DE102023201124A1 - Electric machine, electric axle drive, motor vehicle and method for operating an electric machine - Google Patents

Abstract

An electric machine (100) for a motor vehicle has a stator (105) mounted in a rotationally fixed manner, an inner rotor (110) mounted so as to be rotatable relative to the stator (105), and an outer rotor (115) mounted so as to be rotatable relative to the stator (105). The stator (105) is arranged or can be arranged between the inner rotor (110) and the outer rotor (115).

Description

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

Electric machines with permanently excited or separately excited rotors are known. Gearboxes with multiple gears are also known in order to be able to achieve high top speeds, i.e. high rotational speeds, for example.

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

The advantages that can be achieved with the approach presented here are in particular that an electrical machine can be created that has or enables a high level of efficiency and a high power density.

An electric machine for a motor vehicle has a stator mounted in a rotationally fixed manner, an inner rotor mounted so as to rotate relative to the stator, and an outer rotor mounted so as to rotate relative to the stator. The stator is arranged or can be arranged between the inner rotor and the outer rotor.

The electric machine can drive a motor vehicle, for example, whereby the motor vehicle can be designed as an electrically operated motor vehicle. The motor vehicle can be, for example, a passenger car, truck, bus, work machine or the like. Rotationally fixed can refer to the electric machine as a reference system. The inner rotor and the outer rotor can each be a movable, rotating part of the electric machine. The stator can be a fixed, immovable part of the electric machine.

The approach presented here describes two nested rotors, which can also be referred to as electric machines, which have a common stator. The electric machine can therefore be understood as a rotor-controlled electric machine. This means that components can be saved and a compact arrangement of the inner rotor and the outer rotor can be made possible because not all components are duplicated. Furthermore, costs can be saved because only one stator can be used for both rotors. The approach presented here can therefore also be understood or referred to as a nested electric machine or as two nested electric machines or as nested electric machines with only one stator. The approach presented here can enable different torques as well as different speeds of the rotors and different efficiency maps. Furthermore, a two-speed transmission can be enabled for reliable efficiency and performance.

The stator can have at least one permanent magnet, which can be designed to generate a permanent magnetic field for permanent magnet excitation of the electrical machine. The permanent magnet can be a permanent magnet that can generate the permanent magnetic field independently of current supply. In addition, the stator can have a plurality of permanent magnets. Permanent magnets each have a north pole and a south pole. Magnetic north poles can be areas from which field lines emerge. Areas in which the field lines enter are referred to as south poles. Due to the permanent magnet excitation, the electrical machine can be designed at least partially as a permanently excited synchronous machine.

Additionally or alternatively, the stator can have at least one coil, which can be designed to generate a stator magnetic field for static excitation of the electrical machine when the coil is energized. The coil can be an electrical component that has windings to generate the magnetic field when current flows. If the coil is not energized, the magnetic field cannot have an effect. In addition, the stator can have a plurality of coils. Due to the static excitation, the electrical machine can be designed at least partially as a separately excited synchronous machine.

The electric machine can have an external output connection that can be or can be coupled to the external rotor. In addition, the electric machine can have an internal output connection that can be or can be coupled to the internal rotor. In particular, the external and additionally or alternatively the internal output connection can be designed as a shaft or a gear. This enables the electric machine to function reliably.

The inner rotor and the outer rotor can be mounted around a common axis of rotation. Additionally or alternatively, the inner rotor and the outer rotor can be formed cylindrically around the stator. This enables the electrical machine to function reliably.

The stator can be designed to form a magnetic field axially and additionally or alternatively parallel to the axis of rotation of the inner rotor and additionally or alternatively of the outer rotor. As a result, the electrical machine can be designed as an axial flux motor. An axial flux motor can have a reduced material requirement for copper and iron, which means it can be manufactured cost-effectively. In addition, the axial flux motor can have a high power density and a high torque density.

