Capacitance-increasing device for an electromechanical converter

Abstract

The invention relates to a capacitance-increasing device (24) for increasing an electric capacitance between a first machine element (22), in particular a housing (22a) of an electromechanical converter (10), and a second machine element mounted rotatably relative to the first machine element, in particular a shaft (16a) of the electromechanical converter (10), wherein: the capacitance-increasing device (24) comprises a first electrode (26) comprising a first electrode body (30) and comprising a first electrode surface (27); during operation of the electromechanical converter (10), the first electrode (26) is at a distance from a second electrode (28) comprising a second electrode body (34) comprising a second electrode surface (29); a functionally effective increase capacitance (Ce) is formed by the first electrode (26) and the second electrode (28); the first electrode (26) is electrically conductively connected to the first machine element (22), and the second machine element (16), in particular the second electrode (28), forms the second electrode surface (29), and is capacitively functionally effectively coupled to the first electrode (26), in particular to the first electrode surface (27).

Description

[0001] DESCRIPTION

[0002] Capacity increasing device for an electromechanical converter

[0003] The invention relates to a capacitance increasing device for increasing an electrical capacitance between a housing and / or a stator and a shaft having an axis of an electromechanical converter which has a rotor connected to the shaft and a stator winding.

[0004] Electromechanical converters, especially electric motors and especially those in electric vehicles, are now usually controlled by inverters. The voltage waveform introduced by the inverters into the motor windings, especially the stator windings, exhibits a multitude of high frequencies. Capacitive and inductive effects create electrical voltages in parts of the electromechanical converter, particularly in the rotor and shaft, compared to other, partially insulated parts of the electromechanical converter.

[0005] For example, it is possible that a voltage is capacitively coupled into the shaft with respect to a housing and / or the stator of the electromechanical converter in such a way that this voltage breaks down a breakdown voltage, for example, of a bearing on which the shaft is mounted. This causes irreversible damage and ultimately destruction to the bearing.

[0006] It is known to limit such a destructive current flow through the bearing by, for example, shaft earthing by means of a sliding contact enabling charge flow and potential equalization between the housing and the shaft.

[0007] Against this background, the present invention has the object of proposing a device which extends the service life of a bearing of an electromechanical converter, in particular of an electric motor.

[0008] The object is achieved by a device having the features of patent claim 1. Further advantageous embodiments of the invention are the subject of the dependent claims.

[0009] To achieve the object, a capacity increasing device for increasing an electrical capacity between a first machine element, in particular a housing of an electromechanical converter, and a second machine element, in particular a shaft of the electromechanical converter, which is rotatably mounted relative to the first machine element, wherein the capacity increasing device has a first electrode with a first electrode body and with a first electrode surface, wherein the first electrode is arranged at a distance from a second electrode with a second electrode body with a second electrode surface during operation of the electromechanical converter, wherein a functionally effective increasing capacity (C e), wherein the first electrode is electrically conductively connected to the first machine element and forms the second machine element, in particular the second electrode, in particular the second electrode surface, and is capacitively functionally coupled to the first electrode, in particular to the first electrode surface.

[0010] The resulting capacitively functionally effective increase in capacitance between the stator and rotor, or between the housing and the shaft, reduces the voltage that periodically develops between the stator and rotor. As a result, the maximum voltage of voltage peaks remains below a critical breakdown voltage, for example, of a motor bearing. This reduces the number of breakdowns through the motor bearings, especially during wet operation, resulting in fewer destructive breakdowns and extending the service life of the motor bearings.

[0011] In some embodiments, the capacity increasing device comprises a second electrode configured to be fixedly arranged on and electrically connected to the second machine element, wherein the second electrode is configured to increase the increasing capacity and is arranged relative to the first electrode.

[0012] Such a second electrode, which is designed separately from the second machine element, offers the possibility of more freely determining the shape of the second electrode. The first and second electrodes can thus be more precisely matched to one another or have shapes that would be difficult to realize on the second machine element. By advantageously shaping the first and second electrodes and matching them to one another, the boosted capacitance can thus be efficiently increased. Furthermore, the flexibility of using the capacitance-increasing device is improved.

[0013] In some embodiments, the first electrode comprises a disk-shaped first electrode body arranged in a radial plane of the second machine element, which has a through-opening for the passage of the second machine element.

[0014] This design is particularly simple and cost-effective to manufacture and can be used very flexibly in a variety of installation situations. In some embodiments, the first electrode body and / or the second electrode body are coated at least in sections with an electrically conductive material and / or a dielectric and / or are surrounded by a dielectrically active fluid.

[0015] The effective capacitance of the capacitance-increasing device depends, among other things, on the properties of the space that absorbs the energy stored in the capacitance-increasing device by creating an electric field. If the dielectric is arranged in the energy-storing space of the capacitance-increasing device, it increases the permittivity of the space and thus the capacitance. Thus, an increase in the capacitance can be achieved with the same electrode shape.

[0016] In some embodiments, the second electrode has a disk-shaped second electrode body extending parallel to the first electrode body and arranged at an axial distance therefrom.

[0017] Such an electrode body achieves axial overlap between the first and second electrodes, so that their axial side surfaces face each other. This creates a plate-shaped capacitance-increasing device between each of the opposing electrode surfaces, which increases the capacitance.

[0018] In some embodiments, the electrodes comprise, for example, a base material with at least one polymer, in particular a homopolymer and / or copolymer, and one or more fillers, with at least one electrically conductive filler being provided. Furthermore, different PTFE materials can also be used. In some embodiments, it can be provided that one of the electrodes consists at least partially of an electrically conductive PTFE material.

[0019] In some embodiments, the electrodes comprise, in addition to the base material, an electrically conductive filler, for example, metallic, metallized and / or metal-coated particles, microspheres, microtubes and / or fibers, in order to adjust the conductivity as well as the rigidity or elastic deformation of the electrodes as desired. The weight fraction of the or all of the electrically conductive fillers is preferably in the range between 1% and 25%, more preferably in the range between 5% and 20%, even more preferably in the range between 10% and 15%. The fillers can also be dielectrically effective. In some embodiments, the electrically conductive filler comprises, for example, silver, silver-plated and / or silver-coated particles, microspheres, microtubes and / or fibers. In this case, the metallization, in particular of the particles or fibers, can comprise mainly silver (Ag), i.e.with at least 50% by weight silver as the metallization metal. In some embodiments, copper or gold can also be used instead of silver. Metallized particles or fibers have a metallic coating on their surface, so that they exhibit metallic properties on their outer shell. This results in electrical conductivity when combined. Other properties such as strength and / or density, however, are primarily determined by the inner material of the particles, fibers, etc.

