DE102015120114A1 - Method for operating a drive train of a vehicle - Google Patents

Abstract

The invention relates to a method for operating a drive train (2) of a vehicle (3) with a clutch unit (1), wherein the clutch unit (1) has at least one multi-disc clutch (4) and at least one actuation unit (5) for actuating the multi-disc clutch (4). The method comprises at least the following steps: a) determining at least one real positioning position (6) of the actuating unit (5) in at least one operating point of the actuating unit (5) defined by at least one operating point parameter, b) calculating at least one nominal actuating position (7) c) comparing the determined real positioning position (6) with the calculated nominal positioning position (7) at the operating point, d) forming a positioning correction factor (8) as a function of the comparison of the determined real positioning position (6) with the calculated nominal setting position (7), e) adjusting a r Actuation of the multi-disc clutch (4) as a function of the actuating position correction factor (8).

Description

The present invention relates to a method for operating a drive train of a vehicle with a clutch unit, in particular for distributing torque on a primary axle and a secondary axle of the vehicle.

The invention particularly relates to a method for vehicle dynamics control in demand-oriented four-wheel drive systems and / or adjustable transverse locks or axle locks and in this context adapted equipped vehicles, in which information regarding the current engine torque, the longitudinal acceleration, the lateral acceleration, the yaw rates ( Indicates the speed of rotation of a vehicle about the vertical axis), the steering angle and / or the wheel speeds are present. The invention particularly relates to four-wheel drive vehicles in which either the rear axle or the front axle (proportionally and / or temporarily) can be activated by means of an electronically controlled clutch unit. In other words, the clutch assembly is used to controllably and / or variably transmit a torque from an input shaft to at least one output shaft. Alternatively or cumulatively, the invention can also be applied to axle locks or transverse locks, in particular active and controllable axle locks or transverse locks, in which one side of an axle can be decoupled from an opposite side of the axle by means of an electronically controlled clutch unit. As a result, an on-demand torque distribution between two wheels of an axle can be made.

The clutch unit comprises at least one friction clutch formed as a multi-plate clutch and at least one actuating unit for actuating the multi-plate clutch. In connection with the control or regulation of such a clutch unit has been found that for setting a desired clutch torque and / or a desired contact force does not necessarily have to be provided a direct torque control, which would require the actual clutch torque as a controlled variable. Rather, it has proven to be advantageous to provide for the control or regulation of the clutch unit, a position control based on the setting position of the actuating unit. Such a position control makes it possible, for example, to avoid the so-called friction hysteresis. In addition, the position control regularly improves the positioning speed of the clutch unit.

As part of the position control, for example, to set a desired contact force which is to act between the slats of the multi-plate clutch, a control position of the actuating unit used as a control variable and adjusted or regulated to a value corresponding to the desired contact force. In order to be able to realize such a position control, however, it is first necessary to determine the dependence between the contact force and the control position empirically, in particular by measurements or calculations in advance, and to determine this contact pressure force position relationship as a characteristic, for example in the form of a table (look up-table, LUT) or a function (calculation rule) and to provide a position control method available. This characteristic is usually determined in the factory as a so-called Erstkalibrierung.

Due to setting and / or wear within the clutch unit, however, this contact pressure-actuating position characteristic can shift in the direction of larger actuating positions, which can lead to inaccuracies in the position control. Therefore, this characteristic should be recalibrated regularly. For this purpose, it would be possible to perform separate or specifically for calibration purposes initiated calibration runs at certain time intervals.

Such calibration runs could be performed after switching off the vehicle engine in order to preclude influencing the driving behavior of the vehicle by the calibration. This can be referred to as "recalibration".

The disadvantage, however, is that the calibration runs of the recalibration require a high expenditure of energy which has to be provided solely by the vehicle battery, because the recalibration is carried out after switching off the vehicle engine. In addition, this creates an undesirable noise emission after parking the vehicle.

On this basis, it is an object of the present invention, at least partially solve the problems described with reference to the prior art. In particular, a method for operating a drive train of a vehicle is to be specified, which makes it possible to perform a calibration of a position control of the clutch assembly during operation of the drive train of the vehicle. In particular, an excessive, additional stress on the clutch unit should be avoided. In addition, loads on the vehicle battery and the electrical system as well as unnecessary noise emissions after stopping the vehicle engine should be avoided.

These objects are achieved by a method according to the features of claim 1. Further advantageous embodiments of Method are given in the dependent claims. It should be noted that the features listed individually in the dependent claims can be combined with each other in any technologically meaningful manner and define further embodiments of the invention. In addition, the features specified in the claims are specified and explained in more detail in the description, wherein further preferred embodiments of the invention are shown.

