High-precision ball screw drive used in power steering system

As well as offering drivers optimised handling, modern electromechanical power steering systems can also reduce fuel consumption by up to three per cent compared with conventional hydraulic systems.

The Schaeffler Group has developed a high-precision ball screw drive to meet the demands of electromechanical steering systems - and the first application is in Volkswagen's latest Tiguan model.

Schaeffler supplies the ball screw drive to Volkswagen, as well as a toothed rack that doubles as a spindle on which the drive is located. In the Tiguan, the ball nut is driven by a servomotor, which is linked to the ball screw drive via a belt.

In contrast to hydraulic steering systems, where a pump constantly supplies pressure to provide steering motion, the electric motor becomes active only at the moment when steering motion is initiated. A pump and feeds are therefore no longer required, which reduces the space required for operating the power steering system.

With the new steering system in the Tiguan, Volkswagen is now said to be offering one of the most powerful steering gears in the market. The demands placed on the ball screw drive are therefore particularly high. The ball screw drive can support high dynamic loads thanks to appropriate spindle dimensions and high material strengths. In addition, due to the low internal friction of the ball screw drive, the driver can directly feel the low-frequency changes on the wheel when driving on road surfaces, which is important for improving driver handling.

For applications on other vehicle models, Schaeffler can modify the ball screw drive in such a way that the steering characteristics and driver handling vary, depending on the customer's wishes.

For more information on Schaeffler products and services, visit www.schaeffler.co.uk.