Electric axial flux machine

Abstract

The invention relates to an electrical axial flux machine (1), in particular for a drive train (2) of a hybrid or fully electrically operated motor vehicle (3). The axial flux machine comprises: a stator (4) having a plurality of stator coils (5) distributed over the circumference of the stator (4); power electronics (6) for supplying current to the stator coils (5); and a high-voltage terminal (7) for establishing an electrical connection between the stator coils (5) and the power electronics (6), wherein busbars (8) are located above the stator coils (5) in the radial direction, said busbars enclosing, in an annular manner, the stator (4) and / or a rotor (17) that can be rotated relative to the stator (4), and electrically conductively connecting the stator coils (5) to the high-voltage terminal (7).

Description

[0001] Electric axial flux machine

[0002] The present invention relates to an electric axial flux machine, in particular for a drive train of a hybrid or fully electric motor vehicle, comprising a stator with a plurality of stator coils distributed over the circumference of the stator and power electronics for energizing the stator coils as well as a high-voltage terminal for establishing an electrical connection between the stator coils and the power electronics.

[0003] Electric motors are increasingly being used to power motor vehicles, creating alternatives to combustion engines that require fossil fuels. Considerable efforts have already been made to improve the everyday suitability of electric drives and also to provide users with the same level of driving comfort they are accustomed to.

[0004] A detailed description of an electric drive can be found in an article in the magazine ATZ 113th year, 05 / 2011, pages 360-365 by Erik Schneider, Frank Fickl, Bernd Cebulski and Jens Liebold with the title: Highly integrated and flexible electric drive unit for electric vehicles, which arguably represents the closest state of the art. This article describes a drive unit for one axle of a vehicle which comprises an electric motor which is arranged concentrically and coaxially to a bevel gear differential, with a switchable 2-speed planetary gear set being arranged in the power train between the electric motor and bevel gear differential, which is also positioned coaxially to the electric motor or the bevel gear differential or spur gear differential. The drive unit is very compact and, thanks to the switchable 2-speed planetary gear set, allows a good compromise between climbing ability, acceleration and energy consumption.Such drive units are also referred to as e-axles or electrically operated drive trains.

[0005] Axial flux machines are also increasingly being used in such electric axles. An axial flux machine is a dynamoelectric machine in which the magnetic flux between the rotor and stator runs parallel to the rotor's axis of rotation. Both the stator and rotor are often largely disc-shaped. Axial flux machines are particularly advantageous when the axially available installation space is limited in a given application. This is often the case, for example, with the electric drive systems for electric vehicles described above. In addition to the shortened axial length, another advantage of the axial flux machine is its comparatively high torque density. The reason for this is the larger air gap area available in a given installation space compared to radial flux machines.Furthermore, a smaller iron volume is required compared to conventional machines, which has a positive effect on the efficiency of the machine.

[0006] Due to its disc-shaped main components, an axial flux machine is particularly well-suited for applications where a very short electric motor length is essential and where a relatively large motor diameter is still acceptable. When developing such axial flux machines, it is therefore generally advisable to strive for the shortest possible design, while keeping the outer diameter of the axial flux machine no larger than absolutely necessary. Axial flux machines for motor vehicles also always have to meet the requirements of low weight, high power density, and low cost. This also applies to the power supply of an axial flux machine.

[0007] It is therefore the object of the invention to provide an axial flow machine that is particularly compact both axially and radially.

[0008] This object is achieved by an electric axial flux machine, in particular for a drive train of a hybrid or fully electric motor vehicle, comprising a stator with a plurality of stator coils distributed over the circumference of the stator and power electronics for energizing the stator coils as well as a high-voltage terminal for establishing an electrical connection between the stator coils and the power electronics, wherein busbars are arranged in the radial direction above the stator coils, which busbars enclose the stator and / or a rotor rotatable relative to the stator in a ring shape and electrically connect the stator coils to the high-voltage terminal.

[0009] This provides the advantage of a particularly short axial design for the axial flux machine by arranging the busbar, which supplies power to the stator coils of the electromagnets, radially outside the rotor. All electrical connections between the stator coils can be made radially outside the stator coils or radially outside the rotor. Electrical connections between the coils are not required either in the radial area of ​​the stator coils or in the radial area within the stator coils.

[0010] The ring-shaped busbars can be closed all the way around or open at one point along the circumference. The busbars can also be designed to enclose only part of the circumference.

[0011] First, the individual elements of the claimed subject matter of the invention are explained in the order in which they appear in the set of claims, and subsequently particularly preferred embodiments of the subject matter of the invention are described.

[0012] The magnetic flux in an electric axial flux machine (AFM), such as an electric drive machine of a motor vehicle designed as an axial flux machine, is directed axially to a direction of rotation of the rotor of the axial flux machine in the air gap between stator and rotor.

[0013] Depending on the application, it may be advantageous to design an axial flux machine in an I-arrangement or an H-arrangement. In an I-arrangement, the rotor is arranged axially next to a stator or between two stators. In an H-arrangement, two rotors are arranged on opposite axial sides of a stator. The axial flux machine according to the invention is preferably configured in an I-arrangement.

[0014] In principle, it is also possible for a plurality of I-type and / or H-type rotor-stator configurations to be arranged axially adjacent to one another. In this context, it would also be possible to arrange several I-type rotor-stator configurations axially adjacent to one another. In particular, it is also preferable for the H-type and / or I-type rotor-stator configurations to be essentially identical in design, so that they can be combined in a modular manner to form an overall configuration. Such rotor-stator configurations can, in particular, be arranged coaxially to one another and connected to a common rotor shaft or to multiple rotor shafts.

