Contactless energy transfer device and electrical machine

Abstract

The invention relates to a contactless energy transmission device (1) for a rotor (2) of an electric machine (3), in particular a separately excited synchronous machine within a drive train of a motor vehicle, comprising an inductive transformer (4) which has a currentable primary winding (5) and a secondary winding (6) spaced apart from it, which can be electrically coupled to a winding of the rotor (2), wherein the primary winding (5) is received in a primary flux guide element (7) and the secondary winding (6) in a secondary flux guide element (8), and the primary flux guide element (7) is in turn connected to a metallic primary support element (9) and the secondary flux guide element (7) is connected to a metallic secondary support element (10).wherein a shielding layer (11) is arranged between the primary winding (5) and the secondary winding (6) and that a low-impedance line (12) is led from the connection point (13) of the shielding layer (11) and the metallic primary support element (9) to the power electronics (14) in order to realize a direct return path for the capacitive coupling path.

Description

[0001] The present invention relates to a contactless energy transmission device for a rotor of an electric machine, in particular a separately excited synchronous machine within a drive train of a motor vehicle, comprising an inductive transformer having a currentable primary winding and a secondary winding spaced apart from it, which can be electrically coupled to a winding of the rotor, wherein the primary winding is received in a primary flux guide element and the secondary winding in a secondary flux guide element, and the primary flux guide element is in turn connected to a metallic primary support element and the secondary flux guide element to a metallic secondary support element. The invention further relates to an electric machine.

[0002] Contactless energy transfer for the rotor of an electric machine, particularly in separately excited synchronous machines, represents a significant technological development that is gaining increasing importance, especially in the automotive industry. Separately excited synchronous machines, which, due to their independence from rare-earth materials, represent a promising alternative to permanent magnet synchronous machines, require external excitation of the rotor. This is achieved either via a brushed transformer, which has mechanical contact points and associated wear problems, or via an inductive transformer, which enables contactless energy transfer and thus operates without wear.

[0003] The inductive transformer used for contactless power transmission typically consists of a primary and a secondary winding that are spatially separated. However, this technology also presents a number of challenges, particularly regarding electromagnetic compatibility (EMC), shaft voltage, and bearing currents. The high-frequency alternating currents and the associated dynamic voltage changes result in significant shaft voltages and potential EMC problems. In particular, undesirable capacitive coupling can occur between the primary and secondary windings, leading to the unwanted coupling of interference currents onto the rotor shaft.

[0004] A significant disadvantage of the current state of the art is that capacitive coupling currents can be transferred to the rotor shaft via the inductive transformer. This causes these currents to flow through the bearings or grounding elements on the rotor, leading to damage and increased wear on these components. Since the switching frequency of the inductive transformer is typically 5 to 10 times higher than that of the stator power electronics, this wear occurs earlier and can lead to premature machine failure.

[0005] Furthermore, the air gap between the primary and secondary windings forms a primary path for capacitive coupling. The ferrites and the metallic support elements used for mechanical stabilization and shielding of the windings also contribute to the electrical connection between the secondary winding and the rotor shaft. This creates an electrical return path from the shaft to the power electronics via the bearings or the shaft ground, increasing the risk of electrical antenna formation. This antenna effect can lead to the radio transmission of interference currents to nearby components, further impairing the electromagnetic compatibility of the entire machine.

[0006] In summary, while significant progress has been made in the current state of the art regarding contactless energy transfer devices for rotors of separately excited synchronous machines, considerable disadvantages remain. In particular, the challenges in the area of ​​electromagnetic compatibility and the associated mechanical and electrical problems necessitate further developed solutions to improve the efficiency, reliability, and service life of these machines.

[0007] The object of the invention is therefore to provide a contactless energy transmission device that avoids or at least reduces the problems known from the prior art.

[0008] This problem is solved by a contactless energy transmission device, in particular for a rotor of an electric machine, especially a separately excited synchronous machine within a drive train of a motor vehicle, comprising an inductive transformer which has a currentable primary winding and a secondary winding spaced apart from it, and the primary winding is movable relative to the secondary winding during operation of the energy transmission device, wherein a shielding layer is arranged between the primary winding and the secondary winding, and a low-impedance line is connected from the connection point of the shielding layer to another connection point, in particular an earth, so that a low-impedance return current path is created for the currents capacitively coupled into the shield.

[0009] This energy transmission device offers the advantage that capacitive coupling currents can be effectively suppressed by positioning the shielding layer between the primary and secondary windings. The low-impedance conductor ensures that these currents are controlled and efficiently fed to ground, thereby minimizing unwanted electromagnetic interference. This improves the operational reliability and service life of the electric machine, particularly in applications within automotive powertrains. Furthermore, the connection of the flux guide elements to the metallic support elements provides mechanical stability and effective shielding against electromagnetic interference.

[0010] The present invention relates to a contactless energy transmission device for a rotor of an electric machine, in particular a separately excited synchronous machine within a drive train of a motor vehicle. The device comprises an inductive transformer having a currentable primary winding and a secondary winding spaced apart from it. The primary winding can preferably be accommodated in a primary flux guide element, while the secondary winding can be arranged in a secondary flux guide element. The primary flux guide element can preferably be connected to a primary support element, preferably metallic, and the secondary flux guide element to a secondary support element, preferably metallic.

[0011] The shielding layer provides one-sided decoupling of interference transmission to the secondary side. This means that electromagnetic interference originating in the primary winding, which could potentially be transmitted to the secondary side, is effectively blocked and diverted by the shielding layer. This prevents the coupling of unwanted interference signals to the secondary winding and associated components, such as the rotor of an electric machine, resulting in improved electromagnetic compatibility of the entire device.

