DE102014226638B4 - Method for controlling the drive train of a motor vehicle - Google Patents

Abstract

Method for controlling a drive train (1) of a motor vehicle, which has a drive motor (2) with a drive shaft (3) and a multi-step gearbox (4) with at least one drive shaft (3) of the drive motor (2) via an automated friction clutch (K). connectable input shaft (5) and an output shaft (7) which is drive-connected to drive wheels (11.1, 11.2) of the motor vehicle, with a speed (nGE) of the input shaft (5) being monitored during a shifting process and, depending on the monitoring result, an unfavorable or unsafe operating state of the drive train (1) is prevented, characterized in that in order to identify an operating state of the drive train (1) that endangers traction of the drive wheels (11.1, 11.2), the speed (nGE_neu) of the input shaft (5) present or expected after the shifting operation is divided by at least two independent methods are determined and a drag torque of the drive motor (2) that endangers the traction of the drive wheels (11.1, 11.2) is prevented by a suitable measure if at least one of the independent methods on the input shaft (5) of the multi-step gearbox (4) Speed (nGE_neu) was determined, which reaches or exceeds a definable speed limit value.

Description

The invention relates to a method for controlling the drive train of a motor vehicle, which has a drive motor with a drive shaft and a multi-step gearbox with at least one input shaft that can be connected to the drive shaft of the drive motor via an automated friction clutch and an output shaft that is drive-connected to the drive wheels of the motor vehicle, with Shifting process, especially during a downshift, the speed of the input shaft is monitored and, depending on the monitoring result, an unfavorable or unsafe operating state of the drive train is prevented.

The present invention relates to drive trains of motor vehicles which have a manual or automated shift transmission with at least one input shaft and one output shaft. The at least one input shaft can be connected to the drive shaft of the drive motor, which is preferably designed as an internal combustion engine, via an automated friction clutch, ie one that can be engaged and disengaged by means of a controllable clutch actuator. The output shaft is drive-connected directly or, for example, via a cardan shaft to the final drive of a drive axle of the motor vehicle. The output shaft can also be drive-connected via a transfer case to the axle drives of a number of drive axles and thus to the drive wheels of the motor vehicle.

The multi-step transmission can therefore be a semi-automatic transmission in which only the friction clutch is actuated automatically, but the gears are engaged and disengaged manually using a shift lever. The multi-step transmission can also be a manual transmission in which the gears are engaged and disengaged automatically, but the friction clutch is actuated manually. Likewise, the multi-step transmission required here can also be an automated manual transmission in which, in addition to the automated actuation of the friction clutch, the gears are also automatically engaged and disengaged by means of assigned selector and gear selectors, with the shift initiation being carried out by a control unit using the stored shift characteristics automatically or by actuating a shift actuation element, such as pivoting a shift lever in a manual shift gate of a shift console or actuating a shift paddle arranged behind the steering wheel, can be done manually. In addition, the step-shift transmission assumed here can also be a double-clutch transmission, which has two parallel power transmission branches, each with an input shaft that can be connected to the drive shaft of the drive motor via an automated friction clutch, and with a single output shaft, between which several gears can be shifted automatically.

If a downshift is triggered or carried out in such a stepped shift transmission, i.e. shifted to a lower target gear with a higher transmission ratio, the relevant input shaft is accelerated accordingly when the friction clutch is open during the synchronization of the target gear and the speed of the drive motor is increased before or during the engagement of the associated friction clutch adapted to the increased speed of the input shaft. If this adaptation of the engine speed is not initiated by an engine controller, then the drive engine is accelerated in its speed when the friction clutch is engaged by a corresponding drag torque, which acts as a braking torque on the drive wheels of the drive axle. Depending on the level of the speed difference to be bridged at the friction clutch and the engagement speed of the friction clutch as well as the current traction conditions of the drive wheels, the static friction limit between the road surface and the drive wheels can be exceeded, which in particular causes the lateral stability of the motor vehicle through the drive wheels and thus the driving stability of the motor vehicle to be lost can go.

In order to avoid unfavorable or unsafe operating conditions, methods for controlling the drive train of a motor vehicle are already known in which during a shifting operation the input shaft speed of a step-shift transmission is monitored with regard to exceeding speed limits of a drive motor designed as an internal combustion engine.

So is in the DE 197 45 677 C2 a corresponding method is described according to which the engine speed of the drive motor is recorded during a shifting process instead of the input shaft speed of the multi-step gearbox and, after the target gear has been engaged while the friction clutch is engaged, this is measured for falling below the idling speed as the lower speed limit of the drive motor and for exceeding a predetermined maximum speed as upper speed limit of the drive motor is checked. When the engine speed approaches one of the two speed limits, the friction clutch is disengaged again until it slips and is fully disengaged when the relevant speed limit is reached or exceeded. This is intended to circuit-related stalling or overspeeding of the drive motor can be prevented.

From the DE 199 58 075 A1 a similar method for controlling a drive train provided with an automated friction clutch and an automated manual transmission is known, according to which, when a downshift is requested, based on the current wheel speeds, the engine speed that will occur after the end of the downshift is determined in advance and a predetermined limit speed is exceeded of the drive motor is checked. If the previously determined engine speed exceeds the limit speed of the drive engine, then the gear next higher to the requested target gear is determined as the new target gear of the shifting process. This correction of the target gear is repeated as often as required until the new target gear corresponds to the load gear engaged before the downshift. This is intended to prevent gearshift-related overspeeding of the drive motor.

Another method of this type for controlling a drive train provided with an automated friction clutch and an automated manual transmission is in DE 102 16 548 A1 described. This method provides that during a shifting operation, in particular during a downshift, after the target gear has been engaged, the engagement of the friction clutch is controlled as a function of the engine speed of the drive motor that occurs after the shifting operation has been completed in such a way that the friction clutch is disengaged when a predetermined speed limit is exceeded opened or operated with slip. The relevant engine speed is determined at the beginning of the shifting process from the current wheel speeds either with the translation of the target gear or with the translation of the load gear engaged before the shifting process plus a predetermined speed difference. This is intended to prevent gearshift-related overspeeding of the drive motor.

