New integrated approach to hybrid e-motor design provides improved performance, packaging and weight benefits
Custom designed e-machine maximizes the potential of 48V hybrid architecture while simplifying calibration demands and improving system efficiency
Powertrain engineering specialist, Drive System Design (DSD) will highlight how the design of a bespoke e-machine can unlock the benefits of P2 hybrid arrangement (where the motor is positioned between the IC engine and the transmission) at the forthcoming International CTI Symposium, in Michigan, USA. The company will present a paper entitled ‘Hybridizing the power shift transmission for improved shift feel, ease of calibration & fuel economy’.
The opportunities to reduce CO2 emissions and improve fuel economy by implementing a 48V architecture are well understood, along with the benefits of differing e-machine positions. Usually motors are developed in isolation from other systems, however DSD’s experience shows that a lighter, more compact system with higher efficiency can be designed when optimized and integrated with the transmission.
“Conventional motor designs are not optimized for a P2 arrangement,” explains Ben Chiswick, Senior Design Engineer and paper co-author. “By designing the e-machine precisely for this layout, we have been able to integrate it within a power-shifting transmission, such as a DCT, AT or dual-countershaft. This delivers the traditional hybrid benefits like regenerative braking and torque support, but also offers the opportunity to eliminate the transmission controller’s reliance on engine torque management by utilizing precise motor speed control to achieve smooth ratio changes and constant output torque.”
The paper shows how the custom designed e-machine overcomes the challenges of the P2 arrangement in a power-shifting transmission. It demonstrates the control concepts, efficiency gains and cost savings of utilizing this technology. By modelling the shift events, areas explored include: e-machine sizing to achieve supported shifts; e-machine sizing for traditional hybrid functionalities; and possibilities for furthering e-machine integration into the powertrain.
“The superior controllability of an e-machine, compared to an IC engine, greatly improves shift quality because it circumvents the inaccuracies of engine management and torque reporting,” says Jason Schneider, Senior Control Engineer, the other co-presenter. “Alternatively, taking a whole powertrain perspective, the near instantaneous torque contribution from the e-machine can reduce inefficiencies within the IC engine during transient events such as gear shifts. This could be particularly helpful with the advent of Real Driving Emissions testing.”
The paper will be presented on May 17th at 11.45am as part of the Powertrain Control & Integration session in the Garnet room. The CTI Symposium USA, subtitled Automotive Transmissions, HEV and EV Drives, will be held in Novi and runs from 14-17 May 2018.