WIND TURBINE AND BEARING ARRANGEMENT THEREFOR

A bearing arrangement for a wind turbine includes a bearing and a bearing housing. The bearing housing defines an interior space wherein the bearing is accommodated. A discharge opening is provided for discharging lubricant from the interior space. A pipe system includes a fluidic connection with the discharge opening. The pipe system includes a first part inclining upwardly to a predetermined height relative to the discharge opening to throttle a lubricant flow out of the interior space.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority of European patent application no. 23174821.1, filed May 23, 2023, the entire content of which is incorporated herein by reference.

TECHNICAL FIELD

The disclosure relates to a bearing arrangement for a wind turbine, in particular to a rotor bearing arrangement. The disclosure further relates to a wind turbine, in particular to a wind turbine which includes a bearing arrangement as described herein.

BACKGROUND

A wind turbine may include a rotor that includes a rotatable rotor assembly having multiple rotor blades. The rotor blades transform wind energy into a drive torque that drives the generator via a drive train.

SUMMARY

It is an object of the disclosure to provide a bearing arrangement which provides a reliable operation. It is a further object of the disclosure to provide a wind turbine exhibiting a reliable operation.

Embodiments of the disclosure provide a bearing arrangement for a wind turbine. The bearing arrangement includes a bearing. The bearing arrangement includes a bearing housing. The bearing housing houses an interior space in which the bearing is arranged. The bearing arrangement includes an opening configured to discharge lubricant from the interior surface.

The bearing arrangement includes a pipe system. The pipe system includes a fluidic connection with the opening. The pipe system includes a first part. The first part inclines upwards to a predetermined height relative to the opening to throttle a lubricant flow out of the interior space.

For example, the bearing arrangement is a rotor bearing arrangement of a wind turbine. In an embodiment, the rotor bearing arrangement may correspond to both the rotor side bearing and the gearbox side bearing. The bearing arrangement, and in particular the bearing, is for example lubricated with grease or another lubricant, like an oil. It is important to contain a desired amount of lubricant inside the bearing housing in the interior space. An insufficient amount of lubricant in the bearing leads to higher wear and premature failure. On the other hand, high splashing losses lead to temperature increase and therefore reduce base viscosity which leads to lower film thickness, and eventually to premature failure. Thus, it is important to ensure sufficient lubrication and to avoid lubricant starvation and to keep splashing losses low. An uncontrolled lubricant leakage should be avoided, in particular a leakage through a sealing of the bearing arrangement. Therefore, the opening is provided to allow a controlled draining and discharging of the lubricant.

The pipe system with the first part that inclines upwards acts like a choke or a throttle to dampen, limit or control the outflow of the lubricant. During operation, the lubricant loses its momentum and/or energy as it flows through the first part. The inclining first part leads to a higher friction resistance to the flow of the lubricant, in particular due to at least one of the geodetic height to be overcome and the length of the first part, among other characteristics of the pipe system. Thus, the pipe system with the first part that inclines upwards allows an outflow of the lubricant in a controlled manner, wherein an undesirably high outflow of lubricant can be avoided. The amount of lubricant inside the bearing can be reliably kept within given thresholds. In particular, the predetermined height is predetermined dependent on, but not limited to the given thresholds, overall dimensions of the bearing housing, and/or an angle of inclination of the first part.

The bearing arrangement makes a lubricant level up to 100% possible in the bearing housing. Insufficient lubrication of the bearing can be reliably avoided. The arrangement of the pipe system with the first part inclining upwards functions as an overflow and/or pressure relief valve. For example, if lubricant is added even though the interior space is already 100% full, excess lubricant flows out through the pipe system. The pipe system can be easily and reliably retrofitted to existing bearings and configurations without costly reconfiguration. The need for expensive conversion parts can be avoided.

