User Manual

ManualsBrandsBendix Commercial Vehicle Systems ManualsEquipmentR-7 MODULATING VALVE

Bendix

R-7

™

Modulating Valve

SD-03-4504

MOUNTING

SURFACE

DELIVERY

PORT (2)

SINGLE

CHECK

VALVE

INLET

EXHAUST

VALVE

CONTROL

PISTON

CONTROL

PORT

EXHAUST

INLET

VALVE

SPRING

OUTER SPRING

INNER SPRING

DOUBLE CHECK

VALVE

(SUPPLY PORT &

BALANCE PORT)

BALANCE

PISTON

INLET

VALVE

SEAT

DESCRIPTION

The Bendix

R‑7

™

modulating valve is used in conjunction

with a dual air brake system and spring brake actuators.

Typically the R‑7 modulating valve performs four functions:

1. Limits hold‑off pressure to the spring brake actuators.

2. Provides a quick release of air pressure from the spring

cavity of the spring brake actuator allowing a fast

application of the spring brake actuators. The valve

delivers air to the park brake quick release valve (or

relay) and also releases air in the control line to the

quick release valve (or relay).

3. Modulates spring brake actuator application should a

failure occur in the primary 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 2 for a picture of an inverted

R-7 valve.

MOUNTING

HOLE (2)

EXHAUST

CONTROL

PORT

DELIVERY (2)

SUPPLY PORT

BALANCE PORT

FIGURE 1 ‑ EXTERIOR & SECTIONAL VIEW. INSET FIGURE 2 - INVERTED VIEW

MOUNTING

HOLE (2)

BALANCE

EXHAUST

CONTROL

SUPPLY

INVERTED R-7

™

VALVE

Some early versions

featured an adjusting screw

Summary of content (6 pages)

PAGE 1
SD-03-4504 Bendix® R-7™ Modulating Valve EXHAUST EXHAUST CONTROL PORT MOUNTING HOLE (2) INLET VALVE SPRING BALANCE PORT INLET EXHAUST VALVE MOUNTING SURFACE INLET VALVE SEAT DELIVERY (2) SUPPLY PORT MOUNTING HOLE (2) BALANCE PISTON INNER SPRING SUPPLY CONTROL PORT CONTROL PISTON DOUBLE CHECK VALVE (SUPPLY PORT & BALANCE PORT) SINGLE CHECK VALVE DELIVERY PORT (2) OUTER SPRING BALANCE INVERTED R-7™ VALVE CONTROL Some early versions featured an adjusting screw EXHAUST FIGURE 1 - EXTERIOR & SEC
PAGE 2
GENERAL SAFETY GUIDELINES WARNING! PLEASE READ AND FOLLOW THESE INSTRUCTIONS TO AVOID PERSONAL INJURY OR DEATH: When working on or around a vehicle, the following guidelines should be observed AT ALL TIMES: ▲ Park the vehicle on a level surface, apply the parking brakes and always block the wheels. Always wear personal protection equipment. ▲ Stop the engine and remove the ignition key when working under or around the vehicle.
PAGE 3
BRAKE CHAMBER ANTILOCK MODULATOR - 4 PLACES PARK CONTROL VALVE R-7™ MODULATING VALVE BRAKE VALVE RELAY VALVE QUICK RELEASE VALVE RELAY VALVE AIR DRYER FRONT AXLE Bendix SUPPLY COMPRESSOR REAR AXLE SLACK ADJUSTER FIGURE 3 - TYPICAL SYSTEM SCHEMATIC OPERATION ‑ CHARGING SPRING BRAKE ACTUATORS (FIGURE 3) Air pressure used to control the spring brake actuators enters the Bendix® R-7™ modulating valve through the supply port, passing through one side of the double check valve, through the open inlet
PAGE 4
The pressure differential between the primary and secondary circuits regulates the amount of air pressure released from the spring cavity of the spring brake actuator. This results in a total brake application on the rear axle which is proportionate to the braking on the other axles.
PAGE 5
FIGURE 7 - PARKING FIGURE 8 - ANTI-COMPOUNDING WHILE PARKING OPERATION ‑ PARKING (FIGURE 7) OPERATING TEST When the handle of the parking control valve is placed in the “park” (exhaust) position, the modulating valve’s supply air pressure, along with the air pressure in the spring brake actuator cavities is exhausted.
PAGE 6
LEAKAGE TEST Place the park control valve in the “release” position; using a soap solution, coat the exhaust and vent hole (in the proximity of the adjusting screw). Slight bubble leakage is permitted. If the Bendix® R-7™ valve does not function as described, or if leakage is excessive, it is recommended that it be repaired or replaced with a genuine Bendix® service replacement valve. DISASSEMBLY 1. Remove the exhaust cover screw, exhaust cover and exhaust diaphragm. 2.