DE10225249B4 - Method for controlling a starting process of a drive train - Google Patents

Abstract

Method for controlling a starting process of a drive train (2) with a driven by a prime mover (4) and a planetary gear arranged therebetween (1), wherein the planetary gear (1) via a frictional switching element (10) can be bridged and the variable Transmission of a torque (T_am) of the drive machine (4) with a speed and torque variable machine (6) is operatively connected, characterized in that one of the drive machine (4) to the consumer (9) according to a request to be transmitted target torque (T_soll) in addition continuously controlled via the frictional switching element (10) is adjustable, wherein the target torque (T_soll) as a function of a differential speed (Δn_am) between a target idle speed (n_am_LL_soll) of the prime mover (4) and an actual speed ( n_am_ist) of the drive machine (4) is determined.

Description

The invention relates to a method for controlling a starting process of a drive train according to the closer defined in the preamble of claim 1. Art.

From the DE 199 34 696 A1 an electrodynamic drive system for a vehicle is known, which has a planetary gear between a prime mover and a manual transmission. The planetary gear is formed with a sun gear, a ring gear and a planet carrier. The planetary gear is operatively connected via a first element to the transmission, via a second element to the drive machine and via a third element with at least one electric motor. The electric motor can be operated both as a drive motor and as a generator.

In addition, a further clutch between two elements of the planetary gear for bridging the planetary gear is provided, wherein the clutch is designed as a dog clutch.

The disadvantage here is that a bridging of the planetary gear by the dog clutch is only possible if the mutually engageable coupling teeth have the same speed, d. H. synchronized with each other.

A drive system for a motor vehicle with a arranged on a drive shaft starter and generator unit is from the DE 199 23 316 A1 known. The starter and generator unit described therein has an electric motor operable as an electric motor with starter function and as an electric generator and a planetary gear operatively connected thereto with at least one sun gear, at least one planetary gear and at least one ring gear. In this case, the planetary gear via shafts and switching elements with the electric machine, with the drive shaft and a housing of an arranged in the drive train unit is connectable such that in a start operation, a translation i> 1 and in a generator operation, a translation i = 1 is adjustable.

The ring gear is connectable via a further shaft of a clutch with a housing or its lid for setting a start translation. During a starting operation, first the shaft connected to the sun gear and the rotor of the planetary gear rotates, while the planetary gear is supported via the ring gear, the shaft and the closed clutch. In a generator mode, d. H. in the driving state, however, the coupling connecting the ring gear with the cover is opened, and a further coupling, which connects the sun gear to the drive shaft, is closed. Furthermore, it is provided that in the driving state, the planetary gear rotates by opening the coupling between the ring gear and the cover and simultaneous closing of the further coupling between the sun gear and the drive shaft in a blocked state. The further clutch can be designed as a one-way clutch, as a frictional torque-actuated clutch or as a hydraulically operated clutch.

However, this coupling concept has the disadvantage that for starting a designed as a torque converter or as a starting clutch starting element is required, the thermal load during a start-up or during a partial load starting is high, whereby a lifetime of such a starting element is greatly reduced.

From the DE 199 27 521 C2 an electric machine is known, which is switchable as a starter-generator for an internal combustion engine, in particular a motor vehicle. Here, the electric machine comprises a two-stage planetary gear for coupling to a shaft of the internal combustion engine.

Furthermore, from the publication "Schäfer, Heinz: starter generator with asynchronous machine and field-oriented control in: Automotive Electronics: special edition of ATZ and MTZ, 2000, H. January, pp 44-46, ISSN 0001-2785" known as a starter To use electric motors for torque management.

From the DE 100 21 025 A1 a transmission for motor vehicles is known, with an input shaft which is coupled to at least one, preferably two power-split transmissions which can be coupled to an output shaft, as well as with two with the at least one power-split transmission coupled electric machines. In the known transmission means are provided for coupling the input shaft to the output shaft while bridging the two electric machines and the at least one power-split transmission.

