DE102023203384B3 - Electric machine, electric axle drive and motor vehicle - Google Patents

Abstract

An electrical machine (100) has a rotor (105) with a slip ring (130), a shaft (110) with an electrical line, a brush device (115) and a spring device (120). The rotor (105) is rotatably mounted relative to the shaft (110). The brush device (115) is arranged on the shaft (110) and has a plurality of brushes (125) surrounding the shaft (110) for transmitting an electrical current between the electrical line and the slip ring (130). The spring device (120) is arranged on the shaft (110) and designed to press the brushes (125) of the brush device (115) radially against the slip ring (130).

Description

The present invention relates to an electric machine, an electric axle drive and a motor vehicle.

Conductive excitation in separately excited synchronous machines is typically achieved using carbon brushes. These parts are usually arranged radially to the shaft and in a separate dry space.

Against this background, the present invention provides an improved electric machine, an improved electric axle drive and an improved motor vehicle according to the main claims. Advantageous embodiments emerge from the subclaims and the following description.

The advantage that can be achieved with the approach presented here is in particular that an electrical machine is created that can enable space-saving accommodation for a brush device.

A corresponding electrical machine has a rotor with a slip ring, a shaft with an electrical line, a brush device and a spring device. The rotor is mounted so as to be rotatable relative to the shaft. The brush device is arranged on the shaft and has a plurality of brushes surrounding the shaft for transmitting an electrical current between the electrical line and the slip ring. The spring device is arranged on the shaft and is designed to press the brushes of the brush device radially against the slip ring.

The electric machine can be used to drive a motor vehicle, for example an electrically powered motor vehicle. The electric machine can be designed as a separately excited synchronous machine, for example. The rotor can be understood as a movable, rotating part of the electric machine. The shaft can be a fixed, immovable part of the electric machine. The slip ring can be a component of the electromechanics and enable electrical power or signal transmission between components rotating against each other. The slip ring can, for example, form a sliding contact together with at least one brush of the brush device. The brushes of the brush device can be carbon brushes that can, for example, make electrical contact with the slip ring. The brushes can have graphite as a material, for example electrographite. The material can also be enriched with metallic components, such as copper or silver. The brushes can also be made entirely of metal. The spring device can press the brushes radially inwards and/or outwards. Optionally, the current can be transferred to the brushes via the spring device.

The brushes of the brush device can be trapezoidal, rectangular or sickle-shaped. A trapezoidal shape can, for example, enable a low current density and thus a low heating of the brushes. This can increase the service life of the brushes. A rectangular shape can ensure that the brushes always have the same circumferential distance to a spacer radially outwards when ready for operation and thus cannot wobble. This can have a beneficial effect on the functioning of the electrical machine. If the brushes are sickle-shaped, gaps between the brushes can be avoided. This enables high currents with little brush material. It can also ensure very good heat dissipation.

The electrical machine can have a spacer. The spacer can be arranged on the shaft in a rotationally fixed manner and can be designed to hold the brushes of the brush device. The spacer can be formed in one piece and can reliably hold the brushes radially, axially and in the circumferential direction. Furthermore, the spacer can allow the brushes to slip when they wear out. This enables the electrical machine to function reliably.

The spring device can be formed as a spiral spring that encloses the shaft in a spiral shape. A first end of the spiral spring can be attached to the shaft and an outer spiral section of the spiral spring can press against ends of the brushes of the brush device in order to press the brushes of the brush device radially against the slip ring. The spiral spring can be manufactured inexpensively, in large quantities and easily. Furthermore, the spiral spring can enable the brushes to slide reliably against the slip ring when the brushes wear out in an operational state.

The spring device can have a plurality of spring elements, which can be formed as helical compression springs. The spring elements can each be arranged with a first end on the shaft and with a second end on each end of the brush of the brush device. The helical compression springs can also be referred to as coil springs. where each helical compression spring can have a spring wire that can be wound in a helical shape. Helical compression springs can reliably press the brushes against the slip ring and can be manufactured inexpensively. For example, one helical compression spring can press against each brush. Helical compression springs can be manufactured inexpensively, in large quantities and easily.

The spring device can be designed to press the brushes of the brush device radially outwards or inwards against the slip ring. In this way, electrical contact with the slip ring can be reliably achieved.

