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| Illustration 1 | g06013708 |
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(1) Displacement change valve (left travel motor)
(2) Displacement change valve (right travel motor) (3) Swing brake (4) Passage (5) Swing control valve (6) Implement pressure switch (7) Travel pressure switch (8) Left travel control valve (9) Right travel control valve (10) Boom I control valve (11) Main control valve (12) Line (pilot oil to swing brake solenoid valve) (13) Pilot line (pilot pressure to implement pressure switch) (14) Passage (15) Travel pilot control valve (16) PRV for boom regeneration (17) Swing priority valve (18) Passage (19) Idler pump pressure sensor (20) Straight travel control valve (21) Drive pump pressure sensor (22) Boom II control valve (23) Pilot line (pilot oil to the pressure reducing valve for boom priority) (24) Pressure reducing valve for boom priority (25) Pilot control valve for stick and swing (26) Pressure sensor (boom down control) (27) Pilot control valve for bucket and boom (28) Pilot line (BOOM RAISE) (29) Pilot line (pilot pressure to displacement change valves) (30) Pilot line (STICK IN) (31) Pilot line (BOOM LOWER) (32) Pilot line (pilot oil to pilot control valves) (33) Travel speed solenoid valve (34) Swing brake solenoid valve (35) Passage (36) Pilot manifold (37) Passage (38) Passage (39) Valve (hydraulic activation) (40) Hydraulic activation solenoid valve (41) Pilot line (pilot oil flow to pilot oil manifold) (42) Pilot relief valve (43) Pilot filter (44) Idler pump (45) Proportional reducing valve (power shift pressure) (46) Pilot line (pilot oil flow from pilot pump to pilot oil filter) (47) Drive pump (48) Pilot pump | |
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| Illustration 2 | g06019296 |
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Ports and solenoids at the pilot manifold (33) Travel speed solenoid valve (34) Swing brake solenoid valve (39) Valve (hydraulic activation) (40) Hydraulic activation solenoid valve | |
The pilot circuit pressure is limited by pilot relief valve (42).
The oil delivery from pilot pump (48) 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 automatically 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
- Pressure sensors
- Straight travel valve circuit
- Swing parking brake
- Boom priority
- Swing priority
- Automatic travel speed change
- Boom regeneration
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| Illustration 3 | g02722498 |
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(11) Main control valve
(19) Idler pump pressure sensor (21) Drive pump pressure sensor (44) Idler pump (45) Proportional reducing valve (PS pressure) (47) Drive pump (48) Pilot pump (49) Engine ECM (50) Engine speed pickup (51) Machine ECM (52) Engine speed dial (53) Switch panel ECM (54) Monitor | |
During machine operation, machine ECM (51) receives input signals from the following components:
- Engine ECM (49)
- Switch panel ECM (53)
- Engine speed dial (52)
- Monitor in the cab (54)
- Drive pump pressure sensor (21)
- Idler pump pressure sensor (19)
The machine ECM (51) 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 (45) at the drive pump regulator. The proportional reducing valve assists in controlling the output flow of drive pump (47) and idler pump (44).
The oil delivery from pilot pump (48) flows through the pilot filter to proportional reducing valve (45) at the drive pump regulator. The electrical signal that is sent from machine ECM (51) causes proportional reducing valve (45) 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 (47) and idler pump (44) 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 in order 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.
Oil from pilot pump (48) flows through pilot line (46), pilot filter (43), and pilot line (41) to pilot manifold (36). When the hydraulic activation control lever is shifted to the UNLOCKED position, the machine ECM energizes the hydraulic activation solenoid valve (40). The pilot oil then shifts valve (39). The pilot oil now flows through valve (39) and pilot line (32). The pilot oil now flows to pilot control valves (15), (25) and (27) 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 4 | g03034834 |
When joystick (25) and/or joystick (27) are operated, the pilot control valves send pilot pump oil through the pilot lines to pilot ports at the main control valve in order to shift the spools in the main control valve. Refer to Illustration 4 and Table 1 for the location of the pilot lines and machine operations.
