Torque Converter Lockup Clutch Control, Function - GF27.20-D-3002TSA
Transmission 725.0 in model 907
Function requirements for torque converter lockup clutch control, general
- Circuit 150N
- Internal combustion engine running.
Torque converter lockup clutch control, general
The torque converter lockup clutch solenoid (N15/15y20) is actuated by the fully integrated transmission control (VGS) electric controller unit (N15/15) and influences the torque converter lockup clutch (WUK) regulating valve.
The housing of the torque converter is flowed through by a lubricating oil volume flow. A lubrication oil pressure is thereby set that acts on the torque converter lockup clutch piston and opens it.
The lubrication oil pressure is fed back hydraulically to the torque converter lockup clutch regulating valve and is taken into account when adjusting the piston pressure. The lubrication oil volume flow ensures optimum cooling of the torque converter.
Function sequence for torque converter lockup clutch control
The function sequence is described in the following steps:
- Function sequence for "OPEN"
- Function sequence for "OPEN-SLIP"
- Function sequence for "SLIP"
- Function sequence for "SLIP-OPEN"
The shift strategy for the condition transitions is dependent on the engine load and vehicle speed or vehicle acceleration.
Function sequence for "OPEN"
The torque converter lockup clutch solenoid is in the control position. The working pressure acts upon the torque converter lockup clutch regulating valve.
The pressure from the compensation line for internal pressure compensation of the torque converter acts on the control surfaces of the torque converter lockup clutch regulating valve.
This compensates the converter internal pressure that has an opening effect on the WUK in the torque converter and the solenoid pressure characteristic of the WUK thus becomes independent from the lubricating pressure.
The solenoid is not energized which in turn means that the torque converter lockup clutch does not transfer any power. The torque converter alone transfers the torque.
Function sequence for "OPEN-SLIP"
The torque converter lockup clutch solenoid is in the control position. In addition to the pressure from the compensation line for the internal pressure compensation of the torque converter, energization of the solenoid induces a force to act on the torque converter lockup clutch solenoids.
This increases the pressure in the torque converter lockup clutch, thereby filling it.
Function sequence for "SLIP"
The required slip (specified slip) is stored in the fully integrated transmission control unit (N15/15n4). This calculates the required control current and actuates the torque converter lockup clutch solenoid.
The pressure on the torque converter lockup clutch piston is influenced by this, whereby the torque and slip on the torque converter lockup clutch are then regulated. The actual slip is determined by the comparison of engine speed with turbine speed.
If necessary, a post-regulation is introduced by the fully integrated transmission control unit. The clutch pressure in the torque converter lockup clutch can be increased or reduced by the post-regulation.
Function sequence for "SLIP-OPEN"
In this control state, the clutch pressure in the torque converter lockup clutch is reduced in stages until it is eliminated.
Torque converter with centrifugal pendulum
Fuel consumption can be reduced, depending on the engine version, and the response time to the driver's load change requests improved by means of a regulated minimum slip with low turbine speeds.
Limp-home mode
The WUK is not actuated in limp-home mode. Protection functions are used which constantly monitor the transmission oil temperature, the frictional energy and the functionality in the clutch.
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