Electric machine, especially for a motor vehicle

Abstract

The invention relates to an electric machine (10) designed as a radial flux double-rotor machine and comprising a stator (16) which has a stator core (18) and a winding (20) formed separately from and attached to the stator core (18). A first, outer rotor (28) is provided, which is arranged radially outside the stator (16) and axially overlapping the stator (16) and is rotatable about an axis of rotation (14) relative to the stator (16). A second, inner rotor (30) is provided, which is non-rotatably connected to the first rotor (28), is arranged radially inside the stator (16), radially inside the first rotor (28), axially overlapping the stator (16) and the first rotor (28), and is rotatable about the axis of rotation (14) relative to the stator (16).

Description

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

[0002] Such an electrical machine, designed as a radial flux double-rotor machine, is already known, for example, from WO 2023 / 006440 A2. The electrical machine designed as a radial flux double-rotor machine has a stator comprising a stator core and a winding formed separately from and attached to the stator core. Furthermore, the radial flux double-rotor machine has a first, outer rotor, which is arranged radially outside the stator and axially overlapping with the stator, and is rotatable about an axis of rotation relative to the stator. The radial flux double-rotor machine also has a second, inner rotor, which is rotationally fixed to the first rotor. The second, inner rotor is arranged radially inside the stator and radially inside the first rotor, as well as axially overlapping with the stator and axially overlapping with the first rotor, and is rotatable about the axis of rotation relative to the stator.The state of the art also includes DE 10 2023 101 990 B3, WO 2017 / 173 188 A1, DE 10 2023 104 937 A1, DE 10 2022 205 930 B3, DE 10 2022 202 123 B4 and DE 10 2021 003 942 B4.

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

[0004] This problem is solved by an electric machine with the features of claim 1. Advantageous embodiments with expedient further developments of the invention are specified in the remaining claims.

[0005] To improve an electric machine of the type specified in the preamble of claim 1, the invention provides a holding element common to the rotors, formed separately from the rotors and made from a single piece, which is deep-drawn, in particular, in the axial direction of the electric machine. This gives the holding element a U-shape when viewed in an imaginary plane in which the axis of rotation runs. The rotors and the stator are arranged in this U-shape, with the rotors, which are formed separately from each other and separately from the holding element, being attached to the holding element in this U-shape. Thus, the rotors are connected to each other via the holding element. In particular, each rotor is attached to the holding element in such a way that relative movements between the respective rotor and the holding element are prevented.According to the invention, a support, also referred to as a rotor support, is provided, which is formed separately from the rotors, the holding element, and the stator. The support is welded, in particular directly, to the holding element. The support is connected, in particular directly, in a rotationally fixed manner to a rotor shaft of the electric machine, which is formed separately from the support and rotatable about the axis of rotation relative to the stator, such that the rotors are connected, in each case, to the rotor support via the holding element and to the rotor shaft via the rotor support. The invention allows for a particularly advantageous manufacturing of the electric machine.In particular, the invention enables the electric machine to be manufactured with very low material waste, very low tool wear, and very short production time, thus allowing for more sustainable and cost-effective production of the electric machine compared to conventional solutions. Since the retaining element is deep-drawn, improved mechanical properties can be achieved through work hardening compared to conventional solutions. In other words, work hardening occurs during the deep-drawing of the retaining element, resulting in particularly advantageous mechanical properties of the retaining element and, consequently, of the electric machine as a whole.

[0006] The characteristic that an element such as the retaining element is formed from a single piece means that the retaining element is not composed of several separately formed and connected individual parts, but rather the retaining element is formed from a single piece, so that the retaining element is formed by a body made from a single piece and thus integrally manufactured and designed as a monoblock.

