Claims:1. A thrust bearing (50) for coupling a rotor blade (20) to a hub (18) of a wind turbine (10), the thrust bearing (50) comprising:
an outer bearing race (52) configured to be coupled to the hub (18), the outer bearing race (52) defining a first outer bearing raceway wall (114), the first outer bearing raceway wall (114) defining a curved profile having a center of curvature (124);
an inner bearing race (54) rotatable relative to the outer bearing race (52) and configured to be coupled to the rotor blade (20), the inner bearing race (54) defining a first inner bearing raceway wall (116), the first inner bearing raceway wall (116) defining a curved profile having a center of curvature (128); and
a first plurality of rolling elements (56) disposed between the first inner and outer bearing raceway walls (114, 116),
wherein each of the first plurality of rolling elements (56) defines an outer contact point (136) with the first outer bearing raceway wall (114) and an inner contact point (138) with the first inner bearing raceway wall (116), the inner and outer contact points (136, 138) being aligned along a reference line (144) defining a contact angle (150) of substantially 90 degrees relative to a radial axis (146) of the thrust bearing (50).

2. The thrust bearing (50) of claim 1, wherein the contact angle (150) is between 80-100 degrees relative to a radial axis (146) of the thrust bearing (50).

3. The thrust bearing (50) of claim 1, wherein the contact angle (150) is 90 degrees relative to a radial axis (146) of the thrust bearing (50).

4. The thrust bearing (50) of claim 1, wherein the outer bearing race (52) defines a second outer bearing raceway wall (118) and the inner bearing race (54) defines a second inner bearing raceway wall (120), each of the second inner and outer bearing raceway walls (120, 118) defining a curved profile having a center of curvature (128, 124), further comprising a second plurality of rolling elements (58) disposed between the second inner and outer bearing raceway walls (120, 118), wherein each of the second plurality of rolling elements (58) defines an outer contact point (140) with the second outer bearing raceway wall (118) and an inner contact point (142) with the second inner bearing raceway wall (120), the inner and outer contact points (142, 1402) being aligned along a reference line (144) defining a contact angle (152) of substantially 90 degrees relative to the radial axis (146) of the thrust bearing (50).

5. The thrust bearing (50) of claim 4, wherein the contact angles (150, 152) are between 80-100 degrees relative to a radial axis (146) of the thrust bearing (50).

6. The thrust bearing (50) of claim 4, wherein the contact angle (150, 152) are 90 degrees relative to a radial axis (146) of the thrust bearing (50).

7. The thrust bearing (50) of claim 2, further comprising a raceway rib (160) extending between the first and second plurality of rolling elements (56, 58).

8. The thrust bearing (50) of claim 7, wherein the raceway rib (160) forms an extension of the inner bearing race (54), the raceway rib (160) separating the first inner bearing raceway wall (116) from the second inner bearing raceway wall (120).

9. The thrust bearing (50) of claim 8, wherein the raceway rib (160) is configured such that the first and second inner bearing raceway walls (116, 120) extend beyond a 90 degree location of the first and second plurality of rolling elements (56, 58).

10. The thrust bearing (50) of claim 1, wherein one of the inner bearing race (54) or the outer bearing race (52) includes a split joint (84).

11. The thrust bearing (50) of claim 10, wherein the outer bearing race (52) includes a split joint (84).

12. A thrust bearing (50) for coupling a rotor blade (20) to a hub (18) of a wind turbine (10), the thrust bearing (50) comprising:
an outer bearing race (52) configured to be coupled to the hub (18), the outer bearing race (52) defining a first outer bearing raceway wall (114) and a second outer bearing raceway wall (118), an inner bearing race (54) rotatable relative to the outer bearing race (52) and configured to be coupled to the rotor blade (20), the inner bearing race (54) defining a first inner bearing raceway wall (116) and a second inner bearing raceway wall (120), the inner bearing race (54) being at least partially spaced apart from the outer bearing race (52) such that a first gap (174) is defined between the inner and outer bearing races (54, 52) along an upper portion (176) of the thrust bearing (50) and a second gap (178) is defined between the inner and outer bearing races (54, 52) along a lower portion (180) of the thrust bearing (50); and
a first plurality of rolling elements (56) disposed between the first inner and outer bearing raceway walls (116, 114) and a second plurality of rolling elements (58) disposed between the second inner and outer bearing raceway walls (120, 118);
wherein each of the first plurality of rolling elements (56) defines an outer contact point (136) with the first outer bearing raceway wall (114) and an inner contact point (138) with the first inner bearing raceway wall (116), the inner and outer contact points (138, 136) being aligned along a reference line (144) defining a contact angle (150) of substantially 90 degrees relative to a radial axis (146) of the thrust bearing (50), and
wherein each of the second plurality of rolling elements (58) defines an outer contact (140) point with the second outer bearing raceway wall (118) and an inner contact point (142) with the second inner bearing raceway wall (120), the inner and outer contact points (142, 140) being aligned along a reference line (144) defining a contact angle (152) of substantially 90 degrees relative to the radial axis (146) of the thrust bearing (50).

13. The thrust bearing (50) of claim 12, wherein the contact angles (150, 152) are between 80-100 degrees relative to the radial axis (146) of the thrust bearing (50).

14. The thrust bearing (50) of claim 12, wherein the contact angles (150, 152) are 90 degrees relative to the radial axis (146) of the thrust bearing (50).

15. The thrust bearing (50) of claim 6, wherein one of the outer bearing race (52) or the inner bearing race (54) includes a split joint (84).

16. The thrust bearing (50) of claim 6, further comprising a raceway rib (160) extending between the first and second plurality of rolling elements (56, 58).

