DE102019216543A1 - Method for operating a drive train of a motor vehicle - Google Patents

Abstract

A method for operating a drive train (3) of a motor vehicle (4), the drive train (3) comprising at least one drive unit (5), at least one transmission (6), a heat conduction device (7) and a control unit (8); the drive unit (5) having a variable first efficiency (9) during operation and forming a heat source, the transmission (6) having a variable second efficiency (10) and a heat sink, the control unit (8) for regulating a heat flow (11) is suitably designed via the heat conduction device (7) at least between the drive unit (5) and the transmission (6).

Description

The invention relates to a method for operating a drive train of a motor vehicle. In particular, the method is intended to enable energy-efficient operation of the motor vehicle, especially in a cold start and warm-up phase of a motor vehicle. In particular, this is intended to further reduce fuel consumption or energy consumption of the motor vehicle. The method is intended to regulate a total efficiency, or an overall efficiency, of the drive train during operation of the motor vehicle.

From the DE 10 2010 060 219 A1 a thermal management system for a vehicle drive train is known, by means of which heat from a drive unit can be supplied to a transmission in a targeted manner.

It is the object of the present invention to at least partially solve the problems cited with reference to the prior art. In particular, a total efficiency of a drive train should be regulated so that an energy-efficient operation of a motor vehicle can be made possible.

A method with the features according to patent claim 1 contributes to the solution of these objects. Advantageous further developments are the subject of the dependent claims. The features listed individually in the patent claims can be combined with one another in a technologically sensible manner and can be supplemented by explanatory facts from the description and / or details from the figures, with further design variants of the invention being shown.

1. a) Inbetriebnahme des Antriebsstrangs;
2. b) Ermitteln des aktuell vorliegenden ersten Wirkungsgrads und des aktuell vorliegenden zweiten Wirkungsgrads;
3. c) Bestimmen eines ersten Summenwirkungsrads des Antriebstrangs, der sich zumindest aus dem ersten Wirkungsgrad und dem zweiten Wirkungsgrad ergibt;
4. d) Regeln des Wärmestroms zumindest zwischen der Antriebseinheit und dem Getriebe, um zumindest den zweiten Wirkungsgrad zu ändern und den ersten Summenwirkungsgrad auf einen zweiten Summenwirkungsgrad zu erhöhen.

A method for operating a drive train of a motor vehicle is proposed. The drive train comprises at least: a drive unit, at least one transmission, a heat conduction device and a control device. The drive unit has a variable first efficiency during operation and forms a heat source. The transmission has a variable second efficiency and represents a heat sink. The control device is suitably designed or set up to regulate a heat flow via the heat conduction device, at least between the drive unit and the transmission. The method has at least the following steps:

1. a) commissioning of the drive train;
2. b) determining the currently available first efficiency and the currently available second efficiency;
3. c) determining a first total efficiency wheel of the drive train, which results at least from the first efficiency and the second efficiency;
4. d) regulating the heat flow at least between the drive unit and the transmission in order to change at least the second efficiency and to increase the first cumulative efficiency to a second cumulative efficiency.

In the warm-up phase of the drive train, e.g. B. in a cold start phase of a motor vehicle, d. H. After a longer standstill of the motor vehicle and with a cold drive unit, fuel consumption can be reduced if a warming coolant is used efficiently to heat components in the drive train that are subject to frictional losses. Targeted heating of a gearbox can have a direct effect on the overall mechanical losses of the drive train. B. on the friction losses in the drive unit and transmission. In known drive trains and their operation, the drive unit is given priority during heating, which does not necessarily lead to an improvement in the overall efficiency or overall efficiency.

In particular, the comfort of a user of the motor vehicle is given priority when heating, so z. B. the heating of an interior of the motor vehicle given.

