WO2011076534A1 - Method and device for distributing a driving torque to the wheels of an electrically driven axle of a motor vehicle - Google Patents

Abstract

The invention relates to a method for distributing a driving torque to the wheels of an electrically driven axle of a motor vehicle, wherein an electrical signal from a drive assembly (3, 4) is converted to a torque (EMProp) which is transferred to the wheels (11a, 11b) of the axle (10a, 10b) by an electrically driven axle (10a, 10b). In order to be able to generate not only driving but also braking wheel torque, the wheels (11a, 11b) arranged on the electrically driven axle (10a, 10b) are loaded independently from each other by a driving or braking torque, each overlapped by a differential torque (EMDif).

Description

 Description title

 Method and device for distributing a drive torque to the wheels of an electrically driven axle of a motor vehicle

State of the art

The invention relates to a method for distributing a drive torque to the wheels of an electrically driven axle of a motor vehicle, wherein an electrical signal is converted by a drive unit into a torque which is transmitted from an electrically driven axle to the wheels of the axle and a device for implementation of the procedure.

In electrical drives of a motor vehicle, two groups are distinguished. On the one hand, there are electric wheel drives, in each of which an electric motor is assigned to a driven wheel. In addition, there are electric axle drives in which a arranged on the driven axle differential, the drive torque of an electric motor is transmitted evenly to both wheels, which are fixed to the driven axle.

Disclosure of the invention

The inventive method for distributing a drive torque to the wheels of an electrically driven axle of a motor vehicle having the features of claim 1 has the advantage that a wheel-individual adjustment of the drive torque is possible. The desired drive torque (set by the driver or set automatically) is represented by a sum and a difference torque component. The wheels arranged on the electrically driven axle are superimposed independently with a driving torque acting on each with a differential rotation motor. ment. Characterized in that the arranged on the electrically driven axle wheels are driven individually, a division of the desired drive torque to the two wheels can be made so that the desired difference torque component on this axis is ideally transmitted to the ground. The proposed wheel-individual drive the traction on a roadway in which a drive wheel on a normal road, the other drive wheel but moves to ice, to optimize traction and driving dynamics with high quality with minimal losses can be realized.

Advantageously, an electrical drive torque for each driven wheel is formed by adding or subtracting the differential torque to the drive torque. The additional differential torque on the basis of a precontrol serves for the basic distribution of the drive torque to the driven wheels of an axle.

In a further development, the electric drive torque is determined from a torque of the drive unit driving a wheel by multiplication with a respectively effective torque transmission ratio, which is acted upon by at least one weighting factor, from which a precontrol value for an additional differential torque during cornering is determined. This positively influences the driving dynamics of the vehicle. The differential torque arises in particular when cornering, whereby it acts as an additional yaw moment and supports the insertion of the vehicle in the curve. Against an understeering vehicle is already intervened in the approach. The traction, i. the implementation of the driving force in a propulsion of the vehicle is improved when cornering and increases the driving stability in the curve. Furthermore, the steering effort of the driver is significantly reduced, while the vehicle reacts spontaneously to changes in steering angle of the driver.

In one embodiment, the weighting factor is determined as a function of a wheel load change during acceleration and / or cornering. Both the longitudinal direction (acceleration) and the transverse direction (cornering) of the vehicle are sufficiently considered.

Furthermore, the weighting factor is determined as a function of the vehicle speed. By means of this weighting factor, the maximum permissible differential described torque. This ensures that at a certain vehicle speed, the asymmetrical distribution of the drive torque is reduced to the two wheels of the driven axle. In particular, a resulting weighting factor is formed from the sum of the wheel load-dependent weighting factors, which is multiplied by the vehicle speed-dependent weighting factor. The resulting weighting factor maps the operating mode of the vehicle, depending on whether the vehicle is in normal operation, in sports mode or in an operating state in which the vehicle has already reached its stability limits. This mode of operation is sufficiently taken into account in the formation of the additional differential torque.

