GB2385392A

GB2385392A - A method of operating a vehicle by detecting wheel speed errors

Info

Publication number: GB2385392A
Application number: GB0307782A
Authority: GB
Inventors: Thomas Jaeger; Klaus Henneberger; Martin Vornehm; Jens Schnaebele; Michael Salecker; Holger Stork
Original assignee: LuK Lamellen und Kupplungsbau Beteiligungs KG; LuK Lamellen und Kupplungsbau GmbH
Current assignee: Schaeffler Buehl Verwaltungs GmbH; LuK Lamellen und Kupplungsbau GmbH
Priority date: 1998-12-15
Filing date: 1999-12-02
Publication date: 2003-08-20
Anticipated expiration: 2019-12-02
Also published as: GB0307782D0; GB2385392B

Abstract

A method of operating a motor vehicle that is equipped with sensors to detect the rpm-rates of the driven wheels includes the steps of: a) determining current rpm-rates of one or more driven wheels; b) examining the current rpm-rates for potential errors; c) detecting whether a command for a gear shift has been initiated; and d) in case an error was found in step b), taking protective measures so that the engine cannot be forced to run at rpm-rates detrimental to the safe operation of the vehicle as a consequence of executing and completing the gear shift.

Description

i - 1 - METHOD FOR OPERATING A MOTOR VEHICLE

The invention relates to a method for operating a motor vehicle with wheel speed detection as well as to a motor 5 vehicle.

Methods for operating a motor vehicle with wheel speed detection are already known.

10 With a known method of this kind the wheel speeds of the driven wheels are detected by means of a sensor unit. The sensor values are sent to a control device which processes the wheel speed values for controlling and monitoring certain vehicle parameters. Thus from the detected wheel 15 speeds it is possible to determine the vehicle speed without wheel slip. By including the engine speed it is furthermore possible to determine or define a clutch slip which may occur in the clutch of the motor vehicle.

20 These methods for operating a motor vehicle which are based on detecting wheel speeds make it possible to determine in a comparatively simple way a number of values which help to ensure a safe reliable operation of a motor vehicle. However in certain operating states of the vehicle these methods also lead to the determination of faulty data.

Furthermore there is the danger that these faulty data values trigger consequential errors if they are or were to 30 be used to determine further data or operating parameters or control characteristic values. Such errors or

- 2 - consequential errors can occur for example when the values produced or detected by the wheel sensors do not also correspond to the wheel speeds which are actually occurring or when the wheel speeds which do occur do not 5 always actually exist in the presumed connection with other parameters such as the vehicle speed.

By way of example in certain operating situations with a gear engaged, the gear input speed can be determined as a 10 product of the gear transmission ratio, the differential transmission ratio and half the sum of the speeds each detected at the front wheels - in the case of front wheel drive. If however for example one of these speeds is detected incorrectly, which would be the case for example 15 if one of the speed sensors is faulty, then the control device would produce an incorrect value for the gear input speed. This fault continues when the gear input speed is used for determining further parameters. However a correct detection of the wheel speeds can in known 20 arrangements also lead to determining parameters which are liable to errors if the assumed connections are at times not correct. Thus for example determining the vehicle speed from the aforementioned wheel speeds would lead to a false speed value if one of the wheels spins or locks.

Faulty detected wheel speeds or parameters determined incorrectly by using wheel speeds can have a negative effect on the operating safety of motor vehicles in many different ways. By way of example the fuel consumption 30 can be unnecessarily increased. Furthermore there is the

- 3 - danger that component parts of the vehicle suffer increased wear or that the risk of accidents rises.

Therefore the object of the invention is to provide a 5 method for operating a motor vehicle and a motor vehicle itself with improved operating safety wherein in particular operating parameters and control parameters are determined and processed with higher accuracy and reliability and which in particular with reduced fuel 10 consumption offers increased security against wear or breakdown of component parts wherein the vehicle can be manufactured cost-effectively with low production costs.

According to the invention, there is provided a method for 15 operating a motor vehicle which has - at least one.engine from which a drive torque can be produced; - at least one wheel driven by means of a drive axis; at least one transmission device which is mounted 20 in the torque flow between the drive device and a drive axis; - at least one torque transfer device which is likewise mounted in the torque flow between the drive device and at least one drive axle; and 25 - at least one control device for controlling the proportion of the drive torque which can be transferred from the torque transfer device to the at least one drive axle; and - at least one device for detecting at least one 30 wheel speed

- 4 with the step: monitoring the wheel speed detection and detecting errors in the detection of the wheel speeds.

The method can prevent the appearance of engine speeds 5 which would at least reduce the operating safety of the motor vehicle.

The operating safety is in the sense of this invention characterized in particular by the functioning behaviour 10 of the vehicle and its component parts, which includes both the fault-free interaction of the component parts and also the wear safety and safeguard against breakdown of the component parts, and by the fuel economy and safety for the driver.

By "at least reduce the operating safety" is in the sense of the invention to mean that the operating safety is negatively affected as well as that it is non-existent.

20 It is proposed to check sensed wheel speed values to see -- whether they were detected correctly or can be used for determining predetermined parameters.

By wheel speed errors in the sense of the invention is 25 meant in particular a wheel speed value which has not yet been detected, e.g. as a result of the failure of a sensor. This term preferably also refers to the production of false values or the production of inaccurate values.

The wheel speed errors can be determined qualitatively and/or quantitatively.

It can preferably be determined from a predetermined 5 separating characteristic whether in the absence of a wheel speed sensor value in the driving state there is a short signal interruption or whether there is a longer term fault, more particularly a sensor failure.

10 By way of example the gradients of the wheel speed sensor values detected over the period are analyzed according to the separating characteristic for this purpose.

By way of example when monitoring the gradients it is 15 taken into consideration that in the event of full braking with locking wheels as a result of the mass inertia of the wheels a characteristic gradient path or a characteristic time change is shown.

20 Use is also preferably made of the fact that with a closed drive train a correlation check on the engine speed and wheel speeds can be carried out. This correlation check which is preferably provided further enables wheel spin -

thus not only locking of the wheels - to be detected. A 25 wheel speed sensor failure can be detected through the correlation check according to the invention.

At least one reference value can be determined for at least one wheel speed according to at least one wheel 30 speed characteristic. By reference value is meant an approximate value or an exact value.

- 6 Within time evaluation intervals, a number of impulses is received or sensed, for example a number which depends on the wheel speed. It is particularly preferred if when no 5 impulse was received it is assumed that an impulse is detected immediately after the evaluation interval. This assumed impulse is preferably associated at least also to the previous interval.

