Note: Descriptions are shown in the official language in which they were submitted.
CA 02932802 2016-06-10
Drivetrain bearing arrangement of a wind turbine, and
wind turbine
Description
The invention relates to a drivetrain bearing
arrangement of a wind turbine that has a rotor, a
substantially horizontally aligned rotor shaft, a
planetary gear set and a mainframe, comprising a rotor-
side rotor bearing opposite the planetary gear set, a
planet-carrier bearing for a rotor-side planet carrier
of the planetary gear set, and at least one lateral
torque support, which is connected to the planetary
gear set on one side of the planetary gear set, the
rotor bearing being realized as a fixed bearing for
absorbing axial loads. The invention
additionally
relates to a corresponding wind turbine.
Many modern wind turbines of the megawatt and multi-
megawatt class, in the present case horizontal-axis
wind turbines having substantially horizontal rotor-
shaft axes, have, in a nacelle or enclosure at the tip
of the tower, a gearbox that connects the rotor to a
generator. In these wind turbines, the rotor shaft is
horizontal or slightly inclined relative to the
horizontal, this having the advantage of a greater
distance between the rotor blades and the tower.
Accommodated in the nacelle there is a mainframe, on
which the generator and the gearbox are mounted. Since
the mainframe also has to carry the rotor, in such
cases a three-point bearing arrangement or a four-point
bearing arrangement is normally used as a bearing
arrangement for the drivetrain composed of the rotor,
rotor shaft and gearbox. In the context of the present
invention, in the following, a drivetrain bearing
arrangement is understood to mean a bearing arrangement
of a rotor and gearbox.
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The three-point bearing arrangement that may be cited
by way of example comprises a rolling bearing, as a
rotor bearing, by which the rotor shaft is guided and
which supports the rotor shaft. The rotor
shaft runs
into the gearbox. Two further
bearing points are
disposed laterally on the gearbox, and fasten the
gearbox to the mainframe. These lateral
bearings
absorb the gearbox torque and bending moments of the
rotor shaft, and are referred to as supports or gearbox
supports.
In the case of three-point bearings, all forces arising
from pitching and yawing loads, i.e. bending moments
arising from the rotor shaft, as well as the torque
arising from the rotation of the rotor (torsional
load), are transmitted to the mainframe via the
supports. A soft
bearing-bush design at the lateral
supports then, besides resulting in a reduction of the
torsional excitation and consequently good decoupling
of structure-borne sound, also results in a greater
displacement of the gearbox under bending loads. This
may result in non-permissible displacements of the
generator coupling or even of the main bearing.
Transfer of the bending loads into an open mainframe
design also represents a challenge in this case.
An alternative to this is represented by four-point
bearings, such as those used, for example, in the 5M
series and 6M series of the applicant. The latter,
besides having usually two lateral supports or torque
supports on the gearbox, have two separate bearings for
the rotor shaft in front of the gearbox, one of the
rotor shaft bearings being realized as a floating
bearing and the other as a fixed bearing, which absorbs
axial forces acting on the rotor and deflects them into
the mainframe, such that the gearbox is no longer
subjected to axial loading. The two rotor
shaft
bearings also absorb the bending loads of the rotor
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shaft, such that the torque supports then only have to
absorb torsional loads caused by the rotation of the
rotor, and the gearbox no longer undergoes displacement
as in the case of the three-point bearings.
Against this, the present invention is based on the
object of making available a simple and effective
drivetrain bearing arrangement, and a wind turbine
having a corresponding drivetrain bearing arrangement.
This object is achieved by a drivetrain bearing
arrangement of a wind turbine that has a rotor, a
substantially horizontally aligned rotor shaft, a
planetary gear set and a mainframe, comprising a rotor-
side rotor bearing opposite the planetary gear set, a
planet-carrier bearing for a rotor-side planet carrier
of the planetary gear set, and at least one lateral
torque support, which is connected to the planetary
gear set on one side of the planetary gear set, the
rotor bearing being realized as a fixed bearing for
absorbing axial loads, which drivetrain bearing
arrangement is developed in that, provided for the
purpose of absorbing bending loads of the rotor shaft,
there is a radial bearing, which comprises an annular
elastomer, and which is disposed in a plane of the
planet-carrier bearing and is mounted in a fastening
structure of the mainframe.
