DE102018107979A1 - A method for avoiding too high a slip speed in a friction clutch in a drive train of a vehicle - Google Patents

Abstract

The invention relates to a method for avoiding too high a slip speed in a friction clutch in a drive train of a vehicle, in which the friction clutch transmits a torque of a drive unit to vehicle wheels, wherein a slip speed of the friction clutch is measured. In a method in which overheating of the friction clutch is prevented, the measured during a slip control slip speed of the friction clutch is compared with a slip speed limit, which is closed when exceeding the slip speed limit value on an incorrectly determined by a model torque of the drive unit and the Leave slip control and the friction clutch is closed.

Description

The invention relates to a method for avoiding too high a slip speed in a friction clutch in a drive train of a vehicle, in which the friction clutch transmits a torque of a drive assembly to vehicle wheels, wherein a slip speed of the friction clutch is measured.

For a perfect and comfortable operation of the drive train, the exact knowledge of a torque characteristic of the friction clutch is required, which indicates the respective transmissible clutch torque as a function of a position of a clutch actuator. In an automated friction clutch, which is connected downstream of the engine in the drive train, a model is used in operation for determining the clutch torque, which determines the clutch torque depending on an actuator position, which can be measured. Neither the actually transmitted nor the capacity of the clutch torque can be measured. Due to wear or other changing parameters, the clutch torque changes depending on the actuator position. Two important parameters can be determined by adaptation, which support the coupling model in a software logic and make the clutch torque controllable by varying an actuator position. One of these parameters is the coefficient of friction, which determines the slope of the clutch torque in the clutch characteristic above the actuator position. From the DE 10 2008 027 071 A1 is a method for Reibwertadaption arranged in a hybrid drive train friction clutch is known in which the coefficient of friction of a clutch actuator actuated friction clutch is adapted by a transmitted torque of the friction clutch, which is determined when starting the engine by means of the electric motor. For the adaptation of the coefficient of friction, the friction clutch is brought into slip control, ie a predetermined slip is set by varying the actuator position depending on the engine torque and the measured speed.

The torque of the internal combustion engine also can not be measured, but is determined by a software model about other measurable parameters. In case of errors of the software model, a wrong engine torque is outputted and sent to the control of the friction clutch. Such a false torque of the internal combustion engine adversely affects the slip control, which leads to the unwanted howl of the internal combustion engine, which can no longer be captured by the slip control. This undesired howling of the internal combustion engine results in a slip performance which heats the friction linings of the friction clutch, which leads to loosening of parts of the friction linings at temperatures of approximately 250 ° C. Thus, the coupling function is no longer fully guaranteed.

The invention has for its object to provide a method for avoiding too high a slip speed in a friction clutch, wherein temperature entries are suppressed by an excessive slip speed in the friction clutch.

According to the invention the object is achieved in that the measured during a slip control slip speed of the friction clutch is compared with a slip speed limit, is closed when exceeding the slip speed limit on a incorrectly determined by a model torque of the drive unit and leave the slip control and the friction clutch is closed. By leaving the slip control with subsequent closing of the friction clutch the described howling of the drive unit of the vehicle is suppressed. As a result, energy inputs are minimized in the friction clutch, so that damage to the friction clutch is avoided.

Advantageously, switching from a slip speed-dependent actuator position control to a controlled closing of the friction clutch with maximum dynamics. By closing the friction clutch, the slip state is canceled and thus prevents the friction of the friction linings of the friction clutch to each other. The dynamics are chosen so that a temperature increase during this process is prevented in the friction clutch.

In one embodiment, the friction clutch is closed via a ramp function. This ramp function eliminates a sudden closing of the friction clutch, which prevents vibration of the drive train and driving comfort is further maintained.

In one variant, the slip speed is measured during a friction value adaptation and evaluated via the comparison with the slip speed limit value. The application of this method advantageously amounts to the Reibwertadaption, since for this Reibwertadion the friction clutch must be brought into the slip. However, the method is also advantageous for other states of the friction clutch in which it also unintentionally assumes a slip state.

In one embodiment, the slip speed limit is in a range between 100 rpm and 350 rpm depending on a vehicle comfort selected. The choice of the limit value contributes significantly to maintaining the ride comfort in the vehicle. An abrupt changeover from the slip control to the closing of the friction clutch is thus prevented.

In a further development, a hybrid drive train is used as the drive train of the vehicle, in which the friction clutch is arranged as a separating clutch between a first drive unit designed as an internal combustion engine and a second drive unit designed as an electric motor. Since such a disconnect clutch helps to start the internal combustion engine by means of the electric motor or to transmit torque from the combustion engine as well as from the electric motor to the drive train of the hybrid vehicle when the disconnect clutch is closed, it is particularly sensitive to wear, which is due in particular to excessive temperatures in the friction linings the friction clutch occurs.

The invention allows numerous embodiments. One of them will be explained in more detail with reference to the figures shown in the drawing.

• 1 eine Prinzipdarstellung eines Hybridantriebsstranges eines Fahrzeuges,
• 2 ein Ausführungsbeispiel des erfindungsgemäßen Verfahrens zum Erkennen einer zu hohen Schlupfdrehzahl,
• 3 ein Ausführungsbeispiel des erfindungsgemäßen Verfahrens zum Schließen der Reibkupplung bei erkannter zu hoher Schlupfdrehzahl.

Show it:

• 1 a schematic diagram of a hybrid powertrain of a vehicle,
• 2 An embodiment of the method according to the invention for detecting a high slip speed,
• 3 An embodiment of the method according to the invention for closing the friction clutch when detected to high slip speed.

