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| Illustration 1 | g03862077 |
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View of main control valve (1) Multi combined valve (if equipped) (2) Bucket control valve (3) Travel control valve (4) Stick control valve (5) Blade and stabilizer control valve (6) Boom control valve (7) Fore boom control valve (if equipped) (8) Relief valve group | |
The standard configuration of the main control valve has five sections that are independent. The following standard sections are:
- Bucket control valve (2)
- Travel control valve (3)
- Stick control valve (4)
- Blade and stabilizer control valve (5)
- Boom control valve (6)
The control valves direct flow from the main pump to the various implement or travel circuits. The main control valve is equipped with a main relief valve and load sensing signal limiter valve which are located in relief valve group (8).
Machines can be equipped with the heavy lift option. The heavy lift option becomes active for 60 seconds by pressing the right-hand button in the right-hand joystick. The maximum implement pressure increases from
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| Illustration 2 | g03862078 |
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Main control valve with optional valves (1) Multi combined valve (if equipped) (2) Bucket control valve (3) Travel control valve (4) Stick control valve (5) Blade and stabilizer control valve (6) Boom control valve (7) Fore boom control valve (if equipped) (8) Relief valve group (9) Drift reduction valve (bucket) (10) Manual valves (single or double acting tool) (11) Drift reduction valve (multi combination) (12) Signal drain valve (13) Load sensing signal limiter valve (14) Main relief valve (15) Load sense unloading valve (16) Compensator valve (17) Bypass check valve (18) Main pump pressure sensor (19) Hydraulic oil tank (20) Main pump (21) Hydraulic oil cooler (22) Back pressure valve (23) Pilot manifold (24) Heavy lift solenoid (25) Load sense pressure sensor | |
The main control valve can be equipped with a multi combination valve. The maximum pressure from the multi combination valve is adjusted manually. The flow from the multi combination valve can be adjusted in ET or on the monitor. The multi combination valve is enabled by a solenoid valve. The solenoid valve is energized when the slider on the right joystick is pressed or when the optional pedal is depressed. Both directions of the slider or the pedal result in the same oil flow direction. Oil flows from the left side of the machine to the right side of the machine (looking from the cab).
The machine may also be equipped with a drift reduction valve (11) as shown in Illustration 2.
For more information on the multi combination valve, refer to Systems Operation, "Combined Function Hydraulic System".
Main Control Valve in Neutral Position
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| Illustration 3 | g03862959 |
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Cross section view of a control valve in NEUTRAL position (A) Port (B) Port (16) Compensator valve (26) Load sensing signal (27) Load sensing port (28) Load check valve (29) Line relief and makeup valve (30) Stroke limiter screw (31) Shock reducing valve (32) Pilot line from joystick (33) Pump supply (34) Feeder passage (35) Control spool (36) Pilot line from joystick | |
A control valve in the NEUTRAL position is shown in Illustration 3. Construction of the remaining valves is similar in design and operation. The major components are shown. The control valves are closed center, pilot operated control valves with individual compensator valves (16) in each valve.
Two shock reducing valves (31) are located in the ends of the control valve spool. Shock reducing valves (31) allow control spool (35) to return slowly to the NEUTRAL position. The spools have stroke limiter screws (30) that are used to limit the maximum travel of the spools. The stroke limiter screws are also used to limit the maximum flow through the valves.
Each valve has two combination line relief and makeup valves (29). The pressure setting of each line relief valve is adjustable.
Compensator valve (16) maintains a pressure differential that is controlled across control spool (35) in order to control flow to the circuit. If more than one circuit is used at a time, the circuit with the highest work port pressure is used to regulate the flow through each control valve.
Compensator valves (16) also act as resolver valves in order to compare work port pressures for different circuits. Compensator valves (16) also send a signal pressure back to the main pump that is equal to the highest circuit pressure.
A load sensing signal is shown flowing into the control valve in Illustration 2. Load sensing signal (26) is working with the spring above compensator valve (16) in order to move the compensator valve downward.
Machines have a hydraulic system that is similar to the Proportional Priority Pressure Compensated system that is used on other Caterpillar products. The control valve that is shown in Illustration 3 incorporates the following components into one component that is called a compensator valve: flow control, signal duplication and resolver.
The compensator valve with the highest circuit pressure sends some of the supply oil that is below the compensator through load sensing port (27). This action is due to signal duplication. The signal network consists of all of the compensators, internal passages, and signal lines. The circuit with the actual highest work port pressure is directed through the signal network on other load sensing systems. This signal is sent to the pump control and to all of the other compensator valves.
The spring in the compensator valve has no influence (force above
For example, if the pressure in feeder passage (30) is
In summarizing, the compensator duplicates the work port pressure of the circuit with the highest pressure in order to create a load sensing signal.
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| Illustration 4 | g03863742 |
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Cross section view of a control valve in HIGH PRESSURE position (A) Port (B) Port (16) Compensator valve (26) Load sensing signal (27) Load sensing port (28) Load check valve (29) Line relief and makeup valve (30) Stroke limiter screw (31) Shock reducing valve (32) Pilot line from joystick (33) Pump supply (34) Feeder passage (35) Control spool (36) Pilot line from joystick | |
When pilot pressure moves control spool (35) to the right, the pump supply oil flows into feeder passage (34).
