# Patent

## Title
Method for actuating a clutch of a hydrodynamic torque converter

## Abstract

A clutch of a hydrodynamic torque converter in which the input drive of the hydrodynamic torque converter can be connected to the output drive of the hydrodynamic torque converter. The clutch of the hydrodynamic torque converter is only engaged if a difference between the rotational speeds of the pump and the turbine of the hydrodynamic torque converter is not reached and a predefined distance traveled by the accelerator pedal is exceeded.

## Background
This application is a National Stage completion of PCT/EP2009/062597 filed Sep. 29, 2009, which claims priority from German patent application serial no. 10 2008 043 105.2 filed Oct. 23, 2008.
FIELD OF THE INVENTION
The invention relates to a method for actuating a clutch of a hydrodynamic torque converter.
BACKGROUND OF THE INVENTION
Customary clutches in torque converters are actuated for engagement in order to connect the input drive to the output drive of the torque converter, wherein a direct drive shaft exists from the input drive to the output drive, resulting in improved efficiency. These clutches are frequently actuated for engagement when the turbine torque is the same as the pump torque when the clutch is engaged or disengaged. These shift points are determined by a rotational speed difference between the pump wheel and the turbine wheel of the hydrodynamic torque converter.
DE 35 17 381 C2 describes a lock-up control mechanism for the torque converter of an automatic transmission having a multi-stage transmission with which a lock-up clutch is provided for the hydrodynamic torque converter, wherein for each gear shifting the power-lock clutch is first re-engaged during upshifting when the rotational speed at the output of the torque converter has been decreased, while the lock-up clutch is disengaged by a predetermined rotational speed difference.
SUMMARY OF THE INVENTION
The present invention addresses the problem of creating a method for actuating a clutch of a hydrodynamic torque converter which further improves the operational reliability of the vehicle as well as driving comfort.


DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
According to the invention, the clutch of the hydrodynamic torque converter is actuated for engagement depending on the pedal for determining the desired speed, i.e., the gas pedal of the vehicle.
In a further embodiment of the invention, the clutch functions together with a shiftable reduction gear having multiple reduction gear stages, wherein each reduction gear stage is assigned to a defined position of the gas pedal, wherein if said position is exceeded the clutch is actuated for engagement.
There is the possibility for further factors to be taken into consideration such as, for example, the rotational speed of the turbine and the pump, or pressure from an additional hydraulic load, in order for the clutch to be actuated for engagement.
Should the clutch be actuated exclusively by means of the turbine rotational speed status variable when the clutch is engaged or disengaged, or respectively, if the clutch is only actuated for engagement when the turbine rotational speed is the same for an engaged or disengaged clutch, wherein for this the shifting point is determined by the difference between the rotational speeds of the turbine and the pump of the hydrodynamic torque converter, then the possibility exists that for the lower gears or driving speeds of a working machine, up to the range, for example, of 12 km/h, there will be a clear difference in the driving behavior with an engaged or disengaged clutch.
For this reason, according to the invention, the clutch only engages when a defined distance traveled by the pedal for determining the desired speed of the vehicle, such as the gas pedal for example, has been exceeded and the engagement rotational speed has been obtained at the input drive and at the output drive of the hydrodynamic torque converter. The actuation of the clutch for disengagement is carried out independently of the distance traveled by the accelerator pedal. The limit values of the pedal position are defined separately for each gear of the reduction gearing.
The engagement rotational speed is determined in that the rotational speed of the input drive and the rotational speed of the output drive are detected and the difference in rotational speed is determined. When a predetermined rotational speed difference has been attained, the criterion for the engagement rotational speed has been satisfied.
In a further embodiment of the invention, the position of the pedal is determined by means of a rotational angle sensor, wherein the signal is transmitted directly, or via a CAN bus, to the vehicle electronic system and from there to the transmission electronic system.
The possibility exists for utilizing the method for actuating the clutch of the hydrodynamic torque converter in a working machine, such as, for example, a wheeled loader in with which, even for low gears or driving speeds of up to approx. 12 km/h and short loading cycles, a uniform driving behavior is obtained by means of utilizing the method.

## Claims

1. A method of actuating a clutch of a hydrodynamic torque converter in a vehicle, the method comprising the steps of:
connecting an input drive of the hydrodynamic torque converter to an output drive of the hydrodynamic torque converter when the clutch is engaged;
detecting a position of an accelerator pedal for determining a desired speed of the vehicle;
comparing the position of the accelerator pedal with a predefined position of the accelerator pedal;
engaging the clutch when the predefined position is exceeded; and
maintaining the clutch as disengaged when both the predefined position is exceeded and a difference between a rotational speed of the input drive and the output drive is exceeded.

2. The method of claim 1, further comprising the step of forming a direct drive shaft from the input drive to the output drive when the clutch is engaged.

3. The method of claim 1, further comprising the step of only engaging the clutch when the predefined position is exceeded.

4. A method of actuating a clutch of a hydrodynamic torque converter in a vehicle, the method comprising the steps of:
connecting an input drive of the hydrodynamic torque converter to an output drive of the hydrodynamic torque converter when the clutch is engaged;
detecting a position of an accelerator pedal for determining a desired speed of the vehicle;
comparing the position of the accelerator pedal with a predefined position of the accelerator pedal;
engaging the clutch when the predefined position is exceeded; and
disengaging the clutch when the torque of at the input drive is the same for both an engaged clutch and a disengaged clutch.

5. The method of claim 4, further comprising the step of forming a direct drive shaft from the input drive to the output drive when the clutch is engaged.

6. The method of claim 4, further comprising the step of only engaging the clutch when the predefined position is exceeded.