FR2697783A1 - Automatic control device of a friction clutch of a motor vehicle in emergency operation. - Google Patents

Abstract

The device is used for the automatic control of a friction clutch (3) of a motor vehicle, actuated by a servo-drive (11). It comprises a control circuit (15), which normally controls the servo-drive (11) as a function of a plurality of sensors: speed sensor (19) of the motor (1), speed sensor (31 ) of the gearbox (7), position sensor (27) of the gearbox, and travel sensor (21) of the accelerator pedal (23). Monitoring means (35) check the sensors and actuators and, in case of detection of a fault, switch to an emergency operating mode allowing the control of the servo-drive (11), either from signals from substitution from sensors other than the faulty sensor, either by doing without this sensor, so that the vehicle can remain usable, possibly with reduced driving comfort. Application: actuation of automatic clutches of motor vehicles.

Description

Automatic control device of a friction clutch of a vehicle

  The present invention relates to a device for automatically controlling a friction clutch, actuated by a positioning servo-drive, of a motor vehicle driven by a combustion engine.

  via a gearbox.

  Conventional control devices for an automatic friction clutch, which allow the vehicle to be started as well as the gearshift, in a comfortable manner, require a large number of sensors and actuators. sensor only or a single actuator, in conventional systems, the assembly is generally defective with the result that the vehicle is no longer in working order, because vehicles equipped with such automatic actuating systems of the 'clutch no longer have a clutch pedal for actuating at the foot of

the friction clutch.

  From DE-C-34 43 015 it is known to detect the instantaneous position of the friction clutch, actuated by a positioning servo drive, of a motor vehicle, by means of a position sensor of clutch and control the positioning servo drive by a control circuit, in the form of a microprocessor, both at startup and speed change, depending on a large number of

  sensors responsive to operating parameters.

  In this case the control circuit reacts inter alia to a motor rotation speed sensor detecting the rotation speed of the combustion engine, to an accelerator pedal sensor detecting the travel of an accelerator pedal from its position of rest, a speed sensor detecting the running speed of the vehicle as well as control signals which signal to the control circuit the intention to start or change gears. The positioning drive of the clutch is controlled via a control circuit, which compares the actual position signal provided by the clutch position sensor with the position command signals, which supplies the control circuit with them. characteristic curves memorized according to the signals of the sensors In this way, in normal operation, the clutch can be engaged more or less comfortably and without jerks tan t at startup only

gear switch.

  The clutch position sensor of the known control device provides an output signal which is proportional to the instantaneous state of the clutch, for example of its disengaging device, and which may vary between predetermined limits, it is between a clutch position value and a clutch position value To be able to detect a fault in the clutch position sensor, the sensor output signal is checked to see if it is within the limits data for correct operation If the signal is outside the limits, the control circuit concludes that the clutch position sensor is defective and switches to an emergency operating mode in which the servo-drive is positioning of the friction clutch is controlled, by renouncing the clutch position sensor, following a program that certainly reduces comfort, but continues to allow the operation of the vehicle In the dispo Known, in the event of clutch position sensor failure, the friction clutch is engaged regardless of the operating situation with a constant speed of action. Also in emergency operation mode, with the device clutch control system, that all the sensors, which directly or indirectly detect an operating parameter of the combustion engine, are working properly A defect of such a sensor, for example the engine speed sensor or the engine sensor. accelerator pedal, leads to the total failure of the

clutch control device.

  The object of the invention is to provide a clutch control device which can continue to operate in an emergency mode, including in the event of a fault of a sensor detecting an engine operating parameter.

with combustion.

  The invention starts from a device for automatically controlling a friction clutch, actuated by a positioning servo-drive, of a motor vehicle driven by a combustion engine, by means of a gearbox, having the following characteristics: an engine rotational speed sensor detecting the rotational speed of the combustion engine; means indicative of the initiation of an operating movement of the gearbox, particularly in the form of a shift lever sensor detecting the deflection of a shift lever of the gearbox from a lever position determined by the instantaneous selection of gearbox speed; accelerator pedal detecting the travel of an accelerator pedal from its rest position,

  a control circuit controlling the servo

  positioning drive in a normal operating mode, as a function at least of the engine rotation speed sensor, means detecting the operating movement of the gearbox and depending on the accelerator pedal sensor, for the clutch and disengaging the friction clutch during starting and shifting of the gearbox, the control circuit having function verification means for controlling the operation of at least one of the sensors and, in the case where a function fault of the verified sensor has been detected, switching on a

  emergency mode of operation, commanding the servo-

  positioning drive when starting and shifting the gearbox, in

renouncing the verified sensors.

  In a clutch control device of this type, it is provided according to the invention that the control circuit switches into the emergency operating mode at least in the event of failure of the engine rotational speed sensor, or at least in the event of a failure of the accelerator pedal sensor, and controls the speed of action of the positioning servo drive, when engaging the friction clutch, both for starting and for shifting the speed of the clutch. the box depending on the amount of accelerator pedal travel, detected by the accelerator pedal sensor, when the engine speed sensor is defective or depending on the magnitude of the rotational speed of the engine, detected by the engine speed sensor, when the engine

  accelerator pedal failed.

  The invention is based on the reflection that for an emergency operation taking into account the operating situation, the friction clutch must be controlled in each case according to a sensor directly or indirectly detecting an operating parameter. of the combustion engine, when the comfort reduction must remain limited due to a sensor fault If the engine speed sensor is faulty,

  emergency operation, the speed of action of the servo-

  positioning drive is controlled by the magnitude of the pedal stroke of the accelerator pedal from its rest position, detected by the accelerator pedal sensor If on the other hand the accelerator pedal sensor is faulty, the speed of The action is controlled in the manner of a centrifugal clutch, as a function of the magnitude of the rotational speed of the engine, detected by the engine rotational speed sensor. In these two cases, the driver can nevertheless continue to determine the behavior. at the clutch, via the accelerator pedal, the magnitude of the accelerator pedal stroke influencing the speed of action; in particular, the speed of action increases as the accelerator pedal stroke increases. It is particularly advantageous if the functional relationship between the speed of action on the one hand and the speed is correctly chosen. rotation of the engine or the accelerator pedal stroke on the other hand, it is possible to obtain that the clutch is maintained within its sliding range in which it certainly transmits a torque, but is not not fully engaged and gradually conjecture it in the disengagement direction, if necessary by reducing the accelerator pedal stroke or reducing the motor rotation speed. This way it is possible even in emergency operation mode of

  drive or maneuver at low speed.

  Conventional clutch control devices are generally designed so that the control circuit, for operation of the gearbox in normal operating mode, interprets not only the actuation of the shift lever sensor as an intention to change gears and disengages the clutch accordingly, but that for safety reasons it couples the signal from the shift lever sensor to the signals of other sensors This is how the shift lever sensor signal of speed of conventional control devices is ignored if at the same time the accelerator pedal has left its rest position, since in this case we can admit that the lever

  shift was unintentionally touched.

