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Hydraulic Function, Overview

Fig 1: Active On Demand Coupling Hydraulic Function Overview (2006-)
GLL151311Courtesy of VOLVO CARS CORPORATION
1 Hub with cam curve 11 Electrical feed pump.
2 Rollers 12 Oil filter
3 Check valves, exhaust side 13 Check valve, intake side
4 Pressure limiting valve 14 Piston pump
5 Control valve/axial solenoid 15 Operating piston
6 Oil pressure and temperature sensor 16 Wet plate unit
7 Differential electronic module (DEM) 17 Bearing
8 Control valve/axial solenoid 18 Pressure springs
9 Accumulator 19 Combined check and by-pass valve
10 Oil screen    

The Active On demand Coupling (AOC) can be described as a hydraulic pump.

The basic pressure is generated by the electronic feed pump. This pressurizes the annular pistons with oil so that they are pressed against the hub's cam curve via rollers. The annular pistons generate a working pressure which is led to the operating piston via the check valves on the intake side. This pressure creates a fixed connection between the input and output shafts. The maximum pressure is limited by the pressure limiting valve. Large differences in speed on the input and output shafts enable the annular pistons to create an oil flow. The oil flow is less if the input and output shafts are at the same speed. The oil flow, created by the annular pistons, is controlled by the control valve, which in turn is controlled by the axial solenoid. A closed control valve produces high pressure, which causes maximum pressure on the clutch driven plates. This produces a maximum power transmission. An open control valve produces low pressure, which causes minimum pressure on the clutch driven plates. This produces a limited power transmission.

The accumulator maintains the basic pressure in the system. The oil filter keeps the fluid clean by filtering dirt and small particles which could damage the system.