Sliding bearing element for a rotor shaft with a rotor axis of a wind turbine

Abstract

The invention relates to a sliding bearing element (1) for a rotor shaft (2) with a rotor axis (3) of a wind turbine (4), comprising at least the following components: - a bearing surface (5) for hydrodynamic mounting of a corresponding abutment surface (6) via a bearing gap (7) therebetween which is covered with a film of bearing oil during operation; - a circumferential bearing surface (8) for mounting the sliding bearing element (1) with respect to a bearing receptacle (9) for the sliding bearing element (1); - a hydraulic cylinder (10), by means of which bearing oil can be displaced from an oil chamber (11); - an oil feed (12) between the hydraulic cylinder (10) and the bearing surface (5), wherein bearing oil displaced from the oil chamber (11) via the oil feed (12) can be fed to the bearing gap (7), and wherein the circumferential bearing surface (8) of the sliding bearing element (1) is mounted such that the sliding bearing element is movable with low friction in the circumferential direction (13) with respect to the bearing receptacle (9). The sliding bearing element proposed here makes it possible to considerably and fail-safely reduce a starting torque after a hydrodynamic bearing gap has run dry.

Description

[0001] Plain bearing element for a rotor shaft with a rotor axis of a wind energy plant

[0002] The invention relates to a plain bearing element for a rotor shaft with a rotor axis of a wind turbine, a plain bearing with such a plain bearing element for a rotor shaft of a wind turbine, a rotor with such a plain bearing for a wind turbine, and a wind turbine with such a rotor.

[0003] In the course of the energy transition and the decarbonization of the energy infrastructure, wind turbines are becoming increasingly important. With an output of up to seven megawatts [MW] on land (onshore) and up to over fifteen megawatts offshore per wind turbine, wind turbines will represent the so-called base load of energy consumption in the future. The wind turbine uses the prevailing wind to drive a generator using rotor blades and a rotor shaft connected via a hub (together with the rotor). The generator is designed to generate electrical power from the provided torque. Future (offshore) wind turbines are even expected to achieve outputs of 20 MW or more, which will be reflected in an increase in the size of the rotor blades and the generator, as well as the rotor shaft.

[0004] One of the few disadvantages of wind turbines is their standstill during periods of calm wind or maintenance work, or their start-up behavior after a prolonged standstill. Conventional wind turbines are designed with rolling bearings. As rotor shaft diameters increase, hydrodynamic plain bearings become more practical. However, these would run dry after a longer standstill period (e.g., after half an hour). This means that the hydrodynamically built-up lubricating film in the bearing gap between the rotor shaft and the wetted bearing surface is reduced to an insufficient thickness. This leads to mixed friction and thus to an increased starting torque of the wind turbine. This must be accepted, with the consequence that a wind turbine can only be restarted when the start-up wind load is higher than the minimum operating wind load.Alternatively, lubrication must be provided by a pump as a type of hydrostatic bearing, which results in additional costs and potentially increased maintenance requirements, as well as the likelihood of failure.

[0005] Based on this, the present invention is based on the object of at least partially overcoming the disadvantages known from the prior art. The features of the invention are derived from the independent claims, for which advantageous embodiments are presented in the dependent claims. The features of the claims can be combined in any technically reasonable manner, whereby the explanations from the following description as well as features from the figures, which comprise additional embodiments of the invention, can also be consulted for this purpose.

[0006] The invention relates to a plain bearing element for a rotor shaft with a rotor axis of a wind turbine, comprising at least the following components:

[0007] - a bearing surface for the hydrodynamic support of a corresponding counter-running surface via a bearing gap covered with a film of bearing oil during operation;

[0008] - a circumferential bearing surface for supporting the plain bearing element opposite a bearing seat for the plain bearing element;

[0009] - a hydraulic cylinder by means of which bearing oil can be displaced from an oil chamber;

[0010] - an oil supply between the hydraulic cylinder and the bearing surface, wherein bearing oil displaced from the oil chamber can be supplied to the bearing gap via the oil supply, wherein the plain bearing element is mounted in a low-friction manner relative to the bearing holder in the circumferential direction by means of its circumferential bearing surface.

[0011] In the following, reference is made to the rotor axis mentioned when, without explicit indication to the contrary, the axial direction, radial direction, or rotational direction and corresponding terms are used. Ordinal numbers used in the preceding and following descriptions serve only to clearly distinguish them and do not reflect the order or ranking of the designated components. An ordinal number greater than one does not necessarily imply that another such component must be present.

[0012] The sliding bearing element proposed here is designed to support a rotor shaft of a wind turbine by means of a bearing surface. The bearing surface of the sliding bearing element is designed to hydrodynamically support a corresponding counter-running surface, wherein, during operation, a bearing gap formed by a film of bearing oil (lubricating film) is formed between the counter-running surface and the bearing surface. The film of bearing oil is designed to reduce friction on the rotor shaft during operation. In one embodiment, a plurality of sliding bearing elements are arranged circumferentially around the rotor shaft, preferably uniformly and / or load-adequately.

[0013] Here, it is proposed that the plain bearing element itself be mounted on a circumferential bearing surface opposite a bearing seat in a low-friction manner. In one embodiment, the bearing seat is formed by the rotor shaft of the wind turbine, so that the lubricating film in the bearing gap for the hydrodynamic bearing during (normal) rotational operation of the rotor is formed by the plain bearing element opposite a bearing housing (e.g., a nacelle) of the respective wind turbine. The additional circumferential bearing surface, which supports the plain bearing element with low friction, is then arranged on the plain bearing element radially within the hydrodynamic bearing gap.

