FR2837888A1 - Method for calculating instant of automatic clutch opening when stopping vehicle, comprises calculation based on clutch opening norm, engine speed, speed gradient, idling speed and supplement - Google Patents

Abstract

The optimum instant for clutch opening is calculated by taking into account a clutch opening norm which is determined from fuzzy logic tables reflecting different types of drivers and situations, engine speed and speed gradient, idling speed and a tolerance supplement. The evolution of parameters such as gearbox entry speed (nGE) and engine torque (MsM) for emergency (A) and gentle braking (B) with long declutching are determined.

Description

The invention relates to a method for controlling an actuated clutch.

  automatic which is located in the traction line of a motor vehicle and by means of which, each time depending on the operating state, the torque of an engine is transmitted in whole or in part to a gearbox automated gears or the flow of force between the engine and the gearbox is interrupted, the clutch being opened automatically when the motor vehicle is stopped. In a torque control device, which can be transmitted by an automated clutch, which is present in the traction line of a motor vehicle comprising an engine and a gearbox which is provided with a shifting element ratio, used to select the gear reduction ratio, and a sensor used to detect this ratio (DE 198 23 766 A1), the engine provides a controllable engine torque. A control unit provided for an actuator used to adjust the torque which can be transmitted by the clutch controls this torque, which can be transmitted by the clutch, according to the engine torque present, the clutch torque being controlled by the inside a tolerance band, which can be prefixed, which surrounds the

  motor torque occurring and the tolerance band depending on the gear ratio.

  Automated gearboxes (see for example VDI reports 1610, 19-20 June 2001, pages 83 - 99) have certain advantages, such as reduced additional costs compared to gearboxes manual gears, significantly reduced costs compared to automatic gearboxes, reduced fuel consumption and furthermore the known advantages of all automatic gearboxes, such as driver relief during driving road. In this case, the automatic clutch control is a significant aspect. In addition to actuating the clutch when starting and when changing gears, it is also important to smoothly isolate the line of traction when stopping the vehicle, especially in order to '' prevent the engine from stalling. Furthermore, total isolation should take place as late as possible, so that, during a possible re-acceleration of the vehicle, the inevitable clutch process, which is most often linked to

  blows, which can be felt more or less clearly, and at a delay.

  Document DE 198 23 764 A1 discloses a method for controlling a clutch with automatic action, situated in the traction line of a motor vehicle, according to which the clutch is opened automatically during stopping the vehicle. The clutch opening start in this case is calculated from the engine speed, the engine speed gradient and a speed which is formed by the idle speed of the

engine increased by a supplement.

  The object of the invention is to provide a method for controlling an automatically actuated clutch in the case of which, on the one hand, the opening of the clutch when the motor vehicle is stopped begins at a precise moment and taking into account the situation and, therefore, fluctuations in the line of traction are avoided. On the other hand, the final opening of the traction line must be adapted in an adaptive manner to the driving situation which presents itself each time. To this end, the invention relates to a process, of the generic type defined in the introduction, characterized in that the instant of the start of opening of the clutch during the shutdown is determined as a function of '' a setpoint duration of the clutch, the engine speed, the gradient of the engine speed and a speed which is formed by the idle engine speed at

  which is added a supplement.

  Thus, according to this method, the instant of the start of the stopping operation is determined as a function of a setpoint duration of the declutching, of the speed of rotation of the motor, of the gradient of the speed of rotation of the motor and of '' a shift from the

  engine idling speed.

  The method according to the invention may also have one or more of the following features: - after starting to shutdown, the clutch torque is reduced from the torque currently transmissible to a transmissible torque which is located in the area of the current absolute value of the engine torque increased by a safety supplement, - the desired hardening of the clutch is determined according to the type of driver each time considered and the driving situation of the motor vehicle, - the type of driver and the situation are determined, using fuzzy logic, using measured values of the accelerator pedal position, the accelerator pedal gradient and the engine speed, - the type of driver and driving situation are deposited in characteristic tables and are read therein, - in driving situations in which it is likely that the driving situation t is then abandoned, the instant of the start of stopping is modified as a function of the probability of stopping, - from the setpoint time for disengaging and the time necessary for the disappearance of the torque d '' clutch, a desired and still remaining net disengagement time is calculated, - from the values of the engine torque, the engine speed, the engine speed gradient, the current clutch torque and the time of net clearings desired, a gradient is calculated by means of which the clutch clutch torque is reduced it, by means of a clutch torque or clutch position adjustment member, a prefixed slip is introduced by required when a slip is established on the clutch during stopping, when a slip is established and the brake is not activated, it is introduced by regulation, by means of the idle speed regulator traction motor, a torque by which the speed engine rotation is maintained in the area of

idle speed.

