Patent Description:
In the above described technical field service brakes are used in a yaw drive system of a modern wind turbine. Wind turbines are complex electro-mechanical systems used to generate electricity from wind energy and to supply the generated electricity into an electrical grid. A single wind turbine normally comprises a tower onto which a nacelle and rotor are mounted. The rotor comprises normally a hub and a plurality of blades. The nacelle normally houses components including a frequency converter, a generator, optionally a gearbox, a transformer and a yaw drive system.

Purpose of the yaw drive system is to rotate the nacelle and the rotor, around a tower axis and into the wind, which enables maximum energy extraction from the wind if the rotor axis, by activating the yaw drive system, will be oriented substantially in the direction of the incoming wind. The yaw drive system may also be used to rotate the nacelle and the rotor out of the prevailing wind direction in case of extreme wind speeds and therefore relieve the loads experienced by the wind turbine. The yaw drive system normally comprises a plurality of yaw drives. The yaw drive normally comprises a yaw motor, a yaw motor brake and a yaw drive gearbox with a pinion that may engage with an annular gear fixed either to the nacelle or to the tower. Via a yaw bearing the nacelle can be rotated around the tower axis.

Traditionally, the yaw drive system of a wind turbine may utilize hydraulic disc brakes with a plurality of brake calipers to maintain the desired nacelle position. Additionally, the wind turbine yaw motor brakes may be used to supplement the hydraulic disc brakes and further fix the nacelle position. In the recent wind turbine designs it may be possible to omit the hydraulic disc brakes completely from the wind turbine yaw drive system. In this case, only brakes that are used to maintain the desired nacelle position, are the wind turbine yaw motor brakes. This design change is enabled by increased number of yaw drives in the yaw drive system of wind turbines and increased braking capacity in consequence.

The main technical problem arising from the new wind turbine design with omitted hydraulic brakes, is insufficient braking capacity that may result from the worn-out wind turbine yaw motor brakes. This specific situation may occur, for example, in case of extreme wind events, where the kinetic energy of the wind surpasses the braking capacity of the wind turbine yaw motor brakes and, as a result, the nacelle slides away from the desired nacelle position. During this nacelle sliding event, the wind turbine yaw motor brakes may be worn-out to a degree where they do not provide sufficient braking capacity. Servicing the worn-out yaw motor brakes may then be necessary by service technicians.

Service procedure of the worn-out yaw motor brakes must be performed in a safe manner where any potential danger to service technicians must be minimized. Standard service brakes known in the art might not provide sufficient level of safety because the standard service brake installation may coincide with a potential rotation of the yaw motor shaft. If the standard service brake was activated, it could be propelled from its mounting place and bring an injury to service technicians. Therefore, safety improvement in service brakes is desired.

Prior art systems that have been considered during the patent search and examination procedure are disclosed in the following documents: <CIT>, <CIT>, <CIT> and <CIT>.

This requirement may be met by the subject matter according to the independent claim.

According to the invention it is described a service brake for a wind turbine yaw motor brake, the service brake comprising a brake housing mountable vertically atop the wind turbine yaw motor brake, the brake housing furthermore comprising a brake housing cavity extending axially, in direction of a central axis (a), through the length of the brake housing. Additionally, a brake disc is comprised within the brake housing, the brake disc being rotatable about the central axis (a) in an airgap, preferably between at least two friction plates. A manipulation device, for example embodied as a lever, is connected to the brake housing, the lever, when engaged, is configured to close at least part of the airgap and bring the friction plate(s) in frictional contact with the brake disc. A, preferably removable, centerpiece is arranged, preferably is insertable, within the brake housing cavity along the central axis (a). The centerpiece may comprise a brake disc interface configured to engage with the brake disc and a shaft interface configured to engage with a shaft to be braked. The centerpiece is therefore configurable to transfer braking torque from the brake disc to the shaft to be braked.

The safety improvement feature of the service brake according to the invention, over conventional service brake, reflects in decoupling of the shaft to be braked and the brake disc by means of the centerpiece. During the mounting of the service brake according to the invention, a dangerous possibility that a service technician mounts the activated service brake on the yaw motor brake with the potentially spinning shaft to be braked, is avoided.

In an embodiment, the brake housing may be cylindrical in shape. Preferably this allows to match a shape of the wind turbine yaw motor brake, e.g. for avoiding sharp edges. Additionally, cylindrical shape of the brake housing provides for space-saving in a limited space such as the nacelle.