  In a preferred variant of the invention, in a device of this type indicating the intention to change gears by establishing a link between several sensor signals, it is expected that the control circuit in emergency operating mode disengages exclusively as a function of the actuation of the shift lever sensor or exclusively in the event of detection of the neutral position of the gearbox by a speed position sensor In particular, it is provided that the clutch with friction in emergency operating mode remains disengaged during the duration of the actuation of the shift lever sensor or the intervention of the speed position sensor These means allow the driver, in emergency operating mode and the resulting operating conditions, unusual for him, also disengage the clutch in all cases, by touching the shift lever or possibly By bringing it into neutral If the friction clutch is disengaged even when the gearbox is moved to the neutral position, it can also be disengaged in the event of a shift lever sensor failure, since in the rest position of the accelerator pedal and therefore in the case of an unsolicited kinematic chain, the gearbox can be brought into the neutral position, in spite of

the clutch-in the engaged state.

  In case of failure of the speed sensor

  rotation of the motor, to be able to control the servo

  positioning drive in emergency operating mode, according to the accelerator pedal stroke, not only in the direction of the clutch of the friction clutch, but also in the direction of the clutch, it is expected , in one embodiment

  preferred, that the control circuit controls the servo

  positioning drive in the direction of the clutch, when the associated sensor and accelerator pedal detects an accelerator pedal stroke greater than a predetermined travel value, different from the rest position of the accelerator pedal and the control in the disengagement direction, when the accelerator pedal sensor detects a stroke lower than the predetermined stroke value. If the accelerator pedal is set to the predetermined stroke value, the clutch remains between its disengaged position. and its engaged position, preferably in a position in which it is just beginning to transmit a torque or is already transmitting a reduced torque, causing the vehicle to move very slowly The speed of action with

  which the control circuit controls the servo

  positioning drive in the direction of the clutch and / or in the direction of disengagement may be a function of the magnitude of the travel of the accelerator pedal, for example proportional But preferably the speed of action is independent of the magnitude of the race, to prevent as much as possible of control faults during the emergency operating mode, unusual for the driver Because the speed of action remains constant, the driver has time to adjust to the new operating situation during the clutch engagement or clutch disengagement, especially during maneuvers On the other hand, it may occur, particularly during gearshift, situations that make it desirable to engage or disengage quickly from the clutch. the clutch This can be obtained for example in that the control circuit drives the positioning servo-drive with a speed of action dependent on the variation in the time of the yard accelerator pedal In the sense of a disturbance variable, it is thus possible to use the speed of actuation of the accelerator pedal for the control

of the clutch.

  In the case of accelerator pedal sensor failure, in another preferred embodiment, the control circuit controls the positioning servo drive in emergency operating mode in the clutch direction when the motor rotation speed detects an engine rotational speed greater than a predetermined starting speed value, greater than the idling speed of the combustion engine, and the control in the disengagement direction, when the engine speed sensor is motor detects a speed lower than the value of the starting rotational speed As for the operation described above, in the event of failure of the engine speed sensor, it is also possible here to control the clutch for stopping, if the motor rotation speed is set to the start value,

  by a proper travel of the accelerator pedal.

  Advantageously, the speed of action of the servo

  positioning drive is given or imposed by the control circuit, in proportion to the difference between the rotational speed of the engine recorded by the engine speed sensor and the value of the rotational speed of the engine at start-up. possible, during the maneuvering of the gearbox, to shorten the clutch clutch time and to prevent an unwanted "runaway" of the engine This configuration thus allows not only the start but also the speed change But for Being able to maintain sufficient driving comfort, it is provided in a preferred variant that the control circuit controls the positioning servo-drive in emergency operating mode, in the direction of clutch, with a constant speed of action. when the engine speed sensor detects a speed greater than a predetermined gear change value, greater than the fast Starting the motor By properly staggering the value of the motor rotation speed at start-up and the value of the rotational speed of the motor at the speed change, it is possible to obtain an operating behavior

comfortable enough.

  The emergency operation modes described above in the event of an accelerator pedal sensor failure or a motor speed sensor failure may be performed in the device.

  order separately, but also together.

  The invention is preferably applicable for clutch control devices in which the control circuit comprises a motor rotation speed control circuit, which in normal operating mode, regulates the motor speed at startup by comparison. between actual speed information, detected by the engine speed sensor, and a target speed information, on a rotational speed value corresponding to the target rotational speed information; at start-up, the set rotational speed information being given as a function of the accelerator pedal stroke, in accordance with a predetermined predetermined speed of the predetermined travel speed curve. The control circuits of this type are described for example in FIG.

  DE-A-3935 439 to which reference is made.

  The invention is furthermore particularly suitable for control circuits which, in operating mode

  normal, for gearshift, control the servo

  positioning drive, via a differential rotation speed control circuit, as a function of the instantaneous slipping of the clutch This differential rotation speed control circuit compares a real differential rotation speed information, representing the the difference between the rotational speed of the engine detected by the engine rotational speed sensor and the gearbox input rotational speed, detected by a gearbox rotational speed sensor, with speed information of differential reference rotation provided by the control circuit The control circuit imposes in this case the reference differential speed of rotation signal which decreases in time, according to a ramp characteristic curve-predetermined a control circuit of this type is known for example from DE-A-39 35 438 to which reference is made Da In both variants, in the context of the invention, it is also preferably provided

  position control circuit positioning the servo

  positioning drive according to a

  set position information.

  Proper operation of the clutch control device depends on correct operation of the sensors and actuators Since malfunctions may affect the safe driving of the vehicle, sensor and actuator faults must be detected immediately. as far as possible, so that the appropriate countermeasures can be taken By the document DE-A-34 43 it is known to control the output signal of a sensor, here the clutch position sensor, as to the respect of limits given by document DE-A-37 22 633 it is known to position the throttle valve by means of an actuator, via a position adjustment circuit, according to the position of the pedal of accelerator, detected by means of a sensor and to control the idle speed adjustment of the actuator in the rest position of the accelerator pedal, using switching contacts there However, the known monitoring systems do not, in many cases, meet the increased security requirements or require additional components, for example, supervisory or similar contacts which have the disadvantage of

  constitute themselves sources of default.

  In another aspect, the object of the invention is to provide a device for automatically controlling a friction clutch, actuated by a positioning servo drive, of a motor vehicle, which, with great security, makes it possible to detect faults. the various components of the device, in particular sensors or actuators, and to use them, where appropriate, to

  switch to an appropriate emergency operating mode.

  Starting from a device of the aforementioned type, this is achieved in that the function monitoring means perform at least one of the following monitoring steps: a) determining the difference between the motor rotation speed detected by the motor rotation speed sensor and transmission input rotational speed, detected by the gearbox rotation speed sensor, when the clutch position sensor detects that the friction clutch is fully engaged, and switching to the emergency operating mode, controlling the operation of the clutch according to the accelerator pedal sensor, when the difference in rotational speed is greater than a first predetermined value; (b) before switching to the emergency operation mode at the monitoring step a): determining an input rotational speed of the substituted gearbox based on a gait speed information, detected by means of a speed sensor, and a speed information representing the instantaneous position of the gearbox, detected by means of a speed position sensor, determining the difference between the speed of rotation of the gearbox the substituted gearbox and the gearbox input rotational speed measured by means of the gearbox rotation speed sensor and switching to the emergency operation mode according to the monitoring step a) when the difference in rotational speeds is less than a second predetermined value; c) switching to emergency operating mode, controlling the operation of the clutch according to the engine speed sensor, when a sensor, detecting the setting of the fuel control means, in particular a throttle valve or an injection pump of the combustion engine, detects a rest position of the fuel control means and at the same time the accelerator pedal sensor detects a travel of the accelerator pedal from its rest position or when the sensor, detecting the setting of the fuel control means, detects a different setting of the rest position and at the same time the accelerator pedal sensor detects that the accelerator pedal is in the rest position; d) switching to emergency operating mode, controlling the clutch operation according to the engine speed sensor, when the accelerator pedal sensor detects that the accelerator pedal is in its position of at rest, and at the same time the engine rotational speed sensor detects an engine rotational speed greater than the idle speed and at least one of the following conditions is satisfied: the clutch position sensor detects that the friction clutch is fully disengaged, a speed position sensor detects that the transmission is in the neutral position. The second aspect of the invention, which is of independent inventive importance, regardless of the first aspect, subjects the sensors and actuators of the

  control device to a plausibility check.

