GKN develops world’s smallest all-wheel drive disconnect system

TheGlobal engineering group GKN has developed the world’s first Disconnect All-Wheel Drive System for A-, B- and C-segment vehicle platforms, which improves fuel economy during steady state cruising by up to 4 percent. innovative Disconnect function enables vehicles to combine the enhanced traction, dynamics and stability of all-wheel drive with improved on-highway fuel efficiency.

Senior Programme Director Hannes Prenn said: “As global demand for smaller, more efficient SUVs continues to grow, GKN’s Disconnect All-Wheel Drive System will help open new markets. This compact new system enables manufacturers to offer customers more capable and dynamic vehicles with improved fuel-efficiency and CO₂ emissions.”

The system responds to driver inputs and road conditions, connecting and disengaging drive to the rear axle on demand. By eliminating rotating losses from the driveline, during steady state cruising fuel efficiency can be improved by up to 4 percent compared to permanent all-wheel drive systems.

The result is a tightly packaged all-wheel drive system, which replaces features such as the standard power transfer unit (PTU) with a monoblock housing that fully integrates the propshaft’s constant velocity joint. The arrangement also yields superior NVH characteristics, benefiting the overall refinement of the vehicle. The clutch system at the heart of the disconnect system is a development of the system used in the Range Rover Evoque.

Senior vice-president of engineering, Rob Rickell, said: “With all production, engineering and software development in-house, GKN Driveline is the only supplier able to develop and supply such a tightly integrated all-wheel drive system. The result is the lightest, most compact and capable disconnect all-wheel drive system available in the market. The same hardware can support models built on a common platform but with different performance requirements. GKN’s software engineers fine-tune the electronic control to deliver specific brand characteristics.”

GKN Driveline’s Disconnect All-Wheel Drive System includes a power transfer unit (PTU), linked to the transmission’s final drive differential. The PTU contains a fast-disconnect device and brake that can bring the all-wheel drive system to rest upstream of the PTU’s hypoid gears. An electro-mechanically actuated clutch located in the rear axle both biases drive torque and disengages the all-wheel drive system downstream of the hypoid gears to save fuel.

A dedicated driveline control unit continuously monitors vehicle dynamics and environmental conditions, disconnecting the AWD system during steady-state driving speeds when the AWD function is not needed. If the driver or conditions require more traction, the AWD system reconnects within 300 milliseconds.

An active torque biasing function provides precise control of the distribution of torque between the front and rear wheels, optimising traction, stability and performance. Torque vectoring between the individual rear wheels is also possible with the system and has already been introduced on the Range Rover Evoque.