The known methods for controlling the drive train of a motor vehicle are thus focused on preventing a drive motor designed as an internal combustion engine from stalling or overspeeding during a gear shift, i.e. maintaining the permissible speed range of the drive motor during gear shifts while driving. Since a drive motor that has stalled or been damaged by overspeeding can lead to the drive train being blocked, these known methods also have the side effect of preventing an unfavorable or unsafe operating state of the drive train.

A method adapted for controlling the starting of a vehicle when certain starting-disabling ground conditions prevail, such as loose dirt conditions often encountered off-road, is from US Pat DE 60 2004 012 248 T2 known.

The DE 10 2007 042 354 A1 discloses a differential wear protection system that regulates an engine to prevent damage to a differential driven by the engine.

A method of propelling a vehicle when the vehicle launches on a tread is taught by US Pat DE 11 2010 002 845 T5 disclosed.

The present invention is based on the object of specifying a method for controlling the drive train of a motor vehicle of the type mentioned at the outset, with which a loss of driving stability of the motor vehicle can be prevented with increased safety during a shifting process, in particular during a downshift.

This object is achieved in connection with the features of the preamble of claim 1 in that, in order to detect an operating state of the drive train that endangers the traction of the drive wheels, the speed of the input shaft present or expected after the shifting operation is determined by at least two independent methods and a loss of traction of the drive wheels is prevented by a suitable measure if at least one of the independent methods on the input shaft of the step-shift transmission has determined a speed which reaches or exceeds a predeterminable speed limit value.

Advantageous refinements and developments of the method according to the invention are the subject matter of the dependent claims.

The method according to the invention relates to a drive train of a motor vehicle, known per se, which has a drive motor with a drive shaft and a multi-step gearbox with at least one input shaft that can be connected to the drive shaft of the drive motor via an automated friction clutch and an input shaft that is drive-connected to the final drive of a drive axle of the motor vehicle has stationary output shaft. The method generally provides that during a shifting process, in particular during a downshift, the rotational speed of the input shaft is monitored directly or indirectly and, depending on the monitoring result, an unfavorable or unsafe operating state of the drive train is prevented.

When shifting down, the input shaft of the step-shift transmission is accelerated, so that the drive motor must also be accelerated accordingly before or during engagement of the friction clutch. If this is not prompted by the engine control of the drive motor, then the drive motor is dragged up to the speed of the target gear via the engaging friction clutch. The required drag torque of the drive motor acts as a braking torque on the drive wheels of the drive axle. In order to prevent with increased certainty that too high a drag torque of the drive motor leads to the static friction limit between the roadway and the drive wheels being exceeded, it is provided according to the invention that, in order to detect an operating state of the drive train that endangers the traction of the drive wheels, the operating state present after the shifting process or the speed of the input shaft to be expected is determined by at least two methods that are independent of one another and a drag torque of the drive motor that endangers the traction of the drive wheels is prevented by a suitable measure if at least one of the methods that are independent of each other was used to determine a speed on the input shaft of the multi-step gearbox that reaches or exceeds the specified speed limit. As a result, the lateral guidance of the motor vehicle by the drive wheels and thus the driving stability of the motor vehicle are retained.

The maximum permissible speed of the drive motor, for example, can be defined as a predefinable speed limit value. If, for example, a downshift is to be carried out from a currently engaged gear, for example gear 6, to the next lower gear, for example gear 5, incorrect shifting can result in an incorrect lower gear, for example gear 1, being selected as the new gear instead of the next lower gear is inserted. Such a downshift, for example a downshift from gear 6 to gear 1, would result in the drive engine being dragged up to a speed above the maximum permissible speed of the drive engine when the friction clutch was closed and being mechanically blocked due to the overspeed then occurring. which could lead to a loss of traction of the drive wheels of the motor vehicle.

Alternatively or in addition to the above-described speed limit value, a maximum permissible speed difference between the speed of the input shaft in the new gear and a reference speed of the drive motor should also be understood as a predefinable speed limit value. Due to the direct relationship between the speed of the input shaft and the difference in speed between the speed of the input shaft and the speed of the drive motor, a downshift into an incorrect low gear due to an input shaft speed that is present or expected to be too high after the shifting process on the input shaft would inevitably result in a high speed difference between the speed of the input shaft and the speed of the drive motor. From the maximum permissible differential speed and the reference speed of the drive motor, a maximum permissible speed on the input shaft of the multi-step gearbox can thus be directly inferred, which can also be below the maximum speed of the drive motor. If the speed difference between the speed of the input shaft in the new gear and a reference speed of the drive motor is greater than the maximum permissible speed difference, then the drive train would be severely braked by the drag torque of the drive motor that prevails when the friction clutch is closed, which also leads to the loss of the static friction limit could.

The reference speed of the drive motor is preferably between an idle speed and a maximum speed of the drive motor. The maximum speed of the drive motor can be understood, for example, as a maximum speed specified by the motor manufacturer or a maximum speed specified by the motor manufacturer plus a speed offset. Depending on the engine control, an engine speed lying between the current engine speed and the maximum speed of the drive motor is preferably used as the reference speed of the drive motor. If the engine speed is not automatically increased by the engine control during the downshift, the current engine speed forms the reference speed of the drive engine. If the engine speed is increased by the engine control during the downshift to the maximum permissible speed of the drive engine, the reference speed of the drive engine is between the current engine speed and the maximum speed of the drive engine, depending on the target speed of the input shaft.

In order to be able to detect an impending loss of traction on the drive wheels of the drive axle in advance, i.e. before the shifting process is carried out or completed, it can be provided that a speed gradient is calculated from the speed difference between the speed of the input shaft and the reference speed of the drive motor as well as a predetermined engagement period of the friction clutch is formed, with which the drag torque for acceleration of the drive motor is determined, and that from the drag torque of the Drive motor with the translation of the new gear and the translation of the axle drive determines the wheel braking torque effective on the drive wheels and compares it with the maximum wheel torque that can be transmitted by the drive wheels due to static friction.

