DE10209086C1 - Method for controlling an automatically actuated clutch - Google Patents

Abstract

Controlled is a clutch in the drive train of a motor vehicle, with the torque of an engine completely or partially transmitted to an automated transmission or the power flow between the engine and the transmission is interrupted. The clutch is automatically opened upon stopping the motor vehicle, wherein the time of the start of the stopping process depending on a target duration of the disengaging, the engine speed, the gradient of the engine speed and a supplement to the idle speed of the engine is determined.

Description

The invention relates to a method according to the preamble of Claim 1. This method is used to control a automa table actuated clutch in the drive train of a force vehicle, with the depending on the operating condition, the torque ei completely or partially to an automated engine Transmission transmitted or the power flow between the engine and the transmission is interrupted, the clutch at Stop the motor vehicle is automatically opened.

In a device for controlling the automatic sierten clutch transferable torque in the drive train a motor vehicle with an engine and a transmission that with a switching element for selecting the gear ratio and with a sensor for detecting this translation verse hen is (DE 198 23 766 A1), the engine provides a controllable Motor torque available. A control unit for an actuator for adjusting the torque transmissible by the clutch Tes controls the transmissible by the clutch torque in Depending on the upcoming engine torque, the Kupp moment of inertia within a predefinable tolerance band around the Pending engine torque is controlled and the tolerance band depends on the gear ratio.

Automated manual transmissions (see for example VDI-Berich te 1610, 19.-20. June 2001, pp. 83-99) have several advantages on how small additional costs compared to manual switching driven, significantly reduced costs compared to automatic drove, reduced fuel consumption and moreover the known advantages of all automatic transmissions, like the Relief of the driver in traffic. A significant one Aspect hereby represents the automatic control of the clutch dar. In addition to the operation of the clutch when starting and when It is also important to switch the powertrain when connecting  to disconnect the vehicle smoothly, in particular to prevent the engine from stalling. A complete On the other hand, separating should take place as late as possible point in order to re-accelerate if necessary of the vehicle then the inevitable engagement process, the usually with a more or less noticeable jerk and a time delay is connected, as possible to get around.

From the document DE 198 23 764 A1 is a method for Controlling an automatically operated clutch in the on drivetrain of a motor vehicle known in which the An holding operation of the motor vehicle, the clutch ge automatically opens. The opening of the clutch is off the engine speed, the gradient of the engine speed and a Speed, which consists of the idle speed of the engine plus one Supplement is formed, calculated.

The invention has for its object to provide a method for To provide control of an automatically actuated clutch when opening the clutch when stopping the force On the one hand Begon timely and appropriate to the situation NEN, thereby avoiding vibrations in the drive train to become. On the other hand, the final opening of the on drivetrain adaptively adapted to the current driving situation be fit.

The object of the invention is achieved by a method with the Characteristics of claim 1 solved. In the method, the Time of the beginning of the stopping process depends on one Set time of disengaging, the engine speed, the gradient the engine speed and an offset to the idle speed determined the engine. Expedient developments of the inventions tion are laid down in the subclaims.

The advantages of the invention are in particular that through an online adaptive correction of the final opening  of the powertrain on changes in vehicle dynamics rich tig and can be reacted quickly, and by corre faster or slower opening of the clutch.

Embodiments of the invention will be described below explained the drawings. Show it:

Figure 1 shows a motor vehicle drive with a according to the inven tion actuated automatic clutch.

Fig. 2a + 2b is a structure chart of a program executed in the inventive method program;

Fig. 3 shows the time course of the clutch torque in egg nem stopping operation without brake operation;

FIG. 4 shows the time course of the engine torque at a stopping operation without brake actuation;

Figure 5 shows the time course of the engine and the transmission input speed at a stop without brake operation.

Fig. 6 is a block diagram for calculating the normalized disengaging speed;

Fig. 7 is a block diagram for calculating the Auskuppel time, and

Fig. 8 to 10 three diagrams for explaining the effect of the method according to the invention.

A motor vehicle drive 1 ( Fig. 1) has - as far as it is relevant to the present invention - following Be constituents: a motor 2 , a clutch 3 , a clutch actuator (commonly referred to as an actuator or actuator for the clutch) 4 , a Schaltge gear 5 , a transmission actuator 6 , an electronic Steue tion 8 for the actuator 4 and the transmission actuator 6 and a motor controller. 9 The electronic controller 8 is connected to the actuator 4 through control and signal lines 10 and to the transmission actuator 6 through control and signal lines 11 .

The actuator 4 may be formed as an electric motor driven or as a hydraulically driven actuator. In the embodiment described here, a hydraulic actuator 4 is used, which is connected to the clutch 3 by a power transmission arrangement 12, which is formed for example as a pressure line. The electronic control 8 also contains map memory 13 shown schematically, in which various characteristics for controlling the clutch 3 and the gearbox 5 are stored.

