Bendix Commercial Vehicle Systems R-7 MODULATING VALVE - Manual

1
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Bendix ® R-7 ™ Modulating Valve
SD-03-4504
MOUNTING
SURFACE
DELIVERY
PORT (2)
SINGLE
CHECK
VALVE
INLET
EXHAUST
VALVE
CONTROL
PISTON
CONTROL
PORT
EXHAUST
ADJUSTING SCREW
FIGURE 2 - SECTIONAL VIEW
INLET
VALVE
SPRING
OUTER SPRING
INNER SPRING
DOUBLE CHECK
VALVE (SUPPLY
PORT & BALANCE
PORT)
BALANCE
PISTON
INLET
VALVE
SEAT
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.
Note for model year 2001 and later International Trucks only:
There is an inverted R-7
™ valve, which appears inverted from
the other pictures in this document. A standard R-7 ™ valve
and an inverted R-7 ™ valve are not interchangeable. See
Figure 1 for a picture of an inverted R-7 ™ valve.
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.
MOUNTING
HOLE (2)
EXHAUST CONTROL
PORT
DELIVERY (2)
SUPPLY
PORT
BALANCE
PORT
FIGURE 1 - EXTERIOR & INVERTED VIEW
MOUNTING
HOLE (2)
BALANCE
EXHAUST
CONTROL
SUPPLY