17. The thrust bearing (50) of claim 12, wherein the raceway rib (160) forms an extension of the inner bearing race (54) with the raceway rib (160) separating the first inner bearing raceway wall (116) from the second inner bearing raceway wall (120).

18. The thrust bearing (50) of claim 12, wherein a lubrication port (168) is defined through the outer bearing race (52), the lubrication port (168) configured to supply a lubricant from a location outside the thrust bearing (50) to a location between the first and second plurality of rolling elements (56, 58).

19. The thrust bearing (50) of claim 12, wherein a single contact point (190) is defined directly between each adjacent pair of rolling elements (56, 58) of the first and second plurality of rolling elements (56, 58).

20. A slewing thrust bearing (50) for a wind turbine (10), the slewing thrust bearing (50) comprising:
an outer bearing race (52);
an inner bearing race (54) rotatably coupled to the outer bearing race (52), the inner bearing race (54) being positioned relative to the outer bearing race (52) such that at least one raceway (110, 112) is defined between the inner and outer bearing races (52, 54); and
a plurality of rolling elements (56, 58) extending circumferentially around the raceway (110, 112) such that each of the plurality of rolling elements (56, 58) defines an outer contact point (136, 140) with the outer bearing race (52) and an inner contact point (138, 142) with the inner bearing race (54), the inner and outer contact points (138, 142, 136, 140) being aligned along a reference line (144) defining a contact angle (150, 152) of substantially 90 degrees relative to a radial axis (146) of the thrust bearing (50).
, Description:BACKGROUND
[0001] The disclosure relates generally to wind turbines and, more particularly, to improved bearing configurations for a wind turbine.
[0002] Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades capture kinetic energy from wind using known airfoil principles and transmit the kinetic energy through rotational energy to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
[0003] To ensure that wind power remains a viable energy source, efforts have been made to increase energy outputs by modifying the size and capacity of wind turbines. One such modification has been to increase the length of the rotor blades. However, as is generally understood, the loading on a rotor blade is a function of blade length, along with wind speed and turbine operating states. Thus, longer rotor blades may be subject to increased loading, particularly when a wind turbine is operating in high-speed wind conditions.
[0004] During the operation of a wind turbine, the loads acting on a rotor blade are transmitted through the blade and into the blade root. Thereafter, the loads are transmitted through a bearing, also referred to as a pitch bearing, disposed at the interface between the cantilevered rotor blade and the wind turbine hub. Typically, conventional pitch bearings include an inner ring, an outer ring, and two rows of balls, also referred to as rolling elements, concentrically disposed within separate raceways defined between inner and outer bearing races, with each rolling element being configured to contact its corresponding raceway at four separate contact points. This type of bearing is commonly referred to as a four-point bearing. In known bearing configurations, the predominant load applied to the bearing by the cantilevered blade is in the form of a moment that pries the bearing inner ring out of the outer ring. Any bearing that is expected to do the job of a pitch bearing should have maximum capacity for moment rather than being designed to handle pure axial or radial load. Inside a bearing, this moment translates into forces on the rolling elements that act mainly parallel to the axis of the blade.
[0005] Unlike regular ball bearings, normal operation of pitch bearings in wind turbines involves oscillations about a set pitch angle as opposed to continuous rotation at high speed in one direction. Two-point and four-point bearings include a “contact angle", usually 40° or 60°, which is a measure of the angle of the line of action of a force through the rolling element in a bearing relative to an intuitive baseline. Large deformations combined with complex oscillatory motion can drive the contact angles beyond available limits resulting in serious failures of the raceways. Moreover, the range of contact angles for the rolling elements within the bearing causes differential ball speeds which generate cage wear and failures in extreme cases.

