SAFARI STORME

ANTI LOCK BRAKING SYSTEM (ABS)

2. PRESSURE REDUCTION PHASE

If the ECU detects that the % Slip relative to the

other wheels and vehicle reference speed is still

increasing during the pressure hold phase and the

wheel is tending further towards lock, it will start the

pressure reduction phase, as the existing brake

pressure in the wheel brake is too high. It will

activate the relevant outlet valve within the hydraulic

modulator, switching it from its normally closed

position to open. This will allow fluid to pass from the

wheel brake into the accumulator chamber within the

modulator. At the same time the ECU will activate

the return pump integrated into the modulator to

draw fluid from the accumulator and wheel brake and

return it to the TMC. This fluid being returned to the

TMC is what is felt as the pulsations at the pedal,

and the amplitude of the pulsations is relative to the

amount of fluid that needs to be reduced. Pressure

reduction will continue until the controlled wheel

speed returns to the vehicle reference speed.

Solenoid

valve

Electricity

status

Valve

open-

close

Open-close

channel

INLET

CLOSE Master cylinder

-Wheel cylinder

OUTLET

OPEN

Wheel

cylinder -

reservoir

3. PRESSURE INCREASE PHASE

As the ECU detects that the speed of the controlled

wheel has increased to the vehicle reference speed

and hence the % slip reduced. It will sequentially

deactivate the outlet and inlet valves switching them

to their normal positions. With the outlet valve closed

further pressure reduction is prevented and the inlet

valve can be opened to allow brake fluid from the

TMC to enter the wheel brake increasing the brake

pressure once again. If the driver releases the brake

at any time during ABS control the inlet valves will be

deactivated and fluid can return to the TMC via the

inlet valve and the one way valve.