In a further development, the pre-control value for the additional differential torque during the drive, the freewheel and in Recouperationsbetrieb the

Motor vehicle used and is thus feasible in any driving condition of the vehicle.

Advantageously, a deviation of a yaw angular velocity from a nominal yaw angular velocity and an actual yaw angular velocity is determined, a stabilizing differential torque being determined from the determined deviation. The use of the stabilizing differential torque contributes to the stabilization of the vehicle. Advantageously, the deviation between the desired yaw rate and the actual value of the yaw rate and their change are limited to an allowable range.

In one embodiment, with the same sign of the differential torque determined on the basis of the pilot control value and the stabilizing differential torque, the differential torque and the stabilizing differential torque determined on the basis of the pilot control value are added to a driving dynamic drive torque.

Alternatively, with different signs of the differential torque determined on the basis of the pre-control value and of the stabilizing

Difference torque the amount of the value determined differential torque reduced by the amount of the stabilizing differential torque. Based on this, in the case of an oversteering vehicle, an increase in the drive torque on the inside drive wheel takes place in the drive case, while the outside drive wheel is lowered approximately simultaneously. This generates a reverse yaw moment against the oversteering tendency and at the same time increases the lateral force potential on the outer wheel. In contrast, when the vehicle is understeered, the drive torque of the outside wheel increases in the drive case on the driven axle and a corresponding reduction of the drive torque takes place at the same time approximately at the same time

Rad. This creates a turning yaw moment against the understeer tendency.

In one variant, when a limit value is exceeded by the driving dynamics differential drive torque, a drive slip of the vehicle is limited by a wheel slip control system, preferably a TCS system. If the yaw moment generated by the additional differential torque is insufficient to ensure the stability of the vehicle, a stabilization system inherent in the vehicle intervenes in order to support the vehicle stabilization. In addition to the TCS system, the vehicle also contains an ABS system and an ESP system as additional stabilization systems.

A further development of the invention relates to a method for distributing a drive torque to the wheels of an electrically driven axle of a motor vehicle, wherein an electrical signal is converted by a drive unit into a regeneration torque transmitted from an electrically driven axle to the wheels of the axle becomes. In order to generate not only driving, but also braking acting wheel torques, which are arranged on the electrically driven axle wheels are each superimposed with a braking torque acting drive torque superimposed with a differential torque applied. In each case, a drive unit for individual drive only one wheel on the driven axle is available. Also in the wheel-specific Recouperation, which forms the basis for the realization of differential torques, impairments in the driving dynamics are minimized. The Recouperationspotential is on low friction coefficients of the drive wheels against the ground, as in Ice or snow, expanded. The stability of the vehicle is also improved at high coefficients of friction with a corresponding forced driving style.

Under Recouperation is generally understood the operating condition of an electric motor in which this operates as a generator and converts the energy contained in the driving movement of the vehicle into electrical energy for charging a battery. In this case, the vehicle is braked by the electric motor in its movement. Such a braking operation takes place without putting the mechanical braking system of the vehicle, which is relieved by this procedure, whereby the life of the mechanical brake system increases and the cost of the brake hydraulics is reduced.

With the wheel-specific Recouperation the conflict between a high Recouperationsleistung and a favorable interpretation of the stabilizing effect on the vehicle yawing moments can better compensate.

Advantageously, a Differenzrecouperationsanteil is formed in Recouperationsbetrieb the vehicle for distributing the Recouperationsmoments on the two wheels of the driven axle for precontrol, which depends on the vehicle speed and the lateral acceleration of the vehicle and which in particular a Stabilisierungsrecouperationsmoment is superimposed. Due to this procedure, the recovery of electrical energy can be better adapted to the current driving situation. When cornering can be better coordinated by the wheel-individual drive, the distribution of the braking torque with the additional Differenzrecouperationsmoment. Thus, already in advance of the danger of under- or oversteering behavior of the vehicle can be stopped, since the entire Recouperationsmoment is already distributed by the feedforward control on the wheels that a stabilizing effect is achieved.