[0012] Additionally, a low-impedance conductor runs from the connection point of the shielding layer and the metallic primary support element to the power electronics. This low-impedance conductor ensures that the capacitive coupling currents generated in the shielding layer can be returned directly to ground without significant losses. This increases the efficiency of the power transfer and simultaneously prevents potential interference and damage, for example, to an electric machine equipped with the power transfer device.

[0013] The invention thus offers a technically sophisticated solution for improving electromagnetic compatibility and efficiency in contactless power transmission, particularly in separately excited synchronous machines, especially in applications within drive trains in motor vehicles. The targeted arrangement of the shielding layer and the implementation of a low-impedance conductor ensure stable and interference-free power transmission that meets the specific requirements of modern electric drive systems.

[0014] First, the individual elements of the claimed invention are explained in the order in which they are mentioned in the claim set, and subsequently, particularly preferred embodiments of the invention are described. Energy transmission device

[0015] For the purposes of this patent application, an energy transfer device is an assembly that serves to transfer electrical energy contactlessly between assemblies or parts that are moving relative to each other (e.g., rotary, transient). This device is particularly suitable for use in a separately excited synchronous machine within the drivetrain of a motor vehicle. The function of the energy transfer device is to ensure an efficient and reliable transfer of electrical energy without a direct electrical connection between the static and moving components. This is achieved through induction between the primary and secondary windings. For example, the primary winding can be supplied with alternating current, thereby generating an alternating magnetic field that induces a voltage in the secondary winding.This voltage is then used, for example, to supply a rotor winding of an electric machine.

[0016] The contactless energy transfer device essentially comprises an inductive transformer consisting of a primary winding and a spaced-apart secondary winding. The primary winding can preferably be connected to a power source and generate an alternating magnetic field when a current flows through it. This magnetic field induces an electrical voltage in the secondary winding, which is connected to a load, such as a winding of the rotor of an electric machine. This arrangement allows electrical energy to be efficiently transferred from the primary to the secondary side without the need for a mechanical or conductive connection.

[0017] The structure of the contactless energy transmission device can include various components, such as the primary and secondary windings, which are advantageously each integrated into flux guide elements, which in turn are preferably connected to metallic support elements.

[0018] A shielding layer is arranged between the windings, reducing electromagnetic interference and minimizing capacitive coupling to increase energy transfer efficiency and extend the device's lifespan.

[0019] Several embodiments of the contactless energy transfer device are conceivable, differing particularly in the arrangement of the magnetic flux. In a radial flux arrangement, the magnetic flux is configured to run radially from the center of the device outwards or vice versa. This arrangement is particularly suitable for applications where the windings are arranged concentrically, enabling a compact design and ensuring a uniform distribution of the magnetic flux across the entire surface.

[0020] In an axial flux arrangement, the magnetic flux runs along the axis of the device, that is, parallel to the rotor's axis of rotation. This arrangement is advantageous when a flat design is preferred or when high power density is desired. The axial flux enables efficient coupling of the primary and secondary windings, particularly in applications where the components are arranged along a common axis.

[0021] Both designs offer specific advantages depending on the geometric and functional requirements of the respective application. The choice between a radial or axial flow arrangement depends on the specific operating conditions, such as the available installation space, the power density requirements, and the desired design of the energy transfer device. Inductive transformer

[0022] For the purposes of this patent application, an inductive transformer is a device used for the contactless transfer of electrical energy by induction between two spatially separated windings. This transformer is particularly useful in electrical machines, such as separately excited synchronous machines within the drivetrain of motor vehicles, to enable energy transfer from the stationary part to the rotating or translationally moving part. The function of the inductive transformer is to generate a magnetic field by induction, which induces a voltage in a spatially separated winding. This enables contactless energy transfer, minimizing wear and maintenance and increasing the reliability of the entire device.

[0023] The inductive transformer preferably comprises a magnetic core or a flux guide element made of a ferromagnetic material, maximizing the magnetic coupling between the primary and secondary windings. The windings can be made of copper wire or another suitable conductive material and are preferably arranged on coil formers that define the shape and spacing of the windings. The flux guide element can consist of several segments and completely or partially enclose the windings to optimally concentrate the magnetic field and minimize losses.

[0024] Preferably, the inductive transformer is designed such that the primary and secondary windings are housed in separate flux guide elements, each connected to support elements to ensure mechanical stability and good heat dissipation. These support elements can be annular or have other suitable geometric shapes to enable a uniform distribution of the magnetic field and electromagnetic shielding.

[0025] Advantageously, the inductive transformer can be implemented in various embodiments. A preferred embodiment comprises a single-layer winding, wherein the primary and secondary windings each consist of a single winding layer. Alternatively, the transformer can be designed in a multi-layer configuration, in which several winding layers are arranged one above the other to increase magnetic coupling and transmission efficiency. Another conceivable embodiment involves the use of different winding geometries, such as concentric or nested windings, which can optimize the inductive coupling depending on the specific application.

[0026] Additionally, the inductive transformer can be equipped with special shielding elements that reduce capacitive coupling and electromagnetic interference, thereby further increasing efficiency and operational reliability. These shielding elements can be made of conductive materials and are preferably arranged to surround the windings in areas of maximum susceptibility to interference without impeding the magnetic flux. Primary winding

[0027] For the purposes of this patent application, a primary winding is an electrical winding used to generate a magnetic field, which is then used in an inductive transformer to transfer energy from the primary to the secondary side. The primary winding is energized by an alternating voltage or current, which creates an alternating magnetic field in the surrounding flux-conducting elements. This alternating magnetic field induces an electrical voltage in the spatially separated secondary winding, which is used to transfer energy, for example, to the rotor of an electric machine, in particular a separately excited synchronous machine.

