DE19925664C2 - Arrangement for actuating a motor vehicle friction clutch - Google Patents

Description

The invention is concerned with the control of an automated motor vehicle Stuff friction clutch when starting the vehicle after the Oberbe handle of claim 1.

When starting, it is known to control the clutch so that one before given start-up target engine speed reached and held for as long until the gearbox input speed becomes equal to the engine speed and there is no slip on the clutch. To do this achieve, DE 41 34 669 C2 discloses a pure speed control of the Engine speed. The actual value of the engine speed and the target value become determines a speed difference on the basis of which a differential speed controller Control signal generated that the clutch in the sense of a reduction of this Speed difference. Overspeed of engine speed over the target Speed is also inevitable with this type of clutch control. In particular, a comparatively occurs at the start of the starting process strong overshoot of the engine speed when the engine from the Idling runs up. The control algorithm causes a rapid onset accelerating, comparatively strong acceleration of the vehicle with a brief acceleration increase. This is for sporty drivers Acceleration process acceptable. You will also see the vibrations of the Take the drivetrain into account due to the powerful and slightly jerky Acceleration are stimulated. If a smooth, comfortable start is desired without noticeable excitation of drive train vibrations, the known control algorithm is not suitable, however.

An arrangement for controlling a motor vehicle friction clutch according to the preamble of claim 1 is from DE 196 52 051 A1  known. This document discloses an arrangement or a front way in which a clutch target torque, which ultimately is to be equated with the clutch output torque, as a function the present engine torque and as a function of Engine speed is determined. The clutch output torque determined as the sum of the engine torque and the difference between the actual speed and the target speed, multiplied by one positive constant factor. The target speed is that motor speed that the clutch should reach in the slip-free state and ultimately corresponds to the target engine speed. From the default of this Sizes result in the difference between the actual speed and the target speed is a negative value because in the slip mode and at Starting the vehicle in any case, the actual speed is less than that Set speed. It is therefore a function for the Kupp in this publication target torque set in a linear manner from the rotation number difference between the actual and target speed depends and in this respect linear depends on the actual speed. The closer the actual speed to the target speed is approached, the smaller the factor with a negative sign and the closer the target clutch torque is to the engine torque introduced. When a speed difference between actual and The target speed of 0 is ultimately the target clutch torque at the Engine torque.

Furthermore, EP 0 212 900 B1 describes an arrangement for controlling a specified electromagnetic clutch in a vehicle where just if depending on the difference between the actual engine speed and the target engine speed, the target clutch torque by a linear rule link is regulated so that it decreases with decreasing speed difference approximates the engine torque and this at a speed difference of Finally reached zero.

The object of the invention is an arrangement for actuating a motor vehicle friction clutch  Provide a comfortable, jerk-free Starting allowed.

To achieve this object, an arrangement for Actuation of a motor vehicle friction clutch when starting a Motor vehicle provided according to claim 1.

In the invention, the target for the engine speed and their Actual value a necessary represented by the speed increase target signal total increase in engine speed determined. This is already happening at the start of the start-up process and is preferably repeated continuously, until the engine speed has reached its target value. From the speed The tax determines the increase target signal and the engine torque signal set up the time course of an excess that the engine torque compared to the transmitted clutch torque. the is based on the knowledge that for an increase in engine speed by a given value a certain time integral of the difference between engine torque and clutch torque is required. Even more the engine speed should be increased, the greater the required Integral of this excess engine torque. The control device provides the  Release positioning drive according to the requirements for the Torque integral determined time function of the target engine torque shot until finally the clutch torque is equal to the engine torque is. This procedure prevents overshoot of the engine speed the target speed and allows a smooth, no cant Increase in clutch torque. This is a comfortable approach without jerky acceleration phases and the associated Powertrain vibrations possible.

The target speed setting device can have the position of a Engine power setting device, in particular an accelerator pedal, Detect the power setting sensor and the engine target speed depending on the position of the engine power setting device pretend. The driver can do this by changing the accelerator pedal position Influence the target engine speed. But it’s not out of the question a fixed value or a fixed time course for the motor target specify speed that can not be influenced by the driver.

The torque integral required to reach the target speed can be in any time course of the nominal engine torque surplus be implemented. A preferred solution is that the Control device the time course of the engine torque target excess based on an at least periodically linear increase in the Output torque of the clutch determined. A linear increase in Torque transmitted via the clutch leads to a particularly comfortable starting feel. If that happens during the start-up process Engine torque provided by the engine and / or the target speed can change, an adjustment of the time course of the engine torque Target surplus may be required. In such a case, a result in a polygonal characteristic of the clutch torque, the gradient of which in different periods is different.  

