Method for controlling a drive unit

Abstract

A method for controlling a drive unit in a motor vehicle with an automated clutch and / or an automated transmission and the drive unit, characterized in that a speed of the drive unit and / or a torque of the drive unit is limited during a predetermined situation, wherein the drive unit is an internal combustion engine and wherein the predetermined situation is an opening of the drivetrain due to a referencing process or an opening of the drivetrain due to compensation of a hydraulic system, wherein the opening of the drivetrain occurs independently of the driver's request, wherein the speed of the drive unit is limited to a predetermined value, wherein the predetermined value is dimensioned such that the clutch is not excessively loaded when re-engaging or partially re-engaging after the opening of the drivetrain following the termination of the predetermined situation, characterized in thatthat the predetermined value is 2000 to 4000 revolutions per minute, preferably 2500 to 3500 revolutions per minute, or wherein the speed of the drive unit is limited to a predetermined value, wherein the predetermined value is the engine speed before the drivetrain is opened at the beginning of the predetermined situation, wherein the torque of the drive unit is limited to a predetermined value, wherein the predetermined value is zero, or the predetermined value is such that it compensates for drag torques but does not increase the speed of the drive unit.

Description

The invention relates to a method having the features according to the preamble of claim 1. The invention is generally aimed at vehicles with internal combustion engines and drive trains which, in certain situations, must be temporarily opened against the driver's wishes in order to maintain or restore functionality. This refers specifically to systems with automated clutches and / or automated transmissions, such as dual-clutch transmissions, whose clutch and / or transmission actuators feature incremental position measurement. In real-world operation, a loss of the actual position of an actuator occurs repeatedly, for example, due to electromagnetic interference with the Hall sensors used. In such an event, the actuator position must be re-determined by comparison with one or more reference positions. Such referencing processes generally require the immediate opening of the drivetrain. On the one hand, the reference position of the clutch actuator might be at the "fully open" position; on the other hand, if the clutch's reference position is approached at "fully closed," the drivetrain must be opened for safety reasons, for example, by actively disengaging the current gear.During referencing processes in the gearbox, it may be necessary to actively open the clutch to avoid unexpected starting or acceleration due to incorrect gear selection. Such referencing processes may become necessary during normal driving, i.e., when the accelerator pedal is depressed. Another example of a situation to which the invention extends is the possibly immediate need to equalize a hydraulic path, for example in a device for clutch actuation, the so-called "sniffing". DE 102 21 701 B4 discloses a method for terminating a sailing mode. DE 10 2004 009 833 A1 , DE 44 19 633 B4 , FR 2 890 628 A1 and JP 2001 - 041 065 A disclose methods for controlling a clutch. DE 42 21 044 A1 discloses a control device for an automated transmission. DE 100 43 413 A1 discloses that in a motor vehicle with a drive motor and a control unit for controlling the engine speed and / or the engine torque of the drive motor, wherein in particular in idle operation and / or at low driving speed of the vehicle the engine torque is limited to a predefinable maximum engine torque value. Typically, during the referencing processes described above, the normal driving strategy is interrupted if necessary and then reinitialized. Since such processes can extend over several seconds, the forced opening of the drivetrain when the accelerator pedal is depressed can easily cause the engine speed to reach very high values, up to and including the maximum speed. As a result, the driver experiences an unpleasant engine noise and unnecessary strain on the engine. Upon re-entry into the driving strategy, the high engine speed or the resulting high slip speed – as the difference between engine and transmission speed – can damage the clutch due to high frictional power input. The return to the normal driving strategy when the clutch is closed or partially closed can be unexpectedly harsh and uncomfortable for the driver, as a disturbing acceleration of the combustion engine occurs beforehand during the referencing processes described above. The present invention is based on the objective of further increasing the convenience associated with opening and closing the drive train, for example during referencing processes or when compensating for a hydraulic path. This problem is solved by a method having the features according to claim 1. According to the invention, a method for controlling a drive unit in a motor vehicle is provided, comprising an automated clutch and / or an automated transmission and the drive unit. The invention provides that the rotational speed and / or torque of the drive unit is limited during a predetermined situation, wherein the drive unit is an internal combustion engine and wherein the predetermined situation is the opening of the drivetrain due to a referencing process or the opening of the drivetrain due to the equalization of a hydraulic system. According to the invention, the opening of the drivetrain is provided that it occurs independently of the driver's request. The driver's request can be determined, for example, by the accelerator pedal position and the selector lever position. According to the invention, the rotational speed of the drive unit is limited to a predetermined value, wherein the predetermined value is dimensioned such that the clutch is not excessively stressed when re-engaging or partially re-engaging after the drive train has been opened following the end of the predetermined situation. According to the invention, the specified value is 2000 to 4000 revolutions per minute, preferably 2500 to 3500 revolutions per minute. According to the invention, the rotational speed of the drive unit is limited to a predetermined value, wherein the predetermined value is the motor speed before the drive train is opened at the beginning of the predetermined situation. According to the invention, the torque of the drive unit is limited to a predetermined value, wherein the predetermined value is zero or the predetermined value is dimensioned in such a way that drag torques are compensated, but no increase in the speed of the drive unit occurs. In a preferred embodiment, it is provided that the request for speed limitation or torque limitation is made by the clutch and / or transmission control to the engine control. In an alternative, particularly preferred embodiment, it is provided that the request for speed limitation or torque limitation by the transmission control is made via the more usual channel of the engine torque request or engine torque limitation. In a further preferred embodiment, it is provided that when the situation ceases to exist, the limitation of the speed of the drive unit and / or the torque of the drive unit is terminated. The method according to the invention avoids the unpleasant effects for the driver of opening and closing the drivetrain in the above-mentioned situations, such as a sudden increase in engine speed during driving and a possibly unexpected and / or uncomfortable closing of the drivetrain after the situation has ended. Further advantages and advantageous embodiments of the invention are the subject of the following description. If the powertrain needs to be opened due to immediately necessary referencing processes, contrary to the driver's wishes as indicated by the accelerator pedal and selector lever positions, the engine speed is simultaneously limited to a suitable, predefined value. This can be achieved by a direct speed limiting request from the clutch and transmission control unit to the engine control unit, which, however, requires corresponding functionalities in the engine control unit as well as communication channels between the two control units. Alternatively, the transmission control unit itself can also request an engine speed limit via the usual engine torque request or limiting channel. The engine speed can be limited to a fixed upper limit, designed so that the clutch is not excessively stressed when re-engaged after homing – such a value could be 3000 revolutions per minute. Alternatively, the engine speed present at the start of the homing process can be set as the upper limit, i.e., as the fixed upper limit. Alternatively, instead of limiting the speed, the drive motor's torque can be limited by restricting the drive motor's torque to zero or a slightly positive value to compensate for drag torques during this phase, thus preventing the drive motor from revving up or accelerating. The clutch and transmission actuators of automated powertrains may, in certain situations, require an immediate, temporary opening of the powertrain to ensure correct operation. An example of this is re-establishing actuator reference positions following a temporary malfunction of a Hall sensor. It is proposed to avoid the unpleasant effects for the driver of such processes, such as the sudden increase in engine speed during driving and a potentially unexpected and / or uncomfortable closing of the powertrain after completion, by actively limiting the engine speed and / or engine torque of the internal combustion engine.