The electric machine can have at least one additional rotor that can be mounted so as to be rotatable relative to the stator. The additional rotor can be arranged or can be arranged outside the outer rotor, between the outer rotor and the inner rotor, or inside the inner rotor. This enables the electric machine to function reliably.

The electric machine can have a control unit that can be designed to impress a current through the inner rotor independently of a current through the outer rotor. For example, an alternating current can be impressed. This enables the electric machine to function reliably.

The control unit can be designed to impress a current into the inner rotor and into the outer rotor in such a way that the inner rotor can rotate at a speed and additionally or alternatively a direction of rotation that can differ from a speed and additionally or alternatively a direction of rotation of the outer rotor. This makes it possible to have different operating modes for the rotors, which can enable the electrical machine to function advantageously.

An electric axle drive for a motor vehicle has an embodiment of an electric machine mentioned herein. Optionally, the electric axle drive has a transmission device and a power converter. The power converter can be designed as a power converter 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.

A motor vehicle has an embodiment of an electric axle drive mentioned here and additionally or alternatively an embodiment of an electric machine mentioned here. The motor vehicle can be designed as an electrically operated motor vehicle. The motor vehicle can be, for example, a passenger car, truck, bus, work machine or the like. The advantages of the approach described here can also be implemented very efficiently by such an embodiment.

The motor vehicle can have an internal combustion engine that can be or can be mechanically connected to the outer rotor or the inner rotor. Thus, mechanical energy can be converted into electrical energy.

A method for operating an embodiment of an electric machine mentioned herein comprises a step of applying a first current to the inner rotor and a second current to the outer rotor, wherein the first current differs from the second current in strength and additionally or alternatively in time. The advantages of the approach described here can also be implemented very efficiently by such an embodiment.

The approach presented here also creates a control unit that is designed to carry out, control or implement the step of a variant of a method presented here in a corresponding device. This embodiment of the invention in the form of a control unit can also solve the problem underlying the invention quickly and efficiently.

A control unit can be an electrical device that processes electrical signals, for example sensor signals, and outputs control signals depending on them. The control unit can have one or more suitable interfaces, which can be designed as hardware and/or software. In a hardware design, the interfaces can, for example, be part of an integrated circuit in which the functions of the control unit are implemented. The interfaces can also be their own integrated circuits or at least partially consist of discrete components. In a software design, the interfaces can be software modules that are present, for example, on a microcontroller alongside other software modules.

Also advantageous is a computer program product with program code which can be stored on a machine-readable medium such as a semiconductor memory, a hard disk memory or an optical memory and is used to carry out the method according to one of the embodiments described above when the program is executed on a computer or a control unit.

• 1 eine schematische Schnittdarstellung eines Ausführungsbeispiels einer elektrischen Maschine;
• 2 eine schematische Schnittdarstellung eines Ausführungsbeispiels einer elektrischen Maschine;
• 3 eine schematische Schnittdarstellung eines Ausführungsbeispiels einer elektrischen Maschine;
• 4 eine schematische Darstellung eines Ausführungsbeispiels einer elektrischen Maschine;
• 5 eine schematische Darstellung eines Ausführungsbeispiels eines Kraftfahrzeugs, in dem ein hier vorgestellter Ansatz verwendet wird;
• 6 ein schematisches Ablaufdiagramme eines Ausführungsbeispiels eines Verfahrens zum Betreiben einer elektrischen Maschine; und
• 7 ein schematisches Blockschaltbild eines Ausführungsbeispiels einer Steuereinheit zum Betreiben einer elektrischen Maschine.

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

• 1 a schematic sectional view of an embodiment of an electrical machine;
• 2 a schematic sectional view of an embodiment of an electrical machine;
• 3 a schematic sectional view of an embodiment of an electrical machine;
• 4 a schematic representation of an embodiment of an electrical machine;
• 5 a schematic representation of an embodiment of a motor vehicle in which an approach presented here is used;
• 6 a schematic flow diagram of an embodiment of a method for operating an electrical machine; and
• 7 a schematic block diagram of an embodiment of a control unit for operating an electrical machine.

