Bendix Commercial Vehicle Systems ATR-1 ANTILOCK TRACTION RELAY 02/11 User Manual
Bendix® A TR-1™ AntiLock Traction Relay Valve
TRACTION
CONTROL
SOLENOID
MOUNTING
UNDRILLED
“CON” PORT
SUPPLY
PORT
DELIVERY
PORTS (4)
2 PIN SOLENOID
CONNECTOR
COVER PLATE FOR
REMOTE MOUNT
REMOTE MOUNT
ATR-1™ RELAY
VALVE
BRACKET
BODY
SUPPLY
SERVICE
PORT
PORT
SD-13-4811
CONTROLLER MOUNTING
HOLES (4)
SERVICE
PORT
UNTAPPED PORTS
ALTERNATE
CASTING ON
NEWER VALVES
(NOTE THAT THE
SERVICE PORT
LOCATION IS
CHANGED)
DESCRIPTION
The A TR-1™ antilock traction relay valve is a specialized air
brake valve developed for use on Bendix antilock/traction
equipped vehicles.
It is essentially three separate valves working in
combination in a single housing. An R-14
relay is the base valve and is fi tted with a modifi ed cover
containing a double check valve and a traction control
solenoid. The A TR-1
™
valve contains both air and electric
components to provide the service braking and traction
control (differential braking) functions. A Bendix antilock
traction controller can be mounted to the ATR-1
a cover plate can be installed and the antilock controller
mounted elsewhere on the vehicle. When an A TR-1™ valve
is combined with an antilock traction controller the resulting
assembly is referred to as an antilock traction assembly.
The A TR-1
™
valve replaces the standard relay valve used
to control the rear axle service brakes and performs the
standard relay function. Like the standard relay valve
it replaces, the ATR-1
™
valve (sometimes with attached
antilock controller) is normally mounted near the service
®
style service
™
valve or
FIGURE 1 - ATR-1™ ANTILOCK TRACTION RELAY VALVE
brakes it serves. A mounting bracket, furnished with the
valve, permits either frame or cross member mounting.
™
All air connections on the ATR-1
valve are identifi ed for
ease of installation. The letter identifi cation and air line
connections are shown below for reference.
ATR-1™ VALVE AIR CONNECTION
EMBOSSED
IDENT.
Supply (to reservoir) SUP
Delivery (to brake chamber) DEL
Service (to brake valve rear delivery) SER
Control (not drilled or threaded on
ATR-1™ valve)
CON
The A TR-1™ valve is part of the R-12® family of relay valves
which includes the R-12
®
, R-14®, BP-R1®, AR-1™.
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 ATR-1™ valve is available with various
crack pressures to accommodate specifi c applications,
however, the standard is 4 psi.
1
OPERATION
GENERAL
Because the A TR-1™ is essentially a relay valve, the following
description of operation refers to its function in the vehicles
air brake system and does not address all of 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
™
ATR-1
valve.
SERVICE BRAKES APPLYING (FIGURE 4)
Reservoir air pressure is present at the supply port and
fl ows through internal body and cover passages to the
supply of the normally closed (NC) traction control solenoid.
Brake application air enters the ATR-1
port and is conducted to the single check valve. The check
valve diaphragm fl exes in response to application pressure
and seals the passage to the open exhaust of the traction
solenoid. Air fl ows through the service piston then through
the center of the blend back and through a passage in the
cover to the top of the service relay piston. In response
to air pressure, the relay piston moves into contact with
™
valve’s service
CONTROLLER
ATR-1™ ANTILOCK
TRACTION RELAY
VALVE
FIGURE 2 - ANTILOCK TRACTION ASSEMBLY
the exhaust portion of its inlet and exhaust valve. With
the exhaust passage sealed, continued movement of the
piston unseats the inlet portion of the inlet and exhaust
valve, allowing supply air from the reservoir to fl ow out
the A TR-1
™
valve’s delivery ports to the brake chambers.
SOLENOID
CONNECTOR
BLEND BACK
PISTON
SUPPLY
TRACTION CONTROL
SOLENOID
SERVICE
DOUBLE
CHECK VALVE
RELAY PISTON
INLET-EXHAUST
VALVE
DELIVERY
FIGURE 3 - ATR-1™ ANTILOCK TRACTION ASSEMBLY
2
EXHAUST
CONTROLLER
TRACTION
SOLENOID
BRAKE
VALVE
CHECK VALVE
RELAY PISTON
REAR AXLE
RESERVOIR
FIGURE 4 - SERVICE BRAKE APPLICATION
SERVICE BRAKES HOLDING (FIGURE 5)
The air pressure being delivered to the brake chambers is
also present beneath the relay piston.
When the air pressure above and below the relay piston
is equal, the piston moves slightly allowing the inlet valve
CONTROLLER
INLET EXHAUST
MODULATOR
SPRING BRAKE
to return to its seat. The exhaust valve remains closed.
With both the inlet and exhaust valves closed, air pressure
in the brake chambers is held stable and neither increases
nor decreases.
TRACTION
SOLENOID
RELAY PISTON
REAR AXLE
RESERVOIR
FIGURE 5 - SERVICE BRAKES HOLDING
BRAKE
VALVE
CHECK VALVE
INLET EXHAUST
MODULATOR
SPRING BRAKE
3
CONTROLLER
TRACTION
SOLENOID
RELAY PISTON
REAR AXLE
RESERVOIR
FIGURE 6 - SERVICE BRAKES RELEASING
SERVICE BRAKES RELEASING (FIGURE 6)
When the brake application is released, air from above
the relay piston fl ows back through the blend back and
service pistons to the foot brake valve and is exhausted.
As air pressure is reduced above the relay piston, pressure
beneath it lifts the piston away from the exhaust valve and
opens the exhaust passage. Air from the service brake
chambers returns to the ATR-1
open exhaust.
™
valve and fl ows out the
BRAKE
VALVE
CHECK VALVE
INLET EXHAUST
MODULATOR
EXHAUST
SPRING BRAKE
TRACTION CONTROL SERVICE
BRAKE APPLICATION (FIGURE 7)
GENERAL
While under the control of an antilock traction controller,
the ATR-1™ valve’s solenoid is able to initiate a brake
application that allows the traction system to control wheel
spin upon acceleration under 25 mph. When wheel spin
is detected and the vehicle is stopped, or moving at any
CONTROLLER
TRACTION
SOLENOID
RELAY PISTON
REAR AXLE
RESERVOIR
FIGURE 7 - TRACTION CONTROL SERVICE BRAKE APPLICATION
4
BRAKE
VALVE
CHECK VALVE
INLET EXHAUST
MODULATOR
SPRING BRAKE
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