  The advantages of the invention lie in particular in the fact that by means of an adaptive in-line correction of the final opening of the traction line, it is possible to react in an exact and rapid manner to variations in behavior. dynamics of the vehicle, and this by means of a clutch opening which is more

  fast or slower in an appropriate way.

  Examples of implementation of the invention are set out below with reference to the drawings. We see: in FIG. 1, a traction line of a motor vehicle comprising an automatic clutch actuated in accordance with the invention, in FIGS. 2A and 2B, a structural graph of a program implemented in the method according to the invention , in FIG. 3, the variation over time of the clutch torque in the case of a shutdown without brake actuation, in FIG. 4, the variation in time of the engine torque during a shutdown at standstill without actuation of the brake, in FIG. 5, the variation over time of the input rotation speed of the motor and of the gearbox during a standstill without actuation of brake, in figure 6, a schemablock for the calculation of the normalized clutch release speed, in figure 7, a block diagram for the calculation of the clutch release time and, in figures 8 to 10, three graphs used to expose the how the process

  conforms to the invention exerts its action.

  A motor vehicle traction line 1 (FIG. 1) comprises - insofar as this is of importance for the present invention the following constituent elements: a motor 2, a clutch 3, a clutch actuator (usually also called adjustment member or adjustment control for the clutch) 4, a gearbox 5, a gearbox actuator 6, an electronic control 8 for the adjustment member 4 and the gearbox actuator te of speeds 6, and a motor control 9. The electronic control 8 is connected to the regulating member 4 by control and signal lines 10 and to the actuator

  of gearbox 6 by control lines and signals 11.

  The adjusting member 4 can be produced in the form of an actuator with control by electric motor or in the form of an actuator with hydraulic control. In the embodiment described here, a hydraulic adjustment member 4 is used which is connected to the clutch 3 by means of a force transmission device 12 which is for example produced in the form of a line of pressure. The electronic control 8 also contains characteristic table memories 13 which are represented diagrammatically and in which various characteristic curves are deposited serving to control the clutch 3 and the

gearbox 5.

  In the traction line 1, the gearbox 5 is presently produced structurally in the form of a manually controlled gearbox, but the gearshift operations are however executed automatically and

  the clutch 3 is actuated - by being controlled by the electronic control 8 -

  as soon as the command for a gear change operation is launched. Such a gearbox is called an automated (manual) gearbox. The process according to the invention can also be used with automatic control clutches (called EKS) for conventional manual gearboxes which are actuated as soon as the driver has grasped the gearshift lever or lever

  in order to execute a gear change.

  By means of this method, during the process of stopping the vehicle, the clutch 3 is automatically controlled in such a way that it begins to open at the exact moment and taking account of the situation, so that fluctuations in the traction line are avoided. As indicated, the final opening of the traction line is corrected in an adaptive manner online, that is to say in current operation and in real time, in order to be able to react in an adapted and rapid manner to changes in the dynamic behavior of the vehicle due to more opening

  faster or slower the clutch.

  Thanks to the process according to the invention, the problems posed by the automatic clutch controls existing up to now are avoided: the initiation or the start of the stopping process and therefore the allowed disengagement time takes place taking into account of the situation. The displacement of the clutch, which until now has been controlled as a function of the position of the clutch, is now controlled as a function of the most logical physical quantity which is the clutch torque. The non-linearity of the clutch characteristic is thus taken into account. Up to now, during the hill stop process (especially when going downhill), there has often been an intermittent opening and closing of the clutch, since no slip feedback takes place, but only The clutch is only fully open or closed. A transition from stopping to extra-slow speed and vice versa often takes place smoothly, since the target clutch torque has a zero value at stopping and a final positive value at extra-slow speed . Driving on a level surface with the idle speed controller (as well as cala is common with manual gearboxes in "stop-and-go" or "stop-and-go" situations)

  was not possible until now.

  The automatic control allows a friction clutch to be controlled in operating states such as gear changes, starts and the like. By means of the clutch, the torque of the engine of a motor vehicle is - depending on the operating state - transmitted to the gearbox or the force flow between the engine and the gearbox is interrupted. Furthermore, the clutch is controlled during transitions between the operating states, so that an adaptation of the torque takes place. During such transitions, it also happens that the clutch works with a slip, so that the total torque of the engine is not transmitted to the gearbox or that (in operation on the thrust) the

  full transmission torque is not transmitted to the engine.

