This application claims the benefit of German Application No. DE 102013211710.8 filed Jun. 20, 2013. All of the applications are incorporated by reference herein in their entirety.
The invention relates to a wind power plant having a sliding bearing and to an operation of the wind power plant in order to generate electric current.
A wind power plant is typically intended to be in operation or operationally capable and to generate electric current efficiently for many years, preferably for a number of decades. The requirements in terms of maintenance capability and robustness of the wind power plant are high here. This applies, in particular, to so-called offshore wind power plants, i.e. wind power plants which are installed in water, for example in the sea. Maintenance of offshore wind power plants is often costly owing to the difficulty of access.
Typical wearing parts of a wind power plant are the bearings. At present, roller bearings with rollers and/or rolling bearings with drums are widely used in wind power plants. It is costly to replace the rollers or drums which the roller bearing or rolling bearing has. The drive train of the wind power plant must often be disassembled completely or at least partially. This is generally possible only by means of a crane. However, in particular in the case of an offshore wind power plant the use of such a crane is expensive and costly.
An alternative to a roller bearing or a rolling bearing is, for example, a sliding bearing. In this context, in particular a hydrodynamic sliding bearing and a hydrostatic sliding bearing are possible. It is generally easier to replace the wearing parts, in this case in particular the sliding linings, than to replace the rollers or drums in roller bearings or rolling bearings.
However, the use of sliding bearings in a wind power plant has specific problems: in the case of a hydrodynamic bearing, a high initial torque is necessary if the bearing is to be made to rotate from the stationary state under load owing to gravitation and/or wind. Hydrostatic bearings in which a lubricant is under high pressure have the disadvantage that they require a continuous power supply for a pump system which constitutes, on the one hand, a potential risk of failure and, on the other hand, continuously requires energy, i.e. current.
An object of the invention is therefore to disclose how a sliding bearing of a wind power plant can be improved. Specifically, a lubricant for operating the sliding bearing is to be fed in as efficiently as possible.
This object is achieved according to the independent claims. Advantageous developments are disclosed in the dependent claims.
In order to achieve this object, a wind power plant having a sliding bearing is disclosed, wherein the sliding bearing comprises a first bearing component and a second bearing component. The first bearing component and the second bearing component are arranged such that they can rotate relative to one another about a common rotational axis. The sliding bearing has at least one sliding lining which is arranged between the first bearing component and the second bearing component. The sliding lining has a contact face which is provided for contact with a lubricant. The contact face has a sliding lining duct opening to a sliding lining duct, wherein the sliding lining duct crosses the sliding lining and is provided for feeding lubricant into a region between the first bearing component and the second bearing component. Finally, the sliding lining has a groove on the contact face, and the groove surrounds the sliding lining duct opening.
A wind power plant can convert wind energy into electrical energy. A wind power plant is also referred to as a wind energy plant, wind turbine plant or wind power convertor.
The first bearing component and/or the second bearing component are advantageously in the form of a hollow cylinder. The hollow cylinder can have a circular circumference. In other words, the first bearing component and/or the second bearing component are in the form of a disk with an opening or a hole.
The wind power plant advantageously has a tower, a gondola with a machine frame, a generator and a rotor with a hub. At least one rotor blade, preferably at least two rotor blades, normally preferably precisely three rotor blades, is/are attached to the hub.
In a first alternative, the first bearing component is mechanically connected to the rotor, and the second bearing component is mechanically connected to the machine frame. In a second alternative, the first bearing component is mechanically connected to the machine frame, and the second bearing component is mechanically connected to the rotor. In both alternatives, the first bearing component and the second bearing component are mounted or arranged such that they can rotate relative to one another, in particular about a common coaxial rotational axis.
The rotor is advantageously connected to a generator rotor, which can also be referred to as a rotor part of the generator.
A space between the first bearing component and/or the second bearing component can be referred to as a bearing inner space. The sliding lining is advantageously located in the bearing interior space. The sliding lining preferably has a square shape. Furthermore, the sliding lining can advantageously have an attachment face which is opposed to the contact face and arranged parallel thereto. In advantageous embodiments, the attachment face is directly connected to the first bearing component, the second bearing component and/or a sliding lining carrier.
A function of the sliding lining duct is to feed a lubricant from the outside into the region between the first bearing component and the second bearing component, that is to say for example to the bearing inner space.
