Electric Auxiliary Oil Pump, Basic Function - GF27.57-P-2000A

Model all with transmission 724.0/1 

Overview 

This document contains information on:

• General 
• Function 

General 

The electric auxiliary oil pump supports the oil pump (primary pump) in the following operating statuses:

• At low combustion engine speeds
• During start/stop operation
• During clutch cooling, including at high transmission oil temperatures

Function 

The fully integrated transmission control electrohydraulic controller unit actuates the electrical auxiliary oil pump at a low engine speed. The electric auxiliary oil pump is required to maintain the following functions at low rotational speeds:

• Compensation of low oil pump (primary pump) delivery rate
• To maintain constant oil pressure
• Ensure optimum cooling of transmission components
• Ensure sufficient lubrication of transmission components

In start-stop mode, all actuators switch to a basic unloaded state when the combustion engine is stopped. Gear changes are then no longer possible and the dual clutch can no longer be actuated.

In order to minimize the resulting delay between the start-off request and start-off point, the electric auxiliary oil pump provides the necessary oil pressure before the actual start-off procedure.

Under driving conditions such as frequent start-offs on uphill gradients or when driving with a trailer, an increased oil volume is necessary to cool the clutch.

The fully integrated transmission control electrohydraulic controller unit uses the transmission oil temperature on the clutch plates to determine what is required. If the transmission oil temperature on the clutch plates is too high, the transmission oil flow rate is increased by switching-in the electric auxiliary oil pump.

The increased turnover rate of the transmission oil enables the heat to be dissipated faster. Heat is transmitted via the transmission oil to the transmission oil heat exchanger.

The delivery pressure of the electric auxiliary oil pump is dependent on the length of actuation determined by the fully integrated transmission control electrohydraulic controller unit. The delivery pressure varies between 0 and 8 bar.