DE10121389C1 - Method for operating a drive train of a motor vehicle - Google Patents

Abstract

The invention relates to a method for operating a drive train of a motor vehicle, in which a drive machine can be coupled to a transmission by means of a clutch that can be actuated with the aid of a clutch actuation device. DOLLAR A In order to achieve a particularly comfortable operation of the drive train, it is proposed according to the invention that, if the need to open the clutch has been determined, the setpoint value for the output torque of the drive machine for a first period of time from a preset value, which of is made to a vehicle driver, the different setpoint is then set to a second setpoint which differs from the first setpoint.

Description

The invention relates to a method for operating a Drive train of a motor vehicle, in which a Drive machine by means of a clutch actuating device actuatable clutch with a Torque transmission system can be coupled.

A clutch control is already in DE 198 57 112 A1 method for controlling a disengaging process one of one Clutch actuator operated clutch that between an output shaft of a prime mover in the form of a Internal combustion engine and an input shaft of a torque Transmission system arranged in the form of a step transmission is described. In this procedure, once opening the clutch is requested by the prime mover delivered torque to a preset value reduced. After a preset period of time in which the Limitation of the torque delivered, the Clutch opened by means of a clutch actuator.

DE 199 51 415 A1 describes a method for operating a Drive train of a motor vehicle known in which a Drive machine in the form of a motor by means of one Actuator operated clutch with an automated transmission can be coupled. The motor is controlled by means of a Control unit. If the clutch slips, the one that deviates from a specified value of a vehicle driver Setpoint for the delivered torque of the engine is generated and output to the engine.

The object of the present invention is to provide a method for particularly convenient operation of a drive train with a operable by means of a clutch actuation device Propose clutch.

According to the invention, the object is achieved by a method with the Features of claim 1 solved. The prime mover is from controlled by a control device, which at least a target value for the delivered torque or at least generates a value representing this quantity and to the Drive engine outputs.

If it is determined that the clutch must be opened there is an intervention in the setpoint specification for the Prime mover. The clutch can be opened, for example be necessary due to a desired translation change of gear. Especially if the gearbox is considered a Stepped gearbox is designed to open the clutch when a desired gear change is necessary. An unwanted one To prevent parking of the engine, especially at very low speeds of the motor vehicle and thus associated low engine speeds, it may for example, it may also be necessary to open the clutch.

In the case of the mentioned intervention, the setpoint for the delivered one Torque of the prime mover or at least this size representative value for a first period of time first, from a default value, which is given by a driver is specified by means of a power actuator, deviating setpoint and then for a second Time span to a second, deviating from the first setpoint, Setpoint set. The set value can be changed using the stay the same for the whole period or during the Change duration. The second setpoint can be equal to or not be equal to the value of the torque delivered Prime mover at the time when the need opening of the clutch has been determined and can  also change during the second period. The second The setpoint can be dependent on or independent of the default value of the Be the driver.

After the second period has elapsed, the clutch is released opened by means of the clutch actuation device. For example, the clutch can be opened completely and thus the drive machine completely off the transmission be decoupled. But it is in particular also possible that the clutch to change the gear ratio to influence positively, only partially and for example only is fully opened after a period of time.

By specifying the setpoint for the The torque delivered by the drive machine makes this possible Procedure when opening the clutch a particularly comfortable Powertrain operation.

After the method according to the invention has been carried out the drive train is no longer tense. This allows the Drive machine can be decoupled from the transmission without a Jerk is felt for the driver.

According to a preferred embodiment of the invention second setpoint for the torque delivered Prime mover or for at least one this size representative value from the default value, which from Driver specified by the power actuator becomes independent. However, the setpoint can happen randomly Correspond to the driver's specification.

The method thus enables one when the clutch is opened particularly comfortable operation of the drive train ensure regardless of how the driver of the vehicle Performance request element actuated.  

According to a preferred embodiment of the invention, said intervention in the setpoint specification for the drive machine takes place as a function of an evaluation of variables which describe the state of the motor vehicle at the point in time at which the need to open the clutch was determined. These sizes can be, for example:

• - speed of the motor vehicle,
• - acceleration / deceleration of the motor vehicle,
• - tensioning of the drive train,
• - gear ratio,
• - engine speed,
• - Mass moment of inertia of the drive train.

