Electric rotary transformer for inductive energy transmission and separately excited electric synchronous machine

Abstract

Electric rotary transformer (1) for inductive power transmission, - with a rotary transformer stator (2) having a primary coil (20), - with a rotary transformer rotor (3) rotatable about an axis of rotation (D) relative to the rotary transformer stator (2) and having a secondary coil (21), wherein the secondary coil (21) can be inductively coupled or coupled to the primary coil (20), - with a capacitive coupling device (4) for capacitive electrical signal transmission between the rotary transformer stator (2) and the rotary transformer rotor (3), which is arranged partly on the rotary transformer stator (2) and partly on the rotary transformer rotor (3), characterized in that - the capacitive coupling device (4) comprises a first plate capacitor (5) and a second plate capacitor (6), each with a first plate element and a second plate element (5.1, 5.2, 6.1, 6.2), - the two first plate elements (5.1, 6.1) are arranged on the stator (2) and the two second plate elements (5.2, 6.2) are arranged on the rotary transformer rotor (3), wherein a first plate element (5.1, 6.1) and a second plate element (5.2, 6.2) are opposite each other for capacitive coupling, preferably axially, - the rotary transformer rotor (3) comprises a secondary coil circuit board (7) rotatable about the axis of rotation (D) relative to the rotary transformer stator (2), on which the secondary coil (21) is arranged, wherein the secondary coil (21) is formed by at least one conductor track (37) provided on the secondary coil circuit board (7), - the two second plate elements (5.2, 6.2) are each formed by at least one conductor track (10a, 10b) made of a metal, preferably copper, on the secondary coil circuit board (7), a transformer core (31) made of a magnetic core material, preferably ferrite, is arranged on the rotary transformer stator (2), which has a radially inwardly open recess (33) on its inner circumference (32), in which the secondary coil circuit board (7) is arranged with a radially outer circuit board section (34) on which the secondary coil (21) is arranged.

Description

[0001] The invention relates to an electric rotary transformer for inductive energy transmission and to a separately excited electric synchronous machine with such a rotary transformer.

[0002] So-called separately excited electric synchronous machines require a direct current voltage in their rotary transformer rotor to generate the magnetic rotor field. This process is called "rotor excitation".

[0003] The electrical energy transfer to the rotating rotary transformer rotor is inductive, i.e., wireless. Such a setup, as part of a separately excited synchronous machine, is called a "rotary transformer" or "rotating planar transformer".

[0004] The operating principle of this inductive power transfer is based on an electrical transformer, with the primary winding or primary coil of the transformer being located on the stator of the rotary transformer or synchronous machine, and the secondary winding or secondary coil being located on the rotating rotor of the rotary transformer. Since an alternating voltage is always generated in the secondary coil during inductive power transfer, it is necessary to convert this voltage into a direct voltage to energize the rotor.

[0005] For the operation of the electric rotary transformer or a separately excited electric synchronous machine equipped with this rotary transformer, it is often necessary to transmit data or at least signals from the primary side, i.e., from the stator, to the secondary side, i.e., to the rotor, or in the reverse direction from the rotor to the stator, or in both directions.

[0006] The generic German patent DE 20 2015 101 334 U1 discloses a rotary transformer with all the features of the preamble of claim 1. The rotary transformer comprises a rotating ferrite core that forms part of the rotor of the rotary transformer.

[0007] German patent DE 20 2014 101 753 U1 relates to an optoelectronic sensor for detecting objects in an overlapping area. The sensor can, in particular, be a laser scanner. The sensor comprises circuit boards for data transmission between a stationary base unit and a movable scanning unit.

[0008] WO 2021 / 094 564 A1 relates to a rotary transformer with a first part and a second part configured to rotate about an axis of rotation relative to the first part. The first part comprises a first magnetic core and a capacitive data link component. The second part comprises a second magnetic core for coupling power to the first magnetic core and a second capacitive data link component for transmitting data to and / or from the first capacitive data link component. To attenuate magnetic stray fields from the magnetic core, a resonant shield is provided outside the air gap between the magnetic cores. The resonant shield comprises an open annular structure with two open ends connected by a capacitor. This forms a resonant circuit.