Furthermore, goes from the DE 43 24 010 C2 a method for controlling the torque output of a consisting of an internal combustion engine and an electric motor, a vehicle driving hybrid drive out, in the context of which the vehicle is driven either via the internal combustion engine or via the electric motor or via the internal combustion engine and the electric motor together, wherein during driving and involved in driving the vehicle Electric motor of the hybrid drive is controlled substantially in accordance with the torque characteristic of an internal combustion engine.

The present invention is therefore based on the object to provide a method for controlling a starting process of a drive train and a drive train available that allow a reduction in the thermal load of a starting element during a starting process.

According to the invention this object is achieved by a method according to the features of claim 1 and with a drive train according to the features of claim 14.

With the method according to the invention there is advantageously the possibility to significantly reduce a thermal load formed as a frictional switching element starting element, since a drive torque for a driven by a prime mover consumer is supported by a speed and torque variable machine and upon reaching one to transmitting drive torque, which is no longer supported by the machine, is additionally supported by the frictional switching element.

This is advantageously ensured that at the beginning of a starting process no thermal load of a starting element or a frictional startup clutch occurs and is switched on only after a certain torque to be transmitted to a starting element and is exposed to thermal stress.

The drive train according to the invention has a variable speed and torque variable starting element, which comprises the machine, the frictional switching element and the planetary gear, wherein the frictional switching element is provided for blocking the planetary gear. With this arrangement can be advantageously dispensed with a conventionally provided in conventional solutions starting element, such as a hydrodynamic torque converter or a frictional clutch, which is disposed between a prime mover and a transmission or a transmission and a consumer downstream of the transmission.

Furthermore, the drive train according to the invention has the advantage that with the arrangement of a frictional switching element for blocking the planetary gear, which is additionally controlled as a starting element, no thermal load of the frictional switching element or starting element against starting elements of known arrangements is given when the starting process alone is carried out over the machine. The switching element is needed in this case only for transmitting the static torque.

Further advantages and advantageous embodiments of the invention will become apparent from the claims and the embodiment described in principle with reference to the drawings.

It shows:

1 a highly schematic representation of a planetary gear, which is designed as a superposition gear;

2 a highly schematic representation of a drive train with an electromagnetic starting element;

3 a flow chart of a method for controlling the in 2 illustrated drive train; and

4 a speed-time diagram showing the rotational speeds of the prime mover, the electric machine and an output shaft of the planetary gear during a starting process of the drive train according to 2 represents.

Referring to 1 is a highly schematic representation of a planetary gear designed as a superposition gear 1 one in 2 schematized illustrated drive train 2 a motor vehicle shown. The planetary gear 1 or its ring gear 3 is with a prime mover 4 connected. A sun wheel 5 of the planetary gear 1 is with an electric machine 6 operatively connected. A planet carrier 7 is with an output shaft 8th connected, which at the same time a transmission input shaft of an in 2 illustrated countershaft transmission 9 represents, wherein instead of the countershaft transmission 9 Any other manual transmission or continuously variable transmission can be provided.

The electric machine 6 present in the drive train 2 integrated starter-generator unit, which indirectly through the planetary gear 1 on the countershaft transmission 9 acts. The planetary gear 1 has three degrees of freedom in the rotational movement, each resulting in a function of two speeds, a third speed and superimpose two rotational movements to a third rotational movement.

Furthermore, between the sun wheel 5 and the planet carrier 7 a frictional switching element 10 arranged, which in the closed state to a blocking of the planetary gear 1 leads, being in the locked state of the planetary gear 1 one from the prime mover 4 incoming drive torque with a ratio i = 1 to the transmission input shaft 8th is forwarded. In the open state of the switching element or the coupling 10 indicates the planetary gear 1 a translation of, for example, i ₀ = -3, wherein other translations are possible depending on the particular application case.