10 The wheel speed is correspondingly determined according to the formula wheel speed = 1/tooth number/time period*60[1/min] when no impulse was detected within an evaluation interval.

15 If at least one impulse was detected within an evaluation interval the wheel speed is preferably determined according to the formula wheel speed = number of impulses/tooth number/ time period*60[1/min3.

20 The time period is thereby the time period which has passed since the last evaluation time point.

The difference in the formulae indicates the assumed impulse. 25 - The occurrence of jumps to zero is prevented through the assumed impulse. Particularly if no impulse is detected over several evaluation intervals a hyperbolic path is thus set. This characteristic path enables a sensor 30 failure to be recognized.

i

- 7 By way. of example a wheel speed sensor failure is established when the gradients of the wheel speed reference values run successively in chronological sequence through preset speed ranges or drop down 5 according to a predetermined characteristic. By way of example a wheel speed sensor failure is fixed when a wheel speed sensor value first drops by at least 60 rpm, then by at least 30 1/min and then by at least 15 1/mint lo According to a particularly preferred embodiment it can be analysed, determined or checked from the gradients of the wheel speed reference values whether a wheel speed sensor produces an incorrect value or whether full braking existed when a wheel speed value was detected.

In particular use can be made of the fact that in the event of fully braking as a result of the inertia of the wheels a certain speed is still to be established whilst with the failure of a wheel speed sensor there is mainly 20 no speed at all. By way of example it is hereby possible to take into account the different speed behaviour in the two situations according to a predetermined function.

According to a particularly preferred embodiment it is 25 determined whether a speed, i.e. more particularly a wheel speed is implausible. By this is meant in particular that it is determined whether a value transmitted from a wheel sensor for the wheel speed is permissible or can theoretically occur. To this end for example at least one 30 wheel speed and the speed of a shaft on the engine side coupled to the wheel axles is determined. Then for

- 8 - example at least one of these speeds is converted to the other or converted to a comparison speed. By this is meant that the speed of a second component part is calculated corresponding to the couplings, more 5 particularly corresponding to the transmission ratios, from the speed of a first component part, such as a wheel.

The determined speeds are converted to the same component part. If a deviation of the transformed speeds occurs here it is recognized that the wheel speed is implausible.

10 It is also preferable that the one speed deviates less than a predetermined maximum deviation from the other transformed speed, the wheel speed is still accepted as plausible. 15 It is preferable that the wheel speed is then recognized as implausible if the deviation exists longer than a predetermined minimum time period.

If a wheel speed was recognized as implausible then this 20 wheel speed is preferably not used for any further calculations or determinations of other parameters.

According to a particularly preferred embodiment, the gear input speed is used for calculating the deviation. In the 25 event of a force locking transmission and closed clutch the engine speed is equal to the gear input speed. From the wheel speed values detected from the wheel speed sensors here for example for the wheel speed values detected at the front wheels the gear input speed is 30 produced as a product of the gear transmission ratio and

i - 9 - the differential transmission ratio and a factor which has half the sum of the front wheel speeds (left and right).

According to a particularly preferred embodiment the 5 deviation of the transformed speeds when the gear is engaged and the clutch substantially closed is monitored over a predetermined minimum observation period - more particularly an associated minimum observation period, if the deviation in the initial part of this observation 10 period is greater than a predetermined minimum deviation.

It is particularly preferred that after an observation period which is in particular smaller than or equal to the minimum observation period, at least one speed, such as 15 the wheel speed, is established as plausible when the deviation in the observation period is less than a predetermined highest deviation.

It is also preferable if the predetermined highest 20 deviation is equal to the predetermined minimum deviation.

It is particularly preferred that with an established wheel speed failure, i.e. if it was established that the wheel speed sensor has failed, predetermined shift 25 processes of the transmission device, more particularly all shift processes of the transmission device, are cancelled or interrupted. It is further preferred that this interruption of the shift processes is then or also then undertaken if it is established that the wheel speed 30 was detected incorrectly. Thus it can be prevented in

- 10 particular that false wheel speed values lead to unacceptably high engine speeds after shift processes.

According to a particularly preferred embodiment the wheel 5 speed is replaced at least at times by a substitute speed according to a predetermined characteristic.

It is also preferable if a failure indicator is set when predetermined wheel speeds were not detected correctly or 10 indeed not detected at all. It is particularly preferred here to differentiate between the states "detected but detected incorrectly" and "not detected". It is further preferred that a failure indicator or a failure flag or a bit is then set or only then set when all wheel speeds 15 were detected incorrectly. In the event that only one part of the wheel speeds was detected incorrectly then it is particularly preferred if a substitute speed is used for further calculation processes. This substitute speed is preferably determined from the correctly detected 20 speed.

According to a particularly preferred embodiment the interruption of the shift processes of the transmission device is then lifted if a plausible substitute value was 25 determined or set for the failed wheel speed.

It is also preferable if the interruption of the shift processes which can be produced for example as a type of block, is then lifted if predetermined conditions are 30 fulfilled. A condition proposed of this kind is for example such that it is ensured that no over-rewing of

predetermined shafts can take place. By way of example the condition is such that it is ensured that the engine speed cannot be unacceptably high. Such a case can exist for example when from other parameters it is ensured that 5 even when shifting into first gear no over-re w ing can take place. It is particularly preferred that the predetermined conditions under which shift process are once again permissible include the following three conditions: 1. the engine speed is lower than a predetermined engine speed wherein this engine speed is preferably set to a value of 1200 revolutions; 15 2. the clutch is closed substantially completely; 3. a gear other than neutral is engaged.

It should be noted that other speeds can also be 20 considered as criterion as the predetermined maximum engine speed.

According to a particularly preferred embodiment, in predetermined situations a downshift into a target gear is 25 undertaken stepwise. By this is meant that a shift is made starting with a high possible gear, preferably the highest gear, down into each next lower gear until reaching the target gear. It is particularly preferred if here in each gear stage the gear is kept in this shifted 30 position at least for a predetermined time. This predetermined time is preferably determined so that it is

- 12 ensured that the engine speed and gear input speed are synchronized. Changing down into a falling gear sequence is preferably used when the clutch was opened longer than a predetermined time period or when for example neutral 5 gear was engaged.

It is further preferred if after longer opening of the clutch or after neutral gear is engaged the gears are shifted down stepwise starting with the for example second 10 highest gear.

According to a particularly preferred embodiment, gears are engaged according to a predetermined sequence when predetermined conditions are present.

