Bendix Commercial Vehicle Systems EC-13 TRAILER ANTILOCK CONTROL 8/07 - Manual (Page 3)

3
M-12 ™
Modulator
EC-13 ™
Controller
FIGURE 3 - TYPICAL MC-13 ™ MODULATOR CONTROLLER
(EC-13 ™ CONTROLLER & M-12 ™ MODULATOR)
WS-20 ™ Speed Sensor
90 Degree
Confi guration
FIGURE 4 - WS-20 ™ WHEEL SPEED SENSORS
Connected to the EC-13 ™ controller via a wire harness, the
modulator is essentially a high capacity, on/off air valve that
incorporates a pair of electrical solenoids for control. The
solenoids provide the electric-air link between the antilock
controller electronics and the air brake system.
An optional indicator light can be connected to, and
controlled by, the EC-13
™ controller and serves as a
means of advising the driver of the condition of the antilock
system.
The data link function enables the EC-13 ™ controller to
“report” its operating condition to a specialized, external
computer in response to certain commands it receives.
The EC-13
™ controller data link confi guration conforms to
S.A.E. standard J1708 and the protocol, or coded language
used, conforms to S.A.E. standard J1587. There are two
connections to the EC-13
™ controller devoted to the data
link. While the EC-13 ™ controller is capable of this function,
and connections are provided, it is not always used. Use
of the data link is not essential for the EC-13
™ controller
to be functional.
OPERATION
OPERATIONAL PHILOSOPHY
The Bendix ® EC-13 ™ controller provides axle braking
control by using four speed sensors and two modulators.
By monitoring the rate of deceleration during braking, and
subsequently adjusting the brake application pressure to
each axle, the EC-13
™ controller is able to provide improved
braking while maintaining trailer stability.
The trailer’s rear axle brakes are controlled by the EC-13 ™
controller and two modulators (M-12 ™ or M-12R ™ ). Like
the standard service relay valve it replaces, the modulator
delivers brake application pressure to the service chambers
on each axle. Two speed sensors on each axle “report”
changes in acceleration and deceleration to the EC-13
™
controller. If required, the EC-13 ™ controller adjusts the
application pressure to either axle’s service brakes, via the
modulators, based on the wheel behavior “reported” to it
by the speed sensors on each axle.
The EC-13 ™ controller utilizes a “SELECT SMART” brake
control philosophy for the trailer brakes. This means
that the EC-13
™ controller will initially adjust application
pressure to the service chambers on either an axle based
on the speed information from the fi rst wheel to approach
a locked condition. The initial pressure adjustment will
attempt to prevent either wheel on an axle from locking.
If a substantial braking difference is detected between two
wheels on an axle, the EC-13
™ controller will override the
fi rst air pressure adjustment and allow one wheel to lock.
Both wheels including the locked wheel will continue to be
monitored for speed and braking difference changes that
would require pressure adjustments. Each of the two axles
is treated independent of the other.
NON-ANTILOCK BRAKE APPLICATION
During normal braking, the tractor brake valve simultaneously
delivers air to the control port of the two trailer modulators.
The modulators function the same as standard service relay
valves and apply air to the service brakes. The service
brakes are thus applied.
If the speed sensors do not detect an impending wheel
lock up, the EC-13
™ controller does not initiate any
corrective action and the trailer comes to a stop in a normal
fashion.
ANTILOCK CONTROLLED BRAKE
APPLICATION - SYSTEM FULLY OPERATIONAL
If a service brake application is made and the speed
sensors detect an impending wheel lockup on an axle,
the EC-13
™ controller will immediately begin modifi cation
of the brake application using the antilock modulators at
the affected axle(s).
WS-20 ™ Speed Sensor
Straight Confi guration