Wind turbine pitch bearing with line contact rolling elements

A pitch bearing for coupling a rotor blade to a hub of a wind turbine includes an outer race configured to be coupled to the hub, an inner race rotatable relative to the outer race and configured to be coupled to the rotor blade, and a first plurality of line contact rolling elements. The outer race defines a first outer raceway wall and the inner race defines a first inner raceway wall. The first plurality of line contact rolling elements is disposed between the first inner and outer raceway walls. Each of the plurality of line contact rolling elements defines a predetermined contact angle. The predetermined contact angle is defined as an angle between a reference line extending perpendicular to a longitudinal axis of one of the plurality of line contact rolling elements and a reference line extending parallel to a horizontal plane of the pitch bearing. Further, the predetermined contact angle includes angles between 0 degrees (°) and 90°.

FIELD

The present subject matter relates generally to wind turbines and, more particularly, to a pitch bearing for a wind turbine utilizing line contact rolling elements.

BACKGROUND

Further, the wind turbine may include various bearings to facilitate rotation of its various components. Two examples of such bearings include pitch bearings and yaw bearings. More specifically, yaw bearings are configured to rotate the nacelle with respect to the tower as a function of the incoming wind. In addition, pitch bearings are arranged between a blade root of the rotor blades and the hub. Therefore, the pitch bearings rotate or pitch the rotor blades with respect to the incoming wind.

Such bearings generally include an outer race, an inner race rotatable relative to the outer race, and a plurality of rolling elements therebetween. Many wind turbine bearings include point contact rolling elements, e.g. ball bearings1, such as those illustrated inFIG. 1. Alternatively, as shown inFIG. 2, some wind turbine bearings may include line contact rolling elements, such as cylindrical rolling elements2, having a 0° and 90° contact angle configuration.

Conventional line contact rolling elements typically include the rolling elements arranged in a 0° and 90° contact angle configuration. More specifically, as shown inFIG. 3, a partial, cross-sectional view of a line contact rolling element bearing3according to conventional construction is illustrated. As shown, the line contact rolling element bearing3includes an outer race7and an inner race8rotatable relative to the outer race7via a plurality of line contact rolling elements4,5,6. More specifically, as shown, the upper and lower line contact rolling elements4,5have a 90° contact angle, whereas the middle line contact rolling element6has a 0° contact angle.

In such configurations, the rolling elements having a 90° contact angle experience relative sliding therebetween as well as with raceway in order to function. Successful utilization of line contact rolling elements in a 90° contact angle configuration typically relies on operation in lubrication lambda regimes greater than one such that the relative sliding is not detrimental to bearing performance. However, wind turbine pitch bearings experience lambda ratios approaching zero. Thus, when line contact rolling element bearings are used as pitch bearings, such sliding can scuff and wear interface surfaces, generating heat and debris inside the bearing.

Accordingly, a pitch bearing having line contact rolling elements that addresses the aforementioned issues would be welcomed in the technology. In particular, a pitch bearing with less than three rows of line contact rolling elements would be beneficial.

BRIEF DESCRIPTION

In one aspect, the present disclosure is directed to a pitch bearing for coupling a rotor blade to a hub of a wind turbine. The pitch bearing includes an outer race configured to be coupled to the hub, an inner race rotatable relative to the outer race and configured to be coupled to the rotor blade, and a first plurality of line contact rolling elements. The outer race defines a first outer raceway wall and the inner race defines a first inner raceway wall. The first plurality of line contact rolling elements is disposed between the first inner and outer raceway walls. Each of the plurality of line contact rolling elements defines a predetermined contact angle. The predetermined contact angle is defined as an angle between a reference line extending perpendicular to a longitudinal axis of one of the plurality of line contact rolling elements and a reference line extending parallel to a horizontal plane of the pitch bearing. Further, the predetermined contact angle includes angles between 0 degrees (°) and 90°.

