Method for freeing a motor vehicle by rocking

Patent metadata

Field	Value
Publication number	US-9707965-B2
Application number	US-201514684540-A
Country	US
Kind code	B2
Filing date	Apr 13, 2015
Priority date	Apr 14, 2014
Publication date	Jul 18, 2017
Grant date	Jul 18, 2017

Abstract

A method for rocking a motor vehicle free. The vehicle has a drive-train with an automatic drive torque adjusting element, which transmits torque to a wheel, and a rotational speed and direction sensor system for detecting movement of the vehicle such that when the accelerator pedal is biased to a position different from its non-actuated position a desired drive torque can be produced. The torque adjusting element can be controlled based on the accelerator pedal position in relation to the drive torque that can be produced by the driver, and, in a rocking-free process, alternating deflection and release of the accelerator pedal causes the drive torque to fluctuate. With the rotational speed and direction sensor system, the drive torque adjusting element is controlled to suppress drive torque transmission if the travel direction of a current unpowered vehicle movement is not the same as a forthcoming power-driven vehicle movement.

First claim

The invention claimed is:

1. A method of rocking a motor vehicle free, the motor vehicle comprising a drive-train ( 1 ) that has an automatically controllable drive torque adjusting element ( 3 ) which can transmit drive torque (M) to at least one drivable vehicle wheel ( 5 ), and the motor vehicle having a rotational speed and rotational direction sensor system ( 11 ) which can detect vehicle movement and travel direction as well as a standstill of the motor vehicle, the method comprising the steps of:
producing a desired drive torque when a driver of the motor vehicle deflects an accelerator pedal ( 8 ) to an accelerator pedal position different from a non-actuated position of the accelerator pedal;
controlling the drive torque adjusting element ( 3 ) as a function of the accelerator pedal position in relation to the drive torque (M) that can be produced by the driver;
cyclically fluctuating drive torque at the at least one drivable vehicle wheel ( 5 ) in a rocking-free situation in which the at least one drivable vehicle wheel ( 5 ) has to be moved clear of a depression ( 6 ) when the driver alternately deflects and releases the deflection of the accelerator pedal ( 8 ); and
controlling the drive torque adjusting element ( 3 ) with aid of the rotational speed and rotational direction sensor system ( 11 ) in such manner that a drive torque input to the drive-train ( 1 ), which is specified by the driver by virtue of the accelerator position of the accelerator pedal ( 8 ) actuated by the driver, is suppressed so long as the travel direction ( 10 ) of a current unpowered vehicle movement is different than the travel direction ( 7 ) of a forthcoming power-driven vehicle movement.

2. The method according to claim 1 , further comprising the steps of switching the drive torque adjusting element ( 3 ) to a no-torque condition, after a driven vehicle movement in a first travel direction ( 7 ), either on or shortly after reaching a first travel direction reversal point (B, t U ) to either enable or assist with an unpowered vehicle movement in a second travel direction ( 10 ) opposite to the first travel direction ( 7 ); and
during the unpowered vehicle movement in the second travel direction ( 10 ), suppressing a driver requested drive torque acting in the first travel direction ( 7 ) until a second travel direction reversal point (C, t U ) is reached at an end of the unpowered vehicle movement in the second travel direction ( 10 ).

3. The method according to claim 1 , wherein the drive torque adjusting element ( 3 ) is either a separator or a starting clutch of the drive-train ( 1 ) in a form of a friction clutch, the drive-train ( 1 ) comprises a drive engine ( 2 ) and an automated transmission ( 4 ) which are drivingly connectable with one another by the separator or starting clutch ( 3 ), whereby the drive torque (M(t)) is transmittable to the at least one drivable vehicle wheel ( 5 ) with which the vehicle became stuck in a depression ( 6 ), the method further comprising the steps of:
either on or shortly after reaching a first travel direction reversal point (B, t U ) after vehicle movement in a desired travel direction ( 7 ) with a starting gear engaged, the separator or starting clutch ( 3 ) is either opened or at least adjusted to a target position in which no driving torque (M(t)) is transmittable to either enable or assist an unpowered rolling back of the vehicle in the opposite direction ( 10 );
during the unpowered rolling back of the vehicle, if the driver has actuated the accelerator pedal to call for the drive torque (M(t)) acting in the desired travel direction ( 7 ), suppressing the drive torque acting in the desired travel direction and maintaining the separator or starting clutch ( 3 ) either disengaged or in a no-torque condition until the rolling back movement ends and a second travel direction reversal point (C, t U ) is reached; and
either on or shortly after reaching the second travel direction reversal point (C, t U ), either engaging or at least adjusting the separator or starting clutch ( 3 ) to a target position in which the drive torque (M(t)) is transmittable to enable a new build-up of drive torque (M(t)) in the desired travel direction ( 7 ).

4. The method according to claim 1 , further comprising the step of evaluating a rotational speed gradient (dn/dt) determined by the rotational speed and rotational direction sensor system ( 11 ), the rotational speed gradient represents a change with time of a travel-direction-relevant rotation speed (n), to recognize a travel direction reversal point (B, C, t U ).

5. The method according to claim 4 , further comprising the step of continually determining the rotational speed gradient (dn/dt) so that from the rotational speed gradient (dn(t 0 )/dt) at a current time-point (t 0 ) at which a current rotational speed (n(t 0 )) exists which is higher than a specified limit value, a future time-point (t U,ber )) is calculated, at which the rotation speed (n(t)) will be zero.

6. A method of controlling a drive train of a motor vehicle to rock the motor vehicle free from a position in which at least one wheel of the motor vehicle is caught in a depression, the vehicle having a drive-train comprising a transmission and an automatically controllable clutch, which transmits drive torque to the at least one wheel, and a rotational speed and rotational direction sensor system which detects vehicle movement and a direction of travel of the vehicle, a control system communicates with the drive-train, the rotational speed and rotational direction sensor system, and a pedal deflection sensor which detects deflection of an accelerator pedal, the method comprising the steps of:
activating, with the control system, a rocking-free mode when at least one wheel of the motor vehicle is caught in a depression;
detecting, with the rotational speed and rotational direction sensor system, the vehicle movement and the direction of travel of the motor vehicle and detecting, with the pedal deflection sensor, the deflection of the accelerator pedal;
transmitting, via the drive train, cyclically fluctuating drive torque to the at least one wheel of the motor vehicle when the driver alternately deflects and releases deflection of the accelerator pedal; and
controlling the clutch, with the control system, to suppress the transmission of drive torque to the at least one wheel of the motor vehicle so long as the rotational speed and rotational direction sensor system detects that the direction of travel of the motor vehicle, during unpowered vehicle movement, is different than the direction of travel of the motor vehicle of forthcoming power-driven vehicle movement.

Assignees

• Zahnradfabrik Friedrichshafen

Inventors

• Mair Roland

Classifications

• B60W10/11

  Stepped gearings · CPC title

• B60W10/06

  including control of combustion engines · CPC title

• B60W2710/1022

  Input torque · CPC title

• B60W2710/1005

  Transmission ratio engaged · CPC title

• B60W2710/027

  Clutch torque · CPC title