[0020] Natural plant fibers made of cellulose, as well as artificial cellulose fibers, can also be used. Furthermore, the plant fibers, especially the cellulose fibers, can be impregnated with a dielectric fluid.

[0021] In some embodiments, the second electrode is configured for fixed arrangement with the second machine element, wherein the second electrode is provided for increasing the increasing capacitance and is arranged axially spaced from the first electrode and is capacitively functionally coupled.

[0022] In some embodiments, the second electrode has at least one fastening portion for rotationally fixed fastening to the second machine element.

[0023] In cases where the second machine element is manufactured independently of the second electrode and, for example, the second electrode is added to the second machine element only later, a fixed arrangement, for example such a fastening section, allows an efficient, safe and compact construction of the capacity increasing device.

[0024] In some embodiments, first electrode bodies and second electrode bodies are arranged alternately along an axial direction of the second machine element and are capacitively functionally coupled. For example, at least two, three, or four electrode bodies may be provided.

[0025] This alternating arrangement of electrode bodies leads, in particular, to the formation of plate-shaped capacitance-increasing devices between axially overlapping side surfaces of the electrode bodies. Thus, while maintaining a compact design, the increased capacitance is increased several times. In some embodiments, the first electrode has a first electrode surface that is at least partially frustoconical in shape, and the second electrode has a second electrode surface that is at least partially frustoconical in shape. The first electrode surface forms a first angle and the second electrode surface a second angle with the rotational axis of the second machine element, the first angle and the second angle each being less than 90°.

[0026] The two electrodes are thus arranged like two nested funnels. Because they are oriented diagonally in space in cross-section, large portions of the electrode surfaces face each other, resulting in an increase in the boosting capacity.

[0027] In some embodiments, the first electrode comprises a first electrode body having a funnel portion on which the first electrode surface is formed, wherein the funnel portion has a through-opening for passing through the second machine element and / or the second electrode.

[0028] Such a structure of the first electrode can be carried out very stably and precisely.

[0029] In some embodiments, the second electrode comprises a second electrode body having a funnel portion or a cone portion on which the second electrode surface is formed and having a fastening portion for rotationally fixed fastening to the second machine element.

[0030] Such a structure of the second electrode can be carried out very stably and precisely.

[0031] In some embodiments, the first electrode surface of the first electrode body has an end face facing the second machine element with an end face, wherein the end face is preferably aligned parallel to the second electrode surface.

[0032] In some embodiments, the first electrode and / or the second electrode comprises an elastically deformable electrode body.

[0033] In some embodiments, the electrode bodies can comprise a fluoropolymer such as PTFE, FKM, an elastomer, fluorinated thermoplastic, or a PTFE-based polymer or a corresponding copolymer as the base material. Polytetrafluoroethylene (PTFE), for example, is a plastic with good sliding properties and high mechanical and chemical resistance. The electrode bodies can comprise, in addition to PTFE, a nonwoven fabric as the base material. This nonwoven fabric can, for example, be impregnated with electrically conductive PTFE. The electrical conductivity of nonwoven fabric or PTFE materials can also be achieved, for example, by electrically conductive particles distributed throughout the material.The material from which the particles are made, the quantity and distribution of the particles and also the size of the particles are adapted to the respective conditions of the application in such a way that the electrical conductivity of the electrode achieves a potential equalization between the two machine elements.

[0034] The electrode bodies can, for example, also contain several different PTFE compounds. For example, pure PTFE (homopolymer) or modified PTFE, in which another monomer is polymerized in addition to the PTFE (copolymer), can be used. In some embodiments, the electrode bodies are optimized with different thicknesses in different regions, so that, for example, the edge regions have a predetermined thickness, which optimizes them for elastic deformation.

[0035] Such electrode bodies can adapt their shape to the specific installation situation and, to a certain extent, compensate for inaccuracies. They are therefore more flexible in their application. Furthermore, because their deformability must be taken into account during dimensioning, they can be designed more compactly than rigid electrode bodies.

[0036] In some embodiments, the deformable electrode body has a contact surface for physical contact with the respective other electrode body. During operation of the electromechanical transducer, a hydrodynamic pressure can be generated between the electrode bodies by means of the flow of a moving fluid, in particular an oil and / or air-oil mixture, which causes the electrode bodies to be deformed in such a way that they no longer have physical contact with the respective other electrode body and are functionally and effectively coupled capacitively.

[0037] This ensures complete contact and dissipation of charge from the second machine element when the device is at a standstill, thus creating potential equalization between the machine elements. As a result, when the electromechanical converter is at a standstill, the first and second machine elements have the same electrical potential. If the second machine element is set in motion, the viscosity of the second machine element causes it, for example, to move along with the surface of the second machine element. Due to this viscosity, the oil pushes itself between the machine element and the electrode body, thereby breaking the electrical contact. Furthermore, the oil present between the machine element and the electrode body during operation acts as a dielectric to increase the capacitance.

[0038] In some embodiments, the contact surface and / or the electrode body have structures for forming the hydrodynamic pressure for the deformable electrode body from an oncoming flow of the fluid.

[0039] The strength of the floating effect caused by the hydrodynamic pressure is thus controllable. Depending on the structure, different pressures and thus deformation forces are generated in the electrode bodies at different speeds. Accordingly, a desired deformation and thus a shape of the elastically deformable electrode body can be adjusted during operation. This allows for precise control of when contact is established or broken between the electrode body and the machine element during the transition between operation and standstill of the second machine element.

[0040] In some embodiments, at least one electrode spacing device for defining an electrode spacing is arranged between the first electrode and the second electrode.

[0041] This allows the properties of the capacity-enhancing device to be adjusted more precisely. Furthermore, such an electrode spacing device can prevent uncontrolled contact between the electrodes, for example, due to a malfunction, which in the worst case could result in the destruction of the electrodes. This further improves the safety and service life of the capacity-enhancing device.

[0042] In some embodiments, the capacity increasing device comprises an actuator for adjusting a position and / or an orientation of at least a portion of the first electrode and / or the second electrode.

