Rotor assembly, electric machine, method for controlling a rotor assembly, computer program product and control unit

Abstract

Rotor arrangement (1) for an electric machine (2) of a drive train (3) of a motor vehicle (4) comprising • a rotor (5) with a rotor body (6) which is arranged non-rotatably on a rotor shaft (7), • a cooling circuit (8) which runs section by section through the rotor (5), wherein the cooling circuit (8) in the rotor body (6) has a plurality of circumferentially distributed rotor cooling channels (9) extending in the axial direction through the rotor body (6), • a coolant pump (10) arranged in the cooling circuit (8), which pumps a coolant fluid (11) through the cooling circuit (8), as well as • a control unit (12) for controlling the coolant pump (10), where the control unit (12) is configured, a) to bring the coolant pump (10) into a first pumping state (14) upon the presence of a first start-up signal (13) before and / or during the rotation of the rotor (5) from standstill into a first pumping state, through which the rotor cooling channels (5) are flooded with the cooling fluid (11), and characterized by the fact that the control unit (12) is configured, b) to cause heating of the rotor body (6) when a second start-up signal (13) is present before and / or when the rotor (5) is turned up from standstill, and c) to put the coolant pump (10) into a second pumping state (16) upon the presence of a first discharge signal (15) before and / or when the rotor (5) is turned down to standstill, by which the rotor cooling channels (5) are emptied of the cooling fluid (11) by centrifugal force and / or gravity, and d) to put the coolant pump (10) into a third pumping state (18) when a second discharge signal (17) is present before and / or when the rotor (5) is turned down to standstill, by which the rotor cooling channels (5) are emptied of the cooling fluid (11) by means of the coolant pump (10).

Description

[0001] The present invention relates to a rotor arrangement for an electric machine of a drive train of a motor vehicle, comprising a rotor with a rotor body that is arranged in a rotationally fixed manner on a rotor shaft, a cooling circuit that runs sectionally through the rotor, wherein the cooling circuit has a plurality of rotor cooling channels in the rotor body that are arranged circumferentially and extend in the axial direction through the rotor body, a coolant pump arranged in the cooling circuit that pumps a cooling fluid through the cooling circuit, and a control unit for controlling the coolant pump. The invention further relates to an electric machine, a method for controlling a rotor arrangement, a computer program product, and a control unit.

[0002] 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.

[0003] A detailed description of an electric drive can be found in an article in the magazine ATZ, Volume 113, May 2011, pages 360-365, by Erik Schneider, Frank Fickl, Bernd Cebulski, and Jens Liebold, entitled "Highly Integrated and Flexible Electric Drive Unit for Electric Vehicles." Such drive units are also referred to as e-axles or electrically operated drivetrains.

[0004] In addition to purely electric drivetrains, hybrid drivetrains are also known. Such drivetrains in hybrid vehicles typically comprise a combination of an internal combustion engine and an electric motor, enabling purely electric operation—for example, in urban areas—while maintaining sufficient range and availability, especially for long-distance journeys. Furthermore, in certain operating situations, it is possible to use both the internal combustion engine and the electric motor simultaneously.

[0005] In the development of electric motors intended for electric axles and hybrid modules, there is a continuing need to increase their power densities, making the necessary cooling of the electric motors increasingly important. Due to the necessary cooling performance, hydraulic fluids, such as cooling oils, have become the preferred solution in most concepts for dissipating heat from the thermally stressed areas of an electric motor.

[0006] For the stators of electrical machines, for example, jacket cooling and winding head cooling are known from the state of the art for cooling electrical machines using hydraulic fluids. While jacket cooling transfers the heat generated at the outer surface of the rotor core into a cooling circuit, with winding head cooling, the heat is transferred directly to the fluid at the conductors outside the rotor core in the area of ​​the winding heads.

[0007] In addition to cooling the stators, it is also generally known that the rotors of electrical machines need to be cooled. In this case, undesirable leaks between the rotor laminations can lead to drag torque in the air gap between the rotor and stator and uncontrolled coolant loss, which is often undesirable.

[0008] In addition to such fluid-cooled rotors with a hollow shaft, air-cooled rotors are also known from the prior art, for example, with a blade wheel mounted axially on the rotor. A summary of the relevant prior art can be found, for example, in DE 10 2018 220 810 A1.