In one embodiment, the outer race may further define a second outer raceway wall and the inner race may define a second inner raceway wall. In such embodiments, the pitch bearing may include a second plurality of line contact rolling elements disposed between the second inner and outer raceway walls.

In another embodiment, the first and second plurality of line contact rolling elements may include cylindrical rolling elements.

Alternatively, the first and second plurality of line contact rolling elements may include tapered rolling elements. In such embodiments, reference lines extending parallel to the longitudinal axes of the first and second plurality of tapered rolling elements may converge at a common point of the pitch bearing and define a taper angle. More specifically, in certain embodiments, the inner and outer races may be segments of cones with the rolling elements being tapered so that the conical surfaces of the races and the rolling element axes, if projected, would meet at the same common point on the main axis of the bearing. The convergence of the surfaces of the races and rolling elements defines the taper angle. For example, in certain embodiments, the taper angle may include angles ranging from about 0.25° to about 6°.

In yet another embodiment, the pitch bearing may further include at least one additional plurality of rolling elements. In still a further embodiment, the pitch bearing may also include a raceway rib extending between the first and second plurality of rolling elements.

In another aspect, the present disclosure is directed to a pitch bearing for coupling a rotor blade to a hub of a wind turbine. The pitch bearing includes an outer race configured to be coupled to the hub, an inner race rotatable relative to the outer race and configured to be coupled to the rotor blade, and a first plurality of line contact rolling elements. The outer race defines a first outer raceway wall and the inner race defines a first inner raceway wall. The first plurality of line contact rolling elements is disposed between the first inner and outer raceway walls. Each of the plurality of line contact rolling elements defines a predetermined contact angle. The predetermined contact angle is defined as an angle between a reference line extending perpendicular to a longitudinal axis of one of the plurality of line contact rolling elements and a reference line extending parallel to a horizontal plane of the pitch bearing. Further, the predetermined contact angle includes non-0° angles and non-90° angles. It should be understood that the pitch bearing may further include any of the additional features described herein.

In yet another aspect, the present disclosure is directed to a slewing ring bearing. The slewing ring includes an outer race, an inner race rotatable relative to the outer race, and a plurality of line contact rolling elements. The inner race is positioned relative to the outer race such that at least one raceway is defined between the inner and outer races. The plurality of line contact rolling elements extends circumferentially around the raceway. Each of the plurality of line contact rolling elements defines a predetermined contact angle. The predetermined contact angle is defined as an angle between a reference line extending perpendicular to a longitudinal axis of one of the plurality of line contact rolling elements and a reference line extending parallel to a horizontal plane of the pitch bearing. Further, the predetermined contact angle includes non-0° angles and non-90° angles. It should be understood that the slewing ring bearing may further include any of the additional features described herein.

DETAILED DESCRIPTION

In general, the present subject matter is directed to bearing configurations for a wind turbine. In several embodiments, a pitch bearing of the wind turbine may include first and second rows of line contact rolling elements arranged between inner and outer races of the bearing. It should be appreciated that the disclosed pitch 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 pitch bearing is mounted directly to a relatively flexible rotor blade, pitch bearings must be equipped to handle axial and radial loads that can vary significantly with time. As will be described below, the disclosed bearings provide for non-0° and non-90° contact angles, thereby reducing the resultant loads applied through each rolling element and eliminating sliding therebetween. Accordingly, each rolling element may deflect less and, thus, may retain more of an overall share of the entire load, thereby decreasing the stress on the bearing.

It should also be appreciated that, although the present subject matter will be generally described herein with reference to pitch bearings, the disclosed bearing configurations may be utilized within any suitable wind turbine bearing. For instance, yaw bearings are often subject 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.