[0014] In an alternative embodiment, the bearing support is arranged radially outside the rotor shaft, i.e., in a bearing housing (e.g., a nacelle) of the wind turbine. The additional circumferential bearing surface, which provides low-friction support for the plain bearing element, is then arranged on the plain bearing element radially outside the hydrodynamic bearing gap.

[0015] Due to the low-friction support of the plain bearing element, the plain bearing element can move relative to its bearing mount (on the housing or shaft side) due to increased friction at the bearing surface (due to the lack of a hydrodynamic lubricating film, which can lead to static friction). The frictional resistance at the circumferential bearing surface is designed such that, with an insufficiently hydrodynamically effective lubricating film (in the bearing gap), the resulting frictional force is so great that the plain bearing element follows the torque applied in the circumferential direction from the corresponding counter-running surface. This reduces the required starting torque across the circumferential bearing surface to a desired limit, allowing operation to resume even at lower wind speeds after a prolonged rotor standstill.

[0016] In one embodiment, the plain bearing element is movably mounted on its circumferential bearing surface relative to the bearing receptacle (e.g., the bearing housing) by means of a self-lubricating material pairing. For example, such a material pairing is selected such that one of the partners is coated, for example with a sliding coating, preferably impregnated with a predetermined amount of lubricant for at least mixed friction with sufficiently low frictional resistance to reliably rule out, for example, overheating and / or abrasion. In a (preferably alternative) embodiment, the plain bearing element is mounted on its circumferential bearing surface by means of rolling elements for low-friction movement in the circumferential direction. For example, the rolling elements are balls of a ball bearing.It should be noted that in an optimal embodiment (without an active return system for the plain bearing element to its desired position in normal operation), the frictional resistance (from standstill) on the circumferential bearing surface (together with the antagonistic bearing support) is lower than a frictional resistance in the bearing gap without hydrodynamically built-up fluid friction, but greater than this hydrodynamic fluid friction.

[0017] In order to then also restore a (sufficiently thick) film of bearing oil, i.e. the lubricating film in the bearing gap for a desired (or required) low frictional resistance, it is proposed here that an oil supply is arranged between an oil chamber for storing bearing oil and the bearing surface. The oil supply is therefore arranged to supply bearing oil into the bearing gap between the bearing surface and the corresponding counter-running surface. For example, such an oil supply has a through-bore (and thus an opening) in the bearing surface to the oil chamber. Independently of this, the opening of the oil supply on the bearing surface side is arranged, for example, in a central region of the bearing surface, for example to the respective opposite edges of the bearing surface at an equal distance from at least the central region, preferably an opening of the oil supply on the bearing surface side.

[0018] It should be noted that, in design-compliant operation, the lubricating film in the bearing gap will have built up to a desired thickness at the latest when the maximum circumferential movement of the plain bearing element is reached. Alternatively, at least until then, the friction limit for restarting the wind turbine is undercut, but the frictional resistance is not yet as low as that required and desired for a hydrodynamic plain bearing during regular operation.

[0019] A hydraulic piston displaces the bearing oil from the oil chamber, thus ensuring oil supply to the bearing gap even when the rotor shaft is not rotating. It should be noted that the hydraulic piston is preferably not designed to build up hydrostatic pressure permanently, but rather to press a volume from the oil chamber into the bearing gap via the oil supply once with a single stroke. When the hydraulic piston returns to its original position, in one embodiment, bearing oil is no longer supplied hydrostatically to the bearing gap. This allows the system to be kept very simple and designed to be maintenance-free for the desired service life.Such a single-stroke system is therefore preferably formed by the hydraulic piston together with the oil chamber and the oil supply, wherein the displacement volume of the oil chamber is particularly preferably designed to be sufficiently large for the duration of a design start-up phase.

[0020] It should be noted that for efficient operation in a torque-delivering phase (with a rotating rotor) of the wind turbine, a purely hydrodynamic bearing and no mixed friction is required, i.e., no pressure is built up for a hydrostatic bearing. In one embodiment, such a plain bearing element (described here) (or a plurality thereof, for example, two or three) is arranged only in a predetermined section in the circumferential direction (namely, load-adequate), for example, in an area with the highest load due to the weight force within the Earth's gravitational field. For example, in a two-point bearing, this is at the bottom near the hub of the rotor (relative to a 12-hour clock reference system with 6 o'clock aligned in the direction of the Earth's gravitational field, between, for example, 4 o'clock and 8 o'clock) and at the more distant bearing at the top (in the aforementioned clock reference system, between, for example, 10 o'clock and 2 o'clock).

[0021] It should be noted that a two-point bearing arrangement does not necessarily have to be used, and not every bearing necessarily has to be a plain bearing. It should also be noted that although application in a radial bearing is advantageous due to the main load (weight load of the rotor), application in an axial bearing is also advantageous and / or necessary in one embodiment in order to achieve a sufficiently low starting torque. In addition, angular contact bearings are used, for example, although this results in a significantly different load distribution. For example, such a load distribution results in areas with the highest load due to the weight of the rotor. In a first such angular contact bearing, they are arranged in an O arrangement close to the hub of the rotor at the bottom, and in a second such angular contact bearing in this 0 arrangement, further away from the hub at the top.If an additional bearing (e.g. purely a radial bearing) is provided for in this bearing arrangement, there may not be such an area with a relevant highest load or it may be significantly determined by other effects, for example a shaft deflection due to the starting torque antagonistic to the generator torque.