• a) Ermitteln mindestens einer realen Stellposition der Betätigungseinheit in mindestens einem durch mindestens einen Betriebspunktparameter definierten Betriebspunkt der Betätigungseinheit,
• b) Berechnen mindestens einer nominalen Stellposition der Betätigungseinheit in Abhängigkeit des Betriebspunktparameters,
• c) Vergleichen der ermittelten realen Stellposition mit der berechneten nominalen Stellposition in dem Betriebspunkt,
• d) Bilden eines Stellposition-Korrekturfaktors, insbesondere eines Stellposition-Korrekturoffsets, in Abhängigkeit des Vergleichs der ermittelten realen Stellposition mit der berechneten nominalen Stellposition,
• e) Anpassen einer Betätigung der Lamellenkupplung in Abhängigkeit des Stellposition-Korrekturfaktors.

A method for operating a drive train of a vehicle with a clutch unit contributes to this, wherein the clutch unit is provided and arranged in particular for distributing torque on a primary axle and a secondary axle of the vehicle and / or for distributing torque between two wheels of an axle of the vehicle is. The clutch unit has at least one multi-plate clutch and at least one operating unit for actuating the multi-plate clutch. The method comprises at least the following steps:

• a) determining at least one real positioning position of the actuating unit in at least one operating point of the actuating unit defined by at least one operating point parameter,
• b) calculating at least one nominal actuating position of the actuating unit as a function of the operating point parameter,
• c) comparing the determined real positioning position with the calculated nominal positioning position at the operating point,
• d) forming a parking position correction factor, in particular a parking position correction offset, as a function of the comparison of the determined real parking position with the calculated nominal parking position,
• e) adjusting an operation of the multi-plate clutch in dependence of the setting position correction factor.

This is a special concept for adjusting an operation of a multi-plate clutch, in particular for calibrating a contact pressure-actuating position characteristic of a position control of the clutch unit specified. In particular, the method is used to determine a wear path as a parking position correction factor, which results from the difference between a measured, real actuating position of the actuating unit and a calculated, nominal actuating position of the actuating unit (based on the same operating point). In particular, the method differs significantly from the recalibrations mentioned at the outset in that no separate or specifically calibrating runs initiated specifically for calibration purposes must be performed after the vehicle has been parked. The method can rather be carried out while the drive train is in operation (under normal operating conditions or performance requirements). Thus, the vehicle battery can be spared and unnecessary noise emissions are avoided after parking the vehicle. In addition, the life or service life of the clutch unit can be increased by avoiding additional Kalibrierbetätigungen.

The described advantages of the method result in particular from the fact that one of the measured, real positioning position associated nominal positioning position is calculated. In this case, the "nominal" positioning position describes the actuating position of the actuating unit that would be present without wear. The real positioning position is recorded continuously during operation for control purposes. Since the method advantageously makes it possible to allocate a nominal setting position to the (almost any) real setting position during normal operation of the coupling unit, the calculation of a setting position correction factor (continuous) can take place during ongoing operation of the drive train.

The above-indicated sequence of method steps a) to e) results in a regular sequence of the method. Individual process steps can also be carried out simultaneously or in parallel. At least the method steps a) and b) can take place simultaneously or in parallel. The process can also be carried out repeatedly.

According to step a), at least one real (ie, in particular currently present) positioning position of the actuating unit is determined in at least one (current and / or predetermined) operating point of the actuating unit. The real positioning position is preferably determined or detected by sensors, in particular measured.

Preferably, the actuating unit has at least one electronic servomotor, a reduction gear and a mechanism for implementing the rotational movement of the servomotor in a translational movement for engagement or disengagement of the inner or outer plates of the multi-plate clutch. The mechanism may in this case have at least one support ring and an adjusting ring rotatable with respect to the support ring and thereby axially displaceable. The actuating position of the actuating unit can relate to a translatory or rotational movement direction of the actuating unit. Thus, the setting position may be an engagement position or disengagement position of the adjusting ring and / or a pressure plate or the like contacting the adjusting ring. Preferably, the setting position is a (motor) rotation angle of the Actuator, in particular an armature of the servomotor, and / or a rotation angle of the reduction gear. In this case, the actuating unit can be assigned a setting position sensor for detecting the real setting position.

