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| Illustration 1 | g03411952 |
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(1) Implement pressure switch
(2) Travel pressure switch (3) Line relief valve (stick cylinder head end) (4) Line relief valve (stick cylinder rod end) (5) Stick drift reduction valve (6) Stick I control valve (7) Load check valve (8) Swing control valve (9) Center bypass passage (10) Left travel control valve (11) Right travel control valve (12) Center bypass passage (13) Boom I control valve (14) Boom drift reduction valve (15) Line relief valve (boom cylinder head end) (16) Attachment control valve (17) Bucket control valve (18) Line relief valve (bucket cylinder head end) (19) Line relief valve (bucket cylinder rod end) (20) Swing priority valve (21) Stick regeneration valve (22) Parallel feeder passage (23) Main relief valve (24) Return passage (25) Straight travel control (26) Line relief valve (boom cylinder rod end) (27) Boom II control valve (28) Parallel feeder passage (29) Stick II control valve (30) Orifice (31) Orifice (32) Relief valve (negative flow) (33) Relief valve (negative flow) (34) Inlet port (idler pump) (35) Inlet port (drive pump) (36) Return passage (37) Hydraulic tank (38) Idler pump (39) Pilot pump (40) Drive pump | |
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| Illustration 2 | g03027277 |
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Main control valve ports (AL1) Right travel control valve (REVERSE TRAVEL) (AL2) Boom I control valve (BOOM LOWER) (AL3) Attachment control valve (AL4) Bucket control valve (BUCKET OPEN) (AR1) Left travel control valve (REVERSE TRAVEL) (AR2) Swing control valve (SWING LEFT) (AR3) Stick I control valve (STICK IN) (BL1) Right travel control valve (FORWARD TRAVEL) (BL2) Boom I control valve (BOOM RAISE) (BL3) Attachment control valve (BL4) Bucket control valve (BUCKET CLOSE) (BR1) Left travel control valve (FORWARD TRAVEL) (BR2) Swing control valve (SWING RIGHT) (BR3) Stick I control valve (STICK OUT) (dA1) Drain port at the stick drift reduction valve (dB1) Drain port at the boom drift reduction valve (PA1) Pilot port at the stick drift reduction valve (STICK IN) (PB1) Pilot port at the boom drift reduction valve (BOOM LOWER) (PP) Port for pilot signal oil (PTA) Port for the travel pressure switch (PL) Inlet port (drive pump) (PR) Inlet port (idler pump) (PSW) Port for implement pressure switch (T) Return port (tank) (HL) Negative flow signal pressure port (drive pump) (HR) Negative flow signal pressure port (idler pump) (dB) Drain port (pilot logic) (PLg) Pressure port (drive pump) (PRg) Pressure port (idler pump) (R1) Return port (R2) Return port (swing motor) | |
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| Illustration 3 | g02522836 |
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Main control valve ports (aL1) Pilot port at the right travel control valve (REVERSE TRAVEL) (aL2) Pilot port at the boom I control valve (BOOM LOWER) (aL3) Pilot port at the attachment control valve (aL4) Pilot port at the bucket control valve (BUCKET OPEN) (aL5) Pilot port at the boom II control valve (BOOM LOWER) (aL6) Pilot port at the stick II control valve (STICK IN) (aR1) Pilot port at the left travel control valve (REVERSE TRAVEL) (aR2) Pilot port at the swing control valve (SWING LEFT) (aR3) Pilot port at the stick I control valve (STICK IN) (aR5) Pilot port at the swing priority valve (bL1) Pilot port at the right travel control valve (FORWARD TRAVEL) (bL2) Pilot port at the boom I control valve (BOOM RAISE) (bL3) Pilot port at the attachment control valve (bL4) Pilot port at the bucket control valve (BUCKET CLOSE) (bL5) Pilot port at the boom II control valve (BOOM RAISE) (bL6) Pilot port at the stick II control valve (STICK OUT) (bR1) Pilot port at the left travel control valve (FORWARD TRAVEL) (bR2) Pilot port at the swing control valve (SWING RIGHT) (bR3) Pilot port at the stick I control valve (STICK OUT) (bR4) Pilot port at the stick regeneration valve (dA) Drain port for the stick regeneration valve and straight travel control valve | |
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| Illustration 4 | g03411954 |
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Top - right view of main control valve (4) Line relief valve (stick cylinder rod end) (5) Stick drift reduction valve (14) Boom drift reduction valve (15) Line relief valve (boom cylinder head end) (18) Line relief valve (bucket cylinder head end) (19) Line relief valve (bucket cylinder rod end) (21) Stick regeneration valve (23) Main relief valve (26) Line relief valve (boom cylinder rod end) (27) Boom II control valve (29) Stick II control valve (32) Relief valve (negative flow) (41) Front valve body | |
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| Illustration 5 | g03411955 |
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Bottom - left view of main control valve (6) Stick I control valve (8) Swing control valve (10) Left travel control valve (11) Right travel control valve (13) Boom I control valve (14) Attachment control valve (17) Bucket control valve (20) Swing priority valve (25) Straight travel control (33) Relief valve (negative flow) (34) Inlet port (idler pump) (35) Inlet port (drive pump) (42) Rear valve body | |
The main control valves are located between the pumps and the actuators (cylinders and motors) in the hydraulic system. Depending on the machine operation, the oil flow from the drive pump, the idler pump, and the pilot pump to the hydraulic circuits are controlled by the operation of each component in the main control valve. These functions change the operating direction of the actuators and the speed of the actuators. These functions also limit the pressure within the hydraulic system.
