Claims:We Claim:

1. An attachment arrangement (20-1, 20-2) for securing a bearing (24) on a rotor shaft (22) or in a main frame (37) of a wind turbine (2), the attachment arrangement (20’, 20-1, 20-2) comprising:
a shaft nut (28) mountable coaxially with the rotor shaft (22) whereby the shaft nut (28) engages the rotor shaft (22), an axially inner portion (45) of the shaft nut (28) is arranged besides at least a part of the bearing (24) or a spacer ring (27) between the shaft nut (28) and the bearing (24);
characterized by a plurality of tightening bolts (50), wherein each tightening bolt (50) being configured to apply, in use, an axial pre-loading force to the at least one part of the bearing (24) or to the spacer ring (27).

2. The attachment arrangement according to claim 1 characterized by a load distribution part (44) for applying a preloading force disposed, in use, between the tip portions (34, 34-2) of the tightening bolts (50) and the at least one part of the bearing or the spacer ring (27).

3. The attachment arrangement according to claim 2 characterized in that the load distribution part (44) is an annular load distribution ring (44).

4. The attachment arrangement according to claim 3 characterized in that the radial dimension of the load distribution ring (44) is larger than that of the tightening bolts (50).

5. The attachment arrangement according to claim 4 characterized in that the radial dimension of the load distribution ring (44) is 50-150%, more preferably 60-140%, more preferably 70-130%, more preferably 80-120%, more preferably 90-110%, and more preferably 100% larger than that of the tightening bolts (50).

6. The attachment arrangement according to one of the preceding claims characterized in that an axial dimension of a tip portion (34, 34-2) of the tightening bolt (50) is 40-60%, more preferably 45-55%, and more preferably 50% that of intermediate threaded portion (41) of the tightening bolt (50).

7. The attachment arrangement according to one of the preceding claims characterized in that the tip portion (34) directly abuts the spacer ring (27) for applying the preloading force thereto.

8. The attachment arrangement according to one of the claims 1 to 6, characterized in that an axial dimension of the tip portion (34-2) of the tightening bolt (50) is the same or larger as that of the intermedi-ate threaded portion (41) of the tightening bolt (50).

9. The attachment arrangement according to any of the preceding claims characterized in that the number of tightening bolts (50) lies in the range 10 to 20, and more preferably is 16.

10. The attachment arrangement according to any of the preceding claims characterized in that the tightening bolts (50) comprise M16 bolts.

11. A wind turbine (2) comprises a main frame, a rotor shaft rotatable about an axis on the main frame, and an attachment arrangement (20-1, 20-2) for securing a bearing (24) on a rotor shaft (22) or in a main frame (37) of a wind turbine (2) according to any of the preced-ing claims.

12. A method for securing a rotor shaft (22) on a main frame (37) of a wind turbine (2), the method comprising:
- providing an attachment arrangement (20-1, 20-2) according to any of claims 1 to 10;
- fixing the shaft nut (28) on the rotor shaft (22);
- mounting the one or more tightening bolts (50) on the shaft nut (28); and
- tightening the tightening bolts (50) to apply the axial preloading force to the at least one part of the bearing (24) or to the spacer ring (27).
, Description:FIELD OF INVENTION

The invention relates to components of a wind turbine, and more particu-larly to an attachment arrangement for a main frame of a wind turbine, a wind turbine and a method of mounting.

BACKGROUND

In a wind turbine it is known to use a shaft nut (also referred to as “lock nut”) in order to secure the rotor shaft (main shaft) on one or more support or “shaft supports”, the support(s) being, e.g., on or supported by a main frame within a nacelle. Typically, a shaft nut is locked on the thread on the outer surface of the rotor shaft, and secured by means of Allen/hex bolts, in order to preload the arrangement.

However, it has been found that with this known design, problems arise. That is, the known preloading process cannot, in general, compensate preload losses due to temperature, settlement in the area of the bearing seats and relaxation. The degree of preload can only be ensured at the time of installation. In order to ensure that there is sufficient preload during operation, the preload has to be checked and adjusted in regular intervals.

OBJECT OF THE INVENTION

The present invention seeks to overcome the aforementioned problems and to provide an improved attachment arrangement for a main frame of a wind turbine, a wind turbine and a method of mounting.