[0043] By changing the position and / or orientation, particularly of the electrodes relative to each other, the magnitude of the increased capacitance can be varied. This allows the capacitance-increasing device to be flexibly adapted to current operating conditions. In some embodiments, the capacitance-increasing device comprises a control device configured to control the actuator based on measurement data, wherein the measurement data comprises one or more of the following data types: electrode spacing measurement data, capacitance measurement data, charge measurement data, voltage measurement data, current measurement data, mechanical stress measurement data.

[0044] Based on the measurement data, the booster capacity can be adjusted to suit the current operating condition. Furthermore, certain malfunctions or wear of the electromechanical converter and / or the booster device can be detected from the measurement data.

[0045] In some embodiments, at least one element of the first electrode and / or the second electrode can be disassembled into a plurality of parts in a circumferential direction for assembly and / or disassembly, in particular into two, three, four, five, six, seven, eight or more parts and in particular into parts which each comprise an identical angular range in the circumferential direction.

[0046] Especially when the electromechanical converter exceeds a certain size, it is no longer practical to transport all the individual components in one piece. For example, the components of a wind turbine must be transported long distances and then lifted to a great height to assemble the electromechanical converter. The cost-effective tools available for this purpose have only limited carrying capacity. Furthermore, wind conditions, for example, make handling large parts extremely laborious. Constructing the capacity-enhancing device from easily handled individual parts thus results in more cost-effective and efficient transport and assembly.

[0047] A division along radial lines evenly distributed in the circumferential direction has the advantage that in many cases it is possible to construct a structure from many similar or even identical sub-elements.

[0048] In some embodiments, a capacitor, a controllable capacitor, a resistor and / or an inductance is arranged in the electrical connection between the first electrode and the first machine element.

[0049] This makes it possible, for example, to adapt the reactance of the capacitance-enhancing device to specific frequency ranges and / or operating parameters. In some embodiments, the capacitance-enhancing device comprises an error detection device configured to detect malfunctions, transmit error information via a network, and / or shut down the electromechanical converter in an emergency.

[0050] Such a fault detection device increases the reliability and service life of both the capacitance booster and the electromechanical converter. It allows for remote maintenance, which enables efficient monitoring, particularly for electromechanical converters that are difficult to access (e.g., in wind turbines).

[0051] Further features and variants of the invention are particularly evident from the accompanying figures, which show the inventive forms of the invention only schematically and by way of example. They show in detail:

[0052] Fig. 1 is a schematic cross-section through an electric motor, in which some of the capacitances forming in the motor are identified, according to the prior art;

[0053] Fig. 2 is an equivalent circuit diagram for the electric motor according to Fig. 1;

[0054] Fig. 3 is a schematic cross-section as in Fig. 1 through an electric motor with a capacity increasing device according to an embodiment of the invention;

[0055] Fig. 4 is an enlargement of a detail marked with a dashed circle in Fig. 3;

[0056] Fig. 5 is a radial section through the first electrode of the capacity increasing device of Fig. 3;

[0057] Fig. 6 is an equivalent circuit diagram for the electric motor according to Fig. 3;

[0058] Fig. 7 is a schematic cross-section as in Fig. 1 through an embodiment of a capacity increasing device;

[0059] Fig. 8 is a schematic cross-section as in Fig. 1 through an embodiment of a capacity increasing device;

[0060] Fig. 9 is a schematic cross-section as in Fig. 1 through an embodiment of a capacity increasing device;

[0061] Fig. 10 is an axial plan view of one embodiment of a flexible electrode body; Fig. 11 is an axial plan view of another embodiment of a flexible electrode body;

[0062] Fig. 12 is an axial plan view of a portion of a flexible electrode body according to another embodiment of the invention;

[0063] Fig. 13 is a radial section through the section of the electrode body of Fig. 12 with several tongues and

[0064] Fig. 14 is a radial view of tongues of the electrode body of Fig. 12 with an operational shaping of the tongues.

[0065] Some of the figures contain simplified, schematic representations. Identical reference symbols are used for similar, but possibly not identical, elements. Different views of the same elements may be scaled differently. Directional references such as "left," "right," "top," and "bottom" are to be understood with reference to the respective figure and may vary in the individual illustrations relative to the object depicted.

[0066] Furthermore, elements are not necessarily drawn to scale, particularly for the sake of simplicity and clarity in illustrating their functional relationship. If process steps or elements are provided with enumerative designations such as "first," "second," "third," or "further," these designations, unless explicitly disclosed otherwise, serve merely to distinguish them and do not imply any order or hierarchy.

[0067] An electromechanical converter in the form of an electric motor 10, shown in Fig. 1 and known in the prior art, comprises a stator 12 with a plurality of stator windings 14, and a rotor 18 connected to a second machine element in the form of a shaft 16. The rotor 18 and the shaft 16 are mounted by means of bearings 20 relative to a first machine element in the form of a housing 22 connected to the stator 12.

[0068] In particular, when the electric motor 10 is controlled by switches, for example by a PWM controller or a frequency converter, parasitic voltages arise in various parts of the electric motor 10, particularly due to the interaction of rotating magnetic fields and / or parasitic components. Parasitic components in this case are, in particular, parasitic capacitances that arise between different stator windings 14 (C Ph), between the rotor 18 and the stator windings 14 (C m ), between the stator windings 14 and the stator 12 (Cwf), between the rotor 18 and the stator 12 (Crf), and in the bearings 20 between the

[0069] Housing 22 and shaft 14 (Cb).

[0070] These parasitic capacitances can be summarized in an equivalent circuit diagram as shown in Fig. 2. Only the parasitic capacitances affecting shaft 14 are shown in the equivalent circuit diagram. The potentials of the stator windings 14, the rotor 18, and the housing 22 are marked accordingly. It should be noted that the rotor 18 and the shaft 16 are electrically connected to each other, as are the rotor 12 and the housing 22. Therefore, they each have the same potential.

[0071] A voltage Ub dropped across the bearing 20 depends on the input voltage U y of the stator windings 14 as follows:

[0072] If the voltage Ub exceeds the breakdown voltage of the bearing 20, the resulting flashovers damage parts of the bearing 20, particularly in the smooth surfaces where, for example, the balls of a ball bearing are supposed to roll. This causes irreversible damage to the bearing 20. This damage accumulates over time and ultimately leads to the failure of the bearing 20.