[0009] US 4 558 320 A describes a rotary transformer with two rotatable components that define a radial opening into which a stationary mounting plate projects.

[0010] The object of the present invention is to demonstrate new approaches in the development of rotary transformers. In particular, an improved embodiment of such a rotary transformer is to be created, which enables simple yet efficient signal or data transmission between the primary and secondary sides, i.e., between the stator and rotor.

[0011] This problem is solved by the subject matter of the independent patent claims. Preferred embodiments are the subject matter of the dependent patent claims.

[0012] The basic idea of ​​the present invention is therefore to equip an electric rotary transformer with a capacitive coupling device, by means of which contactless signal transmission is enabled between the stator and the rotor, which is rotatable relative to the stator. This allows the desired signal or data transmission between the stationary primary side and the rotatable secondary side of the rotary transformer. Since the signal or data transmission is electrically separate from the inductive energy transmission, interference with the capacitive signal transmission by electromagnetic influence is excluded. Furthermore, with a suitable configuration of the coupling device, capacitive transmission allows for a high data transmission rate. Finally, such a capacitive coupling device requires very little installation space and proves to be interference-resistant and therefore reliable even in long-term operation.

[0013] An electrical rotary transformer according to the invention for inductive energy transmission, in particular for a vehicle traction motor, comprises a rotary transformer stator having a primary coil. Furthermore, the rotary transformer comprises a rotary transformer rotor rotatable about an axis of rotation relative to the rotary transformer stator and having a secondary coil. The secondary coil can be inductively coupled to the primary coil or is already coupled. According to the invention, the rotary transformer also comprises a capacitive coupling device for capacitive signal transmission between the rotary transformer stator and the rotary transformer rotor. The capacitive coupling device is formed partly on the rotary transformer stator and partly on the rotary transformer rotor.

[0014] For generating and receiving electrical signals, the rotary transformer can include an electrical transmitting and receiving unit located on the rotary transformer stator. Furthermore, for generating and receiving electrical signals, the rotary transformer can include an electrical transmitting and receiving unit arranged on the rotary transformer rotor. For signal transmission between the two transmitting and receiving units, the rotary transformer can be extended by a first and a second electrical conductor path, which—electrically separated from each other and connected in parallel—connect the two transmitting and receiving units electrically.

[0015] According to the invention, the capacitive coupling device comprises a first plate capacitor and a second plate capacitor. Each of the two plate capacitors comprises a first plate element and a second plate element, which is arranged at a distance from the first plate element, forming a gap. The air arranged in the gap can act as a dielectric. In this embodiment, the two first plate elements are arranged on the stator and the two second plate elements on the rotary transformer rotor. The second plate elements are thus rotatable relative to the first plate elements and are also galvanically isolated from them.

[0016] In this configuration, a first plate element and a second plate element are positioned opposite each other for capacitive coupling, preferably axially. This allows each of the two first plate elements to be arranged axially at a very small distance from its corresponding second plate element. This also increases the capacitance of the plate capacitors. Furthermore, the capacitive coupling device requires very little installation space, particularly in the axial direction.

[0017] According to the invention, the rotary transformer rotor has a secondary coil circuit board that is rotatable about the axis of rotation relative to the rotary transformer stator. The secondary coil is arranged on the secondary coil circuit board, axially facing the primary coil. The secondary coil is formed by at least one conductor track present on the secondary coil circuit board. In the context of the present invention, "arranged on the secondary coil circuit board" means that the at least one conductor track forming the secondary coil is arranged—in particular visibly—on the surface of the circuit board or—in particular invisibly—surrounded by the material of the circuit board. A combination of both variants, as can be used particularly in multilayer circuit boards, is also encompassed by the preceding formulation.

