DE102017211978A1 - Method for operating a drive train for a motor vehicle, in particular for a motor vehicle, and drive train for a motor vehicle - Google Patents

Abstract

The invention relates to a method for operating at least one first electric machine (3), at least one second electric machine (8), at least one first axle (2) which can be driven by means of the first electric machine (3) and at least one by means of the second electric machine (8) drivable second axle (6) having drive train (1) for a motor vehicle, wherein at least one of the axes (2, 6) by means of the respective electric machine (3, 8) is driven, comprising the steps of: determining a requested, total drive torque to be provided by the electric machines (3, 8); and distributing the drive torque to the electric machines (3, 8) in response to respective efficiency chains that characterize respective efficiencies with which the respective axles (2, 6) are drivable by the respective electric machines (3, 8).

Description

The invention relates to a method for operating a drive train for a motor vehicle, in particular for a motor vehicle, according to the preamble of patent claim 1. Furthermore, the invention relates to a drive train for a motor vehicle.

Such a method for operating a drive train for a motor vehicle, in particular for a motor vehicle such as a passenger car, for example, already from the DE 10 2005 049 992 A1 known. In this case, the drive train has at least one first electric machine, at least one second electric machine, at least one first axis which can be driven by means of the first electric machine and at least one second axis which can be driven by the second electrical machine, so that, for example, the motor vehicle as a whole can be driven by means of the electrical machines, in particular electrically, can be driven. In the method, at least one of the axes is driven by the respective electric machine.

In addition, the disclosed WO 2015/078557 A1 a hybrid manager control unit for a powertrain of a vehicle, wherein the hybrid manager control unit a Gesamttsollmoment-allocation device for optimizing an efficiency by dividing a Gesamttsollmoment default in a first Achsmoment specification for a first axis of the vehicle and in a second Achsmoment default for a having second axis of the vehicle.

Object of the present invention is to provide a method and a drive train of the type mentioned, so that a particularly efficient operation can be realized.

This object is achieved by a method with the features of claim 1 and by a drive train with the features of claim 8. Advantageous embodiments of the invention are the subject of the dependent claims.

A first aspect of the invention relates to a method for operating a drive train for a motor vehicle, in particular for a motor vehicle such as a passenger car. The drive train comprises at least one first electric machine, at least one second electric machine, at least one first axis which can be driven by means of the first electric machine and at least one second axis which can be driven by means of the second electrical machine. Thus, for example, the motor vehicle as a whole by means of the electric machines, in particular electrically driven, so that the motor vehicle is preferably designed as an electric vehicle. In the method, at least one of the axes is driven by the respective electric machine.

In order to be able to realize a particularly efficient and thus low-energy operation of the drive train and thus of the motor vehicle as a whole, it is provided according to the invention that a requested drive torque to be provided by the electric machine in total is determined. The drive torque is a torque, in particular a total torque, which is requested, for example, by an electronic computing device which is also designated as a control device. The requested drive torque or its requirement results, for example, from a request made by the driver of the motor vehicle, in the context of which the driver, for example, requests a torque by means of which the axles or the motor vehicle as a whole are to be driven. The driver causes his request, for example, such that the driver actuates an operating element and thereby moves, for example, the driver, for example, the control element operated by hand or by foot. The operating element is in particular a so-called accelerator pedal, which the driver can actuate with his foot and thereby move. In particular, the driver may move the accelerator pedal to different positions, the respective position corresponding to a respective torque requested by the driver. For this requested by the driver torque results in the drive torque, which corresponds for example to the torque requested by the driver.

Furthermore, it is conceivable that the drive torque is requested by at least one driver assistance system of the motor vehicle. The driver assistance system is, for example, a cruise control system, an adaptive cruise control (ACC) or an assistance system for performing autonomous driving.

