WO2020025094A1

WO2020025094A1 - Pitch bearing

Info

Publication number: WO2020025094A1
Application number: PCT/DK2019/050236
Authority: WO
Inventors: Robert Rowntree; Michael William James LEWIS
Original assignee: Vestas Wind Systems A/S
Priority date: 2018-08-02
Filing date: 2019-07-29
Publication date: 2020-02-06

Abstract

A pitch bearing for a wind turbine comprises a bearing ring formed of a first annular ring (36) section comprising a first interfacing surface (48) and a second annular ring section (34) comprising a second interfacing surface (50), the annular ring sections being arranged in axial alignment with one another and the first and second interfacing surfaces being contiguous, wherein the bearing ring comprises an annular groove (54) which is provided in the first and/or second interfacing surface, a deformed component (64) arranged in the annular groove, and an annular compressor surface (56) provided in at least one of the first and second interfacing surfaces and radially aligned with the annular groove.

Description

PITCH BEARING

Technical field

The present invention relates to pitch bearings for wind turbine rotors and to a method for assembling a bearing ring of a pitch bearing formed of two or more annular ring sections.

Background

A wind turbine rotor is formed of a plurality of wind turbine blades connected to a hub. The wind turbine blades are connected to the hub via bearings which allow the blades to be rotated relative to the rotor hub, about an axis approximately perpendicular to the axis of rotation of the rotor. The bearings therefore enable adjustment of the pitch of the turbine blades. The pitch bearings are commonly formed from at least two concentric bearing rings, one ring fixedly connected to the hub and the other ring fixedly connected to a wind turbine blade. Rolling elements are typically arranged between the rings to allow relative movement between the two bearing rings.

A pitch bearing must enable rotation about its axis without permitting relative displacement between the concentric bearing rings. It is known therefore to design pitch bearings with an interlocking portion between the concentric bearing rings and rolling elements between the bearing rings to facilitate rotational movement. The interlocking portion of the pitch bearing presents new design constraints in terms of how the pitch bearing is assembled. It is known, for example from applicant’s PCT patent application W02008074322, to design one of the concentric bearing rings of the pitch bearing as two axially aligned annular ring sections that, when assembled, form one of the bearing rings.

Bolts may be used to hold the two annular bearing ring sections of the split bearing ring together. The bolts require a clearance fit through the bearing rings. In some cases for example, the bolts may have a diameter of 30 mm, whilst the corresponding through bores of the bearing ring may be 33 mm in diameter. The clearance between the bolts and corresponding bores is needed to facilitate assembly of the pitch bearing and allow for some manufacturing tolerances in the production of the ring sections.

Firstly some clearance between bolts and bores is required to allow the bolts to be fitted through the bores with ease. Secondly with large components such as pitch bearing rings where diameters may typically exceed 2 metres, manufacturing tolerances in machining the pitch bearing rings can result in rings with less than perfect cylindricity. When designing the pitch bearing there must therefore be an added tolerance allowing for the manufacturing tolerance to ensure that the components do not clash when being assembled. Due to the required clearances and tolerances between the bolts, corresponding bores and bearing rings, relative radial movement between the annular bearing ring sections of the split bearing ring of up to 1.5 mm in the present example may occur in some cases.

During extreme loading of the blade where large bending moments are applied, the annular bearing ring sections could slide radially relative to one another as a result of the aforementioned manufacturing tolerances and clearance between bores and bolts. Tight tolerances between components of the rotor bearing are required for efficient utilisation of the pitch bearing and also to limit wear. For example, seals between the concentric bearing rings may be damaged and their integrity compromised by the relative movement of one of the annular bearing ring sections.

Further, a high preload is required to safely secure the blades to the bearing and/or the bearing to the hub. Under certain design circumstances, this preload may be insufficient to prevent relative radial sliding between the two ring sections, resulting in fretting wear of the contacting surfaces of the bearing ring sections. The interface between the two bearing ring sections may be in close proximity to rolling elements of the pitch bearing. Fretting wear of the interfacing surfaces of the bearing ring sections would be particularly disadvantageous as wear debris could interfere with the rolling elements of the pitch bearing causing the pitch bearing to seize.

WO 2012/069212 discloses a double row tapered bearing assembly, wherein a first portion comprises a first ring and a second ring. By placing at least one member in a cavity formed by grooves of the first ring and the second ring a sliding of the rings in radial direction is avoided. In an embodiment, the at least one member may comprise at least one plastic deformable area.

It is against this background that the present invention has been developed in order to reduce the relative radial sliding between bearing ring sections of a pitch bearing.

Summary According to a first aspect of the invention there is provided a pitch bearing for a wind turbine. The pitch bearing comprises a bearing ring formed of a first annular ring section comprising a first interfacing surface and a second annular ring section comprising a second interfacing surface, the annular ring sections being arranged in axial alignment with one another and the first and second interfacing surfaces being contiguous. The pitch bearing is characterised in that the bearing ring comprises; an annular groove which is provided in the first and/or second interfacing surface, a deformed component arranged in the annular groove, and an annular compressor surface provided in at least one of the first and second interfacing surfaces and radially aligned with the annular groove.

The pitch bearing may further be characterised in that the deformed component has been elastically and/or plastically deformed during assembly of the pitch bearing by compression in an axial direction by the annular compressor surface, the compression having caused the deformed component to expand in a radial direction inside the groove in order to reduce radial sliding between the first and second annular ring sections.