  In the case of situations in which a motor vehicle must be stopped, it must be determined when the traction line must be open or when the torque which can be transmitted by the clutch must be reduced, and this up to what value, in order to get as close as possible to the driver's wish, taking into account the situation. This instant of entry or of launching, which is the shutdown, is obtained from the setpoint declutching time (also called hereinafter duration of declutching or "gross setpoint declutching time"), the engine speed, the engine speed gradient and an offset or additional safety with respect to the idle speed. From these four quantities, it is possible to calculate beforehand when it is foreseeable that the clutch should be opened, namely when the idle speed is reached

plus offset.

  The setpoint time for declutching can be determined according to the type of driver and the driving situation. The values can be deposited in characteristic tables or be determined by means of a fuzzy equation (see for example EP 0 622 570 B1). It is known to divide drivers, on the basis of various driving maneuvers, into categories ranging from drivers emphasizing comfort to drivers with sporty driving. Usually, quantities such as accelerator pedal position, accelerator pedal gradient and engine speed are used for classification. For a driver with an emphasis on comfort, a slow clutch opening and therefore a long clutch release time must be selected, and for an accentuated sporty driver, rather a rapid clutch opening and therefore

significantly shorter clutch release.

  Driving situations which modify the instant of entry into the stopping, that are for example intense braking maneuvers (for example by means of ABS, the brake assistant or the like) and, in a very general way, situations which make it very probable or less probable that the situation of cessation is then left. The instant of the start of the shutdown is then modified according to the probability each time existing. If the driving situation leads to the likelihood that the stop will be left again very soon after (information from a traffic assistance system concerning the state of the traffic lights, previous passage from red to green), entry into shutdown must be delayed even longer. If the driving situation makes it very unlikely that stopping will be quit again soon after, entry into the

  stopping is accelerated (for example during ABS braking).

  After entering the shutdown function, at a first step, the disengaging torque is reduced from the currently transmissible torque to a transmissible torque which is situated in the range of the current absolute value of the engine torque increased by a security offset. This can happen in a fast disappearing way, since in this area the clutch always keeps the line of traction closed in a safe way and also, a displacement making the subject to rapid disappearance does not cause fluctuations. From the desired gross declutching time and the time it takes to clear the torque reserve, we obtain the set net declutching time

which still remains.

  After this disappearance of the torque reserve, it is from the quantities that are the engine torque, the engine rotation speed, the engine rotation speed gradient, the current clutch torque and the net clutch release time. desired, that the gradient with which the declutching torque is reduced is calculated. As the gradient is continuously calculated again, it is possible to react even to new driving situations. In particular, in the case of a modified driving situation, the set gross declutching time and therefore also the

  Net release time can also be changed.

  If the declutching torque is reduced in this way and after a certain period of time a slip on the clutch is established (i.e. a difference in rotational speed between the motor and the drive shaft) entry of the gearbox), a prefixed slip is then introduced then by regulation using the adjusting member 4 provided for the disengaging torque or for the disengagement position. If, on the other hand, no slip is established, the engine idle regulator is then necessarily active

  and then it is then proceeded in the manner described below.

  If a slip is established, this leads to the vehicle continuing to drive in an extra-slow speed state. Then, depending on the driving situation (going up a hill or down a hill, with the brake activated or not activated), the traction motor idle regulator introduced by regulation a torque by means of which the speed of rotation of the engine is maintained in the area of idle speed. Usually when driving downhill without brake, this torque is rather small or negative and, in the case of driving uphill or when the brake is applied, these are large torque values. who appear. This introduction by regulation of a slip is in any event optional. Indeed, it is also possible to proceed next

  immediately as described in the following paragraph.

  If, in this phase, the engine torque exceeds a prefixed limit value, the clutch is fully opened in a manner which is subject to rapid disappearance, in particular in the case of brake actuation, in order to bring about with the vehicle stopped without the clutch slipping. If the frei n is not action born, the cou pie

  clutch can even be reduced to the value of the extra speed torque

  slow (the clutch is therefore not fully open), insofar as the traction line has an extra-slow speed function, and it is thus possible to achieve

  a smooth transition between the states of shutdown and extra-slow speed.

