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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Brake Application At Rear Axle Function - Mercedes Benz Actros

Requirements

• Vehicle moves.
• System pressure (V1, V2) in circuit 1 and circuit 2. 
• The electric brake control is operational.
• No faults are indicated in the driver information system (FIS) display in the Instrument (INS).

V1 System pressure (circuit 1)

V2 System pressure (circuit 2)

a System pressure

b Brake pressure

c Redundant brake pressure

d Control pressure

12.08 Rpm sensor

13.07 Brake value sensor

22.01 Combination brake cylinder

31.08 Drive-axle axle modulator

33.08 Front axle redundancy valve

33.10 Rear axle redundancy valve

A11 Electronic brake system (EBS) control unit

FB Parking brake

Function sequence

1. The brake pedal is depressed.
2. The sensors in the brake value sensor (13.07) register the pedal travel electrically for the brake system (BS) control unit (A11).
3. The brake system (BS) control unit (A11) uses the pedal travel to compute the specified deceleration of the vehicle.
4. Vehicles without code (ZX2) EPB II Via connection 21 the pneumatic component of the brake value sensor (13.07) directs a redundant brake pressure (c) corresponding to the pedal travel to the closed rear axle redundancy valve (33.10).
5. The brake control (BS) control unit (A11) uses the calculated specified deceleration to actuate the electronics of the drive axle-axle modulator (31.08 or 31.13).
6. The electronics of the drive-axle axle modulator (31.08 or 31.13) convert the control command from the brake control (BS) control unit (A11) into electrical control signals for the internal valves and causes them to apply the brake pressure (b).
7. Supply pressure (a) is directed from connections 11 and 12 as brake pressure (b) though connections 21 and 22 of the drive-axle axle modulator (31.08 or 31.13) into the combination brake cylinders (22.01) of the rear wheel brakes; the wheels are braked.
8. During the entire brake application, the electronics of the drive-axle axle modulator (31.08 or 31.13) record the values from the internal pressure sensors and the signals from the rpm sensors (12.08) on the rear wheels and transmits these to the brake control (BS) control unit (A11).
9. To calculate the actual deceleration and the wheel slip, the brake control (BS) control unit (A11) evaluates the signals and values of the drive-axle axle modulator (31.08 and 31.13). If the actual deceleration deviates from the specified deceleration, the brake control (BS) control unit (A11) causes the drive-axle axle modulator (31.08 or 31.13) to reduce or increase the brake pressure (b).
10. The driver releases the brake pedal and the brake application is complete. The applied brake pressure (b) and the applied redundant brake pressure (c) are released again through ventilation connection 3.

In the case of ABS control, the internal valves of the drive-axle axle modulator (31.08 or 31.13) perform the "pressure buildup", "pressure hold" and "pressure release" functions in the same way as the ABS solenoid valves on the front axle.

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Telligent Brake System Function - Mercedes Benz Actros

General - Vehicles without code (ZX2) EPB II

Model 930-934

1 - Trailer/semitrailer data interface

2 - ASIC data bus

E - Electrical component

P - Pneumatic component

a - System pressure 

b - Brake pressure

c - Redundant brake pressure

V1 - System pressure (circuit 1)

V2 - System pressure (circuit 2)

V3 - System pressure (circuit 3)

13.07 - Brake value sensor

16.07 - Proportioning relay valve 

18.07 - Trailer control valve

20.02 - Single-circuit diaphragm brake cylinder

22.01 - Combination brake cylinder 

31.08 - Drive axle axle modulator

33.08 - Front axle redundancy valve

33.10 - Rear axle redundancy valve

35.02 - Coupling head for supply

35.03 - Coupling head for brake 

45.01 - ABS solenoid valve

The Telligent brake system is an electronically monitored and electrically controlled pneumatic brake system. The Telligent brake system consists of a purely pneumatic dual- circuit brake system, which is actuated by the electric brake control. The electric brake control overlays the conventional, purely pneumatically operating control of the service brake and adds to it the following functions:

• Antilock brake system (ABS)
• Acceleration Slip Regulation (ASR)
• Automatic load-dependent brake pressure control (ALB)
• Hill holder
• Brake Assist System

The stability control (SR) function can be integrated in the Telligent brake system as an option. When a trailer or semitrailer is attached, the Telligent brake system is also responsible for controlling the trailer brake system. The pneumatic and electrical control capabilities of the trailer brake mean that trailers or semitrailers with purely pneumatic or electropneumatic brake system can be connected without problem.

The individual regulation of brake pressure for the wheel brakes on the front and rear axles forms the basis for all the functions of the Telligent brake system. The brake circuits of the front axle, the rear axle and the trailer or semitrailer are each safeguarded by a pneumatic safety circuit referred to as the redundancy circuit.

In the event of partial or total failure of the electric brake control, the wheel brakes are actuated with the relevant redundant brake pressure (c) by purely pneumatic means.

Electrically regulated brake application 

The travel of the brake pedal is registered by two sensors in the brake value sensor (13.07) and is converted into electrical values for the brake system (BS) control unit (A11). The brake control (BS) control unit (A11) uses the values to compute the specified deceleration and the brake pressure (b) required for this. The brake pressure (b) necessary for producing the specified deceleration is transmitted over the brakes CAN (CAN 6) by control commands from the brake control (BS) control unit (A11) to the drive axle axle modulator (31.08 or 31.13). The electronics in the brake control (BS) control unit (A11) regulate the brake pressure (b) at the front axle and the electronics in the drive axle axle modulator (31.08 or 31.13) regulate the brake pressure (b) at the rear axle.

The calculated brake pressure (b) is applied at the front axle via the proportioning relay valve (16.07) and at the rear axle direct by the drive axle axle modulator (31.08 or 31.13). The pressure sensors in the proportioning relay valve (16.07) and in the drive axle axle modulator (31.08 or 31.13) monitor the applied brake pressure (b).

At the same time, the brake control (BS) control unit (A11) uses the signals from the rpm sensors (B30, B31, B32, B33) on the axles to calculate the rate of rpm change at the wheels. The brake control (BS) control unit (A11) uses the rpm change to detect the actuati deceleration of the vehicle and the wheel slip.

If there is a difference between the actual deceleration and the specified deceleration, braking is adjusted by an appropriate control command.

• Differential slip control

Differential slip control replaces the conventional ALB function. Differential slip control starts at moderate wheel speed differences.

• ABS control

If one or more wheels shows a tendency to lock up when high rpm differences occur, the brake system (BS) control unit (A11) triggers the familiar ABS control.

• ASR control

If one or more of the drive wheels shows a tendency to spin when high rpm differences occur, the brake system (BS) control unit (A11) triggers the familiar ASR control.

A3 - Drive control (FR) control unit 
A6 - Engine control (MR) control unit 
A7 - Base module (GM)
A11 - Telligent brake system (BS) control unit
A28 - Drive axle axle modulator
A64 - Front module (FM)
A65 - Rear module (HM) 
A68 - Master switch module 4
A77 - Dash support switch module 1
B30 - Left front axle rpm sensor
B31 - Right front axle rpm sensor
B32 - Left 1 st rear axle rpm sensor
B33 - Right 1st rear axle rpm sensor
B36 - Left 1 st front axle brake wear sensor 
B37 - Right 1st front axle brake wear sensor
B40 - Left 1 st rear axle brake wear sensor
B41 - Right 1st rear axle brake wear sensor

P2 - Instrument (INS)
S40 - ASR shutoff switch
S41 - Hill holder switch

CAN 1 - Vehicle CAN
CAN 2 - Interior CAN
CAN 3 - Frame CAN
CAN 6 - Brakes CAN

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