[0028] The primary winding is preferably housed in a primary flux guide element, which concentrates the magnetic field and focuses it onto the secondary winding. The primary flux guide element is, in turn, preferably connected to a primary support element, which provides mechanical stability and simultaneously serves as a shield against external electromagnetic interference. The primary winding is made of a conductive material, preferably copper, which is advantageous due to its high conductivity and low electrical losses. It is wound in one or more layers, with the number of turns and the winding arrangement being tailored to the specific requirements, for example, of an electric machine, to ensure optimal magnetic coupling and energy transfer.

[0029] The primary winding can be implemented in various configurations. One possible configuration is the cylindrical winding, in which the windings are arranged spirally on a cylindrical core. Another configuration is the toroidal winding, in which the windings are wound around a ring-shaped core. This configuration offers the advantage of a closed magnetic field path, resulting in higher energy transfer efficiency. Furthermore, the primary winding can be designed as a single-layer or multi-layer winding, depending on the performance requirements and available space. Secondary winding

[0030] For the purposes of this patent application, a secondary winding is an electrical winding that serves to receive the energy generated in the inductive transformer from the primary side and convert it into electrical energy, which is then transferred, for example, to the rotor of an electric machine, in particular a separately excited synchronous machine. The secondary winding is spatially separated from the primary winding and is located on the secondary side of the transformer. The alternating magnetic field generated in the primary winding induces an electrical voltage in the secondary winding, which is used for energy transfer.

[0031] The secondary winding is preferably housed in a secondary flux guide element, which optimally concentrates the received magnetic field, thus enabling efficient conversion into electrical energy. This secondary flux guide element is advantageously connected to a secondary support element, which not only ensures mechanical stability but also acts as a shield against external electromagnetic interference. The secondary winding is made of a conductive material, preferably copper, which is advantageous due to its high conductivity and low electrical losses. It is wound in one or more layers, with the number of turns and the winding arrangement being tailored to the specific requirements, for example, of an electric machine, to ensure optimal magnetic coupling and energy transfer.

[0032] The secondary winding can be implemented in various configurations. One possible configuration is the cylindrical winding, in which the turns are arranged spirally on a cylindrical core to ensure a uniform magnetic field distribution. Another configuration is the toroidal winding, in which the turns are wound around a ring-shaped core, offering the advantage of a closed magnetic field path and thus leading to higher energy transfer efficiency. The secondary winding can also be designed as a single-layer or multi-layer winding, depending on the power requirements and spatial constraints. These configurations allow the secondary winding to be optimally adapted to the specific conditions of the respective application, resulting in improved performance and efficiency of the electric machine. Flow guiding elements

[0033] For the purposes of this patent application, a flux guide element is a component that serves to guide and concentrate the magnetic flux within a power transmission device to ensure efficient and low-loss power transmission. The function of the flux guide element is therefore to guide the magnetic flux generated by the primary winding and concentrate it onto the secondary winding. By selectively controlling the magnetic flux, induction is maximized, resulting in efficient electrical energy transmission. Furthermore, flux guide elements contribute to minimizing stray losses and increasing the overall performance of the power transmission device. Flux guide elements are preferably made of materials with high magnetic permeability, such as ferrite or soft magnetic metals.These materials offer excellent magnetic properties by effectively guiding and concentrating the magnetic flux. Ferrite is particularly advantageous due to its low losses and high efficiency at high frequencies. The flux guide elements can have different shapes and structures to optimally control the magnetic flux. U-shaped cross-sections, encompassing at least a portion of the corresponding winding, are preferred. This shape enables effective concentration of the magnetic flux and improves the mechanical stability of the entire assembly. The flux guide elements can also form a ring shape to ensure uniform magnetic flux distribution around the circumference of the power transmission device. The flux guide elements are preferably arranged coaxially with the primary and secondary windings to guide the magnetic flux directly through the windings.This arrangement maximizes the induced voltage in the secondary winding and improves the efficiency of energy transfer.

[0034] Advantageously, the flux guide elements can also be joined to form a one-piece ring. Such a one-piece ring ensures uniform and efficient guidance of the magnetic flux around the entire primary or secondary winding. This improves magnetic coupling and further reduces stray losses, thus increasing energy transfer efficiency. Furthermore, a one-piece ring offers increased mechanical stability and facilitates the assembly and alignment of the flux guide elements within the device. Support elements

[0035] For the purposes of this patent application, a primary and secondary primary support element is to be understood as a mechanical and / or electromagnetic support element which accommodates and stabilizes the primary winding or the secondary winding of an inductive transformer.

[0036] The primary primary support element is directly connected to the primary flux guide element and ensures that the primary winding is held in a stable position within the transformer. Advantageously, it can also provide an electrically and / or magnetically conductive structure that contributes to shielding against electromagnetic interference, for example, by serving as a return path for capacitive coupling currents. This can advantageously be achieved by connecting the shielding layer, which is arranged between the primary and secondary windings, to the primary primary support element, thereby enabling effective dissipation of interfering currents to the power electronics. The primary primary support element is preferably made of a metallic material that exhibits both high mechanical stability and good electrical conductivity.This makes it possible to efficiently shield against electromagnetic interference while simultaneously meeting the mechanical requirements of the device.

[0037] The secondary primary support element fulfills a similar function on the secondary side of the transformer. It is connected to the secondary flux guide element and stabilizes the secondary winding within the transformer. Here, too, the secondary primary support element can advantageously contribute to shielding by minimizing electromagnetic interference caused by capacitive coupling.