According to an embodiment, the bearing housing may include the opening. The opening is configured to drain lubricant from the interior space. The opening reaches from the interior space through the bearing housing, in particular a bearing cover, to the outside of the bearing housing. The pipe system is arranged outside of the interior surface. The pipe system is arranged outside of the bearing housing. Lubricant from the interior space flows through the opening first before it enters the pipe system located outside of the bearing housing.

After flowing through the opening, the lubricant is guided in the pipe system outside the bearing housing. This enables an easy retrofitting of the pipe system to the existing bearings to effect discharge of the lubricant when required. Furthermore, installation space can be used efficiently. In the embodiment according to which the pipe system is arranged outside the bearing housing, there is no requirement to access or arrange parts inside the interior space. Thus, the functionality and configuration of the interior space with the bearing does not need to be changed. The bearing housing is provided with the opening extending from the interior space to the outside of the bearing housing, such that the pipe system is fluidically connected to the opening outside of the bearing housing.

According to an embodiment, the pipe system includes the opening. The opening is formed, for example, as an inlet opening of the pipe system. For example, the pipe system is arranged inside the bearing housing, in particular in the interior space, such that the opening in the pipe system comes in fluid communication with the interior space. The lubricant being circulated enters the pipe system through the opening and is guided through a part or portion of the pipe system located inside the interior space. Further, the bearing arrangement includes a second opening. The second opening is configured for letting lubricant out of the interior space to the external environment of the bearing. In particular, the second opening is arranged at the predetermined height, for example, above the first opening. In an embodiment, the opening and the first part are arranged inside the interior space. The first part inclines upwards in the interior space up to the second opening, which reaches through the bearing housing, in particular the bearing cover, from the interior space to the outside of the bearing housing. The lubricant exits the interior space through the second opening after it has been guided through the inclining first part inside the interior space.

The arrangement of the opening and the first part inside the interior space allows for a placement of the first part inside existing dead space of the interior space. Thus, no additional installation space for the first part is necessary outside the bearing housing. Furthermore, the first part inside the interior space reduces dead space and this leads to better lubrication.

According to an embodiment, the pipe system includes a second part. The second part is inclined downwards and includes an outlet port. The second part is fluidically connected to the first part, the first part located either inside or outside the bearing housing. Lubricant is releasable through the outlet port, for example into a collection container. Lubricant which enters the first part through the opening can be reliably transferred to the second part. From the second part the lubricant can be reliably guided to the collection container via the outlet port. This increases flexibility for the arrangement of the collection container, for example at a distance from the bearing housing.

According to an embodiment, each of the first part and the second part includes a hose. For example, the hose of the first part is fluidically connected to the opening outside of the bearing housing. The hose is flexible, for example. This allows freedom for the arrangement of the pipe system relative to the bearing housing.

According to an embodiment, the first part includes a smaller diameter than the second part. This allows a flow characteristic in the first part that is different than in the second part. In an embodiment, the flow characteristic may be, but not limited to pressure and momentum of the lubricant during the flow. Thus, a suction effect of the lubricant present in the second part on the lubricant present in the first part due to the downward inclination of the second part can be reduced or avoided. The throttle and/or choke effect for the lubricant is realized mainly by the first part. The second part realizes a guidance of the lubricant to the collection container.

According to an embodiment, the second part includes an open drain channel instead of a hose. Thus, the suction effect can be completely avoided.

According to an embodiment, the outlet port is arranged above the opening. In particular, the outlet port is arranged above the opening along a vertical direction. The arrangement of the outlet port above the opening leads to a reduction or avoidance of the suction effect.

According to an embodiment, the pipe system includes a transition part. The transition part connects the first part and the second part at the predetermined height. For example, the transition part is arranged outside of the bearing housing. This particularly applies if the pipe system, and in particular the first part, is arranged outside of the bearing housing.

If the first part is arranged inside the interior space, the transition part for example leads through the bearing housing to the second part, which is arranged outside of the bearing housing. For example, the transition part is at least partly realized by the second opening.