In another embodiment brake housing may comprise fastening means, preferably bolts, for securing the brake housing to the wind turbine yaw motor brake. This allows stable and reliable connection of the service brake and the wind turbine yaw motor brake.

In an embodiment the brake disc may comprise a central opening with a grooved surface. This enables to have a surface which could be mated with a corresponding opposite surface of another component to transfer torque to the brake disc.

Advantageously, the brake disc interface is an externally grooved spline shaft. A first groove pattern of the spline shaft may correspond to a second groove pattern of the surface of the central opening, such that the spline shaft is receivable by the brake disc by engaging the first groove pattern of the spline shaft with the second groove pattern of the surface of the central opening. Alternatively, the brake disc interface may have a polygonal cross-sectional profile, preferably a sextant cross-sectional profile.

The shaft interface may have a polygonal cross-sectional profile which, in a preferred embodiment is a sextant profile.

The centerpiece of the service brake may comprise a handle for manual insertion of the centerpiece into the brake housing cavity and/or for removal of the centerpiece from the brake housing cavity. The handle may comprise a radial hole for securing the centerpiece on an external support member.

The invention is further directed to a method for applying the service brake, as defined in the previous sections, on a wind turbine yaw motor brake. Steps of mounting the service brake atop the wind turbine yaw motor brake and inserting the centerpiece in the brake housing cavity are comprised in the method. The centerpiece engages with the brake disc by means of the brake disc interface and engages with the shaft to be braked with the shaft interface. Finally, the method comprises a step of engaging the lever in order to close at least part of the airgap and bring the friction plates in frictional contact with the brake disc, thereby transferring braking torque from the brake disc to the shaft to be braked.

Additionally, invention is directed to a method for locking a wind turbine yaw drive system comprising a plurality of wind turbine yaw motor brakes. Method comprises steps of:.

Finally, invention is directed to a method for servicing a wind turbine component, comprising the steps of:.

The invention is described in more detail hereinafter with reference to examples of embodiment but to which the invention is not limited.

The illustrations in the drawings are schematical. Well known elements are indicated in the further text and have not been described in detail.

<FIG> shows a service brake <NUM> that may be mounted atop a wind turbine yaw motor brake <NUM> via a brake housing <NUM>. The wind turbine yaw motor brake <NUM> and a wind turbine yaw motor <NUM> are standard components of a wind turbine yaw drive and will not be discussed in detail herein. The wind turbine yaw drive houses a yaw motor shaft (not shown in <FIG>) which may be referred to as a shaft <NUM> to be braked (not shown in <FIG>). The wind turbine yaw motor brake <NUM> may become worn-out and it may be desirable to mount the service brake <NUM> atop the wind turbine yaw motor brake <NUM> in order to provide additional braking capacity to the wind turbine yaw drive.

The service brake <NUM> comprises the brake housing <NUM> to which a lever <NUM> may be connected. The lever <NUM> may be used to activate or deactivate the service brake <NUM>. <FIG> shows the lever <NUM> in "disengaged" position. This means that an internal brake disc <NUM> (not shown in <FIG>) is in a free-running state and the service brake <NUM> is deactivated. The brake housing <NUM> serves to house internal components of the service brake <NUM>. The brake housing <NUM> may be cylindrical in shape and might match the wind turbine yaw motor brake <NUM> which might also be cylindrical with a diameter of the same size as the brake housing <NUM>.

<FIG> shows the service brake <NUM> in which the lever <NUM> is in "engaged" position. This means that the brake disc <NUM> (not shown in <FIG>) is not in a free-running state anymore i.e. the service brake <NUM> is activated.

Once the service brake <NUM> is mounted, a service technician may insert a centerpiece <NUM> (not shown in <FIG>) which couples the shaft <NUM> to be braked and the service brake <NUM>. By activating the service brake <NUM>, the worn-out wind turbine yaw motor brake <NUM> is bypassed or its braking capacity supported with the service brake <NUM>. The shaft <NUM> to be braked is braked by the service brake <NUM>. To activate the service brake <NUM>, the service technician puts the lever <NUM> in engaged position (<FIG>). To deactivate the service brake <NUM>, the service technician puts the lever <NUM> in disengaged position (<FIG>).

Alternatively, such operation of the lever <NUM> may also be performed by an electrically driven actuator acting upon the lever <NUM>.

<FIG> shows main components of the service brake <NUM>. The service brake <NUM> comprises the brake housing <NUM> to which the lever <NUM> may be connected. The brake housing <NUM> may house the brake disc <NUM> (not shown in <FIG>).