[0009] It is also known that centrifugal force can be used to guide a coolant in the rotor at speed. For example, US 11 146 133 B2 uses cooling channels with increasing pitch diameters, while DE 10 2017 112 348 A1 describes a conically expanding shaft. In these cases, the work of pumping the coolant is performed by the electric motor itself and not by an external oil pump.

[0010] A rotor arrangement according to the preamble of independent claim 1 is disclosed in US 2018 / 0 241 288 A1. For further prior art, reference is made to US 2020 / 0 350 796 A1, DE 10 2018 101 641 B3, and DE 10 2022 209 152 A1.

[0011] There is a continuing need to increase the efficiency of such hydraulically cooled rotors and thereby also the efficiency of the corresponding electric machine.

[0012] The object of the invention is therefore to provide a rotor assembly improved in this regard and an optimized electric machine. Furthermore, the object of the invention is to implement an optimized method for controlling a rotor assembly, an optimized computer program product, and an improved control unit for controlling a rotor assembly.

[0013] This object is achieved by a rotor arrangement for an electric machine of a drive train of a motor vehicle comprising a rotor with a rotor body which is arranged in a rotationally fixed manner on a rotor shaft, a cooling circuit which runs in sections through the rotor, wherein the cooling circuit in the rotor body has a plurality of rotor cooling channels which are arranged circumferentially and extend in the axial direction through the rotor body, a coolant pump which is arranged in the cooling circuit and which conveys a cooling fluid through the cooling circuit, and a control unit for controlling the coolant pump, wherein the control unit is configured a. to set the coolant pump, when a first start-up signal is present, before and / or when the rotor is rotated from standstill into a first pumping state, through which the rotor cooling channels are flooded with the cooling fluid, and b. to cause heating of the rotor body when a second start-up signal is present before and / or when the rotor is rotated from standstill, and c. to set the coolant pump to a second pumping state when a first run-out signal is present before and / or when the rotor is turned down to a standstill, by means of which the rotor cooling channels are emptied of the cooling fluid by centrifugal force and / or gravity, and d. to set the coolant pump into a third delivery state when a second run-out signal is present before and / or when the rotor is brought to a standstill, by means of which the rotor cooling channels are emptied of the cooling fluid by means of the coolant pump.

[0014] According to the invention, the coolant pump is placed into a first delivery state when a first start-up signal is present before and / or when the rotor starts spinning up from standstill, whereby the rotor cooling channels are flooded with cooling fluid. This is advantageous because in some operating states and drive train configurations the vehicle may be moving but the rotor is not actively supplied with power, for example because there is a second electric motor on a second axle or the vehicle is rolling down a hill. If the passive rotor shaft, which is permanently connected to the vehicle axle, starts rotating again after coming to a standstill and the coolant pump is switched off, this residual oil quantity, which is distributed differently in the individual rotor cooling channels, would create an imbalance.This imbalance would create significant stress on bearings and components at high speeds, which is avoided by setting the coolant pump to an initial flow state, in which the rotor cooling channels are flooded with cooling fluid. For example, before starting to rotate, the coolant pump is briefly operated at a high flow rate to fill all rotor cooling channels and compensate for any potential imbalance.

[0015] However, during extended downtimes, it is possible that a certain residual amount of cooling fluid may remain in the lowest rotor cooling channels in the direction of gravity. These extended downtimes, especially at low temperatures, can cause the coolant to change viscosity, resulting in lower flow rates and thus slower draining or refilling. To counteract this, the cooling fluid in the rotor cooling channels can be specifically heated, for example, by targeted rotor coil excitation. Heating can also occur before the vehicle starts rotating or driving off, for example, when the vehicle is unlocked or when a brake or clutch pedal is depressed.Thus, as an alternative or in addition to the delivery states of the coolant pump, the control unit can cause the rotor body to heat up when a second start-up signal is present before and / or when the rotor starts rotating from a standstill.

[0016] Alternatively or additionally, it is also possible that when an intention to stop is detected, the coolant pump is deactivated prematurely to allow the remaining oil to drain from the heat sinks. Thus, when a first coast-down signal is present before and / or when the rotor is rotated down to a standstill, the coolant pump can be placed in a second delivery state, through which the rotor cooling channels are emptied of cooling fluid by centrifugal force and / or gravity. In this second delivery state, the coolant pump is preferably deactivated and is not actively energized, meaning that it correspondingly does not pump any coolant through the cooling circuit, which can contribute to improving the overall energy efficiency of the rotor arrangement.

