DE102023208028A1 - Method for operating an electric drive train - Google Patents

Abstract

The invention relates to a method for operating an electric drive train (1) which has at least one electric machine (2) for driving a motor vehicle (3) and further electrical components (4, 5, 6) for controlling and operating the electric machine (2), a traction battery (7) and a cooling circuit (8) for controlling the temperature of the traction battery (7), the electric machine (2) and the electrical components (4, 5, 6); wherein the method comprises operating the drive train (1) in certain operating states in such a way that electrical losses are deliberately generated in at least one of the electrical components (2, 4, 5, 6).

Description

The invention relates to a method for operating an electric drive train. The drive train comprises at least one electric machine for driving the motor vehicle and further electrical components for controlling and operating the electric machine, a traction battery and a cooling circuit for controlling the temperature of the traction battery, the electric machine and the electrical components.

Motor vehicles have at least one cooling circuit in which a cooling fluid is pumped through the cooling circuit by one or more pumps (each). The cooling fluid absorbs heat energy from the components integrated in the respective cooling circuit, in particular an electric machine, a pulse-changing rectifier, a charger, a voltage converter, a battery. This heat energy is then released into the environment (air) via an ambient heat exchanger (a cooling device).

Increasing the range of BEVs (exclusively electrically powered vehicles), for example, is a constant challenge. The aim of this paper is to propose a method with which the energy that cannot be stored in the vehicle's traction battery due to thermal recuperation limits can be used to heat the traction battery.

At low temperatures, the traction battery can only be charged with a low current due to the limitations of chemical processes in the traction battery. During braking, the full potential for recovering braking energy cannot therefore be used. The braking energy that cannot be stored in the traction battery must then be dissipated via the braking system, for example. The faster the temperature of the traction battery is increased, the sooner the full potential of recuperation can be used. At a higher temperature of the traction battery, more electrical energy can be recovered and the use of the braking system is reduced. It is known, for example, to increase the temperature of the traction battery using an electrical auxiliary heater or a heat pump. However, both the heat pump and the electrical auxiliary heater require valuable electrical energy from the traction battery, which has a detrimental effect on the range of the vehicle.

Another environmental burden is the emission of fine dust from braking systems and tire wear. Reducing the load on the mechanical braking system leads to a reduction in fine dust pollution through reduced brake wear. On long downhill journeys with a fully charged traction battery, regenerative braking must be used to prevent the braking system from being thermally overloaded. However, recuperation in the traditional sense is only possible if the electrical energy generated can be stored in the traction battery or used directly in the vehicle. If the braking system is at its load limit and the traction battery cannot absorb any more electrical energy, the electrical energy generated by the regenerative braking process must be used directly. It is known that under these operating conditions, high-performance consumers, primarily the heating elements of the interior air conditioning, the air conditioning in AC mode, the heating of the traction battery, the seat heating and other available consumers, are activated. This leads to massive thermal and acoustic impairments in comfort and, over a longer period, also to an impairment of the vehicle user's ability to concentrate. The user has no possibility to intervene in this process or to switch it off.

From the DE 10 2020 126 659 A1 A system for controlling regenerative braking for an electric motor-driven vehicle is known. An electrical resistor is proposed for converting excess electrical energy into thermal energy.

The KR 101526430 B1 is directed to a regenerative braking device for a motor vehicle.

The object of the present invention is to at least partially solve the problems mentioned with reference to the prior art. In particular, a method is to be specified with which a drive train of an electrically powered motor vehicle, and in particular a traction battery, can be operated in an energy-efficient manner.

A method with the features according to claim 1 contributes to the solution of these tasks. Advantageous further developments are the subject of the dependent claims. The features listed individually in the claims can be combined with one another in a technologically meaningful way and can be supplemented by explanatory facts from the description and/or details from the figures, whereby further embodiments of the invention are shown.

A method for operating an electric drive train of a motor vehicle is proposed. The drive train has at least one electric machine for driving the motor vehicle. vehicle and other electrical components for controlling and operating the electrical machine, a traction battery and a cooling circuit for controlling the temperature of the traction battery, the electrical machine and the electrical components. The method includes operating the drive train in certain operating states in such a way that electrical losses are deliberately generated in at least one of the electrical components.

