Balancing body, electric machine and motor vehicle

Abstract

The present invention relates to a balancing body (1) for a rotor (2) of an electric machine (3) for a motor vehicle (4), comprising an axis of rotation (5), a first main side (6) for arrangement on a rotor core (7) of the rotor (2), a second main side (8) arranged opposite the first main side (6), and an inner ring (9) for arrangement on a rotor shaft (10) of the electric machine (3). A plurality of fingers (11) extending outwardly from the inner ring (9) in the radial direction (R) are arranged on the inner ring (9), wherein a free space (12) is formed between two adjacent fingers (11). The fingers (11) comprise a first finger (11a) with a first cooling fluid channel (13), wherein the first cooling fluid channel (13) extends in the axial direction (A) from a first opening (14) formed on the first main side (6) into an inner region of the first finger (11a).The balancing body (1) has an inner cooling fluid channel (15) extending in the radial direction (R) from the first cooling fluid channel (13) through the first finger (11a) and the inner ring (9) to an inner opening (16) of the inner ring (9) facing the rotation axis (5). Furthermore, the invention relates to an electric machine (3) and a motor vehicle (4).

Description

[0001] The present invention relates to a balancing body for a rotor of an electric motor for a motor vehicle. Furthermore, the invention relates to an electric motor for a motor vehicle and a motor vehicle with an electric drive system.

[0002] Electric motors for driving motor vehicles are known in which a balancing disc is arranged on one or both ends of the rotor of the electric motor to balance the rotor. In permanent magnet synchronous machines, balancing discs often fulfill the additional task of positively securing the permanent magnets arranged in the magnetic pockets of the rotor core against slipping out of the magnetic pockets in the axial direction. Due to the often very high material requirements, balancing discs are relatively expensive. Furthermore, balancing discs, especially those made as round discs from solid material, contribute significantly to increasing the inertia of the electric motor.

[0003] Document US 2023 / 0 261 536 A1 shows a balancing disk for a motor rotor, which has recesses to reduce weight. Cooling fluid channels are formed in a rotor shaft of the rotor, which open into an inner region of a rotor core. The balancing disk has a circumferential groove with axially extending through holes through which cooling fluid can be discharged from the rotor core. Such a balancing disk also has a relatively large mass.

[0004] A balancing disk for a motor rotor is known from document CN 112 510 909 B. The balancing disk has a wave-shaped circumferential contour, through which blades for conveying a cooling fluid are formed. The blades have a bore arranged in alignment with a channel extending axially through the rotor. By rotating the rotor in a corresponding direction, a cooling fluid can thus be conveyed into the channel via the blades. Such a balancing disk has the disadvantage of having a relatively large mass. Furthermore, the cooling fluid flow that can be conveyed through the channel depends on the rotational speed of the rotor.

[0005] Document DE 10 2019 217 510 A1 discloses a balancing disk for a rotor of an electric machine, which has a plurality of circumferentially distributed, axially extending through-bores for introducing a cooling fluid into a rotor core. Furthermore, the balancing disk has an outlet channel with an outlet opening pointing outward in the radial direction between each of the through-bores. The electric machine has such a balancing disk on each of its two end faces, which are fluidly coupled to cooling fluid channels of a rotor core of the rotor in such a way that coolant flows can be directed alternately in opposite directions through the rotor and the balancing disks. A similar balancing disk is known from document CN 103 746 482 A. Such balancing disks also have a relatively large mass. Furthermore, introducing the cooling fluid into the rotor is very complex and inefficient.

[0006] It is therefore an object of the present invention to eliminate, or at least partially eliminate, the disadvantages described above in a balancing device. In particular, the object of the present invention is to provide a balancing device for an electric machine that, in a simple and cost-effective manner, prevents an excessive increase in the weight of the electric machine and / or ensures particularly advantageous cooling of the electric machine.

[0007] The above object is achieved by the patent claims. Accordingly, the object is achieved by a balancing body for a rotor of an electric machine for a motor vehicle having the features of independent claim 1, by an electric machine for a motor vehicle having the features of independent claim 9, and by a motor vehicle with an electric drive system having the features of independent claim 10. Further features and details of the invention emerge from the subclaims, the description, and the drawings. Features and details described in connection with the balancing body according to the invention naturally also apply in connection with the electric machine according to the invention and the motor vehicle according to the invention, and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is and can always be made to each other.