[0017] However, if the outlet opening of the rotor cooling channels is not located at its maximum radial outermost position, it may happen that a certain residual amount of cooling fluid remains in the rotor cooling channels, which can happen in particular if the rotor shaft comes to a standstill relatively quickly. However, in order to avoid a maximum radial outer outlet opening, since the pumping effect would be too high and the rotor cooling channels could empty themselves at high speeds, which would have a negative impact on the cooling performance, it can be provided that the coolant pump is put into a third delivery state when a second run-out signal is present before and / or when the rotor rotates down to a standstill, through which the rotor cooling channels are emptied of the cooling fluid by means of the coolant pump. This can preferably be achieved by reversing the delivery direction of the coolant pump.

[0018] In general, the shaft arrangement according to the invention also offers the possibility of demand-oriented control of the coolant pump, i.e., the rotor is preferably not continuously cooled by the energized coolant pump, thereby avoiding high losses due to the coolant pump and drag losses in the rotor bearings caused by the cooling fluid. Uniform distribution of the cooling fluid at very low coolant pump flow rates is generally difficult to achieve, which means that preferably sequential operation of the coolant pump is particularly advantageous. This ensures that the rotor cooling channels are sufficiently filled and, optionally, the rotor bearings are also supplied with cooling fluid.

[0019] A sequential control of the coolant pump by means of the control unit can be particularly advantageous, which can be configured as follows: It is conceivable that the control unit controls the coolant pump in such a way that the coolant is pumped between 2 seconds and 30 seconds after the start-up process with a minimum operating time of 3 seconds and a maximum operating time of 60 seconds.

[0020] Alternatively or additionally, it is also possible for the control unit to control the coolant pump in such a way that the coolant is delivered sequentially, with a time interval of 40 seconds to 15 minutes between two delivery intervals. Here, too, it is preferred that the maximum operating time of the coolant pump be 60 seconds.

[0021] Instead of the specified time intervals or durations, it is also possible for the coolant pump to be controlled based on load. In this case, parameters such as the coolant temperature and / or the engine load and / or the rotor speed can be determined and taken into account by the control unit.

[0022] It is particularly advantageous to determine the cooling frequency and duration using the control unit via a self-learning intelligent system (neural networks). Monitoring the necessary parameters (e.g., losses, noise, temperature) using sensors would be particularly advantageous.

[0023] During passive operation of the electric motor, theoretically no cooling is required for the rotor winding. However, at high shaft speeds, it may be useful to provide a pumping action of the coolant or lubricating fluid to ensure cooling and lubrication of the bearings and shafts.

[0024] A start-up signal can, for example, consist of one or more of the following signals selected from the group of driver door opening signals, clutch actuation signals, brake release signals, accelerator pedal actuation signals, driver seat usage signals, ignition lock actuation signals.

[0025] A coasting signal can, for example, consist of one or more of the following signals selected from the group of brake actuation signals, accelerator pedal release signals, recuperation mode activation signal.

[0026] First, the individual elements of the claimed subject matter of the invention are explained in the order of their relevance or their mention in the set of claims, and particularly preferred embodiments of the subject matter of the invention are described below.

[0027] A rotor is the rotating part of an electrical machine. The rotor includes, in particular, a rotor shaft. The rotor shaft can be hollow, which reduces weight and allows for the supply of lubricant or coolant to the rotor body.

[0028] For the purposes of the invention, a rotor body is understood to mean the rotor without the rotor shaft. The rotor body is therefore composed, in particular, of a rotor core and the permanent magnets incorporated into the pockets of the rotor core or fixed circumferentially to the rotor core, as well as any axial cover parts for closing the pockets.

