Electric rotary transformer for inductive energy transfer

Abstract

The invention relates to an electric resolver (1) for inductive energy transfer. The invention relates to a resolver (1), comprising a resolver stator (3), which has a primary coil (2), and a resolver rotor (6), which is designed so as to be rotatable relative to the resolver stator (3) about an axis of rotation (D), which extends in an axial direction (A), and which has a secondary coil (5), which is designed so as to be rotatable relative to the resolver stator (3). Wherein the secondary coil (5) can be inductively coupled or inductively coupled to the primary coil (2). Furthermore, the rotary transformer (1) comprises a transformer core (4) made of a magnetic material, which is arranged in a stationary manner relative to the primary coil (2), which transformer core at least partially surrounds the primary coil (2) and the secondary coil (5). The primary coil (2) has a primary coil winding (7) that can be energized, and the secondary coil (5) has a secondary coil winding (8) that can be energized. Furthermore, the primary coil winding (7) and the secondary coil winding (8) are arranged next to one another in the axial direction (A) or perpendicular to the axial direction (A) and each comprise an electrically conductive strand (9, 10) or at least one electrically conductive winding wire.

Description

Technical Field

[0001] The invention relates to an electric rotary transformer for inductive energy transmission. Background Art

[0002] So-called externally excited synchronous machines require direct current in their rotors to generate the rotor magnetic field. This process is called "rotor excitation". In conventional externally excited synchronous machines, the rotor current is transmitted as direct current to the rotating rotor by means of so-called carbon brush slip ring contacts. This has the disadvantage that the carbon brushes erode due to wear, especially at high speeds, and undesirable conductive carbon dust is produced in the process.

[0003] As an alternative to such transmission of direct current by means of slip rings, it is known to realize the current transmission to the rotating rotor inductively, ie wirelessly. Such a design as part of an externally excited synchronous machine is also called a "rotating transformer".

[0004] The operating principle of the aforementioned inductive voltage transmission or energy transmission is based on an electrical transformer, wherein the primary winding or primary coil of the transformer is arranged in a fixed manner and the secondary winding or secondary coil is arranged on a rotating rotor. Since an alternating voltage is always initially generated in the secondary coil in the case of inductive energy transmission, it is necessary to convert the generated alternating voltage into a rectified voltage. Summary of the invention

[0005] The object of the present invention is to indicate new paths in the development of rotary transformers. In particular, an improved embodiment for such a rotary transformer should be proposed, which is distinguished by a technically simple design and nevertheless allows the rotary transformer rotor to rotate at high speeds - a property which is often also referred to as "high speed stability" by those skilled in the art.

[0006] This object is achieved by the subject matter of the independent claims. Preferred embodiments are the subject matter of the dependent claims.

[0007] The basic idea of ​​the invention is therefore to equip not only the primary coil on the stator side of the rotary transformer, but also the secondary coil of the rotary transformer, which is rotatable relative to the primary coil about the rotation axis and is therefore on the rotor side, with a coil winding, which is composed of an electrically conductive stranded wire or an electrically conductive winding wire. Such a coil winding can carry high currents and therefore allows high power to be transmitted from the stator to the rotor rotating relative to the stator about the rotation axis. In addition, not only the primary coil but also the secondary coil are respectively constructed as coil windings, which allows: the two coils are arranged directly adjacent to each other in the axial direction in the direction of the rotation axis or in the radial direction, that is, in the direction perpendicular to the rotation axis. As a result, a particularly good magnetic coupling and thus inductive coupling of the two coils is achieved, which has a favorable effect on the efficiency of the power transmission. According to the invention, the magnetic coupling between the primary coil and the secondary coil is also achieved by a transformer core arranged in a fixed position relative to the primary coil, which is arranged in a fixed position relative to the primary coil and surrounds not only the primary coil but also the secondary coil at least partially.

