GB2375803A

GB2375803A - Control of an automatic clutch

Info

Publication number: GB2375803A
Application number: GB0206746A
Authority: GB
Inventors: Florian Strack; Martin Vornehm; Klaus Henneberger; Johannes Moosheimer
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: 2001-03-22
Filing date: 2002-03-22
Publication date: 2002-11-27
Anticipated expiration: 2022-03-22
Also published as: DE10212319A1; GB2375803C; ITMI20020606A0; FR2822415B1; FR2822415A1; GB2375803B; BR0200897A; GB0206746D0; ITMI20020606A1

Abstract

A vehicle 1 has an automatic clutch 3 and an engine 2. The clutch 3 is monitored so that when the engine 2 has been turned off, but the vehicle 1 is still moving and in gear so that engine braking is above a predetermined amount, the torque transferred by the clutch 3 is set to a predetermined value to reduce jolting of the vehicle 2. A control unit 13 and various sensors for detecting wheel speeds, engine speeds 16, throttle position 15 etc generate the necessary information to decide whether to adjust the torque transferred by the clutch 3.

Description

- MOTOR VEHICLE

The invention relates to a motor vehicle having an automatically operable clutch in the drive train with a 5 drive motor and transmission. The invention further relates to a device and method for controlling the clutch. Motor vehicles with an automatic clutch are known for 10 example from DE 195 04 847.

In the case of motor vehicles with an automated clutch, if the driver switches off the engine ignition as the vehicle is driving along and thus switches off the 15 drive motor then the clutch is stopped with the gear engaged closed in the transmission so that the vehicle is braked through the drag torque of the motor until the vehicle becomes stationary.

20 This leads to uncomfortable jolting if the drive motor is turned against the compression of the cylinder whereby particularly when falling below a critical engine speed by reaching the compression points of the cylinder a temporary sharply braking torque occurs 25 which leads to severe irregularity in the running of the engine.

The object of the invention is thus to avoid or at least reduce any uncomfortable behaviour when the 30 ignition of the vehicle is switched off, thus when the

drive motor is switched off whilst a gear is engaged in the drive mode at a certain vehicle speed.

This is achieved with a method mentioned above for 5 controlling an automatic clutch in the drive train of a motor vehicle where the vehicle has an operating actuator controllable by a control unit for controlling the clutch in that when the vehicle drive motor ignition is switched off and the vehicle is rolling the 10 clutch is set to a predeterminable value of torque transferable by the clutch.

It is thereby advantageous if the adjustable value of the torque transferable by the clutch is between zero 15 and the maximum value, preferably close to the disengaged state. It is expedient if the value is in the region between 5 Nm and 15 Nm, preferably between about 9 Nm and 10 Nm.

20 It is also expedient if previously the question is asked whether the ignition of the motor is switched off and/or was already previously switched off.

It is also expedient if the question is previously 25 asked whether the vehicle speed and/or the engine speed exceeds a predeterminable value. Likewise it is expedient if the question was previously asked whether a gear is engaged in the transmission.

30 According to the invention it is expedient if the

torque transferable by the clutch is preferably only set to the value of the coasting torque if a gear is engaged in the transmission and the engine speed and/or the vehicle speed exceeds a limit value.

It is advantageous if the question is previously asked whether there is an error, preferably a sensor error.

It is also expedient if the torque transferable by the 10 clutch is only preferably set to the value of the coasting torque if no error exists.

For safety reasons it is expedient if the clutch is fully engaged again in the event that the vehicle has 15 come to a standstill.

Furthermore the invention relates to a device for controlling a clutch for carrying out the method according to the invention and to a motor vehicle with 20 such a device.

The invention will now be explained in further detail with reference to the embodiments shown in the following drawings in which: Figure 1 shows a diagrammatic view of a vehicle; Figure 2 shows a diagrammatic view of a vehicle and Figure 3 shows a block circuit diagram to explain the invention. n

- 4 Figure 1 shows diagrammatically a vehicle with a drive unit 2, such as a motor or internal combustion engine.