 In a further embodiment, in a tendency to oversteer vehicle, the Recouperationsmoment increases on the outside wheel and reduced almost simultaneously on the inside wheel.

Alternatively, an increase in the Recouperationsmoments at the inside wheel and approximately occur in a tendency to understeer vehicle at the same time lowering the Recouprationsmomentes on the outside wheel.

A further development of the invention relates to a device for distributing a drive torque to the wheels of an electrically driven axle of a motor vehicle, wherein an electrical signal is converted by a drive unit into a torque which is transmitted from the driven axle to the wheels of the axle. In order to enable a wheel-individual adjustment of the drive torque, means are provided which act on the electrically driven axle wheels independently superimposed with a driving or braking torque acting on each superposed with a differential torque. The electric axle drive can thus realize in addition to the actual drive torque and differential moments that would be needed for traction and driving dynamics interventions. The classic axle differential is eliminated. The wheel-individual adjustment of the drive torque is now possible for driving as well as for braking-acting wheel torques.

Advantageously, the wheels of two positioned on the axis, driven independently of each other drive units are driven, wherein a drive unit in each case drives a wheel. The approximately central arrangement of the two electric drive units on the electrically driven axle allows the minimization of unsprung masses on the drive axle, whereby the ride comfort of the motor vehicle is substantially improved. The chassis quality is improved by reducing the unsprung masses.

The invention allows numerous embodiments. One of them will be explained in more detail with reference to the figures shown in the drawing. It shows:

Figure 1: Schematic representation of a double rotor drive unit

Figure 2: an example of the electrical interconnection of the double rotor drive unit FIG. 3 shows a schematic flow diagram for an exemplary embodiment of the method according to the invention

Identical features are identified by the same reference numerals.

1 shows an electric drive in the form of a double-rotor drive unit 1, which is installed in the drive train of a motor vehicle with an electrically driven rear axle. However, this is not intended to be limiting, since it is also possible to use the double-rotor drive unit 1 on a driven front axle. The double rotor drive unit 1 is arranged approximately axially and is located at the position where normally a conventional axle differential is installed, which is replaced in the present example by the double rotor drive unit 1.

The double-rotor drive unit 1 is arranged in a housing 2 and consists of two electric motor part drives 3 and 4. Each electric motor part drive 3 and 4 in this case has a stator winding 5a and 5b, which surrounds a rotor 6a and 6b. The rotor 6a or 6b is in each case arranged on a rotor shaft 7a, 7b, wherein the two rotor shafts 7a and 7b can be connected via a coupling 8 positioned between the two rotor shafts 7a, 7b. The rotor shaft 7a, 7b leads to a gear 9a, 9b, which in each case has a predetermined gear ratio to the necessary speed adjustment. The transmission 9a, 9b in turn is connected to a side shaft 10a, 10b, which leads to the drive wheel 1 1 a, 1 1 b. In addition, each side shaft 10a, 10b is in operative connection with the suspension or a shock absorber leg 12a, 12b of a shock absorber of the motor vehicle.

As can be seen from the preceding description, the drive train, starting from the double-rotor drive unit 1 in the direction of the driven wheel 1 1 a, 1 1 b constructed symmetrically. The gears 9a, 9b are arranged to improve the mass distribution of the motor vehicle in the vicinity of the arranged approximately to the center of the axis double rotor drive unit 1 and can connect the electric motor part drive 3 or 4 with the drive wheel 1 1 a or 1 1 b as needed or interrupt this. The electrical interconnection of the double rotor drive unit 1 will be explained in more detail with reference to FIG 2. Each electric motor part drive 3 or 4 is connected to a power semiconductor module 13a or 13b, by means of which a three-phase current for driving the electric motor part drives 3, 4 is generated. Both power semiconductor modules 13a, 13b lead to an inverter 14, which is also known as