  Once the value of the extra-slow speed torque on the clutch has been reached, a

  transition to the state of extra-slow speed takes place.

  Advantageously, if driving situations which require very rapid opening of the clutch (for example ABS braking or in the case of the engine stall protection) are observed, a slip is not introduced. by equation and an increased engine torque is expected from the idle regulator, but the clutch is definitely completely open, in order to prevent stalling of the

  engine or additional engine thrust in the driving direction.

  The structural graph emerging from FIGS. 2A and 2B provides a computer program which is implemented during the method according to the invention. It includes the following steps: S1: after the start of the program, at one step S2, the gross set-off time is calculated. At a step S3, the question is asked whether or not the "shutdown" state should be activated. If the answer is no, a jump to step S1 then takes place. If the answer is yes, at a step S4, the declutching torque is then reduced until the engine torque increased by a reserve. At step S5, the set net declutching time and the declining torque gradient are calculated. At a step S6, the declutching torque is reduced in accordance with this gradient. At an S7 step, the question is asked whether or not the engine torque is too large. If the answer is no, at a step S8, the question is asked whether a slip is present or not. If the answer is no, a jump to step S5 then takes place. If the answer to question S7 is yes, at step S9, the question is then asked whether or not the vehicle brake is active. If the answer to question S8 is yes, at a step S10, a slip defined in the clutch 3 is then introduced by equation. Then, at step S11, the question is asked whether or not the engine torque is too large. If the answer is no, a jump to step S10 then takes place. If the answer is yes, a jump to question S9 takes place. If the answer to this question is yes, at a step S12, a total opening of the clutch 3 then takes place. If the answer to question S9 is no, one step away

  S13, an extra-slow speed torque is then established on the clutch.

  Both after step S12 and after step S13, the program runs to an end and a jump to step S1 takes place and therefore the start of a new

program progress.

  In the graphs of FIGS. 3 to 5, a typical sequence of a shutdown without brake actuation is shown, with different gradients of motor rotation speed (for example when passing over a flat surface to a hill drive) and with a transition which follows in an extra-slow speed drive (extra speed torque at 15 Nm). FIG. 3 shows the variation over time of the clutch torque, in FIG. 4 the variation over time of the engine torque and in FIG. 5 the variation over time of the engine rotation speed nE and of the

  input rotation speed of gearbox nGE.

  These figures show, by way of example, certain advantages of the present shutdown function in comparison with known clutch controls: the function is activated at an instant t1 in a manner adapted to the situation, more precisely in accordance with the motor rotation speed gradient. The clutch torque gradient is adapted, in the course of the course, to the engine rotation speed gradient (between times t3 and t4). After at time t4, a clutch slip has been observed, a defined slip is introduced by

  equation until the engine torque is too large (between times t4 and t5).

  Since, as assumed, the brake is not active, a torque

  extra-slow is then established and we switch to driving at extra speed.

  Only a variation of the actuation is shown here.

  automatic clutch when stopping a motor vehicle.

  A reduction in the clutch torque when switching off is carried out with the following calculation steps: 1.) The desired normalized disengagement speed (range of values [0 to 1]) is determined according to the type of driver and driving situation (winter operation, wet track, ABS brake operation, etc.), for example by means of a fuzzy system (Figure 6). An output variable "0" here denotes the slowest declutching speed and "1", correspondingly, the fastest declutching speed. Standard clutch release speeds

  any between 0 and 1 are possible.

  2.) The normalized declutching speed is converted by calculation, to give the desired declutching time, by means of a characteristic table in which are

  deposited values determined for the clutch each time considered (Figure 7).

  3.) It is decided whether or not a shutdown should be initiated.

  The "stop" function is activated if the motor speed is less than or equal to a motor speed threshold value nen9, hr, this motor speed threshold value being calculated in accordance with in equation nen9, hr = declutching time * current engine speed gradient * (- 1) + engine idle speed + speed tolerance,

then stored in memory.

  4.) The clutch torque MC is reduced to the absolute value of the current engine torque (this is generally an engine resistance torque MSM) increased

  torque offset (surcharge) OS.

  5.) Then, the clutch torque - more precisely in a cyclical manner - is calculated according to the following formula MC = (TORQUE of engine resistance + offset) * engine rotation speed / (engine rotation speed engine idle + speed tolerance) until a slip occurs and, by means of a regulator, a defined difference Dn between engine speed and gearbox speed either maintained or, on the other hand, the actual engine torque ME, which is required by the engine idling speed control located in the engine control device.

  motor, exceeds the defined threshold value.