Individual sizes or a combination of several sizes.

An intervention is, for example, with a strong tension of the drive train. One is under tension Understanding driveline twist means that a spring energy is stored in the drive train.

This means that the intervention is only carried out if there is no intervention come to an uncomfortable operation of the drive train would. A control device that carries out the method is therefore not loaded and cannot be loaded every time the clutch is opened then do other calculations during this time.

According to a further embodiment of the The method according to the invention takes place in the aforementioned intervention the determination of the target value for the torque delivered Prime mover or at least one this size representative value for a first period of time such that the Amount of the delivered torque of the drive machine is smaller is the amount of torque delivered Prime mover at the time when the need opening of the clutch was determined. For example the first setpoint is selected so that the drive machine  gives no torque. The determination of the second setpoint is done so that the amount of torque delivered Prime mover is greater than the amount of the first Setpoint.

The drive train is closed when the clutch is closed initiated torques excited. When opening the Coupling without intervention in the setpoint specification for the Prime mover the drive train suddenly relaxes, which can lead to jerky vibrations in the drive train. at an intervention if, for example, the first setpoint is so is chosen so that the prime mover does not deliver any torque, the powertrain relaxes very quickly; that means, that the rotation of the drive train by a rotation in the opposite direction is canceled very quickly. This opposite rotation of the drive train would be without further measures turn to an opposite Twisting and thus a renewed bracing of the Drive train. For this reason, after the first time the setpoint for the torque output the prime mover so specified that this opposite Rotation is stopped. So that's the drivetrain completely relaxed and pedal by opening the clutch, if any, only very small vibrations in the drive train on. This is a comfortable operation of the drive train given.

The advantage is particularly evident in motor vehicles which a drive shaft from an output shaft of the transmission to a rear axle gear long as seen in the direction of travel is and the rigidity of the powertrain from the clutch too the tire of the driven axle, as in a motor vehicle with front engine and rear-wheel drive, is insufficient.

According to a further proposal according to the invention, the mentioned intervention the determination of the target value for the delivered torque of the drive machine or at least one  value representing this quantity for a first period of time so that the output torque of the prime mover has the opposite sign as the given torque the prime mover at the time the The need to open the clutch has been determined. The The second setpoint is determined so that the output Torque of the drive machine has the same sign like the delivered torque of the prime mover to that When the need to open the clutch was found. This will powertrain for one Period of time from a train to a push operation or from one Thrust brought into a train operation. So that relaxes Powertrain very quickly and by opening the clutch only very small vibrations occur in the drive train.

Another embodiment of the method according to the invention shows another vibration-reducing measure. The duration the first period for the one that differs from the driver Specification of the first setpoint for the torque delivered Prime mover or at least one this size representative value is one sixth of one Vibration period of the jerky vibration of the drive train. With a period of one sixth of the oscillation period becomes one particularly effective relaxation of the drive train achieved, which makes opening the clutch particularly convenient expires. This particularly suitable duration of the time period results by deriving from a differential equation, which describes the vibration behavior of the drive train.

According to a further embodiment of the inventive method, the method is only in low gears of the gearbox applied. In low gears the gear ratio is large; that means, that the quotient of the speeds at the input and at the output the gear is large. With a gearbox that works as a gearbox with gear stages of six forward gears and one Reverse gear is executed, for example  Reverse gear and forward gears one, two and three low gears in the sense of the invention. Is in low gears a torsional elasticity of the drive train is large, which is why the drive train is strongly twisted when torque is applied. The use of the method is therefore special advantageous.

Further advantages of the invention result from further features of the Subclaims, the description and the drawing. Embodiments of the invention are in the drawings shown in simplified form and in the description below explained in more detail. Show it:

Fig. 1 is a schematic representation of a drive train of a motor vehicle.

Fig. 2 is an illustration of a clutch shown in Fig. 1 with a clutch actuating device.

Fig. 3 is a flowchart of a control program that is executed by an embodiment shown in Fig. 1 controller.

FIG. 4 is a flowchart of a control routine shown in FIG. 3 for calculating the target torque of the prime mover due to an imminent clutch release.

Fig. 5 to Fig. 9 are graphical representations of the desired values for the output torque of the engine upon engagement in the setpoint for the drive machine.