In particular, an efficiency denotes the proportion of energy consumed that is used. The energy of a fuel z. B. is converted into mechanical friction, heat, kinetic energy, etc. in the motor vehicle. Part of the energy of the fuel can be used for the operation of the motor vehicle, so z. B. to generate propulsion, to generate heat in the interior or to heat components of the exhaust gas cleaning, etc., are not used and z. B. dissipated in the form of heat to the environment. The higher the proportion of the energy used to operate the motor vehicle in relation to the energy used (here, for example, measurable through the consumption of fuel), the higher the efficiency. In the present case, a total efficiency of a drive train is considered, the total efficiency being the individual efficiencies of individual components, such as. B. internal combustion engine and transmission, combined into one value, in particular by multiplying the individual efficiencies with each other.

In the present case, in particular, a method for heating up the drive train is to be proposed in which, in particular, all components of the drive train that influence the overall efficiency are taken into account. The aim is to set the highest possible overall efficiency for the drive train, with the user Loss of comfort is saved and the emission of pollutants is to be reduced.

Current operating parameters of the motor vehicle and / or the respective component can be taken into account to determine the degree of efficiency, such as B. Temperatures, times, loads, etc. The operating parameters can be sensed and / or calculated. The efficiencies can in particular be estimated, classified and / or calculated based on the operating parameters. For this purpose, the control unit can comprise at least one efficiency computing unit.

In the context of the method, the transmission is to be heated in particular on short journeys, i.e. journeys of less than ten kilometers, so that the second efficiency of the transmission can be increased as quickly as possible. The heating of the transmission depends in particular on factors other than just the length of the journey, e.g. B. on the load, the speed, the number of start-stop phases, the ambient temperature, etc .. In particular, a torque curve or the torque load of the drive unit and the environmental conditions of the motor vehicle should be taken into account. In the case of internal combustion engines that are operated with a variable or dynamically regulated target temperature, the particular target temperature should be taken into account. In particular, a heating requirement of the interior should also be taken into account.

The drive unit is in particular an internal combustion engine, e.g. B. a diesel or gasoline engine. In particular, the drive unit is operated with a setpoint temperature that changes as a function of the operating state.

The transmission is, in particular, a device for the switchable, possibly continuously or step-wise, change in a translation. A torque of the drive unit is transmitted to at least one wheel of the motor vehicle via the transmission.

The drive unit generates heat during operation and therefore forms a heat source. The method is intended to use the heat generated by the drive unit more efficiently. In particular, the heat should be transferred to the transmission via the heat conduction device, so that a second efficiency of the transmission can be increased as quickly as possible. A dissipation of the heat from the heat source to the environment should be prevented as far as possible, at least until the transmission has reached a certain temperature and the second degree of efficiency can be increased.

The heat conduction device is z. B. a cooling circuit or a lubricant circuit. A medium circulates in the respective circuit, which here transports a heat flow via the heat conduction device. In particular, via a medium, e.g. B. a coolant or a lubricant, the heat generated in the drive unit is transferred to the transmission. The heat conduction device configured as a cooling circuit or lubricant circuit can be designed to be integrated into existing cooling circuits or lubricant circuits of a motor vehicle.

In particular, the control device regulates the heat flow in accordance with step d). For regulation, the control device can regulate at least one valve or switching element or also a multiplicity of valves or switching elements in such a way that a heat flow is not, partially or completely transported from the heat source to the heat sink.

In the context of the method, the overall efficiency of the drive train is to be increased in particular. The total efficiency here includes the first efficiency of the drive unit and the second efficiency of the transmission. In particular, the efficiencies of other components can be determined here and, if necessary, also regulated.

In particular, the efficiencies are essentially dependent on the friction losses of the respective component. As a result of the components being heated as quickly and in a controlled manner as possible, such friction losses or mechanical losses can be reduced as quickly as possible.

In particular, within the scope of the method, a heat flow from the heat source is regulated, at least temporarily, exclusively with a view to increasing the overall efficiency of the drive train. This enables an efficient reduction in fuel consumption.

