ZF active steering

This system essentially comprises a rack-and-pinion power steering, a planetary transmission, an electric motor, some sensors and a control unit.


The additional degree of freedom makes continuous variation of the steering ratio as a function of the situation possible. Depending on the driving situation, the effective steering angle on the wheel is therefore smaller or larger than the one which the driver sets on the steering wheel.


  • Turn the steering wheel (star handle), function of the rotary sleeve valve, the gear rack is displaced, the piston moves. In this context, the stepped planetary wheels and the sun gear move in the housing, as the worm gear has been locked by the electromechanical block via the worm.
  • If the electromechanical block is unlocked (via an electromagnet, here by lifting the anchor), the handle of the electric motor can be turned. Now, the worm gear turns and the drive pinion moves the gear rack. The planetary transmission adds or subtracts an adjustable engine angle to the angle set by the driver. The sum of these two angles then acts on the drive pinion, which generates the steering angle.
  • Function of the electromagnetic valve on the Servotronic 2 rotary sleeve valve.
  • Connection of the oil lines, function of the rack-and-pinion piston.
Category: Drive Train
Item number: 79001317