The brake housing <NUM> may be cylindrical in shape but other shapes of the brake housing <NUM> are possible.

The brake housing <NUM> may be mountable vertically atop the wind turbine yaw motor brake <NUM> and may comprise a brake housing cavity <NUM> extending axially, in direction of a central axis (a), through the length of the brake housing <NUM>.

The brake housing <NUM> may be secured to the wind turbine yaw motor brake <NUM> with fastening means <NUM>. In a preferred embodiment the fastening means <NUM> are bolts.

Also seen on <FIG> is the removable centerpiece <NUM> that may be insertable within the brake housing cavity <NUM>, along the central axis (a). The centerpiece <NUM> may be configured to engage with the brake disc <NUM> (shown in <FIG>) and with the shaft <NUM> to be braked and thereby to transfer braking torque from the brake disc <NUM> to the shaft <NUM> to be braked.

<FIG> shows the service brake <NUM> from another view. The brake housing <NUM> may house the brake disc <NUM>. The brake disc <NUM> is rotatable within the brake housing <NUM> about the central axis (a) in an airgap <NUM> between at least two friction plates <NUM> (see <FIG>). The centerpiece <NUM>, as partially shown in <FIG>, is configured to engage with the brake disc <NUM> via a brake disc interface <NUM> (see <FIG>). The brake disc <NUM> may comprise a central opening <NUM> with a grooved surface <NUM> into which the brake disc interface <NUM> of the centerpiece <NUM> may be received.

Bottom section of the centerpiece <NUM>, as seen on <FIG>, may be a shaft interface <NUM>, configured to engage with the shaft <NUM> to be braked. In an embodiment the shaft interface <NUM> of the centerpiece <NUM> may have a polygonal cross-sectional profile. Preferably, the polygonal cross-sectional profile is a sextant profile as also shown in <FIG>. The sextant profile of the shaft interface <NUM> may engage with a corresponding opening of the shaft <NUM> to be braked.

<FIG> shows the removable centerpiece <NUM>. Removable means that it can be manually - or via an actuating tool - inserted into the brake housing cavity <NUM> and/or manually removed from the brake housing cavity <NUM>. The centerpiece <NUM> may comprise the already mentioned brake disc interface <NUM> which may be configured to engage with the brake disc <NUM> (not shown in <FIG>). In a preferred embodiment, the brake disc interface <NUM> is an externally grooved spline shaft <NUM> as shown in <FIG>. The centerpiece <NUM> is insertable into the brake housing cavity <NUM>. A first groove pattern of the spline shaft <NUM> may correspond to a second groove pattern of the surface <NUM> of the central opening <NUM>. Once the centerpiece <NUM> is inserted, the externally grooved spline shaft <NUM> may engage with the central opening <NUM> of the brake disc <NUM>. In this way direct coupling of the brake disc <NUM> and the centerpiece <NUM> is achieved. This interface defined by mating surfaces of the spline shaft <NUM> and the surface <NUM> of the second groove pattern allows the transmission of torque, like breaking torque.

The centerpiece <NUM> may comprise the shaft interface <NUM>, configured to engage with the shaft <NUM> to be braked (not shown in <FIG>). In a preferred embodiment, the shaft interface <NUM> has a polygonal cross-sectional profile. Preferably, the polygonal profile is a sextant profile (shown in <FIG> but which can better be seen in <FIG>). Once the centerpiece <NUM> is inserted within the brake housing cavity <NUM>, the shaft interface <NUM> may engage with the shaft <NUM> to be braked. The shaft interface <NUM> may protrude into the shaft <NUM> to be braked via a cavity present in the shaft <NUM> to be braked. This cavity in the shaft <NUM> to be braked may be have a substantially same cross-sectional profile as the cross-sectional profile of the shaft interface <NUM>.

The centerpiece <NUM> may comprise a handle <NUM>. The handle <NUM> may be used for manual insertion and/or removal of the centerpiece <NUM> into or from the brake housing cavity <NUM>. The handle <NUM> may, in an embodiment, comprise a hole <NUM> for securing the centerpiece <NUM> on an external support member <NUM>, for example via a pin <NUM> (see <FIG>). The external support member <NUM> may rest on top side of the brake housing <NUM>. The top side of the brake housing <NUM> is the side facing away from the wind turbine yaw motor <NUM>. The centerpiece <NUM> may be secured on the external support member <NUM> in a way that the handle <NUM> protrudes outwards of the brake housing cavity <NUM>. Term outwards may be understood as, for example, along the central axis (a) in the direction facing away from the wind turbine yaw motor <NUM>. By removing the pin and releasing the handle <NUM>, the centerpiece <NUM> may be inserted into the brake housing cavity <NUM>.

