Automatic Transmission -- Basic Knowledge -- 251 Chassis: Specifications Mercedes-Benz R-class W251 facelift

Torque converter component description - GF27.20-P-2010GZ

TRANSMISSION 722.9 in MODEL 164.1/8, 204.0, 216, 221, 251.0/1 up to Model Year 8

Scheme 153

Location

The torque converter is rigidly bolted to the driven plate in the torque converter housing.

Task

When the vehicle is stationary and at idle speed the torque converter reduces the power flow between the engine and automatic transmission to a minimum and multiplies engine torque and continuously adapts RPM and torque during vehicle take-off.

Design

The impeller is connected to the engine, the turbine wheel is connected to the transmission input shaft. The stator is connected to the transmission housing via a freewheel and the stator shaft.

Scheme 154

Function

The impeller pumps the oil through the impeller blades outwards to the turbine wheel as a result of the centrifugal force and thus drives the turbine wheel. The turbine wheel blades direct the oil onto the blades of the stator, which in turn pushes the oil to the impeller. A torque increase occurs due to this reversal at the stator which is supported against the transmission housing via the freewheel. The torque conversion reaches its highest value when the RPM difference between the impeller and turbine wheel is highest.

As of this operating condition, also referred to as the coupling point, the stator turns with the impeller and turbine wheel.

The oil in the torque converter is continuously exchanged so that heat generated during the operating phase can be drawn away by the transmission oil cooler

Torque converter lockup clutch control, function - GF27.20-P-3002AHZ

TRANSMISSION 722.902/903/904/906/907 in MODEL 164.1 as of Model Year 09/Modification year 08 Model refinement package

TRANSMISSION 722.902/903/904 in MODEL 164.8 as of Model Year 09/Modification Year 08

TRANSMISSION 722.902/904/906/999 in MODEL 251.0 as of Model Year 09/Modification year 08

TRANSMISSION 722.902/904/906/999 in MODEL 251.1 as of Model Year 09/Modification year 08

Function requirements for torque converter lockup clutch control, general

1. Circuit 87 ON
2. 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

1. "OPEN" function sequence
2. "OPEN-SLIP" function sequence
3. "SLIP" function sequence
4. "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 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-OPEN" function sequence

In this control state the clutch pressure in the torque converter lockup clutch is reduced in stages until it is eliminated.

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 (VGS).

Torque converter lockup clutch control, function - GF27.20-P-3002GZ

TRANSMISSION 722.9 in MODEL 164.1/8, 216, 221, 251.0/1 up to Model Year 8

The clutch pressure in the torque converter lockup clutch is derived from the working pressure by 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. The torque converter lockup clutch has the following control states

1. Open
2. Open-slipping
3. SLIPPING
4. Slipping-open

"Open" control state"

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.

Control state "open-slipping"

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.

Control state "slipping"

The required slip (specified slip) is stored in the fully integrated transmission control (VGS) control unit (Y3/8n4). The fully integrated transmission control (VGS) control unit 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 (VGS) control unit. The clutch pressure in the torque converter lockup clutch can be increased or reduced by the aftercontrol.

Control state "slipping-open"

In this control state the clutch pressure in the torque converter lockup clutch is reduced in stages until it is eliminated.

The torque converter lockup clutch is not actuated in limp-home mode

Torque converter lockup clutch component description - GF27.20-P-5102GZ

TRANSMISSION 722.9 in MODEL 164.1/8, 216, 221, 251.0/1 up to Model Year 8

Scheme 155

Location

The torque converter lockup clutch is integrated in the torque converter.

Task

The torque converter lockup clutch minimizes the power losses of the torque converter by reducing converter slip. This reduces the engine speed and the efficiency of the transmission is improved.

Design

The external plate carrier is connected to the impeller via the torque converter housing. The internal plate carrier is connected to the turbine wheel.

Scheme 156

Function

When actuated by the fully integrated transmission control (VGS) control unit (Y3/8n4), oil pressure controlled by the torque converter lockup clutch solenoid valve (VGS) (Y3/8y8) is directed through the input shaft to the pressure chamber behind the piston. The piston presses the clutch pack together and thus enables torque to be transmitted directly between the impeller and turbine wheel.

The torque converter lockup clutch is engaged in all gears depending on engine speed and load. The torsional damper damps the vibrations coming from the engine. This improves comfort for the driver and saves wear and tear on the mechanical components of the transmission.

Torque converter lockup clutch control pressure, function - GF27.60-P-3019AHZ

TRANSMISSION 722.902/903/904/906/907 in MODEL 164.1 as of Model Year 09/Modification year 08 Model refinement package

TRANSMISSION 722.902/903/904 in MODEL 164.8 as of Model Year 09/Modification Year 08

TRANSMISSION 722.902/904/906/999 in MODEL 251.0 as of Model Year 09/Modification year 08

TRANSMISSION 722.902/904/906/999 in MODEL 251.1 as of Model Year 09/Modification year 08

Function requirements for torque converter lock-up clutch control pressure, general

1. Circuit 87 ON
2. Circuit 61 (engine running)

Torque converter lock-up clutch control pressure, general

The torque converter lockup clutch is operated at specified slip speeds. In order to make this possible, the variable control pressure has to be applied to the torque converter lockup clutch regulating valve.

The torque converter lock-up clutch control pressure is adapted to the respective operating condition via the torque converter lockup clutch control solenoid valve (VGS) (Y3/8y8) which is actuated by the fully integrated transmission control (VGS) control unit (Y3/8n4).

Torque converter lockup clutch control pressure, function - GF27.60-P-3019GZ

TRANSMISSION 722.9 in MODEL 164.1/8, 216, 221, 251.0/1 up to Model Year 8

The torque converter lockup clutch is operated at specified slip speeds. In order to make this possible the torque converter lockup clutch regulating valve must have variable control pressure applied to it.

The torque converter lock-up clutch control pressure is adapted to the respective operating condition via the torque converter lockup clutch control solenoid valve (VGS) (Y3/8y8) which is actuated by the fully integrated transmission control (VGS) control unit (Y3/8n4).