Bearing ring, bearing, wind turbine, and method for manufacturing a bearing ring

Abstract

The present invention relates to a bearing ring, a wind turbine, and a method for manufacturing a bearing ring. In embodiments of the present invention, the hardness depth of at least one raceway of the bearing ring varies along the circumference of the bearing ring.

Description

Technical Field

[0001] The present invention relates to a bearing ring, a bearing ring, a wind turbine, and a method for manufacturing a bearing ring.

Background Art

[0002] Bearings are used in various technical fields to support, guide the movement between different components, such as between a fixed component and a movable component, and to reduce friction. Bearings may face very high loads in some technical fields, such as the field of wind turbines.

[0003] The hardening of the raceway surface is applied to most rolling bearings. The raceway surface of the bearing is hardened to improve wear resistance and fatigue resistance, leading to an improvement in overall reliability. Conventional hardening methods include case hardening, induction hardening, nitriding, carburizing, case hardening, and cryogenic hardening. In large bearings such as wind turbine bearings, case and induction hardening are frequently used. In case hardening, the surface of the bearing is heated and then rapidly cooled to form a hard outer layer, while the core of the bearing is relatively soft and ductile. In induction hardening, a high-frequency current is used to heat the surface of the bearing. This process allows for the selective hardening of specific parts of the raceway uniformly and precisely. Since the hardening tool hardens a specific section / part of the raceway at a time, the manufacturer starts from an arbitrary or clearly defined position on the bearing ring and continues to go around until the hardening tool returns to the starting position where uniform hardening of the entire circumference has been performed.

[0004] European Patent Application Publication No. 1977126 (EP1977126) describes that in order to avoid annealing of the already hardened raceway and avoid unpredictable material properties, an overlap between the start and end positions of the hardening process is not permitted. As a result, small parts of the raceway are insufficiently hardened, that is, they become "soft spots" of the hardened raceway.

Summary of the Invention

Problems to be Solved by the Invention

[0005] The objective of this invention is to establish an improved hardening process for bearing rings.

[0006] The hardening depth is typically required to be consistent across the entire circumference of the bearing ring raceway. However, according to the present invention, particularly in the case of large slewing bearings with a defined load distribution, it may be advantageous to adjust the mechanical parameters to adapt the hardening depth across the circumference.

[0007] Because certain parts of the ring require a shallower curing depth, the curing process can be optimized. This allows for improved processing speed and reduced costs. Furthermore, it avoids potential failures caused by deep curing.

[0008] Accordingly, the present invention provides a bearing ring comprising at least one raceway, which is hardened in a hardening process to yield a hardening depth profile, which is defined between a maximum hardening depth and a minimum hardening depth, and which has a maximum hardening depth value at less than 180°, preferably less than 90°, of the circumference of the bearing ring.

[0009] The hardening depth of a bearing ensures that the required material properties meet the subsurface stress requirements from ultimate and fatigue loads. Therefore, the hardening depth is load-dependent. Typically, in conventional techniques, the final hardening depth is defined by the most critical load case. The calculated hardening depth is then applied to the entire raceway.

[0010] However, a typical load case for a large slewing bearing with a defined load distribution is greatly affected by bending moment. Therefore, according to the present invention, it is possible to reduce costs and process time by varying the hardening depth along the circumference of the raceway by adapting the machining process. Thus, the hardening depth is reduced in the lower load areas of the bearing.

[0011] In particular, wind turbine bearings generally operate under heavy load conditions where they may be subjected to axial and radial forces, as well as large bending / tilting moments.

[0012] In particular, blade bearings operate under heavy load conditions because they perform restricted oscillating motion instead of continuous rotational motion, while axial and radial forces, as well as large bending / tilting moments, are present.

[0013] As described above, the hardening depth profile is defined between the maximum hardening depth and the minimum hardening depth, and the hardening depth profile has a maximum hardening depth value less than 180°, preferably less than 90°, of the circumference of the bearing ring. Ideally, the hardening depth profile provides hardening depth along the entire circumference of the bearing ring, substantially adapting to what level of hardening is required. Thus, in a preferred embodiment, the maximum hardening depth may be present only less than 45° or less than 20° of the entire circumference.

