BAIC Brake and Fan System Service Manual PDF Download (EN)

SECTION 4 BRAKE AND FAN SYSTEM SECTION 4 BRAKE AND FAN SYSTEM Group 1 Structure and Function - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4-1 Group 2 Operational Checks and Troubleshooting - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4-32 Group 3 Tests and Adjustments - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4-39 Group 4 Disassembly and Assembly - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4-41

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SECTION 4 BRAKE AND FAN SYSTEM SECTION 4 BRAKE AND FAN SYSTEM GROUP 1 STRUCTURE AND FUNCTION GROUP 1 STRUCTURE AND FUNCTION 1. OUTLINE 1. OUTLINE The variable displacement piston pump supplies the hydraulic oil that is required in order to operate the brake and the hydraulic fan system. Oil flows from pump to the cut-off valve. The cut-off valve controls the flow of oil from the pump to the brake accumulators and also controls the flow of oil to the hydraulic fan motor. The cut-off valve contains a priority valve. The brake system has priority. The oil flows to the brake accumulators while the accumulators are charged.

After the accumulators are fully charged, the oil then flows to the hydraulic fan system. The accumulator has pre-charged gas and an inlet check valve to maintain a pressurized volume of oil for reserving brake system. The oil through the accumulator flows to the brake valves. The brake valve is a closed center design, dual circuit operated by a pedal. The front and rear brakes will operate simultaneously with only one brake pedal depressed. The hydraulic fan system is used to meet the cooling requirements. The hydraulic fan system controls the fan speed through the pump output pressure. The desired pressure level can be set by varying the solenoid current.

The hydraulic fan system contains directional valve that reverses the direction of fan. The brake and hydraulic fan system contains the following components : В Fan & brake pump В Cut-off valve В Brake valve В Accumulators В Pressure sensors and switch В Fan motor В Directional valve 4-1

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FULL POWER HYDRAULIC BRAKE FULL POWER HYDRAULIC BRAKE SYSTEM SYSTEM ADVANTAGES ADVANTAGES - The full power hydraulic brake system has several advantages over traditional brake actuation systems. These systems are capable of supplying fluid to a range of very small and large volume service brakes with actuation that is faster than air brake systems. Figure represents a time comparison between a typical air/ hydraulic and full power hydraulic brake actuation system.

Response time Response time Full power brake actuation VS Full power brake actuation VS Air/Hydraulic brake actuation Air/Hydraulic brake actuation 1000 900 800 700 Brake torque(lb В in) 600 Full power systems can supply significantly higher brake pressures with relatively low reactive pedal forces. The reactive pedal force felt by the operator will be proportional to the brake line pressure being generated. This is referred to as brake pressure modulation. Another key design feature of full power systems is the ability to control maximum brake line pressure.

In addition, because these systems operate with hydraulic oil, filtration can be utilized to provide long component life and low maintenance operation. 500 400 300 200 100 0 1 2 3 4 Time(seconds) Because these systems are closed center, by using a properly sized accumulator, emergency power-off braking that is identical to power-on braking can be achieved. These systems can be either dedicated, where the brake system pump supplies only the demands of the brake system or non-dedicated, where the pump supplies the demands of the brake system as well as some secondary down stream hydraulic device.

Another important note is that all seals within these system must be compatible with the fluid medium being used. 4-2 Bra ke pre ss ure ( Fu ll p ow er) Bra ke pr ess ure (A ir/h yd rau lic) Br ak e t orq ue (A ir/ hyd rau lic) B rak e to rq ue (F ull po wer )

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2. HYDRAULIC CIRCUIT 2. HYDRAULIC CIRCUIT 19 Front P1 A1 P2 T1 20 40 T2 A2 Rear 16 17 16 S2 B2 B1 S1 S3 G1 18 PS B3 Parking T/M Return line 18 18 PS G2 PS 41 22 23 24 2 29 P 30 A A D Return line 25 T B B 21 B Main pump L S 7609A4BS01 2 Fan & brake pump 15 Cut-off valve 16 Accumulator 17 Accumulator 18 Pressure sensor 19 Brake valve 20 Pressure switch 21 Hydraulic tank 22 Air breather 23 Return filter 24 Bypass valve 25 Strainer 26 Oil cooler 29 Fan motor 30 Directional valve 40 Axle 41 Parking brake at T/M 4-3 PS 26 26

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