[0015] The stator of the electric axial flux machine according to the invention preferably has a stator body with a plurality of stator windings arranged in the circumferential direction. The stator body can be formed as a single piece or segmented in the circumferential direction. The stator body can be formed from a stator core with a plurality of laminated electrical sheets. Alternatively, the stator body can also be formed from a pressed soft magnetic material, such as the so-called SMC material (Soft Magnetic Compound).

[0016] The rotor of an electric axial flux machine can be designed, at least in part, as a laminated rotor. A laminated rotor is constructed with layers in the radial direction. Alternatively, the rotor of an axial flux machine can also have a rotor carrier, which is equipped with magnetic laminations and / or SMC material and with magnetic elements designed as permanent magnets.

[0017] A rotor shaft is a rotatably mounted shaft of an electrical machine to which the rotor or rotor body is non-rotatably coupled.

[0018] The electric axial flux machine may further comprise a control device. A control device, as can be used in the present invention, serves in particular for the electronic control and / or regulation of one or more technical systems of the electric axial flux machine.

[0019] A control device preferably has a wired or wireless signal input for receiving electrical signals, such as sensor signals. Furthermore, a control device preferably also has a wired or wireless signal output for transmitting electrical signals, in particular.

[0020] Control and / or regulation operations can be performed within the control device. It is particularly preferred that the control device comprises hardware configured to execute software. The control device preferably comprises at least one electronic processor for executing program sequences defined in the software.

[0021] The control device may further comprise one or more electronic memories in which the data contained in the signals transmitted to the control device can be stored and read out again. Furthermore, the control device may comprise one or more electronic memories in which data can be stored in a modifiable and / or non-modifiable manner.

[0022] A control device can comprise a plurality of control units, which are arranged, in particular, spatially separated from one another in the motor vehicle. Control units are also referred to as Electronic Control Units (ECUs) or Electronic Control Modules (ECMs) and preferably have electronic microcontrollers for performing computing operations for processing data, particularly preferably using software. The control units can preferably be networked with one another, enabling wired and / or wireless data exchange between control units. In particular, it is also possible to network the control units with one another via bus systems present in the motor vehicle, such as the CAN bus or LIN bus.

[0023] Most preferably, the control device has at least one processor and at least one memory, which in particular contains a computer program code, wherein the memory and the computer program code are configured, with the processor, to cause the control device to execute the computer program code. The control unit can particularly preferably comprise power electronics for supplying current to the stator or rotor. Power electronics is preferably a combination of various components which control or regulate a current to the electrical machine, preferably including peripheral components required for this purpose, such as cooling elements or power supplies. In particular, the power electronics contains one or more power electronics components which are designed to control or regulate a current. These are particularly preferably one or more power switches, e.g. power transistors.The power electronics particularly preferably have more than two, particularly preferably three, separate phases or current paths, each with at least one dedicated power electronics component. The power electronics are preferably designed to control or regulate a power per phase with a peak power, preferably continuous power, of at least 1,000 W, preferably at least 10,000 W, particularly preferably at least 100,000 W.

[0024] The electric axial flux machine is particularly intended for use within a drive train of a hybrid or fully electric motor vehicle. In particular, the electric machine is dimensioned such that vehicle speeds greater than 50 km / h, preferably greater than 80 km / h, and in particular greater than 100 km / h can be achieved. The electric motor particularly preferably has an output greater than 50 kW, preferably greater than 100 kW, and in particular greater than 250 kW. It is further preferred that the electric machine provides operating speeds greater than 5,000 rpm, particularly preferably greater than 10,000 rpm, and most particularly preferably greater than 12,500 rpm. Most preferably, the electric machine has operating speeds between 5,000 and 15,000 rpm, and most preferably between 7,500 and 13,000 rpm.

[0025] The electric axial flux machine can preferably also be installed in an electrically operated axle drive train. An electric axle drive train of a motor vehicle comprises an electric axial flux machine and a transmission, wherein the electric axial flux machine and the transmission form a structural unit. In particular, it can be provided that the electric axial flux machine and the transmission are arranged in a common drive train housing. Alternatively, it would of course also be possible for the electric axial flux machine to have a motor housing and the transmission to have a transmission housing, wherein the structural unit can then be effected by fixing the transmission relative to the electric axial flux machine. This structural unit is occasionally also referred to as an electric axle.

[0026] The electric axial flux machine can particularly preferably also be provided for use in a hybrid module. In a hybrid module, components and functional elements of a hybridized drive train can be spatially and / or structurally combined and preconfigured, so that a hybrid module can be integrated into a motor vehicle's drive train in a particularly simple manner. In particular, an axial flux machine and a clutch system, in particular with a separating clutch for coupling the axial flux machine into and / or disengaging the axial flux machine from the drive train, can be present in a hybrid module.

[0027] A high-voltage terminal within the meaning of this application is the particularly detachable connection point between the busbars and the electrical conductors (e.g. cables) that connect the electrical machine to the power electronics (and consists of the components forming this connection point). These can, for example, comprise busbars with connection points for the electrical connection to the power electronics and preferably also connection points for the busbars of the electrical machine. The connection points can, for example, be designed as screw and / or plug contacts. In particular, the high-voltage terminal is designed for connecting a multi-phase power connection.