The present invention reduces or even prevents radial sliding between the first and second annular ring section of the pitch bearing primarily in two ways. Firstly, the relative movement between the first and second annular ring sections is reduced by the inclusion of the deformed component in a groove in one of the interfacing surfaces. The deformed component is compressed during assembly of the pitch bearing and the axial compression causes the deformable component to expand in the radial direction. This radial expansion of the deformed component between the first and second annular ring sections serves to occupy any radial clearance between the ring sections. The deformed component therefore provides a physical obstruction to any relative radial movement between the first and second annular ring sections. Secondly, radial sliding is reduced by increasing the effective friction between the first and second annular ring sections due to the geometric design of the ring sections including the groove and compressor surface in combination with the deformed component.

The‘axial direction’ referenced in the present invention refers to the direction of the axis of rotation of the pitch bearing. Similarly, in the context of the present invention,‘axial alignment’ is understood to describe the alignment of two rotatable components via their axes of rotation. For example, axial alignment of the first and second annular ring sections is understood to describe the alignment of the first and second annular ring sections wherein the axes of rotation of the first and second annular ring sections are co- linear with one another. A‘radial direction’, and therefore any radial plane, referenced in the present invention relates to a direction perpendicular to the axial direction of the pitch bearing.

It is noted that, in practice, compression always happens between two opposing surfaces. Here the compression occurs between a bottom of the annular groove and the radially aligned, opposing compressor surface. In some of the exemplary designs that will be described in more detail below with reference to the drawings, turning the bearing ring upside down might interchange the function of the annular groove and the compressor surface, however, without changing the concept of the invention.

The first and second interfacing surfaces of the pitch bearing may comprise a step defining radially inner and outer portions of the first and second interfacing surfaces. The step in each of the first and second interfacing surfaces is an axial step, meaning that the inner and outer portions of the interfacing surfaces are offset in the axial direction. The axial offset between inner and outer portions may be any suitable distance to enable the object of the invention to be achieved and the invention is not limited to a specific axial offset between inner and outer interfacing surfaces. Also, more than one step may be used, dividing the interfacing surfaces up into three or more separate portions.

The annular groove of the pitch bearing may be comprised in the inner or outer portion of the interfacing surface of at least one of the first and second annular ring sections. The axial step between the inner and outer portion may also function as the groove, or as a part of the groove. For example, a wall of the annular groove may be formed by at least a part of the step. In an embodiment where the wall of the annular groove is formed by the whole step, a bottom of the annular groove is formed by part of the inner or outer portion of the first or second interfacing surface.

The annular groove of the pitch bearing has an axial depth which is less than the diameter or axial height of a deformable component arranged in the groove before the deformable component is compressed. This ensures that the deformable component is compressed by the compressor surface during assembly of the pitch bearing. The radial width of the annular groove is greater than the diameter or radial width of the deformable component before the deformable component is compressed. This is in order to allow radial expansion of the deformable component between walls of the annular groove when the deformable component is axially compressed, and to allow the deformable component to be arranged in the annular groove during assembly.

The annular compressor surface and/or a bottom of the annular groove may comprise an axially extending protruding feature. The protruding feature may comprise a tapered profile in which the radial width of the protruding feature increases as it gets closer to the opposing interfacing surface. For example, the protruding feature may comprise a substantially triangular profile. An advantage of the protruding feature is that it further increases the friction between the two interfacing surfaces. During compression of the deformable component, the protruding feature penetrates the deformable component, thereby increasing the amount of radial extension of the deformable component and the friction between the deformed component and the compressor surface after assembly. The tapered and triangular profiles may help to push the protruding feature into the deformable component and to ensure full contact between the component and the protruding feature.

The deformed component of the pitch bearing may be a continuous annulus or may comprise a plurality of separate sections. Alternatively, it may be a single component of a length close or equal to the length of the annular groove and formed into an arc to fit into the groove when assembled. With‘close to’, we mean that after assembly only a small part, preferably only a few degrees, of the full circle of the groove is not occupied by the deformed component. Installation of the single component into the groove will be easier if its length is not exactly equal to the full groove length and the effective friction between the two sections is not significantly reduced by just a small gap. The deformed component may be a solid or hollow body. Alternatively, it may be made of a flexible plate material, bent into a somewhat tubular shape. In the case where the component is a continuous annulus, this component can be used as a seal to avoid bearing lubricant to escape during gapping. In such cases the component may be made of a hard material, as described elsewhere herein, alone, as a rubber element alone or as a combination of a hard seal ring with rubber. It should be noted that gapping occurs over very small distances, i.e. within bolt stretching lengths. The bearing lubricant may be oil, or more preferably grease.

The split bearing ring of the invention described herein may be implemented as the inner ring or the outer ring of a wind turbine pitch bearing. It follows that the split bearing ring may therefore be part of the pitch bearing that is attached to the wind turbine blade, or part of the pitch bearing that is attached to the wind turbine hub.

Typically, said bearing ring includes bores provided in the first and second annular ring sections. In preferred embodiments, said deformed component, for an inner ring, is radially outside said bores, and, for an outer ring, is radially inside said bores. Hereby the deformed component will be between the bearing raceway and the bores for the bolts. This is believed to be preferred for an improved avoidance of gapping as the deformed component will be closer to the rolling elements of the bearing. Furthermore, this is very advantageous when the component also is used for a sealing effect, as the deformed component will avoid grease from the bearing from leaking into the bolting interface (grease will reduce friction in the interface, which is obviously undesired). It will also protect the bearing grease from external contamination originating from the stud holes or bolting interfaces. A seal between the stud holes to the outside cannot protect the same way.

The deformed component of the pitch bearing comprises a deformable material that is softer than the material of construction of the annular bearing rings such as annealed stainless steel, annealed nickel, annealed aluminium, annealed copper. Further, rubber may also be used.