Referring to FIG. 1, a drive train 10 of a motor vehicle through a driving machine 11, which by means of a clutch actuator 27 actuated clutch 13 and an input shaft 14 of a gear 15 to said gear 15 can be coupled via an output shaft 12 by means of a. The converted torque and the speed of the drive machine 11 are transmitted via an output shaft (not shown) of the transmission 15 by means of a drive shaft 16 to an axle drive 17 which, in a manner known per se, transmits the torque in the same or different proportions via two output shafts 18 , 19 to vehicle wheels 20 , 21 transmits.

The transmission 15 is designed as a transmission with shift stages of six forward gears and one reverse gear, in which the gear changes can be carried out by means of actuators (not shown). Such a transmission is usually referred to as an automated manual transmission.

The drive machine 11 is controlled or regulated by a control device 22 . The control device 22 receives, via a signal line 23, information about a measured position of a power actuator 24 which can be actuated by a vehicle driver. Furthermore, the control device 22 receives, via a signal line 25, information about the operating state of the engine 11 , such as a measured speed of the engine 11 and a measured throttle valve position.

The control device 22 is connected to a control device 71 by means of a signal line 70 . The control device 22 sends at least the measured speed of the drive machine 11 to the control device 71 .

The control device 71 sends actuating signals to a clutch actuation device 27 by means of a signal line 26 and receives at least information about an opening degree of the clutch by means of the signal line 26 . The clutch 13 can thus be opened and closed in a controlled manner by the control device 71 . The control device 71 is connected by means of a signal line 72 to a selector lever 37 and by means of a signal line 38 to sensors and actuators of the transmission 15, which are not shown in detail. At least one speed of the input shaft 14 , one speed of the output shaft, the gear engaged and a temperature are detected by means of the sensors mentioned and sent to the control device 71 . The vehicle driver can use the selector lever 37 to send a gear change request to the control device 71 . From the total number of information, the control device 71 determines control signals for the aforementioned actuators of the transmission 15 and the clutch actuation device 27 and sends them to the corresponding actuators. Was appropriate, by the control device 71 the necessary ness, that the coupling must be opened 13, detected by means of the control device 71 sends the signal line 70 a corresponding signal to the control device 22nd

Another control device 30 detects the rotational speeds of the wheels 20 , 21 measured by sensors 33 , 34, among other things, via signal lines 31 , 32 and determines the speed of the motor vehicle therefrom. The control devices 22 , 71 and 30 are connected via a data line 35 such. B. a serial CAN bus connection is coupled, by means of which information such as the vehicle speed is exchanged between the control devices 22 , 71 and 30 .

On the basis of the total number of information, the control device 22 determines control signals, for example for fuel supply, throttle valve position, ignition timing or injection time, which are sent via a signal line 36 to corresponding actuators (not shown) of the drive machine 11 .

The clutch 13 is designed as a single-plate friction clutch, which can be opened and closed by means of a clutch actuation device 27 . As shown in FIG. 2, the clutch 13 has a friction unit 40 . The friction unit 40 has a flywheel 42 and a pressure plate 43 which are connected to one another in a rotationally fixed manner and are rotatably mounted about an axis. The flywheel 42, which is designed as a single-mass flywheel, is in turn non-rotatably connected to the output shaft 12 of the drive machine 11 . Between the flywheel 42 and the pressure plate 43 , a clutch disc 44 is arranged with clutch linings, not shown, which is rotatably connected to the input shaft 14 of the transmission 15 . The friction unit 40 is closed via a clutch spring 45 and opened via the actuating device 27 .

The clutch spring 45 is designed as a plate spring which is pivotably mounted on the clutch cover 46 . At the axially outer edge 47 , the coupling spring 45 can exert an axial force on the pressure plate 43 . In the direction of the gear 15 , a clutch bearing 48 , which is concentric with the input shaft 14 , is arranged on the clutch spring 45 , via which an axial force can be exerted on the clutch spring 45 at the axially inner edge 49 .