[0028] Advantageous embodiments of the invention are specified in the dependent claims. The features listed individually in the dependent claims can be combined with one another in a technologically expedient manner and can define further embodiments of the invention. Furthermore, the features specified in the claims are further specified and explained in the description, where further preferred embodiments of the invention are presented.

[0029] According to an advantageous embodiment of the invention, it can be provided that the high-voltage terminal is positioned radially above the busbars, which also contributes to a compact axial design and good assembly of the power connections.

[0030] According to a further preferred development of the invention, it can also be provided that the stator coils each have a first coil end and a second coil end, wherein the first coil end has a radially extending section and an axially extending section, and the axially extending section electrically contacts one of the busbars and / or the second coil end has a radially extending section and an axially extending section, and the axially extending section electrically contacts one of the busbars or a star point busbar or another coil. This can also support a particularly axially compact design of the axial flux machine. Furthermore, this can also contribute to the formation of an equal number of stator coils, with corresponding cost advantages.

[0031] Furthermore, according to a likewise advantageous embodiment of the invention, it can be provided that the axial flux machine is configured in an I-design, in which the stator has a first disc-shaped stator body and a second disc-shaped stator body axially spaced therefrom, and a rotor is arranged axially between the first stator body and the second stator body, wherein the first stator body has a plurality of first stator coils distributed over the circumference of the first stator body and the second stator body has a plurality of second stator coils distributed over the circumference of the second stator body, and first busbars are arranged in the radial direction above the first stator coils,which surround the first stator body in a ring shape and electrically connect the first stator coils and / or the second stator coils to the high-voltage terminal, and second busbars are arranged in the radial direction above the second stator coils, which surround the second stator body in a ring shape and electrically connect the first stator coils and / or the second stator coils to the high-voltage terminal.

[0032] The advantageous effect of this design is based on the fact that, in an axial flux machine in an I-arrangement, the busbars and the interconnection area for both stator bodies can be arranged radially outside the rotor. Almost all current-carrying components of the interconnection area can thus be arranged radially outside the stator coils of the electromagnets and are also located axially within the axial area, which corresponds to the width of the rotor plus half the width of the two laterally adjacent stator bodies.

[0033] This makes it possible to provide an axial flux machine in an I-configuration whose busbars and interconnection areas for both stator bodies are located axially within the axial area between the side of the stator iron (yoke) of one stator body facing away from the rotor and the side of the stator iron (yoke) of the other stator body facing away from the rotor. Due to the radial arrangement of the busbars and coil interconnection or connection, the axial length of the axial flux machine in the I-configuration can be very short.

[0034] Furthermore, the two opposing stator coils connected in series can preferably be connected to a common busbar system radially outside the rotor. The busbar system can be aligned centrally to the rotor so that the connecting wires of the stator coils in the opposing stator bodies can be made of the same length and thus identical stator coils can be used for both stator bodies. This makes it very easy to implement very short winding ends of the stator coils as well as a series connection of the opposing stator coils. Furthermore, the wiring and contacting positions are easily accessible, which noticeably simplifies assembly. Alternatively, the opposing stator coils (i.e. on opposite sides of the rotor) could also be connected to a common busbar system without the stator coils having to be connected in series.

[0035] According to a further particularly preferred embodiment of the invention, it can be provided that the stator coils are designed essentially identically, which can contribute to a significant cost optimization of the axial flux machine.

[0036] In a likewise preferred embodiment variant of the invention, it can also be provided that the first busbars and the second busbars are connected to the common high-voltage terminal.

[0037] It may also be advantageous to further develop the invention in such a way that the busbars are accommodated at least in sections in an annular or ring-segment-shaped insulating body, which on the one hand simplifies the defined fixing of the busbars to one another and at the same time can provide electrical insulation of the busbars from one another.

[0038] According to a further preferred embodiment of the subject matter of the invention, it can be provided that the insulating body has an E-like contour in cross section with two radially spaced-apart, one-sidedly open grooves in which the busbars are received, which has proven to be particularly advantageous in terms of manufacturing and assembly technology.

[0039] Furthermore, according to a further preferred embodiment of the invention, it is advantageous for axial and radial elastic decoupling of movement to occur between the stator and the power terminals. This can be achieved, for example, by elastically deformable busbars and / or elastically deformable connecting tabs between the busbars and the power terminal bolts. Finally, it may also be preferred for a pair of coils arranged on opposite sides of the rotor to be electrically connected in series.

[0040] The invention will be explained in more detail below with reference to figures without limiting the general inventive concept.

[0041] It shows:

[0042] Figure 1 shows an axial flow machine in a schematic axial sectional view,

[0043] Figure 2 shows a detailed view of the axial flow machine from Figure 1 in an axial section

[0044] Figure 3 shows a detailed view of the axial flow machine from Figure 1 in an axial section

[0045] Figure 4 shows a perspective view of the coil connection of an axial flux machine,

[0046] Figure 5 shows a detailed view of the coil connection of the axial flux machine from Figure 4 in a perspective view,

[0047] Figure 6 shows a hybrid and a fully electric motor vehicle in a block diagram.

[0048] Figure 1 shows an electric axial flux machine 1, in particular for a drive train 2 of a hybrid or fully electric motor vehicle 3, as is sketched by way of example in Figure 6.

[0049] The axial flux machine 1 shown comprises a stator 4 with a plurality of stator coils 5 distributed over the circumference of the stator 4 and power electronics 6 for energizing the stator coils 5 as well as a high-voltage terminal 7 for establishing an electrical connection between the stator coils 5 and the power electronics 6, which can be clearly seen from the combination of Figures 1 and 4.