The centerpiece <NUM> may be configured to engage with the brake disc <NUM> via the brake disc interface <NUM>. The centerpiece <NUM> may also engage with the shaft <NUM> to be braked via the shaft interface <NUM>. In this way direct coupling between the shaft <NUM> to be braked and the brake disc <NUM> may be achieved. If the service brake <NUM> is deactivated, any rotation of the shaft <NUM> to be braked is directly translated to the centerpiece <NUM> and in turn to the free-running brake disc <NUM>. If the service brake <NUM> is activated, braking torque from the brake disc <NUM> is transferred to the shaft <NUM> to be braked.

<FIG> shows the service brake <NUM> mounted vertically atop the wind turbine yaw motor brake <NUM>. The brake housing <NUM> comprises the brake housing cavity <NUM> which extends axially through the length of the brake housing <NUM> and in the direction - i.e. coaxially - of the central axis (a). The service brake <NUM> comprises the brake disc <NUM> within the brake housing <NUM>. The brake disc <NUM> is rotatable about the central axis (a) in a surrounding airgap <NUM>, between at least two friction plates <NUM>. The friction plates <NUM> may be comprised in the brake housing <NUM>.

The brake disc <NUM> may be free-running if the service brake is deactivated. The shaft <NUM> to be braked, as shown in <FIG>, is decoupled from the brake disc <NUM> of the service brake <NUM> because the centerpiece <NUM> is not inserted in the brake housing cavity <NUM>. This decoupling of the shaft <NUM> to be braked and the brake disc <NUM> is a safety feature of the service brake <NUM>. This ensures that mounting of the activated service brake <NUM> on the yaw motor brake <NUM>, even with the potentially spinning shaft <NUM> to be braked, does not result in propelling of the service brake <NUM>. There is clearly no torque transfer from the shaft <NUM> to be braked to the brake disc <NUM> because of the absence of the centerpiece <NUM> that would provide the necessary coupling. Only when the centerpiece <NUM> is inserted into the brake housing cavity <NUM>, by the service technician, does the coupling between the brake disc <NUM> and the shaft <NUM> to be braked exist. This safety feature minimizes the risk that the service brake <NUM> may be propelled within the nacelle because of the potentially spinning shaft <NUM> to be braked.

<FIG> shows the service brake <NUM> positioned vertically atop the wind turbine yaw motor brake <NUM> wherein the centerpiece <NUM> is inserted within the brake housing cavity <NUM>, engaging both with the brake disc <NUM> and the shaft <NUM> to be braked. In this state, the centerpiece <NUM> may serve as a coupling means between the shaft <NUM> to be braked and the brake disc <NUM>. In the deactivated state of the service brake <NUM>, any rotation of the shaft <NUM> to be braked translates directly to rotation of the brake disc <NUM>, via the centerpiece <NUM>. In the activated state of the service brake <NUM>, braking torque of the brake disc <NUM>, via the centerpiece <NUM>, is transferred to braking of the shaft <NUM> to be braked.

<FIG> shows the service brake <NUM> with the centerpiece <NUM> inserted in the brake housing cavity <NUM>, engaging both with the brake disc <NUM> and the shaft <NUM> to be braked. Furthermore, the lever <NUM> is shown to be in engaged position. This means that the service brake <NUM> is activated. The lever <NUM> may be brought to engaged position by the service technician in order to activate the service brake <NUM>. By placing the lever <NUM> in engaged position as indicated in <FIG>, at least a part of the airgap <NUM> is closed and the friction plates <NUM> are brought in frictional contact with the brake disc <NUM>. The brake disc <NUM> may now transmit braking torque to the shaft <NUM> to be braked, via the centerpiece <NUM>. The service brake <NUM> may in this way bypass the wind turbine yaw motor brake <NUM>. Spring mechanism of the service brake <NUM> causing this frictional contact is not considered as part of the invention and is not discussed in detail. Several state-of-art braking mechanisms are known to person skilled-in-the-art.

