Technical Field

The present invention relates to bearing arrangements for main shafts within wind turbine generators, and in particular where the drivetrain of the wind turbine generator is supported by either one main bearing - commonly known as a three- point-mount, or two main bearings - commonly known as either two or four-point mount.

Background Art

Spherical roller bearings are used extensively within the wind turbine industry to support the main shafts of drive trains. They are used within three-point mount systems (one main bearing and two arms of the gearbox) and two / four-point mount systems (two main bearings and two arms of the gearbox). These main shafts are subject to static and dynamic bending, misalignment, radial loads and axial loads. The spherical roller bearings are selected as historically they provide a one-stop- shop to accommodate the above five parameters

Within most non-direct-drive wind turbine generators, the drivetrains of said equipment is supported by either one or two main bearings. These bearings are commonly of the double row spherical roller bearing design. While these bearings are excellent at accommodating misalignment and radial load, they have limited capacity with axial load. This limitation regularly leads to premature failure. Other, more conventional bearing types are available which have superior load capacities but are limited due to their inability to accommodate misalignment, both static and dynamic. WO2016178649 relates to an approach for avoiding this issue when spherical roller bearings are used, which employs preloaded tapered roller bearings in their place. The preloaded, double-row tapered roller bearing design aims to facilitate proper load share between the two rows of rollers to help reduce or eliminate the roller/raceway sliding and skidding/smearing associated with conventional spherical roller bearing damage. However, this approach does not handle large axial (thrust) loads.

The present invention provides a design of bearing housing that allows for the misalignment and static & dynamic bending to be accommodated, and which incorporates conventional bearings and can be retro-fitted to existing installations.

Summary of the Invention

The present invention discloses a wind turbine bearing system for supporting a rotating main shaft of a wind turbine. The system comprises: a bearing assembly and a pillow block housing assembly configured for attachment to a stationary support structure. The bearing assembly comprises a trunnion bearing comprises a trunnion bearing, and the pillow block assembly comprises a spherical bearing between the pillow block and the trunnion bearing.

Brief Description of the Drawings

The invention will now be disclosed with reference to the drawings, in which: Figure 1 shows a side and plan views of a 3-point mount configuration of the present invention; and

Figure 2 shows a side and plan views of a 4-point mount configuration of the present invention. Detailed Description

Referring to Figure 1 , which shows a 3-point mount configuration for a wind turbine using a double row taper roller bearing (DRTB; not shown), a main shaft 1 having an upwind side and a downwind side connects the main rotor (not shown) at the upwind side with the gearbox (not shown) at the downwind side.

Trunnion bearing housing 2 connects to pillow block assemblies 3,8 via a spherical bearing 7. Enclosed by the trunnion bearing housing 2 is a bearing arrangement for supporting shaft 1 . Typically, this is a DRTB, which accommodates misalignment and radial load, whilst the trunnion accommodates axial load. Other bearings able to accommodate misalignment and radial load can be used in place of the DRTB.

The 3-point mount configuration additionally comprises a number of features which are in common with a conventional arrangement not including the

trunnion/spherical bearing feature of the present invention. These facilitate retrofit of the trunnion/spherical bearing feature to an existing wind turbine and include the following: rear inner race lock ring device 4; rear downwind grease retainer ring device 5; and rear upwind grease retainer ring device 6.

Thus, this arrangement facilitates the replacement of the existing bearing assembly with the existing assembly with the trunnion system. When maintenance of the bearings is required, main shaft 1 is removed. Replacement bearing housing mount 3,8 and trunnion bearing housing 2 are fitted in place of the existing bearing housing. The bolt holes and fixings in the bearing housing mounts 3,8 are the same as in the existing bearing housing mount, which has been removed. The replacement DRTB assembly fits inside the trunnion housing, and the main shaft can be slid back into place.

Referring to Figure 2, which shows a 4-point mount configuration for a wind turbine using a double row taper roller bearing (DRTB; not shown) and a cylindrical Roller Bearing (CRB; not shown), a main shaft 1 having an upwind side and a downwind side connects the main rotor (not shown) at the upwind side with the gearbox (not shown) at the downwind side.

At the upwind side, trunnion bearing housing 9 connects to pillow block assemblies 10,15 via a spherical bearing 14. Enclosed by the trunnion bearing housing 9 is a bearing arrangement for supporting shaft 1 . Typically, this is a DRTB, which accommodates misalignment and radial load, whilst the trunnion

accommodates axial load. Other bearings able to accommodate misalignment and radial load can be used in place of the DRTB.

At the downwind side, bearing housing 2 connects to pillow block assemblies 3,8 via a spherical bearing 7. Enclosed by the trunnion bearing housing 2 is a bearing arrangement for supporting shaft 1 . Typically, this is a CRB, which accommodates misalignment and radial load, whilst the trunnion accommodates axial load. Other bearings able to accommodate misalignment and radial load can be used in place of the CRB. The 4-point mount configuration additionally comprises a number of features which are in common with a conventional arrangement not including the

trunnion/spherical bearing feature of the present invention. These facilitate retrofit of the trunnion/spherical bearing feature to an existing wind turbine and include the following: rear inner race lock ring device 4; rear downwind grease retainer ring device 5; rear upwind grease retainer ring device 6; front inner race lock ring device 1 1 ; front downwind grease retainer ring device 12; and front upwind grease retainer ring device 13.

Thus, this arrangement facilitates the replacement of the existing bearing assembly with the existing assembly with the trunnion system. When maintenance of the bearings is required, main shaft 1 is removed. Replacement bearing housing mounts 3,8 and 10, 15 and trunnion bearing housing 2,9 are fitted in place of the existing bearing housing. The bolt holes and fixings in the bearing housing mounts 3,8, 10, 15 are the same as in the existing bearing housing mount, which has been removed. The replacement DRTB or CRB assembly fits inside the trunnion housings 2,9, and main shaft 1 can be slid back into place.