According to an embodiment, the pipe system includes a valve, in particular a breather valve disposed at the transition part. Alternatively, or in addition a throttle valve may be disposed at the transition part to throttle grease flow out of the opening and in turn, from the interior space. The pipe system can be vented in a controlled manner by the use of the breather valve. The throttle valve allows for additional controlled throttling of the lubricant flow through the pipe system.

According to an embodiment, the bearing arrangement includes a control unit which is operatively coupled to at least one of the valves. For example, the control unit is additionally operatively coupled to one or more sensors. The control unit, for example, includes at least one processor and memory storage. The control unit is configured to send operation information and instructions to the valve, for example to set the valves as desired depending on outside conditions.

According to an embodiment, the bearing arrangement includes a thermal control module for regulating the temperature of the pipe system. For example, the thermal control module is an active control module which is operatively coupled to the control unit, such that the control unit can control the thermal control module. For example, the thermal control module is configured to heat and/or cool the pipe system such that lubricant inside the pipe system is heated and/or cooled.

For example, the thermal control module includes an insulation for insulating the pipe system such that an interior of the pipe system can be kept at a different temperature than the outside, for example warmer than the outside or colder than the outside. Alternatively, or in addition, the thermal control module includes a heater for heating the pipe system. Alternatively, or in addition, the thermal control module includes a cooler for cooling the pipe system.

The thermal control module allows control of the temperature of the pipe system depending on external environmental conditions in order to maintain at least one of a desired density, viscosity and/or other properties of the lubricant inside the pipe system.

According to an embodiment, an interior surface of at least a portion of the pipe system includes a predetermined coefficient of friction and/or predetermined roughness to throttle grease flow out of the opening. For example, at least one protrusion and/or a coating is provided on the interior surface to provide the desired roughness and friction. A desired resistance, damping effect and throttle of the lubricant flow can be realized with the pipe system. For example, the first part includes a different coefficient of friction and/or predetermined roughness than the second part. For example, the friction and/or roughness of the interior surface of the first part is greater than that of the second part.

According to an embodiment, the bearing housing has a vertical height such that the predetermined height is at least one eighth of the vertical height of the bearing housing. In an embodiment, the opening is located at a lower hemispherical portion of the bearing housing and the vertical height is arranged at a higher hemispherical portion of the bearing housing. Other heights of the predetermined height are possible, for example from one eighth of the vertical height of the bearing housing to a top of the interior space. It is possible that the predetermined height is at the top of the interior space, such that the interior space is completely filled with lubricant. According to other embodiments, the predetermined height is pre-set so that the interior space is more than 50% filled with lubricant, for example more than 60%, more than 70% or more than 75%.

According to an embodiment, the opening is located at a lower hemispherical portion of the bearing housing. The first part, for example, reaches from the lower hemispherical portion to the upper hemispherical portion, such that the predetermined height is for example equal to or above the center of the bearing. According to a further embodiment, the pipe system is completely arranged in the lower hemispherical portion such that the predetermined height is equal to or below the center of the bearing.

Further embodiments of the disclosure provide a wind turbine, wherein the wind turbine includes a nacelle. The wind turbine includes a bearing arrangement according to one of the described embodiments. The bearing arrangement is arranged within the nacelle.

DETAILED DESCRIPTION

As shown inFIG.1, a wind turbine100includes a tower102. The tower102is connected to a foundation104fixed on ground. The foundation104is formed in and supported by the ground. A nacelle106is arranged on a top end of the tower102opposite to the foundation104. The nacelle106houses the drive train, among other components and sub-assemblies. Inside the nacelle106, for example, a generator is arranged which is connected via the drive train to a rotor108. The drive train includes, for example, a gearbox and a rotor shaft105(FIG.3). The rotor108includes several rotor blades110. The rotor blades110are mounted on a rotor hub112. The rotor hub112is connected to the rotor shaft105.