[0050] Arranged radially above the stator coils 5 are busbars 8, which enclose the stator 4 in a ring shape and electrically connect the stator coils 5 to the high-voltage terminal 7. As shown in Figure 1, the axial flux machine 1 is configured in an I-design, in which the stator 4 has a first disc-shaped stator body 15 and a second disc-shaped stator body 16 axially spaced therefrom, and a rotor 17 is arranged axially between the first stator body 15 and the second stator body 16.

[0051] The first stator body 15 has a plurality of first stator coils 5 distributed over the circumference of the first stator body 15, and the second stator body 16 has a plurality of second stator coils 25 distributed over the circumference of the second stator body 16. Arranged radially above the first stator coils 5 are first busbars 8, which enclose the first stator body 15 in a ring shape and electrically connect the first stator coils 5 and / or the second stator coils 25 to the high-voltage terminal 7. Arranged radially above the second stator coils 25 are second busbars 18, which similarly enclose the second stator body 15 in a ring shape and electrically connect the first stator coils 5 and / or the second stator coils 25 to the high-voltage terminal 7.

[0052] The stator 4 thus consists of two stator bodies 15, 16 that are connected to one another radially on the outside and are each rotationally decoupled from the rotor shaft 22 via a bearing point on the inside. The rotor 17 is fastened to the rotor shaft 22 and consists of a disk-shaped section that extends radially outwards between the two stator bodies 15, 16. Between the two stator bodies 15, 16 and the rotor 17 are the air gaps through which the axial magnetic flux of the axial flux machine 1 flows. The magnetic springs of the axial flux machine 1 can generate a torque that acts on the rotor 17 and is transmitted from the rotor to the rotor shaft 22. The rotor shaft 22 protrudes axially from the axial flux machine 1 and thus forms the transmission element through which the torque of the electrical axial flux machine 1 can be transmitted to an adjacent unit.This adjacent unit can be, for example, a gearbox, a differential, a shaft or a wheel of the motor vehicle 3.

[0053] The stator half facing the gearbox is connected radially inward to the housing 23, which surrounds the electric axial flux machine 1. For this purpose, the housing 23 has a side wall or intermediate wall that is screwed to the second stator body 16. It is advisable to arrange several screws distributed around the circumference. Bearings between the stator bodies 15, 16 and the rotor shaft 22 connect the rotor 17 to the stator 4 in a rotationally decoupled manner.

[0054] In the axial flux machine 1 shown in half section in Figure 1, the rotor 17 is equipped with permanent magnets and the stator 4 with electromagnets. In both stator bodies 15, 16, several electromagnets (poles) are distributed around the circumference, each consisting of a coil 5, 25 that runs around a coil core (a tooth of the stator iron). There is always an electromagnet of one stator body 15, 16 and an electromagnet of the other stator body 15, 16 arranged on the respective opposite sides of the rotor 17. The coils 5, 25 of these two electromagnets form a coil pair, the coils of which are arranged exactly one behind the other in the axial direction (on the opposite sides of the rotor 17). The sectional plane of Figure 1 runs through such a coil pair.In the embodiment shown, these two coils 5,25 are electrically connected in series, so that the output of one coil 5,25 is connected to the input of the other coil 5,25.

[0055] Figure 2 shows, in the sectional plane, how the wire of one coil 5 leads axially away from the wound coil body, then runs radially outwards through an opening between the components forming the support structure of the stator 4, and then runs axially back towards the rotor 17. The opposite coil 25 of the coil pair 5, 25 has a comparable coil end 10 that meets the other coil end 9. Both coil ends 9, 10 meet radially outside the rotor 17 and can be electrically connected to one another there. In the illustrated embodiment, the coil ends 9, 10 overlap. The overlapping parts of the coil ends 9, 10 are free of the insulating layer surrounding the coil wire and are connected to one another, for example by welding, soldering, or pressing.

[0056] The power supply to all coils 5, 25 arranged on the circumference of the axial flux machine 1 is ensured by a system of busbars 8, 18 arranged radially outside the rotor 17. In the exemplary embodiment, three busbars (current phase U, current phase V and current phase W) and a star point busbar are located in the surrounding space formed by the stator 4 and the motor housing 23, radially outside the rotor 17, in which the just described connection point between the coils 5, 25 belonging to a respective coil pair is also located. These four electrical conductors (busbars) are designed as curved sheet metal components (e.g. copper sheet) that run completely or almost completely around the axial flux machine 1. Two of these busbars 8, 18 are each arranged in an insulating body 19 that is open on one side.This insulating body 19 runs in a ring shape around the electric axial flux machine 1 and has a rectangular cross-section with two deep axially running grooves 20,21, so that the cross-section of the insulating body 19 is reminiscent of an “E”.

[0057] In this embodiment, two insulating bodies 19 are arranged on opposite axial sides in the annular space between the stator 4 and the motor housing 23. The grooves 20, 21 of the insulating bodies 19 face toward the center and each accommodate one of the current-carrying busbars 8, 18 or a star point busbar. Starting from the respective circumferential base body of the busbars 8, 18 or a star point busbar, which are arranged completely in the grooves 20, 21 of the insulating bodies 19, several connecting tabs 24 of the busbars 8, 18 or star point busbar, distributed around the circumference, protrude axially from the grooves 20, 21 of the insulating bodies 19. These connecting tabs 24 form the electrical connection points of the busbars 8, 18 and the star point busbar, with which the busbars or star point busbars are connected to the coils 5, 25, as can also be clearly seen in Figure 3.The three current rails for the current phases (current phase U, current phase V and current phase W) also each have a connecting lug 24 which is connected to the phase connection of the axial flux machine 1 (current connection bolt).