A decisive feature of the wind power plant according to the invention is the groove which the sliding lining has on the contact face. A sliding lining whose contact face has a groove with a sliding lining duct opening can cover a larger surface with lubricant than a conventional sliding lining which has a sliding lining duct opening of the same size but no groove. In a startup phase of the sliding bearing, that is to say when the sliding bearing is starting up from the stationary state, the groove can function as a support for the hydrostatic operation. If, for example, a lubricant is pressed onto the contact face by the sliding lining duct, friction, which occurs in the startup phase of the sliding bearing in the hydrostatic operating mode owing to the wetted surface in the groove, can be reduced compared to a sliding lining which only has a sliding lining duct opening and no groove. In the hydrodynamic operating mode, i.e. in an operating mode with, for example, constant rotational speed of the sliding bearing, the force or the pressure to be applied can also be reduced by the groove. As a result a hybrid, i.e. hydrostatic/hydrodynamic, sliding bearing is possible.
The contact face can have one longitudinal side and one transverse side. The transverse side is, for example, of precisely the same length as the longitudinal side, i.e. the contact face is square. In one advantageous embodiment, the longitudinal side is between 100 and 200 times longer than a depth of the groove. The depth of the groove is advantageously between 1 mm and 20 mm, in particular between 5 mm and 10 mm.
In one preferred embodiment, the sliding bearing is a radial bearing and/or an axial bearing.
A radial bearing, also referred to as a transverse bearing or supporting bearing, prevents or impedes movement of the first bearing component and/or of the second bearing component in the radial direction, that is to say essentially perpendicularly with respect to the axial direction. An axial bearing, also referred to as a longitudinal bearing, pressure bearing or pivot bearing, prevents or impedes movement of the first bearing component and/or of the second bearing component in the axial direction. The combination of the radial bearing and axial bearing is referred to as a radiax bearing. An example of a radiax bearing is a simple-acting radial bearing which is supplemented by two axially acting bearing pairs. Another advantageous example of a radiax bearing is a toe bearing, also referred to as a jewel bearing, in which a multiplicity of toe pairings are located opposite one another and are formed, for example, in the shape of a truncated cone.
If the sliding bearing is a radial bearing, the first bearing component advantageously is in the form an outer bearing ring, and the second bearing component is advantageously in the form of an inner bearing ring. The sliding lining is then advantageously attached to an outer side of the inner bearing ring and/or to an inner side of the outer bearing ring.
In a first alternative, the inner bearing ring is mechanically connected to the machine frame, and the sliding lining is attached to the outside of the inner bearing ring. In a second alternative, the outer bearing ring is mechanically connected to the machine frame, and the sliding lining is attached to the inside of the outer bearing ring. In a third alternative, the inner bearing ring is mechanically connected to the rotor, and the sliding lining is attached to the outside of the inner bearing ring. Finally, in a fourth alternative, the outer bearing ring is mechanically connected to the rotor, and the sliding lining is connected to the inside of the outer bearing ring.
If the sliding bearing is an axial bearing, the first bearing component and the second bearing component are both in the form of a bearing washer. Both bearing washers can have a similar shape and size. Both bearing washers are advantageously arranged offset axially from one another, wherein the first bearing washer faces, for example, a hub of the wind power plant, and the second bearing washer faces a generator of the wind power plant.
In one advantageous embodiment, the sliding bearing has a rotational direction which is defined by the first bearing component and second bearing component which can rotate relative to one another. Furthermore, the contact face has a contact face region at the front in the rotational direction, and a contact face region at the rear in the rotational direction. The groove is located in the front contact face region.
The rotational direction relates to a rotation of the first bearing component and of the second bearing component about the common rotational axis.
In a first alternative, the contact face is divided in halves, into the front contact face region and into the rear contact face region. In a second alternative, the contact face has a central contact face region and the contact face is divided, for example into thirds comprising the front contact face region, the central contact face region and the rear contact face region, respectively.
An arrangement of the groove in the front contact face region has multiple advantages. On the one hand, a reduction in the friction is greater in the hydrostatic operating mode of the sliding bearing if the groove is located in the front contact face region compared to a groove in the rear contact face region. On the other hand in the hydrodynamic operating mode of the sliding bearing a groove in the front contact face region is advantageous since the region of the contact face which is “grooveless”, that is to say, for example, planar, is enlarged compared to, for example, a sliding bearing with a groove in the central region of the contact face. This is due, inter alia, to the fact that a continuous grooveless face is advantageous for building up a hydrodynamic pressure.