Electrical components are considered to be in particular an (possibly also another) electrical machine for driving the motor vehicle, a charger, a pulse inverter, a voltage converter (in particular a DC/DC converter, i.e. a direct current converter) and an inverter. These electrical components are generally known in terms of their functionality.

The method is used to specifically generate electrical losses in components of the drive train that are already present. In particular, the electrical losses are generated exclusively in electrical components that are intended for controlling or operating the at least one electrical machine (except for the traction battery). This does not include a heating resistor that has to be provided separately.

1. i. erster Betriebszustand, in dem die Traktionsbatterie eine Temperatur aufweist, die einen Ladestrom beim Rekuperieren auf einen Wert begrenzt, der unterhalb eines maximal möglichen Ladestroms liegt;
2. ii. zweiter Betriebszustand, in dem die Traktionsbatterie keine weitere elektrische Energie aufnehmen kann; und
3. iii. dritter Betriebszustand, in dem die Traktionsbatterie keine weitere elektrische Energie aufnehmen kann und auf eine höhere Temperatur erwärmbar ist (ohne dabei Schaden zu nehmen).

In particular, the targeted generation of electrical losses is carried out in at least one of the following operating states of the drive train or the motor vehicle:

1. i. first operating state in which the traction battery has a temperature that limits a charging current during recuperation to a value that is below a maximum possible charging current;
2. ii. second operating state in which the traction battery cannot absorb any further electrical energy; and
3. iii. third operating state, in which the traction battery can no longer absorb any more electrical energy and can be heated to a higher temperature (without being damaged).

In particular, in the first operating state, the thermal energy generated by the electrical losses is used at least to heat the traction battery (first operating mode of the drive train). In particular, as little of the thermal energy as possible is dissipated, e.g. to the environment, but rather as much thermal energy as possible is passed on to the traction battery. A cooling device of the cooling circuit is thereby bypassed, in particular, via a suitable bypass.

In particular, in the second operating state, the thermal energy generated by the electrical losses is dissipated to an environment of the motor vehicle at least via a cooling device of the cooling circuit (second operating mode of the drive train).

In particular, it is possible to carry out the method in such a way that the thermal energy generated by the electrical losses is used at least temporarily to heat the traction battery and is temporarily dissipated (in parallel and/or at different times) to the environment of the motor vehicle via a cooling device of the cooling circuit. In particular, the method can switch back and forth between these two operating modes (first and second operating modes alternating) (third operating mode of the drive train).

In particular, in the third operating state, the thermal energy generated by the electrical losses is used to further heat the traction battery (fourth operating mode of the drive train). The traction battery should only be heated further to the extent that the traction battery is not damaged. It is particularly irrelevant whether the further heating can increase the charging current during recuperation or whether it is reduced as a result of the heating. The cooling fluid can also be passed through a cooling device in the cooling circuit if necessary.

In particular, you can switch between the different operating modes at any time.

In particular, the electrical losses are generated at least by an intervention in a field-oriented control of the electrical machine or by a change in switching times or a switching frequency of a power electronics intended as an electrical component. In particular, these interventions are not aimed at an otherwise usual efficient operation of the electrical components or one that is considered optimal for the respective operating point of the drive train, but on the contrary at an otherwise inefficient, energy-wasting operation of the drive train. The electrical energy is therefore deliberately generated only to generate as much heat as possible in the electrical components, without it being aimed - as is otherwise usual - at meeting the requirements placed on the drive of the motor vehicle.

The proposed method can be used to recover energy that cannot be stored in the traction battery due to thermal recuperation limits (e.g. if the traction battery is too cold and therefore the charging current must be limited) to heat the traction battery (e.g. in the first operating state). The method generates additional thermal losses in these electrical components through targeted control interventions in the control of the electrical components, so that the traction battery can be heated via the cooling circuit using excess potential and kinetic energy (e.g. first operating mode). For example, this is done by adjusting the field-oriented control of the electrical machine and/or by changing the switching times or the switching frequency of the power electronics.

