Electro-Mechanical Actuating Unit

Electro-mechanical Actuating Unit (EMF): The EMF receives the parking brake request and activates an electric actuator (motor) to tension the parking brake cables. The EMF actuating unit is located under the luggage compartment floor in front of the spare wheel recess.




End Stop: The end stop is the "zero point" for the initial position which is required for the parking brake cable installation (release no tension).

The balance arm rests against the end stop the first time the brake is released when the ignition is on (KL15).




Hall sensors are mounted on the motor to detect the speed and position. The control module detects the end stop by the increase in actuator motor current and the decrease in the motor speed (Hall sensors).
When activated, the spindle is turned by the motor using a gear drive mechanism to apply the parking brakes. The balance arm is pulled by the spindle (worm) and will compensate for the slight difference in side to side cable length. The balance arm is linked by connecting levers to pull the cable pulleys inwards towards the direction of the spindle rotation. The cables are attached to the cable pulleys which are pulled "in" to apply the parking brakes. Once the hold position is reached, the spindle worm gear ensures cable tension and will not release with out spindle rotation.




Gear Drive Mechanism with Coil Spring: This is designed as a three stage (reduction) gear mechanism consisting of a worm, spur gear and spindle. The holding force for the parking brake is assisted by a coil spring mounted on the end of the spindle.




When the brake is released, the spindle is turned by the motor and gear drive mechanism in the opposite direction. The balance arm, connecting levers and cable pulleys are pushed outwards by the spindle (worm). The cables are also pushed "out" to release the parking brakes. To assist in the release, return springs are installed in the parking brake assemblies inside the brake discs.


NOTE: With the manual emergency release, the spindle can be turned through the gear drive mechanism with the tools found in the vehicle tool kit to release the parking brake.