The rotor108is driven in operation by an airflow, for example wind. The rotational movement of the rotor108is transmitted via the drive train to the generator. The generator converts the mechanical output of the rotor108into electrical energy.

The wind turbine100includes a bearing arrangement200. According to the shown embodiments the bearing arrangement200is a rotor bearing arrangement. The rotor shaft105is rotatably supported by the bearing arrangement200. In an embodiment, the rotor bearing arrangement200may correspond to both the rotor side bearing arrangement and the gearbox side bearing arrangement, supporting the shaft105at the rotor side and the gearbox side, respectively.

FIG.2shows a bearing arrangement200according to an embodiment. The bearing arrangement200includes a bearing housing201. The bearing housing201defines an interior space203. A bearing204is located in the interior space203. The interior space203may receive a lubricant, including, but not limited to grease and a lubricating oil from a lubricant source.

The bearing204includes an inner ring, an outer ring and rolling elements205which enable the relative rotation between the inner ring and the outer ring. The inner ring may be connected to the shaft105and the outer ring may be connected to the bearing housing201.

The interior space203is sealed by a bearing cover202on the front side and/or on the rear side of the bearing housing201during operation, wherein the front side corresponds, for example, to a side facing or proximal to the gearbox (not explicitly shown) and the rear side corresponds, for example, to the side opposite to or distant from the gearbox. According to a further example, the front side corresponds to a side facing or proximal to the rotor108and the rear side corresponds, for example, to the side opposite to or distant from the rotor108.

The bearing housing201, and in particular the bearing cover202, includes an opening206. The opening206, which may be a drain hole defined in the bearing housing, provides a passage through the bearing housing201. The opening206, in particular, may be arranged in a lower half of the bearing housing201which is next to a bottom224of the interior space203. In an embodiment, the opening206may serve as a passageway between the bearing interior space203and the bearing exterior. According to further embodiments, the opening206is arranged inside the interior space203, as for example shown inFIGS.11and13.

The lubricant300is provided in the interior space203for lubricating the bearing204and in particular the rolling elements205. The lubricant300in particular includes grease.

The lubricant300is provided in the interior space203with a desired lubricant level301(FIG.3). In particular, the desired lubricant level301reaches an upper hemispherical part209of the bearing housing201, which is arranged between the center and the top225.

Old or dirty lubricant300can be drained via the opening206out of the interior space203. Alternatively or in addition, if too much lubricant300is present in the interior space203, this lubricant300can be released through the opening206in a controlled manner. With the opening206, which can also be referred to as “drain hole206”, uncontrolled outflow of the lubricant300out of the interior space203is avoidable according to embodiments of the disclosure. Further, it can be ensured that a sufficient amount of lubricant300is maintained inside the interior space203by a pipe system210which provides a resistive effect, limiting effect or damping effect, thereby throttling the lubricant flow, which will be explained in more detail below.

FIG.3shows a first example of the bearing arrangement200with the pipe system210. The bearing cover202includes the opening206in a lower hemispherical portion223of the bearing housing201. In particular, the opening206is arranged near a bottom224of the interior space203. The opening206provides a passageway between the interior space203and the outside227of the bearing housing201. The opening206is arranged in advance of the opening206in a direction of rotation101of the shaft105.

The pipe system210includes a first part212. The first part212, for example, includes a hose, in particular an upwards directed hose216. An inlet230of the pipe system210and in particular of the first part212includes fluidic connection211with the opening206. Thus, the lubricant300can get into the first part212through the opening206. In other words, the opening206discharges or directs the lubricant from the interior space203into the first part212.

As shown, the first part212is inclined upwards up to a predetermined height207relative to the opening206, measured along a vertical height of the bearing. In an embodiment, the first part212extends above the opening206up to the predetermined height207, say up to 50% or higher of the overall height of the bearing housing201.