In the classic case of two torque supports that are
disposed symmetrically on both sides of the gearbox,
the drivetrain bearing arrangement according to the
invention is a four-point bearing arrangement. In the
case of a drivetrain having a planetary gear set, the
rotor shaft is flange-connected, on the gearbox side,
to a central planet carrier of a, in particular first,
planetary stage of the planetary gear set, which planet
carrier is disposed in the extension of the rotor
shaft. The planet carrier is mounted, with respect to
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the housing of the planetary gear set, by means of a
planet-carrier bearing, which in most cases is realized
as a rolling bearing.
According to the invention, the annular elastomer is
disposed in the plane of the planet-carrier bearing
such that it supports the housing of the planet carrier
radially with respect to the mainframe. The planet-
carrier bearing, which is present in any case, thus
transmits bending moments to the mainframe via the
annular elastomer. The latter is disposed in the plane
of the planet-carrier bearing, thus at least partially
overlapping with the planet-carrier bearing in the
axial direction, such that a favourable radial flow of
forces is realized without axial offset, i.e. on a most
direct path that is correct in respect of flow of
forces. Bending
moments are thus transferred without
loading the toothed parts of the gearbox.
An adaptation might possibly be indicated in so far as
the planet-carrier bearing is to be designed such that
it withstands the transmission, correct in respect of
flow of forces, of the bending loads from the rotor
shaft to the fastening structure of the mainframe.
The drivetrain bearing arrangement according to the
invention is comparable with a double rotor bearing
arrangement, but without a second rotor bearing. In
comparison with the prior art, according to the
invention there is no gearbox-side dedicated bearing
for the rotor shaft itself that is not at the same time
a bearing for the gearbox. Moreover, the bending loads
and the torsional loads are introduced into the
mainframe structure in a functionally separate manner
via differing elements.
According to the invention, the rotor-side rotor
bearing serves as a fixed bearing for axial loads,
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while the radial bearing disposed in the gearbox, with
the planet-carrier bearing and the annular elastomer,
now absorbs the bending loads of the rotor shaft and
introduces them into the mainframe, which bending loads
were previously absorbed by the gearbox-side rotor
bearing, as a result of which the planet-carrier
bearing had hitherto been relieved of bending moments.
The support according to the invention achieves good
support of the rotor shaft, and has the effect that
there is little stress, resulting from linear and
bending stresses, on the planetary gear set, which in
the context of the invention also includes a
planetary/spur-gear set. Instead of the planetary gear
set, a pure spur-gear set may be mounted
correspondingly.
In an advantageous development, the radial bearing is
realized as a floating bearing for the rotor shaft in
respect of axial loads of the rotor shaft. This
simplifies the design of the radial bearing and is
possible since the rotor-side rotor bearing is already
realized as a fixed bearing.
Preferably, the annular elastomer has a Shore hardness
(A) of more than 70, in particular more than 90, in
particular more than 120. It is therefore designed so
as to be relatively hard, and it minimizes radial
displacements of the gearbox under bending load, with
the effect of also being easy on the gearbox itself.
Advantageously, the annular elastomer is mounted in
segments of the mainframe by means of a bolted or
boltable clamp, or in a full-circumference structure.
The at least one lateral torque support is realized,
advantageously, to absorb torsional loads. For this
purpose, preferably one or more elastomer bodies of the
at least one lateral torque supports is or are realized
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so as to be soft in the direction of compression, in
particular having a Shore hardness (A) of between 30
and 80, in particular between 35 and 65. This
comparatively low hardness allows effective decoupling
of structure-borne sound, which is particularly
important in respect of the torsional excitations. The
choice of such low hardnesses is enabled by the
absorption of the bending loads in the radial bearing
because, owing to the functional separation of the
various elements for absorbing bending loads, or
torsional loads, the gearbox can have a very soft
mounting in respect of torsion without non-permissible
displacement occurring under bending moments.
The torque support or torque supports is or are
preferably designed without preload. This is possible
because an operating preload ensues automatically as a
result of the torque of the rotor always having the
same direction when the wind turbine is in production
operation. As an
alternative or in addition to this,
advantageously, there is a stop buffer for the purpose
of resilience.
