Bendix Commercial Vehicle Systems EC-16 ANTILOCK CONTROLLER 4/08 - Manual (Page 7)

7
TRACTION CONTROL AT VEHICLE SPEEDS
ABOVE 25 MPH
If wheel spin occurs at any speed above 25 mph, the
EC-16
™ controller will instantly blink the traction dash lamp
to advise the driver that a wheel spin is occurring.
If the torque limiting feature is programmed in, the EC-16 ™
controller uses its link to the engine control module and
sends a signal to reduce engine torque to a level suitable for
the available traction.
THE EC-16 ™ CONTROLLER WILL NOT SIGNAL THE ATR
VALVE TO APPLY THE BRAKES, EVEN SLIGHTLY, AT
ANY SPEED ABOVE 25 MPH.
ANTILOCK AND TRACTION SYSTEM
OPERATION DURING COMPONENT FAILURE
The Bendix ® EC-16 ™ controller handles equipment failure
using a conservative fail safe philosophy. Any single electrical
failure of a component devoted to antilock or traction control
results in simultaneous illumination of the appropriate
condition lamp on the dash, a disabling of part or all of the
antilock or traction system, and reversion to standard braking
on wheels no longer under EC-16
™ controller control.
Depending upon the type of failure and its position of
occurrence, the EC-16
™ controller disables all or only a
portion of the antilock and traction system. A power or
controller failure, however, will result in complete disabling
of both systems and reversion to standard braking on all
wheels.
SINGLE FAILURE
The following list and chart describe how the antilock and
traction systems respond to a specific component failure.
(Note: right and left; front, mid and rear are determined from
the driver's seat. Left front is therefore the corner closest to
the driver.)
For example, if the right mid sensor ("RM Sensor" on the
chart) fails, front and rear antilock will still be operative.
Traction will be disabled, and, as always, the system has
standard air braking.
Front modulator - If a front modulator fails, antilock on that
wheel is disabled. Antilock and traction on all other wheels
remains active.
Rear modulator - A rear modulator failure disables the traction
system. Antilock on that wheel will also be disabled, but
antilock on all other wheels remains active.
Front sensor - The wheel is still modulated using input from
the opposite sensor. The traction system is disabled.
Torque Limiting - In order for the torque limiting control feature
to be used, the vehicle must be equipped with an
electronically controlled engine throttle. The torque limiting
feature allows the EC-16
™ controller to reduce engine torque
to a suitable level for the available traction. Torque limiting
helps to minimize the amount (or speed) of wheel spin. It is
especially useful in helping to minimizing a power jackknife
and when all drive wheels are on an equally slippery surface.
Differential Braking - In order for the differential braking control
feature to be used, the vehicle must be equipped with an
antilock traction relay valve such as the Bendix
® ATR-1 ™ or
ATR-2 ™ relay valve. The ATR-1 ™ and ATR-2 ™ relay valve
contain a solenoid assembly which provides this feature.
The differential braking feature allows the EC-16
™ controller
to gently pump the brake on the spinning wheel. Since the
vehicle's differential tends to drive the wheel that presents
the least resistance (the wheel on the slipperiest surface), a
slight brake application to this wheel only, forces the
differential to drive the stationary or slowly spinning wheel.
While a vehicle must be equipped with an electronic throttle
to utilize the torque limiting feature of traction control,
differential braking can be used on all vehicles. Differential
braking can be activated only when vehicle speed is under
25 MPH and one drive wheel is spinning faster than the
other(s).
TRACTION CONTROL AT VEHICLE SPEEDS
OF 0 TO 25 MPH
When wheel spin is detected and the vehicle is stopped, or
moving at any speed up to 25 mph, the EC-16
™ controller
simultaneously executes the following operations:
It instantly blinks the traction dash lamp to advise the driver
that a wheel spin is occurring.
If the torque limiting feature is active, the EC-16 ™ controller
uses its link to the engine control module and sends a signal
to reduce engine torque to a level suitable for the available
traction.
If the differential braking feature is configured into the system,
the EC-16
™ controller energizes the solenoid in the ATR
valve which then applies air to each of the rear axle
modulators. Because the modulators are controlled by the
EC-16
™ controller, the solenoid valves in the appropriate
modulator are opened and closed to gently pump the brake
on the spinning wheel only. This gentle brake application
forces the differential to drive the stationary or slowly spinning
wheel.
Once wheel spin is eliminated, the dash lamp goes out and
the traction system disengages control.