In a second aspect of the invention there is provided a wind turbine rotor, the rotor comprising a rotor hub, at least one rotor blade and at least one pitch bearing according to the first aspect of the invention connecting the rotor hub to the rotor blade. In a further aspect of the invention there is provided a wind turbine comprising the wind turbine rotor as described above.

In another aspect of the invention there is provided a method for assembling a pitch bearing for a wind turbine. The method comprises; providing a first annular ring section comprising a first interfacing surface with an annular groove provided therein, arranging a deformable component in the annular groove, arranging a bearing ring concentrically with the first annular ring section, the bearing ring comprising an interlocking portion, and arranging rolling elements concentrically with the first annular ring section and the bearing ring. After arranging the bearing ring concentrically with the first annular ring section, the method further comprises axially aligning a second annular ring section comprising a second interfacing surface with the first annular ring section, the first and second interfacing surfaces facing one another, and in doing so also radially aligning an annular compressor surface provided in the second interfacing surface with the annular groove.

In an embodiment, the method further comprises axially compressing the annular deformable component in the annular groove by reducing the axial distance between the first and second ring sections until the first and second interfacing surfaces are contiguous, the annular compressor surface compressing the deformable component and thereby deforming the deformable component elastically and/or plastically within the groove causing the deformable component to expand in a radial direction inside the groove.

In a split bearing ring wherein each of the first and second annular ring sections comprises an axial step, it will be appreciated that a portion of the first interfacing surface will be contiguous with a portion of the second interfacing surface following compression of the deformable component. A small tolerance between the remaining portions of the first and second interfacing surfaces may be included in the design of the bearing ring to ensure that the deformable component is compressed to the required axial height and the axial compression is not impeded by a clash between interfacing surfaces before the correct axial height has been reached.

The method may further comprise arranging bolts through bores provided in the first and second annular ring sections and applying a torque on said bolts to clamp the first and second annular ring sections together.

Brief description of the drawings

The present invention will now be described in further detail by way of non-limiting examples only with reference to the following figures in which:

Figure 1 is a schematic perspective view of a wind turbine comprising a rotor with least one pitch bearing according to the present invention;

Figure 2 is a schematic perspective view of the hub of the wind turbine;

Figure 3 is a schematic cross-section of one side of a known pitch bearing; Figures 4 to 8 are schematic cross-sectional detail views of region A of a pitch bearing according to first, second, third, fourth and fifth embodiments of the present invention.

Figure 9 is a schematic cross-section of one side of a pitch bearing according to an embodiment of the present invention in an unassembled state.

Figures 10a to 10c are schematic perspective views of a deformable component according to alternative embodiments of the present invention.

Figures 11a to 11c are schematic cross-sections of the deformable component according to alternative embodiments of the present invention.

Detailed description

Figure 1 is a schematic perspective view of a modern utility-scale wind turbine 10 comprising a rotor 12 in accordance with the present invention. The wind turbine 10 comprises a tower 14 supporting a nacelle 16. The rotor 12 is mounted to the nacelle 16. The rotor 12 comprises a plurality of wind turbine blades 18, which are rotatably attached at their respective root ends 20 to a central hub 22 via a pitch bearing 24 (shown in Figure 2). In this example, the rotor 12 comprises three blades 18, but in other embodiments the rotor 12 may have any number of blades 18.

Figure 2 is a schematic perspective view of the hub 22 of the wind turbine 10 wherein the attachment of a pitch bearing 24 to the hub 22 can be seen more clearly. In this example the rotor 12 comprises three turbine blades 18 and so three pitch bearings 24 would be provided for connecting the turbine blades 18 to the rotor hub 22. The pitch bearings 24 each comprise at least an inner and an outer bearing ring 26, 28 arranged concentrically with one another (shown in more detail in Figures 3 to 8). In the example shown, the outer bearing ring 28 of each pitch bearing 24 is fixedly attached to the rotor hub 22 and the inner bearing ring 26 (not shown) is fixedly attached to the root 20 of a respective turbine blade 18. It will however be appreciated that in other embodiments the inner bearing ring 26 may be attached to the rotor hub 22 and the outer bearing ring 28 to the turbine blade 18.

Figure 3 is a schematic cross-section through one side of a known pitch bearing 24. As mentioned by way of background, the known pitch bearing 24 comprises an interlocking portion 30 extending in a radial direction rto restrict relative movement between the inner and outer rings 26, 28 of the pitch bearing 24 in an axial direction a. Rolling elements 32a, 32b are provided between the inner and outer bearing rings 26, 28 to facilitate relative rotational movement between the bearing rings 26, 28. In the example of Figure 3, the pitch bearing 24 comprises a three rolling element configuration in which three rows of rolling elements 32a, 32b are arranged around the pitch bearing 24. In this configuration, rolling elements 32a are radial rolling elements which act between radially opposite faces and rolling elements 32b are axial rolling elements which act between axially opposite faces. It will be understood that the issues described by way of background and the invention described in the following figures are equally applicable to pitch bearings 24 comprising a two rolling element configuration or a configuration of any other number of rolling elements. In the example shown, the inner bearing ring 26 is formed of first and second annular ring sections 34, 36 to enable assembly of the inner bearing ring 26 around the interlocking portion 30.

The first annular ring section 34 comprises a substantially planar first interfacing surface 38. Similarly, the second annular ring section 36 comprises a substantially planar second interfacing surface 40. In the assembled bearing ring 26, the first and second interfacing surfaces 38, 40 are contiguous.