Pulse inverter is called and which converts a supplied from a high-voltage battery 15 DC voltage of about 230 V in an AC voltage, which are further processed by the two power semiconductor modules 13a, 13b. For completeness, it should be mentioned that when the electric motor part drives 3, 4 operate in a generator mode in which the mechanical energy applied by the vehicle is converted by the electric motor part drives 3, 4 into electrical energy, the pulse-controlled inverter 14 from the electric motor part drives 3, 4 applied AC voltage in the reverse direction into a DC voltage, by means of which the high-voltage battery 15 is charged. In this process, the

Braked vehicle without the use of a non-illustrated mechanical braking system of the vehicle.

Between the pulse inverter 14 and the high-voltage battery 15, a DC / DC converter 16 is arranged, which supplies a low-voltage battery 17 with voltage. The low-voltage battery 17 is at a voltage level of about 14 V, wherein the DC / DC converter converts the voltage applied to the high-voltage battery 15 from 230 V to 14 V. By means of this voltage of 14 volts, the low-voltage battery 17 supplies all control devices of the motor vehicle with energy.

The electronic control of the electric motor part drives 3 and 4 is carried out by a control unit 18 which is connected via a vehicle-specific communication network 19, preferably a CAN bus with other, not shown Steu- ergeräten the motor vehicle and receives information about the current driving situation of the motor vehicle , In evaluation of this information, the control unit 18 controls the two electric motor part drives 3, 4 separately or together, wherein the open in normal operation case clutch 7 is closed by a signal from the control unit 18, when generated by both electric motor part drives 3, 4 in the state of startup Torque on only one drive wheel 1 1 a, 1 1 b to be redirected. The control unit 18 comprises a driving dynamics control system, which consists of a pilot control unit and a control unit. The Stability Control of the ESP (Electronic Stability Program) and the traction control of the ESP use the Electric Double Rotor Drive Unit 1 as an actuator with extended capabilities. The influence of the driving dynamics will be described in detail with the aid of FIG.

The drive torques at the two driven wheels 1 1 a, 1 1 b are initially the same when driving straight ahead and in total correspond to a drive desired torque which is specified by the driver or the control unit 18 for the driven axle 10a, 10b. In block 100, the drive torque EMProp is determined by superimposition and multiplication of the electric motor torques with the respectively effective torque transmission ratio iG_L or iG_R between the respective electric motor part drive 3, 4 and the wheel 11a, 11b driven by the latter.

EMProp = EMmotJ. ^* iG_L + EMmot_R ^* iG_R

The reference symbol L corresponds to the electric motor part drive 3 and the drive wheel 1 1 a, while the reference symbol R corresponds to the electric motor part drive 4 and the drive wheel 1 1 b.

Usually, iG_L = iG_R = iG

A limitation of the drive torque EMProp is due to traction and / or driving dynamic reasons by the TCS system or the ESP. Thereby applies

EMProp = Min (EMPropTar, EMPropTCS), where

EMPropTar the specified electrical target drive torque and EMPropTCS represent a maximum permissible nominal electrical drive torque.

In block 101 weighting factors KoFn _x and KoFn _{y are} calculated in the pilot control unit. KoFn _x = P_KoFn _x ^* P_GewA _x ^* AFn _X R _A FnoRA, where

P_KoFn _x gain parameter

P_GewA _x Weighting factor curve

AFn _XRA Radlaständerung by longitudinal acceleration

Fn ₀ RA static wheel load

P_KoFn _x and AFn _XRA are calculated as a function of the measured or estimated longitudinal acceleration. The weighting factor P_GewA _x is specified as a function of the lateral acceleration. It controls the influence of the weighting factor KoFn _x when driving straight ahead and cornering.