[0006] Under ideal loading conditions, the loads transmitted through the pitch bearing are distributed evenly over all of the rolling elements. However, due to dynamic loading on the pitch bearing and the difference in stiffness between the hub and the rotor blade, only a percentage of the rolling elements actually carry the loads during operation of the wind turbine. As a result, the stresses within such load-carrying rolling elements tend to exceed the design tolerances for the pitch bearing, leading to damage and potential failure of the pitch bearing. Moreover, under dynamic loads, the rolling elements of conventional pitch bearings tend to run up and over the edges of the raceways, resulting in the rolling elements having reduced contact areas with the raceways. This leads to an additional increase in the stresses within the rolling elements, thereby further increasing the potential for damage to the pitch bearing components. Similar issues are also present in conventional yaw bearings for wind turbines.
[0007] Thus, it is highly desirable to provide a wind turbine blade bearing configuration that addresses one or more of the issues described above.
BRIEF DESCRIPTION
[0008] These and other shortcomings of the prior art are addressed by the present disclosure, which includes a thrust bearing for coupling a rotor blade to a hub of a wind turbine.
[0009] Briefly, one aspect of the present disclosure resides in a thrust bearing which includes an outer bearing race configured to be coupled to the hub and an inner bearing race rotatable relative to the outer bearing race and configured to be coupled to the rotor blade. The outer bearing race is configured to be coupled to the hub. The outer bearing race defines a first outer bearing raceway wall defining a curved profile having a center of curvature. The inner bearing race is rotatable relative to the outer bearing race and configured to be coupled to the rotor blade. The inner bearing race defines a first inner bearing raceway wall defining a curved profile having a center of curvature. A first plurality of rolling elements are disposed between the first inner and outer bearing raceway walls. Each of the first plurality of rolling elements defines an outer contact point with the first outer bearing raceway wall and an inner contact point with the first inner bearing raceway wall. The inner and outer contact points are aligned along a reference line defining a contact angle of substantially 90 degrees relative to a radial axis of the thrust bearing.
[0010] Another aspect of the disclosure resides in a thrust bearing which includes an outer bearing race configured to be coupled to the hub and defining a first outer bearing raceway wall and a second outer bearing raceway wall, and an inner bearing race rotatable relative to the outer bearing race and configured to be coupled to the rotor blade. The inner bearing race defining a first inner bearing raceway wall and a second inner bearing raceway wall. The inner bearing race is at least partially spaced apart from the outer bearing race such that a first gap is defined between the inner and outer bearing races along an upper portion of the thrust bearing and a second gap is defined between the inner and outer bearing races along a lower portion of the thrust bearing. A first plurality of rolling elements are disposed between the first inner and outer bearing raceway walls and a second plurality of rolling elements are disposed between the second inner and outer bearing raceway walls. Each of the first plurality of rolling elements defines an outer contact point with the first outer bearing raceway wall and an inner contact point with the first inner bearing raceway wall. The inner and outer contact points being aligned along a reference line defining a contact angle of substantially 90 degrees relative to a radial axis of the thrust bearing. Each of the second plurality of rolling elements defines an outer contact point with the second outer bearing raceway wall and an inner contact point with the second inner bearing raceway wall. The inner and outer contact points are aligned along a reference line defining a contact angle of substantially 90 degrees relative to the radial axis of the thrust bearing.
[0011] Yet another aspect of the disclosure resides in a slewing thrust bearing which includes an outer bearing race, an inner bearing race rotatably coupled to the outer bearing race. The inner bearing race is positioned relative to the outer bearing race such that at least one raceway is defined between the inner and outer bearing races. The slewing thrust bearing further includes a plurality of rolling elements extending circumferentially around the raceway such that each of the plurality of rolling elements defines an outer contact point with the outer bearing race and an inner contact point with the inner bearing race. The inner and outer contact points are aligned along a reference line defining a contact angle of substantially 90 degrees relative to a radial axis of the thrust bearing.
[0012] Various refinements of the features noted above exist in relation to the various aspects of the present disclosure. Further features may also be incorporated in these various aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to one or more of the illustrated embodiments may be incorporated into any of the above-described aspects of the present disclosure alone or in any combination. Again, the brief summary presented above is intended only to familiarize the reader with certain aspects and contexts of the present disclosure without limitation to the claimed subject matter.
DRAWINGS
[0013] These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
[0014] FIG. 1 illustrates a perspective view of one embodiment of a wind turbine, in accordance with one or more embodiments shown or described herein;
[0015] FIG. 2 illustrates a perspective, internal view of the nacelle of the wind turbine shown in FIG. 1, in accordance with one or more embodiments shown or described herein;
[0016] FIG. 3 illustrates a perspective view of one of the rotor blades of the wind turbine shown in FIG. 1, in accordance with one or more embodiments shown or described herein;
[0017] FIG. 4 illustrates a cross-sectional view of one embodiment of a rotor blade coupled to a wind turbine hub via a 2-point angular contact bearing configured in accordance with aspects disclosed herein, in accordance with one or more embodiments shown or described herein;
[0018] FIG. 5 illustrates a perspective view of a portion of the thrust bearing version of the 2-point angular contact bearing shown in FIG. 4, in accordance with one or more embodiments shown or described herein;
[0019] FIG. 6 illustrates a cross-sectional view of a portion of the thrust bearing shown in FIG. 5, in accordance with one or more embodiments shown or described herein;
[0020] FIG. 7 illustrates a close-up, cross-sectional view of a portion of the thrust bearing shown in FIG. 6, in accordance with one or more embodiments shown or described herein;
[0021] FIG. 8 illustrates another cross-sectional view of the thrust bearing shown in FIG. 5, particularly illustrating the contact patch resulting from the disclosed bearing configuration, in accordance with one or more embodiments shown or described herein;
