Related Procedures

Function description of roll-over bar

Roll-over bar system, model 129 (version up to approx. 05/95)





Roll-over bar system, model 129 (version as of approx. 06/95)





General
The U-shaped roll-over bar is mounted on two main bearings on the left and right center pillars. In the retracted state the roll-over bar is positioned in front of the soft top compartment. In the event of an accident or critical driving situation, e.g. extreme inclination of the vehicle, complete extension of the rear axle suspension, the roll-over bar is automatically extended by the roll-over bar crash-actuated trigger module. In the event of crash actuation the central locking mechanism receives a signal to unlock. At a vehicle acceleration/deceleration rate >0.4g or vehicle inclination >22° the automatic belt retractors on the driver's and passenger seat belts are locked. The roll-over bar can also be put up manually with a switch in the center console (convenience feature). This is possible while driving when the hard top is attached or when the soft top is up.

The roll-over bar system consists primarily of the following components and assemblies:
- Roll-over bar
- Control module
- Triggering solenoid
- Convenience switch
- Indicator lamp
- Rear axle switch, up to approx. 05/95 only
- Support and actuating elements
- Automatic belt retractor with electrically controlled belt lock
- Belt buckles
- Hydraulic unit
- Central locking

Location of electrical and hydraulic components

1 Crash actuation for roll-over bar - belt locks (version up to approx. 05/95)





1 Crash actuation for roll-over bar - belt locks (version up to approx. 06/95)




Roll-over bar convenience feature





Design, function: Electrical, Hydraulic, Mechanical systems

A Roll-over bar




The roll-over bar (1) consists of a highly rigid steel tube bent in a U-shape, which is inserted into two half shells on both sides welded to one another. The two main bearings are located at the bottom ends of the roll-over bar. The mounting points for the support and actuating elements (2 and 8) are located on opposite sides. The steel tube is covered with a 30 mm thick layer of PUR foam rubber and matched to the interior fittings.

B Roll-over bar crash-actuated trigger module (N53) up to approx. 05/95




The roll-over bar crash-actuated trigger module is located in the rear on the tunnel between the occasional seats. The control module contains two piezo-electric sensors 1), which measure the vehicle acceleration in the longitudinal direction (X) and lateral direction (Y). They are located in the control module correspondingly (90° angles). The signal from the sensor elements are proportional to the acceleration and are processed mathematically according to the laws of trigonometry, whereby a constant acceleration sensitivity is achieved in any desired direction in the horizontal plane. A position switch senses the vehicle inclination (all around).

Soft top control module (N52) as of approx. 06/95





The roll-over bar trigger module is integrated into the soft top control module and located in the rear behind the right occasional seat. The control module contains two piezo-electric sensors 1), which measure the vehicle acceleration in the longitudinal direction (X) and lateral direction (Y). They are located in the control module correspondingly (90 °angles). The signal from the sensor elements are proportional to the acceleration and are processed mathematically according to the laws of trigonometry, whereby a constant acceleration sensitivity is achieved in any desired direction in the horizontal plane. The control module contains two cone-shaped tilt sensors. The first actuates at a vehicle inclination of 22° all the way around. The belt lock is controlled by this sensor. A second cone- shaped tilt sensor replaces the previous rear axle switch and senses critical situations which can lead to roll-over. This cone-shaped tilt sensor trips at a vehicle inclination of 52 ° triggering the roll-over bar.
1) A damped, piezo-ceramic bender bar mounted in the sensor is bent due to its inertia by negative acceleration, e.g. crash, braking, etc., producing a voltage. This voltage serves for measurement of the acceleration.

All signals are generated and processed digitally.

The electronic control module is subdivided functionally into:
- Acceleration sensors (X and Y)
- Signal generation stage
- Processor
- Output stages
- Monitor
- Error memory

Signal generation stage
The input signals from the two rear axle switches (in version up to approx. 05/95) or the signal from the cone-shaped tilt sensor (in version as of approx. 06/95) and the two front belt buckles (buckled, not buckled) are converted by the signal generation stage to a form which can be used by the processor.