[0073] In order to reduce the voltage Ub, according to the present invention, a capacitance-increasing device 24 is provided, as shown in Figs. 3 to 5. The capacitance-increasing device 24 has a first electrode 26. The first electrode 26 is electrically connected to the housing 22 and thus also to the stator 12. A second electrode 28 is formed by the shaft 16 and connected to the rotor 18. The first electrode 26 has a first electrode body in the form of a disk-shaped first electrode plate 30, which has a through-opening 31 through which the shaft 16 is guided. The first electrode plate 30 does not touch the second electrode 28.

[0074] A first cylindrical electrode surface 27 is arranged along an inner circumferential surface of the first electrode plate 30, which is arranged opposite a cylindrical electrode surface 29 of the shaft 16. The two electrode surfaces 27, 29 are circumferentially spaced radially from one another by an electrode spacing d and define an annular gap 33 between them. The opposing electrode surfaces 27, 29 form a cylindrical capacity increasing device, which has an additional capacity C e This additional capacity C e can be approximately calculated as follows: Formula (2)

[0075] The variables in formula (2) represent:

[0076] L Extension in axial direction (width) a Radius of the inner electrode, here the shaft 16 d Electrode distance, i.e. the radial distance between the electrode surfaces 27, 29 e0Electric field constant (permittivity of the vacuum) sr (Relative) permittivity of the space between the electrode surfaces 27, 29

[0077] To increase the additional capacity C e To increase the size of the object, these variables can be changed. A change in the variables d and s r This is possible with comparatively little effort, since these can be made dependent solely on the design of the capacity-increasing device 10 and do not require any structural changes to the shaft 16 or a housing surrounding the entire device. This applies to all embodiments shown here and also to other embodiments, since C e also for non-cylindrical designs in the same way from d and s r depends on.

[0078] Through more precise manufacturing and assembly, for example, the electrode distance d can be reduced, since such a large margin for inaccuracies no longer needs to be taken into account.

[0079] In some embodiments, for example, at least the electrode surfaces 27, 29 can be coated with a dielectric. For this purpose, PTFE can be used, which has a r of approximately 2.0. In wet operation, in which at least part of the electromechanical converter and the capacitance-enhancing device operates in oil, the space between the electrode surfaces can be filled with oil. The capacitance-enhancing device does not need to be operated in oil for this purpose. It may be sufficient for an oil mist to precipitate or run off a machine element 16, 22 and remain in the annular gap 33 between the electrode surfaces 27, 29 due to adhesion forces.

[0080] Because the first electrode 26 is connected to the housing 22 and the second electrode 28 is connected to the shaft 16 and the stator 18, the capacitance C econnected in parallel to the parasitic capacitance Cb formed in the bearings 20, as shown in the equivalent circuit in Fig. 6. The values ​​of parallel-connected capacitances are added to determine the total capacitance, so that after adding the

[0081] Capacity increasing device 24 changes the above formula (1) as follows:

[0082] Formula (3)

[0083] By adding the capacitance-enhancing device 24, the total capacitance in the denominator of the right-hand side of the equation is increased, thereby reducing the bearing voltage Ub. This reduces the risk of destructive breakdowns through the bearing 20 and thus extends its service life.

[0084] A variety of embodiments of the capacity-increasing device 24 can provide the increased capacity Ce. Only a few of the possible designs are selected here as exemplary embodiments.

[0085] In some embodiments, one of which is shown in Fig. 7, the first electrode 26 has first electrode plates 30, which can be constructed and arranged, for example, as in the embodiment according to Figs. 3 to 5. However, unlike the embodiment according to Figs. 3 to 5, a plurality of first electrode plates 30 are provided, which are arranged one behind the other in the axial direction of the shaft 16. In this case, too, the first electrode 26 is electrically connected to the housing 22.

[0086] The second electrode 28 has second electrode bodies in the form of disc-shaped second electrode plates 34, which protrude radially outward from a sleeve 36, which is placed on the shaft 16. The first and second electrode plates 30, 34 thus have axially aligned first and second electrode surfaces 27, 29. In the axial direction, a first electrode 26 and a second electrode 28 are arranged alternately, so that the electrode surfaces 27, 29 are opposite one another and are spaced apart by an axial electrode distance d a are arranged at a distance from each other. They thus form plate-shaped capacity increasing devices 24, C e .

[0087] In embodiments constructed in this way, the capacitance formed between the radial inner surface and the shaft 16 is available in addition to the capacitance of the plate-shaped capacitance increasing device 24, but the capacitance formed between the electrode plates 30, 34 of the plate-shaped

[0088] Capacity increasing device 24 significantly larger.

[0089] To construct the second electrode 28, a plurality of sleeves 36 can be arranged on the shaft 16 in a rotationally fixed manner, between which the second electrode plates 34 are mounted. Similarly, an outer bushing 36 can have a plurality of sub-bushes, between which the first electrode plates 30 are mounted and secured. The outer bushing 36 can, for example, be designed for press-fitting into a housing or other mounting.

[0090] This construction from several individual parts simplifies the installation of the capacity increase device 24 on the shaft 16. This construction from individual parts makes it particularly easy to achieve the nested structure shown from interlocking electrode plates 30, 34.

[0091] In some embodiments, electrode spacing devices may be arranged between the electrode plates 30, 34 and / or between the electrode plates 30, 34 and the bushing 36 and / or the shaft 16 to define a radial and / or axial distance between the first electrode 26 and the second electrode 28. Such electrode spacing devices may, for example, also serve as a dielectric to increase the capacitance C e cause.

[0092] The electrode spacing can be varied depending on the specific application. Typical electrode spacings range, for example, between 0.1 pm and 1000 pm or between 1 pm and 100 pm. The first electrode 26 and the second electrode 28 do not necessarily have to have flat electrode plates 30, 34 to form the electrode surfaces. In some embodiments, the electrode plates 30, 34 can be cylindrical, conical, or spherical, for example. Furthermore, a section-by-section combination of cylindrical, conical, and / or spherical sections is also possible.

[0093] In some embodiments, one of which is shown by way of example in Fig. 8, the first electrode 26 has a funnel-shaped first electrode body 30. A truncated cone-shaped first electrode surface 27 is arranged on the inside of the first electrode body 30. The first electrode body 30 has a through-opening for receiving the shaft 16 and / or the second electrode body 34 at a distance. The second electrode body 34 has a sleeve section 36, to which a truncated cone section 38 is axially connected, which has the second electrode surface 29. The first electrode body 30 and the second electrode body 34 are arranged coaxially to one another and to the shaft 16, so that the electrode surfaces 27, 29 lie opposite one another and together form a capacitance.