[0022] FIG. 9 illustrates a perspective view of a thrust bearing configured in accordance with aspects disclosed herein, in accordance with one or more embodiments shown or described herein;
[0023] FIG. 10 illustrates a perspective, partially cut-away view of the thrust bearing shown in FIG. 9, particularly illustrating a full complement of rolling elements around each row of rolling elements, in accordance with one or more embodiments shown or described herein; and
[0024] FIG. 11 illustrates a close-up view of a portion of the thrust bearing shown in FIG. 9, in accordance with one or more embodiments shown or described herein.
DETAILED DESCRIPTION
[0025] Reference now will be made in detail to embodiments of the disclosure, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the disclosure, not limitation of the disclosure. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the scope or spirit of the disclosure. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present disclosure covers such modifications and variations as come within the scope of the appended claims and their equivalents.
[0026] In general, the present disclosure is directed to bearing configurations for a wind turbine, and more particularly to pitch bearings including thrust bearing technology, referred to herein as a thrust bearing. Thrust bearing technology provides for the orientation of the primary load carrying elements (rolling elements and raceway grooves) in a way that they are directly bearing the majority of the force applied by the moment in the bearing. In several embodiments, the pitch bearing, and more particularly the disclosed thrust bearing of the wind turbine may include a first raceway and a second raceway defined between inner and outer bearing races of the bearing. The raceways may be configured such that the rolling elements of the bearing contact the raceways at two opposed contact points oriented at a contact angle relative to the radial and axial directions. As will be described below, the disclosed bearing configuration(s) may allow for a reduction in contact angle variation, which causes contact patch truncation resulting in high stress between the rolling element and the edge of the raceway grooves, a reduction in differential ball speeds around the bearing caused by varying contact angles which contribute to excessive ball “bunching” resulting in high separating element (cage/spacer) forces, and a reduction in localized stress, thereby decreasing the likelihood of component damage/failure.
[0027] It should be appreciated that the disclosed thrust bearings have been uniquely configured to handle the dynamic loading of a wind turbine. Specifically, due to erratic moment loading and the fact that each thrust bearing is mounted directly to a relatively flexible rotor blade, the thrust bearings must be equipped to handle axial and radial loads that can vary significantly with time.
[0028] It should also be appreciated that, although the present thrust bearing configuration will be generally described herein with reference to pitch bearings, the disclosed thrust bearing configurations may be utilized within any suitable wind turbine bearing. For instance, yaw bearings are often subjected to dynamic loading during operation of a wind turbine. Thus, the disclosed bearing configurations may also be implemented within the yaw bearing of a wind turbine to reduce stresses within the bearing.
[0029] Referring now to the drawings, FIG. 1 illustrates a side view of one embodiment of a wind turbine 10. As shown, the wind turbine 10 generally includes a tower 12, a nacelle 14 mounted on the tower 12, and a rotor 16 coupled to the nacelle 14. The rotor 16 includes a rotatable hub 18 and at least one rotor blade 20 coupled to and extending outwardly from the hub 18. For example, in the illustrated embodiment, the rotor 16 includes three rotor blades 20. However, in an alternative embodiment, the rotor 16 may include more or less than three rotor blades 20. Each rotor blade 20 may be spaced about the hub 18 to facilitate rotating the rotor 16 to enable kinetic energy to be transferred from the wind into usable mechanical energy, and subsequently, electrical energy. For instance, the hub 18 may be rotatably coupled to an electric generator 30 (FIG. 2) positioned within the nacelle 14 to permit electrical energy to be produced.
[0030] Referring now to FIG. 2, a simplified, internal view of one embodiment of the nacelle 14 of the wind turbine 10 shown in FIG. 1 is illustrated. As shown, the generator 30 may be disposed within the nacelle 16. In general, the generator 30 may be coupled to the rotor 16 of the wind turbine 10 for generating electrical power from the rotational energy generated by the rotor 16. For example, the rotor 16 may include a rotor shaft 17 coupled to the hub 18 for rotation therewith. The generator 30 may then be coupled to the rotor shaft 17 such that rotation of the rotor shaft 17 drives the generator 30. For instance, in the illustrated embodiment, the generator 30 includes a generator shaft 32 rotatably coupled to the rotor shaft 17 through a gearbox 34. However, in other embodiments, it should be appreciated that the generator shaft 32 may be rotatably coupled directly to the rotor shaft 17. Alternatively, the generator 30 may be directly rotatably coupled to the rotor shaft 17 (often referred to as a "direct-drive wind turbine").
[0031] Additionally, the wind turbine 10 may include one or more yaw drive mechanisms 36 mounted to and/or through a bedplate 38 positioned atop the wind turbine tower 12. Specifically, each yaw drive mechanism 36 may be mounted to and/or through the bedplate 38 so as to engage a yaw bearing 40 coupled between the bedplate 38 and the tower 12 of the wind turbine 10. The yaw bearing 40 may be mounted to the bed plate 38 such that, as the yaw bearing 40 rotates about a yaw axis (not shown) of the wind turbine 10, the bedplate 38 and, thus, the nacelle 14 are similarly rotated about the yaw axis.
[0032] In general, it should be appreciated that the yaw drive mechanisms 36 may have any suitable configuration and may include any suitable components known in the art that allow such mechanisms 36 to function as described herein. For example, as shown in FIG. 2, each yaw drive mechanism 36 may include a yaw motor 42 mounted to the bedplate 38. The yaw motor 42 may be coupled to a yaw gear 44 (e.g., a pinion gear) configured to engage the yaw bearing 40. For instance, the yaw motor 42 may be coupled to the yaw gear 44 directly (e.g., by an output shaft (not shown) extending through the bedplate 38) or indirectly through a suitable gear assembly coupled between the yaw motor 42 and the yaw gear 44. As such, the torque generated by the yaw motor 42 may be transmitted through the yaw gear 44 and applied to the yaw bearing 40 to permit the nacelle 14 to be rotated about the yaw axis of the wind turbine 10. It should be appreciated that, although the illustrated wind turbine 10 is shown as including two yaw drive mechanisms 36, the wind turbine 10 may generally include any suitable number of yaw drive mechanisms 36.