[0008] In particular, the electric rotary transformer according to the invention comprises a rotary transformer stator, which has a primary coil. In addition, the rotary transformer comprises a rotary transformer rotor, which has a secondary coil, which is configured to be rotatable relative to the rotary transformer stator about a rotation axis, which extends in the axial direction. The secondary coil can be inductively coupled or inductively coupled with the primary coil for transmitting energy from the primary coil to the secondary coil. The primary coil comprises an energizable primary coil winding. The secondary coil comprises an energizable secondary coil winding. The secondary coil can be inductively coupled or inductively coupled with the primary coil. This means that when the primary coil is energized with an alternating current, an alternating voltage is induced in the secondary coil. In the rotary transformer according to the invention, the primary coil winding and the secondary coil winding are arranged side by side in the axial direction or arranged side by side perpendicular to the axial direction. In the second alternative mentioned, the secondary coil is preferably arranged radially inside relative to the rotation axis, and the primary coil is therefore arranged radially outside. This facilitates the secondary coil to be fastened in a torsion-proof manner on the rotary transformer rotor shaft that can rotate around the rotation axis. In the rotary transformer according to the invention, the primary coil winding and the secondary coil winding each have an electrically conductive litz wire or each include an electrically conductive winding wire. In particular, the primary or secondary coil winding can be formed by enameled wire, litz wire and the like. Finally, the rotary transformer comprises a transformer core made of a magnetic material, which is arranged in a fixed position relative to the primary coil and at least partially surrounds the primary coil and the secondary coil. Preferably, the transformer core is arranged coaxially with the axis of rotation.

[0009] In a preferred embodiment of the rotary transformer according to the invention, the primary coil winding and the secondary coil winding each surround the axis of rotation, preferably multiple times.

[0010] The material of the transformer core can advantageously be ferrite. Such soft magnetic materials have proven to be particularly suitable for influencing the magnetic field generated between the two coils during operation of the rotary transformer. Since the transformer core is arranged in a fixed position relative to the primary coil, i.e. does not follow the rotational movement of the secondary coil, there is also no risk of damage to the mechanically fragile ferrite due to centrifugal forces acting during the rotational movement.

[0011] In a preferred embodiment, the primary coil winding and / or the secondary coil winding are arranged on an annular primary coil winding carrier or secondary coil winding carrier, which surrounds the rotation axis. Particularly preferably, the transformer core also has an annular geometry and has a central longitudinal axis extending coaxially with the rotation axis. In particular, the primary coil winding carrier or the secondary coil winding carrier can be arranged as an annular carrier plate or include such an annular carrier plate, which is preferably arranged concentrically with the rotation axis. By using the annular geometry, undesirable imbalances in the rotational movement of the rotating transformer rotor with the secondary coil are counteracted. Alternatively, the primary coil winding and / or the secondary coil winding can also be arranged on a hollow cylindrical or cylindrical primary coil winding carrier or secondary coil winding carrier, which extends in the axial direction and surrounds the rotation axis in the circumferential direction. This alternative is easy to assemble.

[0012] According to an advantageous extension of the rotary transformer according to the present invention, in a longitudinal section along the axial direction, the transformer core has two core elements axially opposite to each other and a radially inner core element and a radially outer core element, and the two core elements axially opposite to each other and the radially inner core element and the radially outer core element together at least partially surround the core internal space.

[0013] Particularly preferably, the primary coil and the secondary coil are axially or radially opposite each other in the core interior. Both variants ensure effective magnetic coupling of the two coils, namely the primary coil and the secondary coil. This increases the efficiency of the power transmission from the primary coil to the secondary coil. In addition, the first variant requires particularly little construction space in the radial direction, while the second variant requires particularly little construction space in the axial direction. Thus, the variant that is optimal in terms of the available construction space can be selected without thus being accompanied by losses in the magnetic coupling between the two coils.