[0008] According to a first aspect of the invention, the object is achieved by a balancing body for a rotor of an electric machine for a motor vehicle. The balancing body has an axis of rotation, a first main side for arrangement on a rotor core of the rotor, a second main side arranged opposite the first main side, and an inner ring for arrangement on a rotor shaft of the electric machine. According to the invention, a plurality of fingers extending outward in the radial direction from the inner ring are arranged on the inner ring, wherein a free space is formed between two adjacent fingers. The fingers comprise a first finger with a first cooling fluid channel, wherein the first cooling fluid channel extends in the axial direction from a first opening formed on the first main side into an inner region of the first finger.Furthermore, the balancing body has an inner cooling fluid channel which extends in the radial direction from the first cooling fluid channel through the first finger and the inner ring to an inner opening of the inner ring facing the axis of rotation.

[0009] The inner ring is designed for arranging the balancing body on the rotor shaft. For this purpose, the inner ring has an inner ring diameter that corresponds to a seat outer diameter of a balancing body seat of the rotor shaft or corresponds within specified tolerances, for example, according to a fit. The inner ring further has an outer ring diameter that is preferably only slightly larger than the inner ring diameter, so that the weight of the inner ring is as low as possible while still ensuring sufficient stability of the balancing body during operation of the electric machine. According to the invention, the inner ring can have a geometric design with an increased moment of inertia, for example, with a double-T cross-section or the like. The inner ring preferably does not have a balancing bore.The inner ring is preferably made of a metal, in particular of a metal whose use for balancing discs for electrical machines is already known.

[0010] The fingers extend radially outwards from the inner ring. The fingers preferably extend along a straight longitudinal axis that runs through the axis of rotation. The fingers preferably have a greater finger length than finger width. This means that the fingers preferably extend further along the longitudinal axis than in the circumferential direction. The finger length is preferably at least 1.5 times the finger width. More preferably, the finger length is approximately twice the finger width. The fingers are preferably evenly distributed in the circumferential direction of the balancing body. The number of fingers is preferably an even number. According to the invention, for example, six, eight or ten fingers can be provided. The number of fingers preferably corresponds to the number of magnetic poles of the rotor core. The fingers are preferably formed monolithically with the inner ring.The fingers are preferably designed to accommodate one or more balancing bores for balancing the electric machine. The fingers are preferably mirror-symmetrical about the longitudinal axis of the fingers. The fingers can, for example, have a rectangular base. According to the invention, the fingers can have a decreasing thickness in the radial direction away from the axis of rotation. This is preferably achieved by a corresponding inclination of the second main side to the axis of rotation. A free space is formed between two adjacent fingers, so that the balancing body has a significantly reduced overall weight compared to a balancing disc made of solid material.

[0011] Preferably, the fingers and the inner ring together form the first main side and the second main side. The balancing body is preferably plate-shaped, wherein the first main side and / or the second main side may have elevations and / or depressions. In the installed state, the first main side faces the rotor core. In the installed state, the second main side is designed as the visible surface of the balancing body. The rotation axis is preferably perpendicular to the first main side.

[0012] The fingers comprise at least a first finger. The first cooling fluid channel extends in the axial direction from the first opening into the interior region of the first finger. It can be provided that the first cooling fluid channel also has a radial extension component, in particular from the first opening in the direction of the rotation axis. Preferably, the first cooling fluid channel extends over half the thickness of the first finger, preferably up to the longitudinal axis of the finger. The first cooling fluid channel is preferably designed as a bore, for example a blind hole. In the installed state, the first opening points towards the rotor core, such that a fluid flow can be introduced through the first opening into a corresponding fluid channel of the rotor core, which can be arranged in alignment with the first opening.

[0013] The inner cooling fluid channel extends from the inner opening on the inner ring, which faces the rotational axis, in a radial direction through the inner ring and through a portion of the first finger, and opens into the first cooling fluid channel. The inner cooling fluid channel preferably extends along the longitudinal axis of the first finger. The inner cooling fluid channel is preferably designed as a bore, for example, a blind hole. The inner opening can be arranged on the rotor shaft such that a corresponding fluid opening in the rotor shaft is aligned with the inner opening. Thus, for example, cooling fluid can be introduced from the rotor shaft into the inner opening. The balancing body is preferably designed symmetrically about one or more axes.