[0038] Preferred embodiments of the primary and secondary primary support elements can have a ring-shaped design to ensure, for example, uniform shielding around the respective windings. The ring-shaped structure enables optimal distribution of the capacitive coupling currents and contributes to a homogeneous shielding effect. Furthermore, these support elements can be designed in a segmented form, with each segment supporting a specific area of ​​the shielding layer. This segmentation allows for targeted adaptation of the shielding to the requirements of the respective application, particularly in complex geometric arrangements. Shielding layer

[0039] For the purposes of this patent application, a shielding layer is a special structure arranged between the primary and secondary windings of an inductive transformer to effectively suppress capacitive coupling currents and improve the electromagnetic compatibility of the device. The shielding layer serves to dissipate unwanted electrical interference caused by capacitive coupling and thus, for example, to ensure the functionality and longevity of an electric machine, particularly in the powertrain of a motor vehicle.

[0040] The shielding layer preferably consists of several individual conductors applied in one or more layers and arranged to form a planar shielding surface between the primary and secondary windings. These conductors can be implemented as copper layers on an electrically insulating printed circuit board. The printed circuit board itself can be flexible to optimally adapt to the geometric characteristics of the transformer. In particular, a printed circuit board can also be implemented as a foil. The conductors of the shielding layer can be arranged in a grid structure or a tree structure. The grid structure consists of parallel, pin-shaped conductor tracks that minimize eddy current losses, while the tree structure consists of a main conductor and branching sub-conductors that enable efficient distribution and dissipation of the capacitive coupling currents.

[0041] The function of the shielding layer is therefore to shield the direct overlap area between the primary and secondary windings without impairing the magnetic flux between the flux-conducting elements. By diverting the capacitive coupling currents via a low-impedance conductor, for example to the power electronics of an electric machine, the generation of electromagnetic interference is prevented. Advantageously, the shielding layer can be at least partially or completely covered by a potting compound or plastic, which provides additional protection against mechanical influences and increases the stability of the shielding structure.

[0042] Possible embodiments of the shielding layer include the use of segmented shielding segments, preferably attached to an annular metallic primary support element. These segments can be identical to ensure uniform shielding around the entire primary winding. Such a segmented structure allows for flexible adaptation of the shielding effect to specific areas of the transformer and a uniform distribution of capacitive currents, resulting in an overall improvement in the electromagnetic compatibility of the power transmission device. Low-impedant line

[0043] For the purposes of this patent application, a low-impedance conductor is an electrical connection designed to exhibit particularly low resistance to high-frequency currents. This means that the conductor causes only minimal voltage drop when transmitting currents in the high-frequency range, thus enabling efficient dissipation of capacitive coupling currents. The low-impedance conductor can therefore ensure that unwanted capacitive currents are carried away to a suitable location, such as grounding.

[0044] For the purposes of this patent application, a conductor is considered to be low-impedance if its electrical resistance at high-frequency currents >100 kHz, preferably > 1 MHz is less than 1 ohm, preferably less than 10 ohms, and most preferably less than 100 ohms.

[0045] The low-impedance cable is preferably made of a highly conductive material, such as copper or a copper alloy, to further maximize conductivity. It would also be conceivable to manufacture the low-impedance cable from aluminum. It can be designed as a single-core or multi-core stranded wire, with the use of stranded wire advantageously increasing the cable's flexibility while simultaneously minimizing the skin and proximity effects at high-frequency currents. This leads to a further reduction in effective resistance at high frequencies. Such a stranded wire can, for example, consist of numerous fine, twisted individual wires, which together offer a larger surface area and thus transport the current more efficiently.

[0046] Additionally, the low-impedance cable can be surrounded by a suitable insulating layer, which not only ensures reliable electrical isolation but also increases the cable's mechanical stability. This insulating layer can be made of materials such as polyethylene, Teflon, or similar highly insulating plastics. To further optimize the cable, it can be shielded, for example, by an additional metallic sheath, which blocks external electromagnetic interference and ensures unimpeded current transmission within the cable.

[0047] Several variations are conceivable regarding the embodiment of the low-impedance conductor. One preferred embodiment involves the use of a flat conductor track integrated onto a printed circuit board. This flat structure reduces inductive reactance and enables particularly efficient transmission of high-frequency currents. Another embodiment could be a round stranded wire, which is suitable for use in confined spaces and, due to its flexibility, can be easily adapted to the given design parameters. Both embodiments offer specific advantages depending on the design requirements and the electrical conditions under which the power transmission device operates. Connection point

[0048] For the purposes of this patent application, a connection point is the location where an electrical connection is established between the shielding layer and other components of the energy transmission device, in particular the metallic primary support element and / or the low-impedance conductor. The connection point serves to efficiently dissipate capacitive coupling currents, which arise from electromagnetic interference, from the shielding layer and to grounding, in order to prevent, for example, unwanted interference and potential damage to an electrical machine.

[0049] The connection point assembly includes, in particular, a contact surface that is conductively connected to the shielding layer. This contact surface can be realized by soldering, crimping, or a mechanical clamp, depending on the specific requirements for mechanical stability and electrical conductivity. The contact surface is preferably designed to provide a low-impedance connection to the low-impedance conductor, allowing the capacitive coupling currents to be dissipated without significant losses.

[0050] The connection point itself can be made of conductive material, such as copper or a copper alloy, to ensure optimal conductivity.

[0051] Advantageously, the connection point is positioned to enable the shortest and most direct connection possible between the shielding layer and the metallic primary support element and / or the low-impedance conductor. This reduces inductance and prevents the formation of parasitic resonant circuits that could impair the shielding efficiency. Preferably, several connection points can also be arranged widely spaced to ensure uniform current distribution across the entire shielding layer, further improving the electromagnetic compatibility of the power transmission device.

