GF27.20-P-3002AHL Torque Converter Lockup Clutch Control, Function
GF27.20-P-3002AHL Torque Converter Lockup Clutch Control, Function
- TRANSMISSION 722.9 (except 722.930 /931) in MODEL 212
Function requirements for torque converter lockup clutch control, general
^ Circuit 87 (connected circuit 15) ON
^ Circuit 61 "ON" (engine running)
Control of torque converter lockup clutch, general
The torque converter lockup is a slip-controlled system. The fully integrated transmission control unit (Y3/8n4) compares the actual slip with the specified slip. The actual slip is calculated from the difference between engine speed and transmission input speed. The specified slip is a function of transmission input speed and engine load. Depending on the determined specified/actual deviation as well as various influencing quantities (e.g. engine torque) a pressure or current requirement for the corresponding control solenoid valve is produced by the fully integrated transmission control unit.
In addition, there are special strategies for calculation of specified slip/pressure for the following operating conditions:
Clutch filling (corresponds to OPEN-SLIP state), load change phases, gear changes.
Production breakpoints for automatic transmission with torque converter and integral centrifugal pendulum
- Model 212.0/2 with engine 278.9 from 06/2011
- Model 212.0/2 with engine 642.8 from 09/2010
- Model 212.0/2 with engine 651.9 as of 12/2010
The clutch pressure in the torque converter lockup clutch is drawn from the working pressure by means of the torque converter lockup clutch regulating valve. The position of the regulating valve is influenced by the torque converter lockup clutch control solenoid valve (Y3/8y8). The clutch pressure in the torque converter lockup clutch depends on the regulating valve position and thus on the geometry of the torque converter lockup clutch regulating valve.
Control of torque converter lockup clutch, function sequence
The function sequence is described in the following steps:
^ "OPEN" function sequence
^ "OPEN-SLIP" function sequence
^ "SLIP" function sequence
^ "SLIP-CLOSED" function sequence (for torque converter with centrifugal pendulum)
^ "CLOSED-SLIP" function sequence (for torque converter with centrifugal pendulum)
^ "SLIP-OPEN" function sequence
The shifting strategy for the status transitions is based on the engine load and vehicle speed or vehicle acceleration
"OPEN" function sequence
The regulating valve of the torque converter lockup clutch is located in the basic position. The working pressure acts on the converter regulating valve via a connecting line between the torque converter lockup clutch regulating valve and the converter regulating valve.
Lubrication pressure is applied to the converter as a result. The torque converter lockup clutch is in the unpressurized condition
"OPEN-SLIP" function sequence
The torque converter lockup clutch regulating valve is no longer in the basic position and as a result interrupts the connection between the torque converter lockup clutch regulating valve and the converter regulating valve. The torque converter lockup clutch is filled.
"SLIP" function sequence
The required slip (specified slip) is stored in the fully integrated transmission control unit. This calculates the required control current and actuates the torque converter lockup clutch control solenoid valve which influences the torque converter lockup clutch (precontrol). The clutch pressure in the torque converter lockup clutch depends on the regulating valve position and thus on the regulating valve geometry.
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 aftercontrol.
"SLIP-CLOSED" function sequence (for torque converter with centrifugal pendulum)
A rising control current is applied to the control solenoid valve of the torque converter lockup clutch until the oil pressure applied in the torque converter lockup clutch regulating valve has reached the value specified by the fully integrated transmission control unit
The specified value corresponds to the maximum value stored in the characteristics map of the fully integrated transmission control unit
In this control state, the maximum clutch pressure is reached and the torque converter lockup clutch is closed completely. The power flow from the crankshaft to the transmission input shaft is virtually without slip.
"CLOSED-SLIP" function sequence (for torque converter with centrifugal pendulum)
If engine load or vehicle speed changes, the control current of the torque converter lockup clutch control solenoid valve is temporarily reduced and the oil pressure applied by the torque converter lockup clutch regulating valve is lowered.
Clutch pressure in the torque converter lockup clutch is reduced until a target slip value suitable for the operating state is set in the torque converter lockup clutch.
"SLIP-OPEN" function sequence
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 engine version, and the response to the driver's load change requests improved by means of a regulated zero slip.
This is required to minimize any torsional vibrations which arise temporarily as a result of engine load change and changes in vehicle speed.
Limp-home mode
The torque converter lockup clutch is not actuated in limp-home mode. Protection and adaptation functions are deployed to continuously monitor the transmission oil temperature and the frictional energy entering the clutch. Aging effects in the hydraulic components and mechanical components are compensated for by the fully integrated transmission control unit.