[0014] A balancing body according to the invention has the advantage over conventional balancing disks that the weight of the flywheel is reduced using simple means and in a cost-effective manner. Furthermore, a cooling fluid flow can be advantageously directed from the rotor shaft into the rotor core via the inner cooling fluid channel and the first cooling fluid channel, thus ensuring advantageous cooling of the rotor core. Due to the preferably symmetrical design of the balancing body, the balancing body is designed for placement on both end faces of the rotor core, thus reducing the number of parts required compared to conventional balancing disks.

[0015] According to a preferred further development of the invention, a balancing body can be provided with the fingers comprising a second finger, wherein the second finger has a second cooling fluid channel which is designed as a through-bore and extends in the axial direction from the first main side to the second main side through the second finger. The second cooling fluid channel thus extends over the entire thickness of the second finger. In the installed state, the balancing body can be arranged on the rotor laminated core in such a way that a cooling fluid channel of the rotor laminated core is aligned with the second cooling fluid channel. In this way, cooling fluid can be led out of the rotor laminated core via the second cooling fluid channel. The second cooling fluid channel preferably has a radial extension component, so that in the installed state the second cooling fluid channel points radially outwards, away from the rotor laminated core.This allows the cooling fluid to be more easily vented to the outside. This has the advantage of improving cooling of the rotor core using simple and cost-effective means while reducing overall weight.

[0016] According to the invention, it is preferred that the second cooling fluid channel has an outlet opening on the second main side that points obliquely outward from the rotational axis in the radial direction. The outlet opening is preferably designed as a nozzle or a diffuser to discharge a predefined cooling fluid outflow from the outlet opening with a directional component in the axial direction away from the rotor core and a directional component in the radial direction away from the rotational axis. This has the advantage that the removal of the cooling fluid from the rotor core, and thus the cooling of the rotor core, is further improved using simple means and in a cost-effective manner.

[0017] More preferably, the fingers comprise a plurality of first fingers and a plurality of second fingers, which are arranged next to one another in an alternating manner in the circumferential direction. Particularly preferably, a first half of the fingers is designed as first fingers and a second half of the fingers is designed as second fingers. Alternatively, for example, one third of the fingers can be designed as third fingers without a cooling fluid channel, wherein, for example, one third of the fingers is designed as first fingers and one third of the fingers is designed as second fingers. Particularly preferably, the balancing body has eight fingers. In this case, it is preferred that four fingers are designed as first fingers and four fingers as second fingers. Alternatively, two fingers can be designed as first fingers, two fingers as second fingers, and four fingers as third fingers. The first fingers and second fingers and, if applicable,The third fingers are preferably distributed evenly and alternately around the circumference of the balancing body. This has the advantage of further improving cooling of the rotor core in a simple and cost-effective manner while reducing overall weight.

[0018] In a particularly preferred embodiment of the invention, the fingers have a root region arranged on the inner ring and a head region arranged opposite the root region, wherein the fingers have a smaller average finger width in the head region than in the root region. Accordingly, the fingers can, for example, have side edges that extend converging outward in the radial direction. The fingers can thus, for example, have a triangular or trapezoidal base. This has the advantage that the flywheel mass and thus the overall weight of the balancing body can be further reduced using simple means and in a cost-effective manner.

[0019] Further preferably, the head region has a chamfer and / or a rounded portion and / or a point. The fingers are preferably designed to be mirror-symmetrical about the longitudinal axis of the fingers. This has the advantage of further reducing the flywheel mass and thus the overall weight of the balancing body using simple and cost-effective means.

[0020] According to a preferred embodiment of the invention, the finger tapers steadily from the root area to the head area. This has the advantage of further reducing the flywheel mass and thus the overall weight of the balancing body using simple and cost-effective means.

[0021] Particularly preferably, the inner ring has a ring thickness in the radial direction that is smaller than a maximum finger width of the fingers in the circumferential direction. The fingers are thus wider, at least in the root area, than the inner ring is thick. Preferably, the maximum finger width is at least 1.5 times the ring thickness. Particularly preferably, the maximum finger width is approximately twice or 2.5 times the ring thickness. This has the advantage of further reducing the flywheel mass and thus the overall weight of the balancing body using simple and cost-effective means.