  In this case, during the operation of the vehicle, the functional relationships between the sensor signals and / or the Coriander signals and the actuators are checked to see if there are any signal combinations which in the operating state the current vehicle, can not appear If there are combinations of inadmissible signals, it is concluded that

  defect according to the signal combination checked.

  The verification is carried out during the program of the computer-assisted control device, the control procedures being triggered by predetermined output signals of individually defined sensors. Thus, during the monitoring step a), it is concluded that the engine rotational speed sensor or the gearbox input speed sensor is defective if, while the friction clutch is totally inactive, the rotational speed of the measured motor deviates from the input rotational speed of the measured gearbox by a value greater than the value of the first rotational speed Differential quoted in the monitoring step a) By comparing the input rotational speed of the gearbox, measured by means of the respective sensor, with an input rotational speed of the substituted gearbox, which is calculated from a measured running speed information and the speed information representing the ratio currently set in the gearbox detected by the speed position sensor, it is possible to see if this is a transmission input speed sensor or engine speed sensor error If the input gear rotation speed of the substituted gearbox differs from the input speed of rotation of the gearbox when the measured gearbox has a value greater than a second differential value, it is concluded that the gearbox input speed sensor has a defect If the gearbox input rotational speeds measured and substituted differ from each other by less than the second differential rotation speed, that is, if they coincide within these tolerance limits, it is concluded that the speed sensor rotation of the motor The emergency program is selected, as already explained, according to the fault detected. If it is a motor speed sensor fault, it is switched to the emergency operating mode. d depending on the accelerator pedal If, on the other hand, it is only a defect in the gearbox's input speed sensor, the normal operating mode is retained for the most part, but the input gear rotation speed information, required in this operating mode, is replaced by the input rotational speed of the substituted gearbox, i.e. calculated It is well understood that any deviation from the normal operating mode may be

  indicated to the driver by signaling means.

  The accelerator pedal is another important driving parameter for controlling the clutch in normal operating mode The accelerator pedal sensor or a sensor detecting the position of a throttle actuator or an injection pump, insofar as the vehicle has an accelerator pedal system controlling these fuel control means not mechanically but electrically, must also be detected in priority A plausibility check s is obtained, in the case of the sensor reacting to the fuel control means, in that the sensor must indicate a rest position of the throttle valve or the injection pump, that is to say their idling position when the accelerator pedal sensor indicates that it is in the rest position It can be assumed that there is a fault in the sensor of the fuel control means when these two sensors However, it can be assumed that there is a fault in the accelerator pedal sensor when it is in its rest position and at the same time in the rotational speed sensor. of the engine detects an engine speed greater than the idle speed, if at the same time the clutch position sensor signals that the friction clutch is fully disengaged or if the speed position sensor signals that the gearbox is In these two states, the drive train is disconnected from the engine, so that the engine in proper operation can be adjusted to the speed of the engine.

  idle rotation imposed by the accelerator pedal.

  The plausibility checks described below

  above assume that the friction clutch is either in the fully disengaged position or in the fully engaged position The plausibility checks should therefore preferably be preceded by a check of the positioning servo-drive. as has already been said, preferably a position feedback circuit, so that the plausibility check of the positioning servo-drive is preferably performed by comparison between a set position information of the clutch. , provided by the control circuit, in one of the end positions, in particular the fully engaged end position, and the actual clutch position information, provided by the clutch position sensor These two position information must not differ from one another by a value greater than a predefined tolerance value. If the positioning servo drive fails, the following plausibility checks are not carried out and another command of the positioning servo drive is prevented for reasons of

security.

  The plausibility checks of the sensors and actuators are preferably preceded by a verification of the range of values of the electrical voltage and / or the electric current of the sensors and actuators participating in the respective monitoring step, and again the following monitoring step is not executed, if a fault is found during the verification of the range of values In particular for the verification of a defect of the engine speed sensor, the friction clutch must be totally But if a defect of the engine speed sensor is found while the clutch is fully disengaged, without additional means the friction clutch could not be engaged and the verification program could not be done 25 To remedy this, it is provided in a preferred variant only after a defect preventing the clutch clutch during startup in the mode of fo In normal operation, the monitoring means switch the control circuit in an emergency operating mode in which the control circuit controls the friction clutch positioning servo-drive, according to a ramp characteristic curve. predetermined, to the fully engaged position, if an accelerator pedal operation beyond a defined threshold is detected, and then the monitoring circuit performs at least one of the monitoring steps a) or b) previously defined. The plausibility check of the engine rotational speed sensor and the gearbox input rotational speed sensor also makes it possible, when defects of these two sensors can be excluded, to check the plausibility of the sensors used to determine the gearbox's input speed, transmission position and running speed If the difference between the engine's measured rotational speed and the measured input rotation speed of the gearbox velocity deviation is within a first range excluding a rotational speed error, a difference in rotational speed between the substituted input speed and the measured input speed of the gearbox, which is greater than at the second differential speed value, is considered as a fault of either the speed sensor or the speed position sensor A The speed position sensor defect is indicated if the running speed information, provided by the speed sensor, represents a running state and a speed sensor error is indicated, if the speed information supplied step represents a stop of the vehicle But this monitoring step is expediently executed only if the information of the accelerator pedal sensor indicates the rest position of this pedal, a brake pedal sensor indicates a non-activation a vehicle brake and the sensor indicating the setting of the fuel adjustment means has been found without defect In this way it avoids the operating conditions that can lead to slippage of the drive wheels and therefore, when the clutch is engaged at speed differences Sliding drive wheels can lead to a difference between the measured input rotational speed and the rotational speed of the drive. replace the gearbox and simulate a defect in the speed sensor or the speed sensor. When the accelerator pedal is not actuated and the brake is not applied, these faults are excluded. this case and for all other plausibility checks in which is concerned the position of the accelerator pedal or the sensor of the fuel adjustment means, a possible installation of speed control of the vehicle (Tempomat) should not be activated, which should be taken into account as

  entry condition of the plausibility check.

  The driveline of a motor vehicle is subjected to oscillations and the sensors which control components actuated by the driver, can

  also suffer oscillations or rebounds of contact.

  In a preferred variant of the invention, the monitoring circuit comprises a delay device which switches the control circuit to the emergency operating mode, or indicates a fault, only if the information provided by the pedal sensor of accelerator and / or by the sensor detecting the setting of the fuel control means and / or corresponding to the substituted rotational speed of input of the gearbox, have been present continuously for a predetermined period of time. the friction clutch must be engaged during the verification of the speed sensors for a predetermined time interval of two seconds, for example, before the sensors are checked. The same applies for the verification of the pedal sensor. accelerator during which the clutch must be disengaged during a predetermined time interval of two seconds, for example before the verification begins The accelerator pedal sensor is checked after a predetermined time interval of one second, for example after

his rest position.