Processor
In the processor the signals for vehicle acceleration and vehicle inclination are evaluated and compared with set values. If the processor recognizes a vehicle acceleration rate >0.4g 1) or a vehicle inclination >22°, the output stage for the belt lock is actuated. In the version up to approx. 05/95 at a vehicle acceleration rate of >4g 1) or vehicle inclination 22° and when at least one rear axle switch is open, the output stage for the roll-over bar is actuated. As of the version 06/95 the roll-over bar output stage is triggered at a vehicle acceleration >3g 1) or vehicle inclination >52°

Output stages
If the control module recognizes an error, the malfunction indicator lamp is actuated via the corresponding output stage. If the control module recognizes an accident or critical driving situation, the output stage for the roll-over bar is activated and the roll-over bar extended. During a braking maneuver or when driving through a curve the output stage for the seat belts is activated and the belts locked.
1) 1g approx. equal to 9.81 m/sec.sq. (acceleration due to gravity)

In the version up to approx. 05/95 the roll-over bar crash-actuated trigger module and the soft top control module are connected by a data bus (2 lines), which transfers the following information:
- Roll-over bar okay
- Roll-over bar defective
- Vehicle acceleration >0.4g 1)
- Crash actuation

As of approx. 06/95 the roll-over bar control module is integrated into the soft top control module.

Monitor
The processor itself as well as all electrical components outside are monitored. If an error is recognized this is indicated to the driver by the malfunction indicator lamp in the instrument cluster coming on. Simultaneously two LED's come on in the roll-over bar switch (convenience feature). This serves as a request to put up the roll-over bar.
1) 1g approx. equal to 9.81 m/sec.sq. (acceleration due to gravity).

Error memory
The following errors are recognized and stored in a non-volatile memory (EEPROM).
- Control module defective
- Voltage too low
- Left belt locking relay defective
- Right belt locking relay defective
- Roll-over bar trigger solenoid defective
- Rear axle switch short circuited to plus or ground (version up to approx. 05/95)
- Malfunction indicator lamp

Version up to approx. 05/95
The stored errors can be called via pulse readout on the data link connector.

Version as of approx. 06/95
The error memory can be read out and erased with the HHT.

Block diagram, overall function, roll-over bar on version up to approx. 05/95





Block diagram, overall function, roll-over bar on version as of approx. 06/95





C Triggering solenoid (Y57/1)





The triggering solenoid (Y57/1) is located on the right support and actuating element (2). In the event of an accident or critical driving situation it is actuated by the roll-over bar crash actuated triggering module. This opens the lock (7) which holds the roll-over bar in the retracted position (A). The roll-over bar is extended by springs (5) under tension (B).

D Roll-over bar convenience switch (S83)





The roll-over bar can also be extended and retracted while driving with the so-called convenience switch (S83) in the center console. This is possible with the soft top up or down or with the hard top attached. The convenience feature is overridden when the soft top or hard top is being moved. In the event of a defect in the roll-over bar system two LED's in the shape of two upward painting triangles flash in the switch (S83) . This serves to signal to the driver to put up the roll-over bar with the convenience feature to ensure protection in the event of an accident or critical driving situation.
The roll-over bar is automatically retracted when the top is being moved to prevent collision between the roll-over bar and top (roll-over bar extended), and is extended again after the top motion is completed.
The convenience feature also serves for retracting the roll-over bar after crash actuation (see control module for crash actuation). For this purpose the switch (S83) must be pressed up in the direction "extend" for approx. 5s until the lock engages audibly. This causes the hydraulic cylinders to move upward and the lock catches. The roll- over bar can then be retracted.

E Malfunction indicator lamp (A1e29)





The malfunction indicator lamp (A1e29) is located in the left half of the instrument cluster. When the ignition key is turned to position two in the steering wheel lock the malfunction indicator lamp in the instrument cluster comes on and goes off when the engine starts running as long as a malfunction is not present.
If the malfunction indicator lamp continues to burn with the engine running, a malfunction is present.

F Rear axle switch (S83/2,S83/3) Version up to 05/95
The rear axle switches are located on the left and right sides on the spring links for the rear axle. They detect critical driving situations (e.g. rear axle suspension completely extended, rear wheels lifted), which can lead to rolling over. They are designed as normally closed switches. The rear axle switches have two positions each and are labeled.