The actuating device 27 has a release mechanism 50 which is concentric with the input shaft 14 and which is arranged on the side of the release bearing 48 opposite the clutch spring 45 . The stopper 50 has a housing 51 and a guided in the housing 51, concentric to the input shaft 14 release piston 52nd On the side of the release piston 52 facing away from the release bearing 48, the release valve 50 has a first pressure chamber 53 , which is connected to a second pressure chamber 55 via a pressure line 54 . An actuating piston 56 is arranged on the second pressure chamber 55 and is operatively connected to an actuator 74 designed as an electric motor by means of an actuating rod 73 . A sensor 75 is arranged in the vicinity of the actuating rod 73 , with which the position of the actuating rod 73 and thus the position of the actuating piston 56 is detected and sent to the control device 71 by means of the signal line 26 . With the aid of this position, the control device 71 determines the opening degree of the clutch 13 . The control device 71 is also connected to the actuator 74 by means of the signal line 26 . In addition, the second pressure chamber 55 is connected to an expansion tank 58 by means of a trailing hose 57 . The pressure chambers 53 and 55 , the pressure line 54 , the follow-up hose 57 and the expansion tank 58 are filled with a hydraulic fluid.

In the closed state of the clutch 13 , the clutch spring 45 axially presses the flywheel 42 , the pressure plate 43 and the clutch disc 44 , so that they are connected in a rotationally fixed manner by friction. This enables the torque of the drive machine 11 to be transmitted to the input shaft 14 of the transmission 15 .

To open the clutch 13 , the actuating piston 56 is moved into the pressure chamber 55 by means of the actuator 74 and the actuating rod 73 . A pressure builds up in the pressure chamber 55 , in the pressure line 54 and in the pressure chamber 53 , by means of which an axial force in the direction of the friction unit 40 is exerted on the release piston 52 . This causes the release piston 52 to move axially in the direction of the friction unit 40 . As a result, an axial force in the direction of the friction unit 40 is applied to the radially inner edge 49 of the clutch spring 45 via the release bearing 48, as a result of which the pressure plate 43 is axially relieved and the clutch disc 44 is released from the flywheel 42 and the pressure plate 43 . The clutch 13 is thus opened and the drive machine 11 is decoupled from the transmission 15 .

The control program for determining the manipulated variables for the drive machine 11 , which is carried out by the control device 22 , is explained below with reference to the flowchart shown in FIG. 3. The control program is run through cyclically in a defined time grid, for example every 10 ms. In step 101 , the control device 22 determines the desired torque for the output torque of the drive machine 11 of the vehicle driver (M_driver), which the vehicle driver sets by means of the power actuator 24 . It is then checked in step 102 whether there is a signal from the control device 71 that the clutch 13 has to be opened or whether an intervention in the setpoint specification for the drive machine 11 is carried out and thus the variable t_akt is greater than 0.

The signal that the clutch 13 must be opened is generated in a control routine, not shown, which is processed by the control device 71 . Opening is necessary, for example, if the speed of the drive machine falls below a threshold. The clutch can also be opened when changing gear. A gear change can be requested by the vehicle driver by means of the selector lever 37 in a first operating mode of the transmission 15 . In a second operating mode, the time for a gear change is determined by the control device 71 itself. The determination is at least dependent on the position of the power actuator 24 and the speed of the motor vehicle. The driver can set the desired operating mode on the selector lever 37 by means of an adjusting device (not shown).

If the test in step 102 is positive, a target torque is determined in step 103 due to an imminent opening of the clutch 13 (M_Soll_Kup). If the test in step 102 is negative, the control device 22 does not execute step 103 .

In the next step 104 , it is checked whether there are other requirements for the target torque. Other requests can be sent from other control devices, for example for driving dynamics control, to the control device 22 via a data line such as a serial CAN bus connection. However, there may also be requests from other program parts of the control device 22, such as an idle controller. If such requirements exist (test in step 104 positive), they must be implemented. In the subsequent step 105 , the target torque is therefore determined on the basis of these requirements. If there are no other requirements (test in step 104 negative), step 105 is not carried out.

In the subsequent step 106 , the control signals, for example for fuel supply, throttle valve position, ignition timing or injection time, are determined from the target torque, which are then output in step 107 to the corresponding actuators of the drive machine 11 . After processing of step 107 , the processing in the next time step begins again with step 101 .

With reference to FIG. 4, the control routine proceeds from step 103 to determine the desired torque will be explained on the basis of an imminent opening of the clutch 13 (M_Soll_Kup). In step 201 it is checked whether an intervention in the setpoint specification for the drive machine 11 has already been activated in a previous run through the control routine. The check is carried out by querying whether t_akt <0.

