Electric machine for a motor vehicle

Abstract

The invention relates to an electric machine (10) for a motor vehicle, with an outer rotor (14) as the first rotor, with an inner rotor (16) as the second rotor which is non-rotatably connected to the outer rotor (14), and with a stator (12) arranged radially between the inner rotor (16) and the outer rotor (14) of the electric machine (10), whereby the electric machine (10) is designed as a radial flux machine and as an asynchronous machine; the respective rotor is designed as a squirrel-cage rotor and has its own squirrel-cage cage (26, 28); and the squirrel-cage cages (26, 28) are electrically insulated from each other.

Description

[0001] The invention relates to an electric machine for a motor vehicle, according to the preamble of patent claim 1.

[0002] Such an electric machine for a motor vehicle is already known, for example, from DE 10 2019 130 129 B3. The electric machine has an outer rotor and an inner rotor connected to the outer rotor in a rotationally fixed manner, as well as a stator arranged between the inner rotor and the outer rotor in the radial direction of the electric machine. The prior art also includes DE 60 336 474 D1, EP 2 404 365 B1, EP 1 892 814 A1, WO 201044231 A1, EP 1 480 A2, EP 1 843 447 B1, and EP 1 842 278 B1.

[0003] The object of the present invention is to improve an electrical machine of the type mentioned above.

[0004] This object is achieved by an electrical machine having the feature of patent claim 1. Advantageous embodiments with expedient further developments of the invention are set forth in the remaining claims.

[0005] In order to improve an electrical machine of the type specified in the preamble of patent claim 1, it is provided according to the invention that the electrical machine is designed as a radial flux machine (RFM) and as an asynchronous machine, that is to say in particular as a three-phase asynchronous machine. The outer rotor of the electrical machine is an external rotor and is also referred to as the first rotor. The inner rotor of the electrical machine is an internal rotor and is also referred to as the second rotor. According to the invention, the respective rotor of the electrical machine is designed as a respective squirrel-cage rotor, wherein the respective rotor of the electrical machine has its own respective squirrel-cage, for example designed as a short-circuit ring. Furthermore, it is provided according to the invention that the squirrel-cages are electrically insulated from one another, that is to say are electrically separated from one another.

[0006] The outer rotor and the inner rotor form an overall rotor which, viewed in a sectional plane running in the axial direction of the electrical machine, is U-shaped, i.e. is designed as a U-shaped profile. Because the stator is arranged between the rotors in the radial direction of the electrical machine, whose axial direction runs perpendicular to the radial direction of the electrical machine, the stator is arranged axially and radially overlapping the rotors and is thus arranged at least partially within the U-shaped profile. The overall rotor is a double rotor. Compared to conventional solutions, in particular compared to conventional radial flux machines, the invention enables a higher power density and higher efficiency to be achieved, in particular similar to permanent magnet synchronous machines (PSM) and with a smaller volume than comparable conventional radial flux machines in terms of torque.This can, for example, reduce the costs for permanent magnets in the machine compared to conventional solutions.

[0007] The invention is based in particular on the following findings and considerations: Currently, asynchronous machines, mostly radial flux machines, have exactly one stator, with a current-conducting winding, by means of which a magnetic field can be generated and thus provided. According to Lorenz's law, a north pole and a south pole of the magnetic field are created, and a current induced in the rotor generates a second magnetic field. Both magnetic fields repel each other, so that the rotor can be driven and thus rotated relative to the stator. If the magnetic field generated in the stator rotates at a predeterminable or preceding frequency, the rotor is driven and thus rotated about a machine axis of rotation relative to the stator, in particular depending on the frequency at which the stator's magnetic field rotates. Compared to conventional solutions, a starting current can be reduced.Furthermore, a particularly compact and thus space-saving design of the electric machine can be realized, while at the same time the electric machine can provide an advantageously high torque, especially for driving the motor vehicle. Furthermore, a particularly high level of efficiency of the electric machine can be achieved. Compared to conventional radial flux machines, higher efficiency and higher torque can be achieved, especially with the same stator size and the same amount of copper. Similar efficiency and torque can be achieved with more cost-effective production than with PSM. Permanent magnets can be avoided, thus preventing drag torque losses.

[0008] Further advantages, features, and details of the invention will become apparent from the following description of a preferred embodiment and from the drawings. The features and combinations of features mentioned above in the description, as well as those mentioned below in the description of the figures and / or shown alone in the figures, can be used not only in the respective specified combination, but also in other combinations or on their own, without departing from the scope of the invention.

[0009] The drawing shows: Fig. 1 is a schematic perspective view of an electric machine for a motor vehicle; Fig. 2 a schematic longitudinal sectional view of the electrical machine; Fig. 3 a partial schematic cross-sectional view of the electrical machine; Fig. 4 shows a further schematic longitudinal sectional view of the electrical machine; Fig. 5 is a schematic cross-sectional view of the electrical machine; and Fig. 6 shows a further schematic cross-sectional view of the electrical machine.

[0010] In the figures, identical or functionally identical elements are provided with the same reference numerals.

