Working/Lubrication/Shift Pressure, Function - GF27.60-P-3024RFH
Transmission 724.2 in model 205, 253
Function requirements, general
- Terminal 15 ON
- Internal combustion engine or electric auxiliary oil pump (M42) On
The electronic ignition lock control unit (N73) transmits the status of circuit 15 via the chassis FlexRay (Flex E), the powertrain control unit (N127) and the drive train CAN (CAN C1) to the fully integrated transmission control unit (Y3/8n4).
Working pressure
The oil pressure generated by the oil pump is converted into working pressure by the working pressure regulating valve (Y3/8y1). The level of the working pressure depends on the geometry of the regulating valve and therefore on its position. The position of the working pressure regulating valve is influenced by the working pressure control solenoid valve to match load and gear. All other pressures required for transmission control are derived from the working pressures.
Low working pressures make it possible to have lower braking power and reduce fuel consumption.
Lubrication pressure
At the working pressure regulating valve, excess oil is diverted to the lubrication pressure regulating valve and from there used in a regulated manner for lubrication and cooling of the mechanical transmission parts and the wet clutch. The pressure in the wet clutch is also limited by the amount of lubrication pressure.
Shift pressure
The shift pressure (pressure in the multidisk clutch or the multidisk brake) is derived from the working pressure and is dependent on the geometry of the respective regulating valve. The pressure in the multidisk brake or the multidisk clutch varies depending on the position of the regulating valve.
The position of the regulating valve is controlled by the following components:
- K1 clutch control solenoid valve (Y3/8y2)
- K2 clutch control solenoid valve (Y3/8y3)
- K3 clutch control solenoid valve (Y3/8y4)
- B1 multidisk brake control solenoid valve (Y3/8y5)
- B2 multidisk brake control solenoid valve (Y3/8y6)
- B3 multidisk brake control solenoid valve (Y3/8y7)
The electrical auxiliary oil pump (M42) ensures the oil supply when the engine is switched off. The fully integrated transmission control unit actuates the electric auxiliary oil pump depending on the transmission fluid temperature and the required volume flow.
| Overview of system components for automatic transmission hybrid drive | GF27.10-P-9993RFH |