SAFARI

ANTI-LOCK BRAKES

ABS

BRAKINGWITH ABS INTOOPERATION

DESCRIPTION OF OPERATION OF THE

ANTI-LOCK BRAKING SYSTEM

On the basis of the signals received from the rpm

sensors located on the front and rear wheels, the

electronic control unit instructs the hydraulic unit,

so as to vary the pressure of the brake fluid

delivered to the brake calipers & wheel cylinders

passing through the three stages described below:

A. Pressure Maintaining (Hold) Phase

During any panic braking situation, whenever the

wheel tends to lock (because of the higher brake

pressure than optimum). ECU instructs Hydraulic

Unit to block the brake pressure coming from Master

cylinder, so that no further pressure gets into wheel

cylinder. (Refer Fig.6)

By default, the inlet solenoid valve remains open &

the out let solenoid valve remains closed. These

are the positions of the valves under unexcited

condition.

During the pressure maintaining phase, ABS ECU

actuates only the inlet solenoid valve (EV) & there

by closes it. The outlet solenoid valve remains

closed in its default position. Since both the solenoid

valves are shut the liquid channel is interrupted.

The pressure channel is closed, so that further

increase of pressure in the brake circuit is

obstructed. Non return valve mounted in parallel to

the inlet valve helps in speedy reduction of pressure

when brake pedal is released.

Solenoid valve

Electricity status

Valve open-close

Open-close channel

INLET

Master cylinder-Wheel cylinder

OUTLET

OFF

Wheel cylinder-reservoir

Fig. 6