Triggering the Rollover Protection Bars: Notes
The ROC control unit is supplied with load current via terminal 30. Terminal R ON is applied as the switching signal and enables the power circuit-breaker (7). In this way, the voltage regulator (8), the microprocessor (10) and the switching controller (4) are supplied with voltage. The switching controller transforms the voltage into 35 V and charges up the two firing capacitors (3).
When the processor in the Crash Safety Module detects an imminent rollover, it sends two telegrams within a defined time window via the K-bus.
The first telegram instructs the ROC ECU to make itself ready for firing (arming telegram).
The ROC ECU incorporates two firing capacitors (3) connected in parallel for providing the firing energy. Each actuator has one high-side and one low-side power circuit breaker.
The second telegram contains the firing command (firing telegram). The low-side power circuit-breakers (6) are connected to ground and the two high-side power circuit breakers (2) are switched through. The ROC ECU now discharges the two firing capacitors and the two actuators are supplied with voltage.
In normal operating mode, the protection bars are retracted in the support structure. They are pre-tensioned in the direction of their extension by a spring and held in place by a lock on the actuator. The ROC ECU activates the two actuators via the output stages.
Each actuator consists of a single-acting solenoid with a lock for disengaging and engaging its rollover protection bar. The solenoid actuates the lock and releases the spring-loaded protection bar.
The locking pawls on the protection bar press the toothed strip back mechanically as the bar extends. When the protection bar is extended, the locking pawls are supported on the tooth strip. When the car is in the overturned position, the force is transmitted via the locking pawls on the protection bars to the toothed strip.
The rollover protection system may be triggered as follows:
- Automatically when an imminent rollover situation is detected
- By a defined crash severity in a front-end, side-on or rear-end crash
- Via the diagnostic interface
- By a mechanical emergency release mechanism
In order to return the triggered rollover protection bar back into its initial position, it is necessary to press the toothed strap back so that the bar can be pushed in.