[0018] The two second plate elements are each formed by at least one conductor track made of a metal, preferably copper, formed on the secondary coil circuit board. In the context of the present invention, "arranged on the circuit board" means that the conductor tracks forming the plate elements are arranged—particularly visibly—on the surface of the circuit board or—particularly invisibly—surrounded by the material of the circuit board. A combination of both variants, as can be used particularly in multilayer circuit boards, is also encompassed by the above formulation.

[0019] According to the invention, a transformer core made of a magnetic core material, preferably ferrite, is arranged on the rotary transformer stator, which has a radially inwardly open recess on its inner circumference in which the secondary coil circuit board is arranged with a radially outer circuit board section on which the secondary coil is arranged.

[0020] Preferably, the two second plate elements can be arranged radially inside and the secondary coil radially outside on the secondary coil circuit board, or vice versa. This variant is particularly easy to manufacture and therefore involves low production costs, since both the secondary coil of the rotary transformer and the rotatable part of the two plate capacitors are formed as the second plate elements on the same circuit board. Furthermore, this embodiment is particularly compact.

[0021] According to an advantageous embodiment, the two plate capacitors are arranged at a distance from each other along a radial direction extending perpendicularly from the axis of rotation. This variant requires particularly little installation space in the axial direction.

[0022] According to a further advantageous embodiment, the two first plate elements are arranged on at least one additional printed circuit board (PCB) that is axially spaced from the secondary coil PCB. Such an additional PCB is relatively simple to manufacture and therefore cost-effective. Furthermore, the secondary coil PCB and the additional PCB can be arranged axially close to one another. This results in a further saving of installation space along the axial direction. In addition, the capacitance of the two plate capacitors can be increased in this way. In the context of the present invention, "arranged on the additional PCB" means that the conductor tracks forming the plate elements are arranged—particularly visibly—on the surface of the PCB or—particularly invisibly—surrounded by the PCB material.The above formulation also covers a combination of both variants, as can be used particularly in multilayer printed circuit boards.

[0023] Particularly advantageous is the ability to form the first two plate elements with a conductor track made of a metal, preferably copper, on the additional circuit board. This variant is also particularly easy to manufacture.

[0024] According to another preferred embodiment, the two plate capacitors are arranged side by side in an axial direction extending along the axis of rotation. This embodiment is particularly compact in the radial direction. In a further embodiment, the two plate capacitors can be arranged axially side by side and radially offset from each other.

[0025] According to an advantageous embodiment, the two first plate elements are arranged on two different additional printed circuit boards. In this embodiment, the secondary coil printed circuit board is arranged axially between the two additional printed circuit boards.

[0026] According to a further advantageous embodiment, the two second plate elements are arranged on axially opposite sides of the secondary coil circuit board. One of the two second plate elements faces axially towards the first plate element arranged on the first additional circuit board. The other of the two second plate elements faces axially towards the first plate element arranged on the second additional circuit board. This embodiment also features a particularly compact axial design and is furthermore characterized by low susceptibility to electrical / electronic interference.

[0027] Advantageously, the first and second plate elements can each be designed to be rotationally symmetrical about the axis of rotation. This ensures that the functionality of the plate capacitors with regard to the transmission of electrical signals during the rotation of the rotary transformer rotor is guaranteed in every rotational position of the rotary transformer rotor relative to the rotary transformer stator.

[0028] Particularly advantageous is the fact that the first and second plate elements of at least one plate capacitor, preferably of both plate capacitors, can each have a ring-shaped geometry. This ensures, as explained above, that the functionality of the plate capacitors with regard to the transmission of electrical signals during the rotation of the rotor is not impaired.

[0029] The first and second plate elements are preferably arranged coaxially with respect to the axis of rotation. This measure also ensures that the functionality of the plate capacitors is not impaired during the rotation of the rotor.

[0030] The invention further relates to a separately excited electric synchronous machine, in particular a traction motor for a vehicle. The synchronous machine comprises an electrically energizable synchronous machine stator for generating a magnetic stator field. This machine further comprises an electrically energizable synchronous machine rotor, rotatable relative to the synchronous machine stator, for generating a magnetic rotor field, and having a synchronous machine rotor shaft. The synchronous machine also comprises a rotary transformer according to the invention, as described above, which is non-rotatably connected to the synchronous machine rotor shaft. The advantages of the rotary transformer according to the invention, described above, are therefore also transferred to the separately excited electric synchronous machine according to the invention.

