BEARING FOR WIND TURBINE

Abstract

A bearing assembly (12) for a rotating element (13) has one race (15) adapted to be fixed relative to ground (11) and to selectively be free for arcuate movement relative to ground. In a preferred embodiment a selective locking device (18) is provided for the relatively fixed/movable race (15).

Claims

1. A bearing assembly for rotatably supporting a rotating element relative to ground and comprising: a race adapted to be fixed relative to ground and adapted to be freed relative to ground in arcuate movement; a mechanism adapted to selectively free the race which is fixed relative to ground for arcuate movement relative to ground; and an actuator adapted to move the race which is freed relative to ground arcuately.

2. A bearing assembly according to claim 1, wherein the race comprises an inner race, and an outer race concentric with the inner race, one of the inner race or outer race being adapted for fixing against rotation on a ground element.

3. A bearing assembly according to claim 2, further including a locking device adapted to engage one of the inner race or the outer race on demand.

4. A bearing assembly according to claim 3, wherein the locking device is adapted to engage a peripheral surface of one of the inner and outer races.

5. A bearing assembly according to claim 4, wherein the locking device is adapted to engage a circumferential surface of one of the inner and outer races.

6. A bearing assembly according to claim 5, wherein the ground is a shaft and the locking device is an axially movable wedge.

7. A bearing assembly according to claim 1, wherein the actuator comprises a cam ring rotatable about a rotational axis of the bearing assembly.

8. A bearing assembly according to claim 1, wherein the bearing assembly is confined within a tubular envelope defined by an outer diameter of the outer race and an inner diameter of the inner race.

9. A bearing assembly, comprising: an inner race and an outer race, at least one of the inner race and outer race being selectively rotatable or locked against rotation relative to each other or a ground; a locking device to selectively rotationally lock or unlock at least one of the inner race and outer race relative to each other or ground; and an actuator to rotate an unlocked race.

10. A bearing assembly according to claim 9, wherein the inner and outer races are concentric.

11. A bearing assembly according to claim 10, wherein the locking device is adapted to engage one of the races on demand.

12. A bearing assembly according to claim 11, wherein the locking device is adapted to engage a peripheral surface of one of the races.

13. A bearing assembly according to claim 12, wherein the locking device is adapted to engage a circumferential surface of one of the races.

14. A bearing assembly according to claim 13, wherein the locking device is an axially movable wedge.

15. A bearing assembly according to claim 9, wherein the actuator comprises a cam ring rotatable about a rotational axis of the bearing assembly.

16. A bearing assembly according to claim 9, wherein the assembly is confined within a tubular envelope defined by an outer diameter of the outer race and an inner diameter of the inner race.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0045] Other features of the invention will be apparent from the following description of several preferred embodiments shown by way of example only in the accompanying 25 drawings in which:

[0046] FIG. 1 is a schematic axial section through a first embodiment of the invention.

[0047] FIG. 2 is an enlarged view of the circled part of FIG. 1.

[0048] FIG. 3 is a schematic axial section through a second embodiment of the invention.

[0049] FIG. 4 is a schematic axial section through a third embodiment of the invention.

[0050] FIG. 5 is a perspective view of a bearing assembly according to a fourth embodiment of the invention.

[0051] FIG. 6 is a schematic axial section through the embodiment of FIG. 5.

[0052] FIG. 7 is an enlarged view of the indexing mechanism of FIG. 6.

[0053] FIG. 8 is a schematic illustration of the operation of the fourth embodiment.

[0054] FIG. 9 is an exploded view of the components of the fourth embodiment, and

[0055] FIG. 10 is a schematic arrangement of a control system suitable for the invention.

DESCRIPTION-OF PREFERRED EMBODIMENTS

[0056] With reference to FIGS. 1 and 2 a stationary circular hub 11 has thereon a rolling element bearing 12 to support a rotating member 13, which may for example be a rotor of a wind turbine.

[0057] The rolling element bearing comprises an outer race 14 pressed into the rotating member 13, an inner race 15, and a circular array of rollers 16 between the races.

[0058] In order to allow easy fitting and removal of the bearing 12 to the hub 11, the inner race has a frusto-conical radially inner surface 17 adapted to receive a corresponding annular fitting member 18 with a frusto-conical radially outer surface 19. This arrangement permits the rolling element bearing to be placed over the hub, and locked in place by pressing in the fitting member 18 in the direction of arrow A. By suitable selection of the taper angle, in a well-known manner, the fitting member will fix the bearing in place relative to the hub, yet be removable on application of a release load opposite to the direction of arrow A. The fitting member may be self locking, or may be retained by any suitable means, such as a circlip.

