DE10221262B4 - Method for controlling or regulating an automated clutch or an automated transmission of a motor vehicle - Google Patents

Abstract

Method for controlling or regulating an automated clutch or an automated transmission of a motor vehicle, in which a torque reduction is carried out during a disengagement phase, the torque reduction being carried out in such a way that the acceleration of the vehicle is reduced as evenly as possible in order to avoid vibrations in the drive train of the vehicle , characterized in that at the beginning of the torque reduction, slip on the clutch is allowed, that a parabolic reduction of the clutch torque (Tc) is carried out approximately in a time interval (τg), and that a linear reduction of the clutch torque (Tc) approximately after a decay time ( τR) the bucking vibration is provided.

Description

The invention relates to a method having the features according to the preamble of claim 1.

Methods for controlling and / or regulating an automated clutch and / or an automated transmission of a vehicle are known from vehicle technology. By an automated clutch or an automated transmission in particular the disengaging process is automated so that a driver of the vehicle does not have to operate the clutch.

• a) nach Ablauf einer Zeitdauer seit Erfassung eines Schaltwunsches, Verringern eines Kupplungsübertragungsdrehmoments zum Ausrücken einer Kupplung und Verringern eines Abgabedrehmoments eines Antriebesaggregats, wobei das Kupplungsübertragungsdrehmoment dem Abgabedrehmoment vorauseilend verringernd wird,
• b) nach dem Erreichen eines Sollkupplungsübertragungsdrehmoments, Beenden des Verringerns des Kupplungsübertragungsdrehmoments und vorzugsweise Haltens desselben auf einem im Wesentlichen konstanten Wert.

document DE 198 41 856 C1 discloses a method for performing switching procedures, comprising the steps of:

• a) after a lapse of time since a shift request has been detected, decreasing a clutch transmission torque to disengage a clutch and decreasing a output torque of a drive unit, the clutch transmission torque leading to decreasing the output torque,
• b) after reaching a desired clutch transmission torque, stopping the reduction of the clutch transmission torque and preferably keeping it at a substantially constant value.

The DE 43 34 172 A1 discloses a method for controlling an upshift in an automatic transmission.

In known methods, however, the duration of the Auskuppelphase is relatively long, especially in Zughochschaltvorgängen. In addition, it may happen in known methods under certain circumstances that at the end of the Auskuppelphase a pushing torque of the engine is still transmitted to the wheels of the vehicle, which is unfavorable in particular with respect to the life of a clutch.

In order to enable a gear change in a vehicle, the torque transmitted from the engine to the wheels is reduced in the known method. This torque reduction of both the engine torque and the transmittable clutch torque is triggered automatically. For the driver, this can come as a surprise, especially when full break operations are performed. This can lead to a relatively strong jerk or vibrations on the vehicle, which significantly affects the driver's feeling and is perceived as unpleasant.

The present invention is therefore based on the object to provide a method of the type mentioned, in which the jerk is kept as low as possible for a given reduction time of the clutch torque and the excitation and transmission of vibrations of the drive train are avoided on the wheels.

This object is achieved by a method with the features of claim 1.

Advantageous embodiments of the invention are the subject of the dependent claims.

Accordingly, the torque reduction in the inventive method is performed as evenly as possible, so that in particular vibrations of the drive train can be avoided. By a targeted control of the transmittable clutch torque, it is possible to meet this requirement. For the suppression of jerking z. B. the drive train, it is therefore useful, in particular the rotational mass of the engine, for. B. right at the beginning of the torque reduction phase, decouple from the drive train. This can be achieved in particular by a rapid reduction of the clutch torque.

Therefore, it is provided according to a development of the invention that during the disengaging phase, the clutch torque is reduced according to a suitable function. Thus, the transition from sticking to slipping in the clutch can be suppressed from the beginning in an advantageous manner.

It is particularly advantageous if slip is permitted on the clutch at the beginning of the disengaging phase, as may be provided in another development of the invention.

