DESCRIPTION OF OPERATION High Speed Travel Circuit With High Speed Travel, high speeds can be achieved hy setting the slant angel ofthe travel motor tothe smaller one. The travel motor has a circuit, which changes the speed to the lower one by utiliz- ing the load pressure added on the travel motor, only when traveling is made at high speed, Discharged oil from A1 enters the P1 port of control valve entry while discharged oil from AZ enters the P2 port of control valve entry. Each flow goes into the travel motor through the changing over of the left and right travel spools. By these flows, the machine travels forward and backward, Elec tronic signals are sent to the solenoid valve from the travel change—over switch, And the econtroller sends electronic signals to the travel 2—speed solenoid valves in the quadruple solenoid valves and the solenoid valves are changed over. Original pilot pressure (3.9 MPa) from the C1 port of the qua- druple solenoid valves is connected through the central joint to P3 ports of the left and right travel motors. The original pressure (3.9 MPa) entered the P3 ports ofthe left and right travel motors posi- tions the slant angle of the travel motor to smaller inclination side, and make the speed faster. PoaDESCRIPTION OF OPERATION High Speed Travel Circuit F4 < a ry & A HITCH PANEL,DESCRIPTION OF OPERATION Low Speed Travel Circuit This is a normal travel pattern. Even when the traveling position is in high speed, if the key switch is turned OFF andturned ON again, the speed setting will always return to this traveling pattern, Discharged oil from A1 enters into the P1 port of control valve entry while discharged oil from AZ enters into the P2 port of control valve entry. Each flow goes into the travel motor through the changing over of the loft and right travel spools. By these flows, the machine travels forward and backward. The 2 speed travel solenoid valve becomes OFF, and the hydraulic oil in P3 port of the travel motor is connected to the tank line. 10 PoaDESCRIPTION OF OPERATION Low Speed Travel Circuit F4 < a ry & A SMITCH PANE, = TANK LINE == PILOT TANK LINE — aLCIRICLINEDESCRIPTION OF OPERATION Straight Travel Circuit ‘This section describes the case where travel and boom—up operations are conducted at the same time. ‘The hydraulic ol ofthe pilot pump entered the pilot pump from PP, which is connected to the tank via, travel spool, is shut off by changing over of the travel spool Inaddition, diverted passage of the PR, which had been connected to the tank through all the spools of upper mechanism (boom, arm, bucket and swing), is shut off due to the change-over of the spool, on the boom. Accordingly, the hydraulic oi from the pilot pump entered the PR has no place to go and stacks, and goes up to the original pressure (3.9 MPa). This original pressure acts on the pilot. chamber of the straight travel valve and the straight travel valve changes over. Due to the changing over of the straight travel valve, it becomes possible for P1 to drive the travel mechanism and for P2 to drive the upper mechanisms, Travel lines are in the same pressure in the right and left travels as the right and left motors are driven by one pump, which makes the straight travel possible. Addi- tionally, surplus hydraulie pressured oil from P2.is supplied to the travel side through thecheck with travel flow confluence throttle, and keeps the speed reduction to the minimum. Itis the sameas above when the travel and other upper actuators than the boom are operated at the 2 PoaDESCRIPTION OF OPERATION Straight Travel Circuit F4 < a ry & A PRESSURE LINE TLE PILOT PRESSURE LINE PILOT TANK LINE e+ = DRAINING a BCTRICLINEDESCRIPTION OF OPERATION ‘Swing Parking Circuit When the engine is started and the swing lever isin neutral, the swing brake solenoid valveis turned ON (24 V input) and the swing parking brake is activated. When the swing pressure switch is turned ON by operating the lever, output to the swing brake sole- noid valve from the controller is turned OFF and the swing parking brake is released, Thus swing operation is enabled. When the swing lever is in neutral and attachments such as arm, ete. are ‘moved, swing lateral force is produced. In order to prevent the dragging of the brake, this parking bake is designed to be released, Signals from the pressure sensor Al or A2 enters the controller and at the time when either one reaches 14.7 MPa, the output to swing brake solenoid valve from the controller is turned OFF and the swing parking brake is released. In5 seconds after the swing pressure ewitch or attachment prescure switch is turned OFF or the delivery pressure from Al or A2 is below 14.7 MPa, the solenoid valve is