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Mercedes-Benz Actros Introduction
The demands made on braking systems are increasing steadily. Therefore, the development and introduction of an electronic braking system (EBS) is a logical step. EBS increases traffic safety through reduced stopping distance and improved brake stability. The full diagnosis and surveillance functions as well as the display of brake lining wear offer an effective fleet logistics.
Mercedes-Benz Actros Increased brake safety
WABCO did not only take existing regulations into consideration while developing EBS. Top priority was given to safety and user advantages. This is why a vehicle with EBS can clearly do more than is required by law.
EBS reduces service costs considerably.
- The electronic braking system has a lot of functions. The aim is to maximise braking safety at reduced costs, for instance by optimising wheel brake lining wear.
- Setting pressure, according to wear criteria, to the front and rear axle results in uniform lining wear. Overall wear is minimised by making the load on all wheel brakes uniform. Moreover, servicing and lining replacement are done at the same time. This reduces down-time costs.
- Depending on the vehicle utilisation profile and other factors, this also means considerable savings for the vehicle user. In terms of wheel brake service costs alone, a firsthand owner will save more money with an electronically braked bus than with a vehicle with a conventional braking system.
Mercedes-Benz Actros WABCO EBS construction kit
The EBS described here consists of a dual-circuit, purely pneumatic unit and a superimposed single-circuit, electro-pneumatic unit. This configuration is described as 2P/1E system. The single-circuit, electro-pneumatic unit comprises a central electronic control device (central module), the axle modulator with integrated electronic unit for the rear axle, and, if necessary, the axle modulator for the third axle, a brake signal transmitter with two integrated desired value sensors and brake switches, as well as a proportional relay valve and two ABS valves for the front axle.
In terms of structure, the dual-circuit pneumatic unit basically corresponds to that of a conventional braking system. This unit serves as redundancy and only becomes active in case of electro-pneumatic circuit failure.
Mercedes-Benz Actros Brake signal transmitter 480 001/002
The brake signal transmitter is used to produce electrical and pneumatic signals, and to increase and decrease the air pressure of the electronically controlled braking system. The device has a dual-circuit pneumatic and a dual-circuit electrical structure. Actuation start is recorded electronically by a double switch. The operating tappet’s route is controlled and transmitted as pulse-width modulated electrical signal. Further pneumatic redundancy pressure is delivered in circuits 1 and 2. The pressure in the second circuit is retained slightly in the process. In case of (electrical or pneumatic) failure of a circuit, the other circuits remain functional.
Mercedes-Benz Actros EBS central module 446 135
The central module is used to control and monitor the electronically controlled braking system. It determines the vehicle’s nominal delay from the signals received by the brake signal transmitter. The nominal delay and the wheel velocity measured by the speed sensors are input signal for the electro-pneumatic control unit, which uses it to calculate nominal pressure values for the front axle and rear axle(s). The front axle’s nominal pressure value is then compared with the measured actual value, and any existing deviations corrected with the help of the proportional relay valve. Moreover, the wheel velocity is evaluated so that in case of locking, an ABS control can be carried out by modulating the braking pressure in the brake cylinders. The central module exchanges EBS system bus related data with the axle modulators.