[0052] Possible embodiments of the connection point include, for example, a segmented shielding layer in which multiple connection points are distributed across different segments of the shielding layer. This design allows for flexible adaptation of the shielding effect to specific geometric requirements or to different sources of interference. Another possible embodiment could involve the use of flexible contact points that allow minimal movement of the shielding layer during assembly or operation without interrupting the electrical connection. This would be particularly advantageous in applications where mechanical vibrations or thermal expansion may occur. Advantageous embodiments of the invention

[0053] According to an advantageous embodiment of the invention, the shielding layer can consist of several individual conductors arranged relative to one another to form a planar shielding surface between the primary and secondary windings. This results in uniform shielding over the entire overlap area, thereby suppressing capacitive coupling even more effectively. Furthermore, the use of multiple individual conductors allows for flexible adaptation of the shielding characteristics to specific energy transmission requirements, thus further improving electromagnetic compatibility.

[0054] According to a further preferred embodiment of the invention, the shielding layer may also comprise an electrically insulating printed circuit board, and the conductors of the shielding layer, preferably copper layers, may be implemented on and / or in the printed circuit board. This enables a compact and stable design of the shielding layer, which can be easily integrated into the inductive transformer. The use of copper layers ensures high conductivity and effective dissipation of capacitive coupling currents. At the same time, the printed circuit board provides the necessary insulation and structural stability, ensuring that the shielding layer functions reliably even at high voltages and currents.

[0055] Furthermore, according to another advantageous embodiment of the invention, the printed circuit board can be flexible. A flexible printed circuit board allows for easy adaptation to the geometric conditions of the inductive transformer, which is particularly advantageous in confined installation spaces. This flexibility allows the shielding layer to be optimally positioned to achieve the best possible shielding effect without impairing the magnetic flux. This leads to improved electromagnetic compatibility and higher energy transfer efficiency.

[0056] According to a further particularly preferred embodiment of the invention, the conductors, preferably the copper layers, can each have a width of between 0.05 and 1 mm, more preferably 0.25 and 0.75 mm, more preferably 0.35 and 0.65 mm, and more preferably 0.45 and 0.55 mm. Designing the conductors in the shielding layer with a specific width of between 0.05 and 1 mm, more preferably 0.25 and 0.75 mm, more preferably 0.35 and 0.65 mm, and more preferably 0.45 and 0.55 mm, offers the advantage of achieving an optimal balance between conductivity and minimizing eddy current losses. This choice of width ensures that the capacitive coupling currents are efficiently dissipated while simultaneously keeping losses due to induced eddy currents low. This contributes to increased efficiency and reduced heat generation during the operation of the energy transfer device.

[0057] Furthermore, the invention can be further developed such that the individual conductors of the shielding layer are arranged in a single-layer or multi-layer structure, and each layer has either a computational structure formed from the conductors or a tree structure, wherein the computational structure consists of a plurality of parallel, pin-shaped conductor tracks, and the tree structure consists of a main conductor with branching sub-conductors. This enables a targeted design of the shielding layer to minimize eddy current losses and effectively dissipate capacitive coupling currents. The computational structure, consisting of parallel, pin-shaped conductor tracks, and the tree structure, with a main conductor and branching sub-conductors, each offer specific advantages with regard to current distribution and electromagnetic compatibility, resulting in an overall improved performance of the power transmission device.

[0058] Furthermore, it is advantageous if the conductors of different layers are arranged such that they at least partially, and preferably completely, cover the insulation areas between the conductors of the other layer(s) in a planar projection, resulting in a shielding surface that is as continuous as possible in the direction of the projection. The arrangement of conductors in different layers, covering the insulation areas of each other layer, ensures an even denser and more effective shielding surface. This has the advantage of reducing even minimal electromagnetic leakage, which further reduces the undesired capacitively coupled currents and voltages.

[0059] In a further preferred embodiment of the invention, the shielding layer can also be configured to completely cover a direct overlap area between the primary and secondary windings, but not to cover the area between the flux guide elements, in which the magnetic flux preferably flows via the air gap between the flux guide elements, so as not to impair the magnetic flux between the flux guide elements. This ensures effective shielding of the capacitive coupling currents, while the magnetic flux, which is essential for the function of the inductive transformer, is not affected. This leads to improved energy transfer efficiency and higher electromagnetic compatibility.

[0060] It can also be advantageous to further develop the invention such that the shielding layer is at least partially, preferably completely, covered by a potting material or plastic. This covering provides additional protection of the shielding layer against mechanical influences and environmental factors such as moisture or dust. At the same time, the potting material or plastic ensures mechanical stability and can improve heat dissipation, leading to a longer service life and higher reliability of the energy transmission device.

[0061] According to a further preferred embodiment of the invention, the metallic primary support element can also be designed in an annular form. This can offer advantages in terms of manufacturing. Furthermore, it can also be advantageous if the shielding layer is segmented with a plurality of shielding segments, wherein the connection points of the shielding segments are arranged circumferentially distributed on the primary support element.

[0062] According to a further preferred embodiment of the invention, the metallic primary support element can be annular and the shielding layer segmented with a plurality of shielding segments, wherein the connection points of the shielding segments are arranged circumferentially distributed on the primary support element. The annular design of the primary support element enables a uniform distribution of the electromagnetic shielding around the primary winding. The segmented shielding layer allows for flexible adaptation of the shielding to specific areas where particularly strong capacitive coupling could occur. The circumferentially distributed arrangement of the connection points of the shielding segments on the primary support element ensures a uniform current distribution, which further improves electromagnetic compatibility.

[0063] Finally, the invention can also be advantageously implemented such that the shielding segments are essentially identical. This offers the advantage of simple manufacturing and assembly of the shielding layer, since the identical segments can be produced in a standardized production process. Furthermore, the identical design of the segments ensures a uniform shielding effect around the entire primary winding, leading to a consistent reduction in capacitive coupling currents and thus to increased operational reliability and efficiency of the power transmission device.

[0064] The object of the invention can also be solved by an electric machine, in particular a separately excited electric motor, with an energy transmission device according to one of claims 1-13.

[0065] The invention will now be explained in more detail with reference to figures, without limiting the general concept of the invention.