With the proposed method, it is no longer necessary, at least in most cases, to switch on the consumers mentioned (high-performance consumers, primarily the heating elements of the interior air conditioning, the air conditioning in AC mode, the heating of the traction battery, the seat heating and other available consumers) in the operating states mentioned. The disadvantages mentioned can thus also be reduced, for example, during long downhill journeys with a fully charged traction battery. The potential energy of the vehicle is then converted into heat (thermal energy) in the electrical components as part of the proposed method, in particular dissipated from the electrical components by the cooling circuit and released into the environment of the vehicle (i.e. into the ambient air) via a cooling device in the cooling circuit (e.g. a generally known low-temperature cooler) (second operating state or second operating mode). Regenerative braking and thus the relief of the braking system can thus take place without any loss of comfort for the user. The fine dust pollution caused by the brake wear that would otherwise be present is reduced.

The conversion of kinetic energy into thermal energy can be achieved, for example, by adjusting the field-oriented control of the electrical machine and/or by changing the switching times or the switching frequency of the power electronics (one or more of the following components: charger, pulse inverter, voltage converter, inverter).

When the traction battery is at a low temperature, more recuperation energy may be available than can be charged into the traction battery, particularly in certain driving or operating conditions. To avoid damage to the cell chemistry of the traction battery, the charging current of the traction battery must be limited at low temperatures.

It is known that recuperation can be limited by the maximum permissible charging current of the traction battery. When braking outside the recuperation limits, the braking system is used and the energy is not used to temper the traction battery. An increase in the recuperation limits by increasing the temperature of the traction battery does not then occur. The frequency of use of the braking system is also not reduced.

With the proposed method, recuperation is controlled in such a way that the maximum permissible charging current of the traction battery is adhered to. The excess recuperation energy is converted into thermal energy, among other things, by targeted additional electrical losses in the electrical components. This thermal energy is then used to control the temperature of the traction battery.

This means that the frequency of use of the braking system can be reduced. As a result of the increase in temperature in the traction battery, more braking energy can be absorbed by the traction battery than electrical energy, because the maximum possible charging current can be increased further. As the temperature of the traction battery increases, the internal losses of the traction battery also decrease. The better recovery of braking energy and the lower internal resistance of the traction battery increase the energy efficiency of the vehicle.

When a traction battery is fully charged, little braking energy can be stored in the traction battery. In this context, it is common practice to only operate the brake system, for example on a long downhill journey. If the brake system is at its thermal load limit, the brake system must be relieved by regenerative braking. However, since the (fully charged) traction battery cannot absorb any more energy, the excess electrical energy must be dissipated by connecting powerful electrical consumers. This results in a corresponding loss of comfort in the interior of the vehicle.

With the proposed method, additional thermal losses are deliberately generated during regenerative braking and dissipated to a cooling device via the cooling circuit. The load on the braking system is thus reduced and impairment of driving comfort is avoided in many areas of vehicle operation. The reduced use of the braking system also reduces the particulate matter pollution caused by brake wear (e.g. in the second, third or fourth operating mode).

If the traction battery can be heated further (without being damaged as a result), the excess recuperation energy can be stored (exclusively) as thermal energy in the traction battery or (exclusively or additionally) dissipated to the environment via a cooling device.

• • Effizienzsteigerung des Betriebs des Antriebsstrangs und insbesondere des Betriebs der Traktionsbatterie durch gezielt erzeugte thermische Verluste;
• • Reduzierung der Komforteinbußen bei hoher thermischer Belastung der Bremsanlage;
• • geringere Umweltbelastung durch verminderten Bremsenabrieb;
• • Erhöhung der Reichweite des Kraftfahrzeugs.

The proposed method can achieve the following advantages in particular:

• • Increasing the efficiency of the operation of the drive train and in particular the operation of the traction battery through targeted thermal losses;
• • Reduction of comfort losses when the braking system is subjected to high thermal loads;
• • lower environmental impact due to reduced brake wear;
• • Increasing the range of the vehicle.

