Brake Force Boosting, Basic Function - GF42.47-P-1005A
Model All (4xWD, CAR)
Overview
This document contains information on:
- General
- Function requirements
- Function
- Brake force boosting (vacuum brake booster)
- Brake force boosting (electromechanical brake booster)
- Brake Assist System (BAS)
- Fail boost
General
Brake force boosting comprises the following tasks:
- Brake force boosting reduces the control force that the driver must apply in order to reach the desired vehicle braking effect.
- The Brake Assist System (BAS) assists the driver in emergency braking situations in order to reduce the stopping distance. In order to achieve the maximum possible deceleration, the function detects emergency braking situations and increases the brake pressure up to the ABS controlled range.
Function requirements
- Drive train operational
- Drive system started
- Brake and traction system functional
- Vehicle deceleration > 3 m/s2
Function
Brake force boosting (vacuum brake booster)
The driver is supported during braking so that they do not have to use so much pedal force. Brake force boosting occurs pneumatically using vacuum. The vacuum acts in the brake booster.
Brake force boosting (electromechanical brake booster)
The driver is supported during braking so that they do not have to use so much pedal force. Brake force boosting occurs electrically with the aid of an electric motor. Electric brake force boosting acts in the tandem master cylinder.
Brake Assist System (BAS)
The ESP® control unit evaluates the increase in pressure in the brake system and initiates an emergency stop if a certain activation threshold is exceeded. To do so, the system monitors the driver's response. The driver's response is defined by the actuation speed and actuation strength with which the brake pedal is pressed.
Amplification of the brake force is also possible from an unbraked state and during partial braking. The function also triggers even during brake interventions by other systems, e.g. by the ESP®.
If the driver clearly releases the brake pedal during the function intervention, brake force boosting is ended.
Vehicles with driving environment sensor system:
Sensors calculate the deceleration required to prevent a collision. The following information is used for this:
- Distance to vehicle immediately ahead
- Vehicle's own speed and acceleration
- Vehicle speed and acceleration of the vehicle driving in front
Fail boost
The "fail boost" function ensures brake force boosting in the event of a system error. It is activated if the brake booster can no longer adequately support driver braking because of a system error.
The system error is displayed in the instrument cluster. The failure of the brake booster is read out directly by the ESP® control unit.
The "fail boost" function implements hydraulic brake force boosting using a suitable boost factor. The function actuates the solenoid valves and the traction system hydraulic unit.
| Additional basic functions | |||
| Brake light switch, basic function | GF42.10-P-2001A | ||
| Electromechanical brake booster, basic function | Vehicles with automatic operation of service brake function | GF42.31-P-2003A | |
| Brake booster, basic function | GF42.31-P-2004A | ||
| Electronic Stability Program control unit, basic function | GF42.45-P-9890A | ||
| Traction system hydraulic unit, basic function | GF42.50-P-2000A |