A first method for determining the speed of the input shaft now provides that the speed of the input shaft of the multi-step gearbox is detected after the new gear has been engaged by means of a speed sensor which is arranged on the input shaft or on a transmission shaft which is permanently drive-connected to the input shaft.

A second method for determining the speed of the input shaft provides that the speed of the input shaft of the multi-step gearbox is determined from the speed of a countershaft after the new gear has been engaged with the translation of an input constant. The speed of the countershaft of the stepped transmission is preferably detected by means of a speed sensor which is arranged on the countershaft of the stepped transmission.

A third method for determining the speed of the input shaft provides that the speed of the input shaft of the multi-step gearbox is calculated from the speed of the output shaft after the new gear has been engaged, taking into account the translation of the new gear. The rotational speed of the output shaft of the multi-step transmission is preferably detected by means of a rotational speed sensor which is arranged on the output shaft or on a rotating element which is permanently drive-connected to the output shaft.

A fourth method for determining the speed of the input shaft provides that the speed of the input shaft of the multi-step gearbox is calculated from the detected speeds of the drive wheels after the new gear has been engaged, taking into account the translation of the new gear and the translation of an axle drive of a drive axle. For this purpose, the speeds of the drive wheels detected by means of wheel speed sensors are preferably averaged and multiplied by the transmission ratio of the axle drive and the transmission ratio of the new gear.

Another method for determining the speed of the input shaft provides that the speed of the input shaft is calculated from the speed of the output shaft before the new gear is engaged, taking into account the translation of the new gear. The rotational speed of the output shaft of the multiple-ratio transmission is preferably detected by means of a further rotational speed sensor arranged on the output shaft or on a rotating element which is permanently drive-connected to the output shaft.

The method for determining and checking the speed of the input shaft of the multi-step gearbox can be used both in an automatically shiftable multi-step gearbox and in a manually shiftable multi-step gearbox. For example, in a manually shiftable multi-step transmission, the current position of the transmission adjustment mechanism can be detected by sensors, as a result of which the new gear into which the driver will shift can already be determined before the new gear is engaged. Thus, even in the case of a manually shiftable stepped shift transmission, the rotational speed of the input shaft can be calculated from the rotational speed of the output shaft before the new gear is engaged, taking into account the translation of the new gear. The sensors for determining the position of the transmission adjustment mechanism can be arranged, for example, on or in the shift lever.

The at least two mutually independent methods for determining the rotational speed of the input shaft of the step-shift transmission are preferably carried out simultaneously. In this way, a speed at the input shaft of the transmission that exceeds the speed limit value can be detected early and with a high level of certainty. If a method for determining the speed of the input shaft fails, for example due to a defective speed sensor, then the speed of the input shaft can be further determined by the at least one other method. Due to the existing redundant determination of the target speed of the input shaft, higher safety requirements can be met.

Since a speed that is present on the input shaft of the stepped shift transmission and exceeds the speed limit value only leads to an unfavorable or unsafe operating state of the drive train in combination with a closed drive train, in an advantageous development of the method according to the invention, in addition to the current or to be expected after the engagement of the new gear Speed of the input shaft determines a degree of engagement of the friction clutch. A measure to prevent the loss of traction of the drive wheels can preferably be carried out when both a speed exceeding the speed limit value and an engagement of the friction clutch have been detected on the input shaft of the step-shift transmission.

In order to monitor and control the engagement process of the friction clutch, the degree of engagement of the friction clutch can be detected based on the activation of an associated clutch actuator of the friction clutch. In the case of a hydraulically or pneumatically actuated clutch actuator, both an actuating pressure of the clutch actuator and control voltages or control currents of the associated electrohydraulic or electropneumatic control valves can be detected and evaluated for this purpose. In the case of a clutch actuator that can be actuated by an electric motor, both a working current and a control voltage of the clutch actuator can be detected and evaluated for this purpose. To monitor and control the engagement process of the friction clutch, the degree of engagement of the friction clutch can also take place using at least one position or displacement sensor, which is arranged, for example, on the clutch actuator or on an electric motor for actuating the clutch actuator and provides a position or displacement signal.

An alternative or additional possibility for monitoring and controlling the engagement process of the friction clutch consists in detecting the degree of engagement of the friction clutch by means of a travel sensor arranged directly on the friction clutch or on an actuating element of the friction clutch.

In a preferred embodiment of the method according to the invention, it is provided that the degree of engagement of the friction clutch is determined by at least two methods which are independent of one another and are preferably carried out simultaneously. An engagement of the friction clutch can thus be detected early and with a high degree of certainty. A measure to prevent the loss of traction of the drive wheels can preferably be carried out when, on the one hand, a speed has been determined on the input shaft of the step-shift transmission that reaches or exceeds the predefinable speed limit value and, on the other hand, an engagement is carried out using at least one of the mutually independent methods determining the degree of engagement of the friction clutch of the friction clutch is detected. If a method for determining the degree of engagement of the friction clutch fails, then the degree of engagement of the friction clutch can be further determined by the at least one further method. Due to the existing redundant determination of the degree of engagement of the friction clutch, higher safety requirements can thus be met.

If a new gear is already engaged in the multi-step transmission during a shifting process and a speed has been determined on the input shaft of the multi-step transmission that reaches or exceeds the predefinable speed limit value, then various variants are conceivable as implementing measures to prevent a loss of traction of the drive wheels.

In a first variant of the method according to the invention, it is provided that the engagement of the friction clutch is prevented. In the case of an automated multi-step transmission, it is then possible to automatically switch to a higher gear or, if the multi-step transmission is designed as a dual-clutch transmission, to remain in the load gear that is still engaged. In a manually shiftable version of the transmission, the driver can then be prompted by a suitable signal to manually shift to a higher gear.