If the query is positive, a check is made in step 207 as to whether the intervention in the setpoint specification is completed in this run through the control routine. The check is carried out by querying whether t_akt <1. If this is not the case, t_akt = 1 and the intervention in this run is completed. In this case (test in step 207 negative), step 208 is carried out, in which a signal which indicates that the intervention has been completed is generated and sent to the control device 71 . When the control device 71 has received this signal, it can open the clutch 13 by the clutch actuation device 27 by means of suitable control signals.

If the query in step 207 turns out positive, ie if t_akt <1, then M_Soll_Kup is determined in step 202 for the current calculation step. In order to ensure rapid processing, the setpoints are stored in the form of a table in the control device 22 , from which the setpoints are read out, for example, as a function of the tension in the drive train 10 and t_akt. The setpoints entered in the table are determined from one or a combination of several of the following variables:

• - acceleration of the motor vehicle,
• the tension of the drive train 10 ,
• - the gear 15 in gear,
• - The speed of the prime mover 11
• the moment of inertia of the drive train 10 ,
• a number of cylinders of the engine 11 .

The tensioning of the drive train is determined from at least the output torque of the drive machine 11 , the change in the speed of the drive machine 11 , the acceleration of the motor vehicle and the change in the speed of the wheels 20 , 21 .

In the subsequent step 203 , the quantity t_akt is then reduced by 1. The size t_akt serves on the one hand to indicate whether an intervention is active and on the other hand to determine and control the duration of the intervention. After execution of step 203 , the control routine is ended and the control program continues with step 104 .

If the test in step 201 is negative, step 204 is carried out. This is the case if t_akt is not greater than zero and therefore no intervention was active in the previous run through the control routine. In step 204 it is checked whether an intervention is necessary. The test is at least dependent on the speed and acceleration of the motor vehicle, the tension in the drive train 10 , the gear engaged in the transmission 15 and the moment of inertia of the drive train 10 .

If the test in step 204 is positive, the quantity t_akt is determined in step 205 . Since t_akt is reduced by 1 in step 203 and the intervention is only carried out if t_akt <0 (step 201 ), the determination of t_akt specifies the duration of the intervention. The determination depends on the same variables as the test in step 204 . The absolute duration of the intervention then results from t_akt from step 205 and the time grid with which the control program from FIG. 3 is executed. For example, if the value of t_akt is 16 and the time grid is 10 ms, the intervention takes 160 ms. After execution of step 205 , the processing is continued with the described steps 202 and 203 .

If the test in step 204 is negative, step 206 is carried out. M_Soll_Kup is set equal to M_Fahrer. So no intervention is carried out. The original setpoint is not changed. After execution of step 206 , the control routine is ended and the control program continues with step 104 .

FIG. 5 shows a graphical representation of the setpoint value for the output torque of the drive machine 11 when the setpoint value setting for the drive machine intervenes. On an abscissa 59 a is the time; the target value for the output torque of the drive machine 11 is plotted on an ordinate 60 a. A line 61 a shows the course of the setpoint. The drive train 10 is in train operation. At a time 62 a, the control device 22 receives the signal that the clutch 13 is to be opened. The setpoint is immediately set to 0. After a lapse of time of the target value at a time 63 a to the value corresponding to the target value before the time 62 a is set. The time period is one sixth of the oscillation period of the jerky oscillation of the drive train 10 , that is, for. B. 83 ms at a jerk frequency of 2 Hz (83 ms = 500 ms / 6). The oscillation period of the jerky oscillation is strongly dependent on the physical properties such as, for example, the moments of inertia of the drive train 10 and thus also on the gear 15 of the transmission 15 . In addition, there is a slight dependency on the rotational speed and the output torque of the drive machine 11 . The drive train relaxes by lowering and then raising the setpoint again. A relaxation can only take place when the clutch 13 is still closed. At a point in time 67 a, the drive train is completely relaxed and the clutch 13 is opened by means of the clutch actuation device 27 .

