GF42.46-P-0001T Sensor Brake Control (SBC), Function
GF42.46-P-0001T Sensor Brake Control (SBC), function
Component Identification:
Function
The Sensor Brake Control (SBC) is an electro hydraulic brake system.
In normal operation the hydraulic link between brake pedal and wheel brakes is interrupted by separation valves.
In contrast with the conventional braking system, an electro hydraulic control ensues with every type of intervention by the braking system.
^ The SBC provides the following advantages:
^ Improvement in the metering of the required brake pressure, more exact and quicker.
^ Reduction in stopping distance in particular during an emergency stop (improved BAS function).
^ Increase in active vehicle dynamics safety as the vehicle dynamics control systems ABS and BAS as well as ASR and ESP can be used in an optimized manner.
^ Leads to more timely and more comfortable stabilization of the vehicle during ASR or ESP control.
^ Takes care of even wear on the brake linings and better response characteristics of the brake due to optimum brake force distribution between the front and rear axle.
^ Use of the brake force reserve at the rear axle due to increasing the brake force share in the partial braking range and when braking from a low speed.
^ Results in more stable braking performance with optimal deceleration values when cornering as a result of the braking forces being shifted to the outer wheels.
^ No reaction (vibration) on the brake pedal during ABS control intervention functions
^ Additional functions relevant to comfort and safety:
^ SBC-Hold (SBC hold).
^ Softstop (SBC gentle braking to a stop).
^ SBC Stop (SBC hold-on).
^ Dry braking of brake disks under wet conditions and recharging (overcoming the play).
The system is activated via various waking events:
^ Circuit 15R ON
^ Stop light switch (S9/1)
^ Operate parking brake release handle
^ Parking brake indicator switch (S12)
^ Left front door contact switch (S17/3)
^ Right front door contact switch (S17/4)
^ Vehicle unlocking via remote control
After "Waking" the SBC control unit (A7/3n1) carries out a self-test (Pre-Drive Check). The storage pressure is checked and corrected if necessary. In addition, the pressure sensors and the control valves are checked and various leak and operational checks performed. Self-tests are also carried out constantly while driving.
In order to prevent the system being switched off when the vehicle is rolling (e.g. rolling downhill or traffic jam situation) when the ignition is switched off, a signal is transmitted which displays the vehicle standstill.
During the "Pre-Drive Check" pressure is built up in the braking system. In order to prevent the pistons moving out of the brake calipers unintentionally (e.g. when changing the brake pads), the system must be deactivated using the diagnosis tool during work on the brake system.
A7/3n1 The driver's brake actuation is transmitted electronically to the SBC control unit via the SBC pedal travel sensor.B37/1 The brake pressures calculated by the ESP, SPS [PML] and BAS control unit (N47-5) are allocated individually to the individual wheel brakes via the SBC hydraulic unit (A7/3).
The hydraulic energy required for this is provided by a high pressure reservoir which is supplied with pressure from a high-pressure charging pump (A7/3m1).
If faults exist in the electro hydraulic system, the hydraulic link between brake pedal and wheel is automatically restored.
System relationships, Sensor Brake Control (SBC)
The ESP, SPS [PML] and BAS control unit (N47-5) has a higher priority than the SBC control unit (A7/3n1). Both control units are interlinked by their own CAN data bus. The SBC control unit (A7/3n1) conveys data on the driver's braking wish and on the pressures in the system to the ESP, SPS [PML] and BAS control unit (N47-5).
The ESP, SPS [PML] and BAS control unit (N47-5) calculates the specified pressures required and transmits them to the SBC control unit (A7/3n1). A7/3n1 In the SBC control unit the pressures for braking control are then set and the actual pressures signaled back.