In 1 is a schematic diagram of a drive train of a hybrid vehicle shown. This powertrain 1 includes an internal combustion engine 2 and an electric motor 3 , Between the combustion engine 2 and the electric motor 3 is right behind the combustion engine 2 a hybrid disconnect clutch 4 arranged. internal combustion engine 2 and hybrid disconnect coupling 4 are over a crankshaft 5 connected with each other. The electric motor 3 has a rotatable rotor 6 and a fixed stator 7 on. The output shaft 8th the hybrid disconnect clutch 4 is with a gearbox 9 connected, which contains a coupling element, not shown, for example, a second clutch or a torque converter, between the electric motor 3 and the transmission 9 are arranged. The gear 9 transmits that from the internal combustion engine 2 and / or the electric motor 3 generated torque on the drive wheels 10 of the hybrid vehicle. The electric motor 3 and the internal combustion engine 2 be from an engine control unit 11 driven.

The between the internal combustion engine 2 and the electric motor 3 arranged hybrid disconnect coupling 4 is closed during travel of the hybrid vehicle with that of the electric motor 3 generated torque the internal combustion engine 2 to start or during a boost operation with a powered internal combustion engine 2 and electric motor 3 to drive.

In the engine control unit 11 a clutch characteristic is stored, which is a clutch torque via a path of a clutch actuator, the hybrid disconnect clutch 4 moved, determined. At the same time, with a second model, a torque of the internal combustion engine 2 calculated. To prevent the model of torque of the internal combustion engine 2 is faulty, during a Reibwertadaption, in which a slip control of the internal combustion engine 2 is active, a slip speed of the hybrid disconnect clutch 4 measured. Under a slip while a state of the hybrid disconnect clutch 4 understood, in which the hybrid separation clutch 4 is in frictional engagement, but the input speed of the hybrid disconnect clutch 4 different from their output speed is that of the transmission 9 is transmitted. This energy is in the friction linings of the hybrid separation clutch 4 entered. If the comparison with the slip speed limit value GW, which can be for example at 100 rpm, results in the current measured slip speed exceeding this slip speed limit value GW, it is assumed that the model for determining the torque of the internal combustion engine 2 works incorrectly. To set too high a slip speed at the hybrid disconnect clutch 4 and thus damage to the hybrid disconnect clutch 4 will prevent the slip control and the hybrid disconnect clutch 4 closed with high dynamics.

The detection of whether the slip speed due to a false torque of the engine 2 is too high, is in 2 shown. The curve shows A the control of the hybrid disconnect clutch 4 in slipping operation. In the curve B is the torque of the internal combustion engine determined by the torque model 2 shown. In a test mode, the current torque of the internal combustion engine 2 measured in curve C is shown. From this it can be seen that the torque calculated by the model deviates greatly from the actually measured rapidly increasing torque, which results in a high slip on the hybrid disconnect clutch 4 pulls. In curve D is the slip speed due to the control of the internal combustion engine 2 represented with a wrong torque. It is It can be seen that the slip speed increases and increases rapidly, with too high a slip on the hybrid disconnect clutch 4 is sensed.

3 shows, as with a detected too high slip the hybrid disconnect clutch 4 is closed. In particular, a possible procedure is shown in detail in the section on the right. The curve E is determined by a counter which is counted down and which thus determines the time duration in which the hybrid disconnect clutch 4 is closed. Closing the hybrid disconnect clutch 4 is in curve F shown. The hybrid separation clutch 4 can be closed, for example, 5 seconds. To close the hybrid disconnect clutch 4 the actuator position is reduced (curve G ). When closing the hybrid disconnect clutch 4 , which in turn through the curve A is shown, there is no sudden closure, since the hybrid disconnect clutch 4 with a ramp function (curve B and C ) is closed when it has been determined that the slip speed (curve D ) the limit GW has exceeded.

Due to this procedure, an unintentional howling of the internal combustion engine 2 prevented during a slip control. This process prevents more friction energy from being introduced into the friction clutch. Thus, premature wear and reduced life of the automated friction clutch are prevented.

LIST OF REFERENCE NUMBERS

1

powertrain

2

internal combustion engine

3

electric motor

4

Hybrid clutch

5

crankshaft

6

rotor

7

stator

8th

output shaft

9

transmission

10

drive wheels

11

Engine control unit

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102008027071 A1 [0002]

Claims (6)

A method for avoiding too high a slip speed in a friction clutch in a drive train of a vehicle, wherein the friction clutch (4) transmits a torque of a drive unit (2) to vehicle wheels (10), wherein a slip speed of the friction clutch is measured, characterized in that the during a slip control measured slip speed of the friction clutch (4) with a slip speed limit (GW) is compared, which is exceeded when the slip speed limit (GW) on a incorrectly determined by a model torque of the drive unit (2) and leave the slip control and the friction clutch (4) is closed. Method according to Claim 1 , characterized in that is switched from a dependent of the slip speed Aktorpositionsregelung on a controlled closing of the friction clutch (4) with maximum dynamics. Method according to Claim 1 or 2 , characterized in that the friction clutch (4) is closed via a ramp function. Method according to Claim 1 . 2 or 3 , characterized in that the slip speed is measured during a Reibwertadaption and evaluated on the comparison with the slip speed limit value (GW). Method according to at least one of the preceding claims, characterized in that the slip speed limit value (GW) is selected in a range between 100 rpm and 350 rpm as a function of vehicle comfort. Method according to at least one of the preceding claims, characterized in that the drive train of the vehicle is a hybrid drive train (1) is used, in which the friction clutch as a separating clutch (4) between a first as an internal combustion engine (2) formed drive unit and a second as an electric motor (3 ) formed drive unit is arranged.

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