Claims

Method for controlling a drive unit in a motor vehicle with an automated clutch and / or an automated transmission and the drive unit, characterized in that a speed of the drive unit and / or a torque of the drive unit is limited during a predetermined situation, wherein the drive unit is an internal combustion engine and wherein the predetermined situation is an opening of the drivetrain due to a referencing process or an opening of the drivetrain due to compensation of a hydraulic system, wherein the opening of the drivetrain occurs independently of the driver's request, wherein the speed of the drive unit is limited to a predetermined value, wherein the predetermined value is dimensioned such that the clutch is not excessively loaded when re-engaging or partially re-engaging after the opening of the drivetrain following the termination of the predetermined situation, characterized in thatthat the predetermined value is 2000 to 4000 revolutions per minute, preferably 2500 to 3500 revolutions per minute, or wherein the speed of the drive unit is limited to a predetermined value, wherein the predetermined value is the engine speed before the drivetrain is opened at the beginning of the predetermined situation, wherein the torque of the drive unit is limited to a predetermined value, wherein the predetermined value is zero, or the predetermined value is such that it compensates for drag torques but does not increase the speed of the drive unit. Method according to one of the preceding claims, characterized in that the request for speed limitation or torque limitation is made from the clutch and / or transmission control to the engine control. Method according to one of the preceding claims, characterized in that the request for speed limitation or torque limitation is made by the transmission control via the more usual channel of engine torque request or engine torque limitation.