Furthermore a torque transfer system 3 and transmission 4 are shown in the drive train of the vehicle. In this 5 embodiment the torque transfer system 3 is mounted in the force flow between the motor and transmission wherein a drive torque of the motor is transferred through the torque transfer system to the transmission and from the transmission on the output side to an 10 output shaft 5 and an axle 6 as well as wheels 6a.

The torque transfer system 3 is designed as a clutch, such as friction clutch, multi-plate clutch, magnetic powder clutch or loek-,p clutch wherein the clutch can 15 be a self-adjusting wear-compensating clutch. The transmission 4 is shown as a manual shift transmission such as a stepchange gearbox. According to the idea of the invention the transmission can however also be an automatic shift transmission which can be shifted 20 automatically by means of at least one actuator. By automated shift transmission is also meant an automatic gearbox which is shifted with tractive force interruption and where the shift process to change the transmission ratio is carried out controlled by means 25 of at least one actuator.

Furthermore an automatic transmission can also be used where the automatic transmission is a transmission substantially without tractive force interruption 30 during the shift processes and which is as a rule

- 5 comprised of planetary gear stages.

Furthermore a continuously variable transmission such as for example a cone pulley belt contact gearbox can 5 be used. The automatic transmission can also be formed with a torque transfer system 3 such as clutch or friction clutch mounted on the output side. The torque transfer system can furthermore be formed as a start-up clutch and/or turning set clutch for reversing the 10 direction of rotation and/or safety clutch with a deliberately controlled transferable torque. The.

torque transfer system can be a dry friction clutch or a wet running friction clutch which runs for example in a fluid. It can also be a torque converter.

The torque transfer system 3 has a drive side 7 and an output side 8 wherein torque is transferred from the drive side 7 to the output side 8 when the clutch disc 3a is loaded with force by means of the pressure plate 20 3b, plate spring 3c and the release bearing Be as well as the flywheel 3d. To apply this force the release lever 20 is actuated by means of an operating device such as an actuator.

25 The torque transfer system 3 is controlled by means of a control unit 13, such as a control device which can comprise the control electronics 13a and the actuator lab. In another advantageous design the actuator and the control electronics can also be mounted in two 30 different structural units, such as housings.

- 6 The control unit 13 can contain the power and control electronics for controlling the electric motor 12 of the actuator 13b It can thereby advantageously be 5 achieved for example that the system requires as a single structural space the structural space for the actuator with electronics. The actuator consists of a drive motor 12, such as electric motor wherein the electric motor 12 acts on a master cylinder 11 through 1 a transmi ssion, such as wcJnn gearing or spur wheel gearing or clank gearing or threaded spindle gearing.

This action on the master cylinder can be produced direct or through a rod linkage.

15 The movement of the output part of the actuator such as the master cylinder piston lla is detected by a clutch path sensor 14 which detects the position or setting or speed or acceleration of a value which is proportional to the position or engagement position respectively or 20 speed or acceleration of the clutch. The master cylinder 11 is connected to the slave cylinder 10 through the pressurized medium pipe such as hydraulic pipe. The output element lOa of the slave cylinder is in active connection with the release lever or release 25 means 20 so that movement of the output part lOa of the slave cylinder 10 causes the release means 20 likewise to be moved or tilted in order to control the torque transferable by the clutch 3.

30 The actuator 13b for controlling the transferable

- 7 torque of the torque transfer system 3 can be operated by pressurized medium i.e. it can be fitted with a pressurized medium master and slave cylinder. The pressurized medium can be for example a hydraulic fluid , 'j'$ 5 or pneumatic medium. The operation of the pressurized medium master cylinder can be undertaken by an electric motor whereby the electric motor 12 can be controlled electronically. The drive element of the actor 13b can also be in addition to an electromotorized drive 10 element another type of drive element, for example one operated by pressurised medium. Furthermore magnetic actors can be used to adjust the position of an element. 15 With a friction clutch the transferable torque is controlled by the deliberate contact pressure of the friction linings of the clutch disc between the flywheel 3d and the pressure plate 3b. Through the position of the release means 20, such as release fork 20 or central release member it is possible to control the force biasing of the pressure plate and friction linings respectively whereby the pressure plate can thereby be moved between two end positions whereby it can be adjusted and fixed at any point. The one end 25 position corresponds to a fully engaged clutch position and the other end position corresponds to a fully disengaged clutch position. In order to control a transferable torque which is for example lower than the engine torque momentarily existing it is possible to 30 control for example a position of the pressure plate 3b