The shaft can be shaped as a rod and the rotor can be shaped as a shaft. The shaft can be arranged in the rotor. The shaft can be hollow, for example tubular. The brush device can be arranged inside the rotor, which can lead to space savings and simple mechanical integration of the components. The contact area can be increased and at the same time the relative speed on the surface can be reduced. This can lead to lower losses and a higher current carrying capacity. The advantages of the approach described here can also be realized very efficiently through such an embodiment.

Alternatively, the shaft can be shaped as a shaft and the rotor can be shaped as a rod. The rotor can be arranged in the shaft. The shaft can in turn be hollow, for example tubular. This can maximize the contact area and allow the contact force to be adjusted over the service life. The advantages of the approach described here can also be realized very efficiently using such an embodiment.

The spring device can be arranged between the shaft and the brush device. In this arrangement, the spring device can reliably press the brushes of the brush device against the slip ring.

The electrical machine can have a coil that can be arranged on the rotor. The electrical line can electrically connect the coil to the slip ring. The coil can be an electrical component that has windings to generate a magnetic field when current flows.

The electric machine can have a guide disk that can have a plurality of slots. The brushes can be suspended in one of the slots with one suspension point each. For example, each brush can have one suspension point. The slots can be rectangular and the suspension points can be cylindrical, for example, so that the slots can reliably guide the suspension points and thus the brushes.

The spring device can be designed to cause a pressure movement against the guide disk or against the brush device in order to press the brushes of the brush device radially against the slip ring. The brushes can be pressed radially inwards against the slip ring.

The electrical machine can have a further slip ring, a further brush device and a further spring device. The brush device can be arranged on the shaft and have a plurality of further brushes surrounding the shaft for transmitting the electrical current between a further electrical line and the further slip ring. The further spring device can be arranged on the shaft and be designed to press the further brushes of the further brush device radially against the further slip ring. The functioning of the electrical machine can thus be advantageously influenced.

In addition, the invention relates to an electric axle drive for a motor vehicle with an embodiment of an electric machine described herein, a transmission device and a power converter. The power converter can be designed as a power inverter or inverter. Using the power converter, an alternating electrical current required to operate the electric machine can be provided. Using the transmission device, a torque provided by the electric machine can be converted into a drive torque for driving at least one wheel of the motor vehicle. The transmission device can have a transmission for reducing the speed of the electric machine and optionally a differential.

In addition, the invention relates to a motor vehicle with an embodiment of an electric machine mentioned herein and additionally or alternatively with an embodiment of an electric axle drive mentioned herein. The motor vehicle can be designed, for example, as an electrically operated motor vehicle.

• 1 eine schematische Darstellung eines Ausführungsbeispiels einer elektrischen Maschine;
• 2 eine schematische Schnittdarstellung eines Ausführungsbeispiels einer elektrischen Maschine;
• 3 eine schematische Darstellung eines Ausführungsbeispiels einer elektrischen Maschine;
• 4 zeigt eine schematische Schnittdarstellung eines Ausführungsbeispiels einer elektrischen Maschine;
• 5 eine schematische Darstellung eines Ausführungsbeispiels einer elektrischen Maschine;
• 6 eine schematische Draufsicht eines Ausführungsbeispiels einer elektrischen Maschine;
• 7 eine schematische Darstellung eines Abstandshalters für ein Ausführungsbeispiel einer elektrischen Maschine;
• 8 zeigt eine schematische Darstellung eines Ausführungsbeispiels einer elektrischen Maschine;
• 9 zeigt eine schematische Draufsicht eines Ausführungsbeispiels einer elektrischen Maschine;
• 10 eine schematische Darstellung eines Abstandshalters für ein Ausführungsbeispiel einer elektrischen Maschine;
• 11 eine schematische Darstellung eines Ausführungsbeispiels einer elektrischen Maschine;
• 12 eine schematische Darstellung eines Ausführungsbeispiels einer elektrischen Maschine;
• 13 eine schematische Darstellung einer Bürsteneinrichtung und einer weiteren Bürsteneinrichtung für ein Ausführungsbeispiel einer elektrischen Maschine;
• 14 eine schematische Darstellung eines Ausführungsbeispiels einer elektrischen Maschine;
• 15 eine schematische Draufsicht einer Bürsteneinrichtung für ein Ausführungsbeispiel einer elektrischen Maschine; und
• 16 eine schematische Darstellung eines Ausführungsbeispiels eines Kraftfahrzeugs.