[0011] Fig. 1 shows a schematic representation of an electric machine 10 for a motor vehicle. In conjunction with Fig. 2 and Fig. 3 shows that the electric machine 10 has a stator 12, an outer rotor 14, and an inner rotor 16. The outer rotor 14 is an external rotor and is also referred to as the first rotor. The inner rotor 16 is an inner rotor and is also referred to as the second rotor. The outer rotor 14 and the inner rotor 16 form an overall rotor of the electric machine 10, the overall rotor of which can be driven by means of the stator 12 and is thus rotatable about a machine axis of rotation 18 relative to the stator 12. The electric machine 10, whose axial direction coincides with the machine axis of rotation 18, can provide drive torques via its overall rotor for driving the motor vehicle, in particular purely electrically.The electric machine 10, whose radial direction is perpendicular to the axial direction of the electric machine 10 and thus perpendicular to the machine's rotational axis 18, has a rotor shaft 20 that is, in particular, permanently and non-rotatably connected to the inner rotor 16, via which the electric machine 10 can provide the drive torque. Particularly well-known is . Fig. 2 that the stator 12 is arranged in the radial direction between the inner rotor 16 and the outer rotor 14, such that the stator 12 is arranged at least partially radially and axially overlapping the rotors. The outer rotor 14 is rotatably mounted on the stator 12 via at least or exactly one first rolling bearing 22. The inner rotor 16 is rotatably mounted on the stator 12 via at least or exactly one second rolling bearing 24. The rolling bearing 24 is provided in addition to the rolling bearing 22 and vice versa. The rolling bearings 22 and 24 are arranged at the same height in the axial direction. The first rolling bearing 22 is arranged radially outside the second rolling bearing 24, which is arranged axially and radially overlapping the first rolling bearing 22.

[0012] The electric machine 10 is designed as a radial flux machine (RFM). Furthermore, the electric machine 10 is designed as an asynchronous machine, i.e., as a three-phase flush asynchronous machine. Each rotor is designed as a squirrel-cage rotor, each rotor having its own squirrel-cage 26, 28. The squirrel-cage 26 of the outer rotor 14 is designed as a short-circuit ring. The squirrel-cage 28 of the inner rotor 16 is also designed as a short-circuit ring. An insulating element 30, designed as a ring, is arranged between the short-circuit rings, by means of which the short-circuit rings are electrically insulated from one another.

[0013] Out of Fig. 3 shows that the stator 12 has windings 31, by means of which a magnetic field, in particular a magnetic field designed as a rotating field, can be generated, such that the magnetic field is rotatable or rotates about the machine rotational axis 18 at a predeterminable or predetermined frequency, also referred to as the rotational frequency. The entire rotor can be driven by the magnetic field and thus rotated about the machine rotational axis 18 relative to the stator 12.

[0014] Fig. Figure 2 shows the electric machine 10 in a schematic longitudinal sectional view, in a sectional plane in which the machine's rotational axis 18 and thus the axial direction runs. It can be seen that, viewed in the longitudinal sectional plane, the entire rotor, which is also referred to as a double rotor, is U-shaped and thus has a U-profile, with the stator 12 being at least partially arranged within the U-profile.

[0015] Particularly good looking Fig. 4 shows the complete rotor, designated 32, which is U-shaped in the longitudinal section. Also particularly well Fig. 4 shows the rolling bearings 22 and 24, as well as the arrangement of the stator 12 in the U-profile.

[0016] Out of Fig. 5 shows the rotors, the stator 12, the rolling bearings 22 and 24, and the rotor shaft 20.

[0017] Finally, Fig. 6 in a further schematic cross-sectional view of the electric machine 10. Recognizable from Fig.6 is the magnetic field, designated 34, which can be generated by means of the windings 31 and thus by means of the stator 12, and its north pole N and its south pole S. Magnetic fields 36 and 38 can be induced in the rotors by means of the magnetic field 34 of the stator 12, with the magnetic field of the outer rotor 14 being designated 36 and the magnetic field of the inner rotor 16 being designated 38. Respective phases of the electric machine 10 are designated u1, v1, w1, u2, v2, w2, u12, v11, w11, u21, v21, and w21. List of reference symbols 10 electric machine 12 Stator 14 Outer rotor 16 inner rotor 18 Machine rotation axis 20 Rotor shaft 22 first Welz bearing 24 second Welz bearing 26 Squirrel cage 28 Squirrel cage 30 Insulation element 31 winding 32 total rotor 34 Magnetic field 36 Magnetic field 38 Magnetic field N North Pole S South Pole u1 phase v1 Phase w1 phase u2 phase v2 Phase w2 phase u11 phase v11 Phase w11 phase u12 phase v12 phase w12 phase QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2019 130 129 B3

[0002] DE 60 336 474 D1

[0002] EP 2 404 365 B1

[0002] EP 1 892 814 A1

[0002] WO 201044231 A1

[0002] EP 1 843 447 B1

[0002] EP 1 842 278 B1

[0002]

Claims

[1] Electric machine (10) for a motor vehicle, with an outer rotor (14) as the first rotor, with an inner rotor (16) connected to the outer rotor (14) in a rotationally fixed manner as the second rotor, and with a stator (12) arranged in the radial direction of the electric machine (10) between the inner rotor (16) and the outer rotor (14), characterized by , that: - the electrical machine (10) is designed as a radial flux machine and as an asynchronous machine; - the respective rotor is designed as a respective squirrel-cage rotor and has its own respective squirrel-cage (26, 28); and - the short-circuit cages (26, 28) are electrically insulated from each other. [2] Electrical machine (10) according to claim 1, characterized by that the outer rotor (16) is rotatably mounted on the stator (12) via at least one first rolling bearing (22). [3] Electrical machine (10) according to claim 2, characterized bythat the inner rotor (14) is rotatably mounted on the stator (12) via at least one second rolling bearing (24) provided in addition to the first rolling bearing (22). [4] Electrical machine (10) according to claim 3, characterized by that the rolling bearings (22, 24) are arranged at the same height in the axial direction of the electrical machine (10). [5] Electrical machine (10) according to claim 3 or 4, characterized by that the first rolling bearing (22) is arranged radially outside the second rolling bearing (24), which is arranged axially and radially overlapping the first rolling bearing (22).

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