[0022] According to a second aspect of the invention, the object is achieved by an electric machine for a motor vehicle. The electric machine has a stator and a rotor with a rotor shaft and a rotor core arranged on the rotor shaft. The rotor shaft has a central cooling fluid channel extending in the axial direction, wherein the rotor core has an outer cooling fluid channel extending in the axial direction. According to the invention, a balancing body according to the invention is arranged on one side of the rotor core, wherein the inner opening of the inner cooling fluid channel is coupled in a fluid-communicating manner to the central cooling fluid channel, wherein the first opening is coupled in a fluid-communicating manner to the outer cooling fluid channel. The electric machine is preferably designed as a permanent magnet synchronous machine (PMSM).

[0023] The balancing body is arranged coaxially to the rotor shaft. The fingers of the balancing body are preferably of such a length that the fingers at least partially cover the end openings of the magnet pockets of the rotor core and thus positively prevent permanent magnets arranged in the magnet pockets from slipping out in the axial direction. The fingers of the balancing body are preferably less extended in the radial direction than the rotor core, so that the flywheel mass and thus the overall weight of the electric machine are advantageously reduced. The first main side of the balancing body preferably contacts the rotor core. The inner ring of the balancing body is arranged on a balancing body seat of the rotor shaft, preferably in a fit, such as a press fit.

[0024] Preferably, a balancing body according to the invention is arranged on each of the two end faces of the rotor laminated core. The balancing bodies are preferably arranged rotated relative to one another such that the first fingers of the balancing body arranged on a first end face of the rotor laminated core are aligned with the second fingers of the balancing body arranged on a second end face of the rotor laminated core, and vice versa. Thus, the balancing bodies ensure the inflow of cooling fluid into the rotor laminated core and the outflow of coolant from the laminated core. The rotor laminated core preferably has a number of coolant channels that corresponds to the number of fingers of the balancing body or at least to the sum of the first fingers and second fingers of the balancing body.The coolant channels preferably have a radial extension direction away from the rotation axis in the flow direction of the cooling fluid, so that the cooling fluid flow can be amplified by centrifugal force during operation of the electric machine.

[0025] The first opening is aligned with a cooling fluid channel extending through the rotor core. A seal, such as a sealing ring, may be provided to prevent the cooling fluid from flowing out sideways. This improves the flow of cooling fluid from the first cooling fluid channel of the first finger into the cooling fluid channel of the rotor core.

[0026] The inner opening is aligned with a cooling fluid channel of the rotor shaft. A seal, such as a sealing ring, can be provided to prevent the cooling fluid from flowing out laterally. This improves the introduction of the cooling fluid from the rotor shaft into the inner cooling fluid channel of the balancing body. Thus, cooling fluid can be reliably conducted from the rotor shaft via the balancing body into the rotor core. To pump the cooling fluid, the electric machine preferably has a cooling fluid pump. Furthermore, the electric machine preferably has a cooling fluid reservoir for collecting and providing the cooling fluid. The cooling fluid is preferably a liquid, such as oil or the like.

[0027] The electric machine according to the invention offers all the advantages already described for a balancing body according to the first aspect of the invention. Accordingly, the electric machine according to the invention has the advantage over conventional electric machines that the weight of the flywheel is reduced using simple means and in a cost-effective manner. In addition, a cooling fluid flow can be advantageously conducted from the rotor shaft into the rotor laminated core via the inner cooling fluid channel and the first cooling fluid channel, thus ensuring advantageous cooling of the rotor laminated core. Due to the preferably symmetrical design of the balancing body, the balancing body is designed for arrangement on both end faces of the rotor laminated core, thus reducing the variety of parts compared to conventional balancing disks.

[0028] According to a third aspect of the invention, the object is achieved by a motor vehicle. The motor vehicle has an electric drive system with a traction battery for providing electrical energy. According to the invention, the electric drive system has an electric machine according to the invention. The traction battery is designed to provide electrical energy for operating the electric machine to drive the motor vehicle. More preferably, the traction battery is designed as a high-voltage battery, for example with a nominal voltage of between 150 V and 500 V, in particular of approximately 400 V. The traction battery can also have a higher nominal voltage, for example of up to 1000 V. According to the invention, the electric drive system can also have a plurality of electric machines according to the invention.

