Active On Demand Coupling (AOC)

Fig 1: Identifying Active On Demand Coupling Unit

Courtesy of VOLVO CARS CORPORATION

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.