[0066] It shows: Fig. 1 an electric machine with a contactless energy transfer device in a schematic axial sectional view, Fig. 2 an inductive transformer in an axial section view, Fig. 3 a shielding layer on a primary winding in a perspective view, Fig. 4 a shielding segment of a shielding layer in a schematic representation, Fig. 5 an electrical circuit diagram of a contactless energy transmission device as known from the prior art, Fig. 6 an electrical circuit diagram of a contactless energy transfer device according to the invention.

[0067] The basic operating principle of the invention will first be explained using the electrical circuit diagrams of a contactless energy transfer device from the Fig. 5-6 explained in more detail.

[0068] Fig. Figure 5 shows an equivalent electrical circuit of a contactless energy transfer device, as is generally known from the prior art. A significant problem in the energy transfer device 1 under consideration is the formation of parasitic capacitances 26 between the primary winding 5, which is grounded via the mass 23, and the secondary winding 6. These capacitances 26 form due to the spatial proximity of the windings 5 ​​and 6 to each other. Each winding 5 and 6, which acts as an electrical conductor, is surrounded by an electric field when a voltage is applied. The spatial proximity of the primary winding 5 to the secondary winding 6 allows the electric fields of the two windings 5 ​​and 6 to interact and form a capacitor. The resulting capacitances 26 are a direct consequence of the physical arrangement and the geometric proximity of the windings within the device.

[0069] The voltage fluctuations at the primary winding 5, connected to a voltage source 22, caused by switching on and off via a primary clock 21, lead to changes in the electric field strength and thus to a capacitive current flow. This current flows via these parasitic capacitances 26 to the secondary side, to which the electrical load 24 is connected. Since these currents require a return current path 25 to the primary side, this results in capacitive coupling, which, among other things, increases the potential for electromagnetic interference (EMI). This unwanted EMI can disrupt adjacent electronic devices, reduce the efficiency of power transmission, and pose safety risks in certain applications.

[0070] This capacitive current flow therefore seeks a return current path 25 back to the primary winding 5 or to the primary power supply. These currents then flow, for example, via the rotor bearings back to the primary side and can damage these bearings. Depending on the specific return current path 25, conductor loops can also form, which radiate EMC interference like antennas. Due to the impedance of the return current path 25, a high-frequency voltage can be generated on the secondary side (e.g., the rotor). This voltage causes EMC interference, for example, by making the output shafts act like an antenna.

[0071] The exemplary embodiment of the Fig. Figure 6 now describes a contactless energy transfer device 1, which is specifically designed to minimize such capacitive interference within a contactless energy transfer device 1. Here, the primary winding 5 and the secondary winding 6 are separated from each other by a shielding layer 11, which is crucial for reducing electromagnetic interference.

[0072] The shielding layer 11 is arranged between the primary winding 5 and the secondary winding 6, which is rotatably or translationally movable relative to it, and has a connection to a grounding point 27, which ensures that the voltage potential of the shielding layer 11 is ideally kept at ground potential. This is achieved by connecting the shielding layer 11 to a grounding point 27 via a low-impedance conductor 12. The shielding layer 11 protects the voltage from the Fig. The 5 known capacitances 26 are divided into two groups of partial capacitances 26a, 26b, which are thus present between the primary winding 5 and the shielding layer 11 (partial capacitances 26a) and between the secondary winding 6 and the shielding layer 11 (partial capacitances 26b).

[0073] During operation of the energy transmission device 1, capacitive currents, which arise as described above due to voltage fluctuations at the primary winding 5, flow through the capacitive coupling, referred to as partial capacitance 26a, which exists between the primary winding 5 and the shielding layer 11. These currents are discharged via the grounding 27 of the shielding layer 11, thus ensuring a return to the primary side.

[0074] Furthermore, the capacitive currents that could flow from the shielding layer 11 via the partial capacitances 26b to the secondary winding 6 are designed by a suitable return current path 25 such that the sum of these currents is ideally zero. This means that the capacitive current flow that could potentially be directed to the secondary side 6 is measurably reduced by the design and arrangement of the windings 5 ​​and 6, as well as the specific design of the shielding layer 11 and its grounding connection 27.

[0075] Based on this basic principle, a specific technical embodiment of a contactless energy transfer device 1 according to the invention will be explained in more detail below. Fig. Figure 1 shows a contactless energy transmission device 1 for a rotor 2 of an electric machine 3, in particular a separately excited synchronous machine within a drive train of a motor vehicle, as exemplified in the Fig. Figure 1 is sketched. In this embodiment, the secondary winding 6 is arranged to be rotationally fixed, while the primary winding 5 rotates with the rotor 2.

[0076] The contactless energy transmission device 1 comprises an inductive transformer 4, which has a currentable, annular primary winding 5 and a radially spaced annular secondary winding 6, which can be electrically coupled to a winding of the rotor 2. This can be clearly seen from the Fig. 2. The primary winding 5 is contained in an annular primary flux guide element 7 with a U-shaped cross-section, and the secondary winding 6 is contained in an annular secondary flux guide element 8 with a U-shaped cross-section. The primary flux guide element 7 is in turn connected to a metallic primary support element 9, and the secondary flux guide element 8 is connected to a metallic secondary support element 10.

[0077] A shielding layer 11 is arranged between the primary winding 5 and the secondary winding 6, and a low-impedance line 12 leads from the connection point 13 of the shielding layer 11 to the metallic primary support element 9 and further to the power electronics 14 in order to realize a direct return path for the capacitive coupling path. This is shown in the Fig. 3 shown.