At the predetermined height207, the pipe system210includes a transition part218. In particular, the first part212may undergo a transition, including but not limited to a bend. The transition part218includes, for example, a horizontal part effecting the bend. The transition part218, for example, may be a continuous part, in particular a single-piece component. According to further examples, the bended part218includes a multi-pieced connection where the transition part218is a separate element adjoining or connected to the first part212. The transition part218can include a U-shape, can from a 180° bend, a 120° bend or a 90° bend or any other bend between 10° and 270°. As shown inFIGS.3and8, the transition part218may form a hairpin bend with the first part212. Throughout the description, the transition part218may be interchangeably referred to as “bended part218”.

The transition part218, for example, is arranged at a region around a center of the bearing204or above the center of the bearing204along a vertical direction Z. The bended part218is arranged beside the shaft105along a horizontal direction which is perpendicular to the vertical direction Z. The bearing housing201includes a vertical height208along the vertical direction Z. The bended part218is arranged in a middle region of the vertical height208. For example, the bended part218is arranged at an intersection of the lower hemispherical portion223and the upper hemispherical portion209. Alternatively, the bended part218is arranged in the upper hemispherical portion209adjacent to the lower hemispherical portion223along the vertical direction Z. This way, the geodetic height of the bended part218is higher than the opening206which resists upward flow of the lubricant inside the first part212during the rotation of the shaft105and the200bearing. The first part212, which may be the flexible hose216, may be clamped along a circumference or periphery of the bearing cover202as illustrated inFIG.5.

The pipe system210includes a second part213which is arranged subsequently to the bended part218. The second part213, for example, includes a downwards directed hose215which adjoins the first part212via the bended part218. The downwards hose215extends from the bended part218downwards along the vertical direction Z to terminate at an outlet port214. The outlet port214is the exit of the pipe system210and is, for example, part of the second part213. In an embodiment, the outlet port214may be above or below or at same level as of the opening206considered along a vertical direction Z.

The downwards hose215and the upwards hose216are each flexible such that they for example constitute the bended part218to reverse the direction of the lubricant flow.

During operation, the lubricant300exits the interior space203and enters the pipe system210via the opening206. The lubricant300loses its momentum and/or energy while it flows from the opening206upwards in the first part212. Thus, the upwards directed first part212acts as a damper and/or throttle to resist the outflow of the lubricant300out of the interior space203.

If the lubricant300reaches the predetermined height207and the bended part218, which is arranged above the opening206and the inlet230, the lubricant300exits the first part212through the bended part218and subsequently, the second part213. The lubricant flows from the first part212to the second part213through the bended part218.

The second part213, and in particular the outlet port214, is in fluidic communication with a collection container226(FIG.6). The collection container226is provided for collecting lubricant300which gets drained out of the interior space203via the pipe system210.

The pipe system210with the upwardly inclining first part212allows a desired amount of lubricant300to fill or accumulate inside the bearing housing201in the interior space203, for example up to a desired lubricant level301. This way, the pipe system210facilitates maintaining of sufficient level of lubricant inside the bearing housing201. The pipe system210therefore helps to avoid lubrication starvation and to keep splashing losses low. An uncontrolled lubricant leakage out of the interior space can be avoided by the upwardly extending first part212. In particular, an undesired leakage through a sealing235(FIG.12) of the bearing arrangement200in case of sealing malfunction or failure can be minimized. The pipe system210is provided to allow a controlled draining of the lubricant300. In an embodiment, the upwardly inclining first part212facilitates the presence of sufficient lubricant300up to the lubricant level301in the upper hemispherical portion209of the housing201.

A higher lubricant level in the rotor bearing housing201has been shown to result in more lubricant300that is available in the load zone of the roller bearing204.

For example, consider the pipe system210attached on the gearbox side of the bearing housing201.

As shown inFIGS.4and5, at the opening206a nozzle234with, for example, a 90° pipe angle, like an elbow, is connected. For example, the first part212may extend approximately a quarter circle upwards towards the centerline of the shaft105, where the first part212is transitioned by the bended part218, which for example includes a 180° pipe bend. The second part213transitioning from the first part212is led back, for example, parallel or substantially parallel to the first part212towards the vicinity of the nozzle. Thus, the pipe system210is for example comparable to a siphon.

