FR2826700A1 - METHOD FOR CONTROLLING A CLUTCH IN A MOTOR VEHICLE - Google Patents

Abstract

Method for controlling a clutch in a motor vehicle, consisting in detecting the position of a pedal (28) connected by an actuator (24, 26) to disengaging means (16), in generating a control signal of the actuator from a pedal position signal, to apply this signal to the actuator by controlling its position and to accelerate the disengagement with respect to the movement of the pedal, on the dead disengagement strokes, and / or to slow down the disengagement with respect to the movement of the pedal over the useful disengagement travel. The invention makes it possible to improve the efficiency and the precision of the clutch control in a motor vehicle.

Description

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 The invention relates to a method for controlling a clutch in a motor vehicle.

 As is well known, a clutch in a motor vehicle transmits a torque between the output shaft of an internal combustion engine and the input shaft of a transmission, such as in particular a gearbox , and is controlled by a pedal connected by hydraulic or cable means to declutching means acting to open or decouple the clutch when the driver of the vehicle presses the pedal to move it from a rest or depressing position void at an active or depressed position.

 Return means associated with the pedal, such as a spring, return the pedal to its rest position when it is released by the driver, the clutch then passing from the open or decoupled state to the closed or coupled state. .

 The total stroke of the pedal between its extreme zero depressing and fully depressed positions includes a first dead stroke, during which movement of the pedal has no effect on the torque transmissible by the clutch, a useful stroke at during which the clutch is opened or decoupled by the declutching means, and a second dead stroke during which the movement of the pedal continues until the fully depressed position, while the clutch is already open and no longer transmits torque.

 In a friction clutch of a conventional type, the start and the end of the useful pedal travel correspond respectively to the start of the

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 displacement of the declutching means (for example attack of the diaphragm) and at the point of licking (contact without transmission of torque between the disc and the friction plates).

 In known mechanisms, the operation of the clutch is determined entirely by the actuation of the pedal which itself depends on the driver's abilities, his experience, the attention he pays to the maneuver he performs. , etc. In these conditions, an emergency clutch can be made late or too slowly, or a clutch can be made too quickly, with a risk of stalling the engine or slipping of the drive wheels for example. In addition, the dead strokes can be longer or shorter depending on the mechanisms and settings as well as the wear of the clutch, which can offset the useful stroke or shorten it, hence a more delicate control of the 'clutch. The return springs associated with the pedals also contribute significantly to the sensations felt by the drivers when the pedals are actuated and have characteristics which cannot be adapted to all types of drivers and which vary over time.

 The object of the invention is in particular to provide a simple, effective and inexpensive solution to all of these problems.

 To this end, it proposes a method for controlling a clutch mounted between the output shaft of an engine and a transmission in a motor vehicle, by means of a pedal connected to an actuator acting on declutching means,

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 characterized in that it consists in detecting the position of the pedal between its extreme positions of zero depressing and maximum depressing and in generating a signal representing the detected position of the pedal, in developing from this signal a signal of actuator control and to apply it to the actuator, to detect the position of the actuator, of the clutch or clutch control, to generate a signal representing this position and to take it into account in the 'development of the aforementioned control signal, and to accelerate the declutching in relation to the movement of the pedal, on dead strokes having no effect on the transmissible torque, and / or to slow down the declutching in relation to the displacement of the pedal, on the useful stroke during which the torque transmissible by the clutch can be modified.

 The method according to the invention thus makes it possible to increase the useful stroke of the pedal relative to the dead strokes and / or to reduce the dead strokes of the pedal relative to the useful stroke, to allow a driver to have a longer useful stroke for command and control of the clutch. This results in an increase in comfort, precision and speed of the clutch control.

 Advantageously, the start and the end of the useful stroke are determined by detection of the attack of the declutching means and of the licking point.

 According to another characteristic of the invention, this method also consists in detecting the slip limit of the clutch and in accelerating the release in relation to the movement of the pedal between the start of the useful stroke and the slip limit of the clutch.

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 Depending on the value of the torque transmitted by the clutch, the clutch slip limit may be more or less close to the start of the useful clutch release stroke. The part of this useful stroke which is located between the start of the clutch and the slip limit has no effect on the transmission of the torque by the clutch and can therefore be traveled more quickly, which makes it possible to lengthen relatively the part of the useful stroke during which the transmission of the torque by the clutch is modifiable, and therefore to have more comfort, precision and speed for the control of the clutch.

 As a corollary, the method according to the invention also consists in slowing the disengagement with respect to the movement of the pedal between the position corresponding to the slip limit of the clutch and the end of the useful stroke.