SUMMARY OF THE INVENTION

The present invention provides an attachment arrangement for securing a bearing on a rotor shaft or in a main frame of a wind turbine, the attach-ment arrangement comprising: a shaft nut mountable coaxially with the rotor shaft whereby the shaft nut engages the rotor shaft, an axially inner portion of the shaft nut is arranged besides at least a part of the bearing or a spacer ring between the shaft nut and the bearing; characterized by a plurality of tightening bolts, wherein each tightening bolt being configured to apply, in use, an axial preloading force to the at least one part of the bearing or to the spacer ring.

In a preferred embodiment the attachment arrangement characterized by a load distribution part for applying a preloading force disposed, in use, between the tip portions of the tightening bolts and the at least one part of the bearing or the spacer ring.

In a further preferred embodiment the load distribution part is an annular load distribution ring.

In a more preferred embodiment the radial dimension of the load distribu-tion ring is larger than that of the tightening bolts. Advantageously the radial dimension of the load distribution ring is 50-150%, more preferably 60-140%, more preferably 70-130%, more preferably 80-120%, more preferably 90-110%, and more preferably 100% larger than that of the tightening bolts.

In a preferred embodiment an axial dimension of a tip portion of the tight-ening bolt is 40-60%, more preferably 45-55%, and more preferably 50% that of the intermediate portion of the tightening bolt.

In a preferred embodiment the tip portion directly abuts the spacer ring for applying the preloading force thereto.

In a preferred embodiment an axial dimension of the tip portion of the tightening bolt is the same or larger as that of the intermediate portion of the tightening bolt.

In a preferred embodiment the number of tightening bolts lies in the range 10 to 20, and more preferably is 16. Advantageously the tightening bolts comprise M16 bolts.

A further aspect of the invention is directed to a wind turbine comprises a main frame, a rotor shaft rotatable about an axis on the main frame, and the said attachment arrangement for securing a bearing on a rotor shaft or in a main frame.

A further aspect of the invention is directed to 12. A method for secur-ing a rotor shaft (22) on a main frame (37) of a wind turbine (2), wherein the method comprising:
- providing the said attachment arrangement;
- fixing the shaft nut on the rotor shaft;
- mounting the one or more tightening bolts on the shaft nut; and
- tightening the tightening bolts to apply the axial preloading force to the at least one part of the bearing or to the spacer ring.

Advantageously, the inner portion of the shaft nut includes an annular first recess in an axially inner surface thereof.

Advantageously, the inner surface extends radially.

Advantageously, the first recess has an axially extending dimension longer than that of the load distribution ring.

Advantageously when dependent upon any of claims 2 to 4, characterized in that the first recess has an axially extending dimension 2-20%, more preferably 4-18%, more preferably 6-16% , more preferably 8-14%, more preferably 9-13%, more preferably 10-12%, and more preferably 10% longer than that of the load distribution ring.

Advantageously, the inner surface of the shaft nut has a radial dimension larger than that of the load distribution ring.

Advantageously, the inner surface of the shaft nut has a radial dimension 50-100%, more preferably 60-90%, more preferably 70-80%, and more preferably 75% larger than that of the load distribution ring.

Advantageously, the intermediate element comprises a spacer ring be-tween the shaft nut and the main frame.

Advantageously, the tightening bolts each comprise an axially outer head portion, an axially inner tip portion and an intermediate threaded portion there between.

Advantageously, the fixing elements comprise a plurality of preloadable bolts circumferentially arranged spaced apart on the shaft nut and config-ured to tighten an internal first thread on the shaft nut onto a correspond-ing external second thread on the rotor shaft.

Advantages of the invention, at least in embodiments, are
(1) that the main design of the shaft nut does not change;
(2) low risk regarding the exchange of main bearings during the lifetime of the turbine,
(3) longer lifetime of the main bearings due to adjustability;
(4) no additional weight;
(5) compensation of tolerances of shaft nut and unevenness in the contact surface to the bearing inner seat (e.g. inaccuracy of the thread, unevenness of the bearing inner ring to the shaft nut);
(6) the required preload can easily be adjusted if it is required to increase or reduce it;
(7) low maintenance connection;
(8) simplified maintenance and
(9) low additional cost.

BRIEF DESCRIPTION OF DRAWINGS

Further details of the invention will become apparent from the drawings according to the description. In the drawings:

Figure 1 (PRIOR ART) is a perspective view from above of the upper part of a known form of wind turbine;

Figure 2 (PRIOR ART) is a perspective sectional view of a known form of attachment arrangement on a rotor shaft of a wind turbine according to an embodiment of the invention;

Figure 3 is a sectional view of a form of attachment arrangement according to the embodiment of Fig. 2; and

Figure 4 is a sectional view of a form of attachment arrangement according to another embodiment of the invention.

The foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing figures.

DETAILED DESCRIPTION OF THE INVENTION

In the following, like reference numerals are used to designate like ele-ments.

Figure 1 (PRIOR ART) is a perspective view from above of the upper part of a wind turbine (2). As shown, the wind turbine (2) has a tube tower (3) known from the prior art, a nacelle (4) mounted on the tower (3) and a ro-tor (5) with a hub (8) and three rotor blades (6) which are each rotatable mounted about a blade axle. The hub (8) is mounted on a rotor shaft (not shown) which is rotatable mounted on a main frame (not shown) within the nacelle (4). According to this embodiment, the tube tower (3) is formed of multiple tube segments (16).

Figure 2 (PRIOR ART) is a perspective sectional view of an attachment arrangement (20’) on a rotor shaft (22) of a wind turbine (2). The rotor shaft (22) has an outer surface (23) on which components are (form-fittingly / annularly) mounted, as will be described below.

A bearing (24), a lower part (not labelled) of which is fixed to / integral with the rotor shaft (22) has mounted on sides thereof a front seal (25) and a rear seal (26). In this embodiment, a spacer ring (27), annular with but not fixed to the rotor shaft (22), is disposed between the rear seal (26) and the outer surface (23).

The attachment arrangement (20’) comprises a shaft nut (28) and a set of mounting bolts (29). A front surface (30) of the shaft nut (28) abuts, in use, a rear surface (31) of the spacer ring (27). The shaft nut (28) includes an inner thread (not shown) which cooperates with an outer thread (not shown) on the outer surface (23) of the rotor shaft (22); and the shaft nut (28) can thus be mounted on the rotor shaft (22) and secured thereto by screwing.

The shaft nut (28) includes multiple bores (32) for receiving the mounting bolts (29). The mounting bolts (29) each include a head portion (33) and a tip portion (34); and the tip portion (34) includes an external thread for co-operating with an internal thread in a respective bore (32). By tightening the mounting bolts (29), a preload can be applied to the shaft nut (28). In particular, a (n internal) slot or groove (51) within the shaft nut (28) is de-formed through the tightening of the mounting bolts (29), such that the threads of the shaft nut (28) and the rotor shaft (22) are tight-ened/tensioned against each other, so that the loosening of the shaft nut (28) is prevented.

Figure 3 is a transverse cross-sectional view of the attachment arrange-ment 20-1 according to one embodiment of the invention, which shows the attachment arrangement (20-1) in more detail. Components, which are described in Figure 2 and have the same function, gets the same reference number. A bearing (24) includes a bearing inner ring (35) fixed to / integral with the rotor shaft (22), the bearing (24) having mounted on a side thereof a rear seal (26), also referred to as a bearing cover. A bearing outer ring (36) is fixed to the main frame (37). The bearing inner ring (35) is separated from the bearing outer ring (36) by rollers (38) which effec-tively provide bearing surfaces and allow rotation of the bearing inner ring (35) relative to the bearing outer ring (36). The spacer ring (27), annular with but not fixed to the rotor shaft (22), is disposed below the between the rear seal (26) and the outer surface (23). The shaft nut (28) is screwed on the rotor shaft (22) via a thread (39).

As best seen in Fig. 3, the attachment arrangement (20-1) according to an embodiment further includes one or more tightening bolts (50), through which an axial preload can be applied, as will be described in more detail

The shaft nut (28) includes one or more bores (32) for receiving the tight-ening bolt(s) (50). The tightening bolts (50) each include a head portion (33), a tip portion (34) and, integral therewith and disposed there between, an intermediate threaded portion (41). The intermediate threaded portion (41) includes an external thread (42) for cooperating with an internal thread (43) on in a respective bore (32). By tightening the tightening bolt(s) (50), an axial preload can be applied to the spacer ring (27). However, it will be appreciated that, if the spacer ring (27) is omitted, the axial preload can be applied to another element, such as the bearing inner ring (35) or another part of the bearing (24).