  The two FIGS. 8 and 9 illustrate by way of example for which engine rotation speed, each time as a function of a deceleration of the vehicle and of a fixed clutch release time, the stop function is activated, to reduce the clutch torque. FIG. 8 illustrates the variation over time of the different operating variables for a slow opening of the clutch, that is to say in the case

  comfortable driving behavior.

  The input rotation speed of gearbox nGE varies in one case (A), in which the motor vehicle is greatly slowed down, for example in the case of emergency braking, with a markedly steeper slope. large than in a case (B) in which the vehicle is slightly slowed down, for example when one continues to roll by inertia before a traffic light. In the first case, the stop function begins for a first higher threshold speed value of engine speed nen9hr 'and, in the second case, for a second higher speed threshold value

  motor rotation nen9,, hr2 lower.

  - Numerical examples of the operating quantities are as follows: idling speed nN = 750,800 U / min, motor speed threshold value nen9,, hr2 = 900 min4 and nen9, hr '= 2,700 4,000 min engine thrust torque MSM = - - 50 Nm clutch torque MC = 300 Nm

offset 0S = 20 Nm.

  It can clearly be seen that, during a slow opening of the clutch (FIG. 8), there is a long disengagement time to. 'in and, during a quick opening of the clutch (Figure 9), a short duration of to.Quick declutching. A supplement or offset is added to the engine thrust torque so that, in the clutch, when approaching the start of the stop function, a slip does not occur prematurely. A time tolerance At and a rotation speed tolerance An are admissible in the context of the present method. In order to stop, the clutch torque must be reduced in good time, without causing fluctuations in the line of traction, depending on the driving situation which occurs each time, in order to prevent that the engine speed is inadvertently lowered below the engine idle speed. Otherwise, in the worst case, it could result in an engine stall. In any case, however, the engine idle speed regulator would become active with very high torque requirements and a

  unwanted jerky operation of the vehicle would occur.

  FIG. 10 shows variations by way of example of the speed of rotation of the motor nE and of the speed of entry of the gearbox nGE, as well as of the monitoring of the clutch torque Mc during comfortable shutdown according to the process

according to the invention.

Claims (10)

  1. A method of controlling an automatically actuated clutch which is located in the traction line of a motor vehicle and by means of which, each time according to the operating state, the torque of an engine is transmitted in all or part of an automated gearbox or the force flow between the engine and the gearbox is interrupted, the clutch being opened automatically when the motor vehicle is stopped, characterized in that that the instant of the start of opening of the clutch during the shutdown is determined as a function of a setpoint duration of the disengagement, of the speed of rotation of the motor, of the gradient of the speed of rotation of the engine and a speed which is formed from the engine idle speed to which is added a supplement. 2. Method according to claim 1, characterized in that after a start of stopping, the clutch torque is reduced from the currently transmissible torque to a transmissible torque which is located in the region of the current absolute value of the   engine torque increased by additional safety.   3. Method according to claim 1, characterized in that the desired duration of the declutching is determined as a function of the type of driver each time considered and   the driving situation of the motor vehicle.   4. Method according to claim 3, characterized in that the type of driver and the driving situation are determined, by means of fuzzy logic, using values for measuring the accelerator pedal position, the gradient of   accelerator pedal and engine speed.   5. Method according to claim 3, characterized in that the type of driver and the driving situation are deposited in characteristic tables and are read in them.   6. Method according to claim 1, characterized in that, in driving situations in which it is likely that the stopping situation will then be abandoned, the instant of the start of stopping is modified in function of the probability of shutdown.   7. Method according to claim 6, characterized in that from the setpoint duration of the declutching and the time necessary for the disappearance of the torque   clutch, a desired and still remaining net clutch release time is calculated.   8. Method according to claim 7, characterized in that from the values of the engine torque, the engine speed, the engine speed gradient, the current clutch torque and the net clutch release time   desired, a gradient is calculated by which the clutch torque is reduced.   9. Method according to claim 1, characterized in that by means of a member for adjusting the clutch torque or the clutch position, a prefixed slip is introduced by regulation when a slip is established on   the clutch during shutdown.   10. Method according to claim 1, characterized in that, when a slip is established and that the brake is not activated, it is introduced by equation, by means of the idle regulator of the traction motor, a torque at means by which the rotational speed of the motor is maintained in the range of rotational speed idle. :::,: