Roll Bar Hydraulic Actuator: Description and Operation

The roll-over bar is driven on the right side by a hydraulic cylinder (2).






Mechanical locking of actuating element
Since the hydraulic circuit is not under pressure when it is not actuated by the convenience feature, the actuating element piston must be locked mechanically in its lower position (A). It is locked by spring force (4) via balls (5). When the convenience feature is actuated, the locking piston (3) and the piston (2) are put under pressure and act against the force of the spring releasing the lock (B).






Crash actuation
In the retracted position (A) the support element (2) is held by the lock (7) and the triggering solenoid (Y57/1). The triggering solenoid (Y57/1) is actuated by the control module, opens the lock (7) and the element (2) moves upward (B) within approx. 0.3 s under the force of the tensioned spring (5) located in the actuating element. This operation is accompanied by a clicking noise, because the locking pawl (4) engages with the rack during the extension operation beginning at an angle of approx. 14 °. This ensures that the roll-over bar is supported even when it is put under load prematurely.






Convenience feature
When the convenience feature is actuated the hydraulic element is put under pressure on the piston side (arrow A) when the roll-over bar is extended, and on the rod side (arrow B) when the roll-over bar is retracted. This releases the tension on the spring (5) or tensions the spring respectively. The extension speed as well as the extension force of the roll-over bar (resulting from the spring force and hydraulic force) are controlled by a throttle in the actuating element. To prevent noises when the roll-over is extended (locking pawl - rack), the spring-loaded locking pawls (4) are put under pressure on both sides via a hydraulic servo-cylinder and moved away from the rack.

Crash actuation has priority over the convenience feature, i.e. the triggering solenoid can be actuated even when the convenience feature is in operation. In this case the pressure to the servo-cylinder is shut off, the locking pawls (4) swing back to engage in the rack and the roll-over bar is extended by the force of the spring (5).

For retracting the roll-over bar following crash actuation,