| Pilot line | Control Valve | Machine Operation |
| (55) | Bucket control valve | BUCKET CLOSE |
| (56) | Attachment control valve | WORK TOOL (if equipped) |
| (57) | Stick II control valve | STICK OUT |
| (58) | Boom II control valve | BOOM RAISE |
| (59) | Boom I control valve | BOOM RAISE |
| (60) | Right travel control valve | FOWARD RIGHT TRAVEL |
| (61) | Left travel control valve | FOWARD LEFT TRAVEL |
| (62) | Stick regeneration control valve | STICK IN |
| (63) | Swing control valve | SWING RIGHT |
| (64) | Stick I control valve | STICK OUT |
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 (27) flows through pilot line (28) to boom I control valve (10) and boom II control valve (22). The pilot pressure shifts the boom I control valve and the boom II 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 (27) flows through pilot line (31) to boom I control valve (10). The pilot pressure shifts the boom I control valve. The BOOM LOWER operation is now performed.
For more information concerning the operation of the boom, refer to Systems Operation, "Boom System".
When the travel controls are in the NEUTRAL position, the pilot pressure in passage (14) remains low and travel pressure switch (7) is 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 either travel control is moved from the NEUTRAL position, the pilot oil pressure in passage (14) increases and travel pressure switch (7) is ON. The machine ECM activates the AEC system in order to increase the engine rpm.
When the implement controls are in the NEUTRAL position, the pilot pressure in passage (13) remains low and implement pressure switch (6) is 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 implement controls are moved from the NEUTRAL position, the pilot oil pressure in passage (13) increases and implement pressure switch (6) is ON. The machine ECM activates the AEC system in order to increase the engine rpm.
Pressure sensor (26) is connected to pilot oil for boom down control. This pressure sensor sends an electrical signal to the machine ECM.
When a boom DOWN function is performed, pressure sensor (26) sends an electrical signal to the machine ECM. The machine ECM uses the pressure sensor information and then sends a signal to the following components:
- PRV for boom regeneration (16) limits pilot oil to the boom II control valve in order to control boom regeneration.
- The AEC system is activated in order to lower the engine rpm.
Drive pump pressure sensor (21) and idler pump pressure sensor (19) are located on main control valve (11).
When a swing operation and/or implement operation is performed during a travel operation, the increase of pilot pressure in passage (4) and pilot oil flows through passage (18) to straight travel control valve (20). Pilot pressure shifts straight travel control valve (20) downward. The straight travel control valve maintains straight travel even though there is a swing operation or an implement operation during travel. 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 (35) flows through valve (39) and passage (38) in order to provide oil to the swing brake solenoid valve (34). When any of the joysticks are moved from the NEUTRAL position, the increase of pilot pressure activates implement pressure switch (6). The pressure switch sends an electrical signal to the machine ECM. An electrical signal from the machine ECM energizes the swing brake solenoid valve (34) once the pilot oil pressure exceeds
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 (30) and pilot line (23) activates the pressure reducing valve for boom priority (24). The pressure reducing valve for boom priority (24) 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 System".
During a swing operation, pilot oil flows from pilot control valve (25) to swing control valve (5). Pilot oil also flows to swing priority valve (17). The swing priority valve shift and blocks part of the oil supply from the idler pump to the stick control valve. Most of the flow from the idler pump now goes to the swing motor. For more information concerning the swing priority valve, refer to Systems Operation, "Swing System".
Automatic Travel Speed Change Valve
Pilot oil in passage (37) flows to travel speed solenoid valve (33). When the travel speed switch on the right console is set at the HIGH SPEED position, the travel speed solenoid valve opens. This action allows pilot oil to flow through travel speed solenoid valve (33) and through line (29). The oil then flows to the displacement change valve for the left travel motor (1) and the displacement change valve for the right travel motor (2). 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 sensor for the drive pump or idler pump delivery pressure controls 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".
Proportional reducing valve for boom regeneration (16) is used in order to control the amount of regeneration oil in the boom circuit. During a boom DOWN function, pilot oil flows through PRV (16) to the boom II control valve. The pilot oil shifts the boom II control valve allowing regen oil to flow from the head end of the boom cylinder to the rod end.
PRV for boom regeneration (16) can also limit the amount of pilot oil supplied to the boom II control valve. The amount of regeneration oil supplied to the rod end of the boom cylinder depends on the engine speed dial.
For more information concerning the operation of the boom regeneration system, refer to Systems Operation, "Boom System".
For more information concerning the ECM logic of the boom regeneration system, refer to Systems Operation, "Electrical Output Components".