GF42.46-P-0001TA Sensor Brake Control (SBC), Function
GF42.46-P-0001TA 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 a more timely and comfortable stabilization of the vehicle during an ASR or ESP control.
^ Takes care of more uniform wear on the brake pads and improves response characteristics of the brakes as a result of optimal braking force distribution between the front and rear wheels.
^ 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).
^ 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 switch (S12)
^ Left front door contact switch (S17/3)
^ Right front door contact switch (S17/4)
^ Vehicle unlocking via remote control
After "waking up", 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.
The driver's brake actuation is conveyed electronically to the SBC control unit (A7/3n1) via the SBC pedal value sensor (B37/1). The brake pressures computed by the ESP control unit (N47-5) are allocated individually to the individual wheel brakes via the traction system hydraulic unit (A7/3).
The hydraulic energy required for this is provided by a high pressure reservoir which is supplied with pressure by 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 control unit (N47-5) takes priority over the SBC control unit (A7/3n1).Both control units are interlinked by their own CAN data bus. The SBC control unit (A7/3n1) conveys to the ESP control unit (N47-5) data about the driver's braking requirement and pressures in the system.
The ESP control unit (N47-5) computes the specified pressures required and transmits these to the SBC control unit (A7/3n1). The pressures for the control are then adjusted in the SBC control unit (A7/3n1) and the actual pressures reported back.