In particular, a setpoint temperature and an actual temperature of the drive unit are determined in step b). Furthermore, a temperature profile is determined from the actual temperature to the setpoint temperature, at least taking into account the operation of the drive unit, the control of the heat flow being carried out taking into account at least the temperature profile.

In particular, it should be determined how much heat is dissipated from the drive unit at certain times and z. B. can be fed to the transmission. In particular, requirements of the drive unit with regard to consumption-efficient operation and, in particular, a first degree of efficiency are to be taken into account. At the same time, however, a second efficiency should be taken into account so that a total efficiency of the first efficiency and the second efficiency can be maximized.

The above (non-exhaustive) division of the process steps into a) to d) is primarily intended to serve only to differentiate and not to enforce a sequence and / or dependency. The frequency of the process steps z. B. during setup and / or operation of the system may vary. It is also possible for method steps to overlap one another at least partially in time. Process steps b) to d) very particularly preferably take place chronologically after step a) and then continuously and in a chronologically overlapping manner. In particular, steps a) to d) are carried out in the order listed.

In particular, the regulation of the heat flow according to step d) is carried out taking into account at least one ambient temperature. The ambient temperature is in particular the temperature of the surroundings of the motor vehicle.

In particular, the control of the heat flow for the transmission takes place as a function of a torque load of the drive unit and of ambient conditions. The heating of the transmission via the heat flow is preferably regulated by a characteristic map which includes at least the parameters setpoint temperature of the drive unit and ambient temperature. In the characteristics map, an actual temperature can be specified for a setpoint temperature of the drive unit that is present for the respective operating point, and when it is reached and exceeded, a heat flow to the transmission is released.

In particular, the target temperature is dependent on the current torque load applied to the drive unit. The generation of heat by the drive unit is in particular proportional to the current torque load or to the torque provided by the drive unit. A dissipation of heat to the environment is in particular proportional to the ambient temperature.

A generation of heat can also be determined on the basis of other parameters of the drive train or of the motor vehicle, e.g. B. taking into account at least one of the following parameters: current drive power of the drive unit, accelerator pedal position, torque of the drive unit, fuel consumption, intake air mass, turbocharger speed, relative air mass for combustion, boost pressure.

The parameters considered necessary to carry out the method can be, for. B. determined by sensors and / or based on maps.

A dissipation of heat to the environment can also be determined on the basis of other parameters of the drive train or the motor vehicle, e.g. B. taking into account at least one of the following parameters: speed of the motor vehicle, speed of the drive unit, fan control, volume flow of a cooling medium through a cooler or a cooling circuit.

Depending on the setpoint temperature and / or an ambient temperature, a heat flow can be ascertained and determined, which can be dissipated from the drive unit via the heat conduction device. At a low ambient temperature, e.g. B. be taken into account that the heating of the drive unit takes longer or takes place more slowly. In this case, heat dissipation from the drive unit to the transmission could possibly lead to an impermissible cooling of the drive unit.

In particular, the regulation of the heat flow according to step d) is carried out taking into account a torque curve of the drive unit with respect to a limit load torque and taking into account at least one ambient temperature with respect to a limit temperature.

A limit temperature is z. B. 5 degrees Celsius. Below that there is a low ambient temperature, above that there is a high ambient temperature.

A limit load torque is z. B. 20% of a nominal torque of the drive unit.

In particular, taking into account these parameters ambient temperature and torque curve or torque load, several limit states can be provided for which different scenarios for regulating the heat flow are defined.

In particular, if the torque curve is essentially or permanently below the limit load torque and the ambient temperature is below the limit temperature, heat is only dissipated from the drive unit to the transmission via the heat conduction device when the drive unit has reached a target temperature.

