Method for Actuating a Clutch of a Hydrodynamic Torque Converter

The invention relates to a method for actuating a clutch of a hydrodynamic torque converter according to the type more clearly defined in the preamble of claim 1.

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 with each gear shifting the power-lock clutch is first re-engaged during up shifting 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.

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.

The objective is solved with a customary method for operating a clutch of a hydrodynamic torque converter having the distinguishing characteristics of the main claim.

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 is exceeded the clutch is actuated for engagement.

There is the possibility for further factors, such as, for example, the rotational speed of the turbine and the pump, or pressure from an additional hydraulic load, to be taken into consideration 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 in 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 engages only 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, with which even in 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.

Patent Claims

1. A method for actuating a clutch of a hydrodynamic torque converter in a vehicle, whereby the clutch, when actuated for engagement, connects the input drive of the hydrodynamic torque converter to the output drive of the hydrodynamic torque converter, whereby a position of a pedal for determining the desired speed of the vehicle is detected and compared with a predefined position of the accelerator pedal, and when the predefined position has been exceeded, the clutch is actuated for engagement, characterized in that the clutch remains actuated for disengagement when the position of the pedal has been exceeded if a predefined difference between the rotational speed of the input drive of the hydrodynamic torque converter and the output drive of the hydrodynamic torque converter has been exceeded.

2. A method for actuating a clutch of a hydrodynamic torque converter in a vehicle whereby the clutch, when actuated for engagement, connects the input drive of the hydrodynamic torque converter with the output drive of the hydrodynamic torque converter, whereby a position of the pedal for determining the desired speed of the vehicle is detected and compared with a predefined position of the pedal, and upon exceeding the predefined position, the clutch is actuated for engagement, characterized in that the clutch is actuated for disengagement if the rotational speed at the input drive of the hydrodynamic torque converter is the same for both an engaged and a disengaged clutch.

3. The method for actuating a clutch according to claim 1, characterized in that the clutch remains actuated for engagement when the position of the accelerator pedal has been exceeded if a predefined rotational speed difference between the input drive of the hydrodynamic torque converter and the output drive of the hydrodynamic torque converter is exceeded.

4. The method for actuating a clutch according to claim 1, characterized in that the accelerator pedal has a rotational angle sensor with which the position of the pedal can be detected.

5. The method for actuating a clutch according to claim 4, characterized in that the detected position of the pedal is transmitted to a vehicle control unit which further transmits it to a transmission control unit.

6. The method for actuating a clutch according to claim 1, characterized in that the clutch is actuated for disengagement if the vehicle speed falls below a predefined speed level.

7. The method for actuating a clutch according to claim 1, characterized in that the clutch is actuated for disengagement if the torque of the input drive of the hydrodynamic torque converter is the same for both the engaged and disengaged clutch.