[0007] The electrical machine according to the invention is a radial flux machine (RFM) whose rotors are rotationally fixed to one another, thereby forming a double rotor, also referred to as a total rotor. The inner rotor is, so to speak, an internal rotor, while the outer rotor is, so to speak, an external rotor. Thus, the double-rotor radial flux machine is a combination of an internal rotor machine and an external rotor machine. As with a conventional radial flux machine with a single rotor, a magnetic field, which can be generated and thus made available by means of the winding, runs radially through the stator and the respective rotor. The magnetic field can be generated and made available by supplying the winding with electrical energy, in particular electric current, whereby the magnetic field can be provided, in particular, as a rotating magnetic field.In particular, the entire rotor can be driven by means of the magnetic field and thereby rotated about the axis of rotation relative to the stator. The electric machine has two air gaps, namely a first air gap and a second air gap. The first air gap is arranged radially between the inner rotor and the stator, such that the first air gap is bounded radially outwards, in particular directly, by the stator and radially inwards, in particular directly, by the inner rotor. The second air gap is arranged radially between the stator and the outer rotor, in particular such that the second air gap is bounded radially outwards, in particular directly, by the outer rotor and radially inwards, in particular directly, between the stator and the stator.The two air gaps allow for a particularly large air gap area, enabling exceptionally high power and torque capacity of the electric machine. This allows twin-rotor radial flux machines to achieve the same or similar performance data as axial flux machines, but they are based on a well-known and established technology and can therefore be manufactured more cost-effectively compared to axial flux machines, as they require less complex manufacturing processes and materials. The industrialization of radial flux machines is well-established, which simplifies implementation and scaling, resulting in cost savings. Twin-rotor radial flux machines are thus a cost-effective and high-performance alternative to axial flux machines.

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

[0009] The drawing shows in the only Fig. 1. Partial schematic sectional view of an electric machine designed as a radial flux double rotor machine.

[0010] Fig. Figure 1 shows a partial schematic sectional view of an electric machine 10, in particular of a motor vehicle. The electric machine 10 is designed as a radial flux twin-rotor machine. This means that the electric machine 10 is designed as a radial flux machine (RFM) which has a twin rotor 12, also referred to as the overall rotor. The electric machine 10, whose axial direction coincides with a rotation axis 14, also referred to as the machine axis of rotation, has a stator 16. The stator 16 has a stator core 18. Furthermore, the stator 16 has a winding 20, also referred to as the stator winding, which is attached separately from and to the stator core 18. For this purpose, the winding 20 is wound around the stator core 18. The stator core 18 is designed, for example, as a laminated core. The axial direction of the electric machine 10 is illustrated by a double arrow 22.The double rotor 12 can be driven by means of the stator 16 and is thereby rotatable about the axis of rotation 14, also referred to as the machine's axis of rotation, relative to the stator 16. When the axial direction is mentioned before and below, this refers, unless otherwise specified, to the axial direction of the electric machine 10, whose radial direction is perpendicular to the axial direction and thus perpendicular to the axis of rotation 14. The radial direction of the electric machine 10 is illustrated by a double arrow 24. When the radial direction is mentioned before and below, this refers, unless otherwise specified, to the radial direction of the electric machine 10, whose circumferential direction is around the axial direction and thus around the axis of rotation 14, and extends in an imaginary plane that is perpendicular to the axial direction and thus perpendicular to the axis of rotation 14.The circumferential direction of the electric machine 10 is illustrated by a double arrow 26. Whenever the circumferential direction is mentioned before and below, it refers, unless otherwise specified, to the circumferential direction of the electric machine 10.

[0011] It is conceivable that the stator core 18 has several core elements, which are arranged sequentially, for example, in the circumferential direction of the electric machine 10. For example, the core elements are formed separately from one another. For example, each core element is or forms a respective pole of the electric machine 10. Thus, for example, each core element is a respective part of the laminated core. It is conceivable that each core element, in particular, is assigned a respective coil of the winding 20, wherein, for example, the respective coil is wound around the respective core element to which the respective coil is assigned. The coils follow one another in the circumferential direction. Thus, for example, each coil is a respective part of the winding 20.

[0012] Looks especially good Fig. As can be seen from Figure 1, the double rotor 12, and thus the electric machine 10, has a first, outer rotor 28, which is arranged radially outside the stator 16 and axially overlapping the stator 16. The double rotor 12, and thus the electric machine 10, also has a second, inner rotor 30, which is connected, in particular permanently, to the first, outer rotor 28 in a rotationally fixed manner. This second, inner rotor 30 is arranged radially inside the stator 16, radially inside the first rotor 28, and axially overlapping both the stator 16 and the first rotor 28. Since the rotors 28 and 30 are connected, in particular permanently, to each other in a rotationally fixed manner, the rotors 28 and 30 are rotatable about the axis of rotation 14 relative to the stator 16.