In the motor vehicle drive 1 in this case the Schaltge gear 5 is constructively designed as a manual transmission, but the switching operations are performed automatically and the clutch 3 is - controls ge by the electronic control 8 - operated as soon as the controller initiates a switching operation. Such a transmission is referred to as an automated (manual) manual transmission. The procedural ren invention can also be used with automatically controlled clutches (referred to as EKS) for conventional manual transmissions, which are operated as soon as the driver engages the shift lever to perform a gear change.

By this method, the clutch 3 is automatically controlled when stopping the vehicle so that it is begun in a timely manner and commensurate with the situation, thereby avoiding vibrations in the drive train. The final opening of the powertrain, as he mentions, is corrected online-adaptively, ie during operation and in real time, in order to be able to react quickly and more quickly to changes in the vehicle dynamics by opening the hitch faster or slower.

With the method according to the invention problems are hitherto ger automatic clutch controls avoided: the on occurs or start of the stopping process and thus the permitted Disengaging time is more appropriate to the situation. The move the clutch, so far dependent on the coupling position is controlled, now depends on the physically meaningful fuller size clutch torque controlled. This will be the Nonlinearities of the coupling characteristic invoice getra When stopping on the mountain (especially downhill) comes it has often been an intermittent opening and Closing the coupling, as no slip is regulated, but the clutch only fully open or closed becomes. A transition from stopping to crawling and vice versa often done rudely, since the target clutch torque at An  hold the value zero and when crawling a finite posi tive value. Driving in the plane with the empty tiller (as with manual transmissions in stop-and-go Situations is common) has not been possible.

The automatic control becomes a friction clutch in operating states such as switching, starting and the like controlled. With the coupling - depending on the operating condition - the torque of the engine of a motor vehicle to the Ge transmission or the power flow between the engine and interrupted the transmission. In addition, the clutch is at Controlled transitions between the operating states, where a torque adjustment takes place. At such transitions it also happens that the clutch works with slippage, So not the full torque of the engine to the transmission or (in overrun) the transmission transmits to the engine.

In situations where a motor vehicle should stop, is to determine when the powertrain will be opened should or when the transferable by the clutch torque which value must be reduced to the wish of the Fah to come as close as possible to the situation. This one The time of arrest is determined by the set duration of the Auskuppelns (hereinafter also desired duration of Auskup pelns or "target gross Auskuppelzeit" called), the engine speed, the engine speed gradient and an offset or Safety supplement to the idle speed. From these Four sizes can be calculated in advance, when advance obviously the clutch must be open, namely at He range of idle speed plus offset.

The set duration of disengagement can depend on the Driver type and driving situation. The values can be stored in maps or with the help of fuzzy Rules are determined (see, for example, EP 0 622 570 B1). It is known, a driver based on different Fahrmanö to divide into categories ranging from comfort to sport  Lich. Usually, these are sizes such as accelerator pedal ment, accelerator pedal gradient and engine speed for classification used. For a comfort-stressed driver is a long Open the clutch and thus a long disengaging time to choose for a stressed sporting driver rather quick opening of the clutch and thus significantly shorter off dome times.

Driving situations that change the entry point into stopping For example, strong braking maneuvers (such as through ABS, Bremsassistent or the like), and more generally Situati ones, which then leave the arrest situation make it more likely or less likely. Of the Time of the beginning of the stopping process then becomes dependent changed by the respective probability. Lead the Driving situation to that it is likely that very a short time later, the stopping process is left again (Information from a traffic control system via traffic lights stand, impending change from red to green), is the To postpone entry into stopping even longer. Lead the Driving situation to the fact that it is very unlikely that a short time later the stopping process is left again, the entry into stopping is accelerated (for example at an ABS braking).

After entering the stopping function is in a first Step the clutch torque from the currently transmittable Moment reduced to a transmittable moment in the Be rich of the current absolute value of the engine torque plus a security offset. This can happen quickly, since the clutch in this area always with the safety driveline keeps closed and thus a speedy Ver Do not push any vibrations. From the desired breed to-disengage time and the time that is necessary, the momen reserve, the remaining balance will be Target net Auskuppelzeit.  

After this reduction of torque reserve will be out of the sizes Engine torque, engine speed, engine speed gradient, current Clutch torque and desired net disengaging time of Gra is calculated, with which the clutch torque is reduced. As the gradient is constantly recalculated, it can also be up new driving situations are responding. In particular, can be If the driving situation is changed, the target gross Auskup time and thus also the net disengaging time.

