Bendix Commercial Vehicle Systems ATR-3 ANTILOCK TRAC RELAY VLV User Manual

Bendix® A TR-6™ and ATR-3™ Antilock Traction Relay Valves

SD-13-4861

2 PIN

SOLENOID

CONNECTOR

CONTROL

SOLENOID

CONTROL

PORT

COVER

Bendix® ATR-6™ Antilock

Traction Relay Valves

SUPPLY

PORT

DELIVERY PORTS (6)

FIGURE 1 - BENDIX® A TR-6™ (AND ATR-3™) ANTILOCK TRACTION RELAY VALVES

DESCRIPTION

This Service Data sheet covers the operation, and replacement procedures, for both the Bendix® ATR-6™ and the previous ATR-3™ Antilock Traction R elay valves. These valves are specialized air brake valves developed for use on Bendix antilock/traction-equipped vehicles.

This document will refer to the ATR-6™ Antilock Traction Relay valve throughout since the A TR-3™ version operates in an almost identical way. See Figure 1 for external differences.

™

The ATR-6 relay valve ﬁ tted with a modiﬁ ed cover containing a Control Solenoid. It contains both air and electric components to provide the service braking and traction control (differential braking) as well as ESP functions.

Typically the A TR-6™ valve replaces a standard relay valve used to control the rear axle service brakes, though it may be used for both front and rear axles on some advanced ABS vehicle applications. In normal operation, it performs the standard relay function and like the standard relay valve it replaces, the A TR-6 service brakes it serves.

When the ABS Controller operates the ATR-6 example during an antilock traction event, the Control

ESP® is a registered trademark of Daimler and is used by BCVS under license.

Antilock Traction Relay valve is a service

advanced stability system ABS

™

valve is normally mounted near the

™

valve, for

Bendix® ATR-3™ Antilock

Traction Relay Valves

Solenoid is energized and permits delivery air to be supplied to the Antilock Modulator Valves and used as required by the Controller - see Operation below for a full explanation.

For ease of servicing, the inlet/exhaust valve can be replaced without the need to remove the entire valve.

All air connections on the ATR-6™ valve are identiﬁ ed as shown below.

Bendix® A TR-6™ Antilock Traction Relay Valve AIR CONNECTION EMBOSSED IDENT.

Supply (to reservoir). . . . . . . . . . . . . . . . .SUP (1)

Delivery (to brake chamber) . . . . . . . . . . DEL (2)

Control (to brake valve rear delivery) . .CON (4)

The A TR-6™ valve is part of the R-12™ family of relay valves. The internal components of the relay portion of all of these valves are interchangeable with the R-12™ valve and the same basic components are used to service all of them.

The A TR-6™ valve is available with various crack pressures (the control pressure required to initiate air delivery to the brakes) to accommodate speciﬁ c vehicle applications; however the standard is 4 psi (see Figure 7 on Page 5).

Control Shuttle. The small

piston (shown in its normal

rest position). The arrow

indicates spring force

holding it in position.

SUPPLY PORT

INLET /

EXHAUST

VALVE

RESERVOIR

VALVE EXHAUST

WHEEL SPEED

SENSOR

CONTROL

SOLENOID

BRAKE PEDAL

CONTROL PORT

RELAY VALVE

PISTON

DELIVERY PORT

TONE RING

ANTILOCK

MODULATOR

VALVE

BRAKE

CHAMBER

Diagram shows a rear brake application, but this valve may also be used for front brakes

FIGURE 2 - SECTIONAL ATR-6

™

ANTILOCK TRACTION ASSEMBLY

OPERATION GENERAL

See Figure 2. The A TR-6™ Antilock T raction Relay valve is a service relay valve ﬁ tted with a modiﬁ ed cover containing a Control Solenoid. Under normal operating conditions the Control Shuttle, a small piston within the traction solenoid, remains in its rest position, held by spring pressure.

ANTILOCK EVENTS

This document will describe the use of the ATR-6™ valve when used during a traction c ontrol event, although this is only one role for which this valve is used. Advanced Bendix ABS systems also use this valve to help supply speciﬁ c braking delivery for ABS events at a wider range of speeds than typical traction control events occur, however the process of energizing the solenoid and delivery of air is the same.

BRAKE APPLICA TION

See Figure 3. During normal braking, as the driver applies force to the brake pedal, air pressure is delivered from the brake pedal to the relay valve control port. The air pressure passes into the valve, past the Control Shuttle, and moves the relay valve piston down. The piston pushes down and contacts the exhaust seat of the inner (or ‘exhaust’) portion of the inlet/exhaust valve, sealing off the exhaust passage. As the piston moves further down, the outer (or ‘inlet’) portion of the inlet/exhaust valve moves off its seat, permitting supply air from the reservoir to ﬂ ow past the open inlet valve, and into the service brake chambers.

The driver applies

the brakes. The

piston in the relay

valve moves down allowing the waiting air

pressure to pass

to the brake

chambers

RESERVOIR

BRAKE

CHAMBER

FIGURE 3 - SERVICE BRAKE APPLICATION

BALANCE

See Figure 4. The air pressure being delivered by the open inlet valve also is effective on the bottom area of the relay piston. When air pressure beneath the piston equals the service air pressure above, the piston lifts slightly and the inlet spring returns the inlet valve to its seat. The exhaust remains closed as the service line pressure balances the delivery pressure. As delivered air pressure is changed, the valve reacts instantly to the change, holding the brake application at that level.

The pressure

under the piston

equals the

pressure above.

The piston lifts

slightly - the

exhaust remains

closed.

The driver

releases the

brakes. The

piston in the relay

valve moves

up, closing the

delivery, and

opening the

exhaust.

FIGURE 4 - BRAKE APPLICATION HOLDING

EXHAUST (OR RELEASE)

See Figure 5. When the driver releases the brake pedal, air pressure above the relay piston is exhausted at the brake valve exhaust. At the same time, air pressure beneath the piston lifts the relay piston and the exhaust seat moves away from the exhaust valve, opening the exhaust passage at the base of the relay valve. With the exhaust passage open, the air pressure from the brake chambers passes to the Antilock Modulator V alve exhaust port, releasing the brakes, and air pressure between the relay valve and the modulator is released at the relay valve exhaust port.

TRACTION CONTROL

The ABS Controller monitors the driver’s accelerator application, as well as the vehicle’s motion using wheel speed sensors. When the vehicle is stopped, or moving at any speed up to 25 mph and the Controller detects wheel spin, for example where one wheel is slipping on an icy patch, the ABS Controller will intervene to assist the vehicle’s traction.

The ABS Controller obtains braking power for the traction intervention by energizing the Control Solenoid in the ATR-6™ valve. This causes the traction piston to move to its secondary position, allowing the supply air to operate the relay piston and supply air pressure to each of its Antilock Modulator Valves as shown in Figure 6.

The Controller then operates (opens and closes) the solenoid valves in the individual Antilock Modulator Valve for each spinning (slipping ) wheel to slow that wheel. As the

FIGURE 5 - BRAKE RELEASE

The small piston moves to its energized

position. The arrow indicates the direction

it moves. The antilock traction Controller

energizes the solenoid, applying full reservoir

pressure to the antilock modulators.

The Controller

selects the

antilock

modulator to

deliver air to the

brake chamber

FIGURE 6 - TRACTION APPLICATION

spinning wheel slows down, it forces the vehicle differential to drive the other stationary, or slowly-turning wheel on that axle, aiding the vehicle in gaining traction. Note: in some vehicle arrangements a single modulator valve may control air delivery to more than one brake chamber.

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