Brake Application At Front Axle Function - Mercedes Benz Actros

Requirements

• Vehicle moving.
• Max. supply pressure in circuit 1 and 2 (V1, V2).
• No faults indicated in driver information system (FIS) display in instrument (INS). 
• Electronics of brake system (BS) operational.

V1 System pressure (circuit 1)
V2 System pressure (circuit 2)
NV Accessory supply pressure

a System pressure

b Brake pressure

c Redundant brake pressure

12.08 Rpm sensor
13.07 Brake value sensor
16.07 Proportioning relay valve
20.02 Single-circuit diaphragm brake cylinder
22.01 Combination brake cylinder
30.03 Pressure limiting valve with vent
31.08 Drive-axle axle modulator
33.07 3/2-way valve for auxiliary braking effect
33.08 Front axle redundancy valve
33.10 Rear axle redundancy valve
45.01 ABS solenoid valve

A11 Electronic brake system (EBS) control unit
FB Parking brake

Function sequence

1. The brake pedal is depressed :
• The sensors in the brake value sensor (13.07) register the driver's braking requirements electrically for the brake control (BS) control unit (A11).
• Via connection 22, the pneumatic component of the brake value sensor (13.07) actuates the closed front axle redundancy valve (33.08) with a redundant control pressure corresponding to the pedal travel.
2. The electronics of the brake control (BS) control unit (A11) uses the electric signals from the brake value sensor to calculate the specified deceleration for the front and rear axle.
3. The brake control (BS) control unit (A11) uses the specified deceleration signal to actuate the proportioning relay valve (16.07) at the front axle and causes it to apply the brake pressure.
4. Front axle 
• Right : The brake pressure is fed into the right-hand single- circuit diaphragm brake cylinder (20.02) on the front axle via the opened ABS solenoid valve (45.01); the wheel is braked.
• Left : The brake pressure is fed into the left-hand single- circuit diaphragm brake cylinder (20.02) on the front axle via the 3/2-way auxiliary brake valve (33.07) and the opened ABS solenoid valve (45.01); the wheel is braked.
• If the front axle brake circuit fails, the 3/2-way auxiliary brake valve (33.07) boosts the braking effect at the rear axle. As long as brake pressure from the proportioning relay valve (16.07) is available at connection 12 of the 3/2- way auxiliary brake valve (33.07) during the braking operation, the valve will remain inoperative and the brake pressure can flow through freely.
5. To calculate the actual deceleration and the wheel slip, the brake control (BS) control unit (A11) evaluates the signals from the rpm sensors (12.08) at the wheels and from the pressure sensors in the proportioning relay valve (16.07) throughout the entire braking operation.
• If the actual deceleration deviates from the specified deceleration, the brake control (BS) control unit (A11) causes the proportioning relay valve (16.07) to reduce or increase the brake pressure.

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