The electric machine 6 , the planetary gear 1 and the clutch 10 form an electrodynamic starting element, wherein the rotational speeds of the drive machine or the ring gear 3 and the speed of the sun gear 5 or a rotor 11 the electric machine 6 during a starting process with the clutch open 10 to the speed of the planet carrier 7 overlap.

To damage the gears of the planetary gear 1 by non-uniformities of the drive behavior of the prime mover 4 to reduce or avoid is between the prime mover 4 , which is designed here as an internal combustion engine, and the planetary gear 1 a known per se torsion damper 12 interposed.

In the electrodynamic starting system according to 1 and 2 becomes a torque T_am of the prime mover 4 on a shaft of the three-shaft planetary gear 1 , which with the ring gear 3 connected, applied. At the same time acts on another shaft of the planetary gear 1 a torque T_em of the electric machine 6 , which with the sun wheel 5 is actively connected. An output torque on the sum shaft of the planetary gear 1 , which with the planet carrier 7 is connected, acts directly on the transmission input shaft 8th of the countershaft transmission or gearbox 9 ,

This arrangement allows a start of the in 2 shown drive train 2 with a low thermal and mechanical load of a frictional switching element, since the frictional coupling 10 in the drive train 2 provided in the event that the torque T_em of the electric machine 6 is not sufficient to the speeds of the individual components of the planetary gear 1 to synchronize. Furthermore, the frictional clutch 10 provided to the planetary gear 1 after completion of the synchronization process of the planetary gear by fully closing the clutch 10 to bridge.

The 3 shows a flowchart of a starting control of the drive train according to 2 , by means of which a starting process of the drive train 2 Fully automatic with low load on the coupling 10 is controllable. The presented control can be generally applied to all drive trains, which have an integrated starter-generator unit with a variable speed and torque variable machine as starting element, wherein in the present case the starting control is described by way of example with reference to a drive train with an electromechanical starting element.

Furthermore, the in 3 Control shown useful then, if an electrical machine, for example, due to a limited voltage of a 42-volt electrical system or limited Leistungsabgabefähigkeit an energy storage is dimensioned such that their maximum current deliverable torque T_em_max is not large enough to corresponding torques of a prime mover to synchronize To support the speeds of the planetary gear. In such a case, the friction clutch is used in addition to the electric machine for synchronizing the planetary gear.

To reduce thermal stress on the friction clutch 10 becomes the electric machine 6 during a starting process primarily for the synchronization process of the planetary gear 1 used. A dynamic clutch torque is built up only when the maximum torque T_em_max of the electric machine that can currently be output 6 for supporting the drive torque T_am of the prime mover 4 no longer sufficient.

For this purpose, in response to a request "start" of an operator or a driver of a vehicle, which z. B. via an accelerator pedal 14 done by a controller 13 the prime mover 4 a signal for increasing the rotational speed n_am of the prime mover 4 output.

At the same time the control unit determines 13 the prime mover 4 in a step S1, an actual rotational speed n_am_ist of the prime mover 4 , The actual rotational speed n_am_ist becomes the target engine idling speed n_am_LL_soll in a step S2 4 from the target idle speed n_am_LL_soll and the actual speed n_am_ist the prime mover 4 a differential speed Δn_am is determined. In a subsequent step S3, the differential speed Δn_am is used to generate a regulator specification of a theoretical torque value T_reg, in which case a proportional controller is used.

In a step S4, an accelerator pedal position Phi is determined, which as an output signal of step S4 an input value for the control unit 13 the prime mover 4 and another step S5. In step S5, in Dependence of the actual speed n_am_ist and the accelerator pedal position Phi a currently maximum deliverable torque T_am_max the prime mover 4 determined via a stored in another separate control unit map. Of course, it is up to the expert, the further control unit with the map in the control unit 13 the prime mover 4 to integrate.

