Steering: power assistance graded according to the speed of travel

Mercedes-Benz is introducing electromechanic speed-sensitive power steering for the first time in the new A-Class. Here, the power assistance is generated using an electric motor, which transfers it directly to the gearing of the rack-and-pinion steering mechanically rather than hydraulically. This newly developed technology impresses with a host of plus points: lower weight, more compact dimensions, in-creased effectiveness and a reduced energy requirement. However, the most important benefits are without doubt provided by the additional functions offered by this state-of-the-art steering system:

• The electric motor is equipped with a micro computer which is integrated into the databus network of the new A-Class and regularly calls up the latest data on the travelling speed, engine speed, steering angle and torque at the torsion bar. This information is used to grade - or “parameterise”, as the experts would say – the level of power assistance according to the vehicle speed. This has the advan-tage of providing the driver with greater power assistance at lower speeds, making parking and manoeuvring far more comfortable than with a conventional power steering system. The speed-sensitive function is adjusted and programmed precisely for each body and engine variant of the new A-Class. The direct steering ratio and impressive dynamics of the newly developed system ensure precise steering feel. Active response characteristics aid the centring of the steering.
• As the electric motor is only activated when the steering is in use, the system’s energy requirement is lower that of hydraulic steering – and that is reflected in reduced fuel consumption.
• The electromechanic steering works without hydraulic oil, allowing for easier as-sembly and repairs. This technology also scores highly in terms of environ-mental protection, as oil disposal is not an issue.

The steering column consists of an upper steering shaft mounted in the jacket tube and a lower two-piece steering shaft, whose constituent components slide against each other in a frontal collision in order to prevent the steering structure from pene-trating the interior. A universal joint connects the two steering shafts. The driver has various options when it comes to adjusting the attractively designed three-spoke steering wheel (diameter: 380 millimetres). A handle positioned underneath the steering column pulls out to allow full height adjustment (by +/- 20 millimetres), whilst the steering wheel is also available with additional reach adjustment (by +/- 30 millimetres) as an option.

As in other Mercedes model series, the steering wheel for the new A-Class is a central element in the state-of-the-art control and display concept. Thanks to the easy-reach multifunction buttons, the driver no longer has to take his or her hands away from the steering wheel in order to operate the radio, navigation system and car telephone or to access important information on the display in the instrument cluster. The standard-fitted multifunction steering wheel is made out of die-cast magnesium and is designed to deform as required in the event of a crash.