More particularly, in this embodiment, an annular load distribution part (44) is disposed, in use, between the tip portions (34) of the tightening bolts (50) and the spacer ring (27), whereby the preloading force is applied via the load distribution part (44). In the shown embodiment the load distribution part (44) is an annular load distribution ring (44). It should be pointed out that in the following description refers to a load distribution ring (44), which covers the annular load distribution ring as well as the load distribution part. In an embodiment, the radial dimension of the load distribution ring (44) is larger than that of the bolts (29) (e.g. head portions (33) and tip portion (34)). For example, the radial dimension of the load distribution ring (44) may be 50-150%, more preferably 60-140%, more preferably 70-130% , more preferably 80-120%, more preferably 90-110%, and more preferably 100% larger than that of tip portion (34) of the tightening bolt (50). Using the load distribution ring (44), force is distributed over a wider area, leading to more even application of the preload and reducing the possibility of damage to the spacer ring (27) (or whichever element to which the axial preload is applied).

In an embodiment, an inner portion (45) of the shaft nut (28) includes an annular first recess (46) in an axially inner front surface (30) thereof, the front surface (30) preferably extending radially. In an embodiment, the first recess (46) has an axially extending dimension longer than that of the load distribution ring (43), whereby, in use, the load distribution ring (44) is movable in a direction parallel to the axis of the rotor shaft (22). For example, the first recess (46) may have an axially extending dimension 2-20%, more preferably 4-18%, more preferably 6-16% , more preferably 8-14%, more preferably 9-13%, more preferably 10-12%, and more preferably 10% longer than that of the load distribution ring (44).

In an embodiment, the inner surface (52) of the shaft nut (28) has a radial dimension larger than that of the load distribution ring (44). For example, the inner surface (52) may have a radial dimension 50-100%, more pref-erably 60-90%, more preferably 70-80%, and more preferably 75% larger than that of the load distribution ring (44).

In an alternative embodiment, instead of in addition to the annular load distribution ring (44), a disc, washer, plate or other form of load distribution element (e.g. present within a correspondingly-shaped recess in the shaft nut (28)) is used to distribute force over a wider area.

In an embodiment, an axial dimension of the tip portion (34) is 40-60%, more preferably 45-55%, and more preferably 50% that of the intermediate threaded portion (41).

Figure 4 is a sectional view of an attachment arrangement (20-2) accord-ing to a further embodiment of the invention. Components, which are described in Figure 2 to 3 and have the same function, gets the same reference number. The main different between the embodiment described in Fig. 3 and the embodiment of Fig. 4, which is described in detail below, is that a load distribution part (44) is omitted. Instead of this, the length of tightening bolt(s) (50) adapted this way that the preloading force can ap-plied to the spacer ring (27) or to the at least one part of the bearing (24).
In an embodiment, an axial dimension of the tip portion (34-2) is substan-tially the same as that of the intermediate threaded portion (41).

With the tip portion (34-2) directly abutting the spacer ring (27) for applying the preloading force, assembly and component complexity / cost is reduced.

In case the spacer ring (27) is omitted the tip portion (34-2) of the tighten-ing bolt (50) is adapted in this way that the tip portion (34-2) applies the preloading force at least one part of the bearing (24), especially to the in-ner ring (35).

In an embodiment, the number of bolts lies in the range 10 to 20, and more preferably is 16. In an embodiment, the bolts comprise M16 bolts.

In following it will be described a method for securing a rotor shaft on a main frame of a wind turbine, which method is not depicted in a drawing.

The method comprises the steps of
- providing attachment arrangement (20-1, 20-2) as described above;
- fixing the shaft nut (28) on the rotor shaft (22);
- mounting the one or more tightening bolts (50) on the shaft nut (28); and
- tightening the tightening bolts (50) to apply the axial preloading force to the at least one part of the bearing (24) or to the spacer ring (27).

While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention. It is to be understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims.

List of reference signs

2 Wind turbine
3 Tower
4 Nacelle
5 Rotor
6 Blades
8 Hub
16 Tube segments
20’ Attachment arrangement
20-1 Attachment arrangement
20-2 Attachment arrangement
22 Rotor shaft
23 Outer surface
24 Bearing
25 Front seal
26 Rear seal
27 Spacer ring
28 Shaft nut
29 Mounting bolts
30 Front surface
31 Rear surface
32 Bores
33 Head portion
34 Tip portion
34-2 Tip portion
35 Inner ring
36 Outer ring
37 Main frame
38 Rollers
39 Thread
41 Intermediate threaded portion
42 External thread
43 Internal thread
44 Load distribution part / annular load distribution ring
45 Inner portion
46 First recess
50 Tightening bolts
51 Slot or groove
52 Inner surface of shaft nut