[0058] Alternatively, each current-carrying rail (i.e., busbars and star-point rail) can be arranged in its own insulating body 19, or more than two current-carrying rails can be accommodated in one insulating body 19. The insulating body 19 can have its own circumferential groove 20, 21 for each current-carrying rail (for example, several radially staggered grooves 20, 21 one above the other and / or grooves 20, 21 extending from the two axially opposite sides into the cross-section of the insulating body 19). If the current-carrying conductors do not run completely around the electrical axial flux machine 1, several rails can also be arranged in different areas of the circumference in one circumferential groove 20, 21 of an insulating body 19.

[0059] This is particularly useful, for example, if not just one busbar is used per phase connection of the axial flux machine 1 to electrically supply all of the coils 5, 25 to be connected to this phase connection, but rather several busbars are connected to the phase connection and each of these busbars electrically connects only a portion of the coils 5, 25 to the phase connection that must be connected to this phase connection. For example, it is possible to arrange a short busbar (e.g., one covering less than 180° of the axial flux machine 1) in one circumferential direction from a phase connection and a second, comparable busbar in the other circumferential direction around the axial flux machine 1, each busbar electrically connecting only a portion (e.g., half) of the coils 5, 25 to be connected to the phase connection.

[0060] Instead of a circumferential star point busbar (one that is closed or open at one point on the circumference) to which all coil pairs (or all coils 5, 25 of one of the stator bodies 15, 16) are connected, several circumferentially distributed star point busbars can be used, each of which is connected to a coil group or an integer number of coil groups, each consisting of a coil pair connected to the current phase U, a coil pair connected to the current phase V, and a coil pair connected to the current phase W. These star point busbars, which are not connected to all coil pairs, can also be arranged one behind the other in a circumferential groove 20, 21 of an insulating body 19 on the circumference.

[0061] Since the insulating bodies 19 insulate the busbars 8, 18 toward the edge of the annular space, the busbars 8, 18 can be arranged geometrically quite close to the stator components made of electrically conductive material and forming the axial side walls of the annular space, without falling below the required clearance and creepage distances. Towards the inside, where the two oppositely arranged insulating bodies 19 are open, there is sufficient space between the conductors to maintain the required clearance and creepage distances. Radially inward in the annular space there is a further insulating insert 26 (e.g. a plastic film or insulating paper). This insulating insert 26 can be seen in Figure 2 between the connection point of the two coils 5, 25 of the coil pair and the stator casing 27.

[0062] The stator shell 27 is a tubular component that mechanically connects the two stator bodies 15, 16 and separates the rotor chamber from the annular space housing the power supply. The insulating insert 26 creates the necessary clearance and creepage distances radially inward from the current-carrying rails and the connection points of the coils 5, 25 to the adjacent stator components. In the illustrated embodiment, there is sufficient clearance radially outward toward the motor housing 23 to maintain the necessary clearance and creepage distances. Alternatively, another insulating insert can be used to electrically insulate the annular space radially toward the motor housing 23.

[0063] Figure 3 shows a further detail of the axial flux machine 1 already shown in Figures 1-2. The section in Figure 3 is slightly offset circumferentially from that in Figures 1 and 2, so that the section plane passes through a connection point of the star point busbar with a coil 5.25. The connection points between each of the three current busbars (current phase U, current phase V, and current phase W) and a coil 5.25 are technically implemented in a similar manner. The connection points of the power supply system can also be seen in the subsequent perspective illustrations in Figures 4-5.At the connection points between the coils 5, 25 and the busbars 8, 18, which are designed to overlap in this exemplary embodiment, the wire ends of the coils 5, 25 are freed from the insulating layer surrounding the coil wire and electrically connected (for example, welded, soldered, or pressed) to the bare extensions of the current-carrying busbars. Instead of overlapping, the electrical connection points of the axial flux machine 1 can also be designed to butt joint and then, for example, welded or soldered.

[0064] Figures 1-3 show that the interconnection and power supply of the coils 5, 25 is effected via the power supply system arranged radially above the rotor 17, which essentially consists of the busbars 8, 18, the phase connections, and the electrical connecting elements or connections between these components and between these components and the coils 5, 25. No electrical connecting elements are required axially behind the stator iron. In other words, all electrical conductors can be arranged in the central axial region of the axial flux machine 1 using the design principle described here. This region extends from the side of the stator iron [yoke] of one stator body 15 facing away from the rotor 17 to the side of the stator iron [yoke] of the other stator body 16 facing away from the rotor 17.Since no installation space for electrical conductors has to be provided axially behind the stator iron or even behind the stator side walls, the axial flux machine 1 can be constructed with a very short axial length. By integrating the busbars 8, 18 into an annular space formed by the stator casing 27 and closed radially outward by the motor housing 23, the busbars 8, 18 are integrated into the mechanical structure of the stator 4 in a very space-saving manner. Alternatively, the annular space in which the current-carrying busbars are housed can also be covered radially outward by an additional motor element, so that the busbars are completely enclosed by motor parts and no additional motor housing is required to cover the current-carrying busbars.The stator shell 27 is an annular or tubular component (or an annular or tubular assembly) that completely encloses the rotor 17 and has a flange at each of its two axial end regions, each of which extends radially outward past the annular space and to which a stator side wall is attached. Several openings distributed around the circumference are provided in the flanges of the stator shell 27, through which the connecting wires of the coils 5, 25 protrude. It is particularly expedient to pull both coil ends 9, 10 of a coil 5, 25 through the same opening in the flange of the stator shell 27, as this reduces the eddy current losses of the axial flux machine 1. The mechanical connection between the stator shell 27 and the respective stator side wall requires a larger radial installation space than the tubular axial center section of the stator shell 27.