[0094] At an inner portion 40, the first electrode body 30 is cut off axially so that its inner surface forms an end face 27a with an end face surface 27b arranged parallel to an outer surface of the sleeve 36, so that these two surfaces are opposite each other and form an additional capacitance.

[0095] Thus, a predominantly conical gap is formed between the first electrode body 30 and the second electrode body 34, in which the increase capacity C e is trained.

[0096] In some embodiments, one of which is shown by way of example in Fig. 9, the first electrode 26 comprises an elastically deformable first electrode body 30, which is clamped, for example, between two radial flanges for stable and rotationally fixed positioning. In this case, the second electrode 28 can be formed, in particular, by the shaft 16.

[0097] The otherwise disc-shaped first electrode body 30 has a lip portion 42 in which it is protruded in an axial direction of the shaft 16 and rests against the shaft 16 with a side surface as long as the shaft 16 is not rotating. The space surrounding the capacitance-enhancing device 24 contains oil that coats the shaft 16 and also the lip portion 42. When the shaft 16 begins to rotate, the oil on the shaft 16 is drawn along by its viscosity, builds up hydrodynamic pressure, and pushes itself between the shaft 16 and the lip portion 42. This interrupts the contact between the lip portion 42 and the shaft 16, and an oil-filled, insulated space is formed between them. Since charge separation is also possible at this space and the influence effect can take effect, the increased capacitance C is formed at this point. e out of.

[0098] In some such embodiments, the lip portion 42 may have floating structures on one or more surfaces. Such floating structures can better absorb the energy of the viscous, moving oil and thereby achieve a defined electrode distance d between the lip portion 42 and the shaft 16. The lip portion 42 thus floats on the moving oil.

[0099] In this case, the electrode body 30 does not have to be rotationally symmetrical, but can have circumferential openings, for example open-edged recesses 44, as shown, for example, in Figs. 10 and 11.

[0100] In the embodiment of the first electrode body 30 shown in Fig. 10, for example, the lip section 42 is divided into a plurality of electrode segments, each having one or more tongues 50, which in turn form one or more individual lips 46. The individual lips are each held, for example, by a web 48. By designing the material and the geometry of the web 48, in particular, a pressing force of the individual lips 46 against the second electrode 28, for example, the shaft 16a, and thus also the floating properties can be adjusted as described above.

[0101] The embodiment shown in Fig. 11 has a plurality of substantially trapezoidal tongues 50, on the inner surfaces of which the individual lips 46 of the lip portion 42 are formed and between which the recesses 44 are arranged.

[0102] In some embodiments, the tongues 50 have different lengths in the radial direction, as shown in Figs. 12 to 14. When the shaft 16a is inserted, the tongues 50 are deflected to different degrees due to their different lengths and thus bear against tracks 54a, 54b, 54c of the shaft 16a that are different in the axial direction. This distributes the frictional work over a larger area of ​​the shaft 16a, particularly when the shaft 16a starts to move, thus reducing surface wear.

[0103] In order to keep the properties of the electrode segments as constant as possible throughout the service life of the electrode body 30 and to largely avoid a running-in phase with increased abrasion and wear, the individual lips 46 can each be provided with an operating shape 56 on a side facing the shaft 16a. The operating shape 56 corresponds, for example, to a surface shape that can slide along the shaft 16a and float with as little wear as possible. For this purpose, the operating shape 56 can, for example, be cylindrically designed corresponding to a recess in the shape of the shaft 16a. The operating shape 56 can also be inclined according to the orientation of the individual lip 46 during operation.

[0104] In some embodiments, the tongues 50 may have a joint 52, by means of whose material thickness a pressing force of the tongue 50 can be determined. The joint 52 may, in particular, have a radial recess.

[0105] To stabilize and limit the deflection, a limiting or spacing device can be arranged on at least one axial side of the electrode body 30.

[0106] In some embodiments, the electrode body 30 is divided into individual sections, for example, into several disc segments. Each of these sections can, for example, have its own limiting or spacing device. This can also be configured as an adjustable actuator and / or individually monitored by an error detection device.

[0107] The open-edged recesses 44 can furthermore be designed, for example, in a U-shape, a T-shape, a V-shape, as slots, or even in a triangular shape.

[0108] In some embodiments, the recesses 44 can be designed to be closed toward the edge. Recesses 44 arranged in this way can also serve, for example, for pressure equalization.

[0109] In some embodiments, the recesses 44 may be arranged on a radially outer side of the electrode body 30.

[0110] In some embodiments, the first electrode 26 and / or the second electrode 28 may comprise at least one actuator and / or a resilient element, for example, the web 48, with which a position and / or orientation of an element of the electrode 26, 28, for example, an electrode body 30, 34, can be adjusted. The actuator may be controllable by a control device, which, for example, comprises sensors to detect parameters of an operating state.

[0111] In some embodiments, the control device may further comprise a fault detection device that can detect faults and / or wear of the capacity-increasing device 24 and / or the electromechanical converter 10 based on the detected parameters. This control device may further comprise a communication device by means of which the detected faults can be transmitted via a network. In some embodiments, it may also be provided that the control device can deactivate the electromagnetic converter 10 in a controlled manner upon detection of a catastrophic fault.

[0112] In particular, the sensors can provide the following data on the basis of which the control device carries out its detection: electrode gap measurement data, capacitance measurement data and / or mechanical stress measurement data.

[0113] In some embodiments, the connection between the first electrode 26 and the housing 22, which has been largely omitted from the figures for clarity, may include an additional electronic or electrical component. In particular, a capacitor, a controllable capacitor, a resistor, and / or an inductor may be arranged in this connection.

[0114] Different materials can be used to manufacture the electrodes 26, 28. The electrodes 26, 28 can be made of the same materials or material combinations, or they can be made of different materials or material combinations.

[0115] In some embodiments, the electrodes 26, 28 comprise, for example, a base material with at least one polymer, in particular a homopolymer and / or copolymer, and one or more fillers, with at least one electrically conductive filler being provided. Furthermore, different PTFE materials can also be used. In some embodiments, it can be provided that one of the electrodes 26, 28 consists at least partially of an electrically conductive PTFE material.