[0033] Similarly, it should be appreciated that the yaw bearing 40 may generally have any suitable configuration, including one or more of the thrust bearing configurations described below. For instance, in several embodiments, the yaw bearing 40 may include an inner bearing race and an outer bearing race rotatable relative to the inner bearing race, with one or more rows of rolling elements being disposed between the inner and outer bearing races. In such embodiments, the yaw gear 44 may be configured to engage the outer bearing race of the yaw bearing 40 such that the outer bearing race is rotated relative to the inner bearing race to adjust the orientation of the nacelle 14 relative to the direction of the wind.
[0034] Referring still to FIG. 2, the wind turbine 10 may also include a plurality of pitch bearings, including thrust bearing technology, and referred to herein as thrust bearings 50, with each thrust bearing 50 being coupled between the hub 18 and one of the rotor blades 20. As will be described below, each of the thrust bearings 50 is configured as a two-point (2-P) contact thrust bearing (described below) and may allow each rotor blade 20 to be rotated about its pitch axis 46 (e.g., via a pitch adjustment mechanism 48), thereby allowing the orientation of each blade 20 to be adjusted relative to the direction of the wind.
[0035] It should be appreciated that, as used herein, the term "slewing bearing" may be used to refer to the yaw bearing 40 of the wind turbine 10 and/or one of the pitch bearings, and more particularly thrust bearings 50, of the wind turbine 10.
[0036] Referring now to FIG. 3, a perspective view of one of the rotor blades 20 shown in FIGS. 1 and 2 is illustrated in accordance with aspects disclosed herein. As shown, the rotor blade 20 includes a blade root 21 configured for mounting the rotor blade 20 to the hub 18 of a wind turbine 10 (FIG. 1) and a blade tip 22 disposed opposite the blade root 22. A body 23 of the rotor blade 20 may extend lengthwise between the blade root 21 and the blade tip 22 and may generally serve as the outer shell of the rotor blade 20. As is generally understood, the body 23 may define an aerodynamic profile (e.g., by defining an airfoil shaped cross-section, such as a symmetrical or cambered airfoil-shaped cross-section) to enable the rotor blade 20 to capture kinetic energy from the wind using known aerodynamic principles. Thus, the body 23 may generally include a pressure side 24 and a suction side 25 extending between a leading edge 26 and a trailing edge 27. Additionally, the rotor blade 20 may have a span 28 defining the total length of the body 23 between the blade root 21 and the blade tip 22 and a chord 29 defining the total length of the body 23 between the leading edge 26 and the trailing edge 27. As is generally understood, the chord 29 may vary in length with respect to the span 28 as the body 23 extends from the blade root 21 to the blade tip 22.
[0037] Moreover, as shown, the rotor blade 20 may also include a plurality of T-bolts or root attachment assemblies 60 for coupling the blade root 20 to the hub 18 of the wind turbine 10. In general, each root attachment assembly 60 may include a barrel nut 62 mounted within a portion of the blade root 21 and a root bolt 64 coupled to and extending from the barrel nut 62 so as to project outwardly from a root end 66 of the blade root 21. By projecting outwardly from the root end 66, the root bolts 64 may generally be used to couple the blade root 21 to the hub 18 (e.g., via one of the thrust bearings 50), as will be described in greater detail below.
[0038] Referring now to FIG. 4, a partial, cross-sectional view of a portion of the rotor blade 20 shown in FIG. 3 is illustrated, particularly illustrating the rotor blade 20 mounted onto the hub 18 via the thrust bearing 50 configured in accordance with aspects disclosed herein. As shown, the thrust bearing 50 includes an outer bearing race 52, an inner bearing race 54, defining a plurality of raceway grooves 92, and a plurality of rolling elements 56, 58 (e.g., a first row of balls 56 and a second row of balls 58) disposed between the outer and inner bearing races 52, 54. The outer bearing race 52 may generally be configured to be mounted to a hub flange 70 of the hub 18 using a plurality of hub bolts 71 and/or other suitable fastening mechanisms. Similarly, the inner bearing race 54 may be configured to be mounted to the blade root 21 using the root bolts 64 of the root attachment assemblies 60. For example, as shown in FIG. 4, each root bolt 64 may extend between a first end 65 and a second end 66. The first end 65 may be configured to be coupled to a portion of the inner bearing race 54, such as by coupling the first end 65 to the inner bearing race 54 using an attachment nut and/or other suitable fastening mechanism. The second end 67 of each root bolt 64 may be configured to be coupled to the blade root 21 via the barrel nut 62 of each root attachment assembly 60.
[0039] As is generally understood, the inner bearing race 54 may be configured to be rotated relative to the outer bearing race 52 (via the rolling elements 56, 58) to allow the pitch angle of each rotor blade 20 to be adjusted. As shown in FIG. 4, such relative rotation of the outer and inner bearing races 52, 54 may be achieved using a pitch adjustment mechanism 72 mounted within a portion of the hub 18. In general, the pitch adjustment mechanism 72 may include any suitable components and may have any suitable configuration that allows the mechanism 72 to function as described herein. For example, as shown in the illustrated embodiment, the pitch adjustment mechanism 72 may include a pitch drive motor 74 (e.g., an electric motor), a pitch drive gearbox 76, and a pitch drive pinion 78. In such an embodiment, the pitch drive motor 74 may be coupled to the pitch drive gearbox 76 so that the motor 74 imparts mechanical force to the gearbox 76. Similarly, the gearbox 76 may be coupled to the pitch drive pinion 78 for rotation therewith. The pinion 78 may, in turn, be in rotational engagement with the inner bearing race 54. For example, as shown in FIG. 4, a plurality of gear teeth 80 may be formed along the inner circumference of the inner bearing race 54, with the gear teeth 80 being configured to mesh with corresponding gear teeth 82 formed on the pinion 78. Thus, due to meshing of the gear teeth 80, 82, rotation of the pitch drive pinion 78 results in rotation of the inner bearing race 54 relative to the outer bearing race 52 and, thus, rotation of the rotor blade 20 relative to the hub 18.