In certain conditions of the wind turbine operation, plurality of the wind turbine yaw motor brakes <NUM>, comprised in a wind turbine yaw drive system, may become worn-out. This situation may occur for example due to extreme wind load on the wind turbine. In such scenarios there may be a need to lock the complete wind turbine yaw drive system to enable safe repair of a wind turbine component. The wind turbine component may preferably be the worn-out wind turbine yaw motor brake <NUM> or other component inside the wind turbine.

Method for locking the wind turbine yaw drive system which may comprise a plurality of wind turbine yaw motor brakes <NUM>, may include a step of mounting a plurality of service brakes <NUM> atop the plurality of wind turbine yaw motor brakes <NUM>. Each of the plurality of service brakes <NUM> may comprise already described components.

During the mounting process, regardless of state of the plurality of brakes <NUM> being activated or deactivated, there is no danger of any one service brake <NUM> of the plurality of service brakes <NUM> being potentially propelled in case one or more of a plurality of shafts <NUM> to be braked are spinning. This is because, in the plurality of service brakes <NUM>, there is no torque transfer from the respective brake discs <NUM> towards the respective shafts <NUM> to be braked before respective centerpieces <NUM> are inserted in the respective brake housing cavities <NUM>.

Once the mounting step is completed, the centerpieces <NUM> of each of the service brakes <NUM> may be inserted in the respective brake housing cavities <NUM>. Afterwards, the service technician may bring the lever <NUM> of the service brake <NUM> of each of the plurality of service brakes <NUM> in engaged position. The wind turbine yaw drive system may, in this way, be safely locked.

The number of the plurality of mounted service brakes <NUM> may correspond to the number of wind turbine yaw motor brakes <NUM> present in the wind turbine. This provides for a safe environment for service technicians performing inspection or service operations on the wind turbine component.

The number of the plurality of mounted service brakes <NUM> may be less than the number of wind turbine yaw motor brakes <NUM> present in the wind turbine. This also may provide for a safe environment for service technicians to perform service operation on the wind turbine component. The wind turbine component may preferably be a further wind turbine yaw motor brake <NUM>. The further wind turbine yaw motor brake may be free of the service brake <NUM>, i.e. the service brake <NUM> may not be installed on the further wind turbine yaw motor brake <NUM>.

For example, the wind turbine yaw drive system may comprise five to twenty, preferably eight to twelve, for example ten wind turbine yaw motor brakes <NUM> in total and all may become worn-out. The service technician may mount, in an exemplary system of ten wind turbine yaw motor brakes <NUM>, nine service brakes <NUM> atop nine worn-out wind turbine yaw motor brakes <NUM> and leave preferably one yaw motor brake <NUM> without the service brake <NUM>, i.e. the further wind turbine yaw motor brake <NUM>. Then, the service technician may perform service operation on the further wind turbine yaw motor brake <NUM>, onto which the service brake <NUM> is not mounted. In this way a sufficient braking capacity may be achieved which may safely hold the complete wind turbine yaw drive system braked while allowing for simultaneous service operation. In the mentioned example, it may also be possible to achieve similar results with mounting even fewer service brakes <NUM>.

Preferably, for X number of wind turbine yaw motor brakes, X-<NUM> number of service brakes <NUM> may be applied to enable servicing of the remaining wind turbine yaw motor brakes. More generally, X number of wind turbine yaw motor brakes are present in the wind turbine, X-N number of service brakes <NUM> may be applied to enable serving of the remaining number of N wind turbine yaw motor brakes.

Claim 1:
Service brake (<NUM>) for a wind turbine yaw motor brake (<NUM>), the service brake (<NUM>) comprising:
a brake housing (<NUM>) mountable vertically atop the wind turbine yaw motor brake (<NUM>), the brake housing (<NUM>) comprising a brake housing cavity (<NUM>) extending axially, in direction of a central axis (a), through a length of the brake housing (<NUM>);
a brake disc (<NUM>) within the brake housing (<NUM>), the brake disc (<NUM>) being rotatable about the central axis (a) in an airgap (<NUM>);
at least one friction plate (<NUM>) arranged within the brake disc housing (<NUM>) for providing a frictional contact with the brake disc (<NUM>);
a manipulation device connected to the brake housing (<NUM>), the manipulation device, when engaged, configured to bring the friction plate (<NUM>) in frictional contact with the brake disc (<NUM>); and
a centerpiece (<NUM>) comprising a brake disc interface (<NUM>) configured to engage with the brake disc (<NUM>), and a shaft interface (<NUM>) configured to engage with a shaft (<NUM>) to be braked, configurable to transfer braking torque from the brake disc (<NUM>) to the shaft (<NUM>) to be braked.