Compensator valve (16) moves upward in order to provide signal oil (26) to load check valve (28). Load check valve (28) unseats. Oil flows around additional lands on control spool (35) to the circuit. Return oil from the circuit flows around the spool to the tank.
The operation of the compensator was described earlier for the circuit with the highest load pressure.
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| Illustration 5 | g03863753 |
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Cross section view of a control valve in LOW PRESSURE position (A) Port (B) Port (16) Compensator valve (26) Load sensing signal (27) Load sensing port (28) Load check valve (29) Line relief and makeup valve (30) Stroke limiter screw (31) Shock reducing valve (32) Pilot line from joystick (33) Pump supply (34) Feeder passage (35) Control spool (36) Pilot line from joystick | |
When a circuit with a lower pressure is activated at the same time as a circuit with a higher pressure, the higher pressure signal is directed to the spring chamber at the top of flow compensator valve (16).
The supply oil in feeder passage (32) pushes up on compensator valve (16) until the passage below the compensator valve opens. Pump flow is directed through load check valve (26) to the circuit.
The operation of the compensator was described earlier for the circuit with the lower load pressure.
Stick Control Valve with Regeneration
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| Illustration 6 | g03863757 |
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Cross section view of a control valve in LOW PRESSURE position (A) Port (B) Port (16) Compensator valve (26) Load sensing signal (27) Load sensing port (28) Load check valve (29) Line relief and makeup valve (30) Stroke limiter screw (31) Shock reducing valve (32) Pilot line from joystick (33) Pump supply (34) Feeder passage (35) Control spool (36) Pilot line from joystick (37) Check valve (38) Passage | |
The return passage for the rod end of the stick cylinder is designed for a throttling effect of the flow to the tank during fine modulation. This action eliminates the effect of overrunning of the stick due to gravity.
When the stick is moved faster, check valves (37) in the stick circuit provide regeneration. When the stick is moved fast enough the pressure increase in the return side will push the rod end oil through check valves (37) into the supply side.
Note: The valve spool for the stick control valve is physically unchanged by the addition of the regeneration function. Passage (38) is the only visible change that is made to the stick circuit.
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| Illustration 7 | g03863790 |
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Cross section view of the travel control valve in NEUTRAL position (low pressure) (A) Port (B) Port (16) Compensator valve (26) Load sensing signal (27) Load sensing port (28) Load check valve (29) Line relief and makeup valve (30) Stroke limiter screw (31) Shock reducing valve (32) Pilot line from joystick (33) Pump supply (34) Feeder passage (35) Control spool (36) Pilot line from joystick (39) Pressure reducing valve | |
The travel valve spool contains two pressure reducing valves that keep the travel circuit fully charged with oil. The pressure reducing valves ensure that the minimum pressure in the suction line is
In the NEUTRAL position, pump flow is allowed to enter the FORWARD and REVERSE passages. Pressure in the two passages increases until the pressure is able to overcome the force of the spring in the pressure reducing valve. The pressure reducing valve moves to a metering position, maintaining the pressure in the FORWARD and REVERSE passages at the value of the pressure reducing valve.
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| Illustration 8 | g03863793 |
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Cross section view of the boom control valve in NEUTRAL position (low pressure) (A) Port (B) Port (16) Compensator valve (26) Load sensing signal (27) Load sensing port (28) Load check valve (29) Line relief and makeup valve (30) Stroke limiter screw (31) Shock reducing valve (32) Pilot line from joystick (33) Pump supply (34) Feeder passage (35) Control spool (36) Pilot line from joystick | |
The machine gives priority to the stick function when quick boom movements and stick movements are required at the same time during fast leveling action. This condition can cause an irregular leveling operation to occur.
To overcome the normal priority, the boom control valve uses a special compensator valve that directs pressure to the load sensing network after only
When the control valve is actuated and the compensator begins to move upward, a passage inside the compensator is opened from the feeder passage to the signal network by the spool within the compensator. Little movement is required by the compensator in order to open this passage. Oil flows from the feeder passage and through the compensator in order to become signal oil.
Port Locations on Main Control Valve
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| Illustration 9 | g03863796 |
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Front view of main control valve (41) Multi combined valve port "B01" (if equipped) (42) Port "S51" - to hydraulic oil tank through swing drive (43) Bucket open "B1" (44) Reverse travel "B2" (45) Stick out "B3" (46) Blade/stabilizer raise "B4" (47) Boom down "B5" (48) Pump pressure "MP" - to multi combination valve "PMP" (if equipped) (49) Fore boom lower "B6" (if equipped) (50) Load sensing signal "MLS" (51) Port "LS" - not used (52) Fore boom raise "A6" (if equipped) (53) Port "LS AUX" - not used (54) Port "P AUX 1" - to quick coupler (55) Boom up "A5" (56) Blade/stabilizer lower "A4" (57) Stick in "A3" (58) Forward travel "A2" (59) Bucket close "A1" (60) Multi combined valve port "A01" (if equipped) | |
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| Illustration 10 | g03864145 |
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Rear view of main control valve (61) Port "S53" - not used (62) Port "S52" - return oil from medium pressure control valve (63) Bypass check valve "T" - to return filter (64) Port "S5" - not used (65) Port "P''" - not used (66) Pump supply "P" - from main pump (67) Back pressure valve "K" - to hydraulic oil cooler (68) Port "P AUX 2" - not used | |