  It is understood that the sensors can continue to be checked after switching to the emergency operating mode, in order to be able to return to the normal operating mode, in the case of an erroneous interpretation, due to disturbance

  outside, the state of a sensor or actuator.

  Various other features and benefits

  of the invention result from the detailed description which

  Following An embodiment of the invention is shown by way of non-limiting example in the accompanying drawing. The single figure schematically shows the kinematic chain of a motor vehicle whose friction clutch can be automatically controlled in a normal operating mode.

  as in an emergency mode of operation.

  The drive train of the motor vehicle comprises an internal combustion engine 1 which drives, via a conventional friction clutch 3 and a multi-speed gearbox 7 controlled by means of a gearshift lever 5, mounted in downstream of the friction clutch 3, the drive wheels indicated at 9 of the motor vehicle The gearbox 7 can be automated, the shift lever 5 being

  in this case replaced by controlled actuators.

  The clutch 3 is controlled by a servo

  positioning drive 11, acting on its disengagement device not shown, between its fully disengaged disengagement position and its clutch fully engaged position The positioning servoentrainement it is part of a position control circuit 13 of a circuit of control 15, for example in the form of a microprocessor or a microcontroller, which automatically controls the operation of the clutch both at the start of the vehicle or the shift of the gearbox 7 The control circuit Detects for this purpose, by means of a clutch position sensor 17, the real position of the clutch 3, for example the current position of its clutch device or the current position of the positioning servo-drive 11, and it adjusts the positioning servo-drive it to this set position, by means

  an imposed position command information.

  The control circuit 15 is associated with a large number of sensors, hereinafter described in more detail, which enable it in a normal operating mode, to distinguish between a start and a gear change and to engage with -coups and sparing the clutch, depending on the operating situation Au

  starting, the control circuit 15 controls the servo

  positioning drive it above all according to the rotational speed of the combustion engine 1, detected by means of a sensor rotation speed of the motor 19 and according to the current setting, detected by means of a pedal sensor d accelerator 21, a pedal

  accelerator 23 actuated by the driver of the vehicle.

  The control circuit 15 comprises a speed control circuit not shown and adjusts the clutch 3, via the positioning servo-drive 11, so that a real speed information, determined by the motor rotation speed sensor 19, is maintained, by comparison between the actual value and the set value, on a given value, depending on the instantaneous position of the accelerator pedal sensor 21, a speed information For this purpose, a characteristic curve is stored, for example in the form of a table, in the control circuit 15 which stores the setpoint speed information as a function of the position

  instantaneous throttle pedal 23.

  When the vehicle stops, which is detected for example by means of a speed sensor 25 at the output of the gearbox 7, the clutch 3 is totally disengaged, if at the same time a sensor 27, detecting the instantaneous position of the gearbox 7, notes that a forward or reverse gear is engaged The travel of the accelerator pedal 23 from its rest position is interpreted as a starting intention and the clutch 3 is progressively controlled to a position in which the clutch 3 can transmit the starting torque, with a rotational speed of the motor kept constant. DE-A-39 35 439 to which reference is made, details are disclosed. of the start command It is of course, however, possible to resort

  for starting at another control mechanism.

  The gearbox 7 shifts during travel in the embodiment shown, in normal operating mode, as follows: in the event of contact with the gearshift lever 5, a lever sensor the gearshift 29 detects an intention to change gear on the part of the driver and in relation to other information relating to operating parameters, this intention is confirmed and the control circuit 15 disengages accordingly the clutch 3 L clutch engagement after shifting is effected on the basis of actual differential rotational speed information, which the control circuit 15 calculates from the difference in actual engine rotational speed information. , determined by the engine rotational speed sensor 19, and actual input rotational speed information of the gearbox 7, which is measured by a sensor of e gearbox rotation speed 31, for example on the input shaft of the gearbox 7 The control circuit 15 comprises a differential rotation speed adjusting circuit, which, by a comparison between the actual value and the setpoint, sets the differential rotation speed information to a set value determined by a given set differential speed information. To be able to engage the clutch continuously after the gear change, the control circuit The differential reference rotational speed information is varied in the manner of a ramp,

  function of time, in the direction of decreasing values.

  The document DE-A-39 35 438 referred to describes details of such a gearshift control. It is understood that it is possible to provide

  also other types of shift control.

  The control circuit 15 comprises, for the normal operating mode described above, control means indicated at 33 for the normal operating mode, it is necessary that the sensors and actuators that are needed work properly The information determined by the sensors and possibly the information sent by the control means 33 to the actuators, are controlled by monitoring means 35 of the control circuit 15 in the manner described in more detail below, as to the presence of defects of the sensors and the actuators In the case of a fault detected by the monitoring means, the control circuit 15 decides whether the signal of the defective sensor can be replaced by information from other sensors, in order to continue controlling the clutch in the operating mode. normal, or if it is necessary to completely abandon the defective sensor, and if the clutch 3 can continue to be and automatically by emergency operation control means 37, accepting a reduction in comfort, based on the information of a reduced number of sensors, which are essential, so that it can continue to

  operate the vehicle until repair.

  As has been explained, the rotation speed sensor information of the engine 19 and the accelerator pedal sensor position information 21 constitute driving parameters of the operating mode control means. In the event of a fault detected by the monitoring means 35, the control circuit 15 switches either the speed sensor of the motor 19 or the accelerator pedal sensor 21 to a mode that is detected by the monitoring means 35. The emergency control circuit 15 indicates the switching in the emergency operating mode by a signaling means 39 preferably flashing For the execution of the emergency operating mode, in case of the motor rotation speed sensor 19, the emergency control means 37 only need the information of the accelerator pedal sensor 21, the gearbox rotation speed sensor 31, gearshift lever sensor 29 and a signal from a starter or contactor 41 controlling the starting of the combustion engine 1 If the input speed sensor of the gearbox 31 is also defective, the monitoring means 35 can replace the gearbox input rotation speed information by information of the speed sensor 25 It is understood that in the case of a gearbox 7 automated by actuators, instead of the signal of the shift lever sensor 29, shift control request signals from the gearbox control can also replace the lever sensor information. 29. In emergency operating mode, in the event of a failure of the engine speed sensor 19, at the start of the combustion engine 1, the starter is released only when after the opening of the em-stripe 3 by actuation of the contactor 41 If after engaging a speed the accelerator pedal 23 leaves its rest position on a minimum stroke, this is interpreted as a desire to engage and the clutch 3 is engaged at a predetermined speed of action The speed of action may be provided constant, but preferably it is proportional to, or follows another suitable function, the magnitude of the travel of the accelerator pedal 23, when the accelerator pedal 23 is coupled directly mechanically with a throttle valve 43 or an injection pump or the like of the combustion engine 1, or it controls, via a coninande circuit of position 45 of the control circuit 15, an actuator 47 of the throttle valve 43 and consequently influences the rotational speed

of the combustion engine 1.