 According to yet another characteristic of the invention, this method consists in measuring or calculating the speed of movement of the pedal and in slowing down the movement of the actuator over the useful clutch travel when the speed of movement of the pedal is greater to a predetermined limit value. Depending on the case, for example during an accidental release of the clutch pedal, the method according to the invention limits the closing speed of the clutch, keeps it open and / or emits a signal for the attention of the driver.

 This avoids too sudden a clutch and the corresponding drawbacks (deterioration of the transmission components, risk of stalling the engine or slipping of the drive wheels, discomfort for the passengers of the vehicle, etc.).

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 According to another characteristic of the invention, this method also consists in detecting information such as the position of an accelerator pedal or of a member controlled by the accelerator pedal, the rotational speeds of the engine and of the input shaft of the transmission, the gear ratio engaged and the torque supplied by the engine, to use this information and the prerecorded control laws to check whether a control signal corresponding to a detected position of the aforementioned pedal may or may not be applied to the actuator and, as a function of this comparison, to apply to the actuator said control signal or another signal produced from said information and said control laws.

 We can thus avoid the inconvenience and inconvenience that would be caused by an awkward clutch control, by constantly checking whether or not this control falls within an acceptable framework and by replacing it if necessary with another more appropriate control, developed automatically in accordance with pre-recorded control laws.

 This avoids, in particular, the risks associated with a control error by the driver and its unpleasant or harmful consequences for the vehicle and its passengers.

 Advantageously, the information which is detected for this purpose also includes the position of a braking control member and the position of a speed change lever.

 This makes it possible in particular to avoid stalling the engine following sudden braking of the vehicle and at least to reduce, if not cancel, the

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 disadvantages associated with poor speed selection by the driver.

 According to another aspect of the invention, aimed at the case where the vehicle is equipped with an automatic clutch system and with a means for selecting automatic or manual control of this system, the method also consists in using the displacement of the aforementioned pedal to, in manual control mode, give a disengagement or clutch command to the automatic clutch system.

 A vehicle equipped with an automatic clutch can thus also be equipped with a clutch pedal that the driver can use to control the clutches and disengages himself, when he wishes.

 The gearshift lever can also be equipped with contact means (such as a switch or switch for example) for disengaging control. In this case, the declutching is controlled by the first actuated means, that is to say either by the gear change lever, or by the declutching pedal. It is also possible to choose one of these two commands and to inhibit the other.

 According to yet another aspect of the invention aimed at the case where the vehicle is equipped with an alternator starter, the method according to the invention consists in maintaining the clutch in the disengaged state by means of the aforementioned actuator when the vehicle is when the engine is stopped and the engine is cut off automatically, then after an automatic restart of the engine, whether or not to control the actuator to change the clutch to the engaged state depending on the engaged or disengaged position of the aforementioned pedal.

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 This guarantees that the transmission remains disengaged between stopping and automatically restarting the engine, which facilitates restarting the engine while allowing orders given by the driver to be followed.

 According to yet another characteristic of the invention, this method also consists in associating a variable restoring force with the pedal in order to constantly urge it towards its zero depressing position, and in modifying this restoring force as a function of the driving mode of the vehicle.

 Thus, when the driver has a "nervous" driving, the restoring force of the pedal will be increased to give the driver a greater feeling of clutch control. Otherwise, when the driver has a very calm driving, the restoring force of the pedal will be reduced so that the pedal can be moved gently without disturbing the calm driving of the vehicle.

 The invention will be better understood and other characteristics, details and advantages thereof will appear more clearly on reading the description which follows, given by way of example with reference to the appended drawings in which: - Figure 1 shows schematically the essential means of the invention; - Figures 2 and 3 are graphs representing two modes of control of an actuator according to the movement of a pedal; - Figure 4 is a flowchart illustrating the operation according to the invention of a vehicle equipped with an alternator-starter; and

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 - Figures 5 to 9 are flowcharts illustrating various modes of operation of a controlled clutch according to the invention.

 In FIG. 1, the reference 10 designates a clutch in a motor vehicle, comprising a friction disc 12 connected to the input shaft of a transmission (not shown) and mounted coaxially between a pressure plate 14 associated with means declutchers and clutch assemblies such as an annular diaphragm 16, and a reaction plate 18 integral in rotation with the output shaft 20 of an internal combustion engine 22.

 The declutching and clutching means 16 are moved between a engaged position and a disengaged position by means 24, 26 comprising for example a declutching stop 24 well known to those skilled in the art, and an actuator 26 which may be of a type any, mechanical, pneumatic, hydraulic or even electric, acting on the stop 24 and controlled by a clutch pedal 28 pivotally mounted about an axis 30 in the passenger compartment of the vehicle to be moved by the driver in the direction of the arrow 32 from a rest position shown in the drawing.

