Torque converter lockup clutch control, function - GF27.20-P-3002AHS
TRANSMISSION 722.9 in MODEL 216.3 as of model year 2009
/ YoM 08
TRANSMISSION 722.9 in MODEL 216.3 (except 216.374) as of Model Year 2011
/YoM 10 model refinement package
TRANSMISSION 722.9 in MODEL 221.0 as of model year 2009
/ YoM 08
TRANSMISSION 722.9 in MODEL 221.0 (except 221.095)
TRANSMISSION 722.9 in MODEL 221.0 (except 221.074) as of Model Year 2011
/YoM 10
TRANSMISSION 722.9 in MODEL 221.1 as of model year 2009
/ YoM 08
TRANSMISSION 722.9 in MODEL 221.1 (except 221.195)
TRANSMISSION 722.9 in MODEL 221.1 (except 221.174) as of Model Year 2011
/YoM 10
Function requirements for torque converter lockup clutch control, general
- Circuit 87 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 (VGS) (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. The fully integrated transmission control unit (VGS) generates a pressure/current specification for the corresponding control solenoid valve depending on the calculated deviation between specified and actual slip and on different variables (e.g. engine torque).
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.
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 regulating valve position is influenced by the torque converter lockup clutch control solenoid valve (VGS) (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 subdivided into the following steps:
- OPEN
- OPEN-SLIP
- SLIP
- SLIP CLOSED (with model 216 as of model year 2011 /YoM 10 model refinement package with engine 278.9 or model 221 as of model year 2011 /YoM 10 with engine 278.9, 642.8, 651.9)
- SLIP CLOSED (with model 216 as of model year 2011 /YoM 10 model refinement package with engine 278.9 or model 221 as of model year 2011 /YoM 10 with engine 278.9, 642.8, 651.9)
- SLIP-OPEN
The shifting strategy for the status transitions is based on the engine load and vehicle speed or vehicle acceleration.
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 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
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
The required slip (specified slip) is stored in the fully integrated transmission-control control unit (VGS). This calculates the required control current and actuates the torque converter lockup clutch control solenoid valve (VGS) which influences the position of the torque converter lockup clutch regulating valve (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 an aftercontrol is introduced by the fully integrated transmission control unit (VGS). The clutch pressure in the torque converter lockup clutch can be increased or reduced by the aftercontrol.
SLIP CLOSED (with model 216 as of model year 2011 /YoM 10 model refinement package with engine 278.9 or model 221 as of model year 2011 /YoM 10 with engine 278.9, 642.8, 651.9)
The torque converter lockup clutch (VGS) control solenoid valve has a rising control current applied to it until the oil pressure applied to the regulating valve for the torque converter lockup clutch has reached the value specified by the fully integrated transmission control unit (VGS).
The specified value matches a maximum value filed in the characteristics map of the fully integrated transmission control unit (VGS).
The maximum coupling pressure is reached in this switching state and the torque converter lockup clutch is fully closed. An almost slip-free power flow exists between the crankshaft and the transmission input shaft.
SLIP CLOSED (with model 216 as of model year 2011 /YoM 10 model refinement package with engine 278.9 or model 221 as of model year 2011 /YoM 10 with engine 278.9, 642.8, 651.9)
In the event of any changes to the engine load or vehicle speed, the control current for the control solenoid valve of the torque converter lockup clutch (VGS) is reduced and the oil pressure applied to the regulating valve for the torque converter lockup clutch is lowered.
The coupling pressure in the torque converter lockup clutch is therefore reduced until the torque converter lockup clutch reaches an adapted specified slip value that matches the operating condition.
This is necessary to enable any torsional vibration induced by temporary engine load reversal or changes in vehicle speed to be minimized.
SLIP-OPEN
In this control state the clutch pressure in the torque converter lockup clutch is reduced in stages until it is eliminated.
On model 216 as of model year 2011 /YoM 10 model refinement package with engine 278.9 or model 221 as of model year 2011 /YoM 10 with engine 278.9, 642.8, 651.9)
Depending on the motorization a regulated zero slip can help to reduce fuel consumption, and improve the response time to changes in load requests by the driver.
Limp-home mode
The fully integrated transmission control unit (VGS), with integrated protection and adaptation functions, constantly determines the transmission oil temperature and the friction energy at the disks of the torque converter lockup clutch and switches into limp-home mode for overload or implausible signals.
The torque converter lockup clutch is not actuated in limp-home mode. Aging effects in the hydraulic components and mechanical components are compensated for by the fully integrated transmission control unit (VGS).
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