Through a carefully chosen time profile of the transmissible clutch torque vibrations in the drive train are minimized. By simulations has been shown that in particular a time-parabolic degradation of the clutch torque is particularly advantageous. Therefore, according to another embodiment of the invention, it is provided that the clutch torque is preferably predetermined initially by a parabolic function and then by a linear function. Of course, other suitable functions for the time course of the clutch torque can be provided in order to further optimize the inventive method.

It is particularly advantageous if the aforementioned measures in the degradation of the Clutch torque can be combined with each other. This means that at the beginning of the torque reduction slippage is allowed on the clutch and then follows a time-parabolic degradation of the clutch torque. This parabolic degradation of the clutch torque can, after a certain decay time τ _{R of} the bucking oscillations, pass continuously and differentially in a linear progression, as provided by an advantageous development of the invention. By this combination, the ride comfort in the vehicle is further improved in an advantageous manner.

T_c,0

= Anfangskupplungsmoment,

α

= Verhältnis von übertragbarem Kupplungsmoment und dynamischem Motormoment,

T_e,0

= anfängliches Motormoment,

J_e

= Trägheitsmoment des Motors,

ω ._e,0

= Winkelbeschleunigung des Motors zu Beginn des Auskuppelvorgangs.

Another development of the present invention may provide that the time profile of the clutch torque is predetermined by an initial clutch torque and by the slope of the initial clutch torque. Preferably, the initial clutch torque may be determined by the following equation: T _{c, 0} = α · (T _{e, 0} - J _e · ω _{e, 0} ), in which

_{Tc, 0}

= Initial clutch torque,

α

= Ratio of transmissible clutch torque and dynamic engine torque,

T _{e, 0}

= initial engine torque,

J _e

= Moment of inertia of the motor,

ω. _{e, 0}

= Angular acceleration of the motor at the beginning of the declutching process.

It has been found that the ratio α should preferably be in the range of about 1.0 to 1.025. Of course, other values can be used.

T ._c,0

= Steigung des Anfangskupplungsmoments,

β

= Verhältnis von Anfangs- und Endabbaurate des übertragenen Kupplungsmoments,

T ._c,max

= maximale Steigung des Kupplungsmomentes.

For the slope of the initial clutch torque, the following equation can be specified: T. _{c, 0} = β · T. _{c, max} , in which

T. _{c, 0}

= Slope of the initial clutch torque,

β

= Ratio of initial and final decay rates of the transmitted clutch torque,

T. _{c, max}

= maximum slope of the clutch torque.

It has been found that the ratio β should preferably be in the range of 0.3 to 0.6. Of course, other values can also be used here. By the aforementioned relationships or equations vibrations during disengagement can be minimized. In the equations, J _{e is} the moment of inertia of the motor and ω. _{e, 0} denotes the angular acceleration of the motor at the beginning of the disengaging phase. α is the ratio of transferable clutch torque and dynamic engine torque at the beginning of Auskuppelphase, where β is the ratio of the initial and final degradation rate of the transferable clutch torque. The abovementioned conditions for α and β lead to a jerk-minimized disengagement in the method according to the invention. The jerk can be defined as the time derivative of the vehicle acceleration, so that the smaller the amount of the time derivative of the vehicle acceleration, the lower the comfort loss. The abovementioned equations can also be suitably varied or changed in the method according to the invention.

Another embodiment of the present invention may provide that a desired time profile of the clutch torque is described by the following equations: T _c (t) = T _{c, 0} + (s ₀ + b · t) · t for t ≤ τ _g and T _c (t) = c + s · (t - τ _g ) for t> τ _g

c = T_c,0 + (s₀ + b·τ_g)·τ_g In this case, t is the time from the beginning of the disengaging phase and T _{c, 0 is} the transmittable torque to which the clutch is set at the beginning of the disengaging phase. With s is the slope of the linear engine torque reduction and s ₀ denotes the slope at the beginning of engine torque reduction. Since both T _c , so the timing of the clutch torque, as well as T. _c , that is, the slope of the clutch torque curve should be continuous in the transition from the parabolic to the linear curve, b and c should preferably satisfy the following conditions:

c = T _{c, 0} + (s ₀ + b · τ _g ) · τ _g

Of course, other suitable conditions can be used in the method according to the invention.