According to a particularly preferred embodiment, sensed wheel speed values are analysed and checked to see whether the detected wheel speed values are in a predetermined functional connection with the vehicle speed. It is 20 preferable for example if it is established whether one wheel driven by a drive device is executing no pure rolling movement on the ground in the event of a vehicle speed which is other than zero. By way of example categories can also be formed for this purposed. By way 25 of example when knowing the throttle valve angle or the engine torque, with the clutch substantially closed and with a known gear engaged at least a rough estimation of the vehicle speed can be undertaken. It can then be checked from the sensed wheel speed values whether the 30 sensed values are plausible.

f - 13 According to a particularly preferred embodiment, a maximum speed deviation is provided which in basic operation is still acceptable. By maximum speed deviation is meant in this context the maximum acceptable difference 5 between two predetermined wheel speeds. In particular is meant here the difference between the wheel speeds of the left and right front wheel.

In the sense of the invention "basic operation" exists 10 when the wheels are neither locked nor spinning and a correct detection of the wheel speeds is ensured.

According to a particularly preferred embodiment, it is established that the vehicle is located in a state which 15 deviates from basic operation when a wheel speed deviation occurs which is greater than the maximum proposed speed deviation. This particularly applies when the maximum speed deviation was set so that it is the maximum speed deviation which theoretically occurs in basic operation.

20 According to a particularly preferred embodiment the maximum proposed speed deviation is dependent on the minimum curve radius of the motor vehicle. It is particularly preferred that the maximum wheel speed deviation is according to the formula _ 900 * Fz * BreiteKfz net- 2 * 2 *. *. * or mung rRat ZdifJ ZGetr nMot

- 14 in which AnRad: wheel speed deviation Fz: maximum centripetal force of vehicle BreiteKfz: wheel state 5 mFzg: mass of motor vehicle read: Wheel radius Tiff: differential transmission ratio Beer: (momentary) gear transmission ratio nut: engine speed.

It is further preferred if a method according to the invention has any combination of the individual method steps already mentioned above.

15 It is thus proposed that a motor vehicle with at least one over-rev protection safeguard is provided for preventing engine speeds which could reduce the operating safety and which are produced in particular through gear shift processes. In particular this over-rev protection 20 safeguard is formed so as to prevent engine speeds which - reduce the operating safety and which are due to downshift processes. The invention will now be explained in detail with 25 reference to an embodiment which is given by way of example and is in no way restrictive.

In the drawings: 30 Figure 1 shows a diagrammatic view of a first embodiment given by way of example;

- 15 Figure 2 shows a second embodiment in diagrammatic view; Figure 3 shows an example of a flow chart of a method; 5 and Figure 4 shows by way of example a path of calculated speed values over the time when carrying out a method. Figure 1 shows diagrammatically a vehicle 1 with a drive unit 2, such as a motor or internal combustion engine.

This vehicle 1 has for example an over-rev protection device illustrated diagrammatically by the reference 15 numeral 2a and which as diagrammatically indicated by the arrow 2b interacts with vehicle components. The reference numeral 2a represents diagrammatically as an alternative or in addition a wheel speed failure detection device.

Furthermore a torque transfer system 3 and gearbox 4 are 20 shown in the drive train of the vehicle. In this embodiment the torque transfer system 3 is mounted in the force flow between the engine and gearbox, wherein a drive torque of the engine is transferred through the torque transfer system to the gearbox and from the gearbox 4 on 25 the output side to an output shaft 5 and to an axle 6 on the output side as well as to wheels 6a.

The torque transfer system 3 is formed as a clutch such as a friction clutch, multi-plate clutch, magnetic powder 30 clutch or converter lockup clutch wherein the clutch can be a self-adjusting wear-compensating clutch. The gearbox

4 is shown as a manual shift transmission such as a step-

change gearbox. According to the idea of the invention the gearbox can however also be an automated shift transmission which can be shifted automatically by means 5 of an actor. Furthermore by automated shift transmission is meant an automated gearbox which is shifted with a break in drive power and the shift process of the gear transmission ratio is carried out controlled by means of at least one actor.

Furthermore an automatic gearbox can also be used where an automatic gearbox is a gearbox substantially having no break in drive power during the shift processes and which is as a rule built up by planetary gear stages.

Furthermore a continuously variable transmission, such as a cone pulley belt contact gearbox can also be used. The automatic gearbox can also be formed with a torque transfer system 3 on the output side, such as clutch or 20 friction clutch. The torque transfer system can furthermore be formed as a start-up clutch and/or turning set clutch for reversing the direction of rotation and/or safety clutch with a transferable torque which can be purposefully controlled. The torque transfer system can 25 be a dry friction clutch or a wet running friction clutch which runs for example in a fluid. It can likewise be a torque converter.

The torque transfer system 3 has a drive side 7 and an 30 output side 8 wherein torque is transferred from the drive side 7 to the output side 8 in that the clutch disc 3a is

f - 17 loaded with force by means of the pressure plate 3b, the plate spring 3c and the release bearing Be as well as the flywheel 3d. For this load application the release lever 20 is operated by means of an actuating device such as an 5 actor.

The control of the torque transfer system 3 is by means of a control unit 13 such as a control device which can include the control electronics 13a and the actor lab. In 10 another advantageous design the actor and the control electronics can also be mounted in two different structural units such as housings.

The control unit 13 can contain the control and power 15 electronics for controlling the electric motor 12 of the actor lab. It can thereby be reached for example with advantage that the system requires as a single structural space only the structural space for the actor with the electronics. The actor consists of a drive motor 12, such 20 as electric motor, wherein the electric motor 12 acts on a master cylinder 11 through a gearbox, such as worm gearing or spur wheel gearing or crank gearing or threaded spindle gearing. This action on the master cylinder can take place directly or through a rod linkage.

The movement of the output part of the actor, such as the master cylinder piston lla is detected with a clutch path sensor 14 which detects the position or setting or speed or acceleration of a value which is proportional to the 30 position or engagement position or respectively the speed or acceleration of the clutch. The master cylinder 11 is

- 18 connected to the slave cylinder 10 through a pressurised medium line 9, such as a hydraulic line. The output element 10a of the slave cylinder is in active connection with the release lever or release means 20 so that 5 movement of the output part 10a of the slave cylinder 10 causes the release means 20 to likewise be moved or tilted in order to control the torque which can be transferred by the clutch 3.

10 The actor 13b for controlling the transferable torque of the torque transfer system 3 can be operated by pressurized medium, i.e. it can be fitted with pressurized medium master and slave cylinders. The pressurized medium can be for example a hydraulic fluid or a pneumatic 15 medium. Operating the pressurised medium master cylinder can be undertaken by an electric motor wherein the electric motor 12 can be controlled electronically. The drive element of the actor 13b can also be a different drive element for example operated by pressurized medium 20 in addition to a drive element operated by an electric motor. Furthermore magnetic actors can be used in order to set a position of an element.