[0116] The electrodes 26, 28 can comprise a nonwoven fabric as their base material. This nonwoven fabric can, for example, be impregnated with electrically conductive PTFE. The electrical conductivity of nonwoven fabric or PTFE materials can also be achieved, for example, by electrically conductive particles distributed throughout the material. The material of which the particles are made, the quantity and distribution of the particles, and also the size of the particles are adapted to the specific conditions of the application in such a way that the electrical conductivity of the electrodes 26, 28 achieves potential equalization between the two machine elements.

[0117] In some embodiments, the electrodes 26, 28 may comprise at least one fluoropolymer such as PTFE, FKM, an elastomer, fluorinated thermoplastic, or a PTFE-based polymer or a corresponding copolymer as their base material. Polytetrafluoroethylene (PTFE), for example, is a plastic with good sliding properties and high mechanical and chemical resistance.

[0118] In some embodiments, the weight fraction of the base material can be in the range above 45%. The electrodes 26, 28 can also contain several different PTFE compounds, for example. For example, pure PTFE (homopolymer) or modified PTFE, in which another monomer is polymerized in addition to the PTFE (copolymer), can be used.

[0119] In some embodiments, the electrodes 26, 28 are optimized with different thicknesses in different regions, so that, for example, the edge regions have a predetermined thickness, wherein these can be the same thickness or optimized, for example, they can have a relative deviation of the thicknesses from one another of 0.1% to 25%, preferably of 1% to 15%, particularly preferably of 1% to 5%, and they can also be made of different materials with different electrically conductive fillers. In some embodiments, the electrically conductive filler comprises, for example, metallic, metallized and / or metal-coated particles, microspheres, microtubes and / or fibers in order to be able to adjust conductivity as well as rigidity or elastic deformation as desired. The weight proportion of the orof all electrically conductive fillers in the base material is preferably in the range between 1% and 25%, more preferably in the range between 5% and 20%, even more preferably in the range between 10% and 15%.

[0120] In some embodiments, the electrically conductive filler comprises, for example, silver, silver-plated and / or silver-coated particles, microspheres, microtubes, and / or fibers. In this case, the metallization, in particular of the particles or fibers, can comprise primarily silver (Ag), i.e., with at least 50% by weight of silver as the metal of the metallization. In some embodiments, copper or gold can also be used instead of silver.

[0121] Metallized particles or fibers have a metallic coating on their surface, giving them metallic properties on their outer shell. This makes them electrically conductive when combined. Other properties, such as strength and / or density, are primarily determined by the inner material of the particles, fibers, etc.

[0122] In some embodiments, electrically conductive carbon, for example in powder or pigment form, may prove to be a useful filler. The weight fraction of the electrically conductive carbon is, for example, in the range between 1% and 15% and / or is, for example, at least 4%, and / or at least 7%, and / or at least 10%. Conductive carbon is inexpensive, and the desired conductivity of the electrode 26, 28 can thus be easily and precisely adjusted. Additionally or alternatively, electrically conductive carbon fibers, for example, can be considered as fillers.

[0123] Fillers used in further embodiments consist of fibers, in particular glass fibers, to reduce wear. The weight fraction of glass fibers is then, for example, in the range between 5% and 20%, preferably in the range between 6% and 15%, more preferably in the range between 7% and 12%, for example in the range between 8% and 10%. The weight fraction of the at least one fiber filler, or of all fiber fillers, can be, for example, in the range between 1% and 30%, preferably in the range between 5% and 20%, even more preferably in the range between 7.5% and 15%, and for example, 10%. Fiber fillers serve primarily to mechanically reinforce the first electrode 26.

[0124] In some embodiments of the invention, at least one filler consists of a metal oxide or a metal oxide mixture. For example, a filler of tin(IV) oxide, indium tin oxide, or a mixture thereof may be suitable.

[0125] The weight fraction of the metal oxide-containing filler(s) or all of the metal oxide-containing fillers is, for example, in the range between 0.5% and 10%, preferably in the range between 1% and 5%. In some embodiments, dendritic silver can also be used as a filler. The weight fraction of the dendritic silver filler is preferably in the range between 1% and 10%, and more preferably in the range between 1% and 5%.

[0126] In some embodiments, the filler can consist of silver-coated glass fibers. Silver-coated glass fibers enable comparatively good tribological properties of the sealing element. The filler made of silver-coated glass fibers can, for example, have a silver content of 8 to 20 weight percent. The silver content in the filler made of silver-coated glass fibers can, for example, be 12 weight percent. A corresponding silver content enables a good compromise between conductivity and cost. The silver-coated glass fibers in the filler can have an average fiber length of 20 to 200 μm. The average fiber length can, for example, be between 80 and 150 μm. Short fiber lengths allow the use of various standard production processes. At the same time, a satisfactory surface quality can be achieved within the proposed range of average fiber lengths.

[0127] A filler can consist of silver-coated, preferably solid, glass spheres. Hollow glass spheres can also be used in possible alternative embodiments. The use of silver-coated glass spheres as a filler allows standard production processes for the collecting body to be used without major adaptations.

[0128] The filler made of silver-coated glass beads can contain 4 to 20, preferably 4 to 12, percent silver by weight.

[0129] The silver content can be, for example, 12 percent by weight. By using silver-coated glass beads, the utilization of the silver in the filler relative to the filler volume can be particularly efficient. The silver-coated glass beads can, for example, have an average diameter of 10 to 45 pm, preferably 10 to 30 pm. The average diameter of the glass beads can be, for example, 14 pm.

[0130] These diameters are particularly suitable for keeping mechanical stress peaks in the material low and preventing the formation of cracks under alternating loads.

[0131] A filler can consist of silver-coated copper particles. The combination of a highly conductive silver coating on copper particles, which also have very high conductivity, significantly increases the conductivity of the filler. This can increase the conductivity of the electrodes 26, 28 and consequently their effectiveness in dissipating static and dynamic electrical voltages. The silver-coated copper particles can have a dendritic structure to achieve high electrical conductivity between the respective silver-coated copper particles in the filler, since the dendritic structure achieves extensive branching in the collecting element.

[0132] In some embodiments, the filler made of silver-coated copper particles can contain 9 to 19 weight percent silver. This allows for a largely complete coating of dendritic copper particles in particular. The silver-coated copper particles in the filler can have an average diameter of 30 to 55 μm. This allows a good compromise between the mass of the individual copper particles and the mass of the silver coating, as well as the conductivity in the conductive body.