In particular, the different operating modes can also be specifically selected for other reasons (not only due to the current operating conditions). For example, the first operating mode can be preferred with a view to increasing the range and efficiency. With a view to environmental pollution caused by fine dust and future legislation in this context, as well as interior comfort when the braking system is under high load, the second, third and fourth operating modes are preferable.

In particular, the cooling circuit has at least one first bypass for bypassing the traction battery. With the first bypass, the cooling fluid flowing through the cooling circuit can be guided past the traction battery in particular, so that in particular further heating of the traction battery by the thermal energy of the cooling fluid can be prevented. In particular, several first bypasses are provided. In a first bypass, the cooling fluid can be guided, for example, via a so-called chiller, through which the cooling fluid is connected to a coolant circuit of an air conditioning system of the motor vehicle. The cooling fluid can be cooled via the chiller. In another first bypass, the cooling fluid can also be guided past the chiller. The first bypass is used in particular in the second and third operating modes.

In particular, the cooling circuit (in addition to or as an alternative to the first bypass) has at least one second bypass for bypassing a cooling device, wherein heat can be dissipated to the environment of the motor vehicle via the cooling device. This bypass is used in particular in the first operating mode.

As a cooling device, in particular a basically known low-temperature cooler is provided, in which the cooling fluid can be cooled in the ambient air.

In particular, the cooling circuit can have a return line in addition to or as an alternative to the bypasses (or the individual bypasses), via which cooling fluid immediately downstream of the traction battery can be at least partially returned to a connection point immediately upstream of the traction battery. In this return line, a heating heat exchanger and/or a high-voltage heater can be provided in particular.

The cooling fluid can be heated quickly using a high-voltage heater, although this consumes electrical energy from the traction battery. This high-voltage heater can be used in particular in the first operating mode.

Heat can be transferred between the interior and the cooling circuit via the heating heat exchanger. In particular, the heating heat exchanger and high-voltage heater can be arranged in a return system (or in a separately operable part of a system).

In particular, an expansion tank is connected to the cooling circuit. The expansion tank ensures that there is sufficient cooling fluid in the cooling circuit. Furthermore, the expansion tank can be used to compensate for any expansion of the cooling fluid via an air reservoir.

A motor vehicle is also proposed, at least having an electric drive train, which has at least one electric machine for driving the motor vehicle and further electrical components for controlling and operating the electric machine, a traction battery and a cooling circuit for controlling the temperature of the traction battery, the electric machine and the electrical components, as well as a control unit. The control unit has means for carrying out the described method and/or has means that are suitably equipped, configured or programmed for carrying out the described method or that carry out the method.

The means include, for example, a processor and a memory in which instructions to be executed by the processor are stored, as well as data lines or transmission devices which enable the transmission of instructions, measured values, data or similar between the listed elements.

The “means” may in particular comprise one or more of the following components: controller(s), microcontroller, data storage, data connection, display devices (such as a display), counter or timer, at least one further sensor, an energy source, etc.

A computer program is further proposed, comprising instructions which, when the computer program is executed by a computer, cause the computer to carry out the described method.

A computer-readable storage medium is also proposed, comprising instructions which, when executed by a computer, cause the computer to carry out the described method or the steps of the described method.

The statements on the method are particularly transferable to the motor vehicle and/or the computer-implemented method (i.e. the computer program and the computer-readable storage medium) and vice versa.

The use of indefinite articles ("a", "an", "an" and "another"), particularly in the patent claims and the description reflecting them, is to be understood as such and not as a number. Terms or components introduced accordingly are therefore to be understood as being present at least once and, in particular, can also be present multiple times.

As a precaution, it should also be noted that the numerals used here ("first", "second", ...) primarily serve (only) to distinguish between several similar objects, sizes or processes, and in particular do not necessarily specify a dependency and/or sequence of these objects, sizes or processes. If a dependency and/or sequence is required, this is explicitly stated here or it is obvious to the person skilled in the art when studying the specifically described design. If a component can occur multiple times ("at least one"), the description of one of these components can apply equally to all or part of the majority of these components, but this is not mandatory.