According to step b), at least one nominal setting position of the actuating unit is calculated as a function of the operating point parameter. In this case, care must be taken in particular that the real positioning positions and the nominal positioning position which are to be compared relate to the same or to a specific, predetermined operating point. The calculation of the nominal setting position as a function of the operating point parameter can be done on the basis of stored maps, functions and / or tables. If the operating point parameter is, for example, a control torque or engine torque of an electronic servomotor, then first of all a contact pressure force at this operating point can be determined from a (predetermined / predetermined) contact pressure actuating torque relationship (see also the following 3 (b) and the description). Thereafter or subsequently, by means of the specific pressing force, a nominal setting position at the operating point can be derived from a (predetermined / predetermined) pressing-force setting position relationship (see also the following 3 (c) and the description). For example, these relationships may have previously been determined empirically and stored in maps, functions and / or tables in a non-volatile memory of a control unit associated with the operating unit.

Preference is also given in step b) and disturbances or disturbing factors are taken into account, such. B. a temperature of the clutch assembly, in particular a fin temperature, a degree of wetting of the fins with oil or the like. These disturbances can influence or change the transmittable torque and / or the contact pressure. Their consideration can thus serve to increase the accuracy of the calculation in step b).

If the nominal positioning position can not be clearly calculated at the operating point, because, for example, two different values for the contact force can be assigned to the operating point parameter at the operating point (see, for example, in the case of the hysteresis in 3 (b) ), a decision criterion for identifying the unique nominal positioning position can already be used in step b), as explained in more detail below.

According to step c), the determined real actuating position is compared with the (associated) calculated nominal actuating position. In this case, a difference between the real actuating position and the nominal actuating position is preferably formed. For this purpose, a corresponding logic can be set up.

According to step d), the setting position correction factor is formed or calculated as a function of the comparison of the determined real setting position with the calculated nominal setting position. In addition, the adjustment position correction factor can also be determined as a function of one in a preceding method cycle or iteration step and / or as a function of an initialization adjustment position. In addition, it can be considered in step d) whether the nominal positioning position has been reliably calculated. For this purpose, a decision criterion explained in more detail below can serve. Nominal positions that have not been reliably calculated or found to be "inappropriate / defective" may be disregarded in step d). In other words, the comparison result from step c) is in particular only evaluated if a decision criterion shows that the comparison result, in particular the (underlying) calculation of the nominal travel, was or is reliable. A wear path is preferably calculated as the positioning correction factor. In step d), several comparison results from step c) can also be evaluated or taken into account.

According to step e), the adjustment of an actuation of the multi-plate clutch is effected as a function of the setting position correction factor. For this purpose, the determined actuating position correction factor can be made available to a higher-order actuating position controller. Preferably, a setpoint position of the setting position control is corrected with the setting position correction factor. The actuating position correction factor can also be stored in a non-volatile memory, which is associated with a control unit, for example. The adjustment of the operation can also be made such that the adjustment position correction factor is used to incrementally or completely update a stored contact pressure-force position position relationship or a contact force-force position characteristic. In addition, the actuating position correction factor determined in a process cycle can be made available to a subsequent process cycle as an initialization variable or as a starting value.

According to an advantageous embodiment, it is proposed that the method be carried out during the ongoing operation of the drive train. A "running operation" is understood herein as a driving operation of the vehicle (with the engine switched on), in particular during the movement of the vehicle under normal power demand.

• – Stellmoment der Betätigungseinheit,
• – Stellkraft der Betätigungseinheit,
• – Steuerstrom der Betätigungseinheit.

According to an advantageous embodiment, it is proposed that the at least one operating point parameter is at least one of the following parameters:

• - actuating torque of the actuating unit,
• - actuating force of the actuating unit,
• - Control current of the actuator.

Particularly preferably, the operating point parameter is a actuating force of the actuating unit. In other words, in step b) the nominal positioning position of the actuating unit can be calculated from the actuating forces.

If the actuator has an electronic servomotor, the control torque may be an engine torque of the servomotor. The engine torque is usually directly or directly dependent on a control current of the servomotor. Thus, the adjusting torque and / or the actuating force, in particular in the case of an electronic servomotor as an actuating unit, can result directly from the control current. In particular, the same parameter is retained for the proposed method.

According to an advantageous embodiment, it is proposed that, before step e), it be checked on the basis of a decision criterion whether the nominal setting position can be reliably calculated or calculated at the operating point, the nominal setting position being taken into account for adjusting the actuation of the multi-plate clutch only if the decision criterion indicates that the nominal positioning position at the operating point can be reliably calculated or calculated.

According to a further advantageous embodiment, it is proposed that the decision criterion yields that the nominal setting position can be reliably calculated at the operating point or was calculated if there is a monotone change in at least the real setting position or the nominal setting position at the operating point. In other words, the decision criterion is preferably the change or slope of the setting position or of the setting position course. The calculation is reliable if this change or slope is different from zero (0) and not nearly zero (0).

