DE102011105507B4 - Method for controlling an automated friction clutch - Google Patents

Abstract

Method for controlling an automated friction clutch in a drive train of a motor vehicle by means of a clutch actuator controlled by a control unit, the actuator travel of which is determined by means of a clutch characteristic curve spanned by at least two support points determined by means of adaptation values determined during operation of the motor vehicle and stored non-volatile in a memory of the control unit is assigned to the clutch torque that can be transmitted by the friction clutch, with a stored adaptation value of at least one of the interpolation points being corrected to an updated adaptation value as a function of the operating states of the motor vehicle or the friction clutch by means of a currently determined and weighted adaptation value, characterized in that a currently determined adaptation value is dependent on a characteristic curve of at least one Operating state size is weighted.

Description

The invention relates to a method for controlling an automated friction clutch in a drive train of a motor vehicle, having the features according to the preamble of claim 1.

DE 10 2008 026 554 A1 discloses a method for controlling a clutch device. A temperature in the friction clutch is determined to control the clutch. Depending on the determined temperature, a characteristic of the friction clutch is adjusted.

Automated friction clutches and methods for their operation are sufficient from drive trains of motor vehicles, for example from DE 40 118 50 A1 known and are arranged as separating and starting clutches between a crankshaft of an internal combustion engine and a transmission input shaft of a manual transmission or automated manual transmission or in the form of two friction clutches combined to form a dual clutch, each connecting a transmission input shaft of a partial transmission of a dual clutch transmission to the crankshaft. The friction clutches are actuated by clutch actuators, which convert them along an actuator path from an open state to a closed state and vice versa, with a clutch torque that can be transmitted via the friction clutch being varied depending on the actuator path. The connection between the actuator travel and the clutch torque is established by a clutch characteristic curve, which is defined by at least two supporting points, for example the touch point comparable to an axis section at which the friction clutch just begins to transmit clutch torque and a friction value that characterizes the transmittable torque such as the friction torque of the friction clutch and as Slope of the characteristic can be understood. The interpolation points are adapted to the properties and operating states of the friction clutch that change temporarily and over the long term, as required or regularly, in that adaptation values stored in a non-volatile memory are checked by determining current adaptation values and corrected if necessary.

It has been shown here that an adaptation in operating states that exhibit extreme deviations from a normal state can be faulty, for example high clutch temperatures can result in high incorrect adaptations of the coefficient of friction, since this is poorly reproducible in the range of high and strongly fluctuating clutch temperatures and high temperature dependencies having.

The object of the invention is therefore to propose a method for controlling a friction clutch with a robust adaptation of the characteristic curve that establishes the relationship between the actuator travel and the clutch torque.

This object is achieved by a method having the features according to claim 1.

The object is thus achieved by a method for controlling an automated friction clutch in a drive train of a motor vehicle using a clutch actuator controlled by a control unit, the actuator travel of which can be adapted using at least two adaptation values determined during operation of the motor vehicle and stored non-volatile in a memory of the control unit Support points spanned clutch characteristic is assigned to a clutch torque that can be transmitted via the friction clutch, wherein a stored adaptation value of at least one of the support points is corrected to an updated adaptation value depending on the operating states of the motor vehicle or the friction clutch by means of a currently determined and weighted adaptation value. Operating states of the motor vehicle or working states of the friction clutch, in which unreliable adaptation values can occur, are accordingly provided with lower weighted adaptation values according to the invention, so that in principle an adaptation can be carried out in every operating range, but the adaptation value can be compared to a stored adaptation value in the event of large deviations under special conditions has less influence on its correction. In this way, a suspension of the adaptation can be avoided and adapted, but this can be designed to be more robust, for example in that rapidly changing adaptation values in extreme operating situations have less of an impact on rapidly changing support points due to their weighting.

According to an advantageous specific embodiment, a difference between the stored adaptation value and the currently determined adaptation value can be weighted as a function of a characteristic of at least one operating state variable. Depending on this characteristic curve, the difference added to the stored adaptation value is then adapted to the operating state variable that changes the adaptation value.

According to the invention, a currently determined adaptation value is weighted as a function of a characteristic curve of at least one operating state variable, so that a decision is made as to the extent to which a stored adaptation value is dependent on the operating state variable is corrected at all by the currently recorded adaptation value.

