At a Glance

2008/11/25 Steering and Thinking

• Servolectric® electric power steering is standard in the new Golf VI
• 0.3l reduced fuel consumption compared to an hydraulic steering system
• The steering system's system compatibility enables networking with additional safety and driver assistance systems

Various ZF components are included on a volume production basis in the new Golf; among these: The third generation of the Servolectric by ZF Steering Systems. In terms of fuel consumption, thanks to this electromechanic steering system, when compared to hydraulic steering systems about 0.3l can be saved. Another advantage: The system-integration-capacities of the Servolectric, third generation. For the end customer, this relates to enhanced comfort and safety.

Lower fuel consumption without compromises

The Servolectric electromechanic power steering system by ZF Steering Systems, ZF Lenksysteme GmbH is a 50:50 joint venture between Robert Bosch GmbH and ZF Friedrichshafen AG, requires energy only when the driver is actually steering. This way the electric power steering system saves about 0.3 liters fuel per 100 km compared with a servo steering system powered by the engine. With a production figure of almost seven million units until date, annual savings of 210 million liters fuel can be computed thanks to the application of the Servolectric steering system. This relates to overall savings amounting to 498 000 tons of CO2. (assuming an average of 10 000 km driven each year per vehicle).

Power on demand

The Servolectric's steering mechanism is based on the principles of a rack-and-pinion steering, which, in the case of the electromechanic power steering, it is linked to high-performance electronics. As soon as the driver performs a steering motion, the corresponding steering torque and speed are registered by sensors. From this data, the control unit computes the required steering support within milliseconds; then, via a worm gear or a ball-and-nut gear, the servomotor transfers the optimum servo torque to the steering column, pinion, double pinion, or gear rack of the mechanical rack-and-pinion steering system. In addition, the electric power steering system introduced in 2002 has more advantages to offer: Space-saving installation thanks to the elimination of the oil pump and the hosing; this simplifies assembly and, at the same time, relieves the environment. Last but not least, this is the reason why the VW Group already integrated the predecessor of the third Servolectric generation in its entire Gold platform range.

System capability enhances driving safety

The new Servolectric generation can be networked with a huge variety of external systems. Thus, the entire range of information recorded in terms of the steering wheel angle is made available to other systems, such as the ESP or the adaptive chassis and suspension control system. A particularly high level of driving safety is ensured at Volkswagen thanks to the “Lane Assist” track-keeping assistant as well as the “Side Assist” line/track-change assistant. With regard to the driving situation, the corresponding system will intervene and, by means of optical, acoustic, or feedback (haptic) signals, recommends counter-steering motion to the driver. In the case of the parking assistant, manual interaction at the steering wheel is longer required: Here, the Servolectric is completely autonomous in terms of steering motion intervention.

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