Continuing just-auto's series of Q&As with automotive component manufacturers, Matthew Beecham talked with Martin Sattler, general manager of ZF Sachs' electric drives business about the company's integrated starter-alternator technology.

For some time, ZF Sachs has been developing a crankshaft-mounted starter-alternator generator.    The company believes that its so-called Dynastart will revolutionise the drivetrain and power supply of cars at a stroke, combining the function of generator and starter and would be positioned between the engine and transmission. The Dynastart is more efficient than the conventional belt and alternator, delivering 10% potential fuel savings by allowing the vehicle to recover braking energy and release it as an engine booster function. During braking, the system can regenerate electrical current and feed it into the vehicle's electrical system.  When the driver puts his/her foot on the accelerator pedal, DynaStart operates as an engine booster.  By means of the braking energy already stored, the crankshaft starter-generator - now working as an electric motor - helps the combustion engine to put out more torque.

just-auto: What do you see as the main factors behind technical change affecting the integrated starter-alternator?

Martin Sattler: "Fuel economy is the main motivation to bring integrated starter-alternator into the market. With respect to the capabilities of the product, fed by powerful energy storage on a voltage level higher than 42-volts integrated crankshaft mounted electric machines are mainly used in mild hybrid concepts providing start-stop, regenerative braking and boosting."

just-auto: What stage is Dynastart at?

Martin Sattler: "ZF Sachs is just starting volume production."
just-auto: What are the main benefits of the Dynastart and how does it compare to your competitors' technology?

Martin Sattler: "The attractiveness of the ZF Sachs' product may be divided into two categories:

"First, ZF Sachs has developed a unique electric machine specifically adapted to the requirements for powertrain integration. The main features are:

  • Best power and torque density
  • Large diameter and short axial length
  • Large airgap
  • Permanent magnet excitation

"The operational performance of these machines is top of the class.

"Second, the USP we offer to our customers is the competence of powertrain integration. The benefits for our customers are excellent packaging solutions.  For example, by combining the electric machine with other powertrain components such as clutches, dual mass flywheels or special hybrid clutches."

just-auto: What are the specific features about this unit that will appeal to the US market? 

Martin Sattler: "The high torque gives this product an attractive start-stop performance even in combination with huge combustions engines. Furthermore, ISG hybrids are ideal technical solutions to bring gasoline engines to the fuel economy level of diesel engines. This is most attractive in markets where diesel cars do not play a significant role."

just-auto: We've already seen a number of automakers introduce a start-stop system.  What do you see as the main obstacles to overcome before ISG technology is rolled out across different car segments? 

Martin Sattler: "Belt driven start-stop systems which are available today in different cars are cost effective solutions for small and medium sized cars.

"For further improvement of fuel economy up to 20%, it is essential to realize the effective hybrid functions of extensive regenerative braking, boosting (in combination with engine downsizing) and electric driving without combustion engine.  ISGs are the preferred solution when these hybrid functions are required."
just-auto: What are the prospects for ISG applied to diesel engines?

Martin Sattler: "ISGs are attractive for diesel cars as well. Especially, the high starting torque and sufficient power capability make ISGs the ideal start-stop devices for diesel engines. 

"Using ISG with a high voltage electrical system as mild hybrid in combination with diesel engines achieves, concept-wise, the best fuel economy. In markets with relevant penetration of diesel engines, the hybridization of diesel cars is the appropriate option to reduce fleet consumption."

just-auto: What are your predictions for the ISG market in Europe and North America? 

Martin Sattler: "We expect more than 1 million HEVs worldwide in 2010. Less than 50% of these will be in Europe and North America. These figures do not include micro hybrids with belt driven start-stop systems."