That from the actual speed n_am_ist the prime mover 4 converted over the stored in the further control unit engine map current maximum deliverable torque T_am_max the prime mover 4 is by means of a correction value k in a step S6 to the real system or to the drive train 2 customized. The correction value k is a tuning parameter that has been determined empirically and with which a tuning of the system or of the drive train is achieved.

The correction value k assumes values between 0 and 1, wherein with the vote a possible stalling of a trained as an internal combustion engine engine is avoided. Of course, in this case also an adaptation method can be implemented in the start-up control, which has a tuning of the system in operation by a corresponding adaptation of the correction value k result.

The product of the correction value k and the currently maximum deliverable torque T_am_max the prime mover 4 is referred to as a so-called pre-control torque, wherein the desired command torque T_soll corresponding to the driver command input is determined from the sum of the control input T_reg and the pre-control torque k · T_am_max in a step S7.

Parallel to the determination of the engine of the drive 4 To be transmitted desired torque T_soll is in a step S8 by means of a speed sensor, not shown, an actual speed n_em_ist the electric machine 6 determined and in a step S9 one of the actual speed n_em_ist the electric machine 6 corresponding signal generated. In a step S10, depending on the actual rotational speed n_em_ist of the electric machine 6 a currently maximum deliverable torque T_em_max the electric machine 6 via a stored in the other control unit full load characteristic of the electric machine 6 certainly.

In a step S11 it is checked whether the setpoint torque T_soll is less than or equal to the currently maximum deliverable torque T_em_max of the electrical machine 6 is or not. In the case of a positive query result, in a step S12 a torque specification is made such that a setpoint torque T_em_soll of the electrical machine 6 the target torque T_soll corresponds and a target torque T_ku_soll the frictionally engaged clutch 10 is set to the value zero and this remains open. Thus, the clutch load during the starting process until reaching the maximum possible torque T_em_max the electric machine 6 equals zero.

In a negative query result of step S11, the target torque T_em_soll of the electric machine is adjusted to the maximum torque T_em_max in a subsequent step S13, and the target torque T_ku_soll the frictional clutch 10 becomes from the difference of the target torque T_soll and the maximum torque T_em_max of the electric machine 6 formed, wherein below the target torque T_ku_soll the clutch 10 the part of the torque of the prime mover 4 is designated, which is supported by the clutch. This ensures that the starting process can be completed.

With the in 3 schematized control system is a request "startup of a drive train" by pressing the accelerator pedal 14 or by pressing a power request element when engaged first gear or at a Anfahrübersetzung on the accelerator pedal position Phi to the controller 13 the prime mover and the starting control system passed. The speed of the prime mover 4 increases, where the actual speed n_am_ist the prime mover 4 is compared with the predetermined target idle speed n_am_LL_soll.

The differential speed Δn_am causes a response of the proportional controller, wherein the actual speed n_am_ist the prime mover 4 is simultaneously converted over the stored in the further control unit engine map in a possible maximum torque T_am_max, from which the pilot torque k · T_am_max is determined. The sum of the precontrol torque and the regulator specification T_reg yields the setpoint torque T_setpoint, which is subsequently converted into an effective torque T_em_setpoint of the electrical machine 6 and a clutch torque T_ku_soll is divided. The predetermined strategy is such that the electric machine 6 Prior to its power limit is charged before the frictional clutch 10 must apply the respective residual torque or support torque T_ku_soll for the starting process. It is about the actual speed n_em_ist and the stored full load characteristic of the electric machine 6 a currently maximum possible torque T_em_max of the electric machine 6 certainly.

About the logical query of step S11 or at a positive query result of step S11 is only one controller of the electric machine 6 acted upon by a signal which a torque specification corresponding to the desired torque T_soll for the electric machine 6 results. In a negative query result of step S11, the electric machine 6 adjusted to its maximum torque, the remaining differential torque of the frictional clutch 10 must be generated to complete the startup successfully.

