Bendix Commercial Vehicle Systems AR-2 ANTILOCK RELAY VALVE 8/11 - Manual (Page 2)

2
FIGURE 2 - SECTIONAL VIEW BENDIX ® AR-2 ™ ANTILOCK RELAY VALVE
CONTROL PORT
PROPORTIONING
PISTON
INLET/EXHAUST VALVE
The letter identification and air hose connections are shown
below for reference.
Bendix
® AR-2 ™ VALVE
AIR CONNECTION EMBOSSED IDENT.
Supply (to reservoir) SUP
Delivery (to brake chamber) DEL
Service (to brake valve rear service delivery) SER
Control (to delivery of trailer supply valve) CON
The AR‑2 ™ valve is part of the R‑12 ® family of relay valves
which includes the R‑12 ® , R‑14 ® , BP‑R1 ® , and AR‑1 ™
valves. The internal components of the relay portion of all
of these valves are interchangeable with the R‑12 ® valve
and therefore the same basic components are used to
service all of them.
The AR‑2 ™ valve incorporates various crack pressures to
accommodate specific applications, the standard is 4 psi.
OPERATION
GENERAL
Because the AR‑2
™ valve is actually a relay valve, the
following description of operation refers to its function in
the vehicle’s air brake system and does not address the
separate antilock components and their operation. For a
description of antilock operation, refer to the appropriate
Service Data Sheet covering the electronic controller used
with the AR‑2 ™ valve (SD‑13‑4785 covering the EC‑15 ™
electronic controller). Other useful information regarding
antilock system components used in conjunction with the
AR‑2 ™ valve are contained in publications: SD‑13‑4793
(Bendix ® M‑21 ™ antilock modulator); SD‑13‑4870 (Bendix ®
M‑32 ™ and M‑32QR ™ antilock modulators); SD‑13‑4860
(Bendix ® WS‑24 ™ wheel speed sensors); and SD‑13‑4754
(Bendix ® WS‑20 ™ wheel speed sensors).
INITIAL CHARGING
During the initial build up of tractor system air pressure,
reservoir air flows into the supply port and through internal
body and cover passages to the blend back piston. When
sufficient air pressure is applied to the blend back piston,
it moves against the resistance of its spring until it comes
to rest against the service piston.
Activating the trailer supply valve (dash control with red
octagonal button), simultaneously charges the trailer
and the AR‑2 ™ valve control port. Air entering the AR‑2 ™
valve control causes the proportioning piston to move
toward its stop in the cover. The integral inlet and exhaust
valve is carried along with the piston until it seats and
seals the exhaust passage. Continued movement of the
proportioning piston opens the inlet seat. With the tractor
and trailer air system fully charged the vehicle may be
operated.
SPRING (NOT IN ALL
MODELS)
RELAY PISTON
SERVICE PISTON
SERVICE PORT
SPRING
BLEND BACK
PISTON
EXHAUST
INLET/EXHAUST VALVE
SUPPLY PORT
EXHAUST
DELIVERY PORT