KoFn _y = P_KoFn _y ^* AFn _Y R _A FnoRA, where P_KoFn _y gain parameters

AFn _YRA Radlaständerung in lateral acceleration or from compression paths

Fn ₀ RA static wheel load P_KoFn _y and AFn _YRA are used as a function of measured or estimated

Calculated lateral acceleration. The gain parameter P_KoFn _y can be parameterized for three different operating states:

In normal operation, the focus is on the agility and traction of the vehicle. During TCS operation, the emphasis is on stability and traction, as the stability limit has been reached, and in sports the focus is on

Traction, agility and driving fun laid.

As the next step, a further weighting factor KoFn _{vFz is} formed in block 102, which describes the maximum permissible difference torque EMDifPreProp as a function of the vehicle speed:

KoFn _vFz = f (vFz)

The weighting factor KoFn _vFz can be parameterized for two different operating modes: In normal operation, the asymmetrical distribution of the drive torque EMProp is gradually reduced from a certain first vehicle speed. Above a second limit of the vehicle speed, the drive torque EMProp is symmetrically distributed to the drive wheels 1 1 a, 1 1 b.

In sports, the asymmetrical distribution of the drive torque EMProp is fully preserved up to a first limit. Above a second limit, the drive torque EMProp is distributed symmetrically to the drive wheels. In between there is a linear transition.

In block 103, the individual weighting factors KoFn _x, KoFn _y and KoFn _{vFz are combined} to form a resulting weighting factor KoFn. The following applies:

KoFn = MIN ((KoFn _x + KoFn _y ), 1) ^* KoFn _vFz

The differential torque EMDifPreProp necessary for cornering serves on the basis of the precontrol value for the basic distribution of the drive torque EMProp to the driven wheels 11a, 11b of the axle 10a, 10b.

EMDifPreProp = sign (ay) ^* KoFn ^* max (EMprop, EMPropMin), where sign (ay) represents the sign of lateral acceleration.

In the so-called freewheeling case applies:

EMmotJ. = - EMmot_R => EMProp = 0

As a special case, the following can apply in the recuperation plant:

EMmot_L = EMmot_R => EMProp = 0.

In order to be able to generate differential driving moments effective in these situations with EMProp = 0, EMPropMin provides a certain minimum value for the pre-controlled differential torque EMDifPreProp. The feedforward control supports the drive case, the freewheeling case and the operation with Recouperation in such a way that adjusts the most harmonious, stable driving behavior according to the character of the vehicle.

The differential torque EMDifPreProp is set to zero in cases when the vehicle is reversing, in an oversteering vehicle, the estimated slip angles at front and rear axle have different signs or the temperature of at least one component of the Doppelro- drive unit 1 has exceeded a critical temperature limit.

In addition, the difference torque EMDifProp is limited to a permissible range.

EMDifPrePropMin <= EMDifPreProp <= EMDifPrePropMax

In block 104, a stabilizing differential drive torque EMDifStab is determined by a controller from a control deviation of a yaw rate of the vehicle. The control deviation of the yaw rate is determined from evGi (k) = vGiSo (k) - vGi (k)

devgi (k) = evGi (k) - evGi (K-1), where vGiSo is the desired yaw angular velocity

vGi Actual value of the yaw rate

evGi represent deviation of the yaw angular velocity.

devGi Change of the control deviation of the yaw angular velocity.

To determine the stabilizing differential drive torque EMDifStab a control method with PDT characteristic is used, taking into account a controller parameter with a P-gain parameter and a controller parameter with a D-gain parameter, which depends on the estimated coefficient of friction, the driving situation (whether the vehicle oversteer or understeer is) and the vehicle speed are determined. In block 105, the differential torque EMDifPreProp formed on the basis of the precontrol is compared with the stabilizing differential torque EMDifStab. In the case of unequal signs of the difference moment EMDifPreProp and the stabilizing difference moment EMDifStab, the amount of the difference moment EMDifPreProp is reduced by the amount of the stabilizing difference moment EMDifStab. The stabilizing differential moment EMdifStab calculated from driving stability considerations thus retains the decisive function. With the same sign of the difference moment EMDifPreProp and the stabilizing difference moment EMDifStab, the moments from the precontrol and stabilization add up

EMDif = EMDifPreProp + EMDifStab

In block 106 it is now checked whether the vehicle is in an oversteering state or an understeering state, which is counteracted by superposition of the differential torque EMDif the respective state. The vehicle is overdriven if, in terms of magnitude, the yaw rate is greater than the desired yaw rate: I vGi I> I vGiSo I.