[0029] The rotor preferably has a plurality of rotor bodies. Particularly preferably, the rotor bodies are formed from essentially the same parts, in particular essentially identical. It is most preferred for the rotor bodies to be formed from identical, in particular essentially identical rotor laminations. The rotor bodies are therefore particularly preferably formed from a rotor lamination stack, which is composed of a plurality of laminated individual laminations or rotor laminations, generally made of electrical steel sheet, which are layered and packaged one above the other to form a stack, the so-called rotor lamination stack. The individual laminations can be held together in the rotor lamination stack by gluing, welding, or screwing. A rotor lamination stack can, in particular, also have permanent magnets introduced into the pockets of the rotor lamination stack or fixed circumferentially to the rotor lamination stack.It is possible for the rotor cores to be interlaced, meaning they are arranged at an angle to each other. This interlacing can be linear or V-shaped to avoid or at least reduce axial forces.

[0030] The rotor can be designed as a permanently excited rotor or a separately excited rotor.

[0031] The separately excited rotor is a component of an electric radial flux machine used to convert electrical energy into mechanical energy or vice versa. A separately excited rotor is a rotor powered by a separate power source, usually a direct current source. Unlike a self-regulated rotor, which derives its excitation from the stator's alternating current, a separately excited rotor typically requires an external direct current source.

[0032] The separately excited rotor may preferably have a cylindrical rotor body, advantageously made of laminated iron to reduce eddy current losses. Several grooves or slots may be provided on the surface of the rotor body, into which the rotor winding is inserted. This rotor winding is preferably formed from insulated copper or aluminum wires and is guided through the grooves or slots to ensure mechanical stability.

[0033] The rotor winding of the separately excited rotor is preferably divided into coils that are electrically connected to each other. These coils are wound parallel to the rotor axis and are usually designed as multiphase windings to enable efficient conversion of electrical energy into mechanical energy. The number of coils and their arrangement depend on the specific requirements of the machine.

[0034] The external DC power source can be connected to the rotor winding via slip rings and carbon brushes, for example. The carbon brushes ensure a low-friction electrical connection between the stationary power source and the rotating rotor winding. The application of the external DC power source creates a magnetic field in the rotor, which interacts with the magnetic field of the stator-side winding system, thus influencing the torque and power of the machine.

[0035] The separately excited rotor offers the advantage of external control over the rotor excitation. By varying the direct current fed into the rotor, the power and torque of the electric machine can be precisely controlled.

[0036] A rotor body can, in particular, be formed from one or more rotor lamination stacks. A rotor lamination stack is understood to be a plurality of laminated individual laminations or rotor laminations, usually made of electrical steel, which are stacked and stacked together to form a so-called rotor lamination stack. The individual laminations can then be held together in the lamination stack by gluing, welding, or screwing. A rotor lamination stack for a permanently excited rotor can, in particular, also have magnetic elements incorporated into the pockets of the rotor lamination stack or fixed circumferentially to the rotor lamination stack, as well as any axial cover parts for closing the pockets and the like.

[0037] The electric machine can be designed, in particular, as a rotary machine. The rotary machine can be configured, in particular, as a radial flux machine. A radial flux machine is characterized by the fact that the magnetic field lines in the air gap formed between the rotor and stator extend in a radial direction. The air gap is the gap between the rotor and stator. In a radial flux machine, this is a circular-ring-shaped gap in cross-section with a radial width corresponding to the distance between the rotor body and the rotor body.

[0038] The electric machine is intended in particular 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. Particularly preferably, the electric motor has an output greater than 50 kW, preferably greater than 80 kW, and in particular greater than 150 kW. Furthermore, it is preferred that the electric machine provides rotational speeds greater than 8,000 rpm, particularly preferably greater than 12,000 rpm, and most particularly preferably greater than 15,000 rpm.

[0039] For the purposes of this application, motor vehicles are defined as land vehicles that are propelled by mechanical power without being tied to railway tracks. A motor vehicle can, for example, be selected from the group of passenger cars (PCs), trucks (HGVs), mopeds, light motor vehicles, motorcycles, buses (KOMs), or tractors.

[0040] The rotor assembly may further comprise a control unit. A control unit, 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 rotor assembly and / or the electric machine, such as the control / regulation of the coolant pump and / or the current supply to a rotor winding.

[0041] A control unit preferably has a wired or wireless signal input for receiving electrical signals, such as sensor signals. Furthermore, a control unit preferably also has a wired or wireless signal output for transmitting electrical signals, in particular.

