Rear axle redundancy Connection between the central module and the axle modulator(s) is established via an individual CAN system bus (brake bus). The pneumatic redundancy of the rear axle works via Brake signal transmitter with 2 pneumatic circuits (front and rear axle) The brake signal transmitter is separated electrically and has a dual circuit. The actuation process is recognised via two switches. The switches have the following functions:
3/2 relay valve with a 3/2 solenoid valve and a relay valve Relay Valve for the additional axle sensing the beginning of the braking process activating the EBS (if the driving switch is in the ”off” position) Shuttle valves integrated in the rear axle modulator on the brake cylinder of the rear axle(s). the offset values of the nominal value sensors are calibrated and monitored without being activated The inactivated distance sensors transmit the electrical brake nominal value as pulse-width modulated signals to the central module. Both signals of the redundant electrical transmitter are evaluated equally. During hitch-free EBS operation, i.e.
an electronic pressure control is possible on the rear axle, the 3/2 solenoid valve in the 3/2 relay valve is set to ”switch off redundancy”, due to the electronically controlled pressure. The braking pressure on the front axle is regulated with an electrically controlled proportional valve. The actual- pressure sensors are integrated into the valve subassemblies. The actual values are transmitted as analogue signals. Electrical / electronic structure Power is supplied to the electronic braking system via two separate feed lines. Axle load sensing is not required. The braking pressure on each axle is determined by a special braking force distribution function.
The valves are actuated by the central module. Clip 30a: Power supply for the proportional relay valve and the ABS solenoid valve of the front axle and a brake signal transmitter circuit. The EBS system status, for instance available errors, is transmitted by the EBS to a display unit via the vehicle bus (data line). Alternatively, the display can also take place via a red and a yellow warning light, as well as via an TCS light. Clip 30b: Power supply for the axle modulator(s), 3/2 relay valve, and the second circuit of the brake signal transmitter. The central module has a data bus interface for communication with other vehicle systems (engine, gear system, retarder).
Potentiometers must be provided (or possibly alternative limit switches for drum brakes) for sensing brake lining wear, and which are read in for the front axle by the central module. The axle modulator(s), ABS solenoid valve, and proportional relay valve of the front axle can be switched off individually via the short circuit-proof electronic switch in the central module. The grounds for the external pressure and wear sensors are returned to the central module or axle modulator. Direct connection to the vehicle ground is not allowed. The activities of each rear axle wear sensor is recorded by the axle modulator; the results are transmitted via the system bus brake to the central module.
The sensors are supplied individually and per axle with short circuit-proof 5V. Description of the EBS function EBS 4. 15