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 sectional view of an embodiment of an electric machine 100. The electric machine 100 is designed, for example, to drive an electrically powered motor vehicle.

The electric machine 100 has a stator 105, an inner rotor 110 and an outer rotor 115. The stator 105 is mounted in a rotationally fixed manner between the inner rotor 110 and the outer rotor 115, wherein the inner rotor 110 and the outer rotor 115 are mounted rotatably relative to the stator 105.

According to one embodiment, the electric machine 100 has an outer output connection 140, which can also be referred to as output two, and an inner output connection 145, which can also be referred to as output one. The output connections 140, 145 are shown merely as examples in the 1 as a surface to which a shaft can be flanged. Alternatively, the output connections 140, 145 are each formed as a gear that meshes with a gear of a corresponding output shaft, such an embodiment in the 1 is not shown in more detail. The outer output connection 140 is coupled or can be coupled to the outer rotor 115, for example, and the inner output connection 145 is coupled or can be coupled to the inner rotor 110, for example. The inner output connection 145 is arranged centrally in the electrical machine 100, merely as an example. Furthermore, the electrical machine 100 has, merely as an example, a ground connection 155, which is coupled to the stator 105 and defines a reference potential.

According to one embodiment, the electric machine 100 has a control unit 150. The control unit 150 is designed, for example, to impress a current flow through the inner rotor 110, the outer rotor 115 and/or the stator 105. For this purpose, the control unit 150 is connected to the inner rotor 110, the outer rotor 115 and/or the stator 105 via a line (or a pair of lines). After the stator 105 is subjected to a defined current flow, the stator 105 forms a magnetic field corresponding to this current flow. If, for example, current is now impressed into the inner rotor 110 and/or the outer rotor 115, this current flow also results in a magnetic field in the inner rotor 110 or outer rotor 115, which interacts with the magnetic field formed by the current flow through the stator 105. In this case, a different current can be impressed into the inner rotor 110 than into the outer rotor 115, whereby the inner rotor 110 rotates at a speed and/or in a direction of rotation that differs from the speed and/or direction of rotation of the outer rotor 115. In other words, in an operating state of the electrical machine 100, the outer rotor 115 and the inner rotor 110 rotate relative to the stator 105, which is rotationally fixed. The rotors 110, 115 rotate in the same or opposite directions, depending on the impressed current flow through the inner rotor 110 or outer rotor 115. Alternatively, a current flow can also be impressed through only one of the rotors 110, 115, so that then only this one rotor 110, 115 rotates. More precisely, the inner rotor 110 and the outer rotor 115 can be operated in nine different operating modes. In a first operating mode, both rotors 110 rotate, 115 clockwise, wherein in a second operating mode the inner rotor 110 rotates clockwise and the outer rotor 115 rotates anti-clockwise. In a third operating mode the inner rotor 110 rotates clockwise, wherein the outer rotor 115 does not rotate. In a fourth operating mode the inner rotor 110 rotates anti-clockwise and the outer rotor 115 rotates clockwise. The rotors 110, 115 rotate anti-clockwise in a fifth operating mode, wherein in a sixth operating mode the inner rotor 110 rotates anti-clockwise and the outer rotor 115 does not rotate. In a seventh operating mode the inner rotor 110 does not rotate, wherein the outer rotor 115 rotates clockwise. In an eighth operating mode the inner rotor 110 also does not rotate, wherein the outer rotor 115 rotates anti-clockwise. In a ninth operating mode, both rotors 110, 115 do not rotate.