[0022] In a further advantageous embodiment of the plain bearing element, it is proposed that the hydraulic cylinder be actuated by means of a movement of the plain bearing element in the circumferential direction relative to the bearing receptacle, wherein the hydraulic cylinder is preferably fixed to the bearing receptacle in the circumferential direction. Here, it is proposed that the hydraulic cylinder be arranged on the plain bearing element in such a way that, by means of a movement of the plain bearing element in the circumferential direction, the hydraulic cylinder is inevitably moved relative to the bearing receptacle and is thus actuated. Thus, by means of a movement of the plain bearing element, a relative movement of the hydraulic cylinder and, consequently, a displacement of bearing oil from the oil chamber and an oil supply into the bearing gap are ensured.

[0023] In a preferred embodiment, the hydraulic cylinder is fixed to the bearing mount in such a way that the associated hydraulic piston is moved into the oil chamber when the plain bearing element describes a movement relative to the bearing mount. This results in the end of the hydraulic piston responsible for displacement displacing bearing oil from the oil chamber and (to build up the required lubricating film) pumping bearing oil into the bearing gap via the oil supply. The rotor shaft therefore floats hydrostatically, with rotation of the rotor shaft possibly starting even before the final build-up (to a desired height) of the bearing gap in question (for example under mixed friction), and thus a hydrodynamic component contributes early on to the floating of the rotor shaft (i.e. to the build-up of the lubricating film).

[0024] It is further proposed in an advantageous embodiment of the sliding bearing element that the sliding bearing element is held prestressed in the circumferential direction by means of at least one energy storage element.

[0025] In a previously described embodiment, a relationship between the frictional forces of the circumferential bearing surface and the (dry, i.e., insufficiently hydrodynamic) bearing surface is shown. Alternatively or additionally, it is proposed here that the opposing force for movement of the plain bearing element relative to its bearing mount is determined by the sum of the frictional resistance at the circumferential bearing surface, the displacement resistance in the oil chamber (resulting to a significant extent from the mass fraction of the rotor acting on this plain bearing element), and at least one energy storage element. This sum of the forces is designed such that it is lower than the frictional force on the dry bearing surface. This ensures that the hydraulic cylinder is actuated in this situation.

[0026] At the same time, for normal operation (i.e., with sufficient hydrodynamic effectiveness of the bearing surface), a sufficient counterforce is ensured against the onset of movement of the plain bearing element (and the hydraulic cylinder) by means of the at least one energy storage element. The energy storage element is thus preloaded in the circumferential direction such that, during normal operation, the plain bearing element is held in the circumferential direction and, after a relative movement between the plain bearing element and its bearing support induced during (dry) start-up, the plain bearing element is moved back to its initial position.

[0027] In one embodiment, at least one, preferably all, of the energy storage elements are designed as compression springs. For example, such an energy storage element is designed as a solid-state spring, helical compression spring, disc spring, or leaf spring and / or as a spring assembly and / or with a damper. In one embodiment, at least one, preferably all, of the energy storage elements are designed as tension springs. For example, the energy storage element is designed as a solid-state spring, helical tension spring, and / or a spring assembly and / or with a damper. The energy storage element is preferably arranged between a wall of the bearing receptacle and the plain bearing element, preferably near or in an oil sump.

[0028] It is further proposed in an advantageous embodiment of the plain bearing element that the bearing receptacle comprises an oil sump or, in use, the bearing receptacle, and preferably also the peripheral bearing surface, is arranged in an oil sump.

[0029] In a hydrodynamic bearing arrangement, an oil sump is usually provided in the bearing support. Here, it is proposed to arrange the circumferential bearing surface in the oil sump of the bearing support. Thus, by means of such an oil sump, the circumferential bearing surface is configured within precise limits for low-friction support of the plain bearing element. The bearing device for the plain bearing element, preferably the plain bearing element itself, is at least partially immersed in the oil sump. In addition to the low-friction support of the plain bearing element, this also provides improved corrosion resistance for the circumferential bearing (and preferably also for the at least one energy storage element).

[0030] In an advantageous embodiment, the oil sump is configured as a reservoir for bearing oil for the oil chamber. Bearing oil that has been forced out of the oil chamber into the bearing gap during start-up operation is drawn back in from the oil sump, preferably by means of the hydraulic piston. The bearing oil forced out of the bearing gap is preferably transferred from the oil sump (by gravity) into the oil sump.

[0031] It is further proposed in an advantageous embodiment of the plain bearing element that the hydraulic cylinder can be connected by means of a, preferably passive, shuttle valve in such a way that

[0032] - during a relative movement in the circumferential direction by means of the hydraulic cylinder, bearing oil is displaced from the oil chamber and is thus supplied to the bearing surface via the oil supply, and

[0033] - in the case of an opposite relative movement in the circumferential direction, bearing oil is sucked into the oil chamber by means of the hydraulic cylinder, wherein bearing oil can preferably be sucked in from an oil sump, particularly preferably with a plain bearing element according to an embodiment according to the above description.