In the case of a friction clutch the control of the 25 transferable torque is carried out in that the contact pressure of the friction linings of the clutch disc takes place deliberately between the flywheel 3d and the pressure plate 3b. Through the setting of the release means 20, such as the release fork or central release 30 member, it is possible to purposefully control the force biasing of the pressure plate respectively of the friction

- 19 linings whereby the pressure plate can thereby be moved between two end positions and can be fixed and adjusted anywhere between same. One end position corresponds to a fully engaged clutch position and the other end position 5 to a fully disengaged clutch position. In order to control a transferable torque which is for example less than the momentarily existing engine torque, one position of the pressure plate 3b can be controlled for example which lies in an intermediate area between the two end 10 positions. The clutch can be fixed in this position by means of the purposeful control of the release means 20.

However transferable clutch torques can also be controlled which lie defined above the momentary existing engine torques. In such a case the engine torques which actually 15 arise can be transferred whereby the torque irregularities in the drive train in the form of for example torque peaks are damped and/or insulated.

In order to govern, such as control or regulate the torque 20 transfer system, sensors are also used which monitor at least at times the relevant values of the overall system and supply status values, signals and measured values which are necessary for the control and which are processed by the control unit wherein a signal connection 25 to other electronics units, such as for example to an engine electronics or an electronics of an anti-lock braking system (ADS) or anti slip regulating system (ASR) can be provided and can exist. The sensors detect for example speeds, such as wheel speeds, engine speeds, the 30 position of the load lever, the throttle valve position,

- 20 the gear position of the gearbox, a shift intent and further characteristic values specific to the vehicle.

Figure 1 shows that a throttle valve sensor 15, an engine 5 speed sensor 16, as well as a tacho sensor 17 are used and forward measured values or data to the control apparatus.

The electronics unit, such as computer unit, of the control unit 13a processes the system input values and forwards control signals to the actor lab.

The gearbox is formed as a step change gearbox wherein the transmission ratio steps are changed by means of a shift lever or the gearbox is operated or actuated by means of this shift lever. Furthermore at least one sensor l9b is 15 mounted on the operating lever, such as the shift lever 18, of the manual shift transmission, wherein this sensor detects the shift intent and/or the gear position and sends it to the control apparatus. The sensor 19a is attached to the gearbox and detects the actual gear 20 position and/or shift intent. The shift intent recognition using at least one of the two sensors 19a, l9b can thereby be carried out in that the sensor is a force sensor which detects the force acting on the shift lever.

25 Furthermore however the sensor can also be formed as path or position sensor where the control unit detects a shift intent from the time change of the position signal.

The control apparatus is in signal connection at least at 30 times with all the sensors and evaluates the sensor signals and the system input values in a manner and way so

- 21 that the control unit issues control or regulating commands to the atleast one actor in dependence on the actual operating point. The drive element 12 of the actor, such as electric motor receives from the control 5 unit which governs the clutch operation, a setting value in dependence on measured values and/or system input values and/or signals of the connected sensor unit. To this end a control program is implemented in the control apparatus as hardware and/or as software which evaluates 10 the incoming signals and calculates or determines the output values from comparisons and/or functions and/or characteristic fields.

The control apparatus 13 has advantageously a torque 15 determining unit, a gear position determining unit, a slip determining unit and/or an operating state determining unit or it is in signal connection with at least one of these units. These units can be implemented by control programs as hardware and/or as software so that by means 20 of the incoming sensor signals it is possible to determine the torque of the drive unit 2 of the vehicle 1, the gear position of the gearbox 4 as well as the slip which prevails in the region of the torque transfer system as well as the actual operating state of the vehicle. The 25 gear position determining unit determines from the signals of the sensors 19a and l9b the gear which is actually engaged The sensors are thereby connected to the shift lever and/or the setting means inside the gearbox, such as for example a central shift shaft or shift rod, and these 30 detect for example the position and/or speed of these component parts. Furthermore a load lever sensor 31 can

- be mounted on the load lever 30 such as the accelerator pedal, and detects the load lever position. A further sensor 32 can function as an idling switch, i.e. when the accelerator pedal such as load lever is actuated, this 5 idling switch 32 is switched on and if a signal is not activated is switched off so that through this digital information it is possible to detect whether the load lever, such as accelerator pedal is actuated. The load lever sensor 31 detects the degree to which the load lever 10 is operated.

Figure 1 shows in addition to the accelerator pedal 30 such as the load lever, and the sensors connected therewith, a brake operating element 40 for operating the IS operating brake or parking brake, such as brake pedal, hand brake lever or hand or foot operated operating element of the parking brake. At least one sensor 41 is mounted on the operating element 40 and monitors its operation. The sensor 41 is for example formed as a 20 digital sensor, such as switch wherein this detects that the operating element is actuated or not actuated. A signal device, such as brake light can be in signal connection with this sensor which signals that the brake is actuated. This can take place both for the operating 25 brake and for the parking brake. The sensor can however also be formed as an analogue sensor wherein a sensor of this kind, such as for example a potentiometer determines the degree of operation of the operating element. This sensor can also be in signal connection with a signal 30 device.

t K - 23 Figure 2 shows diagrammatically a drive train of a vehicle with a drive unit 100, a torque transfer system 102, a gearbox 103, a differential 104 as well as drive axles 109 and wheels 106. The over-rev protection device 106a 5 interacts with components of the vehicle as diagrammatically illustrated through the arrow 106b. The reference numeral 106a represents as an alternative or in addition a wheel speed failure detection device. The torque transfer system 102 is mounted or fixed on or 10 against a flywheel 102a wherein the flywheel as a rule supports a starting gear ring 102b. The torque transfer system has a pressure plate 102d, a clutch cover 102e, a plate spring 102f and a clutch disc 102c with friction linings. The clutch disc 102c is mounted where necessary 15 with a damping device, between the clutch disc 102d and the flywheel 102a. An energy accumulator, such as a plate spring 102f biases the pressure plate in the axial direction towards the clutch disc wherein a release bearing log, such as for example a central release member 20 operated by pressurized means, is provided for operating the torque transfer system. A release bearing 110 is mounted between the central release member and the plate spring tongues of the plate spring 102f. The plate spring is loaded by an axial displacement of the release bearing 25 and thereby disengages the clutch. The clutch can furthermore be formed as a depressed or pull-type clutch.