[0042] Control and / or regulation operations can be performed within the control unit. It is particularly preferred that the control unit comprises hardware configured to execute software. The control unit preferably comprises at least two electronic processors for executing program sequences defined in a respective software. The two processors can also be structurally integrated into a processor as computer cores, with the corresponding computer cores then each representing a processor within the meaning of the invention.

[0043] The control unit may further comprise one or more electronic memories in which the data contained in the signals transmitted to the control unit can be stored and read again. Furthermore, the control unit may comprise one or more electronic memories in which data can be stored in a modifiable and / or non-modifiable manner.

[0044] A control unit 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.

[0045] Most preferably, the control unit 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 unit to execute the computer program code.

[0046] 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 that control or regulate a current to the electrical machine, preferably including the 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 that 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 has 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 with a peak power, preferably continuous power, of at least 10 W, preferably at least 100 W, particularly preferably at least 1000 W per phase.

[0047] According to an advantageous embodiment of the invention, the first delivery state of the coolant pump can be deactivated by the control unit when a rotor speed between 100 and 300 rpm is reached. The advantage of this embodiment is that the coolant pump initially only needs to be operated from standstill to fill or flood the rotor cooling channels, in order to subsequently avoid imbalance during acceleration due to incompletely or homogeneously filled rotor cooling channels.

[0048] According to a further preferred development of the invention, it can also be provided that the second delivery state of the coolant pump is deactivated by the control unit upon reaching a rotor speed between 100 and 300 rpm. This can result in the cooling fluid flowing out of the rotor cooling channels due to gravity and / or centrifugal force above suitable rotational speeds.

[0049] Furthermore, according to a likewise advantageous embodiment of the invention, it can be provided that in the third delivery state of the coolant pump, the latter is offset in a delivery direction opposite to the delivery direction of the cooling fluid, so that the cooling fluid can be sucked out of the rotor cooling channels by the coolant pump.

[0050] According to another particularly preferred embodiment of the invention, the rotor can be separately excited by means of a rotor winding capable of being energized, and the rotor arrangement can include a control unit for energizing the rotor winding. The ability to separately excite the rotor by means of a rotor winding capable of being energized allows for greater flexibility in controlling the machine. The control unit makes it possible to vary the rotor current and thus control the torque, speed, or other operating parameters of the machine. This enables more precise adaptation to different operating conditions, load requirements, or control objectives.

[0051] Furthermore, the invention can also be further developed such that the rotor winding is de-energized when the coolant pump is in the first pumping state. This allows the rotor to be protected from imbalances even in operating situations where, for example, the vehicle rolls down a slope from a standstill and the rotor is de-energized but still rotates.

[0052] In a likewise preferred embodiment of the invention, it can also be provided that the rotor shaft is rotatably mounted on at least one rolling bearing, with the cooling circuit being routed through the rolling bearing. This allows for improved lubrication and cooling of the rolling bearing, which subsequently also has a positive effect on the efficiency of the rotor assembly.

[0053] The object of the invention can also be achieved by an electrical machine comprising a rotor arrangement according to one of claims 1-7.

[0054] The object of the invention can further be achieved by a method for controlling a rotor arrangement of an electric machine of a drive train of a motor vehicle, comprising a rotor with a rotor body which is arranged in a rotationally fixed manner on a rotor shaft, a cooling circuit which runs partially through the rotor, wherein the cooling circuit in the rotor body has a plurality of rotor cooling channels which are arranged circumferentially and extend in the axial direction through the rotor body, a coolant pump which is arranged in the cooling circuit and which conveys a cooling fluid through the cooling circuit, a control unit for controlling the coolant pump, wherein the control unit is configured to carry out the following method steps: a. When a first start-up signal is present, before and / or when the rotor is rotated from standstill, the coolant pump is set to a first pumping state, through which the rotor cooling channels are flooded with the cooling fluid, and b. Causing heating of the rotor body when a second start-up signal is present before and / or when the rotor is rotated from standstill, and c. When a first stop signal is present, before and / or when the rotor is turned down to a standstill, the coolant pump is put into a second pumping state, by which the rotor cooling channels are emptied of the cooling fluid by centrifugal force and / or gravity, and d. When a second run-out signal is present before and / or when the rotor is brought to a standstill, the coolant pump is placed in a third pumping state, through which the rotor cooling channels are emptied of the cooling fluid by means of the coolant pump.

