BENDIX SD-13-4793 Manuel D’Utilisation
4
NON-ANTILOCK EXHAUST
The manner in which air exhausts through the modulator
differs, depending upon how rapidly the brake application
is released by the driver.
differs, depending upon how rapidly the brake application
is released by the driver.
Normal Exhaust (Figure 5) - During a normal, relatively
"slow", brake release, air moves back through the
modulator in the reverse direction as it fl owed during
application. The internal components of the modulator
will remain in the same position as they assumed during
application until air pressure decreases to approximately
one half psi, at which time the supply diaphragm will seat on
the supply passage. Air will generally not be expelled from
the modulator exhaust port during normal brake release.
"slow", brake release, air moves back through the
modulator in the reverse direction as it fl owed during
application. The internal components of the modulator
will remain in the same position as they assumed during
application until air pressure decreases to approximately
one half psi, at which time the supply diaphragm will seat on
the supply passage. Air will generally not be expelled from
the modulator exhaust port during normal brake release.
Rapid Exhaust (Figure 6) - The rapid exhaust operation
described in the following text only occurs when the
modulator is controlling two type 30 (or larger) service
chambers. During a very rapid brake release the modulator
will exhaust air in a different manner. An example of this
would be the case if the driver made a severe brake
application then lifted his foot from the foot valve. During
a rapid brake release, air from the exhaust diaphragm
fl ows back through the open exhaust solenoid and to the
application device's exhaust. With pressure removed from
the control side of the exhaust diaphragm, air, returning to
the modulator from the service chambers, lifts the exhaust
diaphragm from its seat. Returning air fl ows past the open
exhaust and out the modulator exhaust port. Air will also
described in the following text only occurs when the
modulator is controlling two type 30 (or larger) service
chambers. During a very rapid brake release the modulator
will exhaust air in a different manner. An example of this
would be the case if the driver made a severe brake
application then lifted his foot from the foot valve. During
a rapid brake release, air from the exhaust diaphragm
fl ows back through the open exhaust solenoid and to the
application device's exhaust. With pressure removed from
the control side of the exhaust diaphragm, air, returning to
the modulator from the service chambers, lifts the exhaust
diaphragm from its seat. Returning air fl ows past the open
exhaust and out the modulator exhaust port. Air will also
fl ow past the open supply diaphragm and back to the
application device's exhaust.
application device's exhaust.
ANTILOCK OPERATION
GENERAL
If a service brake application is made and the antilock
system detects an impending wheel lockup, the antilock
controller will immediately begin modifi cation of the brake
application using the modulator.
system detects an impending wheel lockup, the antilock
controller will immediately begin modifi cation of the brake
application using the modulator.
In order to modify the brake application, the coils of the two
solenoid valves contained in the modulator are energized
or de-energized in a pre programmed sequence by the
antilock controller. When a solenoid coil is energized, a
shuttle within the solenoid moves, and depending upon
the function of the specifi c solenoid, it either opens or
closes thereby causing the exhaust or re-application of
air pressure to the brake actuator. The solenoids in the
modulator are controlled independently by the antilock
controller. By opening and closing the solenoid valves in
the modulator, the antilock controller is able to simulate
what the driver does when he "pumps the brakes". It must
be remembered, however, that unlike the driver the antilock
controller is able to "pump" each modulator, along with the
brakes connected to it, independently and with far greater
speed and accuracy.
solenoid valves contained in the modulator are energized
or de-energized in a pre programmed sequence by the
antilock controller. When a solenoid coil is energized, a
shuttle within the solenoid moves, and depending upon
the function of the specifi c solenoid, it either opens or
closes thereby causing the exhaust or re-application of
air pressure to the brake actuator. The solenoids in the
modulator are controlled independently by the antilock
controller. By opening and closing the solenoid valves in
the modulator, the antilock controller is able to simulate
what the driver does when he "pumps the brakes". It must
be remembered, however, that unlike the driver the antilock
controller is able to "pump" each modulator, along with the
brakes connected to it, independently and with far greater
speed and accuracy.
FIGURE 5 - M-21
™
, M-22
™
MODULATOR NON-ANTILOCK EXHAUST OF SERVICE BRAKES (NORMAL)
BRAKE VALVE
SPRING
SUPPLY
DIAPHRAGM
SUPPLY
SOLENOID
SPRING
EXHAUST
DIAPHRAGM
EXHAUST
SOLENOID
BRAKE
CHAMBER
EXHAUST PORT