[0031] The synchronous machine can be used, in particular, in a motor vehicle, which may include a battery as its energy source. The synchronous machine serves primarily to drive the motor vehicle and is therefore specifically designed as a traction motor. Preferably, the traction motor according to the invention has an output or drive power between 100 kW and 240 kW, particularly 140 kW.

[0032] Further important features and advantages of the invention will become apparent from the dependent claims, the drawings and the associated description of the figures based on the drawings.

[0033] Preferred embodiments of the invention are shown in the drawings and are explained in more detail in the following description, wherein identical reference numerals refer to identical or similar or functionally identical components.

[0034] They show, schematically: Fig. 1. In a circuit diagram-like representation, the electrical wiring of an electrical rotary transformer according to the invention, Fig. 2 a diagram illustrating the functional structure of the capacitive coupling device essential to the invention, Fig. 3 the mechanical construction of a first example of the rotary transformer according to the invention, in which the plate capacitors of the capacitive coupling device are arranged radially next to each other, in a longitudinal section, Fig. 4 the rotary transformer of the Fig. 3 in a top view of the secondary coil circuit board, Fig. 5 the mechanical construction of a first example of the rotary transformer according to the invention, in which the plate capacitors of the capacitive coupling device are arranged axially next to each other, in a longitudinal section, Fig. 6 the rotary transformer of the Fig. 5 in a top view of the secondary coil circuit board.

[0035] Fig. Figure 1 shows, in a circuit diagram-like representation, the electrical wiring of an electric rotary transformer 1 according to the invention for inductive power transmission. The rotary transformer 1 can be used in a separately excited electric synchronous machine, in particular in a traction motor for a vehicle. The rotary transformer 1 comprises, on the primary side, a rotary transformer stator 2 with a primary coil 20. Furthermore, on the secondary side, the rotary transformer 1 comprises a rotor that rotates about an axis D relative to the rotary transformer stator 2 (in Fig. 1 (not shown) rotatably designed rotary transformer rotor 3 having a secondary coil 21. The secondary coil 21 is inductively coupled to the primary coil 20.

[0036] For the electrical energy transfer from the primary coil 20 to the secondary coil 21, it is necessary to generate an alternating current in the primary coil 20. The required alternating voltage can be generated by a transistor circuit 22 arranged on the primary side and electrically connected to the primary coil 20. The transistor circuit 22 can comprise four power transistors 23a, 23b, 23c, 23d, which in this example are controlled by a control device 24 with two integrated circuits 25a, 25b. When an alternating current is applied to the primary coil 20, an alternating voltage is also induced in the secondary coil 21.The secondary coil 21 is electrically connected to an electrical rectifier circuit 26, which in this example comprises four rectifier elements 27a, 27b, 27c, 27d and by means of which the induced alternating voltage can be converted into a direct voltage. The four rectifier elements 27a-27d can each be formed by a rectifier diode 28a-28d. The direct current generated in this way serves to supply current to the synchronous machine rotor of the electric synchronous machine, which is located in . Fig. 1 is schematically indicated by an inductance designated by reference numeral 29 and an ohmic resistance designated by reference numeral 38.