[0013] Each rotor 28, 30 has, for example, a laminated core 32, 34. Furthermore, each rotor 28, 30 has, for example, at least one permanent magnet 36, 38. The permanent magnet 36, 38 is also simply referred to as a magnet. In particular, the permanent magnet 36, 38 of each rotor 28, 30 is formed separately from the laminated core 32, 34 of each rotor 28, 30 and is attached to the laminated core 32, 34 of each rotor 28, 30, in particular such that relative movements between the permanent magnet 36, 38 and the laminated core 32, 34 of each rotor 28, 30 are prevented. The rotors 28 and 30 are formed separately from each other and separately from the stator 16.

[0014] For example, the electric machine 10 also has a Fig. The electric machine 10 has a rotor shaft that is not visible but is fixedly connected to the double rotor 12 and can therefore rotate with the double rotor 12 about the axis of rotation 14 relative to the stator 16. In particular, the electric machine 10 can provide drive torques for propelling the motor vehicle via its rotor shaft. The rotor shaft is separate from the stator 16 and separate from the double rotor 12 and is fixedly connected to the rotor 12.

[0015] The feature "axially overlapping" means the following: Two elements, such as the first, outer rotor 28 and the stator 16, are arranged axially overlapping with each other in the axial direction of the electrical machine 10 if they are each arranged at least partially in a region of the same axial coordinates, which run along the axial direction and thus along the axis of rotation 14. Within the scope of the present disclosure, the feature that a first component, such as the inner rotor 30, is arranged radially within a second component, such as the stator 16, means that the first component is arranged in a region of smaller radii than the second component, with respect to the axial direction, wherein said radii run in the radial direction and, in particular, increase radially outwards from the axis of rotation 14, thus becoming larger.Accordingly, within the scope of the present disclosure, the feature that a first component, such as the stator 16, is arranged radially outside a second component, such as the inner rotor 30, is to be understood as meaning that the first component is arranged in a region of larger radii than the second component, with respect to the axis of rotation 14, that is, with respect to the axial direction, wherein the latter radii also run in a radial direction and increase radially outwards from the axis of rotation 14, thus becoming larger.

[0016] To simplify the manufacture of the electric machine 10, a holding element 40, also referred to as a connecting element, is provided. This holding element is common to the rotors 28 and 30, but separate from the rotors 28 and 30 and from the stator 16. It is formed from a single piece. The holding element 40 is deep-drawn, so that it lies in an imaginary plane with the plane of the image. Fig. Viewed in the plane in which the axis of rotation 14 runs, the retaining element 40 is U-shaped. Thus, viewed in this plane, the retaining element 40 has a U-shape, comprising a first, outer leg 42, a second, inner leg 44, and a web 46 extending between the legs 42 and 44, which are connected to each other via the web 46. It can be seen that the web 46 connects to the legs 42 and 44 in the axial direction. The respective legs 42 and 44 are arranged axially overlapping the rotors 28 and 30 and axially overlapping the stator 16. Leg 42 is arranged radially outside the rotors 28 and 30, radially outside the stator 16, and radially outside leg 44. Leg 44 is arranged radially inside leg 42 and radially inside rotors 28 and 30 and radially inside stator 16. The respective rotors 28 and 30 are arranged inside the U-shape.Furthermore, the respective rotors 28 and 30 are attached to the retaining element 40 within the U-shape, in this case such that rotor 28 is attached to leg 42 and rotor 30 to leg 44. Thus, rotors 28 and 30 are rotationally fixed to each other by means of the retaining element 40.

[0017] The electric machine 10 also has a support 48, also referred to as a rotor support, which is separate from the retaining element 40, separate from the stator 16, separate from the rotors 28 and 30, and also separate from the rotor shaft. In particular, the support 48 is rotationally fixed to the rotor shaft. The support 48 is welded to the retaining element 40 and thus connected to it. In this case, the support 48 is welded to the retaining element 40 by means of weld seams 50 and 52, the weld seams 50 and 52 being arranged on axially opposite sides of the support 48.