The main control valve consists of front body (41) and of rear body (42).
- The following control valves are installed in parallel in front body (41):
- Stick I control valve (6)
- Swing control valve (8)
- Left travel control valve (10)
- Right travel control valve (11)
- Boom I control valve (13)
- Attachment control valve (16)
- Bucket control valve (17)
The following components are also installed in the front body.
- Line relief valves
- Line relief valve (3) for the head end of the stick cylinder
- Line relief valve (4) for the rod end of the stick cylinder
- Line relief valve (15) for the head end of the boom cylinder
- Line relief valve (18) for the head end of the bucket cylinder
- Line relief valve (19) for the rod end of the bucket cylinder
- Line relief valve (26) for the rod end of the boom cylinder
- Drift reduction valves
- Stick drift reduction valve (5)
- Boom drift reduction valve (14)
- Load check valves (7)
- The following control valves are installed in parallel in rear body (42):
- Stick regeneration valve (21)
- Boom II control valve (27)
- Stick II control valve (29)
The following components are also installed in the rear body.
- Main relief valve (23)
- Swing priority valve (20)
- Straight travel valve (25)
- Relief valve (32) and relief valve (33)
- Orifice (30) and orifice (31)
For further information of the components that are installed on the main control valve or in the main control valve, refer to the appropriate sections within this module.
Main Control Valve Operation in NEUTRAL Position
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| Illustration 6 | g03411956 |
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(6) Stick I control valve
(8) Swing control valve (9) Center bypass passage (10) Left travel control valve (11) Right travel control valve (12) Center bypass passage (13) Boom I control valve (16) Attachment control valve (17) Bucket control valve (22) Parallel feeder passage (24) Return passage (28) Parallel feeder passage (41) Front body | |
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| Illustration 7 | g03411958 |
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(20) Swing priority valve
(21) Stick regeneration valve (25) Straight travel control valve (27) Boom II control valve (29) Stick II control valve (30) Negative flow control orifice (31) Negative flow control orifice (34) Inlet port (idler pump) (35) Inlet port (drive pump) (42) Rear body | |
The idler pump supplies oil through inlet port (34). The oil then flows through center bypass passage (9) and parallel feeder passage (22). The drive pump supplies oil through inlet port (35). The oil then flows through center bypass passage (12) and parallel feeder passage (28).
When all of the joysticks and/or travel levers/pedals are in the NEUTRAL position, idler pump oil flows through center bypass passage (9), negative flow control orifice (31) and back to the hydraulic tank. Drive pump oil from inlet port (35) flows through center bypass passage (12), negative flow control orifice (30) and back to the hydraulic tank. Oil in parallel feeder passages (22) and (28) remains blocked by each control valve spool.
Activation of any joystick and/or travel levers/pedals provides two paths for drive pump oil. One path flows through center bypass passage (12) to right travel control valve (11). The other path flows through parallel feeder passage (28) to boom I control valve (13), attachment control valve (16), and bucket control valve (17). Activation of any joystick and/or travel levers/pedals also provides two paths for idler pump oil. One path flows through center bypass passage (9) to left travel control valve (10) and stick I control valve (6). The other path flows through parallel feeder passage (22) to swing control valve (8) and stick I control valve (6).
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| Illustration 8 | g03411960 |
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Bucket control valve (NEUTRAL position) (12) Center bypass passage (18) Line relief valve (bucket cylinder rod end) (19) Line relief valve (bucket cylinder head end) (24) Return passage (28) Parallel feeder passage (43) Pilot port (44) Port (45) Passage (46) Load check valve (47) Pilot port (48) Port (49) Spool (50) Spring (51) Spring | |
The bucket control valve is used as a typical example for describing the operation of individual control valves.
When the joysticks and/or travel levers/pedals are in the NEUTRAL position, pilot oil does not flow to port (43) and port (47). Spool (49) is centered in the NEUTRAL position by the force of spring (51) and spring (50). The idler pump oil flows through center bypass passage (12) to the hydraulic tank.
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| Illustration 9 | g03411963 |
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Bucket control valve (CLOSE position) (12) Center bypass passage (24) Return passage (28) Parallel feeder passage (43) Pilot port (44) Port (45) Passage (46) Load check valve (47) Pilot port (48) Port (49) Spool (52) Passage (53) Passage | |
When the joystick for the bucket is moved to the BUCKET CLOSE position, pilot oil is supplied to pilot port (43). Spool (49) moves down. Center bypass passage (12) is closed and passage (53) becomes opened. Port (48) is now connected to return passage (24) through passage (52).
Oil that is in parallel feeder passage (28) flows through load check valve (46), passage (45) and passage (53). The oil then flows to port (44). The bucket cylinder rod extends. When the bucket cylinder rod extends, the displaced oil in the rod end flows to port (48).
Oil flows through port (48) through passage (52) to return passage (24) and back to the hydraulic tank.