[0037] For signal or data transmission between the primary and secondary sides, i.e., between the rotary transformer stator 2 and the rotatable rotary transformer rotor 3, the rotary transformer 1 includes a capacitive coupling device 4. The structure of the capacitive coupling device 4 is shown in Fig. Figure 2 shows a circuit diagram. For sending electrical signals to the rotary transformer rotor 3 and for receiving electrical signals from the rotary transformer rotor 3, the rotary transformer 1 includes an electrical transmitting and receiving unit 40 provided on the rotary transformer stator 2. For sending electrical signals to the rotary transformer stator 2 and for receiving electrical signals from the rotary transformer stator 2, the rotary transformer 1 includes an electrical transmitting and receiving unit 41 provided on the rotary transformer rotor 3. For signal transmission between the two transmitting and receiving units 40, 41, the rotary transformer 1 includes a first and a second electrical conduction path 30a, 30b, which – connected electrically in parallel – electrically connect the two transmitting and receiving units 40, 41. In the first conductor path 30a a first plate capacitor 5 of the coupling device 4 is arranged.In the second conductor path 30b, a second plate capacitor 5 of the coupling device 4 is arranged. By means of the two plate capacitors 5, 6, galvanic isolation is achieved between the transmitting and receiving unit 40 provided on the rotary transformer stator 2 and the transmitting and receiving unit 41 provided on the rotatable rotary transformer rotor 3.

[0038] The first parallel-plate capacitor 5 comprises a first plate element 5.1 and a second plate element 5.2. The second parallel-plate capacitor 6 comprises a second plate element 6.1 and a second plate element 6.2. The two first plate elements 5.1, 6.1 are arranged at a distance, i.e., forming a gap, from their respective second plate elements 5.2, 6.2. The air in this gap acts as the dielectric of the respective parallel-plate capacitor 5, 6.

[0039] How Fig. 2 further illustrated, in both electrical conduction paths 30a, 30b, an electrical filter device 42 or 43 can be provided, respectively, between the transmitting and receiving unit 40 and the two plate capacitors 5, 6, as well as between the transmitting and receiving unit 41 and the two plate capacitors 5, 6, for filtering disturbances from the electrical signals transmitted by means of the two electrical conduction paths 30a, 30b.

[0040] The Fig. Figure 3 illustrates, in a schematic and highly simplified representation, the mechanical structure of the rotary transformer 1 in the transition region between the stator 2 and the rotor 3. The rotary transformer rotor 6 is designed to rotate relative to the rotary transformer stator 2. The rotary transformer rotor 3 comprises a rotor shaft 9 that rotates about the axis of rotation D. A central longitudinal axis M of the rotor shaft 9 is identical to the axis of rotation D. An axial direction A extends along the central longitudinal axis M and thus also along the axis of rotation D. A radial direction R extends perpendicular to the axial direction A from the central longitudinal axis M or axis of rotation D. A circumferential direction U extends perpendicular to the axial direction A and also perpendicular to the radial direction R and rotates around the central longitudinal axis M or axis of rotation D.

[0041] The rotary transformer rotor 3 comprises a secondary coil circuit board 7, which is rotatable about the axis of rotation D relative to the rotary transformer stator 2 and is fixedly connected to the rotor shaft 9. A conductor track 36, which forms the secondary coil 21, is arranged on the secondary coil circuit board 7. The secondary coil 21, or rather the conductor track 36, is electrically connected to the secondary coil 21, as already described in the Fig. 1 explained and also arranged on the secondary coil circuit board 7 (in Fig. (3 not shown) rectifier circuit 26 connected. In the context of the present invention, "arranged on the secondary coil circuit board 7" means that the at least one conductor forming the secondary coil is arranged—particularly visibly—on the surface of the circuit board or—particularly invisibly—is surrounded by the material of the circuit board. A combination of both variants, as can be used particularly in multilayer circuit boards, is also encompassed by the preceding formulation.

[0042] A transformer core 31 made of a magnetic core material, preferably ferrite, is arranged on the rotary transformer stator 3. The transformer core 31 of the rotary transformer stator 2 can be ring-shaped and arranged coaxially to the axis of rotation D. In the example of the Fig. 3 The transformer core 31 has a radially inwardly open recess 33 on its inner circumference 32. The secondary coil circuit board 7 is arranged in this recess 33 with a radially outer circuit board section 34 on which the secondary coil 21 is arranged. The recess 33 can also be configured as shown in Fig. Figure 3 shows an axial recess 35 radially outward, in which the primary coil 20 of the rotary transformer stator 2 is arranged. The primary coil 20 is fixed to the transformer core 31 in the recess 35 such that the primary coil 20 and the secondary coil 21 are positioned opposite each other along the axial direction A. When an alternating current is applied to the primary coil 20, an alternating voltage is induced in the secondary coil 21. The primary coil 20 can be formed by a coil winding 37 made of an electrically conductive winding wire.