It is also possible that the slope s of the linear torque reduction during fine tuning in the vehicle is applied. It can also be considered dependencies of the engine torque and the gear. In order to specify the simplest possible calculation formulas for s ₀ and T _{c, 0} , the following approaches are proposed by way of example: s ₀ = β s, T _{c, 0} = α · (T _{e, 0} - J _e · ω _{e, 0} )

It is with ω. _{e, 0 is} the angular acceleration of the motor at the beginning of disengaging. In the formula given here, values of from 0.8 to 1.1 are preferably given for α, which can be varied in steps of 0.05. For β, values from 0 to 1 are given, which can be varied in steps of 0.2. Of course, other value ranges or other steps are also possible here. The initial engine torque T _{e, 0} was preferably set to 100 Nm. Also with this value variations are possible.

It has been found that, in the method according to the invention, the coupling should preferably be at the slip limit at the beginning of the torque reduction and the initial gradient of the torque reduction should be approximately between 30 and 60% of the final gradient. These indicated values result in the method according to the invention an optimal torque reduction, in which the vibrations of the drive train are minimized. This is because early decoupling of the engine and drive train is made possible in the method according to the invention.

Due to the optimal interaction of temporally non-linear and linear torque reduction, vibration excitations are virtually eliminated already in the beginning and a largely uniform torque reduction is achieved. Advantageously, the number of application parameters is significantly reduced in the inventive method, whereby a vote in the vehicle is facilitated.

Another development of the present invention may provide that a simulation model is used to optimize the method according to the invention. In the simulation model in particular the rotational masses of the engine, the clutch disc, the transmission and the vehicle, as well as the elasticity and damping of the drive shafts and the clutch are taken into account. Of course, other suitable operating parameters or parameters can also be used in the simulation model.

The driving resistance torque can be smaller than the engine torque in the simulation model, so that an acceleration situation can be simulated. The initial conditions can be chosen so that the drive train of the vehicle does not vibrate and the clutch sticks. Various reduction curves can be implemented for the engine and clutch torque so that various engine torque reduction strategies can be investigated with the simulation model.

The most important parameters of the vibration system are preferably the rotational mass of the vehicle J _Fzg = 0.75 kgm ² , the rotational mass of the gear J _Get = 0.025 kgm ² , the rotational mass of the engine J _Mot = 0.165 kgm ² , C _drive = 33 Nm / rad and d _drive = 1 Nms / rad.

This results in a period of the bucking between the engine and the transmission relative to the vehicle a value of 675 ms (1.5 Hz) and the plucking between the transmission relative to the vehicle a value of 170 ms (5.9 Hz).

In the simulation model, the vehicle acceleration can be differentiated, whereby one receives a statement about the present jerk in the vehicle. The negative maximum value of the jerk is a crucial criterion in the evaluation of the different strategies.

M_Kup

= Kupplungsmoment,

KME

= Faktor der Globalstrategie,

M_Mot

= Motormoment

J_Mot

= Trägheitsmoment des Motors,

ω ._Mot

= Winkelbeschleunigung des Motors.

Another development of the present invention may provide that the clutch slip in the torque reduction at the beginning of the disengaging phase is achieved in that a KME factor of the global strategy to a value z. B. is set less than 1. In order to take into account in the simulation also the portion of the engine torque, which is included in the engine's own acceleration, the following approach can be chosen: M _Kup = KME · (M _Mot -J _Mot · _ω.Mot ), in which

M _Kup

= Clutch torque,

KME

= Factor of global strategy,

M _Mot

= Engine torque

J _Mot

= Moment of inertia of the motor,

ω. _Mot

= Angular acceleration of the motor.

It is particularly advantageous if the KME factor is decremented during the torque reduction to a value less than 1 until a specified minimum is reached. Of course, the KME factor can also be reduced and limited elsewhere.

