DE102011105990B4 - Method for controlling a drive train of a motor vehicle - Google Patents

Abstract

Method for controlling a drive train of a motor vehicle with an internal combustion engine, a transmission with at least one transmission input shaft and one between a crankshaft of the internal combustion engine and the at least one transmission input shaft, controlled by a control unit with a microprocessor with a predetermined interrupt clock rate and in a closed state by means of an automated friction clutch operated by a slip control, characterized in that drive train twisting angles detected in successive interrupt intervals are added up until a limit value of the drive train twisting angle is reached and slip is detected when this is reached.

Description

The invention relates to a method for controlling a drive train of a motor vehicle with an internal combustion engine, a transmission with at least one transmission input shaft and one between a crankshaft of the internal combustion engine and the at least one transmission input shaft, controlled by a control unit with a microprocessor with a predetermined interrupt clock rate and in a closed state by means of a slip control operated automated friction clutch.

DE 195 05 561 A1 discloses a method for slip control of friction elements, transmissions or drive trains.

DE 103 51 906 A1 discloses a method for adapting the gripping point of an automated clutch.

DE 10 2008 062 753 A1 discloses a method for controlling a torque transfer device.

DE 697 38 552 T2 discloses an electronically controlled four wheel drive transmission having a control system for engaging four wheel drive

The method provides for the control of known drive trains of a motor vehicle, in which an internal combustion engine drives drive wheels of a motor vehicle. A transmission, for example an automated gearbox with a transmission input shaft or a dual clutch transmission with two transmission input shafts, is provided to spread the usable speed range of the internal combustion engine. Between the crankshaft and the at least one transmission input shaft, a friction clutch or, in the case of double clutch transmissions, a double clutch with two friction clutches are provided, which are controlled by a control unit with a microprocessor, so that these act as separating and starting clutches with one that is open, one that slips during a starting gear, and one that is closed Serve state. Here, in the closed state of the friction clutch, for example, from the DE 10 2008 030 481 A1 known slip control is provided, which dampens torsional vibration loads from the internal combustion engine of the drive train part following the friction clutch. For example, to limit the resulting energy losses, such slip controls should work with the lowest possible slip. The detection of a slip state is, however, difficult to carry out at these low speeds.

The object of the invention is therefore to develop a method for controlling such drive trains for detecting low slip speeds.

The object is achieved by a method for controlling a drive train of a motor vehicle with an internal combustion engine, a transmission with at least one transmission input shaft and one between a crankshaft of the internal combustion engine and the at least one transmission input shaft, controlled and controlled by a control unit with a microprocessor with a predetermined interrupt clock rate released in a closed state by means of a slip control operated automated friction clutch, with the drivetrain angle of rotation detected in successive interrupt intervals being added up until a limit value of the drivetrain angle of rotation is reached and slip is detected when it is reached. The drive train twist angle is understood to mean a pulling up of the drive train, which is designed with finite rigidity, under load, with the internal combustion engine moving the remaining drive train to the drive wheels in positive direction of rotation in a pulling mode and from the drive wheels to the crankshaft of the internal combustion engine against the drag torque of the internal combustion engine in overrun mode winds up in the negative direction of rotation. From the sign of the drive train twisting angle, a pulling operation can therefore also be differentiated from the pushing operation of a drive train and evaluated for the determination of the slip detection.

durch Aufsummierung der Differenzdrehzahlen n_Schlupf (°/ms) zwischen der Kurbelwelle und der zumindest einen Getriebeeingangswelle multipliziert mit den sehr kurzen Interrupt-Intervallen τ_Interrupt der Interrupt-Rate des Mikroprozessors des Steuergeräts beispielsweise in einem Zeittakt von 10 Mikrosekunden. Hierbei wird gemäß einem vorteilhaften Ausführungsbeispiel zuerst in jedem Interrupt-Intervall ein maximaler Triebstrangverdrehwinkel φ_max ermittelt. Hierbei werden charakteristische Größen des Antriebsstrangs zugrunde gelegt, beispielsweise die von einer im Getriebe eingelegten Übersetzung abhängigen Steifigkeit C_TS des Antriebsstrangs, dessen Spiel φ_Spiel, des aktuell anliegenden Motormoments M_MOT und Trägheitsmoments J_Mot der Brennkraftmaschine, der Winkelbeschleunigung der Kurbelwelle ω̇_Mot beziehungsweise der Getriebeeingangswelle ω̇_Getr beispielweise nach folgender Gleichung ermittelt: $${\phi }_{max}={\phi }_{Spiel}+\frac{1}{C_{TS}}\left(M_{Mot}-J_{Mot}{\dot{\omega }}_{Getr}\right)$$

The drive train twist angle is determined after $$\phi ={\displaystyle \sum n_{\mathrm{S.}cHlupf}{\tau }_{\mathrm{I.}nterrupt}}$$

by adding up the differential speeds n _slip (° / ms) between the crankshaft and the at least one transmission input shaft multiplied by the very short interrupt intervals τ _interrupt the interrupt rate of the microprocessor of the control unit, for example in a time cycle of 10 microseconds. According to an advantageous exemplary embodiment, a maximum drive train twist angle φ _{max is first} determined in each interrupt interval. Characteristic values of the drive train are used as a basis, for example the rigidity C _{TS of} the drive train, which _{depends on a gear ratio, its play φ play} , the currently applied engine torque M _MOT and the moment of inertia J _{Mot of} the internal combustion engine, the angular acceleration of the crankshaft ω̇ _Mot or the Transmission input shaft ω̇ Getr _determined, for example, according to the following equation: $${\phi }_{max}={\phi }_{\mathrm{S.}piel}+\frac{1}{{\mathrm{C.}}_{T\mathrm{S.}}}\left({\mathrm{M.}}_{\mathrm{M.}Ot}-J_{\mathrm{M.}Ot}{\dot{\omega }}_{Getr}\right)$$

It has proven to be particularly advantageous _{to record the angular acceleration ω der Getr of} the transmission input shaft, since the mean angular acceleration with constant slip of the crankshaft and transmission input shaft is essentially the same, the values of the angular acceleration of the transmission input shaft to be recorded due to the decoupling of torque fluctuations through the set slip are virtually filtered.