In a second variant of the method according to the invention, it is provided that the engagement period for engaging the friction clutch is extended. The increase in the duration of engagement reduces the speed gradient when the friction clutch is engaged, thereby reducing the drag torque acting as braking torque on the drive wheels to accelerate the drive motor. If this is done to a sufficient extent, the static friction limit between the roadway and the drive wheels of the drive axle can be prevented from being exceeded, and a loss or reduction in the driving stability of the motor vehicle can thus be avoided.

In a third variant of the method according to the invention, it is provided that the new gear already engaged is disengaged again. If no gear is then engaged in the multi-step gearbox, the friction clutch can also be engaged when the input shaft speed is recognized as overspeed, since the engagement of the friction clutch does not lead to an unfavorable or unsafe operating state of the drive train.

If, on the other hand, the speed of the input shaft is calculated from the speed of the output shaft before the new gear is engaged, taking into account the ratio of the new gear, and if a speed is detected on the input shaft of the multi-step gearbox that reaches or exceeds the specified speed limit value, then the measures to be taken to Various variants are also conceivable to prevent a loss of traction of the drive wheels.

Thus, in a fourth variant of the method according to the invention, it is provided that the engagement of the new gear is prevented. In the case of an automated multi-step transmission, the next higher gear can then be used as the new target gear determined and the check according to the invention repeated for the new target gear. This procedure can be repeated until a speed that matches the ratio of the target gear on the input shaft of the transmission has been calculated. If the multi-step transmission is designed as a dual-clutch transmission, it is also possible to remain in the load gear that is still engaged. In a manually shiftable version of the manual transmission, the driver can then be prompted by a suitable signal to manually shift to the next higher gear as the new target gear, and the check according to the invention can be repeated for the new target gear. The engagement of the impermissible gear can, for example, be mechanically blocked in a manual transmission. If the manually shiftable transmission has a shifting device with a shifting aid, for example a servo-assistance device, then the impermissible gear can also be prevented from being engaged by blocking the shifting aid.

In a fifth variant of the method according to the invention, it is provided that although the new gear is engaged, engagement of the friction clutch is prevented. In the case of an automated multi-step transmission, the new gear can then be disengaged again and switched to a higher gear, or if the multi-step transmission is designed as a double-clutch transmission, the load gear that is still engaged can remain. In a manually shiftable version of the transmission, the driver can then be prompted by a suitable signal to manually shift to a higher gear.

In a sixth variant of the method according to the invention, it is provided that although the new gear is engaged, the engagement duration for engaging the friction clutch is extended. If this is done to a sufficient extent, the static friction limit between the roadway and the drive wheels of the drive axle can be prevented from being exceeded, and a loss or reduction in the driving stability of the motor vehicle can thus be avoided.

In a particularly advantageous embodiment of the method according to the invention, the measure for preventing a loss of traction of the drive wheels is configured redundantly via at least two control paths that are independent of one another. Thus, a measure for preventing traction loss of the drive wheels can be carried out with high certainty. If a measure to prevent a loss of traction of the drive wheels fails, then a loss of traction of the drive wheels can be prevented by the at least one further measure. Due to the existing redundant design of the measure to prevent a loss of traction of the drive wheels, higher safety requirements can thus be met.

According to the invention, in addition to the speed of the input shaft that is present or expected after the new gear is engaged, the degree of engagement of the friction clutch can also be determined by at least two independent methods, with the individual methods taking into account different independent input parameters, for example.

The individual methods for determining the speed of the input shaft and the degree of engagement of the friction clutch, as well as the measure to prevent a loss of traction of the drive wheels, can be carried out by means of different signal paths, which are physically separated from one another and/or executed on physically separate control or computing units that are independent of one another become. As a result, even higher security requirements can be met.

The actuation of the friction clutch, like the actuation of a shift actuator for engaging and disengaging transmission gears, can take place via at least two actuation paths connected in parallel. Thus, in each case a plurality of actuators can be provided for actuating the friction clutch or the shift actuator. The actuators can be designed as inlet valves and as outlet valves. Accordingly, two actuators are available in each case for actuating the friction clutch or the shift actuator in both directions of actuation, so that redundant actuators are therefore available for actuation in each direction of actuation. In principle, the redundant actuators are used for a uniform actuation of the friction clutch or the shift actuator, but they can differ in terms of their dimensions. The at least two inlet valves and the at least two outlet valves can thus have different cross sections.

The control device according to the invention for carrying out the method according to the invention comprises a plurality of computing and evaluation units that are independent of one another and signal paths that are independent of one another. The at least two mutually independent methods for determining the rotational speed of the input shaft that is present or to be expected after the new gear has been engaged are executed on two mutually independent computing units. Likewise, the at least two mutually independent methods for determining the degree of indentation of the Rei exercise coupling can be carried out on two independent computing units. The at least two independent measures to prevent a loss of traction of the drive wheels can be triggered by output signals from two independent evaluation units. The mutually independent arithmetic units, like the evaluation units, can be embodied as arithmetic units or evaluation units that are physically separate from one another. Arithmetic or evaluation units are to be understood here, inter alia, as microcontrollers or microprocessors or other electrical circuits familiar to a person skilled in the art, which are suitable for processing or for generating the respective signals.

If a computing or evaluation unit fails, the detection of the speed of the input shaft that is present or expected after the new gear has been engaged or the determination of the degree of engagement of the friction clutch or the measures to prevent a loss of traction of the drive wheels can be carried out by the at least one additional Arithmetic and evaluation unit take place. Higher security requirements can thus be met by the existing redundant computing or evaluation units. If the redundant arithmetic or evaluation units that are present are of diverse design, then an even higher safety requirement can be met through the physical separation.

The motor vehicle according to the invention comprises at least one drive train, which has a drive motor with a drive shaft and a multi-step gearbox with at least one input shaft that can be connected to the drive shaft of the drive motor via an automated friction clutch and an output shaft that is drive-connected to the drive wheels of the motor vehicle, and a control device according to the invention for carrying out the operation according to the invention procedure.