[0078] From the Fig. Figure 4 further shows that the shielding layer 11 consists of several individual conductors 15 arranged relative to each other to form a continuous shielding surface between the primary winding 5 and the secondary winding 6. The shielding layer 11 comprises an electrically insulating circuit board 16, and the conductors 15 of the shielding layer 11 are configured as copper layers 17 on and / or in the circuit board 16. In the illustrated embodiment, the circuit board 16 is flexible. The copper layers 17 each have a width of between 0.25 and 0.75 mm, preferably 0.35 and 0.65 mm, and particularly preferably 0.45 and 0.55 mm. In the illustrated embodiment, the width of the individual copper layers 17 is essentially identical.

[0079] The individual conductors 15 of the shielding layer 11 can be arranged in a single-layer or multi-layer structure, and each layer has either a computational structure formed from the conductors 15 or a tree structure, wherein the computational structure consists of a plurality of parallel, pinion-shaped conductor tracks, and the tree structure consists of a main conductor with branching sub-conductors. In the Fig. Figure 4 shows the computing structure. The shielding layer 11 is at least partially, preferably completely, covered by a potting material or plastic.

[0080] Fig. Figure 2 shows a detailed cross-section through an inductive transformer 4 within a contactless power transmission device 1, which is specifically designed for power transmission to a rotor 2 of a separately excited synchronous machine. The inductive transformer 4 consists of a primary winding 5 and a radially spaced secondary winding 6, each housed in U-shaped flux guide elements 7, 8. The primary winding 5 is received in a primary flux guide element 7, which in turn is connected to a metallic primary support element 9. The secondary flux guide element 8, in which the secondary winding 6 is received, is connected to a metallic secondary support element 10.

[0081] The primary winding 5 is located within the annular primary flux guide element 7, which is formed from ferrite and is held at its radially inner surface by the annular metallic primary support element 9. On the opposite side of the air gap 20, which serves as a capacitive coupling path, is the secondary winding 6, which is also located in a secondary-side ferrite core, i.e., the annular secondary flux guide element 8, and is held by the secondary flux guide element 8 and at its radially outer surface by the metallic secondary support element 10.

[0082] A shielding layer 11 is positioned between the primary winding 5 and the secondary winding 6. Its purpose is to interrupt the capacitive coupling path and dissipate capacitive interference currents. The shielding layer 11 extends completely over the overlap area 18 between the primary winding 5 and the secondary winding 6 to ensure the most complete shielding possible. The shielding layer 11 does not cover the area between the flux guide elements 7 and 8 in order to avoid interfering with the magnetic flux, which is crucial for the function of the transformer 4. Thus, the shielding layer 11 is configured to completely span a direct overlap area 18 between the primary winding 5 and the secondary winding 6, but not to cover the area between the flux guide elements 7 and 8, in order to avoid interfering with the magnetic flux between these elements.

[0083] The positioning of the shielding layer 11 is chosen to minimize various loss mechanisms. The proximity of the shielding layer 11 to the primary winding 5 increases the efficiency of the capacitive decoupling, but leads to higher capacitive coupling currents flowing into the shielding layer 11. On the other hand, the magnetic stray field effect on the shielding layer 11 increases the closer it is to the air gap 20 and the upper edge of the flux guide elements 7, 8, which can lead to increased eddy current losses. These complex interactions necessitate precise adjustment of the position of the shielding layer 11, requiring a compromise that ensures optimal shielding effectiveness with minimal losses. Thermal considerations also play a role, as the shielding layer 11 must function reliably at high temperatures.An additional mechanically stable material, such as potting compound or plastic, can be arranged over the shielding layer 11 to protect it and further increase its stability.

[0084] Fig. Figure 3 illustrates an embodiment of the electrical connection of the shielding layer 11 used in the contactless power transfer device 1. The connection point 13 of the shielding layer 11 must be low-impedance, meaning that it must have a large contact area and a wide, planar connection to efficiently dissipate the capacitive coupling currents, as described in the Fig. Figure 3 shows that this low-impedance design is necessary to ensure that no significant electrical losses or delays occur that could impair the efficiency of the shielding.

[0085] It is evident from the Fig. 3 furthermore, that the metallic primary support element 9 is designed in an annular form and the shielding layer 11 is segmented with a plurality of shielding segments 19, wherein the connection points 13 of the shielding segments 19 are arranged circumferentially distributed on the primary support element 9. The shielding segments 19 are essentially identical in the embodiment shown.

[0086] The electrical connection points 13 of the shielding layer 11 are in the embodiment of the Fig. 3 is evenly distributed circumferentially, ensuring that the shielding effect is uniform across the entire circumference of the primary and secondary windings 5, 6. This prevents the formation of local hotspots that could reduce the shielding efficiency. To maximize electromagnetic functionality, the connection point 13 should not cover any area of ​​the ferrite legs of the flux-conducting elements 7, 8, as these areas are crucial for the magnetic flux and must not be compromised.

[0087] To create the electrical connection point 13, the shielding layer 11 is contacted circumferentially at the division points of the shielding segments 19.

[0088] This specific arrangement utilizes the existing dividing points to enable effective contacting without requiring additional space. A low-impedance line 12 leads directly from the metallic primary support element 9 to the power electronics 14. This line 12 runs parallel to the AC terminals and ensures that the electrical return path is kept as short as possible to avoid additional electrical losses. This configuration also makes it possible to achieve further shielding effects by optimizing the return path of the capacitive currents.

[0089] Fig. Figure 4 shows a detailed structure of the shielding layer 11 as used in the contactless power transmission device 1. The shielding layer 11 is implemented here as a flexible printed circuit board 16 containing several copper layers 17. These copper layers 17 form a full-surface shield that interrupts the capacitive coupling between the primary winding 5 and the secondary winding 6. The flexible printed circuit board 16 allows the shielding layer 11 to be precisely adapted to the geometric requirements of the transformer, which is particularly advantageous in complex or confined installation situations.