In the described vehicle with the driven rear axle 10a, 10b, an increase in the drive torque on the inside wheel and at the same time a corresponding reduction on the outside wheel takes place in the drive case. As a result, a reversing yaw moment is generated against the oversteer tendency and at the same time increases the lateral force potential of the outside wheel.

EMPropj = 0.5 ^* (EMProp + EMDif)

EMProp_a = 0.5 ^* (EMprop - EMDif), where

EMPropj Drive torque at the inside wheel

EMProp_a Drive torque on the outer wheel

For an understeered condition of the vehicle applies I vGi I <I vGiSo I

If the vehicle is in such an understeer state, an increase in the drive torque on the outside wheel and at approximately the same time a corresponding lowering takes place on the inside wheel. This produces a turning yaw moment counter to the tendency to understeer.

EMProp_i = 0.5 ^* (EMProp - EMDif)

EMProp_a = 0.5 ^* (EMprop + EMDif)

Adherence to permissible wheel slip values applies both to the regulation of overdriven and understeered conditions. If too strong a dynamic difference torque EMDif leads to an excessive increase of the wheel drive slip on a wheel, then the differential drive torque EMDif is initially limited as a function of the wheel slip. At the same time, the non-deductible portion of the differential drive torque EMDif on the other drive wheel of the axle is compensated by an increased lowering of the drive torque EMProp or by a corresponding braking torque. Drive slip values which are too high are limited by the TCS system, while excessively high brake slip values are limited by the ABS controller on the respective wheel. If the stabilizing effect is insufficient by superposition of the differential moment, a known per se intervention of the ESP system to reduce the total drive torque EMProp.

As a special case should now be considered whether a wheel is spinning, what happens in a forced cornering or driving on a road that is partially covered with ice and where one wheel of the vehicle moves on the icy ground, while the other wheel on a dry roadway drives. The spinning wheel is usually the unloaded inside wheel or the wheel, which is at the low coefficient of friction with the road. To detect the spinning wheel, the differential speed between the two driven wheels 1 1 a, 1 1 b is evaluated. This differential speed is corrected by the amount of a kinematic differential speed, whereby a control deviation of the differential speed is obtained, because of an excess of the total drive torque EMProp was created. For the control deviation evDif of the differential speed applies

I evDif I> 0.

If this condition is fulfilled, a controller with PID structure generates a differential drive torque EMDifProp

EMDifProp = EMDifPropP + EMDifPropl + EMDifPropD, where

EMDifPropP P component of the differential drive torque

EMDifPropl I component of the differential drive torque

EMDifPropD Represent D component of the differential drive torque. Too high differential drive slip between the wheels 1 1 a, 1 1 b of the driven axle 10a, 10b is compensated by a wheel dynamic differential drive torque EMDifProp. Assuming that the inside wheel has a much larger traction than the wheel outside the curve, one obtains 1 1 a, 1 1 b for the two desired drive torques of the wheels

EMPropj = 0.5 ^* (EMProp - EMDifProp)

EMProp_a = 0.5 ^* (EMProp + EMDifProp)

At the spinning wheel, the drive torque is reduced by half the amount of the wheel dynamic differential drive torque EMDifProp and simultaneously raised at the other stable running wheel by half the amount of the wheel dynamic differential drive torque EMDifProp. This is the synchronization of the two Radantriebsschlupfwerte. A well-known master slip controller monitors compliance with the required axle-sum slip values. Excessive axle slip values are limited by the TCS system by lowering the total drive torque EMProp.