[0034] When the hydraulic piston is actuated in a displacement manner, bearing oil can be supplied to the bearing surface exclusively via the oil supply by means of the shuttle valve proposed here. When the hydraulic piston is actuated backwards, in one embodiment the shuttle valve proposed here can draw bearing oil from a reservoir via a supply line. The shuttle valve is preferably designed to be passive, i.e. it is switched according to the pressure drop generated as a result of the piston movement of the hydraulic piston. Such a passive shuttle valve is, for example, conventionally designed with a spring-loaded closing body for each flow direction. In an alternative embodiment the switching body is designed to be active, i.e., electromechanical, for example, and sensors are also provided, for example a pressure sensor.

[0035] In a preferred embodiment, the bearing oil can be sucked from an oil sump (e.g., one designed as described above) by means of the hydraulic cylinder via the corresponding switching state of the shuttle valve. Reference is made to the preceding description in this regard.

[0036] It is further proposed in an advantageous embodiment of the plain bearing element that rolling elements, preferably needle bodies, are arranged between the circumferential bearing surface of the plain bearing element and the corresponding bearing receptacle and / or preferably run wet in an oil sump, particularly preferably with a plain bearing element according to an embodiment according to the above description, the bearing receptacle.

[0037] To ensure reliable, low-friction movement of the plain bearing element in the circumferential direction, it is proposed that rolling elements be arranged between the circumferential bearing surface and the corresponding bearing mount. In one embodiment, these rolling elements are designed as balls, which are arranged in a rolling manner between the circumferential bearing surface and the bearing mount in a (technically approximate) point contact. In an alternative embodiment, the rolling elements are cylindrical.

[0038] Due to the geometric design of the rolling elements, rolling action occurs in a (technically approximated) line contact, ensuring large-area contact and thus high load-bearing capacity with minimal installation space. It should be noted that the proportion of the rotor's mass acting on such a plain bearing element is significant, and the rolling elements remain unchanged during normal operation and are thus loaded at the same location over a long period of time, almost for the entire intended service life.

[0039] In a preferred embodiment, the rolling elements are designed as needle rollers, with the needle rollers having a smaller diameter but a longer axial extension than in the embodiment with cylindrical rolling elements. Furthermore, with the rolling elements as needle rollers, a smaller radial space requirement is possible, while simultaneously achieving a longer line contact compared to the cylindrical shape due to the longer axial extension. At the same time, the longer line contact of the needle rollers results in laterally stable rolling contact between the peripheral bearing surface and the bearing mount.

[0040] Alternatively or additionally, the rolling elements are arranged in an oil sump of the bearing housing and are designed for wet running within the oil sump. In addition to further reducing friction, the oil sump, in which the rolling elements roll, improves the corrosion resistance of the rolling elements. For example, the oil sump is designed as described above. Reference is made to the previous description in this regard.

[0041] It is further proposed in an advantageous embodiment of the plain bearing element that a section of the bearing surface is formed which is most loaded in the earth's gravitational field by the weight of the mounted rotor shaft, wherein this section is arranged, starting from the central angle line parallel to the earth's gravitational field, at the top and / or bottom in a circumferential angle range of a maximum of ± 30°, preferably a maximum of ± 15°, particularly preferably a maximum of ± 5°.

[0042] Depending on the arrangement in a bearing arrangement for a rotor shaft, the rotor mass must be supported at the bottom in one bearing in the Earth's gravity field and at the top in another. From the standstill at the transition to normal operation, the load caused by the mass usually represents the highest and most significant load. Here, it is proposed that one or more such plain bearing elements with a circumferential bearing surface be arranged exclusively in this, resulting most heavily loaded, section.

[0043] The orbital angle range is defined here as the zero line (i.e., the 0° position) relative to the line perpendicular to the Earth's gravitational field, which intersects the rotor shaft. This is a central angle line (or radius line) of the circular cross-section of the rotor shaft to be supported, which is parallel to the Earth's gravitational field, i.e., the 6 o'clock position in a cross-sectional view. The specification of ± 30° therefore corresponds to an angle of 60° and an angular position of 330° to 30°, or, according to the definition in the unit circle (parallel to the Earth's surface as the starting angle and counterclockwise rotation), 240° to 300°. For the highest load at the top relative to the Earth's gravitational field, the 12 o'clock position applies. The specification ± 30° then also corresponds to an angle of 60°, but to an angular position of 150° to 210°, or according to the definition in the unit circle (parallel to the Earth's surface as the starting angle and counterclockwise direction of rotation) 60° to 120°.

[0044] According to a further aspect, a plain bearing for a rotor shaft of a wind turbine is proposed, comprising at least the following components:

[0045] - a plurality of plain bearing elements, each having a bearing surface for supporting a corresponding counter-running surface via a bearing gap therebetween which is covered with a film of bearing oil during operation, wherein at least one of the plain bearing elements is designed according to an embodiment as described above;

[0046] - a bearing housing; and

[0047] - an oil sump and / or an external source for providing bearing oil for the respective bearing gap, wherein preferably at least one of the bearing receptacles, and preferably also the associated peripheral bearing surface, are arranged in the oil sump.

[0048] To support the rotor shaft of a wind turbine, for example, within a nacelle, it is proposed to use at least one plain bearing, preferably at least as the so-called main bearing or the radial bearing of the main bearing. However, it is also advantageous to use a plain bearing as an axial bearing and / or in a secondary bearing.