[0014] In one embodiment of the present invention, the curing process is an induction curing process.

[0015] In one embodiment of the present invention, the hardening depth profile is defined by a function that includes at least one trigonometric function.

[0016] In one embodiment of the present invention, the hardening depth profile is defined by a combination of multiple periodic functions.

[0017] In one embodiment of the present invention, the hardening depth profile is at least partially designed based on the expected load distribution along the 360° circumference of the bearing ring.

[0018] Furthermore, the present invention relates to a bearing comprising at least two bearing rings having at least one raceway each, and at least one row of bearing rolling elements disposed between these bearing rings and each in contact with at least one raceway.

[0019] In one embodiment of the present invention, the bearing rolling elements are bearing balls or rollers, or a combination thereof.

[0020] Furthermore, the present invention relates to a wind turbine comprising one or more bearings as described above here.

[0021] In one embodiment of the present invention, the one or more bearings are one or more blade bearings.

[0022] Furthermore, the present invention provides a method of manufacturing a bearing ring including at least one raceway, the method including the step of hardening at least one raceway in a hardening process including a hardening tool that provides a hardening depth profile, the hardening process including changing a process parameter of the hardening tool during the hardening process.

[0023] In one embodiment of the present invention, the process parameter is at least one selected from the group consisting of frequency, power, temperature, and speed.

[0024] Hereinafter, the present invention will be described with reference to the drawings.

Brief Description of the Drawings

[0025] [Figure 1] Shows a wind turbine. [Figure 2] Shows an example of a blade bearing for a wind turbine. [Figure 3] Shows 3RRB showing a contact zone. [Figure 4a] Shows a hardening process. [Figure 4b] Shows a hardening process. [Figure 5] Shows an example of variable hardening depth. [Figure 6] Shows an example of variable hardening depth. [Figure 7] Shows an example of variable hardening depth.

Modes for Carrying Out the Invention

[0026] Figure 1 shows a wind turbine 1 mounted on a foundation 6. The wind turbine comprises a tower 2 including multiple tower sections and a wind turbine nacelle 3 located at the top of the tower 2. A yaw mechanism having a yaw bearing and a motor allows the nacelle to rotate relative to the tower so that the wind turbine rotor faces the wind.

[0027] The wind turbine rotor includes at least one blade, and is illustrated with three wind turbine blades 5, connected to a hub 4 via a pitch mechanism. Each pitch mechanism includes a blade bearing 7 that allows the blade to pitch relative to the wind. The hub is connected to the nacelle via a main shaft at the front of the nacelle. The main shaft is connected directly to the generator or indirectly via a gear mechanism and a low-speed / high-speed shaft, and the connection may include one or more shaft bearings, such as rotor and generator bearings.

[0028] Figure 2 shows an example of a blade bearing 7 for a wind turbine. The blades 5 of the wind turbine are connected to the inner ring 8 of the blade bearing 7 by numerous bolts. The outer ring 9 of the blade bearing is also connected to the hub 4 by numerous bolts. Two rows of bearing balls 10 are arranged between the raceways of the bearing rings 8 and 9, so that the wind turbine blades 5 pitch relative to the hub 4.

[0029] In other embodiments, the blades of the wind turbine may be connected to an outer ring, and the hub may be connected to an inner ring.

[0030] Four-point contact ball bearings, thrust bearings (e.g., spherical thrust roller bearings, thrust ball bearings, angular contact thrust ball bearings, and cylindrical roller thrust bearings), slewing bearings such as three-row roller bearings (3RRB) or two-row roller + one-row ball bearings (2RRB+1RBB), and other types of bearings such as self-aligning ball bearings, deep groove ball bearings, or angular contact ball bearings are known to those skilled in the art within the field of bearing technology.

[0031] The roller may be cylindrical, needle-shaped, tapered, barrel-shaped, or spherical, for example.

[0032] Furthermore, a bearing may include only one row of bearing balls / rollers, or two or more rows, such as three rows. Additionally, the rows may be positioned above or next to each other.

[0033] Although the patent claims herein refer to bearing rings having at least one raceway, it is clear that the modified curing processes described herein can be used for multiple raceways of a bearing or bearing ring having the same curing depth profile, or that different curing depth profiles can be advantageously used for different rows of rolling elements.