Fig. 6 shows a further embodiment for the profile of the target value during an intervention. B on an abscissa 59 is the time; the nominal value for the output torque of the drive machine 11 is plotted on an ordinate 60 b. Line 61b shows the course of the setpoint. The drive train 10 is in overrun mode. At a time 62 b, the control device 22 receives the signal that the clutch 13 is to be opened. The setpoint is immediately set from a negative to a positive value, which means that the drive train 10 is transferred from overrun to pulling operation. At a point in time 63b , the setpoint is set to a negative value which does not correspond to the setpoint before point in time 62b . The drive train 10 relaxes particularly quickly due to the push-pull change. At a point in time 67 b, the drive train is completely relaxed and the clutch 13 is opened by means of the clutch actuation device 27 .

Fig. 7 shows a further embodiment for the profile of the target value during an intervention. C is on an abscissa 59 the time; the nominal value for the output torque of the drive machine 11 is plotted on an ordinate 60 c. A line 61c shows the course of the setpoint. The drive train 10 is in train operation. At a time 62 c, the control device 22 receives the signal that the clutch 13 is to be opened. The set point is immediately set to a smaller absolute value, and until a time 64 c kept constant. At time 64 c, the setpoint is set to a larger value, which is smaller than the setpoint before time 62 c. At time 63 c, the setpoint is again set to a value which corresponds to the setpoint before time 62 c. The stage at time 64 c may be necessary, for example, in order to adapt the intervention to an ignition sequence of the engine 11 . At a point in time 67 c, the drive train is completely relaxed and the clutch 13 is opened by means of the clutch actuation device 27 .

Fig. 8 shows a further embodiment for the profile of the target value during an intervention. D on an abscissa 59 is the time; the nominal value for the output torque of the drive machine 11 is plotted on an ordinate 60 d. A line 61d shows the course of the setpoint. The drive train 10 is in train operation. At a time 62 d, the control device 22 receives the signal that the clutch 13 is to be opened. The setpoint is immediately set to 0. After a time the setpoint is from a time point d 63 is not abruptly but until a time 65 d back to a value corresponding to the target value before the time 62 d, is set. At a point in time 67 d, the drive train is completely relaxed and the clutch 13 is opened by means of the clutch actuation device 27 .

Fig. 9 shows a further embodiment for the profile of the target value during an intervention. This embodiment is used particularly when the clutch 13 is to be opened only after a certain period of time after the transmission of the signal that the clutch 13 is to be opened. It may happen that the drive train 10 tensions again after the engagement by the applied torque of the drive machine 11 . On an abscissa 59 e is the time; the target value for the output torque of the drive machine 11 is plotted on an ordinate 60 e. A line 61 e shows the course of the setpoint. The drive train 10 is in train operation. At a time 62 e, the control device 22 receives the signal that the clutch 13 is to be opened. The setpoint is immediately set to 0. After a time the setpoint is at a point 63 e again set to a value corresponding to the target value prior to the time 62 s. The time period is one sixth of the oscillation period of the jerky oscillation of the drive train 10 . After a further period of time, which is also sixth of the oscillation period of the jerky oscillation of the drive train 10 , the setpoint is set to 0 again at a time 66 e, in order to prevent the drive train 10 from being re-tensioned. This setpoint is maintained until clutch 13 is opened at time 67e .

The necessary rapid changes in the intervention Setpoint for the output torque of the drive machine are implemented differently, depending on whether the Drive engine designed as a gasoline or a diesel engine is. With a diesel engine, the torque delivered can be very high quickly and spontaneously by changing the injection time and / or the amount of fuel injected. This is for both an increase and a decrease in the Torque feasible.

In the case of a gasoline engine, the implementation depends on whether the Engine as a direct injection gasoline engine or a gasoline engine with intake manifold injection. With a gasoline engine With direct injection, the torque delivered can do the same like a diesel engine by changing the injection time and / or the amount of fuel injected and be reduced. In a gasoline engine with intake manifold injection can spontaneously reduce the torque by means of  a change in the ignition timing can be achieved. A rapid increase in torque is achieved by a quick Throttle opening reached.

The driven vehicle wheels 20 , 21 can be both the front and rear wheels in the direction of travel. It is also possible for the front and rear wheels to be driven.

The transmission 15 can also be designed as a stepped transmission, in which the vehicle driver changes the gears manually. In this case, the selector lever is mechanically operatively connected to the multi-step transmission. The driver's intention to change gear is then detected by sensors in the selector lever and sent to a control device.