The second part212, for example, does not end significantly below the opening206, so that a possible suction effect, which can lead to undesired removal or drain of lubricant out of the rotor bearing housing, is prevented. However, the lubricant300which escapes out of the outlet port214falls into the collection container226positioned below the outlet port214. The operating principle is based, without being limited to it, on the fact that the hose routing increases the pipe friction resistance due to the geodetic height (to be overcome) and the length of the hoses215,216. This allows the lubricant level301in the rotor bearing housing201to be increased by up to 100%. Other factors such as hose diameter, length, et cetera, influence the extent of throttling of the lubricant. For example, longer hoses tend to increase the suction effect resulting in undesired removal or drain of lubricant out of the interior203by the pipe system210, compared to shorter hoses.

For example, the nozzle, which is connected to the opening206, includes a T-piece with two outlets. The first part212is mounted on a first one of the outlets of the T-piece. The second outlet of the T-piece allows grease exchange (drain only or active flushing) and is plugged with a drain valve or cap during normal operation.

FIG.4shows an example of the pipe system210in which the transition part218is provided as a separate element which is connected to the upwards hose216and the downwards hose215. For example, the hoses215,216are each flexible and the transition part218is rigid. Alternatively, the upward hose216, the transition part218and the downwards hose are formed from a single hose, which is bent at the predetermined height207, as shown inFIG.3.

As shown inFIG.5, the second part213can be omitted. The first part212with the upwards hose216extends upwards from a region around the bottom224. The upwards hose216is connected to the bearing housing201via the fluidic connection211at the opening206. The upwards hose216is arranged at the lower hemispherical portion223. The bended part218, which forms an upper end of the upwards hose216, is arranged next to the upper hemispherical portion209. According to further embodiments, the bended part218is arranged in the upper hemispherical portion209. The arrangement may allow a free fall draining of the lubricant from the bended part218.

FIG.6shows the pipe system210according to a further embodiment. Instead of the downwards hose215ofFIG.3, the second part213according toFIG.6includes a drain channel217. In particular, the drain channel217is an open channel which is not closed radially. In other words, the drain channel217may not adjoin the bended part218along the entire circumference of the bended part218. During operation, the lubricant300exits the bended part218and, for example, drops on and into the drain channel217, for instance, like a free fall. The drain channel217guides the lubricant300to the collection container226. The outlet port214is part of the drain channel217. The drain channel217is inclined upwards from a first end facing the bended part218towards a second end facing the collection container226.

The open drain channel217helps to avoid or mitigate suction effects that may result from lubricant300flowing downwards in the second part213in a closed pipe or hose. Furthermore, because the transition between the bended part218and the drain channel217is not fluid-tight, the pipe system210does not have to be separately vented.

FIG.7shows the pipe system210with the open drain channel217in a further view. The transition part218is provided as a separate element which is connected to the upwards hose216. For example, the hose216is flexible and the transition part218is rigid. Alternatively, the upward hose216and the transition part218are formed from a single hose, which is bent at the predetermined height207, as shown inFIG.6.

FIG.8shows the pipe system210according to a further embodiment. The pipe system210optionally includes a breather valve219. Further, the pipe system210optionally includes a throttle valve220. Further, the pipe system210optionally includes a thermal control module222. It is possible to have just one or more of the breather valve219, the throttle valve220, and the thermal control module222. Furthermore, other sensors and/or valves may be included by the pipe system210.

The breather valve219, the throttle valve220, and/or the thermal control module222may also be included by the pipe system210according to the other embodiments shown in the other figures and described herein. Different combinations of the pipe system210, the first part212, the second part213and the valves and modules219,220,222are possible.