  The magnitude of the speed of action preferably depends on the differential value, sign included, between the travel and the minimum clutch position of the accelerator pedal 23 If the travel of the accelerator pedal 23 exceeds the value of the minimum clutch position, the clutch 3 is moved in the direction of the clutch If the travel of the accelerator pedal 23 remains below the minimum clutch position, the clutch 3 is moved into the clutch. direction of disengagement, with

  a speed of action that is proportional to the gap.

  In this way, the driver can also, by placing the accelerator pedal 23 on the minimum clutch position, possibly also maintain the clutch 3 in the sliding range, which is advantageous for the maneuvers In addition, the speed clutch action

  may also depend on the magnitude of the speed of movement

  accelerator pedal 23.

  For shifting, the clutch is disengaged, when the shift lever 5 is actuated, only by the shift lever sensor 29 for the duration of the operation of the shift lever 5 In the event of a defect of the shift lever sensor 29, the monitoring means 35 may replace the signal of the shift lever sensor 29 by a signal from the transmission position sensor 27, which disengages the clutch. during the period of holding the gearbox 7 in its neutral position The signals of the sensors 27, 29 may be replaced for the purpose mentioned, since it is possible to place the conventional gearboxes in the neutral position. by decreasing the torque by releasing the accelerator pedal, for emergency operation, including when the clutch

3 is clogged.

  After engagement of the new speed and therefore release of the shift lever 5, the clutch 3 engaged at a predetermined constant speed of action, linear function of the time Advantageously, the operating control means emergency 37 automatically distinguish between a speed of action of the clutch 3, depending on the stroke and possibly the speed of movement of the accelerator pedal 23, when starting, and a constant speed of action when the speed of the gearbox 7 is changed, the emergency operation control means 37 monitor for this purpose the gearbox input rotation speed If this speed is greater than a predetermined operating rotation speed of 2 200 revolutions per minute for example, the clutch 3 is controlled at a constant speed of action If the rotational speed of the gearbox is less than At the mentioned rotational speed of rotation, the clutch 3 is controlled at a speed dependent on the distance of the accelerator pedal 23 from its minimum clutch position for starting. In this way it is ensured at the same time. that even at startup, after the speed of rotation of maneuver is reached, it is engaged quickly in all cases When the vehicle stops, the clutch 3 is disengaged at the maximum speed of action, as soon as the speed the gearbox input rotation detected by the rotational speed sensor 31, or a running speed detected by the gait speed sensor 25, is

  less than a predetermined value.

  In case of failure of the accelerator pedal sensor 21, which, as previously described, also exists in the case of an accelerator pedal mechanically coupled with the throttle valve 43 to control the clutch 3 in normal operating mode , or which detects only the rest position of the accelerator pedal 23 to see an intention to start, the clutch 3 is controlled in emergency operating mode both at startup and at the gearbox 7 , in accordance with the engine rotational speed information provided by the engine rotational speed sensor 19 In addition to the engine rotational speed sensor 19, it is necessary for this emergency operating mode only the contactor 41, disengaging the clutch 3 before starting the combustion engine 1, and the shift lever sensor 29 or, in the case of an automatic transmission, its disengagement request information Here again this information can be replaced by the neutral position information of the sensor of

gearbox position 27.

  The emergency operation control means 37 starts the startup in the manner of a centrifugal clutch according to the rotational speed information of the engine detected by means of the engine rotational speed sensor 19 The clutch 3 is engaged as soon as after the accelerator pedal 23 has been applied, the rotation speed of the motor exceeds a minimum clutch speed. The minimum clutch speed is greater than the idling speed of the combustion engine and rises for example at 1200 rpm Exceeding the minimum clutch speed when the clutch is disengaged is interpreted as an intention to start, after which the clutch is operated with a speed of action proportional to the difference, including the sign, between the clutch. motor rotation speed and minimum clutch speed In the case where the rotational speed of the motor is greater than the minimum clutch speed, the clutch 3 is actio born in the direction of the clutch; in the case where the speed of rotation of the motor is lower than the minimum clutch speed, it is actuated in the direction of the clutch The driver, which can influence the speed of rotation of the engine via the pedal accelerator 23, can thus actuate metering the clutch and possibly maintain in the field of sliding

for maneuvers.

  The emergency operation control means 37 also monitor in this emergency mode of operation the rotational speed of the gearbox and engage the clutch with a predetermined speed of action, as soon as the speed of the gearbox gearbox input rotation exceeds the minimum operating speed already mentioned above In this way, the clutch can be controlled according to the accelerator pedal at start, below the minimum maneuvering speed and in the case where the speed of input of the gearbox (or the speed of operation) is sufficiently high, it can be engaged with certainty. To change the speeds of the gearbox 7, the clutch 3 is disengaged, in the same manner as for the emergency operation in the event of a failure of the engine rotation speed sensor 19, as long as the gearshift lever 5 is operated or as long as the box

  7 is in its neutral position.

  After releasing the shift lever 5, the clutch 3 is engaged in the same manner as for starting. This can be done for example in the case where an input speed of rotation of the gearbox is lower than the minimum operating speed, the clutch is engaged with a predetermined lower speed of action and, above the operating speed, it is engaged with a higher speed of action, according to a linear function of the time When the vehicle is stopped, the clutch is disengaged with a maximum speed of action also in this emergency mode of operation, below a rotation speed stop threshold of the speed of rotation of the vehicle. gearbox input or speed stop threshold

walking.

  It can be provided in addition that the control 15 also monitors the proper operation of the position sensor of the gearbox 27 In the event of a fault, it can be switched here also to the emergency operating mode associated with the failure of the

  accelerator pedal sensor 21.

  The monitoring means 35 preferably periodically perform, during operation, checks of the ranges of values of the sensors and the sensors.

  actuators required for clutch control 3.

  For the verification of the value ranges it is assumed that the operating voltage, in particular of the sensors, must vary only within a fixed range of values, the lower limit of which must be above the zero voltage and the upper limit of which must be to be below the supply voltage A drop in voltage below

  the lower limit is interpreted as short-term

  circuit If the voltage rises above the limit

  higher, this is considered a cable break.

  The monitoring means 35 furthermore provide low-pass filtering of the output signals of the sensors, in order to make it possible to eliminate parasitic phenomena in the signals of the sensors. Since for the safety of the vehicle the sensor faults must be detected with certainty, the monitoring means 35 carry out plausibility checks of the positioning servo-drive 11, the rotational speed sensors 19, 31, the speed position 27, speed sensor 25, contactor 41 and accelerator pedal sensor 21 including, where available, an additional accelerator pedal zero switch, which detects the position of the accelerator pedal. the rest of the accelerator pedal 23, and the throttle position sensor 49 The plausibility checks are carried out during operation and correlate the operating parameters, being in a relationship

  functional, to the instantaneous operating situation.

  The plausibility checks are performed only if the sensors and actuators necessary for the respective test have no defects resulting from the verification of the value ranges and if prior plausibility checks revealed no defect in any of the sensors concerned by the verification The plausibility checks are carried out, as described below in more detail, either with the clutch fully disengaged or with the clutch fully engaged. The monitoring means 35 comprise delay means which delay the verification. plausibility of a predetermined time interval, at least two seconds for example with respect to the clutch operation or the disengagement operation In this way it is ensured that the oscillations of the kinematic chain are damped, that can cause parasitic oscillations of the sensor signals, before the Ficat starts ion

plausibility of the sensor.