The wheel-individual drive also makes it possible to better adapt the return of electrical energy (recuperation) to the current driving situation. An energy recovery takes place when the electric motor part drives 3, 4 in the

Generator operation are located. The sum value of the braking effect Recou- Operating torque EMRecoupTar is specified by the control unit 18 and initially distributed in equal parts when driving straight ahead on both driven wheels 1 1 a, 1 1 b. The setpoint of the total permissible recuperation torque EMRecoup is limited in advance by the ESP system for driving stability reasons.

EMRecoup = Min (EMRecoupTar, EMRecoupVDC), where

EMRecoupVDC represents the upper limit of the permissible regeneration torque. When cornering, the distribution of the braking torques in the partial braking area can be better coordinated by the wheel-specific drive with the required Recouperationsmoment.

A pilot control for the distribution of the total Recouperationsmomentes EM Recoup forms a difference portion EMDifRecoupPre, which is determined when cornering as a function of the vehicle speed and the lateral acceleration or the wheelbase forces. Thus, the risk of under- or oversteering of the vehicle during the return feed can be stopped already in advance. If vehicle instability is present, the stabilizing recuperation torque EMDifRecoupstab is additionally superimposed. The resulting difference moment in Recouperation EMDifRecoup is formed as follows: EMDifRecoup = EMDifRecoupPre + EMDifRecoupstab

In the case of a vehicle that tends to oversteer, the recuperation torque or braking torque EMRecoup_a on the outside wheel is increased and reduced approximately simultaneously on the inside wheel (EMRcoup_i). As a result, a backward yaw moment is generated against the oversteer tendency. EMRecoup_i = 0.5 ^* (EMRecoup - EMDifRecoup)

EMRecoup_a = 0.5 ^* (EMRecoup + EMDifRecoup).

Excessive brake slip values are limited by the ABS controller on the respective wheel by limiting the respective regeneration torque EMRecoup_i or EMRecup_a. In an understeering vehicle the Recouperations- or braking torque EMRecoup_i is increased at the inside wheel, while the Recouperations- or braking torque EMRecoup_a is reduced at the outside wheel. This creates a turning yaw moment against the tendency to understeer.

EMRecoup_i = 0.5 (EMRecoup + EMDifRecoup)

EMRecoup_a = 0.5 (EMRecoup - EMDifRecoup)

Excessive brake slip values are also limited in this case by the ABS controller on the respective wheel by limiting the respective Recouperationsmomentes EM Recoup_i or EMRecoup_a.