[0014] According to another advantageous embodiment, a slot is formed in the radially inner core element of the transformer core, through which a fastening section of the secondary coil, in particular the coil body, is passed radially inwardly toward the axis of rotation for fastening the secondary coil to the rotor shaft of the synchronous machine. In this embodiment, the secondary coil can be fastened in a simple manner in a rotationally fixed manner on a rotatable rotor shaft arranged outside the transformer core, without thus being accompanied by losses in the effect of the transformer core on the magnetic field generated by the coil.

[0015] In another preferred embodiment, the rotary transformer rotor, in particular the secondary winding, can be designed without a transformer core, in particular without ferrite. In this way, the rotary transformer can also be operated at high speeds of its rotary transformer rotor without the risk of damaging the rotating transformer core. In addition, experimental studies have shown that by omitting the transformer core used as a heat storage device, the waste heat generated on the rotary transformer rotor during operation can be better discharged from the rotary transformer rotor.

[0016] According to an advantageous development, the rotary transformer has a rotary transformer rotor shaft which is arranged coaxially with the axis of rotation, which is rotatable relative to the transformer core and the primary winding and which is connected to the secondary winding in a rotationally fixed manner. In this way, the rotary transformer can be installed in a simple manner in the synchronous machine, in particular by connecting the rotary transformer rotor shaft to the rotor shaft of the synchronous machine in a rotationally fixed manner. Particularly preferably, the rotor shaft of the synchronous machine can also be used as the rotary transformer rotor shaft.

[0017] According to another advantageous development, the secondary coil is electrically connected to a rectifier circuit of the rotary transformer rotor, which is arranged on a printed circuit board and has at least one rectifier element, preferably two or four rectifier elements, for rectifying the AC voltage electrically induced in the secondary coil. This measure supports the electrical rectification of the AC voltage induced in the secondary coil, so that the AC voltage is suitable as a rectified voltage for generating the rotor magnetic field required in the rotary transformer rotor of an externally excited synchronous machine. Rectifier diodes or rectifier transistors, in particular MOSFETs, can be used as rectifier elements. The printed circuit board can be connected to the rotary transformer rotor shaft of the rotary transformer in a rotationally fixed manner. In addition, the printed circuit board can be arranged axially adjacent to the secondary coil or the winding carrier of the secondary coil.

[0018] Preferably, the rectifier circuit is arranged radially inwardly on the printed circuit board. This can also apply to other electrical components / electronic components of the rotor electronics connected downstream of the rectifier circuit. In this way, the moment of inertia generated by the rectifier elements or the rotor electronics when the transformer rotor shaft and therefore the printed circuit board rotates is kept small, thereby further improving the speed stability of the rotating transformer. In the present context, the expression "radially inwardly" means that the rectifier elements or the rotor electronics are respectively at least closer to the inner peripheral side of the printed circuit board than to the outer peripheral side of the printed circuit board in an axial top view of the printed circuit board. Suitably, all electronic components or parts of the electronic components, in particular the electronic components of the rotor electronics, can also be arranged in the rotating transformer rotor shaft or, as an alternative, can be moved outwardly to an additional, separate rotor printed circuit board.

[0019] Advantageously, at least one rectifier element is arranged on the upper side of the circuit board and / or on the lower side opposite the upper side. This applies particularly advantageously to all existing rectifier elements. This measure facilitates the assembly of the rotating transformer rotor.

[0020] According to an advantageous embodiment, the printed circuit board is arranged on a support structure that can be mounted on the rotary transformer rotor shaft. Particularly preferably, the support structure can be designed as a support plate. Such a support structure enables a stable, rotationally fixed mounting of the printed circuit board on the rotary transformer rotor shaft and, given a suitable design, simultaneously facilitates the assembly of the rotary transformer rotor shaft and the printed circuit board into the rotary transformer rotor of the rotary transformer.