[0029] The motor vehicle according to the invention offers all the advantages already described for a balancing body according to the first aspect of the invention and for an electric machine according to the second aspect of the invention. Accordingly, the motor vehicle according to the invention has the advantage over conventional motor vehicles that the weight of the flywheel mass of the electric machine is reduced using simple means and in a cost-effective manner. In addition, a cooling fluid flow can be advantageously conducted from the rotor shaft into the rotor laminated core via the inner cooling fluid channel and the first cooling fluid channel, thus ensuring advantageous cooling of the rotor laminated core. Due to the preferably symmetrical design of the balancing body, the balancing body is designed for arrangement on both end faces of the rotor laminated core, thus reducing the variety of parts compared to conventional balancing disks.

[0030] A balancing body according to the invention, an electric machine according to the invention, and a motor vehicle according to the invention are explained in more detail below with reference to the drawings. They show schematically: Fig. 1 shows a plan view of a rotor with a balancing body according to a preferred first embodiment of the invention, Fig. 2 shows a detailed view of a rotor with a finger of a balancing body according to a preferred second embodiment of the invention, Fig. 3 shows a detailed view of a rotor with a finger of a balancing body according to a preferred third embodiment of the invention, Fig. 4 shows a detailed view of a rotor with a finger of a balancing body according to a preferred fourth embodiment of the invention, Fig. 5 shows a detailed view of a rotor with a finger of a balancing body according to a preferred fifth embodiment of the invention, Fig. 6 shows a detailed view of a rotor with a finger of a balancing body according to a preferred sixth embodiment of the invention, Fig. 7 shows a sectional view of an electric machine according to a preferred embodiment of the invention, and Fig. 8 shows a side view of a preferred embodiment of a motor vehicle according to the invention.

[0031] Elements with the same function and mode of action are listed in the Fig. 1 - 8 are each provided with the same reference numerals.

[0032] In Fig. 1, a rotor 2 with a balancing body 1 according to a preferred first embodiment of the invention is shown schematically in a plan view. The balancing body 1 is arranged on the rotor 2 in such a way that a first main side 6 (see FIG. 1), which is concealed in this view, is visible. Fig. 7) faces a rotor core 7 of the rotor 2 and preferably touches the rotor core 7. A second main side 8 of the balancing body 1 is arranged in this illustration on the visible side of the balancing body 1. The balancing body 1 extends coaxially to a rotational axis 5 of a rotor shaft 10 of the rotor 2. An inner ring 9 of the balancing body 1 is arranged on the rotor shaft 10, for example, in a press fit.

[0033] Eight fingers 11 extend from the inner ring 9 in the radial direction R away from the rotor shaft 10. Four of the fingers 11 are designed as first fingers 11a. The other four fingers 11 are designed as second fingers 11b. The first fingers 11a and second fingers 11b are arranged alternately next to one another in the circumferential direction U. The fingers 11 each have a root region 19 arranged on the inner ring 9 and a head region 20 facing away from the inner ring 9. A free space 12 is formed between each two fingers 11 adjacent in the circumferential direction U. The fingers 11 have a finger width B that is significantly greater than a ring thickness D of the inner ring 9.

[0034] In each of the first fingers 11a, a first cooling fluid channel 13 is formed, which extends from a first opening 14 formed on the first main side 6 (cf. Fig. 7) extends in the axial direction A into an inner region of the first finger 11a. An inner cooling fluid channel 15 extends from the first cooling fluid channel 13 through the first finger 11a and the inner ring 9 in the radial direction R to an inner opening 16, which is arranged directly adjacent to the rotor shaft 10.

[0035] In each of the second fingers 11b, a second cooling fluid channel 17 is formed, which extends between the first main side 6 and the second main side 8 in the axial direction A. On the second main side 8, the second cooling fluid channel 17 has an outlet opening 18 for the outflow of the cooling fluid.

[0036] A central cooling fluid channel 24 (not shown in this view) is formed in the rotor shaft 10, through which the cooling fluid can be introduced into the inner cooling fluid channels 15 via the inner opening 16. The cooling fluid can be passed on to the first cooling fluid channels 13 via the inner cooling fluid channels 15. The cooling fluid is fed into corresponding outer cooling fluid channels 25 (see FIG. 1) via the first openings 14, not shown in this view. Fig. 7) of the rotor core 7. The cooling fluid can be led out of the rotor core 7 again via the second cooling fluid channels 17.

[0037] Furthermore, magnetic pockets 28 are formed in the rotor core 7, in which permanent magnets 29 are arranged. The fingers 11 cover the open end face of the magnetic pockets 28, so that the permanent magnets are protected against falling out in the axial direction A (see Fig. 7) are secured.