[0059] Thus it will be understood that in the locked condition of the fitting member 18, the inner race 15 may be subjected over time to potentially damaging forces on the load bearing upper face, whereas in the unlocked condition of the fitting member, the inner race is free to be moved arcuately so as to change the load bearing portion thereof.

[0060] Only slight relative movement between the inner race and the fitting member is required to achieve freedom of movement of the inner race, and it is possible for either the fitting element or the inner race to be fixed axially relative to the hub.

[0061] As shown in greater detail in FIG. 2, a circular outer housing 21 is fixed relative to the inner race 15. The outer housing may be split on a diameter and for example mounted to a suitable surface of the inner race by a circular shoulder 22 and circumferential clamp (not shown).

[0062] A Belleville spring washer 23 acts between radially inwardly directed abutment 24 of the outer housing 21, so as to bias the fitting member to a condition in which the inner race 15 is fixed or parked relative to the hub 11.

[0063] A circular inner housing 25 may be press-fitted to the fitting member 18 and has radially outwardly extending portions which co-operate with corresponding portions of the outer housing 21 to define a hydraulic piston chamber 26. Suitable annular sliding seals 27, 28 close the chamber 26. The housing may alternatively be screw-threaded to the fitting member, as illustrated.

[0064] In use hydraulic oil under pressure can be admitted into the chamber 26 to cause the inner housing 25 to be urged to the right (as viewed) relative to the outer housing 21. As a result the fitting member 18 moves to the unlocked condition whereby the inner race 15 is able to move circumferentially.

[0065] In order to promote movement of the fitting member 18, and to facilitate arcuate movement of the inner race 15, hydraulic oil under pressure may also be admitted to the space between surfaces 17 and 19 to form a hydrostatic bearing. Suitable sliding seals may be provided to confine this oil, of which one is shown at 29.

[0066] The hydraulic oil is preferably the same as that used for lubrication of the rolling element bearing.

[0067] A second embodiment is illustrated in FIG. 3, in which parts common to the first embodiment carry the same reference numerals.

[0068] A hydraulic oil feed 31 has passages through shaft 11 to feed both the frusto-conical space 32 between the inner race 15 and the fitting member 18, and the piston chamber 26. The space 32 is open to the chamber 33 housing the Belleville spring 23, but is closed at the opposite end by seal 34. The spring chamber 33 has a vent 35.

[0069] An annular piston 36 is keyed to the fitting member 18 against relative rotation, but can slide axially of the shaft. In the unenergized condition, the piston chamber 26 is unpressurized and the Belleville spring 23 urges the fitting member to the left (as viewed) into locking engagement. The piston 36 is urged to the right by the spring 23 until abutting against an inturned lip 37 of the outer housing 21. This lip 37 also prevents the inner race 15 from sliding off the fitting member to the left as viewed.

[0070] Clearances are somewhat exaggerated in FIG. 3 to demonstrate the principle of operation, but in the engaged condition the inner race 15 is parked against arcuate movement with respect to the shaft 11, the centreline 20 of which is also illustrated.

[0071] Upon pressurization of the oil feed 31, the piston 36 moves to the left away from abutment with the lip 37 (as illustrated) and the fitting member 18 is free to float relatively to the right so as to unlock the inner race 15.

[0072] In FIG. 3, the piston chamber is defined by an annular housing 38 which is held in place by a locking ring 39, but is free to float on an annular extension 40 of the fitting member when unpressurized. Numerous hydraulic seals confine the hydraulic fluid, as will be readily understood. The vent 35 permits fluid pressure to drain from the assembly, and is of a size selected to maintain sufficient operational pressure in the chamber 26 when required.

[0073] Alternatively a suitable restrictor may be placed in the fluid supply line to the space 32.

[0074] A third embodiment is illustrated in FIG. 4 and comprises a two-part fitting member comprising a sleeve 41 fixed to the shaft 11 and having an annular frusto-concial ramp face 42 at one end, and an axially movable annular frusto-conical wedge 43 at the other end.

[0075] The ramp face 42 and wedge 43 confine an inner race 15A which has matching frusto-concial faces on the radially inner side, and can move relatively axially together to lock the inner race 15A to the sleeve 41, thereby to prevent relative rotation of the inner race relative to the shaft 11.

[0076] In the embodiment of FIG. 4, an arcuate cam 44 is located about the sleeve 41 and is movable circumferentially to load or unload the wedge 43, as will be further explained. An abutment 45 is provided for the cam 44, and is retained by a nut 46 or the like. A retainer 47 for the Belleville spring 23 is keyed to the sleeve 41, and suitable rollers 48 are provided between the relatively movable elements, as illustrated. Three or more equispaced cams may be provided to evenly distribute the axial load on the wedge.

