Siemens modular hybrid concept
mild, medium and full hybrids by 2008

Motion Trends,
17th September 2005.

Hybrid drive systems started as a mere temporary solution between the internal combustion engines of today, and the future fuel-cell vehicles.

But the hybrid concept is gaining even faster than anticipated, thanks particularily to Toyota (followed by Honda) who proposed really a convincing hybrid vehicle, the Prius, then in more and more models in its lineup today.

But two other indirect allies are favoring the hybrid solution today:

The first one comes with the uncertainties about the most efficient hydrogen storage techniques for fuel-cell vehicles, on-board or in fixed stations (with the heavy costs of petrol stations conversion in each country), the other necessary development for the fuel-cell technology itself, its reliability in extreme temperature conditions, and especially, in reducing its cost.

The second factor is none but the one hurting our pockets at the pump stations: oil prices.

That is why more and more car manufacturers are  getting "fervent" about the hybrid solution, with more alliances (BMW, DaimlerChrysler and GM announced recently plans to co-develop advanced hybrids) in scope.

On top of that all, hybrid technology does not threaten current internal combustion engine manufacturing (it represents billions of investments and jobs). However, it adds production potential for electric motors, and on top of that, it can adapt to the requirements of the fuel-cell technology when it becomes cost-effective for wide production.

Within this context, Siemens VDO Automotive is presenting its hybrid system solutions at the 61st IAA Motor Show at Frankfurt, Germany (15-25 September).

At the center of the company's presentation is its modular concept for hybrid drives in anticipation of full hybrids with electrical outputs of up to 75 kilowatts being available by 2008. The automotive supplier also is presenting its optimized gasoline and diesel fuel injection systems together with the related electronics.

In the coming decades, automobile manufacturers and suppliers will face the challenges of increased torque and output and further reductions in consumption. While drivers want more driving pleasure, worldwide legislators are imposing increasingly stringent emission standards.

Siemens VDO's hybrid drives combine the conventional combustion engine with the electric motor. But the approach identifies three typical requirement hybrid levels: micro, mild and full.

This modular hybrid concept offers a comprehensive building kit, from which vehicle manufacturers can select system solutions that best suit their advanced propulsion strategy needs.

Instead of the conventional generator, the micro hybrid utilizes an electric motor that is integrated in the belt drive to serve as the starter generator for stop-start operation.

For the mild hybrid the electric motor is connected directly to the crankshaft. Depending on design, start-stop and energy recovery functions are available when braking. The electric motor delivers additional torque during acceleration to offer significantly greater driving pleasure.

Siemens VDO has integrated the micro and mild hybrids in current hybrid demonstration vehicles, tests have revealed reductions in fuel consumption of up to six percent on the micro hybrid and as much as 18 percent on the mild hybrid.

Siemens VDO plans to have the full hybrid on the market by 2008, with electrical outputs of up to 75 kilowatts enabling the vehicle to run on the electric motor alone. The full hybrid utilizes the whole wealth of electric motors, high-temperature electronics and engine and drivetrain management expertise Siemens VDO development engineers have accumulated over the years. Siemens VDO has refined the effective combination of combustion engine, electric drive, engine control unit and all the other auxiliaries.

In spite of the continuing demand for hybrid solutions, the combustion engine will remain the dominant automobile propulsion concept for Siemens VDO in the coming years. This still holds considerable development and cost-reduction potential. Therefore, the hybrid drive does not compete with the diesel or gasoline engine. Holistic system optimization – with or without hybrid drive – must continue to further bring fuel consumption and emission levels down in the coming years.

Petrol (gasoline) engines - In the case of the gasoline engine, the main goal is to minimize consumption. Direct fuel injection has a great deal of potential here and also can simultaneously boost performance. In contrast to conventional manifold injection, Siemens VDO's Piezo direct injection technology yields more output from the same engine capacity, makes for better engine dynamics, lowers consumption by as much as 20 percent and reduces exhaust emissions. With this technology, the future gasoline engines will not only have greater acceleration power, but will be more economical and cleaner.

Direct injection systems based on solenoid technology and manifold injection systems are always being optimized by Siemens VDO. With the new injector technologies the company can offer better mixture preparation with finer fuel atomization and thus cleaner combustion and fewer emissions. The use of alternative fuels such as ethanol, liquefied petroleum gas (LPG) or compressed natural gas (CNG) in gasoline engines is another way to reduce emissions. Siemens VDO supplies the related injection components and control devices and when operating on gas, the traditional internal combustion engine emits up to 75 percent less carbon monoxide, up to 60 percent less hydrocarbons and up to 25 percent less carbon dioxide.

Diesel engines - The diesel engine has strong arguments: up to 20 percent lower carbon dioxide emissions than a comparable gasoline engine, lower consumption figures, and rising performances. Siemens VDO has contributed significantly to this, as the first in the world to use piezo actuators for common rail injection in 2000 and for piezo unit injectors in 2004. The piezo technology results in quieter and cleaner diesel engines.

Besides the consumption and emission advantages of diesel direct injection, the technology also opened the way for exhaust aftertreatment using diesel particle filters. The biggest challenge regarding diesel engines remains the reduction of nitrogen oxide and particle emissions. While preinjections make for a steadier rise in pressure in the combustion chamber, thus reducing combustion noise, postinjections help to improve combustion of the remaining soot particles. The contaminants remaining are then trapped in the exhaust aftertreatment system. Here, Siemens VDO draws on the expertise of Emitec, a joint venture between Siemens VDO and Britain's GKN, to supply metal catalytic filters with open passage structures for filtering out fine diesel soot.

Siemens VDO's focus continues to be on preventing emissions from being generated at all. Additional information about the combustion process – such as combustion chamber pressure – is needed to achieve further emissions reductions with new combustion technologies. A Siemens VDO piezo-based combustion pressure sensor, which is on display in Frankfurt, is just one example of the many sensors which make optimized, clean combustion possible. The sensor signals are processed in the heart of the injection system. The electronic engine control unit ensures the combustion engine and the injection system work optimally together in every driving situation. With a trend-setting engine management concept, Siemens VDO offers standardized software modules that are largely hardware-independent. This means that the EMS 2 system platform with its enhanced modularity can be used for all kinds of spark-injection and diesel engine, as well as hybrid drives.

For Siemens VDO, re-using tried and tested components in new systems is a proven means of assuring even greater reliability and speeding up the development process and making it more flexible. This also is the aim the company is pursuing with its involvement in the AUTOSAR initiative (Automotive Open System Architecture), which Siemens VDO is a founding member. Clearly defined common standards for electronics infrastructure and module compatibility are absolutely essential, given the ever growing electronics content in vehicles.