Hydraulic Pump: Description and Operation

Hydraulic Pump

The hydraulic pump generates the required oil pressure to actuate the clutch and/or perform the gearshifts.

The hydraulic pump is designed as a gear pump and is driven by an electric motor. The current consumption of the pump electric motor is approx. 20 A. The ON current is a maximum of 60 A.

Depending on the oil temperature, if an oil pressure of 35 - 40 bar is not reached, the relay of the hydraulic pump is activated by the SMG control module.

At approx. 55 bar oil pressure, the SMG control module switches the electric motor of the pump off again via the relay.

In order to ensure that there is sufficient oil pressure for an engine start-up, the hydraulic pump is activated once when the door is opened in the case of an accumulator pressure below 35 - 40 bar. When approx. 55 bar is reached in the accumulator, the hydraulic pump is switched off again.

NOTE: Pressure of hydraulic fluid specified at 20 degree c

For every fourth gear shift, the pump is activated for approx. 2 - 5 seconds. When the vehicle is at a standstill, the pump is activated approx. every 30 seconds to keep the clutch open.