Method for reversing the direction of travel of a vehicle

The invention relates to a process for reversing the direction of travel of a vehicle in accordance with the governing expression more precisely defined in claim 1.

Construction machinery, for example wheeled loaders, forklifts, backhoe-loaders or telescopic handler, feature some periods, during their operative application, in which they are driven in reverse mode during short work cycles. When a wheeled loader loads a truck from a pallet, it is operated in a so-called Y-mode during which frequent reversing, i.e., immediate change of driving direction, is required.

DE 44 07 951 C2 discloses a motor vehicle drive with a torque converter and a bypass clutch for the torque converter, which is always actuated in the disengaging manner, when a smooth or swing-free operation of the motor vehicle is not guaranteed.

The subject invention is based on the objective of further improving, via a hydrodynamic torque converter, the reversal of travel direction of a vehicle.

According to the invention, the bypass clutch of the hydrodynamic torque converter is always actuated in the disengaging manner when the vehicle performs a reversal of its driving direction.

In an embodiment of the invention, one identifies a reversal of driving direction, when the driving direction lever is shifted into the opposite driving direction, or when the driving direction clutches are driven is an opposing fashion.

In an additional embodiment of the invention, during reversal of the driving direction below a previously defined speed level, the bypass clutch of the hydrodynamic torque converter is actuated in the disengaging manner, and subsequently the first driving direction clutch, previously actuated in the engaging manner, is actuated in the disengaging manner and the second driving direction clutch in the engaging manner, wherewith the vehicle decelerates very rapidly and subsequently accelerates in the opposite direction, without the driving motor losing substantial revolutions and, respectively stalling during the reversal.

During the reversal above a previously defined speed level, the previously engaged first driving direction clutch remains engaged for so long and the second driving direction clutch remains actuated for so long in the disengaging manner, until the vehicle has been reduced in its speed to the previously defined speed level, wherein during this speed reduction, the bypass clutch of the hydrodynamic torque converter remains actuated in the disengaging manner. When the previously defined speed level is reached, the previously engaged first driving direction clutch is actuated, in the disengaging manner, and the second driving direction clutch, in the engaging manner, wherewith the motor vehicle is further decelerated in its driving speed and subsequently accelerated in the new driving direction. After the completion of the reversal process, the bypass clutch of the hydrodynamic torque converter is disconnected again wherein, upon receiving additional operational parameters, the bypass clutch may be actuated in the engaging manner. For example, the bypass clutch of the hydrodynamic torque converter is actuated in the engaging manner, when the turbine torque present in the clutch actuated in the engaging manner and in the clutch of the hydrodynamic torque converter actuated in the disengaging manner, is almost equal.

Through the fact that during a reversal process, the bypass clutch of the hydrodynamic torque converter is actuated in the disengaging manner, the driving motor is not so drastically reduced in its revolutions during the reversal process.

which would have been the case with an engaged bypass clutch, which allows for a fast change in driving direction.

Patent claims

1. A process for redirecting a driving direction of a vehicle engineered as work machine, from a first driving direction to an opposing second driving direction, wherein the vehicle is equipped with a hydrodynamic torque converter with a bypass clutch and a transmission to shift from the first driving direction to the second driving direction, wherein the bypass clutch can be actuated in the engaging manner, in order to directly connect a drive of the hydrodynamic torque converter to an output drive of the hydrodynamic torque converter, and it can be actuated in the disengaging manner in order to separate this connection, characterized in that, the driving direction is redirected from a driving speed in a first driving direction to a driving speed in a second driving direction, in which:
the bypass clutch is actuated in the disengaging manner,
the previously engaged driving direction clutch in the disengaging manner and a second driving direction clutch for the second driving direction is actuated in engaging manner, wherewith the vehicle is reduced in its speed and is subsequently accelerated in the new driving direction again, and after the conclusion of the reversal process, the bypass clutch is disconnected, wherein, upon receiving additional operational parameters, the bypass clutch may be again actuated in the engaging manner.

2. The process for redirecting a driving direction of a vehicle according to claim 1, characterized in that, the bypass clutch is actuated engaging manner when a torque of the turbine wheel of the torque converter amounts to almost the same with the bypass clutch actuated in the engaging manner or in the disengaging manner.

3. The process for redirecting a driving direction of a vehicle according to claim 1, characterized in that, the shifting point for actuating the bypass clutch, without changing the driving direction, is calculated with the aid of revolutions of a turbine wheel and the revolutions of the pump wheel of the torque converter.

4. The process for redirecting a driving direction of a vehicle according to claim 1,characterized in that, above a previously defined speed after the actuation of the bypass clutch in the disengaging manner, a driving direction clutch for the previously engaged first driving direction in the engaging manner remains actuated until the previously defined speed is reached, and subsequently the previously engaged driving direction clutch in the disengaging manner and a second driving direction clutch for the second driving direction in the engaging manner, is actuated.

5. The process for redirecting a driving direction of a vehicle according to claim 1,characterized in that, above a previously defined speed after the actuation of the bypass clutch in the disengaging manner, a driving direction clutch for the previously engaged first driving direction in the engaging manner remains actuated until the previously defined speed is reached, and subsequently the previously engaged driving direction clutch in the disengaging manner and a second driving direction clutch for the second driving direction in the engaging manner, is actuated.

6. The process for redirecting a driving direction of a vehicle according to claim 1,characterized in that the vehicle is designed as work machine.