• 1: ein Kraftfahrzeug mit einem Antriebsstrang und einer ersten Ausführungsvariante eines Kühlkreislaufs, der in einer ersten Betriebsart betrieben wird;
• 2: ein Kraftfahrzeug mit einem Antriebsstrang und einer zweiten Ausführungsvariante eines Kühlkreislaufs, der in einer ersten Betriebsart betrieben wird;
• 3: das Kraftfahrzeug nach 1, wobei der Kühlkreislauf in einer zweiten Betriebsart betrieben wird;
• 4: das Kraftfahrzeug nach 2, wobei der Kühlkreislauf in einer zweiten Betriebsart betrieben wird;
• 5: das Kraftfahrzeug nach 1 und 3, wobei der Kühlkreislauf in einer vierten Betriebsart betrieben wird; und
• 6: das Kraftfahrzeug nach 2 und 4, wobei der Kühlkreislauf in einer vierten Betriebsart betrieben wird.

The invention and the technical environment are explained in more detail below with reference to the accompanying figures. It should be noted that the invention is not intended to be limited by the exemplary embodiments given. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the facts explained in the figures and combine them with other components and findings from the present description. In particular, it should be noted that the figures and in particular the size relationships shown are only schematic. They show:

• 1 : a motor vehicle with a drive train and a first embodiment of a cooling circuit which is operated in a first operating mode;
• 2 : a motor vehicle with a drive train and a second embodiment of a cooling circuit operated in a first operating mode;
• 3 : the motor vehicle after 1 , wherein the cooling circuit is operated in a second operating mode;
• 4 : the motor vehicle after 2 , wherein the cooling circuit is operated in a second operating mode;
• 5 : the motor vehicle after 1 and 3 , wherein the cooling circuit is operated in a fourth operating mode; and
• 6 : the motor vehicle after 2 and 4 , whereby the cooling circuit is operated in a fourth operating mode.

The 1 shows a motor vehicle 3 with a drive train 1 and a first embodiment of a cooling circuit 8, which is operated in a first operating mode. The motor vehicle 3 has an electric drive train 1, which has two electric machines 2 for driving the motor vehicle 3 and further electric components 4, 5 for controlling and operating the electric machines 2, a traction battery 7 and a cooling circuit 8 for controlling the temperature of the traction battery 7, the electric machines 2 and the electric components 4, 5 as well as a control unit 13.

The electrical components 4, 5, 6 are an electrical machine 2 for driving the motor vehicle 3 as the third electrical component 6, a charger or voltage converter as the first electrical component 4 and a pulse inverter as the second electrical component 5. These electrical components are basically known in terms of their functionality and are used to control and operate the electrical machines 2.

The electric machines 2 can be designed to drive individual wheels or individual axles of the motor vehicle. In particular, at least one electric machine 2 is permanently provided as a traction drive, wherein the other electric machine 2 is only switched on (e.g. to provide a higher drive power or to drive another axle).

A cooling fluid 15 flows through the cooling circuit 8. Two pumps 14 are provided in the cooling circuit 8, by means of which a volume flow of the cooling fluid 15 can be regulated. Control valves 16 are also provided, via which a flow through certain sections of the cooling circuit 8 (in particular also with regard to the respective volume flow) can be regulated.

An expansion tank 17 is connected to the cooling circuit 8. The expansion tank 8 ensures that there is sufficient cooling fluid 15 in the cooling circuit 8. Furthermore, an expansion of the cooling fluid 15 can be compensated via an air reservoir via the expansion tank 17.

The cooling circuit 8 has a first bypass 11 for bypassing the traction battery 7. With the first bypass 11, the cooling fluid 15 flowing through the cooling circuit 8 can optionally be guided past the traction battery 7, so that further heating of the traction battery 7 by the thermal energy of the cooling fluid 15 can be prevented. In the present case, two first bypasses 11 are provided. In a (lower) first bypass 11, the cooling fluid 15 can be guided via a so-called chiller 19, through which the cooling fluid 15 is connected to a coolant circuit of an air conditioning system of the motor vehicle 3. The cooling fluid 15 can be cooled via the chiller 19. In another (upper) first bypass 11, the cooling fluid 15 can also be guided past the chiller 19.