[0021] The invention also relates to an externally excited synchronous machine, in particular a traction motor for a vehicle. The synchronous machine according to the invention comprises an electrically energized synchronous machine stator for generating a stator magnetic field. Furthermore, the rotary transformer comprises an electrically energized synchronous machine rotor rotatable relative to the synchronous machine stator for generating a rotor magnetic field, the synchronous machine rotor having a synchronous machine rotor shaft. Furthermore, the synchronous machine according to the invention comprises an electrical rotary transformer according to the invention, which is connected to the synchronous machine rotor shaft in a rotationally fixed manner. Thus, the above-mentioned advantages of the rotary transformer according to the invention are transferred to the synchronous machine according to the invention.

[0022] The synchronous machine according to the invention can be used in particular in a motor vehicle which can include a battery as an energy source. In this case, the synchronous machine is used in particular to drive a motor vehicle, i.e. is designed in particular as a traction motor. Preferably, the output power or drive power of the traction motor according to the invention is at least 3 kW, preferably at least 30 kW. Particularly preferably, the output power or drive power of the traction motor according to the invention is between 30 kW and 500 kW, most preferably between 100 kW and 300 kW. In the traction motor according to the invention, waste heat can be particularly effectively discharged via the transformer core present in the stator of the rotary transformer, which waste heat occurs in the traction motor according to the invention to a much greater extent than in electric motors with a lower output power.

[0023] Further important features and advantages of the invention emerge from the dependent claims, the drawings and the associated description of the figures based on the drawings.

[0024] It is self-evident that the features mentioned above and those yet to be explained below can be used not only in the respectively stated combination but also in other combinations or alone, without departing from the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Preferred exemplary 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 components or components having the same function.

[0026] The accompanying drawings schematically show:

[0027] Figure 1 An example of a rotary transformer according to the present invention is shown, in which the primary coil and the secondary coil of the rotary transformer are arranged side by side in the axial direction,

[0028] Figure 2 Show Figure 1 A variation of the example of , in which the primary coil and the secondary coil are arranged side by side in the radial direction,

[0029] Figure 3 Show Figure 1 A variant of the example of , in which the primary coil winding carrier or the secondary coil winding carrier has a hollow cylindrical geometry,

[0030] Figure 4 Show Figure 2 A variant of the example of , in which the primary coil winding carrier or the secondary coil winding carrier has a hollow cylindrical geometry. DETAILED DESCRIPTION

[0031] Figure 1A longitudinal section of an example of a rotary transformer 1 according to the invention is shown. The rotary transformer 1 comprises a rotary transformer stator 3 having a primary coil 2. Furthermore, the rotary transformer 1 comprises a rotary transformer rotor 6 having a secondary coil 5, which is rotatably configured relative to the rotary transformer stator 3 about a rotation axis D extending in the axial direction A.

[0032] The rotation axis D extends in the axial direction A. The radial direction R extends perpendicularly to the axial direction A and away from the rotation axis D. Figure 1 2 shows a longitudinal section of a rotary transformer 1 along the axial direction A. The circumferential direction U extends around the axis of rotation D perpendicularly to the axial direction A and also perpendicularly to the radial direction R.

[0033] The secondary coil 5 can be inductively coupled or inductively coupled to the primary coil 2 for transferring energy from the primary coil 2 to the secondary coil 5. The primary coil 2 comprises a primary coil winding 7 which can be energized. The secondary coil 5 comprises a secondary coil winding 8 which can be energized. The primary coil winding 7 and the secondary coil winding 8 are arranged side by side along the axial direction A. The primary coil winding 7 and the secondary coil winding 8 are respectively formed by conductive litz wires 9, 10. Instead of corresponding litz wires 9, 10, conductive winding wires can also be provided.

[0034] Furthermore, the rotary transformer 1 comprises a transformer core 4 made of a magnetic material, which at least partially surrounds the primary coil 2 and the secondary coil 5. The material of the transformer core 4 can be ferrite. The primary coil winding 7 is arranged on an annular primary coil winding carrier 20, which surrounds the rotation axis D in the circumferential direction U. Correspondingly, the secondary coil winding 8 is arranged on an annular secondary coil winding carrier 17, which surrounds the rotation axis D in the circumferential direction U. In the exemplary scenario 4, the transformer core 4 also has an annular geometry and has a central longitudinal axis M, which is arranged coaxially with the rotation axis D. The primary coil winding carrier 20 or the secondary coil winding carrier 17 can be designed as an annular carrier plate, which is arranged concentrically with the rotation axis.

