URAL Motorcycles 4320M, Operation Manual, Page: 135 / 321

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a-handle; b,c-valves; d-discharge hole; e-piston; f-spring; A,B,C-chambers; I-driving; II-parking
Figure 113 - Brake Valve with Manual Control for Trucks Having No Trailer Equipment
4.5.5 Truck Brake System with the Antilock Brake System (ABS)
Antilock Brake System (ABS) is designed to maintain high-efficiency truck stability
when braking at various tire-to-surface friction coefficients. Thanks to ABS the truck ac-
quires a number of advantages:
- active truck safety, stability and steerability improvement especially at wet and slip-
pery roads;
- possibility to improve average safe speed;
- tire life improvement.
ABS consists of angular velocity sensors, brake pressure modulators, electronic control
unit, block of fuses; connection cables, warning lamp; test button and off-road mode switch.
4.5.5.1 Magnetic valve (ABS modulator)
is shown in Figure 108.
4.5.5.2 Electronic control unit (ECU) is the main part of ABS. The control unit is lo-
cated in the driver’s cab on the control panel spacer. The unit serves to treat signals coming from
the angular velocity sensors, deliver control signals to the modulators, trip relay of secondary
brake solenoid valve and warning lamp, as well as to check system components.
Control units are protected from leakage and short circuit, electrostatic discharge, voltage
drop, voltage rise at start-up and other electric transient phenomena.
A control unit has control mode that gives advantage of reducing braking path and keep-
ing steerability and stability on soft road pavements. A driver can switch on “off-road” function
on the control panel. Warning lamp flashing will show to the driver that ABS “off-road” function
is actuated.