Section 33 Chapter 4 - Login Required · 2010. 7. 1. · SECTION 33 - TRAILER BRAKE SYSTEMS - CHAPTER 4 33-9 PNEUMATIC BRAKE SYSTEMS Pneumatic Trailer Brakes The pneumatic trailer

Section 33

Chapter 4

6-14430NH

TRAILER BRAKE SYSTEMS

How It Works

SECTION 33 - TRAILER BRAKE SYSTEMS - CHAPTER 4

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TABLE OF CONTENTS

TRAILER BRAKE SYSTEMS ............................................................................................................................. 33-3

HYDRAULIC BRAKE SYSTEMS ....................................................................................................................... 33-4European / NAO Hydraulic Trailer Brakes ...................................................................................................... 33-4Italian Hydraulic Trailer Brakes ....................................................................................................................... 33-6

PNEUMATIC BRAKE SYSTEMS ....................................................................................................................... 33-9Pneumatic Trailer Brakes ................................................................................................................................ 33-9European Pneumatic Trailer Brakes ............................................................................................................... 33-9Italian Pneumatic Trailer Brakes ................................................................................................................... 33-12ROW (Rest of World) Pneumatic Trailer Brakes (NAR, ANZ, CIS, LAR, EEAA) .......................................... 33-15

European / NAO Hydraulic Trailer Brake Schematic ........................................................................................ 33-17

Italian Hydraulic Trailer Brake Schematic ......................................................................................................... 33-18

Italian Pneumatic Trailer Brake Schematic ....................................................................................................... 33-19


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TRAILER BRAKE SYSTEMS

There are two hydraulic trailer brake systems:

European / NAO hydraulic trailer brakes

Italian hydraulic trailer brakes

And there are three pneumatic trailer brake systems:

European pneumatic trailer brakes

Italian pneumatic trailer brakes

ROW (Rest of world.NAR, ANZ, CIS, LAR,EEAA) pneumatic trailer brakes


33-4

HYDRAULIC BRAKE SYSTEMS

European / NAO Hydraulic Trailer Brakes

The hydraulic trailer brake control system is a load sensing design and consists of a hydraulic trailer brake priorityvalve (7) and trailer brake control valve (5). Both valves are located on the top of the range transmission. Supplyflow for this system is provided from the priority port of the tractor steering priority valve. This provides priority flowto the steering and hydraulic trailer brake circuits over all other functions. The trailer brake priority valve thenensures that steering has priority over the trailer brakes. The PFC piston pump ultimately provides supply flow tothe entire system.

The trailer brake control valve provides supply to the trailer brake coupler only when both tractor service brakepedals are actuated. The trailer brake valve pilot circuit is supplied by teeing into the left hand and right handtractor service brake pressures. The tees supply a shuttle check valve located near the main brake control valve onthe fire wall. The outlet pressure from the shuttle check valve is routed to the pilot manifold of the trailer brakevalve. The shuttle valve will only supply the pilot manifold when both brake pedals are actuated. The pilot manifoldprovides the ratio of tractor brake pressure in comparison to trailer brake pressure, in this case 33:1.

When both brake pedals are actuated, the pilot pressure moves the main spool of the trailer brake valve, sending apressure signal back to the PFC piston pump which supplies the circuit. At the same time the main spool of thetrailer brake valve is controlled by the pilot pressure to provide pressure to the trailer brake coupler in proportion totractor brake pressure (33:1) to a maximum value of 150 bar (2175 PSI).

With no pressure applied to the trailer brake valve main spool, the trailer brake coupler pressure is relieved to zeropressure.


33-5

RI02M073, RI02M074, RH02G335

European / NAO Hydraulic Trailer Brake

2 1

2

3

1

45

6

7

8

1. TO TRAILER BRAKE COUPLER 5. TRAILER BRAKE CONTROL VALVE2. TUBE STEERING SENDER 6. TRAILER BRAKE PILOT TUBE3. STEERING SUPPLY TUBE TO TRAILER BRAKES 7. TRAILER BRAKE PRIORITY VALVE4. CHECK VALVE ASSEMBLY 8. BRAKE COUPLING


33-6

Italian Hydraulic Trailer Brakes

The Italian hydraulic trailer brake control system is a load sensing design and consists of a hydraulic trailer brakepriority valve (2) located on the top of the range transmission and a trailer brake control valve (1) located at the rearof the tractor. Supply flow for this system is provided from the priority port of the tractor steering priority valve. Thisprovides priority flow to the steering and hydraulic trailer brake circuits over all other functions. The trailer brakepriority valve then ensures that steering has priority over the trailer brakes. The PFC piston pump ultimatelyprovides supply flow to the entire system.