It cannot be excluded that the control signal release position actually effected deviates from that position, which the releaser would have to take in order for the desired moments sets the difference between the engine torque and the clutch torque. The reason for this can be, for example, changes in the position of the release be caused by thermal influences on the release positioning drive or occur due to leakage effects in the release positioning drive and remain unnoticed. Such deviations can lead to the Motor target speed is missed. To counteract this is preferred a differential speed control loop is provided, which is based on the actual engine speed a calculated and continuously updated time-varying Current setpoint adjusted. Accordingly, a further development of the Invention before that the control device depending on the engine torque Target excess a time-dependent changing of the current setpoint for the Input speed determined and one of the speed difference between the Input speed and the difference corresponding to their current setpoint speed signal generated and that a differential speed control device is provided, depending on the differential speed signal Release positioning drive in the sense of a reduction in the speed differences limit-setting control correction signal generated.

A moment of difference between the input side and the output side of the Coupling leads to an increase in engine speed that can be determined by formula per unit of time. From this time-related increase in engine speed, the instantaneous setpoint desired at the respective time without further ado determine the engine speed. The control correction signal, which from the Differential speed control device when there is a difference between the current setpoint of the input speed and its actual value is superimposed on the control signal and causes an adjustment the actual value of the input speed at the (changing over time) Currently set value.  

An overshoot-free, asymptotic, exact setting of the actual value the input speed to the current setpoint and thus an exact Adjustment of the friction clutch to the desired engine torque Target excess is possible if the differential speed control device an integrating controller, in particular a proportional-integral Includes differential controller that generates the control correction signal. The differentiating part of the controller enables a quick response behavior of the differential speed control device, the big differences between the actual value of the input speed and its instantaneous setpoint does not let arise.

In the following the invention with reference to the accompanying drawings explained. They represent:

Fig. 1 is a schematic block diagram of an arrangement according to the invention for actuating a motor vehicle friction clutch and

FIG. 2 shows a characteristic diagram of various sizes that occur in the arrangement shown in FIG. 1.

Fig. 1 shows a arranged between an engine 1 and a transmission 3 of a motor vehicle automated friction clutch 5, the input means of a positioning and 7 can be disengaged. The transmission 3 can be a manually shiftable transmission, but also an automated manual transmission. The positioning drive 7 sets the disengagement of the clutch 5 ( not shown in more detail) to a position which is predetermined when changing the gears of the transmission 3 by a clutch control 9 according to a predetermined program. When starting the vehicle, a starting control, generally designated 11, takes over the guidance of the positioning drive 7 .

The power of the internal combustion engine 1 is controlled by a power setting member 13 , for example a throttle valve or an injection pump, by means of an accelerator pedal 15 , the deflection angle α of which is detected by an accelerator pedal sensor 17 . An actuator 19 controls the power actuator 13 in accordance with the detected by the accelerator sensor 17 deflection angle α.

For a comfortable start, the clutch torque transmitted by the clutch 5 should increase as evenly as possible and without overshoot so that the vehicle accelerates smoothly. When starting, the start control 11 supplies a position control signal S to the positioning drive 7 , which defines the release position of the clutch 5 in the sense of the requirements mentioned. The position control signal S is generated based on a calculated engine speed curve, which depends on a target engine speed n _Z specified as the starting target and the engine torque M _M provided by the engine 1 and enables a harmonious acceleration curve.

The target engine speed n _Z is generated by a target speed setting device 21 as a function of the deflection angle α of the accelerator pedal 15 . The dependency of the engine target speed n _Z on the deflection angle α is given by a characteristic curve 23 , which can be linear or non-linear, which is defined in the target speed setting device. A subtraction device 25 forms the difference between the target engine speed n _Z and the input speed n _{M of} the clutch 5 , which is detected by means of an engine speed sensor 27 . The difference Δn _Z thus formed indicates the amount by which the input speed of the clutch 5 must be increased so that it becomes equal to the engine target speed n _Z.

As long as the engine torque M _M available on the clutch input side is greater than the clutch torque M _K available on the clutch output side, the engine 1 can accelerate relative to the clutch output side. The time-related increase in engine speed depends proportionally on the size of the excess of the engine torque M _M compared to the clutch torque M _K. For the desired speed increase Δn _Z , a certain value of the excess torque M _M - M _K accumulated over time is accordingly required. The latter value corresponds to the area enclosed between the time characteristic of the engine torque M _M and the time characteristic of the clutch torque M _K , that is to say the time integral of the excess torque M _M - M _K. A control device 29 determines the value of this torque integral required for the desired speed increase Δn _Z , which in FIG. 1 corresponds to the hatched area A in the functional block representing the control device 29 .

