Operation - BENDIX M-40QR Service Data

If equipped with a Bendix
controller, following the completion of the second round
of PMV & TCV Chuff Tests, the controller (if configured to
do so) will perform a test to cross-check the trailer PMV
operation with the vehicle stop lamps. If the trailer
PMV circuit is mis-wired (including the steer axle TCV),
the PMV will exhaust a large amount of air, or none at all.

OPERATION

Mode
Normal,
Non-Antilock,
Brake Application
Non-Antilock
Hold
Normal,
Non-Antilock,
Relatively "slow"
Brake Release
Rapid,
Non-Antilock,
Exhaust
(e.g., the driver
releases the
brakes after a
severe brake
application)
Antilock Apply
Antilock Exhaust
Antilock Hold
Antilock
"Reapply"
Figure 6 - Bendix M-40QR
®
4
EC-60 (or later) advanced
® ™
Hold
Modulator
Solenoid
Type
State
HF and QR De-energized De-energized
HF and QR De-energized De-energized
HF and QR De-energized De-energized
QR De-energized De-energized
HF De-energized De-energized
HF and QR De-energized De-energized
HF and QR Energized
HF and QR Energized
HF and QR De-energized De-energized
& M-40HF Modulators: Operational Modes
™ ™
ANTILOCK OPERATION
GENERAL
See Figure 6.
The first four rows of this table show normal vehicle braking
where the PMV does not intervene. In the case of a
rapid, non-antilock release of the brakes (e.g. if the driver
releases the brakes after a severe brake application), the
Bendix M-40QR
® ™
brakes by being the point at which the air is exhausted.
The final four rows of the table show the actions taken
during an antilock braking event.
Exhaust
Solenoid
State
Air pressure supplied to the modulator exits
the modulator delivery port and flows to the
service brake chambers.
When the desired air pressure is attained in
the service brake chambers, the air pressure
in the system levels off.
Air from the brake chambers moves back
through the modulator in the reverse
direction as it flowed during application.
Simultaneously, a small amount of air will
generally be expelled from the modulator
exhaust port.
The internal bias piston blocks air from the
brake chamber from moving back through the
modulator. Instead, all the air is exhausted
out the modulator exhaust port.
Air from the brake chambers moves back
through the modulator in the reverse
direction as it flowed during application.
Simultaneously, air will be expelled from the
modulator exhaust port.
Air pressure supplied to the modulator exits
the modulator delivery port and flows to the
service brake chambers.
Air from the brake chambers exhausts
Energized
through the modulator exhaust port.
The modulator prevents supply air from
passing through the modulator and, at the
De-energized
same time, prevents air from the brake
chambers from exhausting.
The modulator re-applies air to the brakes in
the same manner it did during a non-antilock
event.
PMV assists the quick release of the
Description