[0049] The components of the plain bearing are housed in a bearing housing, wherein the components are preferably protected from external influences within the bearing housing. Preferably, one or a plurality of bearing receptacles are formed within the bearing housing, in which further bearing receptacles, preferably an oil sump, are also provided. Alternatively or additionally, the respective bearing receptacle is enclosed by the rotor shaft or fixed to it so that it rotates with it. The bearing housing then forms the counter-running surface for the hydrodynamic bearing surface, or a corresponding component is fixed thereto.

[0050] The plain bearing comprises a plurality of plain bearing elements, each of which forms a hydrodynamic bearing arrangement by means of a bearing gap between a bearing surface of the respective plain bearing element and a corresponding counter-running surface of the rotor shaft or the bearing housing. For this purpose, the bearing gap is coated with a film of bearing oil (lubricating film). In one embodiment, some, preferably a plurality, of the plain bearing elements are designed conventionally (i.e., without a circumferential bearing surface, preferably fixed to the bearing receptacle), with at least one, preferably two or three, of the plain bearing elements being designed according to an embodiment described above. Reference is made to the above description in this regard.

[0051] Additionally, an external source and / or an oil sump is provided for supplying bearing oil to the bearing gaps. In a preferred embodiment, the bearing oil source and / or the oil sump are connectable to the bearing gap via a shuttle valve of a plain bearing element according to one of the preceding embodiments, as described above, for building up a hydrostatic lubricating film using the hydraulic cylinder.

[0052] The plain bearing is designed for a particularly low starting torque for a large and / or heavy shaft (such as a rotor shaft for a multi-megawatt wind turbine). At the same time, high reliability is required, for example, in the event of a failure of the electronics and / or the lubricating oil pump. Due to the robust design of the plain bearing element with its peripheral bearing surface and hydraulic cylinder, it is particularly less susceptible to failure compared to designs with a comparable range of functions.

[0053] According to a further aspect, a rotor for a wind turbine is proposed, comprising at least the following components:

[0054] - a rotor shaft with a rotor axis;

[0055] - at least one plain bearing according to an embodiment as described above;

[0056] - a plurality of rotor blades;

[0057] - a hub, wherein the rotor blades are connected to the rotor shaft via the hub, wherein the rotor shaft is rotatably supported about its rotor axis by means of the hydrodynamic bearing surfaces of the plain bearing elements, respectively axially and / or radially.

[0058] The wind turbine is designed to convert wind energy into electrical power by means of a rotor that can be set in rotation as a result of an air flow and a generator connected to transmit torque.

[0059] For this purpose, the generator is connected by means of a rotor shaft, which is designed to rotate around a rotor axis.

[0060] At least one plain bearing according to the above description is provided for supporting the rotor shaft. Preferably, a plurality of plain bearings are arranged around the rotor shaft, with a corresponding counter-running surface for the bearing surface of the plain bearing elements being formed by the rotor shaft (for example, the outer surface). Alternatively, the plain bearing elements are mounted on the rotor shaft so that they rotate with it, and the counter-running surface is formed on the housing side.

[0061] To convert wind energy into electrical power, a plurality of rotor blades are provided which aerodynamically convert the incoming wind into torque, causing the rotor shaft to rotate and, during load operation, converting the rotational energy into electrical energy at the generator.

[0062] The power of the rotor blades is transmitted to the rotor shaft via a hub. The hub typically contains an adjusting gear to adjust the rotor blades (or their flow profile) to the wind speed and, if necessary (e.g., during a storm), even to transfer them to a neutral position. Furthermore, hydrodynamic bearing surfaces are provided for supporting the rotor shaft. Preferably, one or more plain bearing elements are provided for axial and / or radial support of the rotor shaft. For the axial bearing, in one embodiment, a two-sided shoulder or groove (and radially immersed bearing elements) is formed on the rotor shaft.It should be noted that in one embodiment, two or more bearing points are provided with an axial distance (relative to the rotor axis), of which preferably only one is designed for axial support, so that a so-called fixed-loose bearing arrangement is formed.

[0063] As previously described, the rotor shaft of the rotor is supported with low friction by at least one plain bearing according to an embodiment according to the preceding description with a particularly low starting torque. At the same time, a high degree of reliability is required, for example, in the event of a failure of the electronics and / or the lubricating oil pump, and / or due to the robust design of the plain bearing element with circumferential bearing surface and hydraulic cylinder, it is particularly less susceptible to failure compared to embodiments with a comparable range of functions.

[0064] According to a further aspect, a wind turbine is proposed, comprising

[0065] - a tower with a vertical axis;

[0066] - a nacelle with a generator, the nacelle being arranged on the tower and being rotatable about the vertical axis by means of a wind direction tracking device; and

[0067] - a rotor rotatable about its rotor axis according to an embodiment as described above, wherein the rotor shaft is connected to the generator in a torque-transmitting manner for converting its rotation about the rotor axis into electrical current.

[0068] It should be noted that the plain bearing element or plain bearing (or radial bearing and / or thrust bearing) is particularly advantageous for the explicitly mentioned bearing locations of the wind turbine. However, the use of the plain bearing element or plain bearing is not limited to this or to wind turbines.

[0069] The wind turbine is designed to convert wind energy into electrical power by means of a rotor that can be set in rotation as a result of an air flow and a generator connected to transmit torque.

[0070] The nacelle is designed to support and preferably house the functional components for energy conversion, particularly preferably with a streamlined exterior. The nacelle is rotatable about its vertical axis relative to the tower, allowing the rotor to be aligned according to the operating state (e.g., according to the prevailing wind direction), namely by means of the so-called wind direction tracking device.