The setpoint values for the intervention in the setpoint value specification of the drive machine 11 can also be determined by a control device separate from the control device 22 and sent to the control device 22 . The calculation can be carried out, for example, by the control device 71 , which controls the clutch actuation device 27 and the actuators of the transmission 15 .

The force for the axial movement of the disengaging piston 52 of the releaser 50 can also be applied by means of compressed air or by an electric actuator which acts directly on the disengaging piston 52 .

The opening degree of the clutch 13 can also be determined by measuring the position of the release piston 52 or by measuring the pressure of the hydraulic fluid or the compressed air, for example in the pressure chamber 53 .

The clutch 13 can also be designed as a multi-plate friction clutch.

The flywheel 42 can also be designed as a dual mass flywheel.

The speed of the clutch disc 44 can also be determined by means of a speed measurement in the transmission 15 , for example on the input shaft 14 .

The calculation of M_Soll_Kup in step 202 can also be determined in each calculation step from one or the combination of several of the influencing variables mentioned.

Claims (10)

1. A method for operating a drive train (10) of a motor vehicle, in which a driving machine (11) can be coupled by means of an actuatable by means of a clutch actuating means (27) coupling (13) with a gear (15) and the control of the drive machine (11) is carried out by means of a control device ( 22 ), at least one setpoint for the torque output or at least one value representing this variable being generated and output to the drive machine ( 11 ), with successive steps:

• - determining a need to open the clutch ( 13 );
• - Setting the target value for the output torque of the drive machine ( 11 ) or for at least one value representing this variable for a first period of time to a first target value which deviates from a default value which is specified by a vehicle driver by means of a power actuator ( 24 );
• - Setting the target value for the output torque of the drive machine ( 11 ) or for at least one value representing this variable for a second period of time to a second target value deviating from the first target value;
• - Open the clutch ( 13 ).

2. The method according to claim 1, characterized in that the second setpoint is independent of the default value, which is specified by the driver by means of the power actuator ( 24 ). 3. The method according to claim 1 or 2, characterized in that said intervention in the setpoint for the prime mover as a function of an evaluation of variables that describe the condition of the motor vehicle at the time when the need to open the clutch ( 13th ) was determined. 4. The method according to any one of claims 1, 2 or 3, characterized in that the determination of the first setpoint for the output torque of the drive machine ( 11 ) or at least one value representing this value for the first period of time is carried out so that the amount of the output Torque of the prime mover ( 11 ) is less than the amount of torque delivered by the prime mover ( 11 ) at the time when the need to open the clutch ( 13 ) was determined and the second setpoint is determined so that the amount of the delivered Torque of the drive machine ( 11 ) is greater than the amount of the first setpoint. 5. The method according to any one of claims 1 to 4, characterized in that the determination of the first setpoint for the torque output of the drive machine ( 11 ) or at least one value representing this value is carried out for a first period of time so that the torque output of the drive machine ( 11 ) has an opposite sign to the output torque of the prime mover ( 11 ) at the time when the need to open the clutch ( 13 ) was determined and the second setpoint is determined so that the output torque of the prime mover ( 11 ) has the same sign as the output torque of the engine ( 11 ) at the time when the need to open the clutch ( 13 ) was determined. 6. The method according to any one of claims 1 to 5, characterized in that the duration of the first period of time for the deviating specification of the target value for the output torque of the drive machine ( 11 ) or at least one value representing this value is a sixth of an oscillation period of a jerky vibration of the drive train ( 10 ). 7. The method according to any one of claims 1 to 6, characterized in that after the second period in which the setpoint for the torque output of the drive machine ( 11 ) or at least one value representing this value is set to the second setpoint, the specification of a third The setpoint is such that the engine does not deliver any torque. 8. The method according to claim 7, characterized in that the duration of the first and second time period is one sixth of the oscillation period of the jerky vibration of the drive train ( 10 ). 9. The method according to any one of claims 1 to 8, characterized in that a determination of said setpoints and / or said time spans depending on quantities which describe the condition of the motor vehicle at the time when the need to open the clutch ( 13th ) was found to be carried out. 10. The method according to any one of claims 1 to 9, characterized in that the method is used only at low gears of the transmission ( 15 ).