[0043] How Fig. As can also be seen in Figure 3, the first two plate elements 5.1, 6.1 of the two plate elements 5, 6 are arranged on the rotary transformer stator 2. The second two plate elements 5.2, 6.2 are arranged on the rotary transformer rotor 3. Thus, the second two plate elements 5.2, 6.2 are designed to be rotatable relative to the first two plate elements 5.1, 6.1 about the axis of rotation D. In the example of the Fig. In section 3, the two plate capacitors 5 and 6 are arranged at a distance from each other along the radial direction R. The first two plate elements 5.1 and 6.1 of the two plate capacitors 5 and 6 are arranged on the rotary transformer stator 2. For capacitive coupling, the first and second plate elements 5.1 and 5.2 of the first plate capacitor 5 are arranged axially opposite each other and at a distance from each other. Similarly, for capacitive coupling, the first and second plate elements 6.1 and 6.2 of the second plate capacitor 6 are arranged axially opposite each other and at an axial distance from each other. Air is arranged as the dielectric in an axial space 12a of the first plate capacitor 5 formed between the first plate element 5.1 and the second plate element 5.2 of the first plate capacitor 5. Similarly, air is arranged as the dielectric in a space 12a between the first plate element 6.1 and the second plate element 6.Air is also arranged as a dielectric in the axial space 12b of the second plate capacitor 6 formed in 2 of the second plate capacitor 5.

[0044] Fig. Figure 4 shows the rotary transformer of the Fig. 3 in an axial top view of the secondary coil circuit board 7. The conductor track 36 forming the secondary coil 21 is clearly visible. The conductor track 36 runs spirally around the rotor shaft 9 in the circumferential direction U. The two second plate elements 5.2, 6.2 are as in Fig. 4 each recognizably formed by a conductor track 10a, 10b made of a metal, for example copper, arranged on the secondary coil circuit board 7. In the context of the present invention, "arranged on the secondary coil circuit board 7" means that the conductor tracks 10a, 10b forming the board elements 5.2, 6.2 are arranged—particularly visibly—on the surface of the circuit board or—particularly invisibly—surrounded by the material of the circuit board. A combination of both variants, as can be used particularly in multilayer circuit boards, is also encompassed by the preceding formulation.

[0045] In the example of the Fig. In Figure 4, the two plate capacitors 5 and 6 are arranged radially inwards and the secondary coil 21 radially outwards on the secondary coil circuit board 7. Furthermore, the two second plate elements 5.2 and 6.2 are each rotationally symmetrical about the axis of rotation D. Likewise, the two second plate elements 5.2 and 6.2 each have an annular or circular geometry and extend along the circumferential direction U. In addition, the second plate elements 5.2 and 6.2 are arranged coaxially with respect to the axis of rotation D. The radius R1 of the second plate element 5.2 of the first plate capacitor 5 from the axis of rotation D is larger than the radius R2 of the second plate element 6.2 of the second plate capacitor 6. The preceding explanations regarding the geometry of the two second plate elements 5.2 and 6.2 also apply mutatis mutandis to the two in Figure 4. Fig. 4 not shown first plate elements 5.1, 6.1 of the first or second plate capacitor 5, 6.

[0046] The first two plate elements 5.1, 6.1 can be used as in Fig. 3 are graphically indicated on an additional circuit board 8, which is arranged as part of the rotary transformer stator 2 in the axial direction A at a distance from the secondary coil circuit board 7. The first two plate elements 5.1, 6.1 are each also formed by a conductor track 11a, 11b made of a metal, preferably copper, formed on the additional circuit board 8. In the context of the present invention, "arranged on the additional circuit board" means that the conductor tracks forming the plate elements are arranged—particularly visibly—on the surface of the circuit board 8 or—particularly invisibly—surrounded by the material of the circuit board 8. A combination of both variants, as can be used particularly with multilayer circuit boards 8, is also encompassed by the above formulation.

