freightliner PX113064S T 2016, Руководство пользователя

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WARNING
Manually adjusting an automatic slack adjuster to
bring the pushrod stroke within legal limits is
likely masking a mechanical problem. Adjustment
is not repairing. Before adjusting an automatic
slack adjuster, troubleshoot the foundation brake
system and inspect it for worn or damaged
components. Improperly maintaining the vehicle
braking system may lead to brake failure,
resulting in property damage, personal injury, or
death.
ZF
™
Antilock Braking System
IMPORTANT: For proper ABS system operation,
do not change tire sizes. The sizes of the tires
installed during production are programmed into
the electronic control unit. Installing different-
sized tires could result in a reduced braking
force, leading to longer stopping distances.
The ZF Antilock Braking System (ABS) is an
electronic wheel speed monitoring and control
system that works with the standard air brake
system. ABS passively monitors vehicle wheel speed
at all times, and controls wheel speed during
emergency stops.
ABS includes signal-generating tone wheels and
sensors located in the wheel hubs of each sensed
wheel. The sensors transmit vehicle wheel speed
information to an electronic control unit, located in
the vehicle electronics bay. The control unit’s main
circuit interprets the speed sensor signals and
calculates wheel speed, wheel retardation, and a
vehicle reference speed. If the calculations indicate
wheel lockup, the main circuit signals the appropriate
modulator valve to reduce braking pressure. During
emergency braking, the modulator valve alternately
reduces, increases, or maintains air pressure supply
in the brake chamber to prevent front and rear wheel
lockup.
The electronic control unit (ECU) also has a safety
circuit that constantly monitors the wheel sensors,
traction control valve (if equipped), modulator valves,
and the electrical circuitry.
The ZF Antilock Braking System combines one front-
axle control channel with one rear-axle control
channel to form one control circuit. For example, the
sensor and modulator valve on the left-front axle
form a control circuit with the sensor and modulator
valve on the right-rear axle. If, during vehicle
operation, the safety circuit senses a failure in any
part of the ABS, a warning appears on the driver
display, the tractor ABS telltale, shown in
Fig. 11.13,
illuminates, and the control circuit where the failure
occurred is switched to normal braking action. The
remaining control circuit retains the ABS effect. Even
if the ABS is completely inoperative, normal braking
ability is maintained. An exception would be if a
modulator valve (or combination modulator valve) is
damaged and inoperative. As these components are
an integral part of the air brake system, normal
braking may be impaired or inoperative.
During emergency or reduced-traction stops, fully
depress the brake pedal until the vehicle comes to a
safe stop.
Do not pump the brake pedal . With the
brake pedal fully depressed, the ABS controls all
wheels to provide steering control and a reduced
braking distance. The tractor ABS telltale illuminates
when the ABS is engaged.
Although the ZF ABS improves vehicle control during
emergency braking situations, it is the driver’s
responsibility to change driving styles depending on
existing traffic and road conditions. For example, the
ABS cannot prevent an accident if the driver is
speeding or following too closely.
Trailer ABS Compatibility
The ZF ABS is designed to communicate with a
trailer ABS, if they are compatible. Compatibility
results in the brief illumination of the trailer ABS
telltale, shown in
Fig. 11.14, during vehicle start-up
and fault detection.
The telltale operates as follows when a compatible
trailer is properly connected to the tractor:
f611654a 05/11/2020
Fig. 11.13, Tractor ABS Telltale
f611655a 05/11/2022
Fig. 11.14, Trailer ABS Telltale
Brake Systems
11.7