 Conventionally, in the rest position of the pedal 28, the diaphragm 16 is in the engaged position and the friction disc 12 is clamped between the plates 14 and 18 and transmits the torque of rotation provided by the motor shaft 20.

 When the pedal 28 is moved by the driver in the direction of the arrow 32, the declutching stop 24 controlled by the actuator 26 causes the diaphragm 16 to pass into the disengaged position, by

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 tilting around its supports on a clutch cover, the plates 14 and 18 move away from each other and the transmission of a torque to the input shaft of the transmission is interrupted.

 In the prior art, the pedal 28 is generally connected to the clutch release bearing by a cable connection and by a fork, or else by a hydraulic control.

 According to the present invention, a position sensor 34 of any suitable type makes it possible to detect the position of the pedal 28 between its extreme positions of zero depression and maximum depression and to generate an electrical output signal representing this detected position .

 The output signal of the sensor 34 is applied to an input of information processing means 36, comprising a microcomputer and memories, which also receive as input information supplied by a system 38 of engine control and possibly of other information such as the rotational speed of the drive shaft 20, the rotational speed of the input shaft of the transmission, etc., as will be described in more detail below.

 The means 36 generate a control signal which is applied to an input of the actuator 26, this being for example of the electrical, pneumatic or hydraulic type, such as an electric motor or a pneumatic or hydraulic cylinder, capable of moving the stop. clutch 24 or another equivalent means for actuating the clutch and declutching means 16, in a manner corresponding to the control signal applied to the actuator 26.

 The response of the actuator 26, for example the position of a movable member thereof or of the

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 stop 24, is detected and applied at 40 to an input of information processing means 36. As a variant, it is the position of the clutch or of one of its control means which is detected and applied at 40.

 Return means 42 are associated with the pedal 28 and constantly urge it towards its zero depressing position shown in FIG. 1, and are advantageously associated with means 44 controlled by the information processing means 36 to vary the return force of the pedal 28, for example by controlled modification of the stiffness of a spring or the like.

The device shown in FIG. 1 operates as follows:
The position of the pedal 28 is permanently detected by the sensor 34, which supplies a corresponding position signal to the information processing means 36. The latter generate a control signal applied to the actuator 26 which displaces the clutch release bearing 24 or the like in a position corresponding to the detected position of the pedal.

 The total disengaging stroke between the extreme positions of zero depressing and maximum depressing of the pedal 28 comprises, from the engaged position represented in FIG. 1, a first dead stroke during which the torque transmissible by the clutch n ' is not modified and which corresponds to a dead stroke of all the means used for declutching.

 The first dead stroke is followed by a useful stroke during which the clamping force of the friction disc 12 between the plates 14 and 18 varies between a value allowing the maximum engine torque to be transmitted and a value substantially zero for

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 which the torque transmitted to the input shaft of the transmission becomes zero.

 This useful travel is followed by a second dead travel, during which the movement of the actuator pedal, the stop and the declutching means no longer has an effect on the transmissible torque.

 In the graph of FIG. 2, the stroke of the pedal 28 is shown on the abscissa and that of the actuator 24, 26 is shown on the ordinate. On the abscissa, point 0 corresponds to the engaged position or zero depressing position of pedal 28, points P1 and P2 are the start and end of the useful stroke of the pedal and point P3 corresponds to the position of maximum depressing of the pedal. On the ordinate, point 0 corresponds to the clutch engaged position, point A corresponds to the start of the useful stroke when the transmissible torque becomes modifiable, point B corresponds to the end of the useful stroke when the rotational torque transmitted by the clutch becomes zero and point C corresponds to the end of the declutching stroke.

 The curve I in FIG. 2 represents a control which is substantially proportional to the movement of the pedal 28.

 Curve II represents a displacement of the means 24, 26 and 16 which is accelerated with respect to the displacement of the pedal 28 on the first and the second dead travel. This has the effect of reducing the corresponding dead strokes of the pedal 28, the point Pl being moved to P'1 and the point P2 to P'2, the useful stroke of the pedal 28 becoming P'l-P'2 and being thus increased compared to the part AB which remains unchanged.

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 This also results in a relative slowing down of the displacement of the means 26, 24, 16 over the useful stroke AB compared to the displacement of the pedal 28 over its useful stroke P'l-P'2, which allows the driver to control more effectively and more precisely the operation of the clutch and its passages from the engaged state to the disengaged state, and therefore the variation of the engine torque transmitted by the clutch.