[0038] Fig. Figure 2 shows a rotor 2 with a finger 11 of a balancing body 1 according to a preferred second embodiment of the invention, schematically in a detailed view. In this embodiment, the head region 20 of the finger 11 has a rectangular shape. The root region 19 of the finger 11 (not shown) can, for example, have a corresponding rectangular shape.

[0039] In Fig. Figure 3 shows a schematic detailed view of a rotor 2 with a finger 11 of a balancing body 1 according to a preferred third embodiment of the invention. In this exemplary embodiment, the head region 20 of the finger 11 has a rectangular configuration with two chamfers 21 at the radially outwardly projecting end of the finger 11. The root region 19 of the finger 11 (not shown) can, for example, have a corresponding rectangular configuration.

[0040] Fig. Figure 4 shows a rotor 2 with a finger 11 of a balancing body 1 according to a preferred fourth embodiment of the invention, schematically in a detailed view. In this embodiment, the head region 20 of the finger 11 has a rectangular shape, with the radially outwardly projecting end of the finger 11 having a semicircular curve 22. The root region 19 of the finger 11 (not shown) can, for example, have a corresponding rectangular shape.

[0041] In Fig. Figure 5 shows a schematic detailed view of a rotor 2 with a finger 11 of a balancing body 1 according to a preferred fifth embodiment of the invention. In this exemplary embodiment, the head region 20 of the finger 11 has a triangular shape, so that the radially outwardly projecting end of the finger 11 is formed as a tip 23. The root region 19 of the finger 11 (not shown) can, for example, have a corresponding trapezoidal or rectangular shape.

[0042] Fig. Figure 6 shows a rotor 2 with a finger 11 of a balancing body 1 according to a preferred sixth embodiment of the invention, schematically in a detailed view. In this embodiment, the head region 20 of the finger 11 has a trapezoidal shape. The root region 19 of the finger 11 (not shown) can, for example, have a corresponding trapezoidal or rectangular shape.

[0043] In Fig. 7, an electric machine 3 according to a preferred embodiment of the invention is shown schematically in a sectional view. The electric machine has a rotor 2 which extends in the axial direction A along a rotation axis 5 and is held in a stator 30 so as to be rotatable about the rotation axis 5. The rotor 2 has a rotor laminated core 7 which is held on a rotor shaft 10. A balancing body 1 according to the invention is arranged on each of the two end faces of the rotor laminated core 7 in such a way that a first main side 6 of the balancing body 1 contacts the rotor laminated core 7 and a second main side 8 of the balancing body 1 points away from the rotor laminated core 7. Inner rings 9 of the balancing bodies 1 are arranged on the rotor shaft 10.

[0044] A plurality of outer cooling fluid channels 25 are formed in the rotor core 7, which extend in the axial direction A. A central cooling fluid channel 24 is formed in the rotor shaft 10, which extends largely in the axial direction A and, at the axial height of the balancing bodies 1, in the radial direction to the inner rings 9 of the balancing bodies 1. A cooling fluid flow can be introduced via the central cooling fluid channel 24 into the balancing disks 1 and via the balancing disks 1 into the outer cooling fluid channel 25, and can be led out of the outer cooling fluid channel 25 again via an opposite balancing disk 1. For this purpose, an inner opening 16 of an inner cooling fluid channel 15 formed in a first finger 11a of the balancing body 1 and the inner ring 9 is fluidly coupled to the central cooling fluid channel 24. A first opening 14 of a first cooling fluid channel 13 formed in the first finger 11a is fluidly coupled to the outer cooling fluid channel 25.A second cooling fluid channel 17 formed in a second finger 11b of the opposing balancing disk 1 is fluidly coupled to the outer cooling fluid channel 25. The second cooling fluid channel 17 has an outlet opening 18 for discharging the cooling fluid.

