Working/Lubrication/Shift Pressure, Function - GF27.60-P-3024ANG
Transmission 725.0 (except 725.017) in model 205
Function requirements, general
- Terminal 15 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/lubrication/shift pressure, general
The oil pressures are separated into:
- Working pressure
- Lubrication pressure
- Shift pressure
Working pressure
The oil pressure generated by the oil pumps (primary oil pump and electric auxiliary oil pump (M42)) is converted into working pressure by the working pressure regulating valve.
The level of working pressure depends on the position of the regulating valve and therefore on its geometry.
The position of the working pressure regulating valve is influenced by the working pressure solenoids (Y3/8y19) to match the load and gear. All other pressures required for transmission control are derived from the working pressures.
Fuel consumption-reducing and comfort-enhancing measures at the automatic transmission:
The optimized working-pressure reduction enables lower braking power and therefore reduces the fuel consumption. 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.
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 mechanical transmission parts and the torque converter. Apart from this, the pressure in the torque converter is limited through the lubrication pressure level.
Shift pressure
The shift pressure (pressure in the multidisk clutch or in multidisk brake) is derived from the working pressure.
The respective solenoid valve influences the position of the associated regulating valve. In turn the position of the regulating valve influences the pressure prevailing in the multidisk brake or in multidisk clutch. The pressure thus depends on the geometry of the respective regulating valve. The electrical auxiliary oil pump ensures the oil supply of the hydraulic system when the combustion engine is switched off. Actuation is performed via the fully integrated transmission control unit (Y3/8n4).
| Overview of system components for automatic transmission (AT) | GF27.10-P-9992ANG |