The actor 108 is an actor of an automated shift transmission which likewise contains the operating unit 30 for the torque transfer system. The actor 108 operates shift elements inside the gearbox, such as for example a

f - 24 shift roller or shift rods or a central shift shaft of the gearbox whereby through their operation the gears can be engaged or disengaged in for example sequential sequence or even in any sequence. The clutch operating element 109 5 is operated through the connection 111. The control unit 107 is connected through the signal connection 112 to the actor wherein the signal connections 113 to 115 are connected to the control unit wherein the lead 114 processes incoming signals, the lead 113 processes control 10 signals from the control unit and the connection 115 produces a connection with the other electronic units for example by means of a data bus.

To drive off or start the vehicle substantially from 15 standstill or from a slow rolling movement, such as creeping movement, that is for the deliberate acceleration of the vehicle initiated by the driver, the driver substantially only actuates the accelerator pedal such as the load lever 30 whereby the controlled or regulated 20 automated clutch actuation by means of the actor controls the transferable torque of the torque transfer system during a drive-off process. Through the operation of the load lever the driver's wish is detected by means of the load lever sensor 31 according to a more or less marked or 25 rapid drive-off process and is then controlled accordingly by the control unit. The accelerator pedal and sensor signals of the accelerator pedal are used as input values for controlling the drive process of the vehicle.

30 In the event of a drive process during driving the transferable torque, such as clutch torque Mksoll is

- 25 determined substantially by means of a predeterminable function or from characteristic lines or characteristic fields for example in dependence on the engine speed,

wherein the dependence on the engine speed or on other 5 values such as the engine torque is advantageously brought about through a characteristic field or characteristic

line. If during a drive-off process, basically from stationary lo or from a creeping state, at low speed the load lever or the accelerator pedal is operated to a certain value a then an engine torque is controlled by means of an engine control unit 40. The control unit of the automated clutch actuation 13 controls the transferable torque of the 15 torque transfer system according to predeterminable functions or characteristic fields so that a stationary

equilibrium is set between the controlled engine torque and the clutch torque. The equilibrium state is characterized in dependence on the load lever position a 20 through a defined drive-off speed, start or engine torque as well as a defined transferable torque of the torque transfer system and a torque transferring to the drive wheels, such as for example drive torque. The functional connection of the start-up torque as a function of the 25 starting speed is designated below as the start-up characteristic. The load lever position a is proportional to the position of the throttle valve of the engine.

Figure 2 shows in addition to the accelerator pedal 122, 30 such as load lever, and a sensor 123 connected therewith a brake operating element 120 for operating the operating

- 26 brake or parking brake, such as brake pedal, hand brake lever or hand or foot operated operating element of the parking brake. At least one sensor 121 is mounted on the operating element 120 and monitors its operation. The 5 sensor 121 is formed for example as a digital sensor such as a switch wherein this detects that the operating element is actuated or not actuated. A signal device such as a brake light can be in signal connection with this sensor to signal that a brake is actuated. This can take 10 place both for the operating brake and for the parking brake. The sensor can however also be formed as analogous sensors wherein one such sensor, such as for example a potentiometer, determines the degree of operation of the operating element. This sensor can also be in signal 15 connection with a signal device.

Figure 3 shows an example of a flow chart for a method according to the invention.

20 According to this advantageous embodiment of a method according to the invention it is first checked whether a correlation error is recognized for a wheel speed Step 210). 25 If no correlation error has been detected for the wheel speed then the wheel speed change is set in step 212 to AnRad = nRa,neU - nRad,alt, thus to the difference between the new and old detected wheel speed values.

30 It is then checked in step 214 whether in three successive calculation steps or cycles a wheel speed drop by Anl, An:

K ( - 27 and An3 has been recognized. The values An1, Anz and An3 here stand by way of example for predetermined wheel speed change values whose number - here 3 - was selected by way of example. The value An1 can lie for example at 60 rpm 5 whilst the value An2 is for example at 30 rpm and the value An3 for example at 15 rpm. It is preferably checked in advance whether the chronological sequence of the speed change values exists. If the speed drop values or speed change values were detected in sequence and size then in lo step 216 it is established that an error as been recognized for the speed gradients. A failure flag is set. Then in step 218 it is checked whether a gear is engaged. 15 If however the speed drop does not correspond to the predetermined criteria of the step 214 then in step 220 it is checked whether the speed rises and no correlation error exists. If it has to be answered in the negative that the speed rises and no correlation error exists then 20 in step 218 it is checked whether a gear is engaged.

If however it can be answered in the affirmative that the speed rises and no correlation error exists then it is established in step 222 that no error of the speed 25 gradient exists and the failure flag is cancelled. It is then checked in step 218 whether a gear is engaged.

If a gear is engaged then in step 224 it is checked whether slip exists and the clutch is substantially closed 30 during the observation time.

- 28 If slip was established and it could be determined that the clutch was substantially closed during the observation time then it is established that a correlation error 5 exists (step 226).

If however the check whether slip exists and the clutch is closed during the observation time has to be answered negative, then in step 228 it is checked whether no slip 10 exists and the clutch is closed during the observation time. If this is answered affirmative then in step 230 it is established that no correlation error exists.

The speed is then reflected in step 232 - if a correlation error was previously established.

It is then checked in step 234 whether the slip is 20 basically small, the clutch closed, gear engaged and the wheel speed is greater than 200 rpm.

If this is the case, then in step 236 the error of the speed gradient is cancelled. Then in step 238 it is 25 checked whether both wheel speeds have a correlation error. If this is the case, then a failure flag is set in step 240.

In an enquiry in step 242 it is checked whether a failure 30 flag was set.

i

- 29 If this is the case then in step 244 a shift or shift process is prevented or it is ensured that such a shift process cannot be completely concluded. It is hereby ensured in particular that no inadmissible high engine 5 speeds can occur.

Figure 4 shows an example of a wheel speed path as may appear according to a wheel speed value determination according to the invention. This wheel speed path enables 10 a sensor failure to be recognized.

The wheel speeds recorded on the graph 250 are determined according to the formula nRad = number of impulses/tooth number/ time duration x 60 [1/min] insofar as a number of 15 impulses other than nil was detected within a predetermined evaluation interval. If the number of impulses within this evaluation interval is or was equal to nil then the wheel speed is determined according to the formula nRad = 1/tooth number/time duration x 60 [1/mini.

20 The graph 252 can show that at the point 254 of the path-a sharp bend occurs with the following sharp drop in speed in area 256. The change in the drop in speed then reduces so that it decreases increasingly which is shown in particular between point 258 and point 260 in the graph 25 252. The speed thereby increasingly - more particularly asymptotically approaches zero. This can also be achieved if it is possible to determine and detect the number of impulses = 0 over a longer time period.

