BENDIX R-7 MODULATING VALVE Manual
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®
®
™
Bendix
R-7
Modulating Valve
MOUNTING
HOLE (2)
DELIVERY (2)
BALANCE
PORT
MOUNTING
HOLE (2)
BALANCE
FIGURE 1 - EXTERIOR & INVERTED VIEW
DESCRIPTION
The R-7
™
modulating valve is used in conjunction with a
dual air brake system and spring brake actuators, and
performs four functions:
1. Limits hold-off pressure to the spring brake actuators
(adjustable).
2. Provides for quick release of air pressure from the spring
cavity of the spring brake actuator allowing a fast
application of the spring brake actuators.
3. Modulates spring brake actuator application should a
failure occur in the service brake system.
4. Prevents compounding of service and spring forces.
The valve has one 1/4" control, one 3/8" supply, one 1/4"
balance, two 3/8" delivery NPTF ports, and an exhaust port
protected by an exhaust diaphragm. The valve incorporates
two 13/32" holes for mounting.
EXHAUST
CONTROL
PORT
SUPPLY
PORT
MOUNTING
SURFACE
SUPPLY
CONTROL
EXHAUST
INLET
VALVE
SPRING
INLET
EXHAUST
VALVE
INLET
VALVE
SEAT
BALANCE
PISTON
INNER SPRING
OUTER SPRING
FIGURE 2 - SECTIONAL VIEW
Note for model year 2001 and later International Trucks only:
There is an inverted R-7
the other pictures in this document. A standard R-7
™
and an inverted R-7
Figure 1 for a picture of an inverted R-7
OPERATION - CHARGING SPRING BRAKE
ACTUATORS (FIGURE 3)
Air pressure used to control the spring brake actuators enters
the valve through the supply port, passing through one side
of the double check valve, through the open inlet valve, over
the balance piston, and out the delivery ports to the spring
brake actuators. When air pressure in the spring brake
actuator cavity has released the spring brake actuators and
when air pressure on top of the balance piston is sufficient
to overcome the force of the balance piston spring, the
balance piston moves allowing the inlet valve spring to close
the inlet valve, shutting off further air pressure from the
reservoir supplying the modulating valve.
EXHAUST
CONTROL
PORT
CONTROL
PISTON
DOUBLE CHECK
VALVE (SUPPLY
PORT & BALANCE
SINGLE
CHECK
DELIVERY
PORT (2)
ADJUSTING SCREW
™
valve, which appears inverted from
valve are not interchangeable. See
™
valve.
PORT)
VALVE
™
valve
1