The invention is explained in more detail by way of example with reference to the accompanying drawings. They show:

• 1 a schematic representation of an embodiment of an electrical machine;
• 2 a schematic sectional view of an embodiment of an electrical machine;
• 3 a schematic representation of an embodiment of an electrical machine;
• 4 shows a schematic sectional view of an embodiment of an electrical machine;
• 5 a schematic representation of an embodiment of an electrical machine;
• 6 a schematic plan view of an embodiment of an electrical machine;
• 7 a schematic representation of a spacer for an embodiment of an electrical machine;
• 8th shows a schematic representation of an embodiment of an electrical machine;
• 9 shows a schematic plan view of an embodiment of an electrical machine;
• 10 a schematic representation of a spacer for an embodiment of an electrical machine;
• 11 a schematic representation of an embodiment of an electrical machine;
• 12 a schematic representation of an embodiment of an electrical machine;
• 13 a schematic representation of a brush device and a further brush device for an embodiment of an electrical machine;
• 14 a schematic representation of an embodiment of an electrical machine;
• 15 a schematic plan view of a brush device for an embodiment of an electrical machine; and
• 16 a schematic representation of an embodiment of a motor vehicle.

In the following description of preferred embodiments of the present invention, the same or similar reference numerals are used for the elements shown in the various figures and having a similar effect, whereby a repeated description of these elements is omitted.

1 shows a schematic representation of an embodiment of an electric machine 100. The electric machine 100 is suitable, for example, for driving a motor vehicle.

The electric machine 100 has a rotor 105, a shaft 110, a brush device 115 and a spring device 120.

According to one embodiment, the rotor 105 is formed as a shaft of the electric machine 100 and the shaft 110 as a rod, wherein the shaft 110 is arranged inside the rotor 105. According to one embodiment, the rotor 105 is designed as a cylindrical tube and the shaft 110 is arranged on a longitudinal axis of the tube. The rotor 105 is rotatably mounted relative to the shaft 110, wherein the brush device 115 and the spring device 120 are arranged between the rotor 105 and the shaft 110.

More specifically, the spring device 120 and the brush device 115 are arranged on the shaft 110. Alternatively, the brush device 115 is arranged on the spring device 120, whereby the spring device 120 is arranged between the shaft 110 and the brush device 115. The rotor 105 has a slip ring 130 which is arranged, for example, adjacent to the brush device 115.

The brush device 115 has a plurality of brushes 125, twelve brushes 125 by way of example only. According to one embodiment, the brushes 125 are trapezoidal in shape and arranged around the shaft 110. Alternatively, the brushes 125 are rectangular in shape. According to the embodiment shown here, the spring device 120 is formed as a spiral spring that encloses the shaft 110 in a spiral shape. A first end of the spring device 120 is attached to the shaft 110 or placed against the shaft 110. Due to the spiral shape of the spring device 120, an outer spiral section of the spring device 120 presses against the ends of the brushes 125 of the brush device 115.

The brushes 125 are designed to transmit an electrical current between an electrical line, which is not shown here, and the slip ring 130. For this purpose, the spring device 120 presses the brushes 125 of the brush device 115 radially against the slip ring 130. This enables a reliable current transmission. In In an operational state, the rotor 105 rotates with the slip ring 130, while the spring device 120 presses the brushes 125 radially outward against the slip ring 130. The brushes 125 wear out, with wear occurring at different rates. The further out the brushes 125 are located on the outer spiral section of the spring device 120, the faster they wear out. The brushes 125 therefore have different lengths. When the brushes 125 wear out, they are pressed further radially outward against the slip ring 130 by the spring device 120.

In other words, 1 a placement of the brush device 115, which can also be referred to as a conductive exciter, inside the rotor 105, with the slip ring 130, which can also be referred to as a sliding contact, facing the inner surface of the rotor 105. The brushes 125, which can also be referred to as electrical contacts, are placed in the middle of the contacts, together with the spring device 120, which presses the brushes 125 onto the surface. The connection area is maximized by the geometry and the relative speed is reduced and thus also the losses.

In other words, 1 a housing of the brushes 125 within the rotor 105, which can also be referred to as a shaft, and a pressing of the brushes 125 against the slip ring 130 from radially inside to radially outside by means of the spring device 120, which can also be referred to as a spiral spring. In 1 , and also in 2 , the brush device 115, which can also be referred to as a carbon brush transformer, is shown, which is located within the rotor 105, which can also be referred to as an electric motor shaft. The brushes 125 of the brush device 115 can consist of various materials, for example of electrographite.