According to another embodiment of the invention can be provided that the gradient of the clutch torque in the linear region is determined depending on the driving situation as Schaltkomforparameter. Because the gradient of the clutch torque in the linear range is directly proportional to the jerk maximum together.

The initial jump in the torque reduction together with the initial gradient in the parabolic degradation of the clutch torque determines the size of the first peak in the course of the jerk.

According to a further embodiment of the present invention, it is conceivable that a situation-independent KME factor and / or a torque offset proportional to the gradient in the linear range is used. Of course, other suitable parameters can be used in the method according to the invention.

It is also conceivable that the initial gradient of the clutch torque has a constant percentage of the gradient in the linear range at least gear-dependent. This is because the degree of damping in the drive train is gear-dependent constant.

Regarding the period of the parabolic torque reduction can be considered according to another embodiment of the invention that at the end of the parabolic degradation, the excited natural oscillations in the drive train should be subsided, so that the subsequent linear torque reduction causes no further jerking. Since the natural frequency and the degree of damping in the drive train are gear-dependent constant, the period of parabolic torque reduction may preferably be a gear-dependent constant.

In the aforementioned parameters, to optimize the tuning of these parameters, it is also possible to use the variation of the torque, the rotational speed and of the damping and adaptation parameters of the clutch characteristic in order to obtain statements about the robustness of the strategy. This can then be used to derive results for the control engineering implementation.

The method according to the present invention can be used in any type of torque transmission systems. Particularly advantageous is the use of an electronic clutch management (EKM) and an automatic transmission (ASG).

Further advantages and advantageous embodiments will become apparent from the dependent claims and from the accompanying drawings explanatory description. Show it:

1 a time course of the torque reduction according to the present invention;

2 a time course of the jerk during a Auskuppelphase for two different α-β pairs;

3 a contour plot of the maximum jerk in an α-β plane for a first parameter variation;

4 a contour plot of the maximum jerk in the α-β plane for a second parameter variation;

5 a contour plot of the maximum jerk in the α-β plane for a third parameter variation;

6 a contour plot of the maximum jerk in the α-β plane for a fourth parameter variation;

7 a contour plot of the maximum jerk in the α-β plane for a fifth parameter variation;

8th a contour plot of the maximum jerk in the α-β plane for a sixth parameter variation;

9 a contour plot of the maximum jerk in the α-β plane for a seventh parameter variation;

10 a contour plot of the maximum jerk in the α-β plane for an eighth parameter variation;

11 a schematic representation of a simulation model of a drive train of a vehicle;

12 three diagrams in which different vehicle sizes are shown during a linear torque reduction in 250 ms;

13 three diagrams in which different vehicle sizes are shown in a linear torque reduction in 500 ms;

14 three diagrams in which different vehicle sizes are shown in a parabolic torque reduction in 500 ms;

15 three diagrams in which different vehicle sizes are shown with a linear torque reduction in 500 ms with slip;

16 three diagrams with different vehicle sizes at torque reduction according to the invention; and

17 a graphically displayed measurement result with vehicle data during a switching operation.

In 1 the curves of the engine torque T _e and the clutch torque T _{c are shown} during the disengaging phase. In order to avoid vibrations in the drive train, slip is allowed already at the beginning of the Auskuppelphase. This is followed by a parabolic reduction of the clutch torque, followed by a linear degradation. In order to avoid the motor leaving the track, T _e should sink below T _c towards the end of the disengaging phase, as in 1 is indicated.

In 2 the jerk over time is shown using different αβ pairs in the two diagrams. Out 2 It can be seen that α and β have a noticeable influence on the jerk J of the vehicle. In the upper diagram, the values for α are equal to 0.9 and for β equal to 0. At these values, significant vibrations are noticeable. In the lower diagram, the value for α is 1 and the value for β is 0.6. At these values, the excitation of vibrations is virtually eliminated.