The stator 105 is, for example, statically connected to a housing of the drive and is supplied with direct current and/or with current by means of permanent magnets. In other words, the stator 105 has, for example, a constant magnetic field. For this purpose, the stator 105 according to the embodiment shown here has a plurality of coils 120 and/or permanent magnets 125, which are merely exemplary in the form of a rod. Optionally, the coils 120 and the permanent magnets 125 are arranged alternately on the stator 105, for example spaced apart from one another along a circumference of the stator 105. The at least one permanent magnet 125 is designed, for example, to generate a permanent magnetic field independently of current supply. The coil 120 is designed to generate a stator magnetic field when current is supplied to the coil 120. The permanent magnetic field and the stator magnetic field interact, for example. Thus, the electric machine 100 is at least partially designed as a permanently excited synchronous machine and/or at least partially as an externally excited synchronous machine.

According to one embodiment, an air gap 130 is arranged between the inner rotor 110 and the stator 105 and a further air gap 135 is arranged between the outer rotor 115 and the stator 105. The air gaps 130, 135 are designed, for example, to guide a magnetic flux of the permanent magnetic field generated by the permanent magnet 125 and/or a magnetic flux of the stator magnetic field generated by the coil 120.

In other words, the stator 105 is arranged such that the inner rotor 110, which can also be referred to as rotor one or inner rotor, is arranged inside and the outer rotor 115, which can also be referred to as rotor two or outer rotor, is arranged outside. These rotors 110, 115 are excited, for example, with alternating current, which can also be referred to as AC current. The inner rotor 110, which can also be referred to as a rotor-controlled machine or machine one, therefore rotates inside and the outer rotor 115, which can also be referred to as a rotor-controlled machine or machine two, rotates outside. The two rotors 110, 115 can be operated in nine operating states and can be used either to drive a vehicle or for recuperation. The electric machine 100 has an advantageous compact arrangement and the elimination of an additional stator, since the rotors 110, 115 use the stator 105 together.

gilt. Somit ist es möglich ein Fahrzeug mit zwei Gängen zu betreiben. Der Außenrotor 115 mit hohem Drehmoment wird dann zum Anfahren verwendet, zum Beispiel Hängerbetrieb, und der Innenrotor 110 wird verwendet, um besonders schnell zu fahren. Alternativ sind die Rotoren 110, 115 mit unterschiedlich übersetzten Getrieben verbindbar, so dass eine Rotor-Getriebe-Kombination besonders energieeffizient im niedrigen Drehzahlbereich, zum Beispiel in der Stadt, ist und die andere Rotor-Getriebe-Kombination besonders energieeffizient im hohen Drehzahlbereich, zum Beispiel auf der Autobahn, ist. Die Anordnung ist besonders kompakt und kostengünstig durch den gemeinsam verwendeten Stator 105.In an operational state, the inner rotor 110 can be operated at high speed due to its small diameter, for example. The outer rotor 115 can be operated at high torque due to its large diameter, for example, where the formula $\overrightarrow{M}=\overrightarrow{r}\times \overrightarrow{F}$

applies. This makes it possible to operate a vehicle with two gears. The outer rotor 115 with high torque is then used for starting, for example when towing a trailer, and the inner rotor 110 is used to drive particularly fast. Alternatively, the rotors 110, 115 can be connected to gears with different ratios, so that one rotor-gear combination is particularly energy-efficient in the low speed range, for example in the city, and the other rotor-gear combination is particularly energy-efficient in the high speed range, for example on the highway. The arrangement is particularly compact and cost-effective due to the shared stator 105.

According to one embodiment, the inner rotor 110 or the outer rotor 115 can be used to drive an axle of a commercial vehicle. The inner rotor 110 or the outer rotor 115 can in turn be used as a power take-off to drive various devices on a commercial vehicle. This arrangement is advantageously very compact, and the drive machine can be operated independently of the power take-off machine.

According to an alternative embodiment, the electric machine 100 has at least one additional rotor that can be arranged on the stator 105. The additional rotor can be mounted or supported so as to be rotatable relative to the stator 105, for example. The additional rotor can be arranged outside the outer rotor 115, between the outer rotor 115 and the inner rotor 110, or inside the inner rotor 110.