The breather valve219is arranged at the bended part218to allow venting of the pipe system210, in particular, for the embodiment in which the second part213includes a radially closed downward hose215. Alternately, the breather valve219may also be provided in the transition part218when the transition part218is a distinct element which couples the first part212and the second part213, both being separate hoses, as for example shown inFIG.4. The bended part218is arranged above the first part212and the second part213and therefore air, which is trapped in the pipe system210, accumulates in the bended part218. The breather valve219helps to deflate the air out of the pipe system210.

The throttle valve220provides an additional damping and throttle effect to the pipe system210. In particular, the throttle valve220helps to avoid a suction effect which could be caused by the lubricant300which flows down the second part213. An unwanted suction of the lubricant300out of the interior space203can be avoided with the help of the throttle valve220. For example, the throttle valve220is an adjustable valve, the resistance of which can be changed. According to a further embodiment, the throttle valve220is a valve with a fixed cross-section.

The thermal control module222, for example, includes at least one of a passive thermal insulation, an electrical heating, and an electrical cooling. The thermal control module222is arranged for controlling the temperature inside the pipe system210, in particular, the temperature of the lubricant300in the pipe system210. By controlling the temperature, a desired viscosity and/or other properties of the lubricant300can be realized. Thus, a flow resistance can be kept constant over a wide temperature range and the overflow functionality is preserved even at low nacelle temperatures.

The bearing arrangement200, for example, includes a control unit236to control the breather valve219, the throttle valve220and/or the thermal control module222. For example, the control unit236is connected to other valves and/or sensors. Environmental information, such as environmental temperature, can be determined and the control unit236is configured to control the valves219,220and/or the thermal control module222dependent on the environmental information.

FIG.9shows a schematic detail of the downwards hose215and/or the upwards hose216. An interior surface221of the downwards hose215and/or the upwards hose216includes a given and predetermined coefficient of friction and/or a given and predetermined roughness to obtain a desired throttle of the grease flow in the downwards hose215and/or upwards hose216.

The dimensions of the pipe system210, such as diameters, length, coefficient of friction and/or roughness of the interior surface221, are selected to obtain a desired throttle and damping effect of the pipe system210to throttle a flow of the lubricant300out of the opening206.

FIG.10shows the pipe system210according to a further embodiment. Instead of the downwards hose215and the upwards hose216, the first part212according toFIG.10includes an upward pipe228and the second part213includes a downward pipe229. Pipes228,229and hoses215,216can also be used together with each other as a combination of hoses and pipes. The upwards pipe228and the downwards pipe229are rigid and not flexible.

For example, a diameter or cross-section of the downwards pipe229is larger than the diameter or cross-section of the upwards pipe228. Thus, suction effect effected by lubricant300flowing down the downwards pipe229can be avoided.

According to further embodiments, the diameter or cross-section of the upwards pipe228and of the downwards pipe229are equal.

As shown inFIG.10, a transition between the bended part218and the downwards pipe229may be open, such that for example no additional venting is needed. The transition between the bended part218and the downwards pipe229is tightly closed according to further embodiments (not explicitly shown). For example, an additional breather valve219is arranged in such embodiments at the bended part218.

FIGS.11to14show the pipe system210according to a further embodiment. Differently to the embodiments according toFIGS.2to10, the pipe system201, in particular the first part212, is arranged at least partly inside the interior space203. As shown inFIGS.11to14, the first part212is completely arranged and positioned inside the interior space203of the bearing housing201.

The bearing cover202includes an inward facing side233. The inward facing side233faces the bearing204and the rolling elements205.

The first part212is arranged on the inward facing side233of the bearing cover202. For example, the first part212includes a rectangular pipe or tube in section. It is also possible that the first part212inside the interior space203includes a flexible hose or a round rigid tube or pipe.

The first part212includes the opening206through which lubricant300enters the first part212. The opening206is part of the pipe system210and in particular of the first part212. The opening206does not reach through the bearing cover202as in the other embodiments shown inFIGS.2to10. In particular, the opening206and the inlet230are formed by a single, common inlet to the first part212.