Referring now to the drawings,FIG. 4illustrates a perspective view of one embodiment of a wind turbine10according to the present disclosure. As shown, the wind turbine10generally includes a tower12, a nacelle14mounted on the tower12, and a rotor16coupled to the nacelle14. The rotor16includes a rotatable hub18and at least one rotor blade20coupled to and extending outwardly from the hub18. For example, in the illustrated embodiment, the rotor16includes three rotor blades20. However, in an alternative embodiment, the rotor16may include more or less than three rotor blades20. Each rotor blade20may be spaced about the hub18to facilitate rotating the rotor16to enable kinetic energy to be transferred from the wind into usable mechanical energy, and subsequently, electrical energy. For instance, the hub18may be rotatably coupled to an electric generator25(FIG. 5) positioned within the nacelle14to permit electrical energy to be produced.

Referring now toFIG. 5, a perspective view of one of the rotor blades20shown inFIG. 4is illustrated in accordance with aspects of the present subject matter. As shown, the rotor blade20includes a blade root22configured for mounting the rotor blade20to the hub18of the wind turbine10(FIG. 4) and a blade tip24disposed opposite the blade root22. A body26of the rotor blade20may extend lengthwise between the blade root22and the blade tip24and may generally serve as the outer shell of the rotor blade20. As is generally understood, the body26may 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 blade20to capture kinetic energy from the wind using known aerodynamic principles. Thus, the body26may generally include a pressure side28and a suction side30extending between a leading edge32and a trailing edge34. Additionally, the rotor blade20may have a span36defining the total length of the body26between the blade root22and the blade tip24and a chord38defining the total length of the body26between the leading edge32and the trailing edge34. As is generally understood, the chord38may vary in length with respect to the span26as the body26extends from the blade root22to the blade tip24.

Moreover, as shown, the rotor blade20may also include a plurality of T-bolts or root attachment assemblies40for coupling the blade root20to the hub18of the wind turbine10. In general, each root attachment assembly40may include a barrel nut42mounted within a portion of the blade root22and a root bolt44coupled to and extending from the barrel nut42so as to project outwardly from a root end46of the blade root22. By projecting outwardly from the root end46, the root bolts44may generally be used to couple the blade root22to the hub18(e.g., via one of the pitch bearings50), as will be described in greater detail below.

Referring now toFIG. 6, a simplified, internal view of one embodiment of the nacelle14of the wind turbine10shown inFIG. 4is illustrated. As shown, the generator25may be disposed within the nacelle14. In general, the generator25may be coupled to the rotor16of the wind turbine10for generating electrical power from the rotational energy generated by the rotor16. For example, the rotor16may include a rotor shaft27coupled to the hub18for rotation therewith. The generator25may then be coupled to the rotor shaft27such that rotation of the rotor shaft27drives the generator25. For instance, in the illustrated embodiment, the generator25includes a generator shaft29rotatably coupled to the rotor shaft27through a gearbox31. However, in other embodiments, it should be appreciated that the generator shaft29may be rotatably coupled directly to the rotor shaft27. Alternatively, the generator25may be directly rotatably coupled to the rotor shaft27(often referred to as a “direct-drive wind turbine”).

Referring still toFIG. 6, the wind turbine10may include numerous slewing ring bearings for allowing rotation of various components of the wind turbine10. For example, it should be appreciated that, as used herein, the term “slewing ring bearing” may be used to refer to the yaw bearing35of the wind turbine10and/or one of the pitch bearings50of the wind turbine10. Similarly, it should be appreciated that the slewing ring bearings35,50may generally have any suitable configuration, including one or more of the bearing configurations described below. For instance, in several embodiments, the slewing ring bearings35,50may include an inner race and an outer race rotatable relative to the inner race, with one or more rows of rolling elements being disposed between the inner and outer races.