[0055] The object of the invention can further be achieved by a computer program product stored on a machine-readable carrier, or computer data signal embodied by an electromagnetic wave, with a computer program code suitable for carrying out a method according to claim 8.

[0056] Finally, the object of the invention can also be achieved by a control unit for controlling a rotor arrangement, comprising a processor and a memory containing a computer program code, wherein the memory and the computer program code are configured, with the processor, to cause the control unit to carry out a method according to claim 8.

[0057] The invention will be explained in more detail below with reference to figures without limiting the general inventive concept.

[0058] It shows: Fig. 1 a motor vehicle with an electric drive train in a schematic representation, Fig. 2 an electrical machine in a schematic representation, Fig. 3 a rotor arrangement in a schematic axial section, Fig. 4 a temporal speed and volume flow curve in a first delivery state of the coolant pump, Fig. 5 a temporal speed and volume flow curve for a second delivery state of the coolant pump, Fig. 6 a temporal speed and volume flow curve for a third delivery state of the coolant pump,

[0059] The Fig. 2 shows a rotor arrangement 1 for an electric machine 2 of a drive train 3 of a motor vehicle 4, as is also shown in the Fig. 1. In the illustrated embodiment of the Fig. 1, the electric machine 2 is coupled to a transmission arrangement 26 and forms a structural unit with it, which can also be referred to as an axle drive train.

[0060] As can be seen from the Fig. 2-3, the rotor arrangement 1 comprises a rotor 5 with a rotor body 6, which is arranged in a rotationally fixed manner on a rotor shaft 7, a cooling circuit 8, which runs partially through the rotor 5, wherein the cooling circuit 8 has a plurality of rotor cooling channels 9 in the rotor body 6, which are arranged circumferentially and extend in the axial direction through the rotor body 6. Furthermore, the rotor arrangement 1 has a coolant pump 10 arranged in the cooling circuit 8, which pumps a cooling fluid 11 through the cooling circuit 8 and a control unit 12 for controlling the coolant pump 10. In the exemplary embodiment shown, the electrical machine 2 is designed as a radial flow machine, with a hollow cylindrical stator 23, in which the rotor 5 is rotatably received.

[0061] As can be seen from the Fig. 3, the hollow cylindrical rotor shaft 7 has a plurality of openings in its outer surface through which the cooling fluid 11 can flow radially outward into an annular gap of the rotor 5. This annular gap is connected to the rotor cooling channels 9. On the opposite axial side, the cooling fluid 11 is then led out of the rotor 5 again at a radially inner outlet opening and can from there be fed, for example, to a rolling bearing 20, as shown in the Fig. 3 is shown.

[0062] The rotor 1 can be separately excited by means of an energizable rotor winding 19, and the rotor assembly 1 has a control unit with a rotor power supply 24 for energizing the rotor winding 19. This can be electrically connected to the rotor shaft 7 or the rotor winding 19 via a sliding contact 25. The rotor power supply 24 is connected to the control unit 12. When a second start-up signal 13 is present before and / or when the rotor 5 spins up from a standstill, the energized rotor winding 19 can heat the rotor body 6. The rotor shaft 7 is rotatably mounted on at least one rolling bearing 20, with the cooling circuit 8 being guided through the rolling bearing 20.

[0063] The control unit 12 for controlling the rotor assembly 1 comprises a processor 21 and a memory 22 containing computer program code. The memory and the computer program code are configured, together with the processor 21, to cause the control unit 12 to perform a method that will be described in more detail below. The control unit 12 can have inputs for various signals 13, 15, 17, by means of which the operation of the rotor assembly 1 is controlled or regulated.

[0064] The control unit 12 is now configured to set the coolant pump 10, upon the presence of a first start-up signal 13 before and / or upon the rotor 5 starting to rotate from standstill, into a first delivery state 14, through which the rotor cooling channels 5 are flooded with the cooling fluid 11, wherein this first delivery state 14 of the coolant pump 10 is deactivated by the control unit 12 upon reaching a rotor speed between 50-300 rpm. This first delivery state 14 can also be determined using the diagrams in the Fig. 4. The speed and flow rate curves for an energized and a de-energized rotor are shown there. The first pumping state 14 of the coolant pump 10 can therefore occur with the rotor winding 19 of the rotor 1 energized or de-energized.

