Hydraulic Schematic Of Main Control Valves
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| Illustration 1 | g06015325 |
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(1) Stick drift reduction valve
(2) Line relief valve (stick cylinder rod end) (3) Main control valve (4) Implement/swing pressure switch (5) Pressure switch (travel) (6) Line relief valve (boom cylinder head end) (7) Boom drift reduction valve (8) Boom II control valve (9) Center bypass passage (10) Stick I control valve (11) Load check valve (12) Swing control valve (13) Left travel control valve (14) Straight travel control valve (15) Right travel control valve (16) Load check valve (17) Attachment control valve (18) Bucket control valve (19) Boom I control valve (20) Center bypass passage (21) Negative flow control orifice (22) Relief valve (negative flow control) (23) Return port (24) Negative flow control orifice (25) Relief valve (negative flow control) (26) Line relief valve (stick cylinder head end) (27) Parallel feeder passage (28) Logic valve (29) Main relief valve (30) Inlet port (idler pump) (31) Inlet port (drive pump) (32) Inlet port (pilot pump) (33) Line relief valve (bucket cylinder head end) (34) Line relief valve (bucket cylinder rod end) (35) Line relief valve (boom cylinder rod end) (36) Parallel feeder passage (37) Stick II control valve (38) Negative flow control line (39) Hydraulic tank (40) Pilot pump (41) Drive pump (42) Idler pump (43) Negative flow control line | |
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| Illustration 2 | g01436523 |
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Main control valve ports (AR1) Left travel control valve (FORWARD TRAVEL) (AR2) Swing control valve (SWING LEFT) (AR3) Stick I control valve (STICK OUT) (AR4) Boom II control valve (BOOM RAISE) (APi2) Pilot Port (Stick Regeneration valve) (BR1) Left travel control (REVERSE TRAVEL) (BR2) Swing control valve (SWING RIGHT) (BR3) Stick I control valve (STICK IN) (AL1) Right travel control valve (FORWARD TRAVEL) (AL2) Attachment control valve (port) (AL3) Bucket control valve (BUCKET OPEN) (AL4) Boom I control valve (BOOM RAISE) (BL1) Right travel control valve (FORWARD TRAVEL) (BL2) Attachment control valve (port) (BL3) Bucket control valve (BUCKET CLOSE) (BL4) Boom I control valve (BOOM LOWER) (aR1) Pilot port at left travel control valve (FORWARD TRAVEL) (aR2) Pilot port at swing control valve (SWING LEFT) (aR3) Pilot port at stick I control valve (STICK OUT) (aR4) Pilot port at boom II control valve (BOOM RAISE) (aL1) Pilot port at right travel control valve (FORWARD TRAVEL) (aL2) Pilot port at attachment control valve (aL3) Pilot port at bucket control valve (BUCKET OPEN) (aL4) Pilot port at boom I control valve (BOOM RAISE) (aL5) Pilot port at stick II control valve (drain) (bR1) Pilot port at left travel control valve (REVERSE TRAVEL) (bR2) Pilot port at swing control valve (SWING RIGHT) (bR3) Pilot port at stick I control valve (STICK IN) (bL1) Pilot port at right travel control valve (REVERSE TRAVEL) (bL2) Pilot port at attachment control valve (bL3) Pilot port at bucket control valve (BUCKET CLOSE) (bL5) Pilot port at stick II control valve (STICK IN, STICK OUT, and BOOM DOWN) (APi) Pilot port at stick drift reduction valve (ADr) drain port at stick drift reduction valve (BPi) Pilot port at boom drift reduction valve (BDr) drain port at boom drift reduction valve (dR4) Pilot port at boom II control valve (STICK OUT) (dR5) Pilot port (Regeneration) (dL4) Pilot port at boom I control valve (BOOM LOWER) (dSW) Drain port (pressure control valve) (dST1) Drain port (straight travel control valve) (Dr) Drain port (main control valve) (HL) Negative flow signal pressure port (drive pump) (HR) Negative flow signal pressure port (idler pump) (Pp1) Pilot port to main control valve (Pp2) Pilot port to main control valve (PiH) Pilot port at heavy lift (PiL) Pilot port (pressure control valve) (PL) Inlet port (drive pump) (PR) Inlet port (idler pump) (PAT) Pilot port (pilot logic to attachment spool) (PSL) Pilot port (lock to boom II control valve) (PSW) Pilot port (implement/swing pressure switch) (PTA) Pilot port (travel pressure switch) (X) Port (upper pump flow) (Y) Port (upper pump flow from port (X)) (R1) Return port (tank) (R2) Return port (R3) Return port | |
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| Illustration 3 | g01572919 |
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Main control valve (front view) (1) Stick drift reduction valve (2) Line relief valve (stick cylinder rod end) (4) Pressure switches (Implement and Swing) (5) Travel pressure switch (8) Boom II control valve (10) Stick I control valve (12) Swing control valve (13) Left travel control valve (14) Straight travel control valve (15) Right travel control valve (17) Attachment control valve (18) Bucket control valve (19) Boom I control valve (29) Main relief valve (33) Line relief valve (bucket cylinder head end) (37) Stick II control valve (44) Right body (45) Left body | |
Main control valve (3) is located in the hydraulic system between the pumps and actuators (cylinders and motors). Depending on the machine operation, components and passages in the valve control oil flow and pressure in the circuits from the pumps to actuators.
The main control valve consists of right body (44) and left body (45). The main control valve is coupled together with bolts to make one assembly. The following control valves are in parallel in right body (44).
- Right travel control valve (15).
- Attachment control valve (17).
- Bucket control valve (18).
- Boom I control valve (19).
- Stick II control valve (37).
The following control valves are in parallel in left body (45).