In addition, the decision criterion can also be used to identify the relevant for the calculation of the nominal control position in the respective operating point contact pressure-torque control curve (see hysteresis effect explained in connection with 3 (b) ). If there is an increasing setting position at an operating point, then the contact force-actuating torque characteristic with a lesser slope is relevant. If there is a decreasing setting position in the operating point, then the contact force-actuating torque characteristic with a higher gradient is relevant.

According to an advantageous embodiment, it is proposed that when forming the setting position correction factor in step d), at least two comparison results from step c) are taken into account and averaged. As a result, (signal) disturbances can be filtered out.

According to a further advantageous embodiment, it is proposed that the actuating unit is driven for Verschleißmessungszwecken during operation of the drive train with at least one predetermined actuation profile, wherein the actuation profile is set up and intended not to influence the driving characteristics of the vehicle. For example, in operating phases in which the clutch torque or the transmittable torque has no influence on the driving behavior, z. B. at standstill of the vehicle, specifically predetermined actuation profiles, in particular predetermined (desired) torque curves are driven or requested, in which the determination of the control position correction factor (wear path) is possible. In this way it can be ensured in a deterministic manner that the wear path can be updated sufficiently often. Under a standstill of the vehicle are in particular to understand operating phases in which the vehicle, but not the engine is stationary, z. B. stopping at a traffic light, crossing or the like.

• – zeitliche Betriebsdauer des Kupplungsaggregats,
• – zurückgelegte Fahrstrecke des Fahrzeugs,
• – Energieeintrag in die Lamellenkupplung.

According to a further advantageous embodiment, it is proposed that the method is (only) carried out when a rising in response to the operation of the clutch unit wear variable exceeds a predetermined threshold, the wear variable depends on at least one of the following parameters:

• - duration of service of the coupling unit,
• - traveled distance of the vehicle,
• - Energy input in the multi-plate clutch.

According to a further aspect, a vehicle is proposed with a clutch unit for the variable distribution of torque on different axles of the vehicle, wherein the clutch unit is associated with an electronic control unit which is suitable and adapted for carrying out the method proposed here. For this purpose, the electronic control unit may comprise a program-controlled microprocessor and an electronic memory in which a corresponding control program is stored.

The clutch unit has at least one multi-plate clutch and at least one (externally controllable) actuating unit, in particular for (variable or demand-oriented) activation, or deactivation of torque transmission. The actuating unit may comprise an electronic actuator, in particular an electronic servomotor. The multi-disc clutch usually comprises at least one compressible disc pack which is compressible by means of the actuating unit in order to initiate a torque transmission. The actuation unit is regularly controlled by the electronic control unit, which emits corresponding electrical control currents via corresponding actuation lines to the actuation unit.

The details, features and advantageous embodiments discussed above in connection with the method can accordingly also occur in the vehicle presented here and vice versa. In that regard, reference is made in full to the statements there for a more detailed characterization of the features.

According to a further aspect, it is also proposed to use a method proposed here for determining a wear path in a clutch unit, wherein the wear path is calculated from the difference between the determined real parking position and the calculated nominal parking position.

The details, features and advantageous embodiments discussed above in connection with the method and / or the vehicle can accordingly also occur with the use presented here and vice versa. In that regard, reference is made in full to the statements there for a more detailed characterization of the features.

The invention and the technical environment will be explained in more detail with reference to the figures. It should be noted that the invention should not be limited by the embodiments shown. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the facts explained in the figures and to combine them with other components and findings from the present description. They show schematically:

1 a vehicle having a clutch unit for variably distributing torque to different axles of the vehicle, which is basically suitable and arranged for carrying out the method explained here,

2 A clutch unit which is basically suitable and arranged for carrying out the method explained here.

3 : Course of parameters during operation of a powertrain, and

4 : a control concept with several modules to illustrate the process.

1 schematically shows the structure of a vehicle 3 , concerning the operation of the drive train 2 relevant components. The vehicle 3 has a (fuel and / or electric) engine 14 which a gearbox 15 is assigned directly. The gearbox 15 downstream is a transfer case 22 , which the drive torque from the gearbox 15 in a predetermined symmetric or asymmetrical relationship to a front primary axis 9 and a rear secondary axis 10 of the vehicle 3 divides. The drive torque is so over the side shafts 18 , or the longitudinal shaft 19 to the wheels 16 of the vehicle 3 transfer.