To determine the totalized drive train twist angle, a threshold value of a drive train twist angle is preferably specified in each interrupt interval, and when it is exceeded, slip is detected. A safety margin can be added to this threshold value in order to avoid safety-critical control states. As a result of the dependency of the drive train angle of rotation on the gear ratio engaged in the transmission, the threshold value can be specified as a function of a gear ratio engaged in the transmission.

The drive train twist angle currently determined in each interrupt interval on the basis of the current operating situation such as engine torque and the specified operating parameters such as drive train stiffness can exceed the specified threshold value in a current interrupt interval. If this is the case, the threshold value of the interrupt interval preceding the current interrupt interval is raised to the value of the maximum drive train angle of rotation. If the maximum drive train twist angle of a current interrupt interval is smaller than the threshold value of the previous interrupt interval, the threshold value is preferably regulated to the value of the maximum drive train twist angle by means of a PT1 filter for safety reasons. If all the play and rigidity properties of the drive train can be precisely specified, the threshold value can be adopted directly without a PT1 filter.

If the maximum drive train rotation angle is not reached below a specifiable minimum threshold, this can be set to zero. Furthermore, in the case of negligible drive train vibrations, for example, the drive train rotation angle can be set to the threshold value directly and without prior summation in the form of a prognosis after a sticking phase of the friction clutch. It has proven to be advantageous here if a prognosis is made as a function of a minimum amount of engine torque. For example, a counter can be started that determines the length of a sticking phase. If the duration of the stick phase reaches a minimum value, the drive train twisting angle is set to the threshold value, whereby the slip phase is reached in an accelerated manner by bridging the summation of the drive train twisting angle up to the threshold value.

The invention is explained in more detail using the single figure. This shows the sequence of a method for recognizing a slip process when the friction clutch is closed. Partial diagram I. shows the slip on the friction clutch over time t in the shape of the line 1 . Partial diagram II shows the drive train twist angle φ in the shape of the line 2 . The dashed lines show the threshold values S _train , S _{train, s} , Ss _chub , S _{push, s} for the drive train twist angle φ . Partial diagram III shows the slip detection areas B. over time t in the form of the slip detection area B _Zug during traction operation of the drive train and the slip detection area B _thrust in overrun mode of the drive train. In the time from t = 0 to t = t1, the drive train twist angle is φ with positive slip, i.e. integrated in slip operation. At t = t1, the drive train twisting angle reaches the threshold value to which the safety margin has been applied after continuously adding up over the interrupt intervals of the microprocessor S _{train, s} so that the detection for positive slip (pull) in the slip area B _train is triggered. The drive train twist angle φ is held at its value at t = t2 until the slip crosses zero. When it crosses zero, it immediately jumps back to zero. Then the integration of the drive train twist angle begins φ with negative slip. At t = t3, the drive train twist angle reaches φ the threshold to which the safety margin is applied S _{push, s} and the detection for negative slip (thrust) is in the slip range B _thrust triggered.

List of reference symbols

1

line

2

line

B.

Slip detection area

B _thrust

Slip detection area

B _train

Slip detection area

n

Slip

S _thrust

Threshold

S _{push, s}

Threshold

S _train

Threshold

S _{train, s}

Threshold

t

time

I.

Partial diagram

II

Partial diagram

III

Partial diagram

φ

Driveline twist angle

Claims (10)

Method for controlling a drive train of a motor vehicle with an internal combustion engine, a transmission with at least one transmission input shaft and one between a crankshaft of the internal combustion engine and the at least one transmission input shaft, controlled by a control unit with a microprocessor with a predetermined interrupt clock rate and in a closed state by means of an automated friction clutch operated by a slip control, characterized in that drivetrain twisting angles detected in successive interrupt intervals are added up until a limit value of the drivetrain twisting angle is reached and slip is detected when this is reached. Procedure according to Claim 1 , characterized in that a pulling and pushing operation of the drive train is derived from the detection of the drive train twisting angle. Procedure according to Claim 1 or 2 , characterized in that in each interrupt interval a maximum drive train angle of rotation is determined from differential speeds between the crankshaft and the at least one transmission input shaft. Method according to one of the Claims 1 to 3 , characterized in that a threshold value of a drive train angle of rotation is specified in each interrupt interval, and when it is exceeded, slip is detected. Procedure according to Claim 4 , characterized in that a safety margin is applied to the threshold value. Procedure according to Claim 4 or 5 , characterized in that the threshold value is specified as a function of a gear ratio engaged in the transmission. Method according to one of the Claims 4 to 6th , characterized in that if the maximum drive train twist angle of a current interrupt interval is greater than the threshold value of the interrupt interval preceding this, the threshold value is raised to the value of the maximum drive train twist angle. Method according to one of the Claims 4 to 7th , characterized in that with a smaller maximum drive train twist angle of a current interrupt interval than the threshold value of the previous interrupt interval, the threshold value is regulated to the value of the maximum drive train twist angle by means of a PT1 filter. Method according to one of the Claims 1 to 8th , characterized in that if the maximum drive train rotation angle is not reached below a predeterminable minimum threshold, this is set to zero. Method according to one of the Claims 1 to 9 , characterized in that after a sticking phase of the friction clutch, the drive train rotation angle is set to the threshold value.

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