Contents: Description 🠛 Operating principle 🠛 Electronic emergency braking system 🠛 Mechanical emergency braking system 🠛
Note: The emergency braking system complements the ABS.
Description
Two types of technologies can increase braking force during emergency braking. One is based on the use of electronic components (electronic Emergency Braking System), the other - on the use of mechanical components (mechanical emergency braking system).
The electronic emergency braking system operates under the following conditions:
- vacuum booster with switch, activated when the brake pedal is pressed;
- brake pedal travel sensor;
- master brake cylinder.
The amplification control is performed by the ABS ECU.
The mechanical emergency braking system operates when the vacuum booster with a valve reacts to the speed of movement of the brake pedal.
In both cases, the speed at which the pedal is pressed is determined. This allows the brake booster to create additional pressure in the brake hydraulic drive, which is added to the pressure created when the driver presses the pedal.
The maximum pressure is limited by the vacuum level supplied to the booster.
Operating principle
Emergency Brake Assist enables the system to recognise the situation and act immediately to ensure the shortest possible stopping distance.
Emergency braking is determined by the speed of movement of the brake pedal; at the same time, the braking force immediately becomes maximum, which allows the ABS to be activated as quickly as possible.
ABS-controlled braking continues until the driver releases the brake pedal.
During normal braking, the system operates in normal mode.
Electronic emergency braking system
When braking, the driver presses the brake pedal, which acts on the travel sensor 1 and the deactivator switch 2.
The control unit determines the speed of the pedals and corrects it using two coefficients:
- correction by pedal position;
- correction based on vehicle speed.
If the obtained result exceeds the set threshold and if the switch is turned on as quickly as possible, the control unit activates the brake booster solenoid valve of the vacuum booster, which moves the piston of the main brake cylinder. Otherwise, the vacuum works as usual. The emergency braking system is deactivated as soon as the driver releases the brake pedal.
Mechanical emergency braking system
Built-in mechanical inertia valve in the vacuum booster (spring l ball for maintaining gain) allows you to activate the brake booster in the vacuum booster depending on the speed of pressing the pedal; thereby increasing the pressure in the brake hydraulic drive.
Note: The method for removing the vacuum booster is the same for both electronic and mechanical emergency braking systems.
The only difference is in disconnecting the wiring harness, see Removing the Brake Booster.