[0040] Referring now to FIGs. 5-7, close-up, cross-sectional views of portions of the thrust bearing 50 shown in FIG. 4 are illustrated in accordance with aspects disclosed herein. As shown, the rolling elements 56, 58 are configured to be received within separate raceways defined between the outer and inner bearing races 52, 54. The outer and inner bearing races 52, 54 defining a plurality of raceway grooves 92, also referred to herein as raceways. Specifically, a first raceway 110 is defined between the outer and inner bearing races 52, 54 for receiving the first row of rolling elements 56 and a second raceway 112 is defined between the inner and outer bearing races 52, 54 for receiving the second row of rolling elements 58. In such an embodiment, each raceway 110, 112 may be defined by separate walls of the outer and inner bearing races 52, 54. For instance, as shown in FIGs. 5-7, the first raceway 110 is defined by a first outer bearing raceway wall 114 of the outer bearing race 52 and a first inner bearing raceway wall 116 of the inner bearing race 54. Similarly, the second raceway 112 is defined by a second outer bearing raceway wall 118 of the outer bearing race 52 and a second inner bearing raceway wall 120 of the inner bearing race 54.
[0041] In general, each raceway wall 114, 116, 118, 120 may be configured to define a curved profile. For example, as particularly shown in FIG. 7, the first outer bearing raceway wall 114 generally corresponds to a curved wall extending around the inner circumference of the outer bearing race 52 that defines a radius 122 extending from a center of curvature 124 of such wall. Similarly, the first inner bearing raceway wall 116 generally corresponds to a curved wall extending around the outer circumference of the inner bearing race 54 that defines a radius 126 extending from a center of curvature 128 of such wall. Although not shown, the second outer bearing raceway wall 118 may also define a radius having a center of curvature and the second inner bearing raceway wall 120 may similarly define a radius having a center of curvature.
[0042] In several embodiments, the center of curvature 124, 128 for each raceway wall 114, 116, 118, 120 may be offset from a geometric center 130 of each rolling element 56, 58. By doing so, an internal “preload” is accomplished in the thrust bearing 50 that prevents false brinelling of the ball to raceway contact area and potentially adds some capacity. False brinelling may occur as a result of vibration and light loads over an extended period of time, resulting in material wear or removal. In an embodiment, as shown in FIG. 7, the center of curvature 124 of the first outer bearing raceway wall 114 is offset from the geometric center 130 of the rolling element 56 by a first distance 132 while the center of curvature 128 of the first inner bearing raceway wall 116 is offset from the geometric center 130 by a second distance 134. Although not shown in FIG. 7, it should be appreciated that the second outer and inner bearing raceway walls 118, 120 may be configured similar to the first outer and inner bearing raceway walls 114, 116. For instance, the centers of curvature for the second outer and inner bearing raceway walls 118, 120 may be offset from the geometric center 130 of each rolling element 58 by respective distances (e.g., the first and second distances 132, 134).
[0043] It should also be appreciated that, in one embodiment, the first distance 132 may be the same as the second distance 134. Alternatively, the first distance 132 may differ from the second distance 134. Additionally, it should be appreciated that the distances 132, 134 may generally correspond to any suitable length. For instance, in a particular embodiment, the first and second distances 132, 134 may each correspond to a length substantially 2 millimeters or less.
[0044] By configuring the raceway walls 114, 116, 118, 120 so that each center of curvature 124, 128 is offset from the geometric center 130 of the rolling elements 56, 58, each rolling element 56, 58 may include two contact points 136, 138, 140, 142 defined along reference lines 144 that are angled relative to the radial direction (indicated by arrow 146) and the axial direction (indicated by arrow 148) of the thrust bearing 50. Specifically, as shown in FIGs. 6 and 7, each rolling element 56 is configured to contact the first outer bearing raceway wall 114 at a first outer contact point 136 and the first inner bearing raceway wall 116 at a first inner contact point 138, with the first outer and inner contact points 136, 138 being defined along a reference line 144 oriented at a first contact angle 150. Similarly, each rolling element 58 may be configured to contact the second outer bearing raceway wall 118 at a second outer contact point 140 and the second inner bearing raceway wall 120 at a second inner contact point 142, with the second outer and inner contact points 140, 142 being defined along a reference line 144 oriented at a second contact angle 152.
[0045] It should be appreciated that the contact angles 150, 152 defined by the reference lines 144 may generally correspond to substantially 90 degrees relative to the radial direction 146. However, in several embodiments, each reference line 144 may be configured to extend at a contact angle 150, 152 relative to the radial direction 146 ranging from about 80 degrees to about 100 degrees and any other subranges therebetween. In an embodiment, the contact angle 150, 152 variation is approximately +/-10 degrees from nominal. This is an important benefit to reduce bunching of the rolling elements 56, 58. In an embodiment, contact angles 150, 152 defined by the reference lines 144 may correspond to 90 degrees relative to the radial direction 146.
[0046] It should also be appreciated that first and second contact angles 150, 152 may be the same angle or different angles. Specifically, as the contact angle approaches 90 degrees, and more particularly oriented parallel to the axial or thrust direction, as indicated by arrow 86 (FIG. 8), the corresponding rolling elements 56, 58 may be better equipped to handle axial loads, improve the moment carrying capacity of the bearing 50, increase the truncation margin and reduce the risk of developing cage forces, as described presently.
[0047] By orienting the contact points 136, 138, 140, 142 along reference lines 144 extending at a substantially 90 degree angle relative to the radial direction 146, the rolling elements 56, 58 may be capable of reacting to forces induced by moments without needing to adjust the contact angles 150, 152 significantly.
[0048] Referring still to FIGs. 5-7, the thrust bearing 50 may also include a raceway rib 160 at least partially dividing the first raceway 110 from the second raceway 112. In several embodiments, the raceway rib 160 may form an extension of the inner bearing race 54. For instance, as shown in FIGs. 6-7, the raceway rib 160 may correspond to a radial projection of the inner bearing race 54 that extends between the rolling elements 56, 58 and separates the first inner bearing raceway wall 116 from the second inner bearing raceway wall 120. Alternatively, the raceway rib 160 may be configured to form an extension of the outer bearing race 52. More particularly, the raceway rib 160 may correspond to a radial projection of the outer bearing race 52 configured to extend between the rolling elements 56, 58 and separate the raceway walls.