The torque T_am of the prime mover 4 In the present case, it is produced by an internal combustion engine, wherein the drive torque can also be generated by other suitable power output machines such as a hydrostats, an electric machine, a gas turbine or the like. The torque T_em of the electric machine can also be generated by other suitable torque-generating machines, which are designed as variable-speed and torque-variable machines, such as a hydrostat, a hydrodynamic brake, an eddy-current electro-dynamic brake or the like. The lowest clutch load when starting the engine at the transmission input shaft 8th is achieved when starting an electric or a hydrostatic machine is used in four-quadrant operation using two quadrants their torque to those with the sun 5 of the planetary gear 1 gives off connected wave.

The inventive method for controlling a starting process of a drive train can be in all accordingly 1 apply established powertrains, in which a machine or a vehicle from a main drive machine, such as a crankshaft and an internal combustion engine, via a three-shaft gear, as here a planetary gear, which can be operated as a superposition gear, is driven and driven. The drive train can thus generally be a drive train of a vehicle, a machine tool, an industrial truck, a load-lifting machine or the like. The described control strategy for vehicle drives, which include an automatic transmission, can also be used.

4 each shows a curve of the speed n_am of the prime mover 4 , a speed n_ga of the transmission input shaft 8th and the speed n_em of the electric machine 6 during a start-up process, the different speeds being plotted over time t. At the time t = 0 at which the prime mover 4 , which is designed here as a diesel engine, rotates with the idle speed, the speed n_ga of the gear input shaft is equal to zero. The speed n_em of the electric machine 6 is due to the selected in the present embodiment gear ratio i = -3 of the planetary gear 1 equal to three times the speed n_am of the prime mover 4 , In a corresponding request of a driver of the vehicle by a change in the accelerator pedal position Phi increases the speed n_am the diesel engine.

At the same time, the generator is operated as a generator during this phase 6 Power removed so that from the electric machine 6 a braking torque is generated. The machine 6 is operated in this phase of the starting process in a second map quadrant of a four-quadrant map, wherein the machine has a positive torque and a negative speed in the second map quadrant. This braking torque of the electric machine 6 causes the speed n_em of the electric machine in the direction of a so-called puncture point DP of the diesel engine "pulled up" is. At the same time, the rotational speed n_ga of the transmission input shaft increases in the direction of the rotational speed n_am of the diesel internal combustion engine. The piercing point DP corresponds to the point of the course of the rotational speed n_em of the electric machine 6 at which this is zero.

When the piercing point DP is exceeded, the course of the rotational speed n_em of the electrical machine is exceeded 6 must the electric machine 6 for synchronizing the speeds of the planetary gear 1 be operated by a motor. The machine 6 is operated in this phase of the starting process in a first map quadrant of a four-quadrant map, wherein the machine has a positive torque and a positive speed in the first map quadrant. This is done by the electric machine 6 Power supplied by a power source. Through the motorized operation of the electric machine 6 the speed n_em of the electric machine increases in the direction of the speed n_am of the drive machine 4 or the diesel engine. At the same time, the rotational speed n_ga of the transmission input shaft 8th in the direction of the speed n_am the diesel engine out until the speed n_am the prime mover 4 , the speed n_ga of the transmission input shaft 8th and the speed n_em of the electric machine 6 are identical in the synchronization point SP.

This synchronization of the speeds of the planetary gear 1 is without thermal coupling load of the frictional coupling 10 realized because the torque T_am the prime mover 4 only via the electric machine 6 is supported. After reaching the synchronization point SP, the frictional clutch 10 be closed without slippage. Thereafter, the drive torque of the prime mover 4 directly on the transmission input shaft 8th guided.

In the event that that of the electric machine 6 maximum torque T_em_max for synchronizing the speeds of the planetary gear 1 should not be sufficient, the frictional coupling 10 subjected to a required closing force. The coupling 10 initially supports in a slipping state the non-supportable by the electric machine part of the drive torque of the prime mover 4 off until the planetary gear 1 is synchronized. Subsequently, the frictionally engaged clutch is finally closed.