[0090] The copper layers 17 are designed in such a way that they - as in the Fig.As can be seen in Figure 4, the conductors are arranged in a grid structure consisting of many parallel, prong-shaped traces. This grid structure serves to minimize eddy current losses by preventing the formation of large, closed conductor loops. The traces are preferably arranged to have a width of approximately 0.5 mm, which offers an optimal compromise between minimal eddy current losses and sufficient conductivity to effectively dissipate capacitive coupling currents. Alternatively, a tree structure could be used, in which a main conductor branches into several sub-conductors to distribute the currents evenly across the shielding layer 11 and efficiently dissipate capacitive interference.

[0091] To maximize the surface coverage of the shielding layer 11 without significant eddy current losses, a continuous metallic surface is not used. Instead, the copper conductors of the shielding layer 11 are arranged in many thin, insulated areas. These conductors 15 are interconnected in such a way that no closed loops are formed that would be susceptible to eddy currents. Insulating areas without conductive material are located between the conductors 15 to further optimize the electrical properties.

[0092] The shielding layer 11 can be multi-layered, with the conductors 15 of the different layers arranged offset such that the conductive areas of one layer cover the insulating areas of another layer. This multi-layered structure increases the effectiveness of the shielding by distributing the capacitive coupling currents over the entire area of ​​the shielding layer 11 while simultaneously minimizing eddy current losses.

[0093] The invention is not limited to the embodiments illustrated in the figures. The foregoing description is therefore not to be considered limiting, but rather explanatory. The following claims are to be understood as meaning that a named feature is present in at least one embodiment of the invention. This does not preclude the presence of further features. Insofar as the claims and the foregoing description define 'first' and 'second' features, this designation serves to distinguish between two similar features without establishing any hierarchy. Reference symbol list 1 Energy transmission device 2 Rotor 3 electric machine 4 transformers 5 Primary winding 6 Secondary winding 7 Flow guide element 8 Flow guide element 9 Primary support element 10 Secondary support element 11 Shielding layer 12 Line 13 Connection point 14 Power Electronics 15 ladders 16 circuit board 17 copper layers 18 Coverage area 19 shielding segments 20 air gap 21 Primary clocking 22 Voltage source 23 Mass / Housing 24 consumers 25 Return path 26 capacities 27 Grounding

Claims

[1] Contactless energy transmission device (1), in particular for a rotor (2) of an electric machine (3), in particular a separately excited synchronous machine within a drive train of a motor vehicle, comprising an inductive transformer (4) which has a currentable primary winding (5) and a secondary winding (6) spaced apart from it, and the primary winding (5) is movable relative to the secondary winding (6) during operation of the energy transmission device (1), characterized by , that a shielding layer (11) is arranged between the primary winding (5) and the secondary winding (6) and that a low-impedance line (12) is connected from the connection point (13) of the shielding layer (11) to another connection point, in particular an earthing point (27), so that a low-impedance return current path (25) is created for the currents capacitively coupled into the shielding. [2] Energy transmission device (1) according to claim 1, characterized by, that the shielding layer (11) consists of several individual conductors (15) arranged in such a way as to form a planar shielding surface between the primary winding (5) and the secondary winding (6). [3] Energy transmission device (1) according to claim 1 or 2, characterized by , that the shielding layer (11) comprises an electrically insulating printed circuit board (16), and the conductors (15) of the shielding layer (11), preferably as copper layers (17), are implemented on and / or in the printed circuit board (16). [4] Energy transmission device (1) according to claim 3, characterized by , that the circuit board (16) is flexible. [5] Energy transmission device (1) according to claim 3 or 4, characterized by that the conductors (15), preferably the copper layers (17), each have a width between 0.05-1 mm, preferably 0.25-0.75 mm, particularly preferably 0.35-0.65 mm, particularly preferably 0.45-0.55 mm with a preferred thickness of the copper layers of 15-500 µm. [6] Energy transfer device (1) according to any one of the preceding claims, characterized by , that the individual conductors (15) of the shielding layer (11) are arranged in a single-layer or multi-layer structure and each layer has either a computational structure formed from the conductors (15) or a tree structure, wherein the computational structure consists of a plurality of parallel, pinion-shaped conductor tracks, and the tree structure consists of a main conductor with branching sub-conductors. [7] Energy transmission device (1) according to claim 6, characterized by , that the conductors (15) of different layers are arranged such that they at least partially, preferably completely, cover the insulation areas between the conductors (15) of the other layer(s) in a surface projection, so that a shielding surface that is as closed as possible results in the direction of the projection. [8] Energy transfer device (1) according to any one of the preceding claims, characterized by , that the primary winding (5) is contained in a primary flux guide element (7) and the secondary winding (6) is contained in a secondary flux guide element (8), [9] Energy transmission device (1) according to claim 7, characterized by , that the primary flow guide element (7) is in turn connected to a primary support element (9) and the secondary flow guide element (7) is connected to a secondary support element (10). [10] Energy transfer device (1) according to any one of the preceding claims 7-8, characterized by, that the shielding layer (11) is configured to completely cover a direct overlap area (18) between the primary winding (5) and the secondary winding (6), but does not cover the area between the flux guide elements (7,8) in which the magnetic flux preferably flows over the air gap (20) between the flux guide elements (7,8) in order not to impair the magnetic flux between the flux guide elements (7,8). [11] Energy transfer device (1) according to any one of the preceding claims, characterized by that the shielding layer (11) is at least partially, preferably completely, covered by a potting material or plastic. [12] Energy transfer device (1) according to any one of the preceding claims 7-11, characterized by, that the shielding layer (11) is segmented with a plurality of shielding segments (19), wherein the connection points (13) of the shielding segments (19) are arranged circumferentially distributed on the primary support element (9). [13] Electric machine (3), in particular a separately excited electric motor, with a power transmission device (1) according to one of the preceding claims.

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