Torque Converter Lockup Clutch Control, Function - GF27.20-P-3002AHE
TRANSMISSION 722.9 (except 722.930) in MODEL 205
Function requirements for torque converter lockup clutch control, general
- Circuit 87 (connected circuit 15) ON
- Circuit 61 (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 the engine and input speeds. The specified slip is in turn a function of the 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 states:
Clutch filling (corresponds to OPEN-SLIP state), load change phases, gear changes.
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.
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 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 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.
Function sequence for "OPEN-SLIP"
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.
Function sequence for "SLIP"
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 position of the torque converter lockup clutch regulating valve (pre-control). 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 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.
A regulated minimal slip with low rotational speeds can be used to decrease fuel consumption and the response time for the driver's load change requests are subsequently improved.
Emergency running
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.
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