[0071] The rotor with its rotor blades is connected via its rotor shaft in the nacelle indirectly (for example, via a gearbox and / or an overload clutch) or directly to the generator for power generation. The wind turbine comprises a hydrodynamically plain-bearing rotor shaft which, as described above, is supported with low friction by means of at least one plain bearing according to an embodiment according to the preceding description with a particularly low starting torque. At the same time, a high level of reliability is necessary, for example in the event of a failure of the electronics and / or the lubricating oil pump and / or due to the robust design of the plain bearing element with circumferential bearing surface and hydraulic cylinder, which is particularly less susceptible to failure compared to embodiments with a comparable range of functions.

[0072] The invention described above is explained in detail below against the relevant technical background with reference to the accompanying drawings, which show preferred embodiments. The invention is in no way limited by the purely schematic drawings, whereby it should be noted that the drawings are not to scale and are not suitable for defining proportions. It is shown in

[0073] Fig. 1: a wind turbine with nacelle and rotor; Fig. 2: a schematic side view of a rotor shaft with radial bearings and axial bearings;

[0074] Fig. 3: in a schematic front view, two plain bearing elements of a plain bearing; and

[0075] Fig. 4: in a schematic spatial detailed view of two plain bearing elements of a plain bearing according to Fig. 3.

[0076] Fig. 1 shows a wind turbine 4 with a nacelle 31 and a rotor 26. The vertical axis 30 (shown horizontally here) of the tower 29 is aligned vertically in the Earth's gravitational field 19, and the rotor axis 3 of the rotor shaft 2 (shown vertically here) is aligned horizontally in the Earth's gravitational field 19 (usually slightly inclined, for example, with the hub 28 inclined upwards by approximately 5° [five degrees] to 7° away from the Earth's surface). The nacelle 31 at the top of the tower 29 is supported with low friction by the wind direction tracking device 33 and is designed to be rotatable relative to the tower 29 about the vertical axis 30. The nacelle 31 supports and encloses a generator 32 and (at least a large part of) the rotor shaft 2, as well as a bearing device (e.g., designed as a plain bearing 24) for the rotor shaft 2. The bearing shown is indicated as a fixed bearing with radial bearing and axial bearing. For example, this is the so-called main bearing for the rotor 26.For example, a further support (by means of a secondary bearing) is provided for the rotor shaft 2, for example, integrated into the generator 32. A hub 28 is connected to the rotor shaft 2 (in generator mode, at the front, against the wind flow direction), to which a plurality of (for example, three, two visible here) rotor blades 27 are connected, thus forming the rotor 26, which can rotate about the rotor axis 3. Fig. 2 shows an example of a possible embodiment of a rotor 26 and generator 32 in the nacelle 31 and is explained below.

[0077] Fig. 2 shows a schematic side view of a rotor shaft 2 rotatable about its rotor axis 3 (as can be used, for example, in a wind turbine 4 according to Fig. 1), wherein on the left of the illustration a connected hub 28 and two cut-off rotor blades 27 of the rotor 26 are shown, and on the right a (purely optional) transmission gear 34 and connected generator 32 are shown. The earth's gravitational field 19 is oriented from top to bottom in the illustration. In this embodiment (of many possible ones), the rotor shaft 2 is supported for low-friction rotation by means of a bearing device with a fixed bearing (on the right as shown) and a loose bearing (left). At least one, preferably both, of the bearings of the bearing device is designed as a plain bearing 24 and is to be supplied with bearing oil.

[0078] For example, at least one of the bearings is designed as a hydrodynamic plain bearing 24. Examples of possible embodiments of plain bearing elements 1 for a segmented plain bearing 24 are shown in Fig. 3 and Fig. 4, specifically using a radial bearing as an example, and are explained below.

[0079] Fig. 3 shows a schematic front view of two plain bearing elements 1 of a plain bearing 24, wherein two plain bearing elements 1 are shown here, which are arranged in the orbital angle range 23 between 5 o'clock and 7 o'clock (i.e. ± 30° relative to the central angle line 22 parallel to the Earth's gravitational field 19), for example the most highly loaded section 21 of the plain bearing 24 shown. For example, further bearing segments are arranged distributed over the circumference of the rotor shaft 2, wherein these are preferably of conventional design. The rotor shaft 2 is designed here, as is usually the case, as a hollow shaft and is therefore shown in this diagram as a ring in the center with its rotor axis 3. A bearing housing 25 is schematically indicated around the rotor shaft 2, wherein in the embodiment shown, the plain bearing elements 1 are held in corresponding bearing receptacles 9 of the bearing housing 25, i.e. the rotor shaft 2 rotates relative to the plain bearing elements 1 during normal operation.According to this configuration, the rotor shaft 2 has a counter-running surface 6 (e.g., formed integrally) on its outer circumference, which is designed for direct contact with the hydrodynamic bearing surfaces 5 of the plain bearing elements 1 (and optionally additional bearing segments). It should be noted that, for the sake of clarity, the reference numerals for the two plain bearing elements 1 shown here are shown pars pro toto on one of the plain bearing elements 1. Preferably, the two plain bearing elements 1 are of identical construction.

[0080] Between the counter surface 6 and the bearing surface 5 of each

[0081] In normal operation, the plain bearing element 1 is hydrodynamically supported by bearing oil and as a result of the rotation of the rotor shaft 2 in the circumferential direction 13 around its rotor axis 3.