30 This characteristic speed curve makes it possible to establish that a wheel speed sensor failure does exist.

- 30 The invention is not restricted to the embodiments of the description. Numerous amendments and modifications are

possible within the scope of the invention as defined by 5 the claims, particularly those variations, elements and combinations and/or materials which are combinations or modifications of individual features or elements or process steps contained in the drawings and described in connection with the general description and embodiments

10 and claims.

Claims

if' PATENT CLAIMS

1. Method for operating a motor vehicle which has - at least one engine from which a drive torque can 5 be produced; - at least one wheel driven by means of a drive axis; - at least one transmission device which is mounted in the torque flow between the drive device and a drive axis; 10 at least one torque transfer device which is likewise mounted in the torque flow between the drive device and at least one drive axle; and - at least one control device for controlling the proportion of the drive torque which can be 15 transferred from the torque transfer device to the at least one drive axle; and - at least one device for detecting at least one wheel speed with the step: monitoring the wheel speed detection and 20 detecting errors in the detection of the wheel speeds.

2. Method as claimed in Claim 1, wherein at least one

error can be established qualitatively.

25 3. Method as claimed in Claim 1 or Claim 2, wherein at least one error can be established quantitatively.

4. Method as claimed in any preceding claim, with the step: differentiating according to a separating

(- - 32 characteristic whether there is a short signal interruption or whether there exists a longer term error.

5. Method as claimed in any preceding claim, with the 5 step: analysing the detected wheel speed values according to a differentiation characteristic for differentiating between sensed wheel speed values which were detected by a sensor which has failed at a certain time point, and wheel speed values which were sensed in the event of full 10 braking.

6. Method as claimed in any preceding claim, with the step: ensuring overrev protection at least at times from at least one wheel speed.

7. Method as claimed in any preceding claim, with the steps: monitoring whether the at least one detected wheel speed is correctly detected and introducing a substitute over-rev protection characteristic when errors are 20 detected when detecting the wheel speed, wherein the substitute over-rev protection characteristic is independent of a wheel speed which is detected as faulty and wherein from the substitute over-rev protection characteristic it is ensured that there is no exceeding of 25 an extreme engine speed, more particularly as a result of a downshift process.

8. Method as claimed in any preceding claim, with the step: monitoring at least one operating parameter for the 30 detection of at least one wheel speed error, more

particularly a wheel speed error conditioned through a wheel speed sensor failure.

9. Method as claimed in any preceding claim, with the 5 step: monitoring the wheel speed gradient for wheel speed error detection, more particularly for the detection of a wheel speed error conditioned through a wheel speed sensor failure. 10 10. Method as claimed in any preceding claim, with the step: provision of evaluation intervals.

11. Method as claimed in any preceding claim, with the step: detecting impulses whose rate depends substantially 15 on the speed, more particularly a wheel speed.

12. Method as claimed in any preceding claim, with the step: determining at least one reference value for at least one wheel speed according to at least one wheel 20 speed characteristic.

13. Method as claimed in any preceding claim, with the steps: determining at least one first reference value for at least one wheel speed according to at least one first 25 wheel speed characteristic when within a predetermined evaluation interval at least one speed impulse was detected, and determining at least a second reference value for at least one wheel speed according to at least a second wheel speed characteristic when no speed impulse 30 was detected within a predetermined evaluation interval.

14. Method as claimed in any preceding claim, with the step: determining the wheel speed according to the formula wheel speed = Number of impulses/ number of teeth/time duration * 60[1/min], when at least one impulse was 5 detected within an evaluation interval.

15. Method as claimed in any one of Claims 1 to 13, with the step: determining the wheel speed according to the formula 10 wheel speed = 1/ number of teeth/time duration*60[1/min] when no impulse was detected within an evaluation interval. 16. Method as claimed in any preceding claim, with the 15 step: establishing a wheel speed sensor failure when the gradients of the wheel speed reference values run through predetermined speed ranges in chronological sequence in succession. 20 17. Method as claimed in Claim 16, with the step: establishing a wheel speed sensor failure when the gradients of the speed reference values drop in chronological sequence in succession by at least 60 l/min, then by at least 30 1/min and then by at least 15 1/mint 18. Method as claimed in any one of Claims 5 to 17, with the step: determining from the gradients of the wheel speed reference values whether a wheel speed sensor produces an incorrect value or full braking existed when 30 detecting the wheel speed value.

- ( - 35

19 Method as claimed in any preceding claim, with the step: determining whether a speed, more particularly a wheel speed is implausible, more particularly monitoring the deviation between a predetermined speed on the wheel 5 side, more particularly a wheel speed, and a speed on the engine side, more particularly the engine speed, corresponding to the actual clutch couplings, more particularly corresponding to the transmission ratios and converted to the same wheel-side speed, with the gear 10 engaged and the clutch substantially closed and establishing that a speed, more particularly a wheel speed is implausible when this deviation is at least for a predetermined minimum time period greater than a predetermined minimum deviation.

20. Method as claimed in Claim 18, wherein at least at times this deviation is monitored over a minimum observation time interval with the gear engaged and the clutch substantially closed before a determination is made 20 on the plausibility of a speed when the deviation in the initial term of an observation time interval is greater than a predetermined minimum deviation.

21. Method as claimed in Claim 19 or Claim 20, wherein 25 after an observation time interval at least one speed, more particularly a wheel speed is established as plausible when the deviation in the observation time interval is smaller than a predetermined maximum deviation.

f - 36 22. Method according to Claim 21, wherein the observation time interval is smaller than or equal to the minimum observation time interval.

5 23. Method as claimed in Claim 21, wherein the minimum deviation is equal to the maximum deviation.

24. Method as claimed in any preceding claim, with the step: suppressing predetermined, more particularly all lO shift processes of the transmission device when it has been established that a wheel speed was detected at least incorrectly. 25. Method as claimed in any preceding claim, with the 15 step: substituting the wheel speed which has been established as incorrectly detected by a substitute speed according to a predetermined characteristic.

26. Method as claimed in any preceding claim, with the 20 step: setting a failure flag when predetermined wheel speeds were not correctly detected, more particularly when all.wheel speeds were detected incorrectly.

27. Method as claimed in Claim 26, with the step: halting 25 all shift processes of the transmission device when a failure flag is set.

28. Method as claimed in any one of Claims 24 to 27, with the step: lifting the stop on the shift processes of the 30 transmission device when the failed wheel speed was

- 37 covered with a substitute value, more particularly a plausible substitute value.

29. Method as claimed in any one of Claims 24 to 28, with 5 the step: lifting the block on the predetermined shift processes of the transmission device, more particularly on all shift processes when with the failure of predetermined wheel speeds, more particularly the failure of all wheel speeds, shift processes of the transmission device were 10 suspended and when predetermined conditions are fulfilled.