For example, the first part212is made of a metal and welded to the bearing cover202. Other types of fastening are also possible, such as screwing or gluing. The first part212can also be made of other materials, for example, plastic. A mixture of different materials is also possible. The first part212can be flexible or rigid. A mixture of flexible sections and rigid sections is also possible.

The lubricant300enters the first part212inside the bearing housing201in the interior space203. The lubricant300flows along the inclining or upwardly extending first part212up to the predetermined height207in the interior space203.

At the predetermined height207, a second opening232is arranged. The second opening232provides a passage through the bearing housing201and in particular through the bearing cover202. The second opening232may serve as a passageway between the bearing interior space203and the outside227.

For example, the second part223is fluidically connected to the second opening232at the outside227outside of the bearing housing201.

Old or dirty lubricant can be drained via the opening206into the pipe system210. After flowing through the opening206, the lubricant300then first flows in the first part212inside the interior space203, then exits the bearing housing201and the interior space203at the bended part218through the second opening232. Subsequently, the lubricant300can be guided to the collection container226, for example by the downwards inclined second part213, which is not explicitly shown inFIGS.11to14.

The bearing cover202includes an aperture231which is blocked during normal operation. If the bearing204is to be completely emptied and all lubricant300is to be removed, the aperture231can be selectively opened. During normal operation, the aperture231is closed to achieve the high lubricant level301and the lubricant300exits the interior space203only through the pipe system210.

The first part212in the inside of the bearing housing201in the interior space203contributes to reduce free space in the interior space203. The reduced free space allows a reduction of the amount of lubricant for the initial filling, which enables cost savings. The reduced free space also leads to more movement of the lubricant300during operation. Thus, the lubricant300is mixed better and stays more agile. Back feeding is improved and the overall lubricant regime is improved. Less of the lubricant300remains in the free space and the lubricant300better covers the rolling element205.

The first part212in the inside of the bearing housing201contributes to make the lubricant300in the first part212less dependent on an environmental temperature. The lubricant300in the first part212thus has the same or similar properties as the other lubricant300in the interior space203and on the rolling elements205.

The pipe system210according to the different embodiments and also according to the combination of the different embodiments not explicitly shown in the figures, allows a reliable lubrication of the bearing204. The pipe system210provides a controlled draining of the lubricant300and an uncontrolled lubricant leakage can be avoided, in particular a leakage through the sealing235. If too much of the lubricant300is in the interior space203and hydrodynamic pressure rises, the lubricant300is discharged in a controlled manner through the pipe system210. Leakage at the seal235can be avoided.

The lubricant level301can be sufficiently maintained and thus, metal-metal contact, friction and wear are reduced. A lubricant level301above 90% of capacity of the interior space203is possible. Existing space at the outside227of the bearing housing201can be used flexibly. The first part201can be formed up to the desired predetermined height207through a specific selection of the hose216and/or the pipe228outside or inside the interior space203.

The pipe system210makes the lubricant level301up to 100% possible. Greater safety against insufficient lubrication of the rotor bearing204is possible. The pipe system210, with the first part212inclining upwards, functions like an overflow and/or pressure relief valve. If, for example, lubricant300is added even though the interior space203is already 100% full, excess lubricant flows out through the pipe system210. The pipe system210, in particular according to the embodiments ofFIGS.2to10, can be easily retrofitted to existing bearing housings201and existing configurations without costly reconfiguration. The bearing cover202according toFIGS.11to14can also be retrofitted to existing bearing housings201if enough free space is available for the first part212arranged inside the bearing housing201.

The bearing arrangement200with the pipe system210reduces the risk of failure of the bearing204. Outflow of the lubricant300can be controlled and thereby the amount of lubricant300can be increased and the lubricant can be increased and the lubricant level301can be kept at a desired height.

REFERENCE SIGNS