[0065] Because the power supply system utilizes the radial installation space above the tubular axial center section of the stator shell 27, the axial flux machine 1 is no larger radially over most of its circumference, even with the power supply system arranged radially on the outside, than it would otherwise have to be in order to accommodate the mechanical structure of the stator 4 (e.g. the fastening elements). At the point where the phase connections are arranged radially above the rotor 17, the motor housing 23 must be pulled further radially outward in order to create installation space for the phase connections and, if necessary, to mechanically fix the phase connections. However, this additional radial installation space is only required at one point on the motor circumference in the motor design presented here.

[0066] The annular space in which the power supply system and its connection points are housed is only closed radially outwardly when the axial flux machine 1 is mounted in the motor housing 23. This makes all connection points of the power supply system very easily accessible during the assembly process of the axial flux machine 1. This simplifies assembly and enables welding or soldering processes suitable for large-scale production. The annular space in which the power supply system is housed is sealed by seals (e.g. O-rings) between the stator 4 and the motor housing 23. This prevents the ingress of dirt or moisture and also offers the possibility of flooding the annular space with an intentionally introduced fluid, for example, this allows cooling of the electrical conductors.

[0067] Instead of arranging the phase connections 28 of the high-voltage terminal 7 at a point on the motor circumference radially outside the otherwise cylindrical motor installation space, as shown in the figures, the phase connections 28 can alternatively be arranged at a point on the circumference axially (or axially and radially) outside the otherwise cylindrical motor installation space. Axially offset phase connections 28 can then be positioned, for example, on the same radius as the busbars 8, 18 on the front side of the axial flux machine 1. In other words, deviating from Figure 4 or Figure 5, the phase connections 28 can alternatively also be led out of the axial flux machine 1 axially and / or radially outside the stator geometry. This embodiment can be advantageous depending on the installation space integration of the axial flux machine 1.The three phase connections 28 can also be positioned distributed around the periphery of the axial flux machine 1 instead of in close proximity to each other.

[0068] Figure 4 shows the coils 5, 25 of an axial flux machine 1 together with a few neighboring components in a correspondingly cut-out perspective view. In order to at least partially recognize the busbars 8, 18, the two insulating bodies 19, which actually enclose each current-carrying busbar along its entire circumferential length, have been removed over part of the circumference in the front part of the figures. In the exemplary embodiment shown here, it can be seen that the width of the busbars 8, 18 is gradually reduced the further the areas of the busbars 8, 18 are from the phase connection 28 of the electric axial flux machine 1. Since the electrical current introduced into the busbar 8, 18 from the phase connection 28 is distributed among the coils 5, 25 connected to the busbar 8, 18, the current to be transmitted by the base body of the busbar 8, 18 becomes increasingly lower the more coils 5, 25 have already been supplied with current.Figure 4 shows that, if one imagines the current introduced into the busbar 8,18 from the phase connection 28 to the last coil 5,25 connected at the end of the busbar 8,18, the width of the busbar 8,18 becomes narrower after each connecting lug 24 of the busbar 8,18, via which another coil 5,25 is connected. Since less current needs to be transmitted through the busbar 8,18 after each connecting lug 24, a smaller conductor cross-section is also required. Reducing the cross-section of the busbar 8,18 saves material and reduces weight and costs.

[0069] Figures 4-5 show the phase connections 28 of the axial flux machine 1 on the high-voltage terminal 7. The high-voltage terminal 7 is positioned radially above the busbars 8, 18. Each of the three busbars 8, 18 is connected to a power connection bolt 30 by a connecting tab 29. The three power connection bolts 30 are mechanically connected to the remaining motor components via a common base 31. The base 31 mechanically fixes the power connection bolts 30 and electrically insulates the power connection bolts 30. The base 31 also ensures the required clearance and creepage distances both between the power connection bolts 30 and between the power connection bolts 30 and the electrically conductive stator or housing components. In this exemplary embodiment, the power connection bolts 30 have flattened areas with a threaded hole to which an electrical conductor can be screwed.

[0070] What can also be seen from Figure 4 is that the first busbars 8 and the second busbars 18 are connected to the common high-voltage terminal 7. The busbars 8, 18 are accommodated at least in sections in an annular or ring-segment-shaped insulating body 19, wherein the insulating body 19 has an E-shaped contour in cross-section with two radially spaced-apart, one-sidedly open grooves 20, 21 in which the busbars 8, 18 are accommodated.

[0071] The connecting tabs 29, which connect the busbars 8, 18 to the connecting bolts 30, are intentionally thin and angled in several directions in this embodiment. This allows relative positional deviations and / or slight relative movements and / or axial movements, which may arise, for example, due to component tolerances, elastic component deformations, or thermal expansion between the busbars 8, 18 and the power connection bolts 30, to be compensated for by deformation (preferably elastic deformation) of the connecting tabs 29.This compensating capacity of the connecting plates 29 is particularly useful in the motor concept shown, since the stator 4 of this axial flux machine 1 is bolted radially to a side wall of the housing 23 on one axial side of the motor near the shaft bearings, and the base 31 of the power connection bolts 30 is connected to the housing 23 radially outside the rotor 17 and radially outside the busbars 8, 18. Due to the distant attachment points of the stator 4, which also includes the busbars 8, 18, and the power connection bolts 30, positional inaccuracies during assembly or positional changes during operation of the axial flux machine 1 between the busbars 8, 18 and the power connection bolts 30 are very likely.