In addition to the first bypass 11, the cooling circuit 8 has a second bypass 12 for bypassing a cooling device 9, wherein heat can be dissipated to an environment 10 of the motor vehicle 3 via the cooling device 9. The cooling device 9 is designed as a basically known low-temperature cooler in which the cooling fluid 15 can be cooled in the ambient air.

In addition to the bypasses 11, 12, the cooling circuit 8 has a return line 22, via which the cooling fluid 15 immediately downstream of the traction battery 7 can be at least partially returned to a connection point immediately upstream of the traction battery 7. A high-voltage heater 20 is provided in this return line 22, via which the cooling fluid 15 can be quickly heated, although electrical energy from the traction battery 7 is consumed in the process.

In the cooling circuit 8, several sensors 18 are provided for determining the temperature of the cooling fluid 15.

In the present case, the drive train 1 is operated in a first operating mode. The thermal energy generated by the electrical losses is used at least to heat the traction battery 7. For example, a first operating state of the drive train 1 or the motor vehicle 3 exists in which the traction battery 7 has a temperature that limits a charging current during recuperation to a value that is below a maximum possible charging current.

The purposely generated electrical losses are intended to generate thermal energy, which is then used via the cooling fluid 15 to heat the traction battery 7 as quickly as possible. In the first operating mode, the cooling fluid 15 is specifically guided via the second bypass (and thus past the cooling device 9) and exclusively via the traction battery 7 (and not via one of the first bypasses 11 or the return 22) and back to the electrical components 2, 4, 5, 6.

The 2 shows a motor vehicle 3 with a drive train 1 and a second embodiment of a cooling circuit 8, which is operated in a first operating mode. The explanations for 1 reference is made.

In the second embodiment of the cooling circuit 8, only one electric machine 2 is provided. In addition, the cooling device 9 and the second bypass are arranged downstream of the traction battery 7 and thus between the traction battery 7 and the electrical components 2, 4, 5.

In addition, the cooling circuit 8 has a return line 22, via which the cooling fluid 15 immediately downstream of the traction battery 7 can be at least partially returned to a connection point immediately upstream of the traction battery 7, wherein a heating heat exchanger 21 and a high-voltage heater 20 are provided in this return line 22.

Heat can be transferred between the interior of the motor vehicle 3 and the cooling circuit 8 via the heating heat exchanger 21. The heating heat exchanger 21 and the high-voltage heater 20 are arranged in a separately operable part of the return line 22. A separate pump 14 is arranged in this part of the return line 22 so that the cooling fluid 15 can be conveyed in this part of the return line 22 which is closed to the outside.

In the first operating mode, the cooling fluid 15 is directed specifically via the second bypass 12 (and thus past the cooling device 9) and exclusively via the traction battery 7 (and not via one of the first bypasses 11 or the return line 22) and back to the electrical components 2, 4, 5.

3 the vehicle shows 1 , wherein the cooling circuit 8 is operated in a second operating mode. 4 the motor vehicle 3 points to 2 , whereby the cooling circuit 8 is operated in a second operating mode. The explanations on the 1 and 2 Reference is made to the 3 and 4 are described together below.

In the present case, the drive train 1 is operated in a second operating mode. The thermal energy generated by the electrical losses is dissipated to an environment 10 of the motor vehicle 3 at least via the cooling device 9 of the cooling circuit 8. In this case, there is, for example, a second operating state of the drive train 1 or of the motor vehicle 3 in which the traction battery 7 cannot absorb any further electrical energy (and possibly no thermal energy).

