Magna Powertrain, best known for its all wheel drive systems, is developing a hydrostatic double clutch unit for use with both longitudinal and transverse passenger car transmissions.

Displayed at the December 2008 Berlin CTI transmissions symposium, Magna’s prototype dual clutch transmission has the appearance of a large automatic, with the self-contained hydrostatic clutch pack in the position normally occupied bythe torque converter.

Inside the main casing, however, is a two-shaft gearbox to suit the prototype’s inline layout: the packaging and shaft arrangement would be different for a front-drive, transverse engined application, said drivetrain project manager Ferdinand Tangl.

The clutch module is much smaller than a conventional torque converter or friction clutch, leaving a large amount of surrounding free space in the prototype’s bellhousing. Where the hydrostatic clutch is larger is in its axial length (pictured), necessary to accommodate the various chambers, passages and valves.

It is likely that any eventual production packaging would be much more compact.

Magna engineers were reluctant to provide much detail on the program, except to state that the hydrostatic DCT as currently configured has a torque handling capacity of 400 Nm and that the clutch module has the same efficiency as that of a dry friction clutch.
Magna did not say whether the hydrostatic unit was used for speed variation as well as clutching functions.

Potential advantages, according to Magna’s Tangl, include much smoother operation than a conventional friction double clutch, allowing for an easier control strategy.

The program is now in the advanced development phase, said Tangl, with production possible around 2011 or 2012. Despite the hydrostatic clutch module’s clear complexity, the overall transmission would be cost-comparable with a conventional wet DCT, he noted.

Hydrostatic drives are commonly used on heavy off-highway equipment as well as on luxury garden tractors, where their smooth operation and precise speed control are especially valued.

Story Filed: 1/16/2009
By Tony Lewin, managing editor DCTfacts.com