• 1 eine Ausführungsform eines Antriebsstrangs zur Anwendung des Verfahrens gemäß der Erfindung, und
• 2 ein Blockschaltbild einer erfindungsgemäßen Steuerungseinrichtung zur Durchführung des erfindungsgemäßen Verfahrens.

To further clarify the invention, the description is accompanied by a drawing with two exemplary embodiments. In this shows

• 1 an embodiment of a power train for applying the method according to the invention, and
• 2 a block diagram of a control device according to the invention for carrying out the method according to the invention.

In 1 Accordingly, a first embodiment of a drive train 1 of a motor vehicle is shown schematically, in which the method for avoiding an unfavorable or unsafe operating state can be used.

The drive train 1 has a drive motor 2, embodied as an internal combustion engine, for example, with a drive shaft 3, a manual or automated shift transmission 4 with an input shaft 5 and an output shaft 7, and a drive axle 8 with an axle drive 9, two drive shafts 10.1, 10.2 and two drive wheels 11.1 , 11.2 on. The input shaft 5 of the multiple-ratio transmission 4 can be connected to the drive shaft 3 of the drive motor 2 via a friction clutch K that can be engaged and disengaged automatically. A clutch actuator that can be controlled by a control unit is not shown separately, but is known per se.

The multiple-ratio transmission 4 is designed, for example, as a countershaft design and has a countershaft 6 which is in drive connection with the input shaft 5 via an input constant KE designed as a spur gear stage. Between the countershaft 6 and the output shaft 7 several selectively switchable spur gears with different translations are arranged in a manner not shown, via which the input shaft 5 and the output shaft 7 with the corresponding gear ratio can be brought into driving connection with each other. The output shaft 7 of the multi-step gearbox 4 is in drive connection with the drive wheels 11.1, 11.2 of the drive axle 8 via the axle drive 9 and the two drive shafts 10.1, 10.2.

A speed sensor S1 is arranged on the drive shaft 3 of the drive motor 2 to detect the speed n _M of the drive motor 2 . A speed sensor S2 is arranged on the input shaft 5 of the multi-step gearbox 4 in order to detect the input shaft speed n _GE of the multi-step gearbox 4 . Another speed sensor S3 is arranged on the countershaft 6 of the multi-step gearbox 4 . This rotational speed sensor S3 on the countershaft 6 can be used as an alternative or in addition to the rotational speed sensor S2 arranged on the input shaft 5 to determine the input shaft rotational speed n _GE of the stepped shift transmission 4 . For this purpose, the speed n _GV of the countershaft 6 detected by the speed sensor S3 on the countershaft 6 is multiplied by the translation i _KE of the input constant KE (n _GE =n _GV * i _KE ).

To detect the output shaft speed n _GA of the multi-step gearbox 4, two speed sensors S4, S6 are arranged on the output shaft 7 of the multi-step gearbox 4, for example. A wheel speed sensor S5.1, S5.2 is arranged on each of the drive shafts 10.1, 10.2 of the drive axle 8 for detecting the wheel speeds n _R1 , n _R2 of the drive wheels 11.1, 11.2. The wheel speed sensors S5.1, S5.2 can be part of a driving safety system, such as As an anti-lock braking system, a traction control system or others, but they can also be used to determine the output shaft speed n _GA of the multi-step gearbox 4 as an alternative or in addition to the speed sensors S4, S6 arranged on the output shaft 7. For this purpose, the speeds n _R1 , n _R2 of the drive wheels 11.1, 11.2 detected by the wheel speed sensors S5.1, S5.2 are averaged and multiplied by the translation i _GA of the final drive 9 of the drive axle 8. The output shaft speed n _GA results from the equation n _GA = ½ ∗ (n _R1 + n _R2 ) ∗ i _GA .

When shifting down, the input shaft 5 of the stepped shift transmission 4 is accelerated, so that the drive motor 2 must also be accelerated accordingly before or during the engagement of the friction clutch K. If this is not prompted by the engine control of the drive motor 2, then the drive motor 2 is dragged up to the speed of the new gear via the engaging friction clutch K. The drag torque of the drive motor 2 required for this is effective as a braking torque on the drive wheels 11.1, 11.2 of the drive axle 8. In order to prevent with increased certainty that an excessive drag torque of the drive motor 2 leads to the static friction limit between the roadway and the drive wheels 11.1, 11.2 being exceeded, the invention provides that for the detection of an operating state endangering the traction of the drive wheels 11.1, 11.2 of drive train 1, a _new or expected speed of input shaft 5 after the new gear G has been engaged is determined using at least two methods that are independent of one another, and a loss of traction on drive wheels 11.1, 11.2 is prevented by a suitable measure if at least one of the methods is of the input shaft 5 of the stepped shift transmission 4, a speed n _{GE_new} was determined, which reaches or exceeds a definable speed limit value.