[0034] Figure 3 shows the contact region 13 of the slewing bearing according to the present invention. The contact region 13 corresponds to the raceways of the bearing rings in which the rolling elements (indicated by the bearing rollers 11) mainly contact the bearing rings 8 and 9 and transmit the load force. The contact of the bearing rolling elements on the bearing rings can be varied depending on the magnitude of the load force.

[0035] The bearing is shown as a three-row roller bearing (3RRB), but may also include three rows of rollers (upper and lower rows, supporting bending / tilting moments as well as axial loads) and one row of bearing balls (middle row, supporting radial loads) (2RRB + 1RBB). The contact areas 13 of the six bearing raceways are shown by dotted lines. Note that the ends of the rollers may secondarily contact the bearing rings, thereby defining an additional contact area 14 (only one shown in Figure 3).

[0036] Combinations of radial and thrust rows of rolling elements in a 3-row roller bearing (3RRB) or a 2-row + 1-row roller bearing (2RRB+1RBB) may be used in very heavy load applications such as wind turbines or cranes.

[0037] It is a well-known and standard procedure to harden the portion of the bearing ring most exposed to load / force, i.e., the contact areas 13, 14, by either case hardening or induction hardening. The dominant hardening process in the industry is to use a flame or induction tool along the circumference of the bearing ring until the raceway is hardened, as schematically shown in Figures 4a and 4b.

[0038] For large bearing rings 40, the hardening tool 45 is required to harden only a specific area / part of the raceway at a time. Therefore, the blade bearing manufacturer starts from any or clearly defined position on the bearing ring 40 and continues to move around the circumference until the hardening tool 45 returns to the starting position where uniform hardening of the entire circumference has been performed. In Figure 4b, the hardening tool 45 is at approximately 90° along the circumference, showing the difference between the unhardened portion 41 and the hardened portion 42.

[0039] The curing tool 45 can be a machine equipped with a motion system that moves around a bearing ring 40, the motion system comprising coils supplied by a power source. The speed and heating power can be set to obtain a desired curing depth. During the procedure, when the desired curing depth is achieved, a cooling element can also be used to cool the surface heated by the coil pair.

[0040] This 360° hardening process, which achieves a uniform hardening depth along the entire circumference, is a standard process for large bearings. A uniform hardening depth is meaningful for most types of bearings, especially those in high-speed rotating machinery such as gearboxes and generators, as they are subjected to the same forces and therefore there is no difference in load between circumferential positions. Typically, the hardening depth applied to the entire ring is defined by the most significant load case. The calculated hardening depth is then applied to the entire raceway.

[0041] However, according to the present invention, it has been found that for large slewing bearings with a defined load distribution (such as crane bearings or wind turbine blade bearings), it is meaningful to adjust the mechanical parameters to adapt the hardening depth along the circumference.

[0042] In certain areas of the ring, a shallower curing depth is required, allowing for optimization of the curing process. This, in turn, can improve processing speed and reduce costs. Furthermore, the risk of failure during the curing process can be reduced by applying shallower curing sections.

[0043] To vary the curing depth along the circumference, different curing procedures can be considered. In the case of induction curing, the curing depth can be influenced by several factors, including the frequency and power of the induction field, the speed of the tool, and the temperature of the part during heating.

[0044] The speed and temperature range of the tools used for induction hardening of large bearing rings vary depending on the specific application and the material being treated.

[0045] In some examples, the heating temperature may range from 800°C to 1100°C, and the tool speed may range from 0.1 to 10 meters per minute (m / min), such as 0.5 to 5 m / min. In this case, the speed represents the speed at which the part passes through the induction coil during heating.

[0046] A simple explanation of the standard curing process is as follows: The required hardness is achieved by heating a specific area for a specific amount of time. Depending on the size of the blade bearing, a movable heating source may be used. Industry standards use a constant temperature and speed for the movable heat source. The hardening depth typically reaches several millimeters.

[0047] The improvements to the present invention are as follows: By allowing changes in temperature / speed during the curing process, variations in hardness can be achieved. Cost savings can be achieved in the range of €150 per 1 mm of hardening depth of bearing rings. Therefore, reducing the average hardening depth of each blade bearing ring of a wind turbine by 1 mm or less can result in savings of €900.

