Abstract: A method for operating a motor vehicle having a four-wheel drive and a drive unit, which can be switched on and off during travel, wherein the motor vehicle is driven by a torque provided by the drive unit, and the initially disengaged four-wheel drive is switched on, including: determining at least one limit torque which, while the four-wheel drive is switched off, can be transmitted from at least one wheel of the motor vehicle driven by the drive unit to the ground surface upon which the motor vehicle is travelling, while the slip between the at least one wheel and the ground surface falls below a specifiable threshold value.

Abstract: A method for operating a motor vehicle having a four-wheel drive and a drive unit, which can be switched on and off during travel, wherein the motor vehicle is driven by a torque provided by the drive unit, and the initially disengaged four-wheel drive is switched on, including: determining at least one limit torque which, while the four-wheel drive is switched off, can be transmitted from at least one wheel of the motor vehicle driven by the drive unit to the ground surface upon which the motor vehicle is travelling, while the slip between the at least one wheel and the ground surface falls below a specifiable threshold value.

Abstract: A device and method for operating a multi-axle powertrain for a motor vehicle, with a first axle being permanently in operative connection and a second axle being at least temporarily in operative connection by a drive device via a clutch coupling. It is provided that, when the second axle is decoupled from the drive device and the starting clutch is disengaged, an expected wheel force is predictively ascertained. The determination of the wheel force takes into account a torque caused by a mass moment of inertia of the drive device, and the second axle is coupled with the drive device if the expected wheel force surpasses a maximum wheel force.

Abstract: A device and a method for operating a multi-axle drive train for a vehicle. A first axle is operatively connected permanently and a second axle is operatively connected at least intermittently via a clutch to a drive device. For the second axle coupled to the drive device, a maximum torque of the drive device is reduced by a specific safety value. At drive start, the safety value is set to a specific initial value and subsequently is reduced or increased throughout a specific period of time.

Abstract: A multi-axle drive device and method for operating a multi-axle drive device. The multi-axle drive device is provided with a synchronization clutch present in an operational connection between a first output shaft and a connecting shaft and at least one disconnecting clutch present in an operational connection between the connecting shaft and a second output shaft. The synchronization clutch and the disconnecting clutch are opened in a first operating state and closed in a second operating state. At the same time, with an intended change from the second operating state to the first operating state, the synchronization clutch is maintained at least partially opened and the separation clutch is maintained closed, so that, when a first operating mode is carried out, the disconnecting clutch is opened, and when a second operating mode is carried out, the synchronization clutch is closed again.

Abstract: A device and a method for operating a multi-axle drive device. The multi-axle drive device has a synchronizing clutch present in an operative connection between a first output shaft and a connecting shaft and at least one separating clutch present in an operative connection between the connecting shaft and a second output shaft. The synchronizing clutch and the separating clutch are disengaged in a first operating state and are engaged in a second operating state. When a shifting variable exceeds a first shifting threshold during the first operating state, the synchronizing clutch is at least partially engaged and the separating clutch is engaged only when a second shifting threshold is exceeded.

Abstract: A dog clutch having two clutch members provided with claws or teeth, one of which is movable, as well as a positioning device for engaging and disengaging the clutch by a positioning movement of the movable clutch member. In order to establish a proper engaging of the dog clutch, a sensor is arranged along the movement path of the movable clutch member, which detects the movement of the clutch member into the engaged state, while the clutch member is provided with an activating contour which, upon engaging the clutch, moves past the sensor, which is preferably an electromagnetic actuator for holding the movable clutch member in the disengaged state of the clutch.

Abstract: A method for operating a motor vehicle including an all-wheel drive that can be enabled and disabled, and a drive train including two clutches actuated by a control unit for enabling and disabling the all-wheel drive, and components rotating between the two clutches, which components are driven when the all-wheel drive is enabled and are uncoupled from the remaining drive train when the all-wheel drive is disabled. In order to allow early detection of defects and, in particular, bearing defects of the rotating components, and to determine the applied drag torque even without knowing the oil temperature, in one embodiment, when the all-wheel drive is disabled, the rotational speed (n) of at least one of the uncoupled components is measured in a time interval, and an angular acceleration of the uncoupled components is determined therefrom.

Abstract: A device and a method for operating a multi-axle drive train for a motor vehicle. A first axle and a second axle are operatively connected, at least temporarily, to a drive device. When the second axle is decoupled from the drive device and a request for multi-axle drive with a first value is present, the second axle is coupled to the drive device only when a noise-masking event occurs, or when the second axle is coupled to the drive device and the request for multi-axle drive is absent, the second axle is decoupled from the drive device only when the noise-masking event occurs.