  The plausibility checks have a different rank according to their influence on the clutch. In the example embodiment described above of the invention, the following plausibility checks are carried out:

  a) Plausibility check of the servo

positioning training it:

  There is always a test of the servo

  positioning drive when the monitoring means 35 do not detect a range error of the positioning servo-drive 11, and the control circuit 15 produces a clutch setpoint position signal bringing the clutch into the

  fully engaged position During the servo test

  positioning drive, the clutch set position signal, fully engaging the clutch 3, is compared with the actual clutch position signal provided by the clutch position sensor 17 If the actual position signal of the clutch clutch is not within given tolerance limits, relative to the reference signal, the monitoring means 35 report a plausibility defect of the positioning servo-drive 11 If this fault exists, all the others

  Plausibility tests are blocked.

  b) Plausibility check of the engine rotational speed sensor 19 and the speed sensor of the gearbox 31: A speed sensor test of this type is always carried out when its meets the following conditions: of the positioning servo-drive according to test a), no defect in the range of values of the engine rotational speed sensor 19 and the rotational speed sensor of the gearbox 31, no defect noted during a previous plausibility check of the verification, discussed below, of the speed sensor 25 and the speed position sensor 27 according to the test c). The speed sensor test is performed while the clutch 3 is fully engaged,

  after a delay of at least 2 seconds has elapsed.

  If, when the clutch 3 is erroneous, the rotational speed of the engine measured by the sensor 19 and the input rotational speed of the gearbox measured by the sensor 31 differ from each other more than a predetermined differential rotation speed, of 200 revolutions per minute for example, the monitoring means 35 signal a rotational speed defect In order to be able to distinguish between a defect of the motor rotation speed sensor 19 or a defect of the speed sensor speed of rotation of the gearbox 31, the monitoring means 35 calculate, from the signal of the speed sensor 25 and the signal of the speed position sensor 27, representing the gear ratio, a rotational speed d input of the substituted gearbox If the gearbox input rotation speed, as measured by the sensor 31, differs from the gearbox input rotational speed of rotation thus calculated, of a value greater than a second differential rotation speed, there is a defect of the rotational speed sensor of the gearbox 31 The second differential rotation speed is greater than the first differential rotation speed mentioned above and advantageously around 300 revolutions per minute If the input rotational speed of the gearbox measured and the substituted speed coincide within certain tolerance limits, the monitoring means 35 signal a failure of the sensor of rotation speed: 32

of the engine 19.

  If the failure of the input speed sensor of the gearbox 21 is signaled, the clutch can be continued in a variant of the normal operating mode, in which only the signal of the input rotational speed of the gearbox measured speed, sent by the sensor 31 to the control means 33, is replaced by the rotational speed signal

  input of the substituted gearbox.

  If the monitoring means 35 signal the failure of the engine rotational speed sensor 19, it is switched to the emergency operation mode described above, in the event of a failure of the engine rotational speed sensor. motor rotation speed 19 is one of the most important components of the clutch control device discussed above, it is necessary that a defect of this sensor can also be detected as soon as possible, when the clutch 3 is not not found in its fully engaged position, but in its fully disengaged position The monitoring means 35 therefore trigger a start operation during which the clutch 3 is engaged, with a reduction in comfort, in the case where one suspects a motor speed sensor 19 in an operating situation in which the clutch 3 is disengaged and the driver announces an intenti it is necessary to start by operating the accelerator pedal 23 For this purpose the clutch 3 is engaged according to a ramp characteristic curve when the monitoring means 35 signal the motor rotation speed sensor defect during the sequence of the operating steps following "start combustion engine 1 vehicle in first gear accelerator pedal 23 is operated beyond the minimum clutch position" The start operation is performed for testing during the normal operating mode, in order to then proceed to the test of the rotational speed sensor previously exposed,

  with clutch 3 fully engaged.

  c) Plausibility check of the speed sensor 25 and the speed position sensor 27: This test is carried out when the following conditions are fulfilled: no fault of the positioning servo-drive, no fault of the speed sensor and of the speed position sensor 27 found during the verification of the range of values, no plausibility defect of the engine rotational speed sensor 19 and the input rotational speed sensor of the gearbox 31 found during an earlier plausibility check according to b). For the running speed sensor 25 and the speed position sensor 27 test it is necessary again that the clutch 3 is fully engaged for a time interval greater than a predetermined interval of two seconds, for example the monitoring means 35. signal a fault when the gearbox input speed, measured by the sensor 31, and the input speed of the substituted gearbox, exposed to the test b), differ from a value greater than a gearing speed. predetermined differential rotation, of 300 rpm for example The monitoring means 35 decide according to the magnitude of the output signal of the speed sensor 25, if it is a fault of the speed sensor 25 or a defect of the speed position sensor 27 If the speed sensor signals a stopping of the vehicle, it is a defect of the speed position sensor 27, otherwise

  a speed sensor error 25.

  This distinction, which is simple in itself, can lead to an erroneous signal in the case where the driving wheels 9 skid For example when starting with slipping drive wheels, the clutch 3 is already engaged for more than 2 seconds, which leads to a difference of speed of rotation between the input speed of the measured gearbox and the substituted speed, since the vehicle is stationary despite driving wheels skidding and the running speed is therefore zero The consequence would be a fault detected wrongly On the other hand, even when running, when the clutch is engaged for example on icy road, the driving wheels 9 can also skate, so that at a positive speed of stick, one has to again a difference between the measured speed of rotation of the gearbox input and the speed substituted. As a consequence there is here a fault incorrectly indicated by the speed position sensor. 27. In order to exclude erroneous detections of the aforementioned type, the verification of the speed sensor 25 and that of the speed position sensor 27 is advantageously effected only if the following conditions are also met: the accelerator pedal sensor 21 indicates that the accelerator pedal 23 is in its rest position, a brake pedal sensor 51 signals that a brake pedal 53 is in its rest position, the brake of the vehicle is therefore not actuated , a possible regulation of the speed of operation 55 (Tempomat) maintaining the speed of running on an adjustable value, is not activated, there is no plausibility defect of the zero switch of the accelerator pedal according to the pedal zero switch test

  referred to in point (d) below.

  d) Plausibility Check of the Accelerator Pedal Zero Switch This test can be performed when there is no fault in the range of the throttle valve actuator 47, ie no range fault. of values of the actuator, has not been detected and if the speed control device 55, provided, is not activated When activating the speed control device 55, the accelerator pedal 23 would replace himself in his position

  resting, despite actuation of the throttle valve 43.

  This would lead to the erroneous detection of a defect in

  throttle position sensor 49.