The proposed weighting of adaptation values preferably relates to the supporting points of the characteristic such as the clutch characteristic in the form of the contact point and preferably the coefficient of friction. In particular when adapting the coefficient of friction, greatly varying coefficients of friction of the friction linings of the friction clutch can be weighted in this way. Since the clutch temperatures vary greatly depending on slip situations, especially during overlapping shifts of the friction clutches in a double-clutch transmission, and thus also the friction values of the clutch characteristic curve, it has proven to be particularly advantageous to take the clutch temperature into account as an operating state variable and, depending on this, to use currently determined adaptation values to correct the stored adaptation value weight. For example, a characteristic curve of the clutch temperature can be set to one up to a specified limit temperature, so that at clutch temperatures in the normal temperature range, an adaptation of the coefficient of friction is not influenced and when the limit temperature is exceeded as the clutch temperature increases, so that in high temperature ranges, for example clutch temperatures above 150° to 160° C, the unreliable adaptation values there are taken into account with less influence.

mit $$a=1-f\left(Clutch\_temp\right)$$

According to an advantageous exemplary embodiment, the updated adaptation value FC _mem,new is calculated from the stored adaptation value FC _mem,old of the coefficient of friction as a function of the characteristic curve f(clutch_temp) of the clutch temperature and the currently determined adaptation value FC _adapt of the coefficient of friction according to the following relationship of the following equation (1 ) determined: $$f{C}_{mem,new}=f{C}_{mem,Ol\mathrm{i.e}}*a+f{C}_{a\mathrm{i.e}apt}*f\left(Cl\mathrm{and}tcH\_temp\right)$$

with $$a=1-f\left(Cl\mathrm{and}tcH\_temp\right)$$

The invention is explained in more detail using diagram 1 of characteristic curve f(clutch_temp) over clutch temperature Clutch_temp shown in the only figure. Depending on the value of the characteristic curve f(clutch_temp) used in equation (1), there is no change compared to the determination of the updated adaptation value FC _mem,new in the normal range of the clutch temperature clutch_temp up to a limit temperature GT of 150° C. specified in this exemplary embodiment a known adaptation method, since the stored adaptation value FC _mem,old of the coefficient of friction is completely replaced by the currently determined adaptation value FC _adapt . At clutch temperatures greater than the limit temperature GP, the influence of the currently determined adaptation value FC _adapt on the updated adaptation value FC _mem,new decreases until finally, at clutch temperatures clutch_temp of 400° C., the stored adaptation value FCW _mem,old remains unchanged. For the sake of completeness, it should be mentioned that the updated adaptation value FC _mem,new is saved and used as a factor for correcting the coefficient of friction, and that an actuator travel is determined from the product of the coefficient of friction and the current adaptation value with the aid of the characteristic curve of the clutch, by means of which the friction clutch is engaged transmittable clutch torque is set.

Reference List

f(clutch_temp)

curve

GT

limit temperature

clutch temp

clutch temperature

Claims (6)

Method for controlling an automated friction clutch in a drive train of a motor vehicle by means of a clutch actuator controlled by a control unit, the actuator travel of which is determined by means of a clutch characteristic curve spanned by at least two support points determined by means of adaptation values determined during operation of the motor vehicle and stored non-volatile in a memory of the control unit is assigned to the clutch torque that can be transmitted by the friction clutch, with a stored adaptation value of at least one of the interpolation points depending on the operating states of the motor vehicle or the friction clutch being corrected to an updated adaptation value by means of a currently determined and weighted adaptation value, characterized in that a currently determined adaptation value is dependent on a characteristic curve of at least one Operating state size is weighted. procedure after claim 1 , characterized in that a difference between the stored adaptation value and the currently determined adaptation value is weighted as a function of a characteristic curve of at least one operating state variable. Procedure according to one of Claims 1 until 2 , characterized in that the at least one support point is a coefficient of friction of the friction clutch. Procedure according to one of Claims 1 until 3 , characterized in that the at least one Operating condition variable is the clutch temperature. procedure after claim 4 , characterized in that a characteristic curve of the clutch temperature falls down to a predetermined limit temperature of one and when the limit temperature is exceeded as the clutch temperature increases. procedure after claim 4 or 5 , characterized in that the updated adaptation value is determined from the stored adaptation value of the coefficient of friction as a function of the characteristic curve of the clutch temperature and the currently determined adaptation value of the coefficient of friction according to the following relationship: $$f{C}_{mem,new}=f{C}_{mem,Ol\mathrm{i.e}}*a+f{C}_{a\mathrm{i.e}apt}*f\left(Cl\mathrm{and}tcH\_temp\right)$$

with $$a=1-f\left(Cl\mathrm{and}tcH\_temp\right)$$

where FC _{mem,new designates} the updated adaptation value, FC _mem,old the stored adaptation value of the coefficient of friction, f(clutch_temp) the characteristic curve of the clutch temperature and FC _adapt the currently determined adaptation value of the coefficient of friction.

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