In an advantageous development, the torque support
comprises elastomer bodies placed in the shape of a
roof and/or sleeve-shaped elastomer bodies.
Preferably two torque supports are comprised, disposed
symmetrically on both sides of the planetary gear set.
This arrangement enables torsional forces to be
transferred in a uniform manner into the mainframe,
with less local stress than in the case of a single
torque support.
The object on which the invention is based is further
achieved by a wind turbine that has a rotor, a
substantially horizontally aligned rotor shaft, a
planetary gear set and a mainframe, comprising a
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previously described drivetrain bearing arrangement
according to the invention. The wind
turbine shares
with the drivetrain bearing arrangement according to
the invention the previously described features,
properties and advantages of the latter.
Further advantages of the invention become evident from
the description of embodiments according to the
invention, together with the claims and the appended
drawings. Embodiments
according to the invention may
fulfil individual features or a combination of a
plurality of features.
The invention is described in the following, without
limitation of the general concept of the invention, on
the basis of exemplary embodiments, with reference to
the drawings, and reference is expressly made to the
drawings in respect of all details according to the
invention not explained in greater detail in the text.
There are shown in:
Fig. 1 a schematic cross section through the nacelle
of a known wind turbine,
Fig. 2 a schematic perspective representation of a
drivetrain bearing arrangement according to the
invention, and
Fig. 3 a schematic cross-sectional and perspective
representation of a radial bearing according to
the invention.
In the drawings, elements and/or parts that are the
same or of the same type are in each case denoted by
the same reference numerals, such that presentation in
each case is not repeated.
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Fig. 1 shows a cross-sectional representation through a
nacelle of a known wind turbine, for example the wind
turbine MD70 of the applicant. The nacelle 3 sits on a
tower 2, of which the portion near the nacelle is
represented. Represented on
the left in Fig. 1 is a
rotor, having a rotor hub 4, and rotor blades 5, which
are represented only in the region of the rotor-blade
roots. In the region
of the rotor-blade roots, the
rotor blades 5 each have a rotor-blade bearing 6,
acting upon which is a pitch drive 7. The pitch drive
7 is operated by a controller 8 and alters the pitch
angle of the respective rotor blade 5 when the wind
turbine 1 is in operation.
The nacelle 3 accommodates a mainframe 12, which is
connected to the tower 2 via a nacelle slewing ring 9.
Acting on the nacelle slewing ring 9 there are wind
direction alignment motors 10 of a yaw control system,
which align the nacelle, or rotor, in the direction of
the prevailing wind. For this purpose
there are four
wind direction alignment motors 10, of which two are
disposed on the side represented and two are concealed
behind it, on the other side of the mainframe 12. Also
acting on the nacelle slewing ring 9 are yaw brakes 11,
which serve to lock the yaw setting of the rotor.
The rotor drives a rotor shaft 13, which is rotatably
mounted in a rotor bearing 14 realized as a rolling
bearing. The rotor
shaft 13 drives a planetary gear
set 15, which converts the slow rotational motion of
the rotor shaft into a fast rotational motion of a
generator shaft 19, which is represented with
couplings, which shaft, in turn, drives a generator 20,
equipped with a heat exchanger 21, for the purpose of
generating electricity.
In the case of the MD70 wind turbine of the applicant
shown in Fig. 1, the drivetrain bearing arrangement is
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realized as a three-point bearing. The rotor
bearing
14 in this case is realized as a fixed bearing, which
permits only a few millimetres of play in the axial
direction of the rotor shaft 13. Two further
bearing
points consist in the elastic gearbox suspensions, or
supports 16, of which one is represented in Fig. 1,
while the other is located symmetrically on the other
side of the planetary gear set 15 and is therefore
concealed by the planetary gear set 15. These bearing
points are designed such that they absorb both
torsional loads and bending loads of the rotor shaft 13
that are transmitted, via the planetary gear set 15, to
the supports 16 and further to the mainframe 12.
The support 16, or the elastic gearbox suspension, is
of a conventional design, and consists of hollow-
cylinder elastomer bodies composed of two half-cylinder
partial bodies, which are disposed around a cylindrical
pin. With its cylindrical bearings, the cylinder axis
of which is aligned parallel to the rotor shaft 13, the
support 16 is a floating bearing, since, owing to its
softness in this direction, it absorbs only a small
amount of rotor thrust in the direction of the rotor
shaft axis.