Claims

claims 1 . Method for distributing a drive torque to the wheels of an electrically driven axle of a motor vehicle, wherein an electrical signal from a drive unit (3, 4) is converted into a torque (EMProp_i, EMProp_a) which is generated by an electrically driven axle (10a, 10b) on the wheels (1 1 a, 1 1 b) of the axis (1 Oa, 10b) is transmitted, characterized in that on the electrically driven axle (1 Oa, 10b) arranged wheels (1 1 a, 1 1 b) independently of one another with a driving torque (EMProp) acting on each superimposed with a differential torque (EMDif) are applied. 2. The method according to claim 1, characterized in that an electric drive torque (EMProp_a, EMProp_i) for each driven wheel (1 1 a, 1 1 b) by adding or subtracting the difference torque (EMDifProp) from the drive torque (EMProp) is formed. 3. The method according to claim 2, characterized in that the electric drive torque (EMProp) from the torque (EMmot_L, EMmot_R) of the drive unit driving a wheel (3, 4) is determined by superposition with a respective effective torque transmission ratio, which with at least one weighting factor ( KoFn _x , KoFn _y , KoFn _vFz ) is applied, from which a pre-control value for an additional differential torque (EMDifPreProp) is determined during cornering. 4. The method according to claim 3, characterized in that the weighting factor (KoFn _x , KoFn _y ) is determined as a function of a wheel load change during acceleration and / or cornering. 5. The method according to claim 3, characterized in that the weighting factor (KoFn _vFz ) is determined as a function of the vehicle _speed . 6. The method according to claim 3, 4 and 5, characterized in that a resulting weighting factor (KoFn) is formed from the sum of the wheel load-dependent weighting factors (KoFn _x , KoFn _y ), which multiplies by the vehicle _speed- dependent weighting factor (KoFn _vFz ) becomes. Method according to at least one of the preceding claims, characterized in that a deviation of a yaw rate (evGi) from a desired yaw rate (vGiSo) and an actual value (vGi) of the yaw rate is determined, from the resulting deviation (devGi) a stabilizing differential torque (EM- DifStab ) is determined. 8. The method according to claim 7, characterized in that at the same sign of the determined based on the Vorsteuerungswertes difference torque (EMDifPreProp) and the stabilizing differential torque (EMDifStab) on the basis of the Vorsteuerungswertes determined difference torque (EMDifPreProp) and the stabilizing differential torque (EMDifStab) to a driving dynamic differential drive torque (EMDif) are added. Method according to Claim 7, characterized in that, given different signs of the differential torque (EMDifPreProp) and the stabilizing differential torque (EMDifStab) determined on the basis of the precontrol value, the amount of the differential torque (EMDifPreProp) determined on the basis of the pilot value is increased by the amount of the stabilizing differential torque (EMDifStab ) is reduced. A method according to claim 8, characterized in that when exceeding a limit value by the dynamic driving differential drive torque (EMDif) a drive slip of the vehicle by a Radschlupfregelsystem, preferably an ABS system, is reduced. 1 . A method for distributing a drive torque to the wheels of an electrically driven axle of a motor vehicle, wherein an electrical signal from a drive unit (3, 4) is converted into a Recouperationsmoment which from an electrically driven axle (10a, 10b) on the wheels (1 1 a, 1 1 b) of the axle (10 a, 10 b) is transmitted, characterized in that on the electrically driven axle (10 a, 10 b) arranged wheels (1 1 a, 1 1 b) independently with a braking torque acting respectively superimposed with a differential torque (EMDif) are applied. 2. The method according to claim 1 1 characterized in that in the Recoupera- tion operation of the vehicle for distributing the Recouperationsmoments (EMRecoup) on the two wheels (1 1 a, 1 1 b) of the driven axle (10a, 10b) for pilot control a Differenzrecouperationsanteil ( EMDifRecoupPre) is formed, which depends on the vehicle speed and the lateral acceleration of the vehicle and to which in particular a stabilization regeneration torque (EMDifRecoupStab) is superimposed. 13. The method according to claim 12, characterized in that in a tendency to oversteer vehicle Recouperationsmoment (EMRe- Coup_a, EMRecoup_i) increases on the outside wheel and is reduced approximately simultaneously on the inside wheel. 14. The method according to claim 12, characterized in that in a tendency to understeer vehicle the Recouperationsmoment (EMRe- Coupj, EMRecoup_a) increases at the inside of the bend wheel and is reduced almost simultaneously on the outside wheel. 5. A device for distributing a drive torque to the wheels of an electrically driven axle of a motor vehicle, wherein an electrical signal is converted by a drive unit into a torque which is transmitted from an electrically driven axle to the wheels of the axle, characterized in that means are present are, which arranged on the electrically driven axle (10a, 10b) wheels (1 1 a, 1 1 b) independently with a driving or Apply a braking torque acting on each superimposed with a differential torque (EMDif). 16. The apparatus according to claim 15, characterized in that the wheels (1 1 a, 1 1 b) of two on the axis (10 a, 10 b) positioned, independently operating drive units (3, 4) are driven, wherein a drive unit (3 , 4) in each case a wheel (1 1 a, 1 1 b) drives.