|The concept GETRAG-Bosch hybrid drivetrain. Click to enlarge.|
The GETRAG Corporate Group has introduced a new concept modular hybrid drivetrain based on the combination of a parallel hybrid module and an electric rear axle drive. Getrag developed the concept in partnership with Bosch; the two companies agreed last year to work together on hybrid systems. (Earlier post.)
The concept drivetrain combines a 6-speed Getrag PowerShift transverse transmission, Bosch electric motor, Bosch power electronics and electric rear axle drive (eAD). The system supports all-wheel and hybrid functions, including boost, regenerative braking and all-electric driving.
|Components of the hybrid drive with electric axle. Click to enlarge.|
The foundation of the drive is the GETRAG PowerShift transmission—in this application, a 6-speed dry dual clutch transmission with 250Nm (184 lb-ft) torque capacity. A separate motor-generator (SMG) is mounted axially parallel to the transmission and connected to one or both (switchable) of the two part-transmissions of the dual-clutch transmission via a newly developed electromagnetic shift unit (EMAGS).
This configuration supports the use of different applicable ratios for the connection of the motor, allowing it to run at an optimum operating point. The motor can also be disconnected when necessary.
This enables full hybrid functionality (boost, regenerative braking, pure electric driving) and the operation of the engine and the motor at the optimum operating points for each, resulting in fuel efficiency benefits.
The peak torque of the Bosch separate motor generator (SMG) is scalable by the length of the machine (50-200mm) and ranges from 70-120 Nm (52-89 lb-ft).
The transmission, motor and power electronics constitute a torque-split hybrid module that can be applied with or without the electric axle drive. Similarly, the electric axle drive (eAD) can be applied as a stand-alone unit without the torque-split hybrid module, thereby creating a “through-the-road” hybrid.
The eAD features a 1-speed transmission and a 30 kW motor with peak torque of 858 Nm (633 lb-ft). The eAD’s elimination of PTU/transfer case and propeller shaft helps offset the additional weight of the hybrid components, and also helps reduce drivetrain costs.