If the clutch torque is reduced in this way and turns after a certain time slip on the hitch be (that is, a speed difference between the engine and the transmission input shaft), then with the actuator 4 for the clutch torque or the clutch position a predetermined slip adjusted. If, on the other hand, there is no slippage, the idle speed controller of the motor will inevitably become active and continue as described below.

If a slip occurs, this leads to the fact that the Vehicle continues in a crawling state. Now it will depending on the driving situation (uphill or downhill, brake activated or not activated) the idle controller of the drive motor adjust a torque with which the engine speed in Be rich idle speed is maintained. Usually will This torque at downhill without brake rather small or be negative when driving uphill or when braking who the large moment values occur. This is an adjustment of one Slip is, however, optional. It can be like that continue as described in the next section become.

If the engine torque exceeds one in this phase given limit, so the coupling is especially at Brake lever swiftly fully open to the vehicle without stopping a grinding of the coupling. If the brake is not actuated, then the clutch torque  also reduced to the value of the creep torque of the engine (the clutch so not fully open) - so the powertrain has a creep function - and thus a smooth transition between the states Anhal and creeping be realized. After reaching the value the creep torque at the clutch is in the state of war passed over.

If driving situations are recognized, the very fast opening require the clutch (for example, an ABS brake or in engine stalling protection), so will not expediently a slip be adjusted and on a raised Motormo ment of the idle controller waited, but it will be the Kupp definitely open completely to a stalling of the Mo sector or an additional thrust of the engine in driving line to prevent it.

The structural diagram shown in FIGS . 2A and 2B represents a computer program which is executed in the method according to the invention. It has the following steps:
S1 After the start of the program will be in one step
S2 calculates the target gross disengaging time. In one step
S3 is queried as to whether the "halt" state should be activated. If the answer is no, the system returns to step S1. If the answer is yes, it will be in one step
S4 reduces the clutch torque to the engine torque plus a reserve. In one step
S5, the target net Auskuppelzeit and the Kupplungsmomen tengradient is calculated. In one step
S6, the clutch torque is reduced according to this Gradien th. In one step
S7 is queried as to whether the engine torque is too high. If the answer is no, it will be in one step
S8 queried if there is slippage. If the answer is no, a return to step S5 occurs. If the answer to the query S7 is yes, then it will be in one step
S9 queried whether the vehicle brake is active. If the answer to the query S8 is yes, then it will be in one step
S10 a defined slip in the clutch 3 regulated. After that, in one step
S11 queried whether the engine torque is too large. If the answer is no, a return to step S10 occurs. If the answer is yes, then a jump to the question S9. If the answer to this query is yes, it follows in one step
S12 a complete opening of the clutch 3rd If the answer to query S9 is no, then it will be in one step
S13 on the clutch set a creep torque. Both after step S12 and after step S13, a program pass is on its
At the end of the process, a return to step S1 occurs and thus a start of a new program run.

In the diagrams of Figs. 3 to 5 is a typical from running a stop operation without brake, with ver different engine speed gradients (for example, in a transition from a plane to an uphill) and with a final transition to a crawl (creep torque 15 Nm) shown , In this case, from Fig. 3, the time Ver run of the clutch torque, from Fig. 4, the time course of the engine torque and from Fig. 5, the time course of the engine speed n _E and the transmission input speed n _GE can be seen.

These figures show some advantages of the example lying stop function over the known clutch controls: the function will be at a time t1 situa Activation enabled, according to the engine  speed gradient. The clutch torque gradient is in further course adapted to the engine speed gradient (between times t3 and t4). After that time t4 clutch slip is detected, as long as a defi adjusted slip until the engine torque is too high is (between times t4 and t5). As predicted If no brake is active, then a creep torque will occur set and it is changed into a crawl.

Shown here is just an exemplary course of the car matic clutch operation in a stop operation of a Motor vehicle.

A reduction of the clutch torque during stopping is carried out with the following calculation steps:

• 1. The desired normalized Auskuppelgeschwindigkeit (range of values [0 to 1]) depending on the driver type and the driving situation (winter operation, wet road, ABS braking maneuvers, etc.) - for example, with a fuzzy system - determined ( Fig. 6) , An output "0" denotes the slowest disengaging speed and "1" corresponding to the fastest disengaging speed. There are any normal Auskuppelgeschwindigkeiten between 0 and 1 possible.
• 2. The normalized decoupling speed is converted into the desired decoupling time using a characteristic map in which values determined for the respective clutch are stored ( FIG. 7).
• 3. It is decided whether a stopping process should be initiated.
  The Stop function is activated when the current engine speed is less than or equal to an engine speed threshold n _{eng, thr} , where this engine speed threshold is determined by the equation
  n _{eng, thr} = disengaging time. current engine speed gradients (- 1) + engine idling speed + speed tolerance
  calculated and then saved.
• 4. The clutch torque M _C is reduced to the amount of the current engine torque (this is usually a motor drag torque M _SM ) plus a torque offset (or supplement) OS.
• 5. Subsequently, the clutch torque is calculated - cyclically repeated - according to the following formula
  M _C = (engine drag torque + offset). Engine speed / (idle engine speed + speed tolerance)
  until either
  Slip occurs and is maintained with a controller a defined difference Dn between engine and transmission speed
  or but
  the current engine torque M _E , which is requested by the engine idle speed controller in the engine control unit, the defined threshold is exceeded tet.