• - Erfassen der Drehzahl n_{GE_neu} der Eingangswelle 5 des Stufenschaltgetriebes 4 nach dem Einlegen des neuen Gangs G_neu mittels des Drehzahlsensors S2, der an der Eingangswelle 5 oder an einer permanent mit der Eingangswelle 5 in Triebverbindung stehenden Getriebewelle angeordnet ist,
• - Ermitteln der Drehzahl n_{GE_neu} der Eingangswelle 5 des Stufenschaltgetriebes 4 nach dem Einlegen des neuen Gangs G_neu mit der Übersetzung i_KE der Eingangskonstante KE aus der Drehzahl n_GV einer Vorgelegewelle 6, welche mittels des Drehzahlsensors S3 erfasst wird, der an der Vorgelegewelle 6 des Stufenschaltgetriebes 4 angeordnet ist,
• - Ermitteln der Drehzahl n_{GE_neu} der Eingangswelle 5 des Stufenschaltgetriebes 4 nach dem Einlegen des neuen Gangs G_neu mit der Übersetzung i_{G_neu} des neuen Gangs G_neu aus der Drehzahl n_GA der Ausgangswelle 7, welche mittels dem an der Ausgangswelle 7 angeordneten Drehzahlsensors S4 erfasst wird,
• - Ermitteln der Drehzahl n_{GE_neu} der Eingangswelle 5 des Stufenschaltgetriebes 4 nach dem Einlegen des neuen Gangs mit der Übersetzung i_{G_neu} des neuen Gangs G_neu aus der Drehzahl n_GA der Ausgangswelle 7, welche mittels Raddrehzahlsensoren S5.1, S5.2 ermittelt wird, wobei die von den Raddrehzahlsensoren S5.1, S5.2 erfassten Drehzahlen n_R1, n_R2 der Antriebsräder 11.1, 11.2 gemittelt und mit der Übersetzung i_GA des Achsgetriebes 9 der Antriebsachse 8 multipliziert werden,
• - Ermitteln der Drehzahl n_{GE_neu} der Eingangswelle 5 vor dem Einlegen des neuen Gangs G_neu mit der Übersetzung i_{G_neu} des neuen Gangs G_neu aus der Drehzahl n_GA der Ausgangswelle 7, welche mittels dem an der Ausgangswelle 7 angeordneten Drehzahlsensors S6 erfasst wird.

The speed of the input shaft 5 of the multiple-ratio transmission 4 is determined using at least two of the following methods:

• - Detection of the speed n _{GE_neu} of the input shaft 5 of the multi-step gearbox ₄ after the new gear G has been engaged by means of the speed sensor S2, which is arranged on the input shaft 5 or on a transmission shaft that is permanently drive-connected to the input shaft 5,
• - Determination of the speed n _{GE_neu} of the input shaft 5 of the multi-step gearbox 4 after the engagement of the new gear G _new with the translation i _KE of the input constant KE from the speed n _GV of a countershaft 6, which is detected by the speed sensor S3 on the countershaft 6 of the multi-step gearbox 4 is arranged,
• - Determination of the speed n _{GE_neu} of the input shaft 5 of the multi-step gearbox 4 after the engagement of the new gear G _new with the translation i _{G_neu} of the new gear G _new from the speed n _GA of the output shaft 7, which is detected by means of the speed sensor S4 arranged on the output shaft 7 becomes,
• - Determination of the speed n _{GE_neu} of the input shaft 5 of the multi-step gearbox 4 after engaging the new gear with the translation i _{G_neu} of the new gear G _new from the speed n _GA of the output shaft 7, which is determined by means of wheel speed sensors S5.1, S5.2, where the speeds n _R1 , n _R2 of the drive wheels 11.1, 11.2 detected by the wheel speed sensors S5.1, S5.2 are averaged and multiplied by the translation i _GA of the final drive 9 of the drive axle 8,
• - Determining the speed n _{GE_neu} of the input shaft 5 before engaging the new gear G _new with the translation i _{G_neu} of the new gear G _new from the speed n _GA of the output shaft 7, which is detected by means of the speed sensor S6 arranged on the output shaft 7.

The at least two of the methods mentioned for determining the rotational speed n _{GE_new} of the input shaft 5 of the stepped shift transmission 4 are preferably carried out simultaneously. Thus, an overspeed on the input shaft 5 of the multi-step transmission 4 can be detected early and with a high level of certainty. If a method for determining the rotational speed n _{GE_neu} of the input shaft 5 fails, then the rotational speed n _{GE_neu} of the input shaft 5 can be further determined by the at least one further method. Due to the existing redundant determination of the rotational speed n _{GE_new} of the input shaft 5 of the stepped shift transmission 4, higher safety requirements can thus be met.

Since an overspeed present on the input shaft 5 of the multi-step gearbox 4 only leads to an unfavorable or unsafe operating state of the drive train 1 in combination with a closed drive train 1, it can be provided that in addition to the _newly existing or expected after the engagement of the new gear G Speed n _{GE_neu} of the input shaft 5, a degree of engagement of the friction clutch K is determined. A measure to prevent the loss of traction of the drive wheels 11.1, 11.2 can preferably be carried out when both the input shaft 5 of the multi-speed gearbox 4 as a speed n _{GE_neu} an overspeed as engagement of the friction clutch K was also recognized.

2 shows a block diagram of a control device 12 according to the invention for carrying out the method according to the invention. The control device 12 here comprises a plurality of independent computing units 13, 14, 15. The first computing unit 13 has an input shaft speed n _GE detected by the speed sensor S2 on the input shaft 5 of the step-shift transmission 4 as an input variable, while the second computing unit 14 has an input variable output shaft speed n _GA detected by means of the speed sensor S4 on the output shaft 7 of the stepped shift transmission 4 .

A first method for determining the rotational speed of the input shaft 5 is carried out using the first computing unit 13 and provides that the rotational speed n _{GE_neu} of the input shaft 5 of the multi-step gearbox 4 is _determined after the new gear G has been engaged using a rotational speed signal which is the input shaft 5 arranged speed sensor S2 is generated. On the basis of the speed of the input shaft 5 detected by the speed sensor S2 as an output variable, the first arithmetic unit 13 generates a signal which indicates whether a speed n _{GE_new} is present on the input shaft 5 of the multi-step transmission 4, which reaches or exceeds a definable speed limit value.