  The monitoring means 35 signal a fault of the zero position switch of the accelerator pedal, associated with the accelerator pedal sensor 21, when the throttle position sensor imposes a position other than zero and that at the same time the zero position switch of the accelerator pedal signals the rest position of the accelerator pedal 23 The monitoring means 35 signal a plausibility defect of the zero position switch only after the defect has persisted after a predetermined end of rebound time of 1.5 S for example In the event of a fault in the throttle position sensor 49 or the zero position switch, the monitoring means 35 switch to the operating mode of the urgency explained above, in the event of a failure of the accelerator pedal sensor. As the components of the throttle actuator 47 are generally freely housed in the vehicle engine enclosure, this actuator can remain stuck in unfavorable conditions since such a defect can again be suppressed during running. the effect of other vibrations, it is advantageously provided that during a new plausibility check of the position sensor of the throttle valve 49 or the zero position switch, it returns to the normal operating mode when in the case of a rest position, detected by the activated zero position switch, the throttle position sensor 49 also signals the throttle rest position. Similarly, the fault can be reset if the zero position switch is disabled and if the throttle position sensor

  gas 49 indicates a deflection of the throttle valve.

  e) Accelerator pedal sensor plausibility test 21: This test may be carried out if no fault has occurred during the test b) the speed sensor and the c) speed sensor and sensor test c) In addition, the accelerator pedal sensor range of values 21 is checked beforehand. Contrary to the tests previously described with clutch 3 fully engaged, the monitoring means 35 perform the pedal sensor test. accelerator while the clutch is fully disengaged, as soon as the clutch has been released for a predetermined time interval of at least two seconds If then the rotational speed of entry of the box

  velocity, detected by the sensor 31, is

  below the disengagement speed which causes the control circuit 15 to disengage the clutch 3, in order to prevent the combustion engine 1 from stalling, and if the speed detected by the engine rotational speed sensor 19 is greater than of a predetermined value, at the idling speed, while the accelerator pedal sensor 21 delivers a signal representing the rest position of the accelerator pedal 23, the monitoring means 35

  signal a fault in the accelerator pedal sensor 21.

  Here again it can be provided that the monitoring means signal the fault only if it persists after a rebound end time of one second, for example. In the event of the fault of the accelerator pedal sensor 21, it is switched to the emergency mode of operation described above, in the event of a failure of the accelerator pedal sensor. Since the accelerator pedal 23 can also remain stuck in unfavorable conditions, it is also provided here that after a a new plausibility check of the accelerator pedal sensor 21, it is switched back to the normal operating mode,

  when the default conditions are no longer met.

  f) Plausibility check of the contactor The contactor 41 can be verified in that the monitoring means 35 in the non-ignition position control the engine rotational speed signal supplied by the sensor 19 to know if the combustion engine 1 is when stopped If engine 1 is running, a

  Contactor 41 fault is signaled.

Claims (17)

