The present invention concerns a transmission, specifically a transmission arranged to distribute a torque.

Background

When transmitting relatively large torques, so-called planetary gears are often used. In wind turbines, it is crucial to be able to receive and transmit large tor ques and at the same time be able to divert extreme peak loads due to disorderly load representation and large mass moments of inertia in the wind propeller. A known way to reduce a torque, is by use of so-called planetary gears.

Such a solution is described in the patent document N020130213, wherein two planetary gears are serially mounted. By serially mounting the planetary gears, a torque and a gear-up of the rotational speed from an incoming rotor shaft from the hub and to an outgoing shaft to a generator which is placed in the column of the wind turbine, can occur in two stages.

A problem with the solution described in N020130213 is that the peak loads are not diverted, and the drive line must therefore be dimensioned to be able to ab sorb said peak loads, which results in an unnecessarily powerful transmission and drive line at ordinary loads, and which adds to the drive line weight and costs.

Solutions are therefore sought that make it possible to absorb peak loads in a wind turbine in a way that is simpler and more cost-effective than the ways which are known today. The purpose of the invention is to remedy or reduce at least one of the disad vantages of prior art, or at least provide a useful alternative to prior art.

General description of the invention

The invention is defined by the independent patent claims. The dependent claims define advantageous embodiments of the invention.

According to an aspect of the invention, a transmission for a wind turbine is pro vided, wherein the transmission comprises a gear coupled to a shaft supported in bearing pedestals and connected to a hub with attachments for the connection of wind turbine blades, wherein the gear comprises:

- an incoming shaft which is coupled to a common planetary bearing for two plane tary gears which are arranged in parallel, wherein the first planetary gear compris es a plurality of planetary wheels, a ring gear and a first sun wheel which is con nected to a first outgoing shaft by a first bevel gear, and the second planetary gear comprises a plurality of planetary wheels, a ring gear and a second sun wheel which is connected to a second outgoing shaft by a second bevel gear. The transmission further comprises a differential which comprises a plurality of sun wheels support ed in differential case parts via shafts, and the plurality of sun wheels are engaged with the bevel gears, and the differential case parts are connected to an outgoing flange.

The ring gear can be connected to a moment yoke and further to power absorbers with attachments for foundations.

The shaft can be supported by slide bearing elements against bearing elements connected to bearing pedestals by a spherical surface (spherical bearing).

In a further aspect, a transmission for a wind turbine is provided wherein the transmission may comprise any selection of any of the following characteristics:

- a gear coupled to a shaft supported in bearing pedestals and connected to a hub with attachments for the connection of wind turbine blades, wherein the gear comprises:

- an incoming shaft which is coupled to a planetary bearing for two planetary gears which are arranged in parallel, wherein the first planetary gear comprises a plurali ty of planetary wheels, a ring gear and a first sun wheel connected to a first out going shaft by a first bevel gear, and the second planetary gear comprises a plurali ty of planetary wheels, a ring gear and a second sun wheel which is connected to a second outgoing shaft by a second bevel gear; and

- a differential which comprises a plurality of sun wheels which are supported in dif ferential case parts by shafts, and the plurality of sun wheels are engaged with the bevel gears, and the differential case parts are connected to an outgoing flange.

The ring gear can be connected to a moment yoke and further to power absorbers with attachments for foundations.

The shaft can be supported by slide bearing elements against bearing elements connected to bearing pedestals by a spherical surface (spherical bearing).

The transmission may further comprise any characteristic described anywhere herein.

An effect of the transmission described herein, is that a low incoming rotational speed in a transmission can be transformed to a higher rotational speed, at the same time as an associated high incoming torque can be distributed in the trans mission and reduced. Further advantages of the invention will be made known in the description herein.

In a further aspect, the invention concerns a wind turbine which comprises a transmission according to any of the invention's other aspects.

An advantage to this is that wind turbines with lighter transmissions than prior art may be provided, and where the transmission can reduce dynamic loads on the wind turbine due to peak loads from the wind propeller.

Exemplary embodiments In the following, different embodiments will be described, which are to be consid ered examples only, with reference to the attached drawings, wherein:

Fig. 1 shows a gear configuration with shaft and bearing as well as attachment of wind turbine blades;

Fig. 2 shows the gear from above;

Fig. 3 shows the gear from the side; Fig. 4 shows a cross-section C-C through the gear and an associated differential;

Fig. 5 shows a cross-section F-F through the gear;

Fig. 6 shows an "exploded" configuration of the gear components; Fig. 7 shows the differential;

Fig. 8 shows a cross-section A-A through the differential;

Fig. 9 shows an "exploded" configuration of the differential components;

Fig. 10 shows the main shaft with bearing pedestals; Fig. 11 shows a cross-section through the bearing for the main shaft; and

Fig. 12 shows a detail of the bearing support.

