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| Illustration 1 | g06311873 |
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(1) Swing brake
(2) Displacement change valve (left travel motor) (3) Displacement change valve (right travel motor) (4) Line (pilot oil from swing brake solenoid valve) (5) Travel pilot control valve (6) Pilot line (BOOM LOWER) (7) Pilot line (boom drift reduction valve) (8) Pilot line (STICK IN) (9) Pilot line (stick drift reduction valve) (10) Stick drift reduction valve (11) Main control valve (12) Boom drift reduction valve (13) Solenoid valve (straight travel) (14) Pilot line (pilot pressure to left travel pressure switch) (15) Pilot line (pilot oil to travel pilot control valve) (16) Right travel control valve (17) Boom l control valve (18) Straight travel control valve (19) Travel pressure switch (left) (20) Pilot line (pilot pressure to right travel pressure switch) (21) Travel pressure switch (right) (22) Pilot line (pilot oil to pilot control valve for the stick and swing) (23) Pilot line (pilot oil to pilot control valve for the boom and bucket) (24) Left travel control valve (25) Pilot control valve for stick and swing (26) Pilot control valve for boom and bucket (27) Variable swing priority valve (28) Pilot line (STICK OUT) (29) Pilot line (STICK IN) (30) Pilot line (SWING RIGHT) (31) Pilot line (SWING LEFT) (32) Pilot line (BUCKET CLOSE) (33) Pilot line (BOOM RAISE) (34) Pilot line (BOOM LOWER) (35) Pilot line (BUCKET OPEN) (36) Pilot line (pilot oil from boom pilot control valve) (37) Pilot line (BOOM RAISE) (38) Pilot line (pilot oil to the pressure reducing valve for boom priority) (39) Pilot line (pilot pressure to implement/swing pressure switch) (40) Implement/swing pressure switch (41) Pilot line (pilot pressure to displacement change valves) (42) Pilot line (pilot oil to pressure reducing valve for swing priority) (43) Pilot line (pilot oil to pilot control valves) (44) Pilot line (pilot oil to straight travel control valve) (45) Swing brake solenoid valve (46) Valve (hydraulic activation) (47) Pressure reducing valve for swing priority (48) Pressure reducing valve for boom priority (49) Idler pump (51) Pilot manifold (52) Travel speed solenoid valve (53) Passage (54) Hydraulic activation solenoid valve (55) Passage (56) Passage (57) Passage (58) Drive pump (59) Pilot pump (60) Pilot line (pilot oil flow to pilot oil manifold) (61) Pilot filter (63) Proportional reducing valve (power shift pressure) (64) Pilot relief valve (65) Passage (66) Pilot line (pilot oil flow from pilot pump to pilot oil filter) | |
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| Illustration 2 | g01229667 |
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Ports and solenoids at the pilot manifold (45) Swing brake solenoid valve (46) Valve (hydraulic activation) (52) Travel speed solenoid valve (54) Hydraulic activation solenoid valve | |
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| Illustration 3 | g06311877 |
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(11) Main control valve
(49) Idler pump (58) Drive pump (59) Pilot pump | |
The pilot circuit pressure is limited by pilot relief valve (64).
The oil delivery from pilot pump (59) performs the following main functions:
- Create pilot oil pressure in order to control the output flows of the main pumps.
- Provide pilot oil pressure to the pilot control valves for implements, swing, and travel in order to perform machine operations.
- Create pilot oil pressure in order to operate the control devices.
Note: Each pilot circuit performs one of the functions above.
The pilot circuit is classified into the following circuits:
- Power shift pressure system
- Pilot control valve circuit
- Pressure switch circuits
- Straight travel valve circuit
- Swing brake
- Boom priority
- Swing priority
- Automatic travel speed change
- Heavy Lift (if equipped)
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| Illustration 4 | g06312632 |
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(49) Idler pump
(58) Drive pump (63) Proportional reducing valve (PS pressure) (59) Pilot pump (68) Machine ECM (69) Monitor (70) Engine speed dial (71) Drive pump pressure sensor (72) Idler pump pressure sensor (73) Engine speed pickup | |
During machine operation, machine ECM (68) receives input signals from the following components:
- Engine speed dial (70)
- Engine speed pickup (75) that is located on the flywheel housing
- Drive pump pressure sensor (71)
- Idler pump pressure sensor (72)
- Monitor in the cab (69)
The machine ECM (68) continually monitors all of the input signals. The input signals are processed by the machine ECM and an output signal is sent to proportional reducing valve (63) at the drive pump regulator. The proportional reducing valve assists in controlling the output flow of drive pump (58) and idler pump (49).