Alternatively, instead of an electric machine, it is also possible to use a disk brake for initiating the synchronization operation of the planetary gear, which brakes against a stationary housing of the planetary gear. The same effect as with an electric machine in the regenerative operating range, such as 4 described achieved. The remaining difference in the rotational speeds of the planetary gear between the puncture point DP and the synchronization point SP is eliminated by the then engaged in the slip mode frictional coupling.

When using an electric machine for synchronizing the rotational speeds of a planetary gear and for supporting the dynamic moments of the prime mover there is advantageously the possibility during the generator operation of the electric machine to dissipate power to an electrical system or to a power storage. The use of a current memory in this case again has the advantage that a current source is available for an adjoining the generator operation motor operating range of the electric machine in which the electric machine power must be supplied. Furthermore, the electric machine can be used in conjunction with the power storage for starting a drive engine designed as an internal combustion engine.

LIST OF REFERENCE NUMBERS

1

planetary gear

2

powertrain

3

ring gear

4

prime mover

5

sun

6

electric machine

7

planet carrier

8th

Output shaft, transmission input shaft

9

Manual transmission, countershaft transmission

10

frictional switching element

11

Rotor of the electric machine

12

Dampers

13

Control unit of the prime mover

14

Accelerator pedal, power request element

DP

Intersection point

i

ratio

k

correction value

n_am

Speed of the prime mover

n_am_ist

Actual speed of the prime mover

n_am_LL_soll

Target idle speed of the prime mover

Δn_am

Differential speed

n_em

Speed of the electric machine

n_em_ist

Actual speed of the electric machine

n_ga

Speed of the transmission input shaft

Phi

Accelerator pedal position

S1-S13

step

SP

synchronization point

n

Time

T_am

Torque of the prime mover

T_am_max

maximum torque of the prime mover or currently maximum deliverable torque of the prime mover

T_em

Torque of the electric machine

T_em_max

maximum torque of the electric machine or currently maximum deliverable torque of the electric machine

T_soll

Target torque

k × T_am_max

pre-control torque

T_ku_soll

Target torque of the frictional switching element

T_reg

regulators default

Claims (16)

