Direct steering
The direct steering is a hydraulic rack and pinion steering with a variable steering ratio. The teeth of the rack are different along its length, narrow in the middle and wider on the sides. This changes the steering ratio depending on the steering wheel angle. The aim is to achieve stable straight-line stability at high driving speeds and increased agility when cornering.
Technology and functionality
In addition to a constant ratio, a hydraulic rack and pinion steering can also be designed with a variable ratio. The toothing of the rack is changed over the steering stroke. This method is also used in vehicles with electrical power steering and in purely mechanical steering systems. Direct steering is a special form of hydraulic rack and pinion steering with a variable steering ratio. Here, the transition between indirect steering behavior in the middle area (straight ahead) and direct steering behavior with larger steering wheel rotation angles (to the right and left) is very steep. The driving speed is not taken into account for the steering ratio of the direct steering. This means that the coordination of such a steering system is very tight. It always represents a compromise between agility when cornering and stable straight-line stability at high driving speed. Therefore, the ratio can only be changed slightly in the range of up to +/- 90 ° steering wheel angle compared to other hydraulic steering systems. A clear change from normal ratio (e.g. 1:15) to direct ratio is only possible in a range over 90 ° steering wheel angle. This can lead to unfamiliar steering behavior, which requires special attention from the driver in order to keep in lane.
The direct steering does not allow an additional steering angle to be applied in dangerous situations. Direct steering is not comparable to active steering or dynamic steering . Active steering is an electronic steering system that actively adjusts the steering ratio depending on the driver's steering angle, speed and driving situation. One supplier of direct steering is Mercedes-Benz .