[0133] In some embodiments, the filler can consist of silver-coated nickel particles. Similar to silver-coated copper particles, high conductivities can be achieved in the first electrode 26 with silver-coated nickel particles. In addition, the silver-coated nickel particles can be magnetically aligned, for example, during the manufacturing process in order to provide the mechanical properties of the conductive body with a preferred direction. The filler made of silver-coated nickel particles can have a silver content of 8 to 40 weight percent. The silver content can be, for example, 8 weight percent or, for example, 18 weight percent. The silver-coated nickel particles can have an average diameter of 8 to 32 μm. The average diameter of the particles can be, for example, 31 μm.This allows a good compromise to be achieved between the mass of the individual nickel particles and the mass of the silver coating, as well as the conductivity in the conductive body. A filler can consist of silver-coated glass powder. This allows a particularly fine distribution of the conductive filler. Conventional manufacturing processes can therefore be used without major adjustments. At the same time, mechanical stress peaks in the material of the sealing element at the boundaries to the filler are avoided due to the particularly small particle size of the silver-coated glass powder. The filler made of silver-coated glass powder can have a silver content of 3 to 8 percent by weight. In addition to silver, the coating can, for example, contain 3 to 11 percent by weight of zinc. In this way, a cost-effective reduction in the amount of silver used can be achieved. The glass powder particles can have an average diameter of 3 pm.This enables the aforementioned advantages through a small particle size, while the filler remains practically manageable. The collection element can comprise a mixture of a filler made of silver-coated glass fibers and a filler made of silver-coated glass beads.

[0134] The introduction of electrically conductive filler into the base material of at least one electrode 26, 28 makes it possible to achieve sufficient conductivity and to significantly optimize the properties of the base material with regard to tribological properties, temperature resistance and mechanical properties such as strength.

[0135] In some embodiments, one of the electrodes 26, 28 additionally or alternatively has an electrically conductive surface coating. In this way, a significant increase in the electrical conductivity of the collecting element can be achieved.

[0136] In some embodiments, this may be, for example, a metallic coating, for example based on copper, silver, gold, tin, aluminum, or other metals or alloys. It is also possible to combine multiple layers of metals. Additionally, metals or semiconductors can also be combined with conductive non-metallic components.

[0137] The coating can, for example, be based on non-metallic, conductive materials such as graphene, graphite, carbon nanoparticles, carbon fibers, conductive carbon black, or conductive polymers such as polyaniline or its derivatives, particularly without a cohesive matrix. Metals, such as metallized graphite, can also be incorporated into these layers.

[0138] The coating can be made conductive by metallic components embedded in a matrix, for example, conductive inks with metallic fillers such as copper, silver, gold, tin, or other metals or their alloys. The coating can be made conductive by non-metallic, conductive components embedded in a matrix, for example, conductive inks with non-metallic fillers such as graphene, carbon nanoparticles, carbon fibers, or conductive carbon black. A conductive polymer, such as polyaniline or its derivatives, can serve as the matrix for the aforementioned fillers; non-conductive polymers or resins are also possible.

[0139] The coating can comprise a combination of metallic and non-metallic, conductive components, for example, a combination of copper and graphene or copper and polyaniline, advantageously also as corrosion protection for the copper. Conductive particles can be deposited or applied to the electrode, for example, by chemical, galvanic, or physical processes, such as PVD, CVD, ultrasound, jet deposition (jetting), and the like, onto a base body of a sealing element and / or the protective lip of the lip portion 42. The surface of the first electrode 26 can be provided with the conductive coating completely or partially, in particular on one side, on both sides, or partially in regions of one or both surfaces.

[0140] Depending on which metal is used for the coating, a transfer of the metal from the surface of the electrode 26, 28 to the surface of a machine element, in particular the shaft 16, is possible, which enables a reduction of the contact resistance under dynamic conditions with low radial forces.

[0141] Particularly in embodiments that have a lip portion 42, and in particular a lip portion 42 that floats during operation of the electromechanical transducer 10, at least one of the electrodes 26, 28, in particular the electrode body 30, 34 with the lip portion 42, can comprise a fiber-reinforced polytetrafluoroethylene composite material (PTFE compound). The fibers can be, for example, cellulose fibers impregnated with oil.

[0142] When installing such an electrode body 30, 34, the lip portion 42 is pulled over the shaft 16 and compressed in the process. This compression forces oil out of the fibers, so that when the electromechanical transducer 10 is put into operation, a certain amount of oil is already present at the lip portion 42, allowing an oil film to form between the lip portion 42 and the shaft 16 more quickly and reliably for floating. For this purpose, the compression is increased when the electromechanical transducer 10 is put into operation, so that more oil escapes from the material of the electrode 26, 28.

[0143] Both PTFE and machine oil have a permittivity of approximately 2 and, when used, act as a dielectric that reduces the generated capacitance C e increased.

[0144] Further embodiments can be obtained, for example, by modifying various designs of the capacitance-increasing device 24. In particular, an insulation device is provided instead of a contact surface of the capacitance-increasing device 24.

[0145] In some embodiments, the capacity increasing device 24 may be combined with a seal, in particular a radial shaft seal or a cassette seal.

[0146] Electromechanical converters 10 of the type mentioned here can be operated both as electric motors and as generators. Therefore, the information disclosed here applies equally to electric motors and generators having such a design.

[0147] In some embodiments, the first electrode 26 may, for example, be formed by the housing 22, such that a wall of the housing 22 forms the first electrode surface 27. In some embodiments, the second electrode 28 may, for example, be formed by the shaft 16, such that a surface of the shaft 16 forms the second electrode surface 29.

[0148] "May" refers in particular to optional features of the invention. Accordingly, there are also further developments and / or embodiments of the invention that additionally or alternatively comprise the respective feature(s).

[0149] If necessary, isolated features may also be selected from the combinations of features disclosed herein and used in combination with other features to define the subject matter of the claim, dissolving any structural and / or functional relationship that may exist between the features.