Next is a clutch unit 1 provided, for example, a rear differential gear 23 upstream and a multi-plate clutch 4 , as well as externally controllable actuators 5 for activation, or deactivation, has. It is understood that the clutch unit 1 can also be arranged at another location within the drive train, for example at the front of the connection, or integrated in the transfer case 22 , The operating unit 5 is from an electronic control unit 11 controlled, the corresponding electrical control currents via corresponding control lines 21 to the operating unit 5 emits. For electrical signal transmission from and to the control unit 11 is a serial BUS arrangement 20 provided, which may be formed for example as CAN (controller area network) -BUS. It is understood that as an alternative to a BUS arrangement 20 , also an individual wiring of the various electrical components of the vehicle 3 with the control unit 11 can be provided.

The electronic control unit 11 includes a program-controlled microprocessor and an electronic memory in which a control program is stored. In this case, the microprocessor in accordance with a control program corresponding control signals for the actuator 5 generated. To generate appropriate control signals, the control unit is dependent on information about various operating parameters of the vehicle. For this purpose, the control unit via the BUS arrangement 20 to access various signals, which are for these operating parameters are representative. In particular, wheel sensors for a (each) wheel, and steering sensors for determining a steering angle of the vehicle are provided and (via signal conductors 17 ) with the control unit 11 over the BUS arrangement 20 connected. By way of example, one of the actuating unit 5 assigned positioning position sensor 13 shown for the sensory detection of the real position of the actuating unit 5 furnished and determined. The real positioning position data may be the electronic control unit 11 by means of the BUS arrangement 20 to provide. Analogous to the actuating position sensor, the actuating unit 5 also be associated with a (not shown here) actuating torque sensor.

2 schematically shows a clutch unit 1 which is basically suitable and adapted for carrying out the method explained here. The clutch unit 1 has this as a multi-plate clutch 4 trained friction clutch and an operating unit 5 , In 2 is the clutch unit 1 shown in two different operating states. In 2 (a) is the clutch unit 1 in an open position and in 2 B) shown in a closed position. By actuating the operating unit 5 in Einrücksinn the multi-plate clutch 4 can be an increasing share of one via an input shaft 27 introduced torque on an output shaft 28 be transmitted. The operating unit 5 here includes an example of an electronic servomotor 25 , a reduction gear 26 , a support ring 29 and an adjusting ring 30 ,

As shown 2 is shown schematically that the support ring 29 and the adjusting ring 30 the operating unit 5 with respect to the input shaft 27 are rotatably mounted. The adjusting ring 30 is mounted axially displaceable, whereas the support ring 29 to maintain its axial position. On the sides facing each other have the support ring 29 and the adjusting ring 30 several ball grooves each 32 . 33 , The ball grooves 32 . 33 each extend in the circumferential direction and are with respect to a normal plane to the axis of rotation of the support ring 29 and the adjusting ring 30 ramped in the circumferential direction. In other words, have the ball grooves 32 . 33 in the circumferential direction a varying groove depth. One ball groove each 32 of the support ring 29 and a ball groove 33 the adjusting ring 30 are arranged opposite each other and enclose an associated ball 31 , By turning the support ring 29 and the adjusting ring 30 relative to each other, an axial displacement of the adjusting ring 30 be effected.

As an example, the support ring 29 here in relation to the adjusting ring 30 by means of the servomotor 25 and a reduction gear 26 turned. As a result, the adjusting ring 30 be moved axially in a direction of engagement (here to the right) or a release direction (here to the left). As a rule, the adjusting ring contacts 30 with his support ring 29 opposite side at least indirectly, here for example directly, at least a portion of the inner plates of the multi-plate clutch 4 , Thus, a movement of the adjusting ring 30 in the direction of engagement to a corresponding axial movement of the inner slats towards the outer slats. In 2 B) a situation is shown in which the inner and outer fins contact and on this and between these a pressing force 24 acts. The contact pressure 24 is here via a parking position or a setting torque (motor torque) of the electronic servomotor 25 controllable. That from the input shaft 27 on the output shaft 28 Transmittable torque is directly dependent on the contact pressure 24 , The torque to be transmitted can thus variable or demand-oriented by a corresponding control of the electronic servomotor 25 be specified. This drives the electronic servomotor 25 , via the reduction gear 26 , the support ring 29 to a rotational movement, thereby the adjusting ring 30 to move axially. The angle of rotation 35 of the electronic servomotor 25 represents here by way of example a (real) positioning position in the sense of the method proposed here.