8 - which lies in an intermediate region between the two end positions. The clutch can be fixed in this position by means of the deliberate control of the release means 20. Transferable clutch moments can 5 however also be controlled which lie defined above the engine torques momentarily arising. In such case the engine torques which actually arise can be transferred whereby the torque irregularities in the drive train in the form of for example torque peaks are damped and/or 10 insulated.

Furthermore for managing, such as regulating or controlling the torque transfer system, sensors are used which monitor at least temporarily the relevant 15 values of the entire system and which supply the necessary system parameters, signals and measured values which are processed by the control unit wherein a signal connection can be provided or exist to other-

electronics units, such as for example an engine 20 electronics unit or an electronics unit of an anti-lock braking system (ADS) or an anti slip regulating system (ASR). The sensors detect for example speeds, such as wheel speeds, engine speeds, the position of the load lever, the throttle vale position, gear position of the 25 gearbox, shift intent and further characteristic values specific to the vehicle.

Figure 1 shows that a throttle valve sensor 15, an engine speed sensor 16, as well as a tacho sensor 17 30 are used and send measured values or data to the

9 - control device. The electronics unit, such as computer unit, of the control unit 13a processes the system input parameters and sends signals to the actor lab.

5 The transmission is formed as a step change gearbox wherein the transmission stages are changed by a shift lever or the gearbox is operated or controlled by means of this shift lever. Furthermore at least one sensor l9b is mounted on the operating lever, such as shift 10 lever 18, of the manual shift gearbox, and detects the shift intent and/or gear position which is then passed on to the control device. The sensor 19a is attached to the gearbox and detects the actual gear position and/or shift intent. The shift intent detection using 15 at least one of the two sensors 19a, lob can be undertaken in that the sensor is a force sensor which detects the force acting on the shift lever.

Furthermore the sensor can however also be formed as a path or position sensor wherein the control unit 20 detects a shift intent from the time change of the position signal.

The control device is in signal connection at least temporarily with all sensors and evaluates the sensor 25 signals and system input values in the manner and way so that the control unit issues control or regulating commands to the at least one actuator in dependence on the actual operation point. The drive element 12 of the actuator, such as electric motor, receives from the 30 control unit which controls the clutch actuation, a

- 10 setting value in dependence on measured values andtor system input values and/or signals of the attached sensor unit. To this end a control program is implemented as hard and/or soft ware in the control 5 device to evaluate the incoming signals and calculate or determine the output variables from comparisons and/or functions and/or characteristic fields.

The control device 13 advantageously has an integrated 10 torque determining unit, gear position determining unit, slip determining Wilt and/or operating state determining unit or is in signal connection with at least one of these units. These units can be implemented through control programs as hardware and/or 15 software so that by means 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, and also the 20 actual operating state of the vehicle. The gear position determining unit determines the gear actually engaged from the signals of the sensors 19a and l9b.

The sensors are thereby attached on the shift lever and/or on setting means inside the gearbox, such as for 25 example a central shift shaft or shift rod, and 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 accelerator pedal which detects the load lever position. A further 30 sensor 32 can function as an idling switch, i.e. when

the accelerator pedal such as load lever is actuated this idling switch 32 is switched on and if a signal is not activated it is switched off so that through this digital information it is possible to detect whether 5 the load lever, such as accelerator pedal is actuated.

The load lever sensor 31 detects the degree of actuation of the load lever.

