System Overview

System overview

Active On demand Coupling (AOC)




The main role of Active On demand Coupling and the differential electronic module (DEM) is to regulate the four-wheel drive function, i.e. the distribution of drive between the front and rear axles. The system consists of a coupling combining mechanical, hydraulic and electronic sections. The coupling unit is on the rear axle, between the differential gear and the propeller shaft. The mechanical and hydraulic sections are driven by the rotation of the propeller shaft.
Active On demand Coupling (AOC) has the following characteristics:
- Permanent all wheel drive with electronic control of torque transfer
- Driving characteristics similar to all wheel drive
- Quicker reactions
- No wind-up during slow speed maneuvers and parking
- The system is not sensitive to differences between tires (when driving with a spare wheel for example)
- The system is not sensitive to being towed with one axle raised
- Unaffected by brake tests on a chassis dynamometer.

Coupling unit and control module




The hydraulic section consists of 1-5, the mechanical section consists of 6-10 and the electronic section consists of 11-13.
1. Pressure valves
2. Accumulator
3. Oil filter
4. Annular pistons
5. Control valve/axial solenoid
6. Input shaft
7. Inner and outer wet multi-plate clutch
8. Inner connection hub with sinusoidal cam disc
9. Rollers with annular pistons
10. Output shaft
11. Electrical feed pump
12. Differential electronic module (DEM)
13. Oil pressure and temperature sensor.
The differential electronic module (DEM) is integrated in the coupling unit.
The differential electronic module (DEM) communicates with other control modules using controller area network (CAN) communication.
There are internal diagnostics for the control module.

Signals
The table below summarizes the input signals to and output signals from the differential electronic module (DEM). The following illustration displays the same information with the Volvo component designations.