The initial motor torque is in these representations in 2 equal to 100 Nm, the driving resistance equal to 50 Nm, the damping coefficient of the drive train equal to 1 Nms / rad and the slope equal to -350 Nm / s.

In the 3 to 10 are contour plots of the amount of maximum jerk | J _max | in the α-β plane for different parameter variations. The white areas are areas in which the maximum jerk is not more than 20 rad / s ³ above the absolute minimum of the respective plot. It is assumed that a change of the jerk by 20 rad / s ³ from the driver is still perceived as low. Typical values of the absolute minimums are 260 rad / s ³ at s = -250 Nm / s or 470 rad / s ³ and at s = -350 Nm / s. The α-values belonging to the absolute minima are 1.0 or 1.05, the β-values are 0.4; 0.6 or 0.8. If one forms the intersection of all white areas, then one obtains approximately the already specified conditions for almost jerk-minimized decoupling of α and β. Thereafter, α should be between 1.0 and 1.025 and β should be between 0.3 and 0.6.

This means that the clutch should be at the slip limit at the beginning of torque reduction and the initial torque reduction ramp should be 30 to 60% of the final grade.

In 3 the absolute minimum at 267 rad / s ^{3 is} indicated by a circle and the star indicates the position of the absolute maximum 930 rad / s ³ . On the white surface, the maximum jerk is at most 20 rad / s ³ above the absolute minimum. The engine torque at the beginning of the declutching is 100 Nm, the driving resistance at 90 Nm, the torque reduction rate in the linear range at -200 Nm / s and the damping coefficient of the drive train at 0.5 Nms / rad.

In 4 the circle shows the position of the absolute minimum at 264 rad / s ³ and the star the position of the absolute maximum at 903 rad / s ³ . On the white surface, the maximum jerk is at most 20 rad / s ³ above the absolute minimum. The engine torque at the beginning of the declutching is 100 Nm, the driving resistance at 10 Nm, the torque reduction rate in the linear range at -200 Nm / s and the damping coefficient of the drive train at 1.0 Nms / rad.

In 5 the circle again shows the position of the absolute minimum at 267 rad / s ³ and the star the position of the absolute maximum at 967 rad / s ³ . On the white surface, the maximum jerk is at most 20 rad / s ³ above the absolute minimum. The engine torque at the beginning of the declutching is 100 Nm, the driving resistance at 50 Nm, the torque reduction rate in the linear range at -200 Nm / s and the damping coefficient of the drive train at 1.0 Nms / rad.

In 5 the absolute minimum is indicated by the circle at 267 rad / s ³ and the absolute maximum by the asterisk at 1049 rad / s ³ . On the white surface, the maximum jerk is at most 20 rad / s ³ above the absolute minimum. The engine torque at the beginning of the declutching is 100 Nm, the driving resistance at 90 Nm, the torque reduction rate in the linear range at -200 Nm per second and the damping coefficient of the drive train at 1.0 Nms / rad.

In 7 the circle shows the position of the absolute minimum at 461 rad / s ³ and the star the position of the absolute maximum at 962 rad / s ³ . On the white surface, the maximum jerk is at most 20 rad / s ³ above the absolute minimum. The engine torque at the beginning of the declutching is 100 Nm, the driving resistance at 10 Nm, the torque reduction rate in the linear range at -350 Nm per second and the damping coefficient of the drive train at 1.0 Nms / rad.

In 8th the circle shows the position of the absolute minimum at 461 rad / s ³ and the star the position of the absolute maximum at 1027 rad / s ³ . On the white surface, the maximum jerk is at most 20 rad / s ³ above the absolute minimum. The engine torque at the beginning of the declutching is 100 Nm, the driving resistance at 50 Nm, the torque reduction rate in the linear range at -350 Nm per second and the damping coefficient of the drive train at 1.0 Nms / rad.

In 9 the circle shows the position of the absolute minimum at 462 rad / s ³ and the star the position of the absolute maximum at 1092 rad / s ³ . On the white surface, the maximum jerk is at most 20 rad / s ³ above the absolute minimum. The engine torque at the beginning of the declutching is 100 Nm, the driving resistance at 90 Nm, the torque reduction rate in the linear range at -350 Nm per second and the damping coefficient of the drive train at 1.0 Nms / rad.