The rotor 105 is designed to rotate. The fixed, non-rotating shaft 110 is arranged centrally within the rotor 105. The spring device 120, i.e. the spiral spring, is attached to this for each pole, i.e. generally for the positive pole and the negative pole, which presses radially outward against the brushes 125 and thereby presses them against the slip rings 130, whereby in 1 a slip ring 130 is shown merely as an example. The slip rings 130 are firmly connected to the rotor 105 and rotate with it. The slip rings 130 are electrically insulated both from the rotor 105 and from each other. An insulated line, not shown here, leads from the respective slip ring 130 to and from the coils, also not shown here, of the rotor 105 as the positive and negative pole.

The brushes 125 are shown here as trapezoidal, but can also have a different shape, for example rectangular. They are held at a defined circumferential distance from each other by spacers (not shown). The spacers are, for example, in the 3 , 4 , 7 , 8th , and or 10 shown.

When the brushes 125 wear and thus shorten, they are moved further radially outward by the spring device 120. Since the spring device 120 has a different radial distance from the slip rings 130 at each outer region, the brushes 125 are ideally adapted to this by each brush 125 having a different radial length.

For the two poles plus and minus, the spring devices 120, the brush groups and the slip rings 130 are each present twice, see for example 2 . The current can be transmitted to the brushes 125 either through the spring device 120 or through extra lines, see for example 14 which, for example, run non-rotatingly along the shaft 110 and then open radially outwards into the brushes 125 in the region of the spring device 120.

In the approach presented here, the brush device 115 is arranged inside the rotor 105. This leads to space savings and easier mechanical integration. The contact area can be increased while reducing the relative speed on the surface. This leads to lower losses and a higher current carrying capacity. In other words, this leads to lower mechanical losses due to friction and electrical losses in its contacts.

2 shows a schematic sectional view of an embodiment of an electrical machine 100. The electrical machine 100 is similar or corresponds to the electrical machine from 1 , except that 2 the electrical machine 100 shown in section.

According to one embodiment, the electric machine 100 has a further slip ring 230, a further brush device 215 with further brushes 225 and a further spring device 220.

The further slip ring 230 is arranged, for example, parallel to and at a distance from the slip ring 130 on the rotor 105. The slip rings 230 are connected via their outer circumference to the inner wall of the rotor 105. The further Brush device 215 and brush device 115 are arranged parallel to one another and the further spring device 220 is arranged parallel to the spring device 120. The further spring device 220 is designed, for example, to press the further brushes 225 of the further brush device 215 radially, for example radially outward, against the further slip ring 230.

Alternatively, the rotor 105 is not equipped with separate slip rings 130 and instead has, for example, suitable grinding zones.

3 shows a schematic representation of an embodiment of an electrical machine 100. The electrical machine 100 is similar or corresponds to the electrical machine from 1 , with the exception that the electric machine 100 has a spacer 300 and the spring device 120 and the brushes 125 are designed differently. Furthermore, the shaft 110 has a larger diameter than the shaft in 1 .

The spacer 300 has, for example, an inner ring 310, a middle ring 315 and an outer ring, the outer ring not being shown. The outer ring is shown by way of example in 7 shown. The rings are arranged concentrically around the shaft 110. Starting from the inner ring 310, spacer elements 320 extend, for example, radially in the direction of the slip ring 130, with a spacer element 320 being arranged between two of the brushes 125 in order to space them apart from one another. The inner ring 310 and the middle ring 315 are arranged at different distances from the shaft 110, with the spacer elements 320 extending on both sides of the middle ring 315. The spacer 300 is designed, for example, to hold the brushes 125 and to allow the brushes 125 to slide towards the slip ring 130 when the brushes 125 wear out.

The spring device 120 has, for example, a plurality of spring elements 305. The spring elements 305 are formed, for example, as helical compression springs. The spring elements 305 are arranged in the electrical machine in such a way that, for example, a first end of the spring element 305 is arranged on the shaft 110 and a second end of the spring element 305 is arranged on a brush 125 of the brush device 115. Thus, each spring element 305 presses a brush 125 against the slip ring 130, with the spring elements 305 being supported on the shaft 110. The brushes 125 of the brush device 115 are, for example, trapezoidal in shape and are held by the spacer 300.

