BENDIX EC-14 ANTILOCK CONTROLLER Manual page 6

Rear Axle Brakes - The vehicle's rear axle brakes are
controlled by the MC-14
™
controller and M-12 modulator). Like the standard service
relay valve it replaces, the M-12
application pressure to the service chambers on the rear
axle equally. Two speed sensors on the rear axle "report"
changes in acceleration and deceleration to the EC-14
controller. If required, the EC-14
application pressure to the rear axle service brakes, via the
M-12 ™ modulator, based on the wheel behavior "reported"
to it by the speed sensors. In the case of vehicles equipped
with tandem rear axles (6x2, 6x4), the speed sensors are
installed on the axle that is most likely to lose traction first.
™
The MC-14 modulator controller controls all service brakes
on the tandem equally.
™
The EC-14 controller utilizes a "Select Smart" brake control
philosophy for the rear axle brakes. This means that the
™
EC-14 controller will initially adjust application pressure to
all rear axle service chambers based on the speed information
from the first wheel to approach a locked condition. The
initial pressure adjustment will attempt to prevent all wheels
on the axle(s) from locking. If a substantial braking difference
is detected between the two wheels on the axle equipped
with the speed sensors, the EC-14
the first 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.
Steering Axle Brakes - The steering axle brakes are
controlled by the EC-14 ™
modulator. Although connected to the EC-14
a wire harness, the M-21
integral part of the MC-14
Brake application air passes through the M-21
modulator on its way to the front axle service chambers
from the foot valve.
Two speed sensors on the front axle "report" changes in
acceleration and deceleration to the EC-14
™
The EC-14 controller uses a "Select Low" brake control
philosophy for the front axle brakes. It will attempt to prevent
wheel lock by adjusting application pressure to both front
axle service chambers based on the speed information from
the first wheel to approach a locked condition. The M-21
M-22 ™ modulator provides the EC-14
means of adjusting front axle service application pressure
when required.
NON-ANTILOCK BRAKE APPLICATION
During normal braking, the brake valve simultaneously
delivers air to the control port of the M-12
rear axle(s) as well as to and through the M-21
modulator on the front axle. The M-12
6
™
modulator controller (EC-14
™
modulator delivers brake
™ controller adjusts the
™ controller will override
controller and the M-21 ™ or M-22
™
controller via
™ ™
or M-22 modulator is not an
™
modulator controller assembly.
™
or M-22
™
controller.
™ controller with the
™
modulator on the
™
or M-22
™
modulator functions
the same as standard service relay valve and applies air to
™
the rear axle service brakes. Because the M-21
modulator does not have a relay valve function, service air
passes through it to a quick release valve and from there to
the front axle service chambers. The service brakes are thus
applied.
™
If the speed sensors do not detect an impending wheel lock
up, the EC-14 ™ controller does not initiate any corrective
action and the vehicle 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-14
controller will immediately begin modification of the brake
application using the antilock modulator(s) at the affected
axle(s).
Solenoid valves contained in the modulator are energized
and de energized by the EC-14
the brake application. When a solenoid coil is energized its
shuttle moves, and depending upon the function of the specific
solenoid, it either opens or closes, thereby causing the
exhaust or re-application of air pressure to the brake chamber.
The solenoids in either the M-12
controlled independently by the EC-14
opening and closing the solenoid valves in the appropriate
modulator, the EC-14
the driver does when he "pumps the brakes".
It must be remembered however that unlike the driver, the
™
™
EC-14 controller is able to "pump" brakes on either the
front or rear axle(s), or both, independently and with far greater
speed and accuracy.
™
ANTILOCK SYSTEM OPERATION -
COMPONENT FAULT STRATEGY
The Bendix ® EC-14
using a conservative fail-safe philosophy. Any single electrical
problem with a component devoted to antilock braking,
results in simultaneous illumination of the antilock condition
lamp on the dash and a troubleshooting LED on the EC-14
controller. Depending upon the type of problem and its
position of occurrence the EC-14
™
or
antilock function at a lower performance level, disable all of
the antilock on the vehicle or only a portion. When antilock
is disabled, the brakes on the affected axle(s) revert to
standard air braking.
Complete antilock system shut down will occur if:
•
Electrical power is below or above the 10 to 17 volt
operating range.
•
A controller fault is detected.
™
•
Two or more faults, regardless of where, are detected.
™
controller in order to modify
™ or M-21 ™ modulator are
™ controller. By
™
controller is actually simulating what
™ controller handles equipment faults
™
controller can continue
™ ™
or M-22
™
™