Kaiyi BAIC Full Power Hydraulic Brake System Manual (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 : · Fan & brake pump · Cut-off valve · Brake valve · Accumulators · Pressure sensors and switch · Fan motor · 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 · 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 (OLD) 2. HYDRAULIC CIRCUIT (OLD) 24 FRONT P1 A1 45 T1 P2 T2 A2 25 REAR 21 22 21 20 S2 B2 B1 S1 S3 23 C5 C6 C3 G1 PS P B3 C4 C1 46 G2 PS T/M PARKING T2 23 Return line P 6 Return line A B D L S1 B A Main pump 955A4BS01 2 Fan & brake pump 6 Fan motor 7 Directional valve 8 Oil cooler 20 Cut-off valve 21 Accumulator 22 Accumulator 23 Pressure sensor 24 Brake valve 25 Pressure sensor 26 Hydraulic tank 38 Filter assy 45 Axle 46 Parking brake at T/M 4-3 T1 6 8

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