In this first scenario, that for a low moment load and a low one Ambient temperature, e.g. B. less than 5 degrees Celsius is defined, the comfort of a user of the motor vehicle, so z. B. the heating of an interior, a security of the user, z. B. a window de-icing, as well as low pollutant emissions are prioritized. It can, for. B. low pollutant emissions can be achieved in that the heat generated by the drive unit is not dissipated to the transmission but is used to heat the components for exhaust gas aftertreatment. Furthermore, in this first scenario an unnecessary release of heat to the surroundings of the motor vehicle should be prevented so that the generated heat can be used to further heat components of the motor vehicle. In this context, fuel consumption can be considered subordinate. A drop in a temperature of the drive unit z. B. due to a forwarding of a heat flow to the transmission, can be prevented. In this scenario, the transmission should therefore only be heated by the heat flow of the drive unit when the drive unit has reached the target temperature and, if necessary, exceeded it.

The target temperature is in particular between 80 and 105 degrees Celsius, preferably between 85 and 95 degrees Celsius.

In particular, if the torque curve runs at least in a certain time interval above the limit load torque and the ambient temperature is below the limit temperature, heat is only dissipated from the drive unit to the transmission via the heat conduction device when the drive unit has reached and exceeded a first actual temperature that is at least 5%, preferably at least 10%, below the target temperature.

The time interval is z. B. at least 5 seconds, in particular at least 10 seconds.

In this second scenario, which is defined for a high torque load or a higher torque load than the first scenario, and a low ambient temperature, the comfort and safety of a user of the motor vehicle and low pollutant emissions should be prioritized. It can, for. For example, low pollutant emissions can be achieved in that the heat generated by the drive unit is not dissipated to the transmission but is used to heat the components for exhaust gas aftertreatment. Furthermore, in this second scenario an unnecessary release of heat to the surroundings of the motor vehicle should be prevented so that the generated heat can be used to further heat components of the motor vehicle. In this context, fuel consumption can be considered subordinate. A drop in a temperature of the drive unit z. B. due to a forwarding of a heat flow to the transmission, is not to be expected from the drive unit as a heat source due to the high torque load and the associated heat input. In this second scenario, the transmission can therefore already be heated by the heat flow of the drive unit when the drive unit has not yet reached the setpoint temperature.

In particular, heat can be dissipated when a first actual temperature is reached and exceeded, which has a value between 81 and 91 degrees Celsius.

In particular, heat is dissipated from the drive unit to the transmission at a temperature at which a cooler for the drive unit is not yet integrated into a cooling circuit for the drive unit. This prevents heat from being dissipated to the environment before this heat has been used to heat the gear unit.

A control temperature at which the cooler for the drive unit is integrated into the cooling circuit to dissipate heat is z. B. 80 degrees Celsius.

It is preferred that heat dissipation to the gear unit begins when a first actual temperature of less than 80 degrees Celsius is reached and exceeded. In particular, the first actual temperature has a value between 76 and 85 degrees Celsius.

In particular, if the torque curve is essentially below the limit load torque and the ambient temperature is above the limit temperature, heat is only dissipated from the drive unit to the transmission via the heat conduction device when the drive unit has reached and exceeded a second actual temperature, which is at least 8%, preferably at least 15%, below the target temperature.

In this third scenario, which is defined for a low torque load and high ambient temperature, the comfort and safety of a user should not be considered. In doing so, low pollutant emissions and rapid heating of the exhaust gas aftertreatment can be prioritized. Heat dissipation to the environment is minimal at high ambient temperatures, with little heat being generated by the drive unit due to the low torque load. The risk that a temperature of the drive unit drops in an impermissible manner and a critical temperature range is present in the drive unit when a heat flow is passed on to the gearbox is low here.

In particular, the components of the drive train surrounding the at least one combustion chamber are also significantly warmer than at correspondingly low ambient temperatures and a low torque load. It is preferred that heat dissipation to the gear unit begins when a second actual temperature of less than 75 degrees Celsius is reached and exceeded. In particular, the second actual temperature has a value between 70 and 80 degrees Celsius.