Labelled region A is centred on an interface between the first and second annular ring sections 34, 36 of the bearing ring 26. In Figures 4 to 8 the bearing ring 26, and specifically the interface between first and second annular ring sections 34, 36, will be described with reference to detail views of the region A in a bearing ring 26 according to embodiments of the present invention. In Figures 4 to 8 the invention is described with respect to features and geometry on the outboard side 41a of the bearing ring 26, it will however also be appreciated that the invention is equally applicable to features and geometry on the inboard side 41b of the bearing ring 26. Although the invention is described throughout with reference to the inner bearing ring 26, it will be understood that the invention is equally applicable to an outer bearing ring 28 which is divided into a first and second annular ring section 34, 36. In some embodiments it is anticipated that the invention may be implemented on both an inner 26 and an outer bearing ring 28 in a single pitch bearing 24. For ease of reference, equivalent reference numerals are used to identify equivalent features across the different embodiments of the present invention in the following figures.

Figure 4 is a schematic cross-sectional detail view of region A of a pitch bearing 24 in accordance with a first embodiment of the present invention. The pitch bearing 24 comprises an inner ring 26, formed of first and second annular ring sections 34, 36, and an outer ring 28 arranged concentrically with the inner ring 26. The first and second annular ring sections 34, 36 comprise a first and second interfacing surface 38, 40 respectively.

The first and second interfacing surfaces 38, 40 each comprise a step 42, 44 in the axial direction a which defines a radially inner 46, 48 and outer portion 50, 52 of each of the first and second interfacing surfaces 38, 40 respectively. The inner and outer portions 46, 48 and 50, 52 of the first and second interfacing surfaces 38, 40 are offset in the axial direction a. For example, in this embodiment the inner portion 46 of the first interfacing surface 38 extends beyond the outer portion 50, and the outer portion 52 of the second interfacing surface 40 extends beyond the inner portion 48 in the axial direction a. In some embodiments the configuration of the inner and outer portions 46, 48 and 50, 52 may be reversed. For example in a different embodiment the outer portion 50 of the first interfacing surface 38 may extend beyond the inner portion 46, and the inner portion 48 of the second interfacing surface 40 may extend beyond the outer portion 52 in the axial direction a. The inner and outer portions 46, 50 of the first interfacing surface 38 are contiguous with at least a part of the respective inner and outer portions 48, 52 of the second interfacing surface 40 in the assembled bearing ring 26. In some embodiments a marginal clearance between one of the axially opposite inner portions 46, 48 or the axially opposite outer portions 50, 52 may be included in the design of the bearing ring 26. At least one of the axially opposite inner portions 46, 48 or the axially opposite outer portions 50, 52 are contiguous in the assembled pitch bearing 24.

The bearing ring 26 further comprises an annular groove 54. Although in this embodiment the annular groove 54 is provided in the first interfacing surface 38, it will be appreciated that the annular groove 54 may be provided in the second interfacing surface 40 or alternatively an annular groove 54 may be provided in both the first and second interfacing surfaces 38, 40.

Typically an annular groove 54 will have a profile comprising a bottom of the groove 56 and walls 58, 60 of the groove 54 extending in a direction generally perpendicular to the bottom 56. In the embodiment of the present invention depicted in Figure 4, a first wall 58 of the annular groove 54 is formed by a part of the step 44 in the second interfacing surface 40. The bottom 56 and second wall 60 of the annular groove 54 are formed in the first interfacing surface 38, more specifically in this embodiment in the inner portion 46 of the first interfacing surface 38. The bearing ring 26 comprises an annular compressor surface 62 radially aligned with the annular groove 54. In the embodiment shown in Figure 4 the compressor surface 62 is comprised in and level with the second interfacing surface 40. In other embodiments the compressor surface 62 may not be level with the second interfacing surface 40, e.g. the compressor surface 62 may be axially offset from the second interfacing surface 40. The annular compressor surface 62 is defined as being the surface directly opposite to the bottom 56 of the annular groove 54 in an axial direction a. As can be seen in Figure 4, the annular compressor surface 62 is provided in the inner portion 48 of the second interfacing surface 40, and similarly the annular groove 54 is provided in the inner portion 46 of the first interfacing surface 38.

A deformed component 64 is arranged in the annular groove 54 of the bearing ring 26. The deformed component 64 shown in Figure 4 comprises a solid cross-sectional profile though it will be understood that the deformed component 64 may take any of a number of forms, e.g. as described in further detail below with reference to Figures 10a to 11c. The deformed component 64 is axially compressed during assembly of the pitch bearing 24 by the annular compressor surface 62 resulting in elastic and/or plastic deformation of the component 64. As shown in Figures 11a to 11c, the deformed component 64 comprises a generally circular profile in an uncompressed state (i.e. before the deformation). When axially compressed, as shown in Figures 4 to 8, the component 64 expands in the radial direction r inside the groove 54 to reduce relative radial movement between the first and second annular ring sections 34, 36. Relative radial movement between the first and second annular ring sections 34, 36 as a result of manufacturing tolerances and radial clearances required in the manufacture of the bearing 24 had previously only been limited by the effective friction between the first and second interfacing surfaces 38, 40. According to the present invention, the relative radial movement is further restricted by a physical component 64 occupying any radial clearance between the first and second annular ring sections 34, 36.