 The points P'1 and P'2 which delimit the useful stroke of the pedal 28 are permanently determined by the information processing means 36, the point P'1 corresponding to the tightening of the friction disc for the transmission of the torque maximum provided by the engine, the point P'2 corresponding to the licking point which can be determined by a particular sensor or else from the speed of the input shaft of the transmission, from the speed of the engine shaft and the vehicle speed or from the speed of the motor shaft, the vehicle speed and the transmission ratio used.

 As the position of the licking point depends on the wear of the clutch (wear of the friction linings and the corresponding friction surfaces on the plates 14 and 18), monitoring the licking point P'2 allows monitoring of the 'wear of the clutch and possibly a resetting of the useful stroke of the pedal to keep it constant whatever the wear of the clutch.

 The invention also provides, in the case where the torque supplied by the motor shaft 20 is less than the maximum torque that the motor can provide, to amplify the part of the useful stroke of the pedal which actually corresponds to the opening of

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 the clutch. Indeed, the clamping force of the friction disc 12 between the plates 14 and 18 by the diaphragm 16 is determined to guarantee a transmission of the maximum torque of the motor. When the torque supplied by the drive shaft 20 is less than this maximum, the clamping force applied by the diaphragm 16 is significantly greater than the clamping force which is necessary and sufficient to ensure the transmission of this engine torque by the clutch. . This means that, during a first part of the useful declutching stroke, the axial clamping force applied by the diaphragm 16 decreases without the engine torque transmitted by the clutch decreasing.

 As represented by curve III of FIG. 3, the displacement of the declutching means 26, 24, 16 is accelerated with respect to the displacement of the pedal 28 over this first part of the useful stroke which is represented at P'1-P " 1 in FIG. 3, the point P "l corresponding to the slip limit of the clutch, which can be determined in several ways well known to those skilled in the art.

 The declutching is then slowed down relative to the movement of the pedal 28 over the rest of the useful declutching stroke, which ends at the licking point P'2.

 The useful stroke of the pedal is thus adapted to the instantaneous value of the engine torque supplied by the shaft 20. The feeling felt by the driver when disengaging and clutching is then substantially constant whatever the engine load.

 The invention also provides for taking into account the speed with which the pedal 28 is moved by the driver, in particular in the direction of the clutch, to move the actuator 24, 26 correspondingly but with a higher speed.

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 low if necessary and thus avoid incidents such as a risk of stalling the engine, a risk of loss of grip of the drive wheels (when changing to a lower transmission ratio) and in general to avoid shocks in the transmission and preserve the engine and tires.

 For this, the information processing means 36 which permanently receive a position signal from the pedal 28, calculate the derivative with respect to time of this position and compare it to curves of prerecorded limit values.

 In this case, the invention therefore makes it possible to follow the command given by the driver, but by correcting his speed if necessary to avoid incidents.

 When the information processing means 36 have additional information on the operation of the engine and on the movement of the vehicle, such as in particular the transmission ratio used, the speed of the input shaft of the transmission, the speed of rotation of the engine, the torque provided by the shaft 20 and the position of the accelerator pedal or of a member controlled by the accelerator pedal, the invention makes it possible to check whether the commands given by the driver by means of the pedal 28 may or may not be appropriate, in order to possibly replace them by others which are developed from the above information and from control laws prerecorded in a memory of the means 36.

 The information supplied to the means 36 may also include data on the position of the speed change lever and on the position of a vehicle brake control member, such as the brake pedal for example.

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 The means 36 can then monitor the risks of stalling the engine, which would be due to emergency braking not accompanied by rapid disengagement. The aforementioned information enables the means 36 to detect this emergency braking, to anticipate the risk of stalling the engine and to give an emergency disengaging order to the actuator 26.

 Similarly, the means 36 can also check the position of the gear change lever to intervene when the driver selects and engages a transmission ratio which is not adapted to the conditions of movement of the vehicle, or does so without disengaging, l 'intervention including the emission of a signal, a re-clutch refusal or another means.

 The invention also applies to a vehicle equipped with an automatic clutch, in which the transmission ratio is changed by displacement of a gear lever, the declutching and the clutch being controlled automatically as a function of the speed of the engine. , the speed of the vehicle, and the position of the accelerator pedal or of a member controlled by the accelerator pedal.

 A vehicle of this type can be equipped with a clutch and clutch pedal and with a control means which can be used by the driver to select either an automatic clutch operation or an operation by control using the pedal. .

 In this case, the movement of the pedal by the driver is considered to be a declutching or clutching command which is transmitted to the automatic clutch system and executed by it with a

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 way to avoid operational incidents.