In particular, if the torque curve runs at least in a certain time interval above the limit load torque and the ambient temperature is above the limit temperature, heat is only dissipated from the drive unit to the transmission via the heat conduction device when the drive unit has reached and exceeded a third actual temperature that is at least 10%, preferably at least 20%, below the target temperature.

In this fourth scenario, which is defined for a high torque load, or a higher torque load than the first and third scenarios, and a high ambient temperature, the comfort and safety of a user should not be taken into account. Furthermore, low pollutant emissions and rapid heating of the exhaust gas aftertreatment can be prioritized. Heat dissipation to the environment is minimal at high ambient temperatures, with a great deal of heat being generated by the drive unit due to the high torque load. There is no risk here that a temperature of the drive unit drops in an impermissible manner when a heat flow is passed on to the gearbox and that a critical temperature range is present in the drive unit.

In this fourth scenario, it is important to direct a heat flow to the transmission as early as possible so that as little heat as possible, e.g. B. is discharged to the environment via a cooler. It is preferred that heat dissipation to the gear unit begins when a third actual temperature of less than 65 degrees Celsius is reached and exceeded. In particular, the third actual temperature has a value between 60 and 70 degrees Celsius.

In particular, knocking combustion of the fuel can also be prevented in this way, since the target temperature can be adhered to more precisely, or excessive exceeding of the target temperature can be avoided. Furthermore, by diverting a heat flow from the drive unit at an early stage, the setpoint temperature can be pre-controlled more precisely, so that overshooting of the control, i.e. exceeding the setpoint temperature, can be avoided.

In particular, the transmission can also be heated in several stages. The above describes the heating of the transmission as a function of the reaching of a target temperature, whereby above all the drive unit is given priority with regard to the heating. This approach takes into account fuel consumption and pollutant emissions in particular.

Alternatively, however, the drive train as a whole can be regulated even earlier in terms of efficiency, with an overall efficiency being maximized. For this purpose, in an even earlier phase after a cold start, that is, long before the drive unit has reached a target temperature, the transmission can be brought to a minimum temperature, referred to below as the minimum second temperature. This takes into account, in particular, that the second efficiency has a logarithmic profile as a function of a transmission oil temperature and the associated lower viscosity. At low transmission oil temperatures in particular, significant frictional losses can be reduced with low heat dissipation to the transmission up to a transmission oil temperature of approx. 35 degrees Celsius and thus fuel can be saved.

To enable this early heating of the transmission, the drive unit should have a minimum temperature, hereinafter referred to as the minimum first temperature, e.g. B. 65 degrees Celsius. This first temperature is selected in particular so that there is no negative influence on pollutant emissions.

When the gearbox starts to heat up in this early phase, the current actual temperature of the drive unit can drop. Therefore, a hysteresis, e.g. B. from z. B. 5 Kelvin can be provided, through which the first temperature must be exceeded. This means that impairments in terms of comfort, e.g. B. interior heating, and security, e.g. B. de-icing windows, can be avoided.

When the gear oil has reached a low-friction gear oil temperature of approx. 35 degrees Celsius, the heating of the gear can at least be interrupted or even ended. This means that the entire amount of heat available from the drive unit can be used to heat the drive unit and possibly other components.

In particular, when a higher actual temperature is reached, it is then possible to proceed according to the different limit states or scenarios.

Should the transmission oil temperature drop again in the meantime, e.g. B. up to a threshold below 35 degrees Celsius, so z. B. from 28 degrees Celsius, the heating of the transmission - while maintaining the above minimum first temperature - can be restarted in order to keep the transmission at a consumption-optimized operating temperature.

In particular, when the actual temperature, ie the current temperature, of the drive unit exceeds a minimum first temperature, the heat flow is conducted via the heat conduction device to the transmission until the transmission reaches at least a minimum second temperature.

In particular, when the transmission has reached the minimum second temperature, the dissipation of heat to the transmission is prevented, so that the drive unit is heated up in an accelerated manner.

The first temperature is 65 degrees Celsius. The second temperature is 35 degrees Celsius. A hysteresis of 5 Kelvin can be provided for the first temperature and / or the second temperature.