[0065] How to use the Fig. 4 detects, the coolant pump 10 is activated immediately when the rotor shaft 7 starts rotating or shortly before (e.g., when the brake pedal is released) and fills the rotor cooling channels 9 of the rotor 5 as quickly as possible. As soon as a speed of between 50-300 rpm is reached, the coolant pump 10 can be deactivated because the centrifugal force prevails over gravity and the cooling fluid 11 thus remains in the rotor cooling channels 9. As soon as the electric machine 2 is actively powered again, cooling fluid 11 must be pumped again in accordance with the required cooling capacity.

[0066] With this solution, a residual amount of cooling fluid 11 always remains in the lowest rotor cooling channels 9 in the direction of gravity. Extended downtime at low temperatures can cause the cooling fluid 11 to change viscosity, resulting in lower flow rates and thus slower emptying. To counteract this, the cooling fluid 11 in the rotor cooling channels 9 can be heated by targeted rotor coil excitation. This can also occur before starting to rotate or drive off, for example, as soon as the vehicle is unlocked or when the accelerator, brake, or clutch pedal is depressed.

[0067] Furthermore, it is possible to set the coolant pump 10 into a second delivery state 16 when a first run-down signal 15 is present before and / or when the rotor 5 is brought to a standstill, by which the rotor cooling channels 9 are emptied of the cooling fluid 11 by centrifugal force and / or gravity. In this case, the second delivery state 16 of the coolant pump 10 is deactivated by the control unit 12 when a rotor speed of between 50 and 300 rpm is reached. The corresponding speed and volume flow curve is shown in the Fig. 5. This ensures that all rotor cooling channels 9 are emptied before the rotor shaft 7 comes to a standstill. This is achieved by prematurely shutting off the coolant pump 10, before the speed drops below 50-300 rpm. This premature shutdown ensures that, even during the deceleration process, each rotor cooling channel 9 is temporarily at the top in the direction of gravity and can be emptied as completely as possible by gravity.

[0068] Furthermore, it is possible to set the coolant pump 10 into a third pumping state 18 when a second run-down signal 17 is present before and / or when the rotor 5 is brought to a standstill, by means of which the rotor cooling channels 9 are emptied of the cooling fluid 11 by means of the coolant pump 10. This can also be determined based on the speed and volume flow curve in the Fig. 6. As in the Fig.As shown in Figure 6, in the third delivery state 18 of the coolant pump 10, it has been shifted into a delivery direction opposite to the delivery direction of the cooling fluid 11. Therefore, if complete emptying by switching off the coolant pump 10 during the braking process is not sufficient, the residual fluid can be sucked out of the rotor cooling channels 9 by the inverse operation of the coolant pump 10. For this to happen, the coolant pump 10 must, of course, enable the suction function. This inverse operation of the coolant pump 10 can be operated for approximately 40-80 ms at a volume flow of approximately 8 l / min. For other volume flows, the time changes proportionally.

[0069] 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. List of reference symbols 1 Rotor arrangement 2 electric machine 3 Drivetrain 4 Motor vehicle 5 Rotor 6 rotor bodies 7 Rotor shaft 8 Cooling circuit 9 rotor cooling channels 10 Coolant pump 11 Cooling fluid 12 Control unit 13 Approach signal 14 Production status 15 Exit signal 16 Production status 17 Exit signal 18 Production status 19 Rotor winding 20 rolling bearings 21 processor 22 storage 23 Stator 24 Rotor power supply 25 sliding contact 26 Gear arrangement