3 shows schematically different courses of parameters during operation of a drive train 2 , As above in connection with the 2 1, the mechanical system considered here comprises, by way of example, an electromechanical clutch unit which has a multi-disc clutch controlled by an electronic servomotor. Here, the engine torque or actuating torque of the electronic servomotor is converted by a strong reduction in an acting on the disk set of the multi-plate clutch contact pressure. The contact force delivers a transmissible clutch torque as a function of the coefficient of friction of the slats, the slat dimensions and the number of slats. It should be noted here that the mechanical system is subject to friction, so that the engine torque or actuating torque basically does not permit a direct conclusion to the contact force acting on the disk pack.

The physical or mechanical relationships between the contact force (F) and the setting torque 34 , here motor torque (M), and between the contact pressure (F) and the parking position 6 . 7 , here motor rotation angle (α), according to the representations after 3 exemplified. For this purpose, the system is equipped with an in 3 (a) shown exposed exemplary actuating profile. To operate the multi-plate clutch 4 is here a control torque 34 applied, which in 3 (a) as the time course of the engine torque "M (t)" is shown. Due to hysteresis effects, in particular due to the friction hysteresis, however, an unambiguous assignment between the engine torque (M) and the contact force (F) generated thereby is not always possible, as described in US Pat 3 (b) is illustrated. Only in the case of sufficiently long sections with monotonically increasing or decreasing positioning position is the assignment between the engine torque (M) and the contact force "F (M)" clear. In 3 (b) the right (ascending) straight line of the contact force function "F (M)" shows a section which, in the case of a monotonically increasing course of the positioning position, eg. B. at a steadily increasing engine rotation angle, can adjust. The left (descending) straight line of the contact force function "F (M)" describes a section with monotonically decreasing positioning position. The hysteresis effect between these straight lines is clearly recognizable and responsible for the fact that a precise control of a desired contact force, from which a desired torque to be transmitted directly results, can not be carried out solely on the basis of the actuating torque or engine torque.

In 3 (c) is shown that between the setting position, here the motor rotation angle (α), and the contact force "F (α)" results in a clear and relatively easy to describe relationship. This can be described by the nearly linear function "F (α)", as in 3 (c) is illustrated. In 3 (c) left is the function "F (α)" for the course of the nominal setting position 7 and on the right the function "F (α)" for the course of the real positioning position 7 shown. Due to the elasticity of the system, the contact force (F) correlates well with the motor rotation angle (α). The course of the function "F (α)" is simplified here. In fact, this course is almost linear only from the so-called "kiss point" of the multi-plate clutch. The kiss point here concerns the point at which the fins of the multi-plate clutch touch each other for the first time. Before reaching the Kisspunkts the multi-plate clutch passes through the so-called clearance, in which there is no contact between mutually associated blades and therefore no torque is transferable. In the area of the clearance, ie in the range α <α _KISS , the contact force "F (α)" and thus also the transmittable torque has the value zero (0).

Due to the relatively simple and unambiguous relationship between the contact pressure (F) and the control position (α), this relationship is preferably used for the control of multi-plate clutches, ie for quickly controlling a desired clutch torque. Therefore, this regulation is also called position control. It should be noted, however, that the relationship between the contact force (F) and the control position (α) due to wear in the multi-plate clutch, for example, due to frictional wear of the slats change. Due to the wear of the slats, the kiss point shifts towards higher setting positions. Here it could be observed that the slope of the function "F (α)" does not change significantly, but due to the wear only a parallel shift of the function "F (α)" takes place towards larger α-values. This is in 3 (c) illustrated by the two different courses of the function "F (α)". The left curve describes the function "F (α)" as it would be without wear. This is also referred to as the nominal course. The right curve shows how the function "F (α)" shifts to the right with wear. Accordingly, it requires due to the wear of a "real" parking position 6 which is greater than a "nominal" parking position 7 to produce the same contact force (F).

As shown 3 (c) forms the distance between the real course and the nominal course of the function "F (α)", ie the distance between the real positioning position 6 and the nominal parking position 7 , the so-called "wear path" 12 , The wear path 12 illustrates an example positioning position correction factor 8th in the sense of the method proposed here.

4 schematically shows a control concept (R1) with several modules to illustrate the method explained here. The illustrated control concept (R1) can, for example, in an electronic control unit 11 be executed. The control concept (R1) shown here serves to ensure that an inside of a clutch unit 1 due to wear of material adjusting wear path can be determined continuously.