A control device is also proposed which is equipped, configured or programmed to carry out the method described.

Furthermore, the method can also be carried out by a computer or with a processor of a control unit.

Accordingly, a system for data processing is also proposed which comprises a processor which is adapted / configured in such a way that it carries out the method or part of the steps of the proposed method.

A computer-readable storage medium can be provided which comprises instructions which, when executed by a computer / processor, cause the latter to execute the method or at least some of the steps of the proposed method.

A motor vehicle is also proposed, at least comprising a drive train with at least one drive unit, a transmission, a heat conduction device and a control device. The drive unit has a variable first efficiency during operation and forms a heat source. The transmission has a variable second efficiency and represents a heat sink. The control device is designed to regulate a heat flow via the heat conduction device at least between the drive unit and the transmission.

The statements relating to the method can in particular be transferred to the motor vehicle or the computer-implemented method (that is to say the computer or the processor, the data processing system, the computer-readable storage medium) and vice versa.

The use of indefinite articles (“a”, “an”, “an” and “an”), especially in the patent claims and the description reproducing them, is to be understood as such and not as a numerical word. The terms or components introduced in this way are therefore to be understood in such a way that they are present at least once and, in particular, can also be present several times.

As a precaution, it should be noted that the numerals used here (“first”, “second”, ...) primarily (only) serve to differentiate between several similar objects, sizes or processes, so in particular no dependency and / or sequence of these objects, sizes or prescribe processes to each other. Should a dependency and / or sequence be required, this is explicitly stated here or it is obvious to a person skilled in the art when studying the specifically described embodiment. If a component can appear several 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;
• 2: ein Kennfeld;
• 3: ein erstes Diagramm;
• 4: ein zweites Diagramm; und
• 5: ein drittes Diagramm.

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

• 1 : a motor vehicle;
• 2 : a map;
• 3 : a first diagram;
• 4th : a second diagram; and
• 5 : a third diagram.

The 1 shows a motor vehicle 4th , comprising a drive train 3 with a drive unit 5 , a transmission 6th , a heat conduction device 7th as well as a control unit 8th . The drive unit 5 exhibits a variable first degree of efficiency during operation 9 and forms a source of heat. The gear 6th exhibits a variable second efficiency 10 and represents a heat sink. The control unit 8th is to regulate a heat flow 11 via the heat conduction device 7th at least between the drive unit 5 and the gearbox 6th suitably executed.

The heat conduction device 7th is designed as a cooling circuit via the control unit 8th is adjustable.

The drive unit 5 has a variable target temperature 12th on. In the vicinity of the motor vehicle 4th is an ambient temperature 17th in front. The control unit 8th defines a limit temperature 19th , depending on which a scenario for heating the transmission 6th is determined.

The heating of the transmission 6th can be done in several stages. The drive train can 3 as a whole at an early stage in terms of overall efficiency 1 , 2 are regulated, this starting from a first total efficiency 1 towards a second total efficiency 2 should be maximized. This can be done at an early stage after a cold start, i.e. long before the drive unit 5 a target temperature 12th has reached the transmission 6th to a minimum second temperature 21 to be brought. The drive unit should 5 a minimum first temperature 20th have already achieved. This takes into account that the second efficiency 10 depending on a transmission oil temperature 22nd and the associated lower viscosity 25th a logarithmic course (see 5 ) owns. Especially at low transmission oil temperatures 22nd can be transferred to the gear unit with little heat 6th Reduce friction losses significantly up to a transmission oil temperature of approx. 35 degrees Celsius and thus save fuel.

