The Disconnect-Differential: A low cost - high impact all-wheel-drive (AWD) disconnect system

Nearly all AWD vehicles on the market today feature some sort of disconnect mechanism in their powertrain due to efficiency requirements.

The invention presented herein aims to reduce the cost of such a system, while also reducing the remaining power dissipation in comparison to current systems. A diverse group of students, researchers and experienced industry specialists at the Institute of Machine Components and Methods of Development at the Graz University of Technology teamed up to bring an unconventional idea to life.

© TU Graz/IME

Although the actual AWD drivetrain architectures, and therefore the positioning and execution of the decoupling functions, vary greatly, some common ground can be found. Many of the AWD powertrains manufactured today feature some sort of dog clutch, or dog sleeve, to shut off portions of the drivetrain when AWD is not needed. Some of the largest cost drivers in these assemblies are the switchable torque transmitting elements due to their coupling halves incorporating high strength and high precision teeth.

The Invention

The presented disconnect differential features a simple mechanism that enables the direct utilisation of the differential’s bevel gears as shifting elements. This eliminates the need for costly additional torque transferring elements like a dog clutch or sleeve, while reducing the remaining drag torque to levels below known disconnect systems. Switching the torque transfer is executed by axially moving a shifting collar, which can be realised by various available off-the-shelf actuators.

Development Process

A prototype design of the disconnect differential was derived from an existing series production bevel gear differential, focusing on simplicity and ease of manufacturing. The switching operation in various service conditions was examined using analytic models, as well as a physical technology demonstrator, that was built using rapid prototyping methods.

Finally, the developed system was compared to state-of-the-art technology in terms of weight, size and loss reduction amongst other criteria. The improvements were illustrated and possible combinations and applications for this technology were pointed out.

© TU Graz/IME

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