[0045] Fig. Figure 8 shows a preferred embodiment of a motor vehicle 4 according to the invention schematically in a side view. The motor vehicle 4 has an electric drive system 26 with an electric machine 3 according to the invention for driving the motor vehicle 4 and a traction battery 27 for supplying the electric machine 3 with electrical energy. List of reference symbols 1 balancing body 2 rotors 3 Electric machine 4 Motor vehicle 5 Rotation axis 6 first main page 7 Rotor lamination package 8 second main page 9 inner ring 10 Rotor shaft 11 fingers 11a first finger 11b second finger 12 Free space 13 first cooling fluid channel 14 first opening 15 inner cooling fluid channel 16 inner opening 17 second cooling fluid channel 18 Outlet opening 19 Root area 20 Head area 21 phase 22 Rounding 23 lace 24 central cooling fluid channel 25 outer cooling fluid channel 26 electric drive system 27 Traction battery 28 magnetic pocket 29 Permanent magnet 30 Stator 31 Stator laminated core A axial direction B finger width D Ring thickness R radial direction U circumferential direction 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] US 2023 / 0 261 536 A1

[0003] CN 112 510 909 B

[0004] DE 10 2019 217 510 A1

[0005] CN 103 746 482 A

[0005]

Claims

[1] Balancing body (1) for a rotor (2) of an electric machine (3) for a motor vehicle (4), comprising a rotational axis (5), a first main side (6) for arrangement on a rotor laminated core (7) of the rotor (2), a second main side (8) arranged opposite the first main side (6) and an inner ring (9) for arrangement on a rotor shaft (10) of the electric machine (3), characterized byin that a plurality of fingers (11) extending outwards in the radial direction (R) from the inner ring (9) are arranged on the inner ring (9), wherein a free space (12) is formed between two adjacent fingers (11), wherein the fingers (11) comprise a first finger (11a) with a first cooling fluid channel (13), wherein the first cooling fluid channel (13) extends in the axial direction (A) from a first opening (14) formed on the first main side (6) into an inner region of the first finger (11a), wherein the balancing body (1) has an inner cooling fluid channel (15) which extends in the radial direction (R) from the first cooling fluid channel (13) through the first finger (11a) and the inner ring (9) to an inner opening (16) of the inner ring (9) facing the axis of rotation (5). [2] Balancing body (1) according to claim 1, characterized byin that the fingers (11) comprise a second finger (11b), wherein the second finger (11b) has a second cooling fluid channel (17) which is designed as a through-bore and extends in the axial direction (A) from the first main side (6) to the second main side (8) through the second finger (11b). [3] Balancing body (1) according to claim 2, characterized by that the second cooling fluid channel (17) has an outlet opening (18) on the second main side (8) pointing outwards obliquely from the rotation axis (5) in the radial direction (R). [4] Balancing body (1) according to one of the preceding claims, characterized by that the fingers (11) comprise a plurality of first fingers (11a) and a plurality of second fingers (11b) which are arranged alternately next to one another in the circumferential direction (U). [5] Balancing body (1) according to one of the preceding claims, characterized bythat the fingers (11) have a root region (19) arranged on the inner ring (9) and a head region (20) arranged opposite the root region (19), wherein the fingers (11) have a smaller average finger width (B) in the head region (20) than in the root region (19). [6] Balancing body (1) according to claim 5, characterized by that the head region (20) has a chamfer (21) and / or a rounding (22) and / or a tip (23). [7] Balancing body (1) according to claim 5 or 6, characterized by that the finger (11) tapers continuously from the root area (19) to the head area (20). [8] Balancing body (1) according to one of the preceding claims, characterized by that the inner ring (9) has a ring thickness (D) in the radial direction (R) which is smaller than a maximum finger width (B) of the fingers (11) in the circumferential direction (U). [9] Electric machine (3) for a motor vehicle (4), comprising a stator (30), a rotor (2) with a rotor shaft (10) and a rotor core (7) arranged on the rotor shaft (10), wherein the rotor shaft (10) has a central cooling fluid channel (24) extending in the axial direction (A), and wherein the rotor core (7) has an outer cooling fluid channel (25) extending in the axial direction (A), characterized by that a balancing body (1) according to one of the preceding claims is arranged on one side of the rotor laminated core (7), wherein the inner opening (16) of the inner cooling fluid channel (15) is coupled in a fluid-communicating manner to the central cooling fluid channel (24), and wherein the first opening (14) is coupled in a fluid-communicating manner to the outer cooling fluid channel (25). [10] Motor vehicle (4), comprising an electric drive system (26) with a traction battery (27) for providing electrical energy, characterized bythat the electric drive system (26) comprises an electric machine (3) according to claim 9, wherein the traction battery (27) is designed to provide electrical energy for operating the electric machine (3) for driving the motor vehicle (4).

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