ENERGY- & COST- OPTIMIZED ELECTRIFIED POWERTRAIN
Goal of this work-package is the evolution of the electrified transmission. The optimized gear arrangement shall result to (a) saving of mechanical parts, thus saving costs, and (b) higher degree of freedom for the control, thus laying the basis for improved calibration (and therefore higher performances) as well as higher integration flexibility in different vehicle classes (for purpose of producibility).
MAIN TARGETS & RESULTS
- Cost reduction of electrified transmission for PHEV powertrain by 10% (w.r.t. VECEPT)
- Emission reduction: NEDC <31g CO2/km (as compared to Hybrid VW Golf with 35g CO2/km)
- Reduction of the number of clutch, brake and shifting elements (w.r.t. VECEPT)
- Introduction of thermal gearbox housing concept
- Cost- and efficiency-optimized ICE (gasoline combustion engine 200g/kWh)
- Flexible design for future PHEV powertrains enabling easier integration in larger classes of vehicle (à mass producibility)
Current Highlights of WP2
The most important results of the current activities can be summarized as following:
- Completion of functional requirement list
- Further refinement of DHT transmission development process
- Discovery of several novel DHT transmission concepts which meet expectations
With the completion of the functional requirements of WP2 all main boundaries are set for the whole vehicle. It reaches from driving functionality, physical component definition, cost optimization, to human machine interface. It can be used as the basis for further steps in transmission development and interaction between work packages.
With the given system boundaries as a starting point a unique way of transmission development was chosen. It combines computer aided automated search for novel structures with experience from previous DHT projects. The search was split in two kinds of transmissions: advanced transmissions (AT) with planetary gear sets and multi plate clutches/brakes and conventional transmissions (MT) with spur gears and dog clutches/synchronizers.
It is very positive that this approach resulted in innovative transmission concepts for both kinds of transmissions above described. They are subject of patent application and represent a step forward in terms of transmission technology. The chosen concept from advanced transmissions (AT) was already successfully applied for. It consists of one extended Ravigneaux Planetary gear set, three clutches and one brake (see Figure 1).
Figure 1: Advanced Transmission concept; left: principal sketch; right: transverse arrangement
The number of moving parts has been reduced with respect to VECEPT and the functionality of the transmission has been increased. This transverse transmission is also very flexible because with small modifications it can be used as longitudinal, 48V or conventional AT transmission.
Some innovative concepts were also found for the conventional transmissions (MT). They are very compact, flexible and cost effective due to the use of standard components. Those concepts don’t need a launch clutch which further reduces costs. A patent application will also be filed for them.