[0072] Figures 4-5 also show that all electrical conductors that supply the stator coils 5, 25 with current are arranged radially outside the stator coils 5, 25. Due to the described design principle and the wiring concept, no electrical conductors are required to supply the stator coils 5, 25 in the radial region between the rotational axis of the axial flux machine 1 and the stator coils 5, 25. In the radial region between the radial inner region and the radial outer region of the stator coils 5, 25, no electrical connections are required between the stator coils 5, 25. This is because the stator coils 5, 25 are wound in two layers, with several turns running axially in front of one another in a first winding layer.

[0073] At the end of this first winding layer, the wire is pulled radially outwards slightly so that a second winding layer can be wound on the outside around the first winding layer. In this second winding layer, the wire is wound axially back to the beginning of the first winding layer. Therefore, both coil ends 9, 10 of a stator coil 5, 25 are located axially on one side of the corresponding stator coil. By arranging both coil ends 9, 10 of the stator coils 5, 25 radially outwards on the same axial side in the exemplary embodiment, the path that the wires at the coil ends 9, 10 have to travel to reach the busbars 8, 18 is very short. This simplifies assembly, saves material (e.g. copper) and requires only a small amount of installation space. All of the other features described, such as the fact that no electrical conductors are required radially inwards or tangentially between the stator coils 5, 25, enable an axial flux machine 1 with a very compact axial design.No axial space needs to be provided for electrical conductors that supply the coils with power, and the mechanical and magnetic structure of the stator is not weakened radially inward by openings, recesses, free spaces or channels for electrical conductors that supply the coils.

[0074] Figure 5 shows an arrangement of five coil pairs with their busbars 8, 18 and phase terminals 28. All of the electrical conductors and their connection points described in Figure 4 are clearly visible in Figure 5. Figure 5 also clearly illustrates the wiring principle of the axial flux machine 1 shown. The electrical axial flux machine 1 is supplied with power via the three phase terminals 28. The current flow from one phase terminal 28 is described below. Since this is a three-phase system, the current naturally does not flow solely via one phase terminal 28.

[0075] It can also be clearly seen from Figure 5 that the stator coils 5, 25 each have a first coil end 9 and a second coil end 10, wherein the first coil end 9 has a radially extending section 11 and an axially extending section 12, and the axially extending section 12 electrically contacts one of the busbars 8, 18 and the second coil end 10 has a radially extending section 13 and an axially extending section 14, and the axially extending section 14 electrically contacts the star point busbar.

[0076] The current flows from one of the three power connection bolts 30 into the connected busbar 8, 18 and is then divided into the pairs of stator coils 5, 25 connected to this busbar 8, 18. The current flows partially via one of the connecting tabs 24 of the busbar 8, 18 into a connecting wire (coil input) of one of the coils 25 shown on the right. In the illustrated embodiment, the coil inputs are the wires arranged off-center relative to the coil body. The current then flows through the turns of the stator coil 25 to the coil output wire (centrally arranged wire). The coil output wire of the first stator coil 25 of the coil pair (coil on the right) is connected to the coil input wire (centrally arranged wire) of the left stator coil 5.The current thus flows into the second stator coil 5 of the series-connected coil pair and then flows through its windings to the coil output wire (off-center wire), which is connected to the star-point busbar. From the star-point busbar, the current flows back to the two other phase terminals 28 of the axial flux machine 1. The current flows back from the star-point busbar through stator coils 5, 25, which are connected to the other phase terminals 28. Since the wiring principle of all stator coils 5, 25 is comparable, the current flows through these stator coils 5, 25, as just described, only in the opposite direction, thus passing through the aforementioned elements in reverse order.

[0077] Because the stator coils 5, 25 of a coil pair are connected by their wires exiting the center of the coil body, and the busbars 8, 18 are designed so that the wires branching off-center from the coil bodies always meet the correct connecting lug of the respective current-carrying busbar 8, 18, all stator coils 5, 25 can be identical in construction. This applies not only to the external shape of the stator coils 5, 25, but also to the winding direction of the stator coils 5, 25.

[0078] Figures 4-5 describe how a power supply system consisting of a star point busbar and three busbars (current phase II, current phase V and current phase W) can supply power to all stator coils 5, 25, which are each connected in series to form a coil pair. Alternatively, it is also possible to dispense with the series connection of the opposite stator coils 5, 25. This is also possible using a power supply system consisting of a star point busbar and three busbars (current phase II, current phase V and current phase W). Each stator coil 5, 25 is then directly connected to one of the busbars 8, 18 and the other end of the stator coil 5, 25 is then connected to the star point ring. Alternatively, two star point rings can also be used, so that one star point ring supplies all stator coils 5, 25 of one stator half orof one stator body 15,16 and the other star point ring then connects all stator coils 5,25 of the other stator half or the other stator body 15,16.

[0079] Another alternative power supply system can be formed from two star-point busbars and six busbars. Each stator half or stator body 15, 16 then has its own power supply system consisting of one star-point busbar and three busbars. The two power supply systems can use the same three phase connections, or each power supply system can be equipped with three phase connections. Each stator coil is then always connected on one side to a busbar of its stator half or stator body 15, 16 and on the other end to the star-point busbar of its stator half or stator body 15, 16.