In 10 the circle shows the position of the absolute minimum at 264 rad / s ³ and the star the position of the absolute maximum at 1823 rad / s ³ . On the white surface, the maximum jerk is at most 20 rad / s ³ above the absolute minimum. The engine torque at the beginning of the declutching is 100 Nm, the driving resistance at 90 Nm, the torque reduction rate in the linear range at -200 Nm per second and the damping coefficient of the drive train at 2.0 Nms / rad.

11 shows a simulation model of the drive train of the vehicle. In the simulation model, the rotational masses of the engine, the clutch disc, the transmission and the vehicle as well as the elasticity and damping of the drive shafts and the clutch are included.

In the 12 to 16 the engine torque, clutch torque, torque train, engine speed, transmission speed, output speed, vehicle acceleration, and jerk over time are shown.

In the 12 and 13 is a linear degradation in 250 ms or 500 ms with the condition clutch torque> engine torque shown. In 14 is a parabolic degradation in 500 ms with the condition clutch torque> engine torque indicated.

Out 15 Again, a linear torque reduction in 500 ms with slip is visible. There are the simulation results for the same torque reduction as at 14 indicated, in 15 but a decrement of the KME factor has been made to a value below 1.

In 15 is now also degraded with linear torque reduction with slip. This is achieved by setting the KME factor to a value below 1, as already mentioned. Thus, the resulting clutch torque curve is no longer linear. In this case, the negative jerk is reduced faster in the slipping system. This is due to the higher natural frequency. For the selected parameters, the negative jerk maximum with slipping torque reduction is greater than with non slipping torque reduction. The natural vibration sound faster with the same damping with higher natural frequency, ie slipping clutch. The coupling of the clutch torque to the engine torque by means of the KME value leads with slipping torque reduction (KME <1) to the significant route of the engine. The transmission speed, however, is below the output speed, which can be explained by the relaxation of the drive train.

16 shows both a parabolic and a linear torque reduction, which are combined with each other. The simulation results show that with this approach a nearly constant jerk can be achieved during the torque reduction.

Overall, it can be stated that with linear torque reduction, a contributory maximum _pressure is present after approximately a third of time. In a parabolic torque reduction, the largest amount of jerk occurs towards the end. After the late transition of the coupling from sticking to slipping, the jerk is even more pronounced. In a direct comparison of the two degradation processes, the linear torque reduction can perform better, because the absolute maximum jerk is smaller.

In 16 At the beginning of the torque reduction, a clutch torque jump is provided which generates the slip and thereby excites the higher jerk frequency. This is followed by a parabolic torque reduction at the clutch, wherein the initial gradient is not 0. After the natural oscillations in the drive train have subsided, a constant gradient of the clutch torque follows. The engine torque is degraded towards the end faster than the clutch torque, so that the engine can not Wegtouren and the slip is limited.

In the 16 shown courses show that a nearly constant jerk is achieved during the torque reduction. At a degradation time of 500 ms, the maximum of the deceleration pressure is only -245 rad / s ³ . In the case of a linear torque reduction without slip, on the other hand, a deceleration pressure of -325 rad / s ^{3 is} generated. Thus, the deceleration pressure can be reduced by about 25% in the method according to the invention. In addition, with the method according to the invention, the torque reduction time can be significantly shortened, namely by about 25%.

In 17 is a Vollastzughochschaltvorgang from the second to the third gear shown. During this switching process, the clutch is suddenly opened while the engine torque is stopped, and at the same time the gear change is initiated. The torque build-up takes place after the gear change according to a suitable engagement strategy, preferably by sportive engagement. Out 17 It is clear that the duration of the switching process in the inventive method can be reduced to about 340 ms.