Figure 1 shows in addition the accelerator pedal 30 lo such as load lever and the sensors which are connected therewith, a brake operating element 40 for actuating the operating brake or the parking brake, such as brake pedal, hand brake lever or hand or foot operated operating element of the parking brake. At least one 15 sensor 41 is mounted on the operating element 40 and monitors its operation. The sensor 41 is designed for example as a digital sensor, such as switch wherein this detects that the operating element is or is not actuated. A signal device such as brake light can be 20 connected to this sensor and signals that the brake is actuated. This can take place for both the operating brake and the parking brake. The sensor can however also be formed as an analogue sensor wherein a sensor of this type, such as for example a potentiometer, 25 determines the degree of operation of the operating element. This sensor can also be in signal connection with a signal device.

Figure 2 shows diagrammatically a drive train of a 30 vehicle with a drive unit 100, a torque transfer system

102, a transmission 103, a differential 104 as well as drive axles 109 and wheels 106. The torque transfer system 102 is mounted or fixed on or against a flywheel 102a wherein the flywheel supports as a rule a starting 5 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. Between the clutch disc 102d and the flywheel 102a is a clutch disc 102c with a damping device where 10 necessary. An energy accumulator such as plate spring lO2f biases the pressure plate in the axial direction towards the clutch disc whereby a release bearing 109 such as for example a central release member operated by pressurized medium is provided for operating the 15 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 biased by axial displacement of the release bearing and disengages the clutch. The clutch 20 can furthermore be formed as a depressed or pull-type clutch. The actuator 108 is an actuator of an automated shift transmission which likewise contains the operating unit 25 for the torque transfer system. The actuator 108 operates shift elements inside the gearbox such as for example a shift roller or shift rods or a central shift shaft of the gearbox whereby when operated the gears can be engaged or disengaged in a sequential or any 30 other sequence. The clutch operating element 109 is

- 13 operated through the connection 111. The control unit 107 is connected through the signal connection 112 to the actuator whereby the signal connections 113 to 115 are connected to the control unit wherein the lead 114 5 processes incoming signals, the lead 113 processes the control signals from the control unit and the connection 115 establishes for example by means of a data bus a connection to other electronics units.

10 To drive off or start up the vehicle substantially from stationary or from a slow rolling movement such as creeping movement, that is for the driver to deliberately accelerate the vehicle, the driver need only operate the accelerator pedal such as load lever 15 30 whereby the controlled or regulated automatic clutch actuation controls by means of the actuator the transferable torque of the torque transfer system during a drive-off process. By operating the load lever the driver's wish for a more or less powerful or 20 rapid starting process is detected by means of the load lever sensor 31, and is then controlled accordingly by the control unit. The accelerator pedal and sensor signals of the accelerator pedal are used as input variables for controlling the starting process of the 25 vehicle.

During starting processes when driving off the transferable torque such as clutch moment Mkso1l is determined substantially by means of a predeterminable 30 function or from the characteristic lines or

characteristic fields for example in dependence on the

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

5 characteristic line.

If during start-up, substantially from standstill or from a creeping state, at low speed the load lever or accelerator pedal is operated to a certain value a, 10 then an engine torque is controlled by means of an engine management system 40. The control unit of the automated clutch actuation 13 controls the transferable torque of the torque transfer system according to predeterminable functions or characteristic fields so

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

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

the 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 121 is mounted on the operating element 120 and 5 monitors its operation. The sensor 121 is formed for example as a digital sensor such as switch wherein this detects that the operating element is or is not operated. A signal device such as brake light is in signal connection with the sensor to signal that the 10 brake is operated. This can take place both for the operating brake and the parting brake. The sensor can however also be formed as analogue sensor wherein a sensor of this type such as for example a potentiometer determines the degree of operation of the operating 15 element. This sensor can also be in signal connection with a signal device.