The groove can have the shape of a semicircle in a cross section perpendicular to a longitudinal extent of the groove and perpendicular to the contact face. Likewise, the cross section of the groove can have a triangle. Other shapes such as, for example, half of an ellipse, can be advantageous. With respect to the shape of the groove, hydrodynamic/hydrostatic criteria and simplicity in manufacture have to be balanced against one another.
In one advantageous embodiment, the groove has a groove wall at the front in the rotational direction and a groove wall at the rear in the rotational direction. The front groove wall has a front groove wall inclination angle between the front groove wall and the contact face, and the rear groove wall has a rear groove wall inclination angle between the rear groove wall and the contact face. Furthermore, the front groove wall inclination angle is smaller than the rear groove wall inclination angle.
If the contact face is, for example, a planar face and the groove has in cross section the shape of a semicircle the front groove wall inclination angle and the rear groove wall inclination angle are each 90°. A front groove wall inclination angle which is less than a rear groove wall inclination angle, which can also be referred to as a beveled edge, beveled face or chamfer, has multiple advantages. Firstly, if there is contact between the contact face and the opposite side of the bearing inner space in the stationary state of the sliding bearing, the beveled face can enlarge the face which is covered with pressurized lubricant. As a result, a hydrostatic capacitance, that is to say power of the sliding bearing, can be increased with the same lubricant injection pressure compared to a sliding bearing without a beveled face. On the other hand, in an operating state in which the sliding bearing has a constant rotational speed, the beveled face permits the lubricant to penetrate better between the contact face and the face which lies opposite in the bearing inner space than in a comparable sliding lining without a beveled face. As a result, the beveled edge also permits, for example, the hydrodynamic operating pressure to be reached more quickly.
In a further embodiment, the sliding bearing has a sliding lining carrier which is connected to the sliding lining. Furthermore, the sliding lining carrier has a sliding lining carrier duct which crosses the sliding lining carrier, wherein the sliding lining carrier duct is provided for feeding lubricant into the sliding lining duct.
The sliding lining carrier can be connected in one piece with the sliding lining. The sliding lining carrier can also be connected to the sliding lining by at least one screw, a bolt and/or a nail. The connection between the sliding lining and the sliding lining carrier is advantageously configured in such a way that in the case of wear of the sliding lining the sliding lining can be replaced with little effort.
The sliding lining carrier duct and the sliding lining duct can be in the form of a round cylinder. The sliding lining carrier duct and/or the sliding lining duct can have an internal diameter in a range between 1 mm and 15 mm, in particular in a range between 2 mm and 10 mm.
In a further embodiment, the sliding lining carrier is arranged, by a rotary joint, such that it can rotate relative to the first bearing component and/or can rotate relative to the second bearing component.
The rotary joint can be a mechanical rotary joint which comprises, for example, a point contact and/or a line contact, with the result that the sliding lining carrier is rotatably mounted with the sliding lining. The rotary joint has the advantage that during operation of the sliding lining the sliding lining can change in its orientation in order, for example, to set a uniform thickness of a lubricant film which is located between the contact face and the opposite face of the bearing inner space.
In a further advantageous embodiment, the sliding lining carrier and/or the sliding lining are/is flexible.
One advantage of a flexible sliding lining and/or sliding lining carrier is that the sliding lining and/or the sliding lining carrier can adapted to an optimum shape and an optimum orientation in the sliding bearing.
Given a certain external load, i.e. an external force with a certain size which acts on the sliding lining carrier, the sliding lining carrier deforms in a range between 0 and 1000 μm (micrometers). This deformation is based on the deformation of the sliding lining carrier which has, for example iron, and on the deformation of the sliding lining which has, for example, a polymer compound. In contrast, the lubricant, for example an oil mixture, is compressed in a range between 0 and 100 μm when the same external force acts. In this example, the flexibility of the sliding lining carrier relative to the compressibility of the lubricant film is therefore significant.
In a further embodiment, the sliding lining carrier comprises a sliding lining carrier material which has iron, in particular an iron alloy.
For example, the sliding lining carrier material has steel and/or cast iron.
In a further advantageous embodiment, the wind power plant has a rotor and a gondola, and the sliding bearing is a main bearing for rotatably bearing the rotor relative to the gondola.
The main bearing of a wind power plant has an internal diameter of up to several meters, in particular an internal diameter in a range between a meter and ten meters. It is advantageous in a bearing of this size to use a sliding bearing instead of conventional roller bearings and rolling bearings since the main bearing can be subjected to very large forces. It may therefore be necessary to operate the sliding bearing with lubricant injection pressure. This involves a high energy requirement for maintaining the lubricant injection pressure. In this regard, a sliding bearing with a sliding lining which has a groove is advantageous since the lubricant injection pressure is reduced and as a result the sliding bearing can be operated economically and efficiently in terms of energy.