[0049] As particularly shown in FIG. 7, the raceway rib 160 is configured such that the raceway walls 116 and 120 defining the outer surfaces of the rib 160 extend beyond a 90 degree location of the rolling elements 56, 58, which is indicated by a reference line 162 passing through the geometric center 130 of the rolling elements 56, 58 and extending along the axial direction 148 (i.e., perpendicular to the radial direction 146). For instance, in the illustrated embodiment, the raceway rib 160 extends between the rolling elements 56, 58 such that the arc length of the portion of the inner bearing raceway walls 116, 120 extending beyond the 90 degree location 162 defines an angle 164 ranging from about 0 degrees to about 90 degrees, and as illustrated, approximately 45 degrees, and any other subranges therebetween.
[0050] By configuring the raceway rib 160 to extend beyond the 90 degree location 162, the rolling elements 56, 58 may be fully supported within the thrust bearing 50 during dynamic loading events. For instance, if the rolling elements 56, 58 run up/down the raceway walls 114, 116, 118, 120 towards the 90 degree location 162 during high loading events, the rolling elements 56, 58 may be supported between the inner and outer bearing races 52, 54 without contacting the edges of the raceways 110, 112 (e.g., edges 166 (FIG. 7) defined by the inner bearing raceway walls 116, 120.
[0051] Additionally, in an embodiment, a plurality of lubrication ports 168, as shown FIGs. 6, 7, 9 and 10, may be defined through the outer bearing race 52. As best illustrated in FIGs. 9 and 10, the lubrication ports 168 may be spaced apart circumferentially around the outer circumference of the outer bearing race 52. In general, each lubrication port 168 may be configured to supply a suitable lubricant (e.g., grease, etc.) from a location outside the thrust bearing 50 to a location between the first and second raceways 110, 112. Thus, as shown in FIG. 6, each lubrication port 168 may generally extend between a first end 170 disposed along the outer circumference of the outer bearing race 52 and a second end 172 disposed along the inner circumference of the outer bearing race 52. For instance, in the illustrated embodiment, the second end 172 is defined through the outer bearing race 52 so that lubricant may be delivered into a gap defined between the rib 160 and the outer circumference of the outer bearing race 52. The lubricant may then be directed up and down between the outer and inner bearing races 52, 54 to lubricate the first and second raceways 110, 112. In an alternate embodiment, the lubrication port may be configured in an alternate location to supply a lubricant from a location outside the thrust bearing to a location between the first and second plurality of rolling elements
[0052] Additionally, to maintain the lubricant within the thrust bearing 50, any gaps defined between the outer and inner bearing races 52, 54 may be sealed using suitable sealing mechanisms. For instance, as shown in FIG. 6, the pitch bearing 50 includes a first gap 174 defined between the outer and inner bearing races 52, 54 along an upper portion 176 of the bearing 50 and a second gap 178 defined between the outer and inner bearing races 52, 54 along a lower portion 180 of the bearing 50. In such an embodiment, a first sealing mechanism 182 may be disposed directly between the outer inner bearing races 52, 54 to seal the first gap 174 and a second sealing mechanism 184 may be disposed directly between the outer and inner bearing races 52, 54 to seal the second gap 178.
[0053] It should be appreciated that, although not shown, the rolling elements 56, 58 contained within each row may be spaced apart circumferentially from one another using conventional cages and/or spacers. Alternatively, as will be described below, the thrust bearing 50 may include a full complement of rolling elements 56, 58 extending circumferentially around each raceway 110, 112.
[0054] It should be noted that the assembly of the thrust bearing 50, configured as a 2-P contact thrust bearing, is not possible without having a planar split line or joint 84 in at least one of the rings, and more particularly the inner bearing race 52 or outer bearing race 54, as best illustrated in FIGs. 4-7. Thrust bearings as described in the present disclosure require a planar split line, or joint, 84 on one of the outer or inner bearing races 52, 54 to allow for final assembly. The race bearing which has this feature forms an effective "C" clamp around the rolling elements 56, 58 to capture them in the raceway grooves 92 when bolts, such as hub bolts 71 (FIG. 3) are tightened around the bearing races 52, 54. With correct handling, this feature also provides the mechanism to preload the rolling elements 56, 58 for added bearing capacity. As such, the split joint 84 depends on maintaining adequate pretension in the bolts 71 that clamp the outer and inner bearing races 52, 54 together.
[0055] In an embodiment, assembly bolts may need to be used to secure the split outer or inner bearing races 52, 54 and apply the preload. By design, it is typically not possible to move a split joint to the outer bearing race of a standard 2-point angular contact bearing because the rolling element contacts would be oriented in an adverse direction to the applied load. However, in the pitch bearing, and more specifically in the thrust bearing 50, disclosed herein it is possible to do so because the 90 degree contact angles 150, 152 make the bearing race that includes the split joint 84 neutral. In an embodiment, the bearing 50 performs equally well regardless of which bearing race 52, 54 has the split joint 84. This leads to a significant advantage in terms of reducing the risk at the split joint 84. Other designs have applied this split joint to an inner bearing race element which is subsequently bolted to the relatively weak composite blade through the bolts in the blade root. Experience shows increased risk of bolt loosening at the split joint because of the softer blade material. Accordingly, although as stated, performing equally well regardless of which of the outer or inner bearing race 52, 54 has the split joint 84, in a preferred embodiment, it is desirable to assign the split joint 84 to the hub side, or outer race bearing 52, to take advantage of the more solid anchor the hub flange 70 (FIG. 4) provides over the softer composite blade 20 (FIG. 4). In an embodiment, the split outer bearing race 52 configuration may provide improved pressure distribution compared to a split inner bearing race 54 configuration, as well as reducing the risk of bolt loosening and loss of bearing preload and capacity.
[0056] It should also be appreciated that the bearing configuration(s) shown in FIGs. 4-7 may be utilized with any other suitable wind turbine bearing(s). For instance, in several embodiments, the bearing configuration(s) may be utilized within the yaw bearing 40 (FIG. 2) of the wind turbine 10 (FIG. 1).