Claims (17)

Method for controlling or regulating an automated clutch or an automated transmission of a motor vehicle, in which a torque reduction is performed during a decoupling phase, wherein the torque reduction is performed such that the acceleration of the vehicle is reduced as evenly as possible in order to avoid vibrations of the drive train of the vehicle , characterized in that at the beginning of the torque reduction slip is allowed on the clutch that a parabolic degradation of the clutch torque (T _c ) approximately in a time interval (τ _g ) is performed, and that a linear degradation of the clutch torque (T _c ) approximately after a decay time (τ _R ) of the bucking vibration is provided. A method according to claim 1, characterized in that the time profile of the clutch torque (T _c ) by an initial clutch torque (T _{c, 0} ) or by the slope of the initial clutch torque (T _{c, 0} ) is predetermined. A method according to claim 2, characterized in that the initial clutch torque (T _{c, 0} ) is determined by the following equation: T _{c, 0} = α · (T _{e, 0} - J _e · ω _{e, 0} ), where T _{c, 0} = initial clutch torque, α = ratio of transmittable clutch torque and dynamic engine torque, T _{e, 0} = initial engine torque, J _e = moment of inertia of the engine, ω. _{e, 0} = angular acceleration of the motor at the beginning of the declutching process. A method according to claim 3, characterized in that the ratio (α) is approximately in the range of 1.0 to 1.025. Method according to one of claims 3 or 4, characterized in that the slope of the initial clutch torque (T _{c, 0} ) is determined by the following equation: T. _{c, 0} = β · T. _{c, max} , where T. _{c, 0} = slope of the initial clutch torque, β = ratio of the initial and final decay rates of the transmitted clutch torque, T. _{c, max} = maximum slope of the clutch torque. A method according to claim 5, characterized in that the ratio (β) is in the range of 0.3 to 0.6. Method according to one of claims 1 to 6, characterized in that the temporal desired course of the clutch torque (T _c ) is described by the following equation: T _c (t) = T _{c, 0} + (s ₀ + b · t) · t for t ≤ τ _g and T _c (t) = c + s · (t - τ _g ) for t> τ _g , where T _c = nominal curve of the clutch torque, s ₀ = initial slope of the clutch torque s = slope of the linear torque reduction, t = time at the beginning of the disengaging phase, τ _g = duration of the parabolic clutch torque reduction, b and c = parameter. A method according to claim 7, characterized in that the parameter (b) satisfies the following condition:

Method according to claim 7 or 8, characterized in that the parameter (c) satisfies the following condition: c = T _{c, 0} + (s ₀ + b · τ _g ) · τ _g Method according to one of claims 7 to 9, characterized in that for the slope at the beginning of the torque reduction (see above) the following approach applies: s ₀ = β s, where β = ratio of initial slope of the torque reduction to final slope. Method according to one of claims 7 to 10, characterized in that for the initial slope of the clutch torque (T _{c, 0} ) the following approach is chosen: T _{c, 0} = α · (T _{e, 0} - J _e · ω _{e, 0} ), in which α = ratio of dynamic engine torque to transmittable clutch torque at the beginning of torque reduction, T _{e, 0} = initial engine torque, J _e = moment of inertia of the engine, ω. _{e, 0} = angular acceleration of the motor at the beginning of disengaging. A method according to claim 10, characterized in that the ratio (β) is in the range of 0 to 1 and is varied in steps of 0.2. A method according to claim 11, characterized in that the ratio (α) is in the range of 0.8 to 1.1 and is varied in increments of 0.05 and that the initial engine torque (T _{e, 0} ) is in the range of about 100 Nm is. Method according to one of claims 1 to 13, characterized in that the gradient of the clutch torque in the linear region is determined depending on the driving situation as a shift comfort parameter. Method according to one of claims 1 to 14, characterized in that the initial gradient is combined with the linear torque reduction with a suitable torque offset. Method according to one of claims 1 to 15, characterized in that the initial gradient is set such that it is at least gear-dependent a constant proportion of the gradient in the linear torque reduction. Method according to one of claims 1 to 16, characterized in that a gear-dependent constant is selected as the time duration of the parabolic torque reduction.

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