 The invention also applies to a vehicle equipped with an automatic clutch and an alternator starter making it possible to automatically stop and restart the engine when the vehicle is stationary, in particular to reduce fuel consumption in town and limit the emission of polluting compounds into the atmosphere, the engine being stopped automatically when the vehicle is stopped for more than a few seconds and being restarted automatically in a very short time when the driver gives a corresponding order to restart the vehicle, for example by depressing the accelerator pedal.

 The method according to the invention makes it possible to ensure that the transmission is disengaged when the engine is restarted automatically, which facilitates this restart.

For this, as shown schematically in Figure 4, the sequence of operations can be as follows:
When the vehicle is stopped, for example at a red light or in traffic jams, and the driver leaves the engine running, first gear can be engaged and the transmission disengaged, the driver keeping the clutch pedal depressed, or although the gear lever may be in neutral, as shown in 46.

 When this stop lasts more than a few seconds, a function commercially called "STOP AND GO" is executed, which controls the stopping of the engine until the driver gives an order interpreted as relating to restarting the vehicle, for example a pressure on the pedal

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 accelerator, the engine then being restarted automatically in an extremely short time by means of the alternator-starter.

 The method according to the invention consists, at the start of the application of the "STOP AND GO" function indicated at 48, to control the disengagement or to keep the clutch disengaged by the actuator 26, as indicated at 50, before the '' automatic engine stop indicated in 52.

 As a variant, steps 50 and 52 can be simultaneous or almost simultaneous, or else the automatic stopping of the engine can take place just before declutching or maintaining declutching by means of the actuator 26.

 When the driver gives a start order for the vehicle as indicated in 54, for example by depressing the accelerator pedal, the "STOP AND GO" function controls the automatic starting of the engine, as indicated in 56, the clutch being maintained in the disengaged state by the actuator 26.

 If the pedal 28 is then in the depressed position (corresponding to disengaging), as indicated in 58, the method according to the invention consists in following the orders given by the driver and in engaging to drive the vehicle forward when the driver releases the pedal 28 If on automatic restarting of the engine, the pedal 28 is in the non-depressed position (clutch position) and if the first gear is selected and engaged as indicated in 60, the method according to the invention consists in closing the clutch by means of the actuator 26 to cause the vehicle to slowly advance at idle speed of the engine, then to follow the orders which are given by the driver by means of the pedal

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 acceleration, the clutch pedal or possibly the brake pedal.

 FIG. 5 represents the flowchart of the control operations which are executed in accordance with the invention to prevent stalling of the vehicle engine during a stopping of the vehicle, for example following an emergency braking when the vehicle travels at high relative speed, or when it travels at lower speed in traffic embarrassment.

 The first operation 62 consists in detecting the speed V1 of rotation of the vehicle engine and its derivative Dl to compare them respectively with a minimum value of the speed of rotation and with a maximum value of the derivative.

 If, as shown in 64, the speed Vl becomes less than or equal to the minimum value Vlmin and the derivative V2 becomes greater than or equal to the maximum value Dlmax, the actuator 26 is controlled as indicated in 66 to open the clutch 10 as indicated in 68 in order to avoid stalling the engine in the event of the wheels locking.

 Then, the actuator 26 is again controlled as indicated in 70, for example to bring the clutch 10 to the licking point as indicated in 72, which results in a slow advance of the vehicle at the engine idling speed. Alternatively, if the driver presses the pedal 28 to disengage completely or at least to bring it into a position corresponding to the point of licking the clutch, as indicated in 74, the next step consists in following the driver's orders as shown in 76.

 The invention also provides for stalling the engine to immobilize the vehicle and

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 guarantee its position as indicated in 78, for example if the partial closing of the clutch to the licking point as indicated in 72 is insufficient to maintain the position of the vehicle, or to avoid excessive use of the clutch.

 When the clutch control according to the invention is intended to prevent the engine from stalling when the vehicle starts, the sequence of operations to be executed is also shown in FIG. 5 and includes step 62 of detecting the speed V1 of rotation of the motor and its derivative Dl, comparison of the motor speed with a minimum limit value Vlmin and comparison of the derivative Dl with a maximum value Dlmax, as shown in 64 and the control of the actuator 26 when the speed V1 is less than or equal to the minimum value and the derivative is greater than or equal to the maximum value, to slide the clutch as indicated in 80 in order to adjust the torque passing through the clutch to the instantaneous torque delivered by the engine . Then, if the driver presses the clutch pedal to depress it at least to the position corresponding to the state of the clutch as in step 74 above, the next step 76 consists in following the orders of the driver.