- Straight travel control valve (14).
- Left travel control valve (13).
- Swing control valve (12).
- Stick I control valve (10).
- Boom II control valve (8).
The left body has inlet ports (30) and (31) and return port (23). The drive pump oil flows into inlet port (31). The idler pump oil flows into inlet port (30). The oil flow of the drive pump and the oil flow of the idler pump is controlled by the main control valve. The oil flow is supplied to cylinders and/or motors that are selected for operation. Return oil from cylinders and/or motors enters the main control valve. The oil then flows out of return port (23) and back to hydraulic tank (39) through return line.
- Line relief valves (33) and (34) limit the circuit pressure.
- When the control levers are in the NEUTRAL position or when the control levers are moved partially, relief valve (22) and negative flow control orifice (21) destroke the main pump.
- When the control levers are in the NEUTRAL position, boom drift reduction valve (7) prevents boom cylinder drift.
- Pressure switch (4) generates electric signals for the Automatic Engine Speed Control. Travel pressure switch (5) generates electric signals for the Automatic Engine Speed Control.
- Load check valve (16).
- Stick cylinder relief valves (26) and (2).
- Relief valve (25) and negative flow control orifice (24).
- Stick drift reduction valve (1) prevents stick cylinder drift when the main control valves are in the NEUTRAL position.
- Main relief valve (29) limits the main hydraulic system pressure.
- Load check valve (11).
The following five configurations are the functions of the main control valves.
- When the main control valves are in the NEUTRAL position, no pump oil flows to the cylinders and the motors.
- Individual valve operation
- The main control valve controls the negative flow control signal when the control levers are in the NEUTRAL position or when the control levers are moved partially.
- Prevention of cylinder drift with the load check valve.
- Limit the circuit pressure with the relief valve operation.
The description of some components that are installed on the main control valve or in the main control valves will be listed separately. Refer to the appropriate sections that are in this module for further information on the components.
- For more information on pressure switch (4) and travel pressure switch (5), refer to Systems Operation, "Gear Pump (Pilot)".
- For more information on boom drift reduction valve (7), refer to Systems Operation, "Boom Hydraulic System".
- For more information on straight travel control valve (14), refer to Systems Operation, "Control Valve (Straight Travel)".
Main Control Valve Operation In The NEUTRAL Position
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| Illustration 4 | g01457212 |
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Main control valves (NEUTRAL position) (1) Stick II control valve (2) Boom I control valve (3) Bucket control valve (4) Attachment control valve (5) Right travel control valve (7) Left travel control valve (8) Swing control valve (9) Stick I control valve (10) Boom II control valve (12) Right body (14) Left body (18) Inlet port (19) Inlet port (22) Return port (23) Straight travel control valve (26) Parallel feeder passage (27) Parallel feeder passage (28) Return passage (29) Negative flow control orifice (30) Center bypass passage (31) Center bypass passage (32) Negative flow control orifice (33) Return passage | |
The drive pump supplies oil to right body (12). Oil from the drive pump goes to the right body through inlet port (18). The oil then goes through center bypass passage (30) and parallel feeder passage (26). The idler pump supplies oil to left body (14). Oil from the idler pump goes to the left body through inlet port (19). The oil then goes through center bypass passage (31) and parallel feeder passage (27).
When all the control levers are in the NEUTRAL position, drive pump oil flows through center bypass passage (30), negative flow control orifice (29), return passage (28) and return passage (33). The oil then goes out through return port (22). The oil returns to the hydraulic tank. Idler pump oil from inlet port (19) flows through center bypass passage (31), negative flow control orifice (32), return passage (33), and out return port (22). The oil returns to the hydraulic tank. Oil in parallel feeder passages (26) and (27) remains blocked by each control valve spool.
Activation of any control lever provides two paths for drive pump oil. One path is from center bypass passage (30) to right travel control valve (5). The other path is from parallel feeder passage (26) to attachment control valve (4), bucket control valve (3), and boom I control valve (2). Activation of any control lever also provides two paths for drive pump oil. One path is from center bypass passage (31) to left travel control valve (7) and stick I control valve (9). The other path is from parallel feeder passage (27) to swing control valve (8).
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| Illustration 5 | g06015354 |
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Bucket Control Valve (NEUTRAL Position) (1) Line relief valve (bucket cylinder rod end) (2) Port (3) Parallel feeder passage (4) Load check valve (5) Passage (6) Port (7) Line relief valve (bucket cylinder head end) (8) Pilot port (9) Return passage (10) Spool (11) Center bypass passage (12) Spring (13) Pilot port | |
The bucket control valve is used as a typical example for describing the operation of individual control valves.
When all pilot control valve levers are in the NEUTRAL position, pilot oil does not flow to port (8) and port (13) from the pilot control valve. Spool (10) is centered in the NEUTRAL position by the force of spring (12). The drive pump oil goes through center bypass passage (11) to the hydraulic tank.
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| Illustration 6 | g01836837 |
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Bucket control valve (2) Port (3) Parallel feeder passage (4) Load check valve (5) Passage (6) Port (9) Return passage (10) Spool (11) Center bypass passage (13) Pilot port (14) Passage (15) Passage | |
When the bucket control valve is moved to the BUCKET CLOSE position, pilot oil is supplied to pilot port (13). Spool (10) moves to the left. Center bypass passage (11) is closed and passage (15) becomes opened. Passage (14) is now connected to return passage (9).
Oil that is in parallel feeder passage (3) goes through load check valve (4), passage (5) and passage (15). The oil then goes to port (6). The bucket cylinder rod extends. When the bucket cylinder rod extends, the displaced oil in the rod end flows to port (2).
Oil from port (2) flows through passage (14) to return passage (9) and back to the hydraulic tank.