30. Method as claimed in Claim 29, wherein the predetermined conditions for lifting the block on the shift processes are provided so that it is ensured that no 15 over-revving can take place.

31. Method as claimed in Claim 29 or Claim 30, wherein the predetermined conditions for lifting the block on the shift processes are provided so that it is ensured that 20 the vehicle speed is slow so that even when shifting into - first gear no over-re w ing can take place.

32. Method, as claimed in any one of Claims 29 to 31, wherein the predetermined conditions for lifting the block 25 on the shift processes include the conditions that - the engine speed is less than a predetermined engine speed, more particularly less than a threshold value of for example 100 rpm; - the clutch is substantially closed; and 30 - a gear is engaged.

-

- - 38 33. Method as claimed in Claim 32, wherein the following applies for the threshold value: nmOt cn9chwelle * il/i5 < nmOtm with 5 nm0t = engine speed, nSchwelle = threshold value, it = transmission ratio of first gear, is = transmission ratio of 5th gear or another gear, nm0tm = maximum engine speed.

34. Method as claimed in any preceding claim, with the 10 step: provision of gears in falling sequence when during or directly before a shift wish the clutch is opened substantially longer than a predetermined time period or neutral gear is engaged.

15 35. Method as claimed in any preceding claim, with the steps: provision of a shift wish; and - provision of gears to be shifted in falling sequence, starting with the highest shiftable gear, 20 more particularly with fifth gear, when during or directly before a shift wish the clutch is opened substantially longer than a predetermined time period or neutral gear was engaged.

25 36. Method as claimed in any preceding claim, with the steps: provision of a shift wish; and - provision of gears in falling sequence under predetermined conditions starting with a gear which 30 is not the highest shiftable gear, more particularly with fourth gear when during or

f - 39 directly before a shift wish the clutch im opened substantially longer than a predetermined time period or the neutral gear was engaged.

5 37. Method as claimed in Claim 35 or Claim 36 with the step: engaging the predetermined gears in the predetermined sequence when predetermined conditions are fulfilled. 10 38. Method for operating a motor vehicle with the steps: analysing sensed wheel speed values for detecting detected wheel speed values which deviated from a predetermined functional connection between wheel speed and vehicle speed. 39. Method for operating a motor vehicle with the steps: determining whether a wheel driven by a drive device when the vehicle speed deviates from zero executes no pure rolling motion on a ground surface.

40. Method as claimed in Claim 38 or Claim 39, with the step: provision of a maximum speed deviation which can occur maximum in the basic operation between driven wheels. 41. Method as claimed in Claim 40, with the step: establishing that the motor vehicle is found in a state deviating from basic operation when a wheel speed deviation between two wheels driven by the drive device is 30 greater than the maximum speed deviation.

- l - 40 42. Method as claimed in any one of Claims 38 to 41, with the step: detecting wheel speeds for determining at least one operating parameter of the motor vehicle, more particularly for determining a slip in the case of a 5 clutch.

43. Method as claimed in Claim 42, furthermore with the step: ignoring a detected wheel speed value when determining the operating parameter when the motor vehicle 10 was found outside of the basic operation when determining this wheel speed value.

44. Method as claimed in any one of Claims 38 to 41, wherein the maximum speed deviation is dependent on the 15 minimum curve radius of the motor vehicle.

45. Method as claimed in any one of claims 38 to 44, with the step: provision of the maximum speed deviation according to the formula: 900 * Fz * BreizeK IT me, read Zd ices *nMor with Conrad: Wheel speed deviation Fz maximum centripetal force of vehicle 25 BreiteRfz wheel space mFzg mass of motor vehicle rrad wheel radius idiff differential transmission ratio

41 - iGetr (momentary) transmission ratio nMOt engine speed

Amendments to the claims have been filed QS follows to= PATENT CLAIMS

1. Method for operating a motor vehicle which has an engine from which a drive torque can be produced, at least 5 one wheel driven from the engine by means of a drive axle, a transmission device mounted in the torque flow between the engine and the drive axle, a clutch mounted in the torque flow between the engine and at least one drive axle, a control device for controlling the proportion of 10 the drive torque which can be transferred from the torque transfer device to at least one drive axle; and at least one device for detecting at least one wheel speed, wherein the method comprises the steps of monitoring the deviation between the wheel speed and the engine speed with the 15 transmission device engaged and the clutch substantially closed and establishing that a wheel speed is implausible when this deviation is at least for a predetermined minimum time period greater than a predetermined minimum deviation. 2. Method as claimed in Claim 1, wherein at least one error can be established qualitatively.

3. Method as claimed in Claim 1 or Claim 2, wherein at 25 least one error can be established quantitatively.

4. Method as claimed in any preceding claim, with the step: differentiating according to a separating characteristic whether there is a short signal 30 interruption or whether there exists a longer term error.

5. Method as claimed in any preceding claim, with the step: analyzing the detected wheel speed values according to a differentiation characteristic for differentiating between sensed wheel speed values which were detected by a 5 sensor which has failed at a certain time point, and wheel speed values which were sensed in the event of full braking. 6. Method as claimed in any preceding claim, with the 10 step: ensuring over-rev protection at least at times from at least one wheel speed.

7. Method as claimed in any preceding claim, with the steps: monitoring whether the at least one detected wheel 15 speed is correctly detected and introducing a substitute over-rev protection characteristic when errors are detected when detecting the wheel speed, wherein the substitute over-rev protection characteristic is independent of a wheel speed which is detected as faulty 20 and wherein from the substitute over- rev protection characteristic it is ensured that there is no exceeding of an extreme engine speed, more particularly as a result of a downshift process.

25 8. Method as claimed in any preceding claim, with the step: monitoring at least one operating parameter for the detection of a wheel speed error conditioned through a wheel speed sensor failure.

30 9. Method as claimed in any preceding claim, with the step: monitoring the wheel speed gradient for the

detection of a wheel speed error conditioned through a wheel speed sensor failure.

10. Method as claimed in any preceding claim, with the 5 step: provision of evaluation intervals.

11. Method as claimed in any preceding claim, with the step: detecting impulses whose rate depends substantially on a wheel speed.

12. Method as claimed in any preceding claim, with the step: determining at least one reference value for at least one wheel speed according to at least one wheel speed characteristic.

13. Method as claimed in any preceding claim, with the steps: determining at least one first reference value for at least one wheel speed according to at least one first wheel speed characteristic when within a predetermined 20 evaluation interval at least one speed impulse was detected, and determining at least a second reference value for at least one wheel speed according to at least a second wheel speed characteristic when no speed impulse was detected within a predetermined evaluation interval.