Figure 3 shows a block circuit diagram 200 for explaining the control according to the invention for 20 an automated clutch or a method according to the invention. In block 201 it is asked whether the ignition of the vehicle is switched on. If this is true then it 25 proceeds to block 202, otherwise block 207. In block 202 it is asked whether the engine speed NEng.New is greater than or equal to a limit value K _NEngDetectRunning, thus whether NEng.New > K_EngDetectRunning applies. Thus it is asked whether 30 the actual engine speed is greater than or equal to a

comparable value of the engine speed, where this comparable value K_NEngDetectRunning lies in the speed range from about 600 to 1200 1/mint If this is true then it proceeds to block 203, otherwise it proceeds to 5 block 204.

In block 203 it is asked whether the gear G engaged in the gearbox is unequal to the neutral zone N. If this is the case, then it proceeds to block 206 otherwise it 10 proceeds to block 205.

In each of blocks 204 and 205 a status bit B_EngWasRunningCoastSmoth is set to O and it proceeds to block 207. In block 206 the status bit 15 B_EngWasRunningCoastSmoth is set to 1 and a counter ClOCoastIgnOff is set to O and it proceeds to block 207. Setting the counter ClOCoastIgnOff is a safety counter which ensures that if the vehicle speed is not zero for example when driving on a slope the clutch is 20 nevertheless fully closed after exceeding a threshold of the counter or after a predeterminable time period, see also block 210.

Setting the status bit B_EngWasRunningCoastSmoth to O 25 means that either the actual engine speed is less than a predeterminable threshold and/or the gear of the gearbox is not one of the driving gears 1 to 5 or R for an example of a 5-speed gearbox, but is the neutral zone N. The invention is however not restricted to 30 such gearboxes but is generally valid for multi-speed

- 17 gearboxes. Setting the bit B_EngWasRunningCoastSmoth to 1 means that these two above conditions are met.

In block 207 it is asked whether a predeterminable 5 waiting time CloparkLockDelay 0 has lapsed wherein this lies in the time range from about 0.5 seconds to 2 seconds, more particularly in the range from 1.4 seconds to 1.6 seconds. If this time has lapsed then the process for the present interrupt is terminated.

10 Otherwise the process is continued in block 208.

In block 208 it is checked whether the counter ClOCoastIgnOff < 65535 exists. Thus it is reached that the value does not falsely exceed or overrun a 15 predeterminable value. If the value of ClOCoastIgnOff is less than a predeterminable limit value of for example 65535 then it is increased in block 209 by 1, otherwise it is not increased and then in both cases it proceeds to block 210.

In block 210 it is asked whether the value of the counter ClOCoastIgnOff is greater than a limit value wherein this limit value is selected as F*F_CoastIgnOffTime, with F a scale factor. It is 25 advantageous if this value of F_CoastIgnOffTime is a function of the engaged gear, thus can vary with the engaged gear. If the value of the counter is greater than a limit value, then the waiting time is greater than an ideal waiting time. This then leads if the 30 speed at the end of the time span is not zero to the

clutch being fully closed after exceeding a limit time which may also be dependent on the gear if necessary.

Furthermore it is checked in block 210 whether the gear 5 output speed or a vehicle speed or a wheel speed NOutShaftNew is less than or equal to a predeterminable value. This predeterminable value K_CoastIgnOffClCloseNVelocity is preferably selected in the region of very low vehicle speeds or speeds 10 proportional thereto. By way of example a value can be selected about 0.2 kmfh, which corresponds roughly too about 3 1/min as a speed signal proportional thereto.

This has the effect that the clutch is closed when the vehicle speed is zero or close to zero, thus is 15 substantially stationary, has come to a standstill or is not moving.

Furthermore it is questioned whether the status bit B_EngWasRunningCoastSmoth is equal to 1.

Furthermore it is questioned whether a sensor error is present. If at least one of the conditions of block 210 is met 25 then in block 211 the status bit b_no_coast_smoothing is set equal to 1, otherwise if these conditions are all negative then in block 212 the status bit b_no_coast_smoothing is set equal to 0.

