System Overview

System overview

Active On demand Coupling (AOC)




The main role of Active On demand Coupling (AOC) 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 rear axle gear and the propeller shaft. The mechanical section is partly driven by the propeller shaft. The hydraulic section is driven by the difference in rotation speed between the front and wheels.
Active On demand Coupling (AOC) enables the following characteristics:
- Continuous control of four wheel drive, with electronic control of torque transfer.
- Rapid reactions
- No opposing forces when maneuvering or parking.
- The system manages large variations of the tires, for example, when driving with the spare wheel.
- Not sensitive to towing with an axle lifted.
- Not sensitive to brake testing on a chassis dynamometer.

Clutch unit and control module




The hydraulic section consists of 1-7, the mechanical consists of 8-10 and the electronic section consists of 11-13:
1. Check valves, exhaust side
2. Accumulator
3. Oil filter
4. Ring shaped annular piston
5. Control valve/axial solenoid
6. Check valve, intake side
7. Combined check and by-pass valve
8. Inner and outer wet clutch plates
9. Inner connection hub with splines for output shaft. The hub has a sinusoidal cam curve
10. Input shaft
11. Electrical feed pump.
12. Differential electronic module (DEM)
13. Oil pressure and temperature sensor
The Differential Electronic Module (DEM) is fitted on the clutch unit housing.
The Differential Electronic Module (DEM) communicates with other control modules via Controller Area Network (CAN) communication:
The control module has integrated diagnostics for its own components and functions.

Signals
The table below summarizes input and output signals to and from the Differential Electronic Module (DEM). The illustration below displays the same information with the Volvo component designations.