The trailer brake control valve provides supply to the trailer brake coupler only when both tractor service brakepedals are actuated. The trailer brake valve pilot circuit is supplied by teeing into the left hand and right handtractor service brake pressures. A shuttle check valve ensures that both left hand and right hand brake pressuresare required for the trailer brake valve to respond. If only one service brake is applied (right or left), the shuttlevalve prevents pilot pressure from reaching the trailer brake valve and the trailer brake valve is not actuated. Thisallows free movement of the trailer when pivoting the tractor using the right or left service brake. The pilot manifoldlocated on the trailer brake valve provides the necessary ratio of tractor brake pressure in comparison to trailerbrake pressure.

When the tractor is running with normal system pressures, no service brakes applied, emergency brake off and thetrailer coupled to the trailer brake coupler, the trailer brake provides a control pressure of 12.5 bar (+/- 2.5 bar) tothe trailer brakes through the coupler.

When the service brakes are applied (right and left together), the service brake pressure (pilot pressure) iscommunicated through the shuttle valve to port “Y” on the trailer brake valve. The trailer brake valve is thenactuated using oil from the piston pump entering port “P” suppling it to the coupler where it flows to the trailer brakecylinder, which causes the trailer brakes to respond. The pressure at port “B” and the coupler increases from thecontrol pressure of 12.5 bar proportionally to the service brake pressure and is limited to 130 bar (+/- 10 bar).

If the tractor emergency brake is engaged, or if the transmission is in park, a pressure switch senses the drop inpressure and closes, signaling the trailer brake to dump the 12.5 bar control pressure to zero. This in turn, engagesthe trailer spring brake and stops the trailer. This also turns on the indicator lamp on the right hand console. Ifhydraulic system pressure at the piston pump load sense port drops below a normal value the pressure switch atthis location closes and also signals the trailer brake valve to dump the 12.5 bar control pressure to zero. Thisengages the trailer spring brake and stops the trailer. This also turns on the indicator lamp on the right handconsole.


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RI02M085

RI02M082

TRAILER BRAKES ON

(SPRING APPLIED)

TRAILER BRAKES

RELEASED

TRAILER BRAKES ON (PRESSURE

APPLIED)

130 BAR

12.5 BAR

TRACTOR OFF

TRACTOR ON

NO TRACTOR BRAKING

PEDAL EFFORT TRACTOR BRAKING

TRAILER BRAKE PRESSURE

TRACTOR BRAKE PRESSURE

TRAILER BRAKE

PRESSURE BAR

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5 6

1. TRAILER BRAKE VALVE 4. SHUTTLE VALVE2. TRAILER BRAKE PRIORITY VALVE 5. EMERGENCY BRAKE PRESSURE SWITCH3. HYDRAULIC TRAILER COUPLER 6. LOW SYSTEM PRESSURE SWITCH


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RI02M087

Italian Hydraulic Trailer Brake

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1

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8

1. TRAILER BRAKE VALVE 5. EMERGENCY BRAKE PRESSURE SWITCH2. TRAILER BRAKE PRIORITY VALVE 6. LOW SYSTEM PRESSURE SWITCH3. HYDRAULIC TRAILER COUPLER 7. CHECK VALVE 4. SHUTTLE VALVE 8. TRACTOR SERVICE BRAKE VALVE


33-9

PNEUMATIC BRAKE SYSTEMS

Pneumatic Trailer Brakes

The pneumatic trailer brake control system is comprised of an engine driven compressor, air reservoirs (tanks),pressure unloading/regulator valve, trailer control valve, solenoid valves and air brake couplings. The compressoris located on the forward side of the engine. The air tanks are located on the left and right of the rear axle carriers.The control valves are located on top of the transmission/rear frame and the couplings are at the rear of the tractorabove the hydraulic couplers.

European Pneumatic Trailer Brakes

The pneumatic trailer brake control system for non-Italian European tractors is a combined single and dual linehigh pressure braking system. There are three couplers in this system. The black coupling (single line system) ison the right side, the red coupling (dual line system) is in the center and the yellow coupling (dual line system) is onthe left side.

Dual line braking system: With dual line systems, air pressure is increased to apply positive braking force. Whenthe brake system is not activated, the brake lines have no pressure.

From the compressor, compressed air is supplied to the air reservoirs, with the pressure limited to 8.1 to 8.5 bar(117 to123 PSI) by an unloading regulator valve. Compressed air is supplied from the reservoirs to the inlet port ofthe dual trailer control valve, to the inlet of the emergency brake solenoid valve and to the red coupling, providingfull operating pressure to that coupling at all times.