In block 213 it is asked whether the status bit

b no coast smooth is equal to 1. Furthermore it is asked whether the gear input speed NInpShaft.New is greater than a comparable value K_CoastIgnOffClOpelNVelocity. This value is roughly in 5 the region of 1000 l/mint The clutch is preferably only set to the torque suitable for rolling out, thus is substantially opened when the engine speed drops below a limit value when 10 the clutch is closed. If the clutch was previously opened then the clutch is closed until the corresponding torque can be transferred. The gear input speed can be measured directly or can be determined from the gear output speed or wheel speed t5 and engaged gear.

If at least one of the conditions of the block was true then it proceeds to block 214, otherwise it proceeds to block 220.

In block 214 it is asked whether the clutch is open, thus released. If this is true then the clutch is closed in block 215 and then the routine for the present interrupt is terminated.

If the clutch is not open in block 214 then in block 216 the status of the bit b_no_coast_smoothing is questioned. If it is equal to 1 then in block 217 the bit B_EngWasRunningCoastSmooth is set equal to zero and 30 then the routine for the present interrupt is

- 20 terminated. If it is equal to zero then the routine is immediately terminated for the present interval.

In block 220 the torque trq_cl transferable by the 5 clutch is determined. This can be determined for example from the actual clutch or clutch actuator setting or from the actual clutch operating path in conjunction with a clutch characteristic.

10 In block 221 it is asked whether the torque trq_cl actually set and transferable by the clutch is greater than a first limit value K_CoastIgnOffTrq. This value lies according to the invention at about 5 to 15 Nm, preferably at about Nm to 10 Nm.

If this is the case then it is checked in block 222 whether the torque transferable by the clutch is greater than a second first limit value K_CoastIgnOffTrq + K_CoastIgnOffTrqHyst. This limit 20 value is equal to the first limit value plus a summand which is preferably in the region of 1 Nm, for example 0.5 Nm.

If this is also the case then in clutch 223 the clutch 25 is opened by a slight value, that is the torque transferable by the clutch is reduced before the routine is terminated in this interrupt. If in block 221 the condition is not met then in block 224 the torque transferable by the clutch is increased before 30 the routine is terminated in this interrupt.

- 21 Increasing or reducing the torque actually transferred by the clutch takes place in small stages in the region from 0.2 Nm to about 2 Nm per interrupt so that an 5 operating speed of about 3 to 30 mm/s results.

The invention relates to a method for controlling an automated clutch in the drive train of a motor vehicle, more particularly rolling out a vehicle with the engine 10 ignition switched off with a gear engaged in the gearbox. The gear can be one of the drive gears, thus one of the forward or reverse drive gears The process can preferably be performed on the level or on an incline or drop.

The clutch is controlled so that it remains engaged until the drive motorhas reached or fallen below about 500 1/min to 1000 1/mint In this case the clutch is then set to a transferable torque of about 5 Nm to 15 20 Nm, preferably 9 Nm to 10 Nm. As a result of this the vehicle is smoothly and comfortably braked down to a standstill. The amount of torque transferable by the clutch is such that with more powerful torque shocks through compression in the cylinders the clutch starts 25 to slip and the torque shock is not directed into the drive train. After the vehicle has reached a standstill the clutch is preferably completely closed again to produce a parking lock.

30 In order nevertheless to prevent the clutch from being

- 22 opened in the driving or operating situations where this is not desired or even where it could be critical in terms of safety, different system variables are questioned in the control process.

The clutch is only opened to the coasting torque K_CoastIgnOffTq when a predeterminable critical engine speed K_CoastIgnOffClopenNVelocity is reached or is understepped. If the clutch was previously opened then 10 it is closed until the coasting torque is reached.

The clutch is closed as soon as the vehicle has come to a standstill, thus is moving only very slightly or very slowly or is not moving at all. To this end a speed threshold or velocity threshold K CoastIgnOffClCloseNVelocity is used which can be set substantially to zero or to a very low value whereby the clutch is closed when the speed NInpShaft.New has reached or fallen below this value.