[0077] The embodiment of FIG. 4 has the advantage that the inner race is located axially of the shaft 11, and is not subject to axial loads from the fitting member. In FIG. 4 such axial loads are resisted by the ramp face 32, and thus not transmitted to the outer race 14 as in the embodiment of FIG. 3. Furthermore, the inner race is maintained centrally when unparked.

[0078] FIGS. 5-8 illustrate a fourth embodiment incorporating a mechanical release for the fitting member. As with other embodiments common reference numerals are used for parts having the same function. This embodiment provides a self-contained bearing assembly adapted for fitting to a suitable hub, and in which the actuation mechanism is at one side and within the annulus defined by the hub 11 and the external diameter of the outer race 14.

[0079] The fitting member 18 is coupled against rotation with respect to the hub 11 by a key 51.

[0080] A first hydraulic actuator 52 is connected to a pawl 53 which engages external teeth of a cam ring 54. One stroke of the first actuator indexes the cam ring by one tooth in the direction of arrow B. The actuator is responsive to pressurization from a suitable hydraulic source and control system. Removal of pressure causes the pawl to be withdrawn by a light spring. A leaf spring biases the pawl into engagement with the cam ring as it advances from the retracted condition.

[0081] An anti-reversing lever 55 is pivoted against the centre and has a tooth 56 at one end which is engageable with the teeth of the cam ring 54. A light coil spring 57 pivots the tooth 56 out of engagement, and is opposed by a second hydraulic actuator 58 which can be pressurized to apply a load via a spring (see FIG. 7), so as to place the tooth 56 into engagement with the cam ring. The teeth of the cam ring 54 are ratchet teeth, and pass over tooth 56 in the direction of arrow B when the tooth is biased inwards by the second actuator 58.

[0082] In use, pressurization of first actuator 52 and second actuator 58 causes the cam ring to be advanced in the direction of arrow B, and to be retained in the advanced condition by the tooth 56 ratcheting over an adjacent tooth of the cam ring.

[0083] Upon release of pressure in the first actuator 52, the cam ring 54 remains in the advanced condition. A further pressurization of the first actuator causes the cam ring to advance another step, and so on. Pressurization may be by way of a square wave electrical signal.

[0084] Thus so long as the second actuator 58 remains pressurized, the cam ring 54 can be advanced by successive pressure pulses to the first actuator 52.

[0085] As best seen in FIG. 7, a Belleville spring 23 acts between the fitting member 18 and a backing ring 59, which itself abuts a lip 37 of an outer housing 21 of the inner race 15. Thus as illustrated in FIG. 7, the spring 23 forces the fitting member into engagement with the inner race, which is consequently locked against rotation relative to the shaft 11.

[0086] The cam ring 54 includes one or more cam surfaces adapted to urge the backing ring 59 to the left as viewed. Upon being urged to the left, the backing ring lifts off the lip 37, and the fitting member 18 is free to float to the right, thereby unlocking the inner race 15, and permitting arcuate movement relative to the hub. Consequently it will be understood that successive pressure pulses to the first actuator 52 can rotate the cam ring 54 through angle C (FIG. 8) which is sufficient to release the fitting member and hence the inner race.

[0087] FIG. 7 also illustrates an annular travel stop 61 to prevent excessive movement of the fitting member with respect to the inner race. Oil from the hydrostatic bearing formed between the fitting member and inner race is held back by this travel stop when the inner race is released.

[0088] The fourth embodiment also provides a means of moving the inner race arcuately, when unlocked.

[0089] The number of teeth on the cam ring 54 is limited, and the last tooth is followed by a relatively long ramp face 62 beyond which no recess for the tooth 56 is provided. Consequently when the first actuator has made sufficient strokes for the cam ring 54 to present the last ratchet tooth to the lever 55, further strokes merely allow the cam ring to oscillate back and forth through angle D (FIG. 8).

[0090] However, an adjacent annulus 63 of the cam ring has a radial abutment 64 which is arranged to come into contact with a radial abutment of a nudge ring 65, so that oscillation of the cam ring 54 causes oscillation of the nudge ring 65 against the effect of a light return spring 66.

[0091] The nudge ring 65 is mounted via a conventional one-way clutch, or sprag 65a to an annulus of the inner race 15, such that oscillation of the nudge ring results in repeated one-way indexing of the inner race. In this way the inner race may be repositioned relative to the hub, so as to place a different sector in the position where vertical loads are reacted; successive nudges are indicated at E (FIG. 8).