When the tractor brakes (either service or emergency) are not actuated and the tractor is out of park there shouldbe no pressure at the yellow coupling. When the tractor service brakes are actuated air pressure which isproportional to the service brake pressure is supplied from the trailer brake control valve to the yellow coupler. Themaximum pressure at the yellow coupler is 8.1 to 8.5 bar (117 to 123 PSI). This provides a braking force for thetrailer which is dependent on the tractor service brake force (tractor brake pressure). When the tractor emergencybrake is actuated, the same process applies, the pressure at the yellow coupler will rise continuously to themaximum system operating pressure of 8.1 to 8.5 bar (117 to 123 PSI). When either the service brakes arereleased, or the emergency brake is disengaged the pressure drops to zero.

Single line braking system: With single line systems, air pressure is decreased to apply positive braking force,typically through a spring loaded brake. When this brake system is not activated the brake lines are fullypressurized to maintain the trailer brakes in a released state.

From the compressor, compressed air is supplied to the air reservoirs and to the single line trailer brake controlvalve to the black hose coupling of the single line system. A pressure reducing valve built into the trailer brakecontrol valve limits the output pressure to the black coupler to 4.8 to 5.3 bar (70 to 77 PSI). When the tractorservice brakes are not applied and the tractor is not in park, the trailer control valve maintains 4.8 to 5.3 bar (70 to77 PSI) at the black coupler. When the tractor service brakes or emergency brake is actuated, the pressure at theblack coupler is reduced by the trailer control valve in proportion to the increasing tractor service brake pressure. Atfull tractor brake pressure, the pressure at the black coupling must be zero. When either the tractor service brakesare released, or the emergency brake is disengaged the pressure gradually increases to 4.8 to 5.3 bar (70 to 77PSI).


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RI02M064RI02M065RI02M066

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7

1. AIR BRAKE COUPLER- YELLOW 5. LEFT SIDE AIR RESERVOIR2. AIR BRAKE COUPLER- RED 6. RIGHT SIDE AIR RESERVOIR3. AIR BRAKE COUPLER- BLACK 7. DUAL LINE CONTROL VALVE4. TRAILER CONTROL VALVE


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RI02M067RI02M068 RI02M069

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8

10

8. DOUBLE CHECK VALVE 10. AIR BRAKE UNLOADING VALVE9. SOLENOID VALVE


33-12

Italian Pneumatic Trailer Brakes

The pneumatic trailer brake control system for Italian European tractors is a dual line high pressure brakingsystem. A combined dual coupler is used.


From the compressor, compressed air is supplied to the air reservoirs, with the pressure limited to 7.0 to 7.5 bar(102 to109 PSI) by an unloading regulator valve. Compressed air is supplied from the reservoirs to the inlet port ofthe dual trailer control valve, to the inlet of the emergency brake solenoid valve and to one of the couplings,providing full operating pressure to that coupling at all times.

When the tractor brakes (either service or emergency) are not actuated and the tractor is out of park, the othercoupling must have no pressure. When the tractor service brakes are actuated air pressure which is proportional tothe service brake pressure is supplied from the trailer brake control valve to the one coupler. The maximumpressure at the coupler is 7.0 to 7.5 bar (102 to109 PSI). This provides a braking force for the trailer which isdependent on the tractor service brake force (tractor brake pressure). When the tractor emergency brake isactuated the pressure at the coupler will rise continuously to the maximum system operating pressure of 7.0 to 7.5bar (102 to109 PSI). When either the tractor service brakes are released, or the emergency brake is disengagedthe pressure drops to zero.


33-13

RI02M090, RI02M091 AND RI02M066

Italian Pneumatic Trailer Brake

1

2

3

4

1. ITALIAN AIR BRAKE DUAL COUPLER 3. RIGHT SIDE AIR RESERVOIR2. LEFT SIDE AIR RESERVOIR 4. DUAL LINE CONTROL VALVE


33-14

RI02M067, RI02M092 AND RI02M069

Italian Pneumatic Trailer Brake

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5

7

5. DOUBLE CHECK VALVE 7. AIR BRAKE UNLOADING VALVE6. SOLENOID VALVE


33-15

ROW (Rest of World) Pneumatic Trailer Brakes (NAR, ANZ, CIS, LAR, EEAA)

The pneumatic trailer brake control system for ROW tractors is a dual line high pressure braking system. There aretwo couplers included with this system, the red (emergency) coupling and the blue (service) coupling.


From the compressor, compressed air is supplied to the air reservoirs, with the pressure limited to 7.9 to 8.3 bar(114 to 120 PSI) by an unloading/regulator valve. Compressed air is supplied from the reservoirs to the inlet port ofthe dual trailer control valve, to the inlet of the emergency brake solenoid valve and to the red coupling, providingfull operating pressure to that coupling unless the tractor is in Park, or the manual emergency trailer brake valve isactuated (pushed down).