[0048] Figures 5 through 7 show several examples of variable hardening depth. In all figures, the x-axis represents the circumferential position of the bearing (θ is 0 to 360°), and the y-axis represents the hardening depth at each circumferential position.

[0049] Looking at Figure 5, the gray background indicated by 50 shows the location along the circumference of the bearing where the load is strongest. It is understood that the load is maximum over a range of approximately 270°. Line 51 shows the maximum hardening depth, which is the hardening depth that can be applied to the entire circumference by the conventional method. Line 52 shows the minimum hardening depth required regardless of the circumferential position.

[0050] Different curing depth profiles 55 are shown here in their simplest form, but are suitable for cases where the variable curing depth is a simple sinusoidal curve 55 (where θ=0° is shifted laterally at random intervals). Alternatively, a step curve may be used where a constant depth is maintained along line 51 at 90° and a constant depth is maintained along line 52 at the opposite 90°, and then a step curve is used where the two line segments are connected by a curve or a straight line.

[0051] A more complex configuration is shown in Figure 6, where the gray background, again indicated by 50, is intended to represent two ranges of approximately 90° and 260° along the circumference where the load increases. In this case, the curing depth profile 55 becomes a more complex curve.

[0052] Figure 7 illustrates a situation where the curing variation is perfectly optimized for precise loads / required curing depths at all circumferential positions. This results in a curing depth profile 55 as shown.

[0053] Regardless of the complexity of the desired curve, for programming reasons related to the curing process, it is considered advantageous to define the curve as a function resulting from a number of combined and overlapping functions, such as trigonometric functions. Such a function may allow control of the curing depth by varying the temperature, rate, or a combination thereof.

[0054] The present invention has been illustrated above with reference to a specific example of a blade bearing in a wind turbine. However, it should be understood that the present invention is not limited to a specific example and can be constructed and modified in numerous types, as specified within the scope of the invention, in relation to other applications, such as other wind turbine bearings, and very large bearings facing axial and radial loads and bending / tilting moments, such as large cranes, radar, or satellite aerial bearings.

Claims

1. A bearing ring (8, 9) including at least one track (13), The at least one of the orbitals (13) is cured in the curing process to produce a curing depth profile (55). The hardening depth profile (55) is defined between the maximum hardening depth (51) and the minimum hardening depth (52) in a bearing ring, The hardening depth profile (55) is characterized in that it has a value at the maximum hardening depth (51) at less than 180°, preferably less than 90°, of the circumference of the bearing ring.

2. The bearing ring (8, 9) according to claim 1, wherein the hardening process is an induction hardening process.

3. The bearing ring (8, 9) according to claim 1 or 2, wherein the hardening depth profile (55) is defined by a function that includes at least one trigonometric function.

4. The bearing ring (8, 9) according to any one of claims 1 to 3, wherein the hardening depth profile (55) is defined by a combination of multiple periodic functions.

5. The bearing ring (8, 9) according to any one of claims 1 to 4, wherein the hardening depth profile (55) is at least partially designed based on the expected load distribution along the 360° circumference of the bearing ring.

6. At least two bearing rings (8, 9) according to any one of claims 1 to 5, having at least one track (13), A bearing (7) comprising at least one row of bearing rolling elements (10, 11) arranged between the bearing rings and in contact with at least one of the raceways (13) in each of them.

7. The bearing (7) according to claim 6, wherein the bearing rolling elements are bearing balls (11) or rollers (15), or a combination thereof.

8. A wind turbine (1) comprising one or more bearings (7) according to claim 6 or 7.

9. The wind turbine according to claim 8, wherein the one or more bearings (7) are one or more blade bearings.

10. A method for manufacturing a bearing ring (8, 9) including at least one raceway (13), A method comprising a curing process including a curing tool (45) that provides a curing depth profile (55), the process comprising curing at least one orbital (13), wherein the curing process includes changing process parameters of the curing tool (45) during the curing process.

11. The method according to claim 10, wherein the process parameter is at least one selected from the group consisting of frequency, power, temperature, and speed.

12. The method according to claim 10 or 11, limited by the feature portion described in any one of claims 1 to 4.

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