22
Antilock Brake Application
If a service brake application is made and the wheel speed sensors detect an impend-
ing wheel lockup, the EC-16 controller will immediately begin modification of the brake
application using the antilock modulator(s) at the affected wheel(s). Solenoid valves
contained in the modulator are energized and de-energized by the EC-16 controller, in
order to modify the brake application. When a solenoid coil is energized, its shuttle
moves. Depending upon the function of the specified solenoid, it either opens or clos-
es, thereby causing the exhaust or re-application of air pressure to the brake actuator.
The solenoids in each modulator are controlled independently by the EC-16. By open-
ing and closing the solenoid valves in the appropriate modulator, the EC-16 is actually
simulating what drivers do when they “pump the brakes.” It must be remembered,
however, that unlike the driver, the EC-16 controller is able to “pump” each brake
on the vehicle independently and with far greater speed and accuracy.
Antilock and Traction System Operation During Component Failure
The Bendix EC-16 handles equipment failure using a conservative fail-safe philosophy.
Any single electrical failure of a component devoted to antilock results in simultaneous
illumination of the appropriate condition lamp on the dash, a disabling of part or all of the
antilock, and reversion to standard braking on wheels no longer under EC-16 control.
Depending upon the type of failure and its position of occurrence, the EC-16 disable
all or only a portion of the antilock. A power or controller failure, however, will result
in complete disabling of system and reversion to standard braking of all wheels.
NOTE: A voltage problem and an intermittent ECM wiring problem can “correct”
themselves. For example, a power surge can take the system out of voltage
range for a moment, which will flash the voltage LED. During the time that the
problem is occurring, the dash lamp will also be on. When the problem corrects
itself, the system is restored. The dash lamp and appropriate LED go out.
For all other problems, the system will not be restored in the problem area until the
error is corrected and the EC-16 is cleared with the reset switch. It should be remem-
bered that the driver will be advised of the degraded operation via the dash lamps,
and that standard air braking will be available on those brakes where the EC-16 has
disabled the system.
Separate dash lamps, controlled by the EC-16, advise the driver of the condition of
the entire antilock/traction system. The condition of specific components is provided
by a series of labeled, light emitting diodes (LEDs) in the EC-16 housing. No special
tools or equipment are needed to read or interpret the EC-16 diagnostic display. It
should be noted that the EC-16 diagnostics display is separate from the antilock and
traction condition lamps on the dash. With this separation, the driver is aware of any
problems that occur, but is not confused by diagnostic information.
Air Brake System
Revised 11/15/99
(24 páginas)
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