Operation



In this position the rear axle switch is ready for operation (movable).

Arrested



In this position the rear axle switch is open and arrested mechanically. This position is necessary for adjustment of the rear axle switch.

G Support and actuated elements



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).

H Three-point seat belts with electrically controlled belt lock and emergency tensioning retractors





The complete three-point belt with emergency tensioning retractor is integrated into both front seats. The three-point belt consists of three systems:
- Vehicle-sensitive locking system
- Belt-sensitive locking system
- Emergency tensioning retractor





a) Vehicle-sensitive locking system

In contrast to conventional belt retractors with which the belt is locked by mechanical ball sensors, the control module actuates two electro-mechanical relays (K18/2, K18/3). These relays lock when they are not actuated. In order to fulfill the legal regulations, which require automatic locking in the event of a power failure, and still allow the belt to be fastened, an additional mechanical release for the locking mechanism is installed which releases the belt locking mechanism via a control cable when the belt is not buckled, i.e. the unbuckled belt is released mechanically and can always be fastened. As soon as the belt is buckled this mechanical release is canceled and the electrical function takes over. The control module is in operation as soon as the ignition is switched ON and the one of the front belts is buckled. After the ignition is switched off or one of the front belts is buckled, a function time delay of 60 min. exists in both cases for convenience reasons.

The front belts are locked (relay not under power), when the control module recognizes one of the following conditions:
- Vehicle acceleration/deceleration > 0.4 g
- Vehicle inclination > 22 °

b) Belt-sensitive locking system
The belt sensitive locking system, which reacts to the belt extension speed, consists of a mechanical mechanism integrated into the retractor.

c) Emergency tensioning retractors
The function of the emergency tensioning retractors is the same as previously, whereby the tube points downward. The emergency tensioning retractors are integrated into the front backrests and are activated by the airbag and emergency tensioning retractor control module.





d) Child safety seat retention, (USA) Only
The electrical belt lock is activated by the seat belt lock switch (S68/13) located on the inside of the passenger seat. After the seat belt has been buckled and the locking tongue inserted into the belt buckle, the seat belt can no longer be pulled out any further, because the switch interrupts the electric belt lock. When the belt buckle is actuated the seat belt is retracted in the usual manner and can be pulled out again.

H Valve block, roll-over bar (Y57) up to 12/93




The roll-over bar valve block is located in the rear at the right on the center pillar. The solenoid valves are actuated by the soft top control module when the switch for the soft top is pressed. Solenoid valve (Y11) puts up the roll-over bar, solenoid valve (Y10) retracts the roll-over bar. The locking pawl is put under pressure moving it away from the rack.

K Information from roll-over bar crash-actuated trigger module to soft top control module on version up to 05/95
The roll-over bar crash-actuated trigger module is responsible for the crash actuation, the soft top control module for the convenience feature. These modules are connected to one another by two wires.

The following information is transferred:
a) Roll-over bar okay
b) Roll-over bar defective
C) Vehicle acceleration/deceleration > 0.4 g
d) Crash actuation

Explanations to b, c and d:

b) When the roll-over bar crash-actuated trigger module recognizes a defect (lamp in instrument cluster comes on), the soft top control module checks whether the roll-over bar is down via the limit switch "Roll-over bar down". If the roll-over bar is retracted (limit switch switched) the LED's in the convenience switch are actuated intermittently by the soft top control module. This serves as request to put up the roll-over bar. When the roll-over bar is extended the LED's go out.
c) This signal serves as an additional check of the speed signals (electronic speedometer, ABS, ASR). Actuation of the top is overridden when the proper speed signals are not present.
d) When the soft top control module receives a crash signal from the roll-over bar crash-actuated trigger module, the pressure/electric power to the hydraulic system is switched on immediately if the soft top or roll-over bar is being moved at the moment.

Roll-over bar retracted or actuated (crash actuation)





Roll-over bar crash actuation and lowering following crash actuation





Table: Function, crash actuation and lowering following crash actuation