[0082] Lubricating film 7 is built up, whereby a desired low coefficient of friction or low opposing friction torque is achieved.

[0083] The special feature of the plain bearing elements 1 shown here is that they themselves are mounted so as to be relatively movable relative to the respective bearing receptacle 9 (here the bearing housing 25) via their circumferential bearing surface 8. The exact function is explained in the following Fig. 4. It should be noted in advance that if the bearing gap 7 becomes dry, the frictional torque between the rotor shaft 2 and the respective plain bearing element 1 increases, and as a result, the respective plain bearing element 1 is dragged along by the rotor shaft 2 (for example, during start-up) in the circumferential direction 13 via the resulting frictional engagement.

[0084] Fig. 4 shows a schematic spatial detail view of two plain bearing elements 1 of a plain bearing 24 according to Fig. 3. To provide a clear view of the two plain bearing elements 1 shown, the rotor shaft 2 is shown transparently. Of the plain bearing element 1 on the right in the illustration, the bearing surface 5 is clearly visible, on which the mating surface 6 of the rotor shaft 2 slides during normal operation via the hydrodynamically built-up lubricating film 7. After a period of downtime, however, this bearing gap 7 can dry out (with the result that a lubricating film 7 has an insufficient thickness) and mixed friction can arise between the mating surface 6 and the bearing surface 5, whereby the starting torque to be overcome is considerably higher than the friction torque during normal operation.

[0085] Via the circumferential bearing surface 8 (here on the underside in the illustration) of the respective plain bearing element 1 opposite the bearing surface 5, the plain bearing element 1 itself is supported with low friction relative to the bearing seat 9 (here opposite the bearing housing 25) and can thus move with low friction along the rotor shaft 2 in the circumferential direction 13 over a limited path. In the embodiment shown, rolling elements 17 (purely optionally designed as needle bodies 18) are provided between the bearing seat 9 and the circumferential bearing surface 8 of the plain bearing element 1. Preferably, the bearing seat 9 is arranged in an oil sump 15 so that the rolling elements 17 are designed to be wet-running. Furthermore, a hydraulic cylinder 10 with an oil chamber 11 (indicated schematically by a dashed line in the right-hand plain bearing element 1 shown in the illustration) is provided, here (purely optionally) configured as a passive system.The hydraulic cylinder 10 is supported relative to the bearing mount 9, specifically here on a (radial) wall 35 (preferably fixed to this wall 35). During a relative movement of the plain bearing element 1 in the circumferential direction 13, its hydraulic piston (not visible here) is forced into the oil chamber 11 along its stroke axis 38, thus reducing the (pumping) volume filled with bearing oil in the oil chamber 11. As a result, bearing oil is pumped into the bearing gap 7 via the oil supply 12 (here, a bore between the bearing surface 5 and the oil chamber 11 via a shuttle valve 16 and a check valve 39), thus hydrostatically building up a lubricating film 7. Consequently, the friction coefficient and thus the opposing frictional torque are significantly reduced.It should be noted that in one embodiment there is still mixed friction, i.e. the height of the lubricating film 7 is not yet achieved, as it is present in normal operation due to the hydrodynamic structure.

[0086] In this embodiment shown, the hydraulic piston is still used passively (purely optionally) to refill the oil chamber 11 with bearing oil. For this purpose, two (purely optionally) energy storage elements 14, here designed as helical compression springs, are arranged between the radial wall 35 and an opposite wall 36 of the plain bearing element 1. These energy storage elements 14 are clamped in an antagonistic manner to the engagement movement of the hydraulic piston along its stroke axis 38. As soon as the frictional force between the counter-running surface 6 of the rotor shaft 2 and the bearing surface 5 of the plain bearing element 1 decreases sufficiently (for example, as a result of the bearing oil pumped in from the oil chamber 11), the plain bearing element 1 is pushed away from the radial wall 35 of the bearing mount 9, and thus the displaceable volume (pumping volume) of the oil chamber 11 is increased again by the hydraulic piston. In the process, bearing oil is sucked in due to the negative pressure.However, the bearing oil should not be sucked in from the bearing gap 7 via the oil supply 12. For this purpose, a shuttle valve 16 is provided in the advantageous embodiment shown here. As a result of a movement of the hydraulic piston along its stroke axis 38 into the oil chamber 11 (displacement), it is switched in such a way that bearing oil can flow out via the oil supply 12. As a result of a movement of the hydraulic piston (in the opposite direction) along its stroke axis 38 out of the oil chamber 11 (suction), the shuttle valve 16 is switched in such a way that bearing oil is sucked in from an external source (here purely optionally the oil sump 15) via a suction line 37 and the oil chamber 11 is filled. The shuttle valve 16 is used for this purpose; it closes (preferably modulated via a preload) following an applied pressure gradient or opens when the pressure gradient is reversed.In this embodiment, a check valve 39 prevents the suction of bearing oil from the bearing gap 7, but allows the supply of bearing oil due to a suction in the bearing gap 7 or due to the oil pressure from the hydraulic cylinder 10 to build up the hydrostatic pressure in the bearing gap 7.

[0087] With the plain bearing element proposed here, the starting torque after a hydrodynamic bearing gap has dried out can be reduced considerably and in a fail-safe manner.