On the figures, 1 indicates a gear coupled with a differential 2 which has an out going shaft flange 14. The gear 1 rests on foundations 12 and is coupled to a shaft 6 supported in bearing pedestals 4 and 5 and connected to a hub 7 whereto attach ments 3 for wind turbine blades are arranged. The gear 1 has a central incoming main shaft 8 with rotation about a centre line 18 and with a flange connection 25 to the shaft 6. The main shaft 8 is fixedly connected to a planetary bearing 26 through a connection 29. The planetary bearing 26 is supported by bearings 46 in a housing 11 which in turn is screwed together with bolts 17 and cylindrical disks 15. Two ring gears 27 are supported against cylindrical disks 15 through a bearing lining 28 and connected to a moment yoke 10, so that overload on the torque 36 is transmitted to power absorbers 9 attached to gear foundations 12.

A plurality of planetary wheels 30 are supported in the planetary bearing 26 by shafts 31 and have toothing engagement against the ring gears 27 and a first sun wheel 32 and a second sun wheel 33 which in turn is connected to respectively a first outgoing shaft 34 and a second outgoing shaft 35 concentrically supported on the shaft 8. Incoming torque 36 entering through the flange connection 25 and to the shaft 8 is carried on to the planetary bearing 26 and is distributed equally on parallel planetary wheels 30 which transfer half of the torque to each of the out going shafts 34, 35. With this solution, an incoming, large torque 36 can be distrib uted on two parallel planetary gears, which facilitates transmission of large tor ques.

To collect and distribute the torque evenly from the outgoing shafts 34, 35, a dif ferential 2 is arranged, which consists of a first bevel gear 37 which is coupled to the first outgoing shaft 34 by a spline connection 39, and a second bevel gear 38 which is coupled to the second outgoing shaft 35 by a spline connection 40. A plu rality of sun wheels 41 are supported in shafts 21 which in turn are supported in two case parts 19, 20 which are screwed together with bolts 45. Outgoing torque is transmitted through the shafts 21 to the case parts 19, 20 and further to an out going flange 14.

The shaft 6 is supported in slide bearing elements 53 which in turn rest on bearing elements 52 with a spherical surface 60 against bearing rollers 4 and 5.

Bearing support in spherical surfaces 60 is necessary to avoid unbalanced load on the bearing surfaces at load strain and deformations of the shaft 6 about a centre axis 18 for the shaft 6. Bearing support in spherical surfaces 60 may herein be un derstood as a spherical bearing support.

It should be noted that all embodiments mentioned above illustrate the invention, but do not delimit it, and experts on the area will be able to design many alterna tive embodiments without deviating from the scope of the attached claims. In the claims, the reference numbers in parenthesis shall not be considered delimiting.

The use of the verb "to comprise" and its different forms does not exclude the presence of elements or steps not mentioned in the claims. The indefinite articles "a" or "an" before an element do not exclude the presence of more such elements. The fact that some characteristics are specified in mutually different dependent claims does not indicate that a combination of these characteristics cannot be used advantageously.

The reference to a gear for wind turbines does not in any way delimit the applica tion's scope for use in other contexts.

A gear which is coupled between a wind propeller and for example a generator, is usually located in an elevated nacelle at the top of a pillar.

The gear is needed to transform up the wind turbine's relatively low rotational speed to a rotational speed which is appropriate for a generator.

The gear's dimensions and weight can be considerable, and it is obvious that a re duction of the gear's weight and dimensions will have great impact on costs and embodiments of bearing constructions.

A device for a gear coupled to a shaft supported in bearing pedestals and connect ed to a hub with attachments for the connection of wind turbine blades is provid ed. The gear has an incoming shaft coupled to a planetary bearing and two parallel planetary gears with planetary wheels, ring gear and with sun wheels connected to outgoing shafts coupled to bevel gears engaged with a bevel gear supported in shafts against case parts with connection to an outgoing flange.

More specifically, what is provided is a gear device where an incoming drive shaft in a planetary gear device is coupled to a common planetary bearing for two parallel planetary gears so that the planetary wheels have equal diameter and are engaged with common stationary ring gears. Thereby, an incoming moment can be distrib uted on two planetary gears. Each sun wheel is coupled to its own outgoing shaft concentrically supported about an incoming shaft. The shafts from each sun wheel are coupled to a common outgoing shaft through a differential, so that the load on the sun wheels is distributed evenly. In this case, differential means a device which by means of gears distributes load between two concentric shafts to that outgoing rotational speed and moment exit on only one shaft.

Over time, wear can occur on the gearwheels of the two planetary gears. The wear can be different between the two planetary gears. Therefore, relative and fluctuat ing speed differences may arise between the two outgoing shafts. By the two out going shafts being coupled to the differential, said speed differences and torque may be equalised, and torque from the two shafts may be transmitted to the one outgoing shaft.

To limit large peak moment loads from the wind turbine, the ring gear is supported in such a way that it can rotate in a limited angle and is coupled to a moment yoke with associated moment arms coupled to power absorbers in the form of hydraulic cylinders or coils.

The provided gear with two parallel planetary gears wherein outgoing shafts from the planetary gears are coupled to a differential, may, as the invention describes, provide a significantly increased capacity for torque transmission in relation to di mensions and the number of gearwheels. This is intended herein as the invention being able to provide a gear device which is smaller and lighter than prior art. The shaft is supported by slide bearing elements against bearing elements con nected to bearing pedestals by a spherical surface, known as spherical bearing. Bearing support in spherical surfaces is necessary to avoid unbalanced load on the bearing surfaces at load strain and deformations of the shaft about a centre axis for the shaft.