[0035] like Figure 1As shown, the rotary transformer 1 also has a rotary transformer rotor shaft 18, which is arranged coaxially with the rotation axis D, which is rotatable relative to the transformer core 4 and the primary coil 2, and which is connected to the secondary coil 5 in a rotationally fixed manner. In the longitudinal section shown along the axial direction A, the transformer core 4 has two core elements 12a, 12b axially opposite each other and radially inner and radially outer core elements 13a, 13b, which together at least partially enclose the core interior 14.

[0036] like Figure 1 As shown, the primary coil 2 and the secondary coil 5 are axially opposite in the core inner space 14. A slit 15 is formed in the radially inner core element 13a of the transformer core 4, through which a fastening section 16 of a secondary coil winding carrier 17 of the secondary coil 5 passes radially inward toward the rotation axis D, for fastening the secondary coil to the rotor shaft of the synchronous motor in a rotationally fixed manner.

[0037] The secondary coil 5 can be connected to the circuit board 11 (in Figure 1 ) on a rectifier circuit 19 (in Figure 1 The rectifier circuit is electrically connected to the secondary coil 5 (also only roughly schematically indicated), and the rectifier circuit includes a plurality of rectifier elements (not shown) for rectifying the AC voltage induced in the secondary coil 5. Figure 1 The electrical connection between the rectifier circuit 19 and the secondary coil 5 required for this purpose is omitted.

[0038] like Figure 1 As shown, the printed circuit board 11 can be arranged axially adjacent to the secondary coil 5 or its secondary coil winding carrier 17. The printed circuit board 11 is connected to or fastened to a rotary transformer rotor shaft 18 of the rotary transformer in a rotationally fixed manner.

[0039] Figure 2 Show Figure 1 A variation of the example of Figure 2 The rotating transformer 1 and Figure 2 The difference between the rotary transformer is that Figure 2 In the rotary transformer 1, the primary coil 2 and the secondary coil 5 are arranged radially in the core internal space 14 (i.e., unlike Figure 1 In the example of FIG. Figure 1 In the example, and in Figure 2 In the example of FIG. 5 , the secondary coil 5 of the rotating transformer rotor 6 is designed without a transformer core, ie without magnetic material and thus in particular without ferrite.

[0040] Figure 3 and 4 is with Figure 1 and 2 On the contrary, in Figure 3 In the example of the primary coil winding carrier 20 or the secondary coil winding carrier 17, the primary coil winding carrier 20 or the secondary coil winding carrier 17 does not extend in the radial direction so that the primary coil winding carrier or the secondary coil winding carrier is as in Figure 1 and 2 In particular, the carrier plate can be formed as an annular carrier plate as in the example of FIG. 1 , but it extends not only in the circumferential direction U but also in the axial direction A. That is, in Figure 3 and 4 In the example of , the primary winding carrier 20 or the secondary winding carrier 17 has at least sections of a hollow cylindrical or cylindrical geometry. The slot 15 formed in the transformer core 4 extends in the axial direction A, as does the fastening section 16 of the secondary winding carrier 17 passing through the slot 15 .

Claims

1. An electric rotary transformer (1) for inductive energy transmission, comprising: - a rotating transformer stator (3), said rotating transformer stator having a primary coil (2); a rotary transformer rotor (6) which is rotatable relative to the rotary transformer stator (3) about an axis of rotation (D) and has a secondary coil (5), wherein: The secondary coil (5) and the primary coil (2) are capable of inductive coupling or inductive coupling; a transformer core (4) made of a magnetic material, which is arranged in a fixed position relative to the primary coil (2) and which at least partially surrounds the primary coil (2) and the secondary coil (5), - wherein the primary coil (2) has a primary coil winding (7) that can be energized, and the secondary coil (5) has a secondary coil winding (8) that can be energized, wherein the primary coil winding (7) and the secondary coil winding (8) are arranged side by side along the axial direction (A) or perpendicular to the axial direction (A) and each comprise an electrically conductive litz wire (9, 10) or at least one electrically conductive winding wire.