turned ON and the swing. parking brake is activated Ifthe swing lock switch is turned ON, even when the swing pressure switch or attachment pressure switch is turned ON, the swing lock switch has the priority and the parking brake remains unre- leased. When the swing lock switch is turned ON and the swing lever isin operation, the swing spool in the main control valve is changed over. eyonten | Swingpressire | MAZIMPS) 1 Suing rake | _ Suing motor Bc" | prssuteon | | Steve | mochanal ko ON oF 3 oN oN orswing on on Spent of or on oFF 147 MPaor oF oFr “4 PoaDESCRIPTION OF OPERATION ‘Swing Parking Circuit Poa SRING HRA VALE ‘SOLENOID VALVE -TANCLINE PILOT TANK LINE ee BECRICLINEDESCRIPTION OF OPERATION Swing Priority Variable Throttle Circuit ‘Swing pilot pressure is supplied to Pe port via shuttle valve and acts on the swing priority variable throttle, 7 kkeeping the swing force for the press—digging operation when the arm and swing operations are conducted simultaneously. Additionally, when level digging operation is made, boom up pilot pressure is supplied to Pbu port and the supply of hydraulic oil to the arm (1) is secured through moving the swing variable throttle to the left to open the parallel circuit and the smooth level digging operation can be achieved even is throttles the parallel circuit resulting in raising the swing hydraulic line pressure and, if the center bypass is shut off by the boom (2) spool. When the swing and arm in or boom up is operated at the same time, the swing priority variable throttle romains throttled, and the pressure for the swing motion is designed to be secured. 16 PoaDESCRIPTION OF OPERATION ‘Swing Priority Variable Throttle Circuit F4 < a ry & A carat Hv \ ' | | ib st | | | 1 ssa eae mene PLATA ee BBCTRICLINEDESCRIPTION OF OPERATION Boom up 2 Speed Circuit ‘The discharged oil from P1 is supplied to the boom (2) spool through the parallel oil passage via the right travel spool or the straight travel valve and merges at the downstream of the boom (1) spool (Reduction of pressure loss) ‘The discharged oil from P2 merges with the discharged oil from the boom (2) via the boom (1) spool throughthe parallel oil passage and flows into the bottom side of the boom cylinder via the holding valve, 18 PoaDESCRIPTION OF OPERATION Boom up 2 Speed Circuit Ee < a ry = = TWOK LINE LOT TANK LINE ——— PRESSIRELINE ~ PILOT PRESSURE LINE = DRAINLINE —— BLECTRICLINEDESCRIPTION OF OPERATION Boom Down Load Holding Valve Circuit ‘The pilot pressure of boom down goes into Pb8 port of control valve and the spool of main control valve moves to the left side. At the same time, pilot pressure enters from PbS” port to Pe2 port, the load holding valve spool ‘moves to the left side. The oil in the spring chamber of the load holding valve check passes through the load holding valve spool to the tank. The pressure in the spring chamber decreases and the load holding valve check is released. "The hydraulic oil at the bottom side of the boom cylinder is returned to the tank line, the rod of the boom cylinder is retracted and the boom is lowered 20 PoaDESCRIPTION OF OPERATION Boom Down Load Holding Valve Circuit ‘TOTANKLINE ‘LOND HOLDING ‘VALVE CHECK Bou (2) ——— PRESSURE LINE TALIS PILOT PRESSURE LINE + PILOPTANGLINE DRAINLINE ee ELBCTRICLINE aDESCRIPTION OF OPERATION Boom Down Pressure feedback Circuit When boom down is operated, pilot pressure is supplied to Ph8 and boom spool moves to the left he pilot pressure from PbS" opens the boom load holding valve and some of the At the same time, discharged oil from the bottom side of boom cylinder is retruned to the rod side via the check in the spool. (The lower the load pressure at the eylinder rod side is, the more the returning amount is.) Even though the spool makes a full stroke, due to the bleed~ of oil passage of the central bypass, the negative control pressure is generated and the pump does not deliver the full flow amount. The pressure shortage is compensated by this oil return. Therefore, the engine power can be utilized efft- ciently. Machine Extra movement Prevention Circuit for Starting Boom down motion Duc to the bleeding oil passage of the center bypass, a high pressure occurrence is restricted and the yperated very quickly, since hydraulic ‘machine extra movement is reduced even when boom down: oil is bled, 2 PoaDESCRIPTION OF OPERATION Boom Down Pressure feedback Circuit Machine Extra movement Prevention Circuit for Starting Boom down motion Bocw CLIO NSIATIVE CNTROL Ee < a ry = = 300M UP ——— pressure Line <-—TANRLINE PLAT PRESSURE LINE, PILOTTANK LINE —-o-- DRAINLINE ——— BLECRICLINE 23DESCRIPTION OF OPERATION Arm Out 2 Speed Circuit ‘The discharged oil from A1 is supplied to the arm (1) spool vie parallel oil passage through center bypass oil passage or straight travel spool ‘The discharged oil from A2 is supplied to the arm (2) spool through the center bypass oil passage or parallel oil passage, and merges at the upstream of the arm (1) spool, then, flows into the rod side ofthe arm cylinder via the holding valve. The returned oil from the bottom side returns to the tank. oil passage via the arm (1) and (2) spools. 