[0047] The Fig. 5 shows a variant of the example of Fig. 3. In the so-called “coplanar” arrangement of the Fig. In the example of the following, the two plate capacitors 5, 6 are arranged side by side along the axial direction A and at the same radial distance R1, R2 from the axis of rotation D. Fig. In Figure 5, the first two plate elements 5.1, 6.1 of the two plate capacitors 5, 6 are arranged on two separate additional circuit boards 8a, 8b of the stator 2. The secondary coil circuit board 7 is arranged axially A between the two additional circuit boards 8a, 8b. Furthermore, the second plate elements 5.2, 6.2 are arranged on axially opposite sides 13, 14 of the secondary coil circuit board 7. The second plate element 5.2 of the first plate capacitor 5 is arranged on the first side 13 of the secondary coil circuit board 7. The second plate element 6.2 of the second plate capacitor 6 is arranged on the second side 14 of the secondary coil circuit board 7, which is axially opposite the first side 13. Consequently, the second plate element 5.2 of the first plate capacitor 5 is axially oriented towards and opposite the first plate element 5.1 arranged on the first additional circuit board 8a.Accordingly, the second plate element 6.2 of the second plate capacitor 6 is axially oriented towards the first plate element 6.1 arranged on the second additional circuit board 8b and lies opposite it along the axial direction A.

[0048] Fig. Figure 6 shows – in an analogous way to Fig. 4 - the rotary transformer of the Fig. 5 in an axial top view of side 14 of the secondary coil circuit board 7. The secondary coil 21 is thus formed by a conductor track 36 provided on the secondary coil circuit board 7, which spirals around the rotor shaft 9 in the circumferential direction U. The two second plate elements 5.2, 6.2 are as in Fig. 6 each recognizable by a conductor track 10a, 10b made of a metal, for example copper, arranged on the secondary coil circuit board 7, wherein in Fig. 6 only the second plate element 6.2 of the second plate capacitor 6 is recognizable. The first two plate elements 5.1, 6.1 can also each be formed by a conductor track 11a, 11b made of a metal, for example copper, arranged on the first additional circuit board 8a and on the second additional circuit board 8b respectively (cf. Fig. 5).

[0049] Even in the example of Fig. 5 and Fig. In Figure 6, both the first and second plate elements 5.1, 5.2, 6.1, 6.2 are rotationally symmetrical about the axis of rotation D. Likewise, the first and second plate elements 5.1, 5.2, 6.1, 6.2 each have a ring-shaped or circular geometry and extend along the circumferential direction U. Furthermore, the first and second plate elements 5.1, 5.2, 6.1, 6.2 are arranged coaxially with respect to the axis of rotation D. In the example of the Fig. 5 and Fig. 6 is the radius R1 of the first and second plate elements 5.1, 5.2 of the first plate capacitor 5 from the axis of rotation D equal to the radius R2 of the first and second plate elements 6.1, 6.2 of the second plate capacitor 6.

[0050] In the example of the Fig. 6 are the two plate capacitors 5, 6 in an analogous way, for example, the Fig. 4 radially inside and the secondary coil 21 radially outside on the secondary coil circuit board 7.