This means that, for example, during long downhill journeys with a fully charged traction battery 7, the potential energy of the motor vehicle 3 can be converted into heat (thermal energy) in the electrical components 2, 4, 5, 6 within the framework of the proposed method, dissipated from the electrical components 2, 4, 5, 6 through the cooling circuit 8 and released into the environment 10 of the motor vehicle 3 (i.e. into the ambient air) via the cooling device 9 of the cooling circuit 8. Regenerative braking and thus the relief of the brake system can thus take place without any loss of comfort for the user. The fine dust pollution caused by the brake wear that would otherwise be present is reduced.

5 the motor vehicle 3 points to 1 and 3 , wherein the cooling circuit 8 is operated in a fourth operating mode. 6 the motor vehicle 3 points to 2 and 4 , whereby the cooling circuit 8 is operated in a fourth operating mode. The explanations on the 1 to 4 Reference is made to the 5 and 6 are described together below.

In the present case, the drive train 1 is operated in a fourth operating mode. The thermal energy generated by the electrical losses is dissipated to an environment 10 of the motor vehicle 3 via the cooling device 9 of the cooling circuit 8 and is used to further heat the traction battery 7. For example, there is a third operating state of the drive train 1 or the motor vehicle 3 in which the traction battery 7 cannot absorb any further electrical energy but can be further heated. The traction battery 7 should only be further heated to the extent that the traction battery 7 is not damaged. In this case, it is particularly irrelevant whether the further heating can further increase the charging current during recuperation or whether it is reduced as a result of the heating.

list of reference symbols

1

drivetrain

2

electric machine

3

motor vehicle

4

first electrical component

5

second electrical component

6

third electrical component

7

traction battery

8

cooling circuit

9

cooling device

10

Vicinity

11

first bypass

12

second bypass

13

control unit

14

pump

15

cooling fluid

16

control valve

17

expansion tank

18

sensor

19

chiller

20

high-voltage heater

21

heating heat exchanger

22

repatriation

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10 2020 126 659 A1 [0006]
• KR 101526430 B1 [0007]

Claims (8)

Method for operating an electric drive train (1) which has at least one electric machine (2) for driving a motor vehicle (3) and further electrical components (4, 5, 6) for controlling and operating the electric machine (2), a traction battery (7) and a cooling circuit (8) for controlling the temperature of the traction battery (7), the electric machine (2) and the electrical components (4, 5, 6); wherein the method comprises operating the drive train (1) in certain operating states such that electrical losses are deliberately generated in at least one of the electrical components (2, 4, 5, 6). procedure according to patent claim 1 , wherein the targeted generation of electrical losses is carried out in at least one of the following operating states of the drive train (1): i. first operating state, in which the traction battery (7) has a temperature that limits a charging current during recuperation to a value that is below a maximum possible charging current; ii. second operating state, in which the traction battery (7) cannot absorb any further electrical energy; and iii. third operating state, in which the traction battery (7) cannot absorb any further electrical energy and can be heated to a higher temperature. procedure according to patent claim 2 , wherein in the first operating state the thermal energy generated by the electrical losses is used at least for heating the traction battery (7). procedure according to patent claim 2 , wherein in the second operating state the thermal energy generated by the electrical losses is dissipated to an environment (10) of the motor vehicle (3) at least via a cooling device (9) of the cooling circuit (8). Method according to one of the preceding claims, wherein the electrical losses are generated at least by an intervention in a field-oriented control of the electrical machine (2) or by a change in switching times or a switching frequency of a power electronics provided as an electrical component (4, 5, 6). Method according to one of the preceding claims, wherein the cooling circuit (8) has at least a first bypass (11) for bypassing the traction battery (7). Method according to one of the preceding claims, wherein the cooling circuit (8) has at least one second bypass (12) for bypassing a cooling device (9) arranged in the cooling circuit (8), wherein heat can be dissipated to an environment (10) of the motor vehicle (3) via the cooling device (9). Motor vehicle (3), at least having an electric drive train (1) which has at least one electric machine (2) for driving the motor vehicle (3) and further electrical components (4, 5, 6) for controlling and operating the electric machine (2), a traction battery (7) and a cooling circuit (8) for controlling the temperature of the traction battery (7), the electric machine (2) and the electrical components (4, 5, 6) and a control unit (13) which has means for carrying out the method according to one of the preceding claims.

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