2 shows a schematic sectional view of an embodiment of an electrical electrical machine 100. The electrical machine 100 is similar or corresponds to a part of the electrical machine from 1 with the exception that the outer rotor is omitted.

3 shows a schematic sectional view of an embodiment of an electrical machine 100. The electrical machine 100 is similar or corresponds to a part of the electrical machine from 1 with the exception that the inner rotor with the inner output connection 145 is omitted.

4 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 additional wheels 400, 405 of a motor vehicle are shown.

For example, the inner output connection 145 of the inner rotor 110 is connected to the wheel 400, which can also be referred to as the left wheel. The outer output connection 140 of the outer rotor 115 is connected to the other wheel 405, which can be the right wheel, or vice versa. This makes it possible to implement a torque vectoring drive on an axle, in which a different torque is applied to different wheels on an axle. The advantage of this arrangement is the particular compactness due to the nested rotors 110, 115.

5 shows a schematic representation of an embodiment of a motor vehicle 500 in which a variant of an approach presented here is used. The motor vehicle 500 has an electric machine 100, as described by way of example in the previous figures.

Wheels 400, 405, four wheels only as an example, an electrical energy storage device 510, for example a battery, and an electrical axle drive 515 are shown for the motor vehicle 500. The electrical axle drive 515 comprises a power converter 520, an electrical machine 100 and a transmission device 530.

Electrical energy for operating the electric machine 100 is provided by an energy supply device, here the electrical energy storage device 510. The electrical energy storage device 510 is designed to provide direct current, which is converted into an alternating current, for example a three-phase alternating current, using a power converter 520 of the electric axle drive 515 and is provided to the electric machine 100. A shaft driven by the electric machine 100 is coupled to at least one wheel 400, 405 of the motor vehicle 500 directly or using the transmission device 530. The motor vehicle 500 can thus be moved using the electric machine 100. According to one embodiment, the electric axle drive 515 comprises a housing in which the power converter 520, the electric machine 100 and the transmission device 530 are arranged.

According to one embodiment, the motor vehicle 500 has an internal combustion engine 525, which is connected to the outer rotor or the inner rotor of the electric machine 100 and/or the transmission device 530, which in 5 not shown, is mechanically connected or connectable. In other words, the internal combustion engine 525 can be operated in a stationary manner. A rotor of the electric machine 100 is mechanically driven by the internal combustion engine 525 and thereby generates electricity, which is generated by recuperation and is available in the motor vehicle 500, for example to charge the battery or the electrical energy storage device 510, or to operate another of the rotors of the electric machine 100. One of the rotors is therefore used to convert mechanical energy into electrical energy, the other rotor is then used, for example, to propel the vehicle. The advantage of this arrangement is its particular compactness and low costs due to the omission of an additional stator.

6 shows a flow chart of an embodiment of a method 600 for operating an electrical machine. The electrical machine corresponds to or is similar to the electrical machine from one of the figures described here.

The method 600 includes a step 605 of applying a first current to the inner rotor and a second current to the outer rotor. The first current differs from the second current in terms of strength and/or time course.

7 shows a block diagram of an embodiment of a control unit 150 for operating an electrical machine. The control unit 150 is similar, for example, to the control unit from 1 . The control unit 150 is designed to carry out the method 6 or to carry out and/or control a similar process.

The control unit 150 has a unit 700 for applying a first current to the inner rotor and a second current to the outer rotor. The unit 700 for applying is designed to carry out and/or control the step of applying pressure.

The embodiments described and shown in the figures are selected only as examples. Different embodiments can be combined with each other completely or with regard to individual features. An embodiment can also be supplemented by features of another embodiment.

Furthermore, method steps according to the invention can be repeated and carried out in a different order than that described.

