World’s smallest all-wheel drive disconnect – GKN 08 October 2014

GKN has developed the world's first disconnect all-wheel drive system for A-, B- and C-segment vehicle platforms – improving fuel performance during cruising by up to 4%.

The new function – also claimed to be the smallest – enables vans and SUVs to combine the traction, dynamics and stability benefits of all-wheel drive with two-wheel drive fuel efficiency.

"This compact new system enables manufacturers to offer customers more capable and dynamic vehicles with improved fuel-efficiency and CO2 emissions," states senior programme director Hannes Prenn.

He explains that it responds to driver inputs and road conditions, connecting or disengaging drive to the rear axle on demand – hence achieving the fuel savings by eliminating rotating losses from the driveline when not required.

GKN's new system includes a 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 biases drive torque and disengages the all-wheel drive system 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 AWD is not needed.

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.

The new device is expected to replace PTUs (power transfer units) with a monoblock housing that integrates the propshaft's constant velocity joint.

The arrangement – which also delivers superior NVH characteristics – uses a clutch developed from the system used in the Range Rover Evoque.

"[This] is the lightest, most compact and capable disconnect all-wheel drive system available," states senior vice president of engineering, Rob Rickell.

"The same hardware can support models built on a common platform but with different performance requirements," he continues.

"GKN's software engineers fine-tune the electronic control to deliver specific brand characteristics."

Author
Brian Tinham

Related Companies
GKN Automotive

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