Figure 5 is a schematic cross-sectional detail view of region A of a pitch bearing 24 in accordance with a second embodiment of the present invention. As described with reference to Figure 4, the bearing ring 26 comprises first and second annular ring sections 34, 36 with corresponding first and second interfacing surfaces 38, 40 which each comprise an axial step 42, 44 defining inner 46, 48 and outer portions 50, 52 of each of the first and second interfacing surfaces 38, 40. The bearing ring 26 further comprises an annular groove 54 and corresponding annular compressor surface 62. Notably in the embodiment shown in Figure 5, the annular groove 54 comprises a first wall 58 formed by the whole step 44 in the second interfacing surface 40 and a second wall 60 formed by the whole step 42 in the first interfacing surface 38. The bottom 56 of the annular groove 54 is formed by part of the outer portion 50 of the first interfacing surface 38 and in a similar manner the compressor surface 62 is formed by part of the inner portion 48 of the second interfacing surface 40. This configuration may be advantageous as the number of machining operations required to form the first and second annular ring sections 34, 36 can be reduced which may reduce overall tolerance stack and further improve alignment of the first and second annular ring sections 34, 36. A reduction in the number of machining operations required to form the ring sections 34, 36 also reduces the cost of the component. Finally by forming the walls 60, 58 of the groove 54 by the whole of each of the steps 42, 44, there are fewer surfaces and edges that could clash and so assembly of the bearing 24 is improved.

The deformed component 64 is axially compressed between the bottom 56 of the annular groove 54 and the compressor surface 62. The axial compression results in elastic and/or plastic deformation of the component 64 and causes the deformed component 64 expanding in the radial direction r between the step 42 in the first interfacing surface 38 and the step 44 in the second interfacing surface 40. In variations of this embodiment, a portion of the first interfacing surface 38 may form the compressor surface 62 and a portion of the second interfacing surface 40 may form the bottom 56 of the annular groove 54 and it will be understood that the technical effect is the same.

Figure 6 is a schematic cross-sectional detail view of region A of a pitch bearing 24 in accordance with a third embodiment of the present invention. The bearing ring 26 comprises first and second annular ring sections 34, 36 with corresponding first and second interfacing surfaces 38, 40. The first interfacing surface 38 comprises an annular groove 54 and the second interfacing surface 40 comprises an annular compressor surface 62 radially aligned with the annular groove 54. In the present embodiment, the first and second walls 58, 60 of the annular groove 54 and similarly the bottom 56 of the annular groove 54 are all formed in the first interfacing surface 38.

In the embodiment shown in Figure 6, an axially extending protruding feature 66 is comprised in the annular compressor surface 62. The axially extending protruding feature 66 serves to elastically and/or plastically deform the component 64 arranged in the annular groove 54. As can be seen in Figure 6, the protruding feature 66 extends axially from the second interfacing surface 40 and comprises a tapered profile. The tapering is such that a radial width W of the protruding feature 66 decreases as the axial distance to the bottom of the annular groove 54 increases. In the present embodiment, the protruding feature 66 comprises a substantially triangular profile, however it is anticipated that other shaped profiles are also suitable for achieving the object of deforming a component 64 in the groove 54. For example, the protruding feature 66 may alternatively comprise a substantially semi-circular or square profile.

The axially extending protruding feature 66 in combination with the deformed component 64 in the annular groove 54, serves to increase the effective friction between the first and second interfacing surfaces 38, 40 of the first and second annular bearing ring sections 34, 36 respectively. In a similar manner to the above described embodiments of Figures 4 and 5, the deformed component 64 arranged in the annular groove 54 may take any of a number of suitable forms, e.g. as described below with reference to Figures 10a to 11c.

Figure 7 is a schematic cross-sectional detail view of region A of a pitch bearing 24 in accordance with a fourth embodiment of the present invention. Some of the features of the embodiments described in Figures 4 and 6 have been combined for the fourth embodiment. As in the previously described embodiments, the pitch bearing 24 comprises an inner ring 26, formed of first and second annular ring sections 34, 36, and an outer ring 28 arranged concentrically with the inner ring 26. The first and second annular ring sections 34, 36 comprise a first and second interfacing surface 38, 40 respectively.

The first and second interfacing surfaces 38, 40 each comprise a step 42, 44 in the axial direction a defining a radially inner 46, 48 and outer portion 50, 52 of each of the first and second interfacing surfaces 38, 40 wherein the inner and outer portions 46, 48 and 50, 52 are offset in the axial direction a. The inner and outer portions 46, 50 of the first interfacing surface 38 are contiguous with at least a part of the respective inner and outer portions 48, 52 of the second interfacing surface 40 in the assembled bearing ring 26.

The bearing ring 26 further comprises an annular groove 54. In the embodiment depicted in Figure 7, a first wall 58 of the annular groove 54 is formed by a part of the step 44 in the second interfacing surface 40. The bottom 56 and second wall 60 of the annular groove 54 are formed in the first interfacing surface 38, more specifically in this embodiment in the inner portion 46 of the first interfacing surface 38.

The bearing ring 26 comprises an annular compressor surface 62 radially aligned with the annular groove 54. In the embodiment shown in Figure 7 the compressor surface 62 is comprised in the second interfacing surface 40, due to the annular groove 54 being provided in the first interfacing surface 38. An axially extending protruding feature 66, as described with reference to Figure 6, is comprised in the annular compressor surface 62. The protruding feature 66 extends from the second interfacing surface 40 and comprises a tapered profile. As the protruding feature 66 extends axially further from the second interfacing surface 40 into the annular groove 54, the radial width W of the protruding feature 66 decreases forming a tapered profile. In the present embodiment the protruding feature 66 comprises a substantially triangular profile however it is anticipated that other shaped profiles are also suitable for achieving the object of deforming a component 64 in the groove 54. For example the protruding feature 66 may alternatively comprise a substantially semi-circular or square profile.

A deformed component 64 is arranged in the annular groove 54 of the bearing ring 26. The deformed component 64 comprises a solid cross-sectional profile though it will be understood that the deformed component 64 may take any of a number of forms as described in further detail below with reference to Figures 10a to 11c. The deformed component 64 is axially compressed and elastically and/or plastically deformed during assembly of the pitch bearing 24 by the annular compressor surface 62 and protruding feature 66.

The axial compression results in the radial expansion of the deformed component 64 in the annular groove 54 between the first and second walls 58, 60 of the groove 54. As the first wall 58 is formed by part of the step 44 in the second annular bearing ring section 36 and the second wall 60 is formed in the first interfacing surface 38, the radial expansion of the deformed component 64 in the annular groove 54 thereby occupies any radial clearance or tolerance between the first and second annular bearing ring sections 34, 36.

Figure 8 is a schematic cross-sectional detail view of region A of a pitch bearing 24 in accordance with a fifth embodiment of the present invention. In a similar manner to the embodiment described with reference to Figure 7, the embodiment described in Figure 8 comprises features from the previously described embodiments of Figures 5 and 6.

The bearing ring in Figure 8 comprises first and second annular ring sections 34, 36 with corresponding first and second interfacing surfaces 38, 40 which each comprise an axial step 42, 44 defining inner and outer portions 46, 48 and 50, 52 of each of the first and second interfacing surfaces 38, 40. The bearing ring 26 further comprises an annular groove 54 and corresponding annular compressor surface 62 and axially protruding feature 66 arranged in radial alignment therewith.

As with the embodiment of Figure 5, in the embodiment of Figure 8 the annular groove 54 comprises a first wall 58 formed by the whole step 44 in the second interfacing surface 40 and a second wall 60 formed by the whole step 42 in the first interfacing surface 38. The bottom 56 of the annular groove 54 is formed by part of the outer portion 50 of the first interfacing surface 38 and in a similar manner the compressor surface 62 is formed by part of the inner portion 48 of the second interfacing surface 40.

An axially extending protruding feature 66, as described with reference to Figure 6, is comprised in the annular compressor surface 62. The protruding feature 66 extends from the second interfacing surface 40 and comprises a tapered profile. As the protruding feature 66 extends axially further into the annular groove 54 from the second interfacing surface 40, the radial width W of the protruding feature 66 decreases creating a tapered profile. In the present embodiment the protruding feature 66 comprises a substantially triangular profile.

The deformed component 64 is axially compressed between the bottom 56 of the annular groove 54 and the axially extending protruding feature 66 at the compressor surface 62. The axial compression results in the deformed component 64 expanding in the radial direction r between the step 42 in the first interfacing surface 38 and the step 44 in the second interfacing surface 40.

A method for assembling a pitch bearing 24 for a wind turbine 10 according to the present invention will now be described with reference to Figure 9. For the purpose of illustration the assembly method will be described in relation to the bearing ring 26 of the embodiment depicted in Figure 4. It will be understood that the assembly method is applicable to all previously described embodiments of the invention and that other assembly methods will be available for producing the same. Similarly, a three rolling element bearing is described in this method but it will be appreciated that the method is applicable for pitch bearings comprising other rolling element configurations also.

In the first stage of the assembly method, a first annular ring section 34 as described in reference to any of Figures 4 to 8 is provided. The first annular ring section 34 comprises at least a first interfacing surface 38 and an annular groove 54 formed in the first interfacing surface 38. A deformable component 64 is then arranged in the annular groove 54. The deformable component 64 will be described in more detail hereafter with reference to Figures 10a to 11c.

An outer bearing ring 28 is then arranged concentrically with the first annular ring section 34, the interlocking portion 30 overlapping a portion of the first annular ring section 34 in the radial direction r.

A first set of axial rolling elements 32b are then arranged between the first annular ring section 34 and the bearing ring 28, axially aligned with the first annular ring section 34. Radial rolling elements 32a may be arranged concentrically with the outer bearing ring 28 around the interlocking portion 30 to enable to relative rotation of the inner and outer bearing rings 26, 28 after assembly.

After arranging the bearing ring 28 concentrically with the first annular ring section 34, a second annular ring section 36 is axially aligned with the first annular ring section 34. Further axial rolling elements 32b are arranged between the second annular bearing ring section 36 and the bearing ring 28 and axially aligned with the second annular ring section 36. The second annular ring section 36 comprises at least a second interfacing surface 40 and an annular compressor surface 62. The second annular ring section 36 is the corresponding second annular ring section 36 to the first annular ring section 34 of any one of the embodiments described in Figures 4 to 8. The second annular ring section 36 is arranged with the second interfacing surface 40 facing the first interfacing surface 38 of the first annular ring section 34. Through the axial alignment of the first and second annular ring sections 34, 36, the annular compressor surface 62 of the second ring section 36 is radially aligned with the annular groove 54 in the first interfacing surface 38.

In a further stage of the assembly method, the deformable component 64 arranged in the annular groove 54 is compressed by reducing the axial distance Y between the first and second ring sections 34, 36 until the first and second interfacing surfaces 38, 40 are contiguous. The annular compressor surface 62 compresses the deformable component 64 and thereby deforms the deformable component 64 elastically and/or plastically within the annular groove 54. The deformable component 64 is thereby caused to expand in a radial direction r inside the groove 54.

The method may further comprise arranging bolts (not shown) through bores 68 provided in the first and second annular ring sections 34, 36 respectively. The bolts may be arranged in the bores 68 after the first and second annular ring sections 34, 36 have been arranged together with the deformable component 64 in the groove 54. A torque may then be applied on the bolts to clamp the first and second annular ring sections 34, 36 together. The bolts may aid in distributing a uniform load around the pitch bearing 24 to ensure that the deformable component is uniformly compressed and that the first and second interfacing surfaces are contiguous around the entire bearing ring 26. The bolts may further ensure that the various components of the bearing 24 remain assembled through transport and assembly of the wind turbine 10.

It will be appreciated that the stages of the described assembly method need not be carried out in the specific order described above and the invention is not limited to the specific order of assembly stages above. For example, rolling elements 32a, 32b may be arranged in the bearing 24 after the first and second annular ring sections 34, 36 have been arranged with the bearing ring 28.

The deformed component 64 referenced throughout the above description will now be described in reference to Figures 10a to 11c. Figures 10a to 10c depict the general form of different possible embodiments a deformable component 64, whereas Figures 11a to 11c illustrate possible cross-sectional profiles applicable to the configurations of the deformable component 64 of Figures 10a to 10c.

Figure 10a is a schematic perspective view of a deformable component 64 suitable for use in a bearing ring 26 according to the invention. The deformable component 64 shown in Figure 10a is a single continuous annulus of a deformable material. The deformable component 64 may have a cross-sectional profile according to any one of Figures 11 a to 11 c for example.

The deformable component 64 shown in Figure 10b is similar to that shown in Figure 10a, however instead of being formed of a single component, the deformable component 64 comprises a plurality of separate sections 70 arranged to form a circular configuration. This may have benefits in terms of ease of manufacture of the deformable component 64 and/or ease of assembly of the bearing ring 26. Dividing the deformable component 64 into sections 70 may further be advantageous in packaging and transporting the component 64 which may in its assembled state have a diameter greater than 2 metres.

It should be noted that spaces 72 between the sections 70 of the deformable component 64 are exaggerated in Figure 10b and in practice it would be expected that only a small number of degrees around the circular configuration are not occupied by the deformable component 64. The invention of this embodiment is not limited however to a specified spacing between the individual sections 70 of the deformable component 64, merely to the concept of dividing the deformable component 64 into a plurality of sections 70. The plurality of sections 70 of the deformable component 64 may comprise a cross-sectional profile according to any one of Figures 11a to 11c for example.

Figure 10c shows a further possible configuration of the deformable component 64. The deformable component 64 in Figure 10c is a single component of a length close to or equal to the length of the annular groove 54 of the bearing ring 26 into which it is designed to fit. The deformable component 64 may be formed into an arc before assembly of the bearing ring 26 or may alternatively be a substantially straight component which is formed into an arc upon being arranged in the annular groove 54. Similar to the deformable component 64 of Figure 10b, this embodiment may present advantages in terms of ease and cost of manufacture, and/or in terms of ease of assembly of the bearing ring 26. The deformable component 64 may comprise a cross- sectional profile according to any one of Figures 11 a to 11 c for example.

As previously discussed, Figures 11a to 11c illustrate a number of possible cross-sectional profiles for the deformable component 64 described in Figures 10a to 10c. The diameters D of each of the cross-sectional profiles in Figures 11a to 11c are sufficiently similar to the radial distance between the first and second walls 58, 60 of the annular groove 54 enabling the deformable component 64 to therefore fit into the annular groove 54 when assembled. Whilst the cross-sectional profiles described with reference to Figures 11a to 11c are substantially circular or round, it will be appreciated that other cross-sectional profile shapes such as substantially quadrilateral or trapezoidal profiles may be equally applicable to fulfil the purpose of the deformable component 64.

The first cross-sectional profile, shown in Figure 11a, is a cross-section of a solid deformable component 64 wherein the material is consistent throughout the profile. In an embodiment of the invention wherein the deformable component 64 comprises a solid cross section, it is important for the deformable component 64 to be formed of a softer material than the first and second annular ring sections 34, 36 to allow the groove 54 and compressor surface 62 to deform the component 64. The deformable component may be formed of annealed stainless steel, annealed nickel, annealed aluminium, annealed copper or other soft material that is compatible with the materials of construction.

The selection of a solid or hollow profile depends upon the relative hardness of the material of construction of the annular ring sections 34, 36 and the deformable component 64 in addition to the required radial resistive force to reduce or prevent sliding. This would be achieved by stress analysis or physical testing.

Figure 11b illustrates a second cross-sectional profile of a deformable component 64 in which the deformable component 64 is hollow. The central region 74 of the cross- sectional profile is unfilled and a deformable material is formed into a tubular profile. Profiles shown in Figures 11a and 11 b may be manufactured from continuously formed wire or drawn tubing.

The cross-sectional profile in Figure 11c shows a deformable component 64 formed of a flexible plate material. The flexible plate material is bent into a somewhat tubular shape and formed into any one of the deformable component configurations 64 described with reference to Figures 10a to 10c.

In some embodiments, the deformable component may comprise a different cross- sectional profile in different areas of the deformable component. For example, the deformable component 64 shown in Figure 10b may comprise some sections 70 with a solid cross sectional profile such as shown in Figure 11a, and some sections 70 with a hollow cross-sectional profile such as is shown in Figure 11 b. It will be appreciated that any number of combinations of cross-sectional profiles in a deformable component 64 are possible and the invention is not limited to a deformable component 64 with a single constant cross-sectional profile throughout. Equally, the invention is not limited to a deformable component 64 formed of a single homogenous material, and may comprise areas formed of different materials. The deformable component 64 of Figure 10b for example may comprise sections 70 formed in different materials.

Claims

1. A pitch bearing (24) for a wind turbine (10) comprising a bearing ring (26) formed of a first annular ring section (34) comprising a first interfacing surface (38) and a second annular ring section (36) comprising a second interfacing surface (40), the annular ring sections (34, 36) being arranged in axial alignment with one another and the first and second interfacing surfaces (38, 40) being contiguous, the pitch bearing (24) being characterised in that the bearing ring (26) comprises:

an annular groove (54) which is provided in the first and/or second interfacing surface (38, 40),

a deformed component (64), arranged in the annular groove (54), and

an annular compressor surface (62) provided in at least one of the first and second interfacing surfaces (38, 40), the annular compressor surface (62) being radially aligned with the annular groove (54).

2. The pitch bearing (24) of claim 1 wherein the deformed component (64) has been elastically and/or plastically deformed during assembly of the pitch bearing (24) by compression in an axial direction (a) by the annular compressor surface (62), the compression having caused the deformed component (64) to expand in a radial direction (r) inside the groove (54) in order to reduce radial sliding between the first and second annular ring sections (34, 36).

3. The pitch bearing (24) of claim 1 or 2 wherein the pitch bearing 24 comprises a three rolling element configuration in which three rows of rolling elements (32a, 32b) are arranged around the pitch bearing 24.

4. The pitch bearing (24) of any one of claims 1 to 3 wherein at least one row of rolling elements (32a) comprises radial rolling elements which act between radially opposite faces and at least one row of rolling elements (32b) comprises axial rolling elements which act between axially opposite faces.

5. The pitch bearing (24) of any one of the preceding claims wherein the deformed component (64) is a continuous annulus.

6. The pitch bearing (24) of any one of the preceding claims wherein said deformed component (64) provides a sealing effect for bearing lubricant.

7. The pitch bearing (24) of any one of the preceding claims wherein said bearing lubricant is grease.

8. The pitch bearing (24) of any one of the preceding claims wherein said bearing ring (26) is an inner or outer bearing ring (26, 28) of said pitch bearing (24), and wherein said bearing ring (26) includes bores (68) provided in the first and second annular ring sections (34, 36).

9. The pitch bearing (24) of any one of the preceding claims wherein said deformed component, for an inner ring, is radially outside said bores, and, for an outer ring, is radially inside said bores.

10. The pitch bearing (24) of any one of claims 1-4 wherein the deformed component (64) comprises a plurality of separate sections.

11. The pitch bearing (24) of any one of the preceding claims wherein the first and second interfacing surfaces (38, 40) comprise a step (42, 44) defining radially inner (46, 48) and outer portions (50, 52) of the first and second interfacing surfaces (38, 40), the inner (46, 48) and outer portions (50, 52) of the interfacing surfaces (38, 40) being offset in the axial direction (a).

12. The pitch bearing (24) of claim 11 wherein a wall (58) of the annular groove (54) is formed by at least a part of the step (44).

13. The pitch bearing (24) of claim 12 wherein the wall (58) of the annular groove (54) is formed by the whole step (44) and a bottom (56) of the annular groove (54) is formed by part of the inner (46, 48) or outer portion (50, 52) of the first or second interfacing surface (38, 40).

14. The pitch bearing (24) of any one of the preceding claims wherein the annular compressor surface (62) comprises an axially extending protruding feature (66).

15. The pitch bearing (24) of claim 14 wherein the protruding feature (66) comprises a tapered profile in which a radial width (W) of the protruding feature (66) decreases as the axial distance ( X) to the opposing interfacing surface decreases.

16. The pitch bearing (24) of claim 15 wherein the protruding feature (66) comprises a substantially triangular profile.

17. The pitch bearing (24) of any one of claims 1 to 9 wherein the deformed component (64) is a single component of a length close or equal to the length of the annular groove (54) and formed into an arc to fit into the groove (54) when assembled.

18. The pitch bearing (24) of any one of the preceding claims wherein the deformed component (64) comprises a hollow cross-sectional profile or a solid cross-sectional profile.

19. The pitch bearing (24) of any one of the preceding claims wherein the deformed component (64) comprises a deformable material such as annealed stainless steel, annealed nickel, annealed aluminium, or annealed copper.

20. The pitch bearing (24) of any one of the preceding claims wherein the deformed component (64) comprises rubber.

21. A wind turbine rotor (12), the rotor (12) comprising a rotor hub (22), at least one rotor blade (18) and at least one pitch bearing (24) according to any one of the preceding claims, the pitch bearing (24) connecting the rotor hub (22) to the rotor blade (18).

22. A wind turbine (10) comprising the wind turbine rotor (12) of claim 21.

23. A method for assembling a pitch bearing (24) for a wind turbine (10), the method comprising;

providing a first annular ring section (34) comprising a first interfacing surface (38) with an annular groove (54) provided therein,

arranging a deformable component (64) in the annular groove (54),

arranging a bearing ring (28) concentrically with the first annular ring section (34), the bearing ring (28) comprising an interlocking portion (30), arranging rolling elements (32a, 32b) concentrically with the first annular ring section (34) and the bearing ring (28),

after arranging the bearing ring (28) concentrically with the first annular ring section (34), axially aligning a second annular ring section (36) comprising a second interfacing surface (40) with the first annular ring section (34) the first and second interfacing surfaces (38, 40) facing one another, and in doing so also radially aligning an annular compressor surface (62) provided in the second interfacing surface (40) with the annular groove (54).

24. The method of claim 23 further comprising the step of axially compressing the annular deformable component (64) in the annular groove (54) by reducing the axial distance ( Y) between the first and second ring sections (34, 36) until the first and second interfacing surfaces (38, 40) are contiguous, the annular compressor surface (62) compressing the deformable component (64) and thereby deforming the deformable component (64) elastically and/or plastically within the groove (54) causing the deformable component (64) to expand in a radial direction (r) inside the groove (54).

25. The method of claim 23 or 24 further comprising arranging bolts through bores (68) provided in the first and second annular ring sections (34, 36) and applying a torque on said bolts to clamp the first and second annular ring sections (34, 36) together.