[0018] Out of Fig. Figure 1 shows that the retaining element 40 is designed as a completely closed ring extending circumferentially around the axis of rotation 14, so that the U-shape is completely closed circumferentially. The support 48 and also the welds 50 and 52 are arranged in the ring, so that the support 48 is welded to the retaining element 40 within the ring. In this case, the support 48 is welded to the leg 44 on an inner side S of the leg 44 that points radially inwards and radially away from the rotors 28 and 30 and from the stator 16.

[0019] The double rotor 12, and thus the electric machine 10, can be manufactured particularly easily, and therefore in a particularly time- and cost-effective manner. The design and manufacturing of the double rotor 12 play a central role in the production of the double-rotor radial flux machine. An important criterion here is the mechanical strength of the double rotor 12, especially in conjunction with the mechanical strength of the respective lamination stack 32, 34. These determine the deflection of the rotors 28 and 30 under rotational speed, whereby the strength of the outer rotor 28 may be more critical due to its large outer diameter. It would be particularly advantageous if the retaining element 40, also referred to as the support element, were milled from a solid block, which would be particularly advantageous from a mechanical perspective. However, due to the U-shape of the retaining element 40, it would require very complex machining, which would necessitate an extremely high material removal rate.This would require a long machining time, which would be associated with high costs, high tool wear, and a high amount of material scrap. The aforementioned problems and disadvantages can now be avoided by deep-drawing the retaining element 40. In other words, the retaining element 40 is deep-drawn and then welded to the carrier 48. Deep-drawing the retaining element 40 prevents excessive material scrap, as only minimal post-processing of the retaining element 40 is required. Furthermore, the retaining element 40 exhibits particularly good mechanical properties due to work hardening during deep drawing. Manufacturing the twin rotor 30 with the welded and deep-drawn retaining element 40 is particularly cost-effective, as excessive tool wear and excessive machining time can be avoided.Furthermore, excessive material waste can be avoided, making the electric machine 10 particularly sustainable to manufacture. Reference symbol list 10 electric machine 12 twin rotors 14 axis of rotation 16 Stator 18 Stator core 20 windings 22 Double Arrow 24 Double Arrow 26 Double Arrow 28 first, outer rotor 30 second, inner rotor 32 sheet metal package 34 sheet metal package 36 permanent magnet 38 permanent magnet 40 retaining element 42 thighs 44 thighs 46 Bridge 48 carriers 50 weld seam 52 weld seam S inside QUOTES INCLUDED IN THE DESCRIPTION

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

[0000] WO 2023 / 006440 A2

[0002] DE 10 2023 101 990 B3

[0002] WO 2017 / 173 188 A1

[0002] DE 10 2023 104 937 A1

[0002] DE 10 2022 205 930 B3

[0002] DE 10 2022 202 123 B4

[0002] DE 10 2021 003 942 B4

[0002]

Claims

[1] Electric machine (10) which is designed as a radial flux double rotor machine and has: - a stator (16) comprising a stator core (18) and a winding (20) formed separately from the stator core (18) and attached to the stator core (18); - a first, outer rotor (28) which is arranged radially outside the stator (16) and axially overlapping the stator (16) and is rotatable about an axis of rotation (14) relative to the stator (16); and - a second, inner rotor (30) which is connected to the first rotor (28) in a rotationally fixed manner and which is arranged radially inside the stator (16), radially inside the first rotor (28), axially overlapping with the stator (16) and axially overlapping with the first rotor (28) and is rotatable about the axis of rotation (14) relative to the stator (16); characterized by : - a holding element (40) common to the rotors (28, 30), formed separately from the rotors (28, 30) and made from a single piece, which is deep-drawn and thus, when viewed in an imaginary plane in which the axis of rotation (14) runs, is U-shaped and therefore has a U-shape in which the rotors (28, 30) are arranged and attached to the holding element (40); and - a support (48) formed separately from the rotors (28, 30) and separately from the retaining element (40) and welded to the retaining element (40), which is connected in a rotationally fixed manner to a rotor shaft of the electric machine (10) formed separately from the support (48). [2] Electric machine (10) according to claim 1, characterized by, that the retaining element (40) is designed as a ring that completely circulates in the circumferential direction of the electric machine (10), so that the U-shape completely circulates in the circumferential direction of the electric machine (10). [3] Electric machine (10) according to claim 2, characterized by , that the carrier (48) is arranged in the ring. [4] Electric machine (10) according to claim 3, characterized by , that the carrier (48) is welded to the ring.

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