[0057] Referring now to FIG. 8, analysis of known 4-P contact bearings has shown that the contact angles tend to align with the axial direction of the bearing when subjected to moment forces. Migration of the contact angle in these bearings for highly loaded rolling elements is responsible for contact truncation and cage loading issues. More particularly, application conditions in known 4-P contact bearings may exist which cause the contact area of the rolling elements with the raceways to be severely truncated by the edge of the raceway or rolling elements. Design solutions offered to mitigate the risk of these issues must minimize contact angle variation. As best illustrated in FIG. 8, the thrust bearing 50 provides such design solution by aligning the initial contact angle 150, 152 (FIGs. 6 and 7) relative to the direction of the applied force 86, and more particularly relative to the direction of the bearing pitch axis 46 (Fig. 2). This configuration allows the plurality of rolling elements 56, 58 to react to forces induced by moments without needing to adjust the contact angles 150, 152 significantly. As illustrated in FIG. 8, with a reduction in contact angle variation, contact truncation and damaging cage forces may be minimized, if not eliminated. In the case of the thrust bearing 50, a groove angle, as indicated by shaded area 90, is approximately 30 degrees to 150 degrees relative to a horizontal axis 88 and a contact ellipse position, as schematically represented by dashed line 90, is substantially centrally located in each raceway 110, 112, leaving at least 30 degrees on each side of the groove raceway 92. Accordingly, due to the larger available raceway arc, there is little risk of truncation in the thrust bearing 50.
[0058] By controlling the contact angles 150, 152 tightly, a contact patch 94 between each of the rolling elements 56, 58 and the raceway groove 92 wanders less on the contact surface as the load changes. Additionally, the architecture of the thrust bearing 50 provides more raceway arc for the rolling element/raceway interface than other designs. When small contact angle 150, 152 variations and associated contact patch 94 migrations do exist, they are easily contained within the extra arc length provided by the architecture. Thus, the contact patch 94 remains intact on the contact surface where it needs to be for maximum effect. These characteristics form a natural defense against differential rolling element speeds and contact patch truncation together with its associated edge stress.
[0059] Referring now to FIGs. 9-11, FIG. 9 is a perspective view of the thrust bearing 50 and FIG. 10 is a perspective, partially cut-away view of the thrust bearing 50, each illustration depicting having a full complement of rolling elements 56, 58. Additionally, FIG. 11 illustrates a close-up view of a portion of the thrust bearing 50 shown in FIG. 10. As previously alluded to, in an alternate embodiment the rolling elements 56, 58 contained within each row may be spaced apart circumferentially from one another using conventional cages and/or spacers.
[0060] As shown in the illustrated embodiment, the thrust bearing 50 may include the plurality of rolling elements 56, 58 (i.e., balls) extending circumferentially around each raceway 110, 112, with each rolling element 56, 58 directly contacting its adjacent rolling elements 56, 58. Specifically, as shown in FIG. 11, the rolling elements 56, 58 may be installed within each raceway 110, 112 such that a single contact point 190 is defined between each pair of adjacent rolling elements 56, 58.
[0061] By configuring the thrust bearing 50 to include a full complement of rolling elements 56, 58, additional rolling elements may be installed within the bearing 50. Specifically, conventional bearing configurations typically include separators, such as cages and/or spacers, that are designed to space the rolling elements 56, 58 apart circumferentially around each raceway 110, 112. By removing the cages/spacers, the space typically inhabited by such separators may be replaced with additional rolling elements 56, 58. As such, the load capacity of the bearing 50 may be increased while the stresses acting on the bearing 50 may be reduced.
[0062] It should be appreciated that, in several embodiments, the full complement of rolling elements 56, 58 shown in FIGS. 10 and 11 may be utilized together with the thrust bearing configuration described above with reference to FIGS. 4-8. In an alternate embodiment, cages and/or spacers designed to space the rolling elements 56, 58 may be utilized. Additionally, it should be appreciated that the bearing configuration shown in FIGS. 10 and 11 may be utilized with any other suitable wind turbine bearing(s). For instance, in several embodiments, the full complement of rolling elements 56, 58 may be utilized within the yaw bearing 40 (FIG. 2) of the wind turbine 10 (FIG. 1).
[0063] Accordingly, disclosed is a pitch bearing incorporating thrust bearing technology, and referred to herein as a thrust bearing, that solves many issues in current bearing designs, including, but not limited to, contact truncation thus edge stress, rolling element/ball bunching resulting in excessive separating element (cage/spacer) loads and loss of bearing preload due to loss of bolt pretension. The thrust bearing design disclosed herein offers several advantages over existing pitch bearing designs, including, but not limited to: i) zero contact patch truncation: a larger raceway groove arc of approximately 120 degrees and tighter contact angle control makes it possible to place the contact ellipse in the middle of the raceway groove, thus allowing higher bearing capacity without risk of contact truncation and edge stress; ii) reduced rolling element/ball bunching: thrust bearing having nominal contact angles of 90°. When moment load is applied to the bearing, the rolling elements will make little to no adjustment to react to the loads, thus minimizing contact angle variation. In that the orbital speed of a rolling element is highly dependent on contact angle, tighter control of the contact angle insures the difference in orbital rolling element speeds is minimized thus reducing or eliminating high separating element forces; iii) protection against loss of bearing preload by shifting the split joint to the outer race, thus: reducing the risk of loss of bearing preload due to the more reliable outer race to hub joint; iv) reduced sensitivity to the bolt preload: thrust bearings are shown to be less sensitive to the bolt preload than other angular contact ball bearing designs, thus improving serviceability by making the bearing less sensitive to precise maintenance intervals; and v) cost saving: optimizing the thrust bearing design may reduce the size of the bearing forging, thus saving direct material costs.
[0064] This written description uses examples to disclose the subject matter, including the best mode, and also to enable any person skilled in the art to practice the disclosure, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
[0065] This written description uses examples to disclose the disclosure, including the best mode, and also to enable any person skilled in the art to practice the disclosure, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.
[0066] While there has been shown and described what are at present considered the preferred embodiments of the disclosure, it will be obvious to those skilled in the art that various changes and modifications can be made therein without departing from the scope of the disclosure defined by the appended claims.