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ABS
22
ANTI-LOCK BRAKES
been eliminated from the rear brake circuit.
EBD results in ideal pressure distribution for
the rear axle wheels. With EBD, the rear axle
wheels either lock along with front axle wheels
during partial braking
OR
the rear axle wheels
may lock after the front axle wheels. EBD never
allows the rear axle wheels to lock before the
front axle wheels.
Principle
1.
The principle is precise control of the rear axle
brake pressure such that it follows the ideal
brake pressure distribution curve closely. This
is achieved by the inclusion of a special control
logic to the ABS ECU (instead of LCRV).
2.
Rear brake pressure is controlled so that rear
slip ratio will always be less than or same as
that of front.The brake slip of each wheel during
braking is calculated by means of the wheel
speed signal of the respective wheel.
3.
Therefore rear wheel locking does not
precede that of front wheel.
4.
Consequently brake force at the rear axle can
be made to follow the ideal pressure distribution
curve more closely (Figure 14). This enhances
the contribution of the rear axle wheels for
braking & thereby improves braking efficiency.
5.
With this precise brake force control of each
rear wheel as per its individual requirement, at
the particular point of time, can be achieved.
EBD Working
1.
Just before rear wheel tends to lock preceding
to front wheel, the EBD function of ABS ECU
actuates the inlet solenoid valve & closes it,
so that the brake oil pressure from TMC is
blocked at HU only instead of reaching that
particular wheel cylinder & hence the locking
is prevented. Some times, EBD also actuates
outlet solenoid valve & opens it for very short
intervals of time, so that locking of the rear
wheels is avoided.
2.
Soon after the rear wheels recover from locking
phase, the inlet & outlet solenoid valves are
switched OFF, so that the brake pressure
applied at MC be transmitted to the rear wheel
cylinder/ caliper.
3.
Motor pump does not act at this time.