one ultrasonic sensor arrangement (1, 1') comprises at least one ultrasonic sensor arrangement (1, 1') which is arranged on a tension side (8) or a compression side (9) of the roller bearing.

13. The wind turbine according to claim 11, wherein the rolling elements (5) are designed as balls, wherein the at least one ultrasonic sensor arrangement (1, 1') comprises at least one ultrasonic sensor arrangement (1, 1') which is arranged on a tension side of the roller bearing and comprises at least one ultrasonic sensor arrangement (1, 1') which is arranged on a compression side of the roller bearing.

14. A method for monitoring a wind turbine which has a roller bearing according to one of the preceding claims 1 to 10 as a blade bearing, or a wind turbine according to one of the preceding claims 11 to 13, wherein the inner ring raceway (3a) of the inner ring (3) and / or the outer ring raceway (4a) of the outer ring (4) is monitored.

15. The method according to claim 14, wherein the monitoring takes place during operation and / or while the roller bearing is being rotated.