A second method for determining the speed of the input shaft 5, however, is carried out by means of the second computing unit 14 and provides that the speed n _{GE_neu} of the input shaft 5 of the step-shift transmission 4 after the new gear G _new has been engaged, taking into account the translation i _{G_new} of the new gear G is _recalculated from the speed n _GA of the output shaft 7 . For this purpose, the rotational speed n _GA of the output shaft 7 is detected by means of a rotational speed sensor S4 which is arranged on the output shaft 7 . On the basis of the speed n _GA of the output shaft 7 of the multi-step gearbox 4 detected by the speed sensor S4, the second computing unit 14 generates a signal as an output variable which indicates whether a speed n _{GE_new} is present on the input shaft 5 of the multi-step gearbox 4 and reaches a predefinable speed limit value or exceeds

The output variables of the first arithmetic unit 13 and the second arithmetic unit 14 serve as input variables for a first evaluation unit 16 and are evaluated there accordingly. If at least one output variable of the two computing units 13, 14 on the input shaft 5 of the step-shift transmission 4 indicates a speed n _{GE_new} which reaches or exceeds a definable speed limit value, then the evaluation unit 16 generates a signal as an output variable which indicates this, namely that an the input shaft 5 of the multi-step transmission 4 has a speed n _{GE_new} which reaches or exceeds a definable speed limit value. In this exemplary embodiment, this output signal from the first evaluation unit 16 now serves as an input signal for a second evaluation unit 17. The first evaluation unit 16 can be designed, for example, as a simple OR logic module.

At the third computing unit 15 are according to 2 two input variables, by means of which the degree of engagement of the friction clutch K can be inferred. As the first input variable for determining the degree of engagement of the friction clutch K, control voltages or control currents from electrohydraulic or electropneumatic control valves assigned to a clutch actuator are recorded and evaluated here. As a second input variable for determining the engagement process of the friction clutch K, a signal is evaluated which is made available by a travel sensor arranged directly on the friction clutch or on an actuating element of the friction clutch.

The degree of engagement of the friction clutch K is determined in the arithmetic unit 15 on the basis of the input signals present and is output as an output variable which serves as a further input variable for the second evaluation unit 17 . If it is determined by means of the second evaluation unit 17 that a speed n _{GE_neu} is present on the input shaft 5 of the multi-step gearbox 4, which speed reaches or exceeds a definable speed limit value and the friction clutch is actuated in the closing direction, then a measure to prevent a loss of traction of the drive wheels 11.1, 11.2 carried out. This measure to prevent the loss of traction of the drive wheels 11.1, 11.2 is triggered by a corresponding output signal from the evaluation unit 17 and can be configured differently depending on whether the _new gear G is already engaged in the multi-step gearbox 4 or not. For example, when the new gear G _new is already engaged, the engagement of the friction clutch K can be prevented or the engagement duration for the engagement of the friction clutch K can be extended. If, on the other hand, the new gear G _new has not yet been engaged in the multi-step gearbox 4, then measures to prevent a loss of traction of the drive wheels 11.1, 11.2 can be provided, for example, that the engagement of the new gear G _new is prevented, or that the new gear G _newly inserted, but engagement of the friction clutch K is prevented.

The arithmetic units 13, 14, 15 and evaluation units 16, 17 mentioned here can be microcontrollers or microprocessors or other electrical circuits familiar to a person skilled in the art which are suitable for processing or generating the respective signals.

The input variables mentioned in the exemplary embodiment for determining the speed present on the input shaft 5 of the stepped shift transmission 4 and for determining the degree of engagement of the friction clutch K are to be regarded as examples only and are not intended to limit the invention. The same applies to the measures mentioned in the exemplary embodiment for preventing the drag torque of the drive motor that endangers the traction of the drive wheels. Rather, the features of the invention disclosed in the above description, in the figures and in the patent claims should be able to be taken into account in any combination for the implementation of the invention.

reference list

1

powertrain

2

drive motor, internal combustion engine

3

drive shaft of the drive motor

4

multi-step gearbox

5

Input shaft of multi-step gearbox 4

6

Countershaft of multi-step gearbox 4

7

Output shaft of multi-step gearbox 4

8th

drive axle

9

final drive

10.1

First driveshaft

10.2

Second driveshaft

11.1

First drive wheel

11.2

Second drive wheel

12

control device

13

first unit of account

14

second computing unit

15

third unit of account

16

first evaluation unit

17

second evaluation unit

gneu

new gear of the multi-step gearbox 4

iGA

Translation of the final drive 9

iG_new

Ratio of the multi-step gearbox 4 _new when G is engaged

iKE

Translation of the input constant KE

K

friction clutch

KE

Input constant of the multi-step gearbox 4

nGA

output shaft speed

nGE

input shaft speed

nGE_new

Input shaft speed with new gear G _new

nGV

number of revolutions

nM

engine speed

number 1

Wheel speed of the first drive wheel 11.1

No. 2

Wheel speed of the second drive wheel 11.2

S1

Speed sensor on the drive shaft 3 of the drive motor 2

S2

Speed sensor on the input shaft 5 of the multi-step gearbox 4

S3

Speed sensor on countershaft 6 of multi-step gearbox 4

S4

Speed sensor on output shaft 7 of multi-step gearbox 4

S5.1

Wheel speed sensor on first drive shaft 10.1

S5.2

Wheel speed sensor on second drive shaft 10.2

S6

Speed sensor on output shaft 7 of multi-step gearbox 4

Claims (12)