The clutch is preferably opened if at an earlier time point before switching off the drive motor ignition the engine speed of the engine has exceeded a predeterminable threshold (K_NengDetectRunning). This 2S is indicated by setting the bit K_EngWasRunningCoastSmooth. The clutch is preferably opened or set to the coasting torque when a gear is engaged.

A counter (ClOCoastIgnOff) ensures that if the speed of the vehicle was not zero, e.g. on account of driving on a slope, the clutch is nevertheless engaged at the end of a predeterminable period of time.

Also before closing the clutch a predeterminable period of time can be waited whereby this period of time can be dependent for example on an engine speed when the ignition is switched off or when the combustion engine 10 is switched off. For this a counter ClOParkLockDelay can be interrupted in the event of ignition which can then be decreased cyclically per interrupt.

The interrupt repeat can be roughly in the region of 15 milliseconds, such as for example 10 ms. Other times can however also be selected depending on the electronic equipment.

The patent claims filed with the application are 20 proposed wordings without prejudice for obtaining wider patent protection. The applicant retains the right to claim further features disclosed up until now only in the description and/or drawings.

25 References used in the sub-claims refer to further designs of the subject of the main claim through the features of each relevant sub-claim; they are not to be regarded as dispensing with obtaining an independent subject protection for the features of the sub-claims 30 referred to.

- 24 Since the subjects of these sub-claims can form independent proper inventions in respect of the prior art known at the priority date the applicant reserves 5 the right to make then the subject of independent claims or part declarations. They can furthermore also contain independent inventions which have a configuration independent of the subjects of the preceding sub-claims.

The embodiments are not to be regarded as a limitation of the invention. Rather numerous amendments and modifications are possible within the scope of the invention, particularly those variations, elements and 15 combinations and/or materials which are inventive for example through combination or modification of individual features or elements or process steps contained in the drawings and described in connection with the general description and embodiments and claims

20 and which through combinable features lead to a new subject or to new process steps or sequence of process steps insofar as these refer to manufacturing, test and work processes.

Claims

- 25 Claims

1. Method for controlling an automated clutch in the 5 drive train of a motor vehicle in which the vehicle has an operating actuator controllable by a control unit for controlling the clutch characterized in that when the ignition of the vehicle drive motor is switched off and the vehicle is rolling the clutch is set to a 10 predeterminable value of torque transferable by the clutch.

2. Method according to claim 1 characterized in that the adjustable value of the torque transferable by the 15 clutch lies between zero and the maximum value, preferably close to the disengaged state.

3. Method according to claim 2 characterized in that the value lies in the region between 5 Nm and 15 Nm, 20 preferably between about 9 Nm and 10 Nm.

4. Method according to one of the preceding claims characterized in that the question is previously asked whether the ignition of the motor is switched off 25 and/or was switched off.

5. Method according to one of the preceding claims characterized in that the question is previously asked whether the vehicle speed and/or the engine speed 30 exceeds a predeterminable value.

- 26

6. Method according to one of the preceding claims characterized in that the question is previously asked whether a gear is engaged in the transmission.

7. Method according to at least one of the preceding claims characterized in that the torque transferable by the clutch is preferably only set to the value according to claim 1 when a gear is engaged in the 10 transmission and the engine speed and/or the vehicle speed exceeds a limit value.

8. Method according to one of the preceding claims characterized in that the question is previously asked 15 whether there is an error, preferably a sensor error.

9. Method according to at least one of the preceding claims characterized in that the torque transferable by the clutch is preferably only set to the value 20 according to claim 1 when there is no error.

10. Method according to one of the preceding claims characterized in that the clutch is fully engaged again if the vehicle comes to a standstill.

11. Method according to one of the preceding claims, characterized in that the predeterminable torque is predetermined over a variable predetermined time period and after exceeding the time, the clutch is fully 30 engaged.

- 27

12. Device for controlling a clutch for carrying out a method according to one of claims 1 to 11.

$

13. Motor vehicle with a device according to claim 11.