Additionally, the wind turbine10may include one or more yaw drive mechanisms33mounted to and/or through a bedplate15positioned atop the wind turbine tower12. Specifically, each yaw drive mechanism33may be mounted to and/or through the bedplate15so as to engage the yaw bearing35coupled between the bedplate15and the tower12of the wind turbine10. The yaw bearing35may be mounted to the bed plate15such that, as the yaw bearing35rotates about a yaw axis (not shown) of the wind turbine10, the bedplate15and, thus, the nacelle14are similarly rotated about the yaw axis. It should be appreciated that, although the illustrated wind turbine10is shown as including two yaw drive mechanisms33, the wind turbine10may generally include any suitable number of yaw drive mechanisms232.

Referring still toFIG. 6, the wind turbine10may also include a plurality of pitch bearings50(one of which is shown), with each pitch bearing50being coupled between the hub18and one of the rotor blades20. As will be described below, the pitch bearings50may be configured to allow each rotor blade20to be rotated about its pitch axis39(e.g., via a pitch adjustment mechanism45), thereby allowing the orientation of each blade20to be adjusted relative to the direction of the wind.

In general, it should be appreciated that the pitch and yaw drive mechanisms33,45may have any suitable configuration and may include any suitable components known in the art that allow such mechanisms33,45to function as described herein. For example, as shown in the illustrated embodiment, the pitch adjustment mechanism45may include a pitch drive motor37(e.g., an electric motor), a pitch drive gearbox41, and a pitch drive pinion43. In such an embodiment, the pitch drive motor37may be coupled to the pitch drive gearbox41so that the motor37imparts mechanical force to the gearbox41. Similarly, the gearbox41may be coupled to the pitch drive pinion43for rotation therewith. The pinion43may, in turn, be in rotational engagement with the inner race54.

Referring now toFIGS. 7 and 8, partial, cross-sectional views of the rotor blade20shown inFIG. 5are illustrated, particularly illustrating the rotor blade20mounted onto the hub18via one of the pitch bearings50according to the present disclosure. As shown, the pitch bearing50includes an outer bearing race52, an inner bearing race54, and a plurality of line contact rolling elements56,58(e.g., a first plurality of rolling elements56and a second plurality of rolling elements58) disposed between the outer and inner races52,54. More specifically, as shown inFIGS. 8 and 10, the first and second plurality of line contact rolling elements56,58may include tapered rolling elements76,78. Alternatively, as shown inFIG. 9, the first and second plurality of line contact rolling elements56,58may include cylindrical rolling elements86,88.

Further, as shown, the outer race52may generally be configured to be mounted to a hub flange60of the hub18using a plurality of hub bolts62and/or other suitable fastening mechanisms. Similarly, the inner race54may be configured to be mounted to the blade root22using the root bolts44of the root attachment assemblies40. For example, as shown inFIG. 7, each root bolt44may extend between a first end64and a second end66. The first end64may be configured to be coupled to a portion of the inner race54, such as by coupling the first end64to the inner race54using an attachment nut and/or other suitable fastening mechanism. The second end66of each root bolt44may be configured to be coupled to the blade root22via the barrel nut42of each root attachment assembly40.

As is generally understood, the inner race54may be configured to be rotated relative to the outer race52(via the rolling elements56,58) to allow the pitch angle of each rotor blade20to be adjusted. As shown inFIG. 7, such relative rotation of the outer and inner races52,54may be achieved using a pitch adjustment mechanism45mounted within a portion of the hub18. For example, as shown inFIG. 7, a plurality of gear teeth55may be formed along the inner circumference of the inner race54of the pitch bearing50, with the gear teeth47being configured to mesh with corresponding gear teeth47formed on the pinion78. Thus, due to meshing of the gear teeth47,55, rotation of the pitch drive pinion43results in rotation of the inner race54relative to the outer race52via the plurality of rolling elements56,58and, thus, rotation of the rotor blade20relative to the hub18.

