Electrical Shift Gearbox (ESG) - Consistent Development of the Dual Clutch Transmission to a Mild Hybrid System 2005-01-4182

Major goal for the development of hybrid vehicles is to increase fuel efficiency. Legislation and tax incentives are supporting this motivation. But also the performance can be improved. By realizing a boost function e. g. it is possible to compensate the poor start up behaviour of turbo charged engines.

In case of the hybrid system that will be described in the following article additional targets were defined for the development:

• Add on - structure
• Flexible dimensioning of the starter-generator
• Minimal application efforts.

The definition of the hybrid concept requires first a focus on the base transmission. Driven by above mentioned targets the investigation of existing gearboxes leads to a dual clutch transmission. Regarding the requirements for controllability independent from the combustion engine for start/stop and again good efficiency the electro-mechanical actuation concept is chosen. Using a modular clutch- and actuation-concept both variants are feasible, the dry and the wet clutch. For efficiency reasons a dry clutch should be used where possible. By adding an electrical machine in parallel to the even gear set of a power-shift transmission a powerful hybrid system can be realized, that fulfils all above mentioned targets. This system is called Electrical Shift Gear-Box (ESG),.

Based on an Opel Astra with 1.3 l diesel engine a demonstrator vehicle was built up in cooperation with Opel and Continental ISAD as a mild hybrid system. The electrical machine has a power of 10kW. A combination of ultra-caps and AGM battery is used to store the electrical energy.

Measurements from the vehicle show the predicted benefit in fuel consumption and performance. Traces of some events are shown in the presentation and the engine restarts are discussed. The output torque remains constant during recuperation and the restart time for the combustion engine is very short.