Shop manual máy đào HuynDai R250: An toan, cấu trúc, sơ đồ điện, thủy lực,
3-5The pilot circuit consists of suction circuit, delivery circuit and return circuit.The pilot pump is provided with relief valve, receives the oil from the hydraulic tank through the suctionfilter.The discharged oil from the pilot pump flows to the remote control valve through line filter, EPPRvalve, solenoid valve assemblies, swing parking brake, main control valve and safety lock solenoidvalve.GROUP 3 PILOT CIRCUITRelief valve35kgf/cmRCV pedalRemote control valve(LH lever)Remote control valve(RH lever)Safety locksolenoid valveSwing parking brakePilot pumpSuction filterControl valveTravel speed solenoid valveMain pump2Power boost solenoid valveLine filterMax flow cut off solenoid valveSwing speed reducing valve25073CI03 3-6BUCKET CYLINDERBOOM CYLINDERARM CYLINDERTRAVEL MOTORSWING MOTORSWING ARMTRAVELBUCKET BOOMRCV LEVER(LH)RCV PEDALRCV LEVER(RH)ARM1BUCKETHYDTANKBOOM2SWINGTRAVEL(LH)BOOM1OPTIONTRAVEL(RH)PILOT PUMPARM2STRAINERRELIEF VALVELINEFILTERSAFETYSOLENOID VALVEThe pilot pump receive oil from the hydraulic tank. The discharged oil from the pilot pump flows tothe safety solenoid valve through the line filter. The oil is filtered by the line filter. The pilot reliefvalve is provided in the pilot pump for limiting the pilot circuit pressure.The oil filtered by line filter flows remote control valve through safety solenoid valve.The return oil from remote control valve returned to hydraulic tank. 1. SUCTION, DELIVERY AND RETURN CIRCUIT25073HC03 ARM CYLINDERTRAVEL MOTORSWING MOTORSWING ARMTRAVELBUCKET BOOMRCV LEVER(LH)RCV PEDALRCV LEVER(RH)HYDTANKPILOT PUMPSTRAINERRELIEF VALVELINEFILTERSAFETYSOLENOID VALVEARM1BUCKETBOOM2SWINGTRAVEL(LH)BOOM1OPTIONTRAVEL(RH)ARM2LEVER DOWNLEVER UPBUCKET CYLINDERBOOM CYLINDER3-7When the lever of the safety solenoid valve is moved downward, oil flows into the remote control valvethrough solenoid valve and line filter.When the lever of the safety solenoid valve moved upward, oil does not flows into the remote controlvalve, because of blocked by the spool.2. SAFETY SOLENOID VALVE(SAFETY LEVER)25073HC04 3-8When the power max switch on the left control lever is pushed ON, the power max solenoid valve isactuated, the discharged oil from the pilot pump into Pz port of the main relief valve of main controlvalve ; Then the setting pressure of the main control valve is raises from 330kgf/cm2to 360kgf/cm2forincreasing the digging power. And even when press continuously, it is canceled after 8 seconds. 3. MAIN RELIEF PRESSURE CHANGE CIRCUITARM CYLINDERTRAVEL MOTORSWING MOTORSWING ARMTRAVELBUCKET BOOMRCV LEVER(LH)RCV PEDALRCV LEVER(RH)HYDTANKPILOT PUMPSTRAINERRELIEF VALVELINEFILTERSAFETYSOLENOID VALVEARM1BUCKETBOOM2SWINGTRAVEL(LH)BOOM1OPTIONTRAVEL(RH)ARM2POWER MAXSOLENOID VALVEMAIN RELIEF VALVEPzPzBUCKET CYLINDERBOOM CYLINDER25073HC05 4. SWING PARKING BRAKE RELEASEARM CYLINDERTRAVEL MOTORSWING MOTOR DEVICESWING ARMTRAVELBUCKET BOOMRCV LEVER(LH)RCV