Ecology inspires new hybrid drivetrain options

  • 31-Mar-2008 05:45 EDT

Getrag and Bosch will introduce a range of cooperatively developed parallel hybrid drive systems such as this one, which incorporates a Getrag dry dual-clutch six-speed transmission, Bosch alternator/motor, power electronics, and electric drive rear axle.

Transmission manufacturer Getrag unveiled its new concept in hybrid drivetrains—a dry dual-clutch transmission linked to an electric rear axle—at the Frankfurt Motor Show in September 2007.

In tune with the environmental undercurrent of the show, Getrag launched the concept, developed jointly with Bosch, under the banner of “Ecology Needs Dual Power.” The company also announced the latest transmissions in its PowerShift range, introducing variants with both wet and dry dual-clutch systems.

The agreement between Getrag and Bosch is designed to launch a range of parallel hybrid systems using Getrag PowerShift dual-clutch transmissions and Bosch electrical architecture for the alternator, electric drive system, and power electronics. Designed around a six-speed PowerShift transmission, the resulting systems will feature modular designs that offer flexibility in the hybrid drivetrain.

For instance, the system can be arranged as a conventional parallel hybrid, with the e-machine as a combined alternator/drive motor positioned between the internal-combustion engine and the dual-clutch mechanism.

Alternatively, the e-machine can exploit the dual-clutch transmission’s capabilities by mounting an alternator/motor separately and axially parallel to the transmission. Drive is then taken via an electromagnetic shift unit from one side of the split transmission (either the “odd” or “even” gear sets). The alternator/motor can be driven from one side of the transmission or switched from one to the other as needed. The electromagnetic shift unit can also disengage the alternator/motor drive completely. Getrag has named the system “Torque-Split”.

The principal advantage of the system is that the internal-combustion engine and alternator/motor can be operated at different speeds. As a result, the alternator/motor can operate at its optimum speed—between 14,000 and 20,000 rpm—while the internal-combustion engine operates over the conventional diesel or gasoline speed ranges.

Getrag claims that lighter and less-complex electric components are applied and many parts are common to the PowerShift transmission used with non-hybrid powertrains.

An alternative arrangement is to add an electrically driven rear axle. Since no further modification of the drivetrain is needed, the electric rear axle can be used either as an add-on to the “Torque-Split” hybrid or with the front-drive internal-combustion engine to provide all-wheel drive by switching in drive to the electric rear axle as required.

Used in place of a torque-converter automatic transmission with a conventional internal-combustion-engine drivetrain, Getrag claims that its PowerShift transmission will deliver a minimum fuel consumption reduction of 4 to 8% for both diesel and gasoline engines.

First to market in the revised PowerShift range will be wet clutch systems with production beginning in 2007. Volvo will be the first customer for the six-speed 6DCT450 transmission with a torque rating of 450 N·m (332 lb·ft), and a maximum ratio spread of 6.5, when it appears in fall 2007, followed by Ford. The transmission will be used in conjunction with a 2.0-L diesel engine. A 470-N·m (347-lb·ft) variant is also due in 2007. Seven-speed variants with torque capacities of 600 to 750 N·m (443 to 553 lb·ft) are due to follow in 2008, and the first PowerShift dry clutch transmissions will appear in 2009.

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