 If the driver does not depress the clutch pedal enough or not at all, the actuator 26 is controlled as indicated at 82 to open the clutch 10 in step 84.

 If the torque supplied by the engine is insufficient to guarantee the position of the vehicle on a hill, the invention provides for stalling the engine, the clutch being closed, to immobilize the vehicle as indicated in the above-mentioned step 78.

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 In another case, the clutch control according to the invention is intended to detect the risk of the wheels slipping on the ground and to eliminate this risk by sliding the clutch.

The flow diagram of the corresponding operations is shown in FIG. 6 and comprises a first step 86 of detecting the speed V2 of rotation of a shaft of the transmission (for example the speed of rotation of the secondary shaft of the gearbox) and detecting the speed V3 of the vehicle. As a variant, it is possible to detect and compare the acceleration of a shaft of the gearbox and that of the vehicle.

 The following operation 88 consists in checking the consistency of the speeds V2 and V3, in order to detect a speed V2 which would be clearly greater than a value consistent with the speed V3 of the vehicle. If an inconsistency is detected, the next operation 90 consists in controlling the actuator 26 to open the clutch 10 in order to limit the torque transmitted to the drive wheels of the vehicle. When this limitation of the torque is sufficient for a consistency to be found between the speeds V2 and V3 as indicated in 92, the actuator 26 is again commanded to gradually close the clutch, as indicated in 94.

 This avoids the slip of the drive wheels on the ground as well as the resulting loss of grip and side effects such as excessive increase in engine speed, wear of the clutch, etc.

 In another case which consists in detecting and removing the locking of the driving wheels during an excessive deceleration of the secondary shaft of the gearbox resulting from the

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 passage from a transmission ratio to a lower ratio, the operations executed by the control according to the invention are substantially the same as those represented in FIG. 6, step 88 consisting in detecting an inconsistency between the speeds V2 and V3 when the speed V2 of rotation of the output shaft of the transmission is significantly lower than a value corresponding to the speed V3 of the vehicle. The following operation 90 consists in opening the clutch to raise the speed of the output shaft of the transmission which is then driven by the mass of the vehicle, until a consistency is found between the speeds V2 and V3 as indicated in 92, after which the next step 94 consists in controlling the actuator to close the clutch 10.

 The operations flow diagram shown in FIG. 7 corresponds to the protection of the engine in the event of an overspeed caused by the change from a transmission ratio to a lower ratio.

 The first step 96 consists in detecting the speed V1 of rotation of the engine and the speed V2 of rotation of the output shaft of the transmission (for example the speed of rotation of the secondary shaft of the gearbox) in order to detect, as indicated in 98, a speed V1 which tends towards a value Vlmax and a speed V2 greater than V1.

 The following operation 100 then consists in controlling the actuator 26 to slide the clutch 10 and limit the torque transmitted to the engine by the primary shaft of the gearbox while respecting the maximum speed of rotation of the vehicle engine.

 Then, as the speeds V1 and V2 converge, the following operation 102

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 consists in controlling the actuator to gradually close the clutch 10.

 As a variant, if the driver has depressed the clutch pedal as indicated in 104 to bring it into a position corresponding to the actual state of the clutch, the following operation 106 consists in following the driver's orders.

 In another case, the driver can decide to switch to an automatic clutch control mode, by giving an order by means of an appropriate member, such as a switch for example. In this case, as shown diagrammatically in FIG. 8, the operations flow diagram comprises a step 108 of switching to automatic mode on command of the driver, which is continued until an order given by the driver to switch to manual mode as indicated in 110, or until the vehicle and engine stop as indicated in 112, after which the system returns to manual mode as indicated in 114.

 When the system must return to manual mode on the driver's command, the order given by the driver including actuating a switch or depressing the clutch pedal beyond the position corresponding to the state of the clutch, and that neither the vehicle nor the engine is stopped, several possibilities exist: - the clutch 10 is closed and the clutch pedal is at rest, that is to say in the clutch position as indicated in 116. In this case, the system can return to manual mode without problem as indicated in 118.

 - the clutch 10 is open, but the clutch pedal is in the rest position

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 corresponding to the closing of the clutch, as indicated in 120. In this case, the following operation 122 consists in controlling the actuator 26 to close the clutch and cause the vehicle to advance slowly at the engine idling speed as indicated in 124.

Alternatively, the actuator 26 is controlled to keep the clutch open as indicated in 126 and a signal is sent to the driver as indicated in 128, after which the clutch can be closed if the driver presses the accelerator or depending on driving conditions as indicated in 129.

