Description and operating principle of the anti-lock braking system (Focus 1)

Contents: Hydraulic Electronic Control Unit… ↳ Wheel speed sensors ↳ Electronic brake force distribution ↳

WARNING: Brake fluid contains polyglycerol esters and polyglycerol. Avoid contact with eyes. Wash hands thoroughly after handling brake fluid. If brake fluid gets into eyes, flush eyes with cold running water for 15 minutes. If irritation persists, seek medical attention. If brake fluid is swallowed, drink water and induce vomiting. Seek immediate medical attention. Failure to follow these instructions may result in injury.

The anti-lock braking system functions as follows:

Wheel locking during heavy braking is prevented by modulating (changing) the pressure in the brake system.
The system in most cases allows the driver to maintain control over the steering wheel and stop the car on the shortest possible distance.
When the anti-lock braking system is operating, the driver feels a pulsation in the brake pedal and hears a clicking sound.
The force applied to the brake pedal and the pedal feel during normal braking are similar to those experienced with a conventional vacuum brake booster system.

Hydraulic Electronic Control Unit (HECU)

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The hydraulic electronic control unit (HECU) is an integrated unit. The HECU consists of the following elements:

hydraulic Control Unit (HCU), which includes an aluminum block containing the solenoid valves and the pump motor
electronic Control Unit (ECU), which includes a printed circuit board with microprocessors, firmware, and solenoid coils to control the solenoid valves located in the HCU

The HCU and ECU are serviceable components, but neither unit can be repaired.

Wheel speed sensors

The active wheel sensor system includes:

four wheel speed sensors located on each wheel, with small processors to transmit a digital signal to the ECU
coding ring with magnetic profile

Electronic brake force distribution

Electronic Brake-force Distribution (EBD) is implemented in the pressure-sensitive control valves (PCRV) and load-sensitive distribution valves (LAV) used in conventional brake systems and included in the design of all ABS/TCS systems.

The EBD function is an additional program (software) that complements the ABS program, which allows the rear brakes to be used more effectively before the ABS system intervenes.

This function may be activated during normal braking, depending on the vehicle load and the road surface friction coefficient.

Unlike PCR and LAV, during EBD operation the braking force is determined not by the brake pressure or the vehicle speed, but by the wheel slip.