Method for regulating a starting process of a drive train ( 2 ) with one of a prime mover ( 4 ) driven consumer ( 9 ) and an interposed planetary gear ( 1 ), wherein the planetary gear ( 1 ) about frictional switching element ( 10 ) can be bridged and for the variable transmission of a torque (T_am) of the drive machine ( 4 ) with a variable speed and torque machine ( 6 ) is in operative connection, characterized in that one of the drive machine ( 4 ) to the consumer ( 9 ) in accordance with a requirement to be transmitted desired torque (T_soll) in addition continuously via the frictional switching element ( 10 ) is adjustable, wherein the target torque (T_soll) in dependence of a differential speed (Δn_am) between a target idle speed (n_am_LL_soll) of the prime mover ( 4 ) and an actual speed (n_am_ist) of the prime mover ( 4 ) is determined. A method according to claim 1, characterized in that the setpoint torque (T_soll) up to a value which is a maximum of the current speed and torque variable machine ( 6 ) torque that can be output (T_em_max), via the variable-speed and torque-variable machine ( 6 ) is regulated. A method according to claim 2, characterized in that the desired torque (T_soll) from a value greater than that of the machine ( 6 ) currently maximum deliverable torque (T_em_max), in addition via the switching element ( 10 ) is regulated. A method according to claim 2 or 3, characterized in that a at a current speed (n_em_ist) of the speed and torque variable machine ( 6 ) of this currently maximum deliverable torque (T_em_max) via a stored in a control unit full load characteristic of the speed and torque variable machine ( 6 ) is determined. A method according to claim 1, characterized in that a controller default (T_reg) for the desired torque (T_soll) as a function of the differential speed (Δn_am) is effected by a proportional controller. Method according to one of claims 1 to 5, characterized in that the desired torque (T_soll) in dependence on an actual rotational speed (n_am_ist) of the drive machine ( 4 ) is determined by this maximum deliverable torque (T_am_max). Method according to one of claims 1 to 6, characterized in that one of the drive machine ( 4 ) currently maximum deliverable torque (T_am_max) via a stored in a control unit map depending on the actual speed (n_am_ist) of the prime mover ( 4 ) and a position of a performance request element ( 14 ) of the prime mover ( 4 ) is determined. Method according to one of claims 1 to 7, characterized in that one of the drive machine ( 4 ) currently maximum deliverable torque (T_am_max) is corrected via a correction value (k). A method according to claim 8, characterized in that the target torque (T_soll) from the sum of a pilot torque (k × T_am_max) of the prime mover ( 4 ) and the controller default (T_reg) is formed. Method according to one of claims 1 to 9, characterized in that the desired torque (T_soll) is a torque input for the machine ( 6 ) if the setpoint torque (T_setpoint) is less than or equal to that of the variable-speed and torque-variable machine ( 6 ) currently maximum deliverable torque (T_em_max) is. Method according to one of claims 1 to 10, characterized in that the setpoint torque (T_soll) is a torque input for the variable-speed and torque-variable machine ( 6 ) and the frictional switching element ( 10 ), if the setpoint torque (T_setpoint) is greater than that of the variable-speed and torque-variable machine ( 6 ) is currently the maximum deliverable torque (T_em_max). Method according to claim 11, characterized in that the torque specification for the machine ( 6 ) equal to that of the variable speed and torque machine ( 6 ) is currently the maximum deliverable torque (T_em_max) and the torque specification for the frictionally engaged shift element ( 10 ) a difference torque (T_ku_soll) between the setpoint torque (T_setpoint) and the speed-and-momentum variable machine ( 6 ) currently represents maximum deliverable torque (T_em_max). Method according to one of claims 1 to 12, characterized in that the machine ( 6 ) is designed as an electric machine or as a hydrostatic. Powertrain ( 2 ) with a planetary gear ( 1 ), wherein an engine ( 4 ), a variable-speed and torque-variable machine ( 6 ) and a consumer to be driven by the prime mover ( 9 ) with the planetary gear ( 1 ) are operatively connected and a torque (T_am) of the prime mover ( 4 ) of the speed and torque variable machine ( 6 ) is at least partially supportable during a starting process, wherein a frictional switching element ( 10 ) for blocking the planetary gear ( 1 ) is provided, which is controllable as an additional starting element, wherein one of the drive machine ( 4 ) on the Consumer ( 9 ) in accordance with a requirement to be transmitted desired torque (T_soll) in addition continuously via the frictional switching element ( 10 ) is regulated and wherein the setpoint torque (T_soll) in dependence of a differential speed (Δn_am) between a target idle speed (n_am_LL_soll) of the prime mover ( 4 ) and an actual speed (n_am_ist) of the prime mover ( 4 ) can be determined. Drive train according to claim 14, characterized in that the drive machine ( 4 ) with a ring gear ( 3 ) and the variable-speed and torque-variable machine ( 6 ) with a sun wheel ( 5 ) of the planetary gear ( 1 ) and via the switching element ( 10 ) the sun wheel ( 5 ) of the planetary gear ( 1 ) with its ring gear ( 3 ) or its planet carrier ( 7 ) is firmly connected, wherein the frictional switching element ( 10 ) as a function of a requested setpoint torque (T_soll) for a consumer ( 9 ) can be acted upon with such a closing force, that the desired torque (T_soll) from the prime mover ( 4 ) via the planetary gear ( 1 ) to the consumer ( 9 ) is transferable. Drive train according to claim 14 or 15, characterized in that the speed and torque variable machine ( 6 ) is formed as an electric or a hydrostatic machine.

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