The oil delivery from pilot pump (59) flows through the pilot filter to proportional reducing valve (63) at the drive pump regulator. The electrical signal that is sent from machine ECM (68) causes proportional reducing valve (63) to regulate the pilot pressure to a reduced pressure. This reduced pressure is called power shift pressure (PS). The proportional reducing valve sends the reduced pilot oil pressure through the drive pump regulator and through the idler pump regulator. The output flow of drive pump (58) and idler pump (49) is controlled in accordance with the power shift pressure. The power shift pressure is used to regulate the maximum allowable hydraulic pump output.
The output signal that is sent from the machine ECM to the proportional reducing valve will change when the machine ECM detects a change in any of the input signals. The power shift pressure that is sent to the regulators at the drive pump and the idler pump will change to regulate the maximum allowable hydraulic pump output. The desired engine speed is maintained.
A decrease in engine speed increases the power shift pressure. An increase in power shift pressure causes destroke condition of the drive pump and the idler pump. The maximum allowable hydraulic power output is decreased.
An increase in engine speed decreases the power shift pressure. A decrease in power shift pressure causes an upstroke condition of the drive pump and the idler pump. The maximum allowable hydraulic power output is increased.
Note: For more information concerning the operation of the machine ECM, refer to Systems Operation, "Machine Electronic Control System".
Oil from pilot pump (59) flows through pilot line (66), pilot filter 61, and pilot line (60) to pilot manifold (51). When the hydraulic activation control lever is shifted to the UNLOCKED position, the machine ECM energizes the hydraulic activation solenoid valve (54). The pilot oil then shifts valve (46). The pilot oil now flows through valve (46) and pilot line (43). The pilot oil now flows to pilot control valves (5), (25) and (26) for implements, swing, and travel in order to perform machine operations. When the joysticks and/or travel levers/pedals are moved, the pilot oil flows to main control valve (11) in order to control the machine functions.
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| Illustration 5 | g00932058 |
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Pilot lines at the main control valve (top view) | |
When joystick (25) and/or joystick (26) are operated, the pilot control valves send pilot pump oil through the pilot lines to pilot ports at the main control valve to shift the spools in the main control valve. Refer to Illustration 5 and Table 1 for the location of the pilot lines and machine operations.
| Pilot line | Control Valve | Machine Operation |
| (76) | Boom l control valve | BOOM LOWER |
| (77) | Bucket control valve | BUCKET CLOSE |
| (78) | Swing control valve | SWING LEFT |
| (79) | Boom II control valve | BOOM RAISE |
| (80) | Stick II control valve | STICK IN |
| (81) | Right travel control valve | REVERSE RIGHT TRAVEL |
| (82) | Left travel control valve | REVERSE LEFT TRAVEL |
| (83) | Stick l control valve | STICK IN |
Pilot oil from the pilot control valves flows through pilot lines to the ports on the bottom of the main control valve in order to perform the opposite operation.
The following example is given for the BOOM LOWER operation and the BOOM RAISE operation. Machine operations for a stick operation, bucket operation, travel operation, and swing operation are accomplished in the same manner as the boom operation.
When the joystick for the boom is moved to the BOOM RAISE position, pilot oil from pilot control valve (26) flows through pilot line (37) to boom l control valve (17). The pilot pressure shifts the boom l control valve. The oil delivery from the drive pump flows to the head end of the boom cylinders in order to perform the BOOM RAISE operation.
When the joystick for the boom is moved to the BOOM LOWER position, pilot oil from pilot control valve (26) flows through pilot line (6) to boom l control valve (17). The pilot pressure shifts the boom l control valve. The pilot oil also flows through pilot line (7) in order to open boom drift reduction valve (12). The return oil from the head end of the boom cylinders flows through the boom drift reduction valve and the boom l control valve to the hydraulic tank. The BOOM LOWER operation is now performed.
