Electric Auxiliary Oil Pump, Basic Function - GF27.57-P-2000B
Model All with transmission 725
Example illustration of controller unit for fully integrated transmission control
Overview
This document contains information on:
- General
- Function
- Supporting the working pressure supply
- Support of cooling and lubrication
- Start/stop qualification
- Emergency engaging and emergency release of park pawl
- Oil pan
General
The electric auxiliary oil pump (2) has the following tasks:
- Supporting the working pressure supply
- Support of cooling and lubrication
- Start/stop qualification
- Emergency engaging and emergency release of park pawl
Function
Supporting the working pressure supply
If additional volumetric flow is required (e.g. during shift operations), the electric auxiliary oil pump (2) will support the mechanically driven oil pump (primary pump) as needed. The electric auxiliary oil pump (2) provides supporting flow volume. This counteracts working pressure drops due to undersupply.
Support of cooling and lubrication
In order to provide additional flow volume, the electric auxiliary oil pump (2) is actuated as needed to meet high cooling and lubrication requirements. The primary pump can be downsized due to the option of providing an additional flow volume. This lowers the CO2 output.
Start/stop qualification
If the combustion engine or the electric machine is not in operation during the stop phase, then the electric auxiliary oil pump (2) provides a basic pressure level. As a result, the hydraulic ducts of the electrohydraulic control and the piston chambers of the shift elements remain filled. Through electrically-controlled operation of the electric auxiliary oil pump (2), the exact oil filling capacity necessary to compensate for the leakage in the electrohydraulic actuator (EHS) is delivered. This makes it possible to reduce the power consumption of the electric auxiliary oil pump (2) to a minimum at the start/stop operating point.
Emergency engaging and emergency release of park pawl
If the combustion engine or the electric machine is not in operation and the park pawl lift solenoid is intact, then the electric auxiliary oil pump (2) hydraulically activates the park pawl (Not-P). The park pawl is engaged mechanically by means of a spring.
When the park pawl lift solenoid is defective, the park pawl actuator is released hydraulically. If the combustion engine is not in operation, then the electric auxiliary oil pump (2) is requested. Emergency release/emergency engaging is only possible in direction P, but not from P to Not P.
Oil pan, shown on transmission 725.0
Oil pan, shown on transmission 725.1
Oil pan
Oil is supplied to the electric auxiliary oil pump (2) by a separate electric auxiliary oil pump (4, 11) oil filter integrated in the oil pan (3, 14). The drawn-in transmission oil is supplied into the working pressure duct of the electrohydraulic control system by the electric auxiliary oil pump (2).
In the case of operation solely with the electric auxiliary oil pump (2) (where the combustion engine or electric machine is at a standstill), leakage via the stationary oil pump (primary pump) is prevented by a check valve.
| Component descriptions | |||
| Auxiliary oil pump, component description | Model 206 with transmission 725.1 | GF18.10-P-1000C | |
| Model 254 with transmission 725.1 | GF18.10-P-1000H |