In a further embodiment, the lubricant has lubricating oil.
The lubricating oil has here a viscosity which can depend on a temperature of the lubricating oil. The lubricating oil is advantageously selected as a function of the temperature which occurs and a range of a sliding speed, that is to say a rotational speed of the sliding bearing. For example, at high sliding speeds a sliding oil with low viscosity is advantageous. In contrast, at high temperatures a lubricating oil with relatively high viscosity is advantageous since the viscosity of the lubricating oil can decrease at rising temperatures.
In one advantageous embodiment, the sliding lining has a sliding lining material which has a polymer and/or a white metal.
The sliding lining material advantageously has a polymer compound.
The polymer is, for example nylon.
In a further advantageous embodiment, the sliding bearing has a plurality of sliding linings. In the case of a radial sliding bearing, these can be attached to the outside of the inner bearing ring and/or to the inside of the outer bearing ring.
The sliding bearing advantageously has between two and fifty sliding linings, in particular between ten and forty sliding linings. The plurality of sliding linings can be arranged around the periphery, in particular around the circumference.
The invention also relates to an operation of the wind power plant in order to generate electric current. In other words, the invention relates to a use of the wind power plant for generating electric current.
The sliding bearing is advantageously operated hydrostatically during a startup phase of the rotational movement and/or hydrodynamically during a phase of the rotational movement with a constant rotational speed.
If the sliding bearing is operated hydrostatically or hydrodynamically depending on the phase of the rotational movement, the sliding bearing can also be referred to as a hybrid, i.e. hydrostatic/hydrodynamic, sliding bearing. The operation of a wind power plant with a hybrid sliding bearing is efficient with respect to the energy required to force in or inject the lubricant.
The invention will be explained below on the basis of a plurality of schematic figures which are not true to scale. Furthermore, exemplary embodiments of the invention are described. In the drawing:
The hub 13 with the rotor blades 14 rotates with a rotational speed from 11 revolutions per minute to 15 revolutions per minute about the rotational axis 26. In one alternative exemplary embodiment, the rotational speed can extend up to 20 revolutions per minute.
The sliding bearing comprises a first bearing component 21 which is configured as an outer bearing ring, and surrounds an inner side of the outer bearing ring 22. Furthermore, the sliding bearing surrounds a second bearing component 23 which is configured as an inner bearing ring 23 and surrounds an outer side of the inner bearing ring 24. The two bearing components 21, 23 are each in the shape of a hollow cylinder and are arranged coaxially.
In the exemplary embodiment shown in
The diameter of the inner bearing ring is approximately 1.5 meters. In an alternative exemplary embodiment, the inner bearing ring can have a diameter in the range between 1 meter and 4 meters.
The sliding linings 30 are connected to sliding lining carriers 37. The sliding lining carriers 37 are connected to the outside of the inner bearing ring 24 and are attached thereto. A bearing inner space, which is partially filled with lubricant, is located between the inner bearing ring and the outer bearing ring. The lubricant has lubricating oil, in particular an oil mixture. An average distance between the sliding lining 30 and the inside of the outer bearing 22 is 0.5 mm (millimeters). The lubricating oil at least partially fills this distance.
The contact face has a contact face region 311 which is at the front in the rotational direction 27, a central contact face region 312 and a rear contact face region 313. In the front contact face region 311 there is a groove 40 which is 7 mm deep. Furthermore, the contact face 31 has a sliding lining duct opening 36 which has a diameter of 1 cm. Finally, a sliding lining duct 35 crosses the sliding lining 30.
It is apparent that the front groove wall 41 encloses an angle of 90° with a contact face 31 of the sliding lining 30. In contrast, the rear groove wall 42 encloses an angle of 135° with the contact face 31. The angle between the front groove wall 41 and the contact face 31 is referred to as the front groove wall inclination angle 43; the angle between the rear groove wall 42 and the contact face 31 is referred to as the rear groove wall inclination angle 44. An inclined rear groove wall 42, shown in
In order to efficiently feed lubricant into the groove 40, the sliding lining duct 35 and the sliding lining carrier duct 38 are connected to one another in a flush fashion.
Number | Date | Country | Kind |
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102013211710.8 | Jun 2013 | DE | national |