 - the clutch is closed and the pedal depressed as indicated in 130. The actuator is controlled to open the clutch as indicated in 132, then the system switches to manual mode.

 the clutch 26 is open and the clutch pedal is in the depressed position as indicated in 134, the next step then consisting in returning to manual mode as indicated in 114.

 - the clutch and the clutch pedal are in intermediate positions as indicated in 136 and the next step 138 then consists in achieving a concordance of the positions of the pedal and of the clutch and returning to one of the preceding cases 116, 134, to follow a possible action of the driver on the pedal.

 Another scenario relates to assistance with a change of transmission ratio when the driver forgets to disengage and is illustrated by the flowchart in FIG. 9. In this flowchart, the first operation 140 consists in detecting a displacement of the lever of the change of speed from one of its positions corresponding to neutral or one of the transmission ratios.

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The following operation 142 consists in checking the position of the clutch pedal and, if it is at rest, in controlling the actuator 26 to open the clutch as indicated in 144.

 When the gearshift lever has arrived in another position corresponding to the engagement of another transmission ratio, as indicated in 146, the actuator 26 is again commanded to close the clutch as indicated in 148 and then return to manual mode as indicated in 150, or if the driver has pressed the clutch pedal enough as indicated in 152 to bring it into a position corresponding to the actual state of the clutch, we return to mode manual as indicated in 154.

 As a variant, when the position of the pedal varies suddenly and the new position does not correspond to an acceptable torque transmission, for example following an accidental release of the pedal, the actuator is controlled to keep the clutch open or to limit its closing speed, and a signal is sent to the driver.

 In general, the invention makes it possible to eliminate the drawbacks associated with a mechanical or hydraulic control of a clutch and to benefit from the advantages of an automatic clutch, in particular: - elimination of a significant disengagement effort, in particular in the heavily loaded engines, - elimination of the effect of clutch wear on the pedal, - improvement of safety in the event of an impact due to the elimination of the mechanical crankset,

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 - adjustment of the pedal force at will, - monitoring of the licking point, - monitoring of clutch wear, - engine anti-stalling and wheel traction control functions, - possibility of signaling to the driver excessive use of the clutch (for example excessive slipping of the clutch), - correction of clutch release or clutch commands incorrectly executed by the driver, with possible replacement of an erroneous or dangerous command by a command prerecorded in memory or developed automatically from pre-recorded order laws.

Claims (21)

