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Anti-lock Braking System(ABS)
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ii. HYDRAULIC CONTROL UNIT (HCU) / HYDRAULIC MODULATOR :
MC1 -
Primary brake circuit
MC2 -
Secondary Brake circuit
RP1 -
Recirculating Pump of circuit MC1
RP2 -
Recirculating Pump of circuit MC2
M -
Motor For driving recirculating pumps
X1EV -
Inlet solenoid valve of Rear Left wheel
X2EV - ???
X3EV - ???
X4EV - ???
A1 -
Accumulator of Circuit MC1
A2 -
Accumulator of circuit MC2
X1AV -
Outlet solenoid valve of Rear Left wheel
X2AV - ???
X3AV - ???
X4AV - ???
X1 -
Rear Left
X2 -
Front Right
X3 -
Front Left
X4 -
Rear Right
It consists of a Return Pumps, Solenoid Valves,
Damping Chamber, Accumulator, Non-Return
Valve and Motor. It forms the link between the
TMC and the foundation brakes. It implements the
commands issued by the ECU by using solenoid
valves to control the pressure at the foundation
brakes.
There are four pairs (4-channel system) of Inlet
and Outlet valves located in the modulator.
Solenoid valves are responsible for modulating
the pressure in the wheel brake during active ABS
control.
The Return Pump element is installed in the
center of the modulator and is driven by an
electric Motor. The pump transfers the brake fluid
emerging from the wheel brakes through the
accumulator on its way back to the TMC. The
pump and valve actuation can be felt on the foot
pedal as pulsations. In order to prevent damage to
the TMC primary seals from the compensating
port, the design of TMC is changed to central
valve type (CV/CV).
The accumulator absorbs the surge in brake fluid
that accompanies the pressure reduction phase.
The Damping Chamber suppresses pressure
oscillations within the hydraulic system,
preventing them from being propagated back to
the brake pedal and reduces noise levels in the
system.