  1 Automatic control device of a friction clutch (3), actuated by a positioning servo-drive (11), of a motor vehicle driven by a combustion engine (1) via a gearbox speeds (7), comprising: a motor rotation speed sensor (19) detecting the rotation speed of the combustion engine (1), means (29), which indicate the beginning of a movement movement of the engine (1), gearbox (7), in particular in the form of a shift lever sensor detecting the deflection of a shift lever (5) of the gearbox (7), from a gearbox position of the lever determined by the instantaneous selection of the speed of the gearbox (7), an accelerator pedal sensor (21) detecting the travel of an accelerator pedal (23) from its rest position , a control circuit (15) controlling the positioning servo drive (1 1) in a normal operating mode, according to at least the engine speed sensor (19), means (29) detecting the operating movement of the gearbox (7) and according to the pedal sensor accelerator (21) for clutching and disengaging the friction clutch (3) during starting and shifting of the gearbox (7), the control circuit (15) comprising means function check function (35) for controlling the operation of at least one of the sensors (19, 21, 29) and, in the case where a function fault of the sensor (19, 21, 29) has been verified, detected, switching on   an emergency mode of operation, controlling the servo   positioning drive (11) during starting and shifting of the gearbox (7), by giving up the sensors (19, 21, 29) checked, characterized in that the control circuit (15) switches in the emergency mode of operation at least in the event of failure of the engine rotational speed sensor (19) or at least in case of failure of the accelerator pedal sensor (21) and controls the speed of operation of the servo motor. positioning drive (11), when clutching the friction clutch (3), both for starting and for shifting the gearbox (7) according to the magnitude of the travel of the accelerator pedal (23), detected by the accelerator pedal sensor (21), when the engine rotational speed sensor (19) is defective or depending on the magnitude of the rotational speed of the engine, detected by the engine rotational speed sensor (19), when ue the accelerator pedal sensor (21) is defective.   2 Device according to claim 1, characterized in that the control circuit (15) disengages the friction clutch (3) for the operation of the gearbox (7) in normal operating mode, depending on the actuation the shift lever sensor (29) or a speed position sensor (27), detecting at least the neutral position of the gearbox (7), as well as in addition to at least another sensor (25, 31) and, in emergency operation mode, exclusively according to the actuation of the shift lever sensor (29) or in the case of detection of the neutral position by the sensor position speed (27).   3 Device according to claim 2, characterized in that the control circuit (15) disengages the friction clutch (3) in emergency operating mode for the duration of the actuation of the shift lever sensor ( 29) or the detection of the neutral position by the position sensor of speed (27).   4 Device according to any one of   Claims 1 to 3, characterized in that the circuit   control (15) in normal operating mode responds to a speed position sensor (27), detecting the position of the gearbox, and in case of failure of the speed position sensor (27) switches to the operating mode emergency, controlling the friction clutch (3), depending on the value of the rotational speed of the engine, detected by the speed sensor of the motor (19).   Device according to one of claims 1   to 4, characterized in that the control circuit (15), in the event of failure of the motor rotation speed sensor (19), controls the positioning servo-drive (11) in emergency operation mode, in which the direction of the clutch, when the accelerator pedal sensor (21) detects a travel of the accelerator pedal (23) greater than a predetermined travel value, different from the rest position of the accelerator pedal (23) and the control in the disengagement direction, when the accelerator pedal sensor (21) detects a stroke lower than the predetermined travel value.  6 Device according to claim 5, characterized in that the control circuit (15) controls the positioning servo-drive (11) in the direction of the clutch and / or in the direction of disengagement, with a speed of action independent of the value of the race   the accelerator pedal (23).   7 Device according to claim 5, characterized in that the control circuit (15) controls the positioning servo-drive (11) in the direction of the clutch and / or in the direction of disengagement with a speed of action which is proportional to the deviation of the travel detected by the accelerator pedal sensor   (21) with respect to the predetermined stroke value.   8 Device according to any one of   claim 6 or 7, characterized in that the circuit of   control (15) controls the positioning servo drive (11) in the direction of the clutch and / or in   the direction of disengagement, with a speed of action -   depending on the variation over time of the value of the   accelerator pedal stroke (23).   9 Apparatus according to any one of   Claims 1 to 8, characterized in that the circuit   control (15), in the event of a failure of the accelerator pedal sensor (21), controls the positioning servo-drive (11) in the emergency operating mode, in the clutch direction, when the sensor engine rotational speed (19) detects an engine rotational speed greater than a predetermined starting value, greater than the idling speed of the combustion engine (1), and the control in the disengagement direction, when the sensor engine rotational speed (19) detects a rotational speed of the engine   less than the start value.   Apparatus according to claim 9, characterized in that the control circuit (15) controls the positioning servo-drive (11) in the direction of the clutching and / or in the direction of the dobbling W with a speed of which is proportional to the difference between the engine rotational speed, detected by the engine rotational speed sensor (19), and the value of the engine rotational speed at startup. 30 11 Device according to one any of   9 or 10, characterized in that the circuit of   control (15) controls the positioning servo drive (11) in emergency operating mode, in the clutch direction, with a constant speed of action, when the engine speed sensor (19) detects a rotational speed of the motor greater than a value of rotation speed of the predetermined operating motor, greater than the speed of rotation of the starting the engine.   12 Device according to any one of   Claims 1 to 11, characterized in that the circuits   control circuit (15) includes a motor rotation speed control circuit which, in normal operating mode, adjusts the engine speed at startup by comparison of actual speed information detected by the engine speed sensor ( 19) and a set speed information, to a rotational speed value corresponding to the set rotational speed information and in that the control circuit (15) at startup, in normal operating mode, imposes the setpoint rotation speed information as a function of the accelerator pedal stroke (23), detected by means of the accelerator pedal sensor (21), as a function of a characteristic curve setpoint rotation speed predetermined.   13 Apparatus according to any one of   Claims 1 to 12, characterized in that the circuit   control (15) comprises a gearbox rotation speed sensor (31), detecting the gearbox input rotation speed (7) as well as a differential rotation speed control circuit, which in normal operating mode, during the operation of the gearbox (7), adjusts a real differential rotation speed information, representing the difference between the speed of rotation of the engine, detected by the speed sensor of the motor (19) and the gearbox input rotational speed, detected by the gearbox rotational speed sensor (31), in comparison with a target differential speed information, on a differential rotation speed value corresponding to the reference differential speed of rotation information and in that the control circuit (15) during the operation of the gearbox (7) e n normal operating mode, imposes the differential reference speed information in accordance with a   predetermined ramp characteristic curve.   14 Apparatus according to any one of   1 to 13, characterized in that the servo   positioning drive (11) comprises a position control circuit (13), which detects actual clutch position information, representing the instantaneous position of the friction clutch (3), and by comparing the information of actual clutch position and clutch set position information, sets the position of the clutch to a position corresponding to the set position information and that the control circuit (15), - at least in normal operating mode, preferably also in emergency operating mode, provides the clutch set position information for controlling the positioning servo drive (11) in the clutch direction as well. at startup than at the maneuver the gearbox (7).   Device according to any one of   claims 1 to 14 or according to the preamble to   claim 1 or according to any one of   Claims 1 to 14, with reference to the preamble to   claim 1, wherein the control circuit (15) in   normal operating position controls the servo   positioning drive (11) also according to a gearbox rotational speed sensor (31), detecting the input rotational speed of the gearbox (7), and wherein a position sensor of clutch (17), detecting the adjustment of the friction clutch (3), is associated with the positioning servo-drive (11) of the friction clutch (3), characterized in that the function monitoring means (35) perform at least one of the following monitoring steps: a) determining the difference between the rotational speed of the motor detected by the engine rotational speed sensor (19) and the rotational speed of rotation of the engine. the gearbox, detected by the speed sensor of the gearbox, when the clutch position sensor (17) detects that the friction clutch (3) is fully engaged, and switching to the gear mode. emergency operation, commander the operation of the clutch according to the accelerator pedal sensor (21), when the rotation speed difference is greater than a first predetermined value; b) before switching to the emergency operating mode in the monitoring step a): determining an input rotational speed of the substituted gearbox based on a gait speed information, detected by means of a speed sensor (25), and a speed information representing the instantaneous position of the gearbox (7), detected by means of a speed position sensor (27), determination the difference between the gearbox's rotational speed of rotation and the input speed of the gearbox, measured by means of the speed sensor of the gearbox (31) and switching to the mode emergency operation according to the monitoring step a), when the difference of the rotational speeds is less than a second predetermined value; c) switching to emergency operating mode, controlling the operation of the clutch according to the engine speed sensor (19), when a sensor (49), detecting the setting of the fuel control means ( 43), in particular a throttle valve or an injection pump of the combustion engine (1), detects a rest position of the fuel control means (43) and at the same time the accelerator pedal sensor (21). ) detects a travel of the accelerator pedal (23) from its rest position or when the sensor (49), detecting the setting of the fuel control means (43), detects a different setting of the rest position and at the same time the accelerator pedal sensor (21) detects that the accelerator pedal is in the rest position; d) switching to emergency operating mode, controlling the operation of the clutch according to the engine speed sensor (19), when the accelerator pedal sensor (21) detects that the accelerator pedal (23) is in its home position and at the same time the engine rotational speed sensor (19) detects an engine rotational speed greater than the idle rotation speed and at least one of the following conditions is satisfied: the clutch position sensor (17) detects that the friction clutch (3) is fully disengaged, a speed position sensor (27) detects that the gearbox (7) is in position. neutral position.   Apparatus according to claim 15, characterized in that the positioning servo drive (11) comprises a position control circuit (13) which adjusts, by comparison between actual clutch position information, detected by the position sensor. clutch position information, supplied by the control circuit (15), the friction clutch (3) to a position corresponding to the target position information and the monitoring means (35) execute, before ZI 6, performing at least one of the monitoring steps a) to d), a monitoring step e) during which the steps a) to d) are locked, when a clutch target position information, delivered by the control circuit (15) for a predetermined end position of the friction clutch (3), in particular for the end position fully engaged differs from a predetermined tolerance value of the actual clutch position information provided in   this case by the clutch position sensor (17).   17 Device according to any one of   15 or 16, characterized in that the means   (35) Before each monitoring step, a check is made of the range of values of the electrical voltage and / or the electrical current of the sensors and actuators participating in the monitoring step and block the monitoring step when a defect range of values is detected.   18 Apparatus according to any one of   Claims 15 to 17, characterized in that the means for   monitoring (35) switches the control circuit (15) after a fault occurring when the friction clutch (3) is fully disengaged, which prevents the clutch of the friction clutch (3) from being engaged during start-up. of normal operation, in an emergency operating mode in which the control circuit (15) controls the positioning servo-drive (11) of the friction clutch, according to a predetermined ramp characteristic curve, to the fully engaged position and that the monitoring means (35) then execute at least one of the steps of monitoring a) or b).   19 Apparatus according to any one of   Claims 15 to 18, characterized in that the means for   during step b), if there is a difference between the substituted gearbox input rotation speed and the gearbox input rotation measured speed, which is greater than the second value differential, a monitoring step f) and indicate a speed position sensor failure (27) when the running speed information provided by the speed sensor (25) represents a running state and indicates a fault of the speed sensor (27). speed sensor (25), when the gait speed information provided represents a stop of the vehicle.   Device according to Claim 19, characterized in that the monitoring means (35) switch the control circuit (15) in the case where the difference in speed of rotation is greater than the second differential value, in a mode of emergency operation in which the information of the measured rotational speed of the transmission input is replaced by the information of the rotational speed of rotation of the gearbox input. 21 Apparatus according to any one of   claims 19 or 20, characterized in that the means   (35) perform the monitoring step f) when the accelerator pedal sensor information (21) indicates the rest position of the accelerator pedal (23), a brake pedal sensor (51) ) indicates a non-activation of a vehicle brake and   the monitoring step c) does not indicate any faults.   22 Device according to any one of   Claims 15 to 21, characterized in that the means for   (35) comprise a delay device and do not switch the control circuit (15) to the emergency operating mode or indicate a fault only if the information provided by the accelerator pedal sensor (21) and / or by the sensor (49) detecting the setting of the fuel control means (43) and / or corresponding to the gearbox input rotational speed of rotation, have been present continuously   during a predetermined time interval.