The two FIGS. 8 and 9 illustrate by way of example at which engine speeds, depending on the vehicle deceleration and before the decoupling time, the stopping function is activated in order to reduce the clutch torque. From Fig. 8 the time course of the different operating variables at a slow opening of the clutch, that is, in a com fortable driving behavior, can be seen.

The transmission input speed n _GE runs in a case (A) in which the motor vehicle is greatly decelerated, for example, in emergency braking, significantly steeper than in a case (B), in which the motor vehicle is slightly delayed, for example, when Auslauflassen before Traffic light. In the first case, the stopping function starts at a first, higher engine speed _threshold n _{narrow, thr1} , in the latter case at a second, lower engine speed _threshold n _{eng, thr2} .

Numerical examples for the farm sizes are:
Idling speed: n _N = 750. , , 800 rpm,
Engine speed thresholds: n _{tight, thr2} = 900 min ^-1 and n _{tight, thr1} = 2.700. , , 4,000 min ^-1
Engine drag torque: M _SM = -30. , , -50 Nm
Clutch torque: M _C = 300 Nm
Offset: OS = 20 Nm

It can clearly be seen that, with slow opening of the clutch ( FIG. 8), a long disengaging time t _{0, slow} and with rapid opening of the clutch ( FIG. 9) results in a short disengaging time t _{0, almost} . To the engine drag torque is added to an impact or offset, so that in the clutch approaching at the beginning of the stop function does not prematurely slip occurs. Within the scope of the present method, a time tolerance Δt and a speed tolerance Δn are permissible.

Purpose of the stopping process is the clutch torque without Excitation of driveline vibrations depending on the driving situation reduce in time to prevent the engine speed unintentionally ge under the engine idle speed is pressed. Otherwise, at worst, a stalling of the Motors be the result. In any case, the engine would idling speed controller with very high torque requirements become active and cause unwanted Fahrzeugruckeln.  

Exemplary curves of the engine speed n _E and the Ge input input speed n _GE and the leadership of the clutch torque M _C in a comfortable stopping process according to the method of the invention are shown in Fig. 10 ersicht Lich.

Claims (10)

1. A method for controlling an automatically actuated hitch be in the drive train of a motor vehicle, with the depending on the operating state, the torque of an engine completely or partially transferred to an automated transmission o the force flow between the engine and the transmission is interrupted, the clutch is automatically opened during the stopping process of the motor vehicle, characterized in that the timing of the opening of the clutch at Anhaltevor gear depends on a target duration of the disengaging, the engine speed, the gradient of the engine speed and a speed gebil det of idle speed of the engine with a surcharge is, is determined. 2. The method according to claim 1, characterized in that after a start of the stopping process, the clutch torque of the currently transmittable moment to a transmissible moment is reduced in the range of the current absolute value of the engine torque plus a security surcharge. 3. The method according to claim 1, characterized in that the desired duration of disengagement depending on the jewei liger driver type and the driving situation of the motor vehicle be is true. 4. The method according to claim 3, characterized in that the driver type and the driving situation with a fuzzy logic system based on measured values of the accelerator pedal position, the driving pedal gradients and the engine speed are determined. 5. The method according to claim 3, characterized in that the driver type and the driving situation stored in maps are and are read out by them.   6. The method according to claim 1, characterized in that in Driving situations in which a subsequent leaving the Stopping situation is likely, the time of loading ginns of the stopping process depending on the probability of stopping is changed. 7. The method according to claim 6, characterized in that from the set duration of the disengagement and the time to the Ab Building the clutch torque is required, one more remaining desired net declutching time is calculated. 8. The method according to claim 7, characterized in that from the values of the engine torque, the engine speed, the Mo speed gradient, the current clutch torque and the desired net decoupling time a gradient is calculated, with which the clutch torque is reduced. 9. The method according to claim 1, characterized in that with an actuator for the clutch torque or the Kupp a predetermined slip is adjusted, if Slip on the clutch during the stopping process provides. 10. The method according to claim 1, characterized in that if a slip occurs and the brake is not activated fourth, with the idle controller of the drive motor on Torque is adjusted, with the engine speed in Be rich idle speed is maintained.