Furthermore, it is provided according to the invention that the determined drive torque is distributed or split between the electrical machines as a function of respective efficiency chains, which characterize respective efficiencies with which the respective axes can be driven by the respective electrical machines. In this distribution or division of the drive torque to the electric machines, it is to be understood in particular that a first torque to be provided by the first electric machine and a second torque to be provided by the second electric machine are determined or determined in sum, the first torque and the second torque result in the drive torque requested by the electric machines and thus to be provided. The distribution of the drive torque to the electric machines and thus to the axles is also referred to as the axle torque distribution. Since it is now provided according to the invention to take into account the respective efficiency chains in the Achsmomentverteilung, a particularly efficient and thus low-energy operation of preferably designed as an electric vehicle motor vehicle can be realized, so that for example a particularly high range can be realized.

The respective efficiency chain comprises, for example, at least one efficiency of the respective electrical machine. Furthermore, the respective efficiency chain can comprise at least one efficiency of a further drive component, via which the respective axis can be driven by the respective electric machine. The further drive component is, for example, a transmission and / or a converter. In other words, the respective efficiency chain characterizes, for example, at least one efficiency of a respective drive unit comprising the respective electric machine, by means of which the respective axis can be driven. In this case, the respective drive unit also includes, for example, at least one respective transmission and / or at least one respective converter.

In particular, the motor vehicle is designed, for example, as a battery electric vehicle (BEV). Further, it is conceivable that the motor vehicle is designed as a hybrid vehicle and / or fuel cell powered vehicle and thus, for example, has at least one fuel cell as an energy source, by means of which electrical energy for operating the electric machines can be provided. In the case of battery storage vehicles in addition the voltage level has an influence on the level of the corresponding efficiency differences depending on the unit. The efficiency of an electrical machine is influenced by the applied voltage.

The invention is based in particular on the recognition that in conventional powertrains, especially in axle hybrids, the Achsmomentverteilung follows a logic according to which the driver also called request of the driver is primarily represented or satisfied via a hybrid axis and added an electrical axis if necessary. A hybrid axle can be driven, for example, by means of at least one electric machine and by means of an internal combustion engine, while an electric axle can be driven exclusively by means of at least one electric machine. In conventional four-wheel drive vehicles, in which respective axles can be driven, for example, by means of an internal combustion engine, the axle torque distribution usually takes place primarily on the basis of dynamic driving considerations. In contrast, by means of the method according to the invention, an operating strategy for distributing the drive torque to the axles, which are also referred to as drive axles, can be realized, this operating strategy sufficiently taking into account, for example, the respective one efficiency chain from the respective electric machine to a wheel drivable by the respective electric machine. In this case, the efficiency chain includes, for example, the electric machine, the aforementioned transmission and the aforementioned converter of the drive unit acting as a drive unit. As a result, the respective wheel and thus the axles and the motor vehicle as a whole can be driven particularly efficiently.

Preferably, the electrical machines are independently controllable, so that, for example, the respective electric machine can provide from 0 to 100 percent of the drive torque, wherein the respective other electric machine, the possibly existing remainder of the drive torque, which is not provided by the one electric machine provides , Such a construction of two or more independently controllable electric machines as respective drive units for each axle allows an energetic optimization of the axle torque distribution between the axles, of which one of the axles is designed as a front axle and the other axle as a rear axle. By means of simulations it was found that energy savings can be achieved during operation by means of the method according to the invention, in particular in comparison to conventional operating strategies.

The method can potentially be extended by driving dynamics experienced modes such as a drift mode and / or a permanent four-wheel drive mode, so that can represent a particularly advantageous operation of the drive train.

In an advantageous embodiment of the invention, the respective efficiency chain is used as the respective current efficiency chain, which characterizes at least one current efficiency, with which the respective axis can be driven by the respective electric machine. For example, the electric machine or the drive unit has the current efficiency or the current efficiency chain in a respective current state, in particular operating state or load state or load point, up. In this way, the current efficiency or the current efficiency chain, which has the respective electrical machine or the drive unit, taken into account to perform the Achsmomentverteilung so that situationbeziehungsweise demand as the drive torque can be distributed to the electric machines and thus on the axes. As a result, a particularly efficient operation can be realized.

To realize a particularly efficient and therefore low-energy operation, it is provided in a further embodiment of the invention that the respective efficiency or the respective efficiency chain is calculated as a function of a respective load point of the respective electric machine and thereby determined. For example, the current efficiency is currently or online, that is calculated during a drive of the motor vehicle or during operation of the drive train, or the current efficiency is taken, for example, in particular as a function of the respective load point, from a fixed map, which for example fixed in one Memory device, in particular of the control unit, stored or stored.

As further particularly advantageous, it has been shown that the respective efficiency or the respective efficiency chain is determined as a function of a respective temperature of the respective electric machine. This embodiment is based on the finding that the efficiency of an electrical machine can depend on its temperature, which is now advantageously taken into account in the axle torque distribution. As a result, a particularly efficient operation can be represented. The consideration of the temperature makes it possible, for example, to take into account in the axle torque distribution one of the Achsmomentverteilung beforehand operation or operating history of the respective electric machine, thereby avoiding an overly efficient operation can operation.

The inventive method is particularly suitable when the electrical machines, for example, differ from each other in terms of their respective performance. Since according to the invention the respective efficiencies of the electrical machines are taken into account in the axle torque distribution, an energy-optimized axle torque distribution can always be ensured.

In a particularly advantageous embodiment of the invention, at least one input effected by the driver of the motor vehicle is detected, wherein the drive torque is distributed in dependence on the input to the electric machines. The above-mentioned, energetic optimization of the axle torque distribution can thus be extended by one of the driver, in particular freely, adjustable axle torque distribution, whereby, for example, a particularly advantageous operation can be realized.

A further embodiment is characterized in that the drive torque is distributed as a function of at least one characteristic map permanently stored in a memory device. In this case, for example, the respective efficiency is taken from a respective permanently stored map, so that the drive torque is distributed on the basis of at least one permanently stored map. Thus, for example, the aforementioned efficiency chain is included offline in the axle torque distribution. The map is created for example by surveying and / or simulations, especially in the context of the development of the powertrain, whereupon the map is permanently stored stored for example in the control unit.

Alternatively or additionally, it may be provided that the efficiency chain is included online in the axle torque distribution. For this purpose, it is provided that at least one variable parameter characterizing the respective efficiency is calculated during operation of the drive train, in particular during a drive of the motor vehicle, the drive torque being distributed as a function of the calculated parameter. In this way, an on demand and situation appropriate axle torque distribution can be realized, resulting in a particularly efficient operation results.

A second aspect of the invention relates to a drive train for a motor vehicle, wherein the drive train is designed to carry out a method according to the invention. Advantages and advantageous embodiments of the method according to the invention are to be regarded as advantages and advantageous embodiments of the drive train according to the invention and vice versa.

Further details of the invention will become apparent from the following description of a preferred embodiment with the accompanying drawings. The single FIGURE shows a schematic representation of a drive train according to the invention for a motor vehicle.

The single FIGURE shows a schematic representation of a drive train 1 for a motor vehicle, in particular for a motor vehicle such as a passenger car. As will be explained in more detail below, this is Motor vehicle in total by means of the drive train 1 drivable. The powertrain 1 includes a first axis 2 , which is designed as a front axle. Furthermore, the drive train includes 1 one of the first axis 2 associated first electric machine 3 , by means of which the first axis 2 is drivable. In an embodiment not shown in the figure can be provided that the axis 2 a plurality of first electric machines are assigned, by means of which the first axis 2 is drivable. The first axis 2 includes wheels 4 , which, in particular via a differential gear 5 , from the first electric machine 3 are drivable. By driving the wheels 4 becomes the axis 2 driven. Because the axis 2 is designed as a front axle, the wheels 4 designed as front wheels.

Furthermore, it is conceivable that the differential gear 5 can be omitted. Alternatively or additionally, it is conceivable that the respective electric machine is designed as a wheel hub motor, so that, for example, the wheels 4 by means of a respective, trained as a hub motor electric machine 3 are drivable.

The powertrain 1 further comprises a second axis 6 in the form of a rear axle, which second wheels 7 having in the form of rear wheels. This includes the powertrain 1 a second electric machine 8th , which of the axis 6 assigned. Here is the axis 6 drivable by the electric machine. These are the wheels 7 , in particular via a differential gear 9 , drivable by the electric machine.

Furthermore, it is conceivable that the differential gear 9 can be omitted. Alternatively or additionally, it is conceivable that respective electric machine are provided as a wheel hub motor, so that, for example, the wheels 7 by means of a respective, trained as a hub motor electric machine 8th are drivable.

To the respective wheels 4 respectively 7 and thus the respective axis 2 respectively 6 To drive, the respective electric machine 3 respectively 8th in an engine operation and thus operated as an electric motor. For this purpose, the respective electric machine 3 respectively 8th for example, supplied with electrical energy or with electric current, which is stored in at least one energy store, not shown in the figure. The energy store is designed for example as a high-voltage component and provides an electrical voltage of more than 50 volts, in particular of more than 60 volts, and preferably of several 100 volts ready. In particular, the energy store can be designed as a battery, in particular as a high-voltage battery (HV battery).

In an embodiment not shown in the figure, on the axis 6 several electrical machines may be arranged, by means of which the wheels 7 or the axis 6 are drivable or is. From the Fig. It can be seen that the drive train 1 is designed as an electric drive train, so that the motor vehicle, for example, as an electric vehicle, in particular as a battery electric vehicle (BEV) is formed. This means that the motor vehicle can only be driven electrically and not with the help of fossil fuels. Furthermore, it is possible for the motor vehicle to be designed as a hybrid vehicle and / or as a fuel cell-powered vehicle or another motor vehicle.

Here is the electric machine 3 excluding the axle 2 assigned. This means that the electric machine 3 is designed to, based on the axes 2 and 6 only or exclusively the axis 2 and therefore the wheels 4 drive. The axis 6 or the wheels 7 may or may not be from the electric machine 3 are driven. The same applies to the electrical machine 8th in relation to the axis 6 , This means that the electric machine 8th excluding the axle 6 assigned. Thus, the electric machine 8th designed to, based on the axes 2 and 6 only the axis 6 or the wheels 7 to drive, so that by means of the electric machine 8th the wheels 7 but not the wheels 4 can be driven. Furthermore, it is preferably provided that the electrical machines 3 and 8th are independently controllable.

It is also possible that the respective electric machine 3 respectively 8th in a generator mode and thus can be operated as a generator. In the generator operation, the respective electric machine 3 respectively 8th for example, from the respective wheels 4 respectively 7 and thus driven by the moving motor vehicle, so that at least part of the kinetic energy of the moving motor vehicle is converted by means of the generator into electrical energy, which is provided by the respective generator. The electrical energy provided by the respective generator can be stored, for example, in the energy store.

The powertrain 1 further comprises an electronic computing device 10 , which is also referred to as a control unit or drive control unit. The computing device 10 is, in particular by means of respective cables, with the electrical machines 3 and 8th connected so that the electrical machines 3 and 8th from the control unit (computing device 10 ) and thereby operated, in particular regulated or controlled, can be.

The following is a method for operating the drive train with reference to FIG 1 explained, wherein in the method at least one of the axes 2 and 6 by means of the respective associated electrical machine 3 respectively 8th is driven. In its fully manufactured state, the motor vehicle or the drive train comprises 1 For example, in the figure, not shown operating element, which is actuated by the driver of the motor vehicle and thereby movable, for example, in different positions. In this case, the control element is designed, for example, as an accelerator pedal, which can be actuated by the driver with his foot. The respective position of the operating element corresponds to a respective total torque which is requested by the driver in that the driver moves the operating element into the position corresponding to the total torque. The total torque is, for example, from the powertrain 1 to thereby drive the motor vehicle by means of the total torque. This requirement of the driver is also referred to as driver request or driver request torque. The total torque is a torque which, for example, from the drive train 1 , in particular of the electrical machines 3 and 8th , is to provide a total, to drive the motor vehicle by means of the total torque. Furthermore, it is alternatively or additionally possible that the drive torque is requested by a driver assistance system.

In the method, in particular by means of the computing device 10 , a requested, from the electrical machines 3 and 8th determined in total to be provided drive torque. The drive torque is a torque which is generated by the electric machines 3 and 8th is to be provided together or in total. The drive torque is, for example, by the computing device 10 from the electrical machines 3 and 8th requested. The drive torque results for example from the total torque, so that, for example, the driver, in particular by requesting the total torque, requests the drive torque.

Includes the powertrain 1 For example, only or exclusively the electric machines 3 and 8th , so that the total torque only by means of the electric machines 3 and 8th can be provided, for example, the drive torque corresponds to the total torque. Includes the powertrain 1 For example, at least one, not shown in the figure, further or third electric machine for driving the motor vehicle or includes the drive train 1 more than the two electric machines 3 and 8th This is the case with electrical machines, for example 3 and 8th To be provided torque part of the total torque and in particular less than the total torque, for example, a difference between the drive torque and the total torque of the third electric machine or other, designed to drive the motor vehicle electrical machinery of the drive train 1 is to provide. Overall, it can be seen that, for example, the computing device 10 depending on the driver requested and thus desired by the driver total torque determines the drive torque and the electric machines 3 and 8th requesting that should provide the drive torque.

In the embodiment illustrated in the figure, the drive train comprises 1 only the electrical machines 3 and 8th for driving the motor vehicle, so that in the embodiment illustrated in the figure, the drive torque corresponds to the total torque. Thus, the driver requests the total torque as the drive torque from the electric machines 3 and 8th at.

In addition, it is provided in the method that the drive torque to the electric machines 3 and 8th is distributed as a function of respective efficiency chains that characterize the respective efficiencies with which the respective axis 2 and 6 from the electrical machines 3 and 8th are drivable. Under this distribution of drive torque to the electric machines 3 and 8th and thus on the axles 2 and 6 is to be understood that, in particular by means of the computing device 10 , one from the electric machine 3 to be provided first torque and one of the electric machine 8th is to be provided second torque, wherein the first torque and the second torque sum in the drive torque. By means of the electric machine 3 to be provided first torque are the wheels 4 and thus the axis 2 driven, while or by means of the of the electric machine 8th to be provided second torque the wheels 7 and thus the axis 6 are driven. In order to distinguish the first torque and the second torque conceptually better from other torques, the first torque is also referred to as the first engine torque and the second torque also referred to as the second engine torque.

The respective engine torque can be within a range of 0 percent up to and including 100 percent of the drive torque, so that, for example, the drive torque exclusively from the electric machine 3 or exclusively from the electric machine 8th provided. Distributing the drive torque to the electric machines 3 and 8th is also called axle torque distribution. Is the Achsmomentverteilung of the computing device 10 For example, determined such that one of the engine torque is less than the drive torque, so that a difference between the one engine torque and the drive torque exists, the difference corresponds to the other engine torque. Overall, it can be seen that the drive torque by means of the computing device 10 as a function of the respective efficiency chains on the electric machines 3 and 8th is split that the electric machine 3 a first part of the drive torque and the electric machine 8th provides a second part of the drive torque, wherein the parts can each lie in a range of 0 percent to and including 100 percent of the drive torque and sum in the drive torque. In addition, the electric machines 3 and 8th such from the computing device 10 that drives the electrical machines 3 and 8th provide the respective engine torque, so that in the sequence the motor vehicle is driven in total by at least the requested drive torque.

The respective efficiency chain is, for example, an efficiency chain of the respective electric machine 3 respectively 8th to the respective bike 4 respectively 7 , In this case, the respective efficiency chain, the respective electric machine 3 respectively 8th , At least one gear and at least one inverter or their respective efficiencies characterize. As a result, an energy optimization of the axle torque distribution in comparison to conventional methods can be realized.

It is possible to include the efficiency chain offline in the axle torque distribution. This is done, for example, in the context of the development of the drive train 1 a measurement and / or a simulation, so that then at least one fixed map in the control unit, in particular in a memory device 11 of the control unit, stored or stored. In particular, depending on a respective load or operating point of the respective electric machine 3 respectively 8th , the respective efficiency or the respective Achsmomentverteilung and thus the respective engine torque is taken from the map and finally by appropriate control of the electrical machines 3 and 8th set.

In particular, it is conceivable that the respective efficiency or the respective efficiency chain as a function of a respective temperature of the respective electrical machine 3 respectively 8th is determined so that, for example, the axle torque distribution as a function of the respective temperature of the respective electric machine 3 respectively 8th is carried out.

Furthermore, it is conceivable that the efficiency chain is included online, so for example during a drive of the motor vehicle in the Achsmomentverteilung. For this purpose, the respective efficiency chain or the Achsmomentverteilung each needs or appropriate situation by means of the computing device 10 calculated, so that a particularly efficient operation can be displayed. For this purpose, in particular at least one variable parameter characterizing the respective efficiency during operation of the drive train 1 calculated, wherein the drive torque is distributed in dependence on the calculated parameter.

LIST OF REFERENCE NUMBERS

1

powertrain

2

axis

3

electric machine

4

wheel

5

differential gear

6

axis

7

wheel

8th

electric machine

9

differential gear

10

electronic computing device

11

memory device

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been 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 102005049992 A1 [0002]
• WO 2015/078557 A1 [0003]

Claims (9)

Method for operating at least one first electric machine (3), at least one second electric machine (8), at least one first axle (2) drivable by means of the first electric machine (3) and at least one drivable by means of the second electric machine (8) second axle (6) having a drive train (1) for a motor vehicle, wherein at least one of the axes (2, 6) by means of the respective electric machine (3, 8) is driven, characterized by the steps: - Determining a requested, of the electric machines (3, 8) in total to be provided drive torque; and - distributing the drive torque to the electric machines (3, 8) in response to respective efficiency chains that characterize respective efficiencies with which the respective axles (2, 6) are drivable by the respective electric machines (3, 8). Method according to Claim 1 , characterized in that the respective efficiency chain is used as respective current efficiency chain, which characterizes at least one current efficiency, with which the respective axis (2, 6) of the respective electric machine (3, 8) can be driven. Method according to Claim 1 or 2 , characterized in that the respective efficiency chain in dependence on a respective load point of the respective electric machine (3, 8) is determined. Method according to one of the preceding claims, characterized in that the respective efficiency chain in dependence on a respective temperature of the respective electric machine (3, 8) is determined. Method according to one of the preceding claims, characterized in that at least one input effected by the driver of the motor vehicle is detected and the drive torque is distributed as a function of the input to the electric machines (3, 8). Method according to one of the preceding claims, characterized in that the drive torque is requested by at least one driver assistance system of the motor vehicle. Device according to one of the preceding claims, characterized in that the drive torque as a function of at least one in a memory device (11) permanently stored map is distributed. Method according to one of the preceding claims, characterized in that at least one of the respective efficiency chain characterizing variable parameter during operation of the drive train (1) is calculated, wherein the drive torque is distributed in dependence on the calculated parameter. Drive train (1) for a motor vehicle, wherein the drive train is designed for carrying out a method according to one of the preceding claims.

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