In the method, the drive train is started up in step a) 3 . In step b) the currently available first efficiency 9 the drive unit 5 and the currently available second efficiency 10 of the transmission 6th determined. A first cumulative efficiency is determined in step c) 1 that can be seen at least from the first degree of efficiency 9 and the second efficiency 10 results. The heat flow is regulated in step d) 11 between the drive unit 5 and the gearbox 6th to change at least the second efficiency 10 and to increase the first total efficiency 1 on the second total efficiency 2 . The regulation of the heat flow 11 according to step d), taking into account a torque curve of the drive unit 5 compared to a limit load torque 18th and taking into account at least one ambient temperature 17th compared to a limit temperature 19th carried out.

2 shows a map. In the upper line there are different values for the ambient temperature 17th applied. In the left column are the target temperatures 12th for different operating points of the drive unit 5 applied. The values in the map or the table represent deviations from the respective target temperature 12th The result of a subtraction of the deviation from the respective target temperature 12th gives the respective actual temperature 13th , 14th , 15th , when they are reached or exceeded, the gear unit is heated 6th is initiated.

3 shows a first diagram. On the vertical axis is the second efficiency 10 of the transmission applied. The transmission oil temperature is on the horizontal axis 22nd applied. The curve shown illustrates the change in the second efficiency 10 compared to the transmission oil temperature 22nd . The second degree of efficiency changes in the process 10 in a first area, i.e. at a low transmission oil temperature 22nd , with steeper first gradients 23 and in a second area, at a higher transmission oil temperature 22nd , with a flatter second gradient 24 .

4th shows a second diagram. On the vertical axis are temperatures 12th , 13th , 14th , 15th applied. The time is plotted on the horizontal axis. The different temperature profiles 16 represent the change in the current temperature of the drive unit 5 for the different scenarios 30th , 31 , 32 , 33 represent.

In a first scenario 30th , that for a low moment load and a low ambient temperature 17th is defined, the transmission should be heated 6th about the heat flow 11 the drive unit 5 only from an initial point in time 26th done when the drive unit 5 the target temperature 12th reached and possibly exceeded. The heating of the transmission 6th continues in this first scenario 30th so at the first point in time 26th a.

In a second scenario 31 that for a high, respectively, compared to the first scenario 30th higher moment load and a lower ambient temperature 17th is defined, the transmission should be heated 6th about the heat flow 11 the drive unit 5 already take place when the drive unit 5 the target temperature 12th has not yet reached. In particular, heat is dissipated when a first actual temperature is reached and exceeded 13th . The heating of the transmission 6th continues in this second scenario 31 so at the second point in time 27 a.

In a third scenario 32 , that for a low moment load and high ambient temperature 17th is defined, a heat dissipation should be provided to the transmission 6th as soon as a second actual temperature is reached and exceeded 14th deploy. The heating of the transmission 6th continues in this third scenario 32 so at the third point in time 28 a.

In a fourth scenario 33 that for a high, respectively, compared to the first scenario 30th and third scenario 32 higher moment load and high ambient temperature 17th is defined, a heat flow should be initiated as early as possible 11 towards the transmission 6th are conducted so that as little heat as possible z. B. is discharged to the environment via a cooler. Heat dissipation to the gearbox 6th occurs when a third actual temperature is reached and exceeded 15th . The heating of the transmission 6th continues in this fourth scenario 33 so at the fourth point in time 29 a.

5 shows a third diagram. On the vertical axis is the viscosity 25th of the gear oil applied. The transmission oil temperature is on the horizontal axis 22nd applied. The curve shows the logarithmic curve of the viscosity 25th depending on a transmission oil temperature 22nd .

List of reference symbols

1

first cumulative effect wheel

2

second total effect wheel

3

Powertrain

4th

Motor vehicle

5

Drive unit

6th

transmission

7th

Heat conduction device

8th

Control unit

9

first efficiency

10

second efficiency

11

Heat flow

12th

Target temperature

13th

first actual temperature

14th

second actual temperature

15th

third actual temperature

16

Temperature profile

17th

Ambient temperature

18th

Limit load torque

19th

Limit temperature

20th

first temperature

21

second temperature

22nd

Transmission oil temperature

23

first gradient

24

second gradient

25th

viscosity

26th

first point in time

27

second point in time

28

third point in time

29

fourth point in time

30th

first scenario

31

second scenario

32

third scenario

33

fourth scenario

QUOTES INCLUDED IN THE DESCRIPTION

This list of the 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.