Referring now toFIG. 8, a close-up, cross-sectional view of a portion of the pitch bearing50shown inFIG. 7is illustrated in accordance with aspects of the present subject matter. As shown, the line contact rolling elements56,58are received within separate raceways defined between the inner and outer races52,54. Specifically, a first raceway70is defined between the inner and outer races52,54for receiving the first plurality of rolling elements56and a second raceway72is defined between the inner and outer races52,54for receiving the second plurality of rolling elements58. In such an embodiment, each raceway70,72may be defined by separate walls of the outer and inner races52,54. More specifically, as shown, each of the first and second raceways70,72may define a plurality of first and second protrusions77,79, respectively.

In addition, as shown, the line contact rolling elements56,58correspond to a first and second plurality of tapered rolling elements76,78. In such bearings, the inner and outer races52,54are segments of cones and the rolling elements56,58are tapered so that the conical surfaces of the races52,54and the rolling element axes, if projected, would meet at a common point on the main axis of the bearing50. This geometry prevents sliding motion between the rolling elements56,58within the outer and inner races52,54. For example, as shown inFIG. 8, reference lines57,59drawn through the rolling element axes are projected and converge at common point84of the pitch bearing50. In addition, the surfaces of the races and rolling elements also converge on the same point. As such, the taper angle87is designed and chosen to minimize slip of the tapered rolling elements56,58. More specifically, in certain embodiments, the taper angle87may include angles ranging from about 0.25° to about 6°.

Referring still toFIG. 8, each of the plurality of line contact rolling elements56,58defines a predetermined contact angle80,82. More specifically, a first predetermined contact angle80is defined as the angle between a reference line73extending perpendicular to a longitudinal axis57of one of the first plurality of line contact rolling elements56and a reference line75extending parallel to a horizontal plane of the pitch bearing50. Similarly, a second predetermined contact angle82is defined as the angle between a reference line74extending perpendicular to a longitudinal axis59of one of the second plurality of line contact rolling elements58and a reference line75extending parallel to a horizontal plane of the pitch bearing50. Further, the predetermined contact angles80,82may include any non-0° angles and non-90° angles. For example, in one embodiment, the predetermined contact angles80,82may include angles between 0 degrees (°) and 90°. In addition, the predetermined contact angles80,82may include angles greater than 90° angles.

It should also be appreciated that first and second contact angles80,82may be the same angle or different angles. Specifically, as the contact angle approaches zero degrees, the corresponding rolling elements may be better equipped to handle radial loads whereas, as the contact angle approaches ninety degrees, the corresponding rolling elements may be better equipped to handle axial loads. Thus, by differing the contact angles80,82, each row of rolling elements56,58may be stiffer in a given direction, such as by configuring the first plurality of rolling elements56to be axially stiffer (e.g., by selecting the first contact angle80to be closer to 90 degrees) and the second plurality of rolling elements58to be radially stiffer (e.g., by selecting the second contact angle82to be closer to 0 degrees).

Even though the bearings described herein are capable of achieving required radial, axial, and moment loading with just two rows of line contact rolling elements, it should further be understood that additional rows may also be utilized as desired. For example, as shown inFIG. 11, the pitch bearing50may further include at least one additional plurality of rolling elements65.

Referring generally toFIGS. 8-10, the pitch bearing50may also include a raceway rib68at least partially separating the first raceway70from the second raceway72. In several embodiments, the raceway rib68may form an extension of the outer race52. For instance, as shown in the cross-sectional view ofFIG. 8, the raceway rib68may correspond to a radial projection of the outer race52that extends between the line contact rolling elements56,58. Alternatively, the raceway rib68may be configured to form an extension of the inner race54. For instance, the raceway rib68may correspond to a radial projection of the inner race54configured to extend between the rolling elements56,58.

It should be appreciated that the rolling elements56,58contained within each row may be spaced apart circumferentially from one another using cages and/or spacers. For example, as shown inFIG. 10, one or more cages90may be arranged with the line contact rolling elements56,58to maintain the spacing thereof.

It should also be appreciated that the bearing configuration(s) shown inFIGS. 7-10may 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 bearing35of the wind turbine10.