1 - Method for controlling a clutch mounted between the output shaft of an engine and a transmission in a motor vehicle, by means of a pedal (28) connected to an actuator (24,26) acting on means declutchers (16), characterized in that it consists in detecting the position of the pedal (28) between its extreme positions of zero depression and maximum depression and in generating a signal representing the detected position of the pedal, to be developed from this signal an actuator control signal (24,26) and to apply it to the actuator, to detect the position of the actuator, of the clutch control or of the clutch, to generate a signal representing this position and to take it into account in the development of the control signal, and to accelerate the declutching with respect to the movement of the pedal (28) on dead strokes having no effect on the transmissible torque , and / or to slow down the disengagement compared to the displacement of the pedal (28) during a useful stroke during which the torque transmissible by the clutch is modifiable.  2- A method according to claim 1, characterized in that it consists in increasing the useful stroke of the pedal (28) relative to the useful disengaging stroke.  3- A method according to claim 1 or 2, characterized in that the beginning and the end of the useful stroke are determined by detection of the attack of the declutching means (16) and the point of licking the clutch. <Desc / Clms Page number 27>  4- Method according to one of the preceding claims, characterized in that it consists in accelerating the declutching with respect to the movement of the pedal between the start of the useful clutch travel and the slip limit of the clutch.  5- Method according to one of the preceding claims, characterized in that it consists in slowing the declutching with respect to the displacement of the pedal between the slip limit of the clutch and the end of the useful disengagement race.  6- Method according to one of the preceding claims, characterized in that it consists in measuring or calculating the speed of movement of the pedal (28) and in slowing down the movement of the actuator (24,26) over the useful stroke clutch when the pedal travel speed is higher than a predetermined limit value.  7- Method according to one of the preceding claims, characterized in that it consists in detecting information such as the position of an accelerator pedal or of a member controlled by the accelerator pedal, the speed of rotation of the motor and that of the input shaft of the transmission, the gear ratio engaged and the torque supplied by the motor, to use this information and the prerecorded control laws to check whether a control signal corresponding to a detected position of the pedal (28) may or may not be applied to the actuator (24,26) and according to this comparison, to <Desc / Clms Page number 28>  applying to the actuator said control signal or another signal produced from said information and from the prerecorded control laws.  8- A method according to claim 7, characterized in that the detected information also includes the position of a brake control member and the position of a gear change lever.  9- Method according to claim 7 or 8, characterized in that it consists in detecting the speed (V1) of rotation of the motor and its derivative (Dl) and in comparing them with curves of lower limit values (Vlmin) for the speed of rotation and higher (Dlmax) for the derivative, in order to anticipate an engine stall when these limit values are reached.  10- Method according to claim 9, characterized in that, when these limit values are reached, it consists in controlling the actuator (26) to open the clutch (10) when the risk of stalling results from a braking of or to drag it when the risk of stalling results from starting the vehicle.  11 - Method according to claim 10, characterized in that it then consists, for restarting the vehicle after emergency braking, to control the actuator (26) to bring the clutch to the licking point if the driver n 'does not act sufficiently on the clutch pedal, and not to control the actuator (26) if the driver acts sufficiently on this pedal. <Desc / Clms Page number 29>  12- A method according to claim 10, characterized in that it then consists, for starting the vehicle, to control the opening of the clutch if the pedal is depressed beyond the position corresponding to the controlled sliding of the clutch, or to confirm the actuator command if the pedal position corresponds to the clutch condition, or if the torque supplied by the engine is insufficient to maintain the position of the vehicle, to stall the engine and to close the clutch to immobilize the vehicle.  13 - Method according to claim 7 or 8, characterized in that it consists in detecting the speed of rotation (V2) of the output shaft of the transmission and in comparing it with that (V3) of the vehicle and, in case inconsistency between these two speeds, to command the actuator (26) to open the clutch in order to limit the torque transmitted to the drive wheels until a consistency is detected between said compared speeds (V2, V3), then to close the clutch as and when said compared speeds converge, to prevent the drive wheels from locking up when changing from a transmission ratio to a lower gear or the slip of the drive wheels in the event of excessive acceleration.  14 - Method according to claim 7 or 8, characterized in that, if the speed of rotation of the motor becomes excessive during the transition from a transmission ratio to a lower ratio, it consists in controlling the actuator (26) to open the clutch and slide it by limiting the torque transmitted by the drive wheels to the output shaft <Desc / Clms Page number 30>  of the engine to prevent the engine rotation speed (V1) from exceeding a predetermined maximum value (Vlmax), then to control the actuator (26) to close the clutch as the rotation speeds of the engine converge engine and transmission, or to follow the instructions given by the position of the clutch pedal if it has been depressed at least to a position corresponding to the sliding of the clutch.  15 - Method according to one of the preceding claims, characterized in that it consists in detecting the movements of the gear change lever and in controlling the actuator (26) to quickly open the clutch if the clutch pedal n '' was not actuated in the direction of declutching, then command the actuator to close the clutch after engaging a transmission ratio or to let the driver act on the clutch pedal if it has been depressed minus to a position corresponding to the actual condition of the clutch.  16 - Method according to one of the preceding claims, characterized in that it consists, upon receipt of a corresponding order given by the driver, to control the clutch fully automatically until receipt of a passage order in manual mode or until the vehicle and engine stop.  17- A method according to claim 16, characterized in that the order of switching to manual mode comprises depressing the clutch pedal in a position located beyond that corresponding to the state of the clutch, or comprises <Desc / Clms Page number 31>  actuation of a switch, in which case the order is executed when the position of the clutch pedal is beyond that corresponding to the state of the clutch.  18 - Method according to one of claims 7 to 9, characterized in that, when the position of the clutch pedal varies suddenly and that the new position does not correspond to an acceptable torque transmission, for example due to an accidental release of the clutch pedal, it consists in controlling the actuator (26) to keep the clutch open or in limiting the closing speed of the clutch and / or in emitting a signal for the attention of the driver.  19 - Method according to one of the preceding claims, characterized in that, the vehicle being equipped with an automatic clutch system and with a means of selecting automatic control or manual control of this system, the method consists in use the movement of the aforementioned pedal to, in manual control mode, give a clutch or clutch command to the automatic clutch system.  20 - Method according to one of claims 1 to 19, characterized in that the vehicle being equipped with an alternator-starter, it consists in maintaining the clutch in the disengaged state by means of said actuator (26) when the vehicle is stopped and the engine is cut off automatically, then after an automatic restart of the engine, to control or not the actuator to pass <Desc / Clms Page number 32>  the clutch in the engaged state as a function of the engaged or disengaged position of the pedal (28).  21 - Method according to one of the preceding claims, characterized in that it consists in urging the pedal (28) constantly towards its engaged position by a variable restoring force and in modifying this restoring force according to the driving mode of the vehicle.