[0088] List of reference symbols

[0089] Plain bearing element 35 radial wall of the rotor shaft bearing holder

[0090] Rotor axis 36 opposite wall

[0091] Wind turbine 37 Intake line Bearing area 38 Lifting axis

[0092] Counterface 39 Check valve Bearing gap / lubricating film Circumferential bearing surface Bearing holder Hydraulic cylinder Oil chamber

[0093] Oil supply circumferential direction energy storage element oil sump

[0094] Shuttle valve rolling element needle body earth's gravity field

[0095] Weight force of most heavily loaded section central angle line

[0096] Orbital angle range of plain bearings

[0097] Bearing housing rotor

[0098] rotor blades

[0099] hub

[0100] Tower

[0101] vertical axis

[0102] gondola

[0103] generator

[0104] Wind direction tracking device transmission gear

Claims

Patent claims 1 . A plain bearing element (1) for a rotor shaft (2) with a rotor axis (3) of a wind turbine (4), comprising at least the following components: - a bearing surface (5) for hydrodynamically supporting a corresponding counter-running surface (6) via a bearing gap (7) covered with a film of bearing oil during operation; - a circumferential bearing surface (8) for supporting the plain bearing element (1) relative to a bearing receptacle (9) for the plain bearing element (1); - a hydraulic cylinder (10) by means of which bearing oil can be displaced from an oil chamber (11); - an oil supply (12) between the hydraulic cylinder (10) and the bearing surface (5), wherein bearing oil displaced from the oil chamber (11) can be supplied to the bearing gap (7) via the oil supply (12), wherein the plain bearing element (1) is mounted by means of its circumferential bearing surface (8) relative to the bearing receptacle (9) in the circumferential direction (13) in a low-friction manner.

2. Plain bearing element (1) according to claim 1, wherein the hydraulic cylinder (10) is actuated by means of a movement of the plain bearing element (1) in the circumferential direction (13) relative to the bearing receptacle (9), wherein preferably the hydraulic cylinder (10) is fixed to the bearing receptacle (9) in the circumferential direction (13).

3. Plain bearing element (1) according to claim 1 or claim 2, wherein the plain bearing element (1) is held prestressed in the circumferential direction (13) by means of at least one energy storage element (14).

4. Plain bearing element (1) according to one of the preceding claims, wherein the bearing receptacle (9) comprises an oil sump (15) or, in use, the bearing receptacle (9), and preferably also the peripheral bearing surface (8), is arranged in an oil sump (15).

5. Plain bearing element (1) according to one of the preceding claims, wherein the hydraulic cylinder (10) can be connected by means of a, preferably passive, shuttle valve (16) in such a way that - during a relative movement in the circumferential direction (13) by means of the hydraulic cylinder (10), bearing oil is accordingly displaced from the oil chamber (11) and is thus supplied to the bearing surface (5) via the oil supply (12), and - in the case of an opposite relative movement in the circumferential direction (13) by means of the hydraulic cylinder (10), bearing oil is sucked into the oil chamber (11), wherein bearing oil can preferably be sucked in from an oil sump (15), particularly preferably with a plain bearing element (1) according to claim 4.

6. Plain bearing element (1) according to one of the preceding claims, wherein rolling elements (17) are arranged between the circumferential bearing surface (8) of the plain bearing element (1) and the corresponding bearing receptacle (9), preferably needle bodies (18), and / or preferably wet-running in an oil sump (15), particularly preferably with a plain bearing element (1) according to claim 4, the bearing receptacle (9).

7. Plain bearing element (1) according to one of the preceding claims, wherein a section (21) which is most loaded in the earth's gravitational field (19) by the weight force (20) of the mounted rotor shaft (2) is formed by the bearing surface (5), wherein this section (21) is arranged, starting from the central angle line (22) parallel to the earth's gravitational field (19), at the top and / or bottom in a circumferential angle range (23) of a maximum of ± 30°, preferably a maximum of ± 15°, particularly preferably a maximum of ± 5°.

8. A plain bearing (24) for a rotor shaft (2) of a wind turbine (4), comprising at least the following components: - a plurality of plain bearing elements (1) each having a bearing surface (5) for supporting a corresponding counter-running surface (6) via a bearing gap (7) therebetween which is covered with a film of bearing oil during operation, wherein at least one of the plain bearing elements (1) is designed according to one of the preceding claims; - a bearing housing (25); and - an oil sump (15) and / or an external source for providing bearing oil for the respective bearing gap (7), wherein preferably at least one of the bearing receptacles (9), and preferably also the associated circumferential bearing surface (8), are arranged in the oil sump (15).

9. Rotor (26) for a wind turbine (4), comprising at least the following components: - a rotor shaft (2) with a rotor axis (3); - at least one plain bearing (24) according to claim 8; - a plurality of rotor blades (27); - a hub (28), wherein the rotor blades (27) are connected to the rotor shaft (2) via the hub (28), wherein the rotor shaft (2) is rotatably supported about its rotor axis (3) by means of the hydrodynamic bearing surfaces (5) of the plain bearing elements (1) in each case axially and / or radially.

10. Wind turbine (4), comprising - a tower (29) with a vertical axis (30); - a nacelle (31) with a generator (32), wherein the nacelle (31) is arranged on the tower (29) and is rotatable about the vertical axis (30) by means of a wind direction tracking device (33); and - a rotor (26) rotatable about its rotor axis (3) according to claim 9, wherein the rotor shaft (2) is connected to the generator (32) in a torque-transmitting manner for converting its rotation about the rotor axis (3) into electrical current.

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