Method for controlling a drive train (1) of a motor vehicle, which has a drive motor (2) with a drive shaft (3) and a multi-step gearbox (4) with at least one drive shaft (3) of the drive motor (2) via an automated friction clutch (K). connectable input shaft (5) and with drive wheels (11.1, 11.2) of the motor vehicle in drive connection output shaft (7), wherein during a switching operation, a speed (n _GE ) of the input shaft (5) monitored and depending on the monitoring Calculation result prevents an unfavorable or unsafe operating state of the drive train (1), characterized in that to detect an operating state of the drive train (1) that endangers traction of the drive wheels (11.1, 11.2), the speed (n _{GE_neu} ) that is present or is to be expected after the shifting process of the input shaft (5) is determined by at least two independent methods and a drag torque of the drive motor (2) that endangers the traction of the drive wheels (11.1, 11.2) is prevented by a suitable measure if at least one of the independent methods on the input shaft ( 5) a speed (n _{GE_neu} ) of the stepped shift transmission (4) was determined which reaches or exceeds a predefinable speed limit value. procedure after claim 1 , characterized in that the predefinable speed limit is defined by a maximum permissible speed of the drive motor (2) or by a maximum permissible speed difference between the speed (n _{GE_new} ) of the input shaft in a new gear (G _new ) and a reference speed of the drive motor. procedure after claim 2 , characterized in that the speed of the input shaft (5) of the multi-step gearbox (4) is determined using at least two of the following methods: - detecting the speed (n _{GE_new} ) of the input shaft (5) of the multi-step gearbox (4) after engaging the new gear (G _new ) by means of a speed sensor (S2) which is arranged on the input shaft (5) or on a transmission shaft which is permanently drive-connected to the input shaft (5), - determining the speed (n _{GE_new} ) of the input shaft (5) of the step-shift transmission (4) after inserting the new gear (G _new ) with a translation (i _KE ) of an input constant (KE) from a speed (n _GV ) of a countershaft (6) (n _GE = n _GV ∗ i _KE ), which means a speed sensor (S3), which is arranged on the countershaft (6) of the multi-step gearbox (4), - determining the speed (n _{GE_new} ) of the input shaft (5) of the multi-step gearbox (4) after engaging the new gear (G _new ) with a translation (i _G _ _new ) of the new gear (G _new ) from a speed (n _GA ) of the output shaft (7) (n _{GE_new} = n _GA ∗ i _G _ _new ), which by means of at least one speed sensor (S4) is detected, which is arranged on the output shaft (7) or on a rotating element that is permanently drive-connected to the output shaft (7), - determining the rotational speed (n _{GE_neu} ) of the input shaft (5) of the multi-step gearbox (4) after the new one has been inserted Gears with the translation (i _G _ _new ) of the new gear (G _new ) from the speed (n _GA ) of the output shaft (7) (n _{GE_new} = n _GA ∗ i _G _ _new ), which are determined by means of wheel speed sensors (S5.1, S5.2) is determined, with the speeds (n _R1 , n _R2 ) of the drive wheels (11.1, 11.2) detected by the wheel speed sensors (S5.1, S5.2) being averaged and with a translation (i _GA ) of an axle drive (9). Drive axle (8) are multiplied (n _GA = ½ ∗ (n _R1 + n _R2 ) ∗ i _GA .), - Determining the speed (n _{GE_new} ) of the input shaft (5) before engaging the new gear (G _new ) with the Translation (i _G _ _new ) of the new gear (G _new ) from the speed (n _GA ) of the output shaft (7) (n _{GE_new} = n _GA * i _G _ _new ), which is detected by means of at least one speed sensor (S6), which is arranged on the output shaft (7) or on a rotating element which is permanently in driving connection with the output shaft (7). procedure after claim 2 or 3 , characterized in that in addition to the speed (n _{GE_new} ) of the input shaft (5) present or to be expected after the new gear (G _new ) is engaged, a degree of engagement of the friction clutch (K) is determined and the measure to prevent a loss of traction of the drive wheels (11.1, 11.2) is carried out when both the speed (n _{GE_neu} ) on the input shaft (5) of the multi-step gearbox (4) which reaches or exceeds the predefinable speed limit value and an engagement of the friction clutch (K) has been determined. procedure after claim 4 , characterized in that the degree of engagement of the friction clutch (K) is determined by at least two independent methods. procedure after claim 5 , characterized in that the degree of engagement of the friction clutch (K) is determined using at least two of the following methods: - determining the degree of engagement of the friction clutch (K) based on activation of an associated clutch actuator of the friction clutch (K), - determining the degree of engagement of the friction clutch (K ) by means of a displacement sensor arranged directly on the friction clutch (K), - determining the degree of engagement of the friction clutch (K) by means of a displacement sensor arranged on an actuating element of the friction clutch (K). Procedure according to one of Claims 4 until 6 , characterized in that when the new gear (G _new ) is engaged in the multi-step gearbox (4) and the speed (n _{GE_new} ) has been detected on the input shaft (5) of the multi-step gearbox (4), which reaches the predefinable speed limit value or exceeds at least one of the following measures to prevent traction loss of the drive wheels (11.1, 11.2) is carried out: - preventing engagement of the friction clutch (K), - extending an engagement period for engaging the friction clutch (K) - disengaging the new gear already engaged (G _new ). Procedure according to one of Claims 4 until 6 . _{_ _} is engaged, at least one of the following measures to prevent the loss of traction of the drive wheels (11.1, 11.2) is carried out: - Prevention of engagement of the new gear (G _new ), - Engagement of the new gear (G _new ), but prevention of engagement of the friction clutch (K) - engaging the new gear (G _new ), but extending an engagement period for engaging the friction clutch (K). Procedure according to one of Claims 4 until 8th , characterized in that the measure to prevent the loss of traction of the drive wheels (11.1, 11.2) is designed redundantly via at least two independent control paths. Procedure according to one of Claims 1 until 9 , characterized in that a control of the friction clutch (K) and / or a control of a shift actuator to carry out the shifting process via at least two parallel-connected control paths. Control device (12) comprising a plurality of independent computing units (13, 14, 15), wherein a first arithmetic unit (13) is designed to carry out a first method for determining a speed of an input shaft (5) of a stepped transmission (4), a second computing unit (14) is designed to carry out a second method for determining the speed of the input shaft (5), a third arithmetic unit (17) is designed to carry out two mutually independent methods for determining the degree of engagement of the friction clutch (K), a first evaluation unit (16) is designed to output an output variable from the first arithmetic unit (13) and an output variable from the second arithmetic unit (14) to receive as input variables and to generate an output variable, which serves as input variable for a second expansion unit (17), the second evaluation unit (17) is designed to use the output variable received from the first evaluation unit (16) and an output variable received from the third processing unit (15) to generate an output signal which can be used to trigger a measure to prevent a loss of traction on the drive wheels (11.1, 11.2). is. Motor vehicle comprising a drive train (1) which has a drive motor (2) with a drive shaft (3), a step-shift gearbox (4) with at least one input shaft ( 5) and an output shaft (7) which is drive-connected to drive wheels (11.1, 11.2) of the motor vehicle, and a control device (12) according to claim 11 having.

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