Method and controller for operating a drivetrain of a vehicle

A method of operating a drive-train of a vehicle in order to rock the vehicle free, the drive-train having a drive aggregate (1), a drive output (3) and a transmission (2) which is arranged in the drive-train between the drive aggregate (1) and the drive output (3), a shaft (5) on a drive input side is connected by a controllable clutch (4) to the drive aggregate (1) and a shaft (6) on a drive output side is connected by the clutch (4) to the drive output (3), the method comprising:

• when a rocking-free operating mode is active for rocking the drive-train free, then depending upon an actuation of an accelerator pedal (9) by a driver, automatically actuating the clutch is to rock the vehicle free,
• to rock the vehicle free, automatically actuating the clutch (4) as a function of actuation of the accelerator pedal (9) by the driver and as a function of a rotational speed of the drive output (3), in such manner that
• initially opening the clutch (4) with a defined first opening gradient, when the accelerator pedal (9) is actuated and the actuation of the accelerator pedal (9) is decreased,
• thereafter, as a function of a calculated point in time when a value of a torque from the drive aggregate (1) that acts upon the clutch (4) corresponds to a torque acting upon the clutch (4) from the drive output (3), terminating disengagement of the clutch (4) with the defined first opening gradient and disengaging the clutch (4) by a defined second opening gradient, which is smaller than the first opening gradient,
• then, when a value of a gradient of the rotational speed of the drive output (3) becomes larger than a limit value, commencing engagement the clutch (4) with a defined first closing gradient,
• and then, when the value of the gradient of the rotational speed of the drive output (3) becomes smaller than a limit value, terminating engagement of the clutch (4) with the defined first closing gradient.

A control unit for operating a transmission of a vehicle, such that when a rocking-free operating mode of the drive-train for rocking the vehicle free is active, the control unit automatically actuates a clutch (4) to rock the vehicle free, as a function of an actuation of an accelerator pedal (9) by a driver,

• the control unit automatically actuates the clutch (4) to rock the vehicle free, as a function of actuation of the accelerator pedal (9) by the driver and as a function of a rotational speed of an drive output (3), in such manner that
• when, after an actuation of the accelerator pedal (9), the actuation of the accelerator pedal (9) is decreased, the control unit first actuates the clutch (4) with a defined first opening gradient,
• then, as a function of a calculated point in time when a value of torque from a drive aggregate (1) that acts upon the clutch (4) corresponds to a torque acting upon the clutch (4) from the drive output (3), the control unit terminates the disengagment of the clutch (4) with the defined first opening gradient and actuates the clutch (4) with a defined second opening gradient, which is smaller than the first opening gradient,
• and then, if a value of a gradient of the rotational speed of the drive output (3) becomes larger than a limit value, the control unit actuates the clutch (4) with a defined first closing gradient,
• and then, if the value of the gradient of the rotational speed of the drive output (3) becomes smaller than a limit value, the control unit terminates the engagement of the clutch (4) with the defined first closing gradient.

A method of operating a drive-train of a vehicle for rocking the vehicle free from a depression, the drive-train having, in a direction of toque transmission, a drive aggregate (1) connected to an input shaft (5) of a transmission (2), a controllable clutch (4) having an input side connected to the input shaft and an output side connected to an output shaft (6) of the transmission, the output shaft (6) being connected to a drive output (3), the clutch (4) being automatically actuatable to disengage and engaged to controllably transmit drive from the input shaft to the output shaft, the method comprising:

• activating a rocking-free operating mode for rocking the vehicle free, and automatically actuating the clutch (4) to rock the vehicle free as a function of actuation of the accelerator pedal by a driver and as a function of a rotational speed of the drive output (3) such that:
• disengaging the clutch (4) with a defined first opening gradient when the accelerator pedal (9) is actuated and actuation of the accelerator pedal (9) decreases,
• terminating the disengagement of the clutch (4) with the defined first opening gradient and disengaging the clutch (4) with a defined second opening gradient, which is smaller than the first defined opening gradient, as a function of a calculated point in time when a value of torque from the drive aggregate (1) that acts upon the clutch (4) corresponds to torque acting upon the clutch (4) from the drive output (3),
• initiating engagement of the clutch (4) with a defined first closing gradient when a value of a gradient of the rotational speed of the drive output (3) is larger than a limit value, and
• terminating engagement of the clutch (4) with the defined first closing gradient when the value of the gradient of the rotational speed of the drive output (3) is smaller than the limit value.