Note. The emergency braking system complements the ABS.
Description
Two types of technologies allow for increased 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, triggered by pressing the brake pedal;
- brake pedal travel sensor;
- master brake cylinder.
The gain is controlled by the ABS computer.
The mechanical emergency braking system works when the vacuum booster with valve responds to the speed of the brake pedal.
In both cases, the speed of pressing the pedal is determined. This allows using 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 braking assistance allows the system to recognize the situation and act immediately to ensure the shortest possible stopping distance.
Emergency braking is determined by the speed of the brake pedal; at the same time, the braking force immediately becomes maximum. which allows you to use the ABS as quickly as possible.
ABS controlled braking continues until the driver releases the brake pedal.
During normal braking, the system operates normally.
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 movement of the pedals and corrects it using two coefficients:
- pedal position correction;
- vehicle speed correction.
If the result obtained exceeds the set threshold, and if the switch is turned on as quickly as possible, the control unit activates the brake force boost electrovalve of the vacuum booster, which moves the piston of the brake master 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 vacuum booster mechanical inertia valve (spring l ball to maintain gain) allows, depending on the speed of pressing the pedal, to use the brake force booster in the vacuum booster; thereby increasing the pressure in the hydraulic brakes.
Note. The way to remove the vacuum booster is the same for both electronic and mechanical emergency braking systems.
The only difference is the disconnection of the wire blocks, see removing the brake booster.