PLANETARY GEAR UNIT FOR A GEARBOX FOR A WIND TURBINE
A planetary gear unit ( 20 ) for a gearbox ( 40 ) for a wind turbine includes a housing ( 21 ) and a planet carrier ( 22 ) provided with planet shafts ( 23 ) distributed uniformly around a planet carrier's axis for rotatably supporting planet gears ( 24 ) which are mounted between a sun gear ( 26 ) and a ring gear ( 27 ) for mutual interaction and which are supported by rolling bearings ( 25 ). The planet carrier is rotatably mounted in the housing with sliding bearings ( 28 ). By using sliding bearings which are different from existing classical sliding bearings which are currently used for rotatably mounting the planet carrier in the housing in combination with the use of rolling bearings for supporting other parts of the planetary gear unit, costs of the planetary gear unit may significantly be reduced. A gearbox including such a planetary gear unit and a wind turbine including such a gearbox are also described.
1 . A planetary gear unit ( 20 ) for a gearbox ( 40 ) for a wind turbine, the planetary gear unit ( 20 ) comprising:
a housing ( 21 ), and
a planet carrier ( 22 ) provided with planet shafts ( 23 ) distributed uniformly around a planet carrier's axis for rotatably supporting planet gears ( 24 ) which are mounted between a sun gear ( 26 ) and a ring gear ( 27 ) for mutual interaction and which are supported by rolling bearings ( 25 ),
characterized in that the planet carrier ( 22 ) is rotatably mounted in the housing ( 21 ) by means of sliding bearings ( 28 ).
2 . A planetary gear unit ( 20 ) according to claim 1 , wherein the sliding bearings ( 28 ) are formed of a single material.
3 . A planetary gear unit ( 20 ) according to claim 2 , wherein the sliding bearings ( 28 ) are formed of bronze.
4 . A planetary gear unit ( 20 ) according to claim 2 , the sliding bearings ( 28 ) having raceways, wherein the sliding bearings ( 28 ) furthermore comprise an additional material on their raceway.
5 . A planetary gear unit ( 20 ) according to claim 1 , the sliding bearings ( 28 ) and the planet carrier ( 22 ) having raceways for contacting each other, wherein the raceways of the planet carrier ( 22 ) are hardened.
6 . A planetary gear unit ( 20 ) according to claim 1 , the sliding bearings ( 28 ) and the planet carrier ( 22 ) having raceways for contacting each other, wherein the raceways of the planet carrier ( 22 ) are provided with a hardened ring.
7 . A planetary gear unit ( 20 ) according to claim 1 , furthermore comprising at least one axial fixation mechanism ( 22 b , 30 ) at a rotor side (R) of the planetary gear unit ( 20 ) and/or at a generator side (G) of the planetary gear unit ( 20 ) for preventing the sliding bearings ( 28 ) from moving in axial direction.
8 . A planetary gear unit ( 20 ) according to claim 7 , wherein the axial fixation mechanism ( 22 b , 30 ) is formed as an integral part of the sliding bearing ( 28 ).
9 . A planetary gear unit ( 20 ) according to claim 7 , wherein the axial fixation mechanism ( 22 b , 30 ) is formed by an additional part different from the sliding bearing ( 28 ).
10 . A planetary gear unit ( 20 ) according to claim 9 , wherein the axial fixation mechanism ( 30 ) comprises a cover ( 30 ) which is provided between the housing ( 21 ) and the planet carrier ( 22 ).
11 . A planetary gear unit ( 20 ) according to claim 1 , furthermore comprising at least one radial fixation mechanism ( 29 ) at a rotor side (R) of the planetary gear unit ( 20 ) and/or at a generator side (G) of the planetary gear unit ( 20 ) for preventing the sliding bearings ( 28 ) from rotating.
12 . A planetary gear unit ( 20 ) according to claim 1 , furthermore comprising a seal ( 31 ).
13 . A planetary gear unit ( 20 ) according to claim 1 , wherein the housing ( 21 ) and the sliding bearings ( 28 ) are formed of a same material and in one part.
14 . A gearbox ( 30 ) for a wind turbine, the gearbox ( 30 ) comprising at least one planetary gear unit ( 20 ) according to claim 1 and a parallel gear unit ( 31 ).
15 . A wind turbine comprising a gearbox ( 30 ) according to claim 14 .
16 . A planetary gear unit ( 20 ) according to claim 3 , the sliding bearings ( 28 ) having raceways, wherein the sliding bearings ( 28 ) furthermore comprise an additional material on their raceway.