By contrast, the sleeve-shaped elastomer bodies in the
supports 16 are designed so as to be comparatively
stiff in the radial direction. The planetary gear set
15 additionally has a rotor brake 17 and a slip ring
transmitter 18.
A perspective view of an exemplary embodiment of a
drivetrain bearing arrangement 30 according to the
invention is shown in Fig. 2. Shown at bottom left is
a portion of a rotor bearing 14, which is realized as a
fixed bearing for supporting the rotor shaft 13 axially
and radially. The latter is flange-connected, by means
of a rotor-shaft flange 131, to a planet carrier 151,
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which is part of a first planetary stage of a planetary
gear set 15. The planet
carrier 151 is mounted in
respect of a housing 154 of the planetary gear set 15
by means of a planet-carrier bearing 152, which is not
visible in Fig. 2. A radial bearing 32 is constituted
in that, by means of an annular elastomer 153, the
housing 154 of the planetary gear set 15 is
additionally tensioned and mounted in respect of a
fastening structure 121, which is bolted to the
mainframe 12. For this
purpose, the fastening
structure 121 has a semicircular clamp 122, which
terminates in two clamp bolt-connection flanges that
are bolted to corresponding bolt-connection flanges 124
of the mainframe 12. This radial bearing 32, with the
relatively hard annular elastomer, is designed so as to
be relatively hard.
The combination of the rotor bearing 14 and the radial
bearing 32 absorbs all bending loads of the rotor, or
of the rotor shaft 13, and deflects them into the
mainframe without loading the teeth of the planetary
gear set 15.
The housing 154 of the planetary gear set 15 has, on
both sides, a respective torque support 160, which are
mounted in a respective frame 125 between elastomer
bodies 161. The latter may be of a soft design, since
they only have to absorb torsional loads, but not
bending loads of the rotor shaft 13. The frames
125
are bolted on their underside to the mainframe 12, and
each have a cover 126 on their top side.
The inner structure of the radial bearing 32 from Fig.
2 is shown in a partially perspective cross section in
Fig. 3. In addition to the details that can be seen in
Fig. 2, Fig. 3 shows how the rotor shaft 13 is flange-
connected to the planet carrier 151 by means of the
rotor-shaft flange 131. Also shown is
the planet-
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carrier bearing 152 between the planet carrier 151 and
the housing 154 of the planetary gear set. The housing
154 has a projection in the direction of the rotor
shaft 13, the outside of which is opposite the inside
of the clamp 122 of the fastening structure 121, with a
gap remaining. This gap is
partially filled by the
annular elastomer 153.
The annular elastomer 153 and the planet-carrier
bearing 152 overlap in a plane perpendicular to the
central axis of the rotor shaft 13, such that a direct
radial flow of forces is realized from the planet
carrier 151 via the planet-carrier bearing 152, the
housing 154 and the annular elastomer, to the
circumferential fastening structure 121, and thus to
the mainframe 12.
All stated features, also the features given only by
the drawings and also individual features that have
been disclosed in combination with other features, are
regarded as material to the invention. Embodiments
according to the invention may be fulfilled by
individual features or by a combination of a plurality
of features. Features that are characterized with "in
particular" or "preferably" are to be understood as
optional features in the context of the invention.
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List of references
1 wind turbine
2 tower
3 nacelle
4 rotor hub
5 rotor blade
6 rotor-blade bearing
7 pitch drive
8 controller of the pitch control
9 nacelle slewing ring
10 wind direction alignment motors
11 yaw brakes
12 mainframe
13 rotor shaft
14 rotor bearing
15 planetary gear set
16 elastic gearbox suspension
17 rotor brake
18 slip ring transmitter
19 generator shaft with couplings
20 generator
21 heat exchanger
drivetrain bearing arrangement
25 32 radial bearing
121 fastening structure
122 clamp
123 clamp bolt-connection flange
124 bolt-connection flange
30 125 frame
126 cover
131 rotor-shaft flange
151 planet carrier
152 planet-carrier bearing
153 annular elastomer
154 housing
160 torque support
161 elastomer body