When the tractor service brake system is actuated, air pressure, which is proportional to tractor service brakepressure, is supplied fro the dual line trailer control valve to the blue coupler. The maximum pressure is 7.9 to 8.3bar (114 to 120 PSI). This provides a braking force for the trailer which is dependent on the tractor service brakeforce (tractor brake pressure).

When the tractor is in Park and the manual trailer control valve is up, pressure at the red coupler is zero and thetrailer is braked by the trailer spring brake.

When the tractor is out of Park and the manual trailer control valve is up, pressure at the red coupler is still zeroand the trailer is still braked.

When the tractor is out of Park and the manual trailer control valve is pushed down, pressure is applied to the redcoupler and the trailer spring brake is released. The handle of the manual trailer control valve will stay down (withthe tractor running) and the trailer spring brake released, as long as system air pressure is above 2.4 bar (35 PSI).


33-16

RI02M108, RI02M069 AND RI02M107

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4

8

1. AIR BRAKE COUPLERS 5. UNLOADER VALVE TO RESERVOIR2. HAND CONTROL VALVE 6. PRESSURE SWITCH3. COMBINED UNLOADER VALVE 7. AIR BRAKE TEST PORT4. AIR RESERVOIR 8. DUAL LINE CONTROL VALVE

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1. BRAKE VALVE 9. PRIORITY REGULATOR VALVE 17. TRAILER BRAKE PRIORITY VALVE2. SERVICE BRAKE 10. DUAL GEAR PUMP/CHARGE/REGULATED 18. RETURN FROM STEERING3. PARK SOLENOID SWITCH 11. PFC PISTON PUMP 19. TO STEERING LOAD SENSE4. BRAKE PEDAL 12. OIL COOLERS 20. TO STEERING SUPPLY5. CHECK VALVE 13. AUXILIARY SIGNAL 21. TRAILER BRAKE VALVE6. SHUTTLE VALVE 14. TRANSMISSION LUBE 22. TRAILER BRAKE COUPLER7. TO TRANSMISSION CONTROL VALVE 15. FILTER ASSEMBLY

8. TO AUXILIARY CONTROL VALVE 16. RETURN FROM AUXILIARY VALVES

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EUROPEAN HYDRAULIC TRAILER BRAKE

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1. EMERGENCY BRAKE VALVE 11. SHUTTLE VALVE 21. FILTER ASSEMBLY2. ACCUMULATOR 12. TO TRANSMISSION CONTROL VALVE 22. RETURN FROM AUXILIARY VALVES3. FROM TRANSMISSION CONTROL vALVE 13. TO AUXILIARY CONTROL VALVE 23. TRAILER BRAKE PRIORITY VALVE4. EMERGENCY BRAKE PRESSURE SWITCH 14. PRIORITY REGULATOR VALVE 24. FROM AUXILIARY SUPPLY5. EMERGENCY BRAKE 15. DUAL GEAR PUMP/CHARGE/REGULATED 25. RETURN FROM STEERING6. BRAKE VALVE 16. PFC PISTON PUMP 26. TO STEERING LOAD SENSE7. SERVICE BRAKE 17. LOW SYSTEM PRESSURE SWITCH 27. TO STEERING SUPPLY8. PARK SOLENOID SWITCH 18. OIL COOLERS 28. TRAILER BRAKE VALVE9. BRAKE PEDAL 19. AUXILIARY SIGNAL 29. PRESSURE SWITCH

10. CHECK VALVE 20. TRANSMISSION LUBE 30. TRAILER BRAKE COUPLER

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ITALIAN HYDRAULIC TRAILER BRAKE

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1. COMPRESSOR 7. SOLENOID VALVE 13. YELLOW COUPLER2. UNLOADING VALVE 8. COUPLERS 14. RED COUPLER3. RESERVOIR 9. MAIN BRAKE CONTROL SPOOL 15. TO SERVICE BRAKE SWITCH4. RESERVOIR DRAIN VALVE 10. SHUTTLE VALVE 16. TO PARK BRAKE5. PRESSURE SWITCH 11. BRAKE DIFFERENTIAL LOCK SWITCH 17. TO PARK BRAKE SOLENOID6. DUAL LINE VALVE 12. DOUBLE CHECK VALVE

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ITALIAN PNEUMATIC TRAILER BRAKE


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Documents

Section 33 Chapter 4 - Login Required · 2010. 7. 1. · SECTION 33 - TRAILER BRAKE SYSTEMS - CHAPTER 4 33-9 PNEUMATIC BRAKE SYSTEMS Pneumatic Trailer Brakes The pneumatic trailer