Pressure switches (19) and (21) are connected to travel pilot control valve (5). Pressure switch (40) is connected to pilot control valve (25) and pilot control valve (26). When all of the joysticks and/or travel levers/pedals are in the NEUTRAL position, the pilot oil pressure to the pressure switches is low. Pressure switches (19), (21), and (40) are OFF. The machine ECM recognizes the OFF condition of all of the pressure switches. The AEC system is activated in order to lower the engine rpm.
If any of the joysticks and/or travel levers/pedals are moved from the NEUTRAL position, the increased pilot oil pressure is sent to the pressure switches. If pressure switch (19), (21), and/or (40) is ON, the machine ECM activates the AEC system in order to increase the engine rpm.
If both travel levers/pedals and either one of the joysticks are moved from the NEUTRAL position simultaneously, pilot oil pressure will cause pressure switches (19), (21), and (40) to be in the ON position. An electrical signal is sent to the machine ECM. The machine ECM energizes straight travel solenoid (13). Pilot pressure now activates straight travel control valve (18).
The straight travel control valve provides hydraulic oil flow to travel control valves (24) and (16) from the idler pump. The drive pump supplies all oil delivery to the remaining valves within the main control valve.
If the machine is equipped with a straight travel pedal, there will be a separate pressure switch that sends a signal to the machine ECM. A signal is sent to the machine ECM in order to energize straight travel solenoid (13) when the straight travel pedal is moved from the NEUTRAL position.
For more information concerning the operation of the straight travel control valve, refer to Systems Operation, "Control Valve (Straight Travel)".
When the hydraulic activation control lever is placed in the UNLOCKED position, pilot oil in passage (57) flows through valve (46) and passage (53) in order to swing brake solenoid valve (45). When any of the joysticks are moved from the NEUTRAL position, the increase of pilot pressure in pilot line (39) activates implement/swing pressure switch (40). The implement/swing pressure switch sends an electrical signal to the machine ECM. An electrical signal from the machine ECM energizes the swing brake solenoid valve (45). Pilot oil in line (4) flows to swing brake (1). This oil releases the swing brakes.
For more information concerning the operation of the swing brake, refer to Systems Operation, "Pilot Valve (Swing Parking Brake)".
During combined operations of BOOM RAISE and STICK IN, the pilot oil pressure in pilot line (36) and pilot line (38) activates the pressure reducing valve for boom priority. The pressure reducing valve for boom priority allows priority flow to the head end of the boom cylinders during these combined hydraulic operations by disabling the stick II control valve.
For more information concerning the pressure reducing valve for boom priority, refer to Systems Operation, "Boom Hydraulic System".
During a swing operation, pilot oil flows from pilot control valve (25) to the pressure reducing valve for swing priority (47). The pressure reducing valve for swing priority shifts. The pilot oil flow in pilot line (42) from pilot oil manifold (51) is blocked by the pressure reducing valve for swing priority. Most of the output flow from the idler pump goes to the swing motor.
For more information concerning the pressure reducing valve for swing priority, refer to Systems Operation, "Swing Hydraulic System".
Automatic Travel Speed Change Valve
Pilot oil in passage (56) flows to travel speed solenoid valve (52). When the travel speed switch on the right console is set at the HIGH SPEED position, the travel speed solenoid valve opens. This allows pilot oil to flow through travel speed solenoid valve (52) and through line (41). The oil then flows to the displacement change valve for the left travel motor (2) and the displacement change valve for the right travel motor (3). As the displacement change valve operates, the travel speed is maintained at the HIGH SPEED position.
When the travel speed switch on the right console is set at the HIGH SPEED position, the pressure sensors for the pump delivery pressure control the travel speed in accordance with the travel load. For example, low speed during a high load condition and high speed during a low load condition.
For more information concerning the operation of the displacement change valves, refer to Systems Operation, "Displacement Change Valve".
The machine is equipped with a heavy lift feature that allows higher system pressure in the main hydraulic circuit. A switch on the console activates a solenoid valve. The solenoid valve directs pilot oil pressure to the pilot oil port on the main relief valve. The pilot oil pressure is ported through the valve in order to move a piston that creates a higher spring force on the main relief valve. The increase of spring force on the main relief valve causes the relief pressure in the main hydraulic system to rise.
For more information concerning the operation of the heavy lift system, refer to Systems Operation, "Relief Valve (Main) (Heavy Lift)"