14. Method as claimed in any preceding claim, with the step: determining the wheel speed according to the formula wheel speed = Number of impulses/ number of teeth/time duration * 60[1/min], when at least one impulse was 30 detected within an evaluation interval.

15. Method as claimed in any one of Claims 1 to 13, with the step: determining the wheel speed according to the formula wheel speed = 1/ number of teeth/time duration*60[1/min] 5 when no impulse was detected within an evaluation interval. 16. Method as claimed in any preceding claim, with the step: establishing a wheel speed sensor failure when the 10 gradients of the wheel speed reference values run through predetermined speed ranges in chronological sequence in succession. 17. Method as claimed in Claim 16, with the step: 15 establishing a wheel speed sensor failure when the gradients of the speed reference values drop in chronological sequence in succession by at least 60 1/min, then by at least 30 1/min and then by at least 15 1/mint 20 18. Method as claimed in any one of Claims 5 to 17, with the step: determining from the gradients of the wheel speed reference values whether a wheel speed sensor produces an incorrect value or full braking existed when detecting the wheel speed value.

19. Method as claimed in Claim 18, wherein at least at times this deviation is monitored over a minimum observation time interval with the gear engaged and the clutch substantially closed before a determination is made 30 on the plausibility of a speed when the deviation in the

initial term of an observation time interval is greater than a predetermined minimum deviation.

20. Method as claimed in Claim 19, wherein after an 5 observation time interval at least one wheel speed is established as plausible when the deviation in the observation time interval is smaller than a predetermined maximum deviation.

10 21. Method according to Claim 20, wherein the observation time interval is smaller than or equal to the minimum observation time interval.

22. Method as claimed in Claim 20, wherein the minimum deviation is equal to the maximum deviation.

23. Method as claimed in any preceding claim, with the step: suppressing shift processes of the transmission device when it has been established that a wheel speed was 20 detected at least incorrectly.

24. Method as claimed in any preceding claim, with the step: substituting the wheel speed which has been established as incorrectly detected by a substitute speed 25 according to a predetermined characteristic.

25. Method as claimed in any preceding claim, with the step: setting a failure flag when predetermined wheel speeds were not correctly detected.

4 7 26. Method as claimed in Claim 25, with the step: halting all shift processes of the transmission device when a failure flag is set.

5 27. Method as claimed in any one of Claims 23 to 26, with the step: lifting the stop on the shift processes of the transmission device when the failed wheel speed was replaced with a plausible substitute value.

10 28. Method as claimed in any one of Claims 23 to 27, with the step: lifting the block on shift processes of the transmission device when with the failure of predetermined wheel speeds, shift processes of the transmission device were suspended and when predetermined conditions are 15 fulfilled.

29. Method as claimed in Claim 28, wherein the predetermined conditions for lifting the block on the shift processes are provided so that it is ensured that no 20 over-rewing can take place.

30. Method as claimed in Claim 28 or Claim 29, wherein the predetermined conditions for lifting the block on the shift processes are provided so that it is ensured that 25 the vehicle speed is slow so that even when shifting into first gear no over-re w ing can take place.

31. Method, as claimed in any one of Claims 28 to 30, wherein the predetermined conditions for lifting the block 30 on the shift processes include the conditions that

- the engine speed is less than a predetermined engine speed; - the clutch is substantially closed; and - a gear is engaged.

32. Method as claimed in Claim 31, wherein the following applies for the threshold value: nmOt cnSchwelle * il/i5c notmax with 10 nest = engine speed, nSchwelle = threshold value, it = transmission ratio of first gear, iS = transmission ratio of 5 th gear or another gear, nm0tmax = maximum engine speed.

33. Method as claimed in any preceding claim, with the 15 step: provision of gears in falling sequence when during or directly before a shift wish the clutch is opened substantially longer than a predetermined time period or neutral gear is engaged.

20 34. Method as claimed in any preceding claim, with the steps: provision of a shift wish; and - provision of gears to be shifted in falling sequence, starting with the highest shiftable gear, 25 when during or directly before a shift wish the clutch is opened substantially longer than a predetermined time period or neutral gear was engaged. 30 35. Method as claimed in any preceding claim, with the steps:

- provision of a shift wish; and - provision of gears in falling sequence under predetermined conditions starting with a gear which is not the highest shiftable gear, when during or S directly before a shift wish the clutch is opened substantially longer than a predetermined time period or the neutral gear was engaged.

36. Method as claimed in Claim 34 or Claim 35 with the 10 step: engaging the predetermined gears in the predetermined sequence when predetermined conditions are fulfilled. 37. Method for operating a motor vehicle which has an 15 engine from which a drive torque can be produced, at least one wheel driven from the engine through a drive axle, a transmission device which is mounted in the torque flow between the engine and the drive axle, a torque transfer device which is likewise mounted in the torque flow 20 between the engine and a drive axle, at least one control device for controlling the proportion of the drive torque which can be transferred from the torque transfer device to the at least one drive axle; and at least one device for detecting at least one wheel speed wherein a maximum 25 speed deviation which can occur between driven wheels is set, and this maximum speed deviation is dependent on the minimum turning circle radius of the motor vehicle.

38. Method as claimed in Claim 37, with the step: 30 provision of a maximum speed deviation which can occur maximum in the basic operation between driven wheels.

39. Method as claimed in Claim 38, with the step: establishing that the motor vehicle is found in a state deviating from basic operation when a wheel speed 5 deviation between two wheels driven by the drive device is greater than the maximum speed deviation.

40. Method as claimed in any one of Claims 37 to 39, with the step: detecting wheel speeds for determining at least 10 one operating parameter of the motor vehicle, 41. Method as claimed in Claim 40, wherein the operating parameter is slippage of the clutch.

15 42. Method as claimed in Claim 41, furthermore with the step: ignoring a detected wheel speed value when determining the operating parameter when the motor vehicle was found outside of the basic operation when determining this wheel speed value.

43. Method as claimed in any one of Claims 37 to 42, wherein the maximum speed deviation is dependent on the minimum curve radius of the motor vehicle.

25 44. Method as claimed in any one of claims 37 to 43, with the step: provision of the maximum speed deviation according to the formula: 900 * Fz * Breite,irfz Rad 72 * mF * rRad idly iCetr Mo'

at with i AnRad: Wheel speed deviation Fz maximum centripetal force of vehicle 5 BreiteKfz wheel space mFzg mass of motor vehicle read wheel radius idiff differential transmission ratio Or (momentary) transmission ratio 10 not engine speed At,