Current Positions and Development Trends in Air Brake Systems for Mercedes-Benz Commercial Vehicles 952303
With the increasing demands on commercial vehicles in the last few decades the air-brake system too has been continuously improved. As a supplement to the reliable valve technology, electronic systems such as ABS (Anti-lock brake system) and ASR (Automatic traction control system) have ensured safer driving in recent years. Further progress in the brake system will be achieved by increasing the brake-air pressure level and using disk brakes on all vehicle axles.
In addition to this the performance, operating convenience and economic efficiency of the brake system can be increased by the use of an electro-pneumatic brake system in which compressed-air actuated wheel brakes are activated via electrical control signals and integrated pressure control circuits. Optimized ABS/ASR functions are integrated in the new system. Different types of electro-pneumatic brake systems which are ready for the market are currently in the final phase of development and extensive trials are being carried out.
The main emphasis in the development of the electro-pneumatic brake system is on the benefits the customer can see. The adjustment work required previously to adapt tractor and trailer braking systems are generally no longer necessary with an electro-pneumatic brake system. The tractor and trailer share in the braking work of the complete vehicle combination in accordance with their weight.
The load condition of the vehicle is continuously determined from the wheel speed signals, the optimum braking pressures are regulated via pressure control circuits on the front and rear axle. Despite large differences in load, a commercial vehicle with an electro-pneumatic brake system therefore always brakes like a passenger car in terms of adhesion and comfort.
The state of wear of all the tractor wheel brakes is processed by the electro-pneumatic brake system. During non-critical braking different wear on the brake lining is offset by the pin-pointed correction of the specified pressure values. Together with the extensive diagnosis functions of the electro-pneumatic brake system, this equalization of lining wear creates the conditions for efficient and cost effective vehicle pool logistics.
The brake response times are noticeably shorter particularly at the rear axle due to electrical signal transmission. A reduction in braking distance in the order of magnitude of the length of one passenger car with a fully laden combination represents a significant gain in safety.
The potential of an electro-pneumatic braking system is used to the full by interlinking it and exchanging data with other vehicle systems via a CAN bus system. That then provides all the prerequisites for optimizing the stability of semitrailer rigs and vehicles with trailers mainly in respect of lateral dynamics in ongoing developments. By making a suitable record of the driver's requirements and the actual handling characteristics, critical driving situations such as sudden swerving manoeuvres, skidding or jack-knifing on different road surface qualities can be mastered better with individual-wheel braking interventions by the electro-pneumatic brake system.
The paper discusses the various solutions presented, shows new concepts and promising future potentials of air brakes for commercial vehicles.
Citation: Marwitz, H., Junghans, H., and Fischer, J., "Current Positions and Development Trends in Air Brake Systems for Mercedes-Benz Commercial Vehicles," SAE Technical Paper 952303, 1995, https://doi.org/10.4271/952303. Download Citation