2. The rotary transformer according to claim 1, It is characterized in that The primary coil winding (7) and the secondary coil winding (8) each surround the rotation axis (D), preferably multiple times.

3. The rotary transformer according to claim 1 or 2, It is characterized in that The material of the transformer core (4) is ferrite.

4. The rotary transformer according to any one of claims 1 to 3, It is characterized in that - the primary coil winding (7) and / or the secondary coil winding (8) are arranged on a primary coil winding carrier (20) or a secondary coil winding carrier (17), the primary coil winding carrier or the secondary coil winding carrier surrounds the rotation axis (D) in a circumferential direction (U), the primary coil winding carrier or the secondary coil winding carrier is preferably annular, or - The primary coil winding (7) and / or the secondary coil winding (8) are arranged on a hollow cylindrical primary coil winding carrier (20) or secondary coil winding carrier (17), which extends in an axial direction (A) and surrounds the rotation axis (D) in a circumferential direction (U).

5. A rotary transformer according to any one of the preceding claims, It is characterized in that The transformer core (4) has an annular geometry and has a central longitudinal axis (M) which is arranged coaxially with the rotation axis (D).

6. A rotary transformer according to any one of the preceding claims, It is characterized in that In a longitudinal section along the axial direction (A), the transformer core (4) has two core elements (12a, 12b) axially opposed to each other and a radially inner core element and a radially outer core element (13a, 13b), and the two core elements axially opposed to each other and the radially inner core element and the radially outer core element together at least partially surround the core internal space (14).

7. The rotary transformer according to claim 6, It is characterized in that In the core inner space (14), the primary coil (2) and the secondary coil (5) are axially or radially opposed to each other.

8. A rotary transformer according to any one of the preceding claims, It is characterized in that A split (15) is constructed in the radially inner core element (13a) of the transformer core (4), and a fastening section (16) of the secondary coil (5) passes through the split radially inwardly toward the rotation axis (D) for fastening the secondary coil to the rotor shaft of the synchronous motor.

9. A rotary transformer according to any one of the preceding claims, It is characterized in that The rotary transformer rotor (6), in particular the secondary coil (5), is designed without a transformer core, in particular without ferrite.

10. A rotary transformer according to any one of the preceding claims, It is characterized in that The rotary transformer (1) has a rotary transformer rotor shaft (18), which is arranged coaxially with the rotation axis (D) and can rotate relative to the transformer core (4) and the primary coil (2), and is connected to the secondary coil (5) in a rotationally fixed manner.

11. A rotary transformer according to any one of the preceding claims, It is characterized in that The secondary coil (5) is electrically connected to a rectifier circuit (19) of the rotary transformer rotor (6), wherein the rectifier circuit is arranged on a circuit board (11) and has at least one rectifier element, preferably two or four rectifier elements, for rectifying an AC voltage electrically induced in the secondary coil (5).

12. An externally excited synchronous machine, in particular a traction motor for a vehicle, comprising: - a synchronous motor stator capable of being energized to generate a stator magnetic field; - a synchronous machine rotor that can be energized and can rotate relative to the synchronous machine stator for generating a rotor magnetic field, the synchronous machine rotor having a synchronous machine rotor shaft; - An electrical rotary transformer (1) according to any one of the preceding claims, which is connected to the rotor shaft of the synchronous machine in a rotationally fixed manner.

13. The synchronous motor according to claim 12, It is characterized in that The output power or drive power of the synchronous machine or of the traction motor is at least 3 kW, preferably at least 30 kW, particularly preferably between 30 kW and 500 kW, most preferably between 100 kW and 300 kW.

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