In the sense of method step a), first a real positioning position 6 the operating unit 5 at an operating point of the operating unit 5 measured and the control concept (R1) as input variable (S1) provided. Here, the real positioning position 6 for example by means of a parking position sensor 13 be captured, like this one in 1 is illustrated. As further input variables or input variables, the control concept (R1) is also supplied with a current actuating torque (S2) and an initialization value (S3), which may be an actuating position correction factor determined by way of example in a preceding process cycle. The current control torque (S2) represents here an operating point parameter that defines the respective operating point.

According to step b) of the method, a nominal setting position in a module (SR1) 7 the operating unit 5 depending on the operating point parameter, namely as a function of Actuating torque (S2) of the actuating unit 5 , calculated. The calculation of the nominal positioning position 7 can be determined on the basis of a (in an intermediate step) to be calculated relationship "engine torque / nominal position". The relationship "engine torque / nominal parking position" can be determined on the basis of the above in 3 (b) and 3 (c) illustrated courses done. For this, the in 3 (b) shown relationship between the motor torque (M) and the contact force F (M) and the in 3 (c) shown relationship between the nominal setting position 7 (α) and the contact pressure F (α), for example, (factory) determined empirically and stored in corresponding tables or functions in a non-volatile memory of the control unit. When calculating the nominal positioning position 7 in the module (SR1) can also be further disturbances, such. B. the temperature of the clutch unit 1 , used to increase accuracy.

In a module (SR3), a comparison is made of the sensor-determined real positioning position 6 with the nominal setting position calculated in module (SR1) 7 , in the sense of process step c). In this case, a difference is formed between the real positioning position 6 and the nominal parking position 7 ,

In a module (SR2) system states are identified in which the calculation of the nominal control position based on the engine torque is reliable. This is the case when the (real) control position has changed monotonically, so that the state (unambiguously) on the ascending or descending straight line of the force-engine torque curve (see 3 (b) ) lies. In addition, it can be taken into account here whether the setting position change speed is so low that the process is not disturbed by dynamic forces. As a decision criterion, whether the nominal positioning position 7 can be reliably calculated in the relevant operating point, the change or slope of the measured real actuating position (S1) present at the operating point, ie at the current actuating torque or engine torque (S2), is calculated here by way of example in the module (SR2). If the slope of the real positioning position (S1) is positive, then the contact pressure at the operating point in question is based on the right-hand straight line 3 (b) to investigate. If the slope of the real positioning position (S2) is negative, the opposite is the left straight line 3 (a) to use. If the slope is zero or near zero, the values can not be uniquely assigned and a reliable calculation is not possible in this state. If a contact force for the operating point concerned could be determined clearly and reliably, this contact force is used to calculate the nominal positioning position 7 to use (see 3 (c) ).

In a module (SR4), a positioning correction factor is used in the sense of method step d) 8th educated. For this purpose, the module (SR4) is supplied with the result of the comparison from the module (SR3). The module (SR4) also takes into account that only those comparisons from the module (SR3) are used to form the positioning correction factor 8th should be used, which were determined in phases in which the engine torque-contact force curve was clearly on the ascending or descending branch of the engine torque-contact force characteristic. For this purpose, the module (SR4) receives information about the reliability of the calculation of the nominal setting position from the module (SR2). The module (SR2) can also provide the module (SR4) with information about whether the contact force at the operating point in question is based on the right-hand straight line (increasing actuating position) or the left-hand straight line (decreasing actuating position) 3 (b) is to be determined. Thus, in the module (SR4), the positioning correction factor becomes 8th , calculated or determined by the comparison between (actual) real position and calculated nominal position from the module (SR3) is evaluated only if at the same time the calculation in module (SR2) is identified as reliable.

If the module (SR3) provides a value pair as a result, e.g. B. because in the relevant operating point both an "intersection" with the right line (increasing position) or the left line (decreasing position) from 3 (b) could be determined, then the information from the module (SR2) in the module (SR4) can be used to identify the relevant or applicable value of the value pair. In addition, a filter function can also be provided or implemented in the module (SR4). For example, the calculated actuating position correction factor can be averaged over several determined values in order to filter out disturbances. As a result, the module (SR4) provides a reliably determined adjustment position correction factor 8th , In the case considered here by way of example, this is used as a positioning correction factor 8th a wear path 12 determined.

In the sense of the method step e), an adjustment of an actuation of the multi-plate clutch 4 depending on the positioning correction factor 8th be made such that the determined adjustment position correction factor 8th is provided as output variable (S4) a higher-level control position controller, wherein the adjustment position correction factor, a target position of the control position control is corrected. The output variable (S4) can also be stored in a non-volatile memory, for example the control unit 11 is assigned to be filed. In addition, the output variable (S4) of one cycle can be made available to a subsequent cycle as the initialization variable (S3) or as the start value.