[0080] In all of the described connection variants, the star point busbar can always be replaced by several connecting elements, each of which electrically connects the coil outputs of a coil connected to phase U, one to phase V, and one to phase W. With these alternative connection variants, the power supply systems can also be arranged radially outside the rotor 17. For example, by using insulating bodies with an increased number of slots, more current-carrying bars can be arranged in the annular space radially outside the rotor 17. In principle, a delta connection can also be used as an alternative. In this case, the star point busbar is omitted. The coils are then connected at both ends to a different current busbar (two different current phases). Alternatively, each stator half orFor each stator body 15,16, a separate annular space can also be arranged radially outside the rotor 17 or radially outside the stator coils 5,25 of the respective stator half or the respective stator body 15,16.

[0081] The invention is not limited to the embodiments illustrated in the figures. The above description is therefore not to be considered restrictive, but rather explanatory. The following claims are to be understood in such a way that a stated feature is present in at least one embodiment of the invention. This does not exclude the presence of further features. Where the claims and the above description define 'first' and 'second' features, this designation serves to distinguish between two similar features without establishing a priority.

[0082] The terms “radial”, “axial”, “tangential” and “circumferential direction” used in this application always refer to the axis of rotation of the axial flow machine 1.

[0083] List of reference symbols

[0084] 1 axial flux machine

[0085] 2 Drivetrain

[0086] 3 motor vehicles

[0087] 4 Stator

[0088] 5 stator coils

[0089] 6 Power electronics

[0090] 7 High-voltage terminal

[0091] 8 busbars

[0092] 9 Coil end

[0093] 10 coil ends

[0094] Section 11

[0095] Section 12

[0096] Section 13

[0097] Section 14

[0098] 15 Stator body

[0099] 16 stator bodies

[0100] 17 Rotor

[0101] 18 busbars

[0102] 19 Insulating body

[0103] 20 grooves

[0104] 21 grooves

[0105] 22 Rotor shaft

[0106] 23 housings

[0107] 24 connecting straps

[0108] 25 stator coils

[0109] 26 Insulating insert

[0110] 27 Stator casing

[0111] 28 phase connections

[0112] 29 Connecting tab

[0113] 30 power connection bolts

[0114] 31 bases

Claims

Claims Electric axial flux machine (1) , in particular for a drive train (2) of a hybrid or fully electric motor vehicle (3), comprising a stator (4) with a plurality of stator coils (5) distributed over the circumference of the stator (4) and power electronics (6) for supplying current to the stator coils (5) and a high-voltage terminal (7) for establishing an electrical connection between the stator coils (5) and the power electronics (6), characterized in that busbars (8) are arranged radially above the stator coils (5), which enclose the stator (4) and / or a rotor (17) rotatable relative to the stator (4) in a ring-shaped manner and connect the stator coils (5) electrically to the high-voltage terminal (7).Axial flux machine (1 ) according to claim 1 , characterized in that the high-voltage terminal (7) is positioned radially above the busbars (8) Axial flux machine (1 ) according to one of the preceding claims, characterized in that the rotor (4) of the axial flux machine (1 ) has a first disk-shaped stator body (15) and a second disk-shaped stator body (16) axially spaced from it and a rotor (17) is arranged axially between the first stator body (15) and the second stator body (16). wherein the first stator body (15) has a plurality of first stator coils (5) distributed over the circumference of the first stator body (15) and the second stator body (16) has a plurality of second stator coils (25) distributed over the circumference of the second stator body (16), and first busbars (8) are arranged radially above the first stator coils (5), which enclose the first stator body (15) in an annular manner and electrically connect the first stator coils (5) and / or the second stator coils (25) to the high-voltage terminal (7), and second busbars (18) are arranged radially above the second stator coils (25), which enclose the second stator body (15) and / or the rotor (17) in an annular manner and electrically connect the first stator coils (5) and / or the second stator coils (25) to the high-voltage terminal (7).An axial flux machine (1) according to one of the preceding claims, characterized in that the stator coils (5) each have a first coil end (9) and a second coil end (10), wherein the first coil end (9) has a radially extending section (11) and an axially extending section (12), and the axially extending section (12) electrically contacts one of the busbars (8, 18) or another coil, and / or the second coil end (10) has a radially extending section (13) and an axially extending section (14), and the axially extending section (14) electrically contacts one of the busbars (8, 18) or another coil or a star point busbar. An axial flux machine (1) according to one of the preceding claims. characterized in that the stator coils (5,25) are essentially identical.

6. Axial flux machine (1 ) according to one of the preceding claims, characterized in that the first busbars (8) and the second busbars (18) are essentially identical.

7. Axial flux machine (1 ) according to one of the preceding claims, characterized in that the first busbars (8) and the second busbars (18) are connected to the common high-voltage terminal (7).

8. Axial flux machine (1 ) according to one of the preceding claims, characterized in that the busbars (8,18) and / or the star point busbar are at least partially enclosed in an annular or annular segment-shaped insulating body (19).

9. Axial flux machine (1 ) according to one of the preceding claims, characterized in that the insulating body (19) has an E-shaped contour in cross-section with two radially spaced, one-sided open grooves (20, 21 ) in which the busbars (8, 18) are received.

10. Axial flux machine (1 ) according to one of the preceding claims, characterized in that a pair of coils (5, 25) arranged on opposite sides of the rotor is electrically connected in series.

Images