The assignment between the speed increase Δn _Z and the torque inte gral A can be stored in a table in the storage device 29 . However, it is also possible to currently calculate the torque integral A using a formula stored in the control device 29 . Based on the torque integral A determined in this way and the engine torque M _M provided by the engine 1, the control device 29 determines a time function for the clutch torque M _K that realizes the torque integral A. In particular, the control device 29 determines the characteristic curve for the clutch torque M _K on the basis of the requirement that the clutch torque M _K should increase linearly for a given pair of values of Δn _Z and M _M. Other time profiles of the clutch torque M _K are also conceivable. However, a linear course of the clutch torque M _K is favorable in terms of the computing effort and also ensures a harmonious acceleration of the vehicle.

If at least one of the values of Δn _Z and M _M changes during the starting process, for example because the driver steps on the accelerator pedal 15 more and both a larger deflection angle α and an increased engine torque M _M occur, the control device 29 determines on the basis of the current one Values of Δn _Z and M _M an updated value for the required integral of the excess torque M _M - M _K. This updated value of the torque integral can an adjustment of the _K M - render characteristic required, the control device 29 then from the update time moment a different gradient for the clutch M _K sets. A polygonal characteristic of the clutch torque M _K can thus result over the entire starting process.

In accordance with the time-dependent difference between the engine torque M _M and the clutch torque M _K determined in the above manner, the control device 29 generates an actuating control signal S _O which forms the main component of the position actuating signal S. The control signal S _O effects a setting of the clutch release corresponding to the desired excess torque. The relationship between the Ausrückerposition and the coupling state of the clutch 5, in particular the percentage of power transmitted by it to the torque M _K input side torque M _M, has been determined in advance for this purpose and stored in the control device 29th

The control device 29 receives the engine torque M _M , for example, from an engine control unit 30 that controls the operation of the internal combustion engine 1 . It is also conceivable to use the deflection angle α of the accelerator pedal 15 as a measure of the torque M _M provided by the engine 1 .

Deviations of the portion of the engine torque M _M actually transmitted via the clutch 5 from the percentage specified by the control device 29 can occur. This can lead to restrictions on starting comfort. To eliminate such deviations, a differential speed controller 31 is therefore provided, by means of which the engine speed n _{M is} adjusted to an instantaneously desired value n _target that changes as a function of time. The latter is supplied by the control device 29 by determining, based on the actual value of the engine speed n _M (the idling speed) measured at the start of the starting process, a target curve profile for the engine speed, which is determined by the excess torque M. Available for accelerating the engine _M - M _{K should} result. Another subtraction device 33 forms the difference .DELTA.n between the actual value of the engine speed n _M and the instantaneous target value n _target . The controller 31 operates so that this speed difference Δn becomes zero. For this purpose, it provides an actuating correction signal S _K which is superimposed on the actuating control signal S _O supplied by the control device 29 by means of a summation device 35 . Depending on the amount and the sign of the speed difference Δn, the actuating correction signal S _K corrects the release position brought about by the actuating control signal S _O. If, for example, the engine speed n _{M is} greater than its current setpoint n _target at a given time, the controller 31 generates the actuating correction signal S _K so that the clutch 5 is more engaged and a larger clutch torque M _{K is} transmitted. The reverse applies if the engine speed n _{M is} less than its current setpoint n _set . The controller 31 is preferably a PID controller.

FIG. 2 shows typical characteristics of the engine torque M _M , the clutch torque M _K , the target speed n _Z , the engine speed n _M and the transmission speed n _G that can be measured on the clutch side. When the driver depresses the accelerator pedal 15 , the target speed n _{Z increases} from a value n ₀ (the idling speed) to a value n ₂ proportional to the deflection angle α. At time t ₁ , the driver has reached the accelerator pedal position he desires; the target speed n _Z therefore remains unchanged from time t ₁ . Analog to the target speed n _Z , the engine torque M _M provided by the engine 1 increases in proportion to the accelerator pedal deflection from 0 to the value M ₁ . From time t ₁ it is idealized to be constant.

At a time t ₂ , the clutch torque M _{K reaches} the value M ₁ and becomes equal to the engine torque M _M. In the period between t ₁ and t ₂ , both the engine torque and the target speed are constant. The engine speed has the time t ₁ the value of n. ₁ An increase in speed by the value n ₂ - n ₁ is therefore necessary up to the target speed. For this speed increase, an integral of the excess torque of the engine torque compared to the clutch torque represented by the hatched area B is necessary. At time t ₁ , the clutch torque is M ₂ . Based on the requirement for a linear increase in the clutch torque , the curve of the clutch torque M _K shown in FIG. 2 then results from the time t ₁ . At a point P, the clutch torque characteristic meets the engine torque characteristic.