In other words, 3 an accommodation of the brushes 125 within the rotor 105 and a pressing of the brushes 125 against the slip ring 130 from radially inside to radially outside by means of spring elements 305 of the spring device 120, which can also be referred to as helical compression springs. The brushes 125 are trapezoidal in shape.

In contrast to 1 and 2 are in 3 the brushes 125 are pressed radially from the inside to the outside against the slip rings 130 by the spring elements 305. The spring elements 305 are attached to the shaft 110 and designed to transmit the current to the brushes 125. Alternatively, the current can be transmitted to the brushes 125 via the electrical line, not shown here.

Furthermore, in 3 the spacer 300 is also shown, which holds the brushes 125 in their defined positions radially, axially and in the circumferential direction, but still allows the brushes 125 to slide radially outwards when they wear. The spacer 300 is connected to the shaft 110 in a rotationally fixed and axially fixed manner and is therefore immovable.

In 3 the system is shown as a whole, in 4 on average, in 5 with a hidden rotor 105, a hidden slip ring 130 and a hidden spacer 300. Ideally there are two spacers 300, see for example 4 . One per pole and thus one per brush device 115, which can also be referred to as a brush group, whereby one spacer 300 and one brush device 115 are shown here merely as an example. 6 shows an axial plan view of the electric machine 100 with hidden spacer 300 and 7 shows the spacer 300 as a single part.

The advantage of the trapezoidal shape over a rectangular shape is, for example, a lower current density and therefore less heating of the brushes 125. The temperature at the brushes 125 has a major influence on their service life.

4 shows a schematic sectional view of an embodiment of the 3 shown electrical machine 100.

According to one embodiment, the electric machine 100 has the further slip ring 230, the further brush device 215 with the further brushes 225, the further spring device 220 with further spring elements 405 and a further spacer 400. The brushes 125, 225 and the spring elements 305, 405 have, for example, an identical diameter, whereby the spring elements 305, 405 reliably press the brushes 125, 225 against the slip rings 130, 230. Due to the identical diameters, for example, the spacers 300, 400 hold the spring elements 305, 405 in their position in addition to the brushes 125, 225.

5 shows a schematic representation of an embodiment of a part of the 3 shown electrical machine 100. In contrast to 3 the rotor, the slip ring and the spacer are not shown. This makes the additional slip ring 230 and the additional brush device 215 with the additional brushes 225 visible.

6 shows a schematic plan view of an embodiment of the 3 shown electrical machine 100. In contrast to 3 the rotor and spacer are not shown.

7 shows a schematic representation of a spacer 300 for an embodiment of the in 3 shown electrical machine.

The middle ring 315 of the spacer 300 is arranged between the inner ring 310 and the outer ring 700. The spacer elements 320 run from the inner ring 310 radially outward to the outer ring 700. The outer ring 700 has a larger diameter than the middle ring 315, wherein the middle ring 315 has a larger diameter than the inner ring 310.

The spacer 300 has, for example, a further outer ring 705, a further middle ring 715 and a further inner ring 710. The further rings 705, 715, 710 are arranged opposite the rings 700, 315, 310, so that the spacer elements 320 are arranged between the further rings 705, 715, 710 and the rings 700, 315, 310. Opposite rings 700, 315, 310 and 705, 715, 710 are shaped the same according to one embodiment. A distance between opposing rings 700, 315, 310 and 705, 715, 710 corresponds to a width of the spacer elements 320. According to one embodiment, inwardly directed ends of the spacer elements 320 are at the level of an inner diameter of the inner rings 310, 710 and outwardly directed ends of the spacer elements 320 are at the level of an outer diameter of the outer rings 700, 705. The spacer elements 320 extend radially outward from the inner rings 310, 710. According to one embodiment, the spacer elements 320 have a rectangular surface and a rectangular or wedge-shaped longitudinal section.

8th shows a schematic representation of an embodiment of an electrical machine 100. The electrical machine 100 is similar or corresponds to the electrical machine from 3 , with the exception that the brushes 125 are rectangular in shape, whereby the spacer elements 320 of the spacer 300 also have a different shape than in 3 . The spacer elements 320 have, for example, an at least partially triangular shape in order to be able to reliably hold the rectangular brushes 125 in the spacer 300.

In other words, 8th a housing of the brushes 125 within the rotor 105 and a pressing of the brushes 125 against the slip ring 130 from radially inside to radially outside by means of the spring device 120. The brushes 125 are rectangular. The electrical machine 100 from 8th resembles the electric machine from 3 , with the difference that the brushes 125 are rectangular. This has the advantage that when they move radially outwards they always have the same circumferential distance from the spacer 300 and therefore cannot wobble. 8th therefore shows the preferred embodiment and can also be used with the spiral springs from 1 combine. 8th shows the overall system, the 9 an axial top view with hidden spacers and the 10 one of the two spacers.

9 shows a schematic plan view of an embodiment of the 8th shown electric machine 100, wherein the spacer is not shown.

10 shows a schematic representation of a spacer 300 for an embodiment of the in 8th shown electrical machine. The spacer 300 is similar or corresponds to the spacer from 7 , with the exception that the surfaces of the spacer elements 320 each have a bend and are thus each formed by two rectangular surfaces arranged at an angle to one another. Starting from the outer rings 700, 705, the spacer elements 320 initially taper strongly in terms of their thickness up to the bends, then, i.e. between the bends and the inner rings 310, 710, no longer or only slightly.

11 shows a schematic representation of an embodiment of a section of an electrical machine 100. The shaft and the spring device of the electrical machine 100 are not shown.

The rotor 105 of the electric machine 100 is, for example, shaped as a rod and arranged inside the shaft. The brushes 125 of the brush device 115 are, for example, shaped in a sickle shape, with each brush 125 having a suspension point 1110 on the side. The suspension points 1110 are, for example, shaped in a cylinder shape or rod shape.

According to one embodiment, the electric machine 100 has a guide disk 1100 with a plurality of slots 1105. The slots 1105 are, for example, rectangularly shaped and designed to accommodate the suspension points 1110 of the brushes 125. As a result, the brushes 125 are suspended in the guide disk 1100. The guide disk 1100 is, for example, annularly shaped and designed to press the brushes 125 radially inward against the slip ring 130. This is done, for example, by means of the spring device, which, however, is in 11 is not shown. Thus, according to one embodiment, the number of slots 1105 corresponds at least to the number of brushes 125, so that each of the brushes 125 is held by the guide disk 1100. According to one embodiment, the slots 1105 are formed in the guide disk 1100 so that they are evenly spaced and radially aligned.

In 11 the further brushes 225 of the further brush device 215 are shown, which according to one embodiment are also sickle-shaped and are guided in a corresponding manner by a further guide disk 1115. According to one embodiment, the electrical machine 100 has a second guide disk 1120 and a further second guide disk 1125, wherein the brushes 125 are arranged between the guide disk 1100 and the second guide disk 1120 and the further brushes 225 are arranged between the further guide disk 1115 and the further second guide disk 1125. The second guide disk 1120 is arranged on the further second guide disk 1125. According to one embodiment, the second guide disk 1120 rests on the further second guide disk 1125. Alternatively, the second guide disk 1120 and the further second guide disk 1125 are arranged at a distance from one another.

In other words, 11 a possible brush movement and brush shape according to the iris principle. The brushes 125, 225 press from radially outside to radially inside on the slip rings 130. The reverse is also possible, so that this iris concept can also be accommodated within the rotor 105.

The shape and movement of the brushes 125, 225 is based on the iris principle. This means that the brushes 125, 225 have a sickle-shaped design and, when worn, rotate partly around the rotor 105 and partly around their suspension points 1110 within their guide disk 1100, 1115, 1120, 1125. As a result, they always completely fill the space between them in the circumferential direction and gaps between the brushes 125, 225 are avoided. This concept enables the greatest possible currents with the smallest possible use of brush material. This also results in the best possible heat dissipation.

Thus, 11 the overall system whereas the 12 the system with hidden guide disc 1100 and the 13 only shows the brushes 125, 225 in the worn state into which they have moved.

When the guide disks 1100, 1115, 1120, 1125 rotate about the rotor rotation axis, the brushes 125, 225 move radially inwards or outwards. A constant pressing of the brushes 125, 225 and their continued movement when worn against the slip rings 130 is ensured by springs (not shown) pressing against the guide disks 1100, 1115, 1120, 1125 in their direction of rotation. Alternatively, the springs also press directly in the radial direction against the brushes 125, 225.

12 shows a schematic representation of an embodiment of a portion of the 11 shown electrical machine 100. The shaft and the spring device as well as the guide disks are not shown.

According to one embodiment, the further brushes 225 have further suspension points 1210. According to one embodiment, each of the brushes 125, 225 has a suspension point 1110, 1210 on both sides. According to one embodiment, the suspension points 1110, 1210 are realized by pins that are passed through through openings of the brushes 125, 225. Alternatively, the suspension points 1110, 1210 are formed separately on each side of the brushes.

The brushes 125, 225 are shaped like a sickle or scythe blade. The brushes 125, 225 each have a wide end and a pointed end, with the wide end tapering to a point towards the pointed end. The brushes 125, 225 each have curved edges from the wide end to the tip. The inner edge facing the rotor 105, which is located inside here, is concave and the opposite, outer edge is convex. Sections of the inner edges are in contact with the slip rings 130 for current transmission.

The surfaces of the brushes 125, 225, on which the suspension points 1110, 1210 are located, are designed to be flat according to one embodiment. If the brushes 125, 225 are shaped as described, gaps between the brushes 125, 225 are avoided. This enables large currents with little brush material. This also enables very good heat dissipation. This also makes it possible to maximize the contact area of the brushes 125, 225 and to adjust the contact force over the service life.

13 shows a schematic representation of a brush device 115 and a further brush device 215 for an embodiment of the in 11 shown electrical machine. The brush devices 115, 215 are similar or correspond to the brush devices from 12 , except that the brushes 125, 225 of the brush devices 115, 215 in 13 are shown in a worn state. The brushes 125, 225 are worn in such a way that a gap is arranged between adjacent brushes 125. A gap is also arranged between adjacent brushes 225.

14 shows a schematic representation of an embodiment of an electrical machine 100. The structure of the electrical machine 100 is similar to the structure of 11 .

The rotor 105 is formed as a rod and the shaft 110 is formed as a hollow shaft, with the rotor 105 being arranged in the shaft 110. The brushes 125 and the additional brushes 225 are arranged in an intermediate space extending between the inner rotor 105 and the surrounding shaft 110, merely as an example. The brushes 125 and the additional brushes 225 each form an annular brush arrangement surrounding the shaft 110. Both brush arrangements are arranged spaced apart from one another by a gap, for example.

According to one embodiment, the electric machine 100 has at least one coil 1400, which is arranged on the rotor 105. Connections of the coil 1400 and the brushes 125, 225 are electrically conductively connected to one another via an electrical line 1405 and a further electrical line 1410. The electrical line 1405 connects the coil 1400, or a positive pole of the coil 1400, to the brushes 125 in order to transmit current to the brushes 125. The further electrical line 1410 connects the coil 1400, or a negative pole of the coil 1400, to the further brushes 225 in order to transmit current to the further brushes 225.

15 shows a schematic plan view of a brush device 115 for an embodiment of an electrical machine. The brush device 115 can be the one shown in 14 shown and described brush device 115.

According to one embodiment, the line 1405 and other corresponding lines extend radially over the brushes 125.

In summary, the approach presented here can be described as concepts for brush transformers and as conductive exciters inside the shaft. For example, the 1 to 10 a concept for integrating the brush and slip ring system within the rotor 105, so that extra installation space for the brush device 115 is no longer necessary. The 11 to 15 For example, show a concept for a mechanism for moving the carbon brushes according to the iris principle in order to accommodate more brush material in a smaller installation space and also reduce the current density within the brushes. The approach presented here can therefore also be referred to as a conductive exciter inside the shaft and the iris principle for a conductive exciter.

16 shows a schematic representation of an embodiment of a motor vehicle 1600. The motor vehicle 1600 shows wheels 1605, four wheels by way of example only, an electrical energy storage device 1610, for example a battery, and an electrical axle drive 1615. The electrical axle drive 1615 comprises a power converter 1620, an electrical machine 100 and a transmission device 1630.

Electrical energy for operating the electrical machine 100 is provided by an energy supply device, here the electrical energy storage device 1610. The electrical energy storage device 1610 is designed to provide direct current, which is converted into an alternating current, for example a three-phase alternating current, using a power converter 1620 of the electric axle drive 1615 and is provided to the electrical machine 100. A shaft driven by the electrical machine 100 is coupled directly or using the transmission device 1630 to at least one wheel 1605 of the motor vehicle 1600. The motor vehicle 1600 can thus be moved using the electrical machine 100. According to In one embodiment, the electric axle drive 1615 comprises a housing in which the power converter 1620, the electric machine 100 and the transmission device 1630 are arranged.

Reference symbols

100

electric machine

105

rotor

110

shaft

115

Brush device

120

Spring device

125

to brush

130

Slip ring

215

additional brush device

220

additional spring device

225

more brushes

230

additional slip ring

300

Spacers

305

Spring element

310

inner ring

315

middle ring

320

Spacer element

400

additional spacer

405

additional spring element

700

outer ring

705

further outer ring

710

additional inner ring

715

additional middle ring

1100

Guide disc

1105

slot

1110

Suspension point

1115

additional guide disc

1120

second guide disc

1125

additional second guide disc

1210

additional suspension point

1400

Kitchen sink

1405

electrical line

1410

additional electrical cable

1600

vehicle

1605

Wheels

1610

electrical energy storage

1615

electric axle drive

1620

Power converter

1630

Gearbox device

Claims (15)

Electrical machine (100) having the following features: a rotor (105) with a slip ring (130); a shaft (110) with an electrical line (1405), wherein the rotor (105) is rotatably mounted relative to the shaft (110); a brush device (115) which is arranged on the shaft (110) and has a plurality of brushes (125) surrounding the shaft (110) for transmitting an electrical current between the electrical line (1405) and the slip ring (130); and a spring device (120) which is arranged on the shaft (110) and which is designed to press the brushes (125) of the brush device (115) radially against the slip ring (130). Electrical machine (100) according to Claim 1 , wherein the brushes (125) of the brush device (115) are trapezoidal, rectangular or sickle-shaped. Electrical machine (100) according to one of the preceding claims, with a spacer (300) which is arranged in a rotationally fixed manner on the shaft (110) and is designed to hold the brushes (125) of the brush device (115). Electrical machine (100) according to one of the preceding claims, wherein the spring device (120) is formed as a spiral spring enclosing the shaft (110) in a spiral shape, wherein a first end of the spiral spring is attached to the shaft (110) and an outer spiral portion of the spiral spring presses against ends of the brushes (125) of the brush device (115) in order to press the brushes (125) of the brush device (115) radially against the slip ring (130). Electric machine (100) according to one of the Claims 1 until 3 , wherein the spring device (120) has a plurality of spring elements (305) which are formed as helical compression springs, wherein the spring elements (305) are each arranged with a first end on the shaft (110) and are each arranged with a second end on a respective end of the brush (125) of the brush device (115). Electric machine (100) according to one of the preceding claims, wherein the spring device (120) is designed to press the brushes (125) of the brush device (115) radially outward or inward against the slip ring (130). Electric machine (100) according to one of the preceding claims, wherein the shaft (110) is formed as a rod and wherein the rotor (105) is formed as a shaft, wherein the shaft (110) is arranged in the rotor (105). Electric machine (100) according to one of the preceding Claims 1 until 6 , wherein the shaft (110) is formed as a shaft and wherein the rotor (105) is formed as a rod, wherein the rotor (105) is arranged in the shaft (110). Electric machine (100) according to one of the preceding claims, wherein the spring device (120) is arranged between the shaft (110) and the brush device (115). Electric machine (100) according to one of the preceding claims, with a coil (1400) arranged on the rotor (105), wherein the electrical line (1405) electrically connects the coil (1400) to the slip ring (130). Electrical machine (100) according to one of the preceding claims, with a guide disk (1100) which has a plurality of slots (1105), wherein the brushes (125) of the brush device (115) are each suspended with a suspension point (1110) in one of the slots (1105). Electrical machine (100) according to Claim 11 , wherein the spring device (120) is designed to cause a pressure movement against the guide disc (1100) or against the brush device (115) in order to press the brushes (125) of the brush device (115) radially against the slip ring (130). Electrical machine (100) according to one of the preceding claims, with a further slip ring (230), with a further brush device (215) which is arranged on the shaft (110) and has a plurality of further brushes (225) surrounding the shaft (110) for transmitting the electrical current between a further electrical line (1410) and the further slip ring (230), and with a further spring device (220) which is arranged on the shaft (110) and which is designed to press the further brushes (225) of the further brush device (215) radially against the further slip ring (230). Electric axle drive (1615) for a motor vehicle (1600) with an electric machine (100), a transmission device (1630) and a power converter (1620), characterized in that the electric machine (100) according to one of the Claims 1 until 13 is trained. Motor vehicle (1600), comprising an electric axle drive (1615) according to Claim 14 and/or an electrical machine (100) according to one of the Claims 1 until 13 .

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