Abstract: A device and a method for operating a multi-axle drive device. The multi-axle drive device has a synchronizing clutch present in an operative connection between a first output shaft and a connecting shaft and at least one separating clutch present in an operative connection between the connecting shaft and a second output shaft. The synchronizing clutch and the separating clutch are disengaged in a first operating state and are engaged in a second operating state. When a shifting variable exceeds a first shifting threshold during the first operating state, the synchronizing clutch is at least partially engaged and the separating clutch is engaged only when a second shifting threshold is exceeded.

Abstract: A device and a method for operating a multi-axle drive train for a vehicle. A first axle is operatively connected permanently and a second axle is operatively connected at least intermittently via a clutch to a drive device. For the second axle coupled to the drive device, a maximum torque of the drive device is reduced by a specific safety value. At drive start, the safety value is set to a specific initial value and subsequently is reduced or increased throughout a specific period of time.

Abstract: A method for operating a motor vehicle including an all-wheel drive that can be enabled and disabled, and a drive train including two clutches actuated by a control unit for enabling and disabling the all-wheel drive, and components rotating between the two clutches, which components are driven when the all-wheel drive is enabled and are uncoupled from the remaining drive train when the all-wheel drive is disabled. In order to allow early detection of defects and, in particular, bearing defects of the rotating components, and to determine the applied drag torque even without knowing the oil temperature, in one embodiment, when the all-wheel drive is disabled, the rotational speed (n) of at least one of the uncoupled components is measured in a time interval, and an angular acceleration of the uncoupled components is determined therefrom.

Abstract: A device and method for operating a multi-axle powertrain for a motor vehicle, with a first axle being permanently in operative connection and a second axle being at least temporarily in operative connection by a drive device via a clutch coupling. It is provided that, when the second axle is decoupled from the drive device and the starting clutch is disengaged, an expected wheel force is predictively ascertained. The determination of the wheel force takes into account a torque caused by a mass moment of inertia of the drive device, and the second axle is coupled with the drive device if the expected wheel force surpasses a maximum wheel force.

Abstract: A multi-axle drive device and method for operating a multi-axle drive device. The multi-axle drive device is provided with a synchronization clutch present in an operational connection between a first output shaft and a connecting shaft and at least one disconnecting clutch present in an operational connection between the connecting shaft and a second output shaft. The synchronization clutch and the disconnecting clutch are opened in a first operating state and closed in a second operating state. At the same time, with an intended change from the second operating state to the first operating state, the synchronization clutch is maintained at least partially opened and the separation clutch is maintained closed, so that, when a first operating mode is carried out, the disconnecting clutch is opened, and when a second operating mode is carried out, the synchronization clutch is closed again.

Abstract: A device and a method for operating a multi-axle drive train for a motor vehicle. A first axle and a second axle are operatively connected, at least temporarily, to a drive device. When the second axle is decoupled from the drive device and a request for multi-axle drive with a first value is present, the second axle is coupled to the drive device only when a noise-masking event occurs, or when the second axle is coupled to the drive device and the request for multi-axle drive is absent, the second axle is decoupled from the drive device only when the noise-masking event occurs.

Abstract: A dog clutch having two clutch members provided with claws or teeth, one of which is movable, as well as a positioning device for engaging and disengaging the clutch by a positioning movement of the movable clutch member. In order to establish a proper engaging of the dog clutch, a sensor is arranged along the movement path of the movable clutch member, which detects the movement of the clutch member into the engaged state, while the clutch member is provided with an activating contour which, upon engaging the clutch, moves past the sensor, which is preferably an electromagnetic actuator for holding the movable clutch member in the disengaged state of the clutch.

Abstract: The invention relates to a method for operating a drivetrain (10) of a motor vehicle, having the steps: detecting at least one variable which quantifies and/or influences a movement of the motor vehicle; activating an all-wheel drive system of the motor vehicle as a function of the variable; wherein it is estimated, on the basis of the at least one variable, whether a relevant driving situation is impending, and in this case only, the all-wheel drive system is activated before the onset of the relevant situation. The invention also relates to a system for operating a drivetrain (10) of a motor vehicle.

Abstract: The invention relates to a method for operating a drivetrain (10) of a motor vehicle, having the steps: detecting at least one variable which quantifies and/or influences a movement of the motor vehicle; activating an all-wheel drive system of the motor vehicle as a function of the variable; wherein it is estimated, on the basis of the at least one variable, whether a relevant driving situation is impending, and in this case only, the all-wheel drive system is activated before the onset of the relevant situation. The invention also relates to a system for operating a drivetrain (10) of a motor vehicle.