[0150] 10 electromechanical converter / electric motor

[0151] 12 Stator

[0152] 14 stator windings

[0153] 16 second machine element

[0154] 16a wave

[0155] 18 Rotor

[0156] 20 bearings (engine mounts)

[0157] 22 first machine element

[0158] 22a housing

[0159] 24 Capacity increase device

[0160] 26 first electrode

[0161] 27 first electrode surface

[0162] 27a front side

[0163] 27b Front side surface

[0164] 28 second electrode

[0165] 29 second electrode surface

[0166] 30 first electrode body

[0167] 31 passage opening

[0168] 32 socket

[0169] 33 Annular gap

[0170] 34 second electrode body

[0171] 36 Fastening section, in particular sleeve-shaped

[0172] 38 truncated cone section

[0173] 40 inner section (of the first electrode)

[0174] 42 Lip section

[0175] 44 recess

[0176] 46 single lip

[0177] 48 jetty

[0178] 50 tongue

[0179] 52 joint

[0180] 54a track

[0181] 54b track

[0182] 54c track

[0183] 56 Company design

Claims

Claims 1. Capacitance increasing device (24) for increasing an electrical capacitance between a first machine element (22), in particular a housing (22a) of an electromechanical converter (10), and a second machine element (16) rotatably mounted relative to the first machine element (22), in particular a shaft (16a) of the electromechanical converter (10), wherein the capacitance increasing device (24) has a first electrode (26) with a first electrode body (30) and with a first electrode surface (27), wherein the first electrode (26) is arranged at a distance from a second electrode (28) with a second electrode body (34) with a second electrode surface (29) during operation of the electromechanical converter (10), wherein a functionally effective increasing capacitance (C e), wherein the first electrode (26) is electrically conductively connected to the first machine element (22) and the second machine element (16), in particular the second electrode (28), forms the second electrode surface (29) and is capacitively functionally coupled to the first electrode (26), in particular to the first electrode surface (27).

2. Capacity increasing device according to claim 1, characterized in that the first electrode (26) has a disc-shaped first electrode body (30) arranged in a radial plane of the second machine element, which has a through opening (31) for the passage of the second machine element (16).

3. Capacity increasing device according to claim 1 or 2, characterized in that the first electrode body (30) and / or the second electrode body (34) is coated with an electrically conductive material and / or with a dielectric and / or is surrounded by a dielectrically active fluid.

4. Capacity increasing device according to one of claims 1 to 3, characterized in that the second electrode (28) has a disc-shaped second electrode body (34) extending parallel to the first electrode body (30) and arranged at an axial distance therefrom.

5. Capacity increasing device according to one of claims 1 to 4, characterized in that the second electrode (28) is designed for fixed arrangement with the second machine element (16), wherein the second electrode (28) is designed to increase the increasing capacity (C e) and is arranged axially spaced from the first electrode (26) and is capacitively functionally coupled.

6. Capacity increasing device according to one of claims 1 to 5, characterized in that the second electrode (28) has a fastening section (36) for rotationally fixed fastening to the second machine element (16).

7. Capacity increasing device according to one of claims 1 to 6, characterized in that a first electrode body (30) and a second electrode body (34) are arranged alternately along an axial direction of the second machine element (16) and are capacitively functionally coupled.

8. Capacity increasing device according to one of claims 1 to 7, characterized in that the first electrode (26) has a truncated cone-shaped first electrode surface (27), wherein the second electrode (28) has a truncated cone-shaped second electrode surface (29), wherein the first electrode surface (27) encloses a first angle and the second electrode surface (29) encloses a second angle with the axis of rotation of the second machine element (16), wherein the first angle and the second angle are each less than 90°.

9. Capacity increasing device according to claim 8, characterized in that the first electrode (26) has a first electrode body (30) which has a funnel section on which the first electrode surface (27) is formed, wherein the funnel section has a through opening (31) for the passage of the second machine element (16) and / or the second electrode (28).

10. Capacity increasing device according to claim 9, characterized in that the second electrode (28) has a second electrode body (34) which has a funnel section or a truncated cone section (38) on which the second electrode surface (29) and which has a fastening section (36) for rotationally fixed fastening to the second machine element.

11. Capacity increasing device according to one of claims 1 to 10, characterized in that the first electrode surface (27) of the first electrode body (30) has an end face (27a) facing the second machine element (16) with an end face (27b), wherein the end face (27b) is preferably aligned parallel to the second electrode surface (19).

12. Capacity increasing device according to claim 1 to 11, characterized in that the first electrode (26) and / or the second electrode (28) has an elastically deformable electrode body (30, 34).

13. Capacity increasing device according to claim 12, characterized in that the deformable electrode body (30, 34) has a contact surface for physical contact with the respective other electrode body (30, 34), wherein during operation of the electromechanical converter (10) by means of the flow of a moving fluid, in particular an oil and / or air-oil mixture, a hydrodynamic pressure can be formed between the electrode bodies (30, 34), by means of which the electrode bodies (30, 34) are deformable in such a way that they no longer have physical contact with the respective other electrode body (30, 34) and are capacitively functionally coupled.

14. Capacity increasing device according to claim 13, characterized in that the contact surface and / or the electrode body (30, 34) have structures for forming the hydrodynamic pressure for the deformable electrode body (30, 34) from an onflow of the fluid.

15. Capacity increasing device according to one of the preceding claims, characterized in that at least one electrode spacing device for determining an electrode spacing (d) is arranged between the first electrode (26) and the second electrode (28).

16. Capacity increasing device according to one of the preceding claims, characterized in that the capacity increasing device (24) has an actuator and / or a spring-elastic element for adjusting a position and / or an orientation of at least a portion of the first electrode (26) and / or the second electrode (28).

17. Capacity increasing device according to claim 16, characterized by a control device which is configured to control the actuator on the basis of measurement data, wherein the measurement data comprise one or more of the following data types: electrode distance measurement data, capacitance measurement data, charge measurement data, voltage measurement data, current measurement data, mechanical stress measurement data.

18. Capacity increasing device according to one of the preceding claims, characterized in that at least one element of the first electrode (26) and / or the second electrode (28) can be disassembled into several parts in a circumferential direction for assembly and / or disassembly, in particular into two, three, four, five, six, seven, eight or more parts and in particular into parts which each comprise an identical angular range in the circumferential direction.

19. Capacity increasing device according to one of the preceding claims, characterized in that a capacitor, a controllable capacitor, a resistor and / or an inductance is arranged in the electrical connection between the first electrode (26) and the first machine element (22).

20. Capacity increasing device according to one of the preceding claims, characterized in that the capacity increasing device (24) has an error detection device which is designed to detect malfunctions, to transmit error information via a network and / or to emergency switch off the electromechanical converter (10).

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