If an embodiment includes an “and/or” link between a first feature and a second feature, this can be read as meaning that the embodiment according to one embodiment has both the first feature and the second feature and according to another embodiment has either only the first feature or only the second feature.

Reference symbols

100

electric machine

105

stator

110

Inner rotor

115

Outer rotor

120

Sink

125

Permanent magnet

130

Air gap

135

further air gap

140

external output connection

145

internal output connection

150

Control unit for operating the electrical machine

155

Earth connection

400

wheel

405

another wheel

500

Motor vehicle

510

electrical energy storage

515

electric axle drive

520

Power converter

525

Combustion engine

530

Gearbox device

600

Method for operating an electrical machine

605

Step of loading

705

Unit for applying

Claims (15)

Electric machine (100) for a motor vehicle (500), wherein the electric machine (100) has the following features: a stator (105) mounted in a rotationally fixed manner; an inner rotor (110) mounted rotatably relative to the stator (105); and an outer rotor (115) mounted rotatably relative to the stator (105), wherein the stator (105) is arranged or can be arranged between the inner rotor (110) and the outer rotor (115). Electrical machine (100) according to Claim 1 , wherein the stator (105) has at least one permanent magnet (125) which is designed to generate a permanent magnetic field for a permanent magnet excitation of the electrical machine (100). Electric machine (100) according to one of the preceding claims, wherein the stator (105) has at least one coil (120) which is designed to generate a stator magnetic field for static excitation of the electric machine (100) when the coil (120) is energized. Electric machine (100) according to one of the preceding claims, with an outer output connection (140) which is or can be coupled to the outer rotor (115) and with an inner output connection (145) which is or can be coupled to the inner rotor (110), in particular wherein the outer and/or the inner output connection (140, 145) are designed as a shaft or a gear. Electric machine (100) according to one of the preceding claims, wherein the inner rotor (110) and the outer rotor (115) are mounted about a common axis of rotation and/or wherein the inner rotor (110) and the outer rotor (115) are formed cylindrically around the stator (105). Electric machine (100) according to one of the preceding claims, wherein the stator (105) is designed to form a magnetic field axially and/or parallel to the axis of rotation of the inner rotor (110) and/or the outer rotor (115). Electric machine (100) according to one of the preceding claims, with at least one additional rotor which is rotatably mounted relative to the stator (105), in particular wherein the additional rotor is mounted outside the outer rotor (115), between the outer rotor (115) and the Inner rotor (110) or is arranged or can be arranged within the inner rotor (110). Electric machine (100) according to one of the preceding claims, with a control unit (150) which is designed to impress a current through the inner rotor (110) independently of a current through the outer rotor (115). Electrical machine (100) according to Claim 8 , wherein the control unit (150) is designed to impress a current into the inner rotor (110) and into the outer rotor (115) such that the inner rotor (110) rotates at a speed and/or direction of rotation that differs from a speed and/or direction of rotation of the outer rotor (115). Electric axle drive (515) for a motor vehicle (500) with an electric machine (100) according to one of the preceding Claims 1 until 9 . Motor vehicle (500) with an electric axle drive (515) according to Claim 10 and/or an electrical machine (100) according to one of the Claims 1 until 9 . Motor vehicle (500) according to Claim 11 , with an internal combustion engine (525) which is or can be mechanically connected to the outer rotor (115) or the inner rotor (110). Method (600) for operating an electrical machine (100) according to one of the Claims 1 until 9 , wherein the method (600) comprises the following step: applying (605) the inner rotor (110) with a first current and the outer rotor (115) with a second current, wherein the first current differs from the second current in strength and/or temporal progression. Control unit (150) which is designed to carry out the step (605) of the method (600) according to Claim 13 to be executed and/or controlled in a corresponding unit (705). Computer program product with program code for carrying out the method (600) according to Claim 13 when the computer program product is executed on a control unit (150).

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