PEDALRCV LEVER(RH)HYDTANKPILOT PUMPSTRAINERRELIEF VALVELINEFILTERSAFETYSOLENOID VALVEARM1BUCKETBOOM2SWINGTRAVEL(LH)BOOM1OPTIONTRAVEL(RH)ARM2SHSHUTTLE VALVEPGPGSHABMuBUCKET CYLINDERBOOM CYLINDER3-9When the swing control lever is operated, the pilot oil flows to SH port of shuttle valve, this pressuremove spool so, discharged oil from pilot pump flows to PG port. This pressure is applied to swing motor disc cylinder, thus the brake released. When the swing control lever is set neutral position, oil in the swing motor disc cylinder is drain, thusthe brake is applied. 25073HC06 3-10When the travel speed solenoid valve was placed in the Hi position, the pressure oil from pilot pumpthrough line filter flows to port(Pk) of travel speed change over valve, and the control piston is pushedup, thus minimizing the displacement. When the travel speed solenoid valve was placed in the Lo position, the oil of Pk port return to thetank and the control piston is returned, thus maximizing the displacement. 5. TRAVEL SPEED CONTROL PRESSUREBUCKET CYLINDERBOOM CYLINDERARM CYLINDERTRAVEL MOTORSWING MOTORSWING ARMTRAVELBUCKET BOOMRCV LEVER(LH)RCV PEDALRCV LEVER(RH)ARM1BUCKETHYDTANKBOOM2SWINGTRAVEL(LH)BOOM1OPTIONTRAVEL(RH)PILOT PUMPARM2STRAINERRELIEF VALVELINEFILTERSAFETYSOLENOID VALVE25073HC03 3-11When the breaker operation mode is selected on the cluster, max flow cut off solenoid valve actuatesautomatically. Thus pilot pressure(Pm1,Pm2) is sent to the regulator and pump discharge volume isdecreased.6. MAX FLOW CUT OFF SYSTEMARM CYLINDERTRAVEL MOTORARM1BUCKETBOOM2SWINGTRAVEL(LH)BOOM1OPTIONTRAVEL(RH)ARM2SWING MOTORSWING ARMTRAVELBUCKET BOOMRCV LEVER(LH)RCV PEDALRCV LEVER(RH)HYDTANKLINEFILTERSAFETYSOLENOID VALVEMAX FLOW CUT OFFSOLENOID VALVEPm2MPm2Pm1Pm1BUCKET CYLINDERBOOM CYLINDER25073HC08 3-12When carrying out the combined operation of swing and boom or arm of the left control valve, theboom or arm speed can be lowered than operating speed of swing. When the heary duty workingmode in work mode is selected on the cluster, swing reducing solenoid valve actuates automatically.The oil from pilot pump flows into the solenoid valve through the line filter.Pns pressure from solenoid valve change the swing select spool and decreases the oil flow rate tothe swing section by orifice.This is called the boom priority system.7. BOOM PRIORITY SYSTEMARM CYLINDERTRAVEL MOTORSWING MOTORSWING ARMTRAVELBUCKET BOOMRCV LEVER(LH)RCV PEDALRCV LEVER(RH)HYDTANKPILOT PUMPSTRAINERRELIEF VALVELINEFILTERSAFETYSOLENOID VALVEARM1BUCKETBOOM2SWINGTRAVEL(LH)BOOM1OPTIONTRAVEL(RH)ARM2PnsPnsSWINGSELECTSPOOLSWING REDUCINGSOLENOID VALVEBUCKET CYLINDERBOOM CYLINDER25073HC09 . valveLine filterMax flow cut off solenoid valveSwing speed reducing valve25073CI 03 3- 6 BUCKET CYLINDERBOOM CYLINDERARM CYLINDERTRAVEL MOTORSWING MOTORSWING ARMTRAVELBUCKET. is raises from 33 0kgf/cm2to 36 0kgf/cm2forincreasing the digging power. And even when press continuously, it is canceled after 8 seconds. 3. MAIN RELIEF