Patent literature cited

• DE 102010060219 A1 [0002]

Claims (10)

A method for operating a drive train (3) of a motor vehicle (4), the drive train (3) comprising at least one drive unit (5), at least one transmission (6), a heat conduction device (7) and a control unit (8); the drive unit (5) having a variable first efficiency (9) during operation and forming a heat source, the transmission (6) having a variable second efficiency (10) and a heat sink, the control unit (8) for regulating a heat flow (11) is suitably designed via the heat conduction device (7) at least between the drive unit (5) and the transmission (6); wherein the method comprises at least the following steps: a) commissioning of the drive train (3); b) determining the currently available first efficiency (9) and the currently available second efficiency (10); c) determining a first total efficiency wheel (1) of the drive train (3), which results from at least the first efficiency (9) and the second efficiency (10); d) regulating the heat flow (11) at least between the drive unit (5) and the transmission (6) in order to change at least the second efficiency (10) and to increase the first cumulative efficiency (1) to a second cumulative efficiency (2). Procedure according to Claim 1 , wherein in step b) a target temperature (12) and an actual temperature (13, 14, 15) of the drive unit (5) are determined, with a temperature profile (16) from the actual temperature (13, 14, 15) towards the target temperature (12) is determined at least taking into account the operation of the drive unit (5), the control of the heat flow (11) being carried out taking into account at least the temperature profile (16). Method according to one of the preceding claims, wherein the regulation of the heat flow (11) according to step d) is carried out taking into account at least one ambient temperature (17). Method according to one of the preceding claims, wherein the regulation of the heat flow (11) according to step d) is carried out taking into account a torque curve of the drive unit (5) against a limit load torque (18) and taking into account at least one ambient temperature (17) against a limit temperature (19) becomes. Procedure according to Claim 4 If the torque curve is essentially below the limit load torque (18) and the ambient temperature (17) is below the limit temperature (19), heat is only dissipated from the drive unit (5) to the transmission (6) via the heat conduction device (7) is carried out when the drive unit (5) has reached a target temperature (12). Procedure according to Claim 4 or 5 , wherein, if the torque curve runs at least in a certain time interval above the limit load torque (18) and the ambient temperature (17) is below the limit temperature (19), heat is dissipated from the drive unit (5) to the gear unit (6) via the heat conduction device ( 7) is only carried out when the drive unit (5) has reached and exceeded a first actual temperature (13) which is at least 5% below the target temperature (12). Method according to one of the Claims 4 to 6th If the torque curve is essentially below the limit load torque (18) and the ambient temperature (17) is above the limit temperature (19), heat is only dissipated from the drive unit (5) to the gear unit (6) via the heat conduction device (7) is carried out when the drive unit (5) has reached and exceeded a second actual temperature (14) which is at least 8% below the target temperature (12). Method according to one of the Claims 4 to 7th , wherein, if the torque curve runs at least in a certain time interval above the limit load torque (18) and the ambient temperature (17) is above the limit temperature (19), heat is dissipated from the drive unit (5) to the transmission (6) via the heat conduction device ( 7) is only carried out when the drive unit (5) has reached and exceeded a third actual temperature (15) which is at least 10% below the target temperature (12). Method according to one of the preceding claims, wherein, when the actual temperature (13, 14, 15) of the drive unit (5) exceeds a minimum first temperature (20), the heat flow (11) via the heat conducting device (7) to the transmission ( 6) is passed until the transmission (6) reaches at least a minimum second temperature (21). Procedure according to Claim 9 , wherein, when the gear (6) has reached the minimum second temperature (21), the heat dissipation to the gear (6) is prevented, so that the drive unit (5) is heated accelerated.

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