Claims

[1] Rotor arrangement (1) for an electric machine (2) of a drive train (3) of a motor vehicle (4) comprising • a rotor (5) with a rotor body (6) which is arranged in a rotationally fixed manner on a rotor shaft (7), • a cooling circuit (8) which runs in sections through the rotor (5), wherein the cooling circuit (8) has a plurality of rotor cooling channels (9) in the rotor body (6) which are arranged in a circumferentially distributed manner and extend in the axial direction through the rotor body (6), • a coolant pump (10) arranged in the cooling circuit (8), which pumps a cooling fluid (11) through the cooling circuit (8), and • a control unit (12) for controlling the coolant pump (10), wherein the control unit (12) is configured a) to set the coolant pump (10) in the presence of a first start-up signal (13) before and / or during the rotation of the rotor (5) from standstill into a first delivery state (14), by means of which the rotor cooling channels (5) are flooded with the cooling fluid (11), and characterized by , that the control unit (12) is configured, b) to cause heating of the rotor body (6) when a second start-up signal (13) is present before and / or when the rotor (5) is rotated from standstill, and c) to set the coolant pump (10) into a second conveying state (16) when a first run-out signal (15) is present before and / or when the rotor (5) is brought to a standstill, by means of which the rotor cooling channels (5) are emptied of the cooling fluid (11) by centrifugal force and / or gravity, and d) to place the coolant pump (10) into a third conveying state (18) when a second run-out signal (17) is present before and / or when the rotor (5) is rotated down to a standstill, by means of which the rotor cooling channels (5) are emptied of the cooling fluid (11) by means of the coolant pump (10). [2] Rotor arrangement (1) according to claim 1, characterized by that the first delivery state (14) of the coolant pump (10) is deactivated by the control unit (12) when a rotor speed between 50-300 rpm is reached. [3] Rotor arrangement (1) according to claim 1 or 2, characterized by that the second delivery state (16) of the coolant pump (10) is deactivated by the control unit (12) when a rotor speed between 50-300 rpm is reached. [4] Rotor arrangement (1) according to one of the preceding claims, characterized bythat in the third delivery state (18) of the coolant pump (10) it is offset in a delivery direction opposite to the delivery direction of the cooling fluid (11). [5] Rotor arrangement (1) according to one of the preceding claims, characterized by that the rotor (1) can be externally excited by means of a current-carrying rotor winding (19) and the rotor arrangement (1) has a rotor current supply (24) for supplying current to the rotor winding (19). [6] Rotor arrangement (1) according to claim 5, characterized by that when the first delivery state (14) of the coolant pump (10) is present, the rotor winding (19) of the rotor (1) is de-energized. [7] Rotor arrangement (1) according to one of the preceding claims, characterized by that the rotor shaft (7) is rotatably mounted on at least one rolling bearing (20), wherein the cooling circuit (8) is guided through the rolling bearing (20). [8] Electrical machine (2) comprising a rotor arrangement (1) according to one of the preceding claims. [9] Method for controlling a rotor arrangement (1) of an electric machine (2) of a drive train (3) of a motor vehicle (4) comprising • a rotor (5) with a rotor body (6) which is arranged in a rotationally fixed manner on a rotor shaft (7), • a cooling circuit (8) which runs in sections through the rotor (5), wherein the cooling circuit (8) has a plurality of rotor cooling channels (9) in the rotor body (6) which are arranged in a circumferentially distributed manner and extend in the axial direction through the rotor body (6), • a coolant pump (10) arranged in the cooling circuit (8), which pumps a cooling fluid (11) through the cooling circuit (8) • a control unit (12) for controlling the coolant pump (10), wherein the control unit (12) is configured to carry out the following method steps: a) placing the coolant pump (10) in the presence of a first start-up signal (13) before and / or during the rotation of the rotor (5) from standstill into a first delivery state (14), by means of which the rotor cooling channels (9) are flooded with the cooling fluid (11), and b) causing the rotor body to heat up when a second start-up signal (13) is present before and / or when the rotor (5) is rotated from standstill, and c) placing the coolant pump (10) in a second conveying state (16) when a first run-out signal (15) is present before and / or when the rotor (5) is turned down to a standstill, by means of which the rotor cooling channels (9) are emptied of the cooling fluid (8) by centrifugal force and / or gravity, and d) When a second run-out signal (17) is present, before and / or when the rotor (5) is rotated down to a standstill, the coolant pump (10) is placed in a third conveying state (18), by means of which the rotor cooling channels (9) are emptied of the cooling fluid (11) by means of the coolant pump (10). [10] A computer program product stored on a machine-readable medium or a computer data signal embodied by an electromagnetic wave, comprising a computer program code suitable for carrying out a method according to claim 9. [11] Control unit (12) for controlling a rotor arrangement (1), comprising a processor (21) and a memory (22) containing a computer program code, wherein the memory and the computer program code are configured, with the processor (21), to cause the control unit (9) to carry out a method according to claim 9.

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