Thus, a method is disclosed that at least partially solves the problems described with reference to the prior art. The method makes it possible to perform a calibration of a position control of the clutch assembly during operation of the drive train of the vehicle. In addition, excessive, additional stress on the clutch unit can be avoided. In addition, loads on the vehicle battery and the electrical system and unnecessary noise emissions can be avoided after stopping the vehicle engine.

LIST OF REFERENCE NUMBERS

1

A clutch unit

2

powertrain

3

vehicle

4

multi-plate clutch

5

operating unit

6

Real positioning position

7

Nominal position

8th

Setting position correction factor

9

Primary axis

10

Secondary axis

11

Electronic control unit

12

wear path

13

Setting position sensor

14

engine

15

speed transmission

16

wheel

17

signal conductor

18

sideshaft

19

longitudinal wave

20

BUS arrangement

21

actuating line

22

Transfer Case

23

differential gear

24

contact force

25

Electronic servomotor

26

Reduction gear

27

input shaft

28

output shaft

29

support ring

30

adjusting

31

Bullet

32

Ball grooves of the support ring

33

Ball grooves of the adjusting ring

34

righting moment

35

angle of rotation

Claims (10)

Method for operating a drive train ( 2 ) of a vehicle ( 3 ) with a clutch unit ( 1 ), wherein the clutch unit ( 1 ) at least one multi-plate clutch ( 4 ) and at least one actuator unit ( 5 ) for actuating the multi-plate clutch ( 4 ), the method comprising at least the following steps: a) determining at least one real positioning position ( 6 ) of the operating unit ( 5 ) in at least one operating point of the actuating unit defined by at least one operating point parameter ( 5 b) calculating at least one nominal setting position ( 7 ) of the operating unit ( 5 ) as a function of the operating point parameter, c) comparing the determined real actuating position ( 6 ) with the calculated nominal setting position ( 7 ) at the operating point, d) forming a setting position correction factor ( 8th ) as a function of the comparison of the determined real positioning position ( 6 ) with the calculated nominal setting position ( 7 ), e) adjusting an actuation of the multi-plate clutch ( 4 ) as a function of the positioning correction factor ( 8th ). Method according to claim 1, wherein during the operation of the drive train ( 2 ) is carried out. Method according to claim 1 or 2, wherein the at least one operating point parameter is at least one of the following parameters: - actuating torque of the actuating unit ( 5 ), - actuating force of the actuating unit ( 5 ), - control current of the actuator unit ( 5 ). Method according to one of the preceding claims, wherein before step e) it is checked on the basis of a decision criterion whether the nominal setting position ( 7 ) can be reliably calculated or calculated at the operating point and wherein the nominal positioning position ( 7 ) only for adjusting the operation of the multi-plate clutch ( 4 ) is taken into account when the decision criterion indicates that the nominal positioning position ( 7 ) at the operating point can be reliably calculated or calculated. Method according to claim 4, wherein the decision criterion indicates that the nominal setting position ( 7 ) can be reliably calculated or calculated at the operating point if, at the operating point, a monotonous change in at least the real actuating position ( 6 ) or the nominal positioning position ( 7 ) is present. Method according to one of the preceding claims, wherein in forming the setting position correction factor ( 8th ) in step d) at least two comparison results from step c) are taken into account and averaged. Method according to one of the preceding claims, wherein the actuating unit ( 5 ) too Wear measurement purposes during operation of the drive train ( 2 ) is controlled with at least one predetermined actuation profile, wherein the actuation profile is set up and determined, the driving characteristics of the vehicle ( 3 ) not to influence. Method according to one of the preceding claims, wherein the method is carried out when a function of the operation of the clutch unit ( 1 ) exceeds a predetermined threshold value, the wear variable depending on at least one of the following parameters: - duration of service of the clutch assembly ( 1 ), - the distance traveled by the vehicle ( 3 ), and - energy input into the multi-plate clutch ( 4 ). Vehicle ( 3 ) with a clutch unit ( 1 ) for the variable distribution of torque on different axes ( 9 . 10 ) of the vehicle ( 3 ), wherein the clutch unit ( 1 ) an electronic control unit ( 11 ), which is suitable and arranged for carrying out a method according to one of the preceding claims. Use of a method according to any one of claims 1 to 8 for determining a wear path ( 12 ) in a clutch unit ( 1 ), whereby the wear path ( 12 ) from the difference between the determined real positioning position ( 6 ) and the calculated nominal positioning position ( 7 ) is calculated.

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