24 PoaDESCRIPTION OF OPERATION Arm Out 2 Speed Circuit ——— Pressure Line 2 NK LINE ‘= PILOT PRESSURELINE + PILOT TANK LINE aeoee DRAINLINE + BECIRICLINEDESCRIPTION OF OPERATION Arm In Load Holding Valve Circuit ‘The pilot pressure of the arm in enters Pb5 of the control valve and the spool of arm (1) moves to the right, At the same time, the pilot pressure also enters Pb9 and the spool of the arm (2) moves to the left. Also, pilot pressure detached from Pb5 enters Pel and the load holding valve spool moves to the right. The oil in the spring chamber of the load holding valve check passes through the load holding valve spool to the tank line. The pressure in the spring chamber decreases and the load holding valve check is released, ‘The hydraulic oil at the rod of the arm cylinder is returned lo the tank line, the cylinder extends and the arm is retracted. 26 PoaDESCRIPTION OF OPERATION Arm In Load Holding Valve Circuit —— Press Lne TN LINE '~ PILOT PRESSURELINE PILOT TANKLINE ea PAINE 4 BECTRICLINEDESCRIPTION OF OPERATION Arm In Forced Pressure feedback Circuit ‘This circuit throttles the return passage of the rod side at the forced pressure feedback release valve and forcos the returned oll to be fed back to the bottom side via the check in the arm (1) spool. This secures the speed of the arm for level digging operation, ete. When the load pressure is high at the bottom side, the forced pressure feedback release valve is changed over to the right and the opening of the return at the rod side becomes larger and no pres- sure feedback occurs. 28 PoaDESCRIPTION OF OPERATION Arm In Forced Pressure feedback Circuit DETAIL —— Pressime Line TAN LINE PILOT TANK LINE “= PILOT PRESSURE LINE — DRAINLINE ——— sECRICLINE 29DESCRIPTION OF OPERATION Circuit for Breaker & Crusher (2 Speed Confluence Crusher Circuit) ‘When pushing the switch in the cab to crusher side, the solenoid valve is turned ON, When the option pedal is moved, pilot pressure oil from the remote control valve passes through the solenoid valve via the shuttle valve and enters P port of the holding valve and Pb6 port of the arm (2) spool, ‘The arm (2) spool moves to the left and shuts off the conter bypass. The pilot pressure entered P port of the holding valve first acts on the holding valve release spool; spring chamber of the holding valve check returns to the Lank; and the pressure in the spring chamber decreases. ‘Asa result of these, the check of the holding valve opens. As a result, hydraulic pressure oil at P3 port of the control valve enters upstream PA port of control valve option spool via the holding valve cheek and merges the hydraulie oil from PL ‘Also, pilot pressure oil entered P port of the holding valve acts on the confluence priority spool and the spool is changed over to the right side. Pilot pressure oil from port Pa9 of the control valve arm (2) out returns to the tank via this confluence priority spool. Therefore, the 2 speed oil confluence is prioritized when using the crasher and the arm out operation does not become 2 speed. 30 PoaDESCRIPTION OF OPERATION Circuit for Breaker & Crusher (2 Speed Confluence Crusher Circuit) Crusher Changing Over Change the direction valve to C. cay Honey yy] ay RELEASE SPL, She oS pao fear ea pes 4 RDATTE ey SIE SI =p! sam | somo —— Pressure Line <= TWKLDE PILOT PRESSURE LINE PILOT TANK LINE DRAINLINE + BECRICLIE a1DESCRIPTION OF OPERATION Circuit for Breaker & Crusher (Option Line Holding Valve) ‘ONFLUENCE PRIORITY SPOOL HOLDING VALVE. RELEASE SPOOL. Ea < HOLDING VALVE. CHECK. 7 Fy = z 82DESCRIPTION OF OPERATION Circuit for Breaker & Crusher (Breaker Circuit) ‘When the switch in the cab is turned towards the breaker side and the pedals stepped forward, pilot olutionby thecon sure is detected by the pressure switch, then the engine falls to the preset ro pre troller. ‘The pilot pressure oil entered at Pa2 of the control valve, changes over the option spool while the discharged oil from Al is supplied to the breaker through the direction valve. 33 PoaDESCRIPTION OF OPERATION Circuit for Breaker & Crusher (Breaker Circuit) Breaker Changing Over Change the direction valve to B. F4 < a ry & z —— PRssRELINE —- = RL PILOT PRESSURE LINE PILOT TANK LINE ++ DRAINING ee BLBCTRICLINE 34