Let us now consider the case that the engine 1 only provides an engine torque with the lower value M ₃ from the time t ₁ , but from this time an increase in the engine speed by n ₂ -n _{1 is still} required. The integral of the excess torque required for this speed increase would then correspond unchanged to the area B. Due to the smaller engine torque, however, a different course of the clutch torque would result, which is represented in FIG. 2 by the characteristic curve M _K '. This would meet the engine torque characteristic at a point P '. The point P 'is reached at a time t ₃ and is therefore later than the point P.

Depending on the available engine torque and the required speed increase, the clutch torque characteristic curve varies from case to case. The gradient of the clutch torque characteristic curve influences the increase in the transmission speed n _G and thus the acceleration behavior of the vehicle. It can be seen that a linear Ver the clutch torque leads to a uniform acceleration, which the driver perceives as harmonious and comfortable.

In practice, the target speed and engine torque will not be constant over the entire start-up process. As already mentioned, changes in the target speed and the engine torque already occur at the start of the start-up process when the driver depresses the accelerator pedal more and more. Such changes can be taken into account by integrally recalculating the required excess torques cyclically on the basis of the respective instantaneous values of the engine speed and the target speed and - if necessary - modifying the course of the clutch torque characteristic. In practice, this will result in the clutch torque not increasing linearly over the entire starting process, but following a polygonal characteristic. In FIG. 2 clearly shows the character of the polygonal curve M _K, by the time variability of the target speed and the engine torque before the time t is caused. ₁ The update cycle can be in the range of a few milliseconds, for example approximately 10 ms.

Using the above algorithm, the coupling is from the beginning of the Start-up procedure always set so that on the input side of the Coupling available excess torque just enough to power the engine smoothly bring the speed up to the target speed. The excess moment is always kept so low that overshoot of the engine speed over the target speed can be avoided.

It goes without saying that the algorithm is not just for coupling actuation when starting, but also - modified or supplemented if necessary - to engage the clutch after a gear change.

Claims (6)

1. Arrangement for actuating a motor vehicle friction clutch ( 5 ) when starting the vehicle, the disengaging means of a disengaging positioning drive ( 7 ) from a disengaging position in which the clutch ( 5 ) is completely disengaged into a range of engaging positions, in which torque transmission via the clutch ( 5 ) is made possible, can be positioned, comprising:
an engine speed sensor ( 27 ) which detects the input speed (n _M ) of the clutch ( 5 ),
a target speed setting device ( 21 ) which specifies a motor target speed (n _z ),
a subtraction device ( 25 ) which generates a speed increase target signal (Δn _z ) corresponding to the difference between the target engine speed (n _z ) and the input speed (n _M ),
an engine torque determining device ( 30 ) which delivers an engine torque signal (M _M ) representative of the input torque of the clutch ( 5 ), and
a control device ( 29 ) which determines an output torque (M _K ) of the clutch ( 5 ) as a function of the speed increase target signal (Δn _z ) and the engine torque signal (M _M ) and, based on this, drives the release positioner ( 7 ) generating control signal (S _O ) generated,
characterized in that the control device ( 29 ) is formed from:

• a) based on the speed increase target signal (Δn _z ) to determine an engine torque setpoint integral value (A, B) which is the summed up time difference between the engine torque (M _M ) and the output torque (M _K ) of the clutch ( 5 ) which is required to raise the input speed (n _M ) of the clutch ( 5 ) to the target engine speed (n _z ),
• b) to determine the time profile for the output torque (M _K ) of the clutch ( 5 ) based on the engine torque signal (M _M ) and the engine torque target excess integral value (A, B).

2. Arrangement according to claim 1, characterized in that the target speed setting device ( 21 ) on one of the position (α) of an engine power setting device ( 15 ), such as an accelerator pedal, detecting power setting sensor ( 17 ) and the engine target speed (n _z ) depending on the position (α) of the motor power setting device ( 15 ). 3. Arrangement according to claim 1 or 2, characterized in that the control device ( 29 ) determines the time course of the engine torque target excess on the basis of an at least periodically linear increase in the output torque (M _K ) of the clutch ( 5 ). 4. An arrangement according to one of claims 1 to 3, characterized in that the control means (29) from the motor torque target excess a time-dependently changing momen tan target value _(target n) for the input speed (n _M) is determined and a depending _(to n) of the speed difference between the input speed (n _M) and the current desired value corresponding to the differential speed signal (an) is generated and in that a differential speed-regulating device is provided (31) which depends on the differential speed signal (an) a the releaser-positioning drive ( 7 ) in the sense of a reduction in the speed difference (Δn) adjusting correction signal (S _K ) it produces. 5. Arrangement according to claim 4, characterized in that the differential speed control device ( 31 ) comprises an integrating controller which generates the actuating correction signal (S _K ). 6. Arrangement according to claim 5, characterized in that the integrating controllers as proportional-integral-differential controllers is formed.