[0092] The inner race 14 is mounted via a second one-way clutch 70 grounded on the hub, so as not to reverse back to the position prior to nudging.

[0093] A collar 67 and nut 68 retain the components to the fitting member 18. The collar 67 is keyed to the fitting member as illustrated.

[0094] FIG. 9 is an exploded view of the components of the assembly of FIGS. 5-8.

[0095] The fitting member 18 includes rectangular recesses 71 on the frusta-conical surface thereof, which comprise hydrostatic bearing pads adapted to assist in disengaging the fitting member from the inner race.

[0096] These pads are supplied with hydraulic oil under pressure, as described in relation to the first embodiment.

[0097] In order to permit detection of the number of strokes of the first actuator, and hence the position of the cam ring 54 and inner race 15, a series of axially extending projections 72 of the cam ring may be adapted to ring a bell 73 by simple contact therewith. For example such projections may have the same pitch as the ratchet teeth. The ring may be different according to the position of the cam ring, for example by using a projection of different profile. Ringing of the bell may be detected by suitable accelerometers or the like and provide an input to a control system which is now described with reference to FIG. 10.

[0098] A gearbox 80 for the driveline or gearbox of a wind turbine contains a rotor bearing 81 of the kind described by reference to FIGS. 1-9. Hydraulic oil within the gearbox is circulated to an actuator for a fitting member of the bearing via a pump 82 and valve 83.

[0099] The bearing 81 incorporates a tum function 84 for the inner race, and a release/hold function 85. The hydraulic signal to the release/hold function is via an accumulator 86 having a restricted vent 87.

[0100] In use the valve 83 is opened repeatedly to feed the functions 84 and 85. The fitting member is released, and the inner race turned in the manner described with reference to FIGS. 5-7. The accumulator 86 ensures that pressure is maintained in the second actuator so as to avoid reversing of the cam ring 54.

[0101] Upon final closure of the valve 83, for example when the inner race is in a new position, the hydraulic pressure drains via vent 87 so that the cam ring returns to the start condition whereby the fitting member is re-engaged.

[0102] It will be understood that in the event of a failure of the pump 82 or loss of hydraulic pressure due to a leak or the like, the fitting member will mechanically re-engage under the action of the Belleville spring.

[0103] A percussive signal generator 88, such as a bell, emits a characteristic representative of a specific angular rotation of the cam ring, and this signal is detected by a suitable sensor 89.

[0104] A bearing control unit 90 includes modules for actuation strategy 91, bearing condition calculation 92, and bearing position calculation 93.

[0105] A wind turbine control unit 95 may include a module for bearing condition calculation 96 in place of module 92.

[0106] In use the wind turbine control unit 95 receives typical inputs of for example speed, torque, temperature, state of emergency brake, percentage power de-rating and the like in order to predict the condition of the hub bearing. Thus an algorithm may indicate at what stage rotation of the relatively fixed race is desirable, said algorithm being based upon accumulated knowledge from several bearing installations.

[0107] Upon determining that movement of the fixed race is desired, the control unit 95 will output to the bearing control unit 90 a signal 101 giving, for example, an instruction to move the fixed bearing by a predetermined arcuate amount, say 20.

[0108] The bearing control unit will send successive signals 102 to open the valve 83 in order to release the fixed bearing race, and turn it though the desired angle. Feedback is provided by the vibration sensor signal 103.

[0109] The actuation strategy module 91 controls the valve 83 in a desired manner, and the bearing condition calculation module 92 (or 96) calculates and records the condition of the fixed bearing race.

[0110] A typical strategy for determining position of a fixed bearing race may, for example, to use a look-up table in conjunction with real-time operational information to rotate the race by 20 every 5000 hours. A prime number rotation sequence will avoid the risk of parking the race in the same position with the consequent risk of further localized deterioration.

[0111] A strategy may optimize bearing position over a fixed life, say 20 years, so as to distribute potential deterioration around the circumference of the fixed race.

[0112] Furthermore a strategy may use a determination of a damaged race sector to avoid further parking in the vicinity of that sector. Such a strategy is useful where nonstandard damage is experienced, for example due to a manufacturing defect.

[0113] In the described embodiments, the hub and inner race are assumed to be stationary in normal operation. However it will be understood that outer race and housing thereof could be stationary, and the inner race turn with for example a rotor connector thereto.

[0114] In such circumstances, idling of the outer race is required in order to avoid deterioration of the sector bearing the vertical load.

[0115] The invention requires certain components to be attached together, and which may be of dissimilar materials, such as the inner bearing race 15 and housing 21. Any suitable attachment method may be used, for example heat or friction welding, threaded engagement or dog engagement.