Claims

[1] Electric rotary transformer (1) for inductive power transmission, - with a rotary transformer stator (2) having a primary coil (20), - with a rotary transformer rotor (3) rotatable about an axis of rotation (D) relative to the rotary transformer stator (2) and having a secondary coil (21), wherein the secondary coil (21) can be inductively coupled or coupled to the primary coil (20), - with a capacitive coupling device (4) for capacitive electrical signal transmission between the rotary transformer stator (2) and the rotary transformer rotor (3), which is arranged partly on the rotary transformer stator (2) and partly on the rotary transformer rotor (3), characterized by , that - the capacitive coupling device (4) comprises a first plate capacitor (5) and a second plate capacitor (6), each with a first plate element and a second plate element (5.1, 5.2, 6.1, 6.2), - the two first plate elements (5.1, 6.1) are arranged on the stator (2) and the two second plate elements (5.2, 6.2) are arranged on the rotary transformer rotor (3), wherein a first plate element (5.1, 6.1) and a second plate element (5.2, 6.2) are opposite each other for capacitive coupling, preferably axially, - the rotary transformer rotor (3) comprises a secondary coil circuit board (7) rotatable about the axis of rotation (D) relative to the rotary transformer stator (2), on which the secondary coil (21) is arranged, wherein the secondary coil (21) is formed by at least one conductor track (37) provided on the secondary coil circuit board (7), - the two second plate elements (5.2, 6.2) are each formed by at least one conductor track (10a, 10b) made of a metal, preferably copper, on the secondary coil circuit board (7), a transformer core (31) made of a magnetic core material, preferably ferrite, is arranged on the rotary transformer stator (2), which has a radially inwardly open recess (33) on its inner circumference (32), in which the secondary coil circuit board (7) is arranged with a radially outer circuit board section (34) on which the secondary coil (21) is arranged. [2] Electric rotary transformer according to claim 1 or 2, characterized by , that - the two second plate elements (5.2, 6.2) are arranged radially inside and the secondary coil (21) radially outside on the secondary coil circuit board (7), or vice versa. [3] Electric rotary transformer according to claim 1 or 2, characterized by, that the two plate capacitors (5, 6) are arranged at a distance from each other along a radial direction (R) extending perpendicularly away from the axis of rotation (D). [4] Electric rotary transformer according to any of the preceding claims, characterized by , that the two first plate elements (5.1, 6.1) are arranged on an additional printed circuit board (8; 8a, 8b) which is arranged axially at a distance from the secondary coil printed circuit board (7). [5] Electric rotary transformer according to claim 4, characterized by , that the two first plate elements (5.1, 6.1) are each formed by a conductor track (11a, 11b) made of a metal, preferably copper, formed on the additional circuit board (8; 8a, 8b). [6] Electric rotary transformer according to claim 4 or 5, characterized by , that - the first two plate elements (5.1, 6.1) are arranged on two different additional printed circuit boards (8a, 8b), - the secondary coil circuit board (7) is arranged axially between the two additional circuit boards (8a, 8b). [7] Electric rotary transformer according to claim 6, characterized by , that the two second plate elements (5.2, 6.2) are arranged on axially opposite sides (13, 14) of the secondary coil circuit board (7), such that one of the two second plate elements (5.2) is axially oriented towards the first plate element (5.1) arranged on the first additional circuit board (8a) and the other of the two second plate elements (6,2) is axially oriented towards the first plate element (6.1) arranged on the second additional circuit board (8b). [8] Electric rotary transformer according to any of the preceding claims, characterized by , that the two plate capacitors (5, 6) are arranged next to each other along an axial direction (A) extending along the axis of rotation (D). [9] Electric rotary transformer according to any of the preceding claims, characterized by , that the first two plate elements (5.1, 5.2, 6.1, 6.2) are each rotationally symmetric to the axis of rotation (D). [10] Electric rotary transformer according to any of the preceding claims, characterized by , that the first and second plate elements (5.1, 5.2, 6.1, 6.2) each have a ring-shaped geometry. [11] Electric rotary transformer according to any of the preceding claims, characterized by , that the first and second plate elements (5.1, 5.2, 6.1, 6.2) are arranged coaxially to each other. [12] Externally excited electric synchronous machine, in particular traction motor for an electric or hybrid vehicle, - with an electrically powered synchronous machine stator for generating a magnetic stator field, - with an electrically powered synchronous machine rotor that can be rotated relative to